1,780 research outputs found
Fast transition between Classical and Weak lined T Tauri stars due to external UV dissipation
The discovery of optical jets immersed in the strong UV radiation field of
the Rosette Nebula sheds new light on, but meanwhile poses challenges to, the
study of externally irradiated jets. The jet systems in the Rosette are found
to have a high state of ionization and show unique features. In this paper, we
investigate the evolutionary status of the jet driving sources for young
solar-like stars. To our surprise, these jet sources indicate unexpected near
infrared properties with no excess emission. They are bathed in harsh external
UV radiation such that evaporation leads to a fast dissipation of their
circumstellar material. This could represent a transient phase of evolution of
young solar-like stars between classical and weak lined T Tauri stars. Naked T
Tauri stars formed in this way have indistinguishable evolutionary ages from
those of classical T Tauri stars resulting from the same episode of star
formation. However, it would be hard for such sources to be identified if they
are not driving an irradiated jet in a photoionized medium.Comment: 3 figure
Muon spin relaxation study of the magnetism in unilluminated Prussian Blue analogue photomagnets
We present longitudinal field muon spin relaxation (SR) measurements in
the unilluminated state of the photo-sensitive molecular magnetic Co-Fe
Prussian blue analogues MCo[Fe(CN)] HO, where
M=K and Rb with and , respectively. These results are
compared to those obtained in the stoichiometric limit,
Co[Fe(CN)] HO, which is not photo-sensitive. We find
evidence for correlation between the range of magnetic ordering and the value
of in the unilluminated state which can be explained using a site
percolation model.Comment: 7 pages, 12 figure
One-dimensional structures behind twisted and untwisted superYang-Mills theory
We give a one-dimensional interpretation of the four-dimensional twisted N=1
superYang-Mills theory on a Kaehler manifold by performing an appropriate
dimensional reduction. We prove the existence of a 6-generator superalgebra,
which does not possess any invariant Lagrangian but contains two different
subalgebras that determine the twisted and untwisted formulations of the N=1
superYang-Mills theory.Comment: 12 pages. Final version to appear in Lett. Math. Phys. with improved
notation and misprints correcte
Male breast cancer: a disease distinct from female breast cancer
Purpose: Male breast cancer (BC) is rare, representing approximately 1% of cancers that occur in men and approximately 1% of all BCs worldwide. Because male BC is rare, not much is known about the disease, and treatment recommendations are typically extrapolated from data available from clinical trials enrolling female BC patients. Methods: We review the epidemiology, risk factors, prognosis, and the varied molecular and clinicopathologic features that characterize male BC. In addition, we summarize the available data for the use of systemic therapy in the treatment of male BC and explore the ongoing development of targeted therapeutic agents for the treatment of this subgroup of BCs. Results: There are important biological differences between male and female BC. Male BC is almost exclusively hormone receptor positive (+), including the androgen receptor (AR), and is associated with an increased prevalence of BRCA2 germline mutations, especially in men with increased risk for developing high-risk BC. Additional research is warranted to better characterize male BC. To accomplish this, a multi-national consortium approach, such as the International Male Breast Cancer Program, is needed in response to the scarcity of patients. This approach allows the pooling of information from a large number of men with BC and the creation of registries for future therapeutic-focused clinical trials. Conclusions: Given the unique biology of BC in men, promising new therapeutic targets are currently under investigation, including the use of poly-ADP-ribose polymerase inhibitors or AR-targeted agents either as monotherapy or in combination with other agents
Out-of-equilibrium singlet-triplet Kondo effect in a single C_60 quantum dot
We have used an electromigration technique to fabricate a
single-molecule transistor (SMT). Besides describing our electromigration
procedure, we focus and present an experimental study of a single molecule
quantum dot containing an even number of electrons, revealing, for two
different samples, a clear out-of-equilibrium Kondo effect. Low temperature
magneto-transport studies are provided, which demonstrates a Zeeman splitting
of the finite bias anomaly.Comment: 6 pages, 4 figure
Structure Formation, Melting, and the Optical Properties of Gold/DNA Nanocomposites: Effects of Relaxation Time
We present a model for structure formation, melting, and optical properties
of gold/DNA nanocomposites. These composites consist of a collection of gold
nanoparticles (of radius 50 nm or less) which are bound together by links made
up of DNA strands. In our structural model, the nanocomposite forms from a
series of Monte Carlo steps, each involving reaction-limited cluster-cluster
aggregation (RLCA) followed by dehybridization of the DNA links. These links
form with a probability which depends on temperature and particle
radius . The final structure depends on the number of monomers (i. e. gold
nanoparticles) , , and the relaxation time. At low temperature, the
model results in an RLCA cluster. But after a long enough relaxation time, the
nanocomposite reduces to a compact, non-fractal cluster. We calculate the
optical properties of the resulting aggregates using the Discrete Dipole
Approximation. Despite the restructuring, the melting transition (as seen in
the extinction coefficient at wavelength 520 nm) remains sharp, and the melting
temperature increases with increasing as found in our previous
percolation model. However, restructuring increases the corresponding link
fraction at melting to a value well above the percolation threshold. Our
calculated extinction cross section agrees qualitatively with experiments on
gold/DNA composites. It also shows a characteristic ``rebound effect,''
resulting from incomplete relaxation, which has also been seen in some
experiments. We discuss briefly how our results relate to a possible sol-gel
transition in these aggregates.Comment: 12 pages, 10 figure
Antidepressants have complex associations with longitudinal depressive burden in bipolar disorder
Aims: Antidepressants are common in bipolar disorder (BD), but controversial due to questionable efficacy/tolerability. We assessed baseline antidepressant use/depression associations in BD. Methods: Stanford BD Clinic outpatients, enrolled during 2000\u20132011, assessed with the Systematic Treatment Enhancement Program for BD (STEP-BD) Affective Disorders Evaluation, were monitored up to two years with the STEP-BD Clinical Monitoring Form while receiving naturalistic expert treatment. Prevalence/correlates of baseline antidepressant use in recovered (euthymic 658 weeks)/depressed patients were assessed. Kaplan\u2013Meier survival analyses assessed times to depressive recurrence/recovery in patients with/without baseline antidepressant use, and Cox Proportional Hazard regression analyses assessed covariate effects. Results: Baseline antidepressant use was significantly (albeit without Bonferroni multiple comparison correction) less among 105 recovered (31.4%) versus 153 depressed (44.4%) patients, and among recovered patients (again without Bonferroni correction), associated with Caucasian race, earlier onset, worse Clinical Global Impression scores, and hastened depressive recurrence (only if mood elevation episodes were not censored), driven by lifetime anxiety disorder, and more (even with Bonferroni correction) bipolar II disorder, lifetime anxiety and eating disorders, and core psychotropics. Baseline antidepressant use among depressed patients was associated with significantly (again without Bonferroni correction) older age, female gender, and more (even with Bonferroni correction) anxiolytics/hypnotics, complex pharmacotherapy, and core psychotropics, but no other unfavorable illness characteristic/current mood symptom, and not time to depressive recovery. Limitations: Tertiary BD clinic referral sample receiving open naturalistic expert treatment. Analyses without/with Bonferroni correction. Conclusions: Additional research is required to assess the complex associations between baseline antidepressant use and longitudinal depressive burden in BD
Dirac gaugino as leptophilic dark matter
We investigate the leptophilic properties of Dirac gauginos in an
R--symmetric N=2 supersymmetric model with extended gauge and Higgs sectors.
The annihilation of Dirac gauginos to leptons requires no chirality flip in the
final states so that it is not suppressed as in the Majorana case. This implies
that it can be sizable enough to explain the positron excess observed by the
PAMELA experiment with moderate or no boost factors. When squark masses are
heavy, the annihilation of Dirac gauginos to hadrons is controlled by their
Higgsino fraction and is driven by the and final states.
Moreover, at variance with the Majorana case, Dirac gauginos with a
non-vanishing higgsino fraction can also have a vector coupling with the
gauge boson leading to a sizable spin--independent scattering cross section off
nuclei. Saturating the current antiproton limit, we show that Dirac gauginos
can leave a signal in direct detection experiments at the level of the
sensitivity of dark matter searches at present and in the near future.Comment: 24 pages, 10 figures, typos corrected, final version published on
JCA
Super Yang-Mills Operators from the D3-brane Action in a Curved Background
A consistent truncation of IIB on S^5 has been obtained in the sector of the
metric and the 4-form potential. The ansatz contains 20 scalars and all 15
gauge fields of gauged supergravity in five dimensions. With this
fully non-linear ansatz, the calculations for n-point correlators of super
Yang-Mills (SYM) theory via AdS/CFT are simpler than those in the literature
that use {\em linear} ansatz followed by non-linear field redefinitions. We
work out the SYM operators that couple to the scalars by expanding the
Dirac-Born-Infeld (DBI) action plus Wess-Zumino (WZ) terms around an
AdS_5\timesS^5 background with the metric fluctuations. The resulting
operators agree with those based on a superconformal symmetry argument. We
discuss the significance of our results.Comment: one author's name correcte
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