1,291 research outputs found
An LED-based Flasher System for VERITAS
We describe a flasher system designed for use in monitoring the gains of the
photomultiplier tubes used in the VERITAS gamma-ray telescopes. This system
uses blue light-emitting diodes (LEDs) so it can be operated at much higher
rates than a traditional laser-based system. Calibration information can be
obtained with better statistical precision with reduced loss of observing time.
The LEDs are also much less expensive than a laser. The design features of the
new system are presented, along with measurements made with a prototype mounted
on one of the VERITAS telescopes.Comment: Accepted for publication in Nuclear Instruments and Methods in
Physics Research
Metabolic and cardiovascular adaptation, monkey. NASA SMD 3, project 76, experiment 44 conducted at NASA/JSC, 14-25 May 1977
The biomedical results from an experiment on a monkey subjected to space flight conditions are reported. A background history of the development and testing of an experiment system designed to permit measurement of physiological parameters in subhuman primates during continuous, comfortable, couch restraint for periods of up to 30 days is reviewed. Of major importance in the experimental design of the system was the use of a fiberglass pod, which could be sealed and subdivided into upper and lower parts, to monitor and control the physiological responses for various parts of the animal's body. The experiment was conducted within the Spacelab Simulator for a period of 11 days. Data recorded includes: Spacelab Simulator cabin temperature; ventilation rate; pod internal temperature; fraction percent oxygen; fraction percent carbon dioxide; oxygen consumption rate; carbon dioxide production rate; respiratory quotient; intrathoracic temperature; heart rate; mean aortic pressure; mean ventricular pressure; diurnal variation of parameters measured; comparison of mean preflight, flight, and postflight values of the parameters measured; and correlation matrix for the parameters measured
Long-lived spin entanglement induced by a spatially correlated thermal bath
We investigate how two spatially separated qubits coupled to a common heat
bath can be entangled by purely dissipative dynamics. We identify a dynamical
time scale associated with the lifetime of the dissipatively generated
entanglement and show that it can be much longer than either the typical
single-qubit decoherence time or the time scale on which a direct exchange
interaction can entangle the qubits. We give an approximate analytical
expression for the long-time evolution of the qubit concurrence and propose an
ion trap scheme in which such dynamics should be observable.Comment: 5 pages, 2 figure
Impact of Management on Endophyte Free and Endophyte Infected Tall Fescue Cultivars in Ohio
Ten cultivars of tall fescue (Festuca arundinacea, Schreb.) and one cultivar of orchardgrass (Dactylis glomerata L.) were part of a study to determine changes in endophyte levels of fescue under two different styles of forage management: intensive and extensive. Included in the study were two endophyte infected-cultivars of tall fescue to compare interactions with endophyte free and infected cultivars. After three years, the results demonstrate that under high levels of management and non-endophyte infected crops prior to seeding, introduction of the endophyte can be reduced or delayed. Under lower levels of management and a smother crop into endophyte infected fescue prior to seeding, high yielding endophyte free cultivars maintain the lowest percent of re-infection (25.0- 32.1% infected)
The role of genes, stress, and dopamine in the development of schizophrenia
The dopamine hypothesis is the longest standing pathoetiologic theory of schizophrenia. Because it was initially based on indirect evidence and findings in patients with established schizophrenia, it was unclear what role dopamine played in the onset of the disorder. However, recent studies in people at risk of schizophrenia have found elevated striatal dopamine synthesis capacity and increased dopamine release to stress. Furthermore, striatal dopamine changes have been linked to altered cortical function during cognitive tasks, in line with preclinical evidence that a circuit involving cortical projections to the striatum and midbrain may underlie the striatal dopamine changes. Other studies have shown that a number of environmental risk factors for schizophrenia, such as social isolation and childhood trauma, also affect presynaptic dopaminergic function. Advances in preclinical work and genetics have begun to unravel the molecular architecture linking dopamine, psychosis, and psychosocial stress. Included among the many genes associated with risk of schizophrenia are the gene encoding the dopamine D2 receptor and those involved in the upstream regulation of dopaminergic synthesis, through glutamatergic and gamma-aminobutyric acidergic pathways. A number of these pathways are also linked to the stress response. We review these new lines of evidence and present a model of how genes and environmental factors may sensitize the dopamine system so that it is vulnerable to acute stress, leading to progressive dysregulation and the onset of psychosis. Finally, we consider the implications for rational drug development, in particular regionally selective dopaminergic modulation, and the potential of genetic factors to stratify patients
Nitrogen Options to Increase Yields for Stockpiling Cool Season Grass in Eastern Ohio, USA
Stockpiling cool season grass for grazing in the fall and winter is an option to extend the grazing season. The purpose of this study was to determine the effects of yield and quality by adding urea, urea with AgrotainÂź, and ammonium sulfate to cool season grasses, primarily fescue and orchardgrass. This was the third year of the three location study in Southeast Ohio. Each location had a randomized complete block design with four treatments (control, 112 kg urea ha-1, 112 kg urea ha-1 plus AgrotainÂź, and 245.5 kg ammonium sulfate ha-1) and four replications of each treatment. The application date was August 6, 2018 and the plots were harvested on November 4, 2018. There were no statistical differences in crude protein, acid detergent fiber, and total digestible nutrients (CP, ADF, and TDN) (P \u3c 0.05). There were significant differences in yield between the control and all the treatments, but not within the treatments. The three-site average for the control was 2682 kg/ha-1; urea, 3431 kg/ha-1; urea+AgrotainÂź, 3855 kg/ha-1; and ammonium sulfate, 3468 kg/ha-1. Rainfall in the first 30 days from trial initiation in 2018 ranged from 8.15 to 9.47 cm, and the first significant rainfall (0.28-0.64 cm) was within 30 hours of initiation. This was the third and final year of this study and year three results continue to indicate that adding nitrogen increases yields
Separation-dependent localization in a two-impurity spin-boson model
Using a variational approach we investigate the delocalized to localized
crossover in the ground state of an Ohmic two-impurity spin-boson model,
describing two otherwise non-interacting spins coupled to a common bosonic
environment. We show that a competition between an environment-induced Ising
spin interaction and externally applied fields leads to variations in the
system-bath coupling strength, , at which the delocalized-localized
crossover occurs. Specifically, the crossover regime lies between
and depending upon the spin separation and the
strength of the transverse tunneling field. This is in contrast to the
analogous single spin case, for which the crossover occurs (in the scaling
limit) at fixed . We also discuss links between the
two-impurity spin-boson model and a dissipative two-spin transverse Ising
model, showing that the latter possesses the same qualitative features as the
Ising strength is varied. Finally, we show that signatures of the crossover may
be observed in single impurity observables, as well as in the behaviour of the
system-environment entanglement.Comment: 12 pages, 9 figures. Published version. Expanded discussion of the
distance dependence between the impurities, and added a related figur
A Neutral Hydrogen Self-Absorption Cloud in the SGPS
Using data from the Southern Galactic Plane Survey (SGPS) we analyze an HI
self-absorption cloud centered on l = 318.0 deg, b = -0.5 deg, and velocity, v
= -1.1 km/s. The cloud was observed with the Australia Telescope Compact Array
(ATCA) and the Parkes Radio Telescope, and is at a near kinematic distance of
less than 400 pc with derived dimensions of less than 5 x 11 pc. We apply two
different methods to find the optical depth and spin temperature. In both
methods we find upper limit spin temperatures ranging from 20 K to 25 K and
lower limit optical depths ~ 1. We look into the nature of the HI emission and
find that 60-70% originates behind the cloud. We analyze a second cloud at the
same velocity centered on l = 319 deg and b = 0.4 deg with an upper limit spin
temperature of 20 K and a lower limit optical depth of 1.6. The similarities in
spin temperature, optical depth, velocity, and spatial location are evidence
the clouds are associated, possibly as one large cloud consisting of smaller
clumps of gas. We compare HI emission data with 12CO emission and find a
physical association of the HI self-absorption cloud with molecular gas.Comment: 33 pages, 17 figures, 5 tables; Accepted for publication in ApJ. A
version with higher quality images availabe at
http://www.astro.umn.edu/~dkavars/ms.p
An Automated Method for the Detection and Extraction of HI Self-Absorption in High-Resolution 21cm Line Surveys
We describe algorithms that detect 21cm line HI self-absorption (HISA) in
large data sets and extract it for analysis. Our search method identifies HISA
as spatially and spectrally confined dark HI features that appear as negative
residuals after removing larger-scale emission components with a modified CLEAN
algorithm. Adjacent HISA volume-pixels (voxels) are grouped into features in
(l,b,v) space, and the HI brightness of voxels outside the 3-D feature
boundaries is smoothly interpolated to estimate the absorption amplitude and
the unabsorbed HI emission brightness. The reliability and completeness of our
HISA detection scheme have been tested extensively with model data. We detect
most features over a wide range of sizes, linewidths, amplitudes, and
background levels, with poor detection only where the absorption brightness
temperature amplitude is weak, the absorption scale approaches that of the
correlated noise, or the background level is too faint for HISA to be
distinguished reliably from emission gaps. False detection rates are very low
in all parts of the parameter space except at sizes and amplitudes approaching
those of noise fluctuations. Absorption measurement biases introduced by the
method are generally small and appear to arise from cases of incomplete HISA
detection. This paper is the third in a series examining HISA at high angular
resolution. A companion paper (Paper II) uses our HISA search and extraction
method to investigate the cold atomic gas distribution in the Canadian Galactic
Plane Survey.Comment: 39 pages, including 14 figure pages; to appear in June 10 ApJ, volume
626; figure quality significantly reduced for astro-ph; for full resolution,
please see http://www.ras.ucalgary.ca/~gibson/hisa/cgps1_survey
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