14,933 research outputs found
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The Apollo Virtual Microscope Collection: Lunar Mineralogy and Petrology of Apollo 11, 12, 14, 15 and 16 Rocks
We report on the new Virtual Microscopes on Apollo 16 lunar samples in our Apollo Virtual Microscope collection
Density of bulk trap states in organic semiconductor crystals: discrete levels induced by oxygen in rubrene
The density of trap states in the bandgap of semiconducting organic single
crystals has been measured quantitatively and with high energy resolution by
means of the experimental method of temperature-dependent
space-charge-limited-current spectroscopy (TD-SCLC). This spectroscopy has been
applied to study bulk rubrene single crystals, which are shown by this
technique to be of high chemical and structural quality. A density of deep trap
states as low as ~ 10^{15} cm^{-3} is measured in the purest crystals, and the
exponentially varying shallow trap density near the band edge could be
identified (1 decade in the density of states per ~25 meV). Furthermore, we
have induced and spectroscopically identified an oxygen related sharp hole bulk
trap state at 0.27 eV above the valence band.Comment: published in Phys. Rev. B, high quality figures:
http://www.cpfs.mpg.de/~krellner
Milli-second Oscillations in the Persistent and Bursting Flux of Aql X-1 During an Outburst
The Rossi X-Ray Timing Explorer observed the soft X-Ray transient Aql X-1
during its outburst in February and March 1997. We report the discovery of
quasi-periodic oscillations (QPOs) in its persistent flux with frequencies in
the range of 740 to 830 Hz, Q-value of over 100, and a fractional RMS amplitude
of (6.8 +- 0.6)%, and nearly coherent oscillations (NCOs) during a Type-I burst
with a frequency of 549 Hz. The frequency of the QPOs in the persistent flux is
correlated with the mass accretion rate on time scale of hours, but not on time
scale of days. This is most likely the manifestation in a single source of the
kHz QPO puzzle observed among many sources, i.e., on the one hand, individual
sources show a correlation between the QPO frequency and the inferred mass
accretion rate, on the other hand, the dozen or so sources with luminosities
spanning two decades have essentially the same QPO frequencies. We propose that
this multi-valued QPO frequency and mass accretion rate correlation indicates
the existence of many similar regimes of the accretion disk. These regimes,
with a very similar energy spectrum and QPO frequency, are distinguished from
each other by the mass accretion rate or the total X-ray flux. The NCOs during
the burst can be made almost perfectly coherent by taking into account a large
frequency derivative. This strongly suggests that this frequency is related to
the neutron star spin frequency. The large frequency derivative is attributable
to the expansion or contraction of the neutron star photosphere during the
burst.Comment: 6 pages, LaTex (aas2pp4), Accepted for publication in ApJ Let
New Constraints on Neutralino Dark Matter in the Supersymmetric Standard Model
We investigate the prospects for neutralino dark matter within the
Supersymmetric Standard Model (SSM) including the constraints from universal
soft supersymmetry breaking and radiative breaking of the electroweak symmetry.
The latter is enforced by using the one-loop Higgs effective potential which
automatically gives the one-loop corrected Higgs boson masses. We perform an
exhaustive search of the allowed five-dimensional parameter space and find that
the neutralino relic abundance depends most strongly on the
ratio . For the relic abundance is almost
always much too large, whereas for the opposite occurs. For
there are wide ranges of the remaining parameters for which
. We also determine that m_{\tilde q}\gsim250\GeV and
m_{\tilde l}\gsim100\GeV are necessary in order to possibly achieve
. These lower bounds are much weaker than the corresponding
ones derived previously when radiative breaking was {\it not} enforced.Comment: 12 pages plus 6 figures (not included), CERN-TH.6584/92,
CTP-TAMU-56/92, UAHEP921
Accurate Neutralino Relic Density Computations in Supergravity Models
We investigate the question of the proper thermal averaging of neutralino
annihilation amplitudes which possess poles and thresholds, as they impact on
the calculated neutralino relic density and therefore on the cosmological
viability of supersymmetric models. We focus on two typical resonances, namely
the boson and the lightest Higgs boson (). In the context of
supergravity models with radiative electroweak symmetry breaking, an
exploration of the whole parameter space of the model is possible and the
overall relevance of these sophisticated analyses can be ascertained. As an
example we chose the minimal supergravity model since the presence of
such poles is essential to obtain a cosmologically acceptable model. We find
that the proper thermal averaging is important for individual points in
parameter space and that the fraction of cosmologically acceptable points is
increased somewhat by the accurate procedure. However, qualitatively the new
set of points is very similar to that obtained previously using the usual
series approximations to the thermal average. We conclude that all
phenomenological analyses based on the previously determined cosmologically
allowed set remain valid.Comment: 15 pages, 9 figures (available upon request as uuencoded file or
separate ps files), tex (harvmac) CTP-TAMU-14/9
Metabolic Changes Following a 1-Year Diet and Exercise Intervention in Patients With Type 2 Diabetes
Objective—To characterize the relationships among longterm improvements in peripheral insulin sensitivity (glucose disposal rate [GDR]), fasting glucose, and free fatty acids (FFAs) and concomitant changes in weight and adipose tissue mass and distribution induced by lifestyle intervention in obese individuals with type 2 diabetes. Research Design And Methods—We measured GDR, fasting glucose, and FFAs during a euglycemic clamp and adipose tissue mass and distribution, organ fat, and adipocyte size by dual-energy X-ray absorptiometry, CT scan, and adipose tissue biopsy in 26 men and 32 women in the Look-AHEAD trial before and after 1 year of diet and exercise aimed at weight loss. Results—Weight and fasting glucose decreased significantly (P _ 0.0001) and significantly more in men than in women (_12 vs. _8% and _16 vs. _7%, respectively; P _ 0.05), while FFAs during hyperinsulinemia decreased and GDR increased significantly (P _ 0.00001) and similarly in both sexes (_53 vs. _41% and 63 vs. 43%; P _ NS). Men achieved a more favorable fat distribution by losing more from upper compared with lower and from deeper compared with superficial adipose tissue depots (P _ 0.01). Decreases in weight and adipose tissue mass predicted improvements in GDR but not in fasting glucose or fasting FFAs; however, decreases in FFAs during hyperinsulinemia significantly determined GDR improvements. Hepatic fat was the only regional fat measure whose change contributed independently to changes in metabolic variables. Conclusions—Patients with type 2 diabetes undergoing a 1-year lifestyle intervention had significant improvements in GDR, fasting glucose, FFAs and adipose tissue distribution. However, changes in overall weight (adipose tissue mass) and hepatic fat were the most important determinants of metabolic improvements.Jeanine B. Albu, Leonie K. Heilbronn, David E. Kelley, Steven R. Smith, Koichiro Azuma, Evan S. Berk, F. Xavier Pi-Sunyer, Eric Ravussin, and the Look AHEAD Adipose Research Grou
Urinary ATP and visualization of intracellular bacteria: a superior diagnostic marker for recurrent UTI in renal transplant recipients?
Renal transplant recipients (RTR) are highly susceptible to urinary tract infections (UTIs) with over 50% of patients having at least one UTI within the first year. Yet it is generally acknowledged that there is considerable insensitivity and inaccuracy in routine urinalysis when screening for UTIs. Thus a large number of transplant patients with genuine urine infections may go undiagnosed and develop chronic recalcitrant infections, which can be associated with graft loss and morbidity. Given a recent study demonstrating ATP is released by urothelial cells in response to bacteria exposure, possibly acting at metabotropic P2Y receptors mediating a proinflammatory response, we have investigated alternative, and possibly more appropriate, urinalysis techniques in a cohort of RTRs.Mid-stream urine (MSU) samples were collected from 53 outpatient RTRs. Conventional leukocyte esterase and nitrite dipstick tests, and microscopic pyuria counts (in 1 ?l), ATP concentration measurements, and identification of intracellular bacteria in shed urothelial cells, were performed on fresh unspun samples and compared to ‘gold-standard’ bacterial culture results.Of the 53 RTRs, 22% were deemed to have a UTI by ‘gold-standard’ conventional bacteria culture, whereas 87%, 8% and 4% showed evidence of UTIs according to leukocyte esterase dipstick, nitrite dipstick, and a combination of both dipsticks, respectively. Intracellular bacteria were visualized in shed urothelial cells of 44% of RTRs, however only 1 of the 23 RTRs (44%) was deemed to have a UTI by conventional bacteria culture. A significant association of the ‘gold-standard’ test with urinary ATP concentration combined with visualization of intracellular bacteria in shed urothelial cells was determined using the Fisher’s exact test.It is apparent that standard bedside tests for UTIs give variable results and that seemingly quiescent bacteria in urothelial cells are very common in RTRs and may represent a focus of subclinical infection. Furthermore, our results suggest urinary ATP concentration combined with detection of intracellular bacteria in shed urinary epithelial cells may be a sensitive means by which to detect ‘occult’ infection in RTRs
Low self-control promotes the willingness to sacrifice in close relationships
Although previous theories and research have suggested that human behavior is automatically driven by selfish impulses (e.g., vengeance rather than forgiveness), the present research tested the hypothesis that in close relationships, people's impulsive inclination is to be prosocial and to sacrifice for their partner-to pursue the interests of the partner or of the relationship at some costs for the self. Results from four studies demonstrated that people with low self-control, relative to those with high self-control, reported greater willingness to sacrifice for their close others. Furthermore, Study 4 demonstrated that communal orientation was more strongly associated with sacrifice among participants with low self-control than participants with high self-control. This moderational pattern supports the hypothesis that communal orientation functions as a default approach to sacrifice in the context of close relationships. Taken together, these findings suggest that under certain crucial conditions in close relationships, gut-level impulses are more likely than deliberative considerations to promote prorelationship behavior. © The Author(s) 2013
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Colin Marsh (1996) Handbook for Beginning Teachers. Addison Wesley Longman: Australia. 406 pp
This study examines the relationship between corporate irresponsibility (CI) and social evaluations of the firm. Utilising a large and unique corporate irresponsibility dataset, we explore how, when, and for whom corporate irresponsibility alters stakeholder perceptions of organisational reputation. By combining attribution theory and expectancy violations theory, our study elucidates the conditions under which organisational assessors attribute hypocrisy. Results generally indicate that organisational reputation, derived from the assessments of managers and market analysts, is infrequently influenced by acts of corporate irresponsibility alone. Contrary to previous studies, we find that stakeholder impressions of the firm are largely path dependent. In turn, our findings reveal that firms previously believed to be most socially responsible are perceived as hypocritical and sanctioned when causality for acts of CI can be externally validated. Conversely, our study reveals risks associated with firms believed to be least socially responsible, in that stakeholders may expect firms with reduced social performance to be culpable for corporate irresponsibility when accused of highly egregious behaviour
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