Study on the layer structure of W/C multilayers deposited by magnetron sputtering using x-ray reflectivity

A study on the layer structure of W/C multilayers deposited by magnetron sputtering is reported. In the study, soft x-ray resonant reflectivity and hard x-ray grazing incidence reflectivity of the W/C multilayers were measured. The imperfections at the interface such as interdiffusion and formation of compounds were dealt with by two methods. On analyzing the experimental results, we found that the incorporation of an interlayer was a more suitable method than the traditional statistical method to describe the layer structure of a W/C system we fabricated. The optical constants of each layer at a wavelength of 4.48 nm were also obtained from the analysis. Copyright (C) 2008 John Wiley & Sons, Ltd.

C@rol: Herramienta Web que aplica un nuevo método para la mejora de la efectividad de grupos de estudiantes a través de la identificación de roles en entornos de aprendizaje colaborativo asistido por ordenador

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Estudio de una serie musteriense de La Quina (Charente, Francia): el ejemplo de la trinchera C (excavaciones DR. L. y G. Henri-Martin)

[ES] El análisis de una serie industrial correspondiente a los cinco niveles arqueológicos de la trinchera C de La Quina (Charente, Francia), proveniente de las excavaciones del Dr. L. Henri-Martin y de G. Henri-Martin, pone de manifiesto, junto a la caracterización del conjunto estratigráfico por la presencia de raederas, el progresivo incremento de los denticulados en el devenir temporal. Este hecho asociado a otros particulares fenómenos secundarios (en el alargamiento de las formas, en la tipología de las raederas, en la elaboración del retoque, ... ) traducen una complicación diacrónica creciente en la dinámica de este complejo musteroide, presagiando, quizás, su relativa afinidad con el proceso leptolitizante de las series industriales evolucionadas del Paleolítico medio.

Distribution and life history of two diminutive flatfishes, Citharichthys gymnorhinus and C. cornutus (Pleuronectiformes: Paralichthyidae), in the western North Atlantic

Citharichthys cornutus and C. gymnorhinus, diminutive flatfishes inhabiting continental shelves in the western Atlantic Ocean, are infrequently reported and poorly known. We identified 594 C. cornutus in 56 different field collections (68–287 m; most between 101–200 m) off the eastern United States, Bahamas, and eastern Caribbean Sea. Historical records and recently captured specimens document the northern geographic range of adults on the shelf off New Jersey (40°N, 70°W). Citharichthys cornutus measured 17.2–81.3 mm standard length (SL); males (20.0–79.1 mm SL) and females (28.0–81.3 mm SL) attain similar sizes (sex could not be determined for fish <20 mm SL). Males reach nearly 100% maturity at ≥60 mm SL. The smallest mature females are 41.5 mm SL, and by 55.1 mm SL virtually all are mature. Juveniles are found with adults on the outer shelf. Only 214 C. gymnorhinus were located in 42 different field collections (35–201 m, with 90% between 61 and 120 m) off the east coast of the United States, Bahamas, and eastern Caribbean Sea. Adults are found as far north as the shelf off Cape Hatteras, NC (35°N, 75°W). This diminutive species (to 52.4 mm SL) is among the smallest flatfishes but males (n=131; 20.3–52.4 mm SL) attain a slightly larger maximum size than that of females (n=58; 26.2–48.0 mm SL). Males begin to mature between 29 and 35 mm SL and reach 100% maturity by 35–40 mm SL. Some females are mature at 29 mm SL, and all females >35.1 mm SL are mature. Overlooked specimens in museum collections and literature enabled us to correct long-standing inaccuracies in northern distributional limits that appear in contemporary literature and electronic data bases for these species. Associated locality-data for these specimens allow for proper evaluation of distributional information for these species in relation to hypotheses regarding shifts in species ranges due to climate change effects.

Técnicas de metalistería en una moneda romana del siglo 1 d. C.

[ES] Se analiza un sestercio de Nerón usado como elemento ornamental. Un artesano hizo en el reverso de la moneda algunos radios curvos y cinco agujeros. En el artículo se hacen una serie de consideraciones sobre la realización de este inusual trabajo y su posible función. Por otro lado, también se examinan ciertos aspectos de los usos ornamentales de la moneda y la evaluación moral de la figura de Nerón.

Evolutionary associations between sand seatrout (Cynoscion arenarius) and silver seatrout (C. nothus) inferred from morphological characters, mitochondrial DNA, and microsatellite markers

The evolutionary associations between closely related fish species, both contemporary and historical, are frequently assessed by using molecular markers, such as microsatellites. Here, the presence and variability of microsatellite loci in two closely related species of marine fishes, sand seatrout (Cynoscion arenarius) and silver seatrout (C. nothus), are explored by using heterologous primers from red drum (Sciaenops ocellatus). Data from these loci are used in conjunction with morphological characters and mitochondrial DNA haplotypes to explore the extent of genetic exchange between species offshore of Galveston Bay, TX. Despite seasonal overlap in distribution, low genetic divergence at microsatellite loci, and similar life history parameters of C. arenarius and C. nothus, all three data sets indicated that hybridization between these species does not occur or occurs only rarely and that historical admixture in Galveston Bay after divergence between these species was unlikely. These results shed light upon the evolutionary history of these fishes and highlight the genetic properties of each species that are influenced by their life history and ecology.