532 research outputs found
Modeling the Images of Relativistic Jets Lensed by Galaxies with Different Mass Surface Density Distributions
The images of relativistic jets from extragalactic sources produced by
gravitational lensing by galaxies with different mass surface density
distributions are modeled. In particular, the following models of the
gravitational lens mass distribution are considered: a singular isothermal
ellipsoid, an isothermal ellipsoid with a core, two- and three-component models
with a galactic disk, halo, and bulge. The modeled images are compared both
between themselves and with available observations. Different sets of
parameters are shown to exist for the gravitationally lensed system B0218+357
in multicomponent models. These sets allow the observed geometry of the system
and the intensity ratio of the compact core images to be obtained, but they
lead to a significant variety in the Hubble constant determined from the
modeling results.Comment: 26 pages, 9 figures, will be published in the Astronomy Letters,
2011, v.37, N4, pp. 233-24
Response to: The effect of a preoperative subconjunctival injection of dexamethasone on bloodretinal barrier breakdown following scleral buckling retinal detachment surgery
Gut microbiota-derived propionate reduces cancer cell proliferation in the liver
Peer reviewedPublisher PD
Atom and step economical synthesis of acyclic quaternary centers via iridium-catalyzed hydroarylative cross-coupling of 1,1-disubstituted alkenes
The Peculiar Type Ia Supernova 2005hk
We present a preliminary analysis of an extensive set of optical observations
of the Type Ia SN 2005hk. We show that the evolution of SN 2005hk closely
follows that of the peculiar SN 2002cx. SN 2005hk is more luminous than SN
2002cx, while still under-luminous compared to normal Type Ia supernovae. The
spectrum at 9 days before maximum is dominated by conspicuous Fe III and Ni III
lines, and the Si II 6355 line is also clearly visible. All these features have
low velocity (~6000 km/s). The near maximum spectra show lines of Si II, S II,
Fe II, Fe III, as well as other intermediate mass and iron group elements.
Analysis with the code for synthetic spectra SYNOW indicates that all these
spectral lines have similar velocities.Comment: 6 pages, 3 figures, submitted to the proceedings of the
conference``The Multicoloured Landscape of Compact Objects and their
Explosive Origins'', 2006 June 11--24, Cefalu, Sicily, to be published by AI
Cooperative coupling of ultracold atoms and surface plasmons
Cooperative coupling between optical emitters and light fields is one of the
outstanding goals in quantum technology. It is both fundamentally interesting
for the extraordinary radiation properties of the participating emitters and
has many potential applications in photonics. While this goal has been achieved
using high-finesse optical cavities, cavity-free approaches that are broadband
and easy to build have attracted much attention recently. Here we demonstrate
cooperative coupling of ultracold atoms with surface plasmons propagating on a
plane gold surface. While the atoms are moving towards the surface they are
excited by an external laser pulse. Excited surface plasmons are detected via
leakage radiation into the substrate of the gold layer. A maximum Purcell
factor of is reached at an optimum distance of
from the surface. The coupling leads to the observation of
a Fano-like resonance in the spectrum.Comment: 9 pages, 4 figure
Transplantation of canine olfactory ensheathing cells producing chondroitinase ABC promotes chondroitin sulphate proteoglycan digestion and axonal sprouting following spinal cord injury
Olfactory ensheathing cell (OEC) transplantation is a promising strategy for treating spinal cord injury (SCI), as has been demonstrated in experimental SCI models and naturally occurring SCI in dogs. However, the presence of chondroitin sulphate proteoglycans within the extracellular matrix of the glial scar can inhibit efficient axonal repair and limit the therapeutic potential of OECs. Here we have used lentiviral vectors to genetically modify canine OECs to continuously deliver mammalian chondroitinase ABC at the lesion site in order to degrade the inhibitory chondroitin sulphate proteoglycans in a rodent model of spinal cord injury. We demonstrate that these chondroitinase producing canine OECs survived at 4 weeks following transplantation into the spinal cord lesion and effectively digested chondroitin sulphate proteoglycans at the site of injury. There was evidence of sprouting within the corticospinal tract rostral to the lesion and an increase in the number of corticospinal axons caudal to the lesion, suggestive of axonal regeneration. Our results indicate that delivery of the chondroitinase enzyme can be achieved with the genetically modified OECs to increase axon growth following SCI. The combination of these two promising approaches is a potential strategy for promoting neural regeneration following SCI in veterinary practice and human patients
Atom and step economical synthesis of acyclic quaternary centers via iridium-catalyzed hydroarylative cross-coupling of 1,1-disubstituted alkenes
Quaternary benzylic centers are accessed with high atom and step economy by Ir-catalyzed alkene hydroarylation. These studies provide unique examples of the use of non-polarized 1,1-disubstituted alkenes in branch selective Murai-type hydro(hetero)arylations. Detailed mechanistic studies have been undertaken, and these indicate that the first irreversible step is the demanding alkene carbometallation process. Structure-reactivity studies show that the efficiency of this is critically dependent on key structural features of the ligand. Computational studies have been undertaken to rationalize this experimental data, showing how more sterically demanding ligands reduce the reaction barrier via predistortion of the reacting intermediate. The key insight disclosed here will underpin the ongoing development of increasingly sophisticated branch selective Murai hydroarylations
Credible Autocoding of Convex Optimization Algorithms
International audienceThe efficiency of modern optimization methods, coupled with increasing computational resources, has led to the possibility of real-time optimization algorithms acting in safety critical roles. There is a considerable body of mathematical proofs on on-line optimization programs which can be leveraged to assist in the development and verification of their implementation. In this paper, we demonstrate how theoretical proofs of real-time optimization algorithms can be used to describe functional properties at the level of the code, thereby making it accessible for the formal methods community. The running example used in this paper is a generic semi-definite programming (SDP) solver. Semi-definite programs can encode a wide variety of optimization problems and can be solved in polynomial time at a given accuracy. We describe a top-to-down approach that transforms a high-level analysis of the algorithm into useful code annotations. We formulate some general remarks about how such a task can be incorporated into a convex programming autocoder. We then take a first step towards the automatic verification of the optimization program by identifying key issues to be adressed in future work
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