WorldWideScience

Sample records for asymmetrical flow field-flow

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

    DEFF Research Database (Denmark)

    Kuntsche, Judith; Decker, Christiane; Fahr, Alfred

    2012-01-01

    Liposomes composed of dipalmitoylphosphatidylcholine and dipalmitoylphosphatidylglycerol were analyzed by asymmetrical flow field-flow fractionation coupled with multi-angle laser light scattering. In addition to evaluation of fractionation conditions (flow conditions, sample mass, carrier liquid...

  2. 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

    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 es...

  3. Characterization of enzymatically synthesized amylopectin analogs via asymmetrical flow field flow fractionation

    NARCIS (Netherlands)

    Ciric, Jelena; Rolland-Sabate, Agnes; Guilois, Sophie; Loos, Katja

    2014-01-01

    Asymmetrical flow field flow fractionation (AF4), when coupled with multi-angle laser light scattering (MALLS), is a very powerful technique for determination of the macromolecular structure of high molar mass (branched) polysaccharides. AF4 is a size fractionation technique just as size exclusion c

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

    OpenAIRE

    David eMüller; Stefano eCattaneo; Florian eMeier; Roland eWelz; deMello, Andrew J.

    2015-01-01

    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 ...

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

    OpenAIRE

    Müller, David; Cattaneo, Stefano; Meier, Florian; Welz, Roland; de Mello, Andrew J.

    2015-01-01

    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 down-scaled platform...

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

    Directory of Open Access Journals (Sweden)

    David eMüller

    2015-07-01

    Full Text Available 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.

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

    Science.gov (United States)

    Müller, David; Cattaneo, Stefano; Meier, Florian; Welz, Roland; de Mello, Andrew J

    2015-01-01

    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 down-scaled 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. PMID:26258119

  8. Factors affecting measurement of channel thickness in asymmetrical flow field-flow fractionation.

    Science.gov (United States)

    Dou, Haiyang; Jung, Euo Chang; Lee, Seungho

    2015-05-01

    Asymmetrical flow field-flow fractionation (AF4) has been considered to be a useful tool for simultaneous separation and characterization of polydisperse macromolecules or colloidal nanoparticles. AF4 analysis requires the knowledge of the channel thickness (w), which is usually measured by injecting a standard with known diffusion coefficient (D) or hydrodynamic diameter (dh). An accurate w determination is a challenge due to its uncertainties arising from the membrane's compressibility, which may vary with experimental condition. In the present study, influence of factors including the size and type of the standard on the measurement of w was systematically investigated. The results revealed that steric effect and the particles-membrane interaction by van der Waals or electrostatic force may result in an error in w measurement.

  9. Asymmetric flow field-flow fractionation in the field of nanomedicine.

    Science.gov (United States)

    Wagner, Michael; Holzschuh, Stephan; Traeger, Anja; Fahr, Alfred; Schubert, Ulrich S

    2014-06-01

    Asymmetric flow field-flow fractionation (AF4) is a widely used and versatile technique in the family of field-flow fractionations, indicated by a rapidly increasing number of publications. It represents a gentle separation and characterization method, where nonspecific interactions are reduced to a minimum, allows a broad separation range from several nano- up to micrometers and enables a superior characterization of homo- and heterogenic systems. In particular, coupling to multiangle light scattering provides detailed access to sample properties. Information about molar mass, polydispersity, size, shape/conformation, or density can be obtained nearly independent of the used material. In this Perspective, the application and progress of AF4 for (bio)macromolecules and colloids, relevant for "nano" medical and pharmaceutical issues, will be presented. The characterization of different nanosized drug or gene delivery systems, e.g., polymers, nanoparticles, micelles, dendrimers, liposomes, polyplexes, and virus-like-particles (VLP), as well as therapeutic relevant proteins, antibodies, and nanoparticles for diagnostic usage will be discussed. Thereby, the variety of obtained information, the advantages and pitfalls of this emerging technique will be highlighted. Additionally, the influence of different fractionation parameters in the separation process is discussed in detail. Moreover, a comprehensive overview is given, concerning the investigated samples, fractionation parameters as membrane types and buffers used as well as the chosen detectors and the corresponding references. The perspective ends up with an outlook to the future.

  10. 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. PMID:23261297

  11. Impact of asymmetrical flow field-flow fractionation on protein aggregates stability.

    Science.gov (United States)

    Bria, Carmen R M; Williams, S Kim Ratanathanawongs

    2016-09-23

    The impact of asymmetrical flow field-flow fractionation (AF4) on protein aggregate species is investigated with the aid of multiangle light scattering (MALS) and dynamic light scattering (DLS). The experimental parameters probed in this study include aggregate stability in different carrier liquids, shear stress (related to sample injection), sample concentration (during AF4 focusing), and sample dilution (during separation). Two anti-streptavidin (anti-SA) IgG1 samples composed of low and high molar mass (M) aggregates are subjected to different AF4 conditions. Aggregates suspended and separated in phosphate buffer are observed to dissociate almost entirely to monomer. However, aggregates in citric acid buffer are partially stable with dissociation to 25% and 5% monomer for the low and high M samples, respectively. These results demonstrate that different carrier liquids change the aggregate stability and low M aggregates can behave differently than their larger counterparts. Increasing the duration of the AF4 focusing step showed no significant changes in the percent monomer, percent aggregates, or the average Ms in either sample. Syringe-induced shear related to sample injection resulted in an increase in hydrodynamic diameter (dh) as measured by batch mode DLS. Finally, calculations showed that dilution during AF4 separation is significantly lower than in size exclusion chromatography with dilution occurring mainly at the AF4 channel outlet and not during the separation. This has important ramifications when analyzing aggregates that rapidly dissociate (theory may be more accurate than that measured by online DLS. Experimentally, the dhs determined by online DLS generally agreed with AF4 theory except for the more well retained larger aggregates for which DLS showed smaller sizes. These results highlight the importance of using AF4 retention theory to understand the impacts of dilution on analytes. PMID:27575921

  12. Separation and characterization of poly(tetrafluoroethylene) latex particles by asymmetric flow field flow fractionation with light-scattering detection.

    Science.gov (United States)

    Collins, Melissa E; Soto-Cantu, Erick; Cueto, Rafael; Russo, Paul S

    2014-04-01

    Poly(tetrafluoroethylene) (PTFE) latex particles have been analyzed and sorted according to size using asymmetric flow field flow fractionation (AF4) coupled with multiple-angle light scattering (MALS). Characterization of fractions by regular and depolarized dynamic light scattering confirmed that smaller particles elute prior to larger ones, as expected for field flow fractionation. The measured radii of the optically and geometrically anisotropic particles are consistent with those determined from transmission electron microscopy (TEM). A certain amount of heterogeneity remains in the fractions, but their uniformity for use as diffusion probes is improved. Full characterization of PTFE colloids will require a difficult assessment of the distribution, even within fractions, of the optical anisotropy. A general method to obtain number versus size distributions is presented. This approach is valid even when an online concentration detector is not available or ineffective. The procedure is adaptable to particles of almost any regular shape. PMID:24635125

  13. Analysis of liposomes using asymmetrical flow field-flow fractionation: separation conditions and drug/lipid recovery.

    Science.gov (United States)

    Kuntsche, Judith; Decker, Christiane; Fahr, Alfred

    2012-08-01

    Liposomes composed of dipalmitoylphosphatidylcholine and dipalmitoylphosphatidylglycerol were analyzed by asymmetrical flow field-flow fractionation coupled with multi-angle laser light scattering. In addition to evaluation of fractionation conditions (flow conditions, sample mass, carrier liquid), radiolabeled drug-loaded liposomes were used to determine the liposome recovery and a potential loss of incorporated drug during fractionation. Neither sample concentration nor the cross-flow gradient distinctly affected the size results but at very low sample concentration (injected mass 5 μg) the fraction of larger vesicles was underestimated. Imbalance in the osmolality between the inner and outer aqueous phase resulted in liposome swelling after dilution in hypoosmotic carrier liquids. In contrast, liposome shrinking under hyperosmotic conditions was barely visible. The liposomes themselves eluted 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 of temoporfin (partition coefficient ~9) was only minor (recovery about 80%). All fractionations were well repeatable under the experimental conditions applied in the present study.

  14. 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

    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...

  15. Characterization of sodium hyaluronate blends using frit inlet asymmetrical flow field-flow fractionation and multiangle light scattering.

    Science.gov (United States)

    Ali, Muhammad; Hwang, Euijin; Cho, Il-Hwan; Moon, Myeong Hee

    2012-01-01

    We characterized ultrahigh molecular weight sodium hyaluronate (NaHA) and blended pharmaceutical products containing NaHA using flow field-flow fractionation and multiangle light scattering-differential refractive index (FlFFF-MALS-DRI). NaHA is a water-soluble polysaccharide with a range of molecular weights (MW; 10(5)~10(8) Da) that is found in body fluids and tissues. NaHA is also used commercially in pharmaceutical and cosmetic applications. We used a frit inlet asymmetrical FlFFF channel to separate aqueous polymers according to their hydrodynamic size, and we used on-line measurements of light scattering to obtain the MW distribution (MWD) as well as structural information about NaHA in aqueous solution. In this study, we investigated NaHA and anti-adhesive blend mixtures of NaHA (a commercial NaHA blend mixture containing sodium carboxymethyl cellulose and a new blend with hydroxyethyl starch (HES)) to determine the molecular weight distribution MWD of NaHA and the blend mixtures and to obtain structural information about these compounds in aqueous solution. We also examined the characteristics of NaHA-HES-polylactic-co-glycolic acid film products exposed to gamma radiation for sterilization purposes. PMID:22101460

  16. Development and evaluation of methods for starch dissolution using asymmetrical flow field-flow fractionation. Part II: Dissolution of amylose.

    Science.gov (United States)

    Perez-Rea, Daysi; Bergenståhl, Björn; Nilsson, Lars

    2016-02-01

    In this paper, we investigate whether dissolution in water under autoclaving conditions (140 °C, 20 min) or in dimethyl sulfoxide, DMSO (100 °C, 1 h), is preferable for characterization of amylose. Two types of amylose, potato and maize, were dissolved either in water using an autoclave or in DMSO. On the aqueous solutions obtained, the extent of molecular dissolution of the sample (referred to as the dissolution yield) was determined by enzymatic analysis as well as the molecular properties, such as molar mass and root-mean-square radius, obtained with asymmetrical flow field-flow fractionation coupled to multi-angle light scattering and differential refractive index detection (AF4-MALS-dRI). The results showed that both dissolution methods are efficient at dissolving amylose. However, AF4-MALS-dRI analysis revealed substantial differences. Amylose aqueous solutions obtained by dissolution in DMSO were relatively stable over time, but the dissolution method in autoclave caused some degradation of the molecules, and their solutions display a high tendency to retrograde. PMID:26232931

  17. Field-Flow Fractionation.

    Science.gov (United States)

    Caldwell, Karin D.

    1988-01-01

    Describes a technique for separating samples that range over 15 orders of magnitude in molecular weight. Discusses theory, apparatus, and sample preparation techniques. Lists several types of field-flow fractionation (FFF) and their uses: sedimentation FFF, thermal FFF, flow FFF, electrical FFF, and steric FFF. (ML)

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

    OpenAIRE

    Thao M. Nguyen; Jingyu Liu; Hackley, Vincent A.

    2015-01-01

    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 mixtur...

  19. Characterizing changes in levan physicochemical properties in different pH environments using asymmetric flow field-flow fractionation.

    Science.gov (United States)

    Runyon, J Ray; Nilsson, Lars; Ulmius, Matilda; Castro, Alejandra; Ionescu, Ruxandra; Andersson, Claes; Schmidt, Christoph

    2014-02-01

    The purpose of this study was to assess the stability of the polyfructan levan under different pH solution conditions by monitoring changes in the levan physicochemical properties, such as molar mass (M), root mean square radius (r(rms)), hydrodynamic radius (r(h)), structure factor (r(rms)/r(h)), and aggregation state with respect to solution pH and hydrolysis time. A commercial levan produced from Z. Mobilis was characterized using asymmetric flow field-flow fractionation (AF4) in combination with online multiangle light scattering (MALS) and differential refractive index (dRI) detection. Under neutral pH solution conditions the levan was found to have a M ranging from 10(5) to 5 × 10(7) g/mol, a r(rms) ranging from ~25 to 100 nm and a r(h) from ~3 to 151 nm. Two populations were observed in the sample. One population with a M less than 106 g/mol which represented ~60 % of the sample and a second population with an ultrahigh M up to 5 × 10(7) g/mol, which comprised ~40 % of the sample. The measured r(rms)/r(h) structure factor decreased from 1.8 to 0.65 across the AF4 fractogram indicating that early eluting low M levan species had a random coil configuration and late eluting high M species had more homogeneous spherical structures. The measured apparent density values decreased from 80 to 10 kg/m(3) across the elution profile and suggest that the observed second population also contains aggregates. The stability of levan in different pH conditions ranging from 1.3 to 8.5 was assessed by tracking changes in the average M and r(h), and monitoring the formation of fructose over 1 week. The onset of levan acid hydrolysis was observed to occur sooner at lower pH conditions and no hydrolysis was observed for pH 5.5 and higher. PMID:24121433

  20. Asymmetric flow-field flow fractionation-multidetection coupling for assessing colloidal copper in drain waters from a Bordeaux wine-growing area.

    Science.gov (United States)

    El Hadri, Hind; Lespes, Gaëtane; Chéry, Philippe; Potin-Gautier, Martine

    2014-02-01

    The objective of this study was to show that on-line asymmetric flow-field flow fractionation (AFFFF)-multidetection coupling is useful for studying environmental colloids in a qualitative and quantitative way. The utility of the technique was illustrated by assessing the colloidal fraction of the copper that was extracted from the soil, transferred to an aqueous phase and then transported by drain waters in a wine-growing area. To determine the size and composition of the colloids, AFFFF was coupled to UV, multi-angle light scattering and inductively coupled plasma mass spectrometry detectors. Colloidal copper represents between 20 and 60% of the total copper in the sub 450 nm of drain waters. Copper is mainly associated with organic-rich colloids with a size below 10 nm. It is also found in organo-mineral populations (as clay or (oxy)hydroxides), with sizes ranging between 10 and 450 nm.

  1. 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...... of the Cr-, Co- and Mo-containing wear particles in a hip aspirate sample were in the range 40–150 nm. Off-line spICP-MS was used to confirm these findings for the Co- and Cr-containing nanoparticles. Whilst limited in scope, the results are sufficient to show the interaction of ions with transport proteins...... and give an indication of particle size, providing useful pathological indices. As such, the methods indicate a new way forward for in vivo investigation of the processes which lead to tissue necrosis and hip loosening in patients with MoM hip replacements....

  2. 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...

  3. 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.

  4. 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.

  5. 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.

  6. Characterization of ultrahigh-molecular weight cationic polyacrylamide using frit-inlet asymmetrical flow field-flow fractionation and multi-angle light scattering.

    Science.gov (United States)

    Woo, Sohee; Lee, Ju Yong; Choi, Woonjin; Moon, Myeong Hee

    2016-01-15

    In this study, frit inlet asymmetrical flow field-flow fractionation (FlFFF) with multi-angle light scattering (MALS) and differential refractive index (DRI) detection is utilized for size separation, determination of molecular weight (MW), and conformation of ultrahigh-MW (10(7)-10(9) g/mol) cationic polyacrylamides (C-PAMs), a class of water-soluble copolymers based on acrylamide and vinyl-type comonomers with quaternary ammonium cations that are widely used in wastewater treatment and in paper industries. Linear and branched C-PAM copolymers prepared in two different polymerization methods (solution and emulsion) from varying amounts of crosslinking agent and initiator were size fractionated by FlFFF with field-programming. It was found experimentally that the linear copolymers from both polymerization methods were less than 10(8) g/mol in MW with compact, nearly spherical structures, while the branched C-PAM copolymers from the emulsion polymerization showed a significant increase in average MW up to ∼ 10(9)g/mol, which was about 20-fold greater than those from the solution method, and the branched copolymers had more compact or shrunken conformations. While both linear and branched copolymers less than 10(8) g/mol MW were well resolved in an increasing order of MW (normal mode), it was noted that branched copolymers prepared through emulsion polymerization exhibited significantly larger MWs of 10(8-)10(9) g/mol and eluted in the steric/hyperlayer mode, in which the elution order is reversed in an extreme run condition (strong initial field strength followed by a fast field decay during programming). PMID:26724894

  7. Characterization of ultrahigh-molecular weight cationic polyacrylamide using frit-inlet asymmetrical flow field-flow fractionation and multi-angle light scattering.

    Science.gov (United States)

    Woo, Sohee; Lee, Ju Yong; Choi, Woonjin; Moon, Myeong Hee

    2016-01-15

    In this study, frit inlet asymmetrical flow field-flow fractionation (FlFFF) with multi-angle light scattering (MALS) and differential refractive index (DRI) detection is utilized for size separation, determination of molecular weight (MW), and conformation of ultrahigh-MW (10(7)-10(9) g/mol) cationic polyacrylamides (C-PAMs), a class of water-soluble copolymers based on acrylamide and vinyl-type comonomers with quaternary ammonium cations that are widely used in wastewater treatment and in paper industries. Linear and branched C-PAM copolymers prepared in two different polymerization methods (solution and emulsion) from varying amounts of crosslinking agent and initiator were size fractionated by FlFFF with field-programming. It was found experimentally that the linear copolymers from both polymerization methods were less than 10(8) g/mol in MW with compact, nearly spherical structures, while the branched C-PAM copolymers from the emulsion polymerization showed a significant increase in average MW up to ∼ 10(9)g/mol, which was about 20-fold greater than those from the solution method, and the branched copolymers had more compact or shrunken conformations. While both linear and branched copolymers less than 10(8) g/mol MW were well resolved in an increasing order of MW (normal mode), it was noted that branched copolymers prepared through emulsion polymerization exhibited significantly larger MWs of 10(8-)10(9) g/mol and eluted in the steric/hyperlayer mode, in which the elution order is reversed in an extreme run condition (strong initial field strength followed by a fast field decay during programming).

  8. 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

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

    International Nuclear Information System (INIS)

    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 109AgNPs 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

  10. Accurate Size and Size-Distribution Determination of Polystyrene Latex Nanoparticles in Aqueous Medium Using Dynamic Light Scattering and Asymmetrical Flow Field Flow Fractionation with Multi-Angle Light Scattering

    Directory of Open Access Journals (Sweden)

    Shinichi Kinugasa

    2012-01-01

    Full Text Available Accurate determination of the intensity-average diameter of polystyrene latex (PS-latex by dynamic light scattering (DLS was carried out through extrapolation of both the concentration of PS-latex and the observed scattering angle. Intensity-average diameter and size distribution were reliably determined by asymmetric flow field flow fractionation (AFFFF using multi-angle light scattering (MALS with consideration of band broadening in AFFFF separation. The intensity-average diameter determined by DLS and AFFFF-MALS agreed well within the estimated uncertainties, although the size distribution of PS-latex determined by DLS was less reliable in comparison with that determined by AFFFF-MALS.

  11. 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

    elemental mass 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 acid digestion and colloidal extraction. With the developed method a complete SiO2-ENPs and matrix separation with a Si mass recovery >90% was achieved by acid digestion. The alteration of the particle size distribution was minimized by particle stabilization. The generic procedure...... which also provides 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...

  12. In-house validation of a method for determination of silver nanoparticles in chicken meat based on asymmetric flow field-flow fractionation and inductively coupled plasma mass spectrometric detection

    DEFF Research Database (Denmark)

    Löschner, Katrin; Navratilova, Jana; Grombe, Ringo;

    2015-01-01

    spectrometric detection (AF4-ICP-MS) was applied for quantitative analysis of silver nanoparticles (AgNPs) in a chicken meat matrix following enzymatic sample preparation. For the first time an analytical validation of nanoparticle detection in a food matrix by AF4-ICP-MS has been carried out and the results......Nanomaterials are increasingly used in food production and packaging, and validated methods for detection of nanoparticles (NPs) in foodstuffs need to be developed both for regulatory purposes and product development. Asymmetric flow field-flow fractionation with inductively coupled plasma mass...... showed repeatable and intermediately reproducible determination of AgNP mass fraction and size. The findings demonstrated the potential of AF4-ICP-MS for quantitative analysis of NPs in complex food matrices for use in food monitoring and control. The accurate determination of AgNP size distribution...

  13. Lorentz transformation and vector field flows

    OpenAIRE

    Chiu, S. H.; Kuo, T. K.

    2003-01-01

    The parameter changes resulting from a combination of Lorentz transformation are shown to form vector field flows. The exact, finite Thomas rotation angle is determined and interpreted intuitively. Using phase portraits, the parameters evolution can be clearly visualized. In addition to identifying the fixed points, we obtain an analytic invariant, which correlates the evolution of parameters.

  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

    Energy Technology Data Exchange (ETDEWEB)

    Menendez-Miranda, Mario; Fernandez-Arguelles, Maria T.; Costa-Fernandez, Jose M., E-mail: jcostafe@uniovi.es; Encinar, Jorge Ruiz; Sanz-Medel, Alfredo, E-mail: asm@uniovi.es

    2014-08-11

    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. Asymmetric Flow-Field Flow Fractionation Hyphenated ICP-MS as an Alternative to Cloud Point Extraction for Quantification of Silver Nanoparticles and Silver Speciation: Application for Nanoparticles with a Protein Corona.

    Science.gov (United States)

    Mudalige, Thilak K; Qu, Haiou; Linder, Sean W

    2015-07-21

    Production and application of nanoparticles in consumer products is at an all-time high due to the emerging field of nanotechnology. Direct detection and quantification of trace levels of nanoparticles within consumer products is very challenging and problematic. Although multiple methodologies are available for this purpose, each method has its own set of limitations. Herein, we developed an analytical platform consisting of asymmetric flow-field flow fractionation (AF4) coupled with inductively coupled plasma mass spectroscopy (ICP-MS) for the speciation and quantification of silver ions and silver nanoparticles at the ng/kg level (ppt). AF4 is utilized to concentrate the nanoparticles, and ICP-MS acts as the detector. The protein corona that forms upon exposure of nanoparticles to bovine serum albumin was utilized as a nanoparticle stabilization and AF4 recovery enhancement mechanism. Speciation of silver ions and nanoparticles was achieved with the assistance of penicillamine as a complexation ligand. The effect of nanoparticle size, surface coating, and ionization state toward the detection and quantification of the developed methodology was evaluated. The detection limit was found to be 4 ng/kg with the application of a 5 mL sample loop. Further application of this developed methodology on environmentally relevant samples was demonstrated by the analysis of Arkansas River water spiked with silver nanoparticles and nanoparticle spiked into humic acid solution (50 mg/L) at an environmentally relevant level.

  16. The Application of Asymmetric Flow Field-Flow Fractionation in Nanomaterial and Biopolymers%非对称流场流分离技术在纳米材料及生物分子表征方面的应用

    Institute of Scientific and Technical Information of China (English)

    全灿; 刘攀攀; 金君素

    2013-01-01

    Field-flow fractionation is one of the most versatile separation techniques in the field of analytical separation sciences; it can separate, characterize and purify nanoparticles and proteins. It combines the effects of a laminar flow profile with an exponential concentration profile of analyte components caused by their interactions with a physical field applied perpendicular to the flow of a carrier liquid, and can determine the size, the size distribution and molecular weight distribution of the nanoparticles. Flow Field-flow fractionation provides a continuous and high-resolution separation, and becomes more and more popular. The classification of field-flow fractionation and its basic principle and applications of asymmetric flow field-flow fractionation are introduced. Finally the development tendency of this technology is summarized.%场流分离作为一类分离技术可分离、提纯和收集流体中的悬浮物微粒,它是将流体与外场联合作用于待分离物质,利用样品质量、体积和密度等性质的差异实现分离,然后利用分离物质的保留性质来确定样品颗粒粒径及分布、分子量等性质.其中非对称流场流分离能够提供连续的、高分辨率的分离,近年来越来越受到科研人员的欢迎.本文介绍了场流分离的分类及其原理,重点介绍了非对称流场流分离的原理及其应用,包括非对称流场流分离的影响因素及与其他分离技术的比较;最后总结了该技术的发展趋势.

  17. On the no-field method for void time determination in flow field-flow fractionation.

    Science.gov (United States)

    Martin, Michel; Hoyos, Mauricio

    2011-07-01

    Elution time measurements of colloidal particles injected in a symmetrical flow field-flow fractionation (flow FFF) system when the inlet and outlet cross-flow connections are closed have been performed. This no-field method has been proposed earlier for void time (and void volume) determination in flow FFF Giddings et al. (1977). The elution times observed were much larger than expected on the basis of the channel geometrical volume and the flow rate. In order to explain these discrepancies, a flow model allowing the carrier liquid to flow through the porous walls toward the reservoirs located behind the porous elements and along these reservoirs was developed. The ratio between the observed elution time and expected one is found to depend only on a parameter which is a function of the effective permeability and thickness of the porous elements and of the channel thickness and length. The permeabilities of the frits used in the system were measured. Their values lead to predicted elution times in reasonable agreement with experimental ones, taking into account likely membrane protrusion inside the channel on system assembly. They comfort the basic feature of the flow model, in the no-field case. The carrier liquid mostly bypasses the channel to flow along the system mainly in the reservoir. It flows through the porous walls toward the reservoirs near channel inlet and again through the porous walls from the reservoirs to the channel near channel outlet before exiting the system. In order to estimate the extent of this bypassing process, it is desirable that the hydrodynamic characteristics of the permeable elements (permeability and thickness) are provided by flow FFF manufacturers. The model applies to symmetrical as well as asymmetrical flow FFF systems. PMID:21256498

  18. Asymmetric reactions in continuous flow

    Directory of Open Access Journals (Sweden)

    Xiao Yin Mak

    2009-04-01

    Full Text Available An overview of asymmetric synthesis in continuous flow and microreactors is presented in this review. Applications of homogeneous and heterogeneous asymmetric catalysis as well as biocatalysis in flow are discussed.

  19. 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.

  20. Depolymerization study of sodium hyaluronate by flow field-flow fractionation/multiangle light scattering.

    Science.gov (United States)

    Kwon, Ji Hye; Hwang, Euijin; Cho, Il-Hwan; Moon, Myeong Hee

    2009-09-01

    Thermal depolymerization of ultrahigh-molecular-weight (UHMW) sodium hyaluronate (NaHA) was studied systematically by using frit-inlet asymmetrical flow field-flow fractionation/multiangle light scattering/differential refractive index (FI-AFlFFF/MALS/DRI). FI-AFlFFF was utilized for the size separation of NaHA samples which had been thermally degraded for varied treatment times, followed by light-scattering detection to determine MW and structural information of degraded NaHA products. Analysis of NaHA products showed time-dependent depolymerization of raw molecules into smaller-MW components, as well as unfolding of compact structures of UHMW NaHA. To determine whether the observed decrease in MW of sodium hyaluronate originated from the chain degradation of UHMW molecules or from dissociation of entangled complex particles that may have been formed by intermolecular association, narrow size fractions (1 x 10(7)-6 x 10(7) and >6 x 10(7) MW) of NaHA molecules were collected during FlFFF separation and followed by thermal treatment. Subsequent FI-AFlFFF/MALS analysis of collected fractions after thermal treatment suggested that the ultrahigh-MW region (>10(7) Da) of NaHA is likely to result from supermolecular structures formed by aggregation of large molecules. PMID:19649622

  1. Rapid protein separation and diffusion coefficient measurement by frit inlet flow field-flow fractionation.

    OpenAIRE

    Liu, M. K.; Li, P.; Giddings, J. C.

    1993-01-01

    In this study three flow field-flow fractionation (flow FFF) channels are utilized for the separation of proteins and for the simultaneous measurement of their translational diffusion coefficients, D. One channel has a traditional sample inlet, whereas the other two incorporate a frit inlet design that permits more convenient and rapid sample introduction. The dependence of retention time on D, which leads to differential elution and the opportunity to measure D for protein peaks purified by ...

  2. [Effects of carrier liquid and flow rate on the separation in gravitational field-flow fractionation].

    Science.gov (United States)

    Guo, Shuang; Zhu, Chenqi; Gao-Yang, Yaya; Qiu, Bailing; Wu, Di; Liang, Qihui; He, Jiayuan; Han, Nanyin

    2016-02-01

    Gravitational field-flow fractionation is the simplest field-flow fractionation technique in terms of principle and operation. The earth' s gravity is its external field. Different sized particles are injected into a thin channel and carried by carrier fluid. The different velocities of the carrier liquid in different places results in a size-based separation. A gravitational field-flow fractionation (GrFFF) instrument was designed and constructed. Two kinds of polystyrene (PS) particles with different sizes (20 µm and 6 µm) were chosen as model particles. In this work, the separation of the sample was achieved by changing the concentration of NaN3, the percentage of mixed surfactant in the carrier liquid and the flow rate of carrier liquid. Six levels were set for each factor. The effects of these three factors on the retention ratio (R) and plate height (H) of the PS particles were investigated. It was found that R increased and H decreased with increasing particle size. On the other hand, the R and H increased with increasing flow rate. The R and H also increased with increasing NaN3 concentration. The reason was that the electrostatic repulsive force between the particles and the glass channel wall increased. The force allowed the samples approach closer to the channel wall. The results showed that the resolution and retention time can be improved by adjusting the experimental conditions. These results can provide important values to the further applications of GrFFF technique. PMID:27382718

  3. Magnetic field flow phenomena in a falling particle receiver

    Science.gov (United States)

    Armijo, Kenneth M.; Ho, Clifford; Anderson, Ryan; Christian, Joshua; Babiniec, Sean; Ortega, Jesus

    2016-05-01

    Concentrating solar power (CSP) falling particle receivers are being pursued as a desired means for utilizing low-cost, high-absorptance particulate materials that can withstand high concentration ratios (˜1000 suns), operating temperatures above 700 °C, and inherent storage capabilities which can be used to reduce to levelized cost of electricity (LCOE)1. Although previous falling particle receiver designs have proven outlet temperatures above 800 °C, and thermal efficiencies between 80-90%, performance challenges still exist to operate at higher concentration ratios above 1000 suns and greater solar absorptance levels. To increase absorptance, these receivers will require enhanced particle residence time within a concentrated beam of sunlight. Direct absorption solid particle receivers that can enhance this residence time will have the potential to achieve heat-transfer media temperatures2 over 1000 °C. However, depending on particle size and external forces (e.g., external wind and flow due to convective heat losses), optimized particle flow can be severely affected, which can reduce receiver efficiency. To reduce particle flow destabilization and increase particle residence time on the receiver an imposed magnetic field is proposed based on a collimated design for two different methodologies. These include systems with ferromagnetic and charged particle materials. The approaches will be analytically evaluated based on magnetic field strength, geometry, and particle parameters, such as magnetic moment. A model is developed using the computational fluid dynamics (CFD) code ANSYS FLUENT to analyze these approaches for a ˜2 MWth falling particle receiver at Sandia National Laboratories5,6. Here, assessment will be made with respect to ferromagnetic particles such as iron-oxides, as well as charged particles. These materials will be parametrically assessed (e.g., type, size, dipole moment and geometry) over a range of magnetic permeability, μ values. Modeling

  4. Illustrating Some Principles of Separation Science through Gravitational Field-Flow Fractionation

    Science.gov (United States)

    Beckett, Ronald; Sharma, Reshmi; Andric, Goja; Chantiwas, Rattikan; Jakmunee, Jaroon; Grudpan, Kate

    2007-01-01

    Particle separation is an important but often neglected topic in undergraduate curricula. This article discusses how the method of gravitational field-flow fractionation (GrFFF) can be used to illustrate many principles of separation science and some fundamental concepts of physical chemistry. GrFFF separates particles during their elution through…

  5. 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.

  6. Application of flow field-flow fractionation for the characterization of macromolecules of biological interest: a review

    NARCIS (Netherlands)

    R.N. Qureshi; W.T. Kok

    2011-01-01

    An overview is given of the recent literature on (bio) analytical applications of flow field-flow fractionation (FlFFF). FlFFF is a liquid-phase separation technique that can separate macromolecules and particles according to size. The technique is increasingly used on a routine basis in a variety o

  7. Characterization of magnetic nanoparticles using programmed quadrupole magnetic field-flow fractionation

    OpenAIRE

    Williams, P. Stephen; Carpino, Francesca; Zborowski, Maciej

    2010-01-01

    Quadrupole magnetic field-flow fractionation is a relatively new technique for the separation and characterization of magnetic nanoparticles. Magnetic nanoparticles are often of composite nature having a magnetic component, which may be a very finely divided material, and a polymeric or other material coating that incorporates this magnetic material and stabilizes the particles in suspension. There may be other components such as antibodies on the surface for specific binding to biological ce...

  8. Characterization of magnetic nanoparticles using programmed quadrupole magnetic field-flow fractionation.

    Science.gov (United States)

    Williams, P Stephen; Carpino, Francesca; Zborowski, Maciej

    2010-09-28

    Quadrupole magnetic field-flow fractionation is a relatively new technique for the separation and characterization of magnetic nanoparticles. Magnetic nanoparticles are often of composite nature having a magnetic component, which may be a very finely divided material, and a polymeric or other material coating that incorporates this magnetic material and stabilizes the particles in suspension. There may be other components such as antibodies on the surface for specific binding to biological cells, or chemotherapeutic drugs for magnetic drug delivery. Magnetic field-flow fractionation (MgFFF) has the potential for determining the distribution of the magnetic material among the particles in a given sample. MgFFF differs from most other forms of field-flow fractionation in that the magnetic field that brings about particle separation induces magnetic dipole moments in the nanoparticles, and these potentially can interact with one another and perturb the separation. This aspect is examined in the present work. Samples of magnetic nanoparticles were analysed under different experimental conditions to determine the sensitivity of the method to variation of conditions. The results are shown to be consistent and insensitive to conditions, although magnetite content appeared to be somewhat higher than expected.

  9. 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

    An analytical platform coupling asymmetric flow field-flow fractionation (AF4) 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...... 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...

  10. 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

    sample preparation, field-flow fractionation (FFF) is one of the most promising techniques to achieve relevant characterization.The objective of this review is to present the current status of FFF as an analytical separation technique for the study of NPs in complex food and environmental samples. FFF...... 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...

  11. 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.

  12. Electrochemical response and separation in cyclic electric field-flow fractionation.

    Science.gov (United States)

    Chen, Zhi; Chauhan, Anuj

    2007-03-01

    Electric field-flow fractionation (EFFF) is a separation technique that couples a lateral electric field with axial Poiseuille flow to separate particles on the basis of size and/or mobility. In unidirectional EFFF, the field rapidly decreases in time due to charging of the double layer. The field strength could be increased by performing EFFF with cyclic electric fields. In cyclic electric field-flow fractionation (CEFFF), a periodic voltage, which can be either sinusoidal or square-wave, is applied in the lateral direction. In this paper, we measure the electrochemical response of CEFFF, i.e., the current-time response for a given time-dependent voltage and then utilize this electrochemical response in a transport model to predict separation. The CEFFF device studied here comprises two gold-coated glass plates separated by a spacer. The transient current profiles are measured for a step change and cyclic square-shaped voltage. The current profile is compared with the equivalent circuit model, and is fitted to a sum of two decaying exponentials. The dependence of the electrochemical response on voltage, frequency, channel thickness, and salt concentration is studied. Next, the electrochemical data are utilized in the convection-diffusion equation to develop a model for separation by CEFFF. The equations are solved by using a combination of analytical and numerical techniques to determine the mean velocity and the dispersion coefficient of molecules, and to determine the effect of various parameters on the separation efficiency of the EFFF device. Also, the model predictions are compared with experimental data available in the literature. PMID:17265539

  13. Hydrodynamic chromatography and field flow fractionation in finite aspect ratio channels.

    Science.gov (United States)

    Shendruk, T N; Slater, G W

    2014-04-25

    Hydrodynamic chromatography (HC) and field-flow fractionation (FFF) separation methods are often performed in 3D rectangular channels, though ideal retention theory assumes 2D systems. Devices are commonly designed with large aspect ratios; however, it can be unavoidable or desirable to design rectangular channels with small or even near-unity aspect ratios. To assess the significance of finite-aspect ratio effects and interpret experimental retention results, an ideal, analytical retention theory is needed. We derive a series solution for the ideal retention ratio of HC and FFF rectangular channels. Rather than limiting devices' ability to resolve samples, our theory predicts that retention curves for normal-mode FFF are well approximated by the infinite plate solution and that the performance of HC is actually improved. These findings suggest that FFF devices need not be designed with large aspect ratios and that rectangular HC channels are optimal when the aspect ratio is unity.

  14. Hydrodynamic chromatography and field flow fractionation in finite aspect ratio channels.

    Science.gov (United States)

    Shendruk, T N; Slater, G W

    2014-04-25

    Hydrodynamic chromatography (HC) and field-flow fractionation (FFF) separation methods are often performed in 3D rectangular channels, though ideal retention theory assumes 2D systems. Devices are commonly designed with large aspect ratios; however, it can be unavoidable or desirable to design rectangular channels with small or even near-unity aspect ratios. To assess the significance of finite-aspect ratio effects and interpret experimental retention results, an ideal, analytical retention theory is needed. We derive a series solution for the ideal retention ratio of HC and FFF rectangular channels. Rather than limiting devices' ability to resolve samples, our theory predicts that retention curves for normal-mode FFF are well approximated by the infinite plate solution and that the performance of HC is actually improved. These findings suggest that FFF devices need not be designed with large aspect ratios and that rectangular HC channels are optimal when the aspect ratio is unity. PMID:24674643

  15. Numerical simulation of bioparticle separation by dielectrophoretic field-flow-fractionation (DEP-FFF)

    Science.gov (United States)

    Marchis, Andreea; Neculae, Adrian

    2014-11-01

    The separation systems based on dielectrophoretic field-flow-fractionation (DEP-FFF) are used for a wide range of bioparticle types, including cells, bacteria, viruses, proteins, etc. An array of interdigitated microelectrodes lining the bottom surface of a thin chamber is used to generate dielectrophoretic forces that levitate the bioparticle mixture. The balance between DEP levitation and gravitational forces determines the bioparticles position at equilibrium heights within a fluid-flow profile, and consequently determines their velocities and the corresponding elution times. The elution time depends on the voltage applied on the microelectrodes, geometry of the device, bioparticle dielectric properties and density. This paper analyses numerically the behavior of a bioparticle mixture suspended in a dense and viscous fluid under dielectrophoresis. The controlled spatial separation of bioparticle mixture is performed by a combination of dielectrophoretic and hydrodynamic forces. The theoretical background and a set of numerical results (calculated DEP force, particle trajectories, etc.) are presented. The numerical solutions are obtained using the COMSOL Multiphysics finite element solver. The presented results demonstrate that the DEP-FFF method can be successfully applicable to many biomedical cell separation problems, including microfluidic-scale diagnosis and preparative-scale purification of cell subpopulations.

  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. T...... 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. A theory-based approach to thermal field-flow fractionation of polyacrylates.

    Science.gov (United States)

    Runyon, J Ray; Williams, S Kim Ratanathanawongs

    2011-09-28

    A theory-based approach is presented for the development of thermal field-flow fractionation (ThFFF) of polyacrylates. The use of ThFFF for polymer analysis has been limited by an incomplete understanding of the thermal diffusion which plays an important role in retention and separation. Hence, a tedious trial-and-error approach to method development has been the normal practice when analyzing new materials. In this work, thermal diffusion theories based on temperature dependent osmotic pressure gradient and polymer-solvent interaction parameters were used to estimate thermal diffusion coefficients (D(T)) and retention times (t(r)) for different polymer-solvent pairs. These calculations identified methyl ethyl ketone as a solvent that would cause significant retention of poly(n-butyl acrylate) (PBA) and poly(methyl acrylate) (PMA). Experiments confirmed retention of these two polymers that have not been previously analyzed by ThFFF. Theoretical and experimental D(T)s and t(r)s for PBA, PMA, and polystyrene in different solvents agreed to within 20% and demonstrate the feasibility of this theory-based approach. PMID:21872869

  18. Synthesis and size characterization of silica nanospheres using sedimentation field-flow fractionation (SdFFF).

    Science.gov (United States)

    Kim, Woon Jung; Ahn, Se Young; Kim, Jai Hoon; Chun, Jong Han; Yu, Jong Shin; Jung, Euo Chang; Lee, Seungho

    2012-01-01

    Silica nanoparticles were synthesized by a conventional emulsion polymerization by mixing ethanol, ammonium hydroxide, water and tetra ethyl orthosilicate (TEOS). A new reaction apparatus was assembled for a large scale synthesis of silica nanospheres in the laboratory, which was designed for uniform mixing of the reactants. The apparatus was equipped with a disc type agitator with six rectangular propellers. The new apparatus allowed high reproducibility in terms of the mean size and the size distribution of the silica nanoparticles with the relative standard deviation of less than about 6%. Sedimentation field-flow fractionation (SdFFF) was employed for determination of the size distribution of the silica nanoparticles. SdFFF provided size-based separation of the silica nanoparticles, with the retention time increasing with the size. When SdFFF analysis was repeated three times for the same sample, the standard deviation was less than 4%, showing reliability of SdFFF in size measurement. SdFFF seems to provide more accurate size distribution than DLS, particularly for those having broad and multimodal size distributions. Change in the agitation speed resulted in significant change in the mean diameter of the silica nanoparticles. Agitation speed of 400 rpm in 3 L reaction vessel yielded silica particles of about 100 nm in diameter, while at 200 rpm in 1 L vessel yielded those of about 500 nm. PMID:22524028

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

    International Nuclear Information System (INIS)

    Graphical abstract: -- Highlights: •Four types of SiO2 particles were characterized by SdFFF, PCS and EM techniques. •Clusters of 10 nm nanoparticles were found in some SiO2 samples. •A method was set up to extract SiO2 particles from food matrices. •The effects of the carrier solution composition on SdFFF separations were evaluated. •Particle size distributions were obtained from SiO2 particles extracted from foodstuffs. -- Abstract: 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

  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. 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...

  2. Micropolarity Ramification of Asymmetric Merging Flow

    CERN Document Server

    Siddiqui, Abuzar Abid

    2016-01-01

    The steady, asymmetric and two-dimensional flow of viscous, incompressible micropolar fluid through a rectangular channel with a splitter (parallel to walls) was formulated and simulated numerically. The plane Poiseuille flow was considered far from upstream and downstream of the splitter. The geometric parameter that controls the position of splitter was defined as splitter position parameter. A numerical scheme that comprises a fourth order method followed by special finite-difference method was used to solve the boundary value problem. This numerical scheme transforms the governing equations to system of finite difference equations which we have solved by SOR iterative method. Moreover, the results obtained were further refined and upgraded by the Richardson extrapolation method. The results were compared on different grid sizes as well as with the existing results for symmetric flow of Newtonian fluids. The comparisons were satisfactory. The microrotation effects on the splitter plate were significantly h...

  3. Characterization of silver nanoparticles using flow-field flow fractionation interfaced to inductively coupled plasma mass spectrometry.

    Science.gov (United States)

    Poda, A R; Bednar, A J; Kennedy, A J; Harmon, A; Hull, M; Mitrano, D M; Ranville, J F; Steevens, J

    2011-07-01

    The ability to detect and identify the physiochemical form of contaminants in the environment is important for degradation, fate and transport, and toxicity studies. This is particularly true of nanomaterials that exist as discrete particles rather than dissolved or sorbed contaminant molecules in the environment. Nanoparticles will tend to agglomerate or dissolve, based on solution chemistry, which will drastically affect their environmental properties. The current study investigates the use of field flow fractionation (FFF) interfaced to inductively coupled plasma-mass spectrometry (ICP-MS) as a sensitive and selective method for detection and characterization of silver nanoparticles. Transmission electron microscopy (TEM) is used to verify the morphology and primary particle size and size distribution of precisely engineered silver nanoparticles. Subsequently, the hydrodynamic size measurements by FFF are compared to dynamic light scattering (DLS) to verify the accuracy of the size determination. Additionally, the sensitivity of the ICP-MS detector is demonstrated by fractionation of μg/L concentrations of mixed silver nanoparticle standards. The technique has been applied to nanoparticle suspensions prior to use in toxicity studies, and post-exposure biological tissue analysis. Silver nanoparticles extracted from tissues of the sediment-dwelling, freshwater oligochaete Lumbriculus variegatus increased in size from approximately 31-46nm, indicating a significant change in the nanoparticle characteristics during exposure.

  4. Temperature distribution in front of the liquid-solid interface in the undercooled pure melt influenced by a transverse far field flow

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    The directional solidification in the undercooled pure melt influenced by a transverse far field flow was studied by using the multiple scale method. The result shows that in the boundary layer near the liquid-solid interface, when affected by a transverse far field flow, the temperature distribution in the direction of crystal growth presents an oscillatory and decay front in the side of liquid phase. The crucial distinguishing feature of a temperature pattern due to the transverse convection is the additional periodic modulation of the pattern in the growth direction. The wave number and eigenvalue that satisfy the Mullins-Sekerka dispersion relation are suppressed by the transverse far field flow.

  5. The steady-state solution of dendritic growth from the undercooled binary alloy melt with the far field flow

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    The steady-state dendritic growth from the undercooled binary alloy melt with the far field flow is considered. By neglecting the interface energy, interface kinetics and buoyancy effects in the system, we obtaine the steady-state solution for the case of the large Schmidt number, in terms of the multiple variable expansion method. The changes of the temperature and concentration fields, the morphology of the interface, the normalization parameter and the Peclet number of the system induced by uniform external flow are derived. The results show that, compared with the system of dendritic growth from undercooled pure melt, the convective flow in the system of growth from undercooled binary alloy has stronger effects on the morphology of the interface. Nevertheless, the shape of the interface still remains nearly a paraboloid.

  6. The steady-state solution of dendritic growth from the undercooled binary alloy melt with the far field flow

    Institute of Scientific and Technical Information of China (English)

    CHEN MingWen; WANG ZiDong; XU JianJun

    2009-01-01

    The steady-state dendritic growth from the undercooled binary alloy melt with the far field flow is considered.By neglecting the interface energy,interface kinetics and buoyancy effects in the system,we obtaine the steady-state solution for the case of the large Schmidt number,in terms of the multiple variable expansion method.The changes of thtemperature and concentration fields,the morphology of the interface,the normalization parameter and the Peclet number of the system induced by uniform external flow are derived.The results show that,compared with the system of dendritic growth from undercooled pure melt,the convective flow in the system of growth from undercooled binary alloy has stronger effects on the morphology of the interface.Nevertheless,the shape of the interface still remains nearly a paraboloid.

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

    International Nuclear Information System (INIS)

    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. 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.

  9. A novel method to detect unlabeled inorganic nanoparticles and submicron particles in tissue by sedimentation field-flow fractionation

    Directory of Open Access Journals (Sweden)

    Yost Garold S

    2008-12-01

    Full Text Available Abstract A novel methodology to detect unlabeled inorganic nanoparticles was experimentally demonstrated using a mixture of nano-sized (70 nm and submicron (250 nm silicon dioxide particles added to mammalian tissue. The size and concentration of environmentally relevant inorganic particles in a tissue sample can be determined by a procedure consisting of matrix digestion, particle recovery by centrifugation, size separation by sedimentation field-flow fractionation (SdFFF, and detection by light scattering. Background Laboratory nanoparticles that have been labeled by fluorescence, radioactivity, or rare elements have provided important information regarding nanoparticle uptake and translocation, but most nanomaterials that are commercially produced for industrial and consumer applications do not contain a specific label. Methods Both nitric acid digestion and enzyme digestion were tested with liver and lung tissue as well as with cultured cells. Tissue processing with a mixture of protease enzymes is preferred because it is applicable to a wide range of particle compositions. Samples were visualized via fluorescence microscopy and transmission electron microscopy to validate the SdFFF results. We describe in detail the tissue preparation procedures and discuss method sensitivity compared to reported levels of nanoparticles in vivo. Conclusion Tissue digestion and SdFFF complement existing techniques by precisely identifying unlabeled metal oxide nanoparticles and unambiguously distinguishing nanoparticles (diameter

  10. 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

    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......-line absorbance measurements was found feasible for the chosen model drug, but careful (re-) evaluation of turbidity effects is crucial for other drug and carrier combinations.......-THPP could accurately be determined in the fraction of small vesicles, on-line quantification was impaired in the fraction of the large acceptor liposomes due to the pronounced contribution of turbidity (about 80 % of total UV/VIS extinction signal). The AF4-based release/transfer approach suggested here...

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

    NARCIS (Netherlands)

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

    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 (C-60-pyr

  12. Phoretic flow induced by asymmetric confinement

    CERN Document Server

    Lisicki, Maciej; Lauga, Eric

    2016-01-01

    Internal phoretic flows due to the interactions of solid boundaries with local chemical gradients may be created using chemical patterning. Alternatively, we demonstrate here that internal flows might also be induced by geometric asymmetries of chemically-homogeneous surfaces. We characterise the circulatory flow created in a cavity enclosed between two eccentric cylindrical walls of uniform chemical activity. Local gradients of the diffusing solute induce a slip flow along the surface of the cylinders, leading to a circulatory bulk flow pattern which can be solved analytically in the diffusive limit. The flow strength can be controlled by adjusting the relative positions of the cylinders and an optimal configuration is identified. These results provide a model system for tunable phoretic pumps.

  13. 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. PMID:11407583

  14. 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.

  15. Characterization of winemaking yeast by cell number-size distribution analysis through flow field-flow fractionation with multi-wavelength turbidimetric detection.

    Science.gov (United States)

    Zattoni, Andrea; Melucci, Dora; Reschiglian, Pierluigi; Sanz, Ramsés; Puignou, Lluís; Galceran, Maria Teresa

    2004-10-29

    Yeasts are widely used in several areas of food industry, e.g. baking, beer brewing, and wine production. Interest in new analytical methods for quality control and characterization of yeast cells is thus increasing. The biophysical properties of yeast cells, among which cell size, are related to yeast cell capabilities to produce primary and secondary metabolites during the fermentation process. Biophysical properties of winemaking yeast strains can be screened by field-flow fractionation (FFF). In this work we present the use of flow FFF (FlFFF) with turbidimetric multi-wavelength detection for the number-size distribution analysis of different commercial winemaking yeast varieties. The use of a diode-array detector allows to apply to dispersed samples like yeast cells the recently developed method for number-size (or mass-size) analysis in flow-assisted separation techniques. Results for six commercial winemaking yeast strains are compared with data obtained by a standard method for cell sizing (Coulter counter). The method here proposed gives, at short analysis time, accurate information on the number of cells of a given size, and information on the total number of cells.

  16. Breakdown of doublet recirculation and direct line drives by far-field flow in reservoirs: implications for geothermal and hydrocarbon well placement

    Science.gov (United States)

    Weijermars, R.; van Harmelen, A.

    2016-07-01

    An important real world application of doublet flow occurs in well design of both geothermal and hydrocarbon reservoirs. A guiding principle for fluid management of injection and extraction wells is that mass balance is commonly assumed between the injected and produced fluid. Because the doublets are considered closed loops, the injection fluid is assumed to eventually reach the producer well and all the produced fluid ideally comes from stream tubes connected to the injector of the well pair making up the doublet. We show that when an aquifer background flow occurs, doublets will rarely retain closed loops of fluid recirculation. When the far-field flow rate increases relative to the doublet's strength, the area occupied by the doublet will diminish and eventually vanishes. Alternatively, rather than using a single injector (source) and single producer (sink), a linear array of multiple injectors separated by some distance from a parallel array of producers can be used in geothermal energy projects as well as in waterflooding of hydrocarbon reservoirs. Fluid flow in such an arrangement of parallel source-sink arrays is shown to be macroscopically equivalent to that of a line doublet. Again, any far-field flow that is strong enough will breach through the line doublet, which then splits into two vortices. Apart from fundamental insight into elementary flow dynamics, our new results provide practical clues that may contribute to improve the planning and design of doublets and direct line drives commonly used for flow management of groundwater, geothermal and hydrocarbon reservoirs.

  17. Breakdown of doublet re-circulation and direct line drives by far-field flow in reservoirs: Implications for geothermal and hydrocarbon well placement

    Science.gov (United States)

    Weijermars, R.; van Harmelen, A.

    2016-04-01

    An important real world application of doublet flow occurs in well design of both geothermal and hydrocarbon reservoirs. A guiding principle for fluid management of injection and extraction wells is that mass balance is commonly assumed between the injected and produced fluid. Because the doublets are considered closed loops, the injection fluid is assumed to eventually reach the producer well and all the produced fluid ideally comes from stream tubes connected to the injector of the well pair making up the doublet. We show that when an aquifer background flow occurs, doublets will rarely retain closed loops of fluid re-circulation. When the far-field flow rate increases relative to the doublet's strength, the area occupied by the doublet will diminish and eventually vanishes. Alternatively, rather than using a single injector (source) and single producer (sink), a linear array of multiple injectors separated by some distance from a parallel array of producers can be used in geothermal energy projects as well as in waterflooding of hydrocarbon reservoirs. Fluid flow in such an arrangement of parallel source-sink arrays is shown to be macroscopically equivalent to that of a line doublet. Again, any far-field flow that is strong enough will breach through the line doublet, which then splits into two vortices. Apart from fundamental insight into elementary flow dynamics, our new results provide practical clues that may contribute to improve the planning and design of doublets and direct line drives commonly used for flow management of groundwater, geothermal and hydrocarbon reservoirs.

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

    International Nuclear Information System (INIS)

    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)

  19. Elliptic and Triangular flow in asymmetric heavy-ion collisions

    CERN Document Server

    Haque, Md Rihan; Mohanty, Bedangadas

    2011-01-01

    We present a study of the elliptic (v2) and triangular (v3) flow and their corresponding eccentricity fluctuations for asymmetric (Au+Ag, Au+Cu and Au+Si) collisions at \\sqrt_NN = 200 GeV. These are compared to the corresponding results from symmetric (Au+Au and Cu+Cu) collisions at the same energy. The study which is carried out using a multi-phase transport (AMPT) model shows that triangularity (\\epsilon_3), fluctuations in triangularity and v3 do not show much variation for the different colliding ion sizes studied. However the eccentricity (\\epsilon_2), fluctuations in eccentricity and v2 shows a strong dependence on colliding ion size for a given number of participating nucleons. Our study thus indicates that asymmetric heavy-ion collisions could be used to constrain models dealing with flow fluctuations in heavy-ion collisions.

  20. On the wake flow of asymmetrically beveled trailing edges

    Science.gov (United States)

    Guan, Yaoyi; Pröbsting, Stefan; Stephens, David; Gupta, Abhineet; Morris, Scott C.

    2016-05-01

    Trailing edge and wake flows are of interest for a wide range of applications. Small changes in the design of asymmetrically beveled or semi-rounded trailing edges can result in significant difference in flow features which are relevant for the aerodynamic performance, flow-induced structural vibration and aerodynamically generated sound. The present study describes in detail the flow field characteristics around a family of asymmetrically beveled trailing edges with an enclosed trailing-edge angle of 25° and variable radius of curvature R. The flow fields over the beveled trailing edges are described using data obtained by particle image velocimetry (PIV) experiments. The flow topology for different trailing edges was found to be strongly dependent on the radius of curvature R, with flow separation occurring further downstream as R increases. This variation in the location of flow separation influences the aerodynamic force coefficients, which were evaluated from the PIV data using a control volume approach. Two-point correlations of the in-plane velocity components are considered to assess the structure in the flow field. The analysis shows large-scale coherent motions in the far wake, which are associated with vortex shedding. The wake thickness parameter yf is confirmed as an appropriate length scale to characterize this large-scale roll-up motion in the wake. The development in the very near wake was found to be critically dependent on R. In addition, high-speed PIV measurements provide insight into the spectral characteristics of the turbulent fluctuations. Based on the time-resolved flow field data, the frequency range associated with the shedding of coherent vortex pairs in the wake is identified. By means of time-correlation of the velocity components, turbulent structures are found to convect from the attached or separated shear layers without distinct separation point into the wake.

  1. Comparison of the molecular mass and optical properties of colored dissolved organic material in two rivers and coastal waters by flow field-flow fractionation.

    Science.gov (United States)

    Zanardi-Lamardo, Eliete; Clark, Catherine D; Moore, Cynthia A; Zika, Rod G

    2002-07-01

    Colored dissolved organic material (CDOM) is an important sunlight absorbing substance affecting the optical properties of natural waters. However, little is known about its structural and optical properties mainly due to its complex matrix and the limitation of the techniques available. A comparison of two southwestern Florida rivers [the Caloosahatchee River (CR) and the Shark River (SR)] was done in terms of molecular mass (MM) and diffusion coefficients (D). The novel technique Frit inlet/frit outlet-flow field-flow fractionation (FIFO-FIFFF) with absorbance and fluorescence detectors was used to determine these properties. The SR receives organic material from the Everglades. By contrast, the CR arises from Lake Okeechobee in central Florida, receiving anthropogenic inputs, farming runoff, and natural organics. Both rivers discharge to the Gulf of Mexico. Fluorescence identified, for both rivers, two different MM distributions in low salinity water samples: the first was centered at approximately 1.7 kDa (CR) and approximately 2 kDa (SR); the second centered at approximately 13 kDa for both rivers, which disappeared gradually in the river plumes to below detection limit in coastal waters. Absorbance detected only one MM distribution centered at approximately 2 kDa (CR) and 2.2-2.4 kDa (SR). Fluorescence in general peaked at a lower MM than absorbance, suggesting a different size distribution for fluorophores vs chromophores. A photochemical study showed that, after sunlight, irradiated freshwater samples have similar characteristics to more marine waters, including a shift in MM distribution of chromophores. The differences observed between the rivers in the optical characteristics, MM distributions, and D values suggest that the CDOM sources, physical, and photochemical degradation processes are different for these two rivers. PMID:12144250

  2. Comparison of the molecular mass and optical properties of colored dissolved organic material in two rivers and coastal waters by flow field-flow fractionation.

    Science.gov (United States)

    Zanardi-Lamardo, Eliete; Clark, Catherine D; Moore, Cynthia A; Zika, Rod G

    2002-07-01

    Colored dissolved organic material (CDOM) is an important sunlight absorbing substance affecting the optical properties of natural waters. However, little is known about its structural and optical properties mainly due to its complex matrix and the limitation of the techniques available. A comparison of two southwestern Florida rivers [the Caloosahatchee River (CR) and the Shark River (SR)] was done in terms of molecular mass (MM) and diffusion coefficients (D). The novel technique Frit inlet/frit outlet-flow field-flow fractionation (FIFO-FIFFF) with absorbance and fluorescence detectors was used to determine these properties. The SR receives organic material from the Everglades. By contrast, the CR arises from Lake Okeechobee in central Florida, receiving anthropogenic inputs, farming runoff, and natural organics. Both rivers discharge to the Gulf of Mexico. Fluorescence identified, for both rivers, two different MM distributions in low salinity water samples: the first was centered at approximately 1.7 kDa (CR) and approximately 2 kDa (SR); the second centered at approximately 13 kDa for both rivers, which disappeared gradually in the river plumes to below detection limit in coastal waters. Absorbance detected only one MM distribution centered at approximately 2 kDa (CR) and 2.2-2.4 kDa (SR). Fluorescence in general peaked at a lower MM than absorbance, suggesting a different size distribution for fluorophores vs chromophores. A photochemical study showed that, after sunlight, irradiated freshwater samples have similar characteristics to more marine waters, including a shift in MM distribution of chromophores. The differences observed between the rivers in the optical characteristics, MM distributions, and D values suggest that the CDOM sources, physical, and photochemical degradation processes are different for these two rivers.

  3. Size-based speciation of iron in clay mineral particles by gravitational field-flow fractionation with electrothermal atomic absorption spectrometry

    International Nuclear Information System (INIS)

    Gravitational field-flow fractionation (FFF) coupled to UV and ETAAS detectors has been tested for micron-size particles in the range of 5-20 μm using three Fe-rich clay samples. The iron content estimated after aqua regia extraction was about 20-40 mg kg-1. The ETAAS analysis was performed both off-line from collected fractions and in an online continuous sampling mode using a specially designed flow through vial placed in the autosampler of the ETAAS. Comparison of the direct injection method with total analysis after aqua regia digestion shows that slurry injection of the dilute samples in the gravitational field-flow fractionation (GrFFF) effluent is quite efficient in these samples. In the majority of cases, more than 90% recovery was obtained for the slurry injection method. Fe mass-based particle size distributions and Fe concentration versus particle diameter plots can be generated using certain assumptions. This provides detailed information on size-based speciation of particulate samples. Generally, the Fe concentrations in the particles decreased slightly with an increase in particle size as is often found for soil and sediment samples

  4. A new analytical platform based on field-flow fractionation and olfactory sensor to improve the detection of viable and non-viable bacteria in food.

    Science.gov (United States)

    Roda, Barbara; Mirasoli, Mara; Zattoni, Andrea; Casale, Monica; Oliveri, Paolo; Bigi, Alessandro; Reschiglian, Pierluigi; Simoni, Patrizia; Roda, Aldo

    2016-10-01

    An integrated sensing system is presented for the first time, where a metal oxide semiconductor sensor-based electronic olfactory system (MOS array), employed for pathogen bacteria identification based on their volatile organic compound (VOC) characterisation, is assisted by a preliminary separative technique based on gravitational field-flow fractionation (GrFFF). In the integrated system, a preliminary step using GrFFF fractionation of a complex sample provided bacteria-enriched fractions readily available for subsequent MOS array analysis. The MOS array signals were then analysed employing a chemometric approach using principal components analysis (PCA) for a first-data exploration, followed by linear discriminant analysis (LDA) as a classification tool, using the PCA scores as input variables. The ability of the GrFFF-MOS system to distinguish between viable and non-viable cells of the same strain was demonstrated for the first time, yielding 100 % ability of correct prediction. The integrated system was also applied as a proof of concept for multianalyte purposes, for the detection of two bacterial strains (Escherichia coli O157:H7 and Yersinia enterocolitica) simultaneously present in artificially contaminated milk samples, obtaining a 100 % ability of correct prediction. Acquired results show that GrFFF band slicing before MOS array analysis can significantly increase reliability and reproducibility of pathogen bacteria identification based on their VOC production, simplifying the analytical procedure and largely eliminating sample matrix effects. The developed GrFFF-MOS integrated system can be considered a simple straightforward approach for pathogen bacteria identification directly from their food matrix. Graphical abstract An integrated sensing system is presented for pathogen bacteria identification in food, in which field-flow fractionation is exploited to prepare enriched cell fractions prior to their analysis by electronic olfactory system

  5. Animating streamlines with repeated asymmetric patterns for steady flow visualization

    Science.gov (United States)

    Yeh, Chih-Kuo; Liu, Zhanping; Lee, Tong-Yee

    2012-01-01

    Animation provides intuitive cueing for revealing essential spatial-temporal features of data in scientific visualization. This paper explores the design of Repeated Asymmetric Patterns (RAPs) in animating evenly-spaced color-mapped streamlines for dense accurate visualization of complex steady flows. We present a smooth cyclic variable-speed RAP animation model that performs velocity (magnitude) integral luminance transition on streamlines. This model is extended with inter-streamline synchronization in luminance varying along the tangential direction to emulate orthogonal advancing waves from a geometry-based flow representation, and then with evenly-spaced hue differing in the orthogonal direction to construct tangential flow streaks. To weave these two mutually dual sets of patterns, we propose an energy-decreasing strategy that adopts an iterative yet efficient procedure for determining the luminance phase and hue of each streamline in HSL color space. We also employ adaptive luminance interleaving in the direction perpendicular to the flow to increase the contrast between streamlines.

  6. A quantitative determination of magnetic nanoparticle separation using on-off field operation of quadrupole magnetic field-flow fractionation (QMgFFF).

    Science.gov (United States)

    Orita, Toru; Moore, Lee R; Joshi, Powrnima; Tomita, Masahiro; Horiuchi, Takashi; Zborowski, Maciej

    2013-01-01

    Quadrupole Magnetic Field-Flow Fractionation (QMgFFF) is a technique for characterization of sub-micrometer magnetic particles based on their retention in the magnetic field from flowing suspensions. Different magnetic field strengths and volumetric flow rates were tested using on-off field application and two commercial nanoparticle preparations that significantly differed in their retention parameter, λ (by nearly 8-fold). The fractograms showed a regular pattern of higher retention (98.6% v. 53.3%) for the larger particle (200 nm v. 90 nm) at the higher flow rate (0.05 mL/min v. 0.01 mL/min) at the highest magnetic field (0.52 T), as expected because of its lower retention parameter. The significance of this approach is a demonstration of a system that is simpler in operation than a programmed field QMgFFF in applications to particle mixtures consisting of two distinct particle fractions. This approach could be useful for detection of unwanted particulate contaminants, especially important in industrial and biomedical applications.

  7. On Cauchy conditions for asymmetric mixed convection boundary layer flows

    Energy Technology Data Exchange (ETDEWEB)

    Amaouche, Mustapha [Laboratoire de Physique Theorique, Universite de Bejaia (Algeria); Kessal, Mohand [Departement Transport et Equipement Petrolier, Faculte des Hydrocarbures et de la Chimie, Universite de Boumerdes, 35000, Boumerdes (Algeria)

    2003-06-01

    The fundamental question of how and where does an asymmetric mixed convection boundary layer flow around a heated horizontal circular cylinder begin to develop is raised. We first transform the classical boundary layer equations by using an integral method of Karman-Pohlhausen type and obtain two coupled equations governing the evolutions of the dynamic and thermal boundary layers. Because of its global character, the implemented method allows to bypass the difficulty of downstream-upstream interactions. Cauchy conditions characterizing the starting of the boundary layers are found; they are obtained in a surprisingly simple manner for the limiting cases corresponding to Pr=1, Pr{yields}0 and Pr{yields}{infinity}. Otherwise, these conditions can be found by using a prediction correction algorithm. Some numerical experiments are finally performed in order to illustrate the theory. (authors)

  8. Edge Detection from MRI and DTI Images with an Anisotropic Vector Field Flow Using a Divergence Map

    Directory of Open Access Journals (Sweden)

    Donatella Giuliani

    2012-12-01

    Full Text Available The aim of this work is the extraction of edges from Magnetic Resonance Imaging (MRI and Diffusion Tensor Imaging (DTI images by a deformable contour procedure, using an external force field derived from an anisotropic flow. Moreover, we introduce a divergence map in order to check the convergence of the process. As we know from vector calculus, divergence is a measure of the magnitude of a vector field convergence at a given point. Thus by means level curves of the divergence map, we have automatically selected an initial contour for the deformation process. If the initial curve includes the areas from which the vector field diverges, it will be able to push the curve towards the edges. Furthermore the divergence map highlights the presence of curves pointing to the most significant geometric parts of boundaries corresponding to high curvature values. In this way, the skeleton of the extracted object will be rather well defined and may subsequently be employed in shape analysis and morphological studies.

  9. ASYMMETRIC VORTICES FLOW OVER SLENDER BODY AND ITS ACTIVE CONTROL AT HIGH ANGLE OF ATTACK

    Institute of Scientific and Technical Information of China (English)

    DENG Xueying; WANG Yankui

    2004-01-01

    The studies of asymmetric vortices flow over slender body and its active control at high angles of attack have significant importance for both academic field and engineering area. This paper attempts to provide an update state of art to the investigations on the fields of forebody asymmetric vortices. This review emphasizes the correlation between micro-perturbation on the model nose and its response and evolution behaviors of the asymmetric vortices. The critical issues are discussed,which include the formation and evolution mechanism of asymmetric multi-vortices; main behaviors of asymmetric vortices flow including its deterministic feature and vortices flow structure; the evolution and development of asymmetric vortices under the perturbation on the model nose; forebody vortex active control especially discussed micro-perturbation active control concept and technique in more detail. However present understanding in this area is still very limited and this paper tries to identify the key unknown problems in the concluding remarks.

  10. Agglomeration behaviour of titanium dioxide nanoparticles in river waters: A multi-method approach combining light scattering and field-flow fractionation techniques.

    Science.gov (United States)

    Chekli, L; Roy, M; Tijing, L D; Donner, E; Lombi, E; Shon, H K

    2015-08-15

    Titanium dioxide nanoparticles (TiO2 NPs) are currently one of the most prolifically used nanomaterials, resulting in an increasing likelihood of release to the environment. This is of concern as the potential toxicity of TiO2 NPs has been investigated in several recent studies. Research into their fate and behaviour once entering the environment is urgently needed to support risk assessment and policy development. In this study, we used a multi-method approach combining light scattering and field-flow fractionation techniques to assess both the aggregation behaviour and aggregate structure of TiO2 NPs in different river waters. Results showed that both the aggregate size and surface-adsorbed dissolved organic matter (DOM) were strongly related to the initial DOM concentration of the tested waters (i.e. R(2) > 0.90) suggesting that aggregation of TiO2 NPs is controlled by the presence and concentration of DOM. The conformation of the formed aggregates was also found to be strongly related to the surface-adsorbed DOM (i.e. R(2) > 0.95) with increasing surface-adsorbed DOM leading to more compact structures. Finally, the concentration of TiO2 NPs remaining in the supernatant after sedimentation of the larger aggregates was found to decrease proportionally with both increasing IS and decreasing DOM concentration, resulting in more than 95% sedimentation in the highest IS sample.

  11. Sedimentation field-flow fractionation for characterization of citric acid-modified Hβ zeolite particles: Effect of particle dispersion and carrier composition.

    Science.gov (United States)

    Dou, Haiyang; Bai, Guoyi; Ding, Liang; Li, Yueqiu; Lee, Seungho

    2015-11-27

    In this study, sedimentation field-flow fractionation (SdFFF) was, for the first time, applied for determination of size distribution of Hβ zeolite particles modified by citric acid (CA-Hβ). Effects of the particle dispersion and the carrier liquid composition (type of dispersing reagent (surfactant) and salt added in the carrier liquid, ionic strength, and pH) on SdFFF elution behavior of CA-Hβ zeolite particles were systematically investigated. Also the SdFFF separation efficiency of the particles was discussed in terms of the forces such as van der Waals, hydrophobic, and induced-dipole interactions. Results reveal that the type of salt and pH of the carrier liquid significantly affect the SdFFF separation efficiency of the zeolite particles. It was found that addition of a salt (NaN3) into the carrier liquid affects the characteristic of the SdFFF channel surface. It was found that the use of an acidic medium (pH 3.2) leads to a particle-channel interaction, while the use of a basic medium (pH 10.6) promotes an inter-particle hydrophobic interaction. Result from SdFFF was compared with those from scanning electron microscopy (SEM) and dynamic light scattering (DLS). It seems that, once the experimental conditions are optimized, SdFFF becomes a valuable tool for size characterization of the zeolite particles.

  12. Notes on the implementation of a fully-implicit numerical scheme for a two-phase three-field flow model

    International Nuclear Information System (INIS)

    The development of a fully-implicit scheme to model the two-phase three-field flow and heat transfer problem is presented here. The model was originally developed to simulate the complex phenomena occurring in proximity of the quench front of a nuclear reactor core during the reflood phase of a postulated LOCA. The fully-implicit method allows relative large time steps to be used even on very fine spatial grids which can not be considered when a semi-implicit scheme is applied to solve the conservation equation. The objective of this paper is to capture as much as possible, the lessons learned during the development and coding of the fully-implicit two-phase three-field model. The implementation of the model is one of the most time consuming and a challenging task. The literature on numerical models generally concentrates on the theoretical aspects of the numerical method but available information on the problems encountered during the implementation of such methods for real applications is scarce. The reason is that many of these methods are tailored to specific applications and sometimes are rather empirical. These techniques are the result of a long and tedious trial and error process from the developer. The article presented here attempts to provide some insights and guidelines for future development of this or similar models

  13. The role of nanominerals and mineral nanoparticles in the transport of toxic trace metals: Field-flow fractionation and analytical TEM analyses after nanoparticle isolation and density separation

    Science.gov (United States)

    Plathe, Kelly L.; von der Kammer, Frank; Hassellöv, Martin; Moore, Johnnie N.; Murayama, Mitsuhiro; Hofmann, Thilo; Hochella, Michael F.

    2013-02-01

    Nanominerals and mineral nanoparticles from a mining-contaminated river system were examined to determine their potential to co-transport toxic trace metals. A recent large-scale dam removal project on the Clark Fork River in western Montana (USA) has released reservoir and upstream sediments contaminated with toxic trace metals (Pb, As, Cu and Zn), which had accumulated there as a consequence of more than a century and a half of mining activity proximal to the river's headwaters near the cities of Butte and Anaconda. To isolate the high-density nanoparticle fractions from riverbed and bank sediments, a density separation with sodium polytungstate (2.8 g/cm3) was employed prior to a standard nanoparticle extraction procedure. The stable, dispersed nanoparticulate fraction was then analyzed by analytical transmission electron microscopy (aTEM) and flow field-flow fractionation (FlFFF) coupled to both multi-angle laser light scattering (MALLS) and high-resolution, inductively coupled plasma mass spectrometry (HR-ICPMS). FlFFF analysis revealed a size distribution in the nano range and that the elution profiles of the trace metals matched most closely to that for Fe and Ti. aTEM confirmed these results as the majority of the Fe and Ti oxides analyzed were associated with one or more of the trace metals of interest. The main mineral phases hosting trace metals are goethite, ferrihydrite and brookite. This demonstrates that they are likely playing a significant role in dictating the transport and distribution of trace metals in this river system, which could affect the bioavailability and toxicity of these metals.

  14. 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...... 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...... 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...

  15. 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

    A method of analysis of silver nanoparticles (AgNPs) in chicken meat was developed. The homogenized chicken meat sample, which was spiked with AgNPs, was subjected to enzymolysis by Proteinase K for 40 min at 37 °C. Transmission electron microscopy and inductively coupled plasma mass spectrometry...

  16. Asymmetric Flow Field Flow Fractionation Online with Single Particle – Inductively Coupled Plasma Mass Spectrometry: Detection and Quantification of Silver Nanoparticles in Aqueous Samples

    Science.gov (United States)

    Silver nanoparticles (AgNPs) are increasingly being used in many consumer products as disinfectants. Through the use of these products, AgNPs could likely enter aquatic environments. Because recent studies have shown that AgNPs are toxic to various species, including microorgan...

  17. Asymmetric Flow-Field Flow Fractionation (AF4) of Aqueous C60 Aggregates with Dynamic Light Scattering Size and LC-MS

    Science.gov (United States)

    Current methods for the size determination of nanomaterials in aqueous suspension include dynamic or static light scattering and electron or atomic force microscopy techniques. Light scattering techniques are limited by poor resolution and the scattering intensity dependence on p...

  18. 重力场流分离系统中载液及流速条件对分离的影响%Effects of carrier liquid and flow rate on the separation in gravitational field-flow fractionation

    Institute of Scientific and Technical Information of China (English)

    郭爽; 朱尘琪; 高杨亚雅; 邱百灵; 吴迪; 梁启慧; 何嘉媛; 韩南银

    2016-01-01

    Gravitational field-flow fractionation is the simplest field-flow fractionation technique in terms of principle and operation. The earth's gravity is its external field. Different sized par-ticles are injected into a thin channel and carried by carrier fluid. The different velocities of the carrier liquid in different places results in a size-based separation. A gravitational field-flow frac-tionation(GrFFF)instrument was designed and constructed. Two kinds of polystyrene(PS) particles with different sizes(20 μm and 6 μm)were chosen as model particles. In this work, the separation of the sample was achieved by changing the concentration of NaN 3,the percent-age of mixed surfactant in the carrier liquid and the flow rate of carrier liquid. Six levels were set for each factor. The effects of these three factors on the retention ratio( R)and plate height ( H)of the PS particles were investigated. It was found that R increased and H decreased with increasing particle size. On the other hand,the R and H increased with increasing flow rate. The R and H also increased with increasing NaN 3 concentration. The reason was that the elec-trostatic repulsive force between the particles and the glass channel wall increased. The force allowed the samples approach closer to the channel wall. The results showed that the resolution and retention time can be improved by adjusting the experimental conditions. These results can provide important values to the further applications of GrFFF technique.%重力场流分离作为最简单的一种场流分离技术,常用于分离微米级颗粒.选择两种不同粒径( 20 μm 和 6μm)的聚苯乙烯( PS)颗粒作为样品,通过改变载液中叠氮化钠浓度、混合表面活性剂的比例及载液流速,利用自行设计生产的重力场流分离( gravitational flow field-flow fractionation,GrFFF)仪器,对颗粒混合样品进行分离,得到了相关谱图与数据,考察了这3种因素对分离效果(保留比( R

  19. Local heat transfer in an in-line tube bundle with asymmetrical flow

    DEFF Research Database (Denmark)

    Meyer, Knud Erik

    1999-01-01

    Measurements of the local heat transfer in themiddle of a small in-line tube bundle with longitudinal to transverse pitches of $1.5\\times 1.8$ are performed at a Reynolds number of $30\\,000$. Asymmetrical distributions of the local heat transfer are found. The distributions are in good agreement...... with earlier flow measurements. The mean heat transfer rate is only little affected bythe asymmetrical conditions....

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

    Energy Technology Data Exchange (ETDEWEB)

    Leitner, David M., E-mail: dml@unr.edu [Department of Chemistry and Chemical Physics Program, University of Nevada, Reno, Nevada 89557 (United States); Freiburg Institute for Advanced Studies (FRIAS), Freiburg (Germany); Pandey, Hari Datt [Department of Chemistry and Chemical Physics Program, University of Nevada, Reno, Nevada 89557 (United States)

    2015-10-14

    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.

  1. Stability characteristics of the open channel flow above the asymmetrical irregular sand ripples

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    Sandy bed cannot keep its original smoothness as the flows pass. With the increase of the flow intensity, the bed forms will appear as sand ripples and dune in turn. Among these morphologies, the sand ripple scale is the smallest, which is generally symmetrical when it just appears, but as time goes on, the asymmetrical form gradually develops. Just because of this sand ripples asymmetry, it manifests the influence of the flow on the bed morphology and also the impact on the laminar flow dynamical process, especially the stability characteristics. The stability features of laminar flow on open channels with the asymmetrical sand ripples are discussed, and also the results on the symmetrical sand ripples are compared in detail.

  2. DEM Simulation of Solid Flow Including Asymmetric Phenomena in COREX Shaft Furnace

    Institute of Scientific and Technical Information of China (English)

    Zhi-guo LUO; Heng ZHOU; Tao ZHANG; Yang YOU; Hai-feng LI; Zong-shu ZOU

    2015-01-01

    Based on the principles of the discrete element method (DEM),a scaled-down model was established to analyze burden descending behavior,including asymmetric phenomena,throughout an entire COREX shaft furnace (SF).The applicability of the DEM model was validated by determining its accordance with a previous experiment. The effects of discharge rate and abnormal conditions on solid flow were described in terms of solid flow pattern and microscopic analysis.Results confirmed that the solid flow of the COREX SF can be divided into four different flow regions;the largest normal force exists at the top of the man-made dead zone,and the weak force network exists in the funnel flow region.The basic solid flow profile was identified as a clear Flat→U→W type.Increasing the dis-charge rate decreased the quasi-stagnant zone size,but did not affect the macroscopic motion of particles or the shape of patterns above the bustle.For asymmetric conditions,in which particles were discharged at different rates,the solid flow patterns were asymmetric.Under an abnormal condition where no particles were discharged from the left outlet,a sizeable stagnant zone was formed opposite to the working outlet,and “motionless”particles located in the left stagnant zone showed potential to increase the period of static contacts and sticking effect.

  3. Understanding Symmetric and Asymmetric DNA Patterns by Water Flow on a Solid Surface

    Institute of Scientific and Technical Information of China (English)

    LI Ding; FANG Hai-Ping; LEI Xiao-Ling; WU Shi-Ying; AI Xiao-Bai

    2003-01-01

    In order to use DNA for making molecular device, specific DNA patterns on a solid surface should be constructed. In this paper, we will show that the random interactions between the DNA segments and the solid surface play an important role in the final symmetric and asymmetric DNA patterns obtained by water flow.

  4. Particle-in-cell simulation study of the scaling of asymmetric magnetic reconnection with in-plane flow shear

    CERN Document Server

    Doss, C E; Swisdak, M

    2016-01-01

    We investigate magnetic reconnection in systems simultaneously containing asymmetric (anti-parallel) magnetic fields, asymmetric plasma densities and temperatures, and arbitrary in-plane bulk flow of plasma in the upstream regions. Such configurations are common in the high-latitudes of Earth's magnetopause and in tokamaks. We investigate the convection speed of the X-line, the scaling of the reconnection rate, and the condition for which the flow suppresses reconnection as a function of upstream flow speeds. We use two-dimensional particle-in-cell simulations to capture the mixing of plasma in the outflow regions better than is possible in fluid modeling. We perform simulations with asymmetric magnetic fields, simulations with asymmetric densities, and simulations with magnetopause-like parameters where both are asymmetric. For flow speeds below the predicted cutoff velocity, we find good scaling agreement with the theory presented in Doss et al., J.~Geophys.~Res., 120, 7748 (2015). Applications to planetary...

  5. Asymmetric collapse by dissolution or melting in a uniform flow

    CERN Document Server

    Rycroft, Chris H

    2015-01-01

    An advection--diffusion-limited dissolution model of an object being eroded by a two-dimensional potential flow is presented. By taking advantage of the conformal invariance of the model, a numerical method is introduced that tracks the evolution of the object boundary in terms of a time-dependent Laurent series. Simulations of a variety of dissolving objects are shown, which shrink and then collapse to a single point in finite time. The simulations reveal a surprising exact relationship whereby the collapse point is the root of a non-analytic function given in terms of the flow velocity and the Laurent series coefficients describing the initial shape. This result is subsequently derived using residue calculus. The structure of the non-analytic function is examined for three different test cases, and a practical approach to determine the collapse point using a generalized Newton--Raphson root-finding algorithm is outlined. These examples also illustrate the possibility that the model breaks down in finite tim...

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

    OpenAIRE

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

    2012-01-01

    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 ...

  7. EXPERIMENTAL STUDY ON TURBULENT FEATURES IN THE NEGATIVE TRANSPORT REGION OF ASYMMETRIC PLANE CHANNEL FLOW

    Institute of Scientific and Technical Information of China (English)

    卢志明; 刘宇陆; 蒋剑波

    2001-01-01

    Turbulent features of streamwise and vertical components of velocity in the negative transport region of asymmetric plane channel flow have been studied experimentally in details. Experiments show that turbulent fluctuations in negative transport region are suppressed, and their probability distributions are far from Gaus sian. Besides, the skewness factors attain their negative maxima at the position of the maximum mean velocity, whereas the flatness factors attain their positive maxima at the same position.

  8. Effect of induced magnetic field on peristaltic flow of a micropolar fluid in an asymmetric channel

    OpenAIRE

    Shit, G. C.; Roy, M.; E. Y. K. Ng

    2010-01-01

    Of concern in this paper is an investigation of peristaltic transport of a physiological fluid in an asymmetric channel under long wave length and low-Reynolds number assumptions. The flow is assumed to be incompressible, viscous, electrically conducting micropolar fluid and the effect of induced magnetic field is taken into account. Exact analytical solutions obtained for the axial velocity, microrotation component, stream line pattern, magnetic force function, axial-induced magnetic field a...

  9. Asymmetric and Unsteady Flow Separation in High Mach Number Planar Nozzles

    OpenAIRE

    E. Shimshi; Ben-Dor, G.; Levy, A; A. Krothapalli

    2015-01-01

    This paper presents numerical and experimental findings regarding flow separation phenomenon in a high Mach number over expanded planar nozzle. The experimental work is done using a tapered nozzle with a variable area ratio that can produce separation Mach numbers in the range 2.6-3.5. Shadowgraph visualization reveals that depending on the nozzle pressure ratio and the area ratio, steady symmetric, unsteady symmetric and steady asymmetric separations can occur. These sepa...

  10. Peristaltic Flow of Phan-Thien-Tanner Fluid in an Asymmetric Channel with Porous Medium

    OpenAIRE

    Kuppalapalle Vajravelu; S.Sreenadh; Lakshminarayana, P; G. Sucharitha; Rashidi, M. M.

    2016-01-01

    This paper deals with peristaltic transport of Phan-Thien-Tanner fluid in an asymmetric channel induced by sinusoidal peristaltic waves traveling down the flexible walls of the channel. The flow is investigated in a wave frame of reference moving with the velocity of the waveby using the long wavelength and low Reynolds number approximations.The nonlinear governing equations are solved employing a perturbation method by choosing as the perturbation parameter. The expressions for velocity, s...

  11. Magnetohydrodynamic peristaltic flow of a hyperbolic tangent fluid in a vertical asymmetric channel with heat transfer

    Institute of Scientific and Technical Information of China (English)

    Sohail Nadeem; Safia Akram

    2011-01-01

    In the present paper we discuss the magnetohydrodynamic (MHD) peristaltic flow of a hyperbolic tangent fluid model in a vertical asymmetric channel under a zero Reynolds number and long wavelength approximation. Exact solution of the temperature equation in the absence of dissipation term has been computed and the analytical expression for stream function and axial pressure gradient are established. The flow is analyzed in a wave frame of reference moving with the velocity of wave. The expression for pressure rise has been computed numerically. The physical features of pertinent parameters are analyzed by plotting graphs and discussed in detail.

  12. LATTICE BGK MODEL SIMULATION OF ASYMMETRIC FLOW INSIDE A CONTINUOUS SLAB CASTING MOLD

    Institute of Scientific and Technical Information of China (English)

    ZHANG Xiao-jun; SHEN Hou-fa

    2006-01-01

    The incompressible lattice Bhatnager-Gross-Krook (BGK) model of computational fluid dynamics, from which the unsteady incompressible Navier-Stokes equations can be exactly derived with the limit of small Mach number, was established in continuous casting mold. An asymmetric flow pattern in the two-dimensional central plane of continuous slab casting mold was simulated, and the flow pattern is not stationary but changes over frequently if the Reynolds number is larger than 3000 or so. The results are found to be in excellent agreement with previous experimental results.

  13. Theoretical prediction of stationary positions in the rectangular chamber during asymmetric electroosmotic flow

    Science.gov (United States)

    1985-01-01

    Most microscopic cell electrophoretic work depends on the theortical prediction of stationary positions by Smoluchowski and Komagata. Their theoretical solutions are based on the assumption that the electroosmotic flow in a chamber is symmetric. Because experiences with the rectangular chamber indicate that symmetric flow occurs during less than 8% of the experiments, the existing theory for stationary position determination is expanded to include the more general case of asymmetric flow. Smoluchowski's equation for symmetric electroosmotic flow in a rectangular chamber having a width much smaller than its height or length is examined. Smoluchowski's approach is used to approximate stationary positions in rectangular chambers with height/width ratios greater than 40. Support for the theoretical prediction of stationary positions using is given by three types of experimental evidence.

  14. A Numerical Simulation of Cell Separation by Simplified Asymmetric Pinched Flow Fractionation.

    Science.gov (United States)

    Ma, Jing-Tao; Xu, Yuan-Qing; Tang, Xiao-Ying

    2016-01-01

    As a typical microfluidic cell sorting technique, the size-dependent cell sorting has attracted much interest in recent years. In this paper, a size-dependent cell sorting scheme is presented based on a controllable asymmetric pinched flow by employing an immersed boundary-lattice Boltzmann method (IB-LBM). The geometry of channels consists of 2 upstream branches, 1 transitional channel, and 4 downstream branches (D-branches). Simulations are conducted by varying inlet flow ratio, the cell size, and the ratio of flux of outlet 4 to the total flux. It is found that, after being randomly released in one upstream branch, the cells are aligned in a line close to one sidewall of the transitional channel due to the hydrodynamic forces of the asymmetric pinched flow. Cells with different sizes can be fed into different downstream D-branches just by regulating the flux of one D-branch. A principle governing D-branch choice of a cell is obtained, with which a series of numerical cases are performed to sort the cell mixture involving two, three, or four classes of diameters. Results show that, for each case, an adaptive regulating flux can be determined to sort the cell mixture effectively. PMID:27597877

  15. A Numerical Simulation of Cell Separation by Simplified Asymmetric Pinched Flow Fractionation

    Directory of Open Access Journals (Sweden)

    Jing-Tao Ma

    2016-01-01

    Full Text Available As a typical microfluidic cell sorting technique, the size-dependent cell sorting has attracted much interest in recent years. In this paper, a size-dependent cell sorting scheme is presented based on a controllable asymmetric pinched flow by employing an immersed boundary-lattice Boltzmann method (IB-LBM. The geometry of channels consists of 2 upstream branches, 1 transitional channel, and 4 downstream branches (D-branches. Simulations are conducted by varying inlet flow ratio, the cell size, and the ratio of flux of outlet 4 to the total flux. It is found that, after being randomly released in one upstream branch, the cells are aligned in a line close to one sidewall of the transitional channel due to the hydrodynamic forces of the asymmetric pinched flow. Cells with different sizes can be fed into different downstream D-branches just by regulating the flux of one D-branch. A principle governing D-branch choice of a cell is obtained, with which a series of numerical cases are performed to sort the cell mixture involving two, three, or four classes of diameters. Results show that, for each case, an adaptive regulating flux can be determined to sort the cell mixture effectively.

  16. NUMERICAL STUDY ON TURBULENT COUNTER-GRADIENT-TRANSPORT PHENOMENA IN ASYMMETRIC TURBULENT CHANNEL FLOW

    Institute of Scientific and Technical Information of China (English)

    Wang Li-bing; Liu Yu-lu; Qiu Xiang

    2003-01-01

    In this paper, the turbulence characteristics were numerically investigated in an asymmetric turbulent channel flow and the computational results were compared with the relevant experimental data. It shows that the results are consistent with the experiments and there exist Counter-Gradient Momentum Transport(CGMT) phenomena in the central region near the smooth wall, and this region is as large as 6 percent of the channel width. In addition, a region, in which Counter-Gradient-Transport (CGT) phenomena occur more evidently, is found close to the rough wall. These results can help to gain a deeper insight into the mechanism of CGT phenomena.

  17. Orthogonal wavelet analysis of counter gradient transport phenomena in turbulent asymmetric channel flow

    Institute of Scientific and Technical Information of China (English)

    Jianbo Jiang; Xiang Qiu; Zhiming Lu; Yulu Liu

    2005-01-01

    In this paper four families of orthogonal wavelets are applied to analyze the turbulent counter gradient transport phenomena in fully developed asymmetric channel flows,The results show that: (1) In the instance of counter gradient transport, the principal scale of the coherent structure is responsible for the strong local counter gradient transport; (2)Counter gradient transport phenomena have a strong effect on the intermittency of turbulence; (3) Non-Gaussian part of the principal coherent structure is essential for counter gradient transport phenomena.

  18. Peristaltic flow in an asymmetric channel with convective boundary conditions and Joule heating

    Institute of Scientific and Technical Information of China (English)

    Abbasi Fahad Munir; Hayat Tasawar; Ahmad Bashir

    2014-01-01

    The peristaltic transport of viscous fluid in an asymmetric channel is concentrated. The channel walls exhibit convective boundary conditions. Both cases of hydrodynamic and magnetohydrodynamic (MHD) fluids are considered. Mathematical analysis has been presented in a wave frame of reference. The resulting problems are non-dimensionalized. Long wavelength and low Reynolds number approximations are employed. Joule heating effect on the thermal equation is retained. Analytic solutions for stream function and temperature are constructed. Numerical integration is carried out for pressure rise per wavelength. Effects of influential flow parameters have been pointed out through graphs.

  19. 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

  20. Abundance, size distributions and trace-element binding of organic and iron-rich nanocolloids in Alaskan rivers, as revealed by field-flow fractionation and ICP-MS

    Science.gov (United States)

    Stolpe, Björn; Guo, Laodong; Shiller, Alan M.; Aiken, George R.

    2013-03-01

    Water samples were collected from six small rivers in the Yukon River basin in central Alaska to examine the role of colloids and organic matter in the transport of trace elements in Northern high latitude watersheds influenced by permafrost. Concentrations of dissolved organic carbon (DOC), selected elements (Al, Si, Ca, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Rb, Sr, Ba, Pb, U), and UV-absorbance spectra were measured in 0.45 μm filtered samples. 'Nanocolloidal size distributions' (0.5-40 nm, hydrodynamic diameter) of humic-type and chromophoric dissolved organic matter (CDOM), Cr, Mn, Fe, Co, Ni, Cu, Zn, and Pb were determined by on-line coupling of flow field-flow fractionation (FFF) to detectors including UV-absorbance, fluorescence, and ICP-MS. Total dissolved and nanocolloidal concentrations of the elements varied considerably between the rivers and between spring flood and late summer base flow. Data on specific UV-absorbance (SUVA), spectral slopes, and the nanocolloidal fraction of the UV-absorbance indicated a decrease in aromaticity and size of CDOM from spring flood to late summer. The nanocolloidal size distributions indicated the presence of different 'components' of nanocolloids. 'Fulvic-rich nanocolloids' had a hydrodynamic diameter of 0.5-3 nm throughout the sampling season; 'organic/iron-rich nanocolloids' occurred in the stability constant of the metal (+II)-organic complexes, while stronger association of Cr to the iron-rich nanocolloids was attributed to the higher oxidation states of Cr (+III or +IV). Changes in total dissolved element concentrations, size and composition of CDOM, and occurrence and size of organic/iron and iron-rich nanocolloids were related to variations in their sources from either the upper organic-rich soil or the deeper mineral layer, depending on seasonal variations in hydrological flow patterns and permafrost dynamics.

  1. Theoretical analysis of electrokinetic flow and heat transfer in a microchannel under asymmetric boundary conditions.

    Science.gov (United States)

    Soong, C Y; Wang, S H

    2003-09-01

    The main theme of the present work is to investigate the electrokinetic effects on liquid flow and heat transfer in a flat microchannel of two parallel plates under asymmetric boundary conditions including wall-sliding motion, unequal zeta potentials, and unequal heat fluxes on two walls. Based on the Debye-Huckel approximation, an electrical potential solution to the linearized Poisson-Boltzmann equation is obtained and employed in the analysis. The analytic solutions of the electrical potential, velocity distributions, streaming potential, friction coefficient, temperature distribution, and heat transfer rate are obtained, and thereby the effects of electrokinetic separation distance (K), zeta-potential level (zeta;(1)), ratio of two zeta potentials (r(zeta) identical with zeta;(2)/zeta;(1)), wall-sliding velocity (u(w)), and heat flux ratio (r(q) identical with q"(2)/q"(1)) are investigated. The present results reveal the effects of wall-sliding and zeta-potential ratio on the hydrodynamic nature of microchannel flow, and they are used to provide physical interpretations for the resultant electrokinetic effects and the underlying electro-hydrodynamic interaction mechanisms. In the final part the results of potential and velocity fields are applied in solving the energy equation. The temperature distributions and heat transfer characteristics under the asymmetrical kinematic, electric, and thermal boundary conditions considered presently are dealt with. PMID:12927184

  2. NUMERICAL INVESTIGATION OF TURBULENT COUNTER-GRADIENT-TRANSPORT IN ASYMMETRIC FLOW WITH A JET

    Institute of Scientific and Technical Information of China (English)

    QIU Xiang; GUO Hui-fen; LIU Yu-lu

    2004-01-01

    By using the Reynolds Stress Closure Model(RSM), turbulent Counter-Gradient-Transport (CGT) phenomenon was numerically investigated in asymmetric flow with a jet, and the computational results were compared with experimental data. The computational results show that the negative turbulent energy production only appears at some certain stations in CGT region, this fact indicates that the CGT phenomenon exists more widely than the negative turbulent energy production; while the CGT region exists all along,it gradually shrinks in the favorable pressure gradient zone until the position of the wing central part is reached, where it vanishes, but it appears in the adverse pressure gradient region; in addition, the location in the flow where uv = 0 switched sides, relative to where ()U/()y = 0, from favorable pressure gradient to adverse pressure gradient. The pressure gradient takes an important effect on the region of negative turbulent energy production and CGT.

  3. Effect of induced magnetic field on peristaltic flow of a micropolar fluid in an asymmetric channel

    CERN Document Server

    Shit, G C; Ng, E Y K; 10.1002/cnm.1397

    2010-01-01

    Of concern in this paper is an investigation of peristaltic transport of a physiological fluid in an asymmetric channel under long wave length and low-Reynolds number assumptions. The flow is assumed to be incompressible, viscous, electrically conducting micropolar fluid and the effect of induced magnetic field is taken into account. Exact analytical solutions obtained for the axial velocity, microrotation component, stream line pattern, magnetic force function, axial-induced magnetic field as well as the current density distribution across the channel. The flow phenomena for the pumping characteristics, trapping and reflux are also investigated. The results presented reveal that the velocity decreases with the increase of magnetic field as well as the coupling parameter. Moreover, the trapping fluid can be eliminated by the application of an external magnetic field. Thus, the study bears the promise of important applications in physiological systems.

  4. Particle-in-cell simulation study of the scaling of asymmetric magnetic reconnection with in-plane flow shear

    Science.gov (United States)

    Doss, C. E.; Cassak, P. A.; Swisdak, M.

    2016-08-01

    We investigate magnetic reconnection in systems simultaneously containing asymmetric (anti-parallel) magnetic fields, asymmetric plasma densities and temperatures, and arbitrary in-plane bulk flow of plasma in the upstream regions. Such configurations are common in the high-latitudes of Earth's magnetopause and in tokamaks. We investigate the convection speed of the X-line, the scaling of the reconnection rate, and the condition for which the flow suppresses reconnection as a function of upstream flow speeds. We use two-dimensional particle-in-cell simulations to capture the mixing of plasma in the outflow regions better than is possible in fluid modeling. We perform simulations with asymmetric magnetic fields, simulations with asymmetric densities, and simulations with magnetopause-like parameters where both are asymmetric. For flow speeds below the predicted cutoff velocity, we find good scaling agreement with the theory presented in Doss et al. [J. Geophys. Res. 120, 7748 (2015)]. Applications to planetary magnetospheres, tokamaks, and the solar wind are discussed.

  5. A physical model of asymmetric vortices flow structure in regular state over slender body at high angle of attack

    Institute of Scientific and Technical Information of China (English)

    邓学蓥; 王刚; 陈学锐; 王延奎; 刘沛清; 郗忠祥

    2003-01-01

    In subcritical Reyolds number flow region, the repeatable and determinate asymmetric vortices flow at regular state can be obtained by manually setting mini-perturbation on the nose of a pointed ogive-cylinder model at high angle of attack and zero side slip. Test results of this study involve surface pressure distributions, sectional-side-force distributions and flow visualizations. The analyses of these results revealed a complicated multi-vortices system at regular state in which asymmetric twin vortices with inception region and fully developed region, asymmetric triple vortices, four vortices region, five vortices region and Karman-vortex-street-like flow region are developed along the slender body. The correlation between multi-vortices system structures and corresponding sectional-side-force distribution is given. The behaviors of multi-vortices flow structure at the peculiar points of sectional-side-force distributions and characteristics of corresponding pressure distribution are analysed. Finally, a physical model of asymmetric multi-vortices flow structure in regular state over slender body is developed.

  6. Buoyancy Effects on Unsteady MHD Flow of a Reactive Third-Grade Fluid with Asymmetric Convective Cooling

    Directory of Open Access Journals (Sweden)

    Tirivanhu Chinyoka

    2015-01-01

    Full Text Available This article examines the combined effects of buoyancy force and asymmetrical convective cooling on unsteady MHD channel flow and heat transfer characteristics of an incompressible, reactive, variable viscosity and electrically conducting third grade fluid. The chemical kinetics in the flow system is exothermic and the asymmetric convective heat transfers at the channel walls follow the Newton’s law of cooling. The coupled nonlinear partial differential equations governing the problem are derived and solved numerically using a semi-implicit finite difference scheme. Graphical results are presented and physical aspects of the problem are discussed with respect to various parameters embedded in the system.

  7. An investigation of jet trajectory in flow through scaled vocal fold models with asymmetric glottal passages

    Science.gov (United States)

    Erath, Byron D.; Plesniak, Michael W.

    2006-11-01

    Pulsatile two-dimensional flow through asymmetric static divergent models of the human vocal folds is investigated. Included glottal divergence angles are varied between 10° and 30°, with asymmetry angles between the vocal fold pairs ranging from 5° to 15°. The model glottal configurations represent asymmetries that arise during a phonatory cycle due to voice disorders. The flow is scaled to physiological values of Reynolds, Strouhal, and Euler numbers. Data are acquired in the anterior posterior mid-plane of the vocal fold models using phase-averaged Particle Image Velocimetry (PIV) acquired at ten discrete locations in a phonatory cycle. Glottal jet stability arising from the vocal fold asymmetries is investigated and compared to previously reported work for symmetric vocal fold passages. Jet stability is enhanced with an increase in the included divergence angle, and the glottal asymmetry. Concurrently, the bi-modal jet trajectory and flow unsteadiness diminishes. Consistent with previous findings, the flow attachment due to the Coanda effect occurs when the acceleration of the forcing function is zero.

  8. Peristaltic Flow of Phan-Thien-Tanner Fluid in an Asymmetric Channel with Porous Medium

    Directory of Open Access Journals (Sweden)

    Kuppalapalle Vajravelu

    2016-01-01

    Full Text Available This paper deals with peristaltic transport of Phan-Thien-Tanner fluid in an asymmetric channel induced by sinusoidal peristaltic waves traveling down the flexible walls of the channel. The flow is investigated in a wave frame of reference moving with the velocity of the waveby using the long wavelength and low Reynolds number approximations.The nonlinear governing equations are solved employing a perturbation method by choosing as the perturbation parameter. The expressions for velocity, stream function and pressure gradient are obtained. The features of the flow characteristics are analyzed through graphs and the obtained results are discussed in detail. It is noticed that the peristaltic pumping gets reduced due to an increase in the phase difference of the traveling waves. It is also observed that the size of the trapping bolus is a decreasing function of the permeability parameter and the Weissenberg number. Furthermore, the results obtained for the flow characteristics reveal many interesting behaviors that warrant further study on the non-Newtonian fluid phenomena, especially the Peristaltic flow phenomena.

  9. Asymmetrical Blood Flow in the Temporal Lobe in the Charles Bonnet Syndrome: Serial Neuroimaging Study

    Directory of Open Access Journals (Sweden)

    N. Adachi

    1994-01-01

    Full Text Available Clinical features and results of neuroimagings of an 86 year old woman with the Charles Bonnet syndrome are reported. She had become completely blind bilaterally due to cataracts and glaucoma. Shortly after an operation for cataracts, she developed visual hallucinations which lasted for 22 years. She had no deterioration of intelligence. Computed tomography (CT and magnetic resonance imaging (MRI showed moderate generalized atrophy, particularly of the temporal lobes. A serial single photon emission computed tomography (SPECT study during visual hallucinations demonstrated hyperperfusion in the left temporal region and the basal ganglia and hypoperfusion in the right temporal region. These findings suggest that asymmetrical blood flow, particularly in the temporal regions, may be correlated with visual hallucination in the Charles Bonnet syndrome.

  10. 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. PMID:24891757

  11. Mixed Convection Flow and Heat Transfer of Micropolar Fluid in a Vertical Channel with Symmetric and Asymmetric Wall Heating Conditions

    OpenAIRE

    Patil Mallikarjun B; Chandrali Baishya

    2016-01-01

    Analytical solutions for fully developed mixed convection flow of a micro polar fluid with heat generation or heat absorption in a parallel plate vertical channel with symmetric and asymmetric wall temperature distribution has been presented. The two boundaries of the channel are kept either at equal or at different temperatures as isothermal-isothermal, isoflux-isothermal and isothermal-isoflux cases. Reverse flow conditions are observed with increase in micro vortex viscosity. M...

  12. Analytical Model of an Asymmetric Sunspot with a Steady Plasma Flow in its Penumbra

    Science.gov (United States)

    Solov'ev, A. A.; Kirichek, E. A.

    2016-08-01

    A new exact analytical solution to the stationary problem of ideal magnetohydrodynamics is derived for an unipolar asymmetric sunspot immersed in a realistic solar atmosphere. The radial and vertical profiles of pressure, plasma density, and temperature in the visible layers of the sunspot are calculated. The reduction in plasma density in the magnetic funnel of the sunspot, corresponding to the Wilson depression, is also obtained. The magnetic structure of the sunspot is given analytically in a realistic way: a part of the magnetic flux of the sunspot approaches the surrounding photosphere at the outer edge of the penumbra. The magnetic field of the sunspot is not assumed to be axially symmetric. For the first time, the angular dependence of the physical variables in this model allows us to simulate not only a deviation from the circular shape of the sunspot, but also a fine filamentary structure of the sunspot penumbra. The Alfvén Mach number (the ratio of the plasma speed to the Alfvén speed) is zero at the center of the sunspot and rises slowly toward the periphery of the sunspot; this corresponds to the structure of the Evershed flow in the penumbra. The Evershed flow in our model is mainly concentrated in dark penumbral filaments, as is observed.

  13. Analytical Model of an Asymmetric Sunspot with a Steady Plasma Flow in its Penumbra

    Science.gov (United States)

    Solov'ev, A. A.; Kirichek, E. A.

    2016-06-01

    A new exact analytical solution to the stationary problem of ideal magnetohydrodynamics is derived for an unipolar asymmetric sunspot immersed in a realistic solar atmosphere. The radial and vertical profiles of pressure, plasma density, and temperature in the visible layers of the sunspot are calculated. The reduction in plasma density in the magnetic funnel of the sunspot, corresponding to the Wilson depression, is also obtained. The magnetic structure of the sunspot is given analytically in a realistic way: a part of the magnetic flux of the sunspot approaches the surrounding photosphere at the outer edge of the penumbra. The magnetic field of the sunspot is not assumed to be axially symmetric. For the first time, the angular dependence of the physical variables in this model allows us to simulate not only a deviation from the circular shape of the sunspot, but also a fine filamentary structure of the sunspot penumbra. The Alfvén Mach number (the ratio of the plasma speed to the Alfvén speed) is zero at the center of the sunspot and rises slowly toward the periphery of the sunspot; this corresponds to the structure of the Evershed flow in the penumbra. The Evershed flow in our model is mainly concentrated in dark penumbral filaments, as is observed.

  14. 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.

  15. Directed flow in asymmetric nucleus-nucleus collisions and the inverse Landau-Pomeranchuk-Migdal effect

    CERN Document Server

    Toneev, V D; Kolomeitsev, E E; Cassing, W

    2016-01-01

    It is proposed to identify a strong electric field - created during relativistic collisions of asymmetric nuclei - via the observation of pseudorapidity and transverse momentum distributions of hadrons with the same mass but opposite charge. The results of detailed calculations within the Parton-Hadron String Dynamics (PHSD) approach for the charge-dependent directed flow $v_1$ are presented for semi-central Cu+Au collision at $\\sqrt{s_{NN}}=200$ GeV incorporating the inverse Landau-Pomeranchuk-Migdal (iLPM) effect, which accounts for a delay in the electromagnetic interaction with the charged degree of freedom. Including the iLPM effect we achieve a reasonable agreement of the PHSD results for the charge splitting in $v_1(p_T)$ in line with the recent measurements of the STAR Collaboration for Cu+Au collisions at $\\sqrt{s_{NN}}=200$ GeV while an instant appearance and coupling of electric charges at the hard collision vertex overestimates the splitting by about a factor of 10. We predict that the iLPM effect...

  16. Electrospun carbon nanofibers/electrocatalyst hybrids as asymmetric electrodes for vanadium redox flow battery

    Science.gov (United States)

    Wei, Guanjie; Fan, Xinzhuang; Liu, Jianguo; Yan, Chuanwei

    2015-05-01

    To improve the electrochemical activity of polyacrylonitrile (PAN)-based electrospun carbon nanofibers (ECNFs) toward vanadium redox couples, the multi-wall carbon nanotubes (CNTs) and Bi-based compound as electrocatalyst have been embedded in the ECNFs to make composite electrode, respectively. The morphology and electrochemical properties of pristine ECNFs, CNTs/ECNFs and Bi/ECNFs have been characterized. Among the three kinds of electrodes, the CNTs/ECNFs show best electrochemical activity toward VO2+/VO2+ redox couple, while the Bi/ECNFs present the best electrochemical activity toward V2+/V3+ redox couple. Furthermore, the high overpotential of hydrogen evolution on Bi/ECNFs makes the side-reaction suppressed. Because of the large property difference between the two composite electrodes, the CNTs/ECNFs and Bi/ECNFs are designed to act as positive and negative electrode for vanadium redox flow battery (VRFB), respectively. It not only does improve the kinetics of two electrode reactions at the same time, but also reduce the kinetics difference between them. Due to the application of asymmetric electrodes, performance of the cell is improved greatly.

  17. Asymmetrical gene flow in a hybrid zone of Hawaiian Schiedea (Caryophyllaceae species with contrasting mating systems.

    Directory of Open Access Journals (Sweden)

    Lisa E Wallace

    Full Text Available Asymmetrical gene flow, which has frequently been documented in naturally occurring hybrid zones, can result from various genetic and demographic factors. Understanding these factors is important for determining the ecological conditions that permitted hybridization and the evolutionary potential inherent in hybrids. Here, we characterized morphological, nuclear, and chloroplast variation in a putative hybrid zone between Schiedea menziesii and S. salicaria, endemic Hawaiian species with contrasting breeding systems. Schiedea menziesii is hermaphroditic with moderate selfing; S. salicaria is gynodioecious and wind-pollinated, with partially selfing hermaphrodites and largely outcrossed females. We tested three hypotheses: 1 putative hybrids were derived from natural crosses between S. menziesii and S. salicaria, 2 gene flow via pollen is unidirectional from S. salicaria to S. menziesii and 3 in the hybrid zone, traits associated with wind pollination would be favored as a result of pollen-swamping by S. salicaria. Schiedea menziesii and S. salicaria have distinct morphologies and chloroplast genomes but are less differentiated at the nuclear loci. Hybrids are most similar to S. menziesii at chloroplast loci, exhibit nuclear allele frequencies in common with both parental species, and resemble S. salicaria in pollen production and pollen size, traits important to wind pollination. Additionally, unlike S. menziesii, the hybrid zone contains many females, suggesting that the nuclear gene responsible for male sterility in S. salicaria has been transferred to hybrid plants. Continued selection of nuclear genes in the hybrid zone may result in a population that resembles S. salicaria, but retains chloroplast lineage(s of S. menziesii.

  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. The influence of flow inertia, buoyancy, wind, and flow unsteadiness on mixing at the asymmetrical confluence of two large rivers

    Science.gov (United States)

    Ramón, Cintia L.; Prats, Jordi; Rueda, Francisco J.

    2016-08-01

    The rates and patterns of mixing of two large rivers with large density differences at a strongly asymmetrical confluence in northern Spain are analyzed. We assess the factors controlling the site where the denser river plunges and the mixing rates between the rivers. In particular, we focus on the interaction between inertial and buoyancy forces, the effect of wind forcing, and the unsteady nature of the hydraulic forcing. The steady-state location of the plunge line is shown to be controlled by an inertia-buoyancy balance, which accounts for the relative magnitude of the buoyancy forcing associated with density differences between the confluent rivers, and the magnitudes of both the main-stream and the side-flow (tributary) inertia. The plunge line moves to upstream locations as the inertia of the tributary increases (for low tributary inertia) and/or the density contrast between the rivers increases. This has important consequences for river mixing since mixing rates increase as the plunging occurs at the confluence. The high mixing rates in this case occur as a result of a large mixing interface surface area and high diffusivities. As the plunging area moves upstream or downstream of the confluence, vertical diffusivities or the area of contact available for mixing decrease and constrain mixing rates. Wind forcing, depending on its velocity and direction, affects mixing rates through (1) altering the buoyancy-inertia equilibrium and so changing the location of the plunge line, (2) altering the pattern of secondary circulation within the confluence and/or (3) increasing shear at the confluence. Flow unsteadiness can lead to changes in the location of the plunge line through time and thus can strongly modify mixing rates at the confluence. The downstream movement of the plunge line is advection dominated, while its upstream movement seems to respond to a baroclinic response of the confluence.

  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. Simultaneous effects of Hall and convective conditions on peristaltic flow of couple-stress fluid in an inclined asymmetric channel

    Indian Academy of Sciences (India)

    T Hayat; Maryam Iqbal; Humaira Yasmin; Fuad E Alsaadi; Huijun Gao

    2015-07-01

    A mathematical model is developed to analyse the peristaltic flow of couple-stress fluid in an inclined asymmetric channel with convective conditions. Soret and Dufour and Hall effects are taken into account. Analysis has been carried out in a wave frame of reference. Expressions for velocity, pressure gradient, temperature and concentration are constructed. Pumping and trapping phenomena are examined. Impact of sundry parameters on the velocity, temperature and concentration is discussed.

  2. Does asymmetric gene flow among matrilines maintain the evolutionary potential of the European eel?

    Science.gov (United States)

    Baltazar-Soares, Miguel; Eizaguirre, Christophe

    2016-08-01

    Using evolutionary theory to predict the dynamics of populations is one of the aims of evolutionary conservation. In endangered species, with geographic range extending over continuous areas, the predictive capacity of evolutionary-based conservation measures greatly depends on the accurate identification of reproductive units. The endangered European eel (Anguilla anguilla) is a highly migratory fish species with declining population due to a steep recruitment collapse in the beginning of the 1980s. Despite punctual observations of genetic structure, the population is viewed as a single panmictic reproductive unit. To understand the possible origin of the detected structure in this species, we used a combination of mitochondrial and nuclear loci to indirectly evaluate the possible existence of cryptic demes. For that, 403 glass eels from three successive cohorts arriving at a single location were screened for phenotypic and genetic diversity, while controlling for possible geographic variation. Over the 3 years of sampling, we consistently identified three major matrilines which we hypothesized to represent demes. Interestingly, not only we found that population genetic models support the existence of those matriline-driven demes over a completely panmictic mode of reproduction, but also we found evidence for asymmetric gene flow amongst those demes. We uphold the suggestion that the detection of demes related to those matrilines reflect a fragmented spawning ground, a conceptually plausible consequence of the low abundance that the European eel has been experiencing for three decades. Furthermore, we suggest that this cryptic organization may contribute to the maintenance of the adaptive potential of the species. PMID:27551384

  3. Mixed Convection Flow and Heat Transfer of Micropolar Fluid in a Vertical Channel with Symmetric and Asymmetric Wall Heating Conditions

    Directory of Open Access Journals (Sweden)

    Patil Mallikarjun B

    2016-01-01

    Full Text Available Analytical solutions for fully developed mixed convection flow of a micro polar fluid with heat generation or heat absorption in a parallel plate vertical channel with symmetric and asymmetric wall temperature distribution has been presented. The two boundaries of the channel are kept either at equal or at different temperatures as isothermal-isothermal, isoflux-isothermal and isothermal-isoflux cases. Reverse flow conditions are observed with increase in micro vortex viscosity. Micro polar fluids display reduction in heat transfer rate.

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

    OpenAIRE

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

    2012-01-01

    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 t...

  5. Comparison of radial flow effects on partitions of multifragmenting sources formed in symmetric and asymmetric central collisions

    Directory of Open Access Journals (Sweden)

    Frankland J.D.

    2015-01-01

    Full Text Available The role of collective radial expansion in determining multifragmentation partition properties has previously been explored by comparing different-sized sources of the same excitation energy per nucleon formed by very different reaction mechanisms: excited quasi-projectiles from semi-peripheral Au+Au collisions and quasi-fused sources from central Xe+Sn collisions. New data has been obtained with INDRA on 181Ta+66Zn collisions in order to allow comparison of Xe+Sn data with quasi-fused systems having the same mass, charge and excitation energy per nucleon formed in mass-asymmetric reactions, for which a smaller initial compression is expected. Preliminary results confirm that, ceteris paribus, smaller radial flow leads to less fragments with more asymmetric partitions.

  6. Angiographic analysis for phantom simulations of endovascular aneurysm treatments with a new fully retrievable asymmetric flow diverter

    Science.gov (United States)

    Yoganand, Aradhana; Wood, Rachel P.; Jimenez, Carlos; Siddiqui, Adnan; Snyder, Kenneth; Setlur Nagesh, S. V.; Bednarek, D. R.; Rudin, S.; Baier, Robert; Ionita, Ciprian N.

    2015-03-01

    Digital Subtraction Angiography (DSA) is the main diagnostic tool for intracranial aneurysms (IA) flow-diverter (FD) assisted treatment. Based on qualitative contrast flow evaluation, interventionists decide on subsequent steps. We developed a novel fully Retrievable Asymmetric Flow-Diverter (RAFD) which allows controlled deployment, repositioning and detachment achieve optimal flow diversion. The device has a small low porosity or solid region which is placed such that it would achieve maximum aneurysmal in-jet flow deflection with minimum impairment to adjacent vessels. We tested the new RAFD using a flow-loop with an idealized and a patient specific IA phantom in carotid-relevant physiological conditions. We positioned the deflection region at three locations: distally, center and proximally to the aneurysm orifice and analyzed aneurysm dome flow using DSA derived maps for mean transit time (MTT) and bolus arrival times (BAT). Comparison between treated and untreated (control) maps quantified the RAFD positioning effect. Average MTT, related to contrast presence in the aneurysm dome increased, indicating flow decoupling between the aneurysm and parent artery. Maximum effect was observed in the center and proximal position (~75%) of aneurysm models depending on their geometry. BAT maps, correlated well with inflow jet direction and magnitude. Reduction and jet dispersion as high as about 50% was observed for various treatments. We demonstrated the use of DSA data to guide the placement of the RAFD and showed that optimum flow diversion within the aneurysm dome is feasible. This could lead to more effective and a safer IA treatment using FDs.

  7. The origin of asymmetric behavior of money flow in the business firm network

    Science.gov (United States)

    Miura, W.; Takayasu, H.; Takayasu, M.

    2012-09-01

    In the business firm network, the number of in-degrees and out-degrees show the same scale-free property, however, the distribution of authorities and hubs show asymmetric behavior. Here we show the result of an analysis of the two-link structure of the network to find the origin of this asymmetric behavior. We find the tendency for big construction firms intermediating small subcontracting firms to have higher hub degrees. By measuring the strength of preferential attachment rate of new companies, we also find a abnormally strong preferential attachment for which the exponent is 1.4 with respect to out-degree when a new company forms a business partnership with a construction company. We propose a new model that reproduces the asymmetric behavior of the degrees of authorities and hubs by changing the preferential attachment rate between the in-degree and the out-degree in the business firm network.

  8. 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.

  9. Asymmetric magnetic reconnection with a flow shear and applications to the magnetopause

    CERN Document Server

    Doss, C E; Cassak, P A; Wilder, F D; Eriksson, S; Drake, J F

    2015-01-01

    We perform a theoretical and numerical study of anti-parallel 2D magnetic reconnection with asymmetries in the density and reconnecting magnetic field strength in addition to a bulk flow shear across the reconnection site in the plane of the reconnecting fields, which commonly occurs at planetary magnetospheres. We predict the speed at which an isolated X-line is convected by the flow, the reconnection rate, and the critical flow speed at which reconnection no longer takes place for arbitrary reconnecting magnetic field strengths, densities, and upstream flow speeds, and confirm the results with two-fluid numerical simulations. The predictions and simulation results counter the prevailing model of reconnection at Earth's dayside magnetopause which says reconnection occurs with a stationary X-line for sub-Alfvenic magnetosheath flow, reconnection occurs but the X-line convects for magnetosheath flows between the Alfven speed and double the Alfven speed, and reconnection does not occur for magnetosheath flows g...

  10. Sediment Micromechanics in Sheet Flows Induced by Asymmetric Waves: A CFD-DEM Study

    CERN Document Server

    Sun, Rui

    2016-01-01

    Understanding the sediment transport in oscillatory flows is essential to the investigation of the overall sediment budget for coastal regions. This overall budget is crucial for the prediction of the morphological change of the coastline in engineering applications. Since the sediment transport in oscillatory flows is dense particle-laden flow, appropriate modeling of the particle interaction is critical. Although traditional two-fluid approaches have been applied to the study of sediment transport in oscillatory flows, the approaches do not resolve the interaction of the particles. Particle-resolved modeling of sediment transport in oscillatory flows and the study of micromechanics of sediment particles are still lacking. In this work, a parallel CFD-DEM solver SediFoam that can resolve the inter-particle collision is applied to study the granular micromechanics of sediment particles in oscillatory flows. The results obtained from SediFoam are validated by the experimental data of coarse and medium sands. T...

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

    CERN Document Server

    Wong, Terence T W; 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

    2013-01-01

    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 individu...

  12. On laminar hydromagnetic mixed convection flow in a vertical channel with symmetric and asymmetric wall heating conditions

    Energy Technology Data Exchange (ETDEWEB)

    Chamkha, A.J. [Kuwait University, Safat (Kuwait). Dept. of Mechanical Engineering

    2002-06-01

    The problem of hydromagnetic fully developed laminar mixed convection flow in a vertical channel with symmetric and asymmetric wall heating conditions in the presence or absence of heat generation or absorption effects is considered. Through proper choice of dimensionless variables, the governing equations are developed and three types of thermal boundary conditions are prescribed. These thermal boundary conditions are isothermal-isothermal, isoflux-isothermal, and isothermal-isoflux for the left-right walls of the channel. Analytical solutions for the velocity and temperature profiles for various special cases of the problem are reported. In addition, closed-form expressions for the Nusselt numbers and reversal flow conditions at both the left and right channel walls are derived. The general problem which includes the effects of both viscous dissipation and Joule heating is solved by an implicit finite-difference scheme. Favorable comparisons of special cases with previously published work are obtained. A selected set of graphical results illustrating the effects of the various parameters involved in the problem including viscous and magnetic dissipations on the velocity and temperature profiles, as well as flow reversal situations and Nusselt numbers, is presented and discussed. (author)

  13. An asymmetrical λ-foot of condensing steam flow in the IMP PAN nozzle

    International Nuclear Information System (INIS)

    In the present paper we have focused on the precise prediction of the spontaneous condensation phenomena in wet steam flow. Novelty of our approach lies on modelling both the moment of initiation of a phase transition, as well as the moment of its reverse progress – called here re-vaporization of the condensate phase. The practical issue is to elaborate of a model of spontaneous condensation/vaporization of water steam flow under low-pressure conditions by using methodology of non-equilibrium thermodynamics [2]. The basic tests including comparison with an experimental data have been performed using the IMP PAN nozzle with the de Laval geometry [1]. Having observed the finishing of a foggy flow within the shock wave, according to Puzyrewski's postulate [1], we would like to analyse the topography of the shock wave pattern in the IMP PAN symmetric nozzle. This phenomenon, independently from a type of compressible fluid, has been observed to be the result of interaction between a normal shock wave and the boundary layer – it has been known as a λ – foot structure [3]. The asymmetry of the shock structure is measured by optical system and visible since the foggy flow can be easily observed. Our paper is a trial towards to an explanation of this problem.

  14. Laboratory Experiments of Sand Ripples with Bimodal Size Distributions Under Asymmetric Oscillatory Flows

    Science.gov (United States)

    Calantoni, J.; Landry, B. J.

    2010-12-01

    The dynamics of sand ripples are vital to understanding numerous coastal processes such as sediment transport, wave attenuation, boundary layer development, and seafloor acoustic properties. Though significant laboratory research has been conducted to elucidate oscillatory flow morphodynamics under various constant and transient forcing conditions, the majority of the previous experiments were conducted only for beds with unimodal size distributions of sediment. Recent oscillatory flow experiments as well as past laboratory observations in uniform flows suggest that the presence of heterogeneous size sand compositions may significantly impact ripple morphology, resulting in a variety of observable effects (e.g., sediment sorting, bed armoring, and altered transport rates). Experimental work was conducted in a small oscillatory flow tunnel at the Sediment Dynamics Laboratory at the Naval Research Laboratory, Stennis Space Center. Three different monochromatic oscillatory forcings having velocity asymmetry were used to study sand ripple dynamics over five bimodal and two unimodal sediment beds. The seven different mixtures were composed using two unimodal sands of different colors (blue/white) and median grain diameters (d=0.31 mm / d=0.65 mm) combined into various mixtures by mass (i.e., 0/100; 10/90; 25/75; 50/50; 75/25; 90/10; and 100/0 which denotes mass percentage of blue/white sand, respectively, within each mixture). High-definition video of the sediment bed profile was acquired in conjunction with sediment trap measurements to resolve differences in ripple geometries, migration and evolution rates due to the different sediment mixtures and flow conditions. Observational findings clearly illustrate sediment stratification within ripple crests and the depth of the active mixing layer in addition to supporting sediment sorting in previous research on symmetric oscillatory flows in which the larger grains collect on top of ripple crests and smaller grains in the

  15. Unsteady supersonic flow around delta wings with symmetric and asymmetric flaps oscillation

    Science.gov (United States)

    Kandil, Osama A.; Salman, Ahmed A.

    1991-01-01

    A parametric study is presented to investigate the effect of reduced frequency of the leading-edge flaps on the locally-conical, unsteady, supersonic flow around a delta wing. This study covers symmetric and antisymmetric forced oscillation of the leading-edge flaps. The effects of the freestream Mach number and angle of attack are also presented. The problem is solved using time-accurate integration of the unsteady, compressible, thin-layer Navier-Stokes equations and the unsteady, linearized, Navier-displacement equations. The delta wing is of aspect ratio of 1.5 and its leading-edge flaps are hinged at 65 percent of the local-half span length. The reduced frequency is varied between 2 pi and pi/2. Two supersonic flow conditions have been investigated; the first is for a freestream Mach number of 2.4 and an angle of attack of 19 deg and the second is for a freestream Mach number of 1.5 and an angle attack of 15 deg.

  16. An asymmetric upwind flow, Yellow Sea Warm Current: 1. New observations in the western Yellow Sea

    Science.gov (United States)

    Lin, Xiaopei; Yang, Jiayan; Guo, Jingsong; Zhang, Zhixin; Yin, Yuqi; Song, Xiangzhou; Zhang, Xiaohui

    2011-04-01

    The winter water mass along the Yellow Sea Trough (YST), especially on the western side of the trough, is considerably warmer and saltier than the ambient shelf water mass. This observed tongue-shape hydrographic feature implies the existence of a winter along-trough and onshore current, often referred to as the Yellow Sea Warm Current (YSWC). However, the YSWC has not been confirmed by direct current measurements and therefore skepticism remains regarding its existence. Some studies suggest that the presence of the warm water could be due to frontal instability, eddies, or synoptic scale wind bursts. It is noted that in situ observations used in most previous studies were from the central and eastern sides of the YST even though it is known that the warm water core is more pronounced along the western side. Data from the western side have been scarce. Here we present a set of newly available Chinese observations, including some from a coordinated effort involving three Chinese vessels in the western YST during the 2006-2007 winter. The data show unambiguously the existence of the warm current on the western side of YST. Both the current and hydrography observations indicate a dominant barotropic structure of YSWC. The westward deviation of YSWC axis is particularly obvious to the south of 35°N and is clearly associated with an onshore movement of warm water. To the north of 35°N, the YSWC flows along the bathymetry with slightly downslope movement. We conclude that the barotropic current is mainly responsible for the warm water intrusion, while the Ekman and baroclinic currents play an important but secondary role. These observations help fill an observational gap and establish a more complete view of the YSWC.

  17. 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 (Sr). 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 Sr is coincident with the phase of the minimum static pressure in the vicinity of the leading edge of the splitter blades. PMID:24891758

  18. Thermal and velocity slip effects on the MHD peristaltic flow with carbon nanotubes in an asymmetric channel: application of radiation therapy

    Science.gov (United States)

    Akbar, Noreen Sher; Nadeem, S.; Khan, Zafar Hayat

    2014-10-01

    Peristaltic flow is used to study the flow and heat transfer of carbon nanotubes in an asymmetric channel with thermal and velocity slip effects. Two types of carbon nanotubes, namely, single- and multi-wall carbon nanotubes are utilized to see the analysis with water as base fluids. Empirical correlations are used for the thermo-physical properties of carbon nanotubes (CNTs) in terms of solid volume fraction of CNTs. The governing equations are simplified using long wavelength and low Reynolds number approximation. Exact solutions have been evaluated for velocity, pressure gradient, the solid volume fraction of CNTs and temperature profile. The effects of various flow parameters, i.e. Hatmann number M, the solid volume fraction of the nanoparticles ϕ, Grashof number G, velocity slip parameter β, thermal slip parameter γ and Prandtl number P r are presented graphically for both single- (SWCNT) and multi-wall carbon nanotubes (MWCNT).

  19. Effects of Navier slip on unsteady flow of a reactive variable viscosity non- Newtonian fluid through a porous saturated medium with asymmetric convecti- ve boundary conditions

    Institute of Scientific and Technical Information of China (English)

    RUNDORA Lazarus; MAKINDE Oluwole Daniel

    2015-01-01

    A study on the effects of Navier slip, in conjunction with other flow parameters, on unsteady flow of reactive variable viscosity third-grade fluid through a porous saturated medium with asymmetric convective boundary conditions is presented. The channel walls are assumed to be subjected to asymmetric convective heat exchange with the ambient, and exothermic chemical reactions take place within the flow system. The heat exchange with the ambient obeys Newton’s law of cooling. The coupled equations, arising from the law of conservation of momentum and the first law of thermodynamics, then the derived system are non- dimensionalised and solved using a semi-implicit finite difference scheme. The lower wall slip parameter is observed to increase the fluid velocity profiles, whereas the upper wall slip parameter retards them because of backflow at the upper channel wall. Heat pro- duction in the fluid is seen to increase with the slip parameters. The wall shear stress increases with the slip parameters while the wall heat transfer rate is largely unaltered by the lower wall slip parameter but marginally increased by the upper wall slip parameter.

  20. On Combined Effects of Heat Transfer and Chemical Reaction for the Flow through an Asymmetric Channel with Orthogonally Deformable Porous Walls

    Directory of Open Access Journals (Sweden)

    Syed Tauseef Mohyud-Din

    2016-01-01

    Full Text Available The combined effects of heat transfer and chemical reaction are studied for the flow through a semi-infinite asymmetric channel with orthogonally deformable porous walls. The similarity transforms have been used to reduce the conservation laws to a corresponding system of nonlinear ordinary differential equations. The resulting equations are solved, both analytically and numerically, by using Homotopy Analysis Method (HAM and the fourth-order Runge-Kutta (RK-4 method, respectively. The convergence of the analytical solution is assured through the so-called total squared residual error analysis. The optimal values of auxiliary parameters are obtained by minimizing the total squared residual error.

  1. 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.

  2. Peristaltic flow of a couple stress fluid under the effect of induced magnetic field in an asymmetric channel

    Energy Technology Data Exchange (ETDEWEB)

    Nadeem, Sohail; Akram, Safia [Quaid-i-Azam University, Department of Mathematics, Islamabad (Pakistan)

    2011-01-15

    The present paper investigates the peristaltic transport of a couple stress fluid in an asymmetric channel with the effect of the induced magnetic field. The exact solutions of momentum and the magnetic field equations have been calculated under the assumptions of long wave length and low but finite Reynolds number. The expression for pressure rise has been computed numerically using mathematics software Mathematica. The graphical results have been presented to discuss the physical behavior of various physical parameters of interest. Finally, the trapping phenomena have been discussed for various physical parameters. (orig.)

  3. Peristaltic Flow and Heat Transfer of a Conducting Phan-Thien-Tanner Fluid in an Asymmetric Channel - Application to Chyme Movement in Small Intestine

    Science.gov (United States)

    Vajravelu, K.; Sreenadh, S.; Dhananjaya, S.; Lakshminarayana, P.

    2016-08-01

    In this paper, the influence of heat transfer on the peristaltic flow of a conducting Phan-Thien-Tanner fluid in an asymmetric channel with porous medium is studied. The coupled nonlinear governing differential equations are solved by a perturbation technique. The expressions for the temperature field, the stream function, the axial velocity, and the pressure gradient are obtained. The effects of the various physical parameters such as the magnetic parameter M, the permeability parameter σ, the Brinkman number Br and the Weissenberg number We on the pumping phenomenon are analyzed through graphs and the results are discussed in detail. It is observed that the velocity and the pressure are decreased with increasing the magnetic parameter M whereas the effect of the parameter M on the temperature field is quite the opposite.

  4. An investigation of asymmetric flow features in a scaled-up driven model of the human vocal folds

    Science.gov (United States)

    Erath, Byron D.; Plesniak, Michael W.

    2010-07-01

    Flow through a driven, 7.5 times life-size vocal fold model was investigated at corresponding life-size flow rates of Q mean = 89.1 ml/s, 159.4 ml/s, and 253.0 ml/s. The flow was scaled to match physiological values for Reynolds, Strouhal, and Euler numbers. The models were driven at a life-size frequency of 94 Hz. Particle image velocimetry (PIV) data were acquired in the anterior-posterior midplane of the glottis, and the unsteady transglottal pressure drop across the vocal folds was simultaneously measured. Flow and pressure data were obtained at four discrete instances during the closing phases of the phonatory cycle for which t/T open = 0.60, 0.70, 0.80, and 0.90. The glottal jet trajectory exhibited a bimodal distribution of flow attachment between the two medial surfaces of the glottis. Vortex shedding at the trailing edge separation point generated instabilities in the shear layer, which caused large oscillations in the glottal jet orientation downstream of the glottal exit. The development of the Coanda effect during the glottal cycle was found to have minimal impact on the transglottal pressure drop, suggesting that flow orientation does not directly influence the dipole sound source. The change in transglottal pressure drop as a result of jet trajectory was less than 2% for all three investigated flow rates.

  5. A polystyrene-supported 9-amino(9-deoxy)epi quinine derivative for continuous flow asymmetric Michael reactions.

    Science.gov (United States)

    Izquierdo, Javier; Ayats, Carles; Henseler, Andrea H; Pericàs, Miquel A

    2015-04-14

    A polystyrene (PS)-supported 9-amino(9-deoxy)epi quinine derivative catalyzes Michael reactions affording excellent levels of conversion and enantioselectivity using different nucleophiles and structurally diverse enones. The highly recyclable, immobilized catalyst has been used to implement a single-pass, continuous flow process (residence time: 40 min) that can be operated for 21 hours without significant decrease in conversion and with improved enantioselectivity with respect to batch operation. The flow process has also been used for the sequential preparation of a small library of enantioenriched Michael adducts.

  6. Three Dimensional Separation with Spiral-Focus in a Decelerating Duct Flow (Effect of Asymmetric Inlet Boundary Layer Thickness)

    Institute of Scientific and Technical Information of China (English)

    Yoichi Kinoue; Toshiaki Setoguchi; Kenji Kaneko; Mamun Mohammad; Masahiro Inoue

    2003-01-01

    An experimental apparatus was developed to study the three dimensional separated flow with spiral-foci. The internal decelerating flow was generated by the air suction from a side wall to produce the separation on an opposite-side wall. The relation between the upstream boundary layer and the generation of spiral-foci in the separation region was observed by a tuft method. As a result, it was clarified that the spiral-focus type separation could be produced on the side wall and its behavior was closely related to the vortices supplied into the separation region from the boundary layer developing along top wall or bottom one.

  7. Influence of magnetic field on peristaltic flow of a Casson fluid in an asymmetric channel: Application in crude oil refinement

    Science.gov (United States)

    Sher Akbar, Noreen

    2015-03-01

    The influence of magnetic field on peristaltic flow of a Casson fluid model is considered. The model for peristaltic literature is modelled first time. The governing coupled equations are constructed under long wavelength and low Reynold's number approximation. Exact solutions are evaluated for stream function and pressure gradient. The important findings in this study are the variation of the Hartmann number M, Casson fluid parameter ζ and amplitudes a, b, d and ϕ. The velocity field increases due to increase in Hartmann number M near the channel walls while velocity field decreases at the centre of the channel.

  8. Asymmetric collider

    International Nuclear Information System (INIS)

    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. Engineered Asymmetric Synthetic Vesicles

    Science.gov (United States)

    Lu, Li; Chiarot, Paul

    2013-11-01

    Synthetic vesicles are small, fluid-filled spheres that are enclosed by a bilayer of lipid molecules. They can be used as models for investigating membrane biology and as delivery vehicles for pharmaceuticals. In practice, it is difficult to simultaneously control membrane asymmetry, unilamellarity, vesicle size, vesicle-to-vesicle uniformity, and luminal content. Membrane asymmetry, where each leaflet of the bilayer is composed of different lipids, is of particular importance as it is a feature of most natural membranes. In this study, we leverage microfluidic technology to build asymmetric vesicles at high-throughput. We use the precise flow control offered by microfluidic devices to make highly uniform emulsions, with controlled internal content, that serve as templates to build the synthetic vesicles. Flow focusing, dielectrophoretic steering, and interfacial lipid self-assembly are critical procedures performed on-chip to produce the vesicles. Fluorescent and confocal microscopy are used to evaluate the vesicle characteristics.

  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. Influence of Heat Source, Thermal Radiation and Inclined Magnetic Field on Peristaltic Flow of a Hyperbolic Tangent Nanofluid in a Tapered Asymmetric Channel.

    Science.gov (United States)

    Kothandapani, Munirathinam; Prakash, Jayavel

    2014-10-31

    In the present analytic thinking, we have modeled the governing equations of a two dimensional peristaltic transport of a Hyperbolic tangent nanofluid in the presence of a heat source/sink with the combined effects of thermal radiation and inclined magnetic field in a tapered asymmetric channel. The propagation of waves on the non-uniform walls to have different amplitudes and phase but the same wave speed is produced the tapered asymmetric channel. The equations of dimensionless temperature and nanoparticle concentration are solved analytically under assumptions of long wavelength and low Reynolds number. The governing equations of momentum of a hyperbolic tangent nanofluid for the tapered asymmetric channel have also been solved analytically using the regular perturbation method. The expression for average rise in pressure has been figured using numerical integrations. The effects of various physical parameters entering into the problem are discussed numerically and graphically. The phenomenon of trapping is also investigated. Furthermore, the received results show that the maximum pressure rise gets increased in case of non-Newtonian fluid when equated with Newtonian fluid. PMID:25373110

  13. Asymmetric Wettability Directs Leidenfrost Droplets

    Energy Technology Data Exchange (ETDEWEB)

    Agapov, Rebecca L [ORNL; Boreyko, Jonathan B [ORNL; Briggs, Dayrl P [ORNL; Srijanto, Bernadeta R [ORNL; Retterer, Scott T [ORNL; Collier, Pat [ORNL; Lavrik, Nickolay V [ORNL

    2014-01-01

    Leidenfrost phenomena on nano- and microstructured surfaces are of great importance for increasing control over heat transfer in high power density systems utilizing boiling phenomena. They also provide an elegant means to direct droplet motion in a variety of recently emerging fluidic systems. Here, we report the fabrication and characterization of tilted nanopillar arrays (TNPAs) that exhibit directional Leidenfrost water droplets under dynamic conditions, namely on impact with Weber numbers 40 at T 325 C. The batch fabrication of the TNPAs was achieved by glancing-angle anisotropic reactive ion etching of a thermally dewet platinum mask, with mean pillar diameters of 100 nm and heights of 200-500 nm. In contrast to previously implemented macro- and microscopic Leidenfrost ratchets, our TNPAs induce no preferential directional movement of Leidenfrost droplets under conditions approaching steady-state film boiling, suggesting that the observed droplet directionality is not a result of asymmetric vapor flow. Using high-speed imaging, phase diagrams were constructed for the boiling behavior upon impact for droplets falling onto TNPAs, straight nanopillar arrays, and smooth silicon surfaces. The asymmetric impact and directional trajectory of droplets was exclusive to the TNPAs for impacts corresponding to the transition boiling regime, revealing that asymmetric wettability upon impact is the mechanism for the droplet directionality.

  14. Filter-feeding, near-field flows, and the morphologies of colonial choanoflagellates

    CERN Document Server

    Kirkegaard, Julius B

    2016-01-01

    Efficient uptake of nutrients from the environment is an important component in the fitness of all microorganisms, and its dependence on size may reveal clues to the origins of evolutionary transitions to multicellularity. Because potential benefits in uptake rates must be viewed in the context of other costs and benefits of size, such as varying predation rates and the increased metabolic costs associated with larger and more complex body plans, the uptake rate itself is not necessarily that which is optimized by evolution. Uptake rates can be strongly dependent on local organism geometry and its swimming speed, providing selective pressure for particular arrangements. Here we examine these issues for choanoflagellates, filter-feeding microorganisms that are the closest relatives of the animals. We explore the different morphological variations of the choanoflagellete $Salpingoeca~rosetta$, which can exist as a swimming cell, a sessile thecate cell, and as colonies of cells in various shapes. In the absence ...

  15. Asymmetric-Structure Analysis of Carbon and Energy Markets

    Science.gov (United States)

    Xu, Wei; Cao, Guangxi

    2016-02-01

    This study aimed to investigate the asymmetric structure between the carbon and energy markets from two aspects of different trends (up or down) and volatility-transmission direction using asymmetric detrended cross-correlation analysis (DCCA) cross-correlation coefficient test, multifractal asymmetric DCCA (MF-ADCCA) method, asymmetric volatility-constrained correlation metric and time rate of information-flow approach. We sampled 1283 observations from January 2008 to December 2012 among pairs of carbon and energy markets for analysis. Empirical results show that the (1) asymmetric characteristic from the cross-correlation between carbon and returns in the energy markets is significant, (2) asymmetric cross-correlation between carbon and energy market price returns is persistent and multifractral and (3) volatility of the base assets of energy market returns is more influential to the base asset of the carbon market than that of the energy market.

  16. Cell-sized asymmetric lipid vesicles facilitate the investigation of asymmetric membranes

    Science.gov (United States)

    Kamiya, Koki; Kawano, Ryuji; Osaki, Toshihisa; Akiyoshi, Kazunari; Takeuchi, Shoji

    2016-09-01

    Asymmetric lipid giant vesicles have been used to model the biochemical reactions in cell membranes. However, methods for producing asymmetric giant vesicles lead to the inclusion of an organic solvent layer that affects the mechanical and physical characteristics of the membrane. Here we describe the formation of asymmetric giant vesicles that include little organic solvent, and use them to investigate the dynamic responses of lipid molecules in the vesicle membrane. We formed the giant vesicles via the inhomogeneous break-up of a lipid microtube generated by applying a jet flow to an asymmetric planar lipid bilayer. The asymmetric giant vesicles showed a lipid flip-flop behaviour in the membrane, superficially similar to the lipid flip-flop activity observed in apoptotic cells. In vitro synthesis of membrane proteins into the asymmetric giant vesicles revealed that the lipid asymmetry in bilayer membranes improves the reconstitution ratio of membrane proteins. Our asymmetric giant vesicles will be useful in elucidating lipid–lipid and lipid–membrane protein interactions involved in the regulation of cellular functions.

  17. Asymmetric catalysis with short-chain peptides.

    Science.gov (United States)

    Lewandowski, Bartosz; Wennemers, Helma

    2014-10-01

    Within this review article we describe recent developments in asymmetric catalysis with peptides. Numerous peptides have been established in the past two decades that catalyze a wide variety of transformations with high stereoselectivities and yields, as well as broad substrate scope. We highlight here catalytically active peptides, which have addressed challenges that had thus far remained elusive in asymmetric catalysis: enantioselective synthesis of atropoisomers and quaternary stereogenic centers, regioselective transformations of polyfunctional substrates, chemoselective transformations, catalysis in-flow and reactions in aqueous environments.

  18. Three-dimensional simulation and analysis of heat transfer and flow field in micro-floating zone of LHPG with asymmetrical perturbation

    Science.gov (United States)

    Chen, Peng-Yi; Huang, En-Ping; Lo, Chia-Yao

    2012-12-01

    Under symmetrical conditions, the micro-floating zone of a laser-heated pedestal growth (LHPG) system displays a symmetrical double eddy flow field distribution. However, as the perturbation increases, the double eddy flow field distribution changes from symmetry to tilt, resulting in unstable flow field vibration. This study investigated the influence of the molten zone on the shape (at vapor-liquid and solid-liquid interfaces) and flow field distribution resulting from tilting the CO2 laser heating ring and the gravity field. This tilt is caused by spatial perturbations resulting from mounting the source rod and seed on pedestals with an alignment that slightly deviates from the growth axis of the LHPG system. The feasibility of growing crystal fibers using the micro-floating zone of the LHPG in the horizontal plane was further investigated. After selecting YAG as the growth material, we evaluated various reduction ratios, source rod scales, surface tensions, and thermocapillary coefficients for the two types of perturbation. Deviation in the laser heating ring significantly influenced the solid-liquid interface and the symmetry of the flow field in the molten zone. However, as long as the laser heating ring remained close to symmetrical, the influence on the molten zone of the larger deviation in the gravity field was limited. Therefore, growing crystal fibers using the micro-floating zone of the LHPG system in the horizontal plane is possible for materials that possess the correct physical properties at appropriate source rod scales. The three-dimensional simulation of this asymmetry includes the effects of the diameter reduction ratio and laser heating, and also modifies Lan's thermocapillary floating numerical model. The modified model calculates the physical grid through a non-orthogonal body-fitting grid transformation using the control-volume finite-difference method. To enhance the simulation and represent the physical system more accurately, we compared

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

    Science.gov (United States)

    Hülber, Karl; Sonnleitner, Michaela; Suda, Jan; Krejčíková, Jana; Schönswetter, Peter; Schneeweiss, Gerald M; Winkler, Manuela

    2015-03-01

    Areas of immediate contact of different cytotypes offer a unique opportunity to study evolutionary dynamics within heteroploid species and to assess isolation mechanisms governing coexistence of cytotypes of different ploidy. The degree of reproductive isolation of cytotypes, that is, the frequency of heteroploid crosses and subsequent formation of viable and (partly) fertile hybrids, plays a crucial role for the long-term integrity of lineages in contact zones. Here, we assessed fine-scale distribution, spatial clustering, and ecological niches as well as patterns of gene flow in parental and hybrid cytotypes in zones of immediate contact of di-, tetra-, and hexaploid Senecio carniolicus (Asteraceae) in the Eastern Alps. Cytotypes were spatially separated also at the investigated microscale; the strongest spatial separation was observed for the fully interfertile tetra- and hexaploids. The three main cytotypes showed highly significant niche differences, which were, however, weaker than across their entire distribution ranges in the Eastern Alps. Individuals with intermediate ploidy levels were found neither in the diploid/tetraploid nor in the diploid/hexaploid contact zones indicating strong reproductive barriers. In contrast, pentaploid individuals were frequent in the tetraploid/hexaploid contact zone, albeit limited to a narrow strip in the immediate contact zone of their parental cytotypes. AFLP fingerprinting data revealed introgressive gene flow mediated by pentaploid hybrids from tetra- to hexaploid individuals, but not vice versa. The ecological niche of pentaploids differed significantly from that of tetraploids but not from hexaploids. PMID:25859328

  20. Effects of rotation and magnetic field on the nonlinear peristaltic flow of a second-order fluid in an asymmetric channel through a porous medium

    Institute of Scientific and Technical Information of China (English)

    A.M.Abd-Alla; S.M.Abo-Dahab; H.D.El-Shahrany

    2013-01-01

    In this paper,the effects of both rotation and magnetic field of the peristaltic transport of a second-order fluid through a porous medium in a channel are studied analytically and computed numerically.The material is represented by the constitutive equations for a second-order fluid.Closed-form solutions under the consideration of long wavelength and low Reynolds number is presented.The analytical expressions for the pressure gradient,pressure rise,friction force,stream function,shear stress,and velocity are obtained in the physical domain.The effects of the non-dimensional wave amplitude,porosity,magnetic field,rotation,and the dimensionless time-mean flow in the wave frame are analyzed theoretically and computed numerically.Numerical results are given and illustrated graphically in each case considered.Comparison was made with the results obtained in the presence and absence of rotation,magnetic field,and porosity.The results indicate that the effects of the non-dimensional wave amplitude,porosity,magnetic field,rotation,and the dimensionless time-mean flow are very pronounced in the phenomena.

  1. Asymmetric Wettability Directs Leidenfrost Droplets

    Science.gov (United States)

    Agapov, Rebecca; Boreyko, Jonathan; Briggs, Dayrl; Srijanto, Bernadeta; Retterer, Scott; Collier, C. Patrick; Lavrik, Nickolay

    2014-03-01

    Exploration of Leidenfrost droplets on nano- and microstructured surfaces are of great importance for increasing control over heat transfer in high power density systems using boiling phenomena. They also provide an elegant way to direct droplet motion in a variety of emerging fluidic systems. Here, we report the fabrication and characterization of tilted nanopillar arrays (TNPAs) that exhibit directional Leidenfrost water droplets under dynamic conditions. The batch fabrication of the TNPAs was achieved by glancing-angle anisotropic reactive ion etching of a thermally dewet platinum mask. In contrast to previously implemented macro- and microscopic Leidenfrost ratchets, our TNPAs induce no preferential directional movement of Leidenfrost droplets under conditions approaching steady-state film boiling. This suggests that the observed droplet directionality is not a result of asymmetric vapor flow. Phase diagrams were constructed for the boiling behavior upon droplet impact onto TNPAs, straight nanopillar arrays, and smooth silicon surfaces. Asymmetric wettability and directional trajectory of droplets was exclusive to the TNPAs for impacts corresponding to the transition boiling regime, revealing this to be the mechanism for the droplet directionality. This work was conducted at the Center for Nanophase Materials Sciences, which is sponsored at Oak Ridge National Lab by the Division of Scientific User Facilities, US Dept. of Energy.

  2. Asymmetrical international attitudes

    NARCIS (Netherlands)

    Van Oudenhoven, JP; Askevis-Leherpeux, F; Hannover, B; Jaarsma, R; Dardenne, B

    2002-01-01

    In general, attitudes towards nations have a fair amount of reciprocity: nations either like each other are relatively indifferent to each other or dislike each other Sometimes, however international attitudes are asymmetrical. In this study, we use social identity theory in order to explain asymmet

  3. An asymmetric Kadison's inequality

    CERN Document Server

    Bourin, Jean-Christophe

    2010-01-01

    Some inequalities for positive linear maps on matrix algebras are given, especially asymmetric extensions of Kadison's inequality and several operator versions of Chebyshev's inequality. We also discuss well-known results around the matrix geometric mean and connect it with complex interpolation.

  4. Asymmetric catalysis with helical polymers

    NARCIS (Netherlands)

    Megens, Rik P.; Roelfes, Gerard

    2011-01-01

    Inspired by nature, the use of helical biopolymer catalysts has emerged over the last years as a new approach to asymmetric catalysis. In this Concept article the various approaches and designs and their application in asymmetric catalysis will be discussed.

  5. 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.

  6. Careful numerical study of flowfields about asymmetric external conical corners

    Science.gov (United States)

    Salas, M. D.

    1980-01-01

    A numerical study of the flowfield about asymmetrical external axial corners formed by the juncture of swept compressive wedges is presented. The geometrical configuration allows a unified treatment of external corners typical of delta wings and rectangular inlets. The study investigates how the flow transitions from a symmetrical flowfield with a cross-flow stagnation point at the corner to an asymmetrical flowfield for which the flow spills over the corner. The effects of leading-edge sweep, wedge compression, and corner radius are investigated.

  7. Catalytic Methods in Asymmetric Synthesis Advanced Materials, Techniques, and Applications

    CERN Document Server

    Gruttadauria, Michelangelo

    2011-01-01

    This book covers advances in the methods of catalytic asymmetric synthesis and their applications. Coverage moves from new materials and technologies to homogeneous metal-free catalysts and homogeneous metal catalysts. The applications of several methodologies for the synthesis of biologically active molecules are discussed. Part I addresses recent advances in new materials and technologies such as supported catalysts, supports, self-supported catalysts, chiral ionic liquids, supercritical fluids, flow reactors and microwaves related to asymmetric catalysis. Part II covers advances and milesto

  8. Asymmetric Organocatalytic Cycloadditions

    DEFF Research Database (Denmark)

    Mose, Rasmus

    2016-01-01

    were pioneered by Otto Paul Hermann Diels and Kurt Alder who discovered what later became known as the Diels Alder reaction. The Diels Alder reaction is a [4+2] cycloaddition in which a π4 component reacts with a π2 component via a cyclic transition state to generate a 6 membered ring. This reaction...... reactions constitute the first organocatalytic asymmetric higher order cycloadditions and a rational for the periselectivity and stereoselectivity is provided based on experimental and computational investigations....

  9. Asymmetric synthesis v.4

    CERN Document Server

    Morrison, James

    1984-01-01

    Asymmetric Synthesis, Volume 4: The Chiral Carbon Pool and Chiral Sulfur, Nitrogen, Phosphorus, and Silicon Centers describes the practical methods of obtaining chiral fragments. Divided into five chapters, this book specifically examines initial chiral transmission and extension. The opening chapter describes the so-called chiral carbon pool, the readily available chiral carbon fragments used as building blocks in synthesis. This chapter also provides a list of 375 chiral building blocks, along with their commercial sources, approximate prices, and methods of synthesis. Schemes involving

  10. 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

  11. Asymmetric quantum cloning machines

    International Nuclear Information System (INIS)

    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 px, py and pz. The capacity is proven to be vanishing if (√px, √py, √pz) 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)

  12. Asymmetric inclusion process

    Science.gov (United States)

    Reuveni, Shlomi; Eliazar, Iddo; Yechiali, Uri

    2011-10-01

    We introduce and explore the asymmetric inclusion process (ASIP), an exactly solvable bosonic counterpart of the fermionic asymmetric exclusion process (ASEP). In both processes, random events cause particles to propagate unidirectionally along a one-dimensional lattice of n sites. In the ASEP, particles are subject to exclusion interactions, whereas in the ASIP, particles are subject to inclusion interactions that coalesce them into inseparable clusters. We study the dynamics of the ASIP, derive evolution equations for the mean and probability generating function (PGF) of the sites’ occupancy vector, obtain explicit results for the above mean at steady state, and describe an iterative scheme for the computation of the PGF at steady state. We further obtain explicit results for the load distribution in steady state, with the load being the total number of particles present in all lattice sites. Finally, we address the problem of load optimization, and solve it under various criteria. The ASIP model establishes bridges between statistical physics and queueing theory as it represents a tandem array of queueing systems with (unlimited) batch service, and a tandem array of growth-collapse processes.

  13. Flow

    DEFF Research Database (Denmark)

    2009-01-01

    Flow er en positiv, koncentreret tilstand, hvor al opmærksomhed er samlet om en bestemt aktivitet, som er så krævende og engagerende, at man må anvende mange mentale ressourcer for at klare den. Tidsfornemmelsen forsvinder, og man glemmer sig selv. 'Flow' er den første af en række udsendelser om...

  14. 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

  15. Asymmetric black dyonic holes

    Directory of Open Access Journals (Sweden)

    I. Cabrera-Munguia

    2015-04-01

    Full Text Available A 6-parametric asymptotically flat exact solution, describing a two-body system of asymmetric black dyons, is studied. The system consists of two unequal counterrotating Kerr–Newman black holes, endowed with electric and magnetic charges which are equal but opposite in sign, separated by a massless strut. The Smarr formula is generalized in order to take into account their contribution to the mass. The expressions for the horizon half-length parameters σ1 and σ2, as functions of the Komar parameters and of the coordinate distance, are displayed, and the thermodynamic properties of the two-body system are studied. Furthermore, the seven physical parameters satisfy a simple algebraic relation which can be understood as a dynamical scenario, in which the physical properties of one body are affected by the ones of the other body.

  16. Flow

    DEFF Research Database (Denmark)

    Knoop, Hans Henrik

    2006-01-01

    FLOW. Orden i hovedet på den fede måde Oplevelsesmæssigt er flow-tilstanden kendetegnet ved at man er fuldstændig involveret, fokuseret og koncentreret; at man oplever stor indre klarhed ved at vide hvad der skal gøres, og i hvilket omfang det lykkes; at man ved at det er muligt at løse opgaven...

  17. Asymmetric Gepner Models (Revisited)

    CERN Document Server

    Gato-Rivera, B

    2010-01-01

    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 th...

  18. Magnetically Modified Asymmetric Supercapacitors Project

    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...

  19. 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

  20. On Asymmetric Quantum MDS Codes

    CERN Document Server

    Ezerman, Martianus Frederic; Ling, San

    2010-01-01

    Assuming the validity of the MDS Conjecture, the weight distribution of all MDS codes is known. Using a recently-established characterization of asymmetric quantum error-correcting codes, linear MDS codes can be used to construct asymmetric quantum MDS codes with $d_{z} \\geq d_{x}\\geq 2$ for all possible values of length $n$ for which linear MDS codes over $\\F_{q}$ are known to exist.

  1. Mobile Termination with Asymmetric Networks

    OpenAIRE

    Dewenter, Ralf; Haucap, Justus

    2003-01-01

    This paper examines mobile termination fees and their regulation when networks are asymmetric in size. It is demonstrated that with consumer ignorance about the exact termination rates (a) a mobile network?s termination rate is the higher the smaller the network?s size (as measured through its subscriber base) and (b) asymmetric regulation of only the larger operators in a market will, ce-teris paribus, induce the smaller operators to increase their termination rates. The results are supporte...

  2. 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.

  3. Rectification of motion in nonlinear media with asymmetric random drive

    International Nuclear Information System (INIS)

    We consider moving particles in media with nonlinear friction and drive them by an asymmetric dichotomic Markov process. Due to different energy dissipations, during the forward and backward stroke, we obtain a mean non-vanishing directed flow of the particles. Starting with the stationary velocity distribution, we calculate the stationary current of particles, the variance and the relative variance in dependence on the degree of nonlinearity of the friction, on the asymmetry and for different strengths of friction. In two dimensions the particle performs diffusional motion, if in addition the direction of the asymmetric drive changes stochastically.

  4. 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...... 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...

  5. Evolution of turbulence and in-plane vortices in the near field flow behind multi-scale planar grids

    Science.gov (United States)

    Gan, L.; Krogstad, P.-Å.

    2016-08-01

    In this experimental work, we carry out detailed two-dimensional particle image velocimetry investigations for the near field wakes behind a conventional and two multi-scale planar grids, using stitched camera fields of view. Statistical independent measurements are conducted focusing on the first few mesh distances downstream of the grid. It is found that the multiple integral length scales originated from the grids loose their importance on the turbulence development after about three mesh distances downstream, much earlier than the distance where the turbulence becomes homogeneous. The largest eddy size, represented by the integral length scales, does not show clear differences in its growth rate among the three grids after an initial development of three times the largest grid size downstream. Nevertheless, when examining individual vortex behaviours using conditional averaging and filtering processes, clear differences are found. The grids are found to have different decay rates of peak vorticity and projected vortex strengths. Despite these differences, the in-plane vorticity correlation function reveals that the mean vortex shape of all the grids shows a universal near-Gaussian pattern which does not change much as the turbulence decays.

  6. Chiral magnetic microspheres purified by centrifugal field flow fractionation and microspheres magnetic chiral chromatography for benzoin racemate separation

    OpenAIRE

    Tian, Ailin; Qi, Jing; Liu, Yating; Wang, Fengkang; Ito, Yoichiro; Wei, Yun

    2013-01-01

    Separation of enantiomers still remains a challenge due to their identical physical and chemical properties in a chiral environment, and the research on specific chiral selector along with separation techniques continues to be conducted to resolve individual enantiomers. In our laboratory the promising magnetic chiral microspheres Fe3O4@SiO2@cellulose-2, 3-bis (3, 5-dimethylphenylcarbamate) have been developed to facilitate the resolution using both its magnetic property and chiral recognitio...

  7. Thermal transport across symmetric and asymmetric solid-solid interfaces

    Science.gov (United States)

    Bi, Kedong; Liu, Yadong; Zhang, Chunwei; Li, Jiapeng; Chen, Minhua; Chen, Yunfei

    2016-10-01

    Thermal transport across symmetric and asymmetric solid-solid interfaces is investigated by non-equilibrium molecular dynamics simulations. For symmetric interfaces, simulation results demonstrate that the thermal interface resistance is reduced greatly with the temperature increasing from 20 to 70 K. Besides, the introduction of an interlayer in the region of a highly mismatched interface is predicted to effectively decrease the thermal interface resistance due to the vibrational bridge role of the interlayer in connecting two vibrationally mismatched materials. As for the case of asymmetric interfaces, it is found that the capacity of thermal transport across an asymmetric interface is related to the effective interfacial area, namely the smaller cross-section area of component materials. In addition, effects of the transition angle at asymmetric interfaces on the thermal interface resistance are further studied when heat flows through interfaces from the side with larger cross-section area to the other. It is shown that a smoother transition is preferred for thermal transport through an asymmetric interface.

  8. Asymmetric distances for binary embeddings.

    Science.gov (United States)

    Gordo, Albert; Perronnin, Florent; Gong, Yunchao; Lazebnik, Svetlana

    2014-01-01

    In large-scale query-by-example retrieval, embedding image signatures in a binary space offers two benefits: data compression and search efficiency. While most embedding algorithms binarize both query and database signatures, it has been noted that this is not strictly a requirement. Indeed, asymmetric schemes that binarize the database signatures but not the query still enjoy the same two benefits but may provide superior accuracy. In this work, we propose two general asymmetric distances that are applicable to a wide variety of embedding techniques including locality sensitive hashing (LSH), locality sensitive binary codes (LSBC), spectral hashing (SH), PCA embedding (PCAE), PCAE with random rotations (PCAE-RR), and PCAE with iterative quantization (PCAE-ITQ). We experiment on four public benchmarks containing up to 1M images and show that the proposed asymmetric distances consistently lead to large improvements over the symmetric Hamming distance for all binary embedding techniques.

  9. 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...

  10. 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)

  11. Incompressibility of asymmetric nuclear matter

    OpenAIRE

    Chen, Lie-Wen; Cai, Bao-Jun; Shen, Chun; Ko, Che Ming; Xu, Jun; Li, Bao-An(Department of Physics and Astronomy, Texas A&M University-Commerce, Commerce, TX, 75429-3011, USA)

    2009-01-01

    The incompressibility $K_sat(\\delta)$ of isospin asymmetric nuclear matter at its saturation density. Our results show that in the expansion of $K_sat(\\delta)$ in powers of isospin asymmetry $\\delta$, i.e., $K_sat(\\delta )$=K_{0}+K_{sat,2}\\delta^{2}+K_{sat,4}\\delta^{4}+O(\\delta^{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 matte...

  12. Forces between asymmetric polymer brushes

    OpenAIRE

    Shim, D.F.K.; Cates, M. E.

    1990-01-01

    We study the equilibrium compression of asymmetric polymer brushes grafted on flat plates, under athermal and theta solvent conditions, using a lattice self-consistent field (SCF) approach. We find that the separation d between two plates coated asymmetrically with brushes of type 1 and 2, as a function of the force F, obeys the "bisection rule", d(F) = (d1(F) + d 2(F)) /2 where d1(F)and d 2(F) are the corresponding separations for the symmetric brushes of type 1 and 2 respectively.The bisect...

  13. Research on asymmetric "Jerusalem" unit

    Institute of Scientific and Technical Information of China (English)

    Jun Lu; Jianbo Wang

    2009-01-01

    An asymmetric Jerusalem unit and the frequency selective surface(FSS)structure composed of such units are designed.The transmittance of the designed FSS structure is calculated by mode-matching method and compared with the test results.The comparison results show that the FSS center frequency of the asymmetric structure unit drifts little with the variation of the incident angles of the electromagnetic waves and keeps relatively stable.The research offers a new choice for the application of FSS under the large scanning angle of electromagnetic waves.

  14. A Numerical Comparison of Symmetric and Asymmetric Supersonic Wind Tunnels

    Science.gov (United States)

    Clark, Kylen D.

    Supersonic wind tunnels are a vital aspect to the aerospace industry. Both the design and testing processes of different aerospace components often include and depend upon utilization of supersonic test facilities. Engine inlets, wing shapes, and body aerodynamics, to name a few, are aspects of aircraft that are frequently subjected to supersonic conditions in use, and thus often require supersonic wind tunnel testing. There is a need for reliable and repeatable supersonic test facilities in order to help create these vital components. The option of building and using asymmetric supersonic converging-diverging nozzles may be appealing due in part to lower construction costs. There is a need, however, to investigate the differences, if any, in the flow characteristics and performance of asymmetric type supersonic wind tunnels in comparison to symmetric due to the fact that asymmetric configurations of CD nozzle are not as common. A computational fluid dynamics (CFD) study has been conducted on an existing University of Michigan (UM) asymmetric supersonic wind tunnel geometry in order to study the effects of asymmetry on supersonic wind tunnel performance. Simulations were made on both the existing asymmetrical tunnel geometry and two axisymmetric reflections (of differing aspect ratio) of that original tunnel geometry. The Reynolds Averaged Navier Stokes equations are solved via NASAs OVERFLOW code to model flow through these configurations. In this way, information has been gleaned on the effects of asymmetry on supersonic wind tunnel performance. Shock boundary layer interactions are paid particular attention since the test section integrity is greatly dependent upon these interactions. Boundary layer and overall flow characteristics are studied. The RANS study presented in this document shows that the UM asymmetric wind tunnel/nozzle configuration is not as well suited to producing uniform test section flow as that of a symmetric configuration, specifically one

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

    International Nuclear Information System (INIS)

    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

  16. Asymmetric exchange in flocks

    CERN Document Server

    Dadhichi, Lokrshi Prawar; Maitra, Ananyo; Ramaswamy, Sriram

    2016-01-01

    As the constituents of a flock are polar, one expects a fore-aft asymmetry in their interactions. We show here that the resulting antisymmetric part of the "exchange coupling" between a bird and its neighbours, if large enough, destabilizes the flock through spontaneous turning of the birds. The same asymmetry also yields a natural mechanism for a difference between the speed of advection of information along the flock and the speed of the flock itself. We show that the absence of detailed balance, and not merely the breaking of Galilean invariance, is responsible for this difference. We delineate the conditions on parameters and wavenumber for the existence of the turning instability. Lastly we present an alternative perspective based on flow-alignment effects in an active liquid crystal with turning inertia in contact with a momentum sink.

  17. Synthesis of Asymmetric Propanetriol Analogues

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    From natural tartaric acid, (R)-2-benzyloxy-3-(2-tetrahydropyranyloxy) propanol 3 was designed and synthesized, and (R)-2-benzyloxy-3-(4-methoxybenzyloxy) propanol 7 was prepared in a new method. They can be used as chiral synthons of lysophosphatidic acid and other compounds with asymmetric propanetriol backbone.

  18. Vertical asymmetric double quantum dots

    Science.gov (United States)

    Roßbach, R.; Reischle, M.; Beirne, G. J.; Schweizer, H.; Jetter, M.; Michler, P.

    2007-01-01

    Two layers of differently sized self-assembled InP-quantum dots (QDs) separated by a GaInP spacer layer with varying thickness were grown by metal organic vapor phase epitaxy (MOVPE). Photoluminescence measurements of the QD ensembles and of individual asymmetric double QDS show coupling due to the tunnelling of carriers.

  19. Asymmetrical Switch Costs in Children

    Science.gov (United States)

    Ellefson, Michelle R.; Shapiron, Laura R.; Chater, Nick

    2006-01-01

    Switching between tasks produces decreases in performance as compared to repeating the same task. Asymmetrical switch costs occur when switching between two tasks of unequal difficulty. This asymmetry occurs because the cost is greater when switching to the less difficult task than when switching to the more difficult task. Various theories about…

  20. The Asymmetric Effects of Investor Sentiment

    DEFF Research Database (Denmark)

    Lutz, Chandler

    We use the returns on lottery-like stocks to construct a novel index for investor sentiment in the stock market. This new measure is closely related to previously developed sentiment indicators, but more accurately tracks speculative episodes over the sample period. Using our index, we find...... that the relationship between sentiment and returns is asymmetric: during bear markets, high sentiment predicts low future returns for the cross-section of speculative stocks and the market overall while the relationship during bull markets is weak and often insignificant. Thus, the results suggest that sophisticated...... 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....

  1. The Asymmetric Predictive Effects of Investor Sentiment

    DEFF Research Database (Denmark)

    Lutz, Chandler

    We use the returns on lottery-like stocks to construct a novel index for investor sentiment in the stock market. This new measure is closely related to previously developed sentiment indicators, but more accurately tracks speculative episodes over the sample period. Using our index, we find...... that the relationship between sentiment and returns is asymmetric: during bear markets, high sentiment predicts low future returns for the cross-section of speculative stocks and the market overall while the relationship during bull markets is weak and often insignicant. Thus, the results suggest that sophisticated...... 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....

  2. Asymmetric exclusion processes with shuffled dynamics

    International Nuclear Information System (INIS)

    The asymmetric simple exclusion process (ASEP) with periodic boundary conditions is investigated for shuffled dynamics. In this type of update, in each discrete timestep the particles are updated in a random sequence. Such an update is important for several applications, e.g., for certain models of pedestrian flow in two dimensions. For the ASEP with shuffled dynamics and a related truncated process exact results are obtained for deterministic motion (p = 1). Since the shuffled dynamics is intrinsically stochastic, also this case is nontrivial. For the case of stochastic motion (0 < p < 1) it is shown that, in contrast to all other updates studied previously, the ASEP with shuffled update does not have a product measure steady state. Approximative formulae for the steady-state distribution and fundamental diagram are derived that are in very good agreement with simulation data

  3. Selfhealing of asymmetric Bessel-like modes

    DEFF Research Database (Denmark)

    Israelsen, Stine Møller; Rishøj, Lars Søgaard; Rottwitt, Karsten

    2014-01-01

    We numerically investigate asymmetric Bessel-like modes in an aircladding fiber. The selfhealing ability of asymmetric Bessel-like modes is demonstrated and quantified including the angular dependency of this ability.......We numerically investigate asymmetric Bessel-like modes in an aircladding fiber. The selfhealing ability of asymmetric Bessel-like modes is demonstrated and quantified including the angular dependency of this ability....

  4. A computational study of asymmetric glottal jet deflection during phonation.

    Science.gov (United States)

    Zheng, X; Mittal, R; Bielamowicz, S

    2011-04-01

    Two-dimensional numerical simulations are used to explore the mechanism for asymmetric deflection of the glottal jet during phonation. The model employs the full Navier-Stokes equations for the flow but a simple laryngeal geometry and vocal-fold motion. The study focuses on the effect of Reynolds number and glottal opening angle with a particular emphasis on examining the importance of the so-called "Coanda effect" in jet deflection. The study indicates that the glottal opening angle has no substantial effect on glottal jet deflection. Deflection in the glottal jet is always preceded by large-scale asymmetry in the downstream portion of the glottal jet. A detailed analysis of the velocity and vorticity fields shows that these downstream asymmetric vortex structures induce a flow at the glottal exit which is the primary driver for glottal jet deflection. PMID:21476669

  5. Asymmetric coherent transmission for single particle diode and gyroscope

    OpenAIRE

    Yang, S.; Song, Z; Sun, C. P.

    2009-01-01

    We study the single particle scattering process in a coherent multi-site system consisting of a tight-binding ring threaded by an Aharonov-Bohm flux and several attaching leads. The asymmetric behavior of scattering matrix is discovered analytically in the framework of both Bethe Ansatz and Green's function formalism. It is found that, under certain conditions, a three-site electronic system can behave analogous to a perfect semiconductor diode where current flows only in one direction. The g...

  6. Asymmetric Multilevel Diversity Coding and Asymmetric Gaussian Multiple Descriptions

    CERN Document Server

    Mohajer, Soheil; Diggavi, Suhas N

    2009-01-01

    We consider the asymmetric multilevel diversity (A-MLD) coding problem, where a set of $2^K-1$ information sources, ordered in a decreasing level of importance, is encoded into $K$ messages (or descriptions). There are $2^K-1$ decoders, each of which has access to a non-empty subset of the encoded messages. Each decoder is required to reproduce the information sources up to a certain importance level depending on the combination of descriptions available to it. We obtain a single letter characterization of the achievable rate region for the 3-description problem. In contrast to symmetric multilevel diversity coding, source-separation coding is not sufficient in the asymmetric case, and ideas akin to network coding need to be used strategically. Based on the intuitions gained in treating the A-MLD problem, we derive inner and outer bounds for the rate region of the asymmetric Gaussian multiple description (MD) problem with three descriptions. Both the inner and outer bounds have a similar geometric structure t...

  7. 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 ......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...

  8. 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.

  9. Asymmetric Trade Estimator in Modified Gravity: Corporate Tax Rates and Trade in OECD Countries

    OpenAIRE

    Estelle P. Dauchy; Christopher Balding

    2013-01-01

    To study the potentially distortionary impact of differing corporate income tax rates on international trade flows, we use an augmented empirical specification of the gravity model. Incorporating an asymmetric trade barrier measure into a modified gravity model, we capture the impact of corporate income tax rates via the price mechanism impact on trade. Holding other factors constant in a gravity model, one should theoretically expect asymmetric corporate income tax rates to impact bilateral ...

  10. The design of an asymmetric bionic branching channel for electronic chips cooling

    Science.gov (United States)

    Xu, Shanglong; Qin, Jie; Guo, Wei; Fang, Kuang

    2013-06-01

    Inspired by the wing vein of Lepidoptera, a designment of asymmetric bionic branching channel for electronic chips cooling is developed. Lepidoptera vein D was chosen to measure the angle of first and second branch level. Based on these regular patterns, an asymmetric bionic branching channel is designed in a 35 mm × 35 mm chip. Comparing with fractal-like branching channel, it provides a stronger heat transfer capability, lower pressure drop and lower flow resistance in the experiment.

  11. Terahertz metamaterial with asymmetric transmission

    CERN Document Server

    Singh, R; Menzel, C; Rockstuhl, C; Azad, A K; Cheville, R A; Lederer, F; Zhang, W; Zheludev, N I

    2009-01-01

    We show for the first time that a planar metamaterial, an array of coupled metal split-ring resonators with a unit cell lacking mirror symmetry, exhibits asymmetric transmission of terahertz radiation propagating through it in opposite directions. This intriguing effect, that is compatible with Lorentz reciprocity and time-reversal, depends on a directional difference in conversion efficiency of the incident circularly polarized wave into one of opposite handedness, that is only possible in lossy low-symmetry planar chiral metamaterials. We show that asymmetric transmission is linked to excitation of enantiomerically sensitive plasmons, these are induced charge-field excitations that depend on the mutual handedness of incident wave and metamaterial pattern. Various bands of positive, negative and zero phase and group velocities have been identified indicating the opportunity to develop polarization sensitive negative index and slow light media based on such metamaterials.

  12. Stable walking with asymmetric legs

    International Nuclear Information System (INIS)

    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.

  13. 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.

  14. Entrepreneurship, Asymmetric Information and Unemployment

    OpenAIRE

    Robin Boadway; Nicolas Marceau; Maurice Marchand; Marianne Vigneault

    1998-01-01

    We examine how three sources of asymmetric information affect the supply of entrepreneurs and unemployment. In the first case, banks cannot observe entrepreneurs' risk of failure so ration credit. This increases the number of entrepreneurs and the level of unemployment. In the second case, firms cannot observe workers' effort so offer a wage above the market clearing one. This results in unemployment and too few entrepreneurs. The final case arises when firms cannot observe workers' abilities...

  15. Asymmetric Microscopic Driving Behavior Theory

    OpenAIRE

    Yeo, Hwasoo

    2008-01-01

    Numerous theories on traffic have been developed as traffic congestion gains more and more interest in our daily life. To model traffic phenomena, many traffic theorists have adopted theories from other fields such as fluid mechanics and thermodynamics. However, their efforts to model the traffic at a microscopic level have not been successful yet. Therefore, to overcome the limitations of the existing theories we propose a microscopic asymmetric traffic theory based on analysis of individual...

  16. Asymmetric Information and Consumer Demand

    OpenAIRE

    Ismagilova G. N.; Danilina E. I.; Gafurov I. R.; Ismagilov R. I.; Safiullin L. N.

    2014-01-01

    In the paper study the peculiarities of the formation the consumer demand for durable goods, the so-called «experience goods» in markets with asymmetric information. In the known literature sources studying of the demand is based on the assumption that at the moment of the purchase of goods and services people know exactly what price they are willing to pay for them and what utility they are going to obtain using those goods and services. Consider the signal model in which the initial price a...

  17. Spontaneous baryogenesis from asymmetric inflaton

    Energy Technology Data Exchange (ETDEWEB)

    Takahashi, Fuminobu [Tohoku Univ., Sendai (Japan). Dept. of Physics; Tokyo Univ., Chiba (Japan). Kavli IPMU (WPI), UTIAS; Yamada, Masaki [Tokyo Univ., Chiba (Japan). Kavli IPMU (WPI), UTIAS; Tokyo Univ., Chiba (Japan). Inst. for Cosmic Ray Research; DESY Hamburg (Germany)

    2015-10-15

    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.

  18. 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. PMID:26474211

  19. Transient Stability During Asymmetrical Faults

    OpenAIRE

    Couturier, Nicolas

    2015-01-01

    This research project has been conducted at RTE in order to study the transient stability after asymmetrical faults. When three-phase short-circuits occur in a network, almost all the electrical power is lost on the relevant line(s). Among all short-circuit types, it is the most drastic event and the issue has to be solved very quickly. But oddly, it is also the easiest problem to solve mathematically speaking. This comes from the fact that the system stays balanced, and equations can be simp...

  20. Asymmetric Random Matrices: What do We Need them For?

    International Nuclear Information System (INIS)

    Complex systems are typically represented by large ensembles of observations. Correlation matrices provide an efficient formal framework to extract information from such multivariate ensembles and identify in a quantifiable way patterns of activity that are reproducible with statistically significant frequency compared to a reference chance probability, usually provided by random matrices as fundamental reference. The character of the problem and especially the symmetries involved must guide the choice of random matrices to be used for the definition of a baseline reference. For standard correlation matrices this is the Wishart ensemble of symmetric random matrices. The real world complexity however often shows asymmetric information flows and therefore more general correlation matrices are required to adequately capture the asymmetry. Here we first summarize the relevant theoretical concepts. We then present some examples of human brain activity where asymmetric time-lagged correlations are evident and hence highlight the need for further theoretical developments. (author)

  1. Asymmetric random matrices: What do we need them for?

    CERN Document Server

    Drozdz, Stanislaw; Ioannides, Andreas A; 10.5506/APhysPolB.42.987

    2011-01-01

    Complex systems are typically represented by large ensembles of observations. Correlation matrices provide an efficient formal framework to extract information from such multivariate ensembles and identify in a quantifiable way patterns of activity that are reproducible with statistically significant frequency compared to a reference chance probability, usually provided by random matrices as fundamental reference. The character of the problem and especially the symmetries involved must guide the choice of random matrices to be used for the definition of a baseline reference. For standard correlation matrices this is the Wishart ensemble of symmetric random matrices. The real world complexity however often shows asymmetric information flows and therefore more general correlation matrices are required to adequately capture the asymmetry. Here we first summarize the relevant theoretical concepts. We then present some examples of human brain activity where asymmetric time-lagged correlations are evident and hence...

  2. Enhanced Asymmetric Bilinear Model for Face Recognition

    OpenAIRE

    Wenjuan Gong; Weishan Zhang; Jordi Gonzàlez; Yan Ren; Zhen Li

    2015-01-01

    Bilinear models have been successfully applied to separate two factors, for example, pose variances and different identities in face recognition problems. Asymmetric model is a type of bilinear model which models a system in the most concise way. But seldom there are works exploring the applications of asymmetric bilinear model on face recognition problem with illumination changes. In this work, we propose enhanced asymmetric model for illumination-robust face recognition. Instead of initiali...

  3. Excitons in asymmetric quantum wells

    Science.gov (United States)

    Grigoryev, P. S.; Kurdyubov, A. S.; Kuznetsova, M. S.; Ignatiev, I. V.; Efimov, Yu. P.; Eliseev, S. A.; Petrov, V. V.; Lovtcius, V. A.; Shapochkin, P. Yu.

    2016-09-01

    Resonance dielectric response of excitons is studied for the high-quality InGaAs/GaAs heterostructures with wide asymmetric quantum wells (QWs). To highlight effects of the QW asymmetry, we have grown and studied several heterostructures with nominally square QWs as well as with triangle-like QWs. Several quantum confined exciton states are experimentally observed as narrow exciton resonances. A standard approach for the phenomenological analysis of the profiles is generalized by introducing different phase shifts for the light waves reflected from the QWs at different exciton resonances. Good agreement of the phenomenological fit to the experimentally observed exciton spectra for high-quality structures allowed us to reliably obtain parameters of the exciton resonances: the exciton transition energies, the radiative broadenings, and the phase shifts. A direct numerical solution of the Schrödinger equation for the heavy-hole excitons in asymmetric QWs is used for microscopic modeling of the exciton resonances. Remarkable agreement with the experiment is achieved when the effect of indium segregation is taken into account. The segregation results in a modification of the potential profile, in particular, in an asymmetry of the nominally square QWs.

  4. Asymmetric Laguerre-Gaussian beams

    Science.gov (United States)

    Kovalev, A. A.; Kotlyar, V. V.; Porfirev, A. P.

    2016-06-01

    We introduce a family of asymmetric Laguerre-Gaussian (aLG) laser beams. The beams have been derived via a complex-valued shift of conventional LG beams in the Cartesian plane. While propagating in a uniform medium, the first bright ring of the aLG beam becomes less asymmetric and the energy is redistributed toward peripheral diffraction rings. The projection of the orbital angular momentum (OAM) onto the optical axis is calculated. The OAM is shown to grow quadratically with increasing asymmetry parameter of the aLG beam, which equals the ratio of the shift to the waist radius. Conditions for the OAM becoming equal to the topological charge have been derived. For aLG beams with zero radial index, we have deduced an expression to define the intensity maximum coordinates and shown the crescent-shaped intensity pattern to rotate during propagation. Results of the experimental generation and rotation of aLG beams agree well with theoretical predictions.

  5. Some Remarks on Asymmetric Syntheses from Recent Studies

    OpenAIRE

    Baba, Naomichi

    1990-01-01

    Some asymmetric syntheses were presented here and discussed briefly including NADH model reactions, phase transfer-catalyzed asymmetric epoxidation, enantiotopic group-selective hydrolysis of a malonic anhydride with alkoxide anion, intramolecular acid-catalyzed lactonizations, catalytic asymmetric Diels-Alder synthesis, asymmetric aldol condensation, chiral homoallyl alcohol synthesis, asymmetric addition of diethylzinc to aldehyde, kinetic resolution of racemic hydroperoxides and binaphthol...

  6. Classification of flow patterns in rectangular shallow reservoirs

    OpenAIRE

    DUFRESNE, Matthieu; Dewals, Benjamin; Erpicum, Sébastien; Archambeau, Pierre; Pirotton, Michel

    2010-01-01

    This work focuses on the experimental classification of flow patterns in rectangular shallow reservoirs, including symmetric flows without any reattachment point to asymmetric flows with one reattachment point, two reattachment points, or two reattachment points and one detachment point. The median position and the natural variability of the reattachment lengths of asymmetric flows were measured for forty geometric and hydraulic conditions. The effects of dimensionless flow depth, Froude numb...

  7. Condensation on Slippery Asymmetric Bumps

    CERN Document Server

    Park, Kyoo-Chul; He, Neil; Aizenberg, Joanna

    2015-01-01

    Bumps are omnipresent from human skin to the geological structures on planets, which offer distinct advantages in numerous phenomena including structural color, drag reduction, and extreme wettability. Although the topographical parameters of bumps such as radius of curvature of convex regions significantly influence various phenomena including anti-reflective structures and contact time of impacting droplets, the effect of the detailed bump topography on growth and transport of condensates have not been clearly understood. Inspired by the millimetric bumps of the Namib Desert beetle, here we report the identified role of radius of curvature and width of bumps with homogeneous surface wettability in growth rate, coalescence and transport of water droplets. Further rational design of asymmetric convex topography and synergetic combination with slippery coating simultaneously enable self-transport, leading to unseen five-fold higher growth rate and an order of magnitude faster shedding time of droplets compared...

  8. New asymmetric quantum codes over Fq

    Science.gov (United States)

    Ma, Yuena; Feng, Xiaoyi; Xu, Gen

    2016-07-01

    Two families of new asymmetric quantum codes are constructed in this paper. The first family is the asymmetric quantum codes with length n=qm-1 over Fq, where qge 5 is a prime power. The second one is the asymmetric quantum codes with length n=3m-1. These asymmetric quantum codes are derived from the CSS construction and pairs of nested BCH codes. Moreover, let the defining set T1=T2^{-q}, then the real Z-distance of our asymmetric quantum codes are much larger than δ _max+1, where δ _max is the maximal designed distance of dual-containing narrow-sense BCH code, and the parameters presented here have better than the ones available in the literature.

  9. Asymmetric Information and the Role of Accounting in Emerging Markets Evidences from TSE

    Directory of Open Access Journals (Sweden)

    Aida Dowran

    2013-02-01

    Full Text Available This study examines the value relevance (information content of cash flow and accounting figures in situations where the information is asymmetrical and Compare the relative information content of them to clarify the role of accounting figures in investment decision making and mitigating the agency problems (specifically resulting from the existence of information asymmetry in the emerging markets. Based on testing a sample of 76 firms from Tehran Stock Exchange (TSE during 2005 to 2011, the results support the priority of accounting figures over cash flows in the market (TSE. On the other hand, when the information is asymmetrical, the accounting figures are still more relevant than the cash flows and have more relative information content. At the same time, in small firms, the value relevance of the accounting figures compared to cash flows is more; while in large firms, the relative content of accounting figures and cash flow figures aren't significantly different.

  10. 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.

  11. Computational analysis of asymmetric water entry of wedge and ship section at constant velocity

    Science.gov (United States)

    Rahaman, Md. Mashiur; Ullah, Al Habib; Afroz, Laboni; Shabnam, Sharmin; Sarkar, M. A. Rashid

    2016-07-01

    Water impact problems receive much attention due to their short duration and large unsteady component of hydrodynamic loads. The effect of water entry has several important applications in various aspects of the naval field. Significant attention has been given to various water entry phenomena such as ship slamming, planning hulls, high-speed hydrodynamics of seaplanes, surface-piercing propellers and the interaction of high-speed liquid drops with structural elements. Asymmetric water entry may be caused by various natural phenomena such as weather conditions or strong winds. Since the determination of hydrodynamic impact load plays a vital role in designing safe and effcient vessels, an accurate and reliable prediction method is necessary to investigate asymmetric water entry problems. In this paper, water entry of a two-dimensional wedge and ship section at constant velocity in asymmetric condition will be analysed numerically and the effects of asymmetric impact on the velocity and pressure distribution will be discussed. The finite volume method is employed to solve the dynamic motion of the wedge in two-phase flow. During the water entry, the air and water interface is described implicitly by the volume of fluid (VOF) scheme. The numerical code and method was first validated for symmetric condition by one of the present author is applied for asymmetric wedge and ship section. The free surface, velocity and pressure distribution for asymmetric water entry are investigated and visualized with contour plots at different time steps.

  12. Regenerating a symmetry in asymmetric dark matter.

    Science.gov (United States)

    Buckley, Matthew R; Profumo, Stefano

    2012-01-01

    Asymmetric dark matter theories generically allow for mass terms that lead to particle-antiparticle mixing. Over the age of the Universe, dark matter can thus oscillate from a purely asymmetric configuration into a symmetric mix of particles and antiparticles, allowing for pair-annihilation processes. Additionally, requiring efficient depletion of the primordial thermal (symmetric) component generically entails large annihilation rates. We show that unless some symmetry completely forbids dark matter particle-antiparticle mixing, asymmetric dark matter is effectively ruled out for a large range of masses, for almost any oscillation time scale shorter than the age of the Universe. PMID:22304253

  13. Asymmetric dark matter in braneworld cosmology

    Energy Technology Data Exchange (ETDEWEB)

    Meehan, Michael T.; Whittingham, Ian B., E-mail: Michael.Meehan@my.jcu.edu.au, E-mail: Ian.Whittingham@jcu.edu.au [School of Engineering and Physical Sciences, James Cook University, Townsville, 4811 Australia (Australia)

    2014-06-01

    We investigate the effect of a braneworld expansion era on the relic density of asymmetric dark matter. We find that the enhanced expansion rate in the early universe predicted by the Randall-Sundrum II (RSII) model leads to earlier particle freeze-out and an enhanced relic density. This effect has been observed previously by Okada and Seto (2004) for symmetric dark matter models and here we extend their results to the case of asymmetric dark matter. We also discuss the enhanced asymmetric annihilation rate in the braneworld scenario and its implications for indirect detection experiments.

  14. Regenerating a symmetry in asymmetric dark matter.

    Science.gov (United States)

    Buckley, Matthew R; Profumo, Stefano

    2012-01-01

    Asymmetric dark matter theories generically allow for mass terms that lead to particle-antiparticle mixing. Over the age of the Universe, dark matter can thus oscillate from a purely asymmetric configuration into a symmetric mix of particles and antiparticles, allowing for pair-annihilation processes. Additionally, requiring efficient depletion of the primordial thermal (symmetric) component generically entails large annihilation rates. We show that unless some symmetry completely forbids dark matter particle-antiparticle mixing, asymmetric dark matter is effectively ruled out for a large range of masses, for almost any oscillation time scale shorter than the age of the Universe.

  15. Asymmetric Dark Matter and Effective Operators

    CERN Document Server

    Buckley, Matthew R

    2011-01-01

    In order to annihilate in the early Universe to levels well below the measured dark matter density, asymmetric dark matter must possess large couplings to the Standard Model. In this paper, we consider effective operators which allow asymmetric dark matter to annihilate into quarks. In addition to a bound from requiring sufficient annihilation, the energy scale of such operators can be constrained by limits from direct detection and monojet searches at colliders. We show that the allowed parameter space for these operators is highly constrained, leading to non-trivial requirements that any model of asymmetric dark matter must satisfy.

  16. Peristaltic transport of a Maxwell fluid in a porous asymmetric channel through a porous medium

    Directory of Open Access Journals (Sweden)

    Safia Akram

    2014-12-01

    Full Text Available The present study investigates the peristaltic flow of a Maxwell fluid in a porous asymmetric channel through a porous medium. An analytical solution has been found using regular perturbation method. The stream function and average mean velocity are obtained. The graphical results are presented to discuss the physical behavior of various parameters appearing in the problem.

  17. Experimental adiabatic vortex ratchet effect in Nb films with asymmetric pinning trap

    Indian Academy of Sciences (India)

    J E Villegas; N O nunez; M P Gonzalez; E M Gonalez; J L Vicent

    2006-01-01

    Nb films grown on top of an array of asymmetric pinning centers show a vortex ratchet effect. A net flow of vortices is induced when the vortex lattice is driven by fluctuating forces on an array of pinning centers without reflection symmetry. This effect occurs in the adiabatic regime and it could be mimiced only by reversible DC driven forces.

  18. Slip and heat transfer effects on peristaltic motion of a Carreau fluid in an asymmetric channel

    Energy Technology Data Exchange (ETDEWEB)

    Hayat, Tasawar [Quaid-i-Azam Univ., Islamabad (Pakistan). Dept. of Mathematics; King Saud Univ., Riyadh (Saudi Arabia). Dept. of Mathematics; Saleem, Najma [Quaid-i-Azam Univ., Islamabad (Pakistan). Dept. of Mathematics; Hendi, Awatif A. [Dept. of Physics, Riyadh (Saudi Arabia). Faculty of Science

    2010-12-15

    An analysis has been carried out for peristaltic flow and heat transfer of a Carreau fluid in an asymmetric channel with slip effect. The governing problem is solved under long wavelength approximation. The variations of pertinent dimensionless parameters on temperature are discussed. Pumping and trapping phenomena are studied. (orig.)

  19. 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.

  20. Why Do Nucleosomes Unwrap Asymmetrically?

    Science.gov (United States)

    de Bruin, Lennart; Tompitak, Marco; Eslami-Mossallam, Behrouz; Schiessel, Helmut

    2016-07-01

    Nucleosomes, DNA spools with a protein core, engage about three-quarters of eukaryotic DNA and play a critical role in chromosomal processes, ranging from gene regulation, recombination, and replication to chromosome condensation. For more than a decade, micromanipulation experiments where nucleosomes are put under tension, as well as the theoretical interpretations of these experiments, have deepened our understanding of the stability and dynamics of nucleosomes. Here we give a theoretical explanation for a surprising new experimental finding: nucleosomes wrapped onto the 601 positioning sequence (the sequence used in most laboratories) respond highly asymmetrically to external forces by always unwrapping from the same end. Using a computational nucleosome model, we show that this asymmetry can be explained by differences in the DNA mechanics of two very short stretches on the wrapped DNA portion. Our finding suggests that the physical properties of nucleosomes, here the response to forces, can be tuned locally by the choice of the underlying base-pair sequence. This leads to a new view of nucleosomes: a physically highly varied set of DNA-protein complexes whose properties can be tuned on evolutionary time scales to their specific function in the genomic context. PMID:26991771

  1. Twin Higgs Asymmetric Dark Matter

    CERN Document Server

    García, Isabel García; March-Russell, John

    2015-01-01

    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 $SU(3)' \\times SU(2)'$, a twin Higgs, and only third generation twin fermions. Naturalness requires the QCD$^\\prime$ scale $\\Lambda'_{\\rm QCD} \\simeq 0.5 - 20 \\ {\\rm GeV}$, and $t'$ to be heavy. We focus on the light $b'$ quark regime, $m_{b'} \\lesssim \\Lambda'_{\\rm QCD}$, where QCD$^\\prime$ is characterised by a single scale $\\Lambda'_{\\rm QCD}$ with no light pions. A twin baryon number asymmetry leads to a successful DM candidate: the spin-3/2 twin baryon, $\\Delta' \\sim b'b'b'$, with a dynamically determined mass ($\\sim 5 \\Lambda'_{\\rm QCD}$) in the preferred range for the DM-to-baryon ratio $\\Omega_{\\rm DM}/\\Omega_{\\rm baryon} \\simeq 5$. Gauging the $U(1)'$ group leads to twin atoms ($\\Delta'$ - $\\bar {\\tau'}$ bound states) that are successful ADM candidates in significant regions of parameter space, sometimes with observable changes to DM halo ...

  2. Asymmetric total synthesis of vindoline.

    Science.gov (United States)

    Kato, Daisuke; Sasaki, Yoshikazu; Boger, Dale L

    2010-03-24

    A concise asymmetric total synthesis of (-)-vindoline (1) is detailed based on a tandem intramolecular [4+2]/[3+2] cycloaddition cascade of a 1,3,4-oxadiazole inspired by the natural product structure, in which the tether linking the initiating dienophile and oxadiazole bears a chiral substituent that controls the facial selectivity of the initiating Diels-Alder reaction and sets absolute stereochemistry of the remaining six stereocenters in the cascade cycloadduct. This key reaction introduces three rings and four C-C bonds central to the pentacyclic ring system setting all six stereocenters and introducing essentially all the functionality found in the natural product in a single step. Implementation of the approach also required the development of a unique ring expansion reaction to provide a six-membered ring suitably functionalized for introduction of the Delta (6, 7)-double bond found in the core structure of vindoline and defined our use of a protected hydroxymethyl group as the substituent used to control the stereochemical course of the cycloaddition cascade.

  3. Chaos suppression through asymmetric coupling

    Science.gov (United States)

    Bragard, J.; Vidal, G.; Mancini, H.; Mendoza, C.; Boccaletti, S.

    2007-12-01

    We study pairs of identical coupled chaotic oscillators. In particular, we have used Roessler (in the funnel and no funnel regimes), Lorenz, and four-dimensional chaotic Lotka-Volterra models. In all four of these cases, a pair of identical oscillators is asymmetrically coupled. The main result of the numerical simulations is that in all cases, specific values of coupling strength and asymmetry exist that render the two oscillators periodic and synchronized. The values of the coupling strength for which this phenomenon occurs is well below the previously known value for complete synchronization. We have found that this behavior exists for all the chaotic oscillators that we have used in the analysis. We postulate that this behavior is presumably generic to all chaotic oscillators. In order to complete the study, we have tested the robustness of this phenomenon of chaos suppression versus the addition of some Gaussian noise. We found that chaos suppression is robust for the addition of finite noise level. Finally, we propose some extension to this research.

  4. Force on an Asymmetric Capacitor

    CERN Document Server

    Bahder, T B; Bahder, Thomas B.; Fazi, Chris

    2002-01-01

    When a high voltage (~30 kV) is applied to a capacitor whose electrodes have different physical dimensions, the capacitor experiences a net force toward the smaller electrode (Biefeld-Brown effect). We have verified this effect by building four capacitors of different shapes. The effect may have applications to vehicle propulsion and dielectric pumps. We review the history of this effect briefly through the history of patents by Thomas Townsend Brown. 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: ballistic ionic wind and ionic drift. The calculations indicate that ionic wind is at least three orders of magnitude too small to explain the magnitude of the observed force on the capacitor. The ionic drift transport assumption leads to the correct order of magnitude for the force, however, it is difficult to see how ionic dr...

  5. 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. PMID:26430985

  6. Modeling of asymmetrical boost converters

    Directory of Open Access Journals (Sweden)

    Eliana Isabel Arango Zuluaga

    2014-03-01

    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.

  7. Asymmetric dense matter in holographic QCD

    Directory of Open Access Journals (Sweden)

    Shin Ik Jae

    2012-02-01

    Full Text Available We study asymmetric dense matter in holographic QCD.We construct asymmetric dense matter by considering two quark flavor branes with dierent quark masses in a D4/D6/D6 model. To calculate the symmetry energy in nuclear matter, we consider two quarks with equal masses and observe that the symmetry energy increases with the total charge showing the stiff dependence. This behavior is universal in the sense that the result is independent of parameters in the model. We also study strange (or hyperon matter with one light and one intermediate mass quarks. In addition to the vacuum properties of asymmetric matter, we calculate meson masses in asymmetric dense matter and discuss our results in the light of in-medium kaon masses.

  8. Massless sunset diagrams in finite asymmetric volumes

    CERN Document Server

    Niedermayer, Ferenc

    2016-01-01

    In this paper we present methods to compute massless sunset diagrams in finite asymmetric volumes in the framework of dimensional regularization and lattice regularization. We also consider 1-loop sums in both regularizations.

  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. 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...... short-circuit current was analyzed in order to compare the results with the allowable DC current component based in the IEC. Finally the normal operating condition for the power plant was modeled....

  11. An asymmetric pericyclic cascade approach to oxindoles

    OpenAIRE

    Richmond, Edward

    2014-01-01

    The research in this thesis describes an asymmetric pericyclic cascade approach to the synthesis of a range of enantioenriched oxindoles using enantiopure oxazolidine derived nitrones and disubstituted ketenes. Chapter 1 aims to place this work in the context of the literature, describing other commonly employed or state-of-the-art asymmetric approaches to oxindoles and related compounds. Examples of where these approaches have been used successfully in the total synthesis of related indol...

  12. Asymmetric Federalism in Russia: Cure or Poison?

    OpenAIRE

    Jorge Martinez-Vazquez

    2003-01-01

    In the early years of its existence, the Russian Federation adopted a system of differential treatment of its regions in order to cope with the great degree of diversity present in them. This paper examines the Russian Federation’s asymmetric federalism by evaluating the system’s role, significance and effects on the Federation’s development. The study incorporates a detailed description of the asymmetric federalism over time along with the benefits and costs incurred by its implementation. I...

  13. Asymmetric Membrane Osmotic Capsules for Terbutaline Sulphate

    OpenAIRE

    Gobade, N. G.; Marina Koland; K H Harish

    2012-01-01

    The aim of the present study was to design an asymmetric membrane capsule, an osmotic pump-based drug delivery system of ethyl cellulose for controlled release of terbutaline sulphate. asymmetric membrane capsules contains pore-forming water soluble additive, sorbitol in different concentrations in the capsule shell membrane, which after coming in contact with water, dissolves, resulting in an in situ formation of a microporous structure. The terbutaline sulphate is a β-adrenoreceptor agonist...

  14. Novel strategies for asymmetric hydrogenation reactions

    OpenAIRE

    Chen, Dianjun

    2011-01-01

    This thesis describes two novel possibilities for asymmetric hydrogenation: enantioselective hydrogenation using chiral ionic liquid systems and metal-free hydrogenation with boranes. In the first part, asymmetric hydrogenation systems using chiral ionic liquids in combination with racemic rhodium catalyst are presented. Enantioselectivities up to 69% ee were achieved in homogeneous Rh-catalyzed hydrogenation with tropos ligand (BIPHEP, sulfonated BIPHEP) in a proline derived cation chiral io...

  15. Asymmetric septal hypertrophy and hypothyroidism in children.

    OpenAIRE

    Altman, D I; Murray, J.; Milner, S.; Dansky, R; Levin, S. E.

    1985-01-01

    Any echocardiographic study of two children with hypothyroidism demonstrated the presence of asymmetric septal hypertrophy. One child died aged 11 months, and pronounced thickening of the interventricular septum was confirmed at necropsy. There was also hypertrophy of the left ventricular free wall. Histological examination showed only slight muscle fibre disarray, but there was striking vacuolation and hypertrophy of muscle fibres. In the second case, a child aged five years, the asymmetric ...

  16. 非对称弯曲微流道中粒子惯性聚焦动态过程及流速调控机理研究%Dynamic process and flow-rate regulation mechanism of particle inertial focusing in an asymmetric ally curved microchannel

    Institute of Scientific and Technical Information of China (English)

    唐文来; 项楠; 张鑫杰; 黄笛; 倪中华

    2015-01-01

    In this paper, an asymmetrically curved microchannel device is designed and fabricated to quantitatively characterize the dynamic inertial focusing process of polystyrene particles and blood cells flowing along the channel. The experimental investigations are systematically carried out to probe into the regulation mechanisms of flow rate and particle size. Specifically, based on the particle fluorescent streak images and the corresponding intensity profiles at specific downstream positions, the lateral migration behaviors of particles in the mirochannel can be divided into two stages: the formation of focused streak and the shift of focusing position. It is also found that the channel structures with small radii are dominant during the whole inertial focusing process. A three-stage model is then presented to elucidate the flow-rate regulation mechanism in terms of the competition between inertial lift force and Dean drag force, according to the evolution of particle focusing dynamics with increasing flow rates. By making comparisons of focusing position and focusing ratio between two different-sized particles under various experimental conditions, we find that the larger particles have better focusing performances and stabilities, and the relative focusing position of different-sized particles can be adjusted by changing the driving flow rate. Finally, the applicability of the explored inertial focusing mechanisms for manipulating biological particles with complex features is investigated by analyzing the lateral migration behaviors of blood cells in the asymmetrically curved microchannel. The obtained conclusions are very important for understanding the particle focusing dynamics in micro-scale flows and developing the point-of-care diagnostic instruments.%设计制作了一种具有非对称弯曲微流道结构的微流控芯片,搭建实验平台定量表征聚苯乙烯粒子和血细胞沿流道的动态惯性聚焦过程, 并系统研究了流体流速和粒

  17. High-Flow Asymmetric Reverse-Osmosis Membranes

    Science.gov (United States)

    Katz, M. C.; Wydeven, T. J.

    1984-01-01

    Water-soluble polymer membrane insolubilized by transition-metal salt. Thin layer of lower permeability material joined with thicker layer of highpermeability material. Two layers chemically identical or chemically distinct. They differ in density, compactness or other respects. Used to purify or desalinate seawater, brackish water, or industrial or domestic wastewater.

  18. Asymmetric plasmonic induced ionic noise in metallic nanopores

    Science.gov (United States)

    Li, Yi; Chen, Chang; Willems, Kherim; Lagae, Liesbet; Groeseneken, Guido; Stakenborg, Tim; van Dorpe, Pol

    2016-06-01

    We present distinct asymmetric plasmon-induced noise properties of ionic transport observed through gold coated nanopores. We thoroughly investigated the effects of bias voltage and laser illumination. We show that the potential drop across top-coated silicon nanocavity pores can give rise to a large noise asymmetry (~2-3 orders of magnitude). Varying the bias voltage has an appreciable effect on the noise density spectra, typically in the Lorentzian components. The laser power is found to strongly affect the ionic noise level as well as the voltage threshold for light-induced noise generation. The asymmetric noise phenomenon is attributed to plasmon-induced interfacial reactions which promote light-induced charge fluctuation in the ion flow and allow voltage modulation of photo-induced carriers surmounting over such Schottky junctions. We further compare the ionic noise performances of gold nanocavities containing different material stacks, among which thermal oxide passivation of the silicon successfully mitigates the light-induced noise and is also fully CMOS-compatible. The understanding of the described noise characteristics will help to foster multiple applications using related structures including plasmonic-based sensing or plasmon-induced catalysis such as water splitting or solar energy conversion devices.We present distinct asymmetric plasmon-induced noise properties of ionic transport observed through gold coated nanopores. We thoroughly investigated the effects of bias voltage and laser illumination. We show that the potential drop across top-coated silicon nanocavity pores can give rise to a large noise asymmetry (~2-3 orders of magnitude). Varying the bias voltage has an appreciable effect on the noise density spectra, typically in the Lorentzian components. The laser power is found to strongly affect the ionic noise level as well as the voltage threshold for light-induced noise generation. The asymmetric noise phenomenon is attributed to plasmon

  19. Experimental investigation of flow pattern and sediment deposition in rectangular shallow reservoirs

    Institute of Scientific and Technical Information of China (English)

    Matthieu DUFRESNE; Benjamin J.DEWALS; Sébastien ERPICUM; Pierre ARCHAMBEAU; Michel PIROTTON

    2010-01-01

    This paper reports the experimental investigation of flow pattern, preferential regions of deposition and trap efficiency as a function of the length of rectangular shallow reservoirs. Four flow patterns were identified (from longer to shorter reservoirs): an asymmetric flow with two reattachment points, an asymmetric flow with one reattachment point, an unstable flow, and a symmetric flow without any reattachment point. Using dye visualizations, the median value and the temporal variability of the reattachment lengths were precisely measured for the asymmetric flows. For each stable flow, sediment tests with plastic particles were carried out. The regions of deposition on the bed of the reservoir were clearly a function of the flow pattern. The transition from an asymmetric flow pattern to a symmetric flow pattern was responsible for an abrupt decrease of the trap efficiency; a number of regression laws were discussed to take it into account.

  20. [Development of new methods in asymmetric reactions and their applications].

    Science.gov (United States)

    Node, Manabu

    2002-01-01

    Several novel methods using chiral reagents and biocatalysts for asymmetric reactions are described. Among those reactions, asymmetric reduction via a novel tandem Michael addition/Meerwein-Ponndorf-Verley reduction of acyclic alpha,beta-unsaturated ketones using a chiral mercapto alcohol, asymmetric synthesis of allene-1,3-dicarboxylate via crystallization induced asymmetric transformation, and improved asymmetric nitroolefination of lactones and lactames at alpha-carbon using new chiral reagents were developed. In the reactions using biocatalysts, asymmetric dealkoxycarbonylation of bicyclic beta-keto diesters having sigma-symmetry with lipase or esterase to give optically active beta-keto esters, the asymmetric reduction of bicyclic 1,3-diketones having sigma-symmetry with Baker's yeast to give optically active keto alcohols, and the asymmetric aldol reaction of glycine with threonine aldolase were also developed. The above mentioned products were effectively utilized as chiral building blocks for the asymmetric synthesis of natural products and drugs.

  1. 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....

  2. Dc SQUIDs with asymmetric shunt resistors

    Energy Technology Data Exchange (ETDEWEB)

    Rudolph, Matthias; Nagel, Joachim; Kemmler, Matthias; Koelle, Dieter; Kleiner, Reinhold [Physikalisches Institut - Experimentalphysik II and Center for Collective Quantum Phenomena in LISAplus, Universitaet Tuebingen (Germany); Meckbach, Johannes Maximilian; Ilin, Konstantin; Siegel, Michael [Institut fuer Mikro- und Nanoelektronische Systeme, Karlsruhe Institute of Technology, Karlsruhe (Germany)

    2013-07-01

    We have investigated asymmetrically shunted Nb/Al-AlO{sub x}/Nb dc SQUIDs. Simulations based on the coupled Langevin equations predict that the optimum energy resolution ε, and thus also the noise performance of such an asymmetric SQUID, can be 3-4 times better than that of its symmetric counterpart. While keeping the total resistance R identical to a comparable symmetric SQUID with R{sup -1} = R{sub 1}{sup -1} + R{sub 2}{sup -1}, we shunted only one of the two Josephson junctions with R = R{sub 1,2}/2. Both types of SQUIDs were characterized with respect to their transport and noise properties at temperature T = 4.2 K, and we compared the experimental results with numerical simulations. Experiments yielded ε ∼ 32 ℎ for an asymmetric SQUID with an inductance L = 22 pH, whereas a comparable symmetric device achieved ε = 110 ℎ.

  3. Asymmetric membrane osmotic capsules for terbutaline sulphate

    Directory of Open Access Journals (Sweden)

    N G Gobade

    2012-01-01

    Full Text Available The aim of the present study was to design an asymmetric membrane capsule, an osmotic pump-based drug delivery system of ethyl cellulose for controlled release of terbutaline sulphate. asymmetric membrane capsules contains pore-forming water soluble additive, sorbitol in different concentrations in the capsule shell membrane, which after coming in contact with water, dissolves, resulting in an in situ formation of a microporous structure. The terbutaline sulphate is a β-adrenoreceptor agonist widely used in the treatment of asthma. The oral dosage regimen of terbutaline sulphate is 5 mg twice or thrice daily, the plasma half-life is approximate 3-4 h and it produces GI irritation with extensive first pass metabolism. Hence, terbutaline sulphate was chosen as a model drug with an aim to develop controlled release system. Different formulations of ethyl cellulose were prepared by phase inversion technique using different concentrations of sorbitol as pore forming agent. It was found that the thickness of the prepared asymmetric membrane capsules was increased with increase in concentration of ethyl cellulose and pore forming agent, i.e. sorbitol. The dye release study in water and 10% sodium chloride solution indicates that, the asymmetric membrane capsules follow osmotic principle to release content. The pores formed due to sorbitol were confirmed by microscopic observation of transverse section of capsule membrane. Data of in vitro release study of terbutaline sulphate from asymmetric membrane capsules indicated that, the capsules prepared with 10% and 12.5% of ethyl cellulose and 25% of sorbitol released as much as 97.44% and 76.27% in 12 h, respectively with zero order release rate. Hence asymmetric membrane capsule of 10% ethyl cellulose and 25% of sorbitol is considered as optimum for controlled oral delivery of terbutaline sulphate.

  4. Asymmetric membrane osmotic capsules for terbutaline sulphate.

    Science.gov (United States)

    Gobade, N G; Koland, Marina; Harish, K H

    2012-01-01

    The aim of the present study was to design an asymmetric membrane capsule, an osmotic pump-based drug delivery system of ethyl cellulose for controlled release of terbutaline sulphate. asymmetric membrane capsules contains pore-forming water soluble additive, sorbitol in different concentrations in the capsule shell membrane, which after coming in contact with water, dissolves, resulting in an in situ formation of a microporous structure. The terbutaline sulphate is a β-adrenoreceptor agonist widely used in the treatment of asthma. The oral dosage regimen of terbutaline sulphate is 5 mg twice or thrice daily, the plasma half-life is approximate 3-4 h and it produces GI irritation with extensive first pass metabolism. Hence, terbutaline sulphate was chosen as a model drug with an aim to develop controlled release system. Different formulations of ethyl cellulose were prepared by phase inversion technique using different concentrations of sorbitol as pore forming agent. It was found that the thickness of the prepared asymmetric membrane capsules was increased with increase in concentration of ethyl cellulose and pore forming agent, i.e. sorbitol. The dye release study in water and 10% sodium chloride solution indicates that, the asymmetric membrane capsules follow osmotic principle to release content. The pores formed due to sorbitol were confirmed by microscopic observation of transverse section of capsule membrane. Data of in vitro release study of terbutaline sulphate from asymmetric membrane capsules indicated that, the capsules prepared with 10% and 12.5% of ethyl cellulose and 25% of sorbitol released as much as 97.44% and 76.27% in 12 h, respectively with zero order release rate. Hence asymmetric membrane capsule of 10% ethyl cellulose and 25% of sorbitol is considered as optimum for controlled oral delivery of terbutaline sulphate. PMID:23204625

  5. Experimental investigation of symmetric and asymmetric heating of pressure tube under accident conditions for Indian PHWR

    Energy Technology Data Exchange (ETDEWEB)

    Yadav, Ashwini K., E-mail: ashwinikumaryadav@gmail.com [Department of Mechanical and Industrial Engineering, Indian Institute of Technology, Roorkee-247667 (India); Majumdar, P., E-mail: pmajum@barc.gov.in [Reactor Safety Division, Bhabha Atomic Research Centre, Mumbai-400085 (India); Kumar, Ravi, E-mail: ravikfme@iitr.ernet.in [Department of Mechanical and Industrial Engineering, Indian Institute of Technology, Roorkee-247667 (India); Chatterjee, B., E-mail: barun@barc.gov.in [Reactor Safety Division, Bhabha Atomic Research Centre, Mumbai-400085 (India); Gupta, Akhilesh, E-mail: akhilfme@iitr.ernet.in [Department of Mechanical and Industrial Engineering, Indian Institute of Technology, Roorkee-247667 (India); Lele, H.G., E-mail: hglele@barc.gov.in [Reactor Safety Division, Bhabha Atomic Research Centre, Mumbai-400085 (India)

    2013-01-15

    Highlights: Black-Right-Pointing-Pointer Circumferential temperature gradient for asymmetric heat-up was 400 Degree-Sign C. Black-Right-Pointing-Pointer At same pressure ballooning initiates at lower temperature in asymmetrical heat-up. Black-Right-Pointing-Pointer At 1 MPa ballooning initiated at 408 Degree-Sign C and with expansion rate of 0.005 mm/s. Black-Right-Pointing-Pointer At 2 MPa ballooning initiation at 330 Degree-Sign C and with expansion rate of 0.0056 mm/s. Black-Right-Pointing-Pointer For symmetrical heat-up strain rate was 10 times faster than asymmetric heat-up. - Abstract: In pressurized heavy water reactor (PHWR), under postulated scenario of small break Loss of Coolant Accident (LOCA) coincident with the failure of Emergency Core Cooling System (ECCS), a situation may arise under which reduction in mass flow rate of coolant through individual reactor channel can lead to stratified flow. Such stratified flow condition creates partial uncover of fuel bundle, which creates a circumferential temperature gradient over PT. The present investigation has been carried out to study thermo-mechanical behaviour of PT under asymmetric heating conditions for a 220 MWe PHWR. A 19-pin fuel simulator has been developed in which preferential heating of elements could be done by supplying power to the selected pins. The asymmetric heating of PT has been carried out at pressure 2 MPa and 1 MPa, respectively, by supplying power to upper region heating elements thus creating an half filled stratified flow conditions. The temperature difference up to 425 Degree-Sign C has been observed along top to bottom periphery of PT. A comparison is made between thermo-mechanical behaviour of PT under asymmetrical and symmetrical heat-up, expected from a large break LOCA condition. The radial expansion rate during symmetrical heating is found to be much faster as compared to that for asymmetric ballooning of PT at the same internal pressure. Integrity of PT is found to be

  6. Homogeneous asymmetric catalysis in fragrance chemistry.

    Science.gov (United States)

    Ciappa, Alessandra; Bovo, Sara; Bertoldini, Matteo; Scrivanti, Alberto; Matteoli, Ugo

    2008-06-01

    Opposite enantiomers of a chiral fragrance may exhibit different olfactory activities making a synthesis in high enantiomeric purity commercially and scientifically interesting. Accordingly, the asymmetric synthesis of four chiral odorants, Fixolide, Phenoxanol, Citralis, and Citralis Nitrile, has been investigated with the aim to develop practically feasible processes. In the devised synthetic schemes, the key step that leads to the formation of the stereogenic center is the homogeneous asymmetric hydrogenation of a prochiral olefin. By an appropriate choice of the catalyst and the reaction conditions, Phenoxanol, Citralis, and Citralis Nitrile were obtained in high enantiomeric purity, and odor profiles of the single enantiomers were determined.

  7. Asymmetric counter propagation of domain walls

    Science.gov (United States)

    Andrade-Silva, I.; Clerc, M. G.; Odent, V.

    2016-07-01

    Far from equilibrium systems show different states and domain walls between them. These walls, depending on the type of connected equilibria, exhibit a rich spatiotemporal dynamics. Here, we investigate the asymmetrical counter propagation of domain walls in an in-plane-switching cell filled with a nematic liquid crystal. Experimentally, we characterize the shape and speed of the domain walls. Based on the molecular orientation, we infer that the counter propagative walls have different elastic deformations. These deformations are responsible of the asymmetric counter propagating fronts. Theoretically, based on symmetry arguments, we propose a simple bistable model under the influence of a nonlinear gradient, which qualitatively describes the observed dynamics.

  8. 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.

  9. 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.

  10. Weak chaos in the asymmetric heavy top

    CERN Document Server

    Barrientos, M; Ranada, A F

    1995-01-01

    We consider the dynamics of the slightly asymmetric heavy top, a non-integrable system obtained from the Lagrange top by breaking the symmetry of its inertia tensor. It shows signs of weak chaos, which we study numerically. We argue that it is a good example for introducing students to non-integrability and chaos. (author)

  11. Asymmetric cell division: a persistent issue?

    OpenAIRE

    Aakre, Christopher D.; Laub, Michael T.

    2012-01-01

    Heterogeneity within a clonal population of cells can increase survival in the face of environmental stress. In a recent issue of Science, Aldridge et al. (2012) demonstrate that cell division in mycobacteria is asymmetric, producing daughter cells that differ in size, growth rate, and susceptibility to antibiotics.

  12. Asymmetric Total Synthesis of (-)-Cladospolide B

    Institute of Scientific and Technical Information of China (English)

    WANG,Wen-Kuan; ZHANG,Ji-Yong; HE,Jin-Mei; TANG,Shi-Bing; WANG,Xiao-Lei; SHE,Xue-Gong; PAN,Xin-Fu

    2008-01-01

    An enantioselective total synthesis of (-)-cladospolide B was described.The key steps in this synthesis include (a) a Sharpless asymmetric dihydroxylation to elaborate syn diol at C-4 and C-5 positions;(b) a Mitsunobu esterification to reverse the configuration at C-11 from (S) to (R);and (c) a ring-closing metathesis to access the 12-membered macrocyclic ring.

  13. Evidence of asymmetric top in 130Ba

    International Nuclear Information System (INIS)

    Introduced is a new relation connecting moment of inertia, Lipas parameter and asymmetric rotor model energies and put forward much closer trend in odd even staggering of quasi γ-band. A different view point regarding generation of quasi γ-band in 130Ba have been presented

  14. The Asymmetric Effects of Investor Sentiment

    DEFF Research Database (Denmark)

    Lutz, Chandler

    2016-01-01

    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....

  15. Detection loophole in asymmetric Bell experiments

    OpenAIRE

    Brunner, Nicolas; Gisin, Nicolas; Scarani, Valerio; Simon, Christoph

    2007-01-01

    The problem of closing the detection loophole with asymmetric systems, such as entangled atom-photon pairs, is addressed. We show that, for the Bell inequality I_3322, a minimal detection efficiency of 43% can be tolerated for one of the particles, if the other one is always detected. We also study the influence of noise and discuss the prospects of experimental implementation.

  16. Beam-beam issues in asymmetric colliders

    Energy Technology Data Exchange (ETDEWEB)

    Furman, M.A.

    1992-07-01

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

  17. Attentional Control and Asymmetric Associative Priming

    Science.gov (United States)

    Hutchison, Keith A.; Heap, Shelly J.; Neely, James H.; Thomas, Matthew A.

    2014-01-01

    Participants completed a battery of 3 attentional control (AC) tasks (OSPAN, antisaccade, and Stroop, as in Hutchison, 2007) and performed a lexical decision task with symmetrically associated (e.g., "sister-brother") and asymmetrically related primes and targets presented in both the forward (e.g., "atom-bomb") and backward…

  18. Catalytic asymmetric synthesis of mycocerosic acid

    NARCIS (Netherlands)

    ter Horst, B.; Feringa, B.L.; J. Minnaard, A.

    2007-01-01

    The first catalytic asymmetric total synthesis of mycocerosic acid was achieved via the application of iterative enantioselective 1,4-addition reactions and allows for the efficient construction of 1,3-polymethyl arrays with full stereocontrol; further exemplified by the synthesis of tetramethyl-dec

  19. Asymmetric relationships between proteins shape genome evolution.

    NARCIS (Netherlands)

    Notebaart, R.A.; Kensche, P.R.; Huynen, M.A.; Dutilh, B.E.

    2009-01-01

    BACKGROUND: The relationships between proteins are often asymmetric: one protein (A) depends for its function on another protein (B), but the second protein does not depend on the first. In metabolic networks there are multiple pathways that converge into one central pathway. The enzymes in the conv

  20. Non-geometric fluxes, asymmetric strings and nonassociative geometry

    Energy Technology Data Exchange (ETDEWEB)

    Blumenhagen, R; Deser, A; Luest, D; Rennecke, F [Max-Planck-Institut fuer Physik (Werner-Heisenberg-Institut), Foehringer Ring 6, 80805 Muenchen (Germany); Plauschinn, E, E-mail: blumenha@mpp.mpg.de, E-mail: deser@mpp.mpg.de, E-mail: luest@mpp.mpg.de, E-mail: e.plauschinn@uu.nl, E-mail: rennecke@mpp.mpg.de [Institute for Theoretical Physics and Spinoza Institute, Utrecht University, 3508 TD Utrecht (Netherlands)

    2011-09-23

    We study closed bosonic strings propagating both in a flat background with constant H-flux and in its T-dual configurations. We define a conformal field theory capturing linear effects in the flux and compute scattering amplitudes of tachyons, where the Rogers dilogarithm plays a prominent role. For the scattering of four tachyons, a fluxed version of the Virasoro-Shapiro amplitude is derived and its pole structure is analysed. In the case of an R-flux background obtained after three T-dualities, we find indications for a nonassociative target-space structure which can be described in terms of a deformed tri-product. Remarkably, this product is compatible with crossing symmetry of conformal correlation functions. We finally argue that the R-flux background flows to an asymmetric CFT. (paper)

  1. Asymmetric pedestrian dynamics on a staircase landing from continuous measurements

    CERN Document Server

    Corbetta, Alessandro; Muntean, Adrian; Toschi, Federico

    2015-01-01

    We investigate via extensive experimental data the dynamics of pedestrians walking in a corridor-shaped landing in a building at Eindhoven University of Technology. With year-long automatic measurements employing a Microsoft KinectTM 3D-range sensor and ad hoc tracking techniques, we acquired few hundreds of thousands pedestrian trajectories in real-life conditions. Here we discuss the asymmetric features of the dynamics in the two walking directions with respect to the flights of stairs (i.e. ascending or descending). We provide a detailed analysis of position and speed fields for the cases of pedestrians walking alone undisturbed and for couple of pedestrians in counter-flow. Then, we show average walking velocities exploring all the observed combinations in terms of numbers of pedestrians and walking directions.

  2. The plasmoid instability during asymmetric inflow magnetic reconnection

    CERN Document Server

    Murphy, Nicholas A; Shen, Chengcai; Lin, Jun; Ni, Lei

    2013-01-01

    Theoretical studies of the plasmoid instability generally assume that the reconnecting magnetic fields are symmetric. We relax this assumption by performing two-dimensional resistive magnetohydrodynamic simulations of the plasmoid instability during asymmetric inflow magnetic reconnection. Magnetic asymmetry modifies the onset, scaling, and dynamics of this instability. Magnetic islands develop preferentially into the weak magnetic field upstream region. Outflow jets from individual X-points impact plasmoids obliquely rather than directly as in the symmetric case. Consequently, deposition of momentum by the outflow jets into the plasmoids is less efficient, the plasmoids develop net vorticity, and shear flow slows down secondary merging between islands. Secondary merging events have asymmetry along both the inflow and outflow directions. Downstream plasma is more turbulent in cases with magnetic asymmetry because islands are able to roll around each other after exiting the current sheet. As in the symmetric c...

  3. Asymmetric coherent transmission for single particle diode and gyroscope

    CERN Document Server

    Yang, S; Sun, C P

    2009-01-01

    We study the single particle scattering process in a coherent multi-site system consisting of a tight-binding ring threaded by an Aharonov-Bohm flux and several attaching leads. The asymmetric behavior of scattering matrix is discovered analytically in the framework of both Bethe Ansatz and Green's function formalism. It is found that, under certain conditions, a three-site electronic system can behave analogous to a perfect semiconductor diode where current flows only in one direction. The general result is also valid for a neutral particle system since the effective magnetic flux may be implemented by a globe rotation. This observation means that the three-site system can serve as an orientation measuring gyroscope due to the approximate linear dependence of the current difference of two output leads on the rotational angular velocity.

  4. 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 o

  5. 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...

  6. 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...

  7. Asymmetric Bulkheads for Cylindrical Pressure Vessels

    Science.gov (United States)

    Ford, Donald B.

    2007-01-01

    Asymmetric bulkheads are proposed for the ends of vertically oriented cylindrical pressure vessels. These bulkheads, which would feature both convex and concave contours, would offer advantages over purely convex, purely concave, and flat bulkheads (see figure). Intended originally to be applied to large tanks that hold propellant liquids for launching spacecraft, the asymmetric-bulkhead concept may also be attractive for terrestrial pressure vessels for which there are requirements to maximize volumetric and mass efficiencies. A description of the relative advantages and disadvantages of prior symmetric bulkhead configurations is prerequisite to understanding the advantages of the proposed asymmetric configuration: In order to obtain adequate strength, flat bulkheads must be made thicker, relative to concave and convex bulkheads; the difference in thickness is such that, other things being equal, pressure vessels with flat bulkheads must be made heavier than ones with concave or convex bulkheads. Convex bulkhead designs increase overall tank lengths, thereby necessitating additional supporting structure for keeping tanks vertical. Concave bulkhead configurations increase tank lengths and detract from volumetric efficiency, even though they do not necessitate additional supporting structure. The shape of a bulkhead affects the proportion of residual fluid in a tank that is, the portion of fluid that unavoidably remains in the tank during outflow and hence cannot be used. In this regard, a flat bulkhead is disadvantageous in two respects: (1) It lacks a single low point for optimum placement of an outlet and (2) a vortex that forms at the outlet during outflow prevents a relatively large amount of fluid from leaving the tank. A concave bulkhead also lacks a single low point for optimum placement of an outlet. Like purely concave and purely convex bulkhead configurations, the proposed asymmetric bulkhead configurations would be more mass-efficient than is the flat

  8. 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

  9. 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....

  10. Ants exhibit asymmetric hybridization in a mosaic hybrid zone.

    Science.gov (United States)

    Purcell, Jessica; Zahnd, Sacha; Athanasiades, Anouk; Türler, Rebecca; Chapuisat, Michel; Brelsford, Alan

    2016-10-01

    Research on hybridization between species provides unparalleled insights into the pre- and postzygotic isolating mechanisms that drive speciation. In social organisms, colony-level incompatibilities may provide additional reproductive barriers not present in solitary species, and hybrid zones offer an opportunity to identify these barriers. Here, we use genotyping-by-sequencing to sequence hundreds of markers in a hybrid zone between two socially polymorphic ant species, Formica selysi and Formica cinerea. We characterize the zone, determine the frequency of hybrid workers, infer whether hybrid queens or males are produced and investigate whether hybridization is influenced by colony social organization. We also compare cuticular hydrocarbon profiles and aggression levels between the two species. The hybrid zone exhibits a mosaic structure. The asymmetric distribution of hybrids skewed towards F. cinerea suggests a pattern of unidirectional nuclear gene flow from F. selysi into F. cinerea. The occurrence of backcrossed individuals indicates that hybrid queens and/or males are fertile, and the presence of the F. cinerea mitochondrial haplotype in 97% of hybrids shows that successful F1 hybrids will generally have F. cinerea mothers and F. selysi fathers. We found no evidence that social organization contributes to speciation, because hybrids occur in both single-queen and multiple-queen colonies. Strongly differentiated cuticular hydrocarbon profiles and heightened interspecific aggression further reveal that species recognition cues are both present and perceived. The discovery of fertile hybrids and asymmetrical gene flow is unusual in ants, and this hybrid zone will therefore provide an ideal system with which to investigate speciation in social insects.

  11. Process Design for Hot Forging of Asymmetric to Symmetric Rib-web Shaped Steel

    Directory of Open Access Journals (Sweden)

    H. Cho

    2003-01-01

    Full Text Available The process design of hot forging, asymmetric to symmetric rib-web shaped steel, which is used for the turnout of express rails has been studied. Owing to the great difference in shape between the initial billet and the final forged product, it is impossible to hot forge the rail in a single stage operation. Therefore, multi stage forging and also die design for each stage are necessary for the production process. The numerical simulation for hot forging of asymmetric shape to symmetric shape was carried out using commercial FEM code, DEFORMTM-2D. Modification of the design and repeated simulation was carried out on the basis of the simulation results. For comparison with the simulation results, a flow analysis experiment using plasticine was also carried out. The results of the flow analysis experiment showed good agreement with those of the simulation.

  12. Collective flow in small systems

    International Nuclear Information System (INIS)

    The large density of matter in the interaction region of the proton–nucleus or deuteron–nucleus collisions enables the collective expansion of the fireball. Predictions of a hydrodynamic model for the asymmetric transverse flow are presented and compared to experimental data

  13. Symmetry properties of the heat current in non-ballistic asymmetric junctions: A case study

    International Nuclear Information System (INIS)

    We consider quantum heat flow in two-terminal junctions and inquire on the connection between the transport mechanism and the junction functionality. Using simple models, we demonstrate that the violation of the Landauer behavior in asymmetric junctions does not necessarily imply the onset of thermal rectification. We also demonstrate through a simple example that a spatial inhomogeneity of the energy spectra is not a necessary condition for thermal rectification.

  14. Asymmetric Information and the Role of Accounting in Emerging Markets Evidences from TSE

    OpenAIRE

    Aida Dowran; Hashem Valipour; Javad Moradi

    2013-01-01

    This study examines the value relevance (information content) of cash flow and accounting figures in situations where the information is asymmetrical and Compare the relative information content of them to clarify the role of accounting figures in investment decision making and mitigating the agency problems (specifically resulting from the existence of information asymmetry in the emerging markets). Based on testing a sample of 76 firms from Tehran Stock Exchange (TSE) during 2005 to 2011, t...

  15. A Default Model of The Non-listed Companies Under Asymmetric Information

    Institute of Scientific and Technical Information of China (English)

    Wang Fake

    2013-01-01

    For the financing difficulties of the non-listed companies, A continuous credit risk model is created which is based on the asymmetric information theory.In the model,the value of the non-listed companies is estimated by the free cash flow,and the loan discussed contains the collateral asset.Based on the model,The default probability,the LGD and the largest company debts are discussed.

  16. HEMODYNAMICS FOR ASYMMETRIC INLET AXIAL VELOCITY PROFILE IN CAROTID BIFURCATION MODEL

    Institute of Scientific and Technical Information of China (English)

    DING Zu-rong; LIU Bin; YANG Shuo; XIA Yan

    2008-01-01

    The asymmetric inlet velocity profile has been observed in phantom model using LDA and in health subjects using Magnet Resonance (MR). The effects of asymmetric inlet axial velocity profile on the flow field and the Wall Shear Stress (WSS) ofcarotid bifurcation were numerically studied herein with the TF-AHCB model. The results show that the Wall Shear Stress Gradient (WSSG) in the front part of the sinus for inward-tilting inlet axial velocity profile is nearly 2 times of that for the symmetric one in the beginning of systole, the end of systole, and diastole, respectively. The area of WSS below 5x 10.3 Pa at the outer wall of the sinus for outward-tilting inlet axial velocity profile is 1.5 times of that for the inward-tilting one during diastole of the cardiac cycle. The asymmetric inlet velocity profiles can reduce the flow velocity near the inner wall of the sinus, which has been normally considered a high velocity region. It is concluded that besides bifurcation geometry and flow waveform, the asymmetry of inlet velocity profile is probably a factor influencing atherosclerosis.

  17. Design of Asymmetric Peptide Bilayer Membranes.

    Science.gov (United States)

    Li, Sha; Mehta, Anil K; Sidorov, Anton N; Orlando, Thomas M; Jiang, Zhigang; Anthony, Neil R; Lynn, David G

    2016-03-16

    Energetic insights emerging from the structural characterization of peptide cross-β assemblies have enabled the design and construction of robust asymmetric bilayer peptide membranes. Two peptides differing only in their N-terminal residue, phosphotyrosine vs lysine, coassemble as stacks of antiparallel β-sheets with precisely patterned charged lattices stabilizing the bilayer leaflet interface. Either homogeneous or mixed leaflet composition is possible, and both create nanotubes with dense negative external and positive internal solvent exposed surfaces. Cross-seeding peptide solutions with a preassembled peptide nanotube seed leads to domains of different leaflet architecture within single nanotubes. Architectural control over these cross-β assemblies, both across the bilayer membrane and along the nanotube length, provides access to highly ordered asymmetric membranes for the further construction of functional mesoscale assemblies.

  18. δ Meson Effects on Asymmetric Nuclear Matter

    Science.gov (United States)

    Liu, B.; di Toro, M.; Greco, V.

    The impact of a δ meson field (the scalar-isovector channel) on asymmetric nuclear matter is studied within relativistic mean-field (RMF) models with both constant and density dependent (DD) nucleon-meson couplings. The Equation of State (EOS) for asymmetric nuclear matter and the neutron star properties by the different models are compared. We find that the δ-field in the constant coupling scheme leads to a larger repulsion in dense neutron-rich matter and to a definite splitting of proton and neutron effective masses, finally influencing the stability of the neutron stars. A broader analysis of possible δ-field effects is achieved considering also density dependent nucleon-meson coupling. A remarkable effect on the relation between mass and radius for the neutron stars is seen, showing a significant reduction of the radius along with a moderate mass reduction due to the increase of the effective δ coupling in high density regions.

  19. Enhancing molecule fluorescence with asymmetrical plasmonic antennas.

    Science.gov (United States)

    Lu, Guowei; Liu, Jie; Zhang, Tianyue; Shen, Hongming; Perriat, Pascal; Martini, Matteo; Tillement, Olivier; Gu, Ying; He, Yingbo; Wang, Yuwei; Gong, Qihuang

    2013-07-21

    We propose and justify by the finite-difference time-domain method an efficient strategy to enhance the spontaneous emission of a fluorophore with a multi-resonance plasmonic antenna. The custom-designed asymmetrical antenna consists of two plasmonic nanoparticles with different sizes and is able to couple efficiently to free space light through multiple localized surface plasmon resonances. This design simultaneously permits a large near-field excitation near the antenna as well as a high quantum efficiency, which results in an unusual and significant enhancement of the fluorescence of a single emitter. Such an asymmetrical antenna presents intrinsic advantages over single particle or dimer based antennas made using two identical nanostructures. This promising concept can be exploited in the large domain of light-matter interaction processes involving multiple frequencies.

  20. Cosmological signatures of time-asymmetric gravity

    CERN Document Server

    Cortês, Marina; Smolin, Lee

    2016-01-01

    We develop the model proposed by Cort\\^es, Gomes & Smolin, to predict cosmological signatures of time-asymmetric extensions of general relativity they proposed recently. Within this class of models the equation of motion of chiral fermions is modified by a torsion term. This term leads to a dispersion law for neutrinos that associates a new time-varying energy with each particle. We find a new neutrino contribution to the Friedmann equation resulting from the torsion term in the Ashtekar connection. In this note we explore the phenomenology of this term and observational consequences for cosmological evolution. We show that constraints on the critical energy density will ordinarily render this term unobservably small, a maximum of order $10^{-25}$ of the neutrino energy density today. However, if the time-asymmetric dark energy is tuned to cancel the cosmological constant, the torsion effect may be a dark matter candidate.

  1. Applications of Chiral Anions in Asymmetric Catalysis

    OpenAIRE

    Hamilton, Gregory Lawrence

    2011-01-01

    The synthesis of molecules with control over their three-dimensional configuration, known as absolute stereochemistry, is one of the highest goals of synthetic organic chemists. As is so often the case, we strive to reach the facility and efficiency with which Nature achieves this goal. Fortunately, the chemist's imagination allows us to envision nearly unlimited possibilities for new modes of catalysis. In this dissertation, I discuss one branch of asymmetric catalysis that has in a short ti...

  2. New ruthenium catalysts for asymmetric hydrogenation

    OpenAIRE

    Diaz Valenzuela, Maria Belen

    2007-01-01

    A review on catalytic asymmetric hydrogenation of C=O double bonds is presented in the first chapter. Noyori’s pioneering research on ruthenium complexes containing both phosphine and diamine ligands using [i superscript]PrOH and [t superscript]BuOK is described, this system gave impressive highly chemeo-selectivity for C=O bonds and extremely high enantioselectivity for a range of acetophenone derivatives. Numerous groups have been inspired by Noyori’s catalyst of the ty...

  3. Competitive Price and Quality Under Asymmetric Information

    OpenAIRE

    Gerard J. Tellis; Birger Wernerfelt

    1987-01-01

    We present an analysis of equilibrium in markets with asymmetrically informed consumers. Some consumers know both price and quality of all sellers, whereas others know neither but may search among sellers. The equilibrium correlation between price and quality generally increases with the level of information in the market and can be negative when this level is sufficiently small. A meta-analysis of the available empirical studies strongly supports the model's predictions.

  4. Cosmological signatures of time-asymmetric gravity

    OpenAIRE

    Cortês, Marina; Liddle, Andrew R; Smolin, Lee

    2016-01-01

    We develop the model proposed by Cort\\^es, Gomes & Smolin, to predict cosmological signatures of time-asymmetric extensions of general relativity they proposed recently. Within this class of models the equation of motion of chiral fermions is modified by a torsion term. This term leads to a dispersion law for neutrinos that associates a new time-varying energy with each particle. We find a new neutrino contribution to the Friedmann equation resulting from the torsion term in the Ashtekar conn...

  5. Asymmetric inheritance of cytoophidia in Schizosaccharomyces pombe

    OpenAIRE

    Jing Zhang; Lydia Hulme; Ji-Long Liu

    2014-01-01

    ABSTRACT A general view is that Schizosaccharomyces pombe undergoes symmetric cell division with two daughter cells inheriting equal shares of the content from the mother cell. Here we show that CTP synthase, a metabolic enzyme responsible for the de novo synthesis of the nucleotide CTP, can form filamentous cytoophidia in the cytoplasm and nucleus of S. pombe cells. Surprisingly, we observe that both cytoplasmic and nuclear cytoophidia are asymmetrically inherited during cell division. Our t...

  6. Selective Homogeneous Catalysis in Asymmetric Synthesis

    DEFF Research Database (Denmark)

    Fristrup, Peter

    The subject of this thesis is selectivity in homogeneous asymmetric transition metalcatalyzed reactions. Four different reactions within organic chemistry have been studied by kinetic measurements, computational chemistry (modelling) or both of them in parallel. A Hammett study was performed....... A thorough computational study succeeded in explaining the observed results, although other significant results were also obtained during this study. Finally, an intramolecular reaction was studied computationally, and the rate increase observed under phase transfer catalysis conditions could be related...

  7. On asymmetric collisions with large disruption parameters

    International Nuclear Information System (INIS)

    Collisions between a weak electron bunch and a strong positron bunch are studied within a flat model. Electrons are tracked through the transverse space charge field of the positron bunch, and it is shown that positrons in a storage ring may remain stable after asymmetric collisions with a weak electron bunch in spite of large values of the electron disruption parameter. The plasma oscillations that affect collisions with large disruption parameters may be suppressed by properly matching the electrons. 8 refs., 5 figs

  8. Surface segregation of conformationally asymmetric polymer blends

    OpenAIRE

    Stepanow, Semjon; Fedorenko, Andrei A.

    2005-01-01

    We have generalized the Edwards' method of collective description of dense polymer systems in terms of effective potentials to polymer blends in the presence of a surface. With this method we have studied conformationally asymmetric athermic polymer blends in the presence of a hard wall to the first order in effective potentials. For polymers with the same gyration radius $R_g$ but different statistical segment lengths $l_{A}$ and $l_{B}$ the excess concentration of stiffer polymers at the su...

  9. Neuronal alignment on asymmetric textured surfaces

    OpenAIRE

    Beighley, Ross; Spedden, Elise; Sekeroglu, Koray; Atherton, Timothy; Demirel, Melik C.; Staii, Cristian

    2012-01-01

    Axonal growth and the formation of synaptic connections are key steps in the development of the nervous system. Here, we present experimental and theoretical results on axonal growth and interconnectivity in order to elucidate some of the basic rules that neuronal cells use for functional connections with one another. We demonstrate that a unidirectional nanotextured surface can bias axonal growth. We perform a systematic investigation of neuronal processes on asymmetric surfaces and quantify...

  10. Trapdoor Privacy in Asymmetric Searchable Encryption Schemes

    OpenAIRE

    Delerue Arriaga, Afonso; TANG, QIANG; Ryan, Peter

    2014-01-01

    Asymmetric searchable encryption allows searches to be carried over ciphertexts, through delegation, and by means of trapdoors issued by the owner of the data. Public Key Encryption with Keyword Search (PEKS) is a primitive with such functionality that provides delegation of exact-match searches. As it is important that ciphertexts preserve data privacy, it is also important that trapdoors do not expose the user’s search criteria. The difficulty of formalizing a security model for trapdoor pr...

  11. Legal Dilemmas in Fighting Asymmetrical Conflicts

    Directory of Open Access Journals (Sweden)

    Pnina Sharvit Baruch

    2012-04-01

    Full Text Available What legal rules apply to armed confrontations against non-state elements in areas populated by civilians? What rules apply when the enemy does not honor the basic laws of warfare - does not distinguish itself from the local population, and even uses it for shelter and as a base of operations? This essay, which presents my position on the issue, refers to such confrontations as "asymmetrical conflicts."

  12. Do Daily Retail Gasoline Prices adjust Asymmetrically?

    OpenAIRE

    Bettendorf, Leon; Geest, Stéphanie; Kuper, G.

    2005-01-01

    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 evidence for amount asymmetry,...

  13. Asymmetric Information – Adverse Selection Problem

    Directory of Open Access Journals (Sweden)

    Dumitru MARIN

    2007-01-01

    Full Text Available The present paper makes an introduction in the contract theory starting with the definitions of asymmetric information and some of the problems that generate: moral hazard and adverse selection. We provide an insight of the latest empirical studies in adverse selection in different markets. An adverse selection model, based on Rothchild and Stiglitz is also present to give a perspective of the theoretical framework.

  14. OFFICER AND COMMANDER IN ASYMMETRIC WARFARE OPERATIONS

    OpenAIRE

    Giuseppe CAFORIO

    2013-01-01

    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 ...

  15. Ultralong distance coupling between asymmetric resonant microcavities

    OpenAIRE

    Shu, Fang-Jie; Zou, Chang-Ling; Chen, Wen-Cong; Sun, Fang-Wen

    2013-01-01

    The ultralong distance coupling between two Asymmetric Resonant Microcavities (ARCs) is studied. Different from traditional short distance tunneling coupling between microcavities, the high efficient free space directional emission and excitation allow ultralong distance energy transfer between ARCs. In this paper, a novel unidirectional emission ARC, which shows directionality I40 = 0.54, is designed for materials of refractive index n = 2.0. Compared with regular whispering gallery microres...

  16. Prospects for Asymmetric PNe with ALMA

    CERN Document Server

    Huggins, P J

    2010-01-01

    Millimeter and sub-millimeter observations have made fundamental contributions to our current understanding of the transition from AGB stars to white dwarfs. The approaching era of ALMA brings significantly enhanced observing capabilities at these wavelengths and promises to push back the frontiers in a number of ways. We examine the scientific prospects of this new era for PNe, with an emphasis on how developments may contribute to the goals of the asymmetric PNe community.

  17. Asymmetric Reversal in Inhomogeneous Magnetic Heterostructures

    OpenAIRE

    Li, Zhi-Pan; Petracic, Oleg; Morales, Rafael; Olamit, Justin; Batlle, Xavier; Liu, Kai; Schuller, Ivan K.

    2006-01-01

    Asymmetric magnetization reversal is an unusual phenomenon in antiferromagnet/ferromagnet (AF/FM) exchange biased bilayers. We investigated this phenomenon in a simple model system experimentally and by simulation assuming inhomogeneously distributed interfacial AF moments. The results suggest that the observed asymmetry originates from the intrinsic broken symmetry of the system, which results in local incomplete domain walls parallel to the interface in reversal to negative saturation of th...

  18. 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.

  19. Asymmetrical boundary layer separation at the base of a two cylinder geometry

    Science.gov (United States)

    Boyle, M. T.; Langston, L. S.

    1989-01-01

    This paper reports on the experimental description of the three-dimensional horseshoe vortex system occurring at the base of two cylinder mounted side by side on an endwall. The spacing between the two cylinders is adjusted to generate a family of viscous flows. Flow visualization performed in a water tunnel provides a qualitative understanding of the flow over a range of flow variables. A detailed wind tunnel experiment provides a quantitative description of the flow at a single test condition. At Re(D) = 2.5 x 10 to the 5th the measurements show an asymmetrical primary vortex with a wide flat cross section. A small counterrotating vortex is found between the primary vortex and the cylinder leading edge.

  20. Asymmetric Conditional Volatility in International Stock Markets

    CERN Document Server

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

    2006-01-01

    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 S&P 500, FTSE100, 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 chan...

  1. Asymmetric nuclear matter equation of state

    Energy Technology Data Exchange (ETDEWEB)

    Bombaci, I.; Lombardo, U. (Dipartimento di Fisica, Universita di Catania, Corso Italia 57, Catania (Italy) Istituto Nazionale di Fisica Nucleare, Sezione di Catania, Corso Italia 57, I-95129 Catania (Italy))

    1991-11-01

    Systematic calculations of asymmetric nuclear matter have been performed in the framework of the Brueckner-Bethe-Goldstone approach in a wide range of both density and asymmetry parameter. The empirical parabolic law fulfilled by the binding energy per nucleon is confirmed by the present results in all the range of the asymmetry parameter values. The predominant role of the {sup 3}{ital S}{sub 1-}{sup 3}{ital D}{sub 1} component of the {ital NN} interaction is elucidated. A linear variation of the proton and neutron single-particle potentials is found as increasing the neutron excess; a deviation from the phenomenological potentials occurs for highly asymmetric matter as an effect of the self-consistency. The present calculations of the incompressibility predict a strong softening of the equation of state going from symmetric to asymmetric nuclear matter. The proton fraction in equilibrium with neutron matter has been determined from the beta-stability condition and its relevance to the superfluidity of neutron stars has been investigated.

  2. Multiple Traveling Salesmen in Asymmetric Metrics

    CERN Document Server

    Friggstad, Zachary

    2011-01-01

    We consider some generalizations of the Asymmetric Traveling Salesman Path problem. Suppose we have an asymmetric metric G = (V,A) with two distinguished nodes s,t. We are also given a positive integer k. The goal is to find k paths of minimum total cost from s to t whose union spans all nodes. We call this the k-Person Asymmetric Traveling Salesmen Path problem (k-ATSPP). Our main result for k-ATSPP is a bicriteria approximation that, for some parameter b >= 1 we may choose, finds between k and k + k/b paths of total length O(b log |V|) times the optimum value of an LP relaxation based on the Held-Karp relaxation for the Traveling Salesman problem. On one extreme this is an O(log |V|)-approximation that uses up to 2k paths and on the other it is an O(k log |V|)-approximation that uses exactly k paths. Next, we consider the case where we have k pairs of nodes (s_1,t_1), ..., (s_k,t_k). The goal is to find an s_i-t_i path for every pair such that each node of G lies on at least one of these paths. Simple appro...

  3. 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.

  4. Traceless Synthesis of Asymmetrically Modified Bivalent Nucleosomes.

    Science.gov (United States)

    Lechner, Carolin C; Agashe, Ninad D; Fierz, Beat

    2016-02-18

    Nucleosomes carry extensive post-translational modifications (PTMs), which results in complex modification patterns that are involved in epigenetic signaling. Although two copies of each histone coexist in a nucleosome, they may not carry the same PTMs and are often differently modified (asymmetric). In bivalent domains, a chromatin signature prevalent in embryonic stem cells (ESCs), namely H3 methylated at lysine 4 (H3K4me3), coexists with H3K27me3 in asymmetric nucleosomes. We report a general, modular, and traceless method for producing asymmetrically modified nucleosomes. We further show that in bivalent nucleosomes, H3K4me3 inhibits the activity of the H3K27-specific lysine methyltransferase (KMT) polycomb repressive complex 2 (PRC2) solely on the same histone tail, whereas H3K27me3 stimulates PRC2 activity across tails, thereby partially overriding the H3K4me3-mediated repressive effect. To maintain bivalent domains in ESCs, PRC2 activity must thus be locally restricted or reversed.

  5. Cylindrical Asymmetrical Capacitors for Use in Outer Space

    Science.gov (United States)

    Campbell, Jonathan W.

    2007-01-01

    A report proposes that cylindrical asymmetrical capacitors (CACs) be used to generate small thrusts for precise maneuvering of spacecraft on long missions. The report notes that it has been known for decades that when high voltages are applied to CACs in air, thrusts are generated - most likely as a result of ionization of air molecules and acceleration of the ions by the high electric fields. The report goes on to discuss how to optimize the designs of CACs for operation as thrusters in outer space. Components that could be used to enable outerspace operation include a supply of gas and a shroud, partly surrounding a CAC, into which the gas would flow. Other elements of operation and design discussed in the report include variation of applied voltage and/or of gas flow to vary thrust, effects of CAC and shroud dimensions on thrust and weight, some representative electrode configurations, and several alternative designs, including one in which the basic CAC configuration would be modified into something shaped like a conventional rocket engine with converging/diverging nozzle and an anode with gas feed in the space that, in a conventional rocket engine, would be the combustion chamber.

  6. Numerical Solution of the Asymmetric Water Impact of A Wedge in Three Degrees of Freedom

    Institute of Scientific and Technical Information of China (English)

    H.Ghazizade-Ahsaee; A.H.Nikseresht

    2013-01-01

    Impact problems associated with water entry have important applications in various aspects of naval architecture and ocean engineering.Estimation of hydrodynamic impact forces especially during the first instances after the impact is very important and is of interest.Since the estimation of hydrodynamic impact load plays an important role in safe design and also in evaluation of structural weight and costs,it is better to use a reliable and accurate prediction method instead of a simple estimation resulted by analyzing methods.In landing of flying boats,some phenomena such as weather conditions and strong winds can cause asymmetric instead of symmetric descent.In this paper,a numerical simulation of the asymmetric impact of a wedge,as the step of a flying boat,considering dynamic equations in two-phase flow is taken into account.The dynamic motion of the wedge in two-phase flow is solved based on finite volume method with volume of fluid (VOF) scheme considering dynamic equations.Then the effects of different angles of impact and water depth on the velocity change and slamming forces in an asymmetric impact are investigated.The comparison between the simulation results and experimental data verifies the accuracy of the method applied in the present study.

  7. Asymmetric Synthesis of Both Enantiomers of Disparlure

    Institute of Scientific and Technical Information of China (English)

    王志刚; 郑剑峰; 黄培强

    2012-01-01

    Starting from propargyl alcohol (12), and on the basis of Zhou's modified Sharpless asymmetric epoxidation, the sex pheromone of the Gypsy moth, disparlure (+)-8 and its enantiomer (-)-8 have been synthesized, each in six steps, with overall yields of 29% for (+)-8 and 27% for (-)-8 (ee〉98%). The use of the sequential coupling tactic renders the method flexible, which is applicable to the synthesis of other cis-epoxy pheromones.

  8. Infinite dimensional mixed economies with asymmetric information

    CERN Document Server

    Bhowmik, Anuj

    2011-01-01

    In this paper, we study asymmetric information economies consisting of both non-negligible and negligible agents and having ordered Banach spaces as their commodity spaces. In answering a question of Herv\\'{e}s-Beloso and Moreno-Garc\\'{i}a, we establish a characterization of Walrasian expectations allocations by the veto power of the grand coalition. It is also shown that when an economy contains only negligible agents a Vind's type theorem on the private core with the exact feasibility can be restored. This solves a problem of Pesce.

  9. Quantum optics of lossy asymmetric beam splitters

    CERN Document Server

    Uppu, Ravitej; Tentrup, Tristan B H; Pinkse, Pepijn W H

    2016-01-01

    We theoretically investigate quantum interference of two single photons at a lossy asymmetric beam splitter, the most general passive 2$\\times$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 matrix. Our analysis using the noise operator formalism shows that the loss allows tunability of quantum interference to an extent not possible with a lossless beam splitter. Our theoretical studies support the experimental demonstrations of programmable quantum interference in highly multimodal systems such as opaque scattering media and multimode fibers.

  10. Asymmetric chemical reactions by polarized quantum beams

    Science.gov (United States)

    Takahashi, Jun-Ichi; Kobayashi, Kensei

    One of the most attractive hypothesis for the origin of homochirality in terrestrial bio-organic compounds (L-amino acid and D-sugar dominant) is nominated as "Cosmic Scenario"; a chiral impulse from asymmetric excitation sources in space triggered asymmetric reactions on the surfaces of such space materials as meteorites or interstellar dusts prior to the existence of terrestrial life. 1) Effective asymmetric excitation sources in space are proposed as polarized quantum beams, such as circularly polarized light and spin polarized electrons. Circularly polarized light is emitted as synchrotron radiation from tightly captured electrons by intense magnetic field around neutron stars. In this case, either left-or right-handed polarized light can be observed depending on the direction of observation. On the other hand, spin polarized electrons is emitted as beta-ray in beta decay from radioactive nuclei or neutron fireballs in supernova explosion. 2) The spin of beta-ray electrons is longitudinally polarized due to parity non-conservation in the weak interaction. The helicity (the the projection of the spin onto the direction of kinetic momentum) of beta-ray electrons is universally negative (left-handed). For the purpose of verifying the asymmetric structure emergence in bio-organic compounds by polarized quantum beams, we are now carrying out laboratory simulations using circularly polarized light from synchrotron radiation facility or spin polarized electron beam from beta-ray radiation source. 3,4) The target samples are solid film or aqueous solution of racemic amino acids. 1) K.Kobayashi, K.Kaneko, J.Takahashi, Y.Takano, in Astrobiology: from simple molecules to primitive life; Ed. V.Basiuk; American Scientific Publisher: Valencia, 2008. 2) G.A.Gusev, T.Saito, V.A.Tsarev, A.V.Uryson, Origins Life Evol. Biosphere. 37, 259 (2007). 3) J.Takahashi, H.Shinojima, M.Seyama, Y.Ueno, T.Kaneko, K.Kobayashi, H.Mita, M.Adachi, M.Hosaka, M.Katoh, Int. J. Mol. Sci. 10, 3044

  11. 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.

  12. 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.

  13. The Asymmetric Effects of Investor Sentiment

    DEFF Research Database (Denmark)

    Lutz, Chandler

    2016-01-01

    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......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...... trough-to-peak episodes (sentiment expansions). Overall, these results match theories and anecdotal accounts of investor sentiment....

  14. RHIC operation with asymmetric collisions in 2015

    Energy Technology Data Exchange (ETDEWEB)

    Liu, C. [Brookhaven National Lab. (BNL), Upton, NY (United States); Aschenauer, C. [Brookhaven National Lab. (BNL), Upton, NY (United States); Atoian, G. [Brookhaven National Lab. (BNL), Upton, NY (United States); Blaskiewicz, M. [Brookhaven National Lab. (BNL), Upton, NY (United States); Brown, K. A. [Brookhaven National Lab. (BNL), Upton, NY (United States); Bruno, D. [Brookhaven National Lab. (BNL), Upton, NY (United States); Connolly, R. [Brookhaven National Lab. (BNL), Upton, NY (United States); Ottavio, T. D. [Brookhaven National Lab. (BNL), Upton, NY (United States); Drees, K. A. [Brookhaven National Lab. (BNL), Upton, NY (United States); Fischer, W. [Brookhaven National Lab. (BNL), Upton, NY (United States); Gardner, C. J. [Brookhaven National Lab. (BNL), Upton, NY (United States); Gu, X. [Brookhaven National Lab. (BNL), Upton, NY (United States); Hayes, T. [Brookhaven National Lab. (BNL), Upton, NY (United States); Huang, H. [Brookhaven National Lab. (BNL), Upton, NY (United States); Laster, J. S. [Brookhaven National Lab. (BNL), Upton, NY (United States); Luo, Y. [Brookhaven National Lab. (BNL), Upton, NY (United States); Makdisi, Y. [Brookhaven National Lab. (BNL), Upton, NY (United States); Marr, G. [Brookhaven National Lab. (BNL), Upton, NY (United States); Marusic, A. [Brookhaven National Lab. (BNL), Upton, NY (United States); Meot, F. [Brookhaven National Lab. (BNL), Upton, NY (United States); Mernick, K. [Brookhaven National Lab. (BNL), Upton, NY (United States); Michnoff, R. [Brookhaven National Lab. (BNL), Upton, NY (United States); Minty, M. [Brookhaven National Lab. (BNL), Upton, NY (United States); Montag, C. [Brookhaven National Lab. (BNL), Upton, NY (United States); Morris, J. [Brookhaven National Lab. (BNL), Upton, NY (United States); Narayan, G. [Brookhaven National Lab. (BNL), Upton, NY (United States); Nayak, S. [Brookhaven National Lab. (BNL), Upton, NY (United States); Nemesure, S. [Brookhaven National Lab. (BNL), Upton, NY (United States); Pile, P. [Brookhaven National Lab. (BNL), Upton, NY (United States); Poblaguev, A. [Brookhaven National Lab. (BNL), Upton, NY (United States); Ranjbar, V. [Brookhaven National Lab. (BNL), Upton, NY (United States); Robert-Demolaize, G. [Brookhaven National Lab. (BNL), Upton, NY (United States); Roser, T. [Brookhaven National Lab. (BNL), Upton, NY (United States); Schmidke, B. [Brookhaven National Lab. (BNL), Upton, NY (United States); Schoefer, V. [Brookhaven National Lab. (BNL), Upton, NY (United States); Severino, F. [Brookhaven National Lab. (BNL), Upton, NY (United States); Shrey, T. [Brookhaven National Lab. (BNL), Upton, NY (United States); Smith, K. [Brookhaven National Lab. (BNL), Upton, NY (United States); Steski, D. [Brookhaven National Lab. (BNL), Upton, NY (United States); Tepikian, S. [Brookhaven National Lab. (BNL), Upton, NY (United States); Trbojevic, D. [Brookhaven National Lab. (BNL), Upton, NY (United States); Tsoupas, N. [Brookhaven National Lab. (BNL), Upton, NY (United States); Wang, G. [Brookhaven National Lab. (BNL), Upton, NY (United States); White, S. [Brookhaven National Lab. (BNL), Upton, NY (United States); Yip, K. [Brookhaven National Lab. (BNL), Upton, NY (United States); Zaltsman, A. [Brookhaven National Lab. (BNL), Upton, NY (United States); Zeno, K. [Brookhaven National Lab. (BNL), Upton, NY (United States); Zhang, S. Y. [Brookhaven National Lab. (BNL), Upton, NY (United States)

    2015-08-07

    To study low-x shadowing/saturation physics as well as other nuclear effects [1], [2], proton-gold (p-Au, for 5 weeks) and proton-Aluminum (p-Al, for 2 weeks) collisions were provided for experiments in 2015 at the Relativistic Heavy Ion Collider (RHIC), with polarized proton beam in the Blue ring and Au/Al beam in the Yellow ring. The special features of the asymmetric run in 2015 will be introduced. The operation experience will be reviewed as well in the report.

  15. Asymmetric Hydrogenation of 3-Substituted Pyridinium Salts.

    Science.gov (United States)

    Renom-Carrasco, Marc; Gajewski, Piotr; Pignataro, Luca; de Vries, Johannes G; Piarulli, Umberto; Gennari, Cesare; Lefort, Laurent

    2016-07-01

    The use of an equivalent amount of an organic base leads to high enantiomeric excess in the asymmetric hydrogenation of N-benzylated 3-substituted pyridinium salts into the corresponding piperidines. Indeed, in the presence of Et3 N, a Rh-JosiPhos catalyst reduced a range of pyridinium salts with ee values up to 90 %. The role of the base was elucidated with a mechanistic study involving the isolation of the various reaction intermediates and isotopic labeling experiments. Additionally, this study provided some evidence for an enantiodetermining step involving a dihydropyridine intermediate. PMID:27140832

  16. Quantum optics of lossy asymmetric beam splitters

    Science.gov (United States)

    Uppu, Ravitej; Wolterink, Tom A. W.; Tentrup, Tristan B. H.; Pinkse, Pepijn W. H.

    2016-07-01

    We theoretically investigate quantum interference of two single photons at a lossy asymmetric beam splitter, the most general passive 2$\\times$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 matrix. Our analysis using the noise operator formalism shows that the loss allows tunability of quantum interference to an extent not possible with a lossless beam splitter. Our theoretical studies support the experimental demonstrations of programmable quantum interference in highly multimodal systems such as opaque scattering media and multimode fibers.

  17. Massless sunset diagrams in finite asymmetric volumes

    Science.gov (United States)

    Niedermayer, F.; Weisz, P.

    2016-06-01

    This paper discusses the methods and the results used in an accompanying paper describing the matching of effective chiral Lagrangians in dimensional and lattice regularizations. We present methods to compute 2-loop massless sunset diagrams in finite asymmetric volumes in the framework of these regularizations. We also consider 1-loop sums in both regularizations, extending the results of Hasenfratz and Leutwyler for the case of dimensional regularization and we introduce a new method to calculate precisely the expansion coefficients of the 1-loop lattice sums.

  18. Plasma current resonance in asymmetric toroidal systems

    Energy Technology Data Exchange (ETDEWEB)

    Hazeltine, R. D. [Institute for Fusion Studies, University of Texas at Austin, Austin, Texas 78712 (United States); Catto, Peter J. [Plasma Science and Fusion Center, Massachusetts Institute of Technology, 167 Albany Street, Cambridge, Massachusetts 02139 (United States)

    2015-09-15

    The well-known singularity in the magnetic differential equation for plasma current in an asymmetric toroidal confinement system is resolved by including in the pressure tensor corrections stemming from finite Larmor radius. The result provides an estimate of the amplitude of spikes in the parallel current that occur on rational magnetic surfaces. Resolution of the singularity is shown to depend on both the ambipolarity condition—the requirement of zero surface-averaged radial current—and the form of the magnetic differential equation near the rational surface.

  19. Plasmonic photodetectors based on asymmetric nanogap electrodes

    Science.gov (United States)

    Ge, Junyu; Luo, Manlin; Zou, Wanghui; Peng, Wei; Duan, Huigao

    2016-08-01

    Hot electrons excited by plasmon resonance in nanostructure can be employed to enhance the properties of photodetectors, even when the photon energy is lower than the bandgap of the semiconductor. However, current research has seldom considered how to realize the efficient collection of hot electrons, which restricts the responsivity of the device. In this paper, a type of plasmonic photodetector based on asymmetric nanogap electrodes is proposed. Owing to this structure, the device achieves responsivities as high as 0.45 and 0.25 mA/W for wavelengths of 1310 and 1550 nm, respectively. These insights can aid the realization of efficient plasmon-enhanced photodetectors for infrared detection.

  20. 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.

  1. Security-Preserving Asymmetric Protocol Encapsulation

    OpenAIRE

    Vaudenay, Serge; Phan, Raphael C-W

    2007-01-01

    Query-response based protocols between a client and a server such as SSL, TLS, SSH are asymmetric in the sense that the querying client and the responding server play different roles, and for which there is a need for two-way linkability between queries and responses within the protocol. We are motivated by the observation that though results exist in other related contexts, no provably secure scheme has been applied to the setting of client-server protocols, which differ from conventional co...

  2. Analysis of Asymmetric Piezoelectric Composite Beam

    CERN Document Server

    Chen, J -S; Wu, K -C

    2008-01-01

    This paper deals with the vibration analysis of an asymmetric composite beam composed of glass a piezoelectric material. The Bernoulli's beam theory is adopted for mechanical deformations, and the electric potential field of the piezoelectric material is assumed such that the divergence-free requirement of the electrical displacements is satisfied. The accuracy of the analytic model is assessed by comparing the resonance frequencies obtained by the analytic model with those obtained by the finite element method. The model developed can be used as a tool for designing piezoelectric actuators such as micro-pumps.

  3. Chiral Diamine-catalyzed Asymmetric Aldol Reaction

    Institute of Scientific and Technical Information of China (English)

    LI Hui; XU Da-zhen; WU Lu-lu; WANG Yong-mei

    2012-01-01

    A highly efficient catalytic system composed of a simple and commercially available chiral primary diamine (1R,2R)-cyclohexane-1,2-diamine(6) and trifluoroacetic acid(TFA) was employed for asymmetric Aldol reaction in i-PrOH at room temperature.A loading of 10%(molar fraction) catalyst 6 with TFA as a cocatalyst could catalyze the Aldol reactions of various ketones or aldehydes with a series of aromatic aldehydes,furnishing Aldol products in moderate to high yields(up to >99%) with enantioselectivities of up to >99% and diastereoselectivities of up to 99:1.

  4. Quantum optics of lossy asymmetric beam splitters.

    Science.gov (United States)

    Uppu, Ravitej; Wolterink, Tom A W; Tentrup, Tristan B H; Pinkse, Pepijn W H

    2016-07-25

    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 matrix. Our analysis using the noise operator formalism shows that the loss allows tunability of quantum interference to an extent not possible with a lossless beam splitter. Our theoretical studies support the experimental demonstrations of programmable quantum interference in highly multimodal systems such as opaque scattering media and multimode fibers. PMID:27464096

  5. Long-lived oscillons from asymmetric bubbles

    CERN Document Server

    Adib, A B; Almeida, C A S; Adib, Artur B.; Gleiser, Marcelo; Almeida, Carlos A. S.

    2002-01-01

    The possibility that extremely long-lived, time-dependent, and localized field configurations (``oscillons'') arise during the collapse of asymmetrical bubbles in 2+1 dimensional \\phi^4 models is investigated. It is found that oscillons can develop from a large spectrum of elliptically deformed bubbles. Moreover, it is found that such oscillons are: a) circularly symmetric; and b) stable against small arbitrary radial and angular perturbations. They may thus play an important role in the study of time-dependent nonperturbative configurations in field theory, with applications ranging from nonequilibrium statistical physics to early universe cosmology.

  6. Neuronal Alignment On Asymmetric Textured Surfaces

    CERN Document Server

    Beighley, Ross; Sekeroglu, Koray; Atherton, Timothy; Demirel, Melik C; Staii, Cristian

    2013-01-01

    Axonal growth and the formation of synaptic connections are key steps in the development of the nervous system. Here we present experimental and theoretical results on axonal growth and interconnectivity in order to elucidate some of the basic rules that neuronal cells use for functional connections with one another. We demonstrate that a unidirectional nanotextured surface can bias axonal growth. We perform a systematic investigation of neuronal processes on asymmetric surfaces and quantify the role that biomechanical surface cues play in neuronal growth. These results represent an important step towards engineering directed axonal growth for neuro-regeneration studies.

  7. A carbon nanotube confinement strategy to implement homogeneous asymmetric catalysis in the solid phase.

    Science.gov (United States)

    Hashimoto, Kazuki; Kumagai, Naoya; Shibasaki, Masakatsu

    2015-03-01

    A readily recyclable asymmetric catalyst has been developed based on the self-assembly of a homogeneous catalyst in a fibrous network of multiwalled carbon nanotubes (MWNTs). Dimerization of an amide-based chiral ligand with a suitable spacer allows for the efficient formation of a heterogeneous catalyst by self-assembly on addition of Er(OiPr)3. The self-assembly proceeds in the MWNT fibrous network and small clusters of assembled catalyst are confined in the MWNTs, producing an easily handled solid-phase catalyst. The resulting MWNT-confined catalyst exhibits a good catalytic performance in a catalytic asymmetric Mannich-type reaction, which can be conducted in a repeated batch system and in a continuous-flow platform.

  8. RELATIONSHIP OF TRANSVERSAL ASYMMETRIC FACE AND UNILATERAL POSTERIOR CROSSBITE

    OpenAIRE

    Indah Dwinursanty; Krisnawati Krisnawati; Maria Purbiati

    2006-01-01

    Unilateral posterior crossbite is commonly seen in mixed dentition, but it couldn’t be self corrected. If this condition is not treated properly, it could lead to asymmetric face. Asymmetric face with unilateral posterior crossbite could make the treatment process more difficult. The objective of this study is to find out the relationship between transversal skeletal asymmetry and unilateral posterior crossbite. Patients older than 13 years with skeletal asymmetric face, who had never undergo...

  9. Asymmetric transmission: a generic property of lossy periodic interfaces

    CERN Document Server

    Plum, E; Zheludev, N I

    2010-01-01

    Asymmetric transmission of circularly polarized waves is a well-established property of lossy, anisotropic, two-dimensionally chiral patterns. Here we show that asymmetric transmission can be observed for oblique incidence onto any lossy periodically structured plane. Our results greatly expand the range of natural and artificial materials in which directionally asymmetric transmission can be expected making it a cornerstone electromagnetic effect rather than a curiosity of planar chiral metamaterials. Prime candidates for asymmetric transmission at oblique incidence are rectangular arrays of plasmonic spheres or semiconductor quantum dots, lossy double-periodic gratings and planar metamaterial structures.

  10. Quantity Discount Scheme in Supply Chain under Asymmetric Information

    Institute of Scientific and Technical Information of China (English)

    LI Ji-bin; PENG Zuo-he

    2007-01-01

    Quantity discount scheme plays an important role in supply chain management. The different quantity discount schemes under symmetric (full) information and asymmetric information, are analyzed by using principal-agent and optimal control theory. As a result, the research reveals that the optimal quantity discount solution under symmetric information is a special case of that under asymmetric information. At the same price, the critical value of quantity discount under asymmetric information is much lower than that under asymmetric information. Therefore, this leads to less cost for retailers and smaller profit for their supplier.

  11. Dynamics of asymmetrical hybridization in North American wood ferns: reconciling patterns of inheritance with gametophyte reproductive biology.

    Science.gov (United States)

    Testo, Weston L; Watkins, James E; Barrington, David S

    2015-04-01

    Hybridization is an important evolutionary force in plants, but the mechanisms underlying it have not been well studied for many groups. In particular, the drivers of non-random patterns of interspecific gene flow (asymmetrical hybridization) remain poorly understood, especially in the seed-free vascular plants. Here, we examine patterns of asymmetrical hybridization in two widespread fern hybrids from eastern North America and study the role of gametophyte ecology in the determination of hybridization bias. We characterized the maternal parentage of > 140 hybrid sporophytes by sequencing a c. 350-bp region of chloroplast DNA (cpDNA). To identify factors contributing to patterns of asymmetrical hybridization, we cultured gametophytes of the parental species and evaluated critical aspects of their reproductive biology. We found that asymmetrical hybridization was prevalent across the populations of both hybrids. Reproductive traits varied across species and suggest that selfing potential, antheridiogen responsiveness, sperm dispersal capacity and gamete size all contribute to the mediation of the direction of hybridization in this group. Our findings suggest that asymmetrical hybridization in ferns is driven by an array of reproductive traits. This study helps to sharpen and define a mechanistic understanding of patterns of hybridization in this group and demonstrates the importance of considering gametophyte biology when studying evolutionary processes in ferns.

  12. Particle identification at an asymmetric B Factory

    International Nuclear Information System (INIS)

    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 B0 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

  13. 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.

  14. Asymmetric Twin Representation: the Transfer Matrix Symmetry

    Directory of Open Access Journals (Sweden)

    Anastasia Doikou

    2007-01-01

    Full Text Available The symmetry of the Hamiltonian describing the asymmetric twin model was partially studied in earlier works, and our aim here is to generalize these results for the open transfer matrix. In this spirit we first prove, that the so called boundary quantum algebra provides a symmetry for any generic - independent of the choice of model - open transfer matrix with a trivial left boundary. In addition it is shown that the boundary quantum algebra is the centralizer of the $B$ type Hecke algebra. We then focus on the asymmetric twin representation of the boundary Temperley-Lieb algebra. More precisely, by exploiting exchange relations dictated by the reflection equation we show that the transfer matrix with trivial boundary conditions enjoys the recognized $U_q(sl_2otimes U_i(sl_2$ symmetry. When a non-diagonal boundary is implemented the symmetry as expected is reduced, however again certain familiar boundary non-local charges turn out to commute with the corresponding transfer matrix.

  15. Asymmetric disassembly and robustness in declining networks.

    Science.gov (United States)

    Saavedra, Serguei; Reed-Tsochas, Felix; Uzzi, Brian

    2008-10-28

    Mechanisms that enable declining networks to avert structural collapse and performance degradation are not well understood. This knowledge gap reflects a shortage of data on declining networks and an emphasis on models of network growth. Analyzing >700,000 transactions between firms in the New York garment industry over 19 years, we tracked this network's decline and measured how its topology and global performance evolved. We find that favoring asymmetric (disassortative) links is key to preserving the topology and functionality of the declining network. Based on our findings, we tested a model of network decline that combines an asymmetric disassembly process for contraction with a preferential attachment process for regrowth. Our simulation results indicate that the model can explain robustness under decline even if the total population of nodes contracts by more than an order of magnitude, in line with our observations for the empirical network. These findings suggest that disassembly mechanisms are not simply assembly mechanisms in reverse and that our model is relevant to understanding the process of decline and collapse in a broad range of biological, technological, and financial networks.

  16. Instability of asymmetric continuous shaft system

    Science.gov (United States)

    Srinath, R.; Sarkar, Abhijit; Sekhar, A. S.

    2016-11-01

    In this work, the governing equation of asymmetric continuous shaft in inertial frame of reference is studied. In particular, determination of the parameter ranges for the stability or instability of the shaft response is the focus of the present work. The governing equations are a fourth-order coupled partial differential equations containing time dependent coefficients. The equations are non-dimensionalized in terms of two parameters related to the average moment of inertia and the difference of moments of inertia about the principal axes. Using the latter as the asymptotic parameter and employing modal superposition, a formal methodology based on perturbation methods is developed to ascertain the stability and instability characteristics. The methodology is applicable to shafts subjected to some of the classical boundary conditions viz. simply supported, cantilever, and fixed-fixed. Similar stability curves are obtained for each mode for these different boundary conditions. The novel non-dimensionalization scheme chosen leads to the stability boundaries as well as the loci of varying speeds to be in the form of straight lines. The intersection of these lines determine the stable and unstable speed ranges of different asymmetric shafts. The results are generalized for different material and geometric properties of the shaft.

  17. Properties of asymmetrically evolved community networks

    Institute of Scientific and Technical Information of China (English)

    Cui Di; Gao Zi-You; Zheng Jian-Feng

    2009-01-01

    This paper studies a simple asymmetrically evolved community network with a combination of preferential at-tachment and random properties. An important issue about community networks is to discover the different utility increments of two nodes, where the utility is introduced to investigate the asymmetrical effect of connecting two nodes. On the other hand, the connection of two nodes in community networks can be classified as two nodes belonging to the same or to different communities. The simulation results show that the model can reproduce a power-law utility distribution P(u)~ u-σ,σ=2+ 1/p, which can be obtained by using mean-field approximation methods. Furthermore, the model exhibits exponential behaviour with respect to small values of a parameter denoting the random effect in our model at the low-utility region and a power-law feature with respect to big values of this parameter at the high-utility region, which is in good agreement with theoretical analysis. This kind of community network can reproduce a unique utility distribution by theoretical and numerical analysis.

  18. An asymmetric B factory based on PEP

    International Nuclear Information System (INIS)

    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 1033 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

  19. Asymmetric transition disks: Vorticity or eccentricity?

    CERN Document Server

    Zsom, A; Ghanbari, J

    2013-01-01

    Context. Transition disks typically appear in resolved millimeter observations as giant dust rings surrounding their young host stars. More accurate observations with ALMA have shown several of these rings to be in fact asymmetric: they have lopsided shapes. It has been speculated that these rings act as dust traps, which would make them important laboratories for studying planet formation. It has been shown that an elongated giant vortex produced in a disk with a strong viscosity jump strikingly resembles the observed asymmetric rings. Aims. We aim to study a similar behavior for a disk in which a giant planet is embedded. However, a giant planet can induce two kinds of asymmetries: (1) a giant vortex, and (2) an eccentric disk. We studied under which conditions each of these can appear, and how one can observationally distinguish between them. This is important because only a vortex can trap particles both radially and azimuthally, while the eccentric ring can only trap particles in radial direction. Method...

  20. Asymmetric EPR entanglement in continuous variable systems

    International Nuclear Information System (INIS)

    Continuous variable entanglement can be produced in nonlinear systems or via the interference of squeezed states. In many optical systems such as parametric down conversion, the production of two perfectly symmetric subsystems is usually assumed when demonstrating the existence of entanglement. This symmetry simplifies the description of entanglement. However, asymmetry in entanglement may arise naturally in a real experiment, or be intentionally introduced in a given quantum information protocol. These asymmetries can emerge from having the output beams experience different losses and environmental contamination, or from the availability of non-identical input quantum states in quantum communication protocols. In this paper, we present a visualization of entanglement using quadrature amplitude plots of the twin beams. We quantitatively discuss the strength of asymmetric entanglement using EPR and inseparability criteria and theoretically show that the optimal beamsplitter ratio for entanglement is dependent on the asymmetries and may not be 50 : 50. To support this theory, we present experimental results showing one particular asymmetric entanglement where a 78 : 22 beamsplitter is optimal for observing entanglement. (paper)

  1. Evaluation of an asymmetric stent patch design for a patient specific intracranial aneurysm using computational fluid dynamic (CFD) calculations in the computed tomography (CT) derived lumen

    Science.gov (United States)

    Kim, Minsuok; Ionita, Ciprian; Tranquebar, Rekha; Hoffmann, Kenneth R.; Taulbee, Dale B.; Meng, Hui; Rudin, Stephen

    2006-03-01

    Stenting may provide a new, less invasive therapeutic option for cerebral aneurysms. However, a conventional porous stent may be insufficient in modifying the blood flow for clinical aneurysms. We designed an asymmetric stent consisting of a low porosity patch welded onto a porous stent for an anterior cerebral artery aneurysm of a specific patient geometry to block the strong inflow jet. To evaluate the effect of the patch on aneurysmal flow dynamics, we "virtually" implanted it into the patient's aneurysm geometry and performed Computational Fluid Dynamics (CFD) analysis. The patch was computationally deformed to fit into the vessel lumen segmented from the patient CT reconstructions. After the flow calculations, a patch with the same design was fabricated using laser cutting techniques and welded onto a commercial porous stent, creating a patient-specific asymmetric stent. This stent was implanted into a phantom, which was imaged with X-ray angiography. The hemodynamics of untreated and stented aneurysms were compared both computationally and experimentally. It was found from CFD of the patient aneurysm that the asymmetric stent effectively blocked the strong inflow jet into the aneurysm and eliminated the flow impingement on the aneurysm wall at the dome. The impact zone with elevated wall shear stress was eliminated, the aneurysmal flow activity was substantially reduced, and the flow was considerably reduced. Experimental observations corresponded well qualitatively with the CFD results. The demonstrated asymmetric stent could lead to a new minimally invasive image guided intervention to reduce aneurysm growth and rupture.

  2. Iron-, Cobalt-, and Nickel-Catalyzed Asymmetric Transfer Hydrogenation and Asymmetric Hydrogenation of Ketones.

    Science.gov (United States)

    Li, Yan-Yun; Yu, Shen-Luan; Shen, Wei-Yi; Gao, Jing-Xing

    2015-09-15

    Chiral alcohols are important building blocks in the pharmaceutical and fine chemical industries. The enantioselective reduction of prochiral ketones catalyzed by transition metal complexes, especially asymmetric transfer hydrogenation (ATH) and asymmetric hydrogenation (AH), is one of the most efficient and practical methods for producing chiral alcohols. In both academic laboratories and industrial operations, catalysts based on noble metals such as ruthenium, rhodium, and iridium dominated the asymmetric reduction of ketones. However, the limited availability, high price, and toxicity of these critical metals demand their replacement with abundant, nonprecious, and biocommon metals. In this respect, the reactions catalyzed by first-row transition metals, which are more abundant and benign, have attracted more and more attention. As one of the most abundant metals on earth, iron is inexpensive, environmentally benign, and of low toxicity, and as such it is a fascinating alternative to the precious metals for catalysis and sustainable chemical manufacturing. However, iron catalysts have been undeveloped compared to other transition metals. Compared with the examples of iron-catalyzed asymmetric reduction, cobalt- and nickel-catalyzed ATH and AH of ketones are even seldom reported. In early 2004, we reported the first ATH of ketones with catalysts generated in situ from iron cluster complex and chiral PNNP ligand. Since then, we have devoted ourselves to the development of ATH and AH of ketones with iron, cobalt, and nickel catalysts containing novel chiral aminophosphine ligands. In our study, the iron catalyst containing chiral aminophosphine ligands, which are expected to control the stereochemistry at the metal atom, restrict the number of possible diastereoisomers, and effectively transfer chiral information, are successful catalysts for enantioselective reduction of ketones. Among these novel chiral aminophosphine ligands, 22-membered macrocycle P2N4

  3. Asymmetric diffusion of magnetic field lines in turbulence

    International Nuclear Information System (INIS)

    Stochasticity of magnetic field lines is paramount to understanding particle transport and mixing (Rechester and Rosenbluth 1978 Phys. Rev. Lett. 40 38–41). In this paper we study magnetic field separation in turbulent plasmas, which feature so-called superdiffusion, where field lines separate faster than diffusively. We discovered that turbulent superdiffusion can be pronouncedly asymmetric, so that the separation of field lines will be different if one follows magnetic field lines along the direction of the field or follows them in the opposite direction. Particle transport perpendicular to the magnetic field is primarily due to the field line separation in collisionless, well-magnetized plasmas. The asymmetry in diffusion, however, was certainly unexpected, as it will create free energy in particles that follow field lines, e.g. it will create large-scale streaming out of particle gradients perpendicular to the mean magnetic field. While the symmetry of the flow is broken by the so-called imbalance or cross-helicity, the difference between forward and backward diffusion is not directly due to imbalance, but a non-trivial consequence of both imbalance and non-reversibility of turbulence. It therefore follows that this peculiar property of field lines is directly related to turbulence being a dissipative phenomenon, and that turbulence can directly channel part of its free energy to particles. (invited comment)

  4. Asymmetric Dimethyarginine as Marker and Mediator in Ischemic Stroke

    Directory of Open Access Journals (Sweden)

    Karin Weissenborn

    2012-11-01

    Full Text Available Asymmetric dimethylarginine (ADMA, an endogenous nitric oxide synthase (NOS inhibitor, is known as mediator of endothelial cell dysfunction and atherosclerosis. Circulating ADMA levels are correlated with cardiovascular risk factors such as hypercholesterolemia, arterial hypertension, diabetes mellitus, hyperhomocysteinemia, age and smoking. Accordingly, clinical studies found evidence that increased ADMA levels are associated with a higher risk of cerebrovascular events. After the acute event of ischemic stroke, levels of ADMA and its analog symmetric dimethylarginine (SDMA are elevated through augmentation of protein methylation and oxidative stress. Furthermore, cleavage of ADMA through dimethylarginine dimethylaminohydrolases (DDAHs is reduced. This increase of dimethylarginines might be predictive for adverse clinical outcome. However, the definite role of ADMA after acute ischemic stroke still needs to be clarified. On the one hand, ADMA might contribute to brain injury by reduction of cerebral blood flow. On the other hand, ADMA might be involved in NOS-induced oxidative stress and excitotoxic neuronal death. In the present review, we highlight the current knowledge from clinical and experimental studies on ADMA and its role for stroke risk and ischemic brain injury in the hyperacute stage after stroke. Finally, further studies are warranted to unravel the relevance of the close association of dimethylarginines with stroke.

  5. Classical and wave chaos in asymmetric resonant cavities

    Science.gov (United States)

    Stone, A. Douglas

    2000-12-01

    Deformed cylindrical and spherical dielectric optical resonators are analyzed from the perspective of non-linear dynamics and quantum chaos theory. In the short-wavelength limit such resonators behave like billiard systems with non-zero escape probability due to refraction. A ray model is introduced to predict the resonance lifetimes and emission patterns from such a cavity. A universal wavelength-independent broadening is predicted and found for large deformations of the cavity, however there are significant wave-chaotic corrections as well. Highly directional emission is predicted from chaotic “whispering gallery” modes for index of refraction less than two. The detailed nature of the emission pattern can be understood from the nature of the phase space flow in the billiard, and a dramatic variation of this pattern with index of refraction is found due to an effect called “dynamical eclipsing”. Semiconductor resonators of this type also show highly directional emission and high output power but from different modes associated with periodic orbits. A semiclassical approach to these modes is briefly reviewed. These asymmetric resonant cavities (ARCs) show promise as components in future integrated optical devices.

  6. Asymmetric dimethylarginine: A novel biomarker of gastric mucosal injury?

    Institute of Scientific and Technical Information of China (English)

    Zhe Zhang; Yi-You Zou; Fu-Jun Li; Chang-Ping Hu

    2011-01-01

    Nitric oxide (NO),a multifunctional endogenous gas molecule,is metabolized from L-arginine by enzymatic reaction in the presence of nitric oxide synthase. NO,an important gas signaling molecule,is a gastric mucosa protective factor that contributes significantly to maintain normal gastric mucosa integrity. NO increases gastric mucosa blood flow,regulates the secretion of mucus and bicarbonate,and inhibits the secretion of gastric juice. Asymmetric dimethylarginine (ADMA) has been identified as the major endogenous inhibitor of nitric oxide synthase. The function of ADMA is to decrease NO production via inhibiting nitric oxide synthase activity. Besides inhibiting NO synthesis,ADMA also directly induces oxidative stress and cell apoptosis,and participates in inflammation reaction. Its systemic accumulation was observed in conjunction with several cardiovascular and metabolic diseases. ADMA also mediates gastric ulcer injury induced by ethanol,stress,helicobacter pylori and indomethacin. The mechanism of ADMA directly producing adverse effect in gastric mucosa is incompletely understood. It is widely accepted that NO bioavailability decrease is the majority reason. Promotion of apoptosis and aggravation of inflammation may be other important mechanisms of ADMA-induced gastric injury. ADMA might be a novel clinical and experimental biomarker related to gastric mucosa disorder. Although therapeutic tool targeting to ADMA is available in multiple cardiovascular diseases,it is unknown in gastrointestinal disease. The strategy to inhibit ADMA is beneficial to gastric ulcer induced by ethanol in rats. Thus,ADMA might be a candidate of therapeutic target in gastric mucosa damage.

  7. Critical Differences of Asymmetric Magnetic Reconnection from Standard Models

    Science.gov (United States)

    Nitta, S.; Wada, T.; Fuchida, T.; Kondoh, K.

    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.

  8. Numerical study of asymmetric driven reconnection at dayside magnetopause

    Institute of Scientific and Technical Information of China (English)

    金曙平; 沈俊太; 郝蕾; 胡先鹏

    2000-01-01

    A two-dimensional compressible MHD code has been used to numerically study the asymmetric driven reconnection processes in the vicinity of the magnetopause. The initial magnetic field configuration is assumed to be in a mechanical equilibrium state. The cases with identical temperatures ( Tm0/ Ts0 = 1 .0) and four different ratios of magnetic field strength ( Q = Bm0/Bs0 = 1.0, 1.5, 2.0, 2.5), and the case with Tm0/ Ts0 = 2.0 and O = 1.5 are investigated ( Bm0, Tm0 and B, Ts0 are the initial magnetic strength and temperature outside the current sheet on the magnetosphere and the mag-netosheath, respectively ). When the magnetic field on the magnetosheath side is set as southward, a recurrent formation of multiple magnetic bubbles with various scales occurs under the action of the inward plasma flow imposed at the left and right boundaries. In the simulation, some bubbles coalesce into a bigger one and then it is convected out of the simulation domain; the others are convected through the top boundary all

  9. 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.

  10. Effects of Noise on Asymmetric Bidirectional Controlled Teleportation

    Science.gov (United States)

    Nie, Yi-you; Sang, Ming-huang

    2016-07-01

    We present a scheme for asymmetric bidirectional controlled teleportation via a six-qubit cluster state in noisy environments, which includes the phase-damping and amplitude-damping channels. We analytically derive the fidelities of the asymmetric bidirectional controlled teleportation process in these two noise channels. We show that the fidelities only depend on the initial state and the noisy rate.

  11. Asymmetric Catalytic Reactions Catalyzed by Chiral Titanium Complexes

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    @@ Chiral titanium complexes is very importance catalyst to asymmetric catalytic reactions. A series of catalytic systems based on titanium-chiral ligands complexes has been reported. This presentation will discuss some of our recent progress on asymmetric catalytic reactions catalyzed by chiral titanium complexes.

  12. Asymmetric Catalytic Reactions Catalyzed by Chiral Titanium Complexes

    Institute of Scientific and Technical Information of China (English)

    FENG; XiaoMing

    2001-01-01

    Chiral titanium complexes is very importance catalyst to asymmetric catalytic reactions. A series of catalytic systems based on titanium-chiral ligands complexes has been reported. This presentation will discuss some of our recent progress on asymmetric catalytic reactions catalyzed by chiral titanium complexes.  ……

  13. Asymmetric catalytic synthesis of the proposed structure of trocheliophorolide B.

    Science.gov (United States)

    Trost, Barry M; Quintard, Adrien

    2012-09-01

    A concise catalytic asymmetric synthesis of the proposed structure of trocheliophorolide B is reported. The synthetic sequence notably features an asymmetric acetaldehyde alkynylation, a Ru-catalyzed alder-ene reaction, and a Zn-ProPhenol ynone aldol condensation. Comparison with the reported data suggests a misassignment of the natural product structure.

  14. Asymmetric catalytic synthesis of the proposed structure of trocheliophorolide B

    OpenAIRE

    Trost, Barry M.; Quintard, Adrien

    2012-01-01

    A concise catalytic asymmetric synthesis of the proposed structure of Trocheliophorolide B is reported. The synthetic sequence notably features an asymmetric acetaldehyde alkynylation, Ru-catalyzed alder-ene reaction and Zn-ProPhenol ynone aldol condensation. Comparison with the reported data suggests a miss-assignment of the natural product structure.

  15. ASYMMETRIC HYDROSILYLATION CATALYZED BY POLYMER—SUPPORTED THIAZOLIDINE RHODIUM CATALYSTS

    Institute of Scientific and Technical Information of China (English)

    LEIYanohui; LIHong; 等

    1999-01-01

    Asymmetric hydrisilylation catalyzed by polymeric thiazolidine rhodium catalysts was conducted.Almost the same optical yields have been obtained when comb-shaped polymeric ligands and their corresponding monomer complexed rhodium cataltysts were used to asymmetric hydrosilylation of acetophenone.Optical yield of chiral 1-methylbenzyl alcohol reaches as high as 71.5%.Temperature dependence of enantioselective hydrosilylation of acetophenone was discussed.

  16. Extensive Taguchi's Quality Loss Function Based On Asymmetric tolerances

    Institute of Scientific and Technical Information of China (English)

    ZHU Wei; LI Yuan-sheng; LIU Feng

    2004-01-01

    If specification interval is asymmetric, basic specification is the target value of quality characteristics. In this paper Taguchi's quality loss function is applied to describe quality loss based on asymmetric tolerances. The measurement of quality loss which is caused by the deviation of quality characteristics from basic specification is further presented.

  17. Asymmetric group loans, non-assortative matching and adverse selection

    NARCIS (Netherlands)

    Gangopadhyay, Shubhashis; Lensink, Robert

    2014-01-01

    This paper shows that an asymmetric group debt contract, where one borrower co-signs for another, but not vice versa, leads to heterogeneous matching. The analysis suggests that micro finance organizations can achieve the first best by offering asymmetric group contracts. (C) 2014 Elsevier B.V. All

  18. Isospin violating dark matter being asymmetric

    CERN Document Server

    Okada, Nobuchika

    2013-01-01

    The isospin violating dark matter (IVDM) scenario offers an interesting possibility to reconcile conflicting results among direct dark matter search experiments for a mass range around 10 GeV. We consider two simple renormalizable IVDM models with a complex scalar dark matter and a Dirac fermion dark matter, respectively, whose stability is ensured by the conservation of "dark matter number". Although both models successfully work as the IVDM scenario with destructive interference between effective couplings to proton and neutron, the dark matter annihilation cross section is found to exceed the cosmological/astrophysical upper bounds. Then, we propose a simple scenario to reconcile the IVDM scenario with the cosmological/astrophysical bounds, namely, the IVDM being asymmetric. Assuming a suitable amount of dark matter asymmetry has been generated in the early Universe, the annihilation cross section beyond the cosmological/astrophysical upper bound nicely works to dramatically reduce the anti-dark matter rel...

  19. Asymmetric morphology of the propagating jet

    Science.gov (United States)

    Hardee, Philip E.; Norman, Michael L.

    1990-12-01

    Simulations of slab jets propagating in constant atmospheres are reported for a range of jet velocities and Mach numbers. At early times, the jet maintains approximate axisymmetry within a backflowing cocoon. When the jet has penetrated farther into the external medium, the symmetry is broken by sideways oscillation and the leading edge of the jet moves about within a growing lobe. The oscillation results from nonlinear resonant amplification of the initial perturbation by the Kelvin-Helmholtz instability. Finally, the jet flaps chaotically within the growing lobe. The flapping is driven by turbulent vortices in the lobe. The basic picture of Scheuer's (1982) 'dentist's drill' model of the physical processes underlying asymmetric morphologies in radio galaxies is confirmed. The fluid motions in the lobe are found to govern the location of the drill bit. The morphology is time-dependent on relatively short time scales.

  20. Asymmetric Beam Combination for Optical Interferometry

    CERN Document Server

    Monnier, J D

    2001-01-01

    Optical interferometers increasingly use single-mode fibers as spatial filters to convert varying wavefront distortion into intensity fluctuations which can be monitored for accurate calibration of fringe amplitudes. Here I propose using an asymmetric coupler to allow the photometric intensities of each telescope beam to be measured at the same time as the fringe visibility, but without the need for dedicated photometric outputs, which reduce the light throughput in the interferometric channels. In the read-noise limited case often encountered in the infrared, I show that a 53% improvement in signal-to-noise ratio for the visibility amplitude measurement is achievable, when compared to a balanced coupler setup with 50% photometric taps (e.g., the FLUOR experiment). In the Poisson-noise limit appropriate for visible light, the improvement is reduced to only ~8%. This scheme also reduces the cost and complexity of the beam combination since fewer components and detectors are required, and can be extended to mor...

  1. Asymmetric Ferromagnet-Superconductor-Ferromagnet Switch

    Energy Technology Data Exchange (ETDEWEB)

    Cadden-Zimansky, P.; Bazaliy, Ya.B.; Litvak, L.M.; Jiang, J.S.; Pearson, J.; Gu, J.Y.; You, Chun-Yeol; Beasley, M.R.; Bader, S.D.

    2011-11-04

    In layered ferromagnet-superconductor-ferromagnet F{sub 1} /S/F{sub 2} structures, the critical temperature T{sub c} of the superconductors depends on the magnetic orientation of the ferromagnetic layers F{sub 1} and F{sub 2} relative to each other. So far, the experimentally observed magnitude of change in T{sub c} for structures utilizing weak ferromagnets has been 2 orders of magnitude smaller than is expected from calculations. We theoretically show that such a discrepancy can result from the asymmetry of F/S boundaries, and we test this possibility by performing experiments on structures where F{sub 1} and F{sub 2} are independently varied. Our experimental results indicate that asymmetric boundaries are not the source of the discrepancy. If boundary asymmetry is causing the suppressed magnitude of T{sub c} changes, it may only be possible to detect in structures with thinner ferromagnetic layers.

  2. Magnetoresistive system with concentric ferromagnetic asymmetric nanorings

    Energy Technology Data Exchange (ETDEWEB)

    Avila, J. I., E-mail: javila@ulg.ac.be; Tumelero, M. A.; Pasa, A. A.; Viegas, A. D. C. [Laboratório de Filmes Finos e Superfícies (LFFS), Departamento de Física, Universidade Federal de Santa Catarina, CP 476 Florianópolis (Brazil)

    2015-03-14

    A structure consisting of two concentric asymmetric nanorings, each displaying vortex remanent states, is studied with micromagnetic calculations. By orienting in suitable directions, both the asymmetry of the rings and a uniform magnetic field, the vortices chiralities can be switched from parallel to antiparallel, obtaining in this way the analogue of the ferromagnetic and antiferromagnetic configurations found in bar magnets pairs. Conditions on the thickness of single rings to obtain vortex states, as well as formulas for their remanent magnetization are given. The concentric ring structure enables the creation of magnetoresistive systems comprising the qualities of magnetic nanorings, such as low stray fields and high stability. A possible application is as contacts in spin injection in semiconductors, and estimations obtained here of magnetoresistance change for a cylindrical spin injection based device show significant variations comparable to linear geometries.

  3. Asymmetric correlations on the Croatian equity market

    Directory of Open Access Journals (Sweden)

    Davor Kunovac

    2011-03-01

    Full Text Available This paper compares the equity market in Croatia in bad (bear or turbulent and good (bull, calm market conditions. The two market regimes are formally identifi ed under the Markov Regime Switching (MRS framework. The analysis conducted suggests that correlations between equity prices are more than twice as high during bear than in bull markets. This result holds both for the shares included in the CROBEX and for the relationship among various European equity indices.In the context of international diversifi cation the result suggests only a limited benefi t that foreign investors can count on when diversifying their portfolios by expanding to developing European markets. In addition, by evaluating a portfolio optimization model that takes asymmetric correlations into account in an out-of-sample exercise, this paper also illustrates the losses that may occur if the asymmetry is ignored in practice.

  4. Distributed Function Computation in Asymmetric Communication Scenarios

    CERN Document Server

    Agnihotri, Samar

    2009-01-01

    We consider the distributed function computation problem in asymmetric communication scenarios, where the sink computes some deterministic function of the data split among N correlated informants. The distributed function computation problem is addressed as a generalization of distributed source coding (DSC) problem. We are mainly interested in minimizing the number of informant bits required, in the worst-case, to allow the sink to exactly compute the function. We provide a constructive solution for this in terms of an interactive communication protocol and prove its optimality. The proposed protocol also allows us to compute the worst-case achievable rate-region for the computation of any function. We define two classes of functions: lossy and lossless. We show that, in general, the lossy functions can be computed at the sink with fewer number of informant bits than the DSC problem, while computation of the lossless functions requires as many informant bits as the DSC problem.

  5. Asymmetric pneumatization of the petrous apex.

    Science.gov (United States)

    Roland, P S; Meyerhoff, W L; Judge, L O; Mickey, B E

    1990-07-01

    Three patients with high-intensity MR signals from one petrous apex, but nonpathologic fine-cut computed tomography are reported. In two of the three patients, normal bone marrow within the petrous apex on one side is believed to have generated the high-intensity signal. In one of the three patients, the etiology of the MR image remains obscure, but may represent the earliest stages of petrous cholesterol granuloma or mucocele. We have reviewed 500 head CT scans performed for non-otologic reasons, in an attempt to establish the frequency of this finding. The literature on MR and CT imaging of the petrous apex and asymmetric pneumatization of the petrous apex is reviewed. PMID:2117735

  6. Chilly Dark Sectors and Asymmetric Reheating

    CERN Document Server

    Adshead, Peter; 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, $N_{\\mathrm{eff}}$, 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 ...

  7. Asymmetric EPR entanglement in continuous variable systems

    CERN Document Server

    Wagner, Katherine; Armstrong, Seiji; Morizur, Jean-Francois; Lam, Ping Koy; Bachor, Hans-Albert

    2012-01-01

    Continuous variable entanglement can be produced in nonlinear systems or via interference of squeezed states. In many of optical systems, such as parametric down conversion or interference of optical squeezed states, production of two perfectly symmetric subsystems is usually used for demonstrating the existence of entanglement. This symmetry simplifies the description of the concept of entanglement. However, asymmetry in entanglement may arise naturally in a real experiment, or be intentionally introduced in a given quantum information protocol. These asymmetries can emerge from having the output beams experience different losses and environmental contamination, or from the availability of non-identical input quantum states in quantum communication protocols. In this paper, we present a visualisation of entanglement using quadrature amplitude plots of the twin beams. We quantitatively discuss the strength of asymmetric entanglement using EPR and inseparability criteria and theoretically show that the optimal...

  8. Asymmetric effects of monetary policy in Brazil

    Directory of Open Access Journals (Sweden)

    Edilean Kleber da Silva Bejarano Aragón

    2009-06-01

    Full Text Available In this paper, we check whether the effects of monetary policy actions on output in Brazil are asymmetric. Therefore, we estimate Markov-switching models that allow positive and negative shocks to affect the growth rate of output in an asymmetric fashion in expansion and recession states. In general, results show that: i the real effects of negative monetary shocks are larger than those of positive shocks in an expansion; ii in a recession, the real effects of positive and negative shocks are the same; iii there is no evidence of asymmetry between the effects of countercyclical monetary policies; and iv it is not possible to assert that the effects of a positive (or negative shock are dependent upon the phase of the business cycle.Neste trabalho, examinamos se os efeitos das ações de política monetária sobre o produto são assimétricos no Brasil. Para isto, estimamos modelos Markov-switching que permitem que choques positivos e negativos afetem a taxa de crescimento do produto de forma assimétrica nos estados de expansão e recessão econômica. Em geral, os resultados mostram que: i os efeitos reais de choques monetários negativos são maiores do que os de choques positivos em uma expansão; ii em uma recessão, os efeitos reais de choques positivos e negativos são iguais; iii não há evidência de assimetria entre os efeitos de políticas monetárias contracíclicas; iv não se pode afirmar que os efeitos de choques positivos (ou negativos dependem da fase do ciclo econômico.

  9. Asymmetric facial skin viscoelasticity during climacteric aging

    Directory of Open Access Journals (Sweden)

    Piérard GE

    2014-04-01

    Full Text Available Gérald E Piérard,1 Trinh Hermanns-Lê,1 Ulysse Gaspard,2 Claudine Piérard-Franchimont11Laboratory of Skin Bioengineering and Imaging, Department of Clinical Sciences, University of Liège, 2Department of Gynecology and Obstetrics, University Hospital of Liège, Liège, BelgiumBackground: Climacteric skin aging affects certain biophysical characteristics of facial skin. The purpose of the present study was to assess the symmetric involvement of the cheeks in this stage of the aging process.Methods: Skin viscoelasticity was compared on both cheeks in premenopausal and post-menopausal women with indoor occupational activities somewhat limiting the influence of chronic sun exposure. Eighty-four healthy women comprising 36 premenopausal women and 48 early post-menopausal women off hormone replacement therapy were enrolled in two groups. The tensile characteristics of both cheeks were tested and compared in each group. A computerized suction device equipped with a 2 mm diameter hollow probe was used to derive viscoelasticity parameters during a five-cycle procedure of 2 seconds each. Skin unfolding, intrinsic distensibility, biological elasticity, and creep extension were measured.Results: Both biological elasticity and creep extension were asymmetric on the cheeks of the post-menopausal women. In contrast, these differences were more discrete in the premenopausal women.Conclusion: Facial skin viscoelasticity appeared to be asymmetric following menopause. The possibility of asymmetry should be taken into account in future studies of the effects of hormone replacement therapy and any antiaging procedure on the face in menopausal women.Keywords: climacteric aging, biomechanics, photoaging, skin unfolding, biological elasticity, skin tensile properties

  10. Algebraic Davis Decomposition and Asymmetric Doob Inequalities

    Science.gov (United States)

    Hong, Guixiang; Junge, Marius; Parcet, Javier

    2016-09-01

    In this paper we investigate asymmetric forms of Doob maximal inequality. The asymmetry is imposed by noncommutativity. Let {({M}, τ)} be a noncommutative probability space equipped with a filtration of von Neumann subalgebras {({M}_n)_{n ≥ 1}}, whose union {bigcup_{n≥1}{M}_n} is weak-* dense in {{M}}. Let {{E}_n} denote the corresponding family of conditional expectations. As an illustration for an asymmetric result, we prove that for {1 < p < 2} and {x in L_p({M},τ)} one can find {a, b in L_p({M},τ)} and contractions {u_n, v_n in {M}} such that {E}_n(x) = a u_n + v_n b quad and quad max big{ |a|_p,|b|_p big} ≤ c_p |x|_p. Moreover, it turns out that {a u_n} and {v_n b} converge in the row/column Hardy spaces {{H}_p^r({M})} and {{H}_p^c({M})} respectively. In particular, this solves a problem posed by the Defant and Junge in 2004. In the case p = 1, our results establish a noncommutative form of the Davis celebrated theorem on the relation betwe en martingale maximal and square functions in L 1, whose noncommutative form has remained open for quite some time. Given {1 ≤ p ≤ 2}, we also provide new weak type maximal estimates, which imply in turn left/right almost uniform convergence of {{E}_n(x)} in row/column Hardy spaces. This improves the bilateral convergence known so far. Our approach is based on new forms of Davis martingale decomposition which are of independent interest, and an algebraic atomic description for the involved Hardy spaces. The latter results are new even for commutative von Neumann algebras.

  11. The evolution of cooperation in asymmetric systems

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    Explaining the "Tragedy of the Commons" of the evolution of cooperation remains one of the greatest problems for both biology and social science.Asymmetrical interaction,which is one of the most important characteristics of cooperative systems,has not been sufficiently considered in the existing models of the evolution of cooperation.Considering the inequality in the number and payoff between the cooperative actors and recipients in cooperation systems,discriminative density-dependent interference competition will occur in limited dispersal systems.Our model and simulation show that the local but not the global stability of a cooperative interaction can be maintained if the utilization of common resource remains unsaturated,which can be achieved by density-dependent restraint or competition among the cooperative actors.More intense density dependent interference competition among the cooperative actors and the ready availability of the common resource,with a higher intrinsic contribution ratio of a cooperative actor to the recipient,will increase the probability of cooperation.The cooperation between the recipient and the cooperative actors can be transformed into conflict and,it oscillates chaotically with variations of the affecting factors under different environmental or ecological conditions.The higher initial relatedness(i.e.similar to kin or reciprocity relatedness),which is equivalent to intrinsic contribution ratio of a cooperative actor to the recipient,can be selected for by penalizing less cooperative or cheating actors but rewarding cooperative individuals in asymmetric systems.The initial relatedness is a pivot but not the aim of evolution of cooperation.This explains well the direct conflict observed in almost all cooperative systems.

  12. PEP-II: An asymmetric B factory

    International Nuclear Information System (INIS)

    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 1033 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

  13. Special Issue of "Asymmetric Synthesis"%Special Issue of "Asymmetric Synthesis"

    Institute of Scientific and Technical Information of China (English)

    2012-01-01

    Organic chemistry exploring the world at a molecu- lar level remains essential for our society in the 21st century. Asymmetric synthesis, particularly those em- ploying catalytic approach, is one of the most important research fields in organic synthesis providing chiral compounds in an enantiopure form. The latter is critical since the two enantiomers of one chiral compound, in many cases, have a different response in biological sys- tems. The huge markets of non-racemic chiral com- pounds as synthetic intermediates, pharmaceuticals,

  14. Effect of adiabatic square ribs on natural convection in an asymmetrically heated channel

    Science.gov (United States)

    Abidi-Saad, Aissa; Kadja, Mahfoud; Popa, Catalin; Polidori, Guillaume

    2016-06-01

    A 2-D numerical simulation is carried out to investigate the effect of two adiabatic square ribs on laminar flow and heat transfer in an asymmetrically heated channel. The two ribs are symmetrically located on each wall, exactly above the heating zone. The computational procedure is made by solving the unsteady bi-dimensional continuity, momentum and energy equations with the finite volume method. The investigations focused more specifically on the influence of ribs sizes on the flow structure and heat transfer enhancement. The results showed that the variation of ribs sizes significantly alters the heat transfer and fluid flow distribution along the channel, especially in the vicinity of protrusions. Also, the results show that streamlines, isotherms, and the number, sizes and formation of vortex structures inside the channel strongly depend on the size of protrusions. The changes in heat transfer parameters have also been presented.

  15. Time-headway distribution for periodic totally asymmetric exclusion process with various updates

    Science.gov (United States)

    Hrabák, P.; Krbálek, M.

    2016-03-01

    The totally asymmetric exclusion process (TASEP) with periodic boundaries is considered as traffic flow model. The large-L approximation of the stationary state is used for the derivation of the time-headway distribution (an important microscopic characteristic of traffic flow) for the model with generalized update (genTASEP) in both, forward- and backward-sequential representations. The usually used updates, fully-parallel and regular forward- and backward-sequential, are analyzed as special cases of the genTASEP. It is shown that only for those cases, the time-headway distribution is determined by the flow regardless to the density. The qualitative comparison of the results with traffic data demonstrates that the genTASEP with backward order and attractive interaction evinces similar properties of time-headway distribution as the real traffic sample.

  16. 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.

  17. 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.

  18. 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

  19. Finite Element Analysis of Symmetric and Asymmetric Three-roll Rolling Process

    Directory of Open Access Journals (Sweden)

    Pesin A.

    2015-01-01

    Full Text Available A three-roll process is a significant technique in the production of wire rod, round bars and hexagonal profiles for structural applications. Better mechanical properties of wire rod, round bars and hexagonal profiles can be achieved due to large plastic deformation by the three-roll process. Asymmetric rolling is a novel technique characterised by a kinematic asymmetry linked to the difference in peripheral speed of the rolls, able to introduce additional shear strains through the bar thickness. In order to achieve this, asymmetrical three-roll rolling process was investigated to better control the deformation compared to the conventional three-roll rolling process in a stand with two three-roll calibers located very close to each other. Simulation of round-triangle-triangle pass rolling was performed. FEM simulations were carried out with using software DEFORM 3D. The influence of the friction coefficient and speed asymmetry on the shear strain and material flow was discussed. The results of simulation can be used to optimize the asymmetric three-roll rolling process to improve the mechanical properties of wire rod, round bars and hexagonal profiles.

  20. 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

  1. Effect of breathing pattern on gas mixing in a model with asymmetrical alveolar ducts.

    Science.gov (United States)

    Bowes, C L; Richardson, J D; Cumming, G; Horsfield, K

    1985-01-01

    A model of the pulmonary airways was used to study three single-breath indices of gas mixing, dead space (VD), slope of the alveolar plateau, and alveolar mixing inefficiency (AMI). In the model, discrete elements of airway volume were represented by nodes. Using a finite difference technique the differential equation for simultaneous convection and diffusion was solved for the nodal network. Conducting airways and respiratory bronchioles were modeled symmetrically, but alveolar ducts asymmetrically, permitting interaction between convection and diffusion. VD, alveolar slope, and AMI increased with increasing flow. Similar trends were seen with inspired volume, although slope decreased at high inspired volumes with constant flow. VD was affected most by inspiratory flow and AMI and alveolar slope by expiratory time. VD fell approximately exponentially with time of breath holding. Eight different breathing patterns were compared. They had a small effect on alveolar slope and AMI and a greater effect on VD. The model shows how series and parallel inhomogeneity occur together and interact in asymmetrical systems: the old argument as to which is the more important should be abandoned. PMID:3968008

  2. Asymmetric Quantum Transport in a Double-Stranded Kronig-Penney Model

    Science.gov (United States)

    Cheon, Taksu; Poghosyan, Sergey S.

    2015-06-01

    We introduce a double-stranded Kronig-Penney model and analyze its transport properties. Asymmetric fluxes between two strands with suddenly alternating localization patterns are found as the energy is varied. The zero-size limit of the internal lines connecting two strands is examined using quantum graph vertices with four edges. We also consider a two-dimensional Kronig-Penney lattice with two types of alternating layer with δ and δ' connections, and show the existence of energy bands in which the quantum flux can flow only in selected directions.

  3. Asymmetric bias in user guided segmentations of brain structures.

    Science.gov (United States)

    Maltbie, Eric; Bhatt, Kshamta; Paniagua, Beatriz; Smith, Rachel G; Graves, Michael M; Mosconi, Matthew W; Peterson, Sarah; White, Scott; Blocher, Joseph; El-Sayed, Mohammed; Hazlett, Heather C; Styner, Martin A

    2012-01-16

    Brain morphometric studies often incorporate comparative hemispheric asymmetry analyses of segmented brain structures. In this work, we present evidence that common user guided structural segmentation techniques exhibit strong left-right asymmetric biases and thus fundamentally influence any left-right asymmetry analyses. In this study, MRI scans from ten pediatric subjects were employed for studying segmentations of amygdala, globus pallidus, putamen, caudate, and lateral ventricle. Additionally, two pediatric and three adult scans were used for studying hippocampus segmentation. Segmentations of the sub-cortical structures were performed by skilled raters using standard manual and semi-automated methods. The left-right mirrored versions of each image were included in the data and segmented in a random order to assess potential left-right asymmetric bias. Using shape analysis we further assessed whether the asymmetric bias is consistent across subjects and raters with the focus on the hippocampus. The user guided segmentation techniques on the sub-cortical structures exhibited left-right asymmetric volume bias with the hippocampus displaying the most significant asymmetry values (porigin of this asymmetric bias is considered to be based in laterality of visual perception; therefore segmentations with any degree of user interaction contain an asymmetric bias. The aim of our study is to raise awareness in the neuroimaging community regarding the presence of the asymmetric bias and its influence on any left-right hemispheric analyses. We also recommend reexamining previous research results in the light of this new finding. PMID:21889995

  4. Experimental simulation of asymmetric heat up of coolant channel under small break LOCA condition for PHWR

    Energy Technology Data Exchange (ETDEWEB)

    Yadav, Ashwini K., E-mail: ashwinikumaryadav@gmail.com [Department of Mechanical and Industrial Engineering, Indian Institute of Technology, Roorkee 247667 (India); Majumdar, P., E-mail: pmajum@barc.gov.in [Reactor Safety Division, Bhabha Atomic Research Centre, Mumbai 400085 (India); Kumar, Ravi, E-mail: ravikfme@iitr.ernet.in [Department of Mechanical and Industrial Engineering, Indian Institute of Technology, Roorkee 247667 (India); Chatterjee, B., E-mail: barun@barc.gov.in [Reactor Safety Division, Bhabha Atomic Research Centre, Mumbai 400085 (India); Gupta, Akhilesh, E-mail: akhilfme@iitr.ernet.in [Department of Mechanical and Industrial Engineering, Indian Institute of Technology, Roorkee 247667 (India); Mukhopadhyay, D., E-mail: dmukho@barc.gov.in [Reactor Safety Division, Bhabha Atomic Research Centre, Mumbai 400085 (India)

    2013-02-15

    Highlights: ► Circumferential temperature gradient of PT for asymmetric heat-up was 440 °C. ► At 2 MPa ballooning initiated at 450 °C and with strain rate of 0.0277%/s. ► At 4 MPa ballooning initiated at 390 °C and with strain rate of 0.0305%/s. ► At 4 MPa, PT ruptured under uneven strain and steep temperature gradient. ► Integrity of PT depends on internal pressure and magnitude of decay power. -- Abstract: During postulated small break loss of coolant accident (SBLOCA) for Pressurised Heavy Water Reactors (PHWRs) as well as for postulated SBLOCA coincident with loss of ECCS, a stratified flow condition can arise in the coolant channels as the gravitational force dominates over the low inertial flow arising from small break flow. A Station Blackout condition without operator intervention can also lead to stratified flow condition during a slow channel boil-off condition. For all these conditions the pressure remains high and under stratified flow condition, the horizontal fuel bundles experience different heat transfer environments with respect to the stratified flow level. This causes the bundle upper portion to get heated up higher as compared to the submerged portion. This kind of asymmetrical heating of the bundle is having a direct bearing on the circumferential temperature gradient of pressure tube (PT) component of the coolant channel. The integrity of the PT is important under normal conditions as well as at different accident loading conditions as this component houses the fuel bundles and serves as a coolant pressure boundary of the reactors. An assessment of PT is required with respect to different accident loading conditions. The present investigation aims to study thermo-mechanical behaviour of PT (Zr, 2.5 wt% Nb) under a stratified flow condition under different internal pressures. The component is subjected to an asymmetrical heat-up conditions as expected during the said situation under different pressure conditions which varies from 2

  5. High-Voltage, Asymmetric-Waveform Generator

    Science.gov (United States)

    Beegle, Luther W.; Duong, Tuan A.; Duong, Vu A.; Kanik, Isik

    2008-01-01

    The shapes of waveforms generated by commercially available analytical separation devices, such as some types of mass spectrometers and differential mobility spectrometers are, in general, inadequate and result in resolution degradation in output spectra. A waveform generator was designed that would be able to circumvent these shortcomings. It is capable of generating an asymmetric waveform, having a peak amplitude as large as 2 kV and frequency of several megahertz, which can be applied to a capacitive load. In the original intended application, the capacitive load would consist of the drift plates in a differential-mobility spectrometer. The main advantage to be gained by developing the proposed generator is that the shape of the waveform is made nearly optimum for various analytical devices requiring asymmetric-waveform such as differential-mobility spectrometers. In addition, this waveform generator could easily be adjusted to modify the waveform in accordance with changed operational requirements for differential-mobility spectrometers. The capacitive nature of the load is an important consideration in the design of the proposed waveform generator. For example, the design provision for shaping the output waveform is based partly on the principle that (1) the potential (V) on a capacitor is given by V=q/C, where C is the capacitance and q is the charge stored in the capacitor; and, hence (2) the rate of increase or decrease of the potential is similarly proportional to the charging or discharging current. The proposed waveform generator would comprise four functional blocks: a sine-wave generator, a buffer, a voltage shifter, and a high-voltage switch (see Figure 1). The sine-wave generator would include a pair of operational amplifiers in a feedback configuration, the parameters of which would be chosen to obtain a sinusoidal timing signal of the desired frequency. The buffer would introduce a slight delay (approximately equal to 20 ns) but would otherwise

  6. Simulation of Chaos in Asymmetric Nonlinear Chua's Circuit

    Institute of Scientific and Technical Information of China (English)

    WANG Yu-fei; QIAO Shu-tong; JIANG Jian-guo

    2008-01-01

    In order to describe practical chaotic systems exactly, we presented a simple modified Chua's circuit,which contains an asymmetric nonlinear resistive element. Mathematical analysis was made, and simulation study was performed by MATLAB. By varying the value of linear resistor in the circuit, rich variety dynamical behaviors were observed, such as DC equilibrium point, Hopf bifurcation, period-doubling bifurcation,single-scroll strange attractor, periodic windows, and asymmetric double-scroll strange attractor. The extreme sensitivity in the state trajectory with respect to the initial conditions was exhibited; the special characteristic of asymmetric nonlinear Chua's circuit was found also.

  7. The Dualism of Asymmetric Information in Agricultural Insurance

    Directory of Open Access Journals (Sweden)

    Xuemei Yang

    2013-07-01

    Full Text Available Asymmetric information objectively exists in the insurance market, especially in agricultural insurance, which has a great impact on the insurance contract and market operation. This paper designs two game models to analyse the dualism of asymmetric information in agricultural insurance and its reasons of forming. We find that, the particularity of agricultural production, the agricultural risk diversification and the benefits’ spillover of the agricultural insurance are the main causes of asymmetric information. Therefore, this paper puts forward that establishment of appropriate agricultural insurance mode, optimization of insurance policy design and increasing investment in science and technology, increasing farmers’ insurance consciousness and establishing supervision system

  8. Generic approach for synthesizing asymmetric nanoparticles and nanoassemblies

    Energy Technology Data Exchange (ETDEWEB)

    Sun, Yugang; Hu, Yongxing

    2015-05-26

    A generic route for synthesis of asymmetric nanostructures. This approach utilizes submicron magnetic particles (Fe.sub.3O.sub.4--SiO.sub.2) as recyclable solid substrates for the assembly of asymmetric nanostructures and purification of the final product. Importantly, an additional SiO.sub.2 layer is employed as a mediation layer to allow for selective modification of target nanoparticles. The partially patched nanoparticles are used as building blocks for different kinds of complex asymmetric nanostructures that cannot be fabricated by conventional approaches. The potential applications such as ultra-sensitive substrates for surface enhanced Raman scattering (SERS) have been included.

  9. Basic flow structure in saccular aneurysms: a flow visualization study.

    Science.gov (United States)

    Steiger, H J; Poll, A; Liepsch, D; Reulen, H J

    1987-01-01

    Basic flow patterns were investigated in a set of glass aneurysm models by means of flow visualization methods. Dye injection and streaming double refraction were used to visualize flow. The circulation inside lateral aneurysms arising at a 90 degree angle from a straight parent conduit could not be visualized by the dye-injection technique but could be demonstrated by streaming double refraction. The inflow was seen to arise from the downstream lip of the orifice and to project to the dome of the aneurysm. Backflow to the parent conduit took place along the walls of the aneurysm. In aneurysms located at bifurcations, flow characteristics depended on the geometry of the bifurcation and the flow ratio between the branches. Relatively little intra-aneurysmal flow was demonstrated in side branch-related aneurysms arising distal to an asymmetric 90 degrees bifurcation of the type encountered at the junction of the internal carotid and posterior communicating arteries. Stagnation of flow at the neck and little intra-aneurysmal circulation were found with terminal aneurysms of the basilar bifurcation type if the outflow through the branches was symmetric. With asymmetric outflow, however, or if the axis of the aneurysm did not coincide with that of the afferent vessel, an active rotation developed in these aneurysms. The size of the aneurysm had no influence on the basic pattern of intra-aneurysmal circulation. The use of pulsatile perfusion did not significantly alter the basic flow patterns observed with steady flow. Locally disturbed laminar flow was observed in certain models at physiological Reynold's numbers, but there were no signs of fully developed turbulence.

  10. Asymmetric Swiss-cheese brane-worlds

    Science.gov (United States)

    Gergely, László Á.; Képíró, Ibolya

    2007-07-01

    We study a brane-world cosmological scenario with local inhomogeneities represented by black holes. The brane is asymmetrically embedded into the bulk. The black strings/cigars penetrating the Friedmann brane generate a Swiss-cheese-type structure. This universe forever expands and decelerates, as its general relativistic analogue. The evolution of the cosmological fluid, however, can proceed along four branches, two allowed to have positive energy density, and one of them having the symmetric embedding limit. On this branch a future pressure singularity can arise for either (a) a difference in the cosmological constants of the cosmological and black hole brane regions or (b) a difference in the left and right bulk cosmological constants. While behaviour (a) can be avoided by a redefinition of the fluid variables, (b) establishes a critical value of the asymmetry over which the pressure singularity occurs. We introduce the pressure singularity censorship which bounds the degree of asymmetry in the bulk cosmological constant. We also show as a model-independent generic feature that the asymmetry source term due to the bulk cosmological constant increases in the early universe. In order to obey the nucleosynthesis constraints, the brane tension should be constrained therefore both from below and from above. With the maximal degree of asymmetry obeying the pressure singularity censorship, the higher limit is ten times the lower limit. The degree of asymmetry allowed by present cosmological observations is, however, much less, pushing the upper limit to infinity.

  11. ASYMMETRICALLY SECURED EGMP OVER MANET’S

    Directory of Open Access Journals (Sweden)

    Sayed Mohammed Raja

    2013-06-01

    Full Text Available Group communications are significant in Mobile Ad hoc Networks (MANET. Multicast is an wellorganized technique for applying group communications. Yet, it is interesting to implement effective andaccessible multicast in MANET due to the effort in group member management and multicasting of packets forwarding in an active topology. We suggest a Asymmetrically Secured novel Efficient Geographic Multicast Protocol (EGMP. EGMP uses a practical-zone-based arrangement to implement accessible and effective groupmember management. A network-wide zone-based bi-directional tree is made to attain more well-organized member management and multicast delivery. The location information is used to monitor the zone structure, multicast tree building and multicast packets forwarding, which capably reduce the overhead for route finding and tree structure maintenance. Some approaches have been suggested to further improvement in the efficiency of the protocol, for example, presenting the concept of zone depth for construction an ideal tree structure and adding the position search of group of members with the ordered group member management. To switch empty zone problem met by most routing protocols using a zone structure. Finally, we plan a pattern to switch the security problem faced by the multicasting. The scalability and the productivity of EGMP are assessed through simulations and quantitative analysis. Our results prove that EGMP has great packet delivery ratio, and low control overhead, and is accessible to both group size and network size. EGMP has expressively lower control overhead, data transmission overhead, and multicast group joining delay.

  12. 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.

  13. Evacuation dynamics of asymmetrically coupled pedestrian pairs

    CERN Document Server

    Müller, Frank

    2016-01-01

    We propose and analyze extended floor field cellular automaton models for evacuation dynamics of inhomogeneous pedestrian pairs which are coupled by asymmetric group interactions. Such pairs consist of a leader, who mainly determines the couple's motion and a follower, who has a defined tendency to follow the leader. Examples for such pairs are mother and child or two siblings of different age. We examine the system properties and compare them to the case of a homogeneous crowd. We find a strong impact on evacuation times for the regime of strong pair coupling due to the occurrence of a clogging phenomenon. In addition we obtain a non-trivial dependence of evacuation times on the followers' coupling to the static floor field, which carries the information of the shortest way to the exit location. In particular we find that systems with fully passive followers, who are solely coupled to their leaders, show lower evacuation times than homogeneous systems where all pedestrians have an equal tendency to move towa...

  14. ADMonium: Asymmetric Dark Matter Bound State

    CERN Document Server

    Bi, Xiao-Jun; Ko, P; Li, Jinmian; Li, Tianjun

    2016-01-01

    We propose a novel framework for asymmetric scalar dark matter (ADM), which has interesting collider phenomenology in terms of an unstable ADM bound state (ADMonium) produced via Higgs portals. ADMonium is a natural consequence of the basic features of ADM: the (complex scalar) ADM is charged under a dark local $U(1)_d$ symmetry which is broken at a low scale and provides a light gauge boson $X$. The dark gauge coupling is strong and then ADM can annihilate away into $X$-pair effectively. Therefore, the ADM can form bound state due to its large self-interaction via $X$ mediation. To explore the collider signature of ADMonium, we propose that ADM has a two-Higgs doublet portal. The ADMonium can have a sizable mixing with the heavier Higgs boson, which admits a large cross section of ADMonium production associated with $b\\bar b$. Of particular interest, our setup nicely explains the recent di-photon anomaly at 750 GeV via the events from ${\\rm ADMonium}\\ra 2X(\\ra e^+e^-)$, where the electrons are identified as ...

  15. Asymmetric translation between multiple representations in chemistry

    Science.gov (United States)

    Lin, Yulan I.; Son, Ji Y.; Rudd, James A., II

    2016-03-01

    Experts are more proficient in manipulating and translating between multiple representations (MRs) of a given concept than novices. Studies have shown that instruction using MR can increase student understanding of MR, and one model for MR instruction in chemistry is the chemistry triplet proposed by Johnstone. Concreteness fading theory suggests that presenting concrete representations before abstract representations can increase the effectiveness of MR instruction; however, little work has been conducted on varying the order of different representations during instruction and the role of concreteness in assessment. In this study, we investigated the application of concreteness fading to MR instruction and assessment in teaching chemistry. In two experiments, undergraduate students in either introductory psychology courses or general chemistry courses were given MR instruction on phase changes using different orders of presentation and MR assessment questions based on the representations in the chemistry triplet. Our findings indicate that the order of presentation based on levels of concreteness in MR chemistry instruction is less important than implementation of comprehensive MR assessments. Even after MR instruction, students display an asymmetric understanding of the chemical phenomenon on the MR assessments. Greater emphasis on MR assessments may be an important component in MR instruction that effectively moves novices toward more expert MR understanding.

  16. Computation in dynamically bounded asymmetric systems.

    Directory of Open Access Journals (Sweden)

    Ueli Rutishauser

    2015-01-01

    Full Text Available Previous explanations of computations performed by recurrent networks have focused on symmetrically connected saturating neurons and their convergence toward attractors. Here we analyze the behavior of asymmetrical connected networks of linear threshold neurons, whose positive response is unbounded. We show that, for a wide range of parameters, this asymmetry brings interesting and computationally useful dynamical properties. When driven by input, the network explores potential solutions through highly unstable 'expansion' dynamics. This expansion is steered and constrained by negative divergence of the dynamics, which ensures that the dimensionality of the solution space continues to reduce until an acceptable solution manifold is reached. Then the system contracts stably on this manifold towards its final solution trajectory. The unstable positive feedback and cross inhibition that underlie expansion and divergence are common motifs in molecular and neuronal networks. Therefore we propose that very simple organizational constraints that combine these motifs can lead to spontaneous computation and so to the spontaneous modification of entropy that is characteristic of living systems.

  17. Phase transitions in warm, asymmetric nuclear matter

    International Nuclear Information System (INIS)

    A relativistic mean-field model of nuclear matter with arbitrary proton fraction is studied at finite temperature. An analysis is performed of the liquid-gas phase transition in a system with two conserved charges (baryon number and isospin) using the stability conditions on the free energy, the conservation laws, and Gibbs' criteria for phase equilibrium. For a binary system with two phases, the coexistence surface (binodal) is two dimensional. The Maxwell construction through the phase-separation region is discussed, and it is shown that the stable configuration can be determined uniquely at every density. Moreover, because of the greater dimensionality of the binodal surface, the liquid-gas phase transition is continuous (second order by Ehrenfest's definition), rather than discontinuous (first order), as in familiar one-component systems. Using a mean-field equation of state calibrated to the properties of nuclear matter and finite nuclei, various phase-separation scenarios are considered. The model is then applied to the liquid-gas phase transition that may occur in the warm, dilute matter produced in energetic heavy-ion collisions. In asymmetric matter, instabilities that produce a liquid-gas phase separation arise from fluctuations in the proton concentration (chemical instability), rather than from fluctuations in the baryon density (mechanical instability)

  18. Asymmetric vector mesons produced in nuclear collisions

    CERN Document Server

    Dremin, I M

    2016-01-01

    It is argued that the experimentally observed phenomenon of asymmetric shapes of vector mesons produced in nuclear media during high energy nucleus-nucleus collisions can be explained as Fano-Feshbach resonances. It has been observed that the mass distributions of lepton pairs created at meson decays decline from the traditional Breit-Wigner shape with some excess in the low-mass wing of the resonance. It is clear that the whole phenomenon is related to some interaction with the nuclear medium. Moreover, it can be further detalized in quantum mechanics as the interference of direct and continuum states in Fano-Feshbach effect. To reveal the nature of the interaction it is proposed to use a phenomenological model of the additional contribution due to Cherenkov gluons. They can be created because of the excess of the refractivity index over 1 just in the low-mass wing as required by the classical Cherenkov treatment. In quantum mechanics, this requirement is related to the positive real part of the interaction ...

  19. Barbed congruence of the asymmetric chi calculus

    Institute of Scientific and Technical Information of China (English)

    DONG Xiao-ju; FU Yu-xi

    2006-01-01

    The chi calculus is a model of mobile processes. It has evolved from the pi-calculus with motivations from simplification and communication-as-cut-elimination. This paper studies the chi calculus in the framework incorporating asymmetric communication. The major feature of the calculus is the identification of two actions:x/x and τ. The investigation on the barbed bisimilarity shows how the property affects the observational theory.Based on the definition of the barbed bisimilarity, the simulation properties of the barbed bisimilarity are studied. It shows that the algebraic properties of the barbed bisimilarity have changed greatly compared with the chi calculus. Although the definition of the barbed bisimilarity is very simple, the property of closeness under contexts makes it difficult to understand the barbed bisimilarity directly. Therefore an open style definition of the barbed bisimilarity is given, which is a context free description of barbed bisimilarity. Its definition is complex,but it is a well-behaved relation for it coincides with the barbed bisimilarity. It also helps to build an axiomatization system for the barbed congruence. Besides the axioms for the strong barbed bisimilarity, the paper proposes a new tau law and four new update laws for the barbed congruence. Both the operational and algebraic properties of the enriched calculus improve the understanding of the bisimulation behaviors of the model.

  20. Flexible 3D Nanoporous Graphene for Desalination and Bio-decontamination of Brackish Water via Asymmetric Capacitive Deionization.

    Science.gov (United States)

    El-Deen, Ahmed G; Boom, Remko M; Kim, Hak Yong; Duan, Hongwei; Chan-Park, Mary B; Choi, Jae-Hwan

    2016-09-28

    Nanoporous graphene based materials are a promising nanostructured carbon for energy storage and electrosorption applications. We present a novel and facile strategy for fabrication of asymmetrically functionalized microporous activated graphene electrodes for high performance capacitive desalination and disinfection of brackish water. Briefly, thiocarbohydrazide coated silica nanoparticles intercalated graphene sheets are used as a sacrificial material for creating mesoporous graphene followed by alkaline activation process. This fabrication procedure meets the ideal desalination pore diameter with ultrahigh specific surface area ∼ 2680 m(2) g(-1) of activated 3D graphene based micropores. The obtained activated graphene electrode is modified by carboxymethyl cellulose as negative charge (COO(-2)) and disinfectant quaternary ammonium cellulose with positively charged polyatomic ions of the structure (NR4(+)). Our novel asymmetric coated microporous activated 3D graphene employs nontoxic water-soluble binder which increases the surface wettability and decreases the interfacial resistance and moreover improves the electrode flexibility compared with organic binders. The desalination performance of the fabricated electrodes was evaluated by carrying out single pass mode experiment under various cell potentials with symmetric and asymmetric cells. The asymmetric charge coated microporous activated graphene exhibits exceptional electrosorption capacity of 18.43 mg g(-1) at a flow rate of 20 mL min(-1) upon applied cell potential of 1.4 V with initial NaCl concentration of 300 mg L(-1), high charge efficiency, excellent recyclability, and, moreover, good antibacterial behavior. The present strategy provides a new avenue for producing ultrapure water via green capacitive deionization technology.

  1. Chiral Brønsted Acids for Asymmetric Organocatalysis

    Science.gov (United States)

    Kampen, Daniela; Reisinger, Corinna M.; List, Benjamin

    Chiral Brønsted acid catalysis is an emerging area of organocatalysis. Since the pioneering studies of the groups of Akiyama and Terada in 2004 on the use of chiral BINOL phosphates as powerful Brønsted acid catalysts in asymmetric Mannich-type reactions, numerous catalytic asymmetric transformations involving imine activation have been realized by means of this catalyst class, including among others Friedel-Crafts, Pictet-Spengler, Strecker, cycloaddition reactions, transfer hydrogenations, and reductive aminations. More recently, chiral BINOL phosphates found application in multicomponent and cascade reactions as for example in an asymmetric version of the Biginelli reaction. With the introduction of chiral BINOL-derived N-triflyl phosphoramides in 2006, asymmetric Brønsted acid catalysis is no longer restricted to reactive substrates. Also certain carbonyl compounds can be activated through these stronger Brønsted acid catalysts. In dealing with sensitive substrate classes, chiral dicarboxylic acids proved of particular value.

  2. Asymmetric Aldol Reaction with Formaldehyde: a Challenging Process.

    Science.gov (United States)

    Meninno, Sara; Lattanzi, Alessandra

    2016-08-01

    The asymmetric aldol reaction with formaldehyde is a fundamental carbon-carbon bond-forming reaction in organic synthesis, as well as in the quest of the origin of life, as it is thought to have been the first "molecular brick" involved in the synthetic path to complex sugars. Products of aldol reactions, i.e., the β-hydroxy carbonyl compounds, are versatile building blocks used to access a great variety of functionalised molecules. The employment of formaldehyde, as a C1 symmetric electrophile, in aldol reactions can be likely considered the most challenging, yet simplest, process to introduce a hydroxymethyl group in an asymmetric fashion. In this account, an overview of the progress achieved in the asymmetric metal- and organocatalysed aldol reaction, using readily available formalin or paraformaldehyde sources, is illustrated. Our recent contribution to this area, with the application of asymmetric hydroxymethylation in cascade processes for the synthesis of γ-butyrolactones, is also shown. PMID:27328802

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

    Energy Technology Data Exchange (ETDEWEB)

    Cohen, T.D. [Washington Univ., Seattle, WA (United States). Dept. of Physics; Broniowski, W. [Institute of Nuclear Physics, Cracow (Poland)

    1994-12-01

    We analyze the chiral limit in dense isoptin-asymmetric nuclear matter. It is shown that the pseudo-Goldstone modes in this system are qualitatively different from the case of isospin-symmetric matter. (author). 20 refs.

  4. A novel and practical asymmetric synthesis of dapoxetine hydrochloride

    Directory of Open Access Journals (Sweden)

    Yijun Zhu

    2015-12-01

    Full Text Available A novel and practical asymmetric synthesis of dapoxetine hydrochloride by using the chiral auxiliary (S-tert-butanesulfinamide was explored. The synthesis was concise, mild, and easy to perform. The overall yield and stereoselectivity were excellent.

  5. Asymmetric Synthesis of ( - ) -(2R, 3R, 6S ) -Irnigaine

    Institute of Scientific and Technical Information of China (English)

    MA, Nan; MA, Da-Wei

    2003-01-01

    Asymmetric synthesis of irnigaine was achieved starting from an enantiopure β-amino ester 5 using the condensation of amino alcohol 2 with acetylacetone and the subsequent intramolecular cyclization as the key steps.

  6. 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.

  7. Loss Aversion and the Asymmetric Transmission of Monetary Policy

    DEFF Research Database (Denmark)

    Santoro, Emiliano; Petrella, Ivan; Pfajfar, Damjan;

    2014-01-01

    There is widespread evidence that monetary policy exerts asymmetric effects on output over contractions and expansions in economic activity, while price responses display no sizeable asymmetry. To rationalize these facts we develop a dynamic general equilibrium model where households’ utility...

  8. Asymmetric dynamic phase holographic grating in nematic liquid crystal

    Science.gov (United States)

    Ren, Chang-Yu; Shi, Hong-Xin; Ai, Yan-Bao; Yin, Xiang-Bao; Wang, Feng; Ding, Hong-Wei

    2016-09-01

    A new scheme for recording a dynamic phase grating with an asymmetric profile in C60-doped homeotropically aligned nematic liquid crystal (NLC) was presented. An oblique incidence beam was used to record the thin asymmetric dynamic phase holographic grating. The diffraction efficiency we achieved is more than 40%, exceeding the theoretical limit for symmetric profile gratings. Both facts can be explained by assuming that a grating with an asymmetric saw-tooth profile is formed in the NLC. Finally, physical mechanism and mathematical model for characterizing the asymmetric phase holographic grating were presented, based on the photo-refractive-like (PR-like) effect. Project supported by the Science and Technology Programs of the Educational Committee of Heilongjiang Province, China (Grant No. 12541730) and the National Natural Science Foundation of China (Grant No. 61405057).

  9. 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.

  10. 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.

  11. Abundance of Asymmetric Dark Matter in Brane World Cosmology

    Science.gov (United States)

    Abdusattar, Haximjan; Iminniyaz, Hoernisa

    2016-09-01

    Relic abundance of asymmetric Dark Matter particles in brane world cosmological scenario is investigated in this article. Hubble expansion rate is enhanced in brane world cosmology and it affects the relic abundance of asymmetric Dark Matter particles. We analyze how the relic abundance of asymmetric Dark Matter is changed in this model. We show that in such kind of nonstandard cosmological scenario, indirect detection of asymmetric Dark Matter is possible if the cross section is small enough which let the anti-particle abundance kept in the same amount with the particle. We show the indirect detection signal constraints can be used to such model only when the cross section and the 5-dimensional Planck mass scale are in appropriate values. Supported by the National Natural Science Foundation of China under Grant No. 11365022

  12. Asymmetric wave transmission in a diatomic acoustic/elastic metamaterial

    Science.gov (United States)

    Li, Bing; Tan, K. T.

    2016-08-01

    Asymmetric acoustic/elastic wave transmission has recently been realized using nonlinearity, wave diffraction, or bias effects, but always at the cost of frequency distortion, direction shift, large volumes, or external energy. Based on the self-coupling of dual resonators, we propose a linear diatomic metamaterial, consisting of several small-sized unit cells, to realize large asymmetric wave transmission in low frequency domain (below 1 kHz). The asymmetric transmission mechanism is theoretically investigated, and numerically verified by both mass-spring and continuum models. This passive system does not require any frequency conversion or external energy, and the asymmetric transmission band can be theoretically predicted and mathematically controlled, which extends the design concept of unidirectional transmission devices.

  13. 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.

  14. Numerical study of asymmetric driven reconnection at dayside magnetopause

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    A two-dimensional compressible MHD code has been used to numerically study the asymmetric driven reconnection processes in the vicinity of the magnetopause. The initial magnetic field configuration is assumed to be in a mechanical equilibrium state. The cases with identical temperatures (Tm0/Ts0=1.0) and four different ratios of magnetic field strength (Q=Bm0/Bs0=1.0, 1.5, 2.0, 2.5), and the case with Tm0/Ts0=2.0 and Q=1.5 are investigated (Bm0, Tm0 and Bs0, Ts0 are the initial magnetic strength and temperature outside the current sheet on the magnetosphere and the magnetosheath, respectively ). When the magnetic field on the magnetosheath side is set as southward, a recurrent formation of multiple magnetic bubbles with various scales occurs under the action of the inward plasma flow imposed at the left and right boundaries. In the simulation, some bubbles coalesce into a bigger one and then it is convected out of the simulation domain; the others are convected through the top boundary all alone. Thus, the plasmoid events with different scales and different time intervals take place intermittently and the impulsive features of magnetic reconnection are clearly shown. The multiple magnetic islands are all high-temperature and large-density regions in comparison with the ambient environment. The bipolar signatures or fluctuant variations of normal magnetic field component are generated by the formation of multiple magnetic islands. This result is similar to the FTEs signature.

  15. Corporate underinvestment in the presence of symmetric and asymmetric information

    OpenAIRE

    Hartl, Johannes

    2012-01-01

    Underinvestment and Asymmetric Information: Underinvestment arises when a firm passes up a profitable investment opportunity. The first part of the dissertation deals with corporate underinvestment in the presence of asymmetric information. Specifically, the seminal model by Myers and Majluf (1984) is presented in detail. In this three-period model, corporations have the opportunity to undertake a profitable new investment project, but have to finance it by issuing new shares. There is asy...

  16. Large deviation function of the partially asymmetric exclusion process.

    Science.gov (United States)

    Lee, D S; Kim, D

    1999-06-01

    The large deviation function obtained recently by Derrida and Lebowitz [Phys. Rev. Lett. 80, 209 (1998)] for the totally asymmetric exclusion process is generalized to the partially asymmetric case in the scaling limit. The asymmetry parameter rescales the scaling variable in a simple way. The finite-size corrections to the universal scaling function and the universal cumulant ratio are also obtained to the leading order. PMID:11969632

  17. Equation of state and phase transitions in asymmetric nuclear matter

    OpenAIRE

    Kolomietz, V. M.; Sanzhur, A. I.; Shlomo, S.; Firin, S. A.

    2001-01-01

    The structure of the 3-dimension pressure-temperature-asymmetry surface of equilibrium of the asymmetric nuclear matter is studied within the thermal Thomas-Fermi approximation. Special attention is paid to the difference of the asymmetry parameter between the boiling sheet and that of the condensation sheet of the surface of equilibrium. We derive the condition of existence of the regime of retrograde condensation at the boiling of the asymmetric nuclear matter. We have performed calculation...

  18. Absolute Asymmetric Synthesis: The Origin, Control, and Amplification of Chirality

    OpenAIRE

    Delden, Richard A. van; Feringa, Bernard

    1999-01-01

    One of the fundamental and intriguing aspects of life is the homochirality of the essential molecules. From the early days of stereochemistry, the origin of chirality in biological systems has been a challenge to the chemical sciences and numerous theories and experiments have been reported. Despite the great progress in asymmetric synthesis, there are only a few genuine absolute asymmetric syntheses known today. Novel approaches based on the interplay of molecular biology, organic chemistry,...

  19. 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...

  20. Entangling two oscillators with arbitrary asymmetric initial states

    OpenAIRE

    Yang, Chui-Ping; Su, Qi-Ping; Zheng, Shi-Biao; Nori, Franco; Han, Siyuan

    2016-01-01

    A Hamiltonian is presented, which can be used to convert any asymmetric state $|\\varphi \\rangle_{a}|\\phi \\rangle_{b}$ of two oscillators $a$ and $b$ into an entangled state. Furthermore, with this Hamiltonian and local operations only, two oscillators, initially in any asymmetric initial states, can be entangled with a third oscillator. The prepared entangled states can be engineered with an arbitrary degree of entanglement. A discussion on the realization of this Hamiltonian is given. Numeri...

  1. The Rationality of EIA Forecasts under Symmetric and Asymmetric Loss

    OpenAIRE

    Auffhammer, Maximilian

    2005-01-01

    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 a...

  2. Circular Motion of Asymmetric Self-Propelling Particles

    Science.gov (United States)

    Kümmel, Felix; ten Hagen, Borge; Wittkowski, Raphael; Buttinoni, Ivo; Eichhorn, Ralf; Volpe, Giovanni; Löwen, Hartmut; Bechinger, Clemens

    2013-05-01

    Micron-sized self-propelled (active) particles can be considered as model systems for characterizing more complex biological organisms like swimming bacteria or motile cells. We produce asymmetric microswimmers by soft lithography and study their circular motion on a substrate and near channel boundaries. Our experimental observations are in full agreement with a theory of Brownian dynamics for asymmetric self-propelled particles, which couples their translational and orientational motion.

  3. Cooperative Mechanism of Supply Chain Under Asymmetric Information

    Institute of Scientific and Technical Information of China (English)

    郭敏; 王红卫; 瞿坦

    2003-01-01

    The cooperative mechanism is one main issue in the decentralized supply chain system, especially in an asymmetric information structure. We analyze the non-cooperative game behavior of a 2-echelon distribution supply chain, compare the results with the system optimal solution, and give the supplier dominated cooperative mechanisms. We also analyze the validity of our contract under the asymmetric retailers' holding cost information and give some useful conclusions.

  4. Evidence for asymmetrical hybridization despite pre- and post-pollination reproductive barriers between two Silene species.

    Science.gov (United States)

    Zhang, Jin-Ju; Montgomery, Benjamin R; Huang, Shuang-Quan

    2016-01-01

    Interspecific hybridization is widespread among plants; nevertheless, pre- and post-zygotic isolating mechanisms may maintain species integrity for interfertile species in sympatry despite some gene flow. Interspecific hybridization and potential isolating barriers were evaluated between co-flowering Silene asclepiadea and Silene yunnanensis in an alpine community in southwest China. We investigated morphological and molecular (nuclear microsatellites and chloroplast gene sequence) variation in sympatric populations of S. asclepiadea and S. yunnanensis. Additionally, we analyzed pollinator behaviour and compared reproductive success between the putative hybrids and their parental species. Both the molecular and morphological data indicate that there were putative natural hybrids in the field, with S. asclepiadae the ovule parent and S. yunnanensis the pollen parent. Bumblebees were the primary visitors to S. asclepiadae and putative hybrids, while butterflies were the primary visitors to S. yunnanensis Pollen production and viability were significantly lower in putative hybrids than the parental species. The direction of hybridization is quite asymmetric from S. yunnanensis to S. asclepiadea Protandry combined with later peak flowering of S. yunnanensis, and pollinator preference may have contributed to the asymmetric pattern of hybridization, but putative hybrids were rare. Our results thus suggest that despite gene flow, S. asclepiadea and S. yunnanensis can maintain species boundaries, perhaps as a result of floral isolation and low fecundity of the hybrids. PMID:27178066

  5. Experiments on the water entry of asymmetric wedges using particle image velocimetry

    Science.gov (United States)

    Shams, Adel; Jalalisendi, Mohammad; Porfiri, Maurizio

    2015-02-01

    In this work, we experimentally characterize the water entry of an asymmetric wedge into a quiescent fluid through particle image velocimetry (PIV). The wedge enters the water surface with an orthogonal velocity falling from a fixed height. We systematically vary the heel angle to elucidate the effect of asymmetric impact on the flow physics and on the fluid-structure interaction. The pressure field in the fluid is reconstructed from PIV data by integrating the Poisson equation. We find that the impact configuration significantly influences both the velocity and the pressure field, ultimately, regulating the hydrodynamic loading on the wedge. Specifically, as the heel angle increases, the location of maximum velocity of the flow moves from the pile-up region to the keel. At the same time, the pressure field significantly decreases in the vicinity of the keel, reaching values smaller than the atmospheric pressure. The spatiotemporal evolution of the hydrodynamic loading is thus controlled by the heel angle, with larger heel angles resulting into more rapid and sustained impacts.

  6. Flexible Asymmetric Encapsulation for Dehydration-Responsive Hybrid Microfibers.

    Science.gov (United States)

    Chaurasia, Ankur S; Sajjadi, Shahriar

    2016-08-01

    A new class of smart alginate microfibers with asymmetric oil encapsulates is introduced. These fibers are produced by injecting an aqueous alginate solution into an outer aqueous calcium chloride solution to form alginate fibers, which are asymmetrically loaded with oil entities through eccentrically aligned inner capillaries. The fiber morphology and its degree of asymmetry can be tuned via altering the size, location, and frequency of the oil encapsulates. These asymmetric fibers reveal significant potential for applications where conventional symmetric fibers fail to perform. It is shown how asymmetric oil-encapsulated fibers can become dehydration-sensitive, and trigger the release of encapsulates if their hydration level drops below a critical value. It is also shown how the triggered response could be switched off on demand by stabilizing the oil encapsulates. The capability of asymmetric fibers to carry and release multiple cargos in parallel is demonstrated. The fibers loaded with equal-sized spheres are more asymmetric than those containing unequal drops, have a higher tensile strength, and show better potential for a triggered response. PMID:27352241

  7. Asymmetric central bank preferences and inflation rate in Tunisia

    Directory of Open Access Journals (Sweden)

    Imen KOBBI

    2013-04-01

    Full Text Available This article fits into the new strand of literature related to the asymmetric central bank preferences and its effect on the inflation dynamic. In reality, the central banker preferences are more likely to be asymmetric. Central banker can be, for various reasons, more averse toward deviations from target with one sign more than deviations from target with the other sign. The interaction of asymmetric central bank preferences with uncertainty arising from the volatility of inflation and output may affect the inflation movements. This paper aims to check the hypothesis that asymmetric central bank preferences are able to explain inflation rate for the case of Tunisia and to understand Central Bank of Tunisia preferences toward inflation rate and output during the period ranging from 1993 to 2010. We refer to a standard monetary model that includes asymmetric loss function and a linear supply curve which acts as a constraint on the central bank behavior. The results show that the inflation rate depends on the output gap and on the conditional variance of inflation and provide evidence for asymmetric central bank preferences. The Central Bank of Tunisia seems to be more averse to high inflation which is consistent with its ultimate goal explicitly announced to preserve price stability.

  8. Asymmetric nucleosomes flank promoters in the budding yeast genome.

    Science.gov (United States)

    Ramachandran, Srinivas; Zentner, Gabriel E; Henikoff, Steven

    2015-03-01

    Nucleosomes in active chromatin are dynamic, but whether they have distinct structural conformations is unknown. To identify nucleosomes with alternative structures genome-wide, we used H4S47C-anchored cleavage mapping, which revealed that 5% of budding yeast (Saccharomyces cerevisiae) nucleosome positions have asymmetric histone-DNA interactions. These asymmetric interactions are enriched at nucleosome positions that flank promoters. Micrococcal nuclease (MNase) sequence-based profiles of asymmetric nucleosome positions revealed a corresponding asymmetry in MNase protection near the dyad axis, suggesting that the loss of DNA contacts around H4S47 is accompanied by protection of the DNA from MNase. Chromatin immunoprecipitation mapping of selected nucleosome remodelers indicated that asymmetric nucleosomes are bound by the RSC chromatin remodeling complex, which is required for maintaining nucleosomes at asymmetric positions. These results imply that the asymmetric nucleosome-RSC complex is a metastable intermediate representing partial unwrapping and protection of nucleosomal DNA on one side of the dyad axis during chromatin remodeling.

  9. 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

    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...... 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 process could be adequately described by a single 1st order kinetic model.By varying the donor-to-acceptor lipid mass ratio in the range.......45) and Sudan III (clogP 6.83). For the more lipophilic compounds, the rate of transfer from the donor liposomes followed the rank order Sudan IV (fastest)>Oil Red O>Sudan Black>p-THPP (slowest). For an equimolar donor-to-acceptor lipid mass ratio, half-lifes of transfer in the range of 12min (Sudan IV...

  10. Asymmetric glottal jet deflection: differences of two- and three-dimensional models.

    Science.gov (United States)

    Mattheus, Willy; Brücker, Christoph

    2011-12-01

    Flow is studied through a channel with an oscillating orifice mimicking the motion of the glottal-gap during phonation. Simulations with prescribed flow and wall-motion are carried out for different orifice geometries, a 2D slit-like and a 3D lens-like one. Although the jet emerges from a symmetric orifice a significant deflection occurs in case of the slit-like geometry, contrary to the 3D lens-like one. The results demonstrate the dependency of jet entrainment and vortex dynamics on the orifice geometry and the interpretation of asymmetric jet deflection with regard to the relevance of the Coanda effect in the process of human phonation. PMID:22225129

  11. Asymmetric transfer of auditory perceptual learning

    Directory of Open Access Journals (Sweden)

    Sygal eAmitay

    2012-11-01

    Full Text Available Perceptual skills can improve dramatically even with minimal practice. A major and practical benefit of learning, however, is in transferring the improvement on the trained task to untrained tasks or stimuli, yet the mechanisms underlying this process are still poorly understood. Reduction of internal noise has been proposed as a mechanism of perceptual learning, and while we have evidence that frequency discrimination (FD learning is due to a reduction of internal noise, the source of that noise was not determined. In this study, we examined whether reducing the noise associated with neural phase locking to tones can explain the observed improvement in behavioural thresholds. We compared FD training between two tone durations (15 and 100 ms that straddled the temporal integration window of auditory nerve fibers upon which computational modeling of phase locking noise was based. Training on short tones resulted in improved FD on probe tests of both the long and short tones. Training on long tones resulted in improvement only on the long tones. Simulations of FD learning, based on the computational model and on signal detection theory, were compared with the behavioral FD data. We found that improved fidelity of phase locking accurately predicted transfer of learning from short to long tones, but also predicted transfer from long to short tones. The observed lack of transfer from long to short tones suggests the involvement of a second mechanism. Training may have increased the temporal integration window which could not transfer because integration time for the short tone is limited by its duration. Current learning models assume complex relationships between neural populations that represent the trained stimuli. In contrast, we propose that training-induced enhancement of the signal-to-noise ratio offers a parsimonious explanation of learning and transfer that easily accounts for asymmetric transfer of learning.

  12. 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.

  13. Asymmetric Dimethyl Arginine in Hypothyroid Patients

    International Nuclear Information System (INIS)

    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 T4 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 T4 as compared to controls. There were significant negative correlations between NO and both ADMA (r2 = 0.84) and free T4 (r2 = 0.95) in overt hypothyroid group while significant positive correlation (r2 = 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

  14. Hemispherical anomaly from asymmetric initial states

    Science.gov (United States)

    Ashoorioon, Amjad; Koivisto, Tomi

    2016-08-01

    We investigate if the hemispherical asymmetry in the CMB is produced from "asymmetric" excited initial conditions. We show that in the limit where the deviations from the Bunch-Davies vacuum are large and the scale of new physics is maximally separated from the inflationary Hubble parameter, the primordial power spectrum is modulated only by position-dependent dipole and quadrupole terms. Requiring the dipole contribution in the power spectrum to account for the observed power asymmetry, A =0.07 ±0.022 , we show that the amount of quadrupole terms is roughly equal to A2. The mean local bispectrum, which gets enhanced for the excited initial state, is within the 1 σ bound of Planck 2015 results for a large field model, fNL≃4.17 , but is reachable by future CMB experiments. The amplitude of the local non-Gaussianity modulates around this mean value, depending on the angle that the correlated patches on the 2d CMB surface make with the preferred direction. The amount of variation is minimized for the configuration in which the short and long wavelength modes are around the preferred pole and |k→3|≈|k→l ≈10|≪|k→1|≈|k→2|≈|k→l ≈2500| with fNLmin≈3.64 . The maximum occurs when these modes are at the antipode of the preferred pole, fNLmax≈4.81 . The difference of non-Gaussianity between these two configurations is as large as ≃1.17 , which can be used to distinguish this scenario from other scenarios that try to explain the observed hemispherical asymmetry.

  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. 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.

  17. Impact parameter dependence of collective flow and its disappearance for different mass asymmetries

    CERN Document Server

    Goyal, Supriya

    2011-01-01

    We study the role of impact parameter on the collective flow and its disappearance for different mass asymmetric reactions. The mass asymmetry is varied from 0 to 0.7 keeping the total mass of the system fixed. Our results clearly indicate a significant role of impact parameter on the collective flow and its disappearance for the mass asymmetric reactions. The impact parameter dependence is also found to vary with mass asymmetry of the reaction.

  18. Visualization of entry flow separation for oscillating flow in tubes

    Science.gov (United States)

    Qiu, Songgang; Simon, Terence W.

    1992-01-01

    Neutrally buoyant helium-filled soap bubbles with laser illumination are used to document entry flow separation for oscillating flow in tubes. For a symmetric entry case, the size of the separation zone appears to mildly depend on Reynolds number in the acceleration phase, but is roughly Reynolds number independent in the deceleration phase. For the asymmetric entry case, the separation zone was larger and appeared to grow somewhat during the deceleration phase. The separation zones for both entry geometry cases remain relatively small throughout the cycle. This is different from what would be observed in all-laminar, oscillator flows and is probably due to the high turbulence of the flow, particularly during the deceleration phase of the cycle.

  19. Analysis and testing of two-dimensional vented Coanda ejectors with asymmetric variable area mixing sections

    Science.gov (United States)

    Maroti, L. A.; Hill, P. G.; Armstrong, R. L.; Haines, D. M.

    1976-01-01

    The analysis of asymmetric, curved (Coanda) ejector flow has been completed using a finite difference technique and a quasi-orthogonal streamline coordinate system. The boundary layer type jet mixing analysis accounts for the effect of streamline curvature in pressure gradients normal to the streamlines and on eddy viscosities. The analysis assured perfect gases, free of pressure discontinuities and flow separation and treated three compound flows of supersonic and subsonic streams. Flow parameters and ejector performance were measured in a vented Coanda flow geometry for the verification of the computer analysis. A primary converging nozzle with a discharge geometry of 0.003175 m x 0.2032 m was supplied with 0.283 cu m/sec of air at about 241.3 KPa absolute stagnation pressure and 82 C stagnation temperature. One mixing section geometry was used with a 0.127 m constant radius Coanda surface. Eight tests were run at spacing between the Coanda surface and primary nozzle 0.01915 m and 0.318 m and at three angles of Coanda turning: 22.5 deg, 45.0 deg, and 75.0 deg. The wall static pressures, the loci of maximum stagnation pressures, and the stagnation pressure profiles agree well between analytical and experimental results.

  20. Flow Rounding

    OpenAIRE

    Kang, Donggu; Payor, James

    2015-01-01

    We consider flow rounding: finding an integral flow from a fractional flow. Costed flow rounding asks that we find an integral flow with no worse cost. Randomized flow rounding requires we randomly find an integral flow such that the expected flow along each edge matches the fractional flow. Both problems are reduced to cycle canceling, for which we develop an $O(m \\log(n^2/m))$ algorithm.

  1. High performance of a solid-state flexible asymmetric supercapacitor based on graphene films

    Science.gov (United States)

    Choi, Bong Gill; Chang, Sung-Jin; Kang, Hyun-Wook; Park, Chan Pil; Kim, Hae Jin; Hong, Won Hi; Lee, Sanggap; Huh, Yun Suk

    2012-07-01

    Solid-state flexible energy storage devices hold the key to realizing portable and flexible electronic devices. Achieving fully flexible energy storage devices requires that all of the essential components (i.e., electrodes, separator, and electrolyte) with specific electrochemical and interfacial properties are integrated into a single solid-state and mechanically flexible unit. In this study, we describe the fabrication of solid-state flexible asymmetric supercapacitors based on an ionic liquid functionalized-chemically modified graphene (IL-CMG) film (as the negative electrode) and a hydrous RuO2-IL-CMG composite film (as the positive electrode), separated with polyvinyl alcohol-H2SO4 electrolyte. The highly ordered macroscopic layer structures of these films arising through direct flow self-assembly make them simultaneously excellent electrical conductors and mechanical supports, allowing them to serve as flexible electrodes and current collectors in supercapacitor devices. Our asymmetric supercapacitors have been optimized with a maximum cell voltage up to 1.8 V and deliver a high energy density (19.7 W h kg-1) and power density (6.8 kW g-1), higher than those of symmetric supercapacitors based on IL-CMG films. They can operate even under an extremely high rate of 10 A g-1 with 79.4% retention of specific capacitance. Their superior flexibility and cycling stability are evident in their good performance stability over 2000 cycles under harsh mechanical conditions including twisted and bent states. These solid-state flexible asymmetric supercapacitors with their simple cell configuration could offer new design and fabrication opportunities for flexible energy storage devices that can combine high energy and power densities, high rate capability, and long-term cycling stability.Solid-state flexible energy storage devices hold the key to realizing portable and flexible electronic devices. Achieving fully flexible energy storage devices requires that all of the

  2. 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.

  3. 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.

  4. 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)

  5. Factors affecting the kinematic interpretation of asymmetric boudinage in shear zones

    Science.gov (United States)

    Goldstein, Arthur G.

    Based on work along a major mylonite zone in the northern Appalachians and scale model studies, a new mechanism for the origin of asymmetric boudins in shear zones is proposed. Along the Honey Hill Fault in southern Connecticut, granitic sills intruded into calc-silicate gneisses and schists were oblique to the boundaries of the mylonite zone and experienced the following sequence in the production of sigmoidal boudins: (1) as the calc-silicate schists experienced mylonitization and flow, the more competent, coarse-grained granitic sills deformed by extensional fracturing and quartz veining; (2) continued extension of granitic sills was accommodated by 'normal' shear on early-formed quartz veins; (3) continuing extension of sills and ductile modification of the corners of boudins resulted in granitic 'fish' with tails which stream from the top of the boudin in the 'down-dip' direction and from the bottom in the 'up-dip' direction. Based on a variety of kinematic indicators, the sense of asymmetry of the tails is identical to that expected for recrystallization tails on sheared augen (σ structure). Models composed of silicone putty and Plasticine were created to investigate the effect of pre-shearing geometry on boudin evolution, and were deformed in a simple shear device. The models reproduce the kinematics deduced from field relations and suggest that one of the primary factors in controlling the amount of extension is the angle which early veins make with the shear zone boundary. Varying the angular relationships in the models suggests that other pre-shearing geometric factors may affect the geometry of boudins formed in this way. Boudins formed through this mechanism appear very similar to Hanmer's type II asymmetric boudins. Because the pre-shearing geometry can exert a control on boudin asymmetry, caution should be used when attempting to deduce shear sense or shear strain values from asymmetric boudinage.

  6. Estimation of flood warning runoff thresholds in ungauged basins with asymmetric error functions

    Directory of Open Access Journals (Sweden)

    E. Toth

    2015-06-01

    Full Text Available In many real-world flood forecasting systems, the runoff thresholds for activating warnings or mitigation measures correspond to the flow peaks with a given return period (often the 2-year one, that may be associated with the bankfull discharge. At locations where the historical streamflow records are absent or very limited, the threshold can be estimated with regionally-derived empirical relationships between catchment descriptors and the desired flood quantile. Whatever is the function form, such models are generally parameterised by minimising the mean square error, that assigns equal importance to overprediction or underprediction errors. Considering that the consequences of an overestimated warning threshold (leading to the risk of missing alarms generally have a much lower level of acceptance than those of an underestimated threshold (leading to the issuance of false alarms, the present work proposes to parameterise the regression model through an asymmetric error function, that penalises more the overpredictions. The estimates by models (feedforward neural networks with increasing degree of asymmetry are compared with those of a traditional, symmetrically-trained network, in a rigorous cross-validation experiment referred to a database of catchments covering the Italian country. The analysis shows that the use of the asymmetric error function can substantially reduce the number and extent of overestimation errors, if compared to the use of the traditional square errors. Of course such reduction is at the expense of increasing underestimation errors, but the overall accurateness is still acceptable and the results illustrate the potential value of choosing an asymmetric error function when the consequences of missed alarms are more severe than those of false alarms.

  7. 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.

  8. Asymmetric and axisymmetric dynamics of tropical cyclones

    Science.gov (United States)

    Persing, J.; Montgomery, M. T.; McWilliams, J. C.; Smith, R. K.

    2013-12-01

    during the 3-D intensification process the convection has not yet organized into annular rings, the azimuthally averaged heating rate and radial gradient thereof is considerably less than that in the AX model. This lack of organization results broadly in a slower intensification rate in the 3-D model and leads ultimately to a weaker mature vortex after 12 days of model integration. While azimuthal mean heating rates in the 3-D model are weaker than those in the AX model, local heating rates in the 3-D model exceed those in the AX model and at times the vortex in the 3-D model intensifies more rapidly than AX. Analyses of the 3-D model output do not support a recent hypothesis concerning the key role of small-scale vertical mixing processes in the upper-tropospheric outflow in controlling the intensification process. In the 3-D model, surface drag plays a particularly important role in the intensification process for the prototype intensification problem on meteorologically relevant timescales by helping foster the organization of convection in azimuth. There is a radical difference in the behaviour of the 3-D and AX simulations when the surface drag is reduced or increased from realistic values. Borrowing from ideas developed in a recent paper, we give a partial explanation for this difference in behaviour. Our results provide new qualitative and quantitative insight into the differences between the asymmetric and symmetric dynamics of tropical cyclones and would appear to have important consequences for the formulation of a fluid dynamical theory of tropical cyclone intensification and mature intensity. In particular, the results point to some fundamental limitations of strict axisymmetric theory and modelling for representing the azimuthally averaged behaviour of tropical cyclones in three dimensions.

  9. Asymmetric and axisymmetric dynamics of tropical cyclones

    Directory of Open Access Journals (Sweden)

    J. Persing

    2013-05-01

    into annular rings, the azimuthally-averaged heating rate and radial gradient thereof is considerably less than that in the AX model. This lack of organization results broadly in a slower intensification rate in the 3-D model and leads ultimately to a weaker mature vortex after 12 days of model integration. While axisymmetric heating rates in the 3-D model are weaker than those in the AX model, local heating rates in the 3-D model exceed those in the AX model and at times the vortex in the 3-D model intensifies more rapidly than AX. Analyses of the 3-D model output do not support a recent hypothesis concerning the key role of small-scale vertical mixing processes in the upper-tropospheric outflow in controlling the intensification process. In the 3-D model, surface drag plays a particularly important role in the intensification process for the prototype intensification problem on meteorologically relevant time scales by helping foster the organization of convection in azimuth. There is a radical difference in the behaviour of the 3-D and AX simulations when the surface drag is reduced or increased from realistic values. Borrowing from ideas developed in a recent paper, we give a partial explanation for this difference in behaviour. Our results provide new qualitative and quantitative insight into the differences between the asymmetric and symmetric dynamics of tropical cyclones and would appear to have important consequences for the formulation of a fluid dynamical theory of tropical cyclone intensification and mature intensity. In particular, the results point to some fundamental limitations of strict axisymmetric theory and modelling for representing the azimuthally-averaged behaviour of tropical cyclones in three dimensions.

  10. Continuous Flavor Symmetries and the Stability of Asymmetric Dark Matter

    CERN Document Server

    Bishara, Fady

    2014-01-01

    Generically, the asymmetric interactions in asymmetric dark matter (ADM) models lead to decaying DM. We show that, for ADM that carries nonzero baryon number, the continuous flavor symmetries that generate the flavor structure in the quark sector also imply a looser lower bound on the mass scale of the asymmetric mediators between the dark and visible sectors. The mediators for $B=2$ ADM that can produce a signal in the future indirect dark matter searches can thus also be searched for at the LHC. For two examples of the mediator models, with either the MFV or Froggatt-Nielsen flavor breaking pattern, we derive the FCNC constraints and discuss the search strategies at the LHC.

  11. Experimental Quantification of Asymmetric Einstein-Podolsky-Rosen Steering.

    Science.gov (United States)

    Sun, Kai; Ye, Xiang-Jun; Xu, Jin-Shi; Xu, Xiao-Ye; Tang, Jian-Shun; Wu, Yu-Chun; Chen, Jing-Ling; Li, Chuan-Feng; Guo, Guang-Can

    2016-04-22

    Einstein-Podolsky-Rosen (EPR) steering describes the ability of one observer to nonlocally "steer" the other observer's state through local measurements. EPR steering exhibits a unique asymmetric property; i.e., the steerability can differ between observers, which can lead to one-way EPR steering in which only one observer obtains steerability in the steering process. This property is inherently different from the symmetric concepts of entanglement and Bell nonlocality, and it has attracted increasing interest. Here, we experimentally demonstrate asymmetric EPR steering for a class of two-qubit states in the case of two measurement settings. We propose a practical method to quantify the steerability. We then provide a necessary and sufficient condition for EPR steering and clearly demonstrate one-way EPR steering. Our work provides new insight into the fundamental asymmetry of quantum nonlocality and has potential applications in asymmetric quantum information processing. PMID:27152778

  12. Ballistic thermal rectification in asymmetric three-terminal graphene nanojunctions

    Science.gov (United States)

    Ouyang, Tao; Chen, Yuanping; Xie, Yuee; Wei, X. L.; Yang, Kaike; Yang, Ping; Zhong, Jianxin

    2010-12-01

    Graphene nanojunctions (GNJs) are important components of future nanodevices and nanocircuits. Using the nonequilibrium Green’s function method, we investigate the phononic properties of three-terminal GNJs (TGNJs). The results show that the heat flux runs preferentially along the direction from narrow to wide terminals, presenting an evident ballistic thermal rectification effect in the asymmetric TGNJs. The rectification efficiency is strongly dependent on the asymmetry of the nanojunctions, which increases rapidly with the width discrepancy between the left and right terminals. Meanwhile, the corner form of the TGNJs also plays an important role in the rectification effect. The mechanism of this thermal rectification is explained by a qualitative analysis. Compared to previous thermal rectifiers based on other materials, the asymmetric nanojunctions based on graphene possess much high rectification ratio which can approach about 200%. These indicate that asymmetric TGNJs might be a promising candidate for excellent ballistic thermal (phononic) devices.

  13. New Asymmetric Fuzzy PID Control for Pneumatic Position Control System

    Institute of Scientific and Technical Information of China (English)

    薛阳; 彭光正; 范萌; 伍清河

    2004-01-01

    A fuzzy control algorithm of asymmetric fuzzy strategy is introduced for a servo-pneumatic position system. It can effectively solve the difficult problems of single rod low friction cylinders, which are mainly caused by asymmetric structures and different friction characteristics in two directions. On the basis of this algorithm, a traditional PID control is used to improve dynamic performance. Furthermore, a new asymmetric fuzzy PID control with α factor is advanced to improve the self-adaptability and robustness of the system. Both the theoretical analyses and experimental results prove that, with this control strategy, the dynamic performance of the system can be greatly improved. The system using this control algorithm has strong robustness and it obtains desired overshoot and repeatability in both transient and steady-state responses.

  14. Equation of state and phase transitions in asymmetric nuclear matter

    CERN Document Server

    Kolomietz, V M; Shlomo, S; Firin, S A

    2001-01-01

    The structure of the 3-dimension pressure-temperature-asymmetry surface of equilibrium of the asymmetric nuclear matter is studied within the thermal Thomas-Fermi approximation. Special attention is paid to the difference of the asymmetry parameter between the boiling sheet and that of the condensation sheet of the surface of equilibrium. We derive the condition of existence of the regime of retrograde condensation at the boiling of the asymmetric nuclear matter. We have performed calculations of the caloric curves in the case of isobaric heating. We have shown the presence of the plateau region in caloric curves at the isobaric heating of the asymmetric nuclear matter. The shape of the caloric curve depends on the pressure and is sensitive to the value of the asymmetry parameter. We point out that the experimental value of the plateau temperature T \\approx 7 MeV corresponds to the pressure P = 0.01 MeV/fm^3 at the isobaric boiling.

  15. Role of Asymmetric Clusters in Desynchronization of Coherent Motion

    DEFF Research Database (Denmark)

    Popovych, O.; Maistrenko, Y.; Mosekilde, Erik

    2002-01-01

    The transition from full synchronization (coherent motion) to two-cluster dynamics is studied for a system of N globally coupled logistic maps. When increasing the nonlinearity parameter of the individual map, new periodic and strongly asymmetric two-cluster states are found to emerge in the same...... order as the periodic windows arise in the logistic map. These strongly asymmetric two-cluster states are generally first to stabilize when reducing the coupling strength. Similar phenomena are also observed for a system of globally coupled Henon maps.......The transition from full synchronization (coherent motion) to two-cluster dynamics is studied for a system of N globally coupled logistic maps. When increasing the nonlinearity parameter of the individual map, new periodic and strongly asymmetric two-cluster states are found to emerge in the same...

  16. Asymmetric spindle pole formation in CPAP-depleted mitotic cells.

    Science.gov (United States)

    Lee, Miseon; Chang, Jaerak; Chang, Sunghoe; Lee, Kyung S; Rhee, Kunsoo

    2014-02-21

    CPAP is an essential component for centriole formation. Here, we report that CPAP is also critical for symmetric spindle pole formation during mitosis. We observed that pericentriolar material between the mitotic spindle poles were asymmetrically distributed in CPAP-depleted cells even with intact numbers of centrioles. The length of procentrioles was slightly reduced by CPAP depletion, but the length of mother centrioles was not affected. Surprisingly, the young mother centrioles of the CPAP-depleted cells are not fully matured, as evidenced by the absence of distal and subdistal appendage proteins. We propose that the selective absence of centriolar appendages at the young mother centrioles may be responsible for asymmetric spindle pole formation in CPAP-depleted cells. Our results suggest that the neural stem cells with CPAP mutations might form asymmetric spindle poles, which results in premature initiation of differentiation.

  17. Phase-transfer-catalysed asymmetric synthesis of tetrasubstituted allenes

    Science.gov (United States)

    Hashimoto, Takuya; Sakata, Kazuki; Tamakuni, Fumiko; Dutton, Mark J.; Maruoka, Keiji

    2013-03-01

    Allenes are molecules based on three carbons connected by two cumulated carbon-carbon double bonds. Given their axially chiral nature and unique reactivity, substituted allenes have a variety of applications in organic chemistry as key synthetic intermediates and directly as part of biologically active compounds. Although the demands for these motivated many endeavours to make axially chiral, substituted allenes by exercising asymmetric catalysis, the catalytic asymmetric synthesis of fully substituted ones (tetrasubstituted allenes) remained largely an unsolved issue. The fundamental obstacle to solving this conundrum is the lack of a simple synthetic transformation that provides tetrasubstituted allenes in the action of catalysis. We report herein a strategy to overcome this issue by the use of a phase-transfer-catalysed asymmetric functionalization of 1-alkylallene-1,3-dicarboxylates with N-arylsulfonyl imines and benzylic and allylic bromides.

  18. 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.

  19. Experimental Quantification of Asymmetric Einstein-Podolsky-Rosen Steering.

    Science.gov (United States)

    Sun, Kai; Ye, Xiang-Jun; Xu, Jin-Shi; Xu, Xiao-Ye; Tang, Jian-Shun; Wu, Yu-Chun; Chen, Jing-Ling; Li, Chuan-Feng; Guo, Guang-Can

    2016-04-22

    Einstein-Podolsky-Rosen (EPR) steering describes the ability of one observer to nonlocally "steer" the other observer's state through local measurements. EPR steering exhibits a unique asymmetric property; i.e., the steerability can differ between observers, which can lead to one-way EPR steering in which only one observer obtains steerability in the steering process. This property is inherently different from the symmetric concepts of entanglement and Bell nonlocality, and it has attracted increasing interest. Here, we experimentally demonstrate asymmetric EPR steering for a class of two-qubit states in the case of two measurement settings. We propose a practical method to quantify the steerability. We then provide a necessary and sufficient condition for EPR steering and clearly demonstrate one-way EPR steering. Our work provides new insight into the fundamental asymmetry of quantum nonlocality and has potential applications in asymmetric quantum information processing.

  20. Solitary waves in asymmetric electron-positron-ion plasmas

    Science.gov (United States)

    Lu, Ding; Li, Zi-Liang; Xie, Bai-Song

    2015-10-01

    > By solving the coupled equations of the electromagnetic field and electrostatic potential, we investigate solitary waves in an asymmetric electron-positron plasma and/or electron-positron-ion plasmas with delicate features. It is found that the solutions of the coupled equations can capture multipeak structures of solitary waves in the case of cold plasma, which are left out by using the long-wavelength approximation. By considering the effect of ion motion with respect to non-relativistic and ultra-relativistic temperature plasmas, we find that the ions' mobility can lead to larger-amplitude solitary waves; especially, this becomes more obvious for a high-temperature plasma. The effects of asymmetric temperature between electrons and positrons and the ion fraction on the solitary waves are also studied and presented. It is shown that the amplitudes of solitary waves decrease with positron temperature in asymmetric temperature electron-positron plasmas and decrease also with ion concentration.