IMAGE ANALYSIS FOR STEM

STEM质量测量一直是我们计划的支柱。 几年前，A。史蒂文开发了一套程序来计算 根据测量的投影质量分布图的径向密度分布图 直接在STEM中。 这已经在许多项目中使用， 圆柱形或球形质量-自动程序（"AutoMass"） 用于颗粒定位、分类、对齐， 质量分析与球形或圆柱形密度分析，其中 这是一个很好的工具，广泛用于分析STEM数据。 几 这些因素推动了这一努力。 粒子选择可以通过 数学而不是主观的标准。 STEM中的粗采样 图像会给某些程序带来问题，降低分辨率， 但是可以在定制程序中容易地处理。 使用两个或更多 从同一像素多个记录的数据通道可以产生 簿记问题（例如，大角度减。 小角度信号 具有适当的厚度校正以给出氢映射）。 STEM信号中的各种小的非线性可以在 或者在处理期间。 我们已经调整了这些程序， 标准个人计算机（PCMass）。 并对此进行分析 提供给我们的许多用户谁没有图像处理 设施 第二个PC程序从 蛋白质数据库，从不同的方向进行预测， 这些像素与STEM图像像素，而查看不同的~nce 图像并计算RMS差。 小角散射曲线 可以被计算用于与中子或X射线数据进行比较。 stem图像 在过去一年里，我们的服务器上存档， 互联网或光盘。 PCMass程序还提供了一个 方便查看这些远程文件，并提供了沿着 图像数据。

STEM mass measurements have been a mainstay of our program. Several years ago A. Steven developed a set of programs to compute radial density profiles from the projected mass profile measured directly in the STEM. This has been used in many projects involving cylindrical or spherical symmetry-An automatic program ("AutoMass") was developed for particle location, classification, alignment, and mass analysis with spherical or cylindrical density analysis, where appropriate, and is used extensively for analyzing STEM data. Several factors motivated this effort. Particle selection can be by mathematical rather than subjective criteria. Coarse sampling in STEM images creates problems with some programs, degrading the resolution, but can be handled easily in a custom program. Using two or more channels of data recorded multancously from the same pixel may create bookkeeping problems (e.g., large angle minus . small angle signals with appropriate thickness corrections to give hydrogen mapping). Various small nonlinearities in STEM signals can be corrected before or during processing. We have adapted these programs to run on a standard personal computer (PCMass). This cost and makes analysis available to many of our users who do not have image processing facilities. A second Pc program imports 3-D x-ray structures from the Protein Data Bank, projects these in various directions and compares these pixel by pixel with a STEM image, while viewing the differ~nce image and computing'the RMS difference. Small-angle scattering curves can be computed for comparison to neutron or x-ray data. STEM images for the past year are archived on our server and available over Internet or on optical disk. The PCMass program also provides a convenient viewer for these remote files and is provided along with image data.