Group US Army military portrait including Dr. William Levison (top row, third from left); Schofield Barracks, Hawaii Portraits Groups Men

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U.S. Army Passover Seder; Hawaii Portraits Groups

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Dr. William Levison (seated, far left) with other U.S. Army medial doctors and nurses with Christmas Tree in background Portraits Groups

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Unterprima (eleventh grade) boys school class portrait Portraits Groups Men

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Writer Clara Michelson (second from left) seated at an outdoor table with three unidentified women and one unidentified man; Saint-Brevin-les-Pins, France Portraits Groups

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Strategies for collecting screen-less oscillation data

Screen-less oscillation photography is the method of choice for recording three-dimensional X-ray diffraction data for crystals of biological macromolecules. The geometry of an oscillation camera is extremely simple. However, the manner in which the reciprocal lattice is recorded in any experiment is fairly complex. This depends on the Laue symmetry of the reciprocal lattice, the lattice type, the orientation of the crystal on the camera and to a lesser extent on the unit-cell dimensions. Exploring the relative efficiency of collecting X-ray diffraction data for different crystal orientations prior to data collection might reduce the number of films required to record most of the unique data and the consequent amount of time required for processing these films. Here algorithms are presented suitable for this purpose and results are reported for the 11 Laue groups, different lattice types and crystal orientations often employed in data collection.

Approximation algorithm for maximum independent set in planar traingle-free graphs

The maximum independent set problem is NP-complete even when restricted to planar graphs, cubic planar graphs or triangle free graphs. The problem of finding an absolute approximation still remains NP-complete. Various polynomial time approximation algorithms, that guarantee a fixed worst case ratio between the independent set size obtained to the maximum independent set size, in planar graphs have been proposed. We present in this paper a simple and efficient, O(|V|) algorithm that guarantees a ratio 1/2, for planar triangle free graphs. The algorithm differs completely from other approaches, in that, it collects groups of independent vertices at a time. Certain bounds we obtain in this paper relate to some interesting questions in the theory of extremal graphs.

Portrait of David Baumgardt with Marie Zweig Portraits Groups

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Leo Baeck sitting on grass with Rudolf Seligsohn; Erzgebirge Portraits; Groups; Men

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Hannah Karminski speaking with Mrs. Neuhaus; Conference of Juedisches Frauenbundes; Duerkheim Portraits Groups Women

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Alice Salomon with students on the roof garden of the Sozialen Frauenschule Portraits Groups

Including Hilde Caro, Lotte Lipschitz and Ellen Milch

Albert Einstein with unidentified group; City College, New York Portraits Groups; Men

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