Showing papers on "Resolution (electron density) published in 1976"
TL;DR: In this paper, a method for the measurement of the concentration of hydrogen versus depth in solids using the 1H+15N resonant nuclear reaction is discussed, which has a typical depth resolution of 50-100 A, can be used to a depth of several microns, and can measure hydrogen in concentrations of one part per thousand or greater.
Abstract: A method for the measurement of the concentration of hydrogen versus depth in solids using the 1H+15N resonant nuclear reaction is discussed. This method has a typical depth resolution of 50–100 A, can be used to a depth of several microns, and can measure hydrogen in concentrations of one part per thousand or greater.
341 citations
TL;DR: Estimates of the maximum resolutions obtainable with electrons and photons, consistent with structural survival of the specimen, are obtained, as are data on optimal operating conditions for microscopy with the two particles.
172 citations
172 citations
TL;DR: In this paper, a significantly increased resolution in the proton-coupled 13C NMR spectrum of MeI was achieved by 2-dimensional J spectroscopy, which was used for 2D MeI detection.
Abstract: A significantly increased resolution in the proton-coupled 13C NMR spectrum of MeI was achieved by 2-dimensional J spectroscopy. [on SciFinder (R)]
126 citations
TL;DR: The crystal structure analysis of a human Fc fragment was pursued to 3.5 A resolution and a complete model was built and refined into the isomorphous Fourier map, showing the immunoglobulin fold and the characteristic distribution of contact residues.
Abstract: The crystal structure analysis of a human Fc fragment was pursued to 3.5 A resolution and a complete model was built and refined into the isomorphous Fourier map. The CH2 and CH3 domains show the immunoglobulin fold, with CH3 being closely similar to CH1, but CH2 intermediate in structure between V and CH3. The carbohydrate is rigidly attached to CH2, covering the C face. CH3 dimerizes as CH1-CL, but CH2 has no contact to the second chain. Residues involved in the lateral CH3-CH3 and the longitudinal CH3-CH2 contact are conserved in Ig classes and sub-classes. In IgM and IgE the two C-terminal domains also show this characteristic distribution of contact residues.
117 citations
TL;DR: It turns out that such a short ER refutation of S n does exist, and the purpose of this note is to describe it and show briefly how it motivated the paper on feasibly constructive proofs.
Abstract: asserts intuitively that there is a one-one map from set of clauses must be inconsistent. Several years ago, Dick Karp (for one) noticed that there didn't seem to be any short (i.e. polynomial in n) resolution refutation of the set Sn, and posed the problem of trying to prove this. In fact, I believe the shortest resolution refutation known for S has n (n-l)(n+2)2 n-3 clauses, but no one has been able to prove a non-polynomial lower bound on an arbitrary resolution refutation of S n After reading Tseitin's paper [I] describing extended resolution (ER), the question arose whether there exists a short ER refutation of S n. It turns out that such a short refutation does exist, and it is the purpose of this note to describe it and show briefly how it motivated my paper [2] on feasibly constructive proofs.
97 citations
01 Jan 1976
TL;DR: A multitude of analytical techniques which incorporate an electron optical column in the probe-forming and/or image-forming system have been developed during the last twenty years as mentioned in this paper, including surface-sensitive techniques of Auger electron spectroscopy, thermionic emission microscopy and photoelectron microscopy; the analysis of bulk and thin specimens by X-ray or electron spectrometry.
Abstract: A multitude of analytical techniques which incorporate an electron optical column in the probe-forming and/or image-forming system have been developed during the last twenty years. These include the surface-sensitive technique of Auger electron spectroscopy, thermionic emission microscopy and photoelectron microscopy; the analysis of “bulk” specimens by electron probe microanalysis and the analysis of “thin” specimens by X-ray or electron spectrometry. Auger electron spectroscopy has been developed into a powerful tool for the chemical analysis of surface layers (Chang, 1973). It is particularly sensitive to the light elements C, H and O and has a spatial resolution for analysis of a few microns. Thermionic emission microscopy and photoelectron microscopy are useful techniques for studying phase distributions at a resolution in the micron range (Wegmann, 1972; Kinsman and Aaronson, 1972) but they cannot be classified as techniques of quantitative chemical analysis. Electron probe microanalysis is established as a standard tool for the analysis of bulk specimens, and it has made a very important contribution to mineralogy. The spatial resolution for analysis is a few microns with limits of detection, typically, 10–50 ppm. Procedures for carrying out quantitative analyses are well established and have been discussed by numerous authors (see, for example, Andersen, 1973; Heinrich, 1967).
94 citations
76 citations
TL;DR: Resolution tests on amorphous carbon foils were carried out in an electron microscope with a superconducting system containing 4 lenses including a shielding lens at 200 kV beam voltage, a value which approaches the theoretical resolving power of the electron optical system.
72 citations
71 citations
TL;DR: In this article, an electron density map of glycogen phosphorylase a with the same space group and lattice constants as the b enzyme has been calculated to 6 A resolution using four heavy-atom derivatives.
TL;DR: In this paper, the same authors applied the same technique to a single crystal surface of noble metals in a conventional electron microscope using diffracted electrons for the imaging and achieved a resolution of 20 A for directions perpendicular to the incident beam.
Book•
01 Jan 1976
TL;DR: In this paper, a new procedure for weighting the calculation of phases in the method of isomorphous replacement is described which separates the effects of statistical errors from those of systematic errors.
TL;DR: The crystal structure of a human Fc fragment was analysed at 4 A resolution and a partial interpretation of the electron-density map in terms of domain structure was possible.
Abstract: The crystal structure of a human Fc fragment was analysed at 4 A resolution. A partial interpretation of the electron-density map in terms of domain structure was possible. The molecule has the shape of a mickey mouse. The spherical domain was interpreted visually and by domain Patterson function interpretation as the CH3 dimer. This dimer resembles closely the CH1-CL dimer found in Fab structures. The ellipsoidal "ears" of the molecule represent the CH2 domains. They are widely separated from each other, but closely connected to CH3. Their tertiary structure must be different from CH1, as Patterson domain interpretations were unsuccessful. A chain tracing in CH2 was not yet possible.
TL;DR: The distribution of coat protein on the surface of Southern bean mosaic virus has been determined using single crystal X-ray diffraction techniques using the icosahedral symmetry of the virus, enhancing the external protein with respect to the internal RNA structure.
TL;DR: In this paper, the infrared absorption spectra of several isotopic species of the carbon monoxide molecule have been studied by using a high resolution vacuum infrared spectrograph, and the molecular constants evaluated have been presented and the extent to which the theoretical isotopic relations are valid has been examined.
Patent•
13 Oct 1976
TL;DR: In this paper, a plane wave field from a coherent source variable in either frequency, angle or distance from the object, detecting the wave field transmitted through, or reflected from, the object at some point on the image of the object.
Abstract: The resolution of an imaging system is greatly enhanced by radiating an object with a plane wave field from a coherent source variable in either frequency, angle or distance from the object, detecting the wave field transmitted through, or reflected from, the object at some point on the image of the object, with or without heterodyne detection, and with or without a lens system. The heterodyne detected output of the detector is processed to obtain the Fourier transform as a function of the variable for a direct measurement of the amplitude and surface height structure of the object within a resolution cell centered at the corresponding point on the object. In the case of no heterodyne detection, only intensity data is obtained for a Fourier spectrum.
TL;DR: In this article, the magnetic domain contrast in backscattered electron images of an iron-3% silicon specimen has been measured at 50-200 kV by using a highvoltage scanning electron microscope, and a detailed study has been made of the dependence of the contrast on detection direction and accelerating voltage.
Abstract: Magnetic domain contrast in backscattered electron images of an iron-3% silicon specimen has been measured at 50–200 kV by using a high-voltage scanning electron microscope, and a detailed study has been made of the dependence of the contrast on detection direction and accelerating voltage. The contrast is maximum at a take-off angle of about 60° for both 45° and 60° specimen tilts. The contrast is approximately proportional to the 3/2 power of the accelerating voltage, as shown by Newbury, Yakowitz and Myklebust (1973) and by Fathers, Jakubovics, Joy, Newbury and Yakowitz (1973 b, 1974). The resolution of domain images and the material depth effective for the magnetic contrast have been studied. They are also dependent on the detection direction: the resolution is high and the depth is small at a lower take-off angle than that corresponding to the mirror-symmetrical direction, whereas they are low and large, respectively, at a higher take-off angle. The contrast mechanism is also discussed on th...
TL;DR: An electron density map of crystalline R-TEM Escherichia coli β-lactamase (penicillinase) has been calculated from X-ray diffraction data at 5.5 A resolution with protein phases based on Friedel mates from a high-quality samarium derivative.
TL;DR: The three-dimensional structure of yeast tRNAPhe is reported, determined by fitting a skeletal wire model to an electron density map at a resolution of 2.5 Å, phased by the method of isomorphous replacement.
Abstract: WE have reported the three-dimensional structure of yeast tRNAPhe, determined by fitting a skeletal wire model to an electron density map at a resolution of 2.5 A, phased by the method of isomorphous replacement1. Atomic coordinates have been published for the unrefined structure2. We are in the process of refining our structure using difference Fourier techniques together with the real-space refinement procedure of Diamond3. The crystallographic residual (R) at 2.5 A is 0.31, a value comparable to that found for proteins at a similar stage.
TL;DR: In this paper, the relative intensities of type a and type b transitions of H16OD and H18OD were used to estimate the ratio μ a μ b, where b is the ratio of the two transitions.
TL;DR: In this paper, the librational ground state splitting of the methyl groups in solid dimethylacetylene has been measured by high reso resolution neutron scattering at 4.5 K. A threefold rotational barrier of 45 ± 5 meV (=1.04 kcal/mole) has been obtained.
TL;DR: In this paper, the authors show that the energy resolution of high-purity Ge detectors depends on the dislocation density and distribution in the single crystal, and that this correlation could be shown in a number of planar detectors with different dislocation densities.
Abstract: The energy resolution of high-purity Ge detectors depends on the dislocation density and distribution in the single crystal. This correlation could be shown in a number of planar detectors with different dislocation densities. Scanning with collimated electrons and gamma-rays revealed the strong dependence of local detector performance on dislocation density.
Journal Article•
TL;DR: The sputtering process by an ion beam well collimated and highly accelerated provides a valuable means of high resolution shadowing, replication of a fine object by a combination of pre-shadowing and deposition as well as a preparation of supporting films.
TL;DR: In this paper, a thermal instrument for measurement of low-frequency ac power with a resolution of 1 ppm of maximum input is described, which is well suited to precision measurements. But it is not suitable for high-frequency measurements.
Abstract: A thermal instrument for measurement of low-frequency ac power with a resolution of 1 ppm of maximum input is described. Due to its simple construction and, consequently, low number of error sources, it is well suited to precision measurements. The instrument has been applied to an accurate experimental comparison with the electrodynamic method carried out for identification of errors that cannot be traced by self-checks of each of the systems. The experimental configuration for the comparison is discussed and results of the measurements are given.
TL;DR: The results are used to estimate the applicability, especially with respect to potential resolution, of very high voltage electron microscopy in the study of beam-sensitive organic materials and to indicate that a factor of 2 times improvement in resolution can be expected at 1 MeV compared to 100 keV.
TL;DR: In this paper, a convergent-beam electron diffraction was carried out on graphite for the purpose of examining the symmetry of the structure, and of measuring the structure factors for the 100 and the 110 reflexions.
Abstract: An examination of graphite has been carried out by convergent-beam electron diffraction for the purpose of examining the symmetry of the structure, and of measuring the structure factors for the 100 and the 110 reflexions. Symmetry changes within the sample were related to the fault structure, which was imaged in the defocused convergent beam. The value determined for V100 deviates by approximately 9% from the value determined using Dirac-Slater scattering curves for a spherical atom. A difference Fourier map calculated from the experimental values and computed spherical atom values shows the trigonal regions of bonding potential, but lacks resolution, indicating a need to refine other reflexions in the zone.