7,290 research outputs found
Accelerated Calvarial Healing in Mice Lacking Toll-Like Receptor 4
The bone and immune systems are closely interconnected. The immediate inflammatory response after fracture is known to trigger a healing cascade which plays an important role in bone repair. Toll-like receptor 4 (TLR4) is a member of a highly conserved receptor family and is a critical activator of the innate immune response after tissue injury. TLR4 signaling has been shown to regulate the systemic inflammatory response induced by exposed bone components during long-bone fracture. Here we tested the hypothesis that TLR4 activation affects the healing of calvarial defects. A 1.8 mm diameter calvarial defect was created in wild-type (WT) and TLR4 knockout (TLR4-/-) mice. Bone healing was tested using radiographic, histologic and gene expression analyses. Radiographic and histomorphometric analyses revealed that calvarial healing was accelerated in TLR4-/- mice. More bone was observed in TLR4-/- mice compared to WT mice at postoperative days 7 and 14, although comparable healing was achieved in both groups by day 21. Bone remodeling was detected in both groups on postoperative day 28. In TLR4-/- mice compared to WT mice, gene expression analysis revealed that higher expression levels of IL-1β, IL-6, TNF-α,TGF-β1, TGF-β3, PDGF and RANKL and lower expression level of RANK were detected at earlier time points (≤ postoperative 4 days); while higher expression levels of IL-1β and lower expression levels of VEGF, RANK, RANKL and OPG were detected at late time points (> postoperative 4 days). This study provides evidence of accelerated bone healing in TLR4-/- mice with earlier and higher expression of inflammatory cytokines and with increased osteoclastic activity. Further work is required to determine if this is due to inflammation driven by TLR4 activation. © 2012 Wang et al
Predictions of the causal entropic principle for environmental conditions of the universe
The causal entropic principle has been proposed as a superior alternative to
the anthropic principle for understanding the magnitude of the cosmological
constant. In this approach, the probability to create observers is assumed to
be proportional to the entropy production \Delta S in a maximal causally
connected region -- the causal diamond. We improve on the original treatment by
better quantifying the entropy production due to stars, using an analytic model
for the star formation history which accurately accounts for changes in
cosmological parameters. We calculate the dependence of \Delta S on the density
contrast Q=\delta\rho/\rho, and find that our universe is much closer to the
most probable value of Q than in the usual anthropic approach and that
probabilities are relatively weakly dependent on this amplitude. In addition,
we make first estimates of the dependence of \Delta S on the baryon fraction
and overall matter abundance. Finally, we also explore the possibility that
decays of dark matter, suggested by various observed gamma ray excesses, might
produce a comparable amount of entropy to stars.Comment: RevTeX4, 13pp, 10 figures; v2. clarified introduction, added ref
Kinematic Masses of Super Star Clusters in M82 from High-Resolution Near-Infrared Spectroscopy
Using high-resolution (R~22,000) near-infrared (1.51 -- 1.75 microns) spectra
from Keck Observatory, we measure the kinematic masses of two super star
clusters in M82. Cross-correlation of the spectra with template spectra of cool
evolved stars gives stellar velocity dispersions of sigma_r=15.9 +/- 0.8 km/s
for MGG-9 and sigma_r=11.4 +/- 0.8 km/s for MGG-11. The cluster spectra are
dominated by the light of red supergiants, and correlate most closely with
template supergiants of spectral types M0 and M4.5. We fit King models to the
observed profiles of the clusters in archival HST/NICMOS images to measure the
half-light radii. Applying the virial theorem, we determine masses of 1.5 +/-
0.3 x 10^6 M_sun for MGG-9 and 3.5 +/- 0.7 x 10^5 M_sun for MGG-11. Population
synthesis modelling suggests that MGG-9 is consistent with a standard initial
mass function, whereas MGG-11 appears to be deficient in low-mass stars
relative to a standard IMF. There is, however, evidence of mass segregation in
the clusters, in which case the virial mass estimates would represent lower
limits.Comment: 16 pages, 8 figures; ApJ, in pres
Hot Stars and Cool Clouds: The Photodissociation Region M16
We present high-resolution spectroscopy and images of a photodissociation
region (PDR) in M16 obtained during commissioning of NIRSPEC on the Keck II
telescope. PDRs play a significant role in regulating star formation, and M16
offers the opportunity to examine the physical processes of a PDR in detail. We
simultaneously observe both the molecular and ionized phases of the PDR and
resolve the spatial and kinematic differences between them. The most prominent
regions of the PDR are viewed edge-on. Fluorescent emission from nearby stars
is the primary excitation source, although collisions also preferentially
populate the lowest vibrational levels of H2. Variations in density-sensitive
emission line ratios demonstrate that the molecular cloud is clumpy, with an
average density n = 3x10^5 cm^(-3). We measure the kinetic temperature of the
molecular region directly and find T_H2 = 930 K. The observed density,
temperature, and UV flux imply a photoelectric heating efficiency of 4%. In the
ionized region, n_i=5x10^3 cm^(-3) and T_HII = 9500 K. In the brightest regions
of the PDR, the recombination line widths include a non-thermal component,
which we attribute to viewing geometry.Comment: 5 pages including 2 Postscript figures. To appear in ApJ Letters,
April 200
South Dakota Range and Pasture Judging Handbook
This publication provides information on range and pasture judging schools and contest guidelines. It describes the kinds and condition of rangeland, degree of use, possible treatments, and provides a master range plant list. Pasture land factors and recommended treatments are also included
A silent speech system based on permanent magnet articulography and direct synthesis
In this paper we present a silent speech interface (SSI) system aimed at restoring speech communication for individuals who have lost their voice due to laryngectomy or diseases affecting the vocal folds. In the proposed system, articulatory data captured from the lips and tongue using permanent magnet articulography (PMA) are converted into audible speech using a speaker-dependent transformation learned from simultaneous recordings of PMA and audio signals acquired before laryngectomy. The transformation is represented using a mixture of factor analysers, which is a generative model that allows us to efficiently model non-linear behaviour and perform dimensionality reduction at the same time. The learned transformation is then deployed during normal usage of the SSI to restore the acoustic speech signal associated with the captured PMA data. The proposed system is evaluated using objective quality measures and listening tests on two databases containing PMA and audio recordings for normal speakers. Results show that it is possible to reconstruct speech from articulator movements captured by an unobtrusive technique without an intermediate recognition step. The SSI is capable of producing speech of sufficient intelligibility and naturalness that the speaker is clearly identifiable, but problems remain in scaling up the process to function consistently for phonetically rich vocabularies
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