6,681 research outputs found
On the dust environment of Main-Belt Comet 313P/Gibbs
We present observations carried out using the 10.4 m Gran Telescopio Canarias
and an interpretative model of the dust environment of activated asteroid
313P/Gibbs. We discuss three different models relating to different values of
the dust parameters, i.e, dust loss rate, maximum and minimum sizes of
particles, power index of the size distribution, and emission pattern. The best
model corresponds with an isotropic emission of particles which started on
August 1st. The size of grains were in the range of m, with
velocities for 100 m particles between ms, with a dust
production rate in the range of kgs. The dust tails'
brightness and morphology are best interpreted in terms of a model of sustained
and low dust emission driven by water-ice sublimation, spanning since 2014
August 1st, and triggered by a short impulsive event. This event produced an
emission of small particles of about 0.1 m with velocities of 4
ms. From our model we deduce that the activity of this Main-Belt
Comet continued for, at least, four months, since activation.Comment: 14 pages, 4 figures, 2 tables. Accepted for publication in The
Astrophysical Journa
Dust loss from activated asteroid P/2015 X6
We present observations and dust tail models of activated asteroid P/2015 X6
from deep imaging data acquired at the 10.4m Gran Telescopio Canarias (GTC)
from mid-December 2015 to late January 2016. The results of the modeling
indicate that the asteroid has undergone a sustained dust loss over a two-month
or longer period. The dust parameters, derived from multidimensional fits of
the available images, are compatible with either ice sublimation or rotational
instability processes. An impulsive event, as it could be associated to an
impact with another body, is less likely. A power-law distribution of
particles, with minimum and maximum radius of 1 m and 1 cm, and power
index of --3.3 is found to be consistent with the observations. Depending on
the ejection velocity model adopted, the particle velocities are found in the
0.3 to 10 m s range. The activation time was between 18-26 days before
discovery. The total ejected mass from that time to the most recent observation
is in the range 5-910 kg. No dust features giving indication of
past activity earlier than the activation time have been observed.Comment: Accepted by ApJ, May 15th 201
Early evolution of disrupted asteroid P/2016 G1 (PANSTARRS)
We present deep imaging observations of activated asteroid P/2016 G1
(PANSTARRS) using the 10.4m Gran Telescopio Canarias (GTC) from late April to
early June 2016. The images are best interpreted as the result of a relatively
short-duration event with onset about days before
perihelion (i.e., around 10th February, 2016), starting sharply and decreasing
with a days (Half-width at half-maximum, HWHM). The
results of the modeling imply the emission of 1.710 kg of
dust, if composed of particles of 1 micrometer to 1 cm in radius, distributed
following a power-law of index --3, and having a geometric albedo of 0.15. A
detailed fitting of a conspicuous westward feature in the head of the
comet-like object indicates that a significant fraction of the dust was ejected
along a privileged direction right at the beginning of the event, which
suggests that the parent body has possibly suffered an impact followed by a
partial or total disruption. From the limiting magnitude reachable with the
instrumental setup, and assuming a geometric albedo of 0.15 for the parent
body, an upper limit for the size of possible fragment debris of 50 m in
radius is derived.Comment: Accepted by ApJ Letter
Disrupted asteroid P/2016 G1. II. Follow-up observations from the Hubble Space Telescope
After the early observations of the disrupted asteroid P/2016 G1 with the
10.4m Gran Telescopio Canarias (GTC), and the modeling of the dust ejecta, we
have performed a follow-up observational campaign of this object using the
Hubble Space Telescope (HST) during two epochs (June 28 and July 11, 2016). The
analysis of these HST images with the same model inputs obtained from the GTC
images revealed a good consistency with the predicted evolution from the GTC
images, so that the model is applicable to the whole observational period from
late April to early July 2016. This result confirms that the resulting dust
ejecta was caused by a relatively short-duration event with onset about 350
days before perihelion, and spanning about 30 days (HWHM). For a size
distribution of particles with a geometric albedo of 0.15, having radii limits
of 1 m and 1 cm, and following a power-law with index --3.0, the total
dust mass ejected is 210 kg. As was the case with the GTC
observations, no condensations in the images that could be attributed to a
nucleus or fragments released after the disruption event were found. However,
the higher limiting magnitude reachable with the HST images in comparison with
those from GTC allowed us to impose a more stringent upper limit to the
observed fragments of 30 m.Comment: 10 pages, 2 figures Accepted by Astronomical Journal, Nov. 2, 201
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The role of consumption in material reduction opportunities: the impact of product lifetime in supplying the UK steel demand
Most of the products purchased in the UK are manufactured in other countries. As a result, worldwide greenhouse gases (GHG) emissions released to manufacture all products purchased in the UK are significantly higher than the UK territorial emissions. More than one half of global industrial emissions result from the use of steel, cement, paper, plastics, and aluminium. In this paper, the UK consumption of products that embody these five materials is estimated. For steel, which is the most widely used among these five materials, consumption and accumulation patterns are examined across four product categories. The impact of steel product lifetime extension is examined for the UK as one option for material demand reduction at the consumption stage of the supply chain. Different levels of steel product lifetimes are simulated for the UK in 2050 and their impacts are examined in terms of UK steel production, implicit steel imports, and global carbon dioxide emissions. Steel product lifetime extension promotes a reduction in the need for steel imports, by reducing the demand for new steel, which leads to lower carbon dioxide emissions required to supply the UK steel demand. The results demonstrate the criticality of a focus on the consumption stage, since any interventions made towards demand reduction of end-use goods leads to material reduction across the supply chain
Flexible auditory training, psychophysics, and enrichment of common marmosets with an automated, touchscreen-based system
Devising new and more efficient protocols to analyze the phenotypes of non-human primates, as well as their complex nervous systems, is rapidly becoming of paramount importance. This is because with genome-editing techniques, recently adopted to non-human primates, new animal models for fundamental and translational research have been established. One aspect in particular, namely cognitive hearing, has been difficult to assess compared to visual cognition. To address this, we devised autonomous, standardized, and unsupervised training and testing of auditory capabilities of common marmosets with a cage-based standalone, wireless system. All marmosets tested voluntarily operated the device on a daily basis and went from naïve to experienced at their own pace and with ease. Through a series of experiments, here we show, that animals autonomously learn to associate sounds with images; to flexibly discriminate sounds, and to detect sounds of varying loudness. The developed platform and training principles combine in-cage training of common marmosets for cognitive and psychoacoustic assessment with an enriched environment that does not rely on dietary restriction or social separation, in compliance with the 3Rs principle
Water-ice driven activity on Main-Belt Comet P/2010 A2 (LINEAR) ?
The dust ejecta of Main-Belt Comet P/2010 A2 (LINEAR) have been observed with
several telescopes at the at the Observatorio del Roque de los Muchachos on La
Palma, Spain. Application of an inverse dust tail Monte Carlo method to the
images of the dust ejecta from the object indicates that a sustained, likely
water-ice driven, activity over some eight months is the mechanism responsible
for the formation of the observed tail. The total amount of dust released is
estimated to be 5E7 kg, which represents about 0.3% of the nucleus mass. While
the event could have been triggered by a collision, this cannot be decided from
the currently available data.Comment: Accepted for ApJ Letter
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