6,658 research outputs found
Flux-cutting and flux-transport effects in type-II superconductor slabs in a parallel rotating magnetic field
The magnetic response of irreversible type-II superconductor slabs subjected
to in-plane rotating magnetic field is investigated by applying the circular,
elliptic, extended-elliptic, and rectangular flux-line-cutting critical-state
models. Specifically, the models have been applied to explain experiments on a
PbBi rotating disk in a fixed magnetic field , parallel to the flat
surfaces. Here, we have exploited the equivalency of the experimental situation
with that of a fixed disk under the action of a parallel magnetic field,
rotating in the opposite sense. The effect of both the magnitude of the
applied magnetic field and its angle of rotation upon the
magnetization of the superconductor sample is analyzed. When is smaller
than the penetration field , the magnetization components, parallel and
perpendicular to , oscillate with increasing the rotation angle. On
the other hand, if the magnitude of the applied field, , is larger than
, both magnetization components become constant functions of at
large rotation angles. The evolution of the magnetic induction profiles inside
the superconductor is also studied.Comment: 12 pages, 29 figure
Promotion of Healthy Physical Activity in School Recreation
Los autores desean mostrar su agradecimiento al profesorado de Educación Física de los centros participantes por su colaboración, a los equipos directivos de dichos centros por su apoyo y a las familias de los alumnos por autorizar la realización de la investigaciónEl objetivo de este trabajo fue investigar qué medidas se podrían tomar para aumentar los niveles generales de actividad física del alumnado de sexto de Educación Primaria durante los periodos de recreo escolar. Se implementó un programa específico desde el currículum de la asignatura de Educación Física y, después de haber finalizado la aplicación del citado programa, se comprobó los niveles de actividad física. También se realizó una observación pasados treinta días de su finalización, con el fin de comprobar en qué medida se modifican los hábitos de actividad física. El instrumento de recogida de datos fue el podómetro, que los participantes utilizaron durante los periodos de recreo escolar. El análisis de los resultados permite afirmar que la aplicación del programa específico objeto de estudio incide positivamente sobre el incremento del volumen de actividad física que realiza el alumnado en su tiempo libre y que, pasados treinta días desde su aplicación, el alumnado mantiene parte de incremento adquirido, modificando su hábito de actividad durante el recreo escolarThe objective of this work was to investigate what measures could be taken to increase the general levels of physical activity of students in sixth grade of Primary Education during the school breaks. A specific program was implemented from the curriculum of the subject of Physical Education and, after completing its application, physical activity levels were analyzed. In addition, an observation was conducted thirty days after its completion, in order to verify to what extent the habits of physical activity are modified. The instrument of data collection was the pedometer, which the participants used during the periods of school break. The analysis of the results allows affirming that the application of the specific program object of study affects positively on the increase of the volume of physical activity that the students do in their free time and that, after thirty days from its application, the students keep part of this increase acquired, which means a change in their activity habit during school break
Experimental study on a metal hydride based hydrogen compressor
This is the post-print version of the final paper published in Journal of Alloys and Compounds. The published article is available from the link below. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. Copyright @ 2008 Elsevier B.V.A three-stage metal hydride based hydrogen compressor prototype was built. It has been designed for a hydrogen production facility using a low-pressure alkaline electrolyser. The compression system should transfer heat recovered from the electrolyser into the hydride beds to allow hydrogen desorption flow. The three-stage compressor achieves a compression ratio of 20:1 atm. It performs a thermal cycling of three AB5 hydrides between 20 and 80 °C. Its flow rate, for 25 g of each hydride bed, reaches about 20 l (NTP) of hydrogen per hour. The prototype is now operational. Some improvements in the heat transfer management system are also carried out before proceeding to the interconnection with the electrolyser and to the extent that the hydrogen produced satisfies the high purity requirement of the hydrides used in the compressor.Natural Resources Canada(NRCan), Ministère des Ressources Naturelles
et de la Faune du Québec (MRNF), and Natural Sciences and Engineering Research Council of Canada
Identification of the optical and near-infrared counterpart of GRS 1758-258
Context. Understood to be a microquasar in the Galactic center region, GRS
1758-258 has not yet been unambiguously identified to have an
optical/near-infrared counterpart, mainly because of the high absorption and
the historic lack of suitable astrometric stars, which led to the use of
secondary astrometric solutions. Although it is considered with 1E 1740.7-2942
as the prototypical microquasar in the Galactic center region, the Galactic
origin of both sources has not yet been confirmed. Aims. We attempt to improve
previous astrometry to identify a candidate counterpart to GRS 1758-258. We
present observations with the Gran Telescopio de Canarias (GTC), in which we
try to detect any powerful emission lines that would infer an extragalactic
origin of this source. Methods. We use modern star catalogues to reanalyze
archival images of the GRS 1758-258 field in the optical and near-infrared
wavelengths, and compute a new astrometric solution. We also reanalyzed
archival radio data of GRS 1758-258 to determine a new and more accurate radio
position. Results. Our improved astrometric solution for the GRS 1758-258 field
represents a significant advancement on previous works and allows us to
identify a single optical/near-infrared source, which we propose as the
counterpart of GRS 1758-258. The GTC spectrum of this source is however of low
signal-to-noise ratio and does not rule out a Galactic origin. Hence, new
spectral observations are required to confirm or discard a Galactic nature.Comment: 4 pages, 3 figures, accepted by Astronomy and Astrophysic
In-situ growth rate assessment of hexactinellid sponge Asconema setubalense using 3D photogrammetric reconstruction
We describe the first application of a non-invasive and novel approach to estimate the
growth rate of Asconema setubalense (Porifera, Hexactinellida) through the use of 3D
photogrammetric methodology. Structure-from-Motion techniques (SfM) were applied
to videos acquired with the Politolana ROTV in the El Cachucho Marine Protected Area
(MPA) (Cantabrian Sea) on three different dates (2014, 2017, and 2019) over six years.
With these data, a multi-temporal study was conducted within the framework of MPA
monitoring. A complete 3D reconstruction of the deep-sea floor was achieved with
Pix4D Mapper Pro software for each date. Having 3D point clouds of the study area
enabled a series of measurements that were impossible to obtain in 2D images. In
3D space, the sizes (height, diameter, cup-perimeter, and cup-surface area) of several
A. setubalense specimens were measured each year. The annual growth rates recorded
ranged from zero (“no growth”) for a large size specimen, to an average of 2.2 cm
year�����1 in cup-diameter, and 2.5 cm year�����1 in height for developing specimens. Von
Bertalanffy growth parameters were estimated. Taking into account the size indicators
used in this study and based on the von Bertalanffy growth model, this sponge reaches
95% maximum size at 98 years of age. During the MPA monitoring program, a high
number of specimens disappeared. This raised suspicions of a phenomenon affecting
the survival of this species in the area. This type of image-based methodology does
not cause damage or alterations to benthic communities and should be employed in
vulnerable ecosystem studies and MPA monitoring.
Keywords: underwater photogrammetry, Asconema setubalense, Marine ProtectedPostprin
Changes in compliance with school-based physical activity recommendations in Spanish youth: The UP&DOWN longitudinal study
The study aimed (a) to examine changes in physical activity (PA) during the whole day, school hours, recess, and physical education classes (PEC) during a 2-year period in primary and secondary students; (b) to identify changes in the proportion of compliance with specific PA recommendations for these periods; and (c) to examine whether PA levels at baseline are associated with PA levels 2 years later. Eight hundred and fourteen (51.8% boys) children and 658 (50.1% boys) adolescents from 41 Spanish schools participated in the study. Hip-worn accelerometers were used to assess PA during different time periods. Light PA (LPA) declined during the whole day, school hours, recess (all P < 0.001, except child girls for recess), and PEC (all, P < 0.05) in children and adolescents. Moderate-to-vigorous PA (MVPA) during the whole day and recess declined in child boys (P < 0.01 and P < 0.001, respectively) and adolescent boys (P < 0.001 and P < 0.05, respectively). MVPA during PEC declined in adolescent boys (P < 0.001) and adolescent girls (all P < 0.05). The proportion of compliance with the specific PA recommendations for these periods declined (P < 0.05), except for PEC in adolescent girls. PA during the whole day at baseline was moderately associated with PA during the whole day years later (ICCs = 0.210-0.544, with one exception), but this association was lower for the school-based PA. In conclusion, time spent in MVPA and LPA during the whole day and recess declined over time in child and adolescent boys and during PEC in adolescents. These findings highlight the need to promote PA interventions in these settings
Fano-like interference of plasmon resonances at a single rod-shaped nanoantenna
Single metallic nanorods acting as half-wave antennas in the optical range
exhibit an asymmetric, multi-resonant scattering spectrum that strongly depends
on both their length and dielectric properties. Here we show that such spectral
features can be easily understood in terms of Fano-like interference between
adjacent plasmon resonances. On the basis of analytical and numerical results
for different geometries, we demonstrate that Fano resonances may appear for
such single-particle nanoantennas provided that interacting resonances overlap
in both spatial and frequency domains.Comment: 18 pages, 9 figure
Evaluación cuantitativa del riesgo de entrada del virus de la gripe aviar altamente patógeno en la comunidad valenciana por importación de aves vivas
The Region of Valencia has had many imports of live poultry from different countries that have had several outbreaks of Highly Pathogenic Bird flu during their history. The aim of this paper is to do a quantitative assessment of the risk of entry of HPAI in the Region of Valencia and its provinces due to the importation of live poultry, and identify the countries which entail a higher risk. The results indicate that Alicante is the province with more risk and Italy is the country that represents the greatest proportion of risk due to his imports. The probability to introduce the HPAI virus to the Region of Valencia due to life poultry imports is low.En la Comunidad Valenciana (CV) se importa cantidades altas de aves vivas desde países que han sufrido algún brote de influenza aviar altamente patógena (HPAI) a lo largo de su historia. El objetivo de este trabajo es realizar una evaluación cuantitativa del riesgo que hay de que el virus HPAI entre en la CV y sus provincias por importación de aves vivas, e identificar los países desde los que es más probable introducirlo. Los resultados obtenidos muestran a Alicante como la provincia con más probabilidad de sufrir la entrada del virus y a Italia, el país desde donde hay más probabilidad que entre. La probabilidad de introducir el virus HPAI en la CV mediante importaciones de aves vivas es baja
Small Renal Masses: Incidental Diagnosis, Clinical Symptoms, and Prognostic Factors
Introduction. The small renal masses (SRMs) have increased over the past two decades due to more liberal use of imaging techniques. SRMs have allowed discussions regarding their prognostic, diagnosis, and therapeutic approach. Materials and methods. Clinical presentation, incidental diagnosis, and prognosis factors of SRMs are discussed in this review. Results. SRMs are defined as lesions less than 4 cm in diameter. SRM could be benign, and most malignant SMRs are low stage and low grade. Clinical symptoms like hematuria are very rare, being diagnosed by chance (incidental) in most cases. Size, stage, and grade are still the most consistent prognosis factors in (RCC). An enhanced contrast SRM that grows during active surveillance is clearly malignant, and its aggressive potential increases in those greater than 3 cm. Clear cell carcinoma is the most frequent cellular type of malign SRM. Conclusions. Only some SRMs are benign. The great majority of malign SRMs have good prognosis (low stage and grade, no metastasis) with open or laparoscopic surgical treatment (nephron sparing techniques). Active surveillance is an accepted attitude in selected cases
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