261 research outputs found
Footprints of a possible Ceres asteroid paleo-family
Ceres is the largest and most massive body in the asteroid main belt.
Observational data from the Dawn spacecraft reveal the presence of at least two
impact craters about 280~km in diameter on the Ceres surface, that could have
expelled a significant number of fragments. Yet, standard techniques for
identifying dynamical asteroid families have not detected any Ceres family. In
this work, we argue that linear secular resonances with Ceres deplete the
population of objects near Ceres. Also, because of the high escape velocity
from Ceres, family members are expected to be very dispersed, with a
considerable fraction of km-sized fragments that should be able to reach the
pristine region of the main belt, the area between the 5J:-2A and 7J:-3A
mean-motion resonances, where the observed number of asteroids is low. Rather
than looking for possible Ceres family members near Ceres, here we propose to
search in the pristine region. We identified 156 asteroids whose taxonomy,
colors, albedo could be compatible with being fragments from Ceres. Remarkably,
most of these objects have inclinations near that of Ceres itself.Comment: 12 pages, 6 figures, 1 table. Accepted for publication in MNRA
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
Dynamics in the vicinity of (101955) Bennu: Solar radiation pressure effects in equatorial orbits
Here we study the dynamical effects of the solar radiation pressure (SRP) on
a spacecraft that will survey the near-Earth rotating asteroid (101955) Bennu
when the projected shadow is accounted for. The spacecraft's motion near
(101955) Bennu is modelled in the rotating frame fixed at the centre of the
asteroid, neglecting the sun gravity effects. We calculate the solar radiation
pressure at the perihelion, semi-major axis and aphelion distances of the
asteroid from the Sun. The goals of this work are to analyse the stability for
both homogeneous and inhomogeneous mass distribution and study the effects of
the solar radiation pressure in equatorial orbits close to the asteroid
(101955) Bennu. As results, we find that the mascon model divided into ten
equal layers seems to be the most suitable for this problem. We can highlight
that the centre point 8, which was linearly stable in the case of the
homogeneous mass distribution, becomes unstable in this new model changing its
topological structure. For a Sun initial longitude , starting
with the spacecraft longitude , the orbits suffer fewer impacts
and some (between 0.4 and 0.5 km), remaining unwavering even if the maximum
solar radiation is considered. When we change the initial longitude of the Sun
to , the orbits with initial longitude
appear to be more stable. Finally, when the passage of the spacecraft in the
shadow is accounted for, the effects of solar radiation pressure are softened,
and we find more stable orbits.Comment: Accepted 2017 May 10. Received 2017 April 29; in original form 2017
January 1
Nutrigerontology: A key for achieving successful ageing and longevity
During the last two centuries the average lifespan has increased at a rate of approximately 3 months/year in both sexes, hence oldest old people are becoming the population with the fastest growth in Western World. Although the average life expectancy is increasing dramatically, the healthy lifespan is not going at the same pace. This underscores the importance of studies on the prevention of age-related diseases, in order to satisfactorily decrease the medical, economic and social problems associated to advancing age, related to an increased number of individuals not autonomous and affected by invalidating pathologies. In particular, data from experimental studies in model organisms have consistently shown that nutrient signalling pathways are involved in longevity, affecting the prevalence of age-related loss of function, including age-related diseases. Accordingly, nutrigerontology is defined as the scientific discipline that studies the impact of nutrients, foods, macronutrient ratios, and diets on lifespan, ageing process, and age-related diseases. To discuss the potential relevance of this new science in the attainment of successful ageing and longevity, three original studies performed in Sicily with local foods and two reviews have been assembled in this series. Data clearly demonstrate the positive effects of nutraceuticals, functional foods and Mediterranean Diet on several biological parameters. In fact, they could represent a prevention for many age-related diseases, and, although not a solution for this social plague, at least a remedy to alleviate it. Thus, the possibility to create a dietary pattern, based on the combined strategy of the use of both nutraceuticals and functional foods should permit to create a new therapeutic strategy, based not only on a specific bioactive molecule or on a specific food but on a integrated approach that, starting from the local dietary habits, can be led to a "nutrafunctional diet" applicable worldwide
Machine learning to predict the solar flux and geomagnetic indices to model density and Drag in Satellites
In recent years (2000-2021), human-space activities have been increasing
faster than ever. More than 36000 Earth' orbiting objects, all larger than 10
cm, in orbit around the Earth, are currently tracked by the European Space
Agency (ESA). Around 70\% of all cataloged objects are in Low-Earth Orbit
(LEO). Aerodynamic drag provides one of the main sources of perturbations in
this population, gradually decreasing the semi-major axis and period of the LEO
satellites. Usually, an empirical atmosphere model as a function of solar radio
flux and geomagnetic data is used to calculate the orbital decay and lifetimes
of LEO satellites. In this respect, a good forecast for the space weather data
could be a key tool to improve the model of drag. In this work, we propose
using Time Series Forecasting Model to predict the future behavior of the solar
flux and to calculate the atmospheric density, to improve the analytical models
and reduce the drag uncertainty
An innovative approach to designing digital health solutions addressing the unmet needs of obese patients in Europe
According to the World Health Organization (WHO), the worldwide obesity rate has tripled since 1975. In Europe, more than half of the population is overweight and obese. Around 2.8 million people die each year worldwide as a result of conditions linked to being overweight or obese. This study aimed to analyze the policies, approaches, and solutions that address the social and health unmet needs of obese patients, at different levels, in order to simulate the definition of an integrated approach, and to provide and share examples of innovative solutions supporting health promotion, disease prevention, and integration of services to improve the collaboration between the different health and care stakeholders involved across the country and in the lives of obese patients. A collaborative approach involving various levels of government and regional experts from different European countries was applied to identify, explore, and evaluate different aspects of the topic, from the innovation perspective and focusing on a European and a regional vision. Currently, people prefer more foods rich in fats, sugars, and salt/sodium than fruits, vegetables, and fiber. This behavior leads to a significant negative impact on their health-related quality of life. Changes in healthcare systems, healthy policy, and approaches to patient care and better implementation of the different prevention strategies between all the stakeholders are needed, taking advantage of the digital transformation of health and care. Such changes can support obese patients in their fight against an unhealthy lifestyle and at the same time reduce healthcare costs
On the V-type asteroids outside the Vesta family. I. Interplay of nonlinear secular resonances and the Yarkovsky effect: the cases of 956 Elisa and 809 Lundia
Among the largest objects in the main belt, asteroid 4 Vesta is unique in
showing a basaltic crust. It is also the biggest member of the Vesta family,
which is supposed to originate from a large cratering event about 1 Gyr ago
(Marzari et al. 1996). Most of the members of the Vesta family for which a
spectral classification is available show a V-type spectra. Before the
discovery of 1459 Magnya (Lazzaro et al. 2000) and of several V-type NEA (Xu
1995), all the known V-type asteroids were members of the Vesta family.
Recently two V-type asteroids, 809 Lundia and 956 Elisa, (Florczak et al. 2002)
have been discovered well outside the limits of the family, near the Flora
family. We currently know 22 V-type asteroids outside the family, in the inner
asteroid belt. In this work we investigate the possibility that these objects
are former family members that migrated to their current positions via the
interplay of Yarkovsky effect and nonlinear secular resonances. The main
dynamical feature of 956 Elisa and 809 Lundia is that they are currently inside
the 2(g-g6)+s-s6 (z2 by Milani and Knezevic, 1993) secular resonance. Our
investigations show that members of the Vesta dynamical family may drift in
three-body and weak secular resonances until they are captured in the strong z2
secular resonance. Only asteroids with diameters larger than 16 km can remain
in one of the three-body or secular resonances long enough to reach the region
of the z2 resonance. This two-step mechanism of capture into the z2 resonance
could explain: i) the current resonant orbits of 956 Elisa and 809 Lundia, ii)
why their size is significantly larger than that of the typical member of the
Vesta family, and iii) provide a lower limit on the Vesta family age.Comment: 14 pages, 10 figures, 3 tables. Accepted for publication in A&
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