258 research outputs found
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Revisiting the U-238 thermal capture cross section and gamma-raymission probabilities from Np-239 decay
The precise value of the thermal capture cross section of238U is uncertain, and evaluated cross sections from various sourcesdiffer by more than their assigned uncertainties. A number of theoriginal publications have been reviewed to assess the discrepant data,corrections were made for more recent standard cross sections andotherconstants, and one new measurement was analyzed. Due to the strongcorrelations in activation measurements, the gamma-ray emissionprobabilities from the beta decay of 239Np were also analyzed. As aresult of the analysis, a value of 2.683 +- 0.012 barns was derived forthe thermal capture cross section of 238U. A new evaluation of thegamma-ray emission probabilities from 239Np decay was alsoundertaken
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Development of covariance capabilities in EMPIRE code
The nuclear reaction code EMPIRE has been extended to provide evaluation capabilities for neutron cross section covariances in the thermal, resolved resonance, unresolved resonance and fast neutron regions. The Atlas of Neutron Resonances by Mughabghab is used as a primary source of information on uncertainties at low energies. Care is taken to ensure consistency among the resonance parameter uncertainties and those for thermal cross sections. The resulting resonance parameter covariances are formatted in the ENDF-6 File 32. In the fast neutron range our methodology is based on model calculations with the code EMPIRE combined with experimental data through several available approaches. The model-based covariances can be obtained using deterministic (Kalman) or stochastic (Monte Carlo) propagation of model parameter uncertainties. We show that these two procedures yield comparable results. The Kalman filter and/or the generalized least square fitting procedures are employed to incorporate experimental information. We compare the two approaches analyzing results for the major reaction channels on {sup 89}Y. We also discuss a long-standing issue of unreasonably low uncertainties and link it to the rigidity of the model
FENDL: A library for fusion research and applications
The Fusion Evaluated Nuclear Data Library (FENDL) is a comprehensive and
validated collection of nuclear cross section data coordinated by the
International Atomic Energy Agency (IAEA) Nuclear Data Section (NDS). FENDL
assembles the best nuclear data for fusion applications selected from available
nuclear data libraries and has been under development for decades. FENDL
contains sub-libraries for incident neutron, proton, and deuteron cross
sections including general purpose and activation files used for particle
transport and nuclide inventory calculations.
We describe the history, selection of evaluations for the various
sub-libraries (neutron, proton, deuteron) with the focus on transport and
reactor dosimetry applications, the processing of the nuclear data for
application codes, and the development of the TENDL-2017 library which is the
currently recommended activation library for FENDL. We briefly describe the
IAEA IRDFF library as the recommended library for dosimetry fusion
applications. We also present work on validation of the neutron sub-library
using a variety of fusion relevant computational and experimental benchmarks. A
variety of cross section libraries are used for the validation work including
FENDL-2.1, FENDL-3.1d, FENDL-3.2, ENDF/B-VIII.0, and JEFF-3.2 with the emphasis
on the FENDL libraries. The results of the experimental validation showed that
the performance of FENDL-3.2b is at least as good and in most cases better than
FENDL-2.1.
Future work will consider improved evaluations developed by the International
Nuclear Data Evaluation Network (INDEN). Additional work will be needed to
investigate differences in gas production in structural materials. Covariance
matrices need to be updated to support the development of fusion technology.
Additional validation work for high-energy neutrons, protons and deuterons, and
the activation library will be needed.Comment: 81 pages, 114 figure
New Mediterranean Biodiversity Records (July 2016)
This contribution forms part of a series of collective articles published regularly in Mediterranean Marine Science that report on new biodiversity records from the Mediterranean basin. The current article presents 51 geographically distinct records for 21 taxa belonging to 6 Phyla, extending from the western Mediterranean to the Levantine. The new records, per country, are as follows: Spain: the cryptogenic calcareous sponge Paraleucilla magna is reported from a new location in the Alicante region. Algeria: the rare Atlanto-Mediterranean bivalve Cardium indicum is reported from Annaba. Tunisia: new distribution records for the Indo-Pacific lionfish Pterois miles from Zembra Island and Cape Bon. Italy: the ark clam Anadara transversa is reported from mussel cultures in the Gulf of Naples, while the amphipod Caprella scaura and the isopods Paracerceis sculpta and Paranthura japonica are reported as associated to the –also allochthonous–bryozoan Amathia verticillata in the Adriatic Sea; in the latter region, the cosmopolitan Atlantic tripletail Lobotes surinamensisis also reported, a rare finding for the Mediterranean. Slovenia: a new record of the non-indigenous nudibranch Polycera hedgpethi in the Adriatic. Greece: several new reports of the introduced scleractinian Oculina patagonica, the fangtooth moray Enchelycore anatina, the blunthead puffer Sphoeroides pachygaster (all Atlantic), and the lionfish Pterois miles (Indo-Pacific) suggest their ongoing establishment in the Aegean Sea; the deepest bathymetric record of the invasive alga Caulerpa cylindracea in the Mediterranean Sea is also registered in the Kyklades, at depths exceeding 70 m. Turkey: new distribution records for two non indigenous crustaceans, the blue crab Callinectes sapidus (Atlantic origin) and the moon crab Matuta victor (Indo-Pacific origin) from the Bay of Izmir and Antalya, respectively; in the latter region, the Red Sea goatfish Parupeneus forsskali, is also reported. Lebanon: an array of records of 5 alien and one native Mediterranean species is reported by citizen-scientists; the Pacific jellyfish Phyllorhiza punctata and the Indo-Pacific teleosteans Tylerius spinosissimus, Ostracion cubicus, and Lutjanus argentimaculatus are reported from the Lebanese coast, the latter notably being the second record for the species in the Mediterranean Sea since 1977; the native sand snake-eel Ophisurus serpens, rare in the eastern Mediterranean, is reported for the first time from Lebanon, this being its easternmost distribution range; finally, a substantial number of sightings of the lionfish Pterois miles further confirm the current establishment of this lessepsian species in the Levantine
Sphingomimetic multiple sclerosis drug FTY720 activates vesicular synaptobrevin and augments neuroendocrine secretion
Neurotransmission and secretion of hormones involve a sequence of protein/lipid interactions with lipid turnover impacting on vesicle trafficking and ultimately fusion of secretory vesicles with the plasma membrane. We previously demonstrated that sphingosine, a sphingolipid metabolite, promotes formation of the SNARE complex required for membrane fusion and also increases the rate of exocytosis in isolated nerve terminals, neuromuscular junctions, neuroendocrine cells and in hippocampal neurons. Recently a fungi-derived sphingosine homologue, FTY720, has been approved for treatment of multiple sclerosis. In its non-phosphorylated form FTY720 accumulates in the central nervous system, reaching high levels which could affect neuronal function. Considering close structural similarity of sphingosine and FTY720 we investigated whether FTY720 has an effect on regulated exocytosis. Our data demonstrate that FTY720 can activate vesicular synaptobrevin for SNARE complex formation and enhance exocytosis in neuroendocrine cells and neurons
New Mediterranean Biodiversity Records (April, 2019)
The Collective Article on “New Mediterranean Biodiversity Records” offers the means to publish biodiversity records in the Mediterranean Sea. The current article presents new biodiversity data information on 18 taxa (14 alien, 3 native and 1 cryptogenic species)
belonging to 5 Phyla that are reported for 11 different countries listed according to their geographic position from the western to the
eastern Mediterranean Sea. Algeria: the alien green alga Caulerpa taxifolia var. distichophylla and the heterobranchs Aplysia dactylomeda and Aplysia punctata are first reported from the entire country. France: a new record of the alien hydroid Porpita porpita is
reported from the Corsican Sea, representing the second record of the species in the western Mediterranean Sea. Tunisia: the alien
fish Scatophagus argus is reported from the Gulf of Gabès, probably representing an aquarium release. Italy: the well-established
Mediterranean alien bivalve Malleus regula is first reported from the entire country. Slovenia: the alien marine bivalve Xenostrobus
securis is reported for the first time from the entire country. Croatia: the alien gastropod Biuve fulvipunctata is reported for the
first time from the country but also from the entire Adriatic Sea. Montenegro: the alien bivalve Rapana venosa is reported for the
first time from the Montenegrin waters. Albania: the well-established alien fish Lagocephalus sceleratus and the rare native shark
Rhizoprionodon acutus are reported for the first from the entire country. Greece: the rare native ray Leucoraja circularis is reported
for the first time from the Argolikos Gulf and for the first time for the entire country its identification is confirmed morphologically
and molecularly; additional records of the alien nomad jellyfish Rhopilema nomadic document its expanding distribution, while the
occurrence and the alien fishes Sillago suezensis and Pomadasys stridens are reported for the first time from Hellenic waters. Turkey:
additional records of the Egyptian Prawn Metapenaeopsis aegyptia are reported with some biological information. Cyprus: the alien
fish Variola louti is reported for the first time for the entire Mediterranean Sea, probably released from an aquarium, while the alien
moon crab Matuta victor is reported for the first time from the entire country
Multiple sclerosis drug FTY-720 toxicity is mediated by the heterotypic fusion of organelles in neuroendocrine cells
FTY-720 (Fingolimod) was one of the first compounds authorized for the treatment of multiple sclerosis. Among its other activities, this sphingosine analogue enhances exocytosis in neuroendocrine chromaffin cells, altering the quantal release of catecholamines. Surprisingly, the size of chromaffin granules is reduced within few minutes of treatment, a process that is paralleled by the homotypic fusion of granules and their heterotypic fusion with mitochondria, as witnessed by dynamic confocal and TIRF microscopy. Electron microscopy studies support these observations, revealing the fusion of several vesicles with individual mitochondria to form large, round mixed organelles. This cross-fusion is SNARE-dependent, being partially prevented by the expression of an inactive form of SNAP-25. Fused mitochondria exhibit an altered redox potential, which dramatically enhances cell death. Therefore, the cross-fusion of intracellular organelles appears to be a new mechanism to be borne in mind when considering the effect of FTY-720 on the survival of neuroendocrine cells
Study of photo-proton reactions driven by bremsstrahlung radiation of high-intensity laser generated electrons
Photo-nuclear reactions were investigated using a high power table-top laser. The laser system at the University of Jena ( I similar to 3-5 x 10(19) W cm(-2)) produced hard bremsstrahlung photons ( kT similar to 2(9 MeV) via a laser-gas interaction which served to induce ( gamma, p) and ( gamma, n) reactions in Mg, Ti, Zn and Mo isotopes. Several ( gamma, p) decay channels were identified using nuclear activation analysis to determine their integral reaction yields
The joint evaluated fission and fusion nuclear data library, JEFF-3.3
The joint evaluated fission and fusion nuclear data library 3.3 is described. New evaluations for neutron-induced interactions with the major actinides U, U and Pu, on Am and Na, Ni, Cr, Cu, Zr, Cd, Hf, W, Au, Pb and Bi are presented. It includes new fission yields, prompt fission neutron spectra and average number of neutrons per fission. In addition, new data for radioactive decay, thermal neutron scattering, gamma-ray emission, neutron activation, delayed neutrons and displacement damage are presented. JEFF-3.3 was complemented by files from the TENDL project. The libraries for photon, proton, deuteron, triton, helion and alpha-particle induced reactions are from TENDL-2017. The demands for uncertainty quantification in modeling led to many new covariance data for the evaluations. A comparison between results from model calculations using the JEFF-3.3 library and those from benchmark experiments for criticality, delayed neutron yields, shielding and decay heat, reveals that JEFF-3.3 performes very well for a wide range of nuclear technology applications, in particular nuclear energy
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