Reconstruction of surfaces of revolution from single uncalibrated views

细胞生物学专业词中英文对照第一章细胞学——Cytology细胞生物——Cell biology细胞学说——Cell theory原生质——protoplasm原生质体——protoplast有丝分裂——mitosis福尔根反应——Feulgen reaction哺乳动物雷帕霉素靶蛋白——mammalian target of rapamycin (mTOR)支原体——mycoplast真核细胞——rucaryotic cell真核生物——procaryote原核细胞——prokaryotic cell原核生物——prokaryote类群、域——domain古核细胞——archaea古核生物——archaeon古细菌——archaebacteria真细菌——eubacteria鞭毛——flagellum鞭毛蛋白——flagellin类核——nucleoid质粒——plasmid管蛋白——tubulin蓝细菌——cyanobacteria类囊体——thylakoid异形胞——heterocyst直系同源基因——orthologous gene 盐细菌——halobacteria热源体——thermoplasma硫氧化菌——sulfolobus核小体——nucleosome核纤层——nuclear lamina核纤层蛋白——lamin核基质——nuclear matrix纳米生物学——nanobiology自我装配——self-assembly协助装配——aided-assembly直接装配——direct-assembly次生代谢产物——secondary metabolite天然产物——natural product衣壳——capsid核壳体——nucleocapsid囊膜——envelope第二章光学显微镜——light microscope分辨率——resolution相差显微镜——phase-contrast microscope微分干涉显微镜——differential-interference microscope录像增差显微镜——video-enhance microscope荧光显微镜——fluorescence microscope绿色荧光蛋白——green fluorescent protein, GFP激光扫描共焦显微镜——laser scanning confocal microscope, LSCM全内反射荧光显微术——total internal reflection fluorescence microscopy 光激活定位显微术——photoactivated localization microscopy, PALM随机光学重构显微术——stochastic optical reconstruction microscopy受激发射损耗显微术——stimulated emission depletion microscopy结构照明显微术——structured-illumination microscopy, SIM电子显微镜——electron microscope, EM电荷耦合器件——charge-coupled device, CCD超薄切片——ultrathin section负染色技术——negative staining冷冻蚀刻技术——frezze etching快速冷冻深度蚀刻技术——quick freeze deep etching低温电镜技术——cryo-electron microscopy单颗粒分析技术——single particle analysis电子断层成像技术——electron tomography背散射电子成像——back scattered electron imaging扫描电镜——scanning electron microscope, SEM光-电关联技术——correlative light microscopy and electron microscopy 扫描隧道显微镜——Scanning tunnel microscope, STM原子力显微镜——atomic force microscope, AFM免疫印记——western blotting放射免疫沉淀——radioimmuno-precipitation原位杂交——in situ hybridization流式细胞术——flow cytometry原代细胞——primary culture cell传代细胞——subculture cell单层细胞——single layer cell细胞系——cell line有限细胞系——finite cell line永生细胞系——infinite cell line连续细胞系——continuous cell line细胞株——cell strain成纤维样细胞——fibroblast like cell上皮样细胞——epithelial like cell外殖体——explant愈伤组织——callus细胞融合——cell fusion电融合技术——electrofusion methodB淋巴细胞杂交瘤技术——B-lymphocyte hybridoma technique 单克隆抗体——monoclonal antibody胞质体——cytoplast核质体——karyoplast细胞松弛素B——cytochalasin B显微操作——micromanipulation微量注射——microinjection荧光漂白恢复技术——fluorescence photobleaching recovery, FPR 荧光恢复——fluorescence recovery酵母双杂交系统——yeast two-hybrid systemDNA结合域——DNA binding domain转录激活域——activation domain荧光共振能量转移——fluorescence resonance energy transfer, FRET 放射自显影技术——autoradiography第三章细胞质膜——plasma membrane细胞内膜系统——internal membrane生物膜——biomembrane单位膜模型——unit membrane model流动镶嵌模型——fluid mosaic model菌紫红质——bacteria rhodopsin脂筏模型——lipid raft model辛德毕斯病毒——sindbis virus, SbV甘油磷脂——glycerophosphatide鞘脂——sphingolipid固醇——sterol磷脂酰胆碱——phosphatidylcholine, PC(卵磷脂)磷脂酰乙醇胺——phosphatidylethanolamine, PE磷脂酰丝氨酸——phosphatidyserine, PS磷脂酰肌醇——phosphaditylinositol, PI心磷脂——cardiolipin鞘磷脂——sphingomyelin, SM磷脂——phospholipid豆固醇——stigmasterol麦角固醇——ergosterol翻转酶——flippase脂质体——liposome微团——micelle膜蛋白——membrane protein周边膜蛋白——peripheral membrane protein外在膜蛋白——extrinsic membrane protein整合膜蛋白——integral membrane protein内在膜蛋白——intrinsic membrane protein脂锚定膜蛋白——lipid-anchored membrane protein 磷脂酶——phospholipase蛋白聚糖——proteoglycan磷脂酰肌醇糖脂——glycosylphosphaditylinositol跨膜蛋白——transmembrane protein单次跨膜蛋白——single-pass transmembrane protein 多次跨膜蛋白——multipass transmembrane protein 孔蛋白——porin卷曲结构——coiled-coil水孔蛋白——aquaporin去垢剂——detergent微团临界浓度——critical micelle concentration,CMC相变温度——phase transition temperature扩散常数——diffusion constant细胞外表面——extrocytoplasmic surface, ES外小叶——outer leaflet原生质表面——protoplasmic surface, PS内小叶——inner leaflet细胞外小叶断裂面——extrocytoplasmic face，EF原生质小叶断裂面——protoplasmic face，PF脂肪细胞——adipocyte鞭毛——flagellum纤毛——cilium微绒毛——microvillus膜相关的细胞骨架——membrane associated cytoskeleton 肌动蛋白——actin基于肌动蛋白的膜骨架——actin-based membrane skeleton 细胞皮层——cortex血影——ghost血影蛋白（或红膜肽）——spectrin锚蛋白——ankyrin血型糖蛋白——glycoprotein内收蛋白——adducin阀蛋白——flotillin膜脂微区——membrane lipid microdomain 阿尔兹海默症——Alzheimer disease。

1 Surface reconstruction of the surgicalfield from stereoscopic microscopeviews in neurosurgeryO.J.Fleig,F.Devernay,J.-M.Scarabin and P.JanninLaboratoire SIM,Facultéde Médecine,Universitéde Rennes1,2Avenue du Pr.Léon Bernard,35043Rennes Cedex(France)Carl Zeiss S.A.,60Route de Sartrouville,78230Le Pecq(France)Team ChIR,INRIA,Sophia-Antipolis(France)Department of Neurosurgery,University Hospital of Rennes,(France)We present a technique to reconstruct the surface of the surgicalfield during neurosurgery.The images are taken with a stereo camera mounted on a surgical microscope,which is part of a neuronavigation system.We use an intensity-based method to calculate a dense disparity map over the whole image extend.Correspondences are established by exploiting the epipolar ge-ometry and comparing image intensities along corresponding epipolar lines.The method does not require a strong calibration.Only the colineation denoted by the fundamental matrix,which maps corresponding epipolar lines from one image to the other,has to be known.The results show that our method is able to reconstruct the surface of the surgicalfield upto a few areas.It is limited at points of specular reflections of the wet brain surface and points of uniform texture. Keywords:Stereoscopic reconstruction;neuronavigation;stereo microscope;augmented re-ality;augmented virtuality1.IntroductionIn neurosurgery,guidance systems,which correlate patient imaging data to the surgicalfield using tracked probes or surgical microscopes,have become standard equipment.The most ad-vanced systems dispose of an additional head-up display showing relevant information on a two-dimensional graphical overlay directly within one of the oculars of the microscope.Our experience has shown that to take full advantage of augmented reality,more complex colour and stereoscopic displays are needed for a better understanding and interpretation of the overlaid in-formation[1].Therefore,this basic overlay will be replaced in future by more sophisticated three-dimensional displays being able to render stereoscopic views of a virtual scene.Today’s augmented reality,where the real scene’s information is enhanced with additional information, might be backed by augmented virtuality[2,3].Augmented virtuality fuses multimodal scene information acquired during planning with real-time images from the surgicalfield.To ade-2 quately merge real and virtual information for both augmented reality and virtuality we need to know surface information on the real scene.E.g.to determine which part of a virtual object would be occluded by the real scene,we need to know the surface of the surgicalfield.With the surgical microscope we dispose of the possibility to record corresponding stereo images from the right and left ocular,without expensive additional hardware.A UDETTE proposes in his work on brain deformation[4]the use of a commercial range-sensor and structured laser light to reconstruct the brain surface.S KRINJAR uses a strongly calibrated stereo rig and an integration technique to compute the surface normals from the partial derivatives of intensities in both images[5].Integration techniques accumulate errors and constrain the surface to be continuous and globally follow the Lambertian reflectance model. We also use an intensity-based method,where point correspondences are established by com-paring intensities within a defined window in the left and right image[6].This method works on surfaces which are only locally Lambertian and may contain discontinuities in the disparity. Intensity-based methods calculate dense disparity maps in opposition to feature based methods, which recover only sparse disparity maps.2.Material and Methods2.1.AcquisitionThe Department of Neurosurgery at the University Hospital of Rennes disposes of an SMN zoom lens microscope from C ARL Z EISS(Oberkochen,Germany).A localiser tracks patient, probe,and microscope position.A pair of stereoscopic single CCD cameras mounted on the microscope is used to record still colour images with an off-the-shelf video grabber card on a desktop PC.A video channel switch driven by the parallel port of the PC selects between the left and right ocular.Focus and zoom parameters as well as the tracked microscope position are transferred from the navigation system to the PC via serial port connection.A simple user interface under MS-Windows initiates grabbing of an image pair and stores it along with zoom and focus settings and the microscope position.2.2.Epipolar geometry and fundamental matrixTo reconstruct the surface from two images,point correspondences have to be established. We take advantage of the epipolar geometry to simplify the search for corresponding points [6,7].The epipolar geometry constraints points lying on an epipolar line in the left image to be projected onto the corresponding epipolar line in the right image.The fundamental matrix is a colineation that gives the correspondence between epipolar lines,and allows to establish the equation of the epipolar line in the right image corresponding to a point given in the left image.Tofind a match to a point from the left image,the search is limited to the corresponding epipolar line in the right image.The fundamental matrix is calculated from one or multiple pairs of images with the same settings for zoom and focus.To minimise numerical instability we used multiple views at the same settings by generating additional sets of images of a calibration grid. The colineation between lines in the right and left images described by the fundamental matrix has seven degrees of freedom and can be solved using least square method based on at least eight pairs of corresponding points[8].Points are extracted automatically using curvature operators and matches are automatically established using a relaxation based algorithm.3 2.3.RectificationTo simplify point comparisons the fundamental matrix is used to rectify the image pairs in the way that corresponding epipolar lines are parallel to the abscissa at the same value for the ordinate in the image coordinate system[7,9].Figure1shows the rectified image of the left ocular.2.4.Disparity mapAfter rectification for each point of the left images,a corresponding point has to be found on the epipolar with the same ordinate value.The luminance within a window of predefined size is compared using a zero-mean normalised sum of squared differences(ZNSSD)criterion:,with for the intensity at image point and4Figure1.Rectified image of the left micro-scope view.Figure2.Disparity map from ZNSSD crite-rion.Figure3.Disparity map after medianfilteringand local planefitting.Figure4.Reconstructed surface,textured-mapped with the original image.The holescorrespond to the areas where the disparitymap contains no information.5 the image pairs.Overall calculation of the disparity map performs very good.However,the matching fails on various regions and points in the images and leaves multiple holes in the disparity map.Examination of the regions which were not reconstructed shows that most of them are satu-rated in one or both of the original images due to specular reflection.Other regions which were not reconstructed are areas on the border of the surgicalfield with gauze or cloth where there is no texture to exploit for the luminance comparison.Although the brain surface is speckled with tiny vessels which give it enough texture for reconstruction there are some areas on larger gyri of uniform colour.Those areas are not recovered by the reconstruction either.4.Discussion and ConclusionWe have demonstrated that the stereoscopic reconstruction of the brain is feasible from only the two images of a stereoscopic microscope view.The main problem is the particularity of the intra-operative images of the brain surface.The microscope’s light source is parallel to the optical axes which,in conjunction with the wet brain surface,causes a large amount of specular reflection.We cannot calculate the surface by luminance comparison for pixels in these reflection areas.But the results are still satisfactory as we do not need to know the exact surface of every point.For visual application like the already mentioned occlusion problem it seems sufficient tofill the holes in the disparity map with an interpolation technique by exploiting an a priori knowledge about the surface.Such an a priori knowledge is the fact that the reconstructed surface is a single surface and relatively smooth.For other applications like distance measures for brain-shift evaluation it is preferable not to interpolate,since the accuracy of the reconstructed points is more important than the number of these points.The authors are aware of the fact that validation is of immediate concern for the further use of this method.To validate the accuracy of the reconstruction,we plan to apply the algorithm on known synthetic scene with real intra-operative images as object texture.The microscope calibration has to be recovered in order to pass from the for the moment only projective recon-struction to an euclidian reconstruction.We also have to evaluate the reconstruction of images at a higher magnification.At a higher magnification we might probably loose some texture from the vessels and have larger areas of unrecoverable uniform intensity.We consider intra-operative stereoscopic images from the surgical microscope as a sofar un-exploited additional modality in multimodal neurosurgery.We already mentioned brain-shift estimation and occlusion as possible applications.A surface reconstruction gives us also the possibility to update a scene depending on the progress of the intervention or to verify or estab-lish registration to the patient.There is also the possibility to calculate the volume of resection. Our method does not require expensive additional equipment as long as it is possible to capture intra-operative images from a surgical microscope.REFERENCES1.Pierre Jannin,Oliver J.Fleig,Eric Seigneuret,Christophe Grova,Xavier Morandi,andJean-Marie Scarabin.A data fusion environment for multimodal and multi-informational puter Aided Surgery,5:1–10,2000.6 2.Damini Dey,Piotr J.Slomka,David G.Gobbi,and Terry M.Peters.Mixed Reality Mergingof Endoscopic Images and3-D Surfaces.In Medical Image Computing and Computer-Assisted Intervention(MICCAI),volume1935of Lecture Notes in Computer Science,pages 796–803.Springer Verlag,2000.3.P.Jannin,A.Bouliou,E.Journet,and J.M.Scarabin.Ray-traced texture mapping for en-hanced virtuality in image-guided neurosurgery.In Stud Health Technol Inform,volume29, pages553–563,1996.4.M.A.Audette,K.Siddiqi,and T.M.Peter.Level-set surface segmentation and fast corticalrange image tracking for computing intrasurgical deformations.In Medical Image Com-puting and Computer-Assisted Intervention(MICCAI),volume1679of Lecture Notes in Computer Science,pages788–797.Springer Verlag,1999.5.Oskar Skrinjar,Hemant Tagare,and James Duncan.Surface growing from stereo images.In IEEE Computer Society Conference on Computer Vision and Pattern Recognition(CVPR 2000),volume II,pages571–576,Hilton Head Island,SC,USA,june2000.6.R.Klette,K Schüns,and A puter Vision:Three-Dimensional Data fromImages.Springer,1998.7.Olivier Faugeras.Three-Dimensional Computer Vision:A Geometric Viewpoint.MIT Press,Cambridge,Massachusetts,1993.8.Zhengyou Zhang,Rachid Deriche,Olivier Faugeras,and Q.T.Luong.A robust techniquefor matching two uncalibrated images through the recovery of the unknown epipolar geom-etry.Technical Report RR-2273,Inria,Institut National de Recherche en Informatique et en Automatique,1994.9.N.Ayache.Artificial Vision for Mobile Robots:Stereo Vision and Multi-sensory Percep-tion.MIT Press,Cambridge,MA,1991.10.Frédéric Devernay and puting differential properties of3-D shapesfrom stereoscopic images without3-D models.In Proceedings of the International Confer-ence on Computer Vision and Pattern Recognition,pages208–213,1994.11.Frederic Devernay and Olivier Faugeras.From projective to euclidean reconstruction.InProceedings of the International Conference on Computer Vision and Pattern Recognition, pages264–269,1996.。

1. 自由钟The Liberty Bell, located in Philadelphia, Pennsylvania, is an American bell of great historic sign ificanee. The Liberty Bell is perhaps one of the most prominent symbols associated with early A merican history and the battle for American independence and freedom. Its most famous ringing, on July 8, 1776, summoned citizens for the reading of the Declaration of Independence by the Second Continental Congress. Previously, it had been rung to announce the opening of the First Con ti nen tal Con gress, in 1774, and the Battle of Lex ington and Con cord, in 1775.The bell was not officially known as the "Liberty Bell" until 1837, when it became a symbol of the abolitionist movement. Its cast inscription from Leviticus 25:10 states, "Proclaim Liberty thro ughout all the land unto all the inhabitants thereof." The Liberty Bell is one of the most familia r symbols of in depe ndence and n ati on hood withi n the Un ited States, sec ond only to the Statue of Liberty; strangely perhaps, given its widespread use within the country, the Liberty Bell is hardl y recognized outside of the US, and far less well known as a symbol of America than either th e Statue of Liberty or the Stars and Stripes.2. 自由女神the Statue of LibertyLiberty En lighte ning the World, known more com mon ly as the Statue of Liberty, is a statue give n to the United States by France in 1885, standing at Liberty Island in the mouth of the Hudso n River in New York Harbor as a welcome to all visitors, immigra nts, and returni ng America ns.The copper statue, dedicated on October 28, 1886, commemorates the centennial of the United States and is a gesture of friendship between the two nations. The sculptor was Frederic AugusteBartholdi. Gustave Eiffel, the designer of the Eiffel Tower, engineered the internal structure. Eu g 的e Viollet-le-Duc was responsible for the choice of copper in the statue's construction and ado ption of the Repouss etechnique. The Statue of Liberty is one of the most recognizable icons ofthe U.S. worldwide,[1] and, in a more general sense, represents liberty and escape from oppress ion. The Statue of Liberty was, from 1886 until the Jet age, often the first glimpse of the Unite d States for millio ns of immigra nts after ocea n voyages from Europe. It's said that il San carl one or the Colossusof Rhodes in spired it.3. 华盛顿碑The Washi ngton MonumentThe Washington Monument usually refers to the large white-colored obelisk at the west end of t he National Mall in Washington, D.C.. It is a United States Presidential Memorial constructed fo r George Washi ngton, the first Preside nt of the Un ited States and the leader of the revoluti onaryContinental Army, which won independence from the British following the American Revolution ary War.Other monuments to honor Washington, also known as the "Washington Monument", are in Balti more and Wash ington Coun ty, Maryla nd.The monument is made of marble, granite, and sandstone. It was designed by Robert Mills, a pr ominent American architect of the 1840s. The actual construction of the monument began in 184 8 and was not completed until 1884, almost 30 years after the architect's death, due to lack of f unds and the intervention of the American Civil War. A differenee in shading of the marble (vis ible approximately 150 feet up) clearly delineates the initial construction from its resumption in 1 876. It is gen erally con sidered fortun ate that the Greek Doric rot unda Mills pla nned for the base of the monument was never built.[1]The Washi ngton Monument at duskIts corn erst one was laid on July 4, 1848; the capst one was se t on December 6, 1884, and the completed monument was dedicated on February 21, 1885. It of ficially opened to the public on October 9, 1888. Upon completion, it became the world's tallest structure at 169 m, a title it inherited from the Cologne Cathedral and held until 1889, when th e Eiffel Tower was finished in Paris, France.The Washi ngton Monument reflect ion can be see n in the aptly n amed Reflect ing Pool, a recta ngu lar pool exte nding westward in the direct ion of the Li neol n Memorial.4大峡谷The Grand CanyonThe Grand Canyon is a very colorful, steep-sided gorge, carved by the Colorado River, in northe rn Arizona, USA. It is largely contained within the Grand Canyon National Park —one of the f irst n ati onal parks in the Un ited States. Preside nt Theodore Roosevelt was a major prop onent of the Grand Canyon area, visiting on numerous occasions to hunt mountain lions and enjoy the sce n ery.The canyon, created by the Colorado River cutting a channel over millions of years, is about 27 7 miles (446 km) long, ranges in width from 0.25 to 15 miles (0.4 to 24 kilometers) and attains a depth of more than a mile (1,600 m). Nearly two billion years of the Earth's history has bee n exposed as the Colorado River and its tributaries cut through layer after layer of sediment as t he Colorado Plateaus have uplifted.The first recorded sighting of the Grand Canyon by a European was in 1540, Garca L opez de Cardenas from Spain.[citation needed] The first scientific expedition to the canyon was led by U. S. Major John Wesley Powell in the late 1860s. Powell referred to the sedimentary rock units ex posed in the canyonas "leaves in a great story book." Long before that, the area was in habited by Native America ns who built settleme nts within the canyon walls.5、华尔街Wall Street is the name of a narrow street in lower Manhattan in New York City, running east from Broadway downhill to the East River. Considered to be the historical heart of the FinancialDistrict, it was the first permanent home of the New York Stock Exchange (纽约证券交易所)The phrase "Wall Street" is also used as a metonym (换喻词) to refer to American financial m arkets and finan cial in stituti ons as a whole. Most New York finan cial firms are no Ion ger headqu artered on Wall Street, but elsewhere in lower or midtown Manhattan, Fairfield County, Connecti cut, or New Jersey. JPMorgan Chase, the last major holdout, sold its headquarters tower at 60 Wall Street to Deutsche Bank in November 2001.6、自由女神Statue of LibertyLiberty En lighte ning the World, known more com mon ly as the Statue of Liberty, is a statue give n to the United States by France in 1885, standing at Liberty Island in the mouth of the Hudso n River in New York Harbor as a welcome to all visitors, immigra nts, and returni ng America ns.The copper statue, dedicated on October 28, 1886, commemorates the centennial of the United States and is a gesture of friendship between the two nations. The sculptor was Frederic AugusteBartholdi. Gustave Eiffel, the designer of the Eiffel Tower, engineered the internal structure. Eu g die Viollet-le-Duc was responsible for the choice of copper in the statue's construction and ado ption of the Repousse technique. The Statue of Liberty is one of the most recognizable icons of the U.S. worldwide, and, in a more general sense, represents liberty and escape from oppression. The Statue of Liberty was, from 1886 until the Jet age, often the first glimpse of the United S tates for millio ns of immigra nts after ocea n voyages from Europe. It's said that il San carl one or the Colossus of Rhodes in spired it.7、第五大道The Fifth Avenue is a major thoroughfare in the center of the borough of Manhattan in New Y ork City, USA. It runs through the heart of Midtown and along the eastern side of Central Park, and because of the expensive park-view real estate and historical mansions along its course, it i s a symbol of wealthy New York. It is one of the best shopping streets in the world, often pair ed with London's Oxford Street and the Champs Elys aes in Paris. It is one of the most expensiv e streets in the world, on a par with London and Tokyo lease prices. The "most expensive street in the world" moniker changes depending on currency fluctuations and local economic condition s from year to year. Joseph Winston Herbert Hopkins founded this street. It is the dividing line for the east-west streets in Manhattan, (for example, demarcating the line separating East 59th St reet from West 59th Street) as well as the zero-numbering point for street addresses(numbers in crease in both directions as one moves away from Fifth, with 1 East 59th Street on the corner a t Fifth Avenue, and 300 East 59th Street located several blocks to the East). Fifth Avenue is a one-way street and carries southbound ("downtown") traffic. Some people refer to Fifth Avenue c olloquially as "Fashion Ave," but many refrain from it to avoid confusion with the real Fashion Ave, also known as Seventh Avenue. Fifth Avenue extends from the north side of Washington S quare Park through Greenwich Village, Midtown, and the Upper East Side&白宫Formerly known as the Executive Mansion (1810- 1902) the official office and reside nee of the preside nt of the Uni ted States at 1600 Penn sylva nia Ave nue N.W. in Washi ngton, D.C. The Whit e House and its Ian dscaped grounds occupy 18 acres (7.2 hectares). Since the admi ni strati on of George Washington(1789 - 97), who occupied presidential residences in New York and Philadelp hia, every America n preside nt has resided at the White House. Origi nally called the “ Preside nt's Palace" on early maps, the building was officially named the Executive Mansion in 1810 in ord er to avoid conno tatio ns of royalty. Although the n ame “ White House” was com mon ly used fr om about the same time (because the mansion's white-gray sandstone contrasted strikingly with th e red brick of n earby build in gs), it did not become the official n ame of the build ing un til 1902, whe n it was adopted by Preside nt Theodore Roosevelt (1901 - 09). The White House is the old est federal building in the nation's capital.9、尼加拉瓜大瀑布Niagara Falls in the Niagara River, W N.Y. and S Ont., Canada; one of the most famous specta cles in North America. The falls are on the intern ati on al li ne betwee n the cities of Niagara Falls,N.Y., and Niagara Falls, Ont. Goat Island splits the cataract into the American Falls (167 ft/51 m high and 1,060 ft/323 m wide) and the Horseshoe, or Canadian, Falls (158 ft/48 m high and 2,600 ft/792 m wide). The governments of the United States and Canada control the appearanee of the surrounding area, much of which has been included in parks since 1885.The earliest written description of the falls is that of Louis Hennepin (in Nouvelle D a couverte, 1 697), who was with the expedition of Robert Cavelier, sieur de La Salle, the French explorer, in 1678. In the 19th cent., daredevils attempted to brave the falls in barrels, boats, and rubber ball s. The great Blondin performed (1859) on a tightrope over the falls, which continue to be a maj or center of international tourism. Historical and natural history material relating to the region is in the Niagara Falls Museum in the city of Niagara Falls, N.Y.10、巴拿马运河Panama Canal waterway across the Isthmus of Panama, connecting the Atlantic (by way of the Caribbean Sea) and Pacific oceans, built by the United States (1904-14) on territory leased from the republic of Pan ama . The can al, running S and SE from Lim d n Bay at Col d n on the Atla nti c to the Bay of Panama at Balboa on the Pacific, is 40 mi (64 km) long from shore to shore a nd 51 mi (82 km) long between channel entrances. The Pacific terminus is 27 mi (43 km) east of the Caribbean terminus. The minimum depth is 41 ft (12.5 m).From Lim d n Bay a ship is raised by Gat tn Locks (a set of three) to an elevation 85 ft (25.9 m) above sea level, traverses Gat tn Lake, then crosses the Continental Divide through Gaillard (for merly Culebra) Cut and is lowered by Pedro Miguel Lock to Miraflores Lake and then by theMiraflores Locks （a set of two） to sea level. The average tidal range on the Atlantic side is less than a foot （.3 m）; that on the Pacific side is 12.6 ft （3.8 m）.11、黄石公园The Yellowst one Park Foun dati on is a 501（c）3, non -profit orga ni zati on created in 1996. A group of concerned citizens, working with the National Park Service, started the Foundation in order to protect,preserve, and enhance Yellowstone National Park.The Foundation works to fund important projects and programs, many of which are beyond the f inancial capacity of the National Park Service. The Foundation receives no annual government fu nding; it relies in stead upon the gen erous support of private citize ns, foun dati ons, and corporati on s to ensure that Yellowstone's great gifts to the world will never diminish.Since its inception, the Yellowstone Park Foundation has successfully funded more than 100 proj ects in Yellowst one.12、帝国大厦New York, the Empire State Building was built in March 1930, then use the lightest constructio n materials, built in the West during the economic crisis has become a symbol of U.S. economic recovery, now still and the Statue of Liberty in New York to become a permanent mark. Has world's first high-Building and the New York City Iandmark building.Empire State Buildi ng is a modern high-rise office build in gs, and the Statue of Liberty in New York as a sign. Construction on the 381-metre-high Empire State Building, since 1931, the top world's tallest building, the throne for 40 years. This building in the United States the most econ omically depressed,the most sluggish, with only less than 2 years to build. 102 House and 86 i n a floor observatory, is due to open Taiwan's Wang, the wind power is considerable. Sunny da ys when the Yuanwang to be 100 kilometers away.13、夏威夷For most of us, Hawaii begins to weave her spell （魅力）with some little glimmer （微光）of a ware ness. Golde n beaches and golde n people. Sun, sand, sea, and surf ............... A nd somewhere between the blue skies and the palm trees （棕榈树）.... we're hooked （吸引）The Hawaiian Islands are one of the most beautiful places on earth. The weather is friendly.The temperature ranges from 60-90 degrees all year long. It's a little warmer in summer, and a little cooler in win ter, but every day is a beach day for somebody.There are no strangers in Paradise. Perhaps the most beautiful part of Hawaii is the genuine war mth of people. We call it the spirit of Aloha. It has allowed a melting pot of cultures from all over the world to find com mon ground （共同点）,and a new home, in this most gen tle of plac es.14、百老汇Broadway theatre is the most prestigious form of professional theatre in the United States, as we II as the most well known to the general public and most lucrative for the performers, technician s and others invoIved in putting on the shows.Broadway theatre, or a Broadway show, refers to a performanee, usually a play or musical that appeals to a mass audienee, presented in one of the thirty-nine large professional theatres with 5 00 seats or more located in the Theatre District of the New York City borough of Manhattan. T he shows that reach Broadway and thrive there have historically been perceived as more mainstre am and less cutting edge than those produced Off- and Off-Off-Broadway or in regional non-prof it theatres such as the GuthrieTheatre in Minneapolis and the American Repertory Theatre in Ca mbridge, Massachusetts.。

Proceedings of the 2007 Industrial Engineering Research ConferenceG. Bayraksan, W. Lin, Y. Son, and R. Wysk, eds.Periodic Loci Surface Reconstruction in Nano Material DesignYan WangDepartment of Industrial Engineering and Management SystemsUniversity of Central FloridaOrlando, FL 32816, USAAbstractRecently we proposed a periodic surface (PS) model for computer aided nano design (CAND). This implicit surface model allows for parametric model construction at atomic, molecular, and meso scales. In this paper, loci surface reconstruction is studied based on a generalized PS model. An incremental searching algorithm is developed to reconstruct PS models from crystals. Two metrics to measure the quality of reconstructed loci surfaces are proposed and an optimization method is developed to avoid overfitting.KeywordsPeriodic surface, implicit surface, computer-aided nano-design, reverse engineering1. IntroductionComputer-aided nano-design (CAND) is an extension of computer based engineering design traditionally at bulk scales to nano scales. Enabling efficient structural description is one of the key research issues in CAND. Traditional boundary-based parametric solid modeling methods do not construct nano-scale geometries efficiently due to some special characteristics at the low levels. For example, the boundaries of atoms and molecules are vague and indistinguishable. Volume packing of atoms is the major theme in crystal or protein structures, which have much more complex topology than macro-scale structures. Non-deterministic geometries and topologies are the manifestations of thermodynamic and kinetic properties at the molecular scale.With the observation that hyperbolic surfaces exist in nature ubiquitously and periodic features are common in condensed materials, we recently proposed an implicit surface modeling approach, periodic surface (PS) model [1, 2], to represent the geometric structures in nano scales. This model enables rapid construction of crystal and molecular models. At the molecular scale, periodicity of the model allows thousands of particles to be built efficiently. At the meso scale, inherent porosity of the model is able to characterize morphologies of polymer and macromolecules. Some seemingly complex shapes are easy to build with the PS model.Periodic surfaces are either loci (in which discrete particles are embedded) or foci (by which discrete particles are enclosed). In this paper, we study loci surface reconstruction for reverse engineering purpose. The PS model is generalized with geometric and polynomial description. An incremental searching algorithm is developed to reconstruct loci surfaces from crystals. In the rest of the paper, Section 2 reviews related work. Section 3 describes the generalized PS model. Section 4 presents an incremental searching algorithm, illustrates with several examples, and proposes evaluation metrics for the quality of reconstructed surfaces.2. Background and Related Work2.1 Molecular Surface ModelingTo visualize 3D molecular structures, there has been some research work on molecular surface modeling [3]. Lee and Richards [4] first introduced solvent-accessible surface, the locus of a probe rolling over Van der Waals surface, to represent boundary of molecules. Connolly [5] presented an analytical method to calculate the surface. Recently, Bajaj et al. [6] represent solvent accessible surface by NURBS (non-uniform rational B-spline). Carson [7] represents molecular surface with B-spline wavelet. These research efforts concentrate on boundary representation of molecules mainly for visualization, while model construction itself is not considered.2.2 Periodic SurfaceWe recently proposed a periodic surface (PS) model to represent nano-scale geometries. It has the implicit formC p Ak k k k k =+⋅=∑]2cos[)(λπψ)(r h r (1)where r is the location vector in Euclidean space 3E , k h is the k th lattice vector in reciprocal space, k A is the magnitude factor, k λ is the wavelength of periods, k p is the phase shift, and C is a constant. Specific periodicstructures can be modeled based on this generic form. The periodic surface model can approximate triply periodic minimal surfaces (TPMSs) very well, which have been reported from atomic to meso scales. Compared to the parametric TPMS representation known as Weierstrass formula, the PS model has a much simpler form.Figure 1 lists some examples of PS models, including TPMS structures, such as P-, D-, G-, and I-WP cubic morphologies which are frequently referred to in chemistry literature. Besides the cubic phase, other mesophase Mesh MembraneFigure 1: Periodic surface models of cubic phase and mesophase structures 3. Generalized Periodic Surface ModelIn this paper, periodic surface model is generalized with geometric and polynomial descriptions. This generalization allows us to interpret control parameters geometrically and manipulate surfaces interactively. A periodic surface is defined as()0)(2cos )(11=⋅=∑∑==L l M m T m l lm r p r πκµψ (2) where l κ is the scale parameter , T m m m m m c b a ],,,[θ=p is a basis vector , such as one of{}⎪⎪⎪⎭⎪⎪⎪⎬⎫⎪⎪⎪⎩⎪⎪⎪⎨⎧⎥⎥⎥⎥⎥⎦⎤⎢⎢⎢⎢⎢⎣⎡−⎥⎥⎥⎥⎥⎦⎤⎢⎢⎢⎢⎢⎣⎡−⎥⎥⎥⎥⎥⎦⎤⎢⎢⎢⎢⎢⎣⎡−⎥⎥⎥⎥⎥⎦⎤⎢⎢⎢⎢⎢⎣⎡−⎥⎥⎥⎥⎥⎦⎤⎢⎢⎢⎢⎢⎣⎡−⎥⎥⎥⎥⎥⎦⎤⎢⎢⎢⎢⎢⎣⎡−⎥⎥⎥⎥⎥⎦⎤⎢⎢⎢⎢⎢⎣⎡⎥⎥⎥⎥⎥⎦⎤⎢⎢⎢⎢⎢⎣⎡⎥⎥⎥⎥⎥⎦⎤⎢⎢⎢⎢⎢⎣⎡⎥⎥⎥⎥⎥⎦⎤⎢⎢⎢⎢⎢⎣⎡⎥⎥⎥⎥⎥⎦⎤⎢⎢⎢⎢⎢⎣⎡⎥⎥⎥⎥⎥⎦⎤⎢⎢⎢⎢⎢⎣⎡⎥⎥⎥⎥⎥⎦⎤⎢⎢⎢⎢⎢⎣⎡⎥⎥⎥⎥⎥⎦⎤⎢⎢⎢⎢⎢⎣⎡=……11111111111111101101101111111110110110111100101010011000,,,,,,,,,,,,,,131211109876543210e e e e e e e e e e e e e e (3)which represents a basis plane in the projective 3-space 3P , T w z y x ],,,[=r is the location vector with homogeneous coordinates, and lm µis the periodic moment . We assume 1=w throughout this paper if not explicitly specified. It is also assumed that the scale parameters are natural numbers (N ∈l κ).If mapped to a density space T M s s ],,[1…=s where ))(2cos(r p ⋅=T m m s π, )(s ψcan be represented in a polynomial form, known as Chebyshev polynomial,)1()()(11≤=∑∑==m L l M m m lm s s T l κµψs (4)where ()s s T 1cos cos )(−=κκ. In a Hilbert space, the basis functions κT ’s are orthogonal with respect to density in the normalized domain, with the inner product defined as⎪⎪⎩⎪⎪⎨⎧≠===≠=−=∫−)0(2/)0()(0)()(11:,112j i j i j i ds s T s s T T j i j i ππ (5) where both i and j are natural integers (N ∈j i ,). Orthonormal bases are particularly helpful in surface reconstruction. The periodic moments are determined by the projection)0()()(112,,112≠−==∫−j ds s T s f s T T T f j j j jj πµ (6)Lemma 1. If a periodic surface )(r ψ is scaled up or down to )('r ψ, and there are no common basis vectors at the same scales between the two, then )(r ψ is orthogonal to )('r ψ.4. Loci Surface Reconstruction3D crystal or protein structures are usually inferred by using experimental techniques such as X-ray crystallography and archived in structure databases. Given actual crystal structures, loci surfaces can be reconstructed. This reverse engineering process is valuable in nano material design. It can be widely applied in material re-engineering and re-design, comparison and analysis of unknown structures, and improving interoperability of different models. In general, the loci surface reconstruction process is to find a periodic surface )(r ψ to approximate the original but unknown surface )(r f , assuming there always exists a continuous surface )(r f that passes through a finite number of discrete locations in 3E . Determining the periodic moments from the given locations is the main theme.4.1 Incremental Searching AlgorithmIn the case of sparse location data, spectral analysis is helpful to derive periodic moments. Given N known positions ),,1(3N n n …=∈P r through which a loci surface passes, loci surface reconstruction is to find a 0)(=r ψ such that the sum of Lp norms is minimized in∑=N n p n1)(min r ψ (7)Given a set of scale parameters ),,1(L l l …=κ and a set of basis vectors ),,1(M m m …=p , deriving the moments can be reduced to solving the linear system()()N n L l M m lm n T m l ,,10)(2cos 11…==⋅∑∑==µπκr p (8) or simply denoted as 01=××LM LM N µA(9) Solving (9) is to find the null space of A . The singular value decomposition (SVD) method can be applied. If the decomposed matrix is T LMLM k LM LM j LM N i v w u ×××=][][][A , any column of ][k v whose corresponding j w is zero yields a solution. With the consideration of experimental or numerical errors, least-square approximation is usually used in actual algorithm implementation. We select the last column of ][k v as the approximated solution.In general cases, the periodic vectors and scale parameters may be unknown, an incremental searching algorithm is developed to find moments as well as periodic vectors and scale parameters, as shown in Figure 2. We can use a general set of periodic vectors such as the one in (3) and incrementally reduce the scales (i.e., increase scale parameters). The searching process continues until the maximum approximation error )(max n nr ψ is less than a threshold.In the Hilbert space, the orthogonality of periodic basis functions allows for concise representation in reconstruction. In the incremental searching, the newly created small scale information in iteration t is an approximation of the difference between the original surface )(r f and the previously constructed surface )()1(r −t ψ in iteration 1−t .Input : location vectors ),,1(N n n …=rOutput : periodic moments }{lm µ, scale parameters }{l κ, and periodic vectors }{m p1. Normalize coordinates n r if necessary (e.g. limit them within the range of [0,1]);2. Set an error threshold ε;3. Initialize periodic vectors }{}{0)0(e p =m , initialize scale parameter }1{}{)0(=l κ, t =1;4. Update the periodic vectors },,{}{}{1)1()(M t m t m e e p p …∪=−, update the scale parameters with anew scale t s so that }{}{}{)1()(t t l t l s ∪=−κκ;5. Decompose matrix ()[]T n T m l t UWV r p A =⋅=)(2cos )(πκ and find )(t µ as the last column of V ; 6. If ε<⋅)()(max t t nµA , stop; otherwise, t =t +1, go to Step 4 and repeat.Figure 2: Incremental searching algorithm for loci surface reconstructionLemma 2. If the original surface )(r f is dtimes continuously differentiable, the convergence rate of the incremental searching algorithm is )(d O −κ where κ is the scale parameter.4.2 ExamplesAs the first example, we reconstruct the periodic surface model of a Faujasite crystal. As shown in Figure 3-a, each vertex in the polygon model represents a Si atom of the crystal. Within a periodic unit, we apply the incremental searching algorithm to it. With different stopping criteria, we have two surfaces with 14 and 15 vectors, as shown in Figure 3-b and Figure 3-c respectively. The reconstructed surfaces are listed in Table 1.(a) Faujasite crystal (b) Reconstructed surfacedim.=14, max_error=0.6691 (c) Reconstructed surface dim.=15, max_error= 1.686e-15 Figure 3: Loci surfaces of a Faujasite crystal with 232 atomsTable 1: PS models of the Faujasite crystal in Figure 3 with different dimensionsDimension PS model14 ))(2cos(414070))(2cos(414070))(2cos(414070))(2cos(440820))(2cos(0119920))(2cos(0119920))(2cos(0119920))(2cos(00394820))(2cos(00394820))(2cos(00394820)2cos(00859260)2cos(00859260)2cos(0085926053909.0z y x .x z y .z y x .z y x .z y .x z .y x .z y .z x .y x .z .y .x .−++−+++−+++−−−−−−−+−+−+−−−−−πππππππππππππ15 ))(4cos(0720760))(4cos(0720760))(4cos(0720760))(4cos(0720760))(4cos(103620))(4cos(103620))(4cos(103620))(4cos(103620))(4cos(103620))(4cos(103620))(2cos(402460))(2cos(402460))(2cos(402460))(2cos(402460516620z y x .x z y .z y x .z y x .z y .x z .y x .z y .z x .y x .z y x .x z y .z y x .z y x ..−++−+++−++++−+−+−++−+−+−−+−−+−+−−+++ππππππππππππππThe second example includes surface models of a synthetic Zeolite crystal, as in Figure 4-a. Each vertex represents an O atom. Three surfaces with different numbers of vectors thus different resolutions are shown in Figure 4-b, -c, and -d. The PS models are listed in Table 2.(a) Zeolite crystal (b) Reconstructed surfacedim.=14, max_error=0.2515 (c) Reconstructed surface dim.=24, max_error=0.0092(d) Reconstructed surface dim.=33, max_error=3.059e-15 Figure 4: Loci surfaces of a synthetic Zeolite crystal with 312 atomsTable 2: PS models of the synthetic Zeolite crystal in Figure 4 with different dimensions DimensionPS model 14 ))(2cos(432910))(2cos(432910))(2cos(432910))(2cos(432910))(2cos(001388.0))(2cos(001388.0))(2cos(001388.0))(2cos(001388.0))(2cos(001388.0))(2cos(001388.0)2cos(288870)2cos(288870)2cos(2888700037436.0z y x .x z y .z y x .z y x .z y x z y x z y z x y x z .y .x .−+−−+−+−−++−−+−+−+++++++−−−−πππππππππππππ24 ))(4cos(15927.0))(4cos(15927.0))(4cos(15927.0))(4cos(15927.0))(4cos(24617.0))(4cos(24617.0))(4cos(24617.0))(4cos(24617.0))(4cos(24617.0))(4cos(24617.0)4cos(32147.0)4cos(32147.0)4cos(32147.0))(2cos(000718640))(2cos(000718640))(2cos(000718640))(2cos(000718640))(2cos(18191.0))(2cos(18191.0))(2cos(18191.0))(2cos(18191.0))(2cos(18191.0))(2cos(18191.016232.0z y x x z y z y x z y x z y x z y x z y z x y x z y x z y x .x z y .z y x .z y x .z y x z y x z y z x y x −+−−+−+−−++−−−−−−−+−+−+−−−−−++−+++−++++−+−+−+++++++−πππππππππππππππππππππππ33 ))(8cos(0091814.0))(8cos(0091814.0))(8cos(0091814.0))(8cos(0091814.0))(8cos(081757.0))(8cos(081757.0))(8cos(081757.0))(8cos(081757.0))(8cos(081757.0))(8cos(081757.0)8cos(11405.0)8cos(11405.0)8cos(11405.0))(4cos(020038.0))(4cos(020038.0))(4cos(020038.0))(4cos(020038.0))(4cos(098288.0))(4cos(098288.0))(4cos(098288.0))(4cos(098288.0))(4cos(098288.0))(4cos(098288.0)4cos(086043.0)4cos(086043.0)4cos(086043.0))(2cos(37384.0))(2cos(37384.0))(2cos(37384.0))(2cos(37384.0))(2cos(37384.0))(2cos(37384.001531.0z y x x z y z y x z y x z y x z y x z y z x y x z y x z y x x z y z y x z y x z y x z y x z y z x y x z y x z y x z y x z y z x y x −++−+++−++++−−−−−−+−+−+−−−−−+−−+−+−−++−−−−−−−+−+−+−−−−−+−+−+++++++ππππππππππππππππππππππππππππππππ4.3 Quality of SurfaceThe maximum approximation error used in the incremental searching algorithm is not the only metric to measure the quality of reconstructed surfaces. It should be recognized that the maximum approximation error may cause overfitting during the least square error reconstruction. Thus, another proposed metric to measure the quality of loci surfaces is porosity , which is defined as())(/)(:32P D D D ⊆=∫∫∫∫∫∫∈∈r r r r r d d M ψψφ (11) where )(max r r ψψD ∈∀=M . The porosities of reconstructed surfaces in Figure 3 and Figure 4 are listed in Table 3. Givena fixed number of known positions that surfaces pass through, there are an infinite number of surfaces can be reconstructed. Intuitively, the surfaces with unnecessarily high surface areas have low porosities, which should be avoided.Table 3: Metrics comparison of different PS surfacesDimension Maximum approximation errorPorosity14 0.6691 0.2115Faujasite surface (Figure 3) 15 1.686e-15 0.122614 0.2515 0.0073824 0.0092 0.0394Zeolite surface (Figure 4) 33 3.059e-15 0.0829The quality of reconstructed surfaces depends on the selection of periodic vectors, scale parameters, and volumetric domain of periodic unit. Based on porosity, a surface optimization problem is to solve()),,1()(max ..},{},{max N n t s n n l m …=≤εψκφr p D(12)We apply (12) to optimize basis vectors ),,(m m m c b a of the PS model of Zeolite crystal in Figure 4. The result is shown in Figure 5 and Table 4. The dimension is reduced from 33 to 25 while porosity is increased to 0.1140 with a similar maximum approximation error.Figure 5: Optimized Zeolite surfaceTable 4: Optimized PS model of the synthetic Zeolite crystal in Figure 5Optimized PS model Dimension = 25Porosity = 0.1140Max Approx. Error= 2.1417e-15 ))(8cos(1013.0))(8cos(1013.0))(8cos(1013.0))(8cos(1013.0))(8cos(1013.0))(8cos(1013.0)8cos(13904.0)8cos(13904.0)8cos(13904.0))(4cos(072615.0))(4cos(072615.0))(4cos(072615.0))(4cos(072615.0))(4cos(072615.0))(4cos(072615.0)4cos(036561.0)4cos(036561.0)4cos(036561.0))(2cos(37489.0))(2cos(37489.0))(2cos(37489.0))(2cos(37489.0))(2cos(37489.0))(2cos(37489.0038986.0z y x z y x z y z x y x z y x z y x z y x z y z x y x z y x z y x z y x z y z x y x −+−+−++++++++++−+−+−++++++++++−−−−−−+−+−+−−ππππππππππππππππππππππππ6. Concluding RemarksIn this paper, loci surface reconstruction is studied based on the generalized periodic surface model. An incremental searching algorithm is developed to reconstruct loci surfaces from crystals. To avoid overfitting, metrics of surface quality are proposed and an optimization method is developed. Future research will include reconstruction of foci surfaces.AcknowledgementThis work is supported in part by the NSF CAREER Award CMMI-0645070.References1. Wang, Y., 2006, “Geometric modeling of nano structures with periodic surfaces,” Lecture Notes inComputer Science, 4077, 343-3562. Wang, Y., 2007, “Periodic surface modeling for computer aided nano design,” Computer-Aided Design,39(3), 179-1893. Connolly, M.L., 1996, “Molecular surfaces: A review, Network Science,”/Science/Compchem/index.html4. Lee, B., Richards, F.M., 1971, “The interpretation of protein structures: Estimation of static accessibility,”Journal of Molecular Biology, 55(3), 379-4005. Connolly, M.L., 1983, “Solve-accessible surfaces of proteins and nucleic acids,” Science, 221(4612), 709-7136. Bajaj, C., Pascucci, V., Shamir, A., Holt, R., Netravali, A., 2003, “Dynamic Maintenance and visualizationof molecular surfaces,” Discrete Applied Mathematics, 127(1), 23-517. Carson, M, 1996, “Wavelets and molecular structure,” Journal of Computer Aided Molecular Design, 10(4),273-283。

Surface Treatment(Contributed by The ChemQuest Group)IntroductionFor effective bonding, the adhesive must completely wet the surface of each substrate being joined together. In addition, strong attractive interactions must form between the adhesive and the substrates. To satisfy these conditions, the surface of the substrate must be clean, reasonably smooth, and chemically receptive to the chosen adhesive. Surface treatment is the process whereby the adherend surface is cleaned and/or chemically treated to promote better adhesion.To a large extent the surface treatment determines how well and for how long a bond will hold, Figure 1. If the chosen adhesive can withstand the service conditions to which the bond will be subjected, then the life and service expectancy of that bond will be directly proportional to the degree of surface treatmentFigure 1. The effect of surface treatment on overlap shear strength (epoxy adhesive).Since surface treatment adds another step (and additional expense) to the bonding process there is a tendency to reduce or even eliminate it all together. However, in general, the level of surface treatment used should be the minimum amount that gives a reproducible bonded part having the desired level of performance.Surface treatment promotes adhesion by making it possible for the adhesive to wet the actual surface of the substrate, rather than its apparent surface. In many cases, what appears to be the surface is, in reality, a layer of grease, dirt, oil, or some other contaminant, Figure 2. The method used to prepare such surfaces for adequate wetting willdepend on the type of contaminant and the nature of the adherend.1. Surface contamination (dust, oil,grease, …)2. Absorbed film (moisture)3. Oxide layer, e.g. rust on steel4. Actual metal,e.g. steel, aluminiumFigure 2. Typical surface layers on a metal substrate.As a general rule the adhesive should be applied immediately after the surface treatment. If this is not possible the treated surface should be protected, for example by covering with kraft paper. Avoid putting finger prints on the newly prepared surface. If the substrate is left for more than a day before applying the adhesive it may be necessary to repeat the surface treatment.Metal SurfacesContaminants that create bonding problems on metal surfaces include grease, dust, dirt, oil and oxide caused by air corrosion. Grease and oil not only interfere with bonding, but also make certain types of preparation operations, such as chemical surface modification ineffective.Whether a metal adherend requires solvent cleaning, abrasive blasting, priming, or a combination of preparation methods depends upon how strong and durable the bond must be.Wood SurfacesCommon wood contaminants include resin and wax. Wood also contains absorbed moisture that can lead to large dimensional changes. Before bonding, wood should be dried to the level of moisture content appropriate to its service use when bonded. Surface contamination should be sanded, planed, or machined away. Debris from such mechanical cleaning operations can be removed by compressed air, vacuuming or brushing, or it can be wiped away with a solvent moistened cloth.Plastic SurfacesPlastic surfaces are subject to many of the same sorts of contamination as wood and metal. In addition, components in the plastic may migrate to the surface. The basic methods of surface treatment involve solvent cleaning, abrasion and chemical surface modification. Surface modification, by chemical or physical methods is particularly important in the case of low surface energy plastics. The introduction of polar groups at the surface dramatically improves adhesion to these surfaces.Classification of Surface TreatmentFigure 3. Possible steps involved in surface treatment.Surface treatment may involve one or all of the following (Figure 3):Surface Preparation – the removal of oil, grease and other surface contaminants, i.e. cleaning.Surface Pretreatment – the use of mechanical, chemical or physical methods to remove strongly absorbed surface layers and activate the surface.Surface Post-treatment – the application of adhesion promoters or primers to improve adhesion to the adhesive and/or protect the surface.Surface PreparationSurface preparation encompasses two main types of cleaning: a) detergent, b) solvent. The choice of cleaning method used will depend upon the type of substrate (metallic ornonmetallic) and the extent and nature of contamination. In some instances, it may suffice to merely dust or blow away loose dirt. In other cases, it may be necessary to remove all foreign material from the adherend surface.Detergent CleaningDetergent, soaps, and caustic soda are the least expensive andeasiest cleaning agents to handle. Applied by spraying, scrubbing, or immersing the part in an ultrasonically agitated solution, these cleaners can remove certain kinds of dirt and oil reasonably well. However, such cleaning agents may react with certain metals. After detergent cleaning it is necessary to rinse thoroughly with water and dry.Solvent CleaningFigure 4 summarizes the ability of different solvent types at removing the most common surface contaminants.Figure 4. Cleaning and degreasing with solvents.Solvent cleaning can be accomplished by wiping with a solvent-moistened cloth (or lint-free tissue), immersion in the solvent, or by exposure to the solvent vapor.A ketone, such as methyl ethyl ketone, is generally a good solvent for cleaning metals, but it can be too aggressive for many plastics. An alcohol, such as isopropyl alcohol, is a better choice of solvent for use with plastic substrates.Solvent cleaning should precede any chemical or abrasive surface pretreatment. Abrading a surface coated with oil, grease, or a release agent will serve only to drive the contaminants further into the substrate making it even more adhesion resistant. Further, grease and oil prevent the acid etch solution from reaching the adherend surface.Surface PretreatmentFollowing the preliminary surface preparation it may be necessary to pretreat the surface using one of variety of mechanical, chemical, or physical methods.Mechanical MethodsMechanical methods involve the use of handheld sandpaper orhand cleaning tools like wire brushes and scrapers. Suchinstruments are convenient to remove rust, scale, paint, andweld splatter. But they are too slow to use on large areas.One drawback of the abrasion process is that it causes particlesof debris to accumulate on the abraded surface. These particlescome from the abrasive, the surface contaminants, and thesurface material itself. All such particles must be removed beforeadhesive is applied. This may be accomplished with a cleancloth or brush, or with filtered compressed air.After the abrasion debris has been removed, it is usual to give another solvent clean before bonding. A solvent-moistened cloth is convenient for this, but as the cloth will become contaminated during this operation, it should be renewed frequently.Mechanical cleaning also includes a number of much faster abrading methods such as sandblasting, tumbling, and abrading with power tools.Chemical MethodsIn chemical treatments that alter the surface of the adherend, the part is dipped into a chemically active solution. This solution either dissolves part of the surface or transforms it, making it more chemically active and thus more receptive to adhesive bonding.Acid etching involves immersing a metal substrate in an aqueous acid solution to remove a loose layer of oxide from its surface. The particular acid used depends upon the metal and type of oxide being treated. In many cases acid etching may provide enough surface preparation for bonding - depending, of course, upon the degree of adhesion desired. Acid etching can also be effectively used with certain plastics, for example chromic acid is used to treat polyolefins.Anodization involves the electrochemical modification of the surface. The process deposits a porous and stable oxide layer on top of the oxide layer formed after etching of the substrate.Physical MethodsThese are t echniques where the surface is cleaned and chemically modified by exposure to highly energetic charges or other ionic species. The most common methods are flame treatment, corona discharge and plasma. These pre-treatment methods have been applied to metals and, in particular, composites and plastics.Flame treatment of the substrate surface for just a few seconds withan oxygen-containing (blue) propane or acetylene gas flame leads tothe incorporation of oxygen-containing groups at the surface. Thisimproves the wetting properties and hence the adhesion. Flametreatment is used almost exclusively for polyethylene andpolypropylene substrates. The effect of the pretreatment subsideswithin a short time so that flame-treated substrates must be bondedimmediately.A corona discharge is essentially a plasma generated in air at atmospheric pressure by applying a highfrequency and highvoltage between twoelectrodes. It contains anumber of energeticspecies that can cleanand introduce polargroups, mostlyoxidation products, atthe substrate surface.The corona dischargemay also lead to crosslinking of the polymer surface. The pretreatment effects are short lived so bonding should be carried out immediately. It is used mainly for polyolefin films and is capable of high processing speeds.A plasma is usually generated in a low pressure chamber and so is best suited to batchprocessing. Commercial units of various sizes are available. Theadvantage of this method is that it allows treatment of substratesby plasmas of gasses other than oxygen, for example argon,ammonia, or nitrogen. Plasmas created from inert gases aregenerally used to clean substrate surfaces.Surface Post-TreatmentIt may be necessary to further treat the substrate surface following surface pretreatment by theapplication of a primer or adhesion promoter. These are materials that are adsorbed strongly onto the substrate surface and that also interact strongly with the adhesive. A primer or adhesionpromoter is applied to achieve one or more of the following:Modify the surface energy of the substrate.Promote chemical reaction between adhesive and substrate.Activate the adhesive.Inhibit corrosion of the substrate.Protect the surface after pretreatment.Organo-functional silanes, for example 3-aminopropyl trimethoxysilane, are widely used to improve adhesion. The silane substituent at one end reacts with hydroxyl groups on the surface to give a polysiloxane polymeric layer. The organic substituent on the other end reacts with the adhesive providing a covalent link.Proprietary Surface TreatmentsIn recent years a number of proprietary surface treatments have been introduced that combine both physical and chemical treatments.Silicoater TM This method has been mainly used with dental alloys, to improve adhesion to other materials. The sandblasted alloy is passed through an oxidizing flame into which a solution of tetraethoxysilane is injected. This results in a layer of silica embedded in the surface of the alloy. After cooling the surface is then treated with a solution of anorganosilane coupling agent. The functionalized alloy surface is ready for adhesive bonding.ATmaP TM This method is suggested for use with a variety of materials such as plastics, glass and metals. The surface to be treated is passed through a flame with a controlled amount of oxygen into which a solution of a diamine is injected. The vaporized solutionproduces a number of reactive species in the flame that impinge on the surface resulting in hydroxyl, carboxyl, and nitrogen species being chemically bonded to the surface. Thefunctionalized surface enhances adhesion, immediately after treatment, or, after storage for several months.Rocatec TM This is a tribochemical method for functionalizing surfaces that has been used mainly for dental applications. The part to be treated is first cleaned then blasted with aluminum oxide that has been treated with a surface layer of silica. After impact some of the silica is embedded in the surface. The surface is then treated with a solution of an organosilane coupling agent to give a functionalized surface ready for adhesive bonding.O O O OSi O Si O Si O Si NH 2NH 2NH 2NH 2Surface Treatment in PracticeSome level of surface treatment is usually necessary before adhesive bonding.Although a simple solvent wipe may be sufficient for some applications, the following basic surface treatment is generally found suitable for most materials. A silane coupling agent may be used to improve surface wetting and increase the bonded joint's long-term durability.Basic Surface Treatment1.Solvent wipe to remove oil or grease contamination.2.Abrade or shot blast using medium grit (120 - 200 grit size) preferably alumina.3.Remove coarse debris, if present.4.Solvent wipe to Remove fine debris.5.Ensure surface is completely dry.6.Bond or prime immediately.Additional Chemical PretreatmentsFor some applications it may be necessary to follow the basic surface treatment with an addition pretreatment in order to achieve the level of performance required of the adhesively bonded joint. The following tables summarize chemical pretreatments for specific metals and plastics.Table 1. Chemical Pretreatments for Metalsthe surface treatment. RT = room temperature.Table 2. Chemical Pretreatments for PlasticsPhysical pretreatment (flame, corona, plasma) are also effective on most plastics. RT=room temperature.。

论文中参考文献和图、表的标准格式1.参考文献的作用着录参考文献是科技论文写作的传统贯例和必要内容。

首先，它体现了科学的严肃性、继承性和对他人劳动的尊重。

其次，表明作者使用参考文献的起点和深度。

一份完整的参考文献，也是作者向读者提供的一份有价值的信息检索资料。

第三，为了保持篇章结构的简洁和紧凑，也不宜在正文中过多地赘述参考文献的内容，而善于利用参考文献，则可以适当节省篇幅，提高论文质量。

2.文献的着录规则参考文献的着录要求采用顺序编码标控制，即按引用文献出现的先后顺序，在文献的著者或成果叙述文字的右上角用方括号标注阿拉伯数字编排序号，在参考文献表中按此序号依次著录。

具体讲，有以下几种情况。

参考文献类型：专著［M］，论文集［C］，报纸文章［N］，期刊文章［J］，学位论文［D］，报告［R］，标准［S］，专利［P］，论文集中的析出文献［A］电子文献类型：数据库［DB］，计算机［CP］，电子公告［EB］电子文献的载体类型：互联网［OL］，光盘［CD］，磁带［MT］，磁盘［DK］（1）文内的标注视则①引文写出原著者时，序号应置于著者姓名的右上角。

如在谈到当前我国优质烤烟生产中存在的问题时，朱尊权[2]指出：……②不写出著者时，序号应置于引文之后右上角。

如“营养不良．发育不全，成熟不够．烘烤不当”[3]，这“四不”问题是符合我国烤烟生产实际情况的。

③当将参考文献序号作为文句的组成部分时，不用角码序号，而以正文形式用方括号序号列出。

如烟草增香剂的制各方法见文献[2]。

④当引用多篇文献时，只须将各篇文献的序号在一个角码内全部列出，各序号间用逗号隔开；如通连续序号，应在标注起止序号间加“～”连接。

如早期的研究结果[2，5，7～9]表明，……（2）文后的着录规则①书籍的基本著录项目和着录规则［序号］著者．书名．版本，出版地：出版者，出版年．页次．示例［1］管雨霖，张凤英，马超群，等．烟草病害诊断虫害识别及防治[M]．北京：农业出版社，1989．78-81．②期刊的基本著录项目和着录规则［序号］著者．题（篇）名．刊名，出版年，卷（期）号：页次．示例［1］朱尊权．论当前我国优质烤烟生产技术导向[J]．烟草科技，1994，（1）：2-3．［2］金龙林．关于在论文中标往参考文献顺序码的位置问题[J]．编辑学报，1994，6（4）：240-241．③专利文献的基本著录项目和着录规则［序号］专利申请者．专利题名．专利国别，专利文献种类，专利号．出版日期．示例［1］孙中培，刘清，段完晶．烟草薄片用烟杆纤维物质．中国专利，发明，CNA．1993-07-28．［2］牛聪阳，刘立全，荆海强．固体物料造粒机．中国专利，实用新型，ZL93 2 24039．9．1995-02-12．④报纸的基本著录项目和通用格式［序号］著者．题（篇）名．报纸名，出版年．月．日（版位）．示例［1］刘彩望．保护烟农利益稳定烟叶生产：河南省提高优质烟奖励标准．东方烟草报，1995．1．25（1）．A：专著、论文集、学位论文、报告［序号］主要责任者.文献题名［文献类型标识］.出版地：出版者，出版年.起止页码（可选）［1］刘国钧，陈绍业.图书馆目录［M］.北京：高等教育出版社，1957.15-18.B:期刊文章［序号］主要责任者.文献题名［J］.刊名，年，卷（期）：起止页码［1］何龄修.读南明史［J］.中国史研究，1998,(3):167-173.［2］OU J P，SOONG T T，et al.Recent advance in research on applications of passi ve energy dissipation systems［J］.Earthquack Eng,1997,38(3):358-361.C:论文集中的析出文献［序号］析出文献主要责任者.析出文献题名［A］.原文献主要责任者（可选）.原文献题名［C］.出版地：出版者，出版年.起止页码［7］钟文发.非线性规划在可燃毒物配置中的应用［A］.赵炜.运筹学的理论与应用——中国运筹学会第五届大会论文集［C］.西安：西安电子科技大学出版社，1996.468.D：报纸文章［序号］主要责任者.文献题名［N］.报纸名，出版日期（版次）［8］谢希德.创造学习的新思路［N］.人民日报，1998-12-25（10）.E：电子文献[文献类型/载体类型标识]：[J/OL]网上期刊、[EB/OL]网上电子公告、[M/CD]光盘图书、[DB/OL]网上数据库、[DB/MT]磁带数据库［序号］主要责任者.电子文献题名［电子文献及载体类型标识］.电子文献的出版或获得地址，发表更新日期/引用日期［12］王明亮.关于中国学术期刊标准化数据库系统工程的进展［EB/OL］.http://www.cajcd. /pub/wml.html，1998-08-16/1998-10-01.［8］万锦.中国大学学报文摘（1983-1993）.英文版［DB/CD］.北京：中国大百科全书出版社，1996.参考文献规范格式一、参考文献的类型参考文献（即引文出处）的类型以单字母方式标识，具体如下：M——专著C——论文集N——报纸文章J——期刊文章D——学位论文R——报告对于不属于上述的文献类型，采用字母“Z”标识。

Optimization of ultrasonic extraction of Flammulina velutipes polysaccharides and evaluation of its acetylcholinesterase inhibitory activityWenjian Yang a ,Yong Fang b ,Jin Liang a ,Qiuhui Hu a ,b ,⁎a College of Food Science and Technology,Nanjing Agricultural University,Weigang,Nanjing 210095,ChinabCollege of Food Science and Engineering,Nanjing University of Finance and Economics,Nanjing,210046,People's Republic of Chinaa b s t r a c ta r t i c l e i n f o Article history:Received 19September 2010Accepted 15November 2010Available online xxxxKeywords:Flammulina velutipes Polysaccharides OptimizationResponse surface methodology Ultrasonic extraction AcetylcholinesterasePolysaccharide was testi fied to be the main component of Flammulina velutipes for inhibiting AChE activity in our preliminary study.Therefore,response surface methodology,based on Box –Behnken design,was used to optimize the ultrasonic extraction conditions of F.velutipes polysaccharides (FVP).Four independent variables (ratio of water to raw material,ultrasonic power,ultrasonic time,and ultrasonic temperature)were taken into consideration.A quadratic model,adequate for reasonably predicting the yield of FVP,was constructed between ultrasonic conditions and yield of FVP.A yield of FVP of 8.33%was obtained under a modi fied condition (ratio of water to material of 25ml/g,ultrasonic power of 620W,ultrasonic time of 20min,and ultrasonic temperature of 45°C).Subsequently,acetylcholinesterase (AChE)inhibitory activity and 1,1-diphenyl-2-picryl hydrazine (DPPH)scavenging activity of FVP were determined.AChE inhibitory rate of 18.51%and DPPH scavenging rate of 61.24%were obtained at 0.6mg/ml of FVP,indicating a good potential of FVP to enhance learning and cognitive ability.©2010Elsevier Ltd.All rights reserved.1.IntroductionNowadays,edible mushrooms are distinguished as important natural resources of immunomodulating and anticancer agents and have been cultured on a large scale in Asia (Wasser,2002).Flammulina velutipes ,one of the most popular edible mushrooms,has attracted considerable attention in the fields of biochemistry and pharmacology due to its biological activities.Polysaccharides,as one of the important active components of F.velutipes ,have been proved to be bene ficial in immunomodulating antitumor and anti-in flammatory activities (Leung,Fung &Choy,1997).Therefore,much attention has been paid to the studies of F.velutipes polysaccharides (FVP).Although polysaccharides have been well known for their various pharmacological functions,their extraction is still mainly performed with conventional techniques,which are based on proper solvents,prolonging extraction time,heating process,and agitation to increase extraction yield (Wang,Cheng,Mao,Fan &Wu,2009).In these methods,the extraction process usually consumes a long time and a lot of energy,but the extraction ef ficiency is very low.Therefore,it is essential and desirable to find out an economical and highly ef ficient extraction method.Ultrasonic has been used to increase extraction yield of bioactive substances from natural products,which is mainly attributed to disruption of cell walls,particle-size reduction,and enhanced mass transfer to the cell contents as a result of cavitationbubble collapse (Li,Pordesimo,&Weiss,2004;Vinatoru et al.,1997;Wang et al.,2009).However,there is hardly any report that ultrasonic is applied to separate FVP.Therefore,ultrasonic was employed for the extraction of FVP in our study.Especially,temperature was controlled during the extraction process to prevent overheating-induced oxidation and degradation of polysaccharides.The worldwide population ageing has increased the incidence of cognitive de ficits,such as the age-associated memory impairment and senile dementias and Alzheimer's disease (Hornick et al.,2008).Extensive evidence supports the view that cholinergic mechanisms modulate learning and memory formation.Neuropathological occur-rences of cognitive de ficits are associated with the cholinergic de ficiency (Gold,2003;Roberson &Harrell,1997).Inhibitors of acetylcholinesterase (AChE)have been extensively used to increase the effectiveness of cholinergic transmissions and endogenous acetylcholine levels and thus overcome cognitive de ficits (Hornick et al.,2008;Silman &Sussman,2005).F.velutipes is bene ficial to human memory.FVP has been proven to improve learning and memory ability of scopolamine hydrobromid-induced model mice and rats using step-through test and Morris water test (Zou,Liao,Wu &Liu,2010).However,the effect of FVP on AChE activity has not been studied.In our preliminary study,crude polysaccharide solution was testi fied to be the main fraction in F.velutipes for inhibiting AChE activity.In view of the above,it is necessary to research the AChE inhibitory activity of FVP.In addition,it is suggested that polysaccharides induced cognitive improvement owing to their antioxidant activity (Fan et al.,2005;Zhang,Zhang,Wang &Mao,2008),so antioxidant activity of FVP was also investigated.Food Research International xxx (2010)xxx –xxx⁎Corresponding author.Tel./fax:+862584399086.E-mail address:qiuhuihu@ (Q.Hu).FRIN-03416;No of Pages 70963-9969/$–see front matter ©2010Elsevier Ltd.All rights reserved.doi:10.1016/j.foodres.2010.11.027Contents lists available at ScienceDirectFood Research Internationalj o u r n a l h o me p a g e :w w w.e l s e v i e r.c om /l oc a te /fo o d r e sThe objective of this study was to optimize the ultrasonic-assisted extraction conditions of FVP using response surface methodology. Effects of ratio of water to raw material,ultrasonic power,ultrasonic time,and ultrasonic temperature on the extraction yield of FVP were fully examined.Moreover,AChE inhibitory activity of FVP was investigated to study its potential to improve memory impairment and cognitive deficit.On account of the relationship between oxidative stress and cognitive deficit,1,1-diphenyl-2-picryl hydrazine (DPPH)radicals scavenging assay was also conducted to evaluate the antioxidant ability of FVP.2.Materials and methods2.1.Materials and chemicalsF.velutipes was purchased from local market(Nanjing,China)and then dried at60°C and ground to pass through80mesh screen,the powder was stored at4°C until used.Glucose,phenol,and sulfuric acid were obtained from Shanghai Chemical Co.(Shanghai,China).1,1-Diphenyl-2-picryl hydrazine(DPPH),5,5′-dithio-bis-(2-nitrobenzoic) acid,acetylthiocholine iodide,ascorbic acid,acetylcholinesterase (AChE,type VI-S,EC3.1.1.7),and galanthamine were obtained from Sigma-Aldrich Chemical Co.(St.Louis,MO,USA).All other chemicals used in experiments were of analytical grade.2.2.AChE inhibitory activity of Flammulina velutipes extracts10g F.velutipes powder was extracted with200ml of different solvents(deionized water,ethanol,petroleum ether,and ethyl acetate),respectively,and AChE inhibitory activities of the extracts were compared.Subsequently,the water extract was mixed with quadruplicate anhydrous ethanol and then centrifuged.The precip-itate,crude polysaccharides,was lyophilized and redissolved in water as crude polysaccharide solution(CPS).The supernatant was concentrated under reduced pressure,lyophilized,and redissolved in water as water–ethanol solution(WES).The AChE inhibitory activities of CPS and WES were further investigated.2.3.Ultrasonic extraction and determination of polysaccharidesF.velutipes powder was weighed accurately(10.0g)and extracted with distilled water in ultrasonic cell disintegrator((DCTZ-2000, Beijing Hongxianglong Biotechnology Development Co.Ltd).Subse-quently,the treated mixture was air cooled to room temperature and centrifuged(10,000rpm/min,15min).The supernatant was concen-trated under reduced pressure at65°C.The polysaccharides extracts obtained above were then mixed with4-fold volume anhydrous ethanol(ethanolfinal concentration,80%)and kept at4°C for24h. After centrifugation at5000rpm/min for15min,the precipitate was washed three times with anhydrous ethanol and then dialyzed and lyophilized to yield FVP sample.The percentage polysaccharides yield(%)is calculated as follows:Yield of polysaccharideð%Þ¼weight of dried crude FVPðgÞ×1002.4.Experimental designA three-level-four-factor,Box–Behnken factorial design(BBD)was employed in this optimization study.Ratio of water to raw material (X1),ultrasonic power(X2),ultrasonic time(X3),and ultrasonic temperature(X4)were chosen for independent variables to be optimized for the extraction of FVP.Yield of polysaccharides(Y)was taken as the response of the design experiments.Twenty-nine experiments were carried out in BBD(Table1).Five replicates at the center point were used for estimation of a pure error sum of squares.Triplicate determinations were performed at all design points in randomized order.A quadratic polynomial model wasfitted to correlate the response variable(yield of polysaccharide)to the independent variables.The general form of quadratic polynomial equation is as follows:Y¼β0þ∑4i¼1βi X iþ∑4i¼1βii X i2þ∑i¼1∑4j¼iþ1βijXiXjwhere Y is the response variable,andβ0,βi,βii,andβij are the regression coefficients for intercept,linearity,square,and interaction, respectively,while X i and X j are the independent variables.2.5.AChE inhibitory activityThe AChE inhibitory activity assay was performed according to the protocol described by Langjae,Bussarawit,Yuenyongsawad, Ingkaninan and Plubrukarn(2007)with slight modifications.Briefly, 125μl of3mM5,5′-dithio-bis-(2-nitrobenzoic)acid,25μl of1.5mM acetylthiocholine iodide,50μl of50μM Tris–HCl buffer(pH8.0),25μl of sample,and25μl of0.25U/ml AChE were added consecutively into 96-well plate.Then the absorbance was measured immediately at 412nm using an ELISA plate reader(TECAN Infinite F200, Switzerland).The potency of AChE inhibitory activity of FVP was expressed as the inhibition rate.Galanthamine was used as a positive control.Table1Experiment of ultrasonic extraction of polysaccharides from Flammulina velutipes.(Data presented are the mean of triplicate determinations.)Run X1-ratio(ml/g)X2-ultrasonicpower(W)X3-ultrasonictime(min)X4-ultrasonictemperature(°C)Yield of FVP(%)ActualvaluePredictedvalue 12060015508.218.08 2304001550 6.887.05 32060015507.998.08 4204001565 6.63 6.76 5208001565 6.46 6.38 6208002550 6.64 6.82 7206005357.577.30 820400550 6.45 6.25 9108001550 6.21 6.16 1010600550 6.33 6.57 11104001550 6.18 6.14 1220600565 6.897.09 132040025507.597.56 143060015657.797.48 152060015508.178.08 163080015507.467.61 173********.557.55 182******** 6.58 6.96 193060025508.398.03 202060015508.298.08 21106001565 6.28 5.94 222080015357.917.66 23204001535 6.75 6.70 242060025358.067.98 25106001535 6.63 6.92 26106002550 6.77 6.64 272060015507.788.08 283060015357.427.74 29208005507.577.58 Optimumconditions24.81618.9818.6444.73–8.32Modifiedconditions2562020458.338.302W.Yang et al./Food Research International xxx(2010)xxx–xxx2.6.DPPH radicals scavenging assayThe DPPH radicals scavenging assay was carried out as previously described by Yang et al (2009).Brie fly,0.1ml of FVP in water was added directly to 3.9ml of a DPPH solution in ethanol (0.1mM).The mixture was immediately shaken for 10s using a vortex mixer,kept at 37°C for 30min,and then centrifuged at 5000rpm/min for 10min.Absorbance of the supernatant was measured at 517nm.Antioxidant capability (AA)was expressed as the percentage of DPPH radicals reduced,which was calculated with the following formula:AA DPPH =A B −A S ðÞ=A B ðÞ×100;where A S is the absorbance of the DPPH solution after reacting with FVP sample at a given concentration and A B is the absorbance of the DPPH solution after reacting with distilled water instead of sample.Ascorbic acid was measured as a positive control.2.7.Statistical analysesData were expressed as means of three replicated determinations.Design Expert (Trial Version 7.0.3)was employed for experimental design,analysis of variance (ANOVA),and model building.SPSS 12.0software was used for statistical calculations and correlation analysis.Values of p b 0.05were considered to be statistically signi ficant.3.Result and discussion3.1.AChE inhibitory activities of Flammulina velutipes extracts In order to study the AChE inhibitory activity of F.velutipes ,four solvent extracts of F.velutipes were prepared for AChE inhibitory activities assay.Results showed that the AChE inhibitory activity of water extract was signi ficantly better than the other solvents extracts (ethanol,petroleum ether,and ethyl acetate).Subsequently,water extract of F.velutipes was separated into two parts (CPS and WES).The results of CPS and WES inhibiting AChE activities suggested that polysaccharides were the principal effective fraction of water extract (Fig.1).Therefore,FVP was selected for further study.3.2.Fitting the model and evaluation of the model predictability In order to obtain more polysaccharides,ratio of water to raw material (10–30ml/g),ultrasonic power (400–800W),ultrasonictime (5–25min),and ultrasonic temperature (35–65°C)was adopted to research their effects on the yield of FVP.The experiments were designed to evaluate the effects of four factors on the yield of FVP using ultrasonic extraction method (Table 1).The mathematical model representing the yield of polysaccharides as a function of the independent variables within the region under investigation was expressed as follows:Y =−11:94+0:18d X 1+0:03d X 2+0:30d X 3+0:25d X 4+6:88×10−5d X 1X 2+1:0×10−3d X 1X 3+1:2×10−3d X 1X 4−2:59×10−4d X 2X 3−1:11×10−4d X 2X 4−1:33×10−3d X 3X 4−5:99×10−3d X 21−1:86×10−5d X 22−2:87×10−3d X 23−2:06×10−3d X 24where Y is the yield of polysaccharides,and X 1,X 2,X 3,and X 4represent ratio of water to raw material,ultrasonic power,ultrasonic time,and ultrasonic temperature,respectively.Predicted response values for the yield of polysaccharides could be obtained using this quadratic polynomial equation in terms of independent variables values.ANOVA for the fitted quadratic polynomial model was given to check the model adequacy (Table 2).F -test suggested that model had a high F -value (F =10.627)and a very low p -value (p b 0.0001),indicating that the fitness of this model was highly signi fick of fit is the variation of the data around the fitted model.The F -value and p -value of the lack of fit were 2.576and 0.188,respectively,which implied an insigni ficant difference relative to the pure error and a good fitness of the model.Coef ficient of determination (R 2)is de fined as the ratio of the explained variation to the total variation,and R 2=0.914approaching unity suggested a good relevance of the dependent variables in the model (Yang,Zhao,Shi,Yang &Jiang,2008).The adjusted determination coef ficient of the model (R 2adj =0.828)con firmed that the model was signi ficant,indicating a good degree of correlation between the actual values and the predicted values of FVP yield.Adeq precision measures the signal to noise ratio,and a ratio greater than 4is desirable (Zhu,Heo,&Row,2010).An adequate ratio (Adeq precision =10.00)of this fitted model indicated that it can be used to navigate the design space.Coef ficient of variation (CV)is a standard deviation expressed as a percentage of the mean.The lower the CV,the smaller the residuals relative to the predicted value (Zhong &Wang,2010).A low CV of the model (CV=4.12)suggested a good precision and higher reliability oftheFig. 1.AChE inhibitory activity of Flammulina velutipes extracts.CPS:crude polysaccharide solution,WES:water –ethanol solution.Values are means ±SD.Values with same superscript letters are statistically not signi ficantly different at p b 0.05(analysis of variance).Table 2Analysis of variance for the fitted quadratic polynomial model of extraction of polysaccharides.Source Sum of squares dfMean Square F Value p -value Prob N F X 1 4.1891 4.18947.237b 0.0001X 20.26110.261 2.9440.1082X 30.23210.232 2.6210.1278X 41.1471 1.14712.9340.0029X 1X 20.07610.0760.8530.3714X 1X 30.0410.040.4510.5128X 1X 40.13010.130 1.4610.2467X 2X 3 1.0711 1.07112.0800.0037X 2X 40.44210.442 4.9870.0424X 3X 40.16010.16 1.8040.2006X 12 2.3271 2.32726.2440.0002X 223.5911 3.59140.488b 0.0001X 320.53210.532 6.0040.0280X 42 1.3971 1.39715.7480.0014Model 13.194140.94210.627b 0.0001Residual 1.242140.0887Lack of fit 1.07100.107 2.5760.188Pure error 0.1740.042Cor total14.4428R 2=0.914R 2Adj =0.828CV =4.12Adeq precision =10.003W.Yang et al./Food Research International xxx (2010)xxx –xxxexperiments carried out(Gangadharan,Nampoothir,Sivaramakrishnan, &Pandey,2009).These results suggested that the model equation was adequate for reasonably predicting the yield of polysaccharides under any combination of values of the variables.The correlation between the predicted values and the actual values of FVP yield was analyzed according previous reports(Gan,Abdul Manaf&Latiff,2010).The closer the value of correlation coefficient to 1,the better the correlation between the observed and predicted values(Banik&Pandey,2009).As shown in Fig.2,the Pearson's correlation coefficient R=0.962approaching unity indicated a good agreement between the predicted values and the actual values and a good suitability of thefitted model equation for reflecting the expected optimization.3.3.Effects of extraction conditions on the yield of FVPThe effects of ratio of water to raw material,ultrasonic power, ultrasonic time,and ultrasonic temperature on the yield of poly-saccharides as well as their interactions were analyzed.Three-dimensional response surface plots for the response(the yield of polysaccharides)were plotted in Fig.3.Fig.3a shows the effects of ratio of water to raw material(X1)and ultrasonic power(X2)on the yield of FVP.With the increase of ultrasonic power,the yield of polysaccharides increased to a value and then declined when ratio of water to raw material was low but constantly increased when ratio of water to raw material was high.The yield of polysaccharides increased with increasing of ratio of water to raw material when ultrasonic power,as well as ultrasonic time(Fig.3b)and ultrasonic temperature(Fig.3c)was kept at a constant value.Fig.3b shows the effects of ratio of water to raw material(X1)and ultrasonic time(X3) on the yield of FVP.The yield of polysaccharides increased with the extension of ultrasonic time.Fig.3c shows the effects of ratio of water to raw material(X1)and ultrasonic temperature(X4)on the yield of FVP.The yield of polysaccharides decreased with the elevation of ultrasonic temperature.Fig.3d shows the effects of ultrasonic power (X2)and ultrasonic time(X3)on the yield of FVP.The yield of polysaccharides increased with the increasing of ultrasonic power when extraction bearing a short ultrasonic time,while a contrary result was obtained when extraction bearing a long ultrasonic time. Similarly,the yield of polysaccharides increased with the extension of ultrasonic time when ultrasonic power was low but decreased when ultrasonic power was high.Fig.3e shows the effects of ultrasonic power(X2)and ultrasonic temperature(X4)on the yield of FVP.The extraction yield of polysaccharides decreased with the elevation of ultrasonic temperature when ultrasonic power was high,butfirstly increased to a value and then declined when ultrasonic power was low.The possible mechanism was due to the degradation effect of ultrasonic wave and too high temperature(Yang,Zhao&Jiang,2008). The extraction yield of polysaccharides increased with the increase of ultrasonic power at low ultrasonic temperature,butfirst increased to a value and then declined at high ultrasonic temperature.Fig.3f shows the effects of ultrasonic time(X3)and ultrasonic temperature (X4)on the yield of FVP.The longer ultrasonic time and lower ultrasonic temperature,the higher polysaccharides yield.Taken altogether,the augment of all the four factors in a certain extent could increase the yield of polysaccharides,but higher ultrasonic power,if accompanied with higher ultrasonic temperature or longer ultrasonic time,would lower the yield of the yield of polysaccharides.The significance of each coefficient was checked by F-test and p-value(Table2).Values of“prob N F”less than0.05indicate model terms are significant.It can be seen that the variables with the largest effect on the yield of FVP were X1,X4,X2X3,X2X4,X12,X22,X32,and X42,which suggested that ratio of water to raw material and ultrasonic temperature significantly influenced the yield of FVP.Meanwhile,significant interactions between ultrasonic power and ultrasonic time,and ultrasonic power and ultrasonic temperature were observed.This indicated that high ultrasonic power could reduce extraction time and temperature to avoid oxidation induced by high temperature.3.4.The optimal conditions and validation of the modelBy prediction of computing program,the optimal conditions for the highest yield of polysaccharides were as follows:ratio of water to material of24.81ml/g,ultrasonic power of618.98W,ultrasonic time of18.64min,and ultrasonic temperature of44.73°C.A predicted value of8.32%was obtained for yield of polysaccharides under the optimal conditions.In order to facilitate the practical extraction process of FVP,the optimal conditions were modified as follows:ratio of water to material of25ml/g,ultrasonic power of620W,ultrasonic time of20min,and ultrasonic temperature of45°C.A predicted value of8.30%was obtained under the modified conditions.The modified conditions were used to validate the suitability of thefitted model equation for accurately predicting the responses values.The results showed that the actual values of polysaccharides yield were8.29% under the modified conditions(Table1),which were in agreement with the predict values significantly(p N0.05).Furthermore,FVP was extracted with a conventional method (ratio of water to material of25ml/g,extraction in80°C water bath for4h),and a yield of5.12%was obtained,which is significantly less than that obtained with the ultrasonic extraction method.The results suggested that ultrasonic assistant extraction of FVP was a time and energy saving and high yielding method.3.5.AChE inhibitory activity of FVPAlzheimer's disease,a disorder associated with progressive degeneration of memory and cognitive function,results from a deficit of cholinergic function in brain.The most important changes observed in brain are a decrease in hippocampal and cortical levels of the neurotransmitter acetylcholine and associated choline transferase (López,Bastida,Viladomat&Codina,2002;Perry,1986).Inhibiting AChE activity is considered as one of the most important methods to improve cognitive deficit and learning and memory impairment by restoring the level of acetylcholine.In this study,concentration-dependent inhibition of AChE was observed for galanthamine.FVP exhibited moderate AChE inhibitory activity(up to20%)that was not dose-dependent(Fig.4).It is reported that polyphenol-rich extract of Vaccinium angustifolium exhibited moderate AChE inhibitory activity in vitro(up to30%),but the polyphenol treated mice exhibited a significant improvement in learning and memory(Papandreou et al.,2009).Thesefindings indicated that FVP may be having a potential application value in improving cognitive deficit and memory impairment.It has been reported that FVP improved the learning and memory ability of dysmnesia model animals effectively evaluated bystep-Fig.2.Correlation between the predicted values and actual values of FVP yield.4W.Yang et al./Food Research International xxx(2010)xxx–xxxthrough test and Morris water test (Zou et al.,2010).In the present study,the results of AChE inhibitory activity in vitro suggest a potential application of FVP to improve cognitive de ficit.This may be one of the most important pharmacological mechanisms of enhancing the learning and memory capability of dysmnesia mice,which need our furtherinvestigation.Fig.3.(a)Response surface plots showing the effects of ratio of water to raw material (X 1)and ultrasonic power (X 2)on the yield of FVP (Y ).(b)Response surface plots showing the effects of ratio of water to raw material (X 1)and ultrasonic time (X 3)on the yield of FVP (Y ).(c)Response surface plots showing the effects of ratio of water to raw material (X 1)and ultrasonic temperature (X 4)on the yield of FVP (Y ).(d)Response surface plots showing the effects of ultrasonic power (X 2)and ultrasonic time (X 3)on the yield of FVP (Y ).(e)Response surface plots showing the effects of ultrasonic power (X 2)and ultrasonic temperature (X 4)on the yield of FVP (Y ).(f)Response surface plots showing the effects of ultrasonic time (X 3)and ultrasonic temperature (X 4)on the yield of FVP (Y ).5W.Yang et al./Food Research International xxx (2010)xxx –xxx3.6.DPPH radicals scavenging activity of FVPFree radical species have been reported to contribute to cellular ageing and neuronal damage (Sastre,Pallardo &Vina,2000).Excess amount of reactive oxygen species,which causes oxidative stress,is associated with pathology of memory de ficits and associated diseases including Alzheimer's disease (Silva et al.,2004;Soholm,1998).DPPH radicals have been widely used as model systems to investigate the antioxidant ability of compounds.In this study,the DPPH scavengingactivity of FVP was concentration-dependent and the scavenging rate was up to 61.24%at concentration of 0.6mg/ml (Fig.5).Good antioxidant ability of FVP implies a potential of FVP to protect cognitive impairment.Moreover,polysaccharides have been proved to exhibit indirect antioxidant ability in vivo by increasing glutathione peroxidase and superoxide dismutase activities (Zhang et al.,2003).Therefore,in order to have a thorough knowledge of pharmacological mechanisms of improving cognitive de ficit,the effect of FVP on antioxidant enzymes in vivo needs to be further studied.4.ConclusionExtraction conditions of FVP were optimized using BBD in response surface methodology,and a quadratic model was fitted for the extraction conditions of FVP.Results of ANOVA and validation experiments suggested that the fitted model was adequate for reasonably predicting the yield of FVP.A FVP yield of 8.33%was obtained under the modi fied conditions (ratio of water to material of 25ml/g,ultrasonic power of 620W,ultrasonic time of 20min,and ultrasonic temperature of 45°C).A good potential of FVP to enhance cognitive ability was testi fied by DPPH scavenging activity assay and AChE inhibitory activity test,which indicate that consummation of F.velutipes is bene ficial to improve learning and memory de ficit.AcknowledgmentThis work is financially supported by the earmarked fund for Modern Agro-industry Technology Research System of China.ReferencesBanik,R.M.,&Pandey,S.K.(2009).Selection of metal salts for alkaline phosphataseproduction using response surface methodology.Food Research International ,42,470−475.Fan,Y.,Hu,J.,Li,J.,Yang,Z.,Xin,X.,Wang,J.,Ding,J.,&Geng,M.(2005).Effect of acidicoligosaccharide sugar chain on scopolamine-induced memory impairment in rats and its related mechanisms.Neuroscience Letters ,374,222−226.Gan,C.-Y.,Abdul Manaf,N.H.,&Latiff,A.A.(2010).Optimization of alcohol insolublepolysaccharides (AIPS)extraction from the Parkia speciosa pod using response surface methodology (RSM).Carbohydrate Polymers ,79,825−831.Gangadharan, D.,Nampoothiri,K.M.,Sivaramakrishnan,S.,&Pandey, A.(2009).Immobilized bacterial α-amylase for effective hydrolysis of raw and soluble starch.Food Research International ,42,436−442.Gold,P.E.(2003).Acetylcholine modulation of neural systems involved in learning andmemory.Neurobiology of Learning and Memory ,80,194−210.Hornick,A.,Schwaiger,S.,Rollinger,J.M.,Vo,N.P.,Prast,H.,&Stuppner,H.(2008).Extracts and constituents of Leontopodium alpinum enhance cholinergic transmis-sion:Brain ACh increasing and memory improving properties.Biochemical Pharmacology ,76,236−248.Langjae,R.,Bussarawit,S.,Yuenyongsawad,S.,Ingkaninan,K.,&Plubrukarn,A.(2007).Acetylcholinesterase-inhibiting steroidal alkaloid from the sponge Corticium sp.Steroids ,72,682−685.Leung,M.Y.K.,Fung,K.P.,&Choy,Y.M.(1997).The isolation and characterization of animmunomodulatory and anti-tumor polysaccharide preparation from Flammulina velutipes .Immunopharmacology ,35,255−263.Li,H.,Pordesimo,L.,&Weiss,J.(2004).High intensity ultrasound-assisted extraction ofoil from soybeans.Food Research International ,37(7),731−738.López,S.,Bastida,J.,Viladomat,F.,&Codina,C.(2002).Acetylcholinesterase inhibitoryactivity of some Amaryllidaceae alkaloids and Narcissus extracts.Life Sciences ,71,2521−2529.Papandreou,M.A.,Dimakopoulou,A.,Linardaki,Z.I.,Cordopatis,P.,Klimis-Zacas,D.,Margarity,M.,&Lamari,F.N.(2009).Effect of a polyphenol-rich wild blueberry extract on cognitive performance of mice,brain antioxidant markers and acetylcholinesterase activity.Behavioural Brain Research ,198,352−358.Perry,E.K.(1986).The cholinergic hypothesis —ten years on.British Medical Bulletin ,42,63−69.Roberson,M.R.,&Harrell,L.E.(1997).Cholinergic activity and amyloid precursorprotein metabolism.Brain Research.Brain Research Reviews ,25,50−69.Sastre,J.,Pallardo,F.V.,&Vina,J.(2000).Mitochondrial oxidative stress plays a key rolein aging and apoptosis.IUBMB Life ,49,427−435.Silman,I.,&Sussman,J.L.(2005).Acetylcholinesterase:‘Classical ’and 'non-classical'functions and pharmacology.Current Opinion in Pharmacology ,5,293−302.Silva,R.H.,Abilio,V.C.,Takatsu,A.L.,Kameda,S.R.,Grassl,C.,Chehin,A.B.,Medrano,W.A.,Calzavara,M.B.,Registro,S.,Andersen,M.L.,Machado,R.B.,Carvalho,R.C.,Ribeiro,R.d.A.,Tu fik,S.,&Frussa-Filho,R.(2004).Role of hippocampal oxidative stress in memory de ficits induced by sleep deprivation in mice.Neuropharmacology ,46,895−903.Fig.4.AChE inhibitory activity of galanthamine and FVP with various concentrations (data are in mean ±SD,n =3).Fig. 5.DPPH radicals scavenging activity of FVP and ascorbic acid with various concentrations (data are in mean±SD,n =3).6W.Yang et al./Food Research International xxx (2010)xxx –xxx。

Flocculation of Saccharomyces cerevisiaeYu-Lai Jin a&R.Alex Speers b*a Department of Food Science,Yangzhou University,Yangzhou225009,People's Republic of Chinab Department of Food Science and Technology,Dalhousie University,PO Box1000,Halifax,NS Canada B3J2X4This paper reviews our current understanding of cell¯occulation with particularemphasis of the process in brewing fermentations.While cell¯occulation hasbeen examined for over a century and has been the subject to a number of reviewsin the early part of this decade,our view of the process is cloudy.Flocculation isa ected by cell genetic behavior,cell age as well as the chemical and physicalnature of the surrounding medium.Recently,a number of advances in ourunderstanding of the genes governing the process have occurred.In conjunctionwith these genetic advances,new assay methods have also been developed.Thisreview will discuss and update our current knowledge of cell¯occulation and itsuse in brewing fermentations.#1999Canadian Institute of Food Science andTechnology.Published by Elsevier Science Ltd.All rights reservedKeywords:Saccharomyces cerevisiae,¯occulation,aggregation,brewing yeast.INTRODUCTIONIn the food and biotechnological industries where fer-mentation occurs or cell reactors are employed,sus-pended cells must normally be separated from the media prior to further processing.Beverage alcohol produc-tion is a typical example of this process.Despite the study of cell¯occulation since the time of Pasteur,many details of the process have been subject to debate and remain to be elucidated.Indeed to the occasional reader of cell¯occulation literature,the process must seem obscure.While scientists from many disciplines have examined the¯occulation of various cell species,the majority of research has focused on the¯occulation of brewing yeast.Not surprisingly therefore,this paper will review our understanding of cell¯occulation with particular reference to the brewing process.However,the speci®c ®ndings gained and techniques used from the study of Saccharomyces cerevisiae can often be applied to the ¯occulation of other cells in various biotechnological applications.In selecting a yeast strain for beer production,a brewer considers a number of factors.Yeast's¯occula-tion ability is one of the major concerns.The number of cells suspended in wort during both primary and sec-ondary fermentation is a key factor in¯uencing fermen-tation speed,beer¯avor,maturation and®ltration. Although centrifugation can be applied to separate sus-pended cells,¯occulation is still an important and necessary process for the removal of yeast.As mentioned,brewers and microbiologists have been exploring the mystery of¯occulation of yeast cells since the establishment of pure yeast culture in the last cen-tury.Up to the1960s,researchers examined the e ect of environmental conditions such as salts,sugars,ethanol, pH,temperature,dissolved oxygen content and proteo-lysis on cell¯occulation(Gilliland,1951;Helm et al., 1953;Lindquist,1953;Eddy,1955a,c1958;Eddy and Rudin,1958;Harris,1959;Mill,1964).Since the mid-1970s,genetic studies have helped our understanding of yeast¯occulation at the molecular level(Johnson and Lewis,1974;Lewis et al.,1976;Stewart et al.,1976; Stewart and Russell,1977;Holmberg,1978;Holmberg and Kielland-Brandt,1978;Russell et al.,1980;Stewart and Russell,1981;Teunissen et al.,1993,1995;Teu-nissen and Steensma,1995;Lo and Dranginis,1996;Lo and Dranginis,1998).The mechanism of lectin-like cell±cell interactions has been established to explain yeast¯occulation in the past two decades(Taylor and Orton,1978;Hough et al., 1982a;Miki et al.,1982a,b;Speers et al.,1992a,1993b; Stratford,1992c;Patelakis et al.,1998;Speers et al.,1998).As the lectins found on S.cerevisiae cells have a speci®c role in yeast¯occulation,they have been de®ned as zymolectins to distinguish them from lectins of other yeasts or other microorganisms(Speers et al.,1998). The detection and quanti®cation of zymolectins or yeast cell surface lectins have also been attempted but there has been no report on the correlation between zymo-lectin density and¯occulation(Masy et al.,1992a;Rit-cey,1997;Patelakis et al.,1998).Since the1980s,cell surface hydrophobicity(CSH)has been identi®ed as a second major factor responsible for¯occulation onset and¯occulence of brewing yeast(Straver et al.,1993b, 1994a;Straver and Kijne,1996;Akiyama-Jibiki et al., 1997).Therefore,the relationship between cell surface hydrophobicity and¯occulation also warrants further investigation.This paper will review various aspects of cell¯occu-lation including its measurement,e ect of cell wall structure,genetic and colloidal aspects,the e ect of the environment and our current knowledge of the mechanism of the process.It is the authors'hope that this review will serve to summarize and clarify our current understanding of this fascinating phenomenon.YEAST AND YEAST FLOCCULATIONFactors a ecting attenuationA number of factors in¯uencing attenuation and the fer-mentation process have been recognized.Wort composi-tion and pH are important for yeast growth and fermentation.For this reason,the levels of fermentable carbohydrates,a-amino acids and dissolved oxygen are usually monitored by the ck of contact between yeast and oxygen over successive fermentations decreases attenuation from67to44%where the wort of 0.5m L/L dissolved oxygen was used(Hough et al.,1982b). Pitching rate greatly in¯uences the speed of fermen-tation and therefore in¯uences the time required for fermentation.The amount of yeast reproduced during fermentation depends on the pitching rate although the crop of yeast at the end of fermentation is almost inde-pendent of the pitching rate.On the other hand,the concentration of yeast cells suspended during the fer-mentation depends on mainly the¯occulation behavior of the yeast,the pitching rate,agitation caused by con-vection currents in the fermenter due to rousing or stir-ring,and the size and geometry of the fermenter.It has been recently suggested that aging and senescence of yeast cells may play a role in the`hung fermentations'of the brewing process(Barker and Smart,1996).Para-meters such as fermentation temperature,pressure and time also a ect fermentation pro®les.It is di cult to rank the order of importance of these parameters because of the variations among batches of fermentation, beer types and brewery plants.As well,the importance of the yeast strain should be noted.Characteristics such as the ability of the yeast to ferment maltotriose greatly in¯uence the attenuation. Respiratory-de®cient mutants of brewing yeast may arise spontaneously at frequencies!0.5%.Such RD mutants are unable to respire glucose and usually pro-duce high levels of vicinal diketones particularly diacetyl (Hough et al.,1982c).On contrary,transformed brew-ing yeast containing STA2gene may super-attenuate the wort with pronounced utilization of dextrin in pilot scale of brewing(Hammond,1995).Yeast taxonomyYeasts are protists that possess many characteristics of higher cells,but show a simpler level of biological organi-zation(Hough et al.,1982a).Classi®ed as fungi at the level of family,all yeasts are non-photosynthetic higher protists with rigid cell walls and exist as either unicellular organ-isms or mycelia.Under the genus of Saccharomyces,the old terms to which the fermentation industry is accus-tomed are:S.cerevisiae(ale yeast),S.carlsbergensis(later S.uvarum)(lager yeast),S.ellipsoideus later called S.cer-evisiae var.ellipsoideus(wine yeast),S.oviformis later termed S.bayanus(employed in wine refermentations) and S.pastorianus(used in wine fermentation in cold cli-mates)(Martini and Martini,1989).It is noteworthy that there are over1000individual ale strains of S.cerevisiae (Stewart et al.,1975b;Russell,1995).In the brewing industry,ale and lager beers are normally fermented with S.cerevisiae and S.carlsbergensis,respectively.Tradi-tionally the ale yeasts or top yeasts are collected from the surface by the process of skimming while the lager yeasts or bottom yeasts are cropped from the bottom of the fer-mentation vessel.The di erentiation of lagers and ales on the basis of bottom and top cropping has become less distinct as a result of the application of modern cylin-droconical tanks and centrifuges(Russell,1995).Thus, brewers select less¯occulent strains for use in centrifuge-equipped plants.However,due to cell¯occulation variability,the understanding and monitoring of cell ¯occulation is a concern to all brewers.Originally identi®ed as S.carlsbergensis and S.cere-visiae,the lager and ale yeasts were distinguished on the basis of melibiose fermentation by the American Society of Brewing Chemists(ASBC,1995).Lager yeast strains that possess the MEL gene(s)produce extracellular melibiase or a-galactosidase to utilize melibiose,whereas ale yeast strains that do not produce melibiase are unable to utilize melibiose.In1970,S.carlsbergensis was renamed as S.uvarum as shown in Table1(Lodder, 1970).After exhaustive investigations based on such procedures as electrophoretic analysis of cellular enzymes,proton magnetic resonance spectrum,anti-genic activity of cell wall mannans,and the percentages of guanine and cytosine(mol%G+C)of nuclear DNA, it was unequivocally shown that the yeasts used in the422Y.-L.Jin,R.A.Speersalcoholic fermentation industry consistently fall into the same species,S.cerevisiae in spite of their di erences in some technological properties (Kreger-van Rij,1984;Martini and Martini,1989).However,such di erences of the brewing yeast strains dismissed by the taxonomists are technically important to the brewers.Thus,brewers and brewing scientists use the labels S.cerevisiae and S.uvarum to denote ale and lager yeasts,respectively.Aggregation and ¯occulation of brewing yeastMicrobial aggregation has been de®ned as a collection of microbial cells in intimate contact or as the gathering together of units to make a larger unit (Calleja et al.,1984;Calleja,1987).Therefore,the aggregation may include agglutination (mating)and ¯occulation but not chain formation (Calleja,1987).However,the European Brewery Convention (EBC)suggested that `the aggre-gation of yeast cells into ¯ocs which may be due to either non-separation of cells after budding or coales-cence of single cells into clumps late in fermentation'(EBC Microbiologica,1981).Chain formation has been generally held as a unique type of cell aggregation (Wilcocks and Smart,1995;Stratford,1996a ).Yeast mating involves haploid strains of a and a sexes of S.cerevisiae which exchange small peptide pher-omones or a and a factors followed by aggregation before cell fusion to form a diploid cell.The cell-to-cell bonding in this case is due to protein-protein interac-tions between a and a agglutinins anchored in the com-plementary cell walls (Fig.1a).Chain formation is caused by failure of daughter cells to separate from mother cells during cell division.The cells grow into chains of up to 100cells by further bud-ding of mother and daughter cells (Fig.1b).Such chains can be dispersed irreversibly by mechanical shear rather than ethylenediaminetetraacetic acid (EDTA)since the chain structure is calcium-independent (Stratford,1996a ).Yeast ¯occulation has been de®ned as `the phenom-enon wherein yeast cells adhere in clumps and sediment rapidly from the medium in which they are suspended'(Stewart et al.,1976).The responsible bonding has been proved to involve lectin-like protein-carbohydrate recognition and interaction in a manner of calcium-dependent and sugar sensitive (Fig.1c).A more restric-tive de®nition has been suggested as `the non-sexual aggregation of yeast cells into clumps,dispersible byTable 1.Changes in the nomenclature of S.cerevisiae (Martiniand Martini,1989)The Yeast,a Taxonomic Study,1st edn,1952The Yeast,a Taxonomic Study,2nd edn,1970The Yeast,a Taxonomic Study,3rd edn,1984S.cerevisiae S.cerevisiae S.willianus S.coreanusS.coreanus S.carlsbergensis S.uvarum S.uvarumS.logos S.bayanus S.pastorianus S.oviformis S.bayanus S.beticusS.heterogenicus S.heterogenicus S.chevalieri S.fructuum S.chevalieri S.italicus S.steineri S.italicus S.cerevisiaeS.globosusS.globosus S.acetiS.prostoserdovii S.oleaginosus S.oleaceus S.capensis S.diastaticus S.hienipiensis S.inusitatus S.norbensis S.abuliensis S.cordubensis S.gaditensis S.hispalensis S.cerevisiaeFig.1.Aggregation of brewing yeast (Calleja,1987;Speersand Ritcey,1995).cc c ccc c c c Flocculation of Saccharomyces cerevisiae423EDTA or speci®c sugars and the subsequent removal of these clumps from medium'(Stratford,1996a).In some cases,co-¯occulation may occur between ¯occulent and non-¯occulent strains where non-¯occu-lent cells adhere to¯occulent cells(Curtis and Wenham, 1958;Miki et al.,1982a).So far co-¯occulation has not been found among lager strains(Enari,1995).Eddy (1958)suggested the term of mutual¯occulation for a pair of non-¯occulent yeast strains that¯occulate in the presence of each other but do not¯occulate separately.Measurement and classi®cation of yeast¯occulationMicrobial aggregates may be characterized by their strength,morphology,extent or rate of aggregation (Calleja,1984).The measurements of the extent of cell aggregation are more appropriate for yeast¯occulation quanti®cation.To measure the extent of¯occulation, visual estimation is rather subjective due to judgment variations among observers.However,visual methods are simple and fast(Calleja and Johnson,1977). Recently authors have suggested that the rate of agita-tion may substantially in¯uence the initial rate and the ®nal equilibrium of¯occulation(Stratford,1992c;Speers and Ritcey,1995).After consideration of fermenter shear rates,it has been proposed to control agitation at an average rate of shear of25sÀ1during¯occulation determinations(Speers and Ritcey,1995).For routine¯occulation assays,Gilliland and Helm methods and Variants thereof have been chosen as standard methods(EBC Microbiologica,1981;ASBC, 1986),respectively.In Gilliland's test,yeast strains are classi®ed into four classes.Class I strains are non-¯oc-culent or powdery yeasts.Class II strains are those that ¯occulate into small loose clumps towards the end of fermentation,therefore both Class I and Class II attenuate very well while Class II separate from the medium well(moderately¯occulent).Class III strains can form lumpy masses towards the end of fermentation and sediment rapidly(strongly¯occulent).Class IV strains are those that sediment very soon at the beginning of fermentation due to chain-formation.For Helm's test,suspension of Type1or¯occulent yeast strains separates into two layers near the top.Such an interface falls rapidly and a falling boundary is mea-sured after10min.For the Type2or non-¯occulent strains,an interface forms much more slowly near the bottom and a rising boundary is measured after10min. Both Gilliland's and Helm's methods are quick semi-qua-litative approaches.Gilliland's method has been found to give variable results.The Helm's test was generally con-sistent in distinguishing¯occulent strains from non-¯oc-culent ones but gave mixed results for identifying moderately¯occulent strains(ASBC,1993,1994).To improve the Helm's method with regard to its reproduci-bility,the environmental factors which in¯uence¯occula-tion must be included(D'Hautcourt and Smart,1998).During1993±1996,the ASBC Microbiology Sub-committee selected a standard method suggested by Bendiak(ASBC,1993±1996;Bendiak,1994).The mea-surement is based on Helm's test and uses controlled inoculum,yeast growth,cell density of the suspension, and experiment temperature.The¯occulation is expres-sed as the percentage of A600reduction of the top1.0ml suspension in6min compared with EDTA-treated sus-pension.Strains can be classi®ed as non-¯occulent (<20%),very¯occulent(>85%)and moderately¯oc-culent(20±80%)(ASBC,1996).As a modi®ed Helm's method,the test is not fundamental but relatively qualitative and fast.The on-line measurement of the rate of yeast settling has been attempted(Podgornik et al.,1997).As well other procedures based on sugar de¯occulation(Eddy, 1955b),thermal de¯occulation(Taylor and Orton, 1975),turbidity of suspension in a glass capillary(van Hamersveld et al.,1996),or hydrophobic interaction chromatography(Akiyama-Jibiki et al.,1997)have been employed.One might expect various procedures to be developed and these methods may coexist until a standard method is accepted by both brewers and researchers.THE ROLE OF THE CELL WALL IN YEAST FLOCCULATIONIt is generally agreed that the yeast cell wall is an important indicator of the rate and extent of cell wall ¯occulation(Calleja,1987).Heat-killed cells will¯oc-culate if they were originally¯occulent(Mill,1964).As well,isolated cell walls will¯occulate if originally¯oc-culent whereas walls from non-¯occulent cells will not ¯occulate(Eddy,1955c).Composition and structureAs an easy source of biomass and an important agent in alcoholic beverage industry,S.cerevisiae has been well studied,especially the composition and structure of the cell wall.The yeast cell wall surrounds the periplasmic space,spans100±200nm and represents some15±25%of the total dry mass of the cell(Stratford,1994).It is com-posed about60±85%of carbohydrates,of which some are covalently linked to proteins.Beta-glucans and a-mannans equally comprise the majority of the carbohy-drate of the wall.It has been reported that b-1,3-glucans have an estimated size of1500glucose units(or degree of polymerization or DP),whereas b-1,6-glucans have about130±140DP(Manners et al.,1973a,b).Alpha-mannan is a component of the secreted glyco-proteins which are anchored in the cell wall.Four types of glycosylation in wall mannoproteins have been reported:(1)N-linkage to asparagine,(2)O-linkage to serine or threonine,(3)linkage of glucomanno-side chain to unknown amino acid(AA)residues and(4)424Y.-L.Jin,R.A.Speersattachment of a glycosyl phosphatidyl inositol(GPI) membrane anchor(Fig.2).The N-linked glycosylation is important to yeast viability(Nagasu et al.,1992).The low molecular weight(MW)O-glycosylated proteins are extractable with sodium dodecyl sulphate(SDS),while the high MW N-glycosylated proteins are extractable by zymolyase or glucanase.A substantial amount of b-glu-can is attached to the high MW mannoproteins,which suggests that such mannoproteins are secreted and then anchored to cell wall b-glucan.The attachment of a-agglutinin,the sexual adhesion protein,is believed to be linked by O-glycans(Schreuder et al.,1993;Klis,1994). The best characterized component of the cell wall is the a-mannan(Fig.2).The molecule has an inner core of a-1,6-chain of mannose residues with a-1,2-,a-1,3-linked short side chains.At the end of this inner core are two N-acetyl glucosamine residues(chitobiose)with the terminal residue attached to the side chain of an aspar-agine residue.At the other end of the inner core is an outer chain of100±150mannose residues linked by a-1,6-backbone with a-1,2-and a-1,3-side chains,some of which contain phosphodiester linkages.This inner core and outer chain form N-glycosylated mannans.To the mannoprotein molecule,short a-1,2-and a-1,3-chains of mannose residues varying from1to5in length are attached via serine or threonine hydroxyl groups.The glucomanno-side chains linked to unknown AA resi-dues consist mainly of b-1,6-linked glucose residues and a-1,6-linked mannose residues.The C-terminal mod-i®cation of the mannoproteins is GPI-anchor-linked to the amino group of the AA residue at C-terminus.The GPI-anchor is the sole means of attachment of such proteins to the membrane.This GPI-anchor may exist in a modi®ed form lacking the inositol and phospholi-pid and function as a site linking to b-1,6-,b-1,3-glucans and chitin(Bacon,1981;Hough et al.,1982a;Rose, 1993;Klis,1994;Kollar et al.,1997).Proteins such as FLO(¯occulation)gene products are identi®ed as GPI-anchored,serine/threonine-rich wall proteins(Teunissen et al.,1993;Bidard et al.,1994). These proteins have hydrophobic C-terminals likely to be®tted with GPI membrane anchors when secreted through the endoplasmic reticulum.It is also possible that O-glycosylation may serve to confer stability to proteins exposed to more hostile conditions outside the cell membrane(Stratford,1994).Chitin is known to be an important constituent of bud scars with a major role of its synthesis in septum forma-tion and cell division(Cabib et al.,1997).Cells lacking chitin were found to be resistant to Kluyveromyces lactis killer toxin,which suggested a role for chitin as the toxin receptor(Takita and Castilho-Valavicius,1993).Fig.2.Glycosylation of cell wall proteins in Saccharomyces cerevisiae.The fragment in parentheses indicates the type of side chains rather than a repeating unit.n=10±15.A mannoprotein may not possess all four types of glycosylation(Bacon,1981;Hough et al.,1982a;Rose,1993;Klis,1994;Kollar et al.,1997).Flocculation of Saccharomyces cerevisiae425Extraction of yeast cells with hot alkali left an insoluble fraction consisting of b-1,3-,b-1,6-glucan and chitin. Since b-glucan is in itself soluble in alkali,this suggested that chitin may be responsible for the insolubility of this fraction(Klis,1994).It has been shown that mutations a ecting chitin cause osmotic sensitivity,abnormal morphology,aggregation and growth arrest with elon-gated buds(Takita and Castilho-Valavicius,1993; Stratford,1994).In spite of the very low(less than1%) level of chitin in the S.cerevisiae cell wall,it seems to play an important role in wall structure.Cell wall proteins that are rich in glutamate and aspartate may act as either structural molecules or extracellular enzymes.Enzymes occupy the periplasmic space between the cell membrane and the cell wall.Both b-fructofuranosidase(invertase)and acid phosphatase have a large mannan component similar in structure to cell wall mannan(Bacon,1981).Strains of lager yeast also possess extracellular melibiase(Hough et al.,1982a; ASBC,1995).It has been reported that mannoprotein is attached to b-1,6-glucan through a remnant of a GPI anchor con-taining®ve alpha-linked mannosyl residues.Beta-1,6-glucan has some b-1,3-linked branches,and it is to these branches that the reducing termini of chitin chains appear to be attached via a b-1,4-or b-1,2-linkage.The reducing end of b-1,6-glucan is connected to the non-reducing terminal glucose of b-1,3-glucan through an as yet unknown linkage(Kollar et al.,1997).The cell wall structure is dynamic rather than static.It constantly changes its size and shape,to accompany growth of the cell.During cytokinesis,a specialized var-iant of the cell wall,the septum,is formed to separate the two dividing cells.Some researchers have suggested that lipids have cer-tain structural roles to play in the cell wall.The lipid content of the wall varies both with yeast species and probably with the cultural conditions(Rogers,1968). Presently little is known about the function of cell wall lipids.FunctionsThe prime function of the cell wall is protection. Deprived of the wall,the cell would burst under the stress of osmotic pressure.Abnormal morphology is one of the reported mutational e ects,which is often asso-ciated with yeast osmotic sensitivity.The wall acts as ®lter for large molecules,where the wall permeability determines passage of macromolecules both into and out from the cell.The wall also supports a number of external enzymes.These wall enzymes may be stabilized by phospholipids and wall exoglucanases may be glyco-sylated(Basco et al.,1993).However,cell wall is also responsible for sexual agglutination and¯occulation of brewing yeast.Hap-loid a and strains form pointed morphologies and adhere to each other via a-and a-agglutinins after exchange of pheromones.It is believed that cell surface zymolectins bind to carbohydrate receptors of the neighboring cell walls during¯occulation of brewing yeast.Two types of zymolectins involved in the¯occu-lation in S.cerevisiae have been described.Yeast cells of Flo1phenotype possess a mannose-speci®c zymolectin (MS),while yeasts of NewFlo phenotype contain a zymolectin sensitive to mannose and glucose(GMS) (Stratford,1992a,b;Stratford and Assinder,1991;Bellal et al.,1995).Using protein±FITC conjugates,the zymo-lectin binding sites at the cell surface have been quanti®ed (Masy et al.,1992a;Ritcey,1997;Patelakis et al.,1998).It is believed that zymolectin-mediated aggregation is the major factor in yeast¯occulation(Speers et al.,1992a, 1993b).Those noncatalytic carbohydrate binding domains(CBDs)have been termed zymolectins and are de®ned as protein or glycoprotein structures associated with yeast cell wall speci®c CBDs which may cause or enhance¯occulation of yeast cells(Patelakis et al.,1998; Speers,et al.,1999).GENETIC ASPECTS OF YEAST FLOCCULATIONSince the1950s,it has been recognized that¯occulation is a hereditary characteristic(Gilliland,1951;Thorne, 1951).Two dominant¯occulation genes FLO1and FLO2and a recessive gene¯o3were®rst identi®ed in the 1970s(Johnson and Lewis,1974;Lewis et al.,1976).A dominant gene FLO4was later mapped on chromosome I(Stewart et al.,1976;Stewart and Russell,1977).Fur-ther tetrad analysis of genetic crosses demonstrated that FLO1,FLO2and FLO4were allelic,mapping onto chromosome I,and these genes were then consolidated into the FLO1locus(Russell et al.,1980).The physical location of gene FLO1was con®rmed to be24kb from the right end of chromosome I(Teunissen and Steensma,1990;Teunissen et al.,1993).This gene con-fers¯occulence when introduced into non-¯occulent yeast cells(Teunissen and Steensma,1995).The FLO1 gene product(FLO1p)has been localized at the cell surface by immuno¯uorescent microscopy(Bidard et al.,1995).Further studies showed that the amount of FLO proteins in¯occulent strains increased during yeast growth and the¯occulation level was strongly corre-lated to the FLOp detected.The FLOp availability at the cell surface determined the¯occulation degree of yeast.It is also believed that FLO proteins are polarly incorporated into the cell wall at the bud tip and the mother±daughter neck junction(Bony et al.,1998).It has been suggested that the FLO1p has putative GPI-anchor at its C-terminal domain(Klis,1994).Being rich in serine and/or threonine(Stratford,1994)and with repeated domains of70%of the sequence(Bidard et al., 1995),the GPI-anchored mannoproteins were suggested426Y.-L.Jin,R.A.Speersto extend100±200nm from plasma membrane in extended O-glycosylated form(Teunissen et al.,1993; Stratford,1994,1996a;Watari et al.,1994).One report has suggested that the FLO1p may function to activate a lectin rather than being a lectin itself(Stratford,1994). The GPI-anchor may be modi®ed to serve as a site of linkage to b-1,6-and b-1,3-glucans and chitin(Caro et al.,1997;Kollar et al.,1997).This suggests that the FLO1p may be either modi®ed and GPI-anchored in the wall b-glucan network or GPI-anchored in the plasma membrane.The high glycosylation of FLO1p results in much higher apparent MW than predicted by the gene sequence(Bony et al.,1997).The hydrophobic C-termi-nus was found to be necessary for both the anchoring of FLO1p at the cell surface and the cell±cell interaction. The stabilization of FLO1p in the cell wall by its C-ter-minus suggested that the N-terminal region corresponds to the reacting domain at the cell surface.By expressing a truncated form of FLO1p with AAs50to278deleted, the N-terminal domain proved to be essential for the cell±cell interaction since the truncated form could not trigger a¯occulent phenotype although the protein was detected in the cell wall(Bony et al.,1997).FLO5was found to be a dominant gene not allelic to FLO1and conferred strong¯occulation(Johnson and Reader,1983).It was mapped on chromosome VIII (Teunissen et al.,1995).FLO5p is also GPI-anchored into the cell wall at the bud tip and the mother-daughter neck junction(Bony et al.,1998).The FLO5gene can trigger¯occulation in a non-¯occulent strain(Bidard et al.,1994)and the FLO5p level of cell surface expression increases during growth and correlates with¯occulation (Bony et al.,1998).Irreversible loss of¯occulation con-ferred by FLO1and FLO5genes was achieved by treat-ment with pronase,proteinase K,trypsin or2-mercaptoethanol.However,the FLO1strain was sensi-tive to chymotrypsin and stable to70 C incubation whereas the FLO5strain was thermolabile and chymo-trypsin resistant(Hodgson et al.,1985).The FLO1and FLO5strains were therefore proposed to be di erent phe-notypes although only one strain of each was examined. Recessive genes¯o6and¯o7behaving in a semi-dominant manner have been considered as possible alleles of FLO1(Johnson and Reader,1983).The dominant gene FLO8was mapped onto chromosome VIII(Yamashita and Fukui,1983).It was later localized on chromosome I and was suggested to be allelic to FLO1by genetic and physical mapping(Teunissen et al.,1995).However,this gene was further determined to encode a protein of729AA that has no pronounced hydrophobic regions.It was reported that the FLO8 gene has a signi®cant homogeneity with the S.cerevisiae chromosome V DNA sequence but no homology with the FLO1gene.It was suggested that the FLO8gene mediated¯occulation by transcriptional activation of the FLO1gene since the level of FLO1gene transcription was dependent on its transcription rate(Kobayashi et al.,1996).Another dominant gene FLO9is not present in all strains(Teunissen and Steensma,1995).The FLO9 product has a near similarity over850AAs to FLO1p and74%identity over970AAs to FLO5p(Bossier et al.,1997).It also has strong similarity to FLO1p in the N-terminal region.Yet another FLO gene product, FLO10p has58%similarity to FLO1p(Teunissen et al., 1995)and it is a member of the¯occulin family includ-ing FLO1p,FLO5p and FLO9p(Bossier et al.,1997). FLO11is another dominant gene related to the STA genes encoding secreted glucoamylase.The FLO11gene was localized on chromosome IX.Yeast cells expressing FLO11produce serine/threonine-rich and C-terminal GPI-anchored wall protein that has26%identity to FLO1p and¯occulate in a calcium-dependent manner while the null mutant cannot¯occulate(Lo and Dran-ginis,1996).The FLO11p is a`mucin-like protein'and is required for invasive growth of haploid cells and for diploid cells to form pseudohyphae in response to nitrogen starvation(Lo and Dranginis,1998).The pre-dicted properties of the FLO proteins are available on an internet database(Hodges et al.,1998;Proteome Inc.,1998)and summarized in Table2.Semi-dominant genes fsu1and fsu2have been found to suppress the¯occulence of FLO4strains(Holmberg, 1978;Holmberg and Kielland-Brandt,1978;Stewart and Russell,1981).There are also mutations capable of causing yeast¯occulation such as those of the TUP1 and CYC8loci(Table3).After distinguishing yeast strains by sugar and salt, acid inhibition,protease sensitivity and selective expression of¯occulation,Stratford and Assinder(1991) suggested two phenotypes:Flo1and NewFlo pheno-type,mannospeci®c and gluco-/mannospeci®c respec-tively.The former phenotype includes all strains with known genes a ecting¯occulation whereas the latter phenotype comprises the majority of brewing ale strains.COLLOIDAL ASPECTS OF YEAST FLOCCULATIONYeast¯occulation has been extensively studied in the past from a biochemical perspective,while its colloidal aspects have only recently interested researchers.Calleja (1984)outlined basic colloid theory and noted the importance of shear on the rate of¯occulation.The in¯uence of agitation(shear)has been reported by other researchers(Kihn et al.,1988;Stratford et al.,1988; Stratford and Wilson,1990;Stratford and Keenan, 1987,1988;Stratford,1989a;Speers,1991;Speers et al., 1990;Speers et al.,1992b;Speers and Ritcey,1995). Colloidal theory can help clarify our understanding of how yeast cells associate.While largely ignored in theFlocculation of Saccharomyces cerevisiae427。

Surface chemistry and catalysis : Unlocking the Potential of Chemical ReactionsChemical transformations have been essential in human life for thousands of years. We use chemistry to produce food, medicine, and energy, among other things. These reactions occur on a molecular level, with billions of atoms interacting in complex ways. One of the keys to making these reactions more efficient and effective is understanding the role of surface chemistry and catalysis.Surface chemistry is the study of chemical reactions that occur at the interface between different phases, such as between a solid and a liquid or between gases. These interfaces can greatly impact the speed and efficiency of chemical reactions. For example, imagine trying to dissolve a solid in a glass of water. If the solid particles are large and clumpy, they will take longer to dissolve than if they were small and evenly dispersed. Surface chemistry studies these phenomena and provides insight into how to optimize chemical reactions for different applications.Catalysis is the process of increasing the rate of a chemical reaction by adding a substance called a catalyst. Catalysts are not consumed in the reaction, but they can greatly increase the efficiency of the reaction by lowering the activation energy required for the reaction to occur. For example, in the production of ammonia for fertilizers, a catalyst made from iron and molybdenum is used to convert nitrogen and hydrogen gases into ammonia more efficiently than without a catalyst.Catalysts can be classified into two categories: homogeneous and heterogeneous. Homogeneous catalysts are in the same phase as the reactants, while heterogeneous catalysts are in a different phase. Most industrial catalysts are heterogeneous, as they can be easily separated from the reaction products and reused. One of the most commonly used heterogeneous catalysts is platinum, which is used in catalytic converters in automobiles to convert harmful pollutants into less harmful substances.Surface chemistry and catalysis are closely linked, as the surface properties of a catalyst greatly impact its effectiveness in promoting a reaction. Catalysts typically have a high surface area to volume ratio, allowing for many molecules to be adsorbed onto the surface of the catalyst. These adsorbed molecules can then react with other molecules on the surface, leading to the desired chemical transformation.One area where surface chemistry and catalysis are particularly important is in the production of renewable energy. For example, in the field of solar energy, there is active research into using catalysts to split water into its component parts of hydrogen and oxygen. The hydrogen can then be used as a fuel source, with the only byproduct being water. This process is called water splitting, and catalysts such as nickel and cobalt are being extensively studied for their potential in this application.In addition to energy, surface chemistry and catalysis are also critical in the production of many chemical compounds, from pharmaceuticals to plastics. Catalytic processes are often used to optimize yields and reduce waste in these industries. For example, the synthesis of aspirin involves the use of a catalyst to convert salicylic acid into acetylsalicylic acid, the active ingredient in aspirin.In conclusion, surface chemistry and catalysis are central to many important chemical processes. By studying the interactions between different phases and optimizing catalysts, we can accelerate chemical reactions and produce more efficient and sustainable technologies. The potential applications of surface chemistry and catalysis are vast, and research in these fields is ongoing and promising.。