NWChem: Past, present, and future

Specialized computational chemistry packages have permanently reshaped the landscape of chemical and materials science by providing tools to support and guide experimental efforts and for the prediction of atomistic and electronic properties. In this regard, electronic structure packages have played a special role by using first-principle-driven methodologies to model complex chemical and materials processes. Over the past few decades, the rapid development of computing technologies and the tremendous increase in computational power have offered a unique chance to study complex transformations using sophisticated and predictive many-body techniques that describe correlated behavior of electrons in molecular and condensed phase systems at different levels of theory. In enabling these simulations, novel parallel algorithms have been able to take advantage of computational resources to address the polynomial scaling of electronic structure methods. In this paper, we briefly review the NWChem computational chemistry suite, including its history, design principles, parallel tools, current capabilities, outreach, and outlook.

Deformable primary mirror for a space telescope

A 4-m aperture deformable primary mirror has been designed with the mirror and its supports integrated into a single structure. The integrated active mirror's minimal weight makes it desirable for a space telescope as well as a terrestrial application. Utilizing displacement actuators instead of force actuators, the active controls at the mirror's surface include normal position control and slope control in both the radial and tangential directions at each of forty control points. Influence functions for each of the controls are nearly independent, reducing the complexity of the control system. Experiments with breadboard models verify the structural concept and the techniques used in the finite element method of computer structural analysis. This paper describes the results of finite element analyses.

Dysplasia and cytologic findings in 4,589 young women enrolled in diethylstilbestrol-adenosis (DESAD) project

This report presents the cytologic findings and the rates of dysplasia for 4,589 young women enrolled in the National Cooperative Diethylstilbestrol-Adenosis (DESAD) Project. Mucinous columnar cells and/or metaplastic squamous cells with or without mucinous droplets were encountered in 22% of vaginal scrape smears from all diethylstilbestrol (DES)-exposed participants identified by review of prenatal records and in 43% of women in whom vaginal epithelial changes (VEC) were observed by colposcopy or by iodine staining. The frequency of cellular findings in the vaginal scrape smears was closely related to the timing of the administration of the DES to the mother. With increasing age of the daughters, the overall frequencies of both the mucinous and metaplastic cells decreased; relative to each other, an increasing proportion was metaplastic squamous cells. These data suggest that, as the women grow older, vaginal adenosis regresses by the process of squamous metaplasia. Endometrial type cells were found in 2% of vaginal scrape smears. Their cyclical occurrence during the menstrual cycle and lack of correlation with the presence of VEC indicated an origin from the uterine corpus rather than the tuboendometrial type of adenosis. Squamous cell dysplasia of the vagina and cervix was detected by biopsy or scrape smear specimens in 1.8% of DES-exposed women in the record review group. The rate of unexposed women was twice as high. In general, the rates of dysplasia were higher in the cervix than vagina, and the more severe degrees of dysplasia were encountered only in those women who were referred to the DESAD Project or who themselves requested entry. Four patients who were referred or who themselves requested entry were found to have clear cell adenocarcinoma of the vagina. The vaginal smear provided the first clue to the presence of an abnormality in three of them.

Elastic deformation of lightweight mirrors

Results of analytical and experimental studies on the elastic deformation of lightweight mirrors under various support conditions are presented and compared. The analytical results were obtained using the finite-element method, which employs elements having stretching, bending, and twisting capability. Both structural deformation and deviation from the best-fit sphere are shown to be dependent upon cell-wall thickness and generally independent of cell shape. This suggests that the choice of cell pattern would be governed by ease of fabrication rather than by structural action, provided that the cell size is made sufficiently small to prevent local waffling.

Soft-tissue calcification induced by rare earth metals and its prevention by sodium pyrophosphate

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