David Sayre

David Sayre ( born March 2, 1924 in New York City; † 23 February 2012) was an American crystallographer, computer scientists and physicists.

Life and work

Sayre graduated from Yale University with a bachelor's degree 1943. 1944 / 45 he worked at the Radiation Laboratory at MIT on radar. After the war he continued his studies at Auburn University with a master's degree in 1948 continued, turned to crystallography and received his doctorate in 1951 with Dorothy Hodgkin at Oxford University.

In 1952, he developed an equation named after him, which was one of the foundations of direct methods in crystallography - it allows to obtain probable values ​​for the phase from the X-ray diffraction pattern. Another work from 1952 is regarded as one of the bases for the developed from the 1980s techniques of Coherent Diffraction Imaging ( CDI). In the work, he turned to findings by Claude Shannon ( Nyquist-Shannon sampling theorem ) to the phase problem in X-ray crystallography and showed that the solution of the problem is carried by higher resolution of the diffraction image ( higher resolution standard than the Bragg reflections ).

A program that Sayre wrote by X-ray crystallography at the University of Pennsylvania as part of the structure determination, caught the attention of John W. Backus, who picked him in 1956 to IBM, where he was one of ten programmers who worked on the original Fortran code. He was assistant manager of the Fortran Development Group and later corporate director of programming. In the 1960s, he headed the Programming Research Group and developed the first operating system with virtual memory management at IBM. In M44/M44X-Projekt IBM time-sharing and virtual memory concepts have been tested in the mid- 1960s. Sayre came with his team to the conclusion that virtual memory was superior to the best hand-knitted by programmers overlay structures. These experiments eliminated the lingering doubts of computer system architects and software engineers at the virtual memory concept.

In 1971, he suggested the use of the then developed just for chip production electron beam lithography for the production of Fresnel zone plates for X-ray microscopes. His idea was realized in the 1980s. One of his doctoral students ( Wenbing Yun ) established for this purpose a company Xradia. After spending 1972/73 in Oxford at Dorothy Hodgkin to Sayre turned back to the X-ray diffraction and the development of X-ray microscopes, first in the laboratory and later after his retirement from IBM at the synchrotron radiation source National Synchrotron Light Source at Brookhaven National Laboratory. Sayre remained until 1990 when IBM and was an adjunct professor at the State University of New York at Stony Brook.

In 1980, realized he that with the X-rays from synchrotron sources, his ideas can be realized from 1952 to diffraction images with higher resolution for the solution of the phase problem and he participated then in the development of Coherent Diffraction Imaging ( CDI) or Diffraction Microscopy. He worked there together with his students, Henry Chapman and John Miao.

His wife, Anne Sayre, whom he met at Oxford, and in 1947 married, wrote due to his acquaintance with Rosalind Franklin in the 1950s, the book Rosalind Franklin and DNA. A motive was going to correct the vision of James D. Watson in his book Double Helix, which systematically downplayed Rosalind Franklin's role.

In 1983 he was president of the American Crystallographic Association, whose Fankuchen Award he received in 1989. For his contributions to crystallography, he received the 2008 Ewald Prize of the International Union of Crystallography.