1,487 research outputs found
Light dark matter in the NMSSM: upper bounds on direct detection cross sections
In the Next-to-Minimal Supersymmetric Standard Model, a bino-like LSP can be
as light as a few GeV and satisfy WMAP constraints on the dark matter relic
density in the presence of a light CP-odd Higgs scalar. We study upper bounds
on the direct detection cross sections for such a light LSP in the mass range
2-20 GeV in the NMSSM, respecting all constraints from B-physics and LEP. The
OPAL constraints on e^+ e^- -> \chi^0_1 \chi^0_i (i > 1) play an important role
and are discussed in some detail. The resulting upper bounds on the
spin-independent and spin-dependent nucleon cross sections are ~ 10^{-42}
cm^{-2} and ~ 4\times 10^{-40} cm^{-2}, respectively. Hence the upper bound on
the spin-independent cross section is below the DAMA and CoGeNT regions, but
could be compatible with the two events observed by CDMS-II.Comment: 17 pages, 3 figure
Probing natural SUSY from stop pair production at the LHC
We consider the natural supersymmetry scenario in the framework of the
R-parity conserving minimal supersymmetric standard model (called natural MSSM)
and examine the observability of stop pair production at the LHC. We first scan
the parameters of this scenario under various experimental constraints,
including the SM-like Higgs boson mass, the indirect limits from precision
electroweak data and B-decays. Then in the allowed parameter space we study the
stop pair production at the LHC followed by the stop decay into a top quark
plus a lightest neutralino or into a bottom quark plus a chargino. From
detailed Monte Carlo simulations of the signals and backgrounds, we find the
two decay modes are complementary to each other in probing the stop pair
production, and the LHC with TeV and 100 luminosity is
capable of discovering the stop predicted in natural MSSM up to 450 GeV. If no
excess events were observed at the LHC, the 95% C.L. exclusion limits of the
stop masses can reach around 537 GeV.Comment: 19 pages, 10 figures, version accepted by JHE
Real-Time Cleaning and Refinement of Facial Animation Signals
With the increasing demand for real-time animated 3D content in the
entertainment industry and beyond, performance-based animation has garnered
interest among both academic and industrial communities. While recent solutions
for motion-capture animation have achieved impressive results, handmade
post-processing is often needed, as the generated animations often contain
artifacts. Existing real-time motion capture solutions have opted for standard
signal processing methods to strengthen temporal coherence of the resulting
animations and remove inaccuracies. While these methods produce smooth results,
they inherently filter-out part of the dynamics of facial motion, such as high
frequency transient movements. In this work, we propose a real-time animation
refining system that preserves -- or even restores -- the natural dynamics of
facial motions. To do so, we leverage an off-the-shelf recurrent neural network
architecture that learns proper facial dynamics patterns on clean animation
data. We parametrize our system using the temporal derivatives of the signal,
enabling our network to process animations at any framerate. Qualitative
results show that our system is able to retrieve natural motion signals from
noisy or degraded input animation.Comment: ICGSP 2020: Proceedings of the 2020 The 4th International Conference
on Graphics and Signal Processin
Induction of endothelial cell apoptosis by the antivascular agent 5,6-dimethylxanthenone-4-acetic acid
5,6-Dimethylxanthenone-4-acetic acid, synthesised in this laboratory, reduces tumour blood flow, both in mice and in patients on Phase I trial. We used TUNEL (TdT-mediated dUTP nick end labelling) assays to investigate whether apoptosis induction was involved in its antivascular effect. 5,6-Dimethylxanthenone-4-acetic acid induced dose-dependent apoptosis in vitro in HECPP murine endothelial cells in the absence of up-regulation of mRNA for tumour necrosis factor. Selective apoptosis of endothelial cells was detected in vivo in sections of Colon 38 tumours in mice within 30âmin of administration of 5,6-Dimethylxanthenone-4-acetic acid (25âmgâkgâ1). TUNEL staining intensified with time and after 3âh, necrosis of adjacent tumour tissue was observed. Apoptosis of central vessels in splenic white pulp was also detected in tumour-bearing mice but not in mice without tumours. Apoptosis was not observed in liver tissue. No apoptosis was observed with the inactive analogue 8-methylxanthenone-4-acetic acid. Positive TUNEL staining of tumour vascular endothelium was evident in one patient in a Phase I clinical trial, from a breast tumour biopsy taken 3 and 24âh after infusion of 5,6-Dimethylxanthenone-4-acetic acid (3.1âmgâmâ2). Tumour necrosis and the production of tumour tumour necrosis factor were not observed. No apoptotic staining was seen in tumour biopsies taken from two other patients (doses of 3.7 and 4.9âmgâmâ2). We conclude that 5,6-Dimethylxanthenone-4-acetic acid can induce vascular endothelial cell apoptosis in some murine and human tumours. The action is rapid and appears to be independent of tumour necrosis factor induction
The antitumour activity of 5,6-dimethylxanthenone-4-acetic acid (DMXAA) in TNF receptor-1 knockout mice
5,6-dimethylxanthenone-4-acetic acid, a novel antivascular anticancer drug, has completed Phase I clinical trial. Its actions in mice include tumour necrosis factor induction, serotonin release, tumour blood flow inhibition, and the induction of tumour haemorrhagic necrosis and regression. We have used mice with a targeted disruption of the tumour necrosis factor receptor-1 gene as recipients for the colon 38 carcinoma to determine the role of tumour necrosis factor signalling in the action of 5,6-dimethylxanthenone-4-acetic acid. The pharmacokinetics of 5,6-dimethylxanthenone-4-acetic acid, as well as the degree of induced plasma and tissue tumour necrosis factor, were similar in tumour necrosis factor receptor-1â/â and wild-type mice. However, the maximum tolerated dose of 5,6-dimethylxanthenone-4-acetic acid was considerably higher in tumour necrosis factor receptor-1â/â mice (>100âmgâkgâ1) than in wild-type mice (27.5âmgâkgâ1). The antitumour activity of 5,6-dimethylxanthenone-4-acetic acid (25âmgâkgâ1) was strongly attenuated in tumour necrosis factor receptor-1â/â mice. However, the reduced toxicity in tumour necrosis factor receptor-1â/â mice allowed the demonstration that at a higher dose (50âmgâkgâ1), 5,6-dimethylxanthenone-4-acetic acid was curative and comparable in effect to that of a lower dose (25âmgâkgâ1) in wild-type mice. The 5,6-dimethylxanthenone-4-acetic acid -induced rise in plasma 5-hydroxyindoleacetic acid, used to reflect serotonin production in a vascular response, was larger in colon 38 tumour bearing than in non-tumour bearing tumour necrosis factor receptor-1â/â mice, but in each case the response was smaller than the corresponding response in wild-type mice. The results suggest an important role for tumour necrosis factor in mediating both the host toxicity and antitumour activity of 5,6-dimethylxanthenone-4-acetic acid, but also suggest that tumour necrosis factor can be replaced by other vasoactive factors in its antitumour action, an observation of relevance to current clinical studies
Excluding Electroweak Baryogenesis in the MSSM
In the context of the MSSM the Light Stop Scenario (LSS) is the only region
of parameter space that allows for successful Electroweak Baryogenesis (EWBG).
This possibility is very phenomenologically attractive, since it allows for the
direct production of light stops and could be tested at the LHC. The ATLAS and
CMS experiments have recently supplied tantalizing hints for a Higgs boson with
a mass of ~ 125 GeV. This Higgs mass severely restricts the parameter space of
the LSS, and we discuss the specific predictions made for EWBG in the MSSM.
Combining data from all the available ATLAS and CMS Higgs searches reveals a
tension with the predictions of EWBG even at this early stage. This allows us
to exclude EWBG in the MSSM at greater than (90) 95% confidence level in the
(non-)decoupling limit, by examining correlations between different Higgs decay
channels. We also examine the exclusion without the assumption of a ~ 125 GeV
Higgs. The Higgs searches are still highly constraining, excluding the entire
EWBG parameter space at greater than 90% CL except for a small window of m_h ~
117 - 119 GeV.Comment: 24 Pages, 4 Figures (v3: fixed typos, minor corrections, added
references
ARPES: A probe of electronic correlations
Angle-resolved photoemission spectroscopy (ARPES) is one of the most direct
methods of studying the electronic structure of solids. By measuring the
kinetic energy and angular distribution of the electrons photoemitted from a
sample illuminated with sufficiently high-energy radiation, one can gain
information on both the energy and momentum of the electrons propagating inside
a material. This is of vital importance in elucidating the connection between
electronic, magnetic, and chemical structure of solids, in particular for those
complex systems which cannot be appropriately described within the
independent-particle picture. Among the various classes of complex systems, of
great interest are the transition metal oxides, which have been at the center
stage in condensed matter physics for the last four decades. Following a
general introduction to the topic, we will lay the theoretical basis needed to
understand the pivotal role of ARPES in the study of such systems. After a
brief overview on the state-of-the-art capabilities of the technique, we will
review some of the most interesting and relevant case studies of the novel
physics revealed by ARPES in 3d-, 4d- and 5d-based oxides.Comment: Chapter to appear in "Strongly Correlated Systems: Experimental
Techniques", edited by A. Avella and F. Mancini, Springer Series in
Solid-State Sciences (2013). A high-resolution version can be found at:
http://www.phas.ubc.ca/~quantmat/ARPES/PUBLICATIONS/Reviews/ARPES_Springer.pdf.
arXiv admin note: text overlap with arXiv:cond-mat/0307085,
arXiv:cond-mat/020850
R-parity Conservation via the Stueckelberg Mechanism: LHC and Dark Matter Signals
We investigate the connection between the conservation of R-parity in
supersymmetry and the Stueckelberg mechanism for the mass generation of the B-L
vector gauge boson. It is shown that with universal boundary conditions for
soft terms of sfermions in each family at the high scale and with the
Stueckelberg mechanism for generating mass for the B-L gauge boson present in
the theory, electric charge conservation guarantees the conservation of
R-parity in the minimal B-L extended supersymmetric standard model. We also
discuss non-minimal extensions. This includes extensions where the gauge
symmetries arise with an additional U(1)_{B-L} x U(1)_X, where U(1)_X is a
hidden sector gauge group. In this case the presence of the additional U(1)_X
allows for a Z' gauge boson mass with B-L interactions to lie in the sub-TeV
region overcoming the multi-TeV LEP constraints. The possible tests of the
models at colliders and in dark matter experiments are analyzed including
signals of a low mass Z' resonance and the production of spin zero bosons and
their decays into two photons. In this model two types of dark matter
candidates emerge which are Majorana and Dirac particles. Predictions are made
for a possible simultaneous observation of new physics events in dark matter
experiments and at the LHC.Comment: 38 pages, 7 fig
The Impact of Social Disparity on Prefrontal Function in Childhood
The prefrontal cortex (PFC) develops from birth through late adolescence. This extended developmental trajectory provides many opportunities for experience to shape the structure and function of the PFC. To date, a few studies have reported links between parental socioeconomic status (SES) and prefrontal function in childhood, raising the possibility that aspects of environment associated with SES impact prefrontal function. Considering that behavioral measures of prefrontal function are associated with learning across multiple domains, this is an important area of investigation. In this study, we used fMRI to replicate previous findings, demonstrating an association between parental SES and PFC function during childhood. In addition, we present two hypothetical mechanisms by which SES could come to affect PFC function of this association: language environment and stress reactivity. We measured language use in the home environment and change in salivary cortisol before and after fMRI scanning. Complexity of family language, but not the child's own language use, was associated with both parental SES and PFC activation. Change in salivary cortisol was also associated with both SES and PFC activation. These observed associations emphasize the importance of both enrichment and adversity-reduction interventions in creating good developmental environments for all children
Effects of sample handling and storage on quantitative lipid analysis in human serum
There is sparse information about specific storage and handling protocols that minimize analytical error and variability in samples evaluated by targeted metabolomics. Variance components that affect quantitative lipid analysis in a set of human serum samples were determined. The effects of freeze-thaw, extraction state, storage temperature, and freeze-thaw prior to density-based lipoprotein fractionation were quantified. The quantification of high abundance metabolites, representing the biologically relevant lipid species in humans, was highly repeatable (with coefficients of variation as low as 0.01 and 0.02) and largely unaffected by 1â3 freeze-thaw cycles (with 0â8% of metabolites affected in each lipid class). Extraction state had effects on total lipid class amounts, including decreased diacylglycerol and increased phosphatidylethanolamine in thawed compared with frozen samples. The effects of storage temperature over 1 week were minimal, with 0â4% of metabolites affected by storage at 4°C, â20°C, or â80°C in most lipid classes, and 19% of metabolites in diacylglycerol affected by storage at â20°C. Freezing prior to lipoprotein fractionation by density ultracentrifugation decreased HDL free cholesterol by 37% and VLDL free fatty acid by 36%, and increased LDL cholesterol ester by 35% compared with fresh samples. These findings suggest that density-based fractionation should preferably be undertaken in fresh serum samples because up to 37% variability in HDL and LDL cholesterol could result from a single freeze-thaw cycle. Conversely, quantitative lipid analysis within unfractionated serum is minimally affected even with repeated freeze-thaw cycles
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