11,284 research outputs found
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
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