Showing papers in "Physics Today in 1995"

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

Abstract: Preface 1. Overview 1.0 Chaos, Fractals, and Dynamics 1.1 Capsule History of Dynamics 1.2 The Importance of Being Nonlinear 1.3 A Dynamical View of the World PART I. ONE-DIMENSIONAL FLOWS 2. Flows on the Line 2.0 Introduction 2.1 A Geometric Way of Thinking 2.2 Fixed Points and Stability 2.3 Population Growth 2.4 Linear Stability Analysis 2.5 Existence and Uniqueness 2.6 Impossibility of Oscillations 2.7 Potentials 2.8 Solving Equations on the Computer Exercises 3. Bifurcations 3.0 Introduction 3.1 Saddle-Node Bifurcation 3.2 Transcritical Bifurcation 3.3 Laser Threshold 3.4 Pitchfork Bifurcation 3.5 Overdamped Bead on a Rotating Hoop 3.6 Imperfect Bifurcations and Catastrophes 3.7 Insect Outbreak Exercises 4. Flows on the Circle 4.0 Introduction 4.1 Examples and Definitions 4.2 Uniform Oscillator 4.3 Nonuniform Oscillator 4.4 Overdamped Pendulum 4.5 Fireflies 4.6 Superconducting Josephson Junctions Exercises PART II. TWO-DIMENSIONAL FLOWS 5. Linear Systems 5.0 Introduction 5.1 Definitions and Examples 5.2 Classification of Linear Systems 5.3 Love Affairs Exercises 6. Phase Plane 6.0 Introduction 6.1 Phase Portraits 6.2 Existence, Uniqueness, and Topological Consequences 6.3 Fixed Points and Linearization 6.4 Rabbits versus Sheep 6.5 Conservative Systems 6.6 Reversible Systems 6.7 Pendulum 6.8 Index Theory Exercises 7. Limit Cycles 7.0 Introduction 7.1 Examples 7.2 Ruling Out Closed Orbits 7.3 Poincare-Bendixson Theorem 7.4 Lienard Systems 7.5 Relaxation Oscillators 7.6 Weakly Nonlinear Oscillators Exercises 8. Bifurcations Revisited 8.0 Introduction 8.1 Saddle-Node, Transcritical, and Pitchfork Bifurcations 8.2 Hopf Bifurcations 8.3 Oscillating Chemical Reactions 8.4 Global Bifurcations of Cycles 8.5 Hysteresis in the Driven Pendulum and Josephson Junction 8.6 Coupled Oscillators and Quasiperiodicity 8.7 Poincare Maps Exercises PART III. CHAOS 9. Lorenz Equations 9.0 Introduction 9.1 A Chaotic Waterwheel 9.2 Simple Properties of the Lorenz Equations 9.3 Chaos on a Strange Attractor 9.4 Lorenz Map 9.5 Exploring Parameter Space 9.6 Using Chaos to Send Secret Messages Exercises 10. One-Dimensional Maps 10.0 Introduction 10.1 Fixed Points and Cobwebs 10.2 Logistic Map: Numerics 10.3 Logistic Map: Analysis 10.4 Periodic Windows 10.5 Liapunov Exponent 10.6 Universality and Experiments 10.7 Renormalization Exercises 11. Fractals 11.0 Introduction 11.1 Countable and Uncountable Sets 11.2 Cantor Set 11.3 Dimension of Self-Similar Fractals 11.4 Box Dimension 11.5 Pointwise and Correlation Dimensions Exercises 12. Strange Attractors 12.0 Introductions 12.1 The Simplest Examples 12.2 Henon Map 12.3 Rossler System 12.4 Chemical Chaos and Attractor Reconstruction 12.5 Forced Double-Well Oscillator Exercises Answers to Selected Exercises References Author Index Subject Index

Erbium‐Doped Fiber Amplifiers: Principles and Applications

Abstract: It is now widely recognized that erbium-doped fiber amplifiers have revolutionized optical fiber communications. EDFAs not only made single-channel, multigigabit-rate, long-distance optical communications possible, but they also opened up a wide variety of additional possibilities Such as soliton generation and transmission and multichannel wavelength-division multiplexing communications. While at AT&T Bell Labs (he is now at Alcatel-Alsthom Recherche in a suburb of Paris, France) Emmanuel Desurvire became heavily involved in and contributed enormously to the theoretical and experimental investigation of EDFA characteristics and system applications. His pioneering work has been internationally recognized. In my view, Desurvire is one of those best qualified to cover the subject of EDFAs, in Erbium-Doped Fiber Amplifiers: Principles and Applications, he has accepted the challenge. According to the author, the purpose of the book is "to provide the basic materials of a comprehensive introduction to the principles and applications of EDFAs." The book is divided into three major parts, which to some extent can be considered independently. Nonetheless, it keeps its cohesion throughout. It provides a thorough understanding of the fundamentals in optical amplification while considering the practical issues related to the device and system performance of EDFAs. The first part of the book explores all the fundamental issues related to EDFAs. It introduces the main concepts necessary for the modelling of the erbium atomic transition. The analysis is detailed and covers such parameters as field distributions and overlap integrals under different operating conditions. This section and the numerous relevant appendices contain a number of useful generalizations of existing models that are published for the first time. The author also considers the fundamental quantum properties of noise generation and accumulation in single- and multiple-stage amplification of classical light. The analysis discusses in great depth the nature, origin and inevitability of noise associated with optical amplification - it also provides useful engineering formulas for the measurement of the noise introduced by amplification. I found the treatment of noise and photon statistics particularly detailed and original. Researchers working on this subject can benefit enormously from the analysis. The second part is primarily experimental and focuses on EDFA device characteristics. However, when specific characteristics of the erbium transition are discussed, the necessary theoretical modifications and additions, supplementary to the general formulations given in the first part, are provided. I found that on the important issue of pulse amplification requirements, the book considers briefly only the special (but very exciting) case of solitons and misses the many problems associated with general pulse amplification. The third and final section of the book, on applications, is primarily concerned with some of the up-to-date linear and nonlinear communication systems and local area networks and the enormous impact that EDFAs have had on their successful implementation. The significance of the EDFAs in optically preamplified receivers is stressed. The most significant digital (linear) and soliton (nonlinear) system experiments performed to date are also reviewed. Initations imposed on linear systems by fiber nonlinearities and dispersion are briefly mentioned. The ground that Desurvire sought to cover in the third part is quite diverse and could well have been the subject of several separate volumes. Therefore, its inclusion in this book is inevitably of a review type. However, the book clearly points out how and to what degree these applications are benefited or enhanced by EDFAs. Overall the book gives one of the most comprehensive and detailed accounts of the physics and fundamental principles of erbium-doped fiber amplifiers published so far. I have not the slightest doubt that the book will be of great help to all scientists and engineers working in the field who are struggling to understand EDFAs. The unified and in-depth presentation of the subject will benefit in particular researchers and graduate students who are dealing with problems involving optical amplification. The book imparts the fundamental concepts quite skilfully and can be used as collateral reading The sections dealing with modelling and the entire second part could well be used in undergraduate courses. I do not hesitate to recommend the book enthusiastically to anybody having an interest in EDFAs and their applications.

Electron paramagnetic resonance : elementary theory and practical applications

Abstract: Basic Principles of Electron Paramagnetic Resonance Magnetic Interactions Between Particles Isotropic Hyperfine Effects in EPR Spectra g-Anisotropy in Solids Hyperfine Anisotropy in Solids Systems with More than One Unpaired Electron Paramagnetic Species in Gas Phase Transition-Group Ions The Interpretation of EPR Parameters Relaxation Times, Linewidths and Kinetic Phenomena Time-Dependent Excitation of Spins Double-Resonance Techniques Other Topics.

Spectroscopy and Imaging with Diffusing Light

Abstract: Visually opaque media are ubiquitous in nature. While some materials are opaque because they strongly absorb visible light, others, such as loam, white paint, biological tissue and milk, are opaque because photons traveling within them are predominantly scattered rather than absorbed. A vanishingly small number of photons travel straight through such substances. Instead, light is transported through these materials in a process similar to heat diffusion (figure 1).

The Quantum Theory of Fields, Vol. 1: Foundations

Abstract: Cambridge University Press) Available for the first time in paperback, The Quantum Theory of Fields is a self-contained, comprehensive, and up-to-date introduction to quantum field theory from Nobel Laureate Steven Weinberg. Volume I introduces the foundations of quantum field theory. The development is fresh and logical throughout, with each step carefully motivated by what has gone before. After a brief historical outline, the book begins with the principles of relativity and quantum mechanics, and the properties of particles that follow. Quantum field theory emerges from this as a natural consequence. The classic calculations of quantum electrodynamics are presented in a thoroughly modern way, showing the use of path integrals and dimensional regularization. It contains much original material, and is peppered with examples and insights drawn from the author's experience as a leader of elementary particle research. Exercises are included at the end of each chapter. Keyword(s): INSPIRE: book | quantum mechanics: relativistic | scattering | antiparticle | Feynman graph | quantum electrodynamics | path integral | field theory: nonperturbative | radiative correction | renormalization | infrared problem | bound state | external field | bibliography Record added 1996-05-19, last modified 2015-07-27 Export BibTeX, EndNote, LaTeX(US), LaTeX(EU), Harvmac, MARC, MARCXML, NLM, DC Information References (45) Citations (301) Files Plots The quantum theory of fields. Vol. 1: Foundations

Spin‐Polarized Transport

Abstract: A new field that has come to be called “spin‐polarized transport” is growing dramatically. Although its roots are in the quantum description of solids, only recently have new material fabrication techniques permitted widespread study of the phenomenon and the development of device applications (see figure 1).

Quantum Information and Computation

Abstract: Thpheoretical computer scientists, like their counterparts in physics, suffer and benefit from a high level of intellectual machismo. They believe they have some of the biggest brains around, which they need to think about some of the hardest problems. Like mathematicians, they prove theorems and doubt the seriousness of those who don't. Lately, however, theoretical computer scientists have sought the help of physicists in understanding quantum mechanics, a hard part of physics which they now believe has great significance for their own field.

Self-assembling amphiphilic systems

Abstract: Self-assembling Systems - Surfactants Lipids Fluid Mixtures - Binary and Ternary Systems Containing Amphiphile lnterfaces - Liquid-liquid Theories of Interfaces, Surface Phase Transitions Wetting Membranes.

Scanning Force Microscopy in Biology

Abstract: Microscopes have played a fundamental role in the development of biology as an experimental science It was Robert Hooke who, when using a compound microscope in 1655, noticed that thin slices of cork were made up of identical and small self‐contained units, which he called “cells” The generalization of this observation and its acceptance, though, had to wait until the late 1830s, when German microscopists Matthias Schleiden and Thcodor Schwann—working independently—introduced the “cell theory” of complex organisms By the second half of the 19th century Magnus Retzius, Santiago Ramon y Cajal and Camillo Golgi were busy completing the microscopic anatomical description of the cell

Complex dynamics of mesoscopic magnets

Abstract: For many years physicists thought small structures would be nearly ideal systems in which to explore and manipulate magnetic interactions. On a small enough length scale the interactions between individual atomic spins cause their magnetic moments to align in the ordered pattern of a single domain, without the complication of domain walls separating regions of varying orientation. For particle sizes at or below that of a single domain, many theoretical models of dynamical behavior predict simple, stable magnets with controllable classical properties. However, as with advances in semiconductor physics, the process of miniaturizing magnetic materials has unexpectedly revealed fascinating new classical and quantum mechanical phenomena. Even the simplest magnetic system, the isolated single‐domain particle, exhibits a wealth of exotic behavior that pushes us to the limits of our present understanding of the fundamentals of magnetism.

Thermoacoustic Engines and Refrigerators

Abstract: We ordinarily think of a sound wave in a gas as consisting of coupled pressure and displacement oscillations. However, temperature oscillations always accompany the pressure changes. The combination of all these oscillations, and their interaction with solid boundaries, produces a rich variety of “thermoacoustic” effects. Although these effects as they occur in everyday life are too small to be noticed, one can harness extremely loud sound waves in acoustically sealed chambers to produce powerful heat engines, heat pumps and refrigerators. Whereas typical engines and refrigerators have crankshaft‐coupled pistons or rotating turbines, thermoacoustic engines and refrigerators have at most a single flexing moving part (as in a loudspeaker) with no sliding seals. Thermoacoustic devices may be of practical use where simplicity, reliability or low cost is more important than the highest efficiency (although one cannot say much more about their cost‐competitiveness at this early stage).

Magnetoelectronics Today and Tomorrow

Abstract: Mention magnetics and an image arises of musty physics labs peopled by old codgers with iron filings under their fingernails—good science, this, but not the stuff from which career dreams are spun. Yes, you say, but what about the giant magnetic recording industry—it's still healthy, isn't it? Not according to some. The popular press has made statements about magnetic recording being a technology that has reached its maturity and has limited growth potential. Aficionados of semiconductor memory even advised a few years ago that memory cards based on semiconductor technology would become price competitive with magnetic hard‐disk drives by 1995. This prediction has fallen short by two orders of magnitude.

About Time: Einstein's Unfinished Revolution

Abstract: A very brief history of time time for a change timewarps black holes - gateways to the end of time the beginning of time - when exactly was it? Einstein's greatest triumph? quantum time imaginary time the arrow of time backwards in time time travel - fact or fantasy? but what time is it now? experimenting with time the unfinished revolution.

Special Issue: Magnetoelectronics

Abstract: Magnetism abounds with dichotomies: It was known to the ancients and yet is the focus of exciting new research; its manifestations are apparent to every schoolchild yet its origins are rooted deep in quantum mechanics and relativity; its applications underlie huge industries yet its understanding—even in iron—is still incomplete.

The Encyclopedia of Advanced Materials

Abstract: Actuators, K. Uchino batteries - the materials requirements, C.A. Vincent biomedical polymers, D.F. Williams carbon-carbon composites, L.E. McAllister and S. Awasthi deposition of amorphous silicon for solar cell applications, A. Madan directed metal oxidation, D.G. Brandon electron microprobe analysis, E. Lifshin ellipsometry and its applications to semiconductors, R.W. Collins fullerenes, H.W. Kroto and K. Prassides growth of quantum wells and strain-layer superlattices, P.S. Peercy high resolution electron microscopy - principles and limitations, J.L. Hutchison high temperature superconductors, C.E. Gough ion implantation-induced defects in semiconductors and their annealing behaviour, K.S. Jones interpenetrating polymer networks, L.H. Sperling joining of advanced materials - overview, T.W. Eager liquid crystals - overview, J.W. Goodby modelling - atomistic computer simulation in materials science, V. Vitek nanoelectronics, R.E. Nahory nanoscale materials - mechanical properties of metals, J. Weertman non-equilibrium structures - from chemical percursors, B. Kear nonlinear optical materials - overview, D. Bloor organic molecular beam epitaxy, H. Sasabe organometallic vapor phase epitaxy of II-VI layers, P.J. Sides phase transformations and coarsening processes - grain growth in thin films, C. Thompson photochromic materials, J. Whittall quantum-well and quantum-wire lasers, E. Kapon reactive processing of polymers, A.F. Johnson and P. Coates scanning tunneling microscopy - surface manipulation, Avouris and R.E. Walkup transmission electron microscopy, K. Vecchio ultra-large scale integrated circuits, K.C. Saraswat varistors, T.K. Gupta wear of ceramics, P. Boch X-ray diffraction with position sensitive detectors, M.B. Hursthouse zinc selenide, Hwa Cheng. (Part Contents).

Introduction to the Theory of the Integer Quantum Hall Effect

Abstract: Part 1 Introduction - Basic Facts: The Integer Quantum Hall Effect Classical Dynamics Quantizing Magnetic Fields The Eigenvalue Problem The Landau Model Models of Confinement Bloch Representation Disorder Broadening. Part 2 Quantum Hall Effect for Pedestrians - High Field Model: Confined Cylinder Model Spectral Conditions for the Quantum Hall Effect Systems with Contacts Robustness of the Quantum Hall Effect. Part 3 Linear Response Isothermal Susceptibilities: Dynamic Susceptibilities Conductivity Tensor Spectral Decomposition Conductivitie in Spectral Decomposition Hall Conductivity in Terms of the Center Coordinates - Multi-Probe Systems Conductance and Geometry Problems in Magnetotransport Calculations. Part 3 Phenomenology of Global Conductivities - Quantum Langevin Equation: Mori Theory Localization Criteria Hall Plateaus and Mobility Edges Finite Temperatures. Part 4 Localization in High Landau Bands - Quantum Corrections to the Conductivity: Quantum Wires Weak Localization Regime in the Quantum Hall Effect Localization in the Tails of High Landau Bands. Part 5 Averaging Green Functions - Gaussian Path Integrals: Supersymmetry Method Replica Tyick The Instanton Free Energy. Part 6 Localization in the Lowest Landau Band Density of States: Improved Perturbation Methods Inverse Participation Number Instanton Method - Density of States Localization in Band Tails.

Dusty and Self‐Gravitational Plasmas in Space

Abstract: Preface. Introduction. 1: Electrostatics of Dusty Plasmas. 2: Gravitoelectrodynamics. 3: Cooperative Effects in Self-Gravitational and Dusty Plasmas. 4: Unstable Disturbances in Flows of Dusty and Self-Gravitational Plasmas. 5: Dusty and Self-Gravitational Plasmas of Planetary Rings.

Electro‐Optic Effects in Liquid Crystal Materials

Abstract: 1 Liquid Crystalline State.- 1.1 Structure of Liquid Crystal Phases.- 1.1.1 Molecules.- 1.1.2 Thermotropic Mesophases Formed by Achiral Rod-Like Molecules.- 1.1.3 Thermotropic Chiral Mesophases.- 1.1.4 Mesophases of Disc-Like and Lath-Like Molecules.- 1.1.5 Polymer Liquid Crystals.- 1.1.6 Lyotropic Liquid Crystals.- 1.2 Mixtures.- 1.2.1 Nematic Eutectics.- 1.2.2 Reentrant Phases.- 1.2.3 Mixtures of Smectics.- 1.2.4 Nemato-Cholesteric Compositions.- 1.2.5 Ferroelectric Mixtures.- 1.3 Liquid Crystalline Materials.- 1.3.1 Chemical Classes.- 1.3.2 Chemical Structure and Transition Temperatures.- 1.3.3 Material.- 1.4 Direct Influence of an Electric Field on the Structure of Liquid Crystals.- 1.4.1 Field-Induced Shifts of the Phase Transition Temperatures.- 1.4.2 Influence of the Field on the Order Parameters.- 1.4.3 Field-Induced Changes in Symmetry.- References.- 2 Properties of the Materials.- 2.1 Dielectric Permittivity.- 2.1.1 Isotropic Liquids.- 2.1.2 Dielectric Anisotropy of Nematics.- 2.1.3 Nematic Mixtures.- 2.1.4 Other Phases.- 2.2 Electrical Conductivity.- 2.2.1 Dependence on Impurity Concentration.- 2.2.2 Conductivity Anisotropy.- 2.3 Optical Anisotropy and Dichroism.- 2.3.1 Optical Anisotropy.- 2.3.2 Dichroism.- 2.4 Viscoelastic Properties.- 2.4.1 Elasticity.- 2.4.2 Viscosity.- 2.4.3 Diffusion Coefficients.- References.- 3 Surface Phenomena.- 3.1 Structure of Surface Layers.- 3.1.1 Surface-Induced Changes in the Orientational Order Parameter.- 3.1.2 Surface-Induced Smectic Ordering.- 3.1.3 Polar Surface Order and Surface Polarization.- 3.2 Surface Energy.- 3.2.1 Wetting of a Solid Substrate.- 3.2.2 Surface Energy and Anchorage of a Nematic Liquid Crystal.- 3.2.3 Techniques for Measuring Anchoring Energies.- 3.3 Cells and Orientation.- 3.3.1 Electrooptical Cells.- 3.3.2 Liquid Crystal Orientation.- 3.3.3 Anchoring Transitions.- References.- 4 Electrooptical Effects Due to the Uniform Distortion of Nematic Liquid Crystals.- 4.1 Electrically Controlled Birefringence.- 4.1.1 Director Distribution.- 4.1.2 Tilted Directors at the Boundaries.- 4.1.3 Different Geometries. Simultaneous Action of Electric and Magnetic Fields.- 4.1.4 Effect of Electrical Conductivity.- 4.1.5 The Frederiks Transition for a Weak Anchoring at the Boundaries.- 4.1.6 Dynamics of the Frederiks Transition.- 4.1.7 The Frederiks Transition in Ferronematic Liquid Crystals.- 4.1.8 Optical Characteristics of the Electrically Controlled Birefringence Effect.- 4.2 Twist-Effect.- 4.2.1 Preparation of Twist Cells, Optical Properties at Zero Field.- 4.2.2 Transmission-Voltage Curve for Normal Light Incidence.- 4.2.3 Electrooptics of the Twist Cell for Oblique Incidence.- 4.2.4 Matrix Addressed Displays and Multiplexing Capability of Twist-Effect Materials.- 4.2.5 Dynamics of the Twist Effect.- 4.2.6 New Possibilities.- 4.3 Supertwist Effects.- 4.4 "Guest-Host" Effect.- 4.4.1 Change in Intensity of the Coloring.- 4.4.2 Colorimetry of "Guest-Host" Displays.- 4.4.3 Color Switching.- 4.4.4 Change in Fluorescence.- 4.5 The Flexoelectric Effect.- 4.5.1 Physical Reasons.- 4.5.2 Static Flexoelectric Distortion in Different Geometries Determination of Flexoelectric Moduli.- 4.5.3 Dynamics of the Flexoelectric Effect.- 4.5.4 Microscopic Approach to Determination of the Flexoelectric Coefficients.- 4.6 Reflectivity in an Electric Field.- 4.6.1 Optical Properties of Nontwisted Nematic Layers.- 4.6.2 Various Techniques.- 4.7 Field Behavior of the Isotropic Phase.- 4.7.1 The Kerr Effect in the Isotropic Phase.- 4.7.2 Reorientation of Surface Quasi-Nematic Layers.- 4.8 Electric Field Effects in Nematic Polymers.- 4.8.1 Thermotropic Mesophases.- 4.8.2 Lyotropic Polymers 212.- 4.9 Electrooptical Properties of Polymer Dispersed Liquid Crystal Films.- References.- 5 Modulated and Nonuniform Structures in Nematic Liquid Crystals.- 5.1 Orientational Modulated Structures.- 5.1.1 Flexoelectric Domains.- 5.1.2 Dielectric Two-Dimensional Structure in the Frederiks Transition.- 5.1.3 Other Types of Modulated Structures.- 5.2 Electrohydrodynamic Modulated Structures.- 5.2.1 Low-Frequency Limit The Kapustin-Williams Domains.- 5.2.2 Different Types of Low-Frequency Electrohydrodynamics.- 5.2.3 Electrohydrodynamic Instability in Nematics with Oblique Director Orientation at the Boundaries.- 5.2.4 Electrohydrodynamic Instability: "Chevron" Mode.- 5.2.5 Anisotropic Instabilities for Different Field and Cell Configurations.- 5.2.6 Allowance for Flexoelectricity in Anisotropic Domain Structures.- 5.2.7 High-Frequency Inertia Anisotropic Mode.- 5.2.8 Modulated Structures with Large Periods in Homeotropic Nematics.- 5.2.9 "Isotropic" Mechanism of the Excitation of Electrohydrodynamic Domains.- 5.2.10 Instabilities in Homeotropic Nematics with ?? >0.- 5.2.11 Classification of Threshold Conditions for Different Instabilities in Nematics.- 5.2.12 Electrohydrodynamic Instabilities in Polymer Nematics.- 5.2.13 The Instabilities above the Threshold Voltage. Dynamic Scattering of Light.- 5.3 Nematics in Spatially Nonuniform Fields.- 5.3.1 Homeotropic Orientation.- 5.3.2 Homogeneous Alignment.- 5.3.3 Twist Cells.- References.- 6 Electrooptical Properties of Cholesterics and Nonferroelectric Smectics.- 6.1 The Pitch of Helix and the Optical Properties of Cholesterics.- 6.1.1 Textures.- 6.1.2 Methods of Measuring the Pitch.- 6.1.3 Optical Properties of Planar Cholesteric Textures.- 6.1.4 Diffraction on the Focal-Conic Texture.- 6.1.5 Pitch Dependence on Cell Thickness.- 6.2 Field-Induced Dielectric Instabilities of Cholesterics.- 6.2.1 Texture Transitions.- 6.2.2 Instability of the Planar Cholesteric Texture.- 6.2.3 Field Untwisting of a Cholesteric Helix.- 6.2.4 Electrically Switched Bistable Structures.- 6.3 Electrohydrodynamic Instabilities in Cholesterics.- 6.4 Flexoelectric Effects.- 6.4.1 Fast Linear-in-Field Rotation of the Cholesteric Helix.- 6.4.2 Flexoelectric Domains.- 6.5 Electrooptical Effects in Blue Phases.- 6.5.1 Optical Features.- 6.5.2 Field Behavior.- 6.6 Electric Field Behavior of Nonferroelectric Smectics.- 6.6.1 The Frederiks Transition in a Smectic A.- 6.6.2 Dielectrically Induced Texture Transitions.- 6.6.3 The Frederiks Transition in a Smectic C.- 6.6.4 Electrohydrodynamic Instabilities in Smectics A and C.- References.- 7 Ferroelectric Liquid Crystals.- 7.1 The Physical Properties of Ferroelectric Liquid Crystals. Methods of Measurement.- 7.1.1 The Symmetry.- 7.1.2 The Microscopic Approach. Ferroelectric Mixtures.- 7.1.3 Physical Parameters.- 7.1.4 Tilt Angle.- 7.1.5 Spontaneous Polarization.- 7.1.6 Flexoelectric Polarization.- 7.1.7 Rotational Viscosity.- 7.1.8 Helix Pitch.- 7.1.9 Dielectric Properties.- 7.1.10 Optical Properties.- 7.1.11 Total Free Energy with Allowance for Anchoring.- 7.2 Electrooptical Effects in Ferroelectric Liquid Crystals.- 7.2.1 The Clark-Lagerwall Effect.- 7.2.2 Deformed Helix Ferroelectric Effect.- 7.2.3 Electroclinic Effect Near the Smectic A ? C* Phase Transition.- 7.2.4 Other Electrooptical Effects.- 7.2.5 Orientation of Samples.- 7.2.6 Problems of Bistability Realization.- 7.3 Ferroelectric Liquid Crystal Polymers.- 7.3.1 Introductory Remarks.- 7.3.2 Chemical Structures.- 7.3.3 Ferroelectricity.- 7.3.4 Electrooptical Switching.- References.- 8 Applications of Electrooptical Liquid Crystalline Materials.- 8.1 Displays.- 8.1.1 Active Matrix Addressed Displays.- 8.1.2 Supertwist Displays for Personal Computers.- 8.1.3 Projection Displays.- 8.1.4 Guest-Host Large Area Information Boards.- 8.1.5 General Trends in Display Applications.- 8.2 Optical Data Processing Devices.- 8.2.1 Light Valves.- 8.2.2 Modulators, Shutters.- 8.2.3 Deflectors of Light.- 8.2.4 Integrated Optical Devices.- 8.2.5 Matrix Spatial Light Modulators or Controlled Transparencies.- 8.2.6 Liquid Crystal Logic Elements.- 8.2.7 Optical Filtration.- 8.2.8 Application of Polymer Liquid Crystals in Optoelectronics.- 8.3 Other Applications.- 8.3.1 Storage Devices.- 8.3.2 Stereoscopic Liquid Crystal Sytems.- 8.3.3 Nondestructive Testing.- 8.3.4 Large Area Glass Light Shutters on Polymer Dispersed Liquid Crystal Films.- References.

Micromagnetic Microscopy and Modeling

Abstract: With the miniaturization of magnetic technologies, the need to understand magnetization on length scales below a micron is becoming increasingly important. This booming interest in micro magnetics has fueled a renaissance in both micro‐magnetic modeling and measurement techniques. Conversely, the codevelop‐ment of modeling and imaging has made possible recent advances in this critical area of magnetism. On the modeling side, the rapid development of high‐speed computing has had a tremendous impact on micromagnetics simulations. On the measurement side, a number of microscopies have been developed for imaging on a length scale of tens of nanometers. Figure 1 shows an image of rows of bits in a magneto‐optical medium. The bits were both written and imaged using a magnetic force microscope. Results on this length scale provide information that can be used in models and also challenge models’ predictive capabilities. The image on the cover of this issue shows naturally occurring domain patterns in a single‐cr...

Advances in X‐Ray Analysis

Abstract: The 35th Annual Denver Conference on Applications of X-Ray Analysis was held August 4-8, 1986, on the campus of the University of Denver. Since the previous year's conference had emphasized x-ray diffraction, this year the Plenary Session spotlighted x-ray fluorescence, with the title "Trends in XRF: A World Perspective," featuring renowned speakers from three major areas. XRF IN NORTH AMERICA, by Prof. D. E. Leydon, from Colorado State University, dealt specifically with developments in the fields of instrumentation, data treatment and applications in that part of the world. Prof. H. Ebel, from the Technical University of Vienna, discussed XRF IN EUROPE, concentrating on subjects including total reflection, improved fundamental parameters, quantitation without standards and imaging techniques. Tomoya Arai, of the Rigaku Industrial Corporation in Japan, in considering XRF IN THE FAR EAST, described the scientific activity in XRF and the applications thereof, primarily in Japan and China. These plenary lectures were interspersed with short discussions of PERSONAL OBSERVATIONS on the subject by the co-chairmen of the SeSSion, Ron Jenkins and myself. The intent of this session was to bring the audience up-to-date on the status of the field in various parts of the world, and to give some feeling concerning where it is likely to go in the immediate future. Hopefully, the publication of the written versions of those presentations in this volume will make the authors' thoughts available to many who could not be present at the conference.

Interactions of Ultra‐Intense Laser Light with Matter

Abstract: When the laser made its debut in 1960, it was often called a solution looking for a problem. Today the laser is hailed as one of the most significant inventions of the 20th century. Lasers are used in almost all fields of science and technology, and they have become commonplace in daily life, from supermarket scanners to CD players. The recent development of ultrahigh‐power lasers has opened exciting research opportunities in the field of laser‐matter interactions. They range from the interaction of laser light with single atoms to collective effects in plasmas.

Electronic Pairing in Exotic Superconductors

Abstract: Investigations of rare earth, Aactinide, organic and oxide compounds have yielded several new classes of exotic superconductors. These include magnetically ordered superconductors, A15 superconductors, buckyball superconductors, heavy‐electron superconductors, organic superconductors and high‐Tc oxide superconductors. These materials have properties significantly different from those of conventional superconductors such as Al and Zn, which are described well by the Bardeen‐Cooper‐Schrieffer model of superconductivity. We carefully distinguish between the BCS model and the more general BCS theory. In the BCS theory superconductivity arises, loosely speaking, from electron pairs that behave essentially as bosons and undergo macroscopic condensation to the lowest energy state at the critical temperature Tc The BCS model, presented in 1957, further specifies that the pairing is mediated by exchange of quantized lattice vibrations (phonons) between the electrons, yielding pairs with zero spin S (spin singlet) ...

How Would a Physicist Design a Tennis Racket

Abstract: Tennis players dream of finding Lhe perfect racket that will immediately transform them into champions. While that may be wishful thinking, it is generally agreed that today's rackets are much better than those of 20 years ago. Though they may not turn you into an instant Wimbledon winner (after all, your opponent has one too), they will clearly improve your game. There is still hope among inventors, racket manufacturers and players that a perfect racket will come along someday. If and when such a racket is developed, what will its properties be and how will it affect the game of tennis?

The First Nuclear Era: The Life and Times of a Technological Fixer

Abstract: Alvin Weinberg is one of the most influential nuclear engineers & physicists in the U.S., having participated in many high profile projects from the early days of nuclear research on into the 1980s. This book is his autobiography and it's peppered with first-hand accounts of major historical events. He writes about the events of December 2, 1942, when Fermi set into motion the first chain reaction in a uranium pile and goes on to describe what happened during the "First Nuclear Era" a period he admits that has now largely run its course. A proponent of nuclear power, Weinberg also exposed its down- side risks and for years remained in the forefront of strong science administration.

Symmetry in Physics: Wigner's Legacy

Abstract: Until the twentieth century, principles of symmetry played little explicit role in theoretical physics. Conservation laws, especially those of energy and momentum, were considered to be of fundamental importance. But these were regarded as consequences of the dynamical laws of nature, rather than as consequences of the symmetries that underlay these laws. Maxwell's equations, formulated in 1865, embodied both Lorentz invariance and gauge invariance. But these symmetries of electrodynamics were not fully appreciated for 40 years or more.