1,239 research outputs found
THE ISOTRON
Most methods of separating isotopes depend on the use of a large magnetic field. The isotron is an electromagnetic device for separating isotopes, but it effects the separation by the use of radiofrequency voltages instead of magnetic fields. It has the advantage that plane sources of large area can be used instead of the slit sources to which most magnetic methods are limited. Before entering into any discussion of the details, a simplified description of the principles of the method is given
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Tevatron improvement program
A modest Tevatron improvement program is suggested which would provide a storage ring for dedicated use as a p anti p collider at 2 TeV (cm) and as an ep collider at 0.2 TeV (cm). It could also serve as a useful test facility for some of the new developments necessary for an economical SSC. Because use could be made of utilities and facilities that are already installed as part of the tevatron, the cost of the p anti p option might be about 100 million dollars (not including the interaction halls or detectors). The additional cost of a 10 x 1000 GeV' ep option might be about 70 million dollars. The experimental facilities at B and D of the Tevatron might be extended for use with the new collider. As the technology of superconducting magnets develops, the cm energy of the p anti p and the ep colliders might be doubled. The intention is either to double the capability of TeV I and TeV II, or to extend the capability by addition of an ep facility. Alternatively, by adding another proton ring, a high luminosity pp facility might also result
Coronal Fe XIV Emission During the Whole Heliosphere Interval Campaign
Solar Cycle 24 is having a historically long and weak start. Observations of
the Fe XIV corona from the Sacramento Peak site of the National Solar
Observatory show an abnormal pattern of emission compared to observations of
Cycles 21, 22, and 23 from the same instrument. The previous three cycles have
shown a strong, rapid "Rush to the Poles" (previously observed in polar crown
prominences and earlier coronal observations) in the parameter N(t,l,dt)
(average number of Fe XIV emission features per day over dt days at time t and
latitude l). Cycle 24 displays a weak, intermittent, and slow "Rush" that is
apparent only in the northern hemisphere. If the northern Rush persists at its
current rate, evidence from the Rushes in previous cycles indicates that solar
maximum will occur in early 2013 or late 2012, at least in the northern
hemisphere. At lower latitudes, solar maximum previously occurred when the time
maximum of N(t,l,365) reached approximately 20{\deg} latitude. Currently, this
parameter is at or below 30{\deg}and decreasing in latitude. Unfortunately, it
is difficult at this time to calculate the rate of decrease in N(t,l,365).
However, the southern hemisphere could reach 20{\deg} in 2011. Nonetheless,
considering the levels of activity so far, there is a possibility that the
maximum could be indiscernibleComment: 8 pages, 4 figures; Solar Physics Online First, 2011
http://www.springerlink.com/content/b5kl4040k0626647
Critical temperature for the two-dimensional attractive Hubbard Model
The critical temperature for the attractive Hubbard model on a square lattice
is determined from the analysis of two independent quantities, the helicity
modulus, , and the pairing correlation function, . These
quantities have been calculated through Quantum Monte Carlo simulations for
lattices up to , and for several densities, in the
intermediate-coupling regime. Imposing the universal-jump condition for an
accurately calculated , together with thorough finite-size scaling
analyses (in the spirit of the phenomenological renormalization group) of
, suggests that is considerably higher than hitherto assumed.Comment: 5 pages, 6 figures. Accepted for publication in Phys. Rev.
Foam Diagram Summation at Finite Temperature
We show that large- theory is not trivial if one accepts the
presence of a tachyon with a truly huge mass, and that it allows exact
calculation. We use it to illustrate how to calculate the exact resummed
pressure at finite temperature and verify that it is infrared and ultraviolet
finite even in the zero-mass case. In 3 dimensions a residual effect of the
resummed infrared divergences is that at low temperature or strong coupling the
leading term in the interaction pressure becomes independent of the coupling
and is 4/5 of the free-field pressure. In 4 dimensions the pressure is
well-defined provided that the temperature is below the tachyon mass. We
examine how rapidly this expansion converges and use our analysis to suggest
how one might reorganise perturbation theory to improve the calculation of the
pressure for the QCD plasma.Comment: 18 pages plain tex, with 8 figures embedded with epsf. Equation
(2.15) has been corrected and the consequent changes made to the figures. A
further analytic result has been added to the 3-dimensional calculatio
Healthcare-associated outbreak of meticillin-resistant Staphylococcus aureus bacteraemia: role of a cryptic variant of an epidemic clone
BACKGROUND
New strains of meticillin-resistant Staphylococcus aureus (MRSA) may be associated with changes in rates of disease or clinical presentation. Conventional typing techniques may not detect new clonal variants that underlie changes in epidemiology or clinical phenotype.
AIM
To investigate the role of clonal variants of MRSA in an outbreak of MRSA bacteraemia at a hospital in England.
METHODS
Bacteraemia isolates of the major UK lineages (EMRSA-15 and -16) from before and after the outbreak were analysed by whole-genome sequencing in the context of epidemiological and clinical data. For comparison, EMRSA-15 and -16 isolates from another hospital in England were sequenced. A clonal variant of EMRSA-16 was identified at the outbreak hospital and a molecular signature test designed to distinguish variant isolates among further EMRSA-16 strains.
FINDINGS
By whole-genome sequencing, EMRSA-16 isolates during the outbreak showed strikingly low genetic diversity (P < 1 × 10(-6), Monte Carlo test), compared with EMRSA-15 and EMRSA-16 isolates from before the outbreak or the comparator hospital, demonstrating the emergence of a clonal variant. The variant was indistinguishable from the ancestral strain by conventional typing. This clonal variant accounted for 64/72 (89%) of EMRSA-16 bacteraemia isolates at the outbreak hospital from 2006.
CONCLUSIONS
Evolutionary changes in epidemic MRSA strains not detected by conventional typing may be associated with changes in disease epidemiology. Rapid and affordable technologies for whole-genome sequencing are becoming available with the potential to identify and track the emergence of variants of highly clonal organisms
Digital Simulation for Automobile Maneuvers
A new all-digital simulation of automobile handling allows severe maneuvers involving braking or accel eration and cornering. A novel feature is the in corporation of closed-loop control based on a mathematical model of the human driver. The program is modular and well-documented. The model includes provisions for nonlinear tire and suspension forces and moments; it also allows the user to switch off the nonlinearities and to include an antilock brake system.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/68886/2/10.1177_003754978103700304.pd
Emergence of Bulk CsCl Structure in (CsCl)nCs+ Cluster Ions
The emergence of CsCl bulk structure in (CsCl)nCs+ cluster ions is
investigated using a mixed quantum-mechanical/semiempirical theoretical
approach. We find that rhombic dodecahedral fragments (with bulk CsCl symmetry)
are more stable than rock-salt fragments after the completion of the fifth
rhombic dodecahedral atomic shell. From this size (n=184) on, a new set of
magic numbers should appear in the experimental mass spectra. We also propose
another experimental test for this transition, which explicitely involves the
electronic structure of the cluster. Finally, we perform more detailed
calculations in the size range n=31--33, where recent experimental
investigations have found indications of the presence of rhombic dodecahedral
(CsCl)32Cs+ isomers in the cluster beams.Comment: LaTeX file. 6 pages and 4 pictures. Accepted for publication in Phys.
Rev.
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