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Energy Fluctuations (energy + fluctuation)
Selected AbstractsEvaluation of ferromagnetic shape-memory alloys by the extended Hückel methodIEEJ TRANSACTIONS ON ELECTRICAL AND ELECTRONIC ENGINEERING, Issue 3 2007Kei Ehara Student Member Abstract Ferromagnetic shape-memory alloy (SMA) are powerful candidates as actuators, pressure sensors, magnetic sensors, etc. Magnetic-field-induced strain has been observed in many ferromagnetic SMA. The magnetic-field-induced strain is a reversible transformation in the martensite phase with the magnetic field. We have investigated the property of the ferromagnetic shape-memory materials by the extended Hückel method, and estimated the ferromagnetic shape-memory of Fe,Pt and Fe,Pd alloys at high temperatures. We used two physical quantities, i.e. cohesive energy and energy fluctuation, to measure the stability of the materials. On the basis of the cohesive energy and energy fluctuation, we discuss the characteristics of ferromagnetic SMA, in which the energy fluctuation is a measure of thermal stability of the metals and/or alloys. The martensite structure is unstable, which means that the energy fluctuation has to be controlled to a small value to keep the martensite phase. Furthermore, it is estimated that the energy fluctuation is associated with the Curie temperature. The Curie temperature is an essential parameter for ferromagnetic materials. From the discussion presented above, we can propose the following: (i) Alloys possessing a low cohesive energy are associated with a high mobility of atoms and are suitable for ferromagnetic shape-memory materials; (ii) Alloys showing a low energy fluctuation show ferromagnetic shape-memory and are favored for use as memory devices. We found that I (iodine) is the best dopant for Fe,Pt ferromagnetic SMA, and Tc (technetium) is the best dopant for Fe,Pd ferromagnetic SMA. Copyright © 2007 Institute of Electrical Engineers of Japan© 2007 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc. [source] Positive width function and energy indeterminacies in ammonia moleculeINTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, Issue 8 2007Theodosios G. Douvropoulos A recently published methodology based on the semiclassical path integral theory was applied in a double well structure and gave the analytic form of the system's Green's function. This type of potential can describe the ammonia molecule as far as the motion of the nitrogen atom perpendicular to the hydrogen plane is discussed. Because of the fact that a double well describes a bound system and correspondingly stationary states (constructed by the symmetric and antisymmetric superposition of the eigenstates of the two unperturbed wells), it was expected that the energy spectrum would be real, in a form of doublets due to the splitting effect that takes place. However, the result was a pair of complex poles, which had a clearly positive imaginary part for each member. The present work explains the role of the imaginary parts of the complex poles as the decay rate of quantities defined as the energy indeterminacies, which are directly related to the fact that energy is not well determined in a classically forbidden region of motion. These quantities come as a function of (d,)/dE, which is the derivative of the classical action inside the potential barrier, with respect to energy. The major contribution comes from the turning points, and then the imaginary parts are responsible, not only for the conservation of energy, but for the correct sign of time as well. In this way, a different approach for the tunneling process is adopted, in which the entry or exit of the particle from the potential barrier takes place inside a neighborhood of the turning point, as though the latter was broadened and fluctuating. The magnitude of the previously mentioned decay rate is equal to ,/,, where , is the frequency of the classical oscillations inside one well. In contrast, the inversion frequency is generated by the part of the complex pole that is unrelated to (d,)/dE and is much smaller in magnitude than the classical frequency, since it is given as ,/, exp(,,). In this way, the period of the energy fluctuations is much smaller than the internal period of the system produced by the oscillating communication of the two classically allowed regions of motion. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2007 [source] Large-scale cosmic microwave background anisotropies and dark energyMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 3 2003J. Weller ABSTRACT In this paper we investigate the effects of perturbations in a dark energy component with a constant equation of state on large-scale cosmic microwave background (CMB) anisotropies. The inclusion of perturbations increases the large-scale power. We investigate more speculative dark energy models with w < ,1 and find the opposite behaviour. Overall the inclusion of perturbations in the dark energy component increases the degeneracies. We generalize the parametrization of the dark energy fluctuations to allow for an arbitrary constant sound speed, and we show how constraints from CMB experiments change if this is included. Combining CMB with large-scale structure, Hubble parameter and supernovae observations we obtain w=,1.02 ± 0.16 (1,) as a constraint on the equation of state, which is almost independent of the sound speed chosen. With the presented analysis we find no significant constraint on the constant speed of sound of the dark energy component. [source] Lipolytic and esterolytic activity-based profiling of murine liverPROTEINS: STRUCTURE, FUNCTION AND BIOINFORMATICS, Issue 17 2008Ruth Birner-Gruenberger Abstract In lipid metabolism, the liver acts as a buffer for transient energy fluctuations. It temporarily stores fatty acids as triacylglycerol and secretes them as very low density lipoprotein into the circulation when the period of maximum lipid load has passed. The lipolytic enzymes responsible for mobilization of internal lipid stores in the liver have not been identified yet. We introduced active site-directed chemical probes for lipolytic activity profiling in complex mixtures, known as activity-based proteomics, and employed it for global analysis and functional annotation of lipolytic proteins in mouse adipose tissue. Here we report the combined application of two approaches using fluorescent and biotinylated probes for discovery and discrimination of lipolytic and esterolytic enzymes in mouse liver subproteomes. Proteomes labeled with the fluorescent probes were analyzed by 2-DE while proteomes labeled with the biotinylated probe were subjected to avidin-affinity isolation. Of 37 totally identified proteins, 15 were detected using both approaches while 14 and 8 were solely identified by 2-DE and avidin-affinity isolation, respectively. Moreover, 12 enzymes were classified as potential lipases and/or cholesteryl esterases by their reaction with probes specific for the respective activities directly in their proteomes. [source] A new look at the derivation of the Schrödinger equation from Newtonian mechanicsANNALEN DER PHYSIK, Issue 6 2003L. Fritsche Abstract We present a modified version of Nelson's seminal paper on the derivation of the time-dependent Schrödinger equation which draws on the equation of motion of a particle that moves under the influence of a classical force field and additional stochastic forces. The emphasis of our elaboration is focused on the implication of allowing stochastic forces to occur, viz. that the energy E of the particle is no longer conserved on its trajectory in a conservative force field. We correlate this departure , E from its classical energy with the energy/time uncertainty relation where , t is the average time for , E to persist. The stability of atoms, the zero-point energy of oscillators, the tunneling effect and the diffraction at slits are shown to be directly connected with the occurrence of such energy fluctuations. We discuss and rederive Nelson's theory entirely from this point of view and generalize his approach to systems of N particles which interact via pair forces. Achieving reversibility in a description of particle motion that is akin to Brownian motion, represents a salient point of the derivation. We demonstrate that certain objections raised against Nelson's theory are without substance. We also try to put the particular worldview of this version of stochastic quantum mechanics into perspective with regard to the established Copenhagen interpretation. [source] | |||||||||||||