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Search Results: 1 - 10 of 144308 matches for " B. Loer "
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High fat diet-induced glucose intolerance impairs myocardial function, but not myocardial perfusion during hyperaemia: a pilot study
Charissa E van den Brom, Carolien S E Bulte, B Kloeze, Stephan A Loer, Christa Boer, R Bouwman
Cardiovascular Diabetology , 2012, DOI: 10.1186/1475-2840-11-74
Abstract: Male Wistar rats were randomly exposed to a high fat diet (HFD) or control diet (CD) (n?=?8 per group). After 4?weeks, rats underwent an oral glucose tolerance test. Subsequently, rats underwent (contrast) echocardiography to determine myocardial function and perfusion during baseline and dipyridamole-induced hyperaemia (20?mg/kg for 10?min).Four weeks of HFD feeding resulted in glucose intolerance compared to CD-feeding. Contractile function as represented by fractional shortening was not altered in HFD-fed rats compared to CD-fed rats under baseline conditions. However, dipyridamole increased fractional shortening in CD-fed rats, but not in HFD-fed rats. Basal myocardial perfusion, as measured by estimate of perfusion, was similar in CD- and HFD-fed rats, whereas dipyridamole increased estimate of perfusion in CD-fed rats, but not in HFD-fed rats. However, flow reserve was not different between CD- and HFD-fed rats.Diet-induced glucose intolerance is associated with impaired myocardial function during conditions of hyperaemia, but myocardial perfusion is maintained. These findings may result in new insights into the effect of glucose intolerance on myocardial function and perfusion during hyperaemia.Glucose intolerance defines the intermittent stage between transition from normal glucose levels to type 2 diabetes mellitus [1]. Glucose intolerance is a predictor of cardiovascular disease [2,3] and known to associate with vascular dysfunction and consequent impairment of organ perfusion as one of the appearing consequences [4]. Myocardial perfusion in combination with myocardial performance plays a central role in the balance between myocardial energy supply and demand. Under physiological conditions, myocardial blood flow and function are in balance [5], while pathophysiological conditions leading to vascular dysfunction, such as glucose intolerance, could alter balance between energy supply and demand. Although glucose intolerance-induced vascular dysfunction may
First Large Scale Production of Low Radioactivity Argon From Underground Sources
H. O. Back,F. Calaprice,C. Condon,E. de Haas,R. Ford,C. Galbiati,A. Goretti,T. Hohman,An. Inanni,B. Loer,D. Montanari,A. Nelson,A. Pocar
Physics , 2012,
Abstract: We report on the first large-scale production of low radioactivity argon from underground gas wells. Low radioactivity argon is of general interest, in particular for the construction of large scale WIMP dark matter searches and detectors of reactor neutrinos for non-proliferation efforts. Atmospheric argon has an activity of about 1 Bq/kg from the decays of 39Ar; the concentration of 39Ar in the underground argon we are collecting is at least a factor of 100 lower than this value. The argon is collected from a stream of gas from a CO2 well in southwestern Colorado with a Vacuum Pressure Swing Adsorption (VPSA) plant. The gas from the well contains argon at a concentration of 400-600 ppm, and the VPSA plant produces an output stream with an argon concentration at the level of 30,000-50,000 ppm (3-5%) in a single pass. This gas is sent for further processing to Fermilab where it is purified by cryogenic distillation. The argon production rate is presently 0.5 kg/day.
Function and evolution of the serotonin-synthetic bas-1 gene and other aromatic amino acid decarboxylase genes in Caenorhabditis
Emily E Hare, Curtis M Loer
BMC Evolutionary Biology , 2004, DOI: 10.1186/1471-2148-4-24
Abstract: In the nematode C. elegans, the bas-1 gene is required for both serotonin and dopamine synthesis, and maps genetically near two AADC-homologous sequences. We show by transformation rescue and sequencing of mutant alleles that bas-1 encodes an AADC enzyme. Expression of a reporter construct in transgenics suggests that the bas-1 gene is expressed, as expected, in identified serotonergic and dopaminergic neurons. The bas-1 gene is one of six AADC-like sequences in the C. elegans genome, including a duplicate that is immediately downstream of the bas-1 gene. Some of the six AADC genes are quite similar to known serotonin- and dopamine-synthetic AADC's from other organisms whereas others are divergent, suggesting previously unidentified functions. In comparing the AADC genes of C. elegans with those of the congeneric C. briggsae, we find only four orthologous AADC genes in C. briggsae. Two C. elegans AADC genes – those most similar to bas-1 – are missing from C. briggsae. Phylogenetic analysis indicates that one or both of these bas-1-like genes were present in the common ancestor of C. elegans and C. briggsae, and were retained in the C. elegans line, but lost in the C. briggsae line. Further analysis of the two bas-1-like genes in C. elegans suggests that they are unlikely to encode functional enzymes, and may be expressed pseudogenes.The bas-1 gene of C. elegans encodes a serotonin- and dopamine-synthetic AADC enzyme. Two C. elegans AADC-homologous genes that are closely related to bas-1 are missing from the congeneric C. briggsae; one or more these genes was present in the common ancestor of C. elegans and C. briggsae. Despite their persistence in C. elegans, evidence suggests the bas-1-like genes do not encode functional AADC proteins. The presence of the genes in C. elegans raises questions about how many 'predicted genes' in sequenced genomes are functional, and how duplicate genes are retained or lost during evolution. This is another example of unexpected reten
Prototyping an Active Neutron Veto for SuperCDMS
Robert Calkins,Ben Loer,for the SuperCDMS Collaboration
Physics , 2015, DOI: 10.1063/1.4928018
Abstract: Neutrons, originating cosmogenically or from radioactive decays, can produce signals in dark matter detectors that are indistinguishable from Weakly Interacting Massive Particles (WIMPs). To combat this background for the SuperCDMS SNOLAB experiment, we are investigating designs for an active neutron veto within the constrained space of the compact SuperCDMS passive shielding. The current design employs an organic liquid scintillator mixed with an agent to enhance thermal neutron captures, with the scintillation light collected using wavelength-shifting fibers and read out by silicon photo-multipliers. We will describe the proposed veto and its predicted efficiency in detail and give some recent results from our R&D and prototyping efforts.
A Study of the Residual 39Ar Content in Argon from Underground Sources
J. Xu,F. Calaprice,C. Galbiati,A. Goretti,G. Guray,T. Hohman,D. Holtz,A. Ianni,M. Laubenstein,B. Loer,C. Love,C. J. Martoff,D. Montanari,S. Mukhopadhyay,A. Nelson,S. D. Rountree,R. B. Vogelaar,A. Wright
Physics , 2012,
Abstract: The discovery of argon from underground sources with significantly less 39Ar than atmospheric argon was an important step in the development of direct-detection dark matter experiments using argon as the active target. We report on the design and operation of a low background detector with a single phase liquid argon target that was built to study the 39Ar content of the underground argon. Underground argon from the Kinder Morgan CO2 plant in Cortez, Colorado was determined to have less than 0.65% of the 39Ar activity in atmospheric argon.
First Commissioning of a Cryogenic Distillation Column for Low Radioactivity Underground Argon
H. O. Back,T. Alexander,A. Alton,C. Condon,E. de Haas,C. Galbiati,A. Goretti,T. Hohmann,An. Ianni,C. Kendziora,B. Loer,D. Montanari,P. Mosteiro,S. Pordes
Physics , 2012,
Abstract: We report on the performance and commissioning of a cryogenic distillation column for low radioactivity underground argon at Fermi National Accelerator Laboratory. The distillation column is designed to accept a mixture of argon, helium, and nitrogen and return pure argon with a nitrogen contamination less than 10 ppm. In the first commissioning, we were able to run the distillation column in a continuous mode and produce argon that is 99.9% pure. After running in a batch mode, the argon purity was increased to 99.95%, with 500 ppm of nitrogen remaining. The efficiency of collecting the argon from the gas mixture was between 70% and 81%, at an argon production rate of 0.84-0.98 kg/day.
A Highly Efficient Neutron Veto for Dark Matter Experiments
Alex Wright,Pablo Mosteiro,Ben Loer,Frank Calaprice
Physics , 2010, DOI: 10.1016/j.nima.2011.04.009
Abstract: We present a conceptual design for an active neutron veto, based on boron-loaded liquid scintillator, for use in direct-detection dark matter experiments. The simulated efficiency of a 1 meter thick veto, after including the effects of neutron captures in the inner detector and inefficiencies due to feed-throughs into the veto, is greater than 99.5% for background events produced by radiogenic neutrons, while the background due to externally produced cosmogenic neutrons is reduced by more than 95%. The ability of the veto to both significantly suppress, and provide in situ measurements of, these two dominant sources of background would make the next generation of dark matter experiments much more robust, and dramatically improve the credibility of a dark matter detection claim based on the observation of a few recoil events. The veto would also allow direct extrapolation between the background-free operation of a small detector and the physics reach of a larger detector of similar construction.
Liquid Argon Time Projection Chamber Research and Development in the United States
B. Baller,C. Bromberg,N. Buchanan,F. Cavanna,H. Chen,E. Church,V. Gehman,H. Greenlee,E. Guardincerri,B. Jones,T. Junk,T. Katori,M. Kirby,K. Lang,B. Loer,A. Marchionni,T. Maruyama,C. Mauger,A. Menegolli,D. Montanari,S. Mufson,B. Norris,S. Pordes,J. Raaf,B. Rebel,R. Sanders,M. Soderberg,J. St. John,T. Strauss,A. Szelc,C. Touramanis,C. Thorn,J. Urheim,R. Van de Water,H. Wang,B. Yu,M. Zuckerbrot
Physics , 2013, DOI: 10.1088/1748-0221/9/05/T05005
Abstract: A workshop was held at Fermilab on March 20-21, 2013 to discuss the development of liquid argon time projection chambers (LArTPC) in the United States. The workshop was organized under the auspices of the Coordinating Panel for Advanced Detectors, a body that was initiated by the American Physical Society Division of Particles and Fields. All presentations at the workshop were made in plenary sessions organized into seven topical categories: $i)$ Argon Purity, $ii)$ Cryogenics, $iii)$ TPC and High Voltage, $iv)$ Electronics, Data Acquisition and Triggering, $v)$ Scintillation Light Detection, $vi)$ Calibration and Test Beams, and $vii)$ Software. This document summarizes the current efforts in each of these topical categories. It also highlights areas in LArTPC research and development that are common between neutrino experiments and dark matter experiments.
A New Method for Measuring Coherent Elastic Neutrino Nucleus Scattering at an Off-Axis High-Energy Neutrino Beam Target
S. J. Brice,R. L. Cooper,F. DeJongh,A. Empl,L. M. Garrison,A. Hime,E. Hungerford,T. Kobilarcik,B. Loer,C. Mariani,M. Mocko,G. Muhrer,R. Pattie,Z. Pavlovic,E. Ramberg,K. Scholberg,R. Tayloe,R. T. Thornton,J. Yoo,A. Young
Physics , 2013, DOI: 10.1103/PhysRevD.89.072004
Abstract: We present a new experimental method for measuring the process of Coherent Elastic Neutrino Nucleus Scattering (CENNS). This method uses a detector situated transverse to a high energy neutrino beam production target. This detector would be sensitive to the low energy neutrinos arising from pion decays-at-rest in the target. We discuss the physics motivation for making this measurement and outline the predicted backgrounds and sensitivities using this approach. We report a measurement of neutron backgrounds as found in an off-axis surface location of the Fermilab Booster Neutrino Beam (BNB) target. The results indicate that the Fermilab BNB target is a favorable location for a CENNS experiment.
Observation of the Dependence of Scintillation from Nuclear Recoils in Liquid Argon on Drift Field
T. Alexander,H. O. Back,H. Cao,A. G. Cocco,F. DeJongh,G. Fiorillo,C. Galbiati,C. Ghag,L. Grandi,C. Kendziora,W. H. Lippincott,B. Loer,C. Love,L. Manenti,C. J. Martoff,Y. Meng,D. Montanari,P. Mosteiro,D. Olvitt,S. Pordes,H. Qian,B. Rossi,R. Saldanha,W. Tan,J. Tatarowicz,S. Walker,H. Wang,A. W. Watson,S. Westerdale,J. Yoo
Physics , 2013, DOI: 10.1103/PhysRevD.88.092006
Abstract: We have exposed a dual-phase Liquid Argon Time Projection Chamber (LAr-TPC) to a low energy pulsed narrowband neutron beam, produced at the Notre Dame Institute for Structure and Nuclear Astrophysics to study the scintillation light yield of recoiling nuclei in a LAr-TPC. A liquid scintillation counter was arranged to detect and identify neutrons scattered in the LAr-TPC target and to select the energy of the recoiling nuclei. We report the observation of a significant dependence on drift field of liquid argon scintillation from nuclear recoils of 11 keV. This observation is important because, to date, estimates of the sensitivity of noble liquid TPC dark matter searches are based on the assumption that electric field has only a small effect on the light yield from nuclear recoils.
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