在南非的核查

核实南非申报的核清单及其核武器计划的终止情况曾是一项复杂的任务。     

An automated, parallel processing approach to biomolecular sample preparation

Sample preparation for DNA and RNA assays is a prime candidate for laboratory automation. A novel, parallel processing device that performs the three separate liquid-handling functions necessary for such sample preparation-dispensing, pipetting, and pressurizing-is presented. The device comprises an array of fine nozzles connected by fluidic channels to automatically and precisely distribute flow between one source and an array of points. The design principles, as well as the experimental and computational methods used to develop the device, are described. Test results, including accuracy, uniformity, volume range, and timing, are presented. The functionality of the device is demonstrated by performing a solid-phase extraction of DNA with two types of microcolumns.     

Computed tomographic imaging of the coronary arterial tree-use of local tomography

It has been demonstrated previously (see E.L. Ritman and A.A. Bove, in State of the Art in Quantitative Coronary Arteriography, p.67-78, 1986) that coronary artery anatomy can be visualized using high-speed, volume-scanning X-ray CT (computed tomography). In the current study it is demonstrated that local image reconstruction (i.e. the reconstruction kernel is ~2(+) mm long), as distinct from more conventional global image reconstruction (i.e. 200(+) mm kernel length), has the advantage of reducing the need for operator interactive image processing. In addition, the local reconstruction algorithm eliminates the need for recording the X-ray projection data over the full transaxial extent of the thorax because it requires only the X-ray attenuation data over the region of the heart. This latter aspect reduces the dynamic range requirements for the sensors and could reduce total X-ray exposure.     

Color quantitation through image processing in dermatology

Classical color models and their applications to computer vision are reviewed. The performances of color quantitation from digitized images are compared with those derived from a chromameter. The color quantitation obtained from either digitized color slides or directly digitized images is proved to be more efficient than the conventional visual assessment of observers. A methodology is proposed for determining the specific color indices which are needed in dermatology. An application of this methodology is developed for designing a blanching quantitation index in order to replace the visual assessment during McKenzie tests.     

Small blaze angle gratings with various surface treatments for use in the extreme ultraviolet

Three replica gratings were made from a single master; two were epoxy overcoated with different thicknesses of gold, and one was replicated directly in gold. Their performance in EUV light at grazing incidence angles was measured and compared.     

非饱和水力传导系数的简易实验室测量方法

本文描述一种采用常规的实验装置在短时间内测量土层非饱和水力传导率的简易方法,称为"向上入渗法".这一方法基于在控制压力的条件下测量土的吸水量,从而来估算土层在湿润状态下的水力传导系数.将其结果与恒定加水量法、小增量压力变化法、一步法以及杰克逊理论模型的计算结果进行了比较.采用向上入渗法与采用恒定加水量法的结果很接近,但稍大于一步法而小于杰克逊理论模型的结果.这种测定方法限定负压值约为一米.     

计算机模拟扫描电镜颗粒边缘粗糙度外貌特征

各种石英颗粒表面特征的发育与否,是任何扫描电镜分析重建地质环境的基础,对于在石英颗粒表面获得的许多可见特征来说,虽然已有许多"清单"(Krinsley和Donahue,1968:Cater,1984),但是,专门检测技术的有效性还是一个争论的问题.由这类分析获得的最为重要的物理参数之一是边缘磨蚀,因为圆度值是一种发现于石英砂颗粒的主要形态特征.例如,1984年Goudie和Bull发现两类非洲沉积物之间的主要差异是,在深度风化剖面中总体缺乏边缘磨蚀颗粒,并以此为基础建立了该研究区的斜坡