2,081 research outputs found
Recommended from our members
Improved Technology To Prevent Nuclear Proliferation And Counter Nuclear Terrorism
As the world moves into the 21st century, the possibility of greater reliance on nuclear energy will impose additional technical requirements to prevent proliferation. In addition to proliferation resistant reactors, a careful examination of the various possible fuel cycles from cradle to grave will provide additional technical and nonproliferation challenges in the areas of conversion, enrichment, transportation, recycling and waste disposal. Radiation detection technology and information management have a prominent role in any future global regime for nonproliferation. As nuclear energy and hence nuclear materials become an increasingly global phenomenon, using local technologies and capabilities facilitate incorporation of enhanced monitoring and detection on the regional level. Radiation detection technologies are an important tool in the prevention of proliferation and countering radiological/nuclear terrorism. A variety of new developments have enabled enhanced performance in terms of energy resolution, spatial resolution, passive detection, predictive modeling and simulation, active interrogation, and ease of operation and deployment in the field. For example, various gamma ray imaging approaches are being explored to combine spatial resolution with background suppression in order to enhance sensitivity many-fold at reasonable standoff distances and acquisition times. New materials and approaches are being developed in order to provide adequate energy resolution in field use without the necessity for liquid nitrogen. Different detection algorithms enable fissile materials to be distinguished from other radioisotopes
Anomalous Hall effect in insulating Ga1-xMnxAs
We have investigated the effect of doping by Te on the anomalous Hall effect
in Ga1-xMnxAs (x = 0.085). For this relatively high value of x the temperature
dependence of resistivity shows an insulating behavior. It is well known that
in Ga1-xMnxAs the Mn ions naturally act as acceptors. Additional doping by Te
donors decreases the Curie temperature and increases the anomalous Hall
resistivity. With increasing Te concentration the long-range ferromagnetic
order in Ga1-xMnxAs eventually disappears, and paramagnetic-to-spin glass
transition is observed instead. The critical concentration of holes required
for establishing ferromagnetic order in Ga1-xMnxAs (x = 0.085) has been
estimated by using the magnetic polaron percolation theory proposed by Kaminski
and Das Sarma [Phys.Rev.Lett. 88, 247202 (2002)].Comment: 15 pages, 5 figures. Phys. Rev. B (to be published
Photonuclear reactions on the stable isotopes of selenium at bremsstrahlung end-point energies of 10-23 MeV
The experiments were performed at bremsstrahlung end-point energies of 10-23
MeV with the beam from the MT-25 microtron with the use of the
{\gamma}-activation technique. The experimental values of relative yields were
compared with theoretical results obtained on the basis of TALYS with the
standard parameters and the combined model of photonucleon reactions. Including
isospin splitting in the combined model of photonucleon reactions allows to
describe experimental data on reactions with proton escape in energies range
from 10 to 23 MeV. Therefore, taking into account isospin splitting is
necessary for a correct description of the decay of the GDR.Comment: 22 pages, 8 figure
True Neutrality as a New Type of Flavour
A classification of leptonic currents with respect to C-operation requires
the separation of elementary particles into the two classes of vector C-even
and axial-vector C-odd character. Their nature has been created so that to each
type of lepton corresponds a kind of neutrino. Such pairs are united in
families of a different C-parity. Unlike the neutrino of a vector type, any
C-noninvariant Dirac neutrino must have his Majorana neutrino. They constitute
the purely neutrino families. We discuss the nature of a corresponding
mechanism responsible for the availability in all types of axial-vector
particles of a kind of flavour which distinguishes each of them from others by
a true charge characterized by a quantum number conserved at the interactions
between the C-odd fermion and the field of emission of the corresponding types
of gauge bosons. This regularity expresses the unidenticality of truly neutral
neutrino and antineutrino, confirming that an internal symmetry of a
C-noninvariant particle is described by an axial-vector space. Thereby, a true
flavour together with the earlier known lepton flavour predicts the existence
of leptonic strings and their birth in single and double beta decays as a unity
of flavour and gauge symmetry laws. Such a unified principle explains the
availability of a flavour symmetrical mode of neutrino oscillations.Comment: 19 pages, LaTex, Published version in IJT
Physical inactivity in nine European and Central Asian countries: an analysis of national population-based survey results
Background
Physical inactivity is a major risk factor for non-communicable diseases. However, recent and systematically obtained national-level data to guide policy responses are often lacking, especially in countries in Eastern Europe and Central Asia. This article describes physical inactivity patterns among adults in Armenia, Azerbaijan, Belarus, Georgia, Kyrgyzstan, Republic of Moldova, Tajikistan, Turkey and Uzbekistan.
Methods
Data were collected using the Global Physical Activity Questionnaire drawing nationally representative samples of adults in each country. The national prevalence of physical inactivity was calculated as well as the proportional contribution to total physical activity (PA) during work, transport and leisure-time. An adjusted logistic regression model was applied to analyze the association of age, gender, education, household status and income with physical inactivity.
Results
National prevalence of physical inactivity ranged from 10.1% to 43.6%. The highest proportion of PA was registered during work or in the household in most countries, whereas the lowest was during leisure-time in all countries. Physical inactivity was more likely with older age in eight countries, with female gender in three countries, and with living alone in three countries. There was no clear pattern of association with education and income.
Conclusion
Prevalence of physical inactivity is heterogeneous across the region. PA during leisure-time contributes minimally to total PA in all countries. Policies and programs that increase opportunities for active travel and leisure-time PA, especially for older adults, women and people living alone will be an essential part of strategies to increase overall population PA.The authors gratefully acknowledge support from a grant from the Government of the Russian Federation in the context of the WHO European Office for the Prevention and Control of NCDs
Reeconstructing Sigma0 decays in STAR
Typical comparisons of data from nuclear collisions to particle production
models require a caveat for (anti)Lambda yields from experimental inability to
separate the contributions of those yields from Sigma state decays. Recent
analysis in STAR is leading toward resolving the contribution from excited
Sigma states, but the bulk contribution comes from electromagnetic decays of
the (anti)Sigma0.
In the STAR detector, photon conversions into e+e- pairs in the detector
material have been used to identify photons from pi0 decays. A similar
technique has been used here to identify photons from (anti)Sigma0 decays in
conjunction with STAR's excellent PID capabilities for finding the associated
(anti)Lambda daughters. We report here on progress toward measuring the
(anti)Sigma0 yields in various nuclear collisions at RHIC.Comment: 8 pages, 5 figures, proceedings of Hot Quarks 2004 workshop,
submitted to J. Phys.
- …