9,693 research outputs found
Colour-singlet strangelets at finite temperature
Considering massless and quarks, and massive (150 MeV) quarks in
a bag with the bag pressure constant MeV, a colour-singlet
grand canonical partition function is constructed for temperatures
MeV. Then the stability of finite size strangelets is studied minimizing the
free energy as a function of the radius of the bag. The colour-singlet
restriction has several profound effects when compared to colour unprojected
case: (1) Now bulk energy per baryon is increased by about MeV making the
strange quark matter unbound. (2) The shell structures are more pronounced
(deeper). (3) Positions of the shell closure are shifted to lower -values,
the first deepest one occuring at , famous -particle ! (4) The shell
structure at vanishes only at MeV, though for higher
-values it happens so at MeV.Comment: Revtex file(8 pages)+6 figures(ps files) available on request from
first Autho
Solving the m-mixing problem for the three-dimensional time-dependent Schr\"{o}dinger equation by rotations: application to strong-field ionization of H2+
We present a very efficient technique for solving the three-dimensional
time-dependent Schrodinger equation. Our method is applicable to a wide range
of problems where a fullly three-dimensional solution is required, i.e., to
cases where no symmetries exist that reduce the dimensionally of the problem.
Examples include arbitrarily oriented molecules in external fields and atoms
interacting with elliptically polarized light. We demonstrate that even in such
cases, the three-dimensional problem can be decomposed exactly into two
two-dimensional problems at the cost of introducing a trivial rotation
transformation. We supplement the theoretical framework with numerical results
on strong-field ionization of arbitrarily oriented H2+ molecules.Comment: 5 pages, 4 figure
Bulletin No. 341 - Rambouillet and Columbia-Rambouillet Lambs on the Range and in the Feed Lot
Sheep of predominately Rambouillet breeding have been most popular on southern Utah ranges because of their hardiness and wool-producing ability. In the early years of sheep production in Utah a major portion of the income was derived from the sale of wool. This situation has gradually changed over the past years and now income from the sale of lambs is greater than that from fleeces. Rambouillet rams with improved mutton qualities have been used by some range operators to increase the mutton producing abilities of their ewes. Other operators have used Corriedale, Panama, Columbia, and other white faced crossbred-type rams to achieve more speedily the desired mutton qualities.
Because of the interest of Utah sheepmen in the problem of improving their range ewes, the Utah Agricultural Experiment Station, in cooperation with the Branch Agricultural College at Cedar City, established a range sheep unit at Cedar City in 1943 and 1944. This unit has been used to conduct controlled breeding studies aimed at the determination of the type or breed of sheep most desirable for southern Utah range conditions. This bulletin reviews the initial results and gives attention particularly to the qualities of the lambs produced by mating Columbia rams to grade Rambouillet range ewes compared to those produced by mating Rambouillet rams to ewes similar to those bred to the Columbias
Parasites and other infectious agents in marine finfish and shellfish species posing a hazard to human health (ToR b)
Very Small Strangelets
We study the stability of small strangelets by employing a simple model of
strange matter as a gas of non-interacting fermions confined in a bag. We solve
the Dirac equation and populate the energy levels of the bag one quark at a
time. Our results show that for system parameters such that strange matter is
unbound in bulk, there may still exist strangelets with that are stable
and/or metastable. The lifetime of these strangelets may be too small to detect
in current accelerator experiments, however.Comment: 13 pages, MIT CTP#217
A Quark-Antiquark Condensate in Three-Dimensional QCD
Three-dimensional lattice QCD is studied by Monte Carlo simulations within
the quenched approximation. At zero temperature a quark-antiquark condensate is
observed in the limit of vanishing quark masses. The condensate vanishes
continuously at the finite-temperature deconfinement phase transition of the
theory. A natural interpretation of this phenomenon in the full theory with
dynamical quarks is in terms of the spontaneous flavor symmetry breaking
. In addition, the spectrum of low-lying
Dirac operator eigenvalues is computed and found to be consistent with a flat
distribution at zero temperature, in agreement with analytical predictions.Comment: Extensive revision of the original version. 11 pages, 6 figures
included as EPS files. The problem with figure encapsulation fixe
Manipulating the torsion of molecules by strong laser pulses
A proof-of-principle experiment is reported, where torsional motion of a
molecule, consisting of a pair of phenyl rings, is induced by strong laser
pulses. A nanosecond laser pulse spatially aligns the carbon-carbon bond axis,
connecting the two phenyl rings, allowing a perpendicularly polarized, intense
femtosecond pulse to initiate torsional motion accompanied by an overall
rotation about the fixed axis. The induced motion is monitored by femtosecond
time-resolved Coulomb explosion imaging. Our theoretical analysis accounts for
and generalizes the experimental findings.Comment: 4 pages, 4 figures, submitted to PRL; Major revision of the
presentation of the material; Correction of ion labels in Fig. 2(a
Biodesalination: an emerging technology for targeted removal of Na+and Cl−from seawater by cyanobacteria
Although desalination by membrane processes is a possible solution to the problem of freshwater supply, related cost and energy demands prohibit its use on a global scale. Hence, there is an emerging necessity for alternative, energy and cost-efficient methods for water desalination. Cyanobacteria are oxygen-producing, photosynthetic bacteria that actively grow in vast blooms both in fresh and seawater bodies. Moreover, cyanobacteria can grow with minimal nutrient requirements and under natural sunlight. Taking these observations together, a consortium of five British Universities was formed to test the principle of using cyanobacteria as ion exchangers, for the specific removal of Na+ and Cl− from seawater. This project consisted of the isolation and characterisation of candidate strains, with central focus on their potential to be osmotically and ionically adaptable. The selection panel resulted in the identification of two Euryhaline strains, one of freshwater (Synechocystis sp. Strain PCC 6803) and one of marine origin (Synechococcus sp. Strain PCC 7002) (Robert Gordon University, Aberdeen). Other work packages were as follows. Genetic manipulations potentially allowed for the expression of a light-driven, Cl−-selective pump in both strains, therefore, enhancing the bioaccumulation of specific ions within the cell (University of Glasgow). Characterisation of surface properties under different salinities (University of Sheffield), ensured that cell–liquid separation efficiency would be maximised post-treatment, as well as monitoring the secretion of mucopolysaccharides in the medium during cell growth. Work at Newcastle University is focused on the social acceptance of this scenario, together with an assessment of the potential risks through the generation and application of a Hazard Analysis and Critical Control Points plan. Finally, researchers in Imperial College (London) designed the process, from biomass production to water treatment and generation of a model photobioreactor. This multimodal approach has produced promising first results, and further optimisation is expected to result in mass scaling of this process
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