Visible luminescence in Yb3+-doped gadolinium gallium garnets

In this paper, some results on visible luminescence performed on Yb3+-doped gadolinium gallium garnets under 165 and 940 nm excitation were presented. The upconversion luminescence was ascribed to Yb3+ cooperative luminescence and the presence of rare earth impurity ions. The gain cross-sections of Yb:GGG crystal as a function of excited-state population fraction P were studied. Emission spectra under 165 nm at 20 K showed there was no charge transfer luminescence in Yb:GGG. (c) 2006 Elsevier B.V. All rights reserved.

气相传输平衡法在Sr^2＋：α-BBO衬底上制备β-BBO薄膜的研究

采用气相传输平衡技术在掺Sr^2＋的α-BBO（001）衬底上制备了β-BBO薄膜，研究了粉料配比、VTE处理温度以及恒温时间对薄膜质量的影响。结果表明，在适当的粉料配比、VTE处理温度以及恒温时间下，在Sr^2＋：α-BBO晶片表层制备呈c轴高度择优取向的、没有第二相物质的β-BBO薄膜，其双晶摇摆曲线半峰宽值FWHM为1000＂，显示出β-BBO薄膜较好的结晶质量。并对气相传输平衡技术制备β-BBO薄膜的机理进行了初步的探讨。

Evaluation of rockfish abundance in untrawlable habitat: combining acoustic and complementary sampling tools

Rockfishes (Sebastes spp.) are an important component of North Pacific marine ecosystems and commercial fisheries. Because the rocky, high-relief substrate that rockfishes often inhabit is inaccessible to standard survey trawls, population abundance assessments for many rockfish species are difficult. As part of a large study to classify substrate and compare complementary sampling tools, we investigated the feasibility of using an acoustic survey in conjunction with a lowered stereo-video camera, a remotely operated vehicle, and a modified bottom trawl to estimate rockfish biomass in untrawlable habitat. The Snakehead Bank south of Kodiak Island, Alaska, was surveyed repeatedly over 4 days and nights. Dusky rockfish (S. variabilis), northern rockfish (S. polyspinis), and harlequin rockfish (S. variegatus) were the most abundant species observed on the bank. Backscatter attributed to rockfish were collected primarily near the seafloor at a mean height off the bottom of 1.5 m. Total rockfish backscatter and the height of backscatter off the bottom did not differ among survey passes or between night and day. Biomass estimates for the 41 square nautical-mile area surveyed on this small, predominantly untrawlable bank were 2350 metric tons (t) of dusky rockfish, 331 t of northern rockfish, and 137 t of harlequin rockfish. These biomass estimates are 5–60 times the density estimated for these rockfish species by a regularly conducted bottom trawl survey covering the bank and the surrounding shelf. This finding shows that bottom trawl surveys can underestimate the abundance of rockfishes in untrawlable areas and, therefore, may underestimate overall population abundance for these species.

Charge and spin transport in nanoscale devices

137 p.

Análisis de los factores relacionados con los niveles óseos periimplantarios en senos maxilares injertados

137 p.