Void formation in INCONEL MA-754 by high temperature oxidation

NASA Astrophysics Data System (ADS)

Rosenstein, Alan H.; Tien, John K.; Nix, William D.

1986-01-01

Subsurface void formation in oxide dispersion strengthened MA-754 caused by high temperature oxidation was investigated at temperatures of 1100, 1150, and 1200 °C for times of 1, 10, 50, and 100 hours. Material exposed at 1200 °C was examined using microprobe, SEM, and optical microscopy techniques. After exposure in air at 1200 °C for 100 hours, chromium depletion by as much as 10 wt pct was observed near the surface, and voids of various sizes up to 15 µm in diameter were found to depths of 300 µm. The fraction of voids increases with exposure time and, with the exception of anomalous values near the surface, decreases with depth. The maximum area fraction of voids observed was approximately 8 pct. Correlation of the void area fraction profile with the measured chromium depletion through a diffusion analysis shows that void formation is due to vacancy injection. Similar void formation in Ni-Cr alloys without oxide dispersions suggests that void formation is not dependent upon the presence of oxide dispersions. The diffusion coefficient for chromium in MA-754 at 1200 °C was computed from microprobe data to be 4 × 10-10 cm2 per second.

Critical Void Volume Fraction fc at Void Coalescence for S235JR Steel at Low Initial Stress Triaxiality

NASA Astrophysics Data System (ADS)

Grzegorz Kossakowski, Paweł; Wciślik, Wiktor

2017-10-01

The paper is concerned with the nucleation, growth and coalescence of microdefects in the form of voids in S235JR steel. The material is known to be one of the basic steel grades commonly used in the construction industry. The theory and methods of damage mechanics were applied to determine and describe the failure mechanisms that occur when the material undergoes deformation. Until now, engineers have generally employed the Gurson-Tvergaard- Needleman model. This material model based on damage mechanics is well suited to define and analyze failure processes taking place in the microstructure of S235JR steel. It is particularly important to determine the critical void volume fraction fc , which is one of the basic parameters of the Gurson-Tvergaard-Needleman material model. As the critical void volume fraction fc refers to the failure stage, it is determined from the data collected for the void coalescence phase. A case of multi-axial stresses is considered taking into account the effects of spatial stress state. In this study, the parameter of stress triaxiality η was used to describe the failure phenomena. Cylindrical tensile specimens with a circumferential notch were analysed to obtain low values of initial stress triaxiality (η = 0.556 of the range) in order to determine the critical void volume fraction fc . It is essential to emphasize how unique the method applied is and how different it is from the other more common methods involving parameter calibration, i.e. curve-fitting methods. The critical void volume fraction fc at void coalescence was established through digital image analysis of surfaces of S235JR steel, which involved studying real, physical results obtained directly from the material tested.

Application of Electromagnetic Induction Technique to Measure the Void Fraction in Oil/Gas Two Phase Flow

NASA Astrophysics Data System (ADS)

Wahhab, H. A. Abdul; Aziz, A. R. A.; Al-Kayiem, H. H.; Nasif, M. S.; Reda, M. N.

2018-03-01

In this work, electromagnetic induction technique of measuring void fraction in liquid/gas fuel flow was utilized. In order to improve the electric properties of liquid fuel, an iron oxide Fe3O4 nanoparticles at 3% was blended to enhance the liquid fuel magnetization. Experiments have been conducted for a wide range of liquid and gas superficial velocities. From the experimental results, it was realized that there is an existing linear relationship between the void fraction and the measured electromotive force, when induction coils were connected in series for excitation coils, regardless of increase or decrease CNG bubbles distribution in liquid fuel flow. Therefore, it was revealed that the utilized method yielded quite reasonable account for measuring the void fraction, showing good agreement with the other available measurement techniques in the two-phase flow, and also with the published literature of the bubbly flow pattern. From the results of the present investigation, it has been proven that the electromagnetic induction is a feasible technique for the actual measurement of void fraction in a Diesel/CNG fuel flow.

Self-Sensing Composites: In-Situ Detection of Fibre Fracture

PubMed Central

Malik, Shoaib A.; Wang, Liwei; Curtis, Paul T.; Fernando, Gerard F.

2016-01-01

The primary load-bearing component in a composite material is the reinforcing fibres. This paper reports on a technique to study the fracture of individual reinforcing fibres or filaments in real-time. Custom-made small-diameter optical fibres with a diameter of 12 (±2) micrometres were used to detect the fracture of individual filaments during tensile loading of unreinforced bundles and composites. The unimpregnated bundles were end-tabbed and tensile tested to failure. A simple technique based on resin-infusion was developed to manufacture composites with a negligible void content. In both cases, optical fibre connectors were attached to the ends of the small-diameter optical fibre bundles to enable light to be coupled into the bundle via one end whilst the opposite end was photographed using a high-speed camera. The feasibility of detecting the fracture of each of the filaments in the bundle and composite was demonstrated. The in-situ damage detection technique was also applied to E-glass bundles and composites; this will be reported in a subsequent publication. PMID:27136555

Apparatus for measuring the local void fraction in a flowing liquid containing a gas

DOEpatents

Dunn, P.F.

1979-07-17

The local void fraction in liquid containing a gas is measured by placing an impedance-variation probe in the liquid, applying a controlled voltage or current to the probe, and measuring the probe current or voltage. A circuit for applying the one electrical parameter and measuring the other includes a feedback amplifier that minimizes the effect of probe capacitance and a digitizer to provide a clean signal. Time integration of the signal provides a measure of the void fraction, and an oscilloscope display also shows bubble size and distribution.

Apparatus for measuring the local void fraction in a flowing liquid containing a gas

DOEpatents

Dunn, Patrick F.

1981-01-01

The local void fraction in liquid containing a gas is measured by placing an impedance-variation probe in the liquid, applying a controlled voltage or current to the probe, and measuring the probe current or voltage. A circuit for applying the one electrical parameter and measuring the other includes a feedback amplifier that minimizes the effect of probe capacitance and a digitizer to provide a clean signal. Time integration of the signal provides a measure of the void fraction, and an oscilloscope display also shows bubble size and distribution.

Quantitative void fraction detection with an eddy current flowmeter for generation IV Sodium cooled Fast Reactor

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

Kumar, M.; French Atomic Energy and Alternative Energies Commission; Tordjeman, Ph.

2015-07-01

This study was carried out to understand the response of an eddy current type flowmeter in two phase liquid-metal flow. We use the technique of ellipse fit and correlate the fluctuations in the angle of inclination of this ellipse with the void fraction. The effects of physical parameters such as coil excitation frequency and flow velocity have been studied. The results show the possibility of using an eddy current flowmeter as a gas detector for large void fractions. (authors)

Quantitative void fraction measurement with an eddy current flowmeter for generation IV Sodium cooled Fast Reactor

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

Kumar, M.; CEA, DEN, Nuclear Technology Department, F-13108 Saint-Paul-lez-Durance; Tordjeman, Ph.

2015-07-01

This study was carried out to understand the response of an eddy current type flowmeter in two phase liquid-metal flow. We use the technique of ellipse fit and correlate the fluctuations in the angle of inclination of this ellipse with the void fraction. The effects of physical parameters such as coil excitation frequency and flow velocity have been studied. The results show the possibility of using an eddy current flowmeter as a gas detector for large void fractions. (authors)

Micro-CT and nano-CT analysis of filling quality of three different endodontic sealers.

PubMed

Huang, Yan; Celikten, Berkan; de Faria Vasconcelos, Karla; Ferreira Pinheiro Nicolielo, Laura; Lippiatt, Nicholas; Buyuksungur, Arda; Jacobs, Reinhilde; Orhan, Kaan

2017-12-01

To investigate voids in different root canal sealers using micro-CT and nano-CT, and to explore the feasibility of using nano-CT for quantitative analysis of sealer filling quality. 30 extracted mandibular central incisors were randomly assigned into three groups according to the applied root canal sealers (Total BC Sealer, Sure Seal Root, AH Plus) by the single cone technique. Subsequently, micro-CT and nano-CT were performed to analyse the incidence rate of voids, void fraction, void volume and their distribution in each sample. Micro-CT evaluation showed no significant difference among sealers for the incidence rate of voids or void fraction in the whole filling materials (p > 0.05), whereas a significant difference was found between AH Plus and the other two sealers using nano-CT (p < 0.05). All three sealers presented less void volume in the apical third; however, higher void volumes were observed in the apical and coronal thirds in AH Plus using micro-CT (p < 0.05), while nano-CT results displayed higher void volume in AH Plus among all the sealers and regions (p < 0.05). Bioactive sealers showed higher root filling rate, lower incidence rate of voids, void fraction and void volume than AH Plus under nano-CT analysis, when round root canals were treated by the single cone technique. The disparate results suggest that the higher resolution of nano-CT have a greater ability of distinguishing internal porosity, and therefore suggesting the potential use of nano-CT in quantitative analysis of filling quality of sealers.

Measurements of void fraction distribution in cavitating pipe flow using x-ray CT

NASA Astrophysics Data System (ADS)

Bauer, D.; Chaves, H.; Arcoumanis, C.

2012-05-01

Measuring the void fraction distribution is still one of the greatest challenges in cavitation research. In this paper, a measurement technique for the quantitative void fraction characterization in a cavitating pipe flow is presented. While it is almost impossible to visualize the inside of the cavitation region with visible light, it is shown that with x-ray computed tomography (CT) it is possible to capture the time-averaged void fraction distribution in a quasi-steady pipe flow. Different types of cavitation have been investigated including cloud-like cavitation, bubble cavitation and film cavitation at very high flow rates. A specially designed nozzle was employed to induce very stable quasi-steady cavitation. The obtained results demonstrate the advantages of the measurement technique compared to other ones; for example, structures were observed inside the cavitation region that could not be visualized by photographic images. Furthermore, photographic images and pressure measurements were used to allow comparisons to be made and to prove the superiority of the CT measurement technique.

Bubble and Slug Flow at Microgravity Conditions: State of Knowledge and Open Questions

NASA Technical Reports Server (NTRS)

Colin, C.; Fabre, J.; McQuillen, J.

1996-01-01

Based on the experiments carried out over the past decade at microgravity conditions, an overview of our current knowledge of bubbly and slug flows is presented. The transition from bubble to slug flow, the void fraction and the pressure drop are discussed from the data collected in the literature. The transition from bubble to slug flow may be predicted by introducing a critical void fraction that depends on the fluid properties and the pipe diameter; however, the role of coalescence which controls this transition is not clearly understood. The void fraction may be accurately calculated using a drift-flux model. It is shown from local measurements that the drift of the gas with respect to the mixture is due to non-uniform radial distribution of void fraction. The pressure drop happens to be controlled by the liquid flow for bubbly flow whereas for slug flow the experimental results show that pressure drops is larger than expected. From this study, the guidelines for future research in microgravity are given.

Investigation of Low Power Operation in a Loop Heat Pipe

NASA Technical Reports Server (NTRS)

Ku, Jentung; Ottenstein, Laura; Rogers, Paul; Cheung, Kwok; Powers, Edward I. (Technical Monitor)

2001-01-01

This paper presents test results of an experimental study of low power operation in a loop heat pipe. The main objective was to demonstrate how changes in the vapor void fraction inside the evaporator core would affect the loop behavior, The fluid inventory and the relative tilt between the evaporator and the compensation chamber were varied so as to create different vapor void fractions in the evaporator core. The effect on the loop start-up, operating temperature, and capillary limit was investigated. Test results indicate that the vapor void fraction inside the evaporator core is the single most important factor in determining the loop operation at low powers.

Void fraction, bubble size and interfacial area measurements in co-current downflow bubble column reactor with microbubble dispersion

DOE PAGES

Hernandez-Alvarado, Freddy; Kalaga, Dinesh V.; Turney, Damon; ...

2017-05-06

Micro-bubbles dispersed in bubble column reactors have received great interest in recent years, due to their small size, stability, high gas-liquid interfacial area concentrations and longer residence times. The high gas-liquid interfacial area concentrations lead to high mass transfer rates compared to conventional bubble column reactors. In the present work, experiments have been performed in a down-flow bubble column reactor with micro-bubbles generated and dispersed by a novel mechanism to determine the gas-liquid interfacial area concentrations by measuring the void fraction and bubble size distributions. Gamma-ray densitometry has been employed to determine the axial and radial distributions of void fractionmore » and a high speed camera equipped with a borescope is used to measure the axial and radial variations of bubble sizes. Also, the effects of superficial gas and liquid velocities on the two-phase flow characteristics have been investigated. Further, reconstruction techniques of the radial void fraction profiles from the gamma densitometry's chordal measurements are discussed and compared for a bubble column reactor with dispersed micro-bubbles. The results demonstrate that the new bubble generation technique offers high interfacial area concentrations (1,000 to 4,500 m 2/m 3) with sub-millimeter bubbles (500 to 900 µm) and high overall void fractions (10% – 60%) in comparison with previous bubble column reactor designs. The void fraction data was analyzed using slip velocity model and empirical correlation has been proposed to predict the Sauter mean bubble diameter.« less

Void fraction, bubble size and interfacial area measurements in co-current downflow bubble column reactor with microbubble dispersion

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

Hernandez-Alvarado, Freddy; Kalaga, Dinesh V.; Turney, Damon

Micro-bubbles dispersed in bubble column reactors have received great interest in recent years, due to their small size, stability, high gas-liquid interfacial area concentrations and longer residence times. The high gas-liquid interfacial area concentrations lead to high mass transfer rates compared to conventional bubble column reactors. In the present work, experiments have been performed in a down-flow bubble column reactor with micro-bubbles generated and dispersed by a novel mechanism to determine the gas-liquid interfacial area concentrations by measuring the void fraction and bubble size distributions. Gamma-ray densitometry has been employed to determine the axial and radial distributions of void fractionmore » and a high speed camera equipped with a borescope is used to measure the axial and radial variations of bubble sizes. Also, the effects of superficial gas and liquid velocities on the two-phase flow characteristics have been investigated. Further, reconstruction techniques of the radial void fraction profiles from the gamma densitometry's chordal measurements are discussed and compared for a bubble column reactor with dispersed micro-bubbles. The results demonstrate that the new bubble generation technique offers high interfacial area concentrations (1,000 to 4,500 m 2/m 3) with sub-millimeter bubbles (500 to 900 µm) and high overall void fractions (10% – 60%) in comparison with previous bubble column reactor designs. The void fraction data was analyzed using slip velocity model and empirical correlation has been proposed to predict the Sauter mean bubble diameter.« less

Small-angle X-ray scattering and rheological characterization of alginate gels. 2. Time-resolved studies on ionotropic gels

NASA Astrophysics Data System (ADS)

Yuguchi, Y.; Urakawa, H.; Kajiwara, K.; Draget, K. I.; Stokke, B. T.

2000-10-01

Gelation was observed by time-resolved small-angle X-ray scattering and rheology on 10 mg/ml Ca-alginate gels prepared by in situ release of Ca 2+ from CaEGTA or CaCO 3 with total Ca 2+ concentration in the range 10-20 mM. This was carried out for alginates having a fraction of α- L-GulA (G) of FG=0.39 and 0.68, respectively, obtained by the selection of alginates isolated from two different brown algae, Ascophyllum nodosum and Laminaria hyperborea stipe. Correlation between the rheological data and SAXS data shows that a large fraction of the lateral association precedes the formation of a continuous network through the sample cell. Following the initial association of chain segments in junction zones, the analysis using two-component broken rod model indicates the formation of larger bundles, and that the relative weight of these bundles increases with increasing time. The molecular model for the bundles is proposed by associating 2-16 units (G-blocks) composed of 14 (1→4) linked residues of α- L-GulA in parallel according to the available crystallographic data. The storage modulus increases as the bundles composed of associated alginate chains grow during the gel formation. The gel elasticity is mainly sustained by single chains in the alginate sample with a low fraction of α- L-GulA. The alginates with a high fraction of α- L-GulA associate into thicker bundles which join to form a network. Here the gel elasticity seems to be due to the flexible joints between bundles, since the fraction of single chains is extremely low.

Square-core bundles for astronomical imaging

NASA Astrophysics Data System (ADS)

Bryant, Julia J.; Bland-Hawthorn, Joss

2012-09-01

Optical fibre imaging bundles (hexabundles) are proving to be the next logical step for large galaxy surveys as they offer spatially-resolved spectroscopy of galaxies and can be used with conventional fibre positioners. Hexabundles have been effectively demonstrated in the Sydney-AAO Multi-object IFS (SAMI) instrument at the Anglo- Australian Telescope[5]. Based on the success of hexabundles that have circular cores, we have characterised a bundle made instead from square-core fibres. Square cores naturally pack more evenly, which reduces the interstitial holes and can increase the covering, or filling fraction. Furthermore the regular packing simplifies the process of combining and dithering the final images. We discuss the relative issues of filling fraction, focal ratio degradation (FRD), and cross-talk, and find that square-core bundles perform well enough to warrant further development as a format for imaging fibre bundles.

Void fraction development in gas-liquid flow after a U-bend in a vertically upwards serpentine-configuration large-diameter pipe

NASA Astrophysics Data System (ADS)

Almabrok, Almabrok A.; Aliyu, Aliyu M.; Baba, Yahaya D.; Lao, Liyun; Yeung, Hoi

2018-01-01

We investigate the effect of a return U-bend on flow behaviour in the vertical upward section of a large-diameter pipe. A wire mesh sensor was employed to study the void fraction distributions at axial distances of 5, 28 and 47 pipe diameters after the upstream bottom bend. The study found that, the bottom bend has considerable impacts on up-flow behaviour. In all conditions, centrifugal action causes appreciable misdistribution in the adjacent straight section. Plots from WMS measurements show that flow asymmetry significantly reduces along the axis at L/D = 47. Regime maps generated from three axial locations showed that, in addition to bubbly, intermittent and annular flows, oscillatory flow occurred particularly when gas and liquid flow rates were relatively low. At this position, mean void fractions were in agreement with those from other large-pipe studies, and comparisons were made with existing void fraction correlations. Among the correlations surveyed, drift flux-type correlations were found to give the best predictive results.

Influence of fiber packing structure on permeability

NASA Technical Reports Server (NTRS)

Cai, Zhong; Berdichevsky, Alexander L.

1993-01-01

The study on the permeability of an aligned fiber bundle is the key building block in modeling the permeability of advanced woven and braided preforms. Available results on the permeability of fiber bundles in the literature show that a substantial difference exists between numerical and analytical calculations on idealized fiber packing structures, such as square and hexagonal packing, and experimental measurements on practical fiber bundles. The present study focuses on the variation of the permeability of a fiber bundle under practical process conditions. Fiber bundles are considered as containing openings and fiber clusters within the bundle. Numerical simulations on the influence of various openings on the permeability were conducted. Idealized packing structures are used, but with introduced openings distributed in different patterns. Both longitudinal and transverse flow are considered. The results show that openings within the fiber bundle have substantial effect on the permeability. In the longitudinal flow case, the openings become the dominant flow path. In the transverse flow case, the fiber clusters reduce the gap sizes among fibers. Therefore the permeability is greatly influenced by these openings and clusters, respectively. In addition to the porosity or fiber volume fraction, which is commonly used in the permeability expression, another fiber bundle status parameter, the ultimate fiber volume fraction, is introduced to capture the disturbance within a fiber bundle.

Morphological Segregation in the Surroundings of Cosmic Voids

NASA Astrophysics Data System (ADS)

Ricciardelli, Elena; Cava, Antonio; Varela, Jesus; Tamone, Amelie

2017-09-01

We explore the morphology of galaxies living in the proximity of cosmic voids, using a sample of voids identified in the Sloan Digital Sky Survey Data Release 7. At all stellar masses, void galaxies exhibit morphologies of a later type than galaxies in a control sample, which represent galaxies in an average density environment. We interpret this trend as a pure environmental effect, independent of the mass bias, due to a slower galaxy build-up in the rarefied regions of voids. We confirm previous findings about a clear segregation in galaxy morphology, with galaxies of a later type being found at smaller void-centric distances with respect to the early-type galaxies. We also show, for the first time, that the radius of the void has an impact on the evolutionary history of the galaxies that live within it or in its surroundings. In fact, an enhanced fraction of late-type galaxies is found in the proximity of voids larger than the median void radius. Likewise, an excess of early-type galaxies is observed within or around voids of a smaller size. A significant difference in galaxy properties in voids of different sizes is observed up to 2 R void, which we define as the region of influence of voids. The significance of this difference is greater than 3σ for all the volume-complete samples considered here. The fraction of star-forming galaxies shows the same behavior as the late-type galaxies, but no significant difference in stellar mass is observed in the proximity of voids of different sizes.

Mass flow rate measurements in gas-liquid flows by means of a venturi or orifice plate coupled to a void fraction sensor

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

Oliveira, Jorge Luiz Goes; Passos, Julio Cesar; Verschaeren, Ruud

Two-phase flow measurements were carried out using a resistive void fraction meter coupled to a venturi or orifice plate. The measurement system used to estimate the liquid and gas mass flow rates was evaluated using an air-water experimental facility. Experiments included upward vertical and horizontal flow, annular, bubbly, churn and slug patterns, void fraction ranging from 2% to 85%, water flow rate up to 4000 kg/h, air flow rate up to 50 kg/h, and quality up to almost 10%. The fractional root mean square (RMS) deviation of the two-phase mass flow rate in upward vertical flow through a venturi platemore » is 6.8% using the correlation of Chisholm (D. Chisholm, Pressure gradients during the flow of incompressible two-phase mixtures through pipes, venturis and orifice plates, British Chemical Engineering 12 (9) (1967) 454-457). For the orifice plate, the RMS deviation of the vertical flow is 5.5% using the correlation of Zhang et al. (H.J. Zhang, W.T. Yue, Z.Y. Huang, Investigation of oil-air two-phase mass flow rate measurement using venturi and void fraction sensor, Journal of Zhejiang University Science 6A (6) (2005) 601-606). The results show that the flow direction has no significant influence on the meters in relation to the pressure drop in the experimental operation range. Quality and slip ratio analyses were also performed. The results show a mean slip ratio lower than 1.1, when bubbly and slug flow patterns are encountered for mean void fractions lower than 70%. (author)« less

Two-phase flow characterization based on advanced instrumentation, neural networks, and mathematical modeling

NASA Astrophysics Data System (ADS)

Mi, Ye

1998-12-01

The major objective of this thesis is focused on theoretical and experimental investigations of identifying and characterizing vertical and horizontal flow regimes in two-phase flows. A methodology of flow regime identification with impedance-based neural network systems and a comprehensive model of vertical slug flow have been developed. Vertical slug flow has been extensively investigated and characterized with geometric, kinematic and hydrodynamic parameters. A multi-sensor impedance void-meter and a multi-sensor magnetic flowmeter were developed. The impedance void-meter was cross-calibrated with other reliable techniques for void fraction measurements. The performance of the impedance void-meter to measure the void propagation velocity was evaluated by the drift flux model. It was proved that the magnetic flowmeter was applicable to vertical slug flow measurements. Separable signals from these instruments allow us to unearth most characteristics of vertical slug flow. A methodology of vertical flow regime identification was developed. Supervised neural network and self-organizing neural network systems were employed. First, they were trained with results from an idealized simulation of impedance in a two-phase mixture. The simulation was mainly based on Mishima and Ishii's flow regime map, the drift flux model, and the newly developed model of slug flow. Then, these trained systems were tested with impedance signals. The results showed that the neural network systems were appropriate classifiers of vertical flow regimes. The theoretical models and experimental databases used in the simulation were reliable. Furthermore, this approach was applied successfully to horizontal flow identification. A comprehensive model was developed to predict important characteristics of vertical slug flow. It was realized that the void fraction of the liquid slug is determined by the relative liquid motion between the Taylor bubble tail and the Taylor bubble wake. Relying on this understanding and experimental results, a special relationship was built for the void fraction of the liquid slug. The prediction of the void fraction of the liquid slug was considerably improved. Experimental characterization of vertical slug flows was performed extensively with the impedance void-meter and the magnetic flowmeter. The theoretical predictions were compared with the experimental results. The agreements between them are very satisfactory.

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

Ricciardelli, Elena; Tamone, Amelie; Cava, Antonio

We explore the morphology of galaxies living in the proximity of cosmic voids, using a sample of voids identified in the Sloan Digital Sky Survey Data Release 7. At all stellar masses, void galaxies exhibit morphologies of a later type than galaxies in a control sample, which represent galaxies in an average density environment. We interpret this trend as a pure environmental effect, independent of the mass bias, due to a slower galaxy build-up in the rarefied regions of voids. We confirm previous findings about a clear segregation in galaxy morphology, with galaxies of a later type being found atmore » smaller void-centric distances with respect to the early-type galaxies. We also show, for the first time, that the radius of the void has an impact on the evolutionary history of the galaxies that live within it or in its surroundings. In fact, an enhanced fraction of late-type galaxies is found in the proximity of voids larger than the median void radius. Likewise, an excess of early-type galaxies is observed within or around voids of a smaller size. A significant difference in galaxy properties in voids of different sizes is observed up to 2 R {sub void}, which we define as the region of influence of voids. The significance of this difference is greater than 3 σ for all the volume-complete samples considered here. The fraction of star-forming galaxies shows the same behavior as the late-type galaxies, but no significant difference in stellar mass is observed in the proximity of voids of different sizes.« less

Fuel cell with electrolyte matrix assembly

DOEpatents

Kaufman, Arthur; Pudick, Sheldon; Wang, Chiu L.

1988-01-01

This invention is directed to a fuel cell employing a substantially immobilized electrolyte imbedded therein and having a laminated matrix assembly disposed between the electrodes of the cell for holding and distributing the electrolyte. The matrix assembly comprises a non-conducting fibrous material such as silicon carbide whiskers having a relatively large void-fraction and a layer of material having a relatively small void-fraction.

Gas-liquid Phase Distribution and Void Fraction Measurements Using the MRI

NASA Technical Reports Server (NTRS)

Daidzic, N. E.; Schmidt, E.; Hasan, M. M.; Altobelli, S.

2004-01-01

We used a permanent-magnet MRI system to estimate the integral and spatially- and/or temporally-resolved void-fraction distributions and flow patterns in gas-liquid two-phase flows. Air was introduced at the bottom of the stagnant liquid column using an accurate and programmable syringe pump. Air flow rates were varied between 1 and 200 ml/min. The cylindrical non-conducting test tube in which two-phase flow was measured was placed in a 2.67 kGauss MRI with MRT spectrometer/imager. Roughly linear relationship has been obtained for the integral void-fraction, obtained by volume-averaging of the spatially-resolved signals, and the air flow rate in upward direction. The time-averaged spatially-resolved void fraction has also been obtained for the quasi-steady flow of air in a stagnant liquid column. No great accuracy is claimed as this was an exploratory proof-of-concept type of experiment. Preliminary results show that MRI a non-invasive and non-intrusive experimental technique can indeed provide a wealth of different qualitative and quantitative data and is especially well suited for averaged transport processes in adiabatic and diabatic multi-phase and/or multi-component flows.

Oil field management system

DOEpatents

Fincke, James R.

2003-09-23

Oil field management systems and methods for managing operation of one or more wells producing a high void fraction multiphase flow. The system includes a differential pressure flow meter which samples pressure readings at various points of interest throughout the system and uses pressure differentials derived from the pressure readings to determine gas and liquid phase mass flow rates of the high void fraction multiphase flow. One or both of the gas and liquid phase mass flow rates are then compared with predetermined criteria. In the event such mass flow rates satisfy the predetermined criteria, a well control system implements a correlating adjustment action respecting the multiphase flow. In this way, various parameters regarding the high void fraction multiphase flow are used as control inputs to the well control system and thus facilitate management of well operations.

Nanoparticle coating of a microchannel surface is an effective method for increasing the critical heat flux

NASA Astrophysics Data System (ADS)

Shustov, M. V.; Kuzma-Kichta, Yu. A.; Lavrikov, A. V.

2017-04-01

Results are presented of an investigation into water boiling in a single microchannel 0.2 mm high, 3 mm wide, and 13.7 mm long with a smooth heating surface or with a coating from aluminum oxide nanoparticles. The experimental procedure and the test setup are described. The top wall of the microchannel is made of glass so that video recording in the reflected light of the process can be made. A coating of Al2O3 particles is applied onto the heating surface before the experiments using a method developed by the authors of the paper. The experiments yielded data on heat transfer and void fraction and its fluctuations for the bubble and transient boiling in the microchannel. The dependence was established of the heat flux on the temperature of the microchannel wall with a smooth surface or a surface with Al2O3 nanoparticle coating for various mass flows in the microchannel. The boiling crisis has been found to occur in the microchannel with a nanoparticle coating at a considerably higher heat flux than that in the channel without coating. The experimental data also suggest that the nanoparticle coating improves heat transfer in the transition boiling region. Processing of the data obtained using a high-speed video revealed void fraction fluctuations enabling us to describe two-phase flow regimes with the flow boiling in a microchannel. It has been found that a return flow occurs in the microchannel under certain conditions. A hypothesis for its causes is proposed. The dependence of the void fraction on the steam quality in the microchannel with or without a nanoparticle coating was determined from the video records. The experimental data on void fraction for boiling in the microchannel without coating are approximated by an empirical correlation. The experiments demonstrate that the void fraction during boiling in the microchannel with a nanoparticle coating is higher than during boiling in the channel without coating (where φ and x are the void fraction and the steam quality, respectively) in the region of a sharp increase in the φ( x) curve.

Hexabundles: first results

NASA Astrophysics Data System (ADS)

Bryant, Julia J.; O'Byrne, John W.; Bland-Hawthorn, Joss; Leon-Saval, Sergio G.

2010-07-01

New multi-core imaging fibre bundles - hexabundles - being developed at the University of Sydney will provide simultaneous integral field spectroscopy for hundreds of celestial sources across a wide angular field. These are a natural progression from the use of single fibres in existing galaxy surveys. Hexabundles will allow us to address fundamental questions in astronomy without the biases introduced by a fixed entrance aperture. We have begun to consider instrument concepts that exploit hundreds of hexabundles over the widest possible field of view. To this end, we have characterised the performance of a 61-core fully fused hexabundle and 5 unfused bundles with 7 cores each. All fibres in bundles have 100 micron cores. In the fused bundle, the cores are distorted from a circular shape in order to achieve a higher fill fraction. The unfused bundles have circular cores and five different cladding thicknesses which affect the fill fraction. We compare the optical performance of all 6 bundles and find that the advantage of smaller interstitial holes (higher fill fraction) is outweighed by the increase in FRD, crosstalk and the poor optical performance caused by the deformation of the fibre cores. Uniformly high throughput and low cross-talk are essential for imaging faint astronomical targets with sufficient resolution to disentangle the dynamical structure. Devices already under development will have 100-200 unfused cores, although larger formats are feasible. The light-weight packaging of hexabundles is sufficiently flexible to allow existing robotic positioners to make use of them.

Bubble clustering in a glass of stout beer

NASA Astrophysics Data System (ADS)

Iwatsubo, Fumiya; Watamura, Tomoaki; Sugiyama, Kazuyasu

2017-11-01

To clarify why the texture in stout beer poured into a pint glass descends, we investigated local time development of the void fraction and velocity of bubbles. The propagation of the number density distribution, i.e. the texture, appearing near the inclined wall is observed. We visualized individual advective bubbles near the inclined wall by microscope and measured the local void fraction using brightness of images while the velocity of bubbles by means of Particle Tracking Velocimetry. As the result of measurements, we found the local void fraction and the bubbles advection velocity increase and decrease repeatedly with a time delay. We conclude the texture pattern is composed of fluid blobs which contain less bubbles; extruding and suction flows respectively toward and from the interior of the container form respectively in front and back of the blobs.

A novel method for flow pattern identification in unstable operational conditions using gamma ray and radial basis function.

PubMed

Roshani, G H; Nazemi, E; Roshani, M M

2017-05-01

Changes of fluid properties (especially density) strongly affect the performance of radiation-based multiphase flow meter and could cause error in recognizing the flow pattern and determining void fraction. In this work, we proposed a methodology based on combination of multi-beam gamma ray attenuation and dual modality densitometry techniques using RBF neural network in order to recognize the flow regime and determine the void fraction in gas-liquid two phase flows independent of the liquid phase changes. The proposed system is consisted of one 137 Cs source, two transmission detectors and one scattering detector. The registered counts in two transmission detectors were used as the inputs of one primary Radial Basis Function (RBF) neural network for recognizing the flow regime independent of liquid phase density. Then, after flow regime identification, three RBF neural networks were utilized for determining the void fraction independent of liquid phase density. Registered count in scattering detector and first transmission detector were used as the inputs of these three RBF neural networks. Using this simple methodology, all the flow patterns were correctly recognized and the void fraction was predicted independent of liquid phase density with mean relative error (MRE) of less than 3.28%. Copyright © 2017 Elsevier Ltd. All rights reserved.

Summary and evaluation: fuel dynamics loss-of-flow experiments (tests L2, L3, and L4)

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

Barts, E.W.; Deitrich, L.W.; Eberhart, J.G.

1975-09-01

Three similar experiments conducted to support the analyses of hypothetical LMFBR unprotected-loss-of-flow accidents are summarized and evaluated. The tests, designated L2, L3, and L4, provided experimental data against which accident-analysis codes could be compared, so as to guide further analysis and modeling of the initiating phases of the hypothetical accident. The tests were conducted using seven-pin bundles of mixed-oxide fuel pins in Mark-II flowing-sodium loops in the TREAT reactor. Test L2 used fresh fuel. Tests L3 and L4 used irradiated fuel pins having, respectively, ''intermediate-power'' (no central void) and ''high-power'' (fully developed central void) microstructure. 12 references. (auth)

Mechanical Properties versus Morphology of Ordered Polymers. Volume III. Part I

DTIC Science & Technology

1982-08-01

measured by wide angle x-ray scattering and differential scanning calorimetry, is unrelated to the diffuse scattered intensity [62]. Cellulose acetate which...increasing void fraction, in air swollen cellulose . Comparison of the volume fraction of voids calculated from the SAXS integrated intensity with...1964). 63. P.H. Hermans, D. Heikens, and A. Weidinger, "A Quantitative Investigation on the X-Ray Small Angle Scattering of Cellulose Fibers. Part II

Comparison of thermal insulation performance of fibrous materials for the advanced space suit.

PubMed

Paul, Heather L; Diller, Kenneth R

2003-10-01

The current multi-layer insulation used in the extravehicular mobility unit (EMU) will not be effective in the atmosphere of Mars due to the presence of interstitial gases. Alternative thermal insulation means have been subjected to preliminary evaluation by NASA to attempt to identify a material that will meet the target conductivity of 0.005 W/m-K. This study analyzes numerically the thermal conductivity performance for three of these candidate insulating fiber materials in terms of various denier (size), interstitial void fractions, interstitial void media, and orientations to the applied temperature gradient to evaluate their applicability for the new Mars suit insulation. The results demonstrate that the best conductive insulation is achieved for a high-void-fraction configuration with a grooved fiber cross section, aerogel void medium, and the fibers oriented normal to the heat flux vector. However, this configuration still exceeds the target thermal conductivity by a factor of 1.5.

Note: Void effects on eddy current distortion in two-phase liquid metal.

PubMed

Kumar, M; Tordjeman, Ph; Bergez, W; Cavaro, M

2015-10-01

A model based on the first order perturbation expansion of magnetic flux in a two-phase liquid metal flow has been developed for low magnetic Reynolds number Rem. This model takes into account the distortion of the induced eddy currents due to the presence of void in the conducting medium. Specific experiments with an eddy current flow meter have been realized for two periodic void distributions. The results have shown, in agreement with the model, that the effects of velocity and void on the emf modulation are decoupled. The magnitude of the void fraction and the void spatial frequency can be determined from the spectral density of the demodulated emf.

A Dual Conductance Sensor for Simultaneous Measurement of Void Fraction and Structure Velocity of Downward Two-Phase Flow in a Slightly Inclined Pipe

PubMed Central

Lee, Yeon-Gun; Won, Woo-Youn; Lee, Bo-An; Kim, Sin

2017-01-01

In this study, a new and improved electrical conductance sensor is proposed for application not only to a horizontal pipe, but also an inclined one. The conductance sensor was designed to have a dual layer, each consisting of a three-electrode set to obtain two instantaneous conductance signals in turns, so that the area-averaged void fraction and structure velocity could be measured simultaneously. The optimum configuration of the electrodes was determined through numerical analysis, and the calibration curves for stratified and annular flow were obtained through a series of static experiments. The fabricated conductance sensor was applied to a 45 mm inner diameter U-shaped downward inclined pipe with an inclination angle of 3° under adiabatic air-water flow conditions. In the tests, the superficial velocities ranged from 0.1 to 3.0 m/s for water and from 0.1 to 18 m/s for air. The obtained mean void fraction and the structure velocity from the conductance sensor were validated against the measurement by the wire-mesh sensor and the cross-correlation technique for the visualized images, respectively. The results of the flow regime classification and the corresponding time series of the void fraction at a variety of flow velocities were also discussed. PMID:28481308

How to bridge the gap between "unresolved" model and "resolved" model in CFD-DEM coupled method for sediment transport?

NASA Astrophysics Data System (ADS)

Liu, D.; Fu, X.; Liu, X.

2016-12-01

In nature, granular materials exist widely in water bodies. Understanding the fundamentals of solid-liquid two-phase flow, such as turbulent sediment-laden flow, is of importance for a wide range of applications. A coupling method combining computational fluid dynamics (CFD) and discrete element method (DEM) is now widely used for modeling such flows. In this method, when particles are significantly larger than the CFD cells, the fluid field around each particle should be fully resolved. On the other hand, the "unresolved" model is designed for the situation where particles are significantly smaller than the mesh cells. Using "unresolved" model, large amount of particles can be simulated simultaneously. However, there is a gap between these two situations when the size of DEM particles and CFD cell is in the same order of magnitude. In this work, the most commonly used void fraction models are tested with numerical sedimentation experiments. The range of applicability for each model is presented. Based on this, a new void fraction model, i.e., a modified version of "tri-linear" model, is proposed. Particular attention is paid to the smooth function of void fraction in order to avoid numerical instability. The results show good agreement with the experimental data and analytical solution for both single-particle motion and also group-particle motion, indicating great potential of the new void fraction model.

Application of the ultrasonic technique and high-speed filming for the study of the structure of air-water bubbly flows

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

Carvalho, R.D.M.; Venturini, O.J.; Tanahashi, E.I.

2009-10-15

Multiphase flows are very common in industry, oftentimes involving very harsh environments and fluids. Accordingly, there is a need to determine the dispersed phase holdup using noninvasive fast responding techniques; besides, knowledge of the flow structure is essential for the assessment of the transport processes involved. The ultrasonic technique fulfills these requirements and could have the capability to provide the information required. In this paper, the potential of the ultrasonic technique for application to two-phase flows was investigated by checking acoustic attenuation data against experimental data on the void fraction and flow topology of vertical, upward, air-water bubbly flows inmore » the zero to 15% void fraction range. The ultrasonic apparatus consisted of one emitter/receiver transducer and three other receivers at different positions along the pipe circumference; simultaneous high-speed motion pictures of the flow patterns were made at 250 and 1000 fps. The attenuation data for all sensors exhibited a systematic interrelated behavior with void fraction, thereby testifying to the capability of the ultrasonic technique to measure the dispersed phase holdup. From the motion pictures, basic gas phase structures and different flows patterns were identified that corroborated several features of the acoustic attenuation data. Finally, the acoustic wave transit time was also investigated as a function of void fraction. (author)« less

Stability in a fiber bundle model: Existence of strong links and the effect of disorder

NASA Astrophysics Data System (ADS)

Roy, Subhadeep

2018-05-01

The present paper deals with a fiber bundle model which consists of a fraction α of infinitely strong fibers. The inclusion of such an unbreakable fraction has been proven to affect the failure process in early studies, especially around a critical value αc. The present work has a twofold purpose: (i) a study of failure abruptness, mainly the brittle to quasibrittle transition point with varying α and (ii) variation of αc as we change the strength of disorder introduced in the model. The brittle to quasibrittle transition is confirmed from the failure abruptness. On the other hand, the αc is obtained from the knowledge of failure abruptness as well as the statistics of avalanches. It is observed that the brittle to quasibrittle transition point scales to lower values, suggesting more quasi-brittle-like continuous failure when α is increased. At the same time, the bundle becomes stronger as there are larger numbers of strong links to support the external stress. High α in a highly disordered bundle leads to an ideal situation where the bundle strength, as well as the predictability in failure process is very high. Also, the critical fraction αc, required to make the model deviate from the conventional results, increases with decreasing strength of disorder. The analytical expression for αc shows good agreement with the numerical results. Finally, the findings in the paper are compared with previous results and real-life applications of composite materials.

Phase relationship in three-phase composites which include a void phase

NASA Technical Reports Server (NTRS)

Price, H. L.; Nelson, J. B.

1976-01-01

The paper shows the relationship among polymer, particles, and voids in a three-phase composite and how some of the properties of a composite may be changed by changing the proportions of the phases. The three-phase composite is an aggregate of microspheres bonded together with a small amount of polymer which may not form a continuous matrix. The void space (third phase) is obtained by limiting the amount of polymer which is mixed with the microspheres. A ternary phase diagram is used to show the proportional relationship among the three phases, with each apex representing a volume fraction of unity for a constituent while the side opposite the apex represents a volume fraction of zero for that constituent. The vertical dimension represents some composite property such as density or strength. The effect of composition on composite properties is shown by plotting them on a binary phase diagram which represents a perpendicular plane coincident with the 0.60 volume fraction microsphere line.

Neutron imaging of diabatic two-phase flows relevant to air conditioning

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

Geoghegan, Patrick J; Sharma, Vishaldeep

The design of the evaporator of an air conditioning system relies heavily on heat transfer coefficients and pressure drop correlations that predominantly involve an estimate of the changing void fraction and the underlying two-phase flow regime. These correlations dictate whether the resulting heat exchanger is oversized or not and the amount of refrigerant charge necessary to operate. The latter is particularly important when dealing with flammable or high GWP refrigerants. Traditional techniques to measure the void fraction and visualize the flow are either invasive to the flow or occur downstream of the evaporator, where some of the flow distribution willmore » have changed. Neutron imaging has the potential to visualize two-phase flow in-situ where an aluminium heat exchanger structure becomes essentially transparent to the penetrating neutrons. The subatomic particles are attenuated by the passing refrigerant flow. The resulting image may be directly related to the void fraction and the overall picture provides a clear insight into the flow regime present. This work presents neutron images of the refrigerant Isopentane as it passes through the flow channels of an aluminium evaporator at flowrates relevant to air conditioning. The flow in a 4mm square macro channel is compared to that in a 250 m by 750 m rectangular microchannel in terms of void fraction and regime. All neutron imaging experiments were conducted at the High Flux Isotope Reactor, an Oak Ridge National Laboratory facility« less

Numerical study of the influence of geometrical characteristics of a vertical helical coil on a bubbly flow

NASA Astrophysics Data System (ADS)

Saffari, H.; Moosavi, R.

2014-11-01

In this article, turbulent single-phase and two-phase (air-water) bubbly fluid flows in a vertical helical coil are analyzed by using computational fluid dynamics (CFD). The effects of the pipe diameter, coil diameter, coil pitch, Reynolds number, and void fraction on the pressure loss, friction coefficient, and flow characteristics are investigated. The Eulerian-Eulerian model is used in this work to simulate the two-phase fluid flow. Three-dimensional governing equations of continuity, momentum, and energy are solved by using the finite volume method. The k- ɛ turbulence model is used to calculate turbulence fluctuations. The SIMPLE algorithm is employed to solve the velocity and pressure fields. Due to the effect of a secondary force in helical pipes, the friction coefficient is found to be higher in helical pipes than in straight pipes. The friction coefficient increases with an increase in the curvature, pipe diameter, and coil pitch and decreases with an increase in the coil diameter and void fraction. The close correlation between the numerical results obtained in this study and the numerical and empirical results of other researchers confirm the accuracy of the applied method. For void fractions up to 0.1, the numerical results indicate that the friction coefficient increases with increasing the pipe diameter and keeping the coil pitch and diameter constant and decreases with increasing the coil diameter. Finally, with an increase in the Reynolds number, the friction coefficient decreases, while the void fraction increases.

Recent developments in BWR fuel design

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

Congdon, S.P.; Noble, L.D.; Wood, J.E.

1991-11-01

Substantial increases in the cost effectiveness and performance capability of boiling water reactor (BWR) fuel designs have been implemented in the past 5 to 7 yr. This increase has been driven by (a) utility desires to lower fuel and operating costs and (b) design innovations that have lowered enrichment requirements, improved thermal-hydraulic performance, and increased discharge exposure. Higher discharge exposures reduce disposal costs for European and Asian utilities and enable US utilities to lengthen operating cycles. A typical BWR reload fuel bundle fabricated today has 25% higher {sup 235}U enrichment and a factor of 2 higher gadolinium loading than onemore » made several years ago. Today's BWR fuel bundles also contain more unheated water reduces the axial water density variation, lowers the void coefficient, and enhances the neutron efficiency of the bundle, reducing both the gadolinium poison and the enrichment requirements. In addition to these general trends, the following unique design innovations have further enhanced the fuel cost efficiency and performance characteristics of BWR fuel: ferrule spacer, part length rods, interactive channel, and bundle enhanced spectral shift. GE's fuel designs offer the flexibility for modern BWR fuel requirements and contain unique design features that enhance flexibility for modern BWR fuel requirements and contain unique design features that enhance flexibility and fuel cycle economics.« less

Time dependent voiding mechanisms in polyamide 6 submitted to high stress triaxiality: experimental characterisation and finite element modelling

NASA Astrophysics Data System (ADS)

Selles, Nathan; King, Andrew; Proudhon, Henry; Saintier, Nicolas; Laiarinandrasana, Lucien

2017-08-01

Double notched round bars made of semi-crystalline polymer polyamide 6 (PA6) were submitted to monotonic tensile and creep tests. The two notches had a root radius of 0.45 mm, which imposes a multiaxial stress state and a state of high triaxiality in the net (minimal) section of the specimens. Tests were carried out until the failure occurred from one of the notches. The other one, unbroken but deformed under steady strain rate or steady load, was inspected using the Synchrotron Radiation Computed Tomography (SRCT) technique. These 3D through thickness inspections allowed the study of microstructural evolution at the peak stress for the monotonic tensile test and at the beginning of the tertiary creep for the creep tests. Cavitation features were assessed with a micrometre resolution within the notched region. Spatial distributions of void volume fraction ( Vf) and void morphology were studied. Voiding mechanisms were similar under steady strain rates and steady loads. The maximum values of Vf were located between the axis of revolution of the specimens and the notch surface and voids were considered as flat cylinders with a circular basis perpendicular to the loading direction. A model, based on porous plasticity, was used to simulate the mechanical response of this PA6 material under high stress triaxiality. Both macroscopic behaviour (loading curves) and voiding micro-mechanisms (radial distributions of void volume fraction) were accurately predicted using finite element simulations.

Developpement d'un systeme pour la mesure du taux de vide dans un ecoulement diphasique par une methode utilisant des micro-ondes

NASA Astrophysics Data System (ADS)

Pochet, Steven

The measurement of the void fraction is an important parameter in many industrial fields. Whether it is to prevent the phenomenon of critical heat flux in heat tube of thermal power plants, the explosion of gas pockets in oil rigs’ pipes or to detect bubbles in medical catheters, the knowledge of the void fraction can be a key parameter in many diverse applications. Several invasive and non-invasive measurements techniques have been developed these last decades and are based on the difference between the physical properties of liquid and gas. Some of these techniques are not always possible to implement due to restrictions in the geometry of tubes or regulatory standards limiting their use. Throughout this work we propose a new non-invasive void fraction measurement technique based on the reflection of electromagnetic waves on the water-air interface of the mixture. The reflection of electromagnetic wave is induced by a change in the impedance of the propagation medium. The impedance is function of the dielectric properties of the medium. The characteristics of air and water being distinct, it is possible to calculate the complex reflection coefficient at the interface of a double phase mixture. To this end, mathematical modeling of the response of an electromagnetic wave in a tube containing a two phase mixture was made using the model of transmission lines, applicable to microwave frequencies we use. The effects of the amount of air in water and the position of the bubbles in the section of the tube were simulated. It was shown that the phase of the reflected wave was sensitive to the position of bubbles in the tube’s section and that the magnitude of the reflection coefficient varied with the mixture’s void fraction. Subsequently, we designed and built a six-ports reflectometer operating at 2.45 GHz. This system allows the processing and calculation of the reflected wave from the incident wave. A six-ports network, a patch antenna, a wave generator and an amplifier were simulated using HFSS and ADS software. They were then built using the technology of micro-strips on dielectric laminates and the entire system was then calibrated at 6 different frequencies near 2.45 GHz. To this end, we used 4 and 5 loads calibration algorithms that gave us calibrated results with less than 2 % errors. Afterwards, the system was implemented: the antenna was placed tangent to the wall of a vertical tube and connected to the six-ports which was connected to a computer recording and displaying the results in real time. A valve positioned under the tube allows air into the tube and to vary the flow rate. The results showed that the system was sensitive to changes in void fraction from 1% and followed the predictions of the simulated model to a void fraction of about 10%. Possibly du to a change in the structure of the flow for a void fraction of 10%, the signal no longer varies monotonically with respect to the increasing void fraction possibly because of a change in the flow’s configuration. It was shown that the Rayleigh scattering phenomena of air bubbles was involved in the reflection coefficient response. Pictures of the stream at various void fraction state were taken and confirmed a change in the flow’s configuration. By placing a Plexiglas rod to simulate a flow geometry located in the section of the tube, it was noted that the change in phase of the reflected wave was the same as the model when the rod was placed in an empty tube (very few attenuation loss environment). Hence, it is possible to determine the distance of an object in a section of tube from the measurement of the reflected wave’s phase. When the rod is in a very absorbent medium such as water, it is possible to detect a moving rod when it is sufficiently close to the antenna (less than two wavelengths) thanks again to the phase variation. However, detection is still much more difficult due to the absorption of water and can not function effectively for tubes with high diameters compared with the electromagnetic wavelength used.

Microstructural characterization and simulation of damage for geared sheet components

NASA Astrophysics Data System (ADS)

Gerstein, G.; Isik, K.; Gutknecht, F.; Sieczkarek, P.; Ewert, J.; Tekkaya, A. E.; Clausmeyer, T.; Nürnberger, F.

2017-09-01

The evolution of damage in geared components manufactured from steel sheets was investigated, to analyse the influence of damage caused by the sheet-bulk-metal forming. Due to the inhomogeneous and multi-axial deformation in the investigated parts, different aspects such as the location-dependent shape and size of voids are analysed by means of various microscopic methods. In particular, a method to characterize the state of damage evolution, i. e. void nucleation, growth and coalescence using scanning electron microscopy (SEM) is applied. The investigations reveal a strong dependence of the void area fraction, shape of voids and thus damage evolution on the loading mode. The microstructural analysis is complemented with FEM simulations using material models which consider the characteristics of the void evolution.

Checkerboard seed-blanket thorium fuel core concepts for heavy water moderated reactors

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

Bromley, B.P.; Hyland, B.

2013-07-01

New reactor concepts to implement thorium-based fuel cycles have been explored to achieve maximum resource utilization. Pressure tube heavy water reactors (PT-HWR) are highly advantageous for implementing the use of thorium-based fuels because of their high neutron economy and on-line re-fuelling capability. The use of heterogeneous seed-blanket core concepts in a PT-HWR where higher-fissile-content seed fuel bundles are physically separate from lower-fissile-content blanket bundles allows more flexibility and control in fuel management to maximize the fissile utilization and conversion of fertile fuel. The lattice concept chosen was a 35-element bundle made with a homogeneous mixture of reactor grade Pu (aboutmore » 67 wt% fissile) and Th, and with a central zirconia rod to help reduce coolant void reactivity. Several checkerboard heterogeneous seed-blanket core concepts with plutonium-thorium-based fuels in a 700-MWe-class PT-HWR were analyzed, using a once-through thorium (OTT) cycle. Different combinations of seed and blanket fuel were tested to determine the impact on core-average burnup, fissile utilization, power distributions, and other performance parameters. It was found that various checkerboard core concepts can achieve a fissile utilization that is up to 26% higher than that achieved in a PT-HWR using more conventional natural uranium fuel bundles. Up to 60% of the Pu is consumed; up to 43% of the energy is produced from thorium, and up to 303 kg/year of Pa-233/U-233/U-235 are produced. Checkerboard cores with about 50% of low-power blanket bundles may require power de-rating (65% to 74%) to avoid exceeding maximum limits for channel and bundle powers and linear element ratings. (authors)« less

Annular seed-blanket thorium fuel core concepts for heavy water moderated reactors

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

Bromley, B.P.; Hyland, B.

2013-07-01

New reactor concepts to implement thorium-based fuel cycles have been explored to achieve maximum resource utilization. Pressure tube heavy water reactors (PT-HWR) are highly advantageous for implementing the use of thorium-based fuels because of their high neutron economy and on-line re-fuelling capability. The use of heterogeneous seed-blanket core concepts in a PT-HWR where higher-fissile-content seed fuel bundles are physically separate from lower-fissile-content blanket bundles allows more flexibility and control in fuel management to maximize the fissile utilization and conversion of fertile fuel. The lattice concept chosen is a 35-element bundle made with a homogeneous mixture of reactor grade Pu andmore » Th, and with a central zirconia rod to help reduce coolant void reactivity. Several annular heterogeneous seed-blanket core concepts with plutonium-thorium-based fuels in a 700-MWe-class PT-HWR were analyzed, using a once-through thorium (OTT) cycle. Different combinations of seed and blanket fuel were tested to determine the impact on core-average burnup, fissile utilization, power distributions, and other performance parameters. It was found that the various core concepts can achieve a fissile utilization that is up to 30% higher than is currently achieved in a PT-HWR using conventional natural uranium fuel bundles. Up to 67% of the Pu is consumed; up to 43% of the energy is produced from thorium, and up to 363 kg/year of U-233 is produced. Seed-blanket cores with ∼50% content of low-power blanket bundles may require power de-rating (∼58% to 65%) to avoid exceeding maximum limits for peak channel power, bundle power and linear element ratings. (authors)« less

Advances in the simulation and automated measurement of well-sorted granular material: 2. Direct measures of particle properties

USGS Publications Warehouse

Buscombe, Daniel D.; Rubin, David M.

2012-01-01

1. In this, the second of a pair of papers on the structure of well-sorted natural granular material (sediment), new methods are described for automated measurements from images of sediment, of: 1) particle-size standard deviation (arithmetic sorting) with and without apparent void fraction; and 2) mean particle size in material with void fraction. A variety of simulations of granular material are used for testing purposes, in addition to images of natural sediment. Simulations are also used to establish that the effects on automated particle sizing of grains visible through the interstices of the grains at the very surface of a granular material continue to a depth of approximately 4 grain diameters and that this is independent of mean particle size. Ensemble root-mean squared error between observed and estimated arithmetic sorting coefficients for 262 images of natural silts, sands and gravels (drawn from 8 populations) is 31%, which reduces to 27% if adjusted for bias (slope correction between observed and estimated values). These methods allow non-intrusive and fully automated measurements of surfaces of unconsolidated granular material. With no tunable parameters or empirically derived coefficients, they should be broadly universal in appropriate applications. However, empirical corrections may need to be applied for the most accurate results. Finally, analytical formulas are derived for the one-step pore-particle transition probability matrix, estimated from the image's autocorrelogram, from which void fraction of a section of granular material can be estimated directly. This model gives excellent predictions of bulk void fraction yet imperfect predictions of pore-particle transitions.

Advances in the simulation and automated measurement of well-sorted granular material: 2. Direct measures of particle properties

NASA Astrophysics Data System (ADS)

Buscombe, D.; Rubin, D. M.

2012-06-01

In this, the second of a pair of papers on the structure of well-sorted natural granular material (sediment), new methods are described for automated measurements from images of sediment, of: 1) particle-size standard deviation (arithmetic sorting) with and without apparent void fraction; and 2) mean particle size in material with void fraction. A variety of simulations of granular material are used for testing purposes, in addition to images of natural sediment. Simulations are also used to establish that the effects on automated particle sizing of grains visible through the interstices of the grains at the very surface of a granular material continue to a depth of approximately 4 grain diameters and that this is independent of mean particle size. Ensemble root-mean squared error between observed and estimated arithmetic sorting coefficients for 262 images of natural silts, sands and gravels (drawn from 8 populations) is 31%, which reduces to 27% if adjusted for bias (slope correction between observed and estimated values). These methods allow non-intrusive and fully automated measurements of surfaces of unconsolidated granular material. With no tunable parameters or empirically derived coefficients, they should be broadly universal in appropriate applications. However, empirical corrections may need to be applied for the most accurate results. Finally, analytical formulas are derived for the one-step pore-particle transition probability matrix, estimated from the image's autocorrelogram, from which void fraction of a section of granular material can be estimated directly. This model gives excellent predictions of bulk void fraction yet imperfect predictions of pore-particle transitions.

Molecular weight dependence of LB morphology of poly(n-hexyl isocyanate) (PHIC).

PubMed

Morioka, Takako; Shibata, Osamu; Kawaguchi, Masami

2010-12-07

The morphologies of Langmuir-Blodgett (LB) films of two fractionated poly(n-hexyl isocyanate) (PHIC) and those of their binary mixtures were observed by AFM, together with those of an unfractionated PHIC. The low molecular weight PHIC formed random packing of bundles consisting of rigid rods, while the high molecular weight PHIC formed random packing of bundles consisting of hairy rods. Bundle interpenetration was observed only for the latter in the semidilute regime. In the bilayer region, the area occupied by the PHIC bundles in the upper layer was obviously smaller for the high molecular weight PHIC than for the low molecular weight PHIC, suggesting that the bundles of high molecular weight PHIC more easily interpenetrate than those of low molecular weight PHIC. For the blended films composed of both low and high molecular weight PHICs, the characteristic morphologies of the respective PHIC samples were no longer present. Moreover, the morphologies of the blended films appeared to resemble each other at any molar fraction owing to the ideal miscibility of the low molecular weight and high molecular weight PHICs. The morphologies of the blended films were also similar to that of the unfractionated PHIC film in the dilute regime. In the semidilute regime, the blended films became rounded owing to an increase in bundles interpenetration between PHICs as compared to that in the dilute regime, whereas the morphology of unfractionated PHIC films remained unchanged as compared to that in the dilute regime.

Multiphase flow calculation software

DOEpatents

Fincke, James R.

2003-04-15

Multiphase flow calculation software and computer-readable media carrying computer executable instructions for calculating liquid and gas phase mass flow rates of high void fraction multiphase flows. The multiphase flow calculation software employs various given, or experimentally determined, parameters in conjunction with a plurality of pressure differentials of a multiphase flow, preferably supplied by a differential pressure flowmeter or the like, to determine liquid and gas phase mass flow rates of the high void fraction multiphase flows. Embodiments of the multiphase flow calculation software are suitable for use in a variety of applications, including real-time management and control of an object system.

Ground Based Studies of Gas-Liquid Flows in Microgravity Using Learjet Trajectories

NASA Technical Reports Server (NTRS)

Bousman, W. S.; Dukler, A. E.

1994-01-01

A 1.27 cm diameter two phase gas-liquid flow experiment has been developed with the NASA Lewis Research Center to study two-phase flows in microgravity. The experiment allows for the measurement of void fraction, pressure drop, film thickness and bubble and wave velocities as well as for high speed photography. Three liquids were used to study the effects of liquid viscosity and surface tension, and flow pattern maps are presented for each. The experimental results are used to develop mechanistically based models to predict void fraction, bubble velocity, pressure drop and flow pattern transitions in microgravity.

Two-phase flow measurements with advanced instrumented spool pieces and local conductivity probes

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

Turnage, K.G.; Davis, C.E.

1979-01-01

A series of two-phase, air-water and steam-water tests performed with instrumented spool pieces and with conductivity probes obtained from Atomic Energy of Canada, Ltd. is described. The behavior of the three-beam densitometer, turbine meter, and drag flowmeter is discussed in terms of two-phase models. Application of some two-phase mass flow models to the recorded spool piece data is made and preliminary results are shown. Velocity and void fraction information derived from the conductivity probes is presented and compared to velocities and void fractions obtained using the spool piece instrumentation.

Broadband and flexible acoustic focusing by metafiber bundles

NASA Astrophysics Data System (ADS)

Sun, Hong-Xiang; Chen, Jia-He; Ge, Yong; Yuan, Shou-Qi; Liu, Xiao-Jun

2018-06-01

We report a broadband and flexible acoustic focusing through metafiber bundles in air, in which each metafiber consists of eight circular and narrow rectangular cavities. The fractional bandwidth of the acoustic focusing could reach about 0.2, which arises from the eigenmodes of the metafiber structure. Besides, owing to the flexible characteristic of the metafibers, the focus position can be manipulated by bending the metafiber bundles, and the metafiber bundles could bypass rigid scatterers inside the lens structure. More interestingly, the acoustic propagation and focusing directions can be changed by using a designed right-angled direction converter fabricated by the metafibers, and a waveform converter and a focusing lens of the cylindrical acoustic source are realized based on the metafiber bundles. The proposed focusing lens has the advantages of broad bandwidth, flexible structure, and high focusing performance, showing great potentials in versatile applications.

Experimental and Numerical Investigation of Combined Sensible/Latent Thermal Energy Storage for High-Temperature Applications.

PubMed

Geissbühler, Lukas; Zavattoni, Simone; Barbato, Maurizio; Zanganeh, Giw; Haselbacher, Andreas; Steinfeld, Aldo

2015-01-01

Combined sensible/latent heat storage allows the heat-transfer fluid outflow temperature during discharging to be stabilized. A lab-scale combined storage consisting of a packed bed of rocks and steel-encapsulated AlSi(12) was investigated experimentally and numerically. Due to the small tank-to-particle diameter ratio of the lab-scale storage, void-fraction variations were not negligible, leading to channeling effects that cannot be resolved in 1D heat-transfer models. The void-fraction variations and channeling effects can be resolved in 2D models of the flow and heat transfer in the storage. The resulting so-called bypass fraction extracted from the 2D model was used in the 1D model and led to good agreement with experimental measurements.

Impedance probe to measure local void fraction profiles

NASA Astrophysics Data System (ADS)

Teyssedou, A.; Tapucu, A.; Lortie, M.

1988-04-01

A conductivity-type local void measurement system has been developed. The effects of the sensor tip geometry, the unbalance of the front-end bridge, the comparator threshold level, and the mass fluxes on the response of the instrument have been studied. The system has been calibrated under air-water two-phase flow conditions using the quick-closing-valve technique. Comparison of the void profiles obtained with the conductivity probe with those obtained using an optical probe confirms the applicability of this system for two-phase (air-water) flows.

New Feature Observed in the Raman Resonance Excitation Profiles of (6 , 5) -Enriched, Selectively Bundled SWCNTs

NASA Astrophysics Data System (ADS)

Hight Walker, A. R.; Simpson, J. R.; Roslyak, O.; Haroz, E.; Telg, H.; Duque, J. G.; Crochet, J. J.; Piryatinski, A.; Doorn, S. K.

Understanding the photophysics of exciton behavior in single wall carbon nanotube (SWCNT) bundles remains important for opto-electronic device applications. We report resonance Raman spectroscopy (RRS) measurements on (6 , 5) -enriched SWCNTs, dispersed in aqueous solutions and separated using density gradient ultracentrifugation into fractions of increasing bundling. Near-IR to UV absorption spectroscopy shows a redshift and broadening of the main excitonic transitions with increasing bundling. A continuously tunable dye laser coupled to a triple-grating spectrometer affords measurement of Raman resonance excitation profiles (REPs) over a range of wavelengths covering the (6 , 5) -E22 range (505 to 585) nm. REPs of both the radial breathing mode (RBM) and G-band reveal a redshifting and broadening of the (6 , 5) E22 transition energy with increasing bundling. Additionally, we observe an unexpected peak in the REP of bundled SWCNTs, which is shifted lower in energy than the main E22 and is anomalously narrow. We compare these observations to a theoretical model that examines the origin of this peak in relation to bundle polarization-enhanced exciton response.

Cardiac resynchronization therapy with His bundle pacing as a method of treatment of chronic heart failure in patients with permanent atrial fibrillation and left bundle branch block.

PubMed

Boczar, Krzysztof; Sławuta, Agnieszka; Ząbek, Andrzej; Dębski, Maciej; Gajek, Jacek; Lelakowski, Jacek; Małecka, Barbara

CRT is a therapeutic option for patients with heart failure, sinus rhythm, prolonged QRS complex duration and reduced ejection fraction. We present a case of 71-year-old woman with dilated cardiomyopathy, NYHA functional class III and AF. We implanted CRT combined with direct His-bundle pacing. The indication for such a therapy was a left bundle branch block with a QRS complex of 178ms and a left ventricular EF of 15%, left ventricular end-diastolic diameter (LVEDD) of 75mm. After 8months of follow-up the LVEDD was 60mm with EF 35-40%. Copyright © 2017. Published by Elsevier Inc.

Direct Contact Heat Exchange Interfacial Phenomena for Liquid Metal Reactors: Part II - Void Fraction

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

Abdulla, S.; Liu, X.; Anderson, M.H.

One concept being considered for steam generation in innovative nuclear reactor applications, involves water coming into direct contact with a circulating molten metal. The vigorous agitation of the two fluids, the direct liquid-liquid contact and the consequent large interfacial area can give rise to large heat transfer coefficients and rapid steam generation. For an optimum design of such direct contact heat exchange and vaporization systems, detailed knowledge is necessary of the various flow regimes, interfacial transport phenomena, heat transfer and operational stability. In order to investigate the interfacial transport phenomena, heat transfer and operational stability of direct liquid-liquid contact, amore » series of experiments are being performed in a 1-d test facility at Argonne National Laboratory and a 2-d experimental facility at UW-Madison. Each of the experimental facilities primarily consist of a liquid-metal melt chamber, heated test section (10 cm diameter tube for 1-d facility and 10 cm 50 cm rectangle for 2-d facility), water injection system and steam suppression tank. This paper is part II which, primarily addresses results and analysis of a set of preliminary experiments and void fraction measurements conducted in the 2-d facility at UW-Madison, part I deals with the heat transfer in the 1-d test facility at Argonne National Laboratory. A real-time high energy X-ray imaging system was developed and utilized to visualize the multiphase flow and measure line-average local void fractions, time-dependent void fraction distribution as well as estimates of the vapor bubble sizes and velocities. These measurements allowed us to determine the volumetric heat transfer coefficient and gain insight into the local heat transfer mechanisms. In this study, the images were captured at frame rates of 100 fps with spatial resolution of about 7 mm with a full-field view of a 15 cm square and five different positions along the test section height. The full-field average void fraction increases rapidly to about 15% in these preliminary tests, with the apparent boiling length of less than 20 cm. The volumetric heat transfer coefficient between the liquid metal and water are compared to the CRIEPI data, the only prior data for direct contact heat exchange for these liquid metal/water systems. (authors)« less

Visualization and void-fraction measurements in a molten metal bath

NASA Astrophysics Data System (ADS)

Baker, Michael Charles

In the experimental study of multiphase flow phenomena, including intense multiphase interactions, such as vapor explosions, the fluids are often opaque. To obtain images, suitable for quantitative analysis, of such phenomena requires the use of something other than visible light, such as x-rays or neutrons. In this study a unique flow visualization technique using a continuous high energy x-ray source to measure void fraction with good spatial and temporal resolution in pools of liquid metal has been developed. In the present experiments, 11 to 21 kg of molten tin at 360sp° C to 425sp° C is collected in a pre-heated stainless steel test section of rectangular cross section (18 x 10 cm). In the base of the test section are two injection ports for the introduction of nitrogen gas and water. Each port is composed of two coaxial tubes. Nitrogen gas flows through the annular region and either nitrogen gas or water flows through the central tube. The test section is imaged using a high energy x-ray source (Varian Linatron 3000A) with a peak energy of 9 MeV and a maximum on axis dose rate of 30 Gy/min. The transmitted x-rays are viewed with an imaging system composed of a high density silicate glass screen, a mirror, a lens coupled image intensifier, and a CCD camera. Two interchangeable CCD cameras allow for either high resolution imaging (1128 x 480 pixels) at a frame rate of 30 Hz or low resolution imaging (256 x 256 pixels) at a frame rate of 220 Hz. The collected images are digitally processed to obtain the chordal averaged local and volume integral void fractions. At the experimental conditions examined, estimated relative uncertainty using this measurement technique is 10% for worst case conditions. The upper bound on the relative systematic error due to void dynamics is estimated to be 20%. Reasonable agreement has been demonstrated between the data generated from the processed images, past integral void fraction experimental data, and a semi-empirical drift-flux correlation.

The void spectrum in two-dimensional numerical simulations of gravitational clustering

NASA Technical Reports Server (NTRS)

Kauffmann, Guinevere; Melott, Adrian L.

1992-01-01

An algorithm for deriving a spectrum of void sizes from two-dimensional high-resolution numerical simulations of gravitational clustering is tested, and it is verified that it produces the correct results where those results can be anticipated. The method is used to study the growth of voids as clustering proceeds. It is found that the most stable indicator of the characteristic void 'size' in the simulations is the mean fractional area covered by voids of diameter d, in a density field smoothed at its correlation length. Very accurate scaling behavior is found in power-law numerical models as they evolve. Eventually, this scaling breaks down as the nonlinearity reaches larger scales. It is shown that this breakdown is a manifestation of the undesirable effect of boundary conditions on simulations, even with the very large dynamic range possible here. A simple criterion is suggested for deciding when simulations with modest large-scale power may systematically underestimate the frequency of larger voids.

Small-angle x-ray scattering in amorphous silicon: A computational study

NASA Astrophysics Data System (ADS)

Paudel, Durga; Atta-Fynn, Raymond; Drabold, David A.; Elliott, Stephen R.; Biswas, Parthapratim

2018-05-01

We present a computational study of small-angle x-ray scattering (SAXS) in amorphous silicon (a -Si) with particular emphasis on the morphology and microstructure of voids. The relationship between the scattering intensity in SAXS and the three-dimensional structure of nanoscale inhomogeneities or voids is addressed by generating large high-quality a -Si networks with 0.1%-0.3% volume concentration of voids, as observed in experiments using SAXS and positron annihilation spectroscopy. A systematic study of the variation of the scattering intensity in the small-angle scattering region with the size, shape, number density, and the spatial distribution of the voids in the networks is presented. Our results suggest that the scattering intensity in the small-angle region is particularly sensitive to the size and the total volume fraction of the voids, but the effect of the geometry or shape of the voids is less pronounced in the intensity profiles. A comparison of the average size of the voids obtained from the simulated values of the intensity, using the Guinier approximation and Kratky plots, with that of the same from the spatial distribution of the atoms in the vicinity of void surfaces is presented.

Non-selective His bundle pacing with a biphasic waveform: enhancing septal resynchronization.

PubMed

Ortega, Daniel F; Barja, Luis D; Logarzo, Emilio; Mangani, Nicolas; Paolucci, Analia; Bonomini, Maria P

2018-05-01

His bundle pacing has shown to prevent detrimental effects from right ventricular apical pacing (RVA) and proved to resynchronize many conduction disturbances cases. However, the extent of His bundle pacing resynchronization is limited. An optimized stimulation waveform could expand this limit when implemented in His bundle pacing sets. In this work, we temporarily implemented RVA and Non-selective His bundle pacing with a biphasic anodal-first waveform (AF-nHB) and compared their effects against sinus rhythm (SR). Fifteen patients referred for electrophysiologic study with conduction disturbances, cardiomyopathy and ejection fraction below 35% were enrolled for the study. The following acute parameters were measured: QRS duration, left ventricular activation (RLVT), time of isovolumic contraction (IVCT), ejection fraction (EF), and dP/dtmax. QRS duration and RLVT decreased markedly under AF-nHB (SR: 169 ± 34 ms vs. nHB: 116 ± 31 ms, P < 0.0005) while RVA significantly increased QRS duration (SR: 169 ms vs. RVA: 198 ms, P < 0.05) and did not change RLVT (P = NS). Consistently, IVCT moderately decreased under AF-nHB (SR: 238 ms vs. RVA: 184 ms, P < 0.05 vs. SR) and dP/dtmax showed a 93.35 [mmHg] average increase under AF-nHB against SR. Also, T-wave inversions were observed during AF-nHB immediately after SR and RVA pacing suggesting the occurrence of cardiac memory. AF-nHB corrected bundle branch blocks in patients with severe conduction disturbances, even in those with dilated cardiomiopathy, outstanding from RVA. Also, the occurrence of cardiac memory during AF-nHB turned up as an observational finding of this study.

Application of Jacobian-free Newton–Krylov method in implicitly solving two-fluid six-equation two-phase flow problems: Implementation, validation and benchmark

DOE PAGES

Zou, Ling; Zhao, Haihua; Zhang, Hongbin

2016-03-09

This work represents a first-of-its-kind successful application to employ advanced numerical methods in solving realistic two-phase flow problems with two-fluid six-equation two-phase flow model. These advanced numerical methods include high-resolution spatial discretization scheme with staggered grids (high-order) fully implicit time integration schemes, and Jacobian-free Newton–Krylov (JFNK) method as the nonlinear solver. The computer code developed in this work has been extensively validated with existing experimental flow boiling data in vertical pipes and rod bundles, which cover wide ranges of experimental conditions, such as pressure, inlet mass flux, wall heat flux and exit void fraction. Additional code-to-code benchmark with the RELAP5-3Dmore » code further verifies the correct code implementation. The combined methods employed in this work exhibit strong robustness in solving two-phase flow problems even when phase appearance (boiling) and realistic discrete flow regimes are considered. Transitional flow regimes used in existing system analysis codes, normally introduced to overcome numerical difficulty, were completely removed in this work. As a result, this in turn provides the possibility to utilize more sophisticated flow regime maps in the future to further improve simulation accuracy.« less

Linear Instability Analysis of non-uniform Bubbly Mixing layer with Two-Fluid model

NASA Astrophysics Data System (ADS)

Sharma, Subash; Chetty, Krishna; Lopez de Bertodano, Martin

We examine the inviscid instability of a non-uniform adiabatic bubbly shear layer with a Two-Fluid model. The Two-Fluid model is made well-posed with the closure relations for interfacial forces. First, a characteristic analysis is carried out to study the well posedness of the model over range of void fraction with interfacial forces for virtual mass, interfacial drag, interfacial pressure. A dispersion analysis then allow us to obtain growth rate and wavelength. Then, the well-posed two-fluid model is solved using CFD to validate the results obtained with the linear stability analysis. The effect of the void fraction and the distribution profile on stability is analyzed.

Apparatus and method for determining solids circulation rate

DOEpatents

Ludlow, J Christopher [Morgantown, WV; Spenik, James L [Morgantown, WV

2012-02-14

The invention relates to a method of determining bed velocity and solids circulation rate in a standpipe experiencing a moving packed bed flow, such as the in the standpipe section of a circulating bed fluidized reactor The method utilizes in-situ measurement of differential pressure over known axial lengths of the standpipe in conjunction with in-situ gas velocity measurement for a novel application of Ergun equations allowing determination of standpipe void fraction and moving packed bed velocity. The method takes advantage of the moving packed bed property of constant void fraction in order to integrate measured parameters into simultaneous solution of Ergun-based equations and conservation of mass equations across multiple sections of the standpipe.

A Mechanical, Microstructural, and Damage Study of Various Tailor Hot Stamped Material Conditions Consisting of Martensite, Bainite, Ferrite, and Pearlite

NASA Astrophysics Data System (ADS)

Bardelcik, Alexander; Vowles, Caryn J.; Worswick, Michael J.

2018-04-01

This paper examines the mechanical, microstructural, and damage characteristics of five different material conditions that were created using the tailored hot stamping process with in-die heating. The tailored material conditions, TMC1 to TMC5 (softest-hardest), were created using die temperatures ranging from 700 °C to 400 °C, respectively. The tensile strength (and total elongation) ranged from 615 MPa (0.24) for TMC1 to 1122 MPa (0.11) for TMC5. TMC3 and TMC4 exhibited intermediate strength levels, with almost no increase in total elongation relative to TMC5. FE-SEM microscopy was used to quantify the mixed-phase microstructures, which ranged in volume fractions of ferrite, pearlite, bainite, and martensite. High-resolution optical microscopy was used to quantify void accumulation and showed that the total void area fraction at 0.60 thickness strain was low for TMC1 and TMC5 ( 0.09 pct) and highest for TMC3 (0.31 pct). Damage modes were characterized and revealed that the poor damage behavior of TMC3 (martensite/bainite/ferrite composition) was a result of small martensitic grains forming at grain boundaries and grain boundary junctions, which facilitated void nucleation as shown by the highest measured void density for this particular material condition. The excellent ductility of TMC1 was a result of a large grained ferritic/pearlitic microstructure that was less susceptible to void nucleation and growth. Large titanium nitride (TiN) inclusions were observed in all of the tailored material conditions and it was shown that they noticeably contributed to the total void accumulation, specifically for the TMC3 and TMC4 material conditions.

Evidence of Intertube Excitons Observed in the Raman Resonance Excitation Profiles of (6 , 5) -Enriched SWCNT Bundles

NASA Astrophysics Data System (ADS)

Simpson, J. R.; Hight Walker, A. R.; Roslyak, O.; Haroz, E.; Telg, H.; Duque, J. G.; Crochet, J. J.; Piryatinkski, A.; Doorn, S. K.

Understanding the photophysics of exciton behavior in single wall carbon nanotube (SWCNT) bundles remains important for opto-electronic device applications. We report resonance Raman spectroscopy (RRS) measurements on (6 , 5) -enriched SWCNTs, dispersed in aqueous solutions and separated using density gradient ultracentrifugation into fractions of increasing bundle size. Near-IR to UV absorption spectroscopy demonstrates a redshift and broadening of the main excitonic transitions with bundling. A continuously tunable dye laser coupled to a triple-grating spectrometer affords measurement of Raman resonance excitation profiles (REPs) over a range of wavelengths, (505 to 585) nm, covering the (6 , 5) -E22S excitation. REPs of both the radial breathing mode (RBM) and GLO+reveal a redshifting and broadening of the (6 , 5) E22S transition energy with increasing bundle size. Most interestingly, we observe an additional peak in both the RBM and GLO+REPs of bundled SWCNTs, which is shifted lower in energy than the main E22S and is anomalously narrow. We attribute this additional peak to a transverse, intertube exciton.

The wire-mesh sensor as a two-phase flow meter

NASA Astrophysics Data System (ADS)

Shaban, H.; Tavoularis, S.

2015-01-01

A novel gas and liquid flow rate measurement method is proposed for use in vertical upward and downward gas-liquid pipe flows. This method is based on the analysis of the time history of area-averaged void fraction that is measured using a conductivity wire-mesh sensor (WMS). WMS measurements were collected in vertical upward and downward air-water flows in a pipe with an internal diameter of 32.5 mm at nearly atmospheric pressure. The relative frequencies and the power spectral density of area-averaged void fraction were calculated and used as representative properties. Independent features, extracted from these properties using Principal Component Analysis and Independent Component Analysis, were used as inputs to artificial neural networks, which were trained to give the gas and liquid flow rates as outputs. The present method was shown to be accurate for all four encountered flow regimes and for a wide range of flow conditions. Besides providing accurate predictions for steady flows, the method was also tested successfully in three flows with transient liquid flow rates. The method was augmented by the use of the cross-correlation function of area-averaged void fraction determined from the output of a dual WMS unit as an additional representative property, which was found to improve the accuracy of flow rate prediction.

Micro-Mechanical Modeling of Ductile Fracture in Welded Aluminum-Lithium Alloys

NASA Technical Reports Server (NTRS)

Ibrahim, Ahmed

2002-01-01

This computation model for microscopic crack growth in welded aluminum-lithium alloys consists of a cavity with initial volume specified by the fraction f(sub 0), i.e. the void volume relative to the cell volume. Thus, cell size D and initial porosity f(sub 0) defines the key parameters in this model. The choice of cell size requires: 1) D must be representative of the large inclusion spacing. 2) Predicted R-curves scale almost proportionally with D for fixed f(sub 0). 3) mapping of one finite element per cell must provide adequate resolution of the stress-strain fields in the active layer and the adjacent material. For the ferritic steels studied thus far with this model, calibrated cell sizes range from 50-200 microns with f(sub 0) in the 0.0001 to 0.004 micron range. This range of values for D and f (sub 0) satisfies issues 1) and 3). This computational model employs the Gurson and Tvergaard constitutive model for porous plastic materials to describe the progressive damage of cells due to the growth of pre-existing voids. The model derives from a rigid-plastic limit analysis of a solid having a volume fraction (f) of voids approximated by a homogenous spherical body containing a spherical void.

Bubble Augmented Propulsor Mixture Flow Simulation near Choked Flow Condition

NASA Astrophysics Data System (ADS)

Choi, Jin-Keun; Hsiao, Chao-Tsung; Chahine, Georges

2013-03-01

The concept of waterjet thrust augmentation through bubble injection has been the subject of many patents and publications over the past several decades, and computational and experimental evidences of the augmentation of the jet thrust through bubble growth in the jet stream have been reported. Through our experimental studies, we have demonstrated net thrust augmentation as high as 70%for air volume fractions as high as 50%. However, in order to enable practical designs, an adequately validated modeling tool is required. In our previous numerical studies, we developed and validated a numerical code to simulate and predict the performance of a two-phase flow water jet propulsion system for low void fractions. In the present work, we extend the numerical method to handle higher void fractions to enable simulations for the high thrust augmentation conditions. At high void fractions, the speed of sound in the bubbly mixture decreases substantially and could be as low as 20 m/s, and the mixture velocity can approach the speed of sound in the medium. In this numerical study, we extend our numerical model, which is based on the two-way coupling between the mixture flow field and Lagrangian tracking of a large number of bubbles, to accommodate compressible flow regimes. Numerical methods used and the validation studies for various flow conditions in the bubble augmented propulsor will be presented. This work is supported by Office of Naval Research through contract N00014-11-C-0482 monitored by Dr. Ki-Han Kim.

The coupled effect of fiber volume fraction and void fraction on hydraulic fluid absorption of quartz/BMI laminates

NASA Astrophysics Data System (ADS)

Hurdelbrink, Keith R.; Anderson, Jacob P.; Siddique, Zahed; Altan, M. Cengiz

2016-03-01

Bismaleimide (BMI) resin with quartz (AQ581) fiber reinforcement is a composite material frequently used in aerospace applications, such as engine cowlings and radomes. Various composite components used in aircrafts are exposed to different types of hydraulic fluids, which may lead to anomalous absorption behavior over the service life of the composite. Accurate predictive models for absorption of liquid penetrants are particularly important as the composite components are often exposed to long-term degradation due to absorbed moisture, hydraulic fluids, or similar liquid penetrants. Microstructural features such as fiber volume fraction and void fraction can have a significant effect on the absorption behavior of fiber-reinforced composites. In this paper, hydraulic fluid absorption characteristics of quartz/BMI laminates fabricated from prepregs preconditioned at different relative humidity and subsequently cured at different pressures are presented. The composite samples are immersed into hydraulic fluid at room temperature, and were not subjected to any prior degradation. To generate process-induced microvoids, prepregs were conditioned in an environmental chamber at 2% or 99% relative humidity at room temperature for a period of 24 hours prior to laminate fabrication. To alter the fiber volume fraction, the laminates were fabricated at cure pressures of 68.9 kPa (10 psi) or 482.6 kPa (70 psi) via a hot-press. The laminates are shown to have different levels of microvoids and fiber volume fractions, which were observed to affect the absorption dynamics considerably and exhibited clear non-Fickian behavior. A one-dimensional hindered diffusion model (HDM) was shown to be successful in predicting the hydraulic fluid absorption. Model prediction indicates that as the fabrication pressure increased from 68.9 kPa to 482.6 kPa, the maximum fluid content (M∞) decreased from 8.0% wt. to 1.0% wt. The degree of non-Fickian behavior, measured by hindrance coefficient (μ), was shown to increase with the increased void fraction.

Ultrasonic sensing of powder densification

NASA Technical Reports Server (NTRS)

Lu, Yichi; Wadley, Haydn N. G.; Parthasarathi, Sanjai

1992-01-01

An independent scattering theory has been applied to the interpretation of ultrasonic velocity measurements made on porous metal samples produced either by a cold or a high-temperature compaction process. The results suggest that the pores in both processes are not spherical, an aspect ration of 1:3 fitting best with the data for low (less than 4 percent) pore volume fractions. For the hot compacted powders, the pores are smooth due to active diffusional processes during processing. For these types of voids, the results can be extended to a pore fraction of 10 percent, at which point voids form an interconnected network that violates the model assumptions. The cold pressed samples are not as well predicted by the theory because of poor particle bonding.

Panning for sperm gold: Isolation and purification of apyrene and eupyrene sperm from lepidopterans.

PubMed

Karr, Timothy L; Walters, James R

2015-08-01

We describe a simple and straightforward procedure for the purification and separation of apyrene and eupyrene forms of lepidopteran sperm. The procedure is generally applicable to both butterfly and moth species with results varying according to the relative amounts of sperm produced and size of sperm storage organs. The technique relies upon inherent differences between eupyene sperm bundles and free apyrene sperm morphology. These differences allow for separation of the sperm morphs by repeated "panning" of sperm bundles into the center of a plastic dish. The purified eupyrene sperm bundles can then be removed and apyrene sperm collected from the supernatant by centrifugation. Efficacy of the purification process was confirmed by light microscopy and gel electrophoresis of the resulting fractions. Both one- and two-dimensional gel electrophoresis identified significant protein differences between the fractions further suggesting that the panning procedure effectively separated eurpyrene from apyrene sperm. The panning procedure should provide a convenient and accessible technique for further studies of sperm biology in lepidopterans. Copyright © 2015 Elsevier Ltd. All rights reserved.

Toxicity of irradiated advanced heavy water reactor fuels.

PubMed

Priest, N D; Richardson, R B; Edwards, G W R

2013-02-01

The good neutron economy and online refueling capability of the CANDU® heavy water moderated reactor (HWR) enable it to use many different fuels such as low enriched uranium (LEU), plutonium, or thorium, in addition to its traditional natural uranium (NU) fuel. The toxicity and radiological protection methods for these proposed fuels, unlike those for NU, are not well established. This study uses software to compare the fuel composition and toxicity of irradiated NU fuel against those of two irradiated advanced HWR fuel bundles as a function of post-irradiation time. The first bundle investigated is a CANFLEX® low void reactor fuel (LVRF), of which only the dysprosium-poisoned central element, and not the outer 42 LEU elements, is specifically analyzed. The second bundle investigated is a heterogeneous high-burnup (LEU,Th)O(2) fuelled bundle, whose two components (LEU in the outer 35 elements and thorium in the central eight elements) are analyzed separately. The LVRF central element was estimated to have a much lower toxicity than that of NU at all times after shutdown. Both the high burnup LEU and the thorium fuel had similar toxicity to NU at shutdown, but due to the creation of such inhalation hazards as (238)Pu, (240)Pu, (242)Am, (242)Cm, and (244)Cm (in high burnup LEU), and (232)U and (228)Th (in irradiated thorium), the toxicity of these fuels was almost double that of irradiated NU after 2,700 d of cooling. New urine bioassay methods for higher actinoids and the analysis of thorium in fecal samples are recommended to assess the internal dose from these two fuels.

Framework for shape analysis of white matter fiber bundles.

PubMed

Glozman, Tanya; Bruckert, Lisa; Pestilli, Franco; Yecies, Derek W; Guibas, Leonidas J; Yeom, Kristen W

2018-02-15

Diffusion imaging coupled with tractography algorithms allows researchers to image human white matter fiber bundles in-vivo. These bundles are three-dimensional structures with shapes that change over time during the course of development as well as in pathologic states. While most studies on white matter variability focus on analysis of tissue properties estimated from the diffusion data, e.g. fractional anisotropy, the shape variability of white matter fiber bundle is much less explored. In this paper, we present a set of tools for shape analysis of white matter fiber bundles, namely: (1) a concise geometric model of bundle shapes; (2) a method for bundle registration between subjects; (3) a method for deformation estimation. Our framework is useful for analysis of shape variability in white matter fiber bundles. We demonstrate our framework by applying our methods on two datasets: one consisting of data for 6 normal adults and another consisting of data for 38 normal children of age 11 days to 8.5 years. We suggest a robust and reproducible method to measure changes in the shape of white matter fiber bundles. We demonstrate how this method can be used to create a model to assess age-dependent changes in the shape of specific fiber bundles. We derive such models for an ensemble of white matter fiber bundles on our pediatric dataset and show that our results agree with normative human head and brain growth data. Creating these models for a large pediatric longitudinal dataset may improve understanding of both normal development and pathologic states and propose novel parameters for the examination of the pediatric brain. Copyright © 2017 Elsevier Inc. All rights reserved.

Brittle-to-ductile transition in a fiber bundle with strong heterogeneity.

PubMed

Kovács, Kornél; Hidalgo, Raul Cruz; Pagonabarraga, Ignacio; Kun, Ferenc

2013-04-01

We analyze the failure process of a two-component system with widely different fracture strength in the framework of a fiber bundle model with localized load sharing. A fraction 0≤α≤1 of the bundle is strong and it is represented by unbreakable fibers, while fibers of the weak component have randomly distributed failure strength. Computer simulations revealed that there exists a critical composition α(c) which separates two qualitatively different behaviors: Below the critical point, the failure of the bundle is brittle, characterized by an abrupt damage growth within the breakable part of the system. Above α(c), however, the macroscopic response becomes ductile, providing stability during the entire breaking process. The transition occurs at an astonishingly low fraction of strong fibers which can have importance for applications. We show that in the ductile phase, the size distribution of breaking bursts has a power law functional form with an exponent μ=2 followed by an exponential cutoff. In the brittle phase, the power law also prevails but with a higher exponent μ=9/2. The transition between the two phases shows analogies to continuous phase transitions. Analyzing the microstructure of the damage, it was found that at the beginning of the fracture process cracks nucleate randomly, while later on growth and coalescence of cracks dominate, which give rise to power law distributed crack sizes.

Demonstration of Aflatoxin Inhibitory Activity in a Cotton Seed Coat Xylan

PubMed Central

Mellon, J. E.; Cotty, P. J.; Godshall, M. A.; Roberts, E.

1995-01-01

An inhibitor of aflatoxin biosynthesis localized in the seed coats of developing cotton was partially purified and characterized. Aqueous extracts from 25-day postanthesis seed coat tissue inhibited aflatoxin (B(inf1)) production in liquid cultures of Aspergillus flavus AF13. Inhibition was concentration dependent, with a 50% effective dose of 173 (mu)g of crude extract per ml of medium. The inhibitor was neutral in charge. Two active fractions were obtained from crude preparations by gel filtration chromatography (BioGel P-100). The purest fraction eluted in the void volume. Carbohydrate composition analysis of this void volume inhibitor indicated a composition of xylose (>90%) and mannose. Aflatoxin production in vitro was inversely related to inhibitor concentration in the fermentation medium (log of aflatoxin versus log of [inhibitor]; r(sup2) = 0.82; P < 0.002). The void volume inhibitor had a 50% effective dose of 6.2 (mu)g/ml, a 28-fold purification of the inhibitor material. These data support the hypothesis that seed coat inhibitory activity is associated with a cottonseed-specific xylan. PMID:16535194

Modeling of Thermal Conductivity of CVI-Densified Composites at Fiber and Bundle Level

PubMed Central

Guan, Kang; Wu, Jianqing; Cheng, Laifei

2016-01-01

The evolution of the thermal conductivities of the unidirectional, 2D woven and 3D braided composites during the CVI (chemical vapor infiltration) process have been numerically studied by the finite element method. The results show that the dual-scale pores play an important role in the thermal conduction of the CVI-densified composites. According to our results, two thermal conductivity models applicable for CVI process have been developed. The sensitivity analysis demonstrates the parameter with the most influence on the CVI-densified composites’ thermal conductivity is matrix cracking’s density, followed by volume fraction of the bundle and thermal conductance of the matrix cracks, finally by micro-porosity inside the bundles and macro-porosity between the bundles. The obtained results are well consistent with the reported data, thus our models could be useful for designing the processing and performance of the CVI-densified composites. PMID:28774130

Three-dimensional gas exchange pathways in pome fruit characterized by synchrotron x-ray computed tomography.

PubMed

Verboven, Pieter; Kerckhofs, Greet; Mebatsion, Hibru Kelemu; Ho, Quang Tri; Temst, Kristiaan; Wevers, Martine; Cloetens, Peter; Nicolaï, Bart M

2008-06-01

Our understanding of the gas exchange mechanisms in plant organs critically depends on insights in the three-dimensional (3-D) structural arrangement of cells and voids. Using synchrotron radiation x-ray tomography, we obtained for the first time high-contrast 3-D absorption images of in vivo fruit tissues of high moisture content at 1.4-microm resolution and 3-D phase contrast images of cell assemblies at a resolution as low as 0.7 microm, enabling visualization of individual cell morphology, cell walls, and entire void networks that were previously unknown. Intercellular spaces were always clear of water. The apple (Malus domestica) cortex contains considerably larger parenchyma cells and voids than pear (Pyrus communis) parenchyma. Voids in apple often are larger than the surrounding cells and some cells are not connected to void spaces. The main voids in apple stretch hundreds of micrometers but are disconnected. Voids in pear cortex tissue are always smaller than parenchyma cells, but each cell is surrounded by a tight and continuous network of voids, except near brachyssclereid groups. Vascular and dermal tissues were also measured. The visualized network architecture was consistent over different picking dates and shelf life. The differences in void fraction (5.1% for pear cortex and 23.0% for apple cortex) and in gas network architecture helps explain the ability of tissues to facilitate or impede gas exchange. Structural changes and anisotropy of tissues may eventually lead to physiological disorders. A combined tomography and internal gas analysis during growth are needed to make progress on the understanding of void formation in fruit.

Void initiation from interfacial debonding of spherical silicon particles inside a silicon-copper nanocomposite: a molecular dynamics study

NASA Astrophysics Data System (ADS)

Cui, Yi; Chen, Zengtao

2017-02-01

Silicon particles with diameters from 1.9 nm to 30 nm are embedded in a face-centered-cubic copper matrix to form nanocomposite specimens for simulation. The interfacial debonding of silicon particles from the copper matrix and the subsequent growth of nucleated voids are studied via molecular dynamics (MD). The MD results are examined from several different perspectives. The overall mechanical performance is monitored by the average stress-strain response and the accumulated porosity. The ‘relatively farthest-traveled’ atoms are identified to characterize the onset of interfacial debonding. The relative displacement field is plotted to illustrate both subsequent interfacial debonding and the growth of a nucleated void facilitated by a dislocation network. Our results indicate that the initiation of interfacial debonding is due to the accumulated surface stress if the matrix is initially dislocation-free. However, pre-existing dislocations can make a considerable difference. In either case, the dislocation emission also contributes to the subsequent debonding process. As for the size effect, the debonding of relatively larger particles causes a drop in the stress-strain curve. The volume fraction of second-phase particles is found to be more influential than the size of the simulation box on the onset of interfacial debonding. The volume fraction of second-phase particles also affects the shape of the nucleated void and, therefore, influences the stress response of the composite.

Efficiently mapping structure-property relationships of gas adsorption in porous materials: application to Xe adsorption.

PubMed

Kaija, A R; Wilmer, C E

2017-09-08

Designing better porous materials for gas storage or separations applications frequently leverages known structure-property relationships. Reliable structure-property relationships, however, only reveal themselves when adsorption data on many porous materials are aggregated and compared. Gathering enough data experimentally is prohibitively time consuming, and even approaches based on large-scale computer simulations face challenges. Brute force computational screening approaches that do not efficiently sample the space of porous materials may be ineffective when the number of possible materials is too large. Here we describe a general and efficient computational method for mapping structure-property spaces of porous materials that can be useful for adsorption related applications. We describe an algorithm that generates random porous "pseudomaterials", for which we calculate structural characteristics (e.g., surface area, pore size and void fraction) and also gas adsorption properties via molecular simulations. Here we chose to focus on void fraction and Xe adsorption at 1 bar, 5 bar, and 10 bar. The algorithm then identifies pseudomaterials with rare combinations of void fraction and Xe adsorption and mutates them to generate new pseudomaterials, thereby selectively adding data only to those parts of the structure-property map that are the least explored. Use of this method can help guide the design of new porous materials for gas storage and separations applications in the future.

The Packing of Helical and Zigzag Chains and Distribution of Interstitial Voids in Expanded Liquid Se near the Semiconductor to Metal Transition

NASA Astrophysics Data System (ADS)

Maruyama, Kenji; Hiroi (Sato), Satoshi; Endo, Hirohisa; Hoshino, Hideoki; Odagaki, Takashi; Hensel, Friedrich

2017-08-01

The reverse Monte Carlo (RMC) and Voronoi-Delaunay (VD) void analyses were applied to study the modification of chain geometries near the semiconductor (SC) to metal (M) transition in expanded liquid Se along the isochore of d = 3.4 g/cm3. Fluctuations of dihedral angles with increasing temperature and pressure cause modification of the helical (H) chain to the planar zigzag (Z) chain conformations. The distribution of voids size (rV ) supported by chain segments and distances to the 4th 6th neighbor atoms on the chain segments provide information on the stacking of planar zigzag chains compensated by empty space (L-voids, rV 3.6 Å) which leads to the formation of metallic domains. Near SC-M transition region the number fraction NZ/NH for Z and H chain segments increases.

Method for forming an in situ oil shale retort with horizontal free faces

DOEpatents

Ricketts, Thomas E.; Fernandes, Robert J.

1983-01-01

A method for forming a fragmented permeable mass of formation particles in an in situ oil shale retort is provided. A horizontally extending void is excavated in unfragmented formation containing oil shale and a zone of unfragmented formation is left adjacent the void. An array of explosive charges is formed in the zone of unfragmented formation. The array of explosive charges comprises rows of central explosive charges surrounded by a band of outer explosive charges which are adjacent side boundaries of the retort being formed. The powder factor of each outer explosive charge is made about equal to the powder factor of each central explosive charge. The explosive charges are detonated for explosively expanding the zone of unfragmented formation toward the void for forming the fragmented permeable mass of formation particles having a reasonably uniformly distributed void fraction in the in situ oil shale retort.

The Metallicity of Void Dwarf Galaxies

NASA Astrophysics Data System (ADS)

Kreckel, K.; Croxall, K.; Groves, B.; van de Weygaert, R.; Pogge, R. W.

2015-01-01

The current ΛCDM cosmological model predicts that galaxy evolution proceeds more slowly in lower density environments, suggesting that voids are a prime location to search for relatively pristine galaxies that are representative of the building blocks of early massive galaxies. To test the assumption that void galaxies are more pristine, we compare the evolutionary properties of a sample of dwarf galaxies selected specifically to lie in voids with a sample of similar isolated dwarf galaxies in average density environments. We measure gas-phase oxygen abundances and gas fractions for eight dwarf galaxies (Mr > -16.2), carefully selected to reside within the lowest density environments of seven voids, and apply the same calibrations to existing samples of isolated dwarf galaxies. We find no significant difference between these void dwarf galaxies and the isolated dwarf galaxies, suggesting that dwarf galaxy chemical evolution proceeds independent of the large-scale environment. While this sample is too small to draw strong conclusions, it suggests that external gas accretion is playing a limited role in the chemical evolution of these systems, and that this evolution is instead dominated mainly by the internal secular processes that are linking the simultaneous growth and enrichment of these galaxies.

Thermoelectric Properties of Poly(3-Hexylthiophene) Nanofiber Mat with a Large Void Fraction.

PubMed

Hiura, Shogo; Okada, Naoki; Wakui, Junma; Narita, Hikari; Kanehashi, Shinji; Shimomura, Takeshi

2017-04-28

The thermoelectric properties of a poly(3-hexylthiophene) (P3HT) nanofiber mat which has higher crystallinity-and thus exhibits larger carrier mobility-than a non-fibrous P3HT film, were investigated. No significant difference was observed in the maximum values of the power factor between the P3HT nanofiber mat and the P3HT film. However, the thermal conductivity of the nanofiber mat was less than half that of the film despite having almost the same electrical conductivity. This higher thermoelectric property of the nanofiber mat than the film is attributed to the existence of highly effective conducting pathways and a large void fraction, and the result means that the nanofiber mat was a good candidate for use as a thermoelectric material.

Luminosity distance in Swiss-cheese cosmology with randomized voids and galaxy halos

NASA Astrophysics Data System (ADS)

Flanagan, Éanna É.; Kumar, Naresh; Wasserman, Ira

2013-08-01

We study the fluctuations in luminosity distance due to gravitational lensing produced both by galaxy halos and large-scale voids. Voids are represented via a “Swiss-cheese” model consisting of a ΛCDM Friedmann-Robertson-Walker background from which a number of randomly distributed, spherical regions of comoving radius 35 Mpc are removed. A fraction of the removed mass is then placed on the shells of the spheres, in the form of randomly located halos. The halos are assumed to be nonevolving and are modeled with Navarro-Frenk-White profiles of a fixed mass. The remaining mass is placed in the interior of the spheres, either smoothly distributed or as randomly located halos. We compute the distribution of magnitude shifts using a variant of the method of Holz and Wald [Phys. Rev. D 58, 063501 (1998)], which includes the effect of lensing shear. In the two models we consider, the standard deviation of this distribution is 0.065 and 0.072 magnitudes and the mean is -0.0010 and -0.0013 magnitudes, for voids of radius 35 Mpc and the sources at redshift 1.5, with the voids chosen so that 90% of the mass is on the shell today. The standard deviation due to voids and halos is a factor ˜3 larger than that due to 35 Mpc voids alone with a 1 Mpc shell thickness, which we studied in our previous work. We also study the effect of the existence of evacuated voids, by comparing to a model where all the halos are randomly distributed in the interior of the sphere with none on its surface. This does not significantly change the variance but does significantly change the demagnification tail. To a good approximation, the variance of the distribution depends only on the mean column density of halos (halo mass divided by its projected area), the concentration parameter of the halos, and the fraction of the mass density that is in the form of halos (as opposed to smoothly distributed); it is independent of how the halos are distributed in space. We derive an approximate analytic formula for the variance that agrees with our numerical results to ≲20% out to z≃1.5, and that can be used to study the dependence on halo parameters.

BORAX V EXPONENTIAL EXPERIMENT

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

Kirn, F.S.; Hagen, J.I.

1963-04-01

The cadmium ratio was measured in an exponential mockup of Borax V as a function of the void fraction. The extent of voids, simulated by lengths of closed polyethylene tubes, ranged from 0 to 40%. The corresponding cadmium ratios ranged from 6.1 to 4.6. The exponential was also used to determine the radial flux pattern across a Borax-type fuel assembly and the fine flux detail in and around fuel rods. For a normal loading the maximum-to-average power generation across an assembly was 1.24. (auth)

Three-Dimensional Gas Exchange Pathways in Pome Fruit Characterized by Synchrotron X-Ray Computed Tomography1[C][W][OA

PubMed Central

Verboven, Pieter; Kerckhofs, Greet; Mebatsion, Hibru Kelemu; Ho, Quang Tri; Temst, Kristiaan; Wevers, Martine; Cloetens, Peter; Nicolaï, Bart M.

2008-01-01

Our understanding of the gas exchange mechanisms in plant organs critically depends on insights in the three-dimensional (3-D) structural arrangement of cells and voids. Using synchrotron radiation x-ray tomography, we obtained for the first time high-contrast 3-D absorption images of in vivo fruit tissues of high moisture content at 1.4-μm resolution and 3-D phase contrast images of cell assemblies at a resolution as low as 0.7 μm, enabling visualization of individual cell morphology, cell walls, and entire void networks that were previously unknown. Intercellular spaces were always clear of water. The apple (Malus domestica) cortex contains considerably larger parenchyma cells and voids than pear (Pyrus communis) parenchyma. Voids in apple often are larger than the surrounding cells and some cells are not connected to void spaces. The main voids in apple stretch hundreds of micrometers but are disconnected. Voids in pear cortex tissue are always smaller than parenchyma cells, but each cell is surrounded by a tight and continuous network of voids, except near brachyssclereid groups. Vascular and dermal tissues were also measured. The visualized network architecture was consistent over different picking dates and shelf life. The differences in void fraction (5.1% for pear cortex and 23.0% for apple cortex) and in gas network architecture helps explain the ability of tissues to facilitate or impede gas exchange. Structural changes and anisotropy of tissues may eventually lead to physiological disorders. A combined tomography and internal gas analysis during growth are needed to make progress on the understanding of void formation in fruit. PMID:18417636

Adequacy in voided urine cytology specimens: The role of volume and a repeat void upon predictive values for high-grade urothelial carcinoma.

PubMed

VandenBussche, Christopher J; Rosenthal, Dorothy L; Olson, Matthew T

2016-03-01

Adequacy assessment is one of the most controversial and overlooked components in the daily practice of cytopathology, because it is generally determined from limited samples. Because voided urine varies widely in terms of its volume and cellularity, there is little consensus about the proper role for these variables in assessing specimen adequacy. In this study, the authors explored the role of volume in voided urine specimens to determine whether it plays a role in determining adequacy for the detection of high-grade urothelial carcinoma. Voided urine specimens received at the authors' laboratory over the 9.5 years since the introduction of the Johns Hopkins Template for Reporting Urinary Cytopathology were analyzed for correlations between volume, specimen adequacy, and the diagnosis of high-grade malignancy. The same data set also was queried to determine whether a patient who provided a voided low-volume specimen could yield a higher volume specimen and thereby increase adequacy. In total, 15,731 voided urine specimens with a cumulative volume of 891 liters originating from 8594 individual patients were analyzed. Specimen adequacy increased linearly for each increment of volume submitted to the laboratory up to 30 mL, after which the correlation was nonlinear. Low-volume specimens below this cutoff also had lower fractions of specimens that were diagnosed as malignant or suspicious. Volume is an important component in the evaluation of adequacy for voided urine cytology specimens. © 2015 American Cancer Society.

High Fidelity BWR Fuel Simulations

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

Yoon, Su Jong

This report describes the Consortium for Advanced Simulation of Light Water Reactors (CASL) work conducted for completion of the Thermal Hydraulics Methods (THM) Level 3 milestone THM.CFD.P13.03: High Fidelity BWR Fuel Simulation. High fidelity computational fluid dynamics (CFD) simulation for Boiling Water Reactor (BWR) was conducted to investigate the applicability and robustness performance of BWR closures. As a preliminary study, a CFD model with simplified Ferrule spacer grid geometry of NUPEC BWR Full-size Fine-mesh Bundle Test (BFBT) benchmark has been implemented. Performance of multiphase segregated solver with baseline boiling closures has been evaluated. Although the mean values of void fractionmore » and exit quality of CFD result for BFBT case 4101-61 agreed with experimental data, the local void distribution was not predicted accurately. The mesh quality was one of the critical factors to obtain converged result. The stability and robustness of the simulation was mainly affected by the mesh quality, combination of BWR closure models. In addition, the CFD modeling of fully-detailed spacer grid geometry with mixing vane is necessary for improving the accuracy of CFD simulation.« less

Modeling of the Edwards pipe experiment

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

Tiselj, I.; Petelin, S.

1995-12-31

The Edwards pipe experiment is used as one of the basic benchmarks for the two-phase flow codes due to its simple geometry and the wide range of phenomena that it covers. Edwards and O`Brien filled 4-m-long pipe with liquid water at 7 MPa and 502 K and ruptured one end of the tube. They measured pressure and void fraction during the blowdown. Important phenomena observed were pressure rarefaction wave, flashing onset, critical two-phase flow, and void fraction wave. Experimental data were used to analyze the capabilities of the RELAP5/MOD3.1 six-equation two-phase flow model and to examine two different numerical schemes:more » one from the RELAP5/MOD3.1 code and one from our own code, which was based on characteristic upwind discretization.« less

Propagation of Pressure Waves, Caused by a Thermal Shock, in Liquid Metals Containing Gas Bubbles

NASA Astrophysics Data System (ADS)

Okita, Kohei; Takagi, Shu; Matsumoto, Yoichiro

The propagation of pressure waves caused by a thermal shock in liquid mercury containing micro gas bubbles has been simulated numerically. In the present study, we clarify the influences of the introduced bubble size and void fraction on the absorption of thermal expansion of liquid mercury and attenuation of pressure waves. The mass, momentum and energy conservation equations for both bubbly mixture and gas inside each bubble are solved, in which the bubble dynamics is represented by the Keller equation. The results show that when the initial void fraction is larger than the rate of the thermal expansion of liquid mercury, the pressure rise caused by the thermal expansion decreases with decreasing the bubble radius, because of the increase of the natural frequency of bubbly mixture. On the other hand, as the bubble radius increases, the peak of pressure waves which propagate at the sound speed of mixture decreases gradually due to the dispersion effect of mixture. When the natural frequency of the mixture with large bubbles is lower than that of the thremal shock, the peak pressure at the wall increases because the pressure waves propagate through the mixture at the sound speed of liquid mercury. The comparison of the results with and without heat transfer through the gas liquid interface shows that the pressure waves are attenuated greatly by the thermal damping effect with the decrease of the void fraction which enhances the nonlinearity of bubble oscillation.

Optimisation des proprietes physiques d'un composite carbone epoxy fabrique par le procede RFI

NASA Astrophysics Data System (ADS)

Koanda, Mahamat Mamadou Lamine

The RFI (Resin Film Infusion) process is a composite materials manufacturing process. Especially known for the small investment it requires, RFI processes are more and more widely used in the aeronautical industry. However a number of aspects of this process are still not well controlled. The quality of the final part depends on which process is used. In the case of RFI, controlling physical characteristics such as thickness, fiber volume fraction or void content remains a major challenge. This dissertation deals with the optimization of the physical properties of a carbon composite manufactured with RFI processes. The ASTMD3171 and ASTMD792 standards were used to measure the void content and fiber volume fraction. First, we introduced different layup sequences in the RFI process and evaluate their impact on the physical properties of the final product. The experiments show the primary mode A, with the resin film at the bottom, resulting in much better quality with controlled fiber volume fraction and void content. Mode B (film in the symmetrical plane) yields results identical to mode A except more irregular thicknesses. Mode C (symmetrical film in the laminate) produces locally unacceptable void contents. Mode D (resin film on the top of the laminate) yields much better results than mode A with the exception of the more irregular thicknesses. Making gaps and overlaps with the resin film has negative effects beyond 2.54cm (one inch) and should be avoided. Several C-scan observations of the manufactured samples showed a large accumulation of porosity in the resin rich areas, as well as surface defects. Ultimately we analyzed the cure cycle in light of the thermodynamic porosity models. It is evident that the diffusion phenomenon is essential in this process. Therefore a better conditioning of the resin film made by Cytec is required. An optimal design with a cycle stop and pressure lag yields the optimal cure cycle for the RFI process.

Location-dependent correlation between tissue structure and the mechanical behaviour of the urinary bladder.

PubMed

Morales-Orcajo, Enrique; Siebert, Tobias; Böl, Markus

2018-05-25

The mechanical properties of the urinary bladder wall are important to understand its filling-voiding cycle in health and disease. However, much remains unknown about its mechanical properties, especially regarding regional heterogeneities and wall microstructure. The present study aimed to assess the regional differences in the mechanical properties and microstructure of the urinary bladder wall. Ninety (n=90) samples of porcine urinary bladder wall (ten samples from nine different locations) were mechanically and histologically analysed. Half of the samples (n=45) were equibiaxially tested within physiological conditions, and the other half, matching the sample location of the mechanical tests, was frozen, cryosectioned, and stained with Picro-Sirius red to differentiate smooth muscle cells, extracellular matrix, and fat. The bladder wall shows a non-linear stress-stretch relationship with hysteresis and softening effects. Regional differences were found in the mechanical response and in the microstructure. The trigone region presents higher peak stresses and thinner muscularis layer compared to the rest of the bladder. Furthermore, the ventral side of the bladder presents anisotropic characteristics, whereas the dorsal side features perfect isotropic behaviour. This response matches the smooth muscle fibre bundle orientation within the tunica muscularis. This layer, comprising approximately 78% of the wall thickness, is composed of two fibre bundle arrangements that are cross-oriented, one with respect to the other, varying the angle between them across the organ. That is, the ventral side presents a 60°/120° cross-orientation structure, while the muscle bundles were oriented perpendicular in the dorsal side. In the present study, we demonstrate that the mechanical properties and the microstructure of the urinary bladder wall are heterogeneous across the organ. The mechanical properties and the microstructure of the urinary bladder wall within nine specific locations matching explicitly the mechanical and structural variations have been examined. On the one hand, the results of this study contribute to the understanding of bladder mechanics and thus to their functional understanding of bladder filling and voiding. On the other hand, they are relevant to the fields of constitutive formulation of bladder tissue, whole bladder mechanics, and bladder-derived scaffolds i.e., tissue-engineering grafts. Copyright © 2018 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

A Factorial Design Approach to Analyse the Effect of Coarse Recycled Concrete Aggregates on the Properties of Hot Mix Asphalt

NASA Astrophysics Data System (ADS)

Tanty, Kiranbala; Mukharjee, Bibhuti Bhusan; Das, Sudhanshu Shekhar

2018-06-01

The present study investigates the effect of replacement of coarse fraction of natural aggregates by recycled concrete aggregates on the properties of hot mix asphalt (HMA) using general factorial design approach. For this two factors i.e. recycled coarse aggregates percentage [RCA (%)] and bitumen content percentage [BC (%)] are considered. Tests have been carried out on the HMA type bituminous concrete, prepared with varying RCA (%) and BC (%). Analysis of variance has been performed on the experimental data to determine the effect of the chosen factors on various parameters such as stability, flow, air void, void mineral aggregate, void filled with bitumen and bulk density. The study depicts that RCA (%) and BC (%) have significant effect on the selected responses as p value is less than the chosen significance level. In addition to above, the outcomes of the statistical analysis indicate that interaction between factors have significant effects on void mineral aggregate and bulk density of bituminous concrete.

A Factorial Design Approach to Analyse the Effect of Coarse Recycled Concrete Aggregates on the Properties of Hot Mix Asphalt

NASA Astrophysics Data System (ADS)

Tanty, Kiranbala; Mukharjee, Bibhuti Bhusan; Das, Sudhanshu Shekhar

2018-02-01

The present study investigates the effect of replacement of coarse fraction of natural aggregates by recycled concrete aggregates on the properties of hot mix asphalt (HMA) using general factorial design approach. For this two factors i.e. recycled coarse aggregates percentage [RCA (%)] and bitumen content percentage [BC (%)] are considered. Tests have been carried out on the HMA type bituminous concrete, prepared with varying RCA (%) and BC (%). Analysis of variance has been performed on the experimental data to determine the effect of the chosen factors on various parameters such as stability, flow, air void, void mineral aggregate, void filled with bitumen and bulk density. The study depicts that RCA (%) and BC (%) have significant effect on the selected responses as p value is less than the chosen significance level. In addition to above, the outcomes of the statistical analysis indicate that interaction between factors have significant effects on void mineral aggregate and bulk density of bituminous concrete.

A Comparison of the Properties of Carbon Fiber Epoxy Composites Produced by Non-autoclave with Vacuum Bag Only Prepreg and Autoclave Process

NASA Astrophysics Data System (ADS)

Park, Sang Yoon; Choi, Chi Hoon; Choi, Won Jong; Hwang, Seong Soon

2018-05-01

The non-autoclave curing technique with vacuum bag only (VBO) prepreg has been conceived as a cost-effective manufacturing method for producing high-quality composite part. This study demonstrated the feasibility of improving composite part's performances and established the effective mitigation strategies for manufacturing induced defects, such as internal voids and surface porosity. The experimental results highlighted the fact that voids and surface porosity were clearly dependent on the resin viscosity state at an intermediate dwell stage of the curing process. Thereafter, the enhancement of resin flow could lead to achieving high quality parts with minimal void content (1.3%) and high fiber fraction (53 vol.%). The mechanical testing showed comparable in-plane shear and compressive strength to conventional autoclave. The microscopic observations also supported the evidence of improved interfacial bonding in terms of excellent fiber wet-out and minimal void content for the optimized cure cycle condition.

The effectiveness of transcutaneous electrical neural stimulation therapy in patients with urinary incontinence resistant to initial medical treatment or biofeedback.

PubMed

Tugtepe, H; Thomas, D T; Ergun, R; Kalyoncu, A; Kaynak, A; Kastarli, C; Dagli, T E

2015-06-01

While there are many options for children with treatment refractory urinary incontinence, there is no single accepted method. This study's aim was to prospectively evaluate the effect of transcutaneous electrical nerve stimulation in children with urinary incontinence resistant to standard medical, urological therapy and/or biofeedback. This study was performed at a university hospital. For inclusion, patients >5 years of age first underwent evaluation with urinary ultrasonography, uroflow-electromyogram and voiding diaries. Treatment with biofeedback, alpha adrenergic blockers, anticholinergics and/or urotherapy was commenced according to uroflow-EMG and voiding diary findings. Patients with partial or no response to this standard therapy were then included in this study, performed between April 2012 and February 2014. Patients with anatomical or neurological causes for urinary incontinence were excluded. TENS was performed on S3 dermatome, every day for 3 months. Each session lasted 20 min with a frequency of 10 Hz and generated pulse of 350 μs. Intensity was determined by the child's sensitivity threshold. Medical treatment and urological therapy was continued during TENS. Uroflow parameters (voiding volume as percentage of expected bladder capacity, Qmax, Qave, flow and voiding time, postvoiding residual urine) and urinary system symptoms (presence of urinary tract infection, frequency, urge incontinence, fractionated voiding and constipation) were compared immediately before commencement and immediately after the completion of 3 months of TENS. Twenty-seven patients were included in this study (4 males, 23 females). Patients' average age was 7.2 years, 11 had overactive bladder and 16 had dysfunctional voiding. Comparison of urinary system symptoms and uroflow parameters before and after TENS are shown in Table. After 3 months of TENS; a statistically significant decrease was observed in the number of patients with frequency, urge incontinence, urinary tract infections and constipation. There was a decrease in the number of patients with fractionated voiding, although this change was not statistically significant. Similarly, for uroflow-EMG parameters; bladder capacity, Qmax, Qave and flow time increased while voiding time and PVR decreased. Changes seen in bladder capacity, Qmax and PVR were statically significant, while other changes were not. Patients' response rates after 3 months of TENS were; complete response in 70.4%, partial response in 22.2% and no response in 7.4%. This study has shown that transcutaneous electrical nerve stimulation is a promising treatment option for standard-treatment refractory children with urinary incontinence. Copyright © 2015 Journal of Pediatric Urology Company. Published by Elsevier Ltd. All rights reserved.

Recognition and measurement gas-liquid two-phase flow in a vertical concentric annulus at high pressures

NASA Astrophysics Data System (ADS)

Li, Hao; Sun, Baojiang; Guo, Yanli; Gao, Yonghai; Zhao, Xinxin

2018-02-01

The air-water flow characteristics under pressure in the range of 1-6 MPa in a vertical annulus were evaluated in this report. Time-resolved bubble rising velocity and void fraction were also measured using an electrical void fraction meter. The results showed that the pressure has remarkable effect on the density, bubble size and rise velocity of the gas. Four flow patterns (bubble, cap-bubble, cap-slug, and churn) were also observed instead of Taylor bubble at high pressure. Additionally, the transition process from bubble to cap-bubble was investigated at atmospheric and high pressures, respectively. The results revealed that the flow regime transition criteria for atmospheric pressure do not work at high pressure, hence a new flow regime transition model for annular flow channel geometry was developed to predict the flow regime transition, which thereafter exhibited high accuracy at high pressure condition.

Flow and fouling in membrane filters: Effects of membrane morphology

NASA Astrophysics Data System (ADS)

Sanaei, Pejman; Cummings, Linda J.

2015-11-01

Membrane filters are widely-used in microfiltration applications. Many types of filter membranes are produced commercially, for different filtration applications, but broadly speaking the requirements are to achieve fine control of separation, with low power consumption. The answer to this problem might seem obvious: select the membrane with the largest pore size and void fraction consistent with the separation requirements. However, membrane fouling (an inevitable consequence of successful filtration) is a complicated process, which depends on many parameters other than membrane pore size and void fraction; and which itself greatly affects the filtration process and membrane functionality. In this work we formulate mathematical models that can (i) account for the membrane internal morphology (internal structure, pore size & shape, etc.); (ii) fouling of membranes with specific morphology; and (iii) make some predictions as to what type of membrane morphology might offer optimum filtration performance.

Optimization of Energy Consumption and Mass Transfer Parameters in a Surface Aeration Vessel.

PubMed

Mohammadpour, A; AkhavanBehabadi, M A; Ebrahimzadeh, M; Raisee, M; MajdiNasab, A R; Nosrati, M; Mousavi, S M

2016-04-01

This paper reports tests on a lab-scale surface aeration vessel was equipped with a Rushton turbine to examine its performance in terms of standard aeration efficiency (SAE), mixing time, and void fraction characteristics. These characteristics were investigated by tests using variations of rotor speed, impeller immersion depth, and water level. Results showed that variation of impeller immersion depth had a greater effect on the SAE compared to variation of water level. Moreover, the SAE increased with rotor speeds up to about 150 to 200 rpm and then decreased. In addition, void fraction improved by impeller immersion depth and rotor speed enhancement; however, mixing time and power number were reduced as rotor speed increased. According to the response surface methodology statistical optimizations, optimum values for rotor speed, impeller immersion depth, and water level were 168.90 rpm, 25 mm, and 30 cm, respectively, to achieve the maximum value of SAE.

Stationary organization of the actin cytoskeleton in Vallisneria: the role of stable microfilaments at the end walls.

PubMed

Ryu, J H; Takagi, S; Nagai, R

1995-04-01

In mesophyll cells of the aquatic angiosperm Vallisneria gigantea, bundles of microfilaments (MFs) serve as tracks for the rotational streaming of the cytoplasm, which occurs along the two longer side walls and the two shorter end walls. The stationary organization of these bundles has been shown to depend on the association of the bundles with the plasma membrane at the end walls. To identify the sites of such association, the effects of cytochalasin B (CB) on the configuration of the bundles of MFs were examined. In the case of the side walls, MFs were completely disrupted after treatment with CB at 100 micrograms/ml for 24 hours. By contrast, in the case of the end walls, a number of partially disrupted MFs remained even after 48 hours of treatment. After removal of CB, a completely normal arrangement of bundles of MFs was once again evident within 24 hours after a rather complicated process of reassembly. When reassembly had been completed, the direction of cytoplasmic streaming was reversed only in a small fraction of the treated cells, suggesting that bundles of MFs are anchored and stabilized at the end walls of each cell and that the polarity of reorganized bundles and, therefore, the direction of the cytoplasmic streaming is determined in a manner that depends on the original polarity of MFs that remained in spite of the disruptive action of CB. By contrast, the direction of reinitiated cytoplasmic streaming was reversed in 50% of cells in which the bundles of MFs had been completely disrupted by exogenously applied trypsin prior treatment with CB.(ABSTRACT TRUNCATED AT 250 WORDS)

Validation of Measured Damping Trends for Flight-Like Vehicle Panel/Equipment including a Range of Cable Harness Assemblies

NASA Technical Reports Server (NTRS)

Smith, Andrew M.; Davis, R. Benjamin; LaVerde, Bruce T.; Fulcher, Clay W.; Jones, Douglas C.; Waldon, James M.; Craigmyle, Benjamin B.

2012-01-01

This validation study examines the effect on vibroacoustic response resulting from the installation of cable bundles on a curved orthogrid panel. Of interest is the level of damping provided by the installation of the cable bundles and whether this damping could be potentially leveraged in launch vehicle design. The results of this test are compared with baseline acoustic response tests without cables. Damping estimates from the measured response data are made using a new software tool that leverages a finite element model of the panel in conjunction with advanced optimization techniques. While the full test series is not yet complete, the first configuration of cable bundles that was assessed effectively increased the viscous critical damping fraction of the system by as much as 0.02 in certain frequency ranges.

Bubble velocity, diameter, and void fraction measurements in a multiphase flow using fiber optic reflectometer

NASA Astrophysics Data System (ADS)

Lim, Ho-Joon; Chang, Kuang-An; Su, Chin B.; Chen, Chi-Yueh

2008-12-01

A fiber optic reflectometer (FOR) technique featuring a single fiber probe is investigated for its feasibility of measuring the bubble velocity, diameter, and void fraction in a multiphase flow. The method is based on the interference of the scattered signal from the bubble surface with the Fresnel reflection signal from the tip of the optical fiber. Void fraction is obtained with a high accuracy if an appropriate correction is applied to compensate the underestimated measurement value. Velocity information is accurately obtained from the reflected signals before the fiber tip touches the bubble surface so that several factors affecting the traditional dual-tip probes such as blinding, crawling, and drifting effects due to the interaction between the probe and bubbles can be prevented. The coherent signals reflected from both the front and rear ends of a bubble can provide velocity information. Deceleration of rising bubbles and particles due to the presence of the fiber probe is observed when they are very close to the fiber tip. With the residence time obtained, the bubble chord length can be determined by analyzing the coherent signal for velocity determination before the deceleration starts. The bubble diameters are directly obtained from analyzing the signals of the bubbles that contain velocity information. The chord lengths of these bubbles measured by FOR represent the bubble diameters when the bubble shape is spherical or represent the minor axes when the bubble shape is ellipsoidal. The velocity and size of bubbles obtained from the FOR measurements are compared with those obtained simultaneously using a high speed camera.

Hyperuniformity, quasi-long-range correlations, and void-space constraints in maximally random jammed particle packings. II. Anisotropy in particle shape.

PubMed

Zachary, Chase E; Jiao, Yang; Torquato, Salvatore

2011-05-01

We extend the results from the first part of this series of two papers by examining hyperuniformity in heterogeneous media composed of impenetrable anisotropic inclusions. Specifically, we consider maximally random jammed (MRJ) packings of hard ellipses and superdisks and show that these systems both possess vanishing infinite-wavelength local-volume-fraction fluctuations and quasi-long-range pair correlations scaling as r(-(d+1)) in d Euclidean dimensions. Our results suggest a strong generalization of a conjecture by Torquato and Stillinger [Phys. Rev. E 68, 041113 (2003)], namely, that all strictly jammed saturated packings of hard particles, including those with size and shape distributions, are hyperuniform with signature quasi-long-range correlations. We show that our arguments concerning the constrained distribution of the void space in MRJ packings directly extend to hard-ellipse and superdisk packings, thereby providing a direct structural explanation for the appearance of hyperuniformity and quasi-long-range correlations in these systems. Additionally, we examine general heterogeneous media with anisotropic inclusions and show unexpectedly that one can decorate a periodic point pattern to obtain a hard-particle system that is not hyperuniform with respect to local-volume-fraction fluctuations. This apparent discrepancy can also be rationalized by appealing to the irregular distribution of the void space arising from the anisotropic shapes of the particles. Our work suggests the intriguing possibility that the MRJ states of hard particles share certain universal features independent of the local properties of the packings, including the packing fraction and average contact number per particle.

Towards the damage evaluation using Gurson-Tvergaard-Needleman (GTN) model for hot forming processes

NASA Astrophysics Data System (ADS)

Imran, Muhammad; Bambach, Markus

2018-05-01

In the production of semi-finished metal products, hot forming is used to eliminate the pores and voids from the casting process under compressive stresses and to modify the microstructure for further processing. In the case of caliber and flat rolling processes, tensile stresses occur at certain roll gap ratios which promote pore formation on nonmetallic inclusion. The formation of new pores contributes to ductile damage and reduces the load carrying capacity of the material. In the literature, the damage nucleation and growth during the hot forming process are not comprehensively described. The aim of this study is to understand the damage initiation and growth mechanism during hot forming processes. Hot tensile tests are performed at different temperatures and strain rates for 16MnCrS5 steel. To investigate the influence of geometrical variations on the damage mechanism, specimens with different stress triaxiality ratios are used. Finite element simulations using the Gurson-Tvergaard-Needleman (GTN) damage model are performed to estimate the critical void fraction for the damage initiation and the evolution of the void volume fraction. The results showed that the GTN model underestimates the softening of the material due to the independence of the temperature and the strain rate.

Probabilistic immortality of Cu damascene interconnects

NASA Astrophysics Data System (ADS)

Hau-Riege, Stefan P.

2002-02-01

We have studied electromigration short-line effects in Cu damascene interconnects through experiments on lines of various lengths L, stressed at a variety of current densities j, and embedded in different dielectric materials. We observed two modes of resistance evolution: Either the resistance of the lines remains constant for the duration of the test, so that the lines are considered immortal, or the lines fail due to abrupt open-circuit failure. The resistance was not observed to gradually increase and then saturate, as commonly observed in Al-based interconnects, because the barrier is too thin and resistive to serve as a redundant current path should voiding occur. The critical stress for void nucleation was found to be smaller than 41 MPa, since voiding occurred even under the mildest test conditions of j=2 MA/cm2 and L=10.5 μm at 300 °C. A small fraction of short Cu lines failed even at low current densities, which deems necessary a concept of probabilistic immortality rather than deterministic immortality. Experiments and modeling suggest that the probability of immortality is described by (jL2/B), where B is the effective elastic modulus of the metallization scheme. By contrast, the immortality of Al-based interconnects with shunt layers is described by (jL) if no voids nucleate, and (jL/B) if voids do nucleate. Even though the phenomenology of short-line effects differs for Al- and Cu-based interconnects, the immortality of interconnects of either materials system can be explained by the phenomena of nucleation barriers for void formation and void-growth saturation. The differences are due solely to the absence of a shunt layer and the low critical stress for void nucleation in the case of Cu.

Adsorption site analysis of impurity embedded single-walled carbon nanotube bundles

USGS Publications Warehouse

Agnihotri, S.; Mota, J.P.B.; Rostam-Abadi, M.; Rood, M.J.

2006-01-01

Bundle morphology and adsorptive contributions from nanotubes and impurities are studied both experimentally and by simulation using a computer-aided methodology, which employs a small physisorbed probe molecule to explore the porosity of nanotube samples. Grand canonical Monte Carlo simulation of nitrogen adsorption on localized sites of a bundle is carried out to predict adsorption in its accessible internal pore volume and on its external surface as a function of tube diameter. External adsorption is split into the contributions from the clean surface of the outermost nanotubes of the bundle and from the surface of the impurities. The site-specific isotherms are then combined into a global isotherm for a given sample using knowledge of its tube-diameter distribution obtained by Raman spectroscopy. The structural parameters of the sample, such as the fraction of open-ended nanotubes and the contributions from impurities and nanotube bundles to total external surface area, are determined by fitting the experimental nitrogen adsorption data to the simulated isotherm. The degree of closure between experimental and calculated adsorption isotherms for samples manufactured by two different methods, to provide different nanotube morphology and contamination level, further strengthens the validity and resulting interpretations based on the proposed approach. The average number of nanotubes per bundle and average bundle size, within a sample, are also quantified. The proposed method allows for extrapolation of adsorption properties to conditions where the purification process is 100% effective at removing all impurities and opening access to all intrabundle adsorption sites. ?? 2006 Elsevier Ltd. All rights reserved.

Damage percolation during stretch flange forming of aluminum alloy sheet

NASA Astrophysics Data System (ADS)

Chen, Zengtao; Worswick, Michael J.; Keith Pilkey, A.; Lloyd, David J.

2005-12-01

A multi-scale finite element (FE)-damage percolation model was employed to simulate stretch flange forming of aluminum alloys AA5182 and AA5754. Material softening and strain gradients were captured using a Gurson-based FE model. FE results were then fed into the so-called damage percolation code, from which the damage development was modelled within measured microstructures. The formability of the stretch flange samples was predicted based upon the onset of catastrophic failure triggered by profuse void coalescence within the measured second-phase particle field. Damage development is quantified in terms of crack and void areal fractions, and compared to metallographic results obtained from interrupted stretch flange specimens. Parametric study is conducted on the effect of void nucleation strain in the prediction of formability of stretch flanges to "calibrate" proper nucleation strains for both alloys.

Geometrical and Mechanical Properties Control Actin Filament Organization

PubMed Central

Ennomani, Hajer; Théry, Manuel; Nedelec, Francois; Blanchoin, Laurent

2015-01-01

The different actin structures governing eukaryotic cell shape and movement are not only determined by the properties of the actin filaments and associated proteins, but also by geometrical constraints. We recently demonstrated that limiting nucleation to specific regions was sufficient to obtain actin networks with different organization. To further investigate how spatially constrained actin nucleation determines the emergent actin organization, we performed detailed simulations of the actin filament system using Cytosim. We first calibrated the steric interaction between filaments, by matching, in simulations and experiments, the bundled actin organization observed with a rectangular bar of nucleating factor. We then studied the overall organization of actin filaments generated by more complex pattern geometries used experimentally. We found that the fraction of parallel versus antiparallel bundles is determined by the mechanical properties of actin filament or bundles and the efficiency of nucleation. Thus nucleation geometry, actin filaments local interactions, bundle rigidity, and nucleation efficiency are the key parameters controlling the emergent actin architecture. We finally simulated more complex nucleation patterns and performed the corresponding experiments to confirm the predictive capabilities of the model. PMID:26016478

Microstructure of Desmanthus illinoensis

USDA-ARS?s Scientific Manuscript database

Structure and histochemistry of mature seeds of Desmanthus illinoensis (Illinois bundle flower) show that the seed has typical legume structure. The seed can be separated into two major fractions including the seed coat/endosperm and the embryo. The seed coat consists of a cuticle, palisade sclereid...

Effects of an Isolated Complete Right Bundle Branch Block on Mechanical Ventricular Function.

PubMed

Zhang, Qin; Xue, Minghua; Li, Zhan; Wang, Haiyan; Zhu, Lei; Liu, Xinling; Meng, Haiyan; Hou, Yinglong

2015-12-01

The purpose of this study was to investigate the effects of an isolated complete right bundle branch block on mechanical ventricular function. Two groups of participants were enrolled in this study: a block group, consisting of 98 patients with isolated complete right bundle branch blocks without structural heart disease, and a control group, consisting of 92 healthy adults. The diameter, end-diastolic area, end-systolic area, and right ventricular (RV) fractional area change were obtained to evaluate morphologic and systolic function by 2-dimensional sonographic technology. Systolic and diastolic velocities and time interval parameters were measured to assess mechanical ventricular performance using pulsed wave tissue Doppler imaging. Although there was no significant difference in the RV fractional area change between the patients with blocks and controls, the diameter, end-diastolic area, and end-systolic area of the RV were significantly larger in the patients with blocks (P < .05). In the patients with blocks, the peak velocities during systole and early diastole and the ratio of the peak velocities during early and late diastole decreased. The block group had a prolonged pre-ejection period, electromechanical delay time, and isovolumic relaxation time, a decreased ejection time, and an increased pre-ejection period/ejection time ratio, and the myocardial performance index (Tei index) at the basal RV lateral wall was significantly increased. There were no significant differences in any echocardiographic parameters at different sites of the left ventricle. In patients with isolated complete right bundle branch blocks, systolic and diastolic functions are impaired in the RV, and follow-up is needed. © 2015 by the American Institute of Ultrasound in Medicine.

Luminosity distance in ``Swiss cheese'' cosmology with randomized voids. II. Magnification probability distributions

NASA Astrophysics Data System (ADS)

Flanagan, Éanna É.; Kumar, Naresh; Wasserman, Ira; Vanderveld, R. Ali

2012-01-01

We study the fluctuations in luminosity distances due to gravitational lensing by large scale (≳35Mpc) structures, specifically voids and sheets. We use a simplified “Swiss cheese” model consisting of a ΛCDM Friedman-Robertson-Walker background in which a number of randomly distributed nonoverlapping spherical regions are replaced by mass-compensating comoving voids, each with a uniform density interior and a thin shell of matter on the surface. We compute the distribution of magnitude shifts using a variant of the method of Holz and Wald , which includes the effect of lensing shear. The standard deviation of this distribution is ˜0.027 magnitudes and the mean is ˜0.003 magnitudes for voids of radius 35 Mpc, sources at redshift zs=1.0, with the voids chosen so that 90% of the mass is on the shell today. The standard deviation varies from 0.005 to 0.06 magnitudes as we vary the void size, source redshift, and fraction of mass on the shells today. If the shell walls are given a finite thickness of ˜1Mpc, the standard deviation is reduced to ˜0.013 magnitudes. This standard deviation due to voids is a factor ˜3 smaller than that due to galaxy scale structures. We summarize our results in terms of a fitting formula that is accurate to ˜20%, and also build a simplified analytic model that reproduces our results to within ˜30%. Our model also allows us to explore the domain of validity of weak-lensing theory for voids. We find that for 35 Mpc voids, corrections to the dispersion due to lens-lens coupling are of order ˜4%, and corrections due to shear are ˜3%. Finally, we estimate the bias due to source-lens clustering in our model to be negligible.

Analyzing near infrared scattering from human skin to monitor changes in hematocrit

NASA Astrophysics Data System (ADS)

Chaiken, Joseph; Deng, Bin; Goodisman, Jerry; Shaheen, George; Bussjager, R. J.

2012-01-01

The leading preventable cause of death, world-wide, civilian or military, for all people between the ages of 18-45 is undetected internal hemorrhage. Autonomic compensation mechanisms mask changes such as e.g. hematocrit fluctuations that could give early warning if only they could be monitored continuously with reasonable degrees of precision and relative accuracy. Probing tissue with near infrared radiation (NIR) simultaneously produces remitted fluorescence and Raman scattering (IE) plus Rayleigh/Mie light scattering (EE) that noninvasively give chemical and physical information about the materials and objects within. We model tissue as a three-phase system: plasma and red blood cell (RBC) phases that are mobile and a static tissue phase. In vivo, any volume of tissue naturally experiences spatial and temporal fluctuations of blood plasma and RBC content. Plasma and RBC fractions may be discriminated from each other on the basis of their physical, chemical and optical properties. Thus IE and EE from NIR probing yield information about these fractions. Assuming there is no void volume in viable tissue, or that void volume is constant, changes in plasma and RBC volume fractions may be calculated from simultaneous measurements of the two observables, EE and IE. In a previously published analysis we showed the underlying phenomenology but did not provide an algorithm for calculating volume fractions from experimental data. Here we present a simple analysis that allows continuous monitoring of fluid fraction and hematocrit (Hct) changes by measuring IE and EE, and apply it to some experimental in vivo measurements.

The Relationship between Retinal Ganglion Cell Axon Constituents and Retinal Nerve Fiber Layer Birefringence in the Primate

PubMed Central

Pocock, Ginger M.; Aranibar, Roberto G.; Kemp, Nate J.; Specht, Charles S.; Markey, Mia K.; Rylander, H.G.

2009-01-01

Purpose To determine the degree of correlation between spatial characteristics of the retinal nerve fiber layer (RNFL) birefringence (ΔnRNFL) surrounding the optic nerve head (ONH) with the corresponding anatomy of retinal ganglion cell (RGC) axons and their respective organelles. Methods RNFL phase retardation per unit depth (PR/UD, proportional to ΔnRNFL) was measured in two cynomolgus monkeys using enhanced polarization-sensitive optical coherence tomography (EPS-OCT). The monkeys were perfused with glutaraldehyde and eyes were enucleated and prepared for transmission electron microscopy (TEM) histological analysis. Morphological measurements from TEM images were used to estimate values of neurotubule density (ρRNFL), axoplasmic area (Ax) mode, axon area (Aa) mode, slope (u) of neurotubule number versus axoplasmic area [neurotubule packing density], fractional area of axoplasm in the nerve fiber bundle (f), mitochondrial fractional area in the nerve fiber bundle (xm), mitochondriated axon profile fraction (mp), and length of axonal membrane profiles per unit nerve fiber bundle area (Lam/Ab). Registered PR/UD and morphological parameters from corresponding angular sections were then correlated using Pearson’s correlation and multi-level models. Results In one eye, there was a statistically significant correlation between PR/UD and ρRNFL (r = 0.67, P =0.005) and between PR/UD and neurotubule packing density (r = 0.70, P = 0.002). Correlation coefficients of r = 0.81 (P=0.01) and r = 0.50 (P = 0.05) were observed between PR/UD and (Ax) mode for each respective subject. Conclusion Neurotubules are the primary source of birefringence in the RNFL of the primate retina. PMID:19494208

Analysis of Fractional Flow for Transient Two-Phase Flow in Fractal Porous Medium

NASA Astrophysics Data System (ADS)

Lu, Ting; Duan, Yonggang; Fang, Quantang; Dai, Xiaolu; Wu, Jinsui

2016-03-01

Prediction of fractional flow in fractal porous medium is important for reservoir engineering and chemical engineering as well as hydrology. A physical conceptual fractional flow model of transient two-phase flow is developed in fractal porous medium based on the fractal characteristics of pore-size distribution and on the approximation that porous medium consist of a bundle of tortuous capillaries. The analytical expression for fractional flow for wetting phase is presented, and the proposed expression is the function of structural parameters (such as tortuosity fractal dimension, pore fractal dimension, maximum and minimum diameters of capillaries) and fluid properties (such as contact angle, viscosity and interfacial tension) in fractal porous medium. The sensitive parameters that influence fractional flow and its derivative are formulated, and their impacts on fractional flow are discussed.

Addressing safety through evaluation and optimization of permeable friction course mixtures.

DOT National Transportation Integrated Search

2010-01-01

Permeable friction course (PFC) mixtures are a special type of hot mix asphalt characterized by a : high total air voids content to guarantee proper functionality and stone-on-stone contact of the coarse : aggregate fraction to ensure adequate mixtur...

Micromechanical investigation of ductile failure in Al 5083-H116 via 3D unit cell modeling

NASA Astrophysics Data System (ADS)

Bomarito, G. F.; Warner, D. H.

2015-01-01

Ductile failure is governed by the evolution of micro-voids within a material. The micro-voids, which commonly initiate at second phase particles within metal alloys, grow and interact with each other until failure occurs. The evolution of the micro-voids, and therefore ductile failure, depends on many parameters (e.g., stress state, temperature, strain rate, void and particle volume fraction, etc.). In this study, the stress state dependence of the ductile failure of Al 5083-H116 is investigated by means of 3-D Finite Element (FE) periodic cell models. The cell models require only two pieces of information as inputs: (1) the initial particle volume fraction of the alloy and (2) the constitutive behavior of the matrix material. Based on this information, cell models are subjected to a given stress state, defined by the stress triaxiality and the Lode parameter. For each stress state, the cells are loaded in many loading orientations until failure. Material failure is assumed to occur in the weakest orientation, and so the orientation in which failure occurs first is considered as the critical orientation. The result is a description of material failure that is derived from basic principles and requires no fitting parameters. Subsequently, the results of the simulations are used to construct a homogenized material model, which is used in a component-scale FE model. The component-scale FE model is compared to experiments and is shown to over predict ductility. By excluding smaller nucleation events and load path non-proportionality, it is concluded that accuracy could be gained by including more information about the true microstructure in the model; emphasizing that its incorporation into micromechanical models is critical to developing quantitatively accurate physics-based ductile failure models.

Predicting efficiency of solar cells based on transparent conducting electrodes

NASA Astrophysics Data System (ADS)

Kumar, Ankush

2017-01-01

Efficiency of a solar cell is directly correlated with the performance of its transparent conducting electrodes (TCEs) which dictates its two core processes, viz., absorption and collection efficiencies. Emerging designs of a TCE involve active networks of carbon nanotubes, silver nanowires and various template-based techniques providing diverse structures; here, voids are transparent for optical transmittance while the conducting network acts as a charge collector. However, it is still not well understood as to which kind of network structure leads to an optimum solar cell performance; therefore, mostly an arbitrary network is chosen as a solar cell electrode. Herein, we propose a new generic approach for understanding the role of TCEs in determining the solar cell efficiency based on analysis of shadowing and recombination losses. A random network of wires encloses void regions of different sizes and shapes which permit light transmission; two terms, void fraction and equivalent radius, are defined to represent the TCE transmittance and wire spacings, respectively. The approach has been applied to various literature examples and their solar cell performance has been compared. To obtain high-efficiency solar cells, optimum density of the wires and their aspect ratio as well as active layer thickness are calculated. Our findings show that a TCE well suitable for one solar cell may not be suitable for another. For high diffusion length based solar cells, the void fraction of the network should be low while for low diffusion length based solar cells, the equivalent radius should be lower. The network with less wire spacing compared to the diffusion length behaves similar to continuous film based TCEs (such as indium tin oxide). The present work will be useful for architectural as well as material engineering of transparent electrodes for improvisation of solar cell performance.

An ultrasonic investigation of the effect of voids on the mechanical properties of bread dough and the role of gas cells in determining the cellular structure of freeze- dried breadcrumb

NASA Astrophysics Data System (ADS)

Elmehdi, Hussein Mohamed

This thesis is an analysis of voids in the breadmaking process, more specifically the effect of gas cells entrapped in the dough during mixing, their expansion during fermentation, and their relationship to the breadcrumb structure in the final product. This is important to food scientists because the voids ultimately influence the structural integrity of bread and hence its quality. Understanding how voids affect the viscoelastic properties of dough is also a challenging problem in soft condensed matter physics. Longitudinal ultrasonic velocity and attenuation measurements, performed at 54 kHz, investigated changes in the mechanical properties of dough and bread as void concentration was varied. In the first part of the thesis, the effect of voids on the properties of unyeasted dough at the end of mixing was investigated. As φ is increased, the attenuation coefficient increased linearly with φ hence the change in attenuation is proportional to the number of voids, allowing the combined effects of scattering and absorption by single voids to be directly determined. By contrast, the ultrasonic velocity decreased dramatically with increasing φ in the range 0.0 12 < φ < 0.03, while at higher φ, the velocity decrease was less rapid. An effective medium model successfully modeled the viscoelastic behavior of the dough at all void fraction values, provided that the shear modulus of the matrix was permitted to vary. The same ultrasonic technique was also used to monitor the increase in gas cell size due to CO 2 production during fermentation of yeasted dough. A large decrease in velocity and an increase in the attenuation coefficient were observed as the gas cells grew. In addition, at early fermentation times, a substantial contribution to the velocity decrease arises from a reduction in the shear modulus of the dough matrix. This occurs because the pH drops as CO2 molecules dissolve in the matrix and intermolecular interactions are weakened due to protein chain charge repulsion effects. In the second part of the thesis, freeze-dried breadcrumb structure was investigated. To change the size of the air cells, the dough was proofed for various times. Ultrasonic velocity and amplitude decrease with increasing φ. The experimental data were found to be in reasonable agreement with theoretical models for the elasticity of isotropic cellular foams and tortuosity. The effects of anisotropy in breadcrumb structure were studied by compressing samples uniaxially, thereby transforming the shape of the air cells from approximately spherical to elongated ellipsoids. Ultrasonic measurements were taken in the directions parallel and perpendicular to the strain. These results indicated that the path by which sound propagates is critical. The data were interpreted using the same two theoretical models, taking into account anisotropy effects. The tortuosity model was able to interpret the void fraction dependence of the velocity along the two orthogonal directions, thus giving a way of relating changes in ultrasonic velocity to changes in breadcrumb structure. This thesis demonstrates the potential for using ultrasound as a non-destructive, cheap and accurate tool for studying the effect of voids (and their expansion) on dough properties. These ultrasonic techniques can also be used to investigate the effect of air cells on the structural integrity of breadcrumb and hence be a useful tool for quantitatively assessing bread quality.

Implantable cardioverter defibrillator does not cure the heart.

PubMed

Sławuta, Agnieszka; Boczar, Krzysztof; Ząbek, Andrzej; Gajek, Jacek; Lelakowski, Jacek; Vijayaraman, Pugazhendhi; Małecka, Barbara

2018-01-23

A man with non-ischemic cardiomyopathy, EF 22%, permanent AF and ICD was admitted for elective device replacement. The need for the optimization of the ventricular rate and avoidance of right ventricular pacing made it necessary to up-grade the existing pacing system using direct His bundle pacing and dual chamber ICD. This enabled the regularization of ventricular rate, avoiding the RV pacing and optimize the beta-blocker dose. The one month follow-up already showed reduction in left ventricle diameter, improvement in ejection fraction, NYHA class decrease to II. The His bundle pacing enabled the optimal treatment of the patient resulting in excellent clinical improvement.

Electrical Resistivity Measurement of Petroleum Coke Powder by Means of Four-Probe Method

NASA Astrophysics Data System (ADS)

Rouget, G.; Majidi, B.; Picard, D.; Gauvin, G.; Ziegler, D.; Mashreghi, J.; Alamdari, H.

2017-10-01

Carbon anodes used in Hall-Héroult electrolysis cells are involved in both electrical and chemical processes of the cell. Electrical resistivity of anodes depends on electrical properties of its constituents, of which carbon coke aggregates are the most prevalent. Electrical resistivity of coke aggregates is usually characterized according to the ISO 10143 standardized test method, which consists of measuring the voltage drop in the bed of particles between two electrically conducing plungers through which the current is also applied. Estimation of the electrical resistivity of coke particles from the resistivity of particle bed is a challenging task and needs consideration of the contribution of the interparticle void fraction and the particle/particle contact resistances. In this work, the bed resistivity was normalized by subtracting the interparticle void fraction. Then, the contact size was obtained from discrete element method simulation and the contact resistance was calculated using Holm's theory. Finally, the resistivity of the coke particles was obtained from the bed resistivity.

A compact x-ray system for two-phase flow measurement

NASA Astrophysics Data System (ADS)

Song, Kyle; Liu, Yang

2018-02-01

In this paper, a compact x-ray densitometry system consisting of a 50 kV, 1 mA x-ray tube and several linear detector arrays is developed for two-phase flow measurement. The system is capable of measuring void fraction and velocity distributions with a spatial resolution of 0.4 mm per pixel and a frequency of 1000 Hz. A novel measurement model has been established for the system which takes account of the energy spectrum of x-ray photons and the beam hardening effect. An improved measurement accuracy has been achieved with this model compared with the conventional log model that has been widely used in the literature. Using this system, void fraction and velocity distributions are measured for a bubbly and a slug flow in a 25.4 mm I.D. air-water two-phase flow test loop. The measured superficial gas velocities show an error within  ±4% when compared with the gas flowmeter for both conditions.

Experimental and numerical investigation of one and two phase natural convection in storage tanks

NASA Astrophysics Data System (ADS)

Aszodi, A.; Krepper, E.; Prasser, H.-M.

Experiments were performed to investigate heating up processes of fluids in storage tanks under the influence of an external heat source. As a consequence of an external fire, the heat-up of the inventory may lead to the evaporation of the liquid and to release of significant quantities of dangerous gases into the environment. Several tests were performed both with heating from the bottom and with heating from the side walls. In recent tests in addition to thermocouples, the tank was equipped with needle probes for measuring of the local void fraction. The paper presents experimental and numerical investigations of single and two phase heating up processes of tanks with side wall heating. The measurement of the temperature and of the void fraction makes interesting phenomena evident, which could be explained by an own 2D model. The gained experimental results may be used for the validation of boiling models in 3D CFD codes.

Numerical investigations on cavitation intensity for 3D homogeneous unsteady viscous flows

NASA Astrophysics Data System (ADS)

Leclercq, C.; Archer, A.; Fortes-Patella, R.

2016-11-01

The cavitation erosion remains an industrial issue. In this paper, we deal with the cavitation intensity which can be described as the aggressiveness - or erosive capacity - of a cavitating flow. The estimation of this intensity is a challenging problem both in terms of modelling the cavitating flow and predicting the erosion due to cavitation. For this purpose, a model was proposed to estimate cavitation intensity from 3D unsteady cavitating flow simulations. An intensity model based on pressure and void fraction derivatives was developped and applied to a NACA 65012 hydrofoil tested at LMH-EPFL (École Polytechnique Fédérale de Lausanne) [1]. 2D and 3D unsteady cavitating simulations were performed using a homogeneous model with void fraction transport equation included in Code_Saturne with cavitating module [2]. The article presents a description of the numerical code and the physical approach considered. Comparisons between 2D and 3D simulations, as well as between numerical and experimental results obtained by pitting tests, are analyzed in the paper.

Time-resolved flowmetering of gas-liquid two-phase pipe flow by ultrasound pulse Doppler method

NASA Astrophysics Data System (ADS)

Murai, Yuichi; Tasaka, Yuji; Takeda, Yasushi

2012-03-01

Ultrasound pulse Doppler method is applied for componential volumetric flow rate measurement in multiphase pipe flow consisted of gas and liquid phases. The flowmetering is realized with integration of measured velocity profile over the cross section of the pipe within liquid phase. Spatio-temporal position of interface is detected also with the same ultrasound pulse, which further gives cross sectional void fraction. A series of experimental demonstration was shown by applying this principle of measurement to air-water two-phase flow in a horizontal tube of 40 mm in diameter, of which void fraction ranges from 0 to 90% at superficial velocity from 0 to 15 m/s. The measurement accuracy is verified with a volumetric type flowmeter. We also analyze the accuracy of area integration of liquid velocity distribution for many different patterns of ultrasound measurement lines assigned on the cross section of the tube. The present method is also identified to be pulsation sensor of flow rate that fluctuates with complex gas-liquid interface behavior.

Inviscid dynamics of a wet foam drop with monodisperse bubble size distribution

NASA Astrophysics Data System (ADS)

McDaniel, J. Gregory; Akhatov, Iskander; Holt, R. Glynn

2002-06-01

Motivated by recent experiments involving the acoustic levitation of foam drops, we develop a model for nonlinear oscillations of a spherical drop composed of monodisperse aqueous foam with void fraction below 0.1. The model conceptually divides a foam drop into many cells, each cell consisting of a spherical volume of liquid with a bubble at its center. By treating the liquid as incompressible and inviscid, a nonlinear equation is obtained for bubble motion due to a pressure applied at the outer radius of the liquid sphere. Upon linearizing this equation and connecting the cells at their outer radii, a wave equation is obtained with a dispersion relation for the sound waves in a bubbly liquid. For the spherical drop, this equation is solved by a normal mode expansion that yields the natural frequencies as functions of standard foam parameters. Numerical examples illustrate how the analysis may be used to extract foam parameters, such as void fraction and bubble radius, from the experimentally measured natural frequencies of a foam drop.

Extragalactic magnetic fields unlikely generated at the electroweak phase transition

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

Wagstaff, Jacques M.; Banerjee, Robi, E-mail: jwagstaff@hs.uni-hamburg.de, E-mail: banerjee@hs.uni-hamburg.de

2016-01-01

In this paper we show that magnetic fields generated at the electroweak phase transition are most likely too weak to explain the void magnetic fields apparently observed today unless they have considerable helicity. We show that, in the simplest estimates, the helicity naturally produced in conjunction with the baryon asymmetry is too small to explain observations, which require a helicity fraction at least of order 10{sup −14}–10{sup −10} depending on the void fields constraint used. Therefore new mechanisms to generate primordial helicity are required if magnetic fields generated during the electroweak phase transition should explain the extragalactic fields.

Nanofibre distribution in composites manufactured with epoxy reinforced with nanofibrillated cellulose: model prediction and verification

NASA Astrophysics Data System (ADS)

Aitomäki, Yvonne; Westin, Mikael; Korpimäki, Jani; Oksman, Kristiina

2016-07-01

In this study a model based on simple scattering is developed and used to predict the distribution of nanofibrillated cellulose in composites manufactured by resin transfer moulding (RTM) where the resin contains nanofibres. The model is a Monte Carlo based simulation where nanofibres are randomly chosen from probability density functions for length, diameter and orientation. Their movements are then tracked as they advance through a random arrangement of fibres in defined fibre bundles. The results of the model show that the fabric filters the nanofibres within the first 20 µm unless clear inter-bundle channels are available. The volume fraction of the fabric fibres, flow velocity and size of nanofibre influence this to some extent. To verify the model, an epoxy with 0.5 wt.% Kraft Birch nanofibres was made through a solvent exchange route and stained with a colouring agent. This was infused into a glass fibre fabric using an RTM process. The experimental results confirmed the filtering of the nanofibres by the fibre bundles and their penetration in the fabric via the inter-bundle channels. Hence, the model is a useful tool for visualising the distribution of the nanofibres in composites in this manufacturing process.

Explaining Warm Coronal Loops

NASA Technical Reports Server (NTRS)

Klimchuk, James A.; Karpen, Judy T.; Patsourakos, Spiros

2008-01-01

One of the great mysteries of coronal physics that has come to light in the last few years is the discovery that warn (- 1 INK) coronal loops are much denser than expected for quasi-static equilibrium. Both the excess densities and relatively long lifetimes of the loops can be explained with bundles of unresolved strands that are heated impulsively to very high temperatures. Since neighboring strands are at different stages of cooling, the composite loop bundle is multi-thermal, with the distribution of temperatures depending on the details of the "nanoflare storm." Emission hotter than 2 MK is predicted, but it is not clear that such emission is always observed. We consider two possible explanations for the existence of over-dense warm loops without corresponding hot emission: (1) loops are bundles of nanoflare heated strands, but a significant fraction of the nanoflare energy takes the form of a nonthermal electron beam rather then direct plasma heating; (2) loops are bundles of strands that undergo thermal nonequilibrium that results when steady heating is sufficiently concentrated near the footpoints. We present numerical hydro simulations of both of these possibilities and explore the observational consequences, including the production of hard X-ray emission and absorption by cool material in the corona.

Modeling quiescent phase transport of air bubbles induced by breaking waves

NASA Astrophysics Data System (ADS)

Shi, Fengyan; Kirby, James T.; Ma, Gangfeng

Simultaneous modeling of both the acoustic phase and quiescent phase of breaking wave-induced air bubbles involves a large range of length scales from microns to meters and time scales from milliseconds to seconds, and thus is computational unaffordable in a surfzone-scale computational domain. In this study, we use an air bubble entrainment formula in a two-fluid model to predict air bubble evolution in the quiescent phase in a breaking wave event. The breaking wave-induced air bubble entrainment is formulated by connecting the shear production at the air-water interface and the bubble number intensity with a certain bubble size spectra observed in laboratory experiments. A two-fluid model is developed based on the partial differential equations of the gas-liquid mixture phase and the continuum bubble phase, which has multiple size bubble groups representing a polydisperse bubble population. An enhanced 2-DV VOF (Volume of Fluid) model with a k - ɛ turbulence closure is used to model the mixture phase. The bubble phase is governed by the advection-diffusion equations of the gas molar concentration and bubble intensity for groups of bubbles with different sizes. The model is used to simulate air bubble plumes measured in laboratory experiments. Numerical results indicate that, with an appropriate parameter in the air entrainment formula, the model is able to predict the main features of bubbly flows as evidenced by reasonable agreement with measured void fraction. Bubbles larger than an intermediate radius of O(1 mm) make a major contribution to void fraction in the near-crest region. Smaller bubbles tend to penetrate deeper and stay longer in the water column, resulting in significant contribution to the cross-sectional area of the bubble cloud. An underprediction of void fraction is found at the beginning of wave breaking when large air pockets take place. The core region of high void fraction predicted by the model is dislocated due to use of the shear production in the algorithm for initial bubble entrainment. The study demonstrates a potential use of an entrainment formula in simulations of air bubble population in a surfzone-scale domain. It also reveals some difficulties in use of the two-fluid model for predicting large air pockets induced by wave breaking, and suggests that it may be necessary to use a gas-liquid two-phase model as the basic model framework for the mixture phase and to develop an algorithm to allow for transfer of discrete air pockets to the continuum bubble phase. A more theoretically justifiable air entrainment formulation should be developed.

Enhanced phonon scattering by nanovoids in high thermoelectric power factor polysilicon thin films

NASA Astrophysics Data System (ADS)

Dunham, Marc T.; Lorenzi, Bruno; Andrews, Sean C.; Sood, Aditya; Asheghi, Mehdi; Narducci, Dario; Goodson, Kenneth E.

2016-12-01

The ability to tune the thermal conductivity of semiconductor materials is of interest for thermoelectric applications, in particular, for doped silicon, which can be readily integrated in electronic microstructures and have a high thermoelectric power factor. Here, we examine the impact of nanovoids on the thermal conductivity of highly doped, high-power factor polysilicon thin films using time-domain thermoreflectance. Voids are formed through ion implantation and annealing, evolving from many small (˜4 nm mean diameter) voids after 500 °C anneal to fewer, larger (˜29 nm mean diameter) voids with a constant total volume fraction after staged thermal annealing to 1000 °C. The thermal conductivity is reduced to 65% of the non-implanted reference film conductivity after implantation and 500 °C anneal, increasing with anneal temperature until fully restored after 800 °C anneal. The void size distributions are determined experimentally using small-angle and wide-angle X-ray scattering. While we believe multiple physical mechanisms are at play, we are able to corroborate the positive correlation between measurements of thermal conductivity and void size with Monte Carlo calculations and a scattering probability based on Matthiessen's rule. The data suggest an opportunity for thermal conductivity suppression combined with the high power factor for increased material zT and efficiency of nanostructured polysilicon as a thermoelectric material.

Cellular polypropylene polymer foam as air-coupled ultrasonic transducer materials.

PubMed

Satyanarayan, L; Haberman, Michael R; Berthelot, Yves H

2010-10-01

Cellular polypropylene polymer foams, also known as ferroelectrets, are compelling candidates for air-coupled ultrasonic transducer materials because of their excellent acoustic impedance match to air and because they have a piezoelectric d(33) coefficient superior to that of PVDF. This study investigates the performance of ferroelectret transducers in the generation and reception of ultrasonic waves in air. As previous studies have noted, the piezoelectric coupling coefficients of these foams depend on the number, size, and distribution of charged voids in the microstructure. The present work studies the influence of these parameters both theoretically and experimentally. First, a three-dimensional model is employed to explain the variation of piezoelectric coupling coefficients, elastic stiffness, and dielectric permittivity as a function of void fraction based on void-scale physics and void geometry. Laser Doppler vibrometer (LDV) measurements of the effective d(33) coefficient of a specially fabricated prototype transmitting transducer are then shown which clearly indicate that the charged voids in the ferroelectret material are randomly distributed in the plane of the foam. The frequency-dependent dynamic d(33) coefficient is then reported from 50 to 500 kHz for different excitation voltages and shown to be largely insensitive to drive voltage. Lastly, two ferroelectret transducers are operated in transmit-receive mode and the received signal is shown to accurately represent the corresponding signal generated by the transmitting transducer as measured using LDV.

Liquid level, void fraction, and superheated steam sensor for nuclear-reactor cores. [PWR; BWR

DOEpatents

Tokarz, R.D.

1981-10-27

This disclosure relates to an apparatus for monitoring the presence of coolant in liquid or mixed liquid and vapor, and superheated gaseous phases at one or more locations within an operating nuclear reactor core, such as pressurized water reactor or a boiling water reactor.

Hindlimb unloading alters ligament healing

NASA Technical Reports Server (NTRS)

Provenzano, Paolo P.; Martinez, Daniel A.; Grindeland, Richard E.; Dwyer, Kelley W.; Turner, Joanne; Vailas, Arthur C.; Vanderby, Ray Jr

2003-01-01

We investigated the hypothesis that hindlimb unloading inhibits healing in fibrous connective tissue such as ligament. Male rats were assigned to 3- and 7-wk treatment groups with three subgroups each: sham control, ambulatory healing, and hindlimb-suspended healing. Ambulatory and suspended animals underwent surgical rupture of their medial collateral ligaments, whereas sham surgeries were performed on control animals. After 3 or 7 wk, mechanical and/or morphological properties were measured in ligament, muscle, and bone. During mechanical testing, most suspended ligaments failed in the scar region, indicating the greatest impairment was to ligament and not to bone-ligament insertion. Ligament testing revealed significant reductions in maximum force, ultimate stress, elastic modulus, and low-load properties in suspended animals. In addition, femoral mineral density, femoral strength, gastrocnemius mass, and tibialis anterior mass were significantly reduced. Microscopy revealed abnormal scar formation and cell distribution in suspended ligaments with extracellular matrix discontinuities and voids between misaligned, but well-formed, collagen fiber bundles. Hence, stress levels from ambulation appear unnecessary for formation of fiber bundles yet required for collagen to form structurally competent continuous fibers. Results support our hypothesis that hindlimb unloading impairs healing of fibrous connective tissue. In addition, this study provides compelling morphological evidence explaining the altered structure-function relationship in load-deprived healing connective tissue.

SfM with MRFs: discrete-continuous optimization for large-scale structure from motion.

PubMed

Crandall, David J; Owens, Andrew; Snavely, Noah; Huttenlocher, Daniel P

2013-12-01

Recent work in structure from motion (SfM) has built 3D models from large collections of images downloaded from the Internet. Many approaches to this problem use incremental algorithms that solve progressively larger bundle adjustment problems. These incremental techniques scale poorly as the image collection grows, and can suffer from drift or local minima. We present an alternative framework for SfM based on finding a coarse initial solution using hybrid discrete-continuous optimization and then improving that solution using bundle adjustment. The initial optimization step uses a discrete Markov random field (MRF) formulation, coupled with a continuous Levenberg-Marquardt refinement. The formulation naturally incorporates various sources of information about both the cameras and points, including noisy geotags and vanishing point (VP) estimates. We test our method on several large-scale photo collections, including one with measured camera positions, and show that it produces models that are similar to or better than those produced by incremental bundle adjustment, but more robustly and in a fraction of the time.

Influenza A Virus Hemagglutinin is Required for the Assembly of Viral Components Including Bundled vRNPs at the Lipid Raft.

PubMed

Takizawa, Naoki; Momose, Fumitaka; Morikawa, Yuko; Nomoto, Akio

2016-09-10

The influenza glycoproteins, hemagglutinin (HA) and neuraminidase (NA), which are associated with the lipid raft, have the potential to initiate virion budding. However, the role of these viral proteins in infectious virion assembly is still unclear. In addition, it is not known how the viral ribonucleoprotein complex (vRNP) is tethered to the budding site. Here, we show that HA is necessary for the efficient progeny virion production and vRNP packaging in the virion. We also found that the level of HA does not affect the bundling of the eight vRNP segments, despite reduced virion production. Detergent solubilization and a subsequent membrane flotation analysis indicated that the accumulation of nucleoprotein, viral polymerases, NA, and matrix protein 1 (M1) in the lipid raft fraction was delayed without HA. Based on our results, we inferred that HA plays a role in the accumulation of viral components, including bundled vRNPs, at the lipid raft.

Metabolite pools and carbon flow during C4 photosynthesis in maize: 13CO2 labeling kinetics and cell type fractionation.

PubMed

Arrivault, Stéphanie; Obata, Toshihiro; Szecówka, Marek; Mengin, Virginie; Guenther, Manuela; Hoehne, Melanie; Fernie, Alisdair R; Stitt, Mark

2017-01-01

Worldwide efforts to engineer C 4 photosynthesis into C 3 crops require a deep understanding of how this complex pathway operates. CO 2 is incorporated into four-carbon metabolites in the mesophyll, which move to the bundle sheath where they are decarboxylated to concentrate CO 2 around RuBisCO. We performed dynamic 13 CO 2 labeling in maize to analyze C flow in C 4 photosynthesis. The overall labeling kinetics reflected the topology of C 4 photosynthesis. Analyses of cell-specific labeling patterns after fractionation to enrich bundle sheath and mesophyll cells revealed concentration gradients to drive intercellular diffusion of malate, but not pyruvate, in the major CO 2 -concentrating shuttle. They also revealed intercellular concentration gradients of aspartate, alanine, and phosphenolpyruvate to drive a second phosphoenolpyruvate carboxykinase (PEPCK)-type shuttle, which carries 10-14% of the carbon into the bundle sheath. Gradients also exist to drive intercellular exchange of 3-phosphoglycerate and triose-phosphate. There is rapid carbon exchange between the Calvin-Benson cycle and the CO 2 -concentrating shuttle, equivalent to ~10% of carbon gain. In contrast, very little C leaks from the large pools of metabolites in the C concentration shuttle into respiratory metabolism. We postulate that the presence of multiple shuttles, alongside carbon transfer between them and the Calvin-Benson cycle, confers great flexibility in C 4 photosynthesis. © The Author 2016. Published by Oxford University Press on behalf of the Society for Experimental Biology.

Henry constant and isosteric heat at zero-loading for gas adsorption in carbon nanotubes.

PubMed

Do, D D; Do, H D; Wongkoblap, A; Nicholson, D

2008-12-28

The Henry constant and the isosteric heat of adsorption at zero loading in a carbon nanotube bundle are studied with Monte Carlo integration for the adsorption of gases over a range of temperatures. The spacing between nanotubes in a bundle is determined from the minimization of potential energy of interaction between these tubes. We study different tube configurations with bundles of 2, 3, 4 and 7 tubes. Depending on the configuration it is found that the spacing is of between 0.31 to 0.333 nm, and this falls within the range reported in the literature. The Henry constant has been carefully defined so that it will not become negative at high temperatures. This is done with the aid of accessible volume, rather than the usual absolute void volume. We show that linearity of the van't Hoff plot for the Henry constant is not strictly followed. Furthermore the slope of this plot is not equal to the isosteric heat of adsorption at zero loading, which is found to be a strong function of temperature. From the results we find that the Henry constant and the heat of adsorption depend on the tube configuration. In general the adsorption in the cusp interstices is strongest followed by that inside the tube and finally on the outer surface. However for very small tubes adsorption occurs inside the tube first. For molecules with orientation, the behaviour is even more interesting and the shape of the isosteric heat versus temperature depends on the degree of orientation, tube configuration and the domain of adsorption (interstices, inside the tube and on the outer surface).

Minor actinide transmutation in thorium and uranium matrices in heavy water moderated reactors

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

Bhatti, Zaki; Hyland, B.; Edwards, G.W.R.

2013-07-01

The irradiation of Th{sup 232} breeds fewer of the problematic minor actinides (Np, Am, Cm) than the irradiation of U{sup 238}. This characteristic makes thorium an attractive potential matrix for the transmutation of these minor actinides, as these species can be transmuted without the creation of new actinides as is the case with a uranium fuel matrix. Minor actinides are the main contributors to long term decay heat and radiotoxicity of spent fuel, so reducing their concentration can greatly increase the capacity of a long term deep geological repository. Mixing minor actinides with thorium, three times more common in themore » Earth's crust than natural uranium, has the additional advantage of improving the sustainability of the fuel cycle. In this work, lattice cell calculations have been performed to determine the results of transmuting minor actinides from light water reactor spent fuel in a thorium matrix. 15-year-cooled group-extracted transuranic elements (Np, Pu, Am, Cm) from light water reactor (LWR) spent fuel were used as the fissile component in a thorium-based fuel in a heavy water moderated reactor (HWR). The minor actinide (MA) transmutation rates, spent fuel activity, decay heat and radiotoxicity, are compared with those obtained when the MA were mixed instead with natural uranium and taken to the same burnup. Each bundle contained a central pin containing a burnable neutron absorber whose initial concentration was adjusted to have the same reactivity response (in units of the delayed neutron fraction β) for coolant voiding as standard NU fuel. (authors)« less

Optical apparatus for laser scattering by objects having complex shapes

DOEpatents

Ellingson, William A.; Visher, Robert J.

2006-11-14

Apparatus for observing and measuring in realtime surface and subsurface characteristics of objects having complex shapes includes an optical fiber bundle having first and second opposed ends. The first end includes a linear array of fibers, where the ends of adjacent fibers are in contact and are aligned perpendicular to the surface of the object being studied. The second ends of some of the fibers are in the form of a polished ferrule forming a multi-fiber optical waveguide for receiving laser light. The second ends of the remaining fibers are formed into a linear array suitable for direct connection to a detector, such as a linear CMOS-based optical detector. The output data is analyzed using digital signal processing for the detection of anomalies such as cracks, voids, inclusions and other defects.

Thermoplastic coating of carbon fibers

NASA Technical Reports Server (NTRS)

Edie, D. D.; Lickfield, G. C.

1991-01-01

Using a continuous powder coating process, more than 1500 meters of T 300/LaRC-TPI prepreg were produced. Two different types of heating sections in the coating line, namely electrical resistance and convection heating, were utilized. These prepregs were used to fabricate unidirectional composites. During composite fabrication the cure time of the consolidation was varied, and composites samples were produced with and without vacuum. Under these specimens, the effects of the different heating sections and of the variation of the consolidation parameters on mechanical properties and void content were investigated. The void fractions of the various composites were determined from density measurements, and the mechanical properties were measured by tensile testing, short beam shear testing and dynamic mechanical analysis.

Ground-Based Gas-Liquid Flow Research in Microgravity Conditions: State of Knowledge

NASA Technical Reports Server (NTRS)

McQuillen, J.; Colin, C.; Fabre, J.

1999-01-01

During the last decade, ground-based microgravity facilities have been utilized in order to obtain predictions for spacecraft system designers and further the fundamental understanding of two-phase flow. Although flow regime, pressure drop and heat transfer coefficient data has been obtained for straight tubes and a limited number of fittings, measurements of the void fraction, film thickness, wall shear stress, local velocity and void information are also required in order to develop general mechanistic models that can be utilized to ascertain the effects of fluid properties, tube geometry and acceleration levels. A review of this research is presented and includes both empirical data and mechanistic models of the flow behavior.

Development of Electrical Capacitance Sensors for Accident Tolerant Fuel (ATF) Testing at the Transient Reactor Test (TREAT) Facility

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

Liu, Maolong; Ryals, Matthew; Ali, Amir

2016-08-01

A variety of instruments are being developed and qualified to support the Accident Tolerant Fuels (ATF) program and future transient irradiations at the Transient Reactor Test (TREAT) facility at Idaho National Laboratory (INL). The University of New Mexico (UNM) is working with INL to develop capacitance-based void sensors for determining the timing of critical boiling phenomena in static capsule fuel testing and the volume-averaged void fraction in flow-boiling in-pile water loop fuel testing. The static capsule sensor developed at INL is a plate-type configuration, while UNM is utilizing a ring-type capacitance sensor. Each sensor design has been theoretically and experimentallymore » investigated at INL and UNM. Experiments are being performed at INL in an autoclave to investigate the performance of these sensors under representative Pressurized Water Reactor (PWR) conditions in a static capsule. Experiments have been performed at UNM using air-water two-phase flow to determine the sensitivity and time response of the capacitance sensor under a flow boiling configuration. Initial measurements from the capacitance sensor have demonstrated the validity of the concept to enable real-time measurement of void fraction. The next steps include designing the cabling interface with the flow loop at UNM for Reactivity Initiated Accident (RIA) ATF testing at TREAT and further characterization of the measurement response for each sensor under varying conditions by experiments and modeling.« less

Benefits of Permanent His Bundle Pacing Combined With Atrioventricular Node Ablation in Atrial Fibrillation Patients With Heart Failure With Both Preserved and Reduced Left Ventricular Ejection Fraction.

PubMed

Huang, Weijian; Su, Lan; Wu, Shengjie; Xu, Lei; Xiao, Fangyi; Zhou, Xiaohong; Ellenbogen, Kenneth A

2017-04-01

Clinical benefits from His bundle pacing (HBP) in heart failure patients with preserved and reduced left ventricular ejection fraction are still inconclusive. This study evaluated clinical outcomes of permanent HBP in atrial fibrillation patients with narrow QRS who underwent atrioventricular node ablation for heart failure symptoms despite rate control by medication. The study enrolled 52 consecutive heart failure patients who underwent attempted atrioventricular node ablation and HBP for symptomatic atrial fibrillation. Echocardiographic left ventricular ejection fraction and left ventricular end-diastolic dimension, New York Heart Association classification and use of diuretics for heart failure were assessed during follow-up visits after permanent HBP. Of 52 patients, 42 patients (80.8%) received permanent HBP and atrioventricular node ablation with a median 20-month follow-up. There was no significant change between native and paced QRS duration (107.1±25.8 versus 105.3±23.9 milliseconds, P =0.07). Left ventricular end-diastolic dimension decreased from the baseline ( P <0.001), and left ventricular ejection fraction increased from baseline ( P <0.001) in patients with a greater improvement in heart failure with reduced ejection fraction patients (N=20) than in heart failure with preserved ejection fraction patients (N=22). New York Heart Association classification improved from a baseline 2.9±0.6 to 1.4±0.4 after HBP in heart failure with reduced ejection fraction patients and from a baseline 2.7±0.6 to 1.4±0.5 after HBP in heart failure with preserved ejection fraction patients. After 1 year of HBP, the numbers of patients who used diuretics for heart failure decreased significantly ( P <0.001) when compared to the baseline diuretics use. Permanent HBP post-atrioventricular node ablation significantly improved echocardiographic measurements and New York Heart Association classification and reduced diuretics use for heart failure management in atrial fibrillation patients with narrow QRS who suffered from heart failure with preserved or reduced ejection fraction. © 2017 The Authors. Published on behalf of the American Heart Association, Inc., by Wiley Blackwell.

Studies of hemidesmosomes in human amnion: the use of a detergent extraction protocol for compositional and ultrastructural analysis and preparation of a hemidesmosome-enriched fraction from tissue.

PubMed

Behzad, F; Jones, C J; Ball, S; Alvares, T; Aplin, J D

1995-01-01

A method is described for the sequential detergent and high ionic strength extraction of human amnion with the progressive enrichment of the intermediate filament (IF) cytoskeleton and its associated structures including hemidesmosomes (HD). TEM of the extracted epithelium in situ reveals IF bundles beneath the apical cell surface, around the nucleus and at the lateral edges of the cells where association with desmosomes occurs. IF bundles are also very prominent within basal cell processes where they loop through the cytoplasm adjacent to the HDs. A novel connecting filament network is observed running between the IFs and the hemidesmosomal dense plaque. The adjacent IF network contains both cytokeratin and vimentin, the latter revealed much more fully as a result of the extraction protocol. The hemidesmosomal plasma membrane contains integrin subunits alpha 6 and beta 4 and these are quantitatively retained as the basal cell surface during extraction, while nonjunctional plasma membrane is solubilised. Integrin beta 1 is found at the basolateral cell surface but, like actin, is extracted quantitatively and is not present in HDs. The extracted epithelial cells may be recovered by scraping and the IF network depolymerised to produce a particulate fraction containing short residual IFs, associated thin filaments and plaque material. This fraction contains immunoreactive cytokeratin and vimentin. Integrin alpha 6 beta 4 has been used as a biochemical criterion of the presence of HD material in the fraction. Both subunits are highly enriched. The fraction also contains the hemidesmosomal components HD1, BP230 and BP180. This method is likely to be useful in further characterisation of the HD.

A Theoretical Study of Flow Structure and Radiation for Multiphase Turbulent Diffusion Flames

DTIC Science & Technology

1990-03-01

density function. According to the axial void fraction profile in Fig. 24, the flame length (the total penetration length) extends to x/d=150. By referring...temperature because of subcooling effect. Decreasing liquid temperature will increase condensation which in turn reduces the flame length as defined by

Materials Genome in Action: Identifying the Performance Limits of Physical Hydrogen Storage

PubMed Central

2017-01-01

The Materials Genome is in action: the molecular codes for millions of materials have been sequenced, predictive models have been developed, and now the challenge of hydrogen storage is targeted. Renewably generated hydrogen is an attractive transportation fuel with zero carbon emissions, but its storage remains a significant challenge. Nanoporous adsorbents have shown promising physical adsorption of hydrogen approaching targeted capacities, but the scope of studies has remained limited. Here the Nanoporous Materials Genome, containing over 850 000 materials, is analyzed with a variety of computational tools to explore the limits of hydrogen storage. Optimal features that maximize net capacity at room temperature include pore sizes of around 6 Å and void fractions of 0.1, while at cryogenic temperatures pore sizes of 10 Å and void fractions of 0.5 are optimal. Our top candidates are found to be commercially attractive as “cryo-adsorbents”, with promising storage capacities at 77 K and 100 bar with 30% enhancement to 40 g/L, a promising alternative to liquefaction at 20 K and compression at 700 bar. PMID:28413259

Materials genome in action: Identifying the performance limits of physical hydrogen storage

DOE PAGES

Thornton, Aaron W.; Simon, Cory M.; Kim, Jihan; ...

2017-03-08

The Materials Genome is in action: the molecular codes for millions of materials have been sequenced, predictive models have been developed, and now the challenge of hydrogen storage is targeted. Renewably generated hydrogen is an attractive transportation fuel with zero carbon emissions, but its storage remains a significant challenge. Nanoporous adsorbents have shown promising physical adsorption of hydrogen approaching targeted capacities, but the scope of studies has remained limited. Here the Nanoporous Materials Genome, containing over 850 000 materials, is analyzed with a variety of computational tools to explore the limits of hydrogen storage. Optimal features that maximize net capacitymore » at room temperature include pore sizes of around 6 Å and void fractions of 0.1, while at cryogenic temperatures pore sizes of 10 Å and void fractions of 0.5 are optimal. Finally, our top candidates are found to be commercially attractive as “cryo-adsorbents”, with promising storage capacities at 77 K and 100 bar with 30% enhancement to 40 g/L, a promising alternative to liquefaction at 20 K and compression at 700 bar.« less

Materials genome in action: Identifying the performance limits of physical hydrogen storage

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

Thornton, Aaron W.; Simon, Cory M.; Kim, Jihan

The Materials Genome is in action: the molecular codes for millions of materials have been sequenced, predictive models have been developed, and now the challenge of hydrogen storage is targeted. Renewably generated hydrogen is an attractive transportation fuel with zero carbon emissions, but its storage remains a significant challenge. Nanoporous adsorbents have shown promising physical adsorption of hydrogen approaching targeted capacities, but the scope of studies has remained limited. Here the Nanoporous Materials Genome, containing over 850 000 materials, is analyzed with a variety of computational tools to explore the limits of hydrogen storage. Optimal features that maximize net capacitymore » at room temperature include pore sizes of around 6 Å and void fractions of 0.1, while at cryogenic temperatures pore sizes of 10 Å and void fractions of 0.5 are optimal. Finally, our top candidates are found to be commercially attractive as “cryo-adsorbents”, with promising storage capacities at 77 K and 100 bar with 30% enhancement to 40 g/L, a promising alternative to liquefaction at 20 K and compression at 700 bar.« less

Radioisotope measurement of selected parameters of liquid-gas flow using single detector system

NASA Astrophysics Data System (ADS)

Zych, Marcin; Hanus, Robert; Jaszczur, Marek; Mosorov, Volodymyr; Świsulski, Dariusz

2018-06-01

To determine the parameters of two-phase flows using radioisotopes, usually two detectors are used. Knowing the distance between them, the velocity of the dispersed phase is calculated based on time delay estimation. Such a measurement system requires the use of two gamma-ray sealed sources. But in some situations it is also possible to determine velocity of dispersed phase using only one scintillation probe and one gamma-ray source. However, this requires proper signal analysis and prior calibration. This may also cause larger measurement errors. On the other hand, it allows measurements in hard to reach areas where there is often no place for the second detector. Additionally, by performing a previous calibration, it is possible to determine the void fraction or concentration of the selected phase. In this work an autocorrelation function was used to analyze the signal from the scintillation detector, which allowed for the determination of air velocities in slug and plug flows with an accuracy of 8.5%. Based on the analysis of the same signal, a void fraction with error of 15% was determined.

A Reactive-Heat-Pipe for Combined Heat Generation and Transport

DTIC Science & Technology

1977-12-01

The Lennard - Jones potential parameters a and F-1 can be found in Ar Ar Table 2.3 of Reference [26]. They are a Ar =3.542 A ~Ar -=93.3 K The above...Specific Heat Ratio Wire Spacing of Screen S Volume Fraction of Solid Phase in Wick or Lennard Jones Force Constant e’ Wick Void Fraction 1Viscusity p...Density a Surface Tension G Condensation Coefficient c e Evaporation Coefficient*e U Lennard - Jones Force Constant Subscripts A Position A in Figure 13 Ar

Characterization of voids formed during liquid impregnation of nonwoven multifilament glass networks as related to composite processing

NASA Technical Reports Server (NTRS)

Mahale, Anant D.; Prudhomme, Robert K.; Rebenfeld, Ludwig

1993-01-01

A technique based on matching the refractive index of an invading liquid to that of a fiber mat was used to study entrapment of air ('voids') that occurs during forced in-plane radial flow into nonwoven multifilament glass networks. The usefulness of this technique is demonstrated in quantifying and mapping the air pockets. Experiments with a series of fluids with surface tensions varying from 28 x 10(exp -3) to 36 x 10(exp -3) N/m, viscosities from 45 x 10(exp -3) to 290 x 10(exp -3) Pa.s, and inlet flow rates from 0.15 x 10(exp -6) to 0.75 x 10(exp -6) m(exp 3)/s, showed that void content is a function of the capillary number characterizing the flow process. A critical value of capillary number, Ca = 2.5 x 10(exp -3), identifies a zone below which void content increases exponentially with decreasing capillary number. Above this critical value, negligible entrapment of voids is observed. Similar experiments carried out on surface treated nonwoven mats spanning a range of equilibrium contact angles from 20 deg to 78 deg showed that there is a critical contact angle above which negligible entrapment is observed. Below this value, there is no apparent effect of contact angle on the void fraction - capillary number relationship described earlier. Studies on the effect of filament wettability, and fluid velocity and viscosity on the size of the entrapment (voids) were also carried out. These indicate that larger sized entrapments which envelop more than one pore are favored by a low capillary number in comparison to smaller, pore level bubbles. Experiments were carried out on deformed mats - imposing high permeability spots at regular intervals on a background of low permeability. The effect of these spatial fluctuations in heterogeneity of the mat on entrapment is currently being studied.

Intergalactic Hydrogen Clouds at Low Redshift: Connections to Voids and Dwarf Galaxies

NASA Technical Reports Server (NTRS)

Shull, J. Michael; Stocke, John T.; Penton, Steve

1996-01-01

We provide new post-COSTAR data on one sightline (Mrk 421) and updated data from another (I Zw 1) from our Hubble Space Telescope (HST) survey of intergalactic Ly(alpha) clouds located along sightlines to four bright quasars passing through well-mapped galaxy voids (16000 km/s pathlength) and superclusters (18000 km/s). We report two more definite detections of low-redshift Ly(alpha) clouds in voids: one at 3047 km/s (heliocentric) toward Mrk 421 and a second just beyond the Local Supercluster at 2861 km/s toward I Zw 1, confirming our earlier discovery of Ly(alpha) absorption clouds in voids (Stocke et al., ApJ, 451, 24). We have now identified ten definite and one probable low-redshift neutral hydrogen absorption clouds toward four targets, a frequency of approximately one absorber every 3400 km/s above 10(exp 12.7/sq cm column density. Of these ten absorption systems, three lie within voids; the probable absorber also lies in a void. Thus, the tendency of Ly(alpha) absorbers to 'avoid the voids' is not as clear as we found previously. If the Ly(alpha) clouds are approximated as homogeneous spheres of 100 kpc radius, their masses are approximately 10(exp 9)solar mass (about 0.01 times that of bright L* galaxies) and they are 40 times more numerous, comparable to the density of dwarf galaxies and of low-mass halos in numerical CDM simulations. The Ly(alpha) clouds contribute a fraction Omega(sub cl)approximately equals 0.003/h(sub 75) to the closure density of the universe, comparable to that of luminous matter. These clouds probably require a substantial amount of nonbaryonic dark matter for gravitational binding. They may represent extended haloes of low-mass protogalaxies which have not experienced significant star formation or low-mass dwarf galaxies whose star formation ceased long ago, but blew out significant gaseous material.

Immortality of Cu damascene interconnects

NASA Astrophysics Data System (ADS)

Hau-Riege, Stefan P.

2002-04-01

We have studied short-line effects in fully-integrated Cu damascene interconnects through electromigration experiments on lines of various lengths and embedded in different dielectric materials. We compare these results with results from analogous experiments on subtractively-etched Al-based interconnects. It is known that Al-based interconnects exhibit three different behaviors, depending on the magnitude of the product of current density, j, and line length, L: For small values of (jL), no void nucleation occurs, and the line is immortal. For intermediate values, voids nucleate, but the line does not fail because the current can flow through the higher-resistivity refractory-metal-based shunt layers. Here, the resistance of the line increases but eventually saturates, and the relative resistance increase is proportional to (jL/B), where B is the effective elastic modulus of the metallization system. For large values of (jL/B), voiding leads to an unacceptably high resistance increase, and the line is considered failed. By contrast, we observed only two regimes for Cu-based interconnects: Either the resistance of the line stays constant during the duration of the experiment, and the line is considered immortal, or the line fails due to an abrupt open-circuit failure. The absence of an intermediate regime in which the resistance saturates is due to the absence of a shunt layer that is able to support a large amount of current once voiding occurs. Since voids nucleate much more easily in Cu- than in Al-based interconnects, a small fraction of short Cu lines fails even at low current densities. It is therefore more appropriate to consider the probability of immortality in the case of Cu rather than assuming a sharp boundary between mortality and immortality. The probability of immortality decreases with increasing amount of material depleted from the cathode, which is proportional to (jL2/B) at steady state. By contrast, the immortality of Al-based interconnects is described by (jL) if no voids nucleate, and (jL/B) if voids nucleate.

Multiply Surface-Functionalized Nanoporous Carbon for Vehicular Hydrogen Storage

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

Pfeifer, Peter; Gillespie, Andrew; Stalla, David

The purpose of the project “Multiply Surface-Functionalized Nanoporous Carbon for Vehicular Hydrogen Storage” is the development of materials that store hydrogen (H 2) by adsorption in quantities and at conditions that outperform current compressed-gas H 2 storage systems for electric power generation from hydrogen fuel cells (HFCs). Prominent areas of interest for HFCs are light-duty vehicles (“hydrogen cars”) and replacement of batteries with HFC systems in a wide spectrum of applications, ranging from forklifts to unmanned areal vehicles to portable power sources. State-of-the-art compressed H 2 tanks operate at pressures between 350 and 700 bar at ambient temperature and storemore » 3-4 percent of H 2 by weight (wt%) and less than 25 grams of H 2 per liter (g/L) of tank volume. Thus, the purpose of the project is to engineer adsorbents that achieve storage capacities better than compressed H 2 at pressures less than 350 bar. Adsorption holds H 2 molecules as a high-density film on the surface of a solid at low pressure, by virtue of attractive surface-gas interactions. At a given pressure, the density of the adsorbed film is the higher the stronger the binding of the molecules to the surface is (high binding energies). Thus, critical for high storage capacities are high surface areas, high binding energies, and low void fractions (high void fractions, such as in interstitial space between adsorbent particles, “waste” storage volume by holding hydrogen as non-adsorbed gas). Coexistence of high surface area and low void fraction makes the ideal adsorbent a nanoporous monolith, with pores wide enough to hold high-density hydrogen films, narrow enough to minimize storage as non-adsorbed gas, and thin walls between pores to minimize the volume occupied by solid instead of hydrogen. A monolith can be machined to fit into a rectangular tank (low pressure, conformable tank), cylindrical tank (high pressure), or other tank shape without any waste of volume.« less

Investigation into Behavior of a Steam-Water Mixture Flow Through Holes in a Submerged Perforated Sheet at High Void Fractions

NASA Astrophysics Data System (ADS)

Melikhov, V. I.; Melikhov, O. I.; Nerovnov, A. A.; Nikonov, S. M.

2018-01-01

Processing of experimental data on the pressure difference across a submerged perforated sheet (SPS) revealed that, at sufficiently high void fractions under SPS, the pressure difference across it became less than the pressure difference for the pure steam stream with the same flowrate. To find the cause of this, the effect of a liquid film, which can be formed on the SPS upstream surface as a result of water droplets' impact and can smooth over sharp edges of holes in SDS, was examined. This can decrease the pressure drop across the sharp edges of holes. This assumption was checked through numerical solution to several model problems in the axisymmetric formulation for a steam flow in a round pipe with an orifice. The flow of steam and water was modeled using the viscous incompressible liquid approximation, while the turbulence was described by the k-ɛ model. The evolution of the interfacial area was modeled using the VOF model. The following model problems of steam flow through an orifice were studied: a single-phase flow, a flow through the orifice with a liquid film on its upstream surface, a flow through a chamfered hole, and a flow through the orifice with a liquid film on its upstream surface without liquid supply to the film. The predictions demonstrate that even the approximate account of the liquid film effect on the steam flow yields a considerable decrease in the pressure drop across the hole (from 8 to 24%) due to smoothing its sharp outlet edges over. This makes it possible to make a conclusion that the cause of a decrease in the pressure drop across SPS observed in the experiments at high void fractions is the formation of a liquid film, which smooths the sharp edges of the hole.

Thermo-optic characteristics of hybrid polymer/silica microstructured optical fiber: An analytical approach

NASA Astrophysics Data System (ADS)

Sharma, Dinesh Kumar; Sharma, Anurag; Tripathi, Saurabh Mani

2018-04-01

Microstructured optical fibers (MOFs) allow a variety of advanced materials to be infiltrated in their air-voids for obtaining the increased fiber functionality, and offering a new versatile platform for developing the compact sensors devices. We aim to investigate the thermal characteristics of high-index core triangular hybrid polymer/silica MOFs with circular air-voids infused with polymer by using the analytical field model [1]. We demonstrate that infiltration of air-voids with polymer, e.g., polydimethylsiloxane (PDMS) can facilitate to tune the fundamental modal properties of MOF such as effective index of the mode, near and the far-field profiles, effective mode area and the numerical aperture over the temperature ranging from 0 °C to 100 °C, for different values of relative air-void ratios. The evolution of the mode shape for a given temperature has been investigated in transition from near-field to far-field regime. We have studied the thermal dependence of splice losses between hybrid MOF and the standard step-index single-mode optical fiber in combination with Fresnel losses. For enhancing the evanescent field interactions, we have evaluated fraction of power associated with fundamental mode of hybrid MOF. We have compared the accuracy of our results with those based on full-vector finite-difference (FD) method, as available in the literature.

Acoustic wave propagation in bubbly flow with gas, vapor or their mixtures.

PubMed

Zhang, Yuning; Guo, Zhongyu; Gao, Yuhang; Du, Xiaoze

2018-01-01

Presence of bubbles in liquids could significantly alter the acoustic waves in terms of wave speed and attenuation. In the present paper, acoustic wave propagation in bubbly flows with gas, vapor and gas/vapor mixtures is theoretically investigated in a wide range of parameters (including frequency, bubble radius, void fraction, and vapor mass fraction). Our finding reveals two types of wave propagation behavior depending on the vapor mass fraction. Furthermore, the minimum wave speed (required for the closure of cavitation modelling in the sonochemical reactor design) is analyzed and the influences of paramount parameters on it are quantitatively discussed. Copyright © 2017 Elsevier B.V. All rights reserved.

Morphological transformation of soot: investigation of microphysical processes during the condensation of sulphuric acid and limonene ozonolysis products vapours

NASA Astrophysics Data System (ADS)

Pathak, R. K. P.; Pei, X.; Hallquist, M.; Pagels, J. H.

2017-12-01

Morphological transformation of soot particle by condensation of low volatility materials on it is a dominant atmospheric process with serious implications for its optical and hygroscopic properties, and atmospheric lifetime. In this study, the morphological transformation of soot agglomerate under the influence of condensation of vapours of sulphuric acid, and/or limonene ozonolysis products were investigated systematically using a Differential Mobility Analyser-Aerosol Particle Mass Analyser (DMA-APM) and the Tandem DMA techniques integrated with a laminar flow-tube system. We discovered that the morphology transformation of soot in general was a sequence of two-step process, i.e. (i) filling of void space within soot agglomerate; (ii) growth of particle diameter. These two steps followed and complimented each other. In the very beginning the filling was the dominant process followed by growth until it led to the accumulation of enough material that in turn exerted surface forces that eventually facilitated the further filling. The filling of void space was constrained by the initial morphology of fresh soot and the nature and amount of the material condensed. This process continued in several sequential steps until all void space within the soot agglomerate was filled completely and then growth of a spherical particle continued as long as mass was condensed on it. In this study, we developed a framework to quantify the microphysical transformation of soot upon the condensation of various materials. The framework utilized experimental data and hypothesis of ideal sphere growth and filling of voids to quantify the distribution of condensed materials in these two processes complimenting each other. Using this framework, we have quantified the percentage of material that went into processes of particle growth and void filling at each step. Using the same framework, we further estimated the fraction of internal voids and open voids and used this information to derive the volume equivalent diameter of soot agglomerate containing internal voids and calculated in-situ dynamic shape factor. Our study is the first study that tracks in situ microphysical changes in soot morphology quantitatively, providing the detailed status of both fresh and coated soot particles.

Action potentials recorded from bundles of very thin, gray matter axons in rat cerebellar slices using a grease-gap method.

PubMed

Palani, Damodharan; Pekala, Dobromila; Baginskas, Armantas; Szkudlarek, Hanna; Raastad, Morten

2012-07-15

We investigated the ability of a grease-gap method to record fast and slow changes of the membrane potential from bundles of gray matter axons. Their membrane potentials are of particular interest because these axons are different from most axons that have been investigated using intra-axonal or gap techniques. One of the main differences is that gray matter axons typically have closely spaced presynaptic specializations, called boutons or varicosities, distributed along their entire paths. In response to electrical activation of bundles of parallel fiber axons we were able to record small (128-416μV) but stable signals that we show most likely represented a fraction of the trans-membrane action potentials. A less-than 100% fraction prevents measurements of absolute values for membrane potentials, but the good signal-to-noise ratio (typically 10-16) allows detection of changes in resting membrane potential, action potentials and their after-potentials. Because very little is known about the shape of action potentials and after-potentials in these axons we used several independent methods to make it likely that the grease-gap signal was of intra-axonal origin. We demonstrate the utility of the method by showing that the action potentials in cerebellar parallel fibers and hippocampal Schaffer collaterals had a slowly decaying, depolarized after-potential. The method is ideal for pharmacological tests, which we demonstrate by showing that the slow after-potential was sensitive to 4-AP, and that the membrane potential was reduced by 200μM Ba(2+). Copyright © 2012 Elsevier B.V. All rights reserved.

Electrophysiological characteristics of the Marshall bundle in humans

PubMed Central

Han, Seongwook; Joung, Boyoung; Scanavacca, Mauricio; Sosa, Eduardo; Chen, Peng-Sheng; Hwang, Chun

2010-01-01

BACKGROUND Marshall bundles (MBs) are the muscle bundles within the ligament of Marshall. OBJECTIVE This trial sought to the electrophysiological characteristics of the MB and the anatomical connections between MB and left atrium (LA) in patients with persistent atrial fibrillation (AF). METHODS We enrolled 72 patients (male:female 59:13, age 59.9 ± 9.4 years) who underwent MB mapping and ablation for AF. MB mapping was done via an endocardial or epicardial approach during sinus rhythm and AF. RESULTS Recordings were successful in 64 of 72 patients (89%). A single connection was noted in 11 of 64 patients between the MB and the coronary sinus (CS) muscle sleeves. The MB recordings showed distinct MB potentials with a proximal-to-distal activation pattern during sinus rhythm. During AF, organized passive activations and dissociated slow MB ectopic activities were commonly observed in this type of connection. Double connections to both CS and LA around left pulmonary veins were noted in 23 of 64 patients (36%). After the ablation of the distal connection, MB recording showed typical double potentials as in single connection. Multiple connections were noted in 30 of 64 patients (47%). During sinus rhythm, the earliest activation was in the middle of the MB. The activation patterns were irregular and variable in each patient. During AF, rapid and fractionated complex activations were noted in all patients of this group. CONCLUSION We documented 3 different types of MB–LA connections. Rapid and fractionated activations were most commonly observed in the MB that had multiple LA connections. PMID:20188860

Voids in mixed-cation silicate glasses: Studies by positron annihilation lifetime and Fourier transform infrared spectroscopies

NASA Astrophysics Data System (ADS)

Reben, M.; Golis, E.; Filipecki, J.; Sitarz, M.; Kotynia, K.; Jeleń, P.; Grelowska, I.

2014-08-01

PALS in comparison with FTIR studies have been applied to investigate the structure of different oxide glasses. Three components of the positron lifetime τ (τ1 para- and τ3 ortho-positronium and τ2 intermediate lifetime component) and their intensities were obtained. The results of the calculation of mean values of positron lifetimes for the investigated glasses showed the existence of a long-living component on the positron annihilation lifetime spectra. From the Tao-Eldrup formula we can estimate the size of free volume. On the basis of the measurements we can conclude that the size and fraction of free volume reaches the biggest value for the fused silica glass. The degree of network polymerisation increases void size.

Investigation of the plastic fracture of high-strength aluminum alloys

NASA Technical Reports Server (NTRS)

Van Stone, R. H.; Merchant, R. H.; Low, J. R., Jr.

1974-01-01

In a study of plastic fracture in five high-strength aluminum alloys (2014, 2024, 2124, 7075, and 7079), it has been shown that fracture toughness is affected primarily by the size and volume fraction of the larger (2 to 10 microms) second-phase particles. Certain of these particles crack at small plastic strains, nucleating voids which, with further plastic strain, coalesce to cause fracture. Not all second-phase particles crack at small plastic strains, and qualitative analysis of those which are primarily responsible for void nucleation shows that they contain iron or silicon or both. This result suggests that a reduction in the iron and silicon impurity content of the alloys should improve fracture toughness without loss of strength.

Bundled Postconditioning Therapies Improve Hemodynamics and Neurologic Recovery after 17 Minutes of Untreated Cardiac Arrest

PubMed Central

Bartos, Jason A.; Matsuura, Timothy R.; Sarraf, Mohammad; Youngquist, Scott T.; McKnite, Scott H.; Rees, Jennifer N.; Sloper, Daniel T.; Bates, Frank S.; Segal, Nicolas; Debaty, Guillaume; Lurie, Keith G.; Neumar, Robert W.; Metzger, Joseph M.; Riess, Matthias L.; Yannopoulos, Demetris

2014-01-01

Objective Ischemic postconditioning (stutter CPR) and sevoflurane have been shown to mitigate the effects of reperfusion injury in cardiac tissue after 15 minutes of ventricular fibrillation (VF) cardiac arrest. Poloxamer 188 (P188) has also proven beneficial to neuronal and cardiac tissue during reperfusion injury in human and animal models. We hypothesized that the use of stutter CPR, sevoflurane, and P188 combined with standard advanced life support would improve post-resuscitation cardiac and neurologic function after prolonged VF arrest. Methods Following 17 minutes of untreated VF, 20 pigs were randomized to Control treatment with active compression/decompression (ACD) CPR and impedance threshold device (ITD) (n=8) or Bundle therapy with stutter ACD CPR + ITD + sevoflurane + P188 (n=12). Epinephrine and post-resuscitation hypothermia were given in both groups per standard protocol. Animals that achieved return of spontaneous circulation (ROSC) were evaluated with echocardiography, biomarkers, and a blinded neurologic assessment with a cerebral performance category score. Results Bundle therapy improved hemodynamics during resuscitation, reduced need for epinephrine and repeated defibrillation, reduced biomarkers of cardiac injury and end-organ dysfunction, and increased left ventricular ejection fraction compared to Controls. Bundle therapy also improved rates of ROSC (100% vs. 50%), freedom from major adverse events (50% vs. 0% at 48 hours), and neurologic function (42% with mild or no neurologic deficit and 17% achieving normal function at 48 hours). Conclusions Bundle therapy with a combination of stutter ACD CPR, ITD, sevoflurane, and P188 improved cardiac and neurologic function after 17 minutes of untreated cardiac arrest in pigs. PMID:25447036

9 CFR 201.73-1 - Instructions for weighing livestock.

Code of Federal Regulations, 2011 CFR

2011-01-01

... by the Packers and Stockyards Programs. One copy of the form is to be filed with a regional office of... be marked void and a new one printed before the livestock is removed from the scale. (d) Scale... balanced with the pointer at the center of the target, movement of the fractional poise one graduation will...

9 CFR 201.73-1 - Instructions for weighing livestock.

Code of Federal Regulations, 2010 CFR

2010-01-01

... by the Packers and Stockyards Programs. One copy of the form is to be filed with a regional office of... be marked void and a new one printed before the livestock is removed from the scale. (d) Scale... balanced with the pointer at the center of the target, movement of the fractional poise one graduation will...

9 CFR 201.73-1 - Instructions for weighing livestock.

Code of Federal Regulations, 2014 CFR

2014-01-01

... by the Packers and Stockyards Programs. One copy of the form is to be filed with a regional office of... be marked void and a new one printed before the livestock is removed from the scale. (d) Scale... balanced with the pointer at the center of the target, movement of the fractional poise one graduation will...

Cement-based materials' characterization using ultrasonic attenuation

NASA Astrophysics Data System (ADS)

Punurai, Wonsiri

The quantitative nondestructive evaluation (NDE) of cement-based materials is a critical area of research that is leading to advances in the health monitoring and condition assessment of the civil infrastructure. Ultrasonic NDE has been implemented with varying levels of success to characterize cement-based materials with complex microstructure and damage. A major issue with the application of ultrasonic techniques to characterize cement-based materials is their inherent inhomogeneity at multiple length scales. Ultrasonic waves propagating in these materials exhibit a high degree of attenuation losses, making quantitative interpretations difficult. Physically, these attenuation losses are a combination of internal friction in a viscoelastic material (ultrasonic absorption), and the scattering losses due to the material heterogeneity. The objective of this research is to use ultrasonic attenuation to characterize the microstructure of heterogeneous cement-based materials. The study considers a real, but simplified cement-based material, cement paste---a common bonding matrix of all cement-based composites. Cement paste consists of Portland cement and water but does not include aggregates. First, this research presents the findings of a theoretical study that uses a set of existing acoustics models to quantify the scattered ultrasonic wavefield from a known distribution of entrained air voids. These attenuation results are then coupled with experimental measurements to develop an inversion procedure that directly predicts the size and volume fraction of entrained air voids in a cement paste specimen. Optical studies verify the accuracy of the proposed inversion scheme. These results demonstrate the effectiveness of using attenuation to measure the average size, volume fraction of entrained air voids and the existence of additional larger entrapped air voids in hardened cement paste. Finally, coherent and diffuse ultrasonic waves are used to develop a direct relationship between attenuation and water to cement (w/c) ratio. A phenomenological model based on the existence of fluid-filled capillary voids is used to help explain the experimentally observed behavior. Overall this research shows the potential of using ultrasonic attenuation to quantitatively characterize cement paste. The absorption and scattering losses can be related to the individual microstructural elements of hardened cement paste. By taking a fundamental, mechanics-based approach, it should be possible to add additional components such as scattering by aggregates or even microcracks in a systematic fashion and eventually build a realistic model for ultrasonic wave propagation study for concrete.

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

Margaret A. Marshall; John D. Bess; Yevgeniy Rozhikhin

In the early 1970s Dr. John T. Mihalczo (team leader), J.J. Lynn, and J.R. Taylor performed experiments at the Oak Ridge Critical Experiments Facility (ORCEF) with highly enriched uranium (HEU) metal (called Oak Ridge Alloy or ORALLOY) in an attempt to recreate GODIVA I results with greater accuracy than those performed at Los Alamos National Laboratory in the 1950s (HEU-MET-FAST-001). The purpose of the Oak Ridge ORALLOY Sphere (ORSphere) experiments was to estimate the unreflected and unmoderated critical mass of an idealized sphere of uranium metal corrected to a density, purity, and enrichment such that it could be compared withmore » the GODIVA I experiments[1]. Part of the experimental series was the measurement of the delayed neutron fraction, ßeff, using time correlation measurements and using the central void reactivity measurement. The time correlations measurements were rejected by the experimenter. The measurements using the central void reactivity measurement yielded a ßeff value of 0.00657, which agrees well with the value measured with GODIVA I (0.0066). This measurement is evaluated, found to be acceptable, and discussed in extensive detail in “ORSphere: Physics Measurements for Bare, HEU(93.2) Metal Sphere”[2]. In order to determine the delayed neutron fraction using the central void reactivity delayed neutron parameters must be used. The experimenter utilized the delayed neutron parameters set forth by Keepin, Wimment, and Zeigler[3]. If the derivation of the ßeff is repeated with different delayed neutron parameters from various modern nuclear data sets the resulting values vary greatly from the expected results.« less

Phenylethynyl Terminated Imide (PETI) Composites Made by High Temperature Vartm

NASA Technical Reports Server (NTRS)

Ghose, Sayata; Watson, Kent A.; Cano, Roberto J.; Britton, Sean M.; Jensen, Brian J.; Connell, John W.; Herring, Helen M.; Lineberry, Quentin J.

2010-01-01

The use of composites as primary structures on aerospace vehicles has increased dramatically over the past decade. As these advanced structures increase in size and complexity, their production costs have grown significantly. A major contributor to these manufacturing costs is the requirement of elevated pressures, during high temperature processing, to create fully consolidated composite parts. Recently, NASA Langley has licensed a series of low viscosity Phenyl Ethynyl Terminated Imide, PETI, oligomers that possess a wide processing window to allow for Resin Transfer Molding, RTM, processing. These resins, PETI-8 and PETI-330, demonstrate void fractions of approx.1% under elevated pressure consolidation. However, when used with a standardized thermal curing cycle in a High Temperature Vacuum Assisted RTM (HT-VARTM) process, they display undesirable void contents in excess of 7%. It was determined previously that under the thermal cycles used for laminate fabrication, the phenylethynyl endcap underwent degradation leading to volatile evolution. Modifications to the processing cycle used in the laminate fabrication have reduced the void content significantly (typically less than 3%) for carbon fiber biaxially woven fabric. For carbon fiber uniaxial fabric, void contents of less than 2% have been obtained using both PETI-8 and PETI-330. The resins were infused into carbon fiber preforms at 260 C and cured between 316 C and 371 C. Photomicrographs of the panels were taken and void contents were determined by acid digestion. Mechanical properties of the panels were determined at both room and elevated temperatures. These include short beam shear and flexure tests. The results of this work are presented herein.

Direct band gap measurement of Cu(In,Ga)(Se,S){sub 2} thin films using high-resolution reflection electron energy loss spectroscopy

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

Heo, Sung; College of Information and Communication Engineering, Sungkyunkwan University, Cheoncheon-dong 300, Jangan-gu, Suwon 440-746; Lee, Hyung-Ik

2015-06-29

To investigate the band gap profile of Cu(In{sub 1−x},Ga{sub x})(Se{sub 1−y}S{sub y}){sub 2} of various compositions, we measured the band gap profile directly as a function of in-depth using high-resolution reflection energy loss spectroscopy (HR-REELS), which was compared with the band gap profile calculated based on the auger depth profile. The band gap profile is a double-graded band gap as a function of in-depth. The calculated band gap obtained from the auger depth profile seems to be larger than that by HR-REELS. Calculated band gaps are to measure the average band gap of the spatially different varying compositions with respectmore » to considering its void fraction. But, the results obtained using HR-REELS are to be affected by the low band gap (i.e., out of void) rather than large one (i.e., near void). Our findings suggest an analytical method to directly determine the band gap profile as function of in-depth.« less

Decreased white matter integrity in fronto-occipital fasciculus bundles: relation to visual information processing in alcohol-dependent subjects.

PubMed

Bagga, Deepika; Sharma, Aakansha; Kumari, Archana; Kaur, Prabhjot; Bhattacharya, Debajyoti; Garg, Mohan Lal; Khushu, Subash; Singh, Namita

2014-02-01

Chronic alcohol abuse is characterized by impaired cognitive abilities with a more severe deficit in visual than in verbal functions. Neuropathologically, it is associated with widespread brain structural compromise marked by gray matter shrinkage, ventricular enlargement, and white matter degradation. The present study sought to increase current understanding of the impairment of visual processing abilities in alcohol-dependent subjects, and its correlation with white matter microstructural alterations, using diffusion tensor imaging (DTI). To that end, a DTI study was carried out on 35 alcohol-dependent subjects and 30 healthy male control subjects. Neuropsychological tests were assessed for visual processing skills and deficits were reported as raw dysfunction scores (rDyS). Reduced FA (fractional anisotropy) and increased MD (mean diffusivity) were observed bilaterally in inferior and superior fronto-occipital fasciculus (FOF) fiber bundles. A significant inverse correlation in rDyS and FA values was observed in these fiber tracts whereas a positive correlation of these scores was found with the MD values. Our results suggest that FOF fiber bundles linking the frontal lobe to occipital lobe might be related to visual processing skills. This is the first report of an alteration of the white matter microstructure of FOF fiber bundles that might have functional consequences for visual processing in alcohol-dependent subjects who exhibit no neurological complications. Copyright © 2014 Elsevier Inc. All rights reserved.

The microflow behavior and interphase characterization of fiber-reinforced polymer composites

NASA Astrophysics Data System (ADS)

Foley, Maureen Elizabeth

There is typically a trade off that takes place when designing a composite part for ballistic purposes. Structural strength requirements typically call for less than 1% voids with strong adhesion between the fiber and matrix whereas for ballistic applications, such as spall plates for body armor where energy absorbing properties are paramount, the composites are usually resin lean and have weaker fiber matrix interphases. The energy absorbing properties of a composite can be tailored through the sizings applied to the fiber or through control of the resin infiltration of the composite part. The goal of this research was two pronged. The first was to develop a transverse microflow model that could be used to predict the microflow within a tow assuming it is completely surrounded by resin. The models developed consider the capillary pressure on the flow front, which is typically ignored by literature models, as the main driving force for transverse flow into the fiber bundles. This capillary pressure is a function of the surface properties of the resin and fiber and by tailoring these properties one can control the microflow of the resin. The dynamic model, which takes into account the fiber radius, fiber volume fraction, fiber count, resin contact angle with the fiber and the resin surface tension, was used to study the effects of tow count, fiber volume fraction and contact angle on the infiltration time. The second goal of this research was the development of an interphase characterization methodology that can be used to evaluate the interphase properties, using the Dynamic Interphase Loading Apparatus (DILA), once the fiber preforms are infiltrated. The DILA is a unique piece of equipment that allows one to pushout a fiber from a thin composite slice while recording the resulting force and displacement. The interphase characterization process includes indenter selection, sample and test configuration design, test parameters, post test validation and data reduction. This process was used to evaluate glass fiber reinforced epoxy and vinyl ester systems under quasi-static and cyclic loading as examples of the DILA capabilities.

Meso-Scale Modeling of Spall in a Heterogeneous Two-Phase Material

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

Springer, Harry Keo

2008-07-11

The influence of the heterogeneous second-phase particle structure and applied loading conditions on the ductile spall response of a model two-phase material was investigated. Quantitative metallography, three-dimensional (3D) meso-scale simulations (MSS), and small-scale spall experiments provided the foundation for this study. Nodular ductile iron (NDI) was selected as the model two-phase material for this study because it contains a large and readily identifiable second- phase particle population. Second-phase particles serve as the primary void nucleation sites in NDI and are, therefore, central to its ductile spall response. A mathematical model was developed for the NDI second-phase volume fraction that accountedmore » for the non-uniform particle size and spacing distributions within the framework of a length-scale dependent Gaussian probability distribution function (PDF). This model was based on novel multiscale sampling measurements. A methodology was also developed for the computer generation of representative particle structures based on their mathematical description, enabling 3D MSS. MSS were used to investigate the effects of second-phase particle volume fraction and particle size, loading conditions, and physical domain size of simulation on the ductile spall response of a model two-phase material. MSS results reinforce existing model predictions, where the spall strength metric (SSM) logarithmically decreases with increasing particle volume fraction. While SSM predictions are nearly independent of applied load conditions at lower loading rates, which is consistent with previous studies, loading dependencies are observed at higher loading rates. There is also a logarithmic decrease in SSM for increasing (initial) void size, as well. A model was developed to account for the effects of loading rate, particle size, matrix sound-speed, and, in the NDI-specific case, the probabilistic particle volume fraction model. Small-scale spall experiments were designed and executed for the purpose of validating closely-coupled 3D MSS. While the spall strength is nearly independent of specimen thickness, the fragment morphology varies widely. Detailed MSS demonstrate that the interactions between the tensile release waves are altered by specimen thickness and that these interactions are primarily responsible for fragment formation. MSS also provided insights on the regional amplification of damage, which enables the development of predictive void evolution models.« less

High Temperature VARTM of Phenylethynyl Terminated Imides (PETI) Resins

NASA Technical Reports Server (NTRS)

Ghose, Sayata; Cano, Roberto J.; Britton, Sean M.; Watson, Kent A.; Jensen, Brian J.; Connell, John W.

2010-01-01

Fabrication of composite structures using vacuum assisted resin transfer molding (VARTM) is generally more affordable than conventional autoclave techniques. Recent efforts have focused on adapting VARTM for the fabrication of high temperature composites. Due to their low melt viscosity and long melt stability, certain phenylethynyl terminated imides (PETI) can be processed into composites using high temperature VARTM (HT-VARTM). However, one of the disadvantages of the current HT-VARTM resin systems has been the high porosity of the resultant composites. For aerospace applications a void fraction of less than 2% is desired. In the current study, two PETI resins, LARCTM PETI-330 and LARCTM PETI-8 have been used to fabricate test specimens using HT-VARTM. The resins were infused into carbon fiber preforms at 260 C and cured between 316 C and 371 C. Modifications to the thermal cycle used in the laminate fabrication have reduced the void content significantly (typically < 3%) for carbon fiber biaxially woven fabric. Photomicrographs of the panels were taken and void contents were determined by acid digestion. For carbon fiber uniaxial fabric, void contents of less than 2% have been obtained using both PETI-8 and PETI-330. Mechanical properties of the panels were determined at both room and elevated temperatures. These include short beam shear and flexure tests. The results of this work are presented herein.

Radiation-induced swelling of stainless steel.

PubMed

Shewmon, P G

1971-09-10

Significant swelling (1 to 10 percent due to small voids have been found in stainless steel when it is exposed to fast neutron doses less than expected in commercial fast breeder reactors. The main features of this new effect are: (i) the voids are formed by the precipitation of a small fraction of the radiation-produced vacancies; (ii) the voids form primarily in the temperature range 400 degrees to 600 degrees C (750 degrees to 1100 degrees F); and (iii) the volume increases with dose (fluence) at a rate between linear and parabolic. The limited temperature range of void formation can be explained, but the effects of fluence, microstructure, and composition are determined by a competition between several kinetic processes that are not well understood. This swelling does not affect the feasibility or safety of the breeder reactor,but will have a significant impact on the core design and economics of the breeder.Preliminary results indicate that one cannot eliminate the effect,but cold-working,heat treatment, or small changes in composition can reduce the swelling by a factor of 2 or more. Testing is hampered by the fact that several years in EBR-II are required to accumulate the fluence expected in demonstration plants. Heavyion accelerators,which allow damage rates corresponding to much higher fluxes than those found in EBR-II,hold great promise for short-term tests that will indicate the relative effect of the important variables.

Observations of Gas-Liquid Flows Through Contractions in Microgravity

NASA Technical Reports Server (NTRS)

McQuillen, John

1996-01-01

Tests were conducted for an air-water flow through two sudden contractions aboard the NASA DC-9 low gravity aircraft. Flow rate, residual accelerations, void fraction, film thickness, and pressure drop data were recorded and flow visualization at 250 images per second were recorded. Some preliminary results based on the flow visualization data are presented for bubbly, slug and annular flow.

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

White, D.B.

This paper reports on experiments to examine gas migration rates in drilling muds that were performed in a 15-m-long, 200-mm-ID inclinable flow loop where air injection simulates gas entry during a kick. These tests were conducted using a xanthum gum (a common polymer used in drilling fluids) solution to simulate drilling muds as the liquid phase and air as the gas phase. This work represents a significant extension of existing correlations for gas/liquid flows in large pipe diameters with non- Newtonian fluids. Bubbles rise faster in drilling muds than in water despite the increased viscosity. This surprising result is causedmore » by the change in the flow regime, with large slug-type bubbles forming at lower void fractions. The gas velocity is independent of void fraction, thus simplifying flow modeling. Results show that a gas influx will rise faster in a well than previously believed. This has major implications for kick simulation, with gas arriving at the surface earlier than would be expected and the gas outflow rate being higher than would have been predicted. A model of the two-phase gas flow in drilling mud, including the results of this work, has been incorporated into the joint Schlumberger Cambridge Research (SCR)/BP Intl. kick model.« less

Air-Induced Drag Reduction at High Reynolds Numbers: Velocity and Void Fraction Profiles

NASA Astrophysics Data System (ADS)

Elbing, Brian; Mäkiharju, Simo; Wiggins, Andrew; Dowling, David; Perlin, Marc; Ceccio, Steven

2010-11-01

The injection of air into a turbulent boundary layer forming over a flat plate can reduce the skin friction. With sufficient volumetric fluxes an air layer can separate the solid surface from the flowing liquid, which can produce drag reduction in excess of 80%. Several large scale experiments have been conducted at the US Navy's Large Cavitation Channel on a 12.9 m long flat plate model investigating bubble drag reduction (BDR), air layer drag reduction (ALDR) and the transition between BDR and ALDR. The most recent experiment acquired phase velocities and void fraction profiles at three downstream locations (3.6, 5.9 and 10.6 m downstream from the model leading edge) for a single flow speed (˜6.4 m/s). The profiles were acquired with a combination of electrode point probes, time-of-flight sensors, Pitot tubes and an LDV system. Additional diagnostics included skin-friction sensors and flow-field image visualization. During this experiment the inlet flow was perturbed with vortex generators immediately upstream of the injection location to assess the robustness of the air layer. From these, and prior measurements, computational models can be refined to help assess the viability of ALDR for full-scale ship applications.

Venturi flow meter and Electrical Capacitance Probe in a horizontal two-phase flow

NASA Astrophysics Data System (ADS)

Monni, G.; Caramello, M.; De Salve, M.; Panella, B.

2015-11-01

The paper presents the results obtained with a spool piece (SP) made of a Venturi flow meter (VMF) and an Electrical Capacitance Probe (ECP) in stratified two-phase flow. The objective is to determine the relationship between the test measurements and the physical characteristics of the flow such as superficial velocities, density and void fraction. The outputs of the ECP are electrical signals proportional to the void fraction between the electrodes; the parameters measured by the VFM are the total and the irreversible pressure losses of the two- phase mixture. The fluids are air and demineralized water at ambient conditions. The flow rates are in the range of 0,065-0,099 kg/s for air and 0- 0,039 kg/s (0-140 l/h) for water. The flow patterns recognized during the experiments are stratified, dispersed and annular flow. The presence of the VFM plays an important role on the alteration of the flow pattern due to wall flow detachment phenomena. The signals of differential pressure of the VFM in horizontal configuration are strongly dependent on the superficial velocities and on the flow pattern because of a lower symmetry of the flow with respect to the vertical configuration.

Diffusion amid random overlapping obstacles: Similarities, invariants, approximations

PubMed Central

Novak, Igor L.; Gao, Fei; Kraikivski, Pavel; Slepchenko, Boris M.

2011-01-01

Efficient and accurate numerical techniques are used to examine similarities of effective diffusion in a void between random overlapping obstacles: essential invariance of effective diffusion coefficients (Deff) with respect to obstacle shapes and applicability of a two-parameter power law over nearly entire range of excluded volume fractions (ϕ), except for a small vicinity of a percolation threshold. It is shown that while neither of the properties is exact, deviations from them are remarkably small. This allows for quick estimation of void percolation thresholds and approximate reconstruction of Deff (ϕ) for obstacles of any given shape. In 3D, the similarities of effective diffusion yield a simple multiplication “rule” that provides a fast means of estimating Deff for a mixture of overlapping obstacles of different shapes with comparable sizes. PMID:21513372

Investigation of stress relaxation mechanisms for ductility improvement in SS316L

NASA Astrophysics Data System (ADS)

Varma, Anand; Gokhale, Aditya; Jain, Jayant; Hariharan, Krishnaswamy; Cizek, Pavel; Barnett, Matthew

2018-01-01

Stress relaxation during plastic deformation has been reported to improve ductility and alter the mechanical properties of metallic materials. The aim of the present study is to investigate the role of various mechanisms responsible for this in stainless steel SS 316L. The fractography of the tested samples is analysed using an image analyser and the void fraction at failure is correlated with the corresponding mechanisms. The parametric studies on stress relaxation at different pre-strain and relaxation time correlate well with the fractography results supporting the proposed mechanisms. TEM investigation of dislocation structures and void characterisation further confirm the role of dislocation annihilation. Moreover, a novel indentation technique combining micro- and nano-indentation techniques is used to verify the role of stress homogenisation mechanism.

Permanent His-bundle pacing: a systematic literature review and meta-analysis.

PubMed

Zanon, Francesco; Ellenbogen, Kenneth A; Dandamudi, Gopi; Sharma, Parikshit S; Huang, Weijian; Lustgarten, Daniel L; Tung, Roderick; Tada, Hiroshi; Koneru, Jayanthi N; Bergemann, Tracy; Fagan, Dedra H; Hudnall, John Harrison; Vijayaraman, Pugazhendhi

2018-04-26

Permanent cardiac pacing of the His-bundle restores and retains normal electrical activation of the ventricles. Data on His-bundle pacing (HBP) are largely limited to small single-centre reports, and clinical benefits and risks have not been systematically examined. We sought to systematically examine published studies of patients undergoing permanent HBP and quantify the benefits and risks of the therapy. PubMed, Embase, and Cochrane Library were searched for full-text articles on permanent HBP. Clinical outcomes of interest included implant success rate, procedural and lead complications, pacing thresholds, QRS duration, and ejection fraction at follow-up, and mortality. Data were extracted and summarized. Where possible, meta-analysis of aggregate data was performed. Out of 2876 articles, 26 met the inclusion criteria representing 1438 patients with an implant attempt. Average age of patients was 73 years and 62.1% were implanted due to atrioventricular block. Overall average implant success rate was 84.8% and was higher with use of catheter-delivered systems (92.1%; P < 0.001). Average pacing thresholds were 1.71 V at implant and 1.79 V at >3 months follow-up; although, pulse widths varied at testing. Average left ventricular ejection fractions (LVEFs) were 42.8% at baseline and 49.5% at follow-up. There were 43 complications observed in 907 patients across the 17 studies that reported safety information. Among 26 articles of permanent HBP, the implant success rate averaged 84.8% and LVEF improved by an average of 5.9% during follow-up. Specific reporting of our clinical outcomes of interest varied widely, highlighting the need for uniform reporting in future HBP trials.

Study of galaxies in the Lynx-Cancer void - VII. New oxygen abundances

NASA Astrophysics Data System (ADS)

Pustilnik, S. A.; Perepelitsyna, Y. A.; Kniazev, A. Y.

2016-11-01

We present new or improved oxygen abundances (O/H) for the nearby Lynx-Cancer void updated galaxy sample. They are obtained via the SAO 6-m telescope spectroscopy (25 objects), or derived from the Sloan Digital Sky Survey spectra (14 galaxies, of which for seven objects O/H values were unknown). For eight galaxies with detected [O III] λ4363 line, O/H values are derived via the direct (Te) method. For the remaining objects, O/H was estimated via semi-empirical and empirical methods. For all accumulated O/H data for 81 galaxies of this void (with 40 of them derived via Te method), their relation `O/H versus MB' is compared with that for similar late-type galaxies from denser environments (the Local Volume `reference sample'). We confirm our previous conclusion derived for a subsample of 48 objects: void galaxies show systematically reduced O/H for the same luminosity with respect to the reference sample, in average by 0.2 dex, or by a factor of ˜1.6. Moreover, we confirm the fraction of ˜20 per cent of strong outliers, with O/H of two to four times lower than the typical values for the `reference' sample. The new data are consistent with the conclusion on the slower evolution of the main void galaxy population. We obtained Hα velocity for the faint optical counterpart of the most gas-rich (M(H I)/LB = 25) void object J0723+3624, confirming its connection with the respective H I blob. For similar extremely gas-rich dwarf J0706+3020, we give a tentative O/H ˜(O/H)⊙/45. In Appendix A, we present the results of calibration of semi-empirical method by Izotov & Thuan and of empirical calibrators by Pilyugin & Thuan and Yin et al. on the sample of ˜150 galaxies from the literature with O/H measured by Te method.

Heat Transfar Properties of Flat-Panel Evacuated Porous Insrlators

NASA Astrophysics Data System (ADS)

Yoneno, Hirosyi; Yamamoto, Ryoichi

Flat Panel evacuated porous insulators have been produced by filling powder or fiber (such as perlite powder, diatomaceous earth powder, silica aerogel powder, g lass fiber and ceramic fiber) in film-like laminated plastic container and by evacuating to form vacuum in it is interior. Heat transfer properties of these evacuated insulators have been studied under various conditions (such as particle diameter, surface area, packing density, solid volume fraction and void dimension). The apparent mean thermal conductivity has been measured for the boundary surface temperature at cold face temperature 13°C and hot face temperature 35°. The effect of air pressure ranging from 1 Pa to one atomosphere (105 Pa) was examined. The results were as follows. (1) For each powder the apparent mean thermal conductivity decreases with decreasing residual air pressure, and at very low pressure bellow 1 -103 Pa the conductivity becomes indeqendent of pressure. The thermal conductivity at 1.3Pa is 0.0053 W/mK for perlite powder, 0.0048W/mK for diatomaceous earth powder, 0.0043 W/mK for silica aerogel powder and 0.0029W/mK for glass fiber. (2) With decreasing particle size, the apparent mean thermal conductivity is constant independent of residual air pressure in higher pressure region. It is that void dimension continues to decrease with particle size and the mean free path of air becomes comparable with void dimension. (3) In the range of minor solid volume fraction, the apparent mean thermal conductivity at very low precreases with decreasing particle size. This shows the thermal contact resistance of the solid particle increases with decreasing particle size.

Experimental study on interfacial area transport in downward two-phase flow

NASA Astrophysics Data System (ADS)

Wang, Guanyi

In view of the importance of two group interfacial area transport equations and lack of corresponding accurate downward flow database that can reveal two group interfacial area transport, a systematic database for adiabatic, air-water, vertically downward two-phase flow in a round pipe with inner diameter of 25.4 mm was collected to gain an insight of interfacial structure and provide benchmarking data for two-group interfacial area transport models. A four-sensor conductivity probe was used to measure the local two phase flow parameters and data was collected with data sampling frequency much higher than conventional data sampling frequency to ensure the accuracy. Axial development of local flow parameter profiles including void fraction, interfacial area concentration, and Sauter mean diameter were presented. Drastic inter-group transfer of void fraction and interfacial area was observed at bubbly to slug transition flow. And the wall peaked interfacial area concentration profiles were observed in churn-turbulent flow. The importance of local data about these phenomenon on flow structure prediction and interfacial area transport equation benchmark was analyzed. Bedsides, in order to investigate the effect of inlet conditions, all experiments were repeated after installing the flow straightening facility, and the results were briefly analyzed. In order to check the accuracy of current data, the experiment results were cross-checked with rotameter measurement as well as drift-flux model prediction, the averaged error is less than 15%. Current models for two-group interfacial area transport equation were evaluated using these data. The results show that two-group interfacial area transport equations with current models can predict most flow conditions with error less than 20%, except some bubbly to slug transition flow conditions and some churn-turbulent flow conditions. The disagreement between models and experiments could result from underestimate of inter-group void transfer.

Tachyonic instabilities in 2  +  1 dimensional Yang-Mills theory and its connection to number theory

NASA Astrophysics Data System (ADS)

Chamizo, Fernando; González-Arroyo, Antonio

2017-06-01

We consider the 2  +  1 dimensional Yang-Mills theory with gauge group {{SU}}(N) on a flat 2-torus under twisted boundary conditions. We study the possibility of phase transitions (tachyonic instabilities) when N and the volume vary and certain chromomagnetic flux associated to the topology of the bundle can be adjusted. Under natural assumptions about how to match the perturbative regime and the expected confinement, we prove that the absence of tachyonic instabilities is related to some problems in number theory, namely the Diophantine approximation of irreducible fractions by other fractions of smaller denominator.

Comparison of urine specimen collection times and testing fractions for the detection of high-risk human papillomavirus and high-grade cervical precancer.

PubMed

Senkomago, V; Des Marais, A C; Rahangdale, L; Vibat, C R T; Erlander, M G; Smith, J S

2016-01-01

Urine testing for high-risk human papillomavirus (HR-HPV) detection could provide a non-invasive, simple method for cervical cancer screening. We examined whether HR-HPV detection is affected by urine collection time, portion of urine stream, or urine fraction tested, and assessed the performance of HR-HPV testing in urine for detection of cervical intraepithelial neoplasia grade II or worse (CIN2+). A total of 37 female colposcopy clinic attendees, ≥ 30 years, provided three urine samples: "first void" urine collected at home, and "initial stream" and "mid-stream" urine samples collected at the clinic later in the day. Self- and physician-collected brush specimens were obtained at the same clinic visit. Colposcopy was performed and directed biopsies obtained if clinically indicated. For each urine sample, HR-HPV DNA testing was conducted for unfractionated, pellet, and supernatant fractions using the Trovagene test. HR-HPV mRNA testing was performed on brush specimens using the Aptima HPV assay. HR-HPV prevalence was similar in unfractionated and pellet fractions of all urine samples. For supernatant urine fractions, HR-HPV prevalence appeared lower in mid-stream urine (56.8%[40.8-72.7%]) than in initial stream urine (75.7%[61.9-89.5%]). Sensitivity of CIN2+ detection was identical for initial stream urine and physician-collected cervical specimen (89.9%[95%CI=62.7-99.6%]), and similar to self-collected vaginal specimen (79.1%[48.1-96.6%]). This is among the first studies to compare methodologies for collection and processing of urine for HR-HPV detection. HR-HPV prevalence was similar in first void and initial stream urine, and was highly sensitive for CIN2+ detection. Additional research in a larger and general screening population is needed. Copyright © 2015 Elsevier B.V. All rights reserved.

Chemisorption and Diffusion of H on a Graphene Sheet and Single-Wall Carbon Nanotubes

NASA Technical Reports Server (NTRS)

Srivastava, Deepak; Dzegilenko, Fedor; Menon, Madhu

2000-01-01

Recent experiments on hydrogen storage in single wall nanotubes and nanotube bundles have reported large fractional weight of stored molecular hydrogen which are not in agreement with theoretical estimates based of simulation of hydrogen storage by physisorption mechanisms. Hydrogen storage in catalytically doped nanotube bundles indicate that atomic H might undergo chemisorption changing the basic nature of the storage mechanism under investigation by many groups. Using a generalized tight-binding molecular dynamics (GTBMD) method for reactive C-H dynamics, we investigate chemisorption and diffusion of atomic H on graphene sheet and C nanotubes. Effective potential energy surfaces (EPS) for chemisorption and diffusion are calculated for graphene sheet and nanotubes of different curvatures. Analysis of the activation barriers and quantum rate constants, computed via wave-packet dynamics method, will be discussed in this presentation.

Uncertainty Quantification of Multi-Phase Closures

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

Nadiga, Balasubramanya T.; Baglietto, Emilio

In the ensemble-averaged dispersed phase formulation used for CFD of multiphase ows in nuclear reactor thermohydraulics, closures of interphase transfer of mass, momentum, and energy constitute, by far, the biggest source of error and uncertainty. Reliable estimators of this source of error and uncertainty are currently non-existent. Here, we report on how modern Validation and Uncertainty Quanti cation (VUQ) techniques can be leveraged to not only quantify such errors and uncertainties, but also to uncover (unintended) interactions between closures of di erent phenomena. As such this approach serves as a valuable aide in the research and development of multiphase closures.more » The joint modeling of lift, drag, wall lubrication, and turbulent dispersion|forces that lead to tranfer of momentum between the liquid and gas phases|is examined in the frame- work of validation of the adiabatic but turbulent experiments of Liu and Banko , 1993. An extensive calibration study is undertaken with a popular combination of closure relations and the popular k-ϵ turbulence model in a Bayesian framework. When a wide range of super cial liquid and gas velocities and void fractions is considered, it is found that this set of closures can be validated against the experimental data only by allowing large variations in the coe cients associated with the closures. We argue that such an extent of variation is a measure of uncertainty induced by the chosen set of closures. We also nd that while mean uid velocity and void fraction pro les are properly t, uctuating uid velocity may or may not be properly t. This aspect needs to be investigated further. The popular set of closures considered contains ad-hoc components and are undesirable from a predictive modeling point of view. Consequently, we next consider improvements that are being developed by the MIT group under CASL and which remove the ad-hoc elements. We use non-intrusive methodologies for sensitivity analysis and calibration (using Dakota) to study sensitivities of the CFD representation (STARCCM+) of uid velocity pro les and void fraction pro les in the context of Shaver and Podowski, 2015 correction to lift, and the Lubchenko et al., 2017 formulation of wall lubrication.« less

Studies of Two-Phase Gas-Liquid Flow in Microgravity. Ph.D. Thesis, Dec. 1994

NASA Technical Reports Server (NTRS)

Bousman, William Scott

1995-01-01

Two-phase gas-liquid flows are expected to occur in many future space operations. Due to a lack of buoyancy in the microgravity environment, two-phase flows are known to behave differently than those in earth gravity. Despite these concerns, little research has been conducted on microgravity two-phase flow and the current understanding is poor. This dissertation describes an experimental and modeling study of the characteristics of two-phase flows in microgravity. An experiment was operated onboard NASA aircraft capable of producing short periods of microgravity. In addition to high speed photographs of the flows, electronic measurements of void fraction, liquid film thickness, bubble and wave velocity, pressure drop and wall shear stress were made for a wide range of liquid and gas flow rates. The effects of liquid viscosity, surface tension and tube diameter on the behavior of these flows were also assessed. From the data collected, maps showing the occurrence of various flow patterns as a function of gas and liquid flow rates were constructed. Earth gravity two-phase flow models were compared to the results of the microgravity experiments and in some cases modified. Models were developed to predict the transitions on the flow pattern maps. Three flow patterns, bubble, slug and annular flow, were observed in microgravity. These patterns were found to occur in distinct regions of the gas-liquid flow rate parameter space. The effect of liquid viscosity, surface tension and tube diameter on the location of the boundaries of these regions was small. Void fraction and Weber number transition criteria both produced reasonable transition models. Void fraction and bubble velocity for bubble and slug flows were found to be well described by the Drift-Flux model used to describe such flows in earth gravity. Pressure drop modeling by the homogeneous flow model was inconclusive for bubble and slug flows. Annular flows were found to be complex systems of ring-like waves and a substrate film. Pressure drop was best fitted with the Lockhart- Martinelli model. Force balances suggest that droplet entrainment may be a large component of the total pressure drop.

Diffusion Tensor Imaging of Incentive Effects in Prospective Memory after Pediatric Traumatic Brain Injury

PubMed Central

Wilde, Elisabeth A.; Bigler, Erin D.; Chu, Zili; Yallampalli, Ragini; Oni, Margaret B.; Wu, Trevor C.; Ramos, Marco A.; Pedroza, Claudia; Vásquez, Ana C.; Hunter, Jill V.; Levin, Harvey S.

2011-01-01

Abstract Few studies exist investigating the brain-behavior relations of event-based prospective memory (EB-PM) impairments following traumatic brain injury (TBI). To address this, children with moderate-to-severe TBI performed an EB-PM test with two motivational enhancement conditions and underwent concurrent diffusion tensor imaging (DTI) at 3 months post-injury. Children with orthopedic injuries (OI; n = 37) or moderate-to-severe TBI (n = 40) were contrasted. Significant group differences were found for fractional anisotropy (FA) and apparent diffusion coefficient for orbitofrontal white matter (WM), cingulum bundles, and uncinate fasciculi. The FA of these WM structures in children with TBI significantly correlated with EB-PM performance in the high, but not the low motivation condition. Regression analyses within the TBI group indicated that the FA of the left cingulum bundle (p = 0.003), left orbitofrontal WM (p < 0.02), and left (p < 0.02) and right (p < 0.008) uncinate fasciculi significantly predicted EB-PM performance in the high motivation condition. We infer that the cingulum bundles, orbitofrontal WM, and uncinate fasciculi are important WM structures mediating motivation-based EB-PM responses following moderate-to-severe TBI in children. PMID:21250917

Recruitment Kinetics of Tropomyosin Tpm3.1 to Actin Filament Bundles in the Cytoskeleton Is Independent of Actin Filament Kinetics.

PubMed

Appaduray, Mark A; Masedunskas, Andrius; Bryce, Nicole S; Lucas, Christine A; Warren, Sean C; Timpson, Paul; Stear, Jeffrey H; Gunning, Peter W; Hardeman, Edna C

2016-01-01

The actin cytoskeleton is a dynamic network of filaments that is involved in virtually every cellular process. Most actin filaments in metazoa exist as a co-polymer of actin and tropomyosin (Tpm) and the function of an actin filament is primarily defined by the specific Tpm isoform associated with it. However, there is little information on the interdependence of these co-polymers during filament assembly and disassembly. We addressed this by investigating the recovery kinetics of fluorescently tagged isoform Tpm3.1 into actin filament bundles using FRAP analysis in cell culture and in vivo in rats using intracellular intravital microscopy, in the presence or absence of the actin-targeting drug jasplakinolide. The mobile fraction of Tpm3.1 is between 50% and 70% depending on whether the tag is at the C- or N-terminus and whether the analysis is in vivo or in cultured cells. We find that the continuous dynamic exchange of Tpm3.1 is not significantly impacted by jasplakinolide, unlike tagged actin. We conclude that tagged Tpm3.1 may be able to undergo exchange in actin filament bundles largely independent of the assembly and turnover of actin.

The BEACH protein LRBA is required for hair bundle maintenance in cochlear hair cells and for hearing.

PubMed

Vogl, Christian; Butola, Tanvi; Haag, Natja; Hausrat, Torben J; Leitner, Michael G; Moutschen, Michel; Lefèbvre, Philippe P; Speckmann, Carsten; Garrett, Lillian; Becker, Lore; Fuchs, Helmut; Hrabe de Angelis, Martin; Nietzsche, Sandor; Kessels, Michael M; Oliver, Dominik; Kneussel, Matthias; Kilimann, Manfred W; Strenzke, Nicola

2017-11-01

Lipopolysaccharide-responsive beige-like anchor protein (LRBA) belongs to the enigmatic class of BEACH domain-containing proteins, which have been attributed various cellular functions, typically involving intracellular protein and membrane transport processes. Here, we show that LRBA deficiency in mice leads to progressive sensorineural hearing loss. In LRBA knockout mice, inner and outer hair cell stereociliary bundles initially develop normally, but then partially degenerate during the second postnatal week. LRBA deficiency is associated with a reduced abundance of radixin and Nherf2, two adaptor proteins, which are important for the mechanical stability of the basal taper region of stereocilia. Our data suggest that due to the loss of structural integrity of the central parts of the hair bundle, the hair cell receptor potential is reduced, resulting in a loss of cochlear sensitivity and functional loss of the fraction of spiral ganglion neurons with low spontaneous firing rates. Clinical data obtained from two human patients with protein-truncating nonsense or frameshift mutations suggest that LRBA deficiency may likewise cause syndromic sensorineural hearing impairment in humans, albeit less severe than in our mouse model. © 2017 The Authors.

A porcine model of bladder outlet obstruction incorporating radio-telemetered cystometry.

PubMed

Shaw, Matthew B; Herndon, Claude D; Cain, Mark P; Rink, Richard C; Kaefer, Martin

2007-07-01

To present a novel porcine model of bladder outlet obstruction (BOO) with a standardized bladder outlet resistance and real-time ambulatory radio-telemetered cystometry, as BOO is a common condition with many causes in both adults and children, with significant morbidity and occasional mortality, but attempts to model this condition in many animal models have the fundamental problem of standardising the degree of outlet resistance. BOO was created in nine castrated male pigs by dividing the mid-urethra; outflow was allowed through an implanted bladder drainage catheter containing a resistance valve, allowing urine to flow across the valve only when a set pressure differential was generated across the valve. An implantable radio-telemetered pressure sensor monitored the pressure within the bladder and abdominal cavity, and relayed this information to a remote computer. Four control pigs had an occluded bladder drainage catheter and pressure sensor placed, but were allowed to void normally through the native urethra. Intra-vesical pressure was monitored by telemetry, while the resistance valve was increased weekly, beginning with 2 cmH2O and ultimately reaching 10 cmH2O. The pigs were assessed using conventional cystometry under anaesthesia before death, and samples conserved in formalin for haematoxylin and eosin staining. The pigs had radio-telemetered cystometry for a median of 26 days. All telemetry implants functioned well for the duration of the experiment, but one pig developed a urethral fistula and was excluded from the study. With BOO the bladder mass index (bladder mass/body mass x 10 000) increased from 9.7 to 20 (P = 0.004), with a significant degree of hypertrophy of the detrusor smooth muscle bundles. Obstructed bladders were significantly less compliant than control bladders (8.3 vs 22.1 mL/cmH2O, P = 0.03). Telemetric cystometry showed that there was no statistically significance difference in mean bladder pressure between obstructed and control pigs (4.8 vs 6.7 cmH2O, P = 0.7), but that each void was longer in the pigs with BOO. This new model of BOO provides a method of reliably and precisely defining the bladder outlet resistance; it induces the changes classically seen with BOO, including increased bladder mass, increased smooth muscle bundle size and decreased compliance.

The sea urchin egg jelly coat consists of globular glycoproteins bound to a fibrous fucan superstructure.

PubMed

Bonnell, B S; Keller, S H; Vacquier, V D; Chandler, D E

1994-03-01

Intact egg jelly (EJ) coats surrounding eggs of the sea urchin Strongylocentrotus purpuratus were visualized in stereo images of platinum replicas produced by the quick-freeze, deep-etch, rotary-shadowing technique. The hydrated EJ coat forms an extensive fibrous network that makes contact with the vitelline layer at the egg surface. Fibers are decorated along their length with particles, particle density being highest in the interior regions of the coat. The macromolecular components making up the EJ network were visualized by rotary-shadowing of mica-adsorbed EJ samples. Whole EJ coats solubilized in pH 5 sea-water and spread on the mica surface consist of complex networks of branching fibers decorated with large patches of amorphous material. As we have previously shown (Keller and Vacquier, 1994), EJ boiled in a dissolution buffer containing SDS and beta-mercaptoethanol and applied to a Sephacryl-500 gel filtration column can be separated into three fractions: a 380-kDa fucose sulfate polymer (FSP), which elutes in the void volume, and two column-included fractions consisting of intermediate (300 kDa) and low-molecular-weight (30- to 138-kDa) glycoproteins. Rotary-shadowing of the FSP fraction reveals branched fibrous components similar in appearance to that of solubilized whole EJ but devoid of any particulate decoration. In contrast, intermediate- and low-molecular-weight EJ components are strictly globular in appearance but are distinguishable on the basis of size. Ion-exchange purification of whole EJ yields two glycoproteins, of 82 and 138 kDa, having AR-inducing activity (Keller and Vacquier, 1994). Platinum replication shows these active components to be small spherical molecules about 8 nm in diameter. The above fractionation scheme requires harsh dissociation conditions. Indeed, if EJ is not boiled in SDS buffer before fractionation, the 300-kDa fraction and the FSP appear together in the void volume. Rotary-shadowing of this complex reveals a multistranded polymer, decorated with glycoproteins at specific kink points. Taken together, our data suggest that the EJ network is composed of a fucose sulfate polymer superstructure to which glycoproteins are bound.

Obtaining of Analytical Relations for Hydraulic Parameters of Channels With Two Phase Flow Using Open CFD Toolbox

NASA Astrophysics Data System (ADS)

Varseev, E.

2017-11-01

The present work is dedicated to verification of numerical model in standard solver of open-source CFD code OpenFOAM for two-phase flow simulation and to determination of so-called “baseline” model parameters. Investigation of heterogeneous coolant flow parameters, which leads to abnormal friction increase of channel in two-phase adiabatic “water-gas” flows with low void fractions, presented.

Reduced integrity of the uncinate fasciculus and cingulum in depression: A stem-by-stem analysis.

PubMed

Bhatia, Kartik D; Henderson, Luke A; Hsu, Eugene; Yim, Mark

2018-08-01

The subgenual cingulate gyrus (Brodmann's Area 25: BA25) is hypermetabolic in depression and has been targeted successfully with deep brain stimulation. Two of the white matter tracts that play a role in treatment response are the uncinate fasciculus (UF) and the cingulum bundle. The UF has three prefrontal stems, the most medial of which extends from BA25 (which deals with mood regulation) and the most lateral of which extends from the dorso-lateral prefrontal cortex (concerned with executive function). The cingulum bundle has numerous fibers connecting the lobes of the cerebrum, with the longest fibers extending from BA25 to the amygdala. We hypothesize that there is reduced integrity in the UF, specific to the medial prefrontal stems, as well as in the subgenual and amygdaloid fibers of the cingulum bundle. Our secondary hypothesis is that these changes are present from the early stages of depression. Compare the white matter integrity of stems of the UF and components of the cingulum bundle in first-onset depressed, recurrent/chronic depressed, and non-depressed control subjects. Depressed patients (n = 103, first-onset = 57, chronic = 46) and non-depressed control subjects (n = 74) underwent MRI with 32-directional DTI sequences. The uncinate fasciculi and cingulum bundles were seeded, and the fractional anisotropy (FA) measured in each of the three prefrontal stems and the body of the UF, as well as the subgenual, body, and amygdaloid fiber components of the cingulum bundle. FA measurements were compared between groups using ANOVA testing with post-hoc Tukey analysis. There were significant reductions in FA in the subgenual and polar stems of the UF bilaterally, as well as the subgenual and amygdaloid fibers of the cingulum bundle, in depressed patients compared with controls (p < 0.001). There was no significant difference seen in the lateral UF stem or the main body of the cingulum. No significant difference was demonstrated in any of the tracts between first-onset and chronic depression patients. Depressed patients have reduced white matter integrity in the subgenual and polar stems of the uncinate fasciculi but not the lateral stems, as well as in the subgenual and amygdaloid cingulum fibers. These changes are present from the first-onset of the disease. Copyright © 2018 Elsevier B.V. All rights reserved.

On the structure of nonlinear waves in liquids with gas bubbles

NASA Astrophysics Data System (ADS)

Beylich, Alfred E.; Gülhan, Ali

1990-08-01

Transient wave phenomena in two-phase mixtures with a liquid as the matrix and gas bubbles as the dispersed phase have been studied in a shock tube using glycerine as the liquid and He, N2, and SF6 as gases having a large variation in the ratio of specific heats and the thermal diffusivity. Two different sizes of bubble radii have been produced , R0=1.15 and 1.6 mm, with a dispersion in size of less than 5%. The void fraction was varied over one order of magnitude, φ0=0.2%-2%. The measured pressure profiles were averaged by superimposing many shots, typically 20. Speeds and profiles were measured for shock waves and for wave packets. Investigation of the wave structure allows one to approach the fundamental question of how the physics on the level of the microstructure influences the behavior on the macroscale. In the theoretical work, modeling on the basis of a hierarchy of characteristic length scales is developed. Bubble interactions, transient heat transfer, and dissipation due to molecular and bulk viscosities are included. Solutions for small void fractions and moderate amplitudes are obtained for the steady cases of shock waves and solitons and are compared with the experimental results.

Bubble breakup phenomena in a venturi tube

NASA Astrophysics Data System (ADS)

Fujiwara, Akiko

2005-11-01

Microbubble has distinguished characteristics of large surface area to unit volume and small buoyancy, and it has advantages in many engineering fields. Recently microbubble generators with low energy and high performance are required to wide applications. In the present study, we propose one new effective technique to generate tiny bubbles with less than 200 μm diameter utilizing venturi tube under high void fraction condition. The objective of the present study is to elucidate the mechanism of bubble breakup phenomena in the venturi tube and to clarify the effects of parameters which are necessary to realize an optimum system experimentally. Experiment was conducted with void fraction of 4% and variation of liquid velocity from 9 to 26 m/s at the throat. Under low velocity condition, bubbles which were observed with a high speed camera parted gradually in a wide region. On the contrary under high velocity condition, bubbles expanded after passing through the throat and shrank rapidly. Since the speed of sound in gas-liquid system is extremely lower than that of single-phase flow, the bubble breakup phenomenon in the venturi tube is explained as the supersonic flow in a Laval nozzle. By rapid pressure recovery in diverging area, expanding bubbles collapse violently. The tiny bubbles are generated due to the surface instability of shrinking bubbles.

Space charge neutralization by electron-transparent suspended graphene

PubMed Central

Srisonphan, Siwapon; Kim, Myungji; Kim, Hong Koo

2014-01-01

Graphene possesses many fascinating properties originating from the manifold potential for interactions at electronic, atomic, or molecular levels. Here we report measurement of electron transparency and hole charge induction response of a suspended graphene anode on top of a void channel formed in a SiO2/Si substrate. A two-dimensional (2D) electron gas induced at the oxide interface emits into air and makes a ballistic transport toward the suspended graphene. A small fraction (>~0.1%) of impinging electrons are captured at the edge of 2D hole system in graphene, demonstrating good transparency to very low energy (<3 eV) electrons. The hole charges induced in the suspended graphene anode have the effect of neutralizing the electron space charge in the void channel. This charge compensation dramatically enhances 2D electron gas emission at cathode to the level far surpassing the Child-Langmuir's space-charge-limited emission. PMID:24441774

TRAC-PD2 posttest analysis of CCTF Test C1-16 (Run 025). [Cylindrical Core Test Facility

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

Sugimoto, J.

The TRAC-PD2 code version was used to analyze CCTF Test C1-16 (Run 025). The results indicate that the core heater rod temperatures, the liquid mass in the vessel, and differential pressures in the primary loop are predicted well, but the void fraction distribution in the core and water accumulation in the upper plenum are not in good agreement with the data.

Characterization of Convective Boiling in Branching Channel Heat Sinks

DTIC Science & Technology

2009-05-06

pressure drop was well predicted using the void fraction correlation of Zivi [11] and the phase interaction parameter of Qu and Mudawar [16]. Model...paper number HT2008-56253, ASME Heat Transfer Summer Conference, August 10-14, 2008, Jacksonville, FL. 16. W. Qu, I. Mudawar , Measurement and...level. The Zivi [11] correlation is also recommended, with the two-phase interaction parameter of Qu and Mudawar [16] for use in the one-dimensional

Structural Investigations of Fibers and Films of Poly(p-phenylene benzobisthiazole). Volume 1

DTIC Science & Technology

1982-05-01

differential scanning calorimetry, is unrelated to the diffuse scattered intensity [45]. Cellulose acetate which is known to be noncrystalline exhibits a high...Weidinger [45] found the diffuse scattered intensity increased with decreasing density and therefore, increasing void fraction, in air swollen cellulose ... Cellulose , and Poly(y-Benzyl-L-Glutamate)." J. Polym. Sci., Polym. Phys. Ed., 18, 663-682 (1980). 39. C.H. Kao and J.M. Ottino, personal communication

Diffusion tensor imaging of cingulum bundle and corpus callosum in schizophrenia vs. bipolar disorder.

PubMed

Nenadić, Igor; Hoof, Anna; Dietzek, Maren; Langbein, Kerstin; Reichenbach, Jürgen R; Sauer, Heinrich; Güllmar, Daniel

2017-08-30

Both schizophrenia and bipolar disorder show abnormalities of white matter, as seen in diffusion tensor imaging (DTI) analyses of major brain fibre bundles. While studies in each of the two conditions have indicated possible overlap in anatomical location, there are few direct comparisons between the disorders. Also, it is unclear whether phenotypically similar subgroups (e.g. patients with bipolar disorder and psychotic features) might share white matter pathologies or be rather similar. Using region-of-interest (ROI) analysis of white matter with diffusion tensor imaging (DTI) at 3 T, we analysed fractional anisotropy (FA), radial diffusivity (RD), and apparent diffusion coefficient (ADC) of the corpus callosum and cingulum bundle in 33 schizophrenia patients, 17 euthymic (previously psychotic) bipolar disorder patients, and 36 healthy controls. ANOVA analysis showed significant main effects of group for RD and ADC (both elevated in schizophrenia). Across the corpus callosum ROIs, there was not group effect on FA, but for RD (elevated in schizophrenia, lower in bipolar disorder) and ADC (higher in schizophrenia, intermediate in bipolar disorder). Our findings show similarities and difference (some gradual) across regions of the two major fibre tracts implicated in these disorders, which would be consistent with a neurobiological overlap of similar clinical phenotypes. Copyright © 2017 Elsevier Ireland Ltd. All rights reserved.

Microscopic Analysis of Bacterial Motility at High Pressure

PubMed Central

Nishiyama, Masayoshi; Sowa, Yoshiyuki

2012-01-01

The bacterial flagellar motor is a molecular machine that converts an ion flux to the rotation of a helical flagellar filament. Counterclockwise rotation of the filaments allows them to join in a bundle and propel the cell forward. Loss of motility can be caused by environmental factors such as temperature, pH, and solvation. Hydrostatic pressure is also a physical inhibitor of bacterial motility, but the detailed mechanism of this inhibition is still unknown. Here, we developed a high-pressure microscope that enables us to acquire high-resolution microscopic images, regardless of applied pressures. We also characterized the pressure dependence of the motility of swimming Escherichia coli cells and the rotation of single flagellar motors. The fraction and speed of swimming cells decreased with increased pressure. At 80 MPa, all cells stopped swimming and simply diffused in solution. After the release of pressure, most cells immediately recovered their initial motility. Direct observation of the motility of single flagellar motors revealed that at 80 MPa, the motors generate torque that should be sufficient to join rotating filaments in a bundle. The discrepancy in the behavior of free swimming cells and individual motors could be due to the applied pressure inhibiting the formation of rotating filament bundles that can propel the cell body in an aqueous environment. PMID:22768943

Flexible ex vivo phantoms for validation of diffusion tensor tractography on a clinical scanner.

PubMed

Watanabe, Makoto; Aoki, Shigeki; Masutani, Yoshitaka; Abe, Osamu; Hayashi, Naoto; Masumoto, Tomohiko; Mori, Harushi; Kabasawa, Hiroyuki; Ohtomo, Kuni

2006-11-01

The aim of this study was to develop ex vivo diffusion tensor (DT) flexible phantoms. Materials were bundles of textile threads of cotton, monofilament nylon, rayon, and polyester bunched with spiral wrapping bands and immersed in water. DT images were acquired on a 1.5-Tesla clinical magnetic resonance scanner using echo planar imaging sequences with 15 motion probing gradient directions. DT tractography with seeding and a line-tracking method was carried out by software originally developed on a PC-based workstation. We observed relatively high fractional anisotropy on the polyester phantom and were able to reconstruct tractography. Straight tracts along the bundle were displayed when it was arranged linearly. It was easy to bend arcuately or bifurcate at one end; and tracts followed the course of the bundle, whether it was curved or branched and had good agreement with direct visual observation. Tractography with the other fibers was unsuccessful. The polyester phantom revealed a diffusion anisotropic structure according to its shape and would be utilizable repeatedly under the same conditions, differently from living central neuronal system. It would be useful to validate DT sequences and to optimize an algorithm or parameters of DT tractography software. Additionally, the flexibility of the phantom would enable us to model human axonal projections.

High Temperature VARTM of Phenylethynyl Terminated Imides

NASA Technical Reports Server (NTRS)

Cano, Roberto J.; Britton, Sean M.; Jensen, Brian J.; Connell, John W.; Herring, Helen M.; Linberry, Quentin J.; Ghose, Sayata; Watson, Kent A.

2009-01-01

Fabrication of composite structures using vacuum assisted resin transfer molding (VARTM) is generally more affordable than conventional autoclave techniques. Recent efforts have focused on adapting VARTM for the fabrication of high temperature composites. Due to their low melt viscosity and long melt stability, certain phenylethynyl terminated imides (PETI) can be processed into composites using high temperature VARTM (HT-VARTM). However, one of the disadvantages of the current HT-VARTM resin systems has been the high porosity of the resultant composites. For aerospace applications, the desired void fraction of less than 2% has not yet been achieved. In the current study, two PETI resins, LaRC PETI-330 and LaRC PETI-8 have been used to make test specimens using HT-VARTM. The resins were infused into ten layers of IM7-6K carbon fiber 5-harness satin fabric at 260 C or 280 C and cured at 371 C. Initial runs yielded composites with high void content, typically greater than 7% by weight. A thermogravimetric-mass spectroscopic study was conducted to determine the source of volatiles leading to high porosity. It was determined that under the thermal cycle used for laminate fabrication, the phenylethynyl endcap was undergoing degradation leading to volatile evolution. By modifying the thermal cycle used in laminate fabrication, the void content was reduced significantly (typically approximately 3%). Densities of the composites were determined using a density gradient column and the glass transition temperatures of the cured composites were measured by dynamic mechanical analysis. Photomicrographs of the panels were taken and void contents were determined by acid digestion. The results of this work are presented herein.

Epicardial Breakthrough Waves During Sinus Rhythm: Depiction of the Arrhythmogenic Substrate?

PubMed

Mouws, Elisabeth M J P; Lanters, Eva A H; Teuwen, Christophe P; van der Does, Lisette J M E; Kik, Charles; Knops, Paul; Bekkers, Jos A; Bogers, Ad J J C; de Groot, Natasja M S

2017-09-01

Epicardial breakthrough waves (EBW) during atrial fibrillation are important elements of the arrhythmogenic substrate and result from endo-epicardial asynchrony, which also occurs to some degree during sinus rhythm (SR). We examined the incidence and characteristics of EBW during SR and its possible value in the detection of the arrhythmogenic substrate associated with atrial fibrillation. Intraoperative epicardial mapping (interelectrode distances 2 mm) of the right atrium, Bachmann's bundle, the left atrioventricular groove, and the pulmonary vein area was performed during SR in 381 patients (289 male, 67±10 years) with ischemic or valvular heart disease. EBW were referred to as sinus node breakthrough waves if they were the earliest right atrial activated site. A total of 218 EBW and 57 sinus node breakthrough waves were observed in 168 patients (44%). EBW mostly occurred at right atrium (N=105, 48%) and left atrioventricular groove (N=67, 31%), followed by Bachmann's bundle (N=27, 12%) and pulmonary vein area (N=19, 9%; P <0.001). EBW occurred most often in ischemic heart disease patients (N=114, 49%) compared with (ischemic and) valvular heart disease patients (N=26, 17%; P <0.001). EBW electrograms most often consisted of double and fractionated potentials (N=137, 63%). In case of single potentials, an R wave was observed in 88% (N=71) of EBW, as opposed to 21% of sinus node breakthrough waves (N=5; P <0.001). Fractionated EBW potentials were more often observed at the right atrium and Bachmann's bundle ( P <0.001). During SR, EBW are present in over a third of patients, particularly in thicker parts of the atrial wall. Features of SR EBW indicate that muscular connections between endo- and epicardium underlie EBW and that a slight degree of endo-epicardial asynchrony required for EBW to occur is already present in some areas during SR. Hence, an anatomic substrate is present, which may enhance the occurrence of EBW during atrial fibrillation, thereby promoting atrial fibrillation persistence. © 2017 American Heart Association, Inc.

Simple rules govern the patterns of Arctic sea ice melt ponds

NASA Astrophysics Data System (ADS)

Popovic, P.; Cael, B. B.; Abbot, D. S.; Silber, M.

2017-12-01

Climate change, amplified in the far north, has led to a rapid sea ice decline in recent years. Melt ponds that form on the surface of Arctic sea ice in the summer significantly lower the ice albedo, thereby accelerating ice melt. Pond geometry controls the details of this crucial feedback. However, currently it is unclear how to model this intricate geometry. Here we show that an extremely simple model of voids surrounding randomly sized and placed overlapping circles reproduces the essential features of pond patterns. The model has only two parameters, circle scale and the fraction of the surface covered by voids, and we choose them by comparing the model to pond images. Using these parameters the void model robustly reproduces all of the examined pond features such as the ponds' area-perimeter relationship and the area-abundance relationship over nearly 7 orders of magnitude. By analyzing airborne photographs of sea ice, we also find that the typical pond scale is surprisingly constant across different years, regions, and ice types. These results demonstrate that the geometric and abundance patterns of Arctic melt ponds can be simply described, and can guide future models of Arctic melt ponds to improve predictions of how sea ice will respond to Arctic warming.

Bubble Generation in a Flowing Liquid Medium and Resulting Two-Phase Flow in Microgravity

NASA Technical Reports Server (NTRS)

Pais, S. C.; Kamotani, Y.; Bhunia, A.; Ostrach, S.

1999-01-01

The present investigation reports a study of bubble generation under reduced gravity conditions, using both a co-flow and a cross-flow configuration. This study may be used in the conceptual design of a space-based thermal management system. Ensuing two-phase flow void fraction can be accurately monitored using a single nozzle gas injection system within a continuous liquid flow conduit, as utilized in the present investigation. Accurate monitoring of void fraction leads to precise control of heat and mass transfer coefficients related to a thermal management system; hence providing an efficient and highly effective means of removing heat aboard spacecraft or space stations. Our experiments are performed in parabolic flight aboard the modified DC-9 Reduced Gravity Research Aircraft at NASA Lewis Research Center, using an air-water system. For the purpose of bubble dispersion in a flowing liquid, we use both a co-flow and a cross-flow configuration. In the co-flow geometry, air is introduced through a nozzle in the same direction with the liquid flow. On the other hand, in the cross-flow configuration, air is injected perpendicular to the direction of water flow, via a nozzle protruding inside the two-phase flow conduit. Three different flow conduit (pipe) diameters are used, namely, 1.27 cm, 1.9 cm and 2.54 cm. Two different ratios of nozzle to pipe diameter (D(sub N))sup * are considered, namely (D(sub N))sup * = 0.1 and 0.2, while superficial liquid velocities are varied from 8 to 70 cm/s depending on flow conduit diameter. It is experimentally observed that by holding all other flow conditions and geometry constant, generated bubbles decrease in size with increase in superficial liquid velocity. Detached bubble diameter is shown to increase with air injection nozzle diameter. Likewise, generated bubbles grow in size with increasing pipe diameter. Along the same lines, it is shown that bubble frequency of formation increases and hence the time to detachment of a forming bubble decreases, as the superficial liquid velocity is in-creased. Furthermore, it is shown that the void fraction of the resulting two-phase flow increases with volumetric gas flow rate Q(sub d), pipe diameter and gas injection nozzle diameter, while they decrease with surrounding liquid flow. The important role played by flowing liquid in detaching bubbles in a reduced gravity environment is thus emphasized. We observe that the void fraction can be accurately controlled by using single nozzle gas injection, rather than by employing multiple port injection, since the later system gives rise to unpredictable coalescence of adjacent bubbles. It is of interest to note that empirical bubble size and corresponding void fraction are somewhat smaller for the co-flow geometry than the cross-flow configuration at similar flow conditions with similar pipe and nozzle diameters. In order to supplement the empirical data, a theoretical model is employed to study single bubble generation in the dynamic (Q(sub d) = 1 - 1000 cu cm/s) and bubbly flow regime within the framework of the co-flow configuration. This theoretical model is based on an overall force balance acting on the bubble during the two stages of generation, namely the expansion and the detachment stage. Two sets of forces, one aiding and the other inhibiting bubble detachment are identified. Under conditions of reduced gravity, gas momentum flux enhances, while the surface tension force at the air injection nozzle tip inhibits bubble detachment. In parallel, liquid drag and inertia can act as both attaching and detaching forces, depending on the relative velocity of the bubble with respect to the surrounding liquid. Predictions of the theoretical model compare well with our experimental results. However, at higher superficial liquid velocities, as the bubble loses its spherical form, empirical bubble size no longer matches the theoretical predictions. In summary, we have developed a combined experimental and theoretical work, which describes the complex process of bubble generation and resulting two-phase flow in a microgravity environment. Results of the present study can be used in a wide range of space-based applications, such as thermal energy and power generation, propulsion, cryogenic storage and long duration life support systems, necessary for programs such as NASA's Human Exploration for the Development of Space (HEDS).

A dynamical classification of the cosmic web

NASA Astrophysics Data System (ADS)

Forero-Romero, J. E.; Hoffman, Y.; Gottlöber, S.; Klypin, A.; Yepes, G.

2009-07-01

In this paper, we propose a new dynamical classification of the cosmic web. Each point in space is classified in one of four possible web types: voids, sheets, filaments and knots. The classification is based on the evaluation of the deformation tensor (i.e. the Hessian of the gravitational potential) on a grid. The classification is based on counting the number of eigenvalues above a certain threshold, λth, at each grid point, where the case of zero, one, two or three such eigenvalues corresponds to void, sheet, filament or a knot grid point. The collection of neighbouring grid points, friends of friends, of the same web type constitutes voids, sheets, filaments and knots as extended web objects. A simple dynamical consideration of the emergence of the web suggests that the threshold should not be null, as in previous implementations of the algorithm. A detailed dynamical analysis would have found different threshold values for the collapse of sheets, filaments and knots. Short of such an analysis a phenomenological approach has been opted for, looking for a single threshold to be determined by analysing numerical simulations. Our cosmic web classification has been applied and tested against a suite of large (dark matter only) cosmological N-body simulations. In particular, the dependence of the volume and mass filling fractions on λth and on the resolution has been calculated for the four web types. We also study the percolation properties of voids and filaments. Our main findings are as follows. (i) Already at λth = 0.1 the resulting web classification reproduces the visual impression of the cosmic web. (ii) Between 0.2 <~ λth <~ 0.4, a system of percolated voids coexists with a net of interconnected filaments. This suggests a reasonable choice for λth as the parameter that defines the cosmic web. (iii) The dynamical nature of the suggested classification provides a robust framework for incorporating environmental information into galaxy formation models, and in particular to semi-analytical models.

Poisson-Nernst-Planck-Fermi theory for modeling biological ion channels

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

Liu, Jinn-Liang, E-mail: jinnliu@mail.nhcue.edu.tw; Eisenberg, Bob, E-mail: beisenbe@rush.edu

2014-12-14

A Poisson-Nernst-Planck-Fermi (PNPF) theory is developed for studying ionic transport through biological ion channels. Our goal is to deal with the finite size of particle using a Fermi like distribution without calculating the forces between the particles, because they are both expensive and tricky to compute. We include the steric effect of ions and water molecules with nonuniform sizes and interstitial voids, the correlation effect of crowded ions with different valences, and the screening effect of water molecules in an inhomogeneous aqueous electrolyte. Including the finite volume of water and the voids between particles is an important new part ofmore » the theory presented here. Fermi like distributions of all particle species are derived from the volume exclusion of classical particles. Volume exclusion and the resulting saturation phenomena are especially important to describe the binding and permeation mechanisms of ions in a narrow channel pore. The Gibbs free energy of the Fermi distribution reduces to that of a Boltzmann distribution when these effects are not considered. The classical Gibbs entropy is extended to a new entropy form — called Gibbs-Fermi entropy — that describes mixing configurations of all finite size particles and voids in a thermodynamic system where microstates do not have equal probabilities. The PNPF model describes the dynamic flow of ions, water molecules, as well as voids with electric fields and protein charges. The model also provides a quantitative mean-field description of the charge/space competition mechanism of particles within the highly charged and crowded channel pore. The PNPF results are in good accord with experimental currents recorded in a 10{sup 8}-fold range of Ca{sup 2+} concentrations. The results illustrate the anomalous mole fraction effect, a signature of L-type calcium channels. Moreover, numerical results concerning water density, dielectric permittivity, void volume, and steric energy provide useful details to study a variety of physical mechanisms ranging from binding, to permeation, blocking, flexibility, and charge/space competition of the channel.« less

Effect of alcohols on the structure and dynamics of [BMIM][PF6] ionic liquid: A combined molecular dynamics simulation and Voronoi tessellation investigation

NASA Astrophysics Data System (ADS)

Sharma, Anirban; Ghorai, Pradip Kr.

2018-05-01

The solubility of 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIM][PF6]) ionic liquid (IL) in water is much less, whereas it is highly soluble in alcohol. The composition dependent structural and dynamical properties of [BMIM][PF6] in methanol and ethanol have been investigated by using all-atom molecular dynamics simulation. Though the density of IL/alcohol binary mixtures is nearly identical for different alcohol mole fractions, we observe the unalike structural and dynamical properties of the IL in methanol and ethanol due to different local environments of the IL and polarity of the solvent. Voronoi polyhedral analysis exhibits strong dependence of local environments on alcohol concentrations. Void and neck distribution in Voronoi tessellation are approximately Gaussian for pure IL, but it deviates from the Gaussian behavior at very high alcohol concentration. At low alcohol concentration, void and neck distributions of [BMIM]+ with [PF6]- in both methanol and ethanol are almost identical, whereas the distributions in ethanol are broader with lesser intensity than in methanol at high alcohol concentration. This suggests the existence of a very few larger free space in ethanol than in methanol. Although peak positions in the void and neck distributions in ethanol are at larger void and neck radius than in methanol, peak intensity for medium sized void in methanol is significantly higher than in ethanol. Thus the translational motion of both [BMIM]+ and [PF6]- and the rotational motion of [BMIM]+ are faster in methanol than in ethanol. Hydrogen bonding of [BMIM]+ with [PF6]- is more predominate than the alcohols, hence cation-anion hydrogen bonding plays an important role in determining self-diffusion coefficient (D) of [BMIM]+, whereas for [PF6]-, cooperative motion due to hydrogen bonding with the alcohols is indispensable.

Do we overestimate left ventricular ejection fraction by two-dimensional echocardiography in patients with left bundle branch block?

PubMed

Cabuk, Ali K; Cabuk, Gizem; Sayin, Ahmet; Karamanlioglu, Murat; Kilicaslan, Barış; Ekmekci, Cenk; Solmaz, Hatice; Aslanturk, Omer F; Ozdogan, Oner

2018-02-01

Left bundle branch block (LBBB) causes a dyssynchronized contraction of left ventricle. This is a kind of regional wall-motion abnormality and measuring left ventricular ejection fraction (LVEF) by two-dimensional (2D) echocardiography could be less reliable in this particular condition. Our aim was to evaluate the role of dyssynchrony index (SDI), measured by three-dimensional (3D) echocardiography, in assessment of LVEF and left ventricular volumes accurately in patients with LBBB. In this case-control study, we included 52 of 64 enrolled participants (twelve participants with poor image quality were excluded) with LBBB and normal LVEF or nonischemic cardiomyopathy. Left ventricular ejection fraction (LVEF) and left ventricular volumes were assessed by 2D (modified Simpson's rule) and 3D (four beats full volume analysis) echocardiography and the impact of SDI on results were evaluated. In patients with SDI ≥6%, LVEF measurements were significantly different (46.00% [29.50-52.50] vs 37.60% [24.70-45.15], P < .001) between 2D and 3D echocardiography, respectively. In patients with SDI < 6%, there were no significant differences between two modalities in terms of LVEF measurements (54.50% [49.00-59.00] vs 54.25% [40.00-58.25], P = .193). LV diastolic volumes were not significantly different while systolic volumes were underestimated by 2D echocardiography, and this finding was more pronounced when SDI ≥ 6%. In patients with LBBB and high SDI (≥6%), LVEF values were overestimated and systolic volumes were underestimated by 2D echocardiography compared to 3D echocardiography. © 2017 Wiley Periodicals, Inc.

Kernel Regression Estimation of Fiber Orientation Mixtures in Diffusion MRI

PubMed Central

Cabeen, Ryan P.; Bastin, Mark E.; Laidlaw, David H.

2016-01-01

We present and evaluate a method for kernel regression estimation of fiber orientations and associated volume fractions for diffusion MR tractography and population-based atlas construction in clinical imaging studies of brain white matter. This is a model-based image processing technique in which representative fiber models are estimated from collections of component fiber models in model-valued image data. This extends prior work in nonparametric image processing and multi-compartment processing to provide computational tools for image interpolation, smoothing, and fusion with fiber orientation mixtures. In contrast to related work on multi-compartment processing, this approach is based on directional measures of divergence and includes data-adaptive extensions for model selection and bilateral filtering. This is useful for reconstructing complex anatomical features in clinical datasets analyzed with the ball-and-sticks model, and our framework’s data-adaptive extensions are potentially useful for general multi-compartment image processing. We experimentally evaluate our approach with both synthetic data from computational phantoms and in vivo clinical data from human subjects. With synthetic data experiments, we evaluate performance based on errors in fiber orientation, volume fraction, compartment count, and tractography-based connectivity. With in vivo data experiments, we first show improved scan-rescan reproducibility and reliability of quantitative fiber bundle metrics, including mean length, volume, streamline count, and mean volume fraction. We then demonstrate the creation of a multi-fiber tractography atlas from a population of 80 human subjects. In comparison to single tensor atlasing, our multi-fiber atlas shows more complete features of known fiber bundles and includes reconstructions of the lateral projections of the corpus callosum and complex fronto-parietal connections of the superior longitudinal fasciculus I, II, and III. PMID:26691524

Dual-energy-X-ray imaging to measure phase volume fractions in a transient multiphase flow

NASA Astrophysics Data System (ADS)

Loewen, Eric Paul

1999-12-01

The objective of this research was to visualize the pre-mixing phase of a fuel-coolant interaction (FCI) by using combinations of high-speed cinematography and dual energy X-ray imaging to identify and quantify the spatial and temporal characteristics of the three FCI phases---metal (fuel), liquid (coolant water), and voids (generated steam). (1) The high-speed cinematography imaging subsystem and the low-energy X-ray imaging subsystem provided visual photographs and distinguished generated voids from water. (2) The high-energy X-Ray imaging subsystem provided additional discernment of metal from water and vapor. This is the first time that dynamic dual X-ray images have been provided with quantitative results. The data provide new information concerning the melt fractions, melt jet configuration, melt jet velocity, and qualitative spatial and temporal quantification of the pre-mixing event. This information provides new insight into the FCI phenomenon that could not have been deduced from visible-light imaging or other instrumentation such as thermocouples, void sensors, or pressure transmitters. Significant findings include: (1) the fuel column (molten Pb jet) penetrated deeply (<7 cm) into the coolant (water) while maintaining its columnar shape. (2) Energetic FCIs occurred (and were imaged) below the melt-coolant interface temperature equal to the homogenous nucleation temperature (310°C). (3) The molten jet breakup was observed to be caused by hydrodynamic forces. (4) The Pb/water thermal interaction zone was imaged over melt temperatures from 330°C to 640°C and coolant subcooling of 4°C to 80°C. (5) The interface regions between the molten Pb and coolant was observed to grow with decreasing coolant subcooling. This imaging process can be applied to further study of the FCI phenomena at other test facilities. It can also be applied for observation of other two- or three-phase flow phenomena previously opaque to conventional imaging systems.

Dielectric and Radiative Properties of Sea Foam at Microwave Frequencies: Conceptual Understanding of Foam Emissivity

DTIC Science & Technology

2012-04-27

papers. Anguelova [ 24 ] analyzed the available information to determine suitable formula to predict the complex permittivity of sea foam εf. Anguelova...active whitecaps. Whitecaps in their decaying phase are thinner and dimmer and are referred to as residual whitecaps. Anguelova [ 24 ] gives an extended...considered [ 24 ]. It was shown that various functional forms could represent the shape of the void fraction profile in the foam depth [25]. A review of

Analysis of the Hydrodynamics and Heat Transfer Aspects of Microgravity Two-Phase Flows

NASA Technical Reports Server (NTRS)

Rezkallah, Kamiel S.

1996-01-01

Experimental results for void fractions, flow regimes, and heat transfer rates in two-phase, liquid-gas flows are summarized in this paper. The data was collected on-board NASA's KC-135 reduced gravity aircraft in a 9.525 mm circular tube (i.d.), uniformly heated at the outer surface. Water and air flows were examined as well as three glycerol/water solutions and air. Results are reported for the water-air data.

Analysis of flow reversal test

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

Cheng, L.Y.; Tichler, P.R.

A series of tests has been conducted to measure the dryout power associated with a flow transient whereby the coolant in a heated channel undergoes a change in flow direction. An analysis of the test was made with the aid of a system code, RELAP5. A dryout criterion was developed in terms of a time-averaged void fraction calculated by RELAP5 for the heated channel. The dryout criterion was also compared with several CHF correlations developed for the channel geometry.

Non-homogeneous hybrid rocket fuel for enhanced regression rates utilizing partial entrainment

NASA Astrophysics Data System (ADS)

Boronowsky, Kenny

A concept was developed and tested to enhance the performance and regression rate of hydroxyl terminated polybutadiene (HTPB), a commonly used hybrid rocket fuel. By adding small nodules of paraffin into the HTPB fuel, a non-homogeneous mixture was created resulting in increased regression rates. The goal was to develop a fuel with a simplified single core geometry and a tailorable regression rate. The new fuel would benefit from the structural stability of HTPB yet not suffer from the large void fraction representative of typical HTPB core geometries. Regression rates were compared between traditional HTPB single core grains, 85% HTPB mixed with 15% (by weight) paraffin cores, 70% HTPB mixed with 30% paraffin cores, and plain paraffin single core grains. Each fuel combination was tested at oxidizer flow rates, ranging from 0.9 - 3.3 g/s of gaseous oxygen, in a small scale hybrid test rocket and average regression rates were measured. While large uncertainties were present in the experimental setup, the overall data showed that the regression rate was enhanced as paraffin concentration increased. While further testing would be required at larger scales of interest, the trends are encouraging. Inclusion of paraffin nodules in the HTPB grain may produce a greater advantage than other more noxious additives in current use. In addition, it may lead to safer rocket motors with higher integrated thrust due to the decreased void fraction.

Impact of modeling Choices on Inventory and In-Cask Criticality Calculations for Forsmark 3 BWR Spent Fuel

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

Martinez-Gonzalez, Jesus S.; Ade, Brian J.; Bowman, Stephen M.

2015-01-01

Simulation of boiling water reactor (BWR) fuel depletion poses a challenge for nuclide inventory validation and nuclear criticality safety analyses. This challenge is due to the complex operating conditions and assembly design heterogeneities that characterize these nuclear systems. Fuel depletion simulations and in-cask criticality calculations are affected by (1) completeness of design information, (2) variability of operating conditions needed for modeling purposes, and (3) possible modeling choices. These effects must be identified, quantified, and ranked according to their significance. This paper presents an investigation of BWR fuel depletion using a complete set of actual design specifications and detailed operational datamore » available for five operating cycles of the Swedish BWR Forsmark 3 reactor. The data includes detailed axial profiles of power, burnup, and void fraction in a very fine temporal mesh for a GE14 (10×10) fuel assembly. The specifications of this case can be used to assess the impacts of different modeling choices on inventory prediction and in-cask criticality, specifically regarding the key parameters that drive inventory and reactivity throughout fuel burnup. This study focused on the effects of the fidelity with which power history and void fraction distributions are modeled. The corresponding sensitivity of the reactivity in storage configurations is assessed, and the impacts of modeling choices on decay heat and inventory are addressed.« less

Air Layer Drag Reduction

NASA Astrophysics Data System (ADS)

Ceccio, Steven; Elbing, Brian; Winkel, Eric; Dowling, David; Perlin, Marc

2008-11-01

A set of experiments have been conducted at the US Navy's Large Cavitation Channel to investigate skin-friction drag reduction with the injection of air into a high Reynolds number turbulent boundary layer. Testing was performed on a 12.9 m long flat-plate test model with the surface hydraulically smooth and fully rough at downstream-distance-based Reynolds numbers to 220 million and at speeds to 20 m/s. Local skin-friction, near-wall bulk void fraction, and near-wall bubble imaging were monitored along the length of the model. The instrument suite was used to access the requirements necessary to achieve air layer drag reduction (ALDR). Injection of air over a wide range of air fluxes showed that three drag reduction regimes exist when injecting air; (1) bubble drag reduction that has poor downstream persistence, (2) a transitional regime with a steep rise in drag reduction, and (3) ALDR regime where the drag reduction plateaus at 90% ± 10% over the entire model length with large void fractions in the near-wall region. These investigations revealed several requirements for ALDR including; sufficient volumetric air fluxes that increase approximately with the square of the free-stream speed, slightly higher air fluxes are needed when the surface tension is reduced, higher air fluxes are required for rough surfaces, and the formation of ALDR is sensitive to the inlet condition.

Analytical Deriving of the Field Capacity through Soil Bundle Model

NASA Astrophysics Data System (ADS)

Arnone, E.; Viola, F.; Antinoro, C.; Noto, L. V.

2015-12-01

The concept of field capacity as soil hydraulic parameter is widely used in many hydrological applications. Althought its recurring usage, its definition is not univocal. Traditionally, field capacity has been related to the amount of water that remains in the soil after the excess water has drained away and the water downward movement experiences a significant decresase. Quantifying the drainage of excess of water may be vague and several definitions, often subjective, have been proposed. These definitions are based on fixed thresholds either of time, pressure, or flux to which the field capacity condition is associated. The flux-based definition identifies the field capacity as the soil moisture value corresponding to an arbitrary fixed threshold of free drainage flux. Recently, many works have investigated the flux-based definition by varying either the drainage threshold, the geometry setting and mainly the description of the drainage flux. Most of these methods are based on the simulation of the flux through a porous medium by using the Darcy's law or Richard's equation. Using the above-mentioned flux-based definition, in this work we propose an alternative analytical approach for deriving the field capacity based on a bundle-of-tubes model. The pore space of a porous medium is conceptualized as a bundle of capillary tubes of given length of different radii, derived from a known distribution. The drainage from a single capillary tube is given by the analytical solution of the differential equation describing the water height evolution within the capillary tube. This equation is based on the Poiseuille's law and describes the drainage flux with time as a function of tube radius. The drainage process is then integrated for any portion of soil taking into account the tube radius distribution which in turns depends on the soil type. This methodology allows to analytically derive the dynamics of drainage water flux for any soil type and consequently to define the soil field capacity as the latter reachs a given threshold value. The theoretical model also accounts for the tortuosity which characterizes the water pathways in real soils, but neglects the voids mutual interconnections.

Comparative assessment of therapeutic response to physiotherapy with or without botulinum toxin injection using diffusion tensor tractography and clinical scores in term diplegic cerebral palsy children.

PubMed

Chaturvedi, Saurabh K; Rai, Yogita; Chourasia, Ankita; Goel, Puneet; Paliwal, Vimal K; Garg, Ravindra K; Rathore, Ram Kishore S; Pandey, Chandra M; Gupta, Rakesh K

2013-08-01

The present study was to compare the effects of combined therapy [botulinum (BTX) plus physiotherapy] with physiotherapy alone using diffusion tensor imaging (DTI) derived fractional anisotropy (FA) values of motor and sensory fiber bundles and clinical grade of the disability to see the value of BTX in term children with spastic diplegic cerebral palsy (CP). Clinically diagnosed 36 children participated in the study. All these children were born at term, and had no history of seizures. The study was randomly categorized into two groups: group I (n=18) - physiotherapy alone and group II (n=18) - physiotherapy plus BTX injection. Quantitative diffusion tensor tractography on all these children was performed on motor and sensory fiber bundles on baseline as well as after 6months of therapy. Motor function and clinical grades were also measured by gross motor function measures (GMFM) scale on both occasions. We observed significant change in FA value in motor and sensory fiber bundle as well as in GMFM scores at 6months compared to baseline study in both the groups. However, delta change and relative delta change in FA values of sensory and motor fiber bundle as well as GMFM score between group I and group II was statistically insignificant. We conclude that addition of BTX to physiotherapy regimen does not influence the outcome at 6months with similar insult in children with term diplegic spastic CP. This information may influence management of diplegic CP especially in developing countries, where BTX is beyond the reach of these children. Copyright © 2012 The Japanese Society of Child Neurology. Published by Elsevier B.V. All rights reserved.

Methodology Development of a Gas-Liquid Dynamic Flow Regime Transition Model

NASA Astrophysics Data System (ADS)

Doup, Benjamin Casey

Current reactor safety analysis codes, such as RELAP5, TRACE, and CATHARE, use flow regime maps or flow regime transition criteria that were developed for static fully-developed two-phase flows to choose interfacial transfer models that are necessary to solve the two-fluid model. The flow regime is therefore difficult to identify near the flow regime transitions, in developing two-phase flows, and in transient two-phase flows. Interfacial area transport equations were developed to more accurately predict the dynamic nature of two-phase flows. However, other model coefficients are still flow regime dependent. Therefore, an accurate prediction of the flow regime is still important. In the current work, the methodology for the development of a dynamic flow regime transition model that uses the void fraction and interfacial area concentration obtained by solving three-field the two-fluid model and two-group interfacial area transport equation is investigated. To develop this model, detailed local experimental data are obtained, the two-group interfacial area transport equations are revised, and a dynamic flow regime transition model is evaluated using a computational fluid dynamics model. Local experimental data is acquired for 63 different flow conditions in bubbly, cap-bubbly, slug, and churn-turbulent flow regimes. The measured parameters are the group-1 and group-2 bubble number frequency, void fraction, interfacial area concentration, and interfacial bubble velocities. The measurements are benchmarked by comparing the prediction of the superficial gas velocities, determined using the local measurements with those determined from volumetric flow rate measurements and the agreement is generally within +/-20%. The repeatability four-sensor probe construction process is within +/-10%. The repeatability of the measurement process is within +/-7%. The symmetry of the test section is examined and the average agreement is within +/-5.3% at z/D = 10 and +/-3.4% at z/D = 32. Revised source/sink terms for the two-group interfacial area transport equations are derived and fit to area-averaged experimental data to determine new model coefficients. The average agreement between this model and the experiment data for the void fraction and interfacial area concentration is 10.6% and 15.7%, respectively. This revised two-group interfacial area transport equation and the three-field two-fluid model are used to solve for the group-1 and group-2 interfacial area concentration and void fraction. These values and a dynamic flow regime transition model are used to classify the flow regimes. The flow regimes determined using this model are compared with the flow regimes based on the experimental data and on a flow regime map using Mishima and Ishii's (1984) transition criteria. The dynamic flow regime transition model is shown to predict the flow regimes dynamically and has improved the prediction of the flow regime over that using a flow regime map. Safety codes often employ the one-dimensional two-fluid model to model two-phase flows. The area-averaged relative velocity correlation necessary to close this model is derived from the drift flux model. The effects of the necessary assumptions used to derive this correlation are investigated using local measurements and these effects are found to have a limited impact on the prediction of the area-averaged relative velocity.

Aligning Arrays of Lenses and Single-Mode Optical Fibers

NASA Technical Reports Server (NTRS)

Liu, Duncan

2004-01-01

A procedure now under development is intended to enable the precise alignment of sheet arrays of microscopic lenses with the end faces of a coherent bundle of as many as 1,000 single-mode optical fibers packed closely in a regular array (see Figure 1). In the original application that prompted this development, the precise assembly of lenses and optical fibers serves as a single-mode spatial filter for a visible-light nulling interferometer. The precision of alignment must be sufficient to limit any remaining wavefront error to a root-mean-square value of less than 1/10 of a wavelength of light. This wavefront-error limit translates to requirements to (1) ensure uniformity of both the lens and fiber arrays, (2) ensure that the lateral distance from the central axis of each lens and the corresponding optical fiber is no more than a fraction of a micron, (3) angularly align the lens-sheet planes and the fiber-bundle end faces to within a few arc seconds, and (4) axially align the lenses and the fiber-bundle end faces to within tens of microns of the focal distance. Figure 2 depicts the apparatus used in the alignment procedure. The beam of light from a Zygo (or equivalent) interferometer is first compressed by a ratio of 20:1 so that upon its return to the interferometer, the beam will be magnified enough to enable measurement of wavefront quality. The apparatus includes relay lenses that enable imaging of the arrays of microscopic lenses in a charge-coupled-device (CCD) camera that is part of the interferometer. One of the arrays of microscopic lenses is mounted on a 6-axis stage, in proximity to the front face of the bundle of optical fibers. The bundle is mounted on a separate stage. A mirror is attached to the back face of the bundle of optical fibers for retroreflection of light. When a microscopic lens and a fiber are aligned with each other, the affected portion of the light is reflected back by the mirror, recollimated by the microscopic lens, transmitted through the relay lenses and the beam compressor/expander, then split so that half goes to a detector and half to the interferometer. The output of the detector is used as a feedback control signal for the six-axis stage to effect alignment.

Application of high-order numerical schemes and Newton-Krylov method to two-phase drift-flux model

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

Zou, Ling; Zhao, Haihua; Zhang, Hongbin

This study concerns the application and solver robustness of the Newton-Krylov method in solving two-phase flow drift-flux model problems using high-order numerical schemes. In our previous studies, the Newton-Krylov method has been proven as a promising solver for two-phase flow drift-flux model problems. However, these studies were limited to use first-order numerical schemes only. Moreover, the previous approach to treating the drift-flux closure correlations was later revealed to cause deteriorated solver convergence performance, when the mesh was highly refined, and also when higher-order numerical schemes were employed. In this study, a second-order spatial discretization scheme that has been tested withmore » two-fluid two-phase flow model was extended to solve drift-flux model problems. In order to improve solver robustness, and therefore efficiency, a new approach was proposed to treating the mean drift velocity of the gas phase as a primary nonlinear variable to the equation system. With this new approach, significant improvement in solver robustness was achieved. With highly refined mesh, the proposed treatment along with the Newton-Krylov solver were extensively tested with two-phase flow problems that cover a wide range of thermal-hydraulics conditions. Satisfactory convergence performances were observed for all test cases. Numerical verification was then performed in the form of mesh convergence studies, from which expected orders of accuracy were obtained for both the first-order and the second-order spatial discretization schemes. Finally, the drift-flux model, along with numerical methods presented, were validated with three sets of flow boiling experiments that cover different flow channel geometries (round tube, rectangular tube, and rod bundle), and a wide range of test conditions (pressure, mass flux, wall heat flux, inlet subcooling and outlet void fraction).« less

Application of high-order numerical schemes and Newton-Krylov method to two-phase drift-flux model

DOE PAGES

Zou, Ling; Zhao, Haihua; Zhang, Hongbin

2017-08-07

This study concerns the application and solver robustness of the Newton-Krylov method in solving two-phase flow drift-flux model problems using high-order numerical schemes. In our previous studies, the Newton-Krylov method has been proven as a promising solver for two-phase flow drift-flux model problems. However, these studies were limited to use first-order numerical schemes only. Moreover, the previous approach to treating the drift-flux closure correlations was later revealed to cause deteriorated solver convergence performance, when the mesh was highly refined, and also when higher-order numerical schemes were employed. In this study, a second-order spatial discretization scheme that has been tested withmore » two-fluid two-phase flow model was extended to solve drift-flux model problems. In order to improve solver robustness, and therefore efficiency, a new approach was proposed to treating the mean drift velocity of the gas phase as a primary nonlinear variable to the equation system. With this new approach, significant improvement in solver robustness was achieved. With highly refined mesh, the proposed treatment along with the Newton-Krylov solver were extensively tested with two-phase flow problems that cover a wide range of thermal-hydraulics conditions. Satisfactory convergence performances were observed for all test cases. Numerical verification was then performed in the form of mesh convergence studies, from which expected orders of accuracy were obtained for both the first-order and the second-order spatial discretization schemes. Finally, the drift-flux model, along with numerical methods presented, were validated with three sets of flow boiling experiments that cover different flow channel geometries (round tube, rectangular tube, and rod bundle), and a wide range of test conditions (pressure, mass flux, wall heat flux, inlet subcooling and outlet void fraction).« less

Runoff initiation from falling raindrops - comparison of smooth impervious surface and asphalt pavements. Effects of surface inclination and texture.

NASA Astrophysics Data System (ADS)

Nezlobin, David; Pariente, Sarah; Lavee, Hanoch; Sachs, Eyal; Levenberg, Eyal

2017-04-01

The processes of runoff initiation on smooth impervious surfaces and various asphalt pavements are investigated in laboratory rain simulator experiments and outdoor sprinkling tests. Visual and FLIR observations indicate that runoff initiation is associated with coalescence of drop clusters on the surface and complex changes in micro-connectivity. Depending on surface inclination, several morphological regimes of flow initiation have been observed. In the case of very small inclination the runoff initiation is governed by critical merging of drop clusters on the surface and develops in broad flows (very abrupt, but delayed). For larger inclinations, the runoff occurs in rivulets or strongly directed flow threads. On asphalt pavements the runoff initiation is also strongly affected by pavement SVF (Surface Void Fraction), texture and even by the asphalt hydrophobicity. A simplified bi-level model of the pavement surface may explain principal differences in the runoff initiation on asphalts with small, intermediate and large SVF values. For small SVF (standard fresh asphalts) the runoff develops on the upper surface level, and filling of the surface voids is not always required (especially for the large inclinations). For intermediate SVF (considerably deteriorated asphalts) the runoff develops as well on the upper surface level, but only after considerable filling of the surface voids. Finally, on severely deteriorated asphalts (very large SVFs) the runoff develops on the "bottom" level of asphalt surface, after only partial filling of the surface voids. Other factors, such as drops splash and splitting, also affect the process of runoff initiation and explain rather considerable differences (sometimes of 2-3 mm rain depth) in the runoff thresholds on various non-porous asphalt pavements. Similar phenomena can be probably observed on certain types of rock outcrops.

Hyperuniformity, quasi-long-range correlations, and void-space constraints in maximally random jammed particle packings. I. Polydisperse spheres.

PubMed

Zachary, Chase E; Jiao, Yang; Torquato, Salvatore

2011-05-01

Hyperuniform many-particle distributions possess a local number variance that grows more slowly than the volume of an observation window, implying that the local density is effectively homogeneous beyond a few characteristic length scales. Previous work on maximally random strictly jammed sphere packings in three dimensions has shown that these systems are hyperuniform and possess unusual quasi-long-range pair correlations decaying as r(-4), resulting in anomalous logarithmic growth in the number variance. However, recent work on maximally random jammed sphere packings with a size distribution has suggested that such quasi-long-range correlations and hyperuniformity are not universal among jammed hard-particle systems. In this paper, we show that such systems are indeed hyperuniform with signature quasi-long-range correlations by characterizing the more general local-volume-fraction fluctuations. We argue that the regularity of the void space induced by the constraints of saturation and strict jamming overcomes the local inhomogeneity of the disk centers to induce hyperuniformity in the medium with a linear small-wave-number nonanalytic behavior in the spectral density, resulting in quasi-long-range spatial correlations scaling with r(-(d+1)) in d Euclidean space dimensions. A numerical and analytical analysis of the pore-size distribution for a binary maximally random jammed system in addition to a local characterization of the n-particle loops governing the void space surrounding the inclusions is presented in support of our argument. This paper is the first part of a series of two papers considering the relationships among hyperuniformity, jamming, and regularity of the void space in hard-particle packings.

Technology Advances to Improve Response to Cardiac Resynchronization Therapy: What Clinicians Should Know.

PubMed

Auricchio, Angelo; Heggermont, Ward A

2018-06-01

Cardiac resynchronization therapy (CRT) is a well-established treatment for symptomatic heart failure patients with reduced left ventricular ejection fraction, prolonged QRS duration, and abnormal QRS morphology. The ultimate goals of modern CRT are to improve the proportion of patients responding to CRT and to maximize the response to CRT in patients who do respond. While the rate of CRT nonresponders has moderately but progressively decreased over the last 20 years, mostly in patients with left bundle branch block, in patients without left bundle branch block the response rate is almost unchanged. A number of technological advances have already contributed to achieve some of the objectives of modern CRT. They include novel lead design (the left ventricular quadripolar lead, and multipoint pacing), or the possibility to go beyond conventional delivery of CRT (left ventricular endocardial pacing, His bundle pacing). Furthermore, to improve CRT response, a triad of actions is paramount: reducing the burden of atrial fibrillation, reducing the number of appropriate and inappropriate interventions, and adequately predicting heart failure episodes. As in other fields of cardiology, technology and innovations for CRT delivery have been at the forefront in transforming-improving-patient care; therefore, these innovations are discussed in this review. Copyright © 2018 Sociedad Española de Cardiología. Published by Elsevier España, S.L.U. All rights reserved.

The influence of chemical composition of LNG on the supercritical heat transfer in an intermediate fluid vaporizer

NASA Astrophysics Data System (ADS)

Xu, Shuangqing; Chen, Xuedong; Fan, Zhichao; Chen, Yongdong; Nie, Defu; Wu, Qiaoguo

2018-04-01

A three-dimensional transient computational fluid dynamics (CFD) model has been established for the simulations of supercritical heat transfer of real liquefied natural gas (LNG) mixture in a single tube and a tube bundle of an intermediate fluid vaporizer (IFV). The influence of chemical composition of LNG on the thermal performance has been analyzed. The results have also been compared with those obtained from the one-dimensional steady-state calculations using the distributed parameter model (DPM). It is found that the current DPM approach can give reasonable prediction accuracy for the thermal performance in the tube bundle but unsatisfactory prediction accuracy for that in a single tube as compared with the corresponding CFD data. As benchmarked against pure methane, the vaporization of an LNG containing about 90% (mole fraction) of methane would lead to an absolute deviation of 5.5 K in the outlet NG temperature and a maximum relative deviation of 11.4% in the tube side HTC in a bundle of about 816 U tubes at the inlet pressure of 12 MPa and mass flux of 200 kg·m-2·s-1. It is concluded that the influence of LNG composition on the thermal performance should be taken into consideration in order to obtain an economic and reliable design of an IFV.

Trastuzumab (Herceptin)-associated cardiomyopathy presented as new onset of complete left bundle-branch block mimicking acute coronary syndrome: a case report and literature review.

PubMed

Tu, Chung-Ming; Chu, Kai-Ming; Yang, Shin-Ping; Cheng, Shu-Mung; Wang, Wen-Been

2009-09-01

Trastuzumab (Herceptin) is well documented in reducing suffering and mortality from breast cancer. The clinically most important side effect of Herceptin is cardiotoxicity, which is reported in 2.6% to 4.5% of patients receiving trastuzumab alone and in as many as 27% of patients when trastuzumab is combined with an anthracycline in metastatic disease. We reported the case of a 50-year-old woman who presented to our emergency department (ED) because of chest pain and shortness of breath. On physical examination, holosystolic murmur over apex could be heard. Pulmonary and abdominal examinations were unremarkable. Twelve-lead electrocardiography showed sinus tachycardia and new onset of complete left bundle-branch block. Emergent transthoracic echocardiography revealed generalized hypokinesia of left ventricle and akinesia over interventricular septum and apex. She subsequently underwent immediate coronary angiography that revealed normal coronary angiography, and left ventriculogram revealed generalized hypokinesia with severe left ventricle dysfunction with ejection fraction of 33%. During right heart catheterization and endomyocardial biopsy, cardiac tamponade developed and was successfully relieved by pericardial window. She was discharged event-free 3 weeks later with conservative treatment. Although new onset of complete left bundle-branch block in a patient with chest pain may be acute coronary syndrome, careful review of medicine history is mandatory to avoid unnecessary procedure and complications.

Polyhedral Oligomeric Silsesquioxane (POSS) Dianiline as a Replacement for Toxic Methylenedianiline in PMR-15: Chemistry and Properties

DTIC Science & Technology

2016-08-22

POSS dinadic composite cross-section. Prior to aging, a few voids are seen in the matrix , but no cracks. After the same time aging as with the PMR-15...the composite , fiber and matrix , respectively; σc, σf, and σm are stress in the composite , fiber and matrix , respectively; Vf and Vm are volume...fraction of the fiber and matrix , respectively; Ec, Ef and Em are the moduli of the composite , fiber and matrix , respectively

Irradiation effects on multilayered W/ZrO2 film under 4 MeV Au ions

NASA Astrophysics Data System (ADS)

Wang, Hongwei; Gao, Yuan; Fu, Engang; Yang, Tengfei; Xue, Jianming; Yan, Sha; Chu, Paul K.; Wang, Yugang

2014-12-01

Irradiation induced structural changes in multilayered W/ZrO2 nanocomposites with periodic bilayer thicknesses of (7/14 nm) and (70/140 nm) were investigated following Au+ ion irradiation. The samples were irradiated by 4 MeV Au ions with fluences ranging from 6 × 1014 to 1 × 1016 ions/cm2. The immiscible W/ZrO2 interfaces remained unchanged without intermixing of the layers upon the irradiation. No voids were observed in the samples with different periodic layer thicknesses. The XRD and XTEM studies reveal thickness dependent microstructural changes in the samples. W and ZrO2 grains in the thinner (7/14 nm) bilayer sample exhibit significant resistance to grain growth compared to the thicker (70/140 nm) bilayer sample as well as a W monolayer film. The high fraction of flat interfaces as well as grain boundaries in multilayer films plays a role in suppressing ion irradiation-induced grain growth and void formation.

Shock induced damage in copper: A before and after, three-dimensional study

NASA Astrophysics Data System (ADS)

Menasche, David B.; Lind, Jonathan; Li, Shiu Fai; Kenesei, Peter; Bingert, John F.; Lienert, Ulrich; Suter, Robert M.

2016-04-01

We report on the microstructural features associated with the formation of incipient spall and damage in a fully recrystallized, high purity copper sample. Before and after ballistic shock loading, approximately 0.8 mm3 of the sample's crystal lattice orientation field is mapped using non-destructive near-field High Energy Diffraction Microscopy. Absorption contrast tomography is used to image voids after loading. This non-destructive interrogation of damage initiation allows for novel characterization of spall points vis-a-vis microstructural features and a fully 3D examination of microstructural topology and its influence on incipient damage. The spalled region is registered with and mapped back onto the pre-shock orientation field. As expected, the great majority of voids occur at grain boundaries and higher order microstructural features; however, we find no statistical preference for particular grain boundary types. The damaged region contains a large volume of Σ-3 (60 °<111 >) connected domains with a large area fraction of incoherent Σ-3 boundaries.

Structural features of immunostimulatory polysaccharide purified from pectinase hydrolysate of barley leaf.

PubMed

Kim, Hoon; Kwak, Bong-Shin; Hong, Hee-Do; Suh, Hyung-Joo; Shin, Kwang-Soon

2016-06-01

Four polysaccharide fractions were isolated from young barley leaves treated with or without pectinase followed by ethanol fractionation. Among the polysaccharide fractions, BLE-P isolated from pectinase digested with a high molecular weight had the most enhanced macrophage stimulatory activity, indicating that pectinase digestion of barley leaf is a useful method for enhancement of its activity. BLE-P was further purified by column chromatography to identify the chemical and structural properties. BLE-P-I eluted in void volume fraction showed potent macrophage stimulatory activity. Monosaccharide composition and linkage analysis indicated that at least three kinds of polysaccharide, that is, glucuronoarabinoxylan (GAX; 40-45%), rhamnogalacturonan-I (RG-I) with branching mainly involving a type II arabinogalactan (AG-II) side chain (30-35%), and linear glucan such as starch and cellulose (less than 10%) coexisted in BLE-P-I. Given the association with macrophage stimulatory activity, it is likely that the GAX and to the RG-I polysaccharide branched with an AG-II side chain may be important for expression of the activity in barley leaf. Copyright © 2016 Elsevier B.V. All rights reserved.

Heparin-binding growth factor isolated from human prostatic extracts.

PubMed

Mydlo, J H; Bulbul, M A; Richon, V M; Heston, W D; Fair, W R

1988-01-01

Prostatic tissue extracts from patients with benign prostatic hyperplasia (BPH) and prostatic carcinoma were fractionated using heparin-Sepharose chromatography. The mitogenic activity of eluted fractions on quiescent subconfluent Swiss Albino 3T3 fibroblasts was tested employing a tritiated-thymidine-incorporation assay. Two peaks of activity were consistently noted--one in the void volume and a second fraction which eluted with 1.3-1.6 M NaCl and contained the majority of the mitogenic activity. Both non-heparin- and heparin-binding fractions increased tritiated incorporation into a mouse osteoblast cell line (MC3T3), while only the heparin-binding fractions stimulated a human umbilical vein endothelial cell line (HUV). No increased uptake of thymidine was seen using a human prostatic carcinoma cell line (PC-3). Sodium dodecyl sulfate/polyacrylamide gel electrophoresis (SDS/PAGE) of lyophilized active fractions showed a persistent band at 17,500 daltons. The purified protein demonstrated angiogenic properties using the chick embryo chorioallantoic membrane (CAM) assay. Western blot analysis using antibodies specific to basic fibroblast growth factor (bFGF) or acidic FGF (aFGF) demonstrated that the former, but not the latter, bound to prostatic growth factor (PrGF), and inhibited its mitogenic activity as well. It appears that PrGF shares homology with basic fibroblast growth factors.

Phenylethynyl Terminated Imide (PETI) Composites Made by High Temperature VARTM

NASA Technical Reports Server (NTRS)

Chose, Sayata; Cano, Roberto J.; Britton, Sean M.; Watson, Kent A.; Jensen, Brian J.; Connell, John W.

2010-01-01

Fabrication of composite structures using vacuum assisted resin transfer molding (VARTM) is generally more affordable than conventional autoclave techniques. Recent efforts have focused on adapting VARTM for the fabrication of high temperature composites. Due to their low melt viscosity and long melt stability, certain phenylethynyl terminated imides (PETI) can be processed into composites using high temperature VARTM (HT-VARTM). However, one of the disadvantages of the current HT-VARTM resin systems has been the high porosity of the resultant composites. For aerospace applications, a void fraction of <2% is desired. In the current study, two PETI resins, LARC. PETI-330 and LARC. PETI-8 have been used to fabricate test specimens using HT-VARTM. The resins were infused into carbon fiber preforms at 260 C and cured between 316 and 371 C. Photomicrographs of the panels were taken and void contents were determined by acid digestion. Modifications to the thermal cycle used in the laminate fabrication have reduced the void content significantly; typically .3% for carbon fiber biaxially woven fabric and less than 2% for carbon fiber uniaxial fabric. Mechanical properties (short beam shear and flexure) of the panels were determined at both room and elevated temperatures. The results of this work are presented herein. This paper is declared a work of the U.S. Government and is not subject to copyright protection in the United States.

The sparkling Universe: clustering of voids and void clumps

NASA Astrophysics Data System (ADS)

Lares, Marcelo; Ruiz, Andrés N.; Luparello, Heliana E.; Ceccarelli, Laura; Garcia Lambas, Diego; Paz, Dante J.

2017-07-01

We analyse the clustering of cosmic voids using a numerical simulation and the main galaxy sample from the Sloan Digital Sky Survey. We take into account the classification of voids into two types that resemble different evolutionary modes: those with a rising integrated density profile (void-in-void mode or R-type) and voids with shells (void-in-cloud mode or S-type). The results show that voids of the same type have stronger clustering than the full sample. We use the correlation analysis to define void clumps, associations with at least two voids separated by a distance of at most the mean void separation. In order to study the spatial configuration of void clumps, we compute the minimal spanning tree and analyse their multiplicity, maximum length and elongation parameter. We further study the dynamics of the smaller sphere that enclose all the voids in each clump. Although the global densities of void clumps are different according to their member-void types, the bulk motions of these spheres are remarkably lower than those of randomly placed spheres with the same radius distribution. In addition, the coherence of pairwise void motions does not strongly depend on whether voids belong to the same clump. Void clumps are useful to analyse the large-scale flows around voids, since voids embedded in large underdense regions are mostly in the void-in-void regime, where the expansion of the larger region produces the separation of voids. Similarly, voids around overdense regions form clumps that are in collapse, as reflected in the relative velocities of voids that are mostly approaching.

On the properties of a bundle of flexible actin filaments in an optical trap.

PubMed

Perilli, Alessia; Pierleoni, Carlo; Ciccotti, Giovanni; Ryckaert, Jean-Paul

2016-06-28

We establish the statistical mechanics framework for a bundle of Nf living and uncrosslinked actin filaments in a supercritical solution of free monomers pressing against a mobile wall. The filaments are anchored normally to a fixed planar surface at one of their ends and, because of their limited flexibility, they grow almost parallel to each other. Their growing ends hit a moving obstacle, depicted as a second planar wall, parallel to the previous one and subjected to a harmonic compressive force. The force constant is denoted as the trap strength while the distance between the two walls as the trap length to make contact with the experimental optical trap apparatus. For an ideal solution of reactive filaments and free monomers at fixed free monomer chemical potential μ1, we obtain the general expression for the grand potential from which we derive averages and distributions of relevant physical quantities, namely, the obstacle position, the bundle polymerization force, and the number of filaments in direct contact with the wall. The grafted living filaments are modeled as discrete Wormlike chains, with F-actin persistence length ℓp, subject to discrete contour length variations ±d (the monomer size) to model single monomer (de)polymerization steps. Rigid filaments (ℓp = ∞), either isolated or in bundles, all provide average values of the stalling force in agreement with Hill's predictions Fs (H)=NfkBTln(ρ1/ρ1c)/d, independent of the average trap length. Here ρ1 is the density of free monomers in the solution and ρ1c its critical value at which the filament does not grow nor shrink in the absence of external forces. Flexible filaments (ℓp < ∞) instead, for values of the trap strength suitable to prevent their lateral escape, provide an average bundle force and an average trap length slightly larger than the corresponding rigid cases (few percents). Still the stalling force remains nearly independent on the average trap length, but results from the product of two strongly L-dependent contributions: the fraction of touching filaments ∝〈L〉(O.T.) (2) and the single filament buckling force ∝〈L〉(O.T.) (-2).

Simulation of Biomass Accumulation Pattern in Vapor-Phase Biofilters

PubMed Central

Xi, Jin-Ying; Hu, Hong-Ying; Zhang, Xian

2012-01-01

Abstract Existence of inert biomass and its impact on biomass accumulation patterns and biofilter performance were investigated. Four biofilters were set up in parallel to treat gaseous toluene. Each biofilter operated under different inlet toluene loadings for 100 days. Two microbial growth models, one with an inert biomass assumption and the other without, were established and compared. Results from the model with the inert biomass assumption showed better agreement with the experimental data than those based on the model without the inert biomass assumption thus verifying that inert biomass accumulation cannot be ignored in the long-term operation of biofilters. According to the model with an inert biomass assumption, the ratio of active biomass to total biomass will decrease and the inert biomass will become dominant in total biomass after a period of time. Filter bed structure simulation results showed that the void fraction is more sensitive to biomass accumulation than the specific surface area. The final void fraction of the biofilters with the highest inlet toluene loading is only 67% of its initial level while the final specific surface area is 82%. Identification and quantification of inert biomass will give a better understanding of biomass accumulation in biofilters and will result in a more exact simulation of biomass change during long-term operations. Results also indicate that an ideal biomass control technique should be able to remove most inert biomass while simultaneously preserving as much active biomass as possible. PMID:22693411

Oxide particle size distribution from shearing irradiated and unirradiated LWR fuels in Zircaloy and stainless steel cladding: significance for risk assessment

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

Davis, W. Jr.; West, G.A.; Stacy, R.G.

1979-03-22

Sieve fractionation was performed with oxide particles dislodged during shearing of unirradiated or irradiated fuel bundles or single rods of UO/sub 2/ or 96 to 97% ThO/sub 2/--3 to 4% UO/sub 2/. Analyses of these data by nonlinear least-squares techniques demonstrated that the particle size distribution is lognormal. Variables involved in the numerical analyses include lognormal median size, lognormal standard deviation, and shear cut length. Sieve-fractionation data are presented for unirradiated bundles of stainless-steel-clad or Zircaloy-2-clad UO/sub 2/ or ThO/sub 2/--UO/sub 2/ sheared into lengths from 0.5 to 2.0 in. Data are also presented for irradiated single rods (sheared intomore » lengths of 0.25 to 2.0 in.) of Zircaloy-2-clad UO/sub 2/ from BWRs and of Zircaloy-4-clad UO/sub 2/ from PWRs. Median particle sizes of UO/sub 2/ from shearing irradiated stainless-steel-clad fuel ranged from 103 to 182 ..mu..m; particle sizes of ThO/sub 2/--UO/sub 2/, under these same conditions, ranged from 137 to 202 ..mu..m. Similarly, median particle sizes of UO/sub 2/ from shearing unirradiated Zircaloy-2-clad fuel ranged from 230 to 957 ..mu..m. Irradiation levels of fuels from reactors ranged from 9,000 to 28,000 MWd/MTU. In general, particle sizes from shearing these irradiated fuels are larger than those from the unirradiated fuels; however, unirradiated fuel from vendors was not available for performing comparative shearing experiments. In addition, variations in particle size parameters pertaining to samples of a single vendor varied as much as those between different vendors. The fraction of fuel dislodged from the cladding is nearly proportional to the reciprocal of the shear cut length, until the cut length attains some minimum value below which all fuel is dislodged. Particles of fuel are generally elongated with a long-to-short axis ratio usually less than 3. Using parameters of the lognormal distribution estimates can be made of fractions of dislodged fuel having dimensions less than specified values.« less

A structural model for the osmosensor, transporter, and osmoregulator ProP of Escherichia coli.

PubMed

Wood, Janet M; Culham, Doreen E; Hillar, Alexander; Vernikovska, Yaroslava I; Liu, Feng; Boggs, Joan M; Keates, Robert A B

2005-04-19

Transporter ProP of Escherichia coli, a member of the major facilitator superfamily (MFS), acts as an osmosensor and an osmoregulator in cells and after purification and reconstitution in proteoliposomes. H(+)-osmoprotectant symport via ProP is activated when medium osmolality is elevated with membrane impermeant osmolytes. The three-dimensional structure of ProP was modeled with the crystal structure of MFS member GlpT as a template. This GlpT structure represents the inward (or cytoplasm)-facing conformation predicted by the alternating access model for transport. LacZ-PhoA fusion analysis and site-directed fluorescence labeling substantiated the membrane topology and orientation predicted by this model and most hydropathy analyses. The model predicts the presence of a proton pathway within the N-terminal six-helix bundle of ProP (as opposed to the corresponding pathway found within the C-terminal helix bundle of its paralogue, LacY). Replacement of residues within the N-terminal helix bundle impaired the osmotic activation of ProP, providing the first indication that residues outside the C-terminal domain are involved in osmosensing. Some residues that were accessible from the periplasmic side, as predicted by the structural model, were more susceptible to covalent labeling in permeabilized membrane fractions than in intact bacteria. These residues may be accessible from the cytoplasmic side in structures not represented by our current model, or their limited exposure in vivo may reflect constraints on transporter structure that are related to its osmosensory mechanism.

Tract-based analysis of white matter integrity in psychotic and nonpsychotic bipolar disorder.

PubMed

Ji, Andrew; Godwin, Douglass; Rutlin, Jerrel; Kandala, Sridhar; Shimony, Joshua S; Mamah, Daniel

2017-02-01

At least 50% of individuals with bipolar disorder (BD) present with psychosis during their lifetime. Psychotic symptoms have sometimes been linked to specific genetic and phenotypic markers. This study aims to explore potential differences between bipolar disorder subtypes by measuring white matter integrity of the brain and relationships with clinical measures. Diffusion tensor imaging and clinical measures were acquired from 102 participants, grouped as psychotic bipolar disorder (PBD) (n=48), non-psychotic bipolar disorder (NBD) (n=24), and healthy controls (n=30). We utilized a powerful, automated tool (TRACULA: Tracts Constrained by Underlying Anatomy) to analyze the fractional anisotropy (FA) and mean diffusivity (MD) of 18 white matter tracts. Decreased FA in numerous tracts was observed in bipolar disorder groups compared to healthy controls: bilateral cingulum-cingulate gyrus bundles, corticospinal tracts, and superior longitudinal fasciculi as well as the right hemisphere cingulum-angular bundle. Only left uncinate fasciculus FA differed between PBD and NPBD groups. We found no group differences in MD. Positive symptoms correlated with FA in the superior (inversely) and inferior (directly) longitudinal fasciculi. Negative symptoms directly correlated with mean FA of the corticospinal tract and cingulum-angular bundle. Neurotropic, mood-stabilizing medication prescribed for individuals with BD may interact with measures of white matter integrity in our BD participants. Our results indicate decreased white matter coherence in BD. Minimal differences in white matter FA between PBD and NPBD participants suggest related underlying neurobiology. Copyright © 2016 Elsevier B.V. All rights reserved.

Prenatal exposure to maternal and paternal depressive symptoms and white matter microstructure in children.

PubMed

El Marroun, Hanan; Zou, Runyu; Muetzel, Ryan L; Jaddoe, Vincent W; Verhulst, Frank C; White, Tonya; Tiemeier, Henning

2018-04-01

Prenatal maternal depression has been associated with multiple problems in offspring involving affect, cognition, and neuroendocrine functioning. This suggests that prenatal depression influences neurodevelopment. However, the underlying neurodevelopmental mechanism remains unclear. We prospectively assessed whether maternal depressive symptoms during pregnancy and at the child's age 3 years are related to white matter microstructure in 690 children. The association of paternal depressive symptoms with childhood white matter microstructure was assessed to evaluate genetic or familial confounding. Parental depressive symptoms were measured using the Brief Symptom Inventory. In children aged 6-9 years, we used diffusion tensor imaging to assess white matter microstructure characteristics including fractional anisotropy (FA) and mean diffusivity (MD). Exposure to maternal depressive symptoms during pregnancy was associated with higher MD in the uncinate fasciculus and to lower FA and higher MD in the cingulum bundle. No associations of maternal depressive symptoms at the child's age of 3 years with white matter characteristics were observed. Paternal depressive symptoms also showed a trend toward significance for a lower FA in the cingulum bundle. Prenatal maternal depressive symptoms were associated with higher MD in the uncinate fasciculus and the cingulum bundle. These structures are part of the limbic system, which is involved in motivation, emotion, learning, and memory. As paternal depressive symptoms were also related to lower FA in the cingulum, the observed effect may partly reflect a genetic predisposition and shared environmental family factors and to a lesser extent a specific intrauterine effect. © 2018 Wiley Periodicals, Inc.

Left bundle branch block, an old-new entity.

PubMed

Breithardt, Günter; Breithardt, Ole-Alexander

2012-04-01

Left bundle branch block (LBBB) is generally associated with a poorer prognosis in comparison to normal intraventricular conduction, but also in comparison to right bundle branch block which is generally considered to be benign in the absence of an underlying cardiac disorder like congenital heart disease. LBBB may be the first manifestation of a more diffuse myocardial disease. The typical surface ECG feature of LBBB is a prolongation of QRS above 0.11 s in combination with a delay of the intrinsic deflection in leads V5 and V6 of more than 60 ms and no septal q waves in leads I, V5, and V6 due to the abnormal septal activation from right to left. LBBB may induce abnormalities in left ventricular performance due to abnormal asynchronous contraction patterns which can be compensated by biventricular pacing (resynchronization therapy). Asynchronous electrical activation of the ventricles causes regional differences in workload which may lead to asymmetric hypertrophy and left ventricular dilatation, especially due to increased wall mass in late-activated regions, which may aggravate preexisting left ventricular pumping performance or even induce it. Of special interest are patients with LBBB and normal left ventricular dimensions and normal ejection fraction at rest but who may present with an abnormal increase in pulmonary artery pressure during exercise, production of lactate during high-rate pacing, signs of ischemia on myocardial scintigrams (but no coronary artery narrowing), and abnormal ultrastructural findings on myocardial biopsy. For this entity, the term latent cardiomyopathy had been suggested previously.

Progressive Assessment of Ischemic Injury to White Matter Using Diffusion Tensor Imaging: A Preliminary Study of a Macaque Model of Stroke.

PubMed

Zhang, Xiaodong; Yan, Yumei; Tong, Frank; Li, Chun-Xia; Jones, Benjamin; Wang, Silun; Meng, Yuguang; Muly, E Chris; Kempf, Doty; Howell, Leonard

2018-01-01

Previous Diffusion Tensor Imaging (DTI) studies have demonstrated the temporal evolution of stroke injury in grey matter and white matter can be characterized by DTI indices. However, it still remains not fully understood how the DTI indices of white matter are altered progressively during the hyperacute (first 6 hours) and acute stage of stroke (≤ 1 week). In the present study, DTI was employed to characterize the temporal evolution of infarction and white matter injury after stroke insult using a macaque model with permanent ischemic occlusion. Permanent middle cerebral artery (MCA) occlusion was induced in rhesus monkeys (n=4, 10-21 years old). The brain lesion was examined longitudinally with DTI during the hyperacute phase (2-6 hours, n=4), 48 hours (n=4) and 96 hours (n=3) post-occlusion. Cortical infarction was seen in all animals. The Mean Diffusivity (MD) in lesion regions decreased substantially at the first time point (2 hours post stroke) (35%, p <0.05, compared to the contralateral side) and became pseudo-normalized at 96 hours. In contrast, evident FA reduction was seen at 48 hours (39%, p <0.10) post-stroke. MD reduction in white matter bundles of the lesion area was much less than that in the grey matter during the hyper-acute phase but significant change was observed 4 hours (4.2%, p < 0.05) post stroke . Also, MD pseudonormalisation was seen at 96 hours post stroke. There was a significant correlation between the temporal changes of MD in white matter bundles and those in whole lesion areas during the entire study period. Meanwhile, no obvious fractional anisotropy (FA) changes were seen during the hyper-acute phase in either the entire infarct region or white matter bundles. Significant FA alteration was observed in entire lesion areas and injured white matter bundles 48 and 96 hours post stroke. The stroke lesion in grey matter and white matter was validated by pathological findings. The temporal evolution of ischemic injury to the grey matter and white matter from 2 to 96 hours after stroke onset was characterized using a macaque model and DTI. Progressive MD changes in white matter bundles are seen from hyperacute phase to acute phase after permanent MCA occlusion and temporally correlated with the MD changes in entire infarction regions. MD reduction in white matter bundles is mild in comparison with that in the grey matter but significant and progressive, indicating it may be useful to detect early white matter degeneration after stroke.

The sudden coalescene model of the boiling crisis

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

Carrica, P.M.; Clausse, A.

1995-09-01

A local two-phase flow integral model of nucleate boiling and crisis is presented. The model is based on average balances on a control volume, yielding to a set of three nonlinear differential equations for the local void fraction, bubble number density and velocity. Boiling crisis as critical heat flux is interpreted as a dynamic transition caused by the coalescence of bubbles near the heater. The theoretical dynamic model is compared with experimental results obtained for linear power ramps in a horizontal plate heater in R-113, showing an excellent qualitative agreement.

Ultrasonic evaluation of the strength of unidirectional graphite-polyimide composites

NASA Technical Reports Server (NTRS)

Vary, A.; Bowles, K. J.

1977-01-01

An acoustic-ultrasonic method is described that was successful in ranking unidirectional graphite-polyimide composite specimens according to variations in interlaminar shear strength. Using this method, a quantity termed the stress wave factor was determined. It was found that this factor increases directly with interlaminar shear strength. The key variables in this investigation were composite density, fiber weight fraction, and void content. The stress wave factor and other ultrasonic factors that were studied were found to provide a powerful means for nondestructive evaluation of mechanical strength properties.

Fiber optic sensors; Proceedings of the Meeting, Cannes, France, November 26, 27, 1985

NASA Technical Reports Server (NTRS)

Arditty, Herve J. (Editor); Jeunhomme, Luc B. (Editor)

1986-01-01

The conference presents papers on distributed sensors and sensor networks, signal processing and detection techniques, temperature measurements, chemical sensors, and the measurement of pressure, strain, and displacements. Particular attention is given to optical fiber distributed sensors and sensor networks, tactile sensing in robotics using an optical network and Z-plane techniques, and a spontaneous Raman temperature sensor. Other topics include coherence in optical fiber gyroscopes, a high bandwidth two-phase flow void fraction fiber optic sensor, and a fiber-optic dark-field microbend sensor.

Recognition of white matter bundles using local and global streamline-based registration and clustering.

PubMed

Garyfallidis, Eleftherios; Côté, Marc-Alexandre; Rheault, Francois; Sidhu, Jasmeen; Hau, Janice; Petit, Laurent; Fortin, David; Cunanne, Stephen; Descoteaux, Maxime

2018-04-15

Virtual dissection of diffusion MRI tractograms is cumbersome and needs extensive knowledge of white matter anatomy. This virtual dissection often requires several inclusion and exclusion regions-of-interest that make it a process that is very hard to reproduce across experts. Having automated tools that can extract white matter bundles for tract-based studies of large numbers of people is of great interest for neuroscience and neurosurgical planning. The purpose of our proposed method, named RecoBundles, is to segment white matter bundles and make virtual dissection easier to perform. This can help explore large tractograms from multiple persons directly in their native space. RecoBundles leverages latest state-of-the-art streamline-based registration and clustering to recognize and extract bundles using prior bundle models. RecoBundles uses bundle models as shape priors for detecting similar streamlines and bundles in tractograms. RecoBundles is 100% streamline-based, is efficient to work with millions of streamlines and, most importantly, is robust and adaptive to incomplete data and bundles with missing components. It is also robust to pathological brains with tumors and deformations. We evaluated our results using multiple bundles and showed that RecoBundles is in good agreement with the neuroanatomical experts and generally produced more dense bundles. Across all the different experiments reported in this paper, RecoBundles was able to identify the core parts of the bundles, independently from tractography type (deterministic or probabilistic) or size. Thus, RecoBundles can be a valuable method for exploring tractograms and facilitating tractometry studies. Copyright © 2017 Elsevier Inc. All rights reserved.

Lightweight Concrete Produced Using a Two-Stage Casting Process.

PubMed

Yoon, Jin Young; Kim, Jae Hong; Hwang, Yoon Yi; Shin, Dong Kyu

2015-03-25

The type of lightweight aggregate and its volume fraction in a mix determine the density of lightweight concrete. Minimizing the density obviously requires a higher volume fraction, but this usually causes aggregates segregation in a conventional mixing process. This paper proposes a two-stage casting process to produce a lightweight concrete. This process involves placing lightweight aggregates in a frame and then filling in the remaining interstitial voids with cementitious grout. The casting process results in the lowest density of lightweight concrete, which consequently has low compressive strength. The irregularly shaped aggregates compensate for the weak point in terms of strength while the round-shape aggregates provide a strength of 20 MPa. Therefore, the proposed casting process can be applied for manufacturing non-structural elements and structural composites requiring a very low density and a strength of at most 20 MPa.

On the concept of a filtered bundle

NASA Astrophysics Data System (ADS)

Bruce, Andrew James; Grabowska, Katarzyna; Grabowski, Janusz

We present the notion of a filtered bundle as a generalization of a graded bundle. In particular, we weaken the necessity of the transformation laws for local coordinates to exactly respect the weight of the coordinates by allowing more general polynomial transformation laws. The key examples of such bundles include affine bundles and various jet bundles, both of which play fundamental roles in geometric mechanics and classical field theory. We also present the notion of double filtered bundles which provide natural generalizations of double vector bundles and double affine bundles. Furthermore, we show that the linearization of a filtered bundle — which can be seen as a partial polarization of the admissible changes of local coordinates — is well defined.

Anatomy of the anterior cruciate ligament with regard to its two bundles.

PubMed

Petersen, Wolf; Zantop, Thore

2007-01-01

The anterior cruciate ligament (ACL) consists of two major fiber bundles, namely the anteromedial and posterolateral bundle. When the knee is extended, the posterolateral bundle (PL) is tight and the anteromedial (AM) bundle is moderately lax. As the knee is flexed, the femoral attachment of the ACL becomes a more horizontal orientation; causing the AM bundle to tighten and the PL bundle to relax. There is some degree of variability for the femoral origin of the anterome-dial and posterolateral bundle. The anteromedial bundle is located proximal and anterior in the femoral ACL origin (high and deep in the notch when the knee is flexed at 90 degrees ); the posterolateral bundle starts in the distal and posterior aspect of the femoral ACL origin (shallow and low when the knee is flexed at 90 degrees ). In the frontal plane the anteromedial bundle origin is in the 10:30 clock position and the postero-lateral bundle origin in the 9:30 clock position. At the tibial insertion the ACL fans out to form the foot region. The anteromedial bundle insertion is in the anterior part of the tibial ACL footprint, the posterolateral bundle in the posterior part. While the anteromedial bundle is the primary restraint against anterior tibial translation, the posterolateral bundle tends to stabilize the knee near full extension, particularly against rotatory loads.

Comparison between wire mesh sensor and gamma densitometry void measurements in two-phase flows

NASA Astrophysics Data System (ADS)

Sharaf, S.; Da Silva, M.; Hampel, U.; Zippe, C.; Beyer, M.; Azzopardi, B.

2011-10-01

Wire mesh sensors (WMS) are fast imaging instruments that are used for gas-liquid and liquid-liquid two-phase flow measurements and experimental investigations. Experimental tests were conducted at Helmholtz-Zentrum Dresden-Rossendorf to test both the capacitance and conductance WMS against a gamma densitometer (GD). A small gas-liquid test facility was utilized. This consisted of a vertical round pipe approximately 1 m in length, and 50 mm internal diameter. A 16 × 16 WMS was used with high spatial and temporal resolutions. Air-deionized water was the two-phase mixture. The gas superficial velocity was varied between 0.05 m s-1 and 1.4 m s-1 at two liquid velocities of 0.2 and 0.7 m s-1. The GD consisted of a collimated source and a collimated detector. The GD was placed on a moving platform close to the plane of wires of the sensor, in order to align it accurately using a counter mechanism, with each of the wires of the WMS, and the platform could scan the full section of the pipe. The WMS was operated as a conductivity WMS for a half-plane with eight wires and as a capacitance WMS for the other half. For the cross-sectional void (time and space averaged), along each wire, there was good agreement between WMS and the GD chordal void fraction near the centre of the pipe.

Prediction of a Densely Loaded Particle-Laden Jet using a Euler-Lagrange Dense Spray Model

NASA Astrophysics Data System (ADS)

Pakseresht, Pedram; Apte, Sourabh V.

2017-11-01

Modeling of a dense spray regime using an Euler-Lagrange discrete-element approach is challenging because of local high volume loading. A subgrid cluster of droplets can lead to locally high void fractions for the disperse phase. Under these conditions, spatio-temporal changes in the carrier phase volume fractions, which are commonly neglected in spray simulations in an Euler-Lagrange two-way coupling model, could become important. Accounting for the carrier phase volume fraction variations, leads to zero-Mach number, variable density governing equations. Using pressure-based solvers, this gives rise to a source term in the pressure Poisson equation and a non-divergence free velocity field. To test the validity and predictive capability of such an approach, a round jet laden with solid particles is investigated using Direct Numerical Simulation and compared with available experimental data for different loadings. Various volume fractions spanning from dilute to dense regimes are investigated with and without taking into account the volume displacement effects. The predictions of the two approaches are compared and analyzed to investigate the effectiveness of the dense spray model. Financial support was provided by National Aeronautics and Space Administration (NASA).

Effect of maleic anhydride treatment on the mechanical properties of sansevieria fiber/vinyl ester composites

NASA Astrophysics Data System (ADS)

Pradipta, Rangga; Mardiyati, Steven, Purnomo, Ikhsan

2017-03-01

Sanseviera trifasciata commonly called mother-in-law tongue also known as snake plant is native to Indonesia, India and Africa. Sansevieria is a new fiber in composite research and has showed promising properties as reinforcement material in polymer matrix composites. Chemical treatment on reinforcing fiber is crucial to reduce hydrophilic tendency and thus improve compatibility with the matrix. In this study, effect of maleic anhydride as chemical treatment on the mechanical properties of Sansevieria fiber/vinyl ester composite was investigated. Sansevieria fibers were immersed by using NaOH 3% for two hours at 100°C and then treated by using maleic anhydrate for two hours at 120°C. Composites were prepared by solution casting with various volume fractions of fiber; 0%, 2.5%, 5%, 7.5% and 10%. Actual density, volume fraction of void and mechanical properties of composite were conducted according to ASTM standard testing methods D792, D3171 and D3039. It was found that mechanical properties of composites increased as volume fractions of fiber was increased. The highest tensile strength and modulus of elasticity of composites were 57.45 MPa and 3.47 GPa respectively, obtained from composites with volume fraction of fiber 10%.

Connectomic disturbances in attention-deficit/hyperactivity disorder: a whole-brain tractography analysis.

PubMed

Hong, Soon-Beom; Zalesky, Andrew; Fornito, Alex; Park, Subin; Yang, Young-Hui; Park, Min-Hyeon; Song, In-Chan; Sohn, Chul-Ho; Shin, Min-Sup; Kim, Bung-Nyun; Cho, Soo-Churl; Han, Doug Hyun; Cheong, Jae Hoon; Kim, Jae-Won

2014-10-15

Few studies have sought to identify, in a regionally unbiased way, the precise cortical and subcortical regions that are affected by white matter abnormalities in attention-deficit/hyperactivity disorder (ADHD). This study aimed to derive a comprehensive, whole-brain characterization of connectomic disturbances in ADHD. Using diffusion tensor imaging, whole-brain tractography, and an imaging connectomics approach, we characterized altered white matter connectivity in 71 children and adolescents with ADHD compared with 26 healthy control subjects. White matter differences were further delineated between patients with (n = 40) and without (n = 26) the predominantly hyperactive/impulsive subtype of ADHD. A significant network comprising 25 distinct fiber bundles linking 23 different brain regions spanning frontal, striatal, and cerebellar brain regions showed altered white matter structure in ADHD patients (p < .05, family-wise error-corrected). Moreover, fractional anisotropy in some of these fiber bundles correlated with attentional disturbances. Attention-deficit/hyperactivity disorder subtypes were differentiated by a right-lateralized network (p < .05, family-wise error-corrected) predominantly linking frontal, cingulate, and supplementary motor areas. Fractional anisotropy in this network was also correlated with continuous performance test scores. Using an unbiased, whole-brain, data-driven approach, we demonstrated abnormal white matter connectivity in ADHD. The correlations observed with measures of attentional performance underscore the functional importance of these connectomic disturbances for the clinical phenotype of ADHD. A distributed pattern of white matter microstructural integrity separately involving frontal, striatal, and cerebellar brain regions, rather than direct frontostriatal connectivity, appears to be disrupted in children and adolescents with ADHD. Copyright © 2014 Society of Biological Psychiatry. Published by Elsevier Inc. All rights reserved.

The evolution of voids in the adhesion approximation

NASA Astrophysics Data System (ADS)

Sahni, Varun; Sathyaprakah, B. S.; Shandarin, Sergei F.

1994-08-01

We apply the adhesion approximation to study the formation and evolution of voids in the universe. Our simulations-carried out using 1283 particles in a cubical box with side 128 Mpc-indicate that the void spectrum evolves with time and that the mean void size in the standard Cosmic Background Explorer Satellite (COBE)-normalized cold dark matter (CDM) model with H50 = 1 scals approximately as bar D(z) = bar Dzero/(1+2)1/2, where bar Dzero approximately = 10.5 Mpc. Interestingly, we find a strong correlation between the sizes of voids and the value of the primordial gravitational potential at void centers. This observation could in principle, pave the way toward reconstructing the form of the primordial potential from a knowledge of the observed void spectrum. Studying the void spectrum at different cosmological epochs, for spectra with a built in k-space cutoff we find that the number of voids in a representative volume evolves with time. The mean number of voids first increases until a maximum value is reached (indicating that the formation of cellular structure is complete), and then begins to decrease as clumps and filaments erge leading to hierarchical clustering and the subsequent elimination of small voids. The cosmological epoch characterizing the completion of cellular structure occurs when the length scale going nonlinear approaches the mean distance between peaks of the gravitaional potential. A central result of this paper is that voids can be populated by substructure such as mini-sheets and filaments, which run through voids. The number of such mini-pancakes that pass through a given void can be measured by the genus characteristic of an individual void which is an indicator of the topology of a given void in intial (Lagrangian) space. Large voids have on an average a larger measure than smaller voids indicating more substructure within larger voids relative to smaller ones. We find that the topology of individual voids is strongly epoch dependent, with void topologies generally simplifying with time. This means that as voids grow older they become progressively more empty and have less structure within them. We evaluate the genus measure both for individual voids as well as for the entire ensemble of voids predicted by CDM model. As a result we find that the topology of voids when taken together with the void spectrum is a very useful statistical indicator of the evolution of the structure of the universe on large scales.

The evolution of voids in the adhesion approximation

NASA Technical Reports Server (NTRS)

Sahni, Varun; Sathyaprakah, B. S.; Shandarin, Sergei F.

1994-01-01

We apply the adhesion approximation to study the formation and evolution of voids in the universe. Our simulations-carried out using 128(exp 3) particles in a cubical box with side 128 Mpc-indicate that the void spectrum evolves with time and that the mean void size in the standard Cosmic Background Explorer Satellite (COBE)-normalized cold dark matter (CDM) model with H(sub 50) = 1 scals approximately as bar D(z) = bar D(sub zero)/(1+2)(exp 1/2), where bar D(sub zero) approximately = 10.5 Mpc. Interestingly, we find a strong correlation between the sizes of voids and the value of the primordial gravitational potential at void centers. This observation could in principle, pave the way toward reconstructing the form of the primordialpotential from a knowledge of the observed void spectrum. Studying the void spectrum at different cosmological epochs, for spectra with a built in k-space cutoff we find that the number of voids in a representative volume evolves with time. The mean number of voids first increases until a maximum value is reached (indicating that the formation of cellular structure is complete), and then begins to decrease as clumps and filaments erge leading to hierarchical clustering and the subsequent elimination of small voids. The cosmological epoch characterizing the completion of cellular structure occurs when the length scale going nonlinear approaches the mean distance between peaks of the gravitaional potential. A central result of this paper is that voids can be populated by substructure such as mini-sheets and filaments, which run through voids. The number of such mini-pancakes that pass through a given void can be measured by the genus characteristic of an individual void which is an indicator of the topology of a given void in intial (Lagrangian) space. Large voids have on an average a larger measure than smaller voids indicating more substructure within larger voids relative to smaller ones. We find that the topology of individual voids is strongly epoch dependent, with void topologies generally simplifying with time. This means that as voids grow older they become progressively more empty and have less structure within them. We evaluate the genus measure both for individual voids as well as for the entire ensemble of voids predicted by CDM model. As a result we find that the topology of voids when taken together with the void spectrum is a very useful statistical indicator of the evolution of the structure of the universe on large scales.

Advances in Chemical and Structural Characterization of Concretion with Implications for Modeling Marine Corrosion

NASA Astrophysics Data System (ADS)

Johnson, Donald L.; DeAngelis, Robert J.; Medlin, Dana J.; Carr, James D.; Conlin, David L.

2014-05-01

The Weins number model and concretion equivalent corrosion rate methodology were developed as potential minimum-impact, cost-effective techniques to determine corrosion damage on submerged steel structures. To apply the full potential of these technologies, a detailed chemical and structural characterization of the concretion (hard biofouling) that transforms into iron bearing minerals is required. The fractions of existing compounds and the quantitative chemistries are difficult to determine from x-ray diffraction. Environmental scanning electron microscopy was used to present chemical compositions by means of energy-dispersive spectroscopy (EDS). EDS demonstrates the chemical data in mapping format or in point or selected area chemistries. Selected-area EDS data collection at precise locations is presented in terms of atomic percent. The mechanism of formation and distribution of the iron-bearing mineral species at specific locations will be presented. Based on water retention measurements, porosity in terms of void volume varies from 15 v/o to 30 v/o (vol.%). The void path displayed by scanning electron microscopy imaging illustrates the tortuous path by which oxygen migrates in the water phase within the concretion from seaside to metalside.

Deformation behaviour of Rheocast A356 Al alloy at microlevel considering approximated RVEs

NASA Astrophysics Data System (ADS)

Islam, Sk. Tanbir; Das, Prosenjit; Das, Santanu

2015-03-01

A micromechanical approach is considered here to predict the deformation behaviour of Rheocast A356 (Al-Si-Mg) alloy. Two representative volume elements (RVEs) are modelled in the finite element (FE) framework. Two dimensional approximated microstructures are generated assuming elliptic grains, based on the grain size, shape factor and area fraction of the primary Al phase of the said alloy at different processing condition. Plastic instability is shown using stress and strain distribution between the Al rich primary and Si rich eutectic phases under different boundary conditions. Boundary conditions are applied on the approximated RVEs in such a manner, so that they represent the real life situation depending on their position on a cylindrical tensile test sample. FE analysis is carried out using commercial finite element code ABAQUS without specifying any damage or failure criteria. Micro-level in-homogeneity leads to incompatible deformation between the constituent phases of the rheocast alloy and steers plastic strain localisation. Plastic stain localised regions within the RVEs are predicted as the favourable sites for void nucleation. Subsequent growth of nucleated voids leads to final failure of the materials under investigation.

Correlation between some thermo-mechanical and physico-chemical properties in multi-component glasses of Se-Te-Sn-Cd system

NASA Astrophysics Data System (ADS)

Kumar, Amit; Mehta, Neeraj

2017-06-01

The glass transition phenomenon is guided by the swift cooling of a melt (glass-forming liquid). Consequently, the glass as a final product consists of a considerable number of micro-voids having the size of the order of atomic and/or molecular sizes. The model of free volume fluctuation helps in describing the diverse physico-chemical properties of amorphous materials (like glasses and polymers). This theory is based on the fraction of fluctuation free frozen at the glass transition temperature and it forms a basis for determination of various significant thermo-mechanical properties. In the present work, Vickers hardness test method is employed that provides useful information concerning the mechanical behavior of brittle solids. The present work emphasizes the results of micro-indentation measurements on recently synthesized novel Se78- x Te20Sn2Cd x glassy system. Basic thermo-mechanical parameters such as micro-hardness, volume ( V h), formation energy ( E h) of micro-voids in the glassy network and modulus of elasticity ( E) have been determined and their variation with glass composition has been investigated.

Velocity and void distribution in a counter-current two-phase flow

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

Gabriel, S.; Schulenberg, T.; Laurien, E.

2012-07-01

Different flow regimes were investigated in a horizontal channel. Simulating a hot leg injection in case of a loss of coolant accident or flow conditions in reflux condenser mode, the hydraulic jump and partially reversed flow were identified as major constraints for a high amount of entrained water. Trying to simulate the reflux condenser mode, the test section now includes an inclined section connected to a horizontal channel. The channel is 90 mm high and 110 mm wide. Tests were carried out for water and air at ambient pressure and temperature. High speed video-metry was applied to obtain velocities frommore » flow pattern maps of the rising and falling fluid. In the horizontal part of the channel with partially reversed flow the fluid velocities were measured by planar particle image velocimetry. To obtain reliable results for the gaseous phase, this analysis was extended by endoscope measurements. Additionally, a new method based on the optical refraction at the interface between air and water in a back-light was used to obtain time-averaged void fraction. (authors)« less

Velocity field measurement in gas-liquid metal two-phase flow with use of PIV and neutron radiography techniques.

PubMed

Saito, Y; Mishima, K; Tobita, Y; Suzuki, T; Matsubayashi, M

2004-10-01

To establish reasonable safety concepts for the realization of commercial liquid-metal fast breeder reactors, it is indispensable to demonstrate that the release of excessive energy due to re-criticality of molten core could be prevented even if a severe core damage accident took place. Two-phase flow due to the boiling of fuel-steel mixture in the molten core pool has a larger liquid-to-gas density ratio and higher surface tension in comparison with those of ordinary two-phase flows such as air-water flow. In this study, to investigate the effect of the recirculation flow on the bubble behavior, visualization and measurement of nitrogen gas-molten lead bismuth in a rectangular tank was performed by using neutron radiography and particle image velocimetry techniques. Measured flow parameters include flow regime, two-dimensional void distribution, and liquid velocity field in the tank. The present technique is applicable to the measurement of velocity fields and void fraction, and the basic characteristics of gas-liquid metal two-phase mixture were clarified.

Void effect on mechanical properties of copper nanosheets under biaxial tension by molecular dynamics method

NASA Astrophysics Data System (ADS)

Yang, Zailin; Yang, Qinyou; Zhang, Guowei; Yang, Yong

2018-03-01

The relationship between void size/location and mechanical behavior under biaxial loading of copper nanosheets containing voids are investigated by molecular dynamics method. The void location and the void radius on the model are discussed in the paper. The main reason of break is discovered by the congruent relationship between the shear stress and its dislocations. Dislocations are nucleated at the corner of system and approached to the center of void with increased deformation. Here, a higher stress is required to fail the voided sheets when smaller voids are utilized. The void radius influences the time of destruction. The larger the void radius is, the lower the shear stress and the earlier the model breaks. The void location impacts the dislocation distribution.

A General 3-D Methodology for Quasi-Static Simulation of Drainage and Imbibition: Application to Highly Porous Fibrous Materials

NASA Astrophysics Data System (ADS)

Riasi, S.; Huang, G.; Montemagno, C.; Yeghiazarian, L.

2013-12-01

Micro-scale modeling of multiphase flow in porous media is critical to characterize porous materials. Several modeling techniques have been implemented to date, but none can be used as a general strategy for all porous media applications due to challenges presented by non-smooth high-curvature solid surfaces, and by a wide range of pore sizes and porosities. Finite approaches like the finite volume method require a high quality, problem-dependent mesh, while particle-based approaches like the lattice Boltzmann require too many particles to achieve a stable meaningful solution. Both come at a large computational cost. Other methods such as pore network modeling (PNM) have been developed to accelerate the solution process by simplifying the solution domain, but so far a unique and straightforward methodology to implement PNM is lacking. We have developed a general, stable and fast methodology to model multi-phase fluid flow in porous materials, irrespective of their porosity and solid phase topology. We have applied this methodology to highly porous fibrous materials in which void spaces are not distinctly separated, and where simplifying the geometry into a network of pore bodies and throats, as in PNM, does not result in a topology-consistent network. To this end, we have reduced the complexity of the 3-D void space geometry by working with its medial surface. We have used a non-iterative fast medial surface finder algorithm to determine a voxel-wide medial surface of the void space, and then solved the quasi-static drainage and imbibition on the resulting domain. The medial surface accurately represents the topology of the porous structure including corners, irregular cross sections, etc. This methodology is capable of capturing corner menisci and the snap-off mechanism numerically. It also allows for calculation of pore size distribution, permeability and capillary pressure-saturation-specific interfacial area surface of the porous structure. To show the capability of this method to numerically estimate the capillary pressure in irregular cross sections, we compared our results with analytical solutions available for capillary tubes with non-circular cross sections. We also validated this approach by implementing it on well-known benchmark problems such as a bundle of cylinders and packed spheres.

Infusion Processing of Phenylethynyl Terminated Imides by High Temperature RTM and VARTM

NASA Technical Reports Server (NTRS)

Ghose, Sayata; Lewis, Todd M.; Cano, Roberto J.; Watson, Kent A.; Isayev, Avraam I.

2011-01-01

Fabrication of composite structures using infusion processes such as resin transfer molding (RTM) and vacuum assisted resin transfer molding (VARTM) is generally more affordable than conventional autoclave techniques. Recent efforts have focused on adapting both technologies for the fabrication of high temperature (HT) resistant composites. Due to their low melt viscosity and long melt stability, certain phenylethynyl terminated imides (PETI) can be processed into composites using these high temperature out-of-autoclave processes. In the current study, two PETI resins, LARC(TradeMark) PETI-330 and LARC(TradeMark) PETI-8 have been used to make test specimens using both RTM and VARTM. For aerospace applications, a void fraction of less than 2% is desired. Traditionally, RTM has had the advantage over VARTM for generating composites with low void content. However, the process is limited in terms of size. Work at NASA LaRC has incorporated modifications to the thermal cycle used in laminate fabrication that have reduced the void content significantly (typically 1-3%) using the current HT-VARTM process. For composite fabrication by both RTM and VARTM, the resins were infused into three carbon fiber preforms (T650-35-3k 5HS, IM7-6k 5HS, and IM7-6k Uniweave) at 316 C and 260 C respectively and cured up to 371 C. The details of the RTM processing carried out at the University of Akron are discussed in this work along with a brief description of the HT-VARTM processing carried out at NASA-LaRC. Photomicrographs of the panels were taken and void contents were determined by acid digestion. Mechanical properties (short beam shear, SBS) of the panels fabricated by both infusion processes were determined at room temperature as well as at various elevated temperatures. The results of this work are presented herein.

Loop and void damage during heavy ion irradiation on nanocrystalline and coarse grained tungsten: Microstructure, effect of dpa rate, temperature, and grain size

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

El-Atwani, O.; Esquivel, E.; Efe, M.

Displacement damage, through heavy ion irradiation was studied on two tungsten grades (coarse grained tungsten (CGW) and nanocrystalline and ultrafine grained tungsten (NCW)) using different displacement per atom rates and different irradiation temperatures (RT and 1050 K). Percentage of <111> and <100> type loops at the irradiation conditions was determined. Irradiation damage in the microstructure was quantified using average loop areas and densities (method A) and loop areal fraction in the grain matrices under 2-beam diffraction conditions (method B). Average values of <111> and <100> loops were calculated from method A. Loop coalescence was shown to occur for CGW atmore » 0.25 dpa. Using both methods of quantifying microstructural damage, no effect of dpa rate was observed and damage in CGW was shown to be the same at RT and 1050 K. Swelling from voids observed at 1050 K was quantified. The loop damage in NCW was compared to CGW at the same diffraction and imaging conditions. NCW was shown to possess enhanced irradiation resistance at RT regarding loop damage and higher swelling resistance at 1050 K compared to CGW. For irradiation at 1050 K, the NCW was shown to have a similar defect densities to the CGW which is attributed to higher surface effects in the CGW, vacancy loop growth to voids and a better sink efficiency in the CGW deduced from the vacancy distribution profiles from Kinetic Monte Carlo simulations. Loop density and swelling was shown to have similar values in grains sizes that range from 80-600 nm. No loop or void denuded zones occurred at any of the irradiation conditions. This work has a collection of experiments and conclusions that are of vital importance to materials and nuclear communities.« less

Loop and void damage during heavy ion irradiation on nanocrystalline and coarse grained tungsten: Microstructure, effect of dpa rate, temperature, and grain size

DOE PAGES

El-Atwani, O.; Esquivel, E.; Efe, M.; ...

2018-02-20

Displacement damage, through heavy ion irradiation was studied on two tungsten grades (coarse grained tungsten (CGW) and nanocrystalline and ultrafine grained tungsten (NCW)) using different displacement per atom rates and different irradiation temperatures (RT and 1050 K). Percentage of <111> and <100> type loops at the irradiation conditions was determined. Irradiation damage in the microstructure was quantified using average loop areas and densities (method A) and loop areal fraction in the grain matrices under 2-beam diffraction conditions (method B). Average values of <111> and <100> loops were calculated from method A. Loop coalescence was shown to occur for CGW atmore » 0.25 dpa. Using both methods of quantifying microstructural damage, no effect of dpa rate was observed and damage in CGW was shown to be the same at RT and 1050 K. Swelling from voids observed at 1050 K was quantified. The loop damage in NCW was compared to CGW at the same diffraction and imaging conditions. NCW was shown to possess enhanced irradiation resistance at RT regarding loop damage and higher swelling resistance at 1050 K compared to CGW. For irradiation at 1050 K, the NCW was shown to have a similar defect densities to the CGW which is attributed to higher surface effects in the CGW, vacancy loop growth to voids and a better sink efficiency in the CGW deduced from the vacancy distribution profiles from Kinetic Monte Carlo simulations. Loop density and swelling was shown to have similar values in grains sizes that range from 80-600 nm. No loop or void denuded zones occurred at any of the irradiation conditions. This work has a collection of experiments and conclusions that are of vital importance to materials and nuclear communities.« less

Nonlinear Bubble Dynamics And The Effects On Propagation Through Near-Surface Bubble Layers

NASA Astrophysics Data System (ADS)

Leighton, Timothy G.

2004-11-01

Nonlinear bubble dynamics are often viewed as the unfortunate consequence of having to use high acoustic pressure amplitudes when the void fraction in the near-surface oceanic bubble layer is great enough to cause severe attenuation (e.g. >50 dB/m). This is seen as unfortunate since existing models for acoustic propagation in bubbly liquids are based on linear bubble dynamics. However, the development of nonlinear models does more than just allow quantification of the errors associated with the use of linear models. It also offers the possibility of propagation modeling and acoustic inversions which appropriately incorporate the bubble nonlinearity. Furthermore, it allows exploration and quantification of possible nonlinear effects which may be exploited. As a result, high acoustic pressure amplitudes may be desirable even in low void fractions, because they offer opportunities to gain information about the bubble cloud from the nonlinearities, and options to exploit the nonlinearities to enhance communication and sonar in bubbly waters. This paper presents a method for calculating the nonlinear acoustic cross-sections, scatter, attenuations and sound speeds from bubble clouds which may be inhomogeneous. The method allows prediction of the time dependency of these quantities, both because the cloud may vary and because the incident acoustic pulse may have finite and arbitrary time history. The method can be readily adapted for bubbles in other environments (e.g. clouds of interacting bubbles, sediments, structures, in vivo, reverberant conditions etc.). The possible exploitation of bubble acoustics by marine mammals, and for sonar enhancement, is explored.

On the properties of a bundle of flexible actin filaments in an optical trap

NASA Astrophysics Data System (ADS)

Perilli, Alessia; Pierleoni, Carlo; Ciccotti, Giovanni; Ryckaert, Jean-Paul

2016-06-01

We establish the statistical mechanics framework for a bundle of Nf living and uncrosslinked actin filaments in a supercritical solution of free monomers pressing against a mobile wall. The filaments are anchored normally to a fixed planar surface at one of their ends and, because of their limited flexibility, they grow almost parallel to each other. Their growing ends hit a moving obstacle, depicted as a second planar wall, parallel to the previous one and subjected to a harmonic compressive force. The force constant is denoted as the trap strength while the distance between the two walls as the trap length to make contact with the experimental optical trap apparatus. For an ideal solution of reactive filaments and free monomers at fixed free monomer chemical potential μ1, we obtain the general expression for the grand potential from which we derive averages and distributions of relevant physical quantities, namely, the obstacle position, the bundle polymerization force, and the number of filaments in direct contact with the wall. The grafted living filaments are modeled as discrete Wormlike chains, with F-actin persistence length ℓp, subject to discrete contour length variations ±d (the monomer size) to model single monomer (de)polymerization steps. Rigid filaments (ℓp = ∞), either isolated or in bundles, all provide average values of the stalling force in agreement with Hill's predictions Fs H = N f k B T ln ( ρ 1 / ρ 1 c) / d , independent of the average trap length. Here ρ1 is the density of free monomers in the solution and ρ1c its critical value at which the filament does not grow nor shrink in the absence of external forces. Flexible filaments (ℓp < ∞) instead, for values of the trap strength suitable to prevent their lateral escape, provide an average bundle force and an average trap length slightly larger than the corresponding rigid cases (few percents). Still the stalling force remains nearly independent on the average trap length, but results from the product of two strongly L-dependent contributions: the fraction of touching filaments ∝ (" separators=" < L >O . T .) 2 and the single filament buckling force ∝ (" separators=" < L >O . T .) - 2 .

Verification of the FBR fuel bundle-duct interaction analysis code BAMBOO by the out-of-pile bundle compression test with large diameter pins

NASA Astrophysics Data System (ADS)

Uwaba, Tomoyuki; Ito, Masahiro; Nemoto, Junichi; Ichikawa, Shoichi; Katsuyama, Kozo

2014-09-01

The BAMBOO computer code was verified by results for the out-of-pile bundle compression test with large diameter pin bundle deformation under the bundle-duct interaction (BDI) condition. The pin diameters of the examined test bundles were 8.5 mm and 10.4 mm, which are targeted as preliminary fuel pin diameters for the upgraded core of the prototype fast breeder reactor (FBR) and for demonstration and commercial FBRs studied in the FaCT project. In the bundle compression test, bundle cross-sectional views were obtained from X-ray computer tomography (CT) images and local parameters of bundle deformation such as pin-to-duct and pin-to-pin clearances were measured by CT image analyses. In the verification, calculation results of bundle deformation obtained by the BAMBOO code analyses were compared with the experimental results from the CT image analyses. The comparison showed that the BAMBOO code reasonably predicts deformation of large diameter pin bundles under the BDI condition by assuming that pin bowing and cladding oval distortion are the major deformation mechanisms, the same as in the case of small diameter pin bundles. In addition, the BAMBOO analysis results confirmed that cladding oval distortion effectively suppresses BDI in large diameter pin bundles as well as in small diameter pin bundles.

Dynamic void behavior in polymerizing polymethyl methacrylate cement.

PubMed

Muller, Scott D; McCaskie, Andrew W

2006-02-01

Cement mantle voids remain controversial with respect to survival of total hip arthroplasty. Void evolution is poorly understood, and attempts at void manipulation can only be empirical. We induced voids in a cement model simulating the constraints of the proximal femur. Intravoid pressure and temperature were recorded throughout polymerization, and the initial and final void volumes were measured. Temperature-dependent peak intravoid pressures and void volume increases were observed. After solidification, subatmospheric intravoid pressures were observed. The magnitude of these observations could not be explained by the ideal gas law. Partial pressures of the void gas at peak pressures demonstrated a dominant effect of gaseous monomer, thereby suggesting that void growth is a pressure-driven phenomenon resulting from temperature-dependent evaporation of monomer into existing trapped air voids.

Voids and superstructures: correlations and induced large-scale velocity flows

NASA Astrophysics Data System (ADS)

Lares, Marcelo; Luparello, Heliana E.; Maldonado, Victoria; Ruiz, Andrés N.; Paz, Dante J.; Ceccarelli, Laura; Garcia Lambas, Diego

2017-09-01

The expanding complex pattern of filaments, walls and voids build the evolving cosmic web with material flowing from underdense on to high density regions. Here, we explore the dynamical behaviour of voids and galaxies in void shells relative to neighbouring overdense superstructures, using the Millenium simulation and the main galaxy catalogue in Sloan Digital Sky Survey data. We define a correlation measure to estimate the tendency of voids to be located at a given distance from a superstructure. We find voids-in-clouds (S-types) preferentially located closer to superstructures than voids-in-voids (R-types) although we obtain that voids within ˜40 h-1 Mpc of superstructures are infalling in a similar fashion independently of void type. Galaxies residing in void shells show infall towards the closest superstructure, along with the void global motion, with a differential velocity component depending on their relative position in the shell with respect to the direction to the superstructure. This effect is produced by void expansion and therefore is stronger for R-types. We also find that galaxies in void shells facing the superstructure flow towards the overdensities faster than galaxies elsewhere at the same relative distance to the superstructure. The results obtained for the simulation are also reproduced for the Sky Survey Data Release data with a linearized velocity field implementation.

Evaluation of a mobile voiding diary for pediatric patients with voiding dysfunction: a prospective comparative study.

PubMed

Johnson, Emilie K; Estrada, Carlos R; Johnson, Kathryn L; Nguyen, Hiep T; Rosoklija, Ilina; Nelson, Caleb P

2014-09-01

One potential strategy for improving voiding diary completion rates and data quality is use of a mobile electronic format. We evaluated the acceptability and feasibility of mobile voiding diaries for patients with nonneurogenic lower urinary tract dysfunction, and compared mobile and paper voiding diaries. We prospectively enrolled children presenting with daytime symptoms of lower urinary tract dysfunction between July 2012 and April 2013. We enrolled an initial cohort of patients who were provided a paper voiding diary and a subsequent cohort who were provided a mobile voiding diary. We conducted in person interviews and assessed completion rates and quality, comparing paper and mobile voiding diary groups. We enrolled 45 patients who received a paper voiding diary and 38 who received a mobile voiding diary. Completion rates were 78% for paper voiding diaries and 61% for mobile voiding diaries (p = 0.10). Data quality measures for patients completing paper vs mobile voiding diaries revealed a larger proportion (63% vs 52%) providing a full 5 days of data and a smaller proportion (20% vs 65%) with data gaps. However, the paper voiding diary also demonstrated a lower proportion (80% vs 100%) that was completely legible and a lower proportion (40% vs 65%) with completely prospective data entry. The use of a mobile voiding diary was acceptable and feasible for our patients with lower urinary tract dysfunction, although completion rates were somewhat lower compared to paper voiding diaries. Data quality was not clearly better for either version. The mobile voiding diary format may offer data quality advantages for select groups but it did not display significant superiority when provided universally. Copyright © 2014 American Urological Association Education and Research, Inc. Published by Elsevier Inc. All rights reserved.

Phase-field study on geometry-dependent migration behavior of voids under temperature gradient in UO2 crystal matrix

NASA Astrophysics Data System (ADS)

Chen, Weijin; Peng, Yuyi; Li, Xu'an; Chen, Kelang; Ma, Jun; Wei, Lingfeng; Wang, Biao; Zheng, Yue

2017-10-01

In this work, a phase-field model is established to capture the void migration behavior under a temperature gradient within a crystal matrix, with an appropriate consideration of the surface diffusion mechanism and the vapor transport mechanism. The interfacial energy and the coupling between the vacancy concentration field and the crystal order parameter field are carefully modeled. Simulations are performed on UO2. The result shows that for small voids (with an area ≤ πμm2), the well-known characteristics of void migration, in consistence with the analytical model, can be recovered. The migration is manifested by a constant velocity and a minor change of the void shape. In contrast, for large voids (with an area of ˜10 μm2) initially in circular shapes, significant deformation of the void from a circular to cashew-like shape is observed. After long-time migration, the deformed void would split into smaller voids. The size-dependent behavior of void migration is due to the combined effect of the interfacial energy (which tends to keep the void in circular shape) and the surface diffusion flow (which tends to deform the void due to the nonuniform diffusion along the surface). Moreover, the initial shape of the void modifies the migration velocity and the time point when splitting occurs (for large voids) at the beginning of migration due to the shape relaxation of the void. However, it has a minor effect on the long-time migration. Our work reveals novel void migration behaviors in conditions where the surface-diffusion mechanism is dominant over the vapor transport mechanism; meanwhile, the size of the void lies at a mediate size range.

Effect of filler content on mechanical and dynamic mechanical properties of particulate biphasic calcium phosphate--polylactide composites.

PubMed

Bleach, N C; Nazhat, S N; Tanner, K E; Kellomäki, M; Törmälä, P

2002-04-01

A bioabsorbable self-reinforced polylactide/biphasic calcium phosphate (BCP) composite is being developed for fracture fixation plates. One manufacturing route is to produce preimpregnated sheets by pulling polylactide (PLA) fibres through a suspension of BCP filler in a PLA solution and compression moulding the prepreg to the desired shape. To aid understanding of the process, interactions between the matrix and filler were investigated. Composite films containing 0-0.25 volume fraction filler, produced by solvent casting, were analysed using SEM, tensile testing and dynamic mechanical analysis (DMA). Homogeneous films could be made, although some particle agglomeration was seen at higher filler volume fractions. As the filler content increased, the failure strain decreased due to a reduction in the amount of ductile polymer present and the ultimate tensile strength (UTS) decreased because of agglomeration and void formation at higher filler content. The matrix glass transition temperature increased due to polymer chain adsorption and immobilization onto the BCP particles. Complex damping mechanisms, such as particle-particle agglomeration, may exist at the higher BCP volume fractions.

Free volume of mixed cation borosilicate glass sealants elucidated by positron annihilation lifetime spectroscopy and its correlation with glass properties

NASA Astrophysics Data System (ADS)

Ojha, Prasanta K.; Rath, Sangram K.; Sharma, Sandeep K.; Sudarshan, Kathi; Pujari, Pradeep K.; Chongdar, Tapas K.; Gokhale, Nitin M.

2015-01-01

The role of La+3/Sr+2 ratios, which is varied from 0.08 to 5.09, on density, molar volume, packing fraction, free volume, thermal and electrical properties in strontium lanthanum aluminoborosilicate based glass sealants intended for solid oxide fuel cell (SOFC) applications is evaluated. The studies reveal expansion of the glass network evident from increasing molar volume and decreasing packing fraction of glasses with progressive La+3 substitutions. The molecular origin of these macroscopic structural features can be accounted for by the free volume parameters measured from positron annihilation lifetime spectroscopy (PALS). The La+3 induced expanded glass networks show increased number of subnanoscopic voids with larger sizes, as revealed from the ortho-positronium (o-Ps) lifetime and its intensity. A remarkably direct correspondence between the molar volume and fractional free volume trend is established with progressive La2O3 substitution in the glasses. The effect of these structural changes on the glass transition temperature, softening temperature, coefficient of thermal expansion, thermal stability as well as electrical conductivity has been studied.

Anomalous cosmic ray interaction events for investigations in the SSC and Space Station era - 'Long lived she-devil phenomena'

NASA Technical Reports Server (NTRS)

Takahashi, Y.

1985-01-01

Observational data on anomalous cosmic-ray interaction events are compiled, classified, and briefly characterized. The events are divided into three groups: those confirmed by later observation or experiment, those shown to be the result of observational or analytical error, and those still unexplained. Among the phenomena in the latter group are magnetic-monopole candidates, fractionally charged particles, massive stable particles, anomalons, proton-decay and neutron-oscillation candidates, muon bundles, narrow showers, anomalous photons, fanlike phenomena, quark-gluon-plasma candidates, and anomalous long-range delta rays.

Redshift-space distortions around voids

NASA Astrophysics Data System (ADS)

Cai, Yan-Chuan; Taylor, Andy; Peacock, John A.; Padilla, Nelson

2016-11-01

We have derived estimators for the linear growth rate of density fluctuations using the cross-correlation function (CCF) of voids and haloes in redshift space. In linear theory, this CCF contains only monopole and quadrupole terms. At scales greater than the void radius, linear theory is a good match to voids traced out by haloes; small-scale random velocities are unimportant at these radii, only tending to cause small and often negligible elongation of the CCF near its origin. By extracting the monopole and quadrupole from the CCF, we measure the linear growth rate without prior knowledge of the void profile or velocity dispersion. We recover the linear growth parameter β to 9 per cent precision from an effective volume of 3( h-1Gpc)3 using voids with radius >25 h-1Mpc. Smaller voids are predominantly sub-voids, which may be more sensitive to the random velocity dispersion; they introduce noise and do not help to improve measurements. Adding velocity dispersion as a free parameter allows us to use information at radii as small as half of the void radius. The precision on β is reduced to 5 per cent. Voids show diverse shapes in redshift space, and can appear either elongated or flattened along the line of sight. This can be explained by the competing amplitudes of the local density contrast, plus the radial velocity profile and its gradient. The distortion pattern is therefore determined solely by the void profile and is different for void-in-cloud and void-in-void. This diversity of redshift-space void morphology complicates measurements of the Alcock-Paczynski effect using voids.

Lightweight Concrete Produced Using a Two-Stage Casting Process

PubMed Central

Yoon, Jin Young; Kim, Jae Hong; Hwang, Yoon Yi; Shin, Dong Kyu

2015-01-01

The type of lightweight aggregate and its volume fraction in a mix determine the density of lightweight concrete. Minimizing the density obviously requires a higher volume fraction, but this usually causes aggregates segregation in a conventional mixing process. This paper proposes a two-stage casting process to produce a lightweight concrete. This process involves placing lightweight aggregates in a frame and then filling in the remaining interstitial voids with cementitious grout. The casting process results in the lowest density of lightweight concrete, which consequently has low compressive strength. The irregularly shaped aggregates compensate for the weak point in terms of strength while the round-shape aggregates provide a strength of 20 MPa. Therefore, the proposed casting process can be applied for manufacturing non-structural elements and structural composites requiring a very low density and a strength of at most 20 MPa. PMID:28788007

Electromigration induced high fraction of compound formation in SnAgCu flip chip solder joints with copper column

NASA Astrophysics Data System (ADS)

Xu, Luhua; Han, Jung-Kyu; Liang, Jarrett Jun; Tu, K. N.; Lai, Yi-Shao

2008-06-01

To overcome the effect of current crowding on electromigration-induced pancake-type void formation in flip chip solder joints, two types of Cu column in 90μm flip chip SnAgCu solder joints have been studied. They were (1) the solder contacts the Cu column at bottom and side walls and (2) the solder wets only the bottom surface of the copper column. With a current density of 1.6×104A/cm2 at 135°C, no failure was detected after 1290h. However, the resistance increased by about 10% due to the formation of a large fraction of intermetallic compounds. We found that electromigration has accelerated the consumption rate of copper column and converted almost the entire solder joint into intermetallic compound. Mechanically, drop impact test indicates a brittle fracture failure in the intermetallic. The electromigration critical product for the intermetallic is discussed.

The co-evolution of microstructure features in self-ion irradiated HT9 at very high damage levels

NASA Astrophysics Data System (ADS)

Getto, Elizabeth Margaret

The objective of this study was to understand the co-evolution of microstructure features in self-ion irradiated HT9 at very high damage levels. HT9 (heat 84425) was pre-implanted with 10 atom parts per million helium and then irradiated with 5 MeV Fe++ in the temperature range of 440-480°C to 188 dpa. A damage dependence study from 75 to 650 dpa was performed at the peak swelling temperature of 460°C. The swelling, dislocation and precipitate evolution was determined using Analytic Electron Microscopes in both Conventional Transmission electron microscopy (CTEM) and Scanning Transmission Electron Microscopy (STEM) modes. Void swelling reached a nominally linear rate of 0.03%/dpa from 188 to 650 dpa at 460°C. G phase precipitates were observed by 75 dpa and grew linearly up to 650 dpa. M 2X was observed by 250 dpa and peaked in volume fraction at 450 dpa. Dislocation loop evolution was observed up to 650 dpa including a step change in diameter between 375 and 450 dpa; which correlated with nucleation and growth of M2X. The experimental results were interpreted using a rate theory model, the Radiation Induced Microstructure Evolution (RIME), in the damage range from 188 to 650 dpa. A simple system of voids and dislocations was modeled in which the dislocations measured from experiment were used as input, or the dislocations were allowed to evolve dynamically, resulting in swelling that was overestimated by 63% relative to that observed experimentally. G phase had limited effect on the void or dislocation behavior. The behavior of M2X within the microstructure was characterized as a direct effect as a coherent sink, and as an indirect effect in consuming carbon from the matrix, which had the largest impact on both void and dislocation behavior. A slowly monotonically increasing swelling rate was observed both experimentally and computationally, with swelling rates of ˜0.025%/dpa and ˜0.036%/dpa before and after 450 dpa. The agreement in void behavior between experiment and model when all effects (loops, network, G phase, M2X formation and growth, and removal of carbon) are accounted for demonstrates the importance of characterizing the evolution of the full microstructure over a large dpa range.

Focal ratio degradation in lightly fused hexabundles

NASA Astrophysics Data System (ADS)

Bryant, J. J.; Bland-Hawthorn, J.; Fogarty, L. M. R.; Lawrence, J. S.; Croom, S. M.

2014-02-01

We are now moving into an era where multi-object wide-field surveys, which traditionally use single fibres to observe many targets simultaneously, can exploit compact integral field units (IFUs) in place of single fibres. Current multi-object integral field instruments such as Sydney-AAO Multi-object Integral field spectrograph have driven the development of new imaging fibre bundles (hexabundles) for multi-object spectrographs. We have characterized the performance of hexabundles with different cladding thicknesses and compared them to that of the same type of bare fibre, across the range of fill fractions and input f-ratios likely in an IFU instrument. Hexabundles with 7-cores and 61-cores were tested for focal ratio degradation (FRD), throughput and cross-talk when fed with inputs from F/3.4 to >F/8. The five 7-core bundles have cladding thickness ranging from 1 to 8 μm, and the 61-core bundles have 5 μm cladding. As expected, the FRD improves as the input focal ratio decreases. We find that the FRD and throughput of the cores in the hexabundles match the performance of single fibres of the same material at low input f-ratios. The performance results presented can be used to set a limit on the f-ratio of a system based on the maximum loss allowable for a planned instrument. Our results confirm that hexabundles are a successful alternative for fibre imaging devices for multi-object spectroscopy on wide-field telescopes and have prompted further development of hexabundle designs with hexagonal packing and square cores.

Atypical Frontal-Striatal-Thalamic Circuit White Matter Development in Pediatric Obsessive Compulsive Disorder

PubMed Central

Fitzgerald, Kate D.; Liu, Yanni; Reamer, Elyse N.; Taylor, Stephan F.; Welsh, Robert C.

2015-01-01

Objective Atypical development of frontal-striatal-thalamic circuitry (FSTC) has been hypothesized to underlie the early course of obsessive-compulsive disorder (OCD); however, the development of FSTC white matter tracts remains to be studied in young patients. Method To address this gap, we scanned 36 patients with pediatric OCD compared to 27 healthy controls, aged 8 to 19 years, with diffusion tensor imaging (DTI) to measure fractional anisotropy (FA), an index of white matter coherence. Tract-based spatial statistics (TBSS) were used to test differential effects of age on FA, across the whole brain, in those with OCD compared to healthy youth, followed by analyses in a priori regions of interest (anterior corpus callosum, anterior cingulum bundle and anterior limb of the internal capsule [ALIC]) to further characterize developmental differences between groups. Results Patients with OCD showed more pronounced age-related increases in FA than controls in regions of interest, as well as several other white matter tracts. In patients, greater FA in anterior cingulum bundle correlated with more severe symptoms after controlling for age. Conclusions Our findings support theories of atypical FSTC maturation in pediatric OCD by providing the first evidence for altered trajectories of white matter development in anterior corpus callosum, anterior cingulum bundle, and ALIC in young patients. Steeper age-related increases of FA in these and other select white matter tracts in OCD, compared to healthy controls, may derive from an early delay in white matter development and/or prolonged white matter growth, but confirmation of these possibilities awaits longitudinal work. PMID:25440312

Joint Multi-Fiber NODDI Parameter Estimation and Tractography Using the Unscented Information Filter

PubMed Central

Reddy, Chinthala P.; Rathi, Yogesh

2016-01-01

Tracing white matter fiber bundles is an integral part of analyzing brain connectivity. An accurate estimate of the underlying tissue parameters is also paramount in several neuroscience applications. In this work, we propose to use a joint fiber model estimation and tractography algorithm that uses the NODDI (neurite orientation dispersion diffusion imaging) model to estimate fiber orientation dispersion consistently and smoothly along the fiber tracts along with estimating the intracellular and extracellular volume fractions from the diffusion signal. While the NODDI model has been used in earlier works to estimate the microstructural parameters at each voxel independently, for the first time, we propose to integrate it into a tractography framework. We extend this framework to estimate the NODDI parameters for two crossing fibers, which is imperative to trace fiber bundles through crossings as well as to estimate the microstructural parameters for each fiber bundle separately. We propose to use the unscented information filter (UIF) to accurately estimate the model parameters and perform tractography. The proposed approach has significant computational performance improvements as well as numerical robustness over the unscented Kalman filter (UKF). Our method not only estimates the confidence in the estimated parameters via the covariance matrix, but also provides the Fisher-information matrix of the state variables (model parameters), which can be quite useful to measure model complexity. Results from in-vivo human brain data sets demonstrate the ability of our algorithm to trace through crossing fiber regions, while estimating orientation dispersion and other biophysical model parameters in a consistent manner along the tracts. PMID:27147956

Joint Multi-Fiber NODDI Parameter Estimation and Tractography Using the Unscented Information Filter.

PubMed

Reddy, Chinthala P; Rathi, Yogesh

2016-01-01

Tracing white matter fiber bundles is an integral part of analyzing brain connectivity. An accurate estimate of the underlying tissue parameters is also paramount in several neuroscience applications. In this work, we propose to use a joint fiber model estimation and tractography algorithm that uses the NODDI (neurite orientation dispersion diffusion imaging) model to estimate fiber orientation dispersion consistently and smoothly along the fiber tracts along with estimating the intracellular and extracellular volume fractions from the diffusion signal. While the NODDI model has been used in earlier works to estimate the microstructural parameters at each voxel independently, for the first time, we propose to integrate it into a tractography framework. We extend this framework to estimate the NODDI parameters for two crossing fibers, which is imperative to trace fiber bundles through crossings as well as to estimate the microstructural parameters for each fiber bundle separately. We propose to use the unscented information filter (UIF) to accurately estimate the model parameters and perform tractography. The proposed approach has significant computational performance improvements as well as numerical robustness over the unscented Kalman filter (UKF). Our method not only estimates the confidence in the estimated parameters via the covariance matrix, but also provides the Fisher-information matrix of the state variables (model parameters), which can be quite useful to measure model complexity. Results from in-vivo human brain data sets demonstrate the ability of our algorithm to trace through crossing fiber regions, while estimating orientation dispersion and other biophysical model parameters in a consistent manner along the tracts.

CFD modeling of turbulent mixing through vertical pressure tube type boiling water reactor fuel rod bundles with spacer-grids

NASA Astrophysics Data System (ADS)

Verma, Shashi Kant; Sinha, S. L.; Chandraker, D. K.

2018-05-01

Numerical simulation has been carried out for the study of natural mixing of a Tracer (Passive scalar) to describe the development of turbulent diffusion in an injected sub-channel and, afterwards on, cross-mixing between adjacent sub-channels. In this investigation, post benchmark evaluation of the inter-subchannel mixing was initiated to test the ability of state-of-the-art Computational Fluid Dynamics (CFD) codes to numerically predict the important turbulence parameters downstream of a ring type spacer grid in a rod-bundle. A three-dimensional Computational Fluid Dynamics (CFD) tool (STAR-CCM+) was used to model the single phase flow through a 30° segment or 1/12th of the cross segment of a 54-rod bundle with a ring shaped spacer grid. Polyhedrons were used to discretize the computational domain, along with prismatic cells near the walls, with an overall mesh count of 5.2 M cell volumes. The Reynolds Stress Models (RSM) was tested because of RSM accounts for the turbulence anisotropy, to assess their capability in predicting the velocities as well as mass fraction of potassium nitrate measured in the experiment. In this way, the line probes are located in the different position of subchannels which could be used to characterize the progress of the mixing along the flow direction, and the degree of cross-mixing assessed using the quantity of tracer arriving in the neighbouring sub-channels. The predicted dimensionless mixing scalar along the length, however, was in good agreement with the measurements downstream of spacers.

Gas phase synthesis of non-bundled, small diameter single-walled carbon nanotubes with near-armchair chiralities

NASA Astrophysics Data System (ADS)

Mustonen, K.; Laiho, P.; Kaskela, A.; Zhu, Z.; Reynaud, O.; Houbenov, N.; Tian, Y.; Susi, T.; Jiang, H.; Nasibulin, A. G.; Kauppinen, E. I.

2015-07-01

We present a floating catalyst synthesis route for individual, i.e., non-bundled, small diameter single-walled carbon nanotubes (SWCNTs) with a narrow chiral angle distribution peaking at high chiralities near the armchair species. An ex situ spark discharge generator was used to form iron particles with geometric number mean diameters of 3-4 nm and fed into a laminar flow chemical vapour deposition reactor for the continuous synthesis of long and high-quality SWCNTs from ambient pressure carbon monoxide. The intensity ratio of G/D peaks in Raman spectra up to 48 and mean tube lengths up to 4 μm were observed. The chiral distributions, as directly determined by electron diffraction in the transmission electron microscope, clustered around the (n,m) indices (7,6), (8,6), (8,7), and (9,6), with up to 70% of tubes having chiral angles over 20°. The mean diameter of SWCNTs was reduced from 1.10 to 1.04 nm by decreasing the growth temperature from 880 to 750 °C, which simultaneously increased the fraction of semiconducting tubes from 67% to 80%. Limiting the nanotube gas phase number concentration to ˜105 cm-3 prevented nanotube bundle formation that is due to collisions induced by Brownian diffusion. Up to 80% of 500 as-deposited tubes observed by atomic force and transmission electron microscopy were individual. Transparent conducting films deposited from these SWCNTs exhibited record low sheet resistances of 63 Ω/□ at 90% transparency for 550 nm light.

Signal detection by active, noisy hair bundles

NASA Astrophysics Data System (ADS)

O'Maoiléidigh, Dáibhid; Salvi, Joshua D.; Hudspeth, A. J.

2018-05-01

Vertebrate ears employ hair bundles to transduce mechanical movements into electrical signals, but their performance is limited by noise. Hair bundles are substantially more sensitive to periodic stimulation when they are mechanically active, however, than when they are passive. We developed a model of active hair-bundle mechanics that predicts the conditions under which a bundle is most sensitive to periodic stimulation. The model relies only on the existence of mechanotransduction channels and an active adaptation mechanism that recloses the channels. For a frequency-detuned stimulus, a noisy hair bundle's phase-locked response and degree of entrainment as well as its detection bandwidth are maximized when the bundle exhibits low-amplitude spontaneous oscillations. The phase-locked response and entrainment of a bundle are predicted to peak as functions of the noise level. We confirmed several of these predictions experimentally by periodically forcing hair bundles held near the onset of self-oscillation. A hair bundle's active process amplifies the stimulus preferentially over the noise, allowing the bundle to detect periodic forces less than 1 pN in amplitude. Moreover, the addition of noise can improve a bundle's ability to detect the stimulus. Although, mechanical activity has not yet been observed in mammalian hair bundles, a related model predicts that active but quiescent bundles can oscillate spontaneously when they are loaded by a sufficiently massive object such as the tectorial membrane. Overall, this work indicates that auditory systems rely on active elements, composed of hair cells and their mechanical environment, that operate on the brink of self-oscillation.

Cause Analysis on the Void under Slabs of Cement Concrete Pavement

NASA Astrophysics Data System (ADS)

Wen, Li; Zhu, Guo Xin; Baozhu

2017-06-01

This paper made a systematic analysis on the influence of the construction, environment, water and loads on the void beneath road slabs, and also introduced the formation process of structural void and pumping void, and summarizes the deep reasons for the bottom of the cement concrete pavement. Based on the analysis above, this paper has found out the evolution law of the void under slabs which claimed that the void usually appeared in the slab corners and then the cross joint, resulting void in the four sides with the void area under the front slab larger than the rear one.

Crossed Module Bundle Gerbes; Classification, String Group and Differential Geometry

NASA Astrophysics Data System (ADS)

Jurčo, Branislav

We discuss nonabelian bundle gerbes and their differential geometry using simplicial methods. Associated to any crossed module there is a simplicial group NC, the nerve of the 1-category defined by the crossed module and its geometric realization |NC|. Equivalence classes of principal bundles with structure group |NC| are shown to be one-to-one with stable equivalence classes of what we call crossed module gerbes bundle gerbes. We can also associate to a crossed module a 2-category C'. Then there are two equivalent ways how to view classifying spaces of NC-bundles and hence of |NC|-bundles and crossed module bundle gerbes. We can either apply the W-construction to NC or take the nerve of the 2-category C'. We discuss the string group and string structures from this point of view. Also a simplicial principal bundle can be equipped with a simplicial connection and a B-field. It is shown how in the case of a simplicial principal NC-bundle these simplicial objects give the bundle gerbe connection and the bundle gerbe B-field.

An Experimental Study of Plunging Liquid Jet Induced Air Carryunder and Dispersion

DTIC Science & Technology

1991-12-24

the ’ greenhouse ’ effect (ie, the absorption of CO2 by the oceans), and a number of other important maritime-related applications. In particular, the air entrainment process due to the breaking bow waves of surface ships may cause long (ie, up to 5 km in length) wakes. Naturally easily detectable wakes are undesirable for naval warships. In the present study plunging liquid jet experiments were performed and detailed Laser Doppler Anemometer (LDA) data were taken of the phasic velocity field and the void fraction distribution in the induced two-phase

Liquid level, void fraction, and superheated steam sensor for nuclear reactor cores

DOEpatents

Tokarz, Richard D.

1983-01-01

An apparatus for detecting nominal phase conditions of coolant in a reactor vessel comprising one or more lengths of tubing each leading from a location being monitored to a closed outer end exterior of the vessel. Temperature is sensed at the open end of each length of tubing. Pressure within the tubing is also sensed. Both measurements are directed to an analyzer which compares the measured temperature to the known saturated temperature of the coolant at the measured pressure. In this manner, the nominal phase conditions of the coolant are constantly monitored.

Development of a passive phase separator for space and earth applications

PubMed Central

Wu, Xiongjun; Loraine, Greg; Hsiao, Chao-Tsung; Chahine, Georges L.

2018-01-01

The limited amount of liquids and gases that can be carried to space makes it imperative to recycle and reuse these fluids for extended human operations. During recycling processes gas and liquid phases are often intermixed. In the absence of gravity, separating gases from liquids is challenging due to the absence of buoyancy. This paper describes development of a passive phase separator that is capable of efficiently and reliably separating gas–liquid mixtures of both high and low void fractions in a wide range of flow rates that is applicable to for both space and earth applications. PMID:29628785

Microbubble cloud characterization by nonlinear frequency mixing.

PubMed

Cavaro, M; Payan, C; Moysan, J; Baqué, F

2011-05-01

In the frame of the fourth generation forum, France decided to develop sodium fast nuclear reactors. French Safety Authority requests the associated monitoring of argon gas into sodium. This implies to estimate the void fraction, and a histogram indicating the bubble population. In this context, the present letter studies the possibility of achieving an accurate determination of the histogram with acoustic methods. A nonlinear, two-frequency mixing technique has been implemented, and a specific optical device has been developed in order to validate the experimental results. The acoustically reconstructed histograms are in excellent agreement with those obtained using optical methods.

The formation of giant low surface brightness galaxies

NASA Technical Reports Server (NTRS)

Hoffman, Yehuda; Silk, Joseph; Wyse, Rosemary F. G.

1992-01-01

It is demonstrated that the initial structure of galaxies can be strongly affected by their large-scale environments. In particular, rare (about 3 sigma) massive galaxies in voids will have normal bulges, but unevolved, extended disks; it is proposed that the low surface brightness objects Malin I and Malin II are prototypes of this class of object. The model predicts that searches for more examples of 'crouching giants' should be fruitful, but that such galaxies do not provide a substantial fraction of mass in the universe. The identification of dwarf galaxies is relatively unaffected by their environment.

Modeling of Inverted Annular Film Boiling using an integral method

NASA Astrophysics Data System (ADS)

Sridharan, Arunkumar

In modeling Inverted Annular Film Boiling (IAFB), several important phenomena such as interaction between the liquid and the vapor phases and irregular nature of the interface, which greatly influence the momentum and heat transfer at the interface, need to be accounted for. However, due to the complexity of these phenomena, they were not modeled in previous studies. Since two-phase heat transfer equations and relationships rely heavily on experimental data, many closure relationships that were used in previous studies to solve the problem are empirical in nature. Also, in deriving the relationships, the experimental data were often extrapolated beyond the intended range of conditions, causing errors in predictions. In some cases, empirical correlations that were derived from situations other than IAFB, and whose applicability to IAFB was questionable, were used. Moreover, arbitrary constants were introduced in the model developed in previous studies to provide good fit to the experimental data. These constants have no physical basis, thereby leading to questionable accuracy in the model predictions. In the present work, modeling of Inverted Annular Film Boiling (IAFB) is done using Integral Method. Two-dimensional formulation of IAFB is presented. Separate equations for the conservation of mass, momentum and energy are derived from first principles, for the vapor film and the liquid core. Turbulence is incorporated in the formulation. The system of second-order partial differential equations is integrated over the radial direction to obtain a system of integral differential equations. In order to solve the system of equations, second order polynomial profiles are used to describe the nondimensional velocity and temperatures. The unknown coefficients in the profiles are functions of the axial direction alone. Using the boundary conditions that govern the physical problem, equations for the unknown coefficients are derived in terms of the primary dependent variables: wall shear stress, interfacial shear stress, film thickness, pressure, wall temperature and the mass transfer rate due to evaporation. A system of non-linear first order coupled ordinary differential equations is obtained. Due to the inherent mathematical complexity of the system of equations, simplifying assumptions are made to obtain a numerical solution. The system of equations is solved numerically to obtain values of the unknown quantities at each subsequent axial location. Derived quantities like void fraction and heat transfer coefficient are calculated at each axial location. The calculation is terminated when the void fraction reaches a value of 0.6, the upper limit of IAFB. The results obtained agree with the experimental trends observed. Void fraction increases along the heated length, while the heat transfer coefficient drops due to the increased resistance of the vapor film as expected.

Anatomical approach to permanent His bundle pacing: Optimizing His bundle capture.

PubMed

Vijayaraman, Pugazhendhi; Dandamudi, Gopi

2016-01-01

Permanent His bundle pacing is a physiological alternative to right ventricular pacing. In this article we describe our approach to His bundle pacing in patients with AV nodal and intra-Hisian conduction disease. It is essential for the implanters to understand the anatomic variations of the His bundle course and its effect on the type of His bundle pacing achieved. We describe several case examples to illustrate our anatomical approach to permanent His bundle pacing in this article. Copyright © 2016 Elsevier Inc. All rights reserved.

Experimental and theoretical study of horizontal tube bundle for passive condensation heat transfer

NASA Astrophysics Data System (ADS)

Song, Yong Jae

The research in this thesis supports the design of a horizontal tube bundle condenser for passive heat removal system in nuclear reactors. From nuclear power plant containment, condensation of steam from a steam/noncondensable gas occurs on the primary side and boiling occurs on the secondary side; thus, heat exchanger modeling is a challenge. For the purpose of this experimental study, a six-tube bundle is used, where the outer diameter, inner diameter, and length of each stainless steel tube measures 38.10mm (1.5 inches), 31.75mm (1.25 inches) and 3.96m (156 inches), respectively. The pitch to diameter ratio was determined based on information gathered from literature surveys, and the dimensions were determined from calculations and experimental data. The objective of the calculations, correlations, and experimental data was to obtain complete condensation within the tube bundle. Experimental conditions for the tests in this thesis work were determined from Design Basis Accident (DBA). The applications are for an actual Passive Containment Cooling Systems (PCCS) condenser under postulated accident conditions in future light water reactors. In this research, steady state and transient experiments were performed to investigate the effect of noncondensable gas on steam condensation inside and boiling outside a tube bundle heat exchanger. The condenser tube inlet steam mass flow rate varied from 18.0 to 48.0 g/s, the inlet pressure varied from 100 kPa to 400 kPa, and the inlet noncondensable gas mass fraction varied from 1% to 10%. The effect of the noncondensable gas was examined by comparing the tube centerline temperatures for various inlet and system conditions. As a result, it was determined that the noncondensable gas accumulated near the condensate film causing a decrease of mass and energy transfer. In addition, the effect of the inlet steam flow rate gas was investigated by comparing the tube centerline temperatures, the conclusion being that, as the inlet steam mass flow rate increased, the length required for complete condensation also increased. Comparison of tube centerline temperature profiles was also used to examine the effect of inlet pressure on the heat transfer performance. From this assessment, it was determined that as the inlet pressure increased, the length required for complete condensation decreased. The investigation of tube bundle effects was conducted by comparing the condensate flow rates. The experimental results showed that the upper tubes in the bundle had better heat transfer performance than the lower tubes. In regard to modeling of the heat exchanger in this study, for the primary side, an empirical correlation was developed herein to provide Nusselt numbers for condensation heat transfer in horizontal tubes with noncondensable gases. Nusselt numbers were correlated as: Nu = 106.31·Re m0.147·W a-0.843. The empirical model for condensation heat transfer coefficients and the secondary-side model were integrated within a Matlab program to provide an analysis tool for horizontal tube bundle condenser heat exchangers. Also on the secondary side, two phase heat transfer coefficients were modeled considering both convective boiling and nucleate boiling as: hTP = 10.03·exp(-2.28·alpha)· hCV + 0.076·exp[3.73x10-6·(Re f-1.6x105)]·hNB.

Warps, grids and curvature in triple vector bundles

NASA Astrophysics Data System (ADS)

Flari, Magdalini K.; Mackenzie, Kirill

2018-06-01

A triple vector bundle is a cube of vector bundle structures which commute in the (strict) categorical sense. A grid in a triple vector bundle is a collection of sections of each bundle structure with certain linearity properties. A grid provides two routes around each face of the triple vector bundle, and six routes from the base manifold to the total manifold; the warps measure the lack of commutativity of these routes. In this paper we first prove that the sum of the warps in a triple vector bundle is zero. The proof we give is intrinsic and, we believe, clearer than the proof using decompositions given earlier by one of us. We apply this result to the triple tangent bundle T^3M of a manifold and deduce (as earlier) the Jacobi identity. We further apply the result to the triple vector bundle T^2A for a vector bundle A using a connection in A to define a grid in T^2A . In this case the curvature emerges from the warp theorem.

Accuracy of the Generalized Self-Consistent Method in Modelling the Elastic Behaviour of Periodic Composites

NASA Technical Reports Server (NTRS)

Walker, Kevin P.; Freed, Alan D.; Jordan, Eric H.

1993-01-01

Local stress and strain fields in the unit cell of an infinite, two-dimensional, periodic fibrous lattice have been determined by an integral equation approach. The effect of the fibres is assimilated to an infinite two-dimensional array of fictitious body forces in the matrix constituent phase of the unit cell. By subtracting a volume averaged strain polarization term from the integral equation we effectively embed a finite number of unit cells in a homogenized medium in which the overall stress and strain correspond to the volume averaged stress and strain of the constrained unit cell. This paper demonstrates that the zeroth term in the governing integral equation expansion, which embeds one unit cell in the homogenized medium, corresponds to the generalized self-consistent approximation. By comparing the zeroth term approximation with higher order approximations to the integral equation summation, both the accuracy of the generalized self-consistent composite model and the rate of convergence of the integral summation can be assessed. Two example composites are studied. For a tungsten/copper elastic fibrous composite the generalized self-consistent model is shown to provide accurate, effective, elastic moduli and local field representations. The local elastic transverse stress field within the representative volume element of the generalized self-consistent method is shown to be in error by much larger amounts for a composite with periodically distributed voids, but homogenization leads to a cancelling of errors, and the effective transverse Young's modulus of the voided composite is shown to be in error by only 23% at a void volume fraction of 75%.

Effect of reference conditions on flow rate, modifier fraction and retention in supercritical fluid chromatography.

PubMed

De Pauw, Ruben; Shoykhet Choikhet, Konstantin; Desmet, Gert; Broeckhoven, Ken

2016-08-12

When using compressible mobile phases such as fluidic CO2, the density, the volumetric flow rates and volumetric fractions are pressure dependent. The pressure and temperature definition of these volumetric parameters (referred to as the reference conditions) may alter between systems, manufacturers and operating conditions. A supercritical fluid chromatography system was modified to operate in two modes with different definition of the eluent delivery parameters, referred to as fixed and variable mode. For the variable mode, the volumetric parameters are defined with reference to the pump operating pressure and actual pump head temperature. These conditions may vary when, e.g. changing the column length, permeability, flow rate, etc. and are thus variable reference conditions. For the fixed mode, the reference conditions were set at 150bar and 30°C, resulting in a mass flow rate and mass fraction of modifier definition which is independent of the operation conditions. For the variable mode, the mass flow rate of carbon dioxide increases with system pump operating pressure, decreasing the fraction of modifier. Comparing the void times and retention factor shows that the deviation between the two modes is almost independent of modifier percentage, but depends on the operating pressure. Recalculating the set volumetric fraction of modifier to the mass fraction results in the same retention behaviour for both modes. This shows that retention in SFC can be best modelled using the mass fraction of modifier. The fixed mode also simplifies method scaling as it only requires matching average column pressure. Copyright © 2016 Elsevier B.V. All rights reserved.

Steady-state stiffness of utricular hair cells depends on macular location and hair bundle structure.

PubMed

Spoon, Corrie; Moravec, W J; Rowe, M H; Grant, J W; Peterson, E H

2011-12-01

Spatial and temporal properties of head movement are encoded by vestibular hair cells in the inner ear. One of the most striking features of these receptors is the orderly structural variation in their mechanoreceptive hair bundles, but the functional significance of this diversity is poorly understood. We tested the hypothesis that hair bundle structure is a significant contributor to hair bundle mechanics by comparing structure and steady-state stiffness of 73 hair bundles at varying locations on the utricular macula. Our first major finding is that stiffness of utricular hair bundles varies systematically with macular locus. Stiffness values are highest in the striola, near the line of hair bundle polarity reversal, and decline exponentially toward the medial extrastriola. Striolar bundles are significantly more stiff than those in medial (median: 8.9 μN/m) and lateral (2.0 μN/m) extrastriolae. Within the striola, bundle stiffness is greatest in zone 2 (106.4 μN/m), a band of type II hair cells, and significantly less in zone 3 (30.6 μN/m), which contains the only type I hair cells in the macula. Bathing bundles in media that break interciliary links produced changes in bundle stiffness with predictable time course and magnitude, suggesting that links were intact in our standard media and contributed normally to bundle stiffness during measurements. Our second major finding is that bundle structure is a significant predictor of steady-state stiffness: the heights of kinocilia and the tallest stereocilia are the most important determinants of bundle stiffness. Our results suggest 1) a functional interpretation of bundle height variability in vertebrate vestibular organs, 2) a role for the striola in detecting onset of head movement, and 3) the hypothesis that differences in bundle stiffness contribute to diversity in afferent response dynamics.

Steady-state stiffness of utricular hair cells depends on macular location and hair bundle structure

PubMed Central

Spoon, Corrie; Moravec, W. J.; Rowe, M. H.; Grant, J. W.

2011-01-01

Spatial and temporal properties of head movement are encoded by vestibular hair cells in the inner ear. One of the most striking features of these receptors is the orderly structural variation in their mechanoreceptive hair bundles, but the functional significance of this diversity is poorly understood. We tested the hypothesis that hair bundle structure is a significant contributor to hair bundle mechanics by comparing structure and steady-state stiffness of 73 hair bundles at varying locations on the utricular macula. Our first major finding is that stiffness of utricular hair bundles varies systematically with macular locus. Stiffness values are highest in the striola, near the line of hair bundle polarity reversal, and decline exponentially toward the medial extrastriola. Striolar bundles are significantly more stiff than those in medial (median: 8.9 μN/m) and lateral (2.0 μN/m) extrastriolae. Within the striola, bundle stiffness is greatest in zone 2 (106.4 μN/m), a band of type II hair cells, and significantly less in zone 3 (30.6 μN/m), which contains the only type I hair cells in the macula. Bathing bundles in media that break interciliary links produced changes in bundle stiffness with predictable time course and magnitude, suggesting that links were intact in our standard media and contributed normally to bundle stiffness during measurements. Our second major finding is that bundle structure is a significant predictor of steady-state stiffness: the heights of kinocilia and the tallest stereocilia are the most important determinants of bundle stiffness. Our results suggest 1) a functional interpretation of bundle height variability in vertebrate vestibular organs, 2) a role for the striola in detecting onset of head movement, and 3) the hypothesis that differences in bundle stiffness contribute to diversity in afferent response dynamics. PMID:21918003

Double-bundle anterior cruciate ligament reconstruction is superior to single-bundle reconstruction in terms of revision frequency: a study of 22,460 patients from the Swedish National Knee Ligament Register.

PubMed

Svantesson, Eleonor; Sundemo, David; Hamrin Senorski, Eric; Alentorn-Geli, Eduard; Musahl, Volker; Fu, Freddie H; Desai, Neel; Stålman, Anders; Samuelsson, Kristian

2017-12-01

Studies comparing single- and double-bundle anterior cruciate ligament (ACL) reconstructions often include a combined analysis of anatomic and non-anatomic techniques. The purpose of this study was to compare the revision rates between single- and double-bundle ACL reconstructions in the Swedish National Knee Ligament Register with regard to surgical variables as determined by the anatomic ACL reconstruction scoring checklist (AARSC). Patients from the Swedish National Knee Ligament Register who underwent either single- or double-bundle ACL reconstruction with hamstring tendon autograft during the period 2007-2014 were included. The follow-up period started with primary ACL reconstruction, and the outcome measure was set as revision surgery. An online questionnaire based on the items of the AARSC was used to determine the surgical technique implemented in the single-bundle procedures. These were organized into subgroups based on surgical variables, and the revision rates were compared with the double-bundle ACL reconstruction. Hazard ratios (HR) with 95% confidence interval (CI) was calculated and adjusted for confounders by Cox regression. A total of 22,460 patients were included in the study, of which 21,846 were single-bundle and 614 were double-bundle ACL reconstruction. Double-bundle ACL reconstruction had a revision frequency of 2.0% (n = 12) and single-bundle 3.2% (n = 689). Single-bundle reconstruction had an increased risk of revision surgery compared with double-bundle [adjusted HR 1.98 (95% CI 1.12-3.51), p = 0.019]. The subgroup analysis showed a significantly increased risk of revision surgery in patients undergoing single-bundle with anatomic technique using transportal drilling [adjusted HR 2.51 (95% CI 1.39-4.54), p = 0.002] compared with double-bundle ACL reconstruction. Utilizing a more complete anatomic technique according to the AARSC lowered the hazard rate considerably when transportal drilling was performed but still resulted in significantly increased risk of revision surgery compared with double-bundle ACL reconstruction [adjusted HR 1.87 (95% CI 1.04-3.38), p = 0.037]. Double-bundle ACL reconstruction is associated with a lower risk of revision surgery than single-bundle ACL reconstruction. Single-bundle procedures performed using transportal femoral drilling technique had significantly higher risk of revision surgery compared with double-bundle. However, a reference reconstruction with transportal drilling defined as a more complete anatomic reconstruction reduces the risk of revision surgery considerably. III.

Moisture separator reheater with round tube bundle

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

Byerley, W. M.

1984-11-27

A moisture separator reheater having a central chamber with cylindrical wall protions and a generally round tube bundle, the tube bundle having arcuate plates disposed on each side of the bundle which form a wrapper on each side of the bundle and having a tongue and groove juncture between the wrapper and cylindrical wall portions to provide a seal therebetween and a track for installing and removing the tube bundle from the central chamber.

["Habitual" left branch block alternating with 2 "disguised" bracnch block].

PubMed

Lévy, S; Jullien, G; Mathieu, P; Mostefa, S; Gérard, R

1976-10-01

Two cases of alternating left bundle branch block and "masquerading block" (with left bundle branch morphology in the stnadard leads and right bundle branch block morphology in the precordial leads) were studied by serial tracings and his bundle electrocardiography. In case 1 "the masquerading" block was associated with a first degree AV block related to a prolongation of HV interval. This case is to our knowledge the first cas of alternating bundle branch block in which his bundle activity was recorded in man. In case 2, the patient had atrial fibrilation and His bundle recordings were performed while differents degrees of left bundle branch block were present: The mechanism of the alternation and the concept of "masquerading" block are discussed. It is suggested that this type of block represents a right bundle branch block associated with severe lesions of the "left system".

Characterization of active hair-bundle motility by a mechanical-load clamp

NASA Astrophysics Data System (ADS)

Salvi, Joshua D.; Maoiléidigh, Dáibhid Ó.; Fabella, Brian A.; Tobin, Mélanie; Hudspeth, A. J.

2015-12-01

Active hair-bundle motility endows hair cells with several traits that augment auditory stimuli. The activity of a hair bundle might be controlled by adjusting its mechanical properties. Indeed, the mechanical properties of bundles vary between different organisms and along the tonotopic axis of a single auditory organ. Motivated by these biological differences and a dynamical model of hair-bundle motility, we explore how adjusting the mass, drag, stiffness, and offset force applied to a bundle control its dynamics and response to external perturbations. Utilizing a mechanical-load clamp, we systematically mapped the two-dimensional state diagram of a hair bundle. The clamp system used a real-time processor to tightly control each of the virtual mechanical elements. Increasing the stiffness of a hair bundle advances its operating point from a spontaneously oscillating regime into a quiescent regime. As predicted by a dynamical model of hair-bundle mechanics, this boundary constitutes a Hopf bifurcation.

Bundled payments in orthopedic surgery.

PubMed

Bushnell, Brandon D

2015-02-01

As a result of reading this article, physicians should be able to: 1. Describe the concept of bundled payments and the potential applications of bundled payments in orthopedic surgery. 2. For specific situations, outline a clinical episode of care, determine the participants in a bundling situation, and define care protocols and pathways. 3. Recognize the importance of resource utilization management, quality outcome measurement, and combined economic-clinical value in determining the value of bundled payment arrangements. 4. Identify the implications of bundled payments for practicing orthopedists, as well as the legal issues and potential future directions of this increasingly popular alternative payment method. Bundled payments, the idea of paying a single price for a bundle of goods and services, is a financial concept familiar to most American consumers because examples appear in many industries. The idea of bundled payments has recently gained significant momentum as a financial model with the potential to decrease the significant current costs of health care. Orthopedic surgery as a field of medicine is uniquely positioned for success in an environment of bundled payments. This article reviews the history, logistics, and implications of the bundled payment model relative to orthopedic surgery. Copyright 2015, SLACK Incorporated.

Closure behavior of spherical void in slab during hot rolling process

NASA Astrophysics Data System (ADS)

Cheng, Rong; Zhang, Jiongming; Wang, Bo

2018-04-01

The mechanical properties of steels are heavily deteriorated by voids. The influence of voids on the product quality should be eliminated through rolling processes. The study on the void closure during hot rolling processes is necessary. In present work, the closure behavior of voids at the center of a slab at 800 °C during hot rolling processes has been simulated with a 3D finite element model. The shape of the void and the plastic strain distribution of the slab are obtained by this model. The void decreases along the slab thickness direction and spreads along the rolling direction but hardly changes along the strip width direction. The relationship between closure behavior of voids and the plastic strain at the center of the slab is analyzed. The effects of rolling reduction, slab thickness and roller diameter on the closure behavior of voids are discussed. The larger reduction, thinner slab and larger roller diameter all improve the closure of voids during hot rolling processes. Experimental results of the closure behavior of a void in the slab during hot rolling process mostly agree with the simulation results..

Voiding diary might serve as a useful tool to understand differences between bladder pain syndrome/interstitial cystitis and overactive bladder.

PubMed

Kim, Sung Han; Oh, Shin Ah; Oh, Seung-June

2014-02-01

To identify the voiding characteristics of bladder pain syndrome/interstitial cystitis and overactive bladder. Between September 2005 and June 2010, 3-day voiding diaries of 49 consecutive bladder pain syndrome/interstitial cystitis patients and 301 overactive bladder patients were prospectively collected at an outpatient clinic and retrospectively analyzed. The characteristics of the two groups were not significantly different. However, all voiding variables including volume and frequency were significantly different except for the total voided volume: patients with bladder pain syndrome/interstitial cystitis showed significantly higher voiding frequencies, smaller maximal and mean voided volume, and more constant and narrower ranges of voided volume compared with overactive bladder patients (P < 0.005). Furthermore, mean intervals between voiding in bladder pain syndrome/interstitial cystitis were shorter and more consistent during the day and night (P < 0.001), although mean night-time variances were greater than daytime variances. Logistic regression analysis showed that total night-time frequency, maximal night-time voided volume and mean variance of daytime voiding intervals most significantly differentiated the two groups. Some voiding characteristics of bladder pain syndrome/interstitial cystitis and overactive bladder patients differ significantly according to 3-day voiding diary records. These findings provide additional information regarding the differences between these two diseases in the outpatient clinical setting. © 2013 The Japanese Urological Association.

3D Simulations of Void collapse in Energetic Materials

NASA Astrophysics Data System (ADS)

Rai, Nirmal Kumar; Udaykumar, H. S.

2017-06-01

Voids present in the microstructure of heterogeneous energetic materials effect the sensitivity towards ignition. It is established that the morphology of voids can play a significant role in sensitivity enhancement of energetic materials. Depending on the void shape, sensitivity can be either increased or decreased under given loading conditions. In the past, effects of different void shapes i.e. triangular, ellipse, cylindrical etc. on the sensitivity of energetic materials have been analyzed. However, most of these studies are performed in 2D and are limited under the plain strain assumption. Axisymmetric studies have also been performed in the past to incorporate the 3D effects, however axisymmetric modeling is limited to only certain geometries i.e. sphere. This work analyzes the effects of various void shapes in three dimensions on the ignition behavior of HMX. Various void shapes are analyzed including spherical, prolate and oblate speheroid oriented at different orientations, etc. Three dimensional void collapse simulations are performed on a single void to quantify the effects void morphology on initiation. A Cartesian grid based Eulerian solver SCIMITAR3D is used to perform the void collapse simulations. Various aspects of void morphology i.e. size, thickness of voids, elongation, orientation etc. are considered to obtain a comprehensive analysis. Also, 2D plane strain calculations are compared with the three dimensional analysis to evaluate the salient differences between 2D and 3D modeling.

Tensile property improvement of TWIP-cored three-layer steel sheets fabricated by hot-roll-bonding with low-carbon steel or interstitial-free steel

PubMed Central

Park, Jaeyeong; Kim, Jung-Su; Kang, Minju; Sohn, Seok Su; Cho, Won Tae; Kim, Hyoung Seop; Lee, Sunghak

2017-01-01

TWIP-cored three-layer steel sheets were newly fabricated by hot rolling of TWIP steel sheet surrounded by low-carbon (LC) or interstitial-free (IF) steel sheets. TWIP/LC or TWIP/IF interfaces were well bonded without pores or voids, while a few pearlites were thinly formed along the interfaces. The strengths and elongation of the TWIP-cored sheets increased as the volume fraction of TWIP-cored region increased, and were also well matched with the ones calculated by a rule of mixtures based on volume fraction or force fraction. According to digital image correlation and electron back-scatter diffraction analyses, very high strain hardening effect in the initial deformation stage and active twin formation in the interfacial region beneficially affected the overall homogeneous deformation in the TWIP-cored sheets without any yield point phenomenon occurring in the LC sheet and serrations occurring in the TWIP sheet, respectively. These TWIP-cored sheets can cover a wide range of yield strength, tensile strength, and ductility levels, e.g., 320~498 MPa, 545~878 MPa, and 48~54%, respectively, by controlling the volume fraction of TWIP-cored region, and thus present new applications to multi-functional automotive steel sheets requiring excellent properties. PMID:28067318

Tensile property improvement of TWIP-cored three-layer steel sheets fabricated by hot-roll-bonding with low-carbon steel or interstitial-free steel

NASA Astrophysics Data System (ADS)

Park, Jaeyeong; Kim, Jung-Su; Kang, Minju; Sohn, Seok Su; Cho, Won Tae; Kim, Hyoung Seop; Lee, Sunghak

2017-01-01

TWIP-cored three-layer steel sheets were newly fabricated by hot rolling of TWIP steel sheet surrounded by low-carbon (LC) or interstitial-free (IF) steel sheets. TWIP/LC or TWIP/IF interfaces were well bonded without pores or voids, while a few pearlites were thinly formed along the interfaces. The strengths and elongation of the TWIP-cored sheets increased as the volume fraction of TWIP-cored region increased, and were also well matched with the ones calculated by a rule of mixtures based on volume fraction or force fraction. According to digital image correlation and electron back-scatter diffraction analyses, very high strain hardening effect in the initial deformation stage and active twin formation in the interfacial region beneficially affected the overall homogeneous deformation in the TWIP-cored sheets without any yield point phenomenon occurring in the LC sheet and serrations occurring in the TWIP sheet, respectively. These TWIP-cored sheets can cover a wide range of yield strength, tensile strength, and ductility levels, e.g., 320~498 MPa, 545~878 MPa, and 48~54%, respectively, by controlling the volume fraction of TWIP-cored region, and thus present new applications to multi-functional automotive steel sheets requiring excellent properties.

Tensile property improvement of TWIP-cored three-layer steel sheets fabricated by hot-roll-bonding with low-carbon steel or interstitial-free steel.

PubMed

Park, Jaeyeong; Kim, Jung-Su; Kang, Minju; Sohn, Seok Su; Cho, Won Tae; Kim, Hyoung Seop; Lee, Sunghak

2017-01-09

TWIP-cored three-layer steel sheets were newly fabricated by hot rolling of TWIP steel sheet surrounded by low-carbon (LC) or interstitial-free (IF) steel sheets. TWIP/LC or TWIP/IF interfaces were well bonded without pores or voids, while a few pearlites were thinly formed along the interfaces. The strengths and elongation of the TWIP-cored sheets increased as the volume fraction of TWIP-cored region increased, and were also well matched with the ones calculated by a rule of mixtures based on volume fraction or force fraction. According to digital image correlation and electron back-scatter diffraction analyses, very high strain hardening effect in the initial deformation stage and active twin formation in the interfacial region beneficially affected the overall homogeneous deformation in the TWIP-cored sheets without any yield point phenomenon occurring in the LC sheet and serrations occurring in the TWIP sheet, respectively. These TWIP-cored sheets can cover a wide range of yield strength, tensile strength, and ductility levels, e.g., 320~498 MPa, 545~878 MPa, and 48~54%, respectively, by controlling the volume fraction of TWIP-cored region, and thus present new applications to multi-functional automotive steel sheets requiring excellent properties.

Impregnation quality of shredded semipreg after compression moulding

NASA Astrophysics Data System (ADS)

Vincent, G.; Balakrishnan, V.; de Bruijn, T. A.; Wijskamp, S.; Abdul Rasheed, M. I.

2017-10-01

Manufacturing of thermoplastic composites (TPC) inherently generates scrap, mainly in the form of offcuts or rejected parts. The growth of TPC over recent decades has now reached a point where developing specific recycling solutions for TPC waste has become crucial. While looking at the various steps during which scrap is produced, the nesting of semipreg or prepreg appears to be critical. This work aims to develop a route for recycling semipreg offcuts, comprising shredding and compression moulding. This article focuses on an experimental study of the compression moulding step of carbon fibres reinforced PPS (C/PPS) to investigate the uniformity and impregnation quality of plates. These plates were realised in a picture frame while varying both the fibre volume content between 30% and 50% and the processing parameters. Visual inspection and cross-sectional microscopy were performed to assess the quality of each plate. As a first step, the influence of the type of added matrix (film, powder, pellets) and the type of pre-impregnation (film, powder) was studied. Stacking of polymer powder with shredded powder-coated semipreg gave the best impregnation quality. It was also shown that longer dwell time at melt leads to better consolidation quality. However, the difficulty in obtaining good impregnation comes from the disentangled shredded material, which is composed of three forms: semipreg flakes, dry bundles and pieces of matrix. When dry bundles reach the mould surfaces during the filling of the mould or when they are packed together, the consolidation cycle hardly impregnates them and they remain dry afterwards. Furthermore, large local variations of fibre fraction were noticed, resulting from a random mould filling. Therefore, the recycling solution for shredded semipreg is feasible when the fibre fraction is reduced but improvements on the part variability still have to be made.

Corrosion and hydrogen pick-up behaviors of cladding and structural components in BWR high burnup 9x9 lead use assemblies

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

Miyashita, Toshiyasu; Nakae, Nobuo; Ogata, Keizo

The high burnup BWR 9x9 lead use fuel assemblies, which have been designed for maximum assembly burnup of 55 GWd/t in Japan, have been examined after irradiations to confirm the reliability of the current safety evaluation methodology, and to accumulate data to judge the adequacy to apply it to the future higher burnup fuel. After 3 and 5 cycle irradiations, post irradiation examinations were performed for both 9x9 Type-A and Type-B fuel assemblies. Both Type LUAs utilize Zry-2 claddings, while there are deviation in the contents of impurity and alloying elements between Type-A and Type-B, especially in Fe and Simore » concentration. Measured oxide thicknesses of fuel rods showed no significant difference between after 3 and 5 cycle irradiation except for some rods at corner position in Type B LUA. The axial profile of hydrogen concentration and oxide thickness for the corner rods in Type B LUA after 5 cycle irradiation had peaks at the second lowest span from the bottom. The maximum oxide thickness is about 50 {mu}m on the surface facing the bundle outside at the second lowest span and dense hydrides layer (Hydride rim) is observed in peripheral region of cladding showing unexpected high hydrogen concentration. The results of calculated thermal-hydraulic conditions show that the thermal neutron flux at the corner position was higher than the other position. On the other hand, the void fraction and the mass flux were relatively lower at the corner position. The oxide thickness on spacer band and spacer cell of Zry-2 increases from 3 to 5 cycle irradiations. Spacer band of Zry-4 showed significantly thick oxide after 5 cycle irradiations but Hydrogen concentration was relatively small in contrast its obviously thick oxide in comparison with Zry-2 spacer bands. The large increase in hydrogen concentration was measured in Zry-2 spacers after 5 cycle irradiations and the evaluated hydrogen pick-up rate also increased remarkably. (authors)« less

Collapse of elongated voids in porous energetic materials: Effects of void orientation and aspect ratio on initiation

NASA Astrophysics Data System (ADS)

Rai, Nirmal Kumar; Schmidt, Martin J.; Udaykumar, H. S.

2017-04-01

The sensitivity of porous energetic materials depends on mesostructural heterogeneities such as voids, defects, cracks, and grain boundaries. The mesostructure of pressed explosives contains voids of arbitrary shapes including elongated voids of various orientations and aspect ratios. Mesoscale simulations to date have analyzed the effect of void morphology on the sensitivity of energetic materials for idealized shapes such as cylindrical, conical, and elliptical. This work analyzes the sensitivity behavior of elongated voids in an HMX matrix subject to shock loading. Simulations show that sensitivity of elongated voids depends strongly on orientation as well as aspect ratio. Ranges of orientations and aspects ratios are identified that enhance or inhibit initiation. Insights obtained from single elongated void analyses are used to identify sensitive locations in an imaged mesostructure of a pressed explosive sample.

Friction stir welding process to repair voids in aluminum alloys

NASA Technical Reports Server (NTRS)

Rosen, Charles D. (Inventor); Litwinski, Edward (Inventor); Valdez, Juan M. (Inventor)

1999-01-01

The present invention provides an in-process method to repair voids in an aluminum alloy, particularly a friction stir weld in an aluminum alloy. For repairing a circular void or an in-process exit hole in a weld, the method includes the steps of fabricating filler material of the same composition or compatible with the parent material into a plug form to be fitted into the void, positioning the plug in the void, and friction stir welding over and through the plug. For repairing a longitudinal void (30), the method includes machining the void area to provide a trough (34) that subsumes the void, fabricating filler metal into a strip form (36) to be fitted into the trough, positioning the strip in the trough, and rewelding the void area by traversing a friction stir welding tool longitudinally through the strip. The method is also applicable for repairing welds made by a fusing welding process or voids in aluminum alloy workpieces themselves.

Structural and mechanical design of tissue interfaces in the giant reed Arundo donax.

PubMed

Rüggeberg, Markus; Burgert, Ingo; Speck, Thomas

2010-03-06

The culms of the giant reed Arundo donax represent slender tube-like structures. Several nodes along the culm, a ring of sclerenchymatous fibres in the periphery of the culm wall and numerous isolated vascular bundles enclosed by fibre rings in the culm wall function as stiffening elements. The bundles are embedded in lignified parenchyma. Micromechanical analysis indicated differences in stiffness between the individual tissues of more than one order of magnitude. In case of abrupt transitions in stiffness at the interfaces, stress discontinuities arise under dynamic loads. This eventually leads to critical shear stresses at cell ends, and culm failure may be initiated at these points. Pronounced mechanical differences between individual tissues can be compromised by gradual transitions at their interfaces. Ultrastructural and spectroscopic investigations with high spatial resolution revealed a gradual transition of cell parameters (cell wall area fraction and cell length). However, cell wall parameters (cellulose microfibril angle and lignin content) showed abrupt transitions or remained almost constant across the interfaces between various tissues. The design principles found at the interfaces between tissues in the culm walls of A. donax are discussed as an adaptation strategy to mechanical loads at different levels of hierarchy.

Structural and mechanical design of tissue interfaces in the giant reed Arundo donax

PubMed Central

Rüggeberg, Markus; Burgert, Ingo; Speck, Thomas

2010-01-01

The culms of the giant reed Arundo donax represent slender tube-like structures. Several nodes along the culm, a ring of sclerenchymatous fibres in the periphery of the culm wall and numerous isolated vascular bundles enclosed by fibre rings in the culm wall function as stiffening elements. The bundles are embedded in lignified parenchyma. Micromechanical analysis indicated differences in stiffness between the individual tissues of more than one order of magnitude. In case of abrupt transitions in stiffness at the interfaces, stress discontinuities arise under dynamic loads. This eventually leads to critical shear stresses at cell ends, and culm failure may be initiated at these points. Pronounced mechanical differences between individual tissues can be compromised by gradual transitions at their interfaces. Ultrastructural and spectroscopic investigations with high spatial resolution revealed a gradual transition of cell parameters (cell wall area fraction and cell length). However, cell wall parameters (cellulose microfibril angle and lignin content) showed abrupt transitions or remained almost constant across the interfaces between various tissues. The design principles found at the interfaces between tissues in the culm walls of A. donax are discussed as an adaptation strategy to mechanical loads at different levels of hierarchy. PMID:19726440

Quantitative study of bundle size effect on thermal conductivity of single-walled carbon nanotubes

NASA Astrophysics Data System (ADS)

Feng, Ya; Inoue, Taiki; An, Hua; Xiang, Rong; Chiashi, Shohei; Maruyama, Shigeo

2018-05-01

Compared with isolated single-walled carbon nanotubes (SWNTs), thermal conductivity is greatly impeded in SWNT bundles; however, the measurement of the bundle size effect is difficult. In this study, the number of SWNTs in a bundle was determined based on the transferred horizontally aligned SWNTs on a suspended micro-thermometer to quantitatively study the effect of the bundle size on thermal conductivity. Increasing the bundle size significantly degraded the thermal conductivity. For isolated SWNTs, thermal conductivity was approximately 5000 ± 1000 W m-1 K-1 at room temperature, three times larger than that of the four-SWNT bundle. The logarithmical deterioration of thermal conductivity resulting from the increased bundle size can be attributed to the increased scattering rate with neighboring SWNTs based on the kinetic theory.

Cations Modulate Actin Bundle Mechanics, Assembly Dynamics, and Structure.

PubMed

Castaneda, Nicholas; Zheng, Tianyu; Rivera-Jacquez, Hector J; Lee, Hyun-Ju; Hyun, Jaekyung; Balaeff, Alexander; Huo, Qun; Kang, Hyeran

2018-04-12

Actin bundles are key factors in the mechanical support and dynamic reorganization of the cytoskeleton. High concentrations of multivalent counterions promote bundle formation through electrostatic attraction between actin filaments that are negatively charged polyelectrolytes. In this study, we evaluate how physiologically relevant divalent cations affect the mechanical, dynamic, and structural properties of actin bundles. Using a combination of total internal reflection fluorescence microscopy, transmission electron microscopy, and dynamic light scattering, we demonstrate that divalent cations modulate bundle stiffness, length distribution, and lateral growth. Molecular dynamics simulations of an all-atom model of the actin bundle reveal specific actin residues coordinate cation-binding sites that promote the bundle formation. Our work suggests that specific cation interactions may play a fundamental role in the assembly, structure, and mechanical properties of actin bundles.

Cosmic voids and void lensing in the Dark Energy Survey science verification data

DOE PAGES

Sánchez, C.; Clampitt, J.; Kovacs, A.; ...

2016-10-26

Galaxies and their dark matter halos populate a complicated filamentary network around large, nearly empty regions known as cosmic voids. Cosmic voids are usually identified in spectroscopic galaxy surveys, where 3D information about the large-scale structure of the Universe is available. Although an increasing amount of photometric data is being produced, its potential for void studies is limited since photometric redshifts induce line-of-sight position errors of ~50 Mpc/h or more that can render many voids undetectable. In this paper we present a new void finder designed for photometric surveys, validate it using simulations, and apply it to the high-quality photo-zmore » redMaGiC galaxy sample of the Dark Energy Survey Science Verification (DES-SV) data. The algorithm works by projecting galaxies into 2D slices and finding voids in the smoothed 2D galaxy density field of the slice. Fixing the line-of-sight size of the slices to be at least twice the photo- z scatter, the number of voids found in these projected slices of simulated spectroscopic and photometric galaxy catalogs is within 20% for all transverse void sizes, and indistinguishable for the largest voids of radius ~70 Mpc/h and larger. The positions, radii, and projected galaxy profiles of photometric voids also accurately match the spectroscopic void sample. Applying the algorithm to the DES-SV data in the redshift range 0.2 < z < 0.8 , we identify 87 voids with comoving radii spanning the range 18-120 Mpc/h, and carry out a stacked weak lensing measurement. With a significance of 4.4σ, the lensing measurement confirms the voids are truly underdense in the matter field and hence not a product of Poisson noise, tracer density effects or systematics in the data. In conclusion, it also demonstrates, for the first time in real data, the viability of void lensing studies in photometric surveys.« less

Spinal surgery: variations in health care costs and implications for episode-based bundled payments.

PubMed

Ugiliweneza, Beatrice; Kong, Maiying; Nosova, Kristin; Huang, Kevin T; Babu, Ranjith; Lad, Shivanand P; Boakye, Maxwell

2014-07-01

Retrospective, observational. To simulate what episodes of care in spinal surgery might look like in a bundled payment system and to evaluate the associated costs and characteristics. Episode-based payment bundling has received considerable attention as a potential method to help curb the rise in health care spending and is being investigated as a new payment model as part of the Affordable Care Act. Although earlier studies investigated bundled payments in a number of surgical settings, very few focused on spine surgery, specifically. We analyzed data from MarketScan. Patients were included in the study if they underwent cervical or lumbar spinal surgery during 2000-2009, had at least 2-year preoperative and 90-day postoperative follow-up data. Patients were grouped on the basis of their diagnosis-related group (DRG) and then tracked in simulated episodes-of-care/payment bundles that lasted for the duration of 30, 60, and 90 days after the discharge from the index-surgical hospitalization. The total cost associated with each episode-of-care duration was measured and characterized. A total of 196,918 patients met our inclusion criteria. Significant variation existed between DRGs, ranging from $11,180 (30-day bundle, DRG 491) to $107,642 (30-day bundle, DRG 456). There were significant cost variations within each individual DRG. Postdischarge care accounted for a relatively small portion of overall bundle costs (range, 4%-8% in 90-day bundles). Total bundle costs remained relatively flat as bundle-length increased (total average cost of 30-day bundle: $33,522 vs. $35,165 for 90-day bundle). Payments to hospitals accounted for the largest portion of bundle costs (76%). There exists significant variation in total health care costs for patients who undergo spinal surgery, even within a given DRG. Better characterization of impacts of a bundled payment system in spine surgery is important for understanding the costs of index procedure hospital, physician services, and postoperative care on potential future health care policy decision making. N/A.

Nurses' perceptions of a pressure ulcer prevention care bundle: a qualitative descriptive study.

PubMed

Roberts, Shelley; McInnes, Elizabeth; Wallis, Marianne; Bucknall, Tracey; Banks, Merrilyn; Chaboyer, Wendy

2016-01-01

Pressure ulcer prevention is a critical patient safety indicator for acute care hospitals. An innovative pressure ulcer prevention care bundle targeting patient participation in their care was recently tested in a cluster randomised trial in eight Australian hospitals. Understanding nurses' perspectives of such an intervention is imperative when interpreting results and translating evidence into practice. As part of a process evaluation for the main trial, this study assessed nurses' perceptions of the usefulness and impact of a pressure ulcer prevention care bundle intervention on clinical practice. This qualitative descriptive study involved semi-structured interviews with nursing staff at four Australian hospitals that were intervention sites for a cluster randomised trial testing a pressure ulcer prevention care bundle. Four to five participants were purposively sampled at each site. A trained interviewer used a semi-structured interview guide to question participants about their perceptions of the care bundle. Interviews were digitally recorded, transcribed and analysed using thematic analysis. Eighteen nurses from four hospitals participated in the study. Nurses' perceptions of the intervention are described in five themes: 1) Awareness of the pressure ulcer prevention care bundle and its similarity to current practice; 2) Improving awareness, communication and participation with the pressure ulcer prevention care bundle; 3) Appreciating the positive aspects of patient participation in care; 4) Perceived barriers to engaging patients in the pressure ulcer prevention care bundle; and 5) Partnering with nursing staff to facilitate pressure ulcer prevention care bundle implementation. Overall, nurses found the care bundle feasible and acceptable. They identified a number of benefits from the bundle, including improved communication, awareness and participation in pressure ulcer prevention care among patients and staff. However, nurses thought the care bundle was not appropriate or effective for all patients, such as those who were cognitively impaired. Perceived enablers to implementation of the bundle included facilitation through effective communication and dissemination of evidence about the care bundle; strong leadership and ability to influence staff behaviour; and simplicity of the care bundle.

MOX fuel assembly design

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

Reese, A.P.; Crowther, R.L. Jr.

1992-02-18

This patent describes improvement in a boiling water reactor core having a plurality of vertically upstanding fuel bundles; each fuel bundle containing longitudinally extending sealed rods with fissile material therein; the improvement comprises the fissile material including a mixture of uranium and recovered plutonium in rods of the fuel bundle at locations other than the corners of the fuel bundle; and, neutron absorbing material being located in rods of the fuel bundle at rod locations adjacent the corners of the fuel bundles whereby the neutron absorbing material has decreased shielding from the plutonium and maximum exposure to thermal neutrons formore » shaping the cold reactivity shutdown zone in the fuel bundle.« less

Contortionist bubbles in andesitic enclaves: implications for gas migration and phase segregation in crystal-rich magmas.

NASA Astrophysics Data System (ADS)

Oppenheimer, J. C.; Cashman, K. V.; Rust, A.; Dobson, K. J.; Bacon, C. R.; Dingwell, D. B.

2016-12-01

In order to constrain gas migration behaviors in crystal-rich magmas, we compare results of analogue experiments to frozen structures in andesitic enclaves. In the analogue experiments air was injected into mixtures of syrup and particles sandwiched between glass plates. We observed a significant increase in bubble deformation and coalescence when particle fractions increased beyond a critical value (the random loose packing). At high particle fractions, bubble growth re-organized (compacted) the particles adjacent to the bubble walls. This caused liquid segregation into patches within the particle suspension and into large void spaces near the outer edge of experiments. We compare these experiments to void morphologies in a 58 x 70 x 73 cm andesitic enclave from silicic-andesite lava flows of Mt Mazama, Oregon (Bacon, 1986). This enclave is zoned, with a vesicle-rich center and a glass-rich rim, suggesting gas-driven melt segregation from the center to the rim. We use both 2D (optical microscopy and SEM) and 3D (X-ray tomography) techniques to image crystal textures and bubble shapes. The center of the enclave bears scattered patches of groundmass in the main phenocryst framework. These patches are similar to those observed in experiments, and thus melt segregation in the enclave may have occurred both toward the rim and toward these patches. Bubble morphologies reveal two main types of bubbles. (1) Lobate and finger-like bubbles, similar to the deformed bubbles in experiments, are found exclusively in the groundmass patches. They are also often associated with compacted crystal structures at the bubble walls. (2) Diktytaxitic textures - angular bubbles flattened against phenocrysts - are abundant in the crystal networks. These voids are entirely connected in 3D and formed the gas-rich center of the enclave. They likely represent a gas migration regime where the expanding gas front cannot deform the crystal structure but instead invades the pore-space between crystals, pushing out residual melt (filter pressing). The switch between regimes appears to depend on crystal size and aspect ratio. The similar features between bubbles in the enclave and in experiments are encouraging, and suggest that crystal-induced bubble deformation, and gas-driven melt segregation, may be common in crystal-rich magmas.

Polycation induced actin bundles.

PubMed

Muhlrad, Andras; Grintsevich, Elena E; Reisler, Emil

2011-04-01

Three polycations, polylysine, the polyamine spermine and the polycationic protein lysozyme were used to study the formation, structure, ionic strength sensitivity and dissociation of polycation-induced actin bundles. Bundles form fast, simultaneously with the polymerization of MgATP-G-actins, upon the addition of polycations to solutions of actins at low ionic strength conditions. This indicates that nuclei and/or nascent filaments bundle due to attractive, electrostatic effect of polycations and the neutralization of repulsive interactions of negative charges on actin. The attractive forces between the filaments are strong, as shown by the low (in nanomolar range) critical concentration of their bundling at low ionic strength. These bundles are sensitive to ionic strength and disassemble partially in 100 mM NaCl, but both the dissociation and ionic strength sensitivity can be countered by higher polycation concentrations. Cys374 residues of actin monomers residing on neighboring filaments in the bundles can be cross-linked by the short span (5.4Å) MTS-1 (1,1-methanedyl bismethanethiosulfonate) cross-linker, which indicates a tight packing of filaments in the bundles. The interfilament cross-links, which connect monomers located on oppositely oriented filaments, prevent disassembly of bundles at high ionic strength. Cofilin and the polysaccharide polyanion heparin disassemble lysozyme induced actin bundles more effectively than the polylysine-induced bundles. The actin-lysozyme bundles are pathologically significant as both proteins are found in the pulmonary airways of cystic fibrosis patients. Their bundles contribute to the formation of viscous mucus, which is the main cause of breathing difficulties and eventual death in this disorder. Copyright © 2011 Elsevier B.V. All rights reserved.

Post-natal molecular adaptations in anteromedial and posterolateral bundles of the ovine anterior cruciate ligament: one structure with two parts or two distinct ligaments?

PubMed

Huebner, Kyla D; O'Brien, Etienne J O; Heard, Bryan J; Chung, May; Achari, Yamini; Shrive, Nigel G; Frank, Cyril B

2012-01-01

The human anterior cruciate ligament (ACL) is a composite structure of two anatomically distinct bundles: an anteromedial (AM) and posterolateral (PL) bundles. Tendons are often used as autografts for surgical reconstruction of ACL following severe injury. However, despite successful surgical reconstruction, some people experience re-rupture and later development of osteoarthritis. Understanding the structure and molecular makeup of normal ACL is essential for its optimal replacement. Reportedly the two bundles display different tensions throughout joint motion and may be fundamentally different. This study assessed the similarities and differences in ultrastructure and molecular composition of the AM and PL bundles to test the hypothesis that the two bundles of the ACL develop unique characteristics with maturation. ACLs from nine mature and six immature sheep were compared. The bundles were examined for mRNA and protein levels of collagen types I, III, V, and VI, and two proteoglycans. The fibril diameter composition of the two bundles was examined with transmission electron microscopy. Maturation does alter the molecular and structural composition of the two bundles of ACL. Although the PL band appears to mature slower than the AM band, no significant differences were detected between the bundles in the mature animals. We thus reject our hypothesis that the two ACL bundles are distinct. The two anatomically distinct bundles of the sheep ACL can be considered as two parts of one structure at maturity and material that would result in a structure of similar functionality can be used to replace each ACL bundle in the sheep.

A Cinematic Magnetic Resonance Imaging Study of Milk of Magnesia Laxative and an Antiflatulent Diet to Reduce Intrafraction Prostate Motion

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

Nichol, Alan M.; Warde, Padraig R.; Lockwood, Gina A.

Purpose: To determine the reduction of prostate motion during a typical radiotherapy (RT) fraction from a bowel regimen comprising an antiflatulent diet and daily milk of magnesia. Methods and Materials: Forty-two patients with T1c-T2c prostate cancer voided the bladder and rectum before three cinematic magnetic resonance imaging scans obtained every 9 s for 9 min in a vacuum immobilization device. The MRIs were at baseline without bowel regimen (MRI-BL), before CT planning with bowel regimen (MRI-CT), and before a randomly assigned RT fraction (1-42) with bowel regimen (MRI-RT). A single observer tracked displacement of the posterior midpoint (PM) of themore » prostate. The primary endpoints were comparisons of the proportion of time that the PM was displaced >3 mm (PTPM3) from its initial position, and the secondary endpoints were comparisons of the reduction of initial rectal area, with and without the bowel regimen. Results: The mean rectal area was: 13.5 cm{sup 2} at MRI-BL, 12.7 cm{sup 2} at MRI-CT, and 12.3 cm{sup 2} at MRI-RT (MRI-BL vs. MRI-CT, p = 0.11; MRI-BL vs. MRI-CT, p = 0.07). Moving rectal gas alone (56%) and moving gas and stool (18%) caused 74% of intrafraction prostate motion. The PTPM3 was 11.3% at MRI-BL, 4.8% at MRI-CT, and 12.0% at MRI-RT (MRI-BL vs. MRI-CT, p = 0.12; MRI-BL vs. MRI-RT, p = 0.89). Conclusion: For subjects voiding their rectum before imaging, an antiflatulent diet and milk of magnesia laxative did not significantly reduce initial rectal area or intrafraction prostate motion.« less

Metallographic autopsies of full-scale ITER prototype cable-in-conduit conductors after full cyclic testing in SULTAN: II. Significant reduction of strand movement and strand damage in short twist pitch CICCs

DOE PAGES

Sanabria, Charlos; Lee, Peter J.; Starch, William; ...

2015-10-14

Prototype cable in conduit conductors (CICCs) destined for use in the Toroidal Field (TF) and Central Solenoid (CS) coils of the ITER experimental fusion reactor underwent severe cyclic loading in the SULTAN facility. Their autopsies revealed significant and permanent transverse strand migration due to the large Lorentz forces of the SULTAN test. The movement resulted in a 3 7% void fraction increase on the Low Pressure (LP) side of the longer twist pitch CICCs. However, short twist pitch conductors exhibited less than 1% void fraction increase in the LP side, as well as a complete absence of the Nb 3Snmore » filament fractures observed in the longer twist pitch conductors. We report here a detailed strand to cable analysis of short and longer “baseline” twist pitch CICCs. It was found that the use of Internal Tin strands in the longer “baseline” twist pitch CICCs can be beneficial possibly because of their superior stiffness—which better resist strand movement—while the use of Bronze Process strands showed more movement and poorer cyclic test performance. This was not the case for the short twist pitch CICC. Such conductor design seems to work well with both strand types. But it was found that despite the absence of filament fractures, the short twist pitch CICC made from the Internal Tin strands studied here developed severe strand distortion during cabling which resulted in diffusion barrier breaks and Sn contamination of the Cu stabilizer during the heat treatment. Furthermore, the short twist pitch CICC made from Bronze Process strands preserved diffusion barrier integrity.« less

Behavior of Aging, Micro-Void, and Self-Healing of Glass/Ceramic Materials and Its Effect on Mechanical Properties

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

Liu, Wenning N.; Sun, Xin; Khaleel, Mohammad A.

This chapter first describes tests to investigate the temporal evolution of the volume fraction of ceramic phases, the evolution of micro-damage, and the self-healing behavior of the glass ceramic sealant used in SOFCs, then a phenomenological model based on mechanical analogs is developed to describe the temperature dependent Young’s modulus of glass ceramic seal materials. It was found that after the initial sintering process, further crystallization of the glass ceramic sealant does not stop, but slows down and reduces the residual glass content while boosting the ceramic crystalline content. Under the long-term operating environment, distinct fibrous and needle-like crystals inmore » the amorphous phase disappeared, and smeared/diffused phase boundaries between the glass phase and ceramic phase were observed. Meanwhile, the micro-damage was induced by the cooling-down process from the operating temperature to the room temperature, which can potentially degrade the mechanical properties of the glass/ceramic sealant. The glass/ceramic sealant self-healed upon reheating to the SOFC operating temperature, which can restore the mechanical performance of the glass/ceramic sealant. The phenomenological model developed here includes the effects of continuing aging and devitrification on the ceramic phase volume fraction and the resulted mechanical properties of glass ceramic seal material are considered. The effects of micro-voids and self-healing are also considered using a continuum damage mechanics (CDM) model. The formulation is for glass/ceramic seal in general, and it can be further developed to account for effects of various processing parameters. This model was applied to G18, and the temperature-dependent experimental measurements were used to calibrate the modeling parameters and to validate the model prediction.« less

Two-phase flow characteristics of liquid nitrogen in vertically upward 0.5 and 1.0 mm micro-tubes: Visualization studies

NASA Astrophysics Data System (ADS)

Zhang, P.; Fu, X.

2009-10-01

Application of liquid nitrogen to cooling is widely employed in many fields, such as cooling of the high temperature superconducting devices, cryosurgery and so on, in which liquid nitrogen is generally forced to flow inside very small passages to maintain good thermal performance and stability. In order to have a full understanding of the flow and heat transfer characteristics of liquid nitrogen in micro-tube, high-speed digital photography was employed to acquire the typical two-phase flow patterns of liquid nitrogen in vertically upward micro-tubes of 0.531 and 1.042 mm inner diameters. It was found from the experimental results that the flow patterns were mainly bubbly flow, slug flow, churn flow and annular flow. And the confined bubble flow, mist flow, bubble condensation and flow oscillation were also observed. These flow patterns were characterized in different types of flow regime maps. The surface tension force and the size of the diameter were revealed to be the major factors affecting the flow pattern transitions. It was found that the transition boundaries of the slug/churn flow and churn/annular flow of the present experiment shifted to lower superficial vapor velocity; while the transition boundary of the bubbly/slug flow shifted to higher superficial vapor velocity compared to the results of the room-temperature fluids in the tubes with the similar hydraulic diameters. The corresponding transition boundaries moved to lower superficial velocity when reducing the inner diameter of the micro-tubes. Time-averaged void fraction and heat transfer characteristics for individual flow patterns were presented and special attention was paid to the effect of the diameter on the variation of void fraction.

Metallographic autopsies of full-scale ITER prototype cable-in-conduit conductors after full cyclic testing in SULTAN: II. Significant reduction of strand movement and strand damage in short twist pitch CICCs

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

Sanabria, Charlos; Lee, Peter J.; Starch, William

Prototype cable in conduit conductors (CICCs) destined for use in the Toroidal Field (TF) and Central Solenoid (CS) coils of the ITER experimental fusion reactor underwent severe cyclic loading in the SULTAN facility. Their autopsies revealed significant and permanent transverse strand migration due to the large Lorentz forces of the SULTAN test. The movement resulted in a 3 7% void fraction increase on the Low Pressure (LP) side of the longer twist pitch CICCs. However, short twist pitch conductors exhibited less than 1% void fraction increase in the LP side, as well as a complete absence of the Nb 3Snmore » filament fractures observed in the longer twist pitch conductors. We report here a detailed strand to cable analysis of short and longer “baseline” twist pitch CICCs. It was found that the use of Internal Tin strands in the longer “baseline” twist pitch CICCs can be beneficial possibly because of their superior stiffness—which better resist strand movement—while the use of Bronze Process strands showed more movement and poorer cyclic test performance. This was not the case for the short twist pitch CICC. Such conductor design seems to work well with both strand types. But it was found that despite the absence of filament fractures, the short twist pitch CICC made from the Internal Tin strands studied here developed severe strand distortion during cabling which resulted in diffusion barrier breaks and Sn contamination of the Cu stabilizer during the heat treatment. Furthermore, the short twist pitch CICC made from Bronze Process strands preserved diffusion barrier integrity.« less

Kinematics and dynamics of green water on a fixed platform in a large wave basin in focusing wave and random wave conditions

NASA Astrophysics Data System (ADS)

Chuang, Wei-Liang; Chang, Kuang-An; Mercier, Richard

2018-06-01

Green water kinematics and dynamics due to wave impingements on a simplified geometry, fixed platform were experimentally investigated in a large, deep-water wave basin. Both plane focusing waves and random waves were employed in the generation of green water. The focusing wave condition was designed to create two consecutive plunging breaking waves with one impinging on the frontal vertical wall of the fixed platform, referred as wall impingement, and the other directly impinging on the deck surface, referred as deck impingement. The random wave condition was generated using the JONSWAP spectrum with a significant wave height approximately equal to the freeboard. A total of 179 green water events were collected in the random wave condition. By examining the green water events in random waves, three different flow types are categorized: collapse of overtopping wave, fall of bulk water, and breaking wave crest. The aerated flow velocity was measured using bubble image velocimetry, while the void fraction was measured using fiber optic reflectometry. For the plane focusing wave condition, measurements of impact pressure were synchronized with the flow velocity and void fraction measurements. The relationship between the peak pressures and the pressure rise times is examined. For the high-intensity impact in the deck impingement events, the peak pressures are observed to be proportional to the aeration levels. The maximum horizontal velocities in the green water events in random waves are well represented by the lognormal distribution. Ritter's solution is shown to quantitatively describe the green water velocity distributions under both the focusing wave condition and the random wave condition. A prediction equation for green water velocity distribution under random waves is proposed.

On the abundance of extreme voids II: a survey of void mass functions

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

Chongchitnan, Siri; Hunt, Matthew, E-mail: s.chongchitnan@hull.ac.uk, E-mail: m.d.hunt@2012.hull.ac.uk

2017-03-01

The abundance of cosmic voids can be described by an analogue of halo mass functions for galaxy clusters. In this work, we explore a number of void mass functions: from those based on excursion-set theory to new mass functions obtained by modifying halo mass functions. We show how different void mass functions vary in their predictions for the largest void expected in an observational volume, and compare those predictions to observational data. Our extreme-value formalism is shown to be a new practical tool for testing void theories against simulation and observation.

Atomistic modeling of shock-induced void collapse in copper

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

Davila, L P; Erhart, P; Bringa, E M

2005-03-09

Nonequilibrium molecular dynamics (MD) simulations show that shock-induced void collapse in copper occurs by emission of shear loops. These loops carry away the vacancies which comprise the void. The growth of the loops continues even after they collide and form sessile junctions, creating a hardened region around the collapsing void. The scenario seen in our simulations differs from current models that assume that prismatic loop emission is responsible for void collapse. We propose a new dislocation-based model that gives excellent agreement with the stress threshold found in the MD simulations for void collapse as a function of void radius.

Nanovoid growth in BCC α-Fe: influences of initial void geometry

NASA Astrophysics Data System (ADS)

Xu, Shuozhi; Su, Yanqing

2016-12-01

The growth of voids has a great impact on the mechanical properties of ductile materials by altering their microstructures. Exploring the process of void growth at the nanoscale helps in understanding the dynamic fracture of metals. While some very recent studies looked into the effects of the initial geometry of an elliptic void on the plastic deformation of face-centered cubic metals, a systematic study of the initial void ellipticity and orientation angle in body-centered cubic (BCC) metals is still lacking. In this paper, large scale molecular dynamics simulations with millions of atoms are conducted, investigating the void growth process during tensile loading of metallic thin films in BCC α-Fe. Our simulations elucidate the intertwined influences on void growth of the initial ellipticity and initial orientation angle of the void. It is shown that these two geometric parameters play an important role in the stress-strain response, the nucleation and evolution of defects, as well as the void size/outline evolution in α-Fe thin films. Results suggest that, together with void size, different initial void geometries should be taken into account if a continuum model is to be applied to nanoscale damage progression.

Comparison of sensation-related voiding patterns between continent and incontinent women: a study with a 3-day sensation-related bladder diary (SR-BD).

PubMed

Naoemova, Irina; De Wachter, Stefan; Wyndaele, Jean-Jacques

2008-01-01

To describe and compare voiding patterns on a 3-day sensation-related bladder diary (SR-BD) in women with urinary incontinence (UI) and healthy volunteers. A total of 251 women (224 incontinent patients and 27 healthy volunteers) who recorded a 3-day SR-BD and underwent standard cystometry participated in the study. Parameters from the 3-day SR-BD were compared between incontinent patients and healthy volunteers. Compared to continent women, all groups of incontinent women noted a significantly higher 24 hr voiding frequency, a greater voiding frequency per liter diuresis, a smaller mean voided volume for different degrees of bladder sensation with more voids made with higher intensity of desire to void. The smallest mean voided volumes for different degrees of desire to void and the highest voiding frequency per liter diuresis were observed in the urge incontinence group. There were different sensation-related voiding patterns on the 3-day SR-BD from incontinent women and healthy volunteers. All incontinence groups had increased bladder sensation compared to healthy volunteers. The most severe increase of bladder sensation was observed in the patients with urgency incontinence. (c) 2007 Wiley-Liss, Inc.

The dark matter of galaxy voids

NASA Astrophysics Data System (ADS)

Sutter, P. M.; Lavaux, Guilhem; Wandelt, Benjamin D.; Weinberg, David H.; Warren, Michael S.

2014-03-01

How do observed voids relate to the underlying dark matter distribution? To examine the spatial distribution of dark matter contained within voids identified in galaxy surveys, we apply Halo Occupation Distribution models representing sparsely and densely sampled galaxy surveys to a high-resolution N-body simulation. We compare these galaxy voids to voids found in the halo distribution, low-resolution dark matter and high-resolution dark matter. We find that voids at all scales in densely sampled surveys - and medium- to large-scale voids in sparse surveys - trace the same underdensities as dark matter, but they are larger in radius by ˜20 per cent, they have somewhat shallower density profiles and they have centres offset by ˜ 0.4Rv rms. However, in void-to-void comparison we find that shape estimators are less robust to sampling, and the largest voids in sparsely sampled surveys suffer fragmentation at their edges. We find that voids in galaxy surveys always correspond to underdensities in the dark matter, though the centres may be offset. When this offset is taken into account, we recover almost identical radial density profiles between galaxies and dark matter. All mock catalogues used in this work are available at http://www.cosmicvoids.net.

Prevalence and characteristics of voiding difficulties in women: are subjective symptoms substantiated by objective urodynamic data?

PubMed

Groutz, A; Gordon, D; Lessing, J B; Wolman, I; Jaffa, A; David, M P

1999-08-01

To examine the prevalence and characteristics of voiding difficulties in women. Two hundred six consecutive female patients who attended a urogynecology clinic were recruited. Patients were interviewed regarding the presence and severity of symptoms that would suggest voiding difficulties (ie, hesitancy, straining to void, weak or prolonged stream, intermittent stream, double voiding, incomplete emptying, reduction, and positional changes to start or complete voiding). Urodynamic evidence of voiding difficulty was considered as a peak flow rate less than 12 mL/s (voided volume greater than 100 mL), or residual urine volume greater than 150 mL, on two or more readings. Residual urinary volume, flow patterns, and pressure-flow parameters were analyzed and compared between symptomatic and asymptomatic patients who had urodynamic parameters of voiding difficulties. One hundred twenty-seven (61.7%) women reported having voiding difficulty symptoms; 79 others (38.3%) were free of such symptoms. Urodynamic diagnosis of voiding difficulty was made in 40 women (19.4% of the study population): 27 in the symptomatic group and 13 in the asymptomatic group (21.2% and 16.5%, respectively). Only 1 patient had voiding difficulty due to bladder outlet obstruction. All other cases of low flow rate were due to impaired detrusor contractility. Objective evidence of voiding difficulty may be found in both symptomatic and asymptomatic patients and is usually due to impaired detrusor contractility. The clinical significance of the abnormal flow parameters in asymptomatic patients is unclear.

Nonabelian Bundle Gerbes, Their Differential Geometry and Gauge Theory

NASA Astrophysics Data System (ADS)

Aschieri, Paolo; Cantini, Luigi; Jurčo, Branislav

2005-03-01

Bundle gerbes are a higher version of line bundles, we present nonabelian bundle gerbes as a higher version of principal bundles. Connection, curving, curvature and gauge transformations are studied both in a global coordinate independent formalism and in local coordinates. These are the gauge fields needed for the construction of Yang-Mills theories with 2-form gauge potential.

Bundled payment fails to gain a foothold In California: the experience of the IHA bundled payment demonstration.

PubMed

Ridgely, M Susan; de Vries, David; Bozic, Kevin J; Hussey, Peter S

2014-08-01

To determine whether bundled payment could be an effective payment model for California, the Integrated Healthcare Association convened a group of stakeholders (health plans, hospitals, ambulatory surgery centers, physician organizations, and vendors) to develop, through a consensus process, the methods and means of implementing bundled payment. In spite of a high level of enthusiasm and effort, the pilot did not succeed in its goal to implement bundled payment for orthopedic procedures across multiple payers and hospital-physician partners. An evaluation of the pilot documented a number of barriers, such as administrative burden, state regulatory uncertainty, and disagreements about bundle definition and assumption of risk. Ultimately, few contracts were signed, which resulted in insufficient volume to test hypotheses about the impact of bundled payment on quality and costs. Although bundled payment failed to gain a foothold in California, the evaluation provides lessons for future bundled payment initiatives. Project HOPE—The People-to-People Health Foundation, Inc.

Double-bundle ACL reconstruction can improve rotational stability.

PubMed

Yagi, Masayoshi; Kuroda, Ryosuke; Nagamune, Kouki; Yoshiya, Shinichi; Kurosaka, Masahiro

2007-01-01

Double-bundle anterior cruciate ligament (ACL) reconstruction reproduces anteromedial and posterolateral bundles, and thus has theoretical advantages over conventional single-bundle reconstruction in controlling rotational torque in vitro. However, its superiority in clinical practice has not been proven. We analyzed rotational stability with three reconstruction techniques in 60 consecutive patients who were randomly divided into three groups (double-bundle, anteromedial single-bundle, posterolateral single-bundle). In the reconstructive procedure, the hamstring tendon was harvested and used as a free tendon graft. Followup examinations were performed 1 year after surgery. Anteroposterior laxity of the knee was examined with a KT-1000 arthrometer, whereas rotatory instability, as elicited by the pivot shift test, was assessed using a new measurement system incorporating three-dimensional electromagnetic sensors. Routine clinical evaluations, including KT examination, demonstrated no differences among the three groups. However, using the new measurement system, patients with double-bundle ACL reconstruction showed better pivot shift control of complex instability than patients with anteromedial and posterolateral single-bundle reconstruction.

Cosmic web type dependence of halo clustering

NASA Astrophysics Data System (ADS)

Fisher, J. D.; Faltenbacher, A.

2018-01-01

We use the Millennium Simulation to show that halo clustering varies significantly with cosmic web type. Haloes are classified as node, filament, sheet and void haloes based on the eigenvalue decomposition of the velocity shear tensor. The velocity field is sampled by the peculiar velocities of a fixed number of neighbouring haloes, and spatial derivatives are computed using a kernel borrowed from smoothed particle hydrodynamics. The classification scheme is used to examine the clustering of haloes as a function of web type for haloes with masses larger than 1011 h- 1 M⊙. We find that node haloes show positive bias, filament haloes show negligible bias and void and sheet haloes are antibiased independent of halo mass. Our findings suggest that the mass dependence of halo clustering is rooted in the composition of web types as a function of halo mass. The substantial fraction of node-type haloes for halo masses ≳ 2 × 1013 h- 1 M⊙ leads to positive bias. Filament-type haloes prevail at intermediate masses, 1012-1013 h- 1 M⊙, resulting in unbiased clustering. The large contribution of sheet-type haloes at low halo masses ≲ 1012 h- 1 M⊙ generates antibiasing.

Risk of Revision Was Not Reduced by a Double-bundle ACL Reconstruction Technique: Results From the Scandinavian Registers.

PubMed

Aga, Cathrine; Kartus, Jüri-Tomas; Lind, Martin; Lygre, Stein Håkon Låstad; Granan, Lars-Petter; Engebretsen, Lars

2017-10-01

Double-bundle anterior cruciate ligament (ACL) reconstruction has demonstrated improved biomechanical properties and moderately better objective outcomes compared with single-bundle reconstructions. This could make an impact on the rerupture rate and reduce the risk of revisions in patients undergoing double-bundle ACL reconstruction compared with patients reconstructed with a traditional single-bundle technique. The National Knee Ligament Registers in Scandinavia provide information that can be used to evaluate the revision outcome after ACL reconstructions. The purposes of the study were (1) to compare the risk of revision between double-bundle and single-bundle reconstructions, reconstructed with autologous hamstring tendon grafts; (2) to compare the risk of revision between double-bundle hamstring tendon and single-bundle bone-patellar tendon-bone autografts; and (3) to compare the hazard ratios for the same two research questions after Cox regression analysis was performed. Data collection of primary ACL reconstructions from the National Knee Ligament Registers in Denmark, Norway, and Sweden from July 1, 2005, to December 31, 2014, was retrospectively analyzed. A total of 60,775 patients were included in the study; 994 patients were reconstructed with double-bundle hamstring tendon grafts, 51,991 with single-bundle hamstring tendon grafts, and 7790 with single-bundle bone-patellar tendon-bone grafts. The double-bundle ACL-reconstructed patients were compared with the two other groups. The risk of revision for each research question was detected by the risk ratio, hazard ratio, and the corresponding 95% confidence intervals. Kaplan-Meier analysis was used to estimate survival at 1, 2, and 5 years for the three different groups. Furthermore, a Cox proportional hazard regression model was applied and the hazard ratios were adjusted for country, age, sex, meniscal or chondral injury, and utilized fixation devices on the femoral and tibial sides. There were no differences in the crude risk of revision between the patients undergoing the double-bundle technique and the two other groups. A total of 3.7% patients were revised in the double-bundle group (37 of 994 patients) versus 3.8% in the single-bundle hamstring tendon group (1952 of 51,991; risk ratio, 1.01; 95% confidence interval (CI), 0.73-1.39; p = 0.96), and 2.8% of the patients were revised in the bone-patellar tendon-bone group (219 of the 7790 bone-patellar tendon-bone patients; risk ratio, 0.76; 95% CI, 0.54-1.06; p = 0.11). Cox regression analysis with adjustment for country, age, sex, menisci or cartilage injury, and utilized fixation device on the femoral and tibial sides, did not reveal any further difference in the risk of revision between the single-bundle hamstring tendon and double-bundle hamstring tendon groups (hazard ratio, 1.18; 95% CI, 0.85-1.62; p = 0.33), but the adjusted hazard ratio showed a lower risk of revision in the single-bundle bone-patellar tendon-bone group compared with the double-bundle group (hazard ratio, 0.62; 95% CI, 0.43-0.90; p = 0.01). Comparisons of the graft revision rates reported separately for each country revealed that double-bundle hamstring tendon reconstructions in Sweden had a lower hazard ratio compared with the single-bundle hamstring tendon reconstructions (hazard ratio, 1.00 versus 1.89; 95% CI, 1.09-3.29; p = 0.02). Survival at 5 years after index surgery was 96.0% for the double-bundle group, 95.4% for the single-bundle hamstring tendon group, and 97.0% for the single-bundle bone-patellar tendon-bone group. Based on the data from all three national registers, the risk of revision was not influenced by the reconstruction technique in terms of using single- or double-bundle hamstring tendons, although national differences in survival existed. Using bone-patellar tendon-bone grafts lowered the risk of revision compared with double-bundle hamstring tendon grafts. These findings should be considered when deciding what reconstruction technique to use in ACL-deficient knees. Future studies identifying the reasons for graft rerupture in single- and double-bundle reconstructions would be of interest to understand the findings of the present study. Level III, therapeutic study.

Investigation of natural circulation instability and transients in passively safe novel modular reactor

NASA Astrophysics Data System (ADS)

Shi, Shanbin

The Purdue Novel Modular Reactor (NMR) is a new type small modular reactor (SMR) that belongs to the design of boiling water reactor (BWR). Specifically, the NMR is one third the height and area of a conventional BWR reactor pressure vessel (RPV) with an electric output of 50 MWe. The fuel cycle length of the NMR-50 is extended up to 10 years due to optimized neutronics design. The NMR-50 is designed with double passive engineering safety system. However, natural circulation BWRs (NCBWR) could experience certain operational difficulties due to flow instabilities that occur at low pressure and low power conditions. Static instabilities (i.e. flow excursion (Ledinegg) instability and flow pattern transition instability) and dynamic instabilities (i.e. density wave instability and flashing/condensation instability) pose a significant challenge in two-phase natural circulation systems. In order to experimentally study the natural circulation flow instability, a proper scaling methodology is needed to build a reduced-size test facility. The scaling analysis of the NMR uses a three-level scaling method, which was developed and applied for the design of the Purdue Multi-dimensional Integral Test Assembly (PUMA). Scaling criteria is derived from dimensionless field equations and constitutive equations. The scaling process is validated by the RELAP5 analysis for both steady state and startup transients. A new well-scaled natural circulation test facility is designed and constructed based on the scaling analysis of the NMR-50. The experimental facility is installed with different equipment to measure various thermal-hydraulic parameters such as pressure, temperature, mass flow rate and void fraction. Characterization tests are performed before the startup transient tests and quasi-steady tests to determine the loop flow resistance. The controlling system and data acquisition system are programmed with LabVIEW to realize the real-time control and data storage. The thermal-hydraulic and nuclear coupled startup transients are performed to investigate the flow instabilities at low pressure and low power conditions. Two different power ramps are chosen to study the effect of power density on the flow instability. The experimental startup transient tests show the existence of three different flow instability mechanisms during the low pressure startup transients, i.e., flashing instability, condensation induced instability, and density wave oscillations. Flashing instability in the chimney section of the test loop and density wave oscillation are the main flow instabilities observed when the system pressure is below 0.5 MPa. They show completely different type of oscillations, i.e., intermittent oscillation and sinusoidal oscillation, in void fraction profile during the startup transients. In order to perform nuclear-coupled startup transients with void reactivity feedback, the Point Kinetics model is utilized to calculate the transient power during the startup transients. In addition, the differences between the electric resistance heaters and typical fuel element are taken into account. The reactor power calculated shows some oscillations due to flashing instability during the transients. However, the void reactivity feedback does not have significant influence on the flow instability during the startup procedure for the NMR-50. Further investigation of very small power ramp on the startup transients is carried out for the thermal-hydraulic startup transients. It is found that very small power density can eliminate the flashing oscillation in the single phase natural circulation and stabilize the flow oscillations in the phase of net vapor generation. Furthermore, initially pressurized startup procedure is investigated to eliminate the main flow instabilities. The results show that the pressurized startup procedure can suppress the flashing instability at low pressure and low power conditions. In order to have a deep understanding of natural circulation flow instability, the quasi-steady tests are performed using the test facility installed with preheater and subcooler. The effects of system pressure, core inlet subcooling, core power density, inlet flow resistance coefficient, and void reactivity feedback are investigated in the quasi-steady state tests. The stability boundaries are determined between unstable and stable flow conditions in the dimensionless stability plane of inlet subcooling number and Zuber number. In order to predict the stability boundary theoretically, linear stability analysis in the frequency domain is performed at four sections of the loop. The flashing in the chimney is considered as an axially uniform heat source. The dimensionless characteristic equation of the pressure drop perturbation is obtained by considering the void fraction effect and outlet flow resistance in the chimney section. The flashing boundary shows some discrepancies with previous experimental data from the quasi-steady state tests. In the future, thermal non-equilibrium is recommended to improve the accuracy of flashing instability boundary.

Molecular dynamics simulations of void defects in the energetic material HMX.

PubMed

Duan, Xiao Hui; Li, Wen Peng; Pei, Chong Hua; Zhou, Xiao Qing

2013-09-01

A molecular dynamics (MD) simulation was carried out to characterize the dynamic evolution of void defects in crystalline octahydro-1, 3, 5, 7-tetranitro-1, 3, 5, 7-tetrazocine (HMX). Different models were constructed with the same concentration of vacancies (10 %) to discuss the size effects of void. Energetic ground state properties were determined by annealing simulations. The void formation energy per molecule removed was found to be 55-63 kcal/mol(-1), and the average binding energy per molecule was between 32 and 34 kcal/mol(-1) according to the change in void size. Voids with larger size had lower formation energy. Local binding energies for molecules directly on the void surface decreased greatly compared to those in defect-free lattice, and then gradually increased until the distance away from the void surface was around 10 Å. Analysis of 1 ns MD simulations revealed that the larger the void size, the easier is void collapse. Mean square displacements (MSDs) showed that HMX molecules that had collapsed into void present liquid structure characteristics. Four unique low-energy conformers were found for HMX molecules in void: two whose conformational geometries corresponded closely to those found in HMX polymorphs and two, additional, lower energy conformers that were not seen in the crystalline phases. The ratio of different conformers changed with the simulated temperature, in that the ratio of α conformer increased with the increase in temperature.

Emulation of reactor irradiation damage using ion beams

DOE PAGES

Was, G. S.; Jiao, Z.; Getto, E.; ...

2014-06-14

The continued operation of existing light water nuclear reactors and the development of advanced nuclear reactor depend heavily on understanding how damage by radiation to levels degrades materials that serve as the structural components in reactor cores. The first high dose ion irradiation experiments on a ferritic-martensitic steel showing that ion irradiation closely emulates the full radiation damage microstructure created in-reactor are described. Ferritic-martensitic alloy HT9 (heat 84425) in the form of a hexagonal fuel bundle duct (ACO-3) accumulated 155 dpa at an average temperature of 443°C in the Fast Flux Test Facility (FFTF). Using invariance theory as a guide,more » irradiation of the same heat was conducted using self-ions (Fe++) at 5 MeV at a temperature of 460°C and to a dose of 188 displacements per atom. The void swelling was nearly identical between the two irradiation and the size and density of precipitates and loops following ion irradiation are within a factor of two of those for neutron irradiation. The level of agreement across all of the principal microstructure changes between ion and reactor irradiation establishes the capability of tailoring ion irradiation to emulate the reactor-irradiated microstructure.« less

21 CFR 888.3045 - Resorbable calcium salt bone void filler device.

Code of Federal Regulations, 2012 CFR

2012-04-01

... 21 Food and Drugs 8 2012-04-01 2012-04-01 false Resorbable calcium salt bone void filler device... salt bone void filler device. (a) Identification. A resorbable calcium salt bone void filler device is... entitled “Class II Special Controls Guidance: Resorbable Calcium Salt Bone Void Filler Device; Guidance for...

21 CFR 888.3045 - Resorbable calcium salt bone void filler device.

Code of Federal Regulations, 2014 CFR

2014-04-01

... 21 Food and Drugs 8 2014-04-01 2014-04-01 false Resorbable calcium salt bone void filler device... salt bone void filler device. (a) Identification. A resorbable calcium salt bone void filler device is... entitled “Class II Special Controls Guidance: Resorbable Calcium Salt Bone Void Filler Device; Guidance for...

21 CFR 888.3045 - Resorbable calcium salt bone void filler device.

Code of Federal Regulations, 2011 CFR

2011-04-01

... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Resorbable calcium salt bone void filler device... salt bone void filler device. (a) Identification. A resorbable calcium salt bone void filler device is... entitled “Class II Special Controls Guidance: Resorbable Calcium Salt Bone Void Filler Device; Guidance for...

21 CFR 888.3045 - Resorbable calcium salt bone void filler device.

Code of Federal Regulations, 2010 CFR

2010-04-01

... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Resorbable calcium salt bone void filler device... salt bone void filler device. (a) Identification. A resorbable calcium salt bone void filler device is... entitled “Class II Special Controls Guidance: Resorbable Calcium Salt Bone Void Filler Device; Guidance for...

21 CFR 888.3045 - Resorbable calcium salt bone void filler device.

Code of Federal Regulations, 2013 CFR

2013-04-01

... 21 Food and Drugs 8 2013-04-01 2013-04-01 false Resorbable calcium salt bone void filler device... salt bone void filler device. (a) Identification. A resorbable calcium salt bone void filler device is... entitled “Class II Special Controls Guidance: Resorbable Calcium Salt Bone Void Filler Device; Guidance for...

21 CFR 1305.28 - Canceling and voiding electronic orders.

Code of Federal Regulations, 2014 CFR

2014-04-01

... 21 Food and Drugs 9 2014-04-01 2014-04-01 false Canceling and voiding electronic orders. 1305.28... I AND II CONTROLLED SUBSTANCES Electronic Orders § 1305.28 Canceling and voiding electronic orders. (a) A supplier may void all or part of an electronic order by notifying the purchaser of the voiding...

21 CFR 1305.28 - Canceling and voiding electronic orders.

Code of Federal Regulations, 2010 CFR

2010-04-01

... 21 Food and Drugs 9 2010-04-01 2010-04-01 false Canceling and voiding electronic orders. 1305.28... I AND II CONTROLLED SUBSTANCES Electronic Orders § 1305.28 Canceling and voiding electronic orders. (a) A supplier may void all or part of an electronic order by notifying the purchaser of the voiding...

38 CFR 3.207 - Void or annulled marriage.

Code of Federal Regulations, 2010 CFR

2010-07-01

... 38 Pensions, Bonuses, and Veterans' Relief 1 2010-07-01 2010-07-01 false Void or annulled marriage... Void or annulled marriage. Proof that a marriage was void or has been annulled should consist of: (a... marriage void, together with such other evidence as may be required for a determination. (b) Annulled. A...

Molecular dynamics modeling and simulation of void growth in two dimensions

NASA Astrophysics Data System (ADS)

Chang, H.-J.; Segurado, J.; Rodríguez de la Fuente, O.; Pabón, B. M.; LLorca, J.

2013-10-01

The mechanisms of growth of a circular void by plastic deformation were studied by means of molecular dynamics in two dimensions (2D). While previous molecular dynamics (MD) simulations in three dimensions (3D) have been limited to small voids (up to ≈10 nm in radius), this strategy allows us to study the behavior of voids of up to 100 nm in radius. MD simulations showed that plastic deformation was triggered by the nucleation of dislocations at the atomic steps of the void surface in the whole range of void sizes studied. The yield stress, defined as stress necessary to nucleate stable dislocations, decreased with temperature, but the void growth rate was not very sensitive to this parameter. Simulations under uniaxial tension, uniaxial deformation and biaxial deformation showed that the void growth rate increased very rapidly with multiaxiality but it did not depend on the initial void radius. These results were compared with previous 3D MD and 2D dislocation dynamics simulations to establish a map of mechanisms and size effects for plastic void growth in crystalline solids.

Heat Transfer Analysis in Wire Bundles for Aerospace Vehicles

NASA Technical Reports Server (NTRS)

Rickman, S. L.; Iamello, C. J.

2016-01-01

Design of wiring for aerospace vehicles relies on an understanding of "ampacity" which refers to the current carrying capacity of wires, either, individually or in wire bundles. Designers rely on standards to derate allowable current flow to prevent exceedance of wire temperature limits due to resistive heat dissipation within the wires or wire bundles. These standards often add considerable margin and are based on empirical data. Commercial providers are taking an aggressive approach to wire sizing which challenges the conventional wisdom of the established standards. Thermal modelling of wire bundles may offer significant mass reduction in a system if the technique can be generalized to produce reliable temperature predictions for arbitrary bundle configurations. Thermal analysis has been applied to the problem of wire bundles wherein any or all of the wires within the bundle may carry current. Wire bundles present analytical challenges because the heat transfer path from conductors internal to the bundle is tortuous, relying on internal radiation and thermal interface conductance to move the heat from within the bundle to the external jacket where it can be carried away by convective and radiative heat transfer. The problem is further complicated by the dependence of wire electrical resistivity on temperature. Reduced heat transfer out of the bundle leads to higher conductor temperatures and, hence, increased resistive heat dissipation. Development of a generalized wire bundle thermal model is presented and compared with test data. The steady state heat balance for a single wire is derived and extended to the bundle configuration. The generalized model includes the effects of temperature varying resistance, internal radiation and thermal interface conductance, external radiation and temperature varying convective relief from the free surface. The sensitivity of the response to uncertainties in key model parameters is explored using Monte Carlo analysis.

78 FR 76987 - Adjustment of Determination of Compulsory License Rates for Mechanical and Digital Phonorecords

Federal Register 2010, 2011, 2012, 2013, 2014

2013-12-20

... service bundles, music bundles, paid locker services, and purchased content locker services. The technical... downloads, limited offerings, mixed service bundles, music bundles, paid locker services, and purchased...

Fuzzy Reasoning to More Accurately Determine Void Areas on Optical Micrographs of Composite Structures

NASA Technical Reports Server (NTRS)

Dominquez, Jesus A.; Tate, Lanetra C.; Wright, M. Clara; Caraccio, Anne

2013-01-01

Accomplishing the best-performing composite matrix (resin) requires that not only the processing method but also the cure cycle generate low-void-content structures. If voids are present, the performance of the composite matrix will be significantly reduced. This is usually noticed by significant reductions in matrix-dominated properties, such as compression and shear strength. Voids in composite materials are areas that are absent of the composite components: matrix and fibers. The characteristics of the voids and their accurate estimation are critical to determine for high performance composite structures. One widely used method of performing void analysis on a composite structure sample is acquiring optical micrographs or Scanning Electron Microscope (SEM) images of lateral sides of the sample and retrieving the void areas within the micrographs/images using an image analysis technique. Segmentation for the retrieval and subsequent computation of void areas within the micrographs/images is challenging as the gray-scaled values of the void areas are close to the gray-scaled values of the matrix leading to the need of manually performing the segmentation based on the histogram of the micrographs/images to retrieve the void areas. The use of an algorithm developed by NASA and based on Fuzzy Reasoning (FR) proved to overcome the difficulty of suitably differentiate void and matrix image areas with similar gray-scaled values leading not only to a more accurate estimation of void areas on composite matrix micrographs but also to a faster void analysis process as the algorithm is fully autonomous.

Voids in cosmological simulations over cosmic time

NASA Astrophysics Data System (ADS)

Wojtak, Radosław; Powell, Devon; Abel, Tom

2016-06-01

We study evolution of voids in cosmological simulations using a new method for tracing voids over cosmic time. The method is based on tracking watershed basins (contiguous regions around density minima) of well-developed voids at low redshift, on a regular grid of density field. It enables us to construct a robust and continuous mapping between voids at different redshifts, from initial conditions to the present time. We discuss how the new approach eliminates strong spurious effects of numerical origin when voids' evolution is traced by matching voids between successive snapshots (by analogy to halo merger trees). We apply the new method to a cosmological simulation of a standard Λ-cold-dark-matter cosmological model and study evolution of basic properties of typical voids (with effective radii 6 h-1 Mpc < Rv < 20 h-1 Mpc at redshift z = 0) such as volumes, shapes, matter density distributions and relative alignments. The final voids at low redshifts appear to retain a significant part of the configuration acquired in initial conditions. Shapes of voids evolve in a collective way which barely modifies the overall distribution of the axial ratios. The evolution appears to have a weak impact on mutual alignments of voids implying that the present state is in large part set up by the primordial density field. We present evolution of dark matter density profiles computed on isodensity surfaces which comply with the actual shapes of voids. Unlike spherical density profiles, this approach enables us to demonstrate development of theoretically predicted bucket-like shape of the final density profiles indicating a wide flat core and a sharp transition to high-density void walls.

Cost-Effectiveness of a Central Venous Catheter Care Bundle

PubMed Central

Halton, Kate A.; Cook, David; Paterson, David L.; Safdar, Nasia; Graves, Nicholas

2010-01-01

Background A bundled approach to central venous catheter care is currently being promoted as an effective way of preventing catheter-related bloodstream infection (CR-BSI). Consumables used in the bundled approach are relatively inexpensive which may lead to the conclusion that the bundle is cost-effective. However, this fails to consider the nontrivial costs of the monitoring and education activities required to implement the bundle, or that alternative strategies are available to prevent CR-BSI. We evaluated the cost-effectiveness of a bundle to prevent CR-BSI in Australian intensive care patients. Methods and Findings A Markov decision model was used to evaluate the cost-effectiveness of the bundle relative to remaining with current practice (a non-bundled approach to catheter care and uncoated catheters), or use of antimicrobial catheters. We assumed the bundle reduced relative risk of CR-BSI to 0.34. Given uncertainty about the cost of the bundle, threshold analyses were used to determine the maximum cost at which the bundle remained cost-effective relative to the other approaches to infection control. Sensitivity analyses explored how this threshold alters under different assumptions about the economic value placed on bed-days and health benefits gained by preventing infection. If clinicians are prepared to use antimicrobial catheters, the bundle is cost-effective if national 18-month implementation costs are below $1.1 million. If antimicrobial catheters are not an option the bundle must cost less than $4.3 million. If decision makers are only interested in obtaining cash-savings for the unit, and place no economic value on either the bed-days or the health benefits gained through preventing infection, these cost thresholds are reduced by two-thirds. Conclusions A catheter care bundle has the potential to be cost-effective in the Australian intensive care setting. Rather than anticipating cash-savings from this intervention, decision makers must be prepared to invest resources in infection control to see efficiency improvements. PMID:20862246

Cost-effectiveness of a central venous catheter care bundle.

PubMed

Halton, Kate A; Cook, David; Paterson, David L; Safdar, Nasia; Graves, Nicholas

2010-09-17

A bundled approach to central venous catheter care is currently being promoted as an effective way of preventing catheter-related bloodstream infection (CR-BSI). Consumables used in the bundled approach are relatively inexpensive which may lead to the conclusion that the bundle is cost-effective. However, this fails to consider the nontrivial costs of the monitoring and education activities required to implement the bundle, or that alternative strategies are available to prevent CR-BSI. We evaluated the cost-effectiveness of a bundle to prevent CR-BSI in Australian intensive care patients. A Markov decision model was used to evaluate the cost-effectiveness of the bundle relative to remaining with current practice (a non-bundled approach to catheter care and uncoated catheters), or use of antimicrobial catheters. We assumed the bundle reduced relative risk of CR-BSI to 0.34. Given uncertainty about the cost of the bundle, threshold analyses were used to determine the maximum cost at which the bundle remained cost-effective relative to the other approaches to infection control. Sensitivity analyses explored how this threshold alters under different assumptions about the economic value placed on bed-days and health benefits gained by preventing infection. If clinicians are prepared to use antimicrobial catheters, the bundle is cost-effective if national 18-month implementation costs are below $1.1 million. If antimicrobial catheters are not an option the bundle must cost less than $4.3 million. If decision makers are only interested in obtaining cash-savings for the unit, and place no economic value on either the bed-days or the health benefits gained through preventing infection, these cost thresholds are reduced by two-thirds. A catheter care bundle has the potential to be cost-effective in the Australian intensive care setting. Rather than anticipating cash-savings from this intervention, decision makers must be prepared to invest resources in infection control to see efficiency improvements.

Adhering to a national surgical care bundle reduces the risk of surgical site infections

PubMed Central

Hopmans, Titia E. M.; Soetens, Loes C.; Wille, Jan C.; Geerlings, Suzanne E.; Vos, Margreet C.; van Benthem, Birgit H. B.; de Greeff, Sabine C.

2017-01-01

Background In 2008, a bundle of care to prevent Surgical Site Infections (SSIs) was introduced in the Netherlands. The bundle consisted of four elements: antibiotic prophylaxis according to local guidelines, no hair removal, normothermia and ‘hygiene discipline’ in the operating room (i.e. number of door movements). Dutch hospitals were advised to implement the bundle and to measure the outcome. This study’s goal was to assess how effective the bundle was in reducing SSI risk. Methods Hospitals assessed whether their staff complied with each of the bundle elements and voluntary reported compliance data to the national SSI surveillance network (PREZIES). From PREZIES data, we selected data from 2009 to 2014 relating to 13 types of surgical procedures. We excluded surgeries with missing (non)compliance data, and calculated for each remaining surgery with reported (non)compliance data the level of compliance with the bundle (that is, being compliant with 0, 1, 2, 3, or 4 of the elements). Subsequently, we used this level of compliance to assess the effect of bundle compliance on the SSI risk, using multilevel logistic regression techniques. Results 217 489 surgeries were included, of which 62 486 surgeries (29%) had complete bundle reporting. Within this group, the SSI risk was significantly lower for surgeries with complete bundle compliance compared to surgeries with lower compliance levels. Odds ratios ranged from 0.63 to 0.86 (risk reduction of 14% to 37%), while a 13% risk reduction was demonstrated for each point increase in compliance-level. Sensitivity analysis indicated that due to analysing reported bundles only, we probably underestimated the total effect of implementing the bundle. Conclusions This study demonstrated that adhering to a surgical care bundle significantly reduced the risk of SSIs. Reporting of and compliance with the bundle compliance can, however, still be improved. Therefore an even greater effect might be achieved. PMID:28877223

Pulmonary Right Ventricular Resynchronization in Congenital Heart Disease: Acute Improvement in Right Ventricular Mechanics and Contraction Efficiency.

PubMed

Janoušek, Jan; Kovanda, Jan; Ložek, Miroslav; Tomek, Viktor; Vojtovič, Pavel; Gebauer, Roman; Kubuš, Peter; Krejčíř, Miroslav; Lumens, Joost; Delhaas, Tammo; Prinzen, Frits

2017-09-01

Electromechanical discoordination may contribute to long-term pulmonary right ventricular (RV) dysfunction in patients after surgery for congenital heart disease. We sought to evaluate changes in RV function after temporary RV cardiac resynchronization therapy. Twenty-five patients aged median 12.0 years after repair of tetralogy of Fallot and similar lesions were studied echocardiographically (n=23) and by cardiac catheterization (n=5) after primary repair (n=4) or after surgical RV revalvulation for significant pulmonary regurgitation (n=21). Temporary RV cardiac resynchronization therapy was applied in the presence of complete right bundle branch block by atrial-synchronized RV free wall pacing in complete fusion with spontaneous ventricular depolarization using temporary electrodes. The q-RV interval at the RV free wall pacing site (mean 77.2% of baseline QRS duration) confirmed pacing from a late activated RV area. RV cardiac resynchronization therapy carried significant decrease in QRS duration ( P <0.001) along with elimination of the right bundle branch block QRS morphology, increase in RV filling time ( P =0.002), pulmonary artery velocity time integral ( P =0.006), and RV maximum +dP/dt ( P <0.001), and decrease in RV index of myocardial performance ( P =0.006). RV mechanical synchrony improved: septal-to-lateral RV mechanical delay decreased ( P <0.001) and signs of RV dyssynchrony pattern were significantly abolished. RV systolic stretch fraction reflecting the ratio of myocardial stretching and contraction during systole diminished ( P =0.001). In patients with congenital heart disease and right bundle branch block, RV cardiac resynchronization therapy carried multiple positive effects on RV mechanics, synchrony, and contraction efficiency. © 2017 American Heart Association, Inc.

Altered white matter tract property related to impaired focused attention, sustained attention, cognitive impulsivity and vigilance in attention-deficit/hyperactivity disorder

PubMed Central

Chiang, Huey-Ling; Chen, Yu-Jen; Lo, Yu-Chun; Tseng, Wen-Yih Isaac; Gau, Susan Shur-Fen

2015-01-01

Background The neural substrate for clinical symptoms and neuropsychological performance in individuals with attention-deficit/hyperactivity disorder (ADHD) has rarely been studied and has yielded inconsistent results. We sought to compare the microstructural property of fibre tracts associated with the prefrontal cortex and its association with ADHD symptoms and a wide range of attention performance in youth with ADHD and healthy controls. Methods We assessed youths with ADHD and age-, sex-, handedness-, coil- and intelligence-matched controls using the Conners’ Continuous Performance Test (CCPT) for attention performance and MRI. The 10 target tracts, including the bilateral frontostriatal tracts (caudate to dorsolateral prefrontal cortex, ventrolateral prefrontal cortex and orbitofrontal cortex), superior longitudinal fasciculus (SLF) and cingulum bundle were reconstructed using diffusion spectrum imaging tractography. We computed generalized fractional anisotropy (GFA) values to indicate tract-specific microstructural property. Results We included 50 youths with ADHD and 50 healthy controls in our study. Youths with ADHD had lower GFA in the left frontostriatal tracts, bilateral SLF and right cingulum bundle and performed worse in the CCPT than controls. Furthermore, alteration of the right SLF GFA was most significantly associated with the clinical symptom of inattention in youths with ADHD. Finally, youths with ADHD had differential association patterns of the 10 fibre tract GFA values with attention performance compared with controls. Limitations Ten of the youths with ADHD were treated with methylphenidate, which may have long-term effects on microstructural property. Conclusion Our study highlights the importance of the SLF, cingulum bundle and frontostriatal tracts for clinical symptoms and attention performance in youths with ADHD and demonstrates the involvement of different fibre tracts in attention performance in these individuals. PMID:25871496

Altered white matter tract property related to impaired focused attention, sustained attention, cognitive impulsivity and vigilance in attention-deficit/ hyperactivity disorder.

PubMed

Chiang, Huey-Ling; Chen, Yu-Jen; Lo, Yu-Chun; Tseng, Wen-Yih I; Gau, Susan S

2015-09-01

The neural substrate for clinical symptoms and neuropsychological performance in individuals with attention-deficit/hyperactivity disorder (ADHD) has rarely been studied and has yielded inconsistent results. We sought to compare the microstructural property of fibre tracts associated with the prefrontal cortex and its association with ADHD symptoms and a wide range of attention performance in youth with ADHD and healthy controls. We assessed youths with ADHD and age-, sex-, handedness-, coil- and intelligence-matched controls using the Conners' Continuous Performance Test (CCPT) for attention performance and MRI. The 10 target tracts, including the bilateral frontostriatal tracts (caudate to dorsolateral prefrontal cortex, ventrolateral prefrontal cortex and orbitofrontal cortex), superior longitudinal fasciculus (SLF) and cingulum bundle were reconstructed using diffusion spectrum imaging tractography. We computed generalized fractional anisotropy (GFA) values to indicate tract-specific microstructural property. We included 50 youths with ADHD and 50 healthy controls in our study. Youths with ADHD had lower GFA in the left frontostriatal tracts, bilateral SLF and right cingulum bundle and performed worse in the CCPT than controls. Furthermore, alteration of the right SLF GFA was most significantly associated with the clinical symptom of inattention in youths with ADHD. Finally, youths with ADHD had differential association patterns of the 10 fibre tract GFA values with attention performance compared with controls. Ten of the youths with ADHD were treated with methylphenidate, which may have long-term effects on microstructural property. Our study highlights the importance of the SLF, cingulum bundle and frontostriatal tracts for clinical symptoms and attention performance in youths with ADHD and demonstrates the involvement of different fibre tracts in attention performance in these individuals.

Neural substrates of behavioral variability in attention deficit hyperactivity disorder: based on ex-Gaussian reaction time distribution and diffusion spectrum imaging tractography.

PubMed

Lin, H-Y; Gau, S S-F; Huang-Gu, S L; Shang, C-Y; Wu, Y-H; Tseng, W-Y I

2014-06-01

Increased intra-individual variability (IIV) in reaction time (RT) across various tasks is one ubiquitous neuropsychological finding in attention deficit hyperactivity disorder (ADHD). However, neurobiological underpinnings of IIV in individuals with ADHD have not yet been fully delineated. The ex-Gaussian distribution has been proved to capture IIV in RT. The authors explored the three parameters [μ (mu), σ (sigma), τ (tau)] of an ex-Gaussian RT distribution derived from the Conners' continuous performance test (CCPT) and their correlations with the microstructural integrity of the frontostriatal-caudate tracts and the cingulum bundles. We assessed 28 youths with ADHD (8-17 years; 25 males) and 28 age-, sex-, IQ- and handedness-matched typically developing (TD) youths using the CCPT, Wechsler Intelligence Scale for Children, 3rd edition and magnetic resonance imaging (MRI). Microstructural integrity, indexed by generalized fractional anisotropy (GFA), was measured by diffusion spectrum imaging tractrography on a 3-T MRI system. Youths with ADHD had larger σ (s.d. of Gaussian distribution) and τ (mean of exponential distribution) and reduced GFA in four bilateral frontostriatal tracts. With increased inter-stimulus intervals of CCPT, the magnitude of greater τ in ADHD than TD increased. In ADHD youths, the cingulum bundles and frontostriatal integrity were associated with three ex-Gaussian parameters and with μ (mean of Gaussian distribution) and τ, respectively; while only frontostriatal GFA was associated with μ and τ in TD youths. Our findings suggest the crucial role of the integrity of the cingulum bundles in accounting for IIV in ADHD. Involvement of different brain systems in mediating IIV may relate to a distinctive pathophysiological processing and/or adaptive compensatory mechanism.

Effect of voids on Arrhenius relationship between H-solubility and temperature in nickel

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

Wu, Q.Y.; Sun, X.K.; Hu, Z.Q.

1997-01-15

Many investigations about the states of hydrogen in voids within metals have been carried out over the past years. These probable states of hydrogen in the voids are directly relevant to hydrogen embrittlement mechanisms. Therefore, a knowledge of the states of hydrogen in the voids is important to an understanding of hydrogen-related degradation of material properties. Some results show that hydrogen exists as a molecule in the voids, while others suggest it is in the chemisorbed state on the internal surface of the voids. The results of Sung-Man lee et al. suggested that hydrogen in the voids in nickel existsmore » both in the gaseous and chemisorbed stats, and most of the hydrogen trapped in the voids seems to be present as a chemisorbed state in 1 atm. hydrogen pressure in the temperature range of 350--582 C. But there is no quantitative description concerning the effects of the voids on the solubility of hydrogen in materials. The purpose of this work is to describe quantitatively the effects of the voids on hydrogen solubility in nickel, considering hydrogen exists as gaseous and chemisorbed states in the voids, and the very weak physical adsorption above room temperature is neglected.« less

Physics of hydride fueled PWR

NASA Astrophysics Data System (ADS)

Ganda, Francesco

The first part of the work presents the neutronic results of a detailed and comprehensive study of the feasibility of using hydride fuel in pressurized water reactors (PWR). The primary hydride fuel examined is U-ZrH1.6 having 45w/o uranium: two acceptable design approaches were identified: (1) use of erbium as a burnable poison; (2) replacement of a fraction of the ZrH1.6 by thorium hydride along with addition of some IFBA. The replacement of 25 v/o of ZrH 1.6 by ThH2 along with use of IFBA was identified as the preferred design approach as it gives a slight cycle length gain whereas use of erbium burnable poison results in a cycle length penalty. The feasibility of a single recycling plutonium in PWR in the form of U-PuH2-ZrH1.6 has also been assessed. This fuel was found superior to MOX in terms of the TRU fractional transmutation---53% for U-PuH2-ZrH1.6 versus 29% for MOX---and proliferation resistance. A thorough investigation of physics characteristics of hydride fuels has been performed to understand the reasons of the trends in the reactivity coefficients. The second part of this work assessed the feasibility of multi-recycling plutonium in PWR using hydride fuel. It was found that the fertile-free hydride fuel PuH2-ZrH1.6, enables multi-recycling of Pu in PWR an unlimited number of times. This unique feature of hydride fuels is due to the incorporation of a significant fraction of the hydrogen moderator in the fuel, thereby mitigating the effect of spectrum hardening due to coolant voiding accidents. An equivalent oxide fuel PuO2-ZrO2 was investigated as well and found to enable up to 10 recycles. The feasibility of recycling Pu and all the TRU using hydride fuels were investigated as well. It was found that hydride fuels allow recycling of Pu+Np at least 6 times. If it was desired to recycle all the TRU in PWR using hydrides, the number of possible recycles is limited to 3; the limit is imposed by positive large void reactivity feedback.

Composition of the C6+ Fraction of Natural Gas by Multiple Porous Layer Open Tubular Capillaries Maintained at Low Temperatures.

PubMed

Burger, Jessica L; Lovestead, Tara M; Bruno, Thomas J

2016-03-17

As the sources of natural gas become more diverse, the trace constituents of the C 6 + fraction are of increasing interest. Analysis of fuel gas (including natural gas) for compounds with more than 6 carbon atoms (the C 6 + fraction) has historically been complex and expensive. Hence, this is a procedure that is used most often in troubleshooting rather than for day-to-day operations. The C 6 + fraction affects gas quality issues and safety considerations such as anomalies associated with odorization. Recent advances in dynamic headspace vapor collection can be applied to this analysis and provide a faster, less complex alternative for compositional determination of the C 6 + fraction of natural gas. Porous layer open tubular capillaries maintained at low temperatures (PLOT-cryo) form the basis of a dynamic headspace sampling method that was developed at NIST initially for explosives in 2009. This method has been recently advanced by the combining of multiple PLOT capillary traps into one "bundle," or wafer, resulting in a device that allows the rapid trapping of relatively large amounts of analyte. In this study, natural gas analytes were collected by flowing natural gas from the laboratory (gas out of the wall) or a prepared surrogate gas flowing through a chilled wafer. The analytes were then removed from the PLOT-cryo wafer by thermal desorption and subsequent flushing of the wafer with helium. Gas chromatography (GC) with mass spectrometry (MS) was then used to identify the analytes.

Laser-induced incandescence measurements of soot in turbulent pool fires.

PubMed

Frederickson, Kraig; Kearney, Sean P; Grasser, Thomas W

2011-02-01

We present what we believe to be the first application of the laser-induced incandescence (LII) technique to large-scale fire testing. The construction of an LII instrument for fire measurements is presented in detail. Soot volume fraction imaging from 2 m diameter pool fires burning blended toluene/methanol liquid fuels is demonstrated along with a detailed report of measurement uncertainty in the challenging pool fire environment. Our LII instrument relies upon remotely located laser, optical, and detection systems and the insertion of water-cooled, fiber-bundle-coupled collection optics into the fire plume. Calibration of the instrument was performed using an ethylene/air laminar diffusion flame produced by a Santoro-type burner, which allowed for the extraction of absolute soot volume fractions from the LII images. Single-laser-shot two-dimensional images of the soot layer structure are presented with very high volumetric spatial resolution of the order of 10(-5) cm3. Probability density functions of the soot volume fraction fluctuations are constructed from the large LII image ensembles. The results illustrate a highly intermittent soot fluctuation field with potentially large macroscale soot structures and clipped soot probability densities.

Mechanism of Void Prediction in Flip Chip Packages with Molded Underfill

NASA Astrophysics Data System (ADS)

Wu, Kuo-Tsai; Hwang, Sheng-Jye; Lee, Huei-Huang

2017-08-01

Voids have always been present using the molded underfill (MUF) package process, which is a problem that needs further investigation. In this study, the process was studied using the Moldex3D numerical analysis software. The effects of gas (air vent effect) on the overall melt front were also considered. In this isothermal process containing two fluids, the gas and melt colloid interact in the mold cavity. Simulation enabled an appropriate understanding of the actual situation to be gained, and, through analysis, the void region and exact location of voids were predicted. First, the global flow end area was observed to predict the void movement trend, and then the local flow ends were observed to predict the location and size of voids. In the MUF 518 case study, simulations predicted the void region as well as the location and size of the voids. The void phenomenon in a flip chip ball grid array underfill is discussed as part of the study.

Three-dimensional simulations of void collapse in energetic materials

NASA Astrophysics Data System (ADS)

Rai, Nirmal Kumar; Udaykumar, H. S.

2018-03-01

The collapse of voids in porous energetic materials leads to hot-spot formation and reaction initiation. This work advances the current knowledge of the dynamics of void collapse and hot-spot formation using 3D reactive void collapse simulations in HMX. Four different void shapes, i.e., sphere, cylinder, plate, and ellipsoid, are studied. For all four shapes, collapse generates complex three-dimensional (3D) baroclinic vortical structures. The hot spots are collocated with regions of intense vorticity. The differences in the vortical structures for the different void shapes are shown to significantly impact the relative sensitivity of the voids. Voids of high surface area generate hot spots of greater intensity; intricate, highly contorted vortical structures lead to hot spots of corresponding tortuosity and therefore enhanced growth rates of reaction fronts. In addition, all 3D voids are shown to be more sensitive than their two-dimensional (2D) counterparts. The results provide physical insights into hot-spot formation and growth and point to the limitations of 2D analyses of hot-spot formation.

X-ray Microtomography of Intermittency in Multiphase Flow at Steady State Using a Differential Imaging Method

NASA Astrophysics Data System (ADS)

Gao, Ying; Lin, Qingyang; Bijeljic, Branko; Blunt, Martin J.

2017-12-01

We imaged the steady state flow of brine and decane in Bentheimer sandstone. We devised an experimental method based on differential imaging to examine how flow rate impacts impact the pore-scale distribution of fluids during coinjection. This allows us to elucidate flow regimes (connected, or breakup of the nonwetting phase pathways) for a range of fractional flows at two capillary numbers, Ca, namely 3.0 × 10-7 and 7.5 × 10-6. At the lower Ca, for a fixed fractional flow, the two phases appear to flow in connected unchanging subnetworks of the pore space, consistent with conventional theory. At the higher Ca, we observed that a significant fraction of the pore space contained sometimes oil and sometimes brine during the 1 h scan: this intermittent occupancy, which was interpreted as regions of the pore space that contained both fluid phases for some time, is necessary to explain the flow and dynamic connectivity of the oil phase; pathways of always oil-filled portions of the void space did not span the core. This phase was segmented from the differential image between the 30 wt % KI brine image and the scans taken at each fractional flow. Using the grey scale histogram distribution of the raw images, the oil proportion in the intermittent phase was calculated. The pressure drops at each fractional flow at low and high flow rates were measured by high-precision differential pressure sensors. The relative permeabilities and fractional flow obtained by our experiment at the mm-scale compare well with data from the literature on cm-scale samples.

Ab initio density functional theory investigation of electronic properties of semiconducting single-walled carbon nanotube bundles

NASA Astrophysics Data System (ADS)

Moradian, Rostam; Behzad, Somayeh; Azadi, Sam

2008-09-01

By using ab initio density functional theory we investigated the structural and electronic properties of semiconducting (7, 0), (8, 0) and (10, 0) carbon nanotube bundles. The energetic and electronic evolutions of nanotubes in the bundling process are also studied. The effects of inter-tube coupling on the electronic dispersions of semiconducting carbon nanotube bundles are demonstrated. Our results show that the inter-tube coupling decreases the energy gap in semiconducting nanotubes. We found that bundles of (7, 0) and (8, 0) carbon nanotubes have metallic feature, while (10, 0) bundle is a semiconductor with an energy gap of 0.22 eV. To clarify our results the band structures of isolated and bundled nanotubes are compared.

Methods of predicting aggregate voids.

DOT National Transportation Integrated Search

2013-03-01

Percent voids in combined aggregates vary significantly. Simplified methods of predicting aggregate : voids were studied to determine the feasibility of a range of gradations using aggregates available in Kansas. : The 0.45 Power Curve Void Predictio...

Direct evidence of void passivation in Cu(InGa)(SSe){sub 2} absorber layers

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

Lee, Dongho; Kim, Young-Su; Mo, Chan B.

We have investigated the charge collection condition around voids in copper indium gallium sulfur selenide (CIGSSe) solar cells fabricated by sputter and a sequential process of selenization/sulfurization. In this study, we found direct evidence of void passivation by using the junction electron beam induced current method, transmission electron microscopy, and energy dispersive X-ray spectroscopy. The high sulfur concentration at the void surface plays an important role in the performance enhancement of the device. The recombination around voids is effectively suppressed by field-assisted void passivation. Hence, the generated carriers are easily collected by the electrodes. Therefore, when the S/(S + Se)more » ratio at the void surface is over 8% at room temperature, the device performance degradation caused by the recombination at the voids is negligible at the CIGSSe layer.« less

Log-Normal Distribution of Cosmic Voids in Simulations and Mocks

NASA Astrophysics Data System (ADS)

Russell, E.; Pycke, J.-R.

2017-01-01

Following up on previous studies, we complete here a full analysis of the void size distributions of the Cosmic Void Catalog based on three different simulation and mock catalogs: dark matter (DM), haloes, and galaxies. Based on this analysis, we attempt to answer two questions: Is a three-parameter log-normal distribution a good candidate to satisfy the void size distributions obtained from different types of environments? Is there a direct relation between the shape parameters of the void size distribution and the environmental effects? In an attempt to answer these questions, we find here that all void size distributions of these data samples satisfy the three-parameter log-normal distribution whether the environment is dominated by DM, haloes, or galaxies. In addition, the shape parameters of the three-parameter log-normal void size distribution seem highly affected by environment, particularly existing substructures. Therefore, we show two quantitative relations given by linear equations between the skewness and the maximum tree depth, and between the variance of the void size distribution and the maximum tree depth, directly from the simulated data. In addition to this, we find that the percentage of voids with nonzero central density in the data sets has a critical importance. If the number of voids with nonzero central density reaches ≥3.84% in a simulation/mock sample, then a second population is observed in the void size distributions. This second population emerges as a second peak in the log-normal void size distribution at larger radius.

Theory of Dust Voids in Plasmas

NASA Technical Reports Server (NTRS)

Goree, J.; Morfill, G. E.; Tsytovich, V. N.; Vladimirov, S. V.

1999-01-01

Dusty plasmas in a gas discharge often feature a stable void, i.e., a dust-free region inside the dust cloud. This occurs under conditions relevant to both plasma processing discharges and plasma crystal experiments. The void results from a balance of the electrostatic and ion drag forces on a dust particle. The ion drag force is driven by a flow of ions outward from an ionization source and toward the surrounding dust cloud, which has a negative space charge. In equilibrium the force balance for dust particles requires that the boundary with the dust cloud be sharp, provided that the particles are cold and monodispersive. Numerical solutions of the one-dimensional nonlinear fluid equations are carried out including dust charging and dust-neutral collisions, but not ion-neutral collisions. The regions of parameter space that allow stable void equilibria are identified. There is a minimum ionization rate that can sustain a void. Spatial profiles of plasma parameters in the void are reported. In the absence of ion-neutral collisions, the ion flow enters the dust cloud's edge at Mach number M = 1. Phase diagrams for expanding or contracting voids reveal a stationary point corresponding to a single stable equilibrium void size, provided the ionization rate is constant. Large voids contract and small voids expand until they attain this stationary void size. On the other hand, if the ionization rate is not constant, the void size can oscillate. Results are compared to recent laboratory and microgravity experiments.

VizieR Online Data Catalog: A cosmic void catalog of SDSS DR12 BOSS galaxies (Mao+, 2017)

NASA Astrophysics Data System (ADS)

Mao, Q.; Berlind, A. A.; Scherrer, R. J.; Neyrinck, M. C.; Scoccimarro, R.; Tinker, J. L.; McBride, C. K.; Schneider, D. P.; Pan, K.; Bizyaev, D.; Malanushenko, E.; Malanushenko, V.

2017-08-01

We present a cosmic void catalog using the large-scale structure galaxy catalog from the Baryon Oscillation Spectroscopic Survey (BOSS). This galaxy catalog is part of the Sloan Digital Sky Survey (SDSS) Data Release 12 and is the final catalog of SDSS-III. We take into account the survey boundaries, masks, and angular and radial selection functions, and apply the ZOBOV (Neyrinck 2008MNRAS.386.2101N) void finding algorithm to the Galaxy catalog. We identify a total of 10643 voids. After making quality cuts to ensure that the voids represent real underdense regions, we obtain 1228 voids with effective radii spanning the range 20-100h-1Mpc and with central densities that are, on average, 30% of the mean sample density. We release versions of the catalogs both with and without quality cuts. We discuss the basic statistics of voids, such as their size and redshift distributions, and measure the radial density profile of the voids via a stacking technique. In addition, we construct mock void catalogs from 1000 mock galaxy catalogs, and find that the properties of BOSS voids are in good agreement with those in the mock catalogs. We compare the stellar mass distribution of galaxies living inside and outside of the voids, and find no large difference. These BOSS and mock void catalogs are useful for a number of cosmological and galaxy environment studies. (1 data file).

Cosmic voids detection without density measurements

NASA Astrophysics Data System (ADS)

Elyiv, Andrii; Marulli, Federico; Pollina, Giorgia; Baldi, Marco; Branchini, Enzo; Cimatti, Andrea; Moscardini, Lauro

2015-03-01

Cosmic voids are effective cosmological probes to discriminate among competing world models. Their identification is generally based on density or geometry criteria that, because of their very nature, are prone to shot noise. We propose two void finders that are based on dynamical criterion to select voids in Lagrangian coordinates and minimize the impact of sparse sampling. The first approach exploits the Zel'dovich approximation to trace back in time the orbits of galaxies located in voids and their surroundings; the second uses the observed galaxy-galaxy correlation function to relax the objects' spatial distribution to homogeneity and isotropy. In both cases voids are defined as regions of the negative velocity divergence, which can be regarded as sinks of the back-in-time streamlines of the mass tracers. To assess the performance of our methods we used a dark matter halo mock catalogue CODECS, and compared the results with those obtained with the ZOBOV void finder. We find that the void divergence profiles are less scattered than the density ones and, therefore, their stacking constitutes a more accurate cosmological probe. The significance of the divergence signal in the central part of voids obtained from both our finders is 60 per cent higher than for overdensity profiles in the ZOBOV case. The ellipticity of the stacked void measured in the divergence field is closer to unity, as expected, than what is found when using halo positions. Therefore, our void finders are complementary to the existing methods, which should contribute to improve the accuracy of void-based cosmological tests.

Lexical bundles in an advanced INTOCSU writing class and engineering texts: A functional analysis

NASA Astrophysics Data System (ADS)

Alquraishi, Mohammed Abdulrahman

The purpose of this study is to investigate the functions of lexical bundles in two corpora: a corpus of engineering academic texts and a corpus of IEP advanced writing class texts. This study is concerned with the nature of formulaic language in Pathway IEPs and engineering texts, and whether those types of texts show similar or distinctive formulaic functions. Moreover, the study looked into lexical bundles found in an engineering 1.26 million-word corpus and an ESL 65000-word corpus using a concordancing program. The study then analyzed the functions of those lexical bundles and compared them statistically using chi-square tests. Additionally, the results of this investigation showed 236 unique frequent lexical bundles in the engineering corpus and 37 bundles in the pathway corpus. Also, the study identified several differences between the density and functions of lexical bundles in the two corpora. These differences were evident in the distribution of functions of lexical bundles and the minimal overlap of lexical bundles found in the two corpora. The results of this study call for more attention to formulaic language at ESP and EAP programs.

Biological natural retting for determining the hierarchical structuration of banana fibers.

PubMed

Gañán, Piedad; Zuluaga, Robin; Velez, Juan Manuel; Mondragon, Iñaki

2004-10-20

Extraction processes of natural fibers can be performed by different procedures that include mechanical, chemical and biological methods. Each method presents different advantages or drawbacks according to the amount of fiber produced or the quality and properties of fiber bundles obtained. In this study, biological natural retting was satisfactorily used for obtaining banana fibers from plant bunches. However, the most important contribution of this work refers to the description of the hierarchical microstructural ordering present in banana fiber bundles in both bundle surface and inner region. The chemical composition of banana fiber bundles has been evaluated by FTIR spectroscopy. Through exposure time, the fiber bundle configuration presents small variations in composition. The main changes are related to hemicellulose and pectins as they conform the outer walls of the bundle. Hierarchical helicoidal ordering in the bundle surface as well as orientation on the longitudinal axis of the bundle were observed by optical microscopy (OM) and scanning electron microscopy (SEM) for 3-4 microm surface fibers and 10-15 microm inner elementary fibers, respectively. With increasing exposure time, fiber bundle walls lose integrity, as reflected in their mechanical behavior.

Large-Scale Reactive Atomistic Simulation of Shock-induced Initiation Processes in Energetic Materials

NASA Astrophysics Data System (ADS)

Thompson, Aidan

2013-06-01

Initiation in energetic materials is fundamentally dependent on the interaction between a host of complex chemical and mechanical processes, occurring on scales ranging from intramolecular vibrations through molecular crystal plasticity up to hydrodynamic phenomena at the mesoscale. A variety of methods (e.g. quantum electronic structure methods (QM), non-reactive classical molecular dynamics (MD), mesoscopic continuum mechanics) exist to study processes occurring on each of these scales in isolation, but cannot describe how these processes interact with each other. In contrast, the ReaxFF reactive force field, implemented in the LAMMPS parallel MD code, allows us to routinely perform multimillion-atom reactive MD simulations of shock-induced initiation in a variety of energetic materials. This is done either by explicitly driving a shock-wave through the structure (NEMD) or by imposing thermodynamic constraints on the collective dynamics of the simulation cell e.g. using the Multiscale Shock Technique (MSST). These MD simulations allow us to directly observe how energy is transferred from the shockwave into other processes, including intramolecular vibrational modes, plastic deformation of the crystal, and hydrodynamic jetting at interfaces. These processes in turn cause thermal excitation of chemical bonds leading to initial chemical reactions, and ultimately to exothermic formation of product species. Results will be presented on the application of this approach to several important energetic materials, including pentaerythritol tetranitrate (PETN) and ammonium nitrate/fuel oil (ANFO). In both cases, we validate the ReaxFF parameterizations against QM and experimental data. For PETN, we observe initiation occurring via different chemical pathways, depending on the shock direction. For PETN containing spherical voids, we observe enhanced sensitivity due to jetting, void collapse, and hotspot formation, with sensitivity increasing with void size. For ANFO, we examine the effect of reaction rates on shock direction, fuel oil fraction, and crystal/fuel oil/void microstructural arrangement. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Dept. of Energy's National Nuclear Security Admin. under contract DEAC0494AL85000.

Phenylethynyl Containing Polyarylene Ethers/Polyimides Resin Infiltration of Composites

NASA Technical Reports Server (NTRS)

Dunn, DeRome O.

1998-01-01

The following tasks were performed at NCA&TSU during the second year in performance of the grant. LaRC-LV-1 13 resin was synthesized at NCA&TSU. In order to perform the synthesis, glassware and needed apparatus were purchased with grant funds along with the appropriate monomers. It was found that the LaRC-LV-1 13 resin was easily synthesized by the NMP solvent/toluene imminization/distilled water precipitation process. However, in use this resin exhibited a bubbling/foaming behavior during cure that was detrimental leading to the production of composite panels having a high void content. Composite panels were fabricated using compression molding and resin transfer molding (RTM) techniques. Initial fiber volume determinations were computed at NCA&TSU along with NASA-Langley measured c-scans on the panels produced. The initial results indicated a unsatisfactory level of approximately 20% by volume of voids. Testing of uniaxial coupons in compression to failure also agreed with these results. The uniaxial coupons delaminated as the major mode of failure indicative of an unacceptably low level of resin and to much void content in the final composites produced. In discussions with Dr. Brian Jensen, it was suggested the void fraction needs to be reduced to at least 2% by volume for a useful composite. The panels produced used both resin synthesized at NASA-Langley and NCA&TSU. In reviewing our progress over the past year, it was noted that the resin as formulated by the current synthesis process bubbled at elevated temperature. This was especially observed in neat resin slugs cured at the recommended one, four and eight hour cure temperatures. Pressurized cures where then performed with pressures up to 200 psi and simultaneously the lowest eight hour cure temperatures. Although this procedure reduced the amount of bubbles to some extent in the neat resin slugs it did not completely eliminate them. The cure reaction appears to be very energetic even at the lowest recommended cure temperature. Currently, the pressurized cure apparatus developed at NCA&TSU is limited to 200 psi.

Motion-sensitized SPRITE measurements of hydrodynamic cavitation in fast pipe flow.

PubMed

Adair, Alexander; Mastikhin, Igor V; Newling, Benedict

2018-06-01

The pressure variations experienced by a liquid flowing through a pipe constriction can, in some cases, result in the formation of a bubble cloud (i.e., hydrodynamic cavitation). Due to the nature of the bubble cloud, it is ideally measured through the use of non-optical and non-invasive techniques; therefore, it is well-suited for study by magnetic resonance imaging. This paper demonstrates the use of Conical SPRITE (a 3D, centric-scan, pure phase-encoding pulse sequence) to acquire time-averaged void fraction and velocity information about hydrodynamic cavitation for water flowing through a pipe constriction. Copyright © 2018 Elsevier Inc. All rights reserved.

Buoyancy effects on smoldering combustion

NASA Technical Reports Server (NTRS)

Dosanjh, S.; Peterson, J.; Fernandez-Pello, A. C.; Pagni, P. J.

1985-01-01

The effect of buoyancy on the rate of spread of a concurrent smolder reaction through a porous combustible material is investigated theoretically and experimentally. In the experiments, buoyant forces are controlled by varying the density difference, and the smolder rate spread through porous alpha cellulose (0.83 void fraction) is measured as a function of the ambient air pressure. The smolder velocity is found to increase with the ambient pressure; extinction occurs when the buoyancy forces cannot overcome the drag forces, indicating that diffusion by itself cannot support the spread of a smolder reaction. Theoretical predictions are found to be in good qualitative agreement with the experimental results.

Electromigration Mechanism of Failure in Flip-Chip Solder Joints Based on Discrete Void Formation.

PubMed

Chang, Yuan-Wei; Cheng, Yin; Helfen, Lukas; Xu, Feng; Tian, Tian; Scheel, Mario; Di Michiel, Marco; Chen, Chih; Tu, King-Ning; Baumbach, Tilo

2017-12-20

In this investigation, SnAgCu and SN100C solders were electromigration (EM) tested, and the 3D laminography imaging technique was employed for in-situ observation of the microstructure evolution during testing. We found that discrete voids nucleate, grow and coalesce along the intermetallic compound/solder interface during EM testing. A systematic analysis yields quantitative information on the number, volume, and growth rate of voids, and the EM parameter of DZ*. We observe that fast intrinsic diffusion in SnAgCu solder causes void growth and coalescence, while in the SN100C solder this coalescence was not significant. To deduce the current density distribution, finite-element models were constructed on the basis of the laminography images. The discrete voids do not change the global current density distribution, but they induce the local current crowding around the voids: this local current crowding enhances the lateral void growth and coalescence. The correlation between the current density and the probability of void formation indicates that a threshold current density exists for the activation of void formation. There is a significant increase in the probability of void formation when the current density exceeds half of the maximum value.

Stimulation of hair cells with ultraviolet light

NASA Astrophysics Data System (ADS)

Azimzadeh, Julien B.; Fabella, Brian A.; Hudspeth, A. J.

2018-05-01

Hair bundles are specialized organelles that transduce mechanical inputs into electrical outputs. To activate hair cells, physiologists have resorted to mechanical methods of hair-bundle stimulation. Here we describe a new method of hair-bundle stimulation, irradiation with ultraviolet light. A hair bundle illuminated by ultraviolet light rapidly moves towards its tall edge, a motion typically associated with excitatory stimulation. The motion disappears upon tip-link rupture and is associated with the opening of mechanotransduction channels. Hair bundles can be induced to move sinusoidally with oscillatory modulation of the stimulation power. We discuss the implications of ultraviolet stimulation as a novel hair-bundle stimulus.

Morphology of the supercluster-void network in ΛCDM cosmology

NASA Astrophysics Data System (ADS)

Shandarin, Sergei F.; Sheth, Jatush V.; Sahni, Varun

2004-09-01

We report here the first systematic study of the supercluster-void network in the ΛCDM concordance cosmology in which voids and superclusters are treated on an equal footing. We study the dark matter density field in real space smoothed on a scale of 5 h-1 Mpc. Superclusters are defined as individual members of an overdense excursion set, and voids are defined as individual members of a complementary underdense excursion set at the same density threshold. We determine the geometric, topological and morphological properties of the cosmic web at a large set of density levels by computing Minkowski functionals for every supercluster and void using SURFGEN (described recently by Sheth et al.). The properties of the largest (percolating) supercluster and the complementary void are found to be very different from those of the individual superclusters and voids. In total, the individual superclusters occupy no more than about 5 per cent of the volume and contain no more than 20 per cent of the mass if the largest supercluster is excluded. Likewise, in total, individual voids occupy no more than 14 per cent of the volume and contain no more than 4 per cent of the mass if the largest void is excluded. Although superclusters are more massive and voids are more voluminous, the difference in maximum volumes is no greater than an order of magnitude. The genus value of individual superclusters can be ~5, while the genus of individual voids can reach ~50, implying a significant amount of substructure in superclusters and especially in voids. One of our main results is that large voids, as defined through the dark matter density field in real space, are distinctly non-spherical.

Void Growth and Coalescence in Dynamic Fracture of FCC and BCC Metals - Molecular Dynamics Study

NASA Astrophysics Data System (ADS)

Seppälä, Eira

2004-03-01

In dynamic fracture of ductile metals, the state of tension causes the nucleation of voids, typically from inclusions or grain boundary junctions, which grow and ultimately coalesce to form the fracture surface. Significant plastic deformation occurs in the process, including dislocations emitted to accommodate the growing voids. We have studied at the atomistic scale growth and coalescence processes of voids with concomitant dislocation formation. Classical molecular dynamics (MD) simulations of one and two pre-existing spherical voids initially a few nanometers in radius have been performed in single-crystal face-centered-cubic (FCC) and body-centered-cubic (BCC) lattices under dilational strain with high strain-rates. Million atom simulations of single void growth have been done to study the effect of stress triaxiality,^1 along with strain rate and lattice-structure dependence. An interesting prolate-to-oblate transition in the void shape in uniaxial expansion has been observed and quantitatively analyzed. The simulations also confirm that the plastic strain results directly from the void growth. Interaction and coalescence between two voids have been studied utilizing a parallel MD code in a seven million atom system. In particular, the movement of centers of the voids, linking of the voids, and the shape changes in vicinity of the other void are studied. Also the critical intervoid ligament distance after which the voids can be treated independently has been searched. ^1 E. T. Seppälä, J. Belak, and R. E. Rudd, cond-mat/0310541, submitted to Phys. Rev. B. Acknowledgment: This work was done in collaboration with Dr. James Belak and Dr. Robert E. Rudd, LLNL. It was performed under the auspices of the US Dept. of Energy at the Univ. of Cal./Lawrence Livermore National Laboratory under contract no. W-7405-Eng-48.

Formation and structural organization of the egg-sperm bundle of the scleractinian coral Montipora capitata

NASA Astrophysics Data System (ADS)

Padilla-Gamiño, J. L.; Weatherby, T. M.; Waller, R. G.; Gates, R. D.

2011-06-01

The majority of scleractinian corals are hermaphrodites that broadcast spawn their gametes separately or packaged as egg-sperm bundles during spawning events that are timed to the lunar cycle. The egg-sperm bundle is an efficient way of transporting gametes to the ocean surface where fertilization takes place, while minimizing sperm dilution and maximizing the opportunity for gamete encounters during a spawning event. To date, there are few studies that focus on the formation and structure of egg-sperm bundle. This study explores formation, ultrastructure, and longevity of the egg-sperm bundle in Montipora capitata, a major reef building coral in Hawai`i. Our results show that the egg-sperm bundle is formed by a mucus layer secreted by the oocytes. The sperm package is located at the center of each bundle, possibly reflecting the development of male and female gametes in different mesenteries. Once the egg-sperm bundle has reached the ocean surface, it breaks open within 10-35 min, depending on the environmental conditions (i.e., wind, water turbulence). Although the bundle has an ephemeral life span, the formation of an egg-sperm bundle is a fundamental part of the reproductive process that could be strongly influenced by climate change and deterioration of water quality (due to anthropogenic effects) and thus requires further investigation.

Robust Mapping of Incoherent Fiber-Optic Bundles

NASA Technical Reports Server (NTRS)

Roberts, Harry E.; Deason, Brent E.; DePlachett, Charles P.; Pilgrim, Robert A.; Sanford, Harold S.

2007-01-01

A method and apparatus for mapping between the positions of fibers at opposite ends of incoherent fiber-optic bundles have been invented to enable the use of such bundles to transmit images in visible or infrared light. The method is robust in the sense that it provides useful mapping even for a bundle that contains thousands of narrow, irregularly packed fibers, some of which may be defective. In a coherent fiber-optic bundle, the input and output ends of each fiber lie at identical positions in the input and output planes; therefore, the bundle can be used to transmit images without further modification. Unfortunately, the fabrication of coherent fiber-optic bundles is too labor-intensive and expensive for many applications. An incoherent fiber-optic bundle can be fabricated more easily and at lower cost, but it produces a scrambled image because the position of the end of each fiber in the input plane is generally different from the end of the same fiber in the output plane. However, the image transmitted by an incoherent fiber-optic bundle can be unscrambled (or, from a different perspective, decoded) by digital processing of the output image if the mapping between the input and output fiber-end positions is known. Thus, the present invention enables the use of relatively inexpensive fiber-optic bundles to transmit images.

High Temperature VARTM of Phenylethynyl Terminated Imides

NASA Technical Reports Server (NTRS)

Ghose, Sayata; Cano, Roberto J.; Watson, Kent A.; Britton, Sean M.; Jensen, Brian J.; Connell, John W.; Herring, Helen M.; Linberry, Quentin J.

2009-01-01

Depending on the part type and quantity, fabrication of composite structures using vacuum assisted resin transfer molding (VARTM) can be more affordable than conventional autoclave techniques. Recent efforts have focused on adapting VARTM for the fabrication of high temperature composites. Due to their low melt viscosity and long melt stability, certain phenylethynyl terminated imides (PETI) can be processed into composites using high temperature VARTM (HT-VARTM). However, one of the disadvantages of the current HT-VARTM resin systems has been the high porosity of the resultant composites. For aerospace applications, the desired void fraction of less than 2% has not yet been achieved. In the current study, two PETI resins, LaRC PETI-330 and LaRC PETI-8 have been used to make test specimens using HT-VARTM. The resins were infused into ten layers of IM7-6K carbon fiber 5-harness satin fabric at 260 C or 280 C and cured at temperature up to 371 C. Initial runs yielded composites with high void content, typically greater than 7% by weight. A thermogravimetric-mass spectroscopic study was conducted to determine the source of volatiles leading to high porosity. It was determined that under the thermal cycle used for laminate fabrication, the phenylethynyl endcap was undergoing degradation leading to volatile evolution. This finding was unexpected as high quality composite laminates have been fabricated under higher pressures using these resin systems. The amount of weight loss experienced during the thermal cycle was only about 1% by weight, but this leads to a significant amount of volatiles in a closed system. By modifying the thermal cycle used in laminate fabrication, the void content was significantly reduced (typically 3% or less). The results of this work are presented herein.

Methods of predicting aggregate voids : [technical summary].

DOT National Transportation Integrated Search

2013-03-01

Percent voids in combined aggregates vary significantly. Simplified methods of predicting aggregate voids were studied to determine the feasibility of a range of gradations using aggregates available in Kansas. : The 0.45 Power Curve Void Prediction ...

A compressed sensing approach for resolution improvement in fiber-bundle based endomicroscopy

NASA Astrophysics Data System (ADS)

Dumas, John P.; Lodhi, Muhammad A.; Bajwa, Waheed U.; Pierce, Mark C.

2018-02-01

Endomicroscopy techniques such as confocal, multi-photon, and wide-field imaging have all been demonstrated using coherent fiber-optic imaging bundles. While the narrow diameter and flexibility of fiber bundles is clinically advantageous, the number of resolvable points in an image is conventionally limited to the number of individual fibers within the bundle. We are introducing concepts from the compressed sensing (CS) field to fiber bundle based endomicroscopy, to allow images to be recovered with more resolvable points than fibers in the bundle. The distal face of the fiber bundle is treated as a low-resolution sensor with circular pixels (fibers) arranged in a hexagonal lattice. A spatial light modulator is located conjugate to the object and distal face, applying multiple high resolution masks to the intermediate image prior to propagation through the bundle. We acquire images of the proximal end of the bundle for each (known) mask pattern and then apply CS inversion algorithms to recover a single high-resolution image. We first developed a theoretical forward model describing image formation through the mask and fiber bundle. We then imaged objects through a rigid fiber bundle and demonstrate that our CS endomicroscopy architecture can recover intra-fiber details while filling inter-fiber regions with interpolation. Finally, we examine the relationship between reconstruction quality and the ratio of the number of mask elements to the number of fiber cores, finding that images could be generated with approximately 28,900 resolvable points for a 1,000 fiber region in our platform.

Understanding nurses' views on a pressure ulcer prevention care bundle: a first step towards successful implementation.

PubMed

Chaboyer, Wendy; Gillespie, Brigid M

2014-12-01

To explore nurses' views of the barriers and facilitators to the use of a newly devised patient-centred pressure ulcer prevention care bundle. Given pressure ulcer prevention strategies are not implemented consistently, the use of a pressure ulcer care bundle may improve implementation given bundles generally assist in standardising care. A quality improvement project was undertaken after a pressure ulcer prevention care bundle was developed and pilot-tested. Short, conversational interviews with nurse explored their views of a patient-centred pressure ulcer care bundle. Interviews were audio-taped and transcribed. Inductive content analysis was used to analyse the transcripts. A total of 20 nurses were interviewed. Five categories with corresponding subcategories emerged from the analysis. They were increasing awareness of pressure ulcer prevention, prompting pressure ulcer prevention activities, promoting active patient participation, barriers to using a pressure ulcer prevention care bundle and enabling integration of the pressure ulcer prevention care bundle into routine practice. Benefits of using a patient-centred pressure ulcer prevention care bundle may include prompting patients and staff to implement prevention strategies and promote active patient participation in care. The success of the care bundle relied on both patients' willingness to participate and nurses' willingness to incorporate it into their routine work. A patient-centred pressure ulcer prevention care bundle may facilitate more consistent implementation of pressure ulcer prevention strategies and active patient participation in care. © 2014 John Wiley & Sons Ltd.

Impact of posterior urethral diameter/external urethral sphincter diameter as a new tool to predict detrusor pressure in the voiding phase.

PubMed

Kon, Masafumi; Mitsui, Takahiko; Kitta, Takeya; Moriya, Kimihiko; Shinohara, Nobuo; Takeda, Masayuki; Nonomura, Katsuya

2018-02-01

We measured posterior urethra diameter (PUD) and external urethral sphincter diameter (EUSD), which can also be measured by voiding cystourethrography (VCUG) and investigated the relationship between PUD/EUSD and detrusor pressure (Pdet) during voiding by videourodynamics (VUDS). Sixty-three children, who were 3 years old or less and underwent VUDS, were enrolled in the present study. We measured PUD and EUSD in addition to detrusor pressure at the time of the widest EUS during voiding (Pdet-voiding) by VUDS, and PUD/EUSD was investigated compared to Pdet-voiding. Seventy-eight VUDS were performed in 63 patients, and the median age at VUDS was 10.2 months. These studies revealed a significant correlation between PUD/EUSD and Pdet-voiding (r = 0.641, p < 0.001). However, a significant correlation was not observed between PUD/EUSD and age (r = 0.180). We defined Pdet-voiding of more than 80 cmH 2 O as a high voiding pressure, and a PUD/EUSD of 2.4 was a good predictor for the cutoff value for high voiding pressure. Pdet-voiding was significantly higher in children with a PUD/EUSD of ≥ 2.4 (p < 0.001). In 19 children who had neurological diseases, a significant correlation was found between PUD/EUSD and Pdet-voiding (r = 0.842, p < 0.001), and a PUD/EUSD of 2.4 was a useful cutoff value for high voiding pressure. PUD/EUSD is a valuable tool to predict high voiding pressure in pediatric patients. A PUD/EUSD of ≥ 2.4 in VCUG indicates the need to perform more invasive tests, such as VUDS, in pediatric patients aged 3 and under with neuropathic diseases.

Flow void of cerebrospinal fluid in idiopathic normal pressure hydrocephalus of the elderly: can it predict outcome after shunting?

PubMed

Krauss, J K; Regel, J P; Vach, W; Jüngling, F D; Droste, D W; Wakhloo, A K

1997-01-01

We investigate the predictive value of cerebrospinal fluid (CSF) flow void on outcome after shunting in a prospective series of patients with idiopathic normal pressure hydrocephalus (NPH). The degree and extension of CSF flow void were examined on T2-weighted magnetic resonance imaging scans of 37 elderly patients with idiopathic NPH who underwent subsequent shunting. The degree of flow void was assessed in comparison with the signal of large cerebral arteries. The extension was evaluated via the calculation of sum scores for the occurrence of flow void in different locations of the ventricular system. Those parameters were not considered in the decision to perform shunting. CSF flow void in the aqueduct and the adjacent third and fourth ventricles of the 37 patients with idiopathic NPH was compared with that of 37 age-matched control patients. CSF flow void scores in patients with idiopathic NPH were investigated for correlations between postoperative outcome scores and ventricular width indices. No difference was found between the occurrence of aqueductal CSF flow void in patients with idiopathic NPH and the control group. A significant difference, however, was noted for the extension of the CSF flow void, which was greater in the NPH group. Postoperative improvement was found in 33 of 37 patients with idiopathic NPH at a mean follow-up of 15.6 months. Only small, statistically not significant correlations were found between CSF flow void and postoperative outcome. Flow void sum scores, however, correlated significantly with ventricular width indices. The degree and extension of CSF flow void on T2-weighted magnetic resonance imaging scans have little predictive value for outcome after shunting in patients with idiopathic NPH. The greater extension of the CSF flow void in patients with NPH is most likely related to increased ventricular width. It is not useful to consider CSF flow void findings on conventional magnetic resonance imaging scans in making the decision to offer shunting in patients with idiopathic NPH.

On the observability of coupled dark energy with cosmic voids

NASA Astrophysics Data System (ADS)

Sutter, P. M.; Carlesi, Edoardo; Wandelt, Benjamin D.; Knebe, Alexander

2015-01-01

Taking N-body simulations with volumes and particle densities tuned to match the sloan digital sky survey DR7 spectroscopic main sample, we assess the ability of current void catalogues to distinguish a model of coupled dark matter-dark energy from Λ cold dark matter cosmology using properties of cosmic voids. Identifying voids with the VIDE toolkit, we find no statistically significant differences in the ellipticities, but find that coupling produces a population of significantly larger voids, possibly explaining the recent result of Tavasoli et al. In addition, we use the universal density profile of Hamaus et al. to quantify the relationship between coupling and density profile shape, finding that the coupling produces broader, shallower, undercompensated profiles for large voids by thinning the walls between adjacent medium-scale voids. We find that these differences are potentially measurable with existing void catalogues once effects from survey geometries and peculiar velocities are taken into account.

Mechanical Overstimulation of Hair Bundles: Suppression and Recovery of Active Motility

PubMed Central

Kao, Albert; Meenderink, Sebastiaan W. F.; Bozovic, Dolores

2013-01-01

We explore the effects of high-amplitude mechanical stimuli on hair bundles of the bullfrog sacculus. Under in vitro conditions, these bundles exhibit spontaneous limit cycle oscillations. Prolonged deflection exerted two effects. First, it induced an offset in the position of the bundle. Recovery to the original position displayed two distinct time scales, suggesting the existence of two adaptive mechanisms. Second, the stimulus suppressed spontaneous oscillations, indicating a change in the hair bundle’s dynamic state. After cessation of the stimulus, active bundle motility recovered with time. Both effects were dependent on the duration of the imposed stimulus. External calcium concentration also affected the recovery to the oscillatory state. Our results indicate that both offset in the bundle position and calcium concentration control the dynamic state of the bundle. PMID:23505461

Influence of knee flexion angle and transverse drill angle on creation of femoral tunnels in double-bundle anterior cruciate ligament reconstruction using the transportal technique: Three-dimensional computed tomography simulation analysis.

PubMed

Choi, Chong Hyuk; Kim, Sung-Jae; Chun, Yong-Min; Kim, Sung-Hwan; Lee, Su-Keon; Eom, Nam-Kyu; Jung, Min

2018-01-01

The purpose of this study was to find appropriate flexion angle and transverse drill angle for optimal femoral tunnels of anteromedial (AM) bundle and posterolateral (PL) bundle in double-bundle ACL reconstruction using transportal technique. Thirty three-dimensional knee models were reconstructed. Knee flexion angles were altered from 100° to 130° at intervals of 10°. Maximum transverse drill angle (MTA), MTA minus 10° and 20° were set up. Twelve different tunnels were determined by four flexion angles and three transverse drill angles for each bundle. Tunnel length, wall breakage, inter-tunnel communication and graft-bending angle were assessed. Mean tunnel length of AM bundle was >30mm at 120° and 130° of flexion in all transverse drill angles. Mean tunnel length of PL bundle was >30mm during every condition. There were ≥1 cases of wall breakage except at 120° and 130° of flexion with MTA for AM bundle. There was no case of wall breakage for PL bundle. Considering inter-tunnel gap of >2mm without communication and obtuse graft-bending angle, 120° of flexion and MTA could be recommended as optimal condition for femoral tunnels of AM and PL bundles. Flexion angle and transverse drill angle had combined effect on femoral tunnel in double-bundle ACL reconstruction using transportal technique. Achieving flexion angle of 120° and transverse drill angle close to the medial femoral condyle could be recommended as optimal condition for femoral tunnels of AM and PL bundles to avoid insufficient tunnel length, wall breakage, inter-tunnel communication and acute graft-bending angle. Copyright © 2017 Elsevier B.V. All rights reserved.

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

Hughes, Michael John; McConnaughhay, Johnie Franklin

A combustor includes a tube bundle that extends radially across at least a portion of the combustor. The tube bundle includes an upstream surface axially separated from a downstream surface, and a plurality of tubes extend from the upstream surface through the downstream surface to provide fluid communication through the tube bundle. A barrier extends radially inside the tube bundle between the upstream and downstream surfaces, and a baffle extends axially inside the tube bundle between the upstream surface and the barrier.

Rayleigh-wave diffractions due to a void in the layered half space

USGS Publications Warehouse

Xia, J.; Xu, Y.; Miller, R.D.; Nyquist, Jonathan E.

2006-01-01

Void detection is challenging due to the complexity of near-surface materials and the limited resolution of geophysical methods. Although multichannel, high-frequency, surface-wave techniques can provide reliable shear (S)-wave velocities in different geological settings, they are not suitable for detecting voids directly based on anomalies of the S-wave velocity because of limitations on the resolution of S-wave velocity profiles inverted from surface-wave phase velocities. Xia et al. (2006a) derived a Rayleigh-wave diffraction traveltime equation due to a void in the homogeneous half space. Encouraging results of directly detecting a void from Rayleigh-wave diffractions were presented (Xia et al., 2006a). In this paper we used four two-dimensional square voids in the layered half space to demonstrate the feasibility of detecting a void with Rayleigh-wave diffractions. Rayleigh-wave diffractions were recognizable for all these models after removing direct surface waves by F-K filtering. We evaluate the feasibility of applying the Rayleigh-wave diffraction traveltime equation to a void in the layered earth model. The phase velocity of diffracted Rayleigh waves is predominately determined by surrounding materials of a void. The modeling results demonstrate that the Rayleigh-wave diffraction traveltime equation due to a void in the homogeneous half space can be applied to the case of a void in the layered half space. In practice, only two diffraction times are necessary to define the depth to the top of a void and the average velocity of diffracted Rayleigh waves. ?? 2005 Society of Exploration Geophysicists.

LOG-NORMAL DISTRIBUTION OF COSMIC VOIDS IN SIMULATIONS AND MOCKS

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

Russell, E.; Pycke, J.-R., E-mail: er111@nyu.edu, E-mail: jrp15@nyu.edu

2017-01-20

Following up on previous studies, we complete here a full analysis of the void size distributions of the Cosmic Void Catalog based on three different simulation and mock catalogs: dark matter (DM), haloes, and galaxies. Based on this analysis, we attempt to answer two questions: Is a three-parameter log-normal distribution a good candidate to satisfy the void size distributions obtained from different types of environments? Is there a direct relation between the shape parameters of the void size distribution and the environmental effects? In an attempt to answer these questions, we find here that all void size distributions of thesemore » data samples satisfy the three-parameter log-normal distribution whether the environment is dominated by DM, haloes, or galaxies. In addition, the shape parameters of the three-parameter log-normal void size distribution seem highly affected by environment, particularly existing substructures. Therefore, we show two quantitative relations given by linear equations between the skewness and the maximum tree depth, and between the variance of the void size distribution and the maximum tree depth, directly from the simulated data. In addition to this, we find that the percentage of voids with nonzero central density in the data sets has a critical importance. If the number of voids with nonzero central density reaches ≥3.84% in a simulation/mock sample, then a second population is observed in the void size distributions. This second population emerges as a second peak in the log-normal void size distribution at larger radius.« less

Sampling system and method

DOEpatents

Decker, David L; Lyles, Brad F; Purcell, Richard G; Hershey, Ronald Lee

2014-05-20

An apparatus and method for supporting a tubing bundle during installation or removal. The apparatus includes a clamp for securing the tubing bundle to an external wireline. The method includes deploying the tubing bundle and wireline together, The tubing bundle is periodically secured to the wireline using a clamp.

Fiber-bundle-basis sparse reconstruction for high resolution wide-field microendoscopy.

PubMed

Mekhail, Simon Peter; Abudukeyoumu, Nilupaer; Ward, Jonathan; Arbuthnott, Gordon; Chormaic, Síle Nic

2018-04-01

In order to observe deep regions of the brain, we propose the use of a fiber bundle for microendoscopy. Fiber bundles allow for the excitation and collection of fluorescence as well as wide field imaging while remaining largely impervious to image distortions brought on by bending. Furthermore, their thin diameter, from 200-500 µ m, means their impact on living tissue, though not absent, is minimal. Although wide field imaging with a bundle allows for a high temporal resolution since no scanning is involved, the largest criticism of bundle imaging is the drastically lowered spatial resolution. In this paper, we make use of sparsity in the object being imaged to up sample the low resolution images from the fiber bundle with compressive sensing. We take each image in a single shot by using a measurement basis dictated by the quasi-crystalline arrangement of the bundle's cores. We find that this technique allows us to increase the resolution of a typical image taken through a fiber bundle.

Equilibrium polyelectrolyte bundles with different multivalent counterion concentrations

NASA Astrophysics Data System (ADS)

Sayar, Mehmet; Holm, Christian

2010-09-01

We present the results of molecular-dynamics simulations on the salt concentration dependence of the formation of polyelectrolyte bundles in thermodynamic equilibrium. Extending our results on salt-free systems we investigate here deficiency or excess of trivalent counterions in solution. Our results reveal that the trivalent counterion concentration significantly alters the bundle size and size distribution. The onset of bundle formation takes place at earlier Bjerrum length values with increasing trivalent counterion concentration. For the cases of 80%, 95%, and 100% charge compensation via trivalent counterions, the net charge of the bundles decreases with increasing size. We suggest that competition among two different mechanisms, counterion condensation and merger of bundles, leads to a nonmonotonic change in line-charge density with increasing Bjerrum length. The investigated case of having an abundance of trivalent counterions by 200% prohibits such a behavior. In this case, we find that the difference in effective line-charge density of different size bundles diminishes. In fact, the system displays an isoelectric point, where all bundles become charge neutral.

Identification of dynamin as a septin-binding protein.

PubMed

Maimaitiyiming, Maowulan; Kobayashi, Yuumi; Kumanogoh, Haruko; Nakamura, Shun; Morita, Mitsuhiro; Maekawa, Shohei

2013-02-08

Lipid rafts (detergent-resistant low-density membrane microdomain: DRM) are signal-transducing membrane platforms. In a previous study, we showed maturation-dependent localization of septin in the DRM fraction of rat brain. Mammalian septin is composed with 13-14 isoforms and these isoforms assemble to form rod-shaped hetero-oligomeric complexes. End-to-end polymerization of these complexes results in the formation of higher order structures such as filamentous sheets or bundles of filaments that restrict the fluid-like diffusion of the membrane proteins and lipids. Considering the function of septin as the membrane scaffold, elucidation of the molecular interaction of septin in DRM could be a breakthrough to understand another role of lipid rafts. In order to identify septin-binding proteins in DRM, solubilization and fractionation of septin from DRM was attempted. Several proteins were co-fractionated with septin and LC-MS/MS analysis identified one of these proteins as dynamin and Western blotting using anti-dynamin confirmed this result. Immunoprecipitation of septin11 in a crude supernatant showed co-precipitation of dynamin and dynamin fraction prepared from brain contained several septin isoforms. Within bacterially expressed septin isoforms, septin5 and septin11 bound dynamin but septin9 did not. These results suggest that some septin isoforms participate in the dynamin-related membrane dynamics. Copyright © 2012 Elsevier Ireland Ltd. All rights reserved.

Morphological statistics of the cosmic web

NASA Astrophysics Data System (ADS)

Shandarin, Sergei F.

2004-07-01

We report the first systematic study of the supercluster-void network in the ΛCDM concordance cosmology treating voids and superclusters on an equal footing. We study the dark matter density field in real space smoothed with the Ls = 5 h[minus sign]1Mpc Gaussian window. Superclusters and voids are defined as individual members of over-dense and under-dense excursion sets respectively. We determine the morphological properties of the cosmic web at a large number of dark matter density levels by computing Minkowski functionals for every supercluster and void. At the adopted smoothing scale individual superclusters totally occupy no more than about 5% of the total volume and contain no more than 20% of mass if the largest supercluster is excluded. Likewise, individual voids totally occupy no more than 14% of volume and contain no more than 4% of mass if the largest void is excluded. The genus of individual superclusters can be ˜ 5 while the genus of individual voids reaches ˜ 55, implying significant amount of substructure in superclusters and especially in voids. Large voids are typically distinctly non-spherical.

Fluid intake and voiding; habits and health knowledge in a young, healthy population

PubMed Central

Das, Rebekah N; Grimmer-Somers, Karen A

2012-01-01

Objectives Health professionals commonly advise patients with incontinence and other lower urinary tract symptoms about modifiable contributing factors such as drinking and voiding habits. Poor drinking and voiding habits may begin early in life, before symptoms emerge. However, little is known about the habits and knowledge young people have regarding healthy drinking and voiding behaviors. This research aimed to assess the habits and health knowledge of young people regarding fluid intake and voiding. Methods A questionnaire was used to assess the drinking and voiding behaviors of first year university students and their knowledge about healthy fluid intake and voiding. Results The average daily fluid intake was >2 L/day for both genders. Poor drinking and voiding habits (such as high consumption of caffeinated drinks and alcohol, or nocturia) were common. Widely reported myths about the benefits of a high fluid intake were commonly believed. Conclusion More informed public education regarding healthy fluid intake, and drinking and voiding habits, is required as part of the effort to reduce the development of lower urinary tract symptoms, including incontinence. PMID:24199175

Fluid intake and voiding; habits and health knowledge in a young, healthy population.

PubMed

Das, Rebekah N; Grimmer-Somers, Karen A

2012-01-01

Health professionals commonly advise patients with incontinence and other lower urinary tract symptoms about modifiable contributing factors such as drinking and voiding habits. Poor drinking and voiding habits may begin early in life, before symptoms emerge. However, little is known about the habits and knowledge young people have regarding healthy drinking and voiding behaviors. This research aimed to assess the habits and health knowledge of young people regarding fluid intake and voiding. A questionnaire was used to assess the drinking and voiding behaviors of first year university students and their knowledge about healthy fluid intake and voiding. The average daily fluid intake was >2 L/day for both genders. Poor drinking and voiding habits (such as high consumption of caffeinated drinks and alcohol, or nocturia) were common. Widely reported myths about the benefits of a high fluid intake were commonly believed. More informed public education regarding healthy fluid intake, and drinking and voiding habits, is required as part of the effort to reduce the development of lower urinary tract symptoms, including incontinence.

Overhead electric power transmission line jumpering system for bundles of five or more subconductors

DOEpatents

Winkelman, Paul F.

1982-01-01

Jumpering of electric power transmission lines at a dead end tower. Two transmission line conductor bundles each contain five or more spaced apart subconductors (5) arranged in the shape of a cylinder having a circular cross section. The ends of each bundle of subconductors are attached with insulators to a dead end tower (1). Jumpering allows the electric current to flow between the two bundles of subconductors using jumper buses, internal jumper conductors, and external jumper conductors. One or more current collecting jumper buses (37) are located inside each bundle of subconductors with each jumper bus being attached to the end of a subconductor. Small-diameter internal jumper conductors (33) are located in the inherently electrically shielded area inside each bundle of subconductors with each subconductor (except ones having an attached jumper bus) having one internal jumper conductor connected between that subconductor's end and a jumper bus. Large-diameter external jumper conductors (9) are located outside each bundle of subconductors with one or more external jumper conductors being connected between the jumper buses in one bundle of subconductors and the jumper buses in the other bundle.

Comparison of computational results of the SABRE LMFBR pin bundle blockage code with data from well-instrumented out-of-pile test bundles (THORS bundles 3A and 5A)

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

Dearing, J.F.

The Subchannel Analysis of Blockages in Reactor Elements (SABRE) computer code, developed by the United Kingdom Atomic Energy Authority, is currently the only practical tool available for performing detailed analyses of velocity and temperature fields in the recirculating flow regions downstream of blockages in liquid-metal fast breeder reactor (LMFBR) pin bundles. SABRE is a subchannel analysis code; that is, it accurately represents the complex geometry of nuclear fuel pins arranged on a triangular lattice. The results of SABRE computational models are compared here with temperature data from two out-of-pile 19-pin test bundles from the Thermal-Hydraulic Out-of-Reactor Safety (THORS) Facility atmore » Oak Ridge National Laboratory. One of these bundles has a small central flow blockage (bundle 3A), while the other has a large edge blockage (bundle 5A). Values that give best agreement with experiment for the empirical thermal mixing correlation factor, FMIX, in SABRE are suggested. These values of FMIX are Reynolds-number dependent, however, indicating that the coded turbulent mixing correlation is not appropriate for wire-wrap pin bundles.« less

Characterization of midrib vascular bundles of selected medicinal species in Rubiaceae

NASA Astrophysics Data System (ADS)

Nurul-Syahirah, M.; Noraini, T.; Latiff, A.

2016-11-01

An anatomical study was carried out on mature leaves of five selected medicinal species of Rubiaceae from Peninsular Malaysia. The chosen medicinal species were Aidia densiflora, Aidia racemosa, Chasallia chartacea, Hedyotis auricularia and Ixora grandifolia. The objective of this study is to determine the taxonomic value of midrib anatomical characteristics. Leaves samples were collected from Taman Paku Pakis, Universiti Kebangsaan Malaysia, Bangi, Selangor and Kledang Saiong Forest Reserve, Perak, Malaysia. Leaves samples then were fixed in spirit and acetic acid (3:1), the midrib parts then were sectioned using sliding microtome, cleared using Clorox, stained in Safranin and Alcian blue, mounted in Euparal and were observed under light microscope. Findings in this study have shown all species have collateral bundles. The midrib vascular bundles characteristics that can be used as tool to differentiate between species or genus are vascular bundles system (opened or closed), shape and arrangement of main vascular bundles, presence of both additional and medullary vascular bundles, position of additional vascular bundles, shape of medullary vascular bundles, presence of sclerenchyma cells ensheathed the vascular bundles. As a conclusion, midrib anatomical characteristics can be used to identify and discriminate medicinal plants species studied in the Rubiaceae.

Analysis of a space emergency ammonia dump using the FLOW-NET two-phase flow program

NASA Technical Reports Server (NTRS)

Navickas, J.; Rivard, W. C.

1992-01-01

Venting of cryogenic and non-cryogenic fluids to a vacuum or a very low pressure will take place in many space-based systems that are currently being designed. This may cause liquid freezing either internally within the flow circuit or on external spacecraft surfaces. Typical ammonia flow circuits were investigated to determine the effect of the geometric configuration and initial temperature, pressure, and void fraction on the freezing characteristics of the system. The analysis was conducted also to investigate the ranges of applicability of the FLOW-NET program. It was shown that a typical system can be vented to very low liquid fractions before freezing occurs. However, very small restrictions in the flow circuit can hasten the inception of freezing. The FLOW-NET program provided solutions over broad ranges of system conditions, such as venting of an ammonia tank, initially completely filled with liquid, through a series of contracting and expanding line cross sections to near-vacuum conditions.

Influence of grid resolution, parcel size and drag models on bubbling fluidized bed simulation

DOE PAGES

Lu, Liqiang; Konan, Arthur; Benyahia, Sofiane

2017-06-02

Here in this paper, a bubbling fluidized bed is simulated with different numerical parameters, such as grid resolution and parcel size. We examined also the effect of using two homogeneous drag correlations and a heterogeneous drag based on the energy minimization method. A fast and reliable bubble detection algorithm was developed based on the connected component labeling. The radial and axial solids volume fraction profiles are compared with experiment data and previous simulation results. These results show a significant influence of drag models on bubble size and voidage distributions and a much less dependence on numerical parameters. With a heterogeneousmore » drag model that accounts for sub-scale structures, the void fraction in the bubbling fluidized bed can be well captured with coarse grid and large computation parcels. Refining the CFD grid and reducing the parcel size can improve the simulation results but with a large increase in computation cost.« less

Open-cell glass crystalline porous material

DOEpatents

Anshits, Alexander G.; Sharonova, Olga M.; Vereshchagina, Tatiana A.; Zykova, Irina D.; Revenko, Yurii A.; Tretyakov, Alexander A.; Aloy, Albert S.; Lubtsev, Rem I.; Knecht, Dieter A.; Tranter, Troy J.; Macheret, Yevgeny

2002-01-01

An open-cell glass crystalline porous material made from hollow microspheres which are cenospheres obtained from fly ash, having an open-cell porosity of up to 90 vol. % is produced. The cenospheres are separated into fractions based on one or more of grain size, density, magnetic or non-magnetic, and perforated or non-perforated. Selected fractions are molded and agglomerated by sintering with a binder at a temperature below the softening temperature, or without a binder at a temperature about, or above, the softening temperature but below the temperature of liquidity. The porous material produced has an apparent density of 0.3-0.6 g/cm.sup.3, a compressive strength in the range of 1.2-3.5 MPa, and two types of openings: through-flow wall pores in the cenospheres of 0.1-30 micrometers, and interglobular voids between the cenospheres of 20-100 micrometers. The porous material of the invention has properties useful as porous matrices for immobilization of liquid radioactive waste, heat-resistant traps and filters, supports for catalysts, adsorbents and ion-exchangers.

Open-cell glass crystalline porous material

DOEpatents

Anshits, Alexander G.; Sharonova, Olga M.; Vereshchagina, Tatiana A.; Zykova, Irina D.; Revenko, Yurii A.; Tretyakov, Alexander A.; Aloy, Albert S.; Lubtsev, Rem I.; Knecht, Dieter A.; Tranter, Troy J.; Macheret, Yevgeny

2003-12-23

An open-cell glass crystalline porous material made from hollow microspheres which are cenospheres obtained from fly ash, having an open-cell porosity of up to 90 vol. % is produced. The cenospheres are separated into fractions based on one or more of grain size, density, magnetic or non-magnetic, and perforated or non-perforated. Selected fractions are molded and agglomerated by sintering with a binder at a temperature below the softening temperature, or without a binder at a temperature about, or above, the softening temperature but below the temperature of liquidity. The porous material produced has an apparent density of 0.3-0.6 g/cm.sup.3, a compressive strength in the range of 1.2-3.5 MPa, and two types of openings: through-flow wall pores in the cenospheres of 0.1-30 micrometers, and interglobular voids between the cenospheres of 20-100 micrometers. The porous material of the invention has properties useful as porous matrices for immobilization of liquid radioactive waste, heat-resistant traps and filters, supports for catalysts, adsorbents and ion-exchangers.

MRI contrast agent concentration and tumor interstitial fluid pressure.

PubMed

Liu, L J; Schlesinger, M

2016-10-07

The present work describes the relationship between tumor interstitial fluid pressure (TIFP) and the concentration of contrast agent for dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI). We predict the spatial distribution of TIFP based on that of contrast agent concentration. We also discuss the cases for estimating tumor interstitial volume fraction (void fraction or porosity of porous medium), ve, and contrast volume transfer constant, K(trans), by measuring the ratio of contrast agent concentration in tissue to that in plasma. A linear fluid velocity distribution may reflect a quadratic function of TIFP distribution and lead to a practical method for TIFP estimation. To calculate TIFP, the parameters or variables should preferably be measured along the direction of the linear fluid velocity (this is in the same direction as the gray value distribution of the image, which is also linear). This method may simplify the calculation for estimating TIFP. Crown Copyright © 2016. Published by Elsevier Ltd. All rights reserved.

Reliability of scanning laser acoustic microscopy for detecting internal voids in structural ceramics

NASA Technical Reports Server (NTRS)

Roth, D. J.; Baaklini, G. Y.

1986-01-01

The reliability of 100 MHz scanning laser acoustic microscopy (SLAM) for detecting internal voids in sintered specimens of silicon nitride and silicon carbide was evaluated. The specimens contained artificially implanted voids and were positioned at depths ranging up to 2 mm below the specimen surface. Detection probability of 0.90 at a 0.95 confidence level was determined as a function of material, void diameter, and void depth. The statistical results presented for void detectability indicate some of the strengths and limitations of SLAM as a nondestructive evaluation technique for structural ceramics.

Mechanisms for Ductile Rupture - FY16 ESC Progress Report

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

Boyce, Brad L.; Carroll, Jay D.; Noell, Phillip

2017-01-01

Ductile rupture in metals is generally a multi-step process of void nucleation, growth, and coalescence. Particle decohesion and particle fracture are generally invoked as the primary microstructural mechanisms for room-temperature void nucleation. However, because high-purity materials also fail by void nucleation and coalescence, other microstructural features must also act as sites for void nucleation. Early studies of void initiation in high-purity materials, which included post-mortem fracture surface characterization using scanning electron microscopy (SEM) and high-voltage electron microscopy (HVEM) and in-situ HVEM observations of fracture, established the presence of dislocation cell walls as void initiation sites in high-purity materials. Direct experimentalmore » evidence for this contention was obtained during in-situ HVEM tensile tests of Be single crystals. Voids between 0.2 and 1 μm long appeared suddenly along dislocation cell walls during tensile straining. However, subsequent attempts to replicate these results in other materials, particularly α -Fe single crystals, were unsuccessful because of the small size of the dislocation cells, and these remain the only published in-situ HVEM observations of void nucleation at dislocation cell walls in the absence of a growing macrocrack. Despite this challenge, other approaches to studying void nucleation in high-purity metals also indicate that dislocation cell walls are nucleation sites for voids.« less

Evidence for two populations of hair bundles in the sea anemone, Nematostella vectensis.

PubMed

Menard, Shelcie S; Watson, Glen M

2017-06-01

Cytochalasin D (CD) was employed to disrupt F-actin within stereocilia of anemone hair bundles. CD treatment decreases the abundance of hair bundles (by 85%) while significantly impairing predation. The remaining hair bundles are 'CD-resistant.' Surprisingly, the morphology and F-actin content of resistant hair bundles are comparable to those of untreated controls. However, the resistant hair bundles fail to respond normally to the N-acetylated sugar, NANA, by elongating. Instead, they remain at resting length. Immediately after CD treatment, when only CD-resistant hair bundles are present, nematocyst discharge is normal into targets touched to tentacles in the absence of vibrations (i.e., baseline) but fails to increase normally in the presence of nearby vibrations at 56Hz, a key frequency. After CD treatment, the abundance of hair bundles recovers to control levels within three hours. At 2h after CD treatment, when CD-resistant and CD-sensitive hair bundles are both present, but a full-recovery is not yet complete, somewhat enhanced discharge of nematocysts occurs into targets touched to tentacles in the presence of nearby vibrations at 56Hz (at least as compared to the response of CD-treated animals to contact with test probes in the absence of vibrations). Additionally, at 2h after CD-treatment, prey capture recovers to normal. Thus, two populations of hair bundles may be present on tentacles of sea anemones: those that are CD-resistant and those that are CD-sensitive. The functions of these hair bundles may be distinct. Copyright © 2017 Elsevier Inc. All rights reserved.

Method of simulating spherical voids for use as a radiographic standard

DOEpatents

Foster, Billy E.

1977-01-01

A method of simulating small spherical voids in metal is provided. The method entails drilling or etching a hemispherical depression of the desired diameter in each of two sections of metal, the sections being flat plates or different diameter cylinders. A carbon bead is placed in one of the hemispherical voids and is used as a guide to align the second hemispherical void with that in the other plate. The plates are then bonded together with epoxy, tape or similar material and the two aligned hemispheres form a sphere within the material; thus a void of a known size has been created. This type of void can be used to simulate a pore in the development of radiographic techniques of actual voids (porosity) in welds and serve as a radiographic standard.

Translating Pressure Ulcer Prevention Into Intensive Care Nursing Practice: Overlaying a Care Bundle Approach With a Model for Research Implementation.

PubMed

Tayyib, Nahla; Coyer, Fiona

This article reports on the development and implementation process used to integrate a care bundle approach (a pressure ulcer [PU] prevention bundle to improve patients' skin integrity in intensive care) and the Ottawa Model of Research Use (OMRU). The PU prevention care bundle demonstrated significant reduction in PU incidence, with the OMRU model providing a consolidated framework for the implementation of bundled evidence in an effective and consistent manner into daily clinical nursing practice.

Voids characteristics of asphaltic concrete containing coconut shell

NASA Astrophysics Data System (ADS)

Ezree Abdullah, Mohd; Hannani Madzaili, Amirah; Putra Jaya, Ramadhansyah; Yaacob, Haryati; Hassan, Norhidayah Abdul; Nazri, Fadzli Mohamed

2017-07-01

Asphalt durability is often linked to the thickness of the asphalt coating on the aggregate particles. In order to have adequate film thickness in asphaltic concrete, there must be sufficient space between the aggregate particles in the compacted pavement. This void space is referred to as voids in total mix (VTM), voids with filled bitumen (VFB), and voids in mineral aggregate (VMA). Hence, this study investigates the performance of coconut shell (CS) as coarse aggregate replacement on voids characteristics of asphaltic concrete. Four CS were used as coarse aggregates replacement in asphalt mixture namely 0%, 10%, 20%, 30%, and 40% (by weight volume). The voids properties of asphalt mixture were determined based on Marshall Mix design test. Test results show that VTM and VMA values were decrease with the increasing bitumen content where VFB was increase with increasing bitumen content. Furthermore, increasing the percentage of coconut shell in asphalt mixture was found to increases the voids value up to a peak level and then decreases with further additions of CS.

Localized Statistics for DW-MRI Fiber Bundle Segmentation

PubMed Central

Lankton, Shawn; Melonakos, John; Malcolm, James; Dambreville, Samuel; Tannenbaum, Allen

2013-01-01

We describe a method for segmenting neural fiber bundles in diffusion-weighted magnetic resonance images (DWMRI). As these bundles traverse the brain to connect regions, their local orientation of diffusion changes drastically, hence a constant global model is inaccurate. We propose a method to compute localized statistics on orientation information and use it to drive a variational active contour segmentation that accurately models the non-homogeneous orientation information present along the bundle. Initialized from a single fiber path, the proposed method proceeds to capture the entire bundle. We demonstrate results using the technique to segment the cingulum bundle and describe several extensions making the technique applicable to a wide range of tissues. PMID:23652079

Field Emission Study of Carbon Nanotubes: High Current Density from Nanotube Bundle Arrays

NASA Technical Reports Server (NTRS)

Bronikowski, Micheal J.; Manohara, Harish M.; Siegel, Peter H.; Hunt, Brian D.

2004-01-01

We have investigated the field emission behavior of lithographically patterned bundles of multiwalled carbon nanotubes arranged in a variety of array geometries. Such arrays of nanotube bundles are found to perform significantly better in field emission than arrays of isolated nanotubes or dense, continuous mats of nanotubes, with the field emission performance depending on the bundle diameter and inter-bundle spacing. Arrays of 2-micrometers diameter nanotube bundles spaced 5 micrometers apart (edge-to-edge spacing) produced the largest emission densities, routinely giving 1.5 to 1.8 A/cm(sup 2) at approximately 4 V/micrometer electric field, and greater than 6 A/cm(sup 2) at 20 V/micrometers.

National Partnership for Maternal Safety: Consensus Bundle on Safe Reduction of Primary Cesarean Births-Supporting Intended Vaginal Births.

PubMed

Lagrew, David C; Low, Lisa Kane; Brennan, Rita; Corry, Maureen P; Edmonds, Joyce K; Gilpin, Brian G; Frost, Jennifer; Pinger, Whitney; Reisner, Dale P; Jaffer, Sara

2018-03-01

Cesarean births and associated morbidity and mortality have reached near epidemic proportions. The National Partnership for Maternal Safety under the guidance of the Council on Patient Safety in Women's Health Care responded by developing a patient safety bundle to reduce the number of primary cesarean births. Safety bundles outline critical practices to implement in every maternity unit. This National Partnership for Maternity Safety bundle, as with other bundles, is organized into four domains: Readiness, Recognition and Prevention, Response, and Reporting and Systems Learning. Bundle components may be adapted to individual facilities, but standardization within an institution is advised. Evidence-based resources and recommendations are provided to assist implementation.

Matrix remodeling between cells and cellular interactions with collagen bundle

NASA Astrophysics Data System (ADS)

Kim, Jihan; Sun, Bo

When cells are surrounded by complex environment, they continuously probe and interact with it by applying cellular traction forces. As cells apply traction forces, they can sense rigidity of their local environment and remodel the matrix microstructure simultaneously. Previous study shows that single human carcinoma cell (MDA-MB-231) remodeled its surrounding extracellular matrix (ECM) and the matrix remodeling was reversible. In this study we examined the matrix microstructure between cells and cellular interaction between them using quantitative confocal microscopy. The result shows that the matrix microstructure is the most significantly remodeled between cells consisting of aligned, and densified collagen fibers (collagen bundle)., the result shows that collagen bundle is irreversible and significantly change micromechanics of ECM around the bundle. We further examined cellular interaction with collagen bundle by analyzing dynamics of actin and talin formation along with the direction of bundle. Lastly, we analyzed dynamics of cellular protrusion and migrating direction of cells along the bundle.

Anatomic Double-Bundle Anterior Cruciate Ligament Reconstruction With a Free Quadriceps Tendon Autograft.

PubMed

Caterev, Sergiu; Nistor, Dan Viorel; Todor, Adrian

2016-10-01

Anatomic double-bundle anterior cruciate ligament (ACL) reconstruction aims to restore the 2 functional bundles of the ACL in an attempt to better reproduce the native biomechanics of the injured knee and promote long-term knee health. However, this concept is not fully accepted and is not performed on a standard basis. In addition, the superiority of this technique over the conventional single-bundle technique has been questioned, especially the long-term clinical results. One of the down sides of the double-bundle reconstruction is the complexity of the procedure, with increased risks, operative time, and costs compared with the single-bundle procedure. Also, the revision procedure, if necessary, is more challenging. We propose a technique that has some advantages over the traditional double-bundle procedure, using a single femoral tunnel, 2 tibial tunnels, and a free quadriceps tendon autograft.

Synchronization of Spontaneous Active Motility of Hair Cell Bundles

PubMed Central

Zhang, Tracy-Ying; Ji, Seung; Bozovic, Dolores

2015-01-01

Hair cells of the inner ear exhibit an active process, believed to be crucial for achieving the sensitivity of auditory and vestibular detection. One of the manifestations of the active process is the occurrence of spontaneous hair bundle oscillations in vitro. Hair bundles are coupled by overlying membranes in vivo; hence, explaining the potential role of innate bundle motility in the generation of otoacoustic emissions requires an understanding of the effects of coupling on the active bundle dynamics. We used microbeads to connect small groups of hair cell bundles, using in vitro preparations that maintain their innate oscillations. Our experiments demonstrate robust synchronization of spontaneous oscillations, with either 1:1 or multi-mode phase-locking. The frequency of synchronized oscillation was found to be near the mean of the innate frequencies of individual bundles. Coupling also led to an improved regularity of entrained oscillations, demonstrated by an increase in the quality factor. PMID:26540409

Fluid outlet at the bottom of an in situ oil shale retort

DOEpatents

Hutchins, Ned M.

1984-01-01

Formation is excavated from within the boundaries of a retort site in formation containing oil shale for forming at least one retort level void extending horizontally across the retort site, leaving at least one remaining zone of unfragmented formation within the retort site. A production level drift is excavated below the retort level void, leaving a lower zone of unfragmented formation between the retort level void and the production level drift. A plurality of raises are formed between the production level drift and the retort level void for providing product withdrawal passages distributed generally uniformly across the horizontal cross section of the retort level void. The product withdrawal passages are backfilled with a permeable mass of particles. Explosive placed within the remaining zone of unfragmented formation above the retort level void is detonated for explosively expanding formation within the retort site toward at least the retort level void for forming a fragmented permeable mass of formation particles containing oil shale within the boundaries of the retort site. During retorting operations products of retorting are conducted from the fragmented mass in the retort through the product withdrawal passages to the production level void. The products are withdrawn from the production level void.

Method for explosive expansion toward horizontal free faces for forming an in situ oil shale retort

DOEpatents

Ricketts, Thomas E.

1980-01-01

Formation is excavated from within a retort site in formation containing oil shale for forming a plurality of vertically spaced apart voids extending horizontally across different levels of the retort site, leaving a separate zone of unfragmented formation between each pair of adjacent voids. Explosive is placed in each zone, and such explosive is detonated in a single round for forming an in situ retort containing a fragmented permeable mass of formation particles containing oil shale. The same amount of formation is explosively expanded upwardly and downwardly toward each void. A horizontal void excavated at a production level has a smaller horizontal cross-sectional area than a void excavated at a lower level of the retort site immediately above the production level void. Explosive in a first group of vertical blast holes is detonated for explosively expanding formation downwardly toward the lower void, and explosive in a second group of vertical blast holes is detonated in the same round for explosively expanding formation upwardly toward the lower void and downwardly toward the production level void for forming a generally T-shaped bottom of the fragmented mass.

Autonomous selection of PDE inpainting techniques vs. exemplar inpainting techniques for void fill of high resolution digital surface models

NASA Astrophysics Data System (ADS)

Rahmes, Mark; Yates, J. Harlan; Allen, Josef DeVaughn; Kelley, Patrick

2007-04-01

High resolution Digital Surface Models (DSMs) may contain voids (missing data) due to the data collection process used to obtain the DSM, inclement weather conditions, low returns, system errors/malfunctions for various collection platforms, and other factors. DSM voids are also created during bare earth processing where culture and vegetation features have been extracted. The Harris LiteSite TM Toolkit handles these void regions in DSMs via two novel techniques. We use both partial differential equations (PDEs) and exemplar based inpainting techniques to accurately fill voids. The PDE technique has its origin in fluid dynamics and heat equations (a particular subset of partial differential equations). The exemplar technique has its origin in texture analysis and image processing. Each technique is optimally suited for different input conditions. The PDE technique works better where the area to be void filled does not have disproportionately high frequency data in the neighborhood of the boundary of the void. Conversely, the exemplar based technique is better suited for high frequency areas. Both are autonomous with respect to detecting and repairing void regions. We describe a cohesive autonomous solution that dynamically selects the best technique as each void is being repaired.

Exploring Differential Bundle Functioning in Mathematics by Gender: The Effect of Hierarchical Modelling

ERIC Educational Resources Information Center

Ong, Yoke Mooi; Williams, Julian; Lamprianou, Iasonas

2013-01-01

Researchers interested in exploring substantive group differences are increasingly attending to bundles of items (or testlets): the aim is to understand how gender differences, for instance, are explained by differential performances on different types or bundles of items, hence differential bundle functioning (DBF). Some previous work has…

Universal fiber-optic C.I.E. colorimeter

DOEpatents

Kronberg, James W.

1992-01-01

Apparatus for color measurements according to the C.I.E. system comprises a first fiber optic cable for receiving and linearizing light from a light source, a lens system for spectrally displaying the linearized light and focusing the light on one end of a trifurcated fiber optic assembly that integrates and separates the light according to the three C.I.E. tristimulus functions. The separated light is received by three photodiodes and electronically evaluated to determine the magnitude of the light corresponding to the tristimulus functions. The fiber optic assembly is made by forming, at one end, a bundle of optic fibers to match the contours of one of the tristimulus functions, encapsulating that bundle, adding a second bundle that, together with the first bundle, will match the contours of the first plus one other tristimulus function, encapsulating that second bundle, then adding a third bundle which together with the first and second bundles, has contours matching the sum of all three tristimulus functions. At the other end of the assembly the three bundles are separated and aligned with their respective photodiodes.

Implementing a Daily Maintenance Care Bundle to Prevent Central Line-Associated Bloodstream Infections in Pediatric Oncology Patients.

PubMed

Duffy, Elizabeth A; Rodgers, Cheryl C; Shever, Leah L; Hockenberry, Marilyn J

2015-01-01

Eliminating central line-associated bloodstream infection (CLABSI) is a national priority. Central venous catheter (CVC) care bundles are composed of a series of interventions that, when used together, are effective in preventing CLABSI. A CVC daily maintenance care bundle includes procedural guidelines for hygiene, dressing changes, and access as well as specific timeframes. Failure to complete one of the components of the care bundle predisposes the patient to a bloodstream infection. A nurse-led multidisciplinary team implemented and, for six months, sustained a daily maintenance care bundle for pediatric oncology patients. This quality improvement project focused on nursing staffs' implementation of the daily maintenance care bundle and the sustainment of the intervention. The project used a pre-post program design to evaluate outcomes of CVC daily maintenance care bundle compliancy and CLABSI. A statistically significant increase between the pre- and post-assessments of the compliance was noted with the CVC daily maintenance care bundle. CLABSI infection rates decreased during the intervention. Strategies to implement practice change and promote sustainability are discussed. © 2015 by Association of Pediatric Hematology/Oncology Nurses.

National Partnership for Maternal Safety: Consensus Bundle on Severe Hypertension During Pregnancy and the Postpartum Period.

PubMed

Bernstein, Peter S; Martin, James N; Barton, John R; Shields, Laurence E; Druzin, Maurice L; Scavone, Barbara M; Frost, Jennifer; Morton, Christine H; Ruhl, Catherine; Slager, Joan; Tsigas, Eleni Z; Jaffer, Sara; Menard, M Kathryn

2017-08-01

Complications arising from hypertensive disorders of pregnancy are among the leading causes of preventable severe maternal morbidity and mortality. Timely and appropriate treatment has the potential to significantly reduce hypertension-related complications. To assist health care providers in achieving this goal, this patient safety bundle provides guidance to coordinate and standardize the care provided to women with severe hypertension during pregnancy and the postpartum period. This is one of several patient safety bundles developed by multidisciplinary work groups of the National Partnership for Maternal Safety under the guidance of the Council on Patient Safety in Women's Health Care. These safety bundles outline critical clinical practices that should be implemented in every maternity care setting. Similar to other bundles that have been developed and promoted by the Partnership, the hypertension safety bundle is organized into four domains: Readiness, Recognition and Prevention, Response, and Reporting and Systems Learning. Although the bundle components may be adapted to meet the resources available in individual facilities, standardization within an institution is strongly encouraged. This commentary provides information to assist with bundle implementation.

Microtubule bundling plays a role in ethylene-mediated cortical microtubule reorientation in etiolated Arabidopsis hypocotyls.

PubMed

Ma, Qianqian; Sun, Jingbo; Mao, Tonglin

2016-05-15

The gaseous hormone ethylene is known to regulate plant growth under etiolated conditions (the 'triple response'). Although organization of cortical microtubules is essential for cell elongation, the underlying mechanisms that regulate microtubule organization by hormone signaling, including ethylene, are ambiguous. In the present study, we demonstrate that ethylene signaling participates in regulation of cortical microtubule reorientation. In particular, regulation of microtubule bundling is important for this process in etiolated hypocotyls. Time-lapse analysis indicated that selective stabilization of microtubule-bundling structures formed in various arrays is related to ethylene-mediated microtubule orientation. Bundling events and bundle growth lifetimes were significantly increased in oblique and longitudinal arrays, but decreased in transverse arrays in wild-type cells in response to ethylene. However, the effects of ethylene on microtubule bundling were partially suppressed in a microtubule-bundling protein WDL5 knockout mutant (wdl5-1). This study suggests that modulation of microtubule bundles that have formed in certain orientations plays a role in reorienting microtubule arrays in response to ethylene-mediated etiolated hypocotyl cell elongation. © 2016. Published by The Company of Biologists Ltd.

Abnormal Q waves in right sided chest leads provoked by onset of right bundle-branch block in patients with anteroseptal infarction.

PubMed Central

Rosenbaum, M B; Girotti, L A; Lázzari, J O; Halpern, M S; Elizari, M V

1982-01-01

In five cases of anteroseptal myocardial infarction complicated by intermittent right bundle-branch block, the onset of right bundle-branch block provoked the appearance of abnormal Q waves in leads V1 and V2, whereas a small initial R wave was present in the same leads during normal conduction. The intermittency of the conduction disturbance indicated that the Q waves were "right bundle-branch block dependent". It was also apparent that right bundle-branch block shifted the electrical location of the infarct towards the right, and made it look much larger. Right bundle-branch block dependent Q waves may arise during the acute stage of an anterior infarct suggesting, fallaciously, that an acute extension has occurred, or during the chronic stage, leading to the erroneous supposition that a new infarct had developed. The abnormal Q waves anteroseptal infarction complicated by fixed right bundle-branch block, though obviously related to the infarct, may be dependent on the right bundle-branch block. PMID:7059400

Actin-binding proteins sensitively mediate F-actin bundle stiffness

NASA Astrophysics Data System (ADS)

Claessens, Mireille M. A. E.; Bathe, Mark; Frey, Erwin; Bausch, Andreas R.

2006-09-01

Bundles of filamentous actin (F-actin) form primary structural components of a broad range of cytoskeletal processes including filopodia, sensory hair cell bristles and microvilli. Actin-binding proteins (ABPs) allow the cell to tailor the dimensions and mechanical properties of the bundles to suit specific biological functions. Therefore, it is important to obtain quantitative knowledge on the effect of ABPs on the mechanical properties of F-actin bundles. Here we measure the bending stiffness of F-actin bundles crosslinked by three ABPs that are ubiquitous in eukaryotes. We observe distinct regimes of bundle bending stiffness that differ by orders of magnitude depending on ABP type, concentration and bundle size. The behaviour observed experimentally is reproduced quantitatively by a molecular-based mechanical model in which ABP shearing competes with F-actin extension/compression. Our results shed new light on the biomechanical function of ABPs and demonstrate how single-molecule properties determine mesoscopic behaviour. The bending mechanics of F-actin fibre bundles are general and have implications for cytoskeletal mechanics and for the rational design of functional materials.

Correlation of air void parameters obtained by linear traverse with freeze-thaw durability.

DOT National Transportation Integrated Search

1983-01-01

The correlations obtainable from comparisons of the various air void parameters with the freeze-thaw durability of concretes are listed. It is shown that correlations are no better when only small voids are used than when the total void content is us...

Negative hair-bundle stiffness betrays a mechanism for mechanical amplification by the hair cell.

PubMed

Martin, P; Mehta, A D; Hudspeth, A J

2000-10-24

Hearing and balance rely on the ability of hair cells in the inner ear to sense miniscule mechanical stimuli. In each cell, sound or acceleration deflects the mechanosensitive hair bundle, a tuft of rigid stereocilia protruding from the cell's apical surface. By altering the tension in gating springs linked to mechanically sensitive transduction channels, this deflection changes the channels' open probability and elicits an electrical response. To detect weak stimuli despite energy losses caused by viscous dissipation, a hair cell can use active hair-bundle movement to amplify its mechanical inputs. This amplificatory process also yields spontaneous bundle oscillations. Using a displacement-clamp system to measure the mechanical properties of individual hair bundles from the bullfrog's ear, we found that an oscillatory bundle displays negative slope stiffness at the heart of its region of mechanosensitivity. Offsetting the hair bundle's position activates an adaptation process that shifts the region of negative stiffness along the displacement axis. Modeling indicates that the interplay between negative bundle stiffness and the motor responsible for mechanical adaptation produces bundle oscillation similar to that observed. Just as the negative resistance of electrically excitable cells and of tunnel diodes can be embedded in a biasing circuit to amplify electrical signals, negative stiffness can be harnessed to amplify mechanical stimuli in the ear.

Monoubiquitination Inhibits the Actin Bundling Activity of Fascin*

PubMed Central

Lin, Shengchen; Lu, Shuang; Mulaj, Mentor; Fang, Bin; Keeley, Tyler; Wan, Lixin; Hao, Jihui; Muschol, Martin; Sun, Jianwei; Yang, Shengyu

2016-01-01

Fascin is an actin bundling protein that cross-links individual actin filaments into straight, compact, and stiff bundles, which are crucial for the formation of filopodia, stereocillia, and other finger-like membrane protrusions. The dysregulation of fascin has been implicated in cancer metastasis, hearing loss, and blindness. Here we identified monoubiquitination as a novel mechanism that regulates fascin bundling activity and dynamics. The monoubiquitination sites were identified to be Lys247 and Lys250, two residues located in a positive charge patch at the actin binding site 2 of fascin. Using a chemical ubiquitination method, we synthesized chemically monoubiquitinated fascin and determined the effects of monoubiquitination on fascin bundling activity and dynamics. Our data demonstrated that monoubiquitination decreased the fascin bundling EC50, delayed the initiation of bundle assembly, and accelerated the disassembly of existing bundles. By analyzing the electrostatic properties on the solvent-accessible surface of fascin, we proposed that monoubiquitination introduced steric hindrance to interfere with the interaction between actin filaments and the positively charged patch at actin binding site 2. We also identified Smurf1 as a E3 ligase regulating the monoubiquitination of fascin. Our findings revealed a previously unidentified regulatory mechanism for fascin, which will have important implications for the understanding of actin bundle regulation under physiological and pathological conditions. PMID:27879315

Accuracy of Shack-Hartmann wavefront sensor using a coherent wound fibre image bundle

NASA Astrophysics Data System (ADS)

Zheng, Jessica R.; Goodwin, Michael; Lawrence, Jon

2018-03-01

Shack-Hartmannwavefront sensors using wound fibre image bundles are desired for multi-object adaptive optical systems to provide large multiplex positioned by Starbugs. The use of a large-sized wound fibre image bundle provides the flexibility to use more sub-apertures wavefront sensor for ELTs. These compact wavefront sensors take advantage of large focal surfaces such as the Giant Magellan Telescope. The focus of this paper is to study the wound fibre image bundle structure defects effect on the centroid measurement accuracy of a Shack-Hartmann wavefront sensor. We use the first moment centroid method to estimate the centroid of a focused Gaussian beam sampled by a simulated bundle. Spot estimation accuracy with wound fibre image bundle and its structure impact on wavefront measurement accuracy statistics are addressed. Our results show that when the measurement signal-to-noise ratio is high, the centroid measurement accuracy is dominated by the wound fibre image bundle structure, e.g. tile angle and gap spacing. For the measurement with low signal-to-noise ratio, its accuracy is influenced by the read noise of the detector instead of the wound fibre image bundle structure defects. We demonstrate this both with simulation and experimentally. We provide a statistical model of the centroid and wavefront error of a wound fibre image bundle found through experiment.

Cosmic void clumps

NASA Astrophysics Data System (ADS)

Lares, M.; Luparello, H. E.; Garcia Lambas, D.; Ruiz, A. N.; Ceccarelli, L.; Paz, D.

2017-10-01

Cosmic voids are of great interest given their relation to the large scale distribution of mass and the way they trace cosmic flows shaping the cosmic web. Here we show that the distribution of voids has, in consonance with the distribution of mass, a characteristic scale at which void pairs are preferentially located. We identify clumps of voids with similar environments and use them to define second order underdensities. Also, we characterize its properties and analyze its impact on the cosmic microwave background.

Spatial confinement of active microtubule networks induces large-scale rotational cytoplasmic flow

PubMed Central

Suzuki, Kazuya; Miyazaki, Makito; Takagi, Jun; Itabashi, Takeshi; Ishiwata, Shin’ichi

2017-01-01

Collective behaviors of motile units through hydrodynamic interactions induce directed fluid flow on a larger length scale than individual units. In cells, active cytoskeletal systems composed of polar filaments and molecular motors drive fluid flow, a process known as cytoplasmic streaming. The motor-driven elongation of microtubule bundles generates turbulent-like flow in purified systems; however, it remains unclear whether and how microtubule bundles induce large-scale directed flow like the cytoplasmic streaming observed in cells. Here, we adopted Xenopus egg extracts as a model system of the cytoplasm and found that microtubule bundle elongation induces directed flow for which the length scale and timescale depend on the existence of geometrical constraints. At the lower activity of dynein, kinesins bundle and slide microtubules, organizing extensile microtubule bundles. In bulk extracts, the extensile bundles connected with each other and formed a random network, and vortex flows with a length scale comparable to the bundle length continually emerged and persisted for 1 min at multiple places. When the extracts were encapsulated in droplets, the extensile bundles pushed the droplet boundary. This pushing force initiated symmetry breaking of the randomly oriented bundle network, leading to bundles aligning into a rotating vortex structure. This vortex induced rotational cytoplasmic flows on the length scale and timescale that were 10- to 100-fold longer than the vortex flows emerging in bulk extracts. Our results suggest that microtubule systems use not only hydrodynamic interactions but also mechanical interactions to induce large-scale temporally stable cytoplasmic flow. PMID:28265076

Reducing hospital-acquired pressure ulcers using bundle methodology in pediatric and neonatal patients receiving extracorporeal membrane oxygenation therapy: An integrative review and call to action.

PubMed

Courtwright, Suzanne E; Mastro, Kari A; Preuster, Christa; Dardashti, Navid; McGill, Sandra; Madelon, Myrlene; Johnson, Donna

2017-10-01

This review focuses on identifying (1) evidence of the effectiveness of care bundle methodology to reduce hospital-acquired pressure ulcers (HAPUs) in pediatric and neonatal patients receiving extracorporeal membrane oxygenation (ECMO) therapy and (2) barriers to implementing HAPU care bundles in this at-risk population. An integrative review was conducted and reported following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. A search of the scientific literature was performed. Studies included were published between January 2011 and February 2016. A total of seven articles met inclusion criteria. Data were extracted from each published article and analyzed to identify common themes, specifically bundle methodology and barriers to implementing HAPU bundles, in this population. There is limited research on effectiveness of care bundle methodology in reducing HAPUs in children, and no research specific to its effectiveness in pediatric or neonatal ECMO patients. No research was identified studying barriers to implementation of HAPU care bundles in this population. Nurses are well poised to test innovative strategies to prevent HAPUs. Nurses should consider implementing and testing bundle methodology to reduce HAPU in this at-risk population, and conduct research to identify any barriers to implementing this strategy. There is literature to support the use of nurses as unit-based skin care champions to facilitate teamwork and reliable use of the bundle, both critical components to the success of bundle methodology. © 2017 Wiley Periodicals, Inc.

Gravitational Effects on Closed-Cellular-Foam Microstructure

NASA Technical Reports Server (NTRS)

Noever, David A.; Cronise, Raymond J.; Wessling, Francis C.; McMannus, Samuel P.; Mathews, John; Patel, Darayas

1996-01-01

Polyurethane foam has been produced in low gravity for the first time. The cause and distribution of different void or pore sizes are elucidated from direct comparison of unit-gravity and low-gravity samples. Low gravity is found to increase the pore roundness by 17% and reduce the void size by 50%. The standard deviation for pores becomes narrower (a more homogeneous foam is produced) in low gravity. Both a Gaussian and a Weibull model fail to describe the statistical distribution of void areas, and hence the governing dynamics do not combine small voids in either a uniform or a dependent fashion to make larger voids. Instead, the void areas follow an exponential law, which effectively randomizes the production of void sizes in a nondependent fashion consistent more with single nucleation than with multiple or combining events.

Sustained Reduction of Ventilator-Associated Pneumonia Rates Using Real-Time Course Correction With a Ventilator Bundle Compliance Dashboard.

PubMed

Talbot, Thomas R; Carr, Devin; Parmley, C Lee; Martin, Barbara J; Gray, Barbara; Ambrose, Anna; Starmer, Jack

2015-11-01

The effectiveness of practice bundles on reducing ventilator-associated pneumonia (VAP) has been questioned. To implement a comprehensive program that included a real-time bundle compliance dashboard to improve compliance and reduce ventilator-associated complications. DESIGN Before-and-after quasi-experimental study with interrupted time-series analysis. SETTING Academic medical center. In 2007 a comprehensive institutional ventilator bundle program was developed. To assess bundle compliance and stimulate instant course correction of noncompliant parameters, a real-time computerized dashboard was developed. Program impact in 6 adult intensive care units (ICUs) was assessed. Bundle compliance was noted as an overall cumulative bundle adherence assessment, reflecting the percentage of time all elements were concurrently in compliance for all patients. The VAP rate in all ICUs combined decreased from 19.5 to 9.2 VAPs per 1,000 ventilator-days following program implementation (P<.001). Bundle compliance significantly increased (Z100 score of 23% in August 2007 to 83% in June 2011 [P<.001]). The implementation resulted in a significant monthly decrease in the overall ICU VAP rate of 3.28/1,000 ventilator-days (95% CI, 2.64-3.92/1,000 ventilator-days). Following the intervention, the VAP rate decreased significantly at a rate of 0.20/1,000 ventilator-days per month (95% CI, 0.14-0.30/1,000 ventilator-days per month). Among all adult ICUs combined, improved bundle compliance was moderately correlated with monthly VAP rate reductions (Pearson correlation coefficient, -0.32). A prevention program using a real-time bundle adherence dashboard was associated with significant sustained decreases in VAP rates and an increase in bundle compliance among adult ICU patients.

High-resolution imaging of the retinal nerve fiber layer in normal eyes using adaptive optics scanning laser ophthalmoscopy.

PubMed

Takayama, Kohei; Ooto, Sotaro; Hangai, Masanori; Arakawa, Naoko; Oshima, Susumu; Shibata, Naohisa; Hanebuchi, Masaaki; Inoue, Takashi; Yoshimura, Nagahisa

2012-01-01

To conduct high-resolution imaging of the retinal nerve fiber layer (RNFL) in normal eyes using adaptive optics scanning laser ophthalmoscopy (AO-SLO). AO-SLO images were obtained in 20 normal eyes at multiple locations in the posterior polar area and a circular path with a 3-4-mm diameter around the optic disc. For each eye, images focused on the RNFL were recorded and a montage of AO-SLO images was created. AO-SLO images for all eyes showed many hyperreflective bundles in the RNFL. Hyperreflective bundles above or below the fovea were seen in an arch from the temporal periphery on either side of a horizontal dividing line to the optic disc. The dark lines among the hyperreflective bundles were narrower around the optic disc compared with those in the temporal raphe. The hyperreflective bundles corresponded with the direction of the striations on SLO red-free images. The resolution and contrast of the bundles were much higher in AO-SLO images than in red-free fundus photography or SLO red-free images. The mean hyperreflective bundle width around the optic disc had a double-humped shape; the bundles at the temporal and nasal sides of the optic disc were narrower than those above and below the optic disc (P<0.001). RNFL thickness obtained by optical coherence tomography correlated with the hyperreflective bundle widths on AO-SLO (P<0.001) AO-SLO revealed hyperreflective bundles and dark lines in the RNFL, believed to be retinal nerve fiber bundles and Müller cell septa. The widths of the nerve fiber bundles appear to be proportional to the RNFL thickness at equivalent distances from the optic disc.

High-resolution imaging of retinal nerve fiber bundles in glaucoma using adaptive optics scanning laser ophthalmoscopy.

PubMed

Takayama, Kohei; Ooto, Sotaro; Hangai, Masanori; Ueda-Arakawa, Naoko; Yoshida, Sachiko; Akagi, Tadamichi; Ikeda, Hanako Ohashi; Nonaka, Atsushi; Hanebuchi, Masaaki; Inoue, Takashi; Yoshimura, Nagahisa

2013-05-01

To detect pathologic changes in retinal nerve fiber bundles in glaucomatous eyes seen on images obtained by adaptive optics (AO) scanning laser ophthalmoscopy (AO SLO). Prospective cross-sectional study. Twenty-eight eyes of 28 patients with open-angle glaucoma and 21 normal eyes of 21 volunteer subjects underwent a full ophthalmologic examination, visual field testing using a Humphrey Field Analyzer, fundus photography, red-free SLO imaging, spectral-domain optical coherence tomography, and imaging with an original prototype AO SLO system. The AO SLO images showed many hyperreflective bundles suggesting nerve fiber bundles. In glaucomatous eyes, the nerve fiber bundles were narrower than in normal eyes, and the nerve fiber layer thickness was correlated with the nerve fiber bundle widths on AO SLO (P < .001). In the nerve fiber layer defect area on fundus photography, the nerve fiber bundles on AO SLO were narrower compared with those in normal eyes (P < .001). At 60 degrees on the inferior temporal side of the optic disc, the nerve fiber bundle width was significantly lower, even in areas without nerve fiber layer defect, in eyes with glaucomatous eyes compared with normal eyes (P = .026). The mean deviations of each cluster in visual field testing were correlated with the corresponding nerve fiber bundle widths (P = .017). AO SLO images showed reduced nerve fiber bundle widths both in clinically normal and abnormal areas of glaucomatous eyes, and these abnormalities were associated with visual field defects, suggesting that AO SLO may be useful for detecting early nerve fiber bundle abnormalities associated with loss of visual function. Copyright © 2013 Elsevier Inc. All rights reserved.

The Santiago-Harvard-Edinburgh-Durham void comparison - I. SHEDding light on chameleon gravity tests

NASA Astrophysics Data System (ADS)

Cautun, Marius; Paillas, Enrique; Cai, Yan-Chuan; Bose, Sownak; Armijo, Joaquin; Li, Baojiu; Padilla, Nelson

2018-05-01

We present a systematic comparison of several existing and new void-finding algorithms, focusing on their potential power to test a particular class of modified gravity models - chameleon f(R) gravity. These models deviate from standard general relativity (GR) more strongly in low-density regions and thus voids are a promising venue to test them. We use halo occupation distribution (HOD) prescriptions to populate haloes with galaxies, and tune the HOD parameters such that the galaxy two-point correlation functions are the same in both f(R) and GR models. We identify both three-dimensional (3D) voids and two-dimensional (2D) underdensities in the plane of the sky to find the same void abundance and void galaxy number density profiles across all models, which suggests that they do not contain much information beyond galaxy clustering. However, the underlying void dark matter density profiles are significantly different, with f(R) voids being more underdense than GR ones, which leads to f(R) voids having a larger tangential shear signal than their GR analogues. We investigate the potential of each void finder to test f(R) models with near-future lensing surveys such as EUCLID and LSST. The 2D voids have the largest power to probe f(R) gravity, with an LSST analysis of tunnel (which is a new type of 2D underdensity introduced here) lensing distinguishing at 80 and 11σ (statistical error) f(R) models with parameters, |fR0| = 10-5 and 10-6, from GR.

Implementation of a post-cardiac arrest care bundle including therapeutic hypothermia and hemodynamic optimization in comatose patients with return of spontaneous circulation after out-of-hospital cardiac arrest: a feasibility study.

PubMed

Walters, Elizabeth Lea; Morawski, Kyle; Dorotta, Ihab; Ramsingh, Davinder; Lumen, Kelly; Bland, David; Clem, Kathleen; Nguyen, H Bryant

2011-04-01

Patients who present to the emergency department (ED) with return of spontaneous circulation after cardiac arrest generally have poor outcomes. Guidelines for treatment can be complicated and difficult to implement. This study examined the feasibility of implementing a care bundle including therapeutic hypothermia (TH) and early hemodynamic optimization for comatose patients with return of spontaneous circulation after out-of-hospital cardiac arrest. The study included patients over a 2-year period in the ED and intensive care unit of an academic tertiary-care medical center. The first year (prebundle) provided a historical control, followed by a prospective observational period of bundle implementation during the second year. The bundle elements included (a) TH initiated; (b) central venous pressure/central venous oxygen saturation monitoring in 2 h; (c) target temperature in 4 h; (d) central venous pressure greater than 12 mmHg in 6 h; (e) MAP greater than 65 mmHg in 6 h; (f) central venous oxygen saturation greater than 70% in 6 h; (g) TH maintained for 24 h; and (h) decreasing lactate in 24 h. Fifty-five patients were enrolled, 26 patients in the prebundle phase and 29 patients in the bundle phase. Seventy-seven percent of bundle elements were completed during the bundle phase. In-hospital mortality in bundle compared with prebundle patients was 55.2% vs. 69.2% (P = 0.29). In the bundle patients, those patients who received all elements of the care bundle had mortality 33.3% compared with 60.9% in those receiving some of the bundle elements (P = 0.22). Bundle patients tended to achieve good neurologic outcome compared with prebundle patients, Cerebral Performance Category 1 or 2 in 31 vs. 12% patients, respectively (P = 0.08). Our study demonstrated that a post-cardiac arrest care bundle that incorporates TH and early hemodynamic optimization can be implemented in the ED and intensive care unit collaboratively and can achieve similar clinical benefits compared with those observed in previous clinical trials.

Dynamic left ventricular dyssynchrony and severe mitral regurgitation caused by exercise: should we go beyond the guidelines?

PubMed

Laflamme, Emilie; Philippon, François; O'Connor, Kim; Sarrazin, Jean-François; Auffret, Vincent; Chauvette, Vincent; Dubois, Michelle; Voisine, Pierre; Bergeron, Sébastien; Sénéchal, Mario

2018-01-01

Guidelines for cardiac resynchronization therapy (CRT) have been established, but there may be a subgroup of patients not identified in these guidelines who may benefit from this therapy. We report a patient with a dynamic left ventricular dyssynchrony and severe mitral regurgitation caused by exercise successfully treated with CRT. Exercise testing should be considered in patients with left ventricular ejection fraction <35% and QRS <130 ms with severe heart failure symptoms that are unexplained by rest echocardiography evaluation in order to rule out ischemia and/or dynamic left ventricular dyssynchrony. In the presence of exercise-induced left ventricular bundle branch block, the implantation of CRT should be contemplated.

Turkish and Native English Academic Writers' Use of Lexical Bundles

ERIC Educational Resources Information Center

Öztürk, Yusuf; Köse, Gül Durmusoglu

2016-01-01

Lexical bundles such as "on the other hand" and "as a result of" are extremely common and important in academic discourse. The appropriate use of lexical bundles typical of a specific academic discipline is important for writers and the absence of such bundles may not sound fluent and native-like. Recent studies (e.g. Adel…

Bundles over nearly-Kahler homogeneous spaces in heterotic string theory

NASA Astrophysics Data System (ADS)

Klaput, Michael; Lukas, Andre; Matti, Cyril

2011-09-01

We construct heterotic vacua based on six-dimensional nearly-Kahler homogeneous manifolds and non-trivial vector bundles thereon. Our examples are based on three specific group coset spaces. It is shown how to construct line bundles over these spaces, compute their properties and build up vector bundles consistent with supersymmetry and anomaly cancelation. It turns out that the most interesting coset is SU(3)/U(1)2. This space supports a large number of vector bundles which lead to consistent heterotic vacua, some of them with three chiral families.

Composition of the C6+ Fraction of Natural Gas by Multiple Porous Layer Open Tubular Capillaries Maintained at Low Temperatures*

PubMed Central

Burger, Jessica L.; Lovestead, Tara M.; Bruno, Thomas J.

2017-01-01

As the sources of natural gas become more diverse, the trace constituents of the C6+ fraction are of increasing interest. Analysis of fuel gas (including natural gas) for compounds with more than 6 carbon atoms (the C6+ fraction) has historically been complex and expensive. Hence, this is a procedure that is used most often in troubleshooting rather than for day-to-day operations. The C6+ fraction affects gas quality issues and safety considerations such as anomalies associated with odorization. Recent advances in dynamic headspace vapor collection can be applied to this analysis and provide a faster, less complex alternative for compositional determination of the C6+ fraction of natural gas. Porous layer open tubular capillaries maintained at low temperatures (PLOT-cryo) form the basis of a dynamic headspace sampling method that was developed at NIST initially for explosives in 2009. This method has been recently advanced by the combining of multiple PLOT capillary traps into one “bundle,” or wafer, resulting in a device that allows the rapid trapping of relatively large amounts of analyte. In this study, natural gas analytes were collected by flowing natural gas from the laboratory (gas out of the wall) or a prepared surrogate gas flowing through a chilled wafer. The analytes were then removed from the PLOT-cryo wafer by thermal desorption and subsequent flushing of the wafer with helium. Gas chromatography (GC) with mass spectrometry (MS) was then used to identify the analytes. PMID:29332993

Hollow-Wall Heat Shield for Fuel Injector Component

NASA Technical Reports Server (NTRS)

Hanson, Russell B. (Inventor)

2018-01-01

A fuel injector component includes a body, an elongate void and a plurality of bores. The body has a first surface and a second surface. The elongate void is enclosed by the body and is integrally formed between portions of the body defining the first surface and the second surface. The plurality of bores extends into the second surface to intersect the elongate void. A process for making a fuel injector component includes building an injector component body having a void and a plurality of ports connected to the void using an additive manufacturing process that utilizes a powdered building material, and removing residual powdered building material from void through the plurality of ports.

Probability of detection of internal voids in structural ceramics using microfocus radiography

NASA Technical Reports Server (NTRS)

Baaklini, G. Y.; Roth, D. J.

1986-01-01

The reliability of microfocous X-radiography for detecting subsurface voids in structural ceramic test specimens was statistically evaluated. The microfocus system was operated in the projection mode using low X-ray photon energies (20 keV) and a 10 micro m focal spot. The statistics were developed for implanted subsurface voids in green and sintered silicon carbide and silicon nitride test specimens. These statistics were compared with previously-obtained statistics for implanted surface voids in similar specimens. Problems associated with void implantation are discussed. Statistical results are given as probability-of-detection curves at a 95 precent confidence level for voids ranging in size from 20 to 528 micro m in diameter.

Probability of detection of internal voids in structural ceramics using microfocus radiography

NASA Technical Reports Server (NTRS)

Baaklini, G. Y.; Roth, D. J.

1985-01-01

The reliability of microfocus x-radiography for detecting subsurface voids in structural ceramic test specimens was statistically evaluated. The microfocus system was operated in the projection mode using low X-ray photon energies (20 keV) and a 10 micro m focal spot. The statistics were developed for implanted subsurface voids in green and sintered silicon carbide and silicon nitride test specimens. These statistics were compared with previously-obtained statistics for implanted surface voids in similar specimens. Problems associated with void implantation are discussed. Statistical results are given as probability-of-detection curves at a 95 percent confidence level for voids ranging in size from 20 to 528 micro m in diameter.

Mesoscale Fracture Analysis of Multiphase Cementitious Composites Using Peridynamics

PubMed Central

Yaghoobi, Amin; Chorzepa, Mi G.; Kim, S. Sonny; Durham, Stephan A.

2017-01-01

Concrete is a complex heterogeneous material, and thus, it is important to develop numerical modeling methods to enhance the prediction accuracy of the fracture mechanism. In this study, a two-dimensional mesoscale model is developed using a non-ordinary state-based peridynamic (NOSBPD) method. Fracture in a concrete cube specimen subjected to pure tension is studied. The presence of heterogeneous materials consisting of coarse aggregates, interfacial transition zones, air voids and cementitious matrix is characterized as particle points in a two-dimensional mesoscale model. Coarse aggregates and voids are generated using uniform probability distributions, while a statistical study is provided to comprise the effect of random distributions of constituent materials. In obtaining the steady-state response, an incremental and iterative solver is adopted for the dynamic relaxation method. Load-displacement curves and damage patterns are compared with available experimental and finite element analysis (FEA) results. Although the proposed model uses much simpler material damage models and discretization schemes, the load-displacement curves show no difference from the FEA results. Furthermore, no mesh refinement is necessary, as fracture is inherently characterized by bond breakages. Finally, a sensitivity study is conducted to understand the effect of aggregate volume fraction and porosity on the load capacity of the proposed mesoscale model. PMID:28772518

Irradiation Induced Microstructure Evolution in Nanostructured Materials: A Review

PubMed Central

Liu, Wenbo; Ji, Yanzhou; Tan, Pengkang; Zang, Hang; He, Chaohui; Yun, Di; Zhang, Chi; Yang, Zhigang

2016-01-01

Nanostructured (NS) materials may have different irradiation resistance from their coarse-grained (CG) counterparts. In this review, we focus on the effect of grain boundaries (GBs)/interfaces on irradiation induced microstructure evolution and the irradiation tolerance of NS materials under irradiation. The features of void denuded zones (VDZs) and the unusual behavior of void formation near GBs/interfaces in metals due to the interactions between GBs/interfaces and irradiation-produced point defects are systematically reviewed. Some experimental results and calculation results show that NS materials have enhanced irradiation resistance, due to their extremely small grain sizes and large volume fractions of GBs/interfaces, which could absorb and annihilate the mobile defects produced during irradiation. However, there is also literature reporting reduced irradiation resistance or even amorphization of NS materials at a lower irradiation dose compared with their bulk counterparts, since the GBs are also characterized by excess energy (compared to that of single crystal materials) which could provide a shift in the total free energy that will lead to the amorphization process. The competition of these two effects leads to the different irradiation tolerance of NS materials. The irradiation-induced grain growth is dominated by irradiation temperature, dose, ion flux, character of GBs/interface and nanoprecipitates, although the decrease of grain sizes under irradiation is also observed in some experiments. PMID:28787902

Cosmology with void-galaxy correlations.

PubMed

Hamaus, Nico; Wandelt, Benjamin D; Sutter, P M; Lavaux, Guilhem; Warren, Michael S

2014-01-31

Galaxy bias, the unknown relationship between the clustering of galaxies and the underlying dark matter density field is a major hurdle for cosmological inference from large-scale structure. While traditional analyses focus on the absolute clustering amplitude of high-density regions mapped out by galaxy surveys, we propose a relative measurement that compares those to the underdense regions, cosmic voids. On the basis of realistic mock catalogs we demonstrate that cross correlating galaxies and voids opens up the possibility to calibrate galaxy bias and to define a static ruler thanks to the observable geometric nature of voids. We illustrate how the clustering of voids is related to mass compensation and show that volume-exclusion significantly reduces the degree of stochasticity in their spatial distribution. Extracting the spherically averaged distribution of galaxies inside voids from their cross correlations reveals a remarkable concordance with the mass-density profile of voids.

Design and Analysis of Thorium-fueled Reduced Moderation Boiling Water Reactors

NASA Astrophysics Data System (ADS)

Gorman, Phillip Michael

The Resource-renewable Boiling Water Reactors (RBWRs) are a set of light water reactors (LWRs) proposed by Hitachi which use a triangular lattice and high void fraction to incinerate fuel with an epithermal spectrum, which is highly atypical of LWRs. The RBWRs operate on a closed fuel cycle, which is impossible with a typical thermal spectrum reactor, in order to accomplish missions normally reserved for sodium fast reactors (SFRs)--either fuel self-sufficiency or waste incineration. The RBWRs also axially segregate the fuel into alternating fissile "seed" regions and fertile "blanket" regions in order to enhance breeding and leakage probability upon coolant voiding. This dissertation focuses on thorium design variants of the RBWR: the self-sufficient RBWR-SS and the RBWR-TR, which consumes reprocessed transuranic (TRU) waste from PWR used nuclear fuel. These designs were based off of the Hitachi-designed RBWR-AC and the RBWR-TB2, respectively, which use depleted uranium (DU) as the primary fertile fuel. The DU-fueled RBWRs use a pair of axially segregated seed sections in order to achieve a negative void coefficient; however, several concerns were raised with this multi-seed approach, including difficulty with controlling the reactor and unacceptably high axial power peaking. Since thorium-uranium fuel tends to have much more negative void feedback than uranium-plutonium fuels, the thorium RBWRs were designed to use a single elongated seed to avoid these issues. A series of parametric studies were performed in order to find the design space for the thorium RBWRs, and optimize the designs while meeting the required safety constraints. The RBWR-SS was optimized to maximize the discharge burnup, while the RBWR-TR was optimized to maximize the TRU transmutation rate. These parametric studies were performed on an assembly level model using the MocDown simulator, which calculates an equilibrium fuel composition with a specified reprocessing scheme. A full core model was then created for each design, using the Serpent/PARCS 3-D core simulator, and the full core performance was assessed. The RBWR-SS benefited from a harder spectrum than the RBWR-TR; a hard spectrum promotes breeding and increases the discharge burnup, but reduces the TRU transmutation rate. This led the RBWR-SS to have a very tight lattice, which has a lot of experimental uncertainty in the thermal hydraulic correlations. Two different RBWR-SS designs were created assuming different thermal hydraulic assumptions: the RBWR-SSH used the same assumptions as Hitachi used for the RBWR-AC, while the RBWR-SSM used more conservative correlations recommended by collaborators at MIT. However, the void feedback of the pure Th-fed system was too strongly negative, even with a single elongated seed. Therefore, instead of using just thorium, the self-sustaining designs were fed with a mix of between 30% and 50% DU and the rest thorium in order to keep the void feedback as close to zero as possible. This was not necessary for the RBWR-TR, as the external TRU feed fulfilled a similar role. Unfortunately, it was found that the RBWR-SSM could not sustain a critical cycle without either significantly downgrading the power or supplying an external feed of fissile material. While the RBWR-SSH and the RBWR-TR could reach similar burnups and transmutation rates to their DU-fueled counterparts as designed by Hitachi, the thorium designs were unable to simultaneously have negative void feedback and sufficient shutdown margin to shut down the core. The multi-seed approach of the Hitachi designs allowed their reactors to have much lower magnitudes of Doppler feedback than the single-seed designs, which helps them to have sufficient shutdown margin. It is expected that thorium-fueled RBWRs designed to have multiple seeds would permit adequate shutdown margin, although care would need to be taken in order to avoid running into the same issues as the DU fueled RBWRs. Alternatively, it may be possible to increase the amount of boron in the control blades by changing the assembly and core design. Nonetheless, the uncertainties in the multiplication factor due to nuclear data and void fraction uncertainty were assessed for the RBWR-SSH and the RBWR-TR, as well as for the RBWR-TB2. In addition, the uncertainty associated with the change in reactor states (such as the reactivity insertion in flooding the core) due to nuclear data uncertainties was quantified. The thorium RBWRs have much larger uncertainty of their DU-fueled counterparts as designed by Hitachi, as the fission cross section of 233U has very large uncertainty in the epithermal energy range. The uncertainty in the multiplication factor at reference conditions was about 1350 pcm for the RBWR-SSH, while it was about 900 pcm for the RBWR-TR. The uncertainty in the void coefficient of reactivity for both reactors is between 8 and 10 pcm/% void, which is on the same order of magnitude as the full core value. Finally, since sharp linear heat rate spikes were observed in the RBWR-TB2 simulation, the RBWR-TB2 unit cell was simulated using a much finer mesh than is possible using deterministic codes. It was found that the thermal neutrons reflecting back from the reflectors and the blankets were causing extreme spikes in the power density near the axial boundaries of the seeds, which were artificially smoothed out when using coarser meshes. It is anticipated that these spikes will cause melting in both seeds in the RBWR-TB2, unless design changes--such as reducing the enrichment level near the axial boundaries of the seeds--are made.

46 CFR 154.1210 - Hold space, void space, cofferdam, and spaces containing cargo piping.

Code of Federal Regulations, 2013 CFR

2013-10-01

... 46 Shipping 5 2013-10-01 2013-10-01 false Hold space, void space, cofferdam, and spaces containing... Design, Construction and Equipment Cargo Area: Mechanical Ventilation System § 154.1210 Hold space, void space, cofferdam, and spaces containing cargo piping. (a) Each hold space, void space, cofferdam, and...

46 CFR 154.1210 - Hold space, void space, cofferdam, and spaces containing cargo piping.

Code of Federal Regulations, 2014 CFR

2014-10-01

... 46 Shipping 5 2014-10-01 2014-10-01 false Hold space, void space, cofferdam, and spaces containing... Design, Construction and Equipment Cargo Area: Mechanical Ventilation System § 154.1210 Hold space, void space, cofferdam, and spaces containing cargo piping. (a) Each hold space, void space, cofferdam, and...

46 CFR 154.1210 - Hold space, void space, cofferdam, and spaces containing cargo piping.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 46 Shipping 5 2011-10-01 2011-10-01 false Hold space, void space, cofferdam, and spaces containing... Design, Construction and Equipment Cargo Area: Mechanical Ventilation System § 154.1210 Hold space, void space, cofferdam, and spaces containing cargo piping. (a) Each hold space, void space, cofferdam, and...

46 CFR 154.1210 - Hold space, void space, cofferdam, and spaces containing cargo piping.

Code of Federal Regulations, 2012 CFR

2012-10-01

... 46 Shipping 5 2012-10-01 2012-10-01 false Hold space, void space, cofferdam, and spaces containing... Design, Construction and Equipment Cargo Area: Mechanical Ventilation System § 154.1210 Hold space, void space, cofferdam, and spaces containing cargo piping. (a) Each hold space, void space, cofferdam, and...

46 CFR 154.1210 - Hold space, void space, cofferdam, and spaces containing cargo piping.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 46 Shipping 5 2010-10-01 2010-10-01 false Hold space, void space, cofferdam, and spaces containing... Design, Construction and Equipment Cargo Area: Mechanical Ventilation System § 154.1210 Hold space, void space, cofferdam, and spaces containing cargo piping. (a) Each hold space, void space, cofferdam, and...

Deformation of periodic nanovoid structures in Mg single crystals

NASA Astrophysics Data System (ADS)

Xu, Shuozhi; Su, Yanqing; Zare Chavoshi, Saeed

2018-01-01

Large scale molecular dynamics (MD) simulations in Mg single crystal containing periodic cylindrical voids subject to uniaxial tension along the z direction are carried out. Models with different initial void sizes and crystallographic orientations are explored using two interatomic potentials. It is found that (i) a larger initial void always leads to a lower yield stress, in agreement with an analytic prediction; (ii) in the model with x[\\bar{1}100]-y[0001]-z[11\\bar{2}0] orientations, the two potentials predict different types of tension twins and phase transformation; (iii) in the model with x[0001]-y[11\\bar{2}0]-z[\\bar{1}100] orientations, the two potentials identically predict the nucleation of edge dislocations on the prismatic plane, which then glide away from the void, resulting in extrusions at the void surface; in the case of the smallest initial void, these surface extrusions pinch the void into two voids. Besides bringing new physical understanding of the nanovoid structures, our work highlights the variability and uncertainty in MD simulations arising from the interatomic potential, an issue relatively lightly addressed in the literature to date.