INSTRUMENTAL ANALYSIS

仪器分析

• 批准号: 3853604
• 负责人: G H WEISS
• 金额: --
• 依托单位: CENTER FOR INFORMATION TECHNOLOGY
• 依托单位国家: 美国
• 资助国家: 美国
• 起止时间: 至
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/3853604
• 关键词: X ray crystallography; biomedical equipment; computer data analysis; mathematical model

In past years we have derived an exact probability density for the three- phase invariant which is a widely used tool in direct methods of phase determination in crystallography. The numerical calculation of this function requires a nearly prohibitive use of computer time. Consequently numerical techniques have been developed which allow one to find accurate approximations to the exact results with minimal computing effort, and which are far more accurate than presently available approximations in crystallography. These have been applied to the P1 space group. Calculations are currently in progress to find numerical values of the corresponding probability density for the P2 space group. Initial measurements have been made of background noise in crystallographic measurements. These show that the usually made assumption of a Poisson distribution of the noise is only accurate at large scattering angles, but at lower ones a combination of Poisson distributions is required to characterize the data. Experiments have been initiated to see whether this has a significant effect on structure determination.

在过去的几年里，我们已经得出了三个的精确概率密度： 相位不变量是直接相位法中广泛使用的工具 晶体学测定。 这个数值计算 功能需要几乎禁止使用计算机的时间。 最后 数值技术已经发展起来，可以让人们找到准确的 以最少的计算工作量获得精确结果的近似值，以及 这比目前可用的近似值要准确得多 晶体学。 这些已应用于 P1 空间群。 目前正在进行计算，以找到该值的数值 P2 空间群对应的概率密度。 已对晶体学中的背景噪声进行了初步测量 测量。 这些表明通常采用的泊松假设 噪声的分布仅在大散射角时才准确，但是 在较低的情况下，需要泊松分布的组合 表征数据。 实验已经开始，看看这是否 对结构测定有显着影响。