161 research outputs found
Residual nuclide formation in 206,207,208,nat-Pb and 209-Bi induced by 0.04-2.6 GeV Protons as well as in 56-Fe induced by 0.3-2.6 GeV Protons
5972 independent and cumulative yields of radioactive residuals nuclei have
been measured in 55 thin 206,207,208,nat-Pb and 209-Bi targets irradiated by
0.04, 0.07, 0.10, 0.15, 0.25, 0.6, 0.8, 1.2, 1.4, 1.6, and 2.6 GeV protons.
Besides, 219 yields have been measured in 0.3, 0.5, 0.75, 1.0, 1.5, and 2.6 GeV
proton-irradiated 56-Fe target. The protons were extracted from the ITEP U-10
synchrotron. The measured data are compared with experimental results obtained
elsewhere and with theoretical calculations by LAHET, MCNPX, CEM03, LAQGSM03,
CASCADE, CASCADO, and LAHETO codes. The predictive power was found to be
different for each of the codes tested, but was satisfactory on the whole in
the case of spallation products. At the same time, none of the codes can
de-scribe well the product yields throughout the whole product mass range, and
all codes must be further improved.Comment: 4 pages, 4 figures, 2 tables, only pdf file, to be published in Proc.
Int. Conf. on Nucl. Data for Sci. and Technology (ND2007), Nice, France,
April 22-27, 20
High-energy threshold reaction rates on 0.8 GeV proton-irradiated thick Pb-target
This works presents results of activation-aided determination of threshold
reaction rates in 92 209Bi, natPb, 197Au, 181Ta, 169Tm, natIn, 93Nb, 64Zn,
65Cu, 63Cu, 59Co, 19F, and 12C samples and in 121 27Al samples. All the samples
were aligned with the proton beam axis inside and outside the demountable 92-cm
thick Pb target of 15-cm diameter assembled of 23 4-cm thick discs. The samples
were placed on 12 target disks to reproduce the long axis distribution of
protons and neutrons. In June 2006, the target was exposed for 18 hours to a
800-MeV proton beam extracted from the ITEP U-10 accelerator. The proton
fluence and the proton beam shape were determined using the 27Al(p,x)7Be
monitor reaction. The reaction rates were determined by the direct
gamma-spectrometry techniques. In total, 1196 gamma-spectra have been measured,
and about 1500 reaction rates determined. The measured reaction rates were
simulated by the MCNPX code using the following databases: ENDF/B6 for neutrons
below 20 MeV, MENDL2 for 20-100 MeV neutrons, and MENDL2P for proton cross
sections up to 200 MeV. An acceptable agreement of simulations with
experimental data has been found.Comment: 4 pages, 5 figures, 3 tables, only pdf file, to be published in Proc.
Int. Conf. on Nucl. Data for Sci. and Technology (ND2007), Nice, France,
April 22-27, 200
Potencial parlamentario para garantizar la seguridad del Estado: experiencia constitucional de los países de la era postsoviética
The article presents the author’s analysis of the constitutional acts of the countries of the post-Soviet space in order to consolidate in them the catalog of powers of parliaments in the field of state security. The study revealed two constitutional approaches reflecting the catalog of powers of parliaments in ensuring the security of the state: the parliament acts as a body with the prerogative of introducing exclusive regimes in the state, declaring war and concluding peace; the parliament acts as a body that legalizes decrees of the head of state or government on security issues.El artículo presenta el análisis del autor de los actos constitucionales de los países del espacio postsoviético para consolidar en ellos el catálogo de poderes de los parlamentos en el campo de la seguridad del estado. El estudio reveló dos enfoques constitucionales que reflejan el catálogo de poderes de los parlamentos para garantizar la seguridad del estado: el actúa como un órgano con la prerrogativa de introducir regímenes exclusivos en el estado, declarar la guerra y concluir la paz; el parlamento actúa como un organismo que legaliza los decretos del jefe de estado o gobierno sobre cuestiones de seguridad
Improving the efficiency of university management : teacher’s performance monitoring as a tool to promote the quality of education
This study aims to examine the essence of education monitoring, its place in the higher education management system and the practical implementation of teacher’s performance monitoring as a tool to promote the quality of education.
The article considers theoretical aspects of monitoring as a tool to promote the quality of education, assesses the performance of the university departments, research and teaching staff and discusses the results and suggestions on how to improve monitoring activities in higher education.
Based on their research and findings, the authors claimed that the monitoring of the performance of the university research and teaching staff on the base of an indicator system in terms of education, methodology, research, organization and counselling services would lead to valid conclusions as to the effective performance of both individual researchers and teachers and university departments, in general.peer-reviewe
Tenfold Magnetoconductance in a Non-Magnetic Metal Film
We present magnetoconductance (MC) measurements of homogeneously disordered
Be films whose zero field sheet conductance (G) is described by the
Efros-Shklovskii hopping law . The low field
MC of the films is negative with G decreasing 200% below 1 T. In contrast the
MC above 1 T is strongly positive. At 8 T, G increases 1000% in perpendicular
field and 500% in parallel field. In the simpler parallel case, we observe {\em
field enhanced} variable range hopping characterized by an attenuation of
via the Zeeman interaction.Comment: 9 pages including 5 figure
Superconductivity on the localization threshold and magnetic-field-tuned superconductor-insulator transition in TiN films
Temperature- and magnetic-field dependent measurements of the resistance of
ultrathin superconducting TiN films are presented. The analysis of the
temperature dependence of the zero field resistance indicates an underlying
insulating behavior, when the contribution of Aslamasov-Larkin fluctuations is
taken into account. This demonstrates the possibility of coexistence of the
superconducting and insulating phases and of a direct transition from the one
to the other. The scaling behavior of magnetic field data is in accordance with
a superconductor-insulator transition (SIT) driven by quantum phase
fluctuations in two-dimensional superconductor. The temperature dependence of
the isomagnetic resistance data on the high-field side of the SIT has been
analyzed and the presence of an insulating phase was confirmed. A transition
from the insulating to a metallic phase is found at high magnetic fields, where
the zero-temperature asymptotic value of the resistance being equal to h/e^2.Comment: 5 pages, 4 eps figures, RevTeX4, Published versio
Cross-sections for nuclide production in 56Fe target irradiated by 300, 500,750, 1000, 1500, and 2600 MeV protons compared with data on hydrogen target irradiation by 300, 500, 750, 1000, and 1500 MeV/nucleon 56Fe ions
Cross-sections for radioactive nuclide production in 56Fe(p,x) reactions at
300, 500, 750, 1000, 1500, and 2600 MeV were measured using the ITEP U-10
proton accelerator. In total, 221 independent and cumulative yields of products
of half-lives from 6.6 min to 312 days have been obtained via the
direct-spectrometry method. The measured data have been compared with the
experimental data obtained elsewhere by the direct and inverse kinematics
methods and with calculations by 15 codes, namely: MCNPX (INCL, CEM2k, BERTINI,
ISABEL), LAHET (BERTINI, ISABEL), CEM03 (.01, .G1, .S1), LAQGSM03 (.01, .G1,
>.S1), CASCADE-2004, LAHETO, and BRIEFF. Most of our data are in a good
agreement with the inverse kinematics results and disprove the results of some
earlier activation measurements that were quite different from the inverse
kinematics measurements. The most significant calculation-to-experiment
differences are observed in the yields of the A<30 light nuclei, indicating
that further improvements in nuclear reaction models are needed, and pointing
out as well to a necessity of more complete measurements of such reactions.Comment: 53 pages, 9 figures, 6 tables, only pdf file, submitted to Phys. Rev.
Ambipolar gate effect and low temperature magnetoresistance of ultrathin La0.8Ca0.2MnO3 Films
Ultrathin La0.8Ca0.2MnO3 films have been measured in a field-effect geometry.
The electric field due to the gate produces a large ambipolar decrease in
resistance at low temperatures. This is attributed to the development of a
pseudogap in the density of states and the couple of localized charge to
strain. The gate effect and mangetoresistance are interpreted in a consistent
framework. The implications for the low temperature behavior of a manganite
film in the two dimensional limit are discussed.Comment: 4 pages, 3 figure
Electron-electron interaction at decreasing
The contribution of the electron-electron interaction to conductivity is
analyzed step by step in gated GaAs/InGaAs/GaAs heterostructures with different
starting disorder. We demonstrate that the diffusion theory works down to , where is the Fermi quasimomentum, is the mean free
paths. It is shown that the e-e interaction gives smaller contribution to the
conductivity than the interference independent of the starting disorder and its
role rapidly decreases with decrease.Comment: 5 pages, 6 figure
Long-range transfer of electron-phonon coupling in oxide superlattices
The electron-phonon interaction is of central importance for the electrical
and thermal properties of solids, and its influence on superconductivity,
colossal magnetoresistance, and other many-body phenomena in
correlated-electron materials is currently the subject of intense research.
However, the non-local nature of the interactions between valence electrons and
lattice ions, often compounded by a plethora of vibrational modes, present
formidable challenges for attempts to experimentally control and theoretically
describe the physical properties of complex materials. Here we report a Raman
scattering study of the lattice dynamics in superlattices of the
high-temperature superconductor and the
colossal-magnetoresistance compound that suggests
a new approach to this problem. We find that a rotational mode of the MnO
octahedra in experiences pronounced
superconductivity-induced lineshape anomalies, which scale linearly with the
thickness of the layers over a remarkably long range of
several tens of nanometers. The transfer of the electron-phonon coupling
between superlattice layers can be understood as a consequence of long-range
Coulomb forces in conjunction with an orbital reconstruction at the interface.
The superlattice geometry thus provides new opportunities for controlled
modification of the electron-phonon interaction in complex materials.Comment: 13 pages, 4 figures. Revised version to be published in Nature
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