Structural evaluation of polycrystalline silicon thin films by hot-wire-assisted PECVD

Tungsten wires were introduced into a plasma-enhanced chemical vapor deposition (PECVD) system as a catalyzer: we name this technique 'hot-wire-assisted PECVD' (HW-PECVD). Under constant deposition pressure (p(g)), gas flow ratio and catalyzer position, the effects of the hot wire temperature (T-f) on the structural properties of the poly-Si films have been characterized by X-ray diffraction (XRD), Raman scattering and Fourier-transform infrared (FTIR) spectroscopy. Compared with conventional PECVD, the grain size, crystalline volume fraction (X-e) and deposition rate were all enhanced when a high T-f was used. The best poly-Si film exhibits a preferential (220) orientation, with a full width at half-maximum (FWHM) of 0.2 degrees. The Si-Si TO peak of the Raman scattering spectrum is located at 519.8 cm(-1) with a FWHM of 7.1 cm(-1). The X-c is 0.93. These improvements are mainly the result of promotion of the dissociation of SiH4 and an increase in the atomic H concentration in the gas phase. (C) 2001 Elsevier Science B.V. All rights reserved.

两种聚砜预聚物和多嵌段聚合物的合成及形态结构

以双酚A、酚酞和4，4'-二氯二茉砜为单体，合成了双酚A型聚砜和酚酞型聚砜两系列不同分子量的预聚物。将这两系列预聚物作为硬段，以不同分子量的聚氧化丙烯或聚氧化丙烯-聚二甲基硅氧烷作为软段，以二异氰酸酯二苯甲烷作为硬段和软段间的连接桥，合成了硬、软段分子量不同的双酚A型聚砜-聚氧化丙烯多嵌段聚合物、双酚A型聚砜-（聚氧化丙烯-聚二甲基硅氧烷）多嵌段聚合物的酚酞型聚砜-聚氧化丙烯多嵌段聚合物。经红外光谱分析、分子量测定和粘度测定等表征，确认产物与预想结果相符。用示差扫描量热仪、扭辨分析仪和电子显微镜研究了硬段预聚物和多嵌段聚合物的形态结构及性能。硬段预聚物在实验温度范围（-30到250 ℃）内，具有三种转变，分别为局部短程有序（60到70 ℃）的破坏，玻璃化转变，玻璃化温度与分子量的关系如下式所示：双酚A型聚砜 T_g = 462 - 8.07 * 10~4/M-bar 酚酞型聚砜 Tg = 519 - 8.33 * 10~4/M-bar和较大范围的长程有序性的解离。在双酚A型聚砜-聚氧化丙烯多嵌段聚合物体系中，当硬段分子量固定在1500时，多嵌段聚合物的形态结构随软段的分子量降低由两相结构（软段分子量≥1000）变成为单相结构（软段分子量为450）。当软段分子量固定为2000时，多嵌段聚合物的形态结构随硬段的分子量增加由单相结构（硬段分子量为700）变为两相结构（硬段分子量≥1500）。双酚A型聚砜-（聚氧化丙烯-聚二甲基硅氧烷）多嵌段聚合物均显示两相结构（软段分子量2400，硬段分子量≥700）。在硬段分子量增加到3900就发生相倒转，软段变为分散相，硬段成为连续相。酚酞型聚砜-聚氧化丙烯多嵌段聚合物，当固定分子量为2000时，硬段分子量在本工作的变化范围内，850至1900，所得产物均为两相结构。

Structural evaluation of polycrystalline silicon thin films by hot-wire-assisted PECVD

Tungsten wires were introduced into a plasma-enhanced chemical vapor deposition (PECVD) system as a catalyzer: we name this technique 'hot-wire-assisted PECVD' (HW-PECVD). Under constant deposition pressure (p(g)), gas flow ratio and catalyzer position, the effects of the hot wire temperature (T-f) on the structural properties of the poly-Si films have been characterized by X-ray diffraction (XRD), Raman scattering and Fourier-transform infrared (FTIR) spectroscopy. Compared with conventional PECVD, the grain size, crystalline volume fraction (X-e) and deposition rate were all enhanced when a high T-f was used. The best poly-Si film exhibits a preferential (220) orientation, with a full width at half-maximum (FWHM) of 0.2 degrees. The Si-Si TO peak of the Raman scattering spectrum is located at 519.8 cm(-1) with a FWHM of 7.1 cm(-1). The X-c is 0.93. These improvements are mainly the result of promotion of the dissociation of SiH4 and an increase in the atomic H concentration in the gas phase. (C) 2001 Elsevier Science B.V. All rights reserved.

Aplicação de algoritmos genéticos na optimização de secções de vigas de betão armado

A generalidade dos problemas de ordem prática no domínio do dimensionamento das estruturas incluem variáveis discretas. Os métodos matemáticos tradicionais apresentam dificuldades na procura dos óptimos globais em problemas não lineares discretos. Os algoritmos genéticos constituem uma heurística eficaz na optimização de sistemas estruturais que envolvem variáveis discretas e contínuas. No presente trabalho, descreve-se uma metodologia que visa a optimização da forma geométrica da secção, do dimensionamento e colocação das armaduras em vigas de betão armado, com recurso a algoritmos genéticos. Apresenta-se um exemplo de aplicação da metodologia proposta.

Serum protein profile of hookworm infection in dogs

Hookworms are parasitic nematodes that cause anemia and intestinal infections in dogs, especially with large worm burdens. However, the serum protein profile of this parasitological disease is still poorly understood. The present study was design to evaluate 80 asymptomatic dogs (age; 8 months–2 years) to detect the presence of the hookworm thin-shelled, morulated eggs in faeces using faecal flotation and to evaluate the serum protein fractions determined by means of sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). Forty dogs had an elevated quantity of eggs in faeces (+++) (PD) and 40 dogs were healthy (HD). Infected dogs showed significant increases for IgG estimated concentrations (PD 1.79±0.8 g/dL and HD 1.44±0.72 g/dL, p= 0.04), for ceruloplasmin estimated concentrations (PD 19±15 mg/dL and HD 5±3.5 mg/dL, p=0.0001), for alpha 1-acid glycoprotein estimated concentrations (PD 31.4±17.9 mg/dL and HD 13.5±12.1 mg/dL, p=0.0001) and for a non-identified protein of 23 kDa estimated concentrations (PD 641.5±194.9 mg/dL and HD 519.8± 197.9 mg/dL, p=0.007). Dogs with hookworm infection showed significant differences in the serum protein profile when compared to healthy animals.

「住民参加」によるアフリカ熱帯雨林の保全と開発に向けて -- ガボン南西部ムカラバ・ドゥドゥ国立公園の事例から

アフリカ熱帯雨林とそこにすむ野生動物の保全は喫緊の国際課題であるが、政情不安や経済の停滞にくわえ、地域住民との軋轢が保全政策の大きな障害となっている。有効な保全体制を構築するためには、地域の社会的文脈をふまえ、地域コミュニティごとに固有の特徴と地域住民の多様性を理解することが重要である。そこで筆者は、ガボンの国立公園を対象に、地域コミュニティの歴史的・文化的背景および住民生活の実態について調べた。その結果、(1)地域コミュニティは、その歴史的・文化的背景により、出自や経歴が多様な人々から構成される流動的なものであること、(2)住民生活は、伝統的な自然資源利用を基盤としながらも、伐採事業や保全事業に強く影響を受けていることが明らかになった。一枚岩的な地域住民を前提とした「住民参加」概念を外部から当てはめるのではなく、地域社会の実態に即して内部からコミュニティを抽出し、それをもとに保全と開発事業を進める必要があるといえる。

Chemical composition of B-type supergiants in the OB 8, OB 10, OB 48, OB 78 associations of M 31

Absolute and differential chemical abundances are presented for the largest group of massive stars in M31 studied to date. These results were derived from intermediate resolution spectra of seven B-type supergiants, lying within four OB associations covering a galactocentric distance of 5-12 kpc. The results are mainly based on an LTE analysis, and we additionally present a full non-LTE, unified model atmosphere analysis of one star (OB 78-277) to demonstrate the reliability of the differential LTE technique. A comparison of the stellar oxygen abundance with that of previous nebular results shows that there is an off set of between similar to0.15-0.4 dex between the two methods which is critically dependent on the empirical calibration adopted for the R 23 parameter with [O/H]. However within the typical errors of the stellar and nebular analyses (and given the strength of dependence of the nebular results on the calibration used) the oxygen abundances determined in each method are fairly consistent. We determine the radial oxygen abundance gradient from these stars, and do not detect any systematic gradient across this galactocentric range. We find that the inner regions of M31 are not, as previously thought, very "metal rich". Our abundances of C, N, O, Mg, Si, Al, S and Fe in the M31 supergiants are very similar to those of massive stars in the solar neighbourhood.

The developmental character of cardiac autonomic responses to an acute noxious event in 4- and 8-month-old healthy infants

Heart rate (HR) has been widely studied as a measure of an individual's response to painful stimuli. It remains unclear whether changes in mean HR or the variability of HR are specifically related to the noxious stimulus (i.e. pain). Neither is it well understood how such changes reflect underlying neurologic control mechanisms that produce these responses, or how these mechanisms change during the first year of life. To study the changes in cardiac autonomic modulation that occur with acute pain and with age during early infancy, the relationship between respiratory activity and short-term variations of HR (i.e. respiratory sinus arrhythmia) was quantified in a longitudinal study of term born healthy infants who underwent a finger lance blood collection at 4 months of age (n = 24) and again at 8 months of age (n = 20). Quantitative respiratory activity and HR were obtained during baseline, lance, and recovery periods. Time and frequency domain analyses from 2.2-min epochs of data yielded mean values, spectral measures of low (0.04-0.15 Hz) and high (0.15-0.80 Hz) frequency power (LF and HF), and the LF/HF ratio. To determine sympathetic and parasympathetic cardiac activity, the transfer relation between respiration and HR was used. At both 4 and 8 months, mean HR increased significantly with the noxious event (p > 0.01). There were age-related differences in the pattern of LF, HF, and LF/HF ratio changes. Although these parameters all decreased (p > 0.01) at 4 months, LF and LF/HF increased at 8 months and at 8 months HF remained stable in response to the noxious stimulus. Transfer gain changes with the lance demonstrated a change from predominant vagal baseline to a sympathetic condition at both ages. The primary finding of this study is that a response to an acute noxious stimulus appears to produce an increase in respiratory-related sympathetic HR control and a significant decrease in respiratory-related parasympathetic control at both 4 and 8 months. Furthermore, with increasing age, the sympathetic and parasympathetic changes appear to be less intense, but more sustained.

Synthesis and thermal study of 8-hydroxy-quinoline derivatives of the alkaline Earth metals: I. Strontium complexes

Strontium complexes of 5,7-dibromo-, 5,7-dichloro-, 7-iodo- and 5-chloro-7-iodo-8-hydroxyquinoline were precipitated from an aqueous ammonia and acetone medium. The complexes obtained were Sr[(C9H4ONBr2)2]·2.5H 2O; Sr[(C9H4ONCl2)(OH)]·1.5H2O; Sr[(C9H5ONI)2]·5H2O and Sr[(C9H4ONICl)(OH)]·1.25H2O. The residues of their thermal decomposition were SrBr2; a mixture of SrCl2, SrCO3 and SrO3 SrCO3, and SrCO3, respectively. All were characterized by means of thermogravimetry, differential thermal analysis, complexometry with EDTA, atomic absorption spectroscopy, IR spectroscopy and X-ray diffraction. © 1999 Akadémiai Kiadó.