bluuebunny/crossref_metadata_2025 huggingface dataset:
Pairwise potentials in simple metals
Authors: Finnis Mike
Published: January 2010

This chapter shows how pairwise potentials for simple, s-p bonded metals, can be derived from first-principles. The starting point is jellium, and the ions are specified as pseudopotentials, local or non-local. The application of perturbation theory to second order in the pseudopotentials leads to the energy in the form of a density dependent, structure independent term plus a sum of density dependent, pairwise interactions between the ions. With the help of the Hellmann–Feynman theorem a simple physical interpretation is given in terms of interacting, spherically-symmetric pseudoatpms. A simple example using the Ashcroft empty core pseudopotential and the Thomas–Fermi approximation is worked through to illustrate the concepts. The use of a local density as a parameter within the pair potential is discussed.
Ionic Models
Authors: Finnis Mike
Published: January 2010

This chapter presents models for interatomic potentials in ionic materials. As for the other models described in this book, the derivations are based on density functional theory and the variational principle, which leads to all the commonly used types of model. The simplest model of all is the rigid ion model, or Born model. It is introduced here by changing the charges on the nuclei in a rare gas solid and applying first-order perturbation theory. To go beyond the rigid ion model the second-order functional derived previously is invoked. This leads to a class of models with deformable ions, the simplest example of which has the same structure as the classical shell model. Compressible ion and variable charge transfer models are discussed. Classical charge transfer models are seen as equivalent to self-consistent tight-binding model in which the effect of covalency is neglected.
7 Experimental techniques
Authors: Hempelmann Rolf
Published: January 2010

This chapter describes the practical aspects of quasielastic neutron scattering experiments and the necessary processing of raw data, including tips and tricks. The sample thickness has to be chosen as a compromise between sufficiently high scattering intensity and sufficiently low multiple scattering. For the background subtraction, self-shielding has to be taken into account, and then resolution corrections have to be performed. For complex situations with the superposition of several scattering components, a simultaneous fit enables the extraction of desired information from the data. Another problem is multiple scattering; corresponding correction strategies are outlined. Finally, the two spectrometer types most commonly used for quaisielastic neutron scattering experiments — time-of-flight instruments and backscattering instruments — are described in some detail. As a related method, quasielastic Mössbauer spectroscopy is briefly mentioned.
9 Metals and alloys
Authors: Hempelmann Rolf
Published: January 2010

For the fcc noble metals and for bcc metals of group V and VI such as Mo, W, V, and Nb, atomic diffusion is slow compared to the case of bcc alkali metals Li, Na, or K. The group IV metals Ti, Zr, and Hf have still higher diffusivities. The first section of the chapter describes the investigation of sodium diffusion, in particular presenting the encounter model of vacancy diffusion in detail. The second part deals with similar experiments on bcc-β-titanium, where the relation between high diffusivity and soft modes as measured by triple axis spectrometry is explained. QENS diffusion studies are also performed for some alloys and intermetallic compounds.
Fabrication techniques and methods for semiconductor quantum dots
Authors: Ustinov Victor M. , Zhukov Alexey E. , Egorov Anton Yu. , Maleev Nikolai A.
Published: January 2010

This chapter first considers the basic principles of molecular beam epitaxy (MBE) of III-V materials. It describes a typical MBE system and its components with special attention to the reflection high-energy electron diffraction system for in-situ monitoring of a growth surface. Metal organic chemical vapour deposition (MOCVD), chemical reactions in MOCVD process and typical reactor scheme are then described. The chapter also describes different methods of in situ formation of one- or zero-dimensional quantum size objects, including formation of quantum wires on a V-grooved substrate, quantum wires and dots on high-index surfaces, and selective epitaxial growth of low-dimensional structures. Special attention is paid to a method of quantum dot formation in Stranski–Krastanow growth mode.
Power characteristics of quantum dot lasers
Authors: Ustinov Victor M. , Zhukov Alexey E. , Egorov Anton Yu. , Maleev Nikolai A.
Published: January 2010

This chapter considers the quantum dot active region as a possible candidate for high-power laser applications. Thermal rollover, catastrophic optical mirror damage, and other mechanisms of power limitation in diode lasers are discussed, taking into account specific aspects of quantum dot lasers. Power conversion efficiency in a QD laser is analytically treated, and influence of laser structure and QD parameters is also discussed. Internal loss and other parameters affecting slope efficiency of a QD laser are considered in connection with inherent properties of self-organized quantum dots. The chapter also addresses issues associated with the realization of a continuous-wave lasing regime in QD lasers. Device characteristics are summarized for state-of-the-art high-power quantum dot lasers operating in the 0.9-1.1 and 1.2-1.3 spectral ranges.
Conclusions
Authors: Ustinov Victor M. , Zhukov Alexey E. , Egorov Anton Yu. , Maleev Nikolai A.
Published: January 2010

This chapter presents some concluding remarks. Remarkable progress in the development of self-organized quantum dot lasers is pointed out and the most notable results, e.g. a record-low threshold current density, are briefly summarized. The main parameters of QD arrays affecting the laser’s threshold characteristics are emphasized. It is recognized that device performance of existing QD lasers is still inferior when compared with the theoretical predictions for the ideal quantum dots. Inhomogeneous broadening associated with the size non-uniformity of the islands is the main problem that still remains. An expectation of bright prospects is expressed for device application of quantum dots emitting in wavelength ranges beyond the spectral limit of a quantum well.
Dynamical Theory of X-Ray Diffraction
Authors: Authier André
Published: January 2010

X-ray diffraction is a major tool for the study of crystal structures and the characterization of crystal perfection. Since the discovery of X-ray diffraction by von Laue, Friedrich, and Knipping in 1912 two basic theories have been used to describe this diffraction. One is the approximate geometrical, or kinematical theory, applicable to small or highly imperfect crystals; it is used for the determination of crystal structures and the study of powders and polycrystalline materials. The other one is the rigorous dynamical theory, applicable to perfect or nearly perfect crystals and, for that reason, is the one used for the assessment of the structural properties of high technology materials. It has witnessed exciting developments since the advent of synchrotron radiation. This book provides an account of the dynamical theory of diffraction and of its applications. The first part serves as an introduction to the subject, presenting early developments, Ewald's theory of dispersion and the basic results of Laue's dynamical theory. This is followed in the second part by a detailed development of the diffraction and propagation properties of X-rays in perfect crystals, including the study of anomalous absorption, Pendellösung, grazing incidence diffraction (GID) and n-beam or multiple-beam diffraction. The third part constitutes an extension of the theory to the case of slightly and highly deformed crystals. The last part gives three applications of the theory: X-ray optics for synchrotron radiation, location of atoms at surfaces and interfaces and X-ray diffraction topography.
3 Geometrical theory of X-ray diffraction
Authors: AUTHIER ANDRÉ
Published: January 2010

This chapter describes a concise summary of the geometrical theory of X-ray diffraction, which is not the main topic of the book. The amplitude diffracted by a periodic electron distribution is calculated and the structure factor is introduced. The intensity diffracted by a small crystal is then calculated and the expression of the angular variations of the reflectivity discussed. Finally, the integrated intensity is calculated both in the reflection and the transmission geometries and the mosaic crystal model introduced.
Elementary dynamical theory
Authors: AUTHIER ANDRÉ
Published: January 2010

This chapter presents the basic properties of dynamical diffraction in an elementary way. The relationship with the band theory of solids is explained. The fundamental equations of dynamical theory are given for scalar waves as a simplification; the solutions of the propagation equation are then derived for an incident plane wave in the 2-beam case; and the amplitude ratio between reflected and refracted waves deduced. The notions of wavefields, dispersion surface, and tie points are introduced. Two experimental set-ups are considered: transmission and reflection geometries. The boundary conditions at the entrance surface of the crystal are expressed in each case and the intensities of the refracted and reflected waves calculated as well as the anomalous absorption coefficient, due to the Borrmann effect, the Pendellösung interference fringe pattern and the integrated intensity. It is shown that the geometrical diffraction constitutes a limit of dynamical diffraction by small crystals. At the end of the chapter dynamic diffraction by quasicrystals is considered.
5 Properties of wavefields
Authors: AUTHIER ANDRÉ
Published: January 2010

This chapter is the first of the next few chapters devoted to plane-wave advanced dynamical theory. The fundamental equations of dynamical diffraction are derived for vector waves and the expression of the dispersion equation is given in the two-beam case and for absorbing crystals, the following discussion being limited to geometrical situations where neither the incidence nor the emergence angle is grazing. The notion of wavefields and the dispersion surface are introduced, and it is shown that the Poynting vector, which gives the direction of propagation of the energy, is normal to it. The boundary conditions at the entrance surface are then introduced. Transmission and reflection geometries are treated separately. For each case, the deviation parameter is introduced geometrically and the coordinates of the tiepoints determined, the Pendellösung distance (extinction distance in the reflection geometry), Darwin width, the anomalous absorption coefficient, index of refraction, the phase and amplitude ratios of the reflected and refracted waves are calculated. Borrmann's standing wave interpretation of the anomalous absorption effect is given. The last section is to the case where Bragg's angle is close to π/2.
13 Ray tracing in slightly deformed crystals
Authors: AUTHIER ANDRÉ
Published: January 2010

This chapter is devoted to the propagation of X-ray wavefields in slightly deformed crystals where the deformation is small enough for the notions of dispersion surface and wavefields to be locally valid. A local reciprocal-lattice vector and local effective misorientation are defined. The trajectories of the wavefields (ray tracing) are determined using the Eikonal approximation. The case of a constant strain gradient is considered in detail and it is shown that the ray trajectories are bent, giving rise to the mirage effect; both the transmission and reflection geometries are considered. The diffracted intensities are calculated for an incident plane wave and an incident spherical wave. Shape of the Pendellösung fringes in a deformed crystal is discussed.
16 Location of atoms at surfaces and interfaces using X-ray standing waves
Authors: AUTHIER ANDRÉ
Published: January 2010

This chapter describes the use of dynamical diffraction for the location of atoms and impurities at surfaces and interfaces using the standing waves formed by the superposition of the incident and reflected waves. After an introduction giving the principle of the method and its historical development, the variations of the intensity of the wavefield in the reflection, or Bragg, geometry are calculated and the fluorescent yield determined. Applications to the determination of surface structures, nature and position of impurities, polarity of heteropolar crystals are described. The case of deformed crystals is also considered. The last section concerns standing waves associated with specular reflection.
Better accuracy from simple pendulums
Authors: Matthys Robert James
Published: January 2010

This chapter deals with simple pendulums and with several things that can be done to improve their accuracy. Most of the items have only a minor effect on accuracy, but they add up. The pendulum should be enclosed in a case to protect it from the air currents of an open room, which will push the pendulum around and give erratic timing. A metal pendulum rod is recommended over a wooden one. If the pendulum is not temperature compensated, a low thermal expansion metal like iron must be chosen for the pendulum rod. If the pendulum is not temperature compensated, the bob must be supported at its bottom edge rather than at its middle or top edge. Other tips: use a low drag bob shape, walls dose to the pendulum cause a problem with relative humidity; slide the top end of the suspension spring up and down through a narrow slot; keep the number of piece parts and mechanical joints in a pendulum to a minimum.
Does a pendulum’s axis of rotation shift with amplitude?
Authors: Matthys Robert James
Published: January 2010

This chapter describes an experiment to determine whether a pendulum's axis of rotation moves when the swing amplitude is increased. This issue presupposes that the pendulum has a flat spring type of suspension. A flat suspension spring bends all along a section of its length, so there is no obvious reason to indicate that a pendulum's axis of rotation would remain fixed when the swing amplitude is increased. The axis of rotation is found by measuring the horizontal travel of two points on the pendulum rod, one point a little above the axis of rotation and the other a little below it. The axis of rotation does move downward slightly (down the suspension spring), as the pendulum's swing amplitude increases. This should make the pendulum speed up as the amplitude increases, but in reality a pendulum actually slows down with increasing amplitude.
Putting Q in perspective
Authors: Matthys Robert James
Published: January 2010

Q is a clock oscillator's quality factor, a measure of how low its energy losses are with respect to the total energy stored in the motion of the oscillator. This chapter provides some new information on Q and looks at arguments both for and against it. The value of Q rests on two facts: that increasing a pendulum's Q means lower drive forces, which means less pendulum disturbance, which means a more accurate clock; and that historically (but not scientifically), a higher Q generally means a higher long-term accuracy. On a global scale of wristwatches to atomic frequency standards, Q is historically often proportional to long-term clock accuracy. This makes Q significant as an indicator of clock accuracy on a global clock scale. On the more limited scale of pendulum clocks by themselves, both temperature compensation and aging are more important issues than Q since their errors are bigger than the increased accuracy available from an increased Q.
Barometric compensation with a crossed spring suspension?
Authors: Matthys Robert James
Published: January 2010

A crossed spring suspension provides an axis of rotation characterised by extremely low friction, something that a pendulum can use. The suspension typically consists of four flat strips of spring metal (two sets of two, with the two sets oriented at 90 degrees to each other) that are clamped at the ends. For small rotation angles, the axis of rotation is nominally located at the springs' crossover point in the middle of the springs. The suspension has three important characteristics. First, it has extremely low friction. Second, the rotational stiffness of the suspension springs (in units of torque per unit angle about the axis of rotation) varies with the total weight suspended from the springs, that is, with the weight of the pendulum. Third, the axis of rotation moves horizontally as the pendulum swings away from its vertical orientation in the center of swing. This chapter proposes an idea for barometric compensation of a pendulum using a crossed spring suspension.
Stability of suspension spring materials
Authors: Matthys Robert James
Published: January 2010

A pendulum's suspension spring is so simple physically, and yet so complicated in questions of size, what material to use, bending fatigue, length stability, the effects of its Young's modulus varying with temperature, how to solidly grab hold of its top and bottom ends, whether to use one spring or two, etc. This chapter deals with the first four questions. The suspension spring's length, thickness, and material are varied to determine how these parameters affect the pendulum's timing and thermal hysteresis. The goal is to improve the timing and reduce the thermal hysteresis. This chapter covers what actually happens in practice to a pendulum when the suspension spring's length, thickness, and material are changed. Experimental results show that type 642 aluminum silicon bronze, hard temper, is the best material for a pendulum's suspension spring.
Electronic correction for air pressure variations
Authors: Matthys Robert James
Published: January 2010

At atmospheric pressure, a pendulum is slightly buoyant to a ‘sea’ of air. This buoyancy causes the pendulum's timing to be a little sensitive to the air's density, and consequently to its pressure. Timing error can be corrected mechanically by putting a small bellows-supported weight on the pendulum. As the air pressure increases, the bellows shrinks and lowers the weight resting on top of it, speeding up the pendulum to compensate for its natural slowdown with increasing pressure. This assumes that the bellows' weight is located in the pendulum's upper half. If located in the lower half, the bellows-supported weight must hang below the bellows instead of sitting on top of it. The effect of the air pressure variations can also be corrected for electronically, using a silicon-based pressure sensor, some electronic circuitry, and an electromagnetic (coil and magnet) pendulum drive. This chapter describes an electronic circuit that corrects for a pendulum's air pressure variations.
Boltzmann Equation
Authors: Brilliantov Nikolai V. , Pöschel Thorsten
Published: January 2010

The evolution of the velocity of the distribution function is governed by the Boltzmann equation. This chapter derives the Boltzmann equation for the homogeneous cooling granular gas and discusses the properties of the collision in general.
High-Energy Tail of the Velocity Distribution Function
Authors: Brilliantov Nikolai V. , Pöschel Thorsten
Published: January 2010

The velocity distribution function of particles whose velocities exceed the thermal velocity cannot be described by a Maxwell distribution. This chapter shows that this part of the velocity distribution is described by an exponential function which decays significantly slower than a Maxwell distribution.
Kinetic Coefficients for Granular Gases of Viscoelastic Particles
Authors: Brilliantov Nikolai V. , Pöschel Thorsten
Published: January 2010

This chapter analyzes the kinetic coefficients for granular gases of viscoleastic particles. The kinetic coefficients reveal a much more complicated time and temperature dependence than for the case of ε = const. For such gases, the transport coefficients and cooling rates have different temperature dependencies.
Chapman-Enskog Method for the Self-Diffusion Coefficient
Authors: Brilliantov Nikolai V. , Pöschel Thorsten
Published: January 2010

The coefficient of self-diffusion was previously derived using the velocity-time correlation function. This chapter derives this coefficient using the Chapman–Enskog approach.
Two-Dimensional Granular Gases
Authors: Brilliantov Nikolai V. , Pöschel Thorsten
Published: January 2010

This chapter discusses constant coefficient of restitution and granular gases of viscoelastic particles.
Structure Formation in Granular Gases of Viscoelastic Particles
Authors: Brilliantov Nikolai V. , Pöschel Thorsten
Published: January 2010

This chapter begins with a discussion of linearized equations for hydrodynamic modes. It then discusses stability analysis of the hydrodynamic modes and structure formation, and structure formation as a transient process. The stability analysis of hydrodynamic equations for a gas of viscoleastic particles shows that the conditions of instability for shear and heat modes depend on time. Thus, structure formation in granular gases is a transient process. Over time, the granular gas returns to the homogeneous cooling state.
Two-Dimensional Granular Gases
Authors: Brilliantov Nikolai V. , Pöschel Thorsten
Published: January 2010

This chapter presents hydrodynamic equations for two-dimensional granular gases.
Coherent Interactions
Authors: BARNETT STEPHEN M. , RADMORE PAUL M.
Published: January 2010

This chapter presents some of the models describing the time-dependent interaction between a simple atom and a field, which may be described either classically or fully quantum mechanically. A number of equivalent interaction pictures and the important rotating-wave approximation are introduced. The two-state dynamics of an atom coupled to a classical field is solved, starting with perturbation theory. Non-perturbative behaviour is analysed, leading to Rabi oscillations of the atomic probabilities. The Jaynes–Cummings model of the dynamics of a single two-state atom coupled to a single quantized mode of the electromagnetic field is solved leading to collapses and revivals of the excited state probability. An exactly soluble model of the coupling of a single state to a Bixon–Jortner quasi-continuum of discrete levels is analysed. Finally, the coherent interactions between two field modes, of the type common in nonlinear optics, are discussed.
Dressed States
Authors: BARNETT STEPHEN M. , RADMORE PAUL M.
Published: January 2010

A dressed state is defined as an eigenstate of the total Hamiltonian, including interactions. Once these dressed states are found, and their energies known, the dynamics of the system is simple: the total state is a superposition of these states, the amplitudes being constant. The dressed states are derived for a two-state system, a three-state system and the Bixon–Jortner model. Dissipative systems are treated using Fano theory. Related techniques, suited to the Heisenberg picture, involve dressed operators. Two examples of physical interest are discussed: an imperfect cavity, and the Jaynes–Cummings model.
Lagrangian Theory of Constraints
Authors: Johns Oliver
Published: January 2010

One attractive feature of the Lagrangian method is the ease with which it solves so-called constraint problems. This chapter presents several different ways of solving such problems, with examples of each. In the previous chapter, the generalised coordinates were assumed to be independent variables. However, there are problems of interest in which these coordinates are not independent, but rather are forced into particular relations by constraints. In this chapter, constraints are defined and virtual displacement is discussed, along with virtual work, form of the forces of constraint, general Lagrange equations with constraints, alternate notation for holonomic constraints, reduction of degrees of freedom, recovery of the forces of constraint, generalised energy theorem with constraints, and tractable non-holonomic constraints.
Lagrangian Mechanics with Time as a Coordinate
Authors: Johns Oliver
Published: January 2010

In traditional analytical mechanics, it is assumed that the system traces out a path (one-dimensional curved line) in a D dimensional configuration space that is defined by writing each of the generalised coordinates as a function of the absolute, Newtonian time. The extended Lagrangian theory combines the traditional Lagrange equations and generalised energy theorem into a single set of equations, and restores the symmetry of the mathematical system. The traditional Lagrangian methods are analogous to the ‘coordinate parametric method’ in the calculus of variations and to the recommended ‘general parametric method’ presented earlier. This chapter discusses Lagrangian mechanics in which time is treated as a coordinate, extended momenta, invariance under change of parameter, change of generalised coordinates, redundancy of the extended Lagrange equations, forces of constraint, and reduced Lagrangians with time as a coordinate.
Hamiltonian Mechanics with Time as a Coordinate
Authors: Johns Oliver
Published: January 2010

In the previous chapter, the traditional Lagrange equations were used as the basis for an extended Lagrangian theory in which time is treated as a coordinate. This extended theory combined the Lagrange equations and the generalised energy theorem into one set of equations. In the present chapter, the same is done with the traditional Hamilton equations. The traditional Hamilton equations, including the Hamiltonian form of the generalised energy theorem, are combined into a single set of extended Hamilton equations in which time is treated as a coordinate. The chapter also discusses the extended phase space, dependency relation, shift from traditional to extended Hamiltonian mechanics, equivalence to traditional Hamilton equations, example of extended Hamilton equations, equivalent extended Hamiltonians, alternate Hamiltonians, alternate traditional Hamiltonians, Dirac’s theory of phase-space constraints, Poisson brackets with time as a coordinate, and Poisson brackets and quantum commutators.
Experimental Techniques for Low-Temperature Measurements
Authors: Ekin Jack
Published: January 2010

This book presents an integrated, step-by-step approach to the design and construction of low-temperature measurement apparatus. It is effectively two books in one: a textbook on cryostat design techniques and an appendix data handbook that provides materials-property data for carrying out that design. The main text encompasses a wide range of information. After summarizing cooling methods, Part I provides core information in an accessible style on techniques for cryostat design and fabrication — including heat-transfer design, selection of materials, construction, wiring, and thermometry, accompanied by many graphs, data, and clear examples. Part II gives a practical user's perspective of sample mounting techniques and contact technology. Part III applies the information from Parts I and II to the measurement and analysis of superconductor critical currents, including in-depth measurement techniques and the latest developments in data analysis and scaling theory. The appendix is a ready reference handbook for cryostat design, encompassing seventy tables compiled from the contributions of experts and over fifty years of literature.
Introduction to Measurement Cryostats and Cooling Methods
Authors: Ekin Jack W.
Published: January 2010

This chapter presents an overview of useful types of measurement cryostats for the temperature range from 300 K to about 1 K. It also introduces cooling options and the properties of the most common cryogenic liquids and their powerful cooling capability.
Heat Transfer at Cryogenic Temperatures
Authors: Ekin Jack W.
Published: January 2010

This chapter discusses heat transfer in cryogenic design. Topics covered include heat conduction through solids and gases (and liquids), radiative heat transfer, heat conduction across liquid/solid interfaces, heat conduction across solid/solid interfaces, and heat conduction across solid/gas interfaces. Examples of heat-transfer calculation are presented.
Cryostat Construction
Authors: Ekin Jack W.
Published: January 2010

The first part of this chapter covers techniques common to the construction of most cryostats: materials selection in Secyion 3.2 and joining techniques in Section 3.3. These are then integrated into a practical construction example for a dipper probe in Section 3.4. Specialty construction topics are considered next: sizing parts for mechanical strength, mechanical motion at cryogenic temperature, and, finally, vacuum techniques and cryogenic seals. High- and ultrahigh-vacuum techniques are less commonly needed (but critical for dewar design as well as surface science and microscopy apparatus); they are treated separately as addenda in the final section.
4 Wiring and Connections
Authors: Ekin Jack W.
Published: January 2010

Cryostat wiring requires someone who is skilled and meticulous with his or her hands. It is fine detail work that, in many cases, is done by the experimentalist and not subcontracted outside the laboratory. This chapter focuses on some of the techniques and pitfalls in wiring. It first describes the main guidelines for wiring a cryostat in Section 4.1. Recommendations are made for selecting the right wire material and gauge size in Section 4.2, and wire insulation in Section 4.3. The later sections of the chapter present details about heat-sinking and soldering techniques, as well as information on specialty topics, including thermoelectric voltages, vacuum electrical lead-throughs, radio-frequency coaxial cable selection, high-current leads, and flexible current leads.
Temperature Measurement and Control
Authors: Ekin Jack W.
Published: January 2010

This chapter focuses on cryogenic thermometers. Section 5.1 gives an overview of thermometers and singles out several that will serve well in most measurement situations. It then looks at the selection of thermometers for use in high magnetic fields, installation and checkout of thermometers, and, finally, techniques for controlling temperature. A separate compendium of comments on the wide spectrum of available thermometers is given in an addendum to the chapter, which is keyed to a quantitative tabulation of thermometer properties in Appendix 5.2.
6 Properties of Solids at Low Temperatures
Authors: Ekin Jack W.
Published: January 2010

This chapter discusses the physics of the properties of material used in cryostat construction and presents tables of data for cryostat design. The order of presentation of the first four properties (specific heat; thermal expansion; electrical resistivity; and thermal conductivity) has been chosen because the underlying physics of each one logically flows into the next. The last two properties, magnetic susceptibility and mechanical properties, are not always included in treatments of material properties, but they are absolutely crucial to the selection of materials for cryostat design.
Sample Holders
Authors: Ekin Jack W.
Published: January 2010

Sample holders provide uniform and stable temperature control of the sample; eliminate sample stress due to differential thermal contraction between the sample and holder; minimize noise from induced voltages and magnetic pickup by keeping the effective voltage-tap loop area as small as possible; provide well-designed current and voltage contacts, with enough space between each current contact and the nearest voltage lead to ensure that the current distribution is uniform in the region between the voltage taps; and provide firm mechanical support for the sample, particularly for critical-current measurements where large, magnetic Lorentz forces are a major issue. This chapter considers each of these factors in turn, for both bulk sample holders and thin film sample holders, along with examples and design techniques. It also considers the general nature of four-lead measurements, since this technique determines the overall design of most transport-measurement sample holders.
Sample Contacts
Authors: Ekin Jack W.
Published: January 2010

After designing an effective sample holder, the next step is making electrical contact directly to the test sample itself. If the contacts are resistive and there is significant Joule heating, sample temperature becomes impossible to control and measure. For many materials, sample contacts are straightforward, but not for the high-Tc oxide superconductors (HTS). They have a unique interfacial chemistry that is counterintuitive. This chapter focuses on contact techniques for the more challenging high-Tc oxide superconductors. The chapter is divided into two major parts: the first describes techniques for fabricating contacts to high-current superconductors; the second focuses on contacts to low-current film superconductors.
Critical-Current Measurements
Authors: Ekin Jack W.
Published: January 2010

This chapter presents techniques for critical-current-data acquisition. Firstly it describes the principal ways of defining critical-current density (which can lead to vastly different values). It then offers suggestions of where to put your money when assembling a quality instrumentation system. The next section looks at general, time-proven troubleshooting tips as well as specific methods to avoid and identify critical-current measurement problems. Finally, the chapter illustrates specific examples of various types of cryostats for measuring critical current.
Critical-Current Data Analysis
Authors: Ekin Jack W.
Published: January 2010

This chapter begins with a discussion of the methods of defining critical current that are practical. It then looks at the notorious problem of current-transfer voltages and how to correct them; all too often, these extraneous voltages interfere with obtaining good critical current data on short, high-current samples, but there are effective ways to extract the underlying intrinsic Ic data. The main part of the chapter presents analytic representations of the critical current for use in application design and for accurate intercomparisons of data obtained on different conductors, in different locations, and at different magnetic fields, temperatures, and strain levels.
Correlation studies in organic solids
Authors: GAVEZZOTTI ANGELO
Published: January 2010

Structure correlation studies were first carried out on intramolecular parameters, a classic work of which involved molecular deformations at a carbonyl center as a function of the intermolecular distance to an incoming nucleophile. In further applications, the term ‘structure correlation’ was extended to include all studies in which molecular or crystal properties are analysed in a systematic way over the database, to reveal correlations between structural or energetic properties of crystallised molecules. This chapter discusses correlation studies in organic solids, the Cambridge Structural Database (CSD) of organic crystals, structure correlation, retrieval of crystal and molecular structures from the CSD, the SubHeat database, geometrical categorisation of intermolecular bonding, space analysis of molecular packing modes, empty space versus filled space, close packing in crystals, calculation of intermolecular energies in crystals, basic concepts on lattice energies, sublimation entropies and vapor pressures of crystals, general-purpose force fields for organic crystals, correlation between molecular and crystal properties, and acceptable crystal structures.
Computers
Authors: GAVEZZOTTI ANGELO
Published: January 2010

Chemical applications of force field simulations, of quantum mechanics, as well as X-ray data processing, lattice dynamics, and molecular dynamics simulations are all made possible by fast and reliable numerical computation. Therefore, electronic computers are a theoretical chemist's vital tool, and very few — if any — quantitative results can be obtained without them. Computers handle a very large and very diversified range of tasks on a surprisingly small fundamental basis: the electric representation of only two numbers, zero and one, called binary digits (or bits). Computers use bits to represent numbers in binary notation. In a very successful metaphoric style, all items of the computer world that have to do with programs are called software, while all the rest (electronic parts, wires, input-output devices) are called hardware. This chapter provides an overview of computers, operating systems, computer programming, bugs, program checking and validation, and reproducibility.
Structure-property and structure–activity relationships
Authors: GAVEZZOTTI ANGELO
Published: January 2010

The study of the structure and transformations of organic condensed phases is at the forefront of modern chemistry. One reason for this is that these structures and transformations are poorly understood, and hence stimulate the curiosity of researchers; another reason is that molecular devices are a worldwide and ever expanding market with immense opportunities for money-making. This chapter discusses structure-property relationships as well as structure-activity relationships, use of applied technology in fundamental research, the structure-activity dogma, crystal dissolution, thermal properties, thermal expansion coefficients, heat capacity and heat transport, strain and stress, elastic and viscous properties, optical, electric and magnetic properties, color, optical properties and the polar axis, and electric and magnetic properties.
Mixed Foundations
Authors: LUCY WILLIAM
Published: January 2010

This chapter examines what can be called ‘mixed’ accounts of the normative basis of private law. The first section briefly sketches the limitations of corrective and distributive justice accounts which make consideration of mixed accounts necessary. It also outlines some of the requirements that any successful mixed theory must satisfy. The second section examines in detail one mixed account in light of those requirements and also considers how it responds to the key questions noted in Chapter 7. This section also briefly notes how other ostensibly mixed accounts fare in relation to one of these conditions, thus highlighting that the problems faced by the first account are not unique to it. The third section offers, among other things, a brief prospectus for the future development of mixed accounts.
Prologue: The Prehistory of the English Law of Obligations
Authors: IBBETSON D. J.
Published: January 2010

The Common law of obligations grew out of the intermingling of native ideas and sophisticated Roman learning. The friction between them was a prime force for legal change, and has remained so right up to the present. This chapter identifies these basic building blocks. Topics discussed include prevailing ideas about the legal system in medieval Europe and obligations in Roman law.
10. The Law of Torts in the Twentieth Century: Expansion and Collapse of the Tort of Negligence
Authors: IBBETSON D. J.
Published: January 2010

The tort law of negligence was thoroughly fragmented in the 19th century. This chapter shows how, in the 20th century, the practice moved in the direction of theory as the tendency towards fragmentation was reversed. Detailed duties of care were superseded by a single duty of care. The component parts of the tort—duty, breach, remoteness—increasingly merged into each other. Moreover, it no longer seemed self-evident that there should be a link between legal liability and wrongdoing, with the result that the idea of negligence as a failure to take the care that would have been taken by a reasonable man began to degenerate back to an undifferentiated notion of blameworthiness.
11. Foundations of the Modern Law of Contract
Authors: IBBETSON D. J.
Published: January 2010

This chapter shows how the 17th and 18th centuries marked a period of consolidation of the law of contract, the fleshing out of the skeletal structure that had been locked in place at the end of the 16th century. The most important developments occurred in the Chancery, which had begun to operate along clearly defined, rule-based lines by the time of the Chancellorship of Nottingham (1673-81). The 18th century saw the first attempts to articulate a theory of contractual liability, largely based on the writings of non-lawyers, at least non-Common lawyers. Although these attempts were neither sophisticated nor successful, they did begin the work of accustoming English lawyers to the fact that there were not several sets of rules applicable to different forms of action in Common law and Chancery, but a single body of definable rules that could be called the ‘law of contract’.
15. Legal Change and Legal Continuity
Authors: IBBETSON D. J.
Published: January 2010

This chapter argues that legal change occurs by filling in gaps between the rules in the way that seems the most convenient or most just at the time; through twisting rules, or rediscovering old ones; through reformulating claims into a different conceptual category; through intervening new rules that get tacked onto existing ones; through injecting shifting ideas of fairness or justice; and through adopting wholesale procrustean theoretical frameworks into which existing law can be squeezed. Whatever changes occurred at the surface of law, and whatever accretions have been incorporated into its fabric, at a deep level the structure of the Common law of obligations remained slow-moving.
International Organizations as Law-makers
Authors: Alvarez José E.
Published: January 2010

This book addresses how international organizations with a global reach, such as the UN and the WTO, have changed the mechanisms and reasoning behind the making, implementation, and enforcement of international law. It argues that existing descriptions of international law and international organizations do not do justice to the complex changes resulting from the increased importance of these institutions after World War II and then after the end of the Cold War. In particular, this book examines the impact of the institutions on international law through the day-to-day application and interpretation of institutional law, the making of multilateral treaties, and the decisions of a proliferating number of institutionalized dispute settlers. Part I re-examines the law resulting from the activity of political organs, such as the UN General Assembly and Security Council, technocratic entities within UN specialized agencies, and international financial institutions such as the IMF, and considers their impact on the once sacrosanct ‘domestic jurisdiction’ of states. Part II assesses the impact of the move towards institutions on treaty-making. It addresses the interplay between negotiating venues and procedures and interstate cooperation and asks whether the involvement of international organizations has made modern treaties ‘better’. Part III examines the proliferation of institutionalized dispute settlers, from the UN Secretary General to the WTO's dispute settlement body, and re-examines their role as both settlers of disputes and law-makers. The final chapter considers the promise and the perils of the turn to formal institutions for the making of the new kinds of ‘soft’ and ‘hard’ global law, including the potential for forms of hegemonic international law.
The Varied Forms of International Institutional Law
Authors: ALVAREZ JOSÉ E.
Published: January 2010

This chapter discusses the varied forms of international institutional law. It looks into the role of the Security Council as law-maker and its position between power and law. A selective survey on the standard-setting in other international organizations is also presented. The survey mentions the Codex Alimentarius, ICAO's standards and recommended practices, international organizations ‘advisory’ material, ILO recommendations, and IAEA standards. Also mentioned are the FAO's and UNEP's prior informed consent regime, WTO Soft Law, the WHO's Code on marketing of breast-milk substitutes, the World Bank guidelines, IMF conditionality, and emerging global administrative law. The chapter ends with interim conclusions that are at odds with the standard accounts of the limited role of international organizations in law-making and that describe the emerging global administrative law that these organizations produce.
The Nature of International Adjudication
Authors: ALVAREZ JOSÉ E.
Published: January 2010

This chapter discusses the nature of international adjudication. It also explains the features of a legitimate court, and the instances when courts ‘make law’ and defined more broadly the domain of international institutionalized dispute settlement. That part considers the underlying dynamics of distinct dispute settlement modes and whether it is accurate to describe their primary function as engaging in ‘dispute settlement’ at all. The chapter also considers the characteristics and limitations of law-making in the political, quasi-judicial, and judicial settings discussed, and concludes with an attempt to situate these issues within broader theoretical frameworks. Institutionalized dispute settlers may be regarded as both triadic conflict resolvers and guardians of public values. All else being equal, a dispute settler that shares the characteristics of one who looks like and quacks like a domestic court is more likely to attempt adjudicative law-creation.
Between Hierarchies and Markets
Authors: Thompson Grahame F.
Published: January 2010

This book explores the ways in which the word ‘network’ has been deployed in literature. In particular, it offers a commentary on how the idea of networks has been used to illustrate contemporary forms of socio-economic organisation (as with the idea of a ‘network society’ or a ‘network state’), broadly conceived to also include the political aspects of networks. The term ‘network’ has become a ubiquitous metaphor to describe too many aspects of contemporary life. In doing so, the book argues, the term has lost much of its analytical precision and has no clear conceptual underpinnings. This study brings some intellectual clarity to the discussion of networks by asking whether it is possible to construct a clearly demarcated idea of a network as a separable form of socio-economic coordination and governance mechanism with its own consistent logic. In doing this, the primary contrast is with hierarchies and markets as alternative and already well understood forms of socio-economic coordination each with their own distinctive logic. The book identifies two underlying programmatic issues: the question of whether there can be a particular logic to the network form of organisation, and whether there are any limits to networks. The book contends that if networks are to mean anything then they must not apply to everything, so this raises an obvious limit to their embrace. The questions thus become where and how to draw these limits. These are reviewed in the light of the concrete organisational forms that networks have taken in the contemporary period.
Hierarchies, Markets, and Networks: A Preliminary Comparison
Authors: Thompson Grahame F.
Published: January 2010

This chapter sets out the traditional analysis of network as a different organisational arrangement to either hierarchy or market. The contrast is between hierarchies, markets, and networks as first coordinating devices and then as governance mechanisms. In the first instance, these are set up as ‘rivalrously complementary’ ideal types of social organisation to demarcate the different claims they make on how the organisation of the social is to be understood. The chapter lays out the basic claims made for networks in particular, as to how they are different from hierarchical and market forms of organisation. In other words, the chapter tries to systematise what might be the logic of networks and the legitimate limits to their operation. For hierarchical forms of organisation, the key features for governance are rule-bounded bureaucracy, authority, administration, and superordination and subordination. For market forms, the key features are price, self-interest, competition, and formal contracts.