Table of contents

We review the application of non-relativistic constituent quark models to study one, two and three non-strange baryon systems. We present results for the baryon spectra, potentials and observables of the nucleon–nucleon (NN), NΔ, ΔΔ and NN^*(1440) systems, and binding energies of three non-strange baryon systems. We emphasize the observable effects related to quark antisymmetry and its interplay with quark dynamics.

The majority of the processes used by the manufacturing industry depend upon the accurate measurement and control of temperature. Thermal metrology is also a key factor affecting the efficiency and environmental impact of many high-energy industrial processes, the development of innovative products and the health and safety of the general population. Applications range from the processing, storage and shipment of perishable foodstuffs and biological materials to the development of more efficient and less environmentally polluting combustion processes for steel-making. Accurate measurement and control of temperature is, for instance, also important in areas such as the characterization of new materials used in the automotive, aerospace and semiconductor industries.

This paper reviews the current status of temperature metrology. It starts with the determination of thermodynamic temperatures required on principle because temperature is an intensive quantity. Methods to determine thermodynamic temperatures are reviewed in detail to introduce the underlying physical basis. As these methods cannot usually be applied for practical measurements the need for a practical temperature scale for day-to-day work is motivated. The International Temperature Scale of 1990 and the Provisional Low Temperature Scale PLTS-2000 are described as important parts of the International System of Units to support science and technology. Its main importance becomes obvious in connection with industrial development and international markets. Every country is strongly interested in unique measures, in order to guarantee quality, reproducibility and functionability of products. The eventual realization of an international system, however, is only possible within the well-functioning organization of metrological laboratories. In developed countries the government established scientific institutes have certain metrological duties, as, for instance, the maintenance and dissemination of national units. For the base unit kelvin, this procedure is described in the sections on practical temperature scales, practical thermometry and reference standards.

Testing experimentally the fundamental laws of physics means in practice the precise determination of the fundamental constants appearing in the laws. The essence of current activities is that prototypes, which may vary uncontrollably with time and location, are replaced by abstract experimental prescriptions that relate the units to the constants. This approach is shown for the definition of the kelvin and the Boltzmann constant.

This paper reviews aspects of nonlinear optical spectroscopy of interfaces. The emphasis is put on second-order nonlinear optical techniques, such as sum-frequency generation (SFG), which possess intrinsic surface or interface selectivity and can therefore be used to probe buried interfaces accessible by light. The basic concepts of the second-order nonlinear response of surfaces and interfaces are given. While SFG in the ultraviolet–visible range allows one to achieve surface-specific electronic spectroscopy, infrared–visible SFG spectroscopy allows one to have access to absolute vibrational spectra of adsorbates at an interface. The main experimental schemes commonly employed are described. Selected experimental examples are given for studies of liquid surfaces and interfaces, polymer surfaces and interfaces, solid surfaces under ultra-high vacuum conditions or in inert atmospheres, solid–gas interfaces, solid–liquid interfaces and solid–solid interfaces. Both frequency-resolved studies and time-domain measurements are addressed.

The concept of the photon, central to Einstein's explanation of the photoelectric effect, is exactly 100 years old. Yet, while photons have been detected individually for more than 50 years, devices producing individual photons on demand have only appeared in the last few years. New concepts for single-photon sources, or 'photon guns', have originated from recent progress in the optical detection, characterization and manipulation of single quantum objects. Single emitters usually deliver photons one at a time. This so-called antibunching of emitted photons can arise from various mechanisms, but ensures that the probability of obtaining two or more photons at the same time remains negligible. We briefly recall basic concepts in quantum optics and discuss potential applications of single-photon states to optical processing of quantum information: cryptography, computing and communication. A photon gun's properties are significantly improved by coupling it to a resonant cavity mode, either in the Purcell or strong-coupling regimes. We briefly recall early production of single photons with atomic beams, and the operation principles of macroscopic parametric sources, which are used in an overwhelming majority of quantum-optical experiments. We then review the photophysical and spectroscopic properties and compare the advantages and weaknesses of various single nanometre-scale objects used as single-photon sources: atoms or ions in the gas phase and, in condensed matter, organic molecules, defect centres, semiconductor nanocrystals and heterostructures. As new generations of sources are developed, coupling to cavities and nano-fabrication techniques lead to improved characteristics, delivery rates and spectral ranges. Judging from the brisk pace of recent progress, we expect single photons to soon proceed from demonstrations to applications and to bring with them the first practical uses of quantum information.

This review discusses the diffraction patterns of x-rays or electrons scattered by fibres of helical biological molecules and by carbon nanotubes (CNTs) from the unified point of view of the Fourier–Bessel transform of an atomic helix. This paper is intended for scientists who are not professional crystallographers. X-ray fibre diffraction patterns of Pauling's protein α-helix and of Crick and Pauling's protein coiled-coil are revisited. This is followed by a non-technical comparison between the historic x-ray diffraction patterns of the A and B conformations of DNA, which were crucial for the discovery of the double helix. The qualitative analysis of the diffraction images is supported by novel optical simulation experiments designed to pinpoint the gross structural informational content of the patterns. The spectacular helical structure of the tobacco mosaic virus determined by Rosalind Franklin and co-workers will then be described as an early example of the great power of x-ray crystallography in determining the structure of a large biomolecular edifice. After these mostly historical and didactic case studies, this paper will consider electron diffraction and transmission electron microscopy of CNTs of great current interest, focusing particularly on recent data obtained for single-wall, double-wall and scrolled nanotubes. Several points of convergence between the interpretations of the diffraction patterns of biological helices and CNTs will be emphasized.