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Showing papers on "Resolution (electron density) published in 2002"


Journal ArticleDOI
21 Feb 2002-Nature
TL;DR: A three-dimensional X-ray microscopy technique that uses polychromatic synchrotron X-rays to probe local crystal structure, orientation and strain tensors with submicrometre spatial resolution is described, applicable to single-crystal, polycrystalline, composite and functionally graded materials.
Abstract: Advanced materials and processing techniques are based largely on the generation and control of non-homogeneous microstructures, such as precipitates and grain boundaries. X-ray tomography can provide three-dimensional density and chemical distributions of such structures with submicrometre resolution; structural methods exist that give submicrometre resolution in two dimensions; and techniques are available for obtaining grain-centroid positions and grain-average strains in three dimensions. But non-destructive point-to-point three-dimensional structural probes have not hitherto been available for investigations at the critical mesoscopic length scales (tenths to hundreds of micrometres). As a result, investigations of three-dimensional mesoscale phenomena--such as grain growth, deformation, crumpling and strain-gradient effects--rely increasingly on computation and modelling without direct experimental input. Here we describe a three-dimensional X-ray microscopy technique that uses polychromatic synchrotron X-ray microbeams to probe local crystal structure, orientation and strain tensors with submicrometre spatial resolution. We demonstrate the utility of this approach with micrometre-resolution three-dimensional measurements of grain orientations and sizes in polycrystalline aluminium, and with micrometre depth-resolved measurements of elastic strain tensors in cylindrically bent silicon. This technique is applicable to single-crystal, polycrystalline, composite and functionally graded materials.

689 citations


Journal ArticleDOI
TL;DR: For the first time, the 3D structure of a noncrystalline nanostructured material is experimentally determined at 50 nm resolution using coherent x-ray diffraction and the oversampling phasing method.
Abstract: We have imaged a 2D buried Ni nanostructure at 8 nm resolution using coherent x-ray diffraction and the oversampling phasing method. By employing a 3D imaging reconstruction algorithm, for the first time we have experimentally determined the 3D structure of a noncrystalline nanostructured material at 50 nm resolution. The 2D and 3D imaging resolution is currently limited by the exposure time and the computing power, while the ultimate resolution is limited by the x-ray wavelengths. We believe these results pave the way for the development of atomic resolution 3D x-ray diffraction microscopy.

328 citations


Journal ArticleDOI
TL;DR: MRI reconstruction using super-resolution is presented and shown to improve spatial resolution in cases when spatially-selective RF pulses are used for localization and improves the signal-to-noise efficiency of the data acquisition.

278 citations


Journal ArticleDOI
TL;DR: In this article, the authors provide a brief historical review of how near-field microscopy has developed, including a review of visible and infrared near field microscopy in the context of the main theme, the principles and applications of near-Field microscopy using millimeter to micrometer electromagnetic waves.
Abstract: Conventional optics in the radio frequency (rf) through far-infrared (FIR) regime cannot resolve microscopic features since resolution in the far field is limited by wavelength. With the advent of near-field microscopy, rf and FIR microscopy have gained more attention because of their many applications including material characterization and integrated circuit testing. We provide a brief historical review of how near-field microscopy has developed, including a review of visible and infrared near-field microscopy in the context of our main theme, the principles and applications of near-field microscopy using millimeter to micrometer electromagnetic waves. We discuss and compare aspects of the remarkably wide range of different near-field techniques, which range from scattering type to aperture to waveguide structures.

262 citations


Journal ArticleDOI
TL;DR: In this article, the systematic trends regarding wavelength of emission, maximum obtainable scintillation light output, gamma-ray energy resolution, and scintllation decay time of Ce3+-doped fluorides, chlorides, bromides, iodides, oxides, sulfides, and selenides are reviewed.
Abstract: The systematic trends regarding wavelength of emission, maximum obtainable scintillation light output, gamma-ray energy resolution, and scintllation decay time of Ce3+-doped fluorides, chlorides, bromides, iodides, oxides, sulfides, and selenides are reviewed. Theoretical limits will be compared with actually achieved values. The relation between energy resolution and non-proportional response of scintillators will be discussed.

221 citations


Journal ArticleDOI
TL;DR: Large conformational changes as occur during the functioning of biological macromolecules and assemblies can be elucidated directly from low-resolution structural data through the application of elastic normal mode theory and vector quantization.

211 citations


Journal ArticleDOI
TL;DR: In this article, the authors measured the light output for ∅10 mm×10mm and ∅75mm×75mm NaI(Tl) crystals and energy resolution were measured for γ-ray energies ranging from 16-1333 keV.
Abstract: The light output for ∅10 mm×10 mm and ∅75 mm×75 mm NaI(Tl) crystals and energy resolution were measured for γ-ray energies ranging from 16–1333 keV. These measurements enabled the observation of the light yield nonproportionality behavior and allowed the determination of the intrinsic resolution after correcting for the measured resolution for photomultiplier tube (PMT) statistics. The intrinsic resolution was then compared with the nonproportionality component. The latter was calculated using measured electron response, Monte Carlo N Particle code (MCNP4B), and the simplified cascade sequence for NaI(Tl). This comparison allowed the identification of the intrinsic resolution component associated with δ-rays. Consequently, it was shown that the δ-ray component is the most dominant component of the NaI(Tl) intrinsic resolution.

208 citations


Journal ArticleDOI
TL;DR: A segmentation approach targeting three-dimensional electron density maps derived by electron microscopy, consisting of a novel three- dimensional variant of the immersion-based watershed algorithm that is reliable, efficient, accurate, and applicable to a wide variety of biological problems.

177 citations


Journal ArticleDOI
TL;DR: In this article, the receiver coil sensitivity, gradient strength, and pulse/gradient sequence design were combined to obtain a volume resolution of 3.7±0.4 μm by 3.3± 0.3 μm for a volume of 40 femtoliters, corresponding to ∼3×10 12 proton spins.

132 citations


Book ChapterDOI
TL;DR: A typical analytical electron microscopic method (i.e., energy dispersive X-ray spectroscopy, or EDS) is described in this paper, which is the most standard and reliable one in the field of analytical electron microscopy and is widely used.
Abstract: A typical analytical electron microscopic method (i.e., energy dispersive X-ray spectroscopy, or EDS, sometimes called EDX or EDXS) is described in this chapter. Although some improvement in the resolution of EDS has been attempted, there has been no significant modification introduced in the practice and application of EDS in comparison with electron energyloss spectroscopy (EELS). Still, this method is the most standard and reliable one in the field of analytical electron microscopy and is widely used.

85 citations


Journal ArticleDOI
TL;DR: A high-performance neutron diffractometer for biological crystallography (BIX-3) has been constructed at JRR-3M in the Japan Atomic Energy Research Institute (JAERI) in order to determine the hydrogen-atom positions in biological macromolecules.
Abstract: A high-performance neutron diffractometer for biological crystallography (BIX-3) has been constructed at JRR-3M in the Japan Atomic Energy Research Institute (JAERI) in order to determine the hydrogen-atom positions in biological macromolecules. It uses several recent technical innovations, such as a neutron imaging plate and an elastically bent silicon monochromator developed by the authors. These have made it possible to realise a compact vertical arrangement of the diffractometer. Diffraction data have been collected from the proteins rubredoxin and myoglobin in about one month, to a resolution of 1.5 A. The data were good enough to identify the hydrogen atoms with high accuracy. By adopting a crystal-step scan method for measuring Bragg diffraction intensities, the signal-to-noise ratio was much better than that of the Laue method. This shows that BIX-3 is one of the best-performing machines for neutron protein crystallography in the world today.

Patent
19 Nov 2002
TL;DR: In this paper, a method of enhancing resolution in an electronic imaging device includes capturing an electronic image through a fisheye lens with a photodetector at a resolution native to the photodeter.
Abstract: A method of enhancing resolution in an electronic imaging device includes capturing an electronic image through a fisheye lens with a photodetector at a resolution native to the photodetector. A resolution is selected that is higher than the native resolution of the photodetector. The electronic image is processed to produce a new electronic image at the higher resolution. A fisheye effect caused by the fisheye lens is removed during processing.

Journal ArticleDOI
TL;DR: To visualize the motion of protein domains, movies were generated by similarity ranking of the observed protein configurations by estimating the amplitudes of the domain movements from a large number of single molecule topographs and the corresponding energy landscapes calculated.
Abstract: The atomic force microscope acquires topographs of single native membrane proteins at subnanometer resolution. Owing to the high signal-to-noise ratio, such images allow the conformational space of membrane protein surfaces to be sampled. This is demonstrated by topographs of porin OmpF, aquaporin-Z, and bacteriorhodopsin, all recorded at a lateral resolution of <7 A and a vertical resolution of ~1 A. The amplitudes of the domain movements were estimated from a large number of single molecule topographs and the corresponding energy landscapes calculated. To visualize the motion of protein domains, movies were generated by similarity ranking of the observed protein configurations. Electronic supplementary material to this paper can be obtained by using the Springer Link server located at http://dx.doi.org/10.1007/s00249-001-0197-8

Proceedings ArticleDOI
19 May 2002
TL;DR: Two distinct proofs of an exponential separation between regular resolution and unrestricted resolution are given, the previous best known separation between these systems was quasi-polynomial.
Abstract: Two distinct proofs of an exponential separation between regular resolution and unrestricted resolution are given. The previous best known separation between these systems was quasi-polynomial.

Journal ArticleDOI
TL;DR: In this article, the authors consider the problem of estimating subsurface quantities such as velocity or reflectivity from seismic measurements, which can be computed using the concept of resolution function, which is a quantity readily accessible in the Fourier space of the model.
Abstract: We consider the problem of estimating subsurface quantities such as velocity or reflectivity from seismic measurements. Because of a limited aperture and band-limited signals, the output from a seismic prestack reconstruction method is a distorted or blurred image. This distortion can be computed using the concept of resolution function, which is a quantity readily accessible in the Fourier space of the model. The key parameter is the scattering wavenumber, which at a particular image point is defined by the incident and scattered ray directions in a given background model. Any location in any background model can be considered. In general, the resolution function will depend on the following four quantities: the background velocity model, the frequency bandwidth, the wavefield type and the acquisition geometry. We first establish the resolution function for a general scattering model assuming local reaction. We then adapt this result for two well-known scattering models: Born and Kirchhoff. For each of these approximations the corresponding resolution function is derived and discussed. Finally, by employing a simple synthetic data example we demonstrate the ability of the resolution function to predict the image distortions.

Journal ArticleDOI
TL;DR: In this article, a parabolic refractive x-ray lens was used to image the interior of opaque samples with sub-micrometer resolution, at a resolution well below 1 μm.
Abstract: Based on parabolic refractive x-ray lenses we have built a hard x-ray microscope that allows one to image the interior of opaque samples with submicrometer resolution We have combined magnified imaging with tomography to obtain the three-dimensional structure of the sample at a resolution well below 1 μm Using an aluminum lens to record a magnified tomogram of a test sample (microprocessor), a resolution of slightly above 400 nm was found for the three-dimensional reconstruction Lenses made of beryllium are expected to improve this resolution to well below 100 nm The resulting challenges concerning instrumentation and numerical methods are discussed

Journal ArticleDOI
TL;DR: In this article, a high-resolution X-ray diffractometer devoted to the study of imperfect materials (mainly oxides and ceramics) is presented, based on a rotating anode generator, a four-bounce monochromator, a five-movement sample holder and a curved position-sensitive detector.
Abstract: A high-resolution X-ray diffractometer devoted to the study of imperfect materials (mainly oxides and ceramics) is presented. It is based on a rotating anode generator, a four-bounce monochromator, a five-movement sample holder and a curved position-sensitive detector (PSD). This setup allows rapid acquisition of a reciprocal-space map (in less than 10 h) even for very poorly diffracting materials. The two-dimensional instrumental profile is calculated taking into account each optical element in the beam path. The one-dimensional instrumental profiles corresponding to widely used scans (ω scan, θ–2θ scan, rocking curve and powder scan) are also calculated. In the three former cases, the setup exhibits an excellent angular resolution (0.003°), whereas in the latter case the resolution is lowered by one order of magnitude at the benefit of a strong increase in the collected intensity. The possibilities of this diffractometer are illustrated with three examples: an epitaxic layer, a microstructured single crystal and a powder.

Journal ArticleDOI
TL;DR: In this article, it was shown that the precision depends on the size of the component, the distance between the components, the resolution of the instrument, and the number of electron counts, as well as the orientation of the object with respect to the rotation axis.

Journal ArticleDOI
TL;DR: In this paper, the authors consider strongly confined, cylindrical symmetric potentials and demonstrate their applications in both red and blue-detuned focusing of atoms, and find that a resolution of 1 nm should in principle be possible.


Journal ArticleDOI
TL;DR: A clearly improved 3D resolution was obtained by axial tomography together with reconstruction as compared with reconstruction of confocal data from only a single angular view.
Abstract: By physical rotation of the sample, axial tomography enables the acquisition of otherwise inaccessible spatial information from an object. In combination with confocal microscopy, the method can fundamentally improve the effective three-dimensional (3D) resolution. In this report we present a novel method for high resolution reconstruction of confocal axial tomographic data. The method automatically determines the relative angles of rotation, aligns the data from different rotational views and reconstructs a single high resolution 3D dataset. The reconstruction makes use of a known point spread function and is based on an unconstrained maximum likelihood deconvolution performed simultaneously from multiple (in our case three) angular views. It was applied to simulated as well as to experimental confocal datasets. The gain in resolution was quantified and the effect of choice of overrelaxation factors on the speed of convergence was investigated. A clearly improved 3D resolution was obtained by axial tomography together with reconstruction as compared with reconstruction of confocal data from only a single angular view.

Journal ArticleDOI
TL;DR: This new form of diffraction-based 3D microscopy can be used to image the 3D structures of nanocrystals and noncrystalline samples, with resolution limited only by the quality of sample diffraction.
Abstract: Electron lens aberration is the major barrier limiting the resolution of electron microscopy. Here we describe a novel form of electron microscopy to overcome electron lens aberration. By combining coherent electron diffraction with the oversampling phasing method, we show that the 3D structure of a 2 x 2 x 2 unit cell nano-crystal (framework of LTA [Al12Si12O48]8) can be ab initio determined at the resolution of 1 Angstrom from a series of simulated noisy diffraction pattern projections with rotation angles ranging from -70 degrees to +70 degrees in 5 degrees increments along a single rotation axis. This form of microscopy (which we call 3D electron diffraction microscopy) does not require any reference waves, and can image the 3D structure of nanocrystals, as well as non-crystalline biological and materials science samples, with the resolution limited only by the quality of sample diffraction.

Journal ArticleDOI
TL;DR: In this paper, the spin-forbidden b 1 Σ g + (v ′ = 0)← X 3 ǫ g − (v″=0) band of molecular oxygen in air has been measured to show that broad band continuous wave phase shift cavity ring down spectroscopy can be combined with Fourier transform spectrometers.

Journal ArticleDOI
TL;DR: It is experimentally show that the response of a quantum-chaotic system can display resonance lines sharper than the inverse of the excitation duration, which allows us to discriminate two neighboring frequencies with a resolution nearly 40 times better than the limit set by the Fourier inequality.
Abstract: We experimentally show that the response of a quantum-chaotic system can display resonance lines sharper than the inverse of the excitation duration. This allows us to discriminate two neighboring frequencies with a resolution nearly 40 times better than the limit set by the Fourier inequality. Furthermore, numerical studies indicate that there is no limit, but the loss of signal, to this resolution, opening ways for the development of sub-Fourier quantum-chaotic signal processing.

Journal ArticleDOI
TL;DR: The angle and distance limits found in the correlation for the backbone hydrogen-bond geometry can be used to evaluate the quality of protein structures and for further NMR structure refinement.
Abstract: An analysis of backbone hydrogen bonds has been performed on nine high-resolution protein X-ray crystal structures Backbone hydrogen-bond geometry is compared in the context of X-ray crystal structure resolution A strong correlation between the hydrogen-bond distance, R(HO), and the hydrogen-bond angle, theta(NHO), is observed when the X-ray crystal structure resolution is <100 A Ab initio calculations were performed to substantiate these results The angle and distance limits found in our correlation for the backbone hydrogen-bond geometry can be used to evaluate the quality of protein structures and for further NMR structure refinement

Patent
Takayuki Kitazawa1
16 Aug 2002
TL;DR: In this paper, a low-resolution image of the display screen including an indicated position is captured, and a low resolution image is produced from the captured high resolution image by finding integers A and B so that a value f given by f = X × Y A × B + A × A + B is at a minimum.
Abstract: An image of the display screen including an indicated position is captured, and a low resolution image is produced from the captured high resolution image. A low resolution pixel corresponding to the indicated position is found within the low resolution image, and the indicated position is then found within the captured image based on a unit area that is associated with the low resolution pixel corresponding to the indicated position. A resolution of the low resolution image is determined by finding integers A and B so that a value f given by f = X × Y A × B + A × B is at a minimum, where X denotes a number of high resolution pixels of the captured image in a horizontal direction, Y denotes a number of high resolution pixels of the captured image in a vertical direction, and A denotes a number of high resolution pixels of the unit area in the horizontal direction, and B denotes a number of high resolution pixels of the unit area in the vertical direction. A and B are divisors of X and Y, respectively.


Journal ArticleDOI
01 Aug 2002-Proteins
TL;DR: X‐ray characterization at room temperature of high‐quality crystals of the intensely sweet thaumatin prepared in a sodium tartrate solution gelified with 0.15% (m/v) agarose to improve the quality of macromolecular crystals is reported.
Abstract: One reason for introducing a gel in the crystallization medium of proteins is its ability to reduce convection in solution This can lead to better nucleation and growth conditions, and to crystals having enhanced diffraction properties We report here the X-ray characterization at room temperature of high-quality crystals of the intensely sweet thaumatin prepared in a sodium tartrate solution gelified with 015% (m/v) agarose Using a synchrotron radiation, these crystals diffracted to a previously unachieved resolution A diffraction dataset was collected from four crystals at a resolution of 12 A with a Rsym of 36% and a completeness of 99% Refinement was carried out to a final crystallographic R-factor of 120% The quality of the electron density map allowed for the observation of fine structural details in the protein and its solvation shell Crystallization in gel might be used more generally to improve the quality of macromolecular crystals Advantages provided by the gelified medium in the frame of structural studies are emphasized Proteins 2002;48:146–150 © 2002 Wiley-Liss, Inc

Journal ArticleDOI
TL;DR: The energy filter will be an effective and important tool in the structure analysis of thin 3-D and 2-D crystals, particularly when data are collected at high tilt angle.

Journal ArticleDOI
TL;DR: In this article, the authors describe analytical techniques that allow an observation of heterogeneously catalyzed reactions, close to realistic chemical reaction conditions, with a spatial resolution down to 100 nm.
Abstract: We describe analytical techniques that allow an observation of heterogeneously catalyzed reactions, close to realistic chemical reaction conditions, with a spatial resolution down to 100 nm. Vibrational spectroscopy and scanning-force microscopy are combined to accomplish this goal. Raman microscopy is used for the investigation of the structural changes during heterogeneous catalytic reaction. This results already in a resolution of 1-2 μm, while in combination with scanning near-field optical microscopy (SNOM), a spatial resolution of even 100 nm has been achieved. Surface-enhanced Raman scattering (SERS) improves the sensitivity of Raman spectroscopy by many orders of magnitude and thus allows the study of a much broader range of reactions. As a model reaction system, the Pd catalyzed hydrogenation of benzene to cyclohexane was chosen. Spectra measured under reactive conditions differ significantly from reference spectra of the reactants and products measured under nonreactive conditions. This is explained by a structural change of the adsorbates on the activated surface but also by the possible formation of reaction intermediates.