A method to polarise antiprotons in storage rings and create polarised antineutrons

An intense circularely polarised photon beam interacts with a cooled antiproton beam in a storage ring. Due to spin dependent absorption cross sections for the reaction gamma+antiproton > pi- + antineutron a built-up of polarisation of the stored antiprotons takes place. Figures-of-merit around 0.1 can be reached in principle over a wide range of antiproton energies. In this process antineutrons with Polarisation > 70% emerge. The method is presented for the case of 300 MeV/c cooled antiproton beam

Turbulent small-scale neutral and ion density fluctuations as measured during MAC/Epsilon

During the MAC/Epsilon campaign (Fall 1987, from Andoya, Northern Norway, 69 N, 16 E) a total of four altitude profiles of neutral gas number densities and six profiles of ion number densities were measured with high spatial resolution in the height range from 60 to 120 km. First results of these rocket-borne experiments are presented with emphasis on small scale turbulent density variations and related turbulent parameter as structure function constants and energy dissipation rates

First-principles study of ternary fcc solution phases from special quasirandom structures

In the present work, ternary Special Quasirandom Structures (SQSs) for a fcc solid solution phase are generated at different compositions, $x_A=x_B=x_C=\tfrac{1}{3}$ and $x_A=\tfrac{1}{2}$, $x_B=x_C=\tfrac{1}{4}$, whose correlation functions are satisfactorily close to those of a random fcc solution. The generated SQSs are used to calculate the mixing enthalpy of the fcc phase in the Ca-Sr-Yb system. It is observed that first-principles calculations of all the binary and ternary SQSs in the Ca-Sr-Yb system exhibit very small local relaxation. It is concluded that the fcc ternary SQSs can provide valuable information about the mixing behavior of the fcc ternary solid solution phase. The SQSs presented in this work can be widely used to study the behavior of ternary fcc solid solutions.Comment: 20 pages, 7 figure

Eutectic Colony Formation: A Stability Analysis

Experiments have widely shown that a steady-state lamellar eutectic solidification front is destabilized on a scale much larger than the lamellar spacing by the rejection of a dilute ternary impurity and forms two-phase cells commonly referred to as `eutectic colonies'. We extend the stability analysis of Datye and Langer for a binary eutectic to include the effect of a ternary impurity. We find that the expressions for the critical onset velocity and morphological instability wavelength are analogous to those for the classic Mullins-Sekerka instability of a monophase planar interface, albeit with an effective surface tension that depends on the geometry of the lamellar interface and, non-trivially, on interlamellar diffusion. A qualitatively new aspect of this instability is the occurence of oscillatory modes due to the interplay between the destabilizing effect of the ternary impurity and the dynamical feedback of the local change in lamellar spacing on the front motion. In a transient regime, these modes lead to the formation of large scale oscillatory microstructures for which there is recent experimental evidence in a transparent organic system. Moreover, it is shown that the eutectic front dynamics on a scale larger than the lamellar spacing can be formulated as an effective monophase interface free boundary problem with a modified Gibbs-Thomson condition that is coupled to a slow evolution equation for the lamellar spacing. This formulation provides additional physical insights into the nature of the instability and a simple means to calculate an approximate stability spectrum. Finally, we investigate the influence of the ternary impurity on a short wavelength oscillatory instability that is already present at off-eutectic compositions in binary eutectics.Comment: 26 pages RevTex, 14 figures (28 EPS files); some minor changes; references adde

Free energy and molecular dynamics calculations for the cubic-tetragonal phase transition in zirconia

The high-temperature cubic-tetragonal phase transition of pure stoichiometric zirconia is studied by molecular dynamics (MD) simulations and within the framework of the Landau theory of phase transformations. The interatomic forces are calculated using an empirical, self-consistent, orthogonal tight-binding (SC-TB) model, which includes atomic polarizabilities up to the quadrupolar level. A first set of standard MD calculations shows that, on increasing temperature, one particular vibrational frequency softens. The temperature evolution of the free energy surfaces around the phase transition is then studied with a second set of calculations. These combine the thermodynamic integration technique with constrained MD simulations. The results seem to support the thesis of a second-order phase transition but with unusual, very anharmonic behaviour above the transition temperature

The truth and beauty of chemical potentials

This essay in honour of Mike Brown addresses aspects of chemical equilibrium and equilibration in rocks, with a focus on the role that chemical potentials play. Chemical equilibrium is achieved by diffusive attening of chemical potential gradients. The idea of equilibration volume is developed, and the way equilibration volumes may evolve along a pressure-temperature path is discussed. The effect of the environment of an equilibration volume is key to understanding the evolution of the equilibration volume with changing conditions. The likely behaviour of equilibration volumes is used to suggest why preservation of equilibrium mineral assemblages and mineral compositions from metamorphism tends to occur. This line of logic then provides the conceptual support to conventional equilibrium thermodynamic approaches to studying rocks, using, for example, thermobarometry and pseudosections.PostprintPeer reviewe

Экспериментальная установка для определения тепловых свойств методом Фогеля

Выпускная квалификационная работа состоит из 67 страниц, 14 рисунков, 17 таблиц и 23 источника. Ключевые слова: тепловые свойства, метод пластины, теплопроводность. Объектом исследования является экспериментальная лабораторная установка для исследования тепловых свойств плохих проводников. Целью проекта является исследование и сравнение методов определения тепловых свойств плохих проводников тепла. В процессе выполнения проекта были проанализированы исследования методов измерения плохих проводников тепла. Изготовлены образцы из материала с низким коэффициентом теплопроводности - ТЗМК – 10 (вспененный кварц). Спроектирована вакуумная камера с внутренним водяным охлаждением и размещённым в ней теплоизолированным образцом. Так же в процессе исследований были получены экспериментальные данные.Final qualifying work consists of 67 pages, 14 figures, 17 tables and 23 source. Key words: thermal properties, method plate conductivity. The object of the research is an experimental laboratory installation for study of thermal properties of poor conductors. The aim of the project is to study and compare methods for the determination of thermal properties of bad heat conductors. In the process of implementation of the project has been analyzed and research methods measurement poor conductors of heat. Samples made from a material with a low coefficient of thermal conductivity - TZMK – 10 (foamed quartz). Designed vacuum chamber with internal water cooling and placed on the insulated sample. Also in the research process was the data obtained. Considered the issues of fire, industrial and

Combined LHC/ILC analysis of a SUSY scenario with heavy sfermions

We discuss the potential of combined analyses at the Large Hadron Collider and the planned International Linear Collider to explore low-energy supersymmetry in a difficult region of the parameter space characterized by masses of the scalar SUSY particles around 2 TeV. Precision analyses of cross sections for light chargino production and forward--backward asymmetries of decay leptons and hadrons at the ILC, together with mass information on chi^0_2 and squarks from the LHC, allow us to determine the underlying fundamental gaugino/higgsino MSSM parameters and to constrain the masses of the heavy, kinematically inaccessible sparticles. No assumptions on a specific SUSY-breaking mechanism are imposed. For this analysis the complete spin correlations between production and decay processes are taken into account.Comment: new figure added, updated to match the published versio

Association of Tinnitus and Electromagnetic Hypersensitivity: Hints for a Shared Pathophysiology?

BACKGROUND: Tinnitus is a frequent condition with high morbidity and impairment in quality of life. The pathophysiology is still incompletely understood. Electromagnetic fields are discussed to be involved in the multi-factorial pathogenesis of tinnitus, but data proofing this relationship are very limited. Potential health hazards of electromagnetic fields (EMF) have been under discussion for long. Especially, individuals claiming themselves to be electromagnetic hypersensitive suffer from a variety of unspecific symptoms, which they attribute to EMF-exposure. The aim of the study was to elucidate the relationship between EMF-exposure, electromagnetic hypersensitivity and tinnitus using a case-control design. METHODOLOGY: Tinnitus occurrence and tinnitus severity were assessed by questionnaires in 89 electromagnetic hypersensitive patients and 107 controls matched for age-, gender, living surroundings and workplace. Using a logistic regression approach, potential risk factors for the development of tinnitus were evaluated. FINDINGS: Tinnitus was significantly more frequent in the electromagnetic hypersensitive group (50.72% vs. 17.5%) whereas tinnitus duration and severity did not differ between groups. Electromagnetic hypersensitivity and tinnitus were independent risk factors for sleep disturbances. However, measures of individual EMF-exposure like e.g. cell phone use did not show any association with tinnitus. CONCLUSIONS: Our data indicate that tinnitus is associated with subjective electromagnetic hypersensitivity. An individual vulnerability probably due to an over activated cortical distress network seems to be responsible for, both, electromagnetic hypersensitivity and tinnitus. Hence, therapeutic efforts should focus on treatment strategies (e.g. cognitive behavioral therapy) aiming at normalizing this dysfunctional distress network