1,475 research outputs found
Interference between resonant and Auger mechanisms for charge-exchange processes near surfaces
In this work we solve the dynamics of the Newns-Anderson Hamiltonian supplemented with Auger termsand analyze the case of He1 scattered off an Al ~100! surface. The dynamical solution is compared with resultsof calculations based on much simpler approximations. We prove that resonant and Auger processes can betreated separately and independently in this case and that charge exchange between He and Al proceeds viaresonant and Auger exchange of electrons between the promoted molecular orbital of He and the conductionband states of Al.Fil: García, Evelina Andrea. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; ArgentinaFil: Wang, N.P.. Universidad Autónoma de Madrid; EspañaFil: Monreal, R.C.. Universidad Autónoma de Madrid; EspañaFil: Goldberg, Edith Catalina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; Argentin
Vorticity, phase stiffness and the cuprate phase diagram
We review results obtained from vortex-Nernst experiments in cuprates.
Evidence for a loss of phase coherence at the Meissner transition is
derived from vortex-like excitations that persist to high temperature. Below
, the Nersnt signal provides a determination of the upper critical
field vs. doping . Implications for the cuprate phase diagram are
discussed.Comment: 6 pages, 8 figures, Plenary talk of the 7th International Conference
on Materials and Mechanisms of Superconductivity and High Temperature
Superconductors. To appear in Physica C, the proceeding of M2S-HTSC-VI
Depairing field, onset temperature and the nature of the transition in cuprates
The depairing (upper critical) field in hole-doped cuprates has been
inferred from magnetization curves - measured by torque magnetometry in
fields up to 45 T. We discuss the implications of the results for the pair
binding energy, the Nernst onset temperature, fluctuations and the nature of
the Meissner transition at .Comment: 4 pages, 5 figs., proc. M2S-HTSC-VIII, Dresden 2006, Physica (in
press
Matrix Tensor Product Approach to the Equivalence of Multipartite States under Local Unitary Transformations
The equivalence of multipartite quantum mixed states under local unitary
transformations is studied. A criterion for the equivalence of non-degenerate
mixed multipartite quantum states under local unitary transformations is
presented.Comment: 7 page
Cold Induction of EARLI1, a Putative Arabidopsis Lipid Transfer Protein, Is Light and Calcium Dependent
As sessile organisms, plants must adapt to their environment. One approach toward understanding this adaptation is to investigate environmental regulation of gene expression. Our focus is on the environmental regulation of EARLI1, which is activated by cold and long-day photoperiods. Cold activation of EARLI1 in short-day photoperiods is slow, requiring several hours at 4ºC to detect an increase in mRNA abundance. EARLI1 is not efficiently cold-activated in etiolated seedlings, suggesting that photomorphogenesis is necessary for its cold activation. Cold activation of EARLI1 is inhibited in the presence of the calcium channel blocker lanthanum chloride or the calcium chelator EGTA. Addition of the calcium ionophore Bay K8644 results in cold-independent activation of EARLI1. These data suggest that EARLI1 is not an immediate target of the cold response, and that calcium flux affects its expression. EARLI1 is a putative secreted protein and has motifs found in lipid transfer proteins. Over-expression of EARLI1 in transgenic plants results in reduced electrolyte leakage during freezing damage, suggesting that EARLI1 may affect membrane or cell wall stability in response to low temperature stress
Chemical Instability of the Cobalt Oxyhydrate Superconductor under Ambient Conditions
The layered sodium cobalt oxyhydrate superconductor Na0.3CoO2*1.4H2O is shown
through X-ray diffraction and thermogravimetric studies to be one of a series
of hydrated phases of Na0.3CoO2. Further, it is shown that the material is
exceptionally sensitive to both temperature and humidity near ambient
conditions, easily dehydrating to a non-superconducting lower hydrate. The
observation of this stable lower hydrate with c=13.8 angstroms implies that the
superconductivity turns on in this system between CoO2 layer spacings of 6.9
and 9.9 angstroms at nominally constant chemical doping.Comment: 10 pages and 4 figure
Nernst Effect in Electron-Doped PrCeCuO
The Nernst effect of PrCeCuO (x=0.13, 0.15, and 0.17) has
been measured on thin film samples between 5-120 K and 0-14 T. In comparison to
recent measurements on hole-doped cuprates that showed an anomalously large
Nernst effect above the resistive T and H
\cite{xu,wang1,wang2,capan}, we find a normal Nernst effect above T and
H for all dopings. The lack of an anomalous Nernst effect in the
electron-doped compounds supports the models that explain this effect in terms
of amplitude and phase fluctuations in the hole-doped cuprates. In addition,
the H(T) determined from the Nernst effect shows a conventional behavior
for all dopings. The energy gap determined from H(0) decreases as the
system goes from under-doping to over-dopingin agreement with the recent
tunnelling experiments
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Time-frequency representation of earthquake accelerograms and inelastic structural response records using the adaptive chirplet decomposition and empirical mode decomposition
In this paper, the adaptive chirplet decomposition combined with the Wigner-Ville transform and the empirical mode decomposition combined with the Hilbert transform are employed to process various non-stationary signals (strong ground motions and structural responses). The efficacy of these two adaptive techniques for capturing the temporal evolution of the frequency content of specific seismic signals is assessed. In this respect, two near-field and two far-field seismic accelerograms are analyzed. Further, a similar analysis is performed for records pertaining to the response of a 20-story steel frame benchmark building excited by one of the four accelerograms scaled by appropriate factors to simulate undamaged and severely damaged conditions for the structure. It is shown that the derived joint time–frequency representations of the response time histories capture quite effectively the influence of non-linearity on the variation of the effective natural frequencies of a structural system during the evolution of a seismic event; in this context, tracing the mean instantaneous frequency of records of critical structural responses is adopted.
The study suggests, overall, that the aforementioned techniques are quite viable tools for detecting and monitoring damage to constructed facilities exposed to seismic excitations
Dirac Equation at Finite Temperature
In this paper, we propose finite temperature Dirac equation, which can
describe the quantum systems in an arbitrary temperature for a relativistic
particle of spin-1/2. When the temperature T=0, it become Dirac equation. With
the equation, we can study the relativistic quantum systems in an arbitrary
temperature.Comment: arXiv admin note: text overlap with arXiv:1005.2751,
arXiv:hep-ph/0004125, arXiv:hep-ph/0005272 by other author
Quantitative transcription factor binding kinetics at the single-molecule level
We have investigated the binding interaction between the bacteriophage lambda
repressor CI and its target DNA using total internal reflection fluorescence
microscopy. Large, step-wise changes in the intensity of the red fluorescent
protein fused to CI were observed as it associated and dissociated from
individually labeled single molecule DNA targets. The stochastic association
and dissociation were characterized by Poisson statistics. Dark and bright
intervals were measured for thousands of individual events. The exponential
distribution of the intervals allowed direct determination of the association
and dissociation rate constants, ka and kd respectively. We resolved in detail
how ka and kd varied as a function of 3 control parameters, the DNA length L,
the CI dimer concentration, and the binding affinity. Our results show that
although interaction with non-operator DNA sequences are observable, CI binding
to the operator site is not dependent on the length of flanking non-operator
DNA.Comment: 34 pages, 10 figures, accepted by Biophysical Journa
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