7,557 research outputs found
Environmental changes in a Mediterranean river: implications for the fish assemblage
This study examined the impacts of climate change on hydrology and fish population dynamics in a river in central Spain. The objectives were to: (i) contextualise long-term trends in the hydrology (1943–2012) and climate (1985–2011) of the study area, and (ii) identify the environmental factors driving fish population dynamics (1998–2012). Air and water temperatures progressively increased over the study period, whereas there were substantial reductions in mean spring river discharges but increases in peak-flow discharges during the spawning and early larval period of endemic cyprinids in recent decades. In particular, the changes in spring river discharges could have fundamental implications for the future status of the endemic cyprinids because this study revealed a positive influence of stable and low flow conditions during the spawning and early larval period (in late spring) on recruitment success (young-of-the-year densities). The density of young-of-the-year Salmo trutta appeared most influenced by flow conditions during fry emergence and the early larval period (in early spring), with the highest densities associated with low peak-flow hydrological pulses. Overall, fish abundances were significantly influenced by the frequency and duration of high and low hydrological pulses, but there were interspecific and ontogenetic differences in their influence. We conclude that although it is widely accepted that global warming should favour cyprinid over salmonid species, future shifts in hydrology due to climate change could negatively affect some cyprinids, including endemic species
Submillimeter H2O masers in water-fountain nebulae
We report the first detection of submillimeter water maser emission toward
water-fountain nebulae, which are post-AGB stars that exhibit high-velocity
water masers. Using APEX we found emission in the ortho-H2O (10_29-9_36)
transition at 321.226 GHz toward three sources: IRAS 15445-5449, IRAS
18043-2116 and IRAS 18286-0959. Similarly to the 22 GHz masers, the
submillimeter water masers are expanding with a velocity larger than that of
the OH masers, suggesting that these masers also originate in fast bipolar
outflows. In IRAS 18043-2116 and IRAS 18286-0959, which figure among the
sources with the fastest water masers, the velocity range of the 321 GHz masers
coincides with that of the 22 GHz masers, indicating that they likely coexist.
Towards IRAS 15445-5449 the submillimeter masers appear in a different velocity
range, indicating that they are tracing different regions. The intensity of the
submillimeter masers is comparable to that of the 22 GHz masers, implying that
the kinetic temperature of the region where the masers originate should be Tk >
1000 K. We propose that the passage of two shocks through the same gas can
create the conditions necessary to explain the presence of strong high-velocity
321 GHz masers coexisting with the 22 GHz masers in the same region.Comment: 4 pages, 1 figure. Accepted for publication in A&A Letter
Chemical abundances of stars with brown-dwarf companions
It is well-known that stars with giant planets are on average more metal-rich
than stars without giant planets, whereas stars with detected low-mass planets
do not need to be metal-rich. With the aim of studying the weak boundary that
separates giant planets and brown dwarfs (BDs) and their formation mechanism,
we analyze the spectra of a sample of stars with already confirmed BD
companions both by radial velocity and astrometry. We employ standard and
automatic tools to perform an EW-based analysis and to derive chemical
abundances from CORALIE spectra of stars with BD companions. We compare these
abundances with those of stars without detected planets and with low-mass and
giant-mass planets. We find that stars with BDs do not have metallicities and
chemical abundances similar to those of giant-planet hosts but they resemble
the composition of stars with low-mass planets. The distribution of mean
abundances of -elements and iron peak elements of stars with BDs
exhibit a peak at about solar abundance whereas for stars with low-mass and
high-mass planets the [X/H] and [X/H] peak abundances
remain at ~dex and ~dex, respectively. We display these
element abundances for stars with low-mass and high-mass planets, and BDs
versus the minimum mass, , of the most-massive substellar companion
in each system, and we find a maximum in -element as well as Fe-peak
abundances at jupiter masses. We discuss the
implication of these results in the context of the formation scenario of BDs in
comparison with that of giant planets.Comment: Accepted for publication in Astronomy & Astrophysic
¿Qué opinan los pacientes de nuestros centros de salud? ¿Realizarían cambios? Situación a las puertas de siglo XXI
Corporate Social Responsibility as a Strategic Opportunity for Small Firms during Economic Crises
The aim of this study is to analyze if there is a direct causal relationship between small firms’ orientation toward corporate social responsibility and their competitive success, mediated by innovation and performance. A structural equation model has been applied to a sample of 758 small Spanish firms. The results indicate that, in times of economic crisis, socially responsible strategies are a determining factor in firms’ competitiveness. Pragmatic advice for practitioners derives from research results, considering that social responsibility represents an opportunity for small firms in the complex and turbulent time. The findings encourage small firms to manage operations responsibly as a guarantee of market success
CAD techniques for microwave circuits
In little more than 10 years computer-aided design (CAD) of microwave circuits has moved from dumb terminals on mainframe computers to PCs, and now to powerful RISC workstations. Commercial CAD software now integrates the various stages of microwave circuit design: schematic capture, simulation and layout. This paper reviews the different CAD packages that are available for microwave circuit design. The basic principles employed in the modelling of microstrip circuits are introduced and the reasons for the extensive use of frequency-domain simulations are explored. The developments in nonlinear, electromagnetic and system-level simulation methods are described.The authors would like to acknowledge the financial
support of the Engineering and Physical Sciences
Research Council, and the Comisidn Interministerial de
Ciencia y Technologia (CICr?‘), Spain, under the project
TIC95-0983-C03-02. We would like to thank Hewlett
Packard, Barnard Microsystems, Sonnet Software,
Optimization Systems Associates, Kimberley
Communications Consultants and Ansoft Corporation for
their generous educational discounting. The assistance
of Dr. D. M. Brookbanks at GEC-Marconi Materials
Technology Ltd. (Caswell) is gratefully acknowledged
Haplotyping via minimum recombinant paradigm
<p>Abstract</p> <p>Background</p> <p>Haplotypes can increase the power of gene detection over genotypes and are essential to estimate linkage disequilibrium.</p> <p>Methods</p> <p>Haplotyping was based on the minimum recombinant paradigm, whereby a phase is obtained only if it uniquely minimises the number of recombinants within a full sib family. Performance of this method was tested across three different data sets, consisting of genotypes and pedigree.</p> <p>Results</p> <p>The percentage of phased alleles ranged from ~80% to ~95%, and the percentage of correct phases reached ~99% in all cases. A measure of uncertainty was obtained via simulations. A partial haplotyping algorithm consisting of four deterministic rules was almost as effective as a full one consisting of six deterministic rules, and took up to 5 times less time to compute.</p> <p>Conclusion</p> <p>Haplotyping via the minimum recombinant paradigm is consistently reliable and computationally efficient. A single simulation is enough to produce a population-wide uncertainty estimate associated with a set of all reconstructed haplotypes.</p
Control del curculiónido ferruginoso de las palmeras (Rhynchophorus ferrugineus Olivier) mediante inyecciones al tronco y pulverización foliar
En 1996 se confirmó la presencia en España, en la costa de la provincia de Granada, de una nueva plaga sobre palmeras conocida como curculiónido ferruginoso de las palmeras, Rhynchophorus ferrugineus Olivier. Dentro de las estrategias de lucha contra este insecto se llevaron a cabo una serie de ensayos de efectividad de distintos productos insecticidas aplicados al suelo, por inyección al tronco, en pulverización foliar o una combinación de estos dos últimos métodos. Los mayores porcentajes de eficacia se obtuvieron mediante la aplicación de insecticidas por inyección al tronco de la palmera, combinada con una pulverización foliar con el mismo insecticida para controlar los estadios del insecto situados en la zona exterior, de pencas y cogollo, donde el insecticida aplicado por inyección no consigue distribuirse. Las materias activas insecticidas que presentaron mayor eficacia fueron Carbaril, Fipronil e Imidacloprid. Asimismo se ha observado la idoneidad de mezclar el insecticida aplicado en pulverización foliar con un aceite mineral parafínico o de verano para mejorar su eficacia
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