"Imagination and shrewd guesswork are powerful instruments for acquiring scientific knowledge . . . " 1. H. van't Hoff The last decades have witnessed a rapid growth of quantum chemistry and a tremendous increase in the number of very accurate ab initio calculations of the electronic structure of molecules yielding results of admirable accuracy. This dramatic progress has opened a new stage in the quantum mechanical description of matter at the molecular level. In the first place, highly accurate results provide severe tests of the quantum mecha nics. Secondly, modern quantitative computational ab initio methods can be synergetically combined with various experimen tal techniques thus enabling precise numerical characterization of molecular properties better than ever anticipated earlier. However, the role of theory is not exhausted in disclosing the fundamental laws of Nature and production of ever increasing sets of data of high accuracy. It has to provide additionally a means of systematization, recognition of regularities, and ratio nalization of the myriads of established facts avoiding in this way complete chaos. Additional problems are represented by molecular wavefunctions provided by the modern high-level computational quantum chemistry methods. They involve, in principle, all the information on molecular system, but they are so immensely complex that can not be immediately understood in simple and physically meaningful terms. Both of these aspects, categorization and interpretation, call for conceptual models which should be preferably pictorial, transparent, intuitively appealing and well-founded, being sometimes useful for semi quantitative purposes."

The Sixth International Conference on Miniaturized Chemical and Biochemical Analysis Systems, known as /JTAS2002, will be fully dedicated to the latest scientific and technological developments in the field of miniaturized devices and systems for realizing not only chemical and biochemical analysis but also synthesis. The first /JTAS meeting was held in Enschede in 1994 with approximately 160 participants, bringing together the scientists with background in analytical and biochemistry with those with Micro Electro Mechanical Systems (MEMS) in one workshop. We are grateful to Piet Bergveld and Albert van den Berg of MESA Research Institute of the University of Twente for their great efforts to arrange this exciting first meeting. The policy of the meeting was succeeded by late Prof. Dr. Michael Widmer in the second meeting, /JTAS'96 held in Basel with 275 participants. The first two meetings were held as informal workshops. From the third workshop, /JTAS'98 (420 participants) held in Banff, the workshop had become a worldwide conference. Participants continued to increase in /JTAS2000 (about 500 participants) held in Enschede and /JTAS2001 (about 700 participants) held in Monterey. The number of submitted papers also dramatically increased in this period from 130 in 1998, 230 in 2000 to nearly 400 in 2001. From 2001, /JTAS became an annual symposium. The steering committee meeting held in Monterey, confrrmed the policy of former /JTAS that quality rather than quantity would be the key-point and that the parallel-session format throughout the 3.

Two Symposia on speciation in insects held at the Fourteenth International Congress of Entomology (Canberra, Australia, August 22-30, 1972) are included in this volume. The first, on the more general topic of Genetic Analysis of Speciation Mechanisms, includes four papers on speciation in various groups of Diptera and Orthopteroid insects. The second symposium was devoted to the topic of Evolution in the Hawaiian Drosophilidae; it deals with the explosive speciation of a group of flies with specialized ecological requirements in the complex ecolOgical habitats provided by a recent tropical volcanic archipelago. The Hawaiian Symposium, organized by Professor D. Elmo Hardy, is the latest outcome of a major collaborative research project involving over 20 scientists and about 125 technical assistants over a period of ten years. Some recent books on evolution have taken the standpoint that the funda mental genetic mechanism of speciation is relatively uniform and stereotyped and, in particular, that the 'allopatric' model of its geographic component is universally valid. Certainly, this has been a rather generally accepted viewpoint on the part of students of vertebrate speciation. Workers on speciation in insects have tended, in general, to be less dogmatic and more willing to consider a variety of alternative models of speciation. Thus, in the present volume, several contributions adopt viewpoints which are unorthodox or novel. Only time will tell whether their conclusions will turn out to have been soundly based."

A New-Generation Density Functional: Towards Chemical Accuracy for Chemistry of Main Group Elements covers the most recent progress in the development of a new generation of density functional theory (DFT) for accurate descriptions of thermochemistry, thermochemical kinetics, and nonbonded interactions of main group molecules. In this book, the authors present the doubly hybrid density functionals (DHDFs), which dramatically improve the accuracy for predictions of critical properties by including the role of the virtual (unoccupied) orbitals. The authors not only discuss the theoretical bases of three classes of DHDFs but also demonstrate their performance using some well-established benchmarking data sets.

First-Principles-Based Multiscale, Multiparadigm Molecular Mechanics and Dynamics Methods for Describing Complex Chemical Processes, by A. Jaramillo-Botero, R. Nielsen, R. Abrol, J. Su, T. Pascal, J. Mueller and W. A. Goddard.- Dynamic QM/MM: A Hybrid Approach to Simulating Gas Liquid Interactions, by S. Yockel and G. C. Schatz.- Multiscale Modelling in Computational Heterogeneous Catalysis, by F. J. Keil.- Real-World Predictions from Ab Initio Molecular Dynamics Simulations, by B. Kirchner, P. J. di Dio and J. Hutter.- Nanoscale Wetting Under Electric Field from Molecular Simulations, by C. D. Daub, D. Bratko and A. Luzar.- Molecular Simulations of Retention in Chromatographic Systems: Use of Biased Monte Carlo Techniques to Access Multiple Time and Length Scales, by J. L. Rafferty, J. I. Siepmann, M. R. Schure.- Thermodynamic Properties for Applications in Chemical Industry via Classical Force Fields, by G. Guevara-Carrion, H. Hasse and J. Vrabec.- Multiscale Approaches and Perspectives to Modeling Aqueous Electrolytes and Polyelectrolytes, by L. Delle Site, C. Holm and N. F. A. van der Vegt.- Coarse-Grained Modeling for Macromolecular Chemistry, by H. A. Karimi-Varzaneh and F. Muller-Plathe.-"

The liquid crystalline state may be identified as a distinct and unique state of matter which is characterised by properties which resemble those of both solids and liquids. It was first recognised in the middle of the last century through the study of nerve myelin and derivatives of cholesterol. The research in the area really gathered momentum, however, when as a result of the pioneering work of Gray in the early 1970's organic compounds exhibiting liquid crystalline properties were shown to be suitable to form the basis of display devices in the electronic products. The study of liquid crystals is truly multidisciplinary and has attached the attention of physicists, biologists, chemists, mathematicians and electronics engineers. It is therefore impossible to cover all these aspects fully in two small volumes and therefore it was decided in view of the overall title of the series to concentrate on the structural and bonding aspects of the subject. The Chapters presented in these two volumes have been organised to cover the following fundamental aspects of the subiect. The calculation of the structures of liquid crystals, an account of their dynamical properties and a discussion of computer simulations of liquid crystalline phases formed by Gay Berne mesogens. The relationships between molecular conformation and packing are analysed in some detail. The crystal structures of liquid crystal mesogens and the importance of their X ray scattering properties for characterisational purposes are discussed.

This book presents the most comprehensive analysis of bonding in polyoxometalates and related oxides based on classical bonding concepts and the bond valence model. Numerous tables and figures underline and illuminate the results, making it a valuable resource.

The French chemist Marcelin Berthelot put forward a classical and by now an often cited sentence revealing the quintessence of the chemical science: "La Chimie cree son objet." This is certainly true because the largest number of molecular compounds were and are continuously synthesized by chemists themselves. However, modern computational quantum chemistry has reached a state of maturity that one can safely say: "La Chimie Theorique cree son objet" as well. Indeed, modern theoretical chemistry is able today to provide reliable results on elusive systems such as short living species, reactive intermediates and molecules which will perhaps never be synthesized because of one or another type of instability. It is capable of yielding precious information on the nature of the transition states, reaction paths etc. Additionally, computational chemistry gives some details of the electronic and geometric structure of molecules which remain hidden in experimental examinations. Hence, it follows that powerful numerical techniques have substantially enlarged the domain of classical chemistry. On the other hand, interpretive quantum chemistry has provided a conceptual framework which enabled rationalization and understanding of the precise data offered either by experiment or theory. It is modelling which gives a penetrating insight into the chemical phenomena and provides order in raw experimental results which would otherwise represent just a large catalogue of unrelated facts.

The liquid crystalline state may be identified as a distinct and unique state of matter which is characterised by properties which resembles those of both solids and liquids. It was first recognised in the middle of the last century through the study of nerve myelin and derivatives of cholesterol. The research in the area really gathered momentum, however, when as a result of the pioneering work of Gray in the early 1970's organic compounds showing liquid crystalline properties were shown to be suitable to form the basis of display devices in the electronic products. The study of liquid crystals is truly multidisciplinary and has attached the attention of physicists, biologists, chemists, mathematicians and electronics engineers. It is therefore impossible to cover all these aspects fully in two small volumes and therefore it was decided in view of the overall title of the series to concentrate on the structural and bonding aspects of the subject. The Chapters presented in these two volumes have been organised to cover the following fundamental aspects of the subject. The calculation of the structures of liquid crystals, an account of their dynamical properties and a discussion of computer simulations of liquid crystalline phases formed by Gay Berne mesogens. The relationships between molecular conformation and packing are analysed in some detail. The crystal structures of liquid crystal mesogens and the importance of their X ray scattering properties for characterisational purposes are discussed.

High-throughput screening and combinatorial chemistry are two of the most potent weapons ever to have been used in the discovery of new drugs. At a stroke, it seems to be possible to synthesise more molecules in a month than have previously been made in the whole of the distinguished history of organic chemistry, Furthermore, all the molecules can be screened in the same short period. However, like any weapons of immense power, these techniques must be used with care, to achieve maximum impact. The costs of implementing and running high-throughput screening and combinatorial chemistry are high, as large dedicated facilities must be built and staffed. In addition, the sheer number of chemical leads generated may overwhelm the lead optimisation teams in a hail of friendly fire. Mother nature has not entirely surrendered, as the number of building blocks that could be used to build libraries would require more atoms than there are in the universe. In addition, the progress made by the Human Genome Project has uncovered many proteins with different functions but related binding sites, creating issues of selectivity. Advances in the new field of pharmacogenomics will produce more of these challenges. There is a real need to make hi- throughput screening and combinatorial chemistry into 'smart' weapons, so that their power is not dissipated. That is the challenge for modellers, computational chemists, cheminformaticians and IT experts. In this book, we have broken down this grand challenge into key tasks.

In 1965 a book by P. Bartlett appeared under the title "The Nonclassical Ions" 1). The book is a collection of papers reprinted from various journals. The many reviews that have appeared since 2-22) are either antiquated (the book published in 1972 12) covers the literature mainly before 1968) or relatively biased (e.g., 3.4,10" on brief 2, 7,11). This review attempts to discuss the various points of view on the "nonclassical" carbocations. The main point is to establish the relative role of "nonclassical" and "classical" ions in various chemical processes. The author has followed P. Bartlett's advice 1) that when setting forth the achievements of the human mind one should see how we came to the modern understanding of a given problem (" ... how we know what we know"). The theory of "nonclassical" ions offers an explanation of many unique chemical, stereochemical and kinetic peculiarities of bicyclic compounds. It has expanded our knowledge on chemical bonds in carbocations by introducing electron-deficient bonds (as in boron hydrides). It has accounted for many rearrangements of stable cations. As a "side" result our knowledge has been extended about ionization processes in a solution, as well as about stereochemical methods. 2 Main Terms of Nonclassical Carbocations In 1939 Hevell, Salas and Wilson 23) assumed an intermediate, "bridge" ion 2 to be formed when camphene hydrochloride 1 is rearranged into isobornyl chloride 3. This happened 17 years after Meerwein first postulated the intermediate formation of "carbonium" ions in chemical reactions.

Over the past 40 years, Rotational Isomeric State (RIS) models for hundreds of polymer structures have been developed. The RIS approach is now available in several software packages. The user is often faced with the time-consuming task of finding appropriate RIS parameters from the literature. This book aims at easing this step by providing a comprehensive overview of the models available. It reviews the literature from the first applications of RIS models to the end of 1994, comprises synthetic as well as naturally orccuring macromolecules, and tabulates all the pertinent features of published models. It will help readers, even when not very familiar with the method, to take advantage of this computationally efficient way of assessing the conformational properties of macromolecular systems.

1. R.G. Pearson Chemical Hardness - An Historical Introduction 2. P.K. Chattaraj Density Functional Theory of Chemical Hardness 3. J.L. Gazqu z Hardness and Softness in Density Functional Theory 4. L. Komorowski Hardness Indices for Free and Bonded Atoms 5. N.H. March The Ground-State Energy of Atomic and Molecular Ions and Its Variation with the Number of Elections 6. K. Sen Isoelectronic Changes in energy, Electronegativity, and Hardness in Atoms via the Calculations of 7. P. Politzer, J.S. Murray, M.E. Grice Charge Capacities and Shell Structures of Atoms 8. R. F. Nalewajski The Hardness Based Molecular Charge Sensitivities and Their Use in the Theory of Chemical Reactivity 9. B.G. Baekelandt, R. A. Schoonheydt, W.J. Mortier The EEM Approach to Chemical Hardness in Molecules and Solids: Fundamentals and Applications 10. J.A. Alonso, L. C. Balbas Hardness of Metallic Clusters

1. R. Carlson, A. Nordahl: Exploring Organic Synthetic Experimental Procedures 2. S.J. Cyvin, B.N. Cyvin, J. Brunvoll: Enumeration of Benzenoid Chemical Isomers with a Study of Constant-Isomer Series 3. E.Hladka, J. Koca, M. Kratochvil, V. Kvasnicka, L. Matyska, J. Pospichal, V. Potucek: The Synthon Model and the Program PEGAS for Computer AssistedOrganic Synthesis 4. K. Bley, B. Gruber, M. Knauer, N. Stein, I. Ugi: New Elements in the Representation of the Logical Structure of Chemistry byQualitative Mathematical Models and Corresponding Data Structures