4,163 research outputs found
Gating Properties of a Sodium Channel with Three Arginines Substituted by Histidines in the Central Part of Voltage Sensor S4D4
In voltage-dependent sodium channels there is some functional specialization of the four different S4 voltage sensors with regard to the gating process. Whereas the voltage sensors of domains 1 to 3 control activation gating, the movement of the voltage sensor of domain 4 (S4D4) is known to be tightly coupled to sodium channel inactivation, and there is some experimental evidence that S4D4 also participates in activation gating. To further explore its putative multifunctional role in the gating process, we changed the central part of S4D4 in rat brain IIA (rBIIA) sodium channels by the simultaneous replacement of the third (R1632), fourth (R1635) and fifth (R1638) arginine by histidine (mutation R3/4/5H). As a result, the time course of current decay observed in R3/4/5H was about three times slower, if compared to wild type (WT). On the other hand, the recovery, as well as the voltage dependence of fast inactivation, remained largely unaffected by the mutation. This suggests that at physiological pH (7.5) the effective charge of the voltage sensor was not significantly changed by the amino-acid substitutions. The well-known impact of site-3 toxin (ATX-II) on the inactivation was drastically reduced in R3/4/5H, without changing the toxin affinity of the channel. The activation kinetics of WT and R3/4/5H studied at low temperature (8°C) were indistinguishable, while the inactivation time course of R3/4/5H was then clearly more slowed than in WT. These data suggest that the replacement of arginines by histidines in the central part of S4D4 clearly affects the movement of S4D4 without changing the activation kinetic
Next-to-Next-to-Leading Electroweak Logarithms in W-pair Production at ILC
We derive the high energy asymptotic behavior of gauge boson production cross
section in a spontaneously broken SU(2) gauge theory in the
next-to-next-to-leading logarithmic approximation. On the basis of this result
we obtain the logarithmically enhanced two-loop electroweak corrections to the
differential cross section of W-pair production at ILC/CLIC up to the second
power of the large logarithm.Comment: 17 pages, LaTeX, Eqs. (31) and (35) correcte
Quark resonances and high E_t jets
Possible spin-3/2 quark resonances would have a significant effect on high
E_{\mbox{\rm t}} jet production through their contribution to the subprocess
. Such enhancements are compared to a, recently
reported, anomaly in inclusive jet production at the CDF detector.Comment: 7 pages set in RevTex with four postscript figures appended- all
uuencode
Quantization of the elastic modes in an isotropic plate
We quantize the elastic modes in a plate. For this, we find a complete,
orthogonal set of eigenfunctions of the elastic equations and we normalize
them. These are the phonon modes in the plate and their specific forms and
dispersion relations are manifested in low temperature experiments in
ultra-thin membranes.Comment: 14 pages, 2 figure
QCD Corrections to Toponium Production at Hadron Colliders
Toponium production at future hadron colliders is investigated. Perturbative
QCD corrections to the production cross section for gluon fusion are calculated
as well as the contributions from gluon-quark and quark-antiquark collisions to
the total cross section. The dependence on the renormalization and
factorization scales and on the choice of the parton distribution functions is
explored. QCD corrections to the branching ratio of into
are included and the two-loop QCD potential is used to predict
the wave function at the origin. The branching ratio of into , , and is compared with the channel.Comment: 16 pages (latex) 9 figures (postscript) available upon request,
TTP92-3
Four-pion production in tau decays and e+e- annihilation: an update
An improved description of four-pion production in electron-positron
annihilation and in tau lepton decays is presented. The model amplitude is
fitted to recent data from BaBar which cover a wide energy range and which were
obtained exploiting the radiative return. Predicting tau decay distributions
from e+e- data and comparing these predictions with ALEPH and CLEO results, the
validity of isospin symmetry is confirmed within the present experimental
errors. A good description of two- and three-pion sub-distributions is
obtained. Special emphasis is put on the predictions for omega pi (->
pi+pi-pi0) in e+e- annihilation and in tau decay. The model amplitude is
implemented in the Monte Carlo generator PHOKHARA.Comment: a few typos correcte
Resolution and enhancement in nanoantenna-based fluorescence microscopy
Single gold nanoparticles can act as nanoantennas for enhancing the
fluorescence of emitters in their near-fields. Here we present experimental and
theoretical studies of scanning antenna-based fluorescence microscopy as a
function of the diameter of the gold nanoparticle. We examine the interplay
between fluorescence enhancement and spatial resolution and discuss the
requirements for deciphering single molecules in a dense sample. Resolutions
better than 20 nm and fluorescence enhancement up to 30 times are demonstrated
experimentally. By accounting for the tip shaft and the sample interface in
finite-difference time-domain calculations, we explain why the measured
fluorescence enhancements are higher in the presence of an interface than the
values predicted for a homogeneous environment.Comment: 10 pages, 3 figures. accepted for publication in Nano Letter
The role of Ar III in quantitative spectroscopy on hot argon plasmas
We perform quantitative optical emission spectroscopy on the hot core of the cathode region of a free-burning arc in argon under atmospheric pressure. As the peak temperatures in the centre of the discharge exceed 22 000 K we are able to observe three spectra of argon (Ar I, Ar II and Ar III) and the continuum emission. We report on some inconsistencies concerning the evaluation of Ar III radiation in both line and continuum emission. These are caused by erroneous data in the literature and common misconceptions about the influence of Ar III on the plasma emission. We discuss the impact of this fact on published data
- …