5,220 research outputs found
Flow equations in generalized braneworld scenarios
We discuss the flow equations in the context of general braneworld
cosmologies with a modified Friedmann equation, for either an ordinary scalar
field or a Dirac-Born-Infeld tachyon as inflaton candidates. The 4D,
Randall-Sundrum, and Gauss-Bonnet cases are compared, using the patch formalism
which provides a unified description of these models. The inflationary dynamics
is described by a tower of flow parameters that can be evolved in time to
select a particular subset of points in the space of cosmological observables.
We analyze the stability of the fixed points in all the cosmologies (our
results in the 4D case already extending those in the literature). Numerical
integration of the flow equations shows that the predictions of the
Gauss-Bonnet braneworld differ significantly as compared to the Randall-Sundrum
and 4D scenarios, whereas tachyon inflation gives tensor perturbations smaller
than those in the presence of a normal scalar field. These results are extended
to the realization of a noncommutative space-time preserving maximal symmetry.
In this case the tensor-to-scalar signal is unchanged, while blue-tilted
spectra are favoured.Comment: 10 pages RevTeX4 with 3 figures included. Matches published version.
Note change of title from original submissio
R^2 Corrections for 5D Black Holes and Rings
We study higher-order corrections to two BPS solutions of 5D supergravity,
namely the supersymmetric black ring and the spinning black hole. Due in part
to our current relatively limited understanding of F-type terms in 5D
supergravity, the nature of these corrections is less clear than that of their
4D cousins. Effects of certain terms found in Calabi-Yau compactification
of M-theory are specifically considered. For the case of the black ring, for
which the microscopic origin of the entropy is generally known, the
corresponding higher order macroscopic correction to the entropy is found to
match a microscopic correction, while for the spinning black hole the
corrections are partially matched to those of a 4D black hole.Comment: 9 page
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IL-17A produced by αβ T cells drives airway hyper-responsiveness in mice and enhances mouse and human airway smooth muscle contraction.
Emerging evidence suggests that the T helper 17 (T(H)17) subset of αβ T cells contributes to the development of allergic asthma. In this study, we found that mice lacking the αvβ8 integrin on dendritic cells did not generate T(H)17 cells in the lung and were protected from airway hyper-responsiveness in response to house dust mite and ovalbumin sensitization and challenge. Because loss of T(H)17 cells inhibited airway narrowing without any obvious effects on airway inflammation or epithelial morphology, we examined the direct effects of T(H)17 cytokines on mouse and human airway smooth muscle function. Interleukin-17A (IL-17A), but not IL-17F or IL-22, enhanced contractile force generation of airway smooth muscle through an IL-17 receptor A (IL-17RA)-IL-17RC, nuclear factor κ light-chain enhancer of activated B cells (NF-κB)-ras homolog gene family, member A (RhoA)-Rho-associated coiled-coil containing protein kinase 2 (ROCK2) signaling cascade. Mice lacking integrin αvβ8 on dendritic cells showed impaired activation of this pathway after ovalbumin sensitization and challenge, and the diminished contraction of the tracheal rings in these mice was reversed by IL-17A. These data indicate that the IL-17A produced by T(H)17 cells contributes to allergen-induced airway hyper-responsiveness through direct effects on airway smooth muscle
Chronic exposure to neonicotinoids increases neuronal vulnerability to mitochondrial dysfunction in the bumblebee (Bombus terrestris)
This work was funded jointly by the Biotechnology and Biological Sciences Research Council, the Department for Environment, Food and Rural Affairs, the Natural Environment Research Council, the Scottish Government, and The Wellcome Trust, under the Insect Pollinators Initiative (United Kingdom) Grant BB/ 1000313/1 (to C.N.C.).The global decline in the abundance and diversity of insect pollinators could result from habitat loss, disease, and pesticide exposure. The contribution of the neonicotinoid insecticides (e.g., clothianidin and imidacloprid) to this decline is controversial, and key to understanding their risk is whether the astonishingly low levels found in the nectar and pollen of plants is sufficient to deliver neuroactive levels to their site of action: the bee brain. Here we show that bumblebees (Bombusterrestris audax) fed field levels [10 nM, 2.1 ppb (w/w)] of neonicotinoid accumulate between 4 and 10 nM in their brains within 3 days. Acute (minutes) exposure of cultured neurons to 10 nM clothianidin, but not imidacloprid, causes a nicotinic acetylcholine receptor-dependent rapid mitochondrial depolarization. However, a chronic (2 days) exposure to 1 nM imidacloprid leads to a receptor-dependent increased sensitivity to a normally innocuous level of acetylcholine, which now also causes rapid mitochondrial depolarization in neurons. Finally, colonies exposed to this level of imidacloprid show deficits in colony growth and nest condition compared with untreated colonies. These findings provide a mechanistic explanation for the poor navigation and foraging observed in neonicotinoid treated bumblebee colonies.Publisher PDFPeer reviewe
STM studies of epitaxial graphene
This article reviews the use of scanning tunneling microscopy (STM) and scanning tunneling spectroscopy (STS) to characterize the physical and electronic properties of epitaxial graphene. Topographical variations revealed by STM allow the determination of the number of graphene layers and the detection of lattice mismatch between the graphene and the substrate, as well as rotational disorder. STS allows the local electronic characterization of graphene. STM/STS can also be used to perform local studies of graphene modification through processes such as atomic/molecular adsorption and intercalation
Percutaneous endoscopic gastrostomy site metastasis from head and neck squamous cell carcinoma: case series and literature review
Objectives To present our experience with head and neck squamous cell carcinoma (HNSCC) seeding of percutaneous endoscopic gastrostomy (PEG) sites and to review all reported cases to identify risk factors and develop strategies for complication avoidance.
Materials and methods The records of 4 patients with PEG site metastasis from HNSCC were identified from the authors’ institution. Thirty-eight further cases were reviewed following a PubMed search and evaluation of references in pertinent articles.
Results Review of 42 cases revealed the average time from PEG to diagnosis of metastatic disease to be 8 months. Average time to death from detection of PEG disease was 5.9 months. One-year survival following PEG metastasis was 35.5% with an overall mortality of 87.1%.
Conclusion PEG site metastatic disease portends a poor prognosis. Early detection and aggressive therapy may provide a chance of cure. Changes in PEG technique or in timing of adjunctive therapies are possible avenues in further research to prevent this complication
Molecular Communication for Quorum Sensing Inspired Cooperative Drug Delivery
A cooperative drug delivery system is proposed, where quorum sensing (QS), a
density-dependent bacterial behavior coordination mechanism, is employed by
synthetic bacterium-based nanomachines (B-NMs) for controllable drug delivery.
In our proposed system, drug delivery is only triggered when there are enough
QS molecules, which in turn only happens when there are enough B-NMs. This
makes the proposed system can be used to achieve a high release rate of drug
molecules from a high number of B-NMs when the population density of B-NMs may
not be known. Analytical expressions for i) the expected activation probability
of the B-NM due to randomly-distributed B-NMs and ii) the expected aggregate
absorption rate of drug molecules due to randomly-distributed QS activated
B-NMs are derived. Analytical results are verified by particle-based
simulations. The derived results can help to predict and control the impact of
environmental factors (e.g. diffusion coefficient and degradation rate) on the
absorption rate of drug molecules since rigorous diffusion-based molecular
channels are considered. Our results show that the activation probability at
the B-NM increases as this B-NM is located closer to the center of the B-NM
population and the aggregate absorption rate of the drug molecules non-linearly
increases as the population density increases.Comment: 9 pages; 9 figure
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