169 research outputs found
Neutrino Nucleosynthesis of radioactive nuclei in supernovae
We study the neutrino-induced production of nuclides in explosive supernova
nucleosynthesis for progenitor stars with solar metallicity and initial main
sequence masses between 15 M and 40 M. We improve previous
investigations i) by using a global set of partial differential cross sections
for neutrino-induced charged- and neutral-current reactions on nuclei with
charge numbers and ii) by considering modern supernova neutrino
spectra which have substantially lower average energies compared to those
previously adopted in neutrino nucleosynthesis studies. We confirm the
production of Li, B, La, and Ta by neutrino
nucleosynthesis, albeit at slightly smaller abundances due to the changed
neutrino spectra. We find that for stars with a mass smaller than 20 M,
F is produced mainly by explosive nucleosynthesis while for higher mass
stars it is produced by the process. We also find that neutrino-induced
reactions, either directly or indirectly by providing an enhanced abundance of
light particles, noticeably contribute to the production of the radioactive
nuclides Na and Al. Both nuclei are prime candidates for
gamma-ray astronomy. Other prime targets, Ti and Fe, however, are
insignificantly produced by neutrino-induced reactions. We also find a large
increase in the production of the long-lived nuclei Nb and Tc due
to charged-current neutrino capture.Comment: 6 pages, 2 figures, 2 table
Early protoneutron star deleptonization - consistent modeling of weak processes and equation of state
We discuss the impact of consistent modeling of weak processes and nuclear equation of state (EOS) during the deleptonization phase of protoneutron stars (PNS). They are born in the event of a core-collapse supernova. Being initially hot and lepton rich, PNSs deleptonize via the continuous emission of neutrinos of all flavors. Unlike during the mass accretion phase prior to the onset of the supernova explosion, when the neutrinospheres are located at low densities, they shift to significantly higher densities during the PNS deleptonization phase after the supernova explosion has been launched. Important during this phase is the inclusion of medium modifications to the weak processes, which depend on the nuclear EOS. In particular, these medium modifications depend on the nuclear symmetry energy and its density dependence. We discuss two selected nuclear models and illustrate the early PNS deleptonization phase for a particular EOS. As has been realized recently, including weak processes consistently with the EOS increases the spectral differences of v e and in comparison to simulations that neglect the underlying medium modifications. This has important consequences for the nucleosynthesis relevant conditions of the ejecta as well as for potential neutrino flavor oscillations and hence detection on Earth
Analysis of results on improved welded joints
Recents studies have shown that the use of improvement techniques on welds allows an increase in the level of admissible fatigue strength (even more than 100%). The aim of this study was to collect and validate literature data, create a data base containing the joint characteristics and fatigue results, make a statistical analysis of the data in order to quantify the effect of parameters influencing the fatigue strength and propose new S-N curves which are compared to those given in Eurocode 3. Four improvement techniques (grinding, TIG dressing, hammer peening, shot peening) and four joint types (butt, T joints, cruciform and longitudinal joints) were taken into account. Joint thicknesses less than 25 mm loaded in air with a stress ratio R between 0 and 0.1 were selected. Three classes of yield strength for the base metal were considered: 600. All S-N curves were above those of as-welded assemblies. The best results were obtained with hammer peening. The larger increase in the fatigue strength due to the use of improvement techniques was due to the occurrence of an initiation phase in addition to the crack propagation phase. During the initiation phase, the extension of existing crack-like defects is slowed down or even stopped. The duration of this phase increases with the total fatigue life
Corruption in migration management: a network perspective
This paper explores the relation between networks as an emerging mode of public governance and corruption. Adopting the theoretical lens of actor-network theory (ANT), the paper investigates an Italian episode of corruption related to the awarding of government contracts for the management of the Mineo’s CARA, the Europe's largest reception centre for migrants. The analysis shows that a governance network may turn corruption itself into a network where abuse of power can proliferate thanks to the opacity resulting from the multiplicity of actors, interactions, and fragmentation characterizing the governance system
Characterization of materials used in the manufacture of ceramic tile with incorporation of ornamental rock waste
The production of ceramic tiles, such as tiles, has a great environmental impact, either in
the extraction of natural raw materials or gas emissions in the burning stages. The use of industrial
solid waste in ceramic materials can contribute to the reduction of these impacts, according to the
characteristics of solid waste and its interaction with ceramic materials in the processing steps. Thus,
this study aimed to characterize the materials needed to make a ceramic tile with incorporation of
ornamental rock waste (ORW), thus evaluating its main characteristics regarding the feasibility of this
incorporation. The physical characterization of the clays used in the production of ceramic artifacts
was performed, and for the waste the mineralogical analyzes were performed, through x-ray diffraction
(XRD), microstructure analysis from confocal optical microscopy, after sintering the prototypes and
chemical analysis by X-ray spectroscopy (EDX). Soon after the raw materials went through the step
of conformation and preparation of the prismatic specimens by the process of extrusion of the ceramic
mass, with an incorporation of the ORW in 0% and 15% of the ceramic mass, for its subsequent The
prototypes were sintered at three different temperatures (850 °C, 950 °C and 1,050 °C). The specimens
were submitted to technological tests of mechanical resistance, water absorption, firing shrinkage and
porosity to evaluate the incorporation viability. The results indicated the presence of quartz particles
in all raw materials, and also that the clays of the study region are predominantly kaolinitic. The
presence of these materials in the ceramic masses directly influences the micrographs, because they
result in the formation of liquid phase, inert particles that can turn the site into a stress concentration
point and when incorporated in the ORW the specimens met the technical specifications of the
Brazilian standard for application on ceramic tiles. The results found in the technological tests carried
out, that the incorporation of 15% of ornamental rock waste in both clays did not affect the tile
properties, indicating the feasibility of incorporating this waste in civil construction, minimizing the
impacts generated
Electromagnetic properties of 21O for benchmarking nuclear Hamiltonians
The structure of exotic nuclei provides valuable tests for state-of-the-art
nuclear theory. In particular electromagnetic transition rates are more
sensitive to aspects of nuclear forces and many-body physics than excitation
energies alone. We report the first lifetime measurement of excited states in
O, finding
\,ps. This
result together with the deduced level scheme and branching ratio of several
-ray decays are compared to both phenomenological shell-model and ab
initio calculations based on two- and three-nucleon forces derived from chiral
effective field theory. We find that the electric quadrupole reduced transition
probability of $\rm B(E2;1/2^+ \rightarrow 5/2^+_{g.s.}) = 0.71^{+0.07\
+0.02}_{-0.06\ -0.06}^2^41/2^+$
state, is smaller than the phenomenological result where standard effective
charges are employed, suggesting the need for modifications of the latter in
neutron-rich oxygen isotopes. We compare this result to both large-space and
valence-space ab initio calculations, and by using multiple input interactions
we explore the sensitivity of this observable to underlying details of nuclear
forces.Comment: 23 pages, 3 figure
Spiranthes vernalis Engelm. & A. Gray
https://thekeep.eiu.edu/herbarium_specimens_byname/21408/thumbnail.jp
Inhibition of Enterovirus 71 (EV-71) Infections by a Novel Antiviral Peptide Derived from EV-71 Capsid Protein VP1
Enterovirus 71 (EV-71) is the main causative agent of hand, foot and mouth disease (HFMD). In recent years, EV-71 infections were reported to cause high fatalities and severe neurological complications in Asia. Currently, no effective antiviral or vaccine is available to treat or prevent EV-71 infection. In this study, we have discovered a synthetic peptide which could be developed as a potential antiviral for inhibition of EV-71. Ninety five synthetic peptides (15-mers) overlapping the entire EV-71 capsid protein, VP1, were chemically synthesized and tested for antiviral properties against EV-71 in human Rhabdomyosarcoma (RD) cells. One peptide, SP40, was found to significantly reduce cytopathic effects of all representative EV-71 strains from genotypes A, B and C tested, with IC50 values ranging from 6–9.3 µM in RD cells. The in vitro inhibitory effect of SP40 exhibited a dose dependent concentration corresponding to a decrease in infectious viral particles, total viral RNA and the levels of VP1 protein. The antiviral activity of SP40 peptide was not restricted to a specific cell line as inhibition of EV-71 was observed in RD, HeLa, HT-29 and Vero cells. Besides inhibition of EV-71, it also had antiviral activities against CV-A16 and poliovirus type 1 in cell culture. Mechanism of action studies suggested that the SP40 peptide was not virucidal but was able to block viral attachment to the RD cells. Substitutions of arginine and lysine residues with alanine in the SP40 peptide at positions R3A, R4A, K5A and R13A were found to significantly decrease antiviral activities, implying the importance of positively charged amino acids for the antiviral activities. The data demonstrated the potential and feasibility of SP40 as a broad spectrum antiviral agent against EV-71
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