A fast-Fourier-transform method of topography and interferometry is proposed. By computer processing of a noncontour type of fringe pattern, automatic discrimination is achieved between elevation and depression of the object or wave-front form, which has not been possible by the fringe-contour-generation techniques. The method has advantages over moire topography and conventional fringe-contour interferometry in both accuracy and sensitivity. Unlike fringe-scanning techniques, the method is easy to apply because it uses no moving components.

Fourier-transform method of fringe-pattern analysis for computer-based topography and interferometry

I read this book the same weekend that the Packers took on the Rams, and the experience of the latter event, obviously, colored my judgment. Although I abhor anything that smacks of being a handbook (like, \"How to Earn a Merit Badge in Neurosurgery\") because too many volumes in biomedical science already evince a boyscout-like approach, I must confess that parts of this volume are fast, scholarly, and significant, with certain reservations. I like parts of this well-illustrated book because Dr. Sj6strand, without so stating, develops certain subjects on technique in relation to the acquisition of judgment and sophistication. And this is important! So, given that the author (like all of us) is somewhat deficient in some areas, and biased in others, the book is still valuable if the uninitiated reader swallows it in a general fashion, realizing full well that what will be required from the reader is a modulation to fit his vision, propreception, adaptation and response, and the kind of problem he is undertaking. A major deficiency of this book is revealed by comparison of its use of physics and of chemistry to provide understanding and background for the application of high resolution electron microscopy to problems in biology. Since the volume is keyed to high resolution electron microscopy, which is a sophisticated form of structural analysis, but really morphology in a modern guise, the physical and mechanical background of The instrument and its ancillary tools are simply and well presented. The potential use of chemical or cytochemical information as it relates to biological fine structure , however, is quite deficient. I wonder when even sophisticated morphol-ogists will consider fixation a reaction and not a technique; only then will the fundamentals become self-evident and predictable and this sine qua flon will become less mystical. Staining reactions (the most inadequate chapter) ought to be something more than a technique to selectively enhance contrast of morphological elements; it ought to give the structural addresses of some of the chemical residents of cell components. Is it pertinent that auto-radiography gets singled out for more complete coverage than other significant aspects of cytochemistry by a high resolution microscopist, when it has a built-in minimal error of 1,000 A in standard practice? I don't mean to blind-side (in strict football terminology) Dr. Sj6strand's efforts for what is \"routinely used in our laboratory\"; what is done is usually well done. It's just that …

Methods in Enzymology.

A self-scanned 1024 element photodiode array and minicomputer are used to measure the phase (wavefront) in the interference pattern of an interferometer to lambda/100. The photodiode array samples intensities over a 32 x 32 matrix in the interference pattern as the length of the reference arm is varied piezoelectrically. Using these data the minicomputer synchronously detects the phase at each of the 1024 points by a Fourier series method and displays the wavefront in contour and perspective plot on a storage oscilloscope in less than 1 min (Bruning et al. Paper WE16, OSA Annual Meeting, Oct. 1972). The array of intensities is sampled and averaged many times in a random fashion so that the effects of air turbulence, vibrations, and thermal drifts are minimized. Very significant is the fact that wavefront errors in the interferometer are easily determined and may be automatically subtracted from current or subsequent wavefrots. Various programs supporting the measurement system include software for determining the aperture boundary, sum and difference of wavefronts, removal or insertion of tilt and focus errors, and routines for spatial manipulation of wavefronts. FFT programs transform wavefront data into point spread function and modulus and phase of the optical transfer function of lenses. Display programs plot these functions in contour and perspective. The system has been designed to optimize the collection of data to give higher than usual accuracy in measuring the individual elements and final performance of assembled diffraction limited optical systems, and furthermore, the short loop time of a few minutes makes the system an attractive alternative to constraints imposed by test glasses in the optical shop.

Digital wavefront measuring interferometer for testing optical surfaces and lenses

Supported Catalysts Weiting Yu,† Marc D. Porosoff,† and Jingguang G. Chen*,†,‡,§ †Catalysis Center for Energy Innovation, Department of Chemical and Bimolecular Engineering, University of Delaware, Newark, Delaware 19716, United States ‡Department of Chemical Engineering, Columbia University, New York, New York 10027, United States Chemistry Department, Brookhaven National Laboratory, Upton, New York 11973, United States

Review of Pt-based bimetallic catalysis: from model surfaces to supported catalysts.

The possibility of using sub-micrometer polymeric stomatocytes is investigated to effectuate confined crystallization of inorganic compounds These bowl-shaped polymeric compartments facilitate confined crystallization while their glassy surfaces provide their crystalline cargos with convenient shielding from the electron beam's harsh effects during transmission electron microscopy experiments Stomatocytes host the growth of a single nanocrystal per nanocavity, and the electron diffraction experiments reveal that their glassy membranes do not interfere with the diffraction patterns obtained from their crystalline cargos Therefore, it is expected that the encapsulation and crystallization within these compartments can be considered as a promising template (nanovials) that hold and protect nanocrystals and protein clusters from the direct radiation damage before data acquisition, while they are examined by modern crystallography methodologies such as serial femtosecond crystallography

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Sub‐Micron Polymeric Stomatocytes as Promising Templates for Confined Crystallization and Diffraction Experiments

The theoretical fundamentals of extended X-ray absorption fine-structure (EXAFS) spectroscopy are discussed. This method makes it possible to obtain short-range order parameters for multicomponent amorphous and quasicrystalline media with a high accuracy. Methods of analysis of EXAFS spectra with allowance for the effects of multiple scattering are described. Experimental setups implementing EXAFS spectroscopy on synchrotron radiation beams are considered and the requirements on monochromatization of radiation beams are given. A brief description of the energy-dispersive EXAFS spectrometer at the Kurchatov Synchrotron Radiation Source is given. The results of experimental investigations of tungsten and molybdenum oxides and fullerides are reported.

Development of methods of EXAFS spectroscopy on synchrotron radiation beams: Review

A method of analysis of curves for diffraction reflection from crystals with a disturbed surface layer is developed. It allows to determine, directly from experimental data, the integral characteristics of the disturbed layer, such as the thickness of the disturbed layer, Leff, mean change in the interplanar spacings along the layer and so on. This method is illustrated by an example of analysis of curves of reflection from diffuse layers of silicon for different orders of reflection.



Eine Analysenmethode fur Beugungsreflexion von Kristallen mit einer gestorten Oberflachenschicht wird entwickelt. Sie erlaubt eine direkte Bestimmung der integralen Charakteristiken der gestorten Schicht, wie Dicke der gestorten Schicht Leff, mittlere Anderung der Abstande zwischen den Ebenen auf der Schicht usw., direkt aus den experimentellen Daten. Diese Methode wird mit einem Beispiel von Reflexionskurven von diffusen Siliziumschichten fur verschiedene Reflexionsordnungen illustriert.

X‐ray diffraction in a perfect crystal with disturbed surface layer

The physical nature, potentialities, and prospects of application of a new method of studying the structure of crystals and thin surface layers is discussed. It is based on recording secondary radiations such as external and internal photoelectron emission, as well as x-ray fluorescence, under conditions of dynamic x-ray diffraction in single crystals, in which the intensity of the radiation field in the crystal reproduces the periodicity of the crystal lattice in the form of a standing wave along the diffraction vector. The method allows one to measure the absolute displacements of atomic planes in the crystal in fractions of an Angstrom unit, and also to determine the degree of order in the arrangement of atoms in the surface layer. In addition to presenting the history of the problem and reviewing the most important studies published in this field in the past twenty years, the problems of the theory and the experimental technique of the method of standing x-ray waves are presented in considerable detail.

X-ray standing waves—a new method of studying the structure of crystals

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X-ray-standing-wave-modulated electron emission near absorption edges in centrosymmetric and noncentrosymmetric crystals

The paper presents the results of studying the acoustic characteristics of special X-ray acousto-optical elements designed for precision control of X-ray beam parameters with time resolution. X-ray measurements revealed a number of specific features of oscillations of X-ray acoustic elements not exhibited in standard electromechanical measurements. The existence of these features is confirmed by numerical calculations computations of the acoustic fields in this type of elements.

M. V. Kovalchuk

Papers

Development of methods of EXAFS spectroscopy on synchrotron radiation beams: Review

X‐ray diffraction in a perfect crystal with disturbed surface layer

X-ray standing waves—a new method of studying the structure of crystals

X-ray-standing-wave-modulated electron emission near absorption edges in centrosymmetric and noncentrosymmetric crystals

X-ray acoustic resonators for controlling the spatial characteristics of X-radiation