2,493 research outputs found
Radiative capture reaction for Ne formation within a full three-body model
Background: The breakout from the hot Carbon-Nitrogen-Oxigen (CNO) cycles can
trigger the rp-process in type I x-ray bursts. In this environment, a
competition between and the
two-proton capture reaction is
expected.
Purpose: Determine the three-body radiative capture reaction rate for
formation including sequential and direct, resonant and
non-resonant contributions on an equal footing.
Method: Two different discretization methods have been applied to generate
Ne states in a full three-body model: the analytical transformed
harmonic oscillator method and the hyperspherical adiabatic expansion method.
The binary --O interaction has been adjusted to reproduce the known
spectrum of the unbound F nucleus. The dominant contributions to
the reaction rate have been
calculated from the inverse photodissociation process.
Results: Three-body calculations provide a reliable description of Ne
states. The agreement with the available experimental data on Ne is
discussed. It is shown that the
reaction rates computed within the two methods agree in a broad range of
temperatures. The present calculations are compared with a previous theoretical
estimation of the reaction rate.
Conclusions: It is found that the full three-body model provides a reaction
rate several orders of magnitude larger than the only previous estimation. The
implications for the rp-process in type I x-ray bursts should be investigated.Comment: 10 pages, 10 figures. Corrected versio
Microbial Community Composition during a Bloom of Purple Bacteria in Intertidal Sediments in Vigo (Northwest Spain)
In summer 2019, a large, bright pink microbial mat was visible on top of macroalgal deposits in muddy sediments of an urban beach (Playa do Adro, Vigo). In order to characterize the dominant organisms in these colored mats, results from microscopic observations, photosynthetic pigments, and molecular analysis were gathered. Light microscopy examination revealed pinkish microbial aggregates with minor contributions of larger protists and cyanobacteria. High-performance liquid chromatography (HPLC) pigment analysis documented the dominance of bacteriochlorophyll a and carotenoids whose spectra were compatible with those described in photosynthetic purple bacteria. 16S rRNA gene amplicon sequencing confirmed that the vast majority of reads belonged to Proteobacteria (73.5%), and among them, nearly 88% of those reads belonged to purple sulfur bacteria (Gammaproteobacteria). A single family, Chromatiaceae, constituted the bulk of this assemblage, including the genera Thiohalocapsa (32%), Marichromatium (12.5%), Phaeochromatium (5%), and Halocromatium (2%) as main contributors. Nonetheless, a considerable number of sequences could not be assigned to a particular genus, stressing the large biological diversity in these microbial mats and the potential presence of novel taxa of purple sulfur bacteria.En prens
Análisis nutricional: el consumo de calorías de la población pobre en Argentina
Existe una creencia generalizada entre los economistas que la inseguridad alimentaria y el hambre son el resultado de la pobreza. Muchos sostienen que el crecimiento económico y los aumentos en los niveles de ingreso de los hogares pobres mejorarán la habilidad y el deseo de los mismos por adquirir una dieta adecuada, al menos en términos de la energía aportada por los alimentos (calorías). Teniendo en cuenta la dispar distribución de los gastos en alimentos debido a la creciente desigualdad en los niveles de vida de nuestro país, el objetivo del presente trabajo es analizar las deficiencias de nuestra población en la satisfacción de los requerimientos mínimos nutricionales, evaluar el aporte calórico de los distintos grupos de alimentos y cuantificar el grado de sensibilidad de las calorías a las variaciones en el ingreso. Además se realiza un análisis exploratorio para identificar las características de los hogares con deficiencias calóricas. La generación de información para nuestro país sobre estos aspectos es el paso previo para evaluar la eficacia de programas dirigidos a disminuir los niveles de pobreza y desnutrición otorgando subsidios directos en dinero o raciones de alimentos. Además de orientar las decisiones para la producción de alimentos estratégicos en la mejora de los niveles nutricionales de los hogares más carenciados o vulnerables.Fil: Rodríguez, Elsa Mirta M. Universidad Nacional de Mar del Plata. Facultad de Ciencias Económicas y Sociales; Argentina.Fil: Garrido, Laura. Universidad Nacional de Mar del Plata. Facultad de Ciencias Económicas y Sociales; Argentina.Fil: Gentile, Natacha. Universidad Nacional de Mar del Plata. Facultad de Ciencias Económicas y Sociales; Argentina.Fil: Lupín, Beatriz. Universidad Nacional de Mar del Plata. Facultad de Ciencias Económicas y Sociales; Argentina
Implications of plant material origin, land use history and soil properties in the incidence of verticillium wilt in olive groves
8 páginas, 2 figuras, 1 tabla.The increased presence of Verticillium wilt (Verticillium
dahliae Kleb.) in olive groves is often related to the
use of infected propagation material and to the planting
of new olive trees in contaminated soils. This study assessed
the implications of plant propagation, land-use
history and soil properties on disease prevalence in
southern Spain, the most important olive-growing area
worldwide. To this purpose, a large-scale sampling survey
was carried out in this area, V. dahliae pathotypes
were identified by PCR, and GIS was used to analyze
soil properties and cropland-use history. Finally, multiple
correspondence analysis was performed to show the
statistical association between the variables taken into
account. Results strongly indicated the potential risk of
planting olive in valleys with irrigated cropland history,
especially those that had hosted herbaceous crops, highlighted
the importance of using pathogen-free certified
planting material as a key component for a successful
disease management, and confirmed the role played by
saline, alkaline, and steep-slope soils in enhancing V.
dahliae prevalence.The research was supported by Caja Rural Foundation.Peer reviewe
Three-body structure of low-lying 18Ne states
We investigate to what extent 18Ne can be descibed as a three-body system
made of an inert 16O-core and two protons. We compare to experimental data and
occasionally to shell model results. We obtain three-body wave functions with
the hyperspherical adiabatic expansion method. We study the spectrum of 18Ne,
the structure of the different states and the predominant transition strengths.
Two 0+, two 2+, and one 4+ bound states are found where they are all known
experimentally. Also one 3+ close to threshold is found and several negative
parity states, 1-, 3-, 0-, 2-, most of them bound with respect to the 16O
excited 3- state. The structures are extracted as partial wave components, as
spatial sizes of matter and charge, and as probability distributions.
Electromagnetic decay rates are calculated for these states. The dominating
decay mode for the bound states is E2 and occasionally also M1.Comment: 17 pages, 5 figures (version to appear in EPJA
Una transdisciplina de estudios del discurso.
El análisis del discurso es un vasto dominio en el que convergen múltiples disciplinas y variados enfoques. Todos ellos han de compenetrarse si se quiere dar cabida a la multiplicidad de fenómenos discursivos de los que se viene hablando desde hace ya medio siglo. Lo que pretendemos en este trabajo es desarrollar la idea planteada por T. A. Van Dijk en su artículo "The study of discourse" (1997), en el que defiende la necesidad de crear UIUI. Transdiscisplina de estudios del discurso. Dicha macrodisciplina incluye todas las que hasta ahora han sido consideradas disciplinas involucradas en el análisis discursivo. De este modo se puede dar cuenta y explicar de forma más coherente cada una de las dimensiones discursivas a las que Van Dijk hace referencia en el mencionado artículo y que aquí vamos a presentar
An instrumental puzzle: the modular integration of AOLI
The Adaptive Optics Lucky Imager, AOLI, is an instrument developed to deliver
the highest spatial resolution ever obtained in the visible, 20 mas, from
ground-based telescopes. In AOLI a new philosophy of instrumental prototyping
has been applied, based on the modularization of the subsystems. This modular
concept offers maximum flexibility regarding the instrument, telescope or the
addition of future developments.Comment: 10 pages, 8 figures, Proc. SPIE 9908, Ground-based and Airborne
Instrumentation for Astronomy VI, 99082Z (August 9, 2016
Performance and challenges in the value chain of the Anadara tuberculosa bivalve mollusk in Ecuador
The bivalve mollusk, Anadara tuberculosa (Black Shell, in Spanish Concha Prieta), is found on America’s Pacific coast, where it is harvested for subsistence and commercial markets. This paper aims to diagnose the performance of the black shell’s value chain. We also identify several challenges that must be addressed to improve the sustainability of the black shell fishery in Ecuador. The applied methodology was quantitative and descriptive. Its design was non-experimental, field, cross-sectional and ex post facto. The investigation was carried out from January to October 2019 in the Jambelí archipelago, El Oro province, Ecuador. The study population consisted of 565 individuals, shellfish collectors, shellfish associations managers, traders, and restaurants from the A. tuberculosa production chain. The sample size was estimated at 222 informants. The type of sampling used was probabilistic, random, stratified, and with proportional allocation, with an effective participation rate of those selected of approximately 80%. The questionnaire was applied personally through the structured survey method, in writing, in the work area, and with their consent. The performance of the value chain was diagnosed in the dimensions of productivity, competitiveness, and quality of life, reaching a 75.1% index, a result that indicates that the value chain has a moderate to good performance level. The competitiveness dimension reached the highest performance, followed by productivity. Quality of life was the dimension with the lowest performance. The value chain can be improved if the following challenges are met: (1) Restoration of the mangrove ecosystem, (2) Promotion of low-intensity shellfish aquaculture, (3) Good sanitary management and purification, (4) Promotion of value-focused ventures, (5) Strengthening of organizations and agreements for the use and custody of mangroves, and (6) Strengthening of institutions that contribute to the advancement of these challenge
A photometric monitoring of bright high-amplitude delta Scuti stars. II. Period updates for seven stars
We present new photometric data for seven high-amplitude delta Scuti stars.
The observations were acquired between 1996 and 2002, mostly in the Johnson
photometric system. For one star (GW UMa), our observations are the first since
the discovery of its pulsational nature from the Hipparcos data.The primary
goal of this project was to update our knowledge on the period variations of
the target stars. For this, we have collected all available photometric
observations from the literature and constructed decades-long O-C diagrams of
the stars. This traditional method is useful because of the single-periodic
nature of the light variations. Text-book examples of slow period evolution (XX
Cyg, DY Her, DY Peg) and cyclic period changes due to light-time effect (LITE)
in a binary system (SZ Lyn) are updated with the new observations. For YZ Boo,
we find a period decrease instead of increase. The previously suggested
LITE-solution of BE Lyn (Kiss & Szatmary 1995) is not supported with the new
O-C diagram. Instead of that, we suspect the presence of transient light curve
shape variations mimicking small period changes.Comment: 11 pages, 15 figures, accepted for publication in A&
- …