Precise determination of anomalous scattering factors of Ge by using X-ray resonant scattering

Variations of peak position of the rocking curve in the Bragg case are measured from a Ge thin crystal near the K-absorption edge. The variations are caused by a phase change of the real part of the atomic scattering factor. Based on the measurement, the values of the real part are determined with an accuracy of better than 1%. The values are the most reliable ones among those reported values so far as they are directly determined from the normal atomic scattering factors.

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.

Exploitation and reproduction of the spotted eagle ray (Aetobatus narinari) in the Los Frailes Archipelago, Venezuela

We studied a small artisanal fishery for the spotted eagle ray (Aetobatus narinari) off Margarita Island in northeastern Venezuela. We analyzed data from 413 fishing trips directed at A. narinari over a 29-month sampling period (August 2005–December 2007). These trips yielded 55.9 metric tons and 1352 individuals from which a subsample of 846 females and 321 males was used for biological data. Maximum fishing effort and landings occurred between February and May, and catch per unit of effort was highest between December and February and between July and October with an overall average of 3 individuals and 133 kg per trip. The overall sex ratio was significantly different from 1:1 with a predominance of females. Females ranged in size with disc widths (DW) from 64 to 226 cm. Males ranged in size between 97 and 190 cm DW. There was no statistically significant difference between male and female length-weight relationships. Mean fecundity was estimated at 3.09 embryos per female, and the largest embryo measured 44.5 cm DW. Females in different maturity stages were found in all months, except November 2007, the month when all females were immature. Postgravid females occurred mainly during the periods of January–May and July–October. Mean length (L50) at maturity was estimated at 129.2 cm DW for males and 134.9 cm DW for females. This study provides much needed information on the biology and life history of A. narinari for the management of an intensive, directed, small-scale fishery for this little known species in northeastern Venezuela.