270 research outputs found
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
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
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
Exact controllability to the trajectories for parabolic PDEs with nonlocal nonlinearities
This paper deals with the analysis of the internal control of a parabolic PDE with nonlinear diffusion, nonlocal in space. In our main result, we prove the local exact controllability to the trajectories with distributed controls, locally supported in space. The main ingredients of the proof are a compactness-uniqueness argument and Kakutani’s Fixed-Point Theorem in a suitable functional setting. Some possible extensions and open problems concerning other nonlocal systems are presented.Ministerio de Economía y Competitividad (MINECO). Españ
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
Insensitizing controls for a quasi-linear parabolic equation with diffusion depending on gradient of the state
In this paper, a quasi-linear parabolic equation with a diffusion term
dependent on the gradient to the state with Dirichlet boundary conditions is
considered. The goal of this paper is to prove the existence of control that
insensitizes the system under study which is the case that Xu Liu left open in
2012. It is well known that the insensitizing control problem is equivalent to
a null controllability result for a cascade system, which is obtained by
duality arguments, Carleman estimates, and the Right Inverse mapping theorem.
Also, some possible extensions and open problems concerning other quasi-linear
systems are presented
Prevalence, risk factors, and treatment outcomes of isoniazid- and rifampicin-mono-resistant pulmonary tuberculosis in Lima, Peru
Background : Isoniazid and rifampicin are the two most efficacious first-line agents for tuberculosis (TB) treatment. We assessed the prevalence of isoniazid and rifampicin mono-resistance, associated risk factors, and the association of mono-resistance on treatment outcomes.
Methods : A prospective, observational cohort study enrolled adults with a first episode of smear-positive pulmonary TB from 34 health facilities in a northern district of Lima, Peru, from March 2010 through December 2011. Participants were interviewed and a sputum sample was cultured on Lowenstein-Jensen (LJ) media. Drug susceptibility testing was performed using the proportion method. Medication regimens were documented for each patient. Our primary outcomes were treatment outcome at the end of treatment. The secondary outcome included recurrent episodes among cured patients within two years after completion of the treatment.
Results : Of 1292 patients enrolled, 1039 (80%) were culture-positive. From this subpopulation, isoniazid mono-resistance was present in 85 (8%) patients and rifampicin mono-resistance was present in 24 (2%) patients. In the multivariate logistic regression model, isoniazid mono-resistance was associated with illicit drug use (adjusted odds ratio (aOR) = 2.10; 95% confidence interval (CI): 1.1-4.1), and rifampicin mono-resistance was associated with HIV infection (aOR = 9.43; 95% CI: 1.9-47.8). Isoniazid mono-resistant patients had a higherrisk of poor treatment outcomes including treatment failure (2/85, 2%, p-value<0.01) and death (4/85, 5%, p<0.02). Rifampicin mono-resistant patients had a higher risk of death (2/24,8%, p<0.01).
Conclusion : A high prevalence of isoniazid and rifampicin mono-resistance was found among TB patients in our low HIV burden setting which were similar to regions with high HIV burden. Patients with isoniazid and rifampicin mono-resistance had an increased risk of poor treatment outcomes
Tropical contamination by hydrocarbons: Biotechnological perspective for the remediation of soils in forests, application case Peruvian Amazon, Bagua - Imaza
The objective of the present investigation is to publicize the situation of the forests with respect to the contamination of soils by hydrocarbons. The biotechnological processes applied to soil bioremediation and the feasibility of applying them in the country were investigated. Hydrocarbons are the major contaminants due to their resistance to biodegradation and their ability to bioaccumulate in the soil. In the world it is estimated that around 2,381,000 barrels of oil are spilled per year due to spills. Similarly, only in the Peruvian Amazon there have been 566 oil spills and from 1997 to 2021 87,370.82 barrels of oil have been spilled. All this has caused social conflicts and loss of species. In the case of the Bagua province, Imaza district, Inayo annex that crosses the Norperuano Pipeline, many times due to mismanagement, the pipeline has suffered ruptures and subsequent hydrocarbon leaks. The purpose of the study is to publicize in-situ bioremediation techniques, bioventing, bioaugmentation and biostimulation, and ex-situ Technology remediation techniques such as biopiles and landfarming. As well as the phytoremediation technique. The comparative result of the techniques showed the lines of thought that led to the selection of the most appropriate technique for the Amazonian soil of study.Fondo Nacional de Desarrollo Científico, Tecnológico y de Innovación Tecnológic
Tuberculosis and Cardiovascular Disease: Linking the Epidemics
The burden of tuberculosis and cardiovascular disease (CVD) is enormous worldwide. CVD rates are rapidly increasing in low- and middle-income countries. Public health programs have been challenged with the overlapping tuberculosis and CVD epidemics. Monocyte/macrophages, lymphocytes and cytokines involved in cellular mediated immune responses against Mycobacterium tuberculosis are also main drivers of atherogenesis, suggesting a potential pathogenic role of tuberculosis in CVD via mechanisms that have been described for other pathogens that establish chronic infection and latency. Studies have shown a pro-atherogenic effect of antibody-mediated responses against mycobacterial heat shock protein-65 through cross reaction with self-antigens in human vessels. Furthermore, subsets of mycobacteria actively replicate during latent tuberculosis infection (LTBI), and recent studies suggest that LTBI is associated with persistent chronic inflammation that may lead to CVD. Recent epidemiologic work has shown that the risk of CVD in persons who develop tuberculosis is higher than in persons without a history of tuberculosis, even several years after recovery from tuberculosis. Together, these data suggest that tuberculosis may play a role in the pathogenesis of CVD. Further research to investigate a potential link between tuberculosis and CVD is warranted
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