bluuebunny/crossref_metadata_2025 huggingface dataset:
Reversible Impairment of an Auditory–visual Association Task
Authors: Sierra-Paredes Germán , Fuster Joaquín M
Published: November 2023

The dorsolateral prefrontal cortex (DLPC) of the primate plays an essential role in the temporal organization of goal-directed behavior (Fuster 1997). To perform that role, the DLPC engages sensory and motor cortices in complex functional interactions that integrate information from many sources into sequences of purposive action. The most compelling evidence of the temporal integrative role of the DLPC derives from the deficits that lesions of this cortex induce in delay tasks, where a specific sensory item determines a specific action after a delay of a few seconds. The cooling of DLPC has been shown to impair reversibly the performance of visual (Bauer and Fuster 1976; Quintana et al. 1993) and tactile (Shindy et al. 1994) delay tasks.
Bacterial Symbionts of Protozoa in Aqueous Environments–Potential Pathogens?
Authors: Görtz Hans-Dieter , Michel Rolf
Published: November 2023

The public was shocked in 1976 when a number of American veterans suffered from an enigmatic pneumonia and many of the patients died. The so far unknown type of pneumonia was then termed Legionnaires’ disease. It was caused by an intra cellular bacterium that was designated Legionella pneumophila. It was found that Legionella can exist in protozoa such as Tetrahymena and Acanthamoeba, and the bacteria were isolated from small amoebae from freshwater and soil (Rowbotham 1980, 1986; Barbaree et al. 1986; for a review see Jeon 1991). The first occurrence of Legionnaires’ disease was a warning that newly established technical facilities in human environments may be of epidemiological significance. New facilities may provide suitable habitats for microorganisms or their reservoir hosts. In the specific case of this disease it would be thin water films found in air conditioners resulting from condensing water. Also, the significance of protozoa and invertebrates as reservoir hosts or even vectors of intracellular pathogenic micro organisms had not been realized before.
Palaeobacteriology With Special Reference to Pathogenic Mycobacteria
Authors: Spigelman Mark , Donoghue Helen D
Published: November 2023

Skeletal deformities and the occasional lesion in a preserved corpse or mummy are often highly suggestive of ancient microbial disease. However, until recently it appeared that archaeologists were doomed never to fully identify the origins, extent, and types of these ancient diseases, thus making it impossible to understand the aetiology of epidemics that were so important in determining the course of history. A new science of palaeomicrobi ology can now give insight into the aetiology and nature of many microbial diseases. This chapter deals in the main with bacterial infections, while the chapter that follows – a study in paleo-or archaeovirology – examines a major viral infection, influenza (Taubenberger et al. 2000). In the next sections we shall examine the skeletal evidence for ancient bacterial activity.
Archaevirology: Characterization of the 1918 ‘Spanish’ Influenza Pandemic Virus
Authors: Taubenberger Jeffery K , Reid Ann H
Published: November 2023

The advent of molecular genetic pathology has opened a new venue for the study of infectious dis eases, especially the ability to study ‘fossil’ organ isms not currently circulating. Formalin-fixed, paraffin-embedded (FFPE) tissue samples, the most common form of pathologic tissue collections, can be used not only for histological and immunohisto chemical analyses, but also for molecular genetic analyses of DNA and RNA (Krafft et al. 1997). Indeed, the advent of the polymerase chain reaction (PCR) has made it possible to perform molecular genetic analyses of DNA and RNA from the vast majority of alcohol-and formalin-fixed tissue samples. For infectious diseases, such analyses have found routine use in clinical diagnosis (e.g. whether a liver biopsy is positive for hepatitis C virus) and in research. Tissue archives have also made it possible to identify previously unknown infectious agents [e.g. the identification of human herpes
Cancellation of oscillations, averaging lemmas, regularizing effects
Authors: Perthame Benoît
Published: November 2023

This chapter deals with various regularizing effects for scalar conservation laws that we prove via the kinetic formulation. The first one concerns a better integrability in L  p spaces than that given by the initial data. We prove that the growth at infinity of the flux functions Ai(u) induces a gain on the local L  p integrability but working both in space and time. The method of proof relies on the choice of appropriate entropies, which is not natural at all at the level of the conservation law itself, but which is equivalent to a classical tool for kinetic equations and which is called moment lemmas.
Elements of Synchrotron Light
Authors: Margaritondo Giorgio
Published: November 2023

This is a very simple but complete description of synchrotron sources and free electron lasers and of the corresponding instrumentation and techniques written primarily for scientists and students in the life sciences, medical research and chemistry. Scientists and students in other fields can also profit from a clear and elementary introduction to this rapidly expanding field. The emphasis is on simple concepts and the mathematical formalism is reduced to a minimum. No advanced knowledge of physics and mathematics is required beyond a standard elementary background. The reading is facilitated by a two-level presentation including a very simple descriptive treatment, and slightly more in-depth discussions of specific topics. With the first-level treatment, the readers will be able to understand the notions, terms, and techniques that are required to use a synchrotron facility. The book is therefore an ideal first step for all those beginning to use synchrotron light for their work or are considering such a possibility. The book is also suitable as a text for undergraduate courses as well as for specialized schools and continuing education courses. Thesis advisors active in synchrotron research will find it very useful as a first general introduction for their beginning graduate students. The treated topics include the basic functioning mechanisms of synchrotrons and free electron lasers, a description of synchrotron-based techniques in x-ray imaging and radiology, spectroscopy, microscopy and spectromicroscopy, EXAFS, crystallography and scattering (with special emphasis on macromolecular crystallography), microfabrication, and other techniques. The work is concluded by an analysis of the forseeable future developments in this field.
User’s guide
Authors: Margaritondo Giorgio
Published: November 2023

This book is primarily written for users who do not possess a broad background in physics and chemistry but only basic notions. Its main objective is to explain in simple terms the properties of synchrotron sources, the related instrumentation and the utilization techniques of specific interest to chemistry, biology and medical research. Readers from other disciplines could also profit from the simple presentation, primarily based on qualitative concepts rather than on complicated mathematics or physics.
Review Of Continuum Mechanics
Authors: Bhattacharya Kaushik
Published: November 2023

In this chapter, we quickly review some basic aspects of linear algebra and some basic kinematic concepts of continuum mechanics. A reader who finds this review insufficient is referred to a book on continuum mechanics like those by Fung (1977), Gurtin (1981) and Spencer (1980). We confine our attention to three dimensions.
Martensitic Phase Transform Ation
Authors: Bhattacharya Kaushik
Published: November 2023

We are interested in developing a continuum theory for materials that undergo the martensitic phase transformation. In particular, we are interested in understanding the origin and the nature of the microstructure that is observed in these materials. In this chapter, we introduce the basic concepts of the theory. We confine ourselves for now to specimens that are single crystals in the austenite state.
Special Microstructures
Authors: Bhattacharya Kaushik
Published: November 2023

In this chapter we study some important microstructures. We use two key ideas. The first is that a microstructure can be represented using a weakly converging sequence of deformations with finer and finer details as described in Chapter 6. The second is that that energy minimization forces the gradients of these sequences to take values only in the energy wells as described in Chapter 4.
The supersymmetry algebra and its representations
Authors: Binétruy P
Published: November 2023

Now that we have acquired some familiarity with super symmetry and the techniques involved, we may discuss more thoroughly the super symmetry algebra and its representations. As an example of application, we will then discuss in more details the construction of the representations of N = 2 super symmetry. Of great importance is the appearance of short representations of super symmetry, associated with the concept of BPS states in solition physics. Their study allows us to introduce such notions as moduli, moduli space, etc. important when we discuss super symmetry breaking or string and brane theory. This chapter is intended for the more theoretically oriented reader1.
The minimal supersymmetric model
Authors: Binétruy P
Published: November 2023

As a part of the general effort to implement super symmetry at the level of fundamental interactions, the minimal super symmetric extension of the Standard Model is motivated and described here at tree level. The presentation of its phenomenology requires a discussion of radiative corrections which play here a central roˆle ; it is therefore postponed to Chapter 7. Of great interest for astrophysics is the lightest super symmetric particle (LSP) if it is stable: as a weakly interacting massive particle (WIMP), it provides a candidate for dark matter. The last section of this chapter is devoted to these considerations.
Dynamical breaking. Duality
Authors: Binétruy P
Published: November 2023

A motivation for supersymmetry is the stability of the electroweak breaking scale under quantum corrections arising from fundamental physics at a much higher scale (naturalness problem). One may however turn the argument around: in a theory with a very large fundamental scale, how does one generate a scale as low as the super-symmetry breaking scale (hierarchy problem)? Again, the supersymmetry breaking mechanism should be devised in order to provide a rationale for such a behavior. We will argue in what follows that nonperturbative dynamics may be the answer: there are several examples where nonperturbative phenomena account for the generation of very large ratios of scales. This is referred to under the generic name of dynamical breaking. As we will see, supersymmetry provides new tools to control quantum fluctuations in the nonperturbative regime. One will uncover some duality relations between two regimes of a given theory, or two regimes of two different theories. This duality is often of a strong/weak coupling nature and is thus very promising to study strongly interacting theories.
The challenges of supersymmetry
Authors: Binétruy P
Published: November 2023

Although supersymmetry provides a satisfactory, and probably necessary, framework to address the questions left aside by the Standard Model, it is facing some diﬃcult challenges. We take the opportunity in this last chapter to discuss two of the most diﬃcult questions: the flavor problem and the cosmological constant problem. The lack of a clear solution to either of these problems would be (is?) probably a sign that we are missing an important piece of the jigsaw puzzle and that, if there is supersymmetry, it is probably not realized in the exact way that we presently think it is.
GaN or the history of a scientific explosion driven by applications and markets
Authors: Duboz Jean-Yves , Garcia Jean-Charles
Published: November 2023

In the early 90s, GaN was an exotic semiconductor studied by a few exotic people. The rest of the planet was considering this domain of research as ‘scientifically interesting’, which in certain minds translates as unrealistic, an endless search for a mythical grail, a black hole for time and money. There was even scientific evidence that GaN would remain forever a material as good as wood for optoelectronics.
Excitons in GaN-based low-dimensional systems
Authors: Gil Bernard
Published: November 2023

A review is given about the status of the physics of GaN-AlGaN quantum wells and superlattices
Indium gallium nitride (InGaN)-optical properties and technological implications
Authors: O’Donnell Kevin P
Published: November 2023

The successful introduction of indium into gallium nitride using epitaxial growth techniques has lead to the recent introduction of the InGaN-based blue laser diode and of light-emitting diodes that span the visible spectrum. However, it is believed that indium nitride is insoluble in gallium nitride at the growth temperatures used in fabricating such devices, with the result that a vigorous debate has started on the state of aggregation of the light-emitting material on the nanoscale. While most research has focused upon materials with modest indium nitride fractions, it is at high and low concentrations that we observe the most interesting and puzzling optical effects.
Low-dimensional nitrides: a laboratory for ultrafast physics
Authors: Kavokin Alexey , Malpuech Guillaume
Published: November 2023

Exciton-polariton will be the hero of this chapter. Light-matter coupling phenomena in nitrides will be considered from the point of view of both quantum mechanics and classical optics. We will show that extremely large exciton oscillator strength and peculiar band structure make nitrides excellent candidates for study of the most striking phenomena of solid state optics. Exciton-polaritons, i.e. quasi-particles appearing as a result of photon coupling with an elementary crystal excitation, govern the coherent optical response of low-dimensional semiconductor structures on a femtosecond to picosecond time-scale. Ultra-rapid transport of a neutral electronic excitation by a blue light is a close reality in nitrides. The challenge of the year 2001 is achievement of the strong-coupling regime in GaN-based microcavities that would allow studying of the stimulated scattering of bi-dimensional blue exciton-polaritons that could give way to a new generation of optoelectronic devices (polariton lasers). The principal difficulty for observation of a wide class of striking phenomena predicted theoretically, is a huge inhomogeneous broadening of excitons caused by a potential disorder in presently available nitride-based structures. The problem of exciton-polariton propagation in disordered media is one of the most essential for the correct description of ultrafast optical phenomena in nitrides.
Optoelectronic devices based on low-dimensional nitride heterostructures
Authors: Hangleiter Andreas
Published: November 2023

Group-III-nitride-based optoelectronic devices have been the key driving force in the recent rapid development of nitride technology. Historically, the first light-emitting nitride device was a metal-insulator-semiconductor light-emitting diode (MIS-LED) developed by Jacques Pankove and coworkers [1] in the seventies, with dim pnjunction LEDs following in the late eighties [2]. Until 1992 the brightness of nitride LEDs reached only the millicandela range, still unable to surpass the SiC-based blue LEDs of those days. Only in 1993, were Nakamura and coworkers [3] able to report significant progress in GaN-based blue LED brightness, reaching the one candela level in 1994 [4]. While these first bright GaN-LEDs were still based on donor-acceptor transitions in thick GaN layers, super-bright violet, blue, and green LEDs utilizing the reduced dimensionality in GainN/GaN quantum wells were reported only shortly thereafter [5, 6].
Introduction
Authors: Higgins Julia S , BenoÎt Hendri C
Published: November 2023

When the relationship between their physical properties and their molecular structure is considered, the most obvious characteristic of macromolecules is their length. For example, a polyethylene molecule with 106 repeat units stretched out in its planar zigzag form is 0.2 mm long. The organization of these enormously long molecules, even in dilute solution, let alone in bulk samples, poses fascinating questions. When molecular motion is added too, it is easy to see why research groups, or indeed whole laboratories are set up for the study of molecular properties of polymers.
Theoretical basis of scattering
Authors: Higgins Julia S , BenoÎt Hendri C
Published: November 2023

Some very simple ideas about the basis of neutron scattering theory have already been introduced in Chapter I. It is now necessary to develop mathematically the formalism in which the angular and energy dependence of scattering from model systems can be calculated and then used to interpret experimental data. As was indicated, this formalism is based on two so-called structure factors: S(q), the static structure factor and S(q, AE) the dynamic structure factor where q is the momentum transfer and AE the difference in energy between the incident neutron E; and the scattered neutron Er.
Labelling with deuterium—how, why, and when to use
Authors: Higgins Julia S , BenoÎt Hendri C
Published: November 2023

Anyone reading this chapter who has also been following the neutron scattering literature over the last 15 years cannot have failed to notice that deuterium labelling is at the centre of the small angle scattering technique as far as applications to polymer science are concerned. The reader may also have been puzzled by the question of how much labelling is required or desirable. In the literature there have been several swings which must give the impression that the neutron scatterers are very uncertain about the advantages and dangers of this tool. In the early papers very low concentrations of deuterated molecules were used. Moreover, extrapolations to zero concentration were applied in some cases. Then, in about 1980, levels around 50/50 of ordinary and deuterated species were reported. More recently, studies of the thermodynamic effects of mixing the two species have appeared and the fashion has switched back to lower levels of labelling. These changes have been caused by a deepening of the theoretical and experimental understanding of labelling and its consequences. Generally speaking, an historical approach to teaching science does not aid understanding (though it may well be amusing to follow the intuitive leaps that had to be made and discover some of the blind alleys of the subject). In this case it will be important to look carefully at both the physical interactions and their thermodynamical consequences in order to grasp the potential and the limitations of the technique.
Form factors
Authors: Higgins Julia S , BenoÎt Hendri C
Published: November 2023

We have shown (Chapter 5) that, for an incompressible binary mixture where the volume of the scattering elements O and I are identical, the scattered intensity can be written as
Interacting systems
Authors: Higgins Julia S , BenoÎt Hendri C
Published: November 2023

Up to this point we have discussed the scattering in general terms and shown that the expression for coherent scattering at any angle from a system containing only one species of molecules was given by the quantity
Dynamics
Authors: Higgins Julia S , BenoÎt Hendri C
Published: November 2023

Motion of polymer molecules occurs over many decades of frequency from the slow reorientation of whole molecules in melts just above their glass transition temperatures (T8) which may take hours, to the torsions and vibrations of side groups at around 1014 Hz. As will be seen, the neutron technique samples only the upper end of this frequency range with a limit which has currently been pushed down by the ultrahigh resolution spin echo spectrometer to around 107 Hz.
Neutron reflection for studying surfaces and interfaces
Authors: Higgins Julia S , BenoÎt Hendri C
Published: November 2023

A recent addition to the family of neutron scattering techniques, and one of particular importance for polymeric samples is neutron reflection. This is a technique which explores the variation in composition normal to a surface reflecting the neutrons. In essence it belongs with the small angle scattering experiments, and not a few of the results already published have been obtained on spectrometers constructed for small angle scattering. However, both the formalism adopted to interpret the data and the conceptual design of the experiments are very different from those for small angle scattering, so reflection enjoys the privilege of a short chapter of its own. Although we will be relatively brief, the explosion of interest in the applications of neutron reflection to polymer surfaces and interfaces and to polymers adsorbed at surfaces and interfaces almost rivals the similar explosive growth which occurred when the small angle scattering technique began to be available in the seventies. Again, it is likely to be the usual inhibiting factors of restricted availability and access which limit the applications of the technique. In this case, though, we will see that the actual form of the samples is very important. They must be flat and, usually, thin.
Excitations in Liquid and Solid Helium
Authors: Glyde Henry R
Published: November 2023

Liquid 4He and 3He are the purest Brose and Fermi liquids currently available in nature. Understanding the dynamics and excitations of those quantum systems is a fundamental issue of science and a guide for more complex matter. The book develops the theory of zero sound, phonons, rotons, spin and single particle excitations in quantum solids and fluids in an historical context. The book brings the theory up to date in modern language with similarities between quantum solids and fluids drawn wherever possible. A survey of recent neutron scattering data in each system is presented. A critical comparison of theory and recent data provides a comprehensive assessment of our current understanding of collective and single particle excitations in quantum liquids and solids.
Dynamic Structure Factor Of Solid Helium
Authors: Glyde Henry R
Published: November 2023

In this chapter we set out the dynamic structure factor, S(Q,ω), in solid helium. In the previous chapter we saw that helium atoms interact via a simple two-body potential and form simple lattice structures. However, because of the light mass, the zero point energy in these structures is large and solid helium is highly anharmonic. Helium is therefore a simple solid which dramatically displays anharmonic effects in S(Q, ω;).Our first purpose is to express S(Q,ω) in terms of the characteristic excitations, phonons, and highlight the effects of anharmonic interactions. This is done by expanding S(Q, ω) in the usual way as a sum of terms involving the excitation of single phonons, pairs of phonons, and higher orders plus interference between these orders. We present calculations of these terms to display their character. In this way solid helium displays phonon interactions, damping, and interference effects characteristic of all anharmonic solids.
Self-Consistent Phonon Theory
Authors: Glyde Henry R
Published: November 2023

The self-consistent phonon (SCP) theory is an elegant and pragmatic method for evaluating the dynamics of atoms in anharmonic crystals. In it, anharmonic contributions are summed into a generalized force constant. It is particularly suited to solid helium since, as noted in Chapter 3, the harmonic approximation (HA) is very poor and anharmonic terms are large. Also, the He–He interatomic potential has a steeply repulsive hard core. This makes the quartic and higher even anharmonic terms, that are summed in the lowest order SCP theory, larger than the cubic anharmonic term which appears first in second order. Thus the lowest order SCP theory, denoted the self–consistent harmonic (SCH) approximation, already provides a reasonable description of the phonon energies. This is not the case in alkali metals, for example, where the quartic and cubic anharmonic terms make approximately equal and opposite contributions. The SCH theory applied to solid helium is reviewed by Koehler (1975), Horner (1974a), Varma and Werthamer (1976), Glyde (1976), and Werthamer (1976).
Neutron Studies Of Solid Helium
Authors: Glyde Henry R
Published: November 2023

In this chapter we compare the theory and calculations in Chapters 4 and 5 with neutron data in solid helium. Measurements of S(Q, ω) in solid 4He have been made at the volumes and temperatures indicated in Table 3.1. We begin with the bcc phase at V = 21.1 cm3 mol-1 and move to fee 4He at V = 9.03 cm3 mol-1. In this way we move from the largest volume and most quantum, anharmonic example to the smallest volume and least anharmonic case studied to date. We also begin with measurements made at low momentum transfer. At low Q the aim is to determine one- phonon properties. As Q is increased, interference and multiphonon terms become important so that the observed S(Q, ω) is quite different from the one-phonon component, S  1(Q, ω). At Q≳ 4 Å-1 bcc 4He responds like a collection of weakly interacting atoms. At high Q, the goal is to explore the single-atom properties and how the atoms interact with their neighbours.
Theory Of Liquid 4He
Authors: Glyde Henry R
Published: November 2023

In this section we present the dielectric formulation (DF) of the dynamics of a Bose fluid. It is called a dielectric theory because the density and single-particle response of the fluid is expressed in terms of a wavevector and frequency-dependent dielectric function ϵ (Q, ω). It is also an extension of the field theory or response function theory introduced in §§’s 8.2, 8.4, and 9.4. It represents a coherent theory of the density and single-particle response taking explicit account of the condensate.The DF has its origins in the diagrammatic studies of Bose liquids by Gavoret and Nozieres (1964) and by Hohenberg and Martin (1965). The theory may be said to have two basic motivations. Firstly, when a Bose fluid has a condensate, n  0, the density and single-particle response are coupled, via the condensate. This coupling was discussed in §8.2 where we saw that the single-particle Green function, G, appears as a term in the density dynamic susceptibility χ when there is a condensate. Similarly, the self-energy, Σ, has a term containing the dynamic susceptibility χRgiven by (8.26) and (8.58). Via this term, the density response appears in the single-particle G. The first motivation of the DF is to build this coupling of χ sind G directly in the theory. The full χ and G are expressed in terms of simpler, ‘uncoupled’ [ineq] and [ineq] and the structure of the theory will incorporate the coupling via the condensate.
Dynamic Susceptibility Of Liquid 3He
Authors: Glyde Henry R
Published: November 2023

In this chapter we derive a general integral equation for the dynamic susceptibilities χc(Q, ω) and xI(Q, ω), defined by (2.31) and (2.41), respectively, and used in (2.24) to evaluate S’(Q, ω). The general equation holds for a strongly interacting Fermi liquid at any temperature. For a gas of non-interacting fermions, the first term of this equation reduces to the Lindhard function, χ0(Q, ω), defined in (2.63). Approximations to the general equation are discussed in Chapter 15 and models of S(Q, ω) for liquid 3He based on it are discussed in Chapter 16.
Approximations To The Dynamic Susceptibility
Authors: Glyde Henry R
Published: November 2023

In this chapter we discuss approximations to the dynamic susceptibility used to evaluate χ (Q, ω) in liquid 3He. In the previous chapter we obtained exact equations for χ (Q, ω)- We discuss, firstly, the mean field or random phase approximation (RPA) to these equations. The RPA is obtained from the full equation by approximating the full interaction by a local one and is widely used. In §15.2 we consider the conserving approximations of Baym and Kadanoff (1961). The low Q limit is considered in §15.3 which allows us to relate the interaction to the Landau parameters. Finally, approximations valid at high momentum transfer, Q ≫kF and ω ≃ ωR ≫ ∈ F are presented in §15.4.
Models Of S(Q, ω) In Liquid 3He
Authors: Glyde Henry R
Published: November 2023

In this chapter we survey model calculations of the dynamic structure factor, S(Q, ω), in liquid 3He. We consider low Q models based on Landau theory, on the parmagnon theory, and the more complete polarization potential theory initiated by Aldrich and Pines (1978). At intermediate Q, calculations based on microscopic theory are sketched. All the models begin with the general equation for χ (Q,  ω) derived in Chapter 14 and employ approximations discussed in Chapter 15. Comparisons with experiment are made in both this chapter and in Chapter 13.
Mori And Kinetic Theories Of Liquid 3He
Authors: Glyde Henry R
Published: November 2023

Lovesey (1975), Yoshida and Takeno (1979), and Pathak and Lücke (1983) have evaluated S(Q, ω) in liquid 3 He using techniques initiated by Mori (1965) and Zwanzig (1966). There are many variants of the Mori method. It was developed initially for classical liquids and its use there is reviewed by Copley and Lovesey (1975). Takeno and Yoshida (1978) and Yoshida and Takeno (1989) have presented a parallel treatment of classical and quantum liquids which provides an excellent introduction to their work. The Mori method is also called the memory function formalism. Here we survey the three applications to 3He emphasizing common features.
Intermediate And High Momentum Transfer
Authors: Glyde Henry R
Published: November 2023

In this chapter we discuss neutron scattering from condensed helium at intermediate and high momentum transfer. The aim is to present the basic physics of high Q scattering, introduce experimental data, and relate this to the theory set out in Chapters 18 and 19. The goal of experiment at high Q is to measure single-particle properties: the momentum distribution, particularly the condensate fraction in superfluid 4He, kinetic energies, and the interaction of the struck particle with its neighbours, the final state effects. At intermediate Q these interactions also lead to interesting oscillations of S(<2,uj) with Q.In §2.5 we introduced the impulse approximation (IA) and the final state broadening function. In Chapter 18 we derived the I A, which holds exactly in helium at Q → ∞. In Chapter 19 we derived expressions for S(Q, ω) at high but finite Q and for the final state broadening function, R (Q, ω).
The Physics of Ultracold Neutrons
Authors: Ignatovich V K , Pontecorvo G B
Published: November 2023

Neutrons provide an important tool for investigations in physics. Ultracold neutrons (UCN) belong to the extremely low energy range (10 -7 eV to 10-8 eV), have velocities in the range 1-10 m s-1 and wavelengths of 100-1000 A. Ultracold neutrons can be kept in hermetically sealed vessels for up to 15 minutes until they decay. This time is sufficient to observe the action of very weak fields and gives an insight into the properties of neutrons and their environment. Capture and heating by wall nuclei reduce the storage time of neutrons to below 15 minutes. Present research areas include attempts to understand and prevent the large losses of UCN, improve storage time, and to obtain fundamental results such as an upper limit to the electric dipole moment of neutrons and improved measurements of decay time. These studies have also led to a new approach to diffraction and diffusion theory, which is applicable to any radiation: waves or corpuscles. The book explains how physicists should cope with the problems of UCN research, how UCN can be used for fundamental and applied research, and summarizes the results which have been published.
The interaction of UCN with a magnetic field
Authors: Ignatovich V K , Pontecorvo G B
Published: November 2023

In this chapter the storage of neutrons in magnetic traps will be considered, as well as issues of UCN polarization and methods of analysing it, and also methods of UCN spin reversal. Magnetic traps have the advantage that no absorption or inelastic scattering exists in them within the range of thermal energies. There are, however, certain peculiarities that must be taken into account in estimating the UCN storage time in these traps. The magnetic field in a trap is extremely inhomogeneous and can confine neutrons within a restricted region of space only in the case of a certain neutron spin projection on to the field direction. When the spin direction changes, and in an inhomogeneous field it is sure to undergo changes, the magnetic ‘walls’ win stop being walls and a neutron will leave the trap with ease. It is noteworthy that a spin flip is most probable when the neutron is as far as possible from the ‘magnetic wall’, and not when it impinges upon the ‘wall’.
Dilute ferromagnetic alloys
Authors: Hicks Trevor J
Published: November 2023

Dilute ferromagnetic alloys are an important class of disordered magnetic materials. Because of the dilution, simple models may be employed when discussing the spatial variation of moment. The most important simplifying feature is the independence of the impurity centres so that the description of the scattering can be interpreted in terms of the effect of a single defect on the magnetism of the host. Thus the data from dilute ferromagnetic alloys is a rich source of information about the electronic state of the impurity atoms and their affect on the electronic state of the surrounding host and its spin polarization. However, before describing models particularly for dilute ferromagnetic alloys, we outline some general equations for the neutron scattering, in various situations of experimental importance, from ferromagnetic alloys in general and take a look at a classic diffractometer built especially for the small diffuse cross sections expected from dilute alloys.
Defect scattering from antiferromagnetic alloys
Authors: Hicks Trevor J
Published: November 2023

Antiferromagnetic alloys of the 3d transition series are interesting for the same reason as their ferromagnetic cousins. The problems of measurement of the magnetic defect cross section is, however, quite different. Whereas for the ferromagnetic systems it was possible to separate out the magnetic defect cross section either by manipulating the ferromagnetic direction with a field or by measuring total cross sections for incident polarized neutrons with the polarization along or opposite to the ferromagnetic direction, antiferromagnetic alloys in general do not have such a direction.
Excitations
Authors: Hicks Trevor J
Published: November 2023

Atomic randomness makes a qualitative difference to the excitations in materials with long range magnetic order. Even to predict the correct number of modes, full account must be taken of the range of atomic environments for most materials. This is quite difficult and has only been done for a limited number of materials within the coherent potential approximation. Excitations near the critical temperature for some types of random systems can show very complicated behaviour even to time-dependent effects measurable on laboratory time scales. This chapter explores some of the experiments in which the excitations in magnetically ordered alloys have been measured and the diverse constructs for their analysis.
Nonresonant inelastic X-ray scattering; regime of characteristic valence electron excitations
Authors: Schülke Winfried
Published: November 2023

Nonresonant inelastic X-ray scattering is a photon-in photon-out process and based on that part of the photon–electron interaction which is expressed in the Aterm of the corresponding interaction Hamiltonian. In this chapter we shall deal with scattering processes, which are connected with a momentum transfer q characterized by 2π/q l   c  , where l   c is the mean electron–electron distance, and with an energy transfer, or energy loss, characteristic for excitations of the scattering valence electron system. We designate this special type of scattering process the “regime of characteristic energy losses”.
Vector Spaces
Authors: Wasserman Robert H
Published: November 2023

Since tensor algebras are built from vector spaces we will recall some of the theory of the latter. We will review the basic properties of vector spaces, their representations and mappings, and mention a generalization.
Symmetric and Skew-Symmetric Tensors
Authors: Wasserman Robert H
Published: November 2023

Definition If the values of a tensor remain unchanged when two of its covariantarguments or two of its contravariant arguments are transposed, then the tensor is symmetric in these two arguments.
The Tangent Map of Real Cartesian Spaces
Authors: Wasserman Robert H
Published: November 2023

Up to now we have been discussing certain abstract vector spaces, namely, tensor product spaces. These will be important in the context of our objective of modeling physical phenomena by various mathematical spaces with mappings between them. Tensor product spaces will be part of the structure of the image spaces of our mappings. For now we will focus on their domains.
Differentiation and Integration of Differential Forms
Authors: Wasserman Robert H
Published: November 2023

Theorem 12.1  There exists one and only one operator, d, on the algebra ofdifferential forms with the following properties.
Pseudo-Riemannian Geometry
Authors: Wasserman Robert H
Published: November 2023

In order to have “geometrical” concepts in a manifold, M, such as lengths of curves, surface area, or curvatures of curves or surfaces, we have to impose an additional “structure” on M. Here we assign a metric tensor, g, to Min terms of which we define the length of a curve and the distance between two points. We then examine the important special case when M has an atlas on each coordinate neighborhood of which the components of g are constant.
Connection 1-Forms
Authors: Wasserman Robert H
Published: November 2023

We will describe the Levi-Civita connection and its covariant derivative on a pseudo-Riemannian manifold. Then we abstract the idea of a connection to define a more general class of manifolds. After briefly describing their main features, we go back to pseudo-Riemannian manifolds and discuss their possible connections.
A Spacetime
Authors: Wasserman Robert H
Published: November 2023

In Chapters 18 and 19, we described models of “the motion of systems of particles and rigid bodies” the subject of classical analytical mechanics. In this chapter and the next we describe a certain model of “spacetime,” called Einstein’s theory of relativity.* This is usually more specifically called the special theory of relativity, or the theory of special relativity to distinguish it from Einstein’s theory of gravitation which we will look at in Chapters 22 - 24.
Spacetimes Near an Isolated Star
Authors: Wasserman Robert H
Published: November 2023

A solution of the field equations gives the geometry, i.e., the metric tensor, of the spacetime model - at least locally. The geometry is supposed to be “due to,” or “determined by” a distribution of mass (energy). Thus, a solution will depend on an assumed mass distribution in the spacetime model.
Lie Groups
Authors: Wasserman Robert H
Published: November 2023

We have mentioned Lie groups in passing, in Sections 13.2 and 19.2. To apply tensors and manifolds to current physics a deeper look is indispensable. In particular, we will describe a Lie algebra of vector fields (cf., Section 11.1) on a Lie group, G, whose properties strongly reflect those of G itself.
Fiber Bundles
Authors: Wasserman Robert H
Published: November 2023

In physics one has various fields defined over regions of spacetime, M. Such fields have their values in manifolds, E, such as the tangent manifold, the cotangent manifold, and manifolds of tensor spaces.
Gauge Theory
Authors: Wasserman Robert H
Published: November 2023

We will discuss gauge transformations on fiber bundles and how they act on connections and their curvatures. Then we will briefly indicate how the concepts we have introduced relate to the gauge theory of elementary particle physics.
Introduction to Symplectic Topology
Authors: McDuff Dusa , Salamon Dietmar
Published: November 2023

Symplectic structures underlie the equations of classical mechanics and their properties are reflected in the behaviour of a wide rane of physical systems. Over the years much detailed knowledge has accumulated about the behaviour of particular systems, but the modern global theory of sympletic topology has just emerged. Powerful new methods in analysis and topology have led to a series of striking results, such as Gromov's flexiblity theorem on the existance of symplectic structures, and the various proofs of the Arnold conjectures on the number of fixed points of a symplectic map. This book contains an introduction to the subject, which will acquaint the reader with almost all the new methods in the field, providing proofs of the simplier versions of the most important new theorems. The deepest theorems in the book are proved by a new finite dimensional variational analysis of Hofer-Zehnder.
From Classical to Modern
Authors: McDuff Dusa , Salamon Dietmar
Published: November 2023

Symplectic structures first arose in the study of classical mechanical systems such as the planetary system, and almost all the classical work on symplectic geometry was focused on the attempt to understand how these systems behave. Recently, methods have been developed which give insight into the global features of symplectic geometry, and so the field of symplectic topology was born.
Introduction
Authors: Riviere J C
Published: November 2023

Surface analysis in its most general sense continues to be a growth area of remarkable vitality, and this is true particularly of that part of it that is concerned with attempting to establish the composition of a surface. Twenty or so years ago knowledge of the nature and number of elements at or near a surface could be obtained only by indirect means, and the development of surface science can now be seen in hindsight to have been hindered for that reason. The present situation could hardly be in greater contrast. If a surface scientist requires compositional information he now has a very considerable battery of techniques at his disposal, from which he may pick and choose according to the type of information he wants, and to the area and depth from which he wants it. Such is the range of choice that he may even exercise personal preference if he wishes, though few can afford that luxury, since generally the technique(s) must be matched to the problem and if there is one thing that most of them have in common it is high capital cost.
Photon excitation: ultra-violet photoelectron spectroscopy (UPS) and synchrotron radiation photoelectron spectroscopy (SRPS)
Authors: Riviere J C
Published: November 2023

Ultra-violet radiation from a source of the type described under section 3.2.2 and illustrated in Fig. 3.6 illuminates the surface of the sample. The most commonly used line sources are those of Hel at 21.21 eV and of Hell at 40.82 eV, produced by a discharge in helium gas, but Nel (16.8 eV) and Nell (26.9 eV) are also found occasionally. Just as with XPS, the energies of the photoelectrons ejected from the sample are measured in a CHA. Since the photoelectron energies in UPS are so low and span such a narrow range compared to XPS, elemental quantification is impossible.
Ion excitation: secondary neutral mass spectrometry (SNMS) and glow discharge mass spectrometry (GDMS)
Authors: Riviere J C
Published: November 2023

It has already been stated earlier that most of the particles ejected as a result of ion bombardment are neutrals, either atomic or molecular species. Since the neutral flux does not depend on any ionization mechanism but on the sputtering yield, which is only weakly dependent on matrix composition, it is obvious that if the neutral component could be measured independently, an analysis technique would be available that would be both more sensitive and more quantifiable than SSIMS. To measure the neutral signal requires conversion of the neutral flux to ions after ejection from the surface, followed by mass analysis in the usual way, taking care that interference from true secondary ions is avoided. Both SNMS and GDMS depend on postionization of neutrals, and indeed the two techniques are very similar, differing mainly in the precise conditions used for the ionization.
Neutral excitation: fast atom bombardment mass spectrometry (FABMS)
Authors: Riviere J C
Published: November 2023

In its origination this technique was really only an offshoot of SSIMS, arising from efforts to minimize or avoid the charging problems encountered with SSIMS when attempting to analyse non-conducting materials, and the damage problems when analysing large organic molecules. Indeed the very first papers by Barber et al.2 dealt specifically with the mass spectrometric analysis of biochemicals. The same authors found subsequently that a very useful variant of the technique was to disperse the high molecular weight organic in a matrix of low vapour pressure and good dispersing properties, and for this glycerol has been found to have excellent characteristics. Fragments from the glycerol itself are of course found in the mass spectrum, but their interference can be subtracted by computer.
High field excitation: atom probe field ion microscopy (APFIM)
Authors: Riviere J C
Published: November 2023

The technique of atom probe field ion microscopy has grown out of the older technique of Field Ion Microscopy (FIM), originated by Muller,1 which grew in turn out of field emission microscopy, also originated by Muller. Of all the surface-specific analytical techniques, APFIM is the only one with the ultimate in compositional sensitivity, i.e. a single atom. On the other hand, as will be seen below, analysis using APFIM is performed under somewhat extreme conditions of local electrostatic field, which has meant that nearly all its applications have been metallurgical. APFIM was also the brainchild of Muller and co-workers,3 and it is probably true to say that there is no other area of surface analytical technique that has been so dominated in its early and developmental stages by one man, E.W. Muller, as that of ultra-high resolution imaging and analysis.
Quantum crystal
Authors: Dobbs E R
Published: November 2023

The melting curve of He has been measured to 350 MPa by Mills and Grilly (1955) and found to be very similar to that for He, as shown in Fig. 2.1. The lighter mass of the He atom results in a larger zero point energy, and hence a larger molar volume (Chapter 1). It follows that the melting pressure is a little higher for He at all temperatures, the difference being most marked at zero temperature, where it is 3.44 MPa for He compared to 2.62 MPa for He. In similar way, there are three high-pressure phases for each isotope, the two close packed lattices for spherical atoms being present at the highest pressures. The face-centred cubic structure was first detected by Schuch and Mills (1961), while the hexagonal close-packed and body-centred cubic (Fig. 2.3) forms were identified by X-ray diffraction by Schuch et al. (1958). In this section we discuss first the high-pressure, close-packed solid, then the medium-pressure region with the important body-centred phase, and finally the unusual low-pressure melting curve.
Antiferromagnetism in the b.c.c. phase
Authors: Dobbs E R
Published: November 2023

The magnetic phase transition to an ordered state, which had been predicted for a decade to be around 2 mK, was discovered by Halperin et al. (1974) at Cornell University during the formation of the solid in a Pomeranchuk cell (a more modern one is shown in Fig. 2.8). They measured the latent heat dQ and volume change dV at constant temperature produced by the formation of the additional solid in the cell. The volume change was produced by pressurizing the He surrounding the cell and measuring dV capacitatively from the displacement of the He diaphragm. Pressurizing produces cooling and short pulses of a few nanowatts could be applied to produce heating.