562 research outputs found
Duality symmetric massive type II theories in D=8 and D=6
We study compactification of massive type IIA supergravity in presence
of possible Ramond-Ramond (RR) background fluxes. The resulting theory in D=8
is shown to possess full T-duality symmetry similar to
the massless case. It is shown that elements of duality symmetry interpolate
between massive type IIA compactified on and ordinary type IIA
compactified on with RR 2-form flux. We also discuss relationship between
M-theory vacua and massive type IIA vacua. The D8-brane is found to correspond
to M-theory `pure gravity' solution which is a direct product of 7-dimensional
Minkowski space and a 4-dimensional instanton. We also construct D6-D8 bound
state which preserves 1/2 supersymmetries. We then discuss massive IIA
compactification on and point out that when all possible RR fluxes on
are turned on the six-dimensional theory appears to assume a nice SO(4,4)
invariant form.Comment: 19 pages, JHEP3, typos fixed, references added; v2: small correction
in eq.(5.3), published in JHE
Experimental adiabatic vortex ratchet effect in Nb films with asymmetric pinning trap
Nb films grown on top of an array of asymmetric pinning centers show a vortex ratchet effect. A net flow of vortices is induced when the vortex lattice is driven by fluctuating forces on an array of pinning centers without reflection symmetry. This effect occurs in the adiabatic regime and it could be mimiced only by reversible DC driven forces
Experimental vortex ratchet effect in nanostructured superconductors
Superconducting Nb thin films were grown on different arrays of triangle-shape metallic islands. The vortex lattice dynamics could be strongly modified by these asymmetric vortex traps. These asymmetric pinning potentials lead to a rectification effect on the vortex motion: Injecting an ac supercurrent on the sample yields a net dc vortex flow. This vortex ratchet ffect is adiabatic and reversible: The effect is frequency independent and the polarity of the dc voltage output could be tuned by the applied magnetic fields and the input ac currents
Induction of Nod2 in Myelomonocytic and Intestinal Epithelial Cells via Nuclear Factor-kB Activation
Nod2, a member of the Apaf1/Nod protein family, confers responsiveness to bacterial products and activates NF-kB, a ranscription factor that plays a central role in innate immunity. Recently, genetic variation in Nod2
has been associated with susceptibility to Crohnâs disease.
Here, we report that expression of Nod2 is induced upon differentiation of CD34+ hematopoietic progenitor cells into granulocyte or monocyte/macrophages. In peripheral
blood cells, the highest levels of Nod2 were
observed in CD14+ (monocytes), CD15+ (granulocytes), and CD40+/CD86+ (dendritic cells) cell populations. Notably, stimulation of myeloblastic and epithelial cells with bacterial lipopolysaccharide or TNF resulted in
up-regulation of Nod2. A search for consensus sites within the Nod2 promoter revealed a NF-kB binding element that was required for transcriptional activity in
response to TNF . Moreover, ectopic expression of p65 induced transactivation, whereas that of dominant-negative I B blocked the transcriptional activity of the
Nod2 promoter. Upon stimulation with TNF or lipopolysaccharide, both p50 and p65 subunits of NF-kB were bound to the Nod2 promoter. Thus, Nod2 expression is enhanced by proinflammatory cytokines and bacterial
components via NF-kB, a mechanism that may contribute to the amplification of the innate immune response and susceptibility to inflammatory disease
Bimodal Nd-doped luVo4 nanoprobes functionalized with polyacrilic acid for x-ray computed tomography and NIR luminescent imaging
Uniform Nd3+-doped LuVO4 nanophosphors have been synthesized for the first time in literature by using a poliol-based method at 120 °C from Nd3+ and vanadate precursors. After optimizing the Nd doping level, these phosphors present intense luminescence in the near-infrared biological windows. The X-ray attenuation capacity of the optimum nanophosphor has been found to be higher than that of a commercial X-ray computed tomography contrast agent. After surface coating with polyacrylic acid, such nanoparticles present high colloidal stability in physiological pH medium and high cell viability. Because of these properties, the developed Nd3+-doped LuVO4 nanoparticles have potential applications as a bimodal probe for NIR luminescent bioimaging and X-ray computed tomography
Sulfur K-Edge XAS Studies of the Effect of DNA Binding on the [Fe_4S_4] Site in EndoIII and MutY
S K-edge X-ray absorption spectroscopy (XAS) was used to study the [Fe_4S_4] clusters in the DNA repair glycosylases EndoIII and MutY to evaluate the effects of DNA binding and solvation on FeâS bond covalencies (i.e., the amount of S 3p character mixed into the Fe 3d valence orbitals). Increased covalencies in both ironâthiolate and ironâsulfide bonds would stabilize the oxidized state of the [Fe_4S_4] clusters. The results are compared to those on previously studied [Fe_4S_4] model complexes, ferredoxin (Fd), and to new data on high-potential ironâsulfur protein (HiPIP). A limited decrease in covalency is observed upon removal of solvent water from EndoIII and MutY, opposite to the significant increase observed for Fd, where the [Fe_4S_4] cluster is solvent exposed. Importantly, in EndoIII and MutY, a large increase in covalency is observed upon DNA binding, which is due to the effect of its negative charge on the ironâsulfur bonds. In EndoIII, this change in covalency can be quantified and makes a significant contribution to the observed decrease in reduction potential found experimentally in DNA repair proteins, enabling their HiPIP-like redox behavior
Response to âComment on âTransverse rectification in superconducting thin films with arrays of asymmetric defectsââ [Appl. Phys. Lett. 92, 176101 (2008)]
© 2008 American Institute of PhysicsDepto. de FĂsica de MaterialesFac. de Ciencias FĂsicasTRUEpu
Anatomy of the AGN in NGC 5548: I. A global model for the broadband spectral energy distribution
An extensive multi-satellite campaign on NGC 5548 has revealed this
archetypal Seyfert-1 galaxy to be in an exceptional state of persistent heavy
absorption. Our observations taken in 2013-2014 with XMM-Newton, Swift, NuSTAR,
INTEGRAL, Chandra, HST and two ground-based observatories have together enabled
us to establish that this unexpected phenomenon is caused by an outflowing
stream of weakly ionised gas (called the obscurer), extending from the vicinity
of the accretion disk to the broad-line region. In this work we present the
details of our campaign and the data obtained by all the observatories. We
determine the spectral energy distribution of NGC 5548 from near-infrared to
hard X-rays by establishing the contribution of various emission and absorption
processes taking place along our line of sight towards the central engine. We
thus uncover the intrinsic emission and produce a broadband continuum model for
both obscured (average summer 2013 data) and unobscured ( 2011) epochs of
NGC 5548. Our results suggest that the intrinsic NIR/optical/UV continuum is a
single Comptonised component with its higher energy tail creating the 'soft
X-ray excess'. This component is compatible with emission from a warm,
optically-thick corona as part of the inner accretion disk. We then investigate
the effects of the continuum on the ionisation balance and thermal stability of
photoionised gas for unobscured and obscured epochs.Comment: Accepted for publication in A&A, 19 pages, 13 figure
A fast and long-lived outflow from the supermassive black hole in NGC 5548
Supermassive black holes in the nuclei of active galaxies expel large amounts
of matter through powerful winds of ionized gas. The archetypal active galaxy
NGC 5548 has been studied for decades, and high-resolution X-ray and UV
observations have previously shown a persistent ionized outflow. An observing
campaign in 2013 with six space observatories shows the nucleus to be obscured
by a long-lasting, clumpy stream of ionized gas never seen before. It blocks
90% of the soft X-ray emission and causes simultaneous deep, broad UV
absorption troughs. The outflow velocities of this gas are up to five times
faster than those in the persistent outflow, and at a distance of only a few
light days from the nucleus, it may likely originate from the accretion disk.Comment: 25 pages, 8 figures. This is the author's version of the work. It is
posted here by permission of the AAAS for personal use, not for
redistribution. The definitive version was published in Science,
electronically available at Science Express (June 19, 2014). For a brief
video explaining the key results of this paper, please visit
http://www.issibern.ch/teams/ngc5548/?page_id=2
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