Our previous studies suggest that physical activity (PA) levels are potentially regulated by endogenous metabolic mechanisms such as the vasodilatory roles of nitric oxide (NO) production via the ...precursor arginine (ARG) and ARG-related pathways. We assessed ARG metabolism and its precursors citrulline (CIT), glutamine (GLN), glutamate (GLU), ornithine (ORN), and phenylalanine (PHE) by measuring plasma concentration, whole-body production (WBP), de novo ARG and NO production, and clearance rates in previously classified low-active (LA) or high-active (HA) mice. We assessed LA (n = 23) and HA (n = 20) male mice by administering a stable isotope tracer pulse via jugular catheterization. We measured plasma enrichments via liquid chromatography tandem mass spectrometry (LC-MS/MS) and body compostion by echo-MRI. WBP, clearance rates, and de novo ARG and NO were calculated. Compared to LA mice, HA mice had lower plasma concentrations of GLU (71.1%; 36.8 #177; 2.9 vs. 17.5 #177; 1.7muM; p0.0001), CIT (21%; 57.3 #177; 2.3 vs. 46.4 #177; 1.5muM; p = 0.0003), and ORN (40.1%; 55.4 #177; 7.3 vs. 36.9 #177; 2.6muM; p = 0.0241), but no differences for GLN, PHE, and ARG. However, HA mice had higher estimated NO production ratio (0.64 #177; 0.08; p = 0.0197), higher WBP for CIT (21.8%, 8.6 #177; 0.2 vs. 10.7 #177; 0.3 nmol/g-lbm/min; p0.0001), ARG (21.4%, 35.0 #177; 0.6 vs. 43.4 #177; 0.7 nmol/g-lbm/min; p0.0001), PHE (7.6%, 23.8 #177; 0.5 vs. 25.6 #177; 0.5 nmol/g-lbm/min; p0.0100), and lower GLU (78.5%; 9.4 #177; 1.1 vs. 4.1 #177; 1.6 nmol/g lbm/min; p = 0.0161). We observed no significant differences in WBP for GLN, ORN, PHE, or de novo ARG. We concluded that HA mice have an activated whole-body ARG pathway, which may be associated with regulating PA levels via increased NO production.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
With the rise in physical inactivity and its related diseases, it is necessary to understand the mechanisms involved in physical activity regulation. Biological factors regulating physical activity ...are studied to establish a possible target for improving the physical activity level. However, little is known about the role metabolism plays in physical activity regulation. Therefore, we studied protein fractional synthesis rate (FSR) of multiple organ tissues of 12-week-old male mice that were previously established as inherently low-active (n = 15, C3H/HeJ strain) and high-active (n = 15, C57L/J strain). Total body water of each mouse was enriched to 5% deuterium oxide (D2O) via intraperitoneal injection and maintained with D2O enriched drinking water for about 24 h. Blood samples from the jugular vein and tissues (kidney, heart, lung, muscle, fat, jejunum, ileum, liver, brain, skin, and bone) were collected for enrichment analysis of alanine by LC-MS/MS. Protein FSR was calculated as -ln(1-enrichment). Data are mean±SE as fraction/day (unpaired t-test). Kidney protein FSR in the low-active mice was 7.82% higher than in high-active mice (low-active: 0.1863±0.0018, high-active: 0.1754±0.0028, p = 0.0030). No differences were found in any of the other measured organ tissues. However, all tissues resulted in a generally higher protein FSR in the low-activity mice compared to the high-activity mice (e.g. lung LA: 0.0711±0.0015, HA: 0.0643±0.0020, heart LA: 0.0649± 0.0013 HA: 0.0712±0.0073). Our observations suggest that high-active mice in most organ tissues are no more inherently equipped for metabolic adaptation than low-active mice, but there may be a connection between protein metabolism of kidney tissue and physical activity level. In addition, low-active mice have higher organ-specific baseline protein FSR possibly contributing to the inability to achieve higher physical activity levels.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Simulations of the neutron background for future large-scale particle dark matter detectors are presented. Neutrons were generated in rock and detector elements via spontaneous fission and (α,n) ...reactions, and by cosmic-ray muons. The simulation techniques and results are discussed in the context of the expected sensitivity of a generic liquid xenon dark matter detector. Methods of neutron background suppression are investigated. A sensitivity of 10−9–10−10 pb to WIMP-nucleon interactions can be achieved by a tonne-scale detector.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Future giant liquid argon (LAr) time projection chambers (TPCs) require a purity of better than 0.1 parts per billion (ppb) to allow the ionised electrons to drift without significant capture by any ...electronegative impurities. We present a comprehensive study of the effects of electronegative impurity on gaseous and liquid argon scintillation light, an analysis of the efficiency of various purification chemicals, as well as the Liverpool LAr setup, which utilises a novel re-circulation purification system. Of the impurities tested - Air, O sub(2), H sub(2)O, N sub(2) and CO sub(2) in the range of between 0.01 ppm to 1000 ppm - H sub(2)O was found to have the most profound effect on gaseous argon scintillation light, and N sub(2) was found to have the least. Additionally, a correlation between the slow component decay time and the total energy deposited with 0.01 ppm - 100 ppm O sub(2) contamination levels in liquid argon has been established. The superiority of molecular sieves over anhydrous complexes at absorbing Ar gas, N sub(2) gas and H sub(2)O vapour has been quantified using BET isotherm analysis. The efficiency of Cu and P sub(2)O sub(5) at removing O sub(2) and H sub(2)O impurities from 1 bar N6 argon gas at both room temperature and -130 degree C was investigated and found to be high. A novel, highly scalable LAr re-circulation system has been developed. The complete system, consisting of a motorised bellows pump operating in liquid and a purification cartridge, were designed and built in-house. The system was operated successfully over many days and achieved a re-circulation rate of 27 litres/hour and high purity.
Results of observations of low energy nuclear and electron recoil events in liquid xenon scintillator detectors are given. The relative scintillation efficiency for nuclear recoils is 0.22±0.01 in ...the recoil energy range 40–70 keV. Under the assumption of a single dominant decay component to the scintillation pulse shape the log-normal mean parameter T0 of the maximum likelihood estimator of the decay time constant for 6 keV <Eee<30 keV nuclear recoil events is equal to 21.0±0.5 ns. It is observed that for electron recoils T0 rises slowly with energy, having a value ∼30 ns at Eee∼15 keV. Electron and nuclear recoil pulse shapes are found to be well fitted by single exponential functions although some evidence is found for a double exponential form for the nuclear recoil pulse shape.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
A Micromegas micro pattern charge readout device has been operated at room temperature in Argon and Xenon from 1 to 3.5
atm and also within the saturated vapour phase of a double-phase Xenon target. ...The dependence of the gain on the amplification field, the pressure and the proportion of quencher has been evaluated. From a fit to the Townsend relation
α
=
AP
exp
(
-
BP
/
E
)
the gas parameters
A and
B were derived and compared with existing data.
For the first time Micromegas was operated in double-phase Xenon charge produced within the liquid extracted across the phase boundary prior to amplification in the gas. A 2% concentration of Methane, selected as a quencher to suppress UV photon feedback effects in the gas phase whilst allowing scintillation within the liquid, was blended with Xenon. A maximum gain of 529 was inferred from the measurement of the charge collected at the anode in saturated vapour at 1450
Torr.
Operation in double phase however was limited to periods up to 30
min due to condensation of Xenon within the Micromegas and the corresponding collapse of the amplification field. This situation was partially alleviated by heating the anode.
Possible improvements to the readout configuration are discussed in the context of operation in double-phase Xenon-based dark matter detectors as a replacement for photomultiplier optical readout.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
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