3,981 research outputs found
Systematic review of the efficacy and safety of using mesh in surgery for uterine or vaginal vault prolapse
The original publication is available at www.springerlink.comPeer reviewedPostprin
Multiple inflation
Attempts at building an unified description of the strong, weak and
electromagnetic interactions usually involve several stages of spontaneous
symmetry breaking. We consider the effects of such symmetry breaking during an
era of primordial inflation in supergravity models. In cases that these occur
along flat directions at intermediate scales there will be a succession of
short bursts of inflation which leave a distinctive signature in the spectrum
of the generated scalar density perturbation. Thus measurements of the spectral
index can directly probe the structure of unified theories at very high energy
scales. An observed feature in the power spectrum of galaxy clustering from the
APM survey may well be associated with such structure. If so, this implies a
characteristic suppression of the secondary Doppler peaks in the angular power
spectrum of temperature fluctuations in the cosmic microwave background.Comment: 20 pages (revtex) including 2 figures (epsf); submitted to Nucl.
Phys. B; Postscript also available from
ftp://ftp.physics.ox.ac.uk/pub/local/users/sarkar/MultiInfl.ps.g
Trends in U.S. Public Awareness of Racial and Ethnic Health Disparities (1999-2010): Study Brief
None provided
Enhanced oligonucleotideânanoparticle conjugate stability using thioctic acid modified oligonucleotides
Metallic nanoparticles of gold functionalized with oligonucleotides conventionally use a terminal thiol modification and have been used in a wide range of applications. Although readily available, the oligonucleotideânanoparticle conjugates prepared in this way suffer from a lack of stability when exposed to a variety of small molecules or elevated temperatures. If silver is used in place of gold then this lack of stability is even more pronounced. In this study we report the synthesis of highly stabilized oligonucleotideânanoparticle conjugates using a simple oligonucleotide modification. A modified solid support was used to generate 3âČ-thioctic acid modified oligonucleotides by treatment with an N-hydroxysuccimidyl ester of thioctic acid. Unusually, both gold and silver nanoparticles have been investigated in this study and show that these disulphide-modified oligonucleotide probes offer significant improvements in nanoparticle stability when treated with dithiothreitol (DTT) compared with monothiol analogues. This is a significant advance in oligonucleotideânanoparticle conjugate stability and for the first time allows silver nanoparticles to be prepared that are more stable than standard gold-thiol functionalized nanoparticles. This opens up the possibility of using silver nanoparticles functionalized with oligonucleotides as an alternative to gold
Enhanced oligonucleotideânanoparticle conjugate stability using thioctic acid modified oligonucleotides
Metallic nanoparticles of gold functionalized with oligonucleotides conventionally use a terminal thiol modification and have been used in a wide range of applications. Although readily available, the oligonucleotideânanoparticle conjugates prepared in this way suffer from a lack of stability when exposed to a variety of small molecules or elevated temperatures. If silver is used in place of gold then this lack of stability is even more pronounced. In this study we report the synthesis of highly stabilized oligonucleotideânanoparticle conjugates using a simple oligonucleotide modification. A modified solid support was used to generate 3âČ-thioctic acid modified oligonucleotides by treatment with an N-hydroxysuccimidyl ester of thioctic acid. Unusually, both gold and silver nanoparticles have been investigated in this study and show that these disulphide-modified oligonucleotide probes offer significant improvements in nanoparticle stability when treated with dithiothreitol (DTT) compared with monothiol analogues. This is a significant advance in oligonucleotideânanoparticle conjugate stability and for the first time allows silver nanoparticles to be prepared that are more stable than standard gold-thiol functionalized nanoparticles. This opens up the possibility of using silver nanoparticles functionalized with oligonucleotides as an alternative to gold
Resolving Shelf Break Exchange Around the European Northwest Shelf
Shelf seas act as a significant sink of carbon within the global ocean. This occurs as carbon is exported beneath the permanent oceanic thermocline through the downwelling circulation across the shelf break. This downwelling circulation is quantified here using two regional ocean model configurations of the European northwest shelf, with differing resolution (7â and 1.5âkm grid spacing). The dominant mechanisms and impact of model resolution are assessed along the length of the shelf break. The total downwelling circulation is stronger at higher resolution, due to an increased onâshelf transport at internal depths (20â150 m) and increased offâshelf transport at the base of the water column. At internal depths, these differences increase seasonally, influenced by stratification. Key processes in crossâshelf exchange only begin to be resolved at O(1 km), implying that global models currently used to assess the carbon cycles will be missing these processes
A Search for Nitrogen-Enhanced Metal-Poor Stars
Theoretical models of very metal-poor intermediate-mass Asymptotic Giant
Branch (AGB) stars predict a large overabundance of primary nitrogen. The very
metal-poor, carbon-enhanced, s-process-rich stars, which are thought to be the
polluted companions of now-extinct AGB stars, provide direct tests of the
predictions of these models. Recent studies of the carbon and nitrogen
abundances in metal-poor stars have focused on the most carbon-rich stars,
leading to a potential selection bias against stars that have been polluted by
AGB stars that produced large amounts of nitrogen, and hence have small [C/N]
ratios. We call these stars Nitrogen-Enhanced Metal-Poor (NEMP) stars, and
define them as having [N/Fe] > +0.5 and [C/N] < -0.5. In this paper, we report
on the [C/N] abundances of a sample of 21 carbon-enhanced stars, all but three
of which have [C/Fe] < +2.0. If NEMP stars were made as easily as
Carbon-Enhanced Metal-Poor (CEMP) stars, then we expected to find between two
and seven NEMP stars. Instead, we found no NEMP stars in our sample. Therefore,
this observational bias is not an important contributor to the apparent dearth
of N-rich stars. Our [C/N] values are in the same range as values reported
previously in the literature (-0.5 to +2.0), and all stars are in disagreement
with the predicted [C/N] ratios for both low-mass and high-mass AGB stars. We
suggest that the decrease in [C/N] from the low-mass AGB models is due to
enhanced extra-mixing, while the lack of NEMP stars may be caused by
unfavorable mass ratios in binaries or the difficulty of mass transfer in
binary systems with large mass ratios.Comment: 14 pages, 7 figures, to be published in Ap
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