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Articles 3871 - 3900 of 4084

Full-Text Articles in Physical Sciences and Mathematics

Eigenvalue Problems Of Ginzburg–Landau Operator In Bounded Domains, Kening Lu, Xing-Bin Pan Jun 1990

Eigenvalue Problems Of Ginzburg–Landau Operator In Bounded Domains, Kening Lu, Xing-Bin Pan

Faculty Publications

In this paper we study the eigenvalue problems for the Ginzburg–Landau operator with a large parameter in bounded domains in [openface R]2 under gauge invariant boundary conditions. The estimates for the eigenvalues are obtained and the asymptotic behavior of the associated eigenfunctions is discussed. These results play a key role in estimating the critical magnetic field in the mathematical theory of superconductivity.

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Consistency And Generalization In Incrementally Trained Connectionist Networks, Tony R. Martinez May 1990

Consistency And Generalization In Incrementally Trained Connectionist Networks, Tony R. Martinez

Faculty Publications

This paper discusses aspects of consistency and generalization in connectionist networks which learn through incremental training by examples or rules. Differences between training set learning and incremental rule or example learning are presented. Generalization, the ability to output reasonable mappings when presented with novel input patterns, is discussed in light of the above learning methods. In particular, the contrast between humming distance generalization and generalizing by high order combinations of critical variables is overviewed. Examples of detailed rules for an incremental learning model are presented for both consistency and generalization constraints.

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Norms Of Positive Operators On Lp-Spaces, Ralph Howard, Anton R. Schep May 1990

Norms Of Positive Operators On Lp-Spaces, Ralph Howard, Anton R. Schep

Faculty Publications

No abstract provided.

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Interactive Morphometrics From Three-Dimensional Surface Images, William A. Barrett, Shawn C. Becker May 1990

Interactive Morphometrics From Three-Dimensional Surface Images, William A. Barrett, Shawn C. Becker

Faculty Publications

Techniques have been developed for extracting three-dimensional (3D) measurements directly and interactively from 3D representations of surface anatomy. In order to obtain 3D measurements the anatomical surface is interrogated directly through the use of morphometric tools. Morphometric tools include points, 3D graphical "probes", and logical sectioning functions which interact with the surface through depth buffer compositing operations. Tools are interactively positioned on or through the surface to measure surface dimensions and partial volumes, or to define intersecting functions which allow surface anatomy to be visualized in the context of surrounding anatomy. Visualization is also enhanced because tools reveal much pertaining …

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Chloroplast And Mitochondrial: Dna Polymerases From Cultured Soybean Cells, Sabine Heinhorst, Gordon C. Cannon, Arthur Weissbach Apr 1990

Chloroplast And Mitochondrial: Dna Polymerases From Cultured Soybean Cells, Sabine Heinhorst, Gordon C. Cannon, Arthur Weissbach

Faculty Publications

DNA polymerases were purified from chloroplasts and mitochondria of cultured Glycine max cells. The chloroplast enzyme exists in two forms which are indistinguishable from each other biochemically. All three organellar enzymes have an estimated molecular weight of 85,000 to 90,000 and prefer poly(rA)dT12-18 over activated DNA as a template in vitro. Maximum activity of the chloroplast and mitochondrial DNA polymerases requires KCI and a reducing agent, and the enzymes are completely resistant to inhibitors of DNA polymerase a. Taken together, these properties classify the soybean organellar enzymes as DNA polymerases y. A unique feature that distinguishes the plant enzymes from …

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A Scale Of Linear Spaces Related To The Lp Scale, S J. Dilworth Apr 1990

A Scale Of Linear Spaces Related To The Lp Scale, S J. Dilworth

Faculty Publications

No abstract provided.

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Central And South America Gps Geodesy- Casa Uno, James N. Kellogg, Timothy H. Dixon Mar 1990

Central And South America Gps Geodesy- Casa Uno, James N. Kellogg, Timothy H. Dixon

Faculty Publications

In January 1988, scientists from over 25 organizations in 13 countries and territories cooperated in the largest Global Positioning System (GPS) campaign in the world to date (Table 1). 43 GPS receivers collected approximately 590 station-days of data in America, Samoa, Australia, Canada, Colombia, Costa Rica, Ecuador, New Zealand, Norway, Panama, Sweden, United States, West Germany, and Venezuela. The experiment was entitled CASA UNO, an acronym for Central and South America -- and uno is the Spanish word for one, designating first epoch measurements. The CASA UNO experiment was the first civilian effort implementing a global GPS satellite tracking network. …

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The Extended Tracking Network And Indications Of Baseline Precision And Accuracy In The North Andes, Jeffrey T. Freymueller, James N. Kellogg Mar 1990

The Extended Tracking Network And Indications Of Baseline Precision And Accuracy In The North Andes, Jeffrey T. Freymueller, James N. Kellogg

Faculty Publications

The CASA UNO Global Positioning System (GPS) experiment (January-February 1988) included an extended tracking network which covered three continents in addition to the network of scientific interest in Central and South America. The repeatability of long baselines (400-1000 km) in South America is improved by up to a factor of two in the horizontal vector baseline components by using tracking stations in the Pacific and Europe to supplement stations in North America. In every case but one, the differences between the mean solutions obtained using different tracking networks was equal to or smaller than day-to-day rms repeatabilities for the same …

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First Gps Baseline Results From The North Andes, James N. Kellogg, Jeffrey T. Freymueller, Timothy H. Dixon, Ruth E. Neilan, Clemente Ropain U., Sergio Camargo M., Benjamin Fernandez Ch., James L. Stowell, Anibal Salazar, Jaime Mora V., Luis Espin, Vernon Perdue, Leonard Leos Mar 1990

First Gps Baseline Results From The North Andes, James N. Kellogg, Jeffrey T. Freymueller, Timothy H. Dixon, Ruth E. Neilan, Clemente Ropain U., Sergio Camargo M., Benjamin Fernandez Ch., James L. Stowell, Anibal Salazar, Jaime Mora V., Luis Espin, Vernon Perdue, Leonard Leos

Faculty Publications

The CASA UNO GPS (Global Positioning System) experiment (January-February 1988) has provided the first epoch baseline measurements for the study of plate motions and crustal deformation in and around the North Andes. Two dimensional horizontal baseline repeatabilities are as good as 5 parts in 108 for short baselines (100-1000km), and better than3 parts in 108 for long baselines (>1000km). Vertical repeatabilities are typically 4 -6 cm, with a weak dependence on baseline length. The expected rate of plate convergence across the Colombia Trench is 6-8 cm/yr, which should be detectable by the repeat experiment planned for 1991. …

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Photoluminescence Studies In Znxcd1-Xte Single Crystals, David D. Allred, Jesus González-Hernández, Elías López-Cruz, Worth P. Allred Mar 1990

Photoluminescence Studies In Znxcd1-Xte Single Crystals, David D. Allred, Jesus González-Hernández, Elías López-Cruz, Worth P. Allred

Faculty Publications

The crystalline quality of ZnxCd1-xTe single crystals prepared by a modified Bridgman method with 0≤x≤0.05 has been analyzed using photoluminescence. The spectrum of a typical sample is dominated by lines originating from the recombination of free and bound excitons. Lines due to free excitons in their ground and first excited states are observed in both the pure CdTe and the mixed crystals. Excitons bound to Dc vacancies are observed in the pure CdTe crystal but not in the mixed crystal. Weaker and broader features appearing at energies below the exciton emission range were associated with transitions involving free-to-bound and bound-to-bound …

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On Two Function-Spaces Which Are Similar To L0, S J. Dilworth, D A. Trautman Feb 1990

On Two Function-Spaces Which Are Similar To L0, S J. Dilworth, D A. Trautman

Faculty Publications

No abstract provided.

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Inhomogeneous Broadening In Spectral Bands Of Carbonmonoxymyoglobin: The Connection Between Spectral And Functional Heterogeneity, Todd B. Sauke, P. Ormos, A. Ansari, D. Braunstein, B. R. Cowen, H. Fraunfelder, M. K. Hong, I. E. T. Iben, P. J. Steinbach, R. D. Young Jan 1990

Inhomogeneous Broadening In Spectral Bands Of Carbonmonoxymyoglobin: The Connection Between Spectral And Functional Heterogeneity, Todd B. Sauke, P. Ormos, A. Ansari, D. Braunstein, B. R. Cowen, H. Fraunfelder, M. K. Hong, I. E. T. Iben, P. J. Steinbach, R. D. Young

Faculty Publications

The rebinding kinetics of CO to myoglobin after flash photolysis is nonexponential in time below approximately 180 K; the kinetics is governed by a distribution of enthalpic barriers. This distribution results from inhomogeneities in the protein conformation, referred to as conformational substates. Hole-burning experiments on the Soret and IR CO-stretch bands test the assumption that an inhomogeneous distribution of conformational substates results in inhomogeneously broadened spectra. CO was slowly photolyzed at different wavelengths in the Soret band at 10 K. Both the Soret band and the CO-stretch band A1, centered at 1,945 cm-1, shift during photolysis, demonstrating that different wavelengths …

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A Course In Laboratory And Stockroom Management, John T. Moore Jan 1990

A Course In Laboratory And Stockroom Management, John T. Moore

Faculty Publications

No abstract provided.

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Photoconductive Characterization Of Znxcd1-Xte (0≤X≤0.25) Single Crystal Alloys, David D. Allred, Elías López-Cruz, Jesus González-Hernández, Worth P. Allred Jan 1990

Photoconductive Characterization Of Znxcd1-Xte (0≤X≤0.25) Single Crystal Alloys, David D. Allred, Elías López-Cruz, Jesus González-Hernández, Worth P. Allred

Faculty Publications

Large grain polycrystalline and single crystals of ZnxCd1-xTe grown by a modified Bridgman method were studied using the photoluminescence and photoconductivity techniques. The temperature dependence of the band gap, as determined by photoluminescence, follows the Varshni equation for measuring temperature in the range of 15-290 K. One of the fitted parameters, the Debye temperature, monotonically decreases with the increase of the atomic zinc concentration. A close correlation between the photoluminescence and photoconductivity measurements is also found. Samples in which the photoluminescence spectra exhibit emission bands associated to cadmium vacancies and other structural defects, show a photoresponse curve which includes, in …

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Rheology Of Aqueous Suspensions Of Polystyrene Latex Stabilized By Grafted Poly(Ethylene Oxide), Harry J. Ploehn, J. W. Goodwin Jan 1990

Rheology Of Aqueous Suspensions Of Polystyrene Latex Stabilized By Grafted Poly(Ethylene Oxide), Harry J. Ploehn, J. W. Goodwin

Faculty Publications

A water-soluble carbodiimide has been used to end-graft aminated poly (ethylene oxide)(PEO) chemically onto colloidal polystyrene particles. Two particle sizes (115 and 347 nm diameter) and two PEO molecular weights (112 000 and 615 000 g mol–1) were combined to give suspensions with four different ratios of polymer layer thickness to particle radius. Electrophoresis demonstrated that the PEO was grafted, not just adsorbed. Dynamic light scattering showed that the adsorbed and grafted layers had similar structures and that non-ionic surfactant perturbed the PEO configurations. Steady shear and oscillatory rheometry indicated that long-ranged polymeric forces between particles governed the …

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Lottery Proceeds In California Pay For Installation Of A Ground-Water Monitoring System, June Ann Oberdorfer, J. W. Williams, M. G. Smelser Jan 1990

Lottery Proceeds In California Pay For Installation Of A Ground-Water Monitoring System, June Ann Oberdorfer, J. W. Williams, M. G. Smelser

Faculty Publications

No abstract provided.

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Advanced Infrared Optically Black Baffle Materials, David D. Allred, Ronald D. Seals, C. M. Egert Jan 1990

Advanced Infrared Optically Black Baffle Materials, David D. Allred, Ronald D. Seals, C. M. Egert

Faculty Publications

Infrared optically black baffle surfaces are an essential component of many advanced optical systems. All internal surfaces in advanced infrared optical sensors that require stray light management to achieve resolution are of primary concern in baffle design. Current industrial materials need improvements to meet advanced optical sensor systems requirements for optical, survivability, and endurability. Baffles are required to survive and operate in potentially severe environments. Robust diffuse-absorptive black surfaces, which are (1) thermally and mechanically stable to threats of x-ray, launch, and in-flight maneuver conditions, with specific densities to allow an acceptable weight load, (2) handleable during assembly, (3) cleanable, …

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Annealing Behavior Of The Photoluminescence Lines In Cdte And Znx Cd1-X Te Single Crystals, David D. Allred, A. Reyes-Mena, Jesus González-Hernández, Elías López-Cruz, Worth P. Allred Jan 1990

Annealing Behavior Of The Photoluminescence Lines In Cdte And Znx Cd1-X Te Single Crystals, David D. Allred, A. Reyes-Mena, Jesus González-Hernández, Elías López-Cruz, Worth P. Allred

Faculty Publications

The main lines in the photoluminescence spectra of Zn1Cd1-xTe single crystals grown by a modified Bridgman method in the compositional range of 0≤X≤0.25 have been identified. All crystals show only near-band-edge emission. To assist in the identification, various samples with different compositions were annealed under a Cd atmosphere. In the pure crystals, the prominent (A°, X) bound exciton line, as well as the doublet at longer wavelengths, disappear after the annealing. In contrast, the treatments do not change significantly the PL spectra of the mixed crystals.

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Characterization Of Metal/Carbon Multilayers By Raman Spectroscopy, David D. Allred, Qi Wang, Jesus González-Hernández Jan 1990

Characterization Of Metal/Carbon Multilayers By Raman Spectroscopy, David D. Allred, Qi Wang, Jesus González-Hernández

Faculty Publications

Laser Raman spectroscopy has been found to be useful for characterizing amorphous semiconductor multilayers, especially the interfaces of multilayers. Recently, we have extended this technique to the characterization of magnetron sputtered multilayers commonly used as reflectors in soft x-ray optics. Unlike the multilayers previously studied which contained only semiconductors and dielectrics, these are generally semiconductor/metal multilayers. We report here on the Raman characterization of the most common class of multilayers used in soft x-ray optics, those that contain a high density metal like tungsten interspersed with layers of carbon. In all of the metal/carbon multilayers the dominate feature in the …

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Deposition Of Zinc Selenide By Atomic Layer Epitaxy For Multilayer X-Ray Optics, J.K. Shurtleff, David D. Allred, R. T. Perkins, J. M. Thorne Jan 1990

Deposition Of Zinc Selenide By Atomic Layer Epitaxy For Multilayer X-Ray Optics, J.K. Shurtleff, David D. Allred, R. T. Perkins, J. M. Thorne

Faculty Publications

Thin film deposition techniques currently being used to produce multilayer x-ray optics (MXOs) have difficulty producing smooth, uniform multilayers with d-spacings less than about twelve angstroms. We are investigating atomic layer epitaxy (ALE) as an alternative to these techniques. ALE is a chemical vapor deposition technique which deposits an atomic layer of material during each cycle of the deposition process. The thickness of a film deposited by ALE depends only on the number of cycles. Multilayers deposited by ALE should be smooth and uniform with precise d-spacings which makes ALE an excellent technique for producing multilayer x-ray optics. We have …

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Diffuse Absorbing Beryllium Coatings Produced By Magnetron Sputtering, David D. Allred, C. M. Egert Jan 1990

Diffuse Absorbing Beryllium Coatings Produced By Magnetron Sputtering, David D. Allred, C. M. Egert

Faculty Publications

Beryllium coatings with varying thicknesses and columnar grain sizes were deposited by low temperature magnetron sputtering and wet chemically etched to enhance diffuse absorption of light. After etching these coatings exhibited a matte black surface finish and low specular reflectance (below 2%) in the IR up to a critical wavelength dependent upon the original grain size of the coating. Extremely thick coatings (350 µm) with original grain sizes of 10 to 12 µm were produced which exhibited specular reflectances below 0.5% up to 50 µm wavelength and a Lambertian BRDF at 10.6 µm averaging 4.3x10-3 ster-1. Scanning electron micrographs are …

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Design Of High Performance Soft X-Ray Windows, Raymond T. Perkins, David D. Allred, Larry V. Knight, James M. Thorne Jan 1990

Design Of High Performance Soft X-Ray Windows, Raymond T. Perkins, David D. Allred, Larry V. Knight, James M. Thorne

Faculty Publications

X-ray windows are used in sources and detectors to separate the neighborhood of the x-ray generation or detection from the use environment. While each use has its own requirements, there are some principles that should be used in designing an optimal x-ray window. Because x-rays are absorbed to some extent by all materials, minimizing absorption is one criterion in preparing windows. Also, for most uses there is a pressure difference across the window so that ensuring pinhole-free structure and sufficient mechanical strength to support the differential is another criterion for window design. Traditionally, absorption is minimized by fabricating the window …

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A Relaxation Algorithm For Segmentation Of The Endocardial Surface From Cine Ct, William A. Barrett, Bryan S. Morse Sep 1989

A Relaxation Algorithm For Segmentation Of The Endocardial Surface From Cine Ct, William A. Barrett, Bryan S. Morse

Faculty Publications

A relaxation algorithm has been developed for automated segmentation of the endocardial surface from contrast Cine CT images. The image is contoured at an initial density threshold and a one-dimensional edge operator is applied orthogonally to each point of the contour. Output from the operator is used to generate a histogram, the mode of which identifies a new threshold. The image is contoured again at the new threshold and the process is repeated. Iteration continues with successive threshold estimates converging to a stable value in the region of the endocardial surface. Computer-determined thresholds compare favorably with manual segmentation while reducing …

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Interactive Measurement Of Three-Dimensional Cardiac Morphology, William A. Barrett, Shawn C. Becker Sep 1989

Interactive Measurement Of Three-Dimensional Cardiac Morphology, William A. Barrett, Shawn C. Becker

Faculty Publications

Techniques have been developed for extracting three-dimensional (3D) measurements directly and interactively from 3D representations of Cine CT images. In order to obtain 3D measurements the anatomical surface is interrogated directly through the use of a 3D graphical "probe" (line). The probe is interactively positioned and stretched between any visible surface points to allow direct capture of 3D (linear) distance. Distance measurements are updated in real time as the probe dynamically "penetrates" any intervening anatomy while providing valuable depth cuing for visual feedback and probe placement. Curvilinear distance is obtained by stretching the probe over multiple surface points. The probe …

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Probabilistic Segmentation Of Myocardial Tissue By Deterministic Relaxation, William A. Barrett, Shawn C. Becker, Jerome A. Broekhuijsen Sep 1989

Probabilistic Segmentation Of Myocardial Tissue By Deterministic Relaxation, William A. Barrett, Shawn C. Becker, Jerome A. Broekhuijsen

Faculty Publications

A recently-developed probabilistic model for automatically segmenting regions of interest in abdominal CT scans has been adapted to the challenging task of segmenting myocardial tissue in Cine CT scans. A system has been implemented on relatively low-cost hardware which performs such segmentations. Special techniques have been developed to improve consistency and accuracy. Early results of testing this new modality are encouraging and promising. Based on observations from experimentation, new directions for future work have been identified.

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A Note On Roe's Characterization Of The Sine Function, Ralph Howard Mar 1989

A Note On Roe's Characterization Of The Sine Function, Ralph Howard

Faculty Publications

No abstract provided.

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Inulin-125I-Tyramine, An Improved Residualizing Label For Studies On Sites Of Catabolism Of Circulating Proteins, Janet L. Maxwell, John W. Baynes, Suzanne R. Thorpe Oct 1988

Inulin-125I-Tyramine, An Improved Residualizing Label For Studies On Sites Of Catabolism Of Circulating Proteins, Janet L. Maxwell, John W. Baynes, Suzanne R. Thorpe

Faculty Publications

Residualizing labels for protein, such as dilactitol-125I-tyramine (125I-DLT) and cellobiitol-125I-tyramine, have been used to identify the tissue and cellular sites of catabolism of long-lived plasma proteins, such as albumin, immunoglobulins, and lipoproteins. The radioactive degradation products formed from labeled proteins are relatively large, hydrophilic, resistant to lysosomal hydrolases, and accumulate in lysosomes in the cells involved in degradation of the carrier protein. However, the gradual loss of the catabolites from cells (t1/2 approximately 2 days) has limited the usefulness of residualizing labels in studies on longer lived proteins. We describe here a higher molecular weight (Mr approximately 5000), more efficient …

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Subspaces Of Lp,Q, N L. Carothers, S J. Dilworth Oct 1988

Subspaces Of Lp,Q, N L. Carothers, S J. Dilworth

Faculty Publications

We examine the subspace structure of the Lorentz function space Lp,q[0, oo). Our main result is that a subspace of Lp,q[0, oo), p ^ 2, q < oo,must either strongly embed in Lp[0,1] or contain a complemented copy of lq.

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Dynamic Display And Quantitative Analysis Of Three-Dimensional Left Ventricular Pathology, William A. Barrett, Jayaram K. Udupa Sep 1988

Dynamic Display And Quantitative Analysis Of Three-Dimensional Left Ventricular Pathology, William A. Barrett, Jayaram K. Udupa

Faculty Publications

Techniques have been developed for automated extraction and dynamic interactive display of three-dimensional (3D) left ventricular (LV) surface anatomy from Cine CT images using a PC-based image display architecture. Images of both endocardial and myocardial surface anatomy are generated from multiple views at multiple time instances to demonstrate various LV pathologies including apical akinesis, apical and posterior aneurysms, LV Failure, IHSS, and a left atrial myxoma. Surface generation requires interpolation between scans, surface tracking, and rendering. Generation of 60 views corresponding to a single time instance requires approximately 15 minutes. LV dimensions are measured between two or more surface points …

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A Parallel-Processing Subsystem For Rapid 3-D Interpolation Of Ct Images, William A. Barrett, Stephen J. Allan, Scott R. Cannon Sep 1988

A Parallel-Processing Subsystem For Rapid 3-D Interpolation Of Ct Images, William A. Barrett, Stephen J. Allan, Scott R. Cannon

Faculty Publications

An inexpensive parallel-processing subsystem for the rapid interpolation of CT image planes is demonstrated with a variety of node topologies. The subsystem is based on a tree network of INMOS T414 Transputer processors and is hosted by an AT-based image workstation. The subsystem accepts a stack of eight arbitrarily-spaced 256 x 256 image planes from the host. Subsystem output to the host consists of a stack of 32 scaled and evenly-spaced image planes (256 x 256 x 32 with cubic voxels). Benchmark execution times ranged from 12.3 seconds for three nodes to 5.8 seconds for eight nodes.

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