31,036 research outputs found
A Toll for lupus
Toll-like receptor (TLR)-9 recognizes CpG motifs in microbial DNA. TLR9 signalling stimulates innate antimicrobial immunity and modulates adaptive immune responses including autoimmunity against chromatin, e.g., in systemic lupus erythematosus (SLE). This review summarizes the available data for a role of TLR9 signalling in lupus and discusses the following questions that arise from these observations: 1) Is CpG-DNA/TLR9 interaction involved in infection-induced disease activity of lupus? 2) What are the risks of CpG motifs in vaccine adjuvants for lupus patients? 3) Is TLR9 signalling involved in the pathogenesis of lupus by recognizing self DNA
Airfoil large eddy breakup devices for turbulent drag reduction
It was determined from the present LaRC experiments that tandem, airfoil-shaped large eddy breakup (LEBU) devices can reduce local skin friction as much as 30 percent with a recovery region extending more than 100 boundary layer thicknesses downstream. These airfoils experience near laminar skin friction device drag and produce net drag reductions of up to 7 percent. In contrast to the thin plates used in previous experiments, these airfoils are more than 1000 time stiffer and hence have the potential to withstand the real flight environment (dynamic pressure 36 times larger than in low-speed wing tunnels). In addition, the higher Reynolds numbers of the present tests indicate drag reduction performance is at least as good (or better) as at lower Reynolds numbers
Thermal energies of classical and quantum damped oscillators coupled to reservoirs
We consider the global thermal state of classical and quantum harmonic
oscillators that interact with a reservoir. Ohmic damping of the oscillator can
be exactly treated with a 1D scalar field reservoir, whereas general non-Ohmic
damping is conveniently treated with a continuum reservoir of harmonic
oscillators. Using the diagonalized Hamiltonian of the total system, we
calculate a number of thermodynamic quantities for the damped oscillator: the
mean force internal energy, mean force free energy, and another internal energy
based on the free-oscillator Hamiltonian. The classical mean force energy is
equal to that of a free oscillator, for both Ohmic and non-Ohmic damping and no
matter how strong the coupling to the reservoir. In contrast, the quantum mean
force energy depends on the details of the damping and diverges for strictly
Ohmic damping. These results give additional insight into the steady-state
thermodynamics of open systems with arbitrarily strong coupling to a reservoir,
complementing results for energies derived within dynamical approaches (e.g.
master equations) in the weak-coupling regime.Comment: 13 page
On the quantum stability of Q-balls
We consider the evolution and decay of Q-balls under the influence of quantum
fluctuations. We argue that the most important effect resulting from these
fluctuations is the modification of the effective potential in which the Q-ball
evolves. This is in addition to spontaneous decay into elementary particle
excitations and fission into smaller Q-balls previously considered in the
literature, which -- like most tunnelling processes -- are likely to be
strongly suppressed. We illustrate the effect of quantum fluctuations in a
particular model potential, for which we implement the inhomogeneous
Hartree approximation to quantum dynamics and solve for the evolution of
Q-balls in 3+1 dimensions. We find that the stability range as a function of
(field space) angular velocity is modified significantly compared to
the classical case, so that small- Q-balls are less stable than in the
classical limit, and large- Q-balls are more stable. This can be
understood qualitatively in a simple way.Comment: JHEP format, 17+1 pages, 9 figures; v2: improvements to several
figures, text rewritten to improve legibility, conclusions unchanged,
published in JHE
A Link Loss Model for the On-body Propagation Channel for Binaural Hearing Aids
Binaural hearing aids communicate with each other through a wireless link for
synchronization. A propagation model is needed to estimate the ear-to-ear link
loss for such binaural hearing aids. The link loss is a critical parameter in a
link budget to decide the sensitivity of the transceiver. In this paper, we
have presented a model for the deterministic component of the ear-to-ear link
loss. The model takes into account the dominant paths having most of the power
of the creeping wave from the transceiver in one ear to the transceiver in
other ear and the effect of the protruding part of the outer ear called pinna.
Simulations are done to validate the model using in-the-ear (ITE) placement of
antennas at 2.45 GHz on two heterogeneous phantoms of different age-group and
body size. The model agrees with the simulations. The ear-to-ear link loss
between the antennas for the binaural hearing aids in the homogeneous SAM
phantom is compared with a heterogeneous phantom. It is found that the absence
of the pinna and the lossless shell in the SAM phantom underestimate the link
loss. This is verified by the measurements on a phantom where we have included
the pinnas fabricated by 3D-printing
An Analytical Link Loss Model for On-Body Propagation Around the Body Based on Elliptical Approximation of the Torso with Arms' Influence Included
An analytical model for estimating the link loss for the on-body wave
propagation around the torso is presented. The model is based on the
attenuation of the creeping waves over an elliptical approximation of the human
torso and includes the influence of the arms. The importance of including the
arms' effect for a proper estimation of the link loss is discussed. The model
is validated by the full-wave electromagnetic simulations on a numerical
phantom
N-body simulations of star clusters
Two aspects of our recent N-body studies of star clusters are presented: (1)
What impact does mass segregation and selective mass loss have on integrated
photometry? (2) How well compare results from N-body simulations using NBODY4
and STARLAB/KIRA?Comment: 2 pages, 1 figure with 4 panels (in colour, not well visible in
black-and-white; figures screwed in PDF version, ok in postscript; to see
further details get the paper source). Conference proceedings for IAUS246
'Dynamical Evolution of Dense Stellar Systems', ed. E. Vesperini (Chief
Editor), M. Giersz, A. Sills, Capri, Sept. 2007; v2: references correcte
Leggett-Garg inequalities for quantum fluctuating work
The Leggett-Garg inequalities serve to test whether or not quantum
correlations in time can be explained within a classical macrorealistic
framework. We apply this test to thermodynamics and derive a set of Leggett-
Garg inequalities for the statistics of fluctuating work done on a quantum
system unitarily driven in time. It is shown that these inequalities can be
violated in a driven two-level system, thereby demonstrating that there exists
no general macrorealistic description of quantum work. These violations are
shown to emerge within the standard Two-Projective-Measurement scheme as well
as for alternative definitions of fluctuating work that are based on weak
measurement. Our results elucidate the influences of temporal correlations on
work extraction in the quantum regime and highlight a key difference between
quantum and classical thermodynamics.Comment: v2, 1 figure, accepted version to appear in Entropy (Special Issue on
"Quantum Thermodynamics II"
Entropy production and time-asymmetry in the presence of strong interactions
It is known that the equilibrium properties of open classical systems that
are strongly coupled to a heat bath are described by a set of thermodynamic
potentials related to the system's Hamiltonian of mean force. By adapting this
framework to a more general class of non-equilibrium states, we show that the
equilibrium properties of the bath can be well-defined, even when the system is
arbitrarily far from equilibrium and correlated with the bath. These states,
which retain a notion of temperature, take the form of conditional equilibrium
distributions. For out-of-equilibrium processes we show that the average
entropy production quantifies the extent to which the system-bath state is
driven away from the conditional equilibrium distribution. In addition, we show
that the stochastic entropy production satisfies a generalised Crooks relation
and can be used to quantify time-asymmetry of correlated non-equilibrium
processes. These results naturally extend the familiar properties of entropy
production in weakly-coupled systems to the strong coupling regime.
Experimental measurements of the entropy production at strong coupling could be
pursued using optomechanics or trapped ion systems, which allow strong coupling
to be engineered.Comment: 8 pages, 1 figure, comments welcom
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