289 research outputs found
Stellar explosions powered by the Blandford-Znajek mechanism
In this letter we briefly describe the first results of our numerical study
on the possibility of magnetic origin of relativistic jets of long duration
gamma ray bursters within the collapsar scenario. We track the collapse of
massive rotating stars onto a rotating central black hole using axisymmetric
general relativistic magnetohydrodynamic code that utilizes a realistic
equation of state of stellar matter, takes into account the cooling associated
with emission of neutrinos, and the energy losses due to dissociation of
nuclei. The neutrino heating is not included. We describe the solution for one
particular model where the progenitor star has magnetic field G. The
solution exhibits strong explosion driven by the Poynting-dominated jets whose
power exceeds . The jets originate mainly from the
black hole and they are powered via the Blandford-Znajek mechanism. The full
details of the simulations together with the results of parameter study will be
presented elsewhere. A number of simulation movies can be downloaded from
http://www.maths.leeds.ac.uk/~serguei/research/movies/anim.htmlComment: minor revision, accepted by MNRAS Letters, simulation movies can be
downloaded from
http://www.maths.leeds.ac.uk/~serguei/research/movies/anim.htm
Magnetic acceleration of ultra-relativistic GRB and AGN jets
We present numerical simulations of cold, axisymmetric, magnetically driven
relativistic outflows. The outflows are initially sub-Alfv\'enic and Poynting
flux-dominated, with total--to--rest-mass energy flux ratio up to . To study the magnetic acceleration of jets we simulate flows confined
within a funnel with rigid wall of prescribed shape, which we take to be
(in cylindrical coordinates, with ranging from 1 to 2). This
allows us to eliminate the numerical dissipative effects induced by a free
boundary with an ambient medium. We find that in all cases they converge to a
steady state characterized by a spatially extended acceleration region. For the
jet solutions the acceleration process is very efficient - on the outermost
scale of the simulation more than half of the Poynting flux has been converted
into kinetic energy flux, and the terminal Lorentz factor approached its
maximum possible value (). The acceleration is
accompanied by the collimation of magnetic field lines in excess of that
dictated by the funnel shape. The numerical solutions are generally consistent
with the semi-analytic self-similar jets solutions and the spatially extended
acceleration observed in some astrophysical relativistic jets. In agreement
with previous studies we also find that the acceleration is significantly less
effective for wind solutions suggesting that pulsar winds may remain Poynting
dominated when they reach the termination shock.Comment: 4 pages, 3 figures, HEPRO-2007 Dubli
The origin of peculiar jet-torus structure in the Crab nebula
Recent discoveries of the intriguing ``jet-torus'' structure in the Crab
Nebula and other pulsar nebulae prompted calls for re-examining of their
theory. The most radical proposals involve abolishing of the MHD approximation
altogether and developing of purely electromagnetic models. However, the
classical MHD models of the Crab Nebula were hampered by the assumption of
spherical symmetry made in order to render the flow equations easily
integrable. The impressive progress in computational relativistic
magnetohydrodynamics in recent years has made it possible to study the Crab
nebula via numerical simulations without making such a drastic simplification
of the problem. In this letter we present the results of the first study of
such kind. They show that the jet-torus pattern can be explained within MHD
approximation when anisotropy of pulsar winds is taken into account. They also
indicate that the flow in the nebula is likely to be much more intricate than
it has been widely believed.Comment: Rejected by Nature, submitted to MNRAS Letter
Chemical vapor deposition of 2D crystallized g‑C3N4 layered films
We have developed a technology and for the first time, present here, the fabrication of continuous two-dimensionally crystallized g-C3N4 layered thin films oriented in a hexagonal lattice c-plane on glass and monocrystalline silicon substrates using chemical vapor deposition from a melamine source. Scanning electron microscopy and X-ray diffraction studies revealed that such films with a smooth surface and good crystalline quality as thick as up to 1.2 μm can be formed at a synthesis temperature of 550–625 °C. They are transparent in the visible range and demonstrate intense photoluminescence (PL) at room temperature. It was found that the band gap of the obtained material and its PL spectral range are shifting to the lower energies at high synthesis temperatures. Oriented g-C3N4 layered thin films deposited on flat solid substrates are promising for integrated electronics and optoelectronics
Influence of single amino acid substitutions in the hemagglutinin on the antigenic and receptor-binding properties of influenza virus B/Florida/04/2006 of Yamagata-like evolutionary lineage
Influenza A and B viruses use sialylated oligosaccharide chains expressed on the surface of a host cell as the cell entry receptors. The type of the bond between sialic acid (SA) and the neighboring galactose residue (Gal) is one of the main characteristics that define the type of receptor. Influenza viruses recognize SAα2-3Gal- or SAα2-6Gal-structures on the surface of the cells. Influenza A viruses of avian origin bind α2-3-sialylated glycans, while the human strains bind preferentially α2-6-sialylated ones. However, the receptor-binding specificity of influenza B viruses has not been characterized sufficiently so far. In this study, we selected the escape mutants of influenza B/Florida/04/2006 strain (Yamagata-like lineage) using monoclonal antibodies (mAb) to hemagglutinin (HA). The analysis of the amino acid sequences of mAb-induced escape mutants revealed the single amino acid substitutions 40Tyr→His, 85His→Tyr, 202Asn→Lys and 242Ser→Arg in 10F4-, 8Н11-, 8Н3- and 9А3-induced HA variants, correspondingly. It was shown that the single amino acid substitutions 202Asn→Lys and 242Ser→Arg alter the receptor-binding specificity of the influenza B virus. These findings are important for the understanding of the influence of individual amino acid residues in HA on the receptor-binding properties of influenza B Yamagata-like lineage viruses and allow us to predict the possible ways of their evolution.Influenza A and B viruses use sialylated oligosaccharide chains expressed on the surface of a host cell as the cell entry receptors. The type of the bond between sialic acid (SA) and the neighboring galactose residue (Gal) is one of the main characteristics that define the type of receptor. Influenza viruses recognize SAα2-3Gal- or SAα2-6Gal-structures on the surface of the cells. Influenza A viruses of avian origin bind α2-3-sialylated glycans, while the human strains bind preferentially α2-6-sialylated ones. However, the receptor-binding specificity of influenza B viruses has not been characterized sufficiently so far. In this study, we selected the escape mutants of influenza B/Florida/04/2006 strain (Yamagata-like lineage) using monoclonal antibodies (mAb) to hemagglutinin (HA). The analysis of the amino acid sequences of mAb-induced escape mutants revealed the single amino acid substitutions 40Tyr→His, 85His→Tyr, 202Asn→Lys and 242Ser→Arg in 10F4-, 8Н11-, 8Н3- and 9А3-induced HA variants, correspondingly. It was shown that the single amino acid substitutions 202Asn→Lys and 242Ser→Arg alter the receptor-binding specificity of the influenza B virus. These findings are important for the understanding of the influence of individual amino acid residues in HA on the receptor-binding properties of influenza B Yamagata-like lineage viruses and allow us to predict the possible ways of their evolution
Mutations in human genes that increase the risk for severe influenza infection
The system of genetic control of innate immune responses to influenza infection and gene function allows for the development of systemic treatment of influenza with a focus on the phenotype of mutations based on individual genetic susceptibility to severe disease and/or the development of complications.The system of genetic control of innate immune responses to influenza infection and gene function allows for the development of systemic treatment of influenza with a focus on the phenotype of mutations based on individual genetic susceptibility to severe disease and/or the development of complications
Production of solid dosage forms of immunoglobulin products
At the moment, there are no scientific publications devoted to the technological aspects of production of immunoglobulin solid dosage forms. The aim of the study was to review Russian and foreign literature on production of immunoglobulin solid dosage forms, and present the results of the authors’ own research. The authors analysed data of the National Register of Medicines of the Russian Federation as of mid-2021 on the authorised medicines with a generic name ‘globulin in a solid dosage form’, and summarised their characteristics. They reviewed data on the qualitative and quantitative composition of excipients used in lyophilisation, preparation of tablets and capsules. A number of examples were used to illustrate the effect of technological parameters of immunoglobulin solid form production on the quality of the finished products. It was demonstrated that the production of solid forms of immunoglobulin products prevents aggregation and fragmentation of proteins during storage, which affect the product’s specific activity, and also help to preserve the product’s target characteristics for a longer period of time as compared to liquid dosage forms of immunoglobulins. The results of the study may be used as a basis for development of a manufacturing technology for solid forms of immunoglobulin products
Relativistic spine jets from Schwarzschild black holes: "Application to AGN radioloud sources"
The two types of Fanaroff-Riley radio loud galaxies, FRI and FRII, exhibit
strong jets but with different properties. These differences may be associated
to the central engine and/or the external medium. Aims: The AGN classification
FRI and FRII can be linked to the rate of electromagnetic Poynting flux
extraction from the inner corona of the central engine by the jet. The
collimation results from the distribution of the total electromagnetic energy
across the jet, as compared to the corresponding distribution of the thermal
and gravitational energies. We use exact solutions of the fully relativistic
magnetohydrodynamical (GRMHD) equations obtained by a nonlinear separation of
the variables to study outflows from a Schwarzschild black hole corona. A
strong correlation is found between the jet features and the energetic
distribution of the plasma of the inner corona which may be related to the
efficiency of the magnetic rotator. It is shown that observations of FRI and
FRII jets may be partially constrained by our model for spine jets. The
deceleration observed in FRI jets may be associated with a low magnetic
efficiency of the central magnetic rotator and an important thermal confinement
by the hot surrounding medium. Conversely, the strongly collimated and
accelerated FRII outflows may be self collimated by their own magnetic field
because of the high efficiency of the central magnetic rotator.Comment: Accepted for publication in the A&
Experimental Substantiation of Cultural Technologies Introduction into Manufacturing of Anti-Rabies Immunoglobulin
The review provides information on the major outcomes of research and development work, performed within the frames of the Federal Target Program “National system of chemical and biological safety” (2009-2014), aimed at elaboration and introduction of cultural techniques into the manufacturing of anti-rabies immunoglobulin. Described are the key phases in methodology engineering, deployed for the large-scale cultivation of fixed rabies virus, concentration of cultural liquid, quantitation of rabies virus using PCR, and immunization of producers. Obtained pilot batches of the enhanced anti-rabies immunoglobulin, complying with normative requirements to commercial formulations, testify to the effectiveness of the developed biotechnological and methodological procedures, as well as of the designed engineering-manufacturing project documentation
Magnetic fileds of coalescing neutron stars and the luminosity function of short gamma-ray burst
Coalescing neutron star binaries are believed to be the most reliable sources
for ground-based detectors of gravitational waves and likely progenitors of
short gamma-ray bursts. In the process of coalescence, magnetic fields of
neutron stars can induce interesting observational manifestations and affect
the form of gravitational wave signal. In this papaer we use the population
synthesis method to model the expected distribution of neutron star magnetic
fields during the coalescence under different assumptions on the initial
parameters of neutron stars and their magnetic field evolution. We discuss
possible elecotrmagnetic phenomena preceding the coalescence of magnetized
neutron star binaries and the effect of magnetic field on the gravitational
wave signal. We find that a log-normal (Gaussian in logarithms) distribution of
the initial magnetic fields of neutron stars, which agrees with observed
properties of radio pulsars, produces the distribution of the magnetic field
energy during the coalescence that adequately describes the observed luminosity
function of short gamma-ray bursts under different assumptions on the field
evolution and initial parameters of neutron stars. This agreement lends further
support to the model of coalescing neutron star binaries as progenitors of
gamma-ray bursts.Comment: v.2, LATEX, 25 pages, inc. 7 ps figures, Astron. Lett., in press.
Typos corrected, reference adde
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