Research papers

Support-Vector Networks

Corinna Cortes, Vladimir Vapnik

Support-vector networks

Corinna Cortes, Vladimir Vapnik

An Integrative Model Of Organizational Trust

Roger C. Mayer, James H. Davis, F. David Schoorman

Scholars in various disciplines have considered the causes, nature, and effects of trust. Prior approaches to studying trust are considered, including characteristics of the trustor, the trustee, and the role of risk. A definition of trust and a model of its antecedents and outcomes are presented, which integrate research from multiple disciplines and differentiate trust from similar constructs. Several research propositions based on the model are presented.

Principles of Condensed Matter Physics

P. M. Chaikin, T. C. Lubensky

Now in paperback, this book provides an overview of the physics of condensed matter systems. Assuming a familiarity with the basics of quantum mechanics and statistical mechanics, the book establishes a general framework for describing condensed phases of matter, based on symmetries and conservation laws. It explores the role of spatial dimensionality and microscopic interactions in determining the nature of phase transitions, as well as discussing the structure and properties of materials with different symmetries. Particular attention is given to critical phenomena and renormalization group methods. The properties of liquids, liquid crystals, quasicrystals, crystalline solids, magnetically ordered systems and amorphous solids are investigated in terms of their symmetry, generalised rigidity, hydrodynamics and topological defect structure. In addition to serving as a course text, this book is an essential reference for students and researchers in physics, applied physics, chemistry, materials science and engineering, who are interested in modern condensed matter physics.

Classical Electrostatics in Biology and Chemistry

Barry Honig, Anthony Nicholls

A major revival in the use of classical electrostatics as an approach to the study of charged and polar molecules in aqueous solution has been made possible through the development of fast numerical and computational methods to solve the Poisson-Boltzmann equation for solute molecules that have complex shapes and charge distributions. Graphical visualization of the calculated electrostatic potentials generated by proteins and nucleic acids has revealed insights into the role of electrostatic interactions in a wide range of biological phenomena. Classical electrostatics has also proved to be successful quantitative tool yielding accurate descriptions of electrical potentials, diffusion limited processes, pH-dependent properties of proteins, ionic strength-dependent phenomena, and the solvation free energies of organic molecules.

Supramolecular Chemistry

J.-M. Lehn

Part 1 From molecular to supramolecular chemistry: concepts and language of supramolecular chemistry. Part 2 Molecular recognition: recognition, information, complementarity molecular receptors - design principles spherical recognition - cryptates of metal cations tetrahedral recognition by macrotricyclic cryptands recognition of ammonium ions and related substrates binding and recognition of neutral moelcules. Part 3 Anion co-ordination chemistry and the recognition of anionic substrates. Part 4 Coreceptor molecules and multiple recognition: dinuclear and polynuclear metal ion cryptates linear recognition of molecular length by ditopic coreceptors heterotopic coreceptors - cyclophane receptors, amphiphilic receptors, large molecular cage multiple recognition in metalloreceptors supramolecular dynamics. Part 5 Supramolecular reactivity and catalysis: catalysis by reactive macrocyclic cation receptor molecules catalysis by reactive anion receptor molecules catalysis with cyclophane type receptors supramolecular metallo-catalysis cocatalysis - catalysis of synthetic reactions biomolecular and abiotic catalysis. Part 6 Transport processes and carrier design: carrier-mediated transport cation-transport processes - cation carriers anion transport processes - anion carriers coupled transport processes electron-coupled transpoort in a redox gradient proton-coupled transport in a pH gradient light-coupled transport processes transfer via transmembrane channels. Part 7 From supermolecules to polymolecular assemblies: heterogeneous molecular recognition - supramolecular solid materials from endoreceptors to exoreceptors - molecular recognition at surfaces molecular and supramolecular morphogenesis supramolecular heterogeneous catalysis. Part 8 Molecular and supramolecular devices: molecular recognition, information and signals - semiochemistry supramolecular photochemistry - molecular and supramolecular photonic devices light conversion and energy transfer devices photosensitive molecular receptors photoinduced electron transfer in photoactive devices photoinduced reactions in supramolecular species non-linear optical properties of supramolecular species supramolecular effects in photochemical hole burning molecular and supramolecular electronic devices supramolecular electrochemistry electron conducting devices - molecular wires polarized molecular wires - rectifying devices modified and switchable molecular wires molecular magnetic devices molecular and supramolecular ionic devices tubular mesophases. (Part contents).

<i>The Physics of Liquid Crystals</i>

P. G. de Gennes, Jacques Prost, Robert A. Pelcovits

Part 1 Liquid crystals - main types and properties: introduction - what is a liquid crystal? the building blocks nematics and cholesterics smectics columnar phases more on long-, quasi-long and short-range order remarkable features of liquid crystals. Part 2 Long- and short-range order in nematics: definition of an order parameter statistical theories of the nematic order phenomonological description of the nematic-isotopic mixtures. Part 3 Static distortion in a nematic single crystal: principles of the continuum theory magnetic field effects electric field effects in an insulating nematic fluctuations in the alignment hydrostatics of nematics. Part 4 Defects and textures in nematics: observations disclination lines point disclinations walls under magnetic fields umbilics surface disclinations. Part 5 Dynamical properties of nematics: the equations of nematodynamics experiments measuring the Leslie co-efficients convective instabilities under electric fields molecular motions. Part 6 Cholesterics: optical properties of an ideal helix agents influencing the pitch dynamical properties textures and defects in cholesterics. Part 7 Smectics: symmetry of the main smectic phases continuum description of smectics A and C remarks on phase and precritical phenomena.

Teaching to transgress: education as the practice of freedom

Introduction: Teaching to Transgress 1. Engaged Pedagogy 2. A Revolution of Values: The Promise of Multicultural Change 3. Embracing Change: Teaching in a Multicultural World 4. Paulo Freire 5. Theory as Liberatory Practice 6. Essentialism and Experience 7. Holding My Sister's Hand: Feminist Solidarity 8. Feminist Thinking: In the Classroom Right Now 9. Feminist Scholarship: Black Scholars 10. Building a Teaching Community: A Dialogue 11. Language: Teaching New Worlds / New Words 12. Confronting Class in the Classroom 13. Eros, Eroticism, and the Pedgagogical Process 14. Ecstasy: Teaching and Learning Without Limits

Fast Parallel Algorithms for Short-Range Molecular Dynamics

Steven J. Plimpton

Revisiting the Behavioral Model and Access to Medical Care: Does it Matter?

Ronald Andersen

The Behavioral Model of Health Services Use was initially developed over 25 years ago. In the interim it has been subject to considerable application, reprobation, and alteration. I review its development and assess its continued relevance.

National Science Education Standards

James H. Shea

The Nature of Statistical Learning Theory

Vladimir Vapnik

Bayesian Model Selection in Social Research

Adrian E. Raftery

It is argued that P-values and the tests based upon them give unsatisfactory results, especially in large samples. It is shown that, in regression, when there are many candidate independent variables, standard variable selection procedures can give very misleading results. Also, by selecting a single model, they ignore model uncertainty and so underestimate the uncertainty about quantities of interest. The Bayesian approach to hypothesis testing, model selection, and accounting for model uncertainty is presented. Implementing this is straightforward through the use of the simple and accurate BIC approximation, and it can be done using the output from standard software. Specific results are presented for most of the types of model commonly used in sociology. It is shown that this approach overcomes the difficulties with P-values and standard model selection procedures based on them. It also allows easy comparison of nonnested models, and permits the quantification of the evidence for a null hypothesis of interest, such as a convergence theory or a hypothesis about societal norms.

A Study of Cross-Validation and Bootstrap for Accuracy Estimation and Model Selection

Ron Kohavi

We review accuracy estimation methods and compare the two most common methods: crossvalidation and bootstrap. Recent experimental results on arti cial data and theoretical results in restricted settings have shown that for selecting a good classi er from a set of classiers (model selection), ten-fold cross-validation may be better than the more expensive leaveone-out cross-validation. We report on a largescale experiment| over half a million runs of C4. 5 and a Naive-Bayes algorithm| to estimate the e ects of di erent parameters on these algorithms on real-world datasets. For crossvalidation, we vary the number of folds and whether the folds are strati ed or not; for bootstrap, we vary the number of bootstrap samples. Our results indicate that for real-word datasets similar to ours, the best method to use for model selection is ten-fold strati ed cross validation, even if computation power allows using more folds.

Statistical Physics of Macromolecules

Alexander Y. Grosberg, Alexei R. Khokhlov, H. Eugene Stanley, A. John Mallinckrodt, Susan R. McKay

T he appellation "dirt physics" was given to three schools of physicists who, during the 1970s, began to work on questions related to the statics and dynamics of complex long-chain molecules.This work was called dirt physics because no one could imagine where the "physics" was or even what the general physics principles were.General principles as well as specific new results were found though, in abundance, by members of all three schools (and other "camp followers," including this reviewer).One substantial school grew up in the UK around Sir Sam Edwards, who in the 1960s had already recognized the uncanny parallels between quantum field theory and

Nonlinear Dynamics and Chaos: With Applications to Physics, Biology, Chemistry, and Engineering

Steven H. Strogatz, Mark J. Friedman, A. John Mallinckrodt, Susan R. McKay

Two-equation eddy-viscosity turbulence models for engineering applications

Florian Menter

Two new two-equation eddy-viscosity turbulence models will be presented.They combine different elements of existing models that are considered superior to their alternatives.The first model, referred to as the baseline (BSL) model, utilizes the original k-u model of Wilcox in the inner region of the boundary layer and switches to the standard A>e model in the outer region and in free shear flows.It has a performance similar to the Wilcox model, but avoids that model's strong freestream sensitivity.The second model results from a modification to the definition of the eddy-viscosity in the BSL model, which accounts for the effect of the transport of the principal turbulent shear stress.The new model is called the shear-stress transport-model and leads to major improvements in the prediction of adverse pressure gradient flows.

A simple hydrologically based model of land surface water and energy fluxes for general circulation models

Xu Liang, Dennis P. Lettenmaier, Eric F. Wood, Stephen J. Burges

A generalization of the single soil layer variable infiltration capacity (VIC) land surface hydrological model previously implemented in the Geophysical Fluid Dynamics Laboratory general circulation model (GCM) is described. The new model is comprised of a two‐layer characterization of the soil column, and uses an aerodynamic representation of the latent and sensible heat fluxes at the land surface. The infiltration algorithm for the upper layer is essentially the same as for the single layer VIC model, while the lower layer drainage formulation is of the form previously implemented in the Max‐Planck‐Institut GCM. The model partitions the area of interest (e.g., grid cell) into multiple land surface cover types; for each land cover type the fraction of roots in the upper and lower zone is specified. Evapotranspiration consists of three components: canopy evaporation, evaporation from bare soils, and transpiration, which is represented using a canopy and architectural resistance formulation. Once the latent heat flux has been computed, the surface energy balance is iterated to solve for the land surface temperature at each time step. The model was tested using long‐term hydrologic and climatological data for Kings Creek, Kansas to estimate and validate the hydrological parameters, and surface flux data from three First International Satellite Land Surface Climatology Project Field Experiment intensive field campaigns in the summer‐fall of 1987 to validate the surface energy fluxes.

An Introduction to the Bootstrap

Bradley Efron, Robert Tibshirani

An Introduction to the Bootstrap arms scientists and engineers as well as statisticians with the computational techniques they need to analyze and understand complicated data sets. The bootstrap is a computer-based method of statistical inference that answers statistical questions without formulas and gives a direct appreciation of variance, bias, coverage, and other probabilistic phenomena. This book presents an overview of the bootstrap and related methods for assessing statistical accuracy, concentrating on the ideas rather than their mathematical justification. Not just for beginners, the presentation starts off slowly, but builds in both scope and depth to ideas that are quite sophisticated.

Environmental Chemistry of Soils

Murray B. McBride

This introduction to modern soil chemistry describes chemical processes in soils in terms of established principles of inorganic, organic, and physical chemistry. The text provides an understanding of the structure of the solid mineral and organic materials from which soils are formed, and explains such important processes as cation exchange, chemisorption and physical absorption of organic and inorganic ions and molecules, soil acidification and weathering, oxidation-reduction reactions, and development of soil alkalinity and swelling properties. Environmental rather than agricultural topics are emphasized, with individual chapters on such pollutants as heavy metals, trace elements, and inorganic chemicals.

A Short Physical Performance Battery Assessing Lower Extremity Function: Association With Self-Reported Disability and Prediction of Mortality and Nursing Home Admission

Jack M. Guralnik, E. M. Simonsick, Luigi Ferrucci, Robert J. Glynn, Lisa Berkman, Dan G. Blazer, Paul A. Scherr, Robert B. W…

BACKGROUND: A short battery of physical performance tests was used to assess lower extremity function in more than 5,000 persons age 71 years and older in three communities. METHODS: Balance, gait, strength, and endurance were evaluated by examining ability to stand with the feet together in the side-by-side, semi-tandem, and tandem positions, time to walk 8 feet, and time to rise from a chair and return to the seated position 5 times. RESULTS: A wide distribution of performance was observed for each test. Each test and a summary performance scale, created by summing categorical rankings of performance on each test, were strongly associated with self-report of disability. Both self-report items and performance tests were independent predictors of short-term mortality and nursing home admission in multivariate analyses. However, evidence is presented that the performance tests provide information not available from self-report items. Of particular importance is the finding that in those at the high end of the functional spectrum, who reported almost no disability, the performance test scores distinguished a gradient of risk for mortality and nursing home admission. Additionally, within subgroups with identical self-report profiles, there were systematic differences in physical performance related to age and sex. CONCLUSION: This study provides evidence that performance measures can validly characterize older persons across a broad spectrum of lower extremity function. Performance and self-report measures may complement each other in providing useful information about functional status.

The anomaly of silicon in plant biology.

Emanuel Epstein

Silicon is the second most abundant element in soils, the mineral substrate for most of the world's plant life. The soil water, or the "soil solution," contains silicon, mainly as silicic acid, H4SiO4, at 0.1-0.6 mM--concentrations on the order of those of potassium, calcium, and other major plant nutrients, and well in excess of those of phosphate. Silicon is readily absorbed so that terrestrial plants contain it in appreciable concentrations, ranging from a fraction of 1% of the dry matter to several percent, and in some plants to 10% or even higher. In spite of this prominence of silicon as a mineral constituent of plants, it is not counted among the elements defined as "essential," or nutrients, for any terrestrial higher plants except members of the Equisitaceae. For that reason it is not included in the formulation of any of the commonly used nutrient solutions. The plant physiologist's solution-cultured plants are thus anomalous, containing only what silicon is derived as a contaminant of their environment. Ample evidence is presented that silicon, when readily available to plants, plays a large role in their growth, mineral nutrition, mechanical strength, and resistance to fungal diseases, herbivory, and adverse chemical conditions of the medium. Plants grown in conventional nutrient solutions are thus to an extent experimental artifacts. Omission of silicon from solution cultures may lead to distorted results in experiments on inorganic plant nutrition, growth and development, and responses to environmental stress.

Proceedings 35th Annual Symposium on Foundations of Computer Science

The Physics of Liquid Crystals

P. G. de Gennes, Jacques Prost

Abstract This new edition of this classic text on condensed matter physics includes the great advances that have taken place since its first publication in 1974. New chapters describe the main types and properties of liquid crystals in terms of the new phases discovered since the middle of the 1970's, and advances in the understanding of local order and the nature of the isotropic to nematic transition. There is an extensive discussion of the symmetry, and macroscopic and dynamic properties of smectics and columnar phases, and their defects, illustrated with numerous descriptions of experimental arrangements. The final chapter is devoted to phase transitions in smectics, including the celebrated analogy between Smectic A and superconductors. Throughout the book there is an emphasis on order-of-magnitude considerations. Its topicality and breadth of coverage will ensure that The Physics of Liquid Crystals remains an indispensable guide for students and researchers alike.