842 research outputs found
Massive Stars in the Range : Evolution and Nucleosynthesis. II. the Solar Metallicity Models
We present the evolutionary properties of a set of massive stellar models
(namely 13, 15, 20 and 25 ) from the main sequence phase up to the
onset of the iron core collapse. All these models have initial solar chemical
composition, i.e. Y=0.285 and Z=0.02. A 179 isotope network, extending from
neutron up to and fully coupled to the evolutionary code has been
adopted from the Carbon burning onward. Our results are compared, whenever
possible, to similar computations available in literature.Comment: 42 pages, 18 figures, 26 tables, accepted for publicatin in ApJ
Valorization of lignin waste from hydrothermal treatment of biomass : towards porous carbonaceous composites for continuous hydrogenation
Alkali lignin has been accumulated as a by-product mixed with barium salts during the hydrothermal treatment of rye straw with Ba(OH)2. Direct heat treatment followed by acid washing of such mineralized lignin were performed in order to obtain a porous material that was further exploited for the synthesis of a carbonaceous supported FeNi nanoparticle composite as active catalysts for continuous hydrogenation
FeNi nanoparticles with carbon armor as sustainable hydrogenation catalysts : towards biorefineries
Isochrones and Luminosity Functions for Old White Dwarfs
Using a new grid of models of cooling white dwarfs, we calculate isochrones
and luminosity functions in the Johnson-Kron/Cousins and HST filter sets for
systems containing old white dwarfs. These new models incorporate a non-grey
atmosphere which is necessary to properly describe the effects of molecular
opacity at the cool temperatures of old white dwarfs. The various functions
calculated and extensively tabulated and plotted are meant to be as utilitarian
as possible for observers so all results are listed in quantities that
observers will obtain. The tables and plots developed should eventually prove
critical in interpreting the results of HST's Advanced Camera observations of
the oldest white dwarfs in nearby globular clusters, in understanding the
results of searches for old white dwarfs in the Galactic halo, and in
determining ages for star clusters of all ages using white dwarfs. As a
practical application we demonstrate the use of these results by deriving the
white dwarf cooling age of the old Galactic cluster M67.Comment: 7 pages, 8 tables, accepted for publication in the Astrophysical
Journa
C/O white dwarfs of very low mass: 0.33-0.5 Mo
The standard lower limit for the mass of white dwarfs (WDs) with a C/O core
is roughly 0.5 Mo. In the present work we investigated the possibility to form
C/O WDs with mass as low as 0.33 Mo. Both the pre-WD and the cooling evolution
of such nonstandard models will be described.Comment: Submitted to the "Proceedings of the 16th European White Dwarf
Workshop" (to be published JPCS). 7 pages including 13 figure
Heavy element abundances in giant stars of the globular clusters M4 and M5
We present a comprehensive abundance analysis of 27 heavy elements in bright
giant stars of the globular clusters M4 and M5 based on high resolution, high
signal-to-noise ratio spectra obtained with the Magellan Clay Telescope. We
confirm and expand upon previous results for these clusters by showing that (1)
all elements heavier than, and including, Si have constant abundances within
each cluster, (2) the elements from Ca to Ni have indistinguishable
compositions in M4 and M5, (3) Si, Cu, Zn, and all s-process elements are
approximately 0.3 dex overabundant in M4 relative to M5, and (4) the r-process
elements Sm, Eu, Gd, and Th are slightly overabundant in M5 relative to M4. The
cluster-to-cluster abundance differences for Cu and Zn are intriguing,
especially in light of their uncertain nucleosynthetic origins. We confirm that
stars other than Type Ia supernovae must produce significant amounts of Cu and
Zn at or below the clusters' metallicities. If intermediate-mass AGB stars or
massive stars are responsible for the Cu and Zn enhancements in M4, the similar
[Rb/Zr] ratios and (preliminary) Mg isotope ratios in both clusters may be
problematic for either scenario. For the elements from Ba to Hf, we assume that
the s- and r-process contributions are scaled versions of the solar s- and
r-process abundances. We quantify the relative fractions of s- and r-process
material for each cluster and show that they provide an excellent fit to the
observed abundances.Comment: Accepted for publication in Ap
Laterality of a second player position affects lateral deviation of basketball shooting
Asymmetrically placed visual distractors are known to cause a lateral bias in the execution of a movement directed toward a target. The aim of the present experiment was to verify if the trajectory of the ball and the trajectory of the jump for a basketshot can be affected by the sole position of a second player, who stays in front of the shooting player in one of three possible positions (centre, left or right) but too far to physically interfere with the shot. Young basketball players were asked to perform 60 shots at 6.25 m from a regular basket, with or without a second player staying in front of them in, alternately, a centre, left or right position. A computerised system measured the angular deviation of the jump direction from the vertical direction and the lateral deviation of the ball trajectory from the midline. The results showed that both the jump direction and the entry position of the ball deviated toward the opposite side from the second player’s side; however, these effects were too small to significantly affect the mean goal percentage. This result confirms that some placements of the players can have
an effect as visual distractors. Further studies are necessary to find what game conditions can make such distractors harmful for the athletic performance
The effect of 12C + 12C rate uncertainties on s-process yields
The slow neutron capture process in massive stars (the weak s-process)
produces most of the s-only isotopes in the mass region 60 < A < 90. The
nuclear reaction rates used in simulations of this process have a profound
effect on the final s-process yields. We generated 1D stellar models of a 25
solar mass star varying the 12C + 12C rate by a factor of 10 and calculated
full nucleosynthesis using the post-processing code PPN. Increasing or
decreasing the rate by a factor of 10 affects the convective history and
nucleosynthesis, and consequently the final yields.Comment: Conference proceedings for the Nuclear Physics in Astrophysics IV
conference, 8-12 June 2009. 4 pages, 3 figures. Accepted for publication to
the Journal of Physics: Conference Serie
Alterações de comportamento em Rattus norvegicus experimentalmente infectados por larvas de Toxocara canis
Toxocara canis is a common canine nematode parasite and one of its possible transmission mechanisms is the predation of infected rodents by canids. Fifty Rattus norvegicus were used to study behavioral alterations in rodents infected by T. canis larvae. The rats were divided into three groups: G1, 20 rats infected with 300 T. canis eggs; G2, 20 rats infected with 2,000 T. canis eggs; and G3, 10 non-infected rats. Thirty and 60 days post-infection, rats from all the groups were submitted to an open-field apparatus for five min and subsequently, to an elevated plus-maze apparatus, again for five min. The data obtained indicated improvement in mobility (total locomotion time and rearing frequency) and exploratory behavior in infected rats, principally in G2, which provides some support for the hypothesis that behavioral alterations in rodents infected by Toxocara canis larvae enhance the transmission rate of this ascarid to dogs.Toxocara canis é um nematódeo parasita habitual do intestino delgado de cães. Um dos mecanismos conhecidos de transmissão para cães é representado pela predação de pequenos roedores que, como hospedeiros paratênicos albergam larvas de Toxocara canis em seus tecidos. Para avaliar a ocorrência de alterações de comportamento em roedores infectados por Toxocara canis 50 exemplares de Rattus norvegicus foram utilizados no experimento. Os animais foram divididos em três grupos: G1 - 20 ratos infectados com 300 ovos de Toxocara canis; G2 - 20 ratos infectados com 2.000 ovos de Toxocara canis e G3 - 10 ratos sem infecção. Trinta e 60 dias após a infecção avaliou-se a ocorrência de alterações comportamentais nos três grupos submetendo os animais, primeiramente, a uma arena de campo aberto durante cinco minutos e, a seguir, a labirinto em cruz elevado por mais cinco minutos. Os resultados obtidos indicaram aumento significativo da mobilidade (tempo total de movimentação e número de vezes em que os animais se levantaram nas patas traseiras) e comportamento exploratório nos ratos infectados, principalmente nos pertencentes ao G2, sugerindo a ocorrência de alterações comportamentais que favoreceriam a transmissão de Toxocara canis para canÃdeos por meio de relação presa-predador
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