2,224 research outputs found
Extra-large crystal emulsion detectors for future large-scale experiments
Photographic emulsion is a particle tracking device which features the best
spatial resolution among particle detectors. For certain applications, for
example muon radiography, large-scale detectors are required. Therefore, a huge
surface has to be analyzed by means of automated optical microscopes. An
improvement of the readout speed is then a crucial point to make these
applications possible and the availability of a new type of photographic
emulsions featuring crystals of larger size is a way to pursue this program.
This would allow a lower magnification for the microscopes, a consequent larger
field of view resulting in a faster data analysis. In this framework, we
developed new kinds of emulsion detectors with a crystal size of 600-1000 nm,
namely 3-5 times larger than conventional ones, allowing a 25 times faster data
readout. The new photographic emulsions have shown a sufficient sensitivity and
a good signal to noise ratio. The proposed development opens the way to future
large-scale applications of the technology, e.g. 3D imaging of glacier bedrocks
or future neutrino experiments.Comment: Version accepted for publication in JINS
Free vibration of a three-layered sandwich beam using the dynamic stiffness method and experiment
In this paper, an accurate dynamic stiffness model for a three-layered sandwich
beam of unequal thicknesses is developed and subsequently used to investigate
its free vibration characteristics. Each layer of the beam is idealised by the
Timoshenko beam theory and the combined system is reduced to a tenth-order
system using symbolic computation. An exact dynamic stiffness matrix is then
developed by relating amplitudes of harmonically varying loads to those of the
responses. The resulting dynamic stiffness matrix is used with particular
reference to the Wittrick-Williams algorithm to carry out the free vibration
analysis of a few illustrative examples. The accuracy of the theory is confirmed
both by published literature and by experiment. The paper closes with some
concluding remarks. (c) 2007 Elsevier Ltd. All rights reserved
Development of Nuclear Emulsion Detector for Muon Radiography
AbstractMuon radiography is the non-destructive testing technique of large-scale constructions with cosmic ray muon. Cosmic ray muon has high penetrating power and it always comes from the whole sky. In the same way of taking a X-ray photograph, we can obtain integrated density of constructions which thickness are several tens to several hundreds. We had ever applied this technique to nuclear reactors, volcanos, and so on. Nuclear emulsion is three dimensional track detector with micrometric position accuracy. Thanks to high position resolution, Nuclear emulsion has mrad angular resolution. In addition, the features which require no power supply and can observe in a large area suitable for muon radiography. In Nagoya University, we launched emulsion manufacturing equipment at 2010. It has become possible to flexible development of our detector and succeeded to development of high sensitive nuclear emulsion film (Nagoya emulsion). An important factor is the temperature characteristic to withstand the outdoor observation as a detector to be used in the muon radiography. There is a phenomenon of a latent image fading, whichit is well known in the photographic industry, and this phenomenon is known that temperature and water are involved. So we examined temperature and humidity characteristic of latent image fading about Nagoya emulsion. As a result, we found latent image fading is strongly depends on both temperature and humidity. By dehydrating emulsion film in RH8%, over 95% (Grain Density>40) detection efficiency of muon track keeps over 3months in 25degree, for 2months in 35degree. Additionally it was showed in this test that increasing back ground noise “fog”, which may have occurred by sealing emulsion film in a narrow space, is reduced by buffer space in the bag
Formation of the Terrestrial Planets from a Narrow Annulus
We show that the assembly of the Solar System terrestrial planets can be
successfully modelled with all of the mass initially confined to a narrow
annulus between 0.7 and 1.0 AU. With this configuration, analogues of Mercury
and Mars often form from the collisional evolution of material diffusing out of
the annulus under the scattering of the forming Earth and Venus analogues. The
final systems also possess eccentricities and inclinations that match the
observations, without recourse to dynamical friction from remnant small body
populations. Finally, the characteristic assembly timescale for Earth analogues
is rapid in this model, and consistent with cosmochemical models based on the
Hf--W isotopes. The agreement between this model and the
observations suggests that terrestrial planet systems may also be formed in
`planet traps', as has been proposed recently for the cores of giant planets in
our solar system and others.Comment: 37 pages, 16 figures. to appear in Ap
Aggregation number distributions and mesoglobules in dilute solutions of diblock and triblock copolymers
We investigate the aggregation number and size distributions for
inter-molecular clusters of amphiphilic diblock and triblock copolymers in poor
solvent at very low concentrations. Diblocks and triblocks with hydrophilic
ends are shown to possess narrow distributions corresponding to formation of
monodispersed mesoglobules. Diblocks with hydrophobic ends are found to produce
inter-cluster multimers due to bridging by the hydrophilic middle blocks,
resulting in polydisperse distributions. Implications of these observations for
preparation of monodispersed nanoparticles and, potentially, understanding of
the quaternary structure of proteins are discussed.Comment: 4 pages, 4 PS figures. Accepted for publication in EP
A local prescription for the softening length in self-gravitating gaseous discs
In 2D-simulations of self-gravitating gaseous discs, the potential is often
computed in the framework of "softened gravity" initially designed for N-body
codes. In this special context, the role of the softening length LAMBDA is
twofold: i) to avoid numerical singularities in the integral representation of
the potential (i.e., arising when the relative separation vanishes), and ii) to
acount for stratification of matter in the direction perpendicular to the disc
mid-plane. So far, most studies have considered LAMBDA as a free parameter and
various values or formulae have been proposed without much mathematical
justification. In this paper, we demonstrate by means of a rigorous calculus
that it is possible to define LAMBDA such that the gravitational potential of a
flat disc coincides at order zero with that of a geometically thin disc of the
same surface density. Our prescription for LAMBDA, valid in the local,
axisymmetric limit, has the required properties i) and ii). It is mainly an
analytical function of the radius and disc thickness, and is sensitive to the
vertical stratification. For mass density profiles considered (namely, profiles
expandable over even powers of the altitude), we find that LAMBDA : i) is
independant of the numerical mesh, ii) is always a fraction of the local
thickness H, iii) goes through a minimum at the singularity (i.e., at null
separation), and iv) is such that 0.13 < LAMBDA/H < 0.29 typically (depending
on the separation and on density profile). These results should help us to
improve the quality of 2D- and 3D-simulations of gaseous discs in several
respects (physical realism, accuracy, and computing time).Comment: accepted in A&A, 7 pages, 7 figures, web link for the F90 code and
on-line calculations :
http://www.obs.u-bordeaux1.fr/radio/JMHure/intro2single.ph
High-resolution tracking in a GEM-Emulsion detector
SHiP (Search for Hidden Particles) is a beam dump experiment proposed at the
CERN SPS aiming at the observation of long lived particles very weakly coupled
with ordinary matter mostly produced in the decay of charmed hadrons. The beam
dump facility of SHiP is also a copious factory of neutrinos of all three kinds
and therefore a dedicated neutrino detector is foreseen in the SHiP apparatus.
The neutrino detector exploits the Emulsion Cloud Chamber technique with a
modular structure, alternating walls of target units and planes of electronic
detectors providing the time stamp to the event. GEM detectors are one of the
possible choices for this task. This paper reports the results of the first
exposure to a muon beam at CERN of a new hybrid chamber, obtained by coupling a
GEM chamber and an emulsion detector. Thanks to the micrometric accuracy of the
emulsion detector, the position resolution of the GEM chamber as a function of
the particle inclination was evaluated in two configurations, with and without
the magnetic fiel
Right Inferior Frontal Activation During Alcohol-Specific Inhibition Increases With Craving and Predicts Drinking Outcome in Alcohol Use Disorder
Alcohol use disorder (AUD) is characterized by enhanced cue-reactivity and the opposing control processes being insufficient. The ability to inhibit reactions to alcohol-related cues, alcohol-specific inhibition, is thus crucial to AUD; and trainings strengthening this ability might increase treatment outcome. The present study investigated whether neurophysiological correlates of alcohol-specific inhibition (I) vary with craving, (II) predict drinking outcome in AUD and (III) are modulated by alcohol-specific inhibition training. A total of 45 recently abstinent patients with AUD and 25 controls participated in this study. All participants underwent functional magnetic resonance imaging (fMRI) during a Go-NoGo task with alcohol-related as well as neutral conditions. Patients with AUD additionally participated in a double-blind RCT, where they were randomized to either an alcohol-specific inhibition training or an active control condition (non-specific inhibition training). After the training, patients participated in a second fMRI measurement where the Go-NoGo task was repeated. Percentage of days abstinent was assessed as drinking outcome 3 months after discharge from residential treatment. Whole brain analyses indicated that in the right inferior frontal gyrus (rIFG), activation related to alcohol-specific inhibition varied with craving and predicted drinking outcome at 3-months follow-up. This neurophysiological correlate of alcohol-specific inhibition was however not modulated by the training version. Our results suggest that enhanced rIFG activation during alcohol-specific (compared to neutral) inhibition (I) is needed to inhibit responses when craving is high and (II) fosters sustained abstinence in patients with AUD. As alcoholspecific rIFG activation was not affected by the training, future research might investigate whether potential training effects on neurophysiology are better detectable with other methodological approaches
Pifithrin-alpha inhibits p53 signaling after interaction of the tumor suppressor protein with hsp90 and its nuclear translocation
Pifithrin-alpha (PFTalpha) was originally thought to be a specific inhibitor of signaling by the tumor suppressor protein p53. However, the laboratory that discovered pifithrin recently reported that the compound also inhibits heat shock and glucocorticoid receptor (GR) signaling, and they suggested that PFTalpha targets a factor common to all three signal transduction pathways, such as the hsp90/hsp70-based chaperone machinery (Komarova, E. A., Neznanov, N., Komarov, P. G., Chernov, M. V., Wang, K., and Gudkov, A. V. (2003) J. Biol. Chem. 278, 15465-15468). Because it is important for the mechanistic study of this machinery to identify unique inhibitors of chaperone action, we have examined the effect of PFTalpha on transcriptional activation, the hsp90 heterocomplex assembly, and hsp90-dependent nuclear translocation for both p53 and the GR. At concentrations where PFTalpha blocks p53-mediated induction of p21/Waf-1 in human embryonic kidney cells, we observed no inhibition of GR-mediated induction of a chloramphenicol acetyl transferase reporter in LMCAT cells. PFTalpha did, however, cause a left shift in the dexamethasone dose response curve by increasing intracellular dexamethasone concentration, apparently by competing for dexamethasone efflux from the cell. The assembly of p53 or GR heterocomplexes with hsp90 and immunophilins was not affected by PFTalpha either in vivo or in vitro and did not affect the nuclear translocation of either transcription factor. Thus, we conclude that PFTalpha does not inhibit GR-mediated induction or the function of the chaperone machinery, and, as originally thought, it may specifically inhibit p53 signaling by acting at a stage after p53 translocation to the nucleus.Fil: Murphy, Patrick J.. University of Michigan; Estados UnidosFil: Galigniana, Mario Daniel. University of Michigan; Estados Unidos. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas; ArgentinaFil: Morishima, Yoshihiro. University of Michigan; Estados UnidosFil: Harrell, Jennifer M.. University of Michigan; Estados UnidosFil: Kwok, Roland P.. University of Michigan; Estados UnidosFil: Ljungman, Mats. University of Michigan; Estados UnidosFil: Pratt, William B.. University of Michigan; Estados Unido
- …