1,581 research outputs found
Relativistic nuclear structure effects in quasielastic neutrino scattering
Charged-current cross sections are calculated for quasielastic neutrino and
antineutrino scattering using a relativistic meson-nucleon model. We examine
how nuclear-structure effects, such as relativistic random-phase-approximation
(RPA) corrections and momentum-dependent nucleon self-energies, influence the
extraction of the axial form factor of the nucleon. RPA corrections are
important only at low-momentum transfers. In contrast, the momentum dependence
of the relativistic self-energies changes appreciably the value of the
axial-mass parameter, , extracted from dipole fits to the axial form
factor. Using Brookhaven's experimental neutrino spectrum we estimate the
sensitivity of M to various relativistic nuclear-structure effects.Comment: 26 pages, revtex, 6 postscript figures (available upon request
Energy and transport issues for Gauteng, South Africa
Rapid urbanisation brings unwelcome negative impacts, and places excessive pressure on infra-structure development and maintenance. In partic-ular, transport networks become congested with negative impacts on energy logistics. The liquid fuel situation of South Africa and Gauteng is briefly examined. The paper considers the impact of con-strained oil supply, and supply infrastructure, on transport. The author further suggests that the authorities in Gauteng should critically examine an ultra light rail option in order to reduce reliance on imported oil, while helping reduce road congestion. A more energy efficient transport network for the province, able to meet the transport needs of pas-sengers and business, will help decrease environ-mentally damaging emissions
Energy and transport issues for Gauteng, South Africa
Rapid urbanisation brings unwelcome negative impacts, and places excessive pressure on infra-structure development and maintenance. In partic-ular, transport networks become congested with negative impacts on energy logistics. The liquid fuel situation of South Africa and Gauteng is briefly examined. The paper considers the impact of con-strained oil supply, and supply infrastructure, on transport. The author further suggests that the authorities in Gauteng should critically examine an ultra light rail option in order to reduce reliance on imported oil, while helping reduce road congestion. A more energy efficient transport network for the province, able to meet the transport needs of pas-sengers and business, will help decrease environ-mentally damaging emissions
Relativistic predictions of spin observables for exclusive proton knockout reactions
Within the framework of the relativistic distorted wave impulse approximation
(DWIA), we investigate the sensitivity of complete sets of polarization
transfer observables for exclusive proton knockout from the 3s,
2d and 2d states in Pb, at an incident laboratory
kinetic energy of 202 MeV, and for coincident coplanar scattering angles
(, ), to different distorting optical potentials,
finite-range (FR) versus zero-range (ZR) approximations to the DWIA, as well as
medium-modified meson-nucleon coupling constants and meson masses. Results are
also compared to the nonrelativistic DWIA predictions based on the
Schr\"{o}dinger equation.Comment: Submitted for publication to Physicical Review C, 23 pages, 7 figure
A macro analysis of crop residue and animal wastes as a potential energy source in Africa
Africans are particularly disadvantaged when it comes to access to energy. A significant majority of the continentsâ inhabitants rely on biomass for their energy needs and are of necessity subsistence farm-ers. The production of four important crops in African countries, and the potential magnitude of residues for energy use from these, is analysed in this desktop study. It is clear that there is significant potential for using crop residues as a renewable energy resource in many parts of Africa, effectively combining the need for food and the need for ener-gy. Energy policy must be formulated to leverage the opportunity; however, supporting energy data collected by governmental statistical processes will need to include this additional information
Relativistic predictions of exclusive analyzing powers at an incident energy of 202 MeV
Within the framework of the relativistic distorted wave impulse approximation
(DWIA), we investigate the sensitivity of the analyzing power - for exclusive
proton knockout from the 3s, 2d and 2d states in
Pb, at an incident laboratory kinetic energy of 202 MeV, and for
coincident coplanar scattering angles (, ) - to
different distorting optical potentials, finite-range (FR) versus zero-range
(ZR) approximations to the DWIA, as well as medium-modified coupling constants
and meson masses. Results are also compared to the nonrelativistic DWIA
predictions based on the Schr\"{o}dinger equation. Whereas the nonrelativistic
model fails severely, both ZR and FR relativistic DWIA models provide an
excellent description of the data. For the FR predictions, it is necessary to
invoke a 20% reduction of sigma-nucleon and omega-nucleon coupling constants as
well as for -, - and -meson masses, by the nuclear
medium. On the other hand, the ZR predictions suggest that the strong
interaction in the nuclear medium is adequately represented by the free
nucleon-nucleon interaction associated with the impulse approximation. We also
demonstrate that, although the analyzing power is relatively insensitive to the
use different relativistic global optical potential parameter sets, the
prominent oscillatory behavior of this observable is largely attributed to
distortion of the scattering wave functions relative to their plane wave
values.Comment: 16 pages, 3 figures, submitted to Phys. Rev.
Relativistic analysis of the 208Pb(e,e'p)207Tl reaction at high momentum
The recent 208Pb(e,e'p)207Tl data from NIKHEF-K at high missing momentum
(p_m>300 MeV/c) are compared to theoretical results obtained with a fully
relativistic formalism previously applied to analyze data on the low missing
momentum (p_m < 300 MeV/c) region. The same relativistic optical potential and
mean field wave functions are used in the two p_m-regions. The spectroscopic
factors of the various shells are extracted from the analysis of the low-p_m
data and then used in the high-p_m region. In contrast to previous analyses
using a nonrelativistic mean field formalism, we do not find a substantial
deviation from the mean field predictions other than that of the spectroscopic
factors, which appear to be consistent with both low- and high-p_m data. We
find that the difference between results of relativistic and nonrelativistic
formalisms is enhanced in the p_m<0 region that will be interesting to explore
experimentally.Comment: 12 pages, LaTeX+Revtex, included 3 postscript figures. To appear in
the Physical Review C (Rapid Communications
Sustaining productivity of a Vertisol at Warra, Queensland, with fertilisers, no-tillage, or legumes. 5. Wheat yields, nitrogen benefits and water-use efficiency of chickpea-wheat rotation
In this study, the benefits of chickpeaâwheat rotation compared with continuous wheat cropping (wheatâwheat rotation) were evaluated for their effects on soil nitrate nitrogen, wheat grain yields and grain protein concentrations, and water-use efficiency at Warra, southern Queensland from 1988 to 1996.
Benefits in terms of wheat grain yields varied, from 17% in 1993 to 61% in 1990, with a mean increase in grain yield of 40% (825 kg/ha). Wheat grain protein concentration increased from 9.4% in a wheatâwheat rotation to 10.7% in a chickpeaâwheat rotation, almost a 14% increase in grain protein. There was a mean increase in soil nitrate nitrogen of 35 kg N/ha.1.2 m after 6 months of fallow following chickpea (85 kg N/ha) compared with continuous wheat cropping (50 kg N/ha). This was reflected in additional nitrogen in the wheat grain (20 kg N/ha) and above-ground plant biomass (25 kg N/ha) following chickpea.
Water-use efficiency by wheat increased from a mean value of 9.2 kg grain/ha. mm in a wheatâwheat rotation to 11.7 kg grain/ha.mm in a chickpeaâwheat rotation. The water-use efficiency values were closely correlated with presowing nitrate nitrogen, and showed no marked distinction between the 2 cropping sequences. Although presowing available water in soil in May was similar in both the chickpeaâwheat rotation and the wheatâwheat rotation in all years except 1996, wheat in the former used about 20 mm additional water and enhanced water-use efficiency. Thus, by improving soil fertility through restorative practices such as incorporating chickpea in rotation, water-use efficiency can be enhanced and consequently water runoff losses reduced.
Furthermore, beneficial effects of chickpea in rotation with cereals could be enhanced by early to mid sowing (Mayâmid June) of chickpea, accompanied by zero tillage practice. Wheat of âPrime Hardâ grade protein (â„13%) could be obtained in chickpeaâwheat rotation by supplementary application of fertiliser N to wheat.
In this study, incidence of crown rot of wheat caused by Fusarium graminearum was negligible, and incidence and severity of common root rot of wheat caused by Bipolaris sorokiniana were essentially similar in both cropping sequences and inversely related to the available water in soil at sowing. No other soil-borne disease was observed. Therefore, beneficial effects of chickpea on wheat yields and grain protein were primarily due to additional nitrate nitrogen following the legume crop and consequently better water-use efficiency
Influence of grain-refiner addition on the morphology of fe-bearing intermetallics in a semi-solid processed Al-Mg-Si alloy
© The Minerals, Metals & Materials Society and ASM International 2013The three-dimensional morphologies of the Fe-bearing intermetallics in a semisolid-processed Al-Mg-Si alloy were examined after extracting the intermetallics. α -AlFeSi and ÎČ-AlFeSi are the major Fe-bearing intermetallics. Addition of Al-Ti-B grain refiner typically promotes ÎČ-AlFeSi formation. ÎČ-AlFeSi was observed with a flat, plate-like morphology with angular edges in the alloy with and without grain refiner, whereas α -AlFeSi was observed as "flower"-like morphology in the alloy with grain refiner. © 2013 The Minerals, Metals & Materials Society and ASM International
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