1,071 research outputs found
absorption in hadronic matter
The cross sections of absorption by and mesons are
evaluated in a meson-exchange model. Including form factors with a cutoff
parameter of 1 or 2 GeV, we find that due to the large threshold of these
reactions the thermal average of their cross sections is only about 0.2 mb at a
temperature of 150 MeV. Our results thus suggest that the absorption of
directly produced by hadronic comovers in high energy heavy ion
collisions is unimportant.Comment: 11 pages, revtex, 3 figures, added references and discussion on
higher BBbar state
Impacts of Co-Solvent Flushing on Microbial Populations Capable of Degrading Trichloroethylene
With increased application of co-solvent flushing technologies for removal of nonaqueous phase liquids from groundwater aquifers, concern over the effects of the solvent on native microorganisms and their ability to degrade residual contaminant has also arisen. This study assessed the impact of ethanol flushing on the numbers and activity potentials of trichloroethylene (TCE)-degrading microbial populations present in aquifer soils taken immediately after and 2 years after ethanol flushing of a former dry cleaners site. Polymerase chain reaction analysis revealed soluble methane monooxygenase genes in methanotrophic enrichments, and 16S rRNA analysis identified Methylocystis parvus with 98% similarity, further indicating the presence of a type II methanotroph. Dissimilatory sulfite reductase genes in sulfate-reducing enrichments prepared were also observed. Ethanol flushing was simulated in columns packed with uncontaminated soils from the dry cleaners site that were dosed with TCE at concentrations observed in the field; after flushing, the columns were subjected to a continuous flow of 500 pore volumes of groundwater per week. Total acridine orange direct cell counts of the flushed and nonflushed soils decreased over the 15-week testing period, but after 5 weeks, the flushed soils maintained higher cell counts than the nonflushed soils. Inhibition of methanogenesis by sulfate reduction was observed in all column soils, as was increasing removal of total methane by soils incubated under methanotrophic conditions. These results showed that impacts of ethanol were not as severe as anticipated and imply that ethanol may mitigate the toxicity of TCE to the microorganisms
Association of Exposure to Phthalates with Endometriosis and Uterine Leiomyomata: Findings from NHANES, 1999-2004
BACKGROUND. Phthalates are ubiquitous chemicals used in consumer products. Some phthalates are reproductive toxicants in experimental animals, but human data are limited. OBJECTIVE. We conducted a cross-sectional study of urinary phthalate metabolite concentrations in relation to self-reported history of endometriosis and uterine leiomyomata among 1,227 women 20-54 years of age from three cycles of the National Health and Nutrition Examination Survey (NHANES), 1999-2004. METHODS. We examined four phthalate metabolites: mono(2-ethylhexyl) phthalate (MEHP), monobutyl phthalate (MBP), monoethyl phthalate (MEP), and monobenzyl phthalate (MBzP). From the last two NHANES cycles, we also examined mono(2-ethyl-5-hydroxyhexyl) phthalate (MEHHP) and mono(2-ethyl-5-oxohexyl) phthalate (MEOHP). We used logistic regression to estimate odds ratios (ORs) and 95% confidence intervals (CIs), adjusting for potential confounders. RESULTS. Eighty-seven (7%) and 151 (12%) women reported diagnoses of endometriosis and leiomyomata, respectively. The ORs comparing the highest versus lowest three quartiles of urinary MBP were 1.36 (95% CI, 0.77-2.41) for endometriosis, 1.56 (95% CI, 0.93-2.61) for leiomyomata, and 1.71 (95% CI, 1.07-2.75) for both conditions combined. The corresponding ORs for MEHP were 0.44 (95% CI, 0.19-1.02) for endometriosis, 0.63 (95% CI, 0.35-1.12) for leiomyomata, and 0.59 (95% CI, 0.37-0.95) for both conditions combined. Findings for MEHHP and MEOHP agreed with findings for MEHP with respect to endometriosis only. We observed null associations for MEP and MBzP. Associations were similar when we excluded women diagnosed > 7 years before their NHANES evaluation. CONCLUSION. The positive associations for MBP and inverse associations for MEHP in relation to endometriosis and leiomyomata warrant investigation in prospective studies
All Optical Implementation of Multi-Spin Entanglement in a Semiconductor Quantum Well
We use ultrafast optical pulses and coherent techniques to create spin
entangled states of non-interacting electrons bound to donors (at least three)
and at least two Mn2+ ions in a CdTe quantum well. Our method, relying on the
exchange interaction between localized excitons and paramagnetic impurities,
can in principle be applied to entangle a large number of spins.Comment: 17 pages, 3 figure
Imaging the Two Gaps of the High-TC Superconductor Pb-Bi2Sr2CuO6+x
The nature of the pseudogap state, observed above the superconducting
transition temperature TC in many high temperature superconductors, is the
center of much debate. Recently, this discussion has focused on the number of
energy gaps in these materials. Some experiments indicate a single energy gap,
implying that the pseudogap is a precursor state. Others indicate two,
suggesting that it is a competing or coexisting phase. Here we report on
temperature dependent scanning tunneling spectroscopy of Pb-Bi2Sr2CuO6+x. We
have found a new, narrow, homogeneous gap that vanishes near TC, superimposed
on the typically observed, inhomogeneous, broad gap, which is only weakly
temperature dependent. These results not only support the two gap picture, but
also explain previously troubling differences between scanning tunneling
microscopy and other experimental measurements.Comment: 6 page
Sensory Measurements: Coordination and Standardization
Do sensory measurements deserve the label of “measurement”? We argue that they do. They fit with an epistemological view of measurement held in current philosophy of science, and they face the same kinds of epistemological challenges as physical measurements do: the problem of coordination and the problem of standardization. These problems are addressed through the process of “epistemic iteration,” for all measurements. We also argue for distinguishing the problem of standardization from the problem of coordination. To exemplify our claims, we draw on olfactory performance tests, especially studies linking olfactory decline to neurodegenerative disorders
Deletion of the GABAA α2-subunit does not alter self dministration of cocaine or reinstatement of cocaine seeking
Rationale
GABAA receptors containing α2-subunits are highly represented in brain areas that are involved in motivation and reward, and have been associated with addiction to several drugs, including cocaine. We have shown previously that a deletion of the α2-subunit results in an absence of sensitisation to cocaine.
Objective
We investigated the reinforcing properties of cocaine in GABAA α2-subunit knockout (KO) mice using an intravenous self-administration procedure.
Methods
α2-subunit wildtype (WT), heterozygous (HT) and KO mice were trained to lever press for a 30 % condensed milk solution. After implantation with a jugular catheter, mice were trained to lever press for cocaine (0.5 mg/kg/infusion) during ten daily sessions. Responding was extinguished and the mice tested for cue- and cocaine-primed reinstatement. Separate groups of mice were trained to respond for decreasing doses of cocaine (0.25, 0.125, 0.06 and 0.03 mg/kg).
Results
No differences were found in acquisition of lever pressing for milk. All genotypes acquired self-administration of cocaine and did not differ in rates of self-administration, dose dependency or reinstatement. However, whilst WT and HT mice showed a dose-dependent increase in lever pressing during the cue presentation, KO mice did not.
Conclusions
Despite a reported absence of sensitisation, motivation to obtain cocaine remains unchanged in KO and HT mice. Reinstatement of cocaine seeking by cocaine and cocaine-paired cues is also unaffected. We postulate that whilst not directly involved in reward perception, the α2-subunit may be involved in modulating the “energising” aspect of cocaine’s effects on reward-seeking
Appearance of fluctuating stripes at the onset of the pseudogap in the high-Tc Superconductor Bi2Sr2CaCu2O8+x
Doped Mott insulators have been shown to have a strong propensity to form
patterns of holes and spins often referred to as stripes. In copper-oxides,
doping also gives rise to the pseudogap state, which transforms into a high
temperature superconductor with sufficient doping or by reducing the
temperature. A long standing question has been the interplay between pseudogap,
which is generic to all hole-doped cuprates, and stripes, whose static form
occurs in only one family of cuprates over a narrow range of the phase diagram.
Here we examine the spatial reorganization of electronic states with the onset
of the pseudogap state at T* in the high-temperature superconductor
Bi2Sr2CaCu2O8+x using spectroscopic mapping with the scanning tunneling
microscope (STM). We find that the onset of the pseudogap phase coincides with
the appearance of electronic patterns that have the predicted characteristics
of fluctuating stripes. As expected, the stripe patterns are strongest when the
hole concentration in the CuO2 planes is close to 1/8 (per Cu). While
demonstrating that the fluctuating stripes emerge with the onset of the
pseudogap state and occur over a large part of the cuprate phase diagram, our
experiments indicate that they are a consequence of pseudogap behavior rather
than its cause.Comment: preprint version, 25 pages including supplementary informatio
Interactions of Candida albicans with host epithelial surfaces
Candida albicans is an opportunistic, fungal pathogen of humans that frequently causes superficial infections
of oral and vaginal mucosal surfaces of debilitated and susceptible individuals. The organism is however,
commonly encountered as a commensal in healthy individuals where it is a component of the normal
microflora. The key determinant in the type of relationship that Candida has with its host is how it interacts
with the epithelial surface it colonises. A delicate balance clearly exists between the potentially damaging
effects of Candida virulence factors and the nature of the immune response elicited by the host. Frequently, it
is changes in host factors that lead to Candida seemingly changing from a commensal to pathogenic existence.
However, given the often reported heterogeneity in morphological and biochemical factors that exist between
Candida species and indeed strains of C. albicans, it may also be the fact that colonising strains differ in the
way they exploit resources to allow persistence at mucosal surfaces and as a consequence this too may affect
the way Candida interacts with epithelial cells. The aim of this review is to provide an overview of some of the
possible interactions that may occur between C. albicans and host epithelial surfaces that may in turn dictate
whether Candida removal, its commensal persistence or infection follows
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