3,627 research outputs found
Draft Genome Sequence of a Multi-Metal Resistant Bacterium Pseudomonas putida ATH-43 Isolated from Greenwich Island, Antarctica
Indexación: Web of Science; Scopus.In this report we present the first draft genome sequence of a P. putida strain isolated from the Antarctic continent. The shotgun sequencing strategy, assembly, and subsequent annotation showed that the ATH-43 strain possesses a wide spectrum of genetic determinants involved in heavy metal and antibiotic resistance, apparently to cope with extreme oxidative stress conditions. P. putida ATH-43 genome now forms part of the 65 genomes of this species registered at the NCBI database (September, 2016) and it is highly related with the endophytic strain P. putida W619, which is also resistant to several heavy metals. Further characterization of multi-metal resistant psychrotrophic bacteria such as P. putida ATH-43 will be promising to develop novel strategies for heavy metal bioremediation in low temperature environments. All genome data has been submitted to NCBI.http://journal.frontiersin.org/article/10.3389/fmicb.2016.01777/ful
The distribution of potential West Nile virus vectors, Culex pipiens pipiens and Culex pipiens quinquefasciatus (Diptera: Culicidae), in Mexico City
<p>Abstract</p> <p>Background</p> <p><it>Culex </it>spp. mosquitoes are considered to be the most important vectors of West Nile virus (WNV) detected in at least 34 species of mosquitoes in the United States. In North America, <it>Culex pipiens pipiens, Culex pipiens quinquefasciatus</it>, and <it>Culex tarsalis </it>are all competent vectors of WNV, which is considered to be enzootic in the United States and has also been detected in equines and birds in many states of Mexico and in humans in Nuevo Leon. There is potential for WNV to be introduced into Mexico City by various means including infected mosquitoes on airplanes, migrating birds, ground transportation and infected humans. Little is known of the geographic distribution of <it>Culex pipiens </it>complex mosquitoes and hybrids in Mexico City. <it>Culex pipiens pipiens </it>preferentially feed on avian hosts; <it>Culex pipiens quinquefasciatus </it>have historically been considered to prefer mammalian hosts; and hybrids of these two species could theoretically serve as bridge vectors to transmit WNV from avian hosts to humans and other mammalian hosts. In order to address the potential of WNV being introduced into Mexico City, we have determined the identity and spatial distribution of <it>Culex pipiens </it>complex mosquitoes and their hybrids.</p> <p>Results</p> <p>Mosquito larvae collected from 103 sites throughout Mexico City during 2004-2005 were identified as <it>Culex, Culiseta </it>or <it>Ochlerotatus </it>by morphological analysis. Within the genus <it>Culex</it>, specimens were further identified as <it>Culex tarsalis </it>or as belonging to the <it>Culex pipiens </it>complex. Members of the <it>Culex pipiens </it>complex were separated by measuring the ratio of the dorsal and ventral arms (DV/D ratio) of the male genitalia and also by using diagnostic primers designed for the <it>Ace.2 </it>gene. <it>Culex pipiens quinquefasciatus </it>was the most abundant form collected.</p> <p>Conclusions</p> <p>Important WNV vectors species, <it>Cx. p. pipiens</it>, <it>Cx. p. quinquefasciatus </it>and <it>Cx. tarsalis</it>, are all present in Mexico City. Hybrids of <it>Cx. p. pipiens </it>and <it>Cx. p. quinquefasciatus </it>were also collected and identified. The presence and abundance of these WNV competent vectors is a cause for concern. Understanding the distribution of these vectors can help improve viral surveillance activities and mosquito control efforts in Mexico City.</p
Spectrophotometric Observations of Blue Compact Dwarf Galaxies: Mrk 370
We present results from a detailed spectrophotometric analysis of the blue
compact dwarf galaxy (BCD) Mrk 370, based on deep UBVRI broad-band and Halpha
narrow-band observations, and long-slit and two-dimensional spectroscopy of its
brightest knots. The spectroscopic data are used to derive the internal
extinction, and to compute metallicities, electronic density and temperature in
the knots. By subtracting the contribution of the underlying older stellar
population, modeled by an exponential function, removing the contribution from
emission lines, and correcting for extinction, we can measure the true colors
of the young star-forming knots. We show that the colors obtained this way
differ significantly from those derived without the above corrections, and lead
to different estimates of the ages and star-forming history of the knots. Using
predictions of evolutionary synthesis models, we estimate the ages of both the
starburst regions and the underlying stellar component. We found that we can
reproduce the colors of all the knots with an instantaneous burst of star
formation and the Salpeter initial mass function with an upper mass limit of
100 solar masses. The resulting ages range between 3 and 6 Myrs. The colors of
the low surface brightness component are consistent with ages larger than 5
Gyr. The kinematic results suggest ordered motion around the major axis of the
galaxy.Comment: 26 pages with 14 figures; accepted for publication in Ap
A Herschel/PACS Far Infrared Line Emission Survey of Local Luminous Infrared Galaxies
We present an analysis of [OI]63, [OIII]88, [NII]122 and [CII]158
far-infrared (FIR) fine-structure line observations obtained with
Herschel/PACS, for ~240 local luminous infrared galaxies (LIRGs) in the Great
Observatories All-sky LIRG Survey (GOALS). We find pronounced declines
-deficits- of line-to-FIR-continuum emission for [NII]122, [OI]63 and [CII]158
as a function of FIR color and infrared luminosity surface density,
. The median electron density of the ionized gas in LIRGs,
based on the [NII]122/[NII]205 ratio, is = 41 cm. We find
that the dispersion in the [CII]158 deficit of LIRGs is attributed to a varying
fractional contribution of photo-dissociation-regions (PDRs) to the observed
[CII]158 emission, f([CII]PDR) = [CII]PDR/[CII], which increases from ~60% to
~95% in the warmest LIRGs. The [OI]63/[CII]158PDR ratio is tightly correlated
with the PDR gas kinetic temperature in sources where [OI]63 is not
optically-thick or self-absorbed. For each galaxy, we derive the average PDR
hydrogen density, , and intensity of the interstellar radiation
field, in units of G, and find G/ ratios ~0.1-50 cm,
with ULIRGs populating the upper end of the distribution. There is a relation
between G/ and , showing a critical break at
~ 5 x 10 Lsun/kpc. Below , G/ remains constant, ~0.32 cm, and variations
in are driven by the number density of star-forming regions
within a galaxy, with no change in their PDR properties. Above , G/ increases rapidly with ,
signaling a departure from the typical PDR conditions found in normal
star-forming galaxies towards more intense/harder radiation fields and compact
geometries typical of starbursting sources.Comment: 23 pages, 12 figures. Submitted to ApJ, including 2nd round of
referee comments. Data tables can be found at: http://goals.ipac.caltech.edu/
and will also appear on the electronic version of the journa
Analysis of coal conversion to biomass as a transitional technology
The dominant transitional path towards a low carbon electricity industry for systems which have been heavily dependent upon coal is through its replacement by large scale wind farms and the widespread emergence of distributed solar. In this pathway, maintaining resource adequacy in the context of increased intermittency in generation has become a major concern. This paper examines this requirement to maintain resource adequacy and compare the costs and carbon impacts for new gas turbines or biomass conversions to achieve this in an expedient transitional way. This is formulated as a policy optimization in which the imperative is to replace existing coal with a renewable alternative (in this case study, wind) and to maintain the system security at the existing level, and thereby find the optimal subsidies, either as energy credits ("green certificates" or “contracts-for-differences”) or capital benefits ("capacity payments" or tax
allowances). In a model of the GB system, the results show that that biomass-conversion outperforms investment in peaking gas turbines to deal with the transitional economic externality of extra reserve costs. In particular, the results suggest benefits of 10% lower costs of subsidies, 70% lower implied costs of carbon, and a reduction of 18% in wholesale power prices
MAXI J1659-152: the shortest orbital period black-hole binary
Following the detection of a bright new X-ray source, MAXI J1659-152, a
series of observations was triggered with almost all currently flying
high-energy missions. We report here on XMM-Newton, INTEGRAL and RXTE
observations during the early phase of the X-ray outburst of this transient
black-hole candidate. We confirm the dipping nature in the X-ray light curves.
We find that the dips recur on a period of 2.4139+/-0.0005 hrs, and interpret
this as the orbital period of the system. It is thus the shortest period
black-hole X-ray binary known to date. Using the various observables, we derive
the properties of the source. The inclination of the accretion disk with
respect to the line of sight is estimated to be 60-75 degrees. The companion
star to the black hole is possibly a M5 dwarf star, with a mass and radius of
about 0.15 M_sun and 0.23 R_sun, respectively. The system is rather compact
(orbital separation is about 1.35 R_sun) and is located at a distance of
roughly 7 kpc. In quiescence, MAXI J1659-152 is expected to be optically faint,
about 28 mag in the V-band.Comment: 5 pages, 4 figures, to be published in the proceedings of the 4th
International MAXI Workshop `The First Year of MAXI: Monitoring variable
X-ray sources', 2010 Nov 30 - Dec 2, Tokyo, Japa
Consideration of the bioavailability of metal/metalloid species in freshwaters: experiences regarding the implementation of biotic ligand model-based approaches in risk assessment frameworks
After the scientific development of Biotic Ligand Models (BLMs) in recent decades these models are now considered suitable for implementation in regulatory risk assessment of metals in freshwater bodies. The approach has been developed over several years and has been described in many peer-reviewed publications. The original complex BLMs have been applied in prospective risk assessment reports for metals and metal compounds and are also recommended as suitable concepts for the evaluation of monitoring data in the context of the European Water Framework Directive. Currently, several user-friendly BLM-based bioavailability software tools are available for assessing the aquatic toxicity of a limited number of metals (mainly copper, nickel, and zinc). These tools need only a basic set of water parameters as input (e.g., pH, hardness, dissolved organic matter and dissolved metal concentration). Such tools seem appropriate to foster the implementation in routine water quality assessments. This work aims to review the existing bioavailability-based regulatory approaches and the application of available BLM-based bioavailability tools for this purpose. Advantages and possible drawbacks of these tools (e.g., feasibility, boundaries of validity) are discussed, and recommendations for further implementation are given
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