6,129 research outputs found
Spin-Statistics Violations in Superstring Theory
I describe how superstring theory may violate spin-statistics in an
experimentally observable manner. Reviewing the basics of superstring
interactions and how to utilize these to produce a statistical phase, I then
apply these ideas to two specific examples. The first is the case of heterotic
worldsheet linkings, whereby one small closed string momentarily enlarges
sufficiently to pass over another, producing such a statistical phase. The
second is the braneworld model with noncommutative geometry, whereby matter
composed of open strings may couple to a background in which spacetime
coordinates do not commute, modifying the field (anti)commutator algebra. I
conclude with ways to sharpen and experimentally test these exciting avenues to
possibly verify superstring theory.Comment: 18 pages, 3 figures; v2: references added and typos correcte
The role of the adrenal gland in the survival of white rats subjected to the parotid toxin of the toad, Bufo marinus
Six groups of white labor atory rats were utilized in this experiment. A sham-operated group and an adrenalectomized group were used as controls. Four other groups were adrenalectomized and given replacement therapy of cortisone, deoxycorticosterone acetate, epinephrine, and norepinephrine. All groups were then given injections of toad toxin from the parotid glands of Bufo marinus. Their heart and breathing rates were recorded for 60 minutes.
All of the untreated adrenalectomized rats showed altered heart and breathing rates and were killed by the toxin. Cortisone and nor epinephrine aided the adrenalectomiz ed rats to survive. but cortisone was the more effective of the two
Probing Exciton Localization in Single-Walled Carbon Nanotubes Using High-Resolution Near-Field Microscopy
We observe localization of excitons in semiconducting single-walled carbon nanotubes at room temperature using high-resolution near-field photoluminescence (PL) microscopy. Localization is the result of spatially confined exciton energy minima with depths of more than 15 meV connected to lateral energy gradients exceeding 2 meV/nm as evidenced by energy-resolved PL imaging. Simulations of exciton diffusion in the presence of energy variations support this interpretation predicting strongly enhanced PL at local energy minima
Trends in alcohol-related admissions to hospital by age, sex and socioeconomic deprivation in England, 2002/03 to 2013/14
List of conditions by outcome measure. (DOCX 21 kb
Defect Induced Photoluminescence from Dark Excitonic States in Individual Single-Walled Carbon Nanotubes
We show that new low-energy photoluminescence (PL) bands can be created in
semiconducting single-walled carbon nanotubes by intense pulsed excitation. The
new bands are attributed to PL from different nominally dark excitons that are
"brightened" due to defect-induced mixing of states with different parity
and/or spin. Time-resolved PL studies on single nanotubes reveal a significant
reduction of the bright exciton lifetime upon brightening of the dark excitons.
The lowest energy dark state has longer lifetimes and is not in thermal
equilibrium with the bright state.Comment: 4 pages, 3 figure
The Linear-Size Evolution of Classical Double Radio Sources
Recent investigations of how the median size of extragalactic radio sources
change with redshift have produced inconsistent results. Eales compared the
radio and optical properties of a bright 3C and faint 6C sample and concluded
that (), with being the median
size of the radio sources at a given epoch and z the redshift. Oort, Katgert,
and Windhorst, on the other hand, from a comparison of the properties of a
number of radio samples, found much stronger evolution, with
. In this paper we attempt to resolve the
difference. We have repeated the analysis of Eales using the virtually complete
redshift information that now exists for the 6C sample. Confining our analysis
to FR2 sources, which we argue is the best-understood class of radio sources
and the least likely to be affected by selection effects, we find
() and
(). Our complete redshift information allows us to gain insight
into our result by plotting a radio luminosity-size (P-D) diagram for the 6C
sample. The most obvious difference between the 3C and 6C P-D diagrams is the
clump of sources in the 6C diagram at . These clump sources have similar sizes to the emission-line
regions found around high-redshift radio galaxies, suggesting that the presence
of dense line-emitting gas around high-redshift radio galaxies is responsible
for the size evolution. We show that this explanation can quantitatively
explain the observed size evolution, as long as there is either little X-ray
emitting gas around these objects or, if there is, it is distributed in a
similar way to the emission-line gas: highly anisotropic and inhomogeneous.Comment: compressed and uuencoded postscript file. 33 pages including 5
figures (441951 bytes). Accepted for publication in September Ap
The Starburst Nature of Lyman-Break Galaxies: Testing UV Extinction with X-rays
We derive the bolometric to X-ray correlation for a local sample of normal
and starburst galaxies and use it, in combination with several UV reddening
schemes, to predict the 2--8 keV X-ray luminosity for a sample of 24
Lyman-break galaxies in the HDF/CDF-N. We find that the mean X-ray luminosity,
as predicted from the Meurer UV reddening relation for starburst galaxies,
agrees extremely well with the Brandt stacking analysis. This provides
additional evidence that Lyman-break galaxies can be considered as scaled-up
local starbursts and that the locally derived starburst UV reddening relation
may be a reasonable tool for estimating the UV extinction at high redshift. Our
analysis shows that the Lyman-break sample can not have far-IR to far-UV flux
ratios similar to nearby ULIGs, as this would predict a mean X-ray luminosity
100 times larger than observed, as well as far-IR luminosities large enough to
be detected in the sub-mm. We calculate the UV reddening expected from the
Calzetti effective starburst attenuation curve and the radiative transfer
models of Witt & Gordon for low metallicity dust in a shell geometry with
homogeneous or clumpy dust distributions and find that all are consistent with
the observed X-ray emission. Finally, we show that the mean X-ray luminosity of
the sample would be under predicted by a factor of 6 if the the far-UV is
unattenuated by dust.Comment: 7 pages, 3 figures. Accepted for publication in A
Seasonal patterns of carbonate diagenesis in nearshore terrigenous muds: Relation to spring phytoplankton bloom and temperature
Pore water saturation state with respect to calcite and aragonite minerals in Long Island Sound sediments fluctuates from saturated and near saturated conditions during late fall, to undersaturated during winter, before slowly changing to supersaturated conditions during late spring. Undersaturation occurs during cold, winter periods when lower rates of ΣCO2 production (low rates of heterotrophic metabolism) and oxidation of reduced minerals such as FeS lower calcium carbonate saturation states. Direct evidence that dissolution of both calcites and aragonite are occurring during this season comes from the simultaneous increases in excess pore water carbonate dissolution products Ca2+, F-, and Sr2+ during periods of pore water undersaturation. Higher ΣCO2 production rates during warmer periods cause the CO32- concentration to become supersaturated for both calcite and aragonite. ΣCO2 production is controlled by both temperature and substrate availability so that benthic deposition of organic matter produced during the spring bloom accelerates the seasonal progression of pore waters to supersaturation. These patterns control carbonate dynamics in temperate, nearshore regions, and result in a regularly observed, yearly cycling of calcium carbonate dominated by alternating periods of net dissolution and net precipitation
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