1,104 research outputs found
The INTEGRAL-OMC Scientific Archive
The Optical Monitoring Camera (OMC) on-board the INTEGRAL satellite has, as
one of its scientific goals, the observation of a large number of variable
sources previously selected. After almost 6 years of operations, OMC has
monitored more than 100 000 sources of scientific interest. In this
contribution we present the OMC Scientific Archive
(http://sdc.laeff.inta.es/omc/) which has been developed to provide the
astronomical community with a quick access to the light curves generated by
this instrument.We describe the main characteristics of this archive, as well
as important aspects for the users: object types, temporal sampling of light
curves and photometric accuracy.Comment: 4 pages, 5 figures. "Highlights of Spanish Astrophysics V"
Proceedings of the VIII Scientific Meeting of the Spanish Astronomical
Society (SEA) held in Santander, July 7-11, 200
Assessment of the Impact of Long Integration Time in Geosynchronous SAR Imagery of Agricultural Fields by Means of GB-SAR Data
Geosynchronous Synthetic Aperture Radar (GeoSAR) missions offer the advantage of near-continuous monitoring of specific regions on Earth, making them essential for applications that require continuous information. However, wind induced motion along the inherent long integration time can result in image defocusing, with potential degradation of retrieved information. This paper aims to investigate the impact of GEOSAR long integration time in Synthetic Aperture Radar (SAR) imaging and derived products (time series of backscatter and coherence) required to extract agriculture relevant soil or crop parameters of interest. The study is based on the extensive HydroSoil data acquisition campaign carried out over barley and corn crops, funded by the European Space Agency (ESA). The collected raw data are used to synthesize equivalent apertures with integration times of up to 4 hours, similar to those acquired with a GeoSAR. These Ultra Slow apertures facilitate the assessment of the impact of agricultural scene decorrelation on the generation of images with extended integration times.This work was funded by the European Space Agency (ESA Contract No. 4000132509/20/NL/FF/ab with UPC), supported by the Spanish MCINN funds Unidad de Excelencia Maria de Maeztu MDM-2016-0600 and under projects PID2020-117303GB-C21/AEI/10.13039/501100011033 and PID2020-117303GB-C22/AEI/10.13039/501100011033
Detection of an optical transient following the 13 March 2000 short/hard gamma-ray burst
We imaged the error box of a gamma-ray burst of the short (0.5 s), hard type
(GRB 000313), with the BOOTES-1 experiment in southern Spain, starting 4 min
after the gamma-ray event, in the I-band. A bright optical transient (OT
000313) with I = 9.4 +/- 0.1 was found in the BOOTES-1 image, close to the
error box (3-sigma) provided by BATSE. Late time VRIK'-band deep observations
failed to reveal an underlying host galaxy. If the OT 000313 is related to the
short, hard GRB 000313, this would be the first optical counterpart ever found
for this kind of events (all counterparts to date have been found for bursts of
the long, soft type). The fact that only prompt optical emission has been
detected (but no afterglow emission at all, as supported by theoretical models)
might explain why no optical counterparts have ever been found for short, hard
GRBs.This fact suggests that most short bursts might occur in a low-density
medium and favours the models that relate them to binary mergers in very
low-density enviroments.Comment: Revised version. Accepted for publication in Astronomy and
Astrophysics Letters, 5 pages, 3 figure
Sediment transport to the deep canyons and open-slope of the western Gulf of Lions during the 2006 intense cascading and open-sea convection period
An array of mooring lines deployed between 300 and 1900 m depth along the Lacaze-Duthiers and Cap de Creus canyons and in the adjacent southern open slope was used to study the water and sediment transport on the western Gulf of Lions margin during the 2006 intense cascading period. Deep-reaching cascading pulses occurred in early January, in late January and from early March to mid-April. Dense water and sediment transport to the deep environments occurred not only through submarine canyons, but also along the southern open slope. During the deep cascading pulses, temporary upper and mid-canyon and open slope deposits were an important source of sediment to the deep margin. Significant sediment transport events at the canyon head only occurred in early January because of higher sediment availability on the shelf after the stratified and calm season, and in late February because of the interaction of dense shelf water cascading with a strong E-SE storm. During the January deep cascading pulses, increases in suspended sediment concentration within the canyon were greater and earlier at 1000 m depth than at 300 m depth, whereas during the March-April deep cascading pulses sediment concentration only increased below 300 m depth, indicating resuspension and redistribution of sediments previously deposited at upper and mid-canyon depths. Deeper than 1000 m depth, net fluxes show that most of the suspended sediment left the canyon and flowed along the southern open slope towards the Catalan margin, whereas a small part flowed down-canyon and was exported basinward. Additionally, on the mid- and lower-continental slope there was an increase in the near-bottom currents induced by deep open-sea convection processes and the propagation of eddies. This, combined with the arrival of deep cascading pulses, also generated moderate suspended sediment transport events in the deeper slope regions
Targeting Alzheimer's disease with multimodal polypeptide-based nanoconjugates
Alzheimer’s disease (AD), the most prevalent form of dementia, remains incurable mainly due to our failings in the search for effective pharmacological strategies. Here, we describe the development of targeted multimodal polypeptide-based nanoconjugates as potential AD treatments. Treatment with polypeptide nanoconjugates bearing propargylamine moieties and bisdemethoxycurcumin or genistein afforded neuroprotection and displayed neurotrophic effects, as evidenced by an increase in dendritic density of pyramidal neurons in organotypic hippocampal culture. The additional conjugation of the Angiopep-2 targeting moiety enhanced nanoconjugate passage through the blood-brain barrier and modulated brain distribution with nanoconjugate accumulation in neurogenic areas, including the olfactory bulb. Nanoconjugate treatment effectively reduced neurotoxic β amyloid aggregate levels and rescued impairments to olfactory memory and object recognition in APP/PS1 transgenic AD model mice. Overall, this study provides a description of a targeted multimodal polyglutamate-based nanoconjugate with neuroprotective and neurotrophic potential for AD treatment
The Mechanisms of Codon Reassignments in Mitochondrial Genetic Codes
Many cases of non-standard genetic codes are known in mitochondrial genomes.
We carry out analysis of phylogeny and codon usage of organisms for which the
complete mitochondrial genome is available, and we determine the most likely
mechanism for codon reassignment in each case. Reassignment events can be
classified according to the gain-loss framework. The gain represents the
appearance of a new tRNA for the reassigned codon or the change of an existing
tRNA such that it gains the ability to pair with the codon. The loss represents
the deletion of a tRNA or the change in a tRNA so that it no longer translates
the codon. One possible mechanism is Codon Disappearance, where the codon
disappears from the genome prior to the gain and loss events. In the
alternative mechanisms the codon does not disappear. In the Unassigned Codon
mechanism, the loss occurs first, whereas in the Ambiguous Intermediate
mechanism, the gain occurs first. Codon usage analysis gives clear evidence of
cases where the codon disappeared at the point of the reassignment and also
cases where it did not disappear. Codon disappearance is the probable
explanation for stop to sense reassignments and a small number of reassignments
of sense codons. However, the majority of sense to sense reassignments cannot
be explained by codon disappearance. In the latter cases, by analysis of the
presence or absence of tRNAs in the genome and of the changes in tRNA
sequences, it is sometimes possible to distinguish between the Unassigned Codon
and Ambiguous Intermediate mechanisms. We emphasize that not all reassignments
follow the same scenario and that it is necessary to consider the details of
each case carefully.Comment: 53 pages (45 pages, including 4 figures + 8 pages of supplementary
information). To appear in J.Mol.Evo
Exploiting the potential of autophagy in cisplatin therapy: a new strategy to overcome resistance
Resistance to cisplatin is a major challenge in the current cancer therapy. In order to explore new therapeutic strategies to cisplatin resistance, we evaluated, in a model of lung cancer (H1299 and H460 cell lines), the nature of the pathways leading to cell death. We observed that H1299 displayed a natural resistance to cisplatin due to an inability to trigger an apoptotic response that correlates with the induction of autophagy. However, pharmacological and genetic approaches showed how autophagy was a mechanism associated to cell death rather than to resistance. Indeed, pro-autophagic stimuli such as mTOR or Akt inhibition mediate cell death in both cell lines to a similar extent. We next evaluated the response to a novel platinum compound, monoplatin, able to promote cell death in an exclusive autophagy-dependent manner. In this case, no differences were observed between both cell lines. Furthermore, in response to monoplatin, two molecular hallmarks of cisplatin response (p53 and MAPKs) were not implicated, indicating the ability of this pro-autophagic compound to overcome cisplatin resistance. In summary, our data highlight how induction of autophagy could be used in cisplatin resistant tumours and an alternative treatment for p53 mutated patient in a synthetic lethally approach
The INTEGRAL Galactic bulge monitoring program: the first 1.5 years
The Galactic bulge region is a rich host of variable high-energy point
sources. Since 2005, February 17 we are monitoring the source activity in this
region about every three days with INTEGRAL. Thanks to the large field of view,
the imaging capabilities and the sensitivity at hard X-rays, we are able to
present for the first time a detailed homogeneous (hard) X-ray view of a sample
of 76 sources in the Galactic bulge region. We describe the successful
monitoring program and show the first results for a period of about one and a
half year. We focus on the short (hour), medium (month) and long-term (year)
variability in the 20-60 keV and 60-150 keV bands. When available, we discuss
the simultaneous observations in the 3-10 keV and 10-25 keV bands. Per
visibility season we detect 32/33 sources in the 20-60 keV band and 8/9 sources
in the 60-150 keV band. On average, we find per visibility season one active
bright (>~100 mCrab, 20-60 keV) black-hole candidate X-ray transient and three
active weaker (<~25 mCrab, 20-60 keV) neutron star X-ray transients. Most of
the time a clear anti-correlation can be seen between the soft and hard X-ray
emission in some of the X-ray bursters. Hard X-ray flares or outbursts in X-ray
bursters, which have a duration of the order of weeks, are accompanied by soft
X-ray drops. On the other hand, hard X-ray drops can be accompanied by soft
X-ray flares/outbursts. We found a number of new sources, IGR J17354-3255, IGR
17453-2853, IGR J17454-2703, IGR J17456-2901b, IGR J17536-2339, and IGR
J17541-2252. We report here on some of the high-energy properties of these
sources. The high-energy light curves of all the sources in the field of view,
and the high-energy images of the region, are made available through the WWW at
http://isdc.unige.ch/Science/BULGE/.Comment: 27 pages, 42 figures, accepted for publication in A&A. Abstract
abridged. Tables 3,4,6,7 appear at the end. Images have been compressed and
are reduced in quality; original PostScript images can be retrieved from
http://isdc.unige.ch/~kuulkers/bulge
Evolutive Unification in Composite Active Galactic Nuclei
In this paper we explore an evolutionary Unified scenario involving super
massive black hole and starburst with outflow, that seems capable of explaining
most of the observational properties of at least part of AGNs. Our suggestion
is explored inside the expectations of the Starburst model close associated
with the AGN where the NLR, BLR and BAL region are produced in part by the
outflow process with shells and in compact supernova remnants. The outflow
process in BAL QSOs with extreme IR and Fe II emission is studied. In addition,
the Fe II poblem regarding the BLR of AGN is analysed. Neither the correlations
between the BAL, IR emission, FeII intensity and the intrinsic properties of
the AGN are clearly understood. We suggest here that the behaviour of the BAL,
IR and FeII emission in AGNs can be understood inside an evolutionary and
composite model for AGNs. In our model, strong BAL systems and Fe II emission
are present (and intense) in young IR objects. Orientation/ obscuration effects
take the role of a second parameter providing the segregation between Sy1/Sy2
and BLRG/NLRG.Comment: 14 pages, 6 figures (submitted MNRAS
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