83,827 research outputs found
Cooperative Secure Transmission by Exploiting Social Ties in Random Networks
Social awareness and social ties are becoming increasingly popular with
emerging mobile and handheld devices. Social trust degree describing the
strength of the social ties has drawn lots of research interests in many fields
in wireless communications, such as resource sharing, cooperative communication
and so on. In this paper, we propose a hybrid cooperative beamforming and
jamming scheme to secure communication based on the social trust degree under a
stochastic geometry framework. The friendly nodes are categorized into relays
and jammers according to their locations and social trust degrees with the
source node. We aim to analyze the involved connection outage probability (COP)
and secrecy outage probability (SOP) of the performance in the networks. To
achieve this target, we propose a double Gamma ratio (DGR) approach through
Gamma approximation. Based on this, the COP and SOP are tractably obtained in
closed-form. We further consider the SOP in the presence of Poisson Point
Process (PPP) distributed eavesdroppers and derive an upper bound. The
simulation results verify our theoretical findings, and validate that the
social trust degree has dramatic influences on the security performance in the
networks.Comment: 30 pages, 11 figures, to be published in IEEE Transactions on
Communication
Thermodynamics of pairing in mesoscopic systems
Using numerical and analytical methods implemented for different models we
conduct a systematic study of thermodynamic properties of pairing correlation
in mesoscopic nuclear systems. Various quantities are calculated and analyzed
using the exact solution of pairing. An in-depth comparison of canonical, grand
canonical, and microcanonical ensemble is conducted. The nature of the pairing
phase transition in a small system is of a particular interest. We discuss the
onset of discontinuity in the thermodynamic variables, fluctuations, and
evolution of zeros of the canonical and grand canonical partition functions in
the complex plane. The behavior of the Invariant Correlational Entropy is also
studied in the transitional region of interest. The change in the character of
the phase transition due to the presence of magnetic field is discussed along
with studies of superconducting thermodynamics.Comment: 19 pages, 24 figure
Heterogeneous responses of dorsal root ganglion neurons in neuropathies induced by peripheral nerve trauma and the antiretroviral drug stavudine
© 2014 The Authors. European Journal of Pain published by John Wiley & Sons Ltd on behalf of European Pain Federation - EFIC®. Funding sources E.K.B. was funded by a BBSRC PhD studentship. A.N., A.S.C.R. and T.P. were funded by a Wellcome Trust Strategic Award (London Pain Consortium; ref. 083259). A.S.C.R. and W.H. were funded by the Innovative Medicines Initiative Joint Undertaking (Europain; grant agreement no. 115007). We thank Pfizer for providing stavudine. Conflicts of interest None declared. Funded by BBSRC PhD studentship Wellcome Trust Strategic Award. Grant Number: 083259 Innovative Medicines Initiative Joint Undertaking. Grant Number: 115007Peer reviewedPublisher PD
Formation of Quantum-Degenerate Sodium Molecules
Ultra-cold sodium molecules were produced from an atomic Bose-Einstein
condensate by ramping an applied magnetic field across a Feshbach resonance.
More than molecules were generated with a conversion efficiency of
4%. Using laser light resonant with an atomic transition, the remaining
atoms could be selectively removed, preventing fast collisional relaxation of
the molecules. Time-of-flight analysis of the pure molecular sample yielded an
instantaneous phase-space density greater than 20.Comment: 5 pages, 4 figures (final published version
Electrostatic tuning of magnetism at the conducting (111) (LaSr)(AlTa)/SrTiO interface
We present measurements of the low temperature electrical transport
properties of the two dimensional carrier gas that forms at the interface of
(LaSr)(AlTa)/SrTiO (LSAT/STO) as
a function of applied back gate voltage, . As is found in (111)
LaAlO/SrTiO interfaces, the low-field Hall coefficient is
electron-like, but shows a sharp reduction in magnitude below 20 V,
indicating the presence of hole-like carriers in the system. This same value of
correlates approximately with the gate voltage below which the
magnetoresistance evolves from nonhysteretic to hysteretic behavior at
millikelvin temperatures, signaling the onset of magnetic order in the system.
We believe our results can provide insight into the mechanism of magnetism in
SrTiO based systems.Comment: 5 pages, 3 figure
Heavy Ion Collisions and the Density Dependence of the Local Mean Field
We study the effect of the density dependence of the scalar and the vector
part of the nucleonic self-energy in Relativistic Quantum Molecular Dynamics
(RQMD) on observables like the transversal flow and the rapidity distribution.
The stability of nuclei in RQMD is greatly improved if the density dependence
is included in the self-energies compared to a calculation assuming always
saturation density of nuclear matter. Different approaches are studied: The
main results are calculated with self-energies extracted from a
Dirac-Br\"uckner-Hartree-Fock G-matrix of a one boson exchange model, i.e. the
Bonn potential. These results are compared with those obtained by a
generalization of static Skyrme force, with calculations in the simple linear
Walecka model and results of the Br\"uckner-Hartree-Fock G-matrix of the Reid
soft core potential. The transversal flow is very sensitive to these different
approaches. A comparison with the data is given.Comment: LaTex-file, 13 pages, 5 figures (available upon request), submitted
to Nuclear Physics
Cancellation of Infrared Divergences in Hadronic Annihilation Decays of Heavy Quarkonia
In the framework of a newly developed factorization formalism which is based
on NRQCD, explicit cancellations are shown for the infrared divergences that
appeared in the previously calculated hadronic annihilation decay rates of
P-wave and D-wave heavy quarkonia. We extend them to a more general case that
to leading order in and next-to-leading order in , the infrared
divergences in the annihilation amplitudes of color-singlet
pair can be removed by including the contributions of
color-octet operators ,
, ... in NRQCD. We also give the decay widths of
at leading order in .Comment: 8 pages, LaTex(3 figures included), to be publishe
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