330 research outputs found
Detection of polytreponemal infection in three cases of porcine ulcerative stomatitis by Fluorescent in situ hybridization
Short Time Behavior in De Gennes' Reptation Model
To establish a standard for the distinction of reptation from other modes of
polymer diffusion, we analytically and numerically study the displacement of
the central bead of a chain diffusing through an ordered obstacle array for
times . Our theory and simulations agree quantitatively and show
that the second moment approaches the often viewed as signature of
reptation only after a very long transient and only for long chains (N > 100).
Our analytically solvable model furthermore predicts a very short transient for
the fourth moment. This is verified by computer experiment.Comment: 4 pages, revtex, 4 ps file
On the Flavor Structure of the Constituent Quark
We discuss the dressing of constituent quarks with a pseudoscalar meson cloud
within the effective chiral quark model. SU(3) flavor symmetry breaking effects
are included explicitly. Our results are compared with those of the traditional
meson cloud approach in which pions are coupled to the nucleon. The pionic
dressing of the constituent quarks explains the experimentally observed
violation of the Gottfried Sum Rule and leads to an enhanced nonperturbative
sea of quark-antiquark pairs in the constituent quark and consequently in the
nucleon. We find 2.5 times more pions and 10-15 times more kaons in the nucleon
than in the traditional picture.Comment: 7 pages, LaTeX, 4 Postscript figures, to appear in J. Phys.
Anomalous Dynamics of Translocation
We study the dynamics of the passage of a polymer through a membrane pore
(translocation), focusing on the scaling properties with the number of monomers
. The natural coordinate for translocation is the number of monomers on one
side of the hole at a given time. Commonly used models which assume Brownian
dynamics for this variable predict a mean (unforced) passage time that
scales as , even in the presence of an entropic barrier. However, the time
it takes for a free polymer to diffuse a distance of the order of its radius by
Rouse dynamics scales with an exponent larger than 2, and this should provide a
lower bound to the translocation time. To resolve this discrepancy, we perform
numerical simulations with Rouse dynamics for both phantom (in space dimensions
and 2), and self-avoiding (in ) chains. The results indicate that
for large , translocation times scale in the same manner as diffusion times,
but with a larger prefactor that depends on the size of the hole. Such scaling
implies anomalous dynamics for the translocation process. In particular, the
fluctuations in the monomer number at the hole are predicted to be
non-diffusive at short times, while the average pulling velocity of the polymer
in the presence of a chemical potential difference is predicted to depend on
.Comment: 9 pages, 9 figures. Submitted to Physical Review
Das Verhalten hoher Plutoniumkonzentrationen im Purex-Prozeß und die Entwicklung schneller Extraktoren zur Wiederaufarbeitung von Kernbrennstoffen. EUR 3683. = The behavior of high plutonium concentrations in the Purex process and the development of fast extractors for the reprocessing of nuclear fuels. EUR 3683.
Impact assessment of the biological control of the cassava mealybug, Phenacoccus manihoti Matile-Ferrero (Hemiptera: Pseudococcidae), by the introduced parasitoid Epidinocarsis lopezi (De Santis) (Hymenoptera: Encyrtidae)
The impact of Phenacoccus manihoti Matile-Ferrero on growth and tuber yield of cassava, and the results of its biological control by the exotic parasitoid Epidinocarsis lopezi (De Santis) were investigated in a survey of 60 farmers' fields in Ghana and Ivory Coast over an area of 180 000 km2 of the savana and forest ecosystems. Twenty-nine variables associated with plant growth, agronomic and environmental factors, and insect populations were recorded. Densities of P. manihoti were closely correlated with stunting of the cassava shoot tips and, less so, with the rate of stunting early in the growing season. With increasing mealybug infestations, average harvest indices declined and populations of E. lopezi and of indigenous coccinellids increased, but parasitoids were found at lower host levels than were predators. The length of time E. lopezi had been present in an area was the most important factor influencing mealybug densities. Thus, P. manihoti populations were significantly lower where E. lopezi had been present for more than half the planting season than in areas where E. lopezi was lacking or had been only recently introduced. A significant proportion of the farmers in the savanna zone, where P. manihoti populations were much higher than in the forest zone, had observed this decline due to E. lopezi. Tuber yield losses due to P. manihoti in the absence of E. lopezi were tentatively estimated at 463 g/plant in the savanna zone. No significant effect was found in the forest region. When E. lopezi was present, average P. manihoti damage scores were reduced significantly, both in the savanna and forest regions. The increase in yields was 228g/plant or about 2.48 t/ha in the savanna regio
P-Band Induced Self-Organization and Dynamics with Repulsively Driven Ultracold Atoms in an Optical Cavity.
We investigate a Bose-Einstein condensate strongly coupled to an optical cavity via a repulsive optical lattice. We detect a stable self-ordered phase in this regime, and show that the atoms order through an antisymmetric coupling to the P band of the lattice, limiting the extent of the phase and changing the geometry of the emergent density modulation. Furthermore, we find a nonequilibrium phase with repeated intense bursts of the intracavity photon number, indicating nontrivial driven-dissipative dynamics
Axonopathy in the central nervous system is the hallmark of mice with a novel intragenic null mutation of dystonin.
Dystonia musculorum is a neurodegenerative disorder caused by a mutation in the dystonin gene. It has been described in mice and humans where it is called hereditary sensory autonomic neuropathy. Mutated mice show severe movement disorders and die at the age of 3-4 weeks. This study describes the discovery and molecular, clinical, as well as pathological characterization of a new spontaneously occurring mutation in the dystonin gene in C57BL/6N mice. The mutation represents a 40-kb intragenic deletion allele of the dystonin gene on chromosome 1 with exactly defined deletion borders. It was demonstrated by Western blot, mass spectrometry, and immunohistology that mice with a homozygous mutation were entirely devoid of the dystonin protein. Pathomorphological lesions were restricted to the brain stem and spinal cord and consisted of swollen, argyrophilic axons and dilated myelin sheaths in the white matter and, less frequently, total chromatolysis of neurons in the gray matter. Axonal damage was detected by amyloid precursor protein and nonphosphorylated neurofilament immunohistology. Axonopathy in the central nervous system (CNS) represents the hallmark of this disease. Mice with the dystonin mutation also showed suppurative inflammation in the respiratory tract, presumably due to brain stem lesion-associated food aspiration, whereas skeletal muscles showed no pathomorphological changes. This study describes a novel mutation in the dystonin gene in mice leading to axonopathy in the CNS. In further studies, this model may provide new insights into the pathogenesis of neurodegenerative diseases and may elucidate the complex interactions of dystonin with various other cellular proteins especially in the CNS
Statistical Mechanics of Membrane Protein Conformation: A Homopolymer Model
The conformation and the phase diagram of a membrane protein are investigated
via grand canonical ensemble approach using a homopolymer model. We discuss the
nature and pathway of -helix integration into the membrane that results
depending upon membrane permeability and polymer adsorptivity. For a membrane
with the permeability larger than a critical value, the integration becomes the
second order transition that occurs at the same temperature as that of the
adsorption transition. For a nonadsorbing membrane, the integration is of the
first order due to the aggregation of -helices.Comment: RevTeX with 5 postscript figure
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