1,746 research outputs found
Cosmic Rays from Gamma Ray Bursts in the Galaxy
The rate of terrestrial irradiation events by galactic gamma-ray bursts
(GRBs) is estimated using recent standard-energy results. We assume that GRBs
accelerate high-energy cosmic rays, and present results of three-dimensional
simulations of cosmic rays moving in the Galactic magnetic field and diffusing
through pitch-angle scattering. An on-axis GRB extinction event begins with a
powerful prompt gamma-ray and neutron pulse, followed by a longer-lived phase
from cosmic-ray protons and neutron-decay protons that diffuse towards Earth.
Our results force a reinterpretation of reported ~ 10^{18} eV cosmic-ray
anisotropies and offer a rigorous test of the model where high-energy cosmic
rays originate from GRBs, which will soon be tested with the Auger Observatory.Comment: 9 pages, 4 figures, ApJ Letters, in press. Clarified limit of
test-particle approximation, prediction that Auger will not confirm SUGAR
source. (Data may not appear onscreen at low magnification.) Simulations at
http://heseweb.nrl.navy.mil/gamma/~dermer/invest/sim/index.ht
Models and phenomenology
It is evident that models of the knee should match the observational
phenomenology. In this talk I discuss a few aspects of phenomenology, which are
important not only for the understanding of the knee origin, but also for the
general problem of the origin of cosmic rays. Among them are the shape of the
energy spectrum, its irregularity, the sharpness of the knee and its fine
structure. The classification of models is given and some examples of the most
recent models are discussed. The most probable conclusion deduced from this
examination is that the knee has an astrophysical origin and the so called
'source' models of the knee are most likely among them.Comment: 13 pages, 4 figures, overview talk at 19th European Cosmic Ray
Symposium, Firenze, Italy, 30.08-4.09.2004 (to be published in the
Int.J.Mod.Phys.A
Efectos de tamaño en de hierro ultrafino. Nuevas estructuras: 2D - 3D
This article is devoted to the analysis of the size of iron nanoparticles impact on the structure, to comparison of the results obtained for the nanopowders in the various authors’ researches. The article considers factors that may impact on the form and parameters of the Mössbauer spectra of iron nanopowders obtained by the inert gas condensation technique (Gen-Miller’s method). Possible causes of the new state of the iron are proved with the effective magnetic field at the 57 Fe nucleus (H=365 kOe). But the results related to size effects differ from the researches of other authors. It was revealed that nanoparticles with a mean (X-ray data) particle size of 50 nm have also Angstrem patterns, which can meet the new structure. Presence of small amounts of superparamagnetic oxide could be a catalyst, impetus for the formation of the new structure, and also, at the exchange interactions, could modify the charge of the electron density at the Fe nuclei. Reviewed and other factors can result in appearing of such a high value of the effective magnetic field at the iron nuclei.Este artículo se dedica al análisis del impacto del tamaño de nanopartículas de hierro en su estructura y a la comparación de los resultados obtenidos para los nanopolvos en estudios llevado a cabo por autores diferentes. Aquí también se consideran los factores que pueden afectar la forma y los parámetros de los espectros Mössbauer del nanopolvo de hierro producido por medio de condensar el gas inerte (método Gen-Miller). Se demuestran las causas posibles del estado nuevo del hierro a través de un campo magnético efectivo para el nucleo de 57 Fe (H=365 kOe). Pero los resultados relacionados a efectos del tamaño son diferentes de lo obtenido por otros autores. Se revela que los nanopartículas del tamaño medio de 50 nm (datos de examinaciones con rayos X) también tienen modelos Angstrem que pueden corresponden a la estructura nueva. La ocurrencia del óxido superparamagnético en cantidades pequeñas puede catalizar la formación de la estructura nueva y también, en caso de interacciones de intercambio, modificar la carga de la densidad del electrón en el núcleo de Fe. Los factores examinados y otros factores pueden resultar en la generación del campo magnético de un alta intensidad alrededor del núcleo de hierro
Behavioral phenotyping of mice deficient for tumor necrosis factor
The tumor necrosis factor (TNF) is a cytokine exerting both homeostatic and pathophysiological roles in the central nervous system (CNS). It has been demonstrated that TNF plays roles in such diseases as Alzheimer’s disease, Parkinson’s disease and multiple sclerosis. Nevertheless, the role of TNF in the CNS under normal physiological conditions is poorly studied. A novel mouse strain with TNF deficiency (TNFKO) was developed in S.A. Nedospasov’s laboratory of Engelhardt Institute of Molecular Biology of the Russian Academy of Sciences on the C57Bl/6 (WT) background. In our study, we compared the behavior of TNFKO and WT adult mice in a battery of tests: open-field, elevated plus-maze and the forced-swim test. We showed that TNF deficiency had no effect on locomotor activity or exploration in the openfield test. At the same time, in this test, TNFKO mice spent more time in the center of the arena, but had a higher level of defecation and lower rearing duration. This result indicates that, in the openfield conditions, TNFKO mice show disorientation rather than anxiety-like behavior. There were no differences between TNFKO and WT in anxiety level in the elevated plus-maze test or in depressive-like behavior in the forcedswim test. These data suggest that TNF deficiency leads to changes in neurofunctional interactions that alter the mouse response to mild stress in the open-field test
Developing technological process of obtaining giality casts
The article considers the process of manufacturing castings using sand-resin forms and alloying furnace. Were the optimal technological parameters of manufacturing shell molds for the manufacture of castings of heating equipment. Using the same upon receipt of castings by casting in shell molds furnace alloying and deoxidation of the metal will provide consumers with quality products and have a positive impact on the economy in general engineering
Conducting and automating the water Morris maze test in SPF conditions
The water Morris maze is the basic test to study the spatial ability to learn as well as spatial memory in laboratory rodents. It is a part of a series of tests necessary for behavioral phenotyping of mutant and transgenic mice. At the same time, conducting this test in SPF conditions must comply with very strict regulations concerning pathogen control. A white animal on the surface of whitened water is low contrast and this does not allow the animal to be traced automatically, which represents yet another major problem. A unique installation based on EthoStudio has been developed at the Institute of Cytology and Genetics SB RAS and the Institute of Automation and Electrometry SB RAS. This installation automates the process of tracing mice of any coat color in SPF conditions. This includes a setup to install a plastic water reservoir (110×40 cm), a digital camera and a light source. Water to fill the reservoir was sterilized using a Van Erp Blue Lagoon UV-C Tech 15000 ultraviolet decontaminator. The image of an animal was processed in a frame-by-frame fashion using the EthoStudio program, with the following parameters calculated: latent release time, route covered, cumulative distance to the platform and the time spent in the reservoir sectors. With this installation, we were able to study the spatial ability to learn and spatial memory in mice of the C57BL/6 strain and in mice of the C57BL/6/ Kaiso strain developed on the C57BL/6 background, with the gene encoding the methyl-DNA binding Kaiso protein knocked-out. It has been demonstrated that mice of these strains are able to learn to find the platform in the water Morris maze and have the location of the platform in their memory for at least the next four days
Investigation of the effect of high strength strips steel modification with rare-earth metal (REM)
The present work describes the study on influence of modifying steel with rare-earth metals on metallurgical quality of ingots and finished steel. To achieve the assigned task, the laboratory melting of 08G2NMDFBT (Х100) pipe steel was carried as in open (UIP 100 – 2,4), so in vacuum induction furnace (ISV-0,01 - PI) with use of conditioning agents, which contain rare-earth metals. Next materials were used as conditioning agents: mischmetal (MM), which contain total amount of rare-earth metal (REM) up to 93 %, АlPCIr and RENTN which contain total amount of from 31 to 32,6 %
Pharmacokinetic studies derived indole SS-68 with antiarrhythmic and antianginal properties
A method of quantitative determination of SS-68 derivative of indole in rabbit blood plasma by high performance liquid chromatography with tandem mass spectrometric detector (HPLCMS/ MS). Conducted pharmacokinetic studies SS-68 in the body of rabbits. Set the main pharmacokinetic parameters of the substance that allow you to optimize the future use of it’s as a potential drug in cardiology practic
The Geometry and Moduli of K3 Surfaces
These notes will give an introduction to the theory of K3 surfaces. We begin
with some general results on K3 surfaces, including the construction of their
moduli space and some of its properties. We then move on to focus on the theory
of polarized K3 surfaces, studying their moduli, degenerations and the
compactification problem. This theory is then further enhanced to a discussion
of lattice polarized K3 surfaces, which provide a rich source of explicit
examples, including a large class of lattice polarizations coming from elliptic
fibrations. Finally, we conclude by discussing the ample and Kahler cones of K3
surfaces, and give some of their applications.Comment: 34 pages, 2 figures. (R. Laza, M. Schutt and N. Yui, eds.
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