3,762 research outputs found
Characterising and Testing Deep UV LEDs for Use in Space Applications
Deep ultraviolet (DUV) light sources are used to neutralise isolated test
masses in highly sensitive space-based gravitational experiments. An example is
the LISA Pathfinder charge management system, which uses low-pressure mercury
lamps. A future gravitational-wave observatory such as eLISA will use UV
light-emitting diodes (UV LEDs), which offer numerous advantages over
traditional discharge lamps. Such devices have limited space heritage but are
are now available from a number of commercial suppliers. Here we report on a
test campaign that was carried out to quantify the general properties of three
types of commercially available UV LEDs and demonstrate their suitability for
use in space. Testing included general electrical and UV output measurements,
spectral stability, pulsed performance, temperature dependence as well as
thermal vacuum, radiation and vibration survivability
Testing modified gravity with globular cluster velocity dispersions
Globular clusters (GCs) in the Milky Way have characteristic velocity
dispersions that are consistent with the predictions of Newtonian gravity, and
may be at odds with Modified Newtonian Dynamics (MOND). We discuss a modified
gravity (MOG) theory that successfully predicts galaxy rotation curves, galaxy
cluster masses and velocity dispersions, lensing, and cosmological
observations, yet produces predictions consistent with Newtonian theory for
smaller systems, such as GCs. MOG produces velocity dispersion predictions for
GCs that are independent of the distance from the galactic center, which may
not be the case for MOND. New observations of distant GCs may produce strong
criteria that can be used to distinguish between competing gravitational
theories.Comment: 4 pages, 2 figures; accepted for publication in Ap
Comparison of pre-emptive and reactive strategies to control an incursion of bluetongue virus serotype 1 to Great Britain by vaccination.
Bluetongue (BT) is a disease of ruminants caused by bluetongue virus (BTV), which is spread between its hosts by Culicoides midges. Vaccination is the most effective way to protect susceptible animals against BTV and was used reactively to control the recent northern European outbreak. To assess the consequences of using vaccination pre-emptively we used a stochastic, spatially explicit model to compare reactive and pre-emptive vaccination strategies against an incursion of BTV serotype 1 (BTV-1) into Great Britain. Both pre-emptive and reactive vaccination significantly reduced the number of affected farms and limited host morbidity and mortality. In addition, vaccinating prior to the introduction of disease reduced the probability of an outbreak occurring. Of the strategies simulated, widespread reactive vaccination resulted in the lowest levels of morbidity. The predicted effects of vaccination were found to be sensitive to vaccine efficacy but not to the choice of transmission kernel
Vaccinia virus immune evasion: mechanisms, virulence and immunogenicity
Virus infection of mammalian cells is sensed by pattern recognition receptors and leads to an innate immune response that restricts virus replication and induces adaptive immunity. In response, viruses have evolved many countermeasures that enable them to replicate and be transmitted to new hosts, despite the host innate immune response. Poxviruses, such as vaccinia virus (VACV), have large DNA genomes and encode many proteins that are dedicated to host immune evasion. Some of these proteins are secreted from the infected cell, where they bind and neutralize complement factors, interferons, cytokines and chemokines. Other VACV proteins function inside cells to inhibit apoptosis or signalling pathways that lead to the production of interferons and pro-inflammatory cytokines and chemokines. In this review, these VACV immunomodulatory proteins are described and the potential to create more immunogenic VACV strains by manipulation of the gene encoding these proteins is discussed
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Energetic and Environmental Constraints on the Community Structure of Benthic Microbial Mats in Lake Fryxell, Antarctica.
Ecological communities are regulated by the flow of energy through environments. Energy flow is typically limited by access to photosynthetically active radiation (PAR) and oxygen concentration (O2). The microbial mats growing on the bottom of Lake Fryxell, Antarctica, have well-defined environmental gradients in PAR and (O2). We analyzed the metagenomes of layers from these microbial mats to test the extent to which access to oxygen and light controls community structure. We found variation in the diversity and relative abundances of Archaea, Bacteria and Eukaryotes across three (O2) and PAR conditions: high (O2) and maximum PAR, variable (O2) with lower maximum PAR, and low (O2) and maximum PAR. We found distinct communities structured by the optimization of energy use on a millimeter-scale across these conditions. In mat layers where (O2) was saturated, PAR structured the community. In contrast, (O2) positively correlated with diversity and affected the distribution of dominant populations across the three habitats, suggesting that meter-scale diversity is structured by energy availability. Microbial communities changed across covarying gradients of PAR and (O2). The comprehensive metagenomic analysis suggests that the benthic microbial communities in Lake Fryxell are structured by energy flow across both meter- and millimeter-scales
Improved Simulation of the Mass Charging for ASTROD I
The electrostatic charging of the test mass in ASTROD I (Astrodynamical Space
Test of Relativity using Optical Devices I) mission can affect the quality of
the science data as a result of spurious Coulomb and Lorentz forces. To
estimate the size of the resultant disturbances, credible predictions of
charging rates and the charging noise are required. Using the GEANT4 software
toolkit, we present a detailed Monte Carlo simulation of the ASTROD I test mass
charging due to exposure of the spacecraft to galactic cosmic-ray (GCR) protons
and alpha particles (3He, 4He) in the space environment. A positive charging
rate of 33.3 e+/s at solar minimum is obtained. This figure reduces by 50% at
solar maximum. Based on this charging rate and factoring in the contribution of
minor cosmic-ray components, we calculate the acceleration noise and stiffness
associated with charging. We conclude that the acceleration noise arising from
Coulomb and Lorentz effects are well below the ASTROD I acceleration noise
limit at 0.1 mHz both at solar minimum and maximum. The coherent Fourier
components due to charging are investigated, it needs to be studied carefully
in order to ensure that these do not compromise the quality of science data in
the ASTROD I mission.Comment: 20 pages, 14 figures, submitted to International Journal of Modern
Physics
A prospective study of resuscitative outcomes at a downtown Greenville SC hospital using Connect Care versus CodeNet for cardiac arrest documentation
Our study was looks at the difference between 2 systems used to document cardiac arrests in a hospital setting. One is a new machine that is called CodeNet. This documentation device was compared to the documentation system at Saint Francis Hospital in downtown Greenville, SC. When the details of a cardiac arrest are recorded (e.g., time it began, how many shocks were given, and what interval the shocks were given), this information can be used to look for patterns that predict survival. This can hopefully be used to create new protocols that will increase the patient\u27s chance of survival. This is being accomplished through chart review (cardiac arrest sheet) of cardiopulmonary arrest for 12 months and data collected with the CodeNet from cardiac arrests that occur in theIntensive Care UnitandCritical Care Unit. More data is being collected, but the preliminary results seem to indicate that CodeNet isa much moreefficient way to document the details of a cardiac arrest
The Relationship Between Patient Safety Outcomes and Hospital Characteristics
To augment the discussion of the extent to which quality is universal, this study presents the results of an analysis of 13.5 million inpatient discharges from 1,640 general hospitals from 16 states. Factor analysis was performed on 588 general U.S. hospitals and 18 PSIs were reduced to seven factors. Hospital tiers were profiled utilizing demographic variables. Contrary to expectations the best quality hospitals tended to be smaller, non-teaching hospitals whereas larger, teaching hospitals tended to be poor quality performers. This analysis provided evidence patient safety quality rates may not be universal and organizational context may be an important influencing factor
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