9,148 research outputs found
Extended Optical Model Analyses of Elastic Scattering, Direct Reaction, and Fusion Cross Sections for the 9Be + 208Pb System at Near-Coulomb-Barrier Energies
Based on the extended optical model approach in which the polarization
potential is decomposed into direct reaction (DR) and fusion parts,
simultaneous analyses are performed for elastic scattering, DR, and
fusion cross section data for the Be+Pb system at
near-Coulomb-barrier energies. Similar analyses are also performed
by only taking into account the elastic scattering and fusion data as was
previously done by the present authors, and the results are compared with those
of the full analysis including the DR cross section data as well. We find that
the analyses using only elastic scattering and fusion data can produce very
consistent and reliable predictions of cross sections particularly when the DR
cross section data are not complete. Discussions are also given on the results
obtained from similar analyses made earlier for the Be+Bi system.Comment: 5 figure
Extended Optical Model Analyses of Elastic Scattering and Fusion Cross Sections for 6Li + 208Pb System at Near-Coulomb-Barrier Energies by using Folding Potential
Based on the extended optical model approach in which the polarization
potential is decomposed into direct reaction (DR) and fusion parts,
simultaneous analyses are performed for elastic scattering and
fusion cross section data for the Li+Pb system at
near-Coulomb-barrier energies. A folding potential is used as the bare
potential. It is found that the real part of the resultant DR part of the
polarization potential is repulsive, which is consistent with the results from
the Continuum Discretized Coupled Channel (CDCC) calculations and the
normalization factors needed for the folding potentials. Further, it is found
that both DR and fusion parts of the polarization potential satisfy separately
the dispersion relation.Comment: 6 figure
Gravitational energy in a small region for the modified Einstein and Landau-Lifshitz pseudotensors
The purpose of the classical Einstein and Landau-Lifshitz pseudotensors is
for determining the gravitational energy. Neither of them can guarantee a
positive energy in holonomic frames. In the small sphere approximation, it has
been required that the quasilocal expression for the gravitational
energy-momentum density should be proportional to the Bel-Robinson tensor
. However, we propose a new tensor
which is the sum of certain tensors
and , it has certain properties
so that it gives the same gravitational "energy-momentum" content as
does. Moreover, we show that a modified Einstein
pseudotensor turns out to be one of the Chen-Nester quasilocal expressions,
while the modified Landau-Lifshitz pseudotensor becomes the Papapetrou
pseudotensor; these two modified pseudotensors have positive gravitational
energy in a small region.Comment:
Localization on the D-brane, two-dimensional gauge theory and matrix models
We consider the effective topological field theory on Euclidean D-strings
wrapping on a 2-cycle in the internal space. We evaluate the vev of a suitable
operator corresponding to the chemical potential of vortices bounded to the
D-strings, and find that it reduces to the partition function of generalized
two-dimensional Yang-Mills theory as a result of localization. We argue that
the partition function gives a grand canonical ensemble of multi-instanton
corrections for four-dimensional N=2 gauge theory in a suitable large N limit.
We find two-dimensional gauge theories that provide the instanton partition
function for four-dimensional N=2 theories with the hypermultiplets in the
adjoint and fundamental representations. We also propose a partition function
that gives the instanton contributions to four-dimensional N=2 quiver gauge
theory. We discuss the relation between Nekrasov's instanton partition function
and the Dijkgraaf-Vafa theory in terms of large N phase transitions of the
generalized two-dimensional Yang-Mills theory.Comment: 40 pages, 5 figures, LaTeX2e, typos corrected, references added,
Final version to appear in Physical Review
Examination into the accuracy of exchangeable cation measurement in saline soils
Despite the increasing prevalence of salinity world-wide, the measurement of exchangeable cation concentrations in saline soils remains problematic. Two soil types (Mollisol and Vertisol) were equilibrated with a range of sodium adsorption ratio (SAR) solutions at various ionic strengths. The concentrations of exchangeable cations were then determined using several different types of methods, and the measured exchangeable cation concentrations compared to reference values. At low ionic strength (low salinity), the concentration of exchangeable cations can be accurately estimated from the total soil extractable cations. In saline soils, however, the presence of soluble salts in the soil solution precludes the use of this method. Leaching of the soil with a pre-wash solution (such as alcohol) was found to effectively remove the soluble salts from the soil, thus allowing the accurate measurement of the effective cation exchange capacity (ECEC). However, the dilution associated with this pre-washing increased the exchangeable Ca concentrations while simultaneously decreasing exchangeable Na. In contrast, when calculated as the difference between the total extractable cations and the soil solution cations, good correlations were found between the calculated exchangeable cation concentrations and the reference values for both Na (Mollisol: y=0.873x and Vertisol: y=0.960x) and Ca (Mollisol: y=0.901x and Vertisol: y=1.05x). Therefore, for soils with a soil solution ionic strength greater than 50 mM (electrical conductivity of 4 dS/m) (in which exchangeable cation concentrations are overestimated by the assumption they can be estimated as the total extractable cations), concentrations can be calculated as the difference between total extractable cations and soluble cations
Frequent use of paracetamol and risk of allergic disease among women in an Ethiopian population
Introduction
The hypothesis that paracetamol might increase the risk of asthma and other allergic diseases have gained support from a range of independent studies. However, in studies based in developed countries, the possibility that paracetamol and asthma are associated through aspirin avoidance is difficult to exclude.
Objectives
To explore this hypothesis among women in a developing country, where we have previously reported aspirin avoidance to be rare.
Methods
In 2005/6 a population based cohort of 1065 pregnant women was established in Butajira, Ethiopia and baseline demographic data collected. At 3 years post birth, an interview-based questionnaire administered to 945 (94%) of these women collected data on asthma, eczema, and hay fever in the past 12 month, frequency of paracetamol use and potential confounders. Allergen skin tests to Dermatophagoides pteronyssinus and cockroach were also performed. The independent effects of paracetamol use on allergic outcomes were determined using multiple logistic regression analysis.
Findings
The prevalence of asthma, eczema and hay fever was 1.7%, 0.9% and 3.8% respectively; of any one of these conditions 5.5%, and of allergen sensitization 7.8%. Paracetamol use in the past month was reported by 29%, and associations of borderline significance were seen for eczema (adjusted OR (95% CI) = 8.51 (1.68 to 43.19) for 1–3 tablets and 2.19 (0.36 to 13.38) for ≥4 tablets, compared to no tablets in the past month; overall p = 0.055) and for ‘any allergic condition’ (adjusted OR (95% CI) = 2.73 (1.22 to 6.11) for 1–3 tablets and 1.35 (0.67 to 2.70) for ≥4 tablets compared to 0 in the past month; overall p = 0.071).
Conclusions
This study provides further cross-sectional evidence that paracetamol use increases the risk of allergic disease
On the energy of homogeneous cosmologies
An energy for the homogeneous cosmological models is presented. More
specifically, using an appropriate natural prescription, we find the energy
within any region with any gravitational source for a large class of gravity
theories--namely those with a tetrad description--for all 9 Bianchi types. Our
energy is given by the value of the Hamiltonian with homogeneous boundary
conditions; this value vanishes for all regions in all Bianchi class A models,
and it does not vanish for any class B model. This is so not only for
Einstein's general relativity but, moreover, for the whole 3-parameter class of
tetrad-teleparallel theories. For the physically favored one parameter
subclass, which includes the teleparallel equivalent of Einstein's theory as an
important special case, the energy for all class B models is, contrary to
expectation, negative.Comment: 11 pages, reformated with minor change
Semi-classical Characters and Optical Model Description of Heavy Ion Scattering, Direct Reactions, and Fusion at Near-barrier Energies
An approach is proposed to calculate the direct reaction (DR) and fusion
probabilities for heavy ion collisions at near-Coulomb-barrier energies as
functions of the distance of closest approach D within the framework of the
optical model that introduces two types of imaginary potentials, DR and fusion.
The probabilities are calculated by using partial DR and fusion cross sections,
together with the classical relations associated with the Coulomb trajectory.
Such an approach makes it possible to analyze the data for angular
distributions of the inclusive DR cross section, facilitating the determination
of the radius parameters of the imaginary DR potential in a less ambiguous
manner. Simultaneous -analyses are performed of relevant data for the
O+Pb system near the Coulomb-barrier energy
Ontologies, Mental Disorders and Prototypes
As it emerged from philosophical analyses and cognitive research, most concepts exhibit typicality effects, and resist to the efforts of defining them in terms of necessary and sufficient conditions. This holds also in the case of many medical concepts. This is a problem for the design of computer science ontologies, since knowledge representation formalisms commonly adopted in this field do not allow for the representation of concepts in terms of typical traits. However, the need of representing concepts in terms of typical traits concerns almost every domain of real world knowledge, including medical domains. In particular, in this article we take into account the domain of mental disorders, starting from the DSM-5 descriptions of some specific mental disorders. On this respect, we favor a hybrid approach to the representation of psychiatric concepts, in which ontology oriented formalisms are combined to a geometric representation of knowledge based on conceptual spaces
Super-lattice, rhombus, square, and hexagonal standing waves in magnetically driven ferrofluid surface
Standing wave patterns that arise on the surface of ferrofluids by (single
frequency) parametric forcing with an ac magnetic field are investigated
experimentally. Depending on the frequency and amplitude of the forcing, the
system exhibits various patterns including a superlattice and subharmonic
rhombuses as well as conventional harmonic hexagons and subharmonic squares.
The superlattice arises in a bicritical situation where harmonic and
subharmonic modes collide. The rhombic pattern arises due to the non-monotonic
dispersion relation of a ferrofluid
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