Sucesión y restauración en ambientes semiáridos

Extensas áreas abandonadas del sureste peninsular están experimentando actualmente procesos de sucesión secundaria sobre los que tenemos un conocimiento muy escaso. La sucesión secundaria en ambientes áridos es muy lenta y su resultado incierto, ya que el establecimiento de determinadas especies y comunidades está muy limitado. Los esfuerzos para restaurar zonas abandonadas deben basarse en un conocimiento sólido de la sucesión, empleando especies viables, propias de etapas intermedias, capaces de impulsar la sucesión vegetal

Gain-Reconfigurable Hybrid Metal-Graphene Printed Yagi Antenna for Energy Harvesting Applications

This paper presents a hybrid metal-graphene printed Yagi antenna with reconfigurable gain that operates in the 5.5-GHz band. The balun and the driven elements are made of copper, while the directors are made of graphene. The graphene acts as a tunable material in the design. By switching the conductivity of the graphene, it is achieved a similar effect to adding or subtracting directors in the antenna. Hence the gain of the printed Yagi can be easily controlled. This could be of special interest in RF energy harvesting in the design of reconfigurable harvesting elements.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Oral and contact toxicity of the extract obtained with hexane from Achyrocline satureioides on larvae and adult honey bees

Aim of study: To evaluate the antimicrobial activity of the hexanic extract (HE) of Achyrocline satureioides on Paenibacillus larvae - a gram-positive spore-forming bacillus that affects the larval stage and causes American Foulbrood (AFB) - and its oral and contact toxicity on larvae and adult honey bees.Area of study: A. satureioides plants were collected in Santa Monica (32° 05’ 29” S, 64° 36’ 54” W, Córdoba. Argentina). The larvae and adults of Apis mellifera were obtained from the experimental apiary of the University of Córdoba, Spain.Material and methods: P. larvae 9 was previously isolated and identified in the Laboratory of General Microbiology (Dept. of Microbiology, National University of Río Cuarto, Argentina). The HE was obtained by liquid-liquid extraction. The minimum inhibitory concentration (MIC) of HE was determined by a microdilution method. This concentration and 2 ½ MIC were used for in vitro toxicity tests. Oral toxicity was tested on larvae, feeding them with both concentrations of the HE, while on adult bees the HE was spread to determine contact toxicity.Main results: The HE showed antimicrobial activity, the MIC obtained was 0.4 μg/mL. The HE presented very low toxicity at the MIC and 2 ½ MIC, with survival percentages to be around 95% for adult bees and larvae.Research highlights: The results show that this extract could be used for the development of an alternative product for a safe and effective treatment of AFB

Artificial insemination of queen bees

The race commonly used by spanish beekeepers is Apis mellifera iberica. Up to date, any selection process has been carried out with this race, and a lot of characteristics in the colony can be improved. Artificial insemination is a technique used in order to control genetic origin, and open a way to control those tasks usefull for beekeepers, both productive (honey, pollen or royal jelly production...) o linked with behaviour (agresiveless, short tendency to swarming, natural resistance to disesases...)Apis mellifera iberica es la raza de abeja que utilizan los apicultores actualmente en España. Las características de esta abeja aún están por mejorar, ya que hasta el momento no se ha desarrollado ningún programa de selección que la afecte. La inseminación artificial es la técnica que se utiliza para controlar el origen genético de los progenitores, pudiendo seleccionar aquellos caracteres que sean más interesantes para el apicultor, ya sean estos de tipo productivo (kilogramos de miel, polen, jalea real, etc) o de comportamiento (menor agresividad, menor tendencia a la enjambrazón, resistencia a enfermedades, etc)

Grooming in Apis mellifera iberica

We checked grooming in 8 colonies of the race Apis mellifera iberica. We studied fallen mites on plastic sheets put on the bottom board. Tests were repeated 12 times. Grooming was detected in A. m. iberica race: 5.07 percent of living mites and 50.85 percent of died mites were injuried. Damages were present in legs and body. Grooming can be an important character for selection of tolerant bees to varroosis.El principal problema de índole patológico de la apicultura actual es una parasitosis provocada por el ácaro Varroa jacobsoni Oud. En los últimos tiempos se han descrito comportamientos en diferentes razas de abejas capaces de detectar, morder y eliminar los parásitos. A estos comportamientos se les conoce como grooming, y es una posible vía para la selección de abejas tolerantes a enfermedades, aunque no la única. En nuestro trabajo hemos descrito este comportamiento en Apis mellifera iberica, la raza de abeja habitualmente usada en nuestra apicultura. Los parásitos eran recogidos en bandejas situadas en el fondo de las colmenas. El 5,07 p.100 de los parásitos recogidos vivos y el 50,85 p.100 de los muertos presentaron daños. Los daños se repartieron entre los apéndices y el idiosoma. Esto abre una camino a la esperanza de mejorar la respuesta de autodefensa en la mencionada raza frente al parásito

Queen rearing of apis mellifera iberica

Apis mellifera iberica is the spanish bee race mostly used by breeders. Queen rearing is necessary for genetic selection . Our research team uses the Doolittle method; Mainly it is based on transfering young (a few hours old) worker larvae to artificial queen cells. Larvae are reared in queenless colonies. After sealed, queen cells are kept in an incubator chamber. Mean percentage of alive queens during a season reaches 80 p.100.Apis mellifera iberica es la abeja habitualmente usada por los apicultores en España. Para la mejora de esta raza es esencial la cría controlada de abejas reinas. Nuestro equipo de investigación emplea el método Doolittle, consistente en el transvase de larvas de obreras con pocas horas de vida a celdillas reales artificiales. Estas larvas son criadas en colmenas huérfanas hasta su operculación y, posteriormente, mantenidas en incubadoras hasta el nacimiento. El éxito medio alcanzado a lo largo de la temporada es del 80 p.100

Analytical Approach of Director Tilting in Nematic Liquid Crystals for Electronically Tunable Devices

This paper presents an analytical expression that models the tilt angle of directors in a nematic liquid crystal (LC), depending on its elastic properties, its dielectric anisotropy, and the quasi-static electric field applied. The analytical solution obtained is fast and easily computable in comparison with numerical estimations and is of special interest in radiofrequency; for instance, for the LC modeling in full-wave electromagnetic simulators in the design process of electronically tunable devices, such as microwave phase shifters or electronically steerable antennas for satellite communications. Subsequently, a comparison is made between numerical approaches (self-implemented shooting method) and the analytical formulas when varying the parameters of the LC, being demonstrated its usefulness. The average LC director is then obtained and used to form the full permittivity tensor that completely characterizes the electrical properties of the material. Finally, an electromagnetic simulation is carried out to show the capabilities of the LC as a tunable phase shifter. It is shown that only 5 cm of a commercial 200-mm LC mixture is necessary to achieve 360 of the maximum variable phase shift at the 30-GHz bandThis work was supported in part by the Spanish Research and Development National Program under Project TIN2016-75097-P, and in part by the Ministerio de Economía under Project TEC2017-85529-C3-1-R

N,N′-Bis(4-amino­benz­yl)oxalamide

In the title compound, C16H18N4O2, the two carbonyl groups are in an anti­periplanar conformation with an O=C—C=O torsion angle of 173.86 (17)°. In the crystal, a pair of inter­molecular N—H⋯O hydrogen bonds, forming an R 2 2(10) ring motif, connect the mol­ecules into an inversion dimer. The dimers are further linked by N—H⋯N and C—H⋯π inter­actions, forming a zigzag chain along the b axis