911 research outputs found
Solar Neutrinos: Status and Prospects
We describe the current status of solar neutrino measurements and of the
theory -- both neutrino physics and solar astrophysics -- employed in
interpreting measurements. Important recent developments include
Super-Kamiokande's determination of the neutrino-electron elastic scattering
rate for 8B neutrinos to 3%; the latest SNO global analysis in which the
inclusion of low-energy data from SNO I and II significantly narrowed the range
of allowed values for the neutrino mixing angle theta12; Borexino results for
both the 7Be and pep neutrino fluxes, the first direct measurements
constraining the rate of ppI and ppII burning in the Sun; global reanalyses of
solar neutrino data that take into account new reactor results on theta13; a
new decadal evaluation of the nuclear physics of the pp chain and CNO cycle
defining best values and uncertainties in the nuclear microphysics input to
solar models; recognition of an emerging discrepancy between two tests of solar
metallicity, helioseismological mappings of the sound speed in the solar
interior, and analyses of the metal photoabsorption lines based on our best
current description of the Sun's photosphere; a new round of standard solar
model calculations optimized to agree either with helioseismology or with the
new photospheric analysis; and, motivated by the solar abundance problem, the
development of nonstandard, accreting solar models, in order to investigate
possible consequences of the metal segregation that occurred in the proto-solar
disk. We review this progress and describe how new experiments such as SNO+
could help us further exploit neutrinos as a unique probe of stellar interiors.Comment: 82 pages, 11 figure
Impurity (Fe, Cl, and P)-induced grain boundary and secondary phases in commercially pure titanium (CP-Ti)
A detailed transmission electron microscopy (TEM) study has been made of the microstructures of two as-sintered CP-Ti materials. We show that iron content at the impurity level of 1280 ppm, less than the limit (2000 ppm) for CP-Ti ASTM Grade 1, is sufficient to lead to the formation of a grain boundary (GB) β-Ti phase in the as-sintered microstructure due to segregation. The Fe-stabilized GB β-Ti phase contains ∼7 at. pct Fe and ∼1.5 at. pct Cl. In addition, nano-precipitates of ω-Ti exist in the Fe-stabilized GB β-Ti phase. A phosphorus (P)-enriched Ti-P-based phase was also identified, which has a tetragonal crystal structure with lattice parameters of (a = b = 8.0 ± 0.2 Å and c = 2.7 ± 0.2 Å) and is new to the existing database for Ti-P-enriched phases. As-sintered CP-Ti materials are thus not necessarily a single α-Ti phase material. These impurity-induced phases may exert potential impacts on the properties of sintered CP-Ti
Glutamine synthetase and glutamate synthase activities in relation to nitrogen fixation in Lotus spp.
Plane-symmetric inhomogeneous magnetized viscous fluid universe with a variable
The behavior of magnetic field in plane symmetric inhomogeneous cosmological
models for bulk viscous distribution is investigated. The coefficient of bulk
viscosity is assumed to be a power function of mass density . The values of cosmological constant for these models are
found to be small and positive which are supported by the results from recent
supernovae Ia observations. Some physical and geometric aspects of the models
are also discussed.Comment: 18 pages, LaTex, no figur
Transfer Matrices and Partition-Function Zeros for Antiferromagnetic Potts Models. V. Further Results for the Square-Lattice Chromatic Polynomial
We derive some new structural results for the transfer matrix of
square-lattice Potts models with free and cylindrical boundary conditions. In
particular, we obtain explicit closed-form expressions for the dominant (at
large |q|) diagonal entry in the transfer matrix, for arbitrary widths m, as
the solution of a special one-dimensional polymer model. We also obtain the
large-q expansion of the bulk and surface (resp. corner) free energies for the
zero-temperature antiferromagnet (= chromatic polynomial) through order q^{-47}
(resp. q^{-46}). Finally, we compute chromatic roots for strips of widths 9 <=
m <= 12 with free boundary conditions and locate roughly the limiting curves.Comment: 111 pages (LaTeX2e). Includes tex file, three sty files, and 19
Postscript figures. Also included are Mathematica files data_CYL.m and
data_FREE.m. Many changes from version 1: new material on series expansions
and their analysis, and several proofs of previously conjectured results.
Final version to be published in J. Stat. Phy
Ground state properties of a Tonks-Girardeau Gas in a periodic potential
In this paper, we investigate the ground-state properties of a bosonic
Tonks-Girardeau gas confined in a one-dimensional periodic potential. The
single-particle reduced density matrix is computed numerically for systems up
to bosons. Scaling analysis of the occupation number of the lowest
orbital shows that there are no Bose-Einstein Condensation(BEC) for the
periodically trapped TG gas in both commensurate and incommensurate cases. We
find that, in the commensurate case, the scaling exponents of the occupation
number of the lowest orbital, the amplitude of the lowest orbital and the
zero-momentum peak height with the particle numbers are 0, -0.5 and 1,
respectively, while in the incommensurate case, they are 0.5, -0.5 and 1.5,
respectively. These exponents are related to each other in a universal
relation.Comment: 9 pages, 10 figure
Egg quality determinants in cod (Gadus morhua L.): egg performance and lipids in eggs from farmed and wild broodstock
Lipids and essential fatty acids, particularly the highly unsaturated fatty acids, 20:5n-3 (eicosapentaenoic acid; EPA), 22:6n-3 (docosahexaenoic acid; DHA) and 20:4n-6 (arachidonic acid, AA) have been shown to be crucial determinants of marine fish reproduction directly affecting fecundity, egg quality, hatching success, larval malformation and pigmentation. In Atlantic cod (Gadus morhua L.) culture, eggs from farmed broodstock can have much lower fertilisation and hatching rates than eggs from wild broodstock. The present study aimed to test the hypothesis that potential quality and performance differences between eggs from different cod broodstock would be reflected in differences in lipid and fatty acid composition. Thus eggs were obtained from three broodstock, farmed, wild/fed and wild/unfed, and lipid content, lipid class composition, fatty acid composition and pigment content were determined and related to performance parameters including fertilisation rate, symmetry of cell division and survival to hatching. Eggs from farmed broodstock showed significantly lower fertilisation rates, cell symmetry and survival to hatching rates than eggs from wild broodstock. There were no differences in total lipid content or the proportions of the major lipid classes between eggs from the different broodstock. However, eggs from farmed broodstock were characterised by having significantly lower levels of some quantitatively minor phospholipid classes, particularly phosphatidylinositol. There were no differences between eggs from farmed and wild broodstock in the proportions of saturated, monounsaturated and total polyunsaturated fatty acids. The DHA content was also similar. However, eggs from farmed broodstock had significantly lower levels of AA, and consequently significantly higher EPA/AA ratios than eggs from wild broodstock. Total pigment and astaxanthin levels were significantly higher in eggs from wild broodstock. Therefore, the levels of AA and phosphatidylinositol, the predominant AA-containing lipid class, and egg pigment content were positively related to egg quality or performance parameters such as fertilisation and hatching success rates, and cell symmetry
First Measurement of Z/gamma* Production in Compton Scattering of Quasi-real Photons
We report the first observation of Z/gamma* production in Compton scattering
of quasi-real photons. This is a subprocess of the reaction e+e- to
e+e-Z/gamma*, where one of the final state electrons is undetected.
Approximately 55 pb-1 of data collected in the year 1997 at an e+e-
centre-of-mass energy of 183 GeV with the OPAL detector at LEP have been
analysed. The Z/gamma* from Compton scattering has been detected in the
hadronic decay channel. Within well defined kinematic bounds, we measure the
product of cross-section and Z/gamma* branching ratio to hadrons to be
(0.9+-0.3+-0.1) pb for events with a hadronic mass larger than 60 GeV,
dominated by (e)eZ production. In the hadronic mass region between 5 GeV and 60
GeV, dominated by (e)egamma* production, this product is found to be
(4.1+-1.6+-0.6) pb. Our results agree with the predictions of two Monte Carlo
event generators, grc4f and PYTHIA.Comment: 18 pages, LaTeX, 5 eps figures included, submitted to Physics Letters
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