5,053 research outputs found
Resolution of puzzles from the LSND, KARMEN, and MiniBooNE experiments
This work has attempted to reconcile puzzling neutrino oscillation results
from the LSND, KARMEN and MiniBooNE experiments. We show that the LSND evidence
for oscillations, its long-standing
disagreement with the results from KARMEN, and the anomalous event excess
observed by MiniBooNE in and data could all be
explained by the existence of a heavy sterile neutrino (). All these
results are found to be consistent with each other assuming that the is
created in neutral-current interactions and decays radiatively into a
photon and a light neutrino. Assuming the is produced through mixing
with , the combined analysis of the LSND and MiniBooNe excess events
suggests that the mass is in the range from 40 to 80 MeV, the mixing
strength is , and the lifetime is
s. Surprisingly, this LSND-MiniBooNE parameters
window is found to be unconstrained by the results from the most sensitive
experiments searching for heavy neutrino. We set new limits on
for the LSND-MiniBooNE favorable mass region from the precision measurements of
the Michel spectrum by the TWIST experiment. The results obtained provide a
strong motivation for a sensitive search for the in a near future
decay or neutrino experiments, which fit well in the existing/planned
experimental programs at CERN or FNAL. The question of whether the heavy
neutrino is Dirac or Majorana particle is briefly discussed.Comment: 24 pages, 28 figures, version to appear in PR
Relative fluid novelty differentially alters the time course of limited-access ethanol and water intake in selectively bred high-alcohol-preferring mice
BACKGROUND: The influence of previous alcohol (ethanol [EtOH])-drinking experience on increasing the rate and amount of future EtOH consumption might be a genetically regulated phenomenon critical to the development and maintenance of repeated excessive EtOH abuse. We have recently found evidence supporting this view, wherein inbred C57BL/6J (B6) mice develop progressive increases in the rate of binge EtOH consumption over repeated drinking-in-the-dark (DID) EtOH access sessions (i.e., "front loading"). The primary goal of this study was to evaluate identical parameters in high-alcohol-preferring (HAP) mice to determine whether similar temporal alterations in limited-access EtOH drinking develop in a population selected for high EtOH preference/intake under continuous (24-hour) access conditions.
METHODS: Using specialized volumetric drinking devices, HAP mice received 14 daily 2-hour DID EtOH or water access sessions. A subset of these mice was then given 1 day access to the opposite assigned fluid on day 15. Home cage locomotor activity was recorded concomitantly on each day of these studies. The possibility of behavioral/metabolic tolerance was evaluated on day 16 using experimenter-administered EtOH.
RESULTS: The amount of EtOH consumed within the first 15 minutes of access increased markedly over days. However, in contrast to previous observations in B6 mice, EtOH front loading was also observed on day 15 in mice that only had previous DID experience with water. Furthermore, a decrease in the amount of water consumed within the first 15 minutes of access compared to animals given repeated water access was observed on day 15 in mice with 14 previous days of EtOH access.
CONCLUSIONS: These data further illustrate the complexity and importance of the temporal aspects of limited-access EtOH consumption and suggest that previous procedural/fluid experience in HAP mice selectively alters the time course of EtOH and water consumption
Alterations in the rate of binge ethanol consumption: implications for preclinical studies in mice
The rate at which alcohol (ethanol) is consumed has direct impact on its behavioral and subjective effects. For this reason, alterations in the pattern of ethanol consumption as a function of drinking history might be critical to the development and maintenance of alcoholism. Furthermore, because pharmacological interventions aimed at disrupting the motivation to consume ethanol are dependent on the brain/plasma concentrations present when an individual is most likely to engage in consumption of this substance, characterizing temporal drinking patterns might be useful to determine the timing of such treatments. The primary goal of the present study was to evaluate alterations in the timecourse of daily binge (drinking-in-the-dark; DID) ethanol consumption. We gave 14 daily 2 hour DID ethanol or water access sessions to male C57BL/6J (B6) mice using a state of the art volumetric drinking monitoring device. We then, primarily as a proof-of-principle, used the GABAB allosteric modulator GS39783 (GS) to determine how this compound influenced the timecourse of binge-like ethanol intake. The rate of ethanol consumption increased dramatically over sessions with the majority occurring in the first few minutes of the final session. Additionally, ethanol consumption occurring immediately following access was almost completely abolished in mice pre-treated with GS; an effect which was ethanol-specific only at this early time interval. These data characterize progressive alterations in the rate of ethanol intake using the DID model and suggest that careful consideration of prior ethanol history and timing of drug administration are warranted when interpreting results of pre-clinical drug administration studies
USCT data challenge 2019
Recent years have witnessed the active development of scanning systems and reconstructionalgorithms for ultrasound computed tomography (USCT) with applications to breast imagingfor early cancer detection. Despite these advances in hardware and software development,we encounter the need for reference data to develop, test and compare different imagingmethods. With the goals of encouraging scientific exchange and collaborations, providingbenchmarks of reconstruction algorithms, and standardizing USCT data formats, we havereleased open-source data sets of simulated waveforms that mimic measurements of a USCTscanning aperture using numerical breast phantoms. This is part of ongoing efforts centeredaround the USCT platform for data exchange and collaboration
Dark matter annihilation at cosmological redshifts: possible relic signal from annihilation of weakly interacting massive particles
We discuss the possibility to observe the products of dark matter
annihilation that was going on in the early Universe. Of all the particles that
could be generated by this process we consider only photons, as they are both
uncharged and easily detectable. The earlier the Universe was, the higher the
dark matter concentration and the annihilation rate (proportional to )
were. However, the emission from the very early Universe cannot reach us
because of the opacity. The main part of the signal was generated at the moment
the Universe had just become transparent for the photons produced by the
annihilation. Thus, the dark matter annihilation in the early Universe should
have created a sort of relic emission. We obtain its flux and the spectrum.
If weakly interacting massive particles (WIMPs) constitute dark matter, it is
shown that we may expect an extragalactic gamma-ray signal in the energy range
0.5 - 20 {MeV} with a maximum near 8 {MeV}. We show that an experimentally
observed excess in the gamma-ray background at 0.5 - 20 {MeV} could be created
by the relic WIMPs annihilation only if the dark matter structures in the
universe had appeared before the universe became transparent for the
annihilation products (). We discuss in more detail physical
conditions whereby this interpretation could be possible.Comment: 8 pages, 3 figure
Investigations of fast neutron production by 190 GeV/c muon interactions on different targets
The production of fast neutrons (1 MeV - 1 GeV) in high energy muon-nucleus
interactions is poorly understood, yet it is fundamental to the understanding
of the background in many underground experiments. The aim of the present
experiment (CERN NA55) was to measure spallation neutrons produced by 190 GeV/c
muons scattering on carbon, copper and lead targets. We have investigated the
energy spectrum and angular distribution of spallation neutrons, and we report
the result of our measurement of the neutron production differential cross
section.Comment: 19 pages, 11 figures ep
The 511 keV emission from positron annihilation in the Galaxy
The first gamma-ray line originating from outside the solar system that was
ever detected is the 511 keV emission from positron annihilation in the Galaxy.
Despite 30 years of intense theoretical and observational investigation, the
main sources of positrons have not been identified up to now. Observations in
the 1990's with OSSE/CGRO showed that the emission is strongly concentrated
towards the Galactic bulge. In the 2000's, the SPI instrument aboard ESA's
INTEGRAL gamma-ray observatory allowed scientists to measure that emission
across the entire Galaxy, revealing that the bulge/disk luminosity ratio is
larger than observed in any other wavelength. This mapping prompted a number of
novel explanations, including rather "exotic ones (e.g. dark matter
annihilation). However, conventional astrophysical sources, like type Ia
supernovae, microquasars or X-ray binaries, are still plausible candidates for
a large fraction of the observed total 511 keV emission of the bulge. A closer
study of the subject reveals new layers of complexity, since positrons may
propagate far away from their production sites, making it difficult to infer
the underlying source distribution from the observed map of 511 keV emission.
However, contrary to the rather well understood propagation of high energy
(>GeV) particles of Galactic cosmic rays, understanding the propagation of low
energy (~MeV) positrons in the turbulent, magnetized interstellar medium, still
remains a formidable challenge. We review the spectral and imaging properties
of the observed 511 keV emission and we critically discuss candidate positron
sources and models of positron propagation in the Galaxy.Comment: 62 pages, 35 figures. Review paper to appear in Reviews of Modern
Physic
Limits to in vivo fate changes of epithelia in thymus and parathyroid by ectopic expression of transcription factors Gcm2 and Foxn1
The development of the parathyroid and the thymus from the third pharyngeal pouch depends on the activities of the Gcm2 and Foxn1 transcription factors, respectively, whose expression domains sharply demarcate two regions in the developing third pharyngeal pouch. Here, we have generated novel mouse models to examine whether ectopic co-expression of Gcm2 in the thymic epithelium and of Foxn1 in the parathyroid perturbs the establishment of organ fates in vivo. Expression of Gcm2 in the thymic rudiment does not activate a parathyroid-specific expression programme, even in the absence of Foxn1 activity. Co-expression of Foxn1 in the parathyroid fails to impose thymopoietic capacity. We conclude that the actions of Foxn1 and Gcm2 transcription factors are cell context-dependent and that they each require permissive transcription factor landscapes in order to successfully interfere with organ-specific cell fate
Determining the heritability of ethanol-induced locomotor sensitization in mice using short-term behavioral selection
RATIONALE:
Sensitization to the locomotor stimulant effects of alcohol (ethanol) is thought to be a heritable risk factor for the development of alcoholism that reflects progressive increases in the positive motivational effects of this substance. However, very little is known about the degree to which genes influence this complex behavioral phenomenon.
OBJECTIVES:
The primary goal of this work was to determine the heritability of ethanol-induced locomotor sensitization in mice using short-term behavioral selection.
METHODS:
Genetically heterogeneous C57BL/6J (B6) × DBA/2J (D2) F2 mice were generated from B6D2F1 progenitors, phenotyped for the expression of locomotor sensitization, and bred for high (HLS) and low (LLS) expression of this behavior. Selective breeding was conducted in two independently generated replicate sets to increase the confidence of our heritability estimates and for future correlated trait analyses.
RESULTS:
Large and significant differences in locomotor sensitization between HLS and LLS lines were evident by the fourth generation. Twenty-two percent of the observed line difference(s) were attributable to genes (h² = .22). Interestingly, locomotor activity in the absence of ethanol was genetically correlated with ethanol sensitization; high activity was associated with high sensitization.
CONCLUSIONS:
That changes in ethanol sensitivity following repeated exposures are genetically regulated highlights the relevance of studies aimed at determining how genes regulate susceptibility to ethanol-induced behavioral and neural adaptations. As alcohol use and abuse disorders develop following many repeated alcohol exposures, these data emphasize the need for future studies determining the genetic basis by which changes in response to alcohol occur
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