7,546 research outputs found
Effective cavity pumping from weakly coupled quantum dots
We derive the effective cavity pumping and decay rates for the master
equation of a quantum dot-microcavity system in presence of weakly coupled
dots. We show that the in-flow of photons is not linked to the out-flow by
thermal equilibrium relationships.Comment: 6 pages, 1 figure, PLMCN10 conference proceeding
An Electron-Diffraction Investigation of Several Unsaturated Conjugated Molecules
[Summary]
The electron-diffraction investigation of formaldehyde, glyoxal, dimethylgloxal, oxalyl chloride, and vinyl ether has shown that the conjugating power of two carbon-oxygen double bonds is of the same magnitude as the conjugating power of two carbon-carbon double bonds. The criterion for the magnitude of the conjugating power is the decrease in the carbon-carbon single bond distance. The carbon-carbon single bond distance in glyoxal and dimethylgloxal is 1.47Ã… (lg), and the carbon-carbon single bond distance in butadiene and cyclopentadiene is 1.46Ã… (lh). These distances are the same within the experimental error of the determination.
The investigation of formaldehyde (li) gave a reliable value of the carbon-oxygen double bond distance of 1.21Ã….
In oxalyl chloride the carbon-carbon bond distance is only 1.50Ã… instead of 1.47Ã… as in glyoxal and dimethylgloxal (lg). The carbon-chlorine bond distance in the. same molecule is 1.72Ã…, a shortening of of 0.04Ã…. The value of 1.50Ã… may be explained by the competition of a free electron pair on the chlorine atom with the carbon-carbon single bond for the carbon-oxygen double bond.
In vinyl ether a bond shortening of only 0.02Ã… in each bond or 0.04Ã… total shortening is reported. The shortening may be summed in this molecule as the heat of hydrogenation data(10) show that the amount of resonance in vinyl ether is the same as in ethyl vinyl ether. The shortening is due to the resonance between a tree electron pair on the oxygen atom and the two carbon-carbon double bonds. This shortening is less than that shown by the chloroethylenes(3) but the difference in electronegativity of chlorine and oxygen may well explain this fact.
The molecules glyoxal, dimethylgloxal, oxalyl chloride and vinyl ether are all found to be coplanar and trans with the exception of oxalyl chloride in which the (COCl) groups are rotated 17° from the trans position. The potential barrier restricting rotation in the first three molecules was found to be greater than five kcals. and it is indicated that the potential curve for oxalyl chloride will show a double minimum. No estimate was made at the potential barrier in vinyl ether.</p
A transcranial magnetic stimulation study on response activation and selection in spatial conflict
The Second Swift BAT Gamma-Ray Burst Catalog
We present the second Swift Burst Alert Telescope (BAT) catalog of gamma-ray
bursts (GRBs), which contains 476 bursts detected by the BAT between 2004
December 19 and 2009 December 21. This catalog (hereafter the BAT2 catalog)
presents burst trigger time, location, 90% error radius, duration, fluence,
peak flux, time-averaged spectral parameters and time-resolved spectral
parameters measured by the BAT. In the correlation study of various observed
parameters extracted from the BAT prompt emission data, we distinguish among
long-duration GRBs (L-GRBs), short-duration GRBs (S-GRBs), and short-duration
GRBs with extended emission (S-GRBs with E.E.) to investigate differences in
the prompt emission properties. The fraction of L-GRBs, S-GRBs and S-GRBs with
E.E. in the catalog are 89%, 8% and 2% respectively. We compare the BAT prompt
emission properties with the BATSE, BeppoSAX and HETE-2 GRB samples. We also
correlate the observed prompt emission properties with the redshifts for the
GRBs with known redshift. The BAT T90 and T50 durations peak at 70 s and 30 s,
respectively. We confirm that the spectra of the BAT S-GRBs are generally
harder than those of the L-GRBs. The time-averaged spectra of the BAT S-GRBs
with E.E. are similar to those of the L-GRBs. Whereas, the spectra of the
initial short spikes of the S-GRBs with E.E. are similar to those of the
S-GRBs. We show that the BAT GRB samples are significantly softer than the
BATSE bright GRBs, and that the time-averaged Epeak of the BAT GRBs peaks at 80
keV which is significantly lower energy than those of the BATSE sample which
peak at 320 keV. The time-averaged spectral properties of the BAT GRB sample
are similar to those of the HETE-2 GRB samples. By time-resolved spectral
analysis, we find that only 10% of the BAT observed photon indices are outside
the allowed region of the synchrotron shock model.Comment: 65 pages, 33 figures, 13 tables, Accepted in ApJS, Nine
machine-readable tables are available at
http://swift.gsfc.nasa.gov/docs/swift/results/bat2_catalog
Scrapie infectivity is quickly cleared in tissues of orally-infected farmed fish
BACKGROUND: Scrapie and bovine spongiform encephalopathy (BSE) belongs to the group of animal transmissible spongiform encephalopathy (TSE). BSE epidemic in the UK and elsewhere in Europe has been linked to the use of bovine meat and bone meals (MBM) in the feeding of cattle. There is concern that pigs, poultry and fish bred for human consumption and fed with infected MBM would eventually develop BSE or carry residual infectivity without disease. Although there has been no evidence of infection in these species, experimental data on the susceptibility to the BSE agent of farm animals other than sheep and cow are limited only to pigs and domestic chicken. In the framework of a EU-granted project we have challenged two species of fish largely used in human food consumption, rainbow trout (Oncorhynchus mykiss) and turbot (Scophthalmus maximus), with a mouse-adapted TSE strain (scrapie 139A), to assess the risk related to oral consumption of TSE contaminated food. In trout, we also checked the "in vitro" ability of the pathological isoform of the mouse prion protein (PrP(Sc)) to cross the intestinal epithelium when added to the mucosal side of everted intestine. RESULTS: Fish challenged with a large amount of scrapie mouse brain homogenate by either oral or parenteral routes, showed the ability to clear the majority of infectivity load. None of the fish tissues taken at different time points after oral or parenteral inoculation was able to provoke scrapie disease after intracerebral inoculation in recipient mice. However, a few recipient mice were positive for PrP(Sc )and spongiform lesions in the brain. We also showed a specific binding of PrP(Sc )to the mucosal side of fish intestine in the absence of an active uptake of the prion protein through the intestinal wall. CONCLUSION: These results indicate that scrapie 139A, and possibly BSE, is quickly removed from fish tissues despite evidence of a prion like protein in fish and of a specific binding of PrP(Sc )to the mucosal side of fish intestine
Role of PTGS2-generated PGE2 during gonadotrophin-induced bovine oocyte maturation and cumulus cell expansion
Using 81Kr and Noble Gases to Characterize and Date Groundwater and Brines in the Baltic Artesian Basin on the One-Million-Year Timescale
Analyses for Kr and noble gases on groundwater from the deepest
aquifer system of the Baltic Artesian Basin (BAB) were performed to determine
groundwater ages and uncover the flow dynamics of the system on a timescale of
several hundred thousand years. We find that the system is controlled by mixing
of three distinct water masses: Interglacial or recent meteoric water
(\delta^{18}\text{O} \approx -10.4\unicode{x2030}) with a poorly evolved
chemical and noble gas signature, glacial meltwater (\delta^{18}\text{O} \leq
-18\unicode{x2030}) with elevated noble gas concentrations, and an old,
high-salinity brine component (\delta^{18}\text{O} \geq -4.5\unicode{x2030},
\geq 90 \text{g Cl}^{-}/\text{L}) with strongly depleted atmospheric noble gas
concentrations. The Kr measurements are interpreted within this mixing
framework to estimate the age of the end-members. Deconvoluted Kr ages
range from 300 ka to 1.3 Ma for interglacial or recent meteoric water and
glacial meltwater. For the brine component, ages exceed the dating range of the
ATTA 3 instrument of 1.3 Ma. The radiogenic noble gas components He* and
Ar* are less conclusive but also support an age of > 1 Ma for the brine.
Based on the chemical and noble gas concentrations and the dating results, we
conclude that the brine originates from evaporated seawater that has been
modified by later water-rock interaction. As the obtained tracer ages cover
several glacial cycles, we discuss the impact of the glacial cycles on flow
patterns in the studied aquifer system.Comment: Accepted for publication in Geochimica et Cosmochimica Act
Structure and Stability of an Amorphous Metal
Using molecular dynamics simulations, with a realistic many-body
embedded-atom potential, and a novel method to characterize local order, we
study the structure of pure nickel during the rapid quench of the liquid and in
the resulting glass. In contrast with previous simulations with pair
potentials, we find more crystalline order and fewer icosahedra for slower
quenching rates, resulting in a glass less stable against crystallization. It
is shown that there is not a specific amorphous structure, only the arrest of
the transition from liquid to crystal, resulting in small crystalline clusters
immersed in an amorphous matrix with the same structure of the liquid.Comment: 4 pages, 4 ps figs., to appear in Phys. Rev. Let
Nonsusceptibility of Primate Cells to Taura Syndrome Virus
Primate cells commonly used to test for viruses of the Picornaviridae family are not susceptible to infection by Taura syndrome virus of penaeid shrimp
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