299 research outputs found
On the oldest asteroid families in the main belt
Asteroid families are groups of minor bodies produced by high-velocity
collisions. After the initial dispersions of the parent bodies fragments, their
orbits evolve because of several gravitational and non-gravitational
effects,such as diffusion in mean-motion resonances, Yarkovsky and YORP
effects, close encounters of collisions, etc. The subsequent dynamical
evolution of asteroid family members may cause some of the original fragments
to travel beyond the conventional limits of the asteroid family. Eventually,
the whole family will dynamically disperse and no longer be recognizable.
A natural question that may arise concerns the timescales for dispersion of
large families. In particular, what is the oldest still recognizable family in
the main belt? Are there any families that may date from the late stages of the
Late Heavy Bombardment and that could provide clues on our understanding of the
primitive Solar System? In this work, we investigate the dynamical stability of
seven of the allegedly oldest families in the asteroid main belt. Our results
show that none of the seven studied families has a nominally mean estimated age
older than 2.7 Gyr, assuming standard values for the parameters describing the
strength of the Yarkovsky force. Most "paleo-families" that formed between 2.7
and 3.8 Gyr would be characterized by a very shallow size-frequency
distribution, and could be recognizable only if located in a dynamically less
active region (such as that of the Koronis family). V-type asteroids in the
central main belt could be compatible with a formation from a paleo-Eunomia
family.Comment: 9 pages, 5 figures, 5 tables. Accepted for publication in MNRA
The Rafita asteroid family
The Rafita asteroid family is an S-type group located in the middle main
belt, on the right side of the 3J:-1A mean-motion resonance. The proximity of
this resonance to the family left side in semi-major axis caused many former
family members to be lost. As a consequence, the family shape in the
domain is quite asymmetrical, with a preponderance of objects on the right side
of the distribution. The Rafita family is also characterized by a leptokurtic
distribution in inclination, which allows the use of methods of family age
estimation recently introduced for other leptokurtic families such as Astrid,
Hansa, Gallia, and Barcelona. In this work we propose a new method based on the
behavior of an asymmetry coefficient function of the distribution in the
plane to date incomplete asteroid families such as Rafita. By
monitoring the time behavior of this coefficient for asteroids simulating the
initial conditions at the time of the family formation, we were able to
estimate that the Rafita family should have an age of Myr, in good
agreement with results from independent methods such as Monte Carlo simulations
of Yarkovsky and Yorp dynamical induced evolution and the time behaviour of the
kurtosis of the distribution. Asteroids from the Rafita family can
reach orbits similar to 8\% of the currently known near Earth objects.
1\% of the simulated objects are present in NEO-space during the final
10 Myr of the simulation, and thus would be comparable to objects in the
present-day NEO population.Comment: Accepted 2017 January 19. Received 2017 January 17; in original form
2016 September
Dynamical evolution and chronology of the Hygiea asteroid family
The asteroid (10) Hygiea is the fourth largest asteroid of the Main Belt, by
volume and mass, and it is the largest member of its own family. Previous works
investigated the long-term effects of close encounters with (10) Hygiea of
asteroids in the orbital region of the family, and analyzed the taxonomical and
dynamical properties of members of this family. In this paper we apply the
high-quality SDSS-MOC4 taxonomic scheme of DeMeo and Carry (2013) to members of
the Hygiea family core and halo, we obtain an estimate of the minimum time and
number of encounter necessary to obtain a (or 99.7%) compatible
frequency distribution function of changes in proper caused by close
encounters with (10) Hygiea, we study the behavior of asteroids near secular
resonance configurations, in the presence and absence of the Yarkovsky force,
and obtain a first estimate of the age of the family based on orbital diffusion
by the Yarkovsky and YORP effects with two methods.
The Hygiea family is at least 2 Byr old, with an estimated age of Myr and a relatively large initial ejection velocity field,
according to the approach of Vokrouhlick\'{y} et al. (2006a, b). Surprisingly,
we found that the family age can be shortened by 25% if the dynamical
mobility caused by close encounters with (10) Hygiea is also accounted for,
which opens interesting new research lines for the dynamical evolution of
families associated with massive bodies. In our taxonomical analysis of the
Hygiea asteroid family, we also identified a new V-type candidate: the asteroid
(177904) (2005 SV5). If confirmed, this could be the fourth V-type object ever
to be identified in the outer main belt.Comment: 13 page, 15 figures, and 4 table
Dynamical evolution of V-type asteroids in the central main belt
V-type asteroids are associated with basaltic composition, and are supposed
to be fragments of crust of differentiated objects. Most V-type asteroids in
the main belt are found in the inner main belt, and are either current members
of the Vesta dynamical family (Vestoids), or past members that drifted away.
However, several V-type photometric candidates have been recently identified in
the central and outer main belt.
The origin of this large population of V-type objects is not well understood.
Since it seems unlikely that Vestoids crossing the 3J:-1A mean-motion resonance
with Jupiter could account for the whole population of V-type asteroids in the
central and outer main belt, origin from local sources, such as the parent
bodies of the Eunomia, and of the Merxia and Agnia asteroid families, has been
proposed as an alternative mechanism.
In this work we investigated the dynamical evolution of the V-type
photometric candidates in the central main belt, under the effect of
gravitational and non-gravitational forces. Our results show that dynamical
evolution from the parent bodies of the Eunomia and Merxia/Agnia families on
timescales of 2 Byr or more could be responsible for the current orbital
location of most of the low-inclined V-type asteroids.Comment: 16 pages, 10 figures, 3 tables. Accepted for publication in MNRA
A multi-domain approach to asteroid families identification
Previous works have identified families halos by an analysis in proper
elements domains, or by using Sloan Digital Sky Survey-Moving Object Catalog
data, fourth release (SDSS-MOC4) multi-band photometry to infer the asteroid
taxonomy, or by a combination of the two methods. The limited number of
asteroids for which geometric albedo was known until recently discouraged in
the past the extensive use of this additional parameter, which is however of
great importance in identifying an asteroid taxonomy. The new availability of
geometric albedo data from the Wide-field Infrared Survey Explorer (WISE)
mission for about 100,000 asteroids significantly increased the sample of
objects for which such information, with some errors, is now known.
In this work we proposed a new method to identify families halos in a
multi-domain space composed by proper elements, SDSS-MOC4 (a*,i-z) colors, and
WISE geometric albedo for the whole main belt (and the Hungaria and Cybele
orbital regions). Assuming that most families were created by the breakup of an
undifferentiated parent body, they are expected to be homogeneous in colors and
albedo. The new method is quite effective in determining objects belonging to a
family halo, with low percentages of likely interlopers, and results that are
quite consistent in term of taxonomy and geometric albedo of the halo members.Comment: 23 pages, 18 figures, 6 tables. Accepted for publication in MNRA
Nivel de abandono del adulto mayor en el asilo de San Jose - Casma - 2016
El presente trabajo de investigación titulado: Nivel de abandono del adulto mayor en el Asilo de San José ?Casma ? 2016, tuvo como objetivo, determinar el nivel de abandono del adulto mayor en el asilo San José de Casma-2016.Se trabajó con 25 adultos mayores del asilo San José de Casma que reunieron los criterios de inclusión. Se utilizó como técnica la entrevista para medir las características sociodemográficos, económicos y culturales del adulto mayor. La revisión documentaria de la historia clínica se usó para corroborar los datos de la entrevista y la ficha de observación, para medir la variable de abandono familiar, la mayoría de los adultos encuestados se encuentran en un alto nivel de abandono familiar, los datos se tabularon en el programa Excel luego se procesó la información utilizando el paquete estadístico SPSS.ver,20. Se obtuvieron los siguientes resultados: las edades en que oscilan son en un mayor porcentaje tanto en hombres como mujeres entre 70 a 80 años, así mismo la gran mayoría entre el 86 %y 90 % son viudos, también se encontró que la mayoría son analfabetos seguidos de un mínimo porcentaje que tiene primaria, los adultos antes de ingresar al asilo Vivian con sus hijos en un mayor porcentaje seguidos de los que Vivian con su esposa o esposo, en cuanto a la profesión en las mujeres el mayor porcentaje su casa no tenía profesión y en los hombres el mayor porcentaje eran obreros y algunos que eran comerciantes., en cuanto a su seguro de salud el 100% tiene seguro de SIS. Y finalmente referente a las enfermedades que padecen actualmente en los caballeros en un mayor porcentaje padece de hipertensión arterial de la piel y reumatismo en el caso de las mujeres el mayor porcentaje son diabéticas, también se encontró que el 84 % de los adultos mayores alojados en el asilo San José de Casma se encuentra en un nivel de abandono alto y el 16. % se encuentra en un nivel de abandono medio y el mayor porcentaje corresponde a los adultos de sexo masculino.Trabajo de investigació
\u3cem\u3eMycobacterium marinum\u3c/em\u3e Infection After Exposure to Coal Mine Water
Mycobacterium marinum infection has been historically associated with exposure to aquariums, swimming pools, fish, or other marine fauna. We present a case of M marinum left wrist tenosynovitis and elbow bursitis associated with a puncture injury and exposure to coal mine water in Illinois
Overall assessment of responsiveness to change is just the very first step: a technical commentary on Abanto et al.'s study
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Serosurveillance and Molecular Investigation of Wild Deer in Australia Reveals Seroprevalence of Pestivirus Infection
Since deer were introduced into Australia in the mid-1800s, their wild populations have increased in size and distribution, posing a potential risk to the livestock industry, through their role in pathogen transmission cycles. In comparison to livestock, there are limited data on viral infections in all wildlife, including deer. The aim of this study was to assess blood samples from wild Australian deer for serological evidence of exposure to relevant viral livestock diseases. Blood samples collected across eastern Australia were tested by ELISA to detect antigens and antibodies against Pestivirus and antibodies against bovine herpesvirus 1. A subset of samples was also assessed by RT-PCR for Pestivirus, Simbu serogroup, epizootic hemorrhagic disease virus and bovine ephemeral fever virus. Our findings demonstrated a very low seroprevalence (3%) for ruminant Pestivirus, and none of the other viruses tested were detected. These results suggest that wild deer may currently be an incidental spill-over host (rather than a reservoir host) for Pestivirus. However, deer could be a future source of viral infections for domestic animals in Australia. Further investigations are needed to monitor pathogen activity and quantify possible future infectious disease impacts of wild deer on the Australian livestock industry
Serosurveillance and Molecular Investigation of Wild Deer in Australia Reveals Seroprevalence of Pestivirus Infection
Since deer were introduced into Australia in the mid-1800s, their wild populations have increased in size and distribution, posing a potential risk to the livestock industry, through their role in pathogen transmission cycles. In comparison to livestock, there are limited data on viral infections in all wildlife, including deer. The aim of this study was to assess blood samples from wild Australian deer for serological evidence of exposure to relevant viral livestock diseases. Blood samples collected across eastern Australia were tested by ELISA to detect antigens and antibodies against Pestivirus and antibodies against bovine herpesvirus 1. A subset of samples was also assessed by RT-PCR for Pestivirus, Simbu serogroup, epizootic hemorrhagic disease virus and bovine ephemeral fever virus. Our findings demonstrated a very low seroprevalence (3%) for ruminant Pestivirus, and none of the other viruses tested were detected. These results suggest that wild deer may currently be an incidental spill-over host (rather than a reservoir host) for Pestivirus. However, deer could be a future source of viral infections for domestic animals in Australia. Further investigations are needed to monitor pathogen activity and quantify possible future infectious disease impacts of wild deer on the Australian livestock industry
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