13,871 research outputs found
2MASS J154043.42-510135.7: a new addition to the 5 pc population
The aim of the project is to find the stars nearest to the Sun and to
contribute to the completion of the stellar and substellar census of the solar
neighbourhood. We identified a new late-M dwarf within 5 pc, looking for high
proper motion sources in the 2MASS-WISE cross-match. We collected astrometric
and photometric data available from public large-scale surveys. We complemented
this information with low-resolution optical and near-infrared spectroscopy
with instrumentation on the ESO NTT to confirm the nature of our candidate. We
also present a high-quality medium-resolution VLT/X-shooter spectrum covering
the 400 to 2500 nm wavelength range. We classify this new neighbour as an
M7.00.5 dwarf using spectral templates from the Sloan Digital Sky Survey
and spectral indices. Lithium absorption at 670.8 nm is not detected in the
X-shooter spectrum, indicating that the M7 dwarf is older than 600 Myr and more
massive than 0.06 M. We also derive a trigonometric distance of 4.4
pc, in agreement with the spectroscopic distance estimate, making
2MASS\,J154043.42510135.7 the nearest M7 dwarf to the Sun. This
trigonometric distance is somewhat closer than the 6 pc distance reported
by the ALLWISE team, who independently identified this object recently. This
discovery represents an increase of 25\% in the number of M7--M8 dwarfs already
known at distances closer than 8\,pc from our Sun. We derive a density of
\,=\,1.90.910\,pc for M7 dwarfs in the 8 pc
volume, a value similar to those quoted in the literature. This new ultracool
dwarf is among the 50 nearest systems to the Sun, demonstrating that our
current knowledge of the stellar census within the 5 pc sample remains
incomplete. 2M1540 represents a unique opportunity to search for extrasolar
planets around ultracool dwarfs due to its proximity and brightness.Comment: 8 pages, 5 figures. Acepted in Astronomy & Astrophysics (15/05/2005
Binary frequency of planet-host stars at wide separations: A new brown dwarf companion to a planet-host star
The aim of the project is to improve our knowledge on the multiplicity of
planet-host stars at wide physical separations.
We cross-matched approximately 6200 square degree area of the Southern sky
imaged by the Visible Infrared Survey Telescope for Astronomy (VISTA)
Hemisphere Survey (VHS) with the Two Micron All Sky Survey (2MASS) to look for
wide common proper motion companions to known planet-host stars. We
complemented our astrometric search with photometric criteria.
We confirmed spectroscopically the co-moving nature of seven sources out of
16 companion candidates and discarded eight, while the remaining one stays as a
candidate. Among these new wide companions to planet-host stars, we discovered
a T4.5 dwarf companion at 6.3 arcmin (~9000 au) from HIP70849, a K7V star which
hosts a 9 Jupiter mass planet with an eccentric orbit. We also report two new
stellar M dwarf companions to one G and one metal-rich K star. We infer stellar
and substellar binary frequencies for our complete sample of 37 targets of
5.4+/-3.8% and 2.7+/-2.7% (1 sigma confidence level), respectively, for
projected physical separations larger than ~60-160 au assuming the range of
distances of planet-host stars (24-75 pc). These values are comparable to the
frequencies of non planet-host stars. We find that the period-eccentricity
trend holds with a lack of multiple systems with planets at large
eccentricities (e > 0.2) for periods less than 40 days. However, the lack of
planets more massive than 2.5 Jupiter masses and short periods (<40 days)
orbiting single stars is not so obvious due to recent discoveries by
ground-based transit surveys and space missions.Comment: Accepted for publication in A&A, 13 pages, 5 figures, 3 tables,
optical spectra will be available at CDS Strasbour
Novel efficient genome-wide SNP panels for the conservation of the highly endangered Iberian lynx
Background: The Iberian lynx (Lynx pardinus) has been acknowledged as the most endangered felid species in the world. An intense contraction and fragmentation during the twentieth century left less than 100 individuals split in two isolated and genetically eroded populations by 2002. Genetic monitoring and management so far have been based on 36 STRs, but their limited variability and the more complex situation of current populations demand more efficient molecular markers. The recent characterization of the Iberian lynx genome identified more than 1.6 million SNPs, of which 1536 were selected and genotyped in an extended Iberian lynx sample.
Methods: We validated 1492 SNPs and analysed their heterozygosity, Hardy-Weinberg equilibrium, and linkage disequilibrium. We then selected a panel of 343 minimally linked autosomal SNPs from which we extracted subsets optimized for four different typical tasks in conservation applications: individual identification, parentage assignment, relatedness estimation, and admixture classification, and compared their power to currently used STR panels.
Results: We ascribed 21 SNPs to chromosome X based on their segregation patterns, and identified one additional marker that showed significant differentiation between sexes. For all applications considered, panels of autosomal SNPs showed higher power than the currently used STR set with only a very modest increase in the number of markers.
Conclusions: These novel panels of highly informative genome-wide SNPs provide more powerful, efficient, and flexible tools for the genetic management and non-invasive monitoring of Iberian lynx populations. This example highlights an important outcome of whole-genome studies in genetically threatened species
Hysteroscopic Management of an Interstitial Ectopic Pregnancy
We report a case of an interstitial ectopic pregnancy successfully managed by hysteroscopy. We highlight the benefits of using hysteroscopy, a non-invasive procedure, to preserve fertility
The Metabolic Core and Catalytic Switches Are Fundamental Elements in the Self-Regulation of the Systemic Metabolic Structure of Cells
[Background]
Experimental observations and numerical studies with dissipative metabolic networks have shown that cellular enzymatic activity self-organizes spontaneously leading to the emergence of a metabolic core formed by a set of enzymatic reactions which are always active under all environmental conditions, while the rest of catalytic processes are only intermittently active. The reactions of the metabolic core are essential for biomass formation and to assure optimal metabolic performance. The on-off catalytic reactions and the metabolic core are essential elements of a Systemic Metabolic Structure which seems to be a key feature common to all cellular organisms.
[Methodology/Principal Findings]
In order to investigate the functional importance of the metabolic core we have studied different catalytic patterns of a dissipative metabolic network under different external conditions. The emerging biochemical data have been analysed using information-based dynamic tools, such as Pearson's correlation and Transfer Entropy (which measures effective functionality). Our results show that a functional structure of effective connectivity emerges which is dynamical and characterized by significant variations of bio-molecular information flows.
[Conclusions/Significance]
We have quantified essential aspects of the metabolic core functionality. The always active enzymatic reactions form a hub –with a high degree of effective connectivity- exhibiting a wide range of functional information values being able to act either as a source or as a sink of bio-molecular causal interactions. Likewise, we have found that the metabolic core is an essential part of an emergent functional structure characterized by catalytic modules and metabolic switches which allow critical transitions in enzymatic activity. Both, the metabolic core and the catalytic switches in which also intermittently-active enzymes are involved seem to be fundamental elements in the self-regulation of the Systemic Metabolic Structure.Consejo Superior de Investigaciones Cientificas (CSIC),grant 201020I026. Ministerio de Ciencia e Innovacion (MICINN). Programa Ramon y Cajal. Campus de Excelencia Internacional CEI BioTIC GENIL, grant PYR-2010-14. Junta de Andalucia, grant P09-FQM-4682
Albumin-induced apoptosis of tubular cells is modulated by BASP1
Albuminuria promotes tubular injury and cell death, and is associated with faster progression of chronic kidney disease (CKD) to
end-stage renal disease. However, the molecular mechanisms regulating tubular cell death in response to albuminuria are not fully
understood. Brain abundant signal protein 1 (BASP1) was recently shown to mediate glucose-induced apoptosis in tubular cells.
We have studied the role of BASP1 in albumin-induced tubular cell death. BASP1 expression was studied in experimental
puromycin aminonucleoside-induced nephrotic syndrome in rats and in human nephrotic syndrome. The role of BASP1 in
albumin-induced apoptosis was studied in cultured human HK2 proximal tubular epithelial cells. Puromycin aminonucleoside
induced proteinuria and increased total kidney BASP1 mRNA and protein expression. Immunohistochemistry localized the
increased BASP1 to tubular cells. BASP1 expression colocalized with deoxynucleotidyl-transferase-mediated dUTP nick-end
labeling staining for apoptotic cells. Increased tubular BASP1 expression was observed in human proteinuric nephropathy by
immunohistochemistry, providing evidence for potential clinical relevance. In cultured tubular cells, albumin induced apoptosis
and increased BASP1 mRNA and protein expression at 6–48 h. Confocal microscopy localized the increased BASP1 expression
in albumin-treated cells mainly to the perinuclear area. A peripheral location near the cell membrane was more conspicuous in
albumin-treated apoptotic cells, where it colocalized with actin. Inhibition of BASP1 expression by a BASP1 siRNA protected from
albumin-induced apoptosis. In conclusion, albumin-induced apoptosis in tubular cells is BASP1-dependent. This information may
be used to design novel therapeutic approaches to slow CKD progression based on protection of tubular cells from the adverse
consequences of albuminuriaGrant support: FIS PS09/00447, PI13/00047, CP14/
00133, ISCIII-RETIC, REDinREN/RD06/0016/and RD012/0021 FEDER funds,
Comunidad de Madrid/CIFRA S2010/BMD-2378. Salary support: FIS to MDSN
and ABS (Miguel Servet), Beatriz Fernandez-Fernandez (Rio Hortega). Programa
Intensificación Actividad Investigadora (ISCIII/Agencia Laín-Entralgo/CM) to AO.
IIS-FJD Biobank RD09/0076/0010
Analysis of Li-ion battery degradation using self-organizing maps
This paper proposes a new methodology to identify the different degradation processes of Li-Ion battery cells. The goal of this study is to determine if different degradation factors can be separated by waveform analysis from aged cells with similar remaining capacity. In contrast to other works, the proposed method identifies the past operating conditions in the cell, regardless of the actual State of Health. The methodology is based on a data-driven approach by using a SOM (Self-organizing map), an unsupervised neural network. To verify the hypothesis a SOM has been trained with laboratory data from whole data cycles, to classify cells concerning their degradation path and according to their discharge voltage patterns. Additionally, this new methodology based on the SOM allows discriminating groups of cells with different cycling conditions (based on depth of discharge, ambient temperature and discharge current). This research line is very promising for classification of used cells, not only depending on their current static parameters (capacity, impedance), but also the battery use in their past life. This will allow making predictions of the Remaining Useful Life (RUL) of a battery with greater precision
Nature of the spin-glass phase at experimental length scales
We present a massive equilibrium simulation of the three-dimensional Ising
spin glass at low temperatures. The Janus special-purpose computer has allowed
us to equilibrate, using parallel tempering, L=32 lattices down to T=0.64 Tc.
We demonstrate the relevance of equilibrium finite-size simulations to
understand experimental non-equilibrium spin glasses in the thermodynamical
limit by establishing a time-length dictionary. We conclude that
non-equilibrium experiments performed on a time scale of one hour can be
matched with equilibrium results on L=110 lattices. A detailed investigation of
the probability distribution functions of the spin and link overlap, as well as
of their correlation functions, shows that Replica Symmetry Breaking is the
appropriate theoretical framework for the physically relevant length scales.
Besides, we improve over existing methodologies to ensure equilibration in
parallel tempering simulations.Comment: 48 pages, 19 postscript figures, 9 tables. Version accepted for
publication in the Journal of Statistical Mechanic
Matching microscopic and macroscopic responses in glasses
We first reproduce on the Janus and Janus II computers a milestone experiment
that measures the spin-glass coherence length through the lowering of
free-energy barriers induced by the Zeeman effect. Secondly we determine the
scaling behavior that allows a quantitative analysis of a new experiment
reported in the companion Letter [S. Guchhait and R. Orbach, Phys. Rev. Lett.
118, 157203 (2017)]. The value of the coherence length estimated through the
analysis of microscopic correlation functions turns out to be quantitatively
consistent with its measurement through macroscopic response functions.
Further, non-linear susceptibilities, recently measured in glass-forming
liquids, scale as powers of the same microscopic length.Comment: 6 pages, 4 figure
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