858 research outputs found
Powerful obscured AGN among X-ray hard, optically-dim serendipitous Chandra sources
We present a small sample of Chandra X-ray sources selected from the fields
of ACIS observations which probe fluxes around the break in the hard band
source counts. The targets of these fields include 9 nearby galaxy clusters, 1
distant cluster and 2 powerful radio galaxy fields. The follow-up of this
serendipitous sample was biased towards X-ray hard and optically-dim sources
mostly not seen on the Digitized Sky Survey; for these, we present X-ray
fluxes, optical and near-infrared photometry leading to 51 photometric
redshifts in all and 18 independently measured spectroscopic redshifts. Few
sources are associated with the target fields themselves. Fifty-six of 58
sources imaged in the K-band are detected at K<~20 with K_median=18, and of
these, 38 have hard X-ray count ratios and 24 of these are significantly hard
with most of the counts emerging about 2 keV. We find that almost all are AGN
hosted in massive early-type host galaxies with a photometric redshift
distribution peaking at z~1. Two type 2 quasars with intrinsic X-ray luminosity
L>~10^{45} erg/s, Fe K_alpha emission lines and absorbing column density
nH>10^{23} cm^{-2} -- and nH>~10^{24} cm^{-2} in one case -- are discussed in
detail; the sample contains at least 12 potential type 2 quasars in all. We
discuss various detection strategies for type 2 quasars and calculate their
inferred space density. This combines and extends a number of results from
subsamples already published by us.Comment: MNRAS accepted; 30 pages, 12 figures, 8 tables; Figures of all
targets and other information available in the electronic journal and
temporarily at http://www-xray.ast.cam.ac.uk/~pg/xrbsources/imsp
Comparative phylogeography of two codistributed species of the genus Herichthys (Actinopterygii: Cichliformes: Cichlidae) in northeastern Mexico
Phylogeographic patterns of freshwater fishes in coastal regions are highly susceptible to eustatic sea level changes associated with Pleistocene glaciations. In this context, the Plain Coastal Gulf in northeastern Mexico represents an ideal study area due to its low elevation. Herein, we compare the phylogeographic structures of two cichlid species of the genus Herichthys Baird et Girard, 1854 widely distributed in the Pánuco–Tamesí system in northeastern Mexico using two mitochondrial markers. The species studied were: Herichthys carpintis (Jordan et Snyder, 1899) and Herichthys pantostictus (Taylor et Miller, 1983). We estimate their genetic diversity, gene flow, and demographic history and perform biogeographic reconstructions using a Bayesian computation approach and environmental niche modeling. The biogeographic reconstruction suggests a different history for each species. Environmental niche modeling indicates that both species experienced a demographic expansion during the Pleistocene but responded differently to Pleistocene climatic changes. In summary, their current sympatric distribution could be the outcome of contemporary and not historical processes reflecting a pseudo-incongruent pattern
Large-scale movements of common bottlenose dolphins in the Atlantic : dolphins with an international courtyard
Wide-ranging connectivity patterns of common bottlenose dolphins (Tursiops truncatus) are generally poorly known worldwide and more so within the oceanic archipelagos of Macaronesia in the North East (NE) Atlantic. This study aimed to identify long-range movements between the archipelagos of Macaronesia that lie between 500 and 1,500 km apart, and between Madeira archipelago and the Portuguese continental shelf, through the compilation and comparison of bottlenose dolphin's photo-identification catalogues from different regions: one from Madeira (n = 363 individuals), two from different areas in the Azores (n = 495 and 176), and four from different islands of the Canary Islands (n = 182, 110, 142 and 281), summing up 1791 photographs. An additional comparison was made between the Madeira catalogue and one catalogue from Sagres, on the southwest tip of the Iberian Peninsula (n = 359). Results showed 26 individual matches, mostly between Madeira and the Canary Islands (n = 23), and between Azores and Madeira (n = 3). No matches were found between the Canary Islands and the Azores, nor between Madeira and Sagres. There were no individuals identified in all three archipelagos. The minimum time recorded between sightings in two different archipelagos (≈ 460 km apart) was 62 days. Association patterns revealed that the individuals moving between archipelagos were connected to resident, migrant and transient individuals in Madeira. The higher number of individuals that were re-sighted between Madeira and the Canary Islands can be explained by the relative proximity of these two archipelagos. This study shows the first inter-archipelago movements of bottlenose dolphins in the Macaronesia region, emphasizing the high mobility of this species and supporting the high gene flow described for oceanic dolphins inhabiting the North Atlantic. The dynamics of these long-range movements strongly denotes the need to review marine protected areas established for this species in each archipelago, calling for joint resolutions from three autonomous regions belonging to two EU countries.Partnership Program (US) and project ‘‘Cetáceos, Oceanografía y Biodiversidad de las Aguas Profundas de La Palma y El Hierro’’ funded by ‘‘Ministerio de Ciencia e Innovación’’ of the Spanish Government, grant number CETOBAPH-CGL2009-1311218 supported the work in the Canary Island. In Madeira, this study was supported by the Oceanic Observatory of Madeira through the project M1420-01-0142-FEDER-000001 and by the Portuguese Foundation for Science and Technology through the strategic project UID/MAR/04292/2020. Ana Dinis and Filipe Alves have grants funded by ARDITI— Madeira’s Regional Agency for the Development of Research, Technology and Innovation, throughout the project M1420-09- 5369- FSE- 000002, and Annalisa Sambolino is supported by the Portuguese Foundation for Science and Technology through the PhD grant number SFRH/BD/1416092018. In Azores, the MONICET platform is supported by project MEEMO (ACORES-01-0145-FEDER-000079) and Marta Tobena is supported by a PhD grant (M31a/F/0722015). There was no additional external funding received for this study. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.info:eu-repo/semantics/publishedVersio
The Circumgalactic Medium in Massive Halos
This chapter presents a review of the current state of knowledge on the cool
(T ~ 1e4 K) halo gas content around massive galaxies at z ~ 0.2-2. Over the
last decade, significant progress has been made in characterizing the cool
circumgalactic gas in massive halos of Mh ~ 1e12-1e14 Msun at intermediate
redshifts using absorption spectroscopy. Systematic studies of halo gas around
massive galaxies beyond the nearby universe are made possible by large
spectroscopic samples of galaxies and quasars in public archives. In addition
to accurate and precise constraints for the incidence of cool gas in massive
halos, detailed characterizations of gas kinematics and chemical compositions
around massive quiescent galaxies at z ~ 0.5 have also been obtained. Combining
all available measurements shows that infalling clouds from external sources
are likely the primary source of cool gas detected at d >~ 100 kpc from massive
quiescent galaxies. The origin of the gas closer in is currently less certain,
but SNe Ia driven winds appear to contribute significantly to cool gas found at
d < 100 kpc. In contrast, cool gas observed at d <~ 200 kpc from luminous
quasars appears to be intimately connected to quasar activities on parsec
scales. The observed strong correlation between cool gas covering fraction in
quasar host halos and quasar bolometric luminosity remains a puzzle. Combining
absorption-line studies with spatially-resolved emission measurements of both
gas and galaxies is the necessary next step to address remaining questions.Comment: 29 pages, 7 figures, invited review to appear in "Gas Accretion onto
Galaxies", Astrophysics and Space Science Library, eds. A. Fox & R. Dave, to
be published by Springe
Sulfated Polysaccharide Extracted from the Green Algae Codium bernabei: Physicochemical Characterization and Antioxidant, Anticoagulant and Antitumor Activity
Codium bernabei is a green alga that grows on Chilean coasts. The composition of its structural polysaccharides is still unknown. Hence, the aim of this work is to isolate and characterize the hot water extracted polysaccharide fractions. For this purpose, the water extracts were further precipitated in alcohol (TPs) and acid media (APs), respectively. Both fractions were characterized using different physicochemical techniques such as GC-MS, GPC, FTIR, TGA, and SEM. It is confirmed that the extracted fractions are mainly made of sulfated galactan unit, with a degree of sulfation of 19.3% (TPs) and 17.4% (ATs) and a protein content of 3.5% in APs and 15.6% in TPs. Other neutral sugars such as xylose, glucose, galactose, fucose, mannose, and arabinose were found in a molar ratio (0.05:0.6:1.0:0.02:0.14:0.11) for TPs and (0.05:0.31:1.0:0.03:0.1:0.13) for ATs. The molecular weight of the polysaccharide samples was lower than 20 kDa. Both polysaccharides were thermally stable (Tonset > 190 °C) and showed antioxidant activity according to the ABTS•+ and DPPH tests, where TPs fractions had higher scavenging activity (35%) compared to the APs fractions. The PT and APTTS assays were used to measure the anticoagulant activity of the polysaccharide fractions. In general, the PT activity of the TPs and APs was not different from normal plasma values. The exception was the TPs treatment at 1000 µg mL−1 concentration. The APTTS test revealed that clotting time for both polysaccharides was prolonged regarding normal values at 1000 µg mL−1. Finally, the antitumor test in colorectal carcinoma (HTC-116) cell line, breast cancer (MCF-7) and human leukemia (HL-60) cell lines showed the cytotoxic effect of TPs and APs. Those results suggest the potential biotechnological application of sulfate galactan polysaccharides isolated from a Chilean marine resource
Expedición cangrejo negro : informe técnico
El huracán Iota que pasó por las islas de providencia y Santa catalina el 16 de noviembre de
2020 produjo efectos importantes en los ecosistemas de las islas, así como en los servicios
que estos ofrecen a las comunidades locales y que dan lugar a un atractivo turístico que se
constituye en la principal actividad económica de las islas. Este trabajo corresponde a un
esfuerzo por identificar áreas importantes para la prestación de los servicios ecosistémicos
(SSE) en especial aquellas que pudieron haber resultado especialmente afectadas como
resultado de Iota, para tal fin se aborda un enfoque basado en el análisis de datos
geoespaciales, apoyado por la consulta de información secundaria.
La revisión de la información secundaria permitió identificar SSE relevantes en la isla
fundamentalmente relacionados con protección frente a desastres naturales y servicios de
provisión y regulación hídrica, mientras que los análisis espaciales permitieron identificar
cuencas importantes frente a estos servicios como Freshwater, Bailey, Bowden y Santa
Catalina Sur, los análisis de imágenes satelitales por su parte permitieron identificar áreas
afectadas por la pérdida de vegetación y acumulación de biomasa.Bogot
Canagliflozin and renal outcomes in type 2 diabetes and nephropathy
BACKGROUND Type 2 diabetes mellitus is the leading cause of kidney failure worldwide, but few effective long-term treatments are available. In cardiovascular trials of inhibitors of sodium–glucose cotransporter 2 (SGLT2), exploratory results have suggested that such drugs may improve renal outcomes in patients with type 2 diabetes. METHODS In this double-blind, randomized trial, we assigned patients with type 2 diabetes and albuminuric chronic kidney disease to receive canagliflozin, an oral SGLT2 inhibitor, at a dose of 100 mg daily or placebo. All the patients had an estimated glomerular filtration rate (GFR) of 30 to <90 ml per minute per 1.73 m2 of body-surface area and albuminuria (ratio of albumin [mg] to creatinine [g], >300 to 5000) and were treated with renin–angiotensin system blockade. The primary outcome was a composite of end-stage kidney disease (dialysis, transplantation, or a sustained estimated GFR of <15 ml per minute per 1.73 m2), a doubling of the serum creatinine level, or death from renal or cardiovascular causes. Prespecified secondary outcomes were tested hierarchically. RESULTS The trial was stopped early after a planned interim analysis on the recommendation of the data and safety monitoring committee. At that time, 4401 patients had undergone randomization, with a median follow-up of 2.62 years. The relative risk of the primary outcome was 30% lower in the canagliflozin group than in the placebo group, with event rates of 43.2 and 61.2 per 1000 patient-years, respectively (hazard ratio, 0.70; 95% confidence interval [CI], 0.59 to 0.82; P=0.00001). The relative risk of the renal-specific composite of end-stage kidney disease, a doubling of the creatinine level, or death from renal causes was lower by 34% (hazard ratio, 0.66; 95% CI, 0.53 to 0.81; P<0.001), and the relative risk of end-stage kidney disease was lower by 32% (hazard ratio, 0.68; 95% CI, 0.54 to 0.86; P=0.002). The canagliflozin group also had a lower risk of cardiovascular death, myocardial infarction, or stroke (hazard ratio, 0.80; 95% CI, 0.67 to 0.95; P=0.01) and hospitalization for heart failure (hazard ratio, 0.61; 95% CI, 0.47 to 0.80; P<0.001). There were no significant differences in rates of amputation or fracture. CONCLUSIONS In patients with type 2 diabetes and kidney disease, the risk of kidney failure and cardiovascular events was lower in the canagliflozin group than in the placebo group at a median follow-up of 2.62 years
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