5,821 research outputs found
Astrophysical Observations of a Dark Matter-Baryon Fifth Force
We consider the effects of an attractive, long-range Yukawa interaction
between baryons and dark matter (DM), focusing in particular on temperature and
pulsar timing observations of neutron stars (NSs). We show that such a fifth
force, with strength modestly stronger than gravity at ranges greater than tens
of kilometers (corresponding to mediator masses less than ), can dramatically enhance dark matter kinetic heating, capture, and
pulsar timing Doppler shifts relative to gravity plus short range interactions
alone. Using the coldest observed NS and pulsar timing array (PTA) data, we
derive limits on fifth force strength over a DM mass range spanning light dark
matter up to order solar mass composite DM objects. We also consider an
indirect limit by combining bullet cluster limits on the DM self-interaction
with weak equivalence principle test limits on baryonic self-interactions. We
find the combined indirect limits are moderately stronger than kinetic heating
and PTA limits, except when considering a DM subcomponent.Comment: 40 pages, 6 figures, v2: updated with analysis using another PTA
dataset, figures updated, conclusions unchange
Macroscopic Dark Matter Detection with Gravitational Wave Experiments
We study signatures of macroscopic dark matter (DM) in current and future
gravitational wave (GW) experiments. Transiting DM with a mass of
kg that saturates the local DM density can be potentially
detectable by GW detectors, depending on the baseline of the detector and the
strength of the force mediating the interaction. In the context of laser
interferometers, we derive the gauge invariant observable due to a transiting
DM, including the Shapiro effect, and adequately account for the finite photon
travel time within an interferometer arm. In particular, we find that the
Shapiro effect can be dominant for short-baseline interferometers such as
Holometer and GQuEST. We also find that proposed experiments such as Cosmic
Explorer and Einstein Telescope can constrain a fifth force between DM and
baryons, at the level of strength times stronger than gravity for,
e.g., kg mass DM with a fifth-force range of m.Comment: 40 pages, 6 figure
Interferometer Response to Geontropic Fluctuations
We model vacuum fluctuations in quantum gravity with a scalar field,
characterized by a high occupation number, coupled to the metric. The
occupation number of the scalar is given by a thermal density matrix, whose
form is motivated by fluctuations in the vacuum energy, which have been shown
to be conformal near a light-sheet horizon. For the experimental measurement of
interest in an interferometer, the size of the energy fluctuations is fixed by
the area of a surface bounding the volume of spacetime being interrogated by an
interferometer. We compute the interferometer response to these "geontropic"
scalar-metric fluctuations, and apply our results to current and future
interferometer measurements, such as LIGO and the proposed GQuEST experiment.Comment: 17 pages, 6 figure
Astroclimatic Characterization of Vallecitos: A candidate site for the Cherenkov Telescope Array at San Pedro Martir
We conducted an 18 month long study of the weather conditions of the
Vallecitos, a proposed site in Mexico to harbor the northern array of the
Cherenkov Telescope Array (CTA). It is located in Sierra de San Pedro Martir
(SPM) a few kilometers away from Observatorio Astron\'omico Nacional. The study
is based on data collected by the ATMOSCOPE, a multi-sensor instrument
measuring the weather and sky conditions, which was commissioned and built by
the CTA Consortium. Additionally, we compare the weather conditions of the
optical observatory at SPM to the Vallecitos regarding temperature, humidity,
and wind distributions. It appears that the excellent conditions at the optical
observatory benefit from the presence of microclimate established in the
Vallecitos.Comment: 16 pages, 16 figures, Publication of the Astronomical Society of the
Pacific, accepte
Individual prognosis at diagnosis in nonmetastatic prostate cancer: Development and external validation of the PREDICT Prostate multivariable model.
BACKGROUND: Prognostic stratification is the cornerstone of management in nonmetastatic prostate cancer (PCa). However, existing prognostic models are inadequate-often using treatment outcomes rather than survival, stratifying by broad heterogeneous groups and using heavily treated cohorts. To address this unmet need, we developed an individualised prognostic model that contextualises PCa-specific mortality (PCSM) against other cause mortality, and estimates the impact of treatment on survival. METHODS AND FINDINGS: Using records from the United Kingdom National Cancer Registration and Analysis Service (NCRAS), data were collated for 10,089 men diagnosed with nonmetastatic PCa between 2000 and 2010 in Eastern England. Median follow-up was 9.8 years with 3,829 deaths (1,202 PCa specific). Totals of 19.8%, 14.1%, 34.6%, and 31.5% of men underwent conservative management, prostatectomy, radiotherapy (RT), and androgen deprivation monotherapy, respectively. A total of 2,546 men diagnosed in Singapore over a similar time period represented an external validation cohort. Data were randomly split 70:30 into model development and validation cohorts. Fifteen-year PCSM and non-PCa mortality (NPCM) were explored using separate multivariable Cox models within a competing risks framework. Fractional polynomials (FPs) were utilised to fit continuous variables and baseline hazards. Model accuracy was assessed by discrimination and calibration using the Harrell C-index and chi-squared goodness of fit, respectively, within both validation cohorts. A multivariable model estimating individualised 10- and 15-year survival outcomes was constructed combining age, prostate-specific antigen (PSA), histological grade, biopsy core involvement, stage, and primary treatment, which were each independent prognostic factors for PCSM, and age and comorbidity, which were prognostic for NPCM. The model demonstrated good discrimination, with a C-index of 0.84 (95% CI: 0.82-0.86) and 0.84 (95% CI: 0.80-0.87) for 15-year PCSM in the UK and Singapore validation cohorts, respectively, comparing favourably to international risk-stratification criteria. Discrimination was maintained for overall mortality, with C-index 0.77 (95% CI: 0.75-0.78) and 0.76 (95% CI: 0.73-0.78). The model was well calibrated with no significant difference between predicted and observed PCa-specific (p = 0.19) or overall deaths (p = 0.43) in the UK cohort. Key study limitations were a relatively small external validation cohort, an inability to account for delayed changes to treatment beyond 12 months, and an absence of tumour-stage subclassifications. CONCLUSIONS: 'PREDICT Prostate' is an individualised multivariable PCa prognostic model built from baseline diagnostic information and the first to our knowledge that models potential treatment benefits on overall survival. Prognostic power is high despite using only routinely collected clinicopathological information.The Urology Foundatio
Grid-enabled high throughput in-silico screening against influenza A neuraminidase
PCSV, présenté par H.-C. Lee, à paraître dans les proceedingsEncouraged by the success of first EGEE biomedical data challenge against malaria[1], the second data challenge was kicked off in April, 2006, fighting against avian flu. In the paper, we demonstrated how to adopt a world-wide deployed Grid infrastructure to efficiently produce a large scale virtual screening to speed up the drug design process. The 6-weeks activity of molecular docking on the Grid has covered over 100 years of computing power required for discovering new drug for avian flu. Around 600 Gigabytes of output has also been produced and archived on the Grid for further biological analysis and test
Crossover from Kondo assisted suppression to co-tunneling enhancement of tunneling magnetoresistance via ferromagnetic nanodots in MgO tunnel barriers
Recently, it has been shown that magnetic tunnel junctions with thin MgO
tunnel barriers exhibit extraordinarily high tunneling magnetoresistance (TMR)
values at room temperature1, 2. However, the physics of spin dependent
tunneling through MgO barriers is only beginning to be unravelled. Using planar
magnetic tunnel junctions in which ultra-thin layers of magnetic metals are
deposited in the middle of a MgO tunnel barrier here we demonstrate that the
TMR is strongly modified when these layers are discontinuous and composed of
small pancake shaped nanodots. At low temperatures, in the Coulomb blockade
regime, for layers less than ~1 nm thick, the conductance of the junction is
increased at low bias consistent with Kondo assisted tunneling. In the same
regime we observe a suppression of the TMR. For slightly thicker layers, and
correspondingly larger nanodots, the TMR is enhanced at low bias, consistent
with co-tunneling.Comment: Nano Letters (in press
Literature-based discovery of diabetes- and ROS-related targets
Abstract Background Reactive oxygen species (ROS) are known mediators of cellular damage in multiple diseases including diabetic complications. Despite its importance, no comprehensive database is currently available for the genes associated with ROS. Methods We present ROS- and diabetes-related targets (genes/proteins) collected from the biomedical literature through a text mining technology. A web-based literature mining tool, SciMiner, was applied to 1,154 biomedical papers indexed with diabetes and ROS by PubMed to identify relevant targets. Over-represented targets in the ROS-diabetes literature were obtained through comparisons against randomly selected literature. The expression levels of nine genes, selected from the top ranked ROS-diabetes set, were measured in the dorsal root ganglia (DRG) of diabetic and non-diabetic DBA/2J mice in order to evaluate the biological relevance of literature-derived targets in the pathogenesis of diabetic neuropathy. Results SciMiner identified 1,026 ROS- and diabetes-related targets from the 1,154 biomedical papers (http://jdrf.neurology.med.umich.edu/ROSDiabetes/). Fifty-three targets were significantly over-represented in the ROS-diabetes literature compared to randomly selected literature. These over-represented targets included well-known members of the oxidative stress response including catalase, the NADPH oxidase family, and the superoxide dismutase family of proteins. Eight of the nine selected genes exhibited significant differential expression between diabetic and non-diabetic mice. For six genes, the direction of expression change in diabetes paralleled enhanced oxidative stress in the DRG. Conclusions Literature mining compiled ROS-diabetes related targets from the biomedical literature and led us to evaluate the biological relevance of selected targets in the pathogenesis of diabetic neuropathy.http://deepblue.lib.umich.edu/bitstream/2027.42/78315/1/1755-8794-3-49.xmlhttp://deepblue.lib.umich.edu/bitstream/2027.42/78315/2/1755-8794-3-49-S7.XLShttp://deepblue.lib.umich.edu/bitstream/2027.42/78315/3/1755-8794-3-49-S10.XLShttp://deepblue.lib.umich.edu/bitstream/2027.42/78315/4/1755-8794-3-49-S8.XLShttp://deepblue.lib.umich.edu/bitstream/2027.42/78315/5/1755-8794-3-49-S3.XLShttp://deepblue.lib.umich.edu/bitstream/2027.42/78315/6/1755-8794-3-49-S1.XLShttp://deepblue.lib.umich.edu/bitstream/2027.42/78315/7/1755-8794-3-49-S4.XLShttp://deepblue.lib.umich.edu/bitstream/2027.42/78315/8/1755-8794-3-49-S2.XLShttp://deepblue.lib.umich.edu/bitstream/2027.42/78315/9/1755-8794-3-49-S12.XLShttp://deepblue.lib.umich.edu/bitstream/2027.42/78315/10/1755-8794-3-49-S11.XLShttp://deepblue.lib.umich.edu/bitstream/2027.42/78315/11/1755-8794-3-49-S9.XLShttp://deepblue.lib.umich.edu/bitstream/2027.42/78315/12/1755-8794-3-49-S5.XLShttp://deepblue.lib.umich.edu/bitstream/2027.42/78315/13/1755-8794-3-49-S6.XLShttp://deepblue.lib.umich.edu/bitstream/2027.42/78315/14/1755-8794-3-49.pdfPeer Reviewe
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