3,634 research outputs found
Noise In Nonohmic Regimes Of Disordered Systems
We present here a short review of mainly experimental properties of noise as
disordered systems are driven into non-ohmic regimes by applying voltages of
few volts only. It is found that the noise does not simply follow the
resistance in that the direction of change of noise could be opposite to that
of resistance. It is discussed how this and other properties make the noise a
complementary and incisive tool for studying complex systems, particularly its
dynamic properties. Study of noise in non-ohmic regimes in physical systems is
rather in a nascent stage. Some of the open issues are highlighted.Comment: 9 Pages, 7 figures. Reported in Unsolved Problems of Noise and
Fluctuations: UPoN 2005, Gallipoli, Italy, June 6-10, 200
Stability of Circular Orbits in General Relativity: A Phase Space Analysis
Phase space method provides a novel way for deducing qualitative features of
nonlinear differential equations without actually solving them. The method is
applied here for analyzing stability of circular orbits of test particles in
various physically interesting environments. The approach is shown to work in a
revealing way in Schwarzschild spacetime. All relevant conclusions about
circular orbits in the Schwarzschild-de Sitter spacetime are shown to be
remarkably encoded in a single parameter. The analysis in the rotating Kerr
black hole readily exposes information as to how stability depends on the ratio
of source rotation to particle angular momentum. As a wider application, it is
exemplified how the analysis reveals useful information when applied to motion
in a refractive medium, for instance, that of optical black holes.Comment: 20 pages. Accepted for publication in Int. J. theor. Phy
Scaling of NonOhmic Conduction in Strongly Correlated Systems
A new scaling formalism is used to analyze nonlinear I-V data in the vicinity
of metal-insulator transitions (MIT) in five manganite systems. An exponent,
called the nonlinearity exponent, and an onset field for nonlinearity, both
characteristic of the system under study, are obtained from the analysis. The
onset field is found to have an anomalously low value corroborating the
theoretically predicted electronically soft phases. The scaling functions above
and below the MIT of a polycrystalline sample are found to be the same but with
different exponents which are attributed to the distribution of the MIT
temperatures. The applicability of the scaling in manganites underlines the
universal response of the disordered systems to electric field
Restoration of factorization for low hadron hadroproduction
We discuss the applicability of the factorization theorem to low-
hadron production in hadron-hadron collision in a simple toy model, which
involves only scalar particles and gluons. It has been shown that the
factorization for high- hadron hadroproduction is broken by soft gluons in
the Glauber region, which are exchanged among a transverse-momentum-dependent
(TMD) parton density and other subprocesses of the collision. We explain that
the contour of a loop momentum can be deformed away from the Glauber region at
low , so the above residual infrared divergence is factorized by means of
the standard eikonal approximation. The factorization is then restored in
the sense that a TMD parton density maintains its universality. Because the
resultant Glauber factor is independent of hadron flavors, experimental
constraints on its behavior are possible. The factorization can also be
restored for the transverse single-spin asymmetry in hadron-hadron collision at
low in a similar way, with the residual infrared divergence being
factorized into the same Glauber factor.Comment: 12 pages, 2 figures, version to appear in EPJ
Water Dynamics at Protein Interfaces: Ultrafast Optical Kerr Effect Study
The behavior of water molecules surrounding a protein can have an important bearing on its structure and function. Consequently, a great deal of attention has been focused on changes in the relaxation dynamics of water when it is located at the protein surface. Here we use the ultrafast optical Kerr effect to study the H-bond structure and dynamics of aqueous solutions of proteins. Measurements are made for three proteins as a function of concentration. We find that the water dynamics in the first solvation layer of the proteins are slowed by up to a factor of 8 in comparison to those in bulk water. The most marked slowdown was observed for the most hydrophilic protein studied, bovine serum albumin, whereas the most hydrophobic protein, trypsin, had a slightly smaller effect. The terahertz Raman spectra of these protein solutions resemble those of pure water up to 5 wt % of protein, above which a new feature appears at 80 cm–1, which is assigned to a bending of the protein amide chain
Magnetic structures of the Eu and Cr moments in EuCr As : Neutron diffraction study
The magnetic structures of the Eu2+ and Cr2+ moments in the nonsuperconducting parent compound EuCr2As2 have been determined by using neutron diffraction. While the Eu2+ moments order ferromagnetically with moments along the c direction at TC=21.0(1) K, the ordering temperature of the Cr2+ moments is found to be at very high temperature of 680(40) K by using magnetization measurements. The Cr2+ moments order in a G-type antiferromagnetic structure with moments along the c direction. According to this magnetic structure, the nearest-neighbor Cr2+ moments are antiferromagnetically aligned in the a−b plane as well as in the c direction. The ordered magnetic moment of the Eu2+ and Cr2+ amounts to 6.2(5)μB and 1.7(4)μB, respectively, at T=2 K
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