High dynamic pressures and applications in materials science

Abstract

The high dynamic pressure behaviour of materials is, for many years, of great interest either for scientific studies (equation of state, Hugoniot and off Hugoniot, phase transitions …) or for industrial applications (synthesis of new materials, hardening, welding, powder compaction, jet cutting…

These different aspects are presented and these capabilities certainly will be an important factor in the next future.     

New materials from high pressure experiments: Challenges and opportunities

Recent improvements in high pressure techniques have led to new scientific discoveries in fields ranging from Earth and Planetary Science, to fundamental physics and biology. Here we examine the possibilities for development of new technologically-important materials based on high pressure research.     

Jim Corbett as an author and a physicist

Abstract

Thanks to developments in information science, data on scientific publications can easily be retrieved from specialized computer systems. Not just topical information can be obtained, but also information on selected authors. Moreover, some computer systems offer software which allows simple statistical analysis of the data by just a single command. When we apply this to Jim Corbett's scientific production, a clear picture of his versatility emerges.     

Towards the Objective Speech Assessment of Smoking Status based on Voice Features: A Review of the Literature

Background and ObjectiveIn smoking cessation clinical research and practice, objective validation of self-reported smoking status is crucial for ensuring the reliability of the primary outcome, that is, smoking abstinence. Speech signals convey important information about a speaker, such as age, gender, body size, emotional state, and health state. We investigated (1) if smoking could measurably alter voice features, (2) if smoking cessation could lead to changes in voice, and therefore (3) if the voice-based smoking status assessment has the potential to be used as an objective smoking cessation validation method.MethodsA systematic review of the scientific literature was conducted to compile studies on smoking status assessment based on voice features. We searched nine scientific databases for original studies involving the effects of smoking on voice features, the effects of smoking cessation on voice features.ResultsA total of 34 studies were identified for review. We found that fundamental frequency, jitter, shimmer, harmonics to noise ratio, and other voice features are affected by smoking and could be used to assess smoking status.ConclusionSpeech assessment of smoking status based on voice features has potential as a smoking status validation method, as it is simple, reliable, and less time-consuming. Furthermore, this study provides recommendations for future research on the objective speech assessment of smoking status based on voice features.     

Metallization of fluid hydrogen at 140 GPa (1.4Mbar) by shock compression

Abstract

The minimum electrical conductivity of a metal was produced in dense hydrogen using shock compression. Metallization occurs at 140 GPa (1.4 Mbar), 0.6 g/cm³ (ninefold compression of initial liquid-H₂ density), and 3000 K. The relatively modest temperature generated by a reverberating shock wave produced the metallic state in a warm quantum fluid at a lower pressure than expected previously for the crystallographically ordered solid at low temperatures. Future research directions are discussed. Possible scientific and technological uses of metastable solid metallic hydrogen are speculated upon in the unlikely event that the metallic fluid can be quenched to this state at ambient pressure and temperature.     

Systematic row and zone axis STEM defect image simulations

Transmission electron microscopy (TEM) has been instrumental in advancing the field of crystalline defect analysis. Conventional TEM imaging techniques, such as bright field (BF), dark field (DF), and weak beam dark field (WBDF or g–3g) imaging, have been well-documented in the scientific literature, with simulation methods readily available for each. The present contribution highlights the use of a field-emission TEM, operated in scanning transmission electron microscopy mode, as a viable tool for defect analysis. Common techniques such as two-beam diffraction contrast and zone axis imaging are applied to defect analysis; both experimental and computational results are presented. Effects of experimental parameters such as camera length, beam divergence angle, and diffraction aperture placement are also discussed and illustrated by both experimental and computed micrographs of stacking faults.     

On the optimality of individual entangling-probe attacks against BB84 quantum key distribution

Some MIT researchers [Phys. Rev. A 75, 042327 (2007)] have recently claimed that their implementation of the Slutsky-Brandt attack [Phys. Rev. A 57, 2383 (1998); Phys. Rev. A 71, 042312 (2005)] to the BB84 quantum-key-distribution (QKD) protocol puts the security of this protocol “to the test” by simulating “the most powerful individual-photon attack” [Phys. Rev. A 73, 012315 (2006)]. A related unfortunate news feature by a scientific journal [G. Brumfiel, Quantum cryptography is hacked, News @ Nature (april 2007); Nature 447, 372 (2007)] has spurred some concern in the QKD community and among the general public by misinterpreting the implications of this work. The present article proves the existence of a stronger individual attack on QKD protocols with encrypted error correction, for which tight bounds are shown, and clarifies why the claims of the news feature incorrectly suggest a contradiction with the established “old-style” theory of BB84 individual attacks. The full implementation of a quantum cryptographic protocol includes a reconciliation and a privacy-amplification stage, whose choice alters in general both the maximum extractable secret and the optimal eavesdropping attack. The authors of [Phys. Rev. A 75, 042327 (2007)] are concerned only with the error-free part of the so-called sifted string, and do not consider faulty bits, which, in the version of their protocol, are discarded. When using the provably superior reconciliation approach of encrypted error correction (instead of error discard), the Slutsky-Brandt attack is no more optimal and does not “threaten” the security bound derived by Lütkenhaus [Phys. Rev. A 59, 3301 (1999)]. It is shown that the method of Slutsky and collaborators [Phys. Rev. A 57, 2383 (1998)] can be adapted to reconciliation with error correction, and that the optimal entangling probe can be explicitly found. Moreover, this attack fills Lütkenhaus bound, proving that it is tight (a fact which was not previously known).     

High pressures: Recent trends in materials science

Abstract

Pressure was developed during the 20th century. The most important illustration of the use of high pressure in Materials Science was the synthesis of diamond at the beginning of the fifties.

This contribution will describe the main scientific research axis developed these last years and based on high pressure (synthesis of new materials, stabilization of specific structures, crystal-growth, preparation of finely divided materials…).

In parallel some industrial developments will be analyzed.

In conclusion, the potential of high pressure will be sketched for the near future.     

Voraussetzungen für die Isotopen-Forschung: Grundlegende Entdeckungen in der Physik vor hundert Jahren

Abstract

Reviewed is the transition period in the history of physics between 1895 and 1905, a decade which began 100 years ago and which is characterized by high scientific activity and creativity with significant results for the further development of natural science. A great number of outstanding scientists, especially physicists, worked in this period. Their important discoveries manifest the beginning of the history of isotopic research.     

Segmental Mobility of Liquid Crystals and Liquid Crystalline Polymers in an Electric Field: A Study by Time-Resolved Rapid-Scan and Step-Scan FTIR Spectroscopy

INTRODUCTION

Liquid crystals (LC's) and liquid-crystalline polymers have gained scientific and technical importance due to their applications as display materials and their prospective use for optical information storage and non-linear optics [1-10]. Among other aspects, the study of segmental mobility as a function of an external (electric or electromagnetic) perturbation is of basic interest for the understanding of the dynamics of such molecular processes in liquid-crystalline materials.     

The spring-8 project and the high pressure group in japan

Abstract

Two major synchrotron radiation projects are presented, the conversion of the 30GeV TRISTAN collider into an ultra-high-brilliance machine and Spring-8, the 8 GeV Japanese third generation source. The Japanese high-pressure group is introduced and its plans for Spring-8 are described in the context of the proposed scientific programme which covers physics and chemistry, earth and planetary science, material science and shock wave compression. The equipment programme and requirements include multianvil presses with high-temperature capability, diamond-anvil cells with low- or high-temperature capabilities, shock compression apparatus and image-plate systems. The latest developments include a high-sensitivity ruby fluorescence detector and a fan-type multiple slit system to allow the use of position-sensitive detectors with multianvil devices.

Presented at (he IUCr Workshop on ‘Synchrotron Radiation Instrumentation for HighPressure Crystallography’. Daresbury Laboratory 20-21 July 1991     

Resonant and surface polaritons in quantum wells

Summary We show how the breaking of the translational invariance in a quantum well modifies the concept of polariton with respect to that defined for bulk material. Polaritons in quantum wells result from the combination of the exciton states with the radiation field. They are here obtained as the solutions of Maxwell equations with retardation, provided an appropriate nonlocal response function is used for the electric susceptibility, and Maxwell boundary conditions are imposed. We find two types of polaritons depending on the values of the in-plane wavevectork _II: those atk _II<ω/v (wherev=c/n is the velocity of light in the sample) are resonant with the radiation field in the barrier and those atk _II>ω/v cannot be coupled to waves in the barrier. In both cases explicit expressions are given for radiative shifts and radiative broadenings as functions ofk _II. Numerical results are obtained for GaAs-Ga_1−x Al _x As and for CuCl quantum wells and new experiments are suggested. The existence of resonant and surface polaritons justifies an interpretation of the temperature dependence of the radiative lifetime suggested by the same authors. It also decreases the radiative efficiency in the direction perpendicular to the planes and increases the radiative efficiency parallel to the planes with increasing temperature. Due to the relevance of its scientific content, this paper has been given priority by the Journal Direction.     

Technical Reports: Time-Resolved Activities at the Advanced Photon Source Requiring the Pulsed Structure of the X-ray Beam

Scientific research in the time domain using the pulsed structure of the X-ray beams from a third-generation synchrotron source, such as the Advanced Photon Source (APS), has become a major interest among synchrotron users. The traditional material science, chemistry, and biology communities are getting an early glimpse of the potential impact of fast time-resolved X-ray studies. The scientific disciplines that have benefited from these studies include atomic and molecular physics, biology, chemical science, condensed matter physics, engineering science, environmental science, material science, and nuclear science. Technically, the turn-key-type femtosecond (fs) optical lasers with high peak power, used as pumps in many X-ray pump-probe experiments, have only recently become available.     

Republication of: The cosmological constant and the theory of elementary particles (By Ya. B. Zeldovich)

The seminal paper by Ya. B. Zeldovich (Soviet Physics Uspekhi 11, 381–393, 1968) is reprinted here, together with an editorial comment on its lasting scientific relevance, and a biography of the author.

Two-dimensional detector software: From real detector to idealised image or two-theta scan

Abstract

Detector systems introduce distortions into acquired data. To obtain accurate angle and intensity information, it is necessary to calibrate, and apply corrections. Intensity non-linearity, spatial distortion, and non-uniformity of intensity response, are the primary considerations.

It is better to account for the distortions within scientific analysis software, but often it is more practical to correct the distortions to produce ‘idealised’ data.

Calibration methods and software have been developed for single crystal diffraction experiments, using both approaches. For powder diffraction experiments the additional task of converting a two-dimensional image to a one-dimensional spectrum is used to allow Rietveld analysis. This task may be combined with distortion correction to produce intensity information and error estimates.

High-pressure experiments can introduce additional complications and place new demands on software. Flexibility is needed to be able to integrate different angular regions separately, and to produce profiles as a function of angle of azimuth. Methods to cope with awkward data are described, and examples of the techniques applied to data from high pressure experiments are presented.     

Recent Development on Spectroscopic Methods for Chiral Analysis of Enantiomeric Compounds

Abstract

Chirality has become a central theme in scientific research and is an important task in the field of analytical chemistry. In the past few decades, demand for chiral recognition and separation has increased due to the importance of chirality in many fields such as pharmaceutics, chemical industry, agriculture, and biological and clinical analysis. A survey of the literature suggests that different spectroscopic methods are applied to achieve the analysis of chiral enantiomeric compounds. This article is intended to focus on chiral analysis and affords a brief overview on chiral analysis of enantiomeric compounds using different spectroscopic methods, such as fluorescence spectroscopy, mass spectrometry, and nuclear magnetic resonance spectroscopy. In this review, primarily the intensive studies of how chiral recognition is achieved and an updated view of the different strategies used up to recognize the chirality of enantiomeric compounds are discussed.     

Fluorescence Correlation Spectroscopy (FCS): A Promising Tool for Biological Research

Abstract

Fluorescence correlation spectroscopy (FCS) is an important biophysical technique. FCS is currently being used in many areas of biology to solve several scientific problems. Its properties such as detection at the single molecular level, higher sensitivity, and use of lower sample volume make FCS a promising molecular diagnostic tool. The promising applications of FCS extend from DNA kinetics/dynamics studies to the comprehensive understanding of receptor–ligand interactions. In this article, we review various promising biological applications of FCS.     

Computer Retrieval of Spectral Data

Abstract

In the last few years the empirical interpretation of a spectrum and the quality of information gained from it can be sufficient for the demands of contemporary chemistry. The overall progress in computerization of chemistry and particularly the development of a new scientific discipline-chemical informatics [1]-allows one to apply a new approach of spectra explanation known as computer retrieval of spectral data. Here the usual meaning of “retrieval” is extended to the disclosure of abstract information hidden in various spectral curves.     

Analytical Methods for the Characterization of Organic Dyes in Artworks and in Historical Textiles

Abstract

Dyes are among the most significant components in works of art and archaeological findings. In the scientific examination of historical artefacts, the identification of natural dyestuffs is a challenging task, due to the complexity of their chemical composition and the possible presence of mixtures of chromophores and degradation products. For this reason, in the last few decades, new analytical procedures and techniques have been developed and improved for the characterization of organic dyes and their identification in microsamples. This review looks at the chemical composition of natural organic dyeing materials used in the field of the cultural heritage and focuses on several analytical methods based on spectrometric and chromatographic techniques that have contributed to the study of organic dyes in works of art and archaeological findings.