Showing papers on "Resolution (electron density) published in 1995"
IBM1
TL;DR: Interferometric near-field optical microscopy achieving a resolution of 10 angstroms is demonstrated, sensing the dipole-dipole coupling of two externally driven dipoles as their spacing is modulated.
Abstract: Interferometric near-field optical microscopy achieving a resolution of 10 angstroms is demonstrated. The scattered electric field variation caused by a vibrating probe tip in close proximity to a sample surface is measured by encoding it as a modulation in the optical phase of one arm of an interferometer. Unlike in regular near-field optical microscopes, where the contrast results from a weak source (or aperture) dipole interacting with the polarizability of the sample, the present form of imaging relies on a fundamentally different contrast mechanism: sensing the dipole-dipole coupling of two externally driven dipoles (the tip and sample dipoles) as their spacing is modulated.
644 citations
TL;DR: Estimates of each suggest that near-field fluorescence excitation microscopy/spectroscopy with molecular sensitivity and spatial resolution is possible.
Abstract: We can resolve multiple discrete features within a focal region of m spatial dimensions by first isolating each on the basis of n ≥ 1 unique optical characteristics and then measuring their relative spatial coordinates. The minimum acceptable separation between features depends on the point-spread function in the (m + n)-dimensional space formed by the spatial coordinates and the optical parameters, whereas the absolute spatial resolution is determined by the accuracy to which the coordinates can be measured. Estimates of each suggest that near-field fluorescence excitation microscopy/spectroscopy with molecular sensitivity and spatial resolution is possible.
392 citations
297 citations
TL;DR: Electron cryo-microscopy was used to determine the three-dimensional structure of bovine rhodopsin from tilted two-dimensional crystals embedded in vitrified water and the overall density distribution in the low resolution map shows an arrangement of the helices in which the "arc-shaped" feature is extended by a fourth, less tilted helix.
270 citations
TL;DR: In this paper, the authors proposed a super-resolution method for high-image-density particle image velocimetry (PIV), which combines correlation analysis of the group of particles in a spot with sub-interrogation-spot particle tracking.
Abstract: The spatial resolution of conventional high-image-density particle image velocimetry (PIV) is determined by the size of the interrogation volume, which is typically a fraction of a millimetre. An improved method of PIV analysis is proposed in which the ultimate resolution of PIV is determined by the smaller of the mean spacing between particles and the displacement of the particles between light pulses. Since these distances must be smaller than the interrogation spot size in the high-image-density limit, the new procedure is referred to as super-resolution. The method combines correlation analysis of the group of particles in a spot with sub-interrogation-spot particle tracking. The theory of the procedure is described and evaluated using Monte Carlo simulations. The feasibility of enhancing resolution significantly is demonstrated by re-analysing turbulent flow PIV data reported by Urushihara et al. (1993). The in-plane resolution has been improved from 250 to 100 mu m.
258 citations
TL;DR: In this paper, the radial and azimuthal position of actin-tropomyosin gels was adjusted to fit the X-ray fiber diffraction patterns from oriented actin tropomyosins gels at a resolution of 1/8 A-1.
231 citations
TL;DR: To reduce the scan time in three‐dimensional (3D) imaging, the authors consider alternative trajectories for traversing k‐space that differ from traditional 3D trajectories, such as 3DFT, in that they employ time‐varying gradients allowing longer readouts and in turn a reduced scan time.
Abstract: To reduce the scan time in three-dimensional (3D) imaging, the authors consider alternative trajectories for traversing k-space. They differ from traditional 3D trajectories, such as 3DFT, in that they employ time-varying gradients allowing longer readouts and in turn a reduced scan time. Some of these trajectories reduce by an order of magnitude the number of excitations compared with 3DFT and provide flexibility for trading off signal-to-noise ratio for scan time. Other concerns are the minimum echo time and flow/motion properties. As examples, the authors show two applications: A 3D data set of the head (field of view of 30 x 30 x 7.5 cm and resolution of 1.5 x 1.5 x 1.5 mm) acquired in 56 s using a stack of spirals in 3D k-space; and a 3D movie of the heart (20 x 20 x 20 cm field of view, 2 x 2 x 2 mm resolution, and 16 time frames per cardiac cycle) acquired in 11 min using a cones trajectory.
218 citations
TL;DR: In this paper, the phase differences of all neighbouring pairs of diffracted beams are extracted as a function of probe position, and the beam coherence pattern is used to obtain an aberration-free image that resolves an atomic spacing of 0.136 nm.
Abstract: THE conventional resolution of transmission electron microscopes is orders of magnitude larger than the wavelength of the electrons used. Aberrations of the objective lens corrupt spatial information on length scales below a limit known as the point resolution. Methods to correct for lens aberrations1–5 require knowledge of the phase of the waves which make up the image (this constitutes the 'phase problem'). Beyond the point resolution, information can still be transferred by the microscope, but partial coherence of the scattered beams imposes an ultimate limit (the 'information limit9) on the resolution of the transferred image information. Here we show that this limit can be overcome to obtain images of still higher resolution with a scanning transmission electron microscope. Our approach involves collecting coherent microdiffraction patterns as a function of probe position, enabling us to extract the phase differences of all neighbouring pairs of diffracted beams. Using this approach for a microscope with a conventional point resolution of 0.42 nm and a conventional information limit of 0.33 nm, we are able to form an aberration-free image that resolves an atomic spacing of 0.136 nm.
211 citations
TL;DR: Using a cationic lipid bilayer, it is shown that DNA can be reliably adsorbed to the bilayer surface for atomic force microscopy (AFM) in aqueous buffers at high resolution, and the right‐handedness of the double helix is directly discernible in high resolution AFM images.
183 citations
23 Mar 1995
TL;DR: In this paper, the authors proposed two wide field techniques with substantially improved axial resolution that actually exceeds the lateral resolution, which is related to the angle over which the objective lens collects light.
Abstract: A weakness of standard 3D microscopies--both confocal and widefield+deconvolution-- is that their resolution is substantially worse in the axial direction than in the lateral plane. We describe two new widefield techniques with substantially improved axial resolution that actually exceeds the lateral resolution. As is well known, the resolution is related to the angle over which the objective lens collects light. In our first technique, light is collected over an enlarged set of angles by using two objective lenses on opposite sides of the sample. The two image beams are combined coherently on the same CCD camera. Interference between the beams yields new, previously inaccessible sample information. The second technique applies a similar concept to the illumination light in fluorescence microscopy. Light from an extended, spatially incoherent light source--such as a standard arc lamp--is split and directed through the two opposing objective lenses so as to create a narrow interference fringe at the focal plane in the sample. This spatial structure in the excitation light yields access to new sample information. The two techniques can easily be used together; the combined technique promises an axial resolution improvement of a factor of seven over standard widefield microscopy.
169 citations
TL;DR: The slow normal modes of G-actin were used as structural parameters to refine the F-actIn model against 8-A resolution x-ray fiber diffraction data, and the refined model shows that the nucleotide binding cleft has narrowed and that the DNase I binding loop has twisted to a lower radius.
TL;DR: In this paper, the authors explore the attainable spatial resolution in the elemental maps theoretically and experimentally, and suggest optimized set-up procedures for maximizing the resolution of the resolution.
Abstract: SUMMARY
Imaging filters developed over the last few years permit rapid elemental mapping by energy-filtering transmission electron microscopy (EFTEM), with resolution and sensitivity limited primarily by the sample and by the TEM. We explore the attainable spatial resolution in the elemental maps theoretically and experimentally, and suggest optimized set-up procedures for maximizing the resolution. The chromatic aberration of the objective lens of the microscope is shown to be a major limit. Its influence can be minimized by using small energy intervals and limited collection angles, but this is done at the cost of decreased collection efficiency. Resolution of better than 1 nm and sensitivities to less than a monolayer of elements with favourable edges are readily attainable in elemental maps obtained with acquisition times of 40 s total and less. Resolution better than 0·5 nm should be attainable with further optimization of the acquisition parameters.
TL;DR: An osmo-regulated H2O-channel, aquaporin-CHIP, from bovine red blood cell membranes was purified and reconstituted with lipids, forming two-dimensional crystalline patches that diffract to about 3.0 A resolution, confirming that the osmi-regulated basic packing unit is a tetramer and begins to reveal it's structural design.
TL;DR: In this paper, a method based on morphological image processing that allows one to analyze and correct the enlargement is presented. But the method uses measured, realistic tip shapes, not idealized functions.
Abstract: Atomic force microscopy (AFM) images of biomolecules, and other structures similar in size, are enlarged because of the finite size of the probe tip. We present a method based on morphological image processing that allows one to analyze and correct the enlargement. Morphological restoration is ideal in some regions, giving the exact sample surface. In other regions, it gives a surface with improved resolution. The method uses measured, realistic tip shapes, not idealized functions. Tip surfaces are generated by restoring images of known gold spheres having diameters of about 10 nm. We generate tip images of carbon and Si 3 N 4 probes and find good correlation with scanning electron microscopy. Generated tip surfaces are used to restore images of unknown objects to produce images at enhanced resolution. Diameters of contours at constant elevation are changed by as much as 25%. In addition to improving resolution, morphological restoration also corrects distortions due to imaging with asymmetrical tips. The approach uses methods and software readily available to the atomic force microscopist
TL;DR: In this paper, the authors review the history of the scanning probe SIMS technique and describe several recent developments in the field: improvements conceived to improve simultaneously spatial resolution and sensitivity, which has found applications in many diverse areas, from biology to semiconductors, from cosmochemistry to superconductors.
TL;DR: The structure of cy tochrome b562 from Escherichia coli has been refined at 1.4 A resolution against X-ray data collected on a Picker four-circle diffractometer and a detailed comparison with the structurally similar cytochrome c' from Rhodospirulum molishianum is presented.
TL;DR: In this paper, the authors investigate the effect of annular apertures in two-photon excitation confocal and non-confocal microscopy and show that the use of a transmission annular aperture leads to resolution increase without diffraction fringes.
TL;DR: The crystal structure of coxsackievirus B3 (CVB3) has been determined to 3.5 A resolution and the self-rotation function established pseudo R32 symmetry with each particle sitting on a 32 special position, allowing for a total of six possible monoclinic space-group settings.
Abstract: The crystal structure of coxsackievirus B3 (CVB3) has been determined to 3.5,4, resolution. The icosahedral CVB3 panicles crystallize in the monoclinic space group, P21, (a-- 574.6, b = 302.1, c--- 521.6A, /3--107.7 °) with two virions in the asymmetric unit giving 120-fold non-crystallographic redundancy. The crystals diffracted to 2.7 A resolution and the X-ray data set was 55% complete to 3.0,4, resolution. Systematically weak reflections and the self-rotation function established pseudo R32 symmetry with each particle sitting on a 32 special position. This constrained the orientation and position of each panicle in the monoclinic cell to near face-centered positions and allowed for a total of six possible monoclinic spacegroup settings. Correct interpretation of the highresolution (3.0-3.2~,) self-rotation function was instrumental in determining the deviations from R32 orientations of the virus particles in the unit cell. Accurate particle orientations permitted the correct assignment of the crystal space-group setting amongst the six ambiguous possibilities and for the correct determination of particle positions. Real-space electron-density averaging and phase refinement, using human rhinovius 14 (HRV14) as an initial phasing model, have been carried out to 3.5,~ resolution. The initial structural model has been built and refined to 3.5 ~, resolution using X-PLOR.
Journal Article•
TL;DR: In this paper, a low voltage SEM with a multipole corrector was used for the correction of spherical and chromatic aberrations, achieving a precision of 30 μm and 200 μm, respectively.
Patent•
14 Dec 1995
TL;DR: In this article, a dynamically configurable video signal processing system partitions and encodes data using a variable number of data segments and variable data resolution, by predicting, as a function of the data rate, first and second distortion factors.
Abstract: A dynamically configurable video signal processing system partitions and encodes data using a variable number of data segments and variable data resolution. The system partitions data into a variable number of data segments by predicting, as a function of the data rate, first and second distortion factors for the data partitioned into first and second numbers of data segments. The first and second distortion factors are mutually compared and the data is partitioned into the number of data segments which exhibits the lower distortion factor value. First and second distortion factors for the data encoded with first and second data resolutions are also predicted. The first and second distortion factors are similarly compared and the data is encoded with the resolution exhibiting the lower distortion factor value.
TL;DR: New structural information of different biological systems revealed by the atomic force microscopy is presented and a discussion regarding the contrast, resolution and specimen deformation is provided based on a theoretical model.
TL;DR: The operation of an imaging Nd:YAG microchip-laser synthetic-aperture radar is reported, with which two-dimensional models of military targets are imaged with spatial resolution significantly better than the diffraction limit of the real aperture in the along-track dimension.
Abstract: We report the operation of an imaging Nd:YAG microchip-laser synthetic-aperture radar, with which we imaged two-dimensional (2-D) models of military targets. The images obtained showed spatial resolution significantly better than the diffraction limit of the real aperture in the along-track dimension. The signal processing is described, and the measurement sensitivity is both predicted and verified. In addition, 2-D images with high resolution in both dimensions were generated by using an asymmetric aperture to match the along-track synthetic-aperture resolution with the across-track diffraction-limited resolution.
TL;DR: In this article, an energy-filtered transmission electron microscopy has been applied to Si-Ge superlattices and layered heterostructures in order to explore detection and resolution limits of elemental distribution images obtained by electron spectroscopic imaging (ESI).
TL;DR: In this paper, electron transfer at the interface between two immiscible electrolyte solutions supported at the tip of a micropipet is demonstrated using the 7,7,8,8-tetracyanoquinodimethane (in 1,2 dichloroethane)/ferrocyanide (in water) system.
Abstract: Electron transfer at the interface between two immiscible electrolyte solutions (ITIES) supported at the tip of a micropipet is demonstrated using the 7,7,8,8-tetracyanoquinodimethane (in 1,2 dichloroethane)/ferrocyanide (in water) system This micro-ITIES is then used as a probe in scanning electrochemical microscopy for imaging purposes A micro-ITIES can successfully be used to image surfaces with a resolution comparable to that obtained when using a metallic tip of the same size
TL;DR: The surface of these ribosomal particles is being characterized and procedures are being developed for quantitative detachment of selected Ribosomal proteins and for their incorporation into core particles, for their crystal production in large quantities.
Abstract: Preliminary electron density maps of the large and the small ribosomal particles from halophilic and thermophilic sources, phased by the isomorphous replacement method, have been constructed at int...
21 Oct 1995
TL;DR: In this paper, a new scintillation detector system was designed for application in high-resolution Positron Emission Tomography (PET), which is a bundle of small YAlO/sub 3/:Ce (YAP) crystals closely packed (0.2/spl times/0.0 cm/sup 3/), coupled to a position sensitive photomultiplier tube.
Abstract: A new scintillation detector system has been designed for application in high resolution Positron Emission Tomography (PET). The detector is a bundle of small YAlO/sub 3/:Ce (YAP) crystals closely packed (0.2/spl times/0.2/spl times/3.0 cm/sup 3/), coupled to a position sensitive photomultiplier tube (PSPMT). The preliminary results obtained for spatial resolution, time resolution, energy resolution and efficiency of two such detectors working in coincidence are presented. These are 1.2 mm for the FWHM spatial resolution, 2.0 ns for the FWHM time resolution and 20% for the FWHM energy resolution at 511 keV. The measured efficiency is (44/spl plusmn/3)% with a 150 keV threshold and (20/spl plusmn/2)% with a 300 keV threshold.