180 research outputs found
Floating stones off El Hierro, Canary Islands: xenoliths of pre-island sedimentary origin in the early products of the October 2011 eruption
The eruption that started off the south coast of El Hierro, Canary Islands, in October 2011 has emitted intriguing eruption products found floating in the sea. These specimens appeared as floating volcanic "bombs" that have in the meantime been termed "restingolites" (after the close-by village of La Restinga) and exhibit cores of white and porous pumice-like material. Currently the nature and origin of these "floating stones" is vigorously debated among researchers, with important implications for the interpretation of the hazard potential of the ongoing eruption. The "restingolites" have been proposed to be either (i) juvenile high-silica magma (e.g. rhyolite), (ii) remelted magmatic material (trachyte), (iii) altered volcanic rock, or (iv) reheated hyaloclastites or zeolite from the submarine slopes of El Hierro. Here, we provide evidence that supports yet a different conclusion. We have collected and analysed the structure and composition of samples and compared the results to previous work on similar rocks found in the archipelago. Based on their high silica content, the lack of igneous trace element signatures, and the presence of remnant quartz crystals, jasper fragments and carbonate relicts, we conclude that "restingolites" are in fact xenoliths from pre-island sedimentary rocks that were picked up and heated by the ascending magma causing them to partially melt and vesiculate. They hence represent messengers from depth that help us to understand the interaction between ascending magma and crustal lithologies in the Canary Islands as well as in similar Atlantic islands that rest on sediment/covered ocean crust (e.g. Cape Verdes, Azores). The occurrence of these "restingolites" does therefore not indicate the presence of an explosive high-silica magma that is involved in the ongoing eruption
The Cratering History of Asteroid (21) Lutetia
The European Space Agency's Rosetta spacecraft passed by the main belt
asteroid (21) Lutetia the 10th July 2010. With its ~100km size, Lutetia is one
of the largest asteroids ever imaged by a spacecraft. During the flyby, the
on-board OSIRIS imaging system acquired spectacular images of Lutetia's
northern hemisphere revealing a complex surface scarred by numerous impact
craters, reaching the maximum dimension of about 55km. In this paper, we assess
the cratering history of the asteroid. For this purpose, we apply current
models describing the formation and evolution of main belt asteroids, that
provide the rate and velocity distributions of impactors. These models, coupled
with appropriate crater scaling laws, allow us to interpret the observed crater
size-frequency distribution (SFD) and constrain the cratering history. Thanks
to this approach, we derive the crater retention age of several regions on
Lutetia, namely the time lapsed since their formation or global surface reset.
We also investigate the influence of various factors -like Lutetia's bulk
structure and crater obliteration- on the observed crater SFDs and the
estimated surface ages. From our analysis, it emerges that Lutetia underwent a
complex collisional evolution, involving major local resurfacing events till
recent times. The difference in crater density between the youngest and oldest
recognized units implies a difference in age of more than a factor of 10. The
youngest unit (Beatica) has an estimated age of tens to hundreds of Myr, while
the oldest one (Achaia) formed during a period when the bombardment of
asteroids was more intense than the current one, presumably around 3.6Gyr ago
or older.Comment: Accepted by PSS, to appear on Lutetia Flyby special issu
Photometry of dust grains of comet 67P and connection with nucleus regions
Aims. Multiple pairs of high-resolution images of the dust coma of comet 67P/Churyumov-Gerasimenko have been collected by OSIRIS onboard Rosetta allowing extraction and analysis of dust grain tracks. Methods. We developed a quasi automatic method to recognize and to extract dust tracks in the Osiris images providing size, FWHM and photometric data. The dust tracks characterized by a low signal-to-noise ratio were checked manually. We performed the photometric analysis of 70 dust grain tracks observed on two different Narrow Angle Camera images in the two filters F24 and F28, centered at λ = 480.7 nm and at λ = 743.7 nm, respectively, deriving the color and the reddening of each one. We then extracted several images of the nucleus observed with the same filters and with the same phase angle to be compared with the dust grain reddening. Results. Most of the dust grain reddening is very similar to the nucleus values, confirming they come from the surface or subsurface layer. The histogram of the dust grain reddening has a secondary peak at negative values and shows some grains with values higher than the nucleus, suggesting a different composition from the surface grains. One hypothesis comes from the negative values point at the presence of hydrated minerals in the comet
A collision in 2009 as the origin of the debris trail of asteroid P/2010 A2
The peculiar object P/2010 A2 was discovered by the LINEAR near-Earth
asteroid survey in January 2010 and given a cometary designation due to the
presence of a trail of material, although there was no central condensation or
coma. The appearance of this object, in an asteroidal orbit (small eccentricity
and inclination) in the inner main asteroid belt attracted attention as a
potential new member of the recently recognized class of 'Main Belt Comets'
(MBCs). If confirmed, this new object would greatly expand the range in
heliocentric distance over which MBCs are found. Here we present observations
taken from the unique viewing geometry provided by ESA's Rosetta spacecraft,
far from the Earth, that demonstrate that the trail is due to a single event
rather than a period of cometary activity, in agreement with independent
results from the Hubble Space Telescope (HST). The trail is made up of
relatively large particles of millimetre to centimetre size that remain close
to the parent asteroid. The shape of the trail can be explained by an initial
impact ejecting large clumps of debris that disintegrated and dispersed almost
immediately. We determine that this was an asteroid collision that occurred
around February 10, 2009.Comment: Published in Nature on 14/10/2010. 25 pages, includes supplementary
materia
The TNFalpha gene relates to clinical phenotype in alpha-1-antitrypsin deficiency
<p>Abstract</p> <p>Background</p> <p>Genetic variation may underlie phenotypic variation in chronic obstructive pulmonary disease (COPD) in subjects with and without alpha 1 antitrypsin deficiency (AATD). Genotype specific sub-phenotypes are likely and may underlie the poor replication of previous genetic studies. This study investigated subjects with AATD to determine the relationship between specific phenotypes and <it>TNFα </it>polymorphisms.</p> <p>Methods</p> <p>424 unrelated subjects of the PiZZ genotype were assessed for history of chronic bronchitis, impairment of lung function and radiological presence of emphysema and bronchiectasis. A subset of subjects with 3 years consecutive lung function data was assessed for decline of lung function. Four single nucleotide polymorphisms (SNPs) tagging <it>TNFα </it>were genotyped using TaqMan<sup>® </sup>genotyping technologies and compared between subjects affected by each phenotype and those unaffected. Plasma TNFα levels were measured in all PiZZ subjects.</p> <p>Results</p> <p>All SNPs were in Hardy-Weinberg equilibrium. A significant difference in rs361525 genotype (p = 0.01) and allele (p = 0.01) frequency was seen between subjects with and without chronic bronchitis, independent of the presence of other phenotypes. TNFα plasma level showed no phenotypic or genotypic associations.</p> <p>Conclusion</p> <p>Variation in <it>TNFα </it>is associated with chronic bronchitis in AATD.</p
Corrigendum to "Floating stones off El Hierro, Canary Islands: xenoliths of pre-island sedimentary origin in the early products of the October 2011 eruption" published in Solid Earth, 3, 97–110, 2012
No abstract available
Ejecta Evolution Following a Planned Impact into an Asteroid: The First Five Weeks
The impact of the DART spacecraft into Dimorphos, moon of the asteroid
Didymos, changed Dimorphos' orbit substantially, largely from the ejection of
material. We present results from twelve Earth-based facilities involved in a
world-wide campaign to monitor the brightness and morphology of the ejecta in
the first 35 days after impact. After an initial brightening of ~1.4
magnitudes, we find consistent dimming rates of 0.11-0.12 magnitudes/day in the
first week, and 0.08-0.09 magnitudes/day over the entire study period. The
system returned to its pre-impact brightness 24.3-25.3 days after impact
through the primary ejecta tail remained. The dimming paused briefly eight days
after impact, near in time to the appearance of the second tail. This was
likely due to a secondary release of material after re-impact of a boulder
released in the initial impact, through movement of the primary ejecta through
the aperture likely played a role.Comment: 16 pages, 5 Figures, accepted in the Astrophysical Journal Letters
(ApJL) on October 16, 202
The genetics of chronic obstructive pulmonary disease
Chronic obstructive pulmonary disease (COPD) is a heterogeneous disease caused by the interaction of genetic susceptibility and environmental influences. There is increasing evidence that genes link to disease pathogenesis and heterogeneity by causing variation in protease anti-protease systems, defence against oxidative stress and inflammation. The main methods of genomic research for complex disease traits are described, together with the genes implicated in COPD thus far, their roles in disease causation and the future for this area of investigation
Ejecta Evolution Following a Planned Impact into an Asteroid: The First Five Weeks
The impact of the Double Asteroid Redirection Test spacecraft into Dimorphos, moon of the asteroid Didymos, changed Dimorphos’s orbit substantially, largely from the ejection of material. We present results from 12 Earth-based facilities involved in a world-wide campaign to monitor the brightness and morphology of the ejecta in the first 35 days after impact. After an initial brightening of ∼1.4 mag, we find consistent dimming rates of 0.11–0.12 mag day−1 in the first week, and 0.08–0.09 mag day−1 over the entire study period. The system returned to its pre-impact brightness 24.3–25.3 days after impact though the primary ejecta tail remained. The dimming paused briefly eight days after impact, near in time to the appearance of the second tail. This was likely due to a secondary release of material after re-impact of a boulder released in the initial impact, though movement of the primary ejecta through the aperture likely played a role
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