Patrón temporal de movimientos del mero Epinephelus morio en la plataforma continental norte de la Península de Yucatán, México

Los movimientos estacionales del mero Epinephelus morio en la plataforma continental de Yucatán, son un elemento muy sensible en el manejo de la pesquería de este recurso que actualmente se encuentra sobreexplotado. En este trabajo se estima el patrón de movimientos de la población utilizando un modelo dinámico espacial. Se estimaron tasas de flujo de individuos entre áreas adyacentes considerando explícitamente la estructura de la población (juveniles, preadultos y adultos). El modelo fue aplicado utilizando información de captura por unidad de esfuerzo y distribuciones de frecuencias de longitud de la flota mediana mexicana que operó en la zona durante 1973, correspondiente a la época de las más altas capturas históricas. Se consideró capturabilidad variable con la talla, tiempo y zona así como mortalidad natural variable con la edad. Los resultados muestran patrones temporales de movimientos diferenciados por sector de población. Movimientos asociados a concentraciones de adultos fueron encontrados entre invierno y primavera en el centro y oriente de la plataforma continental, en profundidades de 35 a 60 m, mientras que el movimiento de los preadultos y juveniles fue en sentido contrario dirigiéndose hacia zonas más someras. En primavera-verano la población se desplaza hacia la zona occidental de la plataforma continental. Se detectó una mayor dinámica en adultos que en juveniles, sin embargo, se encontraron movimientos importantes de juveniles hacia el norte de la plataforma continental y frente a las zonas de Dzilam de Bravo-Río Lagartos. Los resultados muestran la importancia de esta información en la orientación de medidas de manejo como la exploración de áreas marinas protegidas o zonas de exclusión a la pesca que permitan la recuperación de la población

Is emamectin benzoate effective against the different stages of Spodoptera exigua (Hübner) (Lepidoptera, Noctuidae)?

peer-reviewedThis work was partially supported by the Spanish Ministry of Science and Innovation (project AGL 2007-66130-C03-02 to P. Medina). F. Amor and P. Bengochea acknowledge the ministry of Education and Culture and the Technical University of Madrid (UPM) for the doctoral fellowships. Special thanks to Syngenta Agro S.A. for their support.The beet armyworm, Spodoptera exigua (Hübner) (Lepidoptera, Noctuidae), is a major polyphagous pest in greenhouses and open fields worldwide and also a main problem in sweet pepper greenhouses. The effectiveness of the pesticide emamectin benzoate was tested in the laboratory on different stages of S. exigua using different concentrations and uptake routes. After dipping young (48-h-old) S. exigua eggs in emamectin benzoate at 0.5, 1 and 1.5 mg/L a.i. the chemical did not exhibit any ovicidal activity. There was, however, progressive neonate mortality at all concentrations, culminating at 72 hours after hatching, when 100% of the larvae from the treated young eggs died. Second and fourth instar S. exigua larvae did not exhibit significant mortality when exposed to the inert surfaces which were treated. In contrast, ingesting a diet contaminated with 0.5 mg/L a.i. of emamectin benzoate caused 100% mortality in L2 and L4 larvae 24 and 72 hours after ingestion, respectively. The LC50 value of the compound against L4 larvae that fed on sprayed sweet pepper leaves for 24 hours was 0.81 mg/L a.i.. When adults were fed on a solution of 0.5 mg/L a.i., there was a reduction in the female and male lifespan of 29.3% and 55.3%, respectively. Fecundity was reduced by more than 99%. These data suggest that emamectin benzoate is not only a useful insecticide when ingested by beet armyworm larvae but it also has ovolarvicidal and adult activity.Spanish Ministry of Science and Innovatio

Physical Layer Security of Large Reflecting Surface Aided Communications with Phase Errors

The physical layer security (PLS) performance of a wireless communication link through a large reflecting surface (LRS) with phase errors is analyzed. Leveraging recent results that express the \ac{LRS}-based composite channel as an equivalent scalar fading channel, we show that the eavesdropper's link is Rayleigh distributed and independent of the legitimate link. The different scaling laws of the legitimate and eavesdroppers signal-to-noise ratios with the number of reflecting elements, and the reasonably good performance even in the case of coarse phase quantization, show the great potential of LRS-aided communications to enhance PLS in practical wireless set-ups.Comment: This work has been submitted to the IEEE for publication. Copyright may be transferred without notice, after which this version may no longer be accessibl

High spatial resolution and high contrast optical speckle imaging with FASTCAM at the ORM

In this paper, we present an original observational approach, which combines, for the first time, traditional speckle imaging with image post-processing to obtain in the optical domain diffraction-limited images with high contrast (1e-5) within 0.5 to 2 arcseconds around a bright star. The post-processing step is based on wavelet filtering an has analogy with edge enhancement and high-pass filtering. Our I-band on-sky results with the 2.5-m Nordic Telescope (NOT) and the lucky imaging instrument FASTCAM show that we are able to detect L-type brown dwarf companions around a solar-type star with a contrast DI~12 at 2" and with no use of any coronographic capability, which greatly simplifies the instrumental and hardware approach. This object has been detected from the ground in J and H bands so far only with AO-assisted 8-10 m class telescopes (Gemini, Keck), although more recently detected with small-class telescopes in the K band. Discussing the advantage and disadvantage of the optical regime for the detection of faint intrinsic fluxes close to bright stars, we develop some perspectives for other fields, including the study of dense cores in globular clusters. To the best of our knowledge this is the first time that high contrast considerations are included in optical speckle imaging approach.Comment: Proceedings of SPIE conference - Ground-based and Airborne Instrumentation for Astronomy III (Conference 7735), San Diego 201

An X-ray study of the SNR G344.7-0.1 and the central object CXOU J170357.8-414302

Aims. We report results of an X-ray study of the supernova remnant (SNR) G344.7-0.1 and the point-like X-ray source located at the geometrical center of the SNR radio structure. Methods. The morphology and spectral properties of the remnant and the central X-ray point-like source were studied using data from the XMM-Newton and Chandra satellites. Archival radio data and infrared Spitzer observations at 8 and 24 $\mu$m were used to compare and study its multi-band properties at different wavelengths. Results. The XMM-Newton and Chandra observations reveal that the overall X-ray emission of G344.7-0.1 is extended and correlates very well with regions of bright radio and infrared emission. The X-ray spectrum is dominated by prominent atomic emission lines. These characteristics suggest that the X-ray emission originated in a thin thermal plasma, whose radiation is represented well by a plane-parallel shock plasma model (PSHOCK). Our study favors the scenario in which G344.7-0.1 is a 6 x 10^3 year old SNR expanding in a medium with a high density gradient and is most likely encountering a molecular cloud on the western side. In addition, we report the discovery of a soft point-like X-ray source located at the geometrical center of the radio SNR structure. The object presents some characteristics of the so-called compact central objects (CCO). However, its neutral hydrogen absorption column (N_{H}) is inconsistent with that of the SNR. Coincident with the position of the source, we found infrared and optical objects with typical early-K star characteristics. The X-ray source may be a foreground star or the CCO associated with the SNR. If this latter possibility were confirmed, the point-like source would be the farthest CCO detected so far and the eighth member of the new population of isolated and weakly magnetized neutron stars.Comment: 9 pages, 8 figures, accepted for publication in Astronomy and Astrophysics. Higher resolution figures can be seen on A&