715 research outputs found
No-Core Shell Model for Nuclear Systems with Strangeness
We report on a novel ab initio approach for nuclear few- and many-body
systems with strangeness. Recently, we developed a relevant no-core shell model
technique which we successfully applied in first calculations of lightest
hypernuclei. The use of a translationally invariant finite harmonic
oscillator basis allows us to employ large model spaces, compared to
traditional shell model calculations, and use realistic nucleon-nucleon and
nucleon-hyperon interactions (such as those derived from EFT). We discuss
formal aspects of the methodology, show first demonstrative results for
H, H and He, and give outlook.Comment: 4 pages, 3 figures; Proceedings of the 22nd European Conference on
Few Body Problems in Physics, 9 - 13 September, 2013, Cracow, Polan
- nucleus relativistic mean field potentials consistent with kaonic atoms
atomic data are used to test several models of the nucleus
interaction. The t() optical potential, due to coupled channel
models incorporating the (1405) dynamics, fails to reproduce these
data. A standard relativistic mean field (RMF) potential, disregarding the
(1405) dynamics at low densities, also fails. The only successful
model is a hybrid of a theoretically motivated RMF approach in the nuclear
interior and a completely phenomenological density dependent potential, which
respects the low density theorem in the nuclear surface region. This best-fit
optical potential is found to be strongly attractive, with a depth of 180
\pm 20 MeV at the nuclear interior, in agreement with previous phenomenological
analyses.Comment: revised, Phys. Rev. C in pres
SmSP2: A serine protease secreted by the blood fluke pathogen Schistosoma mansoni with anti-hemostatic properties.
BackgroundSerine proteases are important virulence factors for many pathogens. Recently, we discovered a group of trypsin-like serine proteases with domain organization unique to flatworm parasites and containing a thrombospondin type 1 repeat (TSR-1). These proteases are recognized as antigens during host infection and may prove useful as anthelminthic vaccines, however their molecular characteristics are under-studied. Here, we characterize the structural and proteolytic attributes of serine protease 2 (SmSP2) from Schistosoma mansoni, one of the major species responsible for the tropical infectious disease, schistosomiasis.Methodology/principal findingsSmSP2 comprises three domains: a histidine stretch, TSR-1 and a serine protease domain. The cleavage specificity of recombinant SmSP2 was determined using positional scanning and multiplex combinatorial libraries and the determinants of specificity were identified with 3D homology models, demonstrating a trypsin-like endopeptidase mode of action. SmSP2 displayed restricted proteolysis on protein substrates. It activated tissue plasminogen activator and plasminogen as key components of the fibrinolytic system, and released the vasoregulatory peptide, kinin, from kininogen. SmSP2 was detected in the surface tegument, esophageal glands and reproductive organs of the adult parasite by immunofluorescence microscopy, and in the excretory/secretory products by immunoblotting.Conclusions/significanceThe data suggest that SmSP2 is secreted, functions at the host-parasite interface and contributes to the survival of the parasite by manipulating host vasodilatation and fibrinolysis. SmSP2 may be, therefore, a potential target for anti-schistosomal therapy
Profiling of proteolytic enzymes in the gut of the tick Ixodes ricinus reveals an evolutionarily conserved network of aspartic and cysteine peptidases
<p>Abstract</p> <p>Background</p> <p>Ticks are vectors for a variety of viral, bacterial and parasitic diseases in human and domestic animals. To survive and reproduce ticks feed on host blood, yet our understanding of the intestinal proteolytic machinery used to derive absorbable nutrients from the blood meal is poor. Intestinal digestive processes are limiting factors for pathogen transmission since the tick gut presents the primary site of infection. Moreover, digestive enzymes may find practical application as anti-tick vaccine targets.</p> <p>Results</p> <p>Using the hard tick, <it>Ixodes ricinus</it>, we performed a functional activity scan of the peptidase complement in gut tissue extracts that demonstrated the presence of five types of peptidases of the cysteine and aspartic classes. We followed up with genetic screens of gut-derived cDNA to identify and clone genes encoding the cysteine peptidases cathepsins B, L and C, an asparaginyl endopeptidase (legumain), and the aspartic peptidase, cathepsin D. By RT-PCR, expression of asparaginyl endopeptidase and cathepsins B and D was restricted to gut tissue and to those developmental stages feeding on blood.</p> <p>Conclusion</p> <p>Overall, our results demonstrate the presence of a network of cysteine and aspartic peptidases that conceivably operates to digest host blood proteins in a concerted manner. Significantly, the peptidase components of this digestive network are orthologous to those described in other parasites, including nematodes and flatworms. Accordingly, the present data and those available for other tick species support the notion of an evolutionary conservation of a cysteine/aspartic peptidase system for digestion that includes ticks, but differs from that of insects relying on serine peptidases.</p
IMPACTS OF DIETARY CYANOBACTERIA ON FISH
Abstract ZIKOVÁ, A., PALÍKOVÁ, M., MAREŠ, J., NAVRÁTIL, S., KOPP, R.: Impacts of dietary cyanobacteria on fi sh. Acta univ. agric. et silvic. Mendel. Brun., 2010, LVIII, No. 4, pp. 277-284 Development of cyanobacterial water bloom became a common issue all over the world. Cyanobacteria are the most important primary producers in aquatic ecosystems but in some abundant species their secondary metabolites called cyanotoxins seem to be harmful for many animal groups especially mammals but also fi sh. In fi shes, adverse eff ects have been demonstrated in several studies applying cyanotoxins by unnatural injection. However, cyanobacteria and fi sh coevolved during ages and therefore the question arises whether cyanobacteria might be even used for fi sh via oral application (fi sh diet). The use of cyanobacteria for fi sh diets is varying including applications of pure cyanobacteria biomass as well as incorporation of cyanotoxin containing cyanobacteria biomass into commercial fi sh diet. The impacts of cyanobacteria in fi sh diets administered via the oral route revealed contradictory fi ndings ranging from moderate negative to growth promoting impacts and it seems that any bioaccumulation of microcystins can become depurated by rearing fi sh in clean water for a short period. According to the results obtained from various experiments, cyanobacteria as primary producers might be used as a component of fi sh diets especially concerning partial replacement of fi sh meal. However, the determination of nutrition value and the bioavailibility of nutrients present in cyanobacteria for diff erent fi sh species needs to be determined. Furthermore thorough research is needed to exclude any harmful problem for the fi nal consumers -humans. blue-green algae; fi sh diet; cyanotoxins Cyanobacteria development became recently the most discussed topic all over the worl
Correlated pairs from the reaction
Correlated pairs emitted after the absorption of negative kaons
at rest in light nuclei and are
studied. -hyperons and deuterons are found to be preferentially
emitted in opposite directions. The invariant mass spectrum of
shows a bump whose mass is 32516 MeV/c. The bump mass (binding
energy), width and yield are reported. The appearance of a bump is discussed in
the realm of the [] clustering process in nuclei. The experiment was
performed with the FINUDA spectrometer at DANE (LNF).Comment: 13 pages, 5 figures, accepted for publication in Phys. Lett.
Observation of the screening signature in the lateral photovoltage of electrons in the Quantum Hall regime
The lateral photovoltage generated in the plane of a two-dimensional electron
system (2DES) by a focused light spot, exhibits a fine-structure in the quantum
oscillations in a magnetic field near the Quantum Hall conductivity minima. A
double peak structure occurs near the minima of the longitudinal conductivity
oscillations. This is the characteristic signature of the interplay between
screening and Landau quantization.Comment: 4 pages, 4 figures, to be published in Phys. Rev.
Negative Kaons in Dense Baryonic Matter
Kaon polarization operator in dense baryonic matter of arbitrary isotopic
composition is calculated including s- and p-wave kaon-baryon interactions. The
regular part of the polarization operator is extracted from the realistic
kaon-nucleon interaction based on the chiral and 1/N_c expansion. Contributions
of the Lambda(1116), Sigma(1195), Sigma*(1385) resonances are taken explicitly
into account in the pole and regular terms with inclusion of mean-field
potentials. The baryon-baryon correlations are incorporated and fluctuation
contributions are estimated. Results are applied for K- in neutron star matter.
Within our model a second-order phase transition to the s-wave K- condensate
state occurs at rho_c \gsim 4 \rho_0 once the baryon-baryon correlations are
included. We show that the second-order phase transition to the p-wave
condensate state may occur at densities in
dependence on the parameter choice. We demonstrate that a first-order phase
transition to a proton-enriched (approximately isospin-symmetric) nucleon
matter with a p-wave K- condensate can occur at smaller densities, \rho\lsim 2
\rho_0. The transition is accompanied by the suppression of hyperon
concentrations.Comment: 41 pages, 24 figures, revtex4 styl
Charge separation relative to the reaction plane in Pb-Pb collisions at TeV
Measurements of charge dependent azimuthal correlations with the ALICE
detector at the LHC are reported for Pb-Pb collisions at TeV. Two- and three-particle charge-dependent azimuthal correlations in
the pseudo-rapidity range are presented as a function of the
collision centrality, particle separation in pseudo-rapidity, and transverse
momentum. A clear signal compatible with a charge-dependent separation relative
to the reaction plane is observed, which shows little or no collision energy
dependence when compared to measurements at RHIC energies. This provides a new
insight for understanding the nature of the charge dependent azimuthal
correlations observed at RHIC and LHC energies.Comment: 12 pages, 3 captioned figures, authors from page 2 to 6, published
version, figures at http://aliceinfo.cern.ch/ArtSubmission/node/286
A note on comonotonicity and positivity of the control components of decoupled quadratic FBSDE
In this small note we are concerned with the solution of Forward-Backward
Stochastic Differential Equations (FBSDE) with drivers that grow quadratically
in the control component (quadratic growth FBSDE or qgFBSDE). The main theorem
is a comparison result that allows comparing componentwise the signs of the
control processes of two different qgFBSDE. As a byproduct one obtains
conditions that allow establishing the positivity of the control process.Comment: accepted for publicatio
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