Showing papers on "Resolution (electron density) published in 1974"
1,580 citations
TL;DR: An objective assessment of the upper limit of the error in the atomic coordinates of the final model is possible by comparing the inhibitor component in the model of the complex with the refined structure of the free inhibitor (Deisenhofer & Steigemann, 1974).
526 citations
260 citations
TL;DR: A condensed description of the fundamental processes involved in radiation damage and the effects of radiation on the physical and chemical properties of organic materials, particularly polymers, is given in this paper, where it is shown that the radiation doses received by specimens in the electron microscope are extremely high, very much greater than those used in radiation chemistry experiments.
Abstract: A condensed description is given of the fundamental processes involved in radiation damage and the effects of radiation on the physical and chemical properties of organic materials, particularly polymers It is shown that the radiation doses received by specimens in the electron microscope are extremely high, very much greater than those used in radiation chemistry experiments Because of this, only qualitative predictions of behaviour in the electron microscope can be made A number of authors have described the changes in the image or diffraction pattern of particular specimen types during observation in the electron microscope and their work is reviewed here In general, contrast features in the image may disappear, due to loss of mass or crystallinity, or new features may appear due to distortion of ordered regions The effects of radiation damage on attainable resolution, and possible methods of improving the resolution are then discussed
225 citations
TL;DR: In this paper, a method for resolving additive mixtures of overlapping curves by combining nonlinear regression and principal component analysis is presented, which makes use of the postulated chemical reaction, and allows one to check the reaction and estimate chemical rate and equilibrium constants.
Abstract: The paper presents a method for resolving additive mixtures of overlapping curves by combining nonlinear regression and principal component analysis. The method can be applied to spectroscopy, chromatography, etc. The method makes use of the postulated chemical reaction, and allows one to check the reaction and estimate chemical rate and equilibrium constants.
147 citations
TL;DR: In this article, the electron density map of crystalline tRNA shows the polynucleotide chain as an alternating series of ribose and phosphate peaks, and a complete 3D model of the L-shaped molecule has been built.
Abstract: At 3A resolution, the electron density map of crystalline tRNA shows the polynucleotide chain as an alternating series of ribose and phosphate peaks. Bases are seen, especially in the double helical stem regions. A complete three-dimensional model of the L-shaped molecule has been built.
134 citations
TL;DR: The use of non-crystallographic symmetry to improve the electron density map is equivalent to the molecular replacement method and a comparison is made with other dehydrogenases.
126 citations
TL;DR: The results of a study in which the computer algorithm DETMAX was used for the purpose of constructing n-run “D-optimal” designs over a cubic region of interest for the first-order model E(y) = β0 + β0 x 1 + … + β p x p are presented.
Abstract: This paper presents the results of a study in which the computer algorithm DETMAX was used for the purpose of constructing n-run “D-optimal” designs over a cubic region of interest for the first-order model E(y) = β0 + β0 x 1 + … + β p x p . These results suggest some general “rules” (actually conjectures) for the construction of such designs. For p ≤ 9, all but 12 combinations of n and p are covered by these “rules;” the 12 exceptions are discussed separately. The resolution IV designs obtained by folding over these “D-optimal” first-order designs are also discussed and are shown to compare favorably with designs previously published.
119 citations
TL;DR: In this article, the in-line holograms of a line-like object of a chemical fiber and a red blood cell were made using AlKα radiation (8.34A) from a two-stage fine focus X-ray generator.
Abstract: X-ray holograms of two- or three-dimensionally distributed objects are recorded and reconstructed. The in-line holograms of a line-like object of a chemical fiber and a point-like object of red blood cell are made using AlKα radiation (8.34A) from a two-stage fine focus X-ray generator. A magnified real image is reconstructed from the negative hologram using a He–Ne laser (6328A). A lateral resolution of about 4 µm and a longitudinal resolution of about 4 mm are obtained in the two-step imaging process.
102 citations
Journal Article•
TL;DR: A variety of crystal imperfections can be observed at point-to-point resolutions down to 3A-intermediate between bond lengths and unit cell dimensions, even at the unit cell scale.
Abstract: Imaging of crystal structures of minerals clearly shows details within ideally periodic regions, even at the unit cell scale. A variety of crystal imperfections can be observed at point-to-point resolutions down to 3A-intermediate between bond lengths and unit cell dimensions. Fluctuations in both structure and composition can be observed in volumes up to 14 orders of magnitude smaller than is possible by standard single crystal X-ray techniques. We have obtained crystal structure images of the following silicate structure types: "ring" structures (beryl and cordierite), isolated and paired tetrahedra (idocrase), single and double chains (orthoenstatite and hornblende), framework (scapolite), and sheet (muscovite). Regular and perturbed regions containing defects are clearly differentiable. Antiphase domains (hornblende) and stacking faults (enstatite) as well as the effects of radiation damage produce recognizable structural effects, only some of which are reflected in the electron diffraction patterns. An example of the usefulness of the technique is the resolution of small regions (several unit cells wide parallel to [100D of clinoenstatite intergrown within orthoenstatite. The technique of high resolution electron microscopy has great potential for mineralogy and geology. Solid solution series may well be resolvable into stoichiometric phases differing only slightly in both composition and/or structure. Homologous phases, potentially resolvable by electron microscopy, have the possibility of providing far more sensitive mineralogical indicators to past history and environments than currently exist.
86 citations
TL;DR: The increased contrast and definition observed in bright‐field images of conventional liver sections suggest that it should be possible to obtain sufficient contrast from stains containing atoms of lower atomic numbers than those employed at present.
Abstract: SUMMARY
A prism-mirror-prism electron energy filter has been inserted into a fixed beam transmission electron microscope. The insertion of the filter has not degraded the spatial resolution of the microscope, while providing an energy resolution of 2.5 eV. The filter greatly reduces the chromatic aberration of the images, increasing resolution in dark field and contrast in bright field. Images of bacteriophage T4 and of polyoma virus indicate that thick unstained and unshadowed biological specimens can now be observed at high resolution in dark field. In addition, the increased contrast and definition observed in bright-field images of conventional liver sections suggest that it should be possible to obtain sufficient contrast from stains containing atoms of lower atomic numbers than those employed at present.
TL;DR: The crystal structure of phosphorylase b in the presence of IMP at 6 A resolution is described, based on two heavy-atom isomorphous derivatives and their anomalous contributions, and the molecular boundary is clearly distinguishable in the electron density map.
TL;DR: In this article, the excitation spectra of shallow acceptors in ultrapure germanium (109 cm-3 < NA − ND < 1012 cm -3) were studied using Fourier transform spectroscopy and photothermal excitation.
TL;DR: In this paper, the structural details observed or contained in electron micrographs which are consistent with, or confirmed by, other data obtained from biochemical or functional experiments or by other physical methods (optical, magnetic, electric).
Abstract: Commercially available electron microscopes routinely provide resolution of some 2–4 A, as determined on the spacing of crystalline lattices of certain stable, small-molecular substances. On biological material either macromolecules or macromolecular assemblies— ‘biologically significant’ details below some 20 A have hitherto not been observed.we consider as ‘biologically significant’ those structural details observed or contained in electronmicrographs which are consistent with, or confirmed by, other data obtained from biochemical or functional experiments or by other physical methods (optical, magnetic, electric).
TL;DR: Direct methods of structure analysis have been used in the interpretation of the X-ray data, and the phases of the first five orders of diffraction of peripheral nerve myelin have been uniquely determined.
TL;DR: In this paper, the authors describe a broad-band absorption spectra of gases at submillimetric wavelengths to high resolution with comparative ease, at a resolution of 0.05 cm/sup-1/ (0.33 to 1.4 THz).
Abstract: Modem interferometric techniques now permit the measurement of broad-band absorption spectra of gases at submillimetric wavelengths to high resolution with comparative ease. This paper describes briefly some new spectra of H/sub 2/O, N/sub2/O, and SO/sub 2/ in the 10-40 cm/sup -1/ (0.33 to 1.4 THz) region, at a resolution of 0.05 cm/sup-1/.
TL;DR: A resolution electron density map of a second crystal form (called BII) of yeast hexokinase B has been obtained and the molecule does not appear to be homologous in detail to other kinases such as phosphoglycerate kinases and adenylate kinase.
TL;DR: In this paper, the different components of an ESCA-system are analyzed theoretically and conditions of optimum performance are used as basis for the design of the ESCA system for different tasks.
TL;DR: In this paper, the fundamental vibrational band of oxygen has been examined with a resolution of 0.05 cm−1 for the Q branch and 0.40 cm− 1 for the S and O branches.
Abstract: The fundamental vibrational band of oxygen has been examined with a resolution of 0.05 cm−1 for the Q branch and 0.40 cm−1 for the S and O branches. All lines of the Q branch were clearly resolved except Q(1) and Q(3). Calculated molecular parameters agree with those previously reported from microwave and electronic spectra. Line width measurements made in the Q branch and on three S branch lines, using a resolution of 0.05 cm−1, are in fair agreement with previously measured and calculated line widths for pure rotational Raman lines.
TL;DR: For the 2-0, 3-1, 4-2, 5-3, 6-4, and 7-5 bands of CO emission, the absolute uncertainty of unblended line positions is on the order of ± 0.0003 cm−1 as mentioned in this paper.
TL;DR: In this paper, the rotational, vibrational and rotational-vibrational excitation by electron impact at 4.5 eV was measured with a resolution of 18-22 meV.
Abstract: The differential cross sections for rotational, vibrational, and rotational-vibrational excitation by electron impact at 4.5 eV in ${\mathrm{H}}_{2}$ have been measured with a resolution of 18-22 meV. The cross-section ratio of pure vibrational excitation ($\ensuremath{\Delta}j=0$) to rotational-vibrational ($j=1\ensuremath{\rightarrow}3$) excitation for $v=1, 2, \mathrm{and} 3$ shows the expected $p$-wave character. However, at a given angle of observation, this ratio decreases as the vibrational quantum number increases. This effect has not been predicted by theory.
TL;DR: In this article, the hyperfine structure in a molecular beam of I2 has been observed with a resolution of one part in 109 using a stable jet stream cw dye laser.
Abstract: Hyperfine structure in a molecular beam of I2 has been observed with a resolution of one part in 109 using a stable jet stream cw dye laser. In addition, the dye laser was long‐term stabilized to six parts in 1013 by using an I2 molecular beam reference.
TL;DR: In this article, a measurement of the spatial resolution of a liquid-argon filled chamber was performed with minimum ionizing particles, and two multi-strip chambers with 20-microm strip spacing operating in the ionization mode were used in the experiment.
01 Jan 1974
TL;DR: The resolution of a telescope has a diffraction limit of ∼λ/D, where λ is the observing wavelength and D is the aperture diameter as discussed by the authors, and the resolution of large optical telescopes is limited to about a half arc second by atmospheric fluctuations.
Abstract: The resolution of a telescope has a diffraction limit of ∼λ/D, where λ is the observing wavelength and D is the aperture diameter The resolution of large optical telescopes is limited to about a half arc second by atmospheric fluctuations, although the diffraction limit is much smaller However, for radio frequencies a diffraction limit of about 1 arc minute at the highest radio frequencies is currently reached using filled-aperture telescopes Further significant increase of the resolution of filled-aperture telescopes is not likely