scholarly journals The Baseline Metrology System of the USNO Astrometric Interferometer

1994 ◽  
Vol 158 ◽  
pp. 174-176 ◽  
Author(s):  
Nicholas M. Elias ◽  
Donald J. Hutter
Keyword(s):  
High Resolution ◽  
Northern Hemisphere ◽  
Three Dimensional ◽  
Optical Interferometer ◽  
Laser Metrology ◽  
Under Construction ◽  
Metrology System ◽  
Better Than

The USNO Astrometric Interferometer (USNOAI; a subarray of the Navy Prototype Optical Interferometer at Lowell Observatory) is presently under construction and expected to begin limited operations within a year. The main goal of the USNOAI observations is to provide a northern hemisphere catalog of several thousand stars with positions known to a few mas. In order to meet this requirement, a baseline laser metrology system must be employed to measure the three-dimensional motions of the baselines with an accuracy better than ~ 0.1 μm. The metrology scheme, as presently conceived, represents the largest and most complex high-resolution laser metrology system ever attempted.

Instrumentation and methodology for electron crystallography

1991 ◽  
Vol 49 ◽  
pp. 420-421
Author(s):  
Kenneth H. Downing
Keyword(s):  
Electron Microscopy ◽  
High Resolution ◽  
Three Dimensional ◽  
Atomic Resolution ◽  
Single Atom ◽  
Electron Crystallography ◽  
Density Map ◽  
Low Exposure ◽  
Under Construction

The determination of three-dimensional structures of macromolecules at atomic resolution remains one oμf the great promises of electron microscopy. Instrumental problems which had to be overcome in order to achieve single-atom resolution have long been recognized and to a large extent overcome. It is interesting to note that most of the instrumental developments were already incorporated in a microscope under construction over 20 years ago. However, the application of techniques to circumvent limitations imposed by the sensitivity of organic specimen to radiation damage are still developing. Electron crystallography, which takes advantage of the ability to obtain useful information from images taken at very low exposure, is close to realizing the potential. The state of electron crystallography has advanced rapidly during the last few years. The structure of one protein, bacteriorhodopsin, has been determined from EM data, and several other structures are advanced to the point of fitting the peptide chain to a high-resolution density map.

scholarly journals The USNO Astrometric Interferometer

1994 ◽  
Vol 158 ◽  
pp. 427-435
Author(s):  
Donald J. Hutter
Keyword(s):  
State Of The Art ◽  
Naval Research ◽  
Delay Lines ◽  
Optical Interferometer ◽  
Zeroth Order ◽  
Matching Accuracy ◽  
Naval Observatory ◽  
Laser Metrology ◽  
Fringe Tracking ◽  
Metrology System

The U.S. Naval Observatory Astrometric Interferometer (USNOAI) will be the dedicated astrometric sub-array of the new Navy Prototype Optical Interferometer (NPOI) at Lowell Observatory, which is being built in collaboration with the Naval Research Laboratory. The USNOAI will be in operation on Anderson Mesa, near Flagstaff, Arizona, in late 1993. The instrument will incorporate four siderostats which will be located in a Y-shaped configuration, and will feature state-of-the-art delay lines, a real-time zeroth-order fringe tracking algorithm, a full-array laser metrology system to monitor baseline motion, and a limiting magnitude of 10. The instrument will be capable of simultaneous observations on six baselines, and will produce star positions accurate to a few mas. With it, we will be able to maintain the HIPPARCOS reference frame with matching accuracy over the next few decades.

scholarly journals Influence of temporal baseline on the vertical absolute accuracies of TSX HS interferometric DSMs: Case Study on Berlin

2014 ◽  
Vol XL-7 ◽  
pp. 155-160
Author(s):  
U. G. Sefercik ◽  
U. Soergel
Keyword(s):  
High Resolution ◽  
Three Dimensional ◽  
Negative Influence ◽  
Absolute Accuracy ◽  
Surface Models ◽  
Sar Imagery ◽  
Image Pairs ◽  
Better Than ◽  
Aperture Radar

In recent years, interferometric sytnthetic aperture radar (InSAR) is one of the most preferred techniques to generate digital surface models (DSM) which are the three dimensional (3D) digital cartographic representations of earth surface including all terrain and non-terrain formations. Interferometric DSM generation using synthetic aperture radar (SAR) imagery is not an easy process and the vertical absolute accuracy of the final product depends on various parameters. In this study, we aimed to demonstrate the influence of temporal baseline between SAR image-pairs on the vertical absolute accuracy of high resolution interferometric DSMs. The application was realized covering 20 km<sup>2</sup> area in Berlin, Germany using 15 descending orbit high resolution spotlight (HS) TerraSAR-X (TSX) images. The suitable interferometric pairs were determined for DSM generation and two of them that have similar parameters except temporal baseline were selected regarding the purposes of the study. The master image was selected as same in the generation of both DSMs and the temporal baselines between this master image and slave images were 11 days (1 period) and 187 days (17 periods), respectively. TSX HS DSMs were generated with 2 m grid spacing and the vertical absolute accuracies were calculated based on the comparison with a reference DSM generated by radargrammetry. The analyses were realized for built-up and forest land classes separately. The results proved that longer temporal baseline has negative influence on the vertical absolute accuracies of TSX HS interferometric DSMs. The first DSM which has the shortest temporal baseline, possible for TSX sensing is better than the second one as approx. 1.5 m both for built-up and forest areas.

scholarly journals The USNO Astrometric Optical Interferometer

1995 ◽  
Vol 166 ◽  
pp. 23-29
Author(s):  
D.J. Hutter ◽  
K.J. Johnston ◽  
D. Mozurkewich
Keyword(s):  
State Of The Art ◽  
Tracking System ◽  
Proper Motions ◽  
Optical Interferometer ◽  
Naval Observatory ◽  
Operational Lifetime ◽  
Visual Magnitude ◽  
Laser Metrology ◽  
Fringe Tracking ◽  
Metrology System

The U.S. Naval Observatory Astrometric Optical Interferometer (AOI) began operation on Anderson Mesa, near Flagstaff, Arizona, in the autumn of 1994. The AOI incorporates four siderostats that are located in a Y-shaped configuration, and features a full-array laser metrology system to monitor baseline motion. The AOI incorporates state-of-the-art delay lines and a real-time fringe-tracking system. The AOI will have a limiting visual magnitude of 10, under typical observing conditions, and will produce star positions accurate to a few milliarcseconds (mas). With a planned operational lifetime of several decades, this instrument will be capable of maintaining the optical reference frame by improving the proper motions of thousands of the brighter HIPPARCOS stars through repeated observations.

scholarly journals A CAD CAM method for custom below-knee sockets

1992 ◽  
Vol 16 (3) ◽  
pp. 183-188 ◽  
Author(s):  
J. R. Engsberg ◽  
G. S. Clynch ◽  
A. G. Lee ◽  
J. S. Allan ◽  
J. A. Harder
Keyword(s):  
High Resolution ◽  
Computer Aided Design ◽  
Three Dimensional ◽  
Numerical Data ◽  
Milling Machine ◽  
Cad Cam ◽  
Design Software ◽  
Aided Design ◽  
User Friendly ◽  
Better Than

The purpose of this investigation was to develop a numerical method for fabricating prosthetic sockets for below-knee amputees. An opticalllaser digitiser scans an amputee's stump and collects three dimensional numerical data describing the surface of the limb and describing specific modification site locations. The numerical data from the laser camera representing the stump and modification sites are altered by the prosthetist using a custom computer aided design software system running on a personal computer. Using the altered numerical data a programme is created for a high resolution numerically controlled milling machine and a mould is made. The prosthetist then fabricates a socket. While the system has been tested with below-knee amputees it has been designed for application in most areas of prosthetics and orthotics. Utilising this method 15 patients were fitted. All patients sujectively stated that their “computer designed” socket fitted better than their conventionally made socket. As the research progressed and experience was gained with the system patients were normally fitted with the first socket iteration. The system overcomes five limitations existing with some of the other numerical systems: 1) accurate high resolution surface topography, 2) specific identification of subject modification sites, 3) flexible, user friendly software, 4) high resolution numerically controlled milling, and 5) integrated expansion to other prosthetic and orthotic areas.

High Resolution Microscopy of Multi-Layered Biological Crystals

1982 ◽  
Vol 40 ◽  
pp. 80-83
Author(s):  
H.A. Cohen ◽  
T.W. Jeng ◽  
W. Chiu
Keyword(s):  
High Resolution ◽  
Low Dose ◽  
Three Dimensional ◽  
Data Interpretation ◽  
Two Dimensional ◽  
Biological Objects ◽  
Density Maps ◽  
Density Map ◽  
Complex Crystal ◽  
High Resolution Microscopy

This tutorial will discuss the methodology of low dose electron diffraction and imaging of crystalline biological objects, the problems of data interpretation for two-dimensional projected density maps of glucose embedded protein crystals, the factors to be considered in combining tilt data from three-dimensional crystals, and finally, the prospects of achieving a high resolution three-dimensional density map of a biological crystal. This methodology will be illustrated using two proteins under investigation in our laboratory, the T4 DNA helix destabilizing protein gp32*I and the crotoxin complex crystal.

Description of a New High Resolution Scanning Transmission EM

1972 ◽  
Vol 30 ◽  
pp. 418-419
Author(s):  
Michael Beer ◽  
J. W. Wiggins ◽  
David Woodruff ◽  
Jon Zubin
Keyword(s):  
High Resolution ◽  
Field Emission ◽  
Energy Dispersive Spectrometer ◽  
Scanning Transmission Electron Microscope ◽  
Objective Lens ◽  
Condenser Lens ◽  
Transmission Electron ◽  
Pattern Size ◽  
Scanning Transmission ◽  
Under Construction

A high resolution scanning transmission electron microscope of the type developed by A. V. Crewe is under construction in this laboratory. The basic design is completed and construction is under way with completion expected by the end of this year.The optical column of the microscope will consist of a field emission electron source, an accelerating lens, condenser lens, objective lens, diffraction lens, an energy dispersive spectrometer, and three electron detectors. For any accelerating voltage the condenser lens function to provide a parallel beam at the entrance of the objective lens. The diffraction lens is weak and its current will be controlled by the objective lens current to give an electron diffraction pattern size which is independent of small changes in the objective lens current made to achieve focus at the specimen. The objective lens demagnifies the image of the field emission source so that its Gaussian size is small compared to the aberration limit.

Electron crystallographic determination of the 3-D structure of staurolite at atomic resolution

1991 ◽  
Vol 49 ◽  
pp. 540-541
Author(s):  
Kenneth H. Downing ◽  
Hu Meisheng ◽  
Hans-Rudolf Went ◽  
Michael A. O'Keefe
Keyword(s):  
High Resolution ◽  
Three Dimensional ◽  
High Resolution Electron Microscopy ◽  
Atomic Resolution ◽  
Dimensional Structure ◽  
Structure Information ◽  
Resolution Electron ◽  
Scattering Effects ◽  
High Resolution Images ◽  
Effects Of Radiation

With current advances in electron microscope design, high resolution electron microscopy has become routine, and point resolutions of better than 2Å have been obtained in images of many inorganic crystals. Although this resolution is sufficient to resolve interatomic spacings, interpretation generally requires comparison of experimental images with calculations. Since the images are two-dimensional representations of projections of the full three-dimensional structure, information is invariably lost in the overlapping images of atoms at various heights. The technique of electron crystallography, in which information from several views of a crystal is combined, has been developed to obtain three-dimensional information on proteins. The resolution in images of proteins is severely limited by effects of radiation damage. In principle, atomic-resolution, 3D reconstructions should be obtainable from specimens that are resistant to damage. The most serious problem would appear to be in obtaining high-resolution images from areas that are thin enough that dynamical scattering effects can be ignored.

Three-Dimensional Immunoelectron Microscopy of Yeast Cells by a New High-Resolution Replica Method

1985 ◽  
Vol 43 ◽  
pp. 562-563
Author(s):  
Hirano T. ◽  
M. Yamaguchi ◽  
M. Hayashi ◽  
Y. Sekiguchi ◽  
A. Tanaka
Keyword(s):  
High Resolution ◽  
Plasma Polymerization ◽  
Three Dimensional ◽  
Freeze Fracture ◽  
Replica Method ◽  
Yeast Cells ◽  
Dynamic Aspect ◽  
Replica Technique ◽  
Gaseous Hydrocarbon ◽  
Transmission Electron

A plasma polymerization film replica method is a new high resolution replica technique devised by Tanaka et al. in 1978. It has been developed for investigation of the three dimensional ultrastructure in biological or nonbiological specimens with the transmission electron microscope. This method is based on direct observation of the single-stage replica film, which was obtained by directly coating on the specimen surface. A plasma polymerization film was deposited by gaseous hydrocarbon monomer in a glow discharge.The present study further developed the freeze fracture method by means of a plasma polymerization film produces a three dimensional replica of chemically untreated cells and provides a clear evidence of fine structure of the yeast plasma membrane, especially the dynamic aspect of the structure of invagination (Figure 1).

Exploring the Multidimensional Facets of Authoritarianism: Authoritarian Aggression and Social Dominance Orientation

2008 ◽  
Vol 67 (1) ◽  
pp. 51-60 ◽  
Author(s):  
Stefano Passini
Keyword(s):  
Social Dominance ◽  
Factor Model ◽  
Three Dimensional ◽  
Social Dominance Orientation ◽  
Model Fit ◽  
Regression Analyses ◽  
One Dimensional ◽  
Confirmatory Factor ◽  
The One ◽  
Better Than

The relation between authoritarianism and social dominance orientation was analyzed, with authoritarianism measured using a three-dimensional scale. The implicit multidimensional structure (authoritarian submission, conventionalism, authoritarian aggression) of Altemeyer’s (1981, 1988) conceptualization of authoritarianism is inconsistent with its one-dimensional methodological operationalization. The dimensionality of authoritarianism was investigated using confirmatory factor analysis in a sample of 713 university students. As hypothesized, the three-factor model fit the data significantly better than the one-factor model. Regression analyses revealed that only authoritarian aggression was related to social dominance orientation. That is, only intolerance of deviance was related to high social dominance, whereas submissiveness was not.

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