354 research outputs found
A Study of the Individual Contributions of Heat Generated by a XRISM/Resolve ADR Stage Magnet and Its Magnetic Shielding
A typical Adiabatic Demagnetization Refrigerator (ADR) has modest cooling power, on the order of a few microwatts. Thus, understanding heat loads going into and generated within the ADR is vital to its efficiency as well as the efficiency of the total cryogenic system of a spacecraft. One of the many sources of heat that effects the total cryogenic system is the parasitic heat due to AC loss in the ADR magnet and hysteretic loss in its magnetic shielding during a ramp. Although the sum of the heat from both of these sources can be measured during the operation of the ADR, the individual contributions are not easily obtainable in situ. Therefore, a study is being conducted to experimentally measure the contributions of the parasitic heat produced during ramping from the magnet only and from the magnet-shield combo. This study will give better inputs to the heat load model of the total cryogenic system being built for the X-Ray Imaging and Spectroscopy Mission (XRISM) slated to launch in 2022
Proteomics: in pursuit of effective traumatic brain injury therapeutics
Effective traumatic brain injury (TBI) therapeutics remain stubbornly elusive. Efforts in the field have been challenged by the heterogeneity of clinical TBI, with greater complexity among underlying molecular phenotypes than initially conceived. Future research must confront the multitude of factors comprising this heterogeneity, representing a big data challenge befitting the coming informatics age. Proteomics is poised to serve a central role in prescriptive therapeutic development, as it offers an efficient endpoint within which to assess post-TBI biochemistry. We examine rationale for multifactor TBI proteomic studies and the particular importance of temporal profiling in defining biochemical sequences and guiding therapeutic development. Lastly, we offer perspective on repurposing biofluid proteomics to develop theragnostic assays with which to prescribe, monitor and assess pharmaceutics for improved translation and outcome for TBI patients
Search for 70 \mu eV Dark Photon Dark Matter with a Dielectrically-Loaded Multi-Wavelength Microwave Cavity
Microwave cavities have been deployed to search for bosonic dark matter
candidates with masses of a few eV. However, the sensitivity of these
cavity detectors is limited by their volume, and the traditionally-employed
half-wavelength cavities suffer from a significant volume reduction at higher
masses. ADMX-Orpheus mitigates this issue by operating a tunable,
dielectrically-loaded cavity at a higher-order mode, which allows the detection
volume to remain large. The ADMX-Orpheus inaugural run excludes dark photon
dark matter with kinetic mixing angle between 65.5 eV
(15.8 GHz) and 69.3 eV (16.8GHz), marking the highest-frequency tunable
microwave cavity dark matter search to date.Comment: 7 pages, 5 figure, to be submitted to PR
ADMX-Orpheus First Search for 70 eV Dark Photon Dark Matter: Detailed Design, Operations, and Analysis
Dark matter makes up 85% of the matter in the universe and 27% of its energy
density, but we don't know what comprises dark matter. It is possible that dark
matter may be composed of either axions or dark photons, both of which can be
detected using an ultra-sensitive microwave cavity known as a haloscope. The
haloscope employed by ADMX consists of a cylindrical cavity operating at the
TM mode and is sensitive to the QCD axion with masses of few eV.
However, this haloscope design becomes challenging to implement for higher
masses. This is because higher masses require smaller-diameter cavities,
consequently reducing the detection volume which diminishes the detected signal
power. ADMX-Orpheus mitigates this issue by operating a tunable,
dielectrically-loaded cavity at a higher-order mode, allowing the detection
volume to remain large. This paper describes the design, operation, analysis,
and results of the inaugural ADMX-Orpheus dark photon search between 65.5
eV (15.8 GHz) and 69.3 eV (16.8 GHz), as well as future directions
for axion searches and for exploring more parameter space.Comment: 21 pages, 29 figures. To be submitted to Physical Review D. arXiv
admin note: substantial text overlap with arXiv:2112.0454
Organ-specific responses during brain death:increased aerobic metabolism in the liver and anaerobic metabolism with decreased perfusion in the kidneys
Hepatic and renal energy status prior to transplantation correlates with graft survival. However, effects of brain death (BD) on organ-specific energy status are largely unknown. We studied metabolism, perfusion, oxygen consumption, and mitochondrial function in the liver and kidneys following BD. BD was induced in mechanically-ventilated rats, inflating an epidurally-placed Fogarty-catheter, with sham-operated rats as controls. A 9.4T-preclinical MRI system measured hourly oxygen availability (BOLD-related R2*) and perfusion (T1-weighted). After 4 hrs, tissue was collected, mitochondria isolated and assessed with high-resolution respirometry. Quantitative proteomics, qPCR, and biochemistry was performed on stored tissue/plasma. Following BD, the liver increased glycolytic gene expression (Pfk-1) with decreased glycogen stores, while the kidneys increased anaerobic- (Ldha) and decreased gluconeogenic-related gene expression (Pck-1). Hepatic oxygen consumption increased, while renal perfusion decreased. ATP levels dropped in both organs while mitochondrial respiration and complex I/ATP synthase activity were unaffected. In conclusion, the liver responds to increased metabolic demands during BD, enhancing aerobic metabolism with functional mitochondria. The kidneys shift towards anaerobic energy production while renal perfusion decreases. Our findings highlight the need for an organ-specific approach to assess and optimise graft quality prior to transplantation, to optimise hepatic metabolic conditions and improve renal perfusion while supporting cellular detoxification
Complement Is Activated During Normothermic Machine Perfusion of Porcine and Human Discarded Kidneys
Background: The gap between demand and supply of kidneys for transplantation
necessitates the use of kidneys from extended criteria donors. Transplantation of these
donor kidneys is associated with inferior results, reflected by an increased risk of delayed
graft function. Inferior results might be explained by the higher immunogenicity of
extended criteria donor kidneys. Normothermic machine perfusion (NMP) could be
used as a platform to assess the quality and function of donor kidneys. In addition, it
could be useful to evaluate and possibly alter the immunological response of donor
kidneys. In this study, we first evaluated whether complement was activated during NMP
of porcine and human discarded kidneys. Second, we examined the relationship between
complement activation and pro-inflammatory cytokines during NMP. Third, we assessed
the effect of complement activation on renal function and injury during NMP of porcine
kidneys. Lastly, we examined local complement C3d deposition in human renal biopsies
after NMP.
Methods: NMP with a blood-based perfusion was performed with both porcine and
discarded human kidneys for 4 and 6 h, respectively. Perfusate samples were taken every
hour to assess complement activation, pro-inflammatory cytokines and renal function.
Biopsies were taken to assess histological injury and complement deposition.
Results: Complement activation products C3a, C3d, and soluble C5b-9 (sC5b-9) were
found in perfusate samples taken during NMP of both porcine and human kidneys. In
addition, complement perfusate levels positively correlated with the cytokine perfusate
levels of IL-6, IL-8, and TNF during NMP of porcine kidneys. Porcine kidneys with high
sC5b-9 perfusate levels had significantly lower creatinine clearance after 4 h of NMP. In line with these findings, high complement perfusate levels were seen during NMP of
human discarded kidneys. In addition, kidneys retrieved from brain-dead donors had
significantly higher complement perfusate levels during NMP than kidneys retrieved from
donors after circulatory death.
Conclusion: Normothermic kidney machine perfusion induces complement activation in
porcine and human kidneys, which is associated with the release of pro-inflammatory
cytokines and in porcine kidneys with lower creatinine clearance. Complement inhibition
during NMP might be a promising strategy to reduce renal graft injury and improve graft
function prior to transplantation
First LIGO search for gravitational wave bursts from cosmic (super)strings
We report on a matched-filter search for gravitational wave bursts from
cosmic string cusps using LIGO data from the fourth science run (S4) which took
place in February and March 2005. No gravitational waves were detected in 14.9
days of data from times when all three LIGO detectors were operating. We
interpret the result in terms of a frequentist upper limit on the rate of
gravitational wave bursts and use the limits on the rate to constrain the
parameter space (string tension, reconnection probability, and loop sizes) of
cosmic string models.Comment: 11 pages, 3 figures. Replaced with version submitted to PR
Search for Gravitational Wave Bursts from Soft Gamma Repeaters
We present the results of a LIGO search for short-duration gravitational
waves (GWs) associated with Soft Gamma Repeater (SGR) bursts. This is the first
search sensitive to neutron star f-modes, usually considered the most efficient
GW emitting modes. We find no evidence of GWs associated with any SGR burst in
a sample consisting of the 27 Dec. 2004 giant flare from SGR 1806-20 and 190
lesser events from SGR 1806-20 and SGR 1900+14 which occurred during the first
year of LIGO's fifth science run. GW strain upper limits and model-dependent GW
emission energy upper limits are estimated for individual bursts using a
variety of simulated waveforms. The unprecedented sensitivity of the detectors
allows us to set the most stringent limits on transient GW amplitudes published
to date. We find upper limit estimates on the model-dependent isotropic GW
emission energies (at a nominal distance of 10 kpc) between 3x10^45 and 9x10^52
erg depending on waveform type, detector antenna factors and noise
characteristics at the time of the burst. These upper limits are within the
theoretically predicted range of some SGR models.Comment: 6 pages, 1 Postscript figur
All-sky LIGO Search for Periodic Gravitational Waves in the Early S5 Data
We report on an all-sky search with the LIGO detectors for periodic
gravitational waves in the frequency range 50--1100 Hz and with the frequency's
time derivative in the range -5.0E-9 Hz/s to zero. Data from the first eight
months of the fifth LIGO science run (S5) have been used in this search, which
is based on a semi-coherent method (PowerFlux) of summing strain power.
Observing no evidence of periodic gravitational radiation, we report 95%
confidence-level upper limits on radiation emitted by any unknown isolated
rotating neutron stars within the search range. Strain limits below 1.E-24 are
obtained over a 200-Hz band, and the sensitivity improvement over previous
searches increases the spatial volume sampled by an average factor of about 100
over the entire search band. For a neutron star with nominal equatorial
ellipticity of 1.0E-6, the search is sensitive to distances as great as 500
pc--a range that could encompass many undiscovered neutron stars, albeit only a
tiny fraction of which would likely be rotating fast enough to be accessible to
LIGO. This ellipticity is at the upper range thought to be sustainable by
conventional neutron stars and well below the maximum sustainable by a strange
quark star.Comment: 6 pages, 1 figur
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