Chicory extracts from Cichorium intybus L.as potential antifungals D.Mares1,C.Romagnoli2,B.Tosi1,E.Andreotti1,G.Chillemi3&F.Poli4
1Department of Natural and Cultural Resources,University of Ferrara,Ferrara,Italy;2Department
of Paleobiology and Botanical Garden,University of Modena and Reggio Emilia,Modena,Italy;3Veneto Agricoltura,Sezione Ricerca e Sperimentazione,Padova,Italy;4Department of Evolutionary and Experimental Biology,University of Bologna,Bologna,Italy
Received4October2004;accepted in revised form23November2004
Abstract
In this work extracts from roots of the common vegetable Cichorium intybus L.,highly appreciated for its bitter taste,were studied to investigate their possible biological activity on fungi from a variety of ecological environments:some are parasites on plants(phytopathogens)or of animals and humans(zoophilic and anthropophilic dermatophytes),others live on the soil and only seldom parasitize animals(geophilic dermatophytes).The extracts were ine?ective on geophilic species and on tested phytopathogens,with the exception of Pythium ultimum,whereas they inhibited the growth of zoophilic and anthropophilic dermatophytes,in particular Trichophyton tonsurans var.sulfureum,whose treatment caused morphological anomalies,here observed by scanning electron microscopy.This behaviour is discussed on the basis of the presence in the chicory extract of the two main sesquiterpene lactones,8-deoxylactucin and11b,13-dihy-drolactucin.
Key words:antifungal activity,Cichorium intybus,dermatophytes,phytopathogens
Introduction
An interest in drugs from natural sources has recently been revived,with consequent renewed attention devoted to plants either as cosmetics or as sources of therapeutically e?ective medicines.
In this work we considered Cichorium intybus L.(Asteraceae),a plant commonly known as chic-ory or as succory,often found on our tables as a vegetable,and highly appreciated for its bitter taste.
Plants with very di?erent morphological and chromatic characteristics of the epigean part were known as chicory;among them, C.intybus L.var.‘Rosso di Chioggia’,with red and variegated leaves,is a speciality of the Veneto region(North-eastern Italy).This species was achieved by a long process of selection,made by horticulturists,in order to obtain a plant forming a heart,having the central leaves tightly imbricated and endowed with a red variegation on the whole surface of the leaf.
Chicory cultivation was mentioned in an ancient Egyptian medical document(1550B.C.) reporting that two types of this plant were appre-ciated in particular:one for the leaves used as salad,the other as a depurant and digestive. Chicory is still used today for its bitter-tonic, diuretic,digestive,lightly laxative and cholagogic properties,due to its content of mucilages,resins and bitter substances[1].Leaves are used as infu-sions for anemia and digestive disorders:roots are employed as infusion to purify the organism and to stimulate the appetite;?owers have cholagogic activity,but they are also utilized externally,such as in skin washing,cooling and softening[2].
The main components of C.intybus are sesqui-terpene lactones,such as lactucin,8-deoxylactucin, lactupicrin and11b-dihydro-terpene derivatives[3], which are responsible for the bitter taste of this plant.Other components are coumarins,such as cichoriin,esculin,umbelliferone,scopoletin and
Mycopathologia(2005)160:85–92óSpringer2005 DOI:10.1007/s11046-004-6635-2
6,7-dihydroxycoumarin[4],?avone derivatives (cichoric acid,chlorogenic acid,apigenin,quercitin) [5,6],carbohydrates(glucose,fructose and inulin) [7]and vitamins[8].
The components vary widely,not only from one cultivar to another,but also within a single cultivar,depending on which period of the year the crop is harvested[9]and also according to the method used for extract preparation[10,11].
The function of the secondary metabolites of chicory could perhaps be connected with a passive defence of the plant against pathogens:in fact a study by Monde et al.[12]showed that the inoc-ulation of the bacterium Pseudomonas cichorii into the plant leads to the formation of a phytoalexin, the guaianolide cichoralexin,with an obvious defence function.It is not known if these defence mechanisms are also e?ective against phytopath-ogenic fungi,which,as a rule,attack the chicory; to our knowledge,the antifungal activity of Cichorium intybus extracts on soil-borne patho-gens has never been studied before.
The purpose of the present work was to eval-uate the e?cacy of chicory extracts on the growth of some groups of pathogenic fungi:some phyto-pathogenic fungi and some fungi parasitic on man and other animals.The latters,known as derma-tophytes,are keratinophilic and keratinolytic,i.e. they are able to digest and use keratin and keratin-like substrates causing diseases known as tineas. Dermatophytes belong to three ecological groups: geophiles(such as Microsporum gypseum and Nannizzia cajetani),that mainly live in the soil, zoophiles(such as Trichophyton mentagrophytes), essentially pathogenic for animals,and anthropo-philes(such as Epidermophyton?occosum,Trich-ophyton rubrum and Trichophyton tonsurans) which generally only infect man.
Materials and methods
Plant material
The plant material was the biennial Cichorium intybus L.var.‘Rosso di Chioggia’,cv.medium-initial,kindly provided by the‘Centro Sperimen-tale Orto?oricolo di Veneto Agricoltura,Po di Tramontana’(Rosolina,Rovigo,Italy).Plants belonging to selection line‘ea1°p5a/38-7-7-6’(C2) were planted in the nursery and,after30days,the plantules were transplanted to the open?eld, following the established cultivation technique [9,13].After60days,for the study on antifungal activity,samples were taken,harvesting,as plant portion,the roots,as they have an higher content of guaianolides than that of the head and outer leaves [7,10].
Preparation of chicory extracts
To have the best results we modi?ed the procedure described by Pyrek[14];our extraction method is the following:200g of dried and pulverized roots were put in a solid–liquid Soxhlet extractor with1000ml of acetone at50°C for24h;then,the acetone was replaced with further1000ml of pure acetone and the extraction continued for24h,obtaining an exhaustive extraction.At this point the acetone extracts(2000ml)were blended and concentrated with a Buchi Rotavapor set at40°C;this solution was then puri?ed for24h with hexane(1000ml) with a liquid–liquid Soxhlet extractor to eliminate lipophilic compounds.The aqueous phase,con-taining hydrophilic substances such as guaianolides, was then separated from hexane and reduced to 100ml in the Rotavapor kept at70°C.Finally the extract was subjected to chromatography. Sesquiterpene lactones
The main sesquiterpene lactones present in the?rst-year-growth samples of C.intybus var.‘Rosso di Chioggia’were the guaianolides8-deoxylactucin and11b,13-dihydrolactucin.These were isolated from the roots in accordance with procedures described above.The chemical–physical character-istics(UV,MS,NMR,TLC,HPLC)are compara-ble to those reported in literature[14–17].The qualitative and quantitative determination of the two guaianolides was performed by an automated multiple development high-performance thin-layer chromatographic analysis(AMD/HPTLC)(Camag, Switzerland)as described by Poli et al.[7].The concentrations of8-deoxylactucin and11b,13-dihy-drolactucin were determined in10samples of the product;the mean amount of8-deoxylactucin and 11b,13-dihydrolactucin contained in the extracts, after?ltration on Millipore0.22l m,were respec-tively240.75(standard deviation 3.1)and50.06 (standard deviation1.5)l g/ml.These mean amounts
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were taken as a reference for experiments of antifungal activity for crude extract and pure compounds.
We used four di?erent doses of the extract:1%, 2%,4%,and20%,corresponding respectively to 2.5,5.0,10.0and50.0l g/ml of8-deoxylactucin and to0.5,1.0,2.0and10.0l g/ml of11b,13-di-hydrolactucin.
One preliminary experiment was performed on one fungus with pure isolated8-deoxylactucin and 11b,13-dihydrolactucin at a single dose of10l g/ ml,where the guaianolides were used separately as standards.
Test organisms
Two groups of fungi were employed as test organisms:dermatophytes and phytopathogens. Dermatophytes:Epidermophyton?occosum (Hartz)Langeron&Milochevitch,strain no. 358.93(CBS),Trichophyton rubrum(Castellani) Sabouraud strain no4321(IHME),Trichophyton mentagrophytes(Robin)Blanchard strain no. 160.66(CBS),Trichophyton tonsurans var.sulfur-eum Malmstem strain no729.88(CBS),Tricho-phyton violaceum Bodin strain no.459.61(CBS), Microsporum gypseum(Bodin)Guiart and Grigo-rakis strain no.3999(IHME),Nannizzia cajetani Ajello strain no.3441(IHME).Phytopathogens: Botrytis cinerea Micheli strain no.48339(ATCC), Fusarium moniliforme Sheldon strain no.36541 (ATCC),Pythium ultimum Trow strain no.58812 (ATCC),Phoma betae Frank(Oud),Alternaria sp.
The CBS fungi were purchased from Centraal Bureau Voor Schimmelcultures,Baarn,The Netherlands;the IHME fungi were purchased from Institute of Hygiene and Epidemiology-Mycology,Brussels,Belgium;the ATCC fungi were purchased from American Type Culture Collection,Rockville,Maryland,USA;Phoma betae and Alternaria were kindly supplied by Prof.
G.D’Ercole,Plant Pathology Institute,University of Bologna,Italy.
The fungi were maintained in liquid nitrogen,in vials containing the appropriate culture medium: (a)Sabouraud Dextrose Agar(SDA)(Oxoid Ltd., England)for dermatophytes and(b)Potate Dex-trose Agar(PDA)(Oxoid Ltd.,England)for phy-topathogens;10%glycerol was added to media.
Media preparation with extracts of C.intybus
The extracts were?ltered on0.22l m Millipore ?lter before being added to the culture medium. The quantity of guaianolides in the extracts was determined by HPTLC chromatographic analyses with Scanner Camag II equipped with CATS Software3(CAMAG).
For the experiments,small mycelium disks of fungi were taken from mother cultures,grown on the appropriate medium(SDA for the dermato-phytes and PDA for the phytopathogens),and placed in Petri dishes containing free medium at 26±2°C until they reached the mid-log phase of growth.They were then transferred to Petri plates containing extract of C.intybus at the above-mentioned doses(1%,2%,4%,and20%).
Only on T.tonsurans,the most inhibited fun-gus,both the guaianolides were tested at the single concentration of10l g/ml;this dose corresponds to that of treatment with the extract at4%for8-deoxylactucin and at20%for
Table1.Percentage of growth inhibition of seven dermatophytes by Cichorium intybus extract evaluated on the8th day from the treatment onset(kept as0time)
Extract
1%2%4%20%
Epidermophyton?occosum 2.1±0.8 3.6±1.122.86±0.730.58±0.5 Trichophyton rubrum 1.4±1.2 2.8±1.819.25±0.658.54±0.9 T.tonsurans var sulfureum9.9±0.924.8±1.336.8±0.588.65±1.5 Trichophyton violaceum7.3±1.115.2±0.640.9±1.454.5±1.3 Trichophyton mentagrophytes 2.6±1.823.6±0.730.2±1.034.8±2.0 Microsporum gypseum)10.4±0.8)4.9±1.79.65±1.425.9±1.4 Nannizzia cajetani)11.7±0.9)3±0.218.2±0.826.1±0.7
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11b,13-dihydrolactucin(see Table1);this single preliminary test was carried out due to scantiness of isolated standards.
The fungal growth was evaluated by measuring the diameter of the cultures for8(dermatophytes) or6(phytopathogens)days from the treatment onset(kept as0time).All of the experiments were prepared in double quantity and were all repeated twice.
Electron microscopy
For SEM observations,the most sensitive fungus Trichophyton tonsurans var.sulfureum,was chosen and routinely processed as previously described [18].The youngest hyphae from untreated and for 24-h-treated mycelia with1–20%chicory extract were?xed with6%glutaraldehyde(GA)in a 0.1M sodium cacodylate bu?er,pH6.8,for24h at4°C,washed with the same bu?er solution and brie?y(1h)post?xed with1%osmium tetroxide (OsO4)in the same bu?er.The samples were then dehydrated in a graded series of acetone,critical point dried and gold coated with an S150Sputter coater(Edwards).SEM observations were per-formed with a Cambridge Stereoscan360scanning electron microscope at20kV owned by the Electron Microscopy Center of University of Ferrara,Italy. Results
Study of the antifungal activity of the Cichorium intybus root extracts started out with the mea-surement of fungal growth.
The response of dermatophytes to treatment with chicory extracts(Table1)varied greater from fungus to fungus;nevertheless it was shown to be dose-dependent,as greater inhibition of growth was observed as the concentration of the extract increased.
At the lowest doses(1and2%),the growth was poorly inhibited,and in two fungi,the geophilic M.gypseum and N.cajetani,it even increased in comparison with the respective untreated controls (=negative inhibition).At the higher doses growth inhibition was stronger,varying,at20%concen-tration,from the smallest value=25.9%,for M. gypseum,to the highest value?88.65%for T. tonsurans var.sulfureum.Nevertheless,even at the higher concentrations,the best results,were in the anthropophilic fungi T.tonsurans,T.rubrum and T.violaceum,with the exception of E.?occosum, which,after treatment with20%extract was only inhibited30.58%.
The zoophilic dermatophyte T.mentagro-phytes,showed an intermediate inhibition,whereas the geophilic M.gypseum and N.cajetani were the least inhibited.
The results of the growth inhibition on the phytopathogenic fungi are reported in Table2. They were unfortunately,disappointing,the extract being ine?ective on treated fungi,with the exception of Alternaria,treated with the higher doses,and of Pythium.This last fungus was the only one which showed a dose–dependent inhibi-tion of growth after treatment with chicory extract at all doses,whereas the other fungi,not only were not inhibited,but grew even more than the untreated controls.
The most sensitive fungus,T.tonsurans var. sulfureum,was also treated with the two pure isolated guaianolides:8-deoxylactucin and11b, 13-dihydrolactucin.Because of lack of availability of isolated standards,only one concentration was used:10l g/ml.This dose corresponds to that of treatment with the extract at4%for8-deoxylac-tucin and at20%for11b,13-dihydrolactucin.This
Table2.Percentage of growth inhibition of?ve phytopathogens on the6th day of treatment with Cichorium intybus extract
Extract
1%2%4%20%
Botrytis cinerea)33.5±1.4)23.4±1.8)14.8±0.7)10.75±1.9 Fusarium moniliforme)18.0±0.6)11.9±1.1)9.0±0.4)0.5±0.3 Pythium ultimum7.2±1.112.4±1.432.4±1.736.1±1.6 Phoma betae)17.3±0.5)10.1±0.7)7.8±1.2 4.2±0.3 Alternaria sp)8.6±1.6)5.0±1.0 6.2±0.923.0±1.2 88
preliminary test indicated that the inhibiting activity of chicory was due,at least partially,to the two lactones:growth inhibition by each guaiano-lide was 28.7%by 8-deoxylactucin and 18.5%by 11b ,13-dihydrolactucin.As a control of the activ-ity,the known antifungal miconazole was used,which blocked the growth of T.tonsurans when it is used at doses between 2and 10l g/ml.
Macroscopic observation of the same fungus,left for 15days in a Petri dish containing the chicory extract,showed an interesting aspect:the mycelium appeared raised up from the culture medium,meaning that the antifungal substances were active for a rather long time.T.tonsurans,var.sulfureum was chosen also for SEM analyses:it was treated for 24h with doses varying from 1%to 20%,then it was harvested for observation.SEM observations of the outermost,and thus youngest,portions of the control mycelium
showed normally linear hyphae with a tapered apex and slightly warty wall (Figure 1a).In the innermost portion of the samples,abundant microconidia were present:they were tear-drop or club-shaped,4–4.5-l m long and 1.6–2l m wide,and borne along the sides of widened hyphae (Figure 1b).After 24h of contact with C ichorium extract,T.tonsurans showed morphologic anom-alies in comparison with the untreated control of the same age,which became more and more severe as the dose of the extract increased.The hyphae became warped and all portions of the mycelium,also the youngest,showed an amor-pho-?brillar extruded material,which,at lower doses of treatment (1–4%),seemed to bridle the microconidia (Figure 1c),while,at the higher doses (20%),it appeared as an abundant amor-phous substance that permeated the twisted hyphae (Figure
1d).
Figure 1.Control and treated samples of T.tonsurans var.sulfureum observed at SEM.Bar ?5l m.(a)Linear-shaped hyphae of control Trichophyton from the youngest portion of the mycelium.(b)Many single-cell microconidia emerging from a conidiophore hypha from the innermost portion of the untreated mycelium.(c)Detail of youngest portion of mycelium treated for 24h with 2%chicory root extract,showing amorphous material bridling hyphae and conidia.(d)Twisted hyphae incorporated in abundant amorphous extruded material,in the fungus treated for 24h with 20%chicory root extract.
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Discussion
The results show that,on the whole,the C.intybus extracts have an interesting activity,even if it dif-fered between the tested fungi.
This activity could be due to the presence in the phytocomplex of various secondary metabo-lites.These could be the components that make C.intybus a plant free from herbivore attack and distasteful to some insects.In fact,the chicory plant is well-known as a source of several sesquiterpene lactones,?avonoids,coumarins,ca?eic acid deriv-atives and phenolics that have been implicated as feeding deterrents or allelopathic agents[7,15,19]. Several sesquiterpene lactones,known as‘bitter principles’,with over500types,are present in Asteraceae plants,where they are the characteristic constituents of this family,except the tribe Tagetae [20].The di?erent types of molecules and the great variation in the content of sequiterpene lactones found in several genera and species belonging to this family have been also considered in chemo-taxonomic studies[21].
Pickman[22]reviewed the biological activity of sesquiterpene lactones,among which there was also antifungal activity,but there was no ref-erence to the sesquiterpene lactones of chicory. This plant is known to contain several sesquiter-pene lactones,[7,23],particularly in the roots[10]. From the extracts of roots of C.intybus var.‘Rosso di Chioggia’has been isolated two guaianolides of di?erent chemical structure:8-de-oxylactucin and11b,13-dihydrolactucin.8-de-oxylactucin has a c-lactone-ring coupled with an exo-a-methylene group,which has been shown to be an essential requisite for cytotoxicity[22], whereas11b,13-dihydrolactucin has two hydroxyl groups that can be easily esteri?ed.Thus,both the lactones could be the responsible for biological activity of the extracts,as demonstrated here by the experiments done with the two pure isolated lactones.
As the growth inhibitions exerted by single lactones were lower than those observed with the extract containing the same quantity of the8-de-oxylactucin(10l g/ml?4%extract)and the 11b,13-dihydrolactucin(10l g/ml?20%extract), we can hypothesize that other substances such as coumarins and?avonoids,present in the phyto-complex,have antifungal activity.It is well-known that some coumarins exert a profound cytotoxic activity on the dermatophytes[24]and also that some?avonoids have antifungal e?ects[25,26].
The response of di?erent fungi to treatment with chicory extract is also interesting.The great-est inhibitory e?ect on fungal growth was achieved on the dermatophytes,whereas it was less pro-nounced or even reversed on the phytopathogens. Among the dermatophytes,the anthropophilic species were the most a?ected by the treatment; the zoophilic species reacted in an intermediate manner,whereas the geophilic species were the least inhibited on the whole.Beyond the di?er-ences in the physiology of the individual fungal species,we think that such behaviour strictly cor-relates to their habitat.The guaianolides,which are normally contained in Asteraceae plants,can be present in the soil in reply to radical exudation or to decomposition of leaf litter.It is possible that fungi that live in the soil(either as mycelium or as sporigen forms),can gradually develop resistance to these secondary metabolites and that some fungi become able to utilize them for their metabolism and,thus,for their growth.
Such behaviour may be carried out by the phytopathogens B.cinerea,F.moniliforme,P.betae and Alternaria and by the geophilic dermatophytes N.cajetani and M.gypseum.All these fungi,when treated with chicory extract,showed an increase, instead of a decrease,in the diametrical growth of the colony in comparison with the untreated control.
Among the phytopathogens,only P.ultimum was poorly inhibited by C.intybus extract at all concentrations.This fact can be simply due to the highest sensitivity of this fungus as was observed before,after treatment with natural[27]and syn-thetic compounds[28].
Among the dermatophytes,the zoophilic T. mentagrophytes showed greater growth inhibition than that observed in geophilic fungi,probably because the fungi which parasitize animals were only partly?t for survival as saprophytes.Conse-quently they have less possibility of getting in contact with the substances contained in C.intybus and can establish only a mild resistance.The highest sensitivity to treatment was showed by the anthropophilic dermatophytes which,living as a rule on humans are unable to adapt or exploit the chicory secondary metabolites.The anomalous extrusion of materials out the wall observed by SEM in T.tonsurans,var.sulfureum,treated with the C.intybus extract,is similar to that previously
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observed in other dermatophytes treated with chemical synthetic antifungal substances[18]or other plant-derived antimycotics[29].Although all these compounds have di?erent modes of action, this anomaly can be seen as a generalized reaction to a treatment which a?ect the normal assembly of the various parietal components.
In conclusion,the extract of Cichorium intybus roots seems to be a possible source of antidermat-ophytic substances,making it a viable alternative to the synthetic chemical drugs currently used to treat illness caused by dermatophytes,whereas environmental compatibility makes chicory extract unsuitable for treating many diseases caused by phytopathogens.
Acknowledgements
This work was supported by research grants from MIUR-URST(Ministero dell’Istruzione, dell’Universita e della Ricerca-Area Universita e Ricerca Scienti?ca e Tecnologica)of Italy and from Veneto Agricoltura(Programma Comuni-tario Leader II–Intervento no36GAL Delta del Po).Special thanks are due to the sta?of the Electron Microscopy Center of Ferrara University and to Dr.I.Maresca and to Mr.A.Bertacchini for their skillful work.This work is dedicated to our dead colleague Arnaldo Donini. References
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Address for correspondence:Prof.Donatella Mares,Depart-ment of Natural and Cultural Resources,University of Ferrara, C.so Porta Mare2,I-44100,Ferrara,Italy
Phone:+39-532-293783;Fax:+39-532-208561
E-mail:mrd@dns.unife.it
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操作系统第四版-课后习题答案
第一章 作者：佚名来源：网络 1、有一台计算机，具有IMB 内存，操作系统占用200KB ，每个用户进程各占200KB 。如果用户进程等待I/O 的时间为80 % ，若增加1MB 内存，则CPU 的利用率提高多少？ 答：设每个进程等待I/O 的百分比为P ，则n 个进程同时等待刀O 的概率是Pn ，当n 个进程同时等待I/O 期间CPU 是空闲的，故CPU 的利用率为1-Pn。由题意可知，除去操作系统，内存还能容纳4 个用户进程，由于每个用户进程等待I/O的时间为80 % , 故： CPU利用率＝l-（80%)4 = 0.59 若再增加1MB 内存，系统中可同时运行9 个用户进程，此时：cPu 利用率＝l-（1-80%)9 = 0.87 故增加IMB 内存使CPU 的利用率提高了47 % : 87 ％/59 ％=147 % 147 ％-100 % = 47 % 2 一个计算机系统，有一台输入机和一台打印机，现有两道程序投入运行，且程序A 先开始做，程序B 后开始运行。程序A 的运行轨迹为：计算50ms 、打印100ms 、再计算50ms 、打印100ms ，结束。程序B 的运行轨迹为：计算50ms 、输入80ms 、再计算100ms ，结束。试说明（1 ）两道程序运行时，CPU有无空闲等待？若有，在哪段时间内等待？为什么会等待？( 2 ）程序A 、B 有无等待CPU 的情况？若有，指出发生等待的时刻。 答：画出两道程序并发执行图如下： （1）两道程序运行期间，CPU存在空闲等待，时间为100 至150ms 之间（见图中有色部分） （2）程序A 无等待现象，但程序B 有等待。程序B 有等待时间段为180rns 至200ms 间（见图中有色部分） 3 设有三道程序，按A 、B 、C优先次序运行，其内部计算和UO操作时间由图给出。
1、“整体对换从逻辑上也扩充了内存，因此也实现了虚拟存储器的功能”这种说法是否正确请说明理由。 答：上述说明法是错误的。整体对换将内存中暂时不用的某个程序及其数据换出至外存，腾出足够的内存空间以装入在外存中的、具备运行条件的进程所对应的程序和数据。虚拟存储器是指仅把作业的一部分装入内存便可运行作业的存储器系统，是指具有请求调入功能和置换功能，能从逻辑上对内存容量进行扩充的一种存储器系统，它的实现必须建立在离散分配的基础上。虽然整体对换和虚拟存储器均能从逻辑上扩充内存空间，但整体对换不具备离散性。实际上，在具有整体对换功能的系统中，进程的大小仍受到实际内存容量的限制。 2、某系统采用页式存储管理策略，拥有逻辑空间32页，每页为2KB，拥有物理空间1MB。 1）写出逻辑地址的格式。 2）若不考虑访问权限等，进程的页表有多少项每项至少有多少位 3）如果物理空间减少一半，页表结构应相应作怎样的改变 答：1）该系统拥有逻辑空间32页，故逻辑地址中页号必须用5位来描述，而每页为2KB，因此，页内地址必须用11位来描述。这样，可得到它的逻辑地址格式如下： 2）每个进程最多有32个页面，因此，进程的页表项最多为32项；若不考虑访问权限等，则页表项中只需给出页所对应的物理块号。1MB的物理空间可分成29个内存块，故每个页表项至少有9位。 3）如果物理空间减少一半，则页表中项表项数仍不变，但每项的长度可减少1位。 3、已知某系统页面长4KB，每个页表项为4B，采用多层分页策略映射64位的用户地址空 间。若限定最高层页表只占1页，则它可采用几层分页策略 答：方法一：由题意可知，该系统的用户地址空间为264B，而页的大小为4KB，故作业最多可有264/212（即252）个页，其页表的大小则为252*4（即254）B。因此，又可将页表分成242个页表页，并为它建立两级页表，两级页表的大小为244B。依次类推，可知道它的3、4、5、6级页表的长度分别是234B、224B、214B、24B，故必须采取6层分页策略。 方法二：页面大小为4KB=212B，页表项4B=22B，因此一个页面可以存放212/22=210个面表项，因此分层数=INT[64/10]=6层 4、对于表所示的段表，请将逻辑地址（0，137）、（1，4000）、（2，3600）、（5，230）转换 成物理地址。 答：[0,137]：50KB+137=51337； [1，4000]：段内地址越界；
一、 HanselandGretel______(live)nearaforestwithhisfatherandstepmother.Oneyear,theweather______(be)sodry thatnofood_____(grow).Thewifetoldherhusbandthatunlesshe________(leave)hischildren______(die)inthe forest,thewholefamilywoulddie.Gretel_________(hear)thattheirstepmotherplanned________(kill)herandh erbrother.ButHanselhadaplan________(save)himselfandhissister.Hewenttogetsomewhitestonesbeforehew enttobedthatnight.Thenextday,thewife_________(send)thechildrentotheforest.Hansel___________(drop)t https://www.doczj.com/doc/0e1577652.html,terthatnight,they________(see)thestonesbecauseoftheshiningmoon.Thestones__ ace)forthisistheHimalayas.TheHimalayasrunalongthe______________(southwest)partofChina.Ofallthem ountains,Qomolangma________(rise)thehighestandis____________(famous).Itis8,844.43metershighands oisverydangerous________(climb).Thickcloudscoverthetopandsnow__________(fall)veryhard.Evenmore serious_______(difficulty)includefreezingweatherconditionsandheavystorms.Itisalsoveryhard_____(take) inairasyougetnearthetop. Thefirstpeople_____(reach)thetopwereTenzingNorgayandEdmundHillaryonMay29,1953.ThefirstChi neseteam__(do)soinI960,whilethefirstwoman_____(succeed)wasJunkoTabeifromJapanin1975. Whydosomanyclimbersrisktheir_____(life)?Oneofthemain_______(reason)isbecausepeoplewant______(c hallenge)themselvesinthefaceofdifficulties. Thespiritoftheseclimbers_____(show)usthatweshouldnevergiveup____(try)toachieveourdreams.Itals
Folk Music 中国民乐 Beijing Opera 京剧 Local Operas 地方戏 Outline ?China, a nation of long history with profound culture, ?inherited and developed a great variety of traditional art forms which suit both refined and popular tastes 雅俗共赏. ?From the melodious and pleasant folk music to the elaborate and touching local dramas, ?from the simple but elegant inkwash painting(水墨画) to the flexible and powerful calligraphy, ?one can always discern the light of sparkling wisdom. ?Traditional Chinese arts have tremendously impressed the world. ?Chinese folk music, with strong nationalistic features, is a treasure of Chinese culture. ?As early as the primitive times, Chinese people began to use musical instruments, ?which evolved today into four main types categorized by the way they are played 吹拉弹打.materials they are made of （丝竹管弦）. stringed instrument 丝：弦乐器 wind instrument 竹：管乐器 ?吹：The first type is wind instrument 管乐器, as show in xiao （a vertical bamboo flute ）箫，flute 笛子, suona horn 唢呐, etc. ?拉：The second type is string instrument 弦乐器, represented by urheen 二胡, jinghu 京胡（a two-string musical instrument similar to urheen ）, banhu fiddle 板胡, etc.
操作系统期末考试（一） 一、单项选择题（在每小题的四个备选答案中，只有一个是正确的，将其号码写在题干的括号中。每小题2分，共20分） 1、文件系统的主要组成部分是（） A、文件控制块及文件 B、I/O文件及块设备文件 C、系统文件及用户文件 D、文件及管理文件的软件 2、实现进程互斥可采用的方法（） A、中断 B、查询 C、开锁和关锁 D、按键处理 3、某页式管理系统中，地址寄存器的低9位表示页内地址，则页面大小为（） A、1024字节 B、512字节 C、1024K D、512K 4、串联文件适合于（）存取 A、直接 B、顺序 C、索引 D、随机 5、进程的同步与互斥是由于程序的（）引起的 A、顺序执行 B、长短不同 C、信号量 D、并发执行 6、信号量的值（） A、总是为正 B、总是为负 C、总是为0 D、可以为负整数 7、多道程序的实质是（） A、程序的顺序执行 B、程序的并发执行 C、多个处理机同时执行 D、用户程序和系统程序交叉执行 8、虚拟存储器最基本的特征是（） A、从逻辑上扩充内存容量 B、提高内存利用率 C、驻留性 D、固定性 9、飞机定票系统是一个（） A、实时系统 B、批处理系统 C、通用系统 D、分时系统 10、操作系统中，被调度和分派资源的基本单位，并可独立执行的实体是（） A、线程 B、程序 C、进程 D、指令 二、名词解释（每小题3分，共15分） 1.死锁: 2.原子操作: 3.临界区: 4.虚拟存储器: 5.文件系统: 三、判断改错题（判断正误，并改正错误，每小题2分，共20分） 1、通道是通过通道程序来对I/O设备进行控制的。（） 2、请求页式管理系统中，既可以减少外零头，又可以减少内零头。（） 3、操作系统中系统调用越多，系统功能就越强，用户使用越复杂。（） 4、一个进程可以挂起自已，也可以激活自已。（） 5、虚拟存储器的最大容量是由磁盘空间决定的。（） 6、单级文件目录可以解决文件的重名问题。（） 7、进程调度只有一种方式：剥夺方式。（） 8、程序的顺度执行具有顺序性，封闭性和不可再现性。（） 9、并行是指两个或多个事件在同一时间间隔内发生，而并发性是指两个或多个事件在 同一时刻发生。（） 10、进程控制一般都由操作系统内核来实现。（） 四、简答题（每小题5分，共25分） 1、简述死锁产生的原因及必要条件。 2、什么是多道程序技术，它带来了什么好处？ 3、有结构文件可分为哪几类，其特点是什么？ 4、分时系统的基本特征是什么？ 5、分页系统与分段系统的区别主要在于哪些方面？