1,084 research outputs found
Control of ionic selectivity by a pore helix residue in the Kv1.2 channel
Interaction between the selectivity filter and the adjacent pore helix of voltage-gated K+ (Kv) channels controls pore stability during K+ conduction. Kv channels, having their selectivity filter destabilized during depolarization, are said to undergo C-type inactivation. We examined the functionality of a residue at the pore helix of the Kv1.2 channel (V370), which reportedly affects C-type inactivation. A mutation into glycine (V370G) caused a shift in reversal potential from around -72 to -9 mV. The permeability ratios (P-Na/P-K) of the wild type and V370G mutant are 0.04 and 0.76, respectively. In the wild-type, P-Rb/P-K, P-Cs/P-K and P-Li/P-K are 0.78, 0.10 and 0.05, respectively. Kv1.2 V370G channels had enhanced permeability to Rb+ and Cs+ (P-Rb/P-K and P-Cs/P-K are 1.63 and 1.18, respectively); however, Li+ permeability was not significantly augmented (P-Li/P-K is 0.13). Therefore, in addition to its known effect on pore stability, V370 of Kv1.2 is also crucial in controlling ion selectivity
Diagnostic for Dilaton Dark Energy
diagnostic can differentiate between different models of dark energy
without the accurate current value of matter density. We apply this geometric
diagnostic to dilaton dark energy(DDE) model and differentiate DDE model from
LCDM. We also investigate the influence of coupled parameter on the
evolutive behavior of with respect to redshift . According to the
numerical result of , we get the current value of equation of state
=-0.952 which fits the WMAP5+BAO+SN very well.Comment: 6 pages and 6 figures
Microbial community analysis in the termite gut and fungus comb of Odontotermes formosanus: the implication of Bacillus as mutualists
The microbial communities harbored in the gut and fungus comb of the fungus-growing termite Odontotermes formosanus were analyzed by both culture-dependent and culture-independent methods to better understand the community structure of their microflora. The microorganisms detected by denaturing gradient gel electrophoresis (DGGE), clonal selection, and culture-dependent methods were hypothesized to contribute to cellulose-hemicellulose hydrolysis, gut fermentation, nutrient production, the breakdown of the fungus comb and the initiation of the growth of the symbiotic fungus Termitomyces. The predominant bacterial cultivars isolated by the cultural approach belonged to the genus Bacillus (Phylum Firmicutes). Apart from their function in lignocellulosic degradation, the Bacillus isolates suppressed the growth of the microfungus Trichoderma harzianum (genus Hypocrea), which grew voraciously on the fungus comb in the absence of termites but grew in harmony with the symbiotic fungus Termitomyces. The in vitro studies suggested that the Bacillus sp. may function as mutualists in the termite-gutfungus-comb microbial ecosystem
Knot Topology of QCD Vacuum
We show that one can express the knot equation of Skyrme theory completely in
terms of the vacuum potential of SU(2) QCD, in such a way that the equation is
viewed as a generalized Lorentz gauge condition which selects one vacuum for
each class of topologically equivalent vacua. From this we show that there are
three ways to describe the QCD vacuum (and thus the knot), by a non-linear
sigma field, a complex vector field, or by an Abelian gauge potential. This
tells that the QCD vacuum can be classified by an Abelian gauge potential with
an Abelian Chern-Simon index.Comment: 4 page
Density distribution profile for internodes and nodes of Phyllostachys edulis (Moso bamboo) by computer tomography scanning
This study aims to quantify the density distribution, and specify the density distribution difference between internodes and nodes parts of Phyllostachys edulis (Moso Bamboo) in the radial, tangential and longitudinal directions. Due to the anatomical complexity of Moso bamboo, the measurement methods of bulk density are insufficient. In this work, Computed Tomography (CT) scanning has been selected to quantify the density distribution of Moso bamboo. Major findings from both anatomical analysis and CT scanning quantifications are that the Moso bamboo density of the internodes parts and the nodes parts reduce from the external surface to the internal surface of the culm wall in the radial direction. In the longitudinal direction, the internode parts of the Moso bamboo have relatively uniform density. Significant density fluctuation variations occur at the nodes parts of the Moso bamboo. The different proportions of the vascular bundles tissues and the parenchyma ground tissues dominate the density variation of the Moso bamboo in the radial direction. In the longitudinal direction, relatively uniform density of the internodes parts of the Moso bamboo is attributed to the straight vascular bundles. The significant density variation in the node parts is caused by the irregular intertwined vascular bundles
Franck-Condon Effect in Central Spin System
We study the quantum transitions of a central spin surrounded by a
collective-spin environment. It is found that the influence of the
environmental spins on the absorption spectrum of the central spin can be
explained with the analog of the Franck-Condon (FC) effect in conventional
electron-phonon interaction system. Here, the collective spins of the
environment behave as the vibrational mode, which makes the electron to be
transitioned mainly with the so-called "vertical transitions" in the
conventional FC effect. The "vertical transition" for the central spin in the
spin environment manifests as, the certain collective spin states of the
environment is favored, which corresponds to the minimal change in the average
of the total spin angular momentum.Comment: 8 pages, 8 figure
Anomalous c-axis charge dynamics in copper oxide materials
Within the t-J model, the c-axis charge dynamics of the copper oxide
materials in the underdoped and optimally doped regimes is studied by
considering the incoherent interlayer hopping. It is shown that the c-axis
charge dynamics is mainly governed by the scattering from the in-plane
fluctuation. In the optimally doped regime, the c-axis resistivity is a linear
in temperatures, and shows the metallic-like behavior for all temperatures,
while the c-axis resistivity in the underdoped regime is characterized by a
crossover from the high temperature metallic-like behavior to the low
temperature semiconducting-like behavior, which are consistent with experiments
and numerical simulations.Comment: 6 pages, Latex, Three figures are adde
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