320 research outputs found
Synthesis of Nanoparticles of Fe-Co-Ni Three-component Alloy Capsulated Into Carbon Matrix of Fe-Co-Ni/C Nanocomposites
Nanoparticles of Fe-Co-Ni three-component alloy capsulated into carbon matrix were synthesized. Structure, phase composition and magnetic properties of obtained materials were defined by diffractometry and magnetometry. It was established that composition of nanoparticles is determine by synthesis temperature, because nanoparticles of three-component alloy are forms by dissolution of cobalt in Fe-Ni alloy. Magnetization of Fe-Co-Ni/C nanocomposites and coercive force increases from 26 up to 58 A·m2/kg during
temperature increase that relates with growth of particles size and increase of cobalt content in the alloy
Synthesis of Nanoparticles of Fe-Co-Ni Three-component Alloy Capsulated Into Carbon Matrix of Fe-Co-Ni/C Nanocomposites
Nanoparticles of Fe-Co-Ni three-component alloy capsulated into carbon matrix were synthesized. Structure, phase composition and magnetic properties of obtained materials were defined by diffractometry and magnetometry. It was established that composition of nanoparticles is determine by synthesis temperature, because nanoparticles of three-component alloy are forms by dissolution of cobalt in Fe-Ni alloy. Magnetization of Fe-Co-Ni/C nanocomposites and coercive force increases from 26 up to 58 A·m2/kg during
temperature increase that relates with growth of particles size and increase of cobalt content in the alloy
Conditins for the Time Dissipative Structure Formation at Nonequilibrium Transitions
We discuss processes of the dissipative structure formation when the nonequilibrium phase transition takes place. The model is considered under assumptions that dispersion of the relaxation time of the order parameter and influence of the external force present. It was found that self-organization occurs through the Hopf bifurcation and results in the dissipative structure formation. Analysis was performed according to the Lyapunov and Floquet exponent investigation. It was found that the complex picture of ordering with two reentrant Hopf bifurcations occurs.
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Cytogenetic effects of neutron therapy in patients with parotid gland tumors and relapse of breast cancer
Aim:To assess the frequency and spectrum of chromosome aberrations and micronuclei in peripheral blood lymphocytes of patients with parotid salivary gland tumors and relapse of breast cancer during the course of neutron therapy. Materials and Methods: Samples of peripheral blood were obtained from 9 patients with parotid salivary gland tumors (T3N0–3M0) and 8 patients with relapse of breast cancer before, after first fraction and at the end of neutron therapy. The treatment course specified 5.5–8.4 Gy (equivalent to 23–44 Gy of photon irradiation) with 1.3–2.2 Gy per fraction for patients with parotid salivary gland tumors and 4,8–8.0 Gy (equivalent to 30–40 Gy of photon irradiation) with 1.6 Gy per fraction for patients with relapse of breast cancer. Control group established for conventional cytogenetic analysis consisted of 15 healthy persons. Assessment of chromosome aberrations frequency was performed on routinely stained metaphase plates. Lymphocytes from the same patients were analyzed by micronucleus test in combination with fluorescent in situ hybridization (FISH) using pancentromeric DNA probe. Results: Level of chromosome aberrations and micronuclei significantly increased in lymphocytes of patients from both groups during neutron therapy (P < 0.05). This increase was mainly due to chromosome-type aberrations and centromere-negative micronuclei. The prevalent types of aberrations are in agreement with theoretical mechanisms of neutron effects on cells. Conclusion: Cytogenetic effects of fast neutron therapy in lymphocytes of patients with parotid salivary gland tumors and relapse of breast cancer were observed. A positive dynamics of radiation-induced chromosomal damages formation during the course was denoted in lymphocytes of cancer patients in both groups
Relativistic many-body calculations of electric-dipole matrix elements, lifetimes and polarizabilities in rubidium
Electric-dipole matrix elements for ns-n'p, nd-n'p, and 6d-4f transitions in
Rb are calculated using a relativistic all-order method. A third-order
calculation is also carried out for these matrix elements to evaluate the
importance of the high-order many-body perturbation theory contributions. The
all-order matrix elements are used to evaluate lifetimes of ns and np levels
with n=6, 7, 8 and nd levels with n=4, 5, 6 for comparison with experiment and
to provide benchmark values for these lifetimes. The dynamic polarizabilities
are calculated for ns states of rubidium. The resulting lifetime and
polarizability values are compared with available theory and experiment.Comment: 8 pages, 2 figure
The process in the energy range 2E_0=1.04 - 1.38 GeV
In the experiment with the SND detector at VEPP-2M e^+e^- collider the
process was studied in the energy range 2E_0 from
1.04 to 1.38 GeV. A broad peak was observed with the visible mass
MeV and cross section in the maximum
nb. The peak can be interpreted as a -like resonance .Comment: 10 pages LATEX and 5 figure
Accurate spline solutions of the Dirac equation with parity-nonconserving potential
The complete system of the B-spline solutions for the Dirac equation with the
parity-nonconserving (PNC) weak interaction effective potential is obtained.
This system can be used for the accurate evaluation of the radiative
corrections to the PNC amplitudes in the multicharged ions and neutral atoms.
The use of the scaling procedure allows for the evaluation of the PNC matrix
elements with relative accuracy .Comment: 7 page
A Circulating Hydrogen Ultra-High Purification System for the MuCap Experiment
The MuCap experiment is a high-precision measurement of the rate for the
basic electroweak process of muon capture, mu- + p -> n + nu . The experimental
approach is based on an active target consisting of a time projection chamber
(TPC) operating with pure hydrogen gas. The hydrogen has to be kept extremely
pure and at a stable pressure. A Circulating Hydrogen Ultrahigh Purification
System was designed at the Petersburg Nuclear Physics Institute (PNPI) to
continuously clean the hydrogen from impurities. The system is based on an
adsorption cryopump to stimulate the hydrogen flow and on a cold adsorbent for
the hydrogen cleaning. It was installed at the Paul Scherrer Institute (PSI) in
2004 and performed reliably during three experiment runs. During several months
long operating periods the system maintained the hydrogen purity in the
detector on the level of 20 ppb for moisture, which is the main contaminant,
and of better than 7 ppb and 5 ppb for nitrogen and oxygen, respectively. The
pressure inside the TPC was stabilized to within 0.024% of 10 bar at a hydrogen
flow rate of 3 standard liters per minute.Comment: submitted to Nucl. Instr. Methods Phys. Res.
Precise calculation of parity nonconservation in cesium and test of the standard model
We have calculated the 6s-7s parity nonconserving (PNC) E1 transition
amplitude, E_{PNC}, in cesium. We have used an improved all-order technique in
the calculation of the correlations and have included all significant
contributions to E_{PNC}. Our final value E_{PNC} = 0.904 (1 +/- 0.5 %) \times
10^{-11}iea_{B}(-Q_{W}/N) has half the uncertainty claimed in old calculations
used for the interpretation of Cs PNC experiments. The resulting nuclear weak
charge Q_{W} for Cs deviates by about 2 standard deviations from the value
predicted by the standard model.Comment: 24 pages, 8 figure
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