1,057 research outputs found
RR Lyrae - Theory vs Observation
The luminosities, effective temperatures and metallicities that are derived
empirically by Kovacs and Jurcsik from the light curves of a large number of
globular cluster and field RRab and RRc stars are compared to theoretical RR
Lyrae models. The strong luminosity dependence of the empirical blue and red
edges (Log L vs Log Teff diagram) is in disagreement with that of both
radiative and convective models. A reexamination of the theoretical
uncertainties in the modelling leads us to conclude that the disagreement is
irreconcilable.Comment: 6 pages, 5 figures (revised april 2000, revisions relatively minor
Can a Logarithmically Running Coupling Mimic a String Tension?
It is shown that a Coulomb potential using a running coupling slightly
modified from the perturbative form can produce an interquark potential that
appears nearly linear over a large distance range. Recent high-statistics SU(2)
lattice gauge theory data fit well to this potential without the need for a
linear string-tension term. This calls into question the accuracy of string
tension measurements which are based on the assumption of a constant
coefficient for the Coulomb term. It also opens up the possibility of obtaining
an effectively confining potential from gluon exchange alone.Comment: 13 pages, LaTeX, two figures not included, available from author.
revision - Line lengths fixed so it will tex properl
Genetic structure and breeding system in a social wasp and its social parasite
© 2008 Hoffman et al; licensee BioMed Central Ltd. The electronic version of this article is the complete one and can be found online at: http://www.biomedcentral.com/1471-2148/8/239DOI: 10.1186/1471-2148-8-239Background: Social insects dominate ecological communities because of their sophisticated group
behaviors. However, the intricate behaviors of social insects may be exploited by social parasites,
which manipulate insect societies for their own benefit. Interactions between social parasites and
their hosts lead to unusual coevolutionary dynamics that ultimately affect the breeding systems and
population structures of both species. This study represents one of the first attempts to understand
the population and colony genetic structure of a parasite and its host in a social wasp system.
Results: We used DNA microsatellite markers to investigate gene flow, genetic variation, and
mating behavior of the facultative social parasite Vespula squamosa and its primary host, V.
maculifrons. Our analyses of genetic variability uncovered that both species possessed similar
amounts of genetic variation and failed to show genetic structure over the sampling area. Our
analysis of mating system of V. maculifrons and V. squamosa revealed high levels of polyandry and no
evidence for inbreeding in the two species. Moreover, we found no significant differences between
estimates of worker relatedness in this study and a previous investigation conducted over two
decades ago, suggesting that the selective pressures operating on queen mate number have
remained constant. Finally, the distribution of queen mate number in both species deviated from
simple expectations suggesting that mate number may be under stabilizing selection.
Conclusion: The general biology of V. squamosa has not changed substantially from that of a
typical, nonparasitic Vespula wasp. For example, population sizes of the host and its parasite appear
to be similar, in contrast to other social parasites, which often display lower population sizes than
their hosts. In addition, parasitism has not caused the mating behavior of V. squamosa queens to
deviate from the high levels of multiple mating that typify Vespula wasps. This stands in contrast to
some socially parasitic ants, which revert to mating with few males. Overall, the general similarity
of the genetic structure of V. maculifrons and V. squamosa presumably reflects the fact that V.
squamosa is still capable of independent colony founding and thus reflects an intermediate stage in
the evolution of social parasitism
Efficacy of temsirolimus in metastatic chromophobe renal cell carcinoma
<p>Background: Renal cell carcinoma (RCC) is a histopathologically and molecularly heterogeneous disease with the chromophobe subtype (chRCC) accounting for approximately 5% of all cases. The median overall survival of advanced RCC has improved significantly since the advent of tyrosine kinase inhibitors and mammalian target of rapamycin (mTOR) inhibitors. However, high-quality evidence for the use of new generation tyrosine kinase inhibitors in patients with advanced chRCC is lacking. Few published case reports have highlighted the use of temsirolimus in chRCC.</p>
<p>Case presentation: Here, we report the case of a 36-year-old Caucasian woman with metastatic chRCC with predominantly skeletal metastases who was refractory to sunitinib who demonstrated a durable clinical response to temsirolimus lasting 20 months. We review the available evidence pertaining to the use of new generation molecularly targeted agents, in particular mTOR inhibitors in chRCC and discuss their emerging role in the management of this disease which would aid the oncologists faced with the challenge of treating this rare type of RCC.</p>
<p>Conclusion: Conducting randomised clinical trials in this rarer sub-group of patients would be challenging and our case report and the evidence reviewed would guide the physicians to make informed decision regarding the management of these patients.</p>
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HIV-1 Envelope Trimer Elicits Higher Neutralizing Antibody Responses than Monomeric Gp120
Taking a Stand Against Air Pollution—The Impact on Cardiovascular Disease
Although the attention of the world and the global health community specifically is deservedly focused on the COVID-19 pandemic, other determinants of health continue to have large impacts and may also interact with COVID-19. Air pollution is one crucial example. Established evidence from other respiratory viruses and emerging evidence for COVID-19 specifically indicates that air pollution alters respiratory defense mechanisms leading to worsened infection severity. Air pollution also contributes to co-morbidities that are known to worsen outcomes amongst those infected with COVID-19, and air pollution may also enhance infection transmission due to its impact on more frequent coughing. Yet despite the massive disruption of the COVID-19 pandemic, there are reasons for optimism: broad societal lockdowns have shown us a glimpse of what a future with strong air pollution measures could yield. Thus, the urgency to combat air pollution is not diminished, but instead heightened in the context of the pandemic
Seasonal variability of the warm Atlantic Water layer in the vicinity of the Greenland shelf break
The warmest water reaching the east and west coast of Greenland is found between 200?m and 600?m. Whilst important for melting Greenland's outlet glaciers, limited winter observations of this layer prohibit determination of its seasonality. To address this, temperature data from Argo profiling floats, a range of sources within the World Ocean Database and unprecedented coverage from marine-mammal borne sensors have been analysed for the period 2002-2011. A significant seasonal range in temperature (~1-2?°C) is found in the warm layer, in contrast to most of the surrounding ocean. The phase of the seasonal cycle exhibits considerable spatial variability, with the warmest water found near the eastern and southwestern shelf-break towards the end of the calendar year. High-resolution ocean model trajectory analysis suggest the timing of the arrival of the year's warmest water is a function of advection time from the subduction site in the Irminger Basin
Universality, vortices and confinement: modified SO(3) lattice gauge theory at non-zero temperature
We investigate the adjoint SU(2) lattice gauge theory in 3+1 dimensions with
the Wilson plaquette action modified by a Z(2) monopole suppression term. For
the zero-twist sector we report indications for the existence of a finite
temperature effect decoupled from the unphysical bulk transitions.Comment: 17 pages, 10 figures. Some figures and text added. To appear on Phys.
Rev.
Non-perturbative contributions to the plane-wave string mass matrix
D-instanton contributions to the mass matrix of arbitrary excited string
states of type IIB string theory in the maximally supersymmetric plane-wave
background are calculated to leading order in the string coupling using a
supersymmetric light-cone boundary state formalism. The explicit
non-perturbative dependence of the mass matrix on the complex string coupling,
the plane-wave mass parameter and the mode numbers of the excited states is
determined.Comment: 25 pages, 1 figure. v3: corrected minor typos, added referenc
Scaling and confinement aspects of tadpole improved SU(2) lattice gauge theory and its abelian projection
Using a tadpole improved SU(2) gluodynamics action, the nonabelian potential
and the abelian potential after the abelian projection are computed. Rotational
invariance is found restored at coarse lattices both in the nonabelian theory
and in the effective abelian theory resulting from maximal abelian projection.
Asymptotic scaling is tested for the SU(2) string tension. Deviation of the
order of is found, for lattice spacings between 0.27 and 0.06 fm. Evidence
for asymptotic scaling and scaling of the monopole density in maximal abelian
projection is also seen, but not at coarse lattices. The scaling behavior is
compared with analyses of Wilson action results, using bare and renormalized
coupling schemes. Using extended monopoles, evidence is found that the gauge
dependence of the abelian projection reflects short distance fluctuations, and
may thus disappear at large scales.Comment: 28 pages, RevTeX, 12 figures using epsfig (included); accepted for
publication in Physical Revie
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