602 research outputs found
The dynamical environment of asteroid 21 Lutetia according to different internal models
One of the most accurate models currently used to represent the gravity field
of irregular bodies is the polyhedral approach. In this model, the mass of the
body is assumed to be homogeneous, which may not be true for a real object. The
main goal of the present paper is to study the dynamical effects induced by
three different internal structures (uniform, three- and four-layers) of
asteroid (21) Lutetia, an object that recent results from space probe suggest
being at least partially differentiated. The Mascon gravity approach used in
the present work, consists of dividing each tetrahedron into eight parts to
calculate the gravitational field around the asteroid. The zero-velocity curves
show that the greatest displacement of the equilibrium points occurs in the
position of the E4 point for the four-layers structure and the smallest one
occurs in the position of the E3 point for the three-layers structure.
Moreover, stability against impact shows that the planar limit gets slightly
closer to the body with the four-layered structure.
We then investigated the stability of orbital motion in the equatorial plane
of (21) Lutetia and propose numerical stability criteria to map the region of
stable motions. Layered structures could stabilize orbits that were unstable in
the homogeneous model.Comment: 10 pages, 7 figures, and 4 Tables. Accepted for publication in MNRA
GASTRO library I: the simulated chemodynamical properties of several GSE-like stellar halos
The Milky Way stellar halo contains relics of ancient mergers that tell the
story of our Galaxy's formation. Some of them are identified due to their
similarity in energy, actions and chemistry, referred to as the "chemodynamical
space", and are often attributed to distinct merger events. It is also known
that our Galaxy went through a significant merger event that shaped the local
stellar halo during its first Gyr. Previous studies using -body only and
cosmological hydrodynamical simulations have shown that such single massive
merger can produce several "signatures" in the chemodynamical space, which can
potentially be misinterpreted as distinct merger events. Motivated by these, in
this work we use a subset of the GASTRO, library which consists of several
SPH+-body models of single accretion event in a Milky Way-like galaxy. Here,
we study models with orbital properties similar to the main merger event of our
Galaxy and explore the implications to known stellar halo substructures. We
find that: supernova feedback efficiency influences the satellite's
structure and orbital evolution, resulting in distinct chemodynamical features
for models with the same initial conditions, very retrograde high energy
stars are the most metal-poor of the accreted dwarf galaxy and could be
misinterpreted as a distinct merger the most bound stars are more
metal-rich in our models, the opposite of what is observed in the Milky Way,
suggesting a secondary massive merger, and finally our models can
reconcile other known substructures to an unique progenitor.Comment: Published in Ap
PCR-based detection of Babesia bovis and Babesia bigemina in their natural host Boophilus microplus and cattle.
PCR and nested-PCR methods were used to assess the frequency of Babesia bovis and Babesia bigemina infection in Boophilus microplus engorged females and eggs and in cattle reared in an area with endemic babesiosis. Blood and the engorged female ticks were from 27 naturally infested calves and 25 crossbred cows. The frequency of both Babesia species was similar in calves and cows (P>0.05). Babesia bovis was detected in 23 (85.2%) calves and in 25 (100%) cows and B. bigemina was detected in 25 (92.6%) calves and in 21 (84%) cows. Mixed infections with the both Babesia species were identified in 42 animals, 21 in each age category. Of female ticks engorged on calves, 34.9% were negative and single species infection with B. bigemina (56.2%) was significantly more frequent (P0.05) to the frequency of single B. bigemina infection (15.9%). Mixed Babesia infection was lower (P<O.OI) than single species infection in female ticks engorged either in cows (5.7%) or in calves (4.3%). An egg sample from each female was analysed for the presence of Babesia species. Of the egg samples from female ticks infected with B. bovis, 26 (47.3%) were infected while from those from female ticks infected with B. bigemina 141 (76.6%) were infected (P<0.01). The results showed that although the frequency of both species of Babesia was similar in calves and cows, the infectivity of B. bigemina was higher to ticks fed on calves while to those ticks fed on cows the infectivity of both Babesia species was similar
Photosynthetic pigment levels in Macroptilium lathyroides L under water deficit.
Título em espanhol: Contenido de pigmentos fotosinteticos Macroptilium lathyroides L en condiciones de sequia
The Kormendy relation of cluster galaxies in PPS regions
We study a sample of 936 early-type galaxies located in 48 low-z regular
galaxy clusters with at . We examine
variations in the Kormendy relation (KR) according to their location in the
projected phase space (PPS) of the clusters. We have used a combination of
Bayesian statistical methods to identify possible differences between the
fitted relations. Our results indicate that the overall KR is better fitted
when we take into account the information about PPS regions. We also find that
objects with time since infall Gyr have a significant statistical
difference of the KR coefficients relative to objects that are more recent in
the cluster environment. We show that giant central ellipticals are responsible
for tilting the KR relation towards smaller slopes. These galaxies present a
late growth probably due to cumulative preprocessing during infall, plus
cannibalism and accretion of smaller stripped objects near the center of the
clusters.Comment: 8 pages, 8 figures, appendix, published in MNRAS. arXiv admin note:
text overlap with arXiv:2302.0428
Preliminary genomic analyses of a brazillian isolate of Haemonchus contortus in a model for monepantel resistance.
Anthelmintic resistance is a worldwide problem in sheep production. Monepantel, the most recent anthelmintic released in market, has some reports of resistance, but it is still the most effective treatment to control gastrointestinal parasites.2 - 7 September 2018
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