Effect of the size of experimental channels of the lead slowing-down spectrometer SVZ-100 (Institute for Nuclear Research, Moscow) on the moderation constant

Lead slowing-down (LSD) spectrometers have a low energy resolution (about 30%), but their luminosity is 10³ to 10⁴ times higher than that of time-of-flight (TOF) spectrometers. A high luminosity of LSD spectrometers makes it possible to use them to measure neutron cross section for samples of mass about several micrograms. These features specify a niche for the application of LSD spectrometers in measuring neutron cross sections for elements hardly available in macroscopic amounts—in particular, for actinides. A mathematical simulation of the parameters of SVZ-100 LSD spectrometer of the Institute for Nuclear Research (INR, Moscow) is performed in the present study on the basis of the MCNPX code. It is found that the moderation constant, which is the main parameter of LSD spectrometers, is highly sensitive to the size and shape of detecting volumes in calculations and, hence, to the real size of experimental channels of the LSD spectrometer.     

On general relations in relativistic kinematics and some of their applications

Two vector fields are considered, a timelike one,u , and an arbitrary one, . The relative expansion and rotation are defined with respect to these fields, their mutual relations are studied, and some general formulas obtained. Applications are made, first to vector fields which are mutually nonrotating in a plane-symmetric metric, then to the electromagnetic field of an arbitrary magnetohydrodynamic fluid.     

The Proof That the Standard Transformations of E and B Are Not the Lorentz Transformations

In this paper it is exactly proved that the standard transformations of the three-dimensional (3D) vectors of the electric and magnetic fields E and B are not relativistically correct transformations. Thence the 3D vectors E and B are not well-defined quantities in the 4D space-time and, contrary to the general belief, the usual Maxwell equations with the 3D E and B are not in agreement with the special relativity. The 4-vectors E ^a and B ^a , as well-defined 4D quantities, are introduced instead of ill-defined 3D E and B. The proof is given in the tensor and the Clifford algebra formalisms.     

On the Integrability of Geodesic Flows of Submersion Metrics

Letters in Mathematical Physics - Suppose we are given a compact Riemannian manifold (Q,g) with a completely integrable geodesic flow. Let G be a compact connected Lie group acting freely on Q by...     

Directivity pattern of neurosurgical endoscopic ultrasonic probes

The objective of this paper is to present recent investigations in characteristics of the sound field generated by neurosurgical endoscopic ultrasonic probes (NEUPs) for minimally invasive surgery. The importance of this information has been investigated and discussed taking into account following facts: 1. According to the International Standard IEC 61847:1998 basic acoustical output characteristics of ultrasonic surgical equipment is declared for and measured in an acoustical free field. The standard generally treats the ultrasonic probe as an omnidirectional point source of the zero order (monopole source). 2. In real conditions, operations with NEUPs are performed within the acoustical near field. Having in mind that the cavitational and hydrodynamic effects are dominant, two theoretical boundary conditions can be present. The first one takes place when operations are performed near the "soft" acoustical boundary (tissue/air), and the second one is near the "rigid" acoustical boundary (tissue/bone). Reflections of sound waves from boundaries have influence on the characteristics of the ultrasonic probe (transducer) and on the sound field. In such cases spherical waves of the first and second order are generated. Directivity of sound sources takes shape in the far field and is easier to measure there. On the basis of measured directivity patterns, the influence of different operational conditions (immersion depth of the probe tip, boundary type, acoustical impedance of the medium etc.) on the radiated sound power and spatial distribution of the sound pressure can be estimated.     

Lattice dynamics and phase diagrams for hydrogen bonded systems

Abstract

A variational correlated ground state wave-function theory is applied to investigate the high-pressure deformation of hydrogen-bond potential described by a double Morse potential functions. The evolution of the hydrogen bond potential with increasing pressure and the effects of deuterium isotope substitution on the quantum-fluctuation-driven phenomena are discussed. The theory was employed for predicting and interpreting the pressure dependence of the phase transition temperatue for KDP-like ferroelectrics and NQR-frequency coefficients for several deuterated and undeuterated crystals.     

A semiclassical model of the interior of Uranus

Abstract

Using the mass and radius of Uranus, as determined by Voyager, and a particular semiclassical theory of dense matter, a model of its interior has been developed. Details of the model, the underlying theory and possible sources of discrepancies with recent work on this topic are briefly presented.     

Radiation hardness of gas discharge tubes and avalanche diodes used for transient voltage suppression

The widespread use of gas discharge tubes (GDTs) and avalanche diodes for transient voltage suppression (TVS) in many cases results in their exposure to ionizing radiation. The aim of this paper is to investigate the influence of irradiation on these TVS devices’ characteristics, by exposing them to a combined neutron/gamma radiation field. Experimental results show that irradiation of TVS diodes causes a lasting degradation of their protective characteristics. On the other hand, GDTs exhibit a temporary change of performance. The observed effects are presented with the accompanying theoretical interpretations, based on the interaction of radiation with materials constituting the investigated devices.     

Difference equations in statistical mechanics. I. Cluster statistics models

A review and some new results are presented for several cluster statistics models, solutions of which can be reduced to difference equations. Mathematical techniques suitable for solving these equations are surveyed.