Lattice paramenter, lattice disorder and resistivity of carbohydrate doepd MgB2 and their correlation with the transition temperature

The change in the lattice parameters or the lattice disorder is claimed as a cause of the slight reduction in the transition temperature by carbon doping in MgB2. In this work, an extensive investigation on the effects of carbohydrate doping has been carried out. It is found that not only the a-axis but also the c-axis lattice parameter increases with the sintering temperature. A linear relation between the unit cell volume and the critical temperature is observed. Compared with the well known correlation between the lattice strain and the critical temperature, the X-ray peak broadening itself shows a closer correlation with the transition temperature. The residual resistivity and the critical temperature are linearly correlated with each other as well and its implication is further discussed.Comment: 3 pages. Accepted by Jouranl of nanoscience and Nanotechnology (JNN

Different Signaling and Cell Death Roles of Heterotrimeric G Protein and Subunits in the Arabidopsis Oxidative Stress Response to Ozone

Arabidopsis thaliana plants with null mutations in the genes encoding the α and β subunits of the single heterotrimeric G protein are less and more sensitive, respectively, to O3 damage than wild-type Columbia-0 plants. The first peak of the bimodal oxidative burst elicited by O3 in wild-type plants is almost entirely missing in both mutants. The late peak is normal in plants lacking the Gβ protein but missing in plants lacking the Gα protein. Endogenous reactive oxygen species (ROS) are first detectable in chloroplasts of leaf epidermal guard cells. ROS production in adjacent cells is triggered by extracellular ROS signals produced by guard cell membrane-associated NADPH oxidases encoded by the AtrbohD and AtrbohF genes. The late, tissue damage–associated component of the oxidative burst requires only the Gα protein and arises from multiple cellular sources. The early component of the oxidative burst, arising primarily from chloroplasts, requires signaling through the heterotrimer (or the Gβγ complex) and is separable from Gα-mediated activation of membrane-bound NADPH oxidases necessary for both intercellular signaling and cell death

Stochastic theory of spin-transfer oscillator linewidths

We present a stochastic theory of linewidths for magnetization oscillations in spin-valve structures driven by spin-polarized currents. Starting from a nonlinear oscillator model derived from spin-wave theory, we derive Langevin equations for amplitude and phase fluctuations due to the presence of thermal noise. We find that the spectral linewidths are inversely proportional to the spin-wave intensities with a lower bound that is determined purely by modulations in the oscillation frequencies. Reasonable quantitative agreement with recent experimental results from spin-valve nanopillars is demonstrated.Comment: Submitted to Physical Review