1,846 research outputs found
Development of CMOS monolithic pixel sensors with in-pixel correlated double sampling and fast readout for the ILC
This paper presents the design and results of detailed tests of a CMOS active
pixel chip for charged particle detection with in-pixel charge storage for
correlated double sampling and readout in rolling shutter mode at frequencies
up to 25 MHz. This detector is developed in the framework of R&D for the Vertex
Tracker for the International Linear Collider.Comment: 3 pages, 4 figures, to appear on the Conference Record of the 2007
IEEE Nuclear Science Symposium, Honolulu, HI, October 200
The applicability of causal dissipative hydrodynamics to relativistic heavy ion collisions
We utilize nonequilibrium covariant transport theory to determine the region
of validity of causal Israel-Stewart dissipative hydrodynamics (IS) and
Navier-Stokes theory (NS) for relativistic heavy ion physics applications. A
massless ideal gas with 2->2 interactions is considered in a 0+1D Bjorken
scenario, appropriate for the early longitudinal expansion stage of the
collision. In the scale invariant case of a constant shear viscosity to entropy
density ratio eta/s ~ const, we find that Israel-Stewart theory is 10% accurate
in calculating dissipative effects if initially the expansion timescale exceeds
half the transport mean free path tau0/lambda0 > ~2. The same accuracy with
Navier-Stokes requires three times larger tau0/lambda0 > ~6. For dynamics
driven by a constant cross section, on the other hand, about 50% larger
tau0/lambda0 > ~3 (IS) and ~9 (NS) are needed. For typical applications at RHIC
energies s_{NN}**(1/2) ~ 100-200 GeV, these limits imply that even the
Israel-Stewart approach becomes marginal when eta/s > ~0.15. In addition, we
find that the 'naive' approximation to Israel-Stewart theory, which neglects
products of gradients and dissipative quantities, has an even smaller range of
applicability than Navier-Stokes. We also obtain analytic Israel-Stewart and
Navier-Stokes solutions in 0+1D, and present further tests for numerical
dissipative hydrodynamics codes in 1+1, 2+1, and 3+1D based on generalized
conservation laws.Comment: 30 pages, 26 EPS figures, revtex stylefil
Development of CMOS monolithic pixel sensors with in-pixel correlated double sampling and fast readout
This paper presents the design and results of detailed tests of a CMOS active
pixel chip for charged particle detection with in-pixel charge storage for
correlated double sampling and readout in rolling shutter mode at frequencies
up to 25 MHz. This detector is developed in the framework of R&D for the Vertex
Tracker for a future e+e- Linear Collider.Comment: 5 pages, 6 figures, submitted to IEEE Trans. Nucl. Sc
The 3D Kinematics of Gas in the Small Magellanic Cloud
We investigate the kinematics of neutral gas in the Small Magellanic Cloud
(SMC) and test the hypothesis that it is rotating in a disk. To trace the 3D
motions of the neutral gas distribution, we identify a sample of young, massive
stars embedded within it. These are stars with radial velocity measurements
from spectroscopic surveys and proper motion measurements from Gaia, whose
radial velocities match with dominant HI components. We compare the observed
radial and tangential velocities of these stars with predictions from the
state-of-the-art rotating disk model based on high-resolution 21 cm
observations of the SMC from the Australian Square Kilometer Array Pathfinder
telescope. We find that the observed kinematics of gas-tracing stars are
inconsistent with disk rotation. We conclude that the kinematics of gas in the
SMC are more complex than can be inferred from the integrated radial velocity
field. As a result of violent tidal interactions with the LMC, non-rotational
motions are prevalent throughout the SMC, and it is likely composed of distinct
sub-structures overlapping along the line of sight.Comment: 9 pages, 5 figures, 1 Appendix; ApJ accepte
Molecular mechanisms of increased cerebral vulnerability after repeated mild blast-induced traumatic brain injury
AbstractThe consequences of a mild traumatic brain injury can be especially severe if it is repeated within the period of increased cerebral vulnerability (ICV) that follows the initial insult. To better understand the molecular mechanisms that contribute to ICV, we exposed rats to different levels of mild blast overpressure (5 exposures; total pressure range: 15.54â19.41psi or 107.14â133.83kPa) at a rate of 1 per 30min, monitored select physiological parameters, and assessed behavior. Two days post-injury or sham, we determined changes in protein biomarkers related to various pathologies in behaviorally relevant brain regions and in plasma. We found that oxygen saturation and heart rate were transiently depressed following mild blast exposure and that injured rats exhibited significantly increased anxiety- and depression-related behaviors. Proteomic analyses of the selected brain regions showed evidence of substantial oxidative stress and vascular changes, altered cell adhesion, and inflammation predominantly in the prefrontal cortex. Importantly, these pathological changes as well as indications of neuronal and glial cell loss/damage were also detected in the plasma of injured rats. Our findings illustrate some of the complex molecular changes that contribute to the period of ICV in repeated mild blast-induced traumatic brain injury. Further studies are needed to determine the functional and temporal relationship between the various pathomechanisms. The validation of these and other markers can help to diagnose individuals with ICV using a minimally invasive procedure and to develop evidence-based treatments for chronic neuropsychiatric conditions
Of detectability and camouflage: evaluating Pollard Walk rules using a common, cryptic butterfly
Abstract Estimating distribution and abundance of species depends on the probability at which individuals are detected. Butterflies are of conservation interest worldwide, but data collected with Pollard walksâthe standard for national monitoring schemesâare often analyzed assuming that changes in detectability are negligible within recommended sampling criteria. The implications of this practice remain poorly understood. Here, we evaluated the effects of sampling conditions on butterfly counts from Pollard walks using the Arctic fritillary, a common but cryptic butterfly in boreal forests of Alberta, Canada. We used an open population binomial Nâmixture model to disentangle the effects of habitat suitability and phenology on abundance of Arctic fritillaries, and its detectability by sampling different conditions of temperature, wind, cloud cover, and hour of the day. Detectability varied by one order of magnitude within the criteria recommended for Pollard walks (P varying between 0.04 and 0.45), and simulations show how sampling in suboptimal conditions increases substantially the risk of falseâabsence records (e.g., falseâabsences are twice as likely than trueâpresences when sampling 10 Arctic fritillaries at P = 0.04). Our results suggest that the risk of falseâabsences is highest for species that are poorly detectable, low in abundance, and with short flight periods. Analysis with open population binomial Nâmixture models could improve estimates of abundance and distribution for rare species of conservation interest, while providing a powerful method for assessing butterfly phenology, abundance, and behavior using counts from Pollard walks, but require more intensive sampling than conventional monitoring schemes
High-sensitive nascent transcript sequencing reveals BRD4-specific control of widespread enhancer and target gene transcription
Gene transcription by RNA polymerase II (Pol II) is under control of promoters and distal regulatory elements known as enhancers. Enhancers are themselves transcribed by Pol II correlating with their activity. How enhancer transcription is regulated and coordinated with transcription at target genes has remained unclear. Here, we developed a high-sensitive native elongating transcript sequencing approach, called HiS-NET-seq, to provide an extended high-resolution view on transcription, especially at lowly transcribed regions such as enhancers. HiS-NET-seq uncovers new transcribed enhancers in human cells. A multi-omics analysis shows that genome-wide enhancer transcription depends on the BET family protein BRD4. Specifically, BRD4 co-localizes to enhancer and promoter-proximal gene regions, and is required for elongation activation at enhancers and their genes. BRD4 keeps a set of enhancers and genes in proximity through long-range contacts. From these studies BRD4 emerges as a general regulator of enhancer transcription that may link transcription at enhancers and genes
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