45,278 research outputs found
Electromagnetic and spin polarisabilities in lattice QCD
We discuss the extraction of the electromagnetic and spin polarisabilities of
nucleons from lattice QCD. We show that the external field method can be used
to measure all the electromagnetic and spin polarisabilities including those of
charged particles. We then turn to the extrapolations required to connect such
calculations to experiment in the context of finite volume chiral perturbation
theory. We derive results relevant for lattice simulations of QCD,
partially-quenched QCD and quenched QCD. Our results for the polarisabilities
show a strong dependence on the lattice volume and quark masses, typically
differing from the infinite volume limit by ~10% for current lattice volumes
and quark masses.Comment: Minor change
A Lattice Test of 1/N_c Baryon Mass Relations
1/N_c baryon mass relations are compared with lattice simulations of baryon
masses using different values of the light-quark masses, and hence different
values of SU(3) flavor-symmetry breaking. The lattice data clearly display both
the 1/N_c and SU(3) flavor-symmetry breaking hierarchies. The validity of 1/N_c
baryon mass relations derived without assuming approximate SU(3)
flavor-symmetry also can be tested by lattice data at very large values of the
strange quark mass. The 1/N_c expansion constrains the form of discretization
effects; these are suppressed by powers of 1/N_c by taking suitable
combinations of masses. This 1/N_c scaling is explicitly demonstrated in the
present work.Comment: 13 pages, 20 figures; v2 version to be published in PR
Tuning grid storage resources for LHC data analysis
Grid Storage Resource Management (SRM) and local file-system solutions are facing significant challenges to support efficient analysis of the data now being produced at the Large Hadron Collider (LHC). We compare the performance of different storage technologies at UK grid sites examining the effects of tuning and recent improvements in the I/O patterns of experiment software. Results are presented for both live production systems and technologies not currently in widespread use. Performance is studied using tests, including real LHC data analysis, which can be used to aid sites in deploying or optimising their storage configuration
Enhanced Stability of Superheavy Nuclei due to High-Spin Isomerism
Configuration-constrained calculations of potential-energy surfaces in
even-even superheavy nuclei reveal systematically the existence at low
excitation energies of multi-quasiparticle states with deformed axially
symmetric shapes and large angular momenta. These results indicate the
prevalence of long-lived, multi-quasiparticle isomers. In a quantal system, the
ground state is usually more stable than the excited states. In contrast, in
superheavy nuclei the multi-qausiparticle excitations decrease the probability
for both fission and decay, implying enhanced stability. Hence, the
systematic occurrence of multi-qausiparticle isomers may become crucial for
future production and study of even heavier nuclei. The energies of
multi-quasiparticle states and their decays are calculated and
compared to available data.Comment: 4 pages, 5 figures, accepted for publication in PR
Evaluation of a Brazilian fuel alcohol yeast strain for Scotch whisky fermentations
Traditionally, distilling companies in Scotland have employed a very limited number of yeast strains in the production of alcohol for Scotch whiskies. Recent changes such as the decline in availability of brewers’ yeast as a secondary yeast strain and the availability of yeast in different formats (e.g., dried and cream yeast as alternatives to compressed yeast) have promoted interest in alternative Scotch whisky distilling yeasts. In previous work, we investigated different strains of yeasts, specifically Brazilian yeasts which had been isolated from and used in fuel alcohol distilleries. One of the Brazilian yeasts (CAT 1) showed a comparable fermentation performance and superior stress tolerance compared with a standard commercial Scotch whisky distilling yeast (M Type). The Brazilian CAT 1 yeast isolate was further assessed in laboratory scale fermentations and subsequent new make spirit was subjected to sensory analyses. The spirits produced using the Brazilian strain had acceptable flavour profiles and exhibited no sensory characteristics that were atypical of Scotch whisky new make spirit. This study highlights the potential of exploiting yeast biodiversity in traditional Scotch whisky distillery fermentation processes
Beef production: potential and output in mid-Canterbury
Climate and pasture production in mid-Canterbury have
been discussed by Rickard (1968). Under “dryland” farming
conditions, pasture
of some 110 to 130 aBys when production is very low
reduction is-limited by (1) winters
and (2) dry periods of variable incidence and duration
during the remainder of the year. These latter not only
restrict output every year but also result in a large “between
years ’ variation in annual pasture production. However,
adequate irrigation eliminates the dry periods and
results in pasture production characterized by :
(1) A higher annual production of some 9,000 to 10,000
lb D.M. per acre.
(2) A very low variability between years.
(3) Well-spread production within the growing season.
(4) Approximately half of total growth occurring after January 1.
For the livestock farmer, the implications of these changes
are very great.
The pattern of irrigated pasture reduction was shown
to coincide more closely with the feed requirements of a
beef-breeding herd than with those of a prime-lamb ewe
flock. However, as more calves become available from increased
cow herds in the foothills and high country, and
these are augmented by calves bred on dairy farms, it
seems probable that beef production on the easier country
will become concentrated on finishing, rather than on
breeding. This paper outlines experimental work into
finishing beef cattle at Winchmore Irrigation Research
Station and considers the potential for beef production
in mid-Canterbury in the light of the results obtained
Evaluation of Ice and Frost Accumulation on the Space Shuttle External Tank
Ice/Frost formation on the Space Shuttle cryogenic propellant tanks presents a different problem from that of past launch vehicles. Lift off weight addition has been the primary concern on past launch vehicles. The primary ice/frost concern on the Shuttle vehicle is damage to the Orbiter Thermal Protection System due to ice/frost impact. The approach used to arrive at a solution to this unique Shuttle problem is presented. The launch vehicle configuration selected and its limitations are described, along with contingency ground support equipment
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