Maximally Random Discrete-Spin Systems with Symmetric and Asymmetric Interactions and Maximally Degenerate Ordering

Discrete-spin systems with maximally random nearest-neighbor interactions that can be symmetric or asymmetric, ferromagnetic or antiferromagnetic, including off-diagonal disorder, are studied, for the number of states $q=3,4$ in $d$ dimensions. We use renormalization-group theory that is exact for hierarchical lattices and approximate (Migdal-Kadanoff) for hypercubic lattices. For all d>1 and all non-infinite temperatures, the system eventually renormalizes to a random single state, thus signaling qxq degenerate ordering. Note that this is the maximally degenerate ordering. For high-temperature initial conditions, the system crosses over to this highly degenerate ordering only after spending many renormalization-group iterations near the disordered (infinite-temperature) fixed point. Thus, a temperature range of short-range disorder in the presence of long-range order is identified, as previously seen in underfrustrated Ising spin-glass systems. The entropy is calculated for all temperatures, behaves similarly for ferromagnetic and antiferromagnetic interactions, and shows a derivative maximum at the short-range disordering temperature. With a sharp immediate contrast of infinitesimally higher dimension 1+\epsilon, the system is as expected disordered at all temperatures for d=1.Comment: Final published version, 4 pages, 5 figure

1/f noise in nanowires

We have measured the low-frequency resistance fluctuations (1 mHz<f<10 Hz) in Ag nanowires of diameter 15 nm<d<200 nm at room temperatures. The power spectral density (PSD) of the fluctuations has a 1/f^{\alpha} character as seen in metallic films and wires of larger dimension. Additionally, the PSD has a significant low-frequency component and the value of \alpha increases from the usual 1 to ~3/2 as the diameter d is reduced. The value of the normalized fluctuation \frac{}{R^2} also increases as the diameter d is reduced. We observe that there are new features in the 1/f noise as the size of the wire is reduced and they become more prominent as the diameter of the wires approaches 15nm. It is important to investigate the origin of the new behavior as 1/f noise may become a limiting factor in the use of metal wires of nanometer dimensions as interconnects.Comment: 9 pages, 6 figures, published in Nanotechnolog

Resolving Octant Degeneracy at LBL experiment by combining Daya Bay Reactor Setup

Long baseline Experiment (LBL) have promised to be a very powerful experimental set up to study various issues related to Neutrinos. Some ongoing and planned LBL and medium baseline experiments are - T2K, MINOS, NOvA, LBNE, LBNO etc. But the long baseline experiments are crippled due to presence of some parameter degeneracies, like the Octant degeneracy. In this work, we first show the presence of Octant degeneracy in LBL experiments, and then combine it with Daya Bay Reactor experiment, at different values of CP violation phase. We show that the Octant degeneracy in LBNE can be resolved completely with this proposal.Comment: 4 pages, 8 figure

Scanning thermal microscope study of a metal film under current stressing: role of temperature inhomogeneity in the damage process

We report direct observation of the evolution of local temperature inhomogeneity and the resulting atomic migration in a metal film (Ag on Si) stressed by a high electrical current is reported. Experiments were carried out by simultaneous temperature mapping and topography imaging using a scanning thermal microscope in combination with resistance measurements. The experimental observation is analysed using a model based simulation. The experimental observation and the simulation show that due to current stressing the temperature of the film becomes significantly inhomogeneous over time (with the local temperature deviating strongly from the mean). This creates local stress as well as local temperature gradients (as high as &#8776;3 &#956;m&#8722;1) that lead to mass migration in addition to electromigration. The local temperature inhomogeneity serves as one of the main agents for local atomic migration which leads to a change in the film microstructure. The migration leads to damage and eventual failure as simultaneously monitored by in situ resistance measurements

Effects of cold rolling (CR) and annealing time on microstructure and mechanical properties of AA 5052 aluminum alloy

In this paper, the influences of cold rolling and annealing time on the microstructure and mechanical behaviors of AA 5052 aluminum alloy were investigated. An aluminum sheet was cold-rolled at room temperature at 15, 30, and 45 % rolling reduction. The 45 % cold-rolled sample was subsequently annealed at 370 °C for 2, 4, and 6 h. The microstructure was observed using optical microscopy whereas the mechanical behaviors were evaluated through hardness and tensile tests. It was found that the equiaxed grains are severely elongated along the rolling direction with increased rolling reduction. The hardness and strength increase significantly with an increase of rolling reduction but the ductility decreases. The annealing treatment reduces hardness and strength but improves the ductility

Effects of cold rolling (CR) and annealing time on microstructure and mechanical properties of AA 5052 aluminum alloy

In this paper, the influences of cold rolling and annealing time on the microstructure and mechanical behaviors of AA 5052 aluminum alloy were investigated. An aluminum sheet was cold-rolled at room temperature at 15, 30, and 45 % rolling reduction. The 45 % cold-rolled sample was subsequently annealed at 370 °C for 2, 4, and 6 h. The microstructure was observed using optical microscopy whereas the mechanical behaviors were evaluated through hardness and tensile tests. It was found that the equiaxed grains are severely elongated along the rolling direction with increased rolling reduction. The hardness and strength increase significantly with an increase of rolling reduction but the ductility decreases. The annealing treatment reduces hardness and strength but improves the ductility

Isolamento, grupo de compatibilidade e crescimento micelial de Phytophthora sp. da pupunha.

Resumo