GRB 070714B - Discovery of the Highest Spectroscopically Confirmed Short Burst Redshift

发现神秘船英语阅读High-tech search vehicles found a famous shipwreck on the ocean floor near Antarctica,an international exploration team announced Wednesday.The famous polar explorer Ernest Shackleton's ship,named Endurance,sank in the dangerous and icy Weddell Sea in 1915.Search teams looked for the Endurance before,but were not able to find it because of the rough conditions.A group organized by the Falklands Maritime Heritage Trust used special cameras and search vehicles to find the Endurance.John Shears of Great Britain led the search team,which operated from a South African ice-breaking ship.He and the crew found the Endurance in good condition on the ocean floor about six kilometers from its last-recordedposition.Mensun Bound is the team's Director of Exploration.He said the team is feeling happy about the discovery."This is by far the finest said.Hecondition"brilliant."Shackleton's story of survival is one of the most famousHis 28-man crew was trying to make a land crossing of the South Pole,but never arrived on land.The crew members escaped the sinking ship and all made it home two years after the wreck.The men rowed over 1,000 kilometers on life boats and survived by eating seals and penguins.They eventually got help from people working in thewhaling industry far off the coast of the southern part of Argentina.The successful expedition to find the ship comes 100 years after Shackleton's death.Dan Snow,a British broadcaster and historian,was aboard the exploration ship.He said the ship itself has only been photographed and nothing was removed,as it is protected by the Antarctic Treaty.The treaty permits only peaceful,scientific observation and exploration of the area.一支国际探险队周三宣布，高科技搜索工具在南极洲附近的海底发现了一艘著名的沉船。

1909年,Boulenger [1]发现棕黑腹链蛇(Am-phiesma sauteri )。

1962年,Malnate [2]厘定了棕黑腹DOI:10.16605/ki.1007-7847.2023.07.0177湖南省爬行动物新纪录———华西腹链蛇及其系统发育分析收稿日期:2023-07-21;修回日期:2023-10-01;网络首发日期:2024-01-22基金项目:湖南高望界国家级自然保护区陆生脊椎动物调查与小灵猫种群监测与研究(GWJ202301);湖南省古丈县域生物多样性调查与研究(GZ202201)作者简介:黄杰(2001—),男,湖南邵阳人,学生,E-mail:*****************;*通信作者:吴涛(1992—),男,苗族,湖南湘西土家族苗族自治州人,讲师,主要从事动物分类及行为生态研究,E-mail:****************;张佑祥(1966—),男,苗族,湖南湘西土家族苗族自治州人,副教授,主要从事动物学研究,E-mail:*****************。

黄杰1,张自亮2,李辉3,杨鑫宇1,胡小龙1,唐依萍1,刘昕1,刘慧1,张佑祥1*,吴涛1*(1.吉首大学生物资源与环境科学学院,中国湖南吉首416000;2.湖南高望界国家级自然保护区管理局,中国湖南湘西自治州416308;3.湖南师范大学生命科学学院脊椎动物学实验室,中国湖南长沙410081)摘要:2023年5月24日于湖南省高望界国家级自然保护区(28°41′36″N,110°09′30″E;212m)采集到东亚腹链蛇属(Hebius )一雌性物种标本,经形态特征比较,符合华西腹链蛇(Hebius maximus )形态描述;基于线粒体cytb 基因构建的东亚腹链蛇属部分物种的贝叶斯系统发育树显示,该标本与华西腹链蛇(H.maximus )聚为一支,其遗传距离为1.7%~2.2%。

IEEE Std C57.124-1991Reconized as an American National Standard (ANSI)IEEE Recommended Practice for theDetection of Partial Discharge and the Measurement of Apparent Charge inDry-Type TransformersSponsorTransformers Committeeof theIEEE Power Engineering SocietyApproved June 27, 1991Reaffirmed February 6, 1997Institute of Electrical and Electronics EngineersApproved October 11, 1991Reaffirmed September 19, 1996American National Standards InstituteAbstract: IEEE Std C57.124-1991 covers the detection of partial discharges occurring in the insulation of dry-type transformers of their components and the measurement of the associated apparent charge at the terminals when alternating test voltage is applied. The wideband method is used. The detection system and calibrator characteristics are described, and the test procedure is established.Keywords: Apparent charge, corona, cost coil transformers, dry-type transformers, partial discharge, ventilated dry-type transformersThe Institute of Electrical and Electronics Engineers, Inc.345 East 47th Street, New York, NY 10017-2394, USACopyright © 1992 byThe Institute of Electrical and Electronics Engineers, Inc.All rights reserved. Published 1992Printed in the United States of AmericaISBN 1-55937-159-5No part of this publication may be reproduced in any form, in an electronic retrieval system or otherwise, without the prior written permission of the publisher.IEEE Standards documents are developed within the Technical Committees of the IEEE Societies and the Standards Coordinating Committees of the IEEE Standards Board. Members of the committees serve voluntarily and without compensation. They are not necessarily members of the Institute. The standards developed within IEEE represent a consensus of the broad expertise on the subject within the Institute as well as those activities outside of IEEE that have expressed an interest in participating in the development of the standard.Use of an IEEE Standard is wholly voluntary. The existence of an IEEE Standard does not imply that there are no other ways to produce, test, measure, purchase, market, or provide other goods and services related to the scope of the IEEE Standard. Furthermore, the viewpoint expressed at the time a standard is approved and issued is subject to change brought about through developments in the state of the art and comments received from users of the standard. Every IEEE Standard is subjected to review at least every five years for revision or reaffirmation. When a document is more than five years old and has not been reaffirmed, it is reasonable to conclude that its contents, although still of some value, do not wholly reflect the present state of the art. Users are cautioned to check to determine that they have the latest edition of any IEEE Standard.Comments for revision of IEEE Standards are welcome from any interested party, regardless of membership affiliation with IEEE. Suggestions for changes in documents should be in the form of a proposed change of text, together with appropriate supporting comments.Interpretations: Occasionally questions may arise regarding the meaning of portions of standards as they relate to specific applications. When the need for interpretations is brought to the attention of IEEE, the Institute will initiate action to prepare appropriate responses. Since IEEE Standards represent a consensus of all concerned interests, it is important to ensure that any interpretation has also received the concurrence of a balance of interests. For this reason IEEE and the members of its technical committees are not able to provide an instant response to interpretation requests except in those cases where the matter has previously received formal consideration.Comments on standards and requests for interpretations should be addressed to:Secretary, IEEE Standards Board445 Hoes LaneP.O. Box 1331Piscataway, NJ 08855-1331USAIEEE Standards documents are adopted by the Institute of Electrical and Electronics Engineers without regard to whether their adoption may involve patents on articles, materials, or processes. Such adoption does not assume any liability to any patent owner, nor does it assume any obligation whatever to parties adopting the standards documents.Foreword(This foreword is not a part of IEEE Std C57.124-1991, IEEE Recommended Practice for the Detection of Partial Discharge and the Measurement of Apparent Charge in Dry-Type Transformers.)This recommended practice for measuring partial discharge of dry-type transformers was conceived for the purpose of establishing a standardized method for conducting partial discharge tests of dry-type transformers. The results of the tests may be compared with various transformer designs and manufacturers to establish a partial discharge limit for dry-type transformers.This recommended practice follows the format of IEEE Std 454, IEEE Recommended Practice for the Detection and Measurement of Partial Discharge (Corona) During Dielectric Tests, and IEEE Std C57.113, IEEE Guide for Partial Discharge Measurement in Liquid-Filled Power Transformers and Shunt Reactors. Sections on current detection were purposely omitted, as this technique is normally not used for dry-type transformers.There is no recognized definition of “partial discharge-free"”when referring to partial discharge inception voltage or extinction voltage. An arbitrary sensitivity of 10 pC is suggested until such time as a more definitive standard is established.Various specifications are already written specifying partial discharge-free transformers from 1.1 p.u. operating voltage to 2.0 p.u. operating voltage. It is the intent of this recommended practice to encourage manufacturers of dry-type transformers and users of dry-type transformers to investigate and report the results of factory tests and field experience of partial discharge in dry-type transformers. It is recognized that Paschen's Law applies to the partial discharge intensity and extinction voltage of dry-type transformers. It is conceivable that a dry-type transformer would test partial discharge-free at 1.65 p.u. voltage at room temperature and be barely partial discharge-free at operating temperature for a Class 220C. system. This correlation should be verified with field experience and reported.The guide specifies no particular discharge testing instruments and systems. Several commercially available units are being used. A measuring system of discreet components readily available has been used for measuring partial discharge. Most manufacturers' laboratories have partial discharge-free HV test sets and oscilloscopes. The only additional components required to complete the detection circuit are a partial discharge-free coupling capacitor composed of two 60 kV, .002 mfd capacitors in series, and an inductance composed of a coil of magnet wire. Calibration is accomplished using a calibrated square wave generator and a calibrated coupling capacitor of .0001 mfd.The following two test procedures are proposed:1)To test partial discharge between the coil and ground, normally accomplished during the applied voltage test.2)The test procedure takes place during the induced voltage test to detect partial discharge within a coil. It issuggested that partial discharge measurements be made in both modes. The partial discharge measurement may be made during the normal sequence of tests, while the applied and induced voltage tests are being made.An alternative sequence is to conduct the partial discharge test immediately following the applied voltage test and induced voltage test.The high-voltage bus bars of high-voltage transformers sometimes cause nondestructive partial discharge. This partial discharge in no way affects the reliability of the transformer coils. It may be necessary to disconnect the bus bar from the coils before conducting the partial discharge test on only the coils in order to test for partial discharge in the transformer coils. A note should be added to any test reports stating that the bus bar was removed for the test.At the time this document was submitted to the Standards Board, the Working Group on Recommended Practice for the Detection of Partial Discharges and the Measurement of Apparent Charge in Dry-Type Transformers had the following members:A.D. Kline, (Chairman)B. F. Allen Roy Bancroft D. A. Barnard A. Bimbiris M. Cambre O. R. Compton J. FrankE. Gearhart R. Hayes R. H. HollisterJ. W. HuppA.M. IversenA. J. JonnattiS. P. KennedyE. KoenigM. L. ManningR. A. MarekM. I. MitelmanJ. J. NayW. F. PattersonR. L. ProvostJ. RoddenV. ThenappanR. E. Uptegraff, Jr.G. H. VaillancourtH. J. WindischThe following persons were on the balloting committee that approved this document for submission to the IEEE Standards Board:E. J. Adolphsen L. C. Aicher D. J. AllanB. AllenR. Allustriarti M. S. Altman J. C. Arnold J. AubinR. Bancroft D. Barnard D. L. Basel P. L. Bellaschi S. Bennon W. B. Binder J. V. Bonucchi J. D. Borst C. V. Brown O. R. Compton F. W. Cook J. L. Corkran D. W. Crofts J. N. Davis D. J. Douglas R. F. Dudley J. C. Dutton J. K. Easley J. A. Ebert D. J. Fallon F. L. Foster M. Frydman H. E. Gabel R. E. Gearhart D. W. Gerlach D. A. Gillies R. S. Girgis R. L. GrubbF. J. GryszkiewiczG. HallJ. H. HarlowF. W. HeinrichsW. R. HenningD. R. HightonP. J. HoeflerC. HoeselR. H. HollisterC. C. HoneyE. HowellsC. HurryG. W. IliffY. P. IijimaR. G. JacobsenD.C. JohnsonD. L. JohnsonA. J. JonnattiC. P. KappelerR. B. KaufmanJ. J. KellyW. N. KennedyJ.P. KinneyB. KlaponskiA.D. KlineE. KoenigJ. G. LackeyR. E. LeeH.F. LightS.R. LindgrenL.W. LongL. A. LowdermilkR. I. LoweM. L. ManningH. B. MargolisT. MassoudaJ. W. MatthewsJ. McGillC. J. McMillenW. J. McNuttS. P. MehtaC. K. MillerC. H. MillianR. E. MinkwitzM. MitelmanH. R. MooreW. E. MorehartR. J. MuselW. H. MutschlerE. T. NortonR. A. OlssonB. K. PatelW. F. PattersonH. A. PearceD. PercoL. W. PierceJ. M. PollittC. P. RaymondC. A. RobbinsL. J. SavioW. E. SaxonD. N, SharmaV. ShenoyW. W. SteinL. R. StenslandD. SundinL. A. SwensonD. S. TakachV. ThenappanR. C. Thomas J. A. Thompson T. P. Traub D. E. Truax W. B. Uhl R. E. Uptegraff, Jr.G. H. VaillancourtA. VeitchL. B. WagenaarR. J. WheartyA. L. WilksW. E. WrennA. C. WurdackE. J. YasudaAt the time this recommended practice was published, it was under consideration for approval as an American National Standard. The Accredited Standards Committee on Transformers, Regulators, and Reactors, C57, had the following members at the time this document was sent to letter ballot:Leo J. Savio, ChairJohn A. Gauthier, SecretaryOrganization of Representative Electric Light and Power Group...............................................................................................P.E. OrehekS. M. A. RizviF. StevensJ. SullivanJ. C. ThompsonM.C. Mingoia (Alt.) Institute of Electrical and Electronics Engineers......................................................................J. D. BorstJ. DavisJ. H. HarlowL. SavioH. D. SmithR. A. VeitchNational Electrical Manufacturers Association........................................................................G. D. CoulterP. DeweverJ. D. DouglasA. A. GhafourianK. R. LinsleyR. L. PlasterH. RobinR. E. Uptegraff, Jr.P. J. Hopkinson (Alt.)J. Nay (Alt.) Tennessee Valley Authority.......................................................................................................F. A. Lewis Underwriters Laboratories, Inc.................................................................................................W. T. O'GradyUS Department of Agriculture, REA........................................................................................J. BohlkUS Department of Energy, Western Area Power Administration.............................................D. R. TorgersonUS Department of the Interior, Bureau of Reclamation............................................................F. W. Cook, Sr.US Department of the Navy, Civil Engineering Carps.............................................................H. P. StickleyWhen the IEEE Standards Board approved this standard on June 27, 1991, it had the following membership:Marco W. Migliaro, ChairDonald C. Loughry, Vice ChairAndrew G. Salem, SecretaryDennis BodsonPaul L. BorrillClyde CampJames M. Daly Donald C. Fleckenstein Jay Forster*David F. Franklin Ingrid Fromm Thomas L. HannanDonald N. HeirmanKenneth D. HendrixJohn W. HorchBen C. JohnsonIvor N. KnightJoseph Koepfinger*Irving KolodnyMichael A. LawlerJohn E. May, Jr.Lawrence V. McCAllT. Don Michael*Stig L. NilssonJohn L. RankineRonald H. ReimerGary S. RobinsonTerrance R. Whittemore*Member EmeritusAlso included are the following nonvoting IEEE Standards Board liaisons:Fernando Aldana Satish K. AggarwalJames Beall Richard B. EngelmanStanley Warshaw Deborah A. CzyzIEEE Standards Project EditorCLAUSE PAGE1. Scope (1)2. Purpose (1)3. References (1)4. Definitions (2)5. Partial Discharge Detection System (3)5.1High-Voltage Coupling Circuit (3)5.2Measuring Impedance Unit (Z m) (4)5.3Filter Characteristics (5)5.4Display Unit (5)5.5Discharge Meter (6)5.6Basic Sensitivity (6)5.7Partial Discharge Detector Basic Sensitivity Test (6)6. Calibrator Characteristics (6)6.1Calibrating Capacitor Value (C q) (7)6.2Pulse Generator Rise Time and Decay Time (7)6.3Pulse Generator Amplitude (U o) (7)6.4Pulse Generator Output Impedance (Z o) (7)6.5Calibrator Output Level Adjustment (7)6.6Pulse Generator Frequency (7)7. Tests (7)7.1General Requirements (7)7.2Conditioning (8)7.3Requirements for the Test Voltage (8)7.4Transformer Connections (8)7.5Significance of Various Test Connections (8)7.6Choice of Test Procedure (9)7.7Disturbances (10)8. Bibliography (18)Annex (informative) Partial Discharge Recognition (24)IEEE Recommended Practice for the Detection and the Measurement of Partial Discharge in Dry-Type Transformers1. ScopeThis recommended practice applies to the detection of partial discharges occurring in the insulation of dry-type transformers or their components, and to the measurement of the associated apparent charge at the terminals when an alternating test voltage is applied.2. PurposePartial discharge measurements in dry-type transformers may preferably be made on the basis of measurement of the apparent charge. Relevant measuring systems are classified as narrow-band or wide-band systems. Both systems are recognized and widely used. Without giving preference to one or the other, it is the object of this document to describe the wide-band method. General principles of partial discharge measurements, including the narrow-band method, are covered in IEEE Std 454-19731 [8]2, IEC 270 (1981) [6]3and IEC 76-3 (1980) [5].3. ReferencesThe following publications should be used in conjunction with this document. When the standards referred to in this guide are superseded by a new revision approved by the relevant standards authority, the latest revision should apply.[1] ANSI C68.1-1968, Standard for Measurement of Voltage In Dielectric Tests.41This standard has been withdrawn, however, copies are available from the Institute of Electrical and Electronics Engineers, Inc., Service Center, 445 Hoes Lane, Piscataway, N.J. 08855, U.S.A.2The numbers in brackets refer to those listed in Section 4.3IEC publications are available from IEC Sales Department, Case Postale 131, 3 rue de Varembé, CH 1211, Genève 20, Switzerland/Suisse. IEC publications are also available in the United States from the Sales Department, American National Standards Institute, 11 West 42nd Street, 13th Floor, New York, NY 10036, USA.4ANSI publications are available from the American National Standards Institute, 11 West 42nd Street, 13th Floor, New York, NY 10036.IEEE Std C57.124-1991IEEE RECOMMENDED PRACTICE FOR THE DETECTION OF PARTIAL DISCHARGE [2] ASTM D1868-81 (1990-E01), Method for Detection and Measurement of Partial Discharge (Corona) Pulses in Evaluation of Insulation Systems.5[3] ASTM STP-669, Engineering Dielectrics, Vol. 1, Corona Measurement and Interpretation.[4] CIGRE Working Group 21-03, "Recognition of Discharges," Electra, No. 11, pp. 61-98, Dec, 1969.6[5] IEC 76-3 (1980), Power Transformers, Part 3: Insulation Levels and Dielectric Tests.7[6] IEC 270 (1981), Partial Discharge Measurements.[7] IEEE Std 436-1991, IEEE Guide for Making Corona (Partial Discharge) Measurements of Electronics Transformers (ANSI).8[8] IEEE Std 454-1973, IEEE Recommended Practice for the Detection and Measurement of Partial Discharge (Corona) During Dielectric Tests.[9] IEEE Std C57.113-1991, IEEE Guide for Partial Discharge Measurement in Oil-Filled Power Transformers and Shunt Reactors (ANSI).4. Definitionspartial discharge: A partial discharge within the terms of this document is an electric discharge that only partially bridges the insulation between conductors. The term “corona ” has also been used frequently with this connotation. Such usage is imprecise and is gradually being discontinued in favor of the term “partial discharge.”apparent charge (terminal charge): The apparent charge (q) of a partial discharge is that charge which, if it could be injected instantaneously between the terminals of the test object, would momentarily change the voltage between its terminals by the same amount as the partial discharge itself. The apparent charge should not be confused with the charge transferred across the discharging cavity in the dielectric medium. Apparent charge within the terms of this document is expressed in coulombs, abbreviated C. One pC is equal to 10-12 coulombs.repetition rate(n).: The partial discharge pulse repetition rate (n) is the average number of partial discharge pulses per second measured over a selected period of time.acceptable terminal partial discharge level: The acceptable terminal partial discharge level is that specified maximum terminal partial discharge value for which measured terminal partial discharge values exceeding the said value are considered unacceptable. The method of measurement and the test voltage for a given test object should be specified with the acceptable terminal partial discharge level.voltage related to partial discharges: Voltage within the terms of this document is the phase-to-ground alternating voltage for applied tests (Fig 1) or terminal to terminal alternating voltage for induced voltage tests (Fig 8). Its value is expressed by its peak value divided by the square root of two.partial discharge inception voltage: The lowest voltage at which partial discharges exceeding a specified level are observed under specified conditions when the voltage applied to the test object is gradually increased from a lower value. This voltage is expressed as the peak value divided by the square root of two.5ASTM publications are available from the American Society for Testing and Materials, Customer Service Dept., 916 Race Street, Philadelphia, P.A. 19103, U.S. A.6CIGRE publications are available from the International Conference on Large-Voltage Electric Systems, 112 Boulevard Haussman, F-75008 Paris, France.7IEC publications are available from IEC Sales Department, Case Postale 131, 3 rue de Varembé, CH 1211, Genève 20, Switzerland/Suisse. IEC publications are also available in the United States from the Sales Department, American National Standards Institute, 11 West 42nd Street, 13th Floor, New York, NY 10036, USA.8IEEE publications are available from the Institute of Electrical and Electronics Engineers, Inc., Service Center, 445 Hoes Lane, Piscataway, N.J. 08855, U.S. A.partial discharge extinction voltage: The voltage at which partial discharges exceeding a specified level cease under specified conditions when the voltage is gradually decreased from a value exceeding the inception voltage. This voltage is expressed as the peak value divided by the square root of two.partial discharge-free test voltage: The partial discharge-free test voltage is a specified voltage, applied in accordance with a specified test procedure, at which the test object should not exhibit partial discharges above the acceptable energized background noise level.energized background noise level: The energized background noise level stated in pC is the residual response of the partial discharge measurement system to background noise of any nature after the test circuit has been calibrated and the test object is energized at a maximum of 50% of its nominal operating voltage.acceptable energized background noise level: The acceptable energized background noise level present during test should not exceed 50% of the acceptable terminal discharge level, and in any case, should be below 100 pC (5 pC if an acceptable terminal discharge level of 10 pC is required.)5. Partial Discharge Detection System(Figs 9 and 10 taken from ASTM STP669)The partial discharge detection system comprises the following components:1) a high-voltage coupling circuit (C1, C v)2) a measuring impedance unit (Z m consisting of R m, C2 and L)3)an amplifier and filter circuit4) a display unit5) a discharge meter6) a calibrator (C q, V l)7) a source filter (Z optional)5.1 High-Voltage Coupling CircuitThe purpose of the high-voltage coupling circuit is to allow the connection of the measuring impedance (Z m) to the high-voltage terminal of the transformer under test. In other types of high-voltage equipment, a single, low-capacitance high-voltage capacitor is usually used for this purpose, but in transformers, the equivalent terminal capacitance is usually very low, so a substantial amount of signal is normally produced by partial discharge of only a few pC, and measurement sensitivity is not a problem. At the same time, due to standing waves within the winding, a certain amount of signal cancellation may occur if the bandwidth is not sufficiently wide. Therefore, to insure that the input circuit of the partial discharge detection system does not act as a differentiator and reduce the total bandwidth of the system, it has been found that a high value for the coupling capacitor is necessary to produce a long-time constant of the input circuit. Even then, however, the low equivalent terminal capacitance of the transformer, usually less than 500 pF, will limit this time constant and it may not be possible to make it sufficiently long. Therefore, the use of a single coupling capacitor is not recommended. On the other hand, a satisfactory time constant can always be obtained by using a second capacitor (C2) as part of the measurement impedance, and this is the recommended method.As shown in Figs 9 and 10, high-voltage capacitor C1, and low-voltage capacitor C2, will form a voltage divider. This voltage divider will reduce the sensitivity of the measurement. To make sure that both the sensitivity is still sufficient and the time constant is sufficiently long, the values of C1, C2, and L should respect the conditions below:(1)≥C1100pF(2)where R m is the parallel resistive part of the measuring impedance unit (Z m ). The value of R m should be determined from the particular partial discharge instrument that is used.Example:For f L = 70kHz ,R m = 2.5k Ω and C 1 = 100pFA value of 1000 pF may be chosen for C 2 since 1000 pF ≥ 909 pF and (3)In cases where an RLC measurement impedance is used, the value of L should satisfy the equation below. This will ensure that the measurement bandwidth is unaffected by the presence of L .(4)If the transformer to be tested is fitted with a capacitive bushing tap, then this can be used directly as the high-voltage coupling circuit, and a separate coupling capacitor C 1 is not needed.5.2 Measuring Impedance Unit (Z m )The measuring impedance unit (Z m ) is located physically close to the high-voltage coupling circuit and serves two main purposes:1)It attenuates the test voltage present on the high-voltage coupling circuit to a safe value for measurement of partial discharge signals;2)It matches the amplifier and filter circuit to the high-voltage coupling circuit in insuring a fiat frequencyresponse across the full measurement bandwidth.The measuring impedance unit (Z m )should be configured in such a way as to permit test voltage level monitoring and to observe the phase relationship between the test voltage and the partial discharge pulses; this technique helps to identify the nature of the discharges.As shown in Figs 9 and 10, capacitor C v , whose capacitance value should be chosen to be at least 500 times that of C 1,may be placed in either one of the following two positions:1)In series with inductor L (Fig 9 or 10), or 2)In series with the low-voltage side of high-voltage capacitor C 1 (Fig 10.)C 212llf L R m -------------------≥C 216.28x 70000x 2500,----------------------------------------------909pF ==1000100-----------1015≤=L 25006.28x 70000,------------------------------- 5.7mH ==C 2C 1------15≤L R m 2llf L -----------≥Figure 9 shows the preferred position for C v since the input impedance of the display unit does not shunt the measurement impedance and can be neglected. However, some voltage will reach the input of the amplifier and filter circuit and may cause it to saturate. This voltage can be decreased by increasing the value of C v until it is less than 5V . If saturation occurs, a 20 nF low-voltage capacitor may be placed in series with the input of the amplifier and filter circuit as shown to decouple voltage at the excitation frequency.In the cases where one can not be absolutely certain that saturation of the amplifier will not occur, it is then advised to place C v in the position shown in Fig 10. The impedance of the display circuit will now shunt the measurement impedance and its input capacitance will need to be considered to calculate the value of C 2, as it will add to it.5.2.1 Lower and Upper Cut-Off Frequencies (f L and f H )The lower and upper cut-off frequencies f L and f H , respectively, are the frequencies at which the response to a constant sinesoidal input voltage has fallen by 6 db from the maximum value occurring inside the recommended bandwidth.f L should be located in the range from 70 to 120 kHz to minimize the effect of winding attenuation on partial discharge signals, and at the same time, to provide adequate rejection of SCR-generated noise present in manufacturing plants.An upper limit on f H of 300 kHz is usually necessary to prevent broadcast stations from interfering with the partial discharge measurement.5.3 Filter CharacteristicsThe filter characteristics of the partial discharge detection circuit should be such as to provide attenuation of at least 50db at 25 kHz, of at least 60 db at 15 kHz and below, and of at least 20 db at 500 kHz and above, with respect to the response at the geometric mean frequency (f C ) of the system pass bandwidth that is given by:The filter may be combined with an amplifier to form an active filter. Care should be taken to prevent the saturation of the filter input by the presence of the applied test voltage.5.3.1 Bandwidth ∆fThe bandwidth ∆f is defined as:∆f = f H − f LThe bandwidth should not be less than 100 kHz. A wider bandwidth provides a response whose level is less sensitive to the location of a partial discharge pulse along a transformer winding and is, therefore, more uniform. A bandwidth wider than 100 kHz is preferable, but may lead to background noise problems.5.3.2 LinearityThe instrument circuit, display unit, and discharge meter should be linear within plus or minus 10% of full scale in the range of 50 to 1000 pC.5.4 Display UnitThe display unit should be a cathode ray oscilloscope with a linear, rectangular, or an elliptical time-base. In all cases,the time-base should be synchronized to the test voltage, and at least 98% of a full cycle should be displayed. The phase relationship of the partial discharges to the test voltage should be easy to determine. A suitable graticule should be provided.f c f L f H •().5=。

Annu.Rev.Mater.Res.2001.31:1–23Copyright c2001by Annual Reviews.All rights reserved S YNTHESIS AND D ESIGN OF S UPERHARDM ATERIALSJ Haines,JM L´e ger,and G BocquillonLaboratoire de Physico-Chimie des Mat´e riaux,Centre National de la Recherche Scientifique,1place Aristide Briand,92190Meudon,France;e-mail:haines@cnrs-bellevue.fr;leger@cnrs-bellevue.frKey Words diamond,cubic boron nitride,carbon nitride,high pressure,stishovite s Abstract The synthesis of the two currently used superhard materials,diamond and cubic boron nitride,is briefly described with indications of the factors influencing the quality of the crystals obtained.The physics of hardness is discussed and the importance of covalent bonding and fixed atomic positions in the crystal structure,which determine high hardness values,is outlined.The materials investigated to date are described and new potentially superhard materials are presented.No material that is thermodynamically stable under ambient conditions and composed of light (small)atoms will have a hardness greater than that of diamond.Materials with hardness values similar to that of cubic boron nitride (cBN)can be obtained.However,increasing the capabilities of the high-pressure devices could lead to the production of better quality cBN compacts without binders.INTRODUCTIONDiamond has always fascinated humans.It is the hardest substance known,based on its ability to scratch any other material.Its optical properties,with the highest refraction index known,have made it the most prized stone in jewelry.Furthermore,diamond exhibits high thermal conductivity,which is nearly five times that of the best metallic thermal conductors (copper or silver)at room temperature and,at the same time,is an excellent electrical insulator,even at high temperature.In industry,the hardness of diamond makes it an irreplaceable material for grinding tools,and diamond is used on a large scale for drilling rocks for oil wells,cutting concrete,polishing stones,machining,and honing.The diamonds used for industry are now mostly man-made because their cutting edges are much sharper than those of natural diamonds,which have been eroded by geological time.The synthesis of diamond has been a goal of science from Moissant at the end of the nineteenth century to the successful synthesis under high pressures in 1955(1).However,diamond has a major drawback in that it reacts with iron and cannot be used for machining steel.This has prompted the synthesis of a second superhard0084-6600/01/0801-0001$14.001A n n u . R e v . M a t e r . R e s . 2001.31:1-23. D o w n l o a d e d f r o m a r j o u r n a l s .a n n u a l r e v i e w s .o r gb y C h i n e s e Ac ade m y of S c i e n c e s - L i b r a r y o n 05/16/09. F o r p e r s o n a l u s e o n l y .2HAINESL ´EGERBOCQUILLONmaterial,cubic boron nitride (cBN),whose structure is derived from that of dia-mond with half the carbon atoms being replaced by boron and the other half by nitrogen atoms.The resulting compound is half as hard as diamond,but it does not react with iron and can be used for machining steel.Cubic boron nitride does not exist in nature and is prepared under high-pressure high-temperature conditions,as is synthetic diamond.However,its synthesis is more difficult,and it has not been possible to prepare large crystals.Industry is thus looking for new superhard ma-terials that will need to be much harder than present ceramics (Si 3N 4,Al 2O 3,TiC).Hardness is a quality less well defined than many other physical properties.Hardness was first defined as the ability of one material to scratch another;this corresponds to the Mohs scale.This scale is highly nonlinear (talc =1,diamond =10);however,this definition of hardness is not reliable because materials of similar hardness can scratch each other and the resulting value depends on the specific details of the contact between the two materials.It is well known (2)that at room temperature copper can scratch magnesium oxide and at high temperatures cBN can scratch diamond (principle of soft indenter).Another,more accurate,way of defining and measuring hardness is by the indentation of the material by a hard indenter.According to the nature and shape of the indenter,different scales are used:Brinell,Rockwell,Vickers,and Knoop.The last two are the most frequently used.The indenter is made of a pyramidal-shaped diamond with a square base (Vickers),or elongated lozenge (Knoop).The hardness is deduced from the size of the indentation produced using a defined load;the unit is the same as that for pressure,the gigapascal (GPa).Superhard materials are defined as having a hardness of above 40GPa.The hardness of diamond is 90GPa;the second hardest material is cBN,with a hardness of 50GPa.The design of new materials with a hardness comparable to diamond is a great challenge to scientists.We first describe the current status of the two known super-hard materials,diamond and cBN.We then describe the search for new bulk super-hard materials,discuss the possibility of making materials harder than diamond,and comment on the new potentially superhard materials and their preparation.DIAMOND AND CUBIC BORON NITRIDE DiamondThe synthesis of diamond is performed under high pressure (5.5–6GPa)and high temperature (1500–1900K).Carbon,usually in the form of graphite,and a transi-tion metal,e.g.iron,cobalt,nickel,or alloys of these metals [called solvent-catalyst (SC)],are treated under high-pressure high-temperature conditions;upon heating,graphite dissolves in the metal and if the pressure and temperature conditions are in the thermodynamic stability field of diamond,carbon can crystallize as dia-mond because the solubility of diamond in the molten metal is less than that of graphite.Some details about the synthesis and qualities of diamond obtained by this spontaneous nucleation method are given below,but we do not describe the growthA n n u . R e v . M a t e r . R e s . 2001.31:1-23. D o w n l o a d e d f r o m a r j o u r n a l s .a n n u a l r e v i e w s .o r gb y C h i n e s e Ac ade m y of S c i e n c e s - L i b r a r y o n 05/16/09. F o r p e r s o n a l u s e o n l y .SUPERHARD MATERIALS 3of single-crystal diamond under high pressure,which is necessary in order to ob-tain large single crystals with dimensions greater than 1mm.Crystals of this size are expensive and represent only a very minor proportion of the diamonds used for machining;they are principally used for their thermal properties.It is well known that making diamonds is relatively straightforward,but control-ling the quality of the diamonds produced is much more difficult.Improvements in the method of synthesis since 1955have greatly extended the size range and the mechanical properties and purity of the synthetic diamond crystals.Depending on the exact pressure (P )and temperature (T )of synthesis,the form and the nature of the carbon,the metal solvent used,the time (t )of synthesis,and the pathways in P-T-t space,diamond crystals (3,4)varying greatly in shape (5),size,and fri-ability are produced.These three characteristics are used to classify diamonds;the required properties differ depending on the industrial application.Friability is related to impact strength.It is the most important mechanical property for the practical use of superhard materials,and low friability is required in order for tools to have a long lifetime.In commercial literature,the various types of diamonds are classed as a function of their uses,which depend mainly on their friabilities,but the numerical values are not given,so it is difficult to compare the qualities of diamonds from various sources.The friability,which is defined by the percentage of diamonds destroyed in a specific grinding process,is obtained by subjecting a defined quantity of diamonds to repeated impacts by grinding in a ball-mill or by the action of a load falling on them.The friability values depend strongly on the experimental conditions used,and only values for crystals measured under the same conditions can be compared.The effect of various synthesis parameters on their quality can be evaluated by considering the total mass of diamond obtained in one experiment,the distribution size of these diamonds,and the friability of the diamonds of a defined size.A first parameter is the source of the carbon.Most carbon-based substance can be used to make diamonds (6),but the nature of the carbon source has an effect on the quantity and the quality of synthetic diamonds.The best carbon source for diamond synthesis is graphite,and its characteristics are important.The effect of the density,gas permeability,and purity of graphite on the diamond yield have been investigated using cobalt as the SC (7).Variations of the density and gas permeability have no effect on the diamond yield,but carbon purity is important.The main impurity in synthetic graphite is CaO.If good quality diamonds are required,the calcium content should be kept below 1000ppm in order to avoid excessive nucleation on the calcium oxide particles.A second factor that alters the quality of diamonds is the nature of the SC.The friability and the size distribution are better with CoFe (alloy of cobalt with a small quantity of iron)than with invar,an iron-nickel alloy (Table 1:Ia,Ib;Figure 1a ).Another parameter is how the mixture of carbon and SC is prepared.When fine or coarse powders of intimately mixed graphite and SC are used,a high yield of diamonds with high friabilities is obtained (8).These diamonds are very small,A n n u . R e v . M a t e r . R e s . 2001.31:1-23. D o w n l o a d e d f r o m a r j o u r n a l s .a n n u a l r e v i e w s .o r g b y C h i n e s e A c a d e m y o f S c i e n c e s - L i b r a r y o n 05/16/09. F o r p e r s o n a l u s e o n l y .4HAINESL ´EGERBOCQUILLONTABLE 1Friabilities of some diamonds as a function of the details of the synthesis process fora selected size of 200–250µmSDA a MBS a 100+70Ia Ib IIa IIb IIc IIIa IIIb Synthesis CoFeInvar 1C-2SC 1C-1SC 2C-2SC Cycle A Cycle B detail stacking stacking stacking Friability 74121395053637250(%)aThe SDA 100+is among De Beers best diamond with a very high strength that is recommended for sawing the hardest stones and cast refractories.MBS 70is in the middle of General Electric’s range of diamonds for sawing and drilling.Other diamonds were obtained in the laboratory using a belt–type apparatus with a working chamber of 40mm diameter.(C,graphite;SC,solvent-catalyst.)with metal inclusions,and they are linked together with numerous cavities filled with SC.A favorable geometry in order to obtain well-formed diamonds is to stack disks of graphite and SC.The effect of local concentration has been exam-ined by changing the stacking of these disks (Table 1:IIa,IIb,IIc;Figure 1b ).The method of stacking modifies the local oversaturation of dissolved carbon and thus the local spontaneous diamond germination.For the synthesis of dia-mond,the heating current goes directly through the graphite-SC mixture.Because the electrical resistivity of the graphite is much greater than that of the SC,the temperature of the graphite is raised by the Joule effect,whereas that of the SC increases mainly because of thermal conduction.Upon increasing the thickness of the SC disk,the local thermal gradient increases and the dissolved atoms of carbon cannot move as easily;the local carbon oversaturation then enhances the spontaneous diamond germination.This enables one to work at lower tempera-tures and pressures,which results in slower growth and therefore better quality diamonds.Another important factor for the yield and the quality of the diamonds is the pathway followed in P-T-t space.The results of two cycles with the same final pressure and temperature are shown.In cycle A (Figure 1d ),the graphite-SC mixture reaches the eutectic melting temperature while it is still far from the equilibrium line between diamond and graphite;as a result spontaneous nucleation is very high and the seeds grow very quickly.These two effects explain the high yield and the poor quality and small size and high friability of the diamonds compared with those obtained in cycle B (Figure 1d ;see Table 1IIIa and IIIb and Figure 1c ).Large crystals (over 400µm)of good quality are obtained when the degree of spontaneous nucleation is limited.The pathway in P-T-t space must then remain near the graphite-diamond phase boundary (Figure 1d ),and the time of the treatment must be extended in the final P-T-t conditions.Usually,friability increases with the size of the diamonds.Nucleation takes place at the beginning of the synthesis when the carbon oversaturation is important,and the carbon in solution is then absorbed by the existing nuclei,which grow larger.A n n u . R e v . M a t e r . R e s . 2001.31:1-23. D o w n l o a d e d f r o m a r j o u r n a l s .a n n u a l r e v i e w s .o r g b y C h i n e s e A c a d e m y o f S c i e n c e s - L i b r a r y o n 05/16/09. F o r p e r s o n a l u s e o n l y .SUPERHARD MATERIALS5Figure 1Size distribution of diamonds in one laboratory run for different synthesis pro-cesses;effects of (panel a )the nature of the metal,(panel b )the stacking of graphite and metal disks,(panel c )the P-T pathway.(Panel d )P-T pathways for synthesis.1:graphite-diamond boundary and 2:melting temperature of the carbon-eutectic.The diamond synthesis occurs between the boundaries 1and 2.The growth time is about the same for all the crystals,thus those that can grow more quickly owing to a greater local thermal gradient become the largest.Owing to their rapid growth rate,they trap more impurities and have more defects,and therefore their friability is higher.Similarly,friability increases with the diamond yield.The diamonds produced by the spontaneous nucleation method range in size up to 800–1000µm.The best conditions for diamond synthesis correspond to a compromise between the quantity and the quality of the diamonds.A n n u . R e v . M a t e r . R e s . 2001.31:1-23. D o w n l o a d e d f r o m a r j o u r n a l s .a n n u a l r e v i e w s .o r g b y C h i n e s e A c a d e m y o f S c i e n c e s - L i b r a r y o n 05/16/09. F o r p e r s o n a l u s e o n l y .6HAINESL ´EGERBOCQUILLONCubic Boron NitrideCubic boron nitride (cBN)is the second hardest material.The synthesis of cBN isperformed in the same pressure range as that for diamond,but at higher tempera-tures,i.e.above 1950K.The general process is the same;dissolution of hexagonal boron nitride (hBN)in a solvent-catalyst (SC),followed by spontaneous nucle-ation of cBN.However,the synthesis is much more complicated.The usual SCs are alkali or alkaline-earth metals and their nitrides (9):Mg,Ca,Li 3N,Mg 3N 2,and Ca 3N 2.All these SCs are hygroscopic,and water or oxygen are poisons for the synthesis.Thus great care must be taken,which requires dehydration of the materials and preparation in glove boxes,to avoid the presence of water in the high-pressure cell.Furthermore,the above compounds react first with hBN to form inter-mediate compounds,Li 3BN 2,Mg 3B 2N 4,or Ca 3B 2N 4,which become the true SC.These compounds and the hBN source are electrical insulators,thus an internal furnace must be used,which makes fabrication of the high pressure cell more complicated and reduces the available volume for the samples.In addition,the chemical reaction involved is complicated by this intermediate step,and in gen-eral the yield of cBN is lower than for diamond.Work is in progress to determine in situ which intermediate compounds are involved in the synthesis process.The crystals of cBN obtained from these processes are of lower quality (Figure 2)and size than for diamond.Depending on the exact conditions,orange-yellow or dark crystals are obtained;the color difference comes from a defect or an excess of boron (less than 1%);the dark crystals,which have an excess of born,are harder.As in the synthesis of diamond,the initial forms of the SC source,hBN,play important roles,but the number of parameters is larger.For the source of BN,it is better to use pressed pellets of hBN powder rather than sintered hBN products,as the latter contain additives (oxides);a very fine powder yields a better reactivity.Doping of Li,Ca,or Mg nitrides with Al,B,Ti,or Si induces a change in the morphology and color of cBN crystals,which are dark instead of orange,are larger (500µm),have better shapes and,in addition,gives a higher yield (10).Use of supercritical fluids enables cBN to be synthesized at lower pressures and temperatures (2GPa,800K),but the resulting crystal size is small (11).Diamond and cBN crystals are produced on a large scale,and the main problem is how to use them for making viable tools for industry.Different compacts of these materials are made (12)for various pacts of diamonds are made using cobalt as the SC.The mixture is treated under high-pressure high-temperature conditions,at which superficial graphitization of the diamonds takes place,and then under the P-T-t diamond synthesis conditions so as to transform the graphite into diamond and induce intergranular growth of diamonds.The diamond compacts produced in this way still contain some cobalt as a binder,but their hardness is close to that of single-crystal pacts of cBN cannot be made in the same way because the SCs are compounds that decompose in air.Sintering without binders (13)is possible at higher pressures of about 7.5–8GPa and temperatures higher than 2200K,but these conditions are currently outside the range of thoseA n n u . R e v . M a t e r . R e s . 2001.31:1-23. D o w n l o a d e d f r o m a r j o u r n a l s .a n n u a l r e v i e w s .o r g b y C h i n e s e A c a d e m y o f S c i e n c e s - L i b r a r y o n 05/16/09. F o r p e r s o n a l u s e o n l y.SUPERHARD MATERIALS7Figure 2SEM photographs of diamond (top )and cBN (bottom )crystals of different qualities depending on the synthesis conditions (the long vertical bar corresponds to a distance of 100µm).Top left :good quality mid-sized diamonds of cubo-octahedral shape with well-defined faces and sharp edges;top right :lower quality diamonds;bottom left :orange cBN crystals;bottom right :very large black cBN crystals of better shapes.A n n u . R e v . M a t e r . R e s . 2001.31:1-23. D o w n l o a d e d f r o m a r j o u r n a l s .a n n u a l r e v i e w s .o r g b y C h i n e s e A c a d e m y o f S c i e n c e s - L i b r a r y o n 05/16/09. F o r p e r s o n a l u s e o n l y .8HAINESL ´EGERBOCQUILLONused in industrial pacts of cBN with TiC or TaN binders are ofmarkedly lower hardness because there is no direct bonding between the superhard crystals,in contrast to diamond compacts.In addition,they are expensive,and this has motivated the search for other superhard materials.SEARCH FOR NEW SUPERHARD MATERIALSOne approach for increasing hardness of known materials is to manipulate the nanostructure.For instance,the effect of particle size on the hardness of materials has been investigated.It is well known that high-purity metals have very low shear strengths;this arises from the low energy required for nucleation and motion of dislocations in metals.The introduction of barriers by the addition of impurities or grain size effects may thus enhance the hardness of the starting phase.In this case,intragranular and intergranular mechanisms are activated and compete with each other.As each mechanism has a different dependency on grain size,there can be a maximum in hardness as the function of the grain size.This effect of increasing the hardness with respect to the single-crystal value does not exist in the case of ceramic materials.In alumina,which has been thoroughly studied,the hardness (14)of fine-grained compacts is at most the hardness of the single crystal.When considering superhard materials,any hardness enhancement would have to come from the intergranular material,which would be by definition of lower hard-ness.In the case of thin films,it has been reported that it is possible to increase the hardness by repeating a layered structure of two materials with nanometer scale dimensions,which are deposited onto a surface (15).This effect arises from the repulsive barrier to the movement of dislocations across the interface between the two materials and is only valid in one direction for nanometer scale defor-mations.This could be suitable for coatings,but having bulk superhard materials would further enhance the unidirectional hardness of such coatings.In addition,hardness in these cases is determined from tests at a nanometer scale with very small loads,and results vary critically (up to a factor of three)with the nature of the substrate and the theoretical models necessary to estimate quantitatively the substrate’s influence (16).We now discuss the search for bulk superhard materials.Physics of HardnessThere is a direct relation between bulk modulus and hardness for nonmetallic ma-terials (Figure 3)(17–24),and here we discuss the fundamental physical properties upon which hardness depends.Hardness is deduced from the size of the inden-tation after an indenter has deformed a material.This process infers that many phenomena are involved.Hardness is related to the elastic and plastic properties of a material.The size of the permanent deformation produced depends on the resistance to the volume compression produced by the pressure created by the indenter,the resistance to shear deformation,and the resistance to the creation and motion of dislocations.These various types of resistance to deformation indicateA n n u . R e v . M a t e r . R e s . 2001.31:1-23. D o w n l o a d e d f r o m a r j o u r n a l s .a n n u a l r e v i e w s .o r g b y C h i n e s e A c a d e m y o f S c i e n c e s - L i b r a r y o n 05/16/09. F o r p e r s o n a l u s e o n l y .SUPERHARD MATERIALS 9Figure 3Hardness as a function of the bulk modulus for selected materials (r-,rutile-type;c,cubic;m,monoclinic).WC and RuO 2do not fill all the requirements to be superhard (see text).which properties a material must have to exhibit the smallest indentation possible and consequently the highest hardness.There are three conditions that must be met in order for a material to be hard:The material must support the volume decrease created by the applied pressure,therefore it must have a high bulk modulus;the material must not deform in a direction different from the applied load,it must have a high shear modulus;the material must not deform plastically,the creation and motion of the dislocations must be as small as possible.These conditions give indications of which materials may be superhard.We first consider the two elastic properties,bulk modulus (B)and shear modulus (G),which are related by Poisson’s ratio (ν).We consider only isotropic materials;a superhard material should preferably be isotropic,otherwise it would deform preferentially in a given direction (the crystal structure of diamond is isotropic,but the mechanical properties of a single crystal are not fully isotropic because cleavage may occur).In the case of isotropic materials,G =(3/2)B (1−2ν)/(1+ν);In order for G to be high,νmust be small,and the above expression reduces thenA n n u . R e v . M a t e r . R e s . 2001.31:1-23. D o w n l o a d e d f r o m a r j o u r n a l s .a n n u a l r e v i e w s .o r g b y C h i n e s e A c a d e m y o f S c i e n c e s - L i b r a r y o n 05/16/09. F o r p e r s o n a l u s e o n l y .10HAINESL ´EGERBOCQUILLONto G =(3/2)B (1−3ν).The value of νis small for covalent materials (typicallyν=0.1),and there is little difference between G and B:G =1.1B.A typical value of νfor ionic materials is 0.25and G =0.6B;for metallic materials νis typically 0.33and G =0.4B;in the extreme case where νis 0.5,G is zero.The bulk and shear moduli can be obtained from elastic constants:B =(c 11+2c 12)/3,G =(c 11−c 12+3c 44)/5.Assuming isotropy c 11−c 12=2c 44,it follows that G =c 44;Actually G is always close to c 44.In order to have high values of B and G,then c 11and c 44must be high with c 12low.This is the opposite of the central forces model in which c 12=c 44(Cauchy relation).The two conditions,that νbe small and that central forces be absent,indicate that bonding must be highly directional and that covalent bonding is the most suitable.This requirement for high bulk moduli and covalent or ionic bonding has been previously established (17–19,21–24)and theoretical calculations (19,25,26)over the last two decades have aimed at finding materials with high values of B (Figure 3).The bulk modulus was used primarily for the reason that it is cheaper to calculate considering the efficient use of computer time,and an effort was made to identify hypothetical materials with bulk moduli exceeding 250–300GPa.At the present time with the power of modern computers,elastic constants can be obtained theoretically and the shear modulus calculated (27).The requirement for having directional bonds arises from the relationship be-tween the shear modulus G and bond bending (28).Materials that exhibit lim-ited bond bending are those with directional bonds in a high symmetry,three-dimensional lattice,with fixed atomic positions.Covalent materials are much better candidates for high hardness than ionic compounds because electrostatic interac-tions are omnidirectional and yield low bond-bending force constants,which result in low shear moduli.The ratio of bond-bending to bond-stretching force constants decreases linearly from about 0.3for a covalent material to essentially zero for a purely ionic compound (29,30).The result of this is that the bulk modulus has very little dependence on ionicity,whereas the shear modulus will exhibit a relative de-crease by a factor of more than three owing entirely to the change in bond character.Thus for a given value of the bulk modulus,an ionic compound will have a lower shear modulus than a covalent material and consequently a lower hardness.There is an added enhancement in the case of first row atoms because s-p hybridization is much more complete than for heavier atoms.The electronic structure also plays an important role in the strength of the bonds.In transition metal carbonitrides,for example,which have the rock-salt structure,the hardness and c 44go through a maximum for a valence electron concentration of about 8.4per unit cell (31).The exact nature of the crystal and electronic structures is thus important for determin-ing the shear modulus,whereas the bulk modulus depends mainly on the molar volume and is less directly related to fine details of the structure.This difference is due to the fact that the bulk modulus is related to the stretching of bonds,which are governed by central forces.Materials with high bulk moduli will thus be based on densely packed three-dimensional networks,and examples can be found among covalent,ionic,and metallic materials.In ionic compounds,the overall structure isA n n u . R e v . M a t e r . R e s . 2001.31:1-23. D o w n l o a d e d f r o m a r j o u r n a l s .a n n u a l r e v i e w s .o r g b y C h i n e s e A c a d e m y o f S c i e n c e s - L i b r a r y o n 05/16/09. F o r p e r s o n a l u s e o n l y .principally defined by the anion sublattice,with the cations occupying interstitial sites,and compounds with high bulk moduli will thus have dense anion packing with short anion-anion distances.The shear modulus,which is related to bond bending,depends on the nature of the bond and decreases dramatically as a func-tion of ionicity.In order for the compound to have a high shear modulus and high hardness (Figure 4),directional (covalent)bonding and a rigid structural topology are necessary in addition to a high bulk modulus.A superhard material will have a high bulk modulus and a three-dimensional isotropic structure with fixed atomic positions and covalent or partially covalent ionic bonds.Hardness also depends strongly on plastic deformation,which is related to the creation and motion of dislocations.This is not controlled by the shear modulus but by the shear strength τ,which varies as much as a factor of 10for different materials with similar shear moduli.It has been theoretically shown that τ/G is of the order of 0.03–0.04for a face-centered cubic metal,0.02for a layer structure such as graphite,0.15for an ionic compound such as sodium chloride,and 0.25for a purely covalent material such as diamond (32).Detailed calculationsmustFigure 4Hardness as a function of the shear modulus for selected materials (r-,rutile-type;c,cubic).A n n u . R e v . M a t e r . R e s . 2001.31:1-23. D o w n l o a d e d f r o m a r j o u r n a l s .a n n u a l r e v i e w s .o r g b y C h i n e s e A c a d e m y o f S c i e n c e s - L i b r a r y o n 05/16/09. F o r p e r s o n a l u s e o n l y .。

·专家论坛·DOI： 10.3969/j.issn.1001-5256.2023.09.005精准医学时代胆囊癌的系统治疗——机遇与挑战并存张瑞，耿智敏西安交通大学第一附属医院肝胆外科，西安 710061通信作者：耿智敏，********************（ORCID： 0000－0003－2645－9808）摘要：胆囊癌是胆道系统最常见的恶性肿瘤类型，由于其高度的侵袭性和对传统的放化疗不敏感，极大地制约了临床疗效。

近些年随着多种高通量测序技术层出不穷，对胆囊癌分子机制的认识也逐渐加深，一些潜在的治疗靶点逐渐被发现，目前相应的临床试验正在如火如荼地进行。

深入探究其异质性的分子分型，对于制订个体化诊疗策略极为重要。

近年来结合多组学特征提出了多种分子分型系统，使临床研究者对胆囊癌分子机制及特征有了更加深刻的认识。

本文结合胆囊癌最新研究进展，探讨了胆囊癌突变靶点和分子分型等相关问题，分析了靶向治疗和免疫治疗的干预新靶标，提出了胆囊癌精准诊断和个体化治疗的新思路。

关键词：胆囊肿瘤；精准医学；治疗学基金项目：国家自然科学基金（62076194）；陕西省重点研发计划（2022SF－606， 2022－YBSF－441）Systemic therapy for gallbladder cancer in the era of precision medicine： Coexistence of opportunities and challengesZHANG Rui，GENG Zhimin.（Department of Hepatobiliary Surgery，The First Affiliated Hospital of Xi’an Jiaotong University， Xi’an 710061， China）Corresponding author： GENG Zhimin，********************（ORCID： 0000－0003－2645－9808）Abstract：Gallbladder cancer is the most common malignant tumor of the biliary system，and its treatment outcome is greatly limited by its invasiveness and insensitivity to conventional radiotherapy and chemotherapy. In recent years，the emergence of various high－throughput sequencing techniques has helped to deepen the understanding of the molecular mechanisms of gallbladder cancer， and promising therapeutic targets have been identified and studied in clinical trials at present. A comprehensive exploration of the molecular subtypes of gallbladder cancer is of great importance for developing individualized diagnosis and treatment strategies. Several molecular subtyping systems have been proposed based on multi－omics features， which enhances the comprehension of the molecular mechanisms and features of gallbladder cancer among clinical researchers. With reference to the latest research advances in gallbladder cancer，this article investigates the challenges in the mutation targets and molecular subtyping of gallbladder cancer， analyzes the novel targets for targeted therapy and immunotherapy， and proposes new ideas for the precise diagnosis and individualized treatment of gallbladder cancer.Key words：Gallbladder Neoplasms； Precision Medicine； TherapeuticsResearch funding：National Natural Science Foundation of China （62076194）；Key Research and Development Plan of Shaanxi Province （2022SF－606， 2022－YBSF－441）胆囊癌（gallbladder carcinoma，GBC）是指来源于胆囊上皮细胞的恶性肿瘤，也是胆道系统常见的肿瘤类型之一。

DISCOVERY探索频道栏目探索频道节目表；探索频道流言终结者(科学新疆界)（Mythbusters）荒野求生(荒野求生秘技)（Man Vs. Wild）Discovery之最透视人体极限恶海捕蟹记干尽苦差事/行行出状元（Dirty Jobs)生活科技大解密（How Do They Do It）时间分解生产线上（Factory Made）制造的原理（How It‘s Made )工程大突破（Build IT Bigger）动力特区--毁灭瞬间、大淘金；阿拉斯（Gold Rush Alaska）、白令海淘金（Bering Sea Gold）工程急救兵魔幻科学绝对好奇强力拖吊科技原来如此（how tech work ）Fast n' Loud美式重型机车（American Chopper）灾难鉴识历史零时差（Zero Hour）新时代武器（Future Weapons）波登不设限（Anthony Bourdain）穿梭时空谈科技惊世重案犯罪鉴识实录机器巨无霸追根究底一线生机非常实验室科幻成真：（Sci Fi Science）抓鬼行动大队（Ghost Lab）重案夜现场人间蒸发亡命之徒逃出鬼门关动物寻奇不可能的物理学成就人生与斯蒂芬·霍金进入宇宙（Into the Universe with Stephen Hawking）人体无敌（亚洲地区）空中巨人：打造空中客车A380台湾人物志》（Portraits Taiwan）《新加坡的历史》（The History of Singapore）聚焦中国（Eye on China）。

了不起的盖茨比第四章英语单词知乎The Great Gatsby is a classic novel written by F. Scott Fitzgerald that tells the story of Jay Gatsby, a wealthy man living in Long Island during the Roaring Twenties. The novel is known for its vivid descriptions of the Jazz Age, as well as its exploration of themes such as love, wealth, and the American Dream.In the fourth chapter of The Great Gatsby, we see the narrator, Nick Carraway, attending one of Gatsby's lavish parties. The chapter provides insight into Gatsby's mysterious past and the extravagant lifestyle he leads. Through Nick's observant eyes, we get a glimpse of the opulence and wealth that define Gatsby's world.One of the key themes explored in this chapter is the idea of perception versus reality. Gatsby is portrayed as a wealthy and successful man, but as the chapter progresses, we begin to see cracks in this facade. Gatsby's parties are a spectacle of excess and indulgence, but underneath it all, there is a sense of loneliness and longing. This contrast between appearances and truth adds depth to Gatsby's character and highlights the complexities of human nature.Another important aspect of the fourth chapter is the introduction of the character Jordan Baker. Jordan is a beautiful and charming woman who captures Nick's attention. She is depicted as confident and self-assured, but there is a sense of detachment in her demeanor. Jordan's presence adds a new dynamic to the story and hints at the complicated relationships that will unfold later in the novel.Overall, the fourth chapter of The Great Gatsby is a pivotal moment in the story. It sets the stage for the drama and intrigue that will unfold in the following chapters, while also delving deeper into the characters and themes that define the novel. Fitzgerald's elegant prose and vivid imagery make this chapter a captivating read, drawing readers into the glamorous and tumultuous world of Jay Gatsby.。

70年代出版的外文书籍《神秘生物调查报告》是一本于1974年出版的外文书籍。

本书由美国作家查尔斯·伯克利所著。

作为一本充满神秘色彩的科幻小说，它运用了生物学、神秘学和推理等多种元素，深受读者喜爱。

本书讲述了一位名叫约翰·哈珀的年轻生物学家的故事。

在进行为期一年的研究实地调查后，他结束了他对一种被称为“神秘生物”的奇特生灵的调查。

这些生物据说是来自未知的虚构物种。

哈珀在追踪和收集“神秘生物”的过程中，发现了一系列离奇的事件和线索，并试图揭示神秘生物背后的真相。

小说中的哈珀发现了一个关于“神秘生物”的秘密组织，他们试图隐藏有关这些奇特生物的存在和信息。

哈珀和他的合作伙伴展开了一系列的追踪和调查，试图解开他们身后的谜团。

在寻找古老文化、神秘符号和隐藏场所的过程中，哈珀逐渐发现，这些生物的存在与一种神秘的力量和意识有着紧密的联系。

在他的调查中，哈珀渐渐得知这些“神秘生物”与人类世界的联系远比他想象的要广泛和深远。

他了解到一些古老的传说和神话故事中提到了这些生物的存在。

他意识到，他们可能是一种曾经在地球上栖息的远古生物，因为某种原因而消失。

然而，当他深入研究这些生物的意义和目的时，他迅速发现这个秘密组织的残酷意图。

本书通过引入许多与传说和神秘学有关的元素，为读者呈现了一个令人兴奋和扣人心弦的故事。

作者伯克利精心构建了角色之间的人际关系，引发了人类与神秘生物之间愈加混乱和复杂的联系。

他展示了人类如何试图理解这些迥异的物种与地球的亲密关系，以及他们对人类自身意义的影响。

总结而言，查尔斯·伯克利的《神秘生物调查报告》是一本引人入胜的外文书籍。

它通过诡异的故事情节、悬疑的情节和令人着迷的生物学要素吸引着读者的兴趣。

同时，该作品也引发了对人类与未知物种之间关系的深思和思考。

无论你是喜爱科幻小说的读者还是对神秘学感兴趣的读者，这本书都能给你带来许多恐怖和扣人心弦的阅读体验。

Curiosity is an essential driving force in human exploration of the universe.As an integral part of our nature,curiosity has propelled us to delve into the mysteries of the cosmos,leading to countless discoveries and advancements in astronomy.From the ancient times when people gazed at the stars and named constellations,to the modern era with sophisticated telescopes and space probes,curiosity has been the catalyst for our understanding of the universe.The desire to explore the unknown has led to the development of various scientific instruments and methodologies that have expanded our horizons.One of the most significant milestones in space exploration was the launch of the Hubble Space Telescope in1990.This remarkable instrument has allowed us to peer deeper into the universe than ever before,revealing the beauty and complexity of distant galaxies, nebulae,and stars.The images captured by Hubble have not only fueled our curiosity but also provided valuable data for scientists to study the formation and evolution of celestial bodies.Another example of our curiositydriven exploration is the Mars Rover missions.These robotic explorers have been sent to the Red Planet to investigate its geological history, climate,and the potential for past life.The discoveries made by these rovers,such as evidence of ancient water flows and organic molecules,have sparked further questions and intensified our desire to understand Mars and its place in our solar system. Curiosity also extends to the search for extraterrestrial life.The recent discovery of potentially habitable exoplanets has ignited a new wave of interest in the possibility of life beyond Earth.Scientists are now working on developing new technologies and missions to study these distant worlds and determine if they could support life as we know it.Moreover,curiosity has led to the development of space tourism,with companies like SpaceX and Blue Origin aiming to make space travel accessible to the general public. This new frontier in exploration not only satisfies our innate desire to explore but also has the potential to inspire a new generation of scientists,engineers,and astronauts.In conclusion,curiosity is the engine that drives our exploration of the cosmos.It has led to groundbreaking discoveries,technological advancements,and a deeper understanding of our place in the universe.As we continue to push the boundaries of our knowledge, curiosity will remain a vital force in our quest to unravel the mysteries of the stars and the depths of space.。

第42 卷第 5 期2023 年5 月Vol.42 No.5621~627分析测试学报FENXI CESHI XUEBAO（Journal of Instrumental Analysis）基于单细胞质谱分析的膀胱癌细胞分型研究孙佳琪1，陈安琪1，2，闫明月2，傅广候4，李刚强1，2，金百冶4*，陈腊1，2*，闻路红1，2，3*（1．宁波大学高等技术研究院，浙江宁波315211；2．宁波华仪宁创智能科技有限公司，浙江宁波315100；3．广州市华粤行仪器有限公司，广东广州511400；4．浙江大学医学院附属第一医院，浙江杭州310009）摘要：单细胞质谱分析能够获得单个细胞的代谢图谱，揭示细胞之间的异质性，在肿瘤学研究中具有重要价值。

该文采用单细胞质谱和机器学习技术，建立了膀胱癌细胞亚型的鉴别方法。

基于所采集的单细胞代谢数据，分别使用线性判别分析、随机森林、支持向量机、逻辑回归建立了机器学习分类模型，并进行了模型的性能评估。

结果表明，各机器学习模型均具有良好的膀胱癌细胞分型能力，分类准确率 ≥ 94.9%，灵敏度 ≥ 88.6%，特异度 ≥ 93.3%。

其中，随机森林算法的分类准确率达100%，模型的受试者工作特征曲线下面积达1。

该方法实现了膀胱癌单细胞的代谢物检测及细胞亚型区分，也为更广泛的单细胞代谢组学研究提供了参考。

关键词：单细胞质谱分析；膀胱癌；代谢物检测；细胞分型中图分类号：O657.63；Q251文献标识码：A 文章编号：1004-4957（2023）05-0621-07Typing of Bladder Cancer Cells Based on Single-cell Mass Spectrometry SUN Jia-qi1，CHEN An-qi1，2，YAN Ming-yue2，FU Guang-hou4，LI Gang-qiang1，2，JIN Bai-ye4*，CHEN La1，2*，WEN Lu-hong1，2，3*（1．The Research Institute of Advanced Technology，Ningbo University，Ningbo 315211，China；2．China Innovation Instrument Co. Ltd.，Ningbo 315100，China；3．Hua Yue EnterpriseHoldings Ltd，Guangzhou 511400，China；4．The First Affiliated Hospital of ZhejiangUniversity School of Medicine，Hangzhou 310009，China）Abstract：Single-cell mass spectrometry analysis enables metabolic profiling of individual cells，helps to reveal the heterogeneity among cells，which is of great significance in oncology research．Bladder cancer is the most common malignant tumor in the urinary system at present．Accurate iden⁃tification on the types of bladder cancer cells has an important value in life science and clinical appli⁃cation in the selection of treatment plan，prognosis judgment and drug resistance evaluation of pa⁃tients．In this paper，single-cell mass spectrometry combined with machine learning was used to identify bladder cancer cells．The metabolic profiles for different bladder cancer cell subtypes were investigated by single-cell mass spectrometry analysis system，and classification algorithms were studied. Based on the collected single cell metabolic data，t-distributed stochastic neighbor embed⁃ding（t-SNE） clustering algorithm was used for dimensionality reduction analysis on the data，and the difference between the single cell metabolic profile was visualized in the two-dimensional space．In order to accurately identify different types of bladder cancer cells，linear discriminant analysis，ran⁃dom forest，support vector machine and logistic regression were respectively used to establish ma⁃chine learning classification models，and grid search method and 5-fold cross-validation were used to optimize the model parameters．Then，five repeats of 10-fold cross-validation were performed on all data sets，and the averaged statistical result was taken as the final result．Accuracy，sensitivity，specificity，receiver operating characteristic（ROC） analysis and other indicators were used to com⁃doi：10.19969/j.fxcsxb.22122804收稿日期：2022－12－28；修回日期：2023－03－20基金项目：国家重点研发计划资助项目（2022YFF0705002）；国家自然科学基金资助项目（81902604）；浙江省重点研发计划项目（2020C03026，2020C02023）；宁波市3315创新团队项目（2017A-17-C）；宁波市重点研发计划项目（2022Z130）；广州市番禺区创新创业领军团队资助项目（2017-R01-5）；宁波大学王宽诚幸福基金项目∗通讯作者：金百冶，博士，主任医师，研究方向：泌尿系肿瘤的临床与基础研究，E-mail：jinbaiye1964@ 陈腊，博士，助理研究员，研究方向：科学分析仪器研究与开发，E-mail：chenla@闻路红，博士，教授，研究方向：科学分析仪器研究与开发，E-mail：wenluhong@622分析测试学报第 42 卷prehensively evaluate the performance of the model．The results showed that the metabolites of a sin⁃gle bladder cancer cell，such as ADP，ATP，glutamic acid，pyroglutamic acid，glutathione，etc，were successfully detected by the single-cell mass spectrometry system．There were significant differ⁃ences among different types of bladder cancer cells，as well as large differences among single cells of the same type，indicating the high heterogeneity of single cell in the tumor．In addition，the four machine learning models all had good typing ability for bladder cancer cells，with a comprehensive accuracy not less than 94.9%，a sensitivity not less than 88.6%and a specificity not less than 93.3%．Compared with other methods，the random forest algorithm has the highest classification ac⁃curacy，sensitivity and specificity，which are all up to 100%，and the area under the ROC curve （AUC） of the model is up to 1，indicating that this method has obvious advantages in classification performance. The method presented in this paper realized the detection of metabolites and differentia⁃tion of cell subtypes at single cell level of bladder cancer，paving the way for more single cell metabo⁃lomics research in future.Key words：single-cell mass spectrometry；bladder cancer；metabolite detection；cell typing细胞是生物体的最基本单位，对细胞的代谢分析能表征其生理状态［1］。