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Sample records for asymmetrical flow field-flow

  1. Nanoparticle separation with a miniaturized asymmetrical flow field-flow fractionation cartridge

    Science.gov (United States)

    Müller, David; Cattaneo, Stefano; Meier, Florian; Welz, Roland; deMello, Andrew

    2015-07-01

    Asymmetrical Flow Field-Flow Fractionation (AF4) is a separation technique applicable to particles over a wide size range. Despite the many advantages of AF4, its adoption in routine particle analysis is somewhat limited by the large footprint of currently available separation cartridges, extended analysis times and significant solvent consumption. To address these issues, we describe the fabrication and characterization of miniaturized AF4 cartridges. Key features of the scale-down platform include simplified cartridge and reagent handling, reduced analysis costs and higher throughput capacities. The separation performance of the miniaturized cartridge is assessed using certified gold and silver nanoparticle standards. Analysis of gold nanoparticle populations indicates shorter analysis times and increased sensitivity compared to conventional AF4 separation schemes. Moreover, nanoparticulate titanium dioxide populations exhibiting broad size distributions are analyzed in a rapid and efficient manner. Finally, the repeatability and reproducibility of the miniaturized platform are investigated with respect to analysis time and separation efficiency.

  2. Rational strategy for characterization of nanoscale particles by asymmetric-flow field flow fractionation: A tutorial

    International Nuclear Information System (INIS)

    Gigault, Julien; Pettibone, John M.; Schmitt, Charlène; Hackley, Vincent A.

    2014-01-01

    Graphical abstract: -- Highlights: •Underlying theory and critical parameters are introduced. •A rational workflow is proposed to optimize and refine A4F methods. •Specific optimization steps and validation parameters are delineated. •Pedagogical examples are provided to demonstrate the process. •Use and relevance of different detection modalities is addressed. -- Abstract: This tutorial proposes a comprehensive and rational measurement strategy that provides specific guidance for the application of asymmetric-flow field flow fractionation (A4F) to the size-dependent separation and characterization of nanoscale particles (NPs) dispersed in aqueous media. A range of fractionation conditions are considered, and challenging applications, including industrially relevant materials (e.g., metal NPs, asymmetric NPs), are utilized in order to validate and illustrate this approach. We demonstrate that optimization is material dependent and that polystyrene NPs, widely used as a reference standard for retention calibration in A4F, in fact represent a class of materials with unique selectivity, recovery and optimal conditions for fractionation; thus use of these standards to calibrate retention for other materials must be validated a posteriori. We discuss the use and relevance of different detection modalities that can potentially yield multi-dimensional and complementary information on NP systems. We illustrate the fractionation of atomically precise nanoclusters, which are the lower limit of the nanoscale regime. Conversely, we address the upper size limit for normal mode elution in A4F. The protocol for A4F fractionation, including the methods described in the present work is proposed as a standardized strategy to realize interlaboratory comparability and to facilitate the selection and validation of material-specific measurement parameters and conditions. It is intended for both novice and advanced users of this measurement technology

  3. Optimization and evaluation of asymmetric flow field-flow fractionation of silver nanoparticles.

    Science.gov (United States)

    Loeschner, Katrin; Navratilova, Jana; Legros, Samuel; Wagner, Stephan; Grombe, Ringo; Snell, James; von der Kammer, Frank; Larsen, Erik H

    2013-01-11

    Asymmetric flow field-flow fractionation (AF(4)) in combination with on-line optical detection and mass spectrometry is one of the most promising methods for separation and quantification of nanoparticles (NPs) in complex matrices including food. However, to obtain meaningful results regarding especially the NP size distribution a number of parameters influencing the separation need to be optimized. This paper describes the development of a separation method for polyvinylpyrrolidone-stabilized silver nanoparticles (AgNPs) in aqueous suspension. Carrier liquid composition, membrane material, cross flow rate and spacer height were shown to have a significant influence on the recoveries and retention times of the nanoparticles. Focus time and focus flow rate were optimized with regard to minimum elution of AgNPs in the void volume. The developed method was successfully tested for injected masses of AgNPs from 0.2 to 5.0 μg. The on-line combination of AF(4) with detection methods including ICP-MS, light absorbance and light scattering was helpful because each detector provided different types of information about the eluting NP fraction. Differences in the time-resolved appearance of the signals obtained by the three detection methods were explained based on the physical origin of the signal. Two different approaches for conversion of retention times of AgNPs to their corresponding sizes and size distributions were tested and compared, namely size calibration with polystyrene nanoparticles (PSNPs) and calculations of size based on AF(4) theory. Fraction collection followed by transmission electron microscopy was performed to confirm the obtained size distributions and to obtain further information regarding the AgNP shape. Characteristics of the absorbance spectra were used to confirm the presence of non-spherical AgNP. Copyright © 2012 Elsevier B.V. All rights reserved.

  4. Asymmetric flow field-flow fractionation of manufactured silver nanoparticles spiked into soil solution.

    Science.gov (United States)

    Koopmans, G F; Hiemstra, T; Regelink, I C; Molleman, B; Comans, R N J

    2015-05-01

    Manufactured metallic silver nanoparticles (AgNP) are intensively utilized in consumer products and this will inevitably lead to their release to soils. To assess the environmental risks of AgNP in soils, quantification of both their concentration and size in soil solution is essential. We developed a methodology consisting of asymmetric flow field-flow fractionation (AF4) in combination with on-line detection by UV-vis spectroscopy and off-line HR-ICP-MS measurements to quantify the concentration and size of AgNP, coated with either citrate or polyvinylpyrrolidone (PVP), in water extracts of three different soils. The type of mobile phase was a critical factor in the fractionation of AgNP by AF4. In synthetic systems, fractionation of a series of virgin citrate- and PVP-coated AgNP (10-90 nm) with reasonably high recoveries could only be achieved with ultrahigh purity water as a mobile phase. For the soil water extracts, 0.01% (w:v) sodium dodecyl sulfate (SDS) at pH 8 was the key to a successful fractionation of the AgNP. With SDS, the primary size of AgNP in all soil water extracts could be determined by AF4, except for PVP-coated AgNP when clay colloids were present. The PVP-coated AgNP interacted with colloidal clay minerals, leading to an overestimation of their primary size. Similar interactions between PVP-coated AgNP and clay colloids can take place in the environment and facilitate their transport in soils, aquifers, and surface waters. In conclusion, AF4 in combination with UV-vis spectroscopy and HR-ICP-MS measurements is a powerful tool to characterize AgNP in soil solution if the appropriate mobile phase is used. Copyright © 2015 Elsevier B.V. All rights reserved.

  5. Stability of phospholipid vesicles studied by asymmetrical flow field-flow fractionation and capillary electrophoresis

    Energy Technology Data Exchange (ETDEWEB)

    Yohannes, Gebrenegus [Laboratory of Analytical Chemistry, Department of Chemistry, P.O. Box 55, FIN-00014 University of Helsinki (Finland); Pystynen, Kati-Henna [Laboratory of Analytical Chemistry, Department of Chemistry, P.O. Box 55, FIN-00014 University of Helsinki (Finland); Riekkola, Marja-Liisa [Laboratory of Analytical Chemistry, Department of Chemistry, P.O. Box 55, FIN-00014 University of Helsinki (Finland); Wiedmer, Susanne K. [Laboratory of Analytical Chemistry, Department of Chemistry, P.O. Box 55, FIN-00014 University of Helsinki (Finland)]. E-mail: susanne.wiedmer@helsinki.fi

    2006-02-23

    The stability of zwitterionic phosphatidylcholine vesicles in the presence of 20 mol% phosphatidyl serine (PS), phosphatidic acid (PA), phosphatidyl inositol (PI), and diacylphosphatidyl glycerol (PG) phospholipid vesicles, and cholesterol or calcium chloride was investigated by asymmetrical flow field-flow fractionation (AsFlFFF). Large unilamellar vesicles (LUV, diameter 100 nm) prepared by extrusion at 25 deg. C were used. Phospholipid vesicles (liposomes) were stored at +4 and -18 deg. C over an extended period of time. Extruded egg yolk phosphatidylcholine (EPC) particle diameters at peak maximum and mean measured by AsFlFFF were 101 {+-} 3 nm and 122 {+-} 5 nm, respectively. No significant change in diameter was observed after storage at +4 deg. C for about 5 months. When the storage period was extended to about 8 months (250 days) larger destabilized aggregates were formed (172 and 215 nm at peak maximum and mean diameters, respectively). When EPC was stored at -18 deg. C, large particles with diameters of 700-800 nm were formed as a result of dehydration, aggregation, and fusion processes. In the presence of calcium chloride, EPC alone did not form large aggregates. Addition of 20 mol% of negatively charged phospholipids (PS, PA, PI, or PG) to 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphatidylcholine (POPC) vesicles increased the electrostatic interactions between calcium ion and the vesicles and large aggregates were formed. In the presence of cholesterol, large aggregates of about 250-350 nm appeared during storage at +4 and -18 deg. C for more than 1 day. The effect of liposome storage temperature on phospholipid coatings applied in capillary electrophoresis (CE) was studied by measuring the electroosmotic flow (EOF). EPC coatings with and without cholesterol, PS, or calcium chloride, prepared from liposomes stored at +25, +4, and -18 deg. C, were studied at 25 deg. C. The performances of the coatings were further evaluated with three uncharged compounds

  6. Fractionating power and outlet stream polydispersity in asymmetrical flow field-flow fractionation. Part I: isocratic operation.

    Science.gov (United States)

    Williams, P Stephen

    2016-05-01

    Asymmetrical flow field-flow fractionation (As-FlFFF) has become the most commonly used of the field-flow fractionation techniques. However, because of the interdependence of the channel flow and the cross flow through the accumulation wall, it is the most difficult of the techniques to optimize, particularly for programmed cross flow operation. For the analysis of polydisperse samples, the optimization should ideally be guided by the predicted fractionating power. Many experimentalists, however, neglect fractionating power and rely on light scattering detection simply to confirm apparent selectivity across the breadth of the eluted peak. The size information returned by the light scattering software is assumed to dispense with any reliance on theory to predict retention, and any departure of theoretical predictions from experimental observations is therefore considered of no importance. Separation depends on efficiency as well as selectivity, however, and efficiency can be a strong function of retention. The fractionation of a polydisperse sample by field-flow fractionation never provides a perfectly separated series of monodisperse fractions at the channel outlet. The outlet stream has some residual polydispersity, and it will be shown in this manuscript that the residual polydispersity is inversely related to the fractionating power. Due to the strong dependence of light scattering intensity and its angular distribution on the size of the scattering species, the outlet polydispersity must be minimized if reliable size data are to be obtained from the light scattering detector signal. It is shown that light scattering detection should be used with careful control of fractionating power to obtain optimized analysis of polydisperse samples. Part I is concerned with isocratic operation of As-FlFFF, and part II with programmed operation.

  7. Comparison of Miniaturized and Conventional Asymmetrical Flow Field-Flow Fractionation (AF4 Channels for Nanoparticle Separations

    Directory of Open Access Journals (Sweden)

    Zengchao You

    2017-03-01

    Full Text Available The performance of a miniaturized channel for the separation of polymer and metal nanoparticles (NP using Asymmetrical Flow Field-Flow Fractionation (AF4 was investigated and compared with a conventional AF4 system. To develop standard separation methods, experimental parameters like cross flow, gradient profile and injection time were varied and optimized. Corresponding chromatographic parameters were calculated and compared. Our results indicate that the chromatographic resolution in the miniaturized channel is lower, whereas significantly shorter analyses time and less solvent consumption were obtained. Moreover, the limit of detection (LOD and limit of quantification (LOQ obtained from hyphenation with a UV-detector are obviously lower than in a conventional channel, which makes the miniaturized channel interesting for trace analysis.

  8. Asymmetrical flow field-flow fractionation with on-line detection for drug transfer studies: a feasibility study

    DEFF Research Database (Denmark)

    Hinna, A.; Steiniger, F.; Hupfeld, S.

    2014-01-01

    Knowledge about drug retention within colloidal carriers is of uppermost importance particularly if drug targeting is anticipated. The aim of the present study was to evaluate asymmetrical flow field-flow fractionation (AF4) with on-line UV/VIS drug quantification for its suitability to determine...... both release and transfer of drug from liposomal carriers to a model acceptor phase consisting of large liposomes. The hydrophobic porphyrin 5,10,15,20-tetrakis(4-hydroxyphenyl)21H,23H-porphine (p-THPP), a fluorescent dye with an absorbance maximum in the visible range and structural similarity...... channel geometries. Drug quantification by on-line absorbance measurements was established by comprehensive evaluation of the size-dependent turbidity contribution in on-line UV/VIS detection and by comparison with off-line results obtained for the respective dye-loaded donor formulations (dissolved...

  9. Physicochemical characterization of titanium dioxide pigments using various techniques for size determination and asymmetric flow field flow fractionation hyphenated with inductively coupled plasma mass spectrometry

    NARCIS (Netherlands)

    Helsper, Hans; Peters, Ruud J.B.; Bemmel, van Greet; Herrera Rivera, Zahira; Wagner, Stephan; Kammer, von der Frank; Tromp, Peter C.; Hofmann, Thilo; Weigel, Stefan

    2016-01-01

    Seven commercial titanium dioxide pigments and two other well-defined TiO2 materials (TiMs) were physicochemically characterised using asymmetric flow field flow fractionation (aF4) for separation, various techniques to determine size distribution and inductively coupled plasma mass

  10. Physicochemical characterization of titanium dioxide pigments using various techniques for size determination and asymmetric flow field flow fractionation hyphenated with inductively coupled plasma mass spectrometry

    NARCIS (Netherlands)

    Helsper, J.P.F.G.; Peters, R.J.B.; Bemmel, M.E.M. van; Rivera, Z.E.H.; Wagner, S.; Kammer, F. von der; Tromp, P.C.; Hofmann, T.; Weigel, S.

    2016-01-01

    Seven commercial titanium dioxide pigments and two other well-defined TiO2 materials (TiMs) were physicochemically characterised using asymmetric flow field flow fractionation (aF4) for separation, various techniques to determine size distribution and inductively coupled plasma mass spectrometry

  11. Asymmetrical flow field-flow fractionation coupled with multiple detections: A complementary approach in the characterization of egg yolk plasma.

    Science.gov (United States)

    Dou, Haiyang; Li, Yueqiu; Choi, Jaeyeong; Huo, Shuying; Ding, Liang; Shen, Shigang; Lee, Seungho

    2016-09-23

    The capability of asymmetrical flow field-flow fractionation (AF4) coupled with UV/VIS, multiangle light scattering (MALS) and quasi-elastic light scattering (QELS) (AF4-UV-MALS-QELS) for separation and characterization of egg yolk plasma was evaluated. The accuracy of hydrodynamic radius (Rh) obtained from QELS and AF4 theory (using both simplified and full expression of AF4 retention equations) was discussed. The conformation of low density lipoprotein (LDL) and its aggregates in egg yolk plasma was discussed based on the ratio of radius of gyration (Rg) to Rh together with the results from bio-transmission electron microscopy (Bio-TEM). The results indicate that the full retention equation is more relevant than simplified version for the Rh determination at high cross flow rate. The Rh from online QELS is reliable only at a specific range of sample concentration. The effect of programmed cross flow rate (linear and exponential decay) on the analysis of egg yolk plasma was also investigated. It was found that the use of an exponentially decaying cross flow rate not only reduces the AF4 analysis time of the egg yolk plasma, but also provides better resolution than the use of either a constant or linearly decaying cross flow rate. A combination of an exponentially decaying cross flow AF4-UV-MALS-QELS and the utilization of full retention equation was proved to be a useful method for the separation and characterization of egg yolk plasma. Copyright © 2016 Elsevier B.V. All rights reserved.

  12. Optimization and evaluation of asymmetric flow field-flow fractionation of silver nanoparticles

    DEFF Research Database (Denmark)

    Löschner, Katrin; Navratilova, Jana; Legros, Samuel

    2013-01-01

    flow rate and spacer height were shown to have a significant influence on the recoveries and retention times of the nanoparticles. Focus time and focus flow rate were optimized with regard to minimum elution of AgNPs in the void volume. The developed method was successfully tested for injected masses...... especially the NP size distribution a number of parameters influencing the separation need to be optimized. This paper describes the development of a separation method for polyvinylpyrrolidone-stabilized silver nanoparticles (AgNPs) in aqueous suspension. Carrier liquid composition, membrane material, cross...... obtained by the three detection methods were explained based on the physical origin of the signal. Two different approaches for conversion of retention times of AgNPs to their corresponding sizes and size distributions were tested and compared, namely size calibration with polystyrene nanoparticles (PSNPs...

  13. Monitoring the Erosion of Hydrolytically-Degradable Nanogels via Multiangle Light Scattering Coupled to Asymmetrical Flow Field-Flow Fractionation

    Science.gov (United States)

    Smith, Michael H.; South, Antoinette B.; Gaulding, Jeffrey C.; Lyon, L. Andrew

    2009-01-01

    We describe the synthesis and characterization of degradable nanogels that display bulk erosion under physiologic conditions (pH = 7.4, 37 °C). Erodible poly(N-isopropylmethacrylamide) nanogels were synthesized by copolymerization with N,O-(dimethacryloyl)hydroxylamine, a cross-linker previously used in the preparation of non-toxic and biodegradable bulk hydrogels. To monitor particle degradation, we employed multiangle light scattering and differential refractometry detection following asymmetrical flow field-flow fractionation. This approach allowed the detection of changes in nanogel molar mass and topology as a function of both temperature and pH. Particle erosion was evident from both an increase in nanogel swelling and a decrease in scattering intensity as a function of time. Following these analyses, the samples were recovered for subsequent characterization by direct particle tracking, which yields hydrodynamic size measurements and enables number density determination. Additionally, we confirmed the conservation of nanogel stimuli-responsivity through turbidity measurements. Thus, we have demonstrated the synthesis of degradable nanogels that erode under conditions and on timescales that are relevant for many drug delivery applications. The combined separation and light scattering detection method is demonstrated to be a versatile means to monitor erosion and should also find applicability in the characterization of other degradable particle constructs. PMID:20000662

  14. Characterization of Silver Nanoparticles under Environmentally Relevant Conditions Using Asymmetrical Flow Field-Flow Fractionation (AF4.

    Directory of Open Access Journals (Sweden)

    Min-Hee Jang

    Full Text Available The development of methods to monitor manufactured nanomaterials in the environment is one of the crucial areas for the assessment of their risk. More specifically, particle size analysis is a key element, because many properties of nanomaterial are size dependent. The sizing of nanomaterials in real environments is challenging due to their heterogeneity and reactivity with other environmental components. In this study, the fractionation and characterization of a mixture of polyvinylpyrrolidone-coated silver nanoparticles (PVP-AgNPs of three different sizes were investigated using asymmetrical flow field-flow fractionation (AF4 coupled with UV-Vis spectrophotometry. In particular, the effects of electrolyte composition and natural organic matter (NOM on the particle size and stability were evaluated. The fractogram peaks (i.e., stability of three different AgNPs decreased in the presence of both 10 mM NaCl and 10 mM CaCl2, while increased with increasing concentration of humic acid (HA. In addition, the hydrodynamic diameters of AgNPs in both electrolytes slightly increased with an increase of HA concentration, suggesting the adsorption (coating of HA onto the particle surface. It is also interesting to note that an increase in the particle size depended on the types of electrolyte, which could be explained by the conformational characteristics of the adsorbed HA layers. Consistent these results, AgNPs suspended in lake water containing relatively high concentration of organic carbon (TOC showed higher particle stability and larger particle size (i.e., by approximately 4 nm than those in river water. In conclusion, the application of AF4 coupled with highly sensitive detectors could be a powerful method to characterize nanoparticles in natural waters.

  15. Characterization of Silver Nanoparticles under Environmentally Relevant Conditions Using Asymmetrical Flow Field-Flow Fractionation (AF4)

    Science.gov (United States)

    Jang, Min-Hee; Lee, Seungho; Hwang, Yu Sik

    2015-01-01

    The development of methods to monitor manufactured nanomaterials in the environment is one of the crucial areas for the assessment of their risk. More specifically, particle size analysis is a key element, because many properties of nanomaterial are size dependent. The sizing of nanomaterials in real environments is challenging due to their heterogeneity and reactivity with other environmental components. In this study, the fractionation and characterization of a mixture of polyvinylpyrrolidone-coated silver nanoparticles (PVP-AgNPs) of three different sizes were investigated using asymmetrical flow field-flow fractionation (AF4) coupled with UV-Vis spectrophotometry. In particular, the effects of electrolyte composition and natural organic matter (NOM) on the particle size and stability were evaluated. The fractogram peaks (i.e., stability) of three different AgNPs decreased in the presence of both 10 mM NaCl and 10mM CaCl2, while increased with increasing concentration of humic acid (HA). In addition, the hydrodynamic diameters of AgNPs in both electrolytes slightly increased with an increase of HA concentration, suggesting the adsorption (coating) of HA onto the particle surface. It is also interesting to note that an increase in the particle size depended on the types of electrolyte, which could be explained by the conformational characteristics of the adsorbed HA layers. Consistent these results, AgNPs suspended in lake water containing relatively high concentration of organic carbon (TOC) showed higher particle stability and larger particle size (i.e., by approximately 4nm) than those in river water. In conclusion, the application of AF4 coupled with highly sensitive detectors could be a powerful method to characterize nanoparticles in natural waters. PMID:26575993

  16. Detection of nanoplastics in food by asymmetric flow field-flow fractionation coupled to multi-angle light scattering: possibilities, challenges and analytical limitations

    DEFF Research Database (Denmark)

    Correia, Manuel; Löschner, Katrin

    2018-01-01

    We tested the suitability of asymmetric flow field-flow fractionation (AF4) coupled to multi-angle light scattering (MALS) for detection of nanoplastics in fish. A homogenized fish sample was spiked with 100 nm polystyrene nanoparticles (PSNPs) (1.3 mg/g fish). Two sample preparation strategies...... were tested: acid digestion and enzymatic digestion with proteinase K. Both procedures were found suitable for degradation of the organic matrix. However, acid digestion resulted in large PSNPs aggregates/agglomerates (> 1 μm). The presence of large particulates was not observed after enzymatic...

  17. Detection and characterization of silver nanoparticles in chicken meat by asymmetric flow field flow fractionation with detection by conventional or single particle ICP-MS

    DEFF Research Database (Denmark)

    Löschner, Katrin; Navratilova, Jana; Købler, Carsten

    2013-01-01

    of the AgNPs took place during the sample preparation stage. The digestate was injected into the asymmetric flow field flow fractionation (AF(4)) -ICP-MS system, which enabled fractionation of nanoparticles from the remaining meat matrix, and resulted in one large peak in the fractograms as well as two...... smaller peaks eluting close to the void volume. The recovery of silver contained in the large AgNP peak was around 80 %. Size determination of AgNPs in the meat matrix, based on external size calibration of the AF(4) channel, was hampered by non-ideal (early elution) behavior of the AgNPs. Single particle...

  18. Combining asymmetrical flow field-flow fractionation with light-scattering and inductively coupled plasma mass spectrometric detection for characterization of nanoclay used in biopolymer nanocomposites

    DEFF Research Database (Denmark)

    Schmidt, Bjørn; Petersen, Jens Højslev; Koch, C. Bender

    2009-01-01

    mechanical and barrier properties and be more suitable for a wider range of food-packaging applications. Natural or synthetic clay nanofillers are being investigated for this purpose in a project called NanoPack funded by the Danish Strategic Research Council. In order to detect and characterize the size...... of clay nanoparticulates, an analytical system combining asymmetrical flow field-flow fractionation (AF4) with multi-angle light-scattering detection (MALS) and inductively coupled plasma mass spectrometry (ICP-MS) is presented. In a migration study, we tested a biopolymer nanocomposite consisting...... of polylactide (PLA) with 5% Cloisite®30B (a derivatized montmorillonite clay) as a filler. Based on AF4-MALS analyses, we found that particles ranging from 50 to 800 nm in radius indeed migrated into the 95% ethanol used as a food simulant. The full hyphenated AF4-MALS-ICP-MS system showed, however, that none...

  19. Feasibility of asymmetric flow field-flow fractionation coupled to ICP-MS for the characterization of wear metal particles and metalloproteins in biofluids from hip replacement patients

    DEFF Research Database (Denmark)

    Löschner, Katrin; Harrington, Chris F.; Kearney, Jacque-Lucca

    2015-01-01

    or other elements, but the current analytical methods used to investigate the processes involved do not provide sufficient information to understand the size or composition of the wear particles generated in vivo. In this qualitative feasibility study, asymmetric flow field-flow fractionation (AF4) coupled...... to ICP-MS was used to confirm the metal–protein associations in the serum samples. Off-line single particle ICP-MS (spICP-MS) analysis was used to confirm the approximate size distribution indicated by AF4 of the wear particles in hip aspirates. In the serum samples, AF4–ICP-MS suggested that Cr...... unidentified compounds; AEC analysis confirmed the Cr results and the association of Co with Alb and a second compound. Enzymatic digestion of the hip aspirate sample, followed by separation using AF4 with detection by UV absorption (280 nm), multi-angle light scattering and ICP-MS, suggested that the sizes...

  20. Asymmetric Flow Field Flow Fractionation of Aqueous C60 Nanoparticles with Size Determination by Dynamic Light Scattering and Quantification by Liquid Chromatography Atmospheric Pressure Photo-Ionization Mass Spectrometry

    Science.gov (United States)

    A size separation method was developed for aqueous C60 fullerene aggregates (aqu/C60) using asymmetric flow field flow fractionation (AF4) coupled to a dynamic light scattering detector in flow through mode. Surfactants, which are commonly used in AF4, were avoided as they may al...

  1. Characterization of oxidized tannins: comparison of depolymerization methods, asymmetric flow field-flow fractionation and small-angle X-ray scattering.

    Science.gov (United States)

    Vernhet, Aude; Dubascoux, Stéphane; Cabane, Bernard; Fulcrand, Hélène; Dubreucq, Eric; Poncet-Legrand, Céline

    2011-09-01

    Condensed tannins are a major class of plant polyphenols. They play an important part in the colour and taste of foods and beverages. Due to their chemical reactivity, tannins are not stable once extracted from plants. A number of chemical reactions can take place, leading to structural changes of the native structures to give so-called derived tannins and pigments. This paper compares results obtained on native and oxidized tannins with different techniques: depolymerization followed by high-performance liquid chromatography analysis, small-angle X-ray scattering (SAXS) and asymmetric flow field-flow fractionation (AF4). Upon oxidation, new macromolecules were formed. Thioglycolysis experiments showed no evidence of molecular weight increase, but thioglycolysis yields drastically decreased. When oxidation was performed at high concentration (e.g., 10 g L(-1)), the weight average degree of polymerization determined from SAXS increased, whereas it remained stable when oxidation was done at low concentration (0.1 g L(-1)), indicating that the reaction was intramolecular, yet the conformations were different. Differences in terms of solubility were observed; ethanol being a better solvent than water. We also separated soluble and non-water-soluble species of a much oxidized fraction. Thioglycolysis showed no big differences between the two fractions, whereas SAXS and AF4 showed that insoluble macromolecules have a weight average molecular weight ten times higher than the soluble ones.

  2. Fractionation and Characterization of High Aspect Ratio Gold Nanorods Using Asymmetric-Flow Field Flow Fractionation and Single Particle Inductively Coupled Plasma Mass Spectrometry

    Directory of Open Access Journals (Sweden)

    Thao M. Nguyen

    2015-07-01

    Full Text Available Gold nanorods (GNRs are of particular interest for biomedical applications due to their unique size-dependent longitudinal surface plasmon resonance band in the visible to near-infrared. Purified GNRs are essential for the advancement of technologies based on these materials. Used in concert, asymmetric-flow field flow fractionation (A4F and single particle inductively coupled mass spectrometry (spICP-MS provide unique advantages for fractionating and analyzing the typically complex mixtures produced by common synthetic procedures. A4F fractions collected at specific elution times were analyzed off-line by spICP-MS. The individual particle masses were obtained by conversion of the ICP-MS pulse intensity for each detected particle event, using a defined calibration procedure. Size distributions were then derived by transforming particle mass to length assuming a fixed diameter. The resulting particle lengths correlated closely with ex situ transmission electron microscopy. In contrast to our previously reported observations on the fractionation of low-aspect ratio (AR GNRs (AR < 4, under optimal A4F separation conditions the results for high-AR GNRs of fixed diameter (≈20 nm suggest normal, rather than steric, mode elution (i.e., shorter rods with lower AR generally elute first. The relatively narrow populations in late eluting fractions suggest the method can be used to collect and analyze specific length fractions; it is feasible that A4F could be appropriately modified for industrial scale purification of GNRs.

  3. Importance of material matching in the calibration of asymmetric flow field-flow fractionation: material specificity and nanoparticle surface coating effects on retention time

    Energy Technology Data Exchange (ETDEWEB)

    Qu, Haiou [U.S. Food and Drug Administration, Office of Regulatory Affairs, Arkansas Regional Laboratory (United States); Quevedo, Ivan R. [Universidad Iberoamericana, Departamento de Ingeniería y Ciencias Químicas (Mexico); Linder, Sean W.; Fong, Andrew; Mudalige, Thilak K., E-mail: Thilak.Mudalige@fda.hhs.gov [U.S. Food and Drug Administration, Office of Regulatory Affairs, Arkansas Regional Laboratory (United States)

    2016-10-15

    Asymmetric flow field-flow fractionation (AF4) coupled with dynamic light scattering or multiangle light scattering detectors is a promising technique for the size-based separation of colloidal particles (nano- and submicron scale) and the online determination of the particle size of the separated fractions in aqueous suspensions. In most cases, the applications of these detectors are problematic due to the material-specific properties of the analyte that results in erroneous calculations, and as an alternative, different nanoparticle size standards are required to properly calibrate the size-based retention in AF4. The availability of nanoparticle size standards in different materials is limited, and this deviation from ideal conditions of retention is mainly due to material-specific and particle coating-specific membrane–particle interactions. Here, we present an experimental method on the applicability of polystyrene nanoparticles (PS NP) as standard for AF4 calibration and compare with gold nanoparticle (Au NP) standards having different nominal sizes and surface functionalities.

  4. Importance of material matching in the calibration of asymmetric flow field-flow fractionation: material specificity and nanoparticle surface coating effects on retention time

    International Nuclear Information System (INIS)

    Qu, Haiou; Quevedo, Ivan R.; Linder, Sean W.; Fong, Andrew; Mudalige, Thilak K.

    2016-01-01

    Asymmetric flow field-flow fractionation (AF4) coupled with dynamic light scattering or multiangle light scattering detectors is a promising technique for the size-based separation of colloidal particles (nano- and submicron scale) and the online determination of the particle size of the separated fractions in aqueous suspensions. In most cases, the applications of these detectors are problematic due to the material-specific properties of the analyte that results in erroneous calculations, and as an alternative, different nanoparticle size standards are required to properly calibrate the size-based retention in AF4. The availability of nanoparticle size standards in different materials is limited, and this deviation from ideal conditions of retention is mainly due to material-specific and particle coating-specific membrane–particle interactions. Here, we present an experimental method on the applicability of polystyrene nanoparticles (PS NP) as standard for AF4 calibration and compare with gold nanoparticle (Au NP) standards having different nominal sizes and surface functionalities.

  5. Multivariate DoE Optimization of Asymmetric Flow Field Flow Fractionation Coupled to Quantitative LC-MS/MS for Analysis of Lipoprotein Subclasses

    Directory of Open Access Journals (Sweden)

    Zsuzsanna Kuklenyik

    2015-02-01

    Full Text Available In this report we demonstrate a practical multivariate design of experiment (DoE approach for asymmetric flow field-flow fractionation (AF4 method optimization using separation of lipoprotein subclasses as an example. First, with the aid of commercially available software, we built a full factorial screening design where the theoretical outcomes were calculated by applying established formulas that govern AF4 channel performance for a 5–35 nm particle size range of interest for lipid particles. Second, using the desirable ranges of instrumental parameters established from theoretical optimization, we performed fractional factorial DoE for AF4 separation of pure albumin and ferritin with UV detection to narrow the range of instrumental parameters and allow optimum size resolution while minimizing losses from membrane immobilization. Third, the optimal range of conditions were tested using response surface DoE for sub-fractionation of high and low density lipoproteins (HDL and LDL in human serum, where the recovery of the analytes were monitored by fraction collection and isotope-dilution LC-MS/MS analysis of each individual fraction for cholesterol and apolipoproteins (ApoA-1 and ApoB-100. Our results show that DoE is an effective tool in combining AF4 theoretical knowledge and experimental data in finding the most optimal set of AF4 instrumental parameters for quantitative coupling with LC-MS/MS measurements.

  6. Optimisation of asymmetric flow field-flow fractionation for the characterisation of nanoparticles in coated polydisperse TiO2 with applications in food and feed.

    Science.gov (United States)

    Omar, J; Boix, A; Kerckhove, G; von Holst, C

    2016-12-01

    Titanium dioxide (TiO 2 ) has various applications in consumer products and is also used as an additive in food and feeding stuffs. For the characterisation of this product, including the determination of nanoparticles, there is a strong need for the availability of corresponding methods of analysis. This paper presents an optimisation process for the characterisation of polydisperse-coated TiO 2 nanoparticles. As a first step, probe ultrasonication was optimised using a central composite design in which the amplitude and time were the selected variables to disperse, i.e., to break up agglomerates and/or aggregates of the material. The results showed that high amplitudes (60%) favoured a better dispersion and time was fixed in mid-values (5 min). In a next step, key factors of asymmetric flow field-flow fraction (AF4), namely cross-flow (CF), detector flow (DF), exponential decay of the cross-flow (CF exp ) and focus time (Ft), were studied through experimental design. Firstly, a full-factorial design was employed to establish the statistically significant factors (p < 0.05). Then, the information obtained from the full-factorial design was utilised by applying a central composite design to obtain the following optimum conditions of the system: CF, 1.6 ml min -1 ; DF, 0.4 ml min -1 ; Ft, 5 min; and CF exp , 0.6. Once the optimum conditions were obtained, the stability of the dispersed sample was measured for 24 h by analysing 10 replicates with AF4 in order to assess the performance of the optimised dispersion protocol. Finally, the recovery of the optimised method, particle shape and particle size distribution were estimated.

  7. Asymmetric flow field-flow fractionation coupled to inductively coupled plasma mass spectrometry for the quantification of quantum dots bioconjugation efficiency.

    Science.gov (United States)

    Menéndez-Miranda, Mario; Encinar, Jorge Ruiz; Costa-Fernández, José M; Sanz-Medel, Alfredo

    2015-11-27

    Hyphenation of asymmetric flow field-flow fractionation (AF4) to an on-line elemental detection (inductively coupled plasma-mass spectrometry, ICP-MS) is proposed as a powerful diagnostic tool for quantum dots bioconjugation studies. In particular, conjugation effectiveness between a "model" monoclonal IgG antibody (Ab) and CdSe/ZnS core-shell Quantum Dots (QDs), surface-coated with an amphiphilic polymer, has been monitored here by such hybrid AF4-ICP-MS technique. Experimental conditions have been optimized searching for a proper separation between the sought bioconjugates from the eventual free reagents excesses employed during the bioconjugation (QDs and antibodies). Composition and pH of the carrier have been found to be critical parameters to ensure an efficient separation while ensuring high species recovery from the AF4 channel. An ICP-MS equipped with a triple quadropole was selected as elemental detector to enable sensitive and reliable simultaneous quantification of the elemental constituents, including sulfur, of the nanoparticulated species and the antibody. The hyphenated technique used provided nanoparticle size-based separation, elemental detection, and composition analysis capabilities that turned out to be instrumental in order to investigate in depth the Ab-QDs bioconjugation process. Moreover, the analytical strategy here proposed allowed us not only to clearly identify the bioconjugation reaction products but also to quantify nanoparticle:antibodies bioconjugation efficiency. This is a key issue in future development of analytical and bioanalytical photoluminescent QDs applications. Copyright © 2015 Elsevier B.V. All rights reserved.

  8. Physicochemical characterization of titanium dioxide pigments using various techniques for size determination and asymmetric flow field flow fractionation hyphenated with inductively coupled plasma mass spectrometry.

    Science.gov (United States)

    Helsper, Johannes P F G; Peters, Ruud J B; van Bemmel, Margaretha E M; Rivera, Zahira E Herrera; Wagner, Stephan; von der Kammer, Frank; Tromp, Peter C; Hofmann, Thilo; Weigel, Stefan

    2016-09-01

    Seven commercial titanium dioxide pigments and two other well-defined TiO2 materials (TiMs) were physicochemically characterised using asymmetric flow field flow fractionation (aF4) for separation, various techniques to determine size distribution and inductively coupled plasma mass spectrometry (ICPMS) for chemical characterization. The aF4-ICPMS conditions were optimised and validated for linearity, limit of detection, recovery, repeatability and reproducibility, all indicating good performance. Multi-element detection with aF4-ICPMS showed that some commercial pigments contained zirconium co-eluting with titanium in aF4. The other two TiMs, NM103 and NM104, contained aluminium as integral part of the titanium peak eluting in aF4. The materials were characterised using various size determination techniques: retention time in aF4, aF4 hyphenated with multi-angle laser light spectrometry (MALS), single particle ICPMS (spICPMS), scanning electron microscopy (SEM) and particle tracking analysis (PTA). PTA appeared inappropriate. For the other techniques, size distribution patterns were quite similar, i.e. high polydispersity with diameters from 20 to >700 nm, a modal peak between 200 and 500 nm and a shoulder at 600 nm. Number-based size distribution techniques as spICPMS and SEM showed smaller modal diameters than aF4-UV, from which mass-based diameters are calculated. With aF4-MALS calculated, light-scattering-based "diameters of gyration" (Øg) are similar to hydrodynamic diameters (Øh) from aF4-UV analyses and diameters observed with SEM, but much larger than with spICPMS. A Øg/Øh ratio of about 1 indicates that the TiMs are oblate spheres or fractal aggregates. SEM observations confirm the latter structure. The rationale for differences in modal peak diameter is discussed.

  9. Ultraviolet-B radiation mobilizes uranium from uranium-dissolved organic carbon complexes in aquatic systems, demonstrated by asymmetrical flow field-flow fractionation.

    Science.gov (United States)

    Nehete, Sachin Vilas; Christensen, Terje; Salbu, Brit; Teien, Hans-Christian

    2017-05-05

    Humic substances have a tendency to form complexes with metal ions in aquatic medium, impacting the metal mobility, decreasing bioavailability and toxicity. Ultraviolet-B (UV-B) radiation exposure degrades the humic substance, changes their molecular weight distribution and their metal binding capacity in aquatic medium. In this study, we experimented the effect of UV-B radiation on the uranium complexed with fulvic acids and humic acids in a soft water system at different pH, uranium concentrations and radiant exposure. The concentration and distribution of uranium in a complexed form were investigated by asymmetrical flow field-flow fractionation coupled to multi detection technique (AsFlFFF-UV-ICP-MS). The major concentration of uranium present in complexes was primarily associated with average and higher molecular weight fulvic and humic acids components. The concentration of uranium in a complexed form increased with increasing fulvic and humic acid concentrations as well as pH of the solution. The higher molecular weight fraction of uranium was degraded due to the UV-B exposure, transforming about 50% of the uranium-dissolved organic carbon complexes into low molecular weight uranium species in complex form with organic ligands and/or free form. The result also suggests AsFlFFF-UV-ICP-MS to be an important separation and detection technique for understanding the interaction of radionuclides with dissolved organic matter, tracking size distribution changes during degradation of organic complexes for understanding mobility, bioavailability and ecosystem transfer of radionuclides as well as metals. Copyright © 2017 Elsevier B.V. All rights reserved.

  10. Differentiation and characterization of isotopically modified silver nanoparticles in aqueous media using asymmetric-flow field flow fractionation coupled to optical detection and mass spectrometry

    Energy Technology Data Exchange (ETDEWEB)

    Gigault, Julien [National Institute of Standards and Technology, Material Measurement Laboratory, 100 Bureau Drive Stop 8520, Gaithersburg, MD 20899-8520 (United States); Hackley, Vincent A., E-mail: vince.hackley@nist.gov [National Institute of Standards and Technology, Material Measurement Laboratory, 100 Bureau Drive Stop 8520, Gaithersburg, MD 20899-8520 (United States)

    2013-02-06

    Highlights: ► Isotopically modified and unmodified AgNPs characterization by A4F-DAD-MALS–DLS-ICP-MS. ► Size-resolved characterization and speciation in simple or complex media. ► Capacity to detect stable isotope enriched AgNPs in a standard estuarine sediment. ► New opportunities to monitor and study fate and transformations of AgNPs. -- Abstract: The principal objective of this work was to develop and demonstrate a new methodology for silver nanoparticle (AgNP) detection and characterization based on asymmetric-flow field flow fractionation (A4F) coupled on-line to multiple detectors and using stable isotopes of Ag. This analytical approach opens the door to address many relevant scientific challenges concerning the transport and fate of nanomaterials in natural systems. We show that A4F must be optimized in order to effectively fractionate AgNPs and larger colloidal Ag particles. With the optimized method one can accurately determine the size, stability and optical properties of AgNPs and their agglomerates under variable conditions. In this investigation, we couple A4F to optical absorbance (UV–vis spectrometer) and scattering detectors (static and dynamic) and to an inductively coupled plasma mass spectrometer. With this combination of detection modes it is possible to determine the mass isotopic signature of AgNPs as a function of their size and optical properties, providing specificity necessary for tracing and differentiating labeled AgNPs from their naturally occurring or anthropogenic analogs. The methodology was then applied to standard estuarine sediment by doping the suspension with a known quantity of isotopically enriched {sup 109}AgNPs stabilized by natural organic matter (standard humic and fulvic acids). The mass signature of the isotopically enriched AgNPs was recorded as a function of the measured particle size. We observed that AgNPs interact with different particulate components of the sediment, and also self-associate to form

  11. The use of asymmetrical flow field-flow fractionation with on-line detection in the study of drug retention within liposomal nanocarriers and drug transfer kinetics.

    Science.gov (United States)

    Hinna, Askell Hvid; Hupfeld, Stefan; Kuntsche, Judith; Brandl, Martin

    2016-05-30

    Due to their solubilizing capabilities, liposomes (phospholipid vesicles) are suited for designing formulations for intravenous administration of drug compounds which are poorly water-soluble. Despite the good in-vitro stability of such formulations with minimal drug leakage, upon i.v. injection there is a risk of premature drug loss due to drug transfer to plasma proteins and cell membranes. Here we report on the refinement of a recently introduced simple in vitro predictive tool by Hinna and colleagues in 2014, which brings small drug loaded (donor) liposomes in contact with large acceptor liposomes, the latter serving as a model mimicking biological sinks in the body. The donor- and acceptor-liposomes were subsequently separated using asymmetrical flow field-flow fractionation (AF4), during which the sample is exposed to a large volume of eluent which corresponds to a dilution factor of approximately 600. The model drug content in the donor- and acceptor fraction was quantified by on-line UV/VIS extinction measurements with correction for turbidity and by off-line HPLC measurements of collected fractions. The refined method allowed for (near) baseline separation of donor and acceptor vesicles as well as reliable quantification of the drug content not only of the donor- but now also of the acceptor-liposomes due to their improved size-homogeneity, colloidal stability and reduced turbidity. This improvement over the previously reported approach allowed for simultaneous quantification of both drug transfer and drug release to the aqueous phase. By sampling at specific incubation times, the release and transfer kinetics of the model compound p-THPP (5,10,15,20-tetrakis(4-hydroxyphenyl)21H,23H-porphine) was determined. p-THPP is structurally closely related to the photosensitizer temoporfin, which is in clinical use and under evaluation in liposomal formulations. The transfer of p-THPP to the acceptor vesicles followed 1st order kinetics with a half-life of

  12. First steps towards a generic sample preparation scheme for inorganic engineered nanoparticles in a complex matrix for detection, characterization, and quantification by asymmetric flow-field flow fractionation coupled to multi-angle light scattering and ICP-MS

    DEFF Research Database (Denmark)

    Wagner, Stephan; Legros, Samuel; Löschner, Katrin

    2015-01-01

    content by asymmetric flow-field flow fractionation coupled to a multi-angle light scattering detector and an inductively coupled plasma mass spectrometer. Following the proposed generic procedure SiO2-ENPs were separated from a tomato soup. Two potential sample preparation methods were tested these being...... quality criteria for method development is urgently needed for standardized and systematic development of procedures for separation of ENPs from a complex matrix. The chosen analytical technique was shown to be suitable for detecting SiO2-ENPs in a complex food matrix like tomato soup and may therefore...

  13. Elemental ratios for characterization of quantum-dots populations in complex mixtures by asymmetrical flow field-flow fractionation on-line coupled to fluorescence and inductively coupled plasma mass spectrometry.

    Science.gov (United States)

    Menendez-Miranda, Mario; Fernandez-Arguelles, Maria T; Costa-Fernandez, Jose M; Encinar, Jorge Ruiz; Sanz-Medel, Alfredo

    2014-08-11

    Separation and identification of nanoparticles of different composition, with similar particle diameter, coexisting in heterogeneous suspensions of polymer-coated CdSe/ZnS quantum dots (QDs) have been thoroughly assessed by asymmetric flow field-flow fractionation (AF4) coupled on-line to fluorescence and inductively coupled plasma mass spectrometry (ICPMS) detectors. Chemical characterization of any previously on-line separated nanosized species was achieved by the measurement of the elemental molar ratios of every element involved in the synthesis of the QDs, using inorganic standards and external calibration by flow injection analysis (FIA). Such elemental molar ratios, strongly limited so far to pure single nanoparticles suspensions, have been achieved with adequate accuracy by coupling for the first time an ICP-QQQ instrument to an AF4 system. This hyphenation turned out to be instrumental to assess the chemical composition of the different populations of nanoparticles coexisting in the relatively complex mixtures, due to its capabilities to detect the hardly detectable elements involved in the synthesis. Interestingly such information, complementary to that obtained by fluorescence, was very valuable to detect and identify unexpected nanosized species, present at significant level, produced during QDs synthesis and hardly detectable by standard approaches. Copyright © 2014. Published by Elsevier B.V.

  14. Elemental ratios for characterization of quantum-dots populations in complex mixtures by asymmetrical flow field-flow fractionation on-line coupled to fluorescence and inductively coupled plasma mass spectrometry

    International Nuclear Information System (INIS)

    Menendez-Miranda, Mario; Fernandez-Arguelles, Maria T.; Costa-Fernandez, Jose M.; Encinar, Jorge Ruiz; Sanz-Medel, Alfredo

    2014-01-01

    Highlights: • The hyphenated system allows unequivocal identification of nanoparticle populations. • AF4 separation permitted detection of unexpected nanosized species in a sample. • ICP-QQQ provides elemental ratios with adequate accuracy in every nanoparticle. • Purity and chemical composition of different quantum dot samples were assessed. - Abstract: Separation and identification of nanoparticles of different composition, with similar particle diameter, coexisting in heterogeneous suspensions of polymer-coated CdSe/ZnS quantum dots (QDs) have been thoroughly assessed by asymmetric flow field-flow fractionation (AF4) coupled on-line to fluorescence and inductively coupled plasma mass spectrometry (ICPMS) detectors. Chemical characterization of any previously on-line separated nanosized species was achieved by the measurement of the elemental molar ratios of every element involved in the synthesis of the QDs, using inorganic standards and external calibration by flow injection analysis (FIA). Such elemental molar ratios, strongly limited so far to pure single nanoparticles suspensions, have been achieved with adequate accuracy by coupling for the first time an ICP-QQQ instrument to an AF4 system. This hyphenation turned out to be instrumental to assess the chemical composition of the different populations of nanoparticles coexisting in the relatively complex mixtures, due to its capabilities to detect the hardly detectable elements involved in the synthesis. Interestingly such information, complementary to that obtained by fluorescence, was very valuable to detect and identify unexpected nanosized species, present at significant level, produced during QDs synthesis and hardly detectable by standard approaches

  15. Trends in Polymer and Particle Characterization by Microfluidic Field-Flow Fractionation Methods: Science or Business?

    Czech Academy of Sciences Publication Activity Database

    Janča, Josef; Sobota, Jaroslav

    2014-01-01

    Roč. 19, 16 May (2014), s. 296-308 ISSN 1023-666X R&D Projects: GA MŠk(CZ) LO1212 Institutional support: RVO:68081731 Keywords : Asymmetrical flow FFF * Electrical FFF * Field-flow fractionation * Flow FFF * Microelectrical FFF * Microfluidic channels * Microthermal FFF * Miniaturization and resolution * Polymers and particles separation * Sedimentation FFF * Technical benefits of microchannels * Thermal FFF Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 1.264, year: 2014

  16. Factors affecting particle retention in thermal field-flow fractionation

    African Journals Online (AJOL)

    colloidal material is illustrated through the evaluation of thermal diffusion coefficient of PS ... Field-flow fractionation (FFF) is a separation method introduced by Giddings in 1966 [1]. It is a ... no stationary phase is used in FFF. .... that the inversion diameter (diameter at which order of retention changes) can be shifted up or.

  17. factors affecting particle retention in thermal field-flow fractionation

    African Journals Online (AJOL)

    In this paper, we report a range of factors which affect the retention of colloidal particles in thermal field-flow fractionation (ThFFF). These results are observed among different sizes of polystyrene (PS) latex particles suspended in both aqueous and nonaqueous liquid carriers and very low density lipoproteins in a phosphate ...

  18. Field-Flow Fractionation of Carbon Nanotubes and Related Materials

    Energy Technology Data Exchange (ETDEWEB)

    John P. Selegue

    2011-11-17

    During the grant period, we carried out FFF studies of carbonaceous soot, single-walled and multi-walled carbon nanotubes, carbon nano-onions and polyoxometallates. FFF alone does not provide enough information to fully characterize samples, so our suite of characterization techniques grew to include light scattering (especially Photon Correlation Spectroscopy), scanning and transmission electron microscopy, thermogravimetric analysis and spectroscopic methods. We developed convenient techniques to deposit and examine minute FFF fractions by electron microscopy. In collaboration with Arthur Cammers (University of Kentucky), we used Flow Field-Flow Fractionation (Fl-FFF) to monitor the solution-phase growth of keplerates, a class of polyoxometallate (POM) nanoparticles. We monitored the evolution of Mo-POM nanostructures over the course of weeks by by using flow field-flow fractionation and corroborated the nanoparticle structures by using transmission electron microscopy (TEM). Total molybdenum in the solution and precipitate phases was monitored by using inductively coupled plasma analyses, and total Mo-POM concentration by following the UV-visible spectra of the solution phase. We observe crystallization-driven formation of (Mo132) keplerate and solution phase-driven evolution of structurally related nanoscopic species (3-60 nm). FFF analyses of other classes of materials were less successful. Attempts to analyze platelets of layered materials, including exfoliated graphite (graphene) and TaS2 and MoS2, were disappointing. We were not able to optimize flow conditions for the layered materials. The metal sulfides react with the aqueous carrier liquid and settle out of suspension quickly because of their high density.

  19. Particle Based Modeling of Electrical Field Flow Fractionation Systems

    Directory of Open Access Journals (Sweden)

    Tonguc O. Tasci

    2015-10-01

    Full Text Available Electrical Field Flow Fractionation (ElFFF is a sub method in the field flow fractionation (FFF family that relies on an applied voltage on the channel walls to effect a separation. ElFFF has fallen behind some of the other FFF methods because of the optimization complexity of its experimental parameters. To enable better optimization, a particle based model of the ElFFF systems has been developed and is presented in this work that allows the optimization of the main separation parameters, such as electric field magnitude, frequency, duty cycle, offset, flow rate and channel dimensions. The developed code allows visualization of individual particles inside the separation channel, generation of realistic fractograms, and observation of the effects of the various parameters on the behavior of the particle cloud. ElFFF fractograms have been generated via simulations and compared with experiments for both normal and cyclical ElFFF. The particle visualizations have been used to verify that high duty cycle voltages are essential to achieve long retention times and high resolution separations. Furthermore, by simulating the particle motions at the channel outlet, it has been demonstrated that the top channel wall should be selected as the accumulation wall for cyclical ElFFF to reduce band broadening and achieve high efficiency separations. While the generated particle based model is a powerful tool to estimate the outcomes of the ElFFF experiments and visualize particle motions, it can also be used to design systems with new geometries which may lead to the design of higher efficiency ElFFF systems. Furthermore, this model can be extended to other FFF techniques by replacing the electrical field component of the model with the fields used in the other FFF techniques.

  20. Analysis of liposomes using asymmetrical flow field-flow fractionation

    DEFF Research Database (Denmark)

    Kuntsche, Judith; Decker, Christiane; Fahr, Alfred

    2012-01-01

    completely (lipid recoveries were close to 100%) but there was a loss of incorporated drugs during separation with a strong dependence on the octanol-water partition coefficient of the drug. Whereas corticosterone (partition coefficient ~2) was washed out more or less completely (recovery about 2%), loss...

  1. Near-field flow structures about subcritical surface roughness

    Science.gov (United States)

    Doolittle, Charles J.; Drews, Scott D.; Goldstein, David B.

    2014-12-01

    Laminar flow over a periodic array of cylindrical surface roughness elements is simulated with an immersed boundary spectral method both to validate the method for subsequent studies and to examine how persistent streamwise vortices are introduced by a low Reynolds number roughness element. Direct comparisons are made with prior studies at a roughness-based Reynolds number Rek (=U(k) k/ν) of 205 and a diameter to spanwise spacing ratio d/λ of 1/3. Downstream velocity contours match present and past experiments very well. The shear layer developed over the top of the roughness element produces the downstream velocity deficit. Upstream of the roughness element, the vortex topology is found to be consistent with juncture flow experiments, creating three cores along the recirculation line. Streamtraces stemming from these upstream cores, however, have unexpectedly little effect on the downstream flowfield as lateral divergence of the boundary layer quickly dissipates their vorticity. Long physical relaxation time of the recirculating wake behind the roughness remains a prominent issue for simulating this type of flowfield.

  2. Analysis of magnetic nanoparticles using quadrupole magnetic field-flow fractionation

    International Nuclear Information System (INIS)

    Carpino, Francesca; Moore, Lee R.; Zborowski, Maciej; Chalmers, Jeffrey J.; Williams, P. Stephen

    2005-01-01

    The new technique of quadrupole magnetic field-flow fractionation is described. It is a separation and characterization technique for particulate magnetic materials. Components of a sample are eluted from the separation channel at times dependent on the strength of their interaction with the magnetic field. A quadrupole electromagnet allows a programmed reduction of field strength during analysis of polydisperse samples

  3. Characterization of Diamond Nanoparticles by High-Speed Micro-Thermal Field-Flow Fractionation

    Czech Academy of Sciences Publication Activity Database

    Janča, Josef

    2015-01-01

    Roč. 20, č. 8 (2015), s. 671-680 ISSN 1023-666X R&D Projects: GA MŠk(CZ) LO1212 Institutional support: RVO:68081731 Keywords : diamond nanoparticles * high-speed microfluidic separation * micro-thermal field-flow fractionation, * article size distribution Subject RIV: JA - Electronics ; Optoelectronics, Electrical Engineering Impact factor: 1.515, year: 2015

  4. Conductivity-Dependent Flow Field-Flow Fractionation of Fulvic and Humic Acid Aggregates

    Directory of Open Access Journals (Sweden)

    Martha J. M. Wells

    2015-09-01

    Full Text Available Fulvic (FAs and humic acids (HAs are chemically fascinating. In water, they have a strong propensity to aggregate, but this research reveals that tendency is regulated by ionic strength. In the environment, conductivity extremes occur naturally—freshwater to seawater—warranting consideration at low and high values. The flow field flow fractionation (flow FFF of FAs and HAs is observed to be concentration dependent in low ionic strength solutions whereas the corresponding flow FFF fractograms in high ionic strength solutions are concentration independent. Dynamic light scattering (DLS also reveals insight into the conductivity-dependent behavior of humic substances (HSs. Four particle size ranges for FAs and humic acid aggregates are examined: (1 <10 nm; (2 10 nm–6 µm; (3 6–100 µm; and (4 >100 µm. Representative components of the different size ranges are observed to dynamically coexist in solution. The character of the various aggregates observed—such as random-extended-coiled macromolecules, hydrogels, supramolecular, and micellar—as influenced by electrolytic conductivity, is discussed. The disaggregation/aggregation of HSs is proposed to be a dynamic equilibrium process for which the rate of aggregate formation is controlled by the electrolytic conductivity of the solution.

  5. Polysaccharide characterization by hollow-fiber flow field-flow fractionation with on-line multi-angle static light scattering and differential refractometry.

    Science.gov (United States)

    Pitkänen, Leena; Striegel, André M

    2015-02-06

    Accurate characterization of the molar mass and size of polysaccharides is an ongoing challenge, oftentimes due to architectural diversity but also to the broad molar mass (M) range over which a single polysaccharide can exist and to the ultra-high M of many polysaccharides. Because of the latter, many of these biomacromolecules experience on-column, flow-induced degradation during analysis by size-exclusion and, even, hydrodynamic chromatography (SEC and HDC, respectively). The necessity for gentler fractionation methods has, to date, been addressed employing asymmetric flow field-flow fractionation (AF4). Here, we introduce the coupling of hollow-fiber flow field-flow fractionation (HF5) to multi-angle static light scattering (MALS) and differential refractometry (DRI) detection for the analysis of polysaccharides. In HF5, less stresses are placed on the macromolecules during separation than in SEC or HDC, and HF5 can offer a higher sensitivity, with less propensity for system overloading and analyte aggregation, than generally found in AF4. The coupling to MALS and DRI affords the determination of absolute, calibration-curve-independent molar mass averages and dispersities. Results from the present HF5/MALS/DRI experiments with dextrans, pullulans, and larch arabinogalactan were augmented with hydrodynamic radius (RH) measurements from off-line quasi-elastic light scattering (QELS) and by RH distribution calculations and fractogram simulations obtained via a finite element analysis implementation of field-flow fractionation theory by commercially available software. As part of this study, we have investigated analyte recovery in HF5 and also possible reasons for discrepancies between calculated and simulated results vis-à-vis experimentally determined data. Published by Elsevier B.V.

  6. Separation of platelets from other blood cells in continuous-flow by dielectrophoresis field-flow-fractionation

    OpenAIRE

    Piacentini, Niccolò; Mernier, Guillaume; Tornay, Raphaël; Renaud, Philippe

    2011-01-01

    We present a microfluidic device capable of separating platelets from other blood cells in continuous flow using dielectrophoresis field-flow-fractionation. The use of hydrodynamic focusing in combination with the application of a dielectrophoretic force allows the separation of platelets from red blood cells due to their size difference. The theoretical cell trajectory has been calculated by numerical simulations of the electrical field and flow speed, and is in agreement with the experiment...

  7. Diffusive processes in the cross-field flow of intense plasma beams

    International Nuclear Information System (INIS)

    Newberger, B.; Rostoker, N.

    1988-09-01

    We consider magnetic field diffusion in the presence of strongly magnetized electrons (ω/sub ce//tau//sub co/ > 1) as a mechanism for the rapid field penetration observed in cross-field flows of high-β plasma beams. The diffusion has been investigated in several cases which are amenable to analytic solution. The flux penetration times are found to be insensitive to the particular configuration. Comparison with two experiments is made. Agreement within the limits of the experiments is found. Both require an anomalous collision rate which is consistent with observed fluctuations in one case but apparently not the other. 17 refs., 1 fig

  8. Colloidal transport of uranium in soil: Size fractionation and characterization by field-flow fractionation-multi-detection

    International Nuclear Information System (INIS)

    Claveranne-Lamolere, C.; Lespes, G.; Dubascoux, St.; Potin-Gautier, M.; Claveranne-Lamolere, C.; Aupiais, J.; Pointurier, F.

    2009-01-01

    The aim of this study was to characterize colloids associated with uranium by using an on-line fractionation/multi-detection technique based on asymmetrical flow field-flow fractionation (As-Fl-FFF) hyphenated with UV detector, multi angle laser light scattering (MALLS) and inductively coupling plasma-mass spectrometry (ICP-MS). Moreover, thanks to the As-Fl-FFF, the different colloidal fractions were collected and characterized by a total organic carbon analyzer (TOC). Thus it is possible to determine the nature (organic or inorganic colloids), molar mass, size (gyration and hydrodynamic radii) and quantitative uranium distribution over the whole colloidal phase. In the case of the site studied, two populations are highlighted. The first population corresponds to humic-like substances with a molar mass of (1500 ± 300) g mol -1 and a hydrodynamic diameter of (2. 0 ± 0. 2) nm. The second one has been identified as a mix of carbonated nano-particles or clays with organic particles (aggregates and/or coating of the inorganic particles) with a size range hydrodynamic diameter between 30 and 450 nm. Each population is implied in the colloidal transport of uranium: maximum 1% of the uranium content in soil leachate is transported by the colloids in the site studied, according to the depth in the soil. Indeed, humic substances are the main responsible of this transport in sub-surface conditions whereas nano-particles drive the phenomenon in depth conditions. (authors)

  9. Circuit modification in electrical field flow fractionation systems generating higher resolution separation of nanoparticles.

    Science.gov (United States)

    Tasci, Tonguc O; Johnson, William P; Fernandez, Diego P; Manangon, Eliana; Gale, Bruce K

    2014-10-24

    Compared to other sub-techniques of field flow fractionation (FFF), cyclical electrical field flow fractionation (CyElFFF) is a relatively new method with many opportunities remaining for improvement. One of the most important limitations of this method is the separation of particles smaller than 100nm. For such small particles, the diffusion rate becomes very high, resulting in severe reductions in the CyElFFF separation efficiency. To address this limitation, we modified the electrical circuitry of the ElFFF system. In all earlier ElFFF reports, electrical power sources have been directly connected to the ElFFF channel electrodes, and no alteration has been made in the electrical circuitry of the system. In this work, by using discrete electrical components, such as resistors and diodes, we improved the effective electric field in the system to allow high resolution separations. By modifying the electrical circuitry of the ElFFF system, high resolution separations of 15 and 40nm gold nanoparticles were achieved. The effects of applying different frequencies, amplitudes and voltage shapes have been investigated and analyzed through experiments. Copyright © 2014 Elsevier B.V. All rights reserved.

  10. Top-down and bottom-up lipidomic analysis of rabbit lipoproteins under different metabolic conditions using flow field-flow fractionation, nanoflow liquid chromatography and mass spectrometry.

    Science.gov (United States)

    Byeon, Seul Kee; Kim, Jin Yong; Lee, Ju Yong; Chung, Bong Chul; Seo, Hong Seog; Moon, Myeong Hee

    2015-07-31

    This study demonstrated the performances of top-down and bottom-up approaches in lipidomic analysis of lipoproteins from rabbits raised under different metabolic conditions: healthy controls, carrageenan-induced inflammation, dehydration, high cholesterol (HC) diet, and highest cholesterol diet with inflammation (HCI). In the bottom-up approach, the high density lipoproteins (HDL) and the low density lipoproteins (LDL) were size-sorted and collected on a semi-preparative scale using a multiplexed hollow fiber flow field-flow fractionation (MxHF5), followed by nanoflow liquid chromatography-ESI-MS/MS (nLC-ESI-MS/MS) analysis of the lipids extracted from each lipoprotein fraction. In the top-down method, size-fractionated lipoproteins were directly infused to MS for quantitative analysis of targeted lipids using chip-type asymmetrical flow field-flow fractionation-electrospray ionization-tandem mass spectrometry (cAF4-ESI-MS/MS) in selected reaction monitoring (SRM) mode. The comprehensive bottom-up analysis yielded 122 and 104 lipids from HDL and LDL, respectively. Rabbits within the HC and HCI groups had lipid patterns that contrasted most substantially from those of controls, suggesting that HC diet significantly alters the lipid composition of lipoproteins. Among the identified lipids, 20 lipid species that exhibited large differences (>10-fold) were selected as targets for the top-down quantitative analysis in order to compare the results with those from the bottom-up method. Statistical comparison of the results from the two methods revealed that the results were not significantly different for most of the selected species, except for those species with only small differences in concentration between groups. The current study demonstrated that top-down lipid analysis using cAF4-ESI-MS/MS is a powerful high-speed analytical platform for targeted lipidomic analysis that does not require the extraction of lipids from blood samples. Copyright © 2015 Elsevier B

  11. Field flow fractionation for assessing neonatal Fc receptor and Fcγ receptor binding to monoclonal antibodies in solution.

    Science.gov (United States)

    Pollastrini, Joey; Dillon, Thomas M; Bondarenko, Pavel; Chou, Robert Y-T

    2011-07-01

    Analysis of the strength and stoichiometry of immunoglobulin G (IgG) binding to neonatal Fc receptor (FcRn) and Fcγ receptor (FcγR) is important for evaluating the pharmacokinetics and effector functions of therapeutic monoclonal antibody (mAb) products, respectively. The current standard for assessing FcγR and FcRn binding is composed of cell-based and surface plasmon resonance (SPR) assays. In this work, asymmetrical flow field flow fractionation (AF4) was evaluated to establish the true stoichiometry of IgG binding in solution. AF4 and liquid chromatography-mass spectrometry (LC-MS) were applied to directly observe IgG/FcγR and IgG/FcRn complexes, which were not observed using nonequilibrium size exclusion chromatography (SEC) analysis. Human serum albumin (HSA), an abundant component of human blood and capable of binding FcRn, was studied in combination with FcRn and IgG. AF4 demonstrated that the majority of large complexes of IgG/FcRn/HSA were at an approximate 1:2:1 molar ratio. In addition, affinity measurements of the complex were performed in the sub-micromolar affinity range. A significant decrease in binding was detected for IgG molecules with increased oxidation in the Fc region. AF4 was useful in detecting weak binding between full-length IgG/Fc fragments and Fc receptors and the effect of chemical modifications on binding. AF4 is a useful technique in the assessment of mAb product quality attributes. Copyright © 2011 Elsevier Inc. All rights reserved.

  12. Analytical scale purification of zirconia colloidal suspension using field programmed sedimentation field flow fractionation.

    Science.gov (United States)

    Van-Quynh, Alexandra; Blanchart, Philippe; Battu, Serge; Clédat, Dominique; Cardot, Philippe

    2006-03-03

    Sedimentation field flow fractionation was used to obtain purified fractions from a polydispersed zirconia colloidal suspension in the potential purpose of optical material hybrid coating. The zirconia particle size ranged from 50/70 nm to 1000 nm. It exhibited a log-Gaussian particle size distribution (in mass or volume) and a 115% polydispersity index (P.I.). Time dependent eluted fractions of the original zirconia colloidal suspension were collected. The particle size distribution of each fraction was determined with scanning electron microscopy and Coulter sub-micron particle sizer (CSPS). These orthogonal techniques generated similar data. From fraction average elution times and granulometry measurements, it was shown that zirconia colloids are eluted according to the Brownian elution mode. The four collected fractions have a Gaussian like distribution and respective average size and polydispersity index of 153 nm (P.I. = 34.7%); 188 nm (P.I. = 27.9%); 228 nm (P.I. = 22.6%), and 276 nm (P.I. = 22.3%). These data demonstrate the strong size selectivity of SdFFF operated with programmed field of exponential profile for sorting particles in the sub-micron range. Using this technique, the analytical production of zirconia of given average size and reduced polydispersity is possible.

  13. Size characterization by Sedimentation Field Flow Fractionation of silica particles used as food additives.

    Science.gov (United States)

    Contado, Catia; Ravani, Laura; Passarella, Martina

    2013-07-25

    Four types of SiO2, available on the market as additives in food and personal care products, were size characterized using Sedimentation Field Flow Fractionation (SdFFF), SEM, TEM and Photon Correlation Spectroscopy (PCS). The synergic use of the different analytical techniques made it possible, for some samples, to confirm the presence of primary nanoparticles (10 nm) organized in clusters or aggregates of different dimension and, for others, to discover that the available information is incomplete, particularly that regarding the presence of small particles. A protocol to extract the silica particles from a simple food matrix was set up, enriching (0.25%, w w(-1)) a nearly silica-free instant barley coffee powder with a known SiO2 sample. The SdFFF technique, in conjunction with SEM observations, made it possible to identify the added SiO2 particles and verify the new particle size distribution. The SiO2 content of different powdered foodstuffs was determined by graphite furnace atomic absorption spectroscopy (GFAAS); the concentrations ranged between 0.006 and 0.35% (w w(-1)). The protocol to isolate the silica particles was so applied to the most SiO2-rich commercial products and the derived suspensions were separated by SdFFF; SEM and TEM observations supported the size analyses while GFAAS determinations on collected fractions permitted element identification. Copyright © 2013 Elsevier B.V. All rights reserved.

  14. Study of equivalent retention among different polymer-solvent systems in thermal field-flow fractionation

    International Nuclear Information System (INIS)

    Kim, Won Suk; Park, Young Hun; Lee, Dai Woon; Moon, Myeong Hee; Yu, Euy Kyung

    1998-01-01

    An equivalent retention has been experimentally observed in thermal field-flow fractionation (ThFF) for different polymer-solvent systems. It is shown that iso-retention between two sets of polymer-solvent systems can be obtained by adjusting the temperature difference (ΔT) according to the difference in the ration of ordinary diffusion coefficient to thermal diffusion coefficient. This method uses a compensation of field strength (ΔT) in ThFFF at a fixed condition of cold wall temperature. It is applied for the calculation of molecular weight of polymers based on a calibration run of different standards obtained at an adjusted ΔT. The polymer standards used in this study are polystyrene (PS), polymethylmethacrylate (PMMA), and polytetrahydrofuran (PTHF). Three carrier solvents, tetrahydrofuran (THF), methylethylketone (MEK) and ethylacetate (ETAc) were employed. Though the accuracy in the calculation of molecular weight is dependent on the difference in the slope of log λ vs. log M which is related to Mark-Houwink constant a, it shows reasonable agreement within about 6% of relative error in molecular weight calculation for the polymer-solvent systems having similar a value

  15. Asymmetric Flow Field-Flow Fractionation of Manufactured Silver Nanoparticles in Soil Water Extracts

    NARCIS (Netherlands)

    Koopmans, G.F.; Hiemstra, T.; Molleman, B.; Regelink, I.C.; Comans, R.N.J.

    2013-01-01

    Manufactured silver nanoparticles (AgNP) are among the most widely used nanoparticles in consumer products and their unintended release into the environment has become a serious concern. For a meaningful assessment of the risks of AgNP in soils, their concentration and particle-size-distribution in

  16. Asymmetric flow field-flow fractionation of superferrimagnetic iron oxide multicore nanoparticles

    DEFF Research Database (Denmark)

    Dutz, Silvio; Kuntsche, Judith; Eberbeck, Dietmar

    2012-01-01

    Magnetic nanoparticles are very useful for various medical applications where each application requires particles with specific magnetic properties. In this paper we describe the modification of the magnetic properties of magnetic multicore nanoparticles (MCNPs) by size dependent fractionation....... The hysteresis curves were measured by vibrating sample magnetometry. Starting from a coercivity of 1.41 kA m(-1) for the original MCNPs the coercivity of the particles in the different fractions varied from 0.41 to 3.83 kA m(-1). In our paper it is shown for the first time that fractions obtained from a broad...... size distributed MCNP fluid classified by AF4 show a strong correlation between hydrodynamic diameter and magnetic properties. Thus we state that AF4 is a suitable technology for reproducible size dependent classification of magnetic multicore nanoparticles suspended as ferrofluids....

  17. Different elution modes and field programming in gravitational field-flow fractionation: Field programming using density and viscosity gradients

    Czech Academy of Sciences Publication Activity Database

    Plocková, Jana; Chmelík, Josef

    2006-01-01

    Roč. 1118, č. 2 (2006), s. 253-260 ISSN 0021-9673 R&D Projects: GA MZe QD1005 Institutional research plan: CEZ:AV0Z40310501 Keywords : gravitational field flow fractionation * focusing elution mode * carrier liquid density Subject RIV: CB - Analytical Chemistry, Separation Impact factor: 3.554, year: 2006

  18. Size characterization by Sedimentation Field Flow Fractionation of silica particles used as food additives

    International Nuclear Information System (INIS)

    Contado, Catia; Ravani, Laura; Passarella, Martina

    2013-01-01

    Graphical abstract: -- Highlights: •Four types of SiO 2 particles were characterized by SdFFF, PCS and EM techniques. •Clusters of 10 nm nanoparticles were found in some SiO 2 samples. •A method was set up to extract SiO 2 particles from food matrices. •The effects of the carrier solution composition on SdFFF separations were evaluated. •Particle size distributions were obtained from SiO 2 particles extracted from foodstuffs. -- Abstract: Four types of SiO 2 , available on the market as additives in food and personal care products, were size characterized using Sedimentation Field Flow Fractionation (SdFFF), SEM, TEM and Photon Correlation Spectroscopy (PCS). The synergic use of the different analytical techniques made it possible, for some samples, to confirm the presence of primary nanoparticles (10 nm) organized in clusters or aggregates of different dimension and, for others, to discover that the available information is incomplete, particularly that regarding the presence of small particles. A protocol to extract the silica particles from a simple food matrix was set up, enriching (0.25%, w w −1 ) a nearly silica-free instant barley coffee powder with a known SiO 2 sample. The SdFFF technique, in conjunction with SEM observations, made it possible to identify the added SiO 2 particles and verify the new particle size distribution. The SiO 2 content of different powdered foodstuffs was determined by graphite furnace atomic absorption spectroscopy (GFAAS); the concentrations ranged between 0.006 and 0.35% (w w −1 ). The protocol to isolate the silica particles was so applied to the most SiO 2 -rich commercial products and the derived suspensions were separated by SdFFF; SEM and TEM observations supported the size analyses while GFAAS determinations on collected fractions permitted element identification

  19. Asymmetric flow events in a VEER 1000

    International Nuclear Information System (INIS)

    Horak, W.C.; Kennett, R.J.; Shier, W.; Guppy, J.G.

    1992-07-01

    This paper describes the simulation of asymmetric loss of flow events in Russian designed VVER-1000 reactors using the RETRAN-02 Mod4 computer code. VVER-1000 reactors have significant differences from United States pressurized water reactors including multi-level emergency response systems and plant operation at reduced power levels with one or more main circulation pumps inoperable. The results of these simulations are compared to similar analyses done by the designers for the Rovno plant

  20. Size characterization by Sedimentation Field Flow Fractionation of silica particles used as food additives

    Energy Technology Data Exchange (ETDEWEB)

    Contado, Catia, E-mail: Catia.Contado@unife.it [University of Ferrara, Department of Chemical and Pharmaceutical Sciences, via L. Borsari, 46, 44121 Ferrara (Italy); Ravani, Laura [University of Ferrara, Department of Life Sciences and Biotechnologies, via L. Borsari, 46, 44121 Ferrara (Italy); Passarella, Martina [University of Ferrara, Department of Chemical and Pharmaceutical Sciences, via L. Borsari, 46, 44121 Ferrara (Italy)

    2013-07-25

    Graphical abstract: -- Highlights: •Four types of SiO{sub 2} particles were characterized by SdFFF, PCS and EM techniques. •Clusters of 10 nm nanoparticles were found in some SiO{sub 2} samples. •A method was set up to extract SiO{sub 2} particles from food matrices. •The effects of the carrier solution composition on SdFFF separations were evaluated. •Particle size distributions were obtained from SiO{sub 2} particles extracted from foodstuffs. -- Abstract: Four types of SiO{sub 2}, available on the market as additives in food and personal care products, were size characterized using Sedimentation Field Flow Fractionation (SdFFF), SEM, TEM and Photon Correlation Spectroscopy (PCS). The synergic use of the different analytical techniques made it possible, for some samples, to confirm the presence of primary nanoparticles (10 nm) organized in clusters or aggregates of different dimension and, for others, to discover that the available information is incomplete, particularly that regarding the presence of small particles. A protocol to extract the silica particles from a simple food matrix was set up, enriching (0.25%, w w{sup −1}) a nearly silica-free instant barley coffee powder with a known SiO{sub 2} sample. The SdFFF technique, in conjunction with SEM observations, made it possible to identify the added SiO{sub 2} particles and verify the new particle size distribution. The SiO{sub 2} content of different powdered foodstuffs was determined by graphite furnace atomic absorption spectroscopy (GFAAS); the concentrations ranged between 0.006 and 0.35% (w w{sup −1}). The protocol to isolate the silica particles was so applied to the most SiO{sub 2}-rich commercial products and the derived suspensions were separated by SdFFF; SEM and TEM observations supported the size analyses while GFAAS determinations on collected fractions permitted element identification.

  1. Different elution modes and field programming in gravitational field-flow fractionation. III. Field programming by flow-rate gradient generated by a programmable pump

    Czech Academy of Sciences Publication Activity Database

    Plocková, Jana; Chmelík, Josef

    2001-01-01

    Roč. 918, č. 2 (2001), s. 361-370 ISSN 0021-9673 R&D Projects: GA AV ČR IAA4031805 Institutional research plan: CEZ:AV0Z4031919 Keywords : field-flow fractionation * field programming * flow-rate gradients Subject RIV: CB - Analytical Chemistry, Separation Impact factor: 2.793, year: 2001

  2. Online Coupling of Flow-Field Flow Fractionation and Single Particle Inductively Coupled Plasma-Mass Spectrometry: Characterization of Nanoparticle Surface Coating Thickness and Aggregation State

    Science.gov (United States)

    Surface coating thickness and aggregation state have strong influence on the environmental fate, transport, and toxicity of engineered nanomaterials. In this study, flow-field flow fractionation coupled on-line with single particle inductively coupled plasma-mass spectrometry i...

  3. Feasibility study of red blood cell debulking by magnetic field-flow fractionation with step-programmed flow.

    Science.gov (United States)

    Moore, Lee R; Williams, P Stephen; Nehl, Franziska; Abe, Koji; Chalmers, Jeffrey J; Zborowski, Maciej

    2014-02-01

    Emerging applications of rare cell separation and analysis, such as separation of mature red blood cells from hematopoietic cell cultures, require efficient methods of red blood cell (RBC) debulking. We have tested the feasibility of magnetic RBC separation as an alternative to centrifugal separation using an approach based on the mechanism of magnetic field-flow fractionation (MgFFF). A specially designed permanent magnet assembly generated a quadrupole field having a maximum field of 1.68 T at the magnet pole tips, zero field at the aperture axis, and a nearly constant radial field gradient of 1.75 T/mm (with a negligible angular component) inside a cylindrical aperture of 1.9 mm (diameter) and 76 mm (length). The cell samples included high-spin hemoglobin RBCs obtained by chemical conversion of hemoglobin to methemoglobin (met RBC) or by exposure to anoxic conditions (deoxy RBC), low-spin hemoglobin obtained by exposure of RBC suspension to ambient air (oxy RBC), and mixtures of deoxy RBC and cells from a KG-1a white blood cell (WBC) line. The observation that met RBCs did not elute from the channel at the lower flow rate of 0.05 mL/min applied for 15 min but quickly eluted at the subsequent higher flow rate of 2.0 mL/min was in agreement with FFF theory. The well-defined experimental conditions (precise field and flow characteristics) and a well-established FFF theory verified by studies with model cell systems provided us with a strong basis for making predictions about potential practical applications of the magnetic RBC separation.

  4. Extraction of hyaluronic acid (HA) from rooster comb and characterization using flow field-flow fractionation (FlFFF) coupled with multiangle light scattering (MALS).

    Science.gov (United States)

    Kang, Dong Young; Kim, Won-Suk; Heo, In Sook; Park, Young Hun; Lee, Seungho

    2010-11-01

    Hyaluronic acid (HA) was extracted in a relatively large scale from rooster comb using a method similar to that reported previously. The extraction method was modified to simplify and to reduce time and cost in order to accommodate a large-scale extraction. Five hundred grams of frozen rooster combs yielded about 500 mg of dried HA. Extracted HA was characterized using asymmetrical flow field-flow fractionation (AsFlFFF) coupled online to a multiangle light scattering detector and a refractive index detector to determine the molecular size, molecular weight (MW) distribution, and molecular conformation of HA. For characterization of HA, AsFlFFF was operated by a simplified two-step procedure, instead of the conventional three-step procedure, where the first two steps (sample loading and focusing) were combined into one to avoid the adsorption of viscous HA onto the channel membrane. The simplified two-step AsFlFFF yielded reasonably good separations of HA molecules based on their MWs. The weight average MW (M(w) ) and the average root-mean-square (RMS) radius of HA extracted from rooster comb were 1.20×10(6) and 94.7 nm, respectively. When the sample solution was filtered through a 0.45 μm disposable syringe filter, they were reduced down to 3.8×10(5) and 50.1 nm, respectively. Copyright © 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  5. Predicting membrane flux decline from complex mixtures using flow-field flow fractionation measurements and semi-empirical theory.

    Science.gov (United States)

    Pellegrino, J; Wright, S; Ranvill, J; Amy, G

    2005-01-01

    Flow-Field Flow Fractionation (FI-FFF) is an idealization of the cross flow membrane filtration process in that, (1) the filtration flux and crossflow velocity are constant from beginning to end of the device, (2) the process is a relatively well-defined laminar-flow hydrodynamic condition, and (3) the solutes are introduced as a pulse-input that spreads due to interactions with each other and the membrane in the dilute-solution limit. We have investigated the potential for relating FI-FFF measurements to membrane fouling. An advection-dispersion transport model was used to provide 'ideal' (defined as spherical, non-interacting solutes) solute residence time distributions (RTDs) for comparison with 'real' RTDs obtained experimentally at different cross-field velocities and solution ionic strength. An RTD moment analysis based on a particle diameter probability density function was used to extract "effective" characteristic properties, rather than uniquely defined characteristics, of the standard solute mixture. A semi-empirical unsteady-state, flux decline model was developed that uses solute property parameters. Three modes of flux decline are included: (1) concentration polarization, (2) cake buildup, and (3) adsorption on/in pores, We have used this model to test the hypothesis-that an analysis of a residence time distribution using FI-FFF can describe 'effective' solute properties or indices that can be related to membrane flux decline in crossflow membrane filtration. Constant flux filtration studies included the changes of transport hydrodynamics (solvent flux to solute back diffusion (J/k) ratios), solution ionic strength, and feed water composition for filtration using a regenerated cellulose ultrafiltration membrane. Tests of the modeling hypothesis were compared with experimental results from the filtration measurements using several correction parameters based on the mean and variance of the solute RTDs. The corrections used to modify the boundary layer

  6. Interaction of Eu, Th and U with bentonite colloids in presence of humic acid: a flow-field flow fractionation study

    International Nuclear Information System (INIS)

    Bouby, M.; Geckeis, H.; Schaefer, Th.; Mihai, S.; Fanghaenell, Th.

    2005-01-01

    Full text of publication follows: The actinide mobility in the far-field of a repository site can be strongly influenced by the presence of colloidal species. Field migration experiments at the Grimsel Test Site under low ionic strength (I=10 -3 mol/L) and high pH (∼9.6) conditions have demonstrated a considerable clay colloid-mediated actinide(III/IV) migration [1]. However, those studies rendered it necessary to take the kinetics of notably the actinide-colloid interaction and colloid stability into account [2]. In the present study, we examine the stability of bentonite clay colloids in natural Grimsel groundwater and their interaction with Cs(I), Eu(III), Th(IV) and U(VI) (conc. ∼ 10 -8 mol/L). Experiments cover 12 months contact times and are performed under anoxic conditions. Humic acid (Gohy-573) is added after different contact times as a competing ligand and the time dependent metal ion desorption is followed. Dedicated experiments and thermodynamic speciation calculations are performed to estimate the metal ion speciation within the colloid system. As the experimental metal ion speciation (i.e. differentiation of clay-colloid bound, humic colloid bound and dissolved metal ion species) at the given low concentration conditions is hardly possible by spectroscopic methods, we use Asymmetric Flow-Field Flow Fractionation coupled to UV-Vis spectrophotometry and ICP-MS detection. Unexpectedly, it is found that small-sized bentonite colloids ( d -values, Cs and U do not interact significantly with bentonite colloids, while Th and Eu do. Eu desorption from clay colloids by humic acid is delayed significantly upon increasing the clay colloid-Eu contact time up to several months. Nevertheless, estimated equilibrium conditions are attained after 7 months desorption time. However, it appears that significant fractions of clay colloid borne Th(IV) do not desorb in presence of humic acid and equilibrium conditions estimated from calculation and experiments are not

  7. Survey of near-field flow calculations for nuclear waste repositories NMA L21

    International Nuclear Information System (INIS)

    Wilson, R.N.; Holland, D.H.

    1979-11-01

    A survey of methods and codes which describe the flow of groundwater and the migration of radioactive waste in and about nuclear repositories was performed. A number of laboratories engaged in studies of waste migration and groundwater flow were visited in order to discuss the general problem and obtain reports of work being performed. The results of this survey are discussed

  8. On the retention mechanisms and secondary effects in microthermal field-flow fractionation of particles

    Czech Academy of Sciences Publication Activity Database

    Janča, J.; Stejskal, Jaroslav

    2009-01-01

    Roč. 1216, č. 52 (2009), s. 9071-9080 ISSN 0021-9673 Institutional research plan: CEZ:AV0Z40500505 Keywords : hydrodynamic lift forces * slow shear-flow * macroscopic rigid spheres Subject RIV: CD - Macromolecular Chemistry Impact factor: 4.101, year: 2009

  9. Cross-field flow and electric potential in a plasma slab

    Directory of Open Access Journals (Sweden)

    J. De Keyser

    2013-08-01

    Full Text Available We consider cross-field plasma flow inside a field-aligned plasma slab embedded in a uniform background in a 1-dimensional geometry. This situation may arise, for instance, when long-lasting reconnection pulses inject plasma into the inner magnetosphere. The present paper presents a detailed analysis of the structure of the interfaces that separate the slab from the background plasma on either side; a fully kinetic model is used to do so. Since the velocity shear across both interfaces has opposite signs, and given the typical gyroradius differences between injected and background ions and electrons, the structure of both interfaces can be very different. The behaviour of the slab and its interfaces depends critically on the flow of the plasma transverse to the magnetic field; in particular, it is shown that there are bounds to the flow speed that can be supported by the magnetised plasma. Further complicating the picture is the effect of the potential difference between the slab and its environment.

  10. Towards 2D field-flow fractionation - Vector separation over slanted open cavities

    Science.gov (United States)

    Bernate, Jorge A.; Yang, Mengfei; Zhao, Hong; Risbud, Sumedh; Paul, Colin; Dallas, Matthew; Konstantopoulos, Konstantinos; Drazer, German; Shaqfeh, Eric S. G.

    2013-11-01

    Planar microfluidic platforms for vector chromatography, in which different species fan out in different directions and can be continuously sorted, are particularly promising for the high throughput separation of multicomponent mixtures. We carry out a computational study of the vector separation of dilute suspensions of rigid and flexible particles transported by a pressure-driven flow over an array of slanted open cavities. The numerical scheme is based on a Stokes flow boundary integral equation method. The simulations are performed in a periodic system without lateral confinement, relevant to microfluidic devices with negligible recirculation in the main channel. We study the deflection of rigid spherical particles, of flexible capsules as a model of white and red blood cells, and of rigid discoidal particles as a model of platelets. We characterize the deflection of different particles as a function of their size, shape, shear elasticity, their release position, and the geometric parameters of the channel. The simulations provide insight into the separation mechanism and allow the optimization of specific devices depending on the application. Good agreement with experiments is observed.

  11. Quantitative characterization of gold nanoparticles by field-flow fractionation coupled online with light scattering detection and inductively coupled plasma mass spectrometry.

    Science.gov (United States)

    Schmidt, Bjørn; Loeschner, Katrin; Hadrup, Niels; Mortensen, Alicja; Sloth, Jens J; Koch, Christian Bender; Larsen, Erik H

    2011-04-01

    An analytical platform coupling asymmetric flow field-flow fractionation (AF(4)) with multiangle light scattering (MALS), dynamic light scattering (DLS), and inductively coupled plasma mass spectrometry (ICPMS) was established and used for separation and quantitative determination of size and mass concentration of nanoparticles (NPs) in aqueous suspension. Mixtures of three polystyrene (PS) NPs between 20 and 100 nm in diameter and mixtures of three gold (Au) NPs between 10 and 60 nm in diameter were separated by AF(4). The geometric diameters of the separated PS NPs and the hydrodynamic diameters of the Au and PS NPs were determined online by MALS and DLS, respectively. The three separated Au NPs were quantified by ICPMS and recovered at 50-95% of the injected masses, which ranged between approximately 8-80 ng of each nanoparticle size. Au NPs adhering to the membrane in the separation channel was found to be a major cause for incomplete recoveries. The lower limit of detection (LOD) ranged between 0.02 ng Au and 0.4 ng Au, with increasing LOD by increasing nanoparticle diameter. The analytical platform was applied to characterization of Au NPs in livers of rats, which were dosed with 10 nm, 60 nm, or a mixture of 10 and 60 nm nanoparticles by intravenous injection. The homogenized livers were solubilized in tetramethylammonium hydroxide (TMAH), and the recovery of Au NPs from the livers amounted to 86-123% of their total Au content. In spite of successful stabilization with bovine serum albumin even in alkaline medium, separation of the Au NPs by AF(4) was not possible due to association with undissolved remains of the alkali-treated liver tissues as demonstrated by electron microscopy images.

  12. Interaction of Eu, Th and U with bentonite colloids in presence of humic acid: a flow-field flow fractionation study

    Energy Technology Data Exchange (ETDEWEB)

    Bouby, M.; Geckeis, H.; Schaefer, Th. [Institut fuer Nukleare Entsorgung, Forschungszentrum Karlsruhe, Postfach 3640, D-76021 Karlsruhe (Germany); Mihai, S. [Institut fuer Nukleare Entsorgung, Forschungszentrum Karlsruhe, Postfach 3640, D-76021 Karlsruhe (Germany)]|[Politehnica University, Faculty of Industrial Chemistry, Calea Grivitei 132, Bucharest 78122 (Romania); Fanghaenell, Th. [Institut fuer Nukleare Entsorgung, Forschungszentrum Karlsruhe, Postfach 3640, D-76021 Karlsruhe (Germany)]|[Physikalisch-Chemisches Institut, Ruprecht-Karls-Universitaet, Im Neuenheimer Feld 253, D- 69120 Heidelberg (Germany)

    2005-07-01

    Full text of publication follows: The actinide mobility in the far-field of a repository site can be strongly influenced by the presence of colloidal species. Field migration experiments at the Grimsel Test Site under low ionic strength (I=10{sup -3} mol/L) and high pH ({approx}9.6) conditions have demonstrated a considerable clay colloid-mediated actinide(III/IV) migration [1]. However, those studies rendered it necessary to take the kinetics of notably the actinide-colloid interaction and colloid stability into account [2]. In the present study, we examine the stability of bentonite clay colloids in natural Grimsel groundwater and their interaction with Cs(I), Eu(III), Th(IV) and U(VI) (conc. {approx} 10{sup -8} mol/L). Experiments cover 12 months contact times and are performed under anoxic conditions. Humic acid (Gohy-573) is added after different contact times as a competing ligand and the time dependent metal ion desorption is followed. Dedicated experiments and thermodynamic speciation calculations are performed to estimate the metal ion speciation within the colloid system. As the experimental metal ion speciation (i.e. differentiation of clay-colloid bound, humic colloid bound and dissolved metal ion species) at the given low concentration conditions is hardly possible by spectroscopic methods, we use Asymmetric Flow-Field Flow Fractionation coupled to UV-Vis spectrophotometry and ICP-MS detection. Unexpectedly, it is found that small-sized bentonite colloids (< 50 nm) not visible by light scattering (PCS) analysis agglomerate and finally reach a steady-state colloid size distribution (50-200 nm) after {approx} 3 months. As estimated from known thermodynamic data and experimentally determined K{sub d}-values, Cs and U do not interact significantly with bentonite colloids, while Th and Eu do. Eu desorption from clay colloids by humic acid is delayed significantly upon increasing the clay colloid-Eu contact time up to several months. Nevertheless, estimated

  13. Development of sedimentation field-flow fractionation-inductively coupled plasma mass-spectrometry for the characterization of environmental colloids

    International Nuclear Information System (INIS)

    Ranville, J.F.; Shanks, F.; Morrison, R.J.S.; Harris, T.; Doss, F.; Beckett, R.; Chittleborough, D.J.

    1999-01-01

    A relatively new hyphenated technique for the simultaneous size separation and elemental analysis of colloids has been further developed and applied to the characterization of soil colloids. Sedimentation field-flow fractionation (SdFFF) was directly interfaced to an inductively coupled plasma-mass spectrometer (ICP-MS) to provide high-resolution sizing and elemental analysis of colloids in the range 0.05-1.0 μm. For this work our existing SdFFF instrument was modified by addition of an upgraded motor and software for centrifuge speed control and data collection. Analytical techniques were developed for the calibration and drift correction of the ICP-MS data collected during on-line SdFFF-ICP-MS analyses. Software was developed to allow off-line computation of drift-corrected, elemental concentrations across the colloid size range. SdFFF-ICP-MS examination of two colloid samples isolated from surface soil horizons showed significant enrichment in iron-containing phases in both the smaller and larger colloids relative to intermediate particle sizes (∼0.3 0.3 μm). These results demonstrate the utility of SdFFF-ICP-MS for examination of soil chemistry and mineralogy and suggests the technique will have application to other environmental and geochemical studies. (Copyright (c) 1999 Elsevier Science B.V., Amsterdam. All rights reserved.)

  14. Relationship between the ratio of large and small starch granules determined by gravitational field-flow fractionation and malting quality of barley varieties

    Czech Academy of Sciences Publication Activity Database

    Chmelík, Josef; Mazanec, Karel; Bohačenko, I.; Psota, V.

    2007-01-01

    Roč. 30, 9-10 (2007), s. 1289-1301 ISSN 1082-6076 R&D Projects: GA MZe QD1005 Institutional research plan: CEZ:AV0Z40310501 Keywords : gravitational field- flow fractionation * starch granules * barley varieties Subject RIV: CB - Analytical Chemistry, Separation Impact factor: 0.977, year: 2007

  15. Different elution modes and field programming in gravitational field-flow fractionation IV. Field programming achieved with channels of non-constant cross-sections

    Czech Academy of Sciences Publication Activity Database

    Plocková, Jana; Matulík, František; Chmelík, Josef

    2002-01-01

    Roč. 955, č. 1 (2002), s. 95-103 ISSN 0021-9673 R&D Projects: GA AV ČR IAA4031805 Institutional research plan: CEZ:AV0Z4031919 Keywords : gravitational field-flow fractionation * field programming * hydrodynamic lift forces Subject RIV: CB - Analytical Chemistry, Separation Impact factor: 3.098, year: 2002

  16. Core microstructure, morphology and chain arrangement of block copolymer self-assemblies as investigated by thermal field-flow fractionation.

    Science.gov (United States)

    Muza, U L; Greyling, G; Pasch, H

    2018-05-28

    The self-assembly of block copolymers (BCPs), as a result of solvent selectivity for one block, has recently received significant attention due to novel applications of BCPs in pharmaceuticals, biomedicine, cosmetics, electronics and nanotechnology. The correlation of BCP microstructure and the structure of the resulting self-assemblies requires advanced analytical methods. However, traditional bulk characterization techniques are limited in the quest of providing detailed information regarding molar mass (M w ), hydrodynamic size (D h ), chemical composition, and morphology for these self-assemblies. In the present study, thermal field-flow fractionation (ThFFF) is utilised to investigate the impact of core microstructure on the resultant solution properties of vesicles prepared from polystyrene-polybutadiene block copolymers (PS-b-PBd) with 1.2- and 1.4-polybutadiene blocks, respectively. As compared to investigations on the impact of the corona microstructure, the impact of core microstructure on micellar properties has largely been neglected in previous work. In N,N-dimethylacetamide (DMAc) these BCPs form vesicles having PS shells and PBd cores. D h , M w , aggregation number, and critical micelle concentration of these micelles are shown to be sensitive to the core microstructure, therefore, demonstrating the potential of microstructural differences to be used for providing tuneable pathways to specific self-assemblies. It is shown that micelles prepared from BCPs of similar PS and PBd block sizes are successfully separated by ThFFF. It is further demonstrated in this study that PS-b-PBd vesicles and PS homopolymers of identical surface chemistry (PS) and comparable D h in DMAc, can be separated by ThFFF. Copyright © 2018. Published by Elsevier B.V.

  17. Aggregation behavior of fullerenes in aqueous solutions: a capillary electrophoresis and asymmetric flow field-flow fractionation study

    NARCIS (Netherlands)

    Astefanei, A.; Núñez, O.; Galceran, M.T.; Kok, W.Th.; Schoenmakers, P.J.

    2015-01-01

    In this work, the electrophoretic behavior of hydrophobic fullerenes [buckminsterfullerene (C-60), C-70, and N-methyl-fulleropyrrolidine (C-60-pyrr)] and water-soluble fullerenes [fullerol (C-60(OH)(24)); polyhydroxy small gap fullerene, hydrated (C-120(OH)(30)); C-60 pyrrolidine tris acid

  18. Different elution modes and field programming in gravitational field-flow fractionation. III. Field programming by flow-rate gradient generated by a programmable pump.

    Science.gov (United States)

    Plocková, J; Chmelík, J

    2001-05-25

    Gravitational field-flow fractionation (GFFF) utilizes the Earth's gravitational field as an external force that causes the settlement of particles towards the channel accumulation wall. Hydrodynamic lift forces oppose this action by elevating particles away from the channel accumulation wall. These two counteracting forces enable modulation of the resulting force field acting on particles in GFFF. In this work, force-field programming based on modulating the magnitude of hydrodynamic lift forces was implemented via changes of flow-rate, which was accomplished by a programmable pump. Several flow-rate gradients (step gradients, linear gradients, parabolic, and combined gradients) were tested and evaluated as tools for optimization of the separation of a silica gel particle mixture. The influence of increasing amount of sample injected on the peak resolution under flow-rate gradient conditions was also investigated. This is the first time that flow-rate gradients have been implemented for programming of the resulting force field acting on particles in GFFF.

  19. Thomson scattering measurements from asymmetric interpenetrating plasma flows

    Energy Technology Data Exchange (ETDEWEB)

    Ross, J. S., E-mail: ross36@llnl.gov; Moody, J. D.; Fiuza, F.; Ryutov, D.; Divol, L.; Huntington, C. M.; Park, H.-S. [Lawrence Livermore National Laboratory, P.O. Box 808, Livermore, California 94551 (United States)

    2014-11-15

    Imaging Thomson scattering measurements of collective ion-acoustic fluctuations have been utilized to determine ion temperature and density from laser produced counter-streaming asymmetric flows. Two foils are heated with 8 laser beams each, 500 J per beam, at the Omega Laser facility. Measurements are made 4 mm from the foil surface using a 60 J 2ω probe laser with a 200 ps pulse length. Measuring the electron density and temperature from the electron-plasma fluctuations constrains the fit of the multi-ion species, asymmetric flows theoretical form factor for the ion feature such that the ion temperatures, ion densities, and flow velocities for each plasma flow are determined.

  20. Flow line asymmetric nonimaging concentrating optics

    Science.gov (United States)

    Jiang, Lun; Winston, Roland

    2016-09-01

    Nonimaging Optics has shown that it achieves the theoretical limits by utilizing thermodynamic principles rather than conventional optics. Hence in this paper the condition of the "best" design are both defined and fulfilled in the framework of thermodynamic arguments, which we believe has profound consequences for the designs of thermal and even photovoltaic systems, even illumination and optical communication tasks. This new way of looking at the problem of efficient concentration depends on probabilities, geometric flux field and radiative heat transfer while "optics" in the conventional sense recedes into the background. Some of the new development of flow line designs will be introduced and the connection between the thermodynamics and flow line design will be officially formulated in the framework of geometric flux field. A new way of using geometric flux to design nonimaging optics will be introduced. And finally, we discuss the possibility of 3D ideal nonimaing optics.

  1. Analysis of humic colloid borne trace elements by flow field-flow fractionation, gel permeation chromatography and icp-mass spectrometry

    International Nuclear Information System (INIS)

    Ngo, Manh Thang; Beck, H.P; Geckeis, H.; Kim, J.I.

    1999-01-01

    Groundwater samples containing aquatic humic substances are analyzed by flow field- flow fractionation (FFFF) and gel permeation chromatography (GPC). Natural concentrations of U, Th and rare earth elements (REE) in a size-fractionated groundwater sample are analyzed by on-line coupling of inductively coupled plasma-mass spectrometry (ICP-MS) to either FFFF or GPC. The uranium, thorium, and REE are found to be quantitatively attached to colloidal species in the investigated groundwater sample. Their distribution in different colloid size fractions, however, is quite heterogeneous. Both, FFFF and GPC reveal that Th and REE are preferentially located in the size fraction > 50 kDalton. U is also attached to low molecular weight humic acid, similar to Fe and Al. This finding could be qualitatively reproduced by sequential ultrafiltration. The results are interpreted in terms of different binding mechanisms for the individual elements in the heterogeneous humic macromolecules. The inclusion of actinides into larger aggregates of aquatic humic acid might explain the considerable kinetic hindrance of actinide-humic acid dissociation reactions described in the literature. (authors)

  2. Instantaneous sediment transport model for asymmetric oscillatory sheet flow.

    Directory of Open Access Journals (Sweden)

    Xin Chen

    Full Text Available On the basis of advanced concentration and velocity profiles above a mobile seabed, an instantaneous analytical model is derived for sediment transport in asymmetric oscillatory flow. The applied concentration profile is obtained from the classical exponential law based on mass conservation, and asymmetric velocity profile is developed following the turbulent boundary layer theory and the asymmetric wave theory. The proposed model includes two parts: the basic part that consists of erosion depth and free stream velocity, and can be simplified to the total Shields parameter power 3/2 in accordance with the classical empirical models, and the extra vital part that consists of phase-lead, boundary layer thickness and erosion depth. The effects of suspended sediment, phase-lag and asymmetric boundary layer development are considered particularly in the model. The observed instantaneous transport rate proportional to different velocity exponents due to phase-lag is unified and summarised by the proposed model. Both instantaneous and half period empirical formulas are compared with the developed model, using extensive data on a wide range of flow and sediment conditions. The synchronous variation in instantaneous transport rate with free stream velocity and its decrement caused by increased sediment size are predicted correctly. Net transport rates, especially offshore transport rates with large phase-lag under velocity skewed flows, which existing instantaneous type formulas failed to predict, are predicted correctly in both direction and magnitude by the proposed model. Net sediment transport rates are affected not only by suspended sediment and phase-lag, but also by the boundary layer difference between onshore and offshore.

  3. Profiling of oxidized phospholipids in lipoproteins from patients with coronary artery disease by hollow fiber flow field-flow fractionation and nanoflow liquid chromatography-tandem mass spectrometry.

    Science.gov (United States)

    Lee, Ju Yong; Byeon, Seul Kee; Moon, Myeong Hee

    2015-01-20

    Oxidized phospholipids (Ox-PLs) are oxidatively modified PLs that are produced during the oxidation of lipoproteins; oxidation of low density lipoproteins especially is known to be associated with the development of coronary artery disease (CAD). In this study, different lipoprotein classes (high density, low density, and very low density lipoproteins) from pooled plasma of CAD patients and pooled plasma from healthy controls were size-sorted on a semipreparative scale by multiplexed hollow fiber flow field-flow fractionation (MxHF5), and Ox-PLs that were extracted from each lipoprotein fraction were quantified by nanoflow liquid chromatography-tandem mass spectrometry (nLC-ESI-MS/MS). The present study showed that oxidation of lipoproteins occurred throughout all classes of lipoproteins with more Ox-PLs identified from CAD patient lipoproteins: molecular structures of 283 unique PL species (including 123 Ox-PLs) from controls and 315 (including 169 Ox-PLs) from patients were identified by data-dependent collision-induced dissociation experiments. It was shown that oxidation of PLs occurred primarily with hydroxylation of PL; in particular, a saturated acyl chain such as 16:0, 18:0, or even 18:1 at the sn-1 location of the glycerol backbone along with sn-2 acyl chains with at least two double bonds were identified. The acyl chain combinations commonly found for hydroxylated Ox-PLs in the lipoproteins of CAD patients were 16:0/18:2, 16:0/20:4, 18:0/18:2, and 18:0/20:4.

  4. Application of a field flow preconcentration system with a minicolumn packed with amberlite XAD-4/1-(2-pyridylazo)-2-naphtol and a flow injection-flame atomic adsorption spectrometric system for lead determination in sea water

    International Nuclear Information System (INIS)

    Carmen Yebra, M. del; Rodriguez, L.; Puig, L.; Moreno-Cid, A.

    2002-01-01

    A field flow preconcentration technique involving a minicolumn containing Amberlite XAD-4 impregnated with the complexing agent 1-(2-pyridylazo)-2-naphthol was used to preconcentrate lead from seawater. Elution of retained lead on the minicolumns was performed by a flow-injection-flame atomic absorption spectrometric system. Factorial designs have been used to optimize the field flow preconcentration system and the flow injection elution process. Factors such as sample pH, sample flow-rate, eluent concentration and volume (hydrochloric acid), elution flow-rate and minicolumn diameter were considered. The results suggest that the sample flow-rate and the eluent volume are statistically significant factors. The detection limit (3σ) of the procedure was 5 ng/L for a sample volume of 1000 ml. The precision (expressed as relative standard deviation) for eleven independent determinations reached values of 4.0-3.1 % in lead solutions of 50-200 ng/L. This procedure has been successfully applied to the determination of lead in seawater from Galicia (Spain). (author)

  5. Modelling the air flow in symmetric and asymmetric street canyons

    Energy Technology Data Exchange (ETDEWEB)

    Santiago, J.L.; Martin, F. [Research Center for Energy, Environment and Technology (CIEMAT), Madrid (Spain). Fossil Fuels Dept., Numerical Simulation and Modelling Program

    2004-07-01

    In recent years a large amount of research has been conducted on urban scale and street canyon. Control of air quality inside cities is important for human health. To achieve this objective, street canyon modelling plays a significant role. Pollutant dispersion inside canyons are determined by wind flow around this complex geometry. Experimental investigations have been made by means of field measurements such as Vachon, G. et al. or wind tunnel experiences as Meroney, R.N. et al. or Kastner-Klein, P. and E.J. Plate. In many of these researches, they have used CFD models in several configurations, for instance Assimakopoulos, V.D. et al. or Sini, J.-F. et al. These models are based on a numerical resolution of Navier-Stokes equations with a turbulence closure. In this study, the aim is contribute to the understanding of air circulation inside street canyons. In order to achieve this purpose, several configurations of canyons are investigated. Two-dimensional sequences of real-scale street canyons (order to obstacles height is meters) with different features (symmetric canyons and asymmetric canyons forming step-up and step-down notch configurations) are simulated. These general configurations are modified to investigate some parameters such as aspect ratio, W/H, where W is the width of street and H is the height of buildings. Flows with high Reynolds numbers are modelling. FLUENT CFD software is used. (orig.)

  6. Field Flows of Dark Energy

    Energy Technology Data Exchange (ETDEWEB)

    Cahn, Robert N.; de Putter, Roland; Linder, Eric V.

    2008-07-08

    Scalar field dark energy evolving from a long radiation- or matter-dominated epoch has characteristic dynamics. While slow-roll approximations are invalid, a well defined field expansion captures the key aspects of the dark energy evolution during much of the matter-dominated epoch. Since this behavior is determined, it is not faithfully represented if priors for dynamical quantities are chosen at random. We demonstrate these features for both thawing and freezing fields, and for some modified gravity models, and unify several special cases in the literature.

  7. Influence of artificial tip perturbation on asymmetric vortices flow over a chined fuselage

    Directory of Open Access Journals (Sweden)

    Shi Wei

    2015-08-01

    Full Text Available An experimental study was conducted with the aim of understanding behavior of asymmetric vortices flow over a chined fuselage. The tests were carried out in a wind tunnel at Reynolds number of 1.87 × 105 under the conditions of high angles of attack and zero angle of sideslip. The results show that leeward vortices flow becomes asymmetric vortices flow when angle of attack increases over 20°. The asymmetric vortices flow is asymmetry of two forebody vortices owing to the increase of angle of attack but not asymmetry of vortex breakdown which appears when angle of attack is above 35°. Asymmetric vortices flow is sensitive to tip perturbation and is non-deterministic due to randomly distributed natural minute geometrical irregularities on the nose tip within machining tolerance. Deterministic asymmetric vortices flow can be obtained by attaching artificial tip perturbation which can trigger asymmetric vortices flow and decide asymmetric vortices flow pattern. Triggered by artificial tip perturbation, the vortex on the same side with perturbation is in a higher position, and the other vortex on the opposite side is in a lower position. Vortex suction on the lower vortex side is larger, which corresponds to a side force pointing to the lower vortex side.

  8. Gravitational field-flow fractionation integrated with chemiluminescence detection for a self-standing point-of-care compact device in bioanalysis.

    Science.gov (United States)

    Casolari, S; Roda, B; Mirasoli, M; Zangheri, M; Patrono, D; Reschiglian, P; Roda, A

    2013-01-07

    A "Point-Of-Care-Testing" (POCT) system relies on portable and simply operated self-standing analytical devices. To fulfill diagnostic requirements, the POCT system should provide highly sensitive simultaneous detection of several biomarkers of the pathology of interest (multiplexing) in a short assay time. One of the main unsolved issues in POCT device development is the integration of pre-analytical sample preparation procedures in the miniaturized device. In this work, an integrated POCT system based on gravitational field-flow fractionation (GrFFF) and chemiluminescence (CL) detection is presented for the on-line sample pre-analytical treatment and/or clean-up and analysis of biological fluids. As a proof of principle for the new GrFFF-CL POCT system, the automatic on-line analysis of plasma alkaline phosphatase activity, a biomarker of obstructive liver diseases and bone disorders, starting from whole blood samples was developed. The GrFFF-CL POCT system was able to give quantitative results on blood samples from control and patients with low sample volume (0.5 μL) and reagent consumption, short analysis time (10 minutes), high reproducibility and with a linear range of 50-1400 IU L(-1). The system can be easily applied to on-line prepare plasma from whole blood for other clinical biomarkers and for other assay formats, based on immunoassay or DNA hybridization.

  9. Synthesis of silica nanoparticles for the manufacture of porous carbon membrane and particle size analysis by sedimentation field-flow fractionation

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Seung Ho; Eum, Chul; Hun; Choi, Seong Ho; Kim, Woon Jung [Dept. of Chemistry, Hannam University, Daejeon (Korea, Republic of)

    2016-11-15

    Silica nanoparticles were synthesized by emulsion polymerization by mixing ethanol, ammonium hydroxide, water, and tetraethyl orthosilicate. An apparatus was designed and assembled for a large-scale synthesis of silica nanospheres, which was aimed for uniform mixing of the reactants. Then sedimentation field-flow fractionation (SdFFF) was used to determine the size distribution of the silica nanoparticles. SdFFF provided mass-based separation where the retention time increased with the particle size, thus the size distribution of silica nanoparticles obtained from SdFFF appeared more accurate than that from dynamic light scattering, particularly for those having broad and multimodal size distributions. A disk-shaped porous carbon membrane (PCM) was manufactured for application as an adsorbent by pressurizing the silica particles, followed by calcination. Results showed that PCM manufactured in this study has relatively high surface area and temperature stability. The PCM surface was modified by attaching a carboxyl group (PCM-COOH) and then by incorporating silver (PCM-COOH-Ag). The amount of COOH group on PCM was measured electrochemically by cyclic voltammetry, and the surface area, pore size, pore volume of PCM-COOH-Ag by Brunauer–Emmet–Teller measurement. The surface area was 40.65 and reduced to 13.02 after loading a COOH group then increased up to 30.37 after incorporating Ag.

  10. Turbulent flow field structure of initially asymmetric jets

    International Nuclear Information System (INIS)

    Kim, Kyung Hoon; Kim, Bong Whan; Kim, Suk Woo

    2000-01-01

    The near field structure of round turbulent jets with initially asymmetric velocity distributions is investigated experimentally. Experiments are carried out using a constant temperature hot-wire anemomentry system to measure streamwise velocity in the jets. The measurements are undertaken across the jet at various streamwise stations in a range starting from the jet exit plane and up to a downstream location of twelve diameters. The experimental results include the distributions of mean and instantaneous velocities, vorticity field, turbulence intensity, and the Reynolds shear stresses. The asymmetry of the jet exit plane was obtained by using circular cross-section pipes with a bend upstream of the exit. Three pipes used here include a straight pipe, and 90 and 160 degree-bend pipes. Therefore, at the upstream of the pipe exit, secondary flow through the bend and mean streamwise velocity distribution could be controlled by changing the curvature of pipes. The jets into the atmosphere have two levels of initial velocity skewness in addition to an axisymmetric jet from a straight pipe. In case of the curved pipe, a six diameterlong straight pipe section follows the bend upstream of the exit. The Reynolds number based on the exit bulk velocity is 13,400. The results indicate that the near field structure is considerably modified by the skewness of an initial mean velocity distribution. As the skewness increases, the decay rate of mean velocity at the centerline also increases

  11. Size Determination of Aqueous C60 by Asymmetric Flow Field-Flow Fractionation (AF4) and in-Line Dynamic Light Scattering

    Science.gov (United States)

    To date, studies on the environmental behaviour of aggregated aqueous fullerene nanomaterials have used the entire size distribution of fullerene aggregates and do not distinguish between different aggregate size classes. This is a direct result of the lack of analytical methods ...

  12. The use of asymmetrical flow field-flow fractionation with on-line detection in the study of drug retention within liposomal nanocarriers and drug transfer kinetics

    DEFF Research Database (Denmark)

    Hinna, Askell Hvid; Hupfeld, Stefan; Kuntsche, Judith

    2016-01-01

    Due to their solubilizing capabilities, liposomes (phospholipid vesicles) are suited for designing formulations for intravenous administration of drug compounds which are poorly water-soluble. Despite the good in-vitro stability of such formulations with minimal drug leakage, upon i.v. injection...... ratio. An initial rapid transfer of p-THPP was found (∼5%) and investigated further by determining the extent of transfer between donor and acceptor during separation. The donor- and acceptor phase were found to be separated within few minutes and only minor (≤2%) transfer could be detected within...

  13. Flow characterization in periodic microchannels containing asymmetric grooves

    Energy Technology Data Exchange (ETDEWEB)

    Osorio-Nesme, A; Delgado, A, E-mail: anuhar.nesme@fau.de [Institute of Fluid Mechanics, Friedrich-Alexander Erlangen-Nuremberg University, Cauerstrasse 4, D-91058 Erlangen (Germany)

    2017-10-15

    Characterization of two-dimensional flows in microchannels with anisotropic periodic grooves is numerically carried out by using the lattice Boltzmann method. Periodically placed microstructures, consisting of novel nozzle-diffuser-like grooves are deliberately designed to introduce a flow-direction dependent resistance. Simulations were conducted for a low-to-moderate Reynolds number in the laminar-transition flow regime. Different channel geometries, defined by the half-angle ϕ of the periodic grooves are considered. The influence of the half-angle on both the flow field and the onset of oscillatory flow regime at different driving body forces is analyzed. At a low Reynolds number, the flow is observed stationary and fully reversible, regardless of the groove geometry. In this regime, higher Reynolds numbers were observed when the geometry acts as a diffuser (negative flow) than as a nozzle (positive flow) for a given driving body force. At sufficiently high Reynolds number the flow turns from a steady state to a time-dependent oscillatory regime through a Hopf bifurcation. Successive flow bifurcations lead the flow structure from a periodic regime to a quasi-chaotic regime with three-dimensional structures. The onset of unsteady flow occurs earlier for positive flows and geometries with small half-angles. For higher driving forces, there is a reduction in the volume flow rate due to the advected material in the transversal direction, causing consequently a decrease in the Reynolds number. (paper)

  14. Asymmetric energy flow in liquid alkylbenzenes: A computational study

    International Nuclear Information System (INIS)

    Leitner, David M.; Pandey, Hari Datt

    2015-01-01

    Ultrafast IR-Raman experiments on substituted benzenes [B. C. Pein et al., J. Phys. Chem. B 117, 10898–10904 (2013)] reveal that energy can flow more efficiently in one direction along a molecule than in others. We carry out a computational study of energy flow in the three alkyl benzenes, toluene, isopropylbenzene, and t-butylbenzene, studied in these experiments, and find an asymmetry in the flow of vibrational energy between the two chemical groups of the molecule due to quantum mechanical vibrational relaxation bottlenecks, which give rise to a preferred direction of energy flow. We compare energy flow computed for all modes of the three alkylbenzenes over the relaxation time into the liquid with energy flow through the subset of modes monitored in the time-resolved Raman experiments and find qualitatively similar results when using the subset compared to all the modes

  15. Directed transverse flow and its disappearance for asymmetric reactions

    International Nuclear Information System (INIS)

    Lovejot; Gautam, S.

    2014-01-01

    We study the directed transverse flow for mass asymmetry reactions. This is done by keeping the target fixed and varying the projectile mass from 4 He to 131 Xe. We find that directed transverse flow is sensitive to the mass of the projectile. We also study the disappearance of flow at a particular impact parameter called Geometry of Vanishing Flow (GVF) for such mass asymmetry reactions. Our results indicate that GVF is sensitive to the beam energy as well as to the mass of the projectile.

  16. Soap-film flow induced by electric fields in asymmetric frames

    Science.gov (United States)

    Mollaei, S.; Nasiri, M.; Soltanmohammadi, N.; Shirsavar, R.; Ramos, A.; Amjadi, A.

    2018-04-01

    Net fluid flow of soap films induced by (ac or dc) electric fields in asymmetric frames is presented. Previous experiments of controllable soap film flow required the simultaneous use of an electrical current passing through the film and an external electric field or the use of nonuniform ac electric fields. Here a single voltage difference generates both the electrical current going through the film and the electric field that actuates on the charge induced on the film. The film is set into global motion due to the broken symmetry that appears by the use of asymmetric frames. If symmetric frames are used, the film flow is not steady but time dependent and irregular. Finally, we study numerically these film flows by employing the model of charge induction in ohmic liquids.

  17. Investigation on asymmetric flow over a blunt-nose slender body at high angle of attack

    Science.gov (United States)

    Zhongyang, Qi; Yankui, Wang; Lei, Wang; Qian, Li

    2017-12-01

    The asymmetric vortices over a blunt-nose slender body are investigated experimentally and numerically at a high angle of attack (AoA, α = 50°) and a Reynolds number of Re D = 1.54 × 105 on the basis of an incoming free-stream velocity and diameter (D) of the model. A micro-perturbation in the form of a hemispherical protrusion with a radius of r = 0.012D is introduced and attached on the nose of the slender body to control the behavior of the asymmetric vortices. Given the predominant role of micro perturbation in the asymmetric vortex pattern, a square wave, which is singly periodic, is observed for side-force variation by setting the circumferential angle (θ) of the micro perturbation from 0° to 360°. The asymmetric vortex pattern and the corresponding side force are manageable and highly dependent on the location of perturbation. The flow structure over the blunt-nose slender body is clarified by building a physical model of asymmetric vortex flow structure in a regular state at a high AoA (α = 50°). This model is divided into several regions by flow structure development along the model body-axis, i.e., inception region at x/D ≤ 3.0, triple-vortex region at 3.0 ≤ x/D ≤ 6.0, four-vortex region at 6.0 ≤ x/D ≤ 8.5, and five-vortex region at 8.5 ≤ x/D ≤ 12. The model reveals a complicated multi-vortex system. The associated pressure distributions and flow characteristics are discussed in detail.

  18. Oscillatory electroosmotic flow in a parallel-plate microchannel under asymmetric zeta potentials

    Science.gov (United States)

    Peralta, M.; Arcos, J.; Méndez, F.; Bautista, O.

    2017-06-01

    In this work, we conduct a theoretical analysis of the start-up of an oscillatory electroosmotic flow (EOF) in a parallel-plate microchannel under asymmetric zeta potentials. It is found that the transient evolution of the flow field is controlled by the parameters {R}ω , {R}\\zeta , and \\bar{κ }, which represent the dimensionless frequency, the ratio of the zeta potentials of the microchannel walls, and the electrokinetic parameter, which is defined as the ratio of the microchannel height to the Debye length. The analysis is performed for both low and high zeta potentials; in the former case, an analytical solution is derived, whereas in the latter, a numerical solution is obtained. These solutions provide the fundamental characteristics of the oscillatory EOFs for which, with suitable adjustment of the zeta potential and the dimensionless frequency, the velocity profiles of the fluid flow exhibit symmetric or asymmetric shapes.

  19. Hollow-fiber flow field-flow fractionation and multi-angle light scattering investigation of the size, shape and metal-release of silver nanoparticles in aqueous medium for nano-risk assessment.

    Science.gov (United States)

    Marassi, Valentina; Casolari, Sonia; Roda, Barbara; Zattoni, Andrea; Reschiglian, Pierluigi; Panzavolta, Silvia; Tofail, Syed A M; Ortelli, Simona; Delpivo, Camilla; Blosi, Magda; Costa, Anna Luisa

    2015-03-15

    Due to the increased use of silver nanoparticles in industrial scale manufacturing, consumer products and nanomedicine reliable measurements of properties such as the size, shape and distribution of these nano particles in aqueous medium is critical. These properties indeed affect both functional properties and biological impacts especially in quantifying associated risks and identifying suitable risk-mediation strategies. The feasibility of on-line coupling of a fractionation technique such as hollow-fiber flow field flow fractionation (HF5) with a light scattering technique such as MALS (multi-angle light scattering) is investigated here for this purpose. Data obtained from such a fractionation technique and its combination thereof with MALS have been compared with those from more conventional but often complementary techniques e.g. transmission electron microscopy, dynamic light scattering, atomic absorption spectroscopy, and X-ray fluorescence. The combination of fractionation and multi angle light scattering techniques have been found to offer an ideal, hyphenated methodology for a simultaneous size-separation and characterization of silver nanoparticles. The hydrodynamic radii determined by fractionation techniques can be conveniently correlated to the mean average diameters determined by multi angle light scattering and reliable information on particle morphology in aqueous dispersion has been obtained. The ability to separate silver (Ag(+)) ions from silver nanoparticles (AgNPs) via membrane filtration during size analysis is an added advantage in obtaining quantitative insights to its risk potential. Most importantly, the methodology developed in this article can potentially be extended to similar characterization of metal-based nanoparticles when studying their functional effectiveness and hazard potential. Copyright © 2014 Elsevier B.V. All rights reserved.

  20. Effects of Inner Surface Roughness and Asymmetric Pipe Flow on Accuracy of Profile Factor for Ultrasonic Flow Meter

    International Nuclear Information System (INIS)

    Michitsugu Mori; Kenichi Tezuka; Yasushi Takeda

    2006-01-01

    Flow profile factors (PFs), which adjust measurements to real flow rates, also strongly depend on flow profiles. To determine profile factors for actual power plants, manufactures of flowmeters usually conduct factory calibration tests under ambient flow conditions. Indeed, flow measurements with high accuracy for reactor feedwater require them to conduct calibration tests under real conditions, such as liquid conditions and piping layouts. On the contrary, as nuclear power plants are highly aging, readings of flowmeters for reactor feedwater systems drift due to the changes of flow profiles. The causes of those deviations are affected by the change of wall roughness of inner surface of pipings. We have conducted experiments to quantify the effects of flow patterns on the PFs due to pipe roughness and asymmetric flow, and the results of our experiments have shown the effects of elbows and pipe inner roughness, which strongly affect to the creation of the flow patterns. Those changes of flow patterns lead to large errors in measurements with transit time (time-of-flight: TOF) ultrasonic flow meters. In those experiments, changes of pipe roughness result in the changes of PFs with certain errors. Therefore, we must take into account those effects in order to measure the flow rates of feedwater with better accuracy in actual power plants. (authors)

  1. Asymmetric flows over symmetric surfaces: capacitive coupling in induced-charge electro-osmosis

    Energy Technology Data Exchange (ETDEWEB)

    Mansuripur, T S [Department of Physics, University of California, Santa Barbara, CA 93106 (United States); Pascall, A J; Squires, T M [Department of Chemical Engineering, University of California, Santa Barbara, CA 93106 (United States)], E-mail: squires@engineering.ucsb.edu

    2009-07-15

    We report curious asymmetric induced-charge electro-osmotic (ICEO) flows over a symmetric, planar gate electrode under applied ac electric fields, whereas symmetric, counter-rotating rolls are expected. Furthermore, the asymmetric component of the flow is consistently directed towards the grounded electrode. We propose that capacitive coupling of the gate electrode to the microscope stage-a comparatively large equipotential surface that acts effectively as a ground-is responsible for this symmetry breaking. This stray capacitance drives the formation of a double layer whose zeta potential is proportional to the potential drop from the electrolyte directly above the gate electrode to the external stage. Therefore, the charge in this 'stray' double layer varies in phase with the driving field, resulting in a rectified, steady flow as with standard ICEO. We experimentally vary the stray capacitance, the electric potential of the stage and the location of the gate electrode, and find that the effect on the stray flow is qualitatively consistent with the predictions of the proposed mechanism. In the process, we demonstrate that capacitive coupling offers an additional means of manipulating fluid flow over a polarizable surface.

  2. Asymmetric flows over symmetric surfaces: capacitive coupling in induced-charge electro-osmosis

    International Nuclear Information System (INIS)

    Mansuripur, T S; Pascall, A J; Squires, T M

    2009-01-01

    We report curious asymmetric induced-charge electro-osmotic (ICEO) flows over a symmetric, planar gate electrode under applied ac electric fields, whereas symmetric, counter-rotating rolls are expected. Furthermore, the asymmetric component of the flow is consistently directed towards the grounded electrode. We propose that capacitive coupling of the gate electrode to the microscope stage-a comparatively large equipotential surface that acts effectively as a ground-is responsible for this symmetry breaking. This stray capacitance drives the formation of a double layer whose zeta potential is proportional to the potential drop from the electrolyte directly above the gate electrode to the external stage. Therefore, the charge in this 'stray' double layer varies in phase with the driving field, resulting in a rectified, steady flow as with standard ICEO. We experimentally vary the stray capacitance, the electric potential of the stage and the location of the gate electrode, and find that the effect on the stray flow is qualitatively consistent with the predictions of the proposed mechanism. In the process, we demonstrate that capacitive coupling offers an additional means of manipulating fluid flow over a polarizable surface.

  3. Mechanism and kinetics of the loss of poorly soluble drugs from liposomal carriers studied by a novel flow field-flow fractionation-based drug release-/transfer-assay.

    Science.gov (United States)

    Hinna, Askell Hvid; Hupfeld, Stefan; Kuntsche, Judith; Bauer-Brandl, Annette; Brandl, Martin

    2016-06-28

    Liposomes represent a versatile drug formulation approach e.g. for improving the water-solubility of poorly soluble drugs but also to achieve drug targeting and controlled release. For the latter applications it is essential that the drug remains associated with the liposomal carrier during transit in the vascular bed. A range of in vitro test methods has been suggested over the years for prediction of the release of drug from liposomal carriers. The majority of these fail to give a realistic prediction for poorly water-soluble drugs due to the intrinsic tendency of such compounds to remain associated with liposome bilayers even upon extensive dilution. Upon i.v. injection, in contrast, rapid drug loss often occurs due to drug transfer from the liposomal carriers to endogenous lipophilic sinks such as lipoproteins, plasma proteins or membranes of red blood cells and endothelial cells. Here we report on the application of a recently introduced in vitro predictive drug transfer assay based on incubation of the liposomal drug carrier with large multilamellar liposomes, the latter serving as a biomimetic model sink, using flow field-flow fractionation as a tool to separate the two types of liposomes. By quantifying the amount of drug remaining associated with the liposomal drug carrier as well as that transferred to the acceptor liposomes at distinct times of incubation, both the kinetics of drug transfer and release to the water phase could be established for the model drug p-THPP (5,10,15,20-tetrakis(4-hydroxyphenyl)21H,23H-porphine). p-THPP is structurally similar to temoporfin, a photosensitizer which is under clinical evaluation in a liposomal formulation. Mechanistic insights were gained by varying the donor-to-acceptor lipid mass ratio, size and lamellarity of the liposomes. Drug transfer kinetics from one liposome to another was found rate determining as compared to redistribution from the outermost to the inner concentric bilayers, such that the overall

  4. Numerical Simulation of Non-Equilibrium Two-Phase Wet Steam Flow through an Asymmetric Nozzle

    Directory of Open Access Journals (Sweden)

    Miah Md Ashraful Alam

    2017-11-01

    Full Text Available The present study reported of the numerical investigation of a high-speed wet steam flow through an asymmetric nozzle. The spontaneous non-equilibrium homogeneous condensation of wet steam was numerically modeled based on the classical nucleation theory and droplet growth rate equation combined with the field conservations within the computational fluid dynamics (CFD code of ANSYS Fluent 13.0. The equations describing droplet formations and interphase change were solved sequentially after solving the main flow conservation equations. The calculations were carried out assuming the flow two-dimensional, compressible, turbulent, and viscous. The SST k-ω model was used for modeling the turbulence within an unstructured mesh solver. The validation of numerical model was accomplished, and the results showed a good agreement between the numerical simulation and experimental data. The effect of spontaneous non-equilibrium condensation on the jet and shock structures was revealed, and the condensation shown a great influence on the jet structure.

  5. Affinity flow fractionation of cells via transient interactions with asymmetric molecular patterns

    Science.gov (United States)

    Bose, Suman; Singh, Rishi; Hanewich-Hollatz, Mikhail; Shen, Chong; Lee, Chia-Hua; Dorfman, David M.; Karp, Jeffrey M.; Karnik, Rohit

    2013-07-01

    Flow fractionation of cells using physical fields to achieve lateral displacement finds wide applications, but its extension to surface molecule-specific separation requires labeling. Here we demonstrate affinity flow fractionation (AFF) where weak, short-range interactions with asymmetric molecular patterns laterally displace cells in a continuous, label-free process. We show that AFF can directly draw neutrophils out of a continuously flowing stream of blood with an unprecedented 400,000-fold depletion of red blood cells, with the sorted cells being highly viable, unactivated, and functionally intact. The lack of background erythrocytes enabled the use of AFF for direct enumeration of neutrophils by a downstream detector, which could distinguish the activation state of neutrophils in blood. The compatibility of AFF with capillary microfluidics and its ability to directly separate cells with high purity and minimal sample preparation will facilitate the design of simple and portable devices for point-of-care diagnostics and quick, cost-effective laboratory analysis.

  6. Is Investment-Cash Flow Sensitivity Caused by the Agency Costs or Asymmetric Information? Evidence from the UK

    NARCIS (Netherlands)

    Pawlina, G.; Renneboog, L.D.R.

    2005-01-01

    We investigate the investment-cash flow sensitivity of a large sample of the UK listed firms and confirm that investment is strongly cash flow-sensitive.Is this suboptimal investment policy the result of agency problems when managers with high discretion overinvest, or of asymmetric information when

  7. Perturbation solutions for flow through symmetrical hoppers with inserts and asymmetrical wedge hoppers

    Science.gov (United States)

    Cox, G. M.; Mccue, S. W.; Thamwattana, N.; Hill, J. M.

    Under certain circumstances, an industrial hopper which operates under the "funnel-flow" regime can be converted to the "mass-flow" regime with the addition of a flow-corrective insert. This paper is concerned with calculating granular flow patterns near the outlet of hoppers that incorporate a particular type of insert, the cone-in-cone insert. The flow is considered to be quasi-static, and governed by the Coulomb-Mohr yield condition together with the non-dilatant double-shearing theory. In two-dimensions, the hoppers are wedge-shaped, and as such the formulation for the wedge-in-wedge hopper also includes the case of asymmetrical hoppers. A perturbation approach, valid for high angles of internal friction, is used for both two-dimensional and axially symmetric flows, with analytic results possible for both leading order and correction terms. This perturbation scheme is compared with numerical solutions to the governing equations, and is shown to work very well for angles of internal friction in excess of 45°.

  8. Comparison of different filtration techniques for the pre-concentration of natural colloidal dispersions for field-flow-fractionation (FFF); Vergleich verschiedener Filtrationstechniken zur Aufkonzentrierung natuerlicher kolloidaler Dispersionen fuer die Feld-Fluss-Fraktionierung (FFF)

    Energy Technology Data Exchange (ETDEWEB)

    Saal, C.; Kammer, F. v.d. [Technische Univ. Hamburg-Harburg, Arbeitsbereich Umweltschutztechnik, Hamburg (Germany)

    2002-07-01

    The objektive of this study was to compare different pre-treatment techniques (active and passive filtration techniques applying various membranes) for field-flow-fractionation (FFF) analysis of natural aquatic colloids. In most cases FFF of natural water samples requires a pre-concentration step prior to analysis. The used FFF-method with online multi-detector-analysis (MDA) is a versatile method to specify the size distribution of particles (> 10 nm) in aqueous systems. Coupling FFF with trace element analysis (e. g. ICP-MS or total reflextion X-ray fluorescence (TXRF)) is a possibility for the determination of element/ size distributions. Analysing natural water samples with FFF a sample pre-treatment is needed in most cases, which can be a coarse filtration (> 5 {mu}m) to separate algea from the sample and a preconcentration of the colloidal fraction. The pre-treatment of the sample has to assure a minimum loss of colloidal particulate matter (CPM) and no change of size distribution. The different pre-concentration techniques were tested with water extractable soil colloids. We have developed methods with concentration factors F < 50 showing minor effects on the colloidal composition of the sample, so that these methods can be used to concentrate CPM of natural waters for size- and trace metal analysis. (orig.)

  9. Effects of rotation on flow in an asymmetric rib-roughened duct: LES study

    International Nuclear Information System (INIS)

    Borello, D.; Salvagni, A.; Hanjalić, K.

    2015-01-01

    Highlights: • Ribbed duct reproduces most of the phenomena occurring in internal cooling channels of blade turbines (rotor and stator). • LES analysis of the flow in a ribbed duct was carried out aiming at detecting the influence of rotation on the turbulence. • In destabilizing conditions, rotation enhances turbulence close to the ribbed duct thus enhancing removal of fluid from the wall and improving mixing. • In stabilizing conditions, turbulence is suppressed by rotation close to the ribbed wall. - Abstract: We report on large-eddy simulations (LES) of fully-developed asymmetric flow in a duct of a rectangular cross-section in which square-sectioned, equally-spaced ribs oriented perpendicular to the flow direction, were mounted on one of the walls. The configuration mimics a passage of internal cooling of a gas-turbine blade. The duct flow at a Reynolds number Re = 15,000 (based on hydraulic diameter D_h and bulk flow velocity U_0) was subjected to clock-wise (stabilising) and anti-clock-wise (destabilising) orthogonal rotation at a moderate rotational number Ro = ΩD_h/U_0 = 0.3, where Ω is the angular velocity. The LES results reproduced well the available experimental results of Coletti et al. (2011) (in the mid-plane adjacent to the ribbed wall) and provided insight into the whole duct complementing the reference PIV measurement. We analyzed the effects of stabilising and destabilising rotation on the flow, vortical structures and turbulence statistics by comparison with the non-rotating case. The analysis includes the identification of depth of penetration of the rib-effects into the bulk flow, influence of flow three-dimensionality and the role of secondary motions, all shown to be strongly affected by the rotation and its direction.

  10. Microfluidic Imaging Flow Cytometry by Asymmetric-detection Time-stretch Optical Microscopy (ATOM).

    Science.gov (United States)

    Tang, Anson H L; Lai, Queenie T K; Chung, Bob M F; Lee, Kelvin C M; Mok, Aaron T Y; Yip, G K; Shum, Anderson H C; Wong, Kenneth K Y; Tsia, Kevin K

    2017-06-28

    Scaling the number of measurable parameters, which allows for multidimensional data analysis and thus higher-confidence statistical results, has been the main trend in the advanced development of flow cytometry. Notably, adding high-resolution imaging capabilities allows for the complex morphological analysis of cellular/sub-cellular structures. This is not possible with standard flow cytometers. However, it is valuable for advancing our knowledge of cellular functions and can benefit life science research, clinical diagnostics, and environmental monitoring. Incorporating imaging capabilities into flow cytometry compromises the assay throughput, primarily due to the limitations on speed and sensitivity in the camera technologies. To overcome this speed or throughput challenge facing imaging flow cytometry while preserving the image quality, asymmetric-detection time-stretch optical microscopy (ATOM) has been demonstrated to enable high-contrast, single-cell imaging with sub-cellular resolution, at an imaging throughput as high as 100,000 cells/s. Based on the imaging concept of conventional time-stretch imaging, which relies on all-optical image encoding and retrieval through the use of ultrafast broadband laser pulses, ATOM further advances imaging performance by enhancing the image contrast of unlabeled/unstained cells. This is achieved by accessing the phase-gradient information of the cells, which is spectrally encoded into single-shot broadband pulses. Hence, ATOM is particularly advantageous in high-throughput measurements of single-cell morphology and texture - information indicative of cell types, states, and even functions. Ultimately, this could become a powerful imaging flow cytometry platform for the biophysical phenotyping of cells, complementing the current state-of-the-art biochemical-marker-based cellular assay. This work describes a protocol to establish the key modules of an ATOM system (from optical frontend to data processing and visualization

  11. Stability Improvement of High-Pressure-Ratio Turbocharger Centrifugal Compressor by Asymmetric Flow Control-Part I: Non-Axisymmetrical Flow in Centrifugal Compressor.

    Science.gov (United States)

    Yang, Mingyang; Zheng, Xinqian; Zhang, Yangjun; Bamba, Takahiro; Tamaki, Hideaki; Huenteler, Joern; Li, Zhigang

    2013-03-01

    This is Part I of a two-part paper documenting the development of a novel asymmetric flow control method to improve the stability of a high-pressure-ratio turbocharger centrifugal compressor. Part I focuses on the nonaxisymmetrical flow in a centrifugal compressor induced by the nonaxisymmetrical geometry of the volute while Part II describes the development of an asymmetric flow control method to avoid the stall on the basis of the characteristic of nonaxisymmetrical flow. To understand the asymmetries, experimental measurements and corresponding numerical simulation were carried out. The static pressure was measured by probes at different circumferential and stream-wise positions to gain insights about the asymmetries. The experimental results show that there is an evident nonaxisymmetrical flow pattern throughout the compressor due to the asymmetric geometry of the overhung volute. The static pressure field in the diffuser is distorted at approximately 90 deg in the rotational direction of the volute tongue throughout the diffuser. The magnitude of this distortion slightly varies with the rotational speed. The magnitude of the static pressure distortion in the impeller is a function of the rotational speed. There is a significant phase shift between the static pressure distributions at the leading edge of the splitter blades and the impeller outlet. The numerical steady state simulation neglects the aforementioned unsteady effects found in the experiments and cannot predict the phase shift, however, a detailed asymmetric flow field structure is obviously obtained.

  12. The source of investment cash flow sensitivity in manufacturing firms: Is it asymmetric information or agency costs?

    Directory of Open Access Journals (Sweden)

    Daniel Makina

    2016-09-01

    Full Text Available In the literature, positive investment cash flow sensitivity is attributed to either asymmetric information induced financing constraints or the agency costs of free cash flow. Using data from a sample of 68 manufacturing firms listed on the South African JSE, this paper contributes to the literature by investigating the source of investment cash flow sensitivity. We have found that asymmetric information explains the positive investment cash flow sensitivity better than agency costs. Furthermore, asymmetric information has been observed to be more pronounced in low-dividend-paying firms and small firms. Despite South Africa’s having a developed financial system by international standards, small firms are seen to be financially constrained. We attribute the absence of investment cash flow sensitivity due to agency costs to good corporate governance of South African listed firms. Thus the paper provides further evidence in support of the proposition in the literature that the source of investment cash flow sensitivity may depend on the institutional setting of a country, such as its corporate governance.

  13. Flow Asymmetric Propargylation: Development of Continuous Processes for the Preparation of a Chiral β-Amino Alcohol.

    Science.gov (United States)

    Li, Hui; Sheeran, Jillian W; Clausen, Andrew M; Fang, Yuan-Qing; Bio, Matthew M; Bader, Scott

    2017-08-01

    The development of a flow chemistry process for asymmetric propargylation using allene gas as a reagent is reported. The connected continuous process of allene dissolution, lithiation, Li-Zn transmetallation, and asymmetric propargylation provides homopropargyl β-amino alcohol 1 with high regio- and diastereoselectivity in high yield. This flow process enables practical use of an unstable allenyllithium intermediate. The process uses the commercially available and recyclable (1S,2R)-N-pyrrolidinyl norephedrine as a ligand to promote the highly diastereoselective (32:1) propargylation. Judicious selection of mixers based on the chemistry requirement and real-time monitoring of the process using process analytical technology (PAT) enabled stable and scalable flow chemistry runs. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  14. Viscoelasticity and nonlinear simple shear flow behavior of an entangled asymmetric exact comb polymer solution

    KAUST Repository

    Snijkers, F.; Kirkwood, K. M.; Vlassopoulos, D.; Leal, L. G.; Nikopoulou, A.; Hadjichristidis, Nikolaos; Coppola, S.

    2016-01-01

    We report upon the characterization of the steady-state shear stresses and first normal stress differences as a function of shear rate using mechanical rheometry (both with a standard cone and plate and with a cone partitioned plate) and optical rheometry (with a flow-birefringence setup) of an entangled solution of asymmetric exact combs. The combs are polybutadienes (1,4-addition) consisting of an H-skeleton with an additional off-center branch on the backbone. We chose to investigate a solution in order to obtain reliable nonlinear shear data in overlapping dynamic regions with the two different techniques. The transient measurements obtained by cone partitioned plate indicated the appearance of overshoots in both the shear stress and the first normal stress difference during start-up shear flow. Interestingly, the overshoots in the start-up normal stress difference started to occur only at rates above the inverse stretch time of the backbone, when the stretch time of the backbone was estimated in analogy with linear chains including the effects of dynamic dilution of the branches but neglecting the effects of branch point friction, in excellent agreement with the situation for linear polymers. Flow-birefringence measurements were performed in a Couette geometry, and the extracted steady-state shear and first normal stress differences were found to agree well with the mechanical data, but were limited to relatively low rates below the inverse stretch time of the backbone. Finally, the steady-state properties were found to be in good agreement with model predictions based on a nonlinear multimode tube model developed for linear polymers when the branches are treated as solvent.

  15. Viscoelasticity and nonlinear simple shear flow behavior of an entangled asymmetric exact comb polymer solution

    KAUST Repository

    Snijkers, F.

    2016-03-31

    We report upon the characterization of the steady-state shear stresses and first normal stress differences as a function of shear rate using mechanical rheometry (both with a standard cone and plate and with a cone partitioned plate) and optical rheometry (with a flow-birefringence setup) of an entangled solution of asymmetric exact combs. The combs are polybutadienes (1,4-addition) consisting of an H-skeleton with an additional off-center branch on the backbone. We chose to investigate a solution in order to obtain reliable nonlinear shear data in overlapping dynamic regions with the two different techniques. The transient measurements obtained by cone partitioned plate indicated the appearance of overshoots in both the shear stress and the first normal stress difference during start-up shear flow. Interestingly, the overshoots in the start-up normal stress difference started to occur only at rates above the inverse stretch time of the backbone, when the stretch time of the backbone was estimated in analogy with linear chains including the effects of dynamic dilution of the branches but neglecting the effects of branch point friction, in excellent agreement with the situation for linear polymers. Flow-birefringence measurements were performed in a Couette geometry, and the extracted steady-state shear and first normal stress differences were found to agree well with the mechanical data, but were limited to relatively low rates below the inverse stretch time of the backbone. Finally, the steady-state properties were found to be in good agreement with model predictions based on a nonlinear multimode tube model developed for linear polymers when the branches are treated as solvent.

  16. Flow-Mediated Dilatation and Asymmetric Dimethylarginine Do Not Predict Mortality in Peritoneal Dialysis Patients

    Directory of Open Access Journals (Sweden)

    Sami Uzun

    2017-09-01

    Full Text Available Aim: Asymmetric dimethylarginine (ADMA is associated with increased coronary artery disease risk through endothelial dysfunction in dialysis patients. We aimed to investigate the role of flow-mediated dilatation (FMD, a non-invasive indicator of endothelial function, and ADMA in mortality in peritoneal dialysis (PD patients. Methods: PD patients aged 18-80 years; with dialysis duration of at least three months were included. FMD measurement and ADMA levels were recorded. Outcome of the patients on the third year were analyzed with binary logistic analyses. Results: The mean age of the 55 patients was 53±15 years and the mean follow-up duration was 36 months. Mean FMD and ADMA levels were 10.6±6.4% and 81.8±48.0 mol/L, respectively. Eighteen patients died during follow-up. Age, presence of diabetes mellitus and ischemic heart disease, ultrafiltration amount and serum albumin level were related with mortality while gender, weekly Kt/V and ADMA levels were not. There was no significant relationship between ADMA level and FMD (p=0.873. FMD was negatively correlated with systolic and diastolic blood pressures (p=0.001, p<0.001, respectively. Hypertension was found to be the most important single factor determining FMD (p=0.037. Conclusion: Estimating endothelial function by FMD or measuring serum ADMA levels may not be useful for predicting mortality in PD patients.

  17. Capacity Decay Mitigation by Asymmetric Positive/Negative Electrolyte Volumes in Vanadium Redox Flow Batteries.

    Science.gov (United States)

    Park, Jong Ho; Park, Jung Jin; Park, O Ok; Yang, Jung Hoon

    2016-11-23

    Capacity decay in vanadium redox flow batteries during charge-discharge cycling has become an important issue because it lowers the practical energy density of the battery. The battery capacity tends to drop rapidly within the first tens of cycles and then drops more gradually over subsequent cycles during long-term operation. This paper analyzes and discusses the reasons for this early capacity decay. The imbalanced crossover rate of vanadium species was found to remain high until the total difference in vanadium concentration between the positive and negative electrolytes reached almost 1 mol dm -3 . To minimize the initial crossover imbalance, we introduced an asymmetric volume ratio between the positive and negative electrolytes during cell operation. Changing this ratio significantly reduced the capacity fading rate of the battery during the early cycles and improved its capacity retention at steady state. As an example, the practical energy density of the battery increased from 15.5 to 25.2 Wh L -1 simply after reduction of the positive volume by 25 %. © 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  18. Spatial genetic structure and asymmetrical gene flow within the Pacific walrus

    Science.gov (United States)

    Sonsthagen, Sarah A.; Jay, Chadwick V.; Fischbach, Anthony S.; Sage, George K.; Talbot, Sandra L.

    2012-01-01

    Pacific walruses (Odobenus rosmarus divergens) occupying shelf waters of Pacific Arctic seas migrate during spring and summer from 3 breeding areas in the Bering Sea to form sexually segregated nonbreeding aggregations. We assessed genetic relationships among 2 putative breeding populations and 6 nonbreeding aggregations. Analyses of mitochondrial DNA (mtDNA) control region sequence data suggest that males are distinct among breeding populations (ΦST=0.051), and between the eastern Chukchi and other nonbreeding aggregations (ΦST=0.336–0.449). Nonbreeding female aggregations were genetically distinct across marker types (microsatellite FST=0.019; mtDNA ΦST=0.313), as was eastern Chukchi and all other nonbreeding aggregations (microsatellite FST=0.019–0.035; mtDNA ΦST=0.386–0.389). Gene flow estimates are asymmetrical from St. Lawrence Island into the southeastern Bering breeding population for both sexes. Partitioning of haplotype frequencies among breeding populations suggests that individuals exhibit some degree of philopatry, although weak. High levels of genetic differentiation among eastern Chukchi and all other nonbreeding aggregations, but considerably lower genetic differentiation between breeding populations, suggest that at least 1 genetically distinct breeding population remained unsampled. Limited genetic structure at microsatellite loci between assayed breeding areas can emerge from several processes, including male-mediated gene flow, or population admixture following a decrease in census size (i.e., due to commercial harvest during 1880–1950s) and subsequent recovery. Nevertheless, high levels of genetic diversity in the Pacific walrus, which withstood prolonged decreases in census numbers with little impact on neutral genetic diversity, may reflect resiliency in the face of past environmental challenges.

  19. Flow patterns and heat transfer characteristics of flat plate pulsating heat pipes with various asymmetric and aspect ratios of the channels

    International Nuclear Information System (INIS)

    Jang, Dong Soo; Lee, Joo Seong; Ahn, Jae Hwan; Kim, Dongwoo; Kim, Yongchan

    2017-01-01

    Highlights: • Flat plate pulsating heat pipes with asymmetric and aspect ratios were tested. • Flow patterns were investigated according to channel geometry and flow condition. • Heat transfer characteristics were analyzed with various heat inputs. • Optimum asymmetric and aspect ratios were suggested for maximum thermal performance. - Abstract: The thermal performance of flat plate pulsating heat pipes (PHPs) in compact electronic devices can be improved by adopting asymmetric channels with increased pressure differences and an unbalanced driving force. The objective of this study is to investigate the heat transfer characteristics of flat plate PHPs with various asymmetric ratios and aspect ratios in the channels. The thermal performance and flow pattern of the flat plate PHPs were measured by varying the asymmetric ratio from 1.0 to 4.0, aspect ratio from 2.5 to 5.0, and heat input from 2 to 28 W. The effects of the asymmetric ratio and aspect ratio on the thermal resistance were analyzed with the measured evaporator temperature and flow patterns at various heat inputs. With heat inputs of 6 W and 12 W, the optimum asymmetric ratio and aspect ratio for the flat plate PHPs were determined to be 4.0 and 2.5, respectively. With the heat input of 18 W, the optimum asymmetric ratio and aspect ratio were determined to be 1.5 and 2.5, respectively.

  20. Calculation and measurement of a neutral air flow velocity impacting a high voltage capacitor with asymmetrical electrodes

    Directory of Open Access Journals (Sweden)

    M. Malík

    2014-01-01

    Full Text Available This paper deals with the effects surrounding phenomenon of a mechanical force generated on a high voltage asymmetrical capacitor (the so called Biefeld-Brown effect. A method to measure this force is described and a formula to calculate its value is also given. Based on this the authors derive a formula characterising the neutral air flow velocity impacting an asymmetrical capacitor connected to high voltage. This air flow under normal circumstances lessens the generated force. In the following part this velocity is measured using Particle Image Velocimetry measuring technique and the results of the theoretically calculated velocity and the experimentally measured value are compared. The authors found a good agreement between the results of both approaches.

  1. Rapid Asymmetric Synthesis of Disubstituted Allenes by Coupling of Flow-Generated Diazo Compounds and Propargylated Amines.

    Science.gov (United States)

    Poh, Jian-Siang; Makai, Szabolcs; von Keutz, Timo; Tran, Duc N; Battilocchio, Claudio; Pasau, Patrick; Ley, Steven V

    2017-02-06

    We report herein the asymmetric coupling of flow-generated unstabilized diazo compounds and propargylated amine derivatives, using a new pyridinebis(imidazoline) ligand, a copper catalyst and base. The reaction proceeds rapidly, generating chiral allenes in 10-20 minutes with high enantioselectivity (89-98 % de/ee), moderate yields and a wide functional group tolerance. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  2. Isolation with asymmetric gene flow during the nonsynchronous divergence of dry forest birds.

    Science.gov (United States)

    Oswald, Jessica A; Overcast, Isaac; Mauck, William M; Andersen, Michael J; Smith, Brian Tilston

    2017-03-01

    Dry forest bird communities in South America are often fragmented by intervening mountains and rainforests, generating high local endemism. The historical assembly of dry forest communities likely results from dynamic processes linked to numerous population histories among codistributed species. Nevertheless, species may diversify in the same way through time if landscape and environmental features, or species ecologies, similarly structure populations. Here we tested whether six co-distributed taxon pairs that occur in the dry forests of the Tumbes and Marañón Valley of northwestern South America show concordant patterns and modes of diversification. We employed a genome reduction technique, double-digest restriction site-associated DNA sequencing, and obtained 4407-7186 genomewide SNPs. We estimated demographic history in each taxon pair and inferred that all pairs had the same best-fit demographic model: isolation with asymmetric gene flow from the Tumbes into the Marañón Valley, suggesting a common diversification mode. Overall, we also observed congruence in effective population size (N e ) patterns where ancestral N e were 2.9-11.0× larger than present-day Marañón Valley populations and 0.3-2.0× larger than Tumbesian populations. Present-day Marañón Valley N e was smaller than Tumbes. In contrast, we found simultaneous population isolation due to a single event to be unlikely as taxon pairs diverged over an extended period of time (0.1-2.9 Ma) with multiple nonoverlapping divergence periods. Our results show that even when populations of codistributed species asynchronously diverge, the mode of their differentiation can remain conserved over millions of years. Divergence by allopatric isolation due to barrier formation does not explain the mode of differentiation between these two bird assemblages; rather, migration of individuals occurred before and after geographic isolation. © 2017 John Wiley & Sons Ltd.

  3. Cross-Layer Scheme to Control Contention Window for Per-Flow in Asymmetric Multi-Hop Networks

    Science.gov (United States)

    Giang, Pham Thanh; Nakagawa, Kenji

    The IEEE 802.11 MAC standard for wireless ad hoc networks adopts Binary Exponential Back-off (BEB) mechanism to resolve bandwidth contention between stations. BEB mechanism controls the bandwidth allocation for each station by choosing a back-off value from one to CW according to the uniform random distribution, where CW is the contention window size. However, in asymmetric multi-hop networks, some stations are disadvantaged in opportunity of access to the shared channel and may suffer severe throughput degradation when the traffic load is large. Then, the network performance is degraded in terms of throughput and fairness. In this paper, we propose a new cross-layer scheme aiming to solve the per-flow unfairness problem and achieve good throughput performance in IEEE 802.11 multi-hop ad hoc networks. Our cross-layer scheme collects useful information from the physical, MAC and link layers of own station. This information is used to determine the optimal Contention Window (CW) size for per-station fairness. We also use this information to adjust CW size for each flow in the station in order to achieve per-flow fairness. Performance of our cross-layer scheme is examined on various asymmetric multi-hop network topologies by using Network Simulator (NS-2).

  4. Effects of a poloidally asymmetric ionization source on toroidal drift wave stability and the generation of sheared parallel flow

    International Nuclear Information System (INIS)

    Ware, A.S.; Diamond, P.H.

    1993-01-01

    The effects of a poloidally asymmetric ionization source on both dissipative toroidal drift wave stability and the generation of mean sheared parallel flow are examined. The first part of this work extends the development of a local model of ionization-driven drift wave turbulence [Phys. Fluids B 4, 877 (1992)] to include the effects of magnetic shear and poloidal source asymmetry, as well as poloidal mode coupling due to both magnetic drifts and the source asymmetry. Numerical and analytic investigation confirm that ionization effects can destabilize collisional toroidal drift waves. However, the mode structure is determined primarily by the magnetic drifts, and is not overly effected by the poloidal source asymmetry. The ionization source drives a purely inward particle flux, which can explain the anomalously rapid uptake of particles which occurs in response to gas puffing. In the second part of this work, the role poloidal asymmetries in both the source and turbulent particle diffusion play in the generation of sheared mean parallel flow is examined. Analysis indicates that predictions of sonic parallel shear flow [v parallel (r)∼c s ] are an unphysical result of the assumption of purely parallel flow (i.e., v perpendicular =0) and the neglect of turbulent parallel momentum transport. Results indicate that the flow produced is subcritical to the parallel shear flow instability when diamagnetic effects are properly considered

  5. Peristaltic flow of Johnson-Segalman fluid in asymmetric channel with convective boundary conditions

    Institute of Scientific and Technical Information of China (English)

    H YASMIN; T HAYAT; A ALSAEDI; HH ALSULAMI

    2014-01-01

    This work is concerned with the peristaltic transport of the Johnson-Segalman fluid in an asymmetric channel with convective boundary conditions. The mathematical modeling is based upon the conservation laws of mass, linear momentum, and energy. The resulting equations are solved after long wavelength and low Reynolds number are used. The results for the axial pressure gradient, velocity, and temperature profiles are obtained for small Weissenberg number. The expressions of the pressure gra-dient, velocity, and temperature are analyzed for various embedded parameters. Pumping and trapping phenomena are also explored.

  6. Numerical simulation of heat transfer to separation tio2/water nanofluids flow in an asymmetric abrupt expansion

    Directory of Open Access Journals (Sweden)

    Oon Cheen Sean

    2015-01-01

    Full Text Available Flow separation and reattachment of 0.2% TiO2 nanofluid in an asymmetric abrupt expansion is studied in this paper. Such flows occur in various engineering and heat transfer applications. Computational fluid dynamics package (FLUENT is used to investigate turbulent nanofluid flow in the horizontal double-tube heat exchanger. The meshing of this model consists of 43383 nodes and 74891 elements. Only a quarter of the annular pipe is developed and simulated as it has symmetrical geometry. Standard k-epsilon second order implicit, pressure based-solver equation is applied. Reynolds numbers between 17050 and 44545, step height ratio of 1 and 1.82 and constant heat flux of 49050 W/m2 was utilized in the simulation. Water was used as a working fluid to benchmark the study of the heat transfer enhancement in this case. Numerical simulation results show that the increase in the Reynolds number increases the heat transfer coefficient and Nusselt number of the flowing fluid. Moreover, the surface temperature will drop to its lowest value after the expansion and then gradually increase along the pipe. Finally, the chaotic movement and higher thermal conductivity of the TiO2 nanoparticles have contributed to the overall heat transfer enhancement of the nanofluid compare to the water.

  7. Impact of induced magnetic field on synovial fluid with peristaltic flow in an asymmetric channel

    Science.gov (United States)

    Afsar Khan, Ambreen; Farooq, Arfa; Vafai, Kambiz

    2018-01-01

    In this paper, we have worked for the impact of induced magnetic field on peristaltic motion of a non-Newtonian, incompressible, synovial fluid in an asymmetric channel. We have solved the problem for two models, Model-1 which behaves as shear thinning fluid and Model-2 which behaves as shear thickening fluid. The problem is solved by using modified Adomian Decomposition method. It has seen that two models behave quite opposite to each other for some parameters. The impact of various parameters on u, dp/dx, Δp and induced magnetic field bx have been studied graphically. The significant findings of this study is that the size of the trapped bolus and the pressure gradient increases by increasing M for both models.

  8. Experimental investigations on the fluid flow through an asymmetric rod bundle (W/D = 1.026)

    International Nuclear Information System (INIS)

    Rehme, K.

    1982-05-01

    Measurements of the distributions of the mean velocity, the wall shear stresses and the turbulence were performed in a wall subchannel of a rod bundle of four parallel rods arranged asymmetrically in a rectangular channel (P/D = 1.07, W/D = 1.026). The Reynolds number of this investigation was Re = 5.46 x 10 4 . The experimental results show that the momentum transport is highly anisotropic especially in the gaps of the rod bundle. Influences of secondary flow cannot be detected in the distribution of the time-mean velocity, however, such influences are found in the distributions of the turbulence intensities and the kinetic energy of turbulence. The comparison between experimental wall shear stress distributions and those calculated with the VELASCO-code shows discrepancies especially in the gap between the rod and channel walls. (orig.) [de

  9. Lattice Boltzmann simulation of asymmetric flow in nematic liquid crystals with finite anchoring

    Science.gov (United States)

    Zhang, Rui; Roberts, Tyler; Aranson, Igor S.; de Pablo, Juan J.

    2016-02-01

    Liquid crystals (LCs) display many of the flow characteristics of liquids but exhibit long range orientational order. In the nematic phase, the coupling of structure and flow leads to complex hydrodynamic effects that remain to be fully elucidated. Here, we consider the hydrodynamics of a nematic LC in a hybrid cell, where opposite walls have conflicting anchoring boundary conditions, and we employ a 3D lattice Boltzmann method to simulate the time-dependent flow patterns that can arise. Due to the symmetry breaking of the director field within the hybrid cell, we observe that at low to moderate shear rates, the volumetric flow rate under Couette and Poiseuille flows is different for opposite flow directions. At high shear rates, the director field may undergo a topological transition which leads to symmetric flows. By applying an oscillatory pressure gradient to the channel, a net volumetric flow rate is found to depend on the magnitude and frequency of the oscillation, as well as the anchoring strength. Taken together, our findings suggest several intriguing new applications for LCs in microfluidic devices.

  10. Separation and reattachment in flows over asymmetric cavities at small Reynolds numbers

    International Nuclear Information System (INIS)

    Tavoularis, S.; Goldman, A.; Floryan, J.M.

    1985-01-01

    Recent experimental and analytical studies of flows at extremely small Reynolds numbers have revealed rather complicated flow patterns, often beyond intuitive explanation. Such flows are common in biological systems as well as in industrial applications involving small particle suspensions. The present study was motivated by Nachtigall's observation that scales on certain butterfly and moth upper wing surfaces appear aerodynamically advantageous, since their removal results in decrease of the lift without an appreciable change of the drag. Since low Reynolds number flows are nearly reversible, it seems that geometrical asymmetry and not random roughness is responsible for this effect. Stokes flows (i.e. at 'zero' Reynolds number) are known to separate behind steps and obstacles, contrary to the expectation that the fluid motion would follow the boundary shape, if its inertia became negligible. (author)

  11. Asymmetric-detection time-stretch optical microscopy (ATOM) for ultrafast high-contrast cellular imaging in flow

    Science.gov (United States)

    Wong, Terence T. W.; Lau, Andy K. S.; Ho, Kenneth K. Y.; Tang, Matthew Y. H.; Robles, Joseph D. F.; Wei, Xiaoming; Chan, Antony C. S.; Tang, Anson H. L.; Lam, Edmund Y.; Wong, Kenneth K. Y.; Chan, Godfrey C. F.; Shum, Ho Cheung; Tsia, Kevin K.

    2014-01-01

    Accelerating imaging speed in optical microscopy is often realized at the expense of image contrast, image resolution, and detection sensitivity – a common predicament for advancing high-speed and high-throughput cellular imaging. We here demonstrate a new imaging approach, called asymmetric-detection time-stretch optical microscopy (ATOM), which can deliver ultrafast label-free high-contrast flow imaging with well delineated cellular morphological resolution and in-line optical image amplification to overcome the compromised imaging sensitivity at high speed. We show that ATOM can separately reveal the enhanced phase-gradient and absorption contrast in microfluidic live-cell imaging at a flow speed as high as ~10 m/s, corresponding to an imaging throughput of ~100,000 cells/sec. ATOM could thus be the enabling platform to meet the pressing need for intercalating optical microscopy in cellular assay, e.g. imaging flow cytometry – permitting high-throughput access to the morphological information of the individual cells simultaneously with a multitude of parameters obtained in the standard assay. PMID:24413677

  12. Turbulent flow structure at a discordant river confluence: Asymmetric jet dynamics with implications for channel morphology

    Science.gov (United States)

    Sukhodolov, Alexander N.; Krick, Julian; Sukhodolova, Tatiana A.; Cheng, Zhengyang; Rhoads, Bruce L.; Constantinescu, George S.

    2017-06-01

    Only a handful of field studies have examined turbulent flow structure at discordant confluences; the dynamics of flow at such confluences have mainly been examined in the laboratory. This paper reports results of a field-based investigation of turbulent flow structure at a discordant river confluence. These results support the hypothesis that flow at a discordant alluvial confluence with a velocity ratio greater than 2 exhibits jet-like characteristics. Scaling analysis shows that the dynamics of the jet core are quite similar to those of free jets but that the complex structure of flow at the confluence imposes strong effects that can locally suppress or enhance the spreading rate of the jet. This jet-like behavior of the flow has important implications for morphodynamic processes at these types of confluences. The highly energetic core of the jet at this discordant confluence is displaced away from the riverbed, thereby inhibiting scour; however, helical motion develops adjacent to the jet, particularly at high flows, which may promote scour. Numerical experiments demonstrate that the presence or absence of a depositional wedge at the mouth of the tributary can strongly influence detachment of the jet from the bed and the angle of the jet within the confluence.

  13. Homeland Security and Information Control: A Model of Asymmetric Information Flows.

    Science.gov (United States)

    Maxwell, Terrence A.

    2003-01-01

    Summarizes some of the activities the United States government has undertaken to control the dissemination of information since 2001. It also explores, through a conceptual model of information flows, potential impacts and discontinuities between policy purposes and outcomes. (AEF)

  14. Regulating Effect of Asymmetrical Impeller on the Flow Distributions of Double-sided Centrifugal Compressor

    Science.gov (United States)

    Yang, Ce; Liu, Yixiong; Yang, Dengfeng; Wang, Benjiang

    2017-11-01

    To achieve the rebalance of flow distributions of double-sided impellers, a method of improving the radius of rear impeller is presented in this paper. It is found that the flow distributions of front and rear impeller can be adjusted effectively by increasing the radius of rear impeller, thus improves the balance of flow distributions of front and rear impeller. Meanwhile, the working conversion mode process of double-sided centrifugal compressor is also changed. Further analysis shows that the flowrates of blade channels in front impeller are mainly influenced by the circumferential distributions of static pressure in the volute. But the flowrates of rear impeller blade channels are influenced by the outlet flow field of bent duct besides the effects of static pressure distributions in the volute. In the airflow interaction area downstream, the flowrate of blade channel is obviously smaller. By increasing the radius of rear impeller, the work capacity of rear impeller is enhanced, the working mode conversion process from parallel working mode of double-sided impeller to the single impeller working mode is delayed, and the stable working range of double-sided compressor is broadened.

  15. Impact of flows on ion temperatures inferred from neutron spectra in asymmetrically driven OMEGA DT implosions

    Science.gov (United States)

    Gatu Johnson, M.; Frenje, J.; Lahmann, B.; Seguin, F.; Petrasso, R.; Appelbe, B.; Chittenden, J.; Walsh, C.; Delettrez, J.; Igumenshchev, I.; Knauer, J. P.; Glebov, V. Yu.; Forrest, C.; Grimble, W.; Marshall, F.; Michel, T.; Stoeckl, C.; Haines, B. M.; Zylstra, A. B.

    2017-10-01

    Ion temperatures (Tion) in Inertial Confinement Fusion (ICF) experiments have traditionally been inferred from the broadening of primary neutron spectra. Directional motion (flow) of the fuel at burn, expected to arise due to asymmetries imposed by e.g. engineering features or drive non-uniformity, also impacts broadening and may lead to artificially inflated ``Tion'' values. Flow due to low-mode asymmetries is expected to give rise to line-of-sight variations in measured Tion, as observed in OMEGA cryogenic DT implosions but not in similar experiments at the NIF. In this presentation, we report on OMEGA experiments with intentional drive asymmetry designed for testing the ability to accurately predict and measure line-of-sight differences in apparent Tion due to low-mode asymmetry-seeded flows. The measurements are contrasted to CHIMERA, RAGE and ASTER simulations, providing insight into implosion dynamics and the relative importance of laser drive non-uniformity, stalk and offset as sources of asymmetry. The results highlight the complexity of hot-spot dynamics, which is a problem that must be mastered to achieve ICF ignition. This work was supported in part by the U.S. DOE, NLUF and LLE.

  16. Measurements of the asymmetric dynamic sheath around a pulse biased sphere immersed in flowing metal plasma

    International Nuclear Information System (INIS)

    Wu Hongchen; Anders, Andre

    2008-01-01

    A long-probe technique was utilized to record the expansion and retreat of the dynamic sheath around a spherical substrate immersed in pulsed cathode arc metal plasma. Positively biased, long cylindrical probes were placed on the side and downstream of a negatively pulsed biased stainless steel sphere of 1 in. (25.4 mm) diameter. The amplitude and width of the negative high voltage pulses (HVPs) were 2 kV, 5 kV, 10 kV, and 2 μs, 4 μs, 10 μs, respectively. The variation of the probe (electron) current during the HVP is a direct measure for the sheath expansion and retreat. Maximum sheath sizes were determined for the different parameters of the HVP. The expected rarefaction zone behind the biased sphere (wake) due to the fast plasma flow was clearly established and quantified.

  17. Measurements of the asymmetric dynamic sheath around a pulse biased sphere immersed in flowing metal plasma

    Science.gov (United States)

    Wu, Hongchen; Anders, André

    2008-08-01

    A long-probe technique was utilized to record the expansion and retreat of the dynamic sheath around a spherical substrate immersed in pulsed cathode arc metal plasma. Positively biased, long cylindrical probes were placed on the side and downstream of a negatively pulsed biased stainless steel sphere of 1 in. (25.4 mm) diameter. The amplitude and width of the negative high voltage pulses (HVPs) were 2 kV, 5 kV, 10 kV, and 2 µs, 4 µs, 10 µs, respectively. The variation of the probe (electron) current during the HVP is a direct measure for the sheath expansion and retreat. Maximum sheath sizes were determined for the different parameters of the HVP. The expected rarefaction zone behind the biased sphere (wake) due to the fast plasma flow was clearly established and quantified.

  18. Forced convection and subcooled flow boiling heat transfer in asymmetrically heated ducts of T-section

    International Nuclear Information System (INIS)

    Abou-Ziyan, Hosny Z.

    2004-01-01

    This paper presents the results of an experimental investigation of heat transfer from the heated bottom side of tee cross-section ducts to an internally flowing fluid. The idea of this work is derived from the cooling of critical areas in the cylinder heads of internal combustion engines. Fully developed single phase forced convection and subcooled flow boiling heat transfer data are reported. Six T-ducts of different width and height aspect ratios are tested with distilled water at velocities of 1, 2 and 3 m/s for bulk temperatures of 60 and 80 deg. C, while the heat flux was varied from about 80 to 700 kW/m 2 . The achieved data cover Reynolds numbers in the range of 5.22 x 10 4 to 2.36 x 10 5 , Prandtl numbers in the range from 2.2 to 3.0, duct width aspect ratio between 2.19 and 3.13 and duct height aspect ratio from 0.69 to 2.0. The results revealed that the increase in either the width or height aspect ratio of the T-ducts enhances the convection heat transfer coefficients and the boiling heat fluxes considerably. The following comparisons are provided for coolant velocity of 2 m/s, bulk temperature of 60 deg. C, wall superheat of 20 K and wall to bulk temperature difference of 20 K. As the width aspect ratio increases by 43%, the convection heat transfer coefficient and the boiling heat flux increase by 27% and 39%, respectively. An increase in the height aspect ratio by 290% enhances the convection heat transfer coefficient and the boiling heat fluxes by 82% and 103%, respectively. When the coolant velocity changes from 1 to 2 m/s, the heat transfer coefficient increases by 60% and the boiling heat flux rises by 62-98% for the various tested ducts. The convection heat transfer coefficient increases by 12% and the boiling heat flux decreases by 31% as the bulk fluid temperature rises from 60 to 80 deg. C. A correlation was developed for Nusselt number as a function of Reynolds number, Prandtl number, viscosity ratio and some aspect ratios of the T-duct

  19. Stability Improvement of High-Pressure-Ratio Turbocharger Centrifugal Compressor by Asymmetrical Flow Control-Part II: Nonaxisymmetrical Self-Recirculation Casing Treatment.

    Science.gov (United States)

    Zheng, Xinqian; Zhang, Yangjun; Yang, Mingyang; Bamba, Takahiro; Tamaki, Hideaki

    2013-03-01

    This is part II of a two-part paper involving the development of an asymmetrical flow control method to widen the operating range of a turbocharger centrifugal compressor with high-pressure ratio. A nonaxisymmetrical self-recirculation casing treatment (SRCT) as an instance of asymmetrical flow control method is presented. Experimental and numerical methods were used to investigate the impact of nonaxisymmetrical SRCT on the surge point of the centrifugal compressor. First, the influence of the geometry of a symmetric SRCT on the compressor performance was studied by means of numerical simulation. The key parameter of the SRCT was found to be the distance from the main blade leading edge to the rear groove (S r ). Next, several arrangements of a nonaxisymmetrical SRCT were designed, based on flow analysis presented in part I. Then, a series of experiments were carried out to analyze the influence of nonaxisymmetrical SRCT on the compressor performance. Results show that the nonaxisymmetrical SRCT has a certain influence on the performance and has a larger potential for stability improvement than the traditional symmetric SRCT. For the investigated SRCT, the surge flow rate of the compressor with the nonaxisymmetrical SRCTs is about 10% lower than that of the compressor with symmetric SRCT. The largest surge margin (smallest surge flow rate) can be obtained when the phase of the largest S r is coincident with the phase of the minimum static pressure in the vicinity of the leading edge of the splitter blades.

  20. Asymmetrical to symmetrical magnetic fabric of dikes: Paleo-flow orientations and Paleo-stresses recorded on feeder-bodies from the Motru Dike Swarm (Romania)

    Science.gov (United States)

    Féménias, Olivier; Diot, Hervé; Berza, Tudor; Gauffriau, Antoine; Demaiffe, Daniel

    2004-08-01

    The fabric in a dike is representative of the magmatic flow, considered as Newtonian. The anisotropy of magnetic susceptibility of the rocks gives a good representation of the shape-preferred orientation which, in turn, is a marker of the magmatic flow. Generally, a symmetrical pattern of the fabric across the dike is in agreement with a flow of magma within a channel: the flow direction is then reliable with this imbrication. An asymmetrical fabric is dependent on the flow and displacement of the wall. We present the case of both symmetrical and asymmetrical dike fabrics recording different emplacements. From a Pan-African calc-alkaline dike swarm (of basaltic-andesitic-dacitic-rhyolitic composition) of the Alpine Danubian window from South Carpathians (Romania), two populations of dikes have been described: thick (1-30 m) N-S-trending dikes and thin (movement of the walls. In contrast, the thin dikes are symmetrical and frequently display an arteritic morphology that limits the dike length, with no cartographic extension. We propose to relate the two types of dikes to the same regional stress field in a continuum of emplacement during a regional brittle event.

  1. Brownian motion and thermophoresis effects on Peristaltic slip flow of a MHD nanofluid in a symmetric/asymmetric channel

    Science.gov (United States)

    Sucharitha, G.; Sreenadh, S.; Lakshminarayana, P.; Sushma, K.

    2017-11-01

    The slip and heat transfer effects on MHD peristaltic transport of a nanofluid in a non-uniform symmetric/asymmetric channel have studied under the assumptions of elongated wave length and negligible Reynolds number. From the simplified governing equations, the closed form solutions for velocity, stream function, temperature and concentrations are obtained. Also dual solutions are discussed for symmetric and asymmetric channel cases. The effects of important physical parameters are explained graphically. The slip parameter decreases the fluid velocity in middle of the channel whereas it increases the velocity at the channel walls. Temperature and concentration are decreasing and increasing functions of radiation parameter respectively. Moreover, velocity, temperature and concentrations are high in symmetric channel when compared with asymmetric channel.

  2. Modeling Asymmetric Flow of Viscoelastic Fluid in Symmetric Planar Sudden Expansion Geometry Based on User-Defined Function in FLUENT CFD Package

    Directory of Open Access Journals (Sweden)

    Zhi-Ying Zheng

    2013-01-01

    Full Text Available Through embedding an in-house subroutine into FLUENT code by utilizing the functionalization of user-defined function provided by the software, a new numerical simulation methodology on viscoelastic fluid flows has been established. In order to benchmark this methodology, numerical simulations under different viscoelastic fluid solution concentrations (with solvent viscosity ratio varied from 0.2 to 0.9, extensibility parameters (100≤L2≤500, Reynolds numbers (0.1 ≤ Re ≤ 100, and Weissenberg numbers (0 ≤ Wi ≤ 20 are conducted on unsteady laminar flows through a symmetric planar sudden expansion with expansion ratio of 1: 3 for viscoelastic fluid flows. The constitutive model used to describe the viscoelastic effect of viscoelastic fluid flow is FENE-P (finitely extensive nonlinear elastic-Peterlin model. The numerical simulation results show that the influences of elasticity, inertia, and concentration on the flow bifurcation characteristics are more significant than those of extensibility. The present simulation results including the critical Reynolds number for which the flow becomes asymmetric, vortex size, bifurcation diagram, velocity distribution, streamline, and pressure loss show good agreements with some published results. That means the newly established method based on FLUENT software platform for simulating peculiar flow behaviors of viscoelastic fluid is credible and suitable for the study of viscoelastic fluid flows.

  3. Large Mass Flux Differences for Opposite Flow Directions of a Condensable Gas through an Asymmetric Porous Membrane

    Czech Academy of Sciences Publication Activity Database

    Uchytil, Petr; Loimer, T.

    2014-01-01

    Roč. 470, NOV 15 (2014), s. 451-457 ISSN 0376-7388 R&D Projects: GA MŠk 7AMB12AT010; GA MŠk(CZ) 7AMB14AT011 Institutional support: RVO:67985858 Keywords : condensation * vapor permeation * asymmetric membrane s Subject RIV: CI - Industrial Chemistry, Chemical Engineering Impact factor: 5.056, year: 2014

  4. Asymmetrical to symmetrical magnetic fabric of dykes: Paleo-flow orientations and Paleo-stresses recorded on feeder-bodies from the Motru Dyke Swarm (Romania)

    Science.gov (United States)

    Femenias, O.; Diot, H.; Berza, T.; Gauffriau, A.; Demaiffe, D.

    2003-04-01

    The fabric of crystals in a dyke is representative of the flow of magma, considered as a newtonian fluid. The AMS of the rocks (=magnetic mineralogy subfabric) gives a good representation of the shape preferred orientation related to the total fabric which, in turn is marker of the magmatic flow acquired during emplacement of the fluid within the dyke width. Generally, a symmetrical distribution of the fabric in terms of foliation and lineation across the dyke is in agreement with a model involving symmetrical differential displacements of the flow of the fluid within a channel. In this case, the flow direction is in relation with the imbrication of the symmetric foliations. In this study, we present the cases of both symmetrical and asymmetrical dyke fabric recording and involving different process of emplacement during a regional deformation. From a regional survey of a large Pan-African calc-alkaline dyke swarm (of basaltic-andesitic-dacitic-rhyolitic composition) of the Alpine Danubian window from South Carpathians of Romania, two populations of dykes have been described: thick (from 1 to 30 meters) N-S trending dykes and thin (less than 1 meter) E-W dykes. These two populations crosscut the country rocks without simple chronological relations between them. The thick dykes display asymmetrical fabric that involve a relatively long history of emplacement and important distance of flow. They record the regional sinistral movement of the walls. By contrast, the thin dykes are symmetrical and display frequently an arteritic morphology that limits the dyke length, with no cartographic extension. The mean orientations of the two types of dykes can be related to the same regional stress field and a continuum of emplacement is proposed for the two types of dykes during the regional deformation.

  5. Asymmetric information and economics

    Science.gov (United States)

    Frieden, B. Roy; Hawkins, Raymond J.

    2010-01-01

    We present an expression of the economic concept of asymmetric information with which it is possible to derive the dynamical laws of an economy. To illustrate the utility of this approach we show how the assumption of optimal information flow leads to a general class of investment strategies including the well-known Q theory of Tobin. Novel consequences of this formalism include a natural definition of market efficiency and an uncertainty principle relating capital stock and investment flow.

  6. Experimental investigations on the fluid flow through an asymmetric rod bundle (P/D = 1.148, W/D = 1.045)

    International Nuclear Information System (INIS)

    Rehme, K.

    1983-11-01

    Measurements of the distributions of the mean velocity, the wall shear stresses and the turbulence were performed in a wall subchannel of a rod bundle of four parallel rods arranged asymmetrically in a rectangular channel (P/D = 1.148, W/D = 1.045). The Reynolds number of this investigations was Re = 5.88 x 10 4 . The experimental results show that the momentum transport is highly anisotropic especially in the gaps of the rod bundle. Influences of secondary flow cannot be detected in the distribution of the time-mean velocity. The comparison between experimental wall shear stress distributions and those calculated with the VELASCO-code shows discrepancies both in the gap between the rod and channel walls and in the gap between the rods caused by the high momentum transport between the two subchannels. (orig.) [de

  7. Experimental investigations on the fluid flow through an asymmetric rod bundle (P/D = 1.148, W/D = 1.074)

    International Nuclear Information System (INIS)

    Rehme, K.

    1984-12-01

    Measurements of the distributions of the mean velocity, the wall shear stresses and the turbulence were performed in a wall subchannel of a rod bundle of four prallel rods arranged asymmetrically in a rectangular (P/D = 1.148, W/D = 1.074). The Reynolds number of this investigations was Re = 7.89 x 10 4 . The results obtained by a fully automated rig are compared with those from manual operation. The experimental results show that the momentum transport is highly anisotropyc especially in the gaps of the rod bundle. Influences of secondary flow cannot be detected in the distribution of the time-mean velocity. The comparison between experimental wall shear stress distributions and those calculated with the VELASCO-code shows discrepancies both in the gap between the rod and channel walls and in the gap between the rods caused by the high momentum transport between the two subchannels. (orig.) [de

  8. Asymmetric collider

    International Nuclear Information System (INIS)

    Bharadwaj, V.; Colestock, P.; Goderre, G.; Johnson, D.; Martin, P.; Holt, J.; Kaplan, D.

    1993-01-01

    The study of CP violation in beauty decay is one of the key challenges facing high energy physics. Much work has not yielded a definitive answer how this study might best be performed. However, one clear conclusion is that new accelerator facilities are needed. Proposals include experiments at asymmetric electron-positron colliders and in fixed-target and collider modes at LHC and SSC. Fixed-target and collider experiments at existing accelerators, while they might succeed in a first observation of the effect, will not be adequate to study it thoroughly. Giomataris has emphasized the potential of a new approach to the study of beauty CP violation: the asymmetric proton collider. Such a collider might be realized by the construction of a small storage ring intersecting an existing or soon-to-exist large synchrotron, or by arranging collisions between a large synchrotron and its injector. An experiment at such a collider can combine the advantages of fixed-target-like spectrometer geometry, facilitating triggering, particle identification and the instrumentation of a large acceptance, while the increased √s can provide a factor > 100 increase in beauty-production cross section compared to Tevatron or HERA fixed-target. Beams crossing at a non-zero angle can provide a small interaction region, permitting a first-level decay-vertex trigger to be implemented. To achieve large √s with a large Lorentz boost and high luminosity, the most favorable venue is the high-energy booster (HEB) at the SSC Laboratory, though the CERN SPS and Fermilab Tevatron are also worth considering

  9. Analysis of the asymmetrically expressed Ablim1 locus reveals existence of a lateral plate Nodal-independent left sided signal and an early, left-right independent role for nodal flow

    Directory of Open Access Journals (Sweden)

    Hilton Helen

    2010-05-01

    Full Text Available Abstract Background Vertebrates show clear asymmetry in left-right (L-R patterning of their organs and associated vasculature. During mammalian development a cilia driven leftwards flow of liquid leads to the left-sided expression of Nodal, which in turn activates asymmetric expression of the transcription factor Pitx2. While Pitx2 asymmetry drives many aspects of asymmetric morphogenesis, it is clear from published data that additional asymmetrically expressed loci must exist. Results A L-R expression screen identified the cytoskeletally-associated gene, actin binding lim protein 1 (Ablim1, as asymmetrically expressed in both the node and left lateral plate mesoderm (LPM. LPM expression closely mirrors that of Nodal. Significantly, Ablim1 LPM asymmetry was detected in the absence of detectable Nodal. In the node, Ablim1 was initially expressed symmetrically across the entire structure, resolving to give a peri-nodal ring at the headfold stage in a flow and Pkd2-dependent manner. The peri-nodal ring of Ablim1 expression became asymmetric by the mid-headfold stage, showing stronger right than left-sided expression. Node asymmetry became more apparent as development proceeded; expression retreated in an anticlockwise direction, disappearing first from the left anterior node. Indeed, at early somite stages Ablim1 shows a unique asymmetric expression pattern, in the left lateral plate and to the right side of the node. Conclusion Left LPM Ablim1 is expressed in the absence of detectable LPM Nodal, clearly revealing existence of a Pitx2 and Nodal-independent left-sided signal in mammals. At the node, a previously unrecognised action of early nodal flow and Pkd2 activity, within the pit of the node, influences gene expression in a symmetric manner. Subsequent Ablim1 expression in the peri-nodal ring reveals a very early indication of L-R asymmetry. Ablim1 expression analysis at the node acts as an indicator of nodal flow. Together these results make

  10. On the flow magnitude and field-flow alignment at Earth's core surface

    DEFF Research Database (Denmark)

    Finlay, Chris; Amit, H.

    ,with results differing from reference values by less than 8%.Application to a high quality geomagnetic field model based on satelliteobservations (the xCHAOS model in epoch 2004.0) leads to a flowmagnitude estimate of 11 - 14 km / yr, in accordance with previousestimates. When applied to the historical...

  11. Asymmetric Ashes

    Science.gov (United States)

    2006-11-01

    that oscillate in certain directions. Reflection or scattering of light favours certain orientations of the electric and magnetic fields over others. This is why polarising sunglasses can filter out the glint of sunlight reflected off a pond. When light scatters through the expanding debris of a supernova, it retains information about the orientation of the scattering layers. If the supernova is spherically symmetric, all orientations will be present equally and will average out, so there will be no net polarisation. If, however, the gas shell is not round, a slight net polarisation will be imprinted on the light. This is what broad-band polarimetry can accomplish. If additional spectral information is available ('spectro-polarimetry'), one can determine whether the asymmetry is in the continuum light or in some spectral lines. In the case of the Type Ia supernovae, the astronomers found that the continuum polarisation is very small so that the overall shape of the explosion is crudely spherical. But the much larger polarization in strongly blue-shifted spectral lines evidences the presence, in the outer regions, of fast moving clumps with peculiar chemical composition. "Our study reveals that explosions of Type Ia supernovae are really three-dimensional phenomena," says Dietrich Baade. "The outer regions of the blast cloud is asymmetric, with different materials found in 'clumps', while the inner regions are smooth." "This study was possible because polarimetry could unfold its full strength thanks to the light-collecting power of the Very Large Telescope and the very precise calibration of the FORS instrument," he adds. The research team first spotted this asymmetry in 2003, as part of the same observational campaign (ESO PR 23/03 and ESO PR Photo 26/05). The new, more extensive results show that the degree of polarisation and, hence, the asphericity, correlates with the intrinsic brightness of the explosion. The brighter the supernova, the smoother, or less clumpy

  12. Electron Jet of Asymmetric Reconnection

    Science.gov (United States)

    Khotyaintsev, Yu. V.; Graham, D. B.; Norgren, C.; Eriksson, E.; Li, W.; Johlander, A.; Vaivads, A.; Andre, M.; Pritchett, P. L.; Retino, A.; hide

    2016-01-01

    We present Magnetospheric Multiscale observations of an electron-scale current sheet and electron outflow jet for asymmetric reconnection with guide field at the subsolar magnetopause. The electron jet observed within the reconnection region has an electron Mach number of 0.35 and is associated with electron agyrotropy. The jet is unstable to an electrostatic instability which generates intense waves with E(sub parallel lines) amplitudes reaching up to 300 mV/m and potentials up to 20% of the electron thermal energy. We see evidence of interaction between the waves and the electron beam, leading to quick thermalization of the beam and stabilization of the instability. The wave phase speed is comparable to the ion thermal speed, suggesting that the instability is of Buneman type, and therefore introduces electron-ion drag and leads to braking of the electron flow. Our observations demonstrate that electrostatic turbulence plays an important role in the electron-scale physics of asymmetric reconnection.

  13. Monitoring of barley starch amylolysis by gravitational field flow fractionation and MALDI-TOF MS

    Czech Academy of Sciences Publication Activity Database

    Mazanec, Karel; Dyčka, Filip; Bobálová, Janette

    2011-01-01

    Roč. 91, č. 15 (2011), s. 2756-2761 ISSN 0022-5142 R&D Projects: GA MŠk 1M0570; GA MŠk 1M06030; GA MŠk 2B06037 Institutional research plan: CEZ:AV0Z40310501 Keywords : barley * starch * malting process Subject RIV: CB - Analytical Chemistry, Separation Impact factor: 1.436, year: 2011

  14. The effect of 25 years of oil field flow line service on epoxy fiberglass pipe

    International Nuclear Information System (INIS)

    Oswald, K.J.

    1988-01-01

    Glass fiber reinforced epoxy and vinyl ester piping systems have been used for over 35 years to control corrosion problems in oil fields and chemical and industrial plants and many case histories have been reported to document the successful performances of fiberglass reinforced thermosetting plastics in a wide range of corrosive services. This information is reinforced by laboratory test data from flat laminates and pipe exposed to numerous chemicals and mixtures of chemicals, but little has been published to document the effect of long-term, in-service exposure on fiberglass equipment. The purpose of this paper is to help to fill this void by comparing data from physical testing of pipe removed from successful corrosive service applications with data obtained from the same type of pipe at the time of manufacture. The information supplied in these papers represents only a few of the successful applications of filament wound epoxy and vinyl ester pipe as it is difficult to obtain permission to remove pipe from an operating line

  15. Separation and characterization of nanoparticles in complex food and environmental samples by field-flow fractionation

    DEFF Research Database (Denmark)

    Kammer, Frank von der; Legros, Samuel; Hofmann, Thilo

    2011-01-01

    The thorough analysis of natural nanoparticles (NPs) and engineered NPs involves the sequence of detection, identification, quantification and, if possible, detailed characterization. In a complex or heterogeneous sample, each step of this sequence is an individual challenge, and, given suitable...... has been applied for separation of various types of NP (e.g., organic macromolecules, and carbonaceous or inorganic NPs) in different types of media (e.g., natural waters, soil extracts or food samples).FFF can be coupled to different types of detectors that offer additional information...... conditions on all types of NP in the sample. A holistic methodological approach is preferable to a technique-focused one....

  16. The role of zonally asymmetric heating in the vertical and temporal structure of the global scale flow fields during FGGE SOP-1

    Science.gov (United States)

    Paegle, J.; Kalnay, E.; Baker, W. E.

    1981-01-01

    The global scale structure of atmospheric flow is best documented on time scales longer than a few days. Theoretical and observational studies of ultralong waves have emphasized forcing due to global scale variations of topography and surface heat flux, possibly interacting with baroclinically unstable or vertically refracting basic flows. Analyses of SOP-1 data in terms of global scale spherical harmonics is documented with emphasis upon weekly transitions.

  17. Principles of asymmetric synthesis

    CERN Document Server

    Gawley, Robert E; Aube, Jeffrey

    2012-01-01

    The world is chiral. Most of the molecules in it are chiral, and asymmetric synthesis is an important means by which enantiopure chiral molecules may be obtained for study and sale. Using examples from the literature of asymmetric synthesis, this book presents a detailed analysis of the factors that govern stereoselectivity in organic reactions. After an explanation of the basic physical-organic principles governing stereoselective reactions, the authors provide a detailed, annotated glossary of stereochemical terms. A chapter on "Practical Aspects of Asymmetric Synthesis" provides a critical overview of the most common methods for the preparation of enantiomerically pure compounds, techniques for analysis of stereoisomers using chromatographic, spectroscopic, and chiroptical methods. The authors then present an overview of the most important methods in contemporary asymmetric synthesis organized by reaction type. Thus, there are four chapters on carbon-carbon bond forming reactions, one chapter on reductions...

  18. Ecological differentiation, lack of hybrids involving diploids, and asymmetric gene flow between polyploids in narrow contact zones of Senecio carniolicus (syn. Jacobaea carniolica, Asteraceae)

    Czech Academy of Sciences Publication Activity Database

    Hülber, K.; Sonnleitner, M.; Suda, Jan; Krejčíková, J.; Schönswetter, P.; Schneeweiss, G. M.; Winkler, M.

    2015-01-01

    Roč. 5, č. 6 (2015), s. 1224-1234 ISSN 2045-7758 R&D Projects: GA ČR GB14-36079G Institutional support: RVO:67985939 Keywords : gene flow * hybridization * polyploidy Subject RIV: EF - Botanics Impact factor: 2.537, year: 2015

  19. Vortex Dynamics of Asymmetric Heave Plates

    Science.gov (United States)

    Rusch, Curtis; Maurer, Benjamin; Polagye, Brian

    2017-11-01

    Heave plates can be used to provide reaction forces for wave energy converters, which harness the power in ocean surface waves to produce electricity. Heave plate inertia includes both the static mass of the heave plate, as well as the ``added mass'' of surrounding water accelerated with the object. Heave plate geometries may be symmetric or asymmetric, with interest in asymmetric designs driven by the resulting hydrodynamic asymmetry. Limited flow visualization has been previously conducted on symmetric heave plates, but flow visualization of asymmetric designs is needed to understand the origin of observed hydrodynamic asymmetries and their dependence on the Keulegan-Carpenter number. For example, it is hypothesized that the time-varying added mass of asymmetric heave plates is caused by vortex shedding, which is related to oscillation amplitude. Here, using direct flow visualization, we explore the relationship between vortex dynamics and time-varying added mass and drag. These results suggest potential pathways for more advanced heave plate designs that can exploit vortex formation and shedding to achieve more favorable hydrodynamic properties for wave energy converters.

  20. Quantifying social asymmetric structures.

    Science.gov (United States)

    Solanas, Antonio; Salafranca, Lluís; Riba, Carles; Sierra, Vicenta; Leiva, David

    2006-08-01

    Many social phenomena involve a set of dyadic relations among agents whose actions may be dependent. Although individualistic approaches have frequently been applied to analyze social processes, these are not generally concerned with dyadic relations, nor do they deal with dependency. This article describes a mathematical procedure for analyzing dyadic interactions in a social system. The proposed method consists mainly of decomposing asymmetric data into their symmetric and skew-symmetric parts. A quantification of skew symmetry for a social system can be obtained by dividing the norm of the skew-symmetric matrix by the norm of the asymmetric matrix. This calculation makes available to researchers a quantity related to the amount of dyadic reciprocity. With regard to agents, the procedure enables researchers to identify those whose behavior is asymmetric with respect to all agents. It is also possible to derive symmetric measurements among agents and to use multivariate statistical techniques.

  1. Asymmetrical field emitter

    Science.gov (United States)

    Fleming, J.G.; Smith, B.K.

    1995-10-10

    A method is disclosed for providing a field emitter with an asymmetrical emitter structure having a very sharp tip in close proximity to its gate. One preferred embodiment of the present invention includes an asymmetrical emitter and a gate. The emitter having a tip and a side is coupled to a substrate. The gate is connected to a step in the substrate. The step has a top surface and a side wall that is substantially parallel to the side of the emitter. The tip of the emitter is in close proximity to the gate. The emitter is at an emitter potential, and the gate is at a gate potential such that with the two potentials at appropriate values, electrons are emitted from the emitter. In one embodiment, the gate is separated from the emitter by an oxide layer, and the emitter is etched anisotropically to form its tip and its asymmetrical structure. 17 figs.

  2. Asymmetric ion trap

    Science.gov (United States)

    Barlow, Stephan E.; Alexander, Michael L.; Follansbee, James C.

    1997-01-01

    An ion trap having two end cap electrodes disposed asymmetrically about a center of a ring electrode. The inner surface of the end cap electrodes are conformed to an asymmetric pair of equipotential lines of the harmonic formed by the application of voltages to the electrodes. The asymmetry of the end cap electrodes allows ejection of charged species through the closer of the two electrodes which in turn allows for simultaneously detecting anions and cations expelled from the ion trap through the use of two detectors charged with opposite polarity.

  3. Ancient female philopatry, asymmetric male gene flow, and synchronous population expansion support the influence of climatic oscillations on the evolution of South American sea lion (Otaria flavescens.

    Directory of Open Access Journals (Sweden)

    Larissa Rosa de Oliveira

    Full Text Available The South American sea lion (Otaria flavescens is widely distributed along the southern Atlantic and Pacific coasts of South America with a history of significant commercial exploitation. We aimed to evaluate the population genetic structure and the evolutionary history of South American sea lion along its distribution by analyses of mitochondrial DNA (mtDNA and 10 nuclear microsatellites loci. We analyzed 147 sequences of mtDNA control region and genotyped 111 individuals of South American sea lion for 10 microsatellite loci, representing six populations (Peru, Northern Chile, Southern Chile, Uruguay (Brazil, Argentina and Falkland (Malvinas Islands and covering the entire distribution of the species. The mtDNA phylogeny shows that haplotypes from the two oceans comprise two very divergent clades as observed in previous studies, suggesting a long period (>1 million years of low inter-oceanic female gene flow. Bayesian analysis of bi-parental genetic diversity supports significant (but less pronounced than mitochondrial genetic structure between Pacific and Atlantic populations, although also suggested some inter-oceanic gene flow mediated by males. Higher male migration rates were found in the intra-oceanic population comparisons, supporting very high female philopatry in the species. Demographic analyses showed that populations from both oceans went through a large population expansion ~10,000 years ago, suggesting a very similar influence of historical environmental factors, such as the last glacial cycle, on both regions. Our results support the proposition that the Pacific and Atlantic populations of the South American sea lion should be considered distinct evolutionarily significant units, with at least two managements units in each ocean.

  4. Ancient female philopatry, asymmetric male gene flow, and synchronous population expansion support the influence of climatic oscillations on the evolution of South American sea lion (Otaria flavescens)

    Science.gov (United States)

    Gehara, Marcelo C. M.; Fraga, Lúcia D.; Lopes, Fernando; Túnez, Juan Ignacio; Cassini, Marcelo H.; Majluf, Patricia; Cárdenas-Alayza, Susana; Pavés, Héctor J.; Crespo, Enrique Alberto; García, Nestor; Loizaga de Castro, Rocío; Hoelzel, A. Rus; Sepúlveda, Maritza; Olavarría, Carlos; Valiati, Victor Hugo; Quiñones, Renato; Pérez-Alvarez, Maria Jose; Ott, Paulo Henrique

    2017-01-01

    The South American sea lion (Otaria flavescens) is widely distributed along the southern Atlantic and Pacific coasts of South America with a history of significant commercial exploitation. We aimed to evaluate the population genetic structure and the evolutionary history of South American sea lion along its distribution by analyses of mitochondrial DNA (mtDNA) and 10 nuclear microsatellites loci. We analyzed 147 sequences of mtDNA control region and genotyped 111 individuals of South American sea lion for 10 microsatellite loci, representing six populations (Peru, Northern Chile, Southern Chile, Uruguay (Brazil), Argentina and Falkland (Malvinas) Islands) and covering the entire distribution of the species. The mtDNA phylogeny shows that haplotypes from the two oceans comprise two very divergent clades as observed in previous studies, suggesting a long period (>1 million years) of low inter-oceanic female gene flow. Bayesian analysis of bi-parental genetic diversity supports significant (but less pronounced than mitochondrial) genetic structure between Pacific and Atlantic populations, although also suggested some inter-oceanic gene flow mediated by males. Higher male migration rates were found in the intra-oceanic population comparisons, supporting very high female philopatry in the species. Demographic analyses showed that populations from both oceans went through a large population expansion ~10,000 years ago, suggesting a very similar influence of historical environmental factors, such as the last glacial cycle, on both regions. Our results support the proposition that the Pacific and Atlantic populations of the South American sea lion should be considered distinct evolutionarily significant units, with at least two managements units in each ocean. PMID:28654647

  5. How Is Nature Asymmetric?

    Indian Academy of Sciences (India)

    Home; Journals; Resonance – Journal of Science Education; Volume 7; Issue 6. How Is Nature Asymmetric? - Discrete Symmetries in Particle Physics and their Violation ... Indian Institute of Technology, Chennai. Aligarh Muslim University. University of Rajasthan, Jaipur. Indian Institute of Science, Bangalore 560012, India.

  6. Exploring asymmetric catalytic transformations

    NARCIS (Netherlands)

    Guduguntla, Sureshbabu

    2017-01-01

    In Chapter 2, we report a highly enantioselective synthesis of β-alkyl-substituted alcohols through a one-pot Cu- catalyzed asymmetric allylic alkylation with organolithium reagents followed by reductive ozonolysis. The synthesis of γ-alkyl-substituted alcohols was also achieved through Cu-catalyzed

  7. PASSIVE CONTROL OF PARTICLE DISPERSION IN A PARTICLE-LADEN CIRCULAR JET USING ELLIPTIC CO-ANNULAR FLOW: A MEANS FOR IMPROVING UTILIZATION AND EMISSION REDUCTIONS IN PULVERIZED COAL BURNER

    Energy Technology Data Exchange (ETDEWEB)

    Ahsan R. Choudhuri

    2003-06-01

    A passive control technology utilizing elliptic co-flow to control the particle flinging and particle dispersion in a particle (coal)-laden flow was investigated using experimental and numerical techniques. Preferential concentration of particles occurs in particle-laden jets used in pulverized coal burner and causes uncontrollable NO{sub x} formation due to inhomogeneous local stoichiometry. This particular project was aimed at characterizing the near-field flow behavior of elliptic coaxial jets. The knowledge gained from the project will serve as the basis of further investigation on fluid-particle interactions in an asymmetric coaxial jet flow-field and thus is important to improve the design of pulverized coal burners where non-homogeneity of particle concentration causes increased NO{sub x} formation.

  8. Investment and Internal Finance: Asymmetric Information or Managerial Discretion?

    NARCIS (Netherlands)

    H. Degryse (Hans); A. de Jong (Abe)

    2001-01-01

    textabstractThis paper examines the relation between cash-flow availability and investment spending in the Netherlands. In particular, we are interested whether managerial discretion and/or asymmetric information drive the positive relation between cash-flow and investment spending. This relation

  9. Multipartite asymmetric quantum cloning

    International Nuclear Information System (INIS)

    Iblisdir, S.; Gisin, N.; Acin, A.; Cerf, N.J.; Filip, R.; Fiurasek, J.

    2005-01-01

    We investigate the optimal distribution of quantum information over multipartite systems in asymmetric settings. We introduce cloning transformations that take N identical replicas of a pure state in any dimension as input and yield a collection of clones with nonidentical fidelities. As an example, if the clones are partitioned into a set of M A clones with fidelity F A and another set of M B clones with fidelity F B , the trade-off between these fidelities is analyzed, and particular cases of optimal N→M A +M B cloning machines are exhibited. We also present an optimal 1→1+1+1 cloning machine, which is an example of a tripartite fully asymmetric cloner. Finally, it is shown how these cloning machines can be optically realized

  10. Asymmetric Evolutionary Games

    Science.gov (United States)

    McAvoy, Alex; Hauert, Christoph

    2015-01-01

    Evolutionary game theory is a powerful framework for studying evolution in populations of interacting individuals. A common assumption in evolutionary game theory is that interactions are symmetric, which means that the players are distinguished by only their strategies. In nature, however, the microscopic interactions between players are nearly always asymmetric due to environmental effects, differing baseline characteristics, and other possible sources of heterogeneity. To model these phenomena, we introduce into evolutionary game theory two broad classes of asymmetric interactions: ecological and genotypic. Ecological asymmetry results from variation in the environments of the players, while genotypic asymmetry is a consequence of the players having differing baseline genotypes. We develop a theory of these forms of asymmetry for games in structured populations and use the classical social dilemmas, the Prisoner’s Dilemma and the Snowdrift Game, for illustrations. Interestingly, asymmetric games reveal essential differences between models of genetic evolution based on reproduction and models of cultural evolution based on imitation that are not apparent in symmetric games. PMID:26308326

  11. Lift production through asymmetric flapping

    Science.gov (United States)

    Jalikop, Shreyas; Sreenivas, K. R.

    2009-11-01

    At present, there is a strong interest in developing Micro Air Vehicles (MAV) for applications like disaster management and aerial surveys. At these small length scales, the flight of insects and small birds suggests that unsteady aerodynamics of flapping wings can offer many advantages over fixed wing flight, such as hovering-flight, high maneuverability and high lift at large angles of attack. Various lift generating mechanims such as delayed stall, wake capture and wing rotation contribute towards our understanding of insect flight. We address the effect of asymmetric flapping of wings on lift production. By visualising the flow around a pair of rectangular wings flapping in a water tank and numerically computing the flow using a discrete vortex method, we demonstrate that net lift can be produced by introducing an asymmetry in the upstroke-to-downstroke velocity profile of the flapping wings. The competition between generation of upstroke and downstroke tip vortices appears to hold the key to understanding this lift generation mechanism.

  12. Predicting tensorial electrophoretic effects in asymmetric colloids

    Science.gov (United States)

    Mowitz, Aaron J.; Witten, T. A.

    2017-12-01

    We formulate a numerical method for predicting the tensorial linear response of a rigid, asymmetrically charged body to an applied electric field. This prediction requires calculating the response of the fluid to the Stokes drag forces on the moving body and on the countercharges near its surface. To determine the fluid's motion, we represent both the body and the countercharges using many point sources of drag known as Stokeslets. Finding the correct flow field amounts to finding the set of drag forces on the Stokeslets that is consistent with the relative velocities experienced by each Stokeslet. The method rigorously satisfies the condition that the object moves with no transfer of momentum to the fluid. We demonstrate that a sphere represented by 1999 well-separated Stokeslets on its surface produces flow and drag force like a solid sphere to 1% accuracy. We show that a uniformly charged sphere with 3998 body and countercharge Stokeslets obeys the Smoluchowski prediction [F. Morrison, J. Colloid Interface Sci. 34, 210 (1970), 10.1016/0021-9797(70)90171-2] for electrophoretic mobility when the countercharges lie close to the sphere. Spheres with dipolar and quadrupolar charge distributions rotate and translate as predicted analytically to 4% accuracy or better. We describe how the method can treat general asymmetric shapes and charge distributions. This method offers promise as a way to characterize and manipulate asymmetrically charged colloid-scale objects from biology (e.g., viruses) and technology (e.g., self-assembled clusters).

  13. Métodos heurísticos construtivos para redução do estoque em processo em ambientes de produção flow shop híbridos com tempos de setup dependentes da sequência Constructive heuristics methods to minimizing work in process in environment production hybrid flow shop with asymmetric sequence dependent setup times

    Directory of Open Access Journals (Sweden)

    Márcia de Fátima Morais

    2010-01-01

    Full Text Available Este artigo apresenta uma investigação sobre o problema de programação da produção em ambientes flow shop com múltiplas máquinas (híbridos e tempos de preparação (setup das máquinas assimétricos e dependentes da sequência, e propõe métodos heurísticos construtivos para a minimização do tempo médio de fluxo (Mean Flow Time, que objetiva uma resposta rápida à demanda e à redução do estoque em processamento. Os algoritmos propostos foram comparados entre si, uma vez que nenhum método de solução para o problema investigado foi encontrado na literatura. Um estudo da influência da relação entre as ordens de grandeza dos tempos de processamento das tarefas e de preparação das máquinas em cada método de solução, bem como a influência do procedimento de programação adotado, foi efetuado com o intuito de avaliar o desempenho dos métodosThis paper presents an investigation about the hybrid flow shop problem with asymmetric sequence dependent setup times and proposes constructive heuristic methods to minimize the mean flow time aiming at fast demand response and work in process reduction. The proposed heuristic methods were compared among themselves since no constructive heuristic method was found in the literature on the scheduling problem considered in this work. A study on the influence of the relation between the orders of magnitude of processing and setup time for each method was carried out. The influence of the scheduling procedure adopted was investigated to assess the performance of the methods use

  14. Salt supply to and significance of asymmetric salt diapirs

    DEFF Research Database (Denmark)

    Koyi, H.; Burliga, S.; Chemia, Zurab

    2012-01-01

    Salt diapirs can be asymmetric both internally and externally reflecting their evolution history. As such, this asymmetry bear a significant amount of information about the differential loading (± lateral forces) and in turn the salt supply that have shaped the diapir. In two dimensions......, In this study we compare results of analogue and numerical models of diapirs with two natural salt diapris (Klodawa and Gorleben diapirs) to explain their salt supply and asymmetric evolution. In a NW-SE section, the Gorleben salt diapir possesses an asymmetric external geometry represented by a large...... southeastern overhang due to salt extrusion during Middle Cretaceous followed by its burial in Tertiary. This external asymmetry is also reflected in the internal configuration of the diapir which shows different rates of salt flow on the two halves of the structure. The asymmetric external and internal...

  15. Asymmetric quantum cloning machines

    International Nuclear Information System (INIS)

    Cerf, N.J.

    1998-01-01

    A family of asymmetric cloning machines for quantum bits and N-dimensional quantum states is introduced. These machines produce two approximate copies of a single quantum state that emerge from two distinct channels. In particular, an asymmetric Pauli cloning machine is defined that makes two imperfect copies of a quantum bit, while the overall input-to-output operation for each copy is a Pauli channel. A no-cloning inequality is derived, characterizing the impossibility of copying imposed by quantum mechanics. If p and p ' are the probabilities of the depolarizing channels associated with the two outputs, the domain in (√p,√p ' )-space located inside a particular ellipse representing close-to-perfect cloning is forbidden. This ellipse tends to a circle when copying an N-dimensional state with N→∞, which has a simple semi-classical interpretation. The symmetric Pauli cloning machines are then used to provide an upper bound on the quantum capacity of the Pauli channel of probabilities p x , p y and p z . The capacity is proven to be vanishing if (√p x , √p y , √p z ) lies outside an ellipsoid whose pole coincides with the depolarizing channel that underlies the universal cloning machine. Finally, the tradeoff between the quality of the two copies is shown to result from a complementarity akin to Heisenberg uncertainty principle. (author)

  16. Cinchona alkaloids in asymmetric organocatalysis

    NARCIS (Netherlands)

    Marcelli, T.; Hiemstra, H.

    2010-01-01

    This article reviews the applications of cinchona alkaloids as asymmetric catalysts. In the last few years, characterized by the resurgence of interest in asymmetric organocatalysis, cinchona derivatives have been shown to catalyze an outstanding array of chemical reactions, often with remarkable

  17. Alternative Asymmetric Stochastic Volatility Models

    NARCIS (Netherlands)

    M. Asai (Manabu); M.J. McAleer (Michael)

    2010-01-01

    textabstractThe stochastic volatility model usually incorporates asymmetric effects by introducing the negative correlation between the innovations in returns and volatility. In this paper, we propose a new asymmetric stochastic volatility model, based on the leverage and size effects. The model is

  18. Asymmetric Realized Volatility Risk

    Directory of Open Access Journals (Sweden)

    David E. Allen

    2014-06-01

    Full Text Available In this paper, we document that realized variation measures constructed from high-frequency returns reveal a large degree of volatility risk in stock and index returns, where we characterize volatility risk by the extent to which forecasting errors in realized volatility are substantive. Even though returns standardized by ex post quadratic variation measures are nearly Gaussian, this unpredictability brings considerably more uncertainty to the empirically relevant ex ante distribution of returns. Explicitly modeling this volatility risk is fundamental. We propose a dually asymmetric realized volatility model, which incorporates the fact that realized volatility series are systematically more volatile in high volatility periods. Returns in this framework display time varying volatility, skewness and kurtosis. We provide a detailed account of the empirical advantages of the model using data on the S&P 500 index and eight other indexes and stocks.

  19. Asymmetric Higgsino dark matter.

    Science.gov (United States)

    Blum, Kfir; Efrati, Aielet; Grossman, Yuval; Nir, Yosef; Riotto, Antonio

    2012-08-03

    In the supersymmetric framework, prior to the electroweak phase transition, the existence of a baryon asymmetry implies the existence of a Higgsino asymmetry. We investigate whether the Higgsino could be a viable asymmetric dark matter candidate. We find that this is indeed possible. Thus, supersymmetry can provide the observed dark matter abundance and, furthermore, relate it with the baryon asymmetry, in which case the puzzle of why the baryonic and dark matter mass densities are similar would be explained. To accomplish this task, two conditions are required. First, the gauginos, squarks, and sleptons must all be very heavy, such that the only electroweak-scale superpartners are the Higgsinos. With this spectrum, supersymmetry does not solve the fine-tuning problem. Second, the temperature of the electroweak phase transition must be low, in the (1-10) GeV range. This condition requires an extension of the minimal supersymmetric standard model.

  20. Asymmetric Organocatalytic Cycloadditions

    DEFF Research Database (Denmark)

    Mose, Rasmus

    2016-01-01

    has gained broad recognition as it has found several applications in academia and industry. The [4+2] cycloaddition has also been performed in an enantioselective aminocatalytic fashion which allows the generation of optically active products. In this thesis it is demonstrated how trienamines can......Since the onset of the new millennium the field of organocatalysis has undergone a great expansion led by investigations in the field of aminocatalysis. This thesis will address some recent developments in aminocatalyzed cycloadditions and provide a theoretical background hereto. Cycloadditions...... undergo cascade reactions with different electron deficient dienophiles in Diels Alder – nucleophilic ring closing reactions. This methodology opens up for the direct asymmetric formation of hydroisochromenes and hydroisoquinolines which may possess interesting biological activities. It is also...

  1. Force on an Asymmetric Capacitor

    National Research Council Canada - National Science Library

    Bahder, Thomas

    2003-01-01

    .... At present, the physical basis for the Biefeld-Brown effect is not understood. The order of magnitude of the net force on the asymmetric capacitor is estimated assuming two different mechanisms of charge conduction between its electrodes...

  2. Asymmetric cation-binding catalysis

    DEFF Research Database (Denmark)

    Oliveira, Maria Teresa; Lee, Jiwoong

    2017-01-01

    The employment of metal salts is quite limited in asymmetric catalysis, although it would provide an additional arsenal of safe and inexpensive reagents to create molecular functions with high optical purity. Cation chelation by polyethers increases the salts' solubility in conventional organic...... solvents, thus increasing their applicability in synthesis. The expansion of this concept to chiral polyethers led to the emergence of asymmetric cation-binding catalysis, where chiral counter anions are generated from metal salts, particularly using BINOL-based polyethers. Alkali metal salts, namely KF...... highly enantioselective silylation reactions in polyether-generated chiral environments, and leading to a record-high turnover in asymmetric organocatalysis. This can lead to further applications by the asymmetric use of other inorganic salts in various organic transformations....

  3. Asymmetric Uncertainty Expression for High Gradient Aerodynamics

    Science.gov (United States)

    Pinier, Jeremy T

    2012-01-01

    When the physics of the flow around an aircraft changes very abruptly either in time or space (e.g., flow separation/reattachment, boundary layer transition, unsteadiness, shocks, etc), the measurements that are performed in a simulated environment like a wind tunnel test or a computational simulation will most likely incorrectly predict the exact location of where (or when) the change in physics happens. There are many reasons for this, includ- ing the error introduced by simulating a real system at a smaller scale and at non-ideal conditions, or the error due to turbulence models in a computational simulation. The un- certainty analysis principles that have been developed and are being implemented today do not fully account for uncertainty in the knowledge of the location of abrupt physics changes or sharp gradients, leading to a potentially underestimated uncertainty in those areas. To address this problem, a new asymmetric aerodynamic uncertainty expression containing an extra term to account for a phase-uncertainty, the magnitude of which is emphasized in the high-gradient aerodynamic regions is proposed in this paper. Additionally, based on previous work, a method for dispersing aerodynamic data within asymmetric uncer- tainty bounds in a more realistic way has been developed for use within Monte Carlo-type analyses.

  4. Multicatalyst system in asymmetric catalysis

    CERN Document Server

    Zhou, Jian

    2014-01-01

    This book introduces multi-catalyst systems by describing their mechanism and advantages in asymmetric catalysis.  Helps organic chemists perform more efficient catalysis with step-by-step methods  Overviews new concepts and progress for greener and economic catalytic reactions  Covers topics of interest in asymmetric catalysis including bifunctional catalysis, cooperative catalysis, multimetallic catalysis, and novel tandem reactions   Has applications for pharmaceuticals, agrochemicals, materials, and flavour and fragrance

  5. Asymmetric Gepner models (revisited)

    Energy Technology Data Exchange (ETDEWEB)

    Gato-Rivera, B. [NIKHEF Theory Group, Kruislaan 409, 1098 SJ Amsterdam (Netherlands)] [Instituto de Fisica Fundamental, CSIC, Serrano 123, Madrid 28006 (Spain); Schellekens, A.N., E-mail: t58@nikhef.n [NIKHEF Theory Group, Kruislaan 409, 1098 SJ Amsterdam (Netherlands)] [Instituto de Fisica Fundamental, CSIC, Serrano 123, Madrid 28006 (Spain)] [IMAPP, Radboud Universiteit, Nijmegen (Netherlands)

    2010-12-11

    We reconsider a class of heterotic string theories studied in 1989, based on tensor products of N=2 minimal models with asymmetric simple current invariants. We extend this analysis from (2,2) and (1,2) spectra to (0,2) spectra with SO(10) broken to the Standard Model. In the latter case the spectrum must contain fractionally charged particles. We find that in nearly all cases at least some of them are massless. However, we identify a large subclass where the fractional charges are at worst half-integer, and often vector-like. The number of families is very often reduced in comparison to the 1989 results, but there are no new tensor combinations yielding three families. All tensor combinations turn out to fall into two classes: those where the number of families is always divisible by three, and those where it is never divisible by three. We find an empirical rule to determine the class, which appears to extend beyond minimal N=2 tensor products. We observe that distributions of physical quantities such as the number of families, singlets and mirrors have an interesting tendency towards smaller values as the gauge groups approaches the Standard Model. We compare our results with an analogous class of free fermionic models. This displays similar features, but with less resolution. Finally we present a complete scan of the three family models based on the triply-exceptional combination (1,16{sup *},16{sup *},16{sup *}) identified originally by Gepner. We find 1220 distinct three family spectra in this case, forming 610 mirror pairs. About half of them have the gauge group SU(3)xSU(2){sub L}xSU(2){sub R}xU(1){sup 5}, the theoretical minimum, and many others are trinification models.

  6. Effect of particle-particle attractive and repulsive interactions on the retention in field-flow fractionation

    Czech Academy of Sciences Publication Activity Database

    Janča, J.; Berneron, J.-F.; Stejskal, Jaroslav

    2010-01-01

    Roč. 15, č. 8 (2010), s. 536-543 ISSN 1023-666X R&D Projects: GA AV ČR IAA400500905 Institutional research plan: CEZ:AV0Z40500505 Keywords : attractive and repulsive interactions * colloidal crystals * colloidal particles Subject RIV: CD - Macromolecular Chemistry Impact factor: 0.814, year: 2010

  7. Does asymmetric correlation affect portfolio optimization?

    Science.gov (United States)

    Fryd, Lukas

    2017-07-01

    The classical portfolio optimization problem does not assume asymmetric behavior of relationship among asset returns. The existence of asymmetric response in correlation on the bad news could be important information in portfolio optimization. The paper applies Dynamic conditional correlation model (DCC) and his asymmetric version (ADCC) to propose asymmetric behavior of conditional correlation. We analyse asymmetric correlation among S&P index, bonds index and spot gold price before mortgage crisis in 2008. We evaluate forecast ability of the models during and after mortgage crisis and demonstrate the impact of asymmetric correlation on the reduction of portfolio variance.

  8. D mesons in asymmetric nuclear matter

    International Nuclear Information System (INIS)

    Mishra, Amruta; Mazumdar, Arindam

    2009-01-01

    We calculate the in-medium D and D meson masses in isospin-asymmetric nuclear matter in an effective chiral model. The D and D mass modifications arising from their interactions with the nucleons and the scalar mesons in the effective hadronic model are seen to be appreciable at high densities and have a strong isospin dependence. These mass modifications can open the channels of the decay of the charmonium states (Ψ ' ,χ c ,J/Ψ) to DD pairs in dense hadronic matter. The isospin asymmetry in the doublet D=(D 0 ,D + ) is seen to be particularly appreciable at high densities and should show in observables such as their production and flow in asymmetric heavy-ion collisions in the compressed baryonic matter experiments in the future facility of FAIR, GSI. The results of the present work are compared to calculations of the D(D) in-medium masses in the literature using the QCD sum rule approach, quark meson coupling model, and coupled channel approach as well as to those from studies of quarkonium dissociation using heavy-quark potentials from lattice QCD at finite temperatures

  9. Asymmetric Modeling of the Industrial Heavy Water Plant (PIAP)

    International Nuclear Information System (INIS)

    Teruel, Federico; Aprea, J; Guido Lavalle, German

    2000-01-01

    Software of asymmetric stationary simulation for the Industrial Heavy Water Plant (PIAP) was developed, based on an existing symmetric simulator (Brigitte 2.0).This software allows to turn off some of the isotopic enrichment twin units present in the plant and to simulate them asymmetrically, in other words, with different selection of parameters between twins.Other incorporations were done, such as passing flows between units and entering flows in strategic points of the plant.The iterative system in which the symmetric simulator is based was insufficient to develop the asymmetric simulator, so the system was modeled according to an implicit scheme for the units that form the simulator.This type of resolution resulted in a simulator that supports a big range of boundary conditions and internal parameters.Moreover, the time of calculus is short (∼3 minutes), making it actually useful.The asymmetric simulator is at the PIAP now, for its study and validation. It shows expected tendencies and results according to the symmetric simulator already validated

  10. Asymmetric Synthesis via Chiral Aziridines

    DEFF Research Database (Denmark)

    Tanner, David Ackland; Harden, Adrian; Wyatt, Paul

    1996-01-01

    A series of chiral bis(aziridines) has been synthesised and evaluated as chelating ligands for a variety of asymmetric transformations mediated by metals [Os (dihydroxylation), Pd (allylic alkylation) Cu (cyclopropanation and aziridination, Li (1,2-addition of organolithiums to imines)]. In the b......A series of chiral bis(aziridines) has been synthesised and evaluated as chelating ligands for a variety of asymmetric transformations mediated by metals [Os (dihydroxylation), Pd (allylic alkylation) Cu (cyclopropanation and aziridination, Li (1,2-addition of organolithiums to imines...

  11. Ideal 3D asymmetric concentrator

    Energy Technology Data Exchange (ETDEWEB)

    Garcia-Botella, Angel [Departamento Fisica Aplicada a los Recursos Naturales, Universidad Politecnica de Madrid, E.T.S.I. de Montes, Ciudad Universitaria s/n, 28040 Madrid (Spain); Fernandez-Balbuena, Antonio Alvarez; Vazquez, Daniel; Bernabeu, Eusebio [Departamento de Optica, Universidad Complutense de Madrid, Fac. CC. Fisicas, Ciudad Universitaria s/n, 28040 Madrid (Spain)

    2009-01-15

    Nonimaging optics is a field devoted to the design of optical components for applications such as solar concentration or illumination. In this field, many different techniques have been used for producing reflective and refractive optical devices, including reverse engineering techniques. In this paper we apply photometric field theory and elliptic ray bundles method to study 3D asymmetric - without rotational or translational symmetry - concentrators, which can be useful components for nontracking solar applications. We study the one-sheet hyperbolic concentrator and we demonstrate its behaviour as ideal 3D asymmetric concentrator. (author)

  12. Asymmetric Penning trap coherent states

    International Nuclear Information System (INIS)

    Contreras-Astorga, Alonso; Fernandez, David J.

    2010-01-01

    By using a matrix technique, which allows to identify directly the ladder operators, the coherent states of the asymmetric Penning trap are derived as eigenstates of the appropriate annihilation operators. They are compared with those obtained through the displacement operator method.

  13. JET and COMPASS asymmetrical disruptions

    Czech Academy of Sciences Publication Activity Database

    Gerasimov, S.N.; Abreu, P.; Baruzzo, M.; Drozdov, V.; Dvornova, A.; Havlíček, Josef; Hender, T.C.; Hronová-Bilyková, Olena; Kruezi, U.; Li, X.; Markovič, Tomáš; Pánek, Radomír; Rubinacci, G.; Tsalas, M.; Ventre, S.; Villone, F.; Zakharov, L.E.

    2015-01-01

    Roč. 55, č. 11 (2015), s. 113006-113006 ISSN 0029-5515 R&D Projects: GA MŠk(CZ) LM2011021 Institutional support: RVO:61389021 Keywords : tokamak * asymmetrical disruption * JET * COMPASS Subject RIV: BL - Plasma and Gas Discharge Physics Impact factor: 4.040, year: 2015

  14. The role of zonally asymmetric heating in the vertical and temporal structure of the global scale flow fields during FGGE SOP-1. [First Global Atmospheric Research Program Global Experiment (FGGE); Special Observing Period (SOP)

    Science.gov (United States)

    Paegle, J.; Kalnay-Rivas, E.; Baker, W. E.

    1981-01-01

    By examining the vertical structure of the low order spherical harmonics of the divergence and vorticity fields, the relative contribution of tropical and monsoonal circulations upon the global wind fields was estimated. This indicates that the overall flow over North America and the Pacific between January and February is quite distinct both in the lower and upper troposphere. In these longitudes there is a stronger tropical overturning and subtropical jet stream in January than February. The divergent flow reversed between 850 and 200 mb. Poleward rotational flow at upper levels is associated with an equatorward rotational flow at low levels. This suggests that the monsoon and other tropical circulations project more amplitude upon low order (global scale) representations of the flow than do the typical midlatitude circulations and that their structures show conspicuous changes on a time scale of a week or less.

  15. Reverse Importing and Asymmetric Trade and FDI: A Networks Explanation

    OpenAIRE

    Theresa Greaney

    2002-01-01

    This paper considers the impact of business and social networks on international trade and foreign direct investment (FDI). I propose that differences in the strength of network effects across countries can produce asymmetric trade and investment flows that may lead to trade friction. This proposition is examined using a model of multi-product producers of a differentiated product. A firm from a country with strong network effects has a cost advantage in selling to buyers from its own country...

  16. Cyclodextrins in Asymmetric and Stereospecific Synthesis

    Directory of Open Access Journals (Sweden)

    Fliur Macaev

    2015-09-01

    Full Text Available Since their discovery, cyclodextrins have widely been used as green and easily available alternatives to promoters or catalysts of different chemical reactions in water. This review covers the research and application of cyclodextrins and their derivatives in asymmetric and stereospecific syntheses, with their division into three main groups: (1 cyclodextrins promoting asymmetric and stereospecific catalysis in water; (2 cyclodextrins’ complexes with transition metals as asymmetric and stereospecific catalysts; and (3 cyclodextrins’ non-metallic derivatives as asymmetric and stereospecific catalysts. The scope of this review is to systematize existing information on the contribution of cyclodextrins to asymmetric and stereospecific synthesis and, thus, to facilitate further development in this direction.

  17. A combined continuous microflow photochemistry and asymmetric organocatalysis approach for the enantioselective synthesis of tetrahydroquinolines

    Directory of Open Access Journals (Sweden)

    Erli Sugiono

    2013-11-01

    Full Text Available A continuous-flow asymmetric organocatalytic photocyclization–transfer hydrogenation cascade reaction has been developed. The new protocol allows the synthesis of tetrahydroquinolines from readily available 2-aminochalcones using a combination of photochemistry and asymmetric Brønsted acid catalysis. The photocylization and subsequent reduction was performed with catalytic amount of chiral BINOL derived phosphoric acid diester and Hantzsch dihydropyridine as hydrogen source providing the desired products in good yields and with excellent enantioselectivities.

  18. Stable walking with asymmetric legs

    International Nuclear Information System (INIS)

    Merker, Andreas; Rummel, Juergen; Seyfarth, Andre

    2011-01-01

    Asymmetric leg function is often an undesired side-effect in artificial legged systems and may reflect functional deficits or variations in the mechanical construction. It can also be found in legged locomotion in humans and animals such as after an accident or in specific gait patterns. So far, it is not clear to what extent differences in the leg function of contralateral limbs can be tolerated during walking or running. Here, we address this issue using a bipedal spring-mass model for simulating walking with compliant legs. With the help of the model, we show that considerable differences between contralateral legs can be tolerated and may even provide advantages to the robustness of the system dynamics. A better understanding of the mechanisms and potential benefits of asymmetric leg operation may help to guide the development of artificial limbs or the design novel therapeutic concepts and rehabilitation strategies.

  19. Variable angle asymmetric cut monochromator

    International Nuclear Information System (INIS)

    Smither, R.K.; Fernandez, P.B.

    1993-09-01

    A variable incident angle, asymmetric cut, double crystal monochromator was tested for use on beamlines at the Advanced Photon Source (APS). For both undulator and wiggler beams the monochromator can expand area of footprint of beam on surface of the crystals to 50 times the area of incident beam; this will reduce the slope errors by a factor of 2500. The asymmetric cut allows one to increase the acceptance angle for incident radiation and obtain a better match to the opening angle of the incident beam. This can increase intensity of the diffracted beam by a factor of 2 to 5 and can make the beam more monochromatic, as well. The monochromator consists of two matched, asymmetric cut (18 degrees), silicon crystals mounted so that they can be rotated about three independent axes. Rotation around the first axis controls the Bragg angle. The second rotation axis is perpendicular to the diffraction planes and controls the increase of the area of the footprint of the beam on the crystal surface. Rotation around the third axis controls the angle between the surface of the crystal and the wider, horizontal axis for the beam and can make the footprint a rectangle with a minimum. length for this area. The asymmetric cut is 18 degrees for the matched pair of crystals, which allows one to expand the footprint area by a factor of 50 for Bragg angles up to 19.15 degrees (6 keV for Si[111] planes). This monochromator, with proper cooling, will be useful for analyzing the high intensity x-ray beams produced by both undulators and wigglers at the APS

  20. Asymmetric information and bank runs

    OpenAIRE

    Gu, Chao

    2007-01-01

    It is known that sunspots can trigger panic-based bank runs and that the optimal banking contract can tolerate panic-based runs. The existing literature assumes that these sunspots are based on a publicly observed extrinsic randomizing device. In this paper, I extend the analysis of panic-based runs to include an asymmetric-information, extrinsic randomizing device. Depositors observe different, but correlated, signals on the stability of the bank. I find that if the signals that depositors o...

  1. Asymmetric information and macroeconomic dynamics

    Science.gov (United States)

    Hawkins, Raymond J.; Aoki, Masanao; Roy Frieden, B.

    2010-09-01

    We show how macroeconomic dynamics can be derived from asymmetric information. As an illustration of the utility of this approach we derive the equilibrium density, non-equilibrium densities and the equation of motion for the response to a demand shock for productivity in a simple economy. Novel consequences of this approach include a natural incorporation of time dependence into macroeconomics and a common information-theoretic basis for economics and other fields seeking to link micro-dynamics and macro-observables.

  2. Asymmetric Synthesis of Apratoxin E.

    Science.gov (United States)

    Mao, Zhuo-Ya; Si, Chang-Mei; Liu, Yi-Wen; Dong, Han-Qing; Wei, Bang-Guo; Lin, Guo-Qiang

    2016-10-21

    An efficient method for asymmetric synthesis of apratoxin E 2 is described in this report. The chiral lactone 8, recycled from the degradation of saponin glycosides, was utilized to prepare the non-peptide fragment 6. In addition to this "from nature to nature" strategy, olefin cross-metathesis (CM) was applied as an alternative approach for the formation of the double bond. Moreover, pentafluorophenyl diphenylphosphinate was found to be an efficient condensation reagent for the macrocyclization.

  3. Comprehensive asymmetric dark matter model

    OpenAIRE

    Lonsdale, Stephen J.; Volkas, Raymond R.

    2018-01-01

    Asymmetric dark matter (ADM) is motivated by the similar cosmological mass densities measured for ordinary and dark matter. We present a comprehensive theory for ADM that addresses the mass density similarity, going beyond the usual ADM explanations of similar number densities. It features an explicit matter-antimatter asymmetry generation mechanism, has one fully worked out thermal history and suggestions for other possibilities, and meets all phenomenological, cosmological and astrophysical...

  4. Synthesis method of asymmetric gold particles.

    Science.gov (United States)

    Jun, Bong-Hyun; Murata, Michael; Hahm, Eunil; Lee, Luke P

    2017-06-07

    Asymmetric particles can exhibit unique properties. However, reported synthesis methods for asymmetric particles hinder their application because these methods have a limited scale and lack the ability to afford particles of varied shapes. Herein, we report a novel synthetic method which has the potential to produce large quantities of asymmetric particles. Asymmetric rose-shaped gold particles were fabricated as a proof of concept experiment. First, silica nanoparticles (NPs) were bound to a hydrophobic micro-sized polymer containing 2-chlorotritylchloride linkers (2-CTC resin). Then, half-planar gold particles with rose-shaped and polyhedral structures were prepared on the silica particles on the 2-CTC resin. Particle size was controlled by the concentration of the gold source. The asymmetric particles were easily cleaved from the resin without aggregation. We confirmed that gold was grown on the silica NPs. This facile method for synthesizing asymmetric particles has great potential for materials science.

  5. LG tools for asymmetric wargaming

    Science.gov (United States)

    Stilman, Boris; Yakhnis, Alex; Yakhnis, Vladimir

    2002-07-01

    Asymmetric operations represent conflict where one of the sides would apply military power to influence the political and civil environment, to facilitate diplomacy, and to interrupt specified illegal activities. This is a special type of conflict where the participants do not initiate full-scale war. Instead, the sides may be engaged in a limited open conflict or one or several sides may covertly engage another side using unconventional or less conventional methods of engagement. They may include peace operations, combating terrorism, counterdrug operations, arms control, support of insurgencies or counterinsurgencies, show of force. An asymmetric conflict can be represented as several concurrent interlinked games of various kinds: military, transportation, economic, political, etc. Thus, various actions of peace violators, terrorists, drug traffickers, etc., can be expressed via moves in different interlinked games. LG tools allow us to fully capture the specificity of asymmetric conflicts employing the major LG concept of hypergame. Hypergame allows modeling concurrent interlinked processes taking place in geographically remote locations at different levels of resolution and time scale. For example, it allows us to model an antiterrorist operation taking place simultaneously in a number of countries around the globe and involving wide range of entities from individuals to combat units to governments. Additionally, LG allows us to model all sides of the conflict at their level of sophistication. Intelligent stakeholders are represented by means of LG generated intelligent strategies. TO generate those strategies, in addition to its own mathematical intelligence, the LG algorithm may incorporate the intelligence of the top-level experts in the respective problem domains. LG models the individual differences between intelligent stakeholders. The LG tools make it possible to incorporate most of the known traits of a stakeholder, i.e., real personalities involved in

  6. Incompressibility of asymmetric nuclear matter

    International Nuclear Information System (INIS)

    Chen, Liewen; Cai, Baojun; Shen, Chun; Ko, Cheming; Xu, Jun; Li, Baoan

    2010-01-01

    Using an isospin- and momentum-dependent modified Gogny (MDI) interaction, the Skyrme-Hartree-Fock (SHF) approach, and a phenomenological modified Skyrme-like (MSL) model, we have studied the incompressibility K sat (δ) of isospin asymmetric nuclear matter at its saturation density. Our results show that in the expansion of K sat (δ) in powers of isospin asymmetry δ, i.e., K sat (δ) = K 0 + K sat,2 δ 2 + K sat,4 δ 4 + O(δ 6 ), the magnitude of the 4th-order K sat,4 parameter is generally small. The 2nd-order K sat,2 parameter thus essentially characterizes the isospin dependence of the incompressibility of asymmetric nuclear matter at saturation density. Furthermore, the K sat,2 can be expressed as K sat,2 = K sym – 6L – J 0 /K 0 L in terms of the slope parameter L and the curvature parameter K sym of the symmetry energy and the third-order derivative parameter J 0 of the energy of symmetric nuclear matter at saturation density, and we find the higher order J 0 contribution to K sat,2 generally cannot be neglected. Also, we have found a linear correlation between K sym and L as well as between J 0 /K 0 and K 0 . Using these correlations together with the empirical constraints on K 0 and L, the nuclear symmetry energy E sym (ρ0) at normal nuclear density, and the nucleon effective mass, we have obtained an estimated value of K sat,2 = -370 ± 120 MeV for the 2nd-order parameter in the isospin asymmetry expansion of the incompressibility of asymmetric nuclear matter at its saturation density. (author)

  7. Asymmetric effects in customer satisfaction

    DEFF Research Database (Denmark)

    Füller, Johann; Matzler, Kurt; Faullant, Rita

    2006-01-01

    The results of this study on customer satisfaction in snowboard areas show that the relationship between an attribute and overall satisfaction can indeed be asymmetric. A 30-item self-administered survey was completed by snowboarders (n=2526) in 51 areas in Austria, Germany, Switzerland and Italy....... Results show that waiting time is a dissatisfier; it has a significant impact on overall customer satisfaction in the low satisfaction condition and becomes insignificant in the high satisfaction situation. Restaurants and bars are hybrids, i.e. importance does not depend on performance. Slopes, fun...

  8. Asymmetric Formal Synthesis of Azadirachtin.

    Science.gov (United States)

    Mori, Naoki; Kitahara, Takeshi; Mori, Kenji; Watanabe, Hidenori

    2015-12-01

    An asymmetric formal synthesis of azadirachtin, a potent insect antifeedant, was accomplished in 30 steps to Ley's synthetic intermediate (longest linear sequence). The synthesis features: 1) rapid access to the optically active right-hand segment starting from the known 5-hydroxymethyl-2-cyclopentenone scaffold; 2) construction of the B and E rings by a key intramolecular tandem radical cyclization; 3) formation of the hemiacetal moiety in the C ring through the α-oxidation of the six-membered lactone followed by methanolysis. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  9. Spontaneous baryogenesis from asymmetric inflaton

    International Nuclear Information System (INIS)

    Takahashi, Fuminobu

    2015-10-01

    We propose a variant scenario of spontaneous baryogenesis from asymmetric inflaton based on current-current interactions between the inflaton and matter fields with a non-zero B-L charge. When the inflaton starts to oscillate around the minimum after inflation, it may lead to excitation of a CP-odd component, which induces an effective chemical potential for the B-L number through the current-current interactions. We study concrete inflation models and show that the spontaneous baryogenesis scenario can be naturally implemented in the chaotic inflation in supergravity.

  10. Clogging and transport of driven particles in asymmetric funnel arrays

    Science.gov (United States)

    Reichhardt, C. J. O.; Reichhardt, C.

    2018-06-01

    We numerically examine the flow and clogging of particles driven through asymmetric funnel arrays when the commensurability ratio of the number of particles per plaquette is varied. The particle–particle interactions are modeled with a soft repulsive potential that could represent vortex flow in type-II superconductors or driven charged colloids. The velocity-force curves for driving in the easy flow direction of the funnels exhibit a single depinning threshold; however, for driving in the hard flow direction, we find that there can be both negative mobility where the velocity decreases with increasing driving force as well as a reentrant pinning effect in which the particles flow at low drives but become pinned at intermediate drives. This reentrant pinning is associated with a transition from smooth 1D flow at low drives to a clogged state at higher drives that occurs when the particles cluster in a small number of plaquettes and block the flow. When the drive is further increased, particle rearrangements occur that cause the clog to break apart. We map out the regimes in which the pinned, flowing, and clogged states appear as a function of plaquette filling and drive. The clogged states remain robust at finite temperatures but develop intermittent bursts of flow in which a clog temporarily breaks apart but quickly reforms.

  11. Field factors for asymmetric collimators

    International Nuclear Information System (INIS)

    Turner, J.R.; Butler, A.P.H.

    1996-01-01

    In recent years manufacturers have been supplying linear accelerators with either a single pair or a dual pair of collimators. The use of a model to relate off-axis field factors to on-axis field factors obviates the need for repeat measurements whenever the asymmetric collimators are employed. We have investigated the variation of collimator scatter Sc, with distance of the central ray x from the central axis for a variety of non square field sizes. Collimator scatter was measured by in-air measurements with a build-up cap. The Primaty-Off-Centre-Ratio (POCR) was measured in-air by scanning orthogonally across the beam with an ionization chamber. The result of the investigation is the useful prediction of off-axis field factors for a range of rectangular asymmetric fields using the simple product of the on-axis field factor and the POCR in air. The effect of asymmetry on the quality of the beam and hence the percent depth dose will be discussed. (author)

  12. Asymmetric Frontal Brain Activity and Parental Rejection

    NARCIS (Netherlands)

    Huffmeijer, R.; Alink, L.R.A.; Tops, M.; Bakermans-Kranenburg, M.J.; van IJzendoorn, M.H.

    2013-01-01

    Asymmetric frontal brain activity has been widely implicated in reactions to emotional stimuli and is thought to reflect individual differences in approach-withdrawal motivation. Here, we investigate whether asymmetric frontal activity, as a measure of approach-withdrawal motivation, also predicts

  13. Worst Asymmetrical Short-Circuit Current

    DEFF Research Database (Denmark)

    Arana Aristi, Iván; Holmstrøm, O; Grastrup, L

    2010-01-01

    In a typical power plant, the production scenario and the short-circuit time were found for the worst asymmetrical short-circuit current. Then, a sensitivity analysis on the missing generator values was realized in order to minimize the uncertainty of the results. Afterward the worst asymmetrical...

  14. Mechanochemistry assisted asymmetric organocatalysis: A sustainable approach

    Directory of Open Access Journals (Sweden)

    Pankaj Chauhan

    2012-12-01

    Full Text Available Ball-milling and pestle and mortar grinding have emerged as powerful methods for the development of environmentally benign chemical transformations. Recently, the use of these mechanochemical techniques in asymmetric organocatalysis has increased. This review highlights the progress in asymmetric organocatalytic reactions assisted by mechanochemical techniques.

  15. Designing asymmetric multiferroics with strong magnetoelectric coupling

    Science.gov (United States)

    Lu, Xuezeng; Xiang, Hongjun; Rondinelli, James; Materials Theory; Design Group Team

    2015-03-01

    Multiferroics offer exciting opportunities for electric-field control of magnetism. Single-phase multiferroics suitable for such applications at room temperature need much more study. Here, we propose the concept of an alternative type of multiferroics, namely, the ``asymmetric multiferroic.'' In asymmetric multiferroics, two locally stable ferroelectric states are not symmetrically equivalent, leading to different magnetic properties between these two states. Furthermore, we predict from first principles that a Fe-Cr-Mo superlattice with the LiNbO3-type structure is such an asymmetric multiferroic. The strong ferrimagnetism, high ferroelectric polarization, and significant dependence of the magnetic transition temperature on polarization make this asymmetric multiferroic an ideal candidate for realizing electric-field control of magnetism at room temperature. Our study suggests that the asymmetric multiferroic may provide an alternative playground for voltage control of magnetism and find its applications in spintronics and quantum computing.

  16. A case of asymmetrical arthrogryposis

    International Nuclear Information System (INIS)

    Hageman, G.; Vette, J.K.; Willemse, J.

    1983-01-01

    Following the introduction of the conception that arthrogryposis is a symptom and not a clinical entity, a case of the very rare asymmetric form of neurogenic arthrogryposis is presented. The asymmetry of congenital contractures and weakness is associated with hemihypotrophy. The value of muscular CT-scanning prior to muscle biopsy is demonstrated. Muscular CT-scanning shows the extension of adipose tissue, which has replaced damaged muscles and therby indicates the exact site for muscle biopsy. Since orthopaedic treatment in arthrogryposis can be unrewarding due to severe muscular degeneration, preoperative scanning may provide additional important information on muscular function and thus be of benefit for surgery. The advantage of muscular CT-scanning in other forms of arthrogryposis requires further determination. The differential diagnosis with Werdnig-Hoffmann disease is discussed. (author)

  17. Turbulent mixed convection in asymmetrically heated vertical channel

    Directory of Open Access Journals (Sweden)

    Mokni Ameni

    2012-01-01

    Full Text Available In this paper an investigation of mixed convection from vertical heated channel is undertaken. The aim is to explore the heat transfer obtained by adding a forced flow, issued from a flat nozzle located in the entry section of a channel, to the up-going fluid along its walls. Forced and free convection are combined studied in order to increase the cooling requirements. The study deals with both symmetrically and asymmetrically heated channel. The Reynolds number based on the nozzle width and the jet velocity is assumed to be 3 103 and 2.104; whereas, the Rayleigh number based on the channel length and the wall temperature difference varies from 2.57 1010 to 5.15 1012. The heating asymmetry effect on the flow development including the mean velocity and temperature the local Nusselt number, the mass flow rate and heat transfer are examined.

  18. ASYMMETRIC MAGNETIC RECONNECTION IN WEAKLY IONIZED CHROMOSPHERIC PLASMAS

    International Nuclear Information System (INIS)

    Murphy, Nicholas A.; Lukin, Vyacheslav S.

    2015-01-01

    Realistic models of magnetic reconnection in the solar chromosphere must take into account that the plasma is partially ionized and that plasma conditions within any two magnetic flux bundles undergoing reconnection may not be the same. Asymmetric reconnection in the chromosphere may occur when newly emerged flux interacts with pre-existing, overlying flux. We present 2.5D simulations of asymmetric reconnection in weakly ionized, reacting plasmas where the magnetic field strengths, ion and neutral densities, and temperatures are different in each upstream region. The plasma and neutral components are evolved separately to allow non-equilibrium ionization. As in previous simulations of chromospheric reconnection, the current sheet thins to the scale of the neutral–ion mean free path and the ion and neutral outflows are strongly coupled. However, the ion and neutral inflows are asymmetrically decoupled. In cases with magnetic asymmetry, a net flow of neutrals through the current sheet from the weak-field (high-density) upstream region into the strong-field upstream region results from a neutral pressure gradient. Consequently, neutrals dragged along with the outflow are more likely to originate from the weak-field region. The Hall effect leads to the development of a characteristic quadrupole magnetic field modified by asymmetry, but the X-point geometry expected during Hall reconnection does not occur. All simulations show the development of plasmoids after an initial laminar phase

  19. Comprehensive asymmetric dark matter model

    Science.gov (United States)

    Lonsdale, Stephen J.; Volkas, Raymond R.

    2018-05-01

    Asymmetric dark matter (ADM) is motivated by the similar cosmological mass densities measured for ordinary and dark matter. We present a comprehensive theory for ADM that addresses the mass density similarity, going beyond the usual ADM explanations of similar number densities. It features an explicit matter-antimatter asymmetry generation mechanism, has one fully worked out thermal history and suggestions for other possibilities, and meets all phenomenological, cosmological and astrophysical constraints. Importantly, it incorporates a deep reason for why the dark matter mass scale is related to the proton mass, a key consideration in ADM models. Our starting point is the idea of mirror matter, which offers an explanation for dark matter by duplicating the standard model with a dark sector related by a Z2 parity symmetry. However, the dark sector need not manifest as a symmetric copy of the standard model in the present day. By utilizing the mechanism of "asymmetric symmetry breaking" with two Higgs doublets in each sector, we develop a model of ADM where the mirror symmetry is spontaneously broken, leading to an electroweak scale in the dark sector that is significantly larger than that of the visible sector. The weak sensitivity of the ordinary and dark QCD confinement scales to their respective electroweak scales leads to the necessary connection between the dark matter and proton masses. The dark matter is composed of either dark neutrons or a mixture of dark neutrons and metastable dark hydrogen atoms. Lepton asymmetries are generated by the C P -violating decays of heavy Majorana neutrinos in both sectors. These are then converted by sphaleron processes to produce the observed ratio of visible to dark matter in the universe. The dynamics responsible for the kinetic decoupling of the two sectors emerges as an important issue that we only partially solve.

  20. A short TE gradient-echo sequence using asymmetric sampling

    International Nuclear Information System (INIS)

    Fujita, Norihiko; Harada, Kohshi; Sakurai, Kosuke; Nakanishi, Katsuyuki; Kim, Shyogen; Kozuka, Takahiro

    1990-01-01

    We have developed a gradient-echo pulse sequence with a short TE less than 4 msec using a data set of asymmetric off-center sampling with a broad bandwidth. The use of such a short TE significantly reduces T 2 * dephasing effect even in a two-dimensional mode, and by collecting an off-center echo, motion-induced phase dispersion is also considerably decreased. High immunity of this sequence to these dephasing effects permits clear visualization of anatomical details near the skull base where large local field inhomogeneities and rapid blood flow such as in the internal carotid artery are present. (author)

  1. Chaos of several typical asymmetric systems

    International Nuclear Information System (INIS)

    Feng Jingjing; Zhang Qichang; Wang Wei

    2012-01-01

    The threshold for the onset of chaos in asymmetric nonlinear dynamic systems can be determined using an extended Padé method. In this paper, a double-well asymmetric potential system with damping under external periodic excitation is investigated, as well as an asymmetric triple-well potential system under external and parametric excitation. The integrals of Melnikov functions are established to demonstrate that the motion is chaotic. Threshold values are acquired when homoclinic and heteroclinic bifurcations occur. The results of analytical and numerical integration are compared to verify the effectiveness and feasibility of the analytical method.

  2. Modelling asymmetric growth in crowded plant communities

    DEFF Research Database (Denmark)

    Damgaard, Christian

    2010-01-01

    A class of models that may be used to quantify the effect of size-asymmetric competition in crowded plant communities by estimating a community specific degree of size-asymmetric growth for each species in the community is suggested. The model consists of two parts: an individual size......-asymmetric growth part, where growth is assumed to be proportional to a power function of the size of the individual, and a term that reduces the relative growth rate as a decreasing function of the individual plant size and the competitive interactions from other plants in the neighbourhood....

  3. Modeling of asymmetrical boost converters

    Directory of Open Access Journals (Sweden)

    Eliana Isabel Arango Zuluaga

    2014-01-01

    Full Text Available The asymmetrical interleaved dual boost (AIDB is a fifth-order DC/DC converter designed to interface photovoltaic (PV panels. The AIDB produces small current harmonics to the PV panels, reducing the power losses caused by the converter operation. Moreover, the AIDB provides a large voltage conversion ratio, which is required to step-up the PV voltage to the large dc-link voltage used in grid-connected inverters. To reject irradiance and load disturbances, the AIDB must be operated in a closed-loop and a dynamic model is required. Given that the AIDB converter operates in Discontinuous Conduction Mode (DCM, classical modeling approaches based on Continuous Conduction Mode (CCM are not valid. Moreover, classical DCM modeling techniques are not suitable for the AIDB converter. Therefore, this paper develops a novel mathematical model for the AIDB converter, which is suitable for control-pur-poses. The proposed model is based on the calculation of a diode current that is typically disregarded. Moreover, because the traditional correction to the second duty cycle reported in literature is not effective, a new equation is designed. The model accuracy is contrasted with circuital simulations in time and frequency domains, obtaining satisfactory results. Finally, the usefulness of the model in control applications is illustrated with an application example.

  4. Asymmetric Supercapacitor Electrodes and Devices.

    Science.gov (United States)

    Choudhary, Nitin; Li, Chao; Moore, Julian; Nagaiah, Narasimha; Zhai, Lei; Jung, Yeonwoong; Thomas, Jayan

    2017-06-01

    The world is recently witnessing an explosive development of novel electronic and optoelectronic devices that demand more-reliable power sources that combine higher energy density and longer-term durability. Supercapacitors have become one of the most promising energy-storage systems, as they present multifold advantages of high power density, fast charging-discharging, and long cyclic stability. However, the intrinsically low energy density inherent to traditional supercapacitors severely limits their widespread applications, triggering researchers to explore new types of supercapacitors with improved performance. Asymmetric supercapacitors (ASCs) assembled using two dissimilar electrode materials offer a distinct advantage of wide operational voltage window, and thereby significantly enhance the energy density. Recent progress made in the field of ASCs is critically reviewed, with the main focus on an extensive survey of the materials developed for ASC electrodes, as well as covering the progress made in the fabrication of ASC devices over the last few decades. Current challenges and a future outlook of the field of ASCs are also discussed. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  5. Bioinspired smart asymmetric nanochannel membranes.

    Science.gov (United States)

    Zhang, Zhen; Wen, Liping; Jiang, Lei

    2018-01-22

    Bioinspired smart asymmetric nanochannel membranes (BSANM) have been explored extensively to achieve the delicate ionic transport functions comparable to those of living organisms. The abiotic system exhibits superior stability and robustness, allowing for promising applications in many fields. In view of the abundance of research concerning BSANM in the past decade, herein, we present a systematic overview of the development of the state-of-the-art BSANM system. The discussion is focused on the construction methodologies based on raw materials with diverse dimensions (i.e. 0D, 1D, 2D, and bulk). A generic strategy for the design and construction of the BSANM system is proposed first and put into context with recent developments from homogeneous to heterogeneous nanochannel membranes. Then, the basic properties of the BSANM are introduced including selectivity, gating, and rectification, which are associated with the particular chemical and physical structures. Moreover, we summarized the practical applications of BSANM in energy conversion, biochemical sensing and other areas. In the end, some personal opinions on the future development of the BSANM are briefly illustrated. This review covers most of the related literature reported since 2010 and is intended to build up a broad and deep knowledge base that can provide a solid information source for the scientific community.

  6. Reflection asymmetric shapes in nuclei

    International Nuclear Information System (INIS)

    Ahmad, I.; Carpenter, M.P.; Emling, H.

    1989-01-01

    Experimental data show that there is no even-even nucleus with a reflection asymmetric shape in its ground state. Maximum octupole- octupole correlations occur in nuclei in the mass 224 (N∼134, Z∼88) region. Parity doublets, which are the characteristic signature of octupole deformation, have been observed in several odd mass Ra, Ac and Pa nuclei. Intertwined negative and positive parity levels have been observed in several even-even Ra and Th nuclei above spin ∼8ℎ. In both cases, the opposite parity states are connected by fast El transitions. In some medium-mass nuclei intertwined negative and positive parity levels have also been observed above spin ∼7ℎ. The nuclei which exhibit octupole deformation in this mass region are 144 Ba, 146 Ba and 146 Ce; 142 Ba, 148 Ce, 150 Ce and 142 Xe do not show these characteristics. No case of parity doublet has been observed in the mass 144 region. 32 refs., 16 figs., 1 tab

  7. Twin Higgs Asymmetric Dark Matter.

    Science.gov (United States)

    García García, Isabel; Lasenby, Robert; March-Russell, John

    2015-09-18

    We study asymmetric dark matter (ADM) in the context of the minimal (fraternal) twin Higgs solution to the little hierarchy problem, with a twin sector with gauged SU(3)^{'}×SU(2)^{'}, a twin Higgs doublet, and only third-generation twin fermions. Naturalness requires the QCD^{'} scale Λ_{QCD}^{'}≃0.5-20  GeV, and that t^{'} is heavy. We focus on the light b^{'} quark regime, m_{b^{'}}≲Λ_{QCD}^{'}, where QCD^{'} is characterized by a single scale Λ_{QCD}^{'} with no light pions. A twin baryon number asymmetry leads to a successful dark matter (DM) candidate: the spin-3/2 twin baryon, Δ^{'}∼b^{'}b^{'}b^{'}, with a dynamically determined mass (∼5Λ_{QCD}^{'}) in the preferred range for the DM-to-baryon ratio Ω_{DM}/Ω_{baryon}≃5. Gauging the U(1)^{'} group leads to twin atoms (Δ^{'}-τ^{'}[over ¯] bound states) that are successful ADM candidates in significant regions of parameter space, sometimes with observable changes to DM halo properties. Direct detection signatures satisfy current bounds, at times modified by dark form factors.

  8. An efficient catalyst for asymmetric Reformatsky reaction

    Indian Academy of Sciences (India)

    rate enantioselectivity using N,N-dialkylnorephedrines as chiral ligands. ..... temperatures also, there was no product conversion. ... Optimization of reaction conditions for asymmetric Reformatsky reaction between benzaldehyde and α-.

  9. Asymmetric cryptography based on wavefront sensing.

    Science.gov (United States)

    Peng, Xiang; Wei, Hengzheng; Zhang, Peng

    2006-12-15

    A system of asymmetric cryptography based on wavefront sensing (ACWS) is proposed for the first time to our knowledge. One of the most significant features of the asymmetric cryptography is that a trapdoor one-way function is required and constructed by analogy to wavefront sensing, in which the public key may be derived from optical parameters, such as the wavelength or the focal length, while the private key may be obtained from a kind of regular point array. The ciphertext is generated by the encoded wavefront and represented with an irregular array. In such an ACWS system, the encryption key is not identical to the decryption key, which is another important feature of an asymmetric cryptographic system. The processes of asymmetric encryption and decryption are formulized mathematically and demonstrated with a set of numerical experiments.

  10. Asymmetrical Representation of Gender in Amharic1

    African Journals Online (AJOL)

    Administrator

    in its grammar. Gender representation in this language is asymmetrical heavily ..... In dictionaries where. Amharic appears either as the target or the source language, verbs are entered ...... The Dialects of Amharic Revisited. Semitica et.

  11. Beam-beam issues in asymmetric colliders

    International Nuclear Information System (INIS)

    Furman, M.A.

    1992-07-01

    We discuss generic beam-beam issues for proposed asymmetric e + - e - colliders. We illustrate the issues by choosing, as examples, the proposals by Cornell University (CESR-B), KEK, and SLAC/LBL/LLNL (PEP-II)

  12. Congenital asymmetric crying face: a case report

    Directory of Open Access Journals (Sweden)

    Semra Kara

    2011-12-01

    Full Text Available Congenital asymmetric crying face is an anomalia caused by unilateral absence or weakness of depressor anguli oris muscle The major finding of the disease is the absence or weakness in the outer and lower movement of the commissure during crying. The other expression muscles are normal and the face is symmetric at rest. The asymmetry in congenital asymmetric crying face is most evident during infancy but decreases by age. Congenital asymmetric crying face can be associated with cervicofacial, musclebone, respiratory, genitourinary and central nervous system anomalia. It is diagnosed by physical examination. This paper presents a six days old infant with Congenital asymmetric crying face and discusses the case in terms of diagnosis and disease features.

  13. Asymmetric total synthesis of cladosporin and isocladosporin.

    Science.gov (United States)

    Zheng, Huaiji; Zhao, Changgui; Fang, Bowen; Jing, Peng; Yang, Juan; Xie, Xingang; She, Xuegong

    2012-07-06

    The first asymmetric total syntheses of cladosporin and isocladosporin were accomplished in 8 steps with 8% overall yield and 10 steps with 26% overall yield, respectively. The relative configuration of isocladosporin was determined via this total synthesis.

  14. Magnetically Modified Asymmetric Supercapacitors, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — This Small Business Innovation Research Phase I project is for the development of an asymmetric supercapacitor that will have improved energy density and cycle life....

  15. Impact of Secondary Interactions in Asymmetric Catalysis

    OpenAIRE

    Frölander, Anders

    2007-01-01

    This thesis deals with secondary interactions in asymmetric catalysis and their impact on the outcome of catalytic reactions. The first part revolves around the metal-catalyzed asymmetric allylic alkylation reaction and how interactions within the catalyst affect the stereochemistry. An OH–Pd hydrogen bond in Pd(0)–π-olefin complexes of hydroxy-containing oxazoline ligands was identified by density functional theory computations and helped to rationalize the contrasting results obtained emplo...

  16. Engineered Asymmetric Composite Membranes with Rectifying Properties.

    Science.gov (United States)

    Wen, Liping; Xiao, Kai; Sainath, Annadanam V Sesha; Komura, Motonori; Kong, Xiang-Yu; Xie, Ganhua; Zhang, Zhen; Tian, Ye; Iyoda, Tomokazu; Jiang, Lei

    2016-01-27

    Asymmetric composite membranes with rectifying properties are developed by grafting pH-stimulus-responsive materials onto the top layer of the composite structure, which is prepared by two novel block copolymers using a phase-separation technique. This engineered asymmetric composite membrane shows potential applications in sensors, filtration, and nanofluidic devices. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  17. Asymmetrical Fault Analysis at the Offshore Network of HVDC connected Wind Power Plants

    DEFF Research Database (Denmark)

    Goksu, Omer; Cutululis, Nicolaos Antonio; Sorensen, Poul

    2017-01-01

    Short-circuit faults for HVDC connected Wind Power Plants (WPPs) have been studied mostly for dc link and onshore ac grid faults, while the offshore ac faults, especially asymmetrical faults, have been mostly omitted in the literature. Requirements related to the offshore asymmetrical faults have...... been kept as future development at national levels in the recent ENTSO-E HVDC network code. In this paper offshore ac faults are studied using the classical power system fault analysis methods. It is shown that suppression of negative sequence current flow is not applicable and negative sequence...

  18. Cilia are required for asymmetric nodal induction in the sea urchin embryo.

    Science.gov (United States)

    Tisler, Matthias; Wetzel, Franziska; Mantino, Sabrina; Kremnyov, Stanislav; Thumberger, Thomas; Schweickert, Axel; Blum, Martin; Vick, Philipp

    2016-08-23

    Left-right (LR) organ asymmetries are a common feature of metazoan animals. In many cases, laterality is established by a conserved asymmetric Nodal signaling cascade during embryogenesis. In most vertebrates, asymmetric nodal induction results from a cilia-driven leftward fluid flow at the left-right organizer (LRO), a ciliated epithelium present during gastrula/neurula stages. Conservation of LRO and flow beyond the vertebrates has not been reported yet. Here we study sea urchin embryos, which use nodal to establish larval LR asymmetry as well. Cilia were found in the archenteron of embryos undergoing gastrulation. Expression of foxj1 and dnah9 suggested that archenteron cilia were motile. Cilia were polarized to the posterior pole of cells, a prerequisite of directed flow. High-speed videography revealed rotating cilia in the archenteron slightly before asymmetric nodal induction. Removal of cilia through brief high salt treatments resulted in aberrant patterns of nodal expression. Our data demonstrate that cilia - like in vertebrates - are required for asymmetric nodal induction in sea urchin embryos. Based on these results we argue that the anterior archenteron represents a bona fide LRO and propose that cilia-based symmetry breakage is a synapomorphy of the deuterostomes.

  19. Continuous control of asymmetric forebody vortices in a bi-stable state

    Science.gov (United States)

    Wang, Qi-te; Cheng, Ke-ming; Gu, Yun-song; Li, Zhuo-qi

    2018-02-01

    Aiming at the problem of continuous control of asymmetric forebody vortices at a high angle of attack in a bi-stable regime, a dual synthetic jet actuator embedded in an ogive forebody was designed. Alternating unsteady disturbance with varying degree asymmetrical flow fields near the nozzles is generated by adjusting the duty cycle of the drive signal of the actuator, specifically embodying the asymmetric time-averaged pattern of jet velocity, vorticity, and turbulent kinetic energy. Experimental results show that within the range of relatively high angles of attack, including the angle-of-attack region in a bi-stable state, the lateral force of the ogive forebody is continuously controlled by adjusting the duty cycle of the drive signal; the position of the forebody vortices in space, the vorticity magnitude, the total pressure coefficient near the vortex core, and the vortex breakdown location are continuously changed with the duty cycle increased observed from the time-averaged flow field. Instantaneous flow field results indicate that although the forebody vortices are in an unsteady oscillation state, a continuous change in the forebody vortices' oscillation balance position as the duty cycle increases leads to a continuous change in the model's surface pressure distribution and time-averaged lateral force. Different from the traditional control principle, in this study, other different degree asymmetrical states of the forebody vortices except the bi-stable state are obtained using the dual synthetic jet control technology.

  20. Hypogenetic chaotic jerk flows

    International Nuclear Information System (INIS)

    Li, Chunbiao; Sprott, Julien Clinton; Xing, Hongyan

    2016-01-01

    Removing the amplitude or polarity information in the feedback loop of a jerk structure shows that special nonlinearities with partial information in the variable can also lead to chaos. Some striking properties are found for this kind of hypogenetic chaotic jerk flow, including multistability of symmetric coexisting attractors from an asymmetric structure, hidden attractors with respect to equilibria but with global attraction, easy amplitude control, and phase reversal which is convenient for chaos applications. - Highlights: • Hypogenetic chaotic jerk flows with incomplete feedback of amplitude or polarity are obtained. • Multistability of symmetric coexisting attractors from an asymmetric structure is found. • Some jerk systems have hidden attractors with respect to equilibria but have global attraction. • These chaotic jerk flows have the properties of amplitude control and phase reversal.

  1. Keep-Left Behavior Induced by Asymmetrically Profiled Walls

    Science.gov (United States)

    Oliveira, C. L. N.; Vieira, A. P.; Helbing, D.; Andrade, J. S.; Herrmann, H. J.

    2016-01-01

    We show, computationally and analytically, that asymmetrically shaped walls can organize the flow of pedestrians driven in opposite directions through a corridor. Precisely, a two-lane ordered state emerges in which people always walk on the left-hand side (or right-hand side), controlled by the system's parameters. This effect depends on features of the channel geometry, such as the asymmetry of the profile and the channel width, as well as on the density and the drift velocity of pedestrians, and the intensity of noise. We investigate in detail the influence of these parameters on the flow and discover a crossover between ordered and disordered states. Our results show that an ordered state only appears within a limited range of drift velocities. Moreover, increasing noise may suppress such flow organization, but the flow is always sustained. This is in contrast with the "freezing by heating" phenomenon according to which pedestrians tend to clog in smooth channels for strong noise [Phys. Rev. Lett. 84, 1240 (2000)]. Therefore, the ratchetlike effect proposed here acts on the system not only to induce a "keep-left" behavior but also to prevent the freezing by heating clogging phenomenon. Besides pedestrian flow, this new phenomenon has other potential applications in microfluidics systems.

  2. Reversible rectification of vortex motion in magnetic and non-magnetic asymmetric pinning potentials

    International Nuclear Information System (INIS)

    Gonzalez, E.M.; Gonzalez, M.P.; Nunez, N.O.; Villegas, J.E.; Anguita, J.V.; Jaafa, M.; Asenjo, A.; Vicent, J.L.

    2006-01-01

    Nb films have been grown on arrays of asymmetric pinning centers. The lattice vortex dynamics could be modified, almost at will, by periodic pinning potentials. In the case of asymmetric pinning potentials a vortex ratchet effect occurs: the vortex lattice motion is rectified. That is, an injected ac current yields an output dc voltage, which polarity could be tuned. The output signal polarity could be switched with the applied magnetic field and the ac current strength. Ratchet effect occurs when asymmetric potentials induce outward particles flow under external fluctuations in the lack of driven direct outward forces. The output signal is similar using magnetic or non-magnetic submicrometric array of pinning centers. This device works as an adiabatic rocking ratchet. This superconducting ratchet could be a model to study biological motors

  3. Inclined asymmetric librations in exterior resonances

    Science.gov (United States)

    Voyatzis, G.; Tsiganis, K.; Antoniadou, K. I.

    2018-04-01

    Librational motion in Celestial Mechanics is generally associated with the existence of stable resonant configurations and signified by the existence of stable periodic solutions and oscillation of critical (resonant) angles. When such an oscillation takes place around a value different than 0 or π , the libration is called asymmetric. In the context of the planar circular restricted three-body problem, asymmetric librations have been identified for the exterior mean motion resonances (MMRs) 1:2, 1:3, etc., as well as for co-orbital motion (1:1). In exterior MMRs the massless body is the outer one. In this paper, we study asymmetric librations in the three-dimensional space. We employ the computational approach of Markellos (Mon Not R Astron Soc 184:273-281, https://doi.org/10.1093/mnras/184.2.273, 1978) and compute families of asymmetric periodic orbits and their stability. Stable asymmetric periodic orbits are surrounded in phase space by domains of initial conditions which correspond to stable evolution and librating resonant angles. Our computations were focused on the spatial circular restricted three-body model of the Sun-Neptune-TNO system (TNO = trans-Neptunian object). We compare our results with numerical integrations of observed TNOs, which reveal that some of them perform 1:2 resonant, inclined asymmetric librations. For the stable 1:2 TNO librators, we find that their libration seems to be related to the vertically stable planar asymmetric orbits of our model, rather than the three-dimensional ones found in the present study.

  4. Reversal modes in asymmetric Ni nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Leighton, B.; Pereira, A. [Departamento de Fisica, Universidad de Santiago de Chile (USACH), Avda. Ecuador 3493, 917-0124 Santiago (Chile); Escrig, J., E-mail: jescrigm@gmail.com [Departamento de Fisica, Universidad de Santiago de Chile (USACH), Avda. Ecuador 3493, 917-0124 Santiago (Chile); Center for the Development of Nanoscience and Nanotechnology (CEDENNA), Avda. Ecuador 3493, 917-0124 Santiago (Chile)

    2012-11-15

    We have investigated the evolution of the magnetization reversal mechanism in asymmetric Ni nanowires as a function of their geometry. Circular nanowires are found to reverse their magnetization by the propagation of a vortex domain wall, while in very asymmetric nanowires the reversal is driven by the propagation of a transverse domain wall. The effect of shape asymmetry of the wire on coercivity and remanence is also studied. Angular dependence of the remanence and coercivity is also addressed. Tailoring the magnetization reversal mechanism in asymmetric nanowires can be useful for magnetic logic and race-track memory, both of which are based on the displacement of magnetic domain walls. Finally, an alternative method to detect the presence of magnetic drops is proposed. - Highlights: Black-Right-Pointing-Pointer Asymmetry strongly modifies the magnetic behavior of a wire. Black-Right-Pointing-Pointer Very asymmetric nanowires reverse their magnetization by a transverse domain wall. Black-Right-Pointing-Pointer An alternative method to detect the presence of magnetic drops is proposed. Black-Right-Pointing-Pointer Tailoring the reversal mode in asymmetric nanowires can be useful for potential applications.

  5. Using Crossflow for Flow Measurements and Flow Analysis

    Energy Technology Data Exchange (ETDEWEB)

    Gurevich, A.; Chudnovsky, L.; Lopeza, A. [Advanced Measurement and Analysis Group Inc., Ontario (Canada); Park, M. H. [Sungjin Nuclear Engineering Co., Ltd., Gyeongju (Korea, Republic of)

    2016-10-15

    Ultrasonic Cross Correlation Flow Measurements are based on a flow measurement method that is based on measuring the transport time of turbulent structures. The cross correlation flow meter CROSSFLOW is designed and manufactured by Advanced Measurement and Analysis Group Inc. (AMAG), and is used around the world for various flow measurements. Particularly, CROSSFLOW has been used for boiler feedwater flow measurements, including Measurement Uncertainty Recovery (MUR) reactor power uprate in 14 nuclear reactors in the United States and in Europe. More than 100 CROSSFLOW transducers are currently installed in CANDU reactors around the world, including Wolsung NPP in Korea, for flow verification in ShutDown System (SDS) channels. Other CROSSFLOW applications include reactor coolant gross flow measurements, reactor channel flow measurements in all channels in CANDU reactors, boiler blowdown flow measurement, and service water flow measurement. Cross correlation flow measurement is a robust ultrasonic flow measurement tool used in nuclear power plants around the world for various applications. Mathematical modeling of the CROSSFLOW agrees well with laboratory test results and can be used as a tool in determining the effect of flow conditions on CROSSFLOW output and on designing and optimizing laboratory testing, in order to ensure traceability of field flow measurements to laboratory testing within desirable uncertainty.

  6. Renewable resource management under asymmetric information

    DEFF Research Database (Denmark)

    Jensen, Frank; Andersen, Peder; Nielsen, Max

    2013-01-01

    Asymmetric information between fishermen and the regulator is important within fisheries. The regulator may have less information about stock sizes, prices, costs, effort, productivity and catches than fishermen. With asymmetric information, a strong analytical tool is principal-agent analysis....... In this paper, we study asymmetric information about productivity within a principal-agent framework and a tax on fishing effort is considered. It is shown that a second best optimum can be achieved if the effort tax is designed such that low-productivity agents rent is exhausted, while high-productivity agents...... receive an information rent. The information rent is equivalent to the total incentive cost. The incentive costs arise as we want to reveal the agent's type....

  7. Asymmetric synthesis II more methods and applications

    CERN Document Server

    Christmann, Mathias

    2012-01-01

    After the overwhelming success of 'Asymmetric Synthesis - The Essentials', narrating the colorful history of asymmetric synthesis, this is the second edition with latest subjects and authors. While the aim of the first edition was mainly to honor the achievements of the pioneers in asymmetric syntheses, the aim of this new edition was bringing the current developments, especially from younger colleagues, to the attention of students. The format of the book remained unchanged, i.e. short conceptual overviews by young leaders in their field including a short biography of the authors. The growing multidisciplinary research within chemistry is reflected in the selection of topics including metal catalysis, organocatalysis, physical organic chemistry, analytical chemistry, and its applications in total synthesis. The prospective reader of this book is a graduate or undergraduate student of advanced organic chemistry as well as the industrial chemist who wants to get a brief update on the current developments in th...

  8. Electroosmosis modulated biomechanical transport through asymmetric microfluidics channel

    Science.gov (United States)

    Jhorar, R.; Tripathi, D.; Bhatti, M. M.; Ellahi, R.

    2018-05-01

    This article addresses the electrokinetically modulated biomechanical transport through a two-dimensional asymmetric microchannel induced by peristaltic waves. Electrokinetic transport with peristaltic phenomena grabbed a significant attention due to its novel applications in engineering. Electrical fields also provide an excellent mode for regulating flows. The electrohydrodynamics problem is modified by means of Debye-Hückel linearization. Firstly, the governing flow problem is described by continuity and momentum equations in the presence of electrokinetic forces in Cartesian coordinates, then long wavelength and low/zero Reynolds ("neglecting the inertial forces") approximations are applied to modify the governing flow problem. The resulting differential equations are solved analytically in order to obtain exact solutions for velocity profile whereas the numerical integration is carried out to analyze the pumping characteristics. The physical behaviour of sundry parameters is discussed for velocity profile, pressure rise and volume flow rate. In particular, the behaviour of electro-osmotic parameter, phase difference, and Helmholtz-Smoluchowski velocity is examined and discussed. The trapping mechanism is also visualized by drawing streamlines against the governing parameters. The present study offers various interesting results that warrant further study on electrokinetic transport with peristalsis.

  9. Dotted collar placed around carotid artery induces asymmetric neointimal lesion formation in rabbits without intravascular manipulations

    Directory of Open Access Journals (Sweden)

    Kivelä Antti

    2012-10-01

    Full Text Available Abstract Background Neointimal formation in atherosclerosis has been subject for intense research. However, good animal models mimicking asymmetrical lesion formation in human subjects have been difficult to establish. The aim of this study was to develop a model which would lead to the formation of eccentric lesions under macroscopically intact non-denuded endothelium. Methods We have developed a new collar model where we placed two cushions or dots inside the collar. Arterial lesions were characterized using histology and ultrasound methods. Results When this dotted collar was placed around carotid and femoral arteries it produced asymmetrical pressure on adventitia and a mild flow disturbance, and hence a change in shear stress. Our hypothesis was that this simple procedure would reproducibly produce asymmetrical lesions without any intraluminal manipulations. Intima/media ratio increased towards the distal end of the collar with the direction of blood flow under macroscopically intact endothelium. Macrophages preferentially accumulated in areas of the thickest neointima thus resembling early steps in human atherosclerotic plaque formation. Proliferating cells in these lesions and underlying media were scarce at eight weeks time point. Conclusion The improved dotted collar model produces asymmetrical human-like atherosclerotic lesions in rabbits. This model should be useful in studies regarding the pathogenesis and formation of eccentric atherosclerotic lesions.

  10. Asymmetric acoustic transmission in multiple frequency bands

    Energy Technology Data Exchange (ETDEWEB)

    Sun, Hong-xiang, E-mail: jsdxshx@ujs.edu.cn [Research Center of Fluid Machinery Engineering and Technology, Jiangsu University, Zhenjiang 212013 (China); Laboratory of Modern Acoustics, Institute of Acoustics, Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093 (China); State Key Laboratory of Acoustics, Institute of Acoustics, Chinese Academy of Sciences, Beijing 100190 (China); Yuan, Shou-qi, E-mail: Shouqiy@ujs.edu.cn [Research Center of Fluid Machinery Engineering and Technology, Jiangsu University, Zhenjiang 212013 (China); Zhang, Shu-yi [Laboratory of Modern Acoustics, Institute of Acoustics, Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093 (China)

    2015-11-23

    We report both experimentally and numerically that the multi-band device of the asymmetric acoustic transmission is realized by placing two periodic gratings with different periods on both sides of two brass plates immersed in water. The asymmetric acoustic transmission can exist in four frequency bands below 1500 kHz, which arises from the interaction between various diffractions from the two gratings and Lamb modes in the brass plates immersed in water. The results indicate that the device has the advantages of multiple band, broader bandwidth, and simpler structure. Our finding should have great potential applications in ultrasonic devices.

  11. Asymmetric acoustic transmission in multiple frequency bands

    International Nuclear Information System (INIS)

    Sun, Hong-xiang; Yuan, Shou-qi; Zhang, Shu-yi

    2015-01-01

    We report both experimentally and numerically that the multi-band device of the asymmetric acoustic transmission is realized by placing two periodic gratings with different periods on both sides of two brass plates immersed in water. The asymmetric acoustic transmission can exist in four frequency bands below 1500 kHz, which arises from the interaction between various diffractions from the two gratings and Lamb modes in the brass plates immersed in water. The results indicate that the device has the advantages of multiple band, broader bandwidth, and simpler structure. Our finding should have great potential applications in ultrasonic devices

  12. Magnetic field and rotation effects on peristaltic transport of a Jeffrey fluid in an asymmetric channel

    International Nuclear Information System (INIS)

    Abd-Alla, A.M.; Abo-Dahab, S.M.

    2015-01-01

    In this paper, the peristaltic flow of a Jeffrey fluid in an asymmetric rotating channel is studied. Mathematical modeling is carried out by utilizing long wavelength and low Reynolds number assumptions. Closed form expressions for the pressure gradient, pressure rise, streamlines, axial velocity and shear stress on the channel walls have been computed numerically. Effects of Hartmann number, the ratio of relaxation to retardation times, time-mean flow, rotation and the phase angle on the pressure gradient, pressure rise, streamline, axial velocity and shear stress are discussed in detail and shown graphically. The results indicate that the effect of the Hartmann number, the ratio of relaxation to retardation times, time-mean flow, rotation and the phase angle are very pronounced in the phenomena. Comparison was made with the results obtained in the asymmetric channel and symmetric channel. - Highlights: • The peristaltic flow of a Jeffrey fluid in an asymmetric rotating channel with magnetic field. • Mathematical modeling for long wavelength and low Reynolds number assumptions. • Closed form expressions for the pressure gradient, pressure rise, stream function, axial velocity and shear stress

  13. Micellar aggregates of amylose-block-polystyrene rod-coil block copolymers in water and THF

    NARCIS (Netherlands)

    Loos, Katja; Böker, Alexander; Zettl, Heiko; Zhang, Mingfu; Krausch, Georg; Müller, Axel H.E.; Boker, A.; Zhang, A.F.

    2005-01-01

    Amylose-block-polystyrenes with various block copolymer compositions were investigated in water and in THF solution. Fluorescence correlation spectroscopy, dynamic light, scattering (DLS), and asymmetric flow field-flow fractionation with multiangle light scattering detection indicate the presence

  14. Optical diagnostics of intermittent flows

    DEFF Research Database (Denmark)

    Okulov, V.L.; Naumov, I.V.; Sørensen, Jens Nørkær

    2007-01-01

    The efficiency of combined use of different optical techniques for flow diagnostics is demonstrated with the practically important case of intense swirling flows. It is shown that, when applied separately, commonly used optical measuring techniques, such as laser Doppler anemometry and particle...... is for the first time applied for diagnostics of the flow pattern in a closed cylinder with a rotating end face with the aim of studying the changeover from the steady axisymmetric to unsteady asymmetric flow over a wide range of flow parameters. It is found that such a transition is notable for azimuthal...

  15. Comparison of Size Characterization of Barley Starch Granules Determined by Electron and Optical Microscopy, Low Angle Laser Light Scattering and Gravitational Field-Flow Fractionation

    Czech Academy of Sciences Publication Activity Database

    Chmelík, Josef; Krumlová, Andrea; Budinská, Marcela; Kruml, Tomáš; Psota, V.; Bohačenko, I.; Mazal, P.; Vydrová, H.

    2001-01-01

    Roč. 107, č. 1 (2001), s. 11-17 ISSN 0046-9750 R&D Projects: GA AV ČR IAA4031805 Grant - others:Copernicus(BE) ERB IC-15-CT98-0909 Institutional research plan: CEZ:AV0Z4031919 Keywords : Barley * starch granules * size determination Subject RIV: CB - Analytical Chemistry, Separation Impact factor: 0.862, year: 2001

  16. Size characterization of barley starch granules by gravitational field-flow fractionation: A rapid, low-cost method to assess the brewing capability of different strains

    Czech Academy of Sciences Publication Activity Database

    Reschiglian, P.; Zattoni, A.; Casolari, S.; Krumlová, Andrea; Budinská, Marcela; Chmelík, Josef

    2002-01-01

    Roč. 92, č. 4 (2002), s. 457-467 ISSN 0003-4592 Grant - others:COPERNICUS(XE) ERB IC-15-CT98-0909 Institutional research plan: CEZ:AV0Z4031919 Keywords : GFFF * starch granules * size distribution Subject RIV: CB - Analytical Chemistry, Separation Impact factor: 0.494, year: 2002

  17. Quantitative Characterization of Gold Nanoparticles by Field-Flow Fractionation Coupled Online with Light Scattering Detection and Inductively Coupled Plasma Mass Spectrometry

    DEFF Research Database (Denmark)

    Schmidt, Bjørn; Löschner, Katrin; Hadrup, Niels

    2011-01-01

    concentration of nanoparticles (NPs) in aqueous suspension. Mixtures of three polystyrene (PS) NPs between 20 and 100 nm in diameter and mixtures of three gold (Au) NPs between 10 and 60 nm in diameter were separated by AF4. The geometric diameters of the separated PS NPs and the hydrodynamic diameters...... nm, or a mixture of 10 and 60 nm nanoparticles by intravenous injection. The homogenized livers were solubilized in tetramethylammonium hydroxide (TMAH), and the recovery of Au NPs from the livers amounted to 86−123% of their total Au content. In spite of successful stabilization with bovine serum...

  18. Standards vs. labels with imperfect competition and asymmetric information

    DEFF Research Database (Denmark)

    Baltzer, Kenneth Thomas

    2012-01-01

    I demonstrate that providing information about product quality is not necessarily the best way to address asymmetric information problems when markets are imperfectly competitive. In a vertical differentiation model I show that a Minimum Quality Standard, which retains asymmetric information...

  19. Standards vs. labels with imperfect competition and asymmetric information

    DEFF Research Database (Denmark)

    Baltzer, Kenneth Thomas

    I demonstrate that providing information about product quality is not necessarily the best way to address asymmetric information problems when markets are imperfectly competitive. In a vertical dierentiation model I show that a Minimum Quality Standard, which retains asymmetric information...

  20. Asymmetric hindwing foldings in rove beetles.

    Science.gov (United States)

    Saito, Kazuya; Yamamoto, Shuhei; Maruyama, Munetoshi; Okabe, Yoji

    2014-11-18

    Foldable wings of insects are the ultimate deployable structures and have attracted the interest of aerospace engineering scientists as well as entomologists. Rove beetles are known to fold their wings in the most sophisticated ways that have right-left asymmetric patterns. However, the specific folding process and the reason for this asymmetry remain unclear. This study reveals how these asymmetric patterns emerge as a result of the folding process of rove beetles. A high-speed camera was used to reveal the details of the wing-folding movement. The results show that these characteristic asymmetrical patterns emerge as a result of simultaneous folding of overlapped wings. The revealed folding mechanisms can achieve not only highly compact wing storage but also immediate deployment. In addition, the right and left crease patterns are interchangeable, and thus each wing internalizes two crease patterns and can be folded in two different ways. This two-way folding gives freedom of choice for the folding direction to a rove beetle. The use of asymmetric patterns and the capability of two-way folding are unique features not found in artificial structures. These features have great potential to extend the design possibilities for all deployable structures, from space structures to articles of daily use.

  1. Mixed gas plasticization phenomena in asymmetric membranes

    NARCIS (Netherlands)

    Visser, Tymen

    2006-01-01

    This thesis describes the thorough investigation of mixed gas transport behavior of asymmetric membranes in the separation of feed streams containing plasticizing gases in order to gain more insights into the complicated behavior of plasticization. To successfully employ gas separation membranes in

  2. Asymmetric conditional volatility in international stock markets

    Science.gov (United States)

    Ferreira, Nuno B.; Menezes, Rui; Mendes, Diana A.

    2007-08-01

    Recent studies show that a negative shock in stock prices will generate more volatility than a positive shock of similar magnitude. The aim of this paper is to appraise the hypothesis under which the conditional mean and the conditional variance of stock returns are asymmetric functions of past information. We compare the results for the Portuguese Stock Market Index PSI 20 with six other Stock Market Indices, namely the SP 500, FTSE 100, DAX 30, CAC 40, ASE 20, and IBEX 35. In order to assess asymmetric volatility we use autoregressive conditional heteroskedasticity specifications known as TARCH and EGARCH. We also test for asymmetry after controlling for the effect of macroeconomic factors on stock market returns using TAR and M-TAR specifications within a VAR framework. Our results show that the conditional variance is an asymmetric function of past innovations raising proportionately more during market declines, a phenomenon known as the leverage effect. However, when we control for the effect of changes in macroeconomic variables, we find no significant evidence of asymmetric behaviour of the stock market returns. There are some signs that the Portuguese Stock Market tends to show somewhat less market efficiency than other markets since the effect of the shocks appear to take a longer time to dissipate.

  3. MHD stability of vertically asymmetric tokamak equilibria

    International Nuclear Information System (INIS)

    Dalhed, H.E.; Grimm, R.C.; Johnson, J.L.

    1981-03-01

    The ideal MHD stability properties of a special class of vertically asymmetric tokamak equilibria are examined. The calculations confirm that no major new physical effects are introduced and the modifications can be understood by conventional arguments. The results indicate that significant departures from up-down symmetry can be tolerated before the reduction in β becomes important for reactor operation

  4. Catalytic asymmetric synthesis of the alkaloid (+)-myrtine

    NARCIS (Netherlands)

    Pizzuti, Maria Gabriefla; Minnaard, Adriaan J.; Feringa, Ben L.

    2008-01-01

    A new protocol for the asymmetric synthesis of trans-2,6-disubstituted-4-piperidones has been developed using a catalytic enantioselective conjugate addition reaction in combination with a diastereoselective lithiation-substitution sequence; an efficient synthesis of (+)-myrtine has been achieved

  5. Asymmetric Aminalization via Cation-Binding Catalysis

    DEFF Research Database (Denmark)

    Park, Sang Yeon; Liu, Yidong; Oh, Joong Suk

    2018-01-01

    Asymmetric cation-binding catalysis, in principle, can generate "chiral" anionic nucleophiles, where the counter cations are coordinated within chiral environments. Nitrogen-nucleophiles are intrinsically basic, therefore, its use as nucleophiles is often challenging and limiting the scope of the...

  6. Volume inequalities for asymmetric Wulff shapes

    OpenAIRE

    Schuster, Franz E.; Weberndorfer, Manuel

    2012-01-01

    Sharp reverse affine isoperimetric inequalities for asymmetric Wulff shapes and their polars are established, along with the characterization of all extremals. These new inequalities have as special cases previously obtained simplex inequalities by Ball, Barthe and Lutwak, Yang, and Zhang. In particular, they provide the solution to a problem by Zhang.

  7. Quantum optics of lossy asymmetric beam splitters

    NARCIS (Netherlands)

    Uppu, Ravitej; Wolterink, Tom; Tentrup, Tristan Bernhard Horst; Pinkse, Pepijn Willemszoon Harry

    2016-01-01

    We theoretically investigate quantum interference of two single photons at a lossy asymmetric beam splitter, the most general passive 2×2 optical circuit. The losses in the circuit result in a non-unitary scattering matrix with a non-trivial set of constraints on the elements of the scattering

  8. Motion in an Asymmetric Double Well

    OpenAIRE

    Brizard, Alain J.; Westland, Melissa C.

    2016-01-01

    The problem of the motion of a particle in an asymmetric double well is solved explicitly in terms of the Weierstrass and Jacobi elliptic functions. While the solution of the orbital motion is expressed simply in terms of the Weierstrass elliptic function, the period of oscillation is more directly expressed in terms of periods of the Jacobi elliptic functions.

  9. Asymmetric output profile of Xe Laser

    NARCIS (Netherlands)

    Blok, F.J.; Rubin, P.L.; Verschuur, Jeroen W.J.; Witteman, W.J.

    2001-01-01

    A new set of asymmetric modes was recently revealed in a Xe slab laser with pronounced lens effects originating from gas heating in the discharge. The appearance of these modes is a threshold effect. Their domain of existence in the Xe laser is discussed. It is shown that mode competition can result

  10. Computing modal dispersion characteristics of radially Asymmetric ...

    African Journals Online (AJOL)

    We developed a matrix theory that applies to with non-circular/circular but concentric layers fibers. And we compute the dispersion characteristics of radially unconventional fiber, known as Asymmetric Bragg fiber. An attempt has been made to determine how the modal characteristics change as circular Bragg fiber is ...

  11. Seasonally asymmetric enhancement of northern vegetation productivity

    Science.gov (United States)

    Park, T.; Myneni, R.

    2017-12-01

    Multiple evidences of widespread greening and increasing terrestrial carbon uptake have been documented. In particular, enhanced gross productivity of northern vegetation has been a critical role leading to observed carbon uptake trend. However, seasonal photosynthetic activity and its contribution to observed annual carbon uptake trend and interannual variability are not well understood. Here, we introduce a multiple-source of datasets including ground, atmospheric and satellite observations, and multiple process-based global vegetation models to understand how seasonal variation of land surface vegetation controls a large-scale carbon exchange. Our analysis clearly shows a seasonally asymmetric enhancement of northern vegetation productivity in growing season during last decades. Particularly, increasing gross productivity in late spring and early summer is obvious and dominant driver explaining observed trend and variability. We observe more asymmetric productivity enhancement in warmer region and this spatially varying asymmetricity in northern vegetation are likely explained by canopy development rate, thermal and light availability. These results imply that continued warming may facilitate amplifying asymmetric vegetation activity and cause these trends to become more pervasive, in turn warming induced regime shift in northern land.

  12. Asymmetric gravitational spreading - Analogue experiments on the Svecofennian orogen

    Science.gov (United States)

    Nikkilä, Kaisa; Korja, Annakaisa; Koyi, Hemin; Eklund, Olav

    2015-04-01

    Over-thickened orogenic crust may suffer from rheological, gravitational and topographical unbalancing resulting in discharging via gravitational spreading. If the thickened orogen is also hot, then increased temperature may reduce the viscosity of the crust that may induce large-scale horizontal flow. The effect of flow on the crustal architecture has previously been modeled with symmetric two-way spreading or asymmetric one- or two-way spreading (like channel flow) experiments. Most models do not take into account of the contrasting mechanical properties of the juxtaposed terranes. We have made analogue experiments to study gravitational one-way spreading and the interplay between two crustal blocks with contrasting rheological properties. The models are 3 cm thick replicas of 60 km thick crust. They have three horizontal layers representing strong lower, weak middle and brittle upper crust. The models have cuts to study the effect of inherited crustal-scale weakness zones. The experiments have been conducted within a large centrifuge in the Hans Ramberg Tectonic Laboratory at Uppsala University. The analogue models propose that asymmetric, unilateral flow has different effect on the contrasting crustal units, in both horizontal and vertical directions. The laterally heterogeneous crust flows towards the direction of extension, and it rotates and extends the pre-existing weakness zones. The weakness zones facilitate exhumation and they increase strain rate. The weakness zones split the crust into subblocks, which stretch individually and which may show signatures of compression or rotation. The changes in thickness of the model reflect changes in the layers, which may thin or thicken depending on the mechanical properties of crustal layers. A consequence of this the total amount of flattening is less than the model extension. The results are compared to geophysical and geological data from Precambrian Svecofennian orogen in Fennoscandia. The comparison suggest

  13. Charge Asymmetric Cosmic Rays as a probe of Flavor Violating Asymmetric Dark Matter

    DEFF Research Database (Denmark)

    Masina, Isabella; Sannino, Francesco

    2011-01-01

    The recently introduced cosmic sum rules combine the data from PAMELA and Fermi-LAT cosmic ray experiments in a way that permits to neatly investigate whether the experimentally observed lepton excesses violate charge symmetry. One can in a simple way determine universal properties of the unknown...... component of the cosmic rays. Here we attribute a potential charge asymmetry to the dark sector. In particular we provide models of asymmetric dark matter able to produce charge asymmetric cosmic rays. We consider spin zero, spin one and spin one-half decaying dark matter candidates. We show that lepton...... flavor violation and asymmetric dark matter are both required to have a charge asymmetry in the cosmic ray lepton excesses. Therefore, an experimental evidence of charge asymmetry in the cosmic ray lepton excesses implies that dark matter is asymmetric....

  14. Asymmetric three-dimensional topography over mantle plumes.

    Science.gov (United States)

    Burov, Evgueni; Gerya, Taras

    2014-09-04

    The role of mantle-lithosphere interactions in shaping surface topography has long been debated. In general, it is supposed that mantle plumes and vertical mantle flows result in axisymmetric, long-wavelength topography, which strongly differs from the generally asymmetric short-wavelength topography created by intraplate tectonic forces. However, identification of mantle-induced topography is difficult, especially in the continents. It can be argued therefore that complex brittle-ductile rheology and stratification of the continental lithosphere result in short-wavelength modulation and localization of deformation induced by mantle flow. This deformation should also be affected by far-field stresses and, hence, interplay with the 'tectonic' topography (for example, in the 'active/passive' rifting scenario). Testing these ideas requires fully coupled three-dimensional numerical modelling of mantle-lithosphere interactions, which so far has not been possible owing to the conceptual and technical limitations of earlier approaches. Here we present new, ultra-high-resolution, three-dimensional numerical experiments on topography over mantle plumes, incorporating a weakly pre-stressed (ultra-slow spreading), rheologically realistic lithosphere. The results show complex surface evolution, which is very different from the smooth, radially symmetric patterns usually assumed as the canonical surface signature of mantle upwellings. In particular, the topography exhibits strongly asymmetric, small-scale, three-dimensional features, which include narrow and wide rifts, flexural flank uplifts and fault structures. This suggests a dominant role for continental rheological structure and intra-plate stresses in controlling dynamic topography, mantle-lithosphere interactions, and continental break-up processes above mantle plumes.

  15. The influence of variability on the optimal shape of an airway tree branching asymmetrically

    International Nuclear Information System (INIS)

    Mauroy, Benjamin; Bokov, Plamen

    2010-01-01

    The asymmetry of the bronchial tree has been reported on numerous occasions, and bronchi in the lung bifurcate most of the time into a major and a minor daughter. Asymmetry is most probably bound to play a role on the hydrodynamic resistance and volume occupation of the bronchial tree. Thus, in this work, we search for an optimal asymmetric airway tree crossed by Poiseuille flow that would be a good candidate to model the distal conductive part of the lung. The geometry is controlled by major and minor diameter reduction factors that depend on the generation. We show that the optimal asymmetric tree has diameter reduction factors that are adimensional from the second level of bifurcation and that they are highly dependent on the asymmetric ratio that defines the relative sizes of the major and minor branches in a bifurcation. This optimization also gives access to a cost function whose particularity is to be asymmetric around its minimum. Thus, the cliff-edge hypothesis predicts that if the system suffers variability, then the best tree is shifted from the optimal. We apply a recent theoretical model of cliff-edge in order to measure the role of variability on the determination of the best asymmetric tree. Then, we compare our results with lung data of the literature. In particular, we are able to quantify the variability needed to fit the data and to give hypothesis that could explain, at least partially, the shift found between the optimal tree and the measures in the case of asymmetric bronchial trees. Finally, our model predicts that, even if the population is adapted at best, there always exist individuals whose bronchial trees are associated with larger costs comparatively to the average and who ought to be more sensitive to geometrical remodeling

  16. Natural convection in asymmetric triangular enclosures heated from below

    Science.gov (United States)

    Kamiyo, O. M.; Angeli, D.; Barozzi, G. S.; Collins, M. W.

    2014-11-01

    Triangular enclosures are typical configurations of attic spaces found in residential as well as industrial pitched-roof buildings. Natural convection in triangular rooftops has received considerable attention over the years, mainly on right-angled and isosceles enclosures. In this paper, a finite volume CFD package is employed to study the laminar air flow and temperature distribution in asymmetric rooftop-shaped triangular enclosures when heated isothermally from the base wall, for aspect ratios (AR) 0.2 <= AR <= 1.0, and Rayleigh number (Ra) values 8 × 105 <= Ra <= 5 × 107. The effects of Rayleigh number and pitch angle on the flow structure and temperature distributions within the enclosure are analysed. Results indicate that, at low pitch angle, the heat transfer between the cold inclined and the hot base walls is very high, resulting in a multi-cellular flow structure. As the pitch angle increases, however, the number of cells reduces, and the total heat transfer rate progressively reduces, even if the Rayleigh number, being based on the enclosure height, rapidly increases. Physical reasons for the above effect are inspected.

  17. Natural convection in asymmetric triangular enclosures heated from below

    International Nuclear Information System (INIS)

    Kamiyo, O M; Angeli, D; Enzo Ferrari, Universita di Modena e Reggio Emilia, via Vignolese 905, I-41125 Modena (Italy))" data-affiliation=" (DIEF – Dipartimento di Ingegneria Enzo Ferrari, Universita di Modena e Reggio Emilia, via Vignolese 905, I-41125 Modena (Italy))" >Barozzi, G S; Collins, M W

    2014-01-01

    Triangular enclosures are typical configurations of attic spaces found in residential as well as industrial pitched-roof buildings. Natural convection in triangular rooftops has received considerable attention over the years, mainly on right-angled and isosceles enclosures. In this paper, a finite volume CFD package is employed to study the laminar air flow and temperature distribution in asymmetric rooftop-shaped triangular enclosures when heated isothermally from the base wall, for aspect ratios (AR) 0.2 ≤ AR ≤ 1.0, and Rayleigh number (Ra) values 8 × 10 5 ≤ Ra ≤ 5 × 10 7 . The effects of Rayleigh number and pitch angle on the flow structure and temperature distributions within the enclosure are analysed. Results indicate that, at low pitch angle, the heat transfer between the cold inclined and the hot base walls is very high, resulting in a multi-cellular flow structure. As the pitch angle increases, however, the number of cells reduces, and the total heat transfer rate progressively reduces, even if the Rayleigh number, being based on the enclosure height, rapidly increases. Physical reasons for the above effect are inspected

  18. Propulsion of a Molecular Machine by Asymmetric Distribution of Reaction Products

    Science.gov (United States)

    Golestanian, Ramin; Liverpool, Tanniemola B.; Ajdari, Armand

    2005-06-01

    A simple model for the reaction-driven propulsion of a small device is proposed as a model for (part of) a molecular machine in aqueous media. The motion of the device is driven by an asymmetric distribution of reaction products. The propulsive velocity of the device is calculated as well as the scale of the velocity fluctuations. The effects of hydrodynamic flow as well as a number of different scenarios for the kinetics of the reaction are addressed.

  19. A nanojet: propulsion of a molecular machine by an asymmetric distribution of reaction--products

    Science.gov (United States)

    Liverpool, Tanniemola; Golestanian, Ramin; Ajdari, Armand

    2006-03-01

    A simple model for the reaction-driven propulsion of a small device is proposed as a model for (part of) a molecular machine in aqueous media. Motion of the device is driven by an asymmetric distribution of reaction products. We calculate the propulsive velocity of the device as well as the scale of the velocity fluctuations. We also consider the effects of hydrodynamic flow as well as a number of different scenarios for the kinetics of the reaction.

  20. Porous asymmetric SiO2-g-PMMA nanoparticles produced by phase inversion

    KAUST Repository

    Munirasu, Selvaraj

    2014-07-22

    A new kind of asymmetric organic-inorganic porous structure has been proposed. Asymmetric lattices of polymer grafted silica nanoparticles were manufactured by casting and phase inversion in water. Silica nanoparticles were first functionalized with 3-(dimethylethoxysilyl)propyl-2-bromoisobutyrate, followed by grafting of poly(methylmethacrylate) (PMMA) segments, performed by atom-transfer radical polymerization. Mechanically stable self-standing films were prepared by casting a dispersion of functionalized nanoparticles in different solvents and immersion in water. The resulting asymmetrically porous morphology and nanoparticle assembly was characterized by scanning electron and atomic force microscopy. The PMMA functionalized SiO2 hybrid material in acetone or acetone/dioxane led to the best-assembled structures. Porous asymmetric membranes were prepared by adding free PMMA and PMMA terminated with hydrophilic hydroxyl group. Nitrogen flow of 2800 L m-2 h -1 was measured at 1.3 bar demonstrating the porosity and potential application for membrane technology. © 2014 Springer Science+Business Media New York.

  1. Direct catalytic asymmetric aldol-Tishchenko reaction.

    Science.gov (United States)

    Gnanadesikan, Vijay; Horiuchi, Yoshihiro; Ohshima, Takashi; Shibasaki, Masakatsu

    2004-06-30

    A direct catalytic asymmetric aldol reaction of propionate equivalent was achieved via the aldol-Tishchenko reaction. Coupling an irreversible Tishchenko reaction to a reversible aldol reaction overcame the retro-aldol reaction problem and thereby afforded the products in high enantio and diastereoselectivity using 10 mol % of the asymmetric catalyst. A variety of ketones and aldehydes, including propyl and butyl ketones, were coupled efficiently, yielding the corresponding aldol-Tishchenko products in up to 96% yield and 95% ee. Diastereoselectivity was generally below the detection limit of 1H NMR (>98:2). Preliminary studies performed to clarify the mechanism revealed that the aldol products were racemic with no diastereoselectivity. On the other hand, the Tishchenko products were obtained in a highly enantiocontrolled manner.

  2. Brownian Motion of Asymmetric Boomerang Colloidal Particles

    Science.gov (United States)

    Chakrabarty, Ayan; Konya, Andrew; Wang, Feng; Selinger, Jonathan; Sun, Kai; Wei, Qi-Huo

    2014-03-01

    We used video microscopy and single particle tracking to study the diffusion and local behaviors of asymmetric boomerang particles in a quasi-two dimensional geometry. The motion is biased towards the center of hydrodynamic stress (CoH) and the mean square displacements of the particles are linear at short and long times with different diffusion coefficients and in the crossover regime it is sub-diffusive. Our model based on Langevin theory shows that these behaviors arise from the non-coincidence of the CoH with the center of the body. Since asymmetric boomerangs represent a class of rigid bodies of more generals shape, therefore our findings are generic and true for any non-skewed particle in two dimensions. Both experimental and theoretical results will be discussed.

  3. Dynamics of asymmetric kinetic Ising systems revisited

    International Nuclear Information System (INIS)

    Huang, Haiping; Kabashima, Yoshiyuki

    2014-01-01

    The dynamics of an asymmetric kinetic Ising model is studied. Two schemes for improving the existing mean-field description are proposed. In the first scheme, we derive the formulas for instantaneous magnetization, equal-time correlation, and time-delayed correlation, considering the correlation between different local fields. To derive the time-delayed correlation, we emphasize that the small-correlation assumption adopted in previous work (Mézard and Sakellariou, 2011 J. Stat. Mech. L07001) is in fact not required. To confirm the prediction efficiency of our method, we perform extensive simulations on single instances with either temporally constant external driving fields or sinusoidal external fields. In the second scheme, we develop an improved mean-field theory for instantaneous magnetization prediction utilizing the notion of the cavity system in conjunction with a perturbative expansion approach. Its efficiency is numerically confirmed by comparison with the existing mean-field theory when partially asymmetric couplings are present. (paper)

  4. Bianisotropic metamaterials based on twisted asymmetric crosses

    International Nuclear Information System (INIS)

    Reyes-Avendaño, J A; Sampedro, M P; Juárez-Ruiz, E; Pérez-Rodríguez, F

    2014-01-01

    The effective bianisotropic response of 3D periodic metal-dielectric structures, composed of crosses with asymmetrically-cut wires, is investigated within a general homogenization theory using the Fourier formalism and the form-factor division approach. It is found that the frequency dependence of the effective permittivity for a system of periodically-repeated layers of metal crosses exhibits two strong resonances, whose separation is due to the cross asymmetry. Besides, bianisotropic metamaterials, having a base of four twisted asymmetric crosses, are proposed. The designed metamaterials possess negative refractive index at frequencies determined by the cross asymmetry, the gap between the arms of adjacent crosses lying on the same plane, and the type of Bravais lattice. (papers)

  5. Improved DFIG Capability during Asymmetrical Grid Faults

    DEFF Research Database (Denmark)

    Zhou, Dao; Blaabjerg, Frede

    2015-01-01

    In the wind power application, different asymmetrical types of the grid fault can be categorized after the Y/d transformer, and the positive and negative components of a single-phase fault, phase-to-phase fault, and two-phase fault can be summarized. Due to the newly introduced negative and even...... the natural component of the Doubly-Fed Induction Generator (DFIG) stator flux during the fault period, their effects on the rotor voltage can be investigated. It is concluded that the phase-to-phase fault has the worst scenario due to its highest introduction of the negative stator flux. Afterwards......, the capability of a 2 MW DFIG to ride through asymmetrical grid faults can be estimated at the existing design of the power electronics converter. Finally, a control scheme aimed to improve the DFIG capability is proposed and the simulation results validate its feasibility....

  6. Asymmetric volatility connectedness on the forex market

    Czech Academy of Sciences Publication Activity Database

    Baruník, Jozef; Kočenda, Evžen; Vácha, Lukáš

    2017-01-01

    Roč. 77, č. 1 (2017), s. 39-56 ISSN 0261-5606 R&D Projects: GA ČR(CZ) GA16-14179S Institutional support: RVO:67985556 Keywords : volatility * connectedness * asymmetric effects Subject RIV: AH - Economics OBOR OECD: Finance Impact factor: 1.853, year: 2016 http://library.utia.cas.cz/separaty/2017/E/barunik-0478477.pdf

  7. Magnetic properties of strongly asymmetric nuclear matter

    International Nuclear Information System (INIS)

    Kutschera, M.; Wojcik, W.

    1988-01-01

    We investigate stability of neutron matter containing a small proton admixture with respect to spin fluctuations. We establish conditions under which strongly asymmetric nuclear matter could acquire a permanent magnetization. It is shown that if the protons are localized, the system becomes unstable to spin fluctuations for arbitrarily weak proton-neutron spin interactions. For non-localized protons there exists a threshold value of the spin interaction above which the system can develop a spontaneous polarization. 12 refs., 2 figs. (author)

  8. Isospin dependent properties of asymmetric nuclear matter

    OpenAIRE

    Chowdhury, P. Roy; Basu, D. N.; Samanta, C.

    2009-01-01

    The density dependence of nuclear symmetry energy is determined from a systematic study of the isospin dependent bulk properties of asymmetric nuclear matter using the isoscalar and the isovector components of density dependent M3Y interaction. The incompressibility $K_\\infty$ for the symmetric nuclear matter, the isospin dependent part $K_{asy}$ of the isobaric incompressibility and the slope $L$ are all in excellent agreement with the constraints recently extracted from measured isotopic de...

  9. Two particle states in an asymmetric box

    OpenAIRE

    Li, Xin; Liu, Chuan

    2004-01-01

    The exact two-particle energy eigenstates in an asymmetric rectangular box with periodic boundary conditions in all three directions are studied. Their relation with the elastic scattering phases of the two particles in the continuum are obtained. These results can be viewed as a generalization of the corresponding formulae in a cubic box obtained by L\\"uscher before. In particular, the s-wave scattering length is related to the energy shift in the finite box. Possible applications of these f...

  10. Symmetric vs. asymmetric punishment regimes for bribery

    OpenAIRE

    Engel, Christoph; Goerg, Sebastian J.; Yu, Gaoneng

    2012-01-01

    In major legal orders such as UK, the U.S., Germany, and France, bribers and recipients face equally severe criminal sanctions. In contrast, countries like China, Russia, and Japan treat the briber more mildly. Given these differences between symmetric and asymmetric punishment regimes for bribery, one may wonder which punishment strategy is more effective in curbing corruption. For this purpose, we designed and ran a lab experiment in Bonn (Germany) and Shanghai (China) with exactly the same...

  11. Asymmetric threat data mining and knowledge discovery

    Science.gov (United States)

    Gilmore, John F.; Pagels, Michael A.; Palk, Justin

    2001-03-01

    Asymmetric threats differ from the conventional force-on- force military encounters that the Defense Department has historically been trained to engage. Terrorism by its nature is now an operational activity that is neither easily detected or countered as its very existence depends on small covert attacks exploiting the element of surprise. But terrorism does have defined forms, motivations, tactics and organizational structure. Exploiting a terrorism taxonomy provides the opportunity to discover and assess knowledge of terrorist operations. This paper describes the Asymmetric Threat Terrorist Assessment, Countering, and Knowledge (ATTACK) system. ATTACK has been developed to (a) data mine open source intelligence (OSINT) information from web-based newspaper sources, video news web casts, and actual terrorist web sites, (b) evaluate this information against a terrorism taxonomy, (c) exploit country/region specific social, economic, political, and religious knowledge, and (d) discover and predict potential terrorist activities and association links. Details of the asymmetric threat structure and the ATTACK system architecture are presented with results of an actual terrorist data mining and knowledge discovery test case shown.

  12. Diagnostic implications of asymmetrical mammographic patterns

    International Nuclear Information System (INIS)

    Asenjo, M.; Ania, B.J.

    1997-01-01

    To analyze the effect of asymmetrical mammographic patterns of the diagnosis of breast cancer. In a series of 6, 476 patients referred to a Breast Imaging Diagnosis Unit, we excluded males, women with previous breast surgery, and cases in which mammography was not performed, which left 5,203 women included. Each breast was classified according to one of four patterns of mammographic parenchymal density. Asymmetry was considered to exist when a patient's breasts had different patterns. Breast cancer was confirmed histologically in 282 (5.4%) women. The mammographic pattern was asymmetrical in 8% of the women with cancer and in 2% of the women without cancer (p<0.001). Fine-needle aspiration biopsy was performed in 78% and 96% (p=0.04), respectively, of the women with and without mammographic asymmetry who had neoplasms, and in 33% and 22% (p=0.02), respectively, of the women with and without mammographic asymmetry who did not have neoplasms. Asymmetrical mammographic pattern was four times more frequent in the women with breast cancer. This asymmetry decreased the frequency of needle biopsy in women with cancer, but increased the frequency of needle biopsy in women without cancer. (Author) 11 refs

  13. Hadron scattering in an asymmetric box

    International Nuclear Information System (INIS)

    Li Xin; Chen Ying; Meng Guozhan; Feng Xu; Gong Ming; He Song; Li Gang; Liu Chuan; Liu Yubin; Ma Jianping; Meng Xiangfei; Shen Yan; Zhang Jianbo

    2007-01-01

    We propose to study hadron-hadron scattering using lattice QCD in an asymmetric box which allows one to access more non-degenerate low-momentum modes for a given volume. The conventional Luescher's formula applicable in a symmetric box is modified accordingly. To illustrate the feasibility of this approach, pion-pion elastic scattering phase shifts in the I = 2, J = 0 channel are calculated within quenched approximation using improved gauge and Wilson fermion actions on anisotropic lattices in an asymmetric box. After the chiral and continuum extrapolation, we find that our quenched results for the scattering phase shifts in this channel are consistent with the experimental data when the three-momentum of the pion is below 300MeV. Agreement is also found when compared with previous theoretical results from lattice and other means. Moreover, with the usage of asymmetric volume, we are able to compute the scattering phases in the low-momentum range (pion three momentum less than about 350MeV in the center of mass frame) for over a dozen values of the pion three-momenta, much more than using the conventional symmetric box with comparable volume

  14. Simulation of Phenix EOL Asymmetric Test

    Energy Technology Data Exchange (ETDEWEB)

    Ha, Kwi Seok; Lee, Kwi Lim; Choi, Chi Woong; Kang, Seok Hun; Chang, Won Pyo; Jeong, Hae Yong [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2012-05-15

    The asymmetric test of End-Of-Life (EOL) tests on the Phenix plant was used for the evaluation of the MARS-LMR in the Generation IV frame as a part of the code validation. The purpose of the test is to evaluate the ability of the system code to describe asymmetric situations and to identify important phenomena during asymmetrical transient such as a three dimensional effect, buoyancy influence, and thermal stratification in the hot and cold pools. 3-dimensional sodium coolant mixing in the pools has different characteristics from the one dimensional full instantaneous mixing. The velocities and temperatures at the core outlet level differ at each sub-assembly and the temperature in the center of the hot pool may be high because the driver fuels are located at the center region. The temperatures in the hot pool are not the same in the radial and axial locations due to the buoyancy effect. The temperatures in the cold pool also differ along with the elevations and azimuthal directions due to the outlet location of IHX and the thermal stratification

  15. Flatfish: an asymmetric perspective on metamorphosis.

    Science.gov (United States)

    Schreiber, Alexander M

    2013-01-01

    The most asymmetrically shaped and behaviorally lateralized of all the vertebrates, the flatfishes are an endless source of fascination to all fortunate enough to study them. Although all vertebrates undergo left-right asymmetric internal organ placement during embryogenesis, flatfish are unusual in that they experience an additional period of postembryonic asymmetric remodeling during metamorphosis, and thus deviate from a bilaterally symmetrical body plan more than other vertebrates. As with amphibian metamorphosis, all the developmental programs of flatfish metamorphosis are ultimately under the control of thyroid hormone. At least one gene pathway involved in embryonic organ lateralization (nodal-lefty-pitx2) is re-expressed in the larval stage during flatfish metamorphosis. Aspects of modern flatfish ontogeny, such as the gradual translocation of one eye to the opposite side of the head and the appearance of key neurocranial elements during metamorphosis, seem to elegantly recapitulate flatfish phylogeny. This chapter highlights the current state of knowledge of the developmental biology of flatfish metamorphosis with emphases on the genetic, morphological, behavioral, and evolutionary origins of flatfish asymmetry. Copyright © 2013 Elsevier Inc. All rights reserved.

  16. Roles of Nitric Oxide and Asymmetric Dimethylarginine in Pregnancy and Fetal Programming

    Directory of Open Access Journals (Sweden)

    You-Lin Tain

    2012-11-01

    Full Text Available Nitric oxide (NO regulates placental blood flow and actively participates in trophoblast invasion and placental development. Asymmetric dimethylarginine (ADMA can inhibit NO synthase, which generates NO. ADMA has been associated with uterine artery flow disturbances such as preeclampsia. Substantial experimental evidence has reliably supported the hypothesis that an adverse in utero environment plays a role in postnatal physiological and pathophysiological programming. Growing evidence suggests that the placental nitrergic system is involved in epigenetic fetal programming. In this review, we discuss the roles of NO and ADMA in normal and compromised pregnancies as well as the link between placental insufficiency and epigenetic fetal programming.

  17. On the study of rotational effects in mass asymmetric colliding nuclei at intermediate energies

    Science.gov (United States)

    Kaur, Kamaldeep; Kumar, Suneel

    2018-05-01

    The rotational dynamics has been studied for different mass asymmetric systems 49122In + 50126Sn, 48114Cs + 54134In, 40100Mo + 64148Gd, 3686Kr + 67162Ho, 3171Ga + 71177Lu, 2860Ni + 76188Os and 2450Cr + 78198 Pt for incident energies between 40 MeV/nucleon and 400 MeV/nucleon for impact parameter range 0.25 free protons have been compared successfully with IQMD model calculations. The rotational flow of free protons with increasing incident energies and elliptic flow (calculated from the fits of azimuthal distributions of free protons) dependence with energy has also been investigated.

  18. Thermal conductivity and rectification in asymmetric archaeal lipid membranes

    Science.gov (United States)

    Youssefian, Sina; Rahbar, Nima; Van Dessel, Steven

    2018-05-01

    Nature employs lipids to construct nanostructured membranes that self-assemble in an aqueous environment to separate the cell interior from the exterior environment. Membrane composition changes among species and according to environmental conditions, which allows organisms to occupy a wide variety of different habitats. Lipid bilayers are phase-change materials that exhibit strong thermotropic and lyotropic phase behavior in an aqueous environment, which may also cause thermal rectification. Among different types of lipids, archaeal lipids are of great interest due to their ability to withstand extreme conditions. In this paper, nonequilibrium molecular dynamics simulations were employed to study the nanostructures and thermal properties of different archaeols and to investigate thermal rectification effects in asymmetric archaeal membranes. In particular, we are interested in understanding the role of bridged phytanyl chains and cyclopentane groups in controlling the phase transition temperature and heat flow across the membrane. Our results indicate that the bridged phytanyl chains decrease the molecular packing of lipids, whereas the existence of cyclopentane rings on the tail groups increases the molecular packing by enhancing the interactions between isoprenoid chains. We found that macrocyclic archaeols have the highest thermal conductivity, whereas macrocyclic archaeols with two cyclopentane rings have the lowest. The effect of the temperature on the variation of thermal conductivity was found to be progressive. Our results further indicate that small thermal rectification effects occur in asymmetric archaeol bilayer membranes at around 25 K temperature gradient. The calculated thermal rectification factor was around 0.09 which is in the range of rectification factor obtained experimentally for nanostructures such as carbon nanotubes (0.07). Such phenomena may be of biological significance and could also be optimized for use in various engineering

  19. Optimal File-Distribution in Heterogeneous and Asymmetric Storage Networks

    Science.gov (United States)

    Langner, Tobias; Schindelhauer, Christian; Souza, Alexander

    We consider an optimisation problem which is motivated from storage virtualisation in the Internet. While storage networks make use of dedicated hardware to provide homogeneous bandwidth between servers and clients, in the Internet, connections between storage servers and clients are heterogeneous and often asymmetric with respect to upload and download. Thus, for a large file, the question arises how it should be fragmented and distributed among the servers to grant "optimal" access to the contents. We concentrate on the transfer time of a file, which is the time needed for one upload and a sequence of n downloads, using a set of m servers with heterogeneous bandwidths. We assume that fragments of the file can be transferred in parallel to and from multiple servers. This model yields a distribution problem that examines the question of how these fragments should be distributed onto those servers in order to minimise the transfer time. We present an algorithm, called FlowScaling, that finds an optimal solution within running time {O}(m log m). We formulate the distribution problem as a maximum flow problem, which involves a function that states whether a solution with a given transfer time bound exists. This function is then used with a scaling argument to determine an optimal solution within the claimed time complexity.

  20. Analysis of slip flow heat transfer between two unsymmetrically

    Indian Academy of Sciences (India)

    This paper presents an analytical investigation to study the heat transfer and fluid flow characteristics in the slip flow region for hydrodynamically and thermally fully developed flow between parallel plates.Both upper and lower plates are subjected to asymmetric heat flux boundary conditions. The effect of first ordervelocity ...

  1. Droplet Breakup in Asymmetric T-Junctions at Intermediate to Large Capillary Numbers

    Science.gov (United States)

    Sadr, Reza; Cheng, Way Lee

    2017-11-01

    Splitting of a parent droplet into multiple daughter droplets of desired sizes is usually desired to enhance production and investigational efficiency in microfluidic devices. This can be done in an active or passive mode depending on whether an external power sources is used or not. In this study, three-dimensional simulations were done using the Volume-of-Fluid (VOF) method to analyze droplet splitting in asymmetric T-junctions with different outlet lengths. The parent droplet is divided into two uneven portions the volumetric ratio of the daughter droplets, in theory, depends on the length ratios of the outlet branches. The study identified various breakup modes such as primary, transition, bubble and non-breakup under various flow conditions and the configuration of the T-junctions. In addition, an analysis with the primary breakup regimes were conducted to study the breakup mechanisms. The results show that the way the droplet splits in an asymmetric T-junction is different than the process in a symmetric T-junction. A model for the asymmetric breakup criteria at intermediate or large Capillary number is presented. The proposed model is an expanded version to a theoretically derived model for the symmetric droplet breakup under similar flow conditions.

  2. A DFT investigation on interactions between asymmetric derivatives of cisplatin and nucleobase guanine

    Science.gov (United States)

    Tai, Truong Ba; Nhat, Pham Vu

    2017-07-01

    The interactions of hydrolysis products of cisplatin and its asymmetric derivatives cis- and trans-[PtCl2(iPram)(Mepz)] with guanine were studied using DFT methods. These interactions are dominated by electrostatic effects, namely hydrogen bond contributions and there exists a charge flow from H-atoms of ligands to the O-atoms of guanine. The replacement of NH3 moieties by larger functional groups accompanies with a moderate reaction between PtII and guanine molecule, diminishing the cytotoxicity of the drug. The asymmetric and symmetric NH2 stretching modes of complexes having strong hydrogen bond interactions are red shifted importantly as compared to complexes without presence of hydrogen bond interactions.

  3. Observation of asymmetric electromagnetic field profiles in chiral metamaterials

    Science.gov (United States)

    Hisamoto, Nobuyuki; Ueda, Tetsuya; Sawada, Kei; Tomita, Satoshi

    2018-02-01

    We experimentally observe asymmetric electromagnetic field profiles along two-dimensional chiral metamaterials. The asymmetric field profiles depending on the chirality and the operation frequency have been reproduced well by the numerical simulation. Around a chiral meta-atom, distribution of a Poynting vector is found to be shifted asymmetrically. These results are explained in terms of an analogy with the side-jump mechanism in the electronic anomalous Hall systems.

  4. Asymmetric forecasting and commitment policy in a robust control problem

    OpenAIRE

    Taro Ikeda

    2013-01-01

    This paper provides a piece of results regarding asymmetric forecasting and commitment monetary policy with a robust control algorithm. Previous studies provide no clarification of the connection between asymmetric preference and robust commitment policy. Three results emerge from general equilibrium modeling with asymmetric preference: (i) the condition for system stability implies an average inflation bias with respect to asymmetry (ii) the effect of asymmetry can be mitigated if policy mak...

  5. Asymmetric acoustic transmission in graded beam

    Energy Technology Data Exchange (ETDEWEB)

    Jing, Li, E-mail: lj94172350@hotmail.com [School of Mechanical Engineering and State Key laboratory for Strength and Vibration of Mechanical Structures, Xi’an Jiaotong University, Xi’an, Shaanxi 710049 (China); Wu, Jiu Hui, E-mail: ejhwu@mail.xjtu.edu.cn [School of Mechanical Engineering and State Key laboratory for Strength and Vibration of Mechanical Structures, Xi’an Jiaotong University, Xi’an, Shaanxi 710049 (China); Guan, Dong; Lu, Kuan [School of Mechanical Engineering and State Key laboratory for Strength and Vibration of Mechanical Structures, Xi’an Jiaotong University, Xi’an, Shaanxi 710049 (China); Gao, Nansha [School of Marine Science and Technology, Northwestern Polytechnical University, Xi’an, Shaanxi 710072 (China); Songhua, Cao [School of Mechanical Engineering and State Key laboratory for Strength and Vibration of Mechanical Structures, Xi’an Jiaotong University, Xi’an, Shaanxi 710049 (China)

    2016-12-01

    We demonstrate the dynamic effective material parameters and vibration performance of a graded beam. The structure of the beam was composed of several unit cells with different fill factors. The dispersion relations and energy band structures of each unit cell were calculated using the finite element method (FEM). The dynamic effective material parameters in each unit cell of the graded beam were determined by the dispersion relations and energy band structures. Longitudinal wave propagation was investigated using a numerical method and FEM. The results show that the graded beam allows asymmetric acoustic transmission over a wide range of frequencies.

  6. OFFICER AND COMMANDER IN ASYMMETRIC WARFARE OPERATIONS

    Directory of Open Access Journals (Sweden)

    Giuseppe CAFORIO

    2013-01-01

    Full Text Available Starting from the data of a field research conducted among soldiers with asymmetric warfare experiences from nine different countries, the author seeks to identify and shed light on the various problems that officers with command responsibilities had to face during their missions. A picture emerges of feelings and experiences relating to their first impression upon arriving in the theatre, relations with local armed forces, relations with the local population and local authorities, relations with NGOs, relations with other armies, the impact of the rules of engagement (ROEs, training and education, and operational experiences. The paper ends with a discussion of the lessons learned.

  7. Nanotribology of Symmetric and Asymmetric Liquid Lubricants

    Directory of Open Access Journals (Sweden)

    Shinji Yamada

    2010-03-01

    Full Text Available When liquid molecules are confined in a narrow gap between smooth surfaces, their dynamic properties are completely different from those of the bulk. The molecular motions are highly restricted and the system exhibits solid-like responses when sheared slowly. This solidification behavior is very dependent on the molecular geometry (shape of liquids because the solidification is induced by the packing of molecules into ordered structures in confinement. This paper reviews the measurements of confined structures and friction of symmetric and asymmetric liquid lubricants using the surface forces apparatus. The results show subtle and complex friction mechanisms at the molecular scale.

  8. Asymmetric Total Synthesis of Ieodomycin B

    Directory of Open Access Journals (Sweden)

    Shuangjie Lin

    2017-01-01

    Full Text Available Ieodomycin B, which shows in vitro antimicrobial activity, was isolated from a marine Bacillus species. A novel asymmetric total synthetic approach to ieodomycin B using commercially available geraniol was achieved. The approach involves the generation of 1,3-trans-dihydroxyl at C-3 and C-5 positions via a Crimmins-modified Evans aldol reaction and a chelation-controlled Mukaiyama aldol reaction of a p-methoxybenzyl-protected aldehyde, as well as the generation of a lactone ring in a deprotection–lactonization one-pot reaction.

  9. The Asymmetric Effects of Investor Sentiment

    DEFF Research Database (Denmark)

    Lutz, Chandler

    2016-01-01

    We use the returns on lottery-like stocks and a dynamic factor model to construct a novel index of investor sentiment. This new measure is highly correlated with other behavioral indicators, but more closely tracks speculative episodes. Our main new finding is that the effects of sentiment...... are asymmetric: During peak-to-trough periods of investor sentiment (sentiment contractions), high sentiment predicts low future returns for the cross section of speculative stocks and for the market overall, whereas the relationship between sentiment and future returns is positive but relatively weak during...... trough-to-peak episodes (sentiment expansions). Overall, these results match theories and anecdotal accounts of investor sentiment....

  10. On asymmetric causal relationships in Petropolitics

    Directory of Open Access Journals (Sweden)

    Balan Feyza

    2016-01-01

    Full Text Available The aim of this paper is to examine whether the First Law of Petropolitics denominated by Friedman in 2006 is valid for OPEC countries. To do this, this paper analyses the relationship between political risk and oil supply by applying the asymmetric panel causality test suggested by Hatemi-J (2011 to these countries for the period 1984-2014. The results show that the First Law of Petropolitics is valid for Angola, Iraq, Kuwait, Libya, Nigeria, Qatar, Saudi Arabia, and the UAE, given that positive oil supply shocks significantly lead to negative political stability shocks, and negative oil supply shocks significantly lead to positive shocks in political stability.

  11. Asymmetric nuclear matter and neutron star properties

    International Nuclear Information System (INIS)

    Engvik, L.; Hjorth-Jensen, M.; Osnes, E.; Bao, G.; Oestgaard, E.

    1994-06-01

    Properties of neutron stars such as mass and radius, using a relativistic Dirac-Brueckner-Hartree-Fock approach, are calculated. Modern meson-exchange potential models are used to evaluate the G-matrix for asymmetric nuclear matter. For pure neutron matter the maximum mass is found to be M max ∼ 2.4M for a radius R ∼ 12 km. With a proton fraction of 30% the result is M max ∼ 2.1M for a radius R ∼ 10.5 km, close to the experimental values. The implications are discussed. 20 refs., 3 figs

  12. Two particle states in an asymmetric box

    International Nuclear Information System (INIS)

    Li Xin; Liu Chuan

    2004-01-01

    The exact two-particle energy eigenstates in an asymmetric rectangular box with periodic boundary conditions in all three directions are studied. Their relation with the elastic scattering phases of the two particles in the continuum are obtained. These results can be viewed as a generalization of the corresponding formulae in a cubic box obtained by Luescher before. In particular, the s-wave scattering length is related to the energy shift in the finite box. Possible applications of these formulae are also discussed

  13. Performance prediction of asymmetrical bladed H-Darrieus VAWT rotors in low wind speed condition using CFD

    Science.gov (United States)

    Mazarbhuiya, Hussain Mahamed Sahed Mostafa; Biswas, Agnimitra; Sharma, Kaushal Kumar

    2018-04-01

    Wind energy is an essential and carbon free form of renewable energy resources. Energy can be easily extracted from wind with the use of Horizontal axis and Vertical axis wind turbine(VAWT). The performance of turbine depends on airfoil shape. The present work emphasizes the aerodynamics of different asymmetrical airfoils used in VAWT rotors. This investigation is conducted for the selection of efficient asymmetrical bladed H-Darrieus VAWT rotor. Five numbers of thick and cambered asymmetrical airfoil is considered for this investigation. A free stream velocity of 6.0 m/s is considered to simulate 2D CFD analysis using k-ɛ turbulence model. The power coefficient (Cp) of all H-Darrieus VAWT rotor increase with increase in TSR value to a certain limit and after it starts decrease with further increase of TSR. In the present investigation the Cp and TSR of NACA 63415 (RT-30%) are found to be higher among all considered asymmetrical airfoils. Moreover, Ct values of NACA 63415 (RT-30%) are also high corresponding to all TSR values. This is due to the long duration of attachment of flow with blade surroundings. Hence, NACA 63415 (RT- 30%) airfoil may be considered as an efficient airfoil among S818, GOE 561, GU25-5(11)8, and KENNEDY AND MARSDEN (kenmar) asymmetrical airfoils.

  14. Asymmetrical Capacitors for Propulsion and the ISR Asymmetrical Capacitator Thruster, Experimental Results and Improved Designs

    Science.gov (United States)

    Canning, Francis; Winet, Ed; Ice, Bob; Melcher, Cory; Pesavento, Phil; Holmes, Alan; Butler, Carey; Cole, John; Campbell, Jonathan

    2004-01-01

    The outline of this viewgraph presentation on asymmetrical capacitor thruster development includes: 1) Test apparatus; 2) Devices tested; 3) Circuits used; 4) Data collected (Time averaged, Time resolved); 5) Patterns observed; 6) Force calculation; 7) Electrostatic modeling; 8) Understand it all.

  15. Chiral ferrocenes in asymmetric catalysis: synthesis and applications

    National Research Council Canada - National Science Library

    Dai, Li-Xin; Hou, Xue-Long

    2010-01-01

    .... It provides a thorough overview of the synthesis and characterization of different types of chiral ferrocene ligands, their application to various catalytic asymmetric reactions, and versatile chiral...

  16. A measurement device for electromagnetic flow tomography

    Science.gov (United States)

    Vauhkonen, M.; Hänninen, A.; Lehtikangas, O.

    2018-01-01

    Electromagnetic flow meters have succesfully been used in many industries to measure the mean flow velocity of conductive liquids. This technology works reliably in single phase flows with axisymmetric flow profiles but can be inaccurate with asymmetric flows, which are encountered, for example, in multiphase flows, pipe elbows and T-junctions. Some computational techniques and measurement devices with multiple excitation coils and measurement electrodes have recently been proposed to be used in cases of asymmetric flows. In earlier studies, we proposed a computational approach for electromagnetic flow tomography (EMFT) for estimating velocity fields utilizing several excitation coils and a set of measurement electrodes attached to the surface of the pipe. This approach has been shown to work well with simulated data but has not been tested extensively with real measurements. In this paper, an EMFT system with four excitation coils and 16 measurement electrodes is introduced. The system is capable of using both square wave and sinusoidal coil current excitations and all the coils can be excited individually, also enabling parallel excitations with multiple frequencies. The studies undertaken in the paper demonstrate that the proposed EMFT system, together with the earlier introduced velocity field reconstruction approach, is capable of producing reliable velocify field estimates in a laboratory environment with both axisymmetric and asymmetric single phase flows.

  17. [Asymmetric hypertrophy of the masticatory muscles].

    Science.gov (United States)

    Arzul, L; Corre, P; Khonsari, R H; Mercier, J-M; Piot, B

    2012-06-01

    Hypertrophy of the masticatory muscles most commonly affects the masseter. Less common cases of isolated or associated temporalis hypertrophy are also reported. Parafunctional habits, and more precisely bruxism, can favor the onset of the hypertrophy. This condition is generally idiopathic and can require both medical and/or surgical management. A 29-year-old patient was referred to our department for an asymmetric swelling of the masticatory muscles. Physical examination revealed a bilateral hypertrophy of the masticatory muscles, predominantly affecting the right temporalis and the left masseter. Major bruxism was assessed by premature dental wearing. The additional examinations confirmed the isolated muscle hypertrophy. Benign asymmetric hypertrophy of the masticatory muscles promoted by bruxism was diagnosed. Treatment with injections of type A botulinum toxin was conducted in association with a splint and relaxation. Its effectiveness has been observed at six months. Few cases of unilateral or bilateral temporalis hypertrophy have been reported, added to the more common isolated masseter muscles hypertrophy. The diagnosis requires to rule out secondary hypertrophies and tumors using Magnetic Resonance Imaging. The condition is thought to be favoured by parafunctional habits such as bruxism. The conservative treatment consists in reducing the volume of the masticatory muscles using intramuscular injections of type A botulinum toxin. Other potential conservative treatments are wearing splints and muscle relaxant drugs. Surgical procedures aiming to reduce the muscle volume and/or the bone volume (mandibular gonioplasty) can be proposed. Copyright © 2012 Elsevier Masson SAS. All rights reserved.

  18. On the Collisionless Asymmetric Magnetic Reconnection Rate

    Science.gov (United States)

    Liu, Yi-Hsin; Hesse, M.; Cassak, P. A.; Shay, M. A.; Wang, S.; Chen, L.-J.

    2018-04-01

    A prediction of the steady state reconnection electric field in asymmetric reconnection is obtained by maximizing the reconnection rate as a function of the opening angle made by the upstream magnetic field on the weak magnetic field (magnetosheath) side. The prediction is within a factor of 2 of the widely examined asymmetric reconnection model (Cassak & Shay, 2007, https://doi.org/10.1063/1.2795630) in the collisionless limit, and they scale the same over a wide parameter regime. The previous model had the effective aspect ratio of the diffusion region as a free parameter, which simulations and observations suggest is on the order of 0.1, but the present model has no free parameters. In conjunction with the symmetric case (Liu et al., 2017, https://doi.org/10.1103/PhysRevLett.118.085101), this work further suggests that this nearly universal number 0.1, essentially the normalized fast-reconnection rate, is a geometrical factor arising from maximizing the reconnection rate within magnetohydrodynamic-scale constraints.

  19. Evolutionary stability in the asymmetric volunteer's dilemma.

    Directory of Open Access Journals (Sweden)

    Jun-Zhou He

    Full Text Available It is often assumed that in public goods games, contributors are either strong or weak players and each individual has an equal probability of exhibiting cooperation. It is difficult to explain why the public good is produced by strong individuals in some cooperation systems, and by weak individuals in others. Viewing the asymmetric volunteer's dilemma game as an evolutionary game, we find that whether the strong or the weak players produce the public good depends on the initial condition (i.e., phenotype or initial strategy of individuals. These different evolutionarily stable strategies (ESS associated with different initial conditions, can be interpreted as the production modes of public goods of different cooperation systems. A further analysis revealed that the strong player adopts a pure strategy but mixed strategies for the weak players to produce the public good, and that the probability of volunteering by weak players decreases with increasing group size or decreasing cost-benefit ratio. Our model shows that the defection probability of a "strong" player is greater than the "weak" players in the model of Diekmann (1993. This contradicts Selten's (1980 model that public goods can only be produced by a strong player, is not an evolutionarily stable strategy, and will therefore disappear over evolutionary time. Our public good model with ESS has thus extended previous interpretations that the public good can only be produced by strong players in an asymmetric game.

  20. An asymmetric B factory based on PEP

    Energy Technology Data Exchange (ETDEWEB)

    1991-02-01

    In this report we describe a design for a high-luminosity Asymmetric B Factory to be built in the PEP tunnel on the SLAC site. This proposal, a collaborative effort SLAC, LBL, and LLNL, is the culmination of more than two years of effort aimed at the design and construction of an asymmetric e{sup +}e{sup {minus}} collider capable of achieving a luminosity of L = 3 {times} 10{sup 33} cm{sup {minus}2} s{sup {minus}1}. The configuration adopted utilizes two storage rings, and electron ring operating at 9 GeV and a positron ring at 3.1 GeV, each with a circumference of 2200 m. The high-energy ring is an upgrade of the PEP storage ring at SLAC; all PEP magnets and most power supplies will be reused. The upgrade consists primarily of replacing the PEP vacuum chamber and RF system with newly designed versions optimized for the high-current environment of the B Factory. The low-energy ring will be newly constructed and will be situated atop the high-energy ring in the PEP tunnel. Utilities already installed in the PEP tunnel are largely sufficient to operate the two B Factory storage rings.

  1. An asymmetric B factory based on PEP

    International Nuclear Information System (INIS)

    1991-02-01

    In this report we describe a design for a high-luminosity Asymmetric B Factory to be built in the PEP tunnel on the SLAC site. This proposal, a collaborative effort SLAC, LBL, and LLNL, is the culmination of more than two years of effort aimed at the design and construction of an asymmetric e + e - collider capable of achieving a luminosity of L = 3 x 10 33 cm -2 s -1 . The configuration adopted utilizes two storage rings, and electron ring operating at 9 GeV and a positron ring at 3.1 GeV, each with a circumference of 2200 m. The high-energy ring is an upgrade of the PEP storage ring at SLAC; all PEP magnets and most power supplies will be reused. The upgrade consists primarily of replacing the PEP vacuum chamber and RF system with newly designed versions optimized for the high-current environment of the B Factory. The low-energy ring will be newly constructed and will be situated atop the high-energy ring in the PEP tunnel. Utilities already installed in the PEP tunnel are largely sufficient to operate the two B Factory storage rings

  2. Particle identification at an asymmetric B Factory

    International Nuclear Information System (INIS)

    Coyle, P.; Eigen, G.; Hitlin, D.; Oddone, P.; Ratcliff, B.; Roe, N.; Va'vra, J.; Ypsilantis, T.

    1991-09-01

    Particle identification systems are an important component of any detector at a high-luminosity, asymmetric B Factory. In particular, excellent hadron identification is required to probe CP violation in B 0 decays to CP eigenstates. The particle identification systems discussed below also provide help in separating leptons from hadrons at low momenta. We begin this chapter with a discussion of the physics motivation for providing particle identification, the inherent limitations due to interactions and decays in flight, and the requirements for hermiticity and angular coverage. A special feature of an asymmetric B Factory is the resulting asymmetry in the momentum distribution as a function of polar angle; this will also be quantified and discussed. In the next section the three primary candidates, time-of-flight (TOF), energy loss (dE/dx), and Cerenkov counters, both ring-imaging and threshold, will be briefly described and evaluated. Following this, one of the candidates, a long-drift Cerenkov ring-imaging device, is described in detail to provide a reference design. Design considerations for a fast RICH are then described. A detailed discussion of aerogel threshold counter designs and associated R ampersand D conclude the chapter. 56 refs., 64 figs., 13 tabs

  3. CRITICAL DIFFERENCES OF ASYMMETRIC MAGNETIC RECONNECTION FROM STANDARD MODELS

    Energy Technology Data Exchange (ETDEWEB)

    Nitta, S. [Hinode Science Project, National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo, 181-8588 (Japan); Wada, T. [Tsukuba University of Technology, 4-3-15 Amakubo, Tsukuba, 305-8520 (Japan); Fuchida, T. [Graduate School of Science and Engineering, Ehime Univesity, 2-5 Bunkyo-cho, Matuyama, Ehime, 790-8577 (Japan); Kondoh, K., E-mail: nittasn@yahoo.co.jp, E-mail: tomohide.wada@gmail.com, E-mail: fuchida@sp.cosmos.ehime-u.ac.jp, E-mail: kondo@cosmos.ehime-u.ac.jp [Research Center for Space and Cosmic Evolution, Ehime University, 2-5 Bunkyo-cho, Matsuyama, Ehime, 790-8577 (Japan)

    2016-09-01

    We have clarified the structure of asymmetric magnetic reconnection in detail as the result of the spontaneous evolutionary process. The asymmetry is imposed as ratio k of the magnetic field strength in both sides of the initial current sheet (CS) in the isothermal equilibrium. The MHD simulation is carried out by the HLLD code for the long-term temporal evolution with very high spatial resolution. The resultant structure is drastically different from the symmetric case (e.g., the Petschek model) even for slight asymmetry k = 2. (1) The velocity distribution in the reconnection jet clearly shows a two-layered structure, i.e., the high-speed sub-layer in which the flow is almost field aligned and the acceleration sub-layer. (2) Higher beta side (HBS) plasma is caught in a lower beta side plasmoid. This suggests a new plasma mixing process in the reconnection events. (3) A new large strong fast shock in front of the plasmoid forms in the HBS. This can be a new particle acceleration site in the reconnection system. These critical properties that have not been reported in previous works suggest that we contribute to a better and more detailed knowledge of the reconnection of the standard model for the symmetric magnetic reconnection system.

  4. Ultrathin-skinned asymmetric membranes by immiscible solvents treatment

    Science.gov (United States)

    Friesen, Dwayne T.; Babcock, Walter C.

    1989-01-01

    Improved semipermeable asymmetric fluid separation membranes useful in gas, vapor and liquid separations are disclosed. The membranes are prepared by substantially filling the pores of asymmetric cellulosic semipermeable membranes having a finely porous layer on one side thereof with a water immiscible organic liquid, followed by contacting the finely porous layer with water.

  5. A new convenient asymmetric approach to herbarumin Ⅲ

    Institute of Scientific and Technical Information of China (English)

    Xue Song Chen; Shi Jun Da; Li Hong Yang; Bo Yan Xu; Zhi Xiang Xie; Ying Li

    2007-01-01

    The asymmetric total synthesis of herbarumin Ⅲ 3, a naturally occurred phytotoxin, along with 8-epi-herbarumin Ⅲ 22, was succeeded in 12 steps from n-butyraldehyde based on Brown's asymmetric allylation, taking modified Julia olefination and Yamaguchi's macro-lactonization as key steps.

  6. Appropriate quantization of asymmetric games with continuous strategies

    International Nuclear Information System (INIS)

    Qin Gan; Chen Xi; Sun Min; Zhou Xianyi; Du Jiangfeng

    2005-01-01

    We establish a new quantization scheme to study the asymmetric Bertrand duopoly with differentiated products. This scheme is more efficient than the previous symmetric one because it can exactly make the optimal cooperative payoffs at quantum Nash equilibrium. It is also a necessary condition for general asymmetric games with continuous strategies to reach such payoffs

  7. An Evolving Asymmetric Game for Modeling Interdictor-Smuggler Problems

    Science.gov (United States)

    2016-06-01

    ASYMMETRIC GAME FOR MODELING INTERDICTOR-SMUGGLER PROBLEMS by Richard J. Allain June 2016 Thesis Advisor: David L. Alderson Second Reader: W...DATES COVERED Master’s thesis 4. TITLE AND SUBTITLE AN EVOLVING ASYMMETRIC GAME FOR MODELING INTERDICTOR- SMUGGLER PROBLEMS 5. FUNDING NUMBERS 6...NAVAL POSTGRADUATE SCHOOL MONTEREY, CALIFORNIA THESIS Approved for public release; distribution is unlimited AN EVOLVING

  8. Decrease in back strength in asymmetric trunk postures

    NARCIS (Netherlands)

    Vink, P.; Daanen, H. A M; Meijst, W. J.; Ligteringen, J.

    1992-01-01

    The extension force against resistance was recorded in 23 postures for 12 subjects to find explanations for the decrease in back strength in asymmetric postures. A reduction in muscle force in asymmetric postures was found up to 40%, but was strongly dependent on the plane in which asymmetry

  9. Subcopula-based measure of asymmetric association for contingency tables.

    Science.gov (United States)

    Wei, Zheng; Kim, Daeyoung

    2017-10-30

    For the analysis of a two-way contingency table, a new asymmetric association measure is developed. The proposed method uses the subcopula-based regression between the discrete variables to measure the asymmetric predictive powers of the variables of interest. Unlike the existing measures of asymmetric association, the subcopula-based measure is insensitive to the number of categories in a variable, and thus, the magnitude of the proposed measure can be interpreted as the degree of asymmetric association in the contingency table. The theoretical properties of the proposed subcopula-based asymmetric association measure are investigated. We illustrate the performance and advantages of the proposed measure using simulation studies and real data examples. Copyright © 2017 John Wiley & Sons, Ltd.

  10. Asymmetric double Langmuir probe: Small signal application

    International Nuclear Information System (INIS)

    Uckan, T.

    1987-11-01

    We discuss the asymmetric double Langmuir probe (ADLP) and demonstrate the possibility of using it to measure plasma temperature T/sub e/ and density n when it is operated in the region of small signal response. The area of one of the ADLP collectors is considerably larger than the other. This probe can be operated at a relatively low applied voltage, eV/sub a/T/sub e/ < 1, and still provides sufficient information to determine the plasma T/sub e/ and n. There is no need for a direct measurement of the ion saturation current, which can be on the order of a few amperes in large fusion devices. This reduces the requirements on the probe power supply. 6 refs., 6 figs

  11. Do Daily Retail Gasoline Prices adjust Asymmetrically?

    Energy Technology Data Exchange (ETDEWEB)

    Bettendorf, L. [Tinbergen Instituut, Amsterdam/Rotterdam (Netherlands); Van der Geest, S. [Erasmus Universiteit, Rotterdam (Netherlands); Kuper, G. [University of Groningen, Groningen (Netherlands)

    2005-04-15

    This paper analyzes adjustments in the Dutch retail gasoline prices. We estimate an error correction model on changes in the daily retail price for gasoline (taxes excluded) for the period 1996-2004 taking care of volatility clustering by estimating an EGARCH model. It turns out the volatility process is asymmetrical: an unexpected increase in the producer price has a larger effect on the variance of the producer price than an unexpected decrease. We do not find strong evidence for amount asymmetry. However, there is a faster reaction to upward changes in spot prices than to downward changes in spot prices. This implies timing or pattern asymmetry. This asymmetry starts three days after the change in the spot price and lasts for four days.

  12. Isospin dependent properties of asymmetric nuclear matter

    Science.gov (United States)

    Chowdhury, P. Roy; Basu, D. N.; Samanta, C.

    2009-07-01

    The density dependence of nuclear symmetry energy is determined from a systematic study of the isospin dependent bulk properties of asymmetric nuclear matter using the isoscalar and isovector components of the density dependent M3Y interaction. The incompressibility K∞ for the symmetric nuclear matter, the isospin dependent part Kasy of the isobaric incompressibility, and the slope L are all in excellent agreement with the constraints recently extracted from measured isotopic dependence of the giant monopole resonances in even-A Sn isotopes, from the neutron skin thickness of nuclei, and from analyses of experimental data on isospin diffusion and isotopic scaling in intermediate energy heavy-ion collisions. This work provides a fundamental basis for the understanding of nuclear matter under extreme conditions and validates the important empirical constraints obtained from recent experimental data.

  13. Asymmetric Spatial Processing Under Cognitive Load.

    Science.gov (United States)

    Naert, Lien; Bonato, Mario; Fias, Wim

    2018-01-01

    Spatial attention allows us to selectively process information within a certain location in space. Despite the vast literature on spatial attention, the effect of cognitive load on spatial processing is still not fully understood. In this study we added cognitive load to a spatial processing task, so as to see whether it would differentially impact upon the processing of visual information in the left versus the right hemispace. The main paradigm consisted of a detection task that was performed during the maintenance interval of a verbal working memory task. We found that increasing cognitive working memory load had a more negative impact on detecting targets presented on the left side compared to those on the right side. The strength of the load effect correlated with the strength of the interaction on an individual level. The implications of an asymmetric attentional bias with a relative disadvantage for the left (vs the right) hemispace under high verbal working memory (WM) load are discussed.

  14. Baryon destruction by asymmetric dark matter

    International Nuclear Information System (INIS)

    Davoudiasl, Hooman; Morrissey, David E.; Tulin, Sean; Sigurdson, Kris

    2011-01-01

    We investigate new and unusual signals that arise in theories where dark matter is asymmetric and carries a net antibaryon number, as may occur when the dark matter abundance is linked to the baryon abundance. Antibaryonic dark matter can cause induced nucleon decay by annihilating visible baryons through inelastic scattering. These processes lead to an effective nucleon lifetime of 10 29 -10 32 yrs in terrestrial nucleon decay experiments, if baryon number transfer between visible and dark sectors arises through new physics at the weak scale. The possibility of induced nucleon decay motivates a novel approach for direct detection of cosmic dark matter in nucleon decay experiments. Monojet searches (and related signatures) at hadron colliders also provide a complementary probe of weak-scale dark-matter-induced baryon number violation. Finally, we discuss the effects of baryon-destroying dark matter on stellar systems and show that it can be consistent with existing observations.

  15. Asymmetric Dark Matter and Dark Radiation

    CERN Document Server

    Blennow, Mattias; Mena, Olga; Redondo, Javier; Serra, Paolo

    2012-01-01

    Asymmetric Dark Matter (ADM) models invoke a particle-antiparticle asymmetry, similar to the one observed in the Baryon sector, to account for the Dark Matter (DM) abundance. Both asymmetries are usually generated by the same mechanism and generally related, thus predicting DM masses around 5 GeV in order to obtain the correct density. The main challenge for successful models is to ensure efficient annihilation of the thermally produced symmetric component of such a light DM candidate without violating constraints from collider or direct searches. A common way to overcome this involves a light mediator, into which DM can efficiently annihilate and which subsequently decays into Standard Model particles. Here we explore the scenario where the light mediator decays instead into lighter degrees of freedom in the dark sector that act as radiation in the early Universe. While this assumption makes indirect DM searches challenging, it leads to signals of extra radiation at BBN and CMB. Under certain conditions, pre...

  16. Asymmetric ion transport through ion-channel-mimetic solid-state nanopores.

    Science.gov (United States)

    Guo, Wei; Tian, Ye; Jiang, Lei

    2013-12-17

    Both scientists and engineers are interested in the design and fabrication of synthetic nanofluidic architectures that mimic the gating functions of biological ion channels. The effort to build such structures requires interdisciplinary efforts at the intersection of chemistry, materials science, and nanotechnology. Biological ion channels and synthetic nanofluidic devices have some structural and chemical similarities, and therefore, they share some common features in regulating the traverse ionic flow. In the past decade, researchers have identified two asymmetric ion transport phenomena in synthetic nanofluidic structures, the rectified ionic current and the net diffusion current. The rectified ionic current is a diode-like current-voltage response that occurs when switching the voltage bias. This phenomenon indicates a preferential direction of transport in the nanofluidic system. The net diffusion current occurs as a direct product of charge selectivity and is generated from the asymmetric diffusion through charged nanofluidic channels. These new ion transport phenomena and the elaborate structures that occur in biology have inspired us to build functional nanofluidic devices for both fundamental research and practical applications. In this Account, we review our recent progress in the design and fabrication of biomimetic solid-state nanofluidic devices with asymmetric ion transport behavior. We demonstrate the origin of the rectified ionic current and the net diffusion current. We also identify several influential factors and discuss how to build these asymmetric features into nanofluidic systems by controlling (1) nanopore geometry, (2) surface charge distribution, (3) chemical composition, (4) channel wall wettability, (5) environmental pH, (6) electrolyte concentration gradient, and (7) ion mobility. In the case of the first four features, we build these asymmetric features directly into the nanofluidic structures. With the final three, we construct

  17. Magnetic Field and Gravity Effects on Peristaltic Transport of a Jeffrey Fluid in an Asymmetric Channel

    Directory of Open Access Journals (Sweden)

    A. M. Abd-Alla

    2014-01-01

    Full Text Available In this paper, the peristaltic flow of a Jeffrey fluid in an asymmetric channel has been investigated. Mathematical modeling is carried out by utilizing long wavelength and low Reynolds number assumptions. Closed form expressions for the pressure gradient, pressure rise, stream function, axial velocity, and shear stress on the channel walls have been computed numerically. Effects of the Hartmann number, the ratio of relaxation to retardation times, time-mean flow, the phase angle and the gravity field on the pressure gradient, pressure rise, streamline, axial velocity, and shear stress are discussed in detail and shown graphically. The results indicate that the effect of Hartmann number, ratio of relaxation to retardation times, time-mean flow, phase angle, and gravity field are very pronounced in the peristaltic transport phenomena. Comparison was made with the results obtained in the presence and absence of magnetic field and gravity field.

  18. On the Electron Diffusion Region in Asymmetric Reconnection with a Guide Magnetic Field

    Science.gov (United States)

    Hesse, Michael; Liu, Yi-Hsin; Chen, Li-Jen; Bessho, Naoki; Kuznetsova, Masha; Birn, Joachim; Burch, James L.

    2016-01-01

    Particle-in-cell simulations in a 2.5-D geometry and analytical theory are employed to study the electron diffusion region in asymmetric reconnection with a guide magnetic field. The analysis presented here demonstrates that similar to the case without guide field, in-plane flow stagnation and null of the in-plane magnetic field are well separated. In addition, it is shown that the electric field at the local magnetic X point is again dominated by inertial effects, whereas it remains dominated by nongyrotropic pressure effects at the in-plane flow stagnation point. A comparison between local electron Larmor radii and the magnetic gradient scale lengths predicts that distribution should become nongyrotropic in a region enveloping both field reversal and flow stagnation points. This prediction is verified by an analysis of modeled electron distributions, which show clear evidence of mixing in the critical region.

  19. Effect of wall compliance on peristaltic transport of a Newtonian fluid in an asymmetric channel

    Directory of Open Access Journals (Sweden)

    Mohamed H. Haroun

    2006-01-01

    Full Text Available Peristaltic transport of an incompressible viscous fluid in an asymmetric compliant channel is studied. The channel asymmetry is produced by choosing the peristaltic wave train on the walls to have different amplitudes and phases. The fluid-solid interaction problem is investigated by considering equations of motion of both the fluid and the deformable boundaries. The driving mechanism of the muscle is represented by assuming the channel walls to be compliant. The phenomenon of the “mean flow reversal” is discussed. The effect of wave amplitude ratio, width of the channel, phase difference, wall elastance, wall tension, and wall damping on mean-velocity and reversal flow has been investigated. The results reveal that the reversal flow occurs near the boundaries which is not possible in the elastic symmetric channel case.

  20. Scaling Effect of Phosphorene Nanoribbon - Uncovering the Origin of Asymmetric Current Transport

    Science.gov (United States)

    Lv, Yawei; Chang, Sheng; Huang, Qijun; Wang, Hao; He, Jin

    2016-01-01

    In this paper, phosphorene nanoribbons (PNRs) are theoretically studied using a multiscale simulation flow from the ab initio level to the tight binding (TB) level. The scaling effects of both armchair PNRs (aPNRs) and zigzag PNRs (zPNRs) from material properties to device properties are explored. The much larger effective mass of holes compared to that of electrons in zPNR is responsible for its asymmetric transport. However, in aPNR, not only the effective mass difference but also the non-equal density of state (DOS) distributions near valence band maximum (VBM) and conduction band minimum (CBM) lead to the asymmetric transport. This non-equal distribution phenomenon is caused by energy band degeneracies near the VBM. Based on these two different mechanisms, PNRs’ asymmetric transport characteristics at the device level are explained, and it is shown that this behaviour can be ameliorated well by reducing the ribbon width in an aPNR MOSFET. Calculation results also indicate that aPNR’s effective mass is comparable to that of a graphene nanoribbon (GNR) at the same bandgap; however, aPNR’s band gap variation is more stable and regular than that of GNR, making it a good candidate for use in low-dimensional nano devices. PMID:27897230

  1. PEP-II: An asymmetric B factory

    International Nuclear Information System (INIS)

    1993-06-01

    In this report, the authors have described an updated conceptual design for the high-luminosity Asymmetric B Factory (PEP-II) to be built in the PEP tunnel culmination of more than four years of effort aimed at the design and construction of an asymmetric e + e - collider capable of achieving a luminosity of L = 3 x 10 33 cm -2 s -1 . All aspects of the conceptual design were scrutinized in March 1991 by a DOE technical review committee chaired by Dr. L. Edward Temple. The design was deemed feasible and capable of achieving its physics goals. Furthermore, the cost estimate, schedule, and management plan for the project were fully endorsed by the committee. This updated conceptual design report captures the technical progress since the March 1991 review and reflects the lower cost estimate corresponding to the improved design. Although the PEP-II design has continued to evolve, no technical scope changes have been made that invalidate the conclusion of the DOE review. The configuration adopted utilizes two storage rings, an electron ring operating at 9 GeV and a positron ring at 3.1 GeV, each with a circumference of 2200 m. The high-energy ring is an upgrade of the PEP storage ring at SLAC; all PEP magnets and most power supplies will be reused. The upgrade consists primarily of replacing the PEP vacuum chamber and RF system with newly designed versions optimized for the high-current environment of PEP-II. The low-energy ring will be newly constructed and will be situated atop the high-energy ring in the PEP tunnel. Utilities already installed in the PEP tunnel are largely sufficient to operate the two PEP-II storage rings

  2. The asymmetric total synthesis of (+)- and (-)-trypargine via Noyori asymmetric transfer hydrogenation

    International Nuclear Information System (INIS)

    Pilli, Ronaldo A.; Rodrigues Junior, Manoel Trindade

    2009-01-01

    A concise and efficient total synthesis of (+)- and (-)-trypargine (6 steps and 38% overall yield), a 1-substituted β-carboline guanidine alkaloid isolated from the skin of the African frog K. senegalensis, was developed based on the construction of the b-carboline moiety via Bischler-Napieralski reaction and the enantioselective reduction of the dihydro-β-carboline intermediate via an asymmetric transfer hydrogenation reaction using Noyori's protocol. (author)

  3. Potential of an asymmetrical agitation in industrial mixing

    Directory of Open Access Journals (Sweden)

    Kazuhiko Nishi

    2013-10-01

    Full Text Available Mixing is one of the most fundamental operations in chemical engineering. Stirred tanks are widely used in the manufacture of such materials as chemicals, paints, inks, electronics materials, ceramics, foods, pharmaceuticals and cosmetics. Suitable mixing is indispensable to the purpose achievement of a process. Eccentric mixing, in which an impeller installed at eccentric position in a vessel, is one of the traditional methods of promoting mixing. An asymmetrical flow which occurs in vessel is complicated, and it promotes mixing, distribution, and mass transfer. In this study, a new mixing method which eccentric mixing using a large type impeller which attracts attention in recent years is shown. The high performance of a large impeller can be combined with the advantages of an eccentric impeller by using the impeller at an eccentric position. The power consumption and mixing time for MAXBLEND, which is a type of large impeller, were investigated. The power consumption, P, and mixing time, θM, were measured under various eccentric conditions. The relation between the power number (Np and Reynolds number (Re and that between the dimensionless mixing time (nθM and Re were investigated. When eccentric mixing is used industrially, we should be concerned about the horizontal load to a agitating shaft. The large oscillating horizontal load causes serious problems, such as the falling off of the impeller or the breakage of the motor, mechanical seal or gearbox. It is, therefore, important to understand the relation between these values and the impeller rotational speed when designing the mixing equipment and determining the operating conditions. In this study, the torque and horizontal load were measured in eccentric mixing under various eccentric conditions. The averages of both, the torque and the horizontal load, and their standard deviations, corresponding to the amplitude of fluctuation, were shown.Doi: 10.12777/ijse.5.2.73-80 [How to cite this

  4. Asymmetric dominance and asymmetric mate choice oppose premating isolation after allopatric divergence.

    Science.gov (United States)

    Sefc, Kristina M; Hermann, Caroline M; Steinwender, Bernd; Brindl, Hanna; Zimmermann, Holger; Mattersdorfer, Karin; Postl, Lisbeth; Makasa, Lawrence; Sturmbauer, Christian; Koblmüller, Stephan

    2015-04-01

    Assortative mating promotes reproductive isolation and allows allopatric speciation processes to continue in secondary contact. As mating patterns are determined by mate preferences and intrasexual competition, we investigated male-male competition and behavioral isolation in simulated secondary contact among allopatric populations. Three allopatric color morphs of the cichlid fish Tropheus were tested against each other. Dyadic male-male contests revealed dominance of red males over bluish and yellow-blotch males. Reproductive isolation in the presence of male-male competition was assessed from genetic parentage in experimental ponds and was highly asymmetric among pairs of color morphs. Red females mated only with red males, whereas the other females performed variable degrees of heteromorphic mating. Discrepancies between mating patterns in ponds and female preferences in a competition-free, two-way choice paradigm suggested that the dominance of red males interfered with positive assortative mating of females of the subordinate morphs and provoked asymmetric hybridization. Between the nonred morphs, a significant excess of negative assortative mating by yellow-blotch females with bluish males did not coincide with asymmetric dominance among males. Hence, both negative assortative mating preferences and interference of male-male competition with positive assortative preferences forestall premating isolation, the latter especially in environments unsupportive of competition-driven spatial segregation.

  5. Experimental observation on asymmetric energy flux within the forbidden frequency band in the LC transmission line

    International Nuclear Information System (INIS)

    Tao Feng; Chen Weizhong; Pan Junting; Xu Wen; Du Sidan

    2012-01-01

    We study the energy flux in a nonlinear electrical transmission line consisting of two coupled segments which are identical in structure and different in parameters. The asymmetry of energy flux caused by nonlinear wave has been observed experimentally in the forbidden band of the line. The experiment shows whether the energy can flow through the transmission line depends on the amplitude of the boundary driving voltages, which can be well explained in the theoretical framework of nonlinear supratransmission. The numerical simulation based on Kirchhoff’s laws further verifies the existence of the asymmetric energy flux in the forbidden band.

  6. Robustness of the filamentation instability for asymmetric plasma shells collision in arbitrarily oriented magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Bret, A. [ETSI Industriales, Universidad de Castilla-La Mancha, 13071 Ciudad Real, Spain and Instituto de Investigaciones Energticas y Aplicaciones Industriales, Campus Universitario de Ciudad Real, 13071 Ciudad Real (Spain)

    2013-10-15

    The filamentation instability triggered when two counter streaming plasma shells overlap appears to be the main mechanism by which collisionless shocks are generated. It has been known for long that a flow aligned magnetic field can completely suppress this instability. In a recent paper [Phys. Plasmas 18, 080706 (2011)], it was demonstrated in two dimensions that for the case of two cold, symmetric, relativistically colliding shells, such cancellation cannot occur if the field is not perfectly aligned. Here, this result is extended to the case of two asymmetric shells. The filamentation instability appears therefore as an increasingly robust mechanism to generate shocks.

  7. Globally aligned states and hydrodynamic traffic jams in confined suspensions of active asymmetric particles.

    Science.gov (United States)

    Lefauve, Adrien; Saintillan, David

    2014-02-01

    Strongly confined active liquids are subject to unique hydrodynamic interactions due to momentum screening and lubricated friction by the confining walls. Using numerical simulations, we demonstrate that two-dimensional dilute suspensions of fore-aft asymmetric polar swimmers in a Hele-Shaw geometry can exhibit a rich variety of novel phase behaviors depending on particle shape, including coherent polarized density waves with global alignment, persistent counterrotating vortices, density shocks and rarefaction waves. We also explain these phenomena using a linear stability analysis and a nonlinear traffic flow model, both derived from a mean-field kinetic theory.

  8. Simulation Analysis and Experiment of Variable-Displacement Asymmetric Axial Piston Pump

    Directory of Open Access Journals (Sweden)

    Youshan Gao

    2017-03-01

    Full Text Available The variable displacement pump control system has greater energy-saving advantages and application prospects than the valve control system. However, the variable displacement pump control of differential cylinder is not concurrent with the existing technologies. The asymmetric pump-controlled cylinder is, therefore, used to balance the unequal volume flow through a single rod cylinder in closed-circuit system. This is considered to be an effective method. Nevertheless, the asymmetric axial piston pump (AAPP is a constant displacement pump. In this study, variable-displacement asymmetric axial piston pump (VAPP is investigated according to the same principle used in investigating AAPP. This study, therefore, aims at investigating the characteristics of VAPP. The variable-displacement output of VAPP is implemented by controlling the swash plate angle with angle feedback control circuit, which is composed of a servo proportional valve and an angular displacement sensor. The angular displacement sensor is connected to the swash plate. The simulation model of VAPP, which is set up through the ITI-SimulationX simulation platform, is used to predict VAPP’s characteristics. The purpose of implementing the experiment is to verify the theoretical results. Both the simulation and the experiment results demonstrated that the swash plate angle is controlled by a variable mechanism; when the swash plate angle increases, the flow of Port B and Port T increases while the response speed of Port B and Port T also accelerates. When the swash plate angle is constant, the flow of Port B and Port T increases along with the increase of pump speed, although the pressure-response speed of Port B is faster than that of Port T. Consequently, the flow pulsation of Port B and Port T tends to decrease gradually along with the increase of pump speed. When the pressure loaded on Port B equals to that of Port T, the flow ripple cycle of Port B is longer than that of Port T

  9. Survey of beta-particle interaction experiments with asymmetric matter

    Science.gov (United States)

    Van Horn, J. David; Wu, Fei

    2018-05-01

    Asymmetry is a basic property found at multiple scales in the universe. Asymmetric molecular interactions are fundamental to the operation of biological systems in both signaling and structural roles. Other aspects of asymmetry are observed and useful in many areas of science and engineering, and have been studied since the discovery of chirality in tartrate salts. The observation of parity violation in beta decay provided some impetus for later experiments using asymmetric particles. Here we survey historical work and experiments related to electron (e-) or positron (e+) polarimetry and their interactions with asymmetric materials in gas, liquid and solid forms. Asymmetric interactions may be classified as: 1) stereorecognition, 2) stereoselection and 3) stereoinduction. These three facets of physical stereochemistry are unique but interrelated; and examples from chemistry and materials science illustrate these aspects. Experimental positron and electron interactions with asymmetric materials may be classified in like manner. Thus, a qualitative assessment of helical and polarized positron experiments with different forms of asymmetric matter from the past 40 years is presented, as well as recent experiments with left-hand and right-hand single crystal quartz and organic compounds. The purpose of this classification and review is to evaluate the field for potential new experiments and directions for positron (or electron) studies with asymmetric materials.

  10. SOLAR CONSTRAINTS ON ASYMMETRIC DARK MATTER

    Energy Technology Data Exchange (ETDEWEB)

    Lopes, Ilidio [Centro Multidisciplinar de Astrofisica, Instituto Superior Tecnico, Universidade Tecnica de Lisboa, Av. Rovisco Pais, 1049-001 Lisboa (Portugal); Silk, Joseph, E-mail: ilidio.lopes@ist.utl.pt, E-mail: silk@astro.ox.ac.uk [Institut d' Astrophysique de Paris, F-75014 Paris (France)

    2012-10-01

    The dark matter content of the universe is likely to be a mixture of matter and antimatter, perhaps comparable to the measured asymmetric mixture of baryons and antibaryons. During the early stages of the universe, the dark matter particles are produced in a process similar to baryogenesis, and dark matter freezeout depends on the dark matter asymmetry and the annihilation cross section (s-wave and p-wave annihilation channels) of particles and antiparticles. In these {eta}-parameterized asymmetric dark matter ({eta}ADM) models, the dark matter particles have an annihilation cross section close to the weak interaction cross section, and a value of dark matter asymmetry {eta} close to the baryon asymmetry {eta}{sub B}. Furthermore, we assume that dark matter scattering of baryons, namely, the spin-independent scattering cross section, is of the same order as the range of values suggested by several theoretical particle physics models used to explain the current unexplained events reported in the DAMA/LIBRA, CoGeNT, and CRESST experiments. Here, we constrain {eta}ADM by investigating the impact of such a type of dark matter on the evolution of the Sun, namely, the flux of solar neutrinos and helioseismology. We find that dark matter particles with a mass smaller than 15 GeV, a spin-independent scattering cross section on baryons of the order of a picobarn, and an {eta}-asymmetry with a value in the interval 10{sup -12}-10{sup -10}, would induce a change in solar neutrino fluxes in disagreement with current neutrino flux measurements. This result is also confirmed by helioseismology data. A natural consequence of this model is suppressed annihilation, thereby reducing the tension between indirect and direct dark matter detection experiments, but the model also allows a greatly enhanced annihilation cross section. All the cosmological {eta}ADM scenarios that we discuss have a relic dark matter density {Omega}h {sup 2} and baryon asymmetry {eta}{sub B} in agreement with

  11. SOLAR CONSTRAINTS ON ASYMMETRIC DARK MATTER

    International Nuclear Information System (INIS)

    Lopes, Ilídio; Silk, Joseph

    2012-01-01

    The dark matter content of the universe is likely to be a mixture of matter and antimatter, perhaps comparable to the measured asymmetric mixture of baryons and antibaryons. During the early stages of the universe, the dark matter particles are produced in a process similar to baryogenesis, and dark matter freezeout depends on the dark matter asymmetry and the annihilation cross section (s-wave and p-wave annihilation channels) of particles and antiparticles. In these η-parameterized asymmetric dark matter (ηADM) models, the dark matter particles have an annihilation cross section close to the weak interaction cross section, and a value of dark matter asymmetry η close to the baryon asymmetry η B . Furthermore, we assume that dark matter scattering of baryons, namely, the spin-independent scattering cross section, is of the same order as the range of values suggested by several theoretical particle physics models used to explain the current unexplained events reported in the DAMA/LIBRA, CoGeNT, and CRESST experiments. Here, we constrain ηADM by investigating the impact of such a type of dark matter on the evolution of the Sun, namely, the flux of solar neutrinos and helioseismology. We find that dark matter particles with a mass smaller than 15 GeV, a spin-independent scattering cross section on baryons of the order of a picobarn, and an η-asymmetry with a value in the interval 10 –12 -10 –10 , would induce a change in solar neutrino fluxes in disagreement with current neutrino flux measurements. This result is also confirmed by helioseismology data. A natural consequence of this model is suppressed annihilation, thereby reducing the tension between indirect and direct dark matter detection experiments, but the model also allows a greatly enhanced annihilation cross section. All the cosmological ηADM scenarios that we discuss have a relic dark matter density Ωh 2 and baryon asymmetry η B in agreement with the current WMAP measured values, Ω DM h 2 = 0

  12. The Asymmetric Continental Shelf Wave in Response to the Synoptic Wind Burst in a Semienclosed Double-Shelf Basin

    Science.gov (United States)

    Qu, Lixin; Lin, Xiaopei; Hetland, Robert D.; Guo, Jingsong

    2018-01-01

    The primary goal of this study is to investigate the asymmetric structure of continental shelf wave in a semienclosed double-shelf basin, such as the Yellow Sea. Supported by in situ observations and realistic numerical simulations, it is found that in the Yellow Sea, the shelf wave response to the synoptic wind forcing does not match the mathematically symmetric solution of classic double-shelf wave theory, but rather exhibits a westward shift. To study the formation mechanism of this asymmetric structure, an idealized model was used and two sets of experiments were conducted. The results confirm that the asymmetric structure is due to the existence of a topographic waveguide connecting both shelves. For a semienclosed basin, such as the Yellow Sea, a connection at the end of the basin eliminates the potential vorticity barrier between the two shelves and hence plays a role as a connecting waveguide for shelf waves. This waveguide enables the shelf wave to propagate from one shelf to the other shelf and produces the asymmetric response in sea level and upwind flow evolutions.

  13. Asymmetric quantum well broadband thyristor laser

    Science.gov (United States)

    Liu, Zhen; Wang, Jiaqi; Yu, Hongyan; Zhou, Xuliang; Chen, Weixi; Li, Zhaosong; Wang, Wei; Ding, Ying; Pan, Jiaoqing

    2017-11-01

    A broadband thyristor laser based on InGaAs/GaAs asymmetric quantum well (AQW) is fabricated by metal organic chemical vapor deposition (MOCVD). The 3-μm-wide Fabry-Perot (FP) ridge-waveguide laser shows an S-shape I-V characteristic and exhibits a flat-topped broadband optical spectrum coverage of ~27 nm (Δ-10 dB) at a center wavelength of ~1090 nm with a total output power of 137 mW under pulsed operation. The AQW structure was carefully designed to establish multiple energy states within, in order to broaden the gain spectrum. An obvious blue shift emission, which is not generally acquired in QW laser diodes, is observed in the broadening process of the optical spectrum as the injection current increases. This blue shift spectrum broadening is considered to result from the prominent band-filling effect enhanced by the multiple energy states of the AQW structure, as well as the optical feedback effect contributed by the thyristor laser structure. Project supported by the National Natural Science Foundation of China (Nos. 61604144, 61504137). Zhen Liu and Jiaqi Wang contributed equally to this work.

  14. Asymmetric Cherenkov acoustic reverse in topological insulators

    Science.gov (United States)

    Smirnov, Sergey

    2014-09-01

    A general phenomenon of the Cherenkov radiation known in optics or acoustics of conventional materials is a formation of a forward cone of, respectively, photons or phonons emitted by a particle accelerated above the speed of light or sound in those materials. Here we suggest three-dimensional topological insulators as a unique platform to fundamentally explore and practically exploit the acoustic aspect of the Cherenkov effect. We demonstrate that by applying an in-plane magnetic field to a surface of a three-dimensional topological insulator one may suppress the forward Cherenkov sound up to zero at a critical magnetic field. Above the critical field the Cherenkov sound acquires pure backward nature with the polar distribution differing from the forward one generated below the critical field. Potential applications of this asymmetric Cherenkov reverse are in the design of low energy electronic devices such as acoustic ratchets or, in general, in low power design of electronic circuits with a magnetic field control of the direction and magnitude of the Cherenkov dissipation.

  15. Asymmetric Spatial Processing Under Cognitive Load

    Directory of Open Access Journals (Sweden)

    Lien Naert

    2018-04-01

    Full Text Available Spatial attention allows us to selectively process information within a certain location in space. Despite the vast literature on spatial attention, the effect of cognitive load on spatial processing is still not fully understood. In this study we added cognitive load to a spatial processing task, so as to see whether it would differentially impact upon the processing of visual information in the left versus the right hemispace. The main paradigm consisted of a detection task that was performed during the maintenance interval of a verbal working memory task. We found that increasing cognitive working memory load had a more negative impact on detecting targets presented on the left side compared to those on the right side. The strength of the load effect correlated with the strength of the interaction on an individual level. The implications of an asymmetric attentional bias with a relative disadvantage for the left (vs the right hemispace under high verbal working memory (WM load are discussed.

  16. Collaborative hierarchy maintains cooperation in asymmetric games.

    Science.gov (United States)

    Antonioni, Alberto; Pereda, María; Cronin, Katherine A; Tomassini, Marco; Sánchez, Angel

    2018-03-29

    The interplay of social structure and cooperative behavior is under much scrutiny lately as behavior in social contexts becomes increasingly relevant for everyday life. Earlier experimental work showed that the existence of a social hierarchy, earned through competition, was detrimental for the evolution of cooperative behaviors. Here, we study the case in which individuals are ranked in a hierarchical structure based on their performance in a collective effort by having them play a Public Goods Game. In the first treatment, participants are ranked according to group earnings while, in the second treatment, their rankings are based on individual earnings. Subsequently, participants play asymmetric Prisoner's Dilemma games where higher-ranked players gain more than lower ones. Our experiments show that there are no detrimental effects of the hierarchy formed based on group performance, yet when ranking is assigned individually we observe a decrease in cooperation. Our results show that different levels of cooperation arise from the fact that subjects are interpreting rankings as a reputation which carries information about which subjects were cooperators in the previous phase. Our results demonstrate that noting the manner in which a hierarchy is established is essential for understanding its effects on cooperation.

  17. Climate policy, asymmetric information and firm survival

    International Nuclear Information System (INIS)

    Hagem, C.

    2001-02-01

    The purpose of this paper is to compare the effect of different domestic climate policy instruments under asymmetric information when the regulator wants to secure the survival of a specific firm. It is a well-known result from economic theory that emission taxes lead to a cost-effective distribution of abatement across polluters. However, if the regulator wants to ensure the survival of a specific firm, it may need to design policy instruments that reduce the firm's cost of complying with an emission tax regime. The climate policy instruments considered in this paper are tradable emission permits with distribution of free permits, emission taxes in combination with a fixed subsidy, and two types of voluntary agreements. It demonstrates first that if distributing free tradable permits shall have a preventing effect, the allocation of permits has to be made contingent on production. It further shows that a voluntary agreement where a specific abatement target is set by the regulator can prevent a shutdown but leads to lower welfare than the use of emission taxes in combination with a fixed subsidy. And finally it illustrates that a voluntary agreement designed as a menu of abatement contracts increases social welfare compared to an emission tax regime

  18. Performance of an AGATA asymmetric detector

    Energy Technology Data Exchange (ETDEWEB)

    Boston, A.J. [Department of Physics, University of Liverpool, Liverpool L69 7ZE (United Kingdom)], E-mail: ajboston@liv.ac.uk; Dimmock, M.R.; Unsworth, C.; Boston, H.C.; Cooper, R.J.; Grint, A.N.; Harkness, L.J. [Department of Physics, University of Liverpool, Liverpool L69 7ZE (United Kingdom); Lazarus, I.H. [STFC Daresbury Laboratory, Daresbury, Warrington WA4 4AD (United Kingdom); Jones, M.; Nolan, P.J.; Oxley, D.C. [Department of Physics, University of Liverpool, Liverpool L69 7ZE (United Kingdom); Simpson, J. [STFC Daresbury Laboratory, Daresbury, Warrington WA4 4AD (United Kingdom); Slee, M. [Department of Physics, University of Liverpool, Liverpool L69 7ZE (United Kingdom)

    2009-06-01

    High-resolution gamma-ray detectors based on high-purity germanium crystals (HPGe) are one of the key workhorses of experimental nuclear science. The technical development of such detector technology has been dramatic in recent years. Large volume, high-granularity, electrically segmented HPGe detectors have been realised and a methodology to improve position sensitivity using pulse-shape analysis coupled with the novel technique of gamma-ray tracking has been developed. Collaborations have been established in Europe (Advanced GAmma Tracking Array (AGATA)) [J. Simpson, Acta Phys. Pol. B 36 (2005) 1383] and the USA (GRETA/GRETINA) [C.W. Beausang, Nucl. Instr. and Meth. B 204 (2003)] to build gamma-ray tracking spectrometers. This paper discusses the performance of the first AGATA asymmetric detector that has been tested at the University of Liverpool. The use of a fully digital data acquisition system has allowed detector charge pulse shapes from a selection of well-defined photon interaction positions to be analysed, yielding important information on the position sensitivity of the detector.

  19. Asymmetric Dark Matter and Dark Radiation

    International Nuclear Information System (INIS)

    Blennow, Mattias; Martinez, Enrique Fernandez; Mena, Olga; Redondo, Javier; Serra, Paolo

    2012-01-01

    Asymmetric Dark Matter (ADM) models invoke a particle-antiparticle asymmetry, similar to the one observed in the Baryon sector, to account for the Dark Matter (DM) abundance. Both asymmetries are usually generated by the same mechanism and generally related, thus predicting DM masses around 5 GeV in order to obtain the correct density. The main challenge for successful models is to ensure efficient annihilation of the thermally produced symmetric component of such a light DM candidate without violating constraints from collider or direct searches. A common way to overcome this involves a light mediator, into which DM can efficiently annihilate and which subsequently decays into Standard Model particles. Here we explore the scenario where the light mediator decays instead into lighter degrees of freedom in the dark sector that act as radiation in the early Universe. While this assumption makes indirect DM searches challenging, it leads to signals of extra radiation at BBN and CMB. Under certain conditions, precise measurements of the number of relativistic species, such as those expected from the Planck satellite, can provide information on the structure of the dark sector. We also discuss the constraints of the interactions between DM and Dark Radiation from their imprint in the matter power spectrum

  20. Asymmetric adaptations to energy price changes

    International Nuclear Information System (INIS)

    Kuper, G.H.; Van Soest, D.P.

    1999-01-01

    The effectiveness of policies to reduce the use of energy depend on the elasticity of substitution between the various inputs and on the rate of technological progress. This paper presents a theoretical model emphasising energy investment characteristics of uncertainty and irreversibility that result in testable hypotheses concerning the relative values of substitution parameters and rates of technological change in periods of high and increasing energy prices and in periods of low prices. Estimation results for a panel of sectors of the Dutch economy show that the elasticity of substitution between energy and other inputs is low in periods of low energy prices, whereas it is significantly higher in the preceding period of high and increasing energy prices. Furthermore, energy-saving technological progress in periods of high and increasing energy prices is also significantly higher than if energy prices are low and falling. The regression results suggest that, due this asymmetric response of firms to changes in energy prices, taxing energy in the current period of low energy prices will not yield substantial reductions in energy use of Dutch industry. 21 refs

  1. Trade Credit Insurance and Asymmetric Information Problem

    Directory of Open Access Journals (Sweden)

    Sokolovska Olena

    2017-03-01

    Full Text Available The presence of different risk factors in international trade gives evidence of the necessity of support in gaps that may affect exporters’ activity. To maximize the trade volumes and in the same time to minimize the exporters’ risks the stakeholders use trade credit insurance. The paper provides analysis of conceptual background of the trade credit insurance in the world. We analyzed briefly the problems, arising in insurance markets due to asymmetric information, such as adverse selection and moral hazard. Also we discuss the main stages of development of trade credit insurance in countries worldwide. Using comparative and graphical analysis we provide a brief evaluation of the dynamics of claims and recoveries for different forms of trade credit insurance. We found that the claims related to the commercial risk for medium and long trade credits in recent years exceed the recoveries, while with the political risk the reverse trend holds. And we originally consider these findings in terms of information asymmetry in the trade credit insurance differentiated by type of risk.

  2. Asymmetric sensory reweighting in human upright stance.

    Directory of Open Access Journals (Sweden)

    David Logan

    Full Text Available To investigate sensory reweighting as a fundamental property of sensor fusion during standing, we probed postural control with simultaneous rotations of the visual scene and surface of support. Nineteen subjects were presented with pseudo-random pitch rotations of visual scene and platform at the ankle to test for amplitude dependencies in the following conditions: low amplitude vision: high amplitude platform, low amplitude vision: low amplitude platform, and high amplitude vision: low amplitude platform. Gain and phase of frequency response functions (FRFs to each stimulus were computed for two body sway angles and a single weighted EMG signal recorded from seven muscles. When platform stimulus amplitude was increased while visual stimulus amplitude remained constant, gain to vision increased, providing strong evidence for inter-modal reweighting between vision and somatosensation during standing. Intra-modal reweighting of vision was also observed as gains to vision decreased as visual stimulus amplitude increased. Such intra-modal and inter-modal amplitude dependent changes in gain were also observed in muscular activity. Gains of leg segment angle and muscular activity relative to the platform, on the other hand, showed only intra-modal reweighting. That is, changing platform motion amplitude altered the responses to both visual and support surface motion whereas changing visual scene motion amplitude did not significantly affect responses to support surface motion, indicating that the sensory integration scheme between somatosensation (at the support surface and vision is asymmetric.

  3. Micromagnetic simulation of Fe asymmetric nanorings

    International Nuclear Information System (INIS)

    Palma, J.L.; Morales-Concha, C.; Leighton, B.; Altbir, D.; Escrig, J.

    2012-01-01

    During the last decade several methods to control the vortex chirality in nanodots have been proposed. One of them, the introduction of asymmetry in the geometry of the dots, originates interesting effects on the magnetic behavior of the particle. However, asymmetry in core-free structures is also interesting to investigate because of the reproducibility of their magnetic properties. In this work we report systematic changes in the coercivity and remanence in asymmetric nanorings. The angular dependence is also addressed. For specific geometries and magnetic field direction newly reversal modes appear associated with important changes in the coercivity and remanence of the rings. - Highlights: → We report that the existence of asymmetry strongly influences the coercivity and the remanence. → Magnetization reversal is driven by the nucleation of a C state and propagation of a vortex state. → We also conclude that the lack of a core contributes to the stability of the vortex state. → Asymmetry can be useful for tailoring specific magnetic characteristics of these systems.

  4. Optimal multicopy asymmetric Gaussian cloning of coherent states

    Science.gov (United States)

    Fiurášek, Jaromír; Cerf, Nicolas J.

    2007-05-01

    We investigate the asymmetric Gaussian cloning of coherent states which produces M copies from N input replicas in such a way that the fidelity of each copy may be different. We show that the optimal asymmetric Gaussian cloning can be performed with a single phase-insensitive amplifier and an array of beam splitters. We obtain a simple analytical expression characterizing the set of optimal asymmetric Gaussian cloning machines and prove the optimality of these cloners using the formalism of Gaussian completely positive maps and semidefinite programming techniques. We also present an alternative implementation of the asymmetric cloning machine where the phase-insensitive amplifier is replaced with a beam splitter, heterodyne detector, and feedforward.

  5. Asymmetrical Polymer Vesicles for Drug delivery and Other Applications

    Directory of Open Access Journals (Sweden)

    Yi Zhao

    2017-06-01

    Full Text Available Scientists have been attracted by polymersomes as versatile drug delivery systems since the last two decades. Polymersomes have the potential to be versatile drug delivery systems because of their tunable membrane formulations, stabilities in vivo, various physicochemical properties, controlled release mechanisms, targeting abilities, and capacities to encapsulate a wide range of drugs and other molecules. Asymmetrical polymersomes are nano- to micro-sized polymeric capsules with asymmetrical membranes, which means, they have different outer and inner coronas so that they can exhibit better endocytosis rate and endosomal escape ability than other polymeric systems with symmetrical membranes. Hence, asymmetrical polymersomes are highly promising as self-assembled nano-delivery systems in the future for in vivo therapeutics delivery and diagnostic imaging applications. In this review, we prepared a summary about recent research progresses of asymmetrical polymersomes in the following aspects: synthesis, preparation, applications in drug delivery and others.

  6. All conducting polymer electrodes for asymmetric solid-state supercapacitors

    KAUST Repository

    Kurra, Narendra; Wang, Ruiqi; Alshareef, Husam N.

    2015-01-01

    electrode material. In addition, the high stability of PEDOT in its oxidised state makes it capable to exhibit electrochemical activity in a wide potential window. This can qualify PEDOT to be used as a negative electrode in fabricating asymmetric solid

  7. Outage Analysis of Asymmetric RF-FSO Systems

    KAUST Repository

    Ansari, Imran Shafique; Abdallah, Mohamed M.; Alouini, Mohamed-Slim; Qaraqe, Khalid A.

    2017-01-01

    In this work, the outage performance analysis of a dual-hop transmission system composed of asymmetric radio frequency (RF) channels cascaded with free-space optical (FSO) links is presented. The RF links are modeled by the Rayleigh fading

  8. Asymmetric H-D exchange reactions of fluorinated aromatic ketones

    KAUST Repository

    Zhao, Yujun; Lim, XiaoZhi; Pan, Yuanhang; Zong, Lili; Feng, Wei; Tan, Choonhong; Huang, Kuo-Wei

    2012-01-01

    Chiral bicyclic guanidine catalyzes the asymmetric H-D exchange reactions. Up to 30% ee was achieved. DFT calculations were employed to elucidate and explain the origin of the reaction's stereoselectivity. © 2012 The Royal Society of Chemistry.

  9. Polarization dependent switching of asymmetric nanorings with a circular field

    Directory of Open Access Journals (Sweden)

    Nihar R. Pradhan

    2016-01-01

    Full Text Available We experimentally investigated the switching from onion to vortex states in asymmetric cobalt nanorings by an applied circular field. An in-plane field is applied along the symmetric or asymmetric axis of the ring to establish domain walls (DWs with symmetric or asymmetric polarization. A circular field is then applied to switch from the onion state to the vortex state, moving the DWs in the process. The asymmetry of the ring leads to different switching fields depending on the location of the DWs and direction of applied field. For polarization along the asymmetric axis, the field required to move the DWs to the narrow side of the ring is smaller than the field required to move the DWs to the larger side of the ring. For polarization along the symmetric axis, establishing one DW in the narrow side and one on the wide side, the field required to switch to the vortex state is an intermediate value.

  10. Optimal multicopy asymmetric Gaussian cloning of coherent states

    International Nuclear Information System (INIS)

    Fiurasek, Jaromir; Cerf, Nicolas J.

    2007-01-01

    We investigate the asymmetric Gaussian cloning of coherent states which produces M copies from N input replicas in such a way that the fidelity of each copy may be different. We show that the optimal asymmetric Gaussian cloning can be performed with a single phase-insensitive amplifier and an array of beam splitters. We obtain a simple analytical expression characterizing the set of optimal asymmetric Gaussian cloning machines and prove the optimality of these cloners using the formalism of Gaussian completely positive maps and semidefinite programming techniques. We also present an alternative implementation of the asymmetric cloning machine where the phase-insensitive amplifier is replaced with a beam splitter, heterodyne detector, and feedforward

  11. Asymmetric continuum extreme processes in solids and fluids

    CERN Document Server

    Teisseyre, Roman

    2014-01-01

    This book deals with a class of basic deformations in asymmetric continuum theory. It describes molecular deformations and transport velocities in fluids, strain deformations in solids as well as the molecular transport, important in fracture processes.

  12. Asymmetric H-D exchange reactions of fluorinated aromatic ketones

    KAUST Repository

    Zhao, Yujun

    2012-01-01

    Chiral bicyclic guanidine catalyzes the asymmetric H-D exchange reactions. Up to 30% ee was achieved. DFT calculations were employed to elucidate and explain the origin of the reaction\\'s stereoselectivity. © 2012 The Royal Society of Chemistry.

  13. Index profile measurement of asymmetrical elliptical preforms or fibers

    NARCIS (Netherlands)

    Blitterswijk, van W.; Smit, M.K.

    1987-01-01

    An extension of the beam-deflection method to the case of elliptical preforms with eccentric core (asymmetrical elliptical preforms) is presented, which can be easily implemented on automatic measurement equipment

  14. Pseudo-Goldstone modes in isospin-asymmetric nuclear matter

    International Nuclear Information System (INIS)

    Cohen, T.D.; Broniowski, W.

    1995-01-01

    The authors analyze the chiral limit in dense isospin-asymmetric nuclear matter. It is shown that the pseudo-Goldstone modes in this system are qualitatively different from the case of isospin-symmetric matter

  15. Subglottic cysts and asymmetrical subglottic narrowing on neck radiograph

    International Nuclear Information System (INIS)

    Holinger, L.D.; Torium, D.M.; Anandappa, E.C.

    1988-01-01

    The congenital subglottic hemangioma typically appears as an asymmetric subglottic narrowing or mass on frontal neck radiograph. Therefore, soft tissue neck radiography has been advocated as a definitive non-operative approach for diagnosing these lesions. However, we have noted similar asymmetric subglottic narrowing in patients with acquired subglottic cysts. These retention cysts occur following long-term intubation in the neonate. The mechanism probably involves subglottic fibrosis which obstructs glands with subsequent cyst formation. Acquired subglottic cysts typically appear as an asymmetric narrowing on frontal or lateral soft tissue neck radiographs. These lesions may produce airway compromise but are effectively treated by forceps or laser removal. Acquired subglottic cysts must be included in the differential diagnosis of asymmetric subglottic narrowing. The definitive diagnosis is made by direct laryngoscopy, not soft tissue neck radiograph. (orig.)

  16. Asymmetric periflexural exanthema: A report in an adult patient

    Directory of Open Access Journals (Sweden)

    Zawar V

    2003-11-01

    Full Text Available Asymmetric periflexural exanthem (APE is a distinctive exanthem, probably viral in origin. It is largely a disease of childhood and is uncommon in adults. We report an adult man presenting with the typical clinical findings of APE.

  17. Fourier synthesis of asymmetrical optical potentials for atoms

    International Nuclear Information System (INIS)

    Ritt, G.

    2007-01-01

    In this work a dissipationless asymmetrical optical potential for cold atoms was produced. In a first step a new type of optical lattice was generated, whose spatial periodicity only corresponds to a quarter of the wavelength of the light used for the generation. This corresponds to the half of the periodicity of a conventional optical lattice, which is formed by the light of the same wavelength. The generation of this new type of optical lattice was reached by the use of two degenerated raman transitions. Virtual processes occur, in which four photons are involved. In conventional optical lattices however virtual two-photon processes occur. By spatially superimposing this optical lattice with a conventional optical lattice an asymmetrical optical potential could be formed. By diffraction of a Bose Einstein condensate of rubidium atoms at the transient activated asymmetrical potential the asymmetrical structure was proven. (orig.)

  18. Kinematics and Dynamics of an Asymmetrical Parallel Robotic Wrist

    DEFF Research Database (Denmark)

    Wu, Guanglei

    2014-01-01

    This paper introduces an asymmetrical parallel robotic wrist, which can generate a decoupled unlimited-torsion motion and achieve high positioning accuracy. The kinematics, dexterity, and singularities of the manipulator are investigated to visualize the performance contours of the manipulator...

  19. Vertical Control and Parallel Trade under Asymmetric Information

    Directory of Open Access Journals (Sweden)

    Alessandro Avenali

    2015-05-01

    profits from the manufacturer to the wholesaler. Therefore, in R&D-intensive industries, such as pharmaceuticals, policy makers should anticipate the likely consequences of PT under asymmetric information on the long-run incentives to innovate.

  20. Mechanism and kinetics of the loss of poorly soluble drugs from liposomal carriers studied by a novel flow field-flow fractionation-based drug release-/transfer-assay

    DEFF Research Database (Denmark)

    Hinna, Askell Hvid; Hupfeld, Stefan; Kuntsche, Judith

    2016-01-01

    Liposomes represent a versatile drug formulation approach e.g. for improving the water-solubility of poorly soluble drugs but also to achieve drug targeting and controlled release. For the latter applications it is essential that the drug remains associated with the liposomal carrier during transit...... in the vascular bed. A range of in vitro test methods has been suggested over the years for prediction of the release of drug from liposomal carriers. The majority of these fail to give a realistic prediction for poorly water-soluble drugs due to the intrinsic tendency of such compounds to remain associated...... the amount of drug remaining associated with the liposomal drug carrier as well as that transferred to the acceptor liposomes at distinct times of incubation, boththe kinetics of drug transfer and release to the water phase could be established for the model drug p-THPP (5,10,15,20-tetrakis(4-hydroxyphenyl...

  1. A Numerical Analysis of Droplet Breakup in Asymmetric T-Junctions with Different Outlet Pressure Gradients

    Science.gov (United States)

    Cheng, Way Lee; Han, Arum; Sadr, Reza

    2016-11-01

    Droplet splitting is the breakup of a parent droplet into two or more daughter droplets of desired sizes. It is done to improve production efficiency and investigational capacity in microfluidic devices. Passive splitting is the breakup of droplets into precise volume ratios at predetermined locations without external power sources. In this study, a 3-D simulation was conducted using the Volume-of-Fluid method to analysis the breakup process of a droplet in asymmetric T-junctions with different outlet arm lengths. The arrangement allows a droplet to be split into two smaller droplets of different sizes, where the volumetric ratio of the daughter droplets depends on the length ratios of the outlet arms. The study identified different breakup regimes such as primary, transition, bubble and non-breakup under different flow conditions and channel configurations. Furthermore, a close analysis to the primary breakup regimes were done to determine the breakup mechanisms at various flow conditions. The analysis show that the breakup mechanisms in asymmetric T-junctions is different than a regular split. A pseudo-phenomenological model for the breakup criteria was presented at the end. The model was an expanded version to a theoretically derived model for the symmetric droplet breakup. The Qatar National Research Fund (a member of the Qatar Founda- tion), under Grant NPRP 5-671-2-278, supported this work.

  2. CFD simulation of a four-loop PWR at asymmetric operation conditions

    Energy Technology Data Exchange (ETDEWEB)

    Cheng, Jian-Ping; Yan, Li-Ming; Li, Feng-Chen, E-mail: lifch@hit.edu.cn

    2016-04-15

    Highlights: • A CFD numerical simulation procedure was established for simulating RPV of VVER-1000. • The established CFD approach was validated by comparing with available data. • Thermal hydraulic characteristics under asymmetric operation condition were investigated. • Apparent influences of the shutdown loop on its neighboring loops were obtained. - Abstract: The pressurized water reactor (PWR) with multiple loops may have abnormal working conditions with coolant pumps out of running in some loops. In this paper, a computational fluid dynamics (CFD) numerical study of the four-loop VVER-1000 PWR pressure vessel model was presented. Numerical simulations of the thermohydrodynamic characteristics in the pressure vessel were carried out at different inlet conditions with four and three loops running, respectively. At normal stead-state condition (four-loop running), different parameters were obtained for the full fluid domain, including pressure losses across different parts, pressure, velocity and temperature distributions in the reactor pressure vessel (RPV) and mass flow distribution of the coolant at the inlet of reactor core. The obtained results for pressure losses matched with the experimental reference values of the VVER-1000 PWR at Tianwan nuclear power plant (NPP). For most fuel assemblies (FAs), the inlet flow rates presented a symmetrical distribution about the center under full-loop operation conditions, which accorded with the practical distribution. These results indicate that it is now possible to study the dynamic transition process between different asymmetric operation conditions in a multi-loop PWR using the established CFD method.

  3. A method of the asymmetric Abel's inversion in plasma diagnosis

    International Nuclear Information System (INIS)

    Matoba, Tohru; Funahashi, Akimasa

    1975-09-01

    In the case of a noncylindrical plasma, axis symmetric components are drawn from observed projected intensities of physical quantities, assuming an asymmetric form. And the radial intensity distribution is determined by Abel's inversion method. The best fitting curve is obtained analytically from measured values by the least-square estimation of nonlinear parameters. The cylindrical symmetric Abel's inversion code ( ABELIC ) and the asymmetric Abel's inversion code ( ABELILSENP 2 ) are described. (auth.)

  4. Fluorescent nanohybrids based on asymmetrical cyanine dyes decorated carbon nanotubes

    OpenAIRE

    Çavuşlar, Özge; Cavuslar, Ozge

    2015-01-01

    In this thesis, we focused on imparting new optical properties to carbon nanotubes (CNTs) to allow their optical detection and visualization in biomedical applications. We investigated the interactions of CNTs and DNA wrapped CNTs with asymmetrical cyanine dye molecules to study the applicability of resulting hybrid materials to fluorescent based systems. When CNTs interacted with asymmetrical cyanine dyes, they constructed a light absorbing nanoarray. However, the fluorescence emission of th...

  5. Asymmetric Effects on Escape Rates of Bistable System

    International Nuclear Information System (INIS)

    Wang Canjun; Mei Dongcheng; Dai Zucheng

    2011-01-01

    The asymmetric effects on the escape rates from the stable states x ± in the bistable system are analyzed. The results indicate that the multiplicative noise and the additive noise always enhance the particle escape from stable states x ± of bistable. However, the asymmetric parameter r enhances the particle escape from stable state x + , and holds back the particle escape from stable state x - . (general)

  6. Method development of damage detection in asymmetric buildings

    Science.gov (United States)

    Wang, Yi; Thambiratnam, David P.; Chan, Tommy H. T.; Nguyen, Andy

    2018-01-01

    Aesthetics and functionality requirements have caused most buildings to be asymmetric in recent times. Such buildings exhibit complex vibration characteristics under dynamic loads as there is coupling between the lateral and torsional components of vibration, and are referred to as torsionally coupled buildings. These buildings require three dimensional modelling and analysis. In spite of much recent research and some successful applications of vibration based damage detection methods to civil structures in recent years, the applications to asymmetric buildings has been a challenging task for structural engineers. There has been relatively little research on detecting and locating damage specific to torsionally coupled asymmetric buildings. This paper aims to compare the difference in vibration behaviour between symmetric and asymmetric buildings and then use the vibration characteristics for predicting damage in them. The need for developing a special method to detect damage in asymmetric buildings thus becomes evident. Towards this end, this paper modifies the traditional modal strain energy based damage index by decomposing the mode shapes into their lateral and vertical components and to form component specific damage indices. The improved approach is then developed by combining the modified strain energy based damage indices with the modal flexibility method which was modified to suit three dimensional structures to form a new damage indicator. The procedure is illustrated through numerical studies conducted on three dimensional five-story symmetric and asymmetric frame structures with the same layout, after validating the modelling techniques through experimental testing of a laboratory scale asymmetric building model. Vibration parameters obtained from finite element analysis of the intact and damaged building models are then applied into the proposed algorithms for detecting and locating the single and multiple damages in these buildings. The results

  7. Asymmetric Price Transmission in Indonesia's Wheat Flour Market

    OpenAIRE

    Varela, Gonzalo J.; Taniguchi, Kiyoshi

    2014-01-01

    Data indicate that its domestic price in Indonesia has been increasing regardless of movements in the international price of wheat. A test for asymmetric price transmission from international wheat to domestic wheat flour markets is conducted using an error correction model and find the presence of asymmetric price transmission. The upward adjustment in the domestic price of wheat flour is much faster than its adjustment downward when it deviates from long-run equilibrium. Our results are rob...

  8. Project financing versus corporate financing under asymmetric information

    OpenAIRE

    Anton Miglo

    2008-01-01

    In recent years financing through the creation of an independent project company or financing by non-recourse debt has become an important part of corporate decisions. Shah and Thakor (JET, 1987) argue that project financing can be optimal when asymmetric information exists between firm's insiders and market participants. In contrast to that paper, we provide an asymmetric information argument for project financing without relying on corporate taxes, costly information production or an assump...

  9. Asymmetric Shaped-Pattern Synthesis for Planar Antenna Arrays

    Directory of Open Access Journals (Sweden)

    T. M. Bruintjes

    2016-01-01

    Full Text Available A procedure to synthesize asymmetrically shaped beam patterns is developed for planar antenna arrays. As it is based on the quasi-analytical method of collapsed distributions, the main advantage of this procedure is the ability to realize a shaped (null-free region with very low ripple. Smooth and asymmetrically shaped regions can be used for Direction-of-Arrival estimation and subsequently for efficient tracking with a single output (fully analog beamformer.

  10. Asymmetric strand segregation: epigenetic costs of genetic fidelity?

    Directory of Open Access Journals (Sweden)

    Diane P Genereux

    2009-06-01

    Full Text Available Asymmetric strand segregation has been proposed as a mechanism to minimize effective mutation rates in epithelial tissues. Under asymmetric strand segregation, the double-stranded molecule that contains the oldest DNA strand is preferentially targeted to the somatic stem cell after each round of DNA replication. This oldest DNA strand is expected to have fewer errors than younger strands because some of the errors that arise on daughter strands during their synthesis fail to be repaired. Empirical findings suggest the possibility of asymmetric strand segregation in a subset of mammalian cell lineages, indicating that it may indeed function to increase genetic fidelity. However, the implications of asymmetric strand segregation for the fidelity of epigenetic information remain unexplored. Here, I explore the impact of strand-segregation dynamics on epigenetic fidelity using a mathematical-modelling approach that draws on the known molecular mechanisms of DNA methylation and existing rate estimates from empirical methylation data. I find that, for a wide range of starting methylation densities, asymmetric -- but not symmetric -- strand segregation leads to systematic increases in methylation levels if parent strands are subject to de novo methylation events. I found that epigenetic fidelity can be compromised when enhanced genetic fidelity is achieved through asymmetric strand segregation. Strand segregation dynamics could thus explain the increased DNA methylation densities that are observed in structured cellular populations during aging and in disease.

  11. Orientation- and position-controlled alignment of asymmetric silicon microrod on a substrate with asymmetric electrodes

    Science.gov (United States)

    Shibata, Akihide; Watanabe, Keiji; Sato, Takuya; Kotaki, Hiroshi; Schuele, Paul J.; Crowder, Mark A.; Zhan, Changqing; Hartzell, John W.; Nakatani, Ryoichi

    2014-03-01

    In this paper, we demonstrate the orientation-controlled alignment of asymmetric Si microrods on a glass substrate with an asymmetric pair of electrodes. The Si microrods have the shape of a paddle with a blade and a shaft part, and the pair of electrodes consists of a narrow electrode and a wide electrode. By applying AC bias to the electrodes, the Si microrods suspended in a fluid align in such a way to settle across the electrode pair, and over 80% of the aligned Si microrods have an orientation with the blade and the shaft of the paddle on the wide and the narrow electrodes, respectively. When Si microrods have a shell of dielectric film and its thickness on the top face is thicker than that on the bottom face, 97.8% of the Si microrods are aligned with the top face facing upwards. This technique is useful for orientation-controlled alignment of nano- and microsized devices that have polarity or a distinction between the top and bottom faces.

  12. Asymmetric Facial Bone Fragmentation Mirrors Asymmetric Distribution of Cranial Neuromasts in Blind Mexican Cavefish

    Directory of Open Access Journals (Sweden)

    Joshua B. Gross

    2016-10-01

    Full Text Available Craniofacial asymmetry is a convergent trait widely distributed across animals that colonize the extreme cave environment. Although craniofacial asymmetry can be discerned easily, other complex phenotypes (such as sensory organ position and numerical variation are challenging to score and compare. Certain bones of the craniofacial complex demonstrate substantial asymmetry, and co-localize to regions harboring dramatically expanded numbers of mechanosensory neuromasts. To determine if a relationship exists between this expansion and bone fragmentation in cavefish, we developed a quantitative measure of positional symmetry across the left-right axis. We found that three different cave-dwelling populations were significantly more asymmetric compared to surface-dwelling fish. Moreover, cave populations did not differ in the degree of neuromast asymmetry. This work establishes a method for quantifying symmetry of a complex phenotype, and demonstrates that facial bone fragmentation mirrors the asymmetric distribution of neuromasts in different cavefish populations. Further developmental studies will provide a clearer picture of the developmental and cellular changes that accompany this extreme phenotype, and help illuminate the genetic basis for facial asymmetry in vertebrates.

  13. Chilly dark sectors and asymmetric reheating

    International Nuclear Information System (INIS)

    Adshead, Peter; Cui, Yanou; Shelton, Jessie

    2016-01-01

    In a broad class of theories, the relic abundance of dark matter is determined by interactions internal to a thermalized dark sector, with no direct involvement of the Standard Model (SM). We point out that these theories raise an immediate cosmological question: how was the dark sector initially populated in the early universe? Motivated in part by the difficulty of accommodating large amounts of entropy carried in dark radiation with cosmic microwave background measurements of the effective number of relativistic species at recombination, N eff , we aim to establish which admissible cosmological histories can populate a thermal dark sector that never reaches thermal equilibrium with the SM. The minimal cosmological origin for such a dark sector is asymmetric reheating, when the same mechanism that populates the SM in the early universe also populates the dark sector at a lower temperature. Here we demonstrate that the resulting inevitable inflaton-mediated scattering between the dark sector and the SM can wash out a would-be temperature asymmetry, and establish the regions of parameter space where temperature asymmetries can be generated in minimal reheating scenarios. Thus obtaining a temperature asymmetry of a given size either restricts possible inflaton masses and couplings or necessitates a non-minimal cosmology for one or both sectors. As a side benefit, we develop techniques for evaluating collision terms in the relativistic Boltzmann equation when the full dependence on Bose-Einstein or Fermi-Dirac phase space distributions must be retained, and present several new results on relativistic thermal averages in an appendix.

  14. Chilly dark sectors and asymmetric reheating

    Energy Technology Data Exchange (ETDEWEB)

    Adshead, Peter [Department of Physics, University of Illinois at Urbana-Champaign,Urbana, IL 61801 (United States); Cui, Yanou [Perimeter Institute for Theoretical Physics,Waterloo, Ontario N2L 2Y5 (Canada); Maryland Center for Fundamental Physics, University of Maryland,College Park, MD 20742 (United States); Shelton, Jessie [Department of Physics, University of Illinois at Urbana-Champaign,Urbana, IL 61801 (United States)

    2016-06-06

    In a broad class of theories, the relic abundance of dark matter is determined by interactions internal to a thermalized dark sector, with no direct involvement of the Standard Model (SM). We point out that these theories raise an immediate cosmological question: how was the dark sector initially populated in the early universe? Motivated in part by the difficulty of accommodating large amounts of entropy carried in dark radiation with cosmic microwave background measurements of the effective number of relativistic species at recombination, N{sub eff}, we aim to establish which admissible cosmological histories can populate a thermal dark sector that never reaches thermal equilibrium with the SM. The minimal cosmological origin for such a dark sector is asymmetric reheating, when the same mechanism that populates the SM in the early universe also populates the dark sector at a lower temperature. Here we demonstrate that the resulting inevitable inflaton-mediated scattering between the dark sector and the SM can wash out a would-be temperature asymmetry, and establish the regions of parameter space where temperature asymmetries can be generated in minimal reheating scenarios. Thus obtaining a temperature asymmetry of a given size either restricts possible inflaton masses and couplings or necessitates a non-minimal cosmology for one or both sectors. As a side benefit, we develop techniques for evaluating collision terms in the relativistic Boltzmann equation when the full dependence on Bose-Einstein or Fermi-Dirac phase space distributions must be retained, and present several new results on relativistic thermal averages in an appendix.

  15. Asymmetric inhibitory treatment effects in multilingual aphasia.

    Science.gov (United States)

    Goral, Mira; Naghibolhosseini, Maryam; Conner, Peggy S

    2013-01-01

    Findings from recent psycholinguistic studies of bilingual processing support the hypothesis that both languages of a bilingual are always active and that bilinguals continually engage in processes of language selection. This view aligns with the convergence hypothesis of bilingual language representation. Furthermore, it is hypothesized that when bilinguals perform a task in one language they need to inhibit their other, nontarget language(s) and that stronger inhibition is required when the task is performed in the weaker language than in the stronger one. The study of multilingual individuals who acquire aphasia resulting from a focal brain lesion offers a unique opportunity to test the convergence hypothesis and the inhibition asymmetry. We report on a trilingual person with chronic nonfluent aphasia who at the time of testing demonstrated greater impairment in her first acquired language (Persian) than in her third, later learned language (English). She received treatment in English followed by treatment in Persian. An examination of her connected language production revealed improvement in her grammatical skills in each language following intervention in that language, but decreased grammatical accuracy in English following treatment in Persian. The increased error rate was evident in structures that are used differently in the two languages (e.g., auxiliary verbs). The results support the prediction that greater inhibition is applied to the stronger language than to the weaker language, regardless of their age of acquisition. We interpret the findings as consistent with convergence theories that posit overlapping neuronal representation and simultaneous activation of multiple languages and with proficiency-dependent asymmetric inhibition in multilinguals.

  16. Chilly dark sectors and asymmetric reheating

    Science.gov (United States)

    Adshead, Peter; Cui, Yanou; Shelton, Jessie

    2016-06-01

    In a broad class of theories, the relic abundance of dark matter is determined by interactions internal to a thermalized dark sector, with no direct involvement of the Standard Model (SM). We point out that these theories raise an immediate cosmological question: how was the dark sector initially populated in the early universe? Motivated in part by the difficulty of accommodating large amounts of entropy carried in dark radiation with cosmic microwave background measurements of the effective number of relativistic species at recombination, N eff , we aim to establish which admissible cosmological histories can populate a thermal dark sector that never reaches thermal equilibrium with the SM. The minimal cosmological origin for such a dark sector is asymmetric reheating, when the same mechanism that populates the SM in the early universe also populates the dark sector at a lower temperature. Here we demonstrate that the resulting inevitable inflaton-mediated scattering between the dark sector and the SM can wash out a would-be temperature asymmetry, and establish the regions of parameter space where temperature asymmetries can be generated in minimal reheating scenarios. Thus obtaining a temperature asymmetry of a given size either restricts possible inflaton masses and couplings or necessitates a non-minimal cosmology for one or both sectors. As a side benefit, we develop techniques for evaluating collision terms in the relativistic Boltzmann equation when the full dependence on Bose-Einstein or Fermi-Dirac phase space distributions must be retained, and present several new results on relativistic thermal averages in an appendix.

  17. Asymmetric Planetary Nebulae VI: the conference summary

    Science.gov (United States)

    De Marco, O.

    2014-04-01

    The Asymmetric Planetary Nebulae conference series, now in its sixth edition, aims to resolve the shaping mechanism of PN. Eighty percent of PN have non spherical shapes and during this conference the last nails in the coffin of single stars models for non spherical PN have been put. Binary theories abound but observational tests are lagging. The highlight of APN6 has been the arrival of ALMA which allowed us to measure magnetic fields on AGB stars systematically. AGB star halos, with their spiral patterns are now connected to PPN and PN halos. New models give us hope that binary parameters may be decoded from these images. In the post-AGB and pre-PN evolutionary phase the naked post-AGB stars present us with an increasingly curious puzzle as complexity is added to the phenomenologies of objects in transition between the AGB and the central star regimes. Binary central stars continue to be detected, including the first detection of longer period binaries, however a binary fraction is still at large. Hydro models of binary interactions still fail to give us results, if we make an exception for the wider types of binary interactions. More promise is shown by analytical considerations and models driven by simpler, 1D simulations such as those carried out with the code MESA. Large community efforts have given us more homogeneous datasets which will yield results for years to come. Examples are the ChanPlaN and HerPlaNe collaborations that have been working with the Chandra and Herschel space telescopes, respectively. Finally, the new kid in town is the intermediate-luminosity optical transient, a new class of events that may have contributed to forming several peculiar PN and pre-PN.

  18. Asymmetric explosion of core-collapse supernovae

    International Nuclear Information System (INIS)

    Kazeroni, Remi

    2016-01-01

    A core-collapse supernova represents the ultimate stage of the evolution of massive stars.The iron core contraction may be followed by a gigantic explosion which gives birth to a neutron star.The multidimensional dynamics of the innermost region, during the first hundreds milliseconds, plays a decisive role on the explosion success because hydrodynamical instabilities are able to break the spherical symmetry of the collapse. Large scale transverse motions generated by two instabilities, the neutrino-driven convection and the Standing Accretion Shock Instability (SASI),increase the heating efficiency up to the point of launching an asymmetric explosion and influencing the birth properties of the neutron star. In this thesis, hydrodynamical instabilities are studied using numerical simulations of simplified models. These models enable a wide exploration of the parameter space and a better physical understanding of the instabilities, generally inaccessible to realistic models.The non-linear regime of SASI is analysed to characterize the conditions under which a spiral mode prevails and to assess its ability to redistribute angular momentum radially.The influence of rotation on the shock dynamics is also addressed. For fast enough rotation rates, a corotation instability overlaps with SASI and greatly impacts the dynamics. The simulations enable to better constrain the effect of non-axisymmetric modes on the angular momentum budget of the iron core collapsing into a neutron star. SASI may under specific conditions spin up or down the pulsar born during the explosion. Finally, an idealised model of the heating region is studied to characterize the non-linear onset of convection by perturbations such as those produced by SASI or pre-collapse combustion inhomogeneities. The dimensionality issue is examined to stress the beneficial consequences of the three-dimensional dynamics on the onset of the explosion. (author) [fr

  19. Affective privilege: Asymmetric interference by emotional distracters

    Directory of Open Access Journals (Sweden)

    Crystal eReeck

    2011-09-01

    Full Text Available Numerous theories posit that affectively salient stimuli are privileged in their capacity to capture attention and disrupt ongoing cognition. Two underlying assumptions in this theoretical position are that the potency of affective stimuli transcends task boundaries (i.e., emotional distracters do not have to belong to a current task-set to disrupt processing and that there is an asymmetry between emotional and cognitive processing (i.e., emotional distracters disrupt cognitive processing, but not vice versa. These assumptions have remained largely untested, as common experimental probes of emotion-cognition interaction rarely manipulate task-relevance and only examine one side of the presumed asymmetry of interference. To test these propositions directly, a face-word Stroop protocol was adapted to independently manipulate (a the congruency between target and distracter stimulus features, (b the affective salience of distracter features, and (c the task-relevance of emotional compared to non-emotional target features. A three-way interaction revealed interdependent effects of distracter relevance, congruence, and affective salience. Compared to task-irrelevant distracters, task-relevant congruent distracters facilitated performance and task-relevant incongruent distracters impaired performance, but the latter effect depended on the nature of the target feature and task. Specifically, task-irrelevant emotional distracters resulted in equivalent performance costs as task-relevant non-emotional distracters, whereas task-irrelevant non-emotional distracters did not produce performance costs comparable to those generated by task-relevant emotional distracters. These results document asymmetric cross-task interference effects for affectively salient stimuli, supporting the notion of affective prioritization in human information processing.

  20. Asymmetric Dimethyl Arginine in Hypothyroid Patients

    International Nuclear Information System (INIS)

    Abdel-Messeih, P.L.

    2012-01-01

    Thyroid diseases may lead to endothelial dysfunction, however, the mechanism underlying the endothelial dysfunction in thyroid disease is still not clear. Asymmetric dimethyl arginine (ADMA), a novel inhibitor of endothelial nitric oxide synthetase (eNOS), was reported to inhibit nitric oxide (NO) synthesis from L-arginine. The present study was carried out to investigate ADMA levels together with effects of dislipidemia in sub-clinical and overt hypothyroid females. There were significant increase in the levels of total cholesterol, low density lipoprotein-cholesterol (LDL-c), high density lipoprotein-cholesterol (HDL-c), thyroid stimulating hormone (TSH) and ADMA in hypothyroid females as compared to controls while the levels of NO and free T 4 were significantly decreased than controls. Sub-clinical hypothyroid females had significant high TSH, LDL-c and non-significantly high ADMA levels and total cholesterol as compared to controls while they had significant decrease in NO, HDL-c and non-significant decrease in free T 4 as compared to controls. There were significant negative correlations between NO and both ADMA (r 2 = 0.84) and free T 4 (r 2 = 0.95) in overt hypothyroid group while significant positive correlation (r 2 = 0.85) was detected between TSH and HDL-c in the same group. These results are highly suggestive that the decrease of nitric oxide secondary to accumulation of ADMA represent an important pathogenic factor together with dyslipidemia in endothelial dysfunction and increased cardiovascular risk especially in hypothyroid females

  1. Asymmetric Dimethyl Arginine in Hypothyroid Patients

    Energy Technology Data Exchange (ETDEWEB)

    Abdel-Messeih, P. L. [Health Radiation Research Department, National Centre for Radiation Research and Technology, Cairo (Egypt)

    2012-07-01

    Thyroid diseases may lead to endothelial dysfunction, however, the mechanism underlying the endothelial dysfunction in thyroid disease is still not clear. Asymmetric dimethyl arginine (ADMA), a novel inhibitor of endothelial nitric oxide synthetase (eNOS), was reported to inhibit nitric oxide (NO) synthesis from L-arginine. The present study was carried out to investigate ADMA levels together with effects of dislipidemia in sub-clinical and overt hypothyroid females. There were significant increase in the levels of total cholesterol, low density lipoprotein-cholesterol (LDL-c), high density lipoprotein-cholesterol (HDL-c), thyroid stimulating hormone (TSH) and ADMA in hypothyroid females as compared to controls while the levels of NO and free T{sub 4} were significantly decreased than controls. Sub-clinical hypothyroid females had significant high TSH, LDL-c and non-significantly high ADMA levels and total cholesterol as compared to controls while they had significant decrease in NO, HDL-c and non-significant decrease in free T{sub 4} as compared to controls. There were significant negative correlations between NO and both ADMA (r{sup 2} = 0.84) and free T{sub 4} (r{sup 2} = 0.95) in overt hypothyroid group while significant positive correlation (r{sup 2} = 0.85) was detected between TSH and HDL-c in the same group. These results are highly suggestive that the decrease of nitric oxide secondary to accumulation of ADMA represent an important pathogenic factor together with dyslipidemia in endothelial dysfunction and increased cardiovascular risk especially in hypothyroid females.

  2. The Asymmetric Predictive Effects of Investor Sentiment

    DEFF Research Database (Denmark)

    Lutz, Chandler

    investors only act as corrective force during certain time periods. We also show that our index predicts implied volatility, media pessimism, and mutual fund flows. Overall, our findings are consistent with both the theories and anecdotal accounts of investor sentiment in the stock market....

  3. The Asymmetric Effects of Investor Sentiment

    DEFF Research Database (Denmark)

    Lutz, Chandler

    investors only act as corrective force during certain time periods. We also show that our index predicts implied volatility, media pessimism, and mutual fund flows. Overall, our findings are consistent with both the theories and anecdotal accounts of investor sentiment in the stock market....

  4. Flow separation and roughness lengths over large bedforms in a tidal environment

    DEFF Research Database (Denmark)

    Lefebvre, Alice; Paarlberg, Andries; Ernstsen, Verner Brandbyge

    2014-01-01

    This study characterises the shape of the flow separation zone (FSZ) and wake region over large asymmetric bedforms under tidal flow conditions. High resolution bathymetry, flow velocity and turbulence data were measured along two parallel transects in a tidal channel covered with bedforms. The f...

  5. Cash Flow and Discount Rate Risk in Up and Down Markets: What is actually priced?

    NARCIS (Netherlands)

    Botshekan, M.; Kraeussl, R.G.W.; Lucas, A.

    2012-01-01

    We test whether asymmetric preferences for losses versus gains affect the prices of cash flow versus discount rate risk. We construct a return decomposition distinguishing cash flow and discount rate betas in up and down markets. Using U.S. data, we find that downside cash flow and discount rate

  6. Effect of surface radiation on natural convection in an asymmetrically heated channel-chimney system

    Science.gov (United States)

    Nasri, Zied; Derouich, Youssef; Laatar, Ali Hatem; Balti, Jalloul

    2018-05-01

    In this paper, a more realistic numerical approach that takes into account the effect of surface radiation on the laminar air flow induced by natural convection in a channel-chimney system asymmetrically heated at uniform heat flux is used. The aim is to enrich the results given in Nasri et al. (Int J Therm Sci 90:122-134, 2015) by varying all the geometric parameters of the system and by taking into account the effect of surface radiation on the flows. The numerical results are first validated against experimental and numerical data available in the literature. The computations have allowed the determination of optimal configurations that maximize the mass flow rate and the convective heat transfer and minimize the heated wall temperatures. The analysis of the temperature fields with the streamlines and the pressure fields has helped to explain the effects of surface radiation and of the different thermo-geometrical parameters on the system performances to improve the mass flow rate and the heat transfer with respect to the simple channel. It is shown that the thermal performance of the channel-chimney system in terms of lower heated wall temperatures is little affected by the surface radiation. At the end, simple correlation equations have been proposed for quickly and easily predict the optimal configurations as well as the corresponding enhancement rates of the induced mass flow rate and the convective heat transfer.

  7. Parallel coupling of symmetric and asymmetric exclusion processes

    International Nuclear Information System (INIS)

    Tsekouras, K; Kolomeisky, A B

    2008-01-01

    A system consisting of two parallel coupled channels where particles in one of them follow the rules of totally asymmetric exclusion processes (TASEP) and in another one move as in symmetric simple exclusion processes (SSEP) is investigated theoretically. Particles interact with each other via hard-core exclusion potential, and in the asymmetric channel they can only hop in one direction, while on the symmetric lattice particles jump in both directions with equal probabilities. Inter-channel transitions are also allowed at every site of both lattices. Stationary state properties of the system are solved exactly in the limit of strong couplings between the channels. It is shown that strong symmetric couplings between totally asymmetric and symmetric channels lead to an effective partially asymmetric simple exclusion process (PASEP) and properties of both channels become almost identical. However, strong asymmetric couplings between symmetric and asymmetric channels yield an effective TASEP with nonzero particle flux in the asymmetric channel and zero flux on the symmetric lattice. For intermediate strength of couplings between the lattices a vertical-cluster mean-field method is developed. This approximate approach treats exactly particle dynamics during the vertical transitions between the channels and it neglects the correlations along the channels. Our calculations show that in all cases there are three stationary phases defined by particle dynamics at entrances, at exits or in the bulk of the system, while phase boundaries depend on the strength and symmetry of couplings between the channels. Extensive Monte Carlo computer simulations strongly support our theoretical predictions. Theoretical calculations and computer simulations predict that inter-channel couplings have a strong effect on stationary properties. It is also argued that our results might be relevant for understanding multi-particle dynamics of motor proteins

  8. Asymmetrical reinforcement and Wolbachia infection in Drosophila.

    Directory of Open Access Journals (Sweden)

    John Jaenike

    2006-10-01

    Full Text Available Reinforcement refers to the evolution of increased mating discrimination against heterospecific individuals in zones of geographic overlap and can be considered a final stage in the speciation process. One the factors that may affect reinforcement is the degree to which hybrid matings result in the permanent loss of genes from a species' gene pool. Matings between females of Drosophila subquinaria and males of D. recens result in high levels of offspring mortality, due to interspecific cytoplasmic incompatibility caused by Wolbachia infection of D. recens. Such hybrid inviability is not manifested in matings between D. recens females and D. subquinaria males. Here we ask whether the asymmetrical hybrid inviability is associated with a corresponding asymmetry in the level of reinforcement. The geographic ranges of D. recens and D. subquinaria were found to overlap across a broad belt of boreal forest in central Canada. Females of D. subquinaria from the zone of sympatry exhibit much stronger levels of discrimination against males of D. recens than do females from allopatric populations. In contrast, such reproductive character displacement is not evident in D. recens, consistent with the expected effects of unidirectional cytoplasmic incompatibility. Furthermore, there is substantial behavioral isolation within D. subquinaria, because females from populations sympatric with D. recens discriminate against allopatric conspecific males, whereas females from populations allopatric with D. recens show no discrimination against any conspecific males. Patterns of general genetic differentiation among populations are not consistent with patterns of behavioral discrimination, which suggests that the behavioral isolation within D. subquinaria results from selection against mating with Wolbachia-infected D. recens. Interspecific cytoplasmic incompatibility may contribute not only to post-mating isolation, an effect already widely recognized, but also to

  9. Performance of JPEG Image Transmission Using Proposed Asymmetric Turbo Code

    Directory of Open Access Journals (Sweden)

    Siddiqi Mohammad Umar

    2007-01-01

    Full Text Available This paper gives the results of a simulation study on the performance of JPEG image transmission over AWGN and Rayleigh fading channels using typical and proposed asymmetric turbo codes for error control coding. The baseline JPEG algorithm is used to compress a QCIF ( "Suzie" image. The recursive systematic convolutional (RSC encoder with generator polynomials , that is, (13/11 in decimal, and 3G interleaver are used for the typical WCDMA and CDMA2000 turbo codes. The proposed asymmetric turbo code uses generator polynomials , that is, (13/11; 13/9 in decimal, and a code-matched interleaver. The effect of interleaver in the proposed asymmetric turbo code is studied using weight distribution and simulation. The simulation results and performance bound for proposed asymmetric turbo code for the frame length , code rate with Log-MAP decoder over AWGN channel are compared with the typical system. From the simulation results, it is observed that the image transmission using proposed asymmetric turbo code performs better than that with the typical system.

  10. Success Factors of Asymmetric Connections - Example of Large Slovenian Enterprises

    Directory of Open Access Journals (Sweden)

    Viktor Vračar

    2014-11-01

    Full Text Available More and more companies realize the fact that networking or partner collaborations, which are based on partner relations between companies, are essential for their long-term existence. In today’s global competitive environment each company is included at least in some different connections. Very common connections occur between large and smaller enterprises, where the so called asymmetric connections occur, which may be understood as the ability of one organisation to establish power, influence and control over the other organisation and its resources. According to numerous statements, the connections between enterprises are very frequently uneffectivenessful, with opinions on the optimal nature of asymmetric connections being quite common as well, whereby it is, as a rule, a synergic complementing of missing content for both partners. To verify the thesis, that companies achieve more competitiveness and effectiveness through connections, whereby the so called asymmetric connections are common, a structural model of the evolution of asymmetric connection has been developed, which connects the theoretically identified factors and all dependent concepts of competitiveness, efficiency and effectiveness. The empirical research also attempts to further expose the factors of asymmetric connections, which affect efficiency and effectiveness of the connected enterprises.

  11. Time-Dependent-Asymmetric-Linear-Parsimonious Ancestral State Reconstruction.

    Science.gov (United States)

    Didier, Gilles

    2017-10-01

    The time-dependent-asymmetric-linear parsimony is an ancestral state reconstruction method which extends the standard linear parsimony (a.k.a. Wagner parsimony) approach by taking into account both branch lengths and asymmetric evolutionary costs for reconstructing quantitative characters (asymmetric costs amount to assuming an evolutionary trend toward the direction with the lowest cost). A formal study of the influence of the asymmetry parameter shows that the time-dependent-asymmetric-linear parsimony infers states which are all taken among the known states, except for some degenerate cases corresponding to special values of the asymmetry parameter. This remarkable property holds in particular for the Wagner parsimony. This study leads to a polynomial algorithm which determines, and provides a compact representation of, the parametric reconstruction of a phylogenetic tree, that is for all the unknown nodes, the set of all the possible reconstructed states associated with the asymmetry parameters leading to them. The time-dependent-asymmetric-linear parsimony is finally illustrated with the parametric reconstruction of the body size of cetaceans.

  12. Citrus asymmetric somatic hybrids produced via fusion of gamma-irradiated and iodoacetamide-treated protoplasts

    Energy Technology Data Exchange (ETDEWEB)

    Bona, Claudine Maria de [Instituto Agronomico do Parana (IAPAR), Curitiba, PR (Brazil)], e-mail: debona@iapar.br; Gould, Jean Howe [Texas A and M University, College Station, TX (United States). Dept. of Ecosystem Science and Management], e-mail: gould@tamu.edu; Miller Junior, J. Creighton [Texas A and M University, College Station, TX (United States). Dept. of Horticultural Sciences], e-mail: jcmillerjr@tamu.edu; Stelly, David [Texas A and M University, College Station, TX (United States). Dept. of Soil and Crop Sciences], e-mail: stelly@tamu.edu; Louzada, Eliezer Silva [Texas A and M University, Kingsville, TX (United States). Citrus Center], e-mail: e-louzada@tamu.edu

    2009-05-15

    The objective of this study was to produce citrus somatic asymmetric hybrids by fusing gamma.irradiated protoplasts with iodoacetamide-treated protoplasts. Protoplasts were isolated from embryogenic suspension cells of grapefruit (Citrus paradisi Macfad.) cultivars Ruby Red and Flame, sweet oranges (C. sinensis Osbeck) 'Itaborai', 'Natal', Valencia', and 'Succari', from 'Satsuma' (C. unshiu Marcow.) and 'Changsha' mandarin (C. reticulata Blanco) and 'Murcott' tangor (C. reticulata x C. sinensis). Donor protoplasts were exposed to gamma rays and receptor protoplasts were treated with 3 mmol L{sup -1} iodoacetamide (IOA), and then they were fused for asymmetric hybridization. Asymmetric embryos were germinated, and the resulting shoots were either grafted onto sour orange, rough lemon or 'Swingle' (C. paradisi x Poncirus trifoliata) x 'Sunki' mandarin rootstock seedlings, or rooted after dipping their bases in indol.butyric acid (IBA) solution. The products were later acclimatized to greenhouse conditions. Ploidy was analyzed by flow cytometry, and hybridity was confirmed by amplified fragment length polymorphism (AFLP) analysis of plantlet DNA samples. The best treatment was the donor-recipient fusion combination of 80 Gy.irradiated 'Ruby Red' protoplasts with 20 min IOA.treated 'Succari' protoplasts. Tetraploid and aneuploid plants were produced. Rooting recalcitrance was solved by dipping shoots' stems in 3,000 mg L{sup -1} IBA solution for 10 min. (author)

  13. Effect of radiation and magnetic field on peristaltic transport of nanofluids through a porous space in a tapered asymmetric channel

    Energy Technology Data Exchange (ETDEWEB)

    Kothandapani, M., E-mail: mkothandapani@gmail.com [Department of Mathematics, University College of Engineering Arni, (A Constituent College of Anna University Chennai), Arni 632326, Tamil Nadu (India); Prakash, J., E-mail: prakashjayavel@yahoo.co.in [Department of Mathematics, Arulmigu Meenakshi Amman College of Engineering, Vadamavandal 604410, Tamil Nadu (India)

    2015-03-15

    Theoretical analyses on the effect of radiation and MHD on the peristaltic flow of a nanofluid through a porous medium in a two dimensional tapered asymmetric channel has been made. The nanofluid is assumed to be electrically conducting in the presence of a uniform magnetic field. The transport equation accounts the both Brownian motion and thermophoresis along with the radiation reaction. The problem has been further simplified with the authentic assumptions of long wavelength and small Reynolds number. The analytical expressions obtained for the axial velocity, stream function, temperature field, nanoparticle fraction field and pressure gradient provide satisfactory explanation. Influence of various parameters on the flow characteristics have been discussed with the help of graphical results. The trapping phenomenon has also been discussed in detail. - Highlights: • Combine effect of thermal radiation and MHD on the peristaltic flow of a Newtonian nanofluid are discussed. • This work may be first attempt dealing the study of Newtonian nanofluid flow in the porous tapered asymmetric channel. • The velocity, stream function, temperature field and nanoparticle fraction field provide satisfactory explanation with help of graphs.

  14. Gravity-induced asymmetric distribution of a plant growth hormone

    Science.gov (United States)

    Bandurski, R. S.; Schulze, A.; Momonoki, Y.

    1984-01-01

    Dolk (1936) demonstrated that gravistimulation induced an asymmetric distribution of auxin in a horizontally-placed shoot. An attempt is made to determine where and how that asymmetry arises, and to demonstrate that the endogenous auxin, indole-3-acetic acid, becomes asymmetrically distributed in the cortical cells of the Zea mays mesocotyl during 3 min of geostimulation. Further, indole-3-acetic acid derived by hydrolysis of an applied transport form of the hormone, indole-3-acetyl-myo-inositol, becomes asymmetrically distributed within 15 min of geostimulus time. From these and prior data is developed a working theory that the gravitational stimulus induces a selective leakage, or secretion, of the hormone from the vascular tissue to the cortical cells of the mesocotyl.

  15. Best Speed Fit EDF Scheduling for Performance Asymmetric Multiprocessors

    Directory of Open Access Journals (Sweden)

    Peng Wu

    2017-01-01

    Full Text Available In order to improve the performance of a real-time system, asymmetric multiprocessors have been proposed. The benefits of improved system performance and reduced power consumption from such architectures cannot be fully exploited unless suitable task scheduling and task allocation approaches are implemented at the operating system level. Unfortunately, most of the previous research on scheduling algorithms for performance asymmetric multiprocessors is focused on task priority assignment. They simply assign the highest priority task to the fastest processor. In this paper, we propose BSF-EDF (best speed fit for earliest deadline first for performance asymmetric multiprocessor scheduling. This approach chooses a suitable processor rather than the fastest one, when allocating tasks. With this proposed BSF-EDF scheduling, we also derive an effective schedulability test.

  16. Lower Bounds in the Asymmetric External Memory Model

    DEFF Research Database (Denmark)

    Jacob, Riko; Sitchinava, Nodari

    2017-01-01

    Motivated by the asymmetric read and write costs of emerging non-volatile memory technologies, we study lower bounds for the problems of sorting, permuting and multiplying a sparse matrix by a dense vector in the asymmetric external memory model (AEM). Given an AEM with internal (symmetric) memory...... of size M, transfers between symmetric and asymmetric memory in blocks of size B and the ratio ω between write and read costs, we show Ω(min (N, ωN/B logω M/B N/B) lower bound for the cost of permuting N input elements. This lower bound also applies to the problem of sorting N elements. This proves...

  17. Electromagnetic resonance in the asymmetric terahertz metamaterials with triangle microstructure

    Science.gov (United States)

    Xing, Yuanyuan; Zhang, Xiaoyu; Zhang, Qiang; Gu, Yanping; Qian, Yunan; Lin, Xingyue; Tang, Yunhai; Cheng, Xinli; Qin, Changfa; Shen, Jiaoyan; Zang, Taocheng; Ma, Chunlan

    2018-05-01

    We investigate terahertz transmission properties and electromagnetic resonance modes in the asymmetric triangle structures with the change of asymmetric distance and the direction of electric field. When the THz electric field is perpendicular to the split gap of triangle, the electric field can better excite the THz absorption in the triangle structures. Importantly, electromagnetically induced transparency (EIT) characteristics are observed in the triangle structures due to the destructive interference of the different excited modes. The distributions of electric field and surface current density simulated by finite difference time domain indicate that the bright mode is excited by the side of triangle structures and dark mode is excited by the gap-side of triangle. The present study is helpful to understand the electromagnetic resonance in the asymmetric triangular metamaterials.

  18. Tourist Demand Reactions: Symmetric or Asymmetric across the Business Cycle?

    Science.gov (United States)

    Bronner, Fred; de Hoog, Robert

    2017-09-01

    Economizing and spending priorities on different types of vacations are investigated during two periods: an economic downturn and returning prosperity. Two nation-wide samples of vacationers are used: one during a downturn, the other one at the start of the recovery period. Through comparing the results, conclusions can be drawn about symmetric or asymmetric tourist demand across the business cycle. The main summer holiday has an asymmetric profile: being fairly crisis-resistant during a recession and showing considerable growth during an expansion. This does not apply to short vacations and day trips, each having a symmetric profile: during a recession they experience substantial reductions and during expansion comparable growth. So when talking about tourist demand in general , one cannot say that it is symmetric or asymmetric across the business cycle: it depends on the type of vacation. Differences in tourist demand are best explained by the role of Quality-of-Life for vacationers.

  19. Two-channel totally asymmetric simple exclusion processes

    International Nuclear Information System (INIS)

    Pronina, Ekaterina; Kolomeisky, Anatoly B

    2004-01-01

    Totally asymmetric simple exclusion processes, consisting of two coupled parallel lattice chains with particles interacting with hard-core exclusion and moving along the channels and between them, are considered. In the limit of strong coupling between the channels, the particle currents, density profiles and a phase diagram are calculated exactly by mapping the system into an effective one-channel totally asymmetric exclusion model. For intermediate couplings, a simple approximate theory, that describes the particle dynamics in vertical clusters of two corresponding parallel sites exactly and neglects the correlations between different vertical clusters, is developed. It is found that, similarly to the case of one-channel totally asymmetric simple exclusion processes, there are three stationary state phases, although the phase boundaries and stationary properties strongly depend on inter-channel coupling. Extensive computer Monte Carlo simulations fully support the theoretical predictions

  20. Controllable asymmetric transmission via gap-tunable acoustic metasurface

    Science.gov (United States)

    Liu, Bingyi; Jiang, Yongyuan

    2018-04-01

    In this work, we utilize the acoustic gradient metasurface (AGM) of a bilayer configuration to realize the controllable asymmetric transmission. Relying on the adjustable gap between the two composing layers, the metasurface could switch from symmetric transmission to asymmetric transmission at a certain gap value. The underlying mechanism is attributed to the interference between the forward diffracted waves scattered by the surface bound waves at two air-AGM interfaces, which is apparently influenced by the interlayer distance. We further utilize the hybrid acoustic elements to construct the desired gradient metasurface with a tunable gap and validate the controllable asymmetric transmission with full-wave simulations. Our work provides the solution for actively controlling the transmission property of an acoustic element, which shows potential application in acoustic communication as a dynamic tunable acoustic diode.

  1. Asymmetric adsorption of alanine by quartz powder from ethanol solution

    Energy Technology Data Exchange (ETDEWEB)

    Furuyama, Shozo; Sawada, Michio; Hachiya, Kinji; Morimoto, Tetsuo (Okayama Univ. (Japan). Faculty of Science)

    1982-11-01

    The asymmetric adsorption of the racemic alanine by the optically active quartz from ethanol solution at 8/sup 0/C was studied by the /sup 14/C-tracer method and the newly developed /sup 14/C-tracer ninhydrin-colorimetry combination method. The preferential adsorption of L-alanine by levorotatory quartz (l-quartz) and D-alanine by dextrorotatory quartz (d-quartz) was confirmed. The asymmetric adsorptivity (Asub(s)) falls in the range of 1.1 - 1.3, which is comparable with the value determined at - 80/sup 0/C in the previous paper. The effects of water content in the ethanol solution and of the adsorption temperature upon the adsorption affinity of alanine to quartz were also measured. The cause for the asymmetric adsorption is discussed from the crystallographic point of view.

  2. Dynamic JUNQ inclusion bodies are asymmetrically inherited in mammalian cell lines through the asymmetric partitioning of vimentin.

    Science.gov (United States)

    Ogrodnik, Mikołaj; Salmonowicz, Hanna; Brown, Rachel; Turkowska, Joanna; Średniawa, Władysław; Pattabiraman, Sundararaghavan; Amen, Triana; Abraham, Ayelet-chen; Eichler, Noam; Lyakhovetsky, Roman; Kaganovich, Daniel

    2014-06-03

    Aging is associated with the accumulation of several types of damage: in particular, damage to the proteome. Recent work points to a conserved replicative rejuvenation mechanism that works by preventing the inheritance of damaged and misfolded proteins by specific cells during division. Asymmetric inheritance of misfolded and aggregated proteins has been shown in bacteria and yeast, but relatively little evidence exists for a similar mechanism in mammalian cells. Here, we demonstrate, using long-term 4D imaging, that the vimentin intermediate filament establishes mitotic polarity in mammalian cell lines and mediates the asymmetric partitioning of damaged proteins. We show that mammalian JUNQ inclusion bodies containing soluble misfolded proteins are inherited asymmetrically, similarly to JUNQ quality-control inclusions observed in yeast. Mammalian IPOD-like inclusion bodies, meanwhile, are not always inherited by the same cell as the JUNQ. Our study suggests that the mammalian cytoskeleton and intermediate filaments provide the physical scaffold for asymmetric inheritance of dynamic quality-control JUNQ inclusions. Mammalian IPOD inclusions containing amyloidogenic proteins are not partitioned as effectively during mitosis as their counterparts in yeast. These findings provide a valuable mechanistic basis for studying the process of asymmetric inheritance in mammalian cells, including cells potentially undergoing polar divisions, such as differentiating stem cells and cancer cells.

  3. Natural convection in an asymmetrically heated vertical channel with an adiabatic auxiliary plate

    International Nuclear Information System (INIS)

    Taieb, Soumaya; Hatem, Laatar Ali; Balti, Jalloul

    2013-01-01

    The effect of an auxiliary plate on natural convection in an asymmetrically heated channel is studied numerically in laminar regime. The computational procedure is made by solving the unsteady two dimensional Navier-Stokes and energy equations. This nonlinear system is integrated by a finite volume approach and then solved in time using the projection method, allowing the decoupling pressure from velocity. More than hundred simulations are performed to determine the best positions of the auxiliary plate that enhance the induced mass flow and the heat transfer rate for modified Rayleigh numbers ranging from Ra m = 10 2 to Ra m = 10 5 . Contour maps are plotted and then used to precise the enhancement rates of the mass flow and the heat transfer for any position of the auxiliary plate in the channel. The numerical results (velocity, pressure and temperature fields) provide detailed information about the evolution of the flow structure according to the geometry considered in this study. In addition, they permit to explain why the mass flow rate and Nusselt number are enhanced for certain positions of the auxiliary plate and are on the contrary deteriorated for others. (authors)

  4. Air distribution in office environment with asymmetric workstation layout using chilled beams

    Energy Technology Data Exchange (ETDEWEB)

    Koskela, Hannu; Haeggblom, Henna [Finnish Institute of Occupational Health, Lemminkaeisenkatu 14-18 B, 20520 Turku (Finland); Kosonen, Risto; Ruponen, Mika [Halton Oy, Niittyvillankuja 4, 01510 Vantaa (Finland)

    2010-09-15

    Air flow patterns and mean air speeds were studied under laboratory conditions representing a full scale open-plan office. Three basic conditions were tested: summer, spring/autumn and winter. Chilled beams were used to provide cooling, outdoor air supply and air distribution in the room. The heat sources had a notable influence on the flow pattern in the room causing large scale circulation and affecting the direction of inlet jets. The maximum air speed in the occupied zone was higher than the recommendations. The mean air speed was also high on at the floor level but low on at the head level. The air speed was highest in the summer case under high cooling load. Results indicate that especially with high heat loads, it is difficult to fulfill the targets of the existing standards in practice. Two main sources of draught risk were found: a) downfall of colliding inlet jets causing local maxima of air speed and b) large scale circulation caused by asymmetric layout of chilled beams and heat sources. The first phenomenon can cause local draught risk when the workstation is located in the downfall area. The flow pattern is not stable and the position of draught risk areas can change in time and also due to changes in room heat sources. The second phenomenon can cause more constant high air speeds on at the floor level. CFD-simulation was able to predict the general flow pattern but somewhat overestimated the air speed compared to measurements. (author)

  5. Self-organized criticality in asymmetric exclusion model with noise for freeway traffic

    Science.gov (United States)

    Nagatani, Takashi

    1995-02-01

    The one-dimensional asymmetric simple-exclusion model with open boundaries for parallel update is extended to take into account temporary stopping of particles. The model presents the traffic flow on a highway with temporary deceleration of cars. Introducing temporary stopping into the asymmetric simple-exclusion model drives the system asymptotically into a steady state exhibiting a self-organized criticality. In the self-organized critical state, start-stop waves (or traffic jams) appear with various sizes (or lifetimes). The typical interval between consecutive jams scales as ≃ Lv with v = 0.51 ± 0.05 where L is the system size. It is shown that the cumulative jam-interval distribution Ns( L) satisfies the finite-size scaling form ( Ns( L) ≃ L- vf( s/ Lv). Also, the typical lifetime ≃ Lv‧ with v‧ = 0.52 ± 0.05. The cumulative distribution Nm( L) of lifetimes satisfies the finite-size scaling form Nm( L)≃ L-1g( m/ Lv‧).

  6. Gonad morphogenesis defects drive hybrid male sterility in asymmetric hybrid breakdown of Caenorhabditis nematodes.

    Science.gov (United States)

    Dey, Alivia; Jin, Qi; Chen, Yen-Chu; Cutter, Asher D

    2014-01-01

    Determining the causes and evolution of reproductive barriers to gene flow between populations, speciation, is the key to understanding the origin of diversity in nature. Many species manifest hybrid breakdown when they intercross, characterized by increasingly exacerbated problems in later generations of hybrids. Recently, Caenorhabditis nematodes have emerged as a genetic model for studying speciation, and here we investigate the nature and causes of hybrid breakdown between Caenorhabditis remanei and C. latens. We quantify partial F1 hybrid inviability and extensive F2 hybrid inviability; the ~75% F2 embryonic arrest occurs primarily during gastrulation or embryonic elongation. Moreover, F1 hybrid males exhibit Haldane's rule asymmetrically for both sterility and inviability, being strongest when C. remanei serves as maternal parent. We show that the mechanism by which sterile hybrid males are incapable of transferring sperm or a copulatory plug involves defective gonad morphogenesis, which we hypothesize results from linker cell defects in migration and/or cell death during development. This first documented case of partial hybrid male sterility in Caenorhabditis follows expectations of Darwin's corollary to Haldane's rule for asymmetric male fitness, providing a powerful foundation for molecular dissection of intrinsic reproductive barriers and divergence of genetic pathways controlling organ morphogenesis. © 2014 Wiley Periodicals, Inc.

  7. Plasma and Energetic Particle Behaviors During Asymmetric Magnetic Reconnection at the Magnetopause

    Science.gov (United States)

    Lee, S. H.; Zhang, H.; Zong, Q.-G.; Otto, A.; Sibeck, D. G.; Wang, Y.; Glassmeier, K.-H.; Daly, P.W.; Reme, H.

    2014-01-01

    The factors controlling asymmetric reconnection and the role of the cold plasma population in the reconnection process are two outstanding questions. We present a case study of multipoint Cluster observations demonstrating that the separatrix and flow boundary angles are greater on the magnetosheath than on the magnetospheric side of the magnetopause, probably due to the stronger density than magnetic field asymmetry at this boundary. The motion of cold plasmaspheric ions entering the reconnection region differs from that of warmer magnetosheath and magnetospheric ions. In contrast to the warmer ions, which are probably accelerated by reconnection in the diffusion region near the subsolar magnetopause, the colder ions are simply entrained by ??×?? drifts at high latitudes on the recently reconnected magnetic field lines. This indicates that plasmaspheric ions can sometimes play only a very limited role in asymmetric reconnection, in contrast to previous simulation studies. Three cold ion populations (probably H+, He+, and O+) appear in the energy spectrum, consistent with ion acceleration to a common velocity.

  8. The rationality of EIA forecasts under symmetric and asymmetric loss

    International Nuclear Information System (INIS)

    Auffhammer, Maximilian

    2007-01-01

    The United States Energy Information Administration publishes annual forecasts of nationally aggregated energy consumption, production, prices, intensity and GDP. These government issued forecasts often serve as reference cases in the calibration of simulation and econometric models, which climate and energy policy are based on. This study tests for rationality of published EIA forecasts under symmetric and asymmetric loss. We find strong empirical evidence of asymmetric loss for oil, coal and electricity prices as well as natural gas consumption, electricity sales, GDP and energy intensity. (author)

  9. Data analysis of asymmetric structures advanced approaches in computational statistics

    CERN Document Server

    Saito, Takayuki

    2004-01-01

    Data Analysis of Asymmetric Structures provides a comprehensive presentation of a variety of models and theories for the analysis of asymmetry and its applications and provides a wealth of new approaches in every section. It meets both the practical and theoretical needs of research professionals across a wide range of disciplines and  considers data analysis in fields such as psychology, sociology, social science, ecology, and marketing. In seven comprehensive chapters this guide details theories, methods, and models for the analysis of asymmetric structures in a variety of disciplines and presents future opportunities and challenges affecting research developments and business applications.

  10. Current drive by asymmetrical heating in a toroidal plasma

    International Nuclear Information System (INIS)

    Gahl, J.M.

    1986-01-01

    This report describes the first experimental observation of current generation by asymmetrical heating of ions. A unidirectional fast Alfven wave launched by a slow-wave antenna inside the Texas Tech Tokamak, asymmetrically heated the ions. Measurements of the asymmetry of the toroidal plasma current with probes at the top and bottom of the toroidal plasma column confirmed the current generation indirectly. Current generation, obtained in a one-species, hydrogen plasma, is a phenomenon which had not been predicted previously. Calculations of the dispersion relation for the fast Alfven wave near the fundamental cyclotron resonance in a one-species, hydrogen plasma, using warm plasma theory, support the experimental results

  11. Climate agreements under limited participation, asymmetric information and market imperfections

    Energy Technology Data Exchange (ETDEWEB)

    Hagem, Cathrine

    1996-12-31

    This thesis relates to climate agreements and cost efficiency by analysing the formation of a system of quota leading to distributed discharge of emissions between countries. Main fields concerned are the greenhouse effect, the political process, efficient and cost-effective climate agreements, and climate agreements under limited participation, asymmetric information and market imperfections covering fields like limited participation in climate agreements, limited participation and indirect impact on non-participating countries` emissions, limited participation and direct impact on non-participating countries` emissions under asymmetric information, and non-competitive market for tradeable quotas. 166 refs., 7 tabs.

  12. Experimental research on photovoltaic module for asymmetrical compound parabolic concentrator

    Energy Technology Data Exchange (ETDEWEB)

    Yuan, Jinshe; Wang, Mingyue [Chongqing Normal University, Chongqing (China). Department of Physics; Yang, Changmin [Xian University of Technology, Xian (China). Department of Applied Physics

    2008-07-01

    The photovoltaic module for the use of fixed asymmetrical CPC concentrator was designed and fabricated based on the performance of polycrystalline-silicon solar cells with back surface field (BSF) structure. The performance of the combination of the module and asymmetrical CPC concentrator was investigated. The results show its effective concentration ratio to be 2.46 and the output power of the PV-a-CPC system to be increased by 2.13 times compared with that of the module approximately. (orig.)

  13. Asymptotic behavior of observables in the asymmetric quantum Rabi model

    Science.gov (United States)

    Semple, J.; Kollar, M.

    2018-01-01

    The asymmetric quantum Rabi model with broken parity invariance shows spectral degeneracies in the integer case, that is when the asymmetry parameter equals an integer multiple of half the oscillator frequency, thus hinting at a hidden symmetry and accompanying integrability of the model. We study the expectation values of spin observables for each eigenstate and observe characteristic differences between the integer and noninteger cases for the asymptotics in the deep strong coupling regime, which can be understood from a perturbative expansion in the qubit splitting. We also construct a parent Hamiltonian whose exact eigenstates possess the same symmetries as the perturbative eigenstates of the asymmetric quantum Rabi model in the integer case.

  14. Testing for asymmetric pricing in the Canadian retail gasoline market

    International Nuclear Information System (INIS)

    Godby, R.; Lintner, A.M.; Stengos, T.; Wandschneider, B.

    2000-01-01

    This paper applies a Threshold Regression model to test for asymmetric pricing in the retail gasoline market in Canada, using weekly data for the period January 1990 to December 1996. We present results for 13 Canadian cities for both premium and regular gasoline. Within the context of an error correction model we test for the presence of asymmetric price behaviour using average changes in crude prices as well as various lags for the change in crude as possible thresholds. We are unable to find any evidence to support this view. 23 refs

  15. Decoding Pure Rotational Molecular Spectra for Asymmetric Molecules

    Directory of Open Access Journals (Sweden)

    S. A. Cooke

    2013-01-01

    Full Text Available Rotational spectroscopy can provide insights of unparalleled precision with respect to the wavefunctions of molecular systems that have relevance in fields as diverse as astronomy and biology. In this paper, we demonstrate how asymmetric molecular pure rotational spectra may be analyzed “pictorially” and with simple formulae. It is shown that the interpretation of such spectra relies heavily upon pattern recognition. The presentation of some common spectral line positions in near-prolate asymmetric rotational spectra provides a means by which spectral assignment, and approximate rotational constant determination, may be usefully explored. To aid in this endeavor we have created a supporting, free, web page and mobile web page.

  16. Ideal MHD beta-limits of poloidally asymmetric equilibria

    Energy Technology Data Exchange (ETDEWEB)

    Todd, A.M.M.; Miller, A.E.; Grimm, R.C.; Okabayashi, M.; Dalhed, H.E. Jr.

    1981-05-01

    The ideal MHD stability of poloidally asymmetric equilibria, which are typical of a tokamak reactor design with a single-null poloidal divertor is examined. As with symmetric equilibria, stability to non-axisymmetric modes improves with increasing triangularity and ellipticity, and with lower edge safety factor. Pressure profiles optimized with respect to ballooning stability are obtained for an asymmetric shape, resulting in ..beta../sub critical/ approx. = 5.7%. The corresponding value for an equivalent symmetric shape is ..beta../sub critical/ approx. = 6.5%.

  17. Axisymmetric stability of vertically asymmetric tokamaks at large beta poloidal

    International Nuclear Information System (INIS)

    Yamazaki, K.; Fishman, H.; Okabayashi, M.; Todd, A.M.M.

    1981-09-01

    The stability of high-β vertically asymmetric tokamak equilibria to rigid displacements is investigated analytically. It is found that vertical stability at large beta poloidal is mainly determined by a coupling between the shape of the plasma surface and the Shafranov shift of the magnetic axis. To the lowest order, symmetric components of the plasma surface shape are found to be the critical destabilizing elements. Asymmetric components have little effect. The inclusion of higher order terms in the high β tokamak expansion leads to further destabilization. Qualitative agreement between these analytic results and numerical stability calculations using the PEST code is demonstrated

  18. Ideal MHD beta-limits of poloidally asymmetric equilibria

    International Nuclear Information System (INIS)

    Todd, A.M.M.; Miller, A.E.; Grimm, R.C.; Okabayashi, M.; Dalhed, H.E. Jr.

    1981-05-01

    The ideal MHD stability of poloidally asymmetric equilibria, which are typical of a tokamak reactor design with a single-null poloidal divertor is examined. As with symmetric equilibria, stability to non-axisymmetric modes improves with increasing triangularity and ellipticity, and with lower edge safety factor. Pressure profiles optimized with respect to ballooning stability are obtained for an asymmetric shape, resulting in β/sub critical/ approx. = 5.7%. The corresponding value for an equivalent symmetric shape is β/sub critical/ approx. = 6.5%

  19. Electron Raman scattering in asymmetrical multiple quantum wells

    International Nuclear Information System (INIS)

    Betancourt-Riera, R; Rosas, R; Marin-Enriquez, I; Riera, R; Marin, J L

    2005-01-01

    Optical properties of asymmetrical multiple quantum wells for the construction of quantum cascade lasers are calculated, and expressions for the electronic states of asymmetrical multiple quantum wells are presented. The gain and differential cross-section for an electron Raman scattering process are obtained. Also, the emission spectra for several scattering configurations are discussed, and the corresponding selection rules for the processes involved are studied; an interpretation of the singularities found in the spectra is given. The electron Raman scattering studied here can be used to provide direct information about the efficiency of the lasers

  20. Six transformer based asymmetrical embedded Z-source inverters

    DEFF Research Database (Denmark)

    Wei, Mo; Poh Chiang, Loh; Chi, Jin

    2013-01-01

    Embedded/Asymmetrical embedded Z-source inverters were proposed to maintain smooth input current/voltage across the dc source and within the impedance network, remain the shoot-through feature used to boost up the dc-link voltage without adding bulky filter at input side. This paper introduces a ...... a class of transformer based asymmetrical embedded Z-source inverters which keep the smooth input current and voltage while achieving enhanced voltage boost capability. The presented inverters are verified by laboratory prototypes experimentally....

  1. Finite stage asymmetric repeated games: Both players' viewpoints

    KAUST Repository

    Li, Lichun

    2017-01-05

    In asymmetric zero-sum games, one player has superior information about the game over the other. It is known that the informed players (maximizer) face the tradeoff of exploiting its superior information at the cost of revealing its superior information, but the basic point of the uninformed player (minimizer)\\'s decision making remains unknown. This paper studies the finite stage asymmetric repeated games from both players\\' viewpoints, and derives that not only security strategies but also the opponents\\' corresponding best responses depends only on the informed player\\'s history action sequences. Moreover, efficient LP formulations to compute both player\\'s security strategies are provided.

  2. The rationality of EIA forecasts under symmetric and asymmetric loss

    Energy Technology Data Exchange (ETDEWEB)

    Auffhammer, Maximilian [Department of Agricultural and Resource Economics, University of California, 207 Giannini Hall 3310, Berkeley, CA 94720 (United States)

    2007-05-15

    The United States Energy Information Administration publishes annual forecasts of nationally aggregated energy consumption, production, prices, intensity and GDP. These government issued forecasts often serve as reference cases in the calibration of simulation and econometric models, which climate and energy policy are based on. This study tests for rationality of published EIA forecasts under symmetric and asymmetric loss. We find strong empirical evidence of asymmetric loss for oil, coal and electricity prices as well as natural gas consumption, electricity sales, GDP and energy intensity. (author)

  3. An optical tweezer in asymmetrical vortex Bessel-Gaussian beams

    Energy Technology Data Exchange (ETDEWEB)

    Kotlyar, V. V.; Kovalev, A. A., E-mail: alexeysmr@mail.ru; Porfirev, A. P. [Image Processing Systems Institute, 151 Molodogvardeiskaya St., 443001 Samara (Russian Federation); Department of Technical cybernetics, Samara State Aerospace University, Samara 443086 (Russian Federation)

    2016-07-14

    We study an optical micromanipulation that comprises trapping, rotating, and transporting 5-μm polystyrene microbeads in asymmetric Bessel-Gaussian (BG) laser beams. The beams that carry orbital angular momentum are generated by means of a liquid crystal microdisplay and focused by a microobjective with a numerical aperture of NA = 0.85. We experimentally show that given a constant topological charge, the rate of microparticle motion increases near linearly with increasing asymmetry of the BG beam. Asymmetric BG beams can be used instead of conventional Gaussian beam for trapping and transferring live cells without thermal damage.

  4. Preview-based Asymmetric Load Reduction of Wind Turbines

    DEFF Research Database (Denmark)

    Madsen, Mathias; Filsø, Jakob; Soltani, Mohsen

    2012-01-01

    Controller (MPC) developed is based on a model with individual blade pitching to utilize the LIDAR measurements. The MPC must also maintain a given power reference while satisfying a set of actuator constraints. The designed controller was tested on a 5 MW wind turbine in the FAST simulator and compared......Fatigue loads on wind turbines caused by an asymmetric wind field become an increasing concern when the scale of wind turbines increases. This paper presents a model based predictive approach to reduce asymmetric loads by using Light Detection And Ranging (LIDAR) measurements. The Model Predictive...

  5. Dicer is dispensable for asymmetric RISC loading in mammals.

    Science.gov (United States)

    Betancur, Juan G; Tomari, Yukihide

    2012-01-01

    In flies, asymmetric loading of small RNA duplexes into Argonaute2-containing RNA-induced silencing complex (Ago2-RISC) requires Dicer-2/R2D2 heterodimer, which acts as a protein sensor for the thermodynamic stabilities of the ends of small RNA duplexes. However, the mechanism of small RNA asymmetry sensing in mammalian RISC assembly remains obscure. Here, we quantitatively examined RISC assembly and target silencing activity in the presence or absence of Dicer in mammals. Our data show that, unlike the well-characterized fly Ago2-RISC assembly pathway, mammalian Dicer is dispensable for asymmetric RISC loading in vivo and in vitro.

  6. Computer simulation of hopper flow

    International Nuclear Information System (INIS)

    Potapov, A.V.; Campbell, C.S.

    1996-01-01

    This paper describes two-dimensional computer simulations of granular flow in plane hoppers. The simulations can reproduce an experimentally observed asymmetric unsteadiness for monodispersed particle sizes, but also could eliminate it by adding a small amount of polydispersity. This appears to be a result of the strong packings that may be formed by monodispersed particles and is thus a noncontinuum effect. The internal stress state was also sampled, which among other things, allows an evaluation of common assumptions made in granular material models. These showed that the internal friction coefficient is far from a constant, which is in contradiction to common models based on plasticity theory which assume that the material is always at the point of imminent yield. Furthermore, it is demonstrated that rapid granular flow theory, another common modeling technique, is inapplicable to this problem even near the exit where the flow is moving its fastest. copyright 1996 American Institute of Physics

  7. Autorefraction versus subjective refraction in a radially asymmetric multifocal intraocular lens

    NARCIS (Netherlands)

    van der Linden, Jan Willem; Vrijman, Violette; Al-Saady, Rana; El-Saady, Rana; van der Meulen, Ivanka J.; Mourits, Maarten P.; Lapid-Gortzak, Ruth

    2014-01-01

    To evaluate whether the automated refraction (AR) correlates with subjective manifest (MR) refraction in eyes implanted with radially asymmetric multifocal intraocular lens (IOLs). This retrospective study evaluated 52 eyes (52 patients) implanted with a radially asymmetric multifocal IOL (LS-312

  8. Autorefraction versus subjective refraction in a radially asymmetric multifocal intraocular lens

    NARCIS (Netherlands)

    Linden, J.W.M. van der; Vrijman, V.; El-Saady, R.; Meulen, I.J. van der; Mourits, M.P.; Lapid-Gortzak, R.

    2014-01-01

    PURPOSE: To evaluate whether the automated refraction (AR) correlates with subjective manifest (MR) refraction in eyes implanted with radially asymmetric multifocal intraocular lens (IOLs). METHODS: This retrospective study evaluated 52 eyes (52 patients) implanted with a radially asymmetric

  9. Numerical investigation on splitting of ferrofluid microdroplets in T-junctions using an asymmetric magnetic field with proposed correlation

    Science.gov (United States)

    Aboutalebi, Mohammad; Bijarchi, Mohamad Ali; Shafii, Mohammad Behshad; Kazemzadeh Hannani, Siamak

    2018-02-01

    The studies surrounding the concept of microdroplets have seen a dramatic increase in recent years. Microdroplets have applications in different fields such as chemical synthesis, biology, separation processes and micro-pumps. This study numerically investigates the effect of different parameters such as Capillary number, Length of droplets, and Magnetic Bond number on the splitting process of ferrofluid microdroplets in symmetric T-junctions using an asymmetric magnetic field. The use of said field that is applied asymmetrically to the T-junction center helps us control the splitting of ferrofluid microdroplets. During the process of numerical simulation, a magnetic field with various strengths from a dipole located at a constant distance from the center of the T-junction was applied. The main advantage of this design is its control over the splitting ratio of daughter droplets and reaching various microdroplet sizes in a T-junction by adjusting the magnetic field strength. The results showed that by increasing the strength of the magnetic field, the possibility of asymmetric splitting of microdroplets increases in a way that for high values of field strength, high splitting ratios can be reached. Also, by using the obtained results at various Magnetic Bond numbers and performing curve fitting, a correlation is derived that can be used to accurately predict the borderline between splitting and non-splitting zones of microdroplets flow in micro T-junctions.

  10. Augmented asymmetrical visual field dependence in asymptomatic diabetics: evidence of subclinical asymmetrical bilateral vestibular dysfunction.

    Science.gov (United States)

    Razzak, Rima Abdul; Bagust, Jeffery; Docherty, Sharon; Hussein, Wiam; Al-Otaibi, Abdullah

    2015-01-01

    Diabetes negatively affects the vestibular system in many ways, with vestibular dysfunction (VD), a co-morbidity with a high prevalence in diabetics. The ability to perceive subjective visual vertical (SVV), as a sign of vestibular dysfunction, and visual field dependence was measured using a computerized rod and frame test (CRAF). Alignment errors recorded from 47 asymptomatic Type II diabetics (no vertigo or falls, without peripheral neuropathy or retinopathy) were compared to 29 healthy age matched (46-69years) controls. Visual field dependence was significantly larger and more asymmetrical in the diabetics than controls. In the absence of any visual references, or when a vertical reference frame was provided, SVV perception was accurate in both groups, with no significant difference between the controls and diabetics. During tilted frame presentations, the proportion of subjects with either SVV deviations, or an asymmetry index, larger than an upper limit derived from the control data was significantly greater in diabetics than controls. These results suggest that the decreased ability to resolve visuo-vestibular conflict in asymptomatic diabetic patients (free of retinopathy and peripheral neuropathy) compared to controls may be related to diabetic complications affecting vestibular structures and thus causing a decompensation of subclinical vestibular asymmetries. Copyright © 2015 Elsevier Inc. All rights reserved.

  11. Option Pricing with Asymmetric Heteroskedastic Normal Mixture Models

    DEFF Research Database (Denmark)

    Rombouts, Jeroen V. K; Stentoft, Lars

    2015-01-01

    We propose an asymmetric GARCH in mean mixture model and provide a feasible method for option pricing within this general framework by deriving the appropriate risk neutral dynamics. We forecast the out-of-sample prices of a large sample of options on the S&P 500 index from January 2006 to December...

  12. Reputations in Markets with Asymmetric Information: A Classroom Game

    Science.gov (United States)

    Wolf, James R.; Myerscough, Mark A.

    2007-01-01

    The authors describe a classroom game used to teach students about the impact of reputations in markets with asymmetric information. The game is an extension of Holt and Sherman's lemons market game and simulates a market under three information conditions. In the full information setting, all participants know both the quality and the price of…

  13. DNA-based asymmetric organometallic catalysis in water

    NARCIS (Netherlands)

    Oelerich, Jens; Roelfes, Gerard

    2013-01-01

    Here, the first examples of DNA-based organometallic catalysis in water that give rise to high enantioselectivities are described. Copper complexes of strongly intercalating ligands were found to enable the asymmetric intramolecular cyclopropanation of alpha-diazo-beta-keto sulfones in water. Up to

  14. Bertrand Competition with Asymmetric Costs: A Solution in Pure Strategies

    NARCIS (Netherlands)

    Demuynck, Thomas; Herings, P. Jean-Jacques; Saulle, Riccardo D.; Seel, Christian

    2018-01-01

    We consider two versions of a Bertrand duopoly with asymmetric costs and homogeneous goods. They differ in whether predatory pricing is allowed. For each version, we derive the Myopic Stable Set in pure strategies as introduced by Demuynck, Herings, Saulle, and Seel (2017). We contrast our

  15. Asymmetric block copolymers confined in a thin film

    NARCIS (Netherlands)

    Huinink, HP; Brokken-Zijp, JCM; van Dijk, MA; Sevink, GJA

    2000-01-01

    We have used a dynamic density functional theory (DDFT) for polymeric systems, to simulate the formation of micro phases in a melt of an asymmetric block copolymer, A(n)B(m)(f(A) = 1/3), both in the bulk and in a thin film. In the DDFT model a polymer is represented as a chain of springs and beads.

  16. On the topology defined by Thurston's asymmetric metric

    DEFF Research Database (Denmark)

    Papadopoulos, Athanase; Theret, Guillaume

    2007-01-01

    that the topology that the asymmetric metric L induces on Teichmüller space is the same as the usual topology. Furthermore, we show that L satisfies the axioms of a (not necessarily symmetric) metric in the sense of Busemann and conclude that L is complete in the sense of Busemann....

  17. Economic Dispatch of Demand Response Balancing through Asymmetric Block Offers

    DEFF Research Database (Denmark)

    O'Connell, Niamh; Pinson, Pierre; Madsen, Henrik

    2015-01-01

    This paper proposes a method of describing the load shifting ability of flexible electrical loads in a manner suitable for existing power system dispatch frameworks. The concept of an asymmetric block offer for flexible loads is introduced. This offer structure describes the ability of a flexible...

  18. All Pseudocapacitive MXene-RuO2 Asymmetric Supercapacitors

    KAUST Repository

    Jiang, Qiu

    2018-01-23

    2D transition metal carbides and nitrides, known as MXenes, are an emerging class of 2D materials with a wide spectrum of potential applications, in particular in electrochemical energy storage. The hydrophilicity of MXenes combined with their metallic conductivity and surface redox reactions is the key for high-rate pseudocapacitive energy storage in MXene electrodes. However, symmetric MXene supercapacitors have a limited voltage window of around 0.6 V due to possible oxidation at high anodic potentials. In this study, the fact that titanium carbide MXene (Ti3C2Tx) can operate at negative potentials in acidic electrolyte is exploited, to design an all-pseudocapacitive asymmetric device by combining it with a ruthenium oxide (RuO2) positive electrode. This asymmetric device operates at a voltage window of 1.5 V, which is about two times wider than the operating voltage window of symmetric MXene supercapacitors, and is the widest voltage window reported to date for MXene-based supercapacitors. The complementary working potential windows of MXene and RuO2, along with proton-induced pseudocapacitance, significantly enhance the device performance. As a result, the asymmetric devices can deliver an energy density of 37 µW h cm−2 at a power density of 40 mW cm−2, with 86% capacitance retention after 20 000 charge–discharge cycles. These results show that pseudocapacitive negative MXene electrodes can potentially replace carbon-based materials in asymmetric electrochemical capacitors, leading to an increased energy density.

  19. Design of activated carbon/activated carbon asymmetric capacitors

    Science.gov (United States)

    Piñeiro-Prado, Isabel; Salinas-Torres, David; Ruiz Rosas, Ramiro; Morallon, Emilia; Cazorla-Amoros, Diego

    2016-03-01

    Supercapacitors are energy storage devices that offer a high power density and a low energy density in comparison with batteries. Their limited energy density can be overcome by using asymmetric configuration in mass electrodes, where each electrode works within their maximum available potential window, rendering the maximum voltage output of the system. Such asymmetric capacitors must be optimized through careful electrochemical characterization of the electrodes for accurate determination of the capacitance and the potential stability limits. The results of the characterization are then used for optimizing mass ratio of the electrodes from the balance of stored charge. The reliability of the design largely depends on the approach taken for the electrochemical characterization. Therefore, the performance could be lower than expected and even the system could break down, if a well thought out procedure is not followed. In this work, a procedure for the development of asymmetric supercapacitors based on activated carbons is detailed. Three activated carbon materials with different textural properties and surface chemistry have been systematically characterized in neutral aqueous electrolyte. The asymmetric configuration of the masses of both electrodes in the supercapacitor has allowed to cover a higher potential window, resulting in an increase of the energy density of the three devices studied when compared with the symmetric systems, and an improved cycle life.

  20. Non-stationary probabilities for the asymmetric exclusion process on ...

    Indian Academy of Sciences (India)

    rich picture of relaxation processes which provides an extension of notions of equi- librium statistical mechanics such as phase transitions and spontaneous symmetry breaking to the non-equilibrium case. The asymmetric exclusion process (ASEP) is the simplest model of non-equilibrium theory of many interacting particles ...

  1. Non-stationary probabilities for the asymmetric exclusion process

    Indian Academy of Sciences (India)

    A solution of the master equation for a system of interacting particles for finite time and particle density is presented. By using a new form of the Bethe ansatz, the totally asymmetric exclusion process on a ring is solved for arbitrary initial conditions and time intervals.

  2. Linguistic Correlates of Asymmetric Motor Symptom Severity in Parkinson's Disease

    Science.gov (United States)

    Holtgraves, Thomas; McNamara, Patrick; Cappaert, Kevin; Durso, Raymond

    2010-01-01

    Asymmetric motor severity is common in Parkinson's Disease (PD) and provides a method for examining the neurobiologic mechanisms underlying cognitive and linguistic deficits associated with the disorder. In the present research, PD participants (N = 31) were assessed in terms of the asymmetry of their motor symptoms. Interviews with the…

  3. Proline-catalysed asymmetric ketol cyclizations: The template ...

    Indian Academy of Sciences (India)

    Unknown

    Abstract. A modified template mechanism based on modelling studies of energy minimised complexes is presented for the asymmetric proline-catalysed cyclization of triketones 1, 2 and 3 to the 2S,3S-ketols. 1a, 2a and 3a respectively. The template model involves a three-point contact as favoured in enzyme– substrate ...

  4. Asymmetric Adjustment in the Ethanol and Grains Markets

    NARCIS (Netherlands)

    C-L. Chang (Chia-Lin); L.H. Chen (Li-Hsueh); S.M. Hammoudeh (Shawkat); M.J. McAleer (Michael)

    2011-01-01

    textabstractThis paper examines the long- and short-run asymmetric adjustments for nine pairs of spot and futures prices, itemized as three own pairs for three different bio-fuel ethanol types, three own pairs for three related agricultural products, namely corn, soybeans and sugar, and three cross

  5. The catalystic asymmetric synthesis of optically active epoxy ketones

    NARCIS (Netherlands)

    Marsman, Bertha Gerda

    1981-01-01

    In this thesis the use of catalytic asymmetric synthesis to prepare optically active epoxy ketones is described. This means that the auxiliary chirality, necessary to obtain an optically active product, is added in a catalytic quantity . In principle this is a very efficient way to make opticlly

  6. Cell Chirality Drives Left-Right Asymmetric Morphogenesis.

    Science.gov (United States)

    Inaki, Mikiko; Sasamura, Takeshi; Matsuno, Kenji

    2018-01-01

    Most macromolecules found in cells are chiral, meaning that they cannot be superimposed onto their mirror image. However, cells themselves can also be chiral, a subject that has received little attention until very recently. In our studies on the mechanisms of left-right (LR) asymmetric development in Drosophila , we discovered that cells can have an intrinsic chirality to their structure, and that this "cell chirality" is generally responsible for the LR asymmetric development of certain organs in this species. The actin cytoskeleton plays important roles in the formation of cell chirality. In addition, Myosin31DF ( Myo31DF ), which encodes Drosophila Myosin ID, was identified as a molecular switch for cell chirality. In other invertebrate species, including snails and Caenorhabditis elegans , chirality of the blastomeres, another type of cell chirality, determines the LR asymmetry of structures in the body. Thus, chirality at the cellular level may broadly contribute to LR asymmetric development in various invertebrate species. Recently, cell chirality was also reported for various vertebrate cultured cells, and studies suggested that cell chirality is evolutionarily conserved, including the essential role of the actin cytoskeleton. Although the biological roles of cell chirality in vertebrates remain unknown, it may control LR asymmetric development or other morphogenetic events. The investigation of cell chirality has just begun, and this new field should provide valuable new insights in biology and medicine.

  7. Asymmetrical Modulation for Uplink Communication in Cooperative Networks

    DEFF Research Database (Denmark)

    Zhang, Qi; Fitzek, Frank H.P.; Iversen, Villy Bæk

    2008-01-01

    -range links with neighboring mobile devices to form cooperative clusters. So far the physical communication over cellular links and over short-range links are separated in time or in frequency. Beyond this state of the art, we exploit a method, referred to as asymmetrical modulation, where a mobile device...

  8. Review of literature on the asymmetric collapse of vapor bubbles

    International Nuclear Information System (INIS)

    Fremd, R.; Froehlich, G.

    1977-06-01

    This report contains a review of literature on the asymmetric collape of vapor bubbles by cavitation with special consideration to vapor explosions. Two numerical models, which describe the collapse of cavities in the neighbourhood of a solid surface, are presented. Moreover experimental results for this case are provided. Propositions to apply the numerical models to vapor explosions are made. (orig.) [de

  9. Symmetrical and asymmetrical growth restriction in preterm-born children

    NARCIS (Netherlands)

    Bocca-Tjeertes, Inger; Bos, Arend; Kerstjens, Jorien; de Winter, Andrea; Reijneveld, Sijmen

    OBJECTIVE: To determine how symmetric (proportionate; SGR) and asymmetric (disproportionate; AGR) growth restriction influence growth and development in preterms from birth to 4 years. METHODS: This community-based cohort study of 810 children comprised 86 SGR, 61 AGR, and 663 non-growth restricted

  10. Analysis of the asymmetrical shortest two-server queueing model

    NARCIS (Netherlands)

    J.W. Cohen

    1995-01-01

    textabstractThis study presents the analytic solution for the asymmetrical two-server queueing model with arriving customers joining the shorter queue for the case with Poisson arrivals and negative exponentially distributed service times. The bivariate generating function of the stationary joint

  11. New approaches in asymmetric synthesis using γ-alkoxybutenolides

    NARCIS (Netherlands)

    Lange, Ben de; Jansen, Johan F.G.A.; Jong, Johannes C. de; Lubben, Marcel; Faber, Wijnand; Schudde, Ebe P.; Feringa, Bernard

    1992-01-01

    The synthesis of a new class of auxiliary based chiral synthons, γ-alkoxy-2(5H)-furanones, is described. The multifunctional compounds enter a variety of asymmetric transformations leading to acyclic- and cyclic-products with up to four new stereogenic centers in a single operation with

  12. Materials dependence of mixed gas plasticization behavior in asymmetric membranes

    NARCIS (Netherlands)

    Visser, Tymen; Masetto, N.; Wessling, Matthias

    2007-01-01

    The mass transport of asymmetric membranes for the separation of carbon dioxide/methane mixtures is determined by competitive sorption and plasticization. With increasing feed pressure in mixed gas experiments, the selectivity decreases due to both effects. Distinction whether one or the other

  13. Design of activated carbon/activated carbon asymmetric capacitors

    Directory of Open Access Journals (Sweden)

    Isabel ePiñeiro-Prado

    2016-03-01

    Full Text Available Supercapacitors are energy storage devices that offer a high power density and a low energy density in comparison with batteries. Their limited energy density can be overcome by using asymmetric configuration in mass electrodes, where each electrode works within their maximum available potential window, rendering the maximum voltage output of the system. Such asymmetric capacitors must be optimized through careful electrochemical characterization of the electrodes for accurate determination of the capacitance and the potential stability limits. The results of the characterization are then used for optimizing mass ratio of the electrodes from the balance of stored charge. The reliability of the design largely depends on the approach taken for the electrochemical characterization. Therefore, the performance could be lower than expected and even the system could break down, if a well thought out procedure is not followed.In this work, a procedure for the development of asymmetric supercapacitors based on activated carbons is detailed. Three activated carbon materials with different textural properties and surface chemistry have been systematically characterized in neutral aqueous electrolyte. The asymmetric configuration of the masses of both electrodes in the supercapacitor has allowed to cover a higher potential window, resulting in an increase of the energy density of the three devices studied when compared with the symmetric systems, and an improved cycle life.

  14. Asymmetric electroresistance of cluster glass state in manganites

    KAUST Repository

    Lourembam, James; Ding, Junfeng; Bera, Ashok; Lin, Weinan; Wu, Tao

    2014-01-01

    cluster glass magnetic state emerges at low temperatures with a spin freezing temperature of about 99 K, which is accompanied by the reentrant insulating state with high resistance below 30 K. In the EDLT, we observe bipolar and asymmetric modulation

  15. Clinical characteristics in patients with asymmetric idiopathic pulmonary fibrosis.

    Science.gov (United States)

    Callahan, Sean J; Xia, Meng; Murray, Susan; Flaherty, Kevin R

    2016-10-01

    A group of patients with idiopathic pulmonary fibrosis (IPF) presents with disease affecting one lung markedly more than the other. At this time, it is unclear how this population differs from those who present with more symmetric disease. We sought to explain the characteristics of the asymmetric group and how their disease progresses. In this retrospective case-control study we accessed an interstitial lung disease (ILD) database and identified 14 asymmetric IPF cases via high-resolution computed tomography (HRCT) scoring of each lung lobe's disease severity. We identified 28 symmetric IPF controls from the same database using the same methods, and compared the clinical features of each group. Patients with asymmetric disease exhibited similar demographics as those in the general IPF population; they were predominantly male (64%), elderly (69 years old), and used tobacco (57%). We found a trend toward significantly increased all-cause mortality in the case population two years following diagnosis (p = 0.089). Pulmonary function tests were significantly lower in the case group at the time of diagnosis, then both groups experienced gradual decline. We found no statistically significant differences in number of IPF exacerbations (cases 43%, controls 39%, p = 0.824) and gastro-esophageal reflux (both groups 50%). Patients with asymmetric IPF resemble patients in the general IPF population but may have a lower overall survival rate. Further systemic factors may be studied to identify reasons for disease asymmetry and clinical decline in this population. Published by Elsevier Ltd.

  16. Simulation of seismic signals from asymmetric LANL hydrodynamic calculations

    International Nuclear Information System (INIS)

    Stevens, J.L.; Rimer, N.; Halda, E.J.; Barker, T.G.; Davis, C.G.; Johnson, W.E.

    1993-01-01

    Hydrodynamic calculations of an asymmetric nuclear explosion source were propagated to teleseismic distances to investigate the effects of the asymmetric source on seismic signals. The source is an explosion in a 12 meter long canister with the device at one end of the canister and a metal plate adjacent to the explosion. This produces a strongly asymmetric two-lobed source in the hydrodynamic region. The hydrodynamic source is propagated to the far field using a three-step process. The Eulerian hydrodynamic code SOIL was used by LANL to calculate the material velocity, density, and internal energy up to a time of 8.9 milliseconds after the explosion. These quantities were then transferred to an initial grid for the Lagrangian elastic/plastic finite difference code CRAM, which was used by S-CUBED to propagate the signal through the region of nonlinear deformation into the external elastic region. The cavity size and shape at the time of the overlay were determined by searching for a rapid density change in the SOIL grid, and this interior region was then rezoned into a single zone. The CRAM calculation includes material strength and gravity, and includes the effect of the free surface above the explosion. Finally, far field body waves were calculated by integrating over a closed surface in the elastic region and using the representation theorem. A second calculation was performed using an initially spherical source for comparison with the asymmetric calculation

  17. Novel Cinchona derived organocatalysts: new asymmetric transformations and catalysis

    NARCIS (Netherlands)

    Breman, A.C.

    2014-01-01

    Cinchona alkaloids have a long history as being a powerful medicine against malaria. Since a relative short period (about 50 years) chemist have also used these alkaloids as chiral catalyst for a wide variety of asymmetric transformations. Especially since the beginning of this century, when strong

  18. Stability of asymmetric lipid bilayers assessed by molecular dynamics simulations

    NARCIS (Netherlands)

    Esteban-Martin, Santi; Risselada, H. Jelger; Salgado, Jesus; Marrink, Siewert J.

    2009-01-01

    The asymmetric insertion of amphiphiles into biological membranes compromises the balance between the inner and outer monolayers. As a result, area expansion of the receiving leaflet and curvature strain may lead to membrane permeation, shape changes, or membrane fusion events. We have conducted

  19. Current Topics in the Asymmetric Transfer Hydrogenation of Imines

    Czech Academy of Sciences Publication Activity Database

    Januščák, J.; Václavík, Jiří; Šot, P.; Pecháček, J.; Vilhanová, B.; Kuzma, Marek; Kačer, P.

    2015-01-01

    Roč. 109, č. 7 (2015), s. 492-498 ISSN 0009-2770 R&D Projects: GA ČR GAP106/12/1276; GA MŠk(CZ) LO1509 Institutional support: RVO:61388971 Keywords : asymmetric transfer hydrogenation * ruthenium * isoquinoline Subject RIV: EE - Microbiology, Virology Impact factor: 0.279, year: 2015

  20. Beamwidth for asymmetric and multilayer semiconductor laser structures

    DEFF Research Database (Denmark)

    Buus, Jens

    1981-01-01

    An expression for the far field of the fundamental TE0mode in an asymmetrical dielectric slab waveguide is derived. By using normalized waveguide parameters, universal plots of the beamwidth are presented. These plots include the obliquity factor correction. Experimental results for symmetrical G...

  1. Accelerating foreign-key joins using asymmetric memory channels

    NARCIS (Netherlands)

    Pirk, H.; Manegold, S.; Kersten, M.

    2011-01-01

    Indexed Foreign-Key Joins expose a very asymmetric access pattern: the Foreign-Key Index is sequentially scanned whilst the Primary-Key table is target of many quasi-random lookups which is the dominant cost factor. To reduce the costs of the random lookups the fact-table can be (re-) partitioned at

  2. Ion Motion Stability in Asymmetric Surface Electrode Ion Traps

    Science.gov (United States)

    Shaikh, Fayaz; Ozakin, Arkadas

    2010-03-01

    Many recently developed designs of the surface electrode ion traps for quantum information processing have asymmetry built into their geometries. The asymmetry helps rotate the trap axes to angles with respect to electrode surface that facilitate laser cooling of ions but introduces a relative angle between the RF and DC fields and invalidates the classical stability analysis of the symmetric case for which the equations of motion are decoupled. For asymmetric case the classical motion of a single ion is given by a coupled, multi-dimensional version of Mathieu's equation. In this poster we discuss the stability diagram of asymmetric surface traps by performing an approximate multiple scale perturbation analysis of the coupled Mathieu equations, and validate the results with numerical simulations. After obtaining the stability diagram for the linear fields, we simulate the motion of an ion in a given asymmetric surface trap, utilizing a method-of-moments calculation of the electrode fields. We obtain the stability diagram and compare it with the ideal case to find the region of validity. Finally, we compare the results of our stability analysis to experiments conducted on a microfabricated asymmetric surface trap.

  3. The on-line asymmetric traveling salesman problem

    NARCIS (Netherlands)

    Ausiello, G.; Bonifaci, V.; Laura, L.

    2008-01-01

    We consider two on-line versions of the asymmetric traveling salesman problem with triangle inequality. For the homing version, in which the salesman is required to return in the city where it started from, we give a -competitive algorithm and prove that this is best possible. For the nomadic

  4. Bertrand Competition with an Asymmetric No-Discrimination Constraint

    NARCIS (Netherlands)

    Bouckaert, J.M.C.; Degryse, H.A.; van Dijk, T.

    2012-01-01

    Abstract: We study the competitive and welfare consequences when only one firm must commit to uniform pricing while the competitor’s pricing policy is left unconstrained. The asymmetric no-discrimination constraint prohibits both behaviour-based price discrimination within the competitive segment

  5. Modulational Instability in Linearly Coupled Asymmetric Dual-Core Fibers

    Directory of Open Access Journals (Sweden)

    Arjunan Govindarajan

    2017-06-01

    Full Text Available We investigate modulational instability (MI in asymmetric dual-core nonlinear directional couplers incorporating the effects of the differences in effective mode areas and group velocity dispersions, as well as phase- and group-velocity mismatches. Using coupled-mode equations for this system, we identify MI conditions from the linearization with respect to small perturbations. First, we compare the MI spectra of the asymmetric system and its symmetric counterpart in the case of the anomalous group-velocity dispersion (GVD. In particular, it is demonstrated that the increase of the inter-core linear-coupling coefficient leads to a reduction of the MI gain spectrum in the asymmetric coupler. The analysis is extended for the asymmetric system in the normal-GVD regime, where the coupling induces and controls the MI, as well as for the system with opposite GVD signs in the two cores. Following the analytical consideration of the MI, numerical simulations are carried out to explore nonlinear development of the MI, revealing the generation of periodic chains of localized peaks with growing amplitudes, which may transform into arrays of solitons.

  6. QUARTZ: a numerical simulation of an asymmetric electrostatic accelerator

    International Nuclear Information System (INIS)

    Wooten, J.W.; Drooks, L.J.; McCollough, D.H.; McGaffey, R.W.; Whealton, J.H.

    1979-01-01

    The physics and numerical aspects of the development of the computer code QUARTZ are given. This code includes the (1) use of a finite element code to obtain solutions of Poisson's equation in an asymmetric, three-dimensional volume; (2) inclusion of space charge neutralization by electrons; and (3) inclusion of ion space charge through an iterative procedure

  7. Simulation of the longitudinal instabilities of the asymmetric bunches

    International Nuclear Information System (INIS)

    Dai Jianping; Zhao Zhentang

    2002-01-01

    The computational model of the code used to simulate the longitudinal instabilities of the asymmetric bunches was introduced. The growth rates of the longitudinal instabilities of the symmetric bunches got by this code were compared with those got by the code ZAP, and they were almost the same. As an example, the simulation results of the BEPC-II were presented

  8. Asymmetric bipolar membrane: A tool to improve product purity

    NARCIS (Netherlands)

    Balster, J.H.; Sumbharaju, R.; Srikantharajah, S.; Punt, Ineke G.M.; Stamatialis, Dimitrios; Jordan, V.; Wessling, Matthias

    2007-01-01

    Bipolar membranes (BPMs) are catalytic membranes for electro-membrane processes splitting water into protons and hydroxyl ions. To improve selectivity and current efficiency of BPMs, we prepare new asymmetric BPMs with reduced salt leakages. The flux of salt ions across a BPM is determined by the

  9. Totally Asymmetric Limit for Models of Heat Conduction

    Science.gov (United States)

    De Carlo, Leonardo; Gabrielli, Davide

    2017-08-01

    We consider one dimensional weakly asymmetric boundary driven models of heat conduction. In the cases of a constant diffusion coefficient and of a quadratic mobility we compute the quasi-potential that is a non local functional obtained by the solution of a variational problem. This is done using the dynamic variational approach of the macroscopic fluctuation theory (Bertini et al. in Rev Mod Phys 87:593, 2015). The case of a concave mobility corresponds essentially to the exclusion model that has been discussed in Bertini et al. (J Stat Mech L11001, 2010; Pure Appl Math 64(5):649-696, 2011; Commun Math Phys 289(1):311-334, 2009) and Enaud and Derrida (J Stat Phys 114:537-562, 2004). We consider here the convex case that includes for example the Kipnis-Marchioro-Presutti (KMP) model and its dual (KMPd) (Kipnis et al. in J Stat Phys 27:6574, 1982). This extends to the weakly asymmetric regime the computations in Bertini et al. (J Stat Phys 121(5/6):843-885, 2005). We consider then, both microscopically and macroscopically, the limit of large externalfields. Microscopically we discuss some possible totally asymmetric limits of the KMP model. In one case the totally asymmetric dynamics has a product invariant measure. Another possible limit dynamics has instead a non trivial invariant measure for which we give a duality representation. Macroscopically we show that the quasi-potentials of KMP and KMPd, which are non local for any value of the external field, become local in the limit. Moreover the dependence on one of the external reservoirs disappears. For models having strictly positive quadratic mobilities we obtain instead in the limit a non local functional having a structure similar to the one of the boundary driven asymmetric exclusion process.

  10. Uniform versus asymmetric shading mediates crown recession in conifers.

    Directory of Open Access Journals (Sweden)

    Amanda L Schoonmaker

    Full Text Available In this study we explore the impact of asymmetrical vs. uniform crown shading on the mortality and growth of upper and lower branches within tree crowns, for two conifer species: shade intolerant lodgepole pine (Pinus contorta and shade tolerant white spruce (Picea glauca. We also explore xylem hydraulics, foliar nutrition, and carbohydrate status as drivers for growth and expansion of the lower and upper branches in various types of shading. This study was conducted over a two-year period across 10 regenerating forest sites dominated by lodgepole pine and white spruce, in the lower foothills of Alberta, Canada. Trees were assigned to one of four shading treatments: (1, complete uniform shading of the entire tree, (2 light asymmetric shading where the lower 1/4-1/3 of the tree crown was shaded, (3 heavy asymmetric shading as in (2 except with greater light reduction and (4 control in which no artificial shading occurred and most of the entire crown was exposed to full light. Asymmetrical shading of only the lower crown had a larger negative impact on the bud expansion and growth than did uniform shading, and the effect was stronger in pine relative to spruce. In addition, lower branches in pine also had lower carbon reserves, and reduced xylem-area specific conductivity compared to spruce. For both species, but particularly the pine, the needles of lower branches tended to store less C than upper branches in the asymmetric shade, which could suggest a movement of reserves away from the lower branches. The implications of these findings correspond with the inherent shade tolerance and self-pruning behavior of these conifers and supports a carbon based mechanism for branch mortality--mediated by an asymmetry in light exposure of the crown.

  11. The Impacts of Dry Dynamic Cores on Asymmetric Hurricane Intensification

    Science.gov (United States)

    Guimond, Stephen R.; Reisner, Jon M.; Marras, Simone; Giraldo, Francis X.

    2016-01-01

    The fundamental pathways for tropical cyclone (TC) intensification are explored by considering axisymmetric and asymmetric impulsive thermal perturbations to balanced, TC-like vortices using the dynamic cores of three different nonlinear numerical models. Attempts at reproducing the results of previous work, which used the community WRF Model, revealed a discrepancy with the impacts of purely asymmetric thermal forcing. The current study finds that thermal asymmetries can have an important, largely positive role on the vortex intensification, whereas other studies find that asymmetric impacts are negligible. Analysis of the spectral energetics of each numerical model indicates that the vortex response to asymmetric thermal perturbations is significantly damped in WRF relative to the other models. Spectral kinetic energy budgets show that this anomalous damping is primarily due to the increased removal of kinetic energy from the vertical divergence of the vertical pressure flux, which is related to the flux of inertia-gravity wave energy. The increased kinetic energy in the other two models is shown to originate around the scales of the heating and propagate upscale with time from nonlinear effects. For very large thermal amplitudes (50 K), the anomalous removal of kinetic energy due to inertia-gravity wave activity is much smaller, resulting in good agreement between models. The results of this paper indicate that the numerical treatment of small-scale processes that project strongly onto inertia-gravity wave energy can lead to significant differences in asymmetric TC intensification. Sensitivity tests with different time integration schemes suggest that diffusion entering into the implicit solution procedure is partly responsible for the anomalous damping of energy.

  12. Holistic metrology qualification extension and its application to characterize overlay targets with asymmetric effects

    Science.gov (United States)

    Dos Santos Ferreira, Olavio; Sadat Gousheh, Reza; Visser, Bart; Lie, Kenrick; Teuwen, Rachel; Izikson, Pavel; Grzela, Grzegorz; Mokaberi, Babak; Zhou, Steve; Smith, Justin; Husain, Danish; Mandoy, Ram S.; Olvera, Raul

    2018-03-01

    Ever increasing need for tighter on-product overlay (OPO), as well as enhanced accuracy in overlay metrology and methodology, is driving semiconductor industry's technologists to innovate new approaches to OPO measurements. In case of High Volume Manufacturing (HVM) fabs, it is often critical to strive for both accuracy and robustness. Robustness, in particular, can be challenging in metrology since overlay targets can be impacted by proximity of other structures next to the overlay target (asymmetric effects), as well as symmetric stack changes such as photoresist height variations. Both symmetric and asymmetric contributors have impact on robustness. Furthermore, tweaking or optimizing wafer processing parameters for maximum yield may have an adverse effect on physical target integrity. As a result, measuring and monitoring physical changes or process abnormalities/artefacts in terms of new Key Performance Indicators (KPIs) is crucial for the end goal of minimizing true in-die overlay of the integrated circuits (ICs). IC manufacturing fabs often relied on CD-SEM in the past to capture true in-die overlay. Due to destructive and intrusive nature of CD-SEMs on certain materials, it's desirable to characterize asymmetry effects for overlay targets via inline KPIs utilizing YieldStar (YS) metrology tools. These KPIs can also be integrated as part of (μDBO) target evaluation and selection for final recipe flow. In this publication, the Holistic Metrology Qualification (HMQ) flow was extended to account for process induced (asymmetric) effects such as Grating Imbalance (GI) and Bottom Grating Asymmetry (BGA). Local GI typically contributes to the intrafield OPO whereas BGA typically impacts the interfield OPO, predominantly at the wafer edge. Stack height variations highly impact overlay metrology accuracy, in particular in case of multi-layer LithoEtch Litho-Etch (LELE) overlay control scheme. Introducing a GI impact on overlay (in nm) KPI check quantifies the

  13. MODELING OF THREE-PHASE THREE LEG TRANSFORMER DEVICES FOR ENGINEERING CALCULATIONS OF ASYMMETRICAL MODES FOR DIFFERENT SCHEMES OF WINDING CONNECTIONS

    Directory of Open Access Journals (Sweden)

    Bosneaga V.A

    2013-08-01

    Full Text Available The model is proposed for the calculation and research of steady state asymmetric modes and transients in three-phase three legs transformer devices with arbitrary diagram of windings connection, taking into account the electromagnetic coupling of the windings, located on different legs. Using as an example distribution transformer of 10/0.4 kV calculations and analysis were performed of the most characteristic steady asymmetrical modes, that occur during short circuit, phase failure, unbalanced load for the most common windings connections and, in particular, associated with the occurrence of zero sequence magnetic flow. For the considered regimes and schemes vector diagrams were constructed for currents and voltages as well as for the relative values of magnetic flow, which give a clear idea about their particular features.

  14. Asymmetric Aldol Additions: A Guided-Inquiry Laboratory Activity on Catalysis

    Science.gov (United States)

    King, Jorge H. Torres; Wang, Hong; Yezierski, Ellen J.

    2018-01-01

    Despite the importance of asymmetric catalysis in both the pharmaceutical and commodity chemicals industries, asymmetric catalysis is under-represented in undergraduate chemistry laboratory curricula. A novel guided-inquiry experiment based on the asymmetric aldol addition was developed. Students conduct lab work to compare the effectiveness of…

  15. Topography significantly influencing low flows in snow-dominated watersheds

    Science.gov (United States)

    Li, Qiang; Wei, Xiaohua; Yang, Xin; Giles-Hansen, Krysta; Zhang, Mingfang; Liu, Wenfei

    2018-03-01

    Watershed topography plays an important role in determining the spatial heterogeneity of ecological, geomorphological, and hydrological processes. Few studies have quantified the role of topography in various flow variables. In this study, 28 watersheds with snow-dominated hydrological regimes were selected with daily flow records from 1989 to 1996. These watersheds are located in the Southern Interior of British Columbia, Canada, and range in size from 2.6 to 1780 km2. For each watershed, 22 topographic indices (TIs) were derived, including those commonly used in hydrology and other environmental fields. Flow variables include annual mean flow (Qmean), Q10 %, Q25 %, Q50 %, Q75 %, Q90 %, and annual minimum flow (Qmin), where Qx % is defined as the daily flow that occurred each year at a given percentage (x). Factor analysis (FA) was first adopted to exclude some redundant or repetitive TIs. Then, multiple linear regression models were employed to quantify the relative contributions of TIs to each flow variable in each year. Our results show that topography plays a more important role in low flows (flow magnitudes ≤ Q75 %) than high flows. However, the effects of TIs on different flow magnitudes are not consistent. Our analysis also determined five significant TIs: perimeter, slope length factor, surface area, openness, and terrain characterization index. These can be used to compare watersheds when low flow assessments are conducted, specifically in snow-dominated regions with the watershed size less than several thousand square kilometres.

  16. Behaviour of tetraalkylammonium ions in high-field asymmetric waveform ion mobility spectrometry.

    Science.gov (United States)

    Aksenov, Alexander A; Kapron, James T

    2010-05-30

    High-field asymmetric waveform ion mobility spectrometry (FAIMS) is an ion-filtering technique recently adapted for use with liquid chromatography/mass spectrometry (LC/MS) to remove interferences during analysis of complex matrices. This is the first systematic study of a series of singly charged tetraalkylammonium ions by FAIMS-MS. The compensation voltage (CV) is the DC offset of the waveform which permits the ion to emerge from FAIMS and it was determined for each member of the series under various conditions. The electrospray ionization conditions explored included spray voltage, vaporizer temperature, and sheath and auxiliary gas pressure. The FAIMS conditions explored included carrier gas flow rate, electrode temperature and composition of the carrier gas. Optimum desolvation was achieved using sufficient carrier gas (flow rate > or = 2 L/min) to ensure stable response. Low-mass ions (m/z 100-200) are more susceptible to changes in electrode temperature and gas composition than high mass ions (m/z 200-700). As a result of this study, ions are reliably analyzed using standard FAIMS conditions (dispersion voltage -5000 V, carrier gas flow rate 3 L/min, 50% helium/50%nitrogen, inner electrode temperature 70 degrees C and outer electrode temperature 90 degrees C). Variation of FAIMS conditions may be of great use for the separation of very low mass tetraalkylammonium (TAA) ions from other TAA ions. The FAIMS conditions do not appear to have a major effect on higher mass ions. Copyright 2010 John Wiley & Sons, Ltd.

  17. Calibration of nozzle for air mass flow measurement

    Science.gov (United States)

    Uher, Jan; Kanta, Lukáš

    2017-09-01

    The effort to make calibration measurement of mass flow through a nozzle was not satisfying. Traversing across the pipe radius with Pitot probe was done. The presence of overshoot behind the bend in the pipe was found. The overshoot led to an asymmetric velocity profile.

  18. Impacts of a jet's exit flow pattern on mixing and combustion performance

    Energy Technology Data Exchange (ETDEWEB)

    Nathan, G.J.; Mi, J.; Newbold, G.J.R.; Nobes, D.S. [Turbulence, Energy and Combustion Group, School of Mechanical Engineering, The University of Adelaide, South Australia 5005 (Australia); Alwahabi, Z.T. [Turbulence, Energy and Combustion Group, Chemical Engineering, The University of Adelaide, South Australia 5005 (Australia)

    2006-09-15

    The influence of modifying a jet's exit flow pattern on both the near and far-field turbulent mixing processes and on the resulting combustion performance, is explored. This reveals that, in contradiction to some common assumptions, increasing the coherence of large-scale motions can decrease molecular mixing rates, and yet can still be beneficial in some applications. Even relatively minor changes to the exit flow pattern of a non-reacting round jet, through changes to the nozzle profile are found to propagate downstream into the far field, apparently through the underlying turbulent structure. Importantly, while a jet from a smoothly contracting nozzle is found to have higher rates of entrainment, mean spread and mean decay of the scalar field than does a long pipe jet, it has a lower rate of molecular mixing. That is, increased large-scale mixing does not necessarily result in increased fine-scale mixing. A range of devices are reviewed which enhance, or stimulate the large-scale, coherent motions in an emerging jet using acoustic, mechanical or fluidic methods. The available evidence suggests that those methods which induce instantaneously asymmetric flow structure are more effective at increasing the near-field spreading than are those which induce instantaneously axisymmetric flow structure. Only limited data are available of the effects of such near-field changes on the far-field properties. Nevertheless, the available data reveal a clear trend that this near-field flow undergoes a transition to a far-field state whose spread and decay is comparable with that of a steady jet, albeit being indelibly altered by the near-field excitation. It also suggests that 'self-exciting' devices (i.e. that are not externally forced), cause a net reduction in the total entrainment relative to the unexcited jet, due to the losses induced by the device itself. Nevertheless, the changes which they can impart to the flow, such as redistributing the turbulent

  19. Impacts of a jet's exit flow pattern on mixing and combustion performance

    Energy Technology Data Exchange (ETDEWEB)

    Nathan, G J; Mi, J; Newbold, G J.R.; Nobes, D S [Turbulence, Energy and Combustion Group, School of Mechanical Engineering, The University of Adelaide, South Australia 5005 (Australia); Alwahabi, Z T [Turbulence, Energy and Combustion Group, Chemical Engineering, The University of Adelaide, South Australia 5005 (Australia)

    2006-09-15

    The influence of modifying a jet's exit flow pattern on both the near and far-field turbulent mixing processes and on the resulting combustion performance, is explored. This reveals that, in contradiction to some common assumptions, increasing the coherence of large-scale motions can decrease molecular mixing rates, and yet can still be beneficial in some applications. Even relatively minor changes to the exit flow pattern of a non-reacting round jet, through changes to the nozzle profile are found to propagate downstream into the far field, apparently through the underlying turbulent structure. Importantly, while a jet from a smoothly contracting nozzle is found to have higher rates of entrainment, mean spread and mean decay of the scalar field than does a long pipe jet, it has a lower rate of molecular mixing. That is, increased large-scale mixing does not necessarily result in increased fine-scale mixing. A range of devices are reviewed which enhance, or stimulate the large-scale, coherent motions in an emerging jet using acoustic, mechanical or fluidic methods. The available evidence suggests that those methods which induce instantaneously asymmetric flow structure are more effective at increasing the near-field spreading than are those which induce instantaneously axisymmetric flow structure. Only limited data are available of the effects of such near-field changes on the far-field properties. Nevertheless, the available data reveal a clear trend that this near-field flow undergoes a transition to a far-field state whose spread and decay is comparable with that of a steady jet, albeit being indelibly altered by the near-field excitation. It also suggests that 'self-exciting' devices (i.e. that are not externally forced), cause a net reduction in the total entrainment relative to the unexcited jet, due to the losses induced by the device itself. Nevertheless, the changes which they can impart to the flow, such as redistributing the turbulent energy from the

  20. Hermite-Pade approximation approach to hydromagnetic flows in convergent-divergent channels

    International Nuclear Information System (INIS)

    Makinde, O.D.

    2005-10-01

    The problem of two-dimensional, steady, nonlinear flow of an incompressible conducting viscous fluid in convergent-divergent channels under the influence of an externally applied homogeneous magnetic field is studied using a special type of Hermite-Pade approximation approach. This semi-numerical scheme offers some advantages over solutions obtained by using traditional methods such as finite differences, spectral method, shooting method, etc. It reveals the analytical structure of the solution function and the important properties of overall flow structure including velocity field, flow reversal control and bifurcations are discussed. (author)