12,320 research outputs found
Disordered graphene Josephson junctions
A tight-binding approach based on the Chebyshev-Bogoliubov-de Gennes method
is used to describe disordered single-layer graphene Josephson junctions.
Scattering by vacancies, ripples or charged impurities is included. We compute
the Josephson current and investigate the nature of multiple Andreev
reflections, which induce bound states appearing as peaks in the density of
states for energies below the superconducting gap. In the presence of single
atom vacancies, we observe a strong suppression of the supercurrent that is a
consequence of strong inter-valley scattering. Although lattice deformations
should not induce inter-valley scattering, we find that the supercurrent is
still suppressed, which is due to the presence of pseudo-magnetic barriers. For
charged impurities, we consider two cases depending on whether the average
doping is zero, i.e. existence of electron-hole puddles, or finite. In both
cases, short range impurities strongly affect the supercurrent, similar to the
vacancies scenario
True airspeed measured by airborne laser Doppler velocimeter
Velocimeter utilizing carbon dioxide laser measures true airspeed of aircraft. Results of flight tests indicate that clear-weather airspeeds can be measured with accuracy better than 0.1% at altitudes up to 3000 meters; measurements can be made at much greater altitudes in cloudy or turbid air
Tight-binding description of intrinsic superconducting correlations in multilayer graphene
Using highly efficient GPU-based simulations of the tight-binding
Bogoliubov-de Gennes equations we solve self-consistently for the pair
correlation in rhombohedral (ABC) and Bernal (ABA) multilayer graphene by
considering a finite intrinsic s-wave pairing potential. We find that the two
different stacking configurations have opposite bulk/surface behavior for the
order parameter. Surface superconductivity is robust for ABC stacked multilayer
graphene even at very low pairing potentials for which the bulk order parameter
vanishes, in agreement with a recent analytical approach. In contrast, for
Bernal stacked multilayer graphene, we find that the order parameter is always
suppressed at the surface and that there exists a critical value for the
pairing potential below which no superconducting order is achieved. We
considered different doping scenarios and find that homogeneous doping strongly
suppresses surface superconductivity while non-homogeneous field-induced doping
has a much weaker effect on the superconducting order parameter. For multilayer
structures with hybrid stacking (ABC and ABA) we find that when the thickness
of each region is small (few layers), high-temperature surface
superconductivity survives throughout the bulk due to the proximity effect
between ABC/ABA interfaces where the order parameter is enhanced.Comment: 7 page
Demodulation system Patent
Development of demodulation system for removing amplitude modulation from two quadrature displaced data bearing signal
Calculable inverse-seesaw neutrino masses in supersymmetry
We provide a scenario where naturally small and calculable neutrino masses
arise from a supersymmetry breaking renormalization-group-induced vacuum
expectation value. We adopt a minimal supergravity scenario without ad hoc
supersymmetric mass parameters. The lightest supersymmetric particle can be an
isosinglet scalar neutrino state, potentially viable as WIMP dark matter
through its Higgs new boson coupling. The scenario leads to a plethora of new
phenomenological implications at accelerators including the Large Hadron
Collider.Comment: LaTeX, 5 pages, 4 figures. Comments and references added. Final
version to appear in PR
Theoretical analysis for critical fluctuations of relaxation trajectory near a saddle-node bifurcation
A Langevin equation whose deterministic part undergoes a saddle-node
bifurcation is investigated theoretically. It is found that statistical
properties of relaxation trajectories in this system exhibit divergent
behaviors near a saddle-node bifurcation point in the weak-noise limit, while
the final value of the deterministic solution changes discontinuously at the
point. A systematic formulation for analyzing a path probability measure is
constructed on the basis of a singular perturbation method. In this
formulation, the critical nature turns out to originate from the neutrality of
exiting time from a saddle-point. The theoretical calculation explains results
of numerical simulations.Comment: 18pages, 17figures.The version 2, in which minor errors have been
fixed, will be published in Phys. Rev.
Microarray and EST database estimates of mRNA expression levels differ: The protein length versus expression curve for C. elegans
BACKGROUND: Various methods for estimating protein expression levels are known. The level of correlation between these methods is only fair, and systematic biases in each of the methods cannot be ruled out. We here investigate systematic biases in the estimation of gene expression rates from microarray data and from abundance within the Expressed Sequence Tag (EST) database. We suggest that length is a significant factor in biases to measured gene expression rates. As a specific example of the importance of the bias of expression rate with length, we address the following evolutionary question: Does the average C. elegans protein length increase or decrease with expression level? Two different answers to this question have been reported in the literature, one method using expression levels estimated by abundance within the EST database and another using microarrays. We have investigated this issue by constructing the full protein length versus expression curve for C. elegans, using both methods for estimating expression levels. RESULTS: The microarray data show a monotonic decrease of length with expression level, whereas the abundance within the EST database data show a non-monotonic behavior. Furthermore, the ratio of the expression level estimated by the EST database to that measured by microarrays is not constant, but rather systematically biased with gene length. CONCLUSIONS: It is suggested that the length bias may lie primarily in the abundance within the EST database method, being not ameliorated by internal standards as it is in the microarray data, and that this bias should be removed before data interpretation. When this is done, both the microarray and the abundance within the EST database give a monotonic decrease of spliced length with expression level, and the correlation between the EST and microarray data becomes larger. We suggest that standard RNA controls be used to normalize for length bias in any method that measures expression
Scattering matrices and expansion coefficients of Martian analogue palagonite particles
We present measurements of ratios of elements of the scattering matrix of
Martian analogue palagonite particles for scattering angles ranging from 3 to
174 degrees and a wavelength of 632.8 nm. To facilitate the use of these
measurements in radiative transfer calculations we have devised a method that
enables us to obtain, from these measurements, a normalized synthetic
scattering matrix covering the complete scattering angle range from 0 to 180
degrees. Our method is based on employing the coefficients of the expansions of
scattering matrix elements into generalized spherical functions. The synthetic
scattering matrix elements and/or the expansion coefficients obtained in this
way, can be used to include multiple scattering by these irregularly shaped
particles in (polarized) radiative transfer calculations, such as calculations
of sunlight that is scattered in the dusty Martian atmosphere.Comment: 34 pages 7 figures 1 tabl
Short-time dynamics of finite-size mean-field systems
We study the short-time dynamics of a mean-field model with non-conserved
order parameter (Curie-Weiss with Glauber dynamics) by solving the associated
Fokker-Planck equation. We obtain closed-form expressions for the first moments
of the order parameter, near to both the critical and spinodal points, starting
from different initial conditions. This allows us to confirm the validity of
the short-time dynamical scaling hypothesis in both cases. Although the
procedure is illustrated for a particular mean-field model, our results can be
straightforwardly extended to generic models with a single order parameter.Comment: accepted for publication in JSTA
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