Radiation damage annealing mechanisms and possible low temperature annealing in silicon solar cells

NASA Technical Reports Server (NTRS)

Weinberg, I.; Swartz, C. K.

1980-01-01

The defect responsible for reverse annealing in 2 ohm/cm n(+)/p silicon solar cells was identified. This defect, with energy level at e sub v + 0.30 eV was tentatively identified as a boron oxygen-vacancy complex. Results indicate that its removal could result in significant annealing for 2 ohm/cm and lower resistivity cells at temperatures as low as 200 C. These results were obtained by use of an expression derived from the Shockley-Read-Hall recombination theory which relates measured diffusion length ratios to relative defect concentrations and electron capture cross sections. The relative defect concentrations and one of the required capture cross sections are obtained from Deep Level Transient Spectroscopy. Four additional capture cross sections are obtained using diffusion length data and data from temperature dependent lifetime studied. These calculated results are in reasonable agreement with experimental data.

Low cost fuel cell diffusion layer configured for optimized anode water management

DOEpatents

Owejan, Jon P; Nicotera, Paul D; Mench, Matthew M; Evans, Robert E

2013-08-27

A fuel cell comprises a cathode gas diffusion layer, a cathode catalyst layer, an anode gas diffusion layer, an anode catalyst layer and an electrolyte. The diffusion resistance of the anode gas diffusion layer when operated with anode fuel is higher than the diffusion resistance of the cathode gas diffusion layer. The anode gas diffusion layer may comprise filler particles having in-plane platelet geometries and be made of lower cost materials and manufacturing processes than currently available commercial carbon fiber substrates. The diffusion resistance difference between the anode gas diffusion layer and the cathode gas diffusion layer may allow for passive water balance control.

CO2 dynamics in the Amargosa Desert: Fluxes and isotopic speciation in a deep unsaturated zone

USGS Publications Warehouse

Walvoord, Michelle Ann; Striegl, Robert G.; Prudic, David E.; Stonestrom, David A.

2005-01-01

Natural unsaturated-zone gas profiles at the U.S. Geological Survey's Amargosa Desert Research Site, near Beatty, Nevada, reveal the presence of two physically and isotopically distinct CO2 sources, one shallow and one deep. The shallow source derives from seasonally variable autotrophic and heterotrophic respiration in the root zone. Scanning electron micrograph results indicate that at least part of the deep CO2 source is associated with calcite precipitation at the 110-m-deep water table. We use a geochemical gas-diffusion model to explore processes of CO2 production and behavior in the unsaturated zone. The individual isotopic species 12CO2, 13CO2, and 14CO2 are treated as separate chemical components that diffuse and react independently. Steady state model solutions, constrained by the measured δ13C (in CO2), and δ14C (in CO2) profiles, indicate that the shallow CO2 source from root and microbial respiration composes ∼97% of the annual average total CO2 production at this arid site. Despite the small contribution from deep CO2 production amounting to ∼0.1 mol m−2 yr−1, upward diffusion from depth strongly influences the distribution of CO2 and carbon isotopes in the deep unsaturated zone. In addition to diffusion from deep CO2 production, 14C exchange with a sorbed CO2 phase is indicated by the modeled δ14C profiles, confirming previous work. The new model of carbon-isotopic profiles provides a quantitative approach for evaluating fluxes of carbon under natural conditions in deep unsaturated zones.

Multiple sclerosis deep grey matter: the relation between demyelination, neurodegeneration, inflammation and iron

PubMed Central

Haider, Lukas; Simeonidou, Constantina; Steinberger, Günther; Hametner, Simon; Grigoriadis, Nikolaos; Deretzi, Georgia; Kovacs, Gabor G; Kutzelnigg, Alexandra; Lassmann, Hans; Frischer, Josa M

2014-01-01

In multiple sclerosis (MS), diffuse degenerative processes in the deep grey matter have been associated with clinical disabilities. We performed a systematic study in MS deep grey matter with a focus on the incidence and topographical distribution of lesions in relation to white matter and cortex in a total sample of 75 MS autopsy patients and 12 controls. In addition, detailed analyses of inflammation, acute axonal injury, iron deposition and oxidative stress were performed. MS deep grey matter was affected by two different processes: the formation of focal demyelinating lesions and diffuse neurodegeneration. Deep grey matter demyelination was most prominent in the caudate nucleus and hypothalamus and could already be seen in early MS stages. Lesions developed on the background of inflammation. Deep grey matter inflammation was intermediate between low inflammatory cortical lesions and active white matter lesions. Demyelination and neurodegeneration were associated with oxidative injury. Iron was stored primarily within oligodendrocytes and myelin fibres and released upon demyelination. In addition to focal demyelinated plaques, the MS deep grey matter also showed diffuse and global neurodegeneration. This was reflected by a global reduction of neuronal density, the presence of acutely injured axons, and the accumulation of oxidised phospholipids and DNA in neurons, oligodendrocytes and axons. Neurodegeneration was associated with T cell infiltration, expression of inducible nitric oxide synthase in microglia and profound accumulation of iron. Thus, both focal lesions as well as diffuse neurodegeneration in the deep grey matter appeared to contribute to the neurological disabilities of MS patients. PMID:24899728

Stretched-to-compressed-exponential crossover observed in the electrical degradation kinetics of some spinel-metallic screen-printed structures

NASA Astrophysics Data System (ADS)

Balitska, V.; Shpotyuk, O.; Brunner, M.; Hadzaman, I.

2018-02-01

Thermally-induced (170 °C) degradation-relaxation kinetics is examined in screen-printed structures composed of spinel Cu0.1Ni0.1Co1.6Mn1.2O4 ceramics with conductive Ag or Ag-Pd layered electrodes. Structural inhomogeneities due to Ag and Ag-Pd diffusants in spinel phase environment play a decisive role in non-exponential kinetics of negative relative resistance drift. If Ag migration in spinel is inhibited by Pd addition due to Ag-Pd alloy, the kinetics attains stretched exponential behavior with ∼0.58 exponent, typical for one-stage diffusion in structurally-dispersive media. Under deep Ag penetration into spinel ceramics, as for thick films with Ag-layered electrodes, the degradation kinetics drastically changes, attaining features of two-step diffusing process governed by compressed-exponential dependence with power index of ∼1.68. Crossover from stretched- to compressed-exponential kinetics in spinel-metallic structures is mapped on free energy landscape of non-barrier multi-well system under strong perturbation from equilibrium, showing transition with a character downhill scenario resulting in faster than exponential decaying.

Mapping saline groundwater beneath the Sea Galilee and its vicinity using time domain electromagnetic (TDEM) geophysical technique

USGS Publications Warehouse

Goldman, M.; Gvirtzman, H.; Hurwitz, S.

2004-01-01

An extensive time domain electromagnetic (TDEM) survey covering the Sea of Galilee with a dense grid of points has been recently carried out. A total of 269 offshore and 33 supplementary onshore TDEM soundings were performed along six N-S and ten W-E profiles and at selected points both offshore and onshore along the whole coastal line. The interpreted resistivities were calibrated with the direct salinity measurements in the Haon-2 borehole and relatively deep (5 m) cores taken from the lake bottom. It was found that resistivities below 1 ohm-m are solely indicative of groundwater salinity exceeding 10,000 mg Cl/l. Such low resistivities (high salinities) were detected at depths greater than 15 m below almost the entire bottom of the lake. At some parts of the lake, particularly in the south, the saline water was detected at shallower depths, sometimes at a few meters below the bottom. Relatively high resistivity (fresh groundwater) was found along the margins of the lake down to roughly 100 m, the maximum exploration depth of the system. The detected sharp lateral contrasts at the lake margin between high and low resistivities coincide with the faults separating the carbonate and clastic units, respectively. The geometry of the fresh/saline groundwater interface below the central part of the lake is very similar to the shape of the lake bottom, probably due to the diffusive salt transport from the bottom sediments to the lake water. The above geophysical observations suggest differentsalt transport mechanisms from the sediments to the central part of the lake (diffusion) and from regional aquifers to the margins of the lake (advection). ?? 2004 Science From Israel/LPPLtd.

q-Space Deep Learning: Twelve-Fold Shorter and Model-Free Diffusion MRI Scans.

PubMed

Golkov, Vladimir; Dosovitskiy, Alexey; Sperl, Jonathan I; Menzel, Marion I; Czisch, Michael; Samann, Philipp; Brox, Thomas; Cremers, Daniel

2016-05-01

Numerous scientific fields rely on elaborate but partly suboptimal data processing pipelines. An example is diffusion magnetic resonance imaging (diffusion MRI), a non-invasive microstructure assessment method with a prominent application in neuroimaging. Advanced diffusion models providing accurate microstructural characterization so far have required long acquisition times and thus have been inapplicable for children and adults who are uncooperative, uncomfortable, or unwell. We show that the long scan time requirements are mainly due to disadvantages of classical data processing. We demonstrate how deep learning, a group of algorithms based on recent advances in the field of artificial neural networks, can be applied to reduce diffusion MRI data processing to a single optimized step. This modification allows obtaining scalar measures from advanced models at twelve-fold reduced scan time and detecting abnormalities without using diffusion models. We set a new state of the art by estimating diffusion kurtosis measures from only 12 data points and neurite orientation dispersion and density measures from only 8 data points. This allows unprecedentedly fast and robust protocols facilitating clinical routine and demonstrates how classical data processing can be streamlined by means of deep learning.

Suppression of Lateral Diffusion and Surface Leakage Currents in nBn Photodetectors Using an Inverted Design

NASA Astrophysics Data System (ADS)

Du, X.; Savich, G. R.; Marozas, B. T.; Wicks, G. W.

2018-02-01

Surface leakage and lateral diffusion currents in InAs-based nBn photodetectors have been investigated. Devices fabricated using a shallow etch processing scheme that etches through the top contact and stops at the barrier exhibited large lateral diffusion current but undetectably low surface leakage. Such large lateral diffusion current significantly increased the dark current, especially in small devices, and causes pixel-to-pixel crosstalk in detector arrays. To eliminate the lateral diffusion current, two different approaches were examined. The conventional solution utilized a deep etch process, which etches through the top contact, barrier, and absorber. This deep etch processing scheme eliminated lateral diffusion, but introduced high surface current along the device mesa sidewalls, increasing the dark current. High device failure rate was also observed in deep-etched nBn structures. An alternative approach to limit lateral diffusion used an inverted nBn structure that has its absorber grown above the barrier. Like the shallow etch process on conventional nBn structures, the inverted nBn devices were fabricated with a processing scheme that only etches the top layer (the absorber, in this case) but avoids etching through the barrier. The results show that inverted nBn devices have the advantage of eliminating the lateral diffusion current without introducing elevated surface current.

Multiple sclerosis deep grey matter: the relation between demyelination, neurodegeneration, inflammation and iron.

PubMed

Haider, Lukas; Simeonidou, Constantina; Steinberger, Günther; Hametner, Simon; Grigoriadis, Nikolaos; Deretzi, Georgia; Kovacs, Gabor G; Kutzelnigg, Alexandra; Lassmann, Hans; Frischer, Josa M

2014-12-01

In multiple sclerosis (MS), diffuse degenerative processes in the deep grey matter have been associated with clinical disabilities. We performed a systematic study in MS deep grey matter with a focus on the incidence and topographical distribution of lesions in relation to white matter and cortex in a total sample of 75 MS autopsy patients and 12 controls. In addition, detailed analyses of inflammation, acute axonal injury, iron deposition and oxidative stress were performed. MS deep grey matter was affected by two different processes: the formation of focal demyelinating lesions and diffuse neurodegeneration. Deep grey matter demyelination was most prominent in the caudate nucleus and hypothalamus and could already be seen in early MS stages. Lesions developed on the background of inflammation. Deep grey matter inflammation was intermediate between low inflammatory cortical lesions and active white matter lesions. Demyelination and neurodegeneration were associated with oxidative injury. Iron was stored primarily within oligodendrocytes and myelin fibres and released upon demyelination. In addition to focal demyelinated plaques, the MS deep grey matter also showed diffuse and global neurodegeneration. This was reflected by a global reduction of neuronal density, the presence of acutely injured axons, and the accumulation of oxidised phospholipids and DNA in neurons, oligodendrocytes and axons. Neurodegeneration was associated with T cell infiltration, expression of inducible nitric oxide synthase in microglia and profound accumulation of iron. Thus, both focal lesions as well as diffuse neurodegeneration in the deep grey matter appeared to contribute to the neurological disabilities of MS patients. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://group.bmj.com/group/rights-licensing/permissions.

Advances in deep-UV processing using cluster tools

NASA Astrophysics Data System (ADS)

Escher, Gary C.; Tepolt, Gary; Mohondro, Robert D.

1993-09-01

Deep-UV laser lithography has shown the capability of supporting the manufacture of multiple generations of integrated circuits (ICs) due to its wide process latitude and depth of focus (DOF) for 0.2 micrometers to 0.5 micrometers feature sizes. This capability has been attained through improvements in deep-UV wide field lens technology, excimer lasers, steppers and chemically amplified, positive deep-UV resists. Chemically amplified deep-UV resists are required for 248 nm lithography due to the poor absorption and sensitivity of conventional novolac resists. The acid catalyzation processes of the new resists requires control of the thermal history and environmental conditions of the lithographic process. Work is currently underway at several resist vendors to reduce the need for these controls, but practical manufacturing solutions exist today. One of these solutions is the integration of steppers and resist tracks into a `cluster tool' or `Lithocell' to insure a consistent thermal profile for the resist process and reduce the time the resist is exposed to atmospheric contamination. The work here reports processing and system integration results with a Machine Technology, Inc (MTI) post-exposure bake (PEB) track interfaced with an advanced GCA XLS 7800 deep-UV stepper [31 mm diameter, variable NA (0.35 - 0.53) and variable sigma (0.3 - 0.74)].

Optimization of chemical compositions in low-carbon Al-killed enamel steel produced by ultra-fast continuous annealing

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dong, Futao, E-mail: dongft@sina.com; Du, Linxiu; Liu, Xianghua

2013-10-15

The influence of Mn,S and B contents on microstructural characteristics, mechanical properties and hydrogen trapping ability of low-carbon Al-killed enamel steel was investigated. The materials were produced and processed in a laboratory and the ultra-fast continuous annealing processing was performed using a continuous annealing simulator. It was found that increasing Mn,S contents in steel can improve its hydrogen trapping ability which is attributed by refined ferrite grains, more dispersed cementite and added MnS inclusions. Nevertheless, it deteriorates mechanical properties of steel sheet. Addition of trace boron results in both good mechanical properties and significantly improved hydrogen trapping ability. The boronmore » combined with nitrogen segregating at grain boundaries, cementite and MnS inclusions, provides higher amount of attractive hydrogen trapping sites and raises the activation energy for hydrogen desorption from them. - Highlights: • We study microstructures and properties in low-carbon Al-killed enamel steel. • Hydrogen diffusion coefficients are measured to reflect fish-scale resistance. • Manganese improves hydrogen trapping ability but decrease deep-drawing ability. • Boron improves both hydrogen trapping ability and deep-drawing ability. • Both excellent mechanical properties and fish-scale resistance can be matched.« less

Diffusion tensor imaging assessment of brain white matter maturation during the first postnatal year.

PubMed

Provenzale, James M; Liang, Luxia; DeLong, David; White, Leonard E

2007-08-01

The purpose of this study was to use diffusion-weighted and diffusion tensor imaging to investigate the status of cerebral white matter (WM) at term gestation and the rate of WM maturation throughout the first year of life in healthy infants. Fifty-three children (35 boys) ranging in age from 1.5 weeks premature to 51.5 weeks (mean age, 22.9 weeks) underwent conventional MRI, diffusion imaging in three directions (b = 1,000 s/mm2), and diffusion tensor imaging with gradient encoding in six directions, all on a 1.5-T MRI system. Apparent diffusion coefficient (ADC) and fractional anisotropy (FA) were measured in three deep WM structures (posterior limb of internal capsule, genu, and splenium of corpus callosum) and two peripheral WM regions (associational WM underlying prefrontal and posterior parietal cortex) with a standard region of interest (44 +/- 4 cm2). ADC and FA were expressed as a percentage of corresponding values measured in a group of healthy young adults. Mean ADC and FA values for deep and peripheral WM were plotted against gestational age normalized to term. The data were fit best with a broken-line linear regression model with a breakpoint at 100 days. ADC and FA values at term were estimated according to the intercept of the initial linear period (before day 100) with day 0. The slope of the linear fits was used to determine the rate of WM maturation in both the early and the late (after day 100) periods. Multivariate analysis of variance tests were used to compare deep and peripheral WM structures at term and at representative early and late ages (days 30 and 200) and to compare rates of ADC and FA maturation in early and late periods within the first year. At term, peripheral WM was less mature than deep WM according to results of extrapolation of ADC and FA values in the first 100 days of life to day 0 (p < 0.01). Mean ADC and FA value (percentage of mean adult value) for peripheral WM were 1.32 x 10(-3) mm2/s (163%) and 0.16 (32%), respectively, and 1.09 x 10(-3) mm2/s (143%) and 0.36 (54%), respectively, for deep WM. On day 30 and day 200, estimated mean ADC and FA continued to show greater diffusion (higher ADC) and less anisotropy (lower FA value) in peripheral WM (p <0.01). During the first year of postnatal life, both ADC and FA matured at higher rates before postnatal day 100 compared with a later time. Differences were observed in rates of maturation in the first 100 days when rates of decrease in ADC and increase in FA were compared between peripheral WM and deep WM; however, the maturational trends differed whether ADC or FA was examined. The early rate of ADC decrease (maturation) was twice as great for peripheral WM than for deep WM (p < 0.01) unexpectedly, but the opposite pattern was observed for FA. The early rate of FA increase (maturation) was approximately one half as great for peripheral WM as for deep WM (p = 0.01). Throughout the rest of the first year, no differences were observed in the rates of change in either index between peripheral WM and deep WM. At term, both ADC and FA differ significantly in peripheral WM and deep WM, deep WM structures being more mature. Both deep WM and peripheral WM mature more rapidly during approximately the first 3 months in comparison with the rest of the first year. Unexpected differences in early (first 100 days) rates of maturation assessed with diffusion-weighted (ADC) and diffusion tensor (FA) imaging suggest that these two techniques may be sensitive to different aspects of WM maturation in the early perinatal period.

CSA-90 Promotes Bone Formation and Mitigates Methicillin-resistant Staphylococcus aureus Infection in a Rat Open Fracture Model.

PubMed

Mills, Rebecca; Cheng, Tegan L; Mikulec, Kathy; Peacock, Lauren; Isaacs, David; Genberg, Carl; Savage, Paul B; Little, David G; Schindeler, Aaron

2018-06-01

Infection of open fractures remains a significant cause of morbidity and mortality to patients worldwide. Early administration of prophylactic antibiotics is known to improve outcomes; however, increasing concern regarding antimicrobial resistance makes finding new compounds for use in such cases a pressing area for further research. CSA-90, a synthetic peptidomimetic compound, has previously demonstrated promising antimicrobial action against Staphylococcus aureus in rat open fractures. However, its efficacy against antibiotic-resistant microorganisms, its potential as a therapeutic agent in addition to its prophylactic effects, and its proosteogenic properties all require further investigation. (1) Does prophylactic treatment with CSA-90 reduce infection rates in a rat open fracture model inoculated with S aureus, methicillin-resistant S aureus (MRSA), and methicillin-resistant Staphylococcus epidermidis (MRSE) as measured by survival, radiographic union, and deep tissue swab cultures? (2) Does CSA-90 reduce infection rates when administered later in the management of an open fracture as measured by survival, radiographic union, and deep tissue swab cultures? (3) Does CSA-90 demonstrate a synergistic proosteogenic effect with bone morphogenetic protein 2 (BMP-2) in a noninfected rat ectopic bone formation assay as assessed by micro-CT bone volume measurement? (4) Can CSA-90 elute and retain its antimicrobial efficacy in vitro when delivered using clinically relevant agents measured using a Kirby-Bauer disc diffusion assay? All in vivo studies were approved by the local animal ethics committee. In the open fracture studies, 12-week-old male Wistar rats underwent open midshaft femoral fractures stabilized with a 1.1-mm Kirschner wire and 10 µg BMP-2 ± 500 µg CSA-90 was applied to the fracture site using a collagen sponge along with 1 x 10 colony-forming units of bacteria (S aureus/MRSA/MRSE; n = 10 per group). In the delayed treatment study, débridement and treatment with 500 µg CSA-90 were performed at Day 1 and Day 5 after injury and bacterial insult (S aureus). All animals were reviewed daily for signs of local infection and/or sepsis. An independent, blinded veterinarian reviewed twice-weekly radiographs, and rats showing osteolysis and/or declining overall health were culled at his instruction. The primary outcome of both fracture studies was fracture infection, incorporating survival, radiographic union, and deep tissue swab cultures. For the ectopic bone formation assay, 0 to 10 µg BMP-2 and 0 to 500 µg CSA-90 were delivered on a collagen sponge into bilateral quadriceps muscle pouches of 8-week-old rats (n = 10 per group). Micro-CT quantification of bone volume and descriptive histologic analysis were performed for all in vivo studies. Modified Kirby-Bauer disc diffusion assays were used to quantify antimicrobial activity in vitro using four different delivery methods, including bone cement. Infection was observed in none of the MRSA inoculated open fractures treated with CSA-90 with 10 of 10 deep tissue swab cultures negative at the time of cull. Median survival was 43 days (range, 11-43 days) in the treated group versus 11 days (range, 8-11 days) in the untreated MRSA inoculated group (p < 0.001). However, delayed débridement and treatment of open fractures with CSA-90 at either Day 1 or Day 5 did not prevent infection, resulting in early culls by Day 21 with positive swab cultures (10 of 10 for each time point). Maximal ectopic bone formation was achieved with 500 μg CSA-90 and 10 μg BMP-2 (mean volume, 9.58 mm; SD, 7.83), creating larger bone nodules than formed with 250 μg CSA-90 and 10 μg BMP-2 (mean volume, 1.7 mm; SD, 1.07; p < 0.001). Disc diffusion assays showed that CSA-90 could successfully elute from four potential delivery agents including calcium sulphate (mean zone of inhibition, 11.35 mm; SD, 0.957) and bone cement (mean, 4.67 mm; SD, 0.516). CSA-90 shows antimicrobial action against antibiotic-resistant Staphylococcal strains in vitro and in an in vivo model of open fracture infection. The antimicrobial properties of CSA-90 combined with further evidence of its proosteogenic potential make it a promising compound to develop further for orthopaedic applications.

Neutral solute transport across osteochondral interface: A finite element approach.

PubMed

Arbabi, Vahid; Pouran, Behdad; Weinans, Harrie; Zadpoor, Amir A

2016-12-08

Investigation of the solute transfer across articular cartilage and subchondral bone plate could nurture the understanding of the mechanisms of osteoarthritis (OA) progression. In the current study, we approached the transport of neutral solutes in human (slight OA) and equine (healthy) samples using both computed tomography and biphasic-solute finite element modeling. We developed a multi-zone biphasic-solute finite element model (FEM) accounting for the inhomogeneity of articular cartilage (superficial, middle and deep zones) and subchondral bone plate. Fitting the FEM model to the concentration-time curves of the cartilage and the equilibrium concentration of the subchondral plate/calcified cartilage enabled determination of the diffusion coefficients in the superficial, middle and deep zones of cartilage and subchondral plate. We found slightly higher diffusion coefficients for all zones in the human samples as compared to the equine samples. Generally the diffusion coefficient in the superficial zone of human samples was about 3-fold higher than the middle zone, the diffusion coefficient of the middle zone was 1.5-fold higher than that of the deep zone, and the diffusion coefficient of the deep zone was 1.5-fold higher than that of the subchondral plate/calcified cartilage. Those ratios for equine samples were 9, 2 and 1.5, respectively. Regardless of the species considered, there is a gradual decrease of the diffusion coefficient as one approaches the subchondral plate, whereas the rate of decrease is dependent on the type of species. Copyright © 2016 Elsevier Ltd. All rights reserved.

Interlaminar Toughening of Fiber Reinforced Polymers

NASA Astrophysics Data System (ADS)

Bian, Dakai

Modification in the resin-rich region between plies, also known as the interlaminar region, was investigated to increase the toughness of laminate composites structures. To achieve suitable modifications, the complexities of the physical and chemical processes during the resin curing procedure must be studied. This includes analyses of the interactions among the co-dependent microstructure, process parameters, and material responses. This dissertation seeks to investigate these interactions via a series of experimental and numerical analyses of the geometric- and temperature-based effects on locally interleaving toughening methods and further interlaminar synergistic toughening without interleaf. Two major weaknesses in composite materials are the brittle resin-rich interlaminar region which forms between the fiber plies after resin infusion, and the ply dropoff region which introduces stress concentration under loads. To address these weaknesses and increase the delamination resistance of the composite specimens, a dual bonding process was explored to alleviate the dropoff effect and toughen the interlaminar region. Hot melt bonding was investigated by applying clamping pressure to ductile thermoplastic interleaf and fiber fabric at an elevated temperature, while diffusion bonding between thermoplastic interleaf and thermoset resin is performed during the resin infusion. This method increased the fracture energy level and thus delamination resistance in the interlaminar region because of deep interleaf penetration into fiber bundles which helped confining crack propagation in the toughened area. The diffusion and precipitation between thermosets and thermoplastics also improved the delamination resistance by forming a semi-interpenetration networks. This phenomenon was investigated in concoctions of low-concentration polystyrene additive modified epoxy system, which facilitates diffusion and precipitation without increasing the viscosity of the system. Additionally, chemical reaction induced phase separation, concentration of polystyrene, and various curing temperatures are used to evaluate their effects on diffusion and precipitation. These effects were directly investigated by performing attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR). The diffusivity and curing kinetics experiments are performed to quantify the diffusivity coefficient of epoxy, hardener and thermoplastics, as well as the reaction rate constant of curing epoxy at various temperatures. Finally, mechanical testing and fracture surface imaging were used to quantify the improvements and characterize the toughening mechanism. Further improvement on delamination resistance was studied through the synergistic effect of combining different modification methods without the interleaf. Polysulfone molecules are end-capped with epoxide groups. Fiber surface is functionalized with amino groups to generate micro-mechanical interlocks. The interaction between two individual modifications chemically links the modified semi-interpenetration networks to the improved interfacial strength between fiber and epoxy to. The impact of the additive on the crosslinking density was examined through glass transition temperatures, and the chemical modification was characterized by Raman spectroscopy. Mode I and II fracture tests were performed to quantify the improvement of delamination resistance under pure opening and shear loads. The mechanism of synergistic effect was explained based on the fracture surface morphology and the interactions between the modification methods.

Resistance to CO2 diffusion in cuticular membranes of amphibious plants and the implication for CO2 acquisition.

PubMed

Frost-Christensen, Henning; Floto, Franz

2007-01-01

Cuticular membranes (CMs) were isolated from leaves of amphibious and submerged plants and their CO2 resistances were determined as a contribution to establish quantitatively the series of resistances met by CO2 diffusing from bulk water to the chloroplasts of submerged leaves. The isolation was performed enzymatically; permeabilities were determined and converted to resistances. The range of permeance values was 3 to 43 x 10(-6) m s(-1) corresponding to resistance values of 23 to 295 x 10(3) s m(-1), i.e. of the same order of magnitude as boundary layer resistances. The sum of boundary layer, CM, leaf cell and carboxylation resistances could be contained within the total diffusion resistance as determined from the photosynthetic CO2 affinity of the leaf. From the same species, the aerial leaf CM resistance was always higher than the aquatic leaf CM resistance. In a terrestrial plant, the CM resistance to CO2 diffusion was found lower in leaves developed submerged.

Double-injection, deep-impurity switch development

NASA Technical Reports Server (NTRS)

Selim, F. A.; Whitson, D. W.

1983-01-01

The overall objective of this program is the development of device design and process techniques for the fabrication of a double-injection, deep-impurity (DI)(2) silicon switch that operates in the 1-10 kV range with conduction current of 10 and 1A, respectively. Other major specifications include a holding voltage of 0 to 5 volts at 1 A anode current, 10 microsecond switching time, and power dissipation of 50 W at 75 C. This report describes work that shows how the results obtained at the University of Cincinnati under NASA Grant NSG-3022 have been applied to larger area and higher voltage devices. The investigations include theoretical, analytical, and experimental studies of device design and processing. Methods to introduce deep levels, such as Au diffusion and electron irradiation, have been carried out to "pin down' the Fermi level and control device-switching characteristics. Different anode, cathode, and gate configurations are presented. Techniques to control the surface electric field of planar structures used for (DI)(2) switches are examined. Various sections of this report describe the device design, wafer-processing techniques, and various measurements which include ac and dc characteristics, 4-point probe, and spreading resistance.

The effects of deep level traps on the electrical properties of semi-insulating CdZnTe

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zha, Gangqiang; Yang, Jian; Xu, Lingyan

2014-01-28

Deep level traps have considerable effects on the electrical properties and radiation detection performance of high resistivity CdZnTe. A deep-trap model for high resistivity CdZnTe was proposed in this paper. The high resistivity mechanism and the electrical properties were analyzed based on this model. High resistivity CdZnTe with high trap ionization energy E{sub t} can withstand high bias voltages. The leakage current is dependent on both the deep traps and the shallow impurities. The performance of a CdZnTe radiation detector will deteriorate at low temperatures, and the way in which sub-bandgap light excitation could improve the low temperature performance canmore » be explained using the deep trap model.« less

Experimental study on the influence of chemical sensitizer on pressure resistance in deep water of emulsion explosives

NASA Astrophysics Data System (ADS)

Liu, Lei; zhang, Zhihua; Wang, Ya; Qin, hao

2018-03-01

The study on the pressure resistance performance of emulsion explosives in deep water can provide theoretical basis for underwater blasting, deep-hole blasting and emulsion explosives development. The sensitizer is an important component of emulsion explosives. By using reusable experimental devices to simulate the charge environment in deep water, the influence of the content of chemical sensitizer on the deep-water pressure resistance performance of emulsion explosives was studied. The experimental results show that with the increasing of the content of chemical sensitizer, the deep-water pressure resistance performance of emulsion explosives gradually improves, and when the pressure is fairly large, the effect is particularly pronounced; in a certain range, with the increase of the content of chemical sensitizer, that emulsion explosives’ explosion performance also gradually improve, but when the content reaches a certain value, the explosion properties declined instead; under the same emulsion matrix condition, when the content of NANO2 is 0.2%, that the emulsion explosives has good resistance to water pressure and good explosion properties. The correctness of the results above was testified in model blasting.

Analyzing the Boundary Thermal Resistance of Epitaxially Grown Fe2VAl/W Layers by Picosecond Time-Domain Thermoreflectance

NASA Astrophysics Data System (ADS)

Hiroi, Satoshi; Choi, Seongho; Nishino, Shunsuke; Seo, Okkyun; Chen, Yanna; Sakata, Osami; Takeuchi, Tsunehiro

2018-06-01

To gain deep insight into the mechanism of phonon scattering at grain boundaries, we investigated the boundary thermal resistance by using picosecond pulsed-laser time-domain thermoreflectance for epitaxially grown W/Fe2VAl/W films. By using radio-frequency magnetron sputtering, we prepared a series of the three-layer films whose Fe2VAl thickness ranged from 1 nm to 37 nm. The fine oscillation of reflectivity associated with the top W layer clearly appeared in synchrotron x-ray reflectivity measurements, indicating a less obvious mixture of elements at the boundary. The areal heat diffusion time, obtained from the time-domain thermoreflectance signal in the rear-heating front-detection configuration, reduced rapidly in samples whose Fe2VAl layer was thinner than 15 nm. The ˜ 10% mismatch in lattice constant between Fe2VAl and W naturally produced the randomly distributed lattice stress near the boundary, causing an effective increase of boundary thermal resistance in the thick samples, but the stress became homogeneous in the thinner layers, which reduced the scattering probability of phonons.

Mechanical Properties and Tribological Behavior of In Situ NbC/Fe Surface Composites

NASA Astrophysics Data System (ADS)

Cai, Xiaolong; Zhong, Lisheng; Xu, Yunhua

2017-01-01

The mechanical properties and tribological behavior of the niobium carbide (NbC)-reinforced gray cast iron surface composites prepared by in situ synthesis have been investigated. Composites are comprised of a thin compound layer and followed by a deep diffusion zone on the surface of gray cast iron. The graded distributions of the hardness and elastic modulus along the depth direction of the cross section of composites form in the ranges of 6.5-20.1 and 159.3-411.2 GPa, respectively. Meanwhile, dry wear tests for composites were implemented on pin-on-disk equipment at sliding speed of 14.7 × 10-2 m/s and under 5 or 20 N, respectively. The result indicates that tribological performances of composites are considerably dependent on the volume fraction and the grain size of the NbC as well as the mechanical properties of the matrices in different areas. The surface compound layer presents the lowest coefficient of friction and wear rate, and exhibits the highest wear resistance, in comparison with diffusion zone and substrate. Furthermore, the worn morphologies observed reveal the dominant wear mechanism is abrasive wear feature in compound layer and diffusion zone.

New processes and materials for ultraviolet detection with solid state devices

NASA Technical Reports Server (NTRS)

Chopra, D.

1977-01-01

The three major effects that degrade external responsivity of silicon from the 1/lambda theoretical curve for a quantum detector are: surface reflectance, surface recombination, and junction depth. Since the p-n junction must be very shallow, problems relating to surface are further enhanced. MOS type of processing is necessary. HCl oxides and numerous acid clean-ups are utilized in order to obtain a contamination free surface with low Qss levels. Stringent process controls such as CV shifts, spreading resistance measurements, thickness monitoring etc., are used to analyze the surface contaminations, surface mobile charges, surface concentrations, junction depth, oxide thickness etc. Low surface concentrations of 10 to the 18th atoms/cu cm are achieved by low temperature boron nitride depositions. Shallow junction depths of the order of a few tenths of a micron are achieved by low temperature controlled diffusions. In order to improve breakdown characteristics of these shallow junction devices, field plate and deep diffused p(+) ring geometries are used.

Use of a corrugated surface to enhance radiation tolerance in a GaAs solar cell

NASA Technical Reports Server (NTRS)

Leon, Rosa P.; Piszczor, Michael F., Jr.

1985-01-01

The use of a corrugated surface on a GaAs solar cell and its effects on radiation resistance were studied. A compute code was developed to determine the performance of the cell for various geometric parameters. The large optical absorption coefficient of GaAs allows grooves to be only 4-5 micrometers deep. Using accepted material parameters for GaAs solar cells the theoretical performances were compared for various corrugated cells before and after minority carrier diffusion length degradation. The total power output was maximized for both n(+)/p and p(+)/n cells. Optimum values of 1.0-1.5 and 5.0 micrometers for groove and ridge widths respectively were determined.

Accumulation of antibiotics and heavy metals in meat duck deep litter and their role in persistence of antibiotic-resistant Escherichia coli in different flocks on one duck farm.

PubMed

Lin, Y; Zhao, W; Shi, Z D; Gu, H R; Zhang, X T; Ji, X; Zou, X T; Gong, J S; Yao, W

2017-04-01

Meat duck deep litter is considered to be an ideal environment for the evolution of bacterial antibiotic resistance if it is under poor management. The aim of this study was to characterize the accumulation of antibiotics and heavy metals in the deep litter and their role in the persistence of antibiotic resistance of Escherichia coli, and evaluate the service life of the deep litter. Samples were collected from initial, middle, and final stages of deep litter within 3 barns (zero, 4, and 8 rounds of meat duck fattening, d 34) and 9 flocks, with known consumption of antibiotics in the controlled trail. The feed and litter levels of consumed antibiotics and heavy metals were measured. E. coli (n = 147) was isolated and typed by Eric-PCR and the phylogenetic grouping technique, while minimal inhibitory concentrations of antibiotics and heavy metals were measured. This study confirmed the continuous accumulation of doxycycline and many heavy metals in the deep litter. The population of resistant certain bacteria to doxycycline (16 mg/L, 100 mg/L) or ofloxacin (8 g/mL, 50 g/mL) increased in the used deep litter (rounds 4 and 8). E. coli isolated from the 3 stages of sampling were highly resistant to ampicillin, tetracycline, florfenicol, and doxycycline. Increased resistance to ceftiofur, enrofloxacin, ofloxacin, and gentamicin were seen in the isolates from the final stage of deep litter. In addition, the percentage of isolates tolerant to zinc, copper, and cadmium and the numbers of Group-B2 isolates all increased in the used deep litter, and the isolates of each stage belonged predominantly to commensal groups. The antibiotic resistance of isolates with identical Eric-PCR patterns had improved from round 4 to 8, and differences still existed in the resistance profiles of isolates with identical Eric-PCR patterns from different barns of the same round. This study concluded that deep litter could be suitable for the evolution of bacterial antibiotic-resistance under conditions of continuous usage or accumulation of antibiotics and heavy metals without proper management. © 2016 Poultry Science Association Inc.

Atelocollagen sponge and recombinant basic fibroblast growth factor combination therapy for resistant wounds with deep cavities.

PubMed

Nakanishi, Asako; Hakamada, Arata; Isoda, Ken-ichi; Mizutani, Hitoshi

2005-05-01

Recent advances in bioengineering have introduced materials that enhance wound healing. Even with such new tools, some deep ulcers surrounded by avascular tissues, including bone, tendon, and fascia, are resistant to various therapies and easily form deep cavities with loss of subcutaneous tissue. Atelocollagen sponges have been used as an artificial dermis to cover full-thickness skin defects. Topical recombinant human basic fibroblast growth factor has been introduced as a growth factor to induce fibroblast proliferation in skin ulcers. We applied these materials in combination in two patients with deep resistant wounds: one with a cavity reaching the mediastinum through a divided sternum and one with deep necrotic wounds caused by electric burns. These wounds did not respond to the topical basic fibroblast growth factor alone. In contrast, the combination therapy closed the wounds rapidly without further surgical treatment. This combination therapy is a potent treatment for resistant wounds with deep cavities.

DeepARG: a deep learning approach for predicting antibiotic resistance genes from metagenomic data.

PubMed

Arango-Argoty, Gustavo; Garner, Emily; Pruden, Amy; Heath, Lenwood S; Vikesland, Peter; Zhang, Liqing

2018-02-01

Growing concerns about increasing rates of antibiotic resistance call for expanded and comprehensive global monitoring. Advancing methods for monitoring of environmental media (e.g., wastewater, agricultural waste, food, and water) is especially needed for identifying potential resources of novel antibiotic resistance genes (ARGs), hot spots for gene exchange, and as pathways for the spread of ARGs and human exposure. Next-generation sequencing now enables direct access and profiling of the total metagenomic DNA pool, where ARGs are typically identified or predicted based on the "best hits" of sequence searches against existing databases. Unfortunately, this approach produces a high rate of false negatives. To address such limitations, we propose here a deep learning approach, taking into account a dissimilarity matrix created using all known categories of ARGs. Two deep learning models, DeepARG-SS and DeepARG-LS, were constructed for short read sequences and full gene length sequences, respectively. Evaluation of the deep learning models over 30 antibiotic resistance categories demonstrates that the DeepARG models can predict ARGs with both high precision (> 0.97) and recall (> 0.90). The models displayed an advantage over the typical best hit approach, yielding consistently lower false negative rates and thus higher overall recall (> 0.9). As more data become available for under-represented ARG categories, the DeepARG models' performance can be expected to be further enhanced due to the nature of the underlying neural networks. Our newly developed ARG database, DeepARG-DB, encompasses ARGs predicted with a high degree of confidence and extensive manual inspection, greatly expanding current ARG repositories. The deep learning models developed here offer more accurate antimicrobial resistance annotation relative to current bioinformatics practice. DeepARG does not require strict cutoffs, which enables identification of a much broader diversity of ARGs. The DeepARG models and database are available as a command line version and as a Web service at http://bench.cs.vt.edu/deeparg .

Implementation of LRFD geotechnical design for deep foundations using Texas Cone Penetrometer (TCP) test.

DOT National Transportation Integrated Search

2015-09-01

This study provides resistance factors (I) for design of deep foundations to implement Load and Resistance Factor Design (LRFD) for bridge foundations using Texas Cone Penetrometer (TCP) Test data. Initial efforts were made to determine resistance fa...

Disturbance of deep-sea environments induced by the M9.0 Tohoku Earthquake

PubMed Central

Kawagucci, Shinsuke; Yoshida, Yukari T.; Noguchi, Takuroh; Honda, Makio C.; Uchida, Hiroshi; Ishibashi, Hidenori; Nakagawa, Fumiko; Tsunogai, Urumu; Okamura, Kei; Takaki, Yoshihiro; Nunoura, Takuro; Miyazaki, Junichi; Hirai, Miho; Lin, Weiren; Kitazato, Hiroshi; Takai, Ken

2012-01-01

The impacts of the M9.0 Tohoku Earthquake on deep-sea environment were investigated 36 and 98 days after the event. The light transmission anomaly in the deep-sea water after 36 days became atypically greater (∼35%) and more extensive (thickness ∼1500 m) near the trench axis owing to the turbulent diffusion of fresh seafloor sediment, coordinated with potential seafloor displacement. In addition to the chemical influx associated with sediment diffusion, an influx of 13C-enriched methane from the deep sub-seafloor reservoirs was estimated. This isotopically unusual methane influx was possibly triggered by the earthquake and its aftershocks that subsequently induced changes in the sub-seafloor hydrogeologic structures. The whole prokaryotic biomass and the development of specific phylotypes in the deep-sea microbial communities could rise and fall at 36 and 98 days, respectively, after the event. We may capture the snap shots of post-earthquake disturbance in deep-sea chemistry and microbial community responses. PMID:22355782

Tackling Drug Resistant Infection Outbreaks of Global Pandemic Escherichia coli ST131 Using Evolutionary and Epidemiological Genomics

PubMed Central

Downing, Tim

2015-01-01

High-throughput molecular screening is required to investigate the origin and diffusion of antimicrobial resistance in pathogen outbreaks. The most frequent cause of human infection is Escherichia coli, which is dominated by sequence type 131 (ST131)—a set of rapidly radiating pandemic clones. The highly infectious clades of ST131 originated firstly by a mutation enhancing conjugation and adhesion. Secondly, single-nucleotide polymorphisms occurred enabling fluoroquinolone-resistance, which is near-fixed in all ST131. Thirdly, broader resistance through beta-lactamases has been gained and lost frequently, symptomatic of conflicting environmental selective effects. This flexible approach to gene exchange is worrying and supports the proposition that ST131 will develop an even wider range of plasmid and chromosomal elements promoting antimicrobial resistance. To stop ST131, deep genome sequencing is required to understand the origin, evolution and spread of antimicrobial resistance genes. Phylogenetic methods that decipher past events can predict future patterns of virulence and transmission based on genetic signatures of adaptation and gene exchange. Both the effect of partial antimicrobial exposure and cell dormancy caused by variation in gene expression may accelerate the development of resistance. High-throughput sequencing can decode measurable evolution of cell populations within patients associated with systems-wide changes in gene expression during treatments. A multi-faceted approach can enhance assessment of antimicrobial resistance in E. coli ST131 by examining transmission dynamics between hosts to achieve a goal of pre-empting resistance before it emerges by optimising antimicrobial treatment protocols. PMID:27682088

In vivo magnetization transfer and diffusion-weighted magnetic resonance imaging detects thrombus composition in a mouse model of deep vein thrombosis.

PubMed

Phinikaridou, Alkystis; Andia, Marcelo E; Saha, Prakash; Modarai, Bijan; Smith, Alberto; Botnar, René M

2013-05-01

Deep vein thrombosis remains a major health problem necessitating accurate diagnosis. Thrombolysis is associated with significant morbidity and is effective only for the treatment of unorganized thrombus. We tested the feasibility of in vivo magnetization transfer (MT) and diffusion-weighted magnetic resonance imaging to detect thrombus organization in a murine model of deep vein thrombosis. Deep vein thrombosis was induced in the inferior vena cava of male BALB/C mice. Magnetic resonance imaging was performed at days 1, 7, 14, 21, and 28 after thrombus induction using MT, diffusion-weighted, inversion-recovery, and T1-mapping protocols. Delayed enhancement and T1 mapping were repeated 2 hours after injection of a fibrin contrast agent. Finally, excised thrombi were used for histology. We found that MT and diffusion-weighted imaging can detect histological changes associated with thrombus aging. MT rate (MTR) maps and percentage of MT rate (%MTR) allowed visualization and quantification of the thrombus protein content, respectively. The %MTR increased with thrombus organization and was significantly higher at days 14, 21, and 28 after thrombus induction (days 1, 7, 14, 21, 28: %MTR=2483±451, 2079±1210, 7029±2490, 10 295±4356, 32 994±25 449; PANOVA<0.05). There was a significant positive correlation between the %MTR and the histological protein content of the thrombus (r=0.70; P<0.05). The apparent diffusion coefficient was lower in erythrocyte-rich and collagen-rich thrombus (0.72±0.10 and 0.69±0.05 [×10(-3) mm(2)/s]). Thrombus at days 7 and 14 had the highest apparent diffusion coefficient values (0.95±0.09 and 1.10±0.18 [×10(-3) mm(2)/s]). MT and diffusion-weighted magnetic resonance imaging sequences are promising for the staging of thrombus composition and could be useful in guiding medical intervention.

In Vivo Magnetization Transfer and Diffusion-Weighted Magnetic Resonance Imaging Detects Thrombus Composition in a Mouse Model of Deep Vein Thrombosis

PubMed Central

Saha, Prakash; Modarai, Bijan; Smith, Alberto; Botnar, René M.

2014-01-01

Background Deep vein thrombosis remains a major health problem necessitating accurate diagnosis. Thrombolysis is associated with significant morbidity and is effective only for the treatment of unorganized thrombus. We tested the feasibility of in vivo magnetization transfer (MT) and diffusion-weighted magnetic resonance imaging to detect thrombus organization in a murine model of deep vein thrombosis. Methods and Results Deep vein thrombosis was induced in the inferior vena cava of male BALB/C mice. Magnetic resonance imaging was performed at days 1, 7, 14, 21, and 28 after thrombus induction using MT, diffusion-weighted, inversion-recovery, and T1-mapping protocols. Delayed enhancement and T1 mapping were repeated 2 hours after injection of a fibrin contrast agent. Finally, excised thrombi were used for histology. We found that MT and diffusion-weighted imaging can detect histological changes associated with thrombus aging. MT rate (MTR) maps and percentage of MT rate (%MTR) allowed visualization and quantification of the thrombus protein content, respectively. The %MTR increased with thrombus organization and was significantly higher at days 14, 21, and 28 after thrombus induction (days 1, 7, 14, 21, 28: %MTR=2483±451, 2079±1210, 7029±2490, 10 295±4356, 32 994±25 449; Panova<0.05). There was a significant positive correlation between the %MTR and the histological protein content of the thrombus (r=0.70; P<0.05). The apparent diffusion coefficient was lower in erythrocyte-rich and collagen-rich thrombus (0.72±0.10 and 0.69±0.05 [×10−3 mm2/s]). Thrombus at days 7 and 14 had the highest apparent diffusion coefficient values (0.95±0.09 and 1.10±0.18 [×10−3 mm2/s]). Conclusions MT and diffusion-weighted magnetic resonance imaging sequences are promising for the staging of thrombus composition and could be useful in guiding medical intervention. PMID:23564561

White Matter Tract Injury is Associated with Deep Gray Matter Iron Deposition in Multiple Sclerosis.

PubMed

Bergsland, Niels; Tavazzi, Eleonora; Laganà, Maria Marcella; Baglio, Francesca; Cecconi, Pietro; Viotti, Stefano; Zivadinov, Robert; Baselli, Giuseppe; Rovaris, Marco

2017-01-01

With respect to healthy controls (HCs), increased iron concentrations in the deep gray matter (GM) and decreased white matter (WM) integrity are common findings in multiple sclerosis (MS) patients. The association between these features of the disease remains poorly understood. We investigated the relationship between deep iron deposition in the deep GM and WM injury in associated fiber tracts in MS patients. Sixty-six MS patients (mean age 50.0 years, median Expanded Disability Status Scale 5.25, mean disease duration 19.1 years) and 29 HCs, group matched for age and sex were imaged on a 1.5T scanner. Susceptibility-weighted imaging and diffusion tensor imaging (DTI) were used for assessing high-pass filtered phase values in the deep GM and normal appearing WM (NAWM) integrity in associated fiber tracts, respectively. Correlation analyses investigated the associations between filtered phase values (suggestive of iron content) and WM damage. Areas indicative of increased iron levels were found in the left and right caudates as well as in the left thalamus. MS patients presented with decreased DTI-derived measures of tissue integrity in the associated WM tracts. Greater mean, axial and radial diffusivities were associated with increased iron levels in all three GM areas (r values .393 to .514 with corresponding P values .003 to <.0001). Global NAWM diffusivity measures were not related to mean filtered phase values within the deep GM. Increased iron concentration in the deep GM is associated with decreased tissue integrity of the connected WM in MS patients. Copyright © 2016 by the American Society of Neuroimaging.

EM Diffusion for a Time-Domain Airborne EM System

NASA Astrophysics Data System (ADS)

Yin, C.; Qiu, C.; Liu, Y.; Cai, J.

2014-12-01

Visualization of EM diffusion for an airborne EM (AEM) system is important for understanding the transient procedure of EM diffusion. The current distribution and diffusion features also provide effective means to evaluate EM footprint, depth of exploration and further help AEM system design and data interpretation. Most previous studies on EM diffusion (or "smoke ring" effect) are based on the static presentation of EM field, where the dynamic features of EM diffusion were not visible. For visualizing the dynamic feature of EM diffusion, we first calculate in this paper the frequency-domain EM field by downward continuation of the EM field at the EM receiver to the deep earth. After that, we transform the results to time-domain via a Fourier transform. We take a homogeneous half-space and a two-layered earth induced by a step pulse to calculate the EM fields and display the EM diffusion in the earth as 3D animated vectors or time-varying contours. The "smoke ring" effect of EM diffusion, dominated by the resistivity distribution of the earth, is clearly observed. The numerical results for an HCP (vertical magnetic dipole) and a VCX (horizontal magnetic dipole) transmitting coil above a homogeneous half-space of 100 ohm-m are shown in Fig.1. We display as example only the distribution of EM field inside the earth for the diffusion time of 0.05ms. The detailed EM diffusion will be shown in our future presentation. From the numerical experiments for different models, we find that 1) the current for either an HCP or a VCX transmitting dipole propagates downward and outward with time, becoming wider and more diffuse, forming a "smoke ring"; 2) for a VCX transmitter, the underground current forms two ellipses, corresponding to the two polarities of the magnetic flux of a horizontal magnetic dipole, injecting into or ejected from the earth; 3) for a HCP transmitter, however, the underground current forms only one circle, corresponding to the polarity of the magnetic flux for a vertical magnetic dipole, injecting into the earth; 4) there exists no vertical current in an isotropic homogeneous half-space. The currents for both HCP and VCX transmitting dipole flow horizontally.

High Speed Trimaran (HST) Seatrain Experiments, Model 5714

DTIC Science & Technology

2013-12-01

Marine Highway 1 Historical Seatrains 1 Objectives 2 Hull &: Model Description 4 Data Acquisition and Instrumentation 7 Carriage II - Deep ...Operational Demonstration Measurement System 10 Experimental Procedures 10 Carriage II - Deep Water Basin Test 10 Calm Water Resistance 11... Deep Water Basin Analysis 17 Calm Water Resistance 17 Longitudinal Flow Through The Propeller Plane 18 Body Forces & Moments 18

Diffusion Dominant Solute Transport Modelling In Deep Repository Under The Effect of Emplacement Media Degradation - 13285

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kwong, S.; Jivkov, A.P.

2013-07-01

Deep geologic disposal of high activity and long-lived radioactive waste is being actively considered and pursued in many countries, where low permeability geological formations are used to provide long term waste contaminant with minimum impact to the environment and risk to the biosphere. A multi-barrier approach that makes use of both engineered and natural barriers (i.e. geological formations) is often used to further enhance the containment performance of the repository. As the deep repository system subjects to a variety of thermo-hydro-chemo-mechanical (THCM) effects over its long 'operational' lifespan (e.g. 0.1 to 1.0 million years, the integrity of the barrier systemmore » will decrease over time (e.g. fracturing in rock or clay)). This is broadly referred as media degradation in the present study. This modelling study examines the effects of media degradation on diffusion dominant solute transport in fractured media that are typical of deep geological environment. In particular, reactive solute transport through fractured media is studied using a 2-D model, that considers advection and diffusion, to explore the coupled effects of kinetic and equilibrium chemical processes, while the effects of degradation is studied using a pore network model that considers the media diffusivity and network changes. Model results are presented to demonstrate the use of a 3D pore-network model, using a novel architecture, to calculate macroscopic properties of the medium such as diffusivity, subject to pore space changes as the media degrade. Results from a reactive transport model of a representative geological waste disposal package are also presented to demonstrate the effect of media property change on the solute migration behaviour, illustrating the complex interplay between kinetic biogeochemical processes and diffusion dominant transport. The initial modelling results demonstrate the feasibility of a coupled modelling approach (using pore-network model and reactive transport model) to examine the long term behaviour of deep geological repositories with media property change under complex geochemical conditions. (authors)« less

Transverse mode selection in vertical-cavity surface-emitting lasers via deep impurity-induced disordering

NASA Astrophysics Data System (ADS)

O'Brien, Thomas R.; Kesler, Benjamin; Dallesasse, John M.

2017-02-01

Top emission 850-nm vertical-cavity surface-emitting lasers (VCSELs) demonstrating transverse mode selection via impurity-induced disordering (IID) are presented. The IID apertures are fabricated via closed ampoule zinc diffusion. A simple 1-D plane wave model based on the intermixing of Group III atoms during IID is presented to optimize the mirror loss of higher-order modes as a function of IID strength and depth. In addition, the impact of impurity diffusion into the cap layer of the lasers is shown to improve contact resistance. Further investigation of the mode-dependent characteristics of the device imply an increase in the thermal impedance associated with the fraction of IID contained within the oxide aperture. The optimization of the ratio of the IID aperture to oxide aperture is experimentally determined. Single fundamental mode output of 1.6 mW with 30 dBm side mode suppression ratio is achieved by a 3.0 μm oxide-confined device with an IID aperture of 1.3 μm indicating an optimal IID aperture size of 43% of the oxide aperture.

Hydrogen passivation of n+p and p+n heteroepitaxial InP solar cell structures

NASA Technical Reports Server (NTRS)

Chatterjee, B.; Ringel, S. A.; Hoffman, R., Jr.

1995-01-01

High-efficiency, heteroepitaxial (HE) InP solar cells, grown on GaAs, Si or Ge substrates, are desirable for their mechanically strong, light-weight and radiation-hard properties. However, dislocations, caused by lattice mismatch, currently limit the performance of the HE cells. This occurs through shunting paths across the active photovoltaic junction and by the formation of deep levels. In previous work we have demonstrated that plasma hydrogenation is an effective and stable means to passivate the electrical activity of dislocations in specially designed HE InP test structures. In this work, we present the first report of successful hydrogen passivation in actual InP cell structures grown on GaAs substrates by metalorganic chemical vapor deposition (MOCVD). We have found that a 2 hour exposure to a 13.56 MHz hydrogen plasma at 275 C reduces the deep level concentration in HE n+n InP cell structures from as-grown values of approximately 10(exp 15)/cm(exp -3), down to 1-2 x 10(exp 13)/cm(exp -3). The deep levels in the p-type base region of the cell structure match those of our earlier p-type test structures, which were attributed to dislocations or related point defect complexes. All dopants were successfully reactivated by a 400 C, 5 minute anneal with no detectable activation of deep levels. I-V analysis indicated a subsequent approximately 10 fold decrease in reverse leakage current at -1 volt reverse bias, and no change in the forward biased series resistance of the cell structure which indicates complete reactivation of the n+ emitter. Furthermore, electrochemical C-V profiling indicates greatly enhanced passivation depth, and hence hydrogen diffusion, for heteroepitaxial structures when compared with identically processed homoepitaxial n+p InP structures. An analysis of hydrogen diffusion in dislocated InP will be discussed, along with comparisons of passivation effectiveness for n+p versus p+n heteroepitaxial cell configurations. Preliminary hydrogen-passivated HE InP cell results will also be presented.

Postmortem diffusion MRI of the human brainstem and thalamus for deep brain stimulator electrode localization

PubMed Central

Calabrese, Evan; Hickey, Patrick; Hulette, Christine; Zhang, Jingxian; Parente, Beth; Lad, Shivanand P.; Johnson, G. Allan

2015-01-01

Deep brain stimulation (DBS) is an established surgical therapy for medically refractory tremor disorders including essential tremor (ET) and is currently under investigation for use in a variety of other neurologic and psychiatric disorders. There is growing evidence that the anti-tremor effects of DBS for ET are directly related to modulation of the dentatorubrothalamic tract (DRT), a white matter pathway that connects the cerebellum, red nucleus, and ventral intermediate nucleus of the thalamus. Emerging white matter targets for DBS, like the DRT, will require improved 3D reference maps of deep brain anatomy and structural connectivity for accurate electrode targeting. High-resolution diffusion MRI of postmortem brain specimens can provide detailed volumetric images of important deep brain nuclei and 3D reconstructions of white matter pathways with probabilistic tractography techniques. We present a high spatial and angular resolution diffusion MRI template of the postmortem human brainstem and thalamus with 3D reconstructions of the nuclei and white matter tracts involved in ET circuitry. We demonstrate accurate registration of these data to in vivo, clinical images from patients receiving DBS therapy, and correlate electrode proximity to tractography of the DRT with improvement of ET symptoms. PMID:26043869

Evaluation of static resistance of deep foundations.

DOT National Transportation Integrated Search

2017-05-01

The focus of this research was to evaluate and improve Florida Department of Transportation (FDOT) FB-Deep software prediction of nominal resistance of H-piles, prestressed concrete piles in limestone, large diameter (> 36) open steel and concrete...

Influence of Hydrostatic Pressure on the Corrosion Behavior of Superhydrophobic Surfaces on Bare and Oxidized Aluminum Substrates.

PubMed

Ou, J F; Fang, X Z; Zhao, W J; Lei, S; Xue, M S; Wang, F J; Li, C Q; Lu, Y L; Li, W

2018-05-22

It is generally recognized that superhydrophobic surfaces in water may be used for corrosion resistance due to the entrapped air in the solid/liquid interface and could find potential applications in the protection of ship hull. For a superhydrophobic surface, as its immersion depth into water increases, the resultant hydrostatic pressure is also increased, and the entrapped air can be squeezed out much more easily. It is therefore predicted that high hydrostatic pressure would cause an unexpected decrease in corrosion resistance for the vessels in deep water (e.g., submarines) because of the unstable entrapped air. In this work, in order to clarify the role of hydrostatic pressure in the corrosion behavior of superhydrophobic surfaces, two typical superhydrophobic surfaces (SHSs) were prepared on bare and oxidized aluminum substrates, respectively, and then were immersed into the NaCl aqueous solutions with different depths of ∼0 cm (hydrostatic pressure ∼0 kPa), 10 cm (1 kPa), and 150 cm (15 kPa). It was found out for the SHSs on the oxidized Al, as the hydrostatic pressure increased, the corrosion behavior became severe. However, for the SHSs on the bare Al, their corrosion behavior was complex due to hydrostatic pressure. It was found that the corrosion resistance under 1 kPa was the highest. Further mechanism analysis revealed that this alleviated corrosion behavior under 1 kPa resulted from suppressing the oxygen diffusion through the liquid and reducing the subsequent corrosion rate as compared with 0 kPa, whereas the relatively low hydrostatic pressure (HP) could stabilize the entrapped air and hence enhance the corrosion resistance, compared with 15 kPa. The present study therefore provided a fundamental understanding for the applications of SHSs to prevent the corrosion, especially for various vessels in deep water.

Comparison of deep and superficial abdominal muscle activity between experienced Pilates and resistance exercise instructors and controls during stabilization exercise.

PubMed

Moon, Ji-Hyun; Hong, Sang-Min; Kim, Chang-Won; Shin, Yun-A

2015-06-01

Pilates and resistance exercises are used for lumbar stabilization training. However, it is unclear which exercise is more effective for lumbar stabilization. In our study, we aimed to compare surface muscle activity and deep muscle thickness during relaxation and spinal stabilization exercise in experienced Pilates and resistance exercise instructors. This study is a retrospective case control study set in the Exercise Prescription Laboratory and Sports Medicine Center. The participants included Pilates instructors (mean years of experience, 3.20±1.76; n=10), resistance exercise instructors (mean years of experience, 2.53±0.63; n=10), and controls (n=10). The participants performed 4 different stabilization exercises: abdominal drawing-in maneuver, bridging, roll-up, and one-leg raise. During the stabilization exercises, surface muscle activity was measured with electromyography, whereas deep muscle thickness was measured by ultrasound imaging. During the 4 stabilization exercises, the thickness of the transverse abdominis (TrA) was significantly greater in the Pilates-trained group than the other 2 other groups. The internal oblique (IO) thickness was significantly greater in the Pilates- and resistance-trained group than the control group, during the 4 exercises. However, the surface muscle activities were similar between the groups. Both Pilates and resistance exercise instructors had greater activation of deep muscles, such as the TrA and IO, than the control subjects. Pilates and resistance exercise are both effective for increasing abdominal deep muscle thickness.

Comparison of deep and superficial abdominal muscle activity between experienced Pilates and resistance exercise instructors and controls during stabilization exercise

PubMed Central

Moon, Ji-Hyun; Hong, Sang-Min; Kim, Chang-Won; Shin, Yun-A

2015-01-01

Pilates and resistance exercises are used for lumbar stabilization training. However, it is unclear which exercise is more effective for lumbar stabilization. In our study, we aimed to compare surface muscle activity and deep muscle thickness during relaxation and spinal stabilization exercise in experienced Pilates and resistance exercise instructors. This study is a retrospective case control study set in the Exercise Prescription Laboratory and Sports Medicine Center. The participants included Pilates instructors (mean years of experience, 3.20±1.76; n=10), resistance exercise instructors (mean years of experience, 2.53±0.63; n=10), and controls (n=10). The participants performed 4 different stabilization exercises: abdominal drawing-in maneuver, bridging, roll-up, and one-leg raise. During the stabilization exercises, surface muscle activity was measured with electromyography, whereas deep muscle thickness was measured by ultrasound imaging. During the 4 stabilization exercises, the thickness of the transverse abdominis (TrA) was significantly greater in the Pilates-trained group than the other 2 other groups. The internal oblique (IO) thickness was significantly greater in the Pilates- and resistance-trained group than the control group, during the 4 exercises. However, the surface muscle activities were similar between the groups. Both Pilates and resistance exercise instructors had greater activation of deep muscles, such as the TrA and IO, than the control subjects. Pilates and resistance exercise are both effective for increasing abdominal deep muscle thickness. PMID:26171383

Characterization of double diffusive convection step and heat budget in the deep Arctic Ocean

NASA Astrophysics Data System (ADS)

Zhou, S.; Lu, Y.

2013-12-01

In this paper, we explore the hydrographic structure and heat budget in deep Canada Basin using data measured with McLane-Moored-Profilers (MMPs), bottom-pressure-recorders (BPRs), and conductivity-temperature-depth (CTD) profilers. From the bottom upward, a homogenous bottom layer and its overlaying double diffusive convection (DDC) steps are well identified at Mooring A (75oN, 150oW). We find that the deep water is in weak diapycnal mixing because the effective diffusivity of the bottom layer is ~1.8×10-5 m 2s-1 while that of the other steps is ~10-6 m 2s-1. The vertical heat flux through DDC steps is evaluated with different methods. We find that the heat flux (0.1-11 mWm-2) is much smaller than geothermal heating (~50 mWm-2), which suggests that the stack of DDC steps acts as a thermal barrier in the deep basin. Moreover, the temporal distributions of temperature and salinity differences across the interface are exponential, while those of heat flux and effective diffusivity are found to be approximately log-normal. Both are the result of strong intermittency. Between 2003 and 2011, temperature fluctuation close to the sea floor distributed asymmetrically and skewed towards positive values, which provides direct indication that geothermal heating is transferred into ocean. Both BPR and CTD data suggest that geothermal heating, not the warming of upper ocean, is the dominant mechanism responsible for the warming of deep water. As the DDC steps prevent the vertical heat transfer, geothermal heating will be unlikely to have significant effect on the middle and upper oceans.

Characterization of double diffusive convection steps and heat budget in the deep Arctic Ocean

NASA Astrophysics Data System (ADS)

Zhou, Sheng-Qi; Lu, Yuan-Zheng

2013-12-01

In this paper, we explore the hydrographic structure and heat budget in the deep Canada Basin by using data measured with McLane-Moored-Profilers (MMP), bottom pressure recorders (BPR), and conductivity-temperature-depth (CTD) profilers. Upward from the bottom, a homogeneous bottom layer and its overlaying double diffusive convection (DDC) steps are well identified at Mooring A (75°N,150°W). We find that the deep water is in weak diapycnal mixing because the effective diffusivity of the bottom layer is ˜1.8 × 10-5 m2s-1, while that of the other steps is ˜10-6 m2s-1. The vertical heat flux through the DDC steps is evaluated by using different methods. We find that the heat flux (0.1-11 mWm -2) is much smaller than geothermal heating (˜50 mWm -2). This suggests that the stack of DDC steps acts as a thermal barrier in the deep basin. Moreover, the temporal distributions of temperature and salinity differences across the interface are exponential, whereas those of heat flux and effective diffusivity are found to be approximately lognormal. Both are the result of strong intermittency. Between 2003 and 2011, temperature fluctuations close to the sea floor were distributed asymmetrically and skewed toward positive values, which provide a direct observation that geothermal heating was transferred into the ocean. Both BPR and CTD data suggest that geothermal heating and not the warming of the upper ocean is the dominant mechanism responsible for the warming of deep water. As the DDC steps prevent vertical heat transfer, geothermal heating is unlikely to have a significant effect on the middle and upper Arctic Ocean.

Enhanced oxygen vacancy diffusion in Ta2O5 resistive memory devices due to infinitely adaptive crystal structure

NASA Astrophysics Data System (ADS)

Jiang, Hao; Stewart, Derek A.

2016-04-01

Metal oxide resistive memory devices based on Ta2O5 have demonstrated high switching speed, long endurance, and low set voltage. However, the physical origin of this improved performance is still unclear. Ta2O5 is an important archetype of a class of materials that possess an adaptive crystal structure that can respond easily to the presence of defects. Using first principles nudged elastic band calculations, we show that this adaptive crystal structure leads to low energy barriers for in-plane diffusion of oxygen vacancies in λ phase Ta2O5. Identified diffusion paths are associated with collective motion of neighboring atoms. The overall vacancy diffusion is anisotropic with higher diffusion barriers found for oxygen vacancy movement between Ta-O planes. Coupled with the fact that oxygen vacancy formation energy in Ta2O5 is relatively small, our calculated low diffusion barriers can help explain the low set voltage in Ta2O5 based resistive memory devices. Our work shows that other oxides with adaptive crystal structures could serve as potential candidates for resistive random access memory devices. We also discuss some general characteristics for ideal resistive RAM oxides that could be used in future computational material searches.

The reduction in fatigue crack growth resistance of dentin with depth.

PubMed

Ivancik, J; Neerchal, N K; Romberg, E; Arola, D

2011-08-01

The fatigue crack growth resistance of dentin was characterized as a function of depth from the dentino-enamel junction. Compact tension (CT) specimens were prepared from the crowns of third molars in the deep, middle, and peripheral dentin. The microstructure was quantified in terms of the average tubule dimensions and density. Fatigue cracks were grown in-plane with the tubules and characterized in terms of the initiation and growth responses. Deep dentin exhibited the lowest resistance to the initiation of fatigue crack growth, as indicated by the stress intensity threshold (ΔK(th) ≈ 0.8 MPa•m(0.5)) and the highest incremental fatigue crack growth rate (over 1000 times that in peripheral dentin). Cracks in deep dentin underwent incremental extension under cyclic stresses that were 40% lower than those required in peripheral dentin. The average fatigue crack growth rates increased significantly with tubule density, indicating the importance of microstructure on the potential for tooth fracture. Molars with deep restorations are more likely to suffer from the cracked-tooth syndrome, because of the lower fatigue crack growth resistance of deep dentin.

Development of Eddy Current Techniques for Detection of Deep Fatigue Cracks in Multi-Layer Airframe Components

NASA Technical Reports Server (NTRS)

Wincheski, Russell A.

2008-01-01

Thick, multi-layer aluminum structure has been widely used in aircraft design in critical wing splice areas. The multi-layer structure generally consists of three or four aluminum layers with different geometry and varying thickness, which are held together with fasteners. The detection of cracks under fasteners with ultrasonic techniques in subsurface layers away from the skin is impeded primarily by interlayer bonds and faying sealant condition. Further, assessment of such sealant condition is extremely challenging in terms of complexity of structure, limited access, and inspection cost. Although Eddy current techniques can be applied on in-service aircraft from the exterior of the skin without knowing sealant condition, the current eddy current techniques are not able to detect defects with wanted sensitivity. In this work a series of low frequency eddy current probes have been designed, fabricated and tested for this application. A probe design incorporating a shielded magnetic field sensor concentrically located in the interior of a drive coil has been employed to enable a localized deep diffusion of the electromagnetic field into the part under test. Due to the required low frequency inspections, probes have been testing using a variety of magnetic field sensors (pickup coil, giant magneto-resistive, anisotropic magneto-resistive, and spin-dependent tunneling). The probe designs as well as capabilities based upon a target inspection for sub-layer cracking in an airframe wing spar joint is presented.

Image Restoration for Fluorescence Planar Imaging with Diffusion Model

PubMed Central

Gong, Yuzhu; Li, Yang

2017-01-01

Fluorescence planar imaging (FPI) is failure to capture high resolution images of deep fluorochromes due to photon diffusion. This paper presents an image restoration method to deal with this kind of blurring. The scheme of this method is conceived based on a reconstruction method in fluorescence molecular tomography (FMT) with diffusion model. A new unknown parameter is defined through introducing the first mean value theorem for definite integrals. System matrix converting this unknown parameter to the blurry image is constructed with the elements of depth conversion matrices related to a chosen plane named focal plane. Results of phantom and mouse experiments show that the proposed method is capable of reducing the blurring of FPI image caused by photon diffusion when the depth of focal plane is chosen within a proper interval around the true depth of fluorochrome. This method will be helpful to the estimation of the size of deep fluorochrome. PMID:29279843

Low-abundance HIV drug-resistant viral variants in treatment-experienced persons correlate with historical antiretroviral use.

PubMed

Le, Thuy; Chiarella, Jennifer; Simen, Birgitte B; Hanczaruk, Bozena; Egholm, Michael; Landry, Marie L; Dieckhaus, Kevin; Rosen, Marc I; Kozal, Michael J

2009-06-29

It is largely unknown how frequently low-abundance HIV drug-resistant variants at levels under limit of detection of conventional genotyping (<20% of quasi-species) are present in antiretroviral-experienced persons experiencing virologic failure. Further, the clinical implications of low-abundance drug-resistant variants at time of virologic failure are unknown. Plasma samples from 22 antiretroviral-experienced subjects collected at time of virologic failure (viral load 1380 to 304,000 copies/mL) were obtained from a specimen bank (from 2004-2007). The prevalence and profile of drug-resistant mutations were determined using Sanger sequencing and ultra-deep pyrosequencing. Genotypes were interpreted using Stanford HIV database algorithm. Antiretroviral treatment histories were obtained by chart review and correlated with drug-resistant mutations. Low-abundance drug-resistant mutations were detected in all 22 subjects by deep sequencing and only in 3 subjects by Sanger sequencing. In total they accounted for 90 of 247 mutations (36%) detected by deep sequencing; the majority of these (95%) were not detected by standard genotyping. A mean of 4 additional mutations per subject were detected by deep sequencing (p<0.0001, 95%CI: 2.85-5.53). The additional low-abundance drug-resistant mutations increased a subject's genotypic resistance to one or more antiretrovirals in 17 of 22 subjects (77%). When correlated with subjects' antiretroviral treatment histories, the additional low-abundance drug-resistant mutations correlated with the failing antiretroviral drugs in 21% subjects and correlated with historical antiretroviral use in 79% subjects (OR, 13.73; 95% CI, 2.5-74.3, p = 0.0016). Low-abundance HIV drug-resistant mutations in antiretroviral-experienced subjects at time of virologic failure can increase a subject's overall burden of resistance, yet commonly go unrecognized by conventional genotyping. The majority of unrecognized resistant mutations correlate with historical antiretroviral use. Ultra-deep sequencing can provide important historical resistance information for clinicians when planning subsequent antiretroviral regimens for highly treatment-experienced patients, particularly when their prior treatment histories and longitudinal genotypes are not available.

Low-Abundance HIV Drug-Resistant Viral Variants in Treatment-Experienced Persons Correlate with Historical Antiretroviral Use

PubMed Central

Le, Thuy; Chiarella, Jennifer; Simen, Birgitte B.; Hanczaruk, Bozena; Egholm, Michael; Landry, Marie L.; Dieckhaus, Kevin; Rosen, Marc I.; Kozal, Michael J.

2009-01-01

Background It is largely unknown how frequently low-abundance HIV drug-resistant variants at levels under limit of detection of conventional genotyping (<20% of quasi-species) are present in antiretroviral-experienced persons experiencing virologic failure. Further, the clinical implications of low-abundance drug-resistant variants at time of virologic failure are unknown. Methodology/Principal Findings Plasma samples from 22 antiretroviral-experienced subjects collected at time of virologic failure (viral load 1380 to 304,000 copies/mL) were obtained from a specimen bank (from 2004–2007). The prevalence and profile of drug-resistant mutations were determined using Sanger sequencing and ultra-deep pyrosequencing. Genotypes were interpreted using Stanford HIV database algorithm. Antiretroviral treatment histories were obtained by chart review and correlated with drug-resistant mutations. Low-abundance drug-resistant mutations were detected in all 22 subjects by deep sequencing and only in 3 subjects by Sanger sequencing. In total they accounted for 90 of 247 mutations (36%) detected by deep sequencing; the majority of these (95%) were not detected by standard genotyping. A mean of 4 additional mutations per subject were detected by deep sequencing (p<0.0001, 95%CI: 2.85–5.53). The additional low-abundance drug-resistant mutations increased a subject's genotypic resistance to one or more antiretrovirals in 17 of 22 subjects (77%). When correlated with subjects' antiretroviral treatment histories, the additional low-abundance drug-resistant mutations correlated with the failing antiretroviral drugs in 21% subjects and correlated with historical antiretroviral use in 79% subjects (OR, 13.73; 95% CI, 2.5–74.3, p = 0.0016). Conclusions/Significance Low-abundance HIV drug-resistant mutations in antiretroviral-experienced subjects at time of virologic failure can increase a subject's overall burden of resistance, yet commonly go unrecognized by conventional genotyping. The majority of unrecognized resistant mutations correlate with historical antiretroviral use. Ultra-deep sequencing can provide important historical resistance information for clinicians when planning subsequent antiretroviral regimens for highly treatment-experienced patients, particularly when their prior treatment histories and longitudinal genotypes are not available. PMID:19562031

Quantification of Sheet Resistance in Boron-Diffused Silicon Using Micro-Photoluminescence Spectroscopy at Room Temperature

DOE PAGES

Nguyen, Hieu T.; Johnston, Steve; Paduthol, Appu; ...

2017-09-01

A micro-photoluminescence-based technique is presented, to quantify and map sheet resistances of boron-diffused layers in silicon solar cell precursors with micron-scale spatial resolution at room temperature. The technique utilizes bandgap narrowing effects in the heavily-doped layers, yielding a broader photoluminescence spectrum at the long-wavelength side compared to the spectrum emitted from lightly doped silicon. By choosing an appropriate spectral range as a metric to assess the doping density, the impacts of photon reabsorption on the analysis can be avoided; thus, an accurate characterization of the sheet resistance can be made. This metric is demonstrated to be better representative of themore » sheet resistance than the surface doping density or the total dopant concentration of the diffused layer. The technique is applied to quantify sheet resistances of 12-um-wide diffused fingers in interdigitated back-contact solar cell precursors and large diffused areas. The results are confirmed by both 4-point probe and time-of-flight secondary-ion mass spectrometry measurements. Lastly, the practical limitations associated with extending the proposed technique into an imaging mode are presented and explained.« less

Quantification of Sheet Resistance in Boron-Diffused Silicon Using Micro-Photoluminescence Spectroscopy at Room Temperature

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nguyen, Hieu T.; Johnston, Steve; Paduthol, Appu

A micro-photoluminescence-based technique is presented, to quantify and map sheet resistances of boron-diffused layers in silicon solar cell precursors with micron-scale spatial resolution at room temperature. The technique utilizes bandgap narrowing effects in the heavily-doped layers, yielding a broader photoluminescence spectrum at the long-wavelength side compared to the spectrum emitted from lightly doped silicon. By choosing an appropriate spectral range as a metric to assess the doping density, the impacts of photon reabsorption on the analysis can be avoided; thus, an accurate characterization of the sheet resistance can be made. This metric is demonstrated to be better representative of themore » sheet resistance than the surface doping density or the total dopant concentration of the diffused layer. The technique is applied to quantify sheet resistances of 12-um-wide diffused fingers in interdigitated back-contact solar cell precursors and large diffused areas. The results are confirmed by both 4-point probe and time-of-flight secondary-ion mass spectrometry measurements. Lastly, the practical limitations associated with extending the proposed technique into an imaging mode are presented and explained.« less

Comparative radiation resistance, temperature dependence and performance of diffused junction indium phosphide solar cells

NASA Technical Reports Server (NTRS)

Weinberg, I.; Swartz, C. K.; Hart, R. E., Jr.; Ghandhi, S. K.; Borrego, J. M.

1987-01-01

Indium phosphide solar cells whose p-n junctions were processed by the open tube capped diffusion and by the closed tube uncapped diffusion of sulfur into Czochralski-grown p-type substrates are compared. Differences found in radiation resistance were attributed to the effects of increased base dopant concentration. Both sets of cells showed superior radiation resistance to that of gallium arsenide cells, in agreement with previous results. No correlation was, however, found between the open-circuit voltage and the temperature dependence of the maximum power.

Postmortem diffusion MRI of the human brainstem and thalamus for deep brain stimulator electrode localization.

PubMed

Calabrese, Evan; Hickey, Patrick; Hulette, Christine; Zhang, Jingxian; Parente, Beth; Lad, Shivanand P; Johnson, G Allan

2015-08-01

Deep brain stimulation (DBS) is an established surgical therapy for medically refractory tremor disorders including essential tremor (ET) and is currently under investigation for use in a variety of other neurologic and psychiatric disorders. There is growing evidence that the anti-tremor effects of DBS for ET are directly related to modulation of the dentatorubrothalamic tract (DRT), a white matter pathway that connects the cerebellum, red nucleus, and ventral intermediate nucleus of the thalamus. Emerging white matter targets for DBS, like the DRT, will require improved three-dimensional (3D) reference maps of deep brain anatomy and structural connectivity for accurate electrode targeting. High-resolution diffusion MRI of postmortem brain specimens can provide detailed volumetric images of important deep brain nuclei and 3D reconstructions of white matter pathways with probabilistic tractography techniques. We present a high spatial and angular resolution diffusion MRI template of the postmortem human brainstem and thalamus with 3D reconstructions of the nuclei and white matter tracts involved in ET circuitry. We demonstrate registration of these data to in vivo, clinical images from patients receiving DBS therapy, and correlate electrode proximity to tractography of the DRT with improvement of ET symptoms. © 2015 Wiley Periodicals, Inc.

Development of variable LRFD \\0x03C6 factors for deep foundation design due to site variability [summary].

DOT National Transportation Integrated Search

2012-01-01

Both the Florida Department of Transportation : (FDOT) and the Federal Highway Administration : (FHWA) specify use of fixed resistance factors () : for Load and Resistance Factored Design (LRFD) of : deep foundations, depending on design approach :...

Robust estimation of cerebral hemodynamics in neonates using multilayered diffusion model for normal and oblique incidences

NASA Astrophysics Data System (ADS)

Steinberg, Idan; Harbater, Osnat; Gannot, Israel

2014-07-01

The diffusion approximation is useful for many optical diagnostics modalities, such as near-infrared spectroscopy. However, the simple normal incidence, semi-infinite layer model may prove lacking in estimation of deep-tissue optical properties such as required for monitoring cerebral hemodynamics, especially in neonates. To answer this need, we present an analytical multilayered, oblique incidence diffusion model. Initially, the model equations are derived in vector-matrix form to facilitate fast and simple computation. Then, the spatiotemporal reflectance predicted by the model for a complex neonate head is compared with time-resolved Monte Carlo (TRMC) simulations under a wide range of physiologically feasible parameters. The high accuracy of the multilayer model is demonstrated in that the deviation from TRMC simulations is only a few percent even under the toughest conditions. We then turn to solve the inverse problem and estimate the oxygen saturation of deep brain tissues based on the temporal and spatial behaviors of the reflectance. Results indicate that temporal features of the reflectance are more sensitive to deep-layer optical parameters. The accuracy of estimation is shown to be more accurate and robust than the commonly used single-layer diffusion model. Finally, the limitations of such approaches are discussed thoroughly.

A global ocean climatological atlas of the Turner angle: implications for double-diffusion and water-mass structure

NASA Astrophysics Data System (ADS)

You, Yuzhu

2002-11-01

The 1994 Levitus climatological atlas is used to calculate the Turner angle (named after J. Stewart Turner) to examine which oceanic water masses are favorable for double-diffusion in the form of diffusive convection or salt-fingering and which are doubly stable. This atlas complements the Levitus climatology. It reveals the major double-diffusive signals associated with large-scale water-mass structure. In total, about 44% of the oceans display double-diffusion, of which 30% is salt-fingering and 14% is diffusive double-diffusion. Results show that various central and deep waters are favorable for salt-fingering. The former is due to positive evaporation minus precipitation, and the latter is due to thermohaline circulation, i.e. the southward spreading of relatively warm, salty North Atlantic Deep Water (NADW) overlying cold, fresh Antarctic Bottom Water. In the northern Indian Ocean and eastern North Atlantic, favorable conditions for salt-fingering are found throughout the water column. The Red Sea (including the Persian Gulf) and Mediterranean Sea are the sources of warm, salty water for the ocean. As consequence, temperature and salinity in these outflow regions both decrease from the sea surface to the bottom. On the other hand, ocean currents are in general sluggish in these regions. In the polar and subpolar regions of Arctic and Antarctic, Okhotsk Sea, Gulf of Alaska, the subpolar gyre of the North Pacific, the Labrador Sea, and the Norwegian Sea, the upper layer water is favorable for diffusive convection because of high latitude surface cooling and ice melting. Weak and shallow diffusive convection is also found throughout tropical regions and the Bay of Bengal. The former is due to excessive precipitation over evaporation and rain cooling, and the latter is due to both precipitation and river runoff. Diffusive convection in the ocean's interior is unique to the South Atlantic between Antarctic Intermediate Water and upper NADW (uNADW). It is the consequence of the intrusive equatorward flow of upper Circumpolar Deep Water, which carries with it the minimum temperature and very low salinity overlying warm, salty uNADW.

Deep intracerebral (basal ganglia) haematomas in fatal non-missile head injury in man.

PubMed Central

Adams, J H; Doyle, D; Graham, D I; Lawrence, A E; McLellan, D R

1986-01-01

Deep intracerebral (basal ganglia) haematomas were found post mortem in 63 of 635 fatal non-missile head injuries. In patients with a basal ganglia haematoma, contusions were more severe, there was a reduced incidence of a lucid interval, and there was an increased incidence of road traffic accidents, gliding contusions and diffuse axonal injury than in patients without this type of haematoma. Intracranial haematoma is usually thought to be a secondary event, that is a complication of the original injury, but these results suggest that a deep intracerebral haematoma is a primary event. If a deep intracerebral haematoma is identified on an early CT scan it is likely that the patient has sustained severe diffuse brain damage at the time of injury. In the majority of head injuries damage to blood vessels or axons predominates. In patients with a traumatic deep intracerebral haematoma, it would appear that the deceleration/acceleration forces are such that both axons and blood vessels within the brain are damaged at the time of injury. Images PMID:3760892

Emergent HIV-1 Drug Resistance Mutations Were Not Present at Low-Frequency at Baseline in Non-Nucleoside Reverse Transcriptase Inhibitor-Treated Subjects in the STaR Study

PubMed Central

Porter, Danielle P.; Daeumer, Martin; Thielen, Alexander; Chang, Silvia; Martin, Ross; Cohen, Cal; Miller, Michael D.; White, Kirsten L.

2015-01-01

At Week 96 of the Single-Tablet Regimen (STaR) study, more treatment-naïve subjects that received rilpivirine/emtricitabine/tenofovir DF (RPV/FTC/TDF) developed resistance mutations compared to those treated with efavirenz (EFV)/FTC/TDF by population sequencing. Furthermore, more RPV/FTC/TDF-treated subjects with baseline HIV-1 RNA >100,000 copies/mL developed resistance compared to subjects with baseline HIV-1 RNA ≤100,000 copies/mL. Here, deep sequencing was utilized to assess the presence of pre-existing low-frequency variants in subjects with and without resistance development in the STaR study. Deep sequencing (Illumina MiSeq) was performed on baseline and virologic failure samples for all subjects analyzed for resistance by population sequencing during the clinical study (n = 33), as well as baseline samples from control subjects with virologic response (n = 118). Primary NRTI or NNRTI drug resistance mutations present at low frequency (≥2% to 20%) were detected in 6.6% of baseline samples by deep sequencing, all of which occurred in control subjects. Deep sequencing results were generally consistent with population sequencing but detected additional primary NNRTI and NRTI resistance mutations at virologic failure in seven samples. HIV-1 drug resistance mutations emerging while on RPV/FTC/TDF or EFV/FTC/TDF treatment were not present at low frequency at baseline in the STaR study. PMID:26690199

Emergent HIV-1 Drug Resistance Mutations Were Not Present at Low-Frequency at Baseline in Non-Nucleoside Reverse Transcriptase Inhibitor-Treated Subjects in the STaR Study.

PubMed

Porter, Danielle P; Daeumer, Martin; Thielen, Alexander; Chang, Silvia; Martin, Ross; Cohen, Cal; Miller, Michael D; White, Kirsten L

2015-12-07

At Week 96 of the Single-Tablet Regimen (STaR) study, more treatment-naïve subjects that received rilpivirine/emtricitabine/tenofovir DF (RPV/FTC/TDF) developed resistance mutations compared to those treated with efavirenz (EFV)/FTC/TDF by population sequencing. Furthermore, more RPV/FTC/TDF-treated subjects with baseline HIV-1 RNA >100,000 copies/mL developed resistance compared to subjects with baseline HIV-1 RNA ≤100,000 copies/mL. Here, deep sequencing was utilized to assess the presence of pre-existing low-frequency variants in subjects with and without resistance development in the STaR study. Deep sequencing (Illumina MiSeq) was performed on baseline and virologic failure samples for all subjects analyzed for resistance by population sequencing during the clinical study (n = 33), as well as baseline samples from control subjects with virologic response (n = 118). Primary NRTI or NNRTI drug resistance mutations present at low frequency (≥2% to 20%) were detected in 6.6% of baseline samples by deep sequencing, all of which occurred in control subjects. Deep sequencing results were generally consistent with population sequencing but detected additional primary NNRTI and NRTI resistance mutations at virologic failure in seven samples. HIV-1 drug resistance mutations emerging while on RPV/FTC/TDF or EFV/FTC/TDF treatment were not present at low frequency at baseline in the STaR study.

Evaluation of the mass transfer process on thin layer drying of papaya seeds from the perspective of diffusive models

NASA Astrophysics Data System (ADS)

Dotto, Guilherme Luiz; Meili, Lucas; Tanabe, Eduardo Hiromitsu; Chielle, Daniel Padoin; Moreira, Marcos Flávio Pinto

2018-02-01

The mass transfer process that occurs in the thin layer drying of papaya seeds was studied under different conditions. The external mass transfer resistance and the dependence of effective diffusivity ( D EFF ) in relation to the moisture ratio ( \\overline{MR} ) and temperature ( T) were investigated from the perspective of diffusive models. It was verified that the effective diffusivity was affected by the moisture content and temperature. A new correlation was proposed for drying of papaya seeds in order to describe these influences. Regarding the use of diffusive models, the results showed that, at conditions of low drying rates ( T ≤ 70 °C), the external mass transfer resistance, as well as the dependence of the effective diffusivity with respect to the temperature and moisture content should be considered. At high drying rates ( T > 90 °C), the dependence of the effective diffusivity with respect to the temperature and moisture content can be neglected, but the external mass transfer resistance was still considerable in the range of air velocities used in this work.

Microtomography-based Inter-Granular Network for the simulation of radionuclide diffusion and sorption in a granitic rock

NASA Astrophysics Data System (ADS)

Iraola, Aitor; Trinchero, Paolo; Voutilainen, Mikko; Gylling, Björn; Selroos, Jan-Olof; Molinero, Jorge; Svensson, Urban; Bosbach, Dirk; Deissmann, Guido

2017-12-01

Field investigation studies, conducted in the context of safety analyses of deep geological repositories for nuclear waste, have pointed out that in fractured crystalline rocks sorbing radionuclides can diffuse surprisingly long distances deep into the intact rock matrix; i.e. much longer distances than those predicted by reactive transport models based on a homogeneous description of the properties of the rock matrix. Here, we focus on cesium diffusion and use detailed micro characterisation data, based on micro computed tomography, along with a grain-scale Inter-Granular Network model, to offer a plausible explanation for the anomalously long cesium penetration profiles observed in these in-situ experiments. The sparse distribution of chemically reactive grains (i.e. grains belonging to sorbing mineral phases) is shown to have a strong control on the diffusive patterns of sorbing radionuclides. The computed penetration profiles of cesium agree well with an analytical model based on two parallel diffusive pathways. This agreement, along with visual inspection of the spatial distribution of cesium concentration, indicates that for sorbing radionuclides the medium indeed behaves as a composite system, with most of the mass being retained close to the injection boundary and a non-negligible part diffusing faster along preferential diffusive pathways.

Antibiotic resistance patterns and occurrence of mecA gene in Staphylococcus intermedius strains of canine origin.

PubMed

Kizerwetter-Swida, M; Chrobak, D; Rzewuska, M; Binek, M

2009-01-01

We have evaluated 102 Staphylococcus intermedius isolates of canine origin for susceptibility to antimicrobial primary agents, i.e. penicillin, amoxicillin, amoxicillin with clavulanic acid, cefuroxime, trimethoprim/sulfonamides, neomycin, streptomycin, gentamicin, norfloxacin, tetracycline, vancomycin, erythromycin and secondary agents, i.e., chloramphenicol, ciprofloxacin, lincomycin, teicoplanin, rifampicin, imipenem, mupirocin. Antimicrobial sensitivity was examined using the disk diffusion method and performed according to NCCLS quidelines. Methicillin resistance was detected using the disk diffusion method with oxacillin, and the occurrence of mecA gene was detected by PCR. Resistance to streptomycin, penicillin, amoxicillin, neomycin, followed by tetracycline was predominant. From 14 mecA-positive strains, 12 were multidrug-resitant, and the remaining two showed atypical susceptibility. One strain resistant to oxacillin in the disc diffusion method was mecA-negative, suggesting a different mechanism of resistance. Our results indicate that the emergence of S. intermedius resistance to methicillin may be underestimated. In case of clinical multidrug-resitant S. intermedius isolates, resistance to methicillin should be considered.

Study on the effect of Cd-diffusion annealing on the electrical properties of CdZnTe

NASA Astrophysics Data System (ADS)

Wanwan, Li; Zechun, Cao; Bin, Zhang; Feng, Zhan; Hongtao, Liu; Wenbin, Sang; Jiahua, Min; Kang, Sun

2006-06-01

In order to meet the requirements for the device design of radiation detectors, CdZnTe (or Cd 1-xZn xTe) crystals grown by Vertical Bridgman Method often need subsequent annealing to increase their resistivity. The nature of this treatment is a diffusion process. Thus, it is meaningful to relate the change of resistivity to the diffusion parameters. A model correlating resistivity and conduction type of CdZnTe with the main diffusion parameter—diffusion coefficient—is put forward in this paper. Combining the model with the analysis of our experimental data, DCd=1.464×10 -10, 1.085×10 -11 and 4.167×10 -13 cm 2/s are the values of Cd self-diffusion coefficient in Cd 0.9Zn 0.1Te at 1073, 973 and 873 K, respectively. The data coincide closely with the Cd self-diffusion coefficient in CdTe provided by different authors [E.D. Jones, N.M. Stewart, Self-diffusion of cadmium in cadmium telluride, J. Crystal Growth 84 (1987) 289-294; P.M. Borsenberger, D.A. Stevenson, J. Phys. Chem. Solids 29 (1968) 1277; R.C. Whelan, D. Shaw, in: D.G. Thomas (Ed.), II -VI Semiconductor Compounds, Benjamin, New York, 1967, p. 451]. With the data, the effects of annealing time on the change of resistivity and conduction type for Cd 0.9Zn 0.1Te wafers, which are annealed in saturated Cd vapor at 1073, 973 and 873 K, were simulated, and good consistency was found. This work suggests an alternative way to obtain the diffusion coefficient in semiconductor materials and also enables ones to analyze the diffusion process quantitatively and predict the annealing results.

Elevated-temperature flow strength, creep resistance and diffusion welding characteristics of Ti-gAl-2Nb-1Ta-0.8Mo

NASA Technical Reports Server (NTRS)

Whittenberger, J. D.; Moore, T. J.

1977-01-01

A study of the flow strength, creep resistance and diffusion welding characteristics of the titanium alloy Ti-6Al-2Nb-1Ta-0.8Mo was conducted. Two mill-processed forms of this alloy were examined. The forged material was essentially processed above the beta transus while the rolled form was subjected to considerable work below the beta transus. Between 1150 and 1250 K, the forged material was stronger and more creep resistant than the rolled alloy. Both forms exhibit superplastic characteristics in this temperature range. Strain measurements during diffusion welding experiments at 1200 K reveal that weld interfaces have no measurable effect on the overall creep deformation. Significant deformation appears to be necessary to produce a quality diffusion weld between superplastic materials. A 'soft' interlayer inserted between faying surfaces would seemingly allow manufacture of quality diffusion welds with little overall deformation.

Oxygen uptake and vertical transport during deep convection events

NASA Astrophysics Data System (ADS)

Sun, D.; Ito, T.; Bracco, A.

2016-02-01

Dissolved oxygen (O2) is essential for the chemistry and living organisms of the oceans. O2 is consumed in the interior ocean due to the respiration of organic matter, and must be replenished by physical ventilation with the O2-rich surface waters. The O2 supply to the deep waters happens only through the subduction and deep convection during cold seasons at high latitude oceans. The Labrador Sea is one of the few regions where deep ventilation occurs. According to observational and modeling studies, the intensity, duration and timing of deep convection events have varied significantly on the interannual and decadal timescales. In this study we develop a theoretical framework to understand the air-sea transfer of O2 during open-ocean deep convection events. The theory is tested against a suite of numerical integrations using MITgcm in non-hydrostatic configuration including the parameterization of diffusive and bubble mediated gas transfer. Forced with realistic air-sea buoyancy fluxes, the model can reproduce the evolution of temperature, salinity and dissolved O2 observed by ARGO floats in the Labrador Sea. Idealized sensitivity experiments are performed changing the intensity and duration of the buoyancy forcing as well as the wind speed for the gas exchange parameterizations. The downward transport of O2 results from the combination of vertical homogenization of existing O2 and the uptake from the air-sea flux. The intensity of the buoyancy forcing controls the vertical extent of convective mixing which brings O2 to the deep ocean. Integrated O2 uptake increases with the duration of convection even when the total buoyancy loss is held constant. The air-sea fluxes are highly sensitive to the wind speed especially for the bubble injection flux, which is a major addition to the diffusive flux under strong winds. However, the bubble injection flux can be partially compensated by the diffusive outgassing in response to the elevated saturation state. Under strong buoyancy forcing, this compensation is suppressed by the entrainment of relatively O2-poor deep waters. These results imply and allow to quantify the direct link between variability of deep convection and the supply of O2 in the North Atlantic.

Radiation effects on p+n InP junctions grown by MOCVD

NASA Technical Reports Server (NTRS)

Messenger, Scott R.; Walters, Robert J.; Panunto, M. J.; Summers, Geoffrey P.

1994-01-01

The superior radiation resistance of InP over other solar cell materials such as Si or GaAs has prompted the development of InP cells for space applications. The early research on radiation effects in InP was performed by Yamaguchi and co-workers who showed that, in diffused p-InP junctions, radiation-induced defects were readily annealed both thermally and by injection, which was accompanied by significant cell recovery. More recent research efforts have been made using p-InP grown by metalorganic chemical vapor deposition (MOCVD). While similar deep level transient spectroscopy (DLTS) results were found for radiation induced defects in these cells and in diffused junctions, significant differences existed in the annealing characteristics. After injection annealing at room temperature, Yamaguchi noticed an almost complete recovery of the photovoltaic parameters, while the MOCVD samples showed only minimal annealing. In searching for an explanation of the different annealing behavior of diffused junctions and those grown by MOCVD, several possibilities have been considered. One possibility is the difference in the emitter structure. The diffused junctions have S-doped graded emitters with widths of approximately 0.3 micrometers, while the MOCVD emitters are often doped with Si and have widths of approximately 300A (0.03 micrometers). The difference in the emitter thickness can have important effects, e.g. a larger fraction of the total photocurrent is generated in the n-type material for thicker emitters. Therefore the properties of the n-InP material may explain the difference in the observed overall annealing behavior of the cells.

Antimicrobial susceptibility of Histophilus somni isolated from clinically affected cattle in Australia.

PubMed

Goldspink, Lauren K; Mollinger, Joanne L; Barnes, Tamsin S; Groves, Mitchell; Mahony, Timothy J; Gibson, Justine S

2015-02-01

This study investigated antimicrobial resistance traits, clonal relationships and epidemiology of Histophilus somni isolated from clinically affected cattle in Queensland and New South Wales, Australia. Isolates (n = 53) were subjected to antimicrobial susceptibility testing against six antimicrobial agents (ceftiofur, enrofloxacin, florfenicol, tetracycline, tilmicosin and tulathromycin) using disc diffusion and minimum inhibitory concentration (MIC) assays. Clonal relationships were assessed using repetitive sequence PCR and descriptive epidemiological analysis was performed. The H. somni isolates appeared to be geographically clonal, with 27/53 (47%) isolates grouping in one cluster from one Australian state. On the basis of disc diffusion, 34/53 (64%) isolates were susceptible to all antimicrobial agents tested; there was intermediate susceptibility to tulathromycin in 12 isolates, tilmicosin in seven isolates and resistance to tilmicosin in one isolate. Using MIC, all but one isolate was susceptible to all antimicrobial agents tested; the non-susceptible isolate was resistant to tetracycline, but this MIC result could not be compared to disc diffusion, since there are no interpretative guidelines for disc diffusion for H. somni against tetracycline. In this study, there was little evidence of antimicrobial resistance in H. somni isolates from Australian cattle. Disc diffusion susceptibility testing results were comparable to MIC results for most antimicrobial agents tested; however, results for isolates with intermediate susceptibility or resistance to tilmicosin and tulathromycin on disc diffusion should be interpreted with caution in the absence of MIC results. Copyright © 2014 Elsevier Ltd. All rights reserved.

Corrosion resistant coatings suitable for elevated temperature application

DOEpatents

Chan, Kwai S [San Antonio, TX; Cheruvu, Narayana Sastry [San Antonio, TX; Liang, Wuwei [Austin, TX

2012-07-31

The present invention relates to corrosion resistance coatings suitable for elevated temperature applications, which employ compositions of iron (Fe), chromium (Cr), nickel (Ni) and/or aluminum (Al). The compositions may be configured to regulate the diffusion of metals between a coating and a substrate, which may then influence coating performance, via the formation of an inter-diffusion barrier layer. The inter-diffusion barrier layer may comprise a face-centered cubic phase.

Effects of epitaxial structure and processing on electrical characteristics of InAs-based nBn infrared detectors

NASA Astrophysics Data System (ADS)

Du, X.; Savich, G. R.; Marozas, B. T.; Wicks, G. W.

2017-02-01

The conventional processing of the III-V nBn photodetectors defines mesa devices by etching the contact n-layer and stopping immediately above the barrier, i.e., a shallow etch. This processing enables great suppression of surface leakage currents without having to explore surface passivation techniques. However, devices that are made with this processing scheme are subject to lateral diffusion currents. To address the lateral diffusion current, we compare the effects of different processing approaches and epitaxial structures of nBn detectors. The conventional solution for eliminating lateral diffusion current, a deep etch through the barrier and the absorber, creates increased dark currents and an increased device failure rate. To avoid deep etch processing, a new device structure is proposed, the inverted-nBn structure. By comparing with the conventional nBn structure, the results show that the lateral diffusion current is effectively eliminated in the inverted-nBn structure without elevating the dark currents.

Sonodynamic inactivation of Gram-positive and Gram-negative bacteria using a Rose Bengal-antimicrobial peptide conjugate.

PubMed

Costley, David; Nesbitt, Heather; Ternan, Nigel; Dooley, James; Huang, Ying-Ying; Hamblin, Michael R; McHale, Anthony P; Callan, John F

2017-01-01

Combating antimicrobial resistance is one of the most serious public health challenges facing society today. The development of new antibiotics or alternative techniques that can help combat antimicrobial resistance is being prioritised by many governments and stakeholders across the globe. Antimicrobial photodynamic therapy is one such technique that has received considerable attention but is limited by the inability of light to penetrate through human tissue, reducing its effectiveness when used to treat deep-seated infections. The related technique sonodynamic therapy (SDT) has the potential to overcome this limitation given the ability of low-intensity ultrasound to penetrate human tissue. In this study, a Rose Bengal-antimicrobial peptide conjugate was prepared for use in antimicrobial SDT (ASDT). When Staphylococcus aureus and Pseudomonas aeruginosa planktonic cultures were treated with the conjugate and subsequently exposed to ultrasound, 5 log and 7 log reductions, respectively, in bacterial numbers were observed. The conjugate also displayed improved uptake by bacterial cells compared with a mammalian cell line (P ≤ 0.01), whilst pre-treatment of a P. aeruginosa biofilm with ultrasound resulted in a 2.6-fold improvement in sensitiser diffusion (P ≤ 0.01). A preliminary in vivo experiment involving ASDT treatment of P. aeruginosa-infected wounds in mice demonstrated that ultrasound irradiation of conjugate-treated wounds affects a substantial reduction in bacterial burden. Combined, the results obtained from this study highlight ASDT as a targeted broad-spectrum novel modality with potential for the treatment of deep-seated bacterial infections. Copyright © 2016. Published by Elsevier B.V.

Primary Dermal Irritation Potential of Components of the M-258A-1 Decontamination Kit (Study 1).

DTIC Science & Technology

1981-09-01

cells and lymphocytes with an occasional heterophil in the connective tissue sheaths of a few hair follicles deep in the dermis. DX: Folliculitis ...acute, diffuse, mild to moderate, dermis, skin. DX: Folliculitis , subacute, multifocal, minimal, hair follicles, skin. Slide 4 - Skin: The entire skin...the dermis. DX: Hyperplasia, diffuse, moderate, epidermis, skin. DX: Degeneration, subacute, diffuse, minimal to mild, dermis, skin. DX: Folliculitis

DIFFUSE: a FORTRAN program for design computation of tritium transport through thermonuclear reactor components by combined ordinary and thermal diffusion when the principal resistance to diffusion is the bulk metal

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pendergrass, J.H.

1977-10-01

Based on the theory developed in an earlier report, a FORTRAN computer program, DIFFUSE, was written. It computes, for design purposes, rates of transport of hydrogen isotopes by temperature-dependent quasi-unidirectional, and quasi-static combined ordinary and thermal diffusion through thin, hot thermonuclear reactor components that can be represented by composites of plane, cylindrical-shell, and spherical-shell elements when the dominant resistance to transfer is that of the bulk metal. The program is described, directions for its use are given, and a listing of the program, together with sample problem results, is presented.

Theoretical and experimental research in space photovoltaics

NASA Technical Reports Server (NTRS)

Faur, Mircea; Faur, Maria

1995-01-01

Theoretical and experimental research is outlined for indium phosphide solar cells, other solar cells for space applications, fabrication and performance measurements of shallow homojunction InP solar cells for space applications, improved processing steps and InP material characterization with applications to fabrication of high efficiency radiation resistant InP solar cells and other opto-electronic InP devices, InP solar cells fabricated by thermal diffusion, experiment-based predicted high efficiency solar cells fabricated by closed-ampoule thermal diffusion, radiation resistance of diffused junction InP solar cells, chemical and electrochemical characterization and processing of InP diffused structures and solar cells, and progress in p(+)n InP diffused solar cells.

The influence of thermal annealing on the characteristics of Au/Ni Schottky contacts on n-type 4 H-SiC

NASA Astrophysics Data System (ADS)

Omotoso, E.; Auret, F. D.; Igumbor, E.; Tunhuma, S. M.; Danga, H. T.; Ngoepe, P. N. M.; Taleatu, B. A.; Meyer, W. E.

2018-05-01

The effects of isochronal annealing on the electrical, morphological and structural characteristics of Au/Ni/4 H-SiC Schottky barrier diodes (SBDs) have been studied. Current-voltage ( I- V), capacitance-voltage ( C- V), deep-level transient spectroscopy, scanning electron microscope (SEM) and X-ray diffraction measurements were employed to study the thermal effect on the characteristics of the SBDs. Prior to thermal annealing of Schottky contacts, the I- V measurements results confirmed the good rectification behaviour with ideality factor of 1.06, Schottky barrier height of 1.20 eV and series resistance of 7 Ω. The rectification properties after annealing was maintained up to an annealing temperature of 500 °C, but deviated slightly above 500 °C. The uncompensated ionized donor concentration decreased with annealing temperature, which could be attributed to out-diffusion of the 4 H-SiC into the Au/Ni contacts and decrease in bonding due to formation of nickel silicides. We observed the presence of four deep-level defects with energies 0.09, 0.11, 0.16 and 0.65 eV below the conduction band before and after the isochronal annealing up to 600 °C. The conclusion drawn was that annealing did not affect the number of deep-level defects present in Au/Ni/4 H-SiC contacts. The variations in electrical properties of the devices were attributed to the phase transformations and interfacial reactions that occurred after isochronal annealing.

Pharmacological Potential of Phylogenetically Diverse Actinobacteria Isolated from Deep-Sea Coral Ecosystems of the Submarine Avilés Canyon in the Cantabrian Sea.

PubMed

Sarmiento-Vizcaíno, Aida; González, Verónica; Braña, Alfredo F; Palacios, Juan J; Otero, Luis; Fernández, Jonathan; Molina, Axayacatl; Kulik, Andreas; Vázquez, Fernando; Acuña, José L; García, Luis A; Blanco, Gloria

2017-02-01

Marine Actinobacteria are emerging as an unexplored source for natural product discovery. Eighty-seven deep-sea coral reef invertebrates were collected during an oceanographic expedition at the submarine Avilés Canyon (Asturias, Spain) in a range of 1500 to 4700 m depth. From these, 18 cultivable bioactive Actinobacteria were isolated, mainly from corals, phylum Cnidaria, and some specimens of phyla Echinodermata, Porifera, Annelida, Arthropoda, Mollusca and Sipuncula. As determined by 16S rRNA sequencing and phylogenetic analyses, all isolates belong to the phylum Actinobacteria, mainly to the Streptomyces genus and also to Micromonospora, Pseudonocardia and Myceligenerans. Production of bioactive compounds of pharmacological interest was investigated by high-performance liquid chromatography (HPLC) and gas chromatography-mass spectrometry (GC-MS) techniques and subsequent database comparison. Results reveal that deep-sea isolated Actinobacteria display a wide repertoire of secondary metabolite production with a high chemical diversity. Most identified products (both diffusible and volatiles) are known by their contrasted antibiotic or antitumor activities. Bioassays with ethyl acetate extracts from isolates displayed strong antibiotic activities against a panel of important resistant clinical pathogens, including Gram-positive and Gram-negative bacteria, as well as fungi, all of them isolated at two main hospitals (HUCA and Cabueñes) from the same geographical region. The identity of the active extracts components of these producing Actinobacteria is currently being investigated, given its potential for the discovery of pharmaceuticals and other products of biotechnological interest.

Topological Hall effect in diffusive ferromagnetic thin films with spin-flip scattering

DOE PAGES

Zhang, Steven S. -L.; Heinonen, Olle

2018-04-02

In this paper, we study the topological Hall (TH) effect in a diffusive ferromagnetic metal thin film by solving a Boltzmann transport equation in the presence of spin-flip scattering. A generalized spin-diffusion equation is derived which contains an additional source term associated with the gradient of the emergent magnetic field that arises from skyrmions. Because of the source term, spin accumulation may build up in the vicinity of the skyrmions. This gives rise to a spin-polarized diffusion current that in general suppresses the bulk TH current. Only when the spin-diffusion length is much smaller than the skyrmion size does themore » TH resistivity approach the value derived by Bruno et al. [Phys. Rev. Lett. 93, 096806 (2004)]. Finally, we derive a general expression of the TH resistivity that applies to thin-film geometries with spin-flip scattering, and show that the corrections to the TH resistivity become large when the size of room temperature skyrmions is further reduced to tens of nanometers.« less

Topological Hall effect in diffusive ferromagnetic thin films with spin-flip scattering

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Steven S. -L.; Heinonen, Olle

In this paper, we study the topological Hall (TH) effect in a diffusive ferromagnetic metal thin film by solving a Boltzmann transport equation in the presence of spin-flip scattering. A generalized spin-diffusion equation is derived which contains an additional source term associated with the gradient of the emergent magnetic field that arises from skyrmions. Because of the source term, spin accumulation may build up in the vicinity of the skyrmions. This gives rise to a spin-polarized diffusion current that in general suppresses the bulk TH current. Only when the spin-diffusion length is much smaller than the skyrmion size does themore » TH resistivity approach the value derived by Bruno et al. [Phys. Rev. Lett. 93, 096806 (2004)]. Finally, we derive a general expression of the TH resistivity that applies to thin-film geometries with spin-flip scattering, and show that the corrections to the TH resistivity become large when the size of room temperature skyrmions is further reduced to tens of nanometers.« less

Topological Hall effect in diffusive ferromagnetic thin films with spin-flip scattering

NASA Astrophysics Data System (ADS)

Zhang, Steven S.-L.; Heinonen, Olle

2018-04-01

We study the topological Hall (TH) effect in a diffusive ferromagnetic metal thin film by solving a Boltzmann transport equation in the presence of spin-flip scattering. A generalized spin-diffusion equation is derived which contains an additional source term associated with the gradient of the emergent magnetic field that arises from skyrmions. Because of the source term, spin accumulation may build up in the vicinity of the skyrmions. This gives rise to a spin-polarized diffusion current that in general suppresses the bulk TH current. Only when the spin-diffusion length is much smaller than the skyrmion size does the TH resistivity approach the value derived by Bruno et al. [Phys. Rev. Lett. 93, 096806 (2004), 10.1103/PhysRevLett.93.096806]. We derive a general expression of the TH resistivity that applies to thin-film geometries with spin-flip scattering, and show that the corrections to the TH resistivity become large when the size of room temperature skyrmions is further reduced to tens of nanometers.

Elevated temperature flow strength, creep resistance and diffusion welding characteristics of Ti-6Al-2Nb-1Ta-0.8Mo

NASA Technical Reports Server (NTRS)

Whittenberger, J. D.; Moore, T. J.

1979-01-01

A study of the flow strength, creep resistance and diffusion welding characteristics of the titanium alloy Ti-6Al-2Nb-1Ta-0.8Mo has been conducted. Two mill-processed forms of this alloy were examined. The forged material had been processed above the beta transus (approximately 1275 K) while the rolled form had been subjected to work below the beta transus. Between 1150 and 1250 K, the forged material was stronger and more creep resistant than the rolled alloy. Both forms exhibit superplastic characteristics in this temperature range. Strain measurements during diffusion welding experiments at 1200 K reveal that weld interfaces have no measurable effect on the overall creep deformation. Significant deformation appears to be necessary to produce a quality diffusion weld between superplastic materials. A 'soft' interlayer inserted between faying surfaces would seemingly allow manufacture of quality diffusion welds with little overall deformation.

Collective Landmarks for Deep Time: A New Tool for Evolution Education

ERIC Educational Resources Information Center

Delgado, Cesar

2014-01-01

Evolution is a fundamental, organising concept in biology, yet there is widespread resistance to evolution among US students and there are rising creationist challenges in Europe. Resistance to evolution is linked to lack of understanding of the age of the Earth. An understanding of deep time is thus essential for effective biology education.…

Mixing and the dynamics of the deep chlorophyll maximum in Lake Tahoe

NASA Technical Reports Server (NTRS)

Abbott, M. R.; Denman, K. L.; Powell, T. M.; Richerson, P. J.; Richards, R. C.; Goldman, C. R.

1984-01-01

Chlorophyll-temperature profiles were measured across Lake Tahoe about every 10 days from April through July 1980. Analysis of the 123 profiles and associated productivity and nutrient data identified three important processes in the formation and dynamics of the deep chlorophyll maximum (DCM): turbulent diffusion, nutrient supply rate, and light availability. Seasonal variation in these three processes resulted in three regimes: a diffusion-dominated regime with a weak DCM, a variable-mixing regime with a pronounced, nutrient supply-dominated DCM, and a stable regime with a deep, moderate light availability-dominated DCM. The transition between the first two regimes occurred in about 10 days, the transition between the last two more gradually over about 3 weeks. The degree of spatial variability of the DCM was highest in the second regime and lowest in the third. These data indicate that the DCM in Lake Tahoe is constant in neither time nor space.

Cellular imaging of deep organ using two-photon Bessel light-sheet nonlinear structured illumination microscopy

PubMed Central

Zhao, Ming; Zhang, Han; Li, Yu; Ashok, Amit; Liang, Rongguang; Zhou, Weibin; Peng, Leilei

2014-01-01

In vivo fluorescent cellular imaging of deep internal organs is highly challenging, because the excitation needs to penetrate through strong scattering tissue and the emission signal is degraded significantly by photon diffusion induced by tissue-scattering. We report that by combining two-photon Bessel light-sheet microscopy with nonlinear structured illumination microscopy (SIM), live samples up to 600 microns wide can be imaged by light-sheet microscopy with 500 microns penetration depth, and diffused background in deep tissue light-sheet imaging can be reduced to obtain clear images at cellular resolution in depth beyond 200 microns. We demonstrate in vivo two-color imaging of pronephric glomeruli and vasculature of zebrafish kidney, whose cellular structures located at the center of the fish body are revealed in high clarity by two-color two-photon Bessel light-sheet SIM. PMID:24876996

Geophysical characterization of Range-Front Faults, Snake Valley, Nevada

USGS Publications Warehouse

Asch, Theodore H.; Sweetkind, Donald S.

2010-01-01

In September 2009, the U.S. Geological Survey, in cooperation with the National Park Service, collected audiomagnetotelluric (AMT) data along two profiles on the eastern flank of the Snake Range near Great Basin National Park to refine understanding of the subsurface geology. Line 1 was collected along Baker Creek, was approximately 6.7-km long, and recorded subsurface geologic conditions to approximately 800-m deep. Line 2, collected farther to the southeast in the vicinity of Kious Spring, was 2.8-km long, and imaged to depths of approximately 600 m. The two AMT lines are similar in their electrical response and are interpreted to show generally similar subsurface geologic conditions. The geophysical response seen on both lines may be described by three general domains of electrical response: (1) a shallow (mostly less than 100-200-m deep) domain of highly variable resistivity, (2) a deep domain characterized by generally high resistivity that gradually declines eastward to lower resistivity with a steeply dipping grain or fabric, and (3) an eastern domain in which the resistivity character changes abruptly at all depths from that in the western domain. The shallow, highly variable domain is interpreted to be the result of a heterogeneous assemblage of Miocene conglomerate and incorporated megabreccia blocks overlying a shallowly eastward-dipping southern Snake Range detachment fault. The deep domain of generally higher resistivity is interpreted as Paleozoic sedimentary rocks (Pole Canyon limestone and Prospect Mountain Quartzite) and Mesozoic and Cenozoic plutonic rocks occurring beneath the detachment surface. The range of resistivity values within this deep domain may result from fracturing adjacent to the detachment, the presence of Paleozoic rock units of variable resistivities that do not crop out in the vicinity of the lines, or both. The eastern geophysical domain is interpreted to be a section of Miocene strata at depth, overlain by Quaternary alluvial fill. These deposits lie east of a steeply east-dipping normal fault that cuts all units and has about 100 m of east-side-down offset.

A multicomponent tracer field experiment to measure the flow volume, surface area, and rectilinear spacing of fractures away from the wellbore

NASA Astrophysics Data System (ADS)

Cathles, L. M.; Sanford, W. E.; Hawkins, A.; Li, Y. V.

2017-12-01

The nature of flow in fractured porous media is important to almost all subsurface processes including oil and gas recovery, contaminant transport and remediation, CO2 sequestration, and geothermal heat extraction. One would like to know, under flowing conditions, the flow volume, surface area, effective aperture, and rectilinear spacing of fractures in a representative volume of rock away from the well bore, but no methods currently allow acquisition of this data. It could, however, be collected by deploying inert tracers with a wide range of aqueous diffusion constants (e.g., rapidly diffusing heat to non-diffusing nanoparticle) in the following fashion: The flow volume is defined by the heated volume measured by resistivity surveys. The fracture volume within this flow volume is indicate by the nanoparticle transit time. The average fracture spacing is indicated by the evolving thermal profile in the monitor and the production wells (measured by fiber optic cable), and by the retention of absorbing tracers. The average fracture aperture is determined by permeability measurements and the average fracture separation. We have proposed a field test to redundantly measure these fracture parameters in the fractured Dakota Sandstone where it approaches the surface in Ft Collins, Colorado. Five 30 m deep wells (an injection, production, and 3 monitor wells) cased to 20 m are proposed. The experiments will involve at least 9 different tracers. The planned field test and its potential significance will be described.

Diffuse flow environments within basalt- and sediment-based hydrothermal vent ecosystems harbor specialized microbial communities.

PubMed

Campbell, Barbara J; Polson, Shawn W; Zeigler Allen, Lisa; Williamson, Shannon J; Lee, Charles K; Wommack, K Eric; Cary, S Craig

2013-01-01

Hydrothermal vents differ both in surface input and subsurface geochemistry. The effects of these differences on their microbial communities are not clear. Here, we investigated both alpha and beta diversity of diffuse flow-associated microbial communities emanating from vents at a basalt-based hydrothermal system along the East Pacific Rise (EPR) and a sediment-based hydrothermal system, Guaymas Basin. Both Bacteria and Archaea were targeted using high throughput 16S rRNA gene pyrosequencing analyses. A unique aspect of this study was the use of a universal set of 16S rRNA gene primers to characterize total and diffuse flow-specific microbial communities from varied deep-sea hydrothermal environments. Both surrounding seawater and diffuse flow water samples contained large numbers of Marine Group I (MGI) Thaumarchaea and Gammaproteobacteria taxa previously observed in deep-sea systems. However, these taxa were geographically distinct and segregated according to type of spreading center. Diffuse flow microbial community profiles were highly differentiated. In particular, EPR dominant diffuse flow taxa were most closely associated with chemolithoautotrophs, and off axis water was dominated by heterotrophic-related taxa, whereas the opposite was true for Guaymas Basin. The diversity and richness of diffuse flow-specific microbial communities were strongly correlated to the relative abundance of Epsilonproteobacteria, proximity to macrofauna, and hydrothermal system type. Archaeal diversity was higher than or equivalent to bacterial diversity in about one third of the samples. Most diffuse flow-specific communities were dominated by OTUs associated with Epsilonproteobacteria, but many of the Guaymas Basin diffuse flow samples were dominated by either OTUs within the Planctomycetes or hyperthermophilic Archaea. This study emphasizes the unique microbial communities associated with geochemically and geographically distinct hydrothermal diffuse flow environments.

Diffuse flow environments within basalt- and sediment-based hydrothermal vent ecosystems harbor specialized microbial communities

PubMed Central

Campbell, Barbara J.; Polson, Shawn W.; Zeigler Allen, Lisa; Williamson, Shannon J.; Lee, Charles K.; Wommack, K. Eric; Cary, S. Craig

2013-01-01

Hydrothermal vents differ both in surface input and subsurface geochemistry. The effects of these differences on their microbial communities are not clear. Here, we investigated both alpha and beta diversity of diffuse flow-associated microbial communities emanating from vents at a basalt-based hydrothermal system along the East Pacific Rise (EPR) and a sediment-based hydrothermal system, Guaymas Basin. Both Bacteria and Archaea were targeted using high throughput 16S rRNA gene pyrosequencing analyses. A unique aspect of this study was the use of a universal set of 16S rRNA gene primers to characterize total and diffuse flow-specific microbial communities from varied deep-sea hydrothermal environments. Both surrounding seawater and diffuse flow water samples contained large numbers of Marine Group I (MGI) Thaumarchaea and Gammaproteobacteria taxa previously observed in deep-sea systems. However, these taxa were geographically distinct and segregated according to type of spreading center. Diffuse flow microbial community profiles were highly differentiated. In particular, EPR dominant diffuse flow taxa were most closely associated with chemolithoautotrophs, and off axis water was dominated by heterotrophic-related taxa, whereas the opposite was true for Guaymas Basin. The diversity and richness of diffuse flow-specific microbial communities were strongly correlated to the relative abundance of Epsilonproteobacteria, proximity to macrofauna, and hydrothermal system type. Archaeal diversity was higher than or equivalent to bacterial diversity in about one third of the samples. Most diffuse flow-specific communities were dominated by OTUs associated with Epsilonproteobacteria, but many of the Guaymas Basin diffuse flow samples were dominated by either OTUs within the Planctomycetes or hyperthermophilic Archaea. This study emphasizes the unique microbial communities associated with geochemically and geographically distinct hydrothermal diffuse flow environments. PMID:23898323

Molecular modeling of diffusion coefficient and ionic conductivity of CO2 in aqueous ionic solutions.

PubMed

Garcia-Ratés, Miquel; de Hemptinne, Jean-Charles; Bonet Avalos, Josep; Nieto-Draghi, Carlos

2012-03-08

Mass diffusion coefficients of CO(2)/brine mixtures under thermodynamic conditions of deep saline aquifers have been investigated by molecular simulation. The objective of this work is to provide estimates of the diffusion coefficient of CO(2) in salty water to compensate the lack of experimental data on this property. We analyzed the influence of temperature, CO(2) concentration,and salinity on the diffusion coefficient, the rotational diffusion, as well as the electrical conductivity. We observe an increase of the mass diffusion coefficient with the temperature, but no clear dependence is identified with the salinity or with the CO(2) mole fraction, if the system is overall dilute. In this case, we notice an important dispersion on the values of the diffusion coefficient which impairs any conclusive statement about the effect of the gas concentration on the mobility of CO(2) molecules. Rotational relaxation times for water and CO(2) increase by decreasing temperature or increasing the salt concentration. We propose a correlation for the self-diffusion coefficient of CO(2) in terms of the rotational relaxation time which can ultimately be used to estimate the mutual diffusion coefficient of CO(2) in brine. The electrical conductivity of the CO(2)-brine mixtures was also calculated under different thermodynamic conditions. Electrical conductivity tends to increase with the temperature and salt concentration. However, we do not observe any influence of this property with the CO(2) concentration at the studied regimes. Our results give a first evaluation of the variation of the CO(2)-brine mass diffusion coefficient, rotational relaxation times, and electrical conductivity under the thermodynamic conditions typically encountered in deep saline aquifers.

Focusing of light energy inside a scattering medium by controlling the time-gated multiple light scattering

NASA Astrophysics Data System (ADS)

Jeong, Seungwon; Lee, Ye-Ryoung; Choi, Wonjun; Kang, Sungsam; Hong, Jin Hee; Park, Jin-Sung; Lim, Yong-Sik; Park, Hong-Gyu; Choi, Wonshik

2018-05-01

The efficient delivery of light energy is a prerequisite for the non-invasive imaging and stimulating of target objects embedded deep within a scattering medium. However, the injected waves experience random diffusion by multiple light scattering, and only a small fraction reaches the target object. Here, we present a method to counteract wave diffusion and to focus multiple-scattered waves at the deeply embedded target. To realize this, we experimentally inject light into the reflection eigenchannels of a specific flight time to preferably enhance the intensity of those multiple-scattered waves that have interacted with the target object. For targets that are too deep to be visible by optical imaging, we demonstrate a more than tenfold enhancement in light energy delivery in comparison with ordinary wave diffusion cases. This work will lay a foundation to enhance the working depth of imaging, sensing and light stimulation.

Evolution of resistance to a multiple-herbivore community: genetic correlations, diffuse coevolution, and constraints on the plant's response to selection.

PubMed

Wise, Michael J; Rausher, Mark D

2013-06-01

Although plants are generally attacked by a community of several species of herbivores, relatively little is known about the strength of natural selection for resistance in multiple-herbivore communities-particularly how the strength of selection differs among herbivores that feed on different plant organs or how strongly genetic correlations in resistance affect the evolutionary responses of the plant. Here, we report on a field study measuring natural selection for resistance in a diverse community of herbivores of Solanum carolinense. Using linear phenotypic-selection analyses, we found that directional selection acted to increase resistance to seven species. Selection was strongest to increase resistance to fruit feeders, followed by flower feeders, then leaf feeders. Selection favored a decrease in resistance to a stem borer. Bootstrapping analyses showed that the plant population contained significant genetic variation for each of 14 measured resistance traits and significant covariances in one-third of the pairwise combinations of resistance traits. These genetic covariances reduced the plant's overall predicted evolutionary response for resistance against the herbivore community by about 60%. Diffuse (co)evolution was widespread in this community, and the diffuse interactions had an overwhelmingly constraining (rather than facilitative) effect on the plant's evolution of resistance. © 2013 The Author(s). Evolution © 2013 The Society for the Study of Evolution.

Antibiotic susceptibility of methicillin-resistant staphylococci (MRS) of food origin: A comparison of agar disc diffusion method and a commercially available miniaturized test.

PubMed

Buzón-Durán, Laura; Capita, Rosa; Alonso-Calleja, Carlos

2018-06-01

Methicillin-resistant staphylococci (MRS) are a major concern to public and animal health. Thirty MRS (Staphylococcus aureus, S. cohnii, S. epidermidis, S. haemolyticus, S. hominis, S. lentus, S. lugdunensis, S. sciuri, and S. xylosus) isolates from meat and poultry preparations were tested for antimicrobial susceptibility to 11 antimicrobials (belonging to seven different categories) of clinical significance using both the standard agar disc diffusion method and a commercially available miniaturized system (Sensi Test Gram-positive). It is worth stressing that 16 isolates (53.33%) exhibited an extensively drug-resistant phenotype (XDR). The average number of resistances per strain was 4.67. These results suggest that retail meat and poultry preparations are a likely vehicle for the transmission of multi-drug resistant MRS. Resistance to erythromycin was the commonest finding (76.67% of strains), followed by tobramycin, ceftazidime (66.67%), ciprofloxacin (56.67%) and fosfomycin (53.33%). An agreement (kappa coefficient) of 0.64 was found between the two testing methods. Using the agar disc diffusion as the reference method, the sensitivity, specificity and accuracy of the miniaturized test were 98.44%, 69.44% and 83.33%, respectively. Most discrepancies between the two methods were due to isolates that were susceptible according to the disc diffusion method but resistant according to the miniaturized test (false positives). Copyright © 2017. Published by Elsevier Ltd.

Antifungal Susceptibility Testing in HIV/AIDS Patients: a Comparison Between Automated Machine and Manual Method.

PubMed

Nelwan, Erni J; Indrasanti, Evi; Sinto, Robert; Nurchaida, Farida; Sosrosumihardjo, Rustadi

2016-01-01

to evaluate the performance of Vitek2 compact machine (Biomerieux Inc. ver 04.02, France) in reference to manual methods for susceptibility test for Candida resistance among HIV/AIDS patients. a comparison study to evaluate Vitek2 compact machine (Biomerieux Inc. ver 04.02, France) in reference to manual methods for susceptibility test for Candida resistance among HIV/AIDS patient was done. Categorical agreement between manual disc diffusion and Vitek2 machine was calculated using predefined criteria. Time to susceptibility result for automated and manual methods were measured. there were 137 Candida isolates comprising eight Candida species with C.albicans and C. glabrata as the first (56.2%) and second (15.3%) most common species, respectively. For fluconazole drug, among the C. albicans, 2.6% was found resistant on manual disc diffusion methods and no resistant was determined by Vitek2 machine; whereas 100% C. krusei was identified as resistant on both methods. Resistant patterns for C. glabrata to fluconazole, voriconazole and amphotericin B were 52.4%, 23.8%, 23.8% vs. 9.5%, 9.5%, 4.8% respectively between manual diffusion disc methods and Vitek2 machine. Time to susceptibility result for automated methods compared to Vitex2 machine was shorter for all Candida species. there is a good categorical agreement between manual disc diffusion and Vitek2 machine, except for C. glabrata for measuring the antifungal resistant. Time to susceptibility result for automated methods is shorter for all Candida species.

Clinical microbiology laboratories do not always detect resistance of Haemophilus influenzae with disk or tablet diffusion methods. Finnish Study Group for Antimicrobial Resistance (FiRe).

PubMed

Manninen, R; Huovinen, P; Nissinen, A

1998-04-01

The performance of disk diffusion testing of Haemophilus influenzae was evaluated in 20 laboratories. Thirteen disk-medium-breakpoint-inoculum modifications were used in Finnish clinical microbiology laboratories. The performance of various methods was evaluated by testing a susceptible control strain and one with non-beta-lactamase-mediated ampicillin resistance 10 times in 16 laboratories. Gaps in millimeters were measured between these two groups of results. The strains were separated by a gap of at least 5 mm in 8/16 laboratories testing ampicillin, in 7/15 laboratories testing cefaclor, in 5/ 16 laboratories testing cefuroxime, and in 15/16 laboratories testing trimethoprim-sulfa. Detection of ampicillin resistance was better with 2.5 microg tablets than with 10 microg disks or 33 microg tablets. For MIC-determinations, 785 isolates and their disk diffusion results were collected. None of the 12 clinical isolates with non-beta-lactamase-mediated ampicillin resistance was detected as resistant in the participating laboratories. The ampicillin and cefaclor results of the isolates were no better even when a laboratory was able to separate the control strains. Cefaclor results were unreliable because of poor disk diffusion-MIC correspondence and incoherent breakpoint references. Interlaboratory variation of the zone diameters caused false intermediate results of cefuroxime-susceptible strains. When ampicillin, cefaclor and cefuroxime were tested, the discrimination of laboratories using disks and tablets was equal, whereas the laboratories using paper disks were better able to detect trimethoprim-sulfa resistance.

Key concepts behind forming-free resistive switching incorporated with rectifying transport properties

PubMed Central

Shuai, Yao; Ou, Xin; Luo, Wenbo; Mücklich, Arndt; Bürger, Danilo; Zhou, Shengqiang; Wu, Chuangui; Chen, Yuanfu; Zhang, Wanli; Helm, Manfred; Mikolajick, Thomas; Schmidt, Oliver G.; Schmidt, Heidemarie

2013-01-01

This work reports the effect of Ti diffusion on the bipolar resistive switching in Au/BiFeO3/Pt/Ti capacitor-like structures. Polycrystalline BiFeO3 thin films are deposited by pulsed laser deposition at different temperatures on Pt/Ti/SiO2/Si substrates. From the energy filtered transmission electron microscopy and Rutherford backscattering spectrometry it is observed that Ti diffusion occurs if the deposition temperature is above 600°C. The current-voltage (I–V) curves indicate that resistive switching can only be achieved in Au/BiFeO3/Pt/Ti capacitor-like structures where this Ti diffusion occurs. The effect of Ti diffusion is confirmed by the BiFeO3 thin films deposited on Pt/sapphire and Pt/Ti/sapphire substrates. The resistive switching needs no electroforming process, and is incorporated with rectifying properties which is potentially useful to suppress the sneak current in a crossbar architecture. Those specific features open a promising alternative concept for nonvolatile memory devices as well as for other memristive devices like synapses in neuromorphic circuits. PMID:23860408

Improving the Corrosion Resistance of Biodegradable Magnesium Alloys by Diffusion Coating Process

NASA Astrophysics Data System (ADS)

Levy, Galit Katarivas; Aghion, Eli

Magnesium alloys suffer from accelerated corrosion in physiological environment and hence their use as a structural material for biodegradable implants is limited. The present study focuses on a diffusion coating treatment that amplifies the beneficial effect of Neodymium on the corrosion resistance of magnesium alloys. The diffusion coating layer was obtained by applying 1 µm Nd coating on EW10X04 magnesium alloy using Electron-gun evaporator and PVD process. The coated alloy was heat treated at 350°C for 3 hours in a protective atmosphere of N2+0.2%SF6. The micro structure characteristics were evaluated by SEM, XRD, and XPS; the corrosion resistance was examined by potentiodynamic polarization and EIS analysis. The corrosion resistance of the diffusion coated alloy was significantly improved compared to the uncoated material. This was related to: (i) formation of Nd2O3 in the outer scale, (ii) integration of Nd in the MgO oxide layer, and (iii) formation of secondary phase Mg41Nd5 along the grain boundaries of α-Mg.

Prevalence and molecular characterization of methicillin resistance among Coagulase-negative Staphylococci at a tertiary care center.

PubMed

Bhatt, Puneet; Tandel, Kundan; Singh, Alina; Kumar, M; Grover, Naveen; Sahni, A K

2016-12-01

Methicillin-resistant Coagulase-negative Staphylococci (MR-CoNS) have emerged as an important cause of nosocomial infections especially in patients with prosthetic devices and implants. This study was conducted with an aim to determine the prevalence of methicillin resistance among CoNS isolates at a tertiary care center by both phenotypic and genotypic methods. This cross sectional study was carried out from September 2011 to February 2014 in which 150 non-repetitive clinical isolates of CoNS were identified at the species level by conventional phenotypic methods. Cefoxitin disk (30 μg) diffusion testing was used to determine methicillin resistance and confirmed by detection of mec A gene by polymerase chain reaction (PCR). Out of 150 CoNS isolates, 51 were methicillin resistant by cefoxitin disk diffusion method. Out of these 51 isolates, mec A gene was detected only in 45 isolates. Moreover, mec A gene was also detected in 4 isolates, which were cefoxitin sensitive. Thus, the prevalence of methicillin resistance among CoNS was found to be 32.7% by PCR. The prevalence of methicillin resistance among Coagulase-negative Staphylococci (CoNS) was 32.7% by PCR detection of mec A gene. The sensitivity and specificity of cefoxitin disk diffusion method against mec A gene detection by PCR were found to be more than 90%. It can be concluded from this study that cefoxitin disk diffusion test can be used as a useful screening method to detect methicillin resistance among CoNS isolates. However, detection of mec A gene by PCR remains a more accurate method of detecting methicillin resistance among CoNS.

Oceanic Uptake of Oxygen During Deep Convection Events Through Diffusive and Bubble-Mediated Gas Exchange

NASA Astrophysics Data System (ADS)

Sun, Daoxun; Ito, Takamitsu; Bracco, Annalisa

2017-10-01

The concentration of dissolved oxygen (O2) plays fundamental roles in diverse chemical and biological processes throughout the oceans. The balance between the physical supply and the biological consumption controls the O2 level of the interior ocean, and the O2 supply to the deep waters can only occur through deep convection in the polar oceans. We develop a theoretical framework describing the oceanic O2 uptake during open-ocean deep convection events and test it against a suite of numerical sensitivity experiments. Our framework allows for two predictions, confirmed by the numerical simulations. First, both the duration and the intensity of the wintertime cooling contribute to the total O2 uptake for a given buoyancy loss. Stronger cooling leads to deeper convection and the oxygenation can reach down to deeper depths. Longer duration of the cooling period increases the total amount of O2 uptake over the convective season. Second, the bubble-mediated influx of O2 tends to weaken the diffusive influx by shifting the air-sea disequilibrium of O2 toward supersaturation. The degree of compensation between the diffusive and bubble-mediated gas exchange depends on the dimensionless number measuring the relative strength of oceanic vertical mixing and the gas transfer velocity. Strong convective mixing, which may occur under strong cooling, reduces the degree of compensation so that the two components of gas exchange together drive exceptionally strong oceanic O2 uptake.

Modelling of processes occurring in deep geological repository - Development of new modules in the GoldSim environment

NASA Astrophysics Data System (ADS)

Vopálka, D.; Lukin, D.; Vokál, A.

2006-01-01

Three new modules modelling the processes that occur in a deep geological repository have been prepared in the GoldSim computer code environment (using its Transport Module). These modules help to understand the role of selected parameters in the near-field region of the final repository and to prepare an own complex model of the repository behaviour. The source term module includes radioactive decay and ingrowth in the canister, first order degradation of fuel matrix, solubility limitation of the concentration of the studied nuclides, and diffusive migration through the surrounding bentonite layer controlled by the output boundary condition formulated with respect to the rate of water flow in the rock. The corrosion module describes corrosion of canisters made of carbon steel and transport of corrosion products in the near-field region. This module computes balance equations between dissolving species and species transported by diffusion and/or advection from the surface of a solid material. The diffusion module that includes also non-linear form of the interaction isotherm can be used for an evaluation of small-scale diffusion experiments.

Backside contacted field effect transistor array for extracellular signal recording.

PubMed

Ingebrandt, S; Yeung, C K; Staab, W; Zetterer, T; Offenhäusser, A

2003-04-01

A new approach to the design of field-effect transistor (FET) sensors and the use of these FETs in detecting extracellular electrophysiological recordings is reported. Backside contacts were engineered by deep reactive ion etching and a gas phase boron doping process of the holes using planar diffusion sources. The metal contacts were designed to fit on top of the bonding pads of a standard industrial 22-pin DIL (dual inline) chip carrier. To minimise contact resistance, the metal backside contacts of the chips were electroless plated with gold. The chips were mounted on top of the bonding pads using a standard flip-chip process and a fineplacer unit previously described. Rat embryonic myocytes were cultured on these new devices (effective growth area 6 x 6 mm(2)) in order to confirm their validity in electrophysiological recording. Copyright 2003 Elsevier Science B.V.

Thermal conductivity and thermal diffusivity of cores from a 26 meter deep borehole drilled in Livingston Island, Maritime Antarctic

NASA Astrophysics Data System (ADS)

Correia, A.; Vieira, G.; Ramos, M.

2012-06-01

During the month of January of 2008 a borehole (Permamodel-Gulbenkian 1 — PG1) 26 m deep was drilled on the top of Mount Reina Sofia (275 m a.s.l.) near the Spanish Antarctic Station of Livingston Island, South Shetland Islands. Cores from 1.5 m to about 26 m deep were collected for measuring several physical properties. The objective of the present work is to report the values of the thermal conductivity and the thermal diffusivity that were measured in the cores from the borehole and the heat production that was estimated for the geological formations intercepted by it. Seven cores were selected to measure the thermal conductivity and the thermal diffusivity. The measured values for the thermal conductivity vary from 2.6 W/mK to 3.3 W/mK while the measured values for the thermal diffusivity vary from 1.1 × 10- 6 m2/s to 1.6 × 10- 6 m2/s. Both thermal conductivity and thermal diffusivity, on average, show a slight increase with depth. Average heat production was also estimated for two portions of the borehole: one from 2 to 12 m and the other from 12 to 25 m. A gamma-ray spectrometer was used to estimate the concentrations of uranium, thorium, and potassium of the cores, from which the heat production per unit volume was calculated. The estimated heat production for the first half of the borehole is 2.218 μW/m3 while for the second half it is 2.173 μW/m3; these heat production values are compatible with acidic rock types. Porosity and density were also estimated for the same cores.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jiang, Hao; Materials Science Program, University of Wisconsin, Madison, Wisconsin 53706; Stewart, Derek A., E-mail: derek.stewart@hgst.com

Metal oxide resistive memory devices based on Ta{sub 2}O{sub 5} have demonstrated high switching speed, long endurance, and low set voltage. However, the physical origin of this improved performance is still unclear. Ta{sub 2}O{sub 5} is an important archetype of a class of materials that possess an adaptive crystal structure that can respond easily to the presence of defects. Using first principles nudged elastic band calculations, we show that this adaptive crystal structure leads to low energy barriers for in-plane diffusion of oxygen vacancies in λ phase Ta{sub 2}O{sub 5}. Identified diffusion paths are associated with collective motion of neighboringmore » atoms. The overall vacancy diffusion is anisotropic with higher diffusion barriers found for oxygen vacancy movement between Ta-O planes. Coupled with the fact that oxygen vacancy formation energy in Ta{sub 2}O{sub 5} is relatively small, our calculated low diffusion barriers can help explain the low set voltage in Ta{sub 2}O{sub 5} based resistive memory devices. Our work shows that other oxides with adaptive crystal structures could serve as potential candidates for resistive random access memory devices. We also discuss some general characteristics for ideal resistive RAM oxides that could be used in future computational material searches.« less

Insights about minority HIV-1 strains in transmitted drug resistance mutation dynamics and disease progression.

PubMed

Leda, Ana Rachel; Hunter, James; Oliveira, Ursula Castro; Azevedo, Inacio Junqueira; Sucupira, Maria Cecilia Araripe; Diaz, Ricardo Sobhie

2018-04-19

The presence of minority transmitted drug resistance mutations was assessed using ultra-deep sequencing and correlated with disease progression among recently HIV-1-infected individuals from Brazil. Samples at baseline during recent infection and 1 year after the establishment of the infection were analysed. Viral RNA and proviral DNA from 25 individuals were subjected to ultra-deep sequencing of the reverse transcriptase and protease regions of HIV-1. Viral strains carrying transmitted drug resistance mutations were detected in 9 out of the 25 patients, for all major antiretroviral classes, ranging from one to five mutations per patient. Ultra-deep sequencing detected strains with frequencies as low as 1.6% and only strains with frequencies >20% were detected by population plasma sequencing (three patients). Transmitted drug resistance strains with frequencies <14.8% did not persist upon established infection. The presence of transmitted drug resistance mutations was negatively correlated with the viral load and with CD4+ T cell count decay. Transmitted drug resistance mutations representing small percentages of the viral population do not persist during infection because they are negatively selected in the first year after HIV-1 seroconversion.

Mass transfer resistance in ASFF reactors for waste water treatment.

PubMed

Ettouney, H M; Al-Haddad, A A; Abu-Irhayem, T M

1996-01-01

Analysis of mass transfer resistances was performed for an aerated submerged fixed-film reactor (ASFF) for the treatment of waste water containing a mixture of sucrose and ammonia. Both external and internal mass transfer resistances were considered in the analysis, and characterized as a function of feed flow-rate and concentration. Results show that, over a certain operating regime, external mass transfer resistance in the system was greater for sucrose removal than ammonia. This is because the reaction rates for carbon removal were much larger than those of nitrogen. As a result, existence of any form of mass transfer resistance caused by inadequate mixing or diffusion limitations, strongly affects the overall removal rates of carbon more than nitrogen. Effects of the internal måss transfer resistance were virtually non-existent for ammonia removal. This behaviour was found over two orders of magnitude range for the effective diffusivity for ammonia, and one order of magnitude for the film specific surface area. However, over the same parameters' range, it is found that sucrose removal was strongly affected upon lowering its effective diffusivity and increasing the film specific surface area.

Copper diffusion in Ti Si N layers formed by inductively coupled plasma implantation

NASA Astrophysics Data System (ADS)

Ee, Y. C.; Chen, Z.; Law, S. B.; Xu, S.; Yakovlev, N. L.; Lai, M. Y.

2006-11-01

Ternary Ti-Si-N refractory barrier films of 15 nm thick was prepared by low frequency, high density, inductively coupled plasma implantation of N into TixSiy substrate. This leads to the formation of Ti-N and Si-N compounds in the ternary film. Diffusion of copper in the barrier layer after annealing treatment at various temperatures was investigated using time-of-flight secondary ion mass spectrometer (ToF-SIMS) depth profiling, X-ray diffractometer (XRD), field emission scanning electron microscopy (FESEM), energy dispersive X-ray (EDX) and sheet resistance measurement. The current study found that barrier failure did not occur until 650 °C annealing for 30 min. The failure occurs by the diffusion of copper into the Ti-Si-N film to form Cu-Ti and Cu-N compounds. FESEM surface morphology and EDX show that copper compounds were formed on the ridge areas of the Ti-Si-N film. The sheet resistance verifies the diffusion of Cu into the Ti-Si-N film; there is a sudden drop in the resistance with Cu compound formation. This finding provides a simple and effective method of monitoring Cu diffusion in TiN-based diffusion barriers.

Antibiotic resistance and polymorphism in the quinolone resistance-determining region of Campylobacter spp. isolated from 1-day-old ducklings.

PubMed

Hamed, Engy A; AbdelRahman, Mona A A; Shalaby, Azhar G; Morsy, Mai M; Nasef, Soad A

2016-05-01

Thirty-three isolates of Campylobacter coli and three isolates of Campylobacter jejuni were recovered from 150 1-day-old ducklings. All isolates were sensitive to chloramphenicol and amikacin, but resistant to sulfamethoxazole-trimethoprim (SXT) by the disc diffusion method. Most isolates were susceptible to tetracycline and erythromycin, but resistant to ofloxacin and ciprofloxacin. Of the 33 C. coli isolates, nine were positive for the tetracycline resistance gene tet(O), although only two of these were resistant to tetracycline in the disc diffusion test. None of the isolates possessed mutations in the quinolone resistance-determining region (QRDR) of the gyrA gene infrequently linked to FQ-resistance. The finding indicated that ducklings may be a source of antibiotic resistant Campylobacter spp. with potential poultry and public health hazard. Copyright © 2016 Elsevier Ltd. All rights reserved.

Optimum DMOS cell doping profiles for high-voltage discrete and integrated device technologies

NASA Astrophysics Data System (ADS)

Shenai, Krishna

1992-05-01

It is shown that the implantation and activation sequences of B and As result in significant variations in the contact resistance and p-base sheet resistance beneath the n+-source diffusion of a DMOSFET cell. For identical process parameters, the contact resistance of As-doped n+ silicon was significantly improved when high-dose B was implanted due to higher As surface concentration. The SUPREM III process modeling results were found to be in qualitative agreement with the measured spreading resistance profiles and the discrepancies could be attributed to larger high-temperature diffusion constants used in SUPREM III and the coupled As-B diffusion/activation effects that are not accounted for in process modeling. The experimental results are discussed within the framework of fabricating high-performance DMOSFET cells and CMOS high-voltage devices on the same chip for discrete and smart-power applications.

Resistivity bound for hydrodynamic bad metals

PubMed Central

Lucas, Andrew; Hartnoll, Sean A.

2017-01-01

We obtain a rigorous upper bound on the resistivity ρ of an electron fluid whose electronic mean free path is short compared with the scale of spatial inhomogeneities. When such a hydrodynamic electron fluid supports a nonthermal diffusion process—such as an imbalance mode between different bands—we show that the resistivity bound becomes ρ≲AΓ. The coefficient A is independent of temperature and inhomogeneity lengthscale, and Γ is a microscopic momentum-preserving scattering rate. In this way, we obtain a unified mechanism—without umklapp—for ρ∼T2 in a Fermi liquid and the crossover to ρ∼T in quantum critical regimes. This behavior is widely observed in transition metal oxides, organic metals, pnictides, and heavy fermion compounds and has presented a long-standing challenge to transport theory. Our hydrodynamic bound allows phonon contributions to diffusion constants, including thermal diffusion, to directly affect the electrical resistivity. PMID:29073054

Characterization of irradiation induced deep and shallow impurities

NASA Astrophysics Data System (ADS)

Treberspurg, Wolfgang; Bergauer, Thomas; Dragicevic, Marko; Krammer, Manfred; Valentan, Manfred

2013-12-01

Silicon Detectors close to the interaction point of the High Luminosity Large Hardron Collider (HL-LHC) have to withstand a harsh irradiation environment. In order to evaluate the behaviour of shallow and deep defects, induced by neutron irradiation, spreading resistance resistivity measurements and capacitance voltage measurements have been performed. These measurements, deliver information about the profile of shallow impurities after irradiation as well as indications of deep defects in the Space Charge Region (SCR) and the Electrical Neutral Bulk (ENB). By considering the theoretical background of the measurement both kinds of defects can be investigated independently from each other.

Evolution of AlGaN deep level defects as a function of alloying and compositional grading and resultant impact on electrical conductivity

DOE PAGES

Armstrong, Andrew M.; Allerman, Andrew A.

2017-07-24

AlGaN:Si epilayers with uniform Al compositions of 60%, 70%, 80%, and 90% were grown by metal-organic vapor phase epitaxy along with a compositionally graded, unintentionally doped (UID) AlGaN epilayer with the Al composition varying linearly between 80% and 100%. The resistivity of AlGaN:Si with a uniform composition increased significantly for the Al content of 80% and greater, whereas the graded UID-AlGaN film exhibited resistivity equivalent to 60% and 70% AlGaN:Si owing to polarization-induced doping. Deep level defect studies of both types of AlGaN epilayers were performed to determine why the electronic properties of uniform-composition AlGaN:Si degraded with increased Al content,more » while the electronic properties of graded UID-AlGaN did not. The deep level density of uniform-composition AlGaN:Si increased monotonically and significantly with the Al mole fraction. Conversely, graded-UID AlGaN had the lowest deep level density of all the epilayers despite containing the highest Al composition. These findings indicate that Si doping is an impetus for point defect incorporation in AlGaN that becomes stronger with the increasing Al content. However, the increase in deep level density with the Al content in uniform-composition AlGaN:Si was small compared to the increase in resistivity. This implies that the primary cause for increasing resistivity in AlGaN:Si with the increasing Al mole fraction is not compensation by deep levels but rather increasing activation energy for the Si dopant. As a result, the graded UID-AlGaN films maintained low resistivity because they do not rely on thermal ionization of Si dopants.« less

Evolution of AlGaN deep level defects as a function of alloying and compositional grading and resultant impact on electrical conductivity

DOE Office of Scientific and Technical Information (OSTI.GOV)

Armstrong, Andrew M.; Allerman, Andrew A.

AlGaN:Si epilayers with uniform Al compositions of 60%, 70%, 80%, and 90% were grown by metal-organic vapor phase epitaxy along with a compositionally graded, unintentionally doped (UID) AlGaN epilayer with the Al composition varying linearly between 80% and 100%. The resistivity of AlGaN:Si with a uniform composition increased significantly for the Al content of 80% and greater, whereas the graded UID-AlGaN film exhibited resistivity equivalent to 60% and 70% AlGaN:Si owing to polarization-induced doping. Deep level defect studies of both types of AlGaN epilayers were performed to determine why the electronic properties of uniform-composition AlGaN:Si degraded with increased Al content,more » while the electronic properties of graded UID-AlGaN did not. The deep level density of uniform-composition AlGaN:Si increased monotonically and significantly with the Al mole fraction. Conversely, graded-UID AlGaN had the lowest deep level density of all the epilayers despite containing the highest Al composition. These findings indicate that Si doping is an impetus for point defect incorporation in AlGaN that becomes stronger with the increasing Al content. However, the increase in deep level density with the Al content in uniform-composition AlGaN:Si was small compared to the increase in resistivity. This implies that the primary cause for increasing resistivity in AlGaN:Si with the increasing Al mole fraction is not compensation by deep levels but rather increasing activation energy for the Si dopant. As a result, the graded UID-AlGaN films maintained low resistivity because they do not rely on thermal ionization of Si dopants.« less

Ion Permeability of Artificial Membranes Evaluated by Diffusion Potential and Electrical Resistance Measurements

ERIC Educational Resources Information Center

Shlyonsky, Vadim

2013-01-01

In the present article, a novel model of artificial membranes that provides efficient assistance in teaching the origins of diffusion potentials is proposed. These membranes are made of polycarbonate filters fixed to 12-mm plastic rings and then saturated with a mixture of creosol and "n"-decane. The electrical resistance and potential…

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pezeshki, Alan M.; Sacci, Robert L.; Delnick, Frank M.

Here, an improved method for quantitative measurement of the charge transfer, finite diffusion, and ohmic overpotentials in redox flow batteries using electrochemical impedance spectroscopy is presented. The use of a pulse dampener in the hydraulic circuit enables the collection of impedance spectra at low frequencies with a peristaltic pump, allowing the measurement of finite diffusion resistances at operationally relevant flow rates. This method is used to resolve the rate-limiting processes for the V 2+/V 3+ redox couple on carbon felt and carbon paper electrodes in the vanadium redox flow battery. Carbon felt was limited by both charge transfer and ohmicmore » resistance, while carbon paper was limited by charge transfer, finite diffusion, and ohmic resistances. The influences of vanadium concentration and flow field design also are quantified.« less

Speckle contrast optical tomography: A new method for deep tissue three-dimensional tomography of blood flow

PubMed Central

Varma, Hari M.; Valdes, Claudia P.; Kristoffersen, Anna K.; Culver, Joseph P.; Durduran, Turgut

2014-01-01

A novel tomographic method based on the laser speckle contrast, speckle contrast optical tomography (SCOT) is introduced that allows us to reconstruct three dimensional distribution of blood flow in deep tissues. This method is analogous to the diffuse optical tomography (DOT) but for deep tissue blood flow. We develop a reconstruction algorithm based on first Born approximation to generate three dimensional distribution of flow using the experimental data obtained from tissue simulating phantoms. PMID:24761306

Bulk and contact resistances of gas diffusion layers in proton exchange membrane fuel cells

NASA Astrophysics Data System (ADS)

Ye, Donghao; Gauthier, Eric; Benziger, Jay B.; Pan, Mu

2014-06-01

A multi-electrode probe is employed to distinguish the bulk and contact resistances of the catalyst layer (CL) and the gas diffusion layer (GDL) with the bipolar plate (BPP). Resistances are compared for Vulcan carbon catalyst layers (CL), carbon paper and carbon cloth GDL materials, and GDLs with microporous layers (MPL). The Vulcan carbon catalyst layer bulk resistance is 100 times greater than the bulk resistance of carbon paper GDL (Toray TG-H-120). Carbon cloth (CCWP) has bulk and contact resistances twice those of carbon paper. Compression of the GDL decreases the GDL contact resistance, but has little effect on the bulk resistance. Treatment of the GDL with polytetrafluoroethylene (PTFE) increases the contact resistance, but has little effect on the bulk resistance. A microporous layer (MPL) added to the GDL decreases the contact resistance, but has little effect on the bulk resistance. An equivalent circuit model shows that for channels less than 1 mm wide the contact resistance is the major source of electronic resistance and is about 10% of the total ohmic resistance associated with the membrane electrode assembly.

Electro-thermo-mechanical coupling analysis of deep drawing with resistance heating for aluminum matrix composites sheet

NASA Astrophysics Data System (ADS)

Zhang, Kaifeng; Zhang, Tuoda; Wang, Bo

2013-05-01

Recently, electro-plastic forming to be a focus of attention in materials hot processing research area, because it is a sort of energy-saving, high efficient and green manufacturing technology. An electro-thermo-mechanical model can be adopted to carry out the sequence simulation of aluminum matrix composites sheet deep drawing via electro-thermal coupling and thermal-mechanical coupling method. The first step of process is resistance heating of sheet, then turn off the power, and the second step is deep drawing. Temperature distribution of SiCp/2024Al composite sheet by resistance heating and sheet deep drawing deformation were analyzed. During the simulation, effect of contact resistances, temperature coefficient of resistance for electrode material and SiCp/2024Al composite on temperature distribution were integrally considered. The simulation results demonstrate that Sicp/2024Al composite sheet can be rapidly heated to 400° in 30s using resistances heating and the sheet temperature can be controlled by adjusting the current density. Physical properties of the electrode materials can significantly affect the composite sheet temperature distribution. The temperature difference between the center and the side of the sheet is proportional to the thermal conductivity of the electrode, the principal cause of which is that the heat transfers from the sheet to the electrode. SiCp/2024Al thin-wall part can be intactly manufactured at strain rate of 0.08s-1 and the sheet thickness thinning rate is limited within 20%, which corresponds well to the experimental result.

SEDS: The Spitzer Extended Deep Survey. Survey Design, Photometry, and Deep IRAC Source Counts

NASA Technical Reports Server (NTRS)

Ashby, M. L. N.; Willner, S. P.; Fazio, G. G.; Huang, J.-S.; Arendt, A.; Barmby, P.; Barro, G; Bell, E. F.; Bouwens, R.; Cattaneo, A.;

Development and pilot line production of lithium doped silicon solar cells

NASA Technical Reports Server (NTRS)

Payne, P. A.

1972-01-01

Scaling up the BCl3 without O2 diffusion beyond 30 to 40 cells was investigated by using a 100 cell capacity diffusion boat which held the cells vertically. Sheet resistances and I-V curves were uniform with 10 to 20 cells spaced along the entire boat, so the quantity was increased to 40 and then 60 cells per diffusion. There was no change in cell output and uniformity going from 20 to 40 cells per diffusion; however only half the lithium cells fabricated from slices diffused in the 60 cell diffusion had efficiencies of 11% or better. Although uniform sheet resistances and I-V characteristic curves were obtained with up to 60 cells in the BCl3 with O2 diffusion, the short circuit currents were approximately 15% lower than the anticipated 135 to 140 mA. Consequently, work on this diffusion process has been aimed solely at increasing the short circuit current. The diffusion temperature was lowered from 1055 to 1000 and 950 C, and at each of these temperatures variations in diffusion time were investigated. At 1000 C short circuit currents were approximately 10 mA higher, 130 rather than 120 mA average.

Diffuse optical correlation tomography of cerebral blood flow during cortical spreading depression in rat brain

NASA Astrophysics Data System (ADS)

Zhou, Chao; Yu, Guoqiang; Furuya, Daisuke; Greenberg, Joel; Yodh, Arjun; Durduran, Turgut

2006-02-01

Diffuse optical correlation methods were adapted for three-dimensional (3D) tomography of cerebral blood flow (CBF) in small animal models. The image reconstruction was optimized using a noise model for diffuse correlation tomography which enabled better data selection and regularization. The tomographic approach was demonstrated with simulated data and during in-vivo cortical spreading depression (CSD) in rat brain. Three-dimensional images of CBF were obtained through intact skull in tissues(~4mm) deep below the cortex.

Study on Ultra-deep Azimuthal Electromagnetic Resistivity LWD Tool by Influence Quantification on Azimuthal Depth of Investigation and Real Signal

NASA Astrophysics Data System (ADS)

Li, Kesai; Gao, Jie; Ju, Xiaodong; Zhu, Jun; Xiong, Yanchun; Liu, Shuai

2018-05-01

This paper proposes a new tool design of ultra-deep azimuthal electromagnetic (EM) resistivity logging while drilling (LWD) for deeper geosteering and formation evaluation, which can benefit hydrocarbon exploration and development. First, a forward numerical simulation of azimuthal EM resistivity LWD is created based on the fast Hankel transform (FHT) method, and its accuracy is confirmed under classic formation conditions. Then, a reasonable range of tool parameters is designed by analyzing the logging response. However, modern technological limitations pose challenges to selecting appropriate tool parameters for ultra-deep azimuthal detection under detectable signal conditions. Therefore, this paper uses grey relational analysis (GRA) to quantify the influence of tool parameters on voltage and azimuthal investigation depth. After analyzing thousands of simulation data under different environmental conditions, the random forest is used to fit data and identify an optimal combination of tool parameters due to its high efficiency and accuracy. Finally, the structure of the ultra-deep azimuthal EM resistivity LWD tool is designed with a theoretical azimuthal investigation depth of 27.42-29.89 m in classic different isotropic and anisotropic formations. This design serves as a reliable theoretical foundation for efficient geosteering and formation evaluation in high-angle and horizontal (HA/HZ) wells in the future.

Noise and degradation of amorphous silicon devices

NASA Astrophysics Data System (ADS)

Bakker, J. P. R.

2003-10-01

Electrical noise measurements are reported on two devices of the disordered semiconductor hydrogenated amorphous silicon (a-Si:H). The material is applied in sandwich structures and in thin-film transistors (TFTs). In a sandwich configuration of an intrinsic layer and two thin doped layers, the observed 1/f resistance noise can be attributed to a distribution of energy levels in the system. Two candidates which eventually could explain the origin of the energy distribution are investigated: generation-recombination noise and long-range potential fluctuations. A simulation program was applied to fit the current-voltage characteristics and resolves the defect density, the energy position and width of the Gaussian distributions of deep defects. Generation-recombination (g-r) is calculated for a one-dimensional semiconductor device with traps, taking the transport of local fluctuations into account. Although the times characterizing capture and emission for deep defects are in the right (ms) range, the calculated noise intensity is five to six orders of magnitude below the measured noise level. Another noise source must cause the 1/f noise in a-Si:H. The alternative is provided by the theory of long-range potential fluctuations. The timescale of the fluctuations is again the capture or emission time for deep defects. When an electron is emitted or captured, the charge state of a deep defect fluctuates. As a result, the potential around that defect will fluctuate, being screened by the surrounding defects. Free electrons will instantaneously adjust to the local potential. The adjustment causes a resistance fluctuation, which is measured as a voltage fluctuation in presence of a constant current. The theory predicts the noise intensity accurately, without any adjustable parameters. Unlike the intensity, the spectral shape is fitted by adjustment of two parameters of the potential landscape. The complete temperature dependence of the noise spectra is consistently described by a Gaussian distribution of potential barriers, located 0.27 eV above the conduction band edge, with a halfwidth of 0.09 eV. A large number of experiments is explained by the theory of long-range potential fluctuations: the thickness dependence, the absence of an isotope effect and the analogous results for oppositely doped devices. From these experiments, it is concluded that a universal potential landscape exists in undoped a-Si:H. Further, the relation between degradation upon prolonged light-soaking and noise is studied. After degradation, the curvature of noise spectra is unaffected, while the intensity increases slightly. These observations are consistent with the theoretical predictions using the observed increase of the defect density. It seems that the potential landscape does not change significantly upon degradation. Noise measurements in the sub-threshold regime of a-Si:H TFTs turn out to yield diffusion noise. Diffusion of electrons through the one-dimensional channel is identified as the source of the noise. The drift mobility extracted from the combined noise and conduction data is below the value that characterizes the on-state. The number of free electrons as determined from combined noise and conduction measurements are in quantitative agreement with an alternative determination from conduction measurements only.

Exploring the hypothesis that limiting diffusion of fungal oxidants underlies decay resistance in acetylated wood

Treesearch

Christopher G. Hunt; Steven Lacher; Kolby Hirth; Linda Lorenz; Kenneth E. Hammel

2017-01-01

The mechanisms by which chemical modifications, specifically acetylation, improve the decay resistance of wood are a topic of active research. In the early stages of decay, fungi secrete lowmolecular- weight oxidants or oxidant precursors. These oxidants diffuse through the wet wood cell wall and oxidize cell wall polymers, which enable the decay process to proceed....

Diffusional falsification of kinetic constants on Lineweaver-Burk plots.

PubMed

Ghim, Y S; Chang, H N

1983-11-07

The effect of mass transfer resistances on the Lineweaver-Burk plots in immobilized enzyme systems has been investigated numerically and with analytical approximate solutions. While Hamilton, Gardner & Colton (1974) studied the effect of internal diffusion resistances in planar geometry, our study was extended to the combined effect of internal and external diffusion in cylindrical and spherical geometries as well. The variation of Lineweaver-Burk plots with respect to the geometries was minimized by modifying the Thiele modulus and the Biot number with the shape factor. Especially for a small Biot number all the three Lineweaver-Burk plots fell on a single line. As was discussed by Hamilton et al. (1974), the curvature of the line for large external diffusion resistances was small enough to be assumed linear, which was confirmed from the two approximate solutions for large and small substrate concentrations. Two methods for obtaining intrinsic kinetic constants were proposed: First, we obtained both maximum reaction rate and Michaelis constant by fitting experimental data to a straight line where external diffusion resistance was relatively large, and second, we obtained Michaelis constant from apparent Michaelis constant from the figure in case we knew maximum reaction rate a priori.

Thin n-i-p silicon solar cell

NASA Technical Reports Server (NTRS)

Meulenberg, A., Jr.; Allison, J. F.; Arndt, R. A.

1980-01-01

A space solar cell concept which combines high cell output with low diffusion length damage coefficients is presented for the purpose of reducing solar cell susceptibility to degradation from the radiation environment. High resistivity n-i-p silicon solar cells ranging from upward of 83 micron-cm were exposed to AM0 ultraviolet illumination. It is shown that high resistivity cells act as extrinsic devices under dark conditions and as intrinsic devices under AM0 illumination. Resistive losses in thin n-i-p cells are found to be comparable to those in low resistivity cells. Present voltage limitations appear to be due to generation and recombination in the diffused regions.

Wavelength-modulated photocapacitance spectroscopy

NASA Technical Reports Server (NTRS)

Kamieniecki, E.; Lagowski, J.; Gatos, H. C.

1980-01-01

Derivative deep-level spectroscopy was achieved with wavelength-modulated photocapacitance employing MOS structures and Schottky barriers. The energy position and photoionization characteristics of deep levels of melt-grown GaAs and the Cr level in high-resistivity GaAs were determined. The advantages of this method over existing methods for deep-level spectroscopy are discussed.

Distinction between epigenic and hypogenic maze caves

NASA Astrophysics Data System (ADS)

Palmer, Arthur N.

2011-11-01

Certain caves formed by dissolution of bedrock have maze patterns composed of closed loops in which many intersecting fractures or pores have enlarged simultaneously. Their origin can be epigenic (by shallow circulation of meteoric groundwater) or hypogenic (by rising groundwater or production of deep-seated solutional aggressiveness). Epigenic mazes form by diffuse infiltration through a permeable insoluble caprock or by floodwater supplied by sinking streams. Most hypogenic caves involve deep sources of aggressiveness. Transverse hypogenic cave origin is a recently proposed concept in which groundwater of mainly meteoric origin rises across strata in the distal portions of large flow systems, to form mazes in soluble rock sandwiched between permeable but insoluble strata. The distinction between maze types is debated and is usually based on examination of diagnostic cave features and relation of caves to their regional setting. In this paper, the principles of mass transfer are applied to clarify the limits of each model, to show how cave origin is related to groundwater discharge, dissolution rate, and time. The results show that diffuse infiltration and floodwater can each form maze caves at geologically feasible rates (typically within 500 ka). Transverse hypogenic mazes in limestone, to enlarge significantly within 1 Ma, require an unusually high permeability of the non-carbonate beds (generally ≥ 10-4 cm/s), large discharge, and calcite saturation no greater than 90%, which is rare in deep diffuse flow in sedimentary rocks. Deep sources of aggressiveness are usually required. The origin of caves by transverse hypogenic flow is much more favorable in evaporite rocks than in carbonate rocks.

Effects of Slow Deep Breathing at High Altitude on Oxygen Saturation, Pulmonary and Systemic Hemodynamics

PubMed Central

Bilo, Grzegorz; Revera, Miriam; Bussotti, Maurizio; Bonacina, Daniele; Styczkiewicz, Katarzyna; Caldara, Gianluca; Giglio, Alessia; Faini, Andrea; Giuliano, Andrea; Lombardi, Carolina; Kawecka-Jaszcz, Kalina; Mancia, Giuseppe; Agostoni, Piergiuseppe; Parati, Gianfranco

2012-01-01

Slow deep breathing improves blood oxygenation (SpO2) and affects hemodynamics in hypoxic patients. We investigated the ventilatory and hemodynamic effects of slow deep breathing in normal subjects at high altitude. We collected data in healthy lowlanders staying either at 4559 m for 2–3 days (Study A; N = 39) or at 5400 m for 12–16 days (Study B; N = 28). Study variables, including SpO2 and systemic and pulmonary arterial pressure, were assessed before, during and after 15 minutes of breathing at 6 breaths/min. At the end of slow breathing, an increase in SpO2 (Study A: from 80.2±7.7% to 89.5±8.2%; Study B: from 81.0±4.2% to 88.6±4.5; both p<0.001) and significant reductions in systemic and pulmonary arterial pressure occurred. This was associated with increased tidal volume and no changes in minute ventilation or pulmonary CO diffusion. Slow deep breathing improves ventilation efficiency for oxygen as shown by blood oxygenation increase, and it reduces systemic and pulmonary blood pressure at high altitude but does not change pulmonary gas diffusion. PMID:23152851

Effects of slow deep breathing at high altitude on oxygen saturation, pulmonary and systemic hemodynamics.

PubMed

Bilo, Grzegorz; Revera, Miriam; Bussotti, Maurizio; Bonacina, Daniele; Styczkiewicz, Katarzyna; Caldara, Gianluca; Giglio, Alessia; Faini, Andrea; Giuliano, Andrea; Lombardi, Carolina; Kawecka-Jaszcz, Kalina; Mancia, Giuseppe; Agostoni, Piergiuseppe; Parati, Gianfranco

2012-01-01

Slow deep breathing improves blood oxygenation (Sp(O2)) and affects hemodynamics in hypoxic patients. We investigated the ventilatory and hemodynamic effects of slow deep breathing in normal subjects at high altitude. We collected data in healthy lowlanders staying either at 4559 m for 2-3 days (Study A; N = 39) or at 5400 m for 12-16 days (Study B; N = 28). Study variables, including Sp(O2) and systemic and pulmonary arterial pressure, were assessed before, during and after 15 minutes of breathing at 6 breaths/min. At the end of slow breathing, an increase in Sp(O2) (Study A: from 80.2±7.7% to 89.5±8.2%; Study B: from 81.0±4.2% to 88.6±4.5; both p<0.001) and significant reductions in systemic and pulmonary arterial pressure occurred. This was associated with increased tidal volume and no changes in minute ventilation or pulmonary CO diffusion. Slow deep breathing improves ventilation efficiency for oxygen as shown by blood oxygenation increase, and it reduces systemic and pulmonary blood pressure at high altitude but does not change pulmonary gas diffusion.

Deep resistivity sounding studies in detecting shear zones: A case study from the southern granulite terrain of India

NASA Astrophysics Data System (ADS)

Singh, S. B.; Stephen, Jimmy

2006-10-01

The resistivity signatures of the major crustal scale shear zones that dissect the southern granulite terrain (SGT) of South India into discrete geological fragments have been investigated. Resistivity structures deduced from deep resistivity sounding measurements acquired with a 10 km long Schlumberger spreads yield significant insights into the resistivity distribution within the E-W trending shear system comprising the Moyar-Bhavani-Salem-Attur shear zone (MBSASZ) and Palghat-Cauvery shear zone (PCSZ). Vertical and lateral extensions of low resistivity features indicate the possible existence of weak zones at different depths throughout the shear zones. The MBSASZ characterized by very low resistivity in its deeper parts (>2500 m), extends towards the south with slightly higher resistivities to encompass the PCSZ. A major resistivity transition between the northern and southern parts is evident in the two-dimensional resistivity images. The northern Archaean granulite terrain exhibits a higher resistivity than the southern Neoproterozoic granulite terrain. Though this resistivity transition is not clear at greater depths, the extension of low resistivity zones has been well manifested. It is speculated here that a network of crustal scale shear zones in the SGT may have influenced the strength of the lithosphere.

Molecular dynamics of acetamide based ionic deep eutectic solvents

NASA Astrophysics Data System (ADS)

Srinivasan, H.; Dubey, P. S.; Sharma, V. K.; Biswas, R.; Mitra, S.; Mukhopadhyay, R.

2018-04-01

Deep eutectic solvents are multi-component mixtures that have freezing point lower than their individual components. Mixture of acetamide+ lithium nitrate in the molar ratio 78:22 and acetamide+ lithium perchlorate in the molar ratio 81:19 are found to form deep eutectic solvents with melting point lower than the room temperature. It is known that the depression in freezing point is due to the hydrogen bond breaking ability of anions in the system. Quasielastic neutron scattering experiments on these systems were carried out to study the dynamics of acetamide molecules which may be influenced by this hydrogen bond breaking phenomena. The motion of acetamide molecules is modeled using jump diffusion mechanism to demonstrate continuous breaking and reforming hydrogen bonds in the solvent. Using the jump diffusion model, it is inferred that the jump lengths of acetamide molecules are better approximated by a Gaussian distribution. The shorter residence time of acetamide in presence of perchlorate ions suggest that the perchlorate ions have a higher hydrogen bond breaking ability compared to nitrate ions.

Deep-tissue temperature mapping by multi-illumination photoacoustic tomography aided by a diffusion optical model: a numerical study

NASA Astrophysics Data System (ADS)

Zhou, Yuan; Tang, Eric; Luo, Jianwen; Yao, Junjie

2018-01-01

Temperature mapping during thermotherapy can help precisely control the heating process, both temporally and spatially, to efficiently kill the tumor cells and prevent the healthy tissues from heating damage. Photoacoustic tomography (PAT) has been used for noninvasive temperature mapping with high sensitivity, based on the linear correlation between the tissue's Grüneisen parameter and temperature. However, limited by the tissue's unknown optical properties and thus the optical fluence at depths beyond the optical diffusion limit, the reported PAT thermometry usually takes a ratiometric measurement at different temperatures and thus cannot provide absolute measurements. Moreover, ratiometric measurement over time at different temperatures has to assume that the tissue's optical properties do not change with temperatures, which is usually not valid due to the temperature-induced hemodynamic changes. We propose an optical-diffusion-model-enhanced PAT temperature mapping that can obtain the absolute temperature distribution in deep tissue, without the need of multiple measurements at different temperatures. Based on the initial acoustic pressure reconstructed from multi-illumination photoacoustic signals, both the local optical fluence and the optical parameters including absorption and scattering coefficients are first estimated by the optical-diffusion model, then the temperature distribution is obtained from the reconstructed Grüneisen parameters. We have developed a mathematic model for the multi-illumination PAT of absolute temperatures, and our two-dimensional numerical simulations have shown the feasibility of this new method. The proposed absolute temperature mapping method may set the technical foundation for better temperature control in deep tissue in thermotherapy.

Evolution of simeprevir-resistant variants over time by ultra-deep sequencing in HCV genotype 1b.

PubMed

Akuta, Norio; Suzuki, Fumitaka; Sezaki, Hitomi; Suzuki, Yoshiyuki; Hosaka, Tetsuya; Kobayashi, Masahiro; Kobayashi, Mariko; Saitoh, Satoshi; Ikeda, Kenji; Kumada, Hiromitsu

2014-08-01

Using ultra-deep sequencing technology, the present study was designed to investigate the evolution of simeprevir-resistant variants (amino acid substitutions of aa80, aa155, aa156, and aa168 positions in HCV NS3 region) over time. In Toranomon Hospital, 18 Japanese patients infected with HCV genotype 1b, received triple therapy of simeprevir/PEG-IFN/ribavirin (DRAGON or CONCERT study). Sustained virological response rate was 67%, and that was significantly higher in patients with IL28B rs8099917 TT than in those with non-TT. Six patients, who did not achieve sustained virological response, were tested for resistant variants by ultra-deep sequencing, at the baseline, at the time of re-elevation of viral loads, and at 96 weeks after the completion of treatment. Twelve of 18 resistant variants, detected at re-elevation of viral load, were de novo resistant variants. Ten of 12 de novo resistant variants become undetectable over time, and that five of seven resistant variants, detected at baseline, persisted over time. In one patient, variants of Q80R at baseline (0.3%) increased at 96-week after the cessation of treatment (10.2%), and de novo resistant variants of D168E (0.3%) also increased at 96-week after the cessation of treatment (9.7%). In conclusion, the present study indicates that the emergence of simeprevir-resistant variants after the start of treatment could not be predicted at baseline, and the majority of de novo resistant variants become undetectable over time. Further large-scale prospective studies should be performed to investigate the clinical utility in detecting simeprevir-resistant variants. © 2014 Wiley Periodicals, Inc.

Note: Thermal analog to atomic force microscopy force-displacement measurements for nanoscale interfacial contact resistance.

PubMed

Iverson, Brian D; Blendell, John E; Garimella, Suresh V

2010-03-01

Thermal diffusion measurements on polymethylmethacrylate-coated Si substrates using heated atomic force microscopy tips were performed to determine the contact resistance between an organic thin film and Si. The measurement methodology presented demonstrates how the thermal contrast signal obtained during a force-displacement ramp is used to quantify the resistance to heat transfer through an internal interface. The results also delineate the interrogation thickness beyond which thermal diffusion in the organic thin film is not affected appreciably by the underlying substrate.

A new diffusion-inhibited oxidation-resistant coating for superalloys

NASA Technical Reports Server (NTRS)

Gedwill, M. A.; Glasgow, T. K.; Levine, S. R.

1981-01-01

A concept for enhanced protection of superalloys consists of adding an oxidation- and diffusion-resistant cermet layer between the superalloy and the outer oxidation-resistant metallic alloy coating. Such a duplex coating was compared with a physical-vapor-deposited (PVD) NiCrAlY coating in cyclic oxidation at 1150 C. The substrate alloy was MA 754 - an oxide-dispersion-strengthened superalloy that is difficult to coat. The duplex coating, applied by plasma spraying, outperformed the PVD coating on the basis of weight change and both macroscopic and metallographic observations.

In Vivo Fluorescence Resonance Energy Transfer Imaging for Targeted Anti-Cancer Drug Delivery Kinetics

NASA Astrophysics Data System (ADS)

Webb, Kevin; Gaind, Vaibhav; Tsai, Hsiaorho; Bentz, Brian; Chelvam, Venkatesh; Low, Philip

2012-02-01

We describe an approach for the evaluation of targeted anti-cancer drug delivery in vivo. The method emulates the drug release and activation process through acceptor release from a targeted donor-acceptor pair that exhibits fluorescence resonance energy transfer (FRET). In this case, folate targeting of the cancer cells is used - 40 % of all human cancers, including ovarian, lung, breast, kidney, brain and colon cancer, over-express folate receptors. We demonstrate the reconstruction of the spatially-dependent FRET parameters in a mouse model and in tissue phantoms. The FRET parameterization is incorporated into a source for a diffusion equation model for photon transport in tissue, in a variant of optical diffusion tomography (ODT) called FRET-ODT. In addition to the spatially-dependent tissue parameters in the diffusion model (absorption and diffusion coefficients), the FRET parameters (donor-acceptor distance and yield) are imaged as a function of position. Modulated light measurements are made with various laser excitation positions and a gated camera. More generally, our method provides a new vehicle for studying disease at the molecular level by imaging FRET parameters in deep tissue, and allows the nanometer FRET ruler to be utilized in deep tissue.

Noncontact diffuse correlation spectroscopy for noninvasive deep tissue blood flow measurement

NASA Astrophysics Data System (ADS)

Lin, Yu; He, Lian; Shang, Yu; Yu, Guoqiang

2012-01-01

A noncontact diffuse correlation spectroscopy (DCS) probe has been developed using two separated optical paths for the source and detector. This unique design avoids the interference between the source and detector and allows large source-detector separations for deep tissue blood flow measurements. The noncontact probe has been calibrated against a contact probe in a tissue-like phantom solution and human muscle tissues; flow changes concurrently measured by the two probes are highly correlated in both phantom (R2=0.89, p<10-5) and real-tissue (R2=0.77, p<10-5, n=9) tests. The noncontact DCS holds promise for measuring blood flow in vulnerable (e.g., pressure ulcer) and soft (e.g., breast) tissues without distorting tissue hemodynamic properties.

Piriformis muscle syndrome with assessment of sciatic nerve using diffusion tensor imaging and tractography: a case report.

PubMed

Wada, Keizo; Goto, Tomohiro; Takasago, Tomoya; Hamada, Daisuke; Sairyo, Koichi

2017-10-01

Piriformis muscle syndrome (PMS) is difficult to diagnose by objective evaluation of sciatic nerve injury. Here we report a case of PMS diagnosed by diffusion tensor imaging (DTI) and tractography of the sciatic nerve, which can assess and visualize the extent of nerve injury. The patient was a 53-year-old man with a 2-year history of continuous pain and numbness in the left leg. His symptoms worsened when sitting. Physical examination, including sensorimotor neurologic tests, the deep tendon reflex test, and the straight leg raise test, revealed no specific findings. The hip flexion adduction and internal rotation test and resisted contraction maneuvers for the piriformis muscle were positive. There were no abnormal findings on magnetic resonance imaging (MRI) of the lumbar spine. The transverse diameter of piriformis muscle was slightly thicker in affected side on MRI of the pelvis. A single DTI sequence was performed during MRI of the pelvis. Fractional anisotropy (FA) and the apparent diffusion coefficient (ADC) of the sciatic nerve were quantified at three levels using the fiber-tracking method. FA values were significantly lower and ADC values were significantly higher distal to the piriformis muscle. We performed endoscopic-assisted resection of the piriformis tendon. Intraoperatively, the motor-evoked potentials in the left gastrocnemius were improved by resection of the piriformis tendon. The patient's symptoms improved immediately after surgery. There was no significant difference in FA or ADC at any level between the affected side and the unaffected side 3 months postoperatively. MRI-DTI may aid the diagnosis of PMS.

Influence of post exposure bake time on EUV photoresist RLS trade-off

NASA Astrophysics Data System (ADS)

Vesters, Yannick; De Simone, Danilo; De Gendt, Stefan

2017-03-01

To achieve high volume manufacturing, EUV photoresists need to push back the "RLS trade-off" by simultaneously improving Resolution, Line-Width Roughness and Sensitivity (exposure dose). Acid diffusion in chemically amplified resist is known to impact these performances. This work studies the diffusion of acid in chemically amplified resist by varying the post exposure bake duration while monitoring the evolution of CD and LWR for 6 chemically amplified EUV photoresists (CAR). We observed a first regime where both CD and LWR quickly decrease during the first 30s of post exposure bake (PEB). This can be related to the deprotection reaction taking place in the exposed part of the resist. After 60s the decrease in CD and LWR slows down significantly, likely related to a regime of acid diffusion from exposed to unexposed region, and acid-quencher neutralization at the interface of these two regions. We tested two resists with different protecting group and the one having lower activation energy shows a faster CD change in the second regime, resulting in a worsening of LWR for longer PEB time. On the contrary, a resist with a high quencher loading shows reduced net diffusion of acid towards the unexposed region and controls the resist edge profile. In other words longer PEB does not degrade LWR, but as it reduces the line CD, sensitivity is impacted. With an appropriate ratio selection of quencher to PAG, an EUV dose reduction of up to 12% can be achieved with a change from a standard 60 second to a 240 second PEB time, while keeping LWR and resolution constant and therefore pushing the RLS performances. Finally, we confirmed that the observations on positive tone development (PTD) resist could be applied to negative tone development (NTD) resist: with a high quencher NTD resist we observed a dose reduction of 8% for longer PEB time, keeping LWR and resolution constant.

Automated array assembly task, phase 1

NASA Technical Reports Server (NTRS)

Carbajal, B. G.

1977-01-01

Various aspects of a sensitivity analysis, in particular, the impact of variations in metal sheet resistivity, metal line width, diffused layer sheet resistance, junction depth, base layer lifetime, optical coating thickness and optical coating refractive index and on process reproducibility for A's diffusion from a polymer dopant source and on module fabrication were studied. Model calculations show that acceptable process windows exist for each of these parameters.

Fiber Orientation Estimation Guided by a Deep Network.

PubMed

Ye, Chuyang; Prince, Jerry L

2017-09-01

Diffusion magnetic resonance imaging (dMRI) is currently the only tool for noninvasively imaging the brain's white matter tracts. The fiber orientation (FO) is a key feature computed from dMRI for tract reconstruction. Because the number of FOs in a voxel is usually small, dictionary-based sparse reconstruction has been used to estimate FOs. However, accurate estimation of complex FO configurations in the presence of noise can still be challenging. In this work we explore the use of a deep network for FO estimation in a dictionary-based framework and propose an algorithm named Fiber Orientation Reconstruction guided by a Deep Network (FORDN). FORDN consists of two steps. First, we use a smaller dictionary encoding coarse basis FOs to represent diffusion signals. To estimate the mixture fractions of the dictionary atoms, a deep network is designed to solve the sparse reconstruction problem. Second, the coarse FOs inform the final FO estimation, where a larger dictionary encoding a dense basis of FOs is used and a weighted ℓ 1 -norm regularized least squares problem is solved to encourage FOs that are consistent with the network output. FORDN was evaluated and compared with state-of-the-art algorithms that estimate FOs using sparse reconstruction on simulated and typical clinical dMRI data. The results demonstrate the benefit of using a deep network for FO estimation.

Carrier Transport and Effective Barrier Height of Low Resistance Metal Contact to Highly Mg-Doped p-GaN

NASA Astrophysics Data System (ADS)

Park, Youngjun; Kim, Hyunsoo

2011-08-01

The effective barrier height and carrier transport mechanism of low resistance Ag-based contact to highly Mg-doped p-GaN were investigated. The specific contact resistance obtained was as low as 7.0×10-4 Ω cm2. The electrical resistivity of p-GaN was found to increase depending on ˜T-1/4, indicating variable-range hopping (VRH) conduction through Mg-related deep-level defects. Based on the VRH conduction model, the effective barrier height for carrier transport could be measured as 0.12 eV, which is low enough to explain the formation of excellent ohmic contact. The deep-level defects were also found to induce surface Fermi pinning.

Titanium aluminide intermetallic alloys with improved wear resistance

DOEpatents

Qu, Jun; Lin, Hua-Tay; Blau, Peter J.; Sikka, Vinod K.

2014-07-08

The invention is directed to a method for producing a titanium aluminide intermetallic alloy composition having an improved wear resistance, the method comprising heating a titanium aluminide intermetallic alloy material in an oxygen-containing environment at a temperature and for a time sufficient to produce a top oxide layer and underlying oxygen-diffused layer, followed by removal of the top oxide layer such that the oxygen-diffused layer is exposed. The invention is also directed to the resulting oxygen-diffused titanium aluminide intermetallic alloy, as well as mechanical components or devices containing the improved alloy composition.

Investigation of LRS dependence on the retention of HRS in CBRAM

NASA Astrophysics Data System (ADS)

Xu, Xiaoxin; Lv, Hangbing; Liu, Hongtao; Luo, Qing; Gong, Tiancheng; Wang, Ming; Wang, Guoming; Zhang, Meiyun; Li, Yang; Liu, Qi; Long, Shibing; Liu, Ming

2015-02-01

The insufficient retention prevents the resistive random access memory from intended application, such as code storage, FPGA, encryption, and others. The retention characteristics of high resistance state (HRS) switching from different low resistance state (LRS) were investigated in a 1-kb array with one transistor and one resistor configuration. The HRS degradation was found strongly dependent on the LRS: the lower the resistance of the LRS ( R LRS) is, the worse HRS retention will be. According to the quantum point contact model, the HRS corresponds to a tiny tunnel gap or neck bridge with atomic size in the filament. The degradation of HRS is due to the filling or widening of the neck point by the diffusion of copper species from the residual filament. As the residual filament is stronger in case of the lower R LRS, the active area around the neck point for copper species diffusion is larger, resulting in higher diffusion probability and faster degradation of HRS during the temperature-accelerated retention measurement.

Diffusion Dominant Solute Transport Modelling in Fractured Media Under Deep Geological Environment - 12211

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kwong, S.; Jivkov, A.P.

2012-07-01

Deep geologic disposal of high activity and long-lived radioactive waste is gaining increasing support in many countries, where suitable low permeability geological formation in combination with engineered barriers are used to provide long term waste contaminant and minimise the impacts to the environment and risk to the biosphere. This modelling study examines the solute transport in fractured media under low flow velocities that are relevant to a deep geological environment. In particular, reactive solute transport through fractured media is studied using a 2-D model, that considers advection and diffusion, to explore the coupled effects of kinetic and equilibrium chemical processes.more » The effects of water velocity in the fracture, matrix porosity and diffusion on solute transport are investigated and discussed. Some illustrative modelled results are presented to demonstrate the use of the model to examine the effects of media degradation on solute transport, under the influences of hydrogeological (diffusion dominant) and microbially mediated chemical processes. The challenges facing the prediction of long term degradation such as cracks evolution, interaction and coalescence are highlighted. The potential of a novel microstructure informed modelling approach to account for these effects is discussed, particularly with respect to investigating multiple phenomena impact on material performance. The GRM code is used to examine the effects of media degradation for a geological waste disposal package, under the combined hydrogeological (diffusion dominant) and chemical effects in low groundwater flow conditions that are typical of deep geological disposal systems. An illustrative reactive transport modelling application demonstrates the use of the code to examine the interplay of kinetic controlled biogeochemical reactive processes with advective and diffusive transport, under the influence of media degradation. The initial model results are encouraging which show the disposal system to evolve in a physically realistic manner. In the example presented the reactive-transport coupling develops chemically reducing zones, which limit the transport of uranium. This illustrates the potential significance of media degradation and chemical effect on the transport of radionuclides which would need to be taken into account when examining the long-term behaviour and containment properties of the geological disposal system. Microstructure-informed modelling and its potential linkage with continuum flow modelling is a subject of ongoing studies. The approach of microstructure-informed modelling is discussed to provide insight and a mechanistic understanding of macroscopic parameters and their evolution. The proposed theoretical and methodological basis for microstructure-informed modelling of porous quasi-brittle media has the potential to develop into an explanatory and predictive tool for deriving mechanism-based, as opposed to phenomenological, evolution laws for macroscopic properties. These concepts in micro-scale modelling are likely to be applicable to the diffusion process, in addition to advective transport illustrated here for porous media. (authors)« less

Performance of the EUCAST Disk Diffusion Method, the CLSI Agar Screen Method, and the Vitek 2 Automated Antimicrobial Susceptibility Testing System for Detection of Clinical Isolates of Enterococci with Low- and Medium-Level VanB-Type Vancomycin Resistance: a Multicenter Study

PubMed Central

Giske, Christian G.; Haldorsen, Bjørg; Matuschek, Erika; Schønning, Kristian; Leegaard, Truls M.; Kahlmeter, Gunnar

2014-01-01

Different antimicrobial susceptibility testing methods to detect low-level vancomycin resistance in enterococci were evaluated in a Scandinavian multicenter study (n = 28). A phenotypically and genotypically well-characterized diverse collection of Enterococcus faecalis (n = 12) and Enterococcus faecium (n = 18) strains with and without nonsusceptibility to vancomycin was examined blindly in Danish (n = 5), Norwegian (n = 13), and Swedish (n = 10) laboratories using the EUCAST disk diffusion method (n = 28) and the CLSI agar screen (n = 18) or the Vitek 2 system (bioMérieux) (n = 5). The EUCAST disk diffusion method (very major error [VME] rate, 7.0%; sensitivity, 0.93; major error [ME] rate, 2.4%; specificity, 0.98) and CLSI agar screen (VME rate, 6.6%; sensitivity, 0.93; ME rate, 5.6%; specificity, 0.94) performed significantly better (P = 0.02) than the Vitek 2 system (VME rate, 13%; sensitivity, 0.87; ME rate, 0%; specificity, 1). The performance of the EUCAST disk diffusion method was challenged by differences in vancomycin inhibition zone sizes as well as the experience of the personnel in interpreting fuzzy zone edges as an indication of vancomycin resistance. Laboratories using Oxoid agar (P < 0.0001) or Merck Mueller-Hinton (MH) agar (P = 0.027) for the disk diffusion assay performed significantly better than did laboratories using BBL MH II medium. Laboratories using Difco brain heart infusion (BHI) agar for the CLSI agar screen performed significantly better (P = 0.017) than did those using Oxoid BHI agar. In conclusion, both the EUCAST disk diffusion and CLSI agar screening methods performed acceptably (sensitivity, 0.93; specificity, 0.94 to 0.98) in the detection of VanB-type vancomycin-resistant enterococci with low-level resistance. Importantly, use of the CLSI agar screen requires careful monitoring of the vancomycin concentration in the plates. Moreover, disk diffusion methodology requires that personnel be trained in interpreting zone edges. PMID:24599985

Determination of diffusion coefficients and diffusion characteristics for chlorferon and diethylthiophosphate in Ca-alginate gel beads.

PubMed

Ha, Jiyeon; Engler, Cady R; Lee, Seung Jae

2008-07-01

Diffusion characteristics of chlorferon and diethylthiophosphate (DETP) in Ca-alginate gel beads were studied to assist in designing and operating bioreactor systems. Diffusion coefficients for chlorferon and DETP in Ca-alginate gel beads determined at conditions suitable for biodegradation studies were 2.70 x 10(-11) m(2)/s and 4.28 x 10(-11) m(2)/s, respectively. Diffusivities of chlorferon and DETP were influenced by several factors, including viscosity of the bulk solution, agitation speed, and the concentrations of diffusing substrate and immobilized cells. Diffusion coefficients increased with increasing agitation speed, probably due to poor mixing at low speed and some attrition of beads at high speeds. Diffusion coefficients also increased with decreasing substrate concentration. Increased cell concentration in the gel beads caused lower diffusivity. Theoretical models to predict diffusivities as a function of cell weight fraction overestimated the effective diffusivities for both chlorferon and DETP, but linear relations between effective diffusivity and cell weight fraction were derived from experimental data. Calcium-alginate gel beads with radii of 1.65-1.70 mm used in this study were not subject to diffusional limitations: external mass transfer resistances were negligible based on Biot number calculations and effectiveness factors indicated that internal mass transfer resistance was negligible. Therefore, the degradation rates of chlorferon and DETP inside Ca-alginate gel beads were reaction-limited. (c) 2007 Wiley Periodicals, Inc.

Microstructure of frontoparietal connections predicts individual resistance to sleep deprivation.

PubMed

Cui, Jiaolong; Tkachenko, Olga; Gogel, Hannah; Kipman, Maia; Preer, Lily A; Weber, Mareen; Divatia, Shreya C; Demers, Lauren A; Olson, Elizabeth A; Buchholz, Jennifer L; Bark, John S; Rosso, Isabelle M; Rauch, Scott L; Killgore, William D S

2015-02-01

Sleep deprivation (SD) can degrade cognitive functioning, but growing evidence suggests that there are large individual differences in the vulnerability to this effect. Some evidence suggests that baseline differences in the responsiveness of a fronto-parietal attention system that is activated during working memory (WM) tasks may be associated with the ability to sustain vigilance during sleep deprivation. However, the neurocircuitry underlying this network remains virtually unexplored. In this study, we employed diffusion tensor imaging (DTI) to investigate the association between the microstructure of the axonal pathway connecting the frontal and parietal regions--i.e., the superior longitudinal fasciculus (SLF)--and individual resistance to SD. Thirty healthy participants (15 males) aged 20-43 years underwent functional magnetic resonance imaging (fMRI) and diffusion tensor imaging (DTI) at rested wakefulness prior to a 28-hour period of SD. Task-related fronto-parietal fMRI activation clusters during a Sternberg WM Task were localized and used as seed regions for probabilistic fiber tractography. DTI metrics, including fractional anisotropy, mean diffusivity, axial and radial diffusivity were measured in the SLF. The psychomotor vigilance test (PVT) was used to evaluate resistance to SD. We found that activation in the left inferior parietal lobule (IPL) and dorsolateral prefrontal cortex (DLPFC) positively correlated with resistance. Higher fractional anisotropy of the left SLF comprising the primary axons connecting IPL and DLPFC was also associated with better resistance. These findings suggest that individual differences in resistance to SD are associated with the functional responsiveness of a fronto-parietal attention system and the microstructural properties of the axonal interconnections. Copyright © 2014 Elsevier Inc. All rights reserved.

Manipulation and simulations of thermal field profiles in laser heat-mode lithography

NASA Astrophysics Data System (ADS)

Wei, Tao; Wei, Jingsong; Wang, Yang; Zhang, Long

2017-12-01

Laser heat-mode lithography is a very useful method for high-speed fabrication of large-area micro/nanostructures. To obtain nanoscale pattern structures, one needs to manipulate the thermal diffusion channels. This work reports the manipulation of the thermal diffusion in laser heat-mode lithography and provides methods to restrain the in-plane thermal diffusion and improve the out-of-plane thermal diffusion. The thermal field profiles in heat-mode resist thin films have been given. It is found that the size of the heat-spot can be decreased by decreasing the thickness of the heat-mode resist thin films, inserting the thermal conduction layers, and shortening the laser irradiation time. The optimized laser writing strategy is also given, where the in-plane thermal diffusion is completely restrained and the out-of-plane thermal diffusion is improved. The heat-spot size is almost equal to that of the laser spot, accordingly. This work provides a very important guide to laser heat-mode lithography.

Diffusion Tensor Imaging of Heterotopia: Changes of Fractional Anisotropy during Radial Migration of Neurons

PubMed Central

Kim, Jinna

2010-01-01

Purpose Diffusion tensor imaging provides better understanding of pathophysiology of congenital anomalies, involving central nervous system. This study was aimed to specify the pathogenetic mechanism of heterotopia, proved by diffusion tensor imaging, and establish new findings of heterotopia on fractional anisotropy maps. Materials and Methods Diffusion-weighted imaging data from 11 patients (M : F = 7 : 4, aged from 1 to 22 years, mean = 12.3 years) who visited the epilepsy clinic and received a routine seizure protocol MRI exam were retrospectively analyzed. Fractional anisotropy (FA) maps were generated from diffusion tensor imaging of 11 patients with heterotopia. Regions of interests (ROI) were placed in cerebral cortex, heterotopic gray matter and deep gray matter, including putamen. ANOVA analysis was performed for comparison of different gray matter tissues. Results Heterotopic gray matter showed signal intensities similar to normal gray matter on T1 and T2 weighted MRI. The measured FA of heterotopic gray matter was higher than that of cortical gray matter (0.236 ± 0.011 vs. 0.169 ± 0.015, p < 0.01, one way ANOVA), and slightly lower than that of deep gray matter (0.236 ± 0.011 vs. 0.259 ± 0.016, p < 0.01). Conclusion Increased FA of heterotopic gray matter suggests arrested neuron during radial migration and provides better understanding of neurodevelopment. PMID:20499428

Correlation Between the Field Line and Particle Diffusion Coefficients in the Stochastic Fields of a Tokamak

NASA Astrophysics Data System (ADS)

Calvin, Mark; Punjabi, Alkesh

1996-11-01

We use the method of quasi-magnetic surfaces to calculate the correlation between the field line and particle diffusion coefficients. The magnetic topology of a tokamak is perturbed by a spectrum of neighboring resonant resistive modes. The Hamiltonian equations of motion for the field line are integrated numerically. Poincare plots of the quasi-magnetic surfaces are generated initially and after the field line has traversed a considerable distance. From the areas of the quasi-magnetic surfaces and the field line distance, we estimate the field line diffusion coefficient. We start plasma particles on the initial quasi-surface, and calculate the particle diffusion coefficient from our Monte Carlo method (Punjabi A., Boozer A., Lam M., Kim H. and Burke K., J. Plasma Phys.), 44, 405 (1990). We then estimate the correlation between the particle and field diffusion as the strength of the resistive modes is varied.

Evaluation of different methods to detect methicillin resistance in Staphylococcus aureus (MRSA).

PubMed

Alipour, Farzad; Ahmadi, Malahat; Javadi, Shahram

2014-01-01

The studies suggest that dogs living with human are potential risk of becoming MRSA carrier and increased risk of infections caused by MRSA. Phenotypic methods to detect methicillin resistance in Staphylococcus aureus (MRSA) are inadequate. The objective of the present study was to determine methicillin resistance in S. aureus by phenotypic susceptibility test (oxacillin disk diffusion, cefoxitin disk diffusion, oxacillin screen agar) and molecular methods (PCR as a gold standard) and the latex agglutination test for the detection of PBP2a and to evaluate the results of these tests for its sensitivity and specificity. A total of 100 swab samples were taken from muzzle site, in more contact with human, of dogs and MRSA were isolated. Oxacillin (1 μg), cefoxitin (30 μg) disk diffusion and oxacillin screen agar method were used. The isolates were also subjected to latex agglutination test for detection of PBP2a and PCR to detect mecA gene. By PCR 37% of isolates show the presence of mecA. Latex agglutination was found to be the most sensitive (97.29%) and cefoxitin disk diffusion to be the most specific (96.82%) tests for detection of MRSA. Our finding showed that combining oxacillin screen agar or cefoxitin disk diffusion with latex agglutination improves sensitivity and specificity to detect methicillin resistance S. aureus (MRSA) isolates. Copyright © 2014 King Saud Bin Abdulaziz University for Health Sciences. Published by Elsevier Ltd. All rights reserved.

Origin of resistivity in reconnection

NASA Astrophysics Data System (ADS)

Treumann, Rudolf A.

2001-06-01

Resistivity is believed to play an important role in reconnection leading to the distinction between resistive and collisionless reconnection. The former is treated in the Sweet-Parker model of long current sheets, and the Petschek model of a small resistive region. Both models in spite of their different dynamics attribute to the violation of the frozen-in condition in their diffusion regions due to the action of resistivity. In collisionless reconnection there is little consensus about the processes breaking the frozen-in condition. The question is whether anomalous processes generate sufficient resistivity or whether other processes free the particles from slavery by the magnetic field. In the present paper we review processes that may cause anomalous resistivity in collisionless current sheets. Our general conclusion is that in space plasma boundaries accessible to in situ spacecraft, wave levels have always been found to be high enough to explain the existence of large enough local diffusivity for igniting local reconnection. However, other processes might take place as well. Non-resistive reconnection can be caused by inertia or diamagnetism.

The Effect of Weak Resistivity and Weak Thermal Diffusion on Short-wavelength Magnetic Buoyancy Instability

NASA Astrophysics Data System (ADS)

Gradzki, Marek J.; Mizerski, Krzysztof A.

2018-03-01

Magnetic buoyancy instability in weakly resistive and thermally conductive plasma is an important mechanism of magnetic field expulsion in astrophysical systems. It is often invoked, e.g., in the context of the solar interior. Here, we revisit a problem introduc`ed by Gilman: the short-wavelength linear stability of a plane layer of compressible isothermal and weakly diffusive fluid permeated by a horizontal magnetic field of strength decreasing with height. In this physical setting, we investigate the effect of weak resistivity and weak thermal conductivity on the short-wavelength perturbations, localized in the vertical direction, and show that the presence of diffusion allows to establish the wavelength of the most unstable mode, undetermined in an ideal fluid. When diffusive effects are neglected, the perturbations are amplified at a rate that monotonically increases as the wavelength tends to zero. We demonstrate that, when the resistivity and thermal conduction are introduced, the wavelength of the most unstable perturbation is established and its scaling law with the diffusion parameters depends on gradients of the mean magnetic field, temperature, and density. Three main dynamical regimes are identified, with the wavelength of the most unstable mode scaling as either λ /d∼ {{ \\mathcal U }}κ 3/5 or λ /d∼ {{ \\mathcal U }}κ 3/4 or λ /d∼ {{ \\mathcal U }}κ 1/3, where d is the layer thickness and {{ \\mathcal U }}κ is the ratio of the characteristic thermal diffusion velocity scale to the free-fall velocity. Our analytic results are backed up by a series of numerical solutions. The two-dimensional interchange modes are shown to dominate over three-dimensional ones when the magnetic field and/or temperature gradients are strong enough.

Aging in deep gray matter and white matter revealed by diffusional kurtosis imaging.

PubMed

Gong, Nan-Jie; Wong, Chun-Sing; Chan, Chun-Chung; Leung, Lam-Ming; Chu, Yiu-Ching

2014-10-01

Diffusion tensor imaging has already been extensively used to probe microstructural alterations in white matter tracts, and scarcely, in deep gray matter. However, results in literature regarding age-related degenerative mechanisms in white matter tracts and parametric changes in the putamen are inconsistent. Diffusional kurtosis imaging is a mathematical extension of diffusion tensor imaging, which could more comprehensively mirror microstructure, particularly in isotropic tissues such as gray matter. In this study, we used the diffusional kurtosis imaging method and a white-matter model that provided metrics of explicit neurobiological interpretations in healthy participants (58 in total, aged from 25 to 84 years). Tract-based whole-brain analyses and regions-of-interest (anterior and posterior limbs of the internal capsule, cerebral peduncle, fornix, genu and splenium of corpus callosum, globus pallidus, substantia nigra, red nucleus, putamen, caudate nucleus, and thalamus) analyses were performed to examine parametric differences across regions and correlations with age. In white matter tracts, evidence was found supportive for anterior-posterior gradient and not completely supportive for retrogenesis theory. Age-related degenerations appeared to be broadly driven by axonal loss. Demyelination may also be a major driving mechanism, although confined to the anterior brain. In terms of deep gray matter, higher mean kurtosis and fractional anisotropy in the globus pallidus, substantia nigra, and red nucleus reflected higher microstructural complexity and directionality compared with the putamen, caudate nucleus, and thalamus. In particular, the unique age-related positive correlations for fractional anisotropy, mean kurtosis, and radial kurtosis in the putamen opposite to those in other regions call for further investigation of exact underlying mechanisms. In summary, the results suggested that diffusional kurtosis can provide measurements in a new dimension that were complementary to diffusivity metrics. Kurtosis together with diffusivity can more comprehensively characterize microstructural compositions and age-related changes than diffusivity alone. Combined with proper model, it may also assist in providing neurobiological interpretations of the identified alterations. Copyright © 2014 Elsevier Inc. All rights reserved.

Diffusibility Enhancement of Rejuvenator by Epoxidized Soybean Oil and Its Influence on the Performance of Recycled Hot Mix Asphalt Mixtures

PubMed Central

Kuang, Dongliang; Jiao, Yuan; Ye, Zhou; Lu, Zaihong; Chen, Huaxin; Yu, Jianying; liu, Ning

2018-01-01

Epoxidized soybean oil (ESO) was employed as a novel penetrant cooperating with a conventional rejuvenator (CR) for the recycling of reclaimed asphalt pavement (RAP). The influence of ESO on the diffusibility and the regenerating effects of CR on RAP were investigated. The diffusibility testing result shows that the diffusibility of CR is enhanced by the addition of ESO because the epoxy group in ESO can facilitate asphaltene dispersion due to its high polarity, which simultaneously reduces the viscosity and improves the fluidity of aged bitumen so as to allow diffusion of the rejuvenator into the aged bitumen. Road performance testing of a recycled hot mix asphalt mixture (RHMA) indicates that the fatigue and cracking resistance properties as well as the water stability of RHMA containing CR can be improved by the addition of ESO due to the diffusibility enhancement of CR, which boosts the regenerating effect of CR on aged bitumen in RAP. The fatigue and cracking resistance properties as well as the water stability of the recycled hot mix asphalt mixture containing CR with 7 wt % ESO approximate those of the hot mix asphalt mixture composed of the same virgin aggregates and bitumen. Taking into account the rutting resistance decline versus the addition of ESO, the content of ESO should not exceed 7 wt % of the conventional rejuvenator. PMID:29783675

Diffusibility Enhancement of Rejuvenator by Epoxidized Soybean Oil and Its Influence on the Performance of Recycled Hot Mix Asphalt Mixtures.

PubMed

Kuang, Dongliang; Jiao, Yuan; Ye, Zhou; Lu, Zaihong; Chen, Huaxin; Yu, Jianying; Liu, Ning

2018-05-18

Epoxidized soybean oil (ESO) was employed as a novel penetrant cooperating with a conventional rejuvenator (CR) for the recycling of reclaimed asphalt pavement (RAP). The influence of ESO on the diffusibility and the regenerating effects of CR on RAP were investigated. The diffusibility testing result shows that the diffusibility of CR is enhanced by the addition of ESO because the epoxy group in ESO can facilitate asphaltene dispersion due to its high polarity, which simultaneously reduces the viscosity and improves the fluidity of aged bitumen so as to allow diffusion of the rejuvenator into the aged bitumen. Road performance testing of a recycled hot mix asphalt mixture (RHMA) indicates that the fatigue and cracking resistance properties as well as the water stability of RHMA containing CR can be improved by the addition of ESO due to the diffusibility enhancement of CR, which boosts the regenerating effect of CR on aged bitumen in RAP. The fatigue and cracking resistance properties as well as the water stability of the recycled hot mix asphalt mixture containing CR with 7 wt % ESO approximate those of the hot mix asphalt mixture composed of the same virgin aggregates and bitumen. Taking into account the rutting resistance decline versus the addition of ESO, the content of ESO should not exceed 7 wt % of the conventional rejuvenator.

Azole drugs are imported by facilitated diffusion in Candida albicans and other pathogenic fungi.

PubMed

Mansfield, Bryce E; Oltean, Hanna N; Oliver, Brian G; Hoot, Samantha J; Leyde, Sarah E; Hedstrom, Lizbeth; White, Theodore C

2010-09-30

Despite the wealth of knowledge regarding the mechanisms of action and the mechanisms of resistance to azole antifungals, very little is known about how the azoles are imported into pathogenic fungal cells. Here the in-vitro accumulation and import of Fluconazole (FLC) was examined in the pathogenic fungus, Candida albicans. In energized cells, FLC accumulation correlates inversely with expression of ATP-dependent efflux pumps. In de-energized cells, all strains accumulate FLC, suggesting that FLC import is not ATP-dependent. The kinetics of import in de-energized cells displays saturation kinetics with a K(m) of 0.64 μM and V(max) of 0.0056 pmol/min/10⁸ cells, demonstrating that FLC import proceeds via facilitated diffusion through a transporter rather than passive diffusion. Other azoles inhibit FLC import on a mole/mole basis, suggesting that all azoles utilize the same facilitated diffusion mechanism. An analysis of related compounds indicates that competition for azole import depends on an aromatic ring and an imidazole or triazole ring together in one molecule. Import of FLC by facilitated diffusion is observed in other fungi, including Cryptococcus neoformans, Saccharomyces cerevisiae, and Candida krusei, indicating that the mechanism of transport is conserved among fungal species. FLC import was shown to vary among Candida albicans resistant clinical isolates, suggesting that altered facilitated diffusion may be a previously uncharacterized mechanism of resistance to azole drugs.

Use of metallic glasses for fabrication of structures with submicron dimensions

DOEpatents

Wiley, John D.; Perepezko, John H.

1986-01-01

Patterned structures of submicron dimension formed of supported or unsupported amorphous metals having submicron feature sizes characterized by etching behavior sufficient to allow delineation of sharp edges and smooth flat flanks, resistance to time-dependent dimensional changes caused by creep, flow, in-diffusion of unwanted impurities, out-diffusion of constituent atoms, void formation, grain growth or phase separation and resistance to phase transformations or compound formation.

Plasmid incidence in bacteria from deep subsurface sediments

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fredrickson, J.K.; Hicks, R.J.; Li, S.W.

Bacteria were isolated from deep terrestrial subsurface sediments underlying the coastal plain of South Carolina. A total of 163 isolates from deep sediments, surface soil, and return drill muds were examined for plasmid DNA content and resistance to the antibiotics penicillin, ampicillin, carbenicillin, streptomycin, kanamycin, and tetracycline. MICs of Cu{sup 2+}, Cr{sup 3+}, and Hg{sup 2+} for each isolate were also determined. The overall frequency of plasmid occurrence in the subsurface bacteria was 33%. Resistance was most frequent to penicillin (70% of all isolates), ampicillin (49%), and carbenicillin (32%) and was concluded to be related to the concentrations of themore » individual antibiotics in the disks used for assaying resistance and to the production of low levels of {beta}-lactamase. The frequencies of resistance to penicillin and ampicillin were significantly greater for isolates bearing plasmids than for plasmidless isolates; however, resistance was not transferable to penicillin-sensitive Escherichia coli. Hybridization of subsurface bacterial plasmids and chromosomal DNA with a whole-TOL-plasmid (pWWO) probe revealed some homology of subsurface bacterial plasmid and chromosomal DNAs, indicating a potential for those bacterial to harbor catabolic genes on plasmids or chromosomes. The incidences of antibiotic resistance and MICs of metals for subsurface bacteria were significantly different from those drill mud bacteria, ruling out the possibility that bacteria from sediments were derived from drill muds.« less

The diffusion of ions in unconsolidated sediments

USGS Publications Warehouse

Manheim, F.T.

1970-01-01

Diffusion in unconsolidated sediments generally proceeds at rates ranging from half to one twentieth of those applying to diffusion of ions and molecules in free solution. Diffusion rates are predictable with respect to porosity and path tortuosity in host sediments, and can be conveniently measured by determinations of electrical resistivity on bulk sediment samples. Net ion flux is further influenced by reactions of diffusing species with enclosing sediments, but such influences should not be confused with or lumped with diffusion processes. ?? 1970.

Electrical leakage phenomenon in heteroepitaxial cubic silicon carbide on silicon

NASA Astrophysics Data System (ADS)

Pradeepkumar, Aiswarya; Zielinski, Marcin; Bosi, Matteo; Verzellesi, Giovanni; Gaskill, D. Kurt; Iacopi, Francesca

2018-06-01

Heteroepitaxial 3C-SiC films on silicon substrates are of technological interest as enablers to integrate the excellent electrical, electronic, mechanical, thermal, and epitaxial properties of bulk silicon carbide into well-established silicon technologies. One critical bottleneck of this integration is the establishment of a stable and reliable electronic junction at the heteroepitaxial interface of the n-type SiC with the silicon substrate. We have thus investigated in detail the electrical and transport properties of heteroepitaxial cubic silicon carbide films grown via different methods on low-doped and high-resistivity silicon substrates by using van der Pauw Hall and transfer length measurements as test vehicles. We have found that Si and C intermixing upon or after growth, particularly by the diffusion of carbon into the silicon matrix, creates extensive interstitial carbon traps and hampers the formation of a stable rectifying or insulating junction at the SiC/Si interface. Although a reliable p-n junction may not be realistic in the SiC/Si system, we can achieve, from a point of view of the electrical isolation of in-plane SiC structures, leakage suppression through the substrate by using a high-resistivity silicon substrate coupled with deep recess etching in between the SiC structures.

Effect of Friction-Induced Deformation on the Structure, Microhardness, and Wear Resistance of Austenitic Chromium—Nickel Stainless Steel Subjected to Subsequent Oxidation

NASA Astrophysics Data System (ADS)

Korshunov, L. G.; Chernenko, N. L.

2016-03-01

The effect of plastic deformation that occurs in the zone of the sliding friction contact on structural transformations in the 12Kh18N9T austenitic steel subjected to subsequent 1-h oxidation in air at temperatures of 300-800°C, as well as on its wear resistance, has been studied. It has been shown that severe deformation induced by dry sliding friction produces the two-phase nanocrystalline γ + α structure in the surface layer of the steel ~10 μm thick. This structure has the microhardness of 5.2 GPa. Subsequent oxidation of steel at temperatures of 300-500°C leads to an additional increase in the microhardness of its deformed surface layer to the value of 7.0 GPa. This is due to the active saturation of the austenite and the strain-assisted martensite (α') with the oxygen atoms, which diffuse deep into the metal over the boundaries of the γ and α' nanocrystals with an increased rate. The concentration of oxygen in the surface layer of the steel and in wear products reaches 8 wt %. The atoms of the dissolved oxygen efficiently pin dislocations in the γ and α' phases, which enhances the strength and wear resistance of the surface of the 12Kh18N9T steel. The oxidation of steel at temperatures of 550-800°C under a light normal load (98 N) results in the formation of a large number of Fe3O4 (magnetite) nanoparticles, which increase the resistance of the steel to thermal softening and its wear resistance during dry sliding friction in a pair with 40Kh13 steel. Under a heavy normal load (196 N), the toughness of 12Kh18N9T steel and, therefore, the wear resistance of its surface layer decrease due to the presence of the brittle oxide phase.

Deep neural network convolution (NNC) for three-class classification of diffuse lung disease opacities in high-resolution CT (HRCT): consolidation, ground-glass opacity (GGO), and normal opacity

NASA Astrophysics Data System (ADS)

Hashimoto, Noriaki; Suzuki, Kenji; Liu, Junchi; Hirano, Yasushi; MacMahon, Heber; Kido, Shoji

2018-02-01

Consolidation and ground-glass opacity (GGO) are two major types of opacities associated with diffuse lung diseases. Accurate detection and classification of such opacities are crucially important in the diagnosis of lung diseases, but the process is subjective, and suffers from interobserver variability. Our study purpose was to develop a deep neural network convolution (NNC) system for distinguishing among consolidation, GGO, and normal lung tissue in high-resolution CT (HRCT). We developed ensemble of two deep NNC models, each of which was composed of neural network regression (NNR) with an input layer, a convolution layer, a fully-connected hidden layer, and a fully-connected output layer followed by a thresholding layer. The output layer of each NNC provided a map for the likelihood of being each corresponding lung opacity of interest. The two NNC models in the ensemble were connected in a class-selection layer. We trained our NNC ensemble with pairs of input 2D axial slices and "teaching" probability maps for the corresponding lung opacity, which were obtained by combining three radiologists' annotations. We randomly selected 10 and 40 slices from HRCT scans of 172 patients for each class as a training and test set, respectively. Our NNC ensemble achieved an area under the receiver-operating-characteristic (ROC) curve (AUC) of 0.981 and 0.958 in distinction of consolidation and GGO, respectively, from normal opacity, yielding a classification accuracy of 93.3% among 3 classes. Thus, our deep-NNC-based system for classifying diffuse lung diseases achieved high accuracies for classification of consolidation, GGO, and normal opacity.

Fronts and intrusions in the upper Deep Polar Water of the Eurasian and Makarov basins

NASA Astrophysics Data System (ADS)

Kuzmina, Natalia; Rudels, Bert; Zhurbas, Natalia; Lyzhkov, Dmitry

2013-04-01

CTD data obtained in the Arctic Basin are analyzed to describe structural features of intrusive layers and fronts encountered in the upper Deep Polar Water. This work is an extension of Arctic intrusions studies by Rudels et al. (1999) and Kuzmina et al. (2011). Numerous examples of fronts and intrusions observed in a deep layer (depth range of 600-1300 m) in the Eurasian and Makarov basins where salinity is increasing, and temperature is decreasing with depth (stable-stable thermohaline stratification), are described. The data are used to estimate hydrological parameters capable of determining different types of fronts and characterizing intrusive layers depending on the front structure. Coherence of intrusive layers is shown to get broken with the change of front structure. An evidence is found that enhanced turbulent mixing above local bottom elevations can prevent from intrusive layering. A linear stability model description of the observed intrusions is developed based on the Merryfield's (2000) assumption that interleaving is caused by differential mixing. Theoretical analysis is focused on prediction of the slopes of unstable modes at baroclinic and thermohaline fronts. Apparent vertical diffusivity due to turbulent mixing at baroclinic and thermohaline fronts is estimated on the basis of comparison of observed intrusion slopes with modeled slopes of the most unstable modes. Apparent lateral diffusivity is estimated too, based on Joyce (1980) approach. These estimates show that intrusive instability of fronts caused by differential mixing can result in sizable values of apparent lateral heat diffusivity in the deep Arctic layer that are quite comparable with those of the upper and intermediate Arctic layers (Walsh, Carmack, 2003; Kuzmina et al., 2011).

Resistivity structure of the Furnas hydrothermal system (Azores archipelago, Portugal) from AMT and ERT imaging.

NASA Astrophysics Data System (ADS)

Byrdina, Svetlana; Vandemeulebrouck, Jean; Rath, Volker; Silva, Catarina; Hogg, Colin; Kiyan, Duygu; Viveiros, Fatima; Eleuterio, Joana; Gresse, Marceau

2016-04-01

The Furnas volcanic complex is located in the eastern part of the São Miguel Island and comprises a 5 km × 8 km summit depression filled by two nested calderas with several craters and a lake. Present-day volcanic activity of Furnas volcano is mostly located in the northern part of the caldera, within the Furnas village and north to Furnas Lake, where hydrothermal manifestations are mainly fumarolic fields, steam vents, thermal springs, and intense soil diffuse degassing. Considering the Furnas volcano as a whole, the total integrated CO2 efflux is extremely high, with a total amount of CO2 close to 1000 ton per day (Viveiros et al., 2009). We present the first results of an electrical resistivity tomography (ERT), combined with audio-magneto-telluric (AMT) measurements aligned along two profiles inside the caldera. The purpose of this survey is to delimit the extent, the geometry, and the depth of the hydrothermal system and to correlate the deep resistivity structure with high resolution cartography of diffuse CO2 flux (Viveiros et al, 2015). The ERT and AMT methods are complementary in terms of resolution and penetration depth: ERT can image the structural details of shallow hydrothermal system (down to 100 m in our study) while AMT can image at lower resolution deeper structures at the roots of a volcano (down to 4 km in our study). Our first independent 2D inversions of the ERT-AMT data show a good agreement between the surficial and deeper features. Below the main fumarole area we observe a low resistivity body (less than 1 Ohmm) which corresponds well to the high CO2 flux at the surface and is associated with an extended conductive body at larger depth. These results strongly suggest the presence of hydrothermal waters at depth or/and the presence of altered clay-rich material. On a larger scale however, the geometry of the conducting zones differs slightly from what was expected from earlier surface studies, and may not be directly related to fault zones mapped at the surface. These slight, but measurable discrepancies might have different origins but they stress the necessity of 3D modelling and the importance of the joint inversion of the data which we consider as a next step in our work.

Tissue microstructure estimation using a deep network inspired by a dictionary-based framework.

PubMed

Ye, Chuyang

2017-12-01

Diffusion magnetic resonance imaging (dMRI) captures the anisotropic pattern of water displacement in the neuronal tissue and allows noninvasive investigation of the complex tissue microstructure. A number of biophysical models have been proposed to relate the tissue organization with the observed diffusion signals, so that the tissue microstructure can be inferred. The Neurite Orientation Dispersion and Density Imaging (NODDI) model has been a popular choice and has been widely used for many neuroscientific studies. It models the diffusion signal with three compartments that are characterized by distinct diffusion properties, and the parameters in the model describe tissue microstructure. In NODDI, these parameters are estimated in a maximum likelihood framework, where the nonlinear model fitting is computationally intensive. Therefore, efforts have been made to develop efficient and accurate algorithms for NODDI microstructure estimation, which is still an open problem. In this work, we propose a deep network based approach that performs end-to-end estimation of NODDI microstructure, which is named Microstructure Estimation using a Deep Network (MEDN). MEDN comprises two cascaded stages and is motivated by the AMICO algorithm, where the NODDI microstructure estimation is formulated in a dictionary-based framework. The first stage computes the coefficients of the dictionary. It resembles the solution to a sparse reconstruction problem, where the iterative process in conventional estimation approaches is unfolded and truncated, and the weights are learned instead of predetermined by the dictionary. In the second stage, microstructure properties are computed from the output of the first stage, which resembles the weighted sum of normalized dictionary coefficients in AMICO, and the weights are also learned. Because spatial consistency of diffusion signals can be used to reduce the effect of noise, we also propose MEDN+, which is an extended version of MEDN. MEDN+ allows incorporation of neighborhood information by inserting a stage with learned weights before the MEDN structure, where the diffusion signals in the neighborhood of a voxel are processed. The weights in MEDN or MEDN+ are jointly learned from training samples that are acquired with diffusion gradients densely sampling the q-space. We performed MEDN and MEDN+ on brain dMRI scans, where two shells each with 30 gradient directions were used, and measured their accuracy with respect to the gold standard. Results demonstrate that the proposed networks outperform the competing methods. Copyright © 2017 Elsevier B.V. All rights reserved.

Developments toward an 18% efficient silicon solar cell

NASA Technical Reports Server (NTRS)

Meulenberg, A., Jr.

1983-01-01

Limitations to increased open-circuit voltage were identified and experimentally verified for 0.1 ohm-cm solar cells with heavily doped emitters. After major reduction in the dark current contribution from the metal-silicon interface of the grid contacts, the surface recombination velocity of the oxide-silicon interface of shallow junction solar cells is the limiting factor. In deep junction solar cells, where the junction field does not aid surface collection, the emitter bulk is the limiting factor. Singly-diffused, shallow junction cells have been fabricated with open circuit voltages in excess of 645 mV. Double-diffusion shallow and deep junctions cells have displayed voltages above 650 mV. MIS solar cells formed on 0.1 ohm-cm substrates have exibited the lowest dark currents produced in the course of the contract work.

Ultrafast atomic layer-by-layer oxygen vacancy-exchange diffusion in double-perovskite LnBaCo2O5.5+δ thin films.

PubMed

Bao, Shanyong; Ma, Chunrui; Chen, Garry; Xu, Xing; Enriquez, Erik; Chen, Chonglin; Zhang, Yamei; Bettis, Jerry L; Whangbo, Myung-Hwan; Dong, Chuang; Zhang, Qingyu

2014-04-22

Surface exchange and oxygen vacancy diffusion dynamics were studied in double-perovskites LnBaCo2O5.5+δ (LnBCO) single-crystalline thin films (Ln = Er, Pr; -0.5 < δ < 0.5) by carefully monitoring the resistance changes under a switching flow of oxidizing gas (O2) and reducing gas (H2) in the temperature range of 250 ~ 800 °C. A giant resistance change ΔR by three to four orders of magnitude in less than 0.1 s was found with a fast oscillation behavior in the resistance change rates in the ΔR vs. t plots, suggesting that the oxygen vacancy exchange diffusion with oxygen/hydrogen atoms in the LnBCO thin films is taking the layer by layer oxygen-vacancy-exchange mechanism. The first principles density functional theory calculations indicate that hydrogen atoms are present in LnBCO as bound to oxygen forming O-H bonds. This unprecedented oscillation phenomenon provides the first direct experimental evidence of the layer by layer oxygen vacancy exchange diffusion mechanism.

Exogenous superoxide dismutase may lose its antidotal ability on rice leaves

USDA-ARS?s Scientific Manuscript database

Leaf diffusates of the resistant rice cultivars suppressed spore germination of blast fungus (Magnaporthe grisea). Bovine Cu-Zn superoxide dismutase (SOD) added to the diffusate abolished its toxicity. However, the enzyme added to the inoculum did not affect the toxicity of the diffusate. Even the s...

Evaluation of static resistance of deep foundation [project summary].

DOT National Transportation Integrated Search

2017-06-01

Various types of deep foundations were investigated including steel H-piles, pre-stressed concrete piles, open cylindrical steel and concrete piles with diameters greater than 36 inches, and drilled shafts with partial length permanent casing. : The ...

Ultra-diffuse hydrothermal venting supports Fe-oxidizing bacteria and massive umber deposition at 5000 m off Hawaii

PubMed Central

Edwards, Katrina J; Glazer, B T; Rouxel, O J; Bach, W; Emerson, D; Davis, R E; Toner, B M; Chan, C S; Tebo, B M; Staudigel, H; Moyer, C L

2011-01-01

A novel hydrothermal field has been discovered at the base of Lōihi Seamount, Hawaii, at 5000 mbsl. Geochemical analyses demonstrate that ‘FeMO Deep', while only 0.2 °C above ambient seawater temperature, derives from a distal, ultra-diffuse hydrothermal source. FeMO Deep is expressed as regional seafloor seepage of gelatinous iron- and silica-rich deposits, pooling between and over basalt pillows, in places over a meter thick. The system is capped by mm to cm thick hydrothermally derived iron-oxyhydroxide- and manganese-oxide-layered crusts. We use molecular analyses (16S rDNA-based) of extant communities combined with fluorescent in situ hybridizations to demonstrate that FeMO Deep deposits contain living iron-oxidizing Zetaproteobacteria related to the recently isolated strain Mariprofundus ferroxydans. Bioenergetic calculations, based on in-situ electrochemical measurements and cell counts, indicate that reactions between iron and oxygen are important in supporting chemosynthesis in the mats, which we infer forms a trophic base of the mat ecosystem. We suggest that the biogenic FeMO Deep hydrothermal deposit represents a modern analog for one class of geological iron deposits known as ‘umbers' (for example, Troodos ophilolites, Cyprus) because of striking similarities in size, setting and internal structures. PMID:21544100

Temperature characteristics of silicon space solar cells and underlying parameters

NASA Technical Reports Server (NTRS)

Anspaugh, B. E.; Kachare, Ram; Garlick, G. F. J.

1987-01-01

Silicon space cells, 2 cm x 2 cm, with 10 ohm-cm p-base resistivity, 8-mil base thickness, and no back-surface fields have been investigated over the temperature range from 301 to 223 K by measurements of dark forward and reverse current-voltage characteristics and current-voltage relations under illumination. From dark forward bias data, the first and second diode saturation currents, I01 and I02, are determined and hence the base diffusion length and lifetime of minority carriers as functions of temperature. Lifetime increases exponentially with temperature and is explained by a Shockley-Read-Hall model with deep recombination levels 0.245 eV above the valence band. The I02 variation with temperature follows the Sah-Noyce-Shockley-Choo model except at low temperature where extra transitions raise the value above the predicted level. Reverse bias current at low voltage is a thermally assisted tunneling process via deep levels which are observed in base recombination at higher temperatures. The tunneling effects tend to become independent of temperature in the low-temperature region. These results demonstrate the ability to deduce basic parameters such as lifetime from simple measurements and show that back-surface fields offer no advantage at temperatures below 230 K. The analysis also explains the fall in lifetimes observed as the base conductivity increases, attributing it to native defects (perhaps carbon-oxygen-vacancy complexes) rather than the concentration of base dopant.

Theoretical examination of effective oxygen diffusion coefficient and electrical conductivity of polymer electrolyte fuel cell porous components

NASA Astrophysics Data System (ADS)

Inoue, Gen; Yokoyama, Kouji; Ooyama, Junpei; Terao, Takeshi; Tokunaga, Tomomi; Kubo, Norio; Kawase, Motoaki

2016-09-01

The reduction of oxygen transfer resistance through porous components consisting of a gas diffusion layer (GDL), microporous layer (MPL), and catalyst layer (CL) is very important to reduce the cost and improve the performance of a PEFC system. This study involves a systematic examination of the relationship between the oxygen transfer resistance of the actual porous components and their three-dimensional structure by direct measurement with FIB-SEM and X-ray CT. Numerical simulations were carried out to model the properties of oxygen transport. Moreover, based on the model structure and theoretical equations, an approach to the design of new structures is proposed. In the case of the GDL, the binder was found to obstruct gas diffusion with a negative effect on performance. The relative diffusion coefficient of the MPL is almost equal to that of the model structure of particle packing. However, that of CL is an order of magnitude less than those of the other two components. Furthermore, an equation expressing the relative diffusion coefficient of each component can be obtained with the function of porosity. The electrical conductivity of MPL, which is lower than that of the carbon black packing, is considered to depend on the contact resistance.

The effects of deep-level defects on the electrical properties of Cd0.9Zn0.1Te crystals

NASA Astrophysics Data System (ADS)

Wang, Pengfei; Nan, Ruihua; Jian, Zengyun

2017-06-01

The deep-level defects of CdZnTe (CZT) crystals grown by the modified vertical Bridgman (MVB) method act as trapping centers or recombination centers in the band gap, which have significant effects on its electrical properties. The resistivity and electron mobility-lifetime product of high resistivity Cd0.9Zn0.1Te wafer marked CZT1 and low resistivity Cd0.9Zn0.1Te wafer marked CZT2 were tested respectively. Their deep-level defects were identified by thermally stimulated current (TSC) spectroscopy and thermoelectric effect spectroscopy (TEES) respectively. Then the trap-related parameters were characterized by the simultaneous multiple peak analysis (SIMPA) method. The deep donor level ({E}{{DD}}) dominating dark current was calculated by the relationship between dark current and temperature. The Fermi-level was characterized by current-voltage measurements of temperature dependence. The width of the band gap was characterized by ultraviolet-visible-infrared transmittance spectroscopy. The results show the traps concentration and capture cross section of CZT1 are lower than CZT2, so its electron mobility-lifetime product is greater than CZT2. The Fermi-level of CZT1 is closer to the middle gap than CZT2. The degree of Fermi-level pinned by {E}{{DD}} of CZT1 is larger than CZT2. It can be concluded that the resistivity of CZT crystals increases as the degree of Fermi-level pinned near the middle gap by the deep donor level enlarges. Project supported by the National Natural Science Foundation of China (No. 51502234) and the Scientific Research Plan Projects of Shaanxi Provincial Department of Education of China (No. 15JS040).

A Poor Relationship Between Sea Level and Deep-Water Sand Delivery

NASA Astrophysics Data System (ADS)

Harris, Ashley D.; Baumgardner, Sarah E.; Sun, Tao; Granjeon, Didier

2018-08-01

The most commonly cited control on delivery of sand to deep water is the rate of relative sea-level fall. The rapid rate of accommodation loss on the shelf causes sedimentation to shift basinward. Field and experimental numerical modeling studies have shown that deep-water sand delivery can occur during any stage of relative sea level position and across a large range of values of rate of relative sea-level change. However, these studies did not investigate the impact of sediment transport efficiency on the relationship between rate of relative sea-level change and deep-water sand delivery rate. We explore this relationship using a deterministic nonlinear diffusion-based numerical stratigraphic forward model. We vary across three orders of magnitude the diffusion coefficient value for marine settings, which controls sediment transport efficiency. We find that the rate of relative sea-level change can explain no more than 1% of the variability in deep-water sand delivery rates, regardless of sediment transport efficiency. Model results show a better correlation with relative sea level, with up to 55% of the variability in deep water sand delivery rates explained. The results presented here are consistent with studies of natural settings which suggest stochastic processes such as avulsion and slope failure, and interactions among such processes, may explain the remaining variance. Relative sea level is a better predictor of deep-water sand delivery than rate of relative sea-level change because it is the sea-level fall itself which promotes sand delivery, not the rate of the fall. We conclude that the poor relationship between sea level and sand delivery is not an artifact of the modeling parameters but is instead due to the inadequacy of relative sea level and the rate of relative sea-level change to fully describe the dimensional space in which depositional systems reside. Subsequently, sea level itself is unable to account for the interaction of multiple processes that contribute to sand delivery to deep water.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Capurro, O. A.; Niello, J. O. Fernandez; Pacheco, A. J.

We have investigated experimental quasielastic cross sections measured at backward angles and at deep sub-barrier energies for the {sup 35}Cl+{sup 105,106,110}Pd and {sup 32}S+{sup 110}Pd systems. Since coupling effects are almost negligible at very low bombarding energies, the quasielastic data allow one to determine the diffuseness parameter of the ion-ion potential. For the analyzed reactions we have obtained a surface diffuseness parameter value around 0.58{+-}0.04 fm.

Study of defects in TlBr, InI as potential semiconductor radiation detectors

NASA Astrophysics Data System (ADS)

Biswas, Koushik; Du, Mao-Hua

2011-03-01

Group III-halides such as TlBr and InI are receiving considerable attention for application in room temperature radiation detector devices. It is however, essential that these detector materials have favorable defect properties which enable good carrier transport when operating under an external bias voltage. We have studied the properties of native defects of InI and Tlbr and several important results emerge: (1) Schottky defects are the dominant low-energy defects in both materials that can potentially pin the Fermi level close to midgap, leading to high resistivity; (2) native defects in TlBr are benign in terms of electron trapping. However, anion-vacancy in InI induces a deep electron trap similar to the F -centers in alkali halides. This can reduce electron mobility-lifetime product in InI; (3) low diffusion barriers of vacancies and ionic conductivity could be responsible for the observed polarization phenomenon in both materials at room temperature. U.S. DOE Office of Nonproliferation Research and Development NA22.

Deep centers in AlGaN-based light emitting diode structures

NASA Astrophysics Data System (ADS)

Polyakov, A. Y.; Smirnov, N. B.; Govorkov, A. V.; Mil'vidskii, M. G.; Usikov, A. S.; Pushnyi, B. V.; Lundin, W. V.

1999-10-01

Deep traps were studied in GaN homojunction and AlGaN/GaN heterojunction light emitting diode (LED) p-i-n structures by means of deep levels transient spectroscopy (DLTS), admittance and electroluminescence (EL) spectra measurements. It is shown that, in homojunction LED structures, the EL spectra comes from recombination involving Mg acceptors in-diffusing into the active i-layer. This Mg in-diffusion is strongly suppressed in heterostructures with the upper p-type layer containing about 5% of Al. As a result the main peak in the EL spectra of heterostructures is shifted toward higher energy compared to homojunctions. Joint doping of the i-layer with Zn and Si allows to shift the main EL peak to longer wavelength. The dominant electron traps observed in the studied LED structures had ionization energies of 0.55 and 0.85 eV. The dominant hole traps had apparent ionization energies of 0.85 and 0.4 eV. The latter traps were shown to be metastable and it is argued that they could be at least in part responsible for the persistent photoconductivity observed in p-GaN.

Differential microstructural and morphological abnormalities in mild cognitive impairment and Alzheimer's disease: Evidence from cortical and deep gray matter.

PubMed

Gong, Nan-Jie; Chan, Chun-Chung; Leung, Lam-Ming; Wong, Chun-Sing; Dibb, Russell; Liu, Chunlei

2017-05-01

One aim of this study is to use non-Gaussian diffusion kurtosis imaging (DKI) for capturing microstructural abnormalities in gray matter of Alzheimer's disease (AD). The other aim is to compare DKI metrics against thickness of cortical gray matter and volume of deep gray matter, respectively. A cohort of 18 patients with AD, 18 patients with amnestic mild cognitive impairment (MCI), and 18 normal controls underwent morphological and DKI MR imaging. Images were investigated using regions-of-interest-based analyses for deep gray matter and vertex-wise analyses for cortical gray matter. In deep gray matter, more regions showed DKI parametric abnormalities than atrophies at the early MCI stage. Mean kurtosis (MK) exhibited the largest number of significant abnormalities among all DKI metrics. At the later AD stage, diffusional abnormalities were observed in fewer regions than atrophies. In cortical gray matter, abnormalities in thickness were mainly in the medial and lateral temporal lobes, which fit the locations of known early pathological changes. Microstructural abnormalities were predominantly in the parietal and even frontal lobes, which fit the locations of known late pathological changes. In conclusion, MK can complement conventional diffusion metrics for detecting microstructural changes, especially in deep gray matter. This study also provides evidence supporting the notion that microstructural changes predate morphological changes. Hum Brain Mapp 38:2495-2508, 2017. © 2017 Wiley Periodicals, Inc. © 2017 Wiley Periodicals, Inc.

4H-SiC p i n diodes grown by sublimation epitaxy in vacuum (SEV) and their application as microwave diodes

NASA Astrophysics Data System (ADS)

Camara, N.; Zekentes, K.; Zelenin, V. V.; Abramov, P. L.; Kirillov, A. V.; Romanov, L. P.; Boltovets, N. S.; Krivutsa, V. A.; Thuaire, A.; Bano, E.; Tsoi, E.; Lebedev, A. A.

2008-02-01

Sublimation epitaxy under vacuum (SEV) was investigated as a method for growing 4H-SiC epitaxial structures for p-i-n diode fabrication. The SEV-grown 4H-SiC material was investigated with scanning electron microscopy (SEM), atomic force microscopy (AFM), x-ray diffraction, photo-luminescence spectroscopy (PL), cathodo-luminescence (CL) spectroscopy, photocurrent method for carrier diffusion length determination, electro-luminescence microscopy (EL), deep level transient spectroscopy (DLTS), C-V profiling and Hall-effect measurements. When possible, the same investigation techniques were used in parallel with similar layers grown by chemical vapour deposition (CVD) epitaxy and the physical properties of the two kind of epitaxied layers were compared. p-i-n diodes were fabricated in parallel on SEV and CVD-grown layers and showed close electrical performances in dc mode in term of capacitance, resistance and transient time switching, despite the lower mobility and the diffusion length of the SEV-grown layers. X-band microwave switches based on the SEV-grown p-i-n diodes have been demonstrated with insertion loss lower than 4 dB and an isolation higher than 17 dB. These single-pole single-throw (SPST) switches were able to handle a pulsed power up to 1800 W in isolation mode, similar to the value obtained with switches incorporating diodes with CVD-grown layers.

Chloride Diffusion and Acid Resistance of Concrete Containing Zeolite and Tuff as Partial Replacements of Cement and Sand

PubMed Central

Mohseni, Ehsan; Tang, Waiching; Cui, Hongzhi

2017-01-01

In this paper, the properties of concrete containing zeolite and tuff as partial replacements of cement and sand were studied. The compressive strength, water absorption, chloride ion diffusion and resistance to acid environments of concretes made with zeolite at proportions of 10% and 15% of binder and tuff at ratios of 5%, 10% and 15% of fine aggregate were investigated. The results showed that the compressive strength of samples with zeolite and tuff increased considerably. In general, the concrete strength increased with increasing tuff content, and the strength was further improved when cement was replaced by zeolite. According to the water absorption results, specimens with zeolite showed the lowest water absorption values. With the incorporation of tuff and zeolite, the chloride resistance of specimens was enhanced significantly. In terms of the water absorption and chloride diffusion results, the most favorable replacement of cement and sand was 10% zeolite and 15% tuff, respectively. However, the resistance to acid attack reduced due to the absorbing characteristic and calcareous nature of the tuff. PMID:28772737

Search for the source of an apparent interfacial resistance to mass transfer of CnEm surfactants to the water/oil interface.

PubMed

Huston, Kyle J; Kiemen, Ashley; Larson, Ronald G

2018-06-12

Experiments have shown that relaxation of oil/water interfacial tension by adsorption of alkyl ethoxylate surfactants from water onto an oil droplet is delayed relative to diffusion-controlled adsorption. We examine possible causes of this delay, and we show that several are implausible. We find that re-dissolution of the surfactant in the oil droplet cannot explain the apparent interfacial resistance at short times, because the interface will preferentially fill before any such re-dissolution occurs. We also perform umbrella sampling with molecular dynamics simulation and do not find any evidence of a free energy barrier or low-diffusivity zone near the interface. Nor do we find evidence from simulation that pre-micellar aggregation slows diffusion enough to cause the observed resistance to interfacial adsorption. We are therefore unable to pinpoint the cause of the resistance, but we suggest that "dead time" associated with the experimental method could be responsible - specifically a local depletion of surfactant by the ejected droplet when creating the fresh interface between the oil and water.

Deep Sequencing of Pyrethroid-Resistant Bed Bugs Reveals Multiple Mechanisms of Resistance within a Single Population

PubMed Central

Adelman, Zach N.; Kilcullen, Kathleen A.; Koganemaru, Reina; Anderson, Michelle A. E.; Anderson, Troy D.; Miller, Dini M.

2011-01-01

A frightening resurgence of bed bug infestations has occurred over the last 10 years in the U.S. and current chemical methods have been inadequate for controlling this pest due to widespread insecticide resistance. Little is known about the mechanisms of resistance present in U.S. bed bug populations, making it extremely difficult to develop intelligent strategies for their control. We have identified bed bugs collected in Richmond, VA which exhibit both kdr-type (L925I) and metabolic resistance to pyrethroid insecticides. Using LD50 bioassays, we determined that resistance ratios for Richmond strain bed bugs were ∼5200-fold to the insecticide deltamethrin. To identify metabolic genes potentially involved in the detoxification of pyrethroids, we performed deep-sequencing of the adult bed bug transcriptome, obtaining more than 2.5 million reads on the 454 titanium platform. Following assembly, analysis of newly identified gene transcripts in both Harlan (susceptible) and Richmond (resistant) bed bugs revealed several candidate cytochrome P450 and carboxylesterase genes which were significantly over-expressed in the resistant strain, consistent with the idea of increased metabolic resistance. These data will accelerate efforts to understand the biochemical basis for insecticide resistance in bed bugs, and provide molecular markers to assist in the surveillance of metabolic resistance. PMID:22039447

Application of interleaving models for the description of intrusive layering at the fronts of deep polar water in the Eurasian Basin (Arctic)

NASA Astrophysics Data System (ADS)

Kuzmina, N. P.; Zhurbas, N. V.; Emelianov, M. V.; Pyzhevich, M. L.

2014-09-01

Interleaving models of pure thermohaline and baroclinic frontal zones are applied to describe intrusions at the fronts found in the upper part of the Deep Polar Water (DPW) when the stratification was absolutely stable. It is assumed that differential mixing is the main mechanism of the intrusion formation. Important parameters of the interleaving such as the growth rate, vertical scale, and slope of the most unstable modes relative to the horizontal plane are calculated. It was found that the interleaving model for a pure thermohaline front satisfactory describes the important intrusion parameters observed at the frontal zone. In the case of a baroclinic front, satisfactory agreement over all the interleaving parameters is observed between the model calculations and observations provided that the vertical momentum diffusivity significantly exceeds the corresponding coefficient of mass diffusivity. Under specific (reasonable) constraints of the vertical momentum diffusivity, the most unstable mode has a vertical scale approximately two-three times smaller than the vertical scale of the observed intrusions. A thorough discussion of the results is presented.

Flat-plate solar array project process development area, process research of non-CZ silicon material

NASA Technical Reports Server (NTRS)

Campbell, R. B.

1984-01-01

The program is designed to investigate the fabrication of solar cells on N-type base material by a simultaneous diffusion of N-type and P-type dopants to form an P(+)NN(+) structure. The results of simultaneous diffusion experiments are being compared to cells fabricated using sequential diffusion of dopants into N-base material in the same resistivity range. The process used for the fabrication of the simultaneously diffused P(+)NN(+) cells follows the standard Westinghouse baseline sequence for P-base material except that the two diffusion processes (boron and phosphorus) are replaced by a single diffusion step. All experiments are carried out on N-type dendritic web grown in the Westinghouse pre-pilot facility. The resistivities vary from 0.5 (UC OMEGA)cm to 5 (UC OMEGA)cm. The dopant sources used for both the simultaneous and sequential diffusion experiments are commercial metallorganic solutions with phosphorus or boron components. After these liquids are applied to the web surface, they are baked to form a hard glass which acts as a diffusion source at elevated temperatures. In experiments performed thus far, cells produced in sequential diffusion tests have properties essentially equal to the baseline N(+)PP(+) cells. However, the simultaneous diffusions have produced cells with much lower IV characteristics mainly due to cross-doping of the sources at the diffusion temperature. This cross-doping is due to the high vapor pressure phosphorus (applied as a metallorganic to the back surface) diffusion through the SiO2 mask and then acting as a diffusant source for the front surface.

Grain boundary engineering for control of tellurium diffusion in GH3535 alloy

NASA Astrophysics Data System (ADS)

Fu, Cai-Tao; Yinling, Wang; Chu, Xiang-Wei; Jiang, Li; Zhang, Wen-Zhu; Bai, Qin; Xia, Shuang; Leng, Bin; Li, Zhi-Jun; Ye, Xiang-Xi; Liu, Fang

2017-12-01

The effect of grain boundary engineering (GBE) on the Te diffusion along the surface grain boundaries was investigated in GH3535 alloy. It can be found that GBE treatment increases obviously the fraction of low-Σ coincidence site lattice (CSL) boundaries, especially the Σ3 ones, and introduces the large-size grain clusters. When the as-received (AR) and GBE-treated (GBET) specimens were exposed to Te vapor, only Σ3 boundaries were found to be resistant to Te diffusion. From the cross section and the surface, the fewer Te-attacked grain boundaries and the thinner corrosion layer can be observed in the GBET sample. The improvement of resistance to Te diffusion in the GBET sample can be attributed to the large size grain-clusters associated with high proportion of the Σ3n boundaries.

Size quantization in high-temperature superconducting cuprates and a link to Einstein's diffusion law

NASA Astrophysics Data System (ADS)

Roeser, H. P.; Bohr, A.; Haslam, D. T.; López, J. S.; Stepper, M.; Nikoghosyan, A. S.

2012-07-01

Optimum doping of high-temperature superconductors (HTSC) defines a superconducting unit volume for each HTSC. For a single-mode HTSC, e.g., a cuprate with one CuO2 plane, the volume is given by Vsc=cx2, where c is the unit cell height and x the doping distance. The experimental resistivity at Tc is connected to the structure by ρ(exp)≈c×h/(2e2). Combining this result with the classical definition of resistivity leads to an equation similar to Einstein's diffusion law x2/(2τ)=h/(2Meff)=D, where τ is the relaxation time, Meff=2me and D the diffusion constant. It has also been shown that the mean free path d=x. The Einstein-Smoluchowski diffusion relation D=μkBTc provides a connection to Tc.

Bounded diffusion impedance characterization of battery electrodes using fractional modeling

NASA Astrophysics Data System (ADS)

Gabano, Jean-Denis; Poinot, Thierry; Huard, Benoît

2017-06-01

This article deals with the ability of fractional modeling to describe the bounded diffusion behavior encountered in modern thin film and nanoparticles lithium battery electrodes. Indeed, the diffusion impedance of such batteries behaves as a half order integrator characterized by the Warburg impedance at high frequencies and becomes a classical integrator described by a capacitor at low frequencies. The transition between these two behaviors depends on the particles geometry. Three of them will be considered in this paper: planar, cylindrical and spherical ones. The fractional representation proposed is a gray box model able to perfectly fit the low and high frequency diffusive impedance behaviors while optimizing the frequency response transition. Identification results are provided using frequential simulation data considering the three electrochemical diffusion models based on the particles geometry. Furthermore, knowing this geometry allows to estimate the diffusion ionic resistance and time constant using the relationships linking these physical parameters to the structural fractional model parameters. Finally, other simulations using Randles impedance models including the charge transfer impedance and the external resistance demonstrate the interest of fractional modeling in order to identify properly not only the charge transfer impedance but also the diffusion physical parameters whatever the particles geometry.

An evaluation of subacute sclerosing panencephalitis patients with diffusion-weighted magnetic resonance imaging.

PubMed

Abuhandan, M; Cece, H; Calik, M; Karakas, E; Dogan, F; Karakas, O

2013-03-01

This study aimed to evaluate the contribution of diffusion weighted magnetic resonance imaging to the diagnosis and staging of subacute sclerosing panencephalitis. The study comprised 26 patients diagnosed with subacute sclerosing panencephalitis at our clinic who were undergoing regular follow-up, and a control group of 18 subjects. Clinical staging was determined by Risk and Haddad classification; 12 at Stage II and 14 at Stage III. Diffusion weighted magnetic resonance images were taken of six areas (frontal, parieto-occipital, cerebellar, deep white matter, thalamus and basal ganglia) and by calculating the apparent diffusion coefficient (ADC) values, and a comparison was made between the stages and with the control group. The ADC values of all the areas of the subacute sclerosing panencephalitis patients were found to be significantly higher compared to the control group (p < 0.05). While the mean ADC values of the deep white matter, basal ganglia, frontal and parieto-occipital areas of the Stage II patients were found to be significant compared to the control group (p < 0.05), there was no significance in the other areas (p > 0.05). The ADC values of all the areas of the Stage III patients were found to be significantly high compared to the Stage II values (p < 0.05). Diffusion weighted magnetic resonance imaging can be used with other diagnostic criteria to confirm diagnosis of subacute sclerosing panencephalitis and to reveal differences between the stages.

Combining tract- and atlas-based analysis reveals microstructural abnormalities in early Tourette syndrome children.

PubMed

Wen, Hongwei; Liu, Yue; Wang, Jieqiong; Rekik, Islem; Zhang, Jishui; Zhang, Yue; Tian, Hongwei; Peng, Yun; He, Huiguang

2016-05-01

Tourette syndrome (TS) is a neurological disorder that causes uncontrolled repetitive motor and vocal tics in children. Examining the neural basis of TS churned out different research studies that advanced our understanding of the brain pathways involved in its development. Particularly, growing evidence points to abnormalities within the fronto-striato-thalamic pathways. In this study, we combined Tract-Based Spatial Statistics (TBSS) and Atlas-based regions of interest (ROI) analysis approach, to investigate the microstructural diffusion changes in both deep and superficial white matter (SWM) in TS children. We then characterized the altered microstructure of white matter in 27 TS children in comparison with 27 age- and gender-matched healthy controls. We found that fractional anisotropy (FA) decreases and radial diffusivity (RD) increases in deep white matter (DWM) tracts in cortico-striato-thalamo-cortical (CSTC) circuit as well as SWM. Furthermore, we found that lower FA values and higher RD values in white matter regions are correlated with more severe tics, but not tics duration. Besides, we also found both axial diffusivity and mean diffusivity increase using Atlas-based ROI analysis. Our work may suggest that microstructural diffusion changes in white matter is not only restricted to the gray matter of CSTC circuit but also affects SWM within the primary motor and somatosensory cortex, commissural and association fibers. Hum Brain Mapp 37:1903-1919, 2016. © 2016 Wiley Periodicals, Inc. © 2016 Wiley Periodicals, Inc.

Susceptibilities of Norwegian Candida albicans strains to fluconazole: emergence of resistance. The Norwegian Yeast Study Group.

PubMed Central

Sandven, P; Bjørneklett, A; Maeland, A

1993-01-01

All Candida albicans isolates in Norwegian microbiological laboratories in 1991 judged clinically important (except vaginal isolates) were collected. The isolates were tested for susceptibility to fluconazole with an agar dilution test and a commercially available agar diffusion test. A total of 212 strains (95%) were susceptible to fluconazole, and MICs for most of the strains (92%) were < or = 1.56 micrograms/ml. The agar diffusion test using a 15-micrograms tablet and a 48-h incubation period separated resistant from susceptible strains with a wide margin. The only exception was a strain for which the MIC was 6.25 micrograms/ml. The difference in zone size between the resistant and the susceptible populations of strains was 11 mm. Accordingly, it appears that the agar diffusion test is an appropriate method for detecting fluconazole resistance. The 12 fluconazole-resistant isolates originated from eight AIDS patients with oral or esophageal Candida infections. Seven of the patients had been given fluconazole for 1 month or more, often as self medication. Four had infections that were clinically resistant to fluconazole; one additional patient responded only when the dose was increased. All isolates recovered from these patients were analyzed by multilocus enzyme electrophoresis. The 12 C. albicans isolates belonged to five electrophoretic types, but three of four patients attending one hospital had isolates belonging to one electrophoretic type. One possible explanation for this finding could be that a nosocomial spread of resistant strains has occurred. PMID:8285631

Local discretization method for overdamped Brownian motion on a potential with multiple deep wells.

PubMed

Nguyen, P T T; Challis, K J; Jack, M W

2016-11-01

We present a general method for transforming the continuous diffusion equation describing overdamped Brownian motion on a time-independent potential with multiple deep wells to a discrete master equation. The method is based on an expansion in localized basis states of local metastable potentials that match the full potential in the region of each potential well. Unlike previous basis methods for discretizing Brownian motion on a potential, this approach is valid for periodic potentials with varying multiple deep wells per period and can also be applied to nonperiodic systems. We apply the method to a range of potentials and find that potential wells that are deep compared to five times the thermal energy can be associated with a discrete localized state while shallower wells are better incorporated into the local metastable potentials of neighboring deep potential wells.

Local discretization method for overdamped Brownian motion on a potential with multiple deep wells

NASA Astrophysics Data System (ADS)

Nguyen, P. T. T.; Challis, K. J.; Jack, M. W.

2016-11-01

We present a general method for transforming the continuous diffusion equation describing overdamped Brownian motion on a time-independent potential with multiple deep wells to a discrete master equation. The method is based on an expansion in localized basis states of local metastable potentials that match the full potential in the region of each potential well. Unlike previous basis methods for discretizing Brownian motion on a potential, this approach is valid for periodic potentials with varying multiple deep wells per period and can also be applied to nonperiodic systems. We apply the method to a range of potentials and find that potential wells that are deep compared to five times the thermal energy can be associated with a discrete localized state while shallower wells are better incorporated into the local metastable potentials of neighboring deep potential wells.

Test of electical resistivity and current diffusion modelling on MAST and JET

NASA Astrophysics Data System (ADS)

Keeling, D. L.; Challis, C. D.; Jenkins, I.; Hawkes, N. C.; Lupelli, I.; Michael, C.; de Bock, M. F. M.; the MAST Team; contributors, JET

2018-01-01

Experiments have been carried out on the MAST and JET tokamaks intended to compare the electrical resistivity of the plasma with theoretical formulations. The tests consist of obtaining motional stark effect (MSE) measurements in MHD-free plasmas during plasma current ramp-up (JET and MAST), ramp-down (MAST) and in stationary state (JET and MAST). Simulations of these plasmas are then performed in which the current profile evolution is calculated according to the poloidal field diffusion equation (PFDE) with classical or neoclassical resistivity. Synthetic MSE data are produced in the simulations for direct comparison with the experimental data. It is found that the toroidal current profile evolution modelled using neoclassical resistivity did not match the experimental observations on either device during current ramp-up or ramp-down as concluded from comparison of experimental and synthetic MSE profiles. In these phases, use of neoclassical resistivity in the modelling systematically overestimates the rate of current profile evolution. During the stationary state however, the modelled toroidal current profile matched experimental observations to a high degree of accuracy on both devices using neoclassical resistivity. Whilst no solution to the mismatch in the dynamic phases of the plasma is proposed, it is suggested that some physical process other than MHD which is not captured by the simple diffusive model of current profile evolution is responsible.

Effect of clamping pressure on ohmic resistance and compression of gas diffusion layers for polymer electrolyte fuel cells

NASA Astrophysics Data System (ADS)

Mason, Thomas J.; Millichamp, Jason; Neville, Tobias P.; El-kharouf, Ahmad; Pollet, Bruno G.; Brett, Daniel J. L.

2012-12-01

This paper describes the use of an in situ analytical technique based on simultaneous displacement and resistance measurement of gas diffusion layers (GDLs) used in polymer electrolyte fuel cells (PEFCs), when exposed to varying compaction pressure. In terms of the losses within fuel cells, the ohmic loss makes up a significant portion. Of this loss, the contact resistance between the GDL and the bipolar plate (BPP) is an important constituent. By analysing the change in thickness and ohmic resistance of GDLs under compression, important mechanical and electrical properties are obtained. Derived parameters such as the 'displacement factor' are used to characterise a representative range of commercial GDLs. Increasing compaction pressure leads to a non-linear decrease in resistance for all GDLs. For Toray paper, compaction becomes more irreversible with pressure with no elastic region observed. Different GDLs have different intrinsic resistance; however, all GDLs of the same class share a common compaction profile (change in resistance with pressure). Cyclic compression of Toray GDL leads to progressive improvement in resistance and reduction in thickness that stabilises after ∼10 cycles.

Deep Throttle Turbopump Technology Design Concepts

NASA Technical Reports Server (NTRS)

Guinzburg, Adiel; Williams, Morgan; Ferguson, Tom; Garcia, Roberto (Technical Monitor)

2002-01-01

The objective of this project is to increase the throttling range of turbopumps from 30 to 120% of the design value, while maintaining high performance levels. Details are given on wide flow range issues, H-Q characteristics, stall characteristics, energy levels, pressure fluctuations at impeller exit, WFR impeller characteristics, commercial diffuser pumps, slotted or tandem vanes, leading edge characteristics, leading edge models, throat models, diffusion passage models, computational fluid dynamics (CFD) methodologies, and CFD flow cases.

1/f model for long-time memory of the ocean surface temperature

NASA Astrophysics Data System (ADS)

Fraedrich, Klaus; Luksch, Ute; Blender, Richard

2004-09-01

The 1/f spectrum of the ocean surface temperature in the Atlantic and Pacific midlatitudes is explained by a simple vertical diffusion model with a shallow mixed layer on top of a deep ocean. The model is forced at the air-sea interface with the total surface heat flux from a 1000 year climate simulation. The analysis reveals the role of ocean advection and substantiates estimates of internal thermal diffusivities.

Investigation of Thermal Interface Materials Using Phase-Sensitive Transient Thermoreflectance Technique: Preprint

DOE Office of Scientific and Technical Information (OSTI.GOV)

Feng, X.; King, C.; DeVoto, D.

2014-08-01

With increasing power density in electronics packages/modules, thermal resistances at multiple interfaces are a bottleneck to efficient heat removal from the package. In this work, the performance of thermal interface materials such as grease, thermoplastic adhesives and diffusion-bonded interfaces are characterized using the phase-sensitive transient thermoreflectance technique. A multi-layer heat conduction model was constructed and theoretical solutions were derived to obtain the relation between phase lag and the thermal/physical properties. This technique enables simultaneous extraction of the contact resistance and bulk thermal conductivity of the TIMs. With the measurements, the bulk thermal conductivity of Dow TC-5022 thermal grease (70 tomore » 75 um bondline thickness) was 3 to 5 W/(m-K) and the contact resistance was 5 to 10 mm2-K/W. For the Btech thermoplastic material (45 to 80 μm bondline thickness), the bulk thermal conductivity was 20 to 50 W/(m-K) and the contact resistance was 2 to 5 mm2-K/W. Measurements were also conducted to quantify the thermal performance of diffusion-bonded interface for power electronics applications. Results with the diffusion-bonded sample showed that the interfacial thermal resistance is more than one order of magnitude lower than those of traditional TIMs, suggesting potential pathways to efficient thermal management.« less

Universal linear-temperature resistivity: possible quantum diffusion transport in strongly correlated superconductors.

PubMed

Hu, Tao; Liu, Yinshang; Xiao, Hong; Mu, Gang; Yang, Yi-Feng

2017-08-25

The strongly correlated electron fluids in high temperature cuprate superconductors demonstrate an anomalous linear temperature (T) dependent resistivity behavior, which persists to a wide temperature range without exhibiting saturation. As cooling down, those electron fluids lose the resistivity and condense into the superfluid. However, the origin of the linear-T resistivity behavior and its relationship to the strongly correlated superconductivity remain a mystery. Here we report a universal relation [Formula: see text], which bridges the slope of the linear-T-dependent resistivity (dρ/dT) to the London penetration depth λ L at zero temperature among cuprate superconductor Bi 2 Sr 2 CaCu 2 O 8+δ and heavy fermion superconductors CeCoIn 5 , where μ 0 is vacuum permeability, k B is the Boltzmann constant and ħ is the reduced Planck constant. We extend this scaling relation to different systems and found that it holds for other cuprate, pnictide and heavy fermion superconductors as well, regardless of the significant differences in the strength of electronic correlations, transport directions, and doping levels. Our analysis suggests that the scaling relation in strongly correlated superconductors could be described as a hydrodynamic diffusive transport, with the diffusion coefficient (D) approaching the quantum limit D ~ ħ/m*, where m* is the quasi-particle effective mass.

Prediction of Tissue Outcome and Assessment of Treatment Effect in Acute Ischemic Stroke Using Deep Learning.

PubMed

Nielsen, Anne; Hansen, Mikkel Bo; Tietze, Anna; Mouridsen, Kim

2018-06-01

Treatment options for patients with acute ischemic stroke depend on the volume of salvageable tissue. This volume assessment is currently based on fixed thresholds and single imagine modalities, limiting accuracy. We wish to develop and validate a predictive model capable of automatically identifying and combining acute imaging features to accurately predict final lesion volume. Using acute magnetic resonance imaging, we developed and trained a deep convolutional neural network (CNN deep ) to predict final imaging outcome. A total of 222 patients were included, of which 187 were treated with rtPA (recombinant tissue-type plasminogen activator). The performance of CNN deep was compared with a shallow CNN based on the perfusion-weighted imaging biomarker Tmax (CNN Tmax ), a shallow CNN based on a combination of 9 different biomarkers (CNN shallow ), a generalized linear model, and thresholding of the diffusion-weighted imaging biomarker apparent diffusion coefficient (ADC) at 600×10 -6 mm 2 /s (ADC thres ). To assess whether CNN deep is capable of differentiating outcomes of ±intravenous rtPA, patients not receiving intravenous rtPA were included to train CNN deep, -rtpa to access a treatment effect. The networks' performances were evaluated using visual inspection, area under the receiver operating characteristic curve (AUC), and contrast. CNN deep yields significantly better performance in predicting final outcome (AUC=0.88±0.12) than generalized linear model (AUC=0.78±0.12; P =0.005), CNN Tmax (AUC=0.72±0.14; P <0.003), and ADC thres (AUC=0.66±0.13; P <0.0001) and a substantially better performance than CNN shallow (AUC=0.85±0.11; P =0.063). Measured by contrast, CNN deep improves the predictions significantly, showing superiority to all other methods ( P ≤0.003). CNN deep also seems to be able to differentiate outcomes based on treatment strategy with the volume of final infarct being significantly different ( P =0.048). The considerable prediction improvement accuracy over current state of the art increases the potential for automated decision support in providing recommendations for personalized treatment plans. © 2018 American Heart Association, Inc.

A first-principles analysis of ballistic conductance, grain boundary scattering and vertical resistance in aluminum interconnects

NASA Astrophysics Data System (ADS)

Zhou, Tianji; Lanzillo, Nicholas A.; Bhosale, Prasad; Gall, Daniel; Quon, Roger

2018-05-01

We present an ab initio evaluation of electron scattering mechanisms in Al interconnects from a back-end-of-line (BEOL) perspective. We consider the ballistic conductance as a function of nanowire size, as well as the impact of surface oxidation on electron transport. We also consider several representative twin grain boundaries and calculate the specific resistivity and reflection coefficients for each case. Lastly, we calculate the vertical resistance across the Al/Ta(N)/Al and Cu/Ta(N)/Cu interfaces, which are representative of typical vertical interconnect structures with diffusion barriers. Despite a high ballistic conductance, the calculated specific resistivities at grain boundaries are 70-100% higher in Al than in Cu, and the vertical resistance across Ta(N) diffusion barriers are 60-100% larger for Al than for Cu. These results suggest that in addition to the well-known electromigration limitations in Al interconnects, electron scattering represents a major problem in achieving low interconnect line resistance at fine dimensions.

Effects of Deep Cryogenic Treatment on the Wear Resistance and Mechanical Properties of AISI H13 Hot-Work Tool Steel

NASA Astrophysics Data System (ADS)

Çiçek, Adem; Kara, Fuat; Kıvak, Turgay; Ekici, Ergün; Uygur, İlyas

2015-11-01

In this study, a number of wear and tensile tests were performed to elucidate the effects of deep cryogenic treatment on the wear behavior and mechanical properties (hardness and tensile strength) of AISI H13 tool steel. In accordance with this purpose, three different heat treatments (conventional heat treatment (CHT), deep cryogenic treatment (DCT), and deep cryogenic treatment and tempering (DCTT)) were applied to tool steel samples. DCT and DCTT samples were held in nitrogen gas at -145 °C for 24 h. Wear tests were conducted on a dry pin-on-disk device using two loads of 60 and 80 N, two sliding velocities of 0.8 and 1 m/s, and a wear distance of 1000 m. All test results showed that DCT improved the adhesive wear resistance and mechanical properties of AISI H13 steel. The formation of small-sized and uniformly distributed carbide particles and the transformation of retained austenite to martensite played an important role in the improvements in the wear resistance and mechanical properties. After cleavage fracture, the surfaces of all samples were characterized by the cracking of primary carbides, while the DCT and DCTT samples displayed microvoid formation by decohesion of the fine carbides precipitated during the cryo-tempering process.

Complex structure of Piton de la Fournaise and its underlying lithosphere revealed by magnetotelluric 3D inversion

NASA Astrophysics Data System (ADS)

Gailler, Lydie-Sarah; Martí, Anna; Lénat, Jean-François

2018-05-01

La Réunion is a large volcanic construction resting on Paleocene oceanic crust. Through the 3D inversion of a large set of magnetotelluric (MT) soundings, our results reveal the general resistivity structure of the western part of Piton de la Fournaise volcano down to its base and the first 10 km or so of the underlying lithosphere. The resistivity pattern shows a general stratification of the resistivity values. An upper resistive layer corresponds to unsaturated and water-saturated lava flows. This layer is thinner (a few hundred meters) in the Enclos and Plaine des Sables/Fond de la Rivière de l'Est areas than on the NW flank where it reaches 2000 m. Below, the rest of the edifice is distinctly more conductive and shows highly conductive patches. The origin of the globally weak resistivity of the lower part of the construction is not established but can be tentatively attributed to a higher degree of alteration. The case of the highly conductive patches is different. Resistivity values of a few Ω·m imply the presence of highly conductive fluids and/or minerals that, in this context, are generally associated with hydrothermal phenomena. In the Enclos, highly conductive patches are unambiguously attributed to the presently active hydrothermal system. Beneath the Plaine des Sables/Fond de la Rivière de l'Est, they may be associated with hydrothermal alteration developed by the ancient volcanic center. The larger highly conductive patches are found below sea level and above the crust beneath the NW flank, at depths significantly larger than the others. This area coincides with the path of the N120 rift zone, with a deep ( 10-20 km) seismicity and with diffuse CO2 degassing. A relationship may therefore be inferred between deep magmatic activity, eruptive activity and postulated highly conductive hydrothermal zone. In the globally weak resistivity of the lower part of the edifice, a dome of moderate resistivity (>1 kΩ·m) is centered beneath the Plaine des Sables. It is wider than a dense intrusive complex inferred from gravity models in the same area. The present resolution of both MT and gravity models cannot exclude a same nature for both structures. Beneath 4 km b.s.l., an increase of the resistivity values underlines an interface in good agreement with the inferred location of the transition between the edifice and the oceanic crust at this depth. The upper lithosphere shows resistivity values above 250 Ω·m. This study therefore demonstrates the capability of the method to image major shallow structures such as the hydrothermally altered zones, and deeper ones such as the heterogeneity of the crust. Fig. A.1. a) Location of the resistivity soundings used in this study at the scale of Piton de la Fournaise. b) Zoom on each set of soundings from various organizations. The study area is framed in red. Fig. B.1. Comparison between the raw data and model responses (xx, xy, yx, yy) at all sites and periods. Circles: measured data; dots: model responses. Black and blue: xx, xy; red and pink: yx and yy.

Radiation tolerance of low resistivity, high voltage silicon solar cells

NASA Technical Reports Server (NTRS)

Weizer, V. G.; Weinberg, I.; Swartz, C. K.

1984-01-01

The radiation tolerance of the following three low resistivity, high voltage silicon solar cells was investigated: (1) the COMSAT MSD (multi-step diffused) cell, (2) the MinMIS cell, and (3) the MIND cell. A description of these solar cells is given along with drawings of their configurations. The diffusion length damage coefficients for the cells were calculated and presented. Solar cell spectral response was also discussed. Cells of the MinMIS type were judged to be unsuitable for use in the space radiation environment.

Deep aquifer as driver for mineral authigenesis in Gulf of Alaska sediments (IODP Expedition 341, Site U1417)

NASA Astrophysics Data System (ADS)

Zindorf, Mark; März, Christian; Wagner, Thomas; Strauss, Harald; Gulick, Sean P. S.; Jaeger, John M.; LeVay, Leah J.

2016-04-01

Bacterial sulphate reduction plays a key role in authigenic mineral formation in marine sediments. Usually, decomposition of organic matter follows a sequence of microbial metabolic pathways, where microbial sulphate reduction leads to sulphate depletion deeper in the sediment. When sulphate is consumed completely from the pore waters, methanogenesis commences. The contact of sulphate- and methane-containing pore waters is a well-defined biogeochemical boundary (the sulphate-methane transition zone, SMTZ). Here authigenic pyrite, barite and carbonates form. Pyrite formation is directly driven by bacterial sulphate reduction since pyrite precipitates from produced hydrogen sulphide. Barite and carbonate formation are secondary effects resulting from changes of the chemical milieu due to microbial activity. However, this mineral authigenesis is ultimately linked to abiotic processes that determine the living conditions for microorganisms. At IODP Site U1417 in the Gulf of Alaska, a remarkable diagenetic pattern has been observed: Between sulphate depletion and methane enrichment, a ~250 m wide gap exists. Consequently, no SMTZ can be found under present conditions, but enrichments of pyrite indicate that such zones have existed in the past. Solid layers consisting of authigenic carbonate-cemented sand were partly recovered right above the methane production zone, likely preventing continued upward methane diffusion. At the bottom of the sediment succession, the lower boundary of the methanogenic zone is constrained by sulphate-rich pore waters that appear to originate from a deeper source. Here, a well-established SMTZ exists, but in reversed order (sulphate diffusing up, methane diffusing down). Sulphur isotopes of pyrite reveal that sulphate reduction here does not occur under closed system conditions. This indicates that a deep aquifer is actively recharging the deep sulphate pool. Similar deep SMTZs have been found at other sites, yet mostly in geologically active environments such as ridge flanks or above subduction zones. Therefore Site U1417, in a relatively inactive intraplate environment, represents a so far under-sampled geochemical setting. Calculated accumulation times for authigenic minerals in the deep SMTZ are on the same order of magnitude as the onset of subduction-related bending of the Pacific Plate, suggesting that both processes are linked. Plate bending could create fractures in the overlying sediments allowing seawater to penetrate and recharge a deep aquifer. Our study provides insights into a newly discovered geological process suitable for delivering sulphate-rich water deep into the sediments and installing diagenetically active environments where microbial activity would otherwise be very limited.

Detection of antimicrobial resistance genes associated with the International Space Station environmental surfaces

DOE Office of Scientific and Technical Information (OSTI.GOV)

Urbaniak, C.; Sielaff, A. Checinska; Frey, K. G.

Antimicrobial resistance (AMR) is a global health issue. In an effort to minimize this threat to astronauts, who may be immunocompromised and thus at a greater risk of infection from antimicrobial resistant pathogens, a comprehensive study of the ISS “resistome’ was conducted. Using whole genome sequencing (WGS) and disc diffusion antibiotic resistance assays, 9 biosafety level 2 organisms isolated from the ISS were assessed for their antibiotic resistance. Molecular analysis of AMR genes from 24 surface samples collected from the ISS during 3 different sampling events over a span of a year were analyzed with Ion AmpliSeq™ and metagenomics. Discmore » diffusion assays showed that Enterobacter bugandensis strains were resistant to all 9 antibiotics tested and Staphylococcus haemolyticus being resistant to none. Ion AmpliSeq™ revealed that 123 AMR genes were found, with those responsible for beta-lactam and trimethoprim resistance being the most abundant and widespread. Using a variety of methods, the genes involved in antimicrobial resistance have been examined for the first time from the ISS. Lastly, this information could lead to mitigation strategies to maintain astronaut health during long duration space missions when return to Earth for treatment is not possible.« less

Detection of antimicrobial resistance genes associated with the International Space Station environmental surfaces

DOE PAGES

Urbaniak, C.; Sielaff, A. Checinska; Frey, K. G.; ...

2018-01-16

Antimicrobial resistance (AMR) is a global health issue. In an effort to minimize this threat to astronauts, who may be immunocompromised and thus at a greater risk of infection from antimicrobial resistant pathogens, a comprehensive study of the ISS “resistome’ was conducted. Using whole genome sequencing (WGS) and disc diffusion antibiotic resistance assays, 9 biosafety level 2 organisms isolated from the ISS were assessed for their antibiotic resistance. Molecular analysis of AMR genes from 24 surface samples collected from the ISS during 3 different sampling events over a span of a year were analyzed with Ion AmpliSeq™ and metagenomics. Discmore » diffusion assays showed that Enterobacter bugandensis strains were resistant to all 9 antibiotics tested and Staphylococcus haemolyticus being resistant to none. Ion AmpliSeq™ revealed that 123 AMR genes were found, with those responsible for beta-lactam and trimethoprim resistance being the most abundant and widespread. Using a variety of methods, the genes involved in antimicrobial resistance have been examined for the first time from the ISS. Lastly, this information could lead to mitigation strategies to maintain astronaut health during long duration space missions when return to Earth for treatment is not possible.« less

Thermal resistance of pressed contacts of aluminum and niobium at liquid helium temperatures

DOE PAGES

Dhuley, R. C.; Geelhoed, M. I.; Thangaraj, J. C. T.

2018-06-15

Here, we examine the resistance to heat flow across contacts of mechanically pressed aluminum and niobium near liquid helium temperatures for designing a thermally conducting joint of aluminum and superconducting niobium. Measurements in the temperature range of 3.5 K to 5.5 K show the thermal contact resistance to grow as a near-cubic function of decreasing temperature, indicating phonons to be the primary heat carriers across the interface. In the 4 kN to 14 kN range of pressing force the contact resistance shows linear drop with the increasing force, in agreement with the model of micro-asperity plastic deformation at pressed contacts.more » Several thermal contact resistance models as well as the phonon diffuse mismatch model of interface thermal resistance are compared with the experimental data. The diffuse mismatch model shows closest agreement. The joints are further augmented with thin foil of indium, which lowers the joint resistance by an order of magnitude. The developed joint has nearly 1 K*cm2/W of thermal resistance at 4.2 K, is demountable, and free of the thermally resistive interfacial alloy layer that typically exists at welded, casted, or soldered joints of dissimilar metals.« less

Detection of antimicrobial resistance genes associated with the International Space Station environmental surfaces.

PubMed

Urbaniak, C; Sielaff, A Checinska; Frey, K G; Allen, J E; Singh, N; Jaing, C; Wheeler, K; Venkateswaran, K

2018-01-16

Antimicrobial resistance (AMR) is a global health issue. In an effort to minimize this threat to astronauts, who may be immunocompromised and thus at a greater risk of infection from antimicrobial resistant pathogens, a comprehensive study of the ISS "resistome' was conducted. Using whole genome sequencing (WGS) and disc diffusion antibiotic resistance assays, 9 biosafety level 2 organisms isolated from the ISS were assessed for their antibiotic resistance. Molecular analysis of AMR genes from 24 surface samples collected from the ISS during 3 different sampling events over a span of a year were analyzed with Ion AmpliSeq ™ and metagenomics. Disc diffusion assays showed that Enterobacter bugandensis strains were resistant to all 9 antibiotics tested and Staphylococcus haemolyticus being resistant to none. Ion AmpliSeq ™ revealed that 123 AMR genes were found, with those responsible for beta-lactam and trimethoprim resistance being the most abundant and widespread. Using a variety of methods, the genes involved in antimicrobial resistance have been examined for the first time from the ISS. This information could lead to mitigation strategies to maintain astronaut health during long duration space missions when return to Earth for treatment is not possible.

Thermal resistance of pressed contacts of aluminum and niobium at liquid helium temperatures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dhuley, R. C.; Geelhoed, M. I.; Thangaraj, J. C. T.

Here, we examine the resistance to heat flow across contacts of mechanically pressed aluminum and niobium near liquid helium temperatures for designing a thermally conducting joint of aluminum and superconducting niobium. Measurements in the temperature range of 3.5 K to 5.5 K show the thermal contact resistance to grow as a near-cubic function of decreasing temperature, indicating phonons to be the primary heat carriers across the interface. In the 4 kN to 14 kN range of pressing force the contact resistance shows linear drop with the increasing force, in agreement with the model of micro-asperity plastic deformation at pressed contacts.more » Several thermal contact resistance models as well as the phonon diffuse mismatch model of interface thermal resistance are compared with the experimental data. The diffuse mismatch model shows closest agreement. The joints are further augmented with thin foil of indium, which lowers the joint resistance by an order of magnitude. The developed joint has nearly 1 K*cm2/W of thermal resistance at 4.2 K, is demountable, and free of the thermally resistive interfacial alloy layer that typically exists at welded, casted, or soldered joints of dissimilar metals.« less

Using RNA-seq and targeted nucleases to identify mechanisms of drug resistance in acute myeloid leukemia.

PubMed

Rathe, Susan K; Moriarity, Branden S; Stoltenberg, Christopher B; Kurata, Morito; Aumann, Natalie K; Rahrmann, Eric P; Bailey, Natashay J; Melrose, Ellen G; Beckmann, Dominic A; Liska, Chase R; Largaespada, David A

2014-08-13

The evolution from microarrays to transcriptome deep-sequencing (RNA-seq) and from RNA interference to gene knockouts using Clustered Regularly Interspaced Short Palindromic Repeats (CRISPRs) and Transcription Activator-Like Effector Nucleases (TALENs) has provided a new experimental partnership for identifying and quantifying the effects of gene changes on drug resistance. Here we describe the results from deep-sequencing of RNA derived from two cytarabine (Ara-C) resistance acute myeloid leukemia (AML) cell lines, and present CRISPR and TALEN based methods for accomplishing complete gene knockout (KO) in AML cells. We found protein modifying loss-of-function mutations in Dck in both Ara-C resistant cell lines. CRISPR and TALEN-based KO of Dck dramatically increased the IC₅₀ of Ara-C and introduction of a DCK overexpression vector into Dck KO clones resulted in a significant increase in Ara-C sensitivity. This effort demonstrates the power of using transcriptome analysis and CRISPR/TALEN-based KOs to identify and verify genes associated with drug resistance.

Comparison of Boron diffused emitters from BN, BSoD and H3BO3 dopants

NASA Astrophysics Data System (ADS)

Singha, Bandana; Singh Solanki, Chetan

2016-12-01

In this work, we are comparing different limited boron dopant sources for the emitter formation in n-type c-Si solar cells. High purity boric acid solution, commercially available boron spin on dopant and boron nitride solid source are used for comparison of emitter doping profiles for the same time and temperature conditions of diffusion. The characterizations done for the similar sheet resistance values for all the dopant sources show different surface morphologies and different device parameters. The measured emitter saturation current densities (Joe) are more than 20 fA cm-2 for all the dopant sources. The bulk carrier lifetimes measured for different diffusion conditions and different solar cell parameters for the similar sheet resistance values show the best result for boric acid diffusion and the least for BN solid source. So, different dopant sources result in different emitter and cell performances.

Influence of deep cryogenic treatment on structure and wear resistance of materials of hydraulic breaker chisels

NASA Astrophysics Data System (ADS)

Bolobov, V. I.; BinhLe, Thanh

2018-03-01

It is shown that shallow cryogenic treatment at -75°C (SCT) of the materials of hydraulic breaker chisels - P20, 1080 and D2 steels leads to a decrease (44 ÷ 82%) in the amount of retained austenite and an increase (26 ÷ 99%) in the amount of carbides in the structure of hardened steel, which is accompanied by an increase in its hardness (1.4 ÷ 2.1%) and abrasive wear resistance (10 ÷ 31%) with a simultaneous decrease in impact toughness (19 ÷ 24%). Deep cryogenic treatment at -196°C (DCT) and subsequent low-temperature tempering of D2 steel leads to a significant increase in its wear resistance (98%) and impact toughness (32%).

PI3Kδ inhibitor idelalisib in combination with BTK inhibitor ONO/GS-4059 in diffuse large B cell lymphoma with acquired resistance to PI3Kδ and BTK inhibitors.

PubMed

Yahiaoui, Anella; Meadows, Sarah A; Sorensen, Rick A; Cui, Zhi-Hua; Keegan, Kathleen S; Brockett, Robert; Chen, Guang; Quéva, Christophe; Li, Li; Tannheimer, Stacey L

2017-01-01

Activated B-cell-like diffuse large B-cell lymphoma relies on B-cell receptor signaling to drive proliferation and survival. Downstream of the B-cell receptor, the key signaling kinases Bruton's tyrosine kinase and phosphoinositide 3-kinase δ offer opportunities for therapeutic intervention by agents such as ibrutinib, ONO/GS-4059, and idelalisib. Combination therapy with such targeted agents could provide enhanced efficacy due to complimentary mechanisms of action. In this study, we describe both the additive interaction of and resistance mechanisms to idelalisib and ONO/GS-4059 in a model of activated B-cell-like diffuse large B-cell lymphoma. Significant tumor regression was observed with a combination of PI3Kδ and Bruton's tyrosine kinase inhibitors in the mouse TMD8 xenograft. Acquired resistance to idelalisib in the TMD8 cell line occurred by loss of phosphatase and tensin homolog and phosphoinositide 3-kinase pathway upregulation, but not by mutation of PIK3CD. Sensitivity to idelalisib could be restored by combining idelalisib and ONO/GS-4059. Further evaluation of targeted inhibitors revealed that the combination of idelalisib and the phosphoinositide-dependent kinase-1 inhibitor GSK2334470 or the AKT inhibitor MK-2206 could partially overcome resistance. Characterization of acquired Bruton's tyrosine kinase inhibitor resistance revealed a novel tumor necrosis factor alpha induced protein 3 mutation (TNFAIP3 Q143*), which led to a loss of A20 protein, and increased p-IκBα. The combination of idelalisib and ONO/GS-4059 partially restored sensitivity in this resistant line. Additionally, a mutation in Bruton's tyrosine kinase at C481F was identified as a mechanism of resistance. The combination activity observed with idelalisib and ONO/GS-4059, taken together with the ability to overcome resistance, could lead to a new therapeutic option in activated B-cell-like diffuse large B-cell lymphoma. A clinical trial is currently underway to evaluate the combination of idelalisib and ONO/GS-4059 (NCT02457598).

Another bipolar deep-sea anemone: new species of Iosactis (Actiniaria, Endomyaria) from Antarctica

NASA Astrophysics Data System (ADS)

Rodríguez, Estefanía

2012-06-01

A new species of deep-sea burrowing sea anemone is described and illustrated from Antarctica. Iosactis antarctica sp. nov. is characterised by easily deciduous tentacles with sphincters in the base, smooth column, endodermal marginal sphincter, same mesenteries proximally and distally, 24 perfect mesenteries regularly arranged, diffuse retractor musculature and basilar muscles well developed. Iosactis antarctica sp. nov. is the second species of the deep-sea abyssal genus Iosactis; it differs from I. vagabunda in internal anatomy, cnidae and geographic distribution. The description of I. antarctica sp. nov. provides the opportunity to revaluate the morphology of the proximal end of this genus.

Naturally occurring dominant drug resistance mutations occur infrequently in the setting of recently acquired hepatitis C.

PubMed

Applegate, Tanya L; Gaudieri, Silvana; Plauzolles, Anne; Chopra, Abha; Grebely, Jason; Lucas, Michaela; Hellard, Margaret; Luciani, Fabio; Dore, Gregory J; Matthews, Gail V

2015-01-01

Direct-acting antivirals (DAAs) are predicted to transform hepatitis C therapy, yet little is known about the prevalence of naturally occurring resistance mutations in recently acquired HCV. This study aimed to determine the prevalence and frequency of drug resistance mutations in the viral quasispecies among HIV-positive and -negative individuals with recent HCV. The NS3 protease, NS5A and NS5B polymerase genes were amplified from 50 genotype 1a participants of the Australian Trial in Acute Hepatitis C. Amino acid variations at sites known to be associated with possible drug resistance were analysed by ultra-deep pyrosequencing. A total of 12% of individuals harboured dominant resistance mutations, while 36% demonstrated non-dominant resistant variants below that detectable by bulk sequencing (that is, <20%) but above a threshold of 1%. Resistance variants (<1%) were observed at most sites associated with DAA resistance from all classes, with the exception of sofosbuvir. Dominant resistant mutations were uncommonly observed in the setting of recent HCV. However, low-level mutations to all DAA classes were observed by deep sequencing at the majority of sites and in most individuals. The significance of these variants and impact on future treatment options remains to be determined. Clinicaltrials.gov NCT00192569.

Simultaneous signal reconstruction from both superficial and deep tissue for fNIRS using depth-selective filtering method

NASA Astrophysics Data System (ADS)

Fujii, M.

2017-07-01

Two variations of a depth-selective back-projection filter for functional near-infrared spectroscopy (fNIRS) systems are introduced. The filter comprises a depth-selective algorithm that uses inverse problems applied to an optically diffusive multilayer medium. In this study, simultaneous signal reconstruction of both superficial and deep tissue from fNIRS experiments of the human forehead using a prototype of a CW-NIRS system is demonstrated.

Resistivity, carrier trapping, and polarization phenomenon in semiconductor radiation detection materials

NASA Astrophysics Data System (ADS)

Du, Mao-Hua; Biswas, Koushik; Singh, David J.

2012-10-01

In this paper, we report theoretical studies of native defects and dopants in a number of room-temperature semiconductor radiation detection materials, i.e., CdTe, TlBr, and Tl6SeI4. We address several important questions, such as what causes high resistivity in these materials, what explains good μτ product (carrier mobility-lifetime product) in soft-lattice ionic compounds that have high defect density, and how to obtain high resistivity and low carrier trapping simultaneously. Our main results are: (1) shallow donors rather than deep ones are responsible for high resistivity in high-quality detectorgrade CdTe; (2) large dielectric screening and the lack of deep levels from low-energy native defects may contribute to the good μτ products for both electrons and holes in TlBr; (3) the polarization phenomenon in Tl6SeI4 is expected to be much reduced compared to that in TlBr.

Imipenem resistance in clinical Escherichia coli from Qom, Iran.

PubMed

Shams, Saeed; Hashemi, Ali; Esmkhani, Mohammad; Kermani, Somaye; Shams, Elham; Piccirillo, Alessandra

2018-05-18

The emergence of metallo-β-lactamase-producing Enterobacteriaceae is a worldwide health concern. In this study, the first evaluation of MBL genes, bla IMP and bla VIM , in Escherichia coli resistant to imipenem isolated from urine and blood specimens in Qom, Iran is described. Three hundred urine and blood specimens were analysed to detect the presence of E. coli. Resistance to imipenem and other antimicrobials was determined by disk diffusion and MIC. MBL production was screened using CDDT. PCR was also carried out to determine the presence of bla IMP and bla VIM genes in imipenem-resistant isolates. In total, 160 E. coli isolates were collected from March to May 2016. According to disk diffusion, high-level of resistance (20%) to cefotaxime was observed, whereas the lowest (1%) was detected for tetracycline. In addition, five isolates showed resistance to imipenem with a MIC ≥ 4 µg/mL. CDDT test confirmed that five isolates were MBL-producing strains, but no bla IMP and bla VIM genes were detected. Results of this study show a very low level of resistance to imipenem in our geographical area.

CD79B limits response of diffuse large B cell lymphoma to ibrutinib.

PubMed

Kim, Joo Hyun; Kim, Won Seog; Ryu, Kyungju; Kim, Seok Jin; Park, Chaehwa

2016-01-01

Blockage of B cell receptor signaling with ibrutinib presents a promising clinical approach for treatment of B-cell malignancies. However, many patients show primary resistance to the drug or develop secondary resistance. In the current study, cDNA microarray and Western blot analyses revealed CD79B upregulation in the activated B cell-like diffuse large B-cell lymphoma (ABC-DLBCL) that display differential resistance to ibrutinib. CD79B overexpression was sufficient to induce resistance to ibrutinib and enhanced AKT and MAPK activation, indicative of an alternative mechanism underlying resistance. Conversely, depletion of CD79B sensitized primary refractory cells to ibrutinib and led to reduced phosphorylation of AKT or MAPK. Combination of the AKT inhibitor or the MAPK inhibitor with ibrutinib resulted in circumvention of both primary and acquired resistance in ABC-DLBCL. Our data collectively indicate that CD79B overexpression leading to activation of AKT/MAPK is a potential mechanism underlying primary ibrutinib resistance in ABC-DLBCL, and support its utility as an effective biomarker to predict therapeutic response to ibrutinib.

Phenotypic Antimicrobial Susceptibility Testing with Deep Learning Video Microscopy.

PubMed

Yu, Hui; Jing, Wenwen; Iriya, Rafael; Yang, Yunze; Syal, Karan; Mo, Manni; Grys, Thomas E; Haydel, Shelley E; Wang, Shaopeng; Tao, Nongjian

2018-05-15

Timely determination of antimicrobial susceptibility for a bacterial infection enables precision prescription, shortens treatment time, and helps minimize the spread of antibiotic resistant infections. Current antimicrobial susceptibility testing (AST) methods often take several days and thus impede these clinical and health benefits. Here, we present an AST method by imaging freely moving bacterial cells in urine in real time and analyzing the videos with a deep learning algorithm. The deep learning algorithm determines if an antibiotic inhibits a bacterial cell by learning multiple phenotypic features of the cell without the need for defining and quantifying each feature. We apply the method to urinary tract infection, a common infection that affects millions of people, to determine the minimum inhibitory concentration of pathogens from both bacteria spiked urine and clinical infected urine samples for different antibiotics within 30 min and validate the results with the gold standard broth macrodilution method. The deep learning video microscopy-based AST holds great potential to contribute to the solution of increasing drug-resistant infections.

Species distribution and susceptibility profile to fluconazole, voriconazole and MXP-4509 of 551 clinical yeast isolates from a Romanian multi-centre study.

PubMed

Minea, B; Nastasa, V; Moraru, R F; Kolecka, A; Flonta, M M; Marincu, I; Man, A; Toma, F; Lupse, M; Doroftei, B; Marangoci, N; Pinteala, M; Boekhout, T; Mares, M

2015-02-01

This is the first multi-centre study regarding yeast infections in Romania. The aim was to determine the aetiological spectrum and susceptibility pattern to fluconazole, voriconazole and the novel compound MXP-4509. The 551 isolates were identified using routine laboratory methods, matrix-assisted laser desorption ionisation time-of-flight mass spectrometry (MALDI-TOF MS) and DNA sequence analysis. Susceptibility testing was performed using the European Committee for Antimicrobial Susceptibility Testing (EUCAST) method and breakpoints. The yeasts originated from superficial infections (SUP, 51.5 %), bloodstream infections (BSI, 31.6 %) and deep-seated infections (DEEP, 16.9 %), from patients of all ages. Nine genera and 30 species were identified. The 20 Candida species accounted for 94.6 % of all isolates. C. albicans was the overall leading pathogen (50.5 %). Lodderomyces elongisporus is reported for the first time as a fungaemia cause in Europe. C. glabrata and Saccharomyces cerevisiae, as well as the non-Candida spp. and non-albicans Candida spp. groups, showed decreased fluconazole susceptibility (<75 %). The overall fluconazole resistance was 10.2 %. C. krusei accounted for 27 of the 56 fluconazole-resistant isolates. The overall voriconazole resistance was 2.5 % and was due mainly to C. glabrata and C. tropicalis isolates. Fluconazole resistance rates for the three categories of infection were similar to the overall value; voriconazole resistance rates differed: 4 % for BSI, 3.2 % for DEEP and 1.4 % for SUP. The antifungal activity of MXP-4509 was superior to voriconazole against C. glabrata and many fluconazole-resistant isolates. There was a large percentage of non-albicans Candida isolates. A large part of the high fluconazole resistance was not acquired but intrinsic, resulting from the high percentage of C. krusei.

Genetic diversity among pandemic 2009 influenza viruses isolated from a transmission chain

PubMed Central

2013-01-01

Background Influenza viruses such as swine-origin influenza A(H1N1) virus (A(H1N1)pdm09) generate genetic diversity due to the high error rate of their RNA polymerase, often resulting in mixed genotype populations (intra-host variants) within a single infection. This variation helps influenza to rapidly respond to selection pressures, such as those imposed by the immunological host response and antiviral therapy. We have applied deep sequencing to characterize influenza intra-host variation in a transmission chain consisting of three cases due to oseltamivir-sensitive viruses, and one derived oseltamivir-resistant case. Methods Following detection of the A(H1N1)pdm09 infections, we deep-sequenced the complete NA gene from two of the oseltamivir-sensitive virus-infected cases, and all eight gene segments of the viruses causing the remaining two cases. Results No evidence for the resistance-causing mutation (resulting in NA H275Y substitution) was observed in the oseltamivir-sensitive cases. Furthermore, deep sequencing revealed a subpopulation of oseltamivir-sensitive viruses in the case carrying resistant viruses. We detected higher levels of intra-host variation in the case carrying oseltamivir-resistant viruses than in those infected with oseltamivir-sensitive viruses. Conclusions Oseltamivir-resistance was only detected after prophylaxis with oseltamivir, suggesting that the mutation was selected for as a result of antiviral intervention. The persisting oseltamivir-sensitive virus population in the case carrying resistant viruses suggests either that a small proportion survive the treatment, or that the oseltamivir-sensitive virus rapidly re-establishes itself in the virus population after the bottleneck. Moreover, the increased intra-host variation in the oseltamivir-resistant case is consistent with the hypothesis that the population diversity of a RNA virus can increase rapidly following a population bottleneck. PMID:23587185

Use of a minimally invasive tubular retraction system for deep-seated tumors in pediatric patients.

PubMed

Recinos, Pablo F; Raza, Shaan M; Jallo, George I; Recinos, Violette Renard

2011-05-01

Microsurgical removal is the preferred treatment for most deep-seated, intraaxial tumors in the pediatric population. The feasibility of surgery as an option has improved with advances in surgical technology and technique. Tubular retractors disperse retraction forces over a greater surface area than do conventional retractors, which can lower the risk of ischemic complications. The authors describe their experience utilizing a new tubular retractor system specifically designed for cranial applications in conjunction with frameless neuronavigation. The Vycor ViewSite retractor was used in 4 pediatric patients (ages 15 months and 9, 10, and 16 years) with deep-seated intraaxial tumors. The lesions included a papillary tumor of the pineal region, a low-grade astrocytoma in the occipital lobe, a dysembryoplastic neuroepithelial tumor arising from the basal ganglia, and an intraventricular low-grade glioma. The extent of white matter damage along the surgical trajectory (based on T2 or FLAIR and diffusion restriction/apparent diffusion coefficient signals) and the extent of resection were assessed on postoperative imaging. Satisfactory resection or biopsy was achieved in all patients. A comparison of pre- and postoperative MR imaging studies revealed evidence of white matter damage along the surgical trajectory in 1 patient. None of the patients demonstrated new neurological deficits postoperatively. Obtaining surgical access to deep-seated, intraaxial tumors is challenging. In this small series of pediatric patients, the combination of the ViewSite tubular retractor and frameless neuronavigation facilitated the surgical approach. The combination of these technologies adds to the armamentarium to safely approach tumors in deep locations.

X-ray and Electrochemical Impedance Spectroscopy Diagnostic Investigations of Liquid Water in Polymer Electrolyte Membrane Fuel Cell Gas Diffusion Layers

NASA Astrophysics Data System (ADS)

Antonacci, Patrick

In this thesis, electrochemical impedance spectroscopy (EIS) and synchrotron x-ray radiography were utilized to characterize the impact of liquid water distributions in polymer electrolyte membrane fuel cell (PEMFC) gas diffusion layers (GDLs) on fuel cell performance. These diagnostic techniques were used to quantify the effects of liquid water visualized on equivalent resistances measured through EIS. The effects of varying the thickness of the microporous layer (MPL) of GDLs were studied using these diagnostic techniques. In a first study on the feasibility of this methodology, two fuel cell cases with a 100 microm-thick and a 150 microm-thick MPL were compared under constant current density operation. In a second study with 10, 30, 50, and 100 microm-thick MPLs, the liquid water in the cathode substrate was demonstrated to affect mass transport resistance, while the liquid water content in the anode (from back diffusion) affected membrane hydration, evidenced through ohmic resistance measurements.

Anti-CD22 CAR-T Therapy for CD19-refractory or Resistant Lymphoma Patients

ClinicalTrials.gov

2017-03-08

Recurrent Adult Diffuse Large Cell Lymphoma; Recurrent Follicular Lymphoma; Recurrent Mantle Cell Lymphoma; Stage III/IV Adult Diffuse Large Cell Lymphoma; Stage III/IV Follicular Lymphoma; Stage III/IV Mantle Cell Lymphoma

Laser processing of solar cells with anti-reflective coating

DOEpatents

Harley, Gabriel; Smith, David D.; Dennis, Tim; Waldhauer, Ann; Kim, Taeseok; Cousins, Peter John

2016-02-16

Contact holes of solar cells are formed by laser ablation to accommodate various solar cell designs. Use of a laser to form the contact holes is facilitated by replacing films formed on the diffusion regions with a film that has substantially uniform thickness. Contact holes may be formed to deep diffusion regions to increase the laser ablation process margins. The laser configuration may be tailored to form contact holes through dielectric films of varying thicknesses.

Diffusion tensor imaging demonstrates brainstem and cerebellar abnormalities in congenital central hypoventilation syndrome.

PubMed

Kumar, Rajesh; Macey, Paul M; Woo, Mary A; Alger, Jeffry R; Harper, Ronald M

2008-09-01

Congenital central hypoventilation syndrome (CCHS) patients show reduced breathing drive during sleep, decreased hypoxic and hypercapnic ventilatory responses, and autonomic and affective deficits, suggesting both brainstem and forebrain injuries. Forebrain damage was previously described in CCHS, but methodological limitations precluded detection of brainstem injury, a concern because genetic mutations in CCHS target brainstem autonomic nuclei. To assess brainstem and cerebellar areas, we used diffusion tensor imaging-based measures, namely axial diffusivity, reflecting water diffusion parallel to fibers, and sensitive to axonal injury, and radial diffusivity, measuring diffusion perpendicular to fibers, and indicative of myelin injury. Diffusion tensor imaging was performed in 12 CCHS and 26 controls, and axial and radial diffusivity maps were compared between groups using analysis of covariance (covariates; age and gender). Increased axial diffusivity in CCHS appeared within the lateral medulla and clusters with injury extended from the dorsal midbrain through the periaqueductal gray, raphé, and superior cerebellar decussation, ventrally to the basal-pons. Cerebellar cortex and deep nuclei, and the superior and inferior cerebellar peduncles showed increased radial diffusivity. Midbrain, pontine, and lateral medullary structures, and the cerebellum and its fiber systems are injured in CCHS, likely contributing to the characteristics found in the syndrome.

Sharp-front wave of strong magnetic field diffusion in solid metal

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xiao, Bo; Gu, Zhuo-wei; Kan, Ming-xian

When a strong magnetic field diffuses into a solid metal, if the metal's resistance possesses an abrupt rise at some critical temperature and the magnetic field strength is above some critical value, the magnetic field will diffuse into the metal in the form of a sharp-front wave. Formulas for the critical conditions under which a sharp-front magnetic diffusion wave emerges and a formula for the wave-front velocity are derived in this work.

Anomalous thermal diffusivity in underdoped YBa2Cu3O6+x

PubMed Central

Levenson-Falk, Eli M.; Ramshaw, B. J.; Bonn, D. A.; Liang, Ruixing; Hardy, W. N.; Hartnoll, Sean A.; Kapitulnik, Aharon

2017-01-01

The thermal diffusivity in the ab plane of underdoped YBCO crystals is measured by means of a local optical technique in the temperature range of 25–300 K. The phase delay between a point heat source and a set of detection points around it allows for high-resolution measurement of the thermal diffusivity and its in-plane anisotropy. Although the magnitude of the diffusivity may suggest that it originates from phonons, its anisotropy is comparable with reported values of the electrical resistivity anisotropy. Furthermore, the anisotropy drops sharply below the charge order transition, again similar to the electrical resistivity anisotropy. Both of these observations suggest that the thermal diffusivity has pronounced electronic as well as phononic character. At the same time, the small electrical and thermal conductivities at high temperatures imply that neither well-defined electron nor phonon quasiparticles are present in this material. We interpret our results through a strongly interacting incoherent electron–phonon “soup” picture characterized by a diffusion constant D∼vB2τ, where vB is the soup velocity, and scattering of both electrons and phonons saturates a quantum thermal relaxation time τ∼ℏ/kBT. PMID:28484003

Application of the marine Ex-Bz transient system for delineating near shore resistive targets

NASA Astrophysics Data System (ADS)

Levi, Eldad; Goldman, Mark

2017-09-01

Under certain conditions, multidimensional coastal effect significantly enhances relative target response of the broadside transient marine Ex-Bz system. The effect is caused by a redistribution of the induced currents between the resistive target and the sea bottom compared to that existing in a 1-D geometry. As a result, the effect strongly depends on specific geoelectric conditions in the near-shore environment. The first study of the effect in the Mediterranean coast of central Israel was addressing shallow groundwater problem under specific geoelectric, hydrogeological and geomorphological conditions. Under different conditions (e.g. deep targets and sharp near-shore bathymetry), the influence of the effect on target response might be significantly different. More general analysis carried out in this study comprises various geoelectric scenarios that include both shallow and deep resistive targets at different distances from the shore line as well as various geometries of the target and the near-shore bathymetry. The study includes three major exploration aspects of the system, namely signal detectability, lateral and vertical resolution. Taking into account poor lateral resolution of the classical frequency domain CSEM and the limited application in shallow sea, the described broadside transient Ex-Bz system might represent a desired alternative for delineating shallow and deep resistive targets in transition zone.

A diffusion source for sodium and potassium in the atmospheres of Mercury and the moon

NASA Technical Reports Server (NTRS)

Sprague, Ann L.

1990-01-01

Deep grain-boundary diffusion and regolith diffusion through a fractured crust and regolith can account not only for the Na/K ratios observed in the Mercurian and lunar atmospheres, but the large Na abundance enhancement of Mercury over lunar levels. A hot component of Na and K at Mercury is noted to be smaller in proportion to the total abundances of these two constituents than at the moon; this hot component is consistent with a population of meteoritic substances similar to lunar ones, as well as with a surface composition which has undergone no greater K depletion than that of the moon.

Phonon cross-plane transport and thermal boundary resistance: effect of heat source size and thermal boundary resistance on phonon characteristics

NASA Astrophysics Data System (ADS)

Ali, H.; Yilbas, B. S.

2016-09-01

Phonon cross-plane transport across silicon and diamond thin films pair is considered, and thermal boundary resistance across the films pair interface is examined incorporating the cut-off mismatch and diffusive mismatch models. In the cut-off mismatch model, phonon frequency mismatch for each acoustic branch is incorporated across the interface of the silicon and diamond films pair in line with the dispersion relations of both films. The frequency-dependent and transient solution of the Boltzmann transport equation is presented, and the equilibrium phonon intensity ratios at the silicon and diamond film edges are predicted across the interface for each phonon acoustic branch. Temperature disturbance across the edges of the films pair is incorporated to assess the phonon transport characteristics due to cut-off and diffusive mismatch models across the interface. The effect of heat source size, which is allocated at high-temperature (301 K) edge of the silicon film, on the phonon transport characteristics at the films pair interface is also investigated. It is found that cut-off mismatch model predicts higher values of the thermal boundary resistance across the films pair interface as compared to that of the diffusive mismatch model. The ratio of equilibrium phonon intensity due to the cut-off mismatch over the diffusive mismatch models remains >1 at the silicon edge, while it becomes <1 at the diamond edge for all acoustic branches.

Development of variable LRFD \\0x03C6 factors for deep foundation design due to site variability.

DOT National Transportation Integrated Search

2012-04-01

The current design guidelines of Load and Resistance Factor Design (LRFD) specifies constant values : for deep foundation design, based on analytical method selected and degree of redundancy of the pier. : However, investigation of multiple sites in ...

Step-off, vertical electromagnetic responses of a deep resistivity layer buried in marine sediments

NASA Astrophysics Data System (ADS)

Jang, Hangilro; Jang, Hannuree; Lee, Ki Ha; Kim, Hee Joon

2013-04-01

A frequency-domain, marine controlled-source electromagnetic (CSEM) method has been applied successfully in deep water areas for detecting hydrocarbon (HC) reservoirs. However, a typical technique with horizontal transmitters and receivers requires large source-receiver separations with respect to the target depth. A time-domain EM system with vertical transmitters and receivers can be an alternative because vertical electric fields are sensitive to deep resistive layers. In this paper, a time-domain modelling code, with multiple source and receiver dipoles that are finite in length, has been written to investigate transient EM problems. With the use of this code, we calculate step-off responses for one-dimensional HC reservoir models. Although the vertical electric field has much smaller amplitude of signal than the horizontal field, vertical currents resulting from a vertical transmitter are sensitive to resistive layers. The modelling shows a significant difference between step-off responses of HC- and water-filled reservoirs, and the contrast can be recognized at late times at relatively short offsets. A maximum contrast occurs at more than 4 s, being delayed with the depth of the HC layer.

Neurostimulation for Drug-Resistant Epilepsy

PubMed Central

DeGiorgio, Christopher M.; Krahl, Scott E.

2013-01-01

Purpose of Review: The purpose of this review is to provide an evidence-based update on the neurostimulation options available for patients with drug-resistant epilepsy in the United States and in European countries. Recent Findings: The field of neurostimulation for epilepsy has grown dramatically since 1997, when vagus nerve stimulation became the first device to be approved for epilepsy by the US Food and Drug Administration (FDA). New data from recently completed randomized controlled trials are available for deep brain stimulation of the anterior thalamus, responsive neurostimulation, and trigeminal nerve stimulation. Although vagus nerve stimulation is the only device currently approved in the United States, deep brain stimulation and responsive neurostimulation devices are awaiting FDA approval. Deep brain stimulation, trigeminal nerve stimulation, and transcutaneous vagus nerve stimulation are now approved for epilepsy in the European Union. In this article, the mechanisms of action, safety, and efficacy of new neurostimulation devices are reviewed, and the key advantages and disadvantages of each are discussed. Summary: The exponential growth of the field of neuromodulation for epilepsy is an exciting development; these new devices provide physicians with new options for patients with drug-resistant epilepsy. PMID:23739108

The effects of lithium counterdoping on radiation damage and annealing in n(+)p silicon solar cells

NASA Technical Reports Server (NTRS)

Weinberg, I.; Brandhorst, H. W., Jr.; Mehta, S.; Swartz, C. K.

1984-01-01

Boron-doped silicon n(+)p solar cells were counterdoped with lithium by ion implantation and the resultant n(+)p cells irradiated by 1 MeV electrons. Performance parameters were determined as a function of fluence and a deep level transient spectroscopy (DLTS) study was conducted. The lithium counterdoped cells exhibited significantly increased radiation resistance when compared to boron doped control cells. Isochronal annealing studies of cell performance indicate that significant annealing occurs at 100 C. Isochronal annealing of the deep level defects showed a correlation between a single defect at E sub v + 0.43 eV and the annealing behavior of short circuit current in the counterdoped cells. The annealing behavior was controlled by dissociation and recombination of this defect. The DLTS studies showed that counterdoping with lithium eliminated three deep level defects and resulted in three new defects. The increased radiation resistance of the counterdoped cells is due to the interaction of lithium with oxygen, single vacancies and divacancies. The lithium-oxygen interaction is the most effective in contributing to the increased radiation resistance.

Adaptive focus for deep tissue using diffuse backscatter

NASA Astrophysics Data System (ADS)

Kress, Jeremy; Pourrezaei, Kambiz

2014-02-01

A system integrating high density diffuse optical imaging with adaptive optics using MEMS for deep tissue interaction is presented. In this system, a laser source is scanned over a high density fiber bundle using Digital Micromirror Device (DMD) and channeled to a tissue phantom. Backscatter is then collected from the tissue phantom by a high density fiber array of different fiber type and channeled to CMOS sensor for image acquisition. Intensity focus is directly verified using a second CMOS sensor which measures intensity transmitted though the tissue phantom. A set of training patterns are displayed on the DMD and backscatter is numerically fit to the transmission intensity. After the training patterns are displayed, adaptive focus is performed using only the backscatter and fitting functions. Additionally, tissue reconstruction and prediction of interference focusing by photoacoustic and optical tomographic methods is discussed. Finally, potential NIR applications such as in-vivo adaptive neural photostimulation and cancer targeting are discussed.

Molecular and ionic diffusion in aqueous - deep eutectic solvent mixtures: probing inter-molecular interactions using PFG NMR.

PubMed

D'Agostino, Carmine; Gladden, Lynn F; Mantle, Mick D; Abbott, Andrew P; Ahmed, Essa I; Al-Murshedi, Azhar Y M; Harris, Robert C

2015-06-21

Pulsed field gradient (PFG) NMR has been used to probe self-diffusion of molecular and ionic species in aqueous mixtures of choline chloride (ChCl) based deep eutectic solvents (DESs), in order to elucidate the effect of water on motion and inter-molecular interactions between the different species in the mixtures, namely the Ch(+) cation and hydrogen bond donor (HBD). The results reveal an interesting and complex behaviour of such mixtures at a molecular level. In general, it is observed that the hydroxyl protons ((1)H) of Ch(+) and the hydrogen bond donor have diffusion coefficients significantly different from those measured for their parent molecules when water is added. This indicates a clear and significant change in inter-molecular interactions. In aqueous Ethaline, the hydroxyl species of Ch(+) and HBD show a stronger interaction with water as water is added to the system. In the case of Glyceline, water has little effect on both hydroxyl proton diffusion of Ch(+) and HBD. In Reline, it is likely that water allows the formation of small amounts of ammonium hydroxide. The most surprising observation is from the self-diffusion of water, which is considerably higher that expected from a homogeneous liquid. This leads to the conclusion that Reline and Glyceline form mixtures that are inhomogeneous at a microscopic level despite the hydrophilicity of the salt and HBD. This work shows that PFG NMR is a powerful tool to elucidate both molecular dynamics and inter-molecular interactions in complex liquid mixtures, such as the aqueous DES mixtures.

Measurement of effective bulk and contact resistance of gas diffusion layer under inhomogeneous compression - Part I: Electrical conductivity

NASA Astrophysics Data System (ADS)

Vikram, Ajit; Chowdhury, Prabudhya Roy; Phillips, Ryan K.; Hoorfar, Mina

2016-07-01

This paper describes a measurement technique developed for the determination of the effective electrical bulk resistance of the gas diffusion layer (GDL) and the contact resistance distribution at the interface of the GDL and the bipolar plate (BPP). The novelty of this study is the measurement and separation of the bulk and contact resistance under inhomogeneous compression, occurring in an actual fuel cell assembly due to the presence of the channels and ribs on the bipolar plates. The measurement of the electrical contact resistance, contributing to nearly two-third of the ohmic losses in the fuel cell assembly, shows a non-linear distribution along the GDL/BPP interface. The effective bulk resistance of the GDL under inhomogeneous compression showed a decrease of nearly 40% compared to that estimated for homogeneous compression at different compression pressures. Such a decrease in the effective bulk resistance under inhomogeneous compression could be due to the non-uniform distribution of pressure under the ribs and the channels. This measurement technique can be used to identify optimum GDL, BPP and channel-rib structures based on minimum bulk and contact resistances measured under inhomogeneous compression.

Relative Roles of Gap Junction Channels and Cytoplasm in Cell-to-Cell Diffusion of Fluorescent Tracers

NASA Astrophysics Data System (ADS)

Safranyos, Richard G. A.; Caveney, Stanley; Miller, James G.; Petersen, Nils O.

1987-04-01

Intercellular (tissue) diffusion of molecules requires cytoplasmic diffusion and diffusion through gap junctional (or cell-to-cell) channels. The rates of tissue and cytoplasmic diffusion of fluorescent tracers, expressed as an effective diffusion coefficient, De, and a cytoplasmic diffusion coefficient, Dcyt, have been measured among the developing epidermal cells of a larval beetle, Tenebrio molitor L., to determine the contribution of the junctional channels to intercellular diffusion. Tracer diffusion was measured by injecting fluorescent tracers into cells and quantitating the rate of subsequent spread into adjacent cells. Cytoplasmic diffusion was determined by fluorescence photobleaching. These experiments show that gap junctional channels constitute approximately 70-80% of the total cell-to-cell resistance to the diffusion of organic tracers at high concentrations in this tissue. At low concentrations, however, the binding of tracer to cytoplasm slows down the cytoplasmic diffusion, which may limit intercellular diffusion.

Diffusive retention of atmospheric gases in chert

NASA Astrophysics Data System (ADS)

Pettitt, E.; Cherniak, D. J.; Watson, E. B.; Schaller, M. F.

2016-12-01

Throughout Earth's history, the volatile contents (N2, CO2, Ar) of both deep and shallow terrestrial reservoirs has been dynamic. Volatiles are important chemical constituents because they play a significant role in regulating Earth's climate, mediating the evolution of complex life, and controlling the properties of minerals and rocks. Estimating levels of atmospheric volatiles in the deep geological past requires interrogation of materials that have acquired and retained a chemical memory from that time. Cherts have the potential to trap atmospheric components during formation and later release those gases for analysis in the laboratory. However, cherts have been underexploited in this regard, partly because their ability to retain a record of volatile components has not been adequately evaluated. Before cherts can be reliably used as indicators of past levels of major atmospheric gases, it is crucial that we understand the diffusive retentiveness of these cryptocrystalline silica phases. As the first step toward quantifying the diffusivity and solubility of carbon dioxide and nitrogen in chert, we have performed 1-atmosphere diffusive-uptake experiments at temperatures up to 450°C. Depth profiles of in-diffusing gases are measured by nuclear reaction analysis (NRA) to help us understand the molecular-scale transport of volatiles and thus the validity of using chert-bound volatiles to record information about Earth history. Data collected to date suggest that at least some cherts are ideal storage containers and can retain volatiles for a geologically long time. In addition to these diffusion experiments, preliminary online-crush fast-scan measurements using a quadrupole mass spectrometer indicate that atmospheric volatiles are released upon crushing various chert samples. By coupling such volatile-release measurements made by mass spectrometry with diffusion experiments, we are uniquely able to address the storage and fidelity of volatiles bound in crustal materials; an important step toward understanding atmospheric evolution over geologic history.

Recipes for lateral spin transport between magnetic contacts, advantage of carbon-based materials.

NASA Astrophysics Data System (ADS)

Fert, Albert

2010-03-01

After the presentation of magneto-transport results [1] on metallic carbon nanotubes (CNT) between LSMO electrodes (MR 60-70%, [VAP -- VP] 60mV), I will discuss the general problem of spin transport in a nonmagnetic lateral channel between spin-polarized contacts in both the diffusive and ballistic regimes. In the diffusive regime, a treatment by the classical drift-diffusion equations applied to a multi-terminal structure is used to calculate what can be expected for the output signal with local or non-local voltage probes. A general result is that the output signal (δR = δV/I where δV is the local or non-local output voltage), directly related to the spin accumulation splitting in the channel, scales with the smallest of the relevant spin and interfaces resistances. In the best situation, that is with only tunnel contacts having the same (large) resistance RT and separated by less than the spin diffusion length (λ) in a lateral channel limited to the zone of the contacts, the signal δR increases in proportion of RT as long as the dwell time is smaller than the spin lifetime. δR can be thus much larger than the spin resistance of the channel (product of its resistivity by the ratio λ/section ). This explain why, in the experiments of Ref.[1] on CNT, δR can be as large as 90 Mφ, that is of the order of the tunnel contact resistances and much larger than the spin resistance of the CNT (smaller signals in experiments with CNT or graphene are often due the leak of spin accumulation in lateral channels extending too far outside the contacts). The relative disadvantage for semiconductors comes from the too long dwell time due to much smaller electron velocities than in metallic CNTs (and graphene). We will conclude by a similar analysis of the ballistic regime and a discussion of experiments with graphene. [4pt] [1] Hueso et al, Nature 445, 410 (2007).

Dual-wavelength photo-Hall effect spectroscopy of deep levels in high resistive CdZnTe with negative differential photoconductivity

NASA Astrophysics Data System (ADS)

Musiienko, A.; Grill, R.; Moravec, P.; Korcsmáros, G.; Rejhon, M.; Pekárek, J.; Elhadidy, H.; Šedivý, L.; Vasylchenko, I.

2018-04-01

Photo-Hall effect spectroscopy was used in the study of deep levels in high resistive CdZnTe. The monochromator excitation in the photon energy range 0.65-1.77 eV was complemented by a laser diode high-intensity excitation at selected photon energies. A single sample characterized by multiple unusual features like negative differential photoconductivity and anomalous depression of electron mobility was chosen for the detailed study involving measurements at both the steady and dynamic regimes. We revealed that the Hall mobility and photoconductivity can be both enhanced and suppressed by an additional illumination at certain photon energies. The anomalous mobility decrease was explained by an excitation of the inhomogeneously distributed deep level at the energy Ev + 1.0 eV, thus enhancing potential non-uniformities. The appearance of negative differential photoconductivity was interpreted by an intensified electron occupancy of that level by a direct valence band-to-level excitation. Modified Shockley-Read-Hall theory was used for fitting experimental results by a model comprising five deep levels. Properties of the deep levels and their impact on the device performance were deduced.

Characterization of iron in silicon by low-temperature photoluminescence and deep-level transient spectroscopy

NASA Astrophysics Data System (ADS)

Nakamura, Minoru; Murakami, Susumu; Udono, Haruhiko

2018-03-01

We investigate the relationship between the intensity of band-edge (BDE) photoluminescence (PL) from 10 to 70 K and the concentration of iron diffused in boron-doped p-type silicon. Because of the nonradiative recombination activity of the interstitial iron-boron complex (FeiB center), the BDE-PL intensity at each temperature varies distinctively and systematically with the iron concentration, which means that this method has the potential to make the accurate measurements of a wide range of interstitial iron concentrations in silicon. The iron precipitates formed in the bulk and/or at the surface are found to exert much weaker recombination activity for excess carriers than FeiB center by exploiting both PL and deep-level transient spectroscopy (DLTS) measurements. The unexpected enhancement in BDE-PL intensity from iron-diffused silicon between 20 and 50 K is attributed to the passivation of the Si-oxide/Si interface by iron. For the samples diffused with trace amounts of iron, the iron concentration within 20 μm of the surface is significantly greater than that in the bulk, as measured by DLTS. This result is tentatively attributed to the affinity of iron with the Si-oxide.

Heterotrophic Proteobacteria in the vicinity of diffuse hydrothermal venting.

PubMed

Meier, Dimitri V; Bach, Wolfgang; Girguis, Peter R; Gruber-Vodicka, Harald R; Reeves, Eoghan P; Richter, Michael; Vidoudez, Charles; Amann, Rudolf; Meyerdierks, Anke

2016-12-01

Deep-sea hydrothermal vents are highly dynamic habitats characterized by steep temperature and chemical gradients. The oxidation of reduced compounds dissolved in the venting fluids fuels primary production providing the basis for extensive life. Until recently studies of microbial vent communities have focused primarily on chemolithoautotrophic organisms. In our study, we targeted the change of microbial community compositions along mixing gradients, focusing on distribution and capabilities of heterotrophic microorganisms. Samples were retrieved from different venting areas within the Menez Gwen hydrothermal field, taken along mixing gradients, including diffuse fluid discharge points, their immediate surroundings and the buoyant parts of hydrothermal plumes. High throughput 16S rRNA gene amplicon sequencing, fluorescence in situ hybridization, and targeted metagenome analysis were combined with geochemical analyses. Close to diffuse venting orifices dominated by chemolithoautotrophic Epsilonproteobacteria, in areas where environmental conditions still supported chemolithoautotrophic processes, we detected microbial communities enriched for versatile heterotrophic Alpha- and Gammaproteobacteria. The potential for alkane degradation could be shown for several genera and yet uncultured clades. We propose that hotspots of chemolithoautotrophic life support a 'belt' of heterotrophic bacteria significantly different from the dominating oligotrophic microbiota of the deep sea. © 2016 Society for Applied Microbiology and John Wiley & Sons Ltd.

Diffusive counter dispersion of mass in bubbly media.

PubMed

Goldobin, Denis S; Brilliantov, Nikolai V

2011-11-01

We consider a liquid bearing gas bubbles in a porous medium. When gas bubbles are immovably trapped in a porous matrix by surface-tension forces, the dominant mechanism of transfer of gas mass becomes the diffusion of gas molecules through the liquid. Essentially, the gas solution is in local thermodynamic equilibrium with vapor phase all over the system, i.e., the solute concentration equals the solubility. When temperature and/or pressure gradients are applied, diffusion fluxes appear and these fluxes are faithfully determined by the temperature and pressure fields, not by the local solute concentration, which is enslaved by the former. We derive the equations governing such systems, accounting for thermodiffusion and gravitational segregation effects, which are shown not to be neglected for geological systems-marine sediments, terrestrial aquifers, etc. The results are applied for the treatment of non-high-pressure systems and real geological systems bearing methane or carbon dioxide, where we find a potential possibility of the formation of gaseous horizons deep below a porous medium surface. The reported effects are of particular importance for natural methane hydrate deposits and the problem of burial of industrial production of carbon dioxide in deep aquifers.

Retrieval of optical properties of skin from measurement and modeling the diffuse reflectance

NASA Astrophysics Data System (ADS)

Douven, Lucien F. A.; Lucassen, Gerald W.

2000-06-01

We present results on the retrieval of skin optical properties obtained by fitting of measurements of the diffuse reflectance of human skin. Reflectance spectra are simulated using an analytical model based on the diffusion approximation. This model is implemented in a simplex fit routine. The skin optical model used consists of five layers representing epidermis, capillary blood plexus, dermis, deep blood plexus and hypodermis. The optical properties of each layer are assumed homogeneously distributed. The main optical absorbers included are melanin in epidermis and blood. The experimental setup consists of a HP photospectrometer equipped with a remote fiber head. Total reflectance spectra were measured in the 400 - 820 nm wavelength range on the volar underarm of 19 volunteers under various conditions influencing the blood content and oxygenation degree. Changes in the reflectance spectra were observed. Using the fit routine changes in blood content in the capillary blood plexus and in the deep blood plexus could be quantified. These showed different influences on the total reflectance. The method can be helpful to quantitatively assess changes in skin color appearance such as occurs in the treatment of port wine stains, blanching, skin irritation and tanning.

Scaling oxygen microprofiles at the sediment interface of deep stratified waters

NASA Astrophysics Data System (ADS)

Schwefel, Robert; Hondzo, Miki; Wüest, Alfred; Bouffard, Damien

2017-02-01

Dissolved oxygen microprofiles at the sediment-water interface of Lake Geneva were measured concurrently with velocities 0.25 to 2 m above the sediment. The measurements and scaling analyses indicate dissolved oxygen fluctuations and turbulent fluxes in exceedance of molecular diffusion in the proximity of the sediment-water interface. The measurements allowed the parameterization of the turbulent diffusion as a function of the dimensionless height above the sediment and the turbulence above the sediment-water interface. Turbulent diffusion depended strongly on the friction velocity and differed from formulations reported in the literature that are based on concepts of turbulent and developed wall-bounded flows. The dissolved oxygen microprofiles and proposed parameterization of turbulent diffusion enable a foundation for the similarity scaling of oxygen microprofiles in proximity to the sediment. The proposed scaling allows the estimation of diffusive boundary layer thickness, oxygen flux, and oxygen microprofile distribution in the near-sediment boundary layer.

Temperature dependence of copper diffusion in different thickness amorphous tungsten/tungsten nitride layer

NASA Astrophysics Data System (ADS)

Asgary, Somayeh; Hantehzadeh, Mohammad Reza; Ghoranneviss, Mahmood

2017-11-01

The amorphous W/WN films with various thickness (10, 30 and 40 nm) and excellent thermal stability were successfully prepared on SiO2/Si substrate with evaporation and reactive evaporation method. The W/WN bilayer has technological importance because of its low resistivity, high melting point, and good diffusion barrier properties between Cu and Si. The thermal stability was evaluated by X-ray diffractometer (XRD) and Scanning Electron Microscope (SEM). In annealing process, the amorphous W/WN barrier crystallized and this phenomenon is supposed to be the start of Cu atoms diffusion through W/WN barrier into Si. With occurrence of the high-resistive Cu3Si phase, the W/WN loses its function as a diffusion barrier. The primary mode of Cu diffusion is the diffusion through grain boundaries that form during heat treatments. The amorphous structure with optimum thickness is the key factor to achieve a superior diffusion barrier characteristic. The results show that the failure temperature increased by increasing the W/WN film thickness from 10 to 30 nm but it did not change by increasing the W/WN film thickness from 30 to 40 nm. It is found that the 10 and 40 nm W/WN films are good diffusion barriers at least up to 800°C while the 30 nm W/WN film shows superior properties as a diffusion barrier, but loses its function as a diffusion barrier at about 900°C (that is 100°C higher than for 10 and 40 nm W/WN films).

Comparison of results of fluconazole disk diffusion testing for Candida species with results from a central reference laboratory in the ARTEMIS global antifungal surveillance program.

PubMed

Pfaller, M A; Hazen, K C; Messer, S A; Boyken, L; Tendolkar, S; Hollis, R J; Diekema, D J

2004-08-01

The accuracy of antifungal susceptibility tests is important for accurate resistance surveillance and for the clinical management of patients with serious infections. Our main objective was to compare the results of fluconazole disk diffusion testing of Candida spp. performed by ARTEMIS participating centers with disk diffusion and MIC results obtained by the central reference laboratory. A total of 2,949 isolates of Candida spp. were tested by NCCLS disk diffusion and reference broth microdilution methods in the central reference laboratory. These results were compared to the results of disk diffusion testing performed in the 54 participating centers. All tests were performed and interpreted following NCCLS recommendations. Overall categorical agreement between participant disk diffusion test results and reference laboratory MIC results was 87.4%, with 0.2% very major errors (VME) and 3.3% major errors (ME). The categorical agreement between the disk diffusion test results obtained in the reference laboratory with the MIC test results was similar: 92.8%. Likewise, good agreement was observed between participant disk diffusion test results and reference laboratory disk diffusion test results: 90.4%, 0.4% VME, and 3.4% ME. The disk diffusion test was especially reliable in detecting those isolates of Candida spp. that were characterized as resistant by reference MIC testing. External quality assurance data obtained by surveillance programs such as the ARTEMIS Global Antifungal Surveillance Program ensure the generation of useful surveillance data and result in the continued improvement of antifungal susceptibility testing practices.

Evaluation of resistivity meters for concrete quality assurance : [research summary].

DOT National Transportation Integrated Search

2015-07-01

This research evaluated a series of MoDOT : concrete mixtures to verify existing : relationships between surface resistivity (SR), : rapid chloride permeability (RCP), chloride ion : diffusion, and the AASHTO penetrability : classes. The research als...

Evaluation of resistivity meters for concrete quality assurance.

DOT National Transportation Integrated Search

2015-06-01

This research evaluated a series of MoDOT concrete mixtures to verify existing relationships between surface resistivity (SR), rapid : chloride permeability (RCP), chloride ion diffusion, and the AASHTO penetrability classes. The research also perfor...

How Diffusivity, Thermocline and Incident Light Intensity Modulate the Dynamics of Deep Chlorophyll Maximum in Tyrrhenian Sea

PubMed Central

Valenti, Davide; Denaro, Giovanni; Spagnolo, Bernardo; Conversano, Fabio; Brunet, Christophe

2015-01-01

During the last few years theoretical works have shed new light and proposed new hypotheses on the mechanisms which regulate the spatio-temporal behaviour of phytoplankton communities in marine pelagic ecosystems. Despite this, relevant physical and biological issues, such as effects of the time-dependent mixing in the upper layer, competition between groups, and dynamics of non-stationary deep chlorophyll maxima, are still open questions. In this work, we analyze the spatio-temporal behaviour of five phytoplankton populations in a real marine ecosystem by using a one-dimensional reaction-diffusion-taxis model. The study is performed, taking into account the seasonal variations of environmental variables, such as light intensity, thickness of upper mixed layer and profiles of vertical turbulent diffusivity, obtained starting from experimental findings. Theoretical distributions of phytoplankton cell concentration was converted in chlorophyll concentration, and compared with the experimental profiles measured in a site of the Tyrrhenian Sea at four different times (seasons) of the year, during four different oceanographic cruises. As a result we find a good agreement between theoretical and experimental distributions of chlorophyll concentration. In particular, theoretical results reveal that the seasonal changes of environmental variables play a key role in the phytoplankton distribution and determine the properties of the deep chlorophyll maximum. This study could be extended to other marine ecosystems to predict future changes in the phytoplankton biomass due to global warming, in view of devising strategies to prevent the decline of the primary production and the consequent decrease of fish species. PMID:25629963

A promising tool for subsurface permafrost mapping-An application of airborne geophysics from the Yukon River Basin, Alaska

USGS Publications Warehouse

Abraham, Jared E.

2011-01-01

In the area of Fort Yukon, the AEM survey shows elevated resistivities extending to depth, likely indicative of thick permafrost. This depth corresponds well to observations from a borehole drilled in the area in the late 1990s, which detected permafrost to a depth of about 100 meters (Clark and others, 2009). In contrast to the area of Fort Yukon, the Yukon River and its floodplain are not associated with deep resistive sediments, suggesting a lack of deep permafrost, at least within the depth range of the AEM mapping (fig. 3).

The Effect of Deep Brain Stimulation on the Speech Motor System

ERIC Educational Resources Information Center

Mücke, Doris; Becker, Johannes; Barbe, Michael T.; Meister, Ingo; Liebhart, Lena; Roettger, Timo B.; Dembek, Till; Timmermann, Lars; Grice, Martine

2014-01-01

Purpose: Chronic deep brain stimulation of the nucleus ventralis intermedius is an effective treatment for individuals with medication-resistant essential tremor. However, these individuals report that stimulation has a deleterious effect on their speech. The present study investigates one important factor leading to these effects: the…

The effect of diffusion induced lattice stress on the open-circuit voltage in silicon solar cells

NASA Technical Reports Server (NTRS)

Weizer, V. G.; Godlewski, M. P.

1984-01-01

It is demonstrated that diffusion induced stresses in low resistivity silicon solar cells can significantly reduce both the open-circuit voltage and collection efficiency. The degradation mechanism involves stress induced changes in both the minority carrier mobility and the diffusion length. Thermal recovery characteristics indicate that the stresses are relieved at higher temperatures by divacancy flow (silicon self diffusion). The level of residual stress in as-fabricated cells was found to be negligible in the cells tested.

The faint galaxy contribution to the diffuse extragalactic background light

NASA Technical Reports Server (NTRS)

Cole, Shaun; Treyer, Marie-Agnes; Silk, Joseph

1992-01-01

Models of the faint galaxy contribution to the diffuse extragalactic background light are presented, which are consistent with current data on faint galaxy number counts and redshifts. The autocorrelation function of surface brightness fluctuations in the extragalactic diffuse light is predicted, and the way in which these predictions depend on the cosmological model and assumptions of biasing is determined. It is confirmed that the recent deep infrared number counts are most compatible with a high density universe (Omega-0 is approximately equal to 1) and that the steep blue counts then require an extra population of rapidly evolving blue galaxies. The faintest presently detectable galaxies produce an interesting contribution to the extragalactic diffuse light, and still fainter galaxies may also produce a significant contribution. These faint galaxies still only produce a small fraction of the total optical diffuse background light, but on scales of a few arcminutes to a few degrees, they produce a substantial fraction of the fluctuations in the diffuse light.

Coronal ``Wave'': Magnetic Footprint of a Coronal Mass Ejection?

NASA Astrophysics Data System (ADS)

Attrill, Gemma D. R.; Harra, Louise K.; van Driel-Gesztelyi, Lidia; Démoulin, Pascal

2007-02-01

We investigate the properties of two ``classical'' EUV Imaging Telescope (EIT) coronal waves. The two source regions of the associated coronal mass ejections (CMEs) possess opposite helicities, and the coronal waves display rotations in opposite senses. We observe deep core dimmings near the flare site and also widespread diffuse dimming, accompanying the expansion of the EIT wave. We also report a new property of these EIT waves, namely, that they display dual brightenings: persistent ones at the outermost edge of the core dimming regions and simultaneously diffuse brightenings constituting the leading edge of the coronal wave, surrounding the expanding diffuse dimmings. We show that such behavior is consistent with a diffuse EIT wave being the magnetic footprint of a CME. We propose a new mechanism where driven magnetic reconnections between the skirt of the expanding CME magnetic field and quiet-Sun magnetic loops generate the observed bright diffuse front. The dual brightenings and the widespread diffuse dimming are identified as innate characteristics of this process.

Spintronics: spin accumulation in mesoscopic systems.

PubMed

Johnson, Mark

2002-04-25

In spintronics, in which use is made of the spin degree of freedom of the electron, issues concerning electrical spin injection and detection of electron spin diffusion are fundamentally important. Jedema et al. describe a magneto-resistance study in which they claim to have observed spin accumulation in a mesoscopic copper wire, but their one-dimensional model ignores two-dimensional spin-diffusion effects, which casts doubt on their analysis. A two-dimensional vector formalism of spin transport is called for to model spin-injection experiments, and the identification of spurious background resistance effects is crucial.

Characterization of water molecular state in in-vivo thick tissues using diffuse optical spectroscopic imaging

NASA Astrophysics Data System (ADS)

Chung, So Hyun

Structural changes in water molecules are related to physiological, anatomical and pathological properties of tissues. Near infrared (NIR) optical absorption methods are sensitive to water; however, detailed characterization of water in thick tissues is difficult to achieve because subtle spectral shifts can be obscured by multiple light scattering. In the NIR, a water absorption peak is observed around 975 nm. The precise NIR peak's shape and position are highly sensitive to water molecular disposition. A bound water index (BWI) was developed that quantifies the spectral shift and shape changes observed in tissue water absorption spectra measured by broadband diffuse optical spectroscopic imaging (DOSI). DOSI quantitatively measures light absorption and scattering spectra in cm-deep tissues and therefore reveals bound water spectral shifts. BWI as a water state index was validated by comparing broadband DOSI to MRI and a conductivity cell using bound water phantoms. Non-invasive BWI measurements of malignant and normal tissues in 18 subjects showed a significantly higher fraction of free water in malignant tissues (p<0.0001) compared to normal tissues. BWI showed potential as a prognostic index based on high correlations with tumor grade and size. An algorithm for absolute temperature measurements in deep tissues was developed based on resolving opposing effects of water vibrational frequency shifts due to macromolecular binding. DOSI measures absolute temperature with a difference of 1.1+/-0.91°C from a thermistor. Deep tissue temperature measured in forearms during cold-stress was consistent with previously reported invasively-measured deep tissue temperature. Finally, the BWI was compared to Apparent Diffusion Coefficient (ADC) of diffusion weighted MRI in 9 breast cancer patients. The BWI and ADC correlated (R=0.8, p=<0.01) and both parameters decreased with increasing bulk water content in cancer tissues. Although BWI and ADC are positively correlated in vivo, BWI appears to be more sensitive to free water in the extracellular matrix while ADC reflects increased tumor cellularity. The relationship between ADC, BWI and bulk water concentration suggests that both parameters have potential for assessing tumor histopathological grade. My results confirm the importance of water as a critical tissue component that can potentially provide unique insight into the molecular pathophysiology of cancer.

Thermal conductivity of a graphite bipolar plate (BPP) and its thermal contact resistance with fuel cell gas diffusion layers: Effect of compression, PTFE, micro porous layer (MPL), BPP out-of-flatness and cyclic load

NASA Astrophysics Data System (ADS)

Sadeghifar, Hamidreza; Djilali, Ned; Bahrami, Majid

2015-01-01

This paper reports on measurements of thermal conductivity of a graphite bipolar plate (BPP) as a function of temperature and its thermal contact resistance (TCR) with treated and untreated gas diffusion layers (GDLs). The thermal conductivity of the BPP decreases with temperature and its thermal contact resistance with GDLs, which has been overlooked in the literature, is found to be dominant over a relatively wide range of compression. The effects of PTFE loading, micro porous layer (MPL), compression, and BPP out-of-flatness are also investigated experimentally. It is found that high PTFE loadings, MPL and even small BPP out-of-flatness increase the BPP-GDL thermal contact resistance dramatically. The paper also presents the effect of cyclic load on the total resistance of a GDL-BPP assembly, which sheds light on the behavior of these materials under operating conditions in polymer electrolyte membrane fuel cells.

Deep Impurity Band Silicon for Subbandgap Photodetection

DTIC Science & Technology

2014-05-02

Standard Form 298 (Rev 8/98) Prescribed by ANSI Std. Z39.18 W911NF-12-1-0196 617-495-9884 Final Report 62016- EL -II.1 a. REPORT 14. ABSTRACT 16...durations were then compared with simulated durations produced by a numerical solution of the 1- Fig. 1: Ab initio calculations of band struc- ture of...using a 1-D finite el - ement model of solute diffusion during pulsed-laser melting to determine the diffusive velocity, vdiff, characterizing the

Laser process and corresponding structures for fabrication of solar cells with shunt prevention dielectric

DOE Office of Scientific and Technical Information (OSTI.GOV)

Harley, Gabriel; Smith, David D.; Dennis, Tim

Contact holes of solar cells are formed by laser ablation to accommodate various solar cell designs. Use of a laser to form the contact holes is facilitated by replacing films formed on the diffusion regions with a film that has substantially uniform thickness. Contact holes may be formed to deep diffusion regions to increase the laser ablation process margins. The laser configuration may be tailored to form contact holes through dielectric films of varying thicknesses.

Process and structures for fabrication of solar cells with laser ablation steps to form contact holes

DOEpatents

Harley, Gabriel; Smith, David D; Dennis, Tim; Waldhauer, Ann; Kim, Taeseok; Cousins, Peter John

2013-11-19

Contact holes of solar cells are formed by laser ablation to accomodate various solar cell designs. Use of a laser to form the contact holes is facilitated by replacing films formed on the diffusion regions with a film that has substantially uniform thickness. Contact holes may be formed to deep diffusion regions to increase the laser ablation process margins. The laser configuration may be tailored to form contact holes through dielectric films of varying thickness.

Development of Less Toxic Treatment Strategies for Metastatic and Drug-Resistant Breast Cancer Using Noninvasive Optical Monitoring

DTIC Science & Technology

2016-09-01

AWARD NUMBER: W81XWH-15-1-0070 TITLE: Development of Less Toxic Treatment Strategies for Metastatic and Drug- Resistant Breast Cancer Using...0070 Development of Less Toxic Treatment Strategies for Metastatic and Drug- Resistant Breast Cancer Using Noninvasive Optical Monitori g 5c. PROGRAM...drug resistant breast cancer. Non-invasive Diffuse Optical Imaging technologies are able to monitor drug response and resistance through quantitative

The role of water management on the oxygen transport resistance in polymer electrolyte fuel cell with ultra-low precious metal loading

NASA Astrophysics Data System (ADS)

Srouji, A. K.; Zheng, L. J.; Dross, R.; Aaron, D.; Mench, M. M.

2017-10-01

Limiting current measurements are used to evaluate oxygen transport resistance in the catalyst layer of a polymer electrolyte fuel cell (PEFC). The pressure independent oxygen transport resistance in the electrode is quantified for two cell architectures and two cathode Pt loadings (0.4 and 0.07 mgPt.cm-2). The compounded effect of the flow field and Pt loading is used to shed light on the nature of the observed transport resistance, especially its response to fundamentally different flow fields, which is shown to directly or indirectly scale with Pt loading in the open literature. By varying gas pressure and using low oxygen concentrations, the total oxygen transport resistance is divided into intermolecular gas diffusion (a pressure-dependent component) and a pressure independent component, which can be attributed to Knudsen diffusion or dissolution film resistance. The pressure-independent oxygen transport resistance in the catalyst layer varies between 13.3 and 34.4 s/m. It is shown that the pressure independent oxygen transport resistance increases with reduced Pt loading, but that effect is greatly exacerbated by using conventional channel/lands. The results indicate that open metallic element architecture improves the oxygen transport resistance in ultra-low Pt loading electrodes, likely due to enhanced water management at the catalyst layer.

Antibiotic Resistance and Antibiotic Resistance Genes in Escherichia coli Isolates from Hospital Wastewater in Vietnam

PubMed Central

Lan, Pham Thi; Chuc, Nguyen Thi Kim; Hoa, Nguyen Quynh; Nhung, Pham Hong; Thoa, Nguyen Thi Minh; Diwan, Vishal; Tamhankar, Ashok J.; Stålsby Lundborg, Cecilia

2017-01-01

The environmental spread of antibiotic-resistant bacteria has been recognised as a growing public health threat for which hospitals play a significant role. The aims of this study were to investigate the prevalence of antibiotic resistance and antibiotic resistance genes (ARGs) in Escherichia coli isolates from hospital wastewater in Vietnam. Wastewater samples before and after treatment were collected using continuous sampling every month over a year. Standard disk diffusion and E-test were used for antibiotic susceptibility testing. Extended-spectrum beta-lactamase (ESBL) production was tested using combined disk diffusion. ARGs were detected by polymerase chain reactions. Resistance to at least one antibiotic was detected in 83% of isolates; multidrug resistance was found in 32%. The highest resistance prevalence was found for co-trimoxazole (70%) and the lowest for imipenem (1%). Forty-three percent of isolates were ESBL-producing, with the blaTEM gene being more common than blaCTX-M. Co-harbouring of the blaCTX-M, blaTEM and qepA genes was found in 46% of isolates resistant to ciprofloxacin. The large presence of antibiotic-resistant E. coli isolates combined with ARGs in hospital wastewater, even post-treatment, poses a threat to public health. It highlights the need to develop effective processes for hospital wastewater treatment plants to eliminate antibiotic resistant bacteria and ARGs. PMID:28661465

Antibiotic Resistance and Antibiotic Resistance Genes in Escherichia coli Isolates from Hospital Wastewater in Vietnam.

PubMed

Lien, La Thi Quynh; Lan, Pham Thi; Chuc, Nguyen Thi Kim; Hoa, Nguyen Quynh; Nhung, Pham Hong; Thoa, Nguyen Thi Minh; Diwan, Vishal; Tamhankar, Ashok J; Stålsby Lundborg, Cecilia

2017-06-29

The environmental spread of antibiotic-resistant bacteria has been recognised as a growing public health threat for which hospitals play a significant role. The aims of this study were to investigate the prevalence of antibiotic resistance and antibiotic resistance genes (ARGs) in Escherichia coli isolates from hospital wastewater in Vietnam. Wastewater samples before and after treatment were collected using continuous sampling every month over a year. Standard disk diffusion and E-test were used for antibiotic susceptibility testing. Extended-spectrum beta-lactamase (ESBL) production was tested using combined disk diffusion. ARGs were detected by polymerase chain reactions. Resistance to at least one antibiotic was detected in 83% of isolates; multidrug resistance was found in 32%. The highest resistance prevalence was found for co-trimoxazole (70%) and the lowest for imipenem (1%). Forty-three percent of isolates were ESBL-producing, with the bla TEM gene being more common than bla CTX-M . Co-harbouring of the bla CTX-M , bla TEM and qepA genes was found in 46% of isolates resistant to ciprofloxacin. The large presence of antibiotic-resistant E. coli isolates combined with ARGs in hospital wastewater, even post-treatment, poses a threat to public health. It highlights the need to develop effective processes for hospital wastewater treatment plants to eliminate antibiotic resistant bacteria and ARGs.

Experimental dissection of oxygen transport resistance in the components of a polymer electrolyte membrane fuel cell

NASA Astrophysics Data System (ADS)

Oh, Hwanyeong; Lee, Yoo il; Lee, Guesang; Min, Kyoungdoug; Yi, Jung S.

2017-03-01

Oxygen transport resistance is a major obstacle for obtaining high performance in a polymer electrolyte membrane fuel cell (PEMFC). To distinguish the major components that inhibit oxygen transport, an experimental method is established to dissect the oxygen transport resistance of the components of the PEMFC, such as the substrate, micro-porous layer (MPL), catalyst layer, and ionomer film. The Knudsen numbers are calculated to determine the types of diffusion mechanisms at each layer by measuring the pore sizes with either mercury porosimetry or BET analysis. At the under-saturated condition where condensation is mostly absent, the molecular diffusion resistance is dissected by changing the type of inert gas, and ionomer film permeation is separated by varying the inlet gas humidity. Moreover, the presence of the MPL and the variability of the substrate thickness allow the oxygen transport resistance at each component of a PEMFC to be dissected. At a low relative humidity of 50% and lower, an ionomer film had the largest resistance, while the contribution of the MPL was largest for the other humidification conditions.

Highly reflective Ag-Cu alloy-based ohmic contact on p-type GaN using Ru overlayer.

PubMed

Son, Jun Ho; Jung, Gwan Ho; Lee, Jong-Lam

2008-12-15

We report on a metallization scheme of high reflectance, low resistance, and smooth surface morphology ohmic contact on p-type GaN. Ag-Cu alloy/Ru contact showed low contact resistivity as low as 6.2 x 10(-6) Ohms cm(2) and high reflectance of 91% at 460 nm after annealing at 400 degrees C in air ambient. The oxidation annealing promoted the out-diffusion of Ga atoms to dissolve in an Ag-Cu layer with the formation of an Ag-Ga solid solution, lowering the contact resistivity. The Ru overlayer acts as a diffusion barrier for excessive oxygen incorporation during oxidation annealing, resulting in high reflectance, good thermal stability, and smooth surface quality of the contact.

Porous Flow and Diffusion of Water in the Mantle Wedge: Melting and Hydration Patterns

NASA Astrophysics Data System (ADS)

Conder, J. A.

2005-12-01

It is widely accepted that melting at volcanic arcs is primarily triggered by fluxing the mantle wedge from the dehydrating subducting slab. However, there is less concensus regarding how water moves into and within the mantle wedge. There are at least four possible mechanisms for water migration in the wedge: buoyant porous flow, diffusion through mineral crystals, advection of hydrated minerals, and compositionally buoyant diapers. The latter two mechanisms require at least one of the first two to occur to get water from the slab into the wedge before they can function. Using geodynamic models of mantle flow in a simplified subduction setting, we explore the implications of diffusion and porous flow of water in the wedge, particularly as they would affect the time for recycling water through the subduction factory and the predicted pattern of basalt hydration across the arc. The slab is assumed to dehydrate in a continuous fashion as the solubility of water in subducted oceanic crust decreases with temperature and pressure and the water then enters the wedge via one of the two transport mechanisms. Diffusion is controlled by temperature and by which minerals are present. Although olivine dominates the mantle mineral fraction, pyroxenes may control the diffusion of water in the wedge as the diffusivity of pyroxene is one or more orders of magnitude greater than olivine. Even assuming the faster diffusion rate of orthopyroxene in the models, diffusion can only be an important transport mechanism when subduction rates are slower than ~3 cm/yr. Flux melting occurs in the wedge above where the slab is ~100-160 km deep with the maximum above where the slab is ~120 km deep. Models including porous flow can result in melting at higher subduction rates provided the permeability of the mantle is greater than 10-17 m2. The true magnitude of the permeability likely varies with the corresponding porosity created by the free phase. With porous flow, melting occurs 20-30 km closer to the trench and the degree of melting is larger than when only diffusion is allowed. The rate of dehydration depends on the thermal structure which can affect the permeability. The dependence of permeability and diffusion with temperature may explain the variations in volcanic front location as observed at different arcs.

Effects of cation contaminants in conductive TiO2 ceramics

NASA Astrophysics Data System (ADS)

Yan, M. F.; Rhodes, W. W.

1982-12-01

Ten cation contaminants, namely Al, Ga, Co, Fe, Mg, Zn, Zr, Ca, Sr, and Ba were investigated for their effects on the electrical properties, microstructures, and discoloration of conductive TiO2 ceramics. It was found that Al, Ga, Co, Fe, and Mg cause discoloration and increase the electrical resistivity by a factor of 104 to 106 in Nb-doped TiO2 ceramics. The other dopants do not introduce such changes in TiO2. The electrical properties, microstructures, and discoloration were measured in specimens of AlxNb0.007Ti0.993-xO2 with 0≤x≤0.01. When the Al content exceeds a critical value, ranging from 0.48% at 1400 °C to 0.25% at 1200 °C, the electrical resistivities and grain size increase rapidly, and the specimen is discolored from the original black to an ivory white color. Color boundary migration induced by Al diffusion in Nb-doped TiO2 was quantitatively measured. From the kinetics of the boundary migration, the Al diffusivity (D) was calculated to be D=2.67 exp(-53.3 kcal/mole/RT) cm2/s in the temperature range of 1200 to 1400 °C. The rapid diffusion of the small cations, namely Al, Ga, Co, Fe, and Mg, results from an interstitial diffusion mechanism. However, other cations, having a radius larger than the interstitial channel (˜0.77 Å radius), cannot diffuse by this mechanism. Defect reactions are proposed to explain the increase in the electrical resistivity and microstructural changes due to Al diffusion. These defect reactions also show that the problem of acceptor contamination cannot be avoided by adding an excess quantity of donor dopant if the solubility of the donor is much less than that of the acceptor contaminant.

Materials for Advanced Turbine Engines (MATE). Project 4: Erosion resistant compressor airfoil coating

NASA Technical Reports Server (NTRS)

Rashid, J. M.; Freling, M.; Friedrich, L. A.

1987-01-01

The ability of coatings to provide at least a 2X improvement in particulate erosion resistance for steel, nickel and titanium compressor airfoils was identified and demonstrated. Coating materials evaluated included plasma sprayed cobalt tungsten carbide, nickel carbide and diffusion applied chromium plus boron. Several processing parameters for plasma spray processing and diffusion coating were evaluated to identify coating systems having the most potential for providing airfoil erosion resistance. Based on laboratory results and analytical evaluations, selected coating systems were applied to gas turbine blades and evaluated for surface finish, burner rig erosion resistance and effect on high cycle fatigue strength. Based on these tests, the following coatings were recommended for engine testing: Gator-Gard plasma spray 88WC-12Co on titanium alloy airfoils, plasma spray 83WC-17Co on steel and nickel alloy airfoils, and Cr+B on nickel alloy airfoils.

Advanced structural multimodal imaging of a patient with subcortical band heterotopia.

PubMed

Kini, Lohith G; Nasrallah, Ilya M; Coto, Carlos; Ferraro, Lindsay C; Davis, Kathryn A

2016-12-01

Subcortical band heterotopia (SBH) is a disorder of neuronal migration most commonly due to mutations of the Doublecortin (DCX) gene. A range of phenotypes is seen, with most patients having some degree of epilepsy and intellectual disability. Advanced diffusion and structural magnetic resonance imaging (MRI) sequences may be useful in identifying heterotopias and dysplasias of different sizes in drug-resistant epilepsy. We describe a patient with SBH and drug-resistant epilepsy and investigate neurite density, neurite dispersion, and diffusion parameters as compared to a healthy control through the use of multiple advanced MRI modalities. Neurite density and dispersion in heterotopia was found to be more similar to white matter than gray matter. Neurite density and dispersion maps obtained using diffusion imaging may be able to better characterize different subtypes of heterotopia.

Multiple doping of silicon-germanium alloys for thermoelectric applications

NASA Technical Reports Server (NTRS)

Fleurial, Jean-Pierre; Vining, Cronin B.; Borshchevsky, Alex

1989-01-01

It is shown that heavy doping of n-type Si/Ge alloys with phosphorus and arsenic (V-V doping interaction) by diffusion leads to a significant enhancement of their carrier concentration and possible improvement of the thermoelectric figure of merit. High carrier concentrations were achieved by arsenic doping alone, but for a same doping level higher carrier mobilities and lower resistivities are obtained through phosphorus doping. By combining the two dopants with the proper diffusion treatments, it was possible to optimize the different properties, obtaining high carrier concentration, good carrier mobility and low electrical resistivity. Similar experiments, using the III-V doping interaction, were conducted on boron-doped p-type samples and showed the possibility of overcompensating the samples by diffusing arsenic, in order to get n-type behavior.

Managing effects in CD control from PED and PEB in advanced DUV photomask manufacturing using FEP-171 resist

NASA Astrophysics Data System (ADS)

Paulsson, Adisa; Xing, Kezhao; Fosshaug, Hans; Lundvall, Axel; Bjoernberg, Charles; Karlsson, Johan

2005-05-01

A continuing improvement in resist process is a necessity for high-end photomask fabrication. In advanced chemically amplified resist systems the lithographic performance is strongly influenced by diffusion of acid and acid quencher (i.e. bases). Beside the resist properties, e.g. size and volatility of the photoacid, the process conditions play important roles for the diffusion control. Understanding and managing these properties influences lithographic characteristics on the photomask such as CD uniformity, CD and pitch linearity, resolution, substrate contamination, clear-dark bias and iso-dense bias. In this paper we have investigated effects on the lithographic characteristics with respect to post exposure bake conditions, when using the chemically amplified resist FEP-171. We used commercially available mask blanks from the Hoya Mask Blank Division with NTAR7 chrome and an optimized resist thickness for the 248 nm laser tool at 3200Å. The photomasks were exposed on the optical DUV (248nm) Sigma7300 pattern generator. Additionally, we investigated the image stability between exposure and post exposure bake. Unlike in wafer fabrication, photomask writing requires several hours, making the resist susceptible to image blur and acid latent image degradation.

Regional two-dimensional magnetotelluric profile in West Bohemia/Vogtland reveals deep conductive channel into the earthquake swarm region

NASA Astrophysics Data System (ADS)

Muñoz, Gerard; Weckmann, Ute; Pek, Josef; Kováčiková, Světlana; Klanica, Radek

2018-03-01

The West Bohemia/Vogtland region, characterized by the intersection of the Eger (Ohře) Rift and the Mariánské Lázně fault, is a geodynamically active area exhibiting repeated occurrence of earthquake swarms, massive CO2 emanations and mid Pleistocene volcanism. The Eger Rift is the only known intra-continental region in Europe where such deep seated, active lithospheric processes currently take place. We present an image of electrical resistivity obtained from two-dimensional inversion of magnetotelluric (MT) data acquired along a regional profile crossing the Eger Rift. At the near surface, the Cheb basin and the aquifer feeding the mofette fields of Bublák and Hartoušov have been imaged as part of a region of very low resistivity. The most striking resistivity feature, however, is a deep reaching conductive channel which extends from the surface into the lower crust spatially correlated with the hypocentres of the seismic events of the Nový Kostel Focal Zone. This channel has been interpreted as imaging a pathway from a possible mid-crustal fluid reservoir to the surface. The resistivity model reinforces the relation between the fluid circulation along deep-reaching faults and the generation of the earthquakes. Additionally, a further conductive channel has been revealed to the south of the profile. This other feature could be associated to fossil hydrothermal alteration related to Mýtina and/or Neualbenreuth Maar structures or alternatively could be the signature of a structure associated to the suture between the Saxo-Thuringian and Teplá-Barrandian zones, whose surface expression is located only a few kilometres away.

Electrical Properties of the Hanging Wall of the Alpine Fault, New Zealand, from DFDP-2 Wireline Data

NASA Astrophysics Data System (ADS)

Remaud, L.; Doan, M. L.; Pezard, P. A.; Celerier, B. P.; Townend, J.; Sutherland, R.; Toy, V.

2015-12-01

The DFDP-2B borehole drilled at Whataroa, New Zealand, provides a first-hand rare opportunity to investigate the damage pattern next to a major active fault. It was drilled along more than 893 m (820 m TVD) within hanging-wall protomylonites and mylonites. The interval between 264 m and 886 m (measured depth) was intensively investigated by wireline logging. Notably, electrical laterolog data were recorded over almost 3 km of cumulative logs, providing a homogeneous, uniformly sampled recording of the electrical properties of the borehole wall. The laterolog tool measures resistivity with two different electrode configurations, and hence achieves two different depths of penetration. Numerical simulations of the tool's response show that the true resistivity of the rock is close to the deep resistivity measurement, which in DFDP-2 varies between 300 Ω.m and 700 Ω.m. The shallow resistivity is about 75% of this value, as it is more sensitive to the presence of conductive borehole fluid. However, the large borehole diameter (averaging 8.5 inch = or 21.59 cm) only partially explains this value. The strong anisotropy suggested by laboratory measurements on outcrop samples also contributes to the separation between deep and shallow resistivity. The shallow and deep resistivities exhibit many significant drops that are coincident with the presence of fractures detected in borehole televiewer data. More than 700 electrical anomalies have been manually picked. The major ones are correlated with attenuation of the sonic data and sometimes with anomalies in fluid conductivity (temperature and conductivity). Their frequency gradually increases with depth, reaching a plateau below 700 m. This increase with depth may be related to closer proximity to the Alpine Fault.

High-efficiency, deep-junction, epitaxial InP solar cells on (100) and (111)B InP substrates

NASA Technical Reports Server (NTRS)

Venkatasubramanian, R.; Timmons, M. L.; Hutchby, J. A.; Walters, Robert J.; Summers, Geoffrey P.

1994-01-01

We report on the development and performance of deep-junction (approximately 0.25 micron), graded-emitter-doped, n(sup +)-p InP solar cells grown by metallorganic chemical vapor deposition (MOCVD). A novel, diffusion-transport process for obtaining lightly-doped p-type base regions of the solar cell is described. The I-V data and external quantum-efficiency response of these cells are presented. The best active-area AMO efficiency for these deep-junction cells on (100)-oriented InP substrates is 16.8 percent, with a J(sub SC) of 31.8 mA/sq cm, a V(sub OC) of 0.843 V, and a fill-factor of 0.85. By comparison, the best cell efficiency on the (111)B-oriented InP substrates was 15.0 percent. These efficiency values for deep-junction cells are encouraging and compare favorably with performance of thin-emitter (0.03 micron) epitaxial cells as well as that of deep-emitter diffused cells. The cell performance and breakdown voltage characteristics of a batch of 20 cells on each of the orientations are presented, indicating the superior breakdown voltage properties and other characteristics of InP cells on the (111)B orientation. Spectral response, dark I-V data, and photoluminescence (PL) measurements on the InP cells are presented with an analysis on the variation in J(sub SC) and V(sub OC) of the cells. It is observed, under open-circuit conditions, that lower-V(sub OC) cells exhibit higher band-edge PL intensity for both the (100) and (111)B orientations. This anomalous behavior suggests that radiative recombination in the heavily-doped n(sup +)-InP emitter may be detrimental to achieving higher V(sub OC) in n(sup +)-p InP solar cells.

Segmentation of the Globus Pallidus Internus Using Probabilistic Diffusion Tractography for Deep Brain Stimulation Targeting in Parkinson Disease.

PubMed

Middlebrooks, E H; Tuna, I S; Grewal, S S; Almeida, L; Heckman, M G; Lesser, E R; Foote, K D; Okun, M S; Holanda, V M

2018-06-01

Although globus pallidus internus deep brain stimulation is a widely accepted treatment for Parkinson disease, there is persistent variability in outcomes that is not yet fully understood. In this pilot study, we aimed to investigate the potential role of globus pallidus internus segmentation using probabilistic tractography as a supplement to traditional targeting methods. Eleven patients undergoing globus pallidus internus deep brain stimulation were included in this retrospective analysis. Using multidirection diffusion-weighted MR imaging, we performed probabilistic tractography at all individual globus pallidus internus voxels. Each globus pallidus internus voxel was then assigned to the 1 ROI with the greatest number of propagated paths. On the basis of deep brain stimulation programming settings, the volume of tissue activated was generated for each patient using a finite element method solution. For each patient, the volume of tissue activated within each of the 10 segmented globus pallidus internus regions was calculated and examined for association with a change in the Unified Parkinson Disease Rating Scale, Part III score before and after treatment. Increasing volume of tissue activated was most strongly correlated with a change in the Unified Parkinson Disease Rating Scale, Part III score for the primary motor region (Spearman r = 0.74, P = .010), followed by the supplementary motor area/premotor cortex (Spearman r = 0.47, P = .15). In this pilot study, we assessed a novel method of segmentation of the globus pallidus internus based on probabilistic tractography as a supplement to traditional targeting methods. Our results suggest that our method may be an independent predictor of deep brain stimulation outcome, and evaluation of a larger cohort or prospective study is warranted to validate these findings. © 2018 by American Journal of Neuroradiology.

Efficacy of Ciprofloxacin for Treatment of Cholera Associated with Diminished Susceptibility to Ciprofloxacin to Vibrio cholerae O1.

PubMed

Khan, Wasif Ali; Saha, Debasish; Ahmed, Sabeena; Salam, Mohammed Abdus; Bennish, Michael Louis

2015-01-01

We identified a poor clinical response to treatment of cholera with a single 1 g dose of ciprofloxacin, a standard treatment for cholera. To determine reasons for the poor response and better therapeutic approaches we examined the minimal inhibitor concentration (MIC, n = 275) and disc-diffusion zone sizes (n = 205) for ciprofloxacin and nalidixic acid of V. cholerae O1 strains isolated in Bangladesh from 1994 to 2012, and reexamined data from 161 patients infected with Vibrio cholerae O1 recruited in four clinical trials who received single- or multiple-dose ciprofloxacin for treatment of cholera and compared their clinical response to the V. cholerae O1 susceptibility. Although all 275 isolates of V. cholerae O1 remained susceptible to ciprofloxacin using standard MIC and disc-diffusion thresholds, the MIC90 to ciprofloxacin increased from 0.010 in 1994 to 0.475 μgm/ml in 2012. Isolates became frankly resistant to nalidixic with the MIC90 increasing from 21 μgm/ml in 1994 to >256 μgm/ml and 166 of 205 isolates from 1994 to 2005 being frankly resistant using disc-diffusion testing. Isolates resistant to nalidixic acid by disc-diffusion testing had a median ciprofloxacin MIC of 0.190 μgm/ml (10th-90th centiles 0.022 to 0.380); nalidixic acid-susceptible isolates had a median ciprofloxacin MIC of 0.002 (0.002 to 0.012).The rate of clinical success with single-dose ciprofloxacin treatment for nalidixic acid-susceptible strains was 94% (61 of 65 patients) and bacteriologic success 97% (63/65) compared to 18% (12/67) and 8% (5/67) respectively with nalidixic acid-resistant strains (P<0.001 for both comparisons). Multiple-dose treatment with ciprofloxacin had 86% and 100% clinical and bacteriologic success rates respectively in patients infected with nalidixic acid-susceptible strains of V. cholerae O1 compared to clinical success 67% and bacteriologic success 60% with nalidixic acid-resistant strains. Single-dose ciprofloxacin is not effective for treating cholera caused by V. cholerae O1 with diminished susceptibility to ciprofloxacin, and nalidixic acid disc-diffusion testing effectively screens for such isolates.

Measurement of diffusion coefficients of VOCs for building materials: review and development of a calculation procedure.

PubMed

Haghighat, F; Lee, C S; Ghaly, W S

2002-06-01

The measurement and prediction of building material emission rates have been the subject of intensive research over the past decade, resulting in the development of advanced sensory and chemical analysis measurement techniques as well as the development of analytical and numerical models. One of the important input parameters for these models is the diffusion coefficient. Several experimental techniques have been applied to estimate the diffusion coefficient. An extensive literature review of the techniques used to measure this coefficient was carried out, for building materials exposed to volatile organic compounds (VOC). This paper reviews these techniques; it also analyses the results and discusses the possible causes of difference in the reported data. It was noted that the discrepancy between the different results was mainly because of the assumptions made in and the techniques used to analyze the data. For a given technique, the results show that there can be a difference of up to 700% in the reported data. Moreover, the paper proposes what is referred to as the mass exchanger method, to calculate diffusion coefficients considering both diffusion and convection. The results obtained by this mass exchanger method were compared with those obtained by the existing method considering only diffusion. It was demonstrated that, for porous materials, the convection resistance could not be ignored when compared with the diffusion resistance.

Numerical and experimental study of the effects of the electrical resistance and diffusivity under clamping pressure on the performance of a metallic gas-diffusion layer in polymer electrolyte fuel cells

NASA Astrophysics Data System (ADS)

Tanaka, Shiro; Bradfield, Warwick W.; Legrand, Cloe; Malan, Arnaud G.

2016-10-01

The performance of a perforated metal-sheet gas-diffusion layer incorporated with a microporous layer in a fuel cell is evaluated with fine-pitch channel/land designs for the gas flow field on a bipolar plate. The combination of metal-sheet gas-diffusion layer and microporous layer exhibits significant performance without a large flooding effect. When comparing the performance with wider and narrower land cases, the land width affects the performance. To investigate the roles of the microporous layer, land width, etc. in the fuel cell with the metal-sheet gas-diffusion layer, a single-phase, isothermal, and multi-physics simulation is developed and coupled with electrical, mechanical, electrochemical and fluid dynamics factors. The simulated current-voltage performance is then compared to the experimentally measure performance. These are shown to be in good agreement apart for very high current-density cases i.e. greater than 1.5 A cm-2. This is due the flooding effect predominantly appearing. It is further demonstrated that the microporous layer serves as the key component in facilitating gas diffusion and for preventing flooding. Furthermore, the pressure is found to have a strong impact on the performance, affecting the gas diffusion and electric resistance around the microporous layer.

Upper Bound on Diffusivity

NASA Astrophysics Data System (ADS)

Hartman, Thomas; Hartnoll, Sean A.; Mahajan, Raghu

2017-10-01

The linear growth of operators in local quantum systems leads to an effective light cone even if the system is nonrelativistic. We show that the consistency of diffusive transport with this light cone places an upper bound on the diffusivity: D ≲v2τeq. The operator growth velocity v defines the light cone, and τeq is the local equilibration time scale, beyond which the dynamics of conserved densities is diffusive. We verify that the bound is obeyed in various weakly and strongly interacting theories. In holographic models, this bound establishes a relation between the hydrodynamic and leading nonhydrodynamic quasinormal modes of planar black holes. Our bound relates transport data—including the electrical resistivity and the shear viscosity—to the local equilibration time, even in the absence of a quasiparticle description. In this way, the bound sheds light on the observed T -linear resistivity of many unconventional metals, the shear viscosity of the quark-gluon plasma, and the spin transport of unitary fermions.

Pore network modeling to explore the effects of compression on multiphase transport in polymer electrolyte membrane fuel cell gas diffusion layers

NASA Astrophysics Data System (ADS)

Fazeli, Mohammadreza; Hinebaugh, James; Fishman, Zachary; Tötzke, Christian; Lehnert, Werner; Manke, Ingo; Bazylak, Aimy

2016-12-01

Understanding how compression affects the distribution of liquid water and gaseous oxygen in the polymer electrolyte membrane fuel cell gas diffusion layer (GDL) is vital for informing the design of improved porous materials for effective water management strategies. Pore networks extracted from synchrotron-based micro-computed tomography images of compressed GDLs were employed to simulate liquid water transport in GDL materials over a range of compression pressures. The oxygen transport resistance was predicted for each sample under dry and partially saturated conditions. A favorable GDL compression value for a preferred liquid water distribution and oxygen diffusion was found for Toray TGP-H-090 (10%), yet an optimum compression value was not recognized for SGL Sigracet 25BC. SGL Sigracet 25BC exhibited lower transport resistance values compared to Toray TGP-H-090, and this is attributed to the additional diffusion pathways provided by the microporous layer (MPL), an effect that is particularly significant under partially saturated conditions.

A physics-based fractional order model and state of energy estimation for lithium ion batteries. Part I: Model development and observability analysis

NASA Astrophysics Data System (ADS)

Li, Xiaoyu; Fan, Guodong; Pan, Ke; Wei, Guo; Zhu, Chunbo; Rizzoni, Giorgio; Canova, Marcello

2017-11-01

The design of a lumped parameter battery model preserving physical meaning is especially desired by the automotive researchers and engineers due to the strong demand for battery system control, estimation, diagnosis and prognostics. In light of this, a novel simplified fractional order electrochemical model is developed for electric vehicle (EV) applications in this paper. In the model, a general fractional order transfer function is designed for the solid phase lithium ion diffusion approximation. The dynamic characteristics of the electrolyte concentration overpotential are approximated by a first-order resistance-capacitor transfer function in the electrolyte phase. The Ohmic resistances and electrochemical reaction kinetics resistance are simplified to a lumped Ohmic resistance parameter. Overall, the number of model parameters is reduced from 30 to 9, yet the accuracy of the model is still guaranteed. In order to address the dynamics of phase-change phenomenon in the active particle during charging and discharging, variable solid-state diffusivity is taken into consideration in the model. Also, the observability of the model is analyzed on two types of lithium ion batteries subsequently. Results show the fractional order model with variable solid-state diffusivity agrees very well with experimental data at various current input conditions and is suitable for electric vehicle applications.

Phylogenetic study of metallo-β-lactamase producing multidrug resistant Pseudomonas aeruginosa isolates from burn patients.

PubMed

Jena, Jayanti; Debata, Nagen Kumar; Sahoo, Rajesh Kumar; Subudhi, Enketeswara

2015-12-01

The present study was carried out to understand the clonal relationship using enterobacteriaceae repetitive intergenic consensus polymerase chain reaction (ERIC-PCR) among metallo-β-lactamase (MBL) producing multidrug resistant Pseudomonas aeruginosa isolates from burn victims and their susceptibility to commonly used anti-pseudomonal agents. In the present study 94 non-duplicate P. aeruginosa strains from the wound samples of burn patients were included. Identification of the isolates was done by biochemical methods and antibiotic sensitivity was done by disc diffusion method following CLSI (Clinical Laboratory Standard Institute) guidelines. By using imipenem (IPM)-EDTA disk diffusion/double disc synergy method carbapenem resistant organisms were tested for MBL. To define the clonal relationship ERIC-PCR was used. Of the 94 isolates, 18 (19.14%) were found resistant to IPM and MBL production was shown 11 (11.70%) by the IPM-EDTA disc diffusion method. From dendrogram of the ERIC-PCR profile four major clusters were obtained (A, B, C and D). Cluster B contained the majority of the isolates (6 strains 1, 4, 8, 9, 10 and 11). This study using ERIC-PCR of randomly collected isolates exhibits high genetic diversity which rules out cross contamination frequency. Copyright © 2015 Elsevier Ltd and ISBI. All rights reserved.

Dynamic characterization of external and internal mass transport in heterotrophic biofilms from microsensors measurements.

PubMed

Guimerà, Xavier; Dorado, Antonio David; Bonsfills, Anna; Gabriel, Gemma; Gabriel, David; Gamisans, Xavier

2016-10-01

Knowledge of mass transport mechanisms in biofilm-based technologies such as biofilters is essential to improve bioreactors performance by preventing mass transport limitation. External and internal mass transport in biofilms was characterized in heterotrophic biofilms grown on a flat plate bioreactor. Mass transport resistance through the liquid-biofilm interphase and diffusion within biofilms were quantified by in situ measurements using microsensors with a high spatial resolution (<50 μm). Experimental conditions were selected using a mathematical procedure based on the Fisher Information Matrix to increase the reliability of experimental data and minimize confidence intervals of estimated mass transport coefficients. The sensitivity of external and internal mass transport resistances to flow conditions within the range of typical fluid velocities over biofilms (Reynolds numbers between 0.5 and 7) was assessed. Estimated external mass transfer coefficients at different liquid phase flow velocities showed discrepancies with studies considering laminar conditions in the diffusive boundary layer near the liquid-biofilm interphase. The correlation of effective diffusivity with flow velocities showed that the heterogeneous structure of biofilms defines the transport mechanisms inside biofilms. Internal mass transport was driven by diffusion through cell clusters and aggregates at Re below 2.8. Conversely, mass transport was driven by advection within pores, voids and water channels at Re above 5.6. Between both flow velocities, mass transport occurred by a combination of advection and diffusion. Effective diffusivities estimated at different biofilm densities showed a linear increase of mass transport resistance due to a porosity decrease up to biofilm densities of 50 g VSS·L(-1). Mass transport was strongly limited at higher biofilm densities. Internal mass transport results were used to propose an empirical correlation to assess the effective diffusivity within biofilms considering the influence of hydrodynamics and biofilm density. Copyright © 2016 Elsevier Ltd. All rights reserved.

Chemical transport models: the combined non-local diffusion and mixing schemes, and calculation of in-canopy resistance for dry deposition fluxes.

PubMed

Mihailovic, Dragutin T; Alapaty, Kiran; Podrascanin, Zorica

2009-03-01

Improving the parameterization of processes in the atmospheric boundary layer (ABL) and surface layer, in air quality and chemical transport models. To do so, an asymmetrical, convective, non-local scheme, with varying upward mixing rates is combined with the non-local, turbulent, kinetic energy scheme for vertical diffusion (COM). For designing it, a function depending on the dimensionless height to the power four in the ABL is suggested, which is empirically derived. Also, we suggested a new method for calculating the in-canopy resistance for dry deposition over a vegetated surface. The upward mixing rate forming the surface layer is parameterized using the sensible heat flux and the friction and convective velocities. Upward mixing rates varying with height are scaled with an amount of turbulent kinetic energy in layer, while the downward mixing rates are derived from mass conservation. The vertical eddy diffusivity is parameterized using the mean turbulent velocity scale that is obtained by the vertical integration within the ABL. In-canopy resistance is calculated by integration of inverse turbulent transfer coefficient inside the canopy from the effective ground roughness length to the canopy source height and, further, from its the canopy height. This combination of schemes provides a less rapid mass transport out of surface layer into other layers, during convective and non-convective periods, than other local and non-local schemes parameterizing mixing processes in the ABL. The suggested method for calculating the in-canopy resistance for calculating the dry deposition over a vegetated surface differs remarkably from the commonly used one, particularly over forest vegetation. In this paper, we studied the performance of a non-local, turbulent, kinetic energy scheme for vertical diffusion combined with a non-local, convective mixing scheme with varying upward mixing in the atmospheric boundary layer (COM) and its impact on the concentration of pollutants calculated with chemical and air-quality models. In addition, this scheme was also compared with a commonly used, local, eddy-diffusivity scheme. Simulated concentrations of NO2 by the COM scheme and new parameterization of the in-canopy resistance are closer to the observations when compared to those obtained from using the local eddy-diffusivity scheme. Concentrations calculated with the COM scheme and new parameterization of in-canopy resistance, are in general higher and closer to the observations than those obtained by the local, eddy-diffusivity scheme (on the order of 15-22%). To examine the performance of the scheme, simulated and measured concentrations of a pollutant (NO2) were compared for the years 1999 and 2002. The comparison was made for the entire domain used in simulations performed by the chemical European Monitoring and Evaluation Program Unified model (version UNI-ACID, rv2.0) where schemes were incorporated.

Effect of annealing on structural changes and oxygen diffusion in amorphous HfO2 using classical molecular dynamics

NASA Astrophysics Data System (ADS)

Shen, Wenqing; Kumari, Niru; Gibson, Gary; Jeon, Yoocharn; Henze, Dick; Silverthorn, Sarah; Bash, Cullen; Kumar, Satish

2018-02-01

Non-volatile memory is a promising alternative to present memory technologies. Oxygen vacancy diffusion has been widely accepted as one of the reasons for the resistive switching mechanism of transition-metal-oxide based resistive random access memory. In this study, molecular dynamics simulation is applied to investigate the diffusion coefficient and activation energy of oxygen in amorphous hafnia. Two sets of empirical potential, Charge-Optimized Many-Body (COMB) and Morse-BKS (MBKS), were considered to investigate the structural and diffusion properties at different temperatures. COMB predicts the activation energy of 0.53 eV for the temperature range of 1000-2000 K, while MBKS predicts 2.2 eV at high temperature (1600-2000 K) and 0.36 eV at low temperature (1000-1600 K). Structural changes and appearance of nano-crystalline phases with increasing temperature might affect the activation energy of oxygen diffusion predicted by MBKS, which is evident from the change in coordination number distribution and radial distribution function. None of the potentials make predictions that are fully consistent with density functional theory simulations of both the structure and diffusion properties of HfO2. This suggests the necessity of developing a better multi-body potential that considers charge exchange.

Calibration of Resistance Factors Needed in the LRFD Design of Drilled Shafts

DOT National Transportation Integrated Search

2010-09-01

The first report on Load and Resistance Factor Design (LRFD) calibration of driven piles in Louisiana (LTRC Final Report 449) was : completed in May 2009. As a continuing effort to implement the LRFD design methodology for deep foundations in Louisia...

Calibration of resistance factors needed in the LRFD design of drilled shafts.

DOT National Transportation Integrated Search

2010-09-01

The first report on Load and Resistance Factor Design (LRFD) calibration of driven piles in Louisiana (LTRC Final Report 449) was completed in May 2009. As a continuing effort to implement the LRFD design methodology for deep foundations in Louisiana...

Calibration of resistance factors for drilled shafts for the new FHWA design method.

DOT National Transportation Integrated Search

2013-01-01

The Load and Resistance Factor Design (LRFD) calibration of deep foundation in Louisiana was first completed for driven piles (LTRC Final Report 449) in May 2009 and then for drilled shafts using 1999 FHWA design method (ONeill and Reese method) (...

Calibration of resistance factors needed in the LRFD design of drilled shafts.

DOT National Transportation Integrated Search

2010-09-01

The first report on Load and Resistance Factor Design (LRFD) calibration of driven piles in Louisiana (LTRC Final Report 449) was : completed in May 2009. As a continuing effort to implement the LRFD design methodology for deep foundations in Louisia...

Pile/shaft designs using artificial neural networks (i.e., genetic programming) with spatial variability considerations : [summary].

DOT National Transportation Integrated Search

2014-03-01

In this project, University of Florida researchers : sought to improve the unit skin friction and tip : resistance correlations embedded in the FB-Deep : software algorithm for estimating driven pile and : drilled shaft resistance. They utilized an a...

Deep electrical resistivity structure of northwestern Costa Rica

NASA Astrophysics Data System (ADS)

Brasse, H.; Kapinos, G.; Mütschard, L.; Alvarado, G. E.; Worzewski, T.; Jegen, M.

2009-01-01

First long-period magnetotelluric investigations were conducted in early 2008 in northwestern Costa Rica, along a profile that extends from the coast of the Pacific Ocean, traverses the volcanic arc and ends currently at the Nicaraguan border. The aim of this study is to gain insight into the electrical resistivity structure and thus fluid distribution at the continental margin where the Cocos plate subducts beneath the Caribbean plate. Preliminary two-dimensional models map the only moderately resistive mafic/ultramafic complexes of the Nicoya Peninsula (resistivity of a few hundred Ωm), the conductive forearc and the backarc basins (several Ωm). Beneath the backarc basin the data image a poor conductor in the basement with a clear termination in the south, which may tentatively be interpreted as the Santa Elena Suture. The volcanic arc shows no pronounced anomaly at depth, but a moderate conductor underlies the backarc with a possible connection to the upper mantle. A conductor at deep-crustal levels in the forearc may reflect fluid release from the downgoing slab.

Development of the EM tomography system by the vertical electromagnetic profiling (VEMP) method

DOE Office of Scientific and Technical Information (OSTI.GOV)

Miura, Y.; Osato, K.; Takasugi, S.

1995-12-31

As a part of the {open_quotes}Deep-Seated Geothermal Resources Survey{close_quotes} project being undertaken by the NEDO, the Vertical ElectroMagnetic Profiling (VEMP) method is being developed to accurately obtain deep resistivity structure. The VEMP method acquires multi-frequency three-component magnetic field data in an open hole well using controlled sources (loop sources or grounded-wire sources) emitted at the surface. Numerical simulation using EM3D demonstrated that phase data of the VEMP method is very sensitive to resistivity structure and the phase data will also indicate presence of deep anomalies. Forward modelling was also used to determine required transmitter moments for various grounded-wire and loopmore » sources for a field test using the WD-1 well in the Kakkonda geothermal area. Field logging of the well was carried out in May 1994 and the processed field data matches well the simulated data.« less

Computer analysis of the negative differential resistance switching phenomenon of double-injection devices

NASA Technical Reports Server (NTRS)

Shieh, Tsay-Jiu

1989-01-01

By directly solving the semiconductor differential equations for the double-injection (DI) devices involving two interacting deep levels, the authors studied the negative differential resistance switching characteristic and its relationship with the device dimension, doping level, and dependence on the deep impurity profile. Computer simulation showed that although one can increase the threshold voltage by increasing the device length, the excessive holding voltage that would follow would put this device in a very limited application such as pulse power source. The excessive leakage current in the low conductance state also jeopardizes the attempt to use the device for any practical purpose. Unless there are new materials and deep impurities found that have a great differential hole and electron capture cross sections and a reasonable energy bandgap for low intrinsic carrier concentration, no big improvement in the fate of DI devices is expected in the near future.

Precision process calibration and CD predictions for low-k1 lithography

NASA Astrophysics Data System (ADS)

Chen, Ting; Park, Sangbong; Berger, Gabriel; Coskun, Tamer H.; de Vocht, Joep; Chen, Fung; Yu, Linda; Hsu, Stephen; van den Broeke, Doug; Socha, Robert; Park, Jungchul; Gronlund, Keith; Davis, Todd; Plachecki, Vince; Harris, Tom; Hansen, Steve; Lambson, Chuck

2005-06-01

Leading resist calibration for sub-0.3 k1 lithography demands accuracy <2nm for CD through pitch. An accurately calibrated resist process is the prerequisite for establishing production-worthy manufacturing under extreme low k1. From an integrated imaging point of view, the following key components must be simultaneously considered during the calibration - high numerical aperture (NA>0.8) imaging characteristics, customized illuminations (measured vs. modeled pupil profiles), resolution enhancement technology (RET) mask with OPC, reticle metrology, and resist thin film substrate. For imaging at NA approaching unity, polarized illumination can impact significantly the contrast formation in the resist film stack, and therefore it is an important factor to consider in the CD-based resist calibration. For aggressive DRAM memory core designs at k1<0.3, pattern-specific illumination optimization has proven to be critical for achieving the required imaging performance. Various optimization techniques from source profile optimization with fixed mask design to the combined source and mask optimization have been considered for customer designs and available imaging capabilities. For successful low-k1 process development, verification of the optimization results can only be made with a sufficiently tunable resist model that can predicate the wafer printing accurately under various optimized process settings. We have developed, for resist patterning under aggressive low-k1 conditions, a novel 3D diffusion model equipped with double-Gaussian convolution in each dimension. Resist calibration with the new diffusion model has demonstrated a fitness and CD predication accuracy that rival or outperform the traditional 3D physical resist models. In this work, we describe our empirical approach to achieving the nm-scale precision for advanced lithography process calibrations, using either measured 1D CD through-pitch or 2D memory core patterns. We show that for ArF imaging, the current resist development and diffusion modeling can readily achieve ~1-2nm max CD errors for common 1D through-pitch and aggressive 2D memory core resist patterns. Sensitivities of the calibrated models to various process parameters are analyzed, including the comparison between the measured and modeled (Gaussian or GRAIL) pupil profiles. We also report our preliminary calibration results under selected polarized illumination conditions.

Comparison of methods to detect the in vitro activity of silver nanoparticles (AgNP) against multidrug resistant bacteria.

PubMed

Cavassin, Emerson Danguy; de Figueiredo, Luiz Francisco Poli; Otoch, José Pinhata; Seckler, Marcelo Martins; de Oliveira, Roberto Angelo; Franco, Fabiane Fantinelli; Marangoni, Valeria Spolon; Zucolotto, Valtencir; Levin, Anna Sara Shafferman; Costa, Silvia Figueiredo

2015-10-05

Multidrug resistant microorganisms are a growing challenge and new substances that can be useful to treat infections due to these microorganisms are needed. Silver nanoparticle may be a future option for treatment of these infections, however, the methods described in vitro to evaluate the inhibitory effect are controversial. This study evaluated the in vitro activity of silver nanoparticles against 36 susceptible and 54 multidrug resistant Gram-positive and Gram-negative bacteria from clinical sources. The multidrug resistant bacteria were oxacilin-resistant Staphylococcus aureus, vancomycin-resistant Enterococcus spp., carbapenem- and polymyxin B-resistant A. baumannii, carbapenem-resistant P. aeruginosa and carbapenem-resistant Enterobacteriaceae. We analyzed silver nanoparticles stabilized with citrate, chitosan and polyvinyl alcohol and commercial silver nanoparticle. Silver sulfadiazine and silver nitrate were used as control. Different methods were used: agar diffusion, minimum inhibitory concentration, minimum bactericidal concentration and time-kill. The activity of AgNPs using diffusion in solid media and the MIC methods showed similar effect against MDR and antimicrobial-susceptible isolates, with a higher effect against Gram-negative isolates. The better results were achieved with citrate and chitosan silver nanoparticle, both with MIC90 of 6.75 μg mL(-1), which can be due the lower stability of these particles and, consequently, release of Ag(+) ions as revealed by X-ray diffraction (XRD). The bactericidal effect was higher against antimicrobial-susceptible bacteria. It seems that agar diffusion method can be used as screening test, minimum inhibitory concentration/minimum bactericidal concentration and time kill showed to be useful methods. The activity of commercial silver nanoparticle and silver controls did not exceed the activity of the citrate and chitosan silver nanoparticles. The in vitro inhibitory effect was stronger against Gram-negative than Gram-positive, and similar against multidrug resistant and susceptible bacteria, with best result achieved using citrate and chitosan silver nanoparticles. The bactericidal effect of silver nanoparticle may, in the future, be translated into important therapeutic and clinical options, especially considering the shortage of new antimicrobials against the emerging antimicrobial resistant microorganisms, in particular against Gram-negative bacteria.

Theoretical modeling of PEB procedure on EUV resist using FDM formulation

NASA Astrophysics Data System (ADS)

Kim, Muyoung; Moon, Junghwan; Choi, Joonmyung; Lee, Byunghoon; Jeong, Changyoung; Kim, Heebom; Cho, Maenghyo

2018-03-01

Semiconductor manufacturing industry has reduced the size of wafer for enhanced productivity and performance, and Extreme Ultraviolet (EUV) light source is considered as a promising solution for downsizing. A series of EUV lithography procedures contain complex photo-chemical reaction on photoresist, and it causes technical difficulties on constructing theoretical framework which facilitates rigorous investigation of underlying mechanism. Thus, we formulated finite difference method (FDM) model of post exposure bake (PEB) process on positive chemically amplified resist (CAR), and it involved acid diffusion coupled-deprotection reaction. The model is based on Fick's second law and first-order chemical reaction rate law for diffusion and deprotection, respectively. Two kinetic parameters, diffusion coefficient of acid and rate constant of deprotection, which were obtained by experiment and atomic scale simulation were applied to the model. As a result, we obtained time evolutional protecting ratio of each functional group in resist monomer which can be used to predict resulting polymer morphology after overall chemical reactions. This achievement will be the cornerstone of multiscale modeling which provides fundamental understanding on important factors for EUV performance and rational design of the next-generation photoresist.

A two-dimensional ocean model for long-term climatic simulations: Stability and coupling to atmospheric and sea ice models

NASA Astrophysics Data System (ADS)

Harvey, L. D. Danny

1992-06-01

A two-dimensional (latitude-depth) deep ocean model is presented which is coupled to a sea ice model and an Energy Balance Climate Model (EBCM), the latter having land-sea and surface-air resolution. The processes which occur in the ocean model are thermohaline overturning driven by the horizontal density gradient, shallow wind-driven overturning cells, convective overturning, and vertical and horizontal diffusion of heat and salt. The density field is determined from the temperature and salinity fields using a nonlinear equation of state. Mixed layer salinity is affected by evaporation, precipitation, runoff from continents, and sea ice freezing and melting, as well as by advective, convective, and diffusive exchanges with the deep ocean. The ocean model is first tested in an uncoupled mode, in which hemispherically symmetric mixed layer temperature and salinity, or salinity flux, are specified as upper boundary conditions. An experiment performed with previous models is repeated in which a mixed layer salinity perturbation is introduced in the polar half of one hemisphere after switching from a fixed salinity to a fixed salinity flux boundary condition. For small values of the vertical diffusion coefficient KV, the model undergoes self-sustained oscillations with a period of about 1500 years. With larger values of KV, the model locks into either an asymmetric mode with a single overturning cell spanning both hemispheres, or a symmetric quiescent state with downwelling near the equator, upwelling at high latitudes, and a warm deep ocean (depending on the value of KV). When the ocean model is forced with observed mixed layer temperature and salinity, no oscillations occur. The model successfully simulates the very weak meridional overturning and strong Antarctic Circumpolar Current at the latitudes of the Drake Passage. The coupled EBCM-deep ocean model displays internal oscillations with a period of 3000 years if the ocean fraction is uniform with latitude and KV and the horizontal diffusion coefficient in the mixed layer are not too large. Globally averaged atmospheric temperature changes of 2 K are driven by oscillations in the heat flux into or out of the deep ocean, with the sudden onset of a heat flux out of the deep ocean associated with the rapid onset of thermohaline overturning after a quiescent period, and the sudden onset of a heat flux into the deep ocean associated with the collapse of thermohaline overturning. When the coupled model is run with prescribed parameters (such as land-sea fraction and precipitation) varying with latitude based on observations, the model does not oscillate and produces a reasonable deep ocean temperature field but a completely unrealistic salinity field. Resetting the mixed layer salinity to observations on each time step (equivalent to the "flux correction" method used in atmosphere-ocean general circulation models) is sufficient to give a realistic salinity field throughout the ocean depth, but dramatically alters the flow field and associated heat transport. Although the model is highly idealized, the finding that the maximum perturbation in globally averaged heat flux from the deep ocean to the surface over a 100-year period is 1.4 W m-2 suggests that effect of continuing greenhouse gas increases, which could result in a heating perturbation of 10 W m-2 by the end of the next century, will swamp possible surface heating perturbations due to changes in oceanic circulation. On the other hand, the extreme sensitivity of the oceanic flow field to variations in precipitation and evaporation suggests that it will not be possible to produce accurate projections of regional climatic change in the near term, if at all.

Noncontact 3-D Speckle Contrast Diffuse Correlation Tomography of Tissue Blood Flow Distribution.

PubMed

Huang, Chong; Irwin, Daniel; Zhao, Mingjun; Shang, Yu; Agochukwu, Nneamaka; Wong, Lesley; Yu, Guoqiang

2017-10-01

Recent advancements in near-infrared diffuse correlation techniques and instrumentation have opened the path for versatile deep tissue microvasculature blood flow imaging systems. Despite this progress there remains a need for a completely noncontact, noninvasive device with high translatability from small/testing (animal) to large/target (human) subjects with trivial application on both. Accordingly, we discuss our newly developed setup which meets this demand, termed noncontact speckle contrast diffuse correlation tomography (nc_scDCT). The nc_scDCT provides fast, continuous, portable, noninvasive, and inexpensive acquisition of 3-D tomographic deep (up to 10 mm) tissue blood flow distributions with straightforward design and customization. The features presented include a finite-element-method implementation for incorporating complex tissue boundaries, fully noncontact hardware for avoiding tissue compression and interactions, rapid data collection with a diffuse speckle contrast method, reflectance-based design promoting experimental translation, extensibility to related techniques, and robust adjustable source and detector patterns and density for high resolution measurement with flexible regions of interest enabling unique application-specific setups. Validation is shown in the detection and characterization of both high and low contrasts in flow relative to the background using tissue phantoms with a pump-connected tube (high) and phantom spheres (low). Furthermore, in vivo validation of extracting spatiotemporal 3-D blood flow distributions and hyperemic response during forearm cuff occlusion is demonstrated. Finally, the success of instrument feasibility in clinical use is examined through the intraoperative imaging of mastectomy skin flap.

Diffusion studies with synchrotron Mössbauer spectroscopy

NASA Astrophysics Data System (ADS)

Jackson, J. M.

2011-12-01

Knowledge of diffusion properties is critical for understanding many physical and chemical processes in planetary interiors. For example, diffusion behavior provides constraints on chemical exchange and viscosity. Nuclear resonances open the window for observing diffusion properties under the extreme conditions that exist deep inside the Earth. Synchrotron Mössbauer spectroscopy (viz. nuclear forward scattering) makes use of synchrotron radiation coherently scattered in the forward direction after nuclear resonant excitation. The decay of the forward-scattered radiation is faster when atoms move on the time scale of the excited-state lifetime because of a loss of coherence. Such diffusion-activated processes lead to accelerated decay and line broadening in the measured signal. In the case of the Mössbauer active isotope 57Fe, the nuclear resonance at 14.4 keV has a natural lifetime of 141 ns. Therefore, one can observe diffusion events ranging from approximately one-sixth to 100 times the natural lifetime of 57Fe, which corresponds to diffusion coefficients of 10-16 and 10-13 m2/s, respectively and a two to three order of magnitude range of suitability. In this contribution, we will describe such measurements that access the microscopic details of the diffusion process for iron-bearing phases.

Quantitative model of diffuse speckle contrast analysis for flow measurement.

PubMed

Liu, Jialin; Zhang, Hongchao; Lu, Jian; Ni, Xiaowu; Shen, Zhonghua

2017-07-01

Diffuse speckle contrast analysis (DSCA) is a noninvasive optical technique capable of monitoring deep tissue blood flow. However, a detailed study of the speckle contrast model for DSCA has yet to be presented. We deduced the theoretical relationship between speckle contrast and exposure time and further simplified it to a linear approximation model. The feasibility of this linear model was validated by the liquid phantoms which demonstrated that the slope of this linear approximation was able to rapidly determine the Brownian diffusion coefficient of the turbid media at multiple distances using multiexposure speckle imaging. Furthermore, we have theoretically quantified the influence of optical property on the measurements of the Brownian diffusion coefficient which was a consequence of the fact that the slope of this linear approximation was demonstrated to be equal to the inverse of correlation time of the speckle.

How effective are simulated molecular-level experiments for teaching diffusion and osmosis?

PubMed

Meir, Eli; Perry, Judith; Stal, Derek; Maruca, Susan; Klopfer, Eric

2005-01-01

Diffusion and osmosis are central concepts in biology, both at the cellular and organ levels. They are presented several times throughout most introductory biology textbooks (e.g., Freeman, 2002), yet both processes are often difficult for students to understand (Odom, 1995; Zuckerman, 1994; Sanger et al., 2001; and results herein). Students have deep-rooted misconceptions about how diffusion and osmosis work, especially at the molecular level. We hypothesized that this might be in part due to the inability to see and explore these processes at the molecular level. In order to investigate this, we developed new software, OsmoBeaker, which allows students to perform inquiry-based experiments at the molecular level. Here we show that these simulated laboratories do indeed teach diffusion and osmosis and help overcome some, but not all, student misconceptions.

How Effective Are Simulated Molecular-level Experiments for Teaching Diffusion and Osmosis?

PubMed Central

2005-01-01

Diffusion and osmosis are central concepts in biology, both at the cellular and organ levels. They are presented several times throughout most introductory biology textbooks (e.g., Freeman, 2002), yet both processes are often difficult for students to understand (Odom, 1995; Zuckerman, 1994; Sanger et al., 2001; and results herein). Students have deep-rooted misconceptions about how diffusion and osmosis work, especially at the molecular level. We hypothesized that this might be in part due to the inability to see and explore these processes at the molecular level. In order to investigate this, we developed new software, OsmoBeaker, which allows students to perform inquiry-based experiments at the molecular level. Here we show that these simulated laboratories do indeed teach diffusion and osmosis and help overcome some, but not all, student misconceptions. PMID:16220144

Consequences of switching from a fixed 2 : 1 ratio of amoxicillin/clavulanate (CLSI) to a fixed concentration of clavulanate (EUCAST) for susceptibility testing of Escherichia coli.

PubMed

Leverstein-van Hall, Maurine A; Waar, Karola; Muilwijk, Jan; Cohen Stuart, James

2013-11-01

The CLSI recommends a fixed 2 : 1 ratio of co-amoxiclav for broth microdilution susceptibility testing of Enterobacteriaceae, while EUCAST recommends a fixed 2 mg/L clavulanate concentration. The aims of this study were: (i) to determine the influence of a switch from CLSI to EUCAST methodology on Escherichia coli susceptibility rates; (ii) to compare susceptibility results obtained using EUCAST-compliant microdilution with those from disc diffusion and the Etest; and (iii) to evaluate the clinical outcome of patients with E. coli sepsis treated with co-amoxiclav in relation to the susceptibility results obtained using either method. Resistance rates were determined in three laboratories that switched from CLSI to EUCAST cards with the Phoenix system (Becton Dickinson) as well as in 17 laboratories that continued to use CLSI cards with the VITEK 2 system (bioMérieux). In one laboratory, isolates were simultaneously tested by both the Phoenix system and either disc diffusion (n = 471) or the Etest (n = 113). Medical and laboratory records were reviewed for E. coli sepsis patients treated with co-amoxiclav monotherapy. Only laboratories that switched methodology showed an increase in resistance rates - from 19% in 2010 to 31% in 2011 (P < 0.0001). All isolates that tested susceptible by microdilution were also susceptible by disc diffusion or the Etest, but of 326 isolates that tested resistant by microdilution, 43% and 59% tested susceptible by disc diffusion and the Etest, respectively. Among the 89 patients included there was a better correlation between clinical response and measured MICs using the Phoenix system than the Etest. EUCAST methodology resulted in higher co-amoxiclav E. coli resistance rates than CLSI methodology, but correlated better with clinical outcome. EUCAST-compliant microdilution and disc diffusion provided discrepant results.

Method of applying a cerium diffusion coating to a metallic alloy

DOEpatents

Jablonski, Paul D [Salem, OR; Alman, David E [Benton, OR

2009-06-30

A method of applying a cerium diffusion coating to a preferred nickel base alloy substrate has been discovered. A cerium oxide paste containing a halide activator is applied to the polished substrate and then dried. The workpiece is heated in a non-oxidizing atmosphere to diffuse cerium into the substrate. After cooling, any remaining cerium oxide is removed. The resulting cerium diffusion coating on the nickel base substrate demonstrates improved resistance to oxidation. Cerium coated alloys are particularly useful as components in a solid oxide fuel cell (SOFC).

Comparison of Agar Dilution, Disk Diffusion, MicroScan, and Vitek Antimicrobial Susceptibility Testing Methods to Broth Microdilution for Detection of Fluoroquinolone-Resistant Isolates of the Family Enterobacteriaceae

PubMed Central

Steward, Christine D.; Stocker, Sheila A.; Swenson, Jana M.; O’Hara, Caroline M.; Edwards, Jonathan R.; Gaynes, Robert P.; McGowan, John E.; Tenover, Fred C.

1999-01-01

Fluoroquinolone resistance appears to be increasing in many species of bacteria, particularly in those causing nosocomial infections. However, the accuracy of some antimicrobial susceptibility testing methods for detecting fluoroquinolone resistance remains uncertain. Therefore, we compared the accuracy of the results of agar dilution, disk diffusion, MicroScan Walk Away Neg Combo 15 conventional panels, and Vitek GNS-F7 cards to the accuracy of the results of the broth microdilution reference method for detection of ciprofloxacin and ofloxacin resistance in 195 clinical isolates of the family Enterobacteriaceae collected from six U.S. hospitals for a national surveillance project (Project ICARE [Intensive Care Antimicrobial Resistance Epidemiology]). For ciprofloxacin, very major error rates were 0% (disk diffusion and MicroScan), 0.9% (agar dilution), and 2.7% (Vitek), while major error rates ranged from 0% (agar dilution) to 3.7% (MicroScan and Vitek). Minor error rates ranged from 12.3% (agar dilution) to 20.5% (MicroScan). For ofloxacin, no very major errors were observed, and major errors were noted only with MicroScan (3.7% major error rate). Minor error rates ranged from 8.2% (agar dilution) to 18.5% (Vitek). Minor errors for all methods were substantially reduced when results with MICs within ±1 dilution of the broth microdilution reference MIC were excluded from analysis. However, the high number of minor errors by all test systems remains a concern. PMID:9986809

Seismicity, shear failure and modes of deformation in deep subduction zones

NASA Technical Reports Server (NTRS)

Lundgren, Paul R.; Giardini, Domenico

1992-01-01

The joint hypocentral determination method is used to relocate deep seismicity reported in the International Seismological Center catalog for earthquakes deeper than 400 km in the Honshu, Bonin, Mariannas, Java, Banda, and South America subduction zones. Each deep seismic zone is found to display planar features of seismicity parallel to the Harvard centroid-moment tensor nodal planes, which are identified as planes of shear failure. The sense of displacement on these planes is one of resistance to deeper penetration.

Variability analysis of the bulk resistivity measured using concrete cylinders.

DOT National Transportation Integrated Search

2011-01-01

"Many agencies are interested in using a rapid test method for measuring the electrical properties of concrete (i.e., the : resistivity or conductivity) since the electrical properties can be related to fluid transport (e.g., ion diffusion). The adva...

How Stressful Is "Deep Bubbling"?

PubMed

Tyrmi, Jaana; Laukkanen, Anne-Maria

2017-03-01

Water resistance therapy by phonating through a tube into the water is used to treat dysphonia. Deep submersion (≥10 cm in water, "deep bubbling") is used for hypofunctional voice disorders. Using it with caution is recommended to avoid vocal overloading. This experimental study aimed to investigate how strenuous "deep bubbling" is. Fourteen subjects, half of them with voice training, repeated the syllable [pa:] in comfortable speaking pitch and loudness, loudly, and in strained voice. Thereafter, they phonated a vowel-like sound both in comfortable loudness and loudly into a glass resonance tube immersed 10 cm into the water. Oral pressure, contact quotient (CQ, calculated from electroglottographic signal), and sound pressure level were studied. The peak oral pressure P(oral) during [p] and shuttering of the outer end of the tube was measured to estimate the subglottic pressure P(sub) and the mean P(oral) during vowel portions to enable calculation of transglottic pressure P(trans). Sensations during phonation were reported with an open-ended interview. P(sub) and P(oral) were higher in "deep bubbling" and P(trans) lower than in loud syllable phonation, but the CQ did not differ significantly. Similar results were obtained for the comparison between loud "deep bubbling" and strained phonation, although P(sub) did not differ significantly. Most of the subjects reported "deep bubbling" to be stressful only for respiratory and lip muscles. No big differences were found between trained and untrained subjects. The CQ values suggest that "deep bubbling" may increase vocal fold loading. Further studies should address impact stress during water resistance exercises. Copyright © 2017 The Voice Foundation. Published by Elsevier Inc. All rights reserved.

Comparative histometric analysis of the effects of high-intensity focused ultrasound and radiofrequency on skin.

PubMed

Suh, Dong Hye; Choi, Jeong Hwee; Lee, Sang Jun; Jeong, Ki-Heon; Song, Kye Yong; Shin, Min Kyung

2015-01-01

High-intensity focused ultrasound (HIFU) and radiofrequency (RF) are used for non-invasive skin tightening. Neocollagenesis and neoelastogenesis have been reported to have a mechanism of controlled thermal injury. To compare neocollagenesis and neoelastogenesis in each layer of the dermis after each session of HIFU and monopolar RF. We analyzed the area fraction of collagen and elastic fibers using the Masson's Trichrome and Victoria blue special stains, respectively, before and after 2 months of treatments. Histometric analyses were performed in each layer of the dermis, including the papillary dermis, and upper, mid, and deep reticular dermis. Monopolar RF led to neocollagenesis in the papillary dermis, and upper, mid, and deep reticular dermis, and neoelastogenesis in the papillary dermis, and upper and mid reticular dermis. HIFU led to neocollagenesis in the mid and deep reticular dermis and neoelastogenesis in the deep reticular dermis. Among these treatment methods, HIFU showed the highest level of neocollagenesis and neoelastogenesis in the deep reticular dermis. HIFU affects deep tissues and impacts focal regions. Monopolar RF also affects deep tissues, but impacts diffuse regions. We believe these data provide further insight into effective skin tightening.

The Fornax Deep Survey with VST. I. The Extended and Diffuse Stellar Halo of NGC 1399 out to 192 kpc

NASA Astrophysics Data System (ADS)

Iodice, E.; Capaccioli, M.; Grado, A.; Limatola, L.; Spavone, M.; Napolitano, N. R.; Paolillo, M.; Peletier, R. F.; Cantiello, M.; Lisker, T.; Wittmann, C.; Venhola, A.; Hilker, M.; D'Abrusco, R.; Pota, V.; Schipani, P.

2016-03-01

We have started a new, deep multi-imaging survey of the Fornax cluster, dubbed the Fornax Deep Survey (FDS), at the VLT Survey Telescope (VST). In this paper we present the deep photometry inside two square degrees around the bright galaxy NGC 1399 in the core of the cluster. We found that the core of the Fornax cluster is characterized by a very extended and diffuse envelope surrounding the luminous galaxy NGC 1399: we map the surface brightness out to 33 arcmin (˜192 kpc) from the galaxy center and down to μg ˜ 31 mag arcsec-2 in the g band. The deep photometry allows us to detect a faint stellar bridge in the intracluster region on the west side of NGC 1399 and toward NGC 1387. By analyzing the integrated colors of this feature, we argue that it could be due to the ongoing interaction between the two galaxies, where the outer envelope of NGC 1387 on its east side is stripped away. By fitting the light profile, we found that there exists a physical break radius in the total light distribution at R = 10 arcmin (˜58 kpc) that sets the transition region between the bright central galaxy and the outer exponential halo, and that the stellar halo contributes 60% of the total light of the galaxy (Section 3.5). We discuss the main implications of this work on the build-up of the stellar halo at the center of the Fornax cluster. By comparing with the numerical simulations of the stellar halo formation for the most massive bright cluster galaxies (I.e., 13\\lt {log}{M}200/{M}⊙ \\lt 14), we find that the observed stellar halo mass fraction is consistent with a halo formed through the multiple accretion of progenitors with stellar mass in the range 108-1011 M⊙. This might suggest that the halo of NGC 1399 has also gone through a major merging event. The absence of a significant number of luminous stellar streams and tidal tails out to 192 kpc suggests that the epoch of this strong interaction goes back to an early formation epoch. Therefore, different from the Virgo cluster, the extended stellar halo around NGC 1399 is characterized by a more diffuse and well-mixed component, including the intracluster light.

Improved 2-D resistivity imaging of features in covered karst terrain with arrays of implanted electrodes

NASA Astrophysics Data System (ADS)

Kiflu, H. G.; Kruse, S. E.; Harro, D.; Loke, M. H.; Wilkinson, P. B.

2013-12-01

Electrical resistivity tomography is commonly used to identify geologic features associated with sinkhole formation. In covered karst terrain, however, it can be difficult to resolve the depth to top of limestone with this method. This is due to the fact that array lengths, and hence depth of resolution, are often limited by residential or commercial lot dimensions in urban environments. Furthermore, the sediments mantling the limestone are often clay-rich and highly conductive. The resistivity method has limited sensitivity to resistive zones beneath conductive zones. This sensitivity can be improved significantly with electrodes implanted at depth in the cover sediments near the top of limestone. An array of deep electrodes is installed with direct push technology in the karst cover. When combined with a surface array in which each surface electrode is underlain by a deep electrode, the array geometry is similar to a borehole array turned on its side. This method, called the Multi-Electrode Resistivity Implant Technique (MERIT), offers the promise of significantly improved resolution of epikarst and cover collapse development zones in the overlying sediment, the limestone or at the sediment-bedrock interface in heterogeneous karst environments. With a non-traditional array design, the question of optimal array geometries arises. Optimizing array geometries is complicated by the fact that many plausible 4-electrode readings will produce negative apparent resistivity values, even in homogeneous terrain. Negative apparent resistivities cannot be used in inversions based on the logarithm of the apparent resistivity. New algorithms for seeking optimal array geometries have been developed by modifying the 'Compare R' method of Wilkinson and Loke. The optimized arrays show significantly improved resolution over basic arrays adapted from traditional 2D surface geometries. Several MERIT case study surveys have been conducted in covered karst in west-central Florida, with 28-electrode arrays with electrodes 2-5 meters apart, and the deep arrays buried at 4-8 meters depth. Ground penetrating radar surveys, SPT borings and coring data provide selected 'ground truthing'. The case studies show that inclusion of the deep electrode array permits karst features such as undulations at the top of limestone and raveling zones within surficial sediments to be imaged. These features are not accessible from surface arrays with equivalent surface footprints. The method also has better resolution at depth at the ends of the lines, where surface arrays are typically plotted with a trapezoidal truncation due to poor resolution at the lower corners of the profile.

Reconnection in the Post-impulsive Phase of Solar Flares

NASA Astrophysics Data System (ADS)

Forbes, Terry G.; Seaton, Daniel B.; Reeves, Katharine K.

2018-05-01

Using a recently developed analytical procedure, we determine the rate of magnetic reconnection in the “standard” model of eruptive solar flares. During the late phase, the neutral line is located near the lower tip of the reconnection current sheet, and the upper region of the current sheet is bifurcated into a pair of Petschek-type shocks. Despite the presence of these shocks, the reconnection rate remains slow if the resistivity is uniform and the flow is laminar. Fast reconnection is achieved only if there is some additional mechanism that can shorten the length of the diffusion region at the neutral line. Observations of plasma flows by the X-ray telescope on Hinode imply that the diffusion region is, in fact, quite short. Two possible mechanisms for reducing the length of the diffusion region are localized resistivity and MHD turbulence.

Evaluation of multi-modal, multi-site neuroimaging measures in Huntington's disease: Baseline results from the PADDINGTON study☆

PubMed Central

Hobbs, Nicola Z.; Cole, James H.; Farmer, Ruth E.; Rees, Elin M.; Crawford, Helen E.; Malone, Ian B.; Roos, Raymund A.C.; Sprengelmeyer, Reiner; Durr, Alexandra; Landwehrmeyer, Bernhard; Scahill, Rachael I.; Tabrizi, Sarah J.; Frost, Chris

2012-01-01

Background Macro- and micro-structural neuroimaging measures provide valuable information on the pathophysiology of Huntington's disease (HD) and are proposed as biomarkers. Despite theoretical advantages of microstructural measures in terms of sensitivity to pathology, there is little evidence directly comparing the two. Methods 40 controls and 61 early HD subjects underwent 3 T MRI (T1- and diffusion-weighted), as part of the PADDINGTON study. Macrostructural volumetrics were obtained for the whole brain, caudate, putamen, corpus callosum (CC) and ventricles. Microstructural diffusion metrics of fractional anisotropy (FA), mean-, radial- and axial-diffusivity (MD, RD, AD) were computed for white matter (WM), CC, caudate and putamen. Group differences were examined adjusting for age, gender and site. A formal comparison of effect sizes determined which modality and metrics provided a statistically significant advantage over others. Results Macrostructural measures showed decreased regional and global volume in HD (p < 0.001); except the ventricles which were enlarged (p < 0.01). In HD, FA was increased in the deep grey-matter structures (p < 0.001), and decreased in the WM (CC, p = 0.035; WM, p = 0.053); diffusivity metrics (MD, RD, AD) were increased for all brain regions (p < 0.001). The largest effect sizes were for putamen volume, caudate volume and putamen diffusivity (AD, RD and MD); each was significantly larger than those for all other metrics (p < 0.05). Conclusion The highest performing macro- and micro-structural metrics had similar sensitivity to HD pathology quantified via effect sizes. Region-of-interest may be more important than imaging modality, with deep grey-matter regions outperforming the CC and global measures, for both volume and diffusivity. FA appears to be relatively insensitive to disease effects. PMID:24179770

Non-invasive measurements of tissue hemodynamics with hybrid diffuse optical methods

NASA Astrophysics Data System (ADS)

Durduran, Turgut

Diffuse optical techniques were used to measure hemodynamics of tissues non-invasively. Spectroscopy and tomography of the brain, muscle and implanted tumors were carried out in animal models and humans. Two qualitatively different methods, diffuse optical tomography and diffuse correlation tomography, were hybridized permitting simultaneous measurement of total hemoglobin concentration, blood oxygen saturation and blood flow. This combination of information was processed further to derive estimates of oxygen metabolism (e.g. CMRO 2) in tissue. The diffuse correlation measurements of blood flow were demonstrated in human tissues, for the first time, demonstrating continous, non-invasive imaging of oxygen metabolism in large tissue volumes several centimeters below the tissue surface. The bulk of these investigations focussed on cerebral hemodynamics. Extensive validation of this methodology was carried out in in vivo rat brain models. Three dimensional images of deep tissue hemodynamics in middle cerebral artery occlusion and cortical spreading depression (CSD) were obtained. CSD hemodynamics were found to depend strongly on partial pressure of carbon dioxide. The technique was then adapted for measurement of human brain. All optical spectroscopic measurements of CMRO2 during functional activation were obtained through intact human skull non-invasively. Finally, a high spatio-temporal resolution measurement of cerebral blood flow due to somatosensory cortex activation following electrical forepaw stimulation in rats was carried out with laser speckle flowmetry. New analysis methods were introduced for laser speckle flowmetry. In other organs, deep tissue hemodynamics were measured on human calf muscle during exercise and cuff-ischemia and were shown to have some clinical utility for peripheral vascular disease. In mice tumor models, the measured hemodynamics were shown to be predictive of photodynamic therapy efficacy, again suggesting promise of clinical utility. In total, the research has pioneered the development of diffuse optical measurements of blood flow, oxygenation and oxygen metabolism in a large range of research and clinical applications.

Misidentification of methicillin-resistant Staphylococcus aureus (MRSA) in hospitals in Tripoli, Libya

PubMed Central

Ahmed, Mohamed O.; Abuzweda, Abdulbaset R.; Alghazali, Mohamed H.; Elramalli, Asma K.; Amri, Samira G.; Aghila, Ezzeddin Sh.; Abouzeed, Yousef M.

2010-01-01

Background Methicillin-resistant Staphylococcus aureus (MRSA) is a nosocomial (hospital-acquired) pathogen of exceptional concern. It is responsible for life-threatening infections in both the hospital and the community. Aims To determine the frequency of MRSA misidentification in hospitals in Tripoli, Libya using current testing methods. Methods One hundred and seventy S. aureus isolates previously identified as MRSA were obtained from three hospitals in Tripoli. All isolates were reidentified by culturing on mannitol salt agar, API 20 Staph System and retested for resistance to methicillin using the cefoxitin disk diffusion susceptibility test and PBP2a. D-tests and vancomycin E-tests (Van-E-tests) were also performed for vancomycin-resistant isolates. Results Of the 170 isolates examined, 86 (51%) were confirmed as MRSA (i.e. 49% were misidentified as MRSA). Fifteen (17%) of the confirmed MRSA strains exhibited inducible clindamycin resistance. Of the 86 confirmed MRSA isolates, 13 (15%) were resistant to mupirocin, 53 (62%) were resistant to ciprofloxacin, 41 (48%) were resistant to trimethoprim-sulfamethoxazole, and none were resistant to linezolid. Although disc-diffusion testing indicated that 23 (27%) of the isolates were resistant to vancomycin, none of the isolates were vancomycin-resistant by Van-E-test. Conclusions Misidentification of nosocomial S. aureus as MRSA is a serious problem in Libyan hospitals. There is an urgent need for the proper training of microbiology laboratory technicians in standard antimicrobial susceptibility procedures and the implementation of quality control programs in microbiology laboratories of Libyan hospitals. PMID:21483574

Vertical distribution and composition of phytoplankton under the influence of an upper mixed layer.

PubMed

Ryabov, Alexei B; Rudolf, Lars; Blasius, Bernd

2010-03-07

The vertical distribution of phytoplankton is of fundamental importance for the dynamics and structure of aquatic communities. Here, using an advection-reaction-diffusion model, we investigate the distribution and competition of phytoplankton species in a water column, in which inverse resource gradients of light and a nutrient can limit growth of the biomass. This problem poses a challenge for ecologists, as the location of a production layer is not fixed, but rather depends on many internal parameters and environmental factors. In particular, we study the influence of an upper mixed layer (UML) in this system and show that it leads to a variety of dynamic effects: (i) Our model predicts alternative density profiles with a maximum of biomass either within or below the UML, thereby the system may be bistable or the relaxation from an unstable state may require a long-lasting transition. (ii) Reduced mixing in the deep layer can induce oscillations of the biomass; we show that a UML can sustain these oscillations even if the diffusivity is less than the critical mixing for a sinking phytoplankton population. (iii) A UML can strongly modify the outcome of competition between different phytoplankton species, yielding bistability both in the spatial distribution and in the species composition. (iv) A light limited species can obtain a competitive advantage if the diffusivity in the deep layers is reduced below a critical value. This yields a subtle competitive exclusion effect, where the oscillatory states in the deep layers are displaced by steady solutions in the UML. Finally, we present a novel graphical approach for deducing the competition outcome and for the analysis of the role of a UML in aquatic systems. 2009 Elsevier Ltd. All rights reserved.

Deep Fabry-Perot Hα observations of two Sculptor group galaxies, NGC 247 and 300

NASA Astrophysics Data System (ADS)

Hlavacek-Larrondo, J.; Marcelin, M.; Epinat, B.; Carignan, C.; de Denus-Baillargeon, M.-M.; Daigle, O.; Hernandez, O.

2011-09-01

It has been suggested that diffuse ionized gas can extend all the way to the end of the H I disc, and even beyond, such as in the case of the warped galaxyNGC 253 (Bland-Hawthorn et al.). Detecting ionized gas at these radii could carry significant implications as to the distribution of dark matter in galaxies. With the aim of detecting this gas, we carried out a deep Hα kinematical analysis of two Sculptor group galaxies, NGC 247 and 300. The Fabry-Perot data were taken at the 36-cm Marseille Telescope in La Silla, Chile, offering a large field of view. With almost 20 hours of observations for each galaxy, very faint diffuse emission is detected. Typical emission measures of 0.1 cm-6 pc are reached. For NGC 247, emission extending up to a radius comparable with that of the H I disc (r˜ 13 arcmin) is found, but no emission is seen beyond the H I disc. For NGC 300, we detect ionized gas on the entirety of our field of view (rmax˜ 14 arcmin), and find that the bright H II regions are embedded in a diffuse background. Using the deep data, extended optical rotation curves are obtained, as well as mass models. These are the most extended optical rotation curves thus far for these galaxies. We find no evidence suggesting that NGC 247 has a warped disc, and to account for our non-detection of Hα emission beyond its H I disc, as opposed to the warped galaxy NGC 253, our results favour the model in which, only through a warp, ionization by hot young stars in the central region of a galaxy can let photons escape and ionize the interstellar medium in the outer parts.

Internal-illumination photoacoustic computed tomography

NASA Astrophysics Data System (ADS)

Li, Mucong; Lan, Bangxin; Liu, Wei; Xia, Jun; Yao, Junjie

2018-03-01

We report a photoacoustic computed tomography (PACT) system using a customized optical fiber with a cylindrical diffuser to internally illuminate deep targets. The traditional external light illumination in PACT usually limits the penetration depth to a few centimeters from the tissue surface, mainly due to strong optical attenuation along the light propagation path from the outside in. By contrast, internal light illumination, with external ultrasound detection, can potentially detect much deeper targets. Different from previous internal illumination PACT implementations using forward-looking optical fibers, our internal-illumination PACT system uses a customized optical fiber with a 3-cm-long conoid needle diffuser attached to the fiber tip, which can homogeneously illuminate the surrounding space and substantially enlarge the field of view. We characterized the internal illumination distribution and PACT system performance. We performed tissue phantom and in vivo animal studies to further demonstrate the superior imaging depth using internal illumination over external illumination. We imaged a 7.5-cm-deep leaf target embedded in optically scattering medium and the beating heart of a mouse overlaid with 3.7-cm-thick chicken tissue. Our results have collectively demonstrated that the internal light illumination combined with external ultrasound detection might be a useful strategy to improve the penetration depth of PACT in imaging deep organs of large animals and humans.

Striations, duration, migration and tidal response in deep tremor.

PubMed

Ide, Satoshi

2010-07-15

Deep tremor in subduction zones is thought to be caused by small repeating shear slip events on the plate interface with significant slow components. It occurs at a depth of about 30 kilometres and provides valuable information on deep plate motion and shallow stress accumulation on the fault plane of megathrust earthquakes. Tremor has been suggested to repeat at a regular interval, migrate at various velocities and be modulated by tidal stress. Here I show that some time-invariant interface property controls tremor behaviour, using precise location of tremor sources with event duration in western Shikoku in the Nankai subduction zone, Japan. In areas where tremor duration is short, tremor is more strongly affected by tidal stress and migration is inhibited. Where tremor lasts longer, diffusive migration occurs with a constant diffusivity of 10(4) m(2) s(-1). The control property may be the ratio of brittle to ductile areas, perhaps determined by the influence of mantle wedge serpentinization on the plate interface. The spatial variation of the controlling property seems to be characterized by striations in tremor source distribution, which follows either the current or previous plate subduction directions. This suggests that the striations and corresponding interface properties are formed through the subduction of inhomogeneous structure, such as seamounts, for periods as long as ten million years.

Detection of Salmonella spp. with the BACTEC 9240 Automated Blood Culture System in 2008 - 2014 in Southern Iran (Shiraz): Biogrouping, MIC, and Antimicrobial Susceptibility Profiles of Isolates.

PubMed

Anvarinejad, Mojtaba; Pouladfar, Gholam Reza; Pourabbas, Bahman; Amin Shahidi, Maneli; Rafaatpour, Noroddin; Dehyadegari, Mohammad Ali; Abbasi, Pejman; Mardaneh, Jalal

2016-04-01

Human salmonellosis continues to be a major international problem, in terms of both morbidity and economic losses. The antibiotic resistance of Salmonella is an increasing public health emergency, since infections from resistant bacteria are more difficult and costly to treat. The aims of the present study were to investigate the isolation of Salmonella spp. with the BACTEC automated system from blood samples during 2008 - 2014 in southern Iran (Shiraz). Detection of subspecies, biogrouping, and antimicrobial susceptibility testing by the disc diffusion and agar dilution methods were performed. A total of 19 Salmonella spp. were consecutively isolated using BACTEC from blood samples of patients between 2008 and 2014 in Shiraz, Iran. The isolates were identified as Salmonella, based on biochemical tests embedded in the API-20E system. In order to characterize the biogroups and subspecies, biochemical testing was performed. Susceptibility testing (disc diffusion and agar dilution) and extended-spectrum β-lactamase (ESBL) detection were performed according to the clinical and laboratory standards institute (CLSI) guidelines. Of the total 19 Salmonella spp. isolates recovered by the BACTEC automated system, all belonged to the Salmonella enterica subsp. houtenae. Five isolates (26.5%) were resistant to azithromycin. Six (31.5%) isolates with the disc diffusion method and five (26.3%) with the agar dilution method displayed resistance to nalidixic acid (minimum inhibitory concentration [MIC] > 32 μg/mL). All nalidixic acid-resistant isolates were also ciprofloxacin-sensitive. All isolates were ESBL-negative. Twenty-one percent of isolates were found to be resistant to chloramphenicol (MIC ≥ 32 μg/mL), and 16% were resistant to ampicillin (MIC ≥ 32 μg/mL). The results indicate that multidrug-resistant (MDR) strains of Salmonella are increasing in number, and fewer antibiotics may be useful for treating S. enterica infections. Routine investigation and reporting of antibiotic MICs in patients presenting with Salmonella infections is suggested.

Scaling of angiosperm xylem structure with safety and efficiency.

PubMed

Hacke, Uwe G; Sperry, John S; Wheeler, James K; Castro, Laura

2006-06-01

We tested the hypothesis that greater cavitation resistance correlates with less total inter-vessel pit area per vessel (the pit area hypothesis) and evaluated a trade-off between cavitation safety and transport efficiency. Fourteen species of diverse growth form (vine, ring- and diffuse-porous tree, shrub) and family affinity were added to published data predominately from the Rosaceae (29 species total). Two types of vulnerability-to-cavitation curves were found. Ring-porous trees and vines showed an abrupt drop in hydraulic conductivity with increasing negative pressure, whereas hydraulic conductivity in diffuse-porous species generally decreased gradually. The ring-porous type curve was not an artifact of the centrifuge method because it was obtained also with the air-injection technique. A safety versus efficiency trade-off was evident when curves were compared across species: for a given pressure, there was a limited range of optimal vulnerability curves. The pit area hypothesis was supported by a strong relationship (r2 = 0.77) between increasing cavitation resistance and diminishing pit membrane area per vessel (A(P)). Small A(P) was associated with small vessel surface area and hence narrow vessel diameter (D) and short vessel length (L)--consistent with an increase in vessel flow resistance with cavitation resistance. This trade-off was amplified at the tissue level by an increase in xylem/vessel area ratio with cavitation resistance. Ring-porous species were more efficient than diffuse-porous species on a vessel basis but not on a xylem basis owing to higher xylem/vessel area ratios in ring-porous anatomy. Across four orders of magnitude, lumen and end-wall resistivities maintained a relatively tight proportionality with a near-optimal mean of 56% of the total vessel resistivity residing in the end-wall. This was consistent with an underlying scaling of L to D(3/2) across species. Pit flow resistance did not increase with cavitation safety, suggesting that cavitation pressure was not related to mean pit membrane porosity.

Highly Sensitive Detection of Isoniazid Heteroresistance in Mycobacterium tuberculosis by DeepMelt Assay.

PubMed

Liang, Bin; Tan, Yaoju; Li, Zi; Tian, Xueshan; Du, Chen; Li, Hui; Li, Guoli; Yao, Xiangyang; Wang, Zhongan; Xu, Ye; Li, Qingge

2018-02-01

Detection of heteroresistance of Mycobacterium tuberculosis remains challenging using current genotypic drug susceptibility testing methods. Here, we described a melting curve analysis-based approach, termed DeepMelt, that can detect less-abundant mutants through selective clamping of the wild type in mixed populations. The singleplex DeepMelt assay detected 0.01% katG S315T in 10 5 M. tuberculosis genomes/μl. The multiplex DeepMelt TB/INH detected 1% of mutant species in the four loci associated with isoniazid resistance in 10 4 M. tuberculosis genomes/μl. The DeepMelt TB/INH assay was tested on a panel of DNA extracted from 602 precharacterized clinical isolates. Using the 1% proportion method as the gold standard, the sensitivity was found to be increased from 93.6% (176/188, 95% confidence interval [CI] = 89.2 to 96.3%) to 95.7% (180/188, 95% CI = 91.8 to 97.8%) compared to the MeltPro TB/INH assay. Further evaluation of 109 smear-positive sputum specimens increased the sensitivity from 83.3% (20/24, 95% CI = 64.2 to 93.3%) to 91.7% (22/24, 95% CI = 74.2 to 97.7%). In both cases, the specificity remained nearly unchanged. All heteroresistant samples newly identified by the DeepMelt TB/INH assay were confirmed by DNA sequencing and even partially by digital PCR. The DeepMelt assay may fill the gap between current genotypic and phenotypic drug susceptibility testing for detecting drug-resistant tuberculosis patients. Copyright © 2018 American Society for Microbiology.

Distribution of Upper Circumpolar Deep Water on the warming continental shelf of the West Antarctic Peninsula

NASA Astrophysics Data System (ADS)

Couto, Nicole; Martinson, Douglas G.; Kohut, Josh; Schofield, Oscar

2017-07-01

We use autonomous underwater vehicles to characterize the spatial distribution of Upper Circumpolar Deep Water (UCDW) on the continental shelf of the West Antarctic Peninsula (WAP) and present the first near-synoptic measurements of mesoscale features (eddies) containing UCDW on the WAP. Thirty-three subsurface eddies with widths on the order of 10 km were detected during four glider deployments. Each eddy contributed an average of 5.8 × 1016 J to the subpycnocline waters, where a cross-shelf heat flux of 1.37 × 1019 J yr-1 is required to balance the diffusive loss of heat to overlying winter water and to the near-coastal waters. Approximately two-thirds of the heat coming onto the shelf diffuses across the pycnocline and one-third diffuses to the coastal waters; long-term warming of the subpycnocline waters is a small residual of this balance. Sixty percent of the profiles that contained UCDW were part of a coherent eddy. Between 20% and 53% of the lateral onshore heat flux to the WAP can be attributed to eddies entering Marguerite Trough, a feature in the southern part of the shelf which is known to be an important conduit for UCDW. A northern trough is identified as additional important location for eddy intrusion.

Electrochemical synthesis of copper nanoparticles using cuprous oxide as a precursor in choline chloride-urea deep eutectic solvent: nucleation and growth mechanism.

PubMed

Zhang, Q B; Hua, Y X

2014-12-28

The electrochemical nucleation and growth kinetics of copper nanoparticles on a Ni electrode have been studied with cyclic voltammetry and chronoamperometry in the choline chloride (ChCl)-urea based deep eutectic solvent (DES). The copper source was introduced into the solvent by the dissolution of Cu(I) oxide (Cu2O). Cyclic voltammetry indicates that the electroreduction of Cu(I) species in the DES is a diffusion-controlled quasi-reversible process. The analysis of the chronoamperometric transient behavior during electrodeposition suggests that the deposition of copper on the Ni electrode at low temperatures follows a progressive nucleation and three-dimensional growth controlled by diffusion. The effect of temperature on the diffusion coefficient of Cu(I) species that is present in the solvent and electron transfer rate constant obeys the Arrhenius law, according to which the activation energies are estimated to be 49.20 and 21.72 kJ mol(-1), respectively. The initial stage of morphological study demonstrates that both electrode potential and temperature play important roles in controlling the nucleation and growth kinetics of the nanocrystals during the electrodeposition process. Electrode potential is observed to affect mainly the nucleation process, whereas temperature makes a major contribution to the growth process.

Identification of ribonucleotide reductase mutation causing temperature-sensitivity of herpes simplex virus isolates from whitlow by deep sequencing.

PubMed

Daikoku, Tohru; Oyama, Yukari; Yajima, Misako; Sekizuka, Tsuyoshi; Kuroda, Makoto; Shimada, Yuka; Takehara, Kazuhiko; Miwa, Naoko; Okuda, Tomoko; Sata, Tetsutaro; Shiraki, Kimiyasu

2015-06-01

Herpes simplex virus 2 caused a genital ulcer, and a secondary herpetic whitlow appeared during acyclovir therapy. The secondary and recurrent whitlow isolates were acyclovir-resistant and temperature-sensitive in contrast to a genital isolate. We identified the ribonucleotide reductase mutation responsible for temperature-sensitivity by deep-sequencing analysis.

Characterization of cesium diffusion behavior into granite matrix using Rutherford backscattering spectrometry

NASA Astrophysics Data System (ADS)

Tsai, Shih-Chin; Lee, Chuan-Pin; Tsai, Tsuey-Lin; Yu, Yueh-Chung

2017-10-01

The characterization of radionuclide diffusion behavior is necessary for performance assessment of granite as a geological barrier for high-level radioactive waste disposal. Rutherford backscattering spectrometry (RBS), a novel nuclear ion-beam technique, was selected in this study because it is suitable for analyzing the concentration gradients of heavy elements in a well-defined matrix and allows measuring diffusion coefficients on a micrometer scale. In this study Cs was selected to represent Cs-135 (a key radionuclide in high-level waste) diffusion in granite. The Cs energy spectrum and concentration deep profile were analyzed and the diffusion coefficient of Cs in granite for three different locations were determined, which were 2.06 × 10-19m2 s-1, 3.58 × 10-19m2 s-1, and 7.19 × 10-19m2 s-1-19m2 s-19m2 s-1, respectively, which were of a similiar order of magnitude. Results from other studies are also compared and discussed in this paper.

Charge Diffusion Variations in Pan-STARRS1 CCDs

NASA Astrophysics Data System (ADS)

Magnier, Eugene A.; Tonry, J. L.; Finkbeiner, D.; Schlafly, E.; Burgett, W. S.; Chambers, K. C.; Flewelling, H. A.; Hodapp, K. W.; Kaiser, N.; Kudritzki, R.-P.; Metcalfe, N.; Wainscoat, R. J.; Waters, C. Z.

2018-06-01

Thick back-illuminated deep-depletion CCDs have superior quantum efficiency over previous generations of thinned and traditional thick CCDs. As a result, they are being used for wide-field imaging cameras in several major projects. We use observations from the Pan-STARRS 3π survey to characterize the behavior of the deep-depletion devices used in the Pan-STARRS 1 Gigapixel Camera. We have identified systematic spatial variations in the photometric measurements and stellar profiles that are similar in pattern to the so-called “tree rings” identified in devices used by other wide-field cameras (e.g., DECam and Hypersuprime Camera). The tree-ring features identified in these other cameras result from lateral electric fields that displace the electrons as they are transported in the silicon to the pixel location. In contrast, we show that the photometric and morphological modifications observed in the GPC1 detectors are caused by variations in the vertical charge transportation rate and resulting charge diffusion variations.

Defects and annealing studies in 1-Me electron irradiated (AlGa)As-GaAs solar cells

NASA Technical Reports Server (NTRS)

Li, S. S.; Wang, W. L.; Loo, R. Y.; Rahilly, W. P.

1982-01-01

The deep-level defects and recombination mechanisms in the one-MeV electron irradiated (AlGa)As-GaAs solar cells under various irradiation and annealing conditions are discussed. Deep-level transient spectroscopy (DLTS) and capacitance-voltage (CV) techniques were used to determine the defect and recombination parameters such as energy levels and defect density, carrier capture cross sections and lifetimes for both electron and hole traps as well as hole diffusion lengths in these electron irradiated GaAs solar cells. GaAs solar cells used in this study were prepared by the infinite solution melt liquid phase epitaxial (LPE) technique at Hughes Research Lab., with (Al0.9Ga0.1)-As window layer, Be-diffused p-GaAs layer on Sn-doped n-GaAs or undoped n-GaAs active layer grown on n(+)-GaAs substrate. Mesa structure with area of 5.86x1000 sq cm was fabricated. Three different irradiation and annealing experiments were performed on these solar cells.

Differences in biological traits composition of benthic assemblages between unimpacted habitats.

PubMed

Bolam, S G; Garcia, C; Eggleton, J; Kenny, A J; Buhl-Mortensen, L; Gonzalez-Mirelis, G; van Kooten, T; Dinesen, G; Hansen, J; Hiddink, J G; Sciberras, M; Smith, C; Papadopoulou, N; Gumus, A; Van Hoey, G; Eigaard, O R; Bastardie, F; Rijnsdorp, A D

2017-05-01

There is an implicit requirement under contemporary policy drivers to understand the characteristics of benthic communities under anthropogenically-unimpacted scenarios. We used a trait-based approach on a large dataset from across the European shelf to determine how functional characteristics of unimpacted benthic assemblages vary between different sedimentary habitats. Assemblages in deep, muddy environments unaffected by anthropogenic disturbance show increased proportions of downward conveyors and surface deposit-feeders, while burrowing, diffusive mixing, scavenging and predation traits assume greater numerical proportions in shallower habitats. Deep, coarser sediments are numerically more dominated by sessile, upward conveyors and suspension feeders. In contrast, unimpacted assemblages of coarse sediments in shallower regions are proportionally dominated by the diffusive mixers, burrowers, scavengers and predators. Finally, assemblages of gravelly sediments exhibit a relatively greater numerical dominance of non-bioturbators and asexual reproducers. These findings may be used to form the basis of ranking habitats along a functional sensitivity gradient. Crown Copyright © 2017. Published by Elsevier Ltd. All rights reserved.

Interior radiances in optically deep absorbing media. III Scattering from Haze L

NASA Technical Reports Server (NTRS)

Kattawar, G. W.; Plass, G. N.

1975-01-01

The interior radiances are calculated within an optically deep absorbing medium scattering according to the Haze L phase function. The dependence on the solar zenith angle, the single scattering albedo, and the optical depth within the medium is calculated by the matrix operator method. The development of the asymptotic angular distribution of the radiance in the diffusion region is illustrated through a number of examples; it depends only on the single scattering albedo and on the phase function for single scattering. The exact values of the radiance in the diffusion region are compared with values calculated from the approximate equations proposed by Van de Hulst. The variation of the radiance near the lower boundary of an optically thick medium is illustrated with examples. The attenuation length is calculated for various single scattering albedos and compared with the corresponding values for Rayleigh scattering. The ratio of the upward to the downward flux is found to be remarkably constant within the medium.

Histological and Immunological Description of the Leishmanin Skin Test in Ibizan Hounds.

PubMed

Ordeix, L; Silva, J E Dos S; Llull, J; Quirola, P; Montserrat-Sangrà, S; Martínez-Orellana, P; Solano-Gallego, L

2018-01-01

The leishmanin skin test (LST), a delayed-type hypersensitivity (DTH) reaction to Leishmania infantum, can specifically identify dogs that have made a cell-mediated immune response to L. infantum infection. The Ibizan hound appears to be more resistant to L. infantum infection than other breeds of dog. The aim of this study was to describe the histological and immunohistochemical changes induced by the LST in Ibizan hounds living in an area highly endemic for leishmaniosis. The majority of dogs were apparently healthy, lacked serum antibody to L. infantum and blood parasitaemia, but had marked specific interferon gamma production after in-vitro blood stimulation with L. infantum. Leishmanin (3 × 10 8 killed promastigotes of L. infantum/ml) was injected intradermally and biopsy samples were obtained from a positive reaction at 72 h from nine Ibizan hounds. A moderate to intense, perivascular to interstitial dermatitis and panniculitis characterized the inflammatory response at the injection site. In addition, three samples had diffuse inflammation in the deep dermis and panniculus. Oedema and necrosis were present in the deep dermis and panniculus. Congestion and haemorrhage were observed in five biopsies. T lymphocytes (CD3 + ) and large mononuclear cells (lysozyme - ) were the most prevalent cells. CD3 + cells were significantly more numerous than CD20 + B cells and lysozyme + cells. B cells were sparsely distributed, especially in the deep dermis and panniculus. Rare neutrophils and macrophages (lysozyme + ) were observed with few eosinophils. Toll-like receptor (TLR)-2 protein was expressed in large mononuclear cells mainly located in the superficial dermis. Leishmania immunohistochemistry was negative and quantitative polymerase chain reaction was positive in all cases. The intradermal injection of killed L. infantum promastigotes in Ibizan hounds causes similar histological and immunohistochemical findings to those described for human subjects and are indicative of a DTH response. Moreover, TLR2 protein is expressed in inflammatory cells similar to findings in clinically affected skin biopsy samples. Copyright © 2017 Elsevier Ltd. All rights reserved.

Gradient boride layers formed by diffusion carburizing and laser boriding

NASA Astrophysics Data System (ADS)

Kulka, M.; Makuch, N.; Dziarski, P.; Mikołajczak, D.; Przestacki, D.

2015-04-01

Laser boriding, instead of diffusion boriding, was proposed to formation of gradient borocarburized layers. The microstructure and properties of these layers were compared to those-obtained after typical diffusion borocarburizing. First method of treatment consists in diffusion carburizing and laser boriding only. In microstructure three zones are present: laser borided zone, hardened carburized zone and carburized layer without heat treatment. However, the violent decrease in the microhardness was observed below the laser borided zone. Additionally, these layers were characterized by a changeable value of mass wear intensity factor thus by a changeable abrasive wear resistance. Although at the beginning of friction the very low values of mass wear intensity factor Imw were obtained, these values increased during the next stages of friction. It can be caused by the fluctuations in the microhardness of the hardened carburized zone (HAZ). The use of through hardening after carburizing and laser boriding eliminated these fluctuations. Two zones characterized the microstructure of this layer: laser borided zone and hardened carburized zone. Mass wear intensity factor obtained a constant value for this layer and was comparable to that-obtained in case of diffusion borocarburizing and through hardening. Therefore, the diffusion boriding could be replaced by the laser boriding, when the high abrasive wear resistance is required. However, the possibilities of application of laser boriding instead of diffusion process were limited. In case of elements, which needed high fatigue strength, the substitution of diffusion boriding by laser boriding was not advisable. The surface cracks formed during laser re-melting were the reason for relatively quickly first fatigue crack. The preheating of the laser treated surface before laser beam action would prevent the surface cracks and cause the improved fatigue strength. Although the cohesion of laser borided carburized layer was sufficient, the diffusion borocarburized layer showed a better cohesion.

Double-diffusive instabilities in ancient seawater

NASA Astrophysics Data System (ADS)

Pawlowicz, Rich; Scheifele, Ben; Zaloga, Artem; Wuest, Alfred; Sommer, Tobias

2015-04-01

Powell Lake, British Columbia, Canada is a geothermally heated lake about 350m deep with a saline lower layer that was isolated from the ocean by coastal uplift about 11000 years ago, after the last ice age. Careful temperature and conductivity profiling measurements show consistent, stable, and spatially/temporally coherent steps resulting from double-diffusive processes in certain ranges of depth, vertically interspersed with other depth ranges where these signatures are not present. These features are quasi-stable for at least several years. Although molecular diffusion has removed about half the salt from the deepest waters and biogeochemical processes have slightly modified the water composition, the lack of tidal processes and shear-driven mixing, as well as an accurate estimate of heat flux from both sediment heat flux measurements and gradient measurements in a region not susceptible to diffusive instabilities, makes this a unique geophysical laboratory to study double diffusion. Here we present a detailed picture of the structure of Powell Lake and its double-diffusive stair cases, and suggest shortcomings with existing parameterizations for fluxes through such staircases.

Anomalously Fast Diffusion of Targeted Carbon Nanotubes in Cellular Spheroids.

PubMed

Wang, Yichun; Bahng, Joong Hwan; Che, Quantong; Han, Jishu; Kotov, Nicholas A

2015-08-25

Understanding transport of carbon nanotubes (CNTs) and other nanocarriers within tissues is essential for biomedical imaging and drug delivery using these carriers. Compared to traditional cell cultures in animal studies, three-dimensional tissue replicas approach the complexity of the actual organs and enable high temporal and spatial resolution of the carrier permeation. We investigated diffusional transport of CNTs in highly uniform spheroids of hepatocellular carcinoma and found that apparent diffusion coefficients of CNTs in these tissue replicas are anomalously high and comparable to diffusion rates of similarly charged molecules with molecular weights 10000× lower. Moreover, diffusivity of CNTs in tissues is enhanced after functionalization with transforming growth factor β1. This unexpected trend contradicts predictions of the Stokes-Einstein equation and previously obtained empirical dependences of diffusivity on molecular mass for permeants in gas, liquid, solid or gel. It is attributed to the planar diffusion (gliding) of CNTs along cellular membranes reducing effective dimensionality of diffusional space. These findings indicate that nanotubes and potentially similar nanostructures are capable of fast and deep permeation into the tissue, which is often difficult to realize with anticancer agents.

Ionic-Electronic Ambipolar Transport in Metal Halide Perovskites: Can Electronic Conductivity Limit Ionic Diffusion?

PubMed

Kerner, Ross A; Rand, Barry P

2018-01-04

Ambipolar transport describes the nonequilibrium, coupled motion of positively and negatively charged particles to ensure that internal electric fields remain small. It is commonly invoked in the semiconductor community where the motion of excess electrons and holes drift and diffuse together. However, the concept of ambipolar transport is not limited to semiconductor physics. Materials scientists working on ion conducting ceramics understand ambipolar transport dictates the coupled diffusion of ions and the rate is limited by the ion with the lowest diffusion coefficient. In this Perspective, we review a third application of ambipolar transport relevant to mixed ionic-electronic conducting materials for which the motion of ions is expected to be coupled to electronic carriers. In this unique situation, the ambipolar diffusion model has been successful at explaining the photoenhanced diffusion of metal ions in chalcogenide glasses and other properties of materials. Recent examples of photoenhanced phenomena in metal halide perovskites are discussed and indicate that mixed ionic-electronic ambipolar transport is similarly important for a deep understanding of these emerging materials.

Antagonistic Activity of Nocardia brasiliensis PTCC 1422 Against Isolated Enterobacteriaceae from Urinary Tract Infections.

PubMed

Jalali, Hossnieh Kafshdar; Salamatzadeh, Abdolreza; Jalali, Arezou Kafshdar; Kashani, Hamed Haddad; Asbchin, Salman Ahmadi; Issazadeh, Khosro

2016-03-01

The main drawback of current antibiotic therapies is the emergence and rapid increase in antibiotic resistance. Nocardiae are aerobic, Gram-positive, catalase-positive, non-motile actinomycetes. Nocardia brasiliensis was reported as antibiotic producer. The purpose of the study was to determine antibacterial activity of N. brasiliensis PTCC 1422 against isolated Enterobacteriaceae from urinary tract infections (UTIs). The common bacteria from UTIs were isolated from hospital samples. Antimicrobial susceptibility test was performed for the isolated pathogens using Kirby-Bauer disk diffusion method according to clinical and Laboratory Standards Institute guideline. Antagonistic activity of N. brasiliensis PTCC 1422 was examined with well diffusion methods. Supernatant of N. brasiliensis PTCC 1422 by submerged culture was analyzed with gas chromatography-mass spectrometry. Isolated strains included Escherichia coli, Klebsiella pneumoniae, Serratia marcescens and Proteus mirabilis. The most common pathogen isolated was E. coli (72.5%). Bacterial isolates revealed the presence of high levels of antimicrobial resistances to ceftriaxone and low levels of resistance to cephalexin. Supernatant of N. brasiliensis PTCC 1422 showed antibacterial activity against all of the isolated microorganisms in well diffusion method. The antibiotic resistance among the uropathogens is an evolving process, so a routine surveillance to monitor the etiologic agents of UTI and the resistance pattern should be carried out timely to choose the most effective empirical treatment by the physicians. Our present investigation indicates that the substances present in the N. brasiliensis PTCC 1422 could be used to inhibit the growth of human pathogen. Antibacterial resistance among bacterial uropathogen is an evolving process. Therefore, in the field on the need of re-evaluation of empirical treatment of UTIs, our present. The study has demonstrated that N. brasiliensis PTCC 1422 has a high potential for the treatment of UTIs.

Nonlinear ELM simulations based on a nonideal peeling–ballooning model using the BOUT++ code

DOE PAGES

Xu, X. Q.; Dudson, B. D.; Snyder, P. B.; ...

2011-09-23

A minimum set of equations based on the peeling–ballooning (P–B) model with nonideal physics effects (diamagnetic drift, E × B drift, resistivity and anomalous electron viscosity) is found to simulate pedestal collapse when using the BOUT++ simulation code, developed in part from the original fluid edge code BOUT. Linear simulations of P–B modes find good agreement in growth rate and mode structure with ELITE calculations. The influence of the E × B drift, diamagnetic drift, resistivity, anomalous electron viscosity, ion viscosity and parallel thermal diffusivity on P–B modes is being studied; we find that (1) the diamagnetic drift and Emore » × B drift stabilize the P–B mode in a manner consistent with theoretical expectations; (2) resistivity destabilizes the P–B mode, leading to resistive P–B mode; (3) anomalous electron and parallel ion viscosities destabilize the P–B mode, leading to a viscous P–B mode; (4) perpendicular ion viscosity and parallel thermal diffusivity stabilize the P–B mode. With addition of the anomalous electron viscosity under the assumption that the anomalous kinematic electron viscosity is comparable to the anomalous electron perpendicular thermal diffusivity, or the Prandtl number is close to unity, it is found from nonlinear simulations using a realistic high Lundquist number that the pedestal collapse is limited to the edge region and the ELM size is about 5–10% of the pedestal stored energy. Furthermore, this is consistent with many observations of large ELMs. The estimated island size is consistent with the size of fast pedestal pressure collapse. In the stable α-zones of ideal P–B modes, nonlinear simulations of viscous ballooning modes or current-diffusive ballooning mode (CDBM) for ITER H-mode scenarios are presented.« less

Effects of neuromuscular joint facilitation on bridging exercises with respect to deep muscle changes.

PubMed

Zhou, Bin; Huang, QiuChen; Zheng, Tao; Huo, Ming; Maruyama, Hitoshi

2015-05-01

[Purpose] This study examined the effects of neuromuscular joint facilitation on bridging exercises by assessing the cross-sectional area of the multifidus muscle and thickness of the musculus transversus abdominis. [Subjects] Twelve healthy men. [Methods] Four exercises were evaluated: (a) supine resting, (b) bridging resistance exercise involving posterior pelvic tilting, (c) bridging resistance exercise involving anterior pelvic tilting, and (d) bridging resistance exercise involving neuromuscular joint facilitation. The cross-sectional area of the multifidus muscle and thickness of the musculus transversus abdominis were measured during each exercise. [Results] The cross-sectional area of the multifidus muscle and thickness of the musculus transversus abdominis were significantly greater in the neuromuscular joint facilitation group than the others. [Conclusion] Neuromuscular joint facilitation intervention improves the function of deep muscles such as the multifidus muscle and musculus transversus abdominis. Therefore, it can be recommended for application in clinical treatments such as that for back pain.

Hall effect analysis in irradiated silicon samples with different resistivities

NASA Astrophysics Data System (ADS)

Borchi, E.; Bruzzi, M.; Dezillie, B.; Lazanu, S.; Li, Z.; Pirollo, S.

1999-08-01

The changes induced by neutron irradiation in n- and p-type silicon samples with starting resistivities from 10 /spl Omega/-cm up to 30 k/spl Omega/-cm, grown using different techniques, as float-zone (FZ), Czochralski (CZ) and epitaxial, have been analyzed by Van der Pauw and Hall effect measurements. Increasing the fluence, each set of samples evolves toward a quasi-intrinsic p-type material. This behavior has been explained in the frame of a two-level model, that considers the introduction during irradiation of mainly two defects. A deep acceptor and a deep donor, probably related to the divacancy and to the C/sub i/O/sub i/ complex, are placed in the upper and lower half of the forbidden gap, respectively. This simple model explains quantitatively the data on resistivity and Hall coefficient of each set of samples up to the fluence of /spl ap/10/sup 14/ n/cm/sup 2/.

Response simulation and theoretical calibration of a dual-induction resistivity LWD tool

NASA Astrophysics Data System (ADS)

Xu, Wei; Ke, Shi-Zhen; Li, An-Zong; Chen, Peng; Zhu, Jun; Zhang, Wei

2014-03-01

In this paper, responses of a new dual-induction resistivity logging-while-drilling (LWD) tool in 3D inhomogeneous formation models are simulated by the vector finite element method (VFEM), the influences of the borehole, invaded zone, surrounding strata, and tool eccentricity are analyzed, and calibration loop parameters and calibration coefficients of the LWD tool are discussed. The results show that the tool has a greater depth of investigation than that of the existing electromagnetic propagation LWD tools and is more sensitive to azimuthal conductivity. Both deep and medium induction responses have linear relationships with the formation conductivity, considering optimal calibration loop parameters and calibration coefficients. Due to the different depths of investigation and resolution, deep induction and medium induction are affected differently by the formation model parameters, thereby having different correction factors. The simulation results can provide theoretical references for the research and interpretation of the dual-induction resistivity LWD tools.

Radiation damage and defect behavior in ion-implanted, lithium counterdoped silicon solar cells

NASA Technical Reports Server (NTRS)

Weinberg, I.; Mehta, S.; Swartz, C. K.

1984-01-01

Boron doped silicon n+p solar cells were counterdoped with lithium by ion implantation and the resuitant n+p cells irradiated by 1 MeV electrons. The function of fluence and a Deep Level Transient Spectroscopy (DLTS) was studied to correlate defect behavior with cell performance. It was found that the lithium counterdoped cells exhibited significantly increased radiation resistance when compared to boron doped control cells. It is concluded that the annealing behavior is controlled by dissociation and recombination of defects. The DLTS studies show that counterdoping with lithium eliminates at least three deep level defects and results in three new defects. It is speculated that the increased radiation resistance of the counterdoped cells is due primarily to the interaction of lithium with oxygen, single vacanies and divacancies and that the lithium-oxygen interaction is the most effective in contributing to the increased radiation resistance.

Radiation damage and defect behavior in ion-implanted, lithium counterdoped silicon solar cells

NASA Technical Reports Server (NTRS)

Weinberg, I.; Mehta, S.; Swartz, C. K.

1984-01-01

Boron doped silicon n+p solar cells were counterdoped with lithium by ion implanation and the resultant n+p cells irradiated by 1 MeV electrons. The function of fluence and a Deep Level Transient Spectroscopy (DLTS) was studied to correlate defect behavior with cell performance. It was found that the lithium counterdoped cells exhibited significantly increased radiation resistance when compared to boron doped control cells. It is concluded that the annealing behavior is controlled by dissociation and recombination of defects. The DLTS studies show that counterdoping with lithium eliminates at least three deep level defects and results in three new defects. It is speculated that the increased radiation resistance of the counterdoped cells is due primarily to the interaction of lithium with oxygen, single vacancies and divacancies and that the lithium-oxygen interaction is the most effective in contributing to the increased radiation resistance.

Development and Application of Wide Bandwidth Magneto-Resistive Sensor Based Eddy Current Probe

NASA Technical Reports Server (NTRS)

Wincheski, Russell A.; Simpson, John

2010-01-01

The integration of magneto-resistive sensors into eddy current probes can significantly expand the capabilities of conventional eddy current nondestructive evaluation techniques. The room temperature solid-state sensors have typical bandwidths in the megahertz range and resolutions of tens of microgauss. The low frequency sensitivity of magneto-resistive sensors has been capitalized upon in previous research to fabricate very low frequency eddy current sensors for deep flaw detection in multilayer conductors. In this work a modified probe design is presented to expand the capabilities of the device. The new probe design incorporates a dual induction source enabling operation from low frequency deep flaw detection to high frequency high resolution near surface material characterization. Applications of the probe for the detection of localized near surface conductivity anomalies are presented. Finite element modeling of the probe is shown to be in good agreement with experimental measurements.

Interpretation of deep directional resistivity measurements acquired in high-angle and horizontal wells using 3-D inversion

NASA Astrophysics Data System (ADS)

Puzyrev, Vladimir; Torres-Verdín, Carlos; Calo, Victor

2018-05-01

The interpretation of resistivity measurements acquired in high-angle and horizontal wells is a critical technical problem in formation evaluation. We develop an efficient parallel 3-D inversion method to estimate the spatial distribution of electrical resistivity in the neighbourhood of a well from deep directional electromagnetic induction measurements. The methodology places no restriction on the spatial distribution of the electrical resistivity around arbitrary well trajectories. The fast forward modelling of triaxial induction measurements performed with multiple transmitter-receiver configurations employs a parallel direct solver. The inversion uses a pre-conditioned gradient-based method whose accuracy is improved using the Wolfe conditions to estimate optimal step lengths at each iteration. The large transmitter-receiver offsets, used in the latest generation of commercial directional resistivity tools, improve the depth of investigation to over 30 m from the wellbore. Several challenging synthetic examples confirm the feasibility of the full 3-D inversion-based interpretations for these distances, hence enabling the integration of resistivity measurements with seismic amplitude data to improve the forecast of the petrophysical and fluid properties. Employing parallel direct solvers for the triaxial induction problems allows for large reductions in computational effort, thereby opening the possibility to invert multiposition 3-D data in practical CPU times.

TiO2 as diffusion barrier at Co/Alq3 interface studied by x-ray standing wave technique

NASA Astrophysics Data System (ADS)

Phatak Londhe, Vaishali; Gupta, A.; Ponpandian, N.; Kumar, D.; Reddy, V. R.

2018-06-01

Nano-scale diffusion at the interfaces in organic spin valve thin films plays a vital role in controlling the performance of magneto-electronic devices. In the present work, it is shown that a thin layer of titanium dioxide at the interface of Co/Alq3 can act as a good diffusion barrier. The buried interfaces of Co/Alq3/Co organic spin valve thin film has been studied using x-ray standing waves technique. A planar waveguide is formed with Alq3 layer forming the cavity and Co layers as the walls of the waveguide. Precise information about diffusion of Co into Alq3 is obtained through excitation of the waveguide modes. It is found that the top Co layer diffuses deep into the Alq3 resulting in incorporation of 3.1% Co in the Alq3 layer. Insertion of a 1.7 nm thick barrier layer of TiO2 at Co/Alq3 interface results in a drastic reduction in the diffusion of Co into Alq3 to a value of only 0.4%. This suggests a better performance of organic spin valve with diffusion barrier of TiO2.

Diffusion of biomass pyrolysis products in H-ZSM-5 by molecular dynamics simulations

DOE PAGES

Bu, Lintao; Nimlos, Mark R.; Robichaud, David J.; ...

2016-12-13

Diffusion of biomass pyrolysis vapors and their upgraded products is an essential catalytic property of zeolites during catalytic fast pyrolysis and likely plays a critical role in the selectivity of these catalysts. Characterizing the diffusivities of representative biofuel molecules is critical to understand shape selectivity and interpret product distribution. Yet, experimental measurements on the diffusivities of oxygenated biofuel molecules at pyrolysis temperatures are very limited in the literature. As an alternative approach, we conducted MD simulations to measure the diffusion coefficients of several selected molecules that are representative of biomass pyrolysis vapors, namely water, methanol, glycolaldehyde, and toluene in H-ZSM-5more » zeolite. The results show the diffusion coefficients calculated via MD simulations are consistent with available NMR measurements at room temperature. The effect of molecular weight and molecular critical diameter on the diffusivity among the chosen model compounds is also examined. Furthermore, we have characterized the diffusivities of representative biofuel molecules, namely xylene isomers, in H-ZSM-5. Our calculations determined that the ratio of the diffusion coefficients for xylene isomers is p-xylene: o-xylene: m-xylene ≈ 83:3:1 at 700 K. Furthermore, our results also demonstrate the different diffusivity between p-xylene and toluene is due to the molecular orientations when the molecules diffuse along the channels in H-ZSM-5 and provide deep insight into the effect of molecular orientation on its diffusivity.« less

Diffusion and ADC-map images detect ongoing demyelination on subcortical white matter in an adult metachromatic leukodystrophy patient with autoimmune Hashimoto thyroiditis

PubMed Central

Miura, Akiko; Kumabe, Yuri; Kimura, En; Yamashita, Satoshi; Ueda, Akihiko; Hirano, Teruyuki; Uchino, Makoto

2010-01-01

Adult-onset metachromatic leukodystrophy (MLD) often shows schizophrenia- or encephalopathy-like symptoms at an early stage, such as behavioural abnormalities, cognitive impairment, mood disorders and hallucinations. The authors report the case of an adult woman with MLD who had been given antipsychotic medication for schizophrenia. In the differential diagnosis, screening of auto-antibodies was important for ruling out other encephalopathies as she had a euthyroid Hashimoto thyroiditis. Diagnosis was based the results of MRI, nerve conduction velocity, sensory evoked potential, motor evoked potential, lysosomal enzyme activity and gene analysis studies. Brain MRI showed diffuse demyelination spreading from the deep white matter to subcortical area as high signals at the edges of these lesions in diffusion and apparent diffusion coefficient-map images with the U-fibres conserved. The authors diagnosed adult-onset MLD coexisting with euthyroid autoimmune Hashimoto thyroiditis. PMID:22798296

Simulations of high Mach number perpendicular shocks with resistive electrons

NASA Technical Reports Server (NTRS)

Quest, K. B.

1986-01-01

A simulation code which models the ions as microparticles and the electrons as a resistive massless fluid is employed to study the structure of high Mach number perpendicular shocks. It is found that stable stationary shock solutions can be obtained for Alfven Mach numbers (M sub A) between 5 and 60 for upstream plasmas where the ratio of the plasma pressure to the magnetic pressure is 1, providing that the upstream resistive diffusion length is much smaller than the ion inertial length. For much larger resistive diffusion lengths, the magnetic field overshoot is damped, and the imbalance in the electron momentum equation results in a periodic fluctuation of the fraction of reflected ions. In the limit of M sub A of less than 10, the magnetic overshoot and the fraction of reflected ions increase with increasing M sub A, while at higher Mach numbers the fraction of reflected ions peaks at about 40 percent and the magnetic field overshoot increases at a much slower rate. Electron inertial effects are also considered.

Plasma membrane microorganization of LR73 multidrug-resistant cells revealed by FCS

NASA Astrophysics Data System (ADS)

Winckler, Pascale; Jaffiol, Rodolphe; Cailler, Aurélie; Morjani, Hamid; Jeannesson, Pierre; Deturche, Régis

2011-03-01

Tumoral cells could present a multidrug resistance (MDR) to chemotherapeutic treatments. This drug resistance would be associated to biomechanisms occurring at the plasma membrane level, involving modification of membrane fluidity, drug permeability, presence of microdomains (rafts, caveolae...), and membrane proteins overexpression such as Pglycoprotein. Fluorescence correlation spectroscopy (FCS) is the relevant method to investigate locally the fluidity of biological membranes through the lateral diffusion of a fluorescent membrane probe. Thus, we use FCS to monitor the plasma membrane local organization of LR73 carcinoma cells and three derived multidrug-resistant cancer cells lines. Measurements were conducted at the single cell level, which enabled us to get a detailed overview of the plasma membrane microviscosity distribution of each cell line studied. Moreover, we propose 2D diffusion simulation based on a Monte Carlo model to investigate the membrane organisation in terms of microdomains. This simulation allows us to relate the differences in the fluidity distributions with microorganization changes in plasma membrane of MDR cells.

GFP as potential cellular viscosimeter.

PubMed

Visser, Antonie J W G; Westphal, Adrie H; Skakun, Victor V; Borst, Jan Willem

2016-08-18

The molecular dimensions of proteins such as green fluorescent protein (GFP) are large as compared to the ones of solvents like water or glycerol. The microscopic viscosity, which determines the resistance to diffusion of, e.g. GFP, is then the same as that determined from the resistance of the solvent to flow, which is known as macroscopic viscosity. GFP in water/glycerol mixtures senses this macroscopic viscosity, because the translational and rotational diffusion coefficients are proportional to the reciprocal value of the viscosity as predicted by the Stokes-Einstein equations. To test this hypothesis, we have performed time-resolved fluorescence anisotropy (reporting on rotational diffusion) and fluorescence correlation spectroscopy (reporting on translational diffusion) experiments of GFP in water/glycerol mixtures. When the solvent also contains macromolecules of similar or larger dimensions as GFP, the microscopic and macroscopic viscosities can be markedly different and the Stokes-Einstein relations must be adapted. It was established from previous dynamic fluorescence spectroscopy observations of diffusing proteins with dextran polysaccharides as co-solvents (Lavalette et al 2006 Eur. Biophys. J. 35 517-22), that rotation and translation sense a different microscopic viscosity, in which the one arising from rotation is always less than that from translation. A microscopic viscosity parameter is defined that depends on scaling factors between GFP and its immediate environment. The direct consequence is discussed for two reported diffusion coefficients of GFP in living cells.

GFP as potential cellular viscosimeter

NASA Astrophysics Data System (ADS)

Visser, Antonie J. W. G.; Westphal, Adrie H.; Skakun, Victor V.; Borst, Jan Willem

2016-09-01

The molecular dimensions of proteins such as green fluorescent protein (GFP) are large as compared to the ones of solvents like water or glycerol. The microscopic viscosity, which determines the resistance to diffusion of, e.g. GFP, is then the same as that determined from the resistance of the solvent to flow, which is known as macroscopic viscosity. GFP in water/glycerol mixtures senses this macroscopic viscosity, because the translational and rotational diffusion coefficients are proportional to the reciprocal value of the viscosity as predicted by the Stokes-Einstein equations. To test this hypothesis, we have performed time-resolved fluorescence anisotropy (reporting on rotational diffusion) and fluorescence correlation spectroscopy (reporting on translational diffusion) experiments of GFP in water/glycerol mixtures. When the solvent also contains macromolecules of similar or larger dimensions as GFP, the microscopic and macroscopic viscosities can be markedly different and the Stokes-Einstein relations must be adapted. It was established from previous dynamic fluorescence spectroscopy observations of diffusing proteins with dextran polysaccharides as co-solvents (Lavalette et al 2006 Eur. Biophys. J. 35 517-22), that rotation and translation sense a different microscopic viscosity, in which the one arising from rotation is always less than that from translation. A microscopic viscosity parameter is defined that depends on scaling factors between GFP and its immediate environment. The direct consequence is discussed for two reported diffusion coefficients of GFP in living cells.

Stripped Elliptical Galaxies as Probes of ICM Physics. III. Deep Chandra Observations of NGC 4552: Measuring the Viscosity of the Intracluster Medium

NASA Astrophysics Data System (ADS)

Kraft, R. P.; Roediger, E.; Machacek, M.; Forman, W. R.; Nulsen, P. E. J.; Jones, C.; Churazov, E.; Randall, S.; Su, Y.; Sheardown, A.

2017-10-01

We present results from a deep (200 ks) Chandra observation of the early-type galaxy NGC 4552 (M89), which is falling into the Virgo cluster. Previous shallower X-ray observations of this galaxy showed a remnant gas core, a tail to the South of the galaxy, and twin “horns” attached to the northern edge of the gas core. In our deeper data, we detect a diffuse, low surface brightness extension to the previously known tail, and measure the temperature structure within the tail. We combine the deep Chandra data with archival XMM-Newton observations to put a strong upper limit on the diffuse emission of the tail out to a large distance (10× the radius of the remnant core) from the galaxy center. In our two previous papers, we presented the results of hydrodynamical simulations of ram pressure stripping specifically for M89 falling into the Virgo cluster and investigated the effect of intracluster medium (ICM) viscosity. In this paper, we compare our deep data with our specifically tailored simulations and conclude that the observed morphology of the stripped tail in NGC 4552 is most similar to the inviscid models. We conclude that, to the extent the transport processes can be simply modeled as a hydrodynamic viscosity, the ICM viscosity is negligible. More generally, any micro-scale description of the transport processes in the high-β plasma of the cluster ICM must be consistent with the efficient mixing observed in the stripped tail on macroscopic scales.

Correlation of transarterial transport of various dextrans with their physicochemical properties.

PubMed

Elmalak, O; Lovich, M A; Edelman, E

2000-11-01

Local vascular drug delivery provides elevated concentrations of drug in the target tissue while minimizing systemic side effects. To better characterize local pharmacokinetics we examined the arterial transport of locally applied dextran and dextran derivatives in vivo. Using a two-compartment pharmacokinetic model to correct the measured transmural flux of these compounds for systemic redistribution and elimination as delivered from a photopolymerizable hydrogel surrounding rat carotid arteries, we found that the diffusivities and the transendothelial permeabilities were strongly dependent on molecular weight and charge. For neutral dextrans, the effective diffusive resistance in the media increased with molecular weight approximately 4.1-fold between the molecular weights of 10 and 282 kDa. Similarly, endothelial resistance increased 28-fold over the same molecular weight range. The effective medial diffusive resistance was unaffected by cationic charge as such molecules moved identically to neutral compounds, but increased approximately 40% when dextrans were negatively charged. Transendothelial resistance was 20-fold lower for the cationic dextrans, and 11-fold higher for the anionic dextrans, when both were compared to neutral counterparts. These results suggest that, while low molecular weight drugs will rapidly traverse the arterial wall with the endothelium posing a minimal barrier, the reverse is true for high molecular weight agents. With these data, the deposition and distribution of locally released vasotherapeutic compounds might be predicted based upon chemical properties, such as molecular weight and charge.

Water vapor diffusion membrane development. [for water recovery purposes onboard manned spacecraft

NASA Technical Reports Server (NTRS)

Tan, M. K.

1974-01-01

The phase separator component used as a membrane in the vapor diffusion process (VRD) for the recovery of potable water from urine on manned space missions of extended duration was investigated, with particular emphasis on cation-selective membranes because of their noted mechanical strength, superior resistance to acids, oxidants, and germicides, and their potential resistance to organic foulants. Two of the membranes were tested for 700 hours continuously, and were selected on the basis of criteria deemed important to an effective water reclamation system onboard spacecraft. The samples of urine were successfully processed by removing 93 percent of their water content in 70 hours using the selected membranes. Pretreatment with an acid-oxidant formulation improved product quality. Cation exchange membranes were shown to possess superior mechanical strength and chemical resistance, as compared to cellulosic membranes.

Reverse weathering in marine sediments and the geochemical cycle of potassium in seawater: Insights from the K isotopic composition (41K/39K) of deep-sea pore-fluids

USGS Publications Warehouse

Santiago Ramos, Danielle P.; Morgan, Leah; Lloyd, Nicholas S.; Higgins, John A.

2018-01-01

In situ Al-silicate formation, also known as “reverse weathering,” is an important sink of many of the major and minor cations in seawater (e.g. Mg, K, and Li). However, the importance of this sink in global geochemical cycles and isotopic budgets of these elements remains poorly constrained. Here, we report on the potassium isotopic composition (41">41K/39">39K) of deep-sea sediment pore-fluids from four (Integrated) Ocean Drilling Program sites (1052, U1378, U1395 and U1403) to characterize potassium isotopic fractionation associated with the formation of authigenic Al-silicate minerals in marine sediments and its role in elevating the 41">41K/39">39K of seawater relative to bulk silicate Earth. Isotopic ratios are obtained by high-resolution multi-collector inductively coupled plasma mass spectrometry (MC-ICP-MS) in cold plasma conditions with a long-term external reproducibility of ca. 0.17‰. We find that, although all sites are characterized by pore-fluid K concentrations that decline with increasing depth, their K isotopic profiles vary systematically from site-to-site; at sites characterized by rapid sedimentation rates, pore-fluid profiles of 41">41K/39">39K are relatively invariant whereas at sites characterized by slow sedimentation rates, 41">41K/39">39K declines with depth by up to 1.8‰. Results from 1-D diffusion-advection-reaction models suggest that these differences may result from a complex interplay between sedimentation rate and fractionation of K isotopes during diffusion, Al-silicate authigenesis, and ion exchange. Model simulations suggest fractionation factors between 0.9980 and 1.0000 for reverse weathering reactions in deep-sea sediments. Although deep-sea sites do not constitute major sinks of K in seawater, some of the processes responsible for K isotopic fractionation at these sites (diffusion and Al-silicate authigenesis) likely play a role in determining the 41">41K/39">39K of seawater.

Assessing the role of clay authigenesis in the seawater potassium cycle: A paired K and Mg isotope study of deep-sea pore fluids

NASA Astrophysics Data System (ADS)

Santiago Ramos, D. P.; Higgins, J. A.

2017-12-01

In situ formation of clays (clay authigenesis) in marine sediments and altered oceanic crust is an important sink of a number of seawater cations. In particular, clay authigenesis is a major, and yet unconstrained, flux in the global seawater potassium cycle. Potassium is the fourth most abundant cation in the ocean, which constitutes an isotopically enriched K reservoir (δ41K 0‰) compared to the solid Earth (δ41K -0.5‰). Understanding what processes control this isotopic offset is the main goal of this study. Here we use a multi-collector inductively coupled plasma mass spectrometer (MC-ICP-MS) to measure the K and Mg isotope ratios (41K/39K and 26Mg/24Mg) of deep-sea pore fluids in order to assess the effects of clay formation in the K isotope composition of seawater. Mg isotopes are used as an independent proxy for clay formation, since marine authigenic clays are isotopically distinct from their detrital counterpart, an abundant component of marine sediments. Our study sites (ODP/IODP 1052, U1378, U1395, U1403) vary in location, lithology, age and sedimentation rates; however, pore-fluids from all sites show decreasing K concentrations with depth, suggesting potassium uptake into the sediments. We find that although K concentration trends are similar across all sites, measured δ41K values vary significantly. Results from 1-D diffusion-advection-reaction models suggest that these differences in isotopic profiles arise from a complex interplay between sedimentation rate and K isotopic fractionation during clay formation, aqueous K diffusion and ion exchange reactions. Further, model simulations yield fractionation factors between 0.9980 and 1.0000 for clay formation in deep-sea sediments. Despite the minor contribution of these deep-sea pore-fluids as sinks of seawater K, the processes responsible for K isotope fractionation in our study sites (clay formation and aqueous K diffusion) are also observed at shallow marine systems (major K sinks) and are thus likely responsible for setting the K isotopic composition of seawater.

Oort spike comets with large perihelion distances

NASA Astrophysics Data System (ADS)

Królikowska, Małgorzata; Dybczyński, Piotr A.

2017-12-01

The complete sample of large-perihelion nearly-parabolic comets discovered during the period 1901-2010 is studied, starting with their orbit determination. Next, an orbital evolution that includes three perihelion passages (previous-observed-next) is investigated in which a full model of Galactic perturbations and perturbations from passing stars is incorporated. We show that the distribution of planetary perturbations suffered by actual large-perihelion comets during their passage through the Solar system has a deep, unexpected minimum around zero, which indicates a lack of 'almost unperturbed' comets. Using a series of simulations we show that this deep well is moderately resistant to some diffusion of the orbital elements of the analysed comets. It seems reasonable to assert that the observed stream of these large-perihelion comets experienced a series of specific planetary configurations when passing through the planetary zone. An analysis of the past dynamics of these comets clearly shows that dynamically new comets can appear only when their original semimajor axes are greater than 20 000 au. On the other hand, dynamically old comets are completely absent for semimajor axes longer than 40 000 au. We demonstrate that the observed 1/aori-distribution exhibits a local minimum separating dynamically new from dynamically old comets. Long-term dynamical studies reveal a wide variety of orbital behaviour. Several interesting examples of the action of passing stars are also described, in particular the impact of Gliese 710, which will pass close to the Sun in the future. However, none of the obtained stellar perturbations is sufficient to change the dynamical status of the analysed comets.

Upper Mantle Anisotropy Under Fast Spreading Mid-ocean Ridges: 2-D Whole Mantle Convection Model With Subduction

NASA Astrophysics Data System (ADS)

Lee, C.; Zhou, Y.; King, S. D.

2008-12-01

Analyses of seismic anisotropy caused by spatial alignments of anisotropic minerals (e.g., olivine) have been widely used to infer mantle flow directions in the upper mantle. Deep seismic anisotropy beneath fast spreading mid-ocean ridges (e.g., East Pacific Rise) has been recently observed at depths of 200-300 km and even down to the transition zone, with polarization changes in radial anisotropy from VSH < VSV (shallow) to VSH < VSV (deep). We investigate the origin of the observed deep seismic anisotropy and polarization changes beneath the EPR in 2-D Cartesian numerical models using both kinematically (prescribed velocity) and dynamically (negative buoyancy) driven ridge spreading. Because subduction is thought to be an important controlling factor in the style of ridge spreading and mantle convection, we consider a subduction zone developing at the prescribed weak zone. A whole mantle domain expressed by a one by four box (2890 by 11560 km) is used to minimize the boundary effects on the subducting slab. For the upper mantle rheology, we consider composite viscosity of diffusion and dislocation creep for dry olivine to evaluate the effects of lateral variation of mantle viscosity and the rheological changes from dislocation to diffusion creep under the mid-ocean ridge. For the lower mantle rheology, we use diffusion creep for dry olivine by increasing grain size to match relevant lower mantle viscosity. We also consider the 660 km phase transition with density and viscosity jump as well as Clapeyron slope. Anisotropy is evaluated using finite-strain ellipses based on the assumption that a-axes of olivine crystals are parallel to the major axes of the finite-strain ellipses. Our preliminary results show 1) in general, the development of VSH < VSV anisotropy is confined only in a narrow region under the ridge axis at depths of 200- 300 km; 2) strong VSH > VSV anisotropy can be found in the 'asthenosphere' beneath the entire spreading oceanic lithosphere; and 3) the dominate creep mechanism changes from dislocation creep to diffusion creep at depths of 300-400 km; indicating a more isotropic lower upper mantle. We conclude that our geodynamical modeling in a passive ridge spreading system does not produce the deep seismic anisotropy recently observed beneath the EPR. However, we do not consider partial melting, dynamic recrystallization and anisotropic viscosity which would change seismic interpretation and mantle flow, and thus further study is required.

Diffusion length variation and proton damage coefficients for InP/In(x)Ga(1-x)As/GaAs solar cells

NASA Technical Reports Server (NTRS)

Jain, R. K.; Weinberg, I.; Flood, D. J.

1993-01-01

Indium phosphide solar cells are more radiation resistant than gallium arsenide and silicon solar cells, and their growth by heteroepitaxy offers additional advantages leading to the development of lighter, mechanically strong and cost-effective cells. Changes in heteroepitaxial InP cell efficiency under 0.5 and 3 MeV proton irradiations are explained by the variation in the minority-carrier diffusion length. The base diffusion length versus proton fluence is calculated by simulating the cell performance. The diffusion length damage coefficient K(L) is plotted as a function of proton fluence.

Characteristics of Superjunction Lateral-Double-Diffusion Metal Oxide Semiconductor Field Effect Transistor and Degradation after Electrical Stress

NASA Astrophysics Data System (ADS)

Lin, Jyh‑Ling; Lin, Ming‑Jang; Lin, Li‑Jheng

2006-04-01

The superjunction lateral double diffusion metal oxide semiconductor field effect has recently received considerable attention. Introducing heavily doped p-type strips to the n-type drift region increases the horizontal depletion capability. Consequently, the doping concentration of the drift region is higher and the conduction resistance is lower than those of conventional lateral-double-diffusion metal oxide semiconductor field effect transistors (LDMOSFETs). These characteristics may increase breakdown voltage (\\mathit{BV}) and reduce specific on-resistance (Ron,sp). In this study, we focus on the electrical characteristics of conventional LDMOSFETs on silicon bulk, silicon-on-insulator (SOI) LDMOSFETs and superjunction LDMOSFETs after bias stress. Additionally, the \\mathit{BV} and Ron,sp of superjunction LDMOSFETs with different N/P drift region widths and different dosages are discussed. Simulation tools, including two-dimensional (2-D) TSPREM-4/MEDICI and three-dimensional (3-D) DAVINCI, were employed to determine the device characteristics.

Convective mixing of air in firn at four polar sites

NASA Astrophysics Data System (ADS)

Kawamura, Kenji; Severinghaus, Jeffrey P.; Ishidoya, Shigeyuki; Sugawara, Satoshi; Hashida, Gen; Motoyama, Hideaki; Fujii, Yoshiyuki; Aoki, Shuji; Nakazawa, Takakiyo

2006-04-01

Air withdrawn from the firn at four polar sites (Dome Fuji, H72 and YM85, Antarctica and North GRIP, Greenland) was measured for δ15N of N 2 and δ18O of O 2 to test for the presence of convective air mixing in the top part of the firn, known as the "convective zone". Understanding the convective zone and its possible relationship to surface conditions is important for constructing accurate ice-core greenhouse gas chronologies and their phasing with respect to climate change. The thickness of the convective zone was inferred from a regression line with barometric slope of the data in the deep firn. It is less than a few meters at H72 and NGRIP, whereas a substantial convective zone is found at Dome Fuji (8.6 ± 2.6 m) and YM85 (14.0 ± 1.8 m). By matching the outputs of a diffusion model to the data, effective eddy diffusivities required to mix the firn air are found. At the surface of Dome Fuji and YM85, these are found to be several times greater than the molecular diffusivity in free air. The crossover from dominance of convection to molecular diffusion takes place at 7 ± 2, 11 ± 2 and 0.5 ± 0.5 m at Dome Fuji, YM85 and NGRIP, respectively. These depths can be used as an alternative definition of the convective zone thickness. The firn permeability at Dome Fuji is expected to be high because of intense firn metamorphism due to the low accumulation rate and large seasonal air temperature variation at the site. The firn layers in the top several meters are exposed to strong temperature gradients for several decades, leading to large firn grains and depth hoar that enhance permeability. The thick convective zone at YM85 is unexpected because the temperature, accumulation rate and near-surface density are comparable to NGRIP. The strong katabatic wind at YM85 is probably responsible for creating the deep convection. The largest convective zone found in this study is still only half of the current inconsistency implied from the deep ice core gas isotopes and firn densification models.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kobulnicky, Henry A.; Alexander, Michael J.; Babler, Brian L.

We characterize the completeness of point source lists from Spitzer Space Telescope surveys in the four Infrared Array Camera (IRAC) bandpasses, emphasizing the Galactic Legacy Infrared Mid-Plane Survey Extraordinaire (GLIMPSE) programs (GLIMPSE I, II, 3D, 360; Deep GLIMPSE) and their resulting point source Catalogs and Archives. The analysis separately addresses effects of incompleteness resulting from high diffuse background emission and incompleteness resulting from point source confusion (i.e., crowding). An artificial star addition and extraction analysis demonstrates that completeness is strongly dependent on local background brightness and structure, with high-surface-brightness regions suffering up to five magnitudes of reduced sensitivity to pointmore » sources. This effect is most pronounced at the IRAC 5.8 and 8.0 {mu}m bands where UV-excited polycyclic aromatic hydrocarbon emission produces bright, complex structures (photodissociation regions). With regard to diffuse background effects, we provide the completeness as a function of stellar magnitude and diffuse background level in graphical and tabular formats. These data are suitable for estimating completeness in the low-source-density limit in any of the four IRAC bands in GLIMPSE Catalogs and Archives and some other Spitzer IRAC programs that employ similar observational strategies and are processed by the GLIMPSE pipeline. By performing the same analysis on smoothed images we show that the point source incompleteness is primarily a consequence of structure in the diffuse background emission rather than photon noise. With regard to source confusion in the high-source-density regions of the Galactic Plane, we provide figures illustrating the 90% completeness levels as a function of point source density at each band. We caution that completeness of the GLIMPSE 360/Deep GLIMPSE Catalogs is suppressed relative to the corresponding Archives as a consequence of rejecting stars that lie in the point-spread function wings of saturated sources. This effect is minor in regions of low saturated star density, such as toward the Outer Galaxy; this effect is significant along sightlines having a high density of saturated sources, especially for Deep GLIMPSE and other programs observing closer to the Galactic center using 12 s or longer exposure times.« less

The relative importance of decomposition and transport mechanisms in accounting for C profiles

NASA Astrophysics Data System (ADS)

Guenet, B.; Eglin, T.; Vasilyeva, N.; Peylin, P.; Ciais, P.; Chenu, C.

2012-10-01

Soil is the major terrestrial reservoirs of carbon, and a substantial part of this carbon is stored in deep layers, typically deeper than 50 cm below the surface. Several studies underlined the quantitative importance of this deep Soil Organic Carbon (SOC) pool and models are needed to better understand this stock and its evolution under climate and land-uses changes. In this study, we test and compare 3 simple theoretical models of vertical transport for SOC against SOC profiles measurements from a long-term bare fallow experiment carried out by the Central-Chernozem State Natural Biosphere Reserve named after V.V. Alekhin, in the Kursk Region of Russia. The transport schemes tested are diffusion, advection or both diffusion and advection. They are coupled to two different formulations of soil carbon decomposition kinetics. The first formulation is a first order kinetics widely used in global SOC decomposition models; the second one links SOC decomposition rate to the amount of fresh organic matter, representing a "priming effect". Field data are from a set of three bare fallow plots where soil received no input during the past 20, 26 and 58 yr respectively. Parameters of the models were optimized using a Bayesian method. The best results are obtained when SOC decomposition is assumed to be controlled by fresh organic matter. In comparison to the first-order kinetic model, the "priming" model reduces the underestimation of SOC decomposition in the top layers and the over estimation in the deep layers. We also observe that the transport scheme that improved the fit with the data depends on the soil carbon mineralization formulation chosen. When soil carbon decomposition is modelled to depend on the fresh organic matter amount, the transport mechanisms which improves best the fit to the SOC profile data is the model representing both advection and diffusion. Interestingly, the older the bare fallow is, the lesser the need for diffusion is. This suggests that stabilized carbon may not be transported within the profile by the same mechanisms than more labile carbon.

The relative importance of decomposition and transport mechanisms in accounting for soil organic carbon profiles

NASA Astrophysics Data System (ADS)

Guenet, B.; Eglin, T.; Vasilyeva, N.; Peylin, P.; Ciais, P.; Chenu, C.

2013-04-01

Soil is the major terrestrial reservoir of carbon and a substantial part of this carbon is stored in deep layers, typically deeper than 50 cm below the surface. Several studies underlined the quantitative importance of this deep soil organic carbon (SOC) pool and models are needed to better understand this stock and its evolution under climate and land-uses changes. In this study, we tested and compared three simple theoretical models of vertical transport for SOC against SOC profiles measurements from a long-term bare fallow experiment carried out by the Central-Chernozem State Natural Biosphere Reserve in the Kursk Region of Russia. The transport schemes tested are diffusion, advection and both diffusion and advection. They are coupled to three different formulations of soil carbon decomposition kinetics. The first formulation is a first order kinetics widely used in global SOC decomposition models; the second one, so-called "priming" model, links SOC decomposition rate to the amount of fresh organic matter, representing the substrate interactions. The last one is also a first order kinetics, but SOC is split into two pools. Field data are from a set of three bare fallow plots where soil received no input during the past 20, 26 and 58 yr, respectively. Parameters of the models were optimised using a Bayesian method. The best results are obtained when SOC decomposition is assumed to be controlled by fresh organic matter (i.e., the priming model). In comparison to the first-order kinetic model, the priming model reduces the overestimation in the deep layers. We also observed that the transport scheme that improved the fit with the data depended on the soil carbon mineralisation formulation chosen. When soil carbon decomposition was modelled to depend on the fresh organic matter amount, the transport mechanism which improved best the fit to the SOC profile data was the model representing both advection and diffusion. Interestingly, the older the bare fallow is, the lesser the need for diffusion is, suggesting that stabilised carbon may not be transported within the profile by the same mechanisms than more labile carbon.

An Extended Eddy-Diffusivity Mass-Flux Scheme for Unified Representation of Subgrid-Scale Turbulence and Convection

NASA Astrophysics Data System (ADS)

Tan, Zhihong; Kaul, Colleen M.; Pressel, Kyle G.; Cohen, Yair; Schneider, Tapio; Teixeira, João.

2018-03-01

Large-scale weather forecasting and climate models are beginning to reach horizontal resolutions of kilometers, at which common assumptions made in existing parameterization schemes of subgrid-scale turbulence and convection—such as that they adjust instantaneously to changes in resolved-scale dynamics—cease to be justifiable. Additionally, the common practice of representing boundary-layer turbulence, shallow convection, and deep convection by discontinuously different parameterizations schemes, each with its own set of parameters, has contributed to the proliferation of adjustable parameters in large-scale models. Here we lay the theoretical foundations for an extended eddy-diffusivity mass-flux (EDMF) scheme that has explicit time-dependence and memory of subgrid-scale variables and is designed to represent all subgrid-scale turbulence and convection, from boundary layer dynamics to deep convection, in a unified manner. Coherent up and downdrafts in the scheme are represented as prognostic plumes that interact with their environment and potentially with each other through entrainment and detrainment. The more isotropic turbulence in their environment is represented through diffusive fluxes, with diffusivities obtained from a turbulence kinetic energy budget that consistently partitions turbulence kinetic energy between plumes and environment. The cross-sectional area of up and downdrafts satisfies a prognostic continuity equation, which allows the plumes to cover variable and arbitrarily large fractions of a large-scale grid box and to have life cycles governed by their own internal dynamics. Relatively simple preliminary proposals for closure parameters are presented and are shown to lead to a successful simulation of shallow convection, including a time-dependent life cycle.

Application of interleaving models to describe intrusive layers in the Deep Polar Water of the Arctic Basin

NASA Astrophysics Data System (ADS)

Zhurbas, Nataliya; Kuzmina, Natalia; Lyzhkov, Dmitry; Izvekova, Yulia N.

2016-04-01

Interleaving models of pure thermohaline and baroclinic frontal zones of finite width are applied to describe intrusions at the fronts found in the upper part of the Deep Polar Water, the Eurasian basin, under stable-stable thermohaline stratification. It is assumed that differential mixing is the main mechanism of the intrusion formation. Different parameterizations of differential mixing (Merrryfield, 2002; Kuzmina et al., 2011) are used in the models. Important parameters of interleaving such as the growth rate, vertical scale, and slope of the most unstable modes are calculated. It is found that the interleaving model of a pure thermohaline front can satisfactory describe the important parameters of intrusions observed at a thermohaline, very low baroclinicity front in the Eurasian basin, just in accordance to Merryfield (2002) findings. In the case of baroclinic front, satisfactory agreement over all the interleaving parameters is found between the model calculations and observations provided that the vertical momentum diffusivity significantly exceeds the corresponding mass diffusivity. Under specific (reasonable) constraints of the vertical momentum diffusivity, the most unstable mode has a vertical scale approximately two-three times smaller than the vertical scale of the observed intrusions. A thorough discussion of the results is presented. References Kuzmina N., Rudels B., Zhurbas V., Stipa T. On the structure and dynamical features of intrusive layering in the Eurasian Basin in the Arctic Ocean. J. Geophys. Res., 2011, 116, C00D11, doi:10.1029/2010JC006920. Merryfield W. J. Intrusions in Double-Diffusively Stable Arctic Waters: Evidence for Differential mixing? J. Phys. Oceanogr., 2002, 32, 1452-1439.

An Extended Eddy‐Diffusivity Mass‐Flux Scheme for Unified Representation of Subgrid‐Scale Turbulence and Convection

PubMed Central

Tan, Zhihong; Kaul, Colleen M.; Pressel, Kyle G.; Cohen, Yair; Teixeira, João

2018-01-01

Abstract Large‐scale weather forecasting and climate models are beginning to reach horizontal resolutions of kilometers, at which common assumptions made in existing parameterization schemes of subgrid‐scale turbulence and convection—such as that they adjust instantaneously to changes in resolved‐scale dynamics—cease to be justifiable. Additionally, the common practice of representing boundary‐layer turbulence, shallow convection, and deep convection by discontinuously different parameterizations schemes, each with its own set of parameters, has contributed to the proliferation of adjustable parameters in large‐scale models. Here we lay the theoretical foundations for an extended eddy‐diffusivity mass‐flux (EDMF) scheme that has explicit time‐dependence and memory of subgrid‐scale variables and is designed to represent all subgrid‐scale turbulence and convection, from boundary layer dynamics to deep convection, in a unified manner. Coherent up and downdrafts in the scheme are represented as prognostic plumes that interact with their environment and potentially with each other through entrainment and detrainment. The more isotropic turbulence in their environment is represented through diffusive fluxes, with diffusivities obtained from a turbulence kinetic energy budget that consistently partitions turbulence kinetic energy between plumes and environment. The cross‐sectional area of up and downdrafts satisfies a prognostic continuity equation, which allows the plumes to cover variable and arbitrarily large fractions of a large‐scale grid box and to have life cycles governed by their own internal dynamics. Relatively simple preliminary proposals for closure parameters are presented and are shown to lead to a successful simulation of shallow convection, including a time‐dependent life cycle. PMID:29780442

Advances in membrane technology for the NASA redox energy storage system

NASA Technical Reports Server (NTRS)

Ling, J. S.; Charleston, J.

1980-01-01

Anion exchange membranes used in the system serve as a charge transferring medium as well as a reactant separator and are the key enabling component in this storage technology. Each membrane formulation undergoes a series of screening tests for area-resistivity, static (non-flow) diffusion rate determination, and performance in Redox systems. The CDIL series of membranes has, by virtue of its chemical stability and high ion exchange capacity, demonstrated superior properties in the redox environment. Additional resistivity results at several acid and iron solution concentrations, iron diffusion rates, and time dependent iron fouling of the various membrane formulations are presented in comparison to past standard formulations.

The structure of a magnetic-field front propagating non-diffusively in low-resistivity multi-species plasma

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rubinstein, B.; Doron, R., E-mail: ramy.doron@weizmann.ac.il; Maron, Y.

2016-04-15

We report on the first experimental verification of the traveling-wave-like picture of a magnetic-field and an associated electric potential hill propagating non-diffusively in low resistivity plasma. High spatial resolution spectroscopic method, developed here, allowed for obtaining the detailed shape of the propagating magnetic-field front. The measurements demonstrated that the ion separation, previously claimed, results from the reflection of the higher charge-to-mass ratio ions from the propagating potential hill and from climbing the hill by the lower charge-to-mass ratio ions. This ion dynamics is found to be consistent with the observed electron density evolution.

Microstructural analysis of mass transport phenomena in gas diffusion media for high current density operation in PEM fuel cells

NASA Astrophysics Data System (ADS)

Kotaka, Toshikazu; Tabuchi, Yuichiro; Mukherjee, Partha P.

2015-04-01

Cost reduction is a key issue for commercialization of fuel cell electric vehicles (FCEV). High current density operation is a solution pathway. In order to realize high current density operation, it is necessary to reduce mass transport resistance in the gas diffusion media commonly consisted of gas diffusion layer (GDL) and micro porous layer (MPL). However, fundamental understanding of the underlying mass transport phenomena in the porous components is not only critical but also not fully understood yet due to the inherent microstructural complexity. In this study, a comprehensive analysis of electron and oxygen transport in the GDL and MPL is conducted experimentally and numerically with three-dimensional (3D) microstructural data to reveal the structure-transport relationship. The results reveal that the mass transport in the GDL is strongly dependent on the local microstructural variations, such as local pore/solid volume fractions and connectivity. However, especially in the case of the electrical conductivity of MPL, the contact resistance between carbon particles is the dominant factor. This suggests that reducing the contact resistance between carbon particles and/or the number of contact points along the transport pathway can improve the electrical conductivity of MPL.

Quasi-ballistic Electronic Thermal Conduction in Metal Inverse Opals.

PubMed

Barako, Michael T; Sood, Aditya; Zhang, Chi; Wang, Junjie; Kodama, Takashi; Asheghi, Mehdi; Zheng, Xiaolin; Braun, Paul V; Goodson, Kenneth E

2016-04-13

Porous metals are used in interfacial transport applications that leverage the combination of electrical and/or thermal conductivity and the large available surface area. As nanomaterials push toward smaller pore sizes to increase the total surface area and reduce diffusion length scales, electron conduction within the metal scaffold becomes suppressed due to increased surface scattering. Here we observe the transition from diffusive to quasi-ballistic thermal conduction using metal inverse opals (IOs), which are metal films that contain a periodic arrangement of interconnected spherical pores. As the material dimensions are reduced from ∼230 nm to ∼23 nm, the thermal conductivity of copper IOs is reduced by more than 57% due to the increase in surface scattering. In contrast, nickel IOs exhibit diffusive-like conduction and have a constant thermal conductivity over this size regime. The quasi-ballistic nature of electron transport at these length scales is modeled considering the inverse opal geometry, surface scattering, and grain boundaries. Understanding the characteristics of electron conduction at the nanoscale is essential to minimizing the total resistance of porous metals for interfacial transport applications, such as the total electrical resistance of battery electrodes and the total thermal resistance of microscale heat exchangers.

Anatomical basis of variation in mesophyll resistance in eastern Australian sclerophylls: news of a long and winding path

PubMed Central

Tosens, Tiina

2012-01-01

In sclerophylls, photosynthesis is particularly strongly limited by mesophyll diffusion resistance from substomatal cavities to chloroplasts (r m), but the controls on diffusion limits by integral leaf variables such as leaf thickness, density, and dry mass per unit area and by the individual steps along the diffusion pathway are imperfectly understood. To gain insight into the determinants of r m in leaves with varying structure, the full CO2 physical diffusion pathway was analysed in 32 Australian species sampled from sites contrasting in soil nutrients and rainfall, and having leaf structures from mesophytic to strongly sclerophyllous. r m was estimated based on combined measurements of gas exchange and chlorophyll fluorescence. In addition, r m was modelled on the basis of detailed anatomical measurements to separate the importance of different serial resistances affecting CO2 diffusion into chloroplasts. The strongest sources of variation in r m were S c/S, the exposed surface area of chloroplasts per unit leaf area, and mesophyll cell wall thickness, t cw. The strong correlation of r m with t cw could not be explained by cell wall thickness alone, and most likely arose from a further effect of cell wall porosity. The CO2 drawdown from intercellular spaces to chloroplasts was positively correlated with t cw, suggesting enhanced diffusional limitations in leaves with thicker cell walls. Leaf thickness and density were poorly correlated with S c/S, indicating that widely varying combinations of leaf anatomical traits occur at given values of leaf integrated traits, and suggesting that detailed anatomical studies are needed to predict r m for any given species. PMID:22888123

Insights into the Enhanced in vivo Fitness of Neisseria gonorrhoeae Driven by a Fluoroquinolone Resistance-Conferring Mutant DNA Gyrase

DTIC Science & Technology

2015-02-05

enhancement in fitness relative to its parent strain was also more resistant to human and bacterial antimicrobial peptides , including the cathelicidins...32 Deep sequencing data analysis.............................................................................. 33 Antimicrobial peptide ...Sensitivity to cationic antimicrobial peptides ....................................................... 57 In vivo competitive infection in wild-type and

Characterization and growth of epitaxial layers of Gs exhibiting high resistivity for ionic implantation

NASA Technical Reports Server (NTRS)

1979-01-01

Either classical or low temperature epitaxial growth techniques can be used to control the deposition of buffer layers of GaAs on semiconducting substrates and to obtain the resistivity and purity desired. Techniques developed to study, as a function of thickness, the evolution of mobilities by photoHall, and the spectroscopy of shallow and deep centers by cathodoluminescence and current transients reveal one very pure layer of medium resistivity and high mobility, and another "dead layer" of elevated resistivity far from the surface. The highly resistive layer remains pure over several microns, which appears interesting for implantation.

Stratigraphic controls on fluid and solute fluxes across the sediment-water interface of an estuary

USGS Publications Warehouse

Sawyer, Audrey H.; Lazareva, Olesya; Kroeger, Kevin D.; Crespo, Kyle; Chan, Clara S.; Stieglitz, Thomas; Michael, Holly A.

2014-01-01

Shallow stratigraphic features, such as infilled paleovalleys, modify fresh groundwater discharge to coastal waters and fluxes of saltwater and nutrients across the sediment–water interface. We quantify the spatial distribution of shallow surface water–groundwater exchange and nitrogen fluxes near a paleovalley in Indian River Bay, Delaware, using a hand resistivity probe, conventional seepage meters, and pore-water samples. In the interfluve (region outside the paleovalley) most nitrate-rich fresh groundwater discharges rapidly near the coast with little mixing of saline pore water, and nitrogen transport is largely conservative. In the peat-filled paleovalley, fresh groundwater discharge is negligible, and saltwater exchange is deep (∼1 m). Long pore-water residence times and abundant sulfate and organic matter promote sulfate reduction and ammonium production in shallow sediment. Reducing, iron-rich fresh groundwater beneath paleovalley peat discharges diffusely around paleovalley margins offshore. In this zone of diffuse fresh groundwater discharge, saltwater exchange and dispersion are enhanced, ammonium is produced in shallow sediments, and fluxes of ammonium to surface water are large. By modifying patterns of groundwater discharge and the nature of saltwater exchange in shallow sediments, paleovalleys and other stratigraphic features influence the geochemistry of discharging groundwater. Redox reactions near the sediment–water interface affect rates and patterns of geochemical fluxes to coastal surface waters. For example, at this site, more than 99% of the groundwater-borne nitrate flux to the Delaware Inland Bays occurs within the interfluve portion of the coastline, and more than 50% of the ammonium flux occurs at the paleovalley margin.

On axisymmetric resistive magnetohydrodynamic equilibria with flow free of Pfirsch-Schlüter diffusion

NASA Astrophysics Data System (ADS)

Throumoulopoulos, G. N.; Tasso, H.

2003-06-01

The equilibrium of an axisymmetric magnetically confined plasma with anisotropic resistivity and incompressible flows parallel to the magnetic field is investigated within the framework of the magnetohydrodynamic (MHD) theory by keeping the convective flow term in the momentum equation. It turns out that the stationary states are determined by a second-order elliptic partial differential equation for the poloidal magnetic flux function ψ along with a decoupled Bernoulli equation for the pressure identical in form with the respective ideal MHD equations; equilibrium consistent expressions for the resistivities η∥ and η⊥ parallel and perpendicular to the magnetic field are also derived from Ohm's and Faraday's laws. Unlike in the case of stationary states with isotropic resistivity and parallel flows [G. N. Throumoulopoulos and H. Tasso, J. Plasma Phys. 64, 601 (2000)] the equilibrium is compatible with nonvanishing poloidal current densities. Also, although exactly Spitzer resistivities either η∥(ψ) or η⊥(ψ) are not allowed, exact solutions with vanishing poloidal electric fields can be constructed with η∥ and η⊥ profiles compatible with roughly collisional resistivity profiles, i.e., profiles having a minimum close to the magnetic axis, taking very large values on the boundary and such that η⊥>η∥. For equilibria with vanishing flows satisfying the relation (dP/dψ)(dI2/dψ)>0, where P and I are the pressure and the poloidal current functions, the difference η⊥-η∥ for the reversed-field pinch scaling, Bp≈Bt, is nearly two times larger than that for the tokamak scaling, Bp≈0.1Bt (Bp and Bt are the poloidal and toroidal magnetic-field components). The particular resistive equilibrium solutions obtained in the present work, inherently free of—but not inconsistent with—Pfirsch-Schlüter diffusion, indicate that parallel flows might result in a reduction of the diffusion observed in magnetically confined plasmas.

Nonvolatile Memory Materials for Neuromorphic Intelligent Machines.

PubMed

Jeong, Doo Seok; Hwang, Cheol Seong

2018-04-18

Recent progress in deep learning extends the capability of artificial intelligence to various practical tasks, making the deep neural network (DNN) an extremely versatile hypothesis. While such DNN is virtually built on contemporary data centers of the von Neumann architecture, physical (in part) DNN of non-von Neumann architecture, also known as neuromorphic computing, can remarkably improve learning and inference efficiency. Particularly, resistance-based nonvolatile random access memory (NVRAM) highlights its handy and efficient application to the multiply-accumulate (MAC) operation in an analog manner. Here, an overview is given of the available types of resistance-based NVRAMs and their technological maturity from the material- and device-points of view. Examples within the strategy are subsequently addressed in comparison with their benchmarks (virtual DNN in deep learning). A spiking neural network (SNN) is another type of neural network that is more biologically plausible than the DNN. The successful incorporation of resistance-based NVRAM in SNN-based neuromorphic computing offers an efficient solution to the MAC operation and spike timing-based learning in nature. This strategy is exemplified from a material perspective. Intelligent machines are categorized according to their architecture and learning type. Also, the functionality and usefulness of NVRAM-based neuromorphic computing are addressed. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Training Deep Convolutional Neural Networks with Resistive Cross-Point Devices

PubMed Central

Gokmen, Tayfun; Onen, Murat; Haensch, Wilfried

2017-01-01

In a previous work we have detailed the requirements for obtaining maximal deep learning performance benefit by implementing fully connected deep neural networks (DNN) in the form of arrays of resistive devices. Here we extend the concept of Resistive Processing Unit (RPU) devices to convolutional neural networks (CNNs). We show how to map the convolutional layers to fully connected RPU arrays such that the parallelism of the hardware can be fully utilized in all three cycles of the backpropagation algorithm. We find that the noise and bound limitations imposed by the analog nature of the computations performed on the arrays significantly affect the training accuracy of the CNNs. Noise and bound management techniques are presented that mitigate these problems without introducing any additional complexity in the analog circuits and that can be addressed by the digital circuits. In addition, we discuss digitally programmable update management and device variability reduction techniques that can be used selectively for some of the layers in a CNN. We show that a combination of all those techniques enables a successful application of the RPU concept for training CNNs. The techniques discussed here are more general and can be applied beyond CNN architectures and therefore enables applicability of the RPU approach to a large class of neural network architectures. PMID:29066942

Training Deep Convolutional Neural Networks with Resistive Cross-Point Devices.

PubMed

Gokmen, Tayfun; Onen, Murat; Haensch, Wilfried

2017-01-01

In a previous work we have detailed the requirements for obtaining maximal deep learning performance benefit by implementing fully connected deep neural networks (DNN) in the form of arrays of resistive devices. Here we extend the concept of Resistive Processing Unit (RPU) devices to convolutional neural networks (CNNs). We show how to map the convolutional layers to fully connected RPU arrays such that the parallelism of the hardware can be fully utilized in all three cycles of the backpropagation algorithm. We find that the noise and bound limitations imposed by the analog nature of the computations performed on the arrays significantly affect the training accuracy of the CNNs. Noise and bound management techniques are presented that mitigate these problems without introducing any additional complexity in the analog circuits and that can be addressed by the digital circuits. In addition, we discuss digitally programmable update management and device variability reduction techniques that can be used selectively for some of the layers in a CNN. We show that a combination of all those techniques enables a successful application of the RPU concept for training CNNs. The techniques discussed here are more general and can be applied beyond CNN architectures and therefore enables applicability of the RPU approach to a large class of neural network architectures.

Studies of a full-scale mechanical prototype line for the ANTARES neutrino telescope and tests of a prototype instrument for deep-sea acoustic measurements

NASA Astrophysics Data System (ADS)

Ageron, M.; Aguilar, J. A.; Albert, A.; Ameli, F.; Anghinolfi, M.; Anton, G.; Anvar, S.; Ardellier-Desages, F.; Aslanides, E.; Aubert, J.-J.; Auer, R.; Barbarito, E.; Basa, S.; Battaglieri, M.; Bazzotti, M.; Becherini, Y.; Béthoux, N.; Beltramelli, J.; Bertin, V.; Bigi, A.; Billault, M.; Blaes, R.; de Botton, N.; Bouwhuis, M. C.; Bruijn, R.; Brunner, J.; Burgio, G. F.; Busto, J.; Cafagna, F.; Caillat, L.; Calzas, A.; Capone, A.; Caponetto, L.; Carmona, E.; Carr, J.; Castel, D.; Castorina, E.; Cavasinni, V.; Cecchini, S.; Ceres, A.; Charvis, P.; Chauchot, P.; Chiarusi, T.; Circella, M.; Coail, J.-Y.; Colnard, C.; Compére, C.; Coniglione, R.; Cottini, N.; Coyle, P.; Cuneo, S.; Cussatlegras, A.-S.; Damy, G.; van Dantzig, R.; Debonis, G.; de Marzo, C.; de Vita, R.; Dekeyser, I.; Delagnes, E.; Denans, D.; Deschamps, A.; Dessa, J.-X.; Destelle, J.-J.; Dinkespieler, B.; Distefano, C.; Donzaud, C.; Drogou, J.-F.; Druillole, F.; Durand, D.; Ernenwein, J.-P.; Escoffier, S.; Falchini, E.; Favard, S.; Fehr, F.; Feinstein, F.; Fiorello, C.; Flaminio, V.; Fratini, K.; Fuda, J.-L.; Galeotti, S.; Gallone, J.-M.; Giacomelli, G.; Girard, N.; Gojak, C.; Goret, Ph.; Graf, K.; Guilloux, F.; Hallewell, G.; Harakeh, M. N.; Hartmann, B.; Heijboer, A.; Heine, E.; Hello, Y.; Hernández-Rey, J. J.; Hößl, J.; Hoffman, C.; Hogenbirk, J.; Hubbard, J. R.; Jaquet, M.; Jaspers, M.; de Jong, M.; Jouvenot, F.; Kalantar-Nayestanaki, N.; Kappes, A.; Karg, T.; Katz, U.; Keller, P.; Kneib, J. P.; Kok, E.; Kok, H.; Kooijman, P.; Kopper, C.; Kouchner, A.; Kretschmer, W.; Kruijer, A.; Kuch, S.; Lagier, P.; Lahmann, R.; Lamanna, G.; Lamare, P.; Lambard, G.; Languillat, J. C.; Laschinsky, H.; Lavalle, J.; Le Guen, Y.; Le Provost, H.; Le van Suu, A.; Lefévre, D.; Legou, T.; Lelaizant, G.; Lim, G.; Lo Presti, D.; Loaec, G.; Loehner, H.; Loucatos, S.; Louis, F.; Lucarelli, F.; Lyashuk, V.; Mangano, S.; Marcelin, M.; Margiotta, A.; Masullo, R.; Mazéas, F.; Mazure, A.; Megna, R.; Melissas, M.; Migneco, E.; Mongelli, M.; Montaruli, T.; Morganti, M.; Moscoso, L.; Motz, H.; Musumeci, M.; Naumann, C.; Naumann-Godo, M.; Niess, V.; Noble, A.; Olivetto, C.; Ostasch, R.; Palanque-Delabrouille, N.; Payre, P.; Peek, H. Z.; Perez, A.; Petta, C.; Piattelli, P.; Pillet, R.; Pineau, J.-P.; Poinsignon, J.; Popa, V.; Pradier, T.; Racca, C.; Randazzo, N.; van Randwijk, J.; Real, D.; Regnier, M.; van Rens, B.; Réthoré, F.; Rewiersma, P.; Riccobene, G.; Rigaud, V.; Ripani, M.; Roca, V.; Roda, C.; Rolin, J. F.; Rostovtsev, A.; Roux, J.; Ruppi, M.; Russo, G. V.; Rusydi, G.; Salesa, F.; Salomon, K.; Sapienza, P.; Schmitt, F.; Schuller, J.-P.; Shanidze, R.; Sokalski, I.; Spona, T.; Spurio, M.; van der Steenhoven, G.; Stolarczyk, T.; Streeb, K.; Sulak, L.; Taiuti, M.; Tamburini, C.; Tao, C.; Tasca, L.; Terreni, G.; Urbano, F.; Valdy, P.; Valente, V.; Vallage, B.; Vaudaine, G.; Venekamp, G.; Verlaat, B.; Vernin, P.; van Wijk, R.; Wijnker, G.; Wobbe, G.; de Wolf, E.; Yao, A.-F.; Zaborov, D.; Zaccone, H.; Zornoza, J. D.; Zúñiga, J.

2007-11-01

A full-scale mechanical prototype line was deployed to a depth of 2500 m to test the leak tightness of the electronics containers and the pressure-resistant properties of an electromechanical cable under evaluation for use in the ANTARES deep-sea neutrino telescope. During a month-long immersion study, line parameter data were taken using miniature autonomous data loggers and shore-based optical time domain reflectometry. Details of the mechanical prototype line, the electromechanical cable and data acquisition are presented. Data taken during the immersion study revealed deficiencies in the pressure resistance of the electromechanical cable terminations at the entry points to the electronics containers. The improvements to the termination, which have been integrated into subsequent detection lines, are discussed. The line also allowed deep-sea acoustic measurements with a prototype hydrophone system. The technical setup of this system is described, and the first results of the data analysis are presented.

Chromium boron surfaced nickel-iron base alloys

NASA Technical Reports Server (NTRS)

Rashid, James M. (Inventor); Friedrich, Leonard A. (Inventor); Freling, Melvin (Inventor)

1984-01-01

Chromium boron diffusion coatings on nickel iron alloys uniquely provide them with improvement in high cycle fatigue strength (up to 30%) and erosion resistance (up to 15 times), compared to uncoated alloy. The diffused chromium layer extends in two essential concentration zones to a total depth of about 40.times.10.sup.-6 m, while the succeeding boron layer is limited to 50-90% of the depth of the richest Cr layer nearest the surface. Both coatings are applied using conventional pack diffusion processes.

A translational study of resistance emergence using sequential direct-acting antiviral agents for hepatitis C using ultra-deep sequencing.

PubMed

Abe, Hiromi; Hayes, C Nelson; Hiraga, Nobuhiko; Imamura, Michio; Tsuge, Masataka; Miki, Daiki; Takahashi, Shoichi; Ochi, Hidenori; Chayama, Kazuaki

2013-09-01

Direct-acting antiviral agents (DAAs) against hepatitis C virus (HCV) have recently been developed and are ultimately hoped to replace interferon-based therapy. However, DAA monotherapy results in rapid emergence of resistant strains and DAAs must be used in combinations that present a high genetic barrier to resistance, although viral kinetics of multidrug-resistant strains remain poorly characterized. The aim of this study is to track the emergence and fitness of resistance using combinations of telaprevir and NS5A or NS5B inhibitors with genotype 1b clones. HCV-infected chimeric mice were treated with DAAs, and resistance was monitored using direct and ultra-deep sequencing. Combination therapy with telaprevir and BMS-788329 (NS5A inhibitor) reduced serum HCV RNA to undetectable levels. The presence of an NS3-V36A telaprevir resistance mutation resulted in poor response to telaprevir monotherapy but showed significant HCV reduction when telaprevir was combined with BMS-788329. However, a BMS-788329-resistant strain emerged at low frequency. Infection with a BMS-788329-resistant NS5A-L31V mutation rapidly resulted in gain of an additional NS5A-Y93A mutation that conferred telaprevir resistance during combination therapy. Infection with dual NS5AL31V/NS5AY93H mutations resulted in poor response to combination therapy and development of telaprevir resistance. Although HCV RNA became undetectable soon after the beginning of combination therapy with BMS-788329 and BMS-821095 (NS5B inhibitor), rebound with emergence of resistance against all three drugs occurred. Triple resistance also occurred following infection with the NS3V36A/NS5AL31V/NS5AY93H triple mutation. Resistant strains easily develop from cloned virus strains. Sequential use of DAAs should be avoided to prevent emergence of multidrug-resistant strains.

Acid diffusion, standing waves, and information theory: a molecular-scale model of chemically amplified resist

NASA Astrophysics Data System (ADS)

Trefonas, Peter, III; Allen, Mary T.

1992-06-01

Shannon's information theory is adapted to analyze the photolithographic process, defining the mask pattern as the prior state. Definitions and constraints to the general theory are developed so that the information content at various stages of the lithographic process can be described. Its application is illustrated by exploring the information content within projected aerial images and resultant latent images. Next, a 3-dimensional molecular scale model of exposure, acid diffusion, and catalytic crosslinking in acid-hardened resists (AHR) is presented. In this model, initial positions of photogenerated acids are determined by probability functions generated from the aerial images and the local light intensity in the film. In order to simulate post-exposure baking processes, acids are diffused in a random walk manner, for which the catalytic chain length and the average distance between crosslinks can be set. Crosslink locations are defined in terms of the topologically minimized number required to link different chains. The size and location of polymer chains involved in a larger scale crosslinked network is established and related to polymer solubility. In this manner, the nature of the crosslinked latent image can be established. Good correlation with experimental data is found for the calculated percent insolubilization as a function of dose when the rms acid diffusion length is about 500 angstroms. Information analysis is applied in detail to the specific example of AHR chemistry. The information contained within the 3-D crosslinked latent image is explored as a function of exposure dose, catalytic chain length, average distance between crosslinks. Eopt (the exposure dose which optimizes the information contained within the latent image) was found to vary with catalytic chain length in a manner similar to that observed experimentally in a plot of E90 versus post-exposure bake time. Surprisingly, the information content of the crosslinked latent image remains high even when rms diffusion lengths are as long as 1500 angstroms. The information content of a standing wave is shown to decrease with increasing diffusion length, with essentially all standing wave information being lost at diffusion lengths greater than 450 angstroms. A unique mechanism for self-contrast enhancement and high resolution in AHR resist is proposed.

Intramuscular pressures in antigravity muscles using gravity-independent, pneumatic hardware.

PubMed

Macias, Brandon R; Minocha, Ranjeet; Cutuk, Adnan A; Hill, James; Shiau, Jonathon; Hargens, Alan R

2008-08-01

Resistive exercise helps prevent muscle atrophy in microgravity, but better exercise equipment is needed. Therefore, the purpose of this study was to determine if a pneumatic, gravity-independent leg-press device (LPD) provides sufficient force to leg musculature. We hypothesized that intramuscular pressure (IMP), a quantitative index of muscle force, is greater in the antigravity superficial posterior and deep posterior compartments than in the non-antigravity anterior compartment during bilateral leg-press exercise. Millar pressure transducers were inserted into the anterior, lateral, superficial posterior, and deep posterior muscle compartments of the left leg of eight healthy subjects (three women, five men). Subjects were supine on the Keiser SX-1, a pneumatic LPD. Then maximal voluntary contraction (MVC) was determined; each subject performed three consecutive voluntary contractions at approximately 18%, 50%, and 100% MVC while continuously measuring IMP. Repeated measures ANOVA were used to determine differences of IMPs between compartments and loads. The magnitudes of IMP (mean +/- SEM) at 18 - 3% (abbreviated approximately 18%), 50%, and 100% MVC in the superficial and deep posterior compartments were significantly greater than that in the anterior compartment during exercise (P < 0.05). Additionally, IMPs in all four compartments significantly rose as resistance increased at approximately 18%, 50%, and 100% MVC (P < 0.05). The LPD provides significantly increased resistance to all four compartments, but with greater loading of the antigravity compartments as compared to the non-antigravity compartment. Since antigravity muscles of the leg are contained primarily in the superficial and deep posterior compartments, the LPD may help prevent muscle atrophy associated with microgravity.

The Professional Identity of Three Innovative Teachers Engaging in Sustained Knowledge Building Using Technology

ERIC Educational Resources Information Center

Vokatis, Barbara; Zhang, Jianwei

2016-01-01

Diffusing inquiry-based pedagogy in schools for deep and lasting change requires teacher transformation and capacity building. This study characterizes the professional identity of three elementary school teachers who have productively engaged in inquiry-based classroom practice using knowledge building pedagogy and Knowledge Forum, a…

Nonequilibrium Synthesis of Highly Porous Single-Crystalline Oxide Nanostructures

DOE PAGES

Lee, Dongkyu; Gao, Xiang; Fan, Lisha; ...

2017-01-20

A novel synthesis route to the formation of vertically aligned single–crystalline oxide nanostructures is found by precisely controlling the nonequilibrium pulsed laser deposition process. Here, the columnar nanostructures with deep crevices offering a large surface area are generated owing to the diffusion limited geometric shadowing effect.

Fluid circulation and structural system of Cerritos Colorados geothermal field in La Primavera volcanic caldera (Mexico) inferred from geophysical surveys

NASA Astrophysics Data System (ADS)

Bolós, X.; Cifuentes-Nava, G.; Macias, J. L.; Sosa-Ceballos, G.; García-Tenorio, F.; Albor, M., III; Juarez, M.; Gamez, V.

2017-12-01

Hydrothermal activity in volcanic calderas is the consequence of energy transfer between deep magmatic chambers and subsurface layers saturated in water. This hydrothermal system is generated by convection of the groundwater supplied by meteoric water recharged and the ascent of hot volcanic gasses exsolved from deep magma reservoirs. Calderas are heterogeneous geological structures that due to their formation and evolution produced a complex stratigraphy. All of these heterogeneities can be affected by deformation and also by the presence of fractures and faults which constitute the main pathways whereby hydrothermal fluids can move easily through the surface as spring discharges and fumarolic activity. Geophysical methods have been used in the last decades to investigate the relationship between structural geology and hydrothermal systems in different volcanic areas around the world. In this work, we have focused on the role of subsurface structures to understand and localize the pathways of fluids related to the hydrothermal system of the Cerritos Colorados geothermal field. We focused in the central area of the caldera (P12 well and Cerritos Colorados graben), where active hydrothermal activity is evidenced by fumaroles, thermal anomalies, CO2 diffuse emission, and sulfur precipitation. We have applied a self-potential method (SP) that combined with temperature measurements that allowed to identify the main infiltration and ascending fluid zones in the area, and their specific surface temperature coinciding with fumarolic activity. From this data we an applied Electrical Resistivity Tomography (ERT) survey in two selected places. One ERT profile (1.2 km in length) was located in the P12 well area. A 3D resistivity model used with the equatorial method was carried out on the Cerritos Colorados graben area. Combining the results of the SP, TºC, and ERT data with a detailed structural map we identified the main degassing zones (i.e. fumaroles) that correspond to higher permeability zones located along normal and strike-slip faults. In conclusion, a strong structural control of the surface manifestation of these hydrothermal systems is deduced from our new data. Then, our results emphasize the importance of old structural boundaries that are controlled by intra-caldera tectonic structures.

Isolated effects of external bath osmolality, solute concentration, and electrical charge on solute transport across articular cartilage.

PubMed

Pouran, Behdad; Arbabi, Vahid; Zadpoor, Amir A; Weinans, Harrie

2016-12-01

The metabolic function of cartilage primarily depends on transport of solutes through diffusion mechanism. In the current study, we use contrast enhanced micro-computed tomography to determine equilibrium concentration of solutes through different cartilage zones and solute flux in the cartilage, using osteochondral plugs from equine femoral condyles. Diffusion experiments were performed with two solutes of different charge and approximately equal molecular weight, namely iodixanol (neutral) and ioxaglate (charge=-1) in order to isolate the effects of solute's charge on diffusion. Furthermore, solute concentrations as well as bath osmolality were changed to isolate the effects of steric hindrance on diffusion. Bath concentration and bath osmolality only had minor effects on the diffusion of the neutral solute through cartilage at the surface, middle and deep zones, indicating that the diffusion of the neutral solute was mainly Fickian. The negatively charged solute diffused considerably slower through cartilage than the neutral solute, indicating a large non-Fickian contribution in the diffusion of charged molecules. The numerical models determined maximum solute flux in the superficial zone up to a factor of 2.5 lower for the negatively charged solutes (charge=-1) as compared to the neutral solutes confirming the importance of charge-matrix interaction in diffusion of molecules across cartilage. Copyright © 2016 IPEM. Published by Elsevier Ltd. All rights reserved.

Determination of antibiotic resistance pattern and bacteriocin sensitivity of Listeria monocytogenes strains isolated from different foods in turkey

USDA-ARS?s Scientific Manuscript database

This study aimed to determine the antibiotic resistance pattern and bacteriocin sensitivity of Listeria monocytogenes strains isolated from animal derived foods. With disc diffusion assay, all fourteen L. monocytogenes strains were susceptible to the antibiotics, including penicillin G, vancomycin, ...

Resistivity dependence on Zn concentration in semi-insulating (Cd,Zn)Te

NASA Astrophysics Data System (ADS)

Fiederle, Michael; Fauler, Alex; Babentsov, Vladimir N.; Franc, Jan; Benz, Klaus Werner

2003-01-01

The resistivity dependence on Zn concentration had been investigated in semi-insulating (Cd,Zn)Te crystals grown by the vertical Bridgman method. A coorelation between the zinc concentration and the resistivity distribution could be found. The obtained resistivity was in the interval of 2 ×109-1010 Ω cm as expected from the model of compensation. The main deep compensating levels detected by Photo Induced Current Transient Spectroscopy (PICTS) were at 0.64 +/- 0.02 eV and close the middle of the band gap at 0.80 +/- 0.02 eV.

[Geriatric Proximal Femoral Fracture and Urinary Tract Infection - Considerations for Perioperative Infection Prophylaxis].

PubMed

Probst, A; Reimers, N; Hecht, A; Langenhan, R

2016-10-01

Background: Perioperative infection prophylaxis with cephalosporins is standard in surgical treatment of proximal femoral fractures (PFF). Geriatric patients (pat.) are at risk of chronic infections and the bacteria from these can lead to unknown hygienic problems in an early operation. We therefore characterised the colonisation of the urinary tract in pat. (≥ 65 years) with PFF and observed bacterial development in deep wound infections over a period of 10 years. The aim was to discover gaps in perioperative infection prophylaxis. Patients and Methods: Between September 2013 and November 2015, colonisation of the urinary tract and microbial resistance were investigated on admission of all pat. (≥ 65 years) with the diagnosis of PFF (n = 351; f/m 263/88; median age [∅] 83.57 [65-100] years). Between 2005 and 2014, 2161 pat. with a PFF were operated in our clinic (f/m 1623/538; ∅ 82.35 [65-101] years). 991 pat. (∅ 81.84 [65-101] years) with femoral neck fracture [FNF] were treated with endoprosthesis/osteosynthesis, 1170 pat. (∅ 82,78 [65-101] years) with per-/subtrochanteric fracture [PTF] were treated with osteosynthesis. In a retrospective data analysis, deep wound infections, microbiological composition and changes in microbial resistances over time were identified. Results: Bacteriuria (BU) was detected in the urine sediment of 35.61 % (n = 125) of our pat. In 47.2 % of these pat., BU was accompanied by laboratory signs of manifest urinary tract infection. In 10.4 % of these pat., colonisation of the urinary tract with multi-resistant pathogens was detected; 26.4 % were resistant to cefuroxime. The rate of deep infections in pat. with endoprosthesis/osteosynthesis in FNF was 2.8 % (n = 28; f/m 19/9; ∅ 81.35 [67-92] years), with osteosynthesis in PTF 1,1 % (n = 14; f/m 10/4; ∅ 81.0 [70-91] years). A comparison of the periods 2005-2009 and 2010-2014 showed a shift in the spectrum of pathogens from cephalosporin-sensitive to cephalosporin-resistant enterococci. Resistance of pathogens against cephalosporins increased from 43 to 81 %. Conclusion: We found an increasing risk in geriatric pat. from multiresistant pathogens in the urinary tract and from an increase in the cephalosporin resistance of pathogens in urinary tract infections and in deep wound infections. This indicates that perioperative infection prophylaxis with a cephalosporin is not effective. Especially in nursing homes, development of resistance to antibiotics is an increasing problem. Thus, concepts of perioperative infection prophylaxis in geriatric patients should be reconsidered. Georg Thieme Verlag KG Stuttgart · New York.

Experimental study of the possibility of reducing the resistance and unevenness of output field of velocities in flat diffuser channels with large opening angles

NASA Astrophysics Data System (ADS)

Dmitriev, S. S.; Vasil'ev, K. E.; Mokhamed, S. M. S. O.; Gusev, A. A.; Barbashin, A. V.

2017-11-01

In modern combined cycle gas turbines (CCGT), when designing the reducers from the output diffuser of a gas turbine to a boiler-utilizer, wide-angle diffusers are used, in which practically from the input a flow separation and transition to jet stream regime occurs. In such channels, the energy loss in the field of velocities sharply rise and the field of velocities in the output from them is characterized by considerable unevenness that worsens the heat transfer process in the first by motion tube bundles of the boiler-utilizer. The results of experimental research of the method for reducing the energy loss and alignment of the field of velocities at the output from a flat asymmetrical diffuser channel with one deflecting wall with the opening angle of 40° by means of placing inside the channel the flat plate parallel to the deflecting wall are presented in the paper. It is revealed that, at this placement of the plate in the channel, it has a chance to reduce the energy loss by 20%, considerably align the output field of velocities, and decrease the dynamic loads on the walls in the output cross-section. The studied method of resistance reduction and alignment of the fields of velocities in the flat diffuser channels was used for optimization of the reducer from the output diffuser of the gas turbine to the boiler-utilizer of CCGT of PGU-450T type of Kaliningrad Thermal Power Plant-2. The obtained results are evidence that the configuration of the reducer installed in the PGU-450T of Kaliningrad Thermal Power Plant-2 is not optimal. It follows also from the obtained data that working-off the reducer should be necessarily conducted by the test results of the channel consisting of the model of reducer with the model of boiler-utilizer installed behind it. Application of the method of alignment of output field of velocities and reducing the resistance in the wide-angle diffusers investigated in the work made it possible—when using the known model of diffusion reducer for PGU-450T, which is bad from the standpoint of aerodynamics— to reduce the value of the coefficient of the total loss by almost 20% as compared with the model of real reducer of PGU-450T.

The time and spatial behavior of solar flare proton anisotropies observed in deep space on Pioneers 10 and 11

NASA Technical Reports Server (NTRS)

Mccarthy, J.; Ogallagher, J. J.

1975-01-01

The anisotropy of solar flare protons from the direction of the 'garden hose' magnetic field line has been analyzed for 24 events observed by the University of Chicago experiment on Pioneers 10 and 11 in 1972 and 1973. The anisotropy versus time profiles during individual events are in general consistent with diffusive propagation, but several cases are observed where the decay is better described by an exponential time decay. The anisotropy amplitude evaluated at the time of maximum intensity for each event shows evidence for a gradual decrease with increasing distance from the sun which is qualitatively consistent with diffusive propagation and suggests that the effective interplanetary diffusion coefficient parallel to the magnetic field increases slowly with heliocentric distance.

Speckle contrast optical spectroscopy, a non-invasive, diffuse optical method for measuring microvascular blood flow in tissue

PubMed Central

Valdes, Claudia P.; Varma, Hari M.; Kristoffersen, Anna K.; Dragojevic, Tanja; Culver, Joseph P.; Durduran, Turgut

2014-01-01

We introduce a new, non-invasive, diffuse optical technique, speckle contrast optical spectroscopy (SCOS), for probing deep tissue blood flow using the statistical properties of laser speckle contrast and the photon diffusion model for a point source. The feasibility of the method is tested using liquid phantoms which demonstrate that SCOS is capable of measuring the dynamic properties of turbid media non-invasively. We further present an in vivo measurement in a human forearm muscle using SCOS in two modalities: one with the dependence of the speckle contrast on the source-detector separation and another on the exposure time. In doing so, we also introduce crucial corrections to the speckle contrast that account for the variance of the shot and sensor dark noises. PMID:25136500

Sensitive Deep-Sequencing-Based HIV-1 Genotyping Assay To Simultaneously Determine Susceptibility to Protease, Reverse Transcriptase, Integrase, and Maturation Inhibitors, as Well as HIV-1 Coreceptor Tropism

PubMed Central

Gibson, Richard M.; Meyer, Ashley M.; Winner, Dane; Archer, John; Feyertag, Felix; Ruiz-Mateos, Ezequiel; Leal, Manuel; Robertson, David L.; Schmotzer, Christine L.

2014-01-01

With 29 individual antiretroviral drugs available from six classes that are approved for the treatment of HIV-1 infection, a combination of different phenotypic and genotypic tests is currently needed to monitor HIV-infected individuals. In this study, we developed a novel HIV-1 genotypic assay based on deep sequencing (DeepGen HIV) to simultaneously assess HIV-1 susceptibilities to all drugs targeting the three viral enzymes and to predict HIV-1 coreceptor tropism. Patient-derived gag-p2/NCp7/p1/p6/pol-PR/RT/IN- and env-C2V3 PCR products were sequenced using the Ion Torrent Personal Genome Machine. Reads spanning the 3′ end of the Gag, protease (PR), reverse transcriptase (RT), integrase (IN), and V3 regions were extracted, truncated, translated, and assembled for genotype and HIV-1 coreceptor tropism determination. DeepGen HIV consistently detected both minority drug-resistant viruses and non-R5 HIV-1 variants from clinical specimens with viral loads of ≥1,000 copies/ml and from B and non-B subtypes. Additional mutations associated with resistance to PR, RT, and IN inhibitors, previously undetected by standard (Sanger) population sequencing, were reliably identified at frequencies as low as 1%. DeepGen HIV results correlated with phenotypic (original Trofile, 92%; enhanced-sensitivity Trofile assay [ESTA], 80%; TROCAI, 81%; and VeriTrop, 80%) and genotypic (population sequencing/Geno2Pheno with a 10% false-positive rate [FPR], 84%) HIV-1 tropism test results. DeepGen HIV (83%) and Trofile (85%) showed similar concordances with the clinical response following an 8-day course of maraviroc monotherapy (MCT). In summary, this novel all-inclusive HIV-1 genotypic and coreceptor tropism assay, based on deep sequencing of the PR, RT, IN, and V3 regions, permits simultaneous multiplex detection of low-level drug-resistant and/or non-R5 viruses in up to 96 clinical samples. This comprehensive test, the first of its class, will be instrumental in the development of new antiretroviral drugs and, more importantly, will aid in the treatment and management of HIV-infected individuals. PMID:24468782

Electrical geophysical study over the Norman Landfill, near Norman, Oklahoma

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bisdorf, R.J.

In 1995 and 1996 the US Geological Survey made 40 Schlumberger dc electrical resistivity soundings at the Norman Landfill, near Norman, Oklahoma. Interpretation of the resistivity data indicates that high resistivities (>300 ohm-m) are related to dry sand, intermediate resistivities (45-300 ohm-m) are related to freshwater saturated sand, and low resistivities (<45 ohm-m) are related to fine-grained materials or materials saturated with the conductive fluids. Interpreted resistivity maps show a low resistivity anomaly that extends from under the landfill to just past a nearby slough. This anomaly corresponds to known areas of ground water contamination. A resistivity cross section, constructedmore » from interpreted Schlumberger soundings, shows that this low resistivity anomaly is about 5 m deep and up to 9 m thick.« less

The consistency of antibiotic resistance' results in two methods of disk diffusion and MIC in isolated organisms from patients with urinary tract infections.

PubMed

Karami, A; Mazloom Zadeh, S; Rastin, A; Karami, A; Shiri, P

2015-01-01

Introduction: The urinary tract infection is the most common infection and drug resistance to it is increasing. Due to the acute infection, the prescribing of medicine is conducted before culture and antibiogram and according to the results, disk diffusion is adjusted. The aim of this study was to compare it with MIC to determine to what extent the current method could be useful. Methods: This descriptive cross-sectional investigation research regarding drug resistance was conducted with the help of two methods of disk diffusion and MIC on the isolations of patients' urine culture with UTI (midstream clean catch). Bacterial resistance was measured, and sensitivity and specificity were evaluated. Results: The MIC method was considered the gold standard and, according to the related formula, the sensitivity and specificity of disk diffusion were related to 13 antibiotics obtained as it follows: ciprofloxacin 69% and 69.1% (0.0001 > p and Kappa = .292), cotrimoxazole 50% and 77.3% (p = 0.010), nitrofurantoin 84.7% and 58.2% (0.0001 > p and Kappa = 0.44), ampicilin 83.3% and 85.3% (0.0001 > p and Kappa = 0.33), ofloxacin 65.5% and 83.9% (0.0001 > p and Kappa = 0.429), cephalexin 46.2% and 75.2% (p = 0.012 and Kappa = 0.116), gentamicin 64.2% and 66% (0.0001 > p and Kappa = 0.276), ceftriaxone 27.6% and 80.9% (p = 0.216 and Kappa = 0.074), nalidixic acid 42.1% and 89.2% (0.0001 > p and Kappa = 0.354), imipenem 63.4% and 70.4% (0.0001 > p and Kappa 0.306), co-amoxiclav 83% and 71% (0.0001 > p and Kappa = 0.412), cefixime 21% and 80.9% (0.0001 > p and Kappa = 0.412), vancomycin 55.9% and 94.7 (0.9001 > p and Kappa = 0.532). Sensitivity and specificity of this method were reported to be lower than MIC. Conclusions: Due to the low sensitivity and specificity of the disk diffusion method, antibiotic therapy should be certainly considered in clinical conditions, and risk factors for the infection and only by this approach cannot prescribe the drug.

Use of cylindrical diffusing fibers as detectors for interstitial tissue spectroscopy

NASA Astrophysics Data System (ADS)

Baran, Timothy M.; Foster, Thomas H.

2015-03-01

Interstitial photodynamic therapy (iPDT) describes the use of implanted optical fibers for delivery of treatment light to activate photosensitizer in regions that can be located deep within the body. Since sensitive healthy structures are often located nearby, this requires careful treatment planning that is dependent on tissue optical properties. Determination of these values usually involves the insertion of additional fibers into the volume, or the use of flat-cleaved optical fibers as both treatment sources and detectors. The insertion of additional fibers is undesirable, and cylindrical diffusers have been shown to offer superior treatment characteristics compared to flat-cleaved fibers. Using cylindrical diffusers as detectors for spectroscopic measurement is therefore attractive. We describe the determination of the detection profile for a particular cylindrical diffuser design and derive the scatterer concentration gradient within the diffuser core. This detection profile is compared to previously characterized diffusers, and is shown to be dependent on the diffuser design. For diffusers with a constant scatterer concentration and distal mirror, the detection profile is localized to the proximal end of the diffusing region. For diffusers with variable scattering concentration along their length and no distal mirror, the detection profile is shown to be more uniform along the diffusing region. We also present preliminary results showing the recovery of optical properties using arrays of cylindrical diffusing fibers as sources and detectors, with a mean error of 4.4% in the determination of μeff. The accuracy of these results is comparable to those obtained with other methods of optical property recovery.

Shiga Toxin-Producing Escherichia coli Isolated from Bovine Mastitic Milk: Serogroups, Virulence Factors, and Antibiotic Resistance Properties

PubMed Central

Momtaz, Hassan; Safarpoor Dehkordi, Farhad; Taktaz, Taghi; Rezvani, Amir; Yarali, Sajad

2012-01-01

The aim of this study was to detect the virulence factors, serogroups, and antibiotic resistance properties of Shiga toxin-producing Escherichia coli, by using 268 bovine mastitic milk samples which were diagnosed using California Mastitis Test. After E. coli identification, PCR assays were developed for detection of different virulence genes, serogroups, and antibiotic resistance genes of Escherichia coli. The antibiotic resistance pattern was studied using disk diffusion method. Out of 268 samples, 73 (27.23%) were positive for Escherichia coli, and, out of 73 positive samples, 15 (20.54%) were O26 and 11 (15.06%) were O157 so they were the highest while O111 was not detected in any sample so it was the lowest serogroup. Out of 73 STEC strains, 11 (15.06%) and 36 (49.31%) were EHEC and AEEC, respectively. All of the EHEC strains had stx1, eaeA, and ehly, virulence genes, while in AEEC strains stx1 had the highest prevalence (77.77%), followed by eaeA (55.55%). Totally, aadA1 (65.95%) had the highest while blaSHV (6.38%) had the lowest prevalence of antibiotic resistance genes. The disk diffusion method showed that the STEC strains had the highest resistance to penicillin (100%), followed by tetracycline (57.44%), while resistance to cephalothin (6.38%) was the lowest. PMID:23213293

Prevalence of Methicillin-Resistant and Methicillin-Susceptible S. Aureusin the Saliva of Health Professionals

PubMed Central

de Carvalho, Milton Jorge; Pimenta, Fabiana Cristina; Hayashida, Miyeko; Gir, Elucir; da Silva, Adriana Maria; Barbosa, Caio Parente; da Silva Canini, Silvia Rita Marin; Santiago, Silvana

2009-01-01

INTRODUCTION: S. aureus is one of the main agents of nosocomial infection and is sometimes difficult to treat with currently available active antimicrobials. PURPOSE: To analyze the prevalence of methicillin-susceptible S.aureus (MSSA) and methicillin-resistant S. aureus (MRSA) as well as the MRSA antimicrobial susceptibility profile isolated in the saliva of health professionals at a large public education hospital. MATERIALS AND METHODS: The project was approved by the research and ethics committee of the institution under study. Three samples of saliva from 340 health professionals were collected. The saliva analysis used to identify S. aureus was based on mannitol fermentation tests, catalase production, coagulase, DNAse, and lecithinase. In order to detect MRSA, samples were submitted to the disk diffusion test and the oxacillin agar screening test. In order to identify the minimum inhibitory concentration, the Etest® technique was used. RESULTS: The prevalence of MSSA was 43.5% (148/340), and MRSA was 4.1% (14/340). MRSA detected by the diffusion disk test, was 100% resistant to penicillin and oxacillin, 92.9% resistant to erythromycin, 57.1% resistant to clindamycin, 42.9% resistant to ciprofloxacin and 57.1% resistant to cefoxetin. CONCLUSION: This subject is important for both the education of health professionals and for preventative measures. Standard and contact-precautions should be employed in professional practice. PMID:19488585

The arbitrary order mimetic finite difference method for a diffusion equation with a non-symmetric diffusion tensor

NASA Astrophysics Data System (ADS)

Gyrya, V.; Lipnikov, K.

2017-11-01

We present the arbitrary order mimetic finite difference (MFD) discretization for the diffusion equation with non-symmetric tensorial diffusion coefficient in a mixed formulation on general polygonal meshes. The diffusion tensor is assumed to be positive definite. The asymmetry of the diffusion tensor requires changes to the standard MFD construction. We present new approach for the construction that guarantees positive definiteness of the non-symmetric mass matrix in the space of discrete velocities. The numerically observed convergence rate for the scalar quantity matches the predicted one in the case of the lowest order mimetic scheme. For higher orders schemes, we observed super-convergence by one order for the scalar variable which is consistent with the previously published result for a symmetric diffusion tensor. The new scheme was also tested on a time-dependent problem modeling the Hall effect in the resistive magnetohydrodynamics.

The arbitrary order mimetic finite difference method for a diffusion equation with a non-symmetric diffusion tensor

DOE PAGES

Gyrya, V.; Lipnikov, K.

2017-07-18

Here, we present the arbitrary order mimetic finite difference (MFD) discretization for the diffusion equation with non-symmetric tensorial diffusion coefficient in a mixed formulation on general polygonal meshes. The diffusion tensor is assumed to be positive definite. The asymmetry of the diffusion tensor requires changes to the standard MFD construction. We also present new approach for the construction that guarantees positive definiteness of the non-symmetric mass matrix in the space of discrete velocities. The numerically observed convergence rate for the scalar quantity matches the predicted one in the case of the lowest order mimetic scheme. For higher orders schemes, wemore » observed super-convergence by one order for the scalar variable which is consistent with the previously published result for a symmetric diffusion tensor. The new scheme was also tested on a time-dependent problem modeling the Hall effect in the resistive magnetohydrodynamics.« less

The arbitrary order mimetic finite difference method for a diffusion equation with a non-symmetric diffusion tensor

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gyrya, V.; Lipnikov, K.

Here, we present the arbitrary order mimetic finite difference (MFD) discretization for the diffusion equation with non-symmetric tensorial diffusion coefficient in a mixed formulation on general polygonal meshes. The diffusion tensor is assumed to be positive definite. The asymmetry of the diffusion tensor requires changes to the standard MFD construction. We also present new approach for the construction that guarantees positive definiteness of the non-symmetric mass matrix in the space of discrete velocities. The numerically observed convergence rate for the scalar quantity matches the predicted one in the case of the lowest order mimetic scheme. For higher orders schemes, wemore » observed super-convergence by one order for the scalar variable which is consistent with the previously published result for a symmetric diffusion tensor. The new scheme was also tested on a time-dependent problem modeling the Hall effect in the resistive magnetohydrodynamics.« less

Magnetic resonance imaging DTI-FT study on schizophrenic patients with typical negative first symptoms.

PubMed

Gu, Chengyu; Zhang, Ying; Wei, Fuquan; Cheng, Yougen; Cao, Yulin; Hou, Hongtao

2016-09-01

Magnetic resonance imaging (MRI) with diffusion-tensor imaging (DTI) together with a white matter fiber tracking (FT) technique was used to assess different brain white matter structures and functionalities in schizophrenic patients with typical first negative symptoms. In total, 30 schizophrenic patients with typical first negative symptoms, comprising an observation group were paired 1:1 according to gender, age, right-handedness, and education, with 30 healthy individuals in a control group. Individuals in each group underwent routine MRI and DTI examination of the brain, and diffusion-tensor tractography (DTT) data were obtained through whole brain analysis based on voxel and tractography. The results were expressed by fractional anisotropy (FA) values. The schizophrenic patients were evaluated using a positive and negative symptom scale (PANSS) as well as a Global Assessment Scale (GAS). The results of the study showed that routine MRIs identified no differences between the two groups. However, compared with the control group, the FA values obtained by DTT from the deep left prefrontal cortex, the right deep temporal lobe, the white matter of the inferior frontal gyrus and part of the corpus callosum were significantly lower in the observation group (P<0.05). The PANSS positive scale value in the observation group averaged 7.7±1.5, and the negative scale averaged 46.6±5.9, while the general psychopathology scale averaged 65.4±10.3, and GAS averaged 53.8±19.2. The Pearson statistical analysis, the left deep prefrontal cortex, the right deep temporal lobe, the white matter of the inferior frontal gyrus and the FA value of part of the corpus callosum in the observation group was negatively correlated with the negative scale (P<0.05), and positively correlated with GAS (P<0.05). In conclusion, a decrease in the FA values of the left deep prefrontal cortex, the right deep temporal lobe, the white matter of the inferior frontal gyrus and part of the corpus callosum may be associated with schizophrenia with typical first negative symptoms and the application of MRI DTI-FT can improve diagnostic accuracy.

Frequency domain fluorescence diffuse tomography of small animals

NASA Astrophysics Data System (ADS)

Orlova, Anna G.; Turchin, Ilya V.; Kamensky, Vladislav A.; Plehanov, Vladimir I.; Balalaeva, Irina V.; Sergeeva, Ekaterina A.; Shirmanova, Marina V.; Kleshnin, Michail S.

2007-05-01

Fluorescent compounds for selective cancer cell marking are used for development of novel medical diagnostic methods, investigation of the influence of external factors on tumor growth, regress and metastasis. Only special tools for turbid media imaging, such as optical diffusion tomography permit noninvasive monitoring of fluorescent-labeled tumor alterations deep in animal tissue. In this work, the results of preliminary experiments utilizing frequency-domain fluorescent diffusion tomography (FD FDT) experimental setup in small animal are presented. Low-frequency modulated light (1 kHz) from Nd:YAG laser with second harmonic generation at the wavelength of 532 nm was used in the setup. The transilluminative planar configuration was used in the setup. A series of model experiments has been conducted and show good agreement between theoretical and experimental fluorescence intensity. Models of deep tumors were created by two methods: (1) glass capsules containing fluorophore solution were inserted into esophagus of small animals to simulate marked tumors; (2) a suspension of transfected HEΚ293-Turbo-RFP cells was subcutaneously injected to small animal. The conducted experiments have shown that FD FDT allows one to detect the presence of labeled tumor cells in small animals, to determine the volume of an experimental tumor, to perform 3D tumor reconstruction, as well as to conduct monitoring investigations. The obtained results demonstrate the potential capability of the FD FDT method for noninvasive whole-body imaging in cancer studies, diagnostics and therapy.

WATER STABILITY OF FILLED ELASTOMERS,

DTIC Science & Technology

ELECTRICAL INSULATION, *BUTYL RUBBER , ELASTOMERS, STABILITY, STABILITY, HYDROLYSIS, CURING AGENTS, ADDITIVES, WATER, ABSORPTION, THICKNESS, ELECTRICAL RESISTANCE, LEAKAGE(ELECTRICAL), DIFFUSION, TALC, ELECTRIC CABLES.

Deep electromagnetic sounding of the moon with Lunokhod 2 data

NASA Technical Reports Server (NTRS)

Vanyan, L. L.; Yegorov, I. V.; Faynberg, E. B.

1977-01-01

Results of electromagnetic sounding distinguished an outer high resistance shell about 200 km thick in the moon's structure. A preliminary petrological interpretation of the moon's layers indicated their origin as a consequence of differentiation of the initial peridotite material. Upon melting, 20% to 40% of the material melts and is removed to form a high resistance basaltic shell underlain by a layer of spinal peridotites enriched in divalent iron oxides and having a reduced resistance.

Diffusion length variation in 0.5- and 3-MeV-proton-irradiated, heteroepitaxial indium phosphide solar cells

NASA Technical Reports Server (NTRS)

Jain, Raj K.; Weinberg, Irving; Flood, Dennis J.

1993-01-01

Indium phosphide (InP) solar cells are more radiation resistant than gallium arsenide (GaAs) and silicon (Si) solar cells, and their growth by heteroepitaxy offers additional advantages leading to the development of light weight, mechanically strong, and cost-effective cells. Changes in heteroepitaxial InP cell efficiency under 0.5- and 3-MeV proton irradiations have been explained by the variation in the minority-carrier diffusion length. The base diffusion length versus proton fluence was calculated by simulating the cell performance. The diffusion length damage coefficient, K(sub L), was also plotted as a function of proton fluence.

Effective defect diffusion lengths in Ar-ion bombarded 3C-SiC

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bayu Aji, L. B.; Wallace, J. B.; Shao, L.

Above room temperature, SiC exhibits pronounced processes of diffusion and interaction of radiation-generated point defects. Here, we use the recently developed pulsed ion beam method to measure effective defect diffusion lengths in 3C-SiC bombarded in the temperature range of 25–200 °C with 500 keV Ar ions. Results reveal a diffusion length of ~10 nm, which exhibits a weak temperature dependence, changing from 9 to 13 nm with increasing temperature. Lastly, these results have important implications for understanding and predicting radiation damage in SiC and for the development of radiation-resistant materials via interface-mediated defect reactions.

Effective defect diffusion lengths in Ar-ion bombarded 3C-SiC

DOE PAGES

Bayu Aji, L. B.; Wallace, J. B.; Shao, L.; ...

2016-04-14

Above room temperature, SiC exhibits pronounced processes of diffusion and interaction of radiation-generated point defects. Here, we use the recently developed pulsed ion beam method to measure effective defect diffusion lengths in 3C-SiC bombarded in the temperature range of 25–200 °C with 500 keV Ar ions. Results reveal a diffusion length of ~10 nm, which exhibits a weak temperature dependence, changing from 9 to 13 nm with increasing temperature. Lastly, these results have important implications for understanding and predicting radiation damage in SiC and for the development of radiation-resistant materials via interface-mediated defect reactions.

Resistance is futile: but it is slowing the pace of EHR adoption nonetheless.

PubMed

Ford, Eric W; Menachemi, Nir; Peterson, Lori T; Huerta, Timothy R

2009-01-01

The purpose of this study is to reassess the projected rate of Electronic Health Record (EHR) diffusion and examine how the federal government's efforts to promote the use of EHR technology have influenced physicians' willingness to adopt such systems. The study recreates and extends the analyses conducted by Ford et al. (1) The two periods examined come before and after the U.S. Federal Government's concerted activity to promote EHR adoption. Meta-analysis and bass modeling are used to compare EHR diffusion rates for two distinct periods of government activity. Very low levels of government activity to promote EHR diffusion marked the first period, before 2004. In 2004, the President of the United States called for a "Universal EHR Adoption" by 2014 (10 yrs), creating the major wave of activity and increased awareness of how EHRs will impact physicians' practices. EHR adoption parameters--external and internal coefficients of influence--are estimated using bass diffusion models and future adoption rates are projected. Comparing the EHR adoption rates before and after 2004 (2001-2004 and 2001-2007 respectively) indicate the physicians' resistance to adoption has increased during the second period. Based on current levels of adoption, less than half the physicians working in small practices will have implemented an EHR by 2014 (47.3%). The external forces driving EHR diffusion have grown in importance since 2004 relative to physicians' internal motivation to adopt such systems. Several national forces are likely contributing to the slowing pace of EHR diffusion.

The mechanistic basis of internal conductance: a theoretical analysis of mesophyll cell photosynthesis and CO2 diffusion.

PubMed

Tholen, Danny; Zhu, Xin-Guang

2011-05-01

Photosynthesis is limited by the conductance of carbon dioxide (CO(2)) from intercellular spaces to the sites of carboxylation. Although the concept of internal conductance (g(i)) has been known for over 50 years, shortcomings in the theoretical description of this process may have resulted in a limited understanding of the underlying mechanisms. To tackle this issue, we developed a three-dimensional reaction-diffusion model of photosynthesis in a typical C(3) mesophyll cell that includes all major components of the CO(2) diffusion pathway and associated reactions. Using this novel systems model, we systematically and quantitatively examined the mechanisms underlying g(i). Our results identify the resistances of the cell wall and chloroplast envelope as the most significant limitations to photosynthesis. In addition, the concentration of carbonic anhydrase in the stroma may also be limiting for the photosynthetic rate. Our analysis demonstrated that higher levels of photorespiration increase the apparent resistance to CO(2) diffusion, an effect that has thus far been ignored when determining g(i). Finally, we show that outward bicarbonate leakage through the chloroplast envelope could contribute to the observed decrease in g(i) under elevated CO(2). Our analysis suggests that physiological and anatomical features associated with g(i) have been evolutionarily fine-tuned to benefit CO(2) diffusion and photosynthesis. The model presented here provides a novel theoretical framework to further analyze the mechanisms underlying diffusion processes in the mesophyll.

The Mechanistic Basis of Internal Conductance: A Theoretical Analysis of Mesophyll Cell Photosynthesis and CO2 Diffusion1[W][OA

PubMed Central

Tholen, Danny; Zhu, Xin-Guang

2011-01-01

Photosynthesis is limited by the conductance of carbon dioxide (CO2) from intercellular spaces to the sites of carboxylation. Although the concept of internal conductance (gi) has been known for over 50 years, shortcomings in the theoretical description of this process may have resulted in a limited understanding of the underlying mechanisms. To tackle this issue, we developed a three-dimensional reaction-diffusion model of photosynthesis in a typical C3 mesophyll cell that includes all major components of the CO2 diffusion pathway and associated reactions. Using this novel systems model, we systematically and quantitatively examined the mechanisms underlying gi. Our results identify the resistances of the cell wall and chloroplast envelope as the most significant limitations to photosynthesis. In addition, the concentration of carbonic anhydrase in the stroma may also be limiting for the photosynthetic rate. Our analysis demonstrated that higher levels of photorespiration increase the apparent resistance to CO2 diffusion, an effect that has thus far been ignored when determining gi. Finally, we show that outward bicarbonate leakage through the chloroplast envelope could contribute to the observed decrease in gi under elevated CO2. Our analysis suggests that physiological and anatomical features associated with gi have been evolutionarily fine-tuned to benefit CO2 diffusion and photosynthesis. The model presented here provides a novel theoretical framework to further analyze the mechanisms underlying diffusion processes in the mesophyll. PMID:21441385

"It's Like This Myth of the Supernegro": Resisting Narratives of Damage and Struggle in the Neoliberal Educational Policy Context

ERIC Educational Resources Information Center

Baldridge, Bianca J.

2017-01-01

As pathologizing, racialized, and patriarchal rhetoric undergirds neoliberal education reform, deficit narratives characterize the education of Black youth. Such narratives present deep challenges for educational policy and community-based educational spaces. This article explores the ways in which community-based educators resist narratives of…

Prevalence of multi drug antimicrobial resistance in isolated from high-risk stocker cattle at arrival and two weeks after processing.

PubMed

Snyder, E; Credille, B; Berghaus, R; Giguère, S

2017-03-01

Bovine respiratory disease (BRD) is the leading cause of morbidity and mortality in North American beef cattle. () is the bacterial pathogen most frequently isolated from cattle with BRD and the prevalence of antimicrobial resistance in this pathogen has been increasing. Administration of antimicrobials to prevent BRD is commonplace in stocker cattle, but the impact of this practice on emergence of resistance in is unknown. High risk, sale barn origin bull and steer calves ( = 169) were transported to a stocker facility in central Georgia and sampled via deep nasopharyngeal swab (NPS) at arrival processing. All calves received the macrolide antimicrobial tulathromycin (2.5 mg/kg subcutaneously) at arrival processing. A second NPS was collected from each calf 10 to 14 d after arrival. The occasional calves diagnosed and treated for BRD prior to 10 to 14 d were swabbed and cultured prior to treatment. Swabs were submitted for culture and antimicrobial susceptibility testing using the Kirby-Bauer disk diffusion method. Of the 169 cattle enrolled, 27 (16.0%) were culture positive for at arrival processing and of these, a multi-drug resistant (MDR) strain of was detected in 1 (3.7%). In contrast, 123 (72.8%) cattle were culture positive for at second sampling and of these, a MDR strain of was detected in 122 (99.2%). The proportions of cattle culture positive for and positive for MDR at arrival processing and at second sampling were significantly different ( < 0.001). At the level of the individual bacterial isolate, 366 individual isolates were collected from the calves at the time of the second sampling. Of these isolates, 361 (98.6%) were intermediate or resistant to all macrolides tested (tilmicosin, gamithromycin, tulathromycin) and the fluoroquinolone enrofloxacin. In addition, 254 isolates (69.4%) were intermediate or resistant to florfenicol and 4 (1.1%) were intermediate or resistant to ceftiofur. There was a significant difference in the proportion of isolates resistant to all of the drug classes except cephalosporins at arrival processing versus second sampling ( < 0.001). Our results show that there was an increase in the proportion of calves positive for from arrival processing to second sampling, and that there was an increase in the proportion of calves that had MDR strains of detected from arrival processing to second sampling. More research is needed to understand the role of metaphylaxis on MDR in and the impact of MDR on morbidity and mortality in stocker cattle.

Rifampicin treatment of canine pyoderma due to multidrug-resistant meticillin-resistant staphylococci: a retrospective study of 32 cases.

PubMed

De Lucia, Michela; Bardagi, Mar; Fabbri, Elisabetta; Ferreira, Diana; Ferrer, Lluis; Scarampella, Fabia; Zanna, Giordana; Fondati, Alessandra

2017-04-01

Rifampicin has received increased interest in veterinary dermatology because of its activity against multidrug-resistant meticillin-resistant staphylococci (MRS). There is limited knowledge about the efficacy and safety of rifampicin in dogs. To provide information on response to treatment and adverse effects in dogs treated with rifampicin for multidrug-resistant MRS pyoderma. Thirty two dogs treated with rifampicin for rifampicin-susceptible multidrug-resistant MRS pyoderma. Retrospective review of medical records, including alanine aminotransferase (ALT) and alkaline phosphatase (ALP) serum activity levels and total bilirubin concentrations, obtained before and throughout the treatment, was performed. Oral rifampicin as sole systemic antimicrobial therapy (median dose 5 mg/kg twice daily) was effective in 71.88% of cases. Topical antimicrobials were used in most cases. Median duration of rifampicin treatment was five weeks for superficial pyoderma and four weeks for deep pyoderma. Gastrointestinal signs were reported in 15% of treated dogs. Statistically significant increases of ALT (P = 0.045) and ALP (P = 0.0002) values after 3-4 weeks of treatment was observed. The median increase was equal to 0.3 and ×1.5 the upper limit of the reference ranges for ALT and ALP, respectively. Oral rifampicin combined with topical antimicrobials can be considered an effective therapeutic option for canine superficial and deep pyoderma caused by rifampicin-susceptible multidrug-resistant MRS. Liver enzyme induction might be the most important cause of ALT and ALP increase associated with rifampicin therapy in dogs. © 2016 ESVD and ACVD.

Highly resistive C-doped hydride vapor phase epitaxy-GaN grown on ammonothermally crystallized GaN seeds

NASA Astrophysics Data System (ADS)

Iwinska, Malgorzata; Piotrzkowski, Ryszard; Litwin-Staszewska, Elzbieta; Sochacki, Tomasz; Amilusik, Mikolaj; Fijalkowski, Michal; Lucznik, Boleslaw; Bockowski, Michal

2017-01-01

GaN crystals were grown by hydride vapor phase epitaxy (HVPE) and doped with C. The seeds were high-structural-quality ammonothermally crystallized GaN. The grown crystals were highly resistive at 296 K and of high structural quality. High-temperature Hall effect measurements revealed p-type conductivity and a deep acceptor level in the material with an activation energy of 1 eV. This is in good agreement with density functional theory calculations based on hybrid functionals as presented by the Van de Walle group. They obtained an ionization energy of 0.9 eV when C was substituted for N in GaN and acted as a deep acceptor.

Use of diffusion tensor imaging to identify similarities and differences between cerebellar and Parkinsonism forms of multiple system atrophy.

PubMed

Wang, Po-Shan; Wu, Hsiu-Mei; Lin, Ching-Po; Soong, Bing-Wen

2011-07-01

We performed diffusion tensor imaging to determine if multiple system atrophy (MSA)-cerebellar (C) and MSA-Parkinsonism (P) show similar changes, as shown in pathological studies. Nineteen patients with MSA-C, 12 patients with MSA-P, 20 patients with Parkinson disease, and 20 healthy controls were evaluated with the use of voxel-based morphometry analysis of diffusion tensor imaging. There was an increase in apparent diffusion coefficient values in the middle cerebellar peduncles and cerebellum and a decrease in fractional anisotropy in the pyramidal tract, middle cerebellar peduncles, and white matter of the cerebellum in patients with MSA-C and MSA-P compared to the controls (P < 0.001). In addition, isotropic diffusion-weighted image values were reduced in the cerebellar cortex and deep cerebellar nuclei in patients with MSA-C and increased in the basal ganglia in patients with MSA-P. These results indicate that despite their disparate clinical manifestations, patients with MSA-C and MSA-P share similar diffusion tensor imaging features in the infratentorial region. Further, the combination of FA, ADC and iDWI images can be used to distinguish between MSA (either form) and Parkinson disease, which has potential therapeutic implications.

Investigation of a combined platinum and electron lifetime control treatment for silicon

NASA Astrophysics Data System (ADS)

Jia, Yunpeng; Cui, Zhihang; Yang, Fei; Zhao, Bao; Zou, Shikai; Liang, Yongsheng

2017-02-01

In silicon, the effect of Combined Lifetime Treatment (CLT) involving platinum diffusion and subsequent electron irradiation is different from the separate treatments of platinum diffusion and electron irradiation, even the treatment of electron irradiation followed by platinum diffusion. In this paper, we investigated the experimental behavior of different kinds of lifetime treated samples. We found that the reverse leakage current (Irr) increases with the increasing platinum diffusion temperature or electron irradiation dose in the separate treatments. Conversely, Irr of the CLT samples decreased with rising platinum diffusion temperature at the same dose of subsequent electron irradiation. By deep-level transient spectroscopy (DLTS), a new energy level E7 (Ec -0.376 eV) was found in our CLT samples. The new level E7 suppresses the dominance of the deeper level E8 (Ec -0.476 eV), which is caused by electron irradiation directly and results in Irr's increase. The formation of the level E7 comes from the complex defect-combined effect between platinum atoms and silicon vacancies, and it affects device's characteristics finally. These research will be helpful to the development of platinum-diffused devices used in intense electron irradiation environments.

COMPARISON BETWEEN AUTOMATED SYSTEM AND PCR-BASED METHOD FOR IDENTIFICATION AND ANTIMICROBIAL SUSCEPTIBILITY PROFILE OF CLINICAL Enterococcus spp

PubMed Central

Furlaneto-Maia, Luciana; Rocha, Kátia Real; Siqueira, Vera Lúcia Dias; Furlaneto, Márcia Cristina

2014-01-01

Enterococci are increasingly responsible for nosocomial infections worldwide. This study was undertaken to compare the identification and susceptibility profile using an automated MicrosScan system, PCR-based assay and disk diffusion assay of Enterococcus spp. We evaluated 30 clinical isolates of Enterococcus spp. Isolates were identified by MicrosScan system and PCR-based assay. The detection of antibiotic resistance genes (vancomycin, gentamicin, tetracycline and erythromycin) was also determined by PCR. Antimicrobial susceptibilities to vancomycin (30 µg), gentamicin (120 µg), tetracycline (30 µg) and erythromycin (15 µg) were tested by the automated system and disk diffusion method, and were interpreted according to the criteria recommended in CLSI guidelines. Concerning Enterococcus identification the general agreement between data obtained by the PCR method and by the automatic system was 90.0% (27/30). For all isolates of E. faecium and E. faecalis we observed 100% agreement. Resistance frequencies were higher in E. faecium than E. faecalis. The resistance rates obtained were higher for erythromycin (86.7%), vancomycin (80.0%), tetracycline (43.35) and gentamicin (33.3%). The correlation between disk diffusion and automation revealed an agreement for the majority of the antibiotics with category agreement rates of > 80%. The PCR-based assay, the van(A) gene was detected in 100% of vancomycin resistant enterococci. This assay is simple to conduct and reliable in the identification of clinically relevant enterococci. The data obtained reinforced the need for an improvement of the automated system to identify some enterococci. PMID:24626409

Influence of Drought on Mesophyll Resistance to CO2 Diffusion and its Impact on Water-Use Efficiency in Trees

NASA Astrophysics Data System (ADS)

Guo, J.; Beverly, D.; Cook, C.; Ewers, B. E.; Williams, D. G.

2015-12-01

The resistance to CO2 diffusion inside leaves (mesophyll resistance; rm) during photosynthesis is often comparable in magnitude to stomatal diffusion resistance, and varies among species and across environmental conditions. Consequently, photosynthesis is strongly limited by rm at low internal CO2 partial pressures, such that its variation may determine patterns of leaf water-use efficiency (WUE). Reduction in stomatal conductance with drought typically increases WUE, but also decreases photosynthesis. In theory, the decrease in photosynthesis could be countered by reduction in rm while maintaining high WUE. It is still uncertain how drought-related changes in rm affect short- and long-term WUE strategies of different tree species. We conducted field observations of instantaneous WUE and 13C discrimination in two dominant conifer species (Pinus contorta and Picea engelmannii) in SE Wyoming over the seasonal dry-down period in the summer of 2015. rm was examined by on-line 13C discrimination using isotope laser spectroscopy. Controlled environment studies on three conifer species (P. contorta, P. engelmannii, and Abies lasiocarpa) and one angiosperm (Populus tremuloides) are in progress. We hypothesize that the plasticity of rm in response to drought accounts for significant adjustments in photosynthetic capacity and WUE. Needle leaf conifers are known to have relatively high rm, and we expect them to show greater improvements in photosynthesis and WUE when rm is decreased compared to angiosperm tree species.

Effect of prolonged hypokinesia on resistance of resistive vessels in rats

NASA Technical Reports Server (NTRS)

Saltykova, V. A.

1982-01-01

Under the effect of prolonged hypokinesia, the perfusion pressure in resistive vessels, measured under conditions of deep anesthesia and complete denervation, increased by approximately the same degree as arterial pressure in non-anesthetized animals. The increase in arterial, perfusion pressure and the resistance of resistive vessels in animals subjected to prolonged hypokinesia was accompanied by an increase in adrenoreactivity. During prolonged hypokinesia, partial obliteration of the vascular bed of the skeletal muscles plays a significant role in the observed increase in resistance of vessels of the extremities. The increase in adrenoreactivity of the vessels during hypokinesia may be realized as a partial case of an increase in the adrenoreactivity of structures whose innervation is disturbed.

Buried homojunction in CdS/Sb2Se3 thin film photovoltaics generated by interfacial diffusion

NASA Astrophysics Data System (ADS)

Zhou, Ying; Li, Yang; Luo, Jiajun; Li, Dengbing; Liu, Xinsheng; Chen, Chao; Song, Huaibing; Ma, Jingyuan; Xue, Ding-Jiang; Yang, Bo; Tang, Jiang

2017-07-01

Antimony selenide (Sb2Se3) emerges as a very promising non-toxic absorber material for thin film photovoltaics, and most of the devices, either in the superstrate or substrate configuration, employed CdS as the buffer layer. Due to the peculiar one-dimensional crystal structure of Sb2Se3, severe interfacial diffusion would be expected. In this letter, the interfacial diffusion in CdS/Sb2Se3 photovoltaics was carefully characterized from a combined material and device physics characterization. The results indicated that a buried homojunction located deep inside the Sb2Se3 absorber layer due to Cd diffusion, instead of the apparent CdS/Sb2Se3 heterojunction, dictated charge separation and device performance in Sb2Se3 thin film solar cells. Cd diffusion converted p-type Sb2Se3 into n-type by introducing a donor level with an activation energy of 0.22 eV. Our studies deepen the understanding of Sb2Se3 photovoltaics and shed light on their further performance optimization.

Correlation between deep fluids, tremor and creep along the central San Andreas fault

USGS Publications Warehouse

Becken, M.; Ritter, O.; Bedrosian, P.A.; Weckmann, U.

2011-01-01

The seismicity pattern along the San Andreas fault near Parkfield and Cholame, California, varies distinctly over a length of only fifty kilometres. Within the brittle crust, the presence of frictionally weak minerals, fault-weakening high fluid pressures and chemical weakening are considered possible causes of an anomalously weak fault northwest of Parkfield. Non-volcanic tremor from lower-crustal and upper-mantle depths is most pronounced about thirty kilometres southeast of Parkfield and is thought to be associated with high pore-fluid pressures at depth. Here we present geophysical evidence of fluids migrating into the creeping section of the San Andreas fault that seem to originate in the region of the uppermost mantle that also stimulates tremor, and evidence that along-strike variations in tremor activity and amplitude are related to strength variations in the lower crust and upper mantle. Interconnected fluids can explain a deep zone of anomalously low electrical resistivity that has been imaged by magnetotelluric data southwest of the Parkfield-Cholame segment. Near Cholame, where fluids seem to be trapped below a high-resistivity cap, tremor concentrates adjacent to the inferred fluids within a mechanically strong zone of high resistivity. By contrast, subvertical zones of low resistivity breach the entire crust near the drill hole of the San Andreas Fault Observatory at Depth, northwest of Parkfield, and imply pathways for deep fluids into the eastern fault block, coincident with a mechanically weak crust and the lower tremor amplitudes in the lower crust. Fluid influx to the fault system is consistent with hypotheses of fault-weakening high fluid pressures in the brittle crust.

Deep Learning Role in Early Diagnosis of Prostate Cancer

PubMed Central

Reda, Islam; Khalil, Ashraf; Elmogy, Mohammed; Abou El-Fetouh, Ahmed; Shalaby, Ahmed; Abou El-Ghar, Mohamed; Elmaghraby, Adel; Ghazal, Mohammed; El-Baz, Ayman

2018-01-01

The objective of this work is to develop a computer-aided diagnostic system for early diagnosis of prostate cancer. The presented system integrates both clinical biomarkers (prostate-specific antigen) and extracted features from diffusion-weighted magnetic resonance imaging collected at multiple b values. The presented system performs 3 major processing steps. First, prostate delineation using a hybrid approach that combines a level-set model with nonnegative matrix factorization. Second, estimation and normalization of diffusion parameters, which are the apparent diffusion coefficients of the delineated prostate volumes at different b values followed by refinement of those apparent diffusion coefficients using a generalized Gaussian Markov random field model. Then, construction of the cumulative distribution functions of the processed apparent diffusion coefficients at multiple b values. In parallel, a K-nearest neighbor classifier is employed to transform the prostate-specific antigen results into diagnostic probabilities. Finally, those prostate-specific antigen–based probabilities are integrated with the initial diagnostic probabilities obtained using stacked nonnegativity constraint sparse autoencoders that employ apparent diffusion coefficient–cumulative distribution functions for better diagnostic accuracy. Experiments conducted on 18 diffusion-weighted magnetic resonance imaging data sets achieved 94.4% diagnosis accuracy (sensitivity = 88.9% and specificity = 100%), which indicate the promising results of the presented computer-aided diagnostic system. PMID:29804518

Long-term viability of carbon sequestration in deep-sea sediments

NASA Astrophysics Data System (ADS)

Teng, Y.; Zhang, D.

2017-12-01

Sequestration of carbon dioxide in deep-sea sediments has been proposed for the long-term storage of anthropogenic CO2, due to the negative buoyancy effect and hydrate formation under conditions of high pressure and low temperature. However, the multi-physics process of injection and post-injection fate of CO2 and the feasibility of sub-seabed disposal of CO2 under different geological and operational conditions have not been well studied. On the basis of a detailed study of the coupled processes, we investigate whether storing CO2 into deep-sea sediments is viable, efficient, and secure over the long term. Also studied are the evolution of the multiphase and multicomponent flow and the impact of hydrate formation on storage efficiency during the upward migration of the injected CO2. It is shown that low buoyancy and high viscosity slow down the ascending plume and the forming of the hydrate cap effectively reduces the permeability and finally becomes an impermeable seal, thus limiting the movement of CO2 towards the seafloor. Different flow patterns at varied time scales are identified through analyzing the mass distribution of CO2 in different phases over time. Observed is the formation of a fluid inclusion, which mainly consists of liquid CO2 and is encapsulated by an impermeable hydrate film in the diffusion-dominated stage. The trapped liquid CO2 and CO2 hydrate finally dissolve into the pore water through diffusion of the CO2 component. Sensitivity analyses are performed on storage efficiency under variable geological and operational conditions. It is found that under a deep-sea setting, CO2 sequestration in intact marine sediments is generally safe and permanent.

Deep Imaging of the HCG 95 Field. I. Ultra-diffuse Galaxies

NASA Astrophysics Data System (ADS)

Shi, Dong Dong; Zheng, Xian Zhong; Zhao, Hai Bin; Pan, Zhi Zheng; Li, Bin; Zou, Hu; Zhou, Xu; Guo, KeXin; An, Fang Xia; Li, Yu Bin

2017-09-01

We present a detection of 89 candidates of ultra-diffuse galaxies (UDGs) in a 4.9 degree2 field centered on the Hickson Compact Group 95 (HCG 95) using deep g- and r-band images taken with the Chinese Near Object Survey Telescope. This field contains one rich galaxy cluster (Abell 2588 at z = 0.199) and two poor clusters (Pegasus I at z = 0.013 and Pegasus II at z = 0.040). The 89 candidates are likely associated with the two poor clusters, giving about 50-60 true UDGs with a half-light radius {r}{{e}}> 1.5 {kpc} and a central surface brightness μ (g,0)> 24.0 mag arcsec-2. Deep z\\prime -band images are available for 84 of the 89 galaxies from the Dark Energy Camera Legacy Survey (DECaLS), confirming that these galaxies have an extremely low central surface brightness. Moreover, our UDG candidates are spread over a wide range in g - r color, and ˜26% are as blue as normal star-forming galaxies, which is suggestive of young UDGs that are still in formation. Interestingly, we find that one UDG linked with HCG 95 is a gas-rich galaxy with H I mass 1.1× {10}9 M ⊙ detected by the Very Large Array, and has a stellar mass of {M}\\star ˜ 1.8× {10}8 M ⊙. This indicates that UDGs at least partially overlap with the population of nearly dark galaxies found in deep H I surveys. Our results show that the high abundance of blue UDGs in the HCG 95 field is favored by the environment of poor galaxy clusters residing in H I-rich large-scale structures.

Geochemical and statistical evidence of recharge, mixing, and controls on spring discharge in an eogenetic karst aquifer

NASA Astrophysics Data System (ADS)

Moore, Paul J.; Martin, Jonathan B.; Screaton, Elizabeth J.

2009-10-01

SummaryInformation about sources of recharge, distributions of flow paths, and the extent of water-rock reactions in karst aquifers commonly result from monitoring spring chemistry and discharge. To investigate the relationship between spring characteristics and the complexities of karst aquifers, we couple variations in surface- and groundwater chemistry to physical conditions including river stage, precipitation, and evapotranspiration (ET) within a sink-rise system through a 6-km portion of the Upper Floridan aquifer (UFA) in north-central Florida. Principal component analysis (PCA) of time series major-element compositions suggests that at least three sources of water affect spring discharge, including allogenic recharge into a swallet, diffuse recharge through a thin vadose zone, and water upwelling from deep within the aquifer. The deep-water source exerts the strongest influence on water chemistry by providing a majority of Na +, Mg 2+, K +, Cl -, and SO42- to the system. Anomalously high temperature at one of several monitoring wells reflects vertical flow of about 1 m/year. Mass-balance calculations suggest diffuse recharge and deep-water upwelling can provide up to 50% of the spring discharge; however, their contributions depend on head gradients between the conduit and surrounding aquifer matrix, which are influenced by variations in precipitation, ET, and river stage. Our results indicate that upwelling from deep flow paths may provide significant contributions of water to spring discharge, and that monitoring only springs limits interpretations of karst systems by masking critical components of the aquifer, such as water sources and flow paths. These results also suggest the matrix in eogenetic aquifers is a major pathway for flow even in a system dominated by conduits.

Ocean chemistry. Dilution limits dissolved organic carbon utilization in the deep ocean.

PubMed

Arrieta, Jesús M; Mayol, Eva; Hansman, Roberta L; Herndl, Gerhard J; Dittmar, Thorsten; Duarte, Carlos M

2015-04-17

Oceanic dissolved organic carbon (DOC) is the second largest reservoir of organic carbon in the biosphere. About 72% of the global DOC inventory is stored in deep oceanic layers for years to centuries, supporting the current view that it consists of materials resistant to microbial degradation. An alternative hypothesis is that deep-water DOC consists of many different, intrinsically labile compounds at concentrations too low to compensate for the metabolic costs associated to their utilization. Here, we present experimental evidence showing that low concentrations rather than recalcitrance preclude consumption of a substantial fraction of DOC, leading to slow microbial growth in the deep ocean. These findings demonstrate an alternative mechanism for the long-term storage of labile DOC in the deep ocean, which has been hitherto largely ignored. Copyright © 2015, American Association for the Advancement of Science.

Conceptual model analysis of interaction at a concrete-Boom Clay interface

NASA Astrophysics Data System (ADS)

Liu, Sanheng; Jacques, Diederik; Govaerts, Joan; Wang, Lian

In many concepts for deep disposal of high-level radioactive waste, cementitious materials are used in the engineered barriers. For example, in Belgium the engineered barrier system is based on a considerable amount of cementitious materials as buffer and backfill in the so-called supercontainer embedded in the hosting geological formation. A potential hosting formation is Boom Clay. Insight in the interaction between the high-pH pore water of the cementitious materials and neutral-pH Boom Clay pore water is required. Two problems are quite common for modeling of such a system. The first one is the computational cost due to the long timescale model assessments envisaged for the deep disposal system. Also a very fine grid (in sub-millimeter), especially at interfaces has to be used in order to accurately predict the evolution of the system. The second one is whether to use equilibrium or kinetic reaction models. The objectives of this paper are twofold. First, we develop an efficient coupled reactive transport code for this diffusion-dominated system by making full use of multi-processors/cores computers. Second, we investigate how sensitive the system is to chemical reaction models especially when pore clogging due to mineral precipitation is considered within the cementitious system. To do this, we selected two portlandite dissolution models, i.e., equilibrium (fastest) and diffusion-controlled model with precipitation of a calcite layer around portlandite particles (diffusion-controlled dissolution). The results show that with shrinking core model portlandite dissolution and calcite precipitation are much slower than with the equilibrium model. Also diffusion-controlled dissolution smooths out dissolution fronts compared to the equilibrium model. However, only a slight difference with respect to the clogging time can be found even though we use a very small diffusion coefficient (10-20 m2/s) in the precipitated calcite layer.

Effects of hydrogen annealing, sulfur segregation and diffusion on the cyclic oxidation resistance of superalloys: A review

NASA Astrophysics Data System (ADS)

Smialek, J. L.; Jayne, D. T.; Schaeffer, J. C.; Murphy, W. H.

1994-12-01

This review is based on the phenomenon of improved oxide scale adhesion for desulfurized superalloys. The proposed adhesion mechanism involves sulfur interfacial segregation and scale-metal bond weakening. Sulfur surface segregation on superalloys is examined as a function of temperature and sulfur content, and is related to the classical behavior predicted by the McLean isotherm. Effective desulfurization to less than 1 ppmw can be accomplished by hydrogen annealing and is described by sulfur diffusion kinetics in nickel. Hydrogen annealing results in excellent cyclic oxidation resistance for a number of advanced superalloys. The concept of a critical sulfur content is discussed in terms of practical annealing conditions and section thicknesses.

Effects of hydrogen annealing, sulfur segregation and diffusion on the cyclic oxidation resistance of superalloys: A review

NASA Technical Reports Server (NTRS)

Smialek, J. L.; Jayne, D. T.; Schaeffer, J. C.; Murphy, W. H.

1994-01-01

This review is based on the phenomenon of improved oxide scale adhesion for desulfurized superalloys. The proposed adhesion mechanism involves sulfur interfacial segregation and scale-metal bond weakening. Sulfur surface segregation on superalloys is examined as a function of temperature and sulfur content, and is related to the classical behavior predicted by the McLean isotherm. Effective desulfurization to less than 1 ppmw can be accomplished by hydrogen annealing and is described by sulfur diffusion kinetics in nickel. Hydrogen annealing results in excellent cyclic oxidation resistance for a number of advanced superalloys. The concept of a critical sulfur content is discussed in terms of practical annealing conditions and section thicknesses.

Effects of Hydrogen Annealing, Sulfur Segregation and Diffusion on the Cyclic Oxidation Resistance of Superalloys: a Review

NASA Technical Reports Server (NTRS)

Smialek, J. L.; Jayne, D. T.; Schaeffer, J. C.; Murphy, W. H.

1994-01-01

This review is based on the phenomenon of improved oxide scale adhesion for desulfurized superalloys. The proposed adhesion mechanism involves sulfur interfacial segregation and scale-metal bond weakening. Sulfur surface segregation on superalloys is examined as a function of temperature and sulfur content and related to classical behavior predicted by the McLean isotherm. Effective desulfurization to less than 1 ppmw can be accomplished by hydrogen annealing and is governed by sulfur diffusion kinetics in nickel. Hydrogen annealing results in excellent cyclic oxidation resistance for a number of advanced superalloys. The concept of a critical sulfur content is discussed in terms of practical annealing conditions and section thicknesses.

Development of lithium diffused radiation resistant solar cells, part 2

NASA Technical Reports Server (NTRS)

Payne, P. R.; Somberg, H.

1971-01-01

The work performed to investigate the effect of various process parameters on the performance of lithium doped P/N solar cells is described. Effort was concentrated in four main areas: (1) the starting material, (2) the boron diffusion, (3) the lithium diffusion, and (4) the contact system. Investigation of starting material primarily involved comparison of crucible grown silicon (high oxygen content) and Lopex silicon (low oxygen content). In addition, the effect of varying growing parameters of crucible grown silicon on lithium cell output was also examined. The objective of the boron diffusion studies was to obtain a diffusion process which produced high efficiency cells with minimal silicon stressing and could be scaled up to process 100 or more cells per diffusion. Contact studies included investigating sintering of the TiAg contacts and evaluation of the contact integrity.

Flame-Resistant Composite Materials For Structural Members

NASA Technical Reports Server (NTRS)

Spears, Richard K.

1995-01-01

Matrix-fiber composite materials developed for structural members occasionally exposed to hot, corrosive gases. Integral ceramic fabric surface layer essential for resistance to flames and chemicals. Endures high temperature, impedes flame from penetrating to interior, inhibits diffusion of oxygen to interior where it degrades matrix resin, resists attack by chemicals, helps resist erosion, and provides additional strength. In original intended application, composite members replace steel structural members of rocket-launching structures that deteriorate under combined influences of atmosphere, spilled propellants, and rocket exhaust. Composites also attractive for other applications in which corrosion- and fire-resistant structural members needed.

Clinical test to detect mecA and antibiotic resistance in Staphylococcus aureus, based on novel biotechnological methods.

PubMed

Shahmohammadi, Mohammad Reza; Nahaei, Mohammad Reza; Akbarzadeh, Abolfazl; Milani, Morteza

2016-09-01

Methicillin-resistant Staphylococcus aureus (MRSA) is one of the most common organisms isolated from clinical samples, and has been associated with morbidity and mortality among hospitalized patients. The aim of this study was to evaluate the prevalence and antibiotic susceptibility patterns among MRSA and methicillin-sensitive S. aureus (MSSA) isolates collected from four hospitals in Iran. A total of 183 isolates of S. aureus were collected from various clinical specimens of four hospitals in Iran. The isolates were identified by using the conventional biochemical tests. Three methods-oxacillin agar disk diffusion, oxacillin agar screening, and PCR- were applied to determine susceptibility to oxacillin. The conventional disk agar diffusion test was used to evaluate the antibiotic sensitivity of our isolates against 15 antibiotics, according to the guidelines of the Clinical and Laboratory Standards Institute (CLSI). Of 183 isolates, 77 isolates (42.1%) were found to be MRSA, by the PCR method. The highest antibiotic resistance was found to be against penicillin, co-trimoxazole, erythromycin, and tetracycline respectively. All isolates were susceptible to vancomycin, according to the results of disk agar diffusion. Among other antibiotics, teicoplanin (84%) and fusidic acid (80.5%) were more active against MRSA isolates. For the different methods evaluated, the sensitivities and specificities were as follows: for disk agar diffusion (84.9% and 95.9%) and for agar screening test with oxacillin concentrations of 0.6 μg/ml (70.8% and 97.4%), 4 μg/ml (96.1%and 97.2%) and 6 μg/ml (96% and 96.3%), respectively. The results of our study showed that 47% of S. aureus isolates were MRSA. Overall, in this research study, resistance to all test antimicrobial agents in MRSA isolates were higher than that of MSSA isolates. Our results also revealed that 85% of mecA-positive isolates and 15% of mecA-negative isolates were resistant to methicillin; while 96% of mecA-negative isolates were sensitive to methicillin. Meanwhile 4% of mecA-positive isolates were also sensitive to methicillin.

A reduced astrocyte response to β-amyloid plaques in the ageing brain associates with cognitive impairment.

PubMed

Mathur, Ryan; Ince, Paul G; Minett, Thais; Garwood, Claire J; Shaw, Pamela J; Matthews, Fiona E; Brayne, Carol; Simpson, Julie E; Wharton, Stephen B

2015-01-01

β-amyloid (Aβ) plaques are a key feature of Alzheimer's disease pathology but correlate poorly with dementia. They are associated with astrocytes which may modulate the effect of Aβ-deposition on the neuropil. This study characterised the astrocyte response to Aβ plaque subtypes, and investigated their association with cognitive impairment. Aβ plaque subtypes were identified in the cingulate gyrus using dual labelling immunohistochemistry to Aβ and GFAP+ astrocytes, and quantitated in two cortical areas: the area of densest plaque burden and the deep cortex near the white matter border (layer VI). Three subtypes were defined for both diffuse and compact plaques (also known as classical or core-plaques): Aβ plaque with (1) no associated astrocytes, (2) focal astrogliosis or (3) circumferential astrogliosis. In the area of densest burden, diffuse plaques with no astrogliosis (β = -0.05, p = 0.001) and with focal astrogliosis (β = -0.27, p = 0.009) significantly associated with lower MMSE scores when controlling for sex and age at death. In the deep cortex (layer VI), both diffuse and compact plaques without astrogliosis associated with lower MMSE scores (β = -0.15, p = 0.017 and β = -0.81, p = 0.03, respectively). Diffuse plaques with no astrogliosis in layer VI related to dementia status (OR = 1.05, p = 0.025). In the area of densest burden, diffuse plaques with no astrogliosis or with focal astrogliosis associated with increasing Braak stage (β = 0.01, p<0.001 and β = 0.07, p<0.001, respectively), and ApoEε4 genotype (OR = 1.02, p = 0.001 and OR = 1.10, p = 0.016, respectively). In layer VI all plaque subtypes associated with Braak stage, and compact amyloid plaques with little and no associated astrogliosis associated with ApoEε4 genotype (OR = 1.50, p = 0.014 and OR = 0.10, p = 0.003, respectively). Reactive astrocytes in close proximity to either diffuse or compact plaques may have a neuroprotective role in the ageing brain, and possession of at least one copy of the ApoEε4 allele impacts the astroglial response to Aβ plaques.

Ethnography, the Internet, and Youth Culture: Strategies for Examining Social Resistance and "Online-Offline" Relationships

ERIC Educational Resources Information Center

Wilson, Brian

2006-01-01

The integration of traditional (offline and face-to-face) and virtual ethnographic methods can aid researchers interested in developing understandings of relationships between online and offline cultural life, and examining the diffuse and sometimes global character of youth resistance. In constructing this argument, I have used insights from…

Turbulent resistivity, diffusion and heating

NASA Technical Reports Server (NTRS)

Fried, B. D.; Kennel, C. F.; Mackenzie, K.; Coroniti, F. V.; Kindel, J. M.; Stenzel, R.; Taylor, R. J.; White, R.; Wong, A. Y.; Bernstein, W.

1971-01-01

Experimental and theoretical studies are reported on ion acoustic and ion cyclotron turbulence and their roles in anomalous resistivity, viscosity, diffusion and heating and in the structure of collisionless electrostatic shocks. Resistance due to ion acoustic turbulence has been observed in experiments with a streaming cesium plasma in which electron current, potential rise due to turbulent resistivity, spectrum of unstable ion acoustic waves, and associated electron heating were all measured directly. Kinetic theory calculations for an expanding, unstable plasma, give results in agreement with the experiment. In a strong magnetic field, with T sub e/T sub i approximately 1 and current densities typical for present Tokomaks, the plasma is stable to ion acoustic but unstable to current driven electrostatic ion cyclotron waves. Relevant characteristics of these waves are calculated and it is shown that for ion, beta greater than m sub e/m sub i, the electromagnetic ion cyclotron wave has a lower instability threshold than the electrostatic one. However, when ion acoustic turbulence is present experiments with double plasma devices show rapid anomalous heating of an ion beam streaming through a plasma.

Project Wild and the Dominant Western Paradigm: A Content Analysis Utilizing Deep Ecology.

ERIC Educational Resources Information Center

Ingraham, Blake

Environmental educators utilize activity guides as a primary method of diffusing environmental education material into educational settings. The most popular environmental education activity guide in use today is Project WILD. Project WILD has come under fire by various groups, especially animal rights groups. Accordingly, a content analysis study…

Desperately Seeking Everett: Some thoughts on Hermeneutic Reading

ERIC Educational Resources Information Center

Solway, David

2010-01-01

One of the major problems from which students suffer has to do with reading: reading with diligence, understanding, and, ideally, with the pleasure that attends discovery. Many students have long been hermeneutical-readers-of-a-sort. The problem has deep roots in a widely diffused media and technocyber environment that thins down and disperses the…

A novel (ex situ) method to quantify oxygen diffusion coefficient of polymer fuel cells backing and catalyst layers

NASA Astrophysics Data System (ADS)

Baricci, Andrea; Casalegno, Andrea

2016-09-01

Limiting current density of oxygen reduction reaction in polymer electrolyte fuel cells is determined by several mass transport resistances that lower the concentration of oxygen on the catalyst active site. Among them, diffusion across porous media plays a significant role. Despite the extensive experimental activity documented in PEMFC literature, only few efforts have been dedicated to the measurement of the effective transport properties in porous layers. In the present work, a methodology for ex situ measurement of the effective diffusion coefficient and Knudsen radius of porous layers for polymer electrolyte fuel cells (gas diffusion layer, micro porous layer and catalyst layer) is described and applied to high temperature polymer fuel cells State of Art materials. Regression of the measured quantities by means of a quasi 2D physical model is performed to quantify the Knudsen effect, which is reported to account, respectively, for 30% and 50% of the mass transport resistance in micro porous layer and catalyst layer. On the other side, the model reveals that pressure gradient consequent to permeation in porous layers of high temperature polymer fuel cells has a negligible effect on oxygen concentration in relevant operating conditions.

The Effect of Temperature on Kinetics and Diffusion Coefficients of Metallocene Derivatives in Polyol-Based Deep Eutectic Solvents

PubMed Central

Bahadori, Laleh; Chakrabarti, Mohammed Harun; Manan, Ninie Suhana Abdul; Hashim, Mohd Ali; Mjalli, Farouq Sabri; AlNashef, Inas Muen; Brandon, Nigel

2015-01-01

The temperature dependence of the density, dynamic viscosity and ionic conductivity of several deep eutectic solvents (DESs) containing ammonium-based salts and hydrogen bond donvnors (polyol type) are investigated. The temperature-dependent electrolyte viscosity as a function of molar conductivity is correlated by means of Walden’s rule. The oxidation of ferrocene (Fc/Fc+) and reduction of cobaltocenium (Cc+/Cc) at different temperatures are studied by cyclic voltammetry and potential-step chronoamperometry in DESs. For most DESs, chronoamperometric transients are demonstrated to fit an Arrhenius-type relation to give activation energies for the diffusion of redox couples at different temperatures. The temperature dependence of the measured conductivities of DES1 and DES2 are better correlated with the Vogel-Tamman-Fulcher equation. The kinetics of the Fc/Fc+ and Cc+/Cc electrochemical systems have been investigated over a temperature range from 298 to 338 K. The heterogeneous electron transfer rate constant is then calculated at different temperatures by means of a logarithmic analysis. The glycerol-based DES (DES5) appears suitable for further testing in electrochemical energy storage devices. PMID:26642045

Methane oxidation in Saanich Inlet during summer stratification

NASA Technical Reports Server (NTRS)

Ward, B. B.; Kilpatrick, K. A.; Wopat, A. E.; Minnich, E. C.; Lidstrom, M. E.

1989-01-01

Saanich Inlet, British Columbia, an fjord on the southeast coast of Vancouver Island, typically stratifies in summer, leading to the formation of an oxic-anoxic interface in the water column and accumulation of methane in the deep water. The results of methane concentration measurements in the water column of the inlet at various times throughout the summer months in 1983 are presented. Methane gradients and calculated diffusive fluxes across the oxic-anoxic interface increased as the summer progressed. Methane distribution and consumption in Saanich Inlet were studied in more detail during August 1986. At this time, a typical summer stratification with an oxic-anoxic interface around 140 m was present. At the interface, steep gradients in nutrient concentrations, bacterial abundance and methane concentration were observed. Methane oxidation was detected in the aerobic surface waters and in the anaerobic deep layer, but highest rates occurred in a narrow layer at the oxic-anoxic interface. Estimated methane oxidation rates were suffcient to consume 100 percent of the methane provided by diffusive flux from the anoxic layer. Methane oxidation is thus a mechanism whereby atmospheric flux from anoxic waters is minimized.

Double-injection, deep-impurity switch development

NASA Technical Reports Server (NTRS)

Whitson, D. W.

1985-01-01

The overall objective of this program was the development of device design and process techniques for the fabrication of a double-injection, deep-impurity (DI) sup 2 silicon switch that operates in the 2-10 kV range with conduction current values of 5 A at 2 kV and 1 A at 10 kV. Other major specifications include a holding voltage of 10 V with no gate current, 10 microsec switching time, and power dissipation of 50 W at 75 C. It was decided to concentrate on the lateral circular devices in order to optimize the gold diffusion. This resulted in devices that are much better switches (approx.1 micro sec switching time), and in a gold diffusion process that is much more controllable than those previously developed. Some results with injection-gated devices were also obtained. The current conduction for V less than VT was analyzed and seen to agree, for the most part, with Lampert's theory. Various sections of this report describe the device designs, wafer-processing techniques, and various measurements which include ac and dc characteristics and four-point probe.

Effects of spin transition on diffusion of Fe2+ in ferropericlase in Earth's lower mantle

NASA Astrophysics Data System (ADS)

Saha, Saumitra; Bengtson, Amelia; Crispin, Katherine L.; van Orman, James A.; Morgan, Dane

2011-11-01

Knowledge of Fe composition in lower-mantle minerals (primarily perovskite and ferropericlase) is essential to a complete understanding of the Earth's interior. Fe cation diffusion potentially controls many aspects of the distribution of Fe in the Earth's lower mantle, including mixing of chemical heterogeneities, element partitioning, and the extent of core-mantle communications. Fe in ferropericlase has been shown to undergo a spin transition starting at about 40 GPa and exists in a mixture of high-spin and low-spin states over a wide range of pressures. Present experimental data on Fe transport in ferropericlase is limited to pressures below 35 GPa and provides little information on the pressure dependence of the activation volume and none on the impact of the spin transition on diffusion. Therefore, known experimental data on Fe diffusion cannot be reliably extrapolated to predict diffusion throughout the lower mantle. Here, first-principles and statistical modeling are combined to predict diffusion of Fe in ferropericlase over the entire lower mantle, including the effects of the Fe spin transition. A thorough statistical thermodynamic treatment is given to fully incorporate the coexistence of high- and low-spin Fe in the model of overall Fe diffusion in the lower mantle. Pure low-spin Fe diffuses approximately 104 times slower than high-spin Fe in ferropericlase but Fe diffusion of the mixed-spin state is only about 10 times slower than that of high-spin Fe. The predicted Fe diffusivities demonstrate that ferropericlase is unlikely to be rate limiting in transporting Fe in deep earth since much slower Fe diffusion in perovskite is predicted.

Atomistic insights into deep eutectic electrolytes: the influence of urea on the electrolyte salt LiTFSI in view of electrochemical applications.

PubMed

Lesch, Volker; Heuer, Andreas; Rad, Babak R; Winter, Martin; Smiatek, Jens

2016-10-19

The influence of urea on the conducting salt lithium bis-(trifluoromethanesulfonyl)-imide (LiTFSI) in terms of lithium ion coordination numbers and lithium ion transport properties is studied via atomistic molecular dynamics simulations. Our results indicate that the presence of urea favors the formation of a deep eutectic electrolyte with pronounced ion conductivities which can be explained by a competition between urea and TFSI in occupying the first coordination shell around lithium ions. All simulation findings verify that high urea concentrations lead to a significant increase of ionic diffusivities and an occurrence of relatively high lithium transference numbers in good agreement with experimental results. The outcomes of our study point at the possible application of deep eutectic electrolytes as ion conducting materials in lithium ion batteries.

Deep Chandra Observations of ESO 428-G014. II. Spectral Properties and Morphology of the Large-scale Extended X-Ray Emission

NASA Astrophysics Data System (ADS)

Fabbiano, G.; Paggi, A.; Karovska, M.; Elvis, M.; Maksym, W. P.; Risaliti, G.; Wang, Junfeng

2018-03-01

We present a deep Chandra spectral and spatial study of the kpc-scale diffuse X-ray emission of the Compton-thick (CT) active galactic nucleus (AGN) ESO 428-G014. The entire spectrum is best fit with composite photoionization + thermal models. The diffuse emission is more extended at lower energies (<3 keV). The smaller extent of the hard continuum and Fe Kα profiles implies that the optically thicker clouds responsible for this scattering may be relatively more prevalent closer to the nucleus. These clouds must not prevent soft ionizing X-rays from the AGN escaping to larger radii, in order to have photoionized ISM at larger radii. This suggests that at smaller radii, there may be a larger population of molecular clouds to scatter the hard X-rays, as in the Milky Way. The diffuse emission is also significantly extended in the cross-cone direction, where the AGN emission would be mostly obscured by the torus in the standard AGN model. Our results suggest that the transmission of the obscuring region in the cross-cone direction is ∼10% of that in the cone direction. In the 0.3–1.5 keV band, the ratio of cross-cone to cone photons increases to ∼84%, suggesting an additional soft diffuse emission component disjoint from the AGN. This could be due to hot ISM trapped in the potential of the galaxy. The luminosity of this component, ∼5 × 1038 erg s‑1, is roughly consistent with the thermal component suggested by the spectral fits in the 170–900 pc annulus.

In vivo diffusion characteristics following perineural injection of the deep branch of the lateral plantar nerve with mepivacaine or iohexol in horses.

PubMed

Contino, E K; King, M R; Valdés-Martínez, A; McIlwraith, C W

2015-03-01

Hindlimb proximal suspensory desmopathy is a common injury of sport horses but diagnosis can be difficult because diagnostic analgesia of the region lacks specificity. Perineural analgesia of the deep branch of the lateral plantar nerve (DBLPN) has been proposed as a more specific method of isolating pain of the proximal aspect of the suspensory ligament but the technique has not been evaluated in vivo. To determine the extent of diffusion of contrast medium and mepivacaine following DBLPN analgesia using a single-needle injection technique and to determine if there is inadvertent involvement of the tarsal sheath and/or tarsometatarsal (TMT) joint using this technique. In vivo experimental study. Perineural injection of the DBLPN was performed in 16 limbs with 3 ml of either mepivacaine hydrochloride or positive contrast medium. Contrast medium-injected limbs were radiographed 5, 15, and 30 min post injection and diffusion characteristics were described. In mepivacaine-injected limbs, synovial fluid from the TMT joint was obtained 10 and 20 min post injection and mepivacaine concentrations were analysed. At 5, 15 and 30 min post injection, the contrast medium extended, on average, 19.6, 20.6 and 21.0 mm proximal and 38.0, 43.5 and 51.9 mm distal to the injection site, respectively. Three of 8 (37.5%) limbs had evidence of contrast medium in the tarsal sheath. Two of 8 (25%) limbs had mepivacaine concentrations within the TMT joint sufficient to produce analgesia (>300 mg/l) at 10 min post injection. Contrast medium diffused further in a distal direction than in a proximal direction. Analgesia of the DBLPN can result in inadvertent involvement of the tarsal sheath and/or TMT joint. © 2014 EVJ Ltd.

Surface geothermal exploration in the Canary Islands by means of soil CO_{2} degassing surveys

NASA Astrophysics Data System (ADS)

García-Merino, Marta; Rodríguez, Fátima; Padrón, Eleazar; Melián, Gladys; Asensio-Ramos, María; Barrancos, José; Hernández, Pedro A.; Pérez, Nemesio M.

2017-04-01

With the exception of the Teide fumaroles, there is not any evidence of hydrothermal fluid discharges in the surficial environment of the Canary Islands, the only Spanish territory with potential high enthalpy geothermal resources. Here we show the results of several diffuse CO2 degassing surveys carried out at five mining licenses in Tenerife and Gran Canaria with the aim of sorting the possible geothermal potential of these five mining licenses. The primary objective of the study was to reduce the uncertainty inherent to the selection of the areas with highest geothermal potential for future exploration works. The yardstick used to classify the different areas was the contribution of volcano-hydrothermal CO2 in the diffuse CO2 degassing at each study area. Several hundreds of measurements of diffuse CO2 emission, soil CO2 concentration and isotopic composition were performed at each mining license. Based in three different endmembers (biogenic, atmospheric and deep-seated CO2) with different CO2 concentrations (100, 0.04 and 100%, respectively) and isotopic compositions (-24, -8 and -3 per mil vs. VPDB respectively) a mass balance to distinguish the different contribution of each endmember in the soil CO2 at each sampling site was made. The percentage of the volcano-hydrothermal contribution in the current diffuse CO2 degassing was in the range 0-19%. The Abeque mining license, that comprises part of the north-west volcanic rift of Tenerife, seemed to show the highest geothermal potential, with an average of 19% of CO2 being released from deep sources, followed by Atidama (south east of Gran Canaria) and Garehagua (southern volcanic rift of Tenerife), with 17% and 12% respectively.

Characterization of Transparent Materials for Erosion Resistance

DTIC Science & Technology

1976-03-01

s. Fyall’s smooth annular depressions surrounding the central undamaged region were observed for Impact velocities up to 500 m/s when deep ring...Section III, however much remains to be learned about the correlation of fracture data with the transient stress distributions In the target...patches of shallow ripples several microns deep are randon y distributed over the surface of the uncoated polycarbonate analogous to those observed on

Silicon MINP solar cells

NASA Technical Reports Server (NTRS)

Olsen, L. C.; Addis, F. W.; Miller, W. A.

1985-01-01

The MINP solar cell concept refers to a cell structure designed to be a base region dominated device. Thus, it is desirable that recombination losses are reduced to the point that they occur only in the base region. The most unique feature of the MINP cell design is that a tunneling contact is utilized for the metallic contact on the front surface. The areas under the collector grid and bus bar are passivated by a thin oxide of tunneling thickness. Efforts must also be taken to minimize recombination at the surface between grid lines, at the junction periphery and within the emitter. Results of both theoretical and experimental studies of silicon MINP cells are given. Performance calculations are described which give expected efficiencies as a function of base resistivity and junction depth. Fabrication and characterization of cells are discussed which are based on 0.2 ohm-cm substrates, diffused emitters on the order of 0.15 to 0.20 microns deep, and with Mg MIS collector grids. A total area AM 1 efficiency of 16.8% was achieved. Detailed analyses of photocurrent and current loss mechanisms are presented and utilized to discuss future directions of research. Finally, results reported by other workers are discussed.

Oxidation Resistant Ti-Al-Fe Diffusion Barrier for FeCrAlY Coatings on Titanium Aluminides

NASA Technical Reports Server (NTRS)

Brady, Michael P. (Inventor); Smialke, James L. (Inventor); Brindley, William J. (Inventor)

1996-01-01

A diffusion barrier to help protect titanium aluminide alloys, including the coated alloys of the TiAl gamma + Ti3Al (alpha2) class, from oxidative attack and interstitial embrittlement at temperatures up to at least 1000 C is disclosed. The coating may comprise FeCrAlX alloys. The diffusion barrier comprises titanium, aluminum, and iron in the following approximate atomic percent: Ti-(50-55)Al-(9-20)Fe. This alloy is also suitable as an oxidative or structural coating for such substrates.

Adsorption of basic dyes on granular activated carbon and natural zeolite.

PubMed

Meshko, V; Markovska, L; Mincheva, M; Rodrigues, A E

2001-10-01

The adsorption of basic dyes from aqueous solution onto granular activated carbon and natural zeolite has been studied using an agitated batch adsorber. The influence of agitation, initial dye concentration and adsorbent mass has been studied. The parameters of Langmuir and Freundlich adsorption isotherms have been determined using the adsorption data. Homogeneous diffusion model (solid diffusion) combined with external mass transfer resistance is proposed for the kinetic investigation. The dependence of solid diffusion coefficient on initial concentration and mass adsorbent is represented by the simple empirical equations.

Comparison of real-time PCR with disk diffusion, agar screen and E-test methods for detection of methicillin-resistant Staphylococcus aureus.

PubMed

Shariati, Laleh; Validi, Majid; Tabatabaiefar, Mohammad Amin; Karimi, Ali; Nafisi, Mohammad Reza

2010-12-01

Methicillin-resistant Staphylococcus aureus (MRSA) is a nosocomial pathogen. Our main objective was to compare oxacillin disk test, oxacillin E-test, and oxacillin agar screen for detection of methicillin resistance in S. aureus, using real-time PCR for mecA as the "gold standard" comparison assay. 196 S. aureus isolates were identified out of 284 Staphylococcus isolates. These isolates were screened for MRSA with several methods: disk diffusion, agar screen (6.0 μg/ml), oxacillin E-test, and real-time PCR for detection of mecA gene. Of the 196 S. aureus isolates tested, 96 isolates (49%) were mecA-positive and 100 isolates (51%) mecA-negative. All methods tested had a statistically significant agreement with real-time PCR. E-test was 100% sensitive and specific for mecA presence. The sensitivity and specificity of oxacillin agar screen method were 98 and 99%, respectively and sensitivity and specificity of oxacillin disk diffusion method were 95 and 93%, respectively. In the present study, oxacillin E-test is proposed as the best phenotypic method. For economic reasons, the oxacillin agar screen method (6.0 μg/ml), which is suitable for the detection of MRSA, is recommended due to its accuracy and low cost.

A Comparison of Resistivity Imaging Techniques Using 1D, 2D and 3D MT Inversions in the Middle Rio Grande Rift, NM

NASA Astrophysics Data System (ADS)

Folsom, M.; Pepin, J.; Person, M. A.; Kelley, S.; Peacock, J.

2016-12-01

Twelve magnetotelluric (MT) soundings were collected along a 40 km profile crossing the Rio Grande rift and a portion of the Socorro Magma Body (SMB). A comparison of 1D, 2D and 3D inverse models highlight the strengths and weaknesses of the respective methods. 2D inversion results are distorted by the 3D nature of the data at longer periods, producing conductive artifacts at depths greater than 3 km. We demonstrate through a 3D forward modelling exercise how it is possible to recreate this effect by placing large resistive and conductive features off of an otherwise perfectly 2D resistivity model. Investigators that image deep conductors using 2D inversion codes should consider the influence of off-axis 3D features. Interpretation of the models currently show no indication of the SMB, but outlines the geometry of syn-rift and pre-rift sediments at the "Socorro Constriction", the southern terminus of the Albuquerque Basin. A strong, northward trending conductor 2-3 km deep and less than 2 ohm-m is coincident with the rift, creating a reversal of induction arrow direction at this point. This is interpreted as deep basin brines, perhaps influenced by evaporates hosted in the Permian Abo and Yeso formations. It has been noted that Rio Grande salinity increases in a stepwise manner, coincident with the terminal ends of sedimentary basins. Our geophysical models suggest a possible connection between rift-bounding faults and deep sedimentary brines, which likely impact the water quality of the Rio Grande. Future work includes adding additional MT stations to better constrain off-axis features and their relationship to the Rio Grande.

Radiance and polarization in the diffusion region with an arbitrary scattering phase matrix

NASA Astrophysics Data System (ADS)

Sun, Bingqiang; Kattawar, George W.; Yang, Ping

2016-11-01

Radiance and polarization patterns in an optically deep region, the so-called diffusion region or asymptotic region, of a homogeneous atmosphere or ocean, depend mainly on the scattering phase matrix and the single-scattering albedo of the medium. The radiance and polarization properties in the diffusion region for an arbitrary scattering phase matrix can be obtained in terms of a series of the generalized spherical functions. The number of terms is closely related to the single-scattering albedo of the medium. If the medium is conservative, the radiance is isotropic in conjunction with no polarization. If the single-scattering albedo is close to 1, several terms are sufficient to obtain the patterns, in which the degree of polarization feature is less than 1%. If the medium is highly absorptive, more expansion terms are required to obtain the diffusion patterns. The examples of simulated radiance and polarization patterns for Rayleigh scattering, Henyey-Greenstein-Rayleigh scattering, and haze L and cloud C1 scattering, defined by Deirmendjian, are calculated.

CdS quantum dots in a novel glass with a very low activation energy and its variation of diffusivity with temperature

NASA Astrophysics Data System (ADS)

Nagpal, Swati

2011-07-01

CdS quantum dots of different average sizes in the range 2 to 3.8 nm were grown by diffusion-limited growth process in indigenously made silicate glass. The absorption spectra showed a strong quantum confinement effect with a blue shift of the order of 500 meV depending on the average size. Critical radius of quantum dots was found to be 1.8 nm. The size dispersion decreased from 15.2 to 12.5% with a 20% increase in the particle size. The activation energy for diffusion was found to be very low i.e. 193 kJ mol-1 and the diffusion coefficient increased by 60% for 10 K rise in temperature. The PL emission spectra showed the presence of only deep traps around 600 nm with a red shift of 200 nm. No shallow traps or band edge emission was observed. The PL peak position changed from 560 to 640 nm with a 35 K increase in annealing temperature.

CO2 diffuse emission from maar lake: An example in Changbai volcanic field, NE China

NASA Astrophysics Data System (ADS)

Sun, Yutao; Guo, Zhengfu; Liu, Jiaqi; Du, Jianguo

2018-01-01

Numerous maars and monogenetic volcanic cones are distributed in northeast China, which are related to westward deep subduction of the Pacific Ocean lithosphere, comprising a significant part of the "Pacific Ring of Fire". It is well known that diffuse CO2 emissions from monogenetic volcanoes, including wet (e.g., maar lake) and dry degassing systems (e.g., soil diffuse emission, fault degassing, etc.), may contribute to budget of globally nature-derived greenhouse gases. However, their relationship between wet (e.g., maar lake) and concomitant dry degassing systems (e.g., soil diffuse emission, fault degassing, etc.) related to monogenetic volcanic field is poorly understood. Yuanchi maar, one of the typical monogenetic volcanic systems, is located on the eastern flank of Tianchi caldera in Changbai volcanic field of northeast China, which displays all of three forms of CO2 degassing including the maar lake, soil micro-seepage and fault degassing. Measurements of efflux of CO2 diffusion from the Yuanchi maar system (YMS) indicate that the average values of CO2 emissions from soil micro-seepage, fault degassing and water-air interface diffusion are 24.3 ± 23.3 g m- 2 d- 1, 39.2 ± 22.4 g m- 2 d- 1 and 2.4 ± 1.1 g m- 2 d- 1, respectively. The minimum output of CO2 diffuse emission from the YMS to the atmosphere is about 176.1 ± 88.3 ton/yr, of which 80.4% results from the dry degassing system. Degassing from the fault contributes to the most of CO2 emissions in all of the three forms of degassing in the YMS. Contributions of mantle, crust, air and organic CO2 to the soil gas are 0.01-0.10%, 10-20%, 32-36% and 48-54%, respectively, which are quantitatively constrained by a He-C isotope coupling calculation model. We propose that CO2 exsolves from the upper mantle melting beneath the Tianchi caldera, which migrates to the crustal magma chamber and further transports to the surface of YMS along the deep fault system. During the transportation processes, the emission of gas experiences crustal contamination, influence of magma chamber beneath the YMS, sub-surface processes and air dilution.

Resistive foil edge grading for accelerator and other high voltage structures

DOEpatents

Caporaso, George J.; Sampayan, Stephen F.; Sanders, David M.

2014-06-10

In a structure or device having a pair of electrical conductors separated by an insulator across which a voltage is placed, resistive layers are formed around the conductors to force the electric potential within the insulator to distribute more uniformly so as to decrease or eliminate electric field enhancement at the conductor edges. This is done by utilizing the properties of resistive layers to allow the voltage on the electrode to diffuse outwards, reducing the field stress at the conductor edge. Preferably, the resistive layer has a tapered resistivity, with a lower resistivity adjacent to the conductor and a higher resistivity away from the conductor. Generally, a resistive path across the insulator is provided, preferably by providing a resistive region in the bulk of the insulator, with the resistive layer extending over the resistive region.

Spin Funneling for Enhanced Spin Injection into Ferromagnets

PubMed Central

Sayed, Shehrin; Diep, Vinh Q.; Camsari, Kerem Yunus; Datta, Supriyo

2016-01-01

It is well-established that high spin-orbit coupling (SOC) materials convert a charge current density into a spin current density which can be used to switch a magnet efficiently and there is increasing interest in identifying materials with large spin Hall angle for lower switching current. Using experimentally benchmarked models, we show that composite structures can be designed using existing spin Hall materials such that the effective spin Hall angle is larger by an order of magnitude. The basic idea is to funnel spins from a large area of spin Hall material into a small area of ferromagnet using a normal metal with large spin diffusion length and low resistivity like Cu or Al. We show that this approach is increasingly effective as magnets get smaller. We avoid unwanted charge current shunting by the low resistive NM layer utilizing the newly discovered phenomenon of pure spin conduction in ferromagnetic insulators via magnon diffusion. We provide a spin circuit model for magnon diffusion in FMI that is benchmarked against recent experiments and theory. PMID:27374496

Spin Funneling for Enhanced Spin Injection into Ferromagnets

NASA Astrophysics Data System (ADS)

Sayed, Shehrin; Diep, Vinh Q.; Camsari, Kerem Yunus; Datta, Supriyo

2016-07-01

It is well-established that high spin-orbit coupling (SOC) materials convert a charge current density into a spin current density which can be used to switch a magnet efficiently and there is increasing interest in identifying materials with large spin Hall angle for lower switching current. Using experimentally benchmarked models, we show that composite structures can be designed using existing spin Hall materials such that the effective spin Hall angle is larger by an order of magnitude. The basic idea is to funnel spins from a large area of spin Hall material into a small area of ferromagnet using a normal metal with large spin diffusion length and low resistivity like Cu or Al. We show that this approach is increasingly effective as magnets get smaller. We avoid unwanted charge current shunting by the low resistive NM layer utilizing the newly discovered phenomenon of pure spin conduction in ferromagnetic insulators via magnon diffusion. We provide a spin circuit model for magnon diffusion in FMI that is benchmarked against recent experiments and theory.

Deconvolution of Voltage Sensor Time Series and Electro-diffusion Modeling Reveal the Role of Spine Geometry in Controlling Synaptic Strength.

PubMed

Cartailler, Jerome; Kwon, Taekyung; Yuste, Rafael; Holcman, David

2018-03-07

Most synaptic excitatory connections are made on dendritic spines. But how the voltage in spines is modulated by its geometry remains unclear. To investigate the electrical properties of spines, we combine voltage imaging data with electro-diffusion modeling. We first present a temporal deconvolution procedure for the genetically encoded voltage sensor expressed in hippocampal cultured neurons and then use electro-diffusion theory to compute the electric field and the current-voltage conversion. We extract a range for the neck resistances of 〈R〉=100±35MΩ. When a significant current is injected in a spine, the neck resistance can be inversely proportional to its radius, but not to the radius square, as predicted by Ohm's law. We conclude that the postsynaptic voltage cannot only be modulated by changing the number of receptors, but also by the spine geometry. Thus, spine morphology could be a key component in determining synaptic transduction and plasticity. Copyright © 2018 Elsevier Inc. All rights reserved.

Mixing of secondary organic aerosols versus relative humidity

PubMed Central

Ye, Qing; Robinson, Ellis Shipley; Ding, Xiang; Ye, Penglin

2016-01-01

Atmospheric aerosols exert a substantial influence on climate, ecosystems, visibility, and human health. Although secondary organic aerosols (SOA) dominate fine-particle mass, they comprise myriad compounds with uncertain sources, chemistry, and interactions. SOA formation involves absorption of vapors into particles, either because gas-phase chemistry produces low-volatility or semivolatile products that partition into particles or because more-volatile organics enter particles and react to form lower-volatility products. Thus, SOA formation involves both production of low-volatility compounds and their diffusion into particles. Most chemical transport models assume a single well-mixed phase of condensing organics and an instantaneous equilibrium between bulk gas and particle phases; however, direct observations constraining diffusion of semivolatile organics into particles containing SOA are scarce. Here we perform unique mixing experiments between SOA populations including semivolatile constituents using quantitative, single-particle mass spectrometry to probe any mass-transfer limitations in particles containing SOA. We show that, for several hours, particles containing SOA from toluene oxidation resist exchange of semivolatile constituents at low relative humidity (RH) but start to lose that resistance above 20% RH. Above 40% RH, the exchange of material remains constant up to 90% RH. We also show that dry particles containing SOA from α-pinene ozonolysis do not appear to resist exchange of semivolatile compounds. Our interpretation is that in-particle diffusion is not rate-limiting to mass transfer in these systems above 40% RH. To the extent that these systems are representative of ambient SOA, we conclude that diffusion limitations are likely not common under typical ambient boundary layer conditions. PMID:27791066

Mixing of secondary organic aerosols versus relative humidity.

PubMed

Ye, Qing; Robinson, Ellis Shipley; Ding, Xiang; Ye, Penglin; Sullivan, Ryan C; Donahue, Neil M

2016-10-24

Atmospheric aerosols exert a substantial influence on climate, ecosystems, visibility, and human health. Although secondary organic aerosols (SOA) dominate fine-particle mass, they comprise myriad compounds with uncertain sources, chemistry, and interactions. SOA formation involves absorption of vapors into particles, either because gas-phase chemistry produces low-volatility or semivolatile products that partition into particles or because more-volatile organics enter particles and react to form lower-volatility products. Thus, SOA formation involves both production of low-volatility compounds and their diffusion into particles. Most chemical transport models assume a single well-mixed phase of condensing organics and an instantaneous equilibrium between bulk gas and particle phases; however, direct observations constraining diffusion of semivolatile organics into particles containing SOA are scarce. Here we perform unique mixing experiments between SOA populations including semivolatile constituents using quantitative, single-particle mass spectrometry to probe any mass-transfer limitations in particles containing SOA. We show that, for several hours, particles containing SOA from toluene oxidation resist exchange of semivolatile constituents at low relative humidity (RH) but start to lose that resistance above 20% RH. Above 40% RH, the exchange of material remains constant up to 90% RH. We also show that dry particles containing SOA from α-pinene ozonolysis do not appear to resist exchange of semivolatile compounds. Our interpretation is that in-particle diffusion is not rate-limiting to mass transfer in these systems above 40% RH. To the extent that these systems are representative of ambient SOA, we conclude that diffusion limitations are likely not common under typical ambient boundary layer conditions.

Transport of neutral solute across articular cartilage: the role of zonal diffusivities.

PubMed

Arbabi, V; Pouran, B; Weinans, H; Zadpoor, A A

2015-07-01

Transport of solutes through diffusion is an important metabolic mechanism for the avascular cartilage tissue. Three types of interconnected physical phenomena, namely mechanical, electrical, and chemical, are all involved in the physics of transport in cartilage. In this study, we use a carefully designed experimental-computational setup to separate the effects of mechanical and chemical factors from those of electrical charges. Axial diffusion of a neutral solute Iodixanol into cartilage was monitored using calibrated microcomputed tomography micro-CT images for up to 48 hr. A biphasic-solute computational model was fitted to the experimental data to determine the diffusion coefficients of cartilage. Cartilage was modeled either using one single diffusion coefficient (single-zone model) or using three diffusion coefficients corresponding to superficial, middle, and deep cartilage zones (multizone model). It was observed that the single-zone model cannot capture the entire concentration-time curve and under-predicts the near-equilibrium concentration values, whereas the multizone model could very well match the experimental data. The diffusion coefficient of the superficial zone was found to be at least one order of magnitude larger than that of the middle zone. Since neutral solutes were used, glycosaminoglycan (GAG) content cannot be the primary reason behind such large differences between the diffusion coefficients of the different cartilage zones. It is therefore concluded that other features of the different cartilage zones such as water content and the organization (orientation) of collagen fibers may be enough to cause large differences in diffusion coefficients through the cartilage thickness.

Speckle contrast diffuse correlation tomography of complex turbid medium flow

DOE Office of Scientific and Technical Information (OSTI.GOV)

Huang, Chong; Irwin, Daniel; Lin, Yu

2015-07-15

Purpose: Developed herein is a three-dimensional (3D) flow contrast imaging system leveraging advancements in the extension of laser speckle contrast imaging theories to deep tissues along with our recently developed finite-element diffuse correlation tomography (DCT) reconstruction scheme. This technique, termed speckle contrast diffuse correlation tomography (scDCT), enables incorporation of complex optical property heterogeneities and sample boundaries. When combined with a reflectance-based design, this system facilitates a rapid segue into flow contrast imaging of larger, in vivo applications such as humans. Methods: A highly sensitive CCD camera was integrated into a reflectance-based optical system. Four long-coherence laser source positions were coupledmore » to an optical switch for sequencing of tomographic data acquisition providing multiple projections through the sample. This system was investigated through incorporation of liquid and solid tissue-like phantoms exhibiting optical properties and flow characteristics typical of human tissues. Computer simulations were also performed for comparisons. A uniquely encountered smear correction algorithm was employed to correct point-source illumination contributions during image capture with the frame-transfer CCD and reflectance setup. Results: Measurements with scDCT on a homogeneous liquid phantom showed that speckle contrast-based deep flow indices were within 12% of those from standard DCT. Inclusion of a solid phantom submerged below the liquid phantom surface allowed for heterogeneity detection and validation. The heterogeneity was identified successfully by reconstructed 3D flow contrast tomography with scDCT. The heterogeneity center and dimensions and averaged relative flow (within 3%) and localization were in agreement with actuality and computer simulations, respectively. Conclusions: A custom cost-effective CCD-based reflectance 3D flow imaging system demonstrated rapid acquisition of dense boundary data and, with further studies, a high potential for translatability to real tissues with arbitrary boundaries. A requisite correction was also found for measurements in the fashion of scDCT to recover accurate speckle contrast of deep tissues.« less

Increased radiation resistance in lithium-counterdoped silicon solar cells

NASA Technical Reports Server (NTRS)

Weinberg, I.; Swartz, C. K.; Mehta, S.

1984-01-01

Lithium-counterdoped n(+)p silicon solar cells are found to exhibit significantly increased radiation resistance to 1-MeV electron irradiation when compared to boron-doped n(+)p silicon solar cells. In addition to improved radiation resistance, considerable damage recovery by annealing is observed in the counterdoped cells at T less than or equal to 100 C. Deep level transient spectroscopy measurements are used to identify the defect whose removal results in the low-temperature aneal. It is suggested that the increased radiation resistance of the counterdoped cells is primarily due to interaction of the lithium with interstitial oxygen.

Resist Parameter Extraction from Line-and-Space Patterns of Chemically Amplified Resist for Extreme Ultraviolet Lithography

NASA Astrophysics Data System (ADS)

Kozawa, Takahiro; Oizumi, Hiroaki; Itani, Toshiro; Tagawa, Seiichi

2010-11-01

The development of extreme ultraviolet (EUV) lithography has progressed owing to worldwide effort. As the development status of EUV lithography approaches the requirements for the high-volume production of semiconductor devices with a minimum line width of 22 nm, the extraction of resist parameters becomes increasingly important from the viewpoints of the accurate evaluation of resist materials for resist screening and the accurate process simulation for process and mask designs. In this study, we demonstrated that resist parameters (namely, quencher concentration, acid diffusion constant, proportionality constant of line edge roughness, and dissolution point) can be extracted from the scanning electron microscopy (SEM) images of patterned resists without the knowledge on the details of resist contents using two types of latest EUV resist.

Development of new resist materials for 193-nm dry and immersion lithography

NASA Astrophysics Data System (ADS)

Sasaki, Takashi; Shirota, Naoko; Takebe, Yoko; Yokokoji, Osamu

2006-03-01

We earlier developed new monocyclic fluoropolymers (FUGU) for F II resist materials. But, it is necessary for FUGU to improve of their characteristics, especially the dry-etching resistance, in order to apply for ArF lithography at fine design rules. We have tried to combine FUGUs with Adamntyl methacrylates based conventional ArF resist polymer. In this paper, we have investigated the role of cyclic fluorinated unit, FUGU, in 193 nm resist polymers by analyzing the dissolution behavior. We found that FGEAM showed high sensitivity and good dissolution contrast, compared with acrylate based conventional samples at low PEB temperature (100 °C). And this difference of sensitivity was clearly found when weak acidity PAGs were used. From the dissolution behaviors of FGEAM, FUGU unit can work to improve the resist sensitivity in acrylate based ArF resist polymers. And we also found that FGEAM showed long acid diffusion length on PEB process, compared with Conventional samples. These result show that FUGU unit has a unique characteristics of the sensitivity with 193nm exposure and the acid diffusion behavior. We also investigated a new series of fluorinated copolymers for 193-nm lithography, combination of FUGU monomer and acrylate units which are used in conventional ArF resist. Six ter-polymers of FUGU, combination of FUGU monomers and EAdMA, GBLMA and HAdMA were prepared. We found that FUGU ter-polymers had a good dry etching resistance keeping high transparency at 193nm. And FUGU ter-polymers showed high sensitivity toward 193nm exposure. FUGU ter-polymers also had a high hydrophobic properties compared conventional type ArF resist polymers. So we also expect FUGU ter-polymers to be useful for ArF dry and immersion lithography.

Electro-codeposition of Ni-SiO2 nanocomposite coatings from deep eutectic solvent with improved corrosion resistance

NASA Astrophysics Data System (ADS)

Li, Ruiqian; Hou, Yuanyuan; Liang, Jun

2016-03-01

Electro-codeposition of nano-sized SiO2 particles into the metal matrix in aqueous solution is generally difficult. In this paper, the nano-sized SiO2 particles were successfully codeposited in the Ni matrix from a choline chloride (ChCl)/ethylene glycol (EG) based deep eutectic solvent (DES) by pulse electro-codeposition. The effects of nano-sized SiO2 particles on electrochemical behaviour of Ni(II) were investigated. The microstructure, composition and corrosion resistance of pure Ni and Ni-SiO2 nanocomposite coatings were explored. Results showed that the SiO2 nanoparticles exhibited excellent dispersion stability in ChCl:2EG DES without any stabilizing additives and the presence of SiO2 nanoparticles have significant effects on the nucleation mechanism of Ni. The maximum content of SiO2 nanoparticles in composite coatings can achieve 4.69 wt.%, which closes to the level of co-deposition micro-sized SiO2 particles from aqueous solution. The Ni-SiO2 nanocomposite coatings exhibit much better corrosion resistance than pure Ni coating, and the corrosion resistance performance increases with increasing SiO2 content in the composite coatings.

A deep crustal fluid channel into the San Andreas Fault system near Parkfield, California

USGS Publications Warehouse

Becken, M.; Ritter, O.; Park, S.K.; Bedrosian, P.A.; Weckmann, U.; Weber, M.

2008-01-01

Magnetotelluric (MT) data from 66 sites along a 45-km-long profile across the San Andreas Fault (SAF) were inverted to obtain the 2-D electrical resistivity structure of the crust near the San Andreas Fault Observatory at Depth (SAFOD). The most intriguing feature of the resistivity model is a steeply dipping upper crustal high-conductivity zone flanking the seismically defined SAF to the NE, that widens into the lower crust and appears to be connected to a broad conductivity anomaly in the upper mantle. Hypothesis tests of the inversion model suggest that upper and lower crustal and upper-mantle anomalies may be interconnected. We speculate that the high conductivities are caused by fluids and may represent a deep-rooted channel for crustal and/or mantle fluid ascent. Based on the chemical analysis of well waters, it was previously suggested that fluids can enter the brittle regime of the SAF system from the lower crust and mantle. At high pressures, these fluids can contribute to fault-weakening at seismogenic depths. These geochemical studies predicted the existence of a deep fluid source and a permeable pathway through the crust. Our resistivity model images a conductive pathway, which penetrates the entire crust, in agreement with the geochemical interpretation. However, the resistivity model also shows that the upper crustal branch of the high-conductivity zone is located NE of the seismically defined SAF, suggesting that the SAF does not itself act as a major fluid pathway. This interpretation is supported by both, the location of the upper crustal high-conductivity zone and recent studies within the SAFOD main hole, which indicate that pore pressures within the core of the SAF zone are not anomalously high, that mantle-derived fluids are minor constituents to the fault-zone fluid composition and that both the volume of mantle fluids and the fluid pressure increase to the NE of the SAF. We further infer from the MT model that the resistive Salinian block basement to the SW of the SAFOD represents an isolated body, being 5-8km wide and reaching to depths >7km, in agreement with aeromagnetic data. This body is separated from a massive block of Salinian crust farther to the SW. The NE terminus of resistive Salinian crust has a spatial relationship with a near-vertical zone of increased seismic reflectivity ???15km SW of the SAF and likely represents a deep-reaching fault zone. ?? 2008 The Authors Journal compilation ?? 2008 RAS.

Effect of screens in wide-angle diffusers

NASA Technical Reports Server (NTRS)

Schubauer, G B; Spangenberg, W G

1949-01-01

An experimental investigation at low airspeeds was made of the filling effect observed when a screen or similar resistance is placed across a diffuser. The filling effect is found to be real in that screens can prevent separation or restore separated flow in diffusers even of extreme divergence and to depend principally on screen location and pressure-drop coefficient of the screen. Results are given for three different diffusers of circular cross section with a variety of screen arrangements. Effects of single screens and multiple screens are shown. The mechanics of the filling effect is explained, and possible efficiencies are discussed. Results of arrangements of multiple screens in wide-angle diffusers are given to show a possible application to damping screens as used in wind tunnels to reduce turbulence. (author)

Cobalt Modification of Thin Rutile Films Magnetron-Sputtered in Vacuum

NASA Astrophysics Data System (ADS)

Afonin, N. N.; Logacheva, V. A.

2018-04-01

Using X-ray phase analysis, atomic force microscopy, and secondary ion mass-spectrometry, the phase formation and component distribution in a Co-TiO2 film system have been investigated during magnetron sputtering of the metal on the oxide and subsequent vacuum annealing. It has been found that cobalt diffuses deep into titanium oxide to form complex oxides CoTi2O5 and CoTiO3. A mechanism behind their formation at grain boundaries throughout the thickness of the TiO2 film is suggested. It assumes the reactive diffusion of cobalt along grain boundaries in the oxide. A quantitative model of reactive interdiffusion in a bilayer polycrystalline metal-oxide film system with limited solubility of components has been developed. The individual diffusion coefficients of cobalt and titanium have been determined in the temperature interval 923-1073 K.

Effect of deposition temperature on thermal stabilities of copper-carbon films in barrier-less Cu metallization

NASA Astrophysics Data System (ADS)

Zhu, Huan; Fu, Zhiqiang; Xie, Qi; Yue, Wen; Wang, Chengbiao; Kang, Jiajie; Zhu, Lina

2018-01-01

Copper-carbon alloy films have been applied in barrier-less Cu metallization as seed layers for improving the thermal stabilities. The effect of the deposition temperature on the microstructure and properties of C-doped Cu films on Si substrates was investigated. The films were prepared by ion beam-assisted deposition at various deposition temperatures by co-sputtering of Cu and graphite targets. No inter-diffusion between Cu and Si was observed in Cu(C) films throughout this experiment, because XRD patterns corresponding to their deep-level reaction product, namely, Cu3Si, were not observed in XRD patterns and EDS results of Cu(C) films. Amorphous carbon layer and SiC layer were found in the interface of Cu(C) as-deposited films when deposition temperature rose to 100 °C by TEM, high-resolution image and Fourier transformation pattern. The Cu(C) films deposited at 100 °C had the best thermal stabilities and the lowest electrical resistivity of 4.44 μW cm after annealing at 400 °C for 1 h. Cu agglomeration was observed in Cu(C) alloy films with deposition temperatures of 200, 300 and 400 °C, and the most serious agglomeration occurred in Cu(C) films deposited at 200 °C. Undesired Cu agglomeration resulted in a sharp increase in the resistivity after annealing at 300 °C for 1 h. The deposition temperature of 100 °C reflected the superior thermal stabilities of Cu(C) seed layers compared with those of other layers.