864 research outputs found
Solid state bistable power switch
Tin and copper provide high current and switching time capabilities for high-current resettable fuses. They show the best performance for trip current and degree of reliability, and have low coefficients of thermal expansion
Solid state bistable power switch study
Feasibility of transforming solid state switches into high current resettable fuse
Response of single junction GaAs/GaAs and GaAs/Ge solar cells to multiple doses of 1 MeV electrons
A comparison of the radiation tolerance of MOCVD-grown GaAs cells and GaAs/Ge cells was undertaken using 1 MeV electrons. The GaAs/Ge cells are somewhat more tolerant of 1 MeV electron irradiation and more responsive to annealing than are the GaAs/GaAs cells examined in this study. However, both types of cells suffer a greater degradation in efficiency than has been observed in other recent studies. The reason for this is not certain, but it may be associated with an emitter thickness which appears to be greater than desired. The deep level transient spectroscopy (DLTS) spectra following irradiation are not significantly different for the GaAs/Ge and the GaAs/GaAs cells, with each having just two peaks. The annealing behavior of these peaks is also similar in the two samples examined. It appears that no penalty in radiation tolerance, and perhaps some benefit, is associated with fabricating MOCVD GaAs cells on Ge substrates rather than GaAs substrates
Slovac Republic repository of radioactive waste
The Slovac Republic Repository of Radioactive Waste (radwaste) in place Mochovce presents a multi-barrier repository of the surface type designed as an ultimate storage of treated solid and fixed, low-and very low-level radwaste generated during the operation and decommissioning of the nuclear power plants, in research institutes, laboratories and hospitals in the Slovak Republic. The isolation of the radwaste and retardation of the radionuclides are provided by the barrier system of the repository. To assess the complete system and parts of one of the most important barriers – the multi-barrier ultimate shielding of the repository – the model of the ultimate shielding of the repository was designed. The monitoring results of the model “ in situ“ will be applicable for projecting the ultimate shielding of the repository
The coupling of a young stellar disc with the molecular torus in the Galactic centre
The Galactic centre hosts, according to observations, a number of early-type
stars. About one half of those which are orbiting the central supermassive
black hole on orbits with projected radii 0.03 pc form a coherently
rotating disc. Observations further reveal a massive gaseous torus and a
significant population of late-type stars. In this paper, we investigate, by
means of numerical N-body computations, the orbital evolution of the stellar
disc, which we consider to be initially thin. We include the gravitational
influence of both the torus and the late-type stars, as well as the
self-gravity of the disc. Our results show that, for a significant set of
system parameters, the evolution of the disc leads, within the lifetime of the
early-type stars, to a configuration compatible with the observations. In
particular, the disc naturally reaches a specific - perpendicular - orientation
with respect to the torus, which is indeed the configuration observed in the
Galactic centre. We, therefore, suggest that all the early-type stars may have
been born within a single gaseous disc.Comment: Accepted for publication in MNRAS; 9 pages, 4 figures, 1 tabl
Impaired object-location learning and recognition memory but enhanced sustained attention in M2 muscarinic receptor-deficient mice
© 2018, The Author(s). Rationale: Muscarinic acetylcholine receptors are known to play key roles in mediating cognitive processes, and impaired muscarinic cholinergic neurotransmission is associated with normal ageing processes and Alzheimer’s disease. However, the specific contributions of the individual muscarinic receptor subtypes (M1–M5) to cognition are presently not well understood. Objectives: The aim of this study was to investigate the contribution of M2-type muscarinic receptor signalling to sustained attention, executive control and learning and memory. Methods: M2 receptor-deficient (M2−/−) mice were tested on a touchscreen-operated task battery testing visual discrimination, behavioural flexibility, object-location associative learning, attention and response control. Spontaneous recognition memory for real-world objects was also assessed. Results: We found that M2−/− mice showed an enhancement of attentional performance, but significant deficits on some tests of learning and memory. Executive control and visual discrimination were unaffected by M2-depletion. Conclusions: These findings suggest that M2 activation has heterogeneous effects across cognitive domains, and provide insights into how acetylcholine may support multiple specific cognitive processes through functionally distinct cholinergic receptor subtypes. They also suggest that therapeutics involving M2 receptor-active compounds should be assessed across a broad range of cognitive domains, as they may enhance some cognitive functions, but impair others
NACO/SAM observations of sources at the Galactic Center
Sparse aperture masking (SAM) interferometry combined with Adaptive Optics
(AO) is a technique that is uniquely suited to investigate structures near the
diffraction limit of large telescopes. The strengths of the technique are a
robust calibration of the Point Spread Function (PSF) while maintaining a
relatively high dynamic range. We used SAM+AO observations to investigate the
circumstellar environment of several bright sources with infrared excess in the
central parsec of the Galaxy. For our observations, unstable atmospheric
conditions as well as significant residuals after the background subtraction
presented serious problems for the standard approach of calibrating SAM data
via interspersed observations of reference stars. We circumvented these
difficulties by constructing a synthesized calibrator directly from sources
within the field-of-view. When observing crowded fields, this novel method can
boost the efficiency of SAM observations because it renders interspersed
calibrator observations unnecessary. Here, we presented the first NaCo/SAM
images reconstructed using this method.Comment: 8 pages, 10 figures, proceedings of the conference "Astrophysics at
High Angular Resolution" (AHAR-2011
Slovac Republic repository of radioactive waste
The Slovac Republic Repository of Radioactive Waste (radwaste) in place Mochovce presents a multi-barrier repository of the surface type designed as an ultimate storage of treated solid and fixed, low-and very low-level radwaste generated during the operation and decommissioning of the nuclear power plants, in research institutes, laboratories and hospitals in the Slovak Republic. The isolation of the radwaste and retardation of the radionuclides are provided by the barrier system of the repository. To assess the complete system and parts of one of the most important barriers – the multi-barrier ultimate shielding of the repository – the model of the ultimate shielding of the repository was designed. The monitoring results of the model “ in situ“ will be applicable for projecting the ultimate shielding of the repository
High angular resolution integral-field spectroscopy of the Galaxy's nuclear cluster: a missing stellar cusp?
We report on the structure of the nuclear star cluster in the innermost 0.16
pc of the Galaxy as measured by the number density profile of late-type giants.
Using laser guide star adaptive optics in conjunction with the integral field
spectrograph, OSIRIS, at the Keck II telescope, we are able to differentiate
between the older, late-type ( 1 Gyr) stars, which are presumed to be
dynamically relaxed, and the unrelaxed young ( 6 Myr) population. This
distinction is crucial for testing models of stellar cusp formation in the
vicinity of a black hole, as the models assume that the cusp stars are in
dynamical equilibrium in the black hole potential. Based on the late-type stars
alone, the surface stellar number density profile, , is flat, with . Monte Carlo simulations of
the possible de-projected volume density profile, n(r) ,
show that is less than 1.0 at the 99.73 % confidence level. These
results are consistent with the nuclear star cluster having no cusp, with a
core profile that is significantly flatter than predicted by most cusp
formation theories, and even allows for the presence of a central hole in the
stellar distribution. Of the possible dynamical interactions that can lead to
the depletion of the red giants observable in this survey -- stellar
collisions, mass segregation from stellar remnants, or a recent merger event --
mass segregation is the only one that can be ruled out as the dominant
depletion mechanism. The lack of a stellar cusp around a supermassive black
hole would have important implications for black hole growth models and
inferences on the presence of a black hole based upon stellar distributions.Comment: 35 pages, 5 tables, 12 figures, accepted by Ap
Gamma-Ray Emission from PWNe Interacting with Molecular Clouds
We consider a situation in which a pulsar (and its nebula) is formed inside
or close to a high density regions of a molecular cloud. We apply a recent
model for the gamma radiation of pulsar wind nebulae (PWN), which includes not
only radiation processes due to injected leptons but also processes due to
injection of relativistic hadrons, in order to calculate the expected gamma-ray
emission from such interacting PWNe. The example calculations have been
performed for two objects of this type from which directions TeV gamma-ray
sources have recently been observed (IC443 and W41). We show that the gamma-ray
emission below a few TeV can be produced by leptons accelerated in the past in
the vicinity of the pulsars. gamma-rays with energies above ~10 TeV can be
produced by hadrons interacting with the matter inside the supernova remnant
and surrounding dense clouds. In contrary to the low energy TeV emission, this
high energy TeV emission should be correlated with the location of dense clouds
able to capture hadrons due to their strong magnetic fields.Comment: Proceedings of the 30th ICRC, Merida, Mexico, 2007, in pres
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