Field and temperature induced colossal strain in Gd5(SixGe1−x)4

Gd₅(Si_xGe_1−x)₄, known for its giant magnetocaloric effect, also exhibits a colossal strain of the order of 10,000 ppm for a single crystal near its coupled first-order magnetic-structural phase transition, which occurs near room temperature for the compositions 0.41≤x≤0.575. Such colossal strain can be utilised for both magnetic sensor and actuator applications. In this study, various measurements have been carried out on strain as a function of magnetic field strength and as a function of temperature on single crystal Gd₅Si₂Ge₂ (x=0.5), and polycrystalline Gd₅Si_1.95Ge_2.05 (x=0.487) and Gd₅Si_2.09Ge_1.91 (x=0.52). Additionally a giant magnetostriction/thermally induced strain of the order of 1800 ppm in polycrystalline Gd₅Si_2.09Ge_1.91 was observed at its first order phase transition on varying temperature using a Peltier cell without the use of bulky equipment such as cryostat or superconducting magnet.     

Extraction of bound-state parameters from dispersive sum rules

The procedure of extracting the ground-state parameters from vacuum-to-vacuum and vacuum-to-hadron correlators within the method of sum rules is considered. The emphasis is laid on the crucial ingredient of this method—the effective continuum threshold. A new algorithm to fix this quantity is proposed and tested. First, a quantum-mechanical potential model which provides the only possibility to probe the reliability and the actual accuracy of this method is used as a study case. In this model, our algorithm is shown to lead to a remarkable improvement of the accuracy of the extracted ground-state parameters compared to the standard procedures adopted in the method and used in all previous applications of dispersive sum rules in QCD. As a next step, it is demonstrated that the procedures of extracting the ground-state decay constant in the potential model and in QCD are quantitatively very close to each other. Therefore, the application of the proposed algorithm in QCD promises a considerable increase of the accuracy of the extracted hadron parameters.     

Multidimensional kinetic theory of phase transitions of the first kind

Leningrad State University. Translated from Teoreticheskaya i Matematicheskaya Fizika, Vol. 81, No. 2, pp. 247–262, November, 1989.     

Localization of acoustic energy in gel systems on solid-phase inhomogeneities

The thermal effects of ultrasound on an agarose gel containing nanoparticles of iron(III) hydroxide and barium sulfate are comparatively studied. The agarose matrix is shown to interact differently with iron(III) hydroxide and barium sulfate. The relative change in ultrasound absorption due to modifier particles located in the gel is estimated. The highest thermal effect is observed for systems in which modifiers are located on separate elements of the matrix bulk. Production of “containers” with ultrasound-controlled drug release on the basis of thermosensitive gels containing solid-phase inclusions is discussed as an example of possible application of the effects described.     

Elucidation of the character of radionuclide concentration changes in the near ground layer of air

The Fokker Planck equation was used to analyze the probability of the appearance of radionuclide impulses of any type. Distribution functions for the stationary state and conditions when different factors influence the impulse amplitude and duration are presented. A high degree of correlation was obtained between our results and an analysis of distribution functions of radioactivity and seismic noises in certain regions in Europe and Japan found in the literature. This presents a contribution to the further explanation of the mechanism of radioactivity changes in the near ground layers of air.