scispace - formally typeset
Search or ask a question

Showing papers by "Oak Ridge National Laboratory published in 1995"


Proceedings ArticleDOI
08 Oct 1995
TL;DR: This paper presents three multilevel voltage source converters: (1) diode-clamp, (2) flying-capacitors, and (3) cascaded-inverters with separate DC sources.
Abstract: Multilevel voltage source converters are emerging as a new breed of power converter options for high-power applications. The multilevel voltage source converters typically synthesize the staircase voltage wave from several levels of DC capacitor voltages. One of the major limitations of the multilevel converters is the voltage unbalance between different levels. The techniques to balance the voltage between different levels normally involve voltage clamping or capacitor charge control. There are several ways of implementing voltage balance in multilevel converters. Without considering the traditional magnetic coupled converters, this paper presents three recently developed multilevel voltage source converters: (1) diode-clamp, (2) flying-capacitors, and (3) cascaded-inverters with separate DC sources. The operating principle, features, constraints, and potential applications of these converters are discussed.

3,232 citations


Journal ArticleDOI
TL;DR: The PVM system, a heterogeneous network computing trends in distributed computing PVM overview other packages, and troubleshooting: geting PVM installed getting PVM running compiling applications running applications debugging and tracing debugging the system.
Abstract: Part 1 Introduction: heterogeneous network computing trends in distributed computing PVM overview other packages. Part 2 The PVM system. Part 3 Using PVM: how to obtain the PVM software setup to use PVM setup summary starting PVM common startup problems running PVM programs PVM console details host file options. Part 4 Basic programming techniques: common parallel programming paradigms workload allocation porting existing applications to PVM. Part 5 PVM user interface: process control information dynamic configuration signalling setting and getting options message passing dynamic process groups. Part 6 Program examples: fork-join dot product failure matrix multiply one-dimensional heat equation. Part 7 How PVM works: components messages PVM daemon libpvm library protocols message routing task environment console program resource limitations multiprocessor systems. Part 8 Advanced topics: XPVM porting PVM to new architectures. Part 9 Troubleshooting: geting PVM installed getting PVM running compiling applications running applications debugging and tracing debugging the system. Appendices: history of PVM versions PVM 3 routines.

2,060 citations


Journal ArticleDOI
TL;DR: In this paper, a multivariate factor analysis was used to identify the common axes (or dimensions) of pattern and structure which were measured by a reduced set of 26 metrics, which were interpreted as composite measures of average patch compaction, overall image texture, average patch shape, patch perimeter-area scaling, number of attribute classes, and large-patch density area scaling.
Abstract: Fifty-five metrics of landscape pattern and structure were calculated for 85 maps of land use and land cover. A multivariate factor analysis was used to identify the common axes (or dimensions) of pattern and structure which were measured by a reduced set of 26 metrics. The first six factors explained about 87% of the variation in the 26 landscape metrics. These factors were interpreted as composite measures of average patch compaction, overall image texture, average patch shape, patch perimeter-area scaling, number of attribute classes, and large-patch density-area scaling. We suggest that these factors can be represented in a simpler way by six univariate metrics - average perimeter-area ratio, contagion, standardized patch shape, patch perimeter-area scaling, number of attribute classes, and large-patch density-area scaling.

1,217 citations


Journal ArticleDOI
TL;DR: In this paper, the authors examined some maximin distance designs constructed within the class of Latin hypercube arrangements, and presented a simulated annealing search algorithm for constructing these designs, and patterns apparent in the optimal designs are discussed.

1,096 citations


Patent
01 Aug 1995
TL;DR: In this paper, a microchip laboratory system and method provide fluid manipulations for a variety of applications, including sample injection for microchip chemical separations, using photolithographic procedures and chemical wet etching.
Abstract: A microchip laboratory system and method provide fluid manipulations for a variety of applications, including sample injection for microchip chemical separations. The microchip is fabricated using standard photolithographic procedures and chemical wet etching, with the substrate and cover plate joined using direct bonding. Capillary electrophoresis and electrochromatography are performed in channels formed in the substrate. Analytes are loaded into a four-way intersection of channels by electrokinetically pumping the analyte through the intersection, followed by switching of the potentials to force an analyte plug into the separation channel.

748 citations


Journal ArticleDOI
TL;DR: In this paper, the competitive and fractional adsorption-desorption of NOM subcomponents were investigated in order to better predict NOM partitioning between the solution and solid phases and, therefore, the transport behavior of the NOM in the subsurface soil environment.

652 citations


Journal ArticleDOI
TL;DR: In this paper, a new tokamak confinement regime has been observed on the Tokamak Fusion Test Reactor (TFTR), where particle and ion thermal diffusivities drop precipitously by a factor of \ensuremath{\sim}40 to the neoclassical level for the particles and to much less than the NE value for the ions in the region with reversed shear.
Abstract: A new tokamak confinement regime has been observed on the Tokamak Fusion Test Reactor (TFTR) where particle and ion thermal diffusivities drop precipitously by a factor of \ensuremath{\sim}40 to the neoclassical level for the particles and to much less than the neoclassical value for the ions in the region with reversed shear. This enhanced reversed shear confinement mode allows the central electron density to rise from 0.45 \ifmmode\times\else\texttimes\fi{} ${10}^{20}$ ${\mathrm{m}}^{\ensuremath{-}3}$ to \ensuremath{\sim}1.2 \ifmmode\times\else\texttimes\fi{} ${10}^{20}$ ${\mathrm{m}}^{\ensuremath{-}3}$ with ${T}_{i}\ensuremath{\sim}24$ keV and ${T}_{e}\ensuremath{\sim}8$ keV. This regime holds promise for significantly improved tokamak performance.

594 citations


Journal ArticleDOI
TL;DR: Values of normalized beta, up to 4 ({percent}-{ital m}-T/MA), energy confinement are a factor of 3 better than {ital L} mode, and at least 50% of the noninductive plasma current in this regime demonstrates compatibility with requirements for a steady-state high-beta tokamak power plant.
Abstract: Peaked pressure profiles and central ion temperatures up to 20 keV are observed in DIII-D $H$-mode discharges with a central region of strongly reversed magnetic shear. Short wavelength ballooning modes are stabilized by access to the second stable regime, longer wavelength modes by a conducting wall and possibly by rotational shear. Values of normalized beta, ${\ensuremath{\beta}}_{N}=\frac{\ensuremath{\beta}\mathrm{aB}}{I}$, up to 4 (%-$m$-T/MA), energy confinement are a factor of 3 better than $L$ mode, and at least 50% of the noninductive plasma current in this regime demonstrates compatibility with requirements for a steady-state high-beta tokamak power plant.

524 citations


Journal ArticleDOI
TL;DR: It is shown that Snell's waltzer encodes an unconventional myosin heavy chain,Myosin VI, which is expressed within the sensory hair cells of the inner ear, and appears to be required for maintaining their structural integrity.
Abstract: The mouse represents an excellent model system for the study of genetic deafness in humans. Many mouse deafness mutants have been identified and the anatomy of the mouse and human ear is similar. Here we report the use of a positional cloning approach to identify the gene encoded by the mouse recessive deafness mutation, Snell's waltzer (sv). We show that sv encodes an unconventional myosin heavy chain, myosin VI, which is expressed within the sensory hair cells of the inner ear, and appears to be required for maintaining their structural integrity. The requirement for myosin VI in hearing makes this gene an excellent candidate for a human deafness disorder.

481 citations


Journal ArticleDOI
TL;DR: In recent years, major advances have taken place in our understanding of welding processes and welded materials because of the complexity of fusion welding processes, solution of many important contemporary problems in fusion welding requires an interdisciplinary approach as mentioned in this paper.
Abstract: In recent years, major advances have taken place in our understanding of welding processes and welded materials Because of the complexity of fusion welding processes, solution of many important contemporary problems in fusion welding requires an interdisciplinary approach Current problems and issues in fusion welding are reviewed Solution of these problems, apart from being a contribution to the advancement of science, is also necessary for science-based tailoring of composition, structure, and properties of the welded materials

454 citations


Journal ArticleDOI
TL;DR: The super-individual concept offers easy possibilities to check whether the observed behaviour is an artifact of following a limited number of individuals or of lumping individuals, and also to verify whether individual variability is indeed an essential ingredient for the observedbehaviour.

Journal ArticleDOI
TL;DR: In this paper, a fused quartz microchip is fabricated to perform capillary electrophoresis of metal ions complexed with 8-hydroxyquinoline-5-sulfonic acid (HQS).
Abstract: A fused quartz microchip is fabricated to perform capillary electrophoresis of metal ions complexed with 8-hydroxyquinoline-5-sulfonic acid (HQS). The channel manifold on the quartz substrate is fabricated using standard photolithographic, etching, and deposition techniques. By incorporating a direct bonding technique during the fabrication of the microchip, the substrate and cover plate can be fused together below the melting temperature for fused quartz. To enhance the resolution for the separation, the electroosmotic flow is minimized by covalently bonding polyacrylamide to the channel walls. A separation length of 16.5 mm and separation field strength of 870 V/cm enable separations to be performed in {<=}15 s. By increasing the concentration of HQS from 5 mM to 20 mM, the separation efficiency improves by approximately 3 times. The low background signal from the fused quartz substrate results in mass detection limits of 85, 61, and 134 amol and concentration detection limits of 46, 57, and 30 ppb for Zn, Cd, and Al, respectively. 30 refs., 6 figs., 2 tabs.

Patent
14 Sep 1995
TL;DR: In this paper, a multilevel cascade voltage source inverter with separate DC sources is described, which is applicable to high voltage, high power applications such as flexible AC transmission systems (FACTS) including static VAR generation, power line conditioning, series compensation, phase shifting and voltage balancing.
Abstract: A multilevel cascade voltage source inverter having separate DC sources is described herein. This inverter is applicable to high voltage, high power applications such as flexible AC transmission systems (FACTS) including static VAR generation (SVG), power line conditioning, series compensation, phase shifting and voltage balancing and fuel cell and photovoltaic utility interface systems. The M-level inverter consists of at least one phase wherein each phase has a plurality of full bridge inverters equipped with an independent DC source. This inverter develops a near sinusoidal approximation voltage waveform with only one switching per cycle as the number of levels, M, is increased. The inverter may have either single-phase or multi-phase embodiments connected in either wye or delta configurations.

Journal ArticleDOI
TL;DR: In this paper, the insertion reaction of several different intercalation materials, amorphous V{sub 2}O{sub 5}, ammorphous LiMn{sub 1}O {sub 4}, and crystalline LiMmn{ sub 2 O{sub 4} films, have been investigated using the completed cathode/electrolyte/lithium thin-film battery.

Journal ArticleDOI
TL;DR: In this paper, the scaling of CO 2 and water vapour transfer from leaf to canopy dimensions was achieved by integrating mechanistic models for physiological (photosynthesis, stomatal conductance and soil/root and bole respiration) and micrometeorological (radiative transfer, turbulent transfer and surface energy exchanges) processes.
Abstract: The scaling of CO 2 and water vapour transfer from leaf to canopy dimensions was achieved by integrating mechanistic models for physiological (photosynthesis, stomatal conductance and soil/root and bole respiration) and micrometeorological (radiative transfer, turbulent transfer and surface energy exchanges) processes. The main objectives of this paper are to describe a canopy photosynthesis and evaporation model for a temperate broadleaf forest and to test it against field measurements. The other goal of this paper is to use the validated model to address some contemporary ecological and physiological questions concerning the transfer of carbon and water between forest canopies and the atmosphere. In particular, we examine the role of simple versus complex radiative transfer models and the effect of environmental (solar radiation and CO 2 ) and ecophysiological (photosynthetic capacity) variables on canopy-scale carbon and water vapour fluxes.

Journal ArticleDOI
TL;DR: An analytical methodology has been developed for predicting optimal protocols to reduce osmotic injury associated with the addition and removal of hypertonic concentrations of glycerol in human spermatozoa.
Abstract: Use of a cryoprotective agent is indispensable to prevent injury to human spermatozoa during the cryopreservation process. However, addition of cryoprotective agents to spermatozoa before cooling and their removal after warming may create severe osmotic stress for the cells, resulting in injury. The objective of this study was to test the hypothesis that the degree (or magnitude) of human sperm volume excursion can be used as an independent indicator to evaluate and predict possible osmotic injury to spermatozoa during the addition and removal of cryoprotective agents. Glycerol was used as a model cryoprotective agent in the present study. To test this hypothesis, first the tolerance limits of spermatozoa to swelling in hypo-osmotic solutions (iso-osmotic medium diluted with water) and to shrinkage in hyperosmotic solutions (iso-osmotic medium with sucrose) were determined. Sperm plasma membrane integrity was measured by fluorescent staining, and sperm motility was assessed by computer-assisted semen analysis before, during and after the anisosomotic exposure. The result indicate firstly that motility was much more sensitive to anisosmotic conditions than membrane integrity, and secondly that motility was substantially more sensitive to hypotonic than to hypertonic conditions. Based on the experimental data, osmotic injury as a function of sperm volume excursion (swelling or shrinking) was determined. The second step, using these sperm volume excursion limits and previously measured glycerol and water permeability coefficients of human spermatozoa, was to predict, by computer simulation, the cell osmotic injury caused by different procedures for the addition and removal of glycerol. The predicted sperm injury was confirmed by experiment. Based on this study, an analytical methodology has been developed for predicting optimal protocols to reduce osmotic injury associated with the addition and removal of hypertonic concentrations of glycerol in human spermatozoa.


Journal ArticleDOI
TL;DR: It is demonstrated conclusively that the ectopic agouti expression is responsible for most, if not all, of the phenotypic traits of the dominant, obese yellow mutants.
Abstract: Mice that carry the lethal yellow (Ay) or viable yellow (Avy) mutation, two dominant mutations of the agouti (a) gene in mouse chromosome 2, exhibit a phenotype that includes yellow fur, marked obesity, a form of type II diabetes associated with insulin resistance, and an increased susceptibility to tumor development Molecular analyses of these and several other dominant "obese yellow" a-locus mutations suggested that ectopic expression of the normal agouti protein gives rise to this complex pleiotropic phenotype We have now tested this hypothesis directly by generating transgenic mice that ectopically express an agouti cDNA clone encoding the normal agouti protein in all tissues examined Transgenic mice of both sexes have yellow fur, become obese, and develop hyperinsulinemia In addition, male transgenic mice develop hyperglycemia by 12-20 weeks of age These results demonstrate conclusively that the ectopic agouti expression is responsible for most, if not all, of the phenotypic traits of the dominant, obese yellow mutants

Journal ArticleDOI
TL;DR: There is a maximum dose and an optimum time for the detection of genetic effects because the toxicity associated with high doses of CP will affect cell division and increases in chromosome damage and gene mutations have been found in the peripheral blood lymphocytes of nurses, pharmacists and female workers occupationally exposured to CP.
Abstract: Cyclophosphamide (CP) is used to treat a wide range of neoplastic diseases as well as some non-malignant ones such as rheumatoid arthritis It is also used as an immunosuppressive agent prior to organ transplantation CP is, however, a known carcinogen in humans and produces secondary tumors There is little absorption either orally or intravenously and 10% of the drug is excreted unchanged CP is activated by hepatic mixed function oxidases and metabolites are delivered to neoplastic cells via the bloodstream Phosphoramide mustard is thought to be the major anti-neoplastic metabolite of CP while acrolein, which is highly toxic and is produced in equimolar amounts, is thought to be responsible for most of the toxic side effects DNA adducts have been formed after CP treatment in a variety of in vitro systems as well as in rats and mice using 3H-labeled CP 32P-postlabeling techniques have also been used in mice However, monitoring of adducts in humans has not yet been carried out CP has also been shown to induce unscheduled DNA synthesis in a human cell line CP has produced mutations in base-pair substituting strains of Salmonella tryphimurium in the presence of metabolic activation, but it has been shown to be negative in the E coli chromotest It has also been shown to be positive in Saccharomyces cerevisiae in D7 strain for many endpoints but negative in D62M for aneuploidy/malsegregation It has produced positive responses in Drosophila melanogaster for various endpoints and in Anopheles stephensi In somatic cells, CP has been shown to produce gene mutations, chromosome aberrations, micronuclei and sister chromatid exchanges in a variety of cultured cells in the presence of metabolic activation as well as sister chromatid exchanges without metabolic activation It has also produced chromosome damage and micronuclei in rats, mice and Chinese hamsters, and gene mutations in the mouse spot test and in the transgenic lacZ construct of Muta Mouse Increases in chromosome damage and gene mutations have been found in the peripheral blood lymphocytes of nurses, pharmacists and female workers occupationally exposured to CP during its production or distribution Chromosome aberrations, sister chromatid exchanges and gene mutations have been observed in somatic cells of patients treated therapeutically with CP In general, there is a maximum dose and an optimum time for the detection of genetic effects because the toxicity associated with high doses of CP will affect cell division In germ cells, CP has been shown to induce genetic damage in mice, rats and hamsters although the vast majority of such studies have used male mice(ABSTRACT TRUNCATED AT 400 WORDS)

Journal ArticleDOI
TL;DR: Using data from the studies generating quantitative information concerning heritability of genetic effects, an assessment of the heritable genetic risk presented by acrylamide is presented and estimates for inhalation or dermal exposures suggest higher risks for induced genetic disease in offspring from fathers exposed in occupational settings.
Abstract: An updated review of the genotoxicity studies with acrylamide is provided. Then, using data from the studies generating quantitative information concerning heritability of genetic effects, an assessment of the heritable genetic risk presented by acrylamide is presented. The review offers a discussion of the reactions and possible mechanisms of genotoxic action by acrylamide and its epoxide metabolite glycidamide. Several genetic risk approaches are discussed, including the parallelogram, direct (actually a modified direct), and doubling dose approaches. Using data from the specific-locus and heritable translocation assays, the modified direct and doubling dose approaches are utilized to quantitate genetic risk. Exposures of male parents to acrylamide via inhalation, ingestion, and dermal routes are also quantitated. With these approaches and measurements and their underlying assumptions concerning extrapolation factors (including germ cell stage specificity, DNA repair variability, locus specificity), number of human loci associated with dominant disease alleles, and spontaneous mutation rates, an assessment of heritable genetic risk for humans is calculated for the three exposure scenarios. The calculated estimates for offspring from fathers exposed to acrylamide via drinking water are up to three offspring potentially affected with induced genetic disease per 10(8) offspring. Estimates for inhalation or dermal exposures suggest higher risks for induced genetic disease in offspring from fathers exposed in occupational settings.

Journal ArticleDOI
TL;DR: The approach provides a simple means of conjugating antibodies directly to the distal end of PEG which is already bound to the liposome membrane, and should contribute to the development of superior targetable drug delivery vehicles for use in diagnostics and therapy.

Journal ArticleDOI
TL;DR: A fused quartz microchip with a serpentine column geometry is fabricated to perform rapid microchip electrophoresis of dansylated amino acids and a stacking injection technique is used to enhance the detection limits.
Abstract: A fused quartz microchip with a serpentine column geometry is fabricated to perform rapid microchip electrophoresis of dansylated amino acids. A 67 mm separation column is constructed in a 7 x 10 mm area on a quartz substrate using standard photolithographic, etching and deposition techniques. Buffer and sample flows within the channel manifold are precisely controlled through potentials applied to the reservoirs. To enhance the detection limits, a stacking injection technique is used to concentrate the sample at the inlet of the separation column. The stacked injections exhibit high reproducibility (2.1% relative standard deviation in peak area). Using a separation length of 67 mm and a separation field strength of 1100 V/cm, separations are performed in < or = 15 s generating approximately 40,000 theoretical plates.

Journal ArticleDOI
TL;DR: In this article, a comparison of displacement cascade evolution in different materials is presented, showing that the evolution of the cascades is similar in both materials, with the development of a highly disordered core and the emission of focusons and replacement collision sequences during collisional phase of the cascade.

Journal ArticleDOI
TL;DR: In this paper, an above-ground treatment method can be designed for the treatment of groundwater contaminated with low molecular weight chlorinated hydrocarbons, such as 1,1,2-Trichloroethylene (TCE), TCE, 1, 1-dichloromethanes, CCl4, CHCl3 and CH2Cl2, on the surface of palladized iron.

Journal ArticleDOI
TL;DR: Using members of the epidermal growth factor (EGF) family as well as site-directed recombinant human EGF mutants, this work investigated how ligand binding properties influence endosomal sorting with marked differences that correlate with the differing pH sensitivities of the ligands' binding properties.

Journal ArticleDOI
TL;DR: In this article, the authors evaluated spatial and temporal variations in the origin of particulate organic matter (POM) in the San Francisco Bay (SFB) estuary using multiple indicators (Chl a, C : N ratios, [6L3C]POC, and two classes of lipid biomarker compounds- sterols and phospholipid ester-linked fatty acids) and two sample types were collected-seston and Potamocorbula amurensis -in order to evaluate the assimilable portion of the POM.
Abstract: Multiple indicators (Chl a, C : N ratios, [6L3C]POC, and two classes of lipid biomarker compounds- sterols and phospholipid ester-linked fatty acids) were used to evaluate spatial and temporal variations in the origin of particulate organic matter (POM) in the San Francisco Bay (SFB) estuary. Comparisons were made between the northern and southern subestuaries of SFB, as well as along the salinity gradient of northern SFB. Two sample types were collected-seston, which was used to characterize the bulk POM, and tissues of the suspension-feeding bivalve Potamocorbula amurensis -in order to evaluate the assimilable portion of the POM. Samples were collected around biological and physical events (phytoplankton blooms and freshwater inflow) thought to be the primary mechanisms controlling temporal variability in organic matter sources. Seston samples indicate that phytoplankton sources of POM are important throughout the entire SFB system, with additional inputs of organic matter from bacterial and terrestrial vascular plant sources delivered to the northern region. Analysis of biomarker compounds in- P. amurensis tissues indicates that phytoplankton supply a large fraction of the assimilable carbon to clams throughout SFB, although isotopic analysis of clam tissues suggests that the origin of this reactive carbon varies spatially and that freshwater algae are an important source of reactive organic matter to clams living in northern SFB.

Journal ArticleDOI
TL;DR: In this paper, the authors examined the Chebyshev tau method for a variety of eigenvalue problems arising in hydrodynamic stability studies, particularly those of Orr-Sommerfeld type.

Journal ArticleDOI
TL;DR: In this article, a complete theoretical model is presented to simulate the electron seeding and the evolution of the plasma of electron-ion in the applied field, and the results of the theory verified by small scale experiments are used to simulate lightning in atmosphere, and helps to define the parameters of a laser system for lightning protection.
Abstract: Ultraviolet pulses of 200 fs duration and low energy (/spl ap/0.2 mJ) have a sufficiently high peak power to ionize oxygen and nitrogen by three- and four-photon ionization, respectively. It is shown that the resultant ionization channel induces a lightning like discharge at half of the natural self-breakdown voltage in nitrogen or air. The laser triggered discharging process is studied by monitoring the voltage between two planar electrodes. The effects of oxygen on the induced breakdown is investigated. A complete theoretical model is presented to simulate: (1) the electron seeding; and (2) the evolution of the plasma of electron-ion in the applied field. The results of the theory verified by small scale experiments-are used to simulate the process of laser triggered lightning in atmosphere, and helps to define the parameters of a laser system for lightning protection. >


Journal ArticleDOI
TL;DR: A new approach to the calculation of the electronic structure of large systems within the local density approximation is outlined and ideal order-{ital N} scaling is obtained.
Abstract: A new approach to the calculation of the electronic structure of large systems within the local density approximation is outlined. The electronic structure problem is formulated using real space multiple scattering theory. Employing a compute-node $\ensuremath{\leftrightarrow}$ atom equivalence, the method has been implemented on a massively parallel processing supercomputer. The method is naturally highly parallel and ideal order- $N$ scaling is obtained. The convergence of the method is demonstrated by comparison with the result of conventional electronic structure calculation for elemental metals and through calculation of the ordering energy of $\ensuremath{\beta}$ brass.