270 research outputs found
Waiting times of entangled electrons in normal-superconducting junctions
We consider a normal-superconducting junction in order to investigate the
effect of new physical ingredients on waiting times. First, we study the
interplay between Andreev and specular scattering at the interface on the
distribution of waiting times of electrons or holes separately. In that case
the distribution is not altered dramatically compared to the case of a single
quantum channel with a quantum point contact since the interface acts as an
Andreev mirror for holes. We then consider a fully entangled state originating
from spliting of Cooper pairs at the interface and demonstrate a significant
enhancement of the probability to detect two consecutive electrons in a short
time interval. Finally, we discuss the electronic waiting time distribution in
the more realistic situation of partial entanglement
Photo-assisted shot noise in Coulomb interacting systems
We consider the fluctuations of the electrical current (shot noise) in the
presence of a voltage time-modulation. For a non-interacting metal, it is known
that the derivative of the photo-assisted noise has a staircase behavior. In
the presence of Coulomb interactions, we show that the photo-assisted noise
presents a more complex profile, in particular for the two following systems:
1) a two-dimensional electron gas in the fractional quantum Hall regime for
which we have obtained evenly spaced singularities in the noise derivative,
with a spacing related to the filling factor and, 2) a carbon nanotube for
which a smoothed staircase in the noise derivative is obtained.Comment: Proceedings of the 6th Rencontres du Vietnam, Hanoi (2006
An electronic Mach-Zehnder interferometer in the Fractional Quantum Hall effect
We compute the interference pattern of a Mach-Zehnder interferometer
operating in the fractional quantum Hall effect. Our theoretical proposal is
inspired by a remarkable experiment on edge states in the Integer Quantum Hall
effect (IQHE). The Luttinger liquid model is solved via two independent
methods: refermionization at nu=1/2 and the Bethe Ansatz solution available for
Laughlin fractions. The current differs strongly from that of single electrons
in the strong backscattering regime. The Fano factor is periodic in the flux,
and it exhibits a sharp transition from sub-Poissonian (charge e/2) to
Poissonian (charge e) in the neighborhood of destructive interferences
Complexity of vaginal microflora as analyzed by PCR denaturing gradient gel electrophoresis in a patient with recurrent bacterial vaginosis.
OBJECTIVE: Gardnerella vaginalis has long been the most common pathogen associated with bacterial vaginosis (BV). We aimed to test our hypothesis that symptoms and signs of BV do not necessarily indicate colonization by this organism, and often will not respond to standard metronidazole or clindamycin treatment. METHODS: Using a relatively new molecular tool, PCR denaturing gradient gel electrophoresis (DGGE), the vaginal microflora of a woman with recalcitrant signs and symptoms of BV was investigated over a 6-week timeframe. RESULTS: The vagina was colonized by pathogenic enterobacteriaceae, staphylococci and Candida albicans. The detection of the yeast by PCR-DGGE is particularly novel and enhances the ability of this tool to examine the true nature of the vaginal microflora. The patient had not responded to antifungal treatment, antibiotic therapy targeted at anaerobic Gram-negative pathogens such as Gardnerella, nor daily oral probiotic intake of Lactobacillus rhamnosus GG. The failure to find the GG strain in the vagina indicated it did not reach the site, and the low counts of lactobacilli demonstrated that therapy with this probiotic did not appear to influence the vaginal flora. CONCLUSIONS: BV is not well understood in terms of its causative organisms, and further studies appear warranted using non-culture, molecular methods. Only when the identities of infecting organisms are confirmed can effective therapy be devized. Such therapy may include the use of probiotic lactobacilli, but only using strains which confer a benefit on the vagina of pre- and postmenopausal women
The evaluation of evaporation by infrared thermography: A critical analysis of the measurements on the Crau test site
Evapotranspiration was calculated for both the dry and irrigated zone by four methods which were compared with the energy balance method serving as a reference. Two methods did not involve the surface temperature. They are ETR(n) = R(n), liable to be valid under wet conditions and ET(eq) = (delta/delta + gamma) R(n) i.e, the first term of Penman's equation, adapted to moderately dry conditions. The methods using surface temperature were the combined energy balance aerodynamic approach and a simplified approach proposed by Jackson et al. Tests show the surface temperature methods give relatively satisfactory results both in the dry and wet zone, with a precision of 10% to 15% compared with the reference method. As was to be expected, ET(eq) gave satisfactory results only in the dry zone and ET(Rn) in the irrigated zone. Thermography increased the precision in the estimate of ET relative to the most suitable classical method by 5% to 8% and is equally suitable for both dry and wet conditions. The Jackson method does not require extensive ground measurements and the evaluation of the surface roughness
Présence de spirochetes dans des lésions cutanées du porcelet
Rossi Paul, Devillard J.-P. Présence de spirochètes dans des lésions cutanées du porcelet (3 figures). In: Bulletin de l'Académie Vétérinaire de France tome 110 n°4, 1957. pp. 155-161
Size segregation and convection
The size segregation of granular materials in a vibrating container is
investigated using Molecular Dynamics. We find that the rising of larger
particles is accompanied by the existence of convection cells even in the case
of the lowest possible frequencies. The convection can, however, also be
triggered by the larger particle itself. The possibility of rising through this
mechanism strongly depends on the depth of the larger particle.Comment: 7 pages, 4 figure
Josephson junction chains with long-range interactions: Phase slip proliferation versus Kosterlitz-Thouless transition
The role of long range badly screened Coulomb interactions in a
one-dimensional chain of Josephson junctions is studied. Correlation functions
for the phase correlator are obtained as a function of the Josephson coupling
energy, the short range part of Coulomb repulsion and its long range component.
Though quasi-long range order is no longer possible and the usual
Kosterlitz-Thouless transition no longer exists, there are remnants of it. As
an application, we calculate the curves for Andreev reflexion when a
normal metal is placed in contact with the chain. Formally, there is always an
offset voltage below which no current can flow, however, in some regimes
can be negligible. Contrary to what happens without long-range
interactions, the Andreev current, as a function of applied voltage, increases
faster than any power law. Signatures of long range interactions and phase
slips appear in the curves. Possible application for quasi
one-dimensional thin superconducting wires is outlined.Comment: 22 pages, 6 figures, accepted in Phys. Rev. B (2011
Numerical study of a non-equilibrium interface model
We have carried out extensive computer simulations of one-dimensional models
related to the low noise (solid-on-solid) non-equilibrium interface of a two
dimensional anchored Toom model with unbiased and biased noise. For the
unbiased case the computed fluctuations of the interface in this limit provide
new numerical evidence for the logarithmic correction to the subnormal L^(1/2)
variance which was predicted by the dynamic renormalization group calculations
on the modified Edwards-Wilkinson equation. In the biased case the simulations
are in close quantitative agreement with the predictions of the Collective
Variable Approximation (CVA), which gives the same L^(2/3) behavior of the
variance as the KPZ equation.Comment: 15 pages revtex, 4 Postscript Figure
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