Proceedings of the Symposium on Active Networks and Feedback

Proceedings of the Symposium on Active Networks and Feedback Systems. New York, N. Y., April 19, 20, 21, 1960. Gerald H. Cohen. J. Am. Chem. Soc. , 19...
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s o v . 20, 1981

with respect to rigor of the theoretical treatment, up-todateness of instrument design, or practical interpretation of data t h a t fall short of achieving a minimum level of sophistication. The subject, Light Scattering, appears in wholly new form as a separate chapter (Oster). For organic chemists, the timeliness of the chapter, Optical Rotatory Dispersion (Klyne and Parker), will be a focal point of interest. The general discussion is very brief; most of the chapter is taken up with a survey of data. The chapters Polarimetry (Heller and Fitts) and Streaming Birefringence (Scheraga and Signer) have been extensively revised and new chapters have been added on the Kerr Effect (Lefevre and Lefevre) and Determination of the Faraday Effect (W’aring and Custer). Altogether these five chapters provide more information on applications of polarized light than is available to the organic chemist in any other single source. The two concluding chapters, Measurement of Dielectric Constant and Loss (Powles and Smyth) arid Dipole Moments (Smyth), have changed little since the earlier edition. DEPARTMENT OF CHEMISTRY UXIVERSITY OF CHICAGO W. G. BROWN CHICAGO 37, ILLISOIS

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but little on microscopical methods), Resinography (12 pages) and on General and Industrial Microscopy. Chemical Microscopy occupies over 50 pages, with major reference to precipitation reactions for a variety of drugs. The portion on morphology and birefringence avoids the correlation between these which is essential for intelligent and reliable description. For those who like t o read encyclopedias this oue should be fascinating, but the alphabet is a poor guide for systematic study. Eveu much digging about in the table of contents may lead t o very spotty information, as compared with what is accessible in fewer words, in more prosaic and orderly books. If the niicroscopist has studied these in his own field, then lie may find the “Encyclopedia” a valuable supplement on selected topics, and a suggestive sampling or preview of what is new or “far out” in the ever-expanding horizons of techniques applied to ever-decreasing details of structure. SCHOOL OF CHEMICAL A N D ~IETALLURGICAL EXGINEERING C. N’. MASON CORNELL USIVERSITY ITHACA, NEW YORK

Proceedings of the Symposium on Active Networks and FeedbackSystems. New York, N. Y., April 19,20,21,1960. Microwave Research Institute Symposia Series. Volume X. Edited by JEROMEF o x Assistant Editor, MARTHA Les Reactions entre Ions Positifs et Molecules en Phase CROWELL Interscience Publishers, Inc., 250 Fifth Gazeuse. Application B la Chimie des Rayonnements. Avenue, S e w York 1, X Y. 1961. xxiv 658 pp. By J . ~ U R U P ,Docteur 6s Sciences. Gauthier-Yillars, 5.5, 15 5 X 23 cm Price, $8.00. quai des Grands Augustins, Paris VI, France. 1960. T8 pp. 15.5 X 24 cm. Price, broch6, 14 Nf; cart., 17 S F It is a treat indeed to find a nostalgic paper reminiscing ($3.75). about the early thoughts and developments in the field of feedback amplifiers theory. It is especially welcome if it is In this short monograph, the reader will find an interesting introduction t o the subject of ion-mclecule reactions. The authored by one of the communication field’s pioneering theoreticians, H . LY. Bode. This article and two others early work, the experimental approaches and the quantum constitute a presentation of the state of the a r t and future and classical theories are revieived briefly. The bibliography extends to the end of 1959. The available informa- trends in the proceedings of the symposium on Active Kettion concerning about two hundred reactions is summarized works and Feedback Systems. Bode’s article, “Feedback-The History of an Idea” and classified in a n extensive table. Applications to radiatakes us back to 1923 and discusses the need for distortiontion chemistry are discussed in the last chapter. About one third of the book deals with theoretical con- free repeaters which had existed in the telephone industry siderations mainly about energies and mechanisms. Endoat that time and described Black’s early invention of feedback amplifiers which helped satisfy the need. The author thermic or highly exothermic processes are shown to have low probabilities. The authnr develops interesting ideas then discusses the work of Nyquist and MacColl and others of his own without confusing his contributions with those of and views the wartime marriage of feedback amplifier others. theory and automatic control. He states that “This marriage has lasted 20 years; perhaps a n amical divorce is in DEPARTMEST DE CHIMIE UNIVERSITELAVAL C. OUELLET order.” The remainder of the articles on Feedback Setworks and QUEBEC,CASADA Systems, however, do not indicate t h a t this divorce is imminent. I n fact, the only paper on the subject of adaptive control “ALT Appraisal and Critique of a Class of Adaptive The Encyclopedia of Microscopy. Edited by GEORGEL. Systems” by I. M. Horowitz seems to indicate that there CLARK, Research Professor of Analytical Chemistry, are a few cases where ordinary feedback is not just as effecEmeritus, University of Illinois, Urbana, Illinois. Rein- tive as a much more costly and complex computer controlled hold Publishing Corporation, 430 Park Avenue, S e w or adaptive system. York 22, K,Y . 1961. xii 693 pp. 18 X 26 cm. Price, Some of Bode’s original work on multiloop feedback $25.00. amplifiers is very lucidly explained by J . H . Xuligan, Jr., This book is arranged in encyclopedia style, in double in terms of transistor amplifier models and general matrix columns with 26 large topics and numerous subtopics in parameters. I n the simple analysis of feedbac.k systems the unilateral “block box” is used. However. t u r a more alphabetic order, and with cross references under most of realistic approach non-reciprocal bilateral elements should these, but n-ith no index. be used. I n his article on “Signal Transniiisioli in S o n It reminds one of a gigantic symposium of symposia, with papers t h a t include reviews, some systematic and corre- reciprocal Systems,” he treats the concepts of return ratio and returii difference for a general system matrix and sliorvs lated developments in textbook style, and highly specialized reports on personal researches or novel instruments. As is the great utility of these ideas. Since many prows, control systems are multivariable, there is no doubt of the fruitinevitable in symposia, the level and scope of the papers vary widely, and the allocation of space is certainly open to fulness of applying these concepts in the analysis and s!mquestion; for example, kidney ultrastructure gets as much as thesis of the control of multivariable systenis. Procehs control systems usually have “plants” which are distributed electron opsics! and 4 pages are devoted to the ultrasonic in nature so t h a t non-rational transfer functions develop. absorption microscope,” a device which can detect a 2 5 p energy-absorbing discontinuity but is hardly a n image- In particular, there is usually a distance velocity or dead former. period lag. A. Papoulis briefly treats this subject and gives T o a considerable degrec, the general emphasis is on stability limits. He apparently has ignored the great quan“appreciation” or potential application, rather than con- tity of material on this subject, since 110 bibliography npcrete techniques that might be followed by the user. On the pears. other hand, there are many striking illustrations of microSince the introduction of the tuuiiel diode, negativc resistradiography and electron microscopy, somewhat slanted ance has become another basic active circuit element. in the direction of biology. The editor contributes about 15 Reports of research in this area constitute the main interpages on various topics. est of the group of papers concerning active networks. Clieinists will be interested in sections o n Lyophobic ColNon linear and time-varying systems constitute the l u i t l i (20 piges), Refmcto~nctry(40 pages, 247 refereiices, rcinaiiider of this collection of paper.;. The control engineer

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has made quite a dent in this complex problem, in particular his contributions concerning the stability aspects. It is perhaps in this area of time-varying systems t h a t tlie flow of information and ideas may be from the control engineer to the networks designer. DEPARTMENT OF ELECTRICAL ENGINEERING THECNIVERSITY OF ROCHESTER GERALDI-I. COHEY ROCHESTER 20, X. 1’.

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theoretical chemists.” This last book, d-scribed in the preceding sentence partly by quotations from its preface and its dust-jacket, has now been written, and very mnsterfully written indeed, by J. S . Griffitn. After a brief introduction apparently in?endetl for physicists who know absolutely no chemistry for whose benefit, apparently, the book is also graced with n table of the names, atomic numbers and symbols of the elenmiis), tlie book proceeds to some chapters ostensibly directed to chemists who ktiow no physics. However, in tlie first of tnese chapters which cover relatively elemeiitary considerations of angular The Theory of Transition-Metal Ions. By J. S. GRIFtr’ITH, momentum and electronic structure of atoms, the author Professor of Chemistry, University of Pennsylvania; remarks that while he “starts from the beginning” (which Serry-Ramsey Fellow in Mathematics, King’s College, is true) “it is rather desirable t h a t the reatler shouid possess Cambridge. Cambridge University Press, 32 East 57th already a little knowledge of quantum meciiatiics: $9 1-22, 455 pp. 18 X Street, New York 22, S. Y . 1961. h 27, 42 and 43 of Prolessor Dirac’s book Quonlum_ 26 cm. Price, $17.50. probably cover all that is really necessary.” I chapters cover what a chemist knoxvirig no physics iroulc: S o field of chemistry has in the last decade been a n y more have to learn before tackling ligdld field theory > u s e but it exciting in its decisive conquest of old problems, its development of new ideas, and its rise to new levels of sophis- seems no small understatement to say that t!ic3e chaptcrs tication than the chemistry of the transition elements, es- would be a very forinidable challengc for the t r These remarks will serve, I hope, t o convey 3 ! pecially their coordination chemistry. This revoiutionary sion of the general level of sophistication of the entire b d c . surge of vigor is due in considerable part, as practically Following the chapters ( 2 - 5 ) on atomic structure thcre everyone knows, to the rediscovery and practical extension by chemists of those theories developed by physicists such as is a n clegant chapter 011 group theory, only inarrc:i in spots by the unfortunate confusion of the terms c;yiiitnetry Bethe, Sclilapp and Penney and most particularly J . H. element aiid symmetry operation. Begiiining with Chapter Van Vleck during the 1930’s. K n o w today in its various 7 , ligand field theory per se is developed brilliant.ly and interrelated forms as crystal field theory or ligand field incisively in three longish chapters. Chapter 10 gives a theory, it provides a powerful conceptual framework and, whirlwind resume of magnetic susceptiblity theory including mirabile dictu, cornputatioiially practical tools for the solupost-Van Vleck developments such as Kotani’s rnethod aiid tion of many problems of spectroscopy, magnetism, bondthe author’s own ingenious modific:ition of it. Cli:rpter 11 ing, structure, reactivity and thermodynamic stability of presents a relatively non-mathematical discLIssio11of tile optransition metal compounds and complexes. tical spectra. of complexes and should he of interest to i m n y But for the chemist t o use this new power he must pay a chemists, even those who would not get much benefit from price. That price is the acquisition of some more difficult earlier chapters. The final chapter is a rather long and thorand sophisticated physics a n d quanturn mechanics than he ough one on paramagnetic resomiice, covering both theory perhaps ever thought would be necessary for a chemist. and representative examples of its application. The book Rapid as it may have seemed in the last decade. the spread of closes with 6s pages of appendices mosr of which are tabuthe ideas aiid technique3 of ligand field theory has not latioiis of data, formulas a n d matrix elements useful in perbeen as rapid i s it might have been because the lack of forming computations. While this reviewer did not attempt textbooks, on any level, iliflated this price beyond the ret o check these tabulations for accuracy, if nile makes the sources of niany. likely assumption that they are relati\-eiy free of errors, I t seeins t o this reviewer t h a t for several years the need it can be said that they constitute a n extremely valuable has existed for three different books. For those whose goal (not necessarily their final one) is acquaintance with the feature of the book. The author has entirely omitted discussion of the f ” coiiimportant qualitative ideas and pictorially expressed cbnfigurations. cepts and therelationship of these to the better known experiThe entire bonk has the distinguished forinat typical of mental facts, a short catechistic book putting emphasis on Cambridge University Press publications and in over four results rather than reasons and principles is required. This months on my shelf iii muggy Massachusetts the covers need has recently been met by L. E. Orgel’s articulate monograph. On the next level, one would desire a book cover- have not buckled as covers on English books so often do. It has lately become one of the most tiresome cliches of ing basic principles and quantitative techniques written for book reviewers t o note in closing how outrageously a book is the willing but mathematically untutored and undistinpriced-right out of reason and reach. I n the present case, guished chemist-in short, a practical but unpretentious I can happily make just the oppoqite observation: this book book. Regrettably, no such book yet exists; it is t o be hoped t h a t one will appear soon. Finally, there has been a seems t o me t o be worth every bit of the $17.50 t h a t is asked for it. need for a mathematically sophisticated and rigorous book DEPARTMENT OF CHEMISTRY presenting “a unified and deductive introduction t o that MASSACHUSETTS part of theoretical physics.. .known as ligand-field theory” IXSTITUTE OF TECHNOLOGY and directed “primarily t o mathematical physicists and CAXBRIDGE39, MASSACHUSETTS F. ALBERT COWON

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