|Died||February 23, 2012 87) (aged|
|Alma mater|| Yale University |
|Known for|| Sayre equation |
Coherent diffraction imaging
|Fields|| X-ray crystallography |
|Institutions|| IBM |
Stony Brook University
|Doctoral advisor||Dorothy Hodgkin|
David Sayre (March 2, 1924 – February 23, 2012) was an American scientist, credited with the early development of direct methods for protein crystallography and of diffraction microscopy (also called coherent diffraction imaging). While working at IBM he was part of the initial team of ten programmers who created FORTRAN, and later suggested the use of electron beam lithography for the fabrication of X-ray Fresnel zone plates.
In crystallography, direct methods are a family of methods for estimating the phases of the Fourier transform of the scattering density from the corresponding magnitudes. The methods generally exploit constraints or statistical correlations between the phases of different Fourier components that result from the fact that the scattering density must be a positive real number.
Coherent diffractive imaging (CDI) is a “lensless” technique for 2D or 3D reconstruction of the image of nanoscale structures such as nanotubes, nanocrystals, porous nanocrystalline layers, defects, potentially proteins, and more. In CDI, a highly coherent beam of x-rays, electrons or other wavelike particle or photon is incident on an object.
A zone plate is a device used to focus light or other things exhibiting wave character. Unlike lenses or curved mirrors however, zone plates use diffraction instead of refraction or reflection. Based on analysis by Augustin-Jean Fresnel, they are sometimes called Fresnel zone plates in his honor. The zone plate's focusing ability is an extension of the Arago spot phenomenon caused by diffraction from an opaque disc.
The International Union of Crystallography awarded Sayre the Ewald Prize in 2008 for the "unique breadth of his contributions to crystallography, which range from seminal contributions to the solving of the phase problem to the complex physics of imaging generic objects by X-ray diffraction and microscopy(...)".
The International Union of Crystallography (IUCr) is an organisation devoted to the international promotion and coordination of the science of crystallography. The IUCr is a member of the International Council for Science (ICSU).
Sayre was born in New York City. He completed his bachelor's degree in physics at Yale University at the age of 19. After working at the MIT Radiation Laboratory, he earned his MS degree at Auburn University in 1948. In 1949, he moved to Oxford with his wife Anne Colquhoun, whom he had married in 1947. Sayre completed his doctoral studies in Dorothy Hodgkin's group in 1951. It is at this time that Sayre discovered the equation now named after him, based on the concept of atomicity. Although the key to most direct methods still in use today, Sayre did not share the 1985 chemistry Nobel prize awarded for their discovery. It is also around this time that Sayre, inspired by Claude Shannon's recent work, suggested in a short paper that the crystallographic phase problem could be solved more easily if one could measure intensities at a higher density than imposed by Bragg's law. This insight is widely seen as the initial spark that lead to recent lensless imaging techniques.
The City of New York, usually called either New York City (NYC) or simply New York (NY), is the most populous city in the United States. With an estimated 2018 population of 8,398,748 distributed over a land area of about 302.6 square miles (784 km2), New York is also the most densely populated major city in the United States. Located at the southern tip of the state of New York, the city is the center of the New York metropolitan area, the largest metropolitan area in the world by urban landmass and one of the world's most populous megacities, with an estimated 19,979,477 people in its 2018 Metropolitan Statistical Area and 22,679,948 residents in its Combined Statistical Area. A global power city, New York City has been described as the cultural, financial, and media capital of the world, and exerts a significant impact upon commerce, entertainment, research, technology, education, politics, tourism, art, fashion, and sports. The city's fast pace has inspired the term New York minute. Home to the headquarters of the United Nations, New York is an important center for international diplomacy.
Yale University is a private Ivy League research university in New Haven, Connecticut. Founded in 1701, it is the third-oldest institution of higher education in the United States and one of the nine Colonial Colleges chartered before the American Revolution. Yale consistently ranks among the top universities in the world.
The Massachusetts Institute of Technology (MIT) is a private research university in Cambridge, Massachusetts. The Institute is a land-grant, sea-grant, and space-grant university, with an urban campus that extends more than a mile (1.6 km) alongside the Charles River. The Institute also encompasses a number of major off-campus facilities such as the MIT Lincoln Laboratory, the Bates Center, and the Haystack Observatory, as well as affiliated laboratories such as the Broad and Whitehead Institutes. Founded in 1861 in response to the increasing industrialization of the United States, MIT adopted a European polytechnic university model and stressed laboratory instruction in applied science and engineering. It has since played a key role in the development of many aspects of modern science, engineering, mathematics, and technology, and is widely known for its innovation and academic strength, making it one of the most prestigious institutions of higher learning in the world.
Back in United States, David Sayre worked on structure determination of a carcinogen molecule in the lab of Peter Friedlander at the University of Pennsylvania in Philadelphia. The structure determination program he wrote for the IBM 701 attracted the attention of John Backus, who hired him to be part of the initial team of 10 programmers that developed the high-level programming language FORTRAN at IBM for the IBM 704 mainframe. Sayre remained at IBM until his retirement in 1990. In the early 1970s, Sayre became interested in X-ray microscopy. He suggested to use the newly developed electron beam lithography apparatus at IBM to produce Fresnel zone plates, a type of X-ray lens now widely used in Synchrotron facilities. In the '80s, he came back to the goal of achieving lensless imaging, which he pursued the rest of his life.
The University of Pennsylvania is a private Ivy League research university in Philadelphia, Pennsylvania. It is one of the nine colonial colleges founded prior to the Declaration of Independence and the first institution of higher learning in the United States to refer to itself as a university. Benjamin Franklin, Penn's founder and first president, advocated an educational program that trained leaders in commerce, government, and public service, similar to a modern liberal arts curriculum.
Philadelphia, known colloquially as Philly, is the largest city in the U.S. state and Commonwealth of Pennsylvania, and the sixth-most populous U.S. city, with a 2018 census-estimated population of 1,584,138. Since 1854, the city has had the same geographic boundaries as Philadelphia County, the most populous county in Pennsylvania and the urban core of the eighth-largest U.S. metropolitan statistical area, with over 6 million residents as of 2017. Philadelphia is also the economic and cultural anchor of the greater Delaware Valley, located along the lower Delaware and Schuylkill Rivers, within the Northeast megalopolis. The Delaware Valley's population of 7.2 million ranks it as the eighth-largest combined statistical area in the United States.
John Warner Backus was an American computer scientist. He directed the team that invented and implemented FORTRAN, the first widely used high-level programming language, and was the inventor of the Backus–Naur form (BNF), a widely used notation to define formal language syntax. He later did research into the function-level programming paradigm, presenting his findings in his influential 1977 Turing Award lecture "Can Programming Be Liberated from the von Neumann Style?"
Crystallography is the experimental science of determining the arrangement of atoms in crystalline solids. The word "crystallography" is derived from the Greek words crystallon "cold drop, frozen drop", with its meaning extending to all solids with some degree of transparency, and graphein "to write". In July 2012, the United Nations recognised the importance of the science of crystallography by proclaiming that 2014 would be the International Year of Crystallography. X-ray crystallography is used to determine the structure of large biomolecules such as proteins. Before the development of X-ray diffraction crystallography, the study of crystals was based on physical measurements of their geometry. This involved measuring the angles of crystal faces relative to each other and to theoretical reference axes, and establishing the symmetry of the crystal in question. This physical measurement is carried out using a goniometer. The position in 3D space of each crystal face is plotted on a stereographic net such as a Wulff net or Lambert net. The pole to each face is plotted on the net. Each point is labelled with its Miller index. The final plot allows the symmetry of the crystal to be established.
X-ray crystallography (XRC) is a technique used to determine the atomic and molecular structure of a crystal, in which the crystalline structure causes a beam of incident X-rays to diffract into many specific directions. By measuring the angles and intensities of these diffracted beams, a crystallographer can produce a three-dimensional picture of the density of electrons within the crystal. From this electron density, the mean positions of the atoms in the crystal can be determined, as well as their chemical bonds, their crystallographic disorder, and various other information.
Electron diffraction refers to the wave nature of electrons. However, from a technical or practical point of view, it may be regarded as a technique used to study matter by firing electrons at a sample and observing the resulting interference pattern. This phenomenon is commonly known as wave–particle duality, which states that a particle of matter can be described as a wave. For this reason, an electron can be regarded as a wave much like sound or water waves. This technique is similar to X-ray and neutron diffraction.
Paul Peter Ewald, FRS was a German crystallographer and physicist, a pioneer of X-ray diffraction methods.
An X-ray microscope uses electromagnetic radiation in the soft X-ray band to produce magnified images of objects. Since X-rays penetrate most objects, there is no need to specially prepare them for X-ray microscopy observations.
The Ewald sphere is a geometric construction used in electron, neutron, and X-ray crystallography which demonstrates the relationship between:
In physics, the phase problem is the problem of loss of information concerning the phase that can occur when making a physical measurement. The name comes from the field of X-ray crystallography, where the phase problem has to be solved for the determination of a structure from diffraction data. The phase problem is also met in the fields of imaging and signal processing. Various approaches have been developed over the years that attempt to solve it.
Electron crystallography is a method to determine the arrangement of atoms in solids using a transmission electron microscope (TEM).
The dynamical theory of diffraction describes the interaction of waves with a regular lattice. The wave fields traditionally described are X-rays, neutrons or electrons and the regular lattice, atomic crystal structures or nanometer scaled multi-layers or self arranged systems. In a wider sense, similar treatment is related to the interaction of light with optical band-gap materials or related wave problems in acoustics.
An X-ray microscope uses electromagnetic radiation in the soft X-ray band to produce images of very small objects.
Xuong Nguyen-Huu is a pioneer of protein crystallography technology. His research focuses on the development of novel methods, such as protein crystallography and cryo-electron microscopy, for the determination of protein structures and biological macromolecules.
Ptychography is a computational method of microscopic imaging. It generates images by processing many coherent interference patterns that have been scattered from an object of interest. Its defining characteristic is translational invariance, which means the interference patterns are generated by one constant function moving laterally by a known amount with respect to another constant function. The interference patterns occur some distance away from these two components, so that the scattered waves spread out and ‘fold into’ one another as shown in the figure.
X-ray lithography, is a process used in electronic industry to selectively remove parts of a thin film. It uses X-rays to transfer a geometric pattern from a mask to a light-sensitive chemical photoresist, or simply "resist," on the substrate. A series of chemical treatments then engraves the produced pattern into the material underneath the photoresist.
Hein Wagenfeld was a German theoretical and experimental physicist known for his work in electron and X-ray crystallography especially X-ray diffraction relating to absorption and the Borrmann effect. He was highly regarded for his commitment to international understanding and peace.
Zone axis, a term sometimes used to refer to "high-symmetry" orientations in a crystal, most generally refers to any direction referenced to the direct lattice of a crystal in three dimensions. It is therefore indexed with direct lattice indices, instead of with Miller indices.
3D X-ray diffraction (3DXRD) is a microscopy technique using hard X-rays to investigate the internal structure of polycrystalline materials in three dimensions. For a given sample, 3DXRD returns the shape, juxtaposition, and orientation of the crystallites ("grains") it is made of. 3DXRD allows investigating micrometer- to millimetre-sized samples with resolution ranging from hundreds of nanometers to micrometers. Other techniques employing X-rays to investigate the internal structure of polycrystalline materials include X-ray diffraction contrast tomography (DCT) and high energy X-ray diffraction (HEDM).
In crystallography, direct methods is a set of techniques used for structure determination using diffraction data and a priori information. It is a solution to the crystallographic phase problem, where phase information is lost during a diffraction measurement. Direct methods provides a method of estimating the phase information by establishing statistical relationships between the recorded amplitude information and phases of strong reflections.
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