841 research outputs found
Complex processing of primary aluminum to remove impurities of non-ferrous metals
The paper presents researches on the complex processing of primary aluminum produced by electrolysis with flux treatment with boron-containing materials and further filtration refining through granular filters. The research methods and applied instruments used for the analysis of the chemical composition and electron microscopy are described. The results are presented before and after the complex treatment of primary aluminum, showing a significant reduction in non-ferrous metal impurities (vanadium, titanium, etc.) and other undesirable impurities
Temperature Dependence of Magnetophonon Resistance Oscillations in GaAs/AlAs Heterostructures at High Filling Factors
The temperature dependence of phonon-induced resistance oscillations has been
investigated in two-dimensional electron system with moderate mobility at large
filling factors at temperature range T = 7.4 - 25.4 K. The amplitude of
phonon-induced oscillations has been found to be governed by quantum relaxation
time which is determined by electron-electron interaction effects. This is in
agreement with results recently obtained in ultra-high mobility two-dimensional
electron system with low electron density [A. T. Hatke et al., Phys. Rev. Lett.
102, 086808 (2009)]. The shift of the main maximum of the magnetophonon
resistance oscillations to higher magnetic fields with increasing temperature
is observed.Comment: 5 pages, 4 figure
Diffusive Radiation in One-dimensional Langmuir Turbulence
We calculate spectra of radiation produced by a relativistic particle in the
presence of one-dimensional Langmuir turbulence which might be generated by a
streaming instability in the plasma, in particular, in the shock front or at
the shock-shock interactions. The shape of the radiation spectra is shown to
depend sensitively on the angle between the particle velocity and electric
field direction. The radiation spectrum in the case of exactly transverse
particle motion is degenerate and similar to that of spatially uniform Langmuir
oscillations. In case of oblique propagation, the spectrum is more complex, it
consists of a number of power-law regions and may contain a distinct
high-frequency spectral peak. %at \omega=2\omega\pe \gamma^2. The emission
process considered is relevant to various laboratory plasma settings and for
astrophysical objects as gamma-ray bursts and collimated jets.Comment: 4 pages, 1 figure, accepted for Phys. Rev.
Determination properties of cast iron used in the installation of anodes
This paper presents the results of determining the cast ironâs properties, which is used in the installation of anodes in the electrolytic production of aluminum. The research methods and applied instruments used for metallographic analysis and chemical composition analysis are described. The results of metallographic analysis of cast iron microstructure âbeforeâ and âafterâ electrolysis are presented. The cast ironâs chemical composition was analyzed by using an X-ray fluorescence spectrometer. The results of experimental melting for testing the casting properties of cast iron for fluidity in a spiral sample are presented
Determination properties of cast iron used in the installation of anodes
This paper presents the results of determining the cast ironâs properties, which is used in the installation of anodes in the electrolytic production of aluminum. The research methods and applied instruments used for metallographic analysis and chemical composition analysis are described. The results of metallographic analysis of cast iron microstructure âbeforeâ and âafterâ electrolysis are presented. The cast ironâs chemical composition was analyzed by using an X-ray fluorescence spectrometer. The results of experimental melting for testing the casting properties of cast iron for fluidity in a spiral sample are presented
Magnetic fields in cosmic particle acceleration sources
We review here some magnetic phenomena in astrophysical particle accelerators
associated with collisionless shocks in supernova remnants, radio galaxies and
clusters of galaxies. A specific feature is that the accelerated particles can
play an important role in magnetic field evolution in the objects. We discuss a
number of CR-driven, magnetic field amplification processes that are likely to
operate when diffusive shock acceleration (DSA) becomes efficient and
nonlinear. The turbulent magnetic fields produced by these processes determine
the maximum energies of accelerated particles and result in specific features
in the observed photon radiation of the sources. Equally important, magnetic
field amplification by the CR currents and pressure anisotropies may affect the
shocked gas temperatures and compression, both in the shock precursor and in
the downstream flow, if the shock is an efficient CR accelerator. Strong
fluctuations of the magnetic field on scales above the radiation formation
length in the shock vicinity result in intermittent structures observable in
synchrotron emission images. Resonant and non-resonant CR streaming
instabilities in the shock precursor can generate mesoscale magnetic fields
with scale-sizes comparable to supernova remnants and even superbubbles. This
opens the possibility that magnetic fields in the earliest galaxies were
produced by the first generation Population III supernova remnants and by
clustered supernovae in star forming regions.Comment: 30 pages, Space Science Review
THE CASE OF Q-WAVE MYOCARDIAL INFARCTION IN A 35-YEARS-OLD FEMALE
The article presents a case of Q-wave myocardial infarction, in a young woman of 35 years old. The patient complained. of pains not typical for angina pectoris. Therefore, the initial diagnosis was incorrect. After 3 months myocardial infarction, of cicatrization, stage was diagnosed. For definition, of further tactics of treatment we used, coronary angiography and recommended, stenting of critical stenosis on left anterior descending artery. For prophylactics of this case electrocardiography should, be routinely used, in all the cases of pain in the neck and. thorax in young women
X-Rays from Accelerated Ion Interactions
We have developed in detail the theory of X-ray line and continuum production
due to atomic interactions of accelerated ions, incorporating in our
calculations information from a broad range of laboratory measurements. We
applied our calculations to the Orion region from which nuclear gamma-ray lines
were observed with the COMPTEL instrument on CGRO. The accelerated particles
which produce this gamma-ray emission via nuclear reactions also produce X-ray
lines via atomic interactions. We predict strong line emission in the range
from 0.5 to 1 keV, mainly due to de-excitations in fast O ions. While much of
the diffuse X-ray emission observed with ROSAT from Orion could be due to
accelerated ions, the current X-ray data do not provide unambiguous signatures
for such an origin. If future observations with high spectral resolution would
confirm the predicted X-rays, the combined analysis of the X-ray and gamma-ray
data will set important constraints on the origin of the accelerated particles
and their interaction model.Comment: 26 pages, 14 figure
Nonlinear shock acceleration beyond the Bohm limit
We suggest a physical mechanism whereby the acceleration time of cosmic rays
by shock waves can be significantly reduced. This creates the possibility of
particle acceleration beyond the knee energy at ~10^15eV. The acceleration
results from a nonlinear modification of the flow ahead of the shock supported
by particles already accelerated to the knee momentum at p ~ p_*. The particles
gain energy by bouncing off converging magnetic irregularities frozen into the
flow in the shock precursor and not so much by re-crossing the shock itself.
The acceleration rate is thus determined by the gradient of the flow velocity
and turns out to be formally independent of the particle mean free path
(m.f.p.). The velocity gradient is, in turn, set by the knee-particles at p ~
p_* as having the dominant contribution to the CR pressure. Since it is
independent of the m.f.p., the acceleration rate of particles above the knee
does not decrease with energy, unlike in the linear acceleration regime. The
reason for the knee formation at p ~ p_* is that particles with are
effectively confined to the shock precursor only while they are within limited
domains in the momentum space, while other particles fall into
``loss-islands'', similar to the ``loss-cone'' of magnetic traps. This
structure of the momentum space is due to the character of the scattering
magnetic irregularities. They are formed by a train of shock waves that
naturally emerge from unstably growing and steepening magnetosonic waves or as
a result of acoustic instability of the CR precursor. These losses steepen the
spectrum above the knee, which also prevents the shock width from increasing
with the maximum particle energy.Comment: aastex, 13 eps figure
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