16,786 research outputs found
Natural regulatory (CD4+CD25+FOXP+) T cells control the production of pro-inflammatory cytokines during Plasmodium chabaudi adami infection and do not contribute to immune evasion.
Different functions have been attributed to natural regulatory CD4+CD25+FOXP+ (Treg) cells during malaria infection. Herein, we assessed the role for Treg cells during infections with lethal (DS) and non-lethal (DK) Plasmodium chabaudi adami parasites, comparing the levels of parasitemia, inflammation and anaemia. Independent of parasite virulence, the population of splenic Treg cells expanded during infection, and the absolute numbers of activated CD69+ Treg cells were higher in DS-infected mice. In vivo depletion of CD25+ T cells, which eliminated 80% of CD4+FOXP3+CD25+ T cells and 60–70% of CD4+FOXP3+ T cells, significantly decreased the number of CD69+ Treg cells in mice with lethal malaria. As a result, higher parasite burden and morbidity were measured in the latter, whereas the kinetics of infection with non-lethal parasites remained unaffected. In the absence of Treg cells, parasite-specific IFN-γ responses by CD4+ T cells increased significantly, both in mice with lethal and non-lethal infections, whereas IL-2 production was only stimulated in mice with non-lethal malaria. Following the depletion of CD25+ T cells, the production of IL-10 by CD90− cells was also enhanced in infected mice. Interestingly, a potent induction of TNF- and IFN-γ production by CD4+ and CD90− lymphocytes was measured in DS-infected mice, which also suffered severe anaemia earlier than non-depleted infected controls. Taken together, our data suggest that the expansion and activation of natural Treg cells represent a counter-regulatory response to the overwhelming inflammation associated with lethal P.c. adami. This response to infection involves TH1 lymphocytes as well as cells from the innate immune system
Particle Production of Vector Fields: Scale Invariance is Attractive
In a model of an Abelian vector boson with a Maxwell kinetic term and non-negative mass-squared it is demonstrated that, under fairly general conditions during inflation, a scale-invariant spectrum of perturbations for the components of a vector field, massive or not, whose kinetic function (and mass) is modulated by the inflaton field is an attractor solution. If the field is massless, or if it remains light until the end of inflation, this attractor solution also generates anisotropic stress, which can render inflation weakly anisotropic. The above two characteristics of the attractor solution can source (independently or combined together) significant statistical anisotropy in the curvature perturbation, which may well be observable in the near future
Collide and Conquer: Constraints on Simplified Dark Matter Models using Mono-X Collider Searches
The use of simplified models as a tool for interpreting dark matter collider
searches has become increasingly prevalent, and while early Run II results are
beginning to appear, we look to see what further information can be extracted
from the Run I dataset. We consider three `standard' simplified models that
couple quarks to fermionic singlet dark matter: an -channel vector mediator
with vector or axial-vector couplings, and a -channel scalar mediator. Upper
limits on the couplings are calculated and compared across three alternate
channels, namely mono-jet, mono- (leptonic) and mono- (hadronic). The
strongest limits are observed in the mono-jet channel, however the
computational simplicity and absence of significant -channel model width
effects in the mono-boson channels make these a straightforward and competitive
alternative. We also include a comparison with relic density and direct
detection constraints.Comment: 32 pages, 8 figures; v2: minor changes, conclusion unchanged, matches
published versio
Finite-time Singularities in Surface-Diffusion Instabilities are Cured by Plasticity
A free material surface which supports surface diffusion becomes unstable
when put under external non-hydrostatic stress. Since the chemical potential on
a stressed surface is larger inside an indentation, small shape fluctuations
develop because material preferentially diffuses out of indentations. When the
bulk of the material is purely elastic one expects this instability to run into
a finite-time cusp singularity. It is shown here that this singularity is cured
by plastic effects in the material, turning the singular solution to a regular
crack.Comment: 4 pages, 3 figure
Avoiding power broadening in optically detected magnetic resonance of single NV defects for enhanced DC-magnetic field sensitivity
We report a systematic study of the magnetic field sensitivity of a magnetic
sensor based on a single Nitrogen-Vacancy (NV) defect in diamond, by using
continuous optically detected electron spin resonance (ESR) spectroscopy. We
first investigate the behavior of the ESR contrast and linewidth as a function
of the microwave and optical pumping power. The experimental results are in
good agreement with a simplified model of the NV defect spin dynamics, yielding
to an optimized sensitivity around 2 \mu T/\sqrt{\rm Hz}. We then demonstrate
an enhancement of the magnetic sensitivity by one order of magnitude by using a
simple pulsed-ESR scheme. This technique is based on repetitive excitation of
the NV defect with a resonant microwave \pi-pulse followed by an optimized
read-out laser pulse, allowing to fully eliminate power broadening of the ESR
linewidth. The achieved sensitivity is similar to the one obtained by using
Ramsey-type sequences, which is the optimal magnetic field sensitivity for the
detection of DC magnetic fields
Ripples in Tapped or Blown Powder
We observe ripples forming on the surface of a granular powder in a container
submitted from below to a series of brief and distinct shocks. After a few
taps, the pattern turns out to be stable against any further shock of the same
amplitude. We find experimentally that the characteristic wavelength of the
pattern is proportional to the amplitude of the shocks. Starting from
consideration involving Darcy's law for air flow through the porous granulate
and avalanche properties, we build up a semi-quantitative model which fits
satisfactorily the set of experimental observations as well as a couple of
additional experiments.Comment: 7 pages, four postscript figures, submitted PRL 11/19/9
High resolution spectroscopy of single NV defects coupled with nearby C nuclear spins in diamond
We report a systematic study of the hyperfine interaction between the
electron spin of a single nitrogen-vacancy (NV) defect in diamond and nearby
C nuclear spins, by using pulsed electron spin resonance spectroscopy.
We isolate a set of discrete values of the hyperfine coupling strength ranging
from 14 MHz to 400 kHz and corresponding to C nuclear spins placed at
different lattice sites of the diamond matrix. For each lattice site, the
hyperfine interaction is further investigated through nuclear spin polarization
measurements and by studying the magnetic field dependence of the hyperfine
splitting. This work provides informations that are relevant for the
development of nuclear-spin based quantum register in diamond.Comment: 8 pages, 5 figure
Effects of cluster diffusion on the island density and size distribution in submonolayer island growth
The effects of cluster diffusion on the submonolayer island density and
island-size distribution are studied for the case of irreversible growth of
compact islands on a 2D substrate. In our model, we assume instantaneous
coalescence of circular islands, while the cluster mobility is assumed to
exhibit power-law decay as a function of island-size with exponent mu. Results
are presented for mu = 1/2, 1, and 3/2 corresponding to cluster diffusion via
Brownian motion, correlated evaporation-condensation, and edge-diffusion
respectively, as well as for higher values including mu = 2,3, and 6. We also
compare our results with those obtained in the limit of no cluster mobility
corresponding to mu = infinity. In agreement with theoretical predictions of
power-law behavior of the island-size distribution (ISD) for mu < 1, for mu =
1/2 we find Ns({\theta}) ~ s^{-\tau} (where Ns({\theta}) is the number of
islands of size s at coverage {\theta}) up to a cross-over island-size S_c.
However, the value of {\tau} obtained in our simulations is higher than the
mean-field (MF) prediction {\tau} = (3 - mu)/2. Similarly, the value of the
exponent {\zeta} corresponding to the dependence of S_c on the average
island-size S (e.g. S_c ~ S^{\zeta}) is also significantly higher than the MF
prediction {\zeta} = 2/(mu+1). A generalized scaling form for the ISD is also
proposed for mu < 1, and using this form excellent scaling is found for mu =
1/2. However, for finite mu >= 1 neither the generalized scaling form nor the
standard scaling form Ns({\theta}) = {\theta} /S^2 f(s/S) lead to scaling of
the entire ISD for finite values of the ratio R of the monomer diffusion rate
to deposition flux. Instead, the scaled ISD becomes more sharply peaked with
increasing R and coverage. This is in contrast to models of epitaxial growth
with limited cluster mobility for which good scaling occurs over a wide range
of coverages.Comment: 12 pages, submitted to Physical Review
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Schwannomatosis of the Spinal Accessory Nerve: A Case Report.
Schwannomatosis is a distinct syndrome characterized by multiple peripheral nerve schwannomas that can be sporadic or familial in nature. Cases affecting the lower cranial nerves are infrequent. Here, the authors present a rare case of schwannomatosis affecting the left spinal accessory nerve. Upon genetic screening, an in-frame insertion at codon p.R177 of the Sox 10 gene was observed. There were no identifiable alterations in NF1, NF2, LZTR1, and SMARCB1. This case demonstrates a rare clinical presentation of schwannomatosis in addition to a genetic aberration that has not been previously reported in this disease context
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