395 research outputs found
Long term fish assemblages as units of management in a temperate estuary (Rio de La Plata - SW Atlantic Ocean)
Demersal fish assemblages from trawl surveys in the Rio de la Plata estuary and its inner continental shelf were analyzed from 1975 to 1995. The first two factors of Principal Component Analysis explained 48% of the variance in species distribution, and they are consistent with the results of a cluster analysis. The analysis indicated the existence of three spatially and temporally distinct fish assemblages: internal and external estuarine and inner continental shelf (Uruguayan coastal assemblages). These assemblages were persistent considering the environmental characteristics and their species composition. Despite the changes registered in the species density during the period surveyed, the fish assemblages tend to persist over time. It was demonstrated that the assemblages can be considered as open systems and that there exists a reciprocal flow of organisms between adjacent associations. However, each assemblage showed high spatial and temporal persistence in accordance with the environmental characteristics of the system analyzed. Therefore, and according to the multispecies fisheries operating in the system, each assemblage defined could be considered a unit of management.Foram analisadas as associações dos peixes demersais provenientes de arrastos de prospecção no estuário do Rio de la Plata e sua plataforma interna no período de 1975 a 1995. Os dois primeiros fatores da Análise de Componentes Principais explicaram 48% da variância na distribuição das espécies sendo consistentes com os resultados da análise de agrupamento. Os resultados mostraram a existência de três associações de peixes espacial e temporalmente distintas: uruguaia costeira, estuarina externa e estuarina interna. Essas associações foram consistentes quanto às características ambientais e de composição de espécies. A despeito das mudanças registradas na densidade das espécies ao longo do período analisado, as associações de peixes foram persistentes ao longo do tempo. No presente trabalho foi demonstrado que embora as associações sejam consideradas um sistema aberto, um fluxo recíproco de organismos acontece entre associações adjacentes. Contudo, cada associação apresenta diferentes graus de estabilidade, dependentes da estabilidade física e temporal do habitat, e das interações das espécies nas associações. No entanto, cada associação mostrou alta persistência espacial e temporal, apesar da variabilidade ambiental no sistema analisado. Nesse sentido, e de acordo com a pesca multiespecífica que opera neste sistema, cada associação poderá ser considerada como uma unidade de gestão
Properties of Mosquito Repellent-Plasticized Poly(lactic acid) Strands
This article belongs to the Special Issue Thermal and Rheological Characterization of Polymeric Materials[Abstract] Poly(lactic acid) (PLA) is an attractive candidate for replacing petrochemical polymers because it is fully biodegradable. This study investigated the potential of PLA as a sustainable and environmentally friendly alternative material that can be developed into commercially viable wearable mosquito repellent devices with desirable characteristics. PLA strands containing DEET and IR3535 were prepared by twin screw extrusion compounding and simultaneously functioned as plasticizers for the polymer. The plasticizing effect was investigated by thermal and rheological studies. DSC studies showed that the addition of DEET and IR3535 into PLA strands reduced the glass transition temperature consistent with predictions of the Fox equation, thus proving their efficiency as plasticizers. The rheology of molten samples of neat PLA and PLA/repellents blends, evaluated at 200 °C, was consistent with shear-thinning pseudoplastic behaviour. Raman studies revealed a nonlinear concentration gradient for DEET in the PLA strand, indicating non-Fickian Type II transport controlling the desorption process. Release data obtained at 50 °C showed initial rapid release followed by a slower, near constant rate at longer times. The release rate data were fitted to a novel modification of the Peppas-Sahlin desorption modelThis work was financially supported from the Deutsche Forschungsgemeinschaft (DFG), Germany [Grant number AN 212/22-2] and University of Pretoria (UP) Postdoctoral Fellowship programme. The research has been also supported by Spanish MINECO grant MTM2017-82724-R through the ERDFDeutsche Forschungsgemeinschaft (DFG); AN 212/22-2https://www.mdpi.com/journal/molecules/special_issues/Thermal_Rheological_Polymeric_Material
Material tipo de insectos en el Laboratorio de Sanidad Vegetal, SENASA, Lima, Perú
A list of the type material of Insecta deposited in the Laboratorio de Sanidad Vegetal, Servicio Nacional de Sanidad Agraria (SENASA), Lima, Peru, presented here includes 21 species of Psylloidea (Hemiptera), 4 of Cicadellidae (Hemiptera), 4 of Curculionidae (Coleoptera), and 2 of Tachinidae (Diptera), all of them from Peruvian localities. The types of Tachinidae described by Charles Townsend have not been included in this list.Se presenta la lista de material tipo de Insecta depositado en la colección del Laboratorio de Sanidad Vegetal, Servicio Nacional de Sanidad Agraria (SENASA), Lima, Perú, comprendiendo 21 especies de Psylloidea (Hemiptera), 4 de Cicadellidae (Hemiptera), 4 de Curculionidae (Coleoptera) y 2 de Tachinidae (Diptera), todas provenientes de localidades peruanas. Los tipos de Tachinidae descritos por Charles Townsend no han sido incluidos en esta relación
A 33 GHz Survey of Local Major Mergers: Estimating the Sizes of the Energetically Dominant Regions from High Resolution Measurements of the Radio Continuum
We present Very Large Array observations of the 33 GHz radio continuum
emission from 22 local ultraluminous and luminous infrared (IR) galaxies
(U/LIRGs). These observations have spatial (angular) resolutions of 30--720 pc
(0.07"-0.67") in a part of the spectrum that is likely to be optically thin.
This allows us to estimate the size of the energetically dominant regions. We
find half-light radii from 30 pc to 1.7 kpc. The 33 GHz flux density correlates
well with the IR emission, and we take these sizes as indicative of the size of
the region that produces most of the energy. Combining our 33 GHz sizes with
unresolved measurements, we estimate the IR luminosity and star formation rate
per area, and the molecular gas surface and volume densities. These quantities
span a wide range (4 dex) and include some of the highest values measured for
any galaxy (e.g., ). At least sources appear Compton thick (). Consistent with previous work, contrasting these data
with observations of normal disk galaxies suggests a nonlinear and likely
multi-valued relation between SFR and molecular gas surface density, though
this result depends on the adopted CO-to-H conversion factor and the
assumption that our 33 GHz sizes apply to the gas. 11 sources appear to exceed
the luminosity surface density predicted for starbursts supported by radiation
pressure and supernovae feedback, however we note the need for more detailed
observations of the inner disk structure. U/LIRGs with higher surface
brightness exhibit stronger [{\sc Cii}] 158m deficits, consistent with the
suggestion that high energy densities drive this phenomenon.Comment: 32 pages, 11 figures, 7 tables. Accepted for publication in Ap
The Herschel Comprehensive (U)LIRG Emission Survey (HerCULES): CO Ladders, fine structure lines, and neutral gas cooling
(Ultra) Luminous Infrared Galaxies ((U)LIRGs) are objects characterized by
their extreme infrared (8-1000 m) luminosities (L and L). The Herschel Comprehensive ULIRG
Emission Survey (HerCULES; PI van der Werf) presents a representative
flux-limited sample of 29 (U)LIRGs that spans the full luminosity range of
these objects (10). With the \emph{Herschel
Space Observatory}, we observe [CII] 157 m, [OI] 63 m, and [OI] 145
m line emission with PACS, CO J=4-3 through J=13-12, [CI] 370 m, and
[CI] 609 m with SPIRE, and low-J CO transitions with ground-based
telescopes. The CO ladders of the sample are separated into three classes based
on their excitation level. In 13 of the galaxies, the [OI] 63 m emission
line is self absorbed. Comparing the CO excitation to the IRAS 60/100 m
ratio and to far infrared luminosity, we find that the CO excitation is more
correlated to the far infrared colors. We present cooling budgets for the
galaxies and find fine-structure line flux deficits in the [CII], [SiII], [OI],
and [CI] lines in the objects with the highest far IR fluxes, but do not
observe this for CO . In order to study the heating of the
molecular gas, we present a combination of three diagnostic quantities to help
determine the dominant heating source. Using the CO excitation, the CO J=1-0
linewidth, and the AGN contribution, we conclude that galaxies with large CO
linewidths always have high-excitation CO ladders, and often low AGN
contributions, suggesting that mechanical heating is important
Resistencia antimicrobiana de cepas de Escherichia coli aisladas de contenidos de bursa de Fabricio de aves para engorde
The aim of this study was to determine the percentage of sensitivity or resistance of strains of E. coli isolated from asymptomatic broiler chicken against 18 common antibiotics used in poultry and in human medicine. In addition, strains that produce extended-spectrum beta-lactamases (ESBL) from a farm or slaughterhouses in the poultry area of Santander, Colombia. The circulation of strains resistant to beta-lactams, cephalosporins, aminoglycosides, quinolones and sulfonamides was determined, as well as antibiotics widely used in other non-farm environments. The content of the bursa of Fabricius was cultivated in McConkey agar obtaining 46 strains of E. coli. Susceptibility tests (n=18) were conducted to the isolated strains, and 91% of the strains were resistant to ampicillin and 80% to cephalosporins. The association of antibiotics with beta-lactamase inhibitors (ampicillin sulbactam and amoxicillin / clavulanic acid) showed 30% resistance. The double disc test was used to evaluate the presence of strains of E. coli producing extendedspectrum beta-lactamases (ESBL) confirming its presence in 63% of the samples. Results showed the presence of E. coli strains in asymptomatic chicken broilers with high antimicrobial resistance, including expression of ESBL.El objetivo de la presente investigación fue determinar el porcentaje de sensibilidad o resistencia de cepas de E. coli aisladas de pollo de engorde asintomático frente a 18 antibióticos comunes utilizados en avicultura y medicina humana; a su vez, cepas productoras de betalactamasas de espectro extendido (BLEES), procedentes de granja o plantas de beneficio de la zona avícola de Santander, Colombia. Se determinó la circulación de cepas resistentes a betalactámicos, cefalosporinas, aminoglucósidos, quinolonas y sulfonamidas, así como antibióticos de amplio uso en ambientes ajenos a las granjas. Se aislaron 46 cepas de E. coli del contenido de bolsas de Fabricio de 100 pollos de engorde entre 2 y 6 semanas de edad (20 procedentes de una granja avícola y 80 de una planta de sacrificio) en Santander, Colombia. Las muestras fueron cultivadas en agar McConkey. Se realizaron pruebas de sensibilidad a las cepas aisladas con 18 antimicrobianos. El 91% de las cepas fueron resistentes a la ampicilina y el 80% a las cefalosporinas; así mismo, al enfrentar las cepas con la asociación de antibióticos con inhibidores de betalactamasas (ampicilina sulbactam y amoxacilina/ácido clavulánico), se encontró 30% de resistencia. Se utilizó la prueba del doble disco para evaluar la presencia de cepas de E. coli productoras de betalactamasas de espectro extendido (BLEES) confirmando su presencia en el 63% de las muestras. Se evidencia la presencia de cepas de E. coli en aves de engorde asintomáticas, con alta resistencia antimicrobiana, incluyendo expresión de BLEES
Mapping the cold dust temperatures and masses of nearby Kingfish galaxies with Herschel
Taking advantage of the sensitivity and angular resolution of the Herschel
Space Observatory at far-infrared and submm wavelengths, we aim to characterize
the physical properties of cold dust within nearby galaxies and study the
robustness of the parameters we derive using different modified blackbody
models. For a pilot subsample of the KINGFISH program, we perform 2 temperature
fits of the Spitzer and Herschel photometric data (24 to 500um), with a warm
and a cold component, globally and in each resolution element.At global scales,
we observe ranges of values for beta_c(0.8 to 2.5) and Tc(19.1 to 25.1K).We
compute maps of our parameters with beta fixed or free to test the robustness
of the temperature and dust surface density maps we deduce. When the emissivity
is fixed, we observe temperature gradients as a function of radius.When the
emissivity is fitted as a free parameter, barred galaxies tend to have uniform
fitted emissivities.Gathering resolved elements in a Tc-beta_c diagram
underlines an anti-correlation between the two parameters.It remains difficult
to assess whether the dominant effect is the physics of dust grains, noise, or
mixing along the line of sight and in the beam. We finally observe in both
cases that the dust column density peaks in central regions of galaxies and bar
ends (coinciding with molecular gas density enhancements usually found in these
locations).We also quantify how the total dust mass varies with our assumptions
about the emissivity index as well as the influence of the wavelength coverage
used in the fits. We show that modified blackbody fits using a shallow
emissivity (beta_c < 2.0) lead to significantly lower dust masses compared to
the beta_c < 2.0 case, with dust masses lower by up to 50% if beta_c=1.5 for
instance.The working resolution affects our total dust mass estimates: masses
increase from global fits to spatially-resolved fits.Comment: 26 pages, 12 figures, 4 tables, accepted for publication in MNRAS,
2012 June 2
Caribbean Corals in Crisis: Record Thermal Stress, Bleaching, and Mortality in 2005
BACKGROUND The rising temperature of the world's oceans has become a major threat to coral reefs globally as the severity and frequency of mass coral bleaching and mortality events increase. In 2005, high ocean temperatures in the tropical Atlantic and Caribbean resulted in the most severe bleaching event ever recorded in the basin. METHODOLOGY/PRINCIPAL FINDINGS Satellite-based tools provided warnings for coral reef managers and scientists, guiding both the timing and location of researchers' field observations as anomalously warm conditions developed and spread across the greater Caribbean region from June to October 2005. Field surveys of bleaching and mortality exceeded prior efforts in detail and extent, and provided a new standard for documenting the effects of bleaching and for testing nowcast and forecast products. Collaborators from 22 countries undertook the most comprehensive documentation of basin-scale bleaching to date and found that over 80% of corals bleached and over 40% died at many sites. The most severe bleaching coincided with waters nearest a western Atlantic warm pool that was centered off the northern end of the Lesser Antilles. CONCLUSIONS/SIGNIFICANCE Thermal stress during the 2005 event exceeded any observed from the Caribbean in the prior 20 years, and regionally-averaged temperatures were the warmest in over 150 years. Comparison of satellite data against field surveys demonstrated a significant predictive relationship between accumulated heat stress (measured using NOAA Coral Reef Watch's Degree Heating Weeks) and bleaching intensity. This severe, widespread bleaching and mortality will undoubtedly have long-term consequences for reef ecosystems and suggests a troubled future for tropical marine ecosystems under a warming climate.This work was partially supported by salaries from the NOAA Coral Reef Conservation Program to the NOAA Coral Reef Conservation Program authors. NOAA provided funding to Caribbean ReefCheck investigators to undertake surveys of bleaching and mortality. Otherwise, no funding from outside authors' institutions was necessary for the undertaking of this study. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript
Analysis of MOST light curves of five young stars in Taurus-Auriga and Lupus 3 Star Forming Regions
Continuous photometric observations of five young stars obtained by the MOST
satellite in 2009 and 2010 in the Taurus and Lupus star formation regions are
presented. Using light curve modelling under the assumption of internal
invariability of spots, we obtained small values of the solar-type
differential-rotation parameter (k=0.0005-0.009) for three spotted weak-line T
Tau stars, V410 Tau, V987 Tau and Lupus 3-14; for another spotted WTTS, Lupus
3-48, the data are consistent with a rigidly rotating surface (k=0). Three
flares of similar rise (4 min 30 sec) and decay (1 h 45 min) times were
detected in the light curve of Lupus 3-14. The brightness of the classical T
Tau star RY Tau continuously decreased over 3 weeks of its observations with a
variable modulation not showing any obvious periodic signal.Comment: Accepted by MNRA
Calibration and Characterization of the IceCube Photomultiplier Tube
Over 5,000 PMTs are being deployed at the South Pole to compose the IceCube
neutrino observatory. Many are placed deep in the ice to detect Cherenkov light
emitted by the products of high-energy neutrino interactions, and others are
frozen into tanks on the surface to detect particles from atmospheric cosmic
ray showers. IceCube is using the 10-inch diameter R7081-02 made by Hamamatsu
Photonics. This paper describes the laboratory characterization and calibration
of these PMTs before deployment. PMTs were illuminated with pulses ranging from
single photons to saturation level. Parameterizations are given for the single
photoelectron charge spectrum and the saturation behavior. Time resolution,
late pulses and afterpulses are characterized. Because the PMTs are relatively
large, the cathode sensitivity uniformity was measured. The absolute photon
detection efficiency was calibrated using Rayleigh-scattered photons from a
nitrogen laser. Measured characteristics are discussed in the context of their
relevance to IceCube event reconstruction and simulation efforts.Comment: 40 pages, 12 figure
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