Spectator-model operators in point-form relativistic quantum mechanics

We address the construction of transition operators for electromagnetic, weak, and hadronic reactions of relativistic few-quark systems along the spectator model. While the problem is of relevance for all forms of relativistic quantum mechanics, we specifically adhere to the point form, since it preserves the spectator character of the corresponding transition operators in any reference frame. The conditions imposed on the construction of point-form spectator-model operators are discussed and their implications are exemplified for mesonic decays of baryon resonances within a relativistic constituent quark model.Comment: 10 pages, 4 figures, updated version accepted for publication in Europ. Phys. J.

Management Strategy Evaluation for the Atlantic Surfclam (Spisula solidissima) Using a Spatially Explicit, Vessel-Based Fisheries Model

The commercially valuable Atlantic surfclam (Spisula solidissima) is harvested along the northeastern continental shelf of the United States. Its range has contracted and shifted north, driven by warmer bottom water temperatures. Declining landings per unit of effort (LPUE) in the Mid-Atlantic Bight (MAB) is one result. Declining stock abundance and LPUE suggest that overfishing may be occurring off New Jersey. A management strategy evaluation (MSE) for the Atlantic surfclam is implemented to evaluate rotating closures to enhance Atlantic surfclam productivity and increase fishery viability in the MAB. Active agents of the MSE model are individual fishing vessels with performance and quota constraints influenced by captains\u27 behavior over a spatially varying population. Management alternatives include 2 rules regarding closure locations and 3 rules regarding closure durations. Simulations showed that stock biomass increased, up to 17%, under most alternative strategies in relation to estimated stock biomass under present- day management, and LPUE increased under most alternative strategies, by up to 21%. When incidental mortality caused by the fishery increased, the benefits seen under the alternative management were enhanced. These outcomes suggest that area management involving rotating closures could be valuable in insulating the stock and the commercial fishery from further declines as a northerly shift in range proceeds

Rituximab administration in third trimester of pregnancy suppresses neonatal B-cell development

We describe the effect on the neonate of administration of rituximab to a woman with idiopathic thrombocytopenic purpura (ITP). Rituximab, an anti-CD20 antibody, was given weekly for 4 weeks to a woman with ITP in her third trimester of pregnancy. One month after the last rituximab administration a healthy girl was born. She had normal growth and development during the first six months. At birth, B-lymphocytes were not detectable. Rituximab levels in mother and neonate were 24000 and 6700 ng/mL, respectively. Only 7 cases of rituximab administration during pregnancy were described. No adverse events are described for fetus and neonate. We demonstrate that rituximab passes the placenta and inhibits neonatal B-lymphocyte development. However, after 6 months B-lymphocyte levels normalized and vaccination titres after 10 months were adequate. No infection-related complications occurred. Rituximab administration during pregnancy appears to be safe for the child but further studies are warranted. Copyright © 2008 D. T. Klink et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. 1

Regge and Okamoto symmetries

We will relate the surprising Regge symmetry of the Racah-Wigner 6j symbols to the surprising Okamoto symmetry of the Painleve VI differential equation. This then presents the opportunity to give a conceptual derivation of the Regge symmetry, as the representation theoretic analogue of the author's previous derivation of the Okamoto symmetry. [The resulting derivation is quite simple, so it would be surprising if it has not been previously observed. Any references would be appreciated!]Comment: 14 page

Evaluatie verplaatsingsregelingen MKZ

De Minister van LNV heeft bij de aankondiging van de maatregelen, genomen naar aanleiding van de MKZ-uitbraak, de Tweede Kamer laten weten dat de betreffende maatregelen na een jaar zouden worden geëvalueerd. De directie Voedsel- en Veterinaire Aangelegenheden (VVA) heeft het Expertisecentrum LNV (EC-LNV) verzocht om deze evaluatie uit te voeren. In overleg met de opdrachtgever zijn drie vragen opgesteld waar de evaluatie een uitspraak over moet doen. Ten eerste dient de evaluatie te achterhalen of de regelingen in de praktijk worden nageleefd en of de maatregelen in de praktijk uitvoerbaar waren. Ten tweede is verzocht om na te gaan in hoeverre de contactstructuur na de MKZepidemie is gewijzigd ten opzichte van de periode voor de MKZ-uitbraak. Door een analyse uit te voeren van de I&R-gegevens van runderen is hiervan een beeld gekregen. Ten derde zou duidelijkheid verschaft moeten worden over het risicorendement van de maatregelen die genomen zijn naar aanleiding van de MKZ. Om daar een uitspraak over te kunnen doen, zijn met behulp van modelberekeningen enkele mond- en klauwzeeruitbraken gesimuleer

Transition metal ion ensembles in crystals as solid-state coherent spin-photon interfaces: The case of nickel in magnesium oxide

We present general guidelines for finding solid-state systems that could serve as coherent electron spin-photon interfaces even at relatively high temperatures, where phonons are abundant but cooling is easier, and show that transition metal ions in various crystals could comply with these guidelines. As an illustrative example, we focus on divalent nickel ions in magnesium oxide. We perform electron spin resonance spectroscopy and polarization-sensitive magneto-optical fluorescence spectroscopy of a dense ensemble of these ions and find that (i) the ground-state electron spin stays coherent at liquid-helium temperatures for several microseconds, and (ii) there exists energetically well-isolated excited states which can couple to two ground state spin sub-levels via optical transitions of orthogonal polarizations. The latter implies that fast, coherent optical control over the electron spin is possible. We then propose schemes for optical initialization and control of the ground-state electron spin using polarized optical pulses, as well as two schemes for implementing a noise-free, broadband quantum-optical memory at near-telecom wavelengths in this material system.Comment: 21 pages, 8 figures. Revised versio

Decolorization of synthetic dyes by laccase immobilized on epoxy-activated carriers

The Myceliophthora thermophila laccase was covalently immobilized on polymethacrylate-based polymers (Sepabeads EC-EP3 and Dilbeads NK) activated with epoxy groups. The enzyme immobilized on Sepabeads EC-EP3 exhibited notable activity (203 U/g) along with remarkably improved stability towards pH, temperature and storage time, but no increased resistance to organic solvents. In addition, the immobilized laccase also showed good operational stability, maintaining 84% of its initial activity after 17 cycles of oxidation of ABTS. The immobilized biocatalyst was applied to the decolorization of six synthetic dyes. Immobilized laccase retained 41% activity in the decolorization of Methyl Green in a fixed-bed reactor after five cycles. The features of these biocatalysts are very attractive for their application on the decolorization of dyes in the textile industry in batch and continuous fixed-bed bioreactors. To our knowledge, this is the first report on immobilization of laccase on Sepabeads carriers and its efficient dyes decolorization.We thank Drs. Moreno Daminati and Paolo Caimi (Resindion) and Vyasa Rajasekar (DilComplex) for providing us Sepabeads EC-EP3 and Dilbeads NK polymers, respectively. We are grateful to Ramiro Martínez (Novozymes A/S, Spain) for DeniLite II S samples. This material is based upon work founded by Spanish MEC (Projects VEM2004-08559 and CTQ2005-08925-C02-02/PPQ); European Union (Project NMP2-CT-2006-026456) and CSIC (Project 200580M121). Spanish MEC is also thanked for the post-doctoral fellowship (SB2004-0011) of Dr. A. Kunamneni and for the Ramon y Cajal contracts of Drs. S. Camarero and M. Alcalde.This material is based upon work financed by Spanish MEC (Projects VEM2004-08559 and CTQ2005-08925-C02-02/PPQ); European Union (Project NMP2-CT-2006-026456) and CSIC (Project 200580M121). Spanish MEC is also thanked for the post-doctoral fellowship (SB2004-0011) of Dr. A. Kunamneni and for the Ramon y Cajal contracts of Drs. S. Camarero and M. Alcalde.Peer reviewe

Stimulus - response curves of a neuronal model for noisy subthreshold oscillations and related spike generation

We investigate the stimulus-dependent tuning properties of a noisy ionic conductance model for intrinsic subthreshold oscillations in membrane potential and associated spike generation. On depolarization by an applied current, the model exhibits subthreshold oscillatory activity with occasional spike generation when oscillations reach the spike threshold. We consider how the amount of applied current, the noise intensity, variation of maximum conductance values and scaling to different temperature ranges alter the responses of the model with respect to voltage traces, interspike intervals and their statistics and the mean spike frequency curves. We demonstrate that subthreshold oscillatory neurons in the presence of noise can sensitively and also selectively be tuned by stimulus-dependent variation of model parameters.Comment: 19 pages, 7 figure

Point-Form Analysis of Elastic Deuteron Form Factors

Point-form relativistic quantum mechanics is applied to elastic electron-deuteron scattering. The deuteron is modeled using relativistic interactions that are scattering-equivalent to the nonrelativistic Argonne $v_{18}$ and Reid '93 interactions. A point-form spectator approximation (PFSA) is introduced to define a conserved covariant current in terms of single-nucleon form factors. The PFSA is shown to provide an accurate description of data up to momentum transfers of 0.5 ${\rm GeV}^2$, but falls below the data at higher momentum transfers. Results are sensitive to the nucleon form factor parameterization chosen, particularly to the neutron electric form factor.Comment: RevTex, 31 pages, 1 table, 13 figure