108 research outputs found
Neutron irradiation of coated conductors
Various commercial coated conductors were irradiated with fast neutrons in
order to introduce randomly distributed, uncorrelated defects which increase
the critical current density, Jc, in a wide temperature and field range. The
Jc-anisotropy is significantly reduced and the angular dependence of Jc does
not obey the anisotropic scaling approach. These defects enhance the
irreversibility line in not fully optimized tapes, but they do not in
state-of-the-art conductors. Neutron irradiation provides a clear distinction
between the low field region, where Jc is limited by the grain boundaries, and
the high field region, where depinning leads to dissipation
Calculation of coercivity of magnetic nanostructures at finite temperatures
We report a finite temperature micromagnetic method (FTM) that allows for the
calculation of the coercive field of arbitrary shaped magnetic nanostructures
at time scales of nanoseconds to years. Instead of directly solving the
Landau-Lifshitz-Gilbert equation, the coercive field is obtained without any
free parameter by solving a non linear equation, which arises from the
transition state theory. The method is applicable to magnetic structures where
coercivity is determined by one thermally activated reversal or nucleation
process. The method shows excellent agreement with experimentally obtained
coercive fields of magnetic nanostructures and provides a deeper understanding
of the mechanism of coercivity.Comment: submitted to Phys. Rev.
Thermodynamic systematics of oxides of americium, curium, and neighboring elements
Recently-obtained calorimetric data on the sesquioxides and dioxides of americium and curium are summarized. These data are combined with other properties of the actinide elements to elucidate the stability relationships among these oxides and to predict the behavior of neighboring actinide oxides. 45 references, 4 figures, 5 tables
Non-operative treatment for perforated gastro-duodenal peptic ulcer in Duchenne Muscular Dystrophy: a case report
BACKGROUND: Clinical characteristics and complications of Duchenne muscular dystrophy caused by skeletal and cardiac muscle degeneration are well known. Gastro-intestinal involvement has also been recognised in these patients. However an acute perforated gastro-duodenal peptic ulcer has not been documented up to now. CASE PRESENTATION: A 26-year-old male with Duchenne muscular dystrophy with a clinical and radiographic diagnosis of acute perforated gastro-duodenal peptic ulcer is treated non-operatively with naso-gastric suction and intravenous medication. Gastrointestinal involvement in Duchenne muscular dystrophy and therapeutic considerations in a high risk patient are discussed. CONCLUSION: Non-surgical treatment for perforated gastro-duodenal peptic ulcer should be considered in high risk patients, as is the case in patients with Duchenne muscular dystrophy. Patients must be carefully observed and operated on if non-operative treatment is unsuccessful
Maturation of active zone assembly by Drosophila Bruchpilot
Synaptic vesicles fuse at active zone (AZ) membranes where Ca2+ channels are clustered and that are typically decorated by electron-dense projections. Recently, mutants of the Drosophila melanogaster ERC/CAST family protein Bruchpilot (BRP) were shown to lack dense projections (T-bars) and to suffer from Ca2+ channelâclustering defects. In this study, we used high resolution light microscopy, electron microscopy, and intravital imaging to analyze the function of BRP in AZ assembly. Consistent with truncated BRP variants forming shortened T-bars, we identify BRP as a direct T-bar component at the AZ center with its N terminus closer to the AZ membrane than its C terminus. In contrast, Drosophila Liprin-α, another AZ-organizing protein, precedes BRP during the assembly of newly forming AZs by several hours and surrounds the AZ center in few discrete punctae. BRP seems responsible for effectively clustering Ca2+ channels beneath the T-bar density late in a protracted AZ formation process, potentially through a direct molecular interaction with intracellular Ca2+ channel domains
Alkali metal actinide complex halides : thermochemical and structural considerations
L'auteur passe en revue l'état actuel de nos connaissances dans le domaine de la thermodynamique des complexes halogénés d'actinides avec les ions alcalins, en portant une attention toute spéciale aux dérivés chlorés et bromés. Lorsque les données thermodynamiques et structurales sont accessibles, il tente de déduire l'évolution de l'énergie de la liaison actinide-halogÚne au sein d'une série de composés isomorphes ou analogues. Enfin, la variation énergétique au cours de la formation du complexe halogéné à partir des halogénures binaires d'actinides et de métaux alcalins est prise pour base en vue de prévoir la stabilité de composés nouveaux, spécialement ceux pour lesquels l'halogénure binaire d'actinide n'a pas été préparé ou est de faible stabilité. Diverses méthodes de préparation sont évoquées.The present status of our information on the thermodynamics of the actinide halogeno-complexes with alkali metal ions is reviewed, with special emphasis on chloro- and bromo-derivatives. Where enough thermodynamic and structural data are available, attempts are made to deduce the evolution of the energetics of the actinide-halogen bonds along a series of isomorphous or analogous compounds. The energy change upon the formation of the halogeno-complexes from binary actinide halides and alkali metal halides is discussed with the aim of predicting the stability of new compounds, especially those for which the corresponding binary actinide halides have not been characterized or are of low stabilities. Possible preparative routes for such compounds are also outlined
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ION-EXCHANGE BEHAVIOR AND DISSOCIATION CONSTANTS OF AMERICIUM, CURIUM, AMD CALIFORNIUM COMPLEXES WITH ETHYLENEDIAMINETETRA-ACETIC ACID
Preparation, crystal structure and enthalpy of formation of dicaesium hexabromoneptunate
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