322 research outputs found
The effect of concurrent infections with Pasteurella multocida and Ascaridia galli on free range chickens
Pasteurella multocida and Ascaridia galli are observed with high prevalences in free range chickens in Denmark, but the impact is unknown. A study was carried out to examine the interaction between A. galli and P. multocida in chickens and the impact on production. Five groups, each with 20 18-week-old Lohmann Brown chickens were infected. Group I was orally infected with 1000 +/- 50 embryonated A. galli eggs. Group 2 received 10(4) cfu p. multocida intratracheally. Group 3 was infected with A. galli and subsequently with P. multocida. Group 4 was infected with P. multocida followed by A. galli. Group 5 was the control. The study ran for I I weeks where clinical manifestations, weight gain and egg production were recorded. Excretion of P. multocida was determined on individual basis and blood smears were made for differential counts. At the end of the study pathological lesions and the number of adult worms, larvae and eggs in the faeces were recorded. The birds were more severely affected when infected with both pathogens compared to single infections with A. galli or P. multocida, respectively. A lower weight gain and egg production was observed with dual infections. A. galli infection followed by a secondary P. multocida infection resulted in more birds with pathological lesions and continued P. multocida excretion. In conclusion a negative interaction between A. galli and R multocida was observed and it is postulated that free range chickens are at higher risk of being subjected to outbreaks of fowl cholera when they are infected with A. galli
Deployment Evaluation Methodology for the Electrometallurgical Treatment of DOE-EM Spent Nuclear Fuel
The Department of Energy - Environmental Management (DOE-EM) National Spent Nuclear Fuel Program (NSNFP) is charged with the disposition of legacy spent nuclear fuel (SNF). While direct repository disposal of the SNF is the preferred disposition option, some DOE SNF may need treatment to meet acceptance criteria at various disposition sites. The treatments may range from electrometallurgical treatment (EMT) and chemical dissolution to engineering controls. As a planning basis, a need is assumed for a treatment process, either as a primary or backup technology, that is compatible with, and cost-effective for, this portion of the DOE-EM inventory. The current planning option for treating this SNF, pending completion of development work and National Environmental Policy Act (NEPA) analysis, is the EMT process under development by Argonne National Laboratory - West (ANL-W). A decision on the deployment of the EMT is pending completion of an engineering scale demonstration currently in progress at ANL-W. For this study, a set of questions was developed for the EMT process for fuels at several locations. The set of questions addresses all issues associated with design, construction, and operation of a production facility. A matrix table was developed to determine questions applicable to various fuel treatment options. A work breakdown structure (WBS) was developed to identify a treatment process and costs from initial design to shipment of treatment products to final disposition. Costs were applied to determine the life-cycle cost of each option. This technique can also be applied to other treatment techniques for treating SNF
Phase space formalisms of quantum mechanics with singular kernel
The equivalence of the Rivier-Margenau-Hill and Born-Jordan-Shankara phase
space formalisms to the conventional operator approach of quantum mechanics is
demonstrated. It is shown that in spite of the presence of singular kernels the
mappings relating phase space functions and operators back and forth are
possible.Comment: 15 pages, no figures, LATE
Decoherence of molecular wave packets in an anharmonic potential
The time evolution of anharmonic molecular wave packets is investigated under
the influence of the environment consisting of harmonic oscillators. These
oscillators represent photon or phonon modes and assumed to be in thermal
equilibrium. Our model explicitly incorporates the fact that in the case of a
nonequidistant spectrum the rates of the environment induced transitions are
different for each transition. The nonunitary time evolution is visualized by
the aid of the Wigner function related to the vibrational state of the
molecule. The time scale of decoherence is much shorter than that of
dissipation, and gives rise to states which are mixtures of localized states
along the phase space orbit of the corresponding classical particle. This
behavior is to a large extent independent of the coupling strength, the
temperature of the environment and also of the initial state.Comment: 7 pages, 4 figure
Testing one-body density functionals on a solvable model
There are several physically motivated density matrix functionals in the
literature, built from the knowledge of the natural orbitals and the occupation
numbers of the one-body reduced density matrix. With the help of the equivalent
phase-space formalism, we thoroughly test some of the most popular of those
functionals on a completely solvable model.Comment: Latex, 16 pages, 4 figure
Fine structure of excitons in CuO
Three experimental observations on 1s-excitons in CuO are not consistent
with the picture of the exciton as a simple hydrogenic bound state: the
energies of the 1s-excitons deviate from the Rydberg formula, the total exciton
mass exceeds the sum of the electron and hole effective masses, and the
triplet-state excitons lie above the singlet. Incorporating the band structure
of the material, we calculate the corrections to this simple picture arising
from the fact that the exciton Bohr radius is comparable to the lattice
constant. By means of a self-consistent variational calculation of the total
exciton mass as well as the ground-state energy of the singlet and the
triplet-state excitons, we find excellent agreement with experiment.Comment: Revised abstract; 10 pages, revtex, 3 figures available from G.
Kavoulakis, Physics Department, University of Illinois, Urban
Auger decay of degenerate and Bose-condensed excitons in CuO
We study the non-radiative Auger decay of excitons in CuO, in which two
excitons scatter to an excited electron and hole. The exciton decay rate for
the direct and the phonon-assisted processes is calculated from first
principles; incorporating the band structure of the material leads to a
relatively shorter lifetime of the triplet state ortho excitons. We compare our
results with the Auger decay rate extracted from data on highly degenerate
triplet excitons and Bose-condensed singlet excitons in CuO.Comment: 15 pages, revtex, figures available from G. Kavoulaki
Quantum saturation and condensation of excitons in CuO: a theoretical study
Recent experiments on high density excitons in CuO provide evidence for
degenerate quantum statistics and Bose-Einstein condensation of this nearly
ideal gas. We model the time dependence of this bosonic system including
exciton decay mechanisms, energy exchange with phonons, and interconversion
between ortho (triplet-state) and para (singlet-state) excitons, using
parameters for the excitonic decay, the coupling to acoustic and low-lying
optical phonons, Auger recombination, and ortho-para interconversion derived
from experiment. The single adjustable parameter in our model is the
optical-phonon cooling rate for Auger and laser-produced hot excitons. We show
that the orthoexcitons move along the phase boundary without crossing it (i.e.,
exhibit a ``quantum saturation''), as a consequence of the balance of entropy
changes due to cooling of excitons by phonons and heating by the non-radiative
Auger two-exciton recombination process. The Auger annihilation rate for
para-para collisions is much smaller than that for ortho-para and ortho-ortho
collisions, explaining why, under the given experimental conditions, the
paraexcitons condense while the orthoexcitons fail to do so.Comment: Revised to improve clarity and physical content 18 pages, revtex,
figures available from G. Kavoulakis, Physics Department, University of
Illinois, Urban
The Fuzzy Disc
We introduce a finite dimensional matrix model approximation to the algebra
of functions on a disc based on noncommutative geometry. The algebra is a
subalgebra of the one characterizing the noncommutative plane with a * product
and depends on two parameters N and theta. It is composed of functions which
decay exponentially outside a disc. In the limit in which the size of the
matrices goes to infinity and the noncommutativity parameter goes to zero the
disc becomes sharper. We introduce a Laplacian defined on the whole algebra and
calculate its eigenvalues. We also calculate the two--points correlation
function for a free massless theory (Green's function). In both cases the
agreement with the exact result on the disc is very good already for relatively
small matrices. This opens up the possibility for the study of field theories
on the disc with nonperturbative methods. The model contains edge states, a
fact studied in a similar matrix model independently introduced by
Balachandran, Gupta and Kurkcuoglu.Comment: 17 pages, 8 figures, references added and correcte
Insights into the function of silver as an oxidation catalyst by ab initio, atomistic thermodynamics
To help understand the high activity of silver as an oxidation catalyst,
e.g., for the oxidation of ethylene to epoxide and the dehydrogenation of
methanol to formaldehyde, the interaction and stability of oxygen species at
the Ag(111) surface has been studied for a wide range of coverages. Through
calculation of the free energy, as obtained from density-functional theory and
taking into account the temperature and pressure via the oxygen chemical
potential, we obtain the phase diagram of O/Ag(111). Our results reveal that a
thin surface-oxide structure is most stable for the temperature and pressure
range of ethylene epoxidation and we propose it (and possibly other similar
structures) contains the species actuating the catalysis. For higher
temperatures, low coverages of chemisorbed oxygen are most stable, which could
also play a role in oxidation reactions. For temperatures greater than about
775 K there are no stable oxygen species, except for the possibility of O atoms
adsorbed at under-coordinated surface sites Our calculations rule out thicker
oxide-like structures, as well as bulk dissolved oxygen and molecular
ozone-like species, as playing a role in the oxidation reactions.Comment: 15 pages including 9 figures, Related publications can be found at
http://www.fhi-berlin.mpg.de/th/paper.htm
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