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Sample records for dimensional directed acyclic

  1. Directed Acyclic Graphs for Oral Disease Research.

    PubMed

    Akinkugbe, A A; Sharma, S; Ohrbach, R; Slade, G D; Poole, C

    2016-07-01

    Directed acyclic graphs (DAGs) are nonparametric graphical tools used to depict causal relations in the epidemiologic assessment of exposure-outcome associations. Although their use in dental research was first advocated in 2002, DAGs have yet to be widely adopted in this field. DAGs help identify threats to causal inference such as confounders, bias due to subject selection, and inappropriate handling of missing data. DAGs can also inform the data analysis strategy based on relations among variables depicted on it. This article uses the example of a study of temporomandibular disorders (TMDs), investigating causal effects of facial injury on subsequent risk of TMD. We illustrate how DAGs can be used to identify 1) potential confounders, 2) mediators and the consequences of attempt to estimate direct causal effects, 3) colliders and the consequences of conditioning on colliders, and 4) variables that are simultaneously mediators and confounders and the consequences of adjustment for such variables. For example, one DAG shows that statistical adjustment for the pressure pain threshold would necessarily bias the causal relation between facial injury and TMD. Finally, we discuss the usefulness of DAGs during study design, subject selection, and choosing variables to be measured in a study. PMID:27000052

  2. Analyzing microarray data with transitive directed acyclic graphs.

    PubMed

    Phan, Vinhthuy; Olusegun George, E; Tran, Quynh T; Goodwin, Shirlean; Bodreddigari, Sridevi; Sutter, Thomas R

    2009-02-01

    Post hoc assignment of patterns determined by all pairwise comparisons in microarray experiments with multiple treatments has been proven to be useful in assessing treatment effects. We propose the usage of transitive directed acyclic graphs (tDAG) as the representation of these patterns and show that such representation can be useful in clustering treatment effects, annotating existing clustering methods, and analyzing sample sizes. Advantages of this approach include: (1) unique and descriptive meaning of each cluster in terms of how genes respond to all pairs of treatments; (2) insensitivity of the observed patterns to the number of genes analyzed; and (3) a combinatorial perspective to address the sample size problem by observing the rate of contractible tDAG as the number of replicates increases. The advantages and overall utility of the method in elaborating drug structure activity relationships are exemplified in a controlled study with real and simulated data. PMID:19226664

  3. A Directed Acyclic Graph-Large Margin Distribution Machine Model for Music Symbol Classification

    PubMed Central

    Wen, Cuihong; Zhang, Jing; Rebelo, Ana; Cheng, Fanyong

    2016-01-01

    Optical Music Recognition (OMR) has received increasing attention in recent years. In this paper, we propose a classifier based on a new method named Directed Acyclic Graph-Large margin Distribution Machine (DAG-LDM). The DAG-LDM is an improvement of the Large margin Distribution Machine (LDM), which is a binary classifier that optimizes the margin distribution by maximizing the margin mean and minimizing the margin variance simultaneously. We modify the LDM to the DAG-LDM to solve the multi-class music symbol classification problem. Tests are conducted on more than 10000 music symbol images, obtained from handwritten and printed images of music scores. The proposed method provides superior classification capability and achieves much higher classification accuracy than the state-of-the-art algorithms such as Support Vector Machines (SVMs) and Neural Networks (NNs). PMID:26985826

  4. A Directed Acyclic Graph-Large Margin Distribution Machine Model for Music Symbol Classification.

    PubMed

    Wen, Cuihong; Zhang, Jing; Rebelo, Ana; Cheng, Fanyong

    2016-01-01

    Optical Music Recognition (OMR) has received increasing attention in recent years. In this paper, we propose a classifier based on a new method named Directed Acyclic Graph-Large margin Distribution Machine (DAG-LDM). The DAG-LDM is an improvement of the Large margin Distribution Machine (LDM), which is a binary classifier that optimizes the margin distribution by maximizing the margin mean and minimizing the margin variance simultaneously. We modify the LDM to the DAG-LDM to solve the multi-class music symbol classification problem. Tests are conducted on more than 10000 music symbol images, obtained from handwritten and printed images of music scores. The proposed method provides superior classification capability and achieves much higher classification accuracy than the state-of-the-art algorithms such as Support Vector Machines (SVMs) and Neural Networks (NNs). PMID:26985826

  5. Analytic Bounds on Causal Risk Differences in Directed Acyclic Graphs Involving Three Observed Binary Variables

    PubMed Central

    Kaufman, Sol; Kaufman, Jay S.; MacLehose, Richard F.

    2009-01-01

    We apply a linear programming approach which uses the causal risk difference (RDC) as the objective function and provides minimum and maximum values that RDC can achieve under any set of linear constraints on the potential response type distribution. We consider two scenarios involving binary exposure X, covariate Z and outcome Y. In the first, Z is not affected by X, and is a potential confounder of the causal effect of X on Y. In the second, Z is affected by X and intermediate in the causal pathway between X and Y. For each scenario we consider various linear constraints corresponding to the presence or absence of arcs in the associated directed acyclic graph (DAG), monotonicity assumptions, and presence or absence of additive-scale interactions. We also estimate Z-stratum-specific bounds when Z is a potential effect measure modifier and bounds for both controlled and natural direct effects when Z is affected by X. In the absence of any additional constraints deriving from background knowledge, the well-known bounds on RDc are duplicated: −Pr(Y≠X) ≤ RDC ≤ Pr(Y=X). These bounds have unit width, but can be narrowed by background knowledge-based assumptions. We provide and compare bounds and bound widths for various combinations of assumptions in the two scenarios and apply these bounds to real data from two studies. PMID:20161106

  6. Lanthanide-directed synthesis of luminescent self-assembly supramolecular structures and mechanically bonded systems from acyclic coordinating organic ligands.

    PubMed

    Barry, Dawn E; Caffrey, David F; Gunnlaugsson, Thorfinnur

    2016-06-01

    Herein some examples of the use of lanthanide ions (f-metal ions) to direct the synthesis of luminescent self-assembly systems (architectures) will be discussed. This area of lanthanide supramolecular chemistry is fast growing, thanks to the unique physical (magnetic and luminescent) and coordination properties of the lanthanides, which are often transferred to the resulting supermolecule. The emphasis herein will be on systems that are luminescent, and hence, generated by using either visibly emitting ions (such as Eu(III), Tb(III) and Sm(III)) or near infrared emitting ions (like Nd(III), Yb(III) and Er(III)), formed through the use of templating chemistry, by employing structurally simple ligands, possessing oxygen and nitrogen coordinating moieties. As the lanthanides have high coordination requirements, their use often allows for the formation of coordination compounds and supramolecular systems such as bundles, grids, helicates and interlocked molecules that are not synthetically accessible through the use of other commonly used templating ions such as transition metal ions. Hence, the use of the rare-earth metal ions can lead to the formation of unique and stable species in both solution and in the solid state, as well as functional and responsive structures. PMID:27137947

  7. Acyclic colorings of graphs with bounded degree

    NASA Astrophysics Data System (ADS)

    Fiedorowicz, Anna; Sidorowicz, Elżbieta

    2016-07-01

    A $k$-colouring (not necessarily proper) of vertices of a graph is called {\\it acyclic}, if for every pair of distinct colours $i$ and $j$ the subgraph induced by the edges whose endpoints have colours $i$ and $j$ is acyclic. In the paper we consider some generalised acyclic $k$-colourings, namely, we require that each colour class induces an acyclic or bounded degree graph. Mainly we focus on graphs with maximum degree 5. We prove that any such graph has an acyclic $5$-colouring such that each colour class induces an acyclic graph with maximum degree at most 4. We prove that the problem of deciding whether a graph $G$ has an acyclic 2-colouring in which each colour class induces a graph with maximum degree at most 3 is NP-complete, even for graphs with maximum degree 5. We also give a linear-time algorithm for an acyclic $t$-improper colouring of any graph with maximum degree $d$ assuming that the number of colors is large enough.

  8. Acyclic Lipids in Amazon Shelf Waters

    NASA Astrophysics Data System (ADS)

    Elias, V. O.; Cardoso, J. N.; Simoneit, B. R. T.

    2000-02-01

    Acyclic lipids were analysed for dissolved (<1·2 μm) and particulate (>1·2 μm) material from surface water of the Amazon continental shelf to correlate the direct inputs with diagenetic processes of the organic matter and to assess the differences in compound distribution patterns of the samples. The dissolved samples contained n -alkanes with an unusual even-to-odd carbon number predominance acyclic lipids indicates an origin from micro-organisms, probably diatoms. Although minor, a contribution of components derived from plant waxes are more abundant in the particulate phase with profiles indicating a remineralized residue. Plant waxes are effectively biodegraded in the shelf waters during downstream transport in the Amazon River. Furthermore, the Pr/Ph ratios calculated for the dissolved samples indicate that the organic matter in the surface of the highly turbid waters passed through an anaerobic stage. The differences in the acyclic hydrocarbon profiles of the dissolved and particulate phases show that organic inputs are preserved differently in smaller and larger particles.

  9. Cardioleader use in acyclic types of sports

    NASA Technical Reports Server (NTRS)

    Bondin, V. I.

    1980-01-01

    The use of the cardioleader method in regulating training loads and tests for athletes in acyclic sports was investigated. It was found that the use of this method increases the effectiveness of the training process.

  10. Direct Linear Transformation Method for Three-Dimensional Cinematography

    ERIC Educational Resources Information Center

    Shapiro, Robert

    1978-01-01

    The ability of Direct Linear Transformation Method for three-dimensional cinematography to locate points in space was shown to meet the accuracy requirements associated with research on human movement. (JD)

  11. Biodegradation of acyclic isoprenoids by Pseudomonas species.

    PubMed Central

    Cantwell, S G; Lau, E P; Watt, D S; Fall, R R

    1978-01-01

    The ability of various pseudomonads to utilize acyclic isoprenoids as a sole carbon source was investigated. Tests for utilization of acyclic isoprenols such as citronellol and geraniol were complicated by toxic effects of these alcohols, and most species tested were killed by exposure to citronellol or geraniol (0.1%, vol/vol) in liquid culture. In the case of Pseudomonas citronellolis, sensitivity to isoprenols is reduced by prior induction of the isoprenoid degradative pathway via either growth on succinate in the presence of citronellol or growth on citronellic acid. For this species, citronellic acid proved to be the best isoprenoid growth substrate tested. Geraniol utilization as a taxonomic indicator for different subgroups of pseudomonads is discussed. Only a few of the species tested were able to utilize acyclic isoprenoids. Two species which utilize C10 acyclic isoprenoids, P. aeruginosa and P. mendocina, were shown to contain the inducible enzyme geranyl-coenzyme A carboxylase, one of the unique enzymes in the isoprenol degradative pathway known to occur in P. citronellolis. Of the species which utilized geranitol, none showed definite growth on the homologous C15 and C20 isoprenols. PMID:681275

  12. Modification of DIRECT for high-dimensional design problems

    NASA Astrophysics Data System (ADS)

    Tavassoli, Arash; Haji Hajikolaei, Kambiz; Sadeqi, Soheil; Wang, G. Gary; Kjeang, Erik

    2014-06-01

    DIviding RECTangles (DIRECT), as a well-known derivative-free global optimization method, has been found to be effective and efficient for low-dimensional problems. When facing high-dimensional black-box problems, however, DIRECT's performance deteriorates. This work proposes a series of modifications to DIRECT for high-dimensional problems (dimensionality d>10). The principal idea is to increase the convergence speed by breaking its single initialization-to-convergence approach into several more intricate steps. Specifically, starting with the entire feasible area, the search domain will shrink gradually and adaptively to the region enclosing the potential optimum. Several stopping criteria have been introduced to avoid premature convergence. A diversification subroutine has also been developed to prevent the algorithm from being trapped in local minima. The proposed approach is benchmarked using nine standard high-dimensional test functions and one black-box engineering problem. All these tests show a significant efficiency improvement over the original DIRECT for high-dimensional design problems.

  13. CHARMM Additive All-Atom Force Field for Acyclic Polyalcohols, Acyclic Carbohydrates and Inositol

    PubMed Central

    Hatcher, Elizabeth; Guvench, Olgun; MacKerell, Alexander D.

    2009-01-01

    Parametrization of the additive all-atom CHARMM force field for acyclic polyalcohols, acyclic carbohydrates and inositol is conducted. Initial parameters were transferred from the alkanes and hexopyranose carbohydrates, with subsequent development and optimization of parameters unique to the molecules considered in this study. Using the model compounds acetone and acetaldehyde, nonbonded parameters for carbonyls were optimized targeting quantum mechanical interaction data for solute-water pairs and pure solvent thermodynamic data. Bond and angle parameters were adjusted by comparing optimized geometries to small molecule crystal survey data and by performing vibrational analyses on acetone, acetaldehyde and glycerol. C-C-C-C, C-C-C-O, C-C-OH and O-C-C-O torsional parameters for polyol chains were fit to quantum mechanical dihedral potential energy scans comprising over 1500 RIMP2/cc-pVTZ//MP2/6-31G(d) conformations using an automated Monte Carlo simulated annealing procedure. Comparison of computed condensed-phase data, including crystal lattice parameters and densities, NMR proton-proton couplings, densities and diffusion coefficients of aqueous solutions, to experimental data validated the optimized parameters. Parameter development for these compounds proved particularly challenging because of the flexibility of the acyclic sugars and polyalcohols as well as the intramolecular hydrogen bonding between vicinal hydroxyls for all of the compounds. The newly optimized additive CHARMM force field parameters are anticipated to be of utility for atomic level of detail simulations of acyclic polyalcohols, acyclic carbohydrates and inositol in solution. PMID:20160980

  14. Directional ocean spectra by three-dimensional displacement time series

    SciTech Connect

    Su, T.Z.

    1984-01-01

    The directionality of ocean waves is considered as the most problem area of today's wave measurement technology. In 1982 the University of Hawaii Ocean ''Engineering Department began a research project Engineering Development of a Directional Wave Spectrum Measurement System for OTEC Applications'' to address this problem. A new technology was developed in this research. This technology uses acoustic signals to determine the trajectory of a floating buoy which simulates the movement of a surface water particle. Transfer functions of the three-dimensional displacement time series are used to describe the wave kinematics. The described wave kinematics are directly applied to calculate hydrodynamic loading. Cospectra and quadrature spectra determine the directional distribution function. The resultant directional distribution function is used to predict the directional progression of ocean waves.

  15. Mueller matrix three-dimensional directional imaging of collagen fibers.

    PubMed

    Ellingsen, Pål Gunnar; Aas, Lars Martin Sandvik; Hagen, Vegard Stenhjem; Kumar, Rajesh; Lilledahl, Magnus Borstad; Kildemo, Morten

    2014-02-01

    A method for measuring three-dimensional (3-D) direction images of collagen fibers in biological tissue is presented. Images of the 3-D directions are derived from the measured transmission Mueller matrix images (MMIs), acquired at different incidence angles, by taking advantage of the form birefringence of the collagen fibers. The MMIs are decomposed using the recently developed differential decomposition, which is more suited to biological tissue samples than the common polar decomposition method. Validation of the 3-D direction images was performed by comparing them with images from second-harmonic generation microscopy. The comparison found a good agreement between the two methods. It is envisaged that 3-D directional imaging could become a useful tool for understanding the collagen framework for fibers smaller than the diffraction limit. PMID:24503637

  16. Modeling direct interband tunneling. II. Lower-dimensional structures

    SciTech Connect

    Pan, Andrew; Chui, Chi On

    2014-08-07

    We investigate the applicability of the two-band Hamiltonian and the widely used Kane analytical formula to interband tunneling along unconfined directions in nanostructures. Through comparisons with k·p and tight-binding calculations and quantum transport simulations, we find that the primary correction is the change in effective band gap. For both constant fields and realistic tunnel field-effect transistors, dimensionally consistent band gap scaling of the Kane formula allows analytical and numerical device simulations to approximate non-equilibrium Green's function current characteristics without arbitrary fitting. This allows efficient first-order calibration of semiclassical models for interband tunneling in nanodevices.

  17. Bioinspired one-dimensional materials for directional liquid transport.

    PubMed

    Ju, Jie; Zheng, Yongmei; Jiang, Lei

    2014-08-19

    One-dimensional materials (1D) capable of transporting liquid droplets directionally, such as spider silks and cactus spines, have recently been gathering scientists' attention due to their potential applications in microfluidics, textile dyeing, filtration, and smog removal. This remarkable property comes from the arrangement of the micro- and nanostructures on these organisms' surfaces, which have inspired chemists to develop methods to prepare surfaces with similar directional liquid transport ability. In this Account, we report our recent progress in understanding how this directional transport works, as well our advances in the design and fabrication of bioinspired 1D materials capable of transporting liquid droplets directionally. To begin, we first discuss some basic theories on droplet directional movement. Then, we discuss the mechanism of directional transport of water droplets on natural spider silks. Upon contact with water droplets, the spider silk undergoes what is known as a wet-rebuilt, which forms periodic spindle-knots and joints. We found that the resulting gradient of Laplace pressure and surface free energy between the spindle-knots and joints account for the cooperative driving forces to transport water droplets directionally. Next, we discuss the directional transport of water droplets on desert cactus. The integration of multilevel structures of the cactus and the resulting integration of multiple functions together allow the cactus spine to transport water droplets continuously from tip to base. Based on our studies of natural spider silks and cactus spines, we have prepared a series of artificial spider silks (A-SSs) and artificial cactus spines (A-CSs) with various methods. By changing the surface roughness and chemical compositions of the artificial spider silks' spindle-knots, or by introducing stimulus-responsive molecules, such as thermal-responsive and photoresponsive molecules, onto the spindle-knots, we can reversibly manipulate

  18. N-Branched acyclic nucleoside phosphonates as monomers for the synthesis of modified oligonucleotides.

    PubMed

    Hocková, Dana; Rosenbergová, Šárka; Ménová, Petra; Páv, Ondřej; Pohl, Radek; Novák, Pavel; Rosenberg, Ivan

    2015-04-21

    Protected N-branched nucleoside phosphonates containing adenine and thymine bases were prepared as the monomers for the introduction of aza-acyclic nucleotide units into modified oligonucleotides. The phosphotriester and phosphoramidite methods were used for the incorporation of modified and natural units, respectively. The solid phase synthesis of a series of nonamers containing one central modified unit was successfully performed in both 3'→5' and 5'→3' directions. Hybridization properties of the prepared oligoribonucleotides and oligodeoxyribonucleotides were evaluated. The measurement of thermal characteristics of the complexes of modified nonamers with the complementary strand revealed a considerable destabilizing effect of the introduced units. We also examined the substrate/inhibitory properties of aza-acyclic nucleoside phosphono-diphosphate derivatives (analogues of nucleoside triphosphates) but neither inhibition of human and bacterial DNA polymerases nor polymerase-mediated incorporation of these triphosphate analogues into short DNA was observed. PMID:25766752

  19. Direct Volume Rendering with Shading via Three-Dimensional Textures

    NASA Technical Reports Server (NTRS)

    Van Gelder, Allen; Kim, Kwansik

    1996-01-01

    A new and easy-to-implement method for direct volume rendering that uses 3D texture maps for acceleration, and incorporates directional lighting, is described. The implementation, called Voltx, produces high-quality images at nearly interactive speeds on workstations with hardware support for three-dimensional texture maps. Previously reported methods did not incorporate a light model, and did not address issues of multiple texture maps for large volumes. Our research shows that these extensions impact performance by about a factor of ten. Voltx supports orthographic, perspective, and stereo views. This paper describes the theory and implementation of this technique, and compares it to the shear-warp factorization approach. A rectilinear data set is converted into a three-dimensional texture map containing color and opacity information. Quantized normal vectors and a lookup table provide efficiency. A new tesselation of the sphere is described, which serves as the basis for normal-vector quantization. A new gradient-based shading criterion is described, in which the gradient magnitude is interpreted in the context of the field-data value and the material classification parameters, and not in isolation. In the rendering phase, the texture map is applied to a stack of parallel planes, which effectively cut the texture into many slabs. The slabs are composited to form an image.

  20. Two-dimensional tricycle arsenene with a direct band gap.

    PubMed

    Ma, ShuangYing; Zhou, Pan; Sun, L Z; Zhang, K W

    2016-03-28

    Based on a comprehensive investigation including ab initio phonon and finite-temperature molecular dynamics calculations, we find that two-dimensional tricycle-shaped arsenene (T-As) is robust and even stable under high temperature. T-As is energetically comparable to previously reported chair-shaped arsenene (C-As) and more stable than stirrup-shaped arsenene (S-As). In contrast to C-As and S-As, the monolayer T-As is a direct band gap semiconductor with an energy gap of 1.377 eV. Our results indicate that the electronic structure of T-As can be effectively modulated by stacking, strain, and patterning, which shows great potential of T-As in future nano-electronics. Moreover, by absorbing H or F atoms on the surface of T-As along a specific direction, nanoribbons with desired edge type and even width can be obtained, which is suitable for the fabrication of nano-devices. PMID:26954607

  1. Oscillatory cellular patterns in three-dimensional directional solidification

    DOE PAGESBeta

    Tourret, D.; Debierre, J. -M.; Song, Y.; Mota, F. L.; Bergeon, N.; Guerin, R.; Trivedi, R.; Billia, B.; Karma, A.

    2015-09-11

    We present a phase-field study of oscillatory breathing modes observed during the solidification of three-dimensional cellular arrays in micro-gravity. Directional solidification experiments conducted onboard the International Space Station have allowed for the first time to observe spatially extended homogeneous arrays of cells and dendrites while minimizing the amount of gravity-induced convection in the liquid. In situ observations of transparent alloys have revealed the existence, over a narrow range of control parameters, of oscillations in cellular arrays with a period ranging from about 25 to 125 minutes. Cellular patterns are spatially disordered, and the oscillations of individual cells are spatiotemporally uncorrelatedmore » at long distance. However, in regions displaying short-range spatial ordering, groups of cells can synchronize into oscillatory breathing modes. Quantitative phase-field simulations show that the oscillatory behavior of cells in this regime is linked to a stability limit of the spacing in hexagonal cellular array structures. For relatively high cellular front undercooling (\\ie low growth velocity or high thermal gradient), a gap appears in the otherwise continuous range of stable array spacings. Close to this gap, a sustained oscillatory regime appears with a period that compares quantitatively well with experiment. For control parameters where this gap exist, oscillations typically occur for spacings at the edge of the gap. However, after a change of growth conditions, oscillations can also occur for nearby values of control parameters where this gap just closes and a continuous range of spacings exists. In addition, sustained oscillations at to the opening of this stable gap exhibit a slow periodic modulation of the phase-shift among cells with a slower period of several hours. While long-range coherence of breathing modes can be achieved in simulations for a perfect spatial arrangement of cells as initial condition, global

  2. Oscillatory cellular patterns in three-dimensional directional solidification

    NASA Astrophysics Data System (ADS)

    Tourret, D.; Debierre, J.-M.; Song, Y.; Mota, F. L.; Bergeon, N.; Guérin, R.; Trivedi, R.; Billia, B.; Karma, A.

    2015-10-01

    We present a phase-field study of oscillatory breathing modes observed during the solidification of three-dimensional cellular arrays in microgravity. Directional solidification experiments conducted onboard the International Space Station have allowed us to observe spatially extended homogeneous arrays of cells and dendrites while minimizing the amount of gravity-induced convection in the liquid. In situ observations of transparent alloys have revealed the existence, over a narrow range of control parameters, of oscillations in cellular arrays with a period ranging from about 25 to 125 min. Cellular patterns are spatially disordered, and the oscillations of individual cells are spatiotemporally uncorrelated at long distance. However, in regions displaying short-range spatial ordering, groups of cells can synchronize into oscillatory breathing modes. Quantitative phase-field simulations show that the oscillatory behavior of cells in this regime is linked to a stability limit of the spacing in hexagonal cellular array structures. For relatively high cellular front undercooling (i.e., low growth velocity or high thermal gradient), a gap appears in the otherwise continuous range of stable array spacings. Close to this gap, a sustained oscillatory regime appears with a period that compares quantitatively well with experiment. For control parameters where this gap exists, oscillations typically occur for spacings at the edge of the gap. However, after a change of growth conditions, oscillations can also occur for nearby values of control parameters where this gap just closes and a continuous range of spacings exists. In addition, sustained oscillations at to the opening of this stable gap exhibit a slow periodic modulation of the phase-shift among cells with a slower period of several hours. While long-range coherence of breathing modes can be achieved in simulations for a perfect spatial arrangement of cells as initial condition, global disorder is observed in both

  3. Oscillatory cellular patterns in three-dimensional directional solidification.

    PubMed

    Tourret, D; Debierre, J-M; Song, Y; Mota, F L; Bergeon, N; Guérin, R; Trivedi, R; Billia, B; Karma, A

    2015-10-01

    We present a phase-field study of oscillatory breathing modes observed during the solidification of three-dimensional cellular arrays in microgravity. Directional solidification experiments conducted onboard the International Space Station have allowed us to observe spatially extended homogeneous arrays of cells and dendrites while minimizing the amount of gravity-induced convection in the liquid. In situ observations of transparent alloys have revealed the existence, over a narrow range of control parameters, of oscillations in cellular arrays with a period ranging from about 25 to 125 min. Cellular patterns are spatially disordered, and the oscillations of individual cells are spatiotemporally uncorrelated at long distance. However, in regions displaying short-range spatial ordering, groups of cells can synchronize into oscillatory breathing modes. Quantitative phase-field simulations show that the oscillatory behavior of cells in this regime is linked to a stability limit of the spacing in hexagonal cellular array structures. For relatively high cellular front undercooling (i.e., low growth velocity or high thermal gradient), a gap appears in the otherwise continuous range of stable array spacings. Close to this gap, a sustained oscillatory regime appears with a period that compares quantitatively well with experiment. For control parameters where this gap exists, oscillations typically occur for spacings at the edge of the gap. However, after a change of growth conditions, oscillations can also occur for nearby values of control parameters where this gap just closes and a continuous range of spacings exists. In addition, sustained oscillations at to the opening of this stable gap exhibit a slow periodic modulation of the phase-shift among cells with a slower period of several hours. While long-range coherence of breathing modes can be achieved in simulations for a perfect spatial arrangement of cells as initial condition, global disorder is observed in both

  4. Oscillatory cellular patterns in three-dimensional directional solidification

    SciTech Connect

    Tourret, D.; Debierre, J. -M.; Song, Y.; Mota, F. L.; Bergeon, N.; Guerin, R.; Trivedi, R.; Billia, B.; Karma, A.

    2015-09-11

    We present a phase-field study of oscillatory breathing modes observed during the solidification of three-dimensional cellular arrays in micro-gravity. Directional solidification experiments conducted onboard the International Space Station have allowed for the first time to observe spatially extended homogeneous arrays of cells and dendrites while minimizing the amount of gravity-induced convection in the liquid. In situ observations of transparent alloys have revealed the existence, over a narrow range of control parameters, of oscillations in cellular arrays with a period ranging from about 25 to 125 minutes. Cellular patterns are spatially disordered, and the oscillations of individual cells are spatiotemporally uncorrelated at long distance. However, in regions displaying short-range spatial ordering, groups of cells can synchronize into oscillatory breathing modes. Quantitative phase-field simulations show that the oscillatory behavior of cells in this regime is linked to a stability limit of the spacing in hexagonal cellular array structures. For relatively high cellular front undercooling (\\ie low growth velocity or high thermal gradient), a gap appears in the otherwise continuous range of stable array spacings. Close to this gap, a sustained oscillatory regime appears with a period that compares quantitatively well with experiment. For control parameters where this gap exist, oscillations typically occur for spacings at the edge of the gap. However, after a change of growth conditions, oscillations can also occur for nearby values of control parameters where this gap just closes and a continuous range of spacings exists. In addition, sustained oscillations at to the opening of this stable gap exhibit a slow periodic modulation of the phase-shift among cells with a slower period of several hours. While long-range coherence of breathing modes can be achieved in simulations for a perfect spatial arrangement of cells as initial condition, global disorder is

  5. Direct human cartilage repair using three-dimensional bioprinting technology.

    PubMed

    Cui, Xiaofeng; Breitenkamp, Kurt; Finn, M G; Lotz, Martin; D'Lima, Darryl D

    2012-06-01

    Current cartilage tissue engineering strategies cannot as yet fabricate new tissue that is indistinguishable from native cartilage with respect to zonal organization, extracellular matrix composition, and mechanical properties. Integration of implants with surrounding native tissues is crucial for long-term stability and enhanced functionality. In this study, we developed a bioprinting system with simultaneous photopolymerization capable for three-dimensional (3D) cartilage tissue engineering. Poly(ethylene glycol) dimethacrylate (PEGDMA) with human chondrocytes were printed to repair defects in osteochondral plugs (3D biopaper) in layer-by-layer assembly. Compressive modulus of printed PEGDMA was 395.73±80.40 kPa, which was close to the range of the properties of native human articular cartilage. Printed human chondrocytes maintained the initially deposited positions due to simultaneous photopolymerization of surrounded biomaterial scaffold, which is ideal in precise cell distribution for anatomic cartilage engineering. Viability of printed human chondrocytes increased 26% in simultaneous polymerization than polymerized after printing. Printed cartilage implant attached firmly with surrounding tissue and greater proteoglycan deposition was observed at the interface of implant and native cartilage in Safranin-O staining. This is consistent with the enhanced interface failure strength during the culture assessed by push-out testing. Printed cartilage in 3D biopaper had elevated glycosaminoglycan (GAG) content comparing to that without biopaper when normalized to DNA. These observations were consistent with gene expression results. This study indicates the importance of direct cartilage repair and promising anatomic cartilage engineering using 3D bioprinting technology. PMID:22394017

  6. Direct three-dimensional coherently scattered x-ray microtomography

    PubMed Central

    Cui, Congwu; Jorgensen, Steven M.; Eaker, Diane R.; Ritman, Erik L.

    2010-01-01

    Purpose: It has been shown that coherently scattered x rays can be used to discriminate and identify specific components in a mixture of low atomic weight materials. The authors demonstrated a new method of doing coherently scattered x-ray tomography with a thin sheet of x ray. Methods: A collimated x-ray fan-beam, a parallel polycapillary collimator, and a phantom consisting of several biocompatible materials of low attenuation-based contrast were used to investigate the feasibility of the method. Because of the particular experimental setup, only the phantom translation perpendicular to the x-ray beam is needed and, thus, there is no need of Radon-type tomographic reconstruction, except for the correction of the attenuation to the primary and scattered x rays, which was performed by using a conventional attenuation-based tomographic image data set. The coherent scatter image contrast changes with momentum transfer among component materials in the specimen were investigated with multiple x-ray sources with narrow bandwidth spectra generated with anode and filter combinations of Cu∕Ni (8 keV), Mo∕Zr (18 keV), and Ag∕Pd (22 keV) and at multiple scatter angles by orienting the detector and polycapillary collimator at different angles to the illuminating x ray. Results: The contrast among different materials changes with the x-ray source energy and the angle at which the image was measured. The coherent scatter profiles obtained from the coherent scatter images are consistent with the published results. Conclusions: This method can be used to directly generate the three-dimensional coherent scatter images of small animal, biopsies, or other small objects with low atomic weight biological or similar synthetic materials with low attenuation contrast. With equipment optimized, submillimeter spatial resolution may be achieved. PMID:21302788

  7. Direct Human Cartilage Repair Using Three-Dimensional Bioprinting Technology

    PubMed Central

    Cui, Xiaofeng; Breitenkamp, Kurt; Finn, M.G.; Lotz, Martin

    2012-01-01

    Current cartilage tissue engineering strategies cannot as yet fabricate new tissue that is indistinguishable from native cartilage with respect to zonal organization, extracellular matrix composition, and mechanical properties. Integration of implants with surrounding native tissues is crucial for long-term stability and enhanced functionality. In this study, we developed a bioprinting system with simultaneous photopolymerization capable for three-dimensional (3D) cartilage tissue engineering. Poly(ethylene glycol) dimethacrylate (PEGDMA) with human chondrocytes were printed to repair defects in osteochondral plugs (3D biopaper) in layer-by-layer assembly. Compressive modulus of printed PEGDMA was 395.73±80.40 kPa, which was close to the range of the properties of native human articular cartilage. Printed human chondrocytes maintained the initially deposited positions due to simultaneous photopolymerization of surrounded biomaterial scaffold, which is ideal in precise cell distribution for anatomic cartilage engineering. Viability of printed human chondrocytes increased 26% in simultaneous polymerization than polymerized after printing. Printed cartilage implant attached firmly with surrounding tissue and greater proteoglycan deposition was observed at the interface of implant and native cartilage in Safranin-O staining. This is consistent with the enhanced interface failure strength during the culture assessed by push-out testing. Printed cartilage in 3D biopaper had elevated glycosaminoglycan (GAG) content comparing to that without biopaper when normalized to DNA. These observations were consistent with gene expression results. This study indicates the importance of direct cartilage repair and promising anatomic cartilage engineering using 3D bioprinting technology. PMID:22394017

  8. On the acyclicity of the solution sets of operator equations

    SciTech Connect

    Gel'man, Boris D

    2010-12-07

    A parameter-dependent completely continuous map is considered. The acyclicity of the set of fixed points of this map is proved for some fixed value of the parameter under the assumption that for close values of the parameter the map has a unique fixed point. The results obtained are used to prove the acyclicity of the set of fixed points of a 'nonscattering' map, as well as to study the topological structure of the set of fixed points of an abstract Volterra map. Bibliography: 13 titles.

  9. Directed assembly of three-dimensional microvascular networks

    NASA Astrophysics Data System (ADS)

    Therriault, Daniel

    Three-dimensional (3-D) microvascular networks with pervasive, interconnected channels less than 300 mum in diameter may find widespread application in microfluidic devices, biotechnology, sensors, and autonomic healing materials. Although microchannel arrays are readily constructed in two-dimensions by photolithographic or soft lithographic techniques, their construction in three-dimensions remains a challenging problem. The development of a microfabrication method to build 3-D microvascular networks based on direct-write assembly is described is this thesis. The method is based on the robotic deposition of a fugitive organic ink to form a free-standing scaffold structure. Secondary infiltration of a structural resin followed by setting of the matrix and removal of the scaffold yields an embedded pervasive network of smooth cylindrical channels (˜10--500 mum) with defined connectivity. Rheological and other material properties studies of fugitive organic ink were performed in order to identify the critical characteristics required for successful deposition of 3-D scaffolds by direct-write assembly. Guided by the results of these studies, several new ink formulations were screened for improved deposition performance. The most successful of these inks (40wt% microcrystalline wax, 60wt% petroleum jelly) showed excellent deposition and had an equilibrium modulus at room temperature (G 'eq ˜ 7.70 kPa 1 Hz) nearly two orders of magnitude higher than the original ink. The optimized ink was used to successfully build thick (i.e., ˜100 layers) scaffold structures at room temperature with negligible time-dependent deformation post-deposition. Secondary infiltration of the resin was accomplished at room temperature while maintaining the scaffold architecture. The optimized ink was also successfully extruded through small micronozzles (1 mum). The construction of 3-D microvascular networks enables microfluidic devices with unparallel geometric complexity. In one example, a

  10. Sensitivity and bias in the discrimination of two-dimensional and three-dimensional motion direction.

    PubMed

    Cooper, Emily A; van Ginkel, Marcus; Rokers, Bas

    2016-08-01

    Sensory systems are faced with an essentially infinite number of possible environmental events but have limited processing resources. Posed with this challenge, it makes sense to allocate these resources to prioritize the discrimination of events with the most behavioral relevance. Here, we asked if such relevance is reflected in the processing and perception of motion. We compared human performance on a rapid motion direction discrimination task, including monocular and binocular viewing. In particular, we determined sensitivity and bias for a binocular motion-in-depth (three-dimensional; 3D) stimulus and for its constituent monocular (two-dimensional; 2D) signals over a broad range of speeds. Consistent with prior work, we found that binocular 3D sensitivity was lower than monocular sensitivity for all speeds. Although overall sensitivity was worse for 3D discrimination, we found that the transformation from 2D to 3D motion processing also incorporated a pattern of potentially advantageous biases. One such bias is reflected by a criterion shift that occurs at the level of 3D motion processing and results in an increased hit rate for motion toward the head. We also observed an increase in sensitivity for 3D motion trajectories presented on crossed rather than uncrossed disparity pedestals, privileging motion trajectories closer to the observer. We used these measurements to determine the range of real-world trajectories for which rapid 3D motion discrimination is most useful. These results suggest that the neural mechanisms that underlie motion perception privilege behaviorally relevant motion and provide insights into the nature of human motion sensitivity in the real world. PMID:27537702

  11. Recent Applications of Acyclic (Diene)iron Complexes and (Dienyl)iron Cations in Organic Synthesis

    PubMed Central

    Chaudhury, Subhabrata

    2009-01-01

    Complexation of (tricarbonyl)iron to an acyclic diene serves to protect the ligand against oxidation, reduction and cycloaddition reactions while the steric bulk of this adjunct serves to direct the approach reagents to unsaturated groups attached to the diene onto the face opposite to iron. Furthermore, the Fe(CO)3 moiety can serve to stabilize carbocation centers adjacent to the diene (i.e. pentadienyl-iron cations). Recent applications of these reactivities to the synthesis of polyene, cyclopropane, cycloheptadiene and cyclohexenone containing natural products or analogs will be presented. PMID:21709767

  12. Direct three-dimensional patterning using nanoimprint lithography

    NASA Astrophysics Data System (ADS)

    Li, Mingtao; Chen, Lei; Chou, Stephen Y.

    2001-05-01

    We demonstrated that nanoimprint lithography (NIL) can create three-dimensional patterns, sub-40 nm T-gates, and air-bridge structures, in a single step imprint in polymer and metal by lift-off. A method based on electron beam lithography and reactive ion etching was developed to fabricate NIL molds with three-dimensional protrusions. The low-cost and high-throughput nanoimprint lithography for three-dimensional nanostructures has many significant applications such as monolithic microwave integrated circuits and nanoelectromechanical system.

  13. New acyclic diterpenic acids from yacon (Smallanthus sonchifolius) leaves.

    PubMed

    Mercado, María I; Coll Aráoz, María V; Grau, Alfredo; Catalán, César A N

    2010-11-01

    Two new acyclic diterpenoids, smaditerpenic acid E (1a) and F (2a), along with nineteen melampolide-type sesquiterpene lactones, six of them not previously reported in yacon, were isolated from the methylene chloride leaf rinse extract. Their structures were elucidated from 1D and 2D NMR experiments and gas chromatography coupled to mass spectrometry. PMID:21213966

  14. New directions in science and technology: two-dimensional crystals

    NASA Astrophysics Data System (ADS)

    Castro Neto, A. H.; Novoselov, K.

    2011-08-01

    Graphene is possibly one of the largest and fastest growing fields in condensed matter research. However, graphene is only one example in a large class of two-dimensional crystals with unusual properties. In this paper we briefly review the properties of graphene and look at the exciting possibilities that lie ahead.

  15. Sandia One-Dimensional Direct and Inverse Thermal Code

    Energy Science and Technology Software Center (ESTSC)

    1995-02-27

    SODDIT is a reliable tool for solving a wide variety of one-dimensional transient heat conduction problems. Originally developed in 1972 to predict the ablation of graphite/carbon bodies reentering the earth''s atmosphere, it has since been modified by the authors to extend its capabilities well beyond its original scope.

  16. Directivity benchmarks using an automated three-dimensional scanning system

    NASA Astrophysics Data System (ADS)

    Burns, Thomas

    2005-09-01

    In clinical studies relating a patient's perception in noise, it is interesting to note that the hearing industry has used exclusively the Directivity Index as an objective performance benchmark for the hearing aid. Considering, for example, that a dipole directional pattern has the same DI as a cardioid pattern, it is reasonable to require that additional directional performance benchmarks be reported in these clinical studies, along with the room acoustics parameters related to noise/source positions and the relationship between direct and reverberant fields. The purpose of this study is to describe an automated 3-D scanning system for benchmarking directional performance, and to review the traditional repertoire of directional benchmarking that has been used in the broader engineering acoustics community; namely, the null angle, maximum response angle, random energy efficiency, front to total random energy ratio, distance factor, and omni to directional array gain. Lastly, visualization of 3-D polar responses will be explored.

  17. Highly directional thermal emission from two-dimensional silicon structures.

    PubMed

    Ribaudo, Troy; Peters, David W; Ellis, A Robert; Davids, Paul S; Shaner, Eric A

    2013-03-25

    We simulate, fabricate, and characterize near perfectly absorbing two-dimensional grating structures in the thermal infrared using heavily doped silicon (HdSi) that supports long wave infrared surface plasmon polaritons (LWIR SPP's). The devices were designed and optimized using both finite difference time domain (FDTD) and rigorous coupled wave analysis (RCWA) simulation techniques to satisfy stringent requirements for thermal management applications requiring high thermal radiation absorption over a narrow angular range and low visible radiation absorption over a broad angular range. After optimization and fabrication, characterization was performed using reflection spectroscopy and normal incidence emissivity measurements. Excellent agreement between simulation and experiment was obtained. PMID:23546065

  18. Direct force wall shear measurements in pressure-driven three-dimensional turbulent boundary layers

    NASA Technical Reports Server (NTRS)

    Mcallister, J. E.; Tennant, M. H.; Pierce, F. J.

    1982-01-01

    Unique, simultaneous direct measurements of the magnitude and direction of the local wall shear stress in a pressure-driven three-dimensional turbulent boundary layer are presented. The flow is also described with an oil streak wall flow pattern, a map of the wall shear stress-wall pressure gradient orientations, a comparison of the wall shear stress directions relative to the directions of the nearest wall velocity as measured with a typical, small boundary layer directionally sensitive claw probe, as well as limiting wall streamline directions from the oil streak patterns, and a comparison of the freestream streamlines and the wall flow streamlines. A review of corrections for direct force sensing shear meters for two-dimensional flows is presented with a brief discussion of their applicability to three-dimensional devices.

  19. Medicinal chemistry of fluorinated cyclic and acyclic nucleoside phosphonates.

    PubMed

    Baszczyňski, Ondřej; Janeba, Zlatko

    2013-11-01

    The fluorine atom plays an important role in medicinal chemistry because fluorine substitution has a strong impact on the physical, chemical, and biological properties of bioactive compounds. Such fluorine modifications have also been extensively studied among the pharmaceutically important class of nucleoside phosphonates, nucleotide analogues in which the phosphate group is replaced by the enzymatically and chemically stable phosphonate moiety. The fluorinated nucleoside phosphonates abound with antiviral, antiparasitic, and anticancer properties because they are able to act as inhibitors of important enzymes of nucleoside/nucleotide metabolism. In this paper, we review the biological properties of cyclic and acyclic nucleoside phosphonates modified by the attachment of one or more fluorine atoms to various parts of the molecule, namely to nucleobases, alkylphosphonate groups, cyclic or acyclic linkers, or to prodrug moieties. PMID:23893552

  20. Three-dimensional imaging for indirect-direct bonding.

    PubMed

    El-Timamy, Ahmed M; El-Sharaby, Fouad A; Eid, Faten H; Mostafa, Yehya A

    2016-06-01

    The aim of this article is to introduce a new concept of bracket positioning with special consideration to root axes. Cone-beam computed tomography imaging and computer-aided manufacturing were used to produce stereolithographic trays for indirect-direct bonding. PMID:27242004

  1. Photographic observation of magnetic domain structure with three-dimensional local magnetization direction

    NASA Astrophysics Data System (ADS)

    Meguro, Sakae; Akahane, Koichi; Saito, Shin

    2016-07-01

    The direction of magnetization of a magnetic material is possibly oriented three-dimensionally because of the presence of magnetic anisotropy field, self-demagnetizing field, and stray field. Therefore, the three-dimensional detection of the direction of magnetization is required. The method of magnetic domain observation by photographic imaging utilizing the Kerr effect is widely used. If the perpendicular magnetization components exist, there is a problem that obliquely incident light has superimposed longitudinal Kerr and polar Kerr effects. To perform the three-dimensional detection of magnetization direction, it is necessary to eliminate the influence of the polar Kerr effect from the Kerr effect of obliquely incident light. We report the photographic observation of the magnetic domain structure and the detection of the three-dimensional local magnetization direction using the Kerr effect, applying only an in-plane saturation magnetic field.

  2. Two-dimensional location and direction estimating method.

    PubMed

    Haga, Teruhiro; Tsukamoto, Sosuke; Hoshino, Hiroshi

    2008-01-01

    In this paper, a method of estimating both the position and the rotation angle of an object on a measurement stage was proposed. The system utilizes the radio communication technology and the directivity of an antenna. As a prototype system, a measurement stage (a circle 240mm in diameter) with 36 antennas that placed in each 10 degrees was developed. Two transmitter antennas are settled in a right angle on the stage as the target object, and the position and the rotation angle is estimated by measuring efficiency of the radio communication of each 36 antennas. The experimental result revealed that even when the estimated location is not so accurate (about a 30 mm error), the rotation angle is accurately estimated (about 2.33 degree error on average). The result suggests that the proposed method will be useful for estimating the location and the direction of an object. PMID:19162938

  3. Parallel direct numerical simulation of three-dimensional spray formation

    NASA Astrophysics Data System (ADS)

    Chergui, Jalel; Juric, Damir; Shin, Seungwon; Kahouadji, Lyes; Matar, Omar

    2015-11-01

    We present numerical results for the breakup mechanism of a liquid jet surrounded by a fast coaxial flow of air with density ratio (water/air) ~ 1000 and kinematic viscosity ratio ~ 60. We use code BLUE, a three-dimensional, two-phase, high performance, parallel numerical code based on a hybrid Front-Tracking/Level Set algorithm for Lagrangian tracking of arbitrarily deformable phase interfaces and a precise treatment of surface tension forces. The parallelization of the code is based on the technique of domain decomposition where the velocity field is solved by a parallel GMRes method for the viscous terms and the pressure by a parallel multigrid/GMRes method. Communication is handled by MPI message passing procedures. The interface method is also parallelized and defines the interface both by a discontinuous density field as well as by a triangular Lagrangian mesh and allows the interface to undergo large deformations including the rupture and/or coalescence of interfaces. EPSRC Programme Grant, MEMPHIS, EP/K0039761/1.

  4. The dimensional nature of eating pathology: Evidence from a direct comparison of categorical, dimensional, and hybrid models.

    PubMed

    Luo, Xiaochen; Donnellan, M Brent; Burt, S Alexandra; Klump, Kelly L

    2016-07-01

    Eating disorders are conceptualized as categorical rather than dimensional in the current major diagnostic system (Diagnostic and Statistical Manual of Mental Disorders; 5th ed.; American Psychiatric Association, 2013) and in many previous studies. However, previous research has not critically evaluated this assumption or tested hybrid models (e.g., modeling latent variables with both dimensional and categorical features). Accordingly, the current study directly compared categorical, dimensional, and hybrid models for eating pathology in a large, population-based sample. Participants included 3,032 female and male twins (ages 9-30 years) from the Michigan State University Twin Registry. The Minnesota Eating Behaviors Survey was used to assess disordered eating symptoms including body dissatisfaction, weight preoccupation, binge eating, and compensatory behaviors. Results showed that dimensional models best fit the data in the overall sample as well as across subgroups divided by sex and pubertal status (e.g., prepubertal vs. postpubertal). It is interesting to note that the results favored more categorical models when using a case-control subset of our sample with participants who either endorsed substantial eating pathology or no/little eating pathology. Overall, findings provide support for a dimensional conceptualization of eating pathology and underscore the importance of using community samples to capture the full range of severity of eating pathology when investigating questions about taxonomy. (PsycINFO Database Record PMID:27214062

  5. Logarithmic corrections in (4+1) -dimensional directed percolation.

    PubMed

    Grassberger, Peter

    2009-05-01

    We simulate directed site percolation on two lattices with four spatial and one timelike dimensions (simple and body-centered hypercubic in space) with the standard single cluster spreading scheme. For efficiency, the code uses the same ingredients (hashing, histogram reweighing, and improved estimators) as described by Grassberger [Phys. Rev. E 67, 036101 (2003)]. Apart from providing the most precise estimates for p_{c} on these lattices, we provide a detailed comparison with the logarithmic corrections calculated by [Janssen and Stenull [Phys. Rev. E 69, 016125 (2004)]. Fits with the leading logarithmic terms alone would give estimates of the powers of these logarithms which are too big by typically 50%. When the next-to-leading terms are included, each of the measured quantities (the average number of sites wetted at time t , their average distance from the seed, and the probability of cluster survival) can be fitted nearly perfectly. But these fits would not be mutually consistent. With a consistent set of fit parameters, one obtains still much improvement over the leading log approximation. In particular we show that there is one combination of these three observables which seems completely free of logarithmic terms. PMID:19518501

  6. Vinculin regulates directionality and cell polarity in two- and three-dimensional matrix and three-dimensional microtrack migration

    PubMed Central

    Rahman, Aniqua; Carey, Shawn P.; Kraning-Rush, Casey M.; Goldblatt, Zachary E.; Bordeleau, Francois; Lampi, Marsha C.; Lin, Deanna Y.; García, Andrés J.; Reinhart-King, Cynthia A.

    2016-01-01

    During metastasis, cells can use proteolytic activity to form tube-like “microtracks” within the extracellular matrix (ECM). Using these microtracks, cells can migrate unimpeded through the stroma. To investigate the molecular mechanisms of microtrack migration, we developed an in vitro three-dimensional (3D) micromolded collagen platform. When in microtracks, cells tend to migrate unidirectionally. Because focal adhesions are the primary mechanism by which cells interact with the ECM, we examined the roles of several focal adhesion molecules in driving unidirectional motion. Vinculin knockdown results in the repeated reversal of migration direction compared with control cells. Tracking the position of the Golgi centroid relative to the position of the nucleus centroid reveals that vinculin knockdown disrupts cell polarity in microtracks. Vinculin also directs migration on two-dimensional (2D) substrates and in 3D uniform collagen matrices, as indicated by reduced speed, shorter net displacement, and decreased directionality in vinculin-deficient cells. In addition, vinculin is necessary for focal adhesion kinase (FAK) activation in three dimensions, as vinculin knockdown results in reduced FAK activation in both 3D uniform collagen matrices and microtracks but not on 2D substrates, and, accordingly, FAK inhibition halts cell migration in 3D microtracks. Together these data indicate that vinculin plays a key role in polarization during migration. PMID:26960796

  7. Acyclic nucleoside/nucleotide analogues with an imidazole ring skeleton.

    PubMed

    Chen, H M; Hosmane, R S

    2001-08-01

    Syntheses of a few acyclic nucleoside and acyclic nucleoside phosphonate analogues containing an imidazole ring have been reported. These analogues include methyl 1-(2-hydroxyethoxymethyl)imidazole-4, 5-dicarbo-xylate (1), 4,5-dicarbamoyl-1-(2-hydroxyethoxymethyl)imidazole (2), 4,5-dicyano-1-(2-hydroxyethoxymethyl)imidazole (4), Methyl 1-(2-bromoethoxymethyl)imidazole-4,5-dicarboxylate (7), 4,5-dicyano-(2-bromoethoxymethyl)imidazole (8), and Methyl 1-(2-phosphonomethoxyethyl)imidazole (10). Also reported are a few potential prodrugs of the above compounds, including the acetyl derivatives 5 and 6 (of 1 and 4, respectively), and the diethyl phosphonate ester 9 (of 10). In addition, the corresponding benzyl-protected precursors 11 and 12 (of 1 and 4, respectively), along with their common hydrolysis product, 1-(2-benzyloxy-ethoxymethyl)-4,5-imidazoledicarboxylic acid (3), are reported. Another potential prodrug included in the list is 1-(2-acetoxyethyl)-4,5-dicyanoimidazole (15). The compounds were screened for in vitro antiviral activity against a wide variety of herpes and respiratory viruses. The most active compound was the phosphonate analogue 9 which exhibited an anti-measles virus activity with an EC50 of <2.5 microg/mL and an SI value of > 176. PMID:11554548

  8. Estimating changes in lighting direction in binocularly viewed three-dimensional scenes

    PubMed Central

    Gerhard, Holly E.; Maloney, Laurence T.

    2010-01-01

    We examine human ability to detect changes in scene lighting. Thirteen observers viewed three-dimensional rendered scenes stereoscopically. Each scene consisted of a randomly generated three-dimensional “Gaussian bump” surface rendered under a combination of collimated and diffuse light sources. During each trial, the collimated source underwent a small, quick change of position in one of four directions. The observer's task was to classify the direction of the lighting change. All observers were above chance in performing the task. We developed a model that combined two sources of information, a shape map and a shading map, to predict lighting change direction. We used this model to predict patterns of errors both across observers and across scenes differing in shape. We found that errors in estimating lighting direction were primarily the result of errors in representing surface shape. We characterized the surface features that affected performance in the classification task. PMID:21106676

  9. Acyclic CB[n]-Type Molecular Containers: Effect of Solubilizing Group on their Function as Solubilizing Excipients

    PubMed Central

    Zhang, Ben; Zavalij, Peter Y.; Isaacs, Lyle

    2014-01-01

    We report the synthesis and x-ray crystal structures of three acyclic CB[n]-type molecular containers (2a, 2h, 2f) that differ in the charge on their solubilizing groups (SO3−, OH, NH3+). The x-ray crystal structures of compounds 2h and 2f reveal a self-folding of the ArOCH2CH2X wall into the cavity driven by π–π interactions, H-bonds and ion-dipole interactions. The need to reverse this self-folding phenomenon upon guest binding decreases the affinity of 2h and 2f toward cationic guests in water relative to 2a as revealed by direct 1H NMR and UV/Vis titrations as well as UV/Vis competition experiments. We determined the pKa of 6-aminocoumarin 7 (pKa = 3.6) on its own and in the presence anionic, neutral, and cationic hosts (2a: pKa = 4.9; 2h: pKa = 4.1; 2f, pKa = 3.4) which reflect in part the relevance of direct ion-ion interactions between the arms of the host and the guest toward the recognition properties of acyclic CB[n]-type containers. Finally, we showed that the weaker binding affinities measured for neutral and positively charged hosts 2h and 2f compared to anionic 2a results in a decreased ability to act as solubilizing agents for either cationic (tamoxifen), neutral (17α–ethynylestradiol), or anionic (indomethacin) drugs in water. The results establish that acyclic CB[n] compounds that bear anionic solubilizing groups are most suitable for development as general purpose solubilizing excipients for insoluble pharmaceutical agents. PMID:24595500

  10. Amplification and directional emission of surface acoustic waves by a two-dimensional electron gas

    SciTech Connect

    Shao, Lei; Pipe, Kevin P.

    2015-01-12

    Amplification of surface acoustic waves (SAWs) by electron drift in a two-dimensional electron gas (2DEG) is analyzed analytically and confirmed experimentally. Calculations suggest that peak power gain per SAW radian occurs at a more practical carrier density for a 2DEG than for a bulk material. It is also shown that SAW emission with tunable directionality can be achieved by modulating a 2DEG's carrier density (to effect SAW generation) in the presence of an applied DC field that amplifies SAWs propagating in a particular direction while attenuating those propagating in the opposite direction.

  11. Iridium-Catalyzed Diastereoselective and Enantioselective Allylic Substitutions with Acyclic α-Alkoxy Ketones.

    PubMed

    Jiang, Xingyu; Chen, Wenyong; Hartwig, John F

    2016-05-01

    The asymmetric alkylation of acyclic ketones is a longstanding challenge in organic synthesis. Reported herein are diastereoselective and enantioselective allylic substitutions with acyclic α-alkoxy ketones catalyzed by a metallacyclic iridium complex to form products with contiguous stereogenic centers derived from the nucleophile and electrophile. These reactions occur between allyl methyl carbonates and unstabilized copper(I) enolates generated in situ from acyclic α-alkoxy ketones. The resulting products can be readily converted into enantioenriched tertiary alcohols and tetrahydrofuran derivatives without erosion of enantiomeric purity. PMID:27038004

  12. Forming Stereogenic Centers in Acyclic Systems from Alkynes.

    PubMed

    Vabre, Roxane; Island, Biana; Diehl, Claudia J; Schreiner, Peter R; Marek, Ilan

    2015-08-17

    The combined carbometalation/zinc homologation followed by reactions with α-heterosubstituted aldehydes and imines proceed through a chair-like transition structure with the substituent of the incoming aldehyde residue preferentially occupying a pseudo-axial position to avoid the two gauche interactions. The heteroatom in the axial position produces a chelated intermediate (and not a Cornforth-Evans transition structure for α-chloro aldehydes and imines) leading to a face differentiation in the allylation reaction. This method provides access to functionalized products in which three new carbon-carbon bonds and two to three stereogenic centers, including a quaternary one, were created in acyclic systems in a single-pot operation from simple alkynes. PMID:26130570

  13. Tautomerism and stereodynamics of acyclic. beta. -diketo esters

    SciTech Connect

    Romas, A.D.; Esakov, S.M.; Petrov, Al.An.; Ershov, B.A.

    1986-04-10

    The tautomeric transformations and stereodynamics of a series of ring-substituted acyclic ..beta..-diketo esters p-XC/sub 6/H/sub 4/COCH(CH/sub 3/CO)CO/sub 2/CH/sub 3/ in hexachlorobutadiene and nitrobenzene were investigated by proton and carbon magnetic resonance spectroscopy. The enolization of the compounds is accompanied by the formation of two cis-enol forms (of the three theoretically possible forms) with nonchelated benzene of methoxycarbonyl groups respectively. The form with the nonchelated methoxycarbonyl group predominates in the equilibrium on account of the smaller loss of entropy during its formation compared with the enol containing the nonchelated benzoyl group. The kinetic characteristics of the mutual transformations of the enolic forms in hexachlorobutadiene and nitrobenzene respectively were determined by integration and dynamic nuclear magnetic resonance.

  14. Direct method for the design of optimal three-dimensional aerodynamic shapes

    NASA Astrophysics Data System (ADS)

    Isakova, N. P.; Kraiko, A. A.; P'yankov, K. S.

    2012-11-01

    A direct optimization method for a broad class of three-dimensional aerodynamic shapes based on the approximation of the desired geometry by Bernstein-Bézier surfaces is developed. The high efficiency of the method is demonstrated by applying it to the design of an optimal supersonic section of an axisymmetric maximum-thrust de Laval nozzle. The method is also tested as applied to the design of a three-dimensional supersonic nozzle section in a dense multi-nozzle setup. In addition to three-dimensional supersonic nozzle sections with a circular throat, nozzles with a varying throat shape are considered. The results suggest that the method can be applied to various problems of 3D shape optimization.

  15. Direct numerical simulation of steady state, three dimensional, laminar flow around a wall mounted cube

    NASA Astrophysics Data System (ADS)

    Liakos, Anastasios; Malamataris, Nikolaos A.

    2014-05-01

    The topology and evolution of flow around a surface mounted cubical object in three dimensional channel flow is examined for low to moderate Reynolds numbers. Direct numerical simulations were performed via a home made parallel finite element code. The computational domain has been designed according to actual laboratory experiment conditions. Analysis of the results is performed using the three dimensional theory of separation. Our findings indicate that a tornado-like vortex by the side of the cube is present for all Reynolds numbers for which flow was simulated. A horseshoe vortex upstream from the cube was formed at Reynolds number approximately 1266. Pressure distributions are shown along with three dimensional images of the tornado-like vortex and the horseshoe vortex at selected Reynolds numbers. Finally, and in accordance to previous work, our results indicate that the upper limit for the Reynolds number for which steady state results are physically realizable is roughly 2000.

  16. Direct design of aspherical lenses for extended non-Lambertian sources in two-dimensional geometry

    PubMed Central

    Wu, Rengmao; Hua, Hong; Benítez, Pablo; Miñano, Juan C.

    2016-01-01

    Illumination design for extended sources is very important for practical applications. The existing direct methods that are all developed for extended Lambertian sources are not applicable to extended non-Lambertian sources whose luminance is a function of position and direction. What we present in this Letter is to our knowledge the first direct method for extended non-Lambertian sources. In this method, the edge rays and the interior rays are both used, and the output intensity at a given direction is calculated to be the integral of the luminance function of all the outgoing rays at this direction. No cumbersome iterative illuminance compensation is needed. Two examples are presented to demonstrate the elegance of this method in prescribed intensity design for extended non-Lambertian sources in two-dimensional geometry. PMID:26125361

  17. Multigroup Neutron/Gamma-Ray Direct Integration Transport Code System for Two-Dimensional Cylindrical Geometry.

    Energy Science and Technology Software Center (ESTSC)

    1980-10-15

    Version 00 PALLAS-2DCY-FX is a code for direct integration of the transport equation in two-dimensional (r,z) geometry. It solves the energy and angular-dependent Boltzmann transport equation with general anisotropic scattering in cylindrical geometry. Its principal applications are to neutron or gamma-ray transport problems in the forward mode. The code is particularly designed for and suited to the solution of deep penetration radiation transport problems with an external (fixed) source.

  18. A combined direct/inverse three-dimensional transonic wing design method for vector computers

    NASA Technical Reports Server (NTRS)

    Weed, R. A.; Carlson, L. A.; Anderson, W. K.

    1984-01-01

    A three-dimensional transonic-wing design algorithm for vector computers is developed, and the results of sample computations are presented graphically. The method incorporates the direct/inverse scheme of Carlson (1975), a Cartesian grid system with boundary conditions applied at a mean plane, and a potential-flow solver based on the conservative form of the full potential equation and using the ZEBRA II vectorizable solution algorithm of South et al. (1980). The accuracy and consistency of the method with regard to direct and inverse analysis and trailing-edge closure are verified in the test computations.

  19. Direct TEM observations of growth mechanisms of two-dimensional MoS2 flakes

    NASA Astrophysics Data System (ADS)

    Fei, Linfeng; Lei, Shuijin; Zhang, Wei-Bing; Lu, Wei; Lin, Ziyuan; Lam, Chi Hang; Chai, Yang; Wang, Yu

    2016-07-01

    A microscopic understanding of the growth mechanism of two-dimensional materials is of particular importance for controllable synthesis of functional nanostructures. Because of the lack of direct and insightful observations, how to control the orientation and the size of two-dimensional material grains is still under debate. Here we discern distinct formation stages for MoS2 flakes from the thermolysis of ammonium thiomolybdates using in situ transmission electron microscopy. In the initial stage (400 °C), vertically aligned MoS2 structures grow in a layer-by-layer mode. With the increasing temperature of up to 780 °C, the orientation of MoS2 structures becomes horizontal. When the growth temperature reaches 850 °C, the crystalline size of MoS2 increases by merging adjacent flakes. Our study shows direct observations of MoS2 growth as the temperature evolves, and sheds light on the controllable orientation and grain size of two-dimensional materials.

  20. A direct algorithm for solution of incompressible three-dimensional unsteady Navier-Stokes equations

    NASA Technical Reports Server (NTRS)

    Osswald, G. A.; Ghia, K. N.; Ghia, U.

    1987-01-01

    A direct, implicit, numerical solution algorithm, with second-order accuracy in space and time, is constructed for the three-dimensional unsteady incompressible Navier-Stokes equations formulated in terms of velocity and vorticity, using generalized orthogonal coordinates to achieve the accurate solution of complex viscous flow configurations. A numerically stable, efficient, direct inversion procedure is developed for the computationally intensive divergence-curl elliptic velocity problem. This overdetermined partial differential operator is first formulated as a uniquely determined, nonsingular matrix-vector problem; this aspect of the procedure is a unique feature of the present analysis. The three-dimensional vorticity-transport equation is solved by a modified factorization technique which completely eliminates the need for any block-matrix inversions and only scalar tridiagonal matrices need to be inverted. The method is applied to the test problem of the three-dimensional flow within a shear-driven cubical box. Coherent streamwise vortex structures are observed within the steady-state flow at Re = 100.

  1. Direct TEM observations of growth mechanisms of two-dimensional MoS2 flakes.

    PubMed

    Fei, Linfeng; Lei, Shuijin; Zhang, Wei-Bing; Lu, Wei; Lin, Ziyuan; Lam, Chi Hang; Chai, Yang; Wang, Yu

    2016-01-01

    A microscopic understanding of the growth mechanism of two-dimensional materials is of particular importance for controllable synthesis of functional nanostructures. Because of the lack of direct and insightful observations, how to control the orientation and the size of two-dimensional material grains is still under debate. Here we discern distinct formation stages for MoS2 flakes from the thermolysis of ammonium thiomolybdates using in situ transmission electron microscopy. In the initial stage (400 °C), vertically aligned MoS2 structures grow in a layer-by-layer mode. With the increasing temperature of up to 780 °C, the orientation of MoS2 structures becomes horizontal. When the growth temperature reaches 850 °C, the crystalline size of MoS2 increases by merging adjacent flakes. Our study shows direct observations of MoS2 growth as the temperature evolves, and sheds light on the controllable orientation and grain size of two-dimensional materials. PMID:27412892

  2. Direct TEM observations of growth mechanisms of two-dimensional MoS2 flakes

    PubMed Central

    Fei, Linfeng; Lei, Shuijin; Zhang, Wei-Bing; Lu, Wei; Lin, Ziyuan; Lam, Chi Hang; Chai, Yang; Wang, Yu

    2016-01-01

    A microscopic understanding of the growth mechanism of two-dimensional materials is of particular importance for controllable synthesis of functional nanostructures. Because of the lack of direct and insightful observations, how to control the orientation and the size of two-dimensional material grains is still under debate. Here we discern distinct formation stages for MoS2 flakes from the thermolysis of ammonium thiomolybdates using in situ transmission electron microscopy. In the initial stage (400 °C), vertically aligned MoS2 structures grow in a layer-by-layer mode. With the increasing temperature of up to 780 °C, the orientation of MoS2 structures becomes horizontal. When the growth temperature reaches 850 °C, the crystalline size of MoS2 increases by merging adjacent flakes. Our study shows direct observations of MoS2 growth as the temperature evolves, and sheds light on the controllable orientation and grain size of two-dimensional materials. PMID:27412892

  3. Dipolar colloids in apolar media: direct microscopy of two-dimensional suspensions

    PubMed Central

    Janai, Erez; Cohen, Avner P.; Butenko, Alexander V.; Schofield, Andrew B.; Schultz, Moty; Sloutskin, Eli

    2016-01-01

    Spherical colloids, in an absence of external fields, are commonly assumed to interact solely through rotationally-invariant potentials, u(r). While the presence of permanent dipoles in aqueous suspensions has been previously suggested by some experiments, the rotational degrees of freedom of spherical colloids are typically neglected. We prove, by direct experiments, the presence of permanent dipoles in commonly used spherical poly(methyl methacrylate) (PMMA) colloids, suspended in an apolar organic medium. We study, by a combination of direct confocal microscopy, computer simulations, and theory, the structure and other thermodynamical properties of organic suspensions of colloidal spheres, confined to a two-dimensional (2D) monolayer. Our studies reveal the effects of the dipolar interactions on the structure and the osmotic pressure of these fluids. These observations have far-reaching consequences for the fundamental colloidal science, opening new directions in self-assembly of complex colloidal clusters. PMID:27346611

  4. Dimensional and material characteristics of direct deposited tool steel by CO II laser

    NASA Astrophysics Data System (ADS)

    Choi, J.

    2006-01-01

    Laser aided direct metalimaterial deposition (DMD) process builds metallic parts layer-by-layer directly from the CAD representation. In general, the process uses powdered metaUmaterials fed into a melt pool, creating fully dense parts. Success of this technology in the die and tool industry depends on the parts quality to be achieved. To obtain designed geometric dimensions and material properties, delicate control of the parameters such as laser power, spot diameter, traverse speed and powder mass flow rate is critical. In this paper, the dimensional and material characteristics of directed deposited H13 tool steel by CO II laser are investigated for the DMD process with a feedback height control system. The relationships between DMD process variables and the product characteristics are analyzed using statistical techniques. The performance of the DMD process is examined with the material characteristics of hardness, porosity, microstructure, and composition.

  5. Dipolar colloids in apolar media: direct microscopy of two-dimensional suspensions

    NASA Astrophysics Data System (ADS)

    Janai, Erez; Cohen, Avner P.; Butenko, Alexander V.; Schofield, Andrew B.; Schultz, Moty; Sloutskin, Eli

    2016-06-01

    Spherical colloids, in an absence of external fields, are commonly assumed to interact solely through rotationally-invariant potentials, u(r). While the presence of permanent dipoles in aqueous suspensions has been previously suggested by some experiments, the rotational degrees of freedom of spherical colloids are typically neglected. We prove, by direct experiments, the presence of permanent dipoles in commonly used spherical poly(methyl methacrylate) (PMMA) colloids, suspended in an apolar organic medium. We study, by a combination of direct confocal microscopy, computer simulations, and theory, the structure and other thermodynamical properties of organic suspensions of colloidal spheres, confined to a two-dimensional (2D) monolayer. Our studies reveal the effects of the dipolar interactions on the structure and the osmotic pressure of these fluids. These observations have far-reaching consequences for the fundamental colloidal science, opening new directions in self-assembly of complex colloidal clusters.

  6. Two-dimensional directional proton emission in dissociative ionization of H(2).

    PubMed

    Gong, Xiaochun; He, Peilun; Song, Qiying; Ji, Qinying; Pan, Haifeng; Ding, Jingxin; He, Feng; Zeng, Heping; Wu, Jian

    2014-11-14

    An intense phase-controlled orthogonally polarized two-color ultrashort laser pulse is used to singly ionize and dissociate H_{2} into a neutral hydrogen atom and a proton. Emission-direction and kinetic-energy dependent asymmetric dissociation of H_{2} is observed as a function of the relative phase of the orthogonally polarized two-color pulse. Significant asymmetric proton emission is measured in the direction between two polarization axes. Our numerical simulations of the time-dependent Schrödinger equation reproduce many of the observed features. The asymmetry is attributed to the coherent superposition of two-dimensional nuclear wave packets with opposite parities, which have the same energies and overlap in the same emission directions. PMID:25432039

  7. Dipolar colloids in apolar media: direct microscopy of two-dimensional suspensions.

    PubMed

    Janai, Erez; Cohen, Avner P; Butenko, Alexander V; Schofield, Andrew B; Schultz, Moty; Sloutskin, Eli

    2016-01-01

    Spherical colloids, in an absence of external fields, are commonly assumed to interact solely through rotationally-invariant potentials, u(r). While the presence of permanent dipoles in aqueous suspensions has been previously suggested by some experiments, the rotational degrees of freedom of spherical colloids are typically neglected. We prove, by direct experiments, the presence of permanent dipoles in commonly used spherical poly(methyl methacrylate) (PMMA) colloids, suspended in an apolar organic medium. We study, by a combination of direct confocal microscopy, computer simulations, and theory, the structure and other thermodynamical properties of organic suspensions of colloidal spheres, confined to a two-dimensional (2D) monolayer. Our studies reveal the effects of the dipolar interactions on the structure and the osmotic pressure of these fluids. These observations have far-reaching consequences for the fundamental colloidal science, opening new directions in self-assembly of complex colloidal clusters. PMID:27346611

  8. Visualization of Bloch surface waves and directional propagation effects on one-dimensional photonic crystal substrate.

    PubMed

    Hung, Yu-Ju; Lin, I-Sheng

    2016-07-11

    This paper reports a novel approach to the direct observation of Bloch surface waves, wherein a layer of fluorescent material is deposited directly on the surface of a semi-infinite periodic layered cell. A set of surface nano-gratings is used to couple pumping light to Bloch surface waves, while the sample is rotated until the pumping light meets the quasi-phase matching conditions. This study investigated the directional propagation of waves on stripe and circular one-dimensional grating structures by analyzing the dispersion relationship of the first two eigen modes. Our results demonstrate the efficacy of the proposed scheme in visualizing Bloch surface waves, which could be extended to a variety of other devices. PMID:27410869

  9. Three-dimensional viscous-flow computations using a directionally hybrid implicit-explicit procedure

    NASA Astrophysics Data System (ADS)

    Rizk, Y. M.; Chaussee, D. S.

    A new, directionally dependent, hybrid numerical algorithm for solving the unsteady, three-dimensional Navier-Stokes equations has been developed and used to compute the viscous supersonic flow over complex configurations, which may generate local regions of embedded subsonic or streamwise separated flows or both. The new hybrid implicit-explicit algorithm is derived from the more general implicit Beam-Warming algorithm and is particularly suitable for viscous computations in which the grid spacing in the direction outward from the body is considerably smaller than the spacing in the other two directions. Numerical results obtained from both the hybrid and implicit schemes are presented and compared on the basis of numerical stability, convergence history, and computer and core memory requirements.

  10. Two-dimensional diffusion time correlation experiment using a single direction gradient

    NASA Astrophysics Data System (ADS)

    Paulsen, Jeffrey L.; Song, Yi-Qiao

    2014-07-01

    The time dependence of the diffusion coefficient is a well known property of porous media and commonly obtained by pulsed field gradient (PFG) NMR. In practical materials, its analysis can be complicated by the presence of a broad pore size distribution and multiple fluid phases with different diffusion coefficients. We propose a two-dimensional Diffusion Time Correlation experiment (DTC), which utilizes the double-PFG with a single-direction gradient to yield a two-dimensional correlation function of the diffusion coefficient for two different diffusion times. This correlation map separates out restricted diffusion from the bulk diffusion process and we demonstrate this on a plant and bulk water sample. In its development, we show that the d-PFG should then be thought of as correlating two apparent diffusion coefficients measured by two overlapping gradient waveforms.

  11. Three-dimensional buried polymer waveguides via femtosecond direct laser writing with two-photon absorption

    NASA Astrophysics Data System (ADS)

    Nguyen, Duc H. H.; Kaleta, Kerstin; Hengsbach, Stefan; Ostrzinski, Ute; Pfeiffer, Karl; Hollenbach, Uwe; Mohr, Jürgen

    2014-05-01

    Free-form three-dimensional buried waveguides with symmetric and adjustable core dimensions have been fabricated via femtosecond direct laser writing in a novel photopolymer. High refractive index contrast of 0.013 between the core and the cladding is achieved by external diffusion of a low refractive index monomer. Measured near-field intensity at the end facet of the waveguides shows single-mode Gaussian profile. Voxel size and refractive index profile can be adjusted by adapting writing speed and laser intensity. The waveguide length is several centimeters which is suitable for on-board interconnects. This concept can be used to produce three-dimensional arrays of optical waveguide network routers, optofans, pitch converters or splitters.

  12. Structural Interactions within Lithium Salt Solvates. Acyclic Carbonates and Esters

    SciTech Connect

    Afroz, Taliman; Seo, D. M.; Han, Sang D.; Boyle, Paul D.; Henderson, Wesley A.

    2015-03-06

    Solvate crystal structures serve as useful models for the molecular-level interactions within the diverse solvates present in liquid electrolytes. Although acyclic carbonate solvents are widely used for Li-ion battery electrolytes, only three solvate crystal structures with lithium salts are known for these and related solvents. The present work, therefore, reports six lithium salt solvate structures with dimethyl and diethyl carbonate: (DMC)2:LiPF6, (DMC)1:LiCF3SO3, (DMC)1/4:LiBF4, (DEC)2:LiClO4, (DEC)1:LiClO4 and (DEC)1:LiCF3SO3 and four with the structurally related methyl and ethyl acetate: (MA)2:LiClO4, (MA)1:LiBF4, (EA)1:LiClO4 and (EA)1:LiBF4.

  13. Study on the Mechanical Properties of Three-Dimensional Directly Binding Hydroxyapatite Powder.

    PubMed

    Wang, Yanen; Li, Xinpei; Wei, Qinghua; Yang, Mingming; Wei, Shengmin

    2015-05-01

    In the three-dimensional directly fabricating hydroxyapatite composite artificial bone scaffold process, the liquid bio-binder is sprayed on the surface of bioceramics powder layer. The spraying volume and the powder size directly influence the mechanical properties of the bone scaffold and the future biodegradation performance. When the size of powder is stable, the amount of binder spraying will directly affect the mechanical strength of bone scaffold. In order to figure out the solidification mechanism of α-n-butyl cyanoacrylate (NBCA) bio-binder on the hydroxyapatite (HA) powder layer, the molecular dynamics simulation method is applied to investigate the binding energy shifts between NBCA on HA crystallographic planes. The mechanical properties can be deduced from this methodology; furthermore, the Knoop identification experiments are used to investigate the effective elastic modules of pure HA system and HA/NBCA composite model. Both the simulation and the experiments results elucidate that HA (110) has the highest binding energy with NBCA as the high planar atom density and the mechanical properties of HA/NBCA mixed system are stronger than the pure HA system on three-dimensional crystallographic; in this sense, the bone scaffolds with different strengths could be fabricated by controlling various NBCA binders liquid doses on the surface of HA powder layers during the 3D printing process. PMID:25556069

  14. Acyclic diterpene glycosides, capsianosides VIII, IX, X, XIII, XV and XVI from the fruits of Paprika Capsicum annuum L. var. grossum BAILEY and Jalapeño Capsicum annuum L. var. annuum.

    PubMed

    Lee, Jong-Hyun; Kiyota, Naoko; Ikeda, Tsuyoshi; Nohara, Toshihiro

    2006-10-01

    Paprika and Jalapeño are used as vegetables and spices. We have obtained six new acyclic diterpene glycosides, called capsianosides XIII (2), XV (3), IX (4), XVI (5), X (6) and VIII (7) together with known capsianoside II (1) from the fruits of the Paprika and Jalapeño. The structures of these compounds have been elucidated by the (1)H- and (13)C-NMR spectra and two-dimensional NMR methods. PMID:17015971

  15. Directional coding of three-dimensional movements by the vestibular semicircular canals.

    PubMed

    Rabbitt, R D

    1999-06-01

    A morphologically descriptive mathematical model was developed to study the role of labyrinthine geometry in determining sensitivities of each semicircular canal to angular motion stimuli in three-dimensional (3D) space. For this, equations describing viscous flow of the endolymph and poro-elastic response of the cupulae were coupled together and solved within a 3D reconstructed geometry. Results predict the existence of prime rotational directions about which the labyrinth resolves 3D angular movements into separate vectorial components. The components are predicted to be transmitted to the brain separately, one coded by each canal nerve. Prime directions predicted by the model are non-orthogonal, distinct from the anatomical canal planes, and distinct from the directions of rotation which elicit maximal responses of individual canal nerves. They occur for each canal along the intersection of the two null planes defined by its sister canals. Hence, rotation about a prime direction excites only one canal nerve. This contrasts the situation for rotations about anatomical canal planes, or about maximal response directions, where the model predicts activation of multiple canal nerves. The prime directions are sensitive to labyrinthine morphology and, hence, are predicted to vary between species and, to a lesser extent, vary between individual animals. Prime directions were estimated in the present work using a mathematical model, but could be determined experimentally based on the directional sensitivities of individual canal nerves. The model also predicts the existence of dominant eigenmodes and time constants associated with rotation in each of the prime directions. Results may have implications regarding the central representation of angular head movements in space as well as the neuronal mappings between three-canal afferent inputs and motor outputs. PMID:10420568

  16. Three-dimensional direct cell patterning in collagen hydrogels with near-infrared femtosecond laser

    NASA Astrophysics Data System (ADS)

    Hribar, Kolin C.; Meggs, Kyle; Liu, Justin; Zhu, Wei; Qu, Xin; Chen, Shaochen

    2015-11-01

    We report a methodology for three-dimensional (3D) cell patterning in a hydrogel in situ. Gold nanorods within a cell-encapsulating collagen hydrogel absorb a focused near-infrared femtosecond laser beam, locally denaturing the collagen and forming channels, into which cells migrate, proliferate, and align in 3D. Importantly, pattern resolution is tunable based on writing speed and laser power, and high cell viability (>90%) is achieved using higher writing speeds and lower laser intensities. Overall, this patterning technique presents a flexible direct-write method that is applicable in tissue engineering systems where 3D alignment is critical (such as vascular, neural, cardiac, and muscle tissue).

  17. Generation of two-dimensional dust vortex flows in a direct current discharge plasma

    SciTech Connect

    Uchida, Giichiro; Iizuka, Satoru; Kamimura, Tetsuo; Sato, Noriyoshi

    2009-05-15

    The two-dimensional dust vortex flows are observed in a direct current discharge plasma near the edge of a metal plate which is situated in the dust-particle levitation region. Applying negative dc potential to the metal plate, dust particles are strongly accelerated toward the metal plate edge, and two symmetric dust vortex flows are generated on both sides of the metal plate. Numerical calculation including the effect of the ion drag force well demonstrates the dust vortex formation as in the experiment. A mechanism of the dust vortex generation could be explained by effect of an asymmetry of ion drag force near the metal plate.

  18. Three-Dimensional Dielectrophoretic Microparticle Separator Fabricated by Ultraviolet-Assisted Direct-Write Assembly.

    PubMed

    Dalir, Hamid; Farahani, Rouhollah D; Hernandez, Lewith; Aldebert, Clément; Lévesque, Martin; Therriault, Daniel

    2016-01-01

    The design and fabrication of complex microfluidic devices is a subject of broad biomedical and technological interest. In this paper, we demonstrate the fabrication of a three-dimensional (3D) dielectrophoretic microparticle separator involving ultraviolet (UV)-assisted direct-write assembly of a UV-curable polyurethane. This approach yields a series of 3D microcoil interdigitated electrodes with defined geometry promoting particle separation through dielectrophoresis. These vertical microcoils give rise to considerable improvements in separation relative to standard planar (2D) microelectrodes. We envisage that the complex 3D electrodes will provide an enabling platform for a wide array of fluidic- and electronic-based applications. PMID:27398520

  19. Three-dimensional direct cell patterning in collagen hydrogels with near-infrared femtosecond laser

    PubMed Central

    Hribar, Kolin C.; Meggs, Kyle; Liu, Justin; Zhu, Wei; Qu, Xin; Chen, Shaochen

    2015-01-01

    We report a methodology for three-dimensional (3D) cell patterning in a hydrogel in situ. Gold nanorods within a cell-encapsulating collagen hydrogel absorb a focused near-infrared femtosecond laser beam, locally denaturing the collagen and forming channels, into which cells migrate, proliferate, and align in 3D. Importantly, pattern resolution is tunable based on writing speed and laser power, and high cell viability (>90%) is achieved using higher writing speeds and lower laser intensities. Overall, this patterning technique presents a flexible direct-write method that is applicable in tissue engineering systems where 3D alignment is critical (such as vascular, neural, cardiac, and muscle tissue). PMID:26603915

  20. Direct numerical simulation of steady state, three dimensional, laminar flow around a wall mounted cube

    NASA Astrophysics Data System (ADS)

    Liakos, Anastasios; Malamataris, Nikolaos

    2014-11-01

    The topology and evolution of flow around a surface mounted cubical object in three dimensional channel flow is examined for low to moderate Reynolds numbers. Direct numerical simulations were performed via a home made parallel finite element code. The computational domain has been designed according to actual laboratory experimental conditions. Analysis of the results is performed using the three dimensional theory of separation. Our findings indicate that a tornado-like vortex by the side of the cube is present for all Reynolds numbers for which flow was simulated. A horse-shoe vortex upstream from the cube was formed at Reynolds number approximately 1266. Pressure distributions are shown along with three dimensional images of the tornado-like vortex and the horseshoe vortex at selected Reynolds numbers. Finally, and in accordance to previous work, our results indicate that the upper limit for the Reynolds number for which steady state results are physically realizable is roughly 2000. Financial support of author NM from the Office of Naval Research Global (ONRG-VSP, N62909-13-1-V016) is acknowledged.

  1. The Dimensional Nature of Externalizing Behaviors in Adolescence: Evidence from a Direct Comparison of Categorical, Dimensional, and Hybrid Models

    ERIC Educational Resources Information Center

    Walton, Kate E.; Ormel, Johan; Krueger, Robert F.

    2011-01-01

    Researchers have recognized the importance of developing an accurate classification system for externalizing disorders, though much of this work has been framed by a priori preferences for categorical vs. dimensional constructs. Newer statistical technologies now allow categorical and dimensional models of psychopathology to be compared…

  2. Vorticity statistics in the direct cascade of two-dimensional turbulence.

    PubMed

    Falkovich, Gregory; Lebedev, Vladimir

    2011-04-01

    For the direct cascade of steady two-dimensional (2D) Navier-Stokes turbulence, we derive analytically the probability of strong vorticity fluctuations. When ϖ is the vorticity coarse-grained over a scale R, the probability density function (PDF), P(ϖ), has a universal asymptotic behavior lnP~-ϖ/ϖ(rms) at ϖ≫ϖ(rms)=[Hln(L/R)](1/3), where H is the enstrophy flux and L is the pumping length. Therefore, the PDF has exponential tails and is self-similar, that is, it can be presented as a function of a single argument, ϖ/ϖ(rms), in distinction from other known direct cascades. PMID:21599229

  3. Three-dimensional multiscale modeling of dendritic spacing selection during Al-Si directional solidification

    SciTech Connect

    Tourret, Damien; Clarke, Amy J.; Imhoff, Seth D.; Gibbs, Paul J.; Gibbs, John W.; Karma, Alain

    2015-05-27

    We present a three-dimensional extension of the multiscale dendritic needle network (DNN) model. This approach enables quantitative simulations of the unsteady dynamics of complex hierarchical networks in spatially extended dendritic arrays. We apply the model to directional solidification of Al-9.8 wt.%Si alloy and directly compare the model predictions with measurements from experiments with in situ x-ray imaging. The focus is on the dynamical selection of primary spacings over a range of growth velocities, and the influence of sample geometry on the selection of spacings. Simulation results show good agreement with experiments. The computationally efficient DNN model opens new avenues for investigating the dynamics of large dendritic arrays at scales relevant to solidification experiments and processes.

  4. Optical tuning of three-dimensional photonic crystals fabricated by femtosecond direct writing

    NASA Astrophysics Data System (ADS)

    McPhail, Dennis; Straub, Martin; Gu, Min

    2005-08-01

    In this letter, we report on an optically tunable three-dimensional photonic crystal that exhibits main gaps in the 3-4μm range. The photonic crystal is manufactured via a femtosecond direct writing technique. Optical tuning is achieved by a luminary polling technique with a low-power polarized laser beam. The refractive index variation resulting from liquid-crystal rotation causes a shift in the photonic band gap of up to 65 nm with an extinction of transmission of up to 70% in the stacking direction. Unlike other liquid-crystal tuning techniques where a pregenerated structure is infiltrated, this optical tuning method is a one-step process that allows arbitrary structures to be written into a solid liquid-crystal-polymer composite and leads to a high dielectric contrast.

  5. Multi-Dimensional Effective Field Theory Analysis for Direct Detection of Dark Matter

    NASA Astrophysics Data System (ADS)

    Rogers, Hannah; SuperCDMS Collaboration

    2016-03-01

    Experiments like the Cryogenic Dark Matter Search (CDMS) attempt to find dark matter (non-luminous matter that makes up approximately 80% of the matter in the universe) through direct detection of interactions between dark matter and a target material. The Effective Field Theory (EFT) approach increases the number of considered interactions between dark matter and the normal, target matter from two (spin independent and spin dependent interactions) to eleven operators with four possible interference terms. These additional operators allow for a more complete analysis of complimentary direct dark matter searches; however, the higher dimensional likelihoods necessary to span an increase in operators requires a clever computational tool such as MultiNest. I present here analyses of published and projected data from CDMS (Si and Ge targets) and LUX (liquid Xe target) assuming operator parameter spaces ranging from 3 - 5 dimensions and folding in information on energy-dependent backgrounds when possible.

  6. Three-dimensional patterning and morphological control of porous nanomaterials by gray-scale direct imprinting

    PubMed Central

    Ryckman, Judson D.; Jiao, Yang; Weiss, Sharon M.

    2013-01-01

    We present a method for direct three-dimensional (3D) patterning of porous nanomaterials through the application of a premastered and reusable gray-scale stamp. Four classes of 3D nanostructures are demonstrated for the first time in porous media: gradient profiles, digital patterns, curves and lens shapes, and sharp features including v-grooves, nano-pits, and ‘cookie-cutter’ particles. Further, we demonstrate this technique enables morphological tuning and direct tailoring of nanomaterial properties, including porosity, average pore size, dielectric constant, and plasmonic response. This work opens a rapid and low-cost route for fabricating novel nanostructures and devices utilizing porous nanomaterials, with promising applications spanning diffractive and plasmonic sensing, holography, micro- and transformation optics, and drug delivery and imaging. PMID:23518798

  7. Three-dimensional multiscale modeling of dendritic spacing selection during Al-Si directional solidification

    DOE PAGESBeta

    Tourret, Damien; Clarke, Amy J.; Imhoff, Seth D.; Gibbs, Paul J.; Gibbs, John W.; Karma, Alain

    2015-05-27

    We present a three-dimensional extension of the multiscale dendritic needle network (DNN) model. This approach enables quantitative simulations of the unsteady dynamics of complex hierarchical networks in spatially extended dendritic arrays. We apply the model to directional solidification of Al-9.8 wt.%Si alloy and directly compare the model predictions with measurements from experiments with in situ x-ray imaging. The focus is on the dynamical selection of primary spacings over a range of growth velocities, and the influence of sample geometry on the selection of spacings. Simulation results show good agreement with experiments. The computationally efficient DNN model opens new avenues formore » investigating the dynamics of large dendritic arrays at scales relevant to solidification experiments and processes.« less

  8. Three-dimensional patterning and morphological control of porous nanomaterials by gray-scale direct imprinting.

    PubMed

    Ryckman, Judson D; Jiao, Yang; Weiss, Sharon M

    2013-01-01

    We present a method for direct three-dimensional (3D) patterning of porous nanomaterials through the application of a premastered and reusable gray-scale stamp. Four classes of 3D nanostructures are demonstrated for the first time in porous media: gradient profiles, digital patterns, curves and lens shapes, and sharp features including v-grooves, nano-pits, and 'cookie-cutter' particles. Further, we demonstrate this technique enables morphological tuning and direct tailoring of nanomaterial properties, including porosity, average pore size, dielectric constant, and plasmonic response. This work opens a rapid and low-cost route for fabricating novel nanostructures and devices utilizing porous nanomaterials, with promising applications spanning diffractive and plasmonic sensing, holography, micro- and transformation optics, and drug delivery and imaging. PMID:23518798

  9. Gridding-based direct Fourier inversion of the three-dimensional ray transform.

    PubMed

    Penczek, Pawel A; Renka, Robert; Schomberg, Hermann

    2004-04-01

    We describe a fast and accurate direct Fourier method for reconstructing a function f of three variables from a number of its parallel beam projections. The main application of our method is in single particle analysis, where the goal is to reconstruct the mass density of a biological macromolecule. Typically, the number of projections is extremely large, and each projection is extremely noisy. The projection directions are random and initially unknown. However, it is possible to determine both the directions and f by an iterative procedure; during each stage of the iteration, one has to solve a reconstruction problem of the type considered here. Our reconstruction algorithm is distinguished from other direct Fourier methods by the use of gridding techniques that provide an efficient means to compute a uniformly sampled version of a function g from a nonuniformly sampled version of Fg, the Fourier transform of g, or vice versa. We apply the two-dimensional reverse gridding method to each available projection of f, the function to be reconstructed, in order to obtain Ff on a special spherical grid. Then we use the three-dimensional gridding method to reconstruct f from this sampled version of Ff. This stage requires a proper weighting of the samples of Ff to compensate for their nonuniform distribution. We use a fast method for computing appropriate weights that exploits the special properties of the spherical sampling grid for Ff and involves the computation of a Voronoi diagram on the unit sphere. We demonstrate the excellent speed and accuracy of our method by using simulated data. PMID:15078020

  10. Direct and third-body mediated resonance energy transfer in dimensionally constrained nanostructures

    NASA Astrophysics Data System (ADS)

    Weeraddana, Dilusha; Premaratne, Malin; Andrews, David L.

    2015-07-01

    The process of resonance energy transfer (RET) in a nanostructure influenced by a vicinal, nonabsorbing third body is studied within the framework of molecular quantum electrodynamics. Direct RET and the influence of neighboring matter have been studied previously, mainly for molecules. However, a complete study or unified understanding of direct and indirect RET in nanostructures with different dimensionalities is still lacking. Therefore, there is a strong need for a complete theory that models RET for the cases of quantum wells, nanowires, and quantum dots. We construct a detailed picture of excitation energy transfer in nanostructures and how it is affected by another quantum object, which includes the derivation of quantum amplitudes based on second- and fourth-order time-dependent perturbation theories, and the derivation of transfer rates and distance dependencies, providing a complete picture and understanding of RET in nanostructures. The results of the derivations indicate that the dimensionality of the nanostructure determines the controllability of the RET rate. Furthermore, third-body mediation leads to a nonvanishing RET in the coupling of nanowire to nanowire and quantum dot to quantum dot.

  11. Direct Imaging of a Two-Dimensional Silica Glass on Graphene

    NASA Astrophysics Data System (ADS)

    Huang, P. Y.; Kurasch, S.; Srivastava, A.; Skakalova, V.; Kotakoski, J.; Krasheninnikov, A. V.; Hovden, R. M.; Mao, Q.; Meyer, J. C.; Smet, J.; Muller, D. A.; Kaiser, U.

    2012-02-01

    Large-area graphene substrates [1] are a promising lab bench for synthesizing and characterizing novel low-dimensional materials such as two-dimensional (2D) glasses. Unlike 2D crystals such as graphene, 2D glasses are almost entirely unexplored--yet they have enormous applicability for understanding amorphous structures, which are difficult to probe in 3D. We report direct observations of the structure of an amorphous 2D silica supported on graphene. To our knowledge, these results represent the first discovery of an extended 2D glass. The 2D glass enables aberration-corrected scanning transmission electron microscopy and spectroscopy, producing the first atomically-resolved experimental images of a glass. The images strikingly resemble Zachariasen's seminal 1932 cartoons of a 2D continuous random network glass [2] and allow direct structural analyses not possible in 3D glassy materials. DFT calculations indicate that van der Waals interactions with graphene energetically favor the 2D structure over bulk SiO2, suggesting that graphene can be instrumental in stabilizing new 2D materials. [1] J. C. Meyer et al., Nature 454, 319--322 (2008). [2] W. H. Zachariasen, J. Am. Chem. Soc. 54, 3841--3851 (1932).

  12. Bandgaps and directional properties of two-dimensional square beam-like zigzag lattices

    SciTech Connect

    Wang, Yan-Feng; Wang, Yue-Sheng; Zhang, Chuanzeng

    2014-12-15

    In this paper we propose four kinds of two-dimensional square beam-like zigzag lattice structures and study their bandgaps and directional propagation of elastic waves. The band structures are calculated by using the finite element method. Both the in-plane and out-of-plane waves are investigated simultaneously via the three-dimensional Euler beam elements. The mechanism of the bandgap generation is analyzed by studying the vibration modes at the bandgap edges. The effects of the geometry parameters of the xy- and z-zigzag lattices on the bandgaps are investigated and discussed. Multiple complete bandgaps are found owing to the separation of the degeneracy by introducing bending arms. The bandgaps are sensitive to the geometry parameters of the periodic systems. The deformed displacement fields of the harmonic responses of a finite lattice structure subjected to harmonic loads at different positions are illustrated to show the directional wave propagation. An extension of the proposed concept to the hexagonal lattices is also presented. The research work in this paper is relevant to the practical design of cellular structures with enhanced vibro-acoustics performance.

  13. Acyclic cucurbit[n]uril molecular containers enhance the solubility and bioactivity of poorly soluble pharmaceuticals

    NASA Astrophysics Data System (ADS)

    Ma, Da; Hettiarachchi, Gaya; Nguyen, Duc; Zhang, Ben; Wittenberg, James B.; Zavalij, Peter Y.; Briken, Volker; Isaacs, Lyle

    2012-06-01

    The solubility characteristics of 40-70% of new drug candidates are so poor that they cannot be formulated on their own, so new methods for increasing drug solubility are highly prized. Here, we describe a new class of general-purpose solubilizing agents—acyclic cucurbituril-type containers—which increase the solubility of ten insoluble drugs by a factor of between 23 and 2,750 by forming container-drug complexes. The containers exhibit low in vitro toxicity in human liver, kidney and monocyte cell lines, and outbred Swiss Webster mice tolerate high doses of the container without sickness or weight loss. Paclitaxel solubilized by the acyclic cucurbituril-type containers kills cervical and ovarian cancer cells more efficiently than paclitaxel alone. The acyclic cucurbituril-type containers preferentially bind cationic and aromatic drugs, but also solubilize neutral drugs such as paclitaxel, and represent an attractive extension of cyclodextrin-based technology for drug solubilization and delivery.

  14. Direct-write Bioprinting Three-Dimensional Biohybrid Systems for Future Regenerative Therapies

    PubMed Central

    Chang, Carlos C.; Boland, Eugene D.; Williams, Stuart K.; Hoying, James B.

    2013-01-01

    Regenerative medicine seeks to repair or replace dysfunctional tissues with engineered biological or biohybrid systems. Current clinical regenerative models utilize simple uniform tissue constructs formed with cells cultured onto biocompatible scaffolds. Future regenerative therapies will require the fabrication of complex three-dimensional constructs containing multiple cell types and extracellular matrices. We believe bioprinting technologies will provide a key role in the design and construction of future engineered tissues for cell-based and regenerative therapies. This review describes the current state-of-the-art bioprinting technologies, focusing on direct-write bioprinting. We describe a number of process and device considerations for successful bioprinting of composite biohybrid constructs. In addition, we have provided baseline direct-write printing parameters for a hydrogel system (Pluronic F127) often used in cardiovascular applications. Direct-write dispensed lines (gels with viscosities ranging from 30 mPa*s to greater than 600×106 mPa*s) were measured following mechanical and pneumatic printing via three commercially available needle sizes (20ga, 25ga, and 30ga). Example patterns containing microvascular cells and isolated microvessel fragments were also bioprinted into composite 3D structures. Cells and vessel fragments remained viable and maintained in vitro behavior after incorporation into biohybrid structures. Direct-write bioprinting of biologicals provides a unique method to design and fabricate complex, multi-component 3D structures for experimental use. We hope our design insights and baseline parameter descriptions of direct-write bioprinting will provide a useful foundation for colleagues to incorporate this 3D fabrication method into future regenerative therapies. PMID:21504055

  15. Directional Scaling Symmetry of High-symmetry Two-dimensional Lattices

    PubMed Central

    Liao, Longguang; Cao, Zexian

    2014-01-01

    Two-dimensional lattices provide the arena for many physics problems of essential importance, a scale symmetry, which rarely exists as noticed by Galileo, in such lattices can help reveal the underlying physics. Here we report the discovery and proof of directional scaling symmetry for high symmetry 2D lattices, i.e., the square lattice, the equilateral triangular lattice and thus the honeycomb lattice, with aid of the function y = arcsin(sin(2πxn)), where the parameter x is either the platinum number or the silver number , which are related to the 12-fold and 8-fold quasiperiodic structures, respectively. The directions and scale factors for the symmetric scaling transformation are determined. The revealed scale symmetry may have a bearing on various physical problems modeled on 2D lattices, and the function adopted here can be used to generate quasiperiodic lattices with enumeration of lattice points. Our result is expected to initiate the search of directional scaling symmetry in more complicated geometries. PMID:25156083

  16. Direct two-dimensional reconstruction algorithm for an inverse-geometry CT system.

    PubMed

    Baek, Jongduk; Pelc, Norbert J

    2009-02-01

    An inverse-geometry computed tomography (IGCT) system uses a large source array opposite a smaller detector array. A previously described IGCT reconstruction algorithm uses gridding, but this gridding step produces blurring in the reconstructed image. In this article, the authors describe a two-dimensional (2D) IGCT reconstruction algorithm without gridding. In the transverse direction, the raw data of the IGCT system can be viewed as being composed of many fan beams. Because the spacing between source spots is larger than the spot width, each fan beam has undersampled projection data, but the missing samples are effectively provided by other undersampled fan beam views. In the proposed method, a direct fan beam reconstruction algorithm is used to process each undersampled fan beam. Initial images with this method showed ring artifacts caused by nonuniform sampling in the radial direction as compared to an ideal fan beam. A new method for correcting this effect was developed. With this correction, high quality images were obtained. The noise performance of the proposed 2D IGCT reconstruction algorithm was investigated, and it was comparable to that of the fan beam system. A MTF study showed that the proposed method achieves better resolution than the gridding method. PMID:19291978

  17. Directional scaling symmetry of high-symmetry two-dimensional lattices.

    PubMed

    Liao, Longguang; Cao, Zexian

    2014-01-01

    Two-dimensional lattices provide the arena for many physics problems of essential importance, a scale symmetry, which rarely exists as noticed by Galileo, in such lattices can help reveal the underlying physics. Here we report the discovery and proof of directional scaling symmetry for high symmetry 2D lattices, i.e., the square lattice, the equilateral triangular lattice and thus the honeycomb lattice, with aid of the function y = arcsin(sin(2πxn)), where the parameter x is either the platinum number μ = 2 - √3 or the silver number λ = √2 - 1, which are related to the 12-fold and 8-fold quasiperiodic structures, respectively. The directions and scale factors for the symmetric scaling transformation are determined. The revealed scale symmetry may have a bearing on various physical problems modeled on 2D lattices, and the function adopted here can be used to generate quasiperiodic lattices with enumeration of lattice points. Our result is expected to initiate the search of directional scaling symmetry in more complicated geometries. PMID:25156083

  18. Direct imaging of a two-dimensional silica glass on graphene.

    PubMed

    Huang, Pinshane Y; Kurasch, Simon; Srivastava, Anchal; Skakalova, Viera; Kotakoski, Jani; Krasheninnikov, Arkady V; Hovden, Robert; Mao, Qingyun; Meyer, Jannik C; Smet, Jurgen; Muller, David A; Kaiser, Ute

    2012-02-01

    Large-area graphene substrates provide a promising lab bench for synthesizing, manipulating, and characterizing low-dimensional materials, opening the door to high-resolution analyses of novel structures, such as two-dimensional (2D) glasses, that cannot be exfoliated and may not occur naturally. Here, we report the accidental discovery of a 2D silica glass supported on graphene. The 2D nature of this material enables the first atomic resolution transmission electron microscopy of a glass, producing images that strikingly resemble Zachariasen's original 1932 cartoon models of 2D continuous random network glasses. Atomic-resolution electron spectroscopy identifies the glass as SiO(2) formed from a bilayer of (SiO(4))(2-) tetrahedra and without detectable covalent bonding to the graphene. From these images, we directly obtain ring statistics and pair distribution functions that span short-, medium-, and long-range order. Ab initio calculations indicate that van der Waals interactions with graphene energetically stabilizes the 2D structure with respect to bulk SiO(2). These results demonstrate a new class of 2D glasses that can be applied in layered graphene devices and studied at the atomic scale. PMID:22268818

  19. Direct evidence for three-dimensional off-axis trapping with single Laguerre-Gaussian beam

    NASA Astrophysics Data System (ADS)

    Otsu, T.; Ando, T.; Takiguchi, Y.; Ohtake, Y.; Toyoda, H.; Itoh, H.

    2014-04-01

    Optical tweezers are often applied to control the dynamics of objects by scanning light. However, there is a limitation that objects fail to track the scan when the drag exceeds the trapping force. In contrast, Laguerre-Gaussian (LG) beams can directly control the torque on objects and provide a typical model for nonequilibrium systems such as Brownian motion under external fields. Although stable ``mid-water'' trapping is essential for removing extrinsic hydrodynamic effects in such studies, three-dimensional trapping by LG beams has not yet been clearly established. Here we report the three-dimensional off-axis trapping of dielectric spheres using high-quality LG beams generated by a special holographic method. The trapping position was estimated as ~ half the wavelength behind the beam waist. These results establish the scientific groundwork of LG trapping and the technical basis of calibrating optical torque to provide powerful tools for studying energy-conversion mechanisms and the nonequilibrium nature of biological molecules under torque.

  20. Direct evidence for three-dimensional off-axis trapping with single Laguerre-Gaussian beam.

    PubMed

    Otsu, T; Ando, T; Takiguchi, Y; Ohtake, Y; Toyoda, H; Itoh, H

    2014-01-01

    Optical tweezers are often applied to control the dynamics of objects by scanning light. However, there is a limitation that objects fail to track the scan when the drag exceeds the trapping force. In contrast, Laguerre-Gaussian (LG) beams can directly control the torque on objects and provide a typical model for nonequilibrium systems such as Brownian motion under external fields. Although stable "mid-water" trapping is essential for removing extrinsic hydrodynamic effects in such studies, three-dimensional trapping by LG beams has not yet been clearly established. Here we report the three-dimensional off-axis trapping of dielectric spheres using high-quality LG beams generated by a special holographic method. The trapping position was estimated as ~ half the wavelength behind the beam waist. These results establish the scientific groundwork of LG trapping and the technical basis of calibrating optical torque to provide powerful tools for studying energy-conversion mechanisms and the nonequilibrium nature of biological molecules under torque. PMID:24694781

  1. Three dimensional graphene transistor for ultra-sensitive pH sensing directly in biological media.

    PubMed

    Ameri, Shideh Kabiri; Singh, Pramod K; Sonkusale, Sameer R

    2016-08-31

    In this work, pH sensing directly in biological media using three dimensional liquid gated graphene transistors is presented. The sensor is made of suspended network of graphene coated all around with thin layer of hafnium oxide (HfO2), showing high sensitivity and sensing beyond the Debye-screening limit. The performance of the pH sensor is validated by measuring the pH of isotonic buffered, Dulbecco's phosphate buffered saline (DPBS) solution, and of blood serum derived from Sprague-Dawley rat. The pH sensor shows high sensitivity of 71 ± 7 mV/pH even in high ionic strength media with molarities as high as 289 ± 1 mM. High sensitivity of this device is owing to suspension of three dimensional graphene in electrolyte which provides all around liquid gating of graphene, leading to higher electrostatic coupling efficiency of electrolyte to the channel and higher gating control of transistor channel by ions in the electrolyte. Coating graphene with hafnium oxide film (HfO2) provides binding sites for hydrogen ions, which results in higher sensitivity and sensing beyond the Debye-screening limit. The 3D graphene transistor offers the possibility of real-time pH measurement in biological media without the need for desaltation or sample preparation. PMID:27506362

  2. Laser direct-write for fabrication of three-dimensional paper-based devices.

    PubMed

    He, P J W; Katis, I N; Eason, R W; Sones, C L

    2016-08-16

    We report the use of a laser-based direct-write (LDW) technique that allows the design and fabrication of three-dimensional (3D) structures within a paper substrate that enables implementation of multi-step analytical assays via a 3D protocol. The technique is based on laser-induced photo-polymerisation, and through adjustment of the laser writing parameters such as the laser power and scan speed we can control the depths of hydrophobic barriers that are formed within a substrate which, when carefully designed and integrated, produce 3D flow paths. So far, we have successfully used this depth-variable patterning protocol for stacking and sealing of multi-layer substrates, for assembly of backing layers for two-dimensional (2D) lateral flow devices and finally for fabrication of 3D devices. Since the 3D flow paths can also be formed via a single laser-writing process by controlling the patterning parameters, this is a distinct improvement over other methods that require multiple complicated and repetitive assembly procedures. This technique is therefore suitable for cheap, rapid and large-scale fabrication of 3D paper-based microfluidic devices. PMID:27436100

  3. Stereodefined acyclic trisubstituted metal enolates towards the asymmetric formation of quaternary carbon stereocentres.

    PubMed

    Minko, Yury; Marek, Ilan

    2014-10-28

    Reactions that involve metal enolate species are amongst the most versatile carbon-carbon bond forming processes available to synthetic chemists. Enolate species are involved in a multitude of powerful applications in asymmetric organic synthesis, but the generation of fully substituted enolates in a geometrically defined form is not easily achieved especially in acyclic systems. In this Feature Article we focus on the most prominent examples reported in the literature describing the formation of highly diastereo- and enantiomerically enriched quaternary stereocentres in acyclic molecules derived from stereodefined non-cyclic trisubstituted metal enolates. PMID:25054432

  4. Correlation of Chemical Bond Directions and Functional Group Orientations in Solids by Two-Dimensional NMR

    NASA Astrophysics Data System (ADS)

    Weliky, D. P.; Dabbagh, G.; Tycko, R.

    We describe a new two-dimensional NMR technique for structural studies of polycrystalline and noncrystalline solids. The technique is a variant of 2D exchange spectroscopy applicable to organic molecules, macromolecules, or molecular complexes that are doubly 13C-labeled at a specific carboncarbon bond and singly 13C labeled at a specific functional group. A Carr-Purcell sequence is used to obtain dipolar spectra in the t1 dimension. Spectra in the t2 dimension are determined primarily by the chemical-shift anisotropy. With spin diffusion among the labeled sites between the t1 and t2 periods, the resulting 2D spectra reveal correlations between the direction of the labeled bond and the orientation of the labeled functional group. Experimental spectra of two polycrystalline model compounds, dimethyl succinate and diammonium succinate, are presented and compared with simulations to illustrate the structural information contained in the 2D spectra.

  5. Three-dimensional Dendritic Needle Network model with application to Al-Cu directional solidification experiments

    SciTech Connect

    Tourret, D.; Karma, A.; Clarke, A. J.; Gibbs, P. J.; Imhoff, S. D.

    2015-06-11

    We present a three-dimensional (3D) extension of a previously proposed multi-scale Dendritic Needle Network (DNN) approach for the growth of complex dendritic microstructures. Using a new formulation of the DNN dynamics equations for dendritic paraboloid-branches of a given thickness, one can directly extend the DNN approach to 3D modeling. We validate this new formulation against known scaling laws and analytical solutions that describe the early transient and steady-state growth regimes, respectively. Finally, we compare the predictions of the model to in situ X-ray imaging of Al-Cu alloy solidification experiments. The comparison shows a very good quantitative agreement between 3D simulations and thin sample experiments. It also highlights the importance of full 3D modeling to accurately predict the primary dendrite arm spacing that is significantly over-estimated by 2D simulations.

  6. Three-dimensional Dendritic Needle Network model with application to Al-Cu directional solidification experiments

    DOE PAGESBeta

    Tourret, D.; Karma, A.; Clarke, A. J.; Gibbs, P. J.; Imhoff, S. D.

    2015-06-11

    We present a three-dimensional (3D) extension of a previously proposed multi-scale Dendritic Needle Network (DNN) approach for the growth of complex dendritic microstructures. Using a new formulation of the DNN dynamics equations for dendritic paraboloid-branches of a given thickness, one can directly extend the DNN approach to 3D modeling. We validate this new formulation against known scaling laws and analytical solutions that describe the early transient and steady-state growth regimes, respectively. Finally, we compare the predictions of the model to in situ X-ray imaging of Al-Cu alloy solidification experiments. The comparison shows a very good quantitative agreement between 3D simulationsmore » and thin sample experiments. It also highlights the importance of full 3D modeling to accurately predict the primary dendrite arm spacing that is significantly over-estimated by 2D simulations.« less

  7. Augmentation of direct laser writing fabrication throughput for three-dimensional structures by varying focusing conditions

    NASA Astrophysics Data System (ADS)

    Jonušauskas, Linas; Rekštytė, Sima; Malinauskas, Mangirdas

    2014-12-01

    We propose a laser fabrication approach for single monolith structure by varying beam focusing lenses (NA1=1.4 and NA2=0.45). With this, we show great improvement of the manufacturing throughput while keeping the desired spatial resolution and feature definition. To quantitatively evaluate its efficiency, we theoretically calculate and experimentally measure the polymerized volume using different focusing conditions and show that the augmentation can reach more than sevenfold. Based on this, sample structures of hybrid organic-inorganic SZ2080 and hydrogel polyethylene (glycol) diacrylate photopolymers were successfully manufactured. These three-dimensional structures included prototype scaffolds for cell growth and microfluidic components. Their quality was assessed and possible difficulties as well as limitations that arose were discussed. The new structures were compared to alternative direct laser writing throughput increasing techniques. Finally, we discussed potential applications in manufacturing various elements for regenerative medicine and microfluidics.

  8. Direct exfoliation and dispersion of two-dimensional materials in pure water via temperature control

    NASA Astrophysics Data System (ADS)

    Kim, Jinseon; Kwon, Sanghyuk; Cho, Dae-Hyun; Kang, Byunggil; Kwon, Hyukjoon; Kim, Youngchan; Park, Sung O.; Jung, Gwan Yeong; Shin, Eunhye; Kim, Wan-Gu; Lee, Hyungdong; Ryu, Gyeong Hee; Choi, Minseok; Kim, Tae Hyeong; Oh, Junghoon; Park, Sungjin; Kwak, Sang Kyu; Yoon, Suk Wang; Byun, Doyoung; Lee, Zonghoon; Lee, Changgu

    2015-09-01

    The high-volume synthesis of two-dimensional (2D) materials in the form of platelets is desirable for various applications. While water is considered an ideal dispersion medium, due to its abundance and low cost, the hydrophobicity of platelet surfaces has prohibited its widespread use. Here we exfoliate 2D materials directly in pure water without using any chemicals or surfactants. In order to exfoliate and disperse the materials in water, we elevate the temperature of the sonication bath, and introduce energy via the dissipation of sonic waves. Storage stability greater than one month is achieved through the maintenance of high temperatures, and through atomic and molecular level simulations, we further discover that good solubility in water is maintained due to the presence of platelet surface charges as a result of edge functionalization or intrinsic polarity. Finally, we demonstrate inkjet printing on hard and flexible substrates as a potential application of water-dispersed 2D materials.

  9. Direct exfoliation and dispersion of two-dimensional materials in pure water via temperature control

    PubMed Central

    Kim, Jinseon; Kwon, Sanghyuk; Cho, Dae-Hyun; Kang, Byunggil; Kwon, Hyukjoon; Kim, Youngchan; Park, Sung O.; Jung, Gwan Yeong; Shin, Eunhye; Kim, Wan-Gu; Lee, Hyungdong; Ryu, Gyeong Hee; Choi, Minseok; Kim, Tae Hyeong; Oh, Junghoon; Park, Sungjin; Kwak, Sang Kyu; Yoon, Suk Wang; Byun, Doyoung; Lee, Zonghoon; Lee, Changgu

    2015-01-01

    The high-volume synthesis of two-dimensional (2D) materials in the form of platelets is desirable for various applications. While water is considered an ideal dispersion medium, due to its abundance and low cost, the hydrophobicity of platelet surfaces has prohibited its widespread use. Here we exfoliate 2D materials directly in pure water without using any chemicals or surfactants. In order to exfoliate and disperse the materials in water, we elevate the temperature of the sonication bath, and introduce energy via the dissipation of sonic waves. Storage stability greater than one month is achieved through the maintenance of high temperatures, and through atomic and molecular level simulations, we further discover that good solubility in water is maintained due to the presence of platelet surface charges as a result of edge functionalization or intrinsic polarity. Finally, we demonstrate inkjet printing on hard and flexible substrates as a potential application of water-dispersed 2D materials. PMID:26369895

  10. Piezoelectric two-dimensional nanosheets/anionic layer heterojunction for efficient direct current power generation

    NASA Astrophysics Data System (ADS)

    Kim, Kwon-Ho; Kumar, Brijesh; Lee, Keun Young; Park, Hyun-Kyu; Lee, Ju-Hyuck; Lee, Hyun Hwi; Jun, Hoin; Lee, Dongyun; Kim, Sang-Woo

    2013-06-01

    Direct current (DC) piezoelectric power generator is promising for the miniaturization of a power package and self-powering of nanorobots and body-implanted devices. Hence, we report the first use of two-dimensional (2D) zinc oxide (ZnO) nanostructure and an anionic nanoclay layer to generate piezoelectric DC output power. The device, made from 2D nanosheets and an anionic nanoclay layer heterojunction, has potential to be the smallest size power package, and could be used to charge wireless nano/micro scale systems without the use of rectifier circuits to convert alternating current into DC to store the generated power. The combined effect of buckling behaviour of the ZnO nanosheets, a self-formed anionic nanoclay layer, and coupled semiconducting and piezoelectric properties of ZnO nanosheets contributes to efficient DC power generation. The networked ZnO nanosheets proved to be structurally stable under huge external mechanical loads.

  11. The Calculation of Thermal Conductivities by Three Dimensional Direct Simulation Monte Carlo Method.

    PubMed

    Zhao, Xin-Peng; Li, Zeng-Yao; Liu, He; Tao, Wen-Quan

    2015-04-01

    Three dimensional direct simulation Monte Carlo (DSMC) method with the variable soft sphere (VSS) collision model is implemented to solve the Boltzmann equation and to acquire the heat flux between two parallel plates (Fourier Flow). The gaseous thermal conductivity of nitrogen is derived based on the Fourier's law under local equilibrium condition at temperature from 270 to 1800 K and pressure from 0.5 to 100,000 Pa and compared with the experimental data and Eucken relation from Chapman and Enskog (CE) theory. It is concluded that the present results are consistent with the experimental data but much higher than those by Eucken relation especially at high temperature. The contribution of internal energy of molecule to the gaseous thermal conductivity becomes significant as increasing the temperature. PMID:26353582

  12. Liquid Phase Exfoliation of Two-Dimensional Materials by Directly Probing and Matching Surface Tension Components.

    PubMed

    Shen, Jianfeng; He, Yongmin; Wu, Jingjie; Gao, Caitian; Keyshar, Kunttal; Zhang, Xiang; Yang, Yingchao; Ye, Mingxin; Vajtai, Robert; Lou, Jun; Ajayan, Pulickel M

    2015-08-12

    Exfoliation of two-dimensional (2D) materials into mono- or few layers is of significance for both fundamental studies and potential applications. In this report, for the first time surface tension components were directly probed and matched to predict solvents with effective liquid phase exfoliation (LPE) capability for 2D materials such as graphene, h-BN, WS2, MoS2, MoSe2, Bi2Se3, TaS2, and SnS2. Exfoliation efficiency is enhanced when the ratios of the surface tension components of the applied solvent is close to that of the 2D material in question. We enlarged the library of low-toxic and common solvents for LPE. Our study provides distinctive insight into LPE and has pioneered a rational strategy for LPE of 2D materials with high yield. PMID:26200657

  13. Whistlers and plasmaspheric hiss: Wave directions and three-dimensional propagation

    SciTech Connect

    Draganov, A.B.; Inan, U.S.; Sonwalkar, V.S.; Bell, T.F.

    1993-07-01

    Wave data from the DE 1 satellite showing simultaneously nonducted whistlers and hiss are analyzed to determine wave propagation directions. At L = 3.8 and a geographic latitude of {lambda}{sub g} = 12{degrees}S, the average wave normal directions of discrete whistlers are measured to be {approximately}51{degrees} for f = 4.5 kHz and {approximately}60{degrees} for f = 3.5 kHz, forming a small (<20{degrees}) angle with the magnetic meridional plane. Hiss wave normal angles are determined as {approximately}70{degrees} and {approximately}77{degrees} for f = 3.5 kHz and f = 2.5 kHz, respectively, with the wave vector being almost perpendicular to the meridional plane. While the measured wave normal angles of whistlers and hiss are consistent with generation of hiss by magnetospheric whistlers, existence of a significant azimuthal component indicates that further assessment of this connection must be based on three-dimensional ray tracing. A new approximate analytical formulation of three-dimensional propagation of whistler waves is developed and used to model the drift of magnetospherically reflected whistlers in azimuth. The results show that depending on initial parameters, the time of arrival of whistler rays at a fixed observation point can differ by 10-20 s, with signals from different magnetospherically reflected whistlers overlapping to evolve into a hiss like signal. The total azimuthal drift of whistler rays is found to not exceed {approximately}30{degrees}, so that plasmaspheric hiss may be produced by nonducted whistlers at longitudes correlated with the location of thunderstorm activity. 22 refs., 11 figs.

  14. Hierarchical development of three direct-design methods for two-dimensional axial-turbomachinery cascades

    SciTech Connect

    Korakianitis, T. )

    1993-04-01

    The direct and inverse blade-design iterations for the selection of isolated airfoils and gas turbine blade cascades are enormously reduced if the initial blade shape has performance characteristics near the desirable ones. This paper presents the hierarchical development of three direct blade-design methods of increasing utility for generating two-dimensional blade shapes. The methods can be used to generate inputs to the direct- or inverse-blade-design sequences for subsonic or supersonic airfoils for compressors and turbines, or isolated airfoils. The first method specifies the airfoil shapes with analytical polynomials. It shows that continuous curvature and continuous slope of curvature are necessary conditions to minimize the possibility of flow separation, and to lead to improved blade designs. The second method specifies the airfoil shapes with parametric fourth-order polynomials, which result in continuous-slope-of-curvature airfoils, with smooth Mach number and pressure distributions. This method is time consuming. The third method specifies the airfoil shapes by using a mixture of analytical polynomials and mapping the airfoil surfaces from a desirable curvature distribution. The third method provides blade surfaces with desirable performance in very few direct-design iterations. In all methods the geometry near the leading edge is specified by a thickness distribution added to a construction line, which eliminates the leading edge overspeed and laminar-separation regions. The blade-design methods presented in this paper can be used to improve the aerodynamic and heat transfer performance of turbomachinery cascades, and they can result in high-performance airfoils in very few iterations.

  15. Direct Simulation of Evolution and Control of Three-Dimensional Instabilities in Attachment-Line Boundary Layers

    NASA Technical Reports Server (NTRS)

    Joslin, Ronald D.

    1995-01-01

    The spatial evolution of three-dimensional disturbances in an attachment-line boundary layer is computed by direct numerical simulation of the unsteady, incompressible Navier-Stokes equations. Disturbances are introduced into the boundary layer by harmonic sources that involve unsteady suction and blowing through the wall. Various harmonic- source generators are implemented on or near the attachment line, and the disturbance evolutions are compared. Previous two-dimensional simulation results and nonparallel theory are compared with the present results. The three-dimensional simulation results for disturbances with quasi-two-dimensional features indicate growth rates of only a few percent larger than pure two-dimensional results; however, the results are close enough to enable the use of the more computationally efficient, two-dimensional approach. However, true three-dimensional disturbances are more likely in practice and are more stable than two-dimensional disturbances. Disturbances generated off (but near) the attachment line spread both away from and toward the attachment line as they evolve. The evolution pattern is comparable to wave packets in at-plate boundary-layer flows. Suction stabilizes the quasi-two-dimensional attachment-line instabilities, and blowing destabilizes these instabilities; these results qualitatively agree with the theory. Furthermore, suction stabilizes the disturbances that develop off the attachment line. Clearly, disturbances that are generated near the attachment line can supply energy to attachment-line instabilities, but suction can be used to stabilize these instabilities.

  16. A multiple-direction Trefftz method for solving the multi-dimensional wave equation in an arbitrary spatial domain

    NASA Astrophysics Data System (ADS)

    Liu, Chein-Shan; Kuo, Chung-Lun

    2016-09-01

    In this paper we first express the wave equation in terms of the Minkowskian polar coordinates and generate a set of complete hyperbolic type Trefftz bases: rk cosh ⁡ (kθ) and rk sinh ⁡ (kθ), which are further transformed to wave polynomials as the trial solution bases for the one-dimensional wave equation. In order to stably solve the wave propagation problems long-term we develop a multiple-scale Trefftz method (MSTM), of which the scales are determined a priori by the collocation points. Then we derive a very simple method of multi-dimensional wave polynomials, equipped with different spatial directions which being the normalized wavenumber vectors, as the polynomial Trefftz bases for solving the multi-dimensional wave equations, which is named a multiple-direction Trefftz method (MDTM). Several numerical examples of two- and three-dimensional wave equations demonstrate that the present method is efficient and stable.

  17. Degradation-mediated cellular traction directs stem cell fate in covalently crosslinked three-dimensional hydrogels

    NASA Astrophysics Data System (ADS)

    Khetan, Sudhir; Guvendiren, Murat; Legant, Wesley R.; Cohen, Daniel M.; Chen, Christopher S.; Burdick, Jason A.

    2013-05-01

    Although cell-matrix adhesive interactions are known to regulate stem cell differentiation, the underlying mechanisms, in particular for direct three-dimensional encapsulation within hydrogels, are poorly understood. Here, we demonstrate that in covalently crosslinked hyaluronic acid (HA) hydrogels, the differentiation of human mesenchymal stem cells (hMSCs) is directed by the generation of degradation-mediated cellular traction, independently of cell morphology or matrix mechanics. hMSCs within HA hydrogels of equivalent elastic moduli that permit (restrict) cell-mediated degradation exhibited high (low) degrees of cell spreading and high (low) tractions, and favoured osteogenesis (adipogenesis). Moreover, switching the permissive hydrogel to a restrictive state through delayed secondary crosslinking reduced further hydrogel degradation, suppressed traction, and caused a switch from osteogenesis to adipogenesis in the absence of changes to the extended cellular morphology. Furthermore, inhibiting tension-mediated signalling in the permissive environment mirrored the effects of delayed secondary crosslinking, whereas upregulating tension induced osteogenesis even in the restrictive environment.

  18. Direct laser writing of three-dimensional photonic-crystal templates for telecommunications.

    PubMed

    Deubel, Markus; von Freymann, Georg; Wegener, Martin; Pereira, Suresh; Busch, Kurt; Soukoulis, Costas M

    2004-07-01

    The past decade has witnessed intensive research efforts related to the design and fabrication of photonic crystals. These periodically structured dielectric materials can represent the optical analogue of semiconductor crystals, and provide a novel platform for the realization of integrated photonics. Despite intensive efforts, inexpensive fabrication techniques for large-scale three-dimensional photonic crystals of high enough quality, with photonic bandgaps at near-infrared frequencies, and built-in functional elements for telecommunication applications, have been elusive. Direct laser writing by multiphoton polymerization of a photoresist has emerged as a technique for the rapid, cheap and flexible fabrication of nanostructures for photonics. In 1999, so-called layer-by-layer or woodpile photonic crystals were fabricated with a fundamental stop band at 3.9 microm wavelength. In 2002, a corresponding 1.9 microm was achieved, but the important face-centred-cubic (f.c.c.) symmetry was abandoned. Importantly, fundamental stop bands or photonic bandgaps at telecommunication wavelengths have not been demonstrated. In this letter, we report the fabrication--through direct laser writing--and detailed characterization of high-quality large-scale f.c.c. layer-by-layer structures, with fundamental stop bands ranging from 1.3 to 1.7 microm. PMID:15195083

  19. One-dimensional hybrid-direct kinetic simulation of the discharge plasma in a Hall thruster

    SciTech Connect

    Hara, Kentaro; Boyd, Iain D.; Kolobov, Vladimir I.

    2012-11-15

    In order to model the non-equilibrium plasma within the discharge region of a Hall thruster, the velocity distribution functions (VDFs) must be obtained accurately. A direct kinetic (DK) simulation method that directly solves the plasma Boltzmann equation can achieve better resolution of VDFs in comparison to particle simulations, such as the particle-in-cell (PIC) method that inherently include statistical noise. In this paper, a one-dimensional hybrid-DK simulation, which uses a DK simulation for heavy species and a fluid model for electrons, is developed and compared to a hybrid-PIC simulation. Time-averaged results obtained from the hybrid-DK simulation are in good agreement with hybrid-PIC results and experimental data. It is shown from a comparison of using a kinetic simulation and solving the continuity equation that modeling of the neutral atoms plays an important role for simulations of the Hall thruster discharge plasma. In addition, low and high frequency plasma oscillations are observed. Although the kinetic nature of electrons is not resolved due to the use of a fluid model, the hybrid-DK model provides spatially and temporally well-resolved plasma properties and an improved resolution of VDFs for heavy species with less statistical noise in comparison to the hybrid-PIC method.

  20. Production of Two-Dimensional Nanomaterials via Liquid-Based Direct Exfoliation.

    PubMed

    Niu, Liyong; Coleman, Jonathan N; Zhang, Hua; Shin, Hyeonsuk; Chhowalla, Manish; Zheng, Zijian

    2016-01-20

    Tremendous efforts have been devoted to the synthesis and application of two-dimensional (2D) nanomaterials due to their extraordinary and unique properties in electronics, photonics, catalysis, etc., upon exfoliation from their bulk counterparts. One of the greatest challenges that scientists are confronted with is how to produce large quantities of 2D nanomaterials of high quality in a commercially viable way. This review summarizes the state-of-the-art of the production of 2D nanomaterials using liquid-based direct exfoliation (LBE), a very promising and highly scalable wet approach for synthesizing high quality 2D nanomaterials in mild conditions. LBE is a collection of methods that directly exfoliates bulk layered materials into thin flakes of 2D nanomaterials in liquid media without any, or with a minimum degree of, chemical reactions, so as to maintain the high crystallinity of 2D nanomaterials. Different synthetic methods are categorized in the following, in which material characteristics including dispersion concentration, flake thickness, flake size and some applications are discussed in detail. At the end, we provide an overview of the advantages and disadvantages of such synthetic methods of LBE and propose future perspectives. PMID:26663877

  1. Three-dimensional micro-/nano-structuring via direct write polymerization with picosecond laser pulses.

    PubMed

    Malinauskas, Mangirdas; Danilevičius, Paulius; Juodkazis, Saulius

    2011-03-14

    We demonstrate capability to structure photo-polymers with sub-wavelength resolution, ∼200-500 nm, and retrieve three-dimensional (3D) structures using a picosecond laser exposure. This alternative to commonly used ultra-short femtosecond lasers extends accessibility of 3D direct write. A popular hybrid sol-gel resist SZ2080 was used for quantitative determination of structuring resolution at 1064 nm and 532 nm wavelengths and for pulses of 8-25 ps duration at the repetition rates of 0.2-1 MHz. Systematic study of feature size dependence of 3D suspended nano-rods shows that linear power dependence of photopolymerization on the dose-per-pulse becomes dominant at higher repetition rates (≥0.5 MHz) while the two-photon nonlinear absorption is still distinguishable at rates lower than 0.2 MHz and shorter pulses (≤8 ps). Thermal accumulation defines polymerization when cooling time of the focal volume is larger than separation between pulses. Photopolymerization and its scaling mechanisms, quality, and fidelity at tight focusing of fs-, ps-, and cw-laser radiation are revealed and explained. 3D scaffolds for biomedicine and microlenses for optical applications are fabricated by the ps-laser direct write. PMID:21445200

  2. Three-dimensional direct measurement of cardiomyocyte volume, nuclearity, and ploidy in thick histological sections

    NASA Astrophysics Data System (ADS)

    Bensley, Jonathan Guy; de Matteo, Robert; Harding, Richard; Black, Mary Jane

    2016-04-01

    Quantitative assessment of myocardial development and disease requires accurate measurement of cardiomyocyte volume, nuclearity (nuclei per cell), and ploidy (genome copies per cell). Current methods require enzymatically isolating cells, which excludes the use of archived tissue, or serial sectioning. We describe a method of analysis that permits the direct simultaneous measurement of cardiomyocyte volume, nuclearity, and ploidy in thick histological sections. To demonstrate the utility of our technique, heart tissue was obtained from four species (rat, mouse, rabbit, sheep) at up to three life stages: prenatal, weaning and adulthood. Thick (40 μm) paraffin sections were stained with Wheat Germ Agglutinin-Alexa Fluor 488 to visualise cell membranes, and DAPI (4‧,6-diamidino-2-phenylindole) to visualise nuclei and measure ploidy. Previous methods have been restricted to thin sections (2–10 μm) and offer an incomplete picture of cardiomyocytes. Using confocal microscopy and three-dimensional image analysis software (Imaris Version 8.2, Bitplane AG, Switzerland), cardiomyocyte volume, nuclearity, and ploidy were measured. This method of staining and analysis of cardiomyocytes enables accurate morphometric measurements in thick histological sections, thus unlocking the potential of archived tissue. Our novel time-efficient method permits the entire cardiomyocyte to be visualised directly in 3D, eliminating the need for precise alignment of serial sections.

  3. Three-dimensional direct measurement of cardiomyocyte volume, nuclearity, and ploidy in thick histological sections.

    PubMed

    Bensley, Jonathan Guy; De Matteo, Robert; Harding, Richard; Black, Mary Jane

    2016-01-01

    Quantitative assessment of myocardial development and disease requires accurate measurement of cardiomyocyte volume, nuclearity (nuclei per cell), and ploidy (genome copies per cell). Current methods require enzymatically isolating cells, which excludes the use of archived tissue, or serial sectioning. We describe a method of analysis that permits the direct simultaneous measurement of cardiomyocyte volume, nuclearity, and ploidy in thick histological sections. To demonstrate the utility of our technique, heart tissue was obtained from four species (rat, mouse, rabbit, sheep) at up to three life stages: prenatal, weaning and adulthood. Thick (40 μm) paraffin sections were stained with Wheat Germ Agglutinin-Alexa Fluor 488 to visualise cell membranes, and DAPI (4',6-diamidino-2-phenylindole) to visualise nuclei and measure ploidy. Previous methods have been restricted to thin sections (2-10 μm) and offer an incomplete picture of cardiomyocytes. Using confocal microscopy and three-dimensional image analysis software (Imaris Version 8.2, Bitplane AG, Switzerland), cardiomyocyte volume, nuclearity, and ploidy were measured. This method of staining and analysis of cardiomyocytes enables accurate morphometric measurements in thick histological sections, thus unlocking the potential of archived tissue. Our novel time-efficient method permits the entire cardiomyocyte to be visualised directly in 3D, eliminating the need for precise alignment of serial sections. PMID:27048757

  4. Three-dimensional direct measurement of cardiomyocyte volume, nuclearity, and ploidy in thick histological sections

    PubMed Central

    Bensley, Jonathan Guy; De Matteo, Robert; Harding, Richard; Black, Mary Jane

    2016-01-01

    Quantitative assessment of myocardial development and disease requires accurate measurement of cardiomyocyte volume, nuclearity (nuclei per cell), and ploidy (genome copies per cell). Current methods require enzymatically isolating cells, which excludes the use of archived tissue, or serial sectioning. We describe a method of analysis that permits the direct simultaneous measurement of cardiomyocyte volume, nuclearity, and ploidy in thick histological sections. To demonstrate the utility of our technique, heart tissue was obtained from four species (rat, mouse, rabbit, sheep) at up to three life stages: prenatal, weaning and adulthood. Thick (40 μm) paraffin sections were stained with Wheat Germ Agglutinin-Alexa Fluor 488 to visualise cell membranes, and DAPI (4′,6-diamidino-2-phenylindole) to visualise nuclei and measure ploidy. Previous methods have been restricted to thin sections (2–10 μm) and offer an incomplete picture of cardiomyocytes. Using confocal microscopy and three-dimensional image analysis software (Imaris Version 8.2, Bitplane AG, Switzerland), cardiomyocyte volume, nuclearity, and ploidy were measured. This method of staining and analysis of cardiomyocytes enables accurate morphometric measurements in thick histological sections, thus unlocking the potential of archived tissue. Our novel time-efficient method permits the entire cardiomyocyte to be visualised directly in 3D, eliminating the need for precise alignment of serial sections. PMID:27048757

  5. Acyclic and star colorings of joins of graphs and an algorithm for cographs.

    SciTech Connect

    Lyons, A.; Mathematics and Computer Science; Univ. of Chicago

    2009-01-01

    An acyclic coloring of a graph is a proper vertex coloring such that the subgraph induced by the union of any two color classes is a disjoint collection of trees. The more restricted notion of star coloring requires that the union of any two color classes induces a disjoint collection of stars. The acyclic and star chromatic numbers of a graph G are defined analogously to the chromatic number {chi}(G) and are denoted by {chi}{sub a}(G) and {chi}{sub s}(G), respectively. In this paper, we consider acyclic and star colorings of graphs that are decomposable with respect to the join operation, which builds a new graph from a collection of two or more disjoint graphs by adding all possible edges between them. In particular, we present a recursive formula for the acyclic chromatic number of joins of graphs and show that a similar formula holds for the star chromatic number. We also demonstrate the algorithmic implications of our results for the cographs, which have the unique property that they are recursively decomposable with respect to the join and disjoint union operations.

  6. Alteration in substrate specificity of horse liver alcohol dehydrogenase by an acyclic nicotinamide analog of NAD(+).

    PubMed

    Malver, Olaf; Sebastian, Mina J; Oppenheimer, Norman J

    2014-11-01

    A new, acyclic NAD-analog, acycloNAD(+) has been synthesized where the nicotinamide ribosyl moiety has been replaced by the nicotinamide (2-hydroxyethoxy)methyl moiety. The chemical properties of this analog are comparable to those of β-NAD(+) with a redox potential of -324mV and a 341nm λmax for the reduced form. Both yeast alcohol dehydrogenase (YADH) and horse liver alcohol dehydrogenase (HLADH) catalyze the reduction of acycloNAD(+) by primary alcohols. With HLADH 1-butanol has the highest Vmax at 49% that of β-NAD(+). The primary deuterium kinetic isotope effect is greater than 3 indicating a significant contribution to the rate limiting step from cleavage of the carbon-hydrogen bond. The stereochemistry of the hydride transfer in the oxidation of stereospecifically deuterium labeled n-butanol is identical to that for the reaction with β-NAD(+). In contrast to the activity toward primary alcohols there is no detectable reduction of acycloNAD(+) by secondary alcohols with HLADH although these alcohols serve as competitive inhibitors. The net effect is that acycloNAD(+) has converted horse liver ADH from a broad spectrum alcohol dehydrogenase, capable of utilizing either primary or secondary alcohols, into an exclusively primary alcohol dehydrogenase. This is the first example of an NAD analog that alters the substrate specificity of a dehydrogenase and, like site-directed mutagenesis of proteins, establishes that modifications of the coenzyme distance from the active site can be used to alter enzyme function and substrate specificity. These and other results, including the activity with α-NADH, clearly demonstrate the promiscuity of the binding interactions between dehydrogenases and the riboside phosphate of the nicotinamide moiety, thus greatly expanding the possibilities for the design of analogs and inhibitors of specific dehydrogenases. PMID:25280628

  7. Orthogonal-polarized directional backlight-based three-dimensional display with high horizontal resolution and low crosstalk.

    PubMed

    Lv, Guo-Jiao; Wang, Qiong-Hua; Zhao, Wu-Xiang

    2014-06-20

    An orthogonal-polarized directional backlight-based three-dimensional (3D) display is proposed. This backlight consists of an orthogonal-polarized backlight and a parallax barrier, so it can project light with different polarized directions to different spatial directions. The backlight can project the pixels with different polarized directions on the two-dimensional display in different directions and form 3D images. With this backlight, the proposed display can provide double horizontal resolution. A prototype of this display is developed. Experiment results show that this display with double horizontal resolution can provide a better display effect than the conventional one, and it can decrease crosstalk to a low level. PMID:24979435

  8. New Directions in Asymptotically Stable Finite-dimensional Adaptive Control of Linear Distributed Parameter Systems

    NASA Technical Reports Server (NTRS)

    Balas, M. J.

    1985-01-01

    Distributed Parameter Systems (DPS), such as systems described by partial differential equations, require infinite-dimensional state space descriptions to correctly model their dynamical behavior. However, any adaptive control algorithm must be finite-dimensional in order to be implemented via on-line digital computers. Finite-dimensional adaptive control of linear DPS requires stability analysis of nonlinear, time-varying, infinite-dimensional systems. The structure of nonadaptive finite-dimensional control of linear DPS is summarized as it relates to the existence of limiting systems for adaptive control. Two candidate schemes for finite-dimensional adaptive control of DPS are described and critical issues in infinite-dimensional stability analysis are discussed, in particular, the invariance principle, center manifold theory, and relationships between input-output and internal stability.

  9. Three-dimensional modeling of direct-drive cryogenic implosions on OMEGA

    DOE PAGESBeta

    Igumenshchev, Igor V.; Goncharov, V. N.; Marshall, F. J.; Knauer, J. P.; Campbell, E. M.; Forrest, C. J.; Froula, D. H.; Glebov, V. Yu; McCrory, R. L.; Regan, S. P.; et al

    2016-05-04

    In this study, the effects of large-scale (with Legendre modes ≲10) laser-imposed nonuniformities in direct-drive cryogenic implosions on the OMEGA Laser System are investigated using three-dimensional hydrodynamic simulations performed using the newly developed code ASTER. Sources of these nonuniformities include an illumination pattern produced by 60 OMEGA laser beams; capsule offsets (~10 to 20 μm); and imperfect pointing, power balance, and timing of the beams (with typical σrms ~10 microns, 10%, and 5 ps, respectively). Two implosion designs using 26-kJ triple-picket laser pulses were studied: a nominal design, in which an 874-μm-diameter capsule is illuminated by about the same-diameter beams,more » and a more hydrodynamically efficient ''R75" design using a 900-μm-diameter capsule and beams of 75% of this diameter. Simulations show that nonuniformities caused by capsule offsets and beam imbalance have the largest effect on implosion performance. These nonuniformities lead to significant distortions of implosion cores, resulting in an increased residual kinetic energy and incomplete stagnation. The shape of distorted cores can be well characterized using neutron images, but is less represented by 4-8 keV x-ray images. Simulated neutron spectra from perturbed implosions show large directional variations because of bulk motion effects and up to an ~2 keV variation of the hot-spot temperature inferred from these spectra. The R75 design suffers more from illumination nonuniformities. Simulations show an advantage of this design over the nominal design when the target offset and beam power imbalance σrms are reduced to less than 5 μm and 5%, respectively.« less

  10. Direct Two-Dimensional Access to the Spatial Location of Covert Attention in Macaque Prefrontal Cortex.

    PubMed

    Astrand, Elaine; Wardak, Claire; Baraduc, Pierre; Ben Hamed, Suliann

    2016-07-11

    Direct access to motor cortical information now enables tetraplegic patients to precisely control neuroprostheses and recover some autonomy. In contrast, explicit access to higher cortical cognitive functions, such as covert attention, has been missing. Indeed, this cognitive information, known only to the subject, can solely be inferred by an observer from the subject's overt behavior. Here, we present direct two-dimensional real-time access to where monkeys are covertly paying attention, using machine-learning decoding methods applied to their ongoing prefrontal cortical activity. Decoded attention was highly predictive of overt behavior in a cued target-detection task. Indeed, monkeys had a higher probability of detecting a visual stimulus as the distance between decoded attention and stimulus location decreased. This was true whether the visual stimulus was presented at the cued target location or at another distractor location. In error trials, in which the animals failed to detect the cued target stimulus, both the locations of attention and visual cue were misencoded. This misencoding coincided with a specific state of the prefrontal cortical population in which the shared variability between its different neurons (or noise correlations) was high, even before trial onset. This observation strongly suggests a functional link between high noise-correlation states and attentional failure. Overall, this real-time access to the attentional spotlight, as well as the identification of a neural signature of attentional lapses, open new perspectives both to the study of the neural bases of attention and to the remediation or enhancement of the attentional function using neurofeedback. PMID:27238280

  11. Three-dimensional modeling of direct-drive cryogenic implosions on OMEGA

    NASA Astrophysics Data System (ADS)

    Igumenshchev, I. V.; Goncharov, V. N.; Marshall, F. J.; Knauer, J. P.; Campbell, E. M.; Forrest, C. J.; Froula, D. H.; Glebov, V. Yu.; McCrory, R. L.; Regan, S. P.; Sangster, T. C.; Skupsky, S.; Stoeckl, C.

    2016-05-01

    The effects of large-scale (with Legendre modes ≲ 10 ) laser-imposed nonuniformities in direct-drive cryogenic implosions on the OMEGA Laser System are investigated using three-dimensional hydrodynamic simulations performed using the newly developed code ASTER. Sources of these nonuniformities include an illumination pattern produced by 60 OMEGA laser beams, capsule offsets (˜10-20 μm), and imperfect pointing, power balance, and timing of the beams (with typical σ rms ˜ 10 μm, 10%, and 5 ps, respectively). Two implosion designs using 26-kJ triple-picket laser pulses were studied: a nominal design, in which an 874-μm-diameter capsule is illuminated by about the same-diameter beams, and a more hydrodynamically efficient "R75" design using a 900-μm-diameter capsule and beams of 75% of this diameter. Simulations show that nonuniformities caused by capsule offsets and beam imbalance have the largest effect on implosion performance. These nonuniformities lead to significant distortions of implosion cores, resulting in an increased residual kinetic energy and incomplete stagnation. The shape of distorted cores can be well characterized using neutron images but is less represented by 4-8 keV x-ray images. Simulated neutron spectra from perturbed implosions show large directional variations because of bulk motion effects and up to an ˜2 keV variation of the hot-spot temperature inferred from these spectra. The R75 design suffers more from illumination nonuniformities. Simulations show an advantage of this design over the nominal design when the target offset and beam power imbalance σ rms are reduced to less than 5 μm and 5%, respectively.

  12. Two-dimensional boron-nitrogen-carbon monolayers with tunable direct band gaps.

    PubMed

    Zhang, Miao; Gao, Guoying; Kutana, Alex; Wang, Yanchao; Zou, Xiaolong; Tse, John S; Yakobson, Boris I; Li, Hongdong; Liu, Hanyu; Ma, Yanming

    2015-07-28

    The search for new candidate semiconductors with direct band gaps of ∼1.4 eV has attracted significant attention, especially among the two-dimensional (2D) materials, which have become potential candidates for next-generation optoelectronics. Herein, we systematically studied 2D B(x)/2N(x/2)C(1-x) (0 < x < 1) compounds in particular focus on the four stoichiometric B(x)/2N(x/2)C(1-x) (x = 2/3, 1/2, 2/5 and 1/3) using a recently developed global optimization method (CALYPSO) in conjunction with density functional theory. Furthermore, we examine more stoichiometries by the cluster expansion technique based on a hexagonal lattice. The results reveal that all monolayer B(x)/2N(x/2)C(1-x) stoichiometries adopt a planar honeycomb character and are dynamically stable. Remarkably, electronic structural calculations show that most of B(x)/2N(x/2)C(1-x) phases possess direct band gaps within the optical range, thereby they can potentially be used in high-efficiency conversion of solar energy to electric power, as well as in p-n junction photovoltaic modules. The present results also show that the band gaps of B(x)/2N(x/2)C(1-x) can be widely tuned within the optical range by changing the concentration of carbon, thus allowing the fast development of band gap engineered materials in optoelectronics. These new findings may enable new approaches to the design of microelectronic devices. PMID:26111661

  13. Protein-directed assembly of arbitrary three-dimensional nanoporous silica architectures.

    PubMed

    Khripin, Constantine Y; Pristinski, Denis; Dunphy, Darren R; Brinker, C Jeffrey; Kaehr, Bryan

    2011-02-22

    Through precise control of nanoscale building blocks, such as proteins and polyamines, silica condensing microorganisms are able to create intricate mineral structures displaying hierarchical features from nano- to millimeter-length scales. The creation of artificial structures of similar characteristics is facilitated through biomimetic approaches, for instance, by first creating a bioscaffold comprised of silica condensing moieties which, in turn, govern silica deposition into three-dimensional (3D) structures. In this work, we demonstrate a protein-directed approach to template silica into true arbitrary 3D architectures by employing cross-linked protein hydrogels to controllably direct silica condensation. Protein hydrogels are fabricated using multiphoton lithography, which enables user-defined control over template features in three dimensions. Silica deposition, under acidic conditions, proceeds throughout protein hydrogel templates via flocculation of silica nanoparticles by protein molecules, as indicated by dynamic light scattering (DLS) and time-dependent measurements of elastic modulus. Following silica deposition, the protein template can be removed using mild thermal processing yielding high surface area (625 m(2)/g) porous silica replicas that do not undergo significant volume change compared to the starting template. We demonstrate the capabilities of this approach to create bioinspired silica microstructures displaying hierarchical features over broad length scales and the infiltration/functionalization capabilities of the nanoporous silica matrix by laser printing a 3D gold image within a 3D silica matrix. This work provides a foundation to potentially understand and mimic biogenic silica condensation under the constraints of user-defined biotemplates and further should enable a wide range of complex inorganic architectures to be explored using silica transformational chemistries, for instance silica to silicon, as demonstrated herein. PMID

  14. Direct numerical simulation of a turbulent pipe with systematically varied three-dimensional roughness

    NASA Astrophysics Data System (ADS)

    Chan, Leon; MacDonald, Michael; Chung, Daniel; Hutchins, Nicholas; Ooi, Andrew

    2014-11-01

    Direct Numerical Simulations (DNS) are conducted at low to medium Reynolds numbers for a turbulent pipe flow with roughness. The roughness, which is comprised of three-dimensional sinusoidal elements, causes a downward shift in the mean velocity profile known as the Hama roughness function ΔU+ . In engineering applications, ΔU+ (which is related to the coefficient of drag Cf) is an important parameter as it is used to quantify the increase in drag and the decrease in efficiency. To have a better understanding of roughness and how it affects the flow, a range of numerical studies were conducted where the roughness height h+, wavelength λ+ and Reynolds number of the flow are varied. For the range of cases simulated, it is found that the roughness average height ka+ (which is proportional to h+) is strongly correlated to the roughness function ΔU+ whereas λ+ has a weaker influence on the flow. Results from simulations of more complicated surfaces comprised of two superimposed modes of different wavelength are also presented. Analysis of the turbulence statistics convincingly supports Townsend's outer-layer hypothesis for all of the cases simulated.

  15. Action Direction of Muscle Synergies in Three-Dimensional Force Space

    PubMed Central

    Hagio, Shota; Kouzaki, Motoki

    2015-01-01

    Redundancy in the musculoskeletal system was supposed to be simplified by muscle synergies, which modularly organize muscles. To clarify the underlying mechanisms of motor control using muscle synergies, it is important to examine the spatiotemporal contribution of muscle synergies in the task space. In this study, we quantified the mechanical contribution of muscle synergies as considering spatiotemporal correlation between the activation of muscle synergies and endpoint force fluctuations. Subjects performed isometric force generation in the three-dimensional force space. The muscle-weighting vectors of muscle synergies and their activation traces across different trials were extracted from electromyogram data using decomposing technique. We then estimated mechanical contribution of muscle synergies across each trial based on cross-correlation analysis. The contributing vectors were averaged for all trials, and the averaging was defined as action direction (AD) of muscle synergies. As a result, we extracted approximately five muscle synergies. The ADs of muscle synergies mainly depended on the anatomical functions of their weighting muscles. Furthermore, the AD of each muscle indicated the synchronous activation of muscles, which composed of the same muscle synergy. These results provide the spatiotemporal characteristics of muscle synergies as neural basis. PMID:26618156

  16. Two Dimensional Simulations of Plastic-Shell, Direct-Drive Implosions on OMEGA

    SciTech Connect

    Radha, P B; Goncharov, V N; Collins, T B; Delettrez, J A; Elbaz, Y; Glebov, V Y; Keck, R L; Keller, D E; Knauer, J P; Marozas, J A; Marshall, F J; McKenty, P W; Meyerhofer, D D; Regan, S P; Sangster, T C; Shvarts, D; Skupsky, S; Srebro, Y; Town, R J; Stoeckl, C

    2004-09-27

    Multidimensional hydrodynamic properties of high-adiabat direct-drive plastic-shell implosions on the OMEGA laser system [T. R. Boehly et al., Opt. Commun. 133, 495 (1997)] are investigated using the multidimensional hydrodynamic code, DRACO. Multimode simulations including the effects of nonuniform illumination and target roughness indicate that shell stability during the acceleration phase plays a critical role in determining target performance. For thick shells that remain integral during the acceleration phase, target yields are significantly reduced by the combination of the long-wavelength ({ell} < 10) modes due to surface roughness and beam imbalance and the intermediate modes (20 {le} {ell} {le} 50) due to single-beam nonuniformities. The neutron-production rate for these thick shells truncates relative to one-dimensional (1-D) predictions. The yield degradation in the thin shells is mainly due to shell breakup at short wavelengths ({lambda} {approx} {Delta}, where {Delta} is the in-flight shell thickness). The neutron-rate curves for the thinner shells have significantly lower amplitudes and a fall-off that is less steep than 1-D rates. DRACO simulation results are consistent with experimental observations.

  17. Direct fabrication of high-resolution three-dimensional polymeric scaffolds using electrohydrodynamic hot jet plotting

    NASA Astrophysics Data System (ADS)

    Wei, Chuang; Dong, Jingyan

    2013-02-01

    This paper presents the direct three-dimensional (3D) fabrication of polymer scaffolds with sub-10 µm structures using electrohydrodynamic jet (EHD-jet) plotting of melted thermoplastic polymers. Traditional extrusion-based fabrication approaches of 3D periodic porous structures are very limited in their resolution, due to the excessive pressure requirement for extruding highly viscous thermoplastic polymers. EHD-jet printing has become a high-resolution alternative to other forms of nozzle deposition-based fabrication approaches by generating micro-scale liquid droplets or a fine jet through the application of a large electrical voltage between the nozzle and the substrate. In this study, we successfully apply EHD-jet plotting technology with melted biodegradable polymer (polycaprolactone, or PCL) for the fabrication of 2D patterns and 3D periodic porous scaffold structures in potential tissue engineering applications. Process conditions (e.g. electrical voltage, pressure, plotting speed) have been thoroughly investigated to achieve reliable jet printing of fine filaments. We have demonstrated for the first time that the EHD-jet plotting process is capable of the fabrication of 3D periodic structures with sub-10 µm resolution, which has great potential in advanced biomedical applications, such as cell alignment and guidance.

  18. Direct observation of melting in a two-dimensional driven granular system

    NASA Astrophysics Data System (ADS)

    Sun, Xiaoyan; Li, Yang; Ma, Yuqiang; Zhang, Zexin

    2016-04-01

    Melting is considered to be one of the most fundamental problems in physical science. Generally, dimensionality plays an important role in melting. In three-dimension, it’s well known that a crystal melts directly into a liquid via a first-order transition. In two-dimension (2D), however, the melting process has been widely debated whether it is a first-order transition or a two-step transition with an intermediate hexatic phase. Experimentally 2D melting has been intensively studied in equilibrium systems such as molecular and colloidal crystals, but rarely been explored in non-equilibrium system such as granular materials. In this paper, we experimentally studied the 2D melting in a driven granular model system at single particle level using video recording and particle tracking techniques. Measurements of orientational/translational correlation functions show evidences that the melting is a two-step transition. A novel concept of orientational/translational susceptibilities enable us to clearly resolve the intermediate hexatic phase. Our results are in excellent agreement with the two-step melting scenario predicted by KTHNY theory, and demonstrate that the KTHNY melting scenario can be extended to non-equilibrium systems.

  19. Direct three-dimensional imaging of structure in a strongly-coupled dusty plasma

    NASA Astrophysics Data System (ADS)

    Quinn, R. A.; Goree, J.; Pieper, J. B.

    1996-11-01

    Using direct imaging of 9 μ m plastic spheres suspended in low-power Krypton discharges, we have constructed three-dimensional images showing the crystalline structure of a strongly-coupled dusty plasma. The spheres, which are highly charged and levitated by the electrode sheath, form a strongly-coupled system. A horizontal laser sheet illuminates a slice through the suspension, and a video camera views at 90^circ . Using a vertical stack of digitized images of particles in equally-spaced horizontal planes, we reconstructed the 3-D structure. We found bcc (body-centered cubic) and simple hexagonal structures coexisting in the same suspension. This coexistence is attributed to a bistability owing to an attractive potential region downstream of a charged grain in the presence of flowing ions. The probability of the system arranging in itself in the bcc or simple hexagonal phases is found to depend on the rf power that is used to sustain the discharge, and this in turn affects the particle charge and Debye length.(J. B. Pieper, J. Goree, R. A. Quinn, submitted to Phys. Rev. E) Work supported by NSF and NASA

  20. The Local Front Reconstruction Method for direct simulation of two- and three-dimensional multiphase flows

    NASA Astrophysics Data System (ADS)

    Shin, Seungwon; Yoon, Ikroh; Juric, Damir

    2011-07-01

    We present a new interface reconstruction technique, the Local Front Reconstruction Method (LFRM), for incompressible multiphase flows. This new method falls in the category of Front Tracking methods but it shares automatic topology handling characteristics of the previously proposed Level Contour Reconstruction Method (LCRM). The LFRM tracks the phase interface explicitly as in Front Tracking but there is no logical connectivity between interface elements thus greatly easing the algorithmic complexity. Topological changes such as interfacial merging or pinch off are dealt with automatically and naturally as in the Level Contour Reconstruction Method. Here the method is described for both two- and three-dimensional flow geometries. The interfacial reconstruction technique in the LFRM differs from that in the LCRM formulation by foregoing using an Eulerian distance field function. Instead, the LFRM uses information from the original interface elements directly to generate the new interface in a mass conservative way thus showing significantly improved local mass conservation. Because the reconstruction procedure is independently carried out in each individual reconstruction cell after an initial localization process, an adaptive reconstruction procedure can be easily implemented to increase the accuracy while at the same time significantly decreasing the computational time required to perform the reconstruction. Several benchmarking tests are performed to validate the improved accuracy and computational efficiency as compared to the LCRM. The results demonstrate superior performance of the LFRM in maintaining detailed interfacial shapes and good local mass conservation especially when using low-resolution Eulerian grids.

  1. Direct observation of melting in a two-dimensional driven granular system

    PubMed Central

    Sun, Xiaoyan; Li, Yang; Ma, Yuqiang; Zhang, Zexin

    2016-01-01

    Melting is considered to be one of the most fundamental problems in physical science. Generally, dimensionality plays an important role in melting. In three-dimension, it’s well known that a crystal melts directly into a liquid via a first-order transition. In two-dimension (2D), however, the melting process has been widely debated whether it is a first-order transition or a two-step transition with an intermediate hexatic phase. Experimentally 2D melting has been intensively studied in equilibrium systems such as molecular and colloidal crystals, but rarely been explored in non-equilibrium system such as granular materials. In this paper, we experimentally studied the 2D melting in a driven granular model system at single particle level using video recording and particle tracking techniques. Measurements of orientational/translational correlation functions show evidences that the melting is a two-step transition. A novel concept of orientational/translational susceptibilities enable us to clearly resolve the intermediate hexatic phase. Our results are in excellent agreement with the two-step melting scenario predicted by KTHNY theory, and demonstrate that the KTHNY melting scenario can be extended to non-equilibrium systems. PMID:27052190

  2. A facile method for integrating direct-write devices into three-dimensional printed parts

    NASA Astrophysics Data System (ADS)

    Chang, Yung-Hang; Wang, Kan; Wu, Changsheng; Chen, Yiwen; Zhang, Chuck; Wang, Ben

    2015-06-01

    Integrating direct-write (DW) devices into three-dimensional (3D) printed parts is key to continuing innovation in engineering applications such as smart material systems and structural health monitoring. However, this integration is challenging because: (1) most 3D printing techniques leave rough or porous surfaces if they are untreated; (2) the thermal sintering process required for most conductive inks could degrade the polymeric materials of 3D printed parts; and (3) the extensive pause needed for the DW process during layer-by-layer fabrication may cause weaker interlayer bonding and create structural weak points. These challenges are rather common during the insertion of conductive patterns inside 3D printed structures. As an avoidance tactic, we developed a simple ‘print-stick-peel’ method to transfer the DW device from the polytetrafluoroethylene or perfluoroalkoxy alkanes film onto any layer of a 3D printed object. This transfer can be achieved using the self-adhesion of 3D printing materials or applying additional adhesive. We demonstrated this method by transferring Aerosol Jet® printed strain sensors into parts fabricated by PolyJet™ printing. This report provides an investigation and discussion on the sensitivity, reliability, and influence embedding the sensor has on mechanical properties.

  3. Direct Observation of Three-dimensional Electroconvective Vortices on a Charge Selective Surface

    NASA Astrophysics Data System (ADS)

    Kwak, Rhokyun; Han, Jongyoon; Lee, Taikjin; Kwak, Ho-Young

    2015-11-01

    We present a visualization of three-dimensional electroconvective vortices (EC) by ion concentration polarization (ICP) on a cation selective membrane. The vortices are initiated between two transparent Nafion membranes under no-shear/shear conditions with various applied voltages and flow velocities. Fluorescent imaging and spatial Fourier transform allow us to capture vortex structures. In this 3-D system, EC shows three distinguished structures: i) polygonal shapes with no-shear and ii) transverse and/or iii) longitudinal vortex rolls with shear flow, which is reminiscent of 3-D Rayleigh-Benard instability. Under shear flow, as flow velocity (Reynolds number: Re) increases or voltage (electric Rayleigh number: Ra) decreases, pure longitudinal vortices are presented; in the inverse case, transverse vortices are also formed. It is noteworthy that if we confine EC in quasi 2-D system with high Ra (>10,000), we obtain pure transverse vortices; high Ra induces chaotic EC in this 3-D system, instead of 2-D stable transverse vortices. To the best of our knowledge, this is the first direct observation of 3-D EC, which will occur in realistic electrochemical devices, e.g. electrodialysis.

  4. Anisotropic characteristics of the kraichnan direct cascade in two-dimensional hydrodynamic turbulence

    NASA Astrophysics Data System (ADS)

    Kuznetsov, E. A.; Sereshchenko, E. V.

    2015-12-01

    The statistical characteristics of the Kraichnan direct cascade for two-dimensional hydrodynamic turbulence are numerically studied (with spatial resolution 8192 × 8192) in the presence of pumping and viscous-like damping. It is shown that quasi-shocks of vorticity and their Fourier partnerships in the form of jets introduce an essential influence in turbulence leading to strong angular dependencies for correlation functions. The energy distribution as a function of modulus k for each angle in the inertial interval has the Kraichnan behavior, ~ k -4, and simultaneously a strong dependence on angles. However, angle average provides with a high accuracy the Kraichnan turbulence spectrum E k = C Kη2/3k-3, where η is the enstrophy flux and the Kraichnan constant C K ≃ 1.3, in correspondence with the previous simulations. Familiar situation takes place for third-order velocity structure function S 3 L which, as for the isotropic turbulence, gives the same scaling with respect to the separation length R and η, S 3 L = C 3η R 3, but the average over the angles and time differs from its isotropic value.

  5. Direct Numerical Simulation of Particle Behaviour in a Gas-Solid Three Dimensional Plane Jet

    SciTech Connect

    Qazi, N. A.; Tang, J. C. K.; Hawkes, E. R.; Yeoh, G. H.; Grout, Ray W.; Sitaraman, Hariswaran; Talei, M.; Taylor, R. A.; Bolla, M.; Wang, H.

    2014-12-08

    In this paper, direct numerical simulations (DNS) of a three-dimensional (3D), non-reacting, temporally evolving planar jet laden with mono-dispersed solid particles in the two-way coupling (TWC) regime are performed. Three different particles Stokes numbers (St = 0.1, 1, 10) have been considered. This has been achieved by varying the particle diameter while keeping the particle mass loading (fm = 1) and the jet Reynolds number (Rejet = 2000) unchanged. The objective is to study the effect of the particle Stokes number TWC regime on the temporal development of the planar jet. Two-way coupled momentum and heat transfer has been studied by investigating mean relative velocity and temperature. Results indicate that the relative parameters are more pronounced on the edges of the jet and decrease in time in general. At the center of the jet however, the mean value first increases and then decreases again. Additionally, lighter particles spread farther than heavier particles from the center of the jet. Furthermore, the heavier particles delay the development of the jet due to TWC effects.

  6. Error analysis of a direct current electromagnetic tracking system in digitizing 3-dimensional surface geometries.

    PubMed

    Milne, A D; Lee, J M

    1999-01-01

    The direct current electromagnetic tracking device has seen increasing use in biomechanics studies of joint kinematics and anatomical surface geometry. In these applications, a stylus is attached to a sensor to measure the spatial location of three-dimensional landmarks. Stylus calibration is performed by rotating the stylus about a fixed point in space and using regression analysis to determine the tip offset vector. Measurement errors can be induced via several pathways, including; intrinsic system errors in sensor position or angle and tip offset calibration errors. A detailed study was performed to determine the errors introduced in digitizing small surfaces with different stylus lengths (35, 55, and 65 mm) and approach angles (30 and 45 degrees) using a plastic calibration board and hemispherical models. Two-point discrimination errors increased to an average of 1.93 mm for a 254 mm step size. Rotation about a single point produced mean errors of 0.44 to 1.18 mm. Statistically significant differences in error were observed with increasing approach angles (p < 0.001). Errors of less than 6% were observed in determining the curvature of a 19 mm hemisphere. This study demonstrates that the "Flock of Birds" can be used as a digitizing tool with accuracy better than 0.76% over 254 mm step sizes. PMID:11143353

  7. Two-dimensional two-phase thermal model for passive direct methanol fuel cells

    NASA Astrophysics Data System (ADS)

    Chen, R.; Zhao, T. S.; Yang, W. W.; Xu, C.

    A two-dimensional two-phase thermal model is presented for direct methanol fuel cells (DMFC), in which the fuel and oxidant are fed in a passive manner. The inherently coupled heat and mass transport, along with the electrochemical reactions occurring in the passive DMFC is modeled based on the unsaturated flow theory in porous media. The model is solved numerically using a home-written computer code to investigate the effects of various operating and geometric design parameters, including methanol concentration as well as the open ratio and channel and rib width of the current collectors, on cell performance. The numerical results show that the cell performance increases with increasing methanol concentration from 1.0 to 4.0 M, due primarily to the increased operating temperature resulting from the exothermic reaction between the permeated methanol and oxygen on the cathode and the increased mass transfer rate of methanol. It is also shown that the cell performance upgrades with increasing the open ratio and with decreasing the rib width as the result of the increased mass transfer rate on both the anode and cathode.

  8. Stable Direct Adaptive Control of Linear Infinite-dimensional Systems Using a Command Generator Tracker Approach

    NASA Technical Reports Server (NTRS)

    Balas, M. J.; Kaufman, H.; Wen, J.

    1985-01-01

    A command generator tracker approach to model following contol of linear distributed parameter systems (DPS) whose dynamics are described on infinite dimensional Hilbert spaces is presented. This method generates finite dimensional controllers capable of exponentially stable tracking of the reference trajectories when certain ideal trajectories are known to exist for the open loop DPS; we present conditions for the existence of these ideal trajectories. An adaptive version of this type of controller is also presented and shown to achieve (in some cases, asymptotically) stable finite dimensional control of the infinite dimensional DPS.

  9. Direct calculation of wall interferences and wall adaptation for two-dimensional flow in wind tunnels with closed walls

    NASA Technical Reports Server (NTRS)

    Amecke, Juergen

    1986-01-01

    A method for the direct calculation of the wall induced interference velocity in two dimensional flow based on Cauchy's integral formula was derived. This one-step method allows the calculation of the residual corrections and the required wall adaptation for interference-free flow starting from the wall pressure distribution without any model representation. Demonstrated applications are given.

  10. Rear actomyosin contractility-driven directional cell migration in three-dimensional matrices: a mechano-chemical coupling mechanism

    PubMed Central

    Chi, Qingjia; Yin, Tieying; Gregersen, Hans; Deng, Xiaoyan; Fan, Yubo; Zhao, Jingbo; Liao, Donghua; Wang, Guixue

    2014-01-01

    Cell migration is of vital importance in many biological processes, including organismal development, immune response and development of vascular diseases. For instance, migration of vascular smooth muscle cells from the media to intima is an essential part of the development of atherosclerosis and restenosis after stent deployment. While it is well characterized that cells use actin polymerization at the leading edge to propel themselves to move on two-dimensional substrates, the migration modes of cells in three-dimensional matrices relevant to in vivo environments remain unclear. Intracellular tension, which is created by myosin II activity, fulfils a vital role in regulating cell migration. We note that there is compelling evidence from theoretical and experimental work that myosin II accumulates at the cell rear, either isoform-dependent or -independent, leading to three-dimensional migration modes driven by posterior myosin II tension. The scenario is not limited to amoeboid migration, and it is also seen in mesenchymal migration in which a two-dimensional-like migration mode based on front protrusions is often expected, suggesting that there may exist universal underlying mechanisms. In this review, we aim to shed some light on how anisotropic myosin II localization induces cell motility in three-dimensional environments from a biomechanical view. We demonstrate an interesting mechanism where an interplay between mechanical myosin II recruitment and biochemical myosin II activation triggers directional migration in three-dimensional matrices. In the case of amoeboid three-dimensional migration, myosin II first accumulates at the cell rear to induce a slight polarization displayed as a uropod-like structure under the action of a tension-dependent mechanism. Subsequent biochemical signalling pathways initiate actomyosin contractility, producing traction forces on the adhesion system or creating prominent motile forces through blebbing activity, to drive cells

  11. Three-Dimensional Viscous Alternating Direction Implicit Algorithm and Strategies for Shape Optimization

    NASA Technical Reports Server (NTRS)

    Pandya, Mohagna J.; Baysal, Oktay

    1997-01-01

    A gradient-based shape optimization based on quasi-analytical sensitivities has been extended for practical three-dimensional aerodynamic applications. The flow analysis has been rendered by a fully implicit, finite-volume formulation of the Euler and Thin-Layer Navier-Stokes (TLNS) equations. Initially, the viscous laminar flow analysis for a wing has been compared with an independent computational fluid dynamics (CFD) code which has been extensively validated. The new procedure has been demonstrated in the design of a cranked arrow wing at Mach 2.4 with coarse- and fine-grid based computations performed with Euler and TLNS equations. The influence of the initial constraints on the geometry and aerodynamics of the optimized shape has been explored. Various final shapes generated for an identical initial problem formulation but with different optimization path options (coarse or fine grid, Euler or TLNS), have been aerodynamically evaluated via a common fine-grid TLNS-based analysis. The initial constraint conditions show significant bearing on the optimization results. Also, the results demonstrate that to produce an aerodynamically efficient design, it is imperative to include the viscous physics in the optimization procedure with the proper resolution. Based upon the present results, to better utilize the scarce computational resources, it is recommended that, a number of viscous coarse grid cases using either a preconditioned bi-conjugate gradient (PbCG) or an alternating-direction-implicit (ADI) method, should initially be employed to improve the optimization problem definition, the design space and initial shape. Optimized shapes should subsequently be analyzed using a high fidelity (viscous with fine-grid resolution) flow analysis to evaluate their true performance potential. Finally, a viscous fine-grid-based shape optimization should be conducted, using an ADI method, to accurately obtain the final optimized shape.

  12. Direct and Large Eddy Simulations of Three Dimensional Round Turbulent Jets

    NASA Astrophysics Data System (ADS)

    Lienau, Jeffrey Jay

    1994-01-01

    The turbulent flow in a spatially developing three dimensional incompressible round jet is simulated numerically. High order accurate finite difference methods are developed using compact differencing with formal accuracy varying from second to seventh order in the spatial directions. A large eddy simulation model is used to simulate the effect of the unresolved part of the motion. The spatially developing flow in a round jet is computed starting with the inviscid solution and structural and statistical properties of the flow are established. The Kelvin-Helmholtz instability is induced with small disturbances at the jet pipe. The vortex sheet rolls up into rings that interact and produce a variety of structures. The structures emerging in the development of the flow are analyzed using the local and global properties of kinetic energy and vorticity. It is found that the dynamics of breakdown in the round turbulent jet consists of four mechanisms. The first is the evolution of the vortex rings via the Kelvin Helmholtz instability. The second is the instability of the vorticity between the rings which develops into the braid region. The third is the interaction of the braids with the rings and the final is the transition to turbulent flow. The transport of particles is simulated numerically in the round turbulent jet. The particles investigated were the fluid particles, hexadecane particles ranging in size from 35 to 160 μm and vaporizing pentane particles in both heated and non-heated environments. For the heated environments, limiting cases of zero and infinite heat conductivity within the droplet were investigated. Particle dispersion, time of flight, average velocity and droplet diameter are presented for the first sixty diameters of the jet and compared to experimental data. The comparisons are good which provides support for the computational results.

  13. Direct and large eddy simulations of three dimensional round turbulent jets

    NASA Astrophysics Data System (ADS)

    Lienau, Jeffrey Jay

    1994-01-01

    The turbulent flow in a spatially developing three dimensional incompressible round jet is simulated numerically. High order accurate finite difference methods are developed using compact differencing with formal accuracy varying from second to seventh order in the spatial directions. A large eddy simulation model is used to simulate the effect of the unresolved part of the motion. The spatially developing flow in a round jet is computed starting with the inviscid solution and structural and statistical properties of the flow are established. The Kelvin-Helmholtz instability is induced with small disturbances at the jet pipe. The vortex sheet rolls up into rings that interact and produce a variety of structures. The structures emerging in the development of the flow are analyzed using the local and global properties of kinetic energy and vorticity. It is found that the dynamics of breakdown in the round turbulent jet consists of four mechanisms. The first is the evolution of the vortex rings via the Kelvin Helmholtz instability. The second is the instability of the vorticity between the rings which develops into the braid region. The third is the interaction of the braids with the rings and the final is the transition to turbulent flow. The transport of particles is simulated numerically in the round turbulent jet. The particles investigated were the fluid particles, hexadecane particles ranging in size from 35 to 160 micrometers and vaporizing pentane particles in both heated and nonheated environments. For the heated environments, limiting cases of zero and infinite heat conductivity within the droplet were investigated. Particle dispersion time of flight, average velocity and droplet diameter are presented for the first sixty diameters of the jet and compared to experimental data. The comparisons are good which provides support for the computational results.

  14. Three-Dimensional Stereoscopic Tracking Velocimetry and Experimental/Numerical Comparison of Directional Solidification

    NASA Technical Reports Server (NTRS)

    Lee, David; Ge, Yi; Cha, Soyoung Stephen; Ramachandran, Narayanan; Rose, M. Franklin (Technical Monitor)

    2001-01-01

    Measurement of three-dimensional (3-D) three-component velocity fields is of great importance in both ground and space experiments for understanding materials processing and fluid physics. The experiments in these fields most likely inhibit the application of conventional planar probes for observing 3-D phenomena. Here, we present the investigation results of stereoscopic tracking velocimetry (STV) for measuring 3-D velocity fields, which include diagnostic technology development, experimental velocity measurement, and comparison with analytical and numerical computation. STV is advantageous in system simplicity for building compact hardware and in software efficiency for continual near-real-time monitoring. It has great freedom in illuminating and observing volumetric fields from arbitrary directions. STV is based on stereoscopic observation of particles-Seeded in a flow by CCD sensors. In the approach, part of the individual particle images that provide data points is likely to be lost or cause errors when their images overlap and crisscross each other especially under a high particle density. In order to maximize the valid recovery of data points, neural networks are implemented for these two important processes. For the step of particle overlap decomposition, the back propagation neural network is utilized because of its ability in pattern recognition with pertinent particle image feature parameters. For the step of particle tracking, the Hopfield neural network is employed to find appropriate particle tracks based on global optimization. Our investigation indicates that the neural networks are very efficient and useful for stereoscopically tracking particles. As an initial assessment of the diagnostic technology performance, laminar water jets with and without pulsation are measured. The jet tip velocity profiles are in good agreement with analytical predictions. Finally, for testing in material processing applications, a simple directional solidification

  15. Modified ambient template-directed synthesis, characterization and applications of one-dimensional nanomaterials

    NASA Astrophysics Data System (ADS)

    Zhang, Fen

    2009-12-01

    Nanomaterials have attracted considerable attention due to their unique physical properties and potential applications as building blocks in nanoscale devices. In particular, the intrinsic anisotropy inherent in one-dimensional (1D) nanomaterials renders them the smallest dimension structures that can be utilized for the efficient transport of electron and optical excitation. The template-directed synthesis technique represents the most straightforward and versatile route for achieving 1D growth. However, there are still challenges including (1) the development of an environmentally-friendly synthetic method, (2) a deep understanding of the relationship between size, composition, and physical properties in 1D nanostructures, (3) the design of 1D nanomaterials with novel properties, and (4) the application of 1D nanostructures in various fields, such as energy, catalysis, and biotechnology. Hence, the synthesis and characterization of 1D nanostructures, as well as the complementary study of the novel properties and potential applications of the resulting nanomaterials have been the focal points of my graduate study. Specifically, a modified template-directed technique has been developed, using a double-diffusion setup via a biomimetic crystallization process, which has enabled the successful preparation of various single-crystalline 1D nanostructures, including fluorides, tungstates, sulfides, and phosphates, under ambient, room-temperature conditions, without using either very harmful precursors or solvents, and without generating particularly toxic byproducts. The family of alkaline-earth metal binary and perovskite ternary fluoride nanowires, doped with rare-earth ions, has displayed unique luminescence properties, with applications in optical devices. In addition, the generation of tungstate solid solution 1D nanostructures provides for a fundamental understanding of composition-modulated luminescence properties, leading to key structure-property correlations. A

  16. Two-directional two-dimensional modified Fisher principal component analysis: an efficient approach for thermal face verification

    NASA Astrophysics Data System (ADS)

    Wang, Ning; Li, Qiong; El-Latif, Ahmed A. Abd; Peng, Jialiang; Niu, Xiamu

    2013-04-01

    In recent years, verification based on thermal face images has been extensively studied because of its invariance to illumination and immunity to forgery. However, most of them have not given full consideration to high-verification performance and singular within-class scatter matrix problems. We propose a novel thermal face verification algorithm, which is named two-directional two-dimensional modified Fisher principal component analysis. First, two-dimensional principal component analysis (2-DPCA) is utilized to extract the optimal projective vector in the row direction. Then, 2-D modified Fisher linear discriminant analysis is implemented to overcome the singular within-class scatter matrix problem of the 2-DPCA space in the column direction. Comparative experiments on the natural visible and infrared facial expression thermal face subdatabase demonstrate that the proposed approach outperforms state-of-the-art methods in terms of verification performance.

  17. Preston tube calibrations and direct force floating element measurements in a two-dimensional turbulent boundary layer

    NASA Technical Reports Server (NTRS)

    Mcallister, J. E.; Tennant, M. H.; Pierce, F. J.

    1982-01-01

    Preston tubes provide a convenient means of estimating local wall shear stress. Practical difficulties arise from a lack of calibration data obtained in turbulent boundary layer flows and from the wide choice of calibration equations available mainly from pipe flow calibrations. The results of an experimental study comparing a large number of direct force local wall shear stress measurements in a near-zero pressure gradient two-dimensional turbulent boundary layer flow are presented. The results indicate that there is consistent and excellent agreement between the Patel intermediate calibration formula and the direct force measurements. Typical differences among the direct force measurements and several other proposed calibration equations are also shown.

  18. Ultra-directional source of longitudinal acoustic waves based on a two-dimensional solid/solid phononic crystal

    SciTech Connect

    Morvan, B.; Tinel, A.; Sainidou, R.; Rembert, P.; Vasseur, J. O.; Hladky-Hennion, A.-C.; Swinteck, N.; Deymier, P. A.

    2014-12-07

    Phononic crystals (PC) can be used to control the dispersion properties of acoustic waves, which are essential to direct their propagation. We use a PC-based two-dimensional solid/solid composite to demonstrate experimentally and theoretically the spatial filtering of a monochromatic non-directional wave source and its emission in a surrounding water medium as an ultra-directional beam with narrow angular distribution. The phenomenon relies on square-shaped equifrequency contours (EFC) enabling self-collimation of acoustic waves within the phononic crystal. Additionally, the angular width of collimated beams is controlled via the EFC size-shrinking when increasing frequency.

  19. Acyclic monoterpenes in tree essential oils as a shrinking agent for waste-expanded polystyrene.

    PubMed

    Shimotori, Yasutaka; Hattori, Kazuyuki; Aoyama, Masakazu; Miyakoshi, Tetsuo

    2011-01-01

    We examined the dissolution of polystyrene (PS) into acyclic monoterpenes present in tree essential oils, to develop an environmentally friendly shrinking agent for waste-expanded polystyrene (EPS). The dissolving powers of geranyl acetate, geranylacetone, and geranyl formate [221.8-241.2 g PS (100 g solvent)(-1)] compared favorably with that of (R)-limonene [181.7 g PS (100 g solvent)(-1)]. Their favorable dissolving powers for PS can be explained by their flexible linear structures, which may be more accessible to the inside of bulk PS compared with cyclic monoterpenes. These acyclic monoterpenes and PS were recovered almost quantitatively by simple steam distillation of the PS solution. PMID:21644162

  20. Regulation of the survival and differentiation of hepatic stem/progenitor cells by acyclic retinoid.

    PubMed

    Kamiya, Akihide

    2015-01-01

    During embryonic liver development, hepatic stem/progenitor cells (HpSCs) have a high proliferative ability and bipotency to differentiate into hepatocytes and cholangiocytes. Retinoic acid is a derivative of vitamin A and is involved in the proliferation and differentiation of stem/progenitor cells in several tissues. However, whether retinoic acid regulates the characteristics of HpSCs in the normal liver is still unknown. A recent study has shown that acyclic retinoid regulates the survival and proliferation of HpSCs derived from mouse foetal liver. Acyclic retinoid suppressed the expansion of CD29(+)CD49f(+) HpSCs through the induction of hepatocytic differentiation and progression of apoptosis. PMID:26021438

  1. [Synthesis of acyclic 1,3-polyols and its application to structural study of natural products].

    PubMed

    Mori, Y

    1993-06-01

    A 1,3-polyhydroxylated chain is often found on the backbone of biologically important natural products. The acyclic nature and the regular array of many hydroxyl groups are main obstacles to structural and synthetic studies, and many efforts have been made to this end. We have developed a new general synthetic method of 1,3-polyols based on the coupling of a chiral dithiane, a four-carbon unit, and an epoxide, followed by 1,3-diastereoselective reduction. We applied the method to the synthesis of polymethoxy-1-alkenes isolated from blue-green algae to establish their absolute stereochemistry. Moreover, a general procedure for assigning the absolute stereochemistry of acyclic 1,3-polyols by the difference circular dichroism (CD) method have been established. Combination of the method and a reiterative degradation enables one to determine the absolute configuration of 1,3-polyols, even if the relative stereochemistry is unknown. PMID:8355146

  2. Cascade Cyclizations of Acyclic and Macrocyclic Alkynones: Studies toward the Synthesis of Phomactin A

    PubMed Central

    Ciesielski, Jennifer; Gandon, Vincent; Frontier, Alison J.

    2013-01-01

    A study of the reactivity and diastereoselectivity of the Lewis acid-promoted cascade cyclizations of both acyclic and macrocyclic alkynones is described. In these reactions, a β-iodoallenolate intermediate is generated via conjugate addition of iodide to an alkynone, followed by an intramolecular aldol reaction with a tethered aldehyde to afford a cyclohexenyl alcohol. The Lewis acid magnesium iodide (MgI2) was found to promote irreversible ring closure, while cyclizations using BF3·OEt2 as promoter occurred reversibly. For both acyclic and macrocyclic ynones, high diastereoselectivity was observed in the intramolecular aldol reaction. The MgI2 protocol for cyclization was applied to the synthesis of advanced intermediates relevant to the synthesis of phomactin natural products, during which a novel transannular cation-olefin cyclization was observed. DFT calculations were conducted to analyze the mechanism of this unusual MgI2-promoted process. PMID:23724905

  3. Triphosgene-Pyridine Mediated Stereoselective Chlorination of Acyclic Aliphatic 1,3-Diols†

    PubMed Central

    Villalpando, Andrés; Saputra, Mirza A.; Tugwell, Thomas H.; Kartika, Rendy

    2015-01-01

    We describe a strategy to chlorinate stereocomplementary acyclic aliphatic 1,3-diols using a mixture of triphosgene and pyridine. While 1,3-anti diols readily led to 1,3-anti dichlorides, 1,3-syn diols must be converted to 1,3-syn diol monosilylethers to access the corresponding 1,3-syn dichlorides. These dichlorination protocols were operationally simple, very mild, and readily tolerated by advanced synthetic intermediates. PMID:26323232

  4. An analysis of lower-dimensional approximations to the scalar dissipation rate using direct numerical simulations of plane jet flames

    SciTech Connect

    Chen, Jackie; Sankaran, Ramanan; Hawkes, Evatt R

    2009-05-01

    The difficulty of experimental measurements of the scalar dissipation rate in turbulent flames has required researchers to estimate the true three-dimensional (3D) scalar dissipation rate from one-dimensional (1D) or two-dimensional (2D) gradient measurements. In doing so, some relationship must be assumed between the true values and their lower dimensional approximations. We develop these relationships by assuming a form for the statistics of the gradient vector orientation, which enables several new results to be obtained and the true 3D scalar dissipation PDF to be reconstructed from the lower-dimensional approximations. We use direct numerical simulations (DNS) of turbulent plane jet flames to examine the orientation statistics, and verify our assumptions and final results. We develop and validate new theoretical relationships between the lower-dimensional and true moments of the scalar dissipation PDF assuming a log-normal true PDF. We compare PDFs reconstructed from lower-dimensional gradient projections with the true values and find an excellent agreement for a 2D simulated measurement and also for a 1D simulated measurement perpendicular to the mean flow variations. Comparisons of PDFs of thermal dissipation from DNS with those obtained via reconstruction from 2D experimental measurements show a very close match, indicating this PDF is not unique to a particular flame configuration. We develop a technique to reconstruct the joint PDF of the scalar dissipation and any other scalar, such as chemical species or temperature. Reconstructed conditional means of the hydroxyl mass fraction are compared with the true values and an excellent agreement is obtained.

  5. Fabrication of three-dimensional microfluidic channels inside glass using nanosecond laser direct writing.

    PubMed

    Liu, Changning; Liao, Yang; He, Fei; Shen, Yinglong; Chen, Danping; Cheng, Ya; Xu, Zhizhan; Sugioka, Koji; Midorikawa, Katsumi

    2012-02-13

    We show that fabrication of three-dimensional microfluidic channels embedded in glass can be achieved by using a Q-switched, frequency-doubled Nd:YAG laser. The processing mainly consists of two steps: (1) formation of hollow microfluidic channels in porous glass immersed in Rhodamine 6G dissolved in water by nanosecond laser ablation; and (2) postannealing of the fabricated porous glass sample at 1120 °C for consolidation of the sample. In particular, a bilayer microfluidic structure is created in glass substrate using this technique for showcasing its capability of three-dimensional structuring. PMID:22418188

  6. On the direct insulator-quantum Hall transition in two-dimensional electron systems in the vicinity of nanoscaled scatterers

    PubMed Central

    2011-01-01

    A direct insulator-quantum Hall (I-QH) transition corresponds to a crossover/transition from the insulating regime to a high Landau level filling factor ν > 2 QH state. Such a transition has been attracting a great deal of both experimental and theoretical interests. In this study, we present three different two-dimensional electron systems (2DESs) which are in the vicinity of nanoscaled scatterers. All these three devices exhibit a direct I-QH transition, and the transport properties under different nanaoscaled scatterers are discussed. PMID:21711637

  7. Anti-EGFRvIII monoclonal antibody armed with 177Lu: in vivo comparison of macrocyclic and acyclic ligands

    PubMed Central

    Hens, Marc; Vaidyanathan, Ganesan; Zhao, Xiao-Guang; Bigner, Darell D.; Zalutsky, Michael R.

    2010-01-01

    Introduction Monoclonal antibody (mAb) L8A4 binds specifically to the epidermal growth factor receptor variant III (EGFRvIII) that is present on gliomas but not normal tissues, and is internalized rapidly after receptor binding. Because of the short range of its β-emissions, labeling this mAb with177Lu would be an attractive approach for the treatment of residual tumor margins remaining after surgical debulking of brain tumors. Materials and Methods L8A4 mAb was labeled with 177Lu using the acyclic ligands [(R)-2-Amino-3-(4-isothiocyanatophenyl)propyl]-trans-(S,S)-cyclohexane-1,2-diamine- pentaacetic acid (CHX-A″-DTPA) and 2-(4-Isothiocyanatobenzyl)-6-methyldiethylene- triaminepentaacetic acid (1B4M-DTPA), and the macrocyclic ligands S-2-(4- Isothiocyanatobenzyl)-1,4,7,10-tetraazacyclododecane-tetraacetic acid (C-DOTA) and α-(5-isothiocyanato-2-methoxyphenyl)-1,4,7,10-tetraazacyclododecane-1,4,7,10- tetraacetic acid (MeO-DOTA). Paired-label tissue distribution experiments were performed in athymic mice bearing subcutaneous EGFRvIII-expressing U87.)EGFR glioma xenografts over a period of 1 to 8 days to directly compare 177Lu-labeled L8A4 to L8A4 labeled with 125I using N-succinimidyl 4-guanidinomethyl-3-[125I]iodobenzoate ([125I]SGMIB). Results Except with C-DOTA, tumor uptake for the 177Lu-labeled mAb was significantly higher than the co-administered radioiodinated preparation; however, this was also the case for spleen, liver, bone and kidneys. Tumor:normal tissue ratios for 177Lu-1B4M-DTPA-L8A4 and to an even greater extent, 177Lu-MeO-DOTA-L8A4, were higher than those for [125I]SGMIB-L8A4 in most other tissues. Conclusions Tumor and normal tissue distribution patterns for this anti-EGFRvIII mAb were dependent on the nature of the bifunctional chelate used for 177Lu labeling. Optimal results were obtained with 1B4M-DTPA and MeO-DOTA, suggesting no clear advantage for acyclic vs. macrocyclic ligands for this application. PMID:20870149

  8. Multigroup Three-Dimensional Direct Integration Method Radiation Transport Analysis Code System.

    Energy Science and Technology Software Center (ESTSC)

    1987-09-18

    Version 00 TRISTAN solves the three-dimensional, fixed-source, Boltzmann transport equation for neutrons or gamma rays in rectangular geometry. The code can solve an adjoint problem as well as a usual transport problem. TRISTAN is a suitable tool to analyze radiation shielding problems such as streaming and deep penetration problems.

  9. Projection of two-dimensional diffusion in narrow asymmetric channels onto the longitudinal direction

    SciTech Connect

    Pineda, Inti; Dagdug, Leonardo

    2014-01-14

    Diffusive transport of particles is a ubiquitous feature of physical, chemical and biological systems. Typical structures like pores, tubes or fibers, are quasi one-dimensional, such that we need to solve 2+1 or 3+1 dimensional differential equations to describe correctly transport along them. The so-called Fick-Jacobs approach dramatically simplifies the problem if one assumes that a solute distribution in any cross-section of the channel is uniform at equilibrium. That study focuses on the mapping of the diffusion equation in a two-dimensional narrow asymmetric channel of varying cross section onto the longitudinal coordinate. We present a generalization to the case of an asymmetric channel using the projection method introduced earlier by Kalinay and Percus. We derive an expansion of the effective diffusion coefficient, which represents corrections to the Fick-Jacobs equation and contains the well-known previous results as special cases. Finally, we study numerically some specific two-dimensional asymmetric channel configurations to test and show the broader applicability of this effective diffusion coefficient formula.

  10. Acyclic monoterpene primary alcohol:NADP+ oxidoreductase of Rauwolfia serpentina cells: the key enzyme in biosynthesis of monoterpene alcohols.

    PubMed

    Ikeda, H; Esaki, N; Nakai, S; Hashimoto, K; Uesato, S; Soda, K; Fujita, T

    1991-02-01

    Acyclic monoterpene primary alcohol:NADP+ oxidoreductase, a key enzyme in the biosynthesis of monoterpene alcohols in plants, is unstable and has been only poorly characterized. However we have established conditions which stabilize the enzyme from Rauwolfia serpentina cells, and then purified it to homogeneity. It is a monomer with a molecular weight of about 44,000 and contains zinc ions. Various branched-chain allylic primary alcohols such as nerol, geraniol, and 10-hydroxygeraniol were substrates, but ethanol was inert. The enzyme exclusively requires NADP+ or NADPH as the cofactor. Steady-state kinetic studies showed that the nerol dehydrogenation proceeds by an ordered Bi-Bi mechanism. NADP+ binds the enzyme first and then NADPH is the second product released from it. Gas chromatography-mass spectrometric analysis of the reaction products showed that 10-hydroxygeraniol undergoes a reversible dehydrogenation to produce 10-oxogeraniol or 10-hydroxygeranial, which are oxidized further to give 10-oxogeranial, the direct precursor of iridodial. The enzyme has been found to exclusively transfer the pro-R hydrogen of NADPH to neral. The N-terminal sequence of the first 21 amino acids revealed no significant homology with those of various other proteins including the NAD(P)(+)-dependent alcohol dehydrogenases registered in a protein data bank. PMID:1864846

  11. Bacterial twitching motility is coordinated by a two-dimensional tug-of-war with directional memory.

    PubMed

    Marathe, Rahul; Meel, Claudia; Schmidt, Nora C; Dewenter, Lena; Kurre, Rainer; Greune, Lilo; Schmidt, M Alexander; Müller, Melanie J I; Lipowsky, Reinhard; Maier, Berenike; Klumpp, Stefan

    2014-01-01

    Type IV pili are ubiquitous bacterial motors that power surface motility. In peritrichously piliated species, it is unclear how multiple pili are coordinated to generate movement with directional persistence. Here we use a combined theoretical and experimental approach to test the hypothesis that multiple pili of Neisseria gonorrhoeae are coordinated through a tug-of-war. Based on force-dependent unbinding rates and pilus retraction speeds measured at the level of single pili, we build a tug-of-war model. Whereas the one-dimensional model robustly predicts persistent movement, the two-dimensional model requires a mechanism of directional memory provided by re-elongation of fully retracted pili and pilus bundling. Experimentally, we confirm memory in the form of bursts of pilus retractions. Bursts are seen even with bundling suppressed, indicating re-elongation from stable core complexes as the key mechanism of directional memory. Directional memory increases the surface range explored by motile bacteria and likely facilitates surface colonization. PMID:24806757

  12. Bacterial twitching motility is coordinated by a two-dimensional tug-of-war with directional memory

    NASA Astrophysics Data System (ADS)

    Marathe, Rahul; Meel, Claudia; Schmidt, Nora C.; Dewenter, Lena; Kurre, Rainer; Greune, Lilo; Alexander Schmidt, M.; Müller, Melanie J. I.; Lipowsky, Reinhard; Maier, Berenike; Klumpp, Stefan

    2014-05-01

    Type IV pili are ubiquitous bacterial motors that power surface motility. In peritrichously piliated species, it is unclear how multiple pili are coordinated to generate movement with directional persistence. Here we use a combined theoretical and experimental approach to test the hypothesis that multiple pili of Neisseria gonorrhoeae are coordinated through a tug-of-war. Based on force-dependent unbinding rates and pilus retraction speeds measured at the level of single pili, we build a tug-of-war model. Whereas the one-dimensional model robustly predicts persistent movement, the two-dimensional model requires a mechanism of directional memory provided by re-elongation of fully retracted pili and pilus bundling. Experimentally, we confirm memory in the form of bursts of pilus retractions. Bursts are seen even with bundling suppressed, indicating re-elongation from stable core complexes as the key mechanism of directional memory. Directional memory increases the surface range explored by motile bacteria and likely facilitates surface colonization.

  13. Direct observation of charge state in the quasi-one-dimensional conductor Li0.9Mo6O17

    PubMed Central

    Wu, Guoqing; Ye, Xiao-shan; Zeng, Xianghua; Wu, Bing; Clark, W. G.

    2016-01-01

    The quasi-one-dimensional conductor Li0.9Mo6O17 has been of great interest because of its unusual properties. It has a conducting phase with properties different from a simple Fermi liquid, a poorly understood “insulating” phase as indicated by a metal-“insulator” crossover (a mystery for over 30 years), and a superconducting phase which may involve spin triplet Cooper pairs as a three-dimensional (p-wave) non-conventional superconductor. Recent evidence suggests a density wave (DW) gapping regarding the metal-“insulator” crossover. However, the nature of the DW, such as whether it is due to the change in the charge state or spin state, and its relationship to the dimensional crossover and to the spin triplet superconductivity, remains elusive. Here by performing 7Li-/95Mo-nuclear magnetic resonance (NMR) spectroscopy, we directly observed the charge state which shows no signature of change in the electric field gradient (nuclear quadrupolar frequency) or in the distribution of it, thus providing direct experimental evidences demonstrating that the long mysterious metal-“insulator” crossover is not due to the charge density wave (CDW) that was thought, and the nature of the DW gapping is not CDW. This discovery opens a parallel path to the study of the electron spin state and its possible connections to other unusual properties. PMID:26853454

  14. Direct observation of charge state in the quasi-one-dimensional conductor Li0.9Mo6O17.

    PubMed

    Wu, Guoqing; Ye, Xiao-shan; Zeng, Xianghua; Wu, Bing; Clark, W G

    2016-01-01

    The quasi-one-dimensional conductor Li0.9Mo6O17 has been of great interest because of its unusual properties. It has a conducting phase with properties different from a simple Fermi liquid, a poorly understood "insulating" phase as indicated by a metal-"insulator" crossover (a mystery for over 30 years), and a superconducting phase which may involve spin triplet Cooper pairs as a three-dimensional (p-wave) non-conventional superconductor. Recent evidence suggests a density wave (DW) gapping regarding the metal-"insulator" crossover. However, the nature of the DW, such as whether it is due to the change in the charge state or spin state, and its relationship to the dimensional crossover and to the spin triplet superconductivity, remains elusive. Here by performing (7)Li-/(95)Mo-nuclear magnetic resonance (NMR) spectroscopy, we directly observed the charge state which shows no signature of change in the electric field gradient (nuclear quadrupolar frequency) or in the distribution of it, thus providing direct experimental evidences demonstrating that the long mysterious metal-"insulator" crossover is not due to the charge density wave (CDW) that was thought, and the nature of the DW gapping is not CDW. This discovery opens a parallel path to the study of the electron spin state and its possible connections to other unusual properties. PMID:26853454

  15. Direct Observation of Mode-Coupling Instability in Two-Dimensional Plasma Crystals

    SciTech Connect

    Coueedel, L.; Nosenko, V.; Ivlev, A. V.; Zhdanov, S. K.; Thomas, H. M.; Morfill, G. E.

    2010-05-14

    Dedicated experiments on melting of two-dimensional plasma crystals were carried out. The melting was always accompanied by spontaneous growth of the particle kinetic energy, suggesting a universal plasma-driven mechanism underlying the process. By measuring three principal dust-lattice wave modes simultaneously, it is unambiguously demonstrated that the melting occurs due to the resonance coupling between two of the dust-lattice modes. The variation of the wave modes with the experimental conditions, including the emergence of the resonant (hybrid) branch, reveals exceptionally good agreement with the theory of mode-coupling instability.

  16. DNA origami-directed, discrete three-dimensional plasmonic tetrahedron nanoarchitectures with tailored optical chirality.

    PubMed

    Dai, Gaole; Lu, Xuxing; Chen, Zhong; Meng, Chun; Ni, Weihai; Wang, Qiangbin

    2014-04-23

    Discrete, three-dimensional (3D) gold nanoparticle (AuNP) tetrahedron nanoarchitectures are successfully self-assembled with DNA origami as template with high purity (>85%). A distinct plasmonic chiral response is experimentally observed from the AuNP tetrahedron nanoarchitectures and appears in a configuration-dependent manner. The chiral optical properties are then rationally engineered by modifying the structural parameters including the AuNP size and interparticle distance. Theoretical study of the AuNP tetrahedron nanoarchitectures shows the dependence of the chiral optical property on the AuNP size and interparticle distance, consistent with the ensemble averaged measurements. PMID:24716524

  17. Direct Observations of Three Dimensional Growth of Hydrates Hosted in Porous Media

    SciTech Connect

    Kerkar, P.; Jones, K; Kleinberg, R; Lindquist, W; Tomov, S; Feng, H; Mahajan, D

    2009-01-01

    The visualization of time-resolved three-dimensional growth of tetrahydrofuran hydrates with glass spheres of uniform size as porous media using synchrotron x-ray computed microtomography is presented. The images of hydrate patches, formed from excess tetrahydrofuran in aqueous solution, show random nucleation and growth concomitant with grain movement but independent of container-wall effect. Away from grain surfaces, hydrate surface curvature was convex showing that liquid, not hydrate, was the wetting phase, similar to ice growth in porous media. The extension of the observed behavior to methane hydrates could have implications in understanding their role in seafloor stability and climate change.

  18. Emission of direct-gap band in germanium with Ge-GeSn layers on one-dimensional structure

    NASA Astrophysics Data System (ADS)

    Huang, Zhong-Mei; Huang, Wei-Qi; Liu, Shi-Rong; Dong, Tai-Ge; Wang, Gang; Wu, Xue-Ke; Qin, Cao-Jian

    2016-04-01

    In our experiment, it was observed that the emission of direct-gap band in germanium with Ge-GeSn layers on one-dimensional (1D) structure. The results of experiment and calculation demonstrate that the uniaxial tensile strain in the (111) and (110) direction can efficiently transform Ge to a direct bandgap material with the bandgap energy useful for technological application. It is interested that under the tensile strain from Ge-GeSn layers on 1D structure in which the uniaxial strain could be obtained by curved layer (CL) effect, the two bandgaps EΓg and ELg in the (111) direction become nearly equal at 0.83 eV related to the emission of direct-gap band near 1500 nm in the experiments. It is discovered that the red-shift of the peaks from 1500 nm to 1600 nm occurs with change of the uniaxial tensile strain, which proves that the peaks come from the emission of direct-gap band.

  19. Emission of direct-gap band in germanium with Ge-GeSn layers on one-dimensional structure.

    PubMed

    Huang, Zhong-Mei; Huang, Wei-Qi; Liu, Shi-Rong; Dong, Tai-Ge; Wang, Gang; Wu, Xue-Ke; Qin, Cao-Jian

    2016-01-01

    In our experiment, it was observed that the emission of direct-gap band in germanium with Ge-GeSn layers on one-dimensional (1D) structure. The results of experiment and calculation demonstrate that the uniaxial tensile strain in the (111) and (110) direction can efficiently transform Ge to a direct bandgap material with the bandgap energy useful for technological application. It is interested that under the tensile strain from Ge-GeSn layers on 1D structure in which the uniaxial strain could be obtained by curved layer (CL) effect, the two bandgaps EΓg and ELg in the (111) direction become nearly equal at 0.83 eV related to the emission of direct-gap band near 1500 nm in the experiments. It is discovered that the red-shift of the peaks from 1500 nm to 1600 nm occurs with change of the uniaxial tensile strain, which proves that the peaks come from the emission of direct-gap band. PMID:27097990

  20. Emission of direct-gap band in germanium with Ge-GeSn layers on one-dimensional structure

    PubMed Central

    Huang, Zhong-Mei; Huang, Wei-Qi; Liu, Shi-Rong; Dong, Tai-Ge; Wang, Gang; Wu, Xue-Ke; Qin, Cao-Jian

    2016-01-01

    In our experiment, it was observed that the emission of direct-gap band in germanium with Ge-GeSn layers on one-dimensional (1D) structure. The results of experiment and calculation demonstrate that the uniaxial tensile strain in the (111) and (110) direction can efficiently transform Ge to a direct bandgap material with the bandgap energy useful for technological application. It is interested that under the tensile strain from Ge-GeSn layers on 1D structure in which the uniaxial strain could be obtained by curved layer (CL) effect, the two bandgaps EΓg and ELg in the (111) direction become nearly equal at 0.83 eV related to the emission of direct-gap band near 1500 nm in the experiments. It is discovered that the red-shift of the peaks from 1500 nm to 1600 nm occurs with change of the uniaxial tensile strain, which proves that the peaks come from the emission of direct-gap band. PMID:27097990

  1. On Kraichnan's 'direct interaction approximation' and Kolmogoroff's theory in two-dimensional plasma turbulence

    SciTech Connect

    Kulsrud, R.M.; Sudan, R.N.

    1981-04-01

    The nonlinear damping in a strongly turbulent convecting plasma computed by Kraichnan's modified direct inteaction approximation and the power spectrum are rederived in a physically transparent form using Kolmogoroff's theory of turbulence.

  2. Three-dimensional direct numerical simulation of soot formation and transport in a temporally evolving nonpremixed ethylene jet flame

    SciTech Connect

    Lignell, David O.; Chen, Jacqueline H.; Smith, Philip J.

    2008-10-15

    Three-dimensional direct numerical simulation of soot formation with complex chemistry is presented. The simulation consists of a temporally evolving, planar, nonpremixed ethylene jet flame with a validated, 19-species reduced mechanism. A four-step, three-moment, semiempirical soot model is employed. Previous two-dimensional decaying turbulence simulations have shown the importance of multidimensional flame dynamical effects on soot concentration [D.O. Lignell, J.H. Chen, P.J. Smith, T. Lu, C.K. Law, Combust. Flame 151 (1-2) (2007) 2-28]. It was shown that flame curvature strongly impacts the diffusive motion of the flame relative to soot (which is essentially convected with the flow), resulting in soot being differentially transported toward or away from the flame zone. The proximity of the soot to the flame directly influences soot reactivity and radiative properties. Here, the analysis is extended to three dimensions in a temporal jet configuration with mean shear. Results show that similar local flame dynamic effects of strain and curvature are important, but that enhanced turbulent mixing of fuel and oxidizer streams has a first-order effect on transport of soot toward flame zones. Soot modeling in turbulent flames is a challenge due to the complexity of soot formation and transport processes and the lack of detailed experimental soot-flame-flow structural data. The present direct numerical simulation provides the first step toward providing such data. (author)

  3. Direct-referencing Two-dimensional-array Digital Microfluidics Using Multi-layer Printed Circuit Board

    PubMed Central

    Gong, Jian; Kim, Chang-Jin “CJ”

    2008-01-01

    Digital (i.e. droplet-based) microfluidics, by the electrowetting-on-dielectric (EWOD) mechanism, has shown great potential for a wide range of applications, such as lab-on-a-chip. While most reported EWOD chips use a series of electrode pads essentially in one-dimensional line pattern designed for specific tasks, the desired universal chips allowing user-reconfigurable paths would require the electrode pads in two-dimensional pattern. However, to electrically access the electrode pads independently, conductive lines need to be fabricated underneath the pads in multiple layers, raising a cost issue especially for disposable chip applications. In this article, we report the building of digital microfluidic plates based on a printed-circuit-board (PCB), in which multilayer electrical access lines were created inexpensively using mature PCB technology. However, due to its surface topography and roughness and resulting high resistance against droplet movement, as-fabricated PCB surfaces require unacceptably high (~500 V) voltages unless coated with or immersed in oil. Our goal is EWOD operations of aqueous droplets not only on oil-covered but also on dry surfaces. To meet varying levels of performances, three types of gradually complex post-PCB microfabrication processes are developed and evaluated. By introducing land-grid-array (LGA) sockets in the packaging, a scalable digital microfluidics system with reconfigurable and low-cost chip is also demonstrated. PMID:19234613

  4. Acyclic phosph(on)ate inhibitors of Plasmodium falciparum hypoxanthine-guanine-xanthine phosphoribosyltransferase

    PubMed Central

    Clinch, Keith; Crump, Douglas R.; Evans, Gary B.; Hazleton, Keith Z.; Mason, Jennifer M.; Schramm, Vern L.

    2013-01-01

    The pathogenic protozoa responsible for malaria lack enzymes for the de novo synthesis of purines and rely on purine salvage from the host. In Plasmodium falciparum (Pf), hypoxanthine-guanine-xanthine phosphoribosyltransferase (HGXPRT) converts hypoxanthine to inosine monophosphate and is essential for purine salvage making the enzyme an anti-malarial drug target. We have synthesized a number of simple acyclic aza-C- nucleosides and shown that some are potent inhibitors of Pf HGXPRT while showing excellent selectivity for the Pf versus the human enzyme. PMID:23810424

  5. Characterization of cyclic and acyclic alkanes in Forties and Kuwait petroleum crudes

    SciTech Connect

    Jones, D.W. ); Pakdel, H. ); Bartle, K.D. )

    1990-01-01

    Alkane hydrocarbon fractions from Forties (North Sea) and Kuwait petroleum crudes, separated by distillation, solvent extraction and silicagel column chromatography and sub-fractionated by molecular-sieve adsorption, have been examined by gas chromatography (GC), {sup 1}H and {sup 13}C NMR spectroscopy, GC-mass spectrometry (MS) and field desorption (FD)MS. GC indicates that Forties contains rather more acyclic isoprenoids and cyclic alkanes than Kuwait; FDMS of Kuwait shows molecular-weight ranges for mono-, di-, tri-, tetra-, and pentacyclic alkanes. {sup 13}C NMR spectra provide evidence of higher aromatic carbon, C{sub A}, in Forties than Kuwait and longer T{sub 1} relaxation times.

  6. A Practical Approach for Scalable Conjunctive Query Answering on Acyclic {EL}^+ Knowledge Base

    NASA Astrophysics Data System (ADS)

    Mei, Jing; Liu, Shengping; Xie, Guotong; Kalyanpur, Aditya; Fokoue, Achille; Ni, Yuan; Li, Hanyu; Pan, Yue

    Conjunctive query answering for {EL}^{++} ontologies has recently drawn much attention, as the Description Logic {EL}^{++} captures the expressivity of many large ontologies in the biomedical domain and is the foundation for the OWL 2 EL profile. In this paper, we propose a practical approach for conjunctive query answering in a fragment of {EL}^{++}, namely acyclic {EL}^+, that supports role inclusions. This approach can be implemented with low cost by leveraging any existing relational database management system to do the ABox data completion and query answering. We conducted a preliminary experiment to evaluate our approach using a large clinical data set and show our approach is practical.

  7. Alternating-direction implicit numerical solution of the time-dependent, three-dimensional, single fluid, resistive magnetohydrodynamic equations

    SciTech Connect

    Finan, C.H. III

    1980-12-01

    Resistive magnetohydrodynamics (MHD) is described by a set of eight coupled, nonlinear, three-dimensional, time-dependent, partial differential equations. A computer code, IMP (Implicit MHD Program), has been developed to solve these equations numerically by the method of finite differences on an Eulerian mesh. In this model, the equations are expressed in orthogonal curvilinear coordinates, making the code applicable to a variety of coordinate systems. The Douglas-Gunn algorithm for Alternating-Direction Implicit (ADI) temporal advancement is used to avoid the limitations in timestep size imposed by explicit methods. The equations are solved simultaneously to avoid syncronization errors.

  8. A novel intramolecular through-space interaction between F and CN: a strategy for the conformational control of an acyclic system.

    PubMed

    Nishide, K; Hagimoto, Y; Hasegawa, H; Shiro, M; Node, M

    2001-11-21

    X-Ray crystallographic analyses of fluorocyanides anti-1 and 2 revealed a novel intramolecular through-space interaction between F and CN in an acyclic system, which was applied to a stereoselective protonation of acyclic fluorocyanides 2 having flexible conformation. PMID:12240092

  9. A new strategy to construct acyclic nucleosides via Ag(I)-catalyzed addition of pronucleophiles to 9-allenyl-9H-purines.

    PubMed

    Wei, Tao; Xie, Ming-Sheng; Qu, Gui-Rong; Niu, Hong-Ying; Guo, Hai-Ming

    2014-02-01

    A new strategy to construct acyclic nucleosides with diverse side chains was developed. With Ag(I) salts as catalysts, the hydrocarboxylation, hydroamination, and hydrocarbonation reactions proceeded well, affording acyclic nucleosides in good yields (41 examples, 60-98% yields). Meanwhile, these reactions exhibited high chemoselectivities and E-selectivities. PMID:24437554

  10. Parallelised direct numerical simulation of three-dimensional wavy falling films

    NASA Astrophysics Data System (ADS)

    Juric, Damir; Chergui, Jalel; Kahouadji, Lyes; Matar, Omar; Shin, Seungwon

    2015-11-01

    We present a computational study of falling liquid films in a three-dimensional inclined rectangular domain using the new massively parallel code, BLUE. Calculations are carried out in order to obtain several wave patterns such as occasional solitary waves, which travel downstream at a constant velocity, or less coherent structures. BLUE uses parallelization algorithms based on MPI and algebraic domain decomposition. The velocity field is solved by a parallel GMRES method for the viscous terms and the pressure by a parallel multigrid method. The method for the treatment of the fluid interfaces and capillary forces uses a parallelized Front Tracking/Level Set technique which defines the interface both by a discontinuous density field as well as by a local triangular Lagrangian mesh. This structure allows the interface to undergo large deformations including the rupture and/or coalescence of fluid interfaces. EPSRC Programme Grant, MEMPHIS, EP/K0039761/1.

  11. Three dimensional complex plasma structures in a combined radio frequency and direct current discharge

    NASA Astrophysics Data System (ADS)

    Mitic, S.; Klumov, B. A.; Khrapak, S. A.; Morfill, G. E.

    2013-04-01

    We report on the first detailed analysis of large three dimensional (3D) complex plasma structures in experiments performed in pure rf and combined rf+dc discharge modes. Inductively coupled plasma is generated by an rf coil wrapped around the vertically positioned cylindrical glass tube at a pressure of 0.3 mbar. In addition, dc plasma can be generated by applying voltage to the electrodes at the ends of the tube far from the rf coil. The injected monodisperse particles are levitated in the plasma below the coil. A scanning laser sheet and a high resolution camera are used to determine the 3D positions of about 105 particles. The observed bowl-shaped particle clouds reveal coexistence of various structures, including well-distinguished solid-like, less ordered liquid-like, and pronounced string-like phases. New criteria to identify string-like structures are proposed.

  12. Three dimensional complex plasma structures in a combined radio frequency and direct current discharge

    SciTech Connect

    Mitic, S.; Morfill, G. E.; Klumov, B. A.; Khrapak, S. A.

    2013-04-15

    We report on the first detailed analysis of large three dimensional (3D) complex plasma structures in experiments performed in pure rf and combined rf+dc discharge modes. Inductively coupled plasma is generated by an rf coil wrapped around the vertically positioned cylindrical glass tube at a pressure of 0.3 mbar. In addition, dc plasma can be generated by applying voltage to the electrodes at the ends of the tube far from the rf coil. The injected monodisperse particles are levitated in the plasma below the coil. A scanning laser sheet and a high resolution camera are used to determine the 3D positions of about 10{sup 5} particles. The observed bowl-shaped particle clouds reveal coexistence of various structures, including well-distinguished solid-like, less ordered liquid-like, and pronounced string-like phases. New criteria to identify string-like structures are proposed.

  13. Detailed Multi‐dimensional Modeling of Direct Internal Reforming Solid Oxide Fuel Cells

    PubMed Central

    Tseronis, K.; Fragkopoulos, I.S.; Bonis, I.

    2016-01-01

    Abstract Fuel flexibility is a significant advantage of solid oxide fuel cells (SOFCs) and can be attributed to their high operating temperature. Here we consider a direct internal reforming solid oxide fuel cell setup in which a separate fuel reformer is not required. We construct a multidimensional, detailed model of a planar solid oxide fuel cell, where mass transport in the fuel channel is modeled using the Stefan‐Maxwell model, whereas the mass transport within the porous electrodes is simulated using the Dusty‐Gas model. The resulting highly nonlinear model is built into COMSOL Multiphysics, a commercial computational fluid dynamics software, and is validated against experimental data from the literature. A number of parametric studies is performed to obtain insights on the direct internal reforming solid oxide fuel cell system behavior and efficiency, to aid the design procedure. It is shown that internal reforming results in temperature drop close to the inlet and that the direct internal reforming solid oxide fuel cell performance can be enhanced by increasing the operating temperature. It is also observed that decreases in the inlet temperature result in smoother temperature profiles and in the formation of reduced thermal gradients. Furthermore, the direct internal reforming solid oxide fuel cell performance was found to be affected by the thickness of the electrochemically‐active anode catalyst layer, although not always substantially, due to the counter‐balancing behavior of the activation and ohmic overpotentials. PMID:27570502

  14. Direct Observation of the Fermi Arc Surface State in the Three-Dimensional Dirac Semimetal Na3Bi

    NASA Astrophysics Data System (ADS)

    Liang, Aiji; Wang, Zhijun; Chen, Chaoyu; Shi, Youguo; Yi, Hemian; Feng, Ya; Xie, Zhuojin; He, Shaolong; He, Junfeng; Peng, Yingying; Liu, Xu; Liu, Yan; Zhao, Lin; Liu, Guodong; Zhang, Jun; Nakatake, M.; Arita, M.; Shimada, K.; Namatame, H.; Taniguchi, M.; Xu, Zuyan; Chen, Chuangtian; Dai, Xi; Fang, Zhong; Zhou, Xingjiang

    2015-03-01

    The three dimensional (3D) Dirac semimetals have linearly dispersive 3D Dirac nodes where the conduction and valence bands connect to each other. Here we report the direct observation of the linearly dispersive 3D bulk Dirac points at the natural (001) cleaving surface of Na3Bi single crystal by high resolution ARPES. In addition, we have directly observed two separated 3D bulk Dirac nodes by elaborately cleaving Na3Bi samples at a non-natural-cleavage (100) crystalline surface. We further unveil the unusual Fermi-arc surface states connecting the two 3D Dirac nodes. At this unique (100) crystalline surface, the identification of the 3D Dirac semimetal state in Na3Bi paves the way for systematically exploring rich exotic topological physics such as topological insulator and Weyl semimetal state.

  15. Patterned and functionalized nanofiber scaffolds in three-dimensional hydrogel constructs enhance neurite outgrowth and directional control

    NASA Astrophysics Data System (ADS)

    McMurtrey, Richard J.

    2014-12-01

    Objective. Neural tissue engineering holds incredible potential to restore functional capabilities to damaged neural tissue. It was hypothesized that patterned and functionalized nanofiber scaffolds could control neurite direction and enhance neurite outgrowth. Approach. A method of creating aligned electrospun nanofibers was implemented and fiber characteristics were analyzed using environmental scanning electron microscopy. Nanofibers were composed of polycaprolactone (PCL) polymer, PCL mixed with gelatin, or PCL with a laminin coating. Three-dimensional hydrogels were then integrated with embedded aligned nanofibers to support neuronal cell cultures. Microscopic images were captured at high-resolution in single and multi-focal planes with eGFP-expressing neuronal SH-SY5Y cells in a fluorescent channel and nanofiber scaffolding in another channel. Neuronal morphology and neurite tracking of nanofibers were then analyzed in detail. Main results. Aligned nanofibers were shown to enable significant control over the direction of neurite outgrowth in both two-dimensional (2D) and three-dimensional (3D) neuronal cultures. Laminin-functionalized nanofibers in 3D hyaluronic acid (HA) hydrogels enabled significant alignment of neurites with nanofibers, enabled significant neurite tracking of nanofibers, and significantly increased the distance over which neurites could extend. Specifically, the average length of neurites per cell in 3D HA constructs with laminin-functionalized nanofibers increased by 66% compared to the same laminin fibers on 2D laminin surfaces, increased by 59% compared to 2D laminin-coated surface without fibers, and increased by 1052% compared to HA constructs without fibers. Laminin functionalization of fibers also doubled average neurite length over plain PCL fibers in the same 3D HA constructs. In addition, neurites also demonstrated tracking directly along the fibers, with 66% of neurite lengths directly tracking laminin-coated fibers in 3D HA

  16. Investigation of diastereoselective acyclic α-alkoxydithioacetal substitutions involving thiacarbenium intermediates.

    PubMed

    Prévost, Michel; Dostie, Starr; Waltz, Marie-Ève; Guindon, Yvan

    2014-11-01

    Reported herein is an experimental and theoretical study that elucidates why silylated nucleobase additions to acyclic α-alkoxythiacarbenium intermediates proceed with high 1,2-syn stereocontrol (anti-Felkin-Anh), which is opposite to what would be expected with corresponding activated aldehydes. The acyclic thioaminals formed undergo intramolecular cyclizations to provide nucleoside analogues with anticancer and antiviral properties. The factors influencing the selectivity of the substitution reaction have been examined thoroughly. Halothioether species initially form, ionize in the presence (low dielectric media) or absence (higher dielectric media) of the nucleophile, and react through SN2-like transition structures (TS A and D), where the α-alkoxy group is gauche to the thioether moiety. An important, and perhaps counterintuitive, observation in this work was that calculations done in the gas phase or low dielectric media (toluene) are essential to locate the product- and rate-determining transition structures (C-N bond formation) that allow the most reasonable prediction of selectivity and isotope effects for more polar solvents (THF, MeCN). The ΔΔG(⧧) (G(TSA-TSD)) obtained in silico are consistent with the preferential formation of 1,2-syn product and with the trends of stereocontrol displayed by 2,3-anti and 2,3-syn α,β-bis-alkoxydithioacetals. PMID:25280088

  17. Low-field one-dimensional and direction-dependent relaxation imaging of bovine articular cartilage

    NASA Astrophysics Data System (ADS)

    Rössler, Erik; Mattea, Carlos; Mollova, Ayret; Stapf, Siegfried

    2011-12-01

    The structure of articular cartilage is separated into three layers of differently oriented collagen fibers, which is accompanied by a gradient of increasing glycosaminoglycan (GAG) and decreasing water concentration from the top layer towards the bone interface. The combined effect of these structural variations results in a change of the longitudinal and transverse relaxation times as a function of the distance from the cartilage surface. In this paper, this dependence is investigated at a magnetic field strength of 0.27 T with a one-dimensional depth resolution of 50 μm on bovine hip and stifle joint articular cartilage. By employing this method, advantage is taken of the increasing contrast of the longitudinal relaxation rate found at lower magnetic field strengths. Furthermore, evidence for an orientational dependence of relaxation times with respect to an axis normal to the surface plane is given, an observation that has recently been reported using high-field MRI and that was explained by preferential orientations of collagen bundles in each of the three cartilage zones. In order to quantify the extent of a further contrast mechanism and to estimate spatially dependent glycosaminoglycan concentrations, the data are supplemented by proton relaxation times that were acquired in bovine articular cartilage that was soaked in a 0.8 mM aqueous Gd ++ solution.

  18. Short peptide-directed synthesis of one-dimensional platinum nanostructures with controllable morphologies

    PubMed Central

    Tao, Kai; Wang, Jiqian; Li, Yanpeng; Xia, Daohong; Shan, Honghong; Xu, Hai; Lu, Jian R.

    2013-01-01

    Although one dimensional (1D) Pt nanostructures with well-defined sizes and shapes have fascinating physiochemical properties, their preparation remains a great challenge. Here we report an easy and novel synthesis of 1D Pt nanostructures with controllable morphologies, through the combination of designer self-assembling I3K and phage-displayed P7A peptides. The nanofibrils formed via I3K self-assembly acted as template. Pt precursors ((PtCl4)2− and (PtCl6)2−) were immobilized by electrostatic interaction on the positively charged template surface and subsequent reduction led to the formation of 1D Pt nanostructures. P7A was applied to tune the continuity of the Pt nanostructures. Here, the electrostatic repulsion between the deprotonated C-terminal carboxyl groups of P7A molecules was demonstrated to play a key role. We finally showed that continuous and ordered 1D Pt morphology had a significantly improved electrochemical performance for the hydrogen and methanol electro-oxidation in comparison with either 1D discrete Pt nanoparticle assemblies or isolated Pt nanoparticles. PMID:23995118

  19. Microstructure Analysis and Multi-Unit Cell Model of Three Dimensionally Four-Directional Braided Composites

    NASA Astrophysics Data System (ADS)

    Xu, Kun; Qian, Xiaomei

    2015-02-01

    In this paper, a new multi-unit cell model of three dimensionally braided composites is presented on the basis of the microstructure analysis of 3D braided preforms produced by four-step 1 × 1 method. According to a new unit cell partition scheme, the multi-unit cell model possesses five kinds of unit cells, namely interior, exterior surface, interior surface, exterior corner and interior corner unit cells. Each type of the representative volume cell has unique microstructure and volume fraction in braided composites. On the basis of these five unit cell models, the structural geometry parameters of the preforms are analyzed and the relationship between the structural parameters and the braiding parameters in different regions are derived in detail, such as the braiding angles, fiber volume fraction, yarn packing factor, braiding pitch and so on. Finally, by using the multi-unit cell model, the main structural parameters of braided composites specimens are calculated to validate the effectiveness of the model. The results are in good agreement with the available experimental data. In addition, the effect of braiding angle on the squeezing condition of braiding yarn is analyzed. The variations of the volume proportion of five unit cells to the whole specimen with rows and columns are discussed, respectively. The presented multi-unit cell model can be adopted to design 3D braided composites and predict their mechanical properties.

  20. Transition metal ion directed supramolecular assembly of one- and two-dimensional polyrotaxanes incorporating cucurbituril.

    PubMed

    Park, Ki-Min; Whang, Dongmok; Lee, Eunsung; Heo, Jungseok; Kim, Kimoon

    2002-01-18

    This paper reports a synthetic strategy to construct one- and two-dimensional (1D and 2D) polyrotaxanes, in which a number of rings are threaded onto a coordination polymer, by the combination of self-assembly and coordination chemistry. Our approach to construct polyrotaxanes with high structural regularity involves threading a cucurbituril (CB) "bead" with a short "string" to form a stable pseudorotaxane, followed by linking the pseudorotaxanes with metal ions as "linkers" to organize into a 1D or 2D polyrotaxane. A 4- or 3-pyridylmethyl group is attached to each end of 1,4-diaminobutane or 1,5-diaminopentane to produce the short "strings", which then react with the cucurbituril "bead" to form stable pseudorotaxanes. The reaction of the pseudorotaxanes with various transition metal ions including CuII, CoII, NiII, AgI, and CdII produces 1D or 2D polyrotaxanes, in which many molecular "beads" are threaded onto 1D or 2D coordination polymers as confirmed by X-ray crystallography. The overall structure of a polyrotaxane is the result of interplay among various factors that include the coordination preferences of the metal ion, spatial disposition of the donor atoms with respect to the CB beads in the pseudorotaxane, and the size and coordination ability of the counteranion. PMID:11843162

  1. Direct three-dimensional characterization and multiscale visualization of wheat straw deconstruction by white rot fungus.

    PubMed

    Liu, Li; Qian, Chen; Jiang, Lei; Yu, Han-Qing

    2014-08-19

    Microbial degradation of lignocellulose for resource and energy recovery has received increasing interest. Despite its obvious importance, the mechanism behind the biodegradation, especially the changes of morphological structure and surface characteristics, has not been fully understood. Here, we used three-dimensional (3D) characterization and multiscale visualization methods, in combination with chemical compositional analyses, to elucidate the degradation process of wheat straw by a white rot fungus, Phanerochaete chrysosporium. It was found that the fungal attack initiated from stomata. Lignin of the straw decayed in both size and quantity, and heterogeneity in the biodegradation was observed. After treatment with the fungus, the straw surface turned from hydrophobic to hydrophilic, and the adhesion of the straw surface increased in the fungal degradation. The morphology of the straw outer layer became heterogeneous and loose with the formation of many holes with various sizes. The wasp-tunnels-like structure of the collenchyma and parenchyma of the straw as well as the fungal hyphae interspersed inside the straw structure were clearly visualized in the 3D reconstruction structure. This work offers a new insight into the mechanism of lignocellulose biodegradation and demonstrates that multiscale visualization methods could be a useful tool to explore such complex processes. PMID:25072830

  2. Enhancement of direct urea-hydrogen peroxide fuel cell performance by three-dimensional porous nickel-cobalt anode

    NASA Astrophysics Data System (ADS)

    Guo, Fen; Cao, Dianxue; Du, Mengmeng; Ye, Ke; Wang, Guiling; Zhang, Wenping; Gao, Yinyi; Cheng, Kui

    2016-03-01

    A novel three-dimensional (3D) porous nickel-cobalt (Ni-Co) film on nickel foam is successfully prepared and further used as an efficient anode for direct urea-hydrogen peroxide fuel cell (DUHPFC). By varying the cobalt/nickel mole ratios into 0%, 20%, 50%, 80% and 100%, the optimized Ni-Co/Ni foam anode with a ratio of 80% is obtained in terms of the best cell performance among five anodes. Effects of the KOH and urea concentrations, the flow rate and operation temperature on the fuel cell performance are investigated. Results show DUHPFC with the 3D Ni-Co/Ni foam anode exhibits a higher performance than those reported direct urea fuel cells. The cell gives an open circuit voltage of 0.83 V and a peak power density as high as 17.4 and 31.5 mW cm-2 at 20 °C and 70 °C, respectively, when operating on 7.0 mol L-1 KOH and 0.5 mol L-1 urea as the fuel at a flow rate of 15 mL min-1. Besides, when the human urine is directly fed as the fuel, direct urine-hydrogen peroxide fuel cell reaches a maximum power density of 7.5 mW cm-2 with an open circuit voltage of 0.80 V at 20 °C, showing a good application prospect in wastewater treatment.

  3. Three-dimensional bioprinting of embryonic stem cells directs highly uniform embryoid body formation.

    PubMed

    Ouyang, Liliang; Yao, Rui; Mao, Shuangshuang; Chen, Xi; Na, Jie; Sun, Wei

    2015-12-01

    With the ability to manipulate cells temporarily and spatially into three-dimensional (3D) tissue-like construct, 3D bioprinting technology was used in many studies to facilitate the recreation of complex cell niche and/or to better understand the regulation of stem cell proliferation and differentiation by cellular microenvironment factors. Embryonic stem cells (ESCs) have the capacity to differentiate into any specialized cell type of the animal body, generally via the formation of embryoid body (EB), which mimics the early stages of embryogenesis. In this study, extrusion-based 3D bioprinting technology was utilized for biofabricating ESCs into 3D cell-laden construct. The influence of 3D printing parameters on ESC viability, proliferation, maintenance of pluripotency and the rule of EB formation was systematically studied in this work. Results demonstrated that ESCs were successfully printed with hydrogel into 3D macroporous construct. Upon process optimization, about 90% ESCs remained alive after the process of bioprinting and cell-laden construct formation. ESCs continued proliferating into spheroid EBs in the hydrogel construct, while retaining the protein expression and gene expression of pluripotent markers, like octamer binding transcription factor 4, stage specific embryonic antigen 1 and Nanog. In this novel technology, EBs were formed through cell proliferation instead of aggregation, and the quantity of EBs was tuned by the initial cell density in the 3D bioprinting process. This study introduces the 3D bioprinting of ESCs into a 3D cell-laden hydrogel construct for the first time and showed the production of uniform, pluripotent, high-throughput and size-controllable EBs, which indicated strong potential in ESC large scale expansion, stem cell regulation and fabrication of tissue-like structure and drug screening studies. PMID:26531008

  4. Future directions in 3-dimensional imaging and neurosurgery: stereoscopy and autostereoscopy.

    PubMed

    Christopher, Lauren A; William, Albert; Cohen-Gadol, Aaron A

    2013-01-01

    Recent advances in 3-dimensional (3-D) stereoscopic imaging have enabled 3-D display technologies in the operating room. We find 2 beneficial applications for the inclusion of 3-D imaging in clinical practice. The first is the real-time 3-D display in the surgical theater, which is useful for the neurosurgeon and observers. In surgery, a 3-D display can include a cutting-edge mixed-mode graphic overlay for image-guided surgery. The second application is to improve the training of residents and observers in neurosurgical techniques. This article documents the requirements of both applications for a 3-D system in the operating room and for clinical neurosurgical training, followed by a discussion of the strengths and weaknesses of the current and emerging 3-D display technologies. An important comparison between a new autostereoscopic display without glasses and current stereo display with glasses improves our understanding of the best applications for 3-D in neurosurgery. Today's multiview autostereoscopic display has 3 major benefits: It does not require glasses for viewing; it allows multiple views; and it improves the workflow for image-guided surgery registration and overlay tasks because of its depth-rendering format and tools. Two current limitations of the autostereoscopic display are that resolution is reduced and depth can be perceived as too shallow in some cases. Higher-resolution displays will be available soon, and the algorithms for depth inference from stereo can be improved. The stereoscopic and autostereoscopic systems from microscope cameras to displays were compared by the use of recorded and live content from surgery. To the best of our knowledge, this is the first report of application of autostereoscopy in neurosurgery. PMID:23254802

  5. Three-dimensional spray distributions in a direct injection diesel engine

    SciTech Connect

    Yoshizaki, Takuo; Nishida, Keiya; Hiroyasu, Hiroyuki; Song, K.K.

    1994-09-01

    Experiments and modeling of a spray impinged onto a cavity wall of a simulated piston were performed under simulated diesel engine conditons (pressure and density) at an ambient temperature. The diesel fuel was delivered from a Bosch-type injection pump to a single-hole nozzle, the hole being drilled in the same direction as the original five-hole nozzle. The fuel was injected into a high-pressure bomb in which an engine combustion chamber, composed of a piston, a cylinder head and a cylinder liner, was installed. Distributions of the spray impinging on the simulated combustion chamber were observed from various directions while changing some of the experimental parameters, such as combustion chamber shape, nozzle projection and top-clearance. High-speed photography was used in the constant volume bomb to examine the effect of these parameters on the spray distributions. The spray distributions obtained in the simulated combustion chamber are compared to the distributions calculated by a spray model based on a multi-package, spray model 3 refs., 13 figs., 1 tab.

  6. In Vivo CT Direct Volume Rendering: A Three-Dimensional Anatomical Description of the Heart

    PubMed Central

    Cutroneo, Giuseppina; Bruschetta, Daniele; Trimarchi, Fabio; Cacciola, Alberto; Cinquegrani, Maria; Duca, Antonio; Rizzo, Giuseppina; Alati, Emanuela; Gaeta, Michele; Milardi, Demetrio

    2016-01-01

    Summary Background Since cardiac anatomy continues to play an important role in the practice of medicine and in the development of medical devices, the study of the heart in three dimensions is particularly useful to understand its real structure, function and proper location in the body. Material/Methods This study demonstrates a fine use of direct volume rendering, processing the data set images obtained by Computed Tomography (CT) of the heart of 5 subjects with age range between 18 and 42 years (2 male, 3 female), with no history of any overt cardiac disease. The cardiac structure in CT images was first extracted from the thorax by marking manually the regions of interest on the computer, and then it was stacked to create new volumetric data. Results The use of a specific algorithm allowed us to observe with a good perception of depth the heart and the skeleton of the thorax at the same time. Besides, in all examined subjects, it was possible to depict its structure and its position within the body and to study the integrity of papillary muscles, the fibrous tissue of cardiac valve and chordae tendineae and the course of coronary arteries. Conclusions Our results demonstrated that one of the greatest advantages of algorithmic modifications of direct volume rendering parameters is that this method provides much necessary information in a single radiologic study. It implies a better accuracy in the study of the heart, being complementary to other diagnostic methods and facilitating the therapeutic plans. PMID:26858778

  7. Whistlers and plasmaspheric hiss - Wave directions and three-dimensional propagation

    NASA Technical Reports Server (NTRS)

    Draganov, A. B.; Inan, U. S.; Sonwalkar, V. S.; Bell, T. F.

    1993-01-01

    Wave propagation directions are determined on the basis of wave data from the DE 1 satellite showing simultaneously nonducted whistlers and hiss. Hiss wave normal angles are determined as about 70 and 77 deg for f = 3.5 and 2.5 kHz, respectively, with the wave vector being almost perpendicular to the meridional plane. A novel approximate analytical formulation of 3D propagation of whistler waves is developed and used to model the drift of magnetospherically reflected whistlers in azimuth. It is shown that depending on initial parameters, the time of arrival of whistler rays at a fixed observation point can differ by 10-20 s, with signals from different magnetospherically reflected whistlers overlapping to evolve into a hisslike signal. The total azimuthal drift of whistler rays is found to not exceed about 30 deg, so that plasmaspheric hiss may be produced by nonducted whistlers at longitudes correlated with the location of thunderstorm activity.

  8. An Integrative Biosensor Based on Contra-Directional Coupling Two-dimensional Photonic Crystal Waveguides

    NASA Astrophysics Data System (ADS)

    Mao, Xiao-Yu; Yao, Di-Bi; Zhao, Ling-Yun; Huang, Yi-Dong; Zhang, Wei; Peng, Jiang-De

    2008-01-01

    We propose an integrative biochemical sensor utilizing the dip in the transmission spectrum of a normal single-line defect photonic crystal (PC) waveguide, which has a contra-directional coupling with another PC waveguide. When the air holes in the PC slab are filled with a liquid analyte with different refractive indices, the dip has a wavelength shift By detecting the output power variation at a certain fixed wavelength, a sensitivity of 1.2 × 10-4 is feasible. This structure is easy for integration due to its plane waveguide structure and omissible pump source. In addition, high signal to noise ratio can be expected because signal transmits via a normal single-line defect PC waveguide instead of the PC hole area or analyte.

  9. Direct manufacturing of ultrathin graphite on three-dimensional nanoscale features

    NASA Astrophysics Data System (ADS)

    Pacios, Mercè; Hosseini, Peiman; Fan, Ye; He, Zhengyu; Krause, Oliver; Hutchison, John; Warner, Jamie H.; Bhaskaran, Harish

    2016-03-01

    There have been many successful attempts to grow high-quality large-area graphene on flat substrates. Doing so at the nanoscale has thus far been plagued by significant scalability problems, particularly because of the need for delicate transfer processes onto predefined features, which are necessarily low-yield processes and which can introduce undesirable residues. Herein we describe a highly scalable, clean and effective, in-situ method that uses thin film deposition techniques to directly grow on a continuous basis ultrathin graphite (uG) on uneven nanoscale surfaces. We then demonstrate that this is possible on a model system of atomic force probe tips of various radii. Further, we characterize the growth characteristics of this technique as well as the film’s superior conduction and lower adhesion at these scales. This sets the stage for such a process to allow the use of highly functional graphite in high-aspect-ratio nanoscale components.

  10. Note: Fast compact laser shutter using a direct current motor and three-dimensional printing

    SciTech Connect

    Zhang, Grace H. Braverman, Boris; Kawasaki, Akio; Vuletić, Vladan

    2015-12-15

    We present a mechanical laser shutter design that utilizes a direct current electric motor to rotate a blade which blocks and unblocks a light beam. The blade and the main body of the shutter are modeled with computer aided design (CAD) and are produced by 3D printing. Rubber flaps are used to limit the blade’s range of motion, reducing vibrations and preventing undesirable blade oscillations. At its nominal operating voltage, the shutter achieves a switching speed of (1.22 ± 0.02) m/s with 1 ms activation delay and 10 μs jitter in its timing performance. The shutter design is simple, easy to replicate, and highly reliable, showing no failure or degradation in performance over more than 10{sup 8} cycles.

  11. Direct manufacturing of ultrathin graphite on three-dimensional nanoscale features.

    PubMed

    Pacios, Mercè; Hosseini, Peiman; Fan, Ye; He, Zhengyu; Krause, Oliver; Hutchison, John; Warner, Jamie H; Bhaskaran, Harish

    2016-01-01

    There have been many successful attempts to grow high-quality large-area graphene on flat substrates. Doing so at the nanoscale has thus far been plagued by significant scalability problems, particularly because of the need for delicate transfer processes onto predefined features, which are necessarily low-yield processes and which can introduce undesirable residues. Herein we describe a highly scalable, clean and effective, in-situ method that uses thin film deposition techniques to directly grow on a continuous basis ultrathin graphite (uG) on uneven nanoscale surfaces. We then demonstrate that this is possible on a model system of atomic force probe tips of various radii. Further, we characterize the growth characteristics of this technique as well as the film's superior conduction and lower adhesion at these scales. This sets the stage for such a process to allow the use of highly functional graphite in high-aspect-ratio nanoscale components. PMID:26939862

  12. Constraints on Universal Extra-Dimensional Dark Matter from Direct Detection Results

    NASA Astrophysics Data System (ADS)

    Torpin, Trevor; Duda, Gintaras

    2011-04-01

    Detection of dark matter is one of the most challenging and important problems in astro-particle physics. One theory that produces a viable particle dark matter candidate is Universal Extra Dimensions (UED), in which the existence of a 4th spatial dimension is theorized. The extra dimension is not seen because it is compactifed on a circular orbifold whose radius is too small to be observed with current technology. What separates this theory over other Kaluza-Klein-type theories is that UED allows all standard model particles and fields to propagate in the extra dimension. The dark matter candidate in UED theories is a stable particle known as the Lightest Kaluza-Klein Particle or LKP, and the LKP can exist with sufficient relic density to serve as the dark matter. This work will present bounds on UED model parameters from direct dark matter searches such as the CDMS II.

  13. Direct manufacturing of ultrathin graphite on three-dimensional nanoscale features

    PubMed Central

    Pacios, Mercè; Hosseini, Peiman; Fan, Ye; He, Zhengyu; Krause, Oliver; Hutchison, John; Warner, Jamie H.; Bhaskaran, Harish

    2016-01-01

    There have been many successful attempts to grow high-quality large-area graphene on flat substrates. Doing so at the nanoscale has thus far been plagued by significant scalability problems, particularly because of the need for delicate transfer processes onto predefined features, which are necessarily low-yield processes and which can introduce undesirable residues. Herein we describe a highly scalable, clean and effective, in-situ method that uses thin film deposition techniques to directly grow on a continuous basis ultrathin graphite (uG) on uneven nanoscale surfaces. We then demonstrate that this is possible on a model system of atomic force probe tips of various radii. Further, we characterize the growth characteristics of this technique as well as the film’s superior conduction and lower adhesion at these scales. This sets the stage for such a process to allow the use of highly functional graphite in high-aspect-ratio nanoscale components. PMID:26939862

  14. Dynamical scaling behavior of the one-dimensional conserved directed-percolation universality class.

    PubMed

    Kwon, Sungchul; Kim, Yup

    2012-05-01

    We investigate the dynamical scaling behavior of the static diffusive epidemic process and a fixed-energy Manna sandpile model, undergoing nonequilibrium absorbing phase transitions in one dimension. These models belong to the so-called conserved directed-percolation or Manna universality class characterized by the conservation of the total particle number, activity coupled to a nondiffusive conserved field and infinitely many absorbing states. We measure the dynamical exponents of these models in one dimension by using the critical spreading simulation of a localized activity in absorbing configurations. In the spreading simulations, boundaries are never touched, so the results are free from the finite-size effects. In contrast to the scattered results for the different models from the previous finite-size scaling analyses, we obtain consistent estimates of the dynamical exponents for both models. PMID:23004715

  15. Note: Fast compact laser shutter using a direct current motor and three-dimensional printing

    NASA Astrophysics Data System (ADS)

    Zhang, Grace H.; Braverman, Boris; Kawasaki, Akio; Vuletić, Vladan

    2015-12-01

    We present a mechanical laser shutter design that utilizes a direct current electric motor to rotate a blade which blocks and unblocks a light beam. The blade and the main body of the shutter are modeled with computer aided design (CAD) and are produced by 3D printing. Rubber flaps are used to limit the blade's range of motion, reducing vibrations and preventing undesirable blade oscillations. At its nominal operating voltage, the shutter achieves a switching speed of (1.22 ± 0.02) m/s with 1 ms activation delay and 10 μs jitter in its timing performance. The shutter design is simple, easy to replicate, and highly reliable, showing no failure or degradation in performance over more than 108 cycles.

  16. Synthesis and antiviral activity evaluation of acyclic 2'-azanucleosides bearing a phosphonomethoxy function in the side chain.

    PubMed

    Koszytkowska-Stawińska, Mariola; De Clercq, Erik; Balzarini, Jan

    2009-06-01

    Acyclic 2'-azanucleosides with a phosphonomethoxy function in the side chain were obtained by coupling of diethyl {2-[N-(pivaloyloxymethyl)-N-(p-toluenesulfonyl)amino]ethoxymethyl}phosphonate with the pyrimidine nucleobases via the Vorbrüggen-type protocol. The compounds were evaluated in vitro for activity against a broad variety of RNA and DNA viruses. PMID:19442526

  17. Anomalous Reactivity and Selectivity in the Intermolecular Diels-Alder Reactions of Multisubstituted Acyclic Dienes with Geometrical Isomers of Enals.

    PubMed

    Zhou, Jia-Hui; Cai, Sai-Hu; Xu, Yun-He; Loh, Teck-Peng

    2016-05-20

    A Lewis-acid catalyzed intermolecular Diels-Alder reaction between multisubstituted acyclic dienes and the E and Z isomers of α,β-enals was studied. It was found that the diene reacted selectively with the Z-isomer of the α,β-enal. PMID:27132468

  18. Facile formation of branched titanate nanotubes to grow a three-dimensional nanotubular network directly on a solid substrate.

    PubMed

    Zhang, Haimin; Liu, Porun; Wang, Hongjuan; Yu, Hua; Zhang, Shanqing; Zhu, Huaiyong; Peng, Feng; Zhao, Huijun

    2010-02-01

    The hydrothermal formation of branched titanate nanotubes that grow a 3D nanotubular network directly onto a titanium substrate is reported. The resultant 3D nanotubular network exhibits a unique all-dimensional uniform porous structure. The inner and outer tubular diameters of branched titanate nanotubes were found to be approximately 6 and 12 nm, respectively. For the majority of the nanotubes, the wall is formed from three layers of titanate with an approximate 7.7 A interlayer space. In terms of individual nanotubes, these characteristics are quantitatively similar to those of previously reported nonbranched nanotubes. However, in terms of how nanotubes are arranged in the film, the all-dimensional uniform nanotubular network structure obtained here is distinctively different from those of previously reported structures. The 3D nanotubular network structure was formed by the jointing of branched nanotubes. In contrast, the previously reported nanotubes tend to grow vertically on the substrate, and the resultant tubular films are formed by interwoven nonbranched nanotubes. The branched titanate nanotubes can be readily formed on titanium substrates but not in solution suspension forms. A continuous seed formation-oriented crystal growth mechanism was proposed for the branched titanate nanotubular network formation. Such a network structure could be useful for applications such as photocatalysis, membrane separation, field emission, and photovoltaic devices. PMID:20039654

  19. Directed assembly of cell-laden microgels for building porous three-dimensional tissue constructs.

    PubMed

    Yanagawa, Fumiki; Kaji, Hirokazu; Jang, Yun-Ho; Bae, Hojae; Yanan, Du; Fukuda, Junji; Qi, Hao; Khademhosseini, Ali

    2011-04-01

    The organization of cells within a well-defined microenvironment is important in generating the resulting tissue function. However, the cellular organization within biodegradable scaffolds often does not resemble those of native tissues. In this study, we present directed assembly of microgels to organize cells for building porous 3D tissue constructs. Cell-laden microgels were generated by molding photocrosslinkable polyethylene glycol diacrylate within a poly(dimethyl siloxane) stencil. The resulting microgels were subsequently packed as individual layers (1 mm in height) on a glass substrate by removing the excess prepolymer solution around the microgels. These clusters were crosslinked and stacked on one another to fabricate thick 3D constructs that were greater than 1 cm in width and 3 mm in thickness. To generate pores within the engineered structures, sodium alginate microgels were integrated in the engineered constructs and used as a sacrificial template. These pores may be potentially useful for fabricating a vascular network to supply oxygen and nutrients to the engineered tissue constructs. This simple and versatile building approach may be a useful tool for various 3D tissue culture and engineering applications. PMID:21319297

  20. Directed assembly of cell-laden microgels for building porous three-dimensional tissue constructs

    PubMed Central

    Yanagawa, Fumiki; Kaji, Hirokazu; Jang, Yun-Ho; Bae, Hojae; Yanan, Du; Fukuda, Junji; Qi, Hao; Khademhosseini, Ali

    2011-01-01

    The organization of cells within a well-defined microenvironment is important in generating the resulting tissue function. However, the cellular organization within biodegradable scaffolds often does not resemble those of native tissues. In this study, we present directed assembly of microgels to organize cells for building porous 3D tissue constructs. Cell-laden microgels were generated by molding photocrosslinkable polyethylene glycol diacrylate (PEGDA) within a poly(dimethyl siloxane) (PDMS) stencil. The resulting microgels were subsequently packed as individual layers (1 mm in height) on a glass substrate by removing the excess pre-polymer solution around the microgels. These clusters were crosslinked and stacked on one another to fabricate thick 3D constructs that were greater than 1 cm in width and 3 mm in thickness. To generate pores within the engineered structures, sodium alginate microgels were integrated in the engineered constructs and used as a sacrificial template. These pores may be potentially useful for fabricating a vascular network to supply oxygen and nutrients to the engineered tissue constructs. This simple and versatile building approach may be a useful tool for various 3D tissue culture and engineering applications. PMID:21319297

  1. Direct laser writing of three-dimensional network structures as templates for disordered photonic materials

    NASA Astrophysics Data System (ADS)

    Haberko, Jakub; Muller, Nicolas; Scheffold, Frank

    2013-10-01

    In the present article we substantially expand on our recent study about the fabrication of mesoscale polymeric templates of disordered photonic network materials [Haberko and Scheffold, Opt. Expr.OPEXFF1094-408710.1364/OE.21.001057 21, 1057 (2013)]. We present a detailed analysis and discussion of important technical aspects related to the fabrication and characterization of these fascinating materials. Compared to our initial report we were able to reduce the typical structural length scale of the seed pattern from a=3.3μm to a=2μm, bringing it closer to the technologically relevant fiber-optic communications wavelength range around λ˜1.5μm. We have employed scanning electron microscopy coupled with focused ion beam cutting to look inside the bulk of the samples of different heights. Moreover, we demonstrate the use of laser scanning confocal microscopy to assess the real space structure of the samples fabricated by direct laser writing. We address in detail questions about scalability, finite size effects, and geometrical distortions. We also study the effect of the lithographic voxel shape, that is, the ellipsoidal shape of the laser pen used in the fabrication process. To this end we employ detailed numerical modeling of the scattering function using a discrete dipole approximation scheme.

  2. A PARALIND Decomposition-Based Coherent Two-Dimensional Direction of Arrival Estimation Algorithm for Acoustic Vector-Sensor Arrays

    PubMed Central

    Zhang, Xiaofei; Zhou, Min; Li, Jianfeng

    2013-01-01

    In this paper, we combine the acoustic vector-sensor array parameter estimation problem with the parallel profiles with linear dependencies (PARALIND) model, which was originally applied to biology and chemistry. Exploiting the PARALIND decomposition approach, we propose a blind coherent two-dimensional direction of arrival (2D-DOA) estimation algorithm for arbitrarily spaced acoustic vector-sensor arrays subject to unknown locations. The proposed algorithm works well to achieve automatically paired azimuth and elevation angles for coherent and incoherent angle estimation of acoustic vector-sensor arrays, as well as the paired correlated matrix of the sources. Our algorithm, in contrast with conventional coherent angle estimation algorithms such as the forward backward spatial smoothing (FBSS) estimation of signal parameters via rotational invariance technique (ESPRIT) algorithm, not only has much better angle estimation performance, even for closely-spaced sources, but is also available for arbitrary arrays. Simulation results verify the effectiveness of our algorithm. PMID:23604030

  3. Direct-numerical simulation of the glottal jet and vocal-fold dynamics in a three-dimensional laryngeal model

    PubMed Central

    Zheng, X.; Mittal, R.; Xue, Q.; Bielamowicz, S.

    2011-01-01

    An immersed-boundary method based flow solver coupled with a finite-element solid dynamics solver is employed in order to conduct direct-numerical simulations of phonatory dynamics in a three-dimensional model of the human larynx. The computed features of the glottal flow including mean and peak flow rates, and the open and skewness quotients are found to be within the normal physiological range. The flow-induced vibration pattern shows the classical “convergent-divergent” glottal shape, and the vibration amplitude is also found to be typical for human phonation. The vocal fold motion is analyzed through the method of empirical eigenfunctions and this analysis indicates a 1:1 modal entrainment between the “adduction-abduction” mode and the “mucosal wave” mode. The glottal jet is found to exhibit noticeable cycle-to-cycle asymmetric deflections and the mechanism underlying this phenomenon is examined. PMID:21786908

  4. Two-dimensional phase-field study of competitive grain growth during directional solidification of polycrystalline binary alloy

    NASA Astrophysics Data System (ADS)

    Takaki, Tomohiro; Ohno, Munekazu; Shibuta, Yasushi; Sakane, Shinji; Shimokawabe, Takashi; Aoki, Takayuki

    2016-05-01

    Selections of growing crystals during directional solidification of a polycrystalline binary alloy were numerically investigated using two-dimensional phase-field simulations. To accelerate the simulations, parallel graphics processing unit (GPU) simulations were performed using the GPU-rich supercomputer TSUBAME2.5 at the Tokyo Institute of Technology. Twenty simulations with a combination of five sets of different seed orientation distributions and four different temperature gradients covering dendritic and cellular growth regions were performed. The unusual grain selection phenomenon, in which the unfavorably oriented grains preferentially grow instead of the favorably oriented grains, was observed frequently. The unusual selection was more remarkable in the cellular structure than in the dendritic structure.

  5. Three-dimensional symmetry analysis of a direct-drive irradiation scheme for the laser megajoule facility

    SciTech Connect

    Ramis, R.; Temporal, M.; Canaud, B.; Brandon, V.

    2014-08-15

    The symmetry of a Direct-Drive (DD) irradiation scheme has been analyzed by means of three-dimensional (3D) simulations carried out by the code MULTI (R. Ramis et al., Comput. Phys. Commun. 49, 475 (1988)) that includes hydrodynamics, heat transport, and 3D laser ray-tracing. The implosion phase of a target irradiated by the Laser Megajoule (LMJ) facility in the context of the Shock Ignition scheme has been considered. The LMJ facility has been designed for Indirect-Drive, and by this reason that the irradiation scheme must be modified when used for DD. Thus, to improve the implosion uniformity to acceptable levels, the beam centerlines should be realigned and the beam power balance should be adjusted. Several alternatives with different levels of complexity are presented and discussed.

  6. Direct-numerical simulation of the glottal jet and vocal-fold dynamics in a three-dimensional laryngeal model.

    PubMed

    Zheng, X; Mittal, R; Xue, Q; Bielamowicz, S

    2011-07-01

    An immersed-boundary method based flow solver coupled with a finite-element solid dynamics solver is employed in order to conduct direct-numerical simulations of phonatory dynamics in a three-dimensional model of the human larynx. The computed features of the glottal flow including mean and peak flow rates, and the open and skewness quotients are found to be within the normal physiological range. The flow-induced vibration pattern shows the classical "convergent-divergent" glottal shape, and the vibration amplitude is also found to be typical for human phonation. The vocal fold motion is analyzed through the method of empirical eigenfunctions and this analysis indicates a 1:1 modal entrainment between the "adduction-abduction" mode and the "mucosal wave" mode. The glottal jet is found to exhibit noticeable cycle-to-cycle asymmetric deflections and the mechanism underlying this phenomenon is examined. PMID:21786908

  7. Resistance of human immunodeficiency virus type 1 to acyclic 6-phenylselenenyl- and 6-phenylthiopyrimidines.

    PubMed Central

    Nguyen, M H; Schinazi, R F; Shi, C; Goudgaon, N M; McKenna, P M; Mellors, J W

    1994-01-01

    Acyclic 6-phenylselenenyl- and 6-phenylthiopyrimidine derivatives are potent and specific inhibitors of human immunodeficiency virus type 1 (HIV-1). The development of in vitro resistance to two derivatives, 5-ethyl-1-(ethoxymethyl)-(6-phenylthio)-uracil (E-EPU), was evaluated by serial passage of HIV-1 in increasing concentrations of inhibitor. HIV-1 variants exhibiting > 500-fold resistance to E-EPSeU and E-EPU were isolated after sequential passage in 1, 5, and 10 microM inhibitor. The resistant variants exhibited coresistance to related acyclic 6-substituted pyrimidines and the HIV-1-specific inhibitors (+)-(5S)-4,5,6,7-tetrahydro-5- pyrimidines and the HIV-1-specific inhibitors (+)-(5S)-4,5,6,7-tetrahydro-5- methyl-6-(3-methyl-2-butenyl)imidazo[4,5,1-jk]benzodiazepin-2(1H)- thione (TIBO R82150) and nevirapine, but remained susceptible to 3'-azido-3'-deoxythymidine, 2',3'-dideoxycytidine, 2',3'-dideoxyinosine, and phosphonoformic acid. DNA sequence analysis of reverse transcriptase (RT) derived from E-EPSeU-resistant virus identified a Tyr (TAT)-to-Cys (TGT) mutation at either codon 188 (Cys-188; 9 of 15 clones) or codon 181 (Cys-181; 5 of 15 clones). The same amino acid changes were found in RT from E-EPU-resistant virus, but the Cys-181 mutation was more common (9 of 10 clones) than the Cys-188 mutation (1 of 10 clones). Site-specific mutagenesis and production of mutant recombinant viruses demonstrated that both the Cys-181 and Cys-188 mutations cause resistance to E-EPSeU and E-EPU. Of the two mutations, the Cys-188 substitution produced greater E-EPSeU and E-EPU resistance. The predominance of the Cys-188 mutation in E-EPSeU-resistant variants has not been noted for other classes of HIV-1 specific RT inhibitors. HIV-1 resistance is likely to limit the therapeutic efficacy of acyclic 6-substituted pyrimidines if they are used as monotherapy. PMID:7840579

  8. Directional migration and differentiation of neural stem cells within three-dimensional microenvironments.

    PubMed

    Shamloo, Amir; Heibatollahi, Motahare; Mofrad, Mohammad R K

    2015-03-01

    Harnessing neural stem cells to repair neuronal damage is a promising potential treatment for neuronal diseases. To enable future therapeutic efficacy, the survival, proliferation, migration and differentiation of neural stem/progenitor cells (NPCs) should be accurately studied and optimized in in vitro platforms before transplanting these cells into the body for treatment purposes. Such studies can determine the appropriate quantities of the biochemical and biomechanical factors needed to control and optimize NPC behavior in vivo. In this study, NPCs were cultured within a microfluidic device while being encapsulated within the collagen matrix. The migration and differentiation of NPCs were studied in response to varying concentrations of nerve growth factor (NGF) and within varying densities of collagen matrices. It was shown that the migration and differentiation of NPCs can be significantly improved by providing the appropriate range of NGF concentrations while encapsulating the cells within the collagen matrix of optimal density. In particular, it was observed that within collagen matrices of intermediate density (0.9 mg ml(-1)), NPCs have a higher ability to migrate farther and in a collective manner while their differentiation into neurons is significantly higher and the cells can form protrusions and connections with their neighboring cells. Within collagen matrices with higher densities (1.8 mg ml(-1)), the cells did not migrate significantly as compared to the ones within lower matrix densities; within the matrices with lower collagen densities (0.45 mg ml(-1)) most of the cells migrated in an individual manner. However, no significant differentiation into neurons was observed for these two cases. It was also found that depending on the collagen matrix density, a minimum concentration of NGF caused a collective migration of NPCs, and a minimum concentration gradient of this factor stimulated the directional navigation of the cells. The results of this

  9. Quantitative MCsn+ - SIMS for direct compositional analysis of interfaces of low-dimensional structures

    NASA Astrophysics Data System (ADS)

    Chakraborty, Purushottam

    2012-06-01

    Excellent detection sensitivity, high dynamic range and good depth resolution make the Secondary ion Mass spectrometry (SIMS) technique extremely powerful for the chemical analysis of surfaces and interfaces of condensed matter systems. However, a serious problem in SIMS analysis is its "matrix effect" that hinders the quantification of a certain species in a sample and consequently, probing the composition of surfaces or interfaces by SIMS is greatly hindered. Appropriate corrective measures are therefore, needed to calibrate the secondary ion currents into respective concentrations for accurate compositional analysis. Working in the MCs+-SIMS mode (M - element to be analyzed, Cs+ - bombarding ions) can circumvent the matrix effect. The emission process for the species M0 is decoupled from the MCs+ ion formation process, in analogy with the ion formation in secondary neutral mass spectrometry (SNMS), resulting in a drastic decrease in matrix effect in the MCs+ - SIMS mode. Although this technique has found its applicability in direct quantification, it generally suffers from a low useful yield. In such cases, detection of MCsn+ (n = 2, 3, ...) molecular ions offers a better sensitivity (even by several orders of magnitude), as the yields of such molecular ion complexes have often been found to be higher than that of MCs+ ions. Several works have been reported on the emission of MCsn + molecular ions, but a complete understanding on the formation mechanisms of these ion complexes is still lacking. However, irrespective of the formation mechanisms, MCsn +-SIMS technique in all its complexities has great relevance in the elemental analysis of materials. The talk will address on the possible formation mechanisms and potential applications of MCsn+ molecular ion complexes in the interfacial analysis of ultrathin films, metallic multilayers, semiconductor superlattices, quantum structures and also in the compositional analysis of MBE grown Si1-xGex alloys.

  10. Development of a gallium-doped germanium far-infrared photoconductor direct hybrid two-dimensional array.

    PubMed

    Fujiwara, Mikio; Hirao, Takanori; Kawada, Mitsunobu; Shibai, Hiroshi; Matsuura, Shuji; Kaneda, Hidehiro; Patrashin, Mikhail; Nakagawa, Takao

    2003-04-20

    To our knowledge, we are the first to successfully report a direct hybrid two-dimensional (2D) detector array in the far-infrared region. Gallium-doped germanium (Ge:Ga) has been used extensively to produce sensitive far-infrared detectors with a cutoff wavelength of approximately equal to 110 microm (2.7 THz). It is widely used in the fields of astronomy and molecular and solid spectroscopy. However, Ge:Ga photoconductors must be cooled below 4.2 K to reduce thermal noise, and this operating condition makes it difficult to develop a large format array because of the need for a warm amplifier. Development of Ge:Ga photoconductor arrays to take 2D terahertz images is now an important target in such research fields as space astronomy. We present the design of a 20 x 3 Ge:Ga far-infrared photoconductor array directly hybridized to a Si p-type metal-oxide-semiconductor readout integrated circuit using indium-bump technology. The main obstacles in creating this 2D array were (1) fabricating a monolithic Ge:Ga 2D array with a longitudinal configuration, (2) developing a cryogenic capacitive transimpedance amplifer, and (3) developing a technology for connecting the detector to the electronics. With this technology, a prototype Ge:Ga photoconductor with a direct hybrid structure has shown a responsivity as high as 14.6 A/W and a minimum detectable power of 5.6 x 10(-17) W for an integration time of 0.14 s when it was cooled to 2.1 K. Its noise is limited by the readout circuit with 20 microV/Hz(1/2) at 1 Hz. Vibration and cooling tests demonstrated that this direct hybrid structure is strong enough for spaceborne instruments. This detector array will be installed on the Japanese infrared satellite ASTRO-F. PMID:12716158

  11. Halogen bonding in water results in enhanced anion recognition in acyclic and rotaxane hosts.

    PubMed

    Langton, Matthew J; Robinson, Sean W; Marques, Igor; Félix, Vítor; Beer, Paul D

    2014-12-01

    Halogen bonding (XB), the attractive interaction between an electron-deficient halogen atom and a Lewis base, has undergone a dramatic development as an intermolecular force analogous to hydrogen bonding (HB). However, its utilization in the solution phase remains underdeveloped. Furthermore, the design of receptors capable of strong and selective recognition of anions in water remains a significant challenge. Here we demonstrate the superiority of halogen bonding over hydrogen bonding for strong anion binding in water, to the extent that halide recognition by a simple acyclic mono-charged receptor is achievable. Quantification of iodide binding by rotaxane hosts reveals the strong binding by the XB-rotaxane is driven exclusively by favourable enthalpic contributions arising from the halogen-bonding interactions, whereas weaker association with the HB-rotaxanes is entropically driven. These observations demonstrate the unique nature of halogen bonding in water as a strong alternative interaction to the ubiquitous hydrogen bonding in molecular recognition and assembly. PMID:25411880

  12. Diversity-oriented synthesis of acyclic nucleosides via ring-opening of vinyl cyclopropanes with purines.

    PubMed

    Niu, Hong-Ying; Du, Cong; Xie, Ming-Sheng; Wang, Yong; Zhang, Qian; Qu, Gui-Rong; Guo, Hai-Ming

    2015-02-25

    The diversity-oriented synthesis of acyclic nucleosides has been achieved via ring-opening of vinyl cyclopropanes with purines. With Pd2(dba)3·CHCl3 as a catalyst, the 1,5-ring-opening reaction proceeded well and afforded N9 adducts as the major form, in which the C=C bonds in the side chain were exclusively E-form. In the presence of AlCl3, the 1,3-ring-opening reaction occurred smoothly, giving N9 adducts as the dominate products. Meanwhile, when MgI2 was used as the catalyst, the 1,3-ring-opening reaction also worked well to form N7 adducts. PMID:25572827

  13. Antimalarial activity of prodrugs of N-branched acyclic nucleoside phosphonate inhibitors of 6-oxopurine phosphoribosyltransferases.

    PubMed

    Hocková, Dana; Janeba, Zlatko; Naesens, Lieve; Edstein, Michael D; Chavchich, Marina; Keough, Dianne T; Guddat, Luke W

    2015-09-01

    Acyclic nucleoside phosphonates (ANPs) that contain a 6-oxopurine base are good inhibitors of the human and Plasmodium falciparum 6-oxopurine phosphoribosyltransferases (PRTs), key enzymes of the purine salvage pathway. Chemical modifications, based on the crystal structures of several inhibitors in complex with the human PRTase, led to the design of a new class of inhibitors--the aza-ANPs. Because of the negative charges of the phosphonic acid moiety, their ability to cross cell membranes is, however, limited. Thus, phosphoramidate prodrugs of the aza-ANPs were prepared to improve permeability. These prodrugs arrest parasitemia with IC50 values in the micromolar range against Plasmodium falciparum-infected erythrocyte cultures (both chloroquine-sensitive and chloroquine-resistant Pf strains). The prodrugs exhibit low cytotoxicity in several human cell lines. Thus, they fulfill two essential criteria to qualify them as promising antimalarial drug leads. PMID:26275679

  14. Molecular Motion of the Junction Points in Model Networks Prepared by Acyclic Triene Metathesis.

    PubMed

    da Silva, Lucas Caire; Bowers, Clifford R; Graf, Robert; Wagener, Kenneth B

    2016-03-01

    The junction dynamics in a selectively deuterated model polymer network containing junctions on every 21st chain carbon is studied by solid state (2) H echo NMR. Polymer networks are prepared via acyclic triene metathesis of deuteron-labeled symmetric trienes with deuteron probes precisely placed at the alpha carbon relative to the junction point. The effect of decreasing the cross-link density on the junction dynamics is studied by introduction of polybutadiene chains in-between junctions. The networks are characterized by swelling, gel content, and solid state (1) H MAS NMR. Line shape analysis of the (2) H quadrupolar echo spectra reveals that the degree of motion anisotropy and the distribution of motion correlation times depend on the cross-link density and structural heterogeneity of the polymer networks. A detailed model of the junction dynamics at different temperatures is proposed and explained in terms of the intermolecular cooperativity in densely-packed systems. PMID:26787457

  15. The Acyclic Retinoid Peretinoin Inhibits Hepatitis C Virus Replication and Infectious Virus Release in Vitro

    NASA Astrophysics Data System (ADS)

    Shimakami, Tetsuro; Honda, Masao; Shirasaki, Takayoshi; Takabatake, Riuta; Liu, Fanwei; Murai, Kazuhisa; Shiomoto, Takayuki; Funaki, Masaya; Yamane, Daisuke; Murakami, Seishi; Lemon, Stanley M.; Kaneko, Shuichi

    2014-04-01

    Clinical studies suggest that the oral acyclic retinoid Peretinoin may reduce the recurrence of hepatocellular carcinoma (HCC) following surgical ablation of primary tumours. Since hepatitis C virus (HCV) infection is a major cause of HCC, we assessed whether Peretinoin and other retinoids have any effect on HCV infection. For this purpose, we measured the effects of several retinoids on the replication of genotype 1a, 1b, and 2a HCV in vitro. Peretinoin inhibited RNA replication for all genotypes and showed the strongest antiviral effect among the retinoids tested. Furthermore, it reduced infectious virus release by 80-90% without affecting virus assembly. These effects could be due to reduced signalling from lipid droplets, triglyceride abundance, and the expression of mature sterol regulatory element-binding protein 1c and fatty acid synthase. These negative effects of Peretinoin on HCV infection may be beneficial in addition to its potential for HCC chemoprevention in HCV-infected patients.

  16. Generation and exploitation of acyclic azomethine imines in chiral Brønsted acid catalysis

    NASA Astrophysics Data System (ADS)

    Hashimoto, Takuya; Kimura, Hidenori; Kawamata, Yu; Maruoka, Keiji

    2011-08-01

    Successful implementation of a catalytic asymmetric synthesis strategy to produce enantiomerically enriched compounds requires the adoption of suitable prochiral substrates. The combination of an azomethine imine electrophile with various nucleophiles could give straightforward access to a number of synthetically useful chiral hydrazines, but is used rarely. Here we report the exploitation of acyclic azomethine imines as a new type of prochiral electrophile. They can be generated in situ by the condensation of N‧-benzylbenzoylhydrazide with a variety of aldehydes in the presence of a catalytic amount of an axially chiral dicarboxylic acid. By trapping these electrophiles with alkyl diazoacetate or (diazomethyl)phosphonate nucleophiles, we produced a diverse array of chiral α-diazo-β-hydrazino esters and phosphonates with excellent enantioselectivities.

  17. Versatile synthesis of oxime-containing acyclic nucleoside phosphonates--synthetic solutions and antiviral activity.

    PubMed

    Solyev, Pavel N; Jasko, Maxim V; Kleymenova, Alla A; Kukhanova, Marina K; Kochetkov, Sergey N

    2015-11-28

    New oxime-containing acyclic nucleoside phosphonates 9-{2-[(phosphonomethyl)oximino]ethyl}adenine (1), -guanine (2) and 9-{2-[(phosphonomethyl)oximino]propyl}adenine (3) with wide spectrum activity against different types of viruses were synthesized. The key intermediate, diethyl aminooxymethylphosphonate, was obtained by the Mitsunobu reaction. Modified conditions for the by-product separation (without chromatography and distillation) allowed us to obtain 85% yield of the aminooxy intermediate. The impact of DBU and Cs2CO3 on the N(9)/N(7) product ratio for adenine and guanine alkylation was studied. A convenient procedure for aminooxy group detection was found. The synthesized phosphonates were tested and they appeared to display moderate activity against different types of viruses (HIV, herpes viruses in cell cultures, and hepatitis C virus in the replicon system) without toxicity up to 1000 μM. PMID:26383895

  18. Acyclic Immucillin Phosphonates. Second-Generation Inhibitors of Plasmodium falciparum Hypoxanthine- Guanine-Xanthine Phosphoribosyltransferase

    SciTech Connect

    Hazelton, Keith Z.; Ho, Meng-Chaio; Cassera, Maria B.; Clinch, Keith; Crump, Douglas R.; Rosario Jr., Irving; Merino, Emilio F.; Almo, Steve C.; Tyler, Peter C.; Schramm, Vern L.

    2012-06-22

    We found that Plasmodium falciparum is the primary cause of deaths from malaria. It is a purine auxotroph and relies on hypoxanthine salvage from the host purine pool. Purine starvation as an antimalarial target has been validated by inhibition of purine nucleoside phosphorylase. Hypoxanthine depletion kills Plasmodium falciparum in cell culture and in Aotus monkey infections. Hypoxanthine-guanine-xanthine phosphoribosyltransferase (HGXPRT) from P. falciparum is required for hypoxanthine salvage by forming inosine 5'-monophosphate, a branchpoint for all purine nucleotide synthesis in the parasite. We present a class of HGXPRT inhibitors, the acyclic immucillin phosphonates (AIPs), and cell permeable AIP prodrugs. The AIPs are simple, potent, selective, and biologically stable inhibitors. The AIP prodrugs block proliferation of cultured parasites by inhibiting the incorporation of hypoxanthine into the parasite nucleotide pool and validates HGXPRT as a target in malaria.

  19. Acyclic N-halamine-immobilized polyurethane: Preparation and antimicrobial and biofilm-controlling functions

    PubMed Central

    Luo, Jie; Porteous, Nuala; Lin, Jiajin; Sun, Yuyu

    2015-01-01

    Hydroxyl groups were introduced onto polyurethane surfaces through 1,6-hexamethylene diisocyanate activation, followed by diethanolamine hydroxylation. Polymethacrylamide was covalently attached to the hydroxylated polyurethane through surface grafting polymerization of methacrylamide using cerium (IV) ammonium nitrate as an initiator. After bleach treatment, the amide groups of the covalently bound polymethacrylamide chains were transformed into N-halamines. The new N-halamine-immobilized polyurethane provided a total sacrifice of 107–108 colony forming units per milliliter of Staphylococcus aureus (Gram-positive bacteria), Escherichia coli (Gram-negative bacteria), and Candida albicans (fungi) within 10 min and successfully prevented bacterial and fungal biofilm formation. The antimicrobial and biofilm-controlling effects were both durable and rechargeable, pointing to great potentials of the new acyclic N-halamine-immobilized polyurethane for a broad range of related applications. PMID:26089593

  20. Acyclic hydrocarbon environments ⩾ n-C 18 on the early terrestrial planets

    NASA Astrophysics Data System (ADS)

    Marcano, Vicente; Benitez, Pedro; Palacios-Prü, Ernesto

    2003-03-01

    The possible occurrence on the surface of the early Earth, Mars and Venus of hydrocarbon environments mainly composed by acyclic alkane molecules ⩾ n-C 18 has been revised. These hydrocarbons could be accumulated from the contribution of endogenous Fischer-Tropsh-type reactions and post-impact recombination reactions, as well as from exogenous sources such as comets, meteorites and dust particles. Such heavy alkane environments could offer protection for the synthesis and survival of biomolecules on the early terrestrial planets. Amounts of heavy n-alkanes delivered by large impactors, dust particles or produced by post-impact recombination on Venus would have been higher than those delivered or produced by the same sources on Earth and Mars before 3600 Myr ago. However, the high values of the total frequency of impacts by bolides >14-km in diameter estimated in this time period (viz. 3.9×10 3, Mars; 2.2×10 4, Earth, and 3.8×10 4 Venus) and the high surface temperatures generated by those impactors suggest the existence of very unstable conditions on the early terrestrial planets for the survival and long-term accumulation of acyclic hydrocarbons. Therefore, the most significant accumulation of n-alkanes could have occurred only during the longer intervals (10 5- 10 7 yr) between each impact through the contribution mainly of IDPs, and thereby a high decomposition rate would be expected for the accumulated n-alkanes by successive impacts. Amounts of n-alkanes accumulated from IDPs in these intervals have been estimated between 2.3×10 9 and 2.2×10 10 kg 3600- 3800 Myr ago. These processes are expected to occur on other planetary bodies or satellites belonging to our solar system and probably in analogs of the early solar system.

  1. Direct experimental visualization of the global Hamiltonian progression of two-dimensional Lagrangian flow topologies from integrable to chaotic state

    NASA Astrophysics Data System (ADS)

    Baskan, O.; Speetjens, M. F. M.; Metcalfe, G.; Clercx, H. J. H.

    2015-10-01

    Countless theoretical/numerical studies on transport and mixing in two-dimensional (2D) unsteady flows lean on the assumption that Hamiltonian mechanisms govern the Lagrangian dynamics of passive tracers. However, experimental studies specifically investigating said mechanisms are rare. Moreover, they typically concern local behavior in specific states (usually far away from the integrable state) and generally expose this indirectly by dye visualization. Laboratory experiments explicitly addressing the global Hamiltonian progression of the Lagrangian flow topology entirely from integrable to chaotic state, i.e., the fundamental route to efficient transport by chaotic advection, appear non-existent. This motivates our study on experimental visualization of this progression by direct measurement of Poincaré sections of passive tracer particles in a representative 2D time-periodic flow. This admits (i) accurate replication of the experimental initial conditions, facilitating true one-to-one comparison of simulated and measured behavior, and (ii) direct experimental investigation of the ensuing Lagrangian dynamics. The analysis reveals a close agreement between computations and observations and thus experimentally validates the full global Hamiltonian progression at a great level of detail.

  2. Direct experimental visualization of the global Hamiltonian progression of two-dimensional Lagrangian flow topologies from integrable to chaotic state

    SciTech Connect

    Baskan, O.; Clercx, H. J. H; Speetjens, M. F. M.; Metcalfe, G.

    2015-10-15

    Countless theoretical/numerical studies on transport and mixing in two-dimensional (2D) unsteady flows lean on the assumption that Hamiltonian mechanisms govern the Lagrangian dynamics of passive tracers. However, experimental studies specifically investigating said mechanisms are rare. Moreover, they typically concern local behavior in specific states (usually far away from the integrable state) and generally expose this indirectly by dye visualization. Laboratory experiments explicitly addressing the global Hamiltonian progression of the Lagrangian flow topology entirely from integrable to chaotic state, i.e., the fundamental route to efficient transport by chaotic advection, appear non-existent. This motivates our study on experimental visualization of this progression by direct measurement of Poincaré sections of passive tracer particles in a representative 2D time-periodic flow. This admits (i) accurate replication of the experimental initial conditions, facilitating true one-to-one comparison of simulated and measured behavior, and (ii) direct experimental investigation of the ensuing Lagrangian dynamics. The analysis reveals a close agreement between computations and observations and thus experimentally validates the full global Hamiltonian progression at a great level of detail.

  3. Direct method of three-dimensional imaging using the multiple-wavelength range-gated active imaging principle.

    PubMed

    Matwyschuk, Alexis

    2016-05-10

    The tomography executed with mono-wavelength active imaging systems uses the recording of several images to restore a three-dimensional (3D) scene. Thus, in order to show the depth in the scene, a different color is attributed to each recorded image. Therefore, the 3D restoration depends on the video frame rate of the camera. By using a multiple-wavelength range-gated active imaging system, it is possible to restore the 3D scene directly in a single image at the moment of recording with a video camera. Each emitted light pulse with a different wavelength corresponds to a visualized zone at a different distance in the scene. The camera shutter opens just once during the emission of light pulses with the different wavelengths. Thus, the restoration can be executed in real time with regard to the video frame rate of the camera. From an analytical model and from a graphical approach, we demonstrated the feasibility of this new method of 3D restoration. The non-overlapping conditions between two consecutive visualized zones are analyzed. The experimental test results confirm these different conditions and validate the theoretical principle to directly restore the 3D scene in a color image with a multiple-wavelength laser source, an RGB filter, and a triggerable intensified camera. PMID:27168293

  4. Direct reconstruction in CT-analogous pharmacokinetic diffuse fluorescence tomography: two-dimensional simulative and experimental validations

    NASA Astrophysics Data System (ADS)

    Wang, Xin; Zhang, Yanqi; Zhang, Limin; Li, Jiao; Zhou, Zhongxing; Zhao, Huijuan; Gao, Feng

    2016-04-01

    We present a generalized strategy for direct reconstruction in pharmacokinetic diffuse fluorescence tomography (DFT) with CT-analogous scanning mode, which can accomplish one-step reconstruction of the indocyanine-green pharmacokinetic-rate images within in vivo small animals by incorporating the compartmental kinetic model into an adaptive extended Kalman filtering scheme and using an instantaneous sampling dataset. This scheme, compared with the established indirect and direct methods, eliminates the interim error of the DFT inversion and relaxes the expensive requirement of the instrument for obtaining highly time-resolved date-sets of complete 360 deg projections. The scheme is validated by two-dimensional simulations for the two-compartment model and pilot phantom experiments for the one-compartment model, suggesting that the proposed method can estimate the compartmental concentrations and the pharmacokinetic-rates simultaneously with a fair quantitative and localization accuracy, and is well suitable for cost-effective and dense-sampling instrumentation based on the highly-sensitive photon counting technique.

  5. Application of a Three-Dimensional Shell Theory to the Free Vibration of Shells Arbitrarily Deep in One Direction

    NASA Astrophysics Data System (ADS)

    YOUNG, P. G.

    2000-11-01

    A three-dimensional shell theory is presented which is applicable to doubly curved thick open shells which are arbitrarily deep (have a large side-length to radius of curvature ratio) in one principal direction but are shallow in the other direction. The strain-displacement equations for the proposed “deep-shallow” shell theory are expressed in Cartesian co-ordinates and the limits of applicability of these equations are discussed. These equations are then used in a Ritz variational formulation with algebraic polynomials as trial functions to solve for the natural frequencies of a number of doubly curved shell problems. A novel approach is also proposed in which penalty functions are introduced to enforce continuity of displacements at two opposite ends of a shell of rectangular platform, increasing the range of problems which can be treated to include closed shells, such as cylinders, barrels, cooling-tower-type structures, toroids, rings, etc. (a sub-class of shells of revolution).

  6. Direct reconstruction in CT-analogous pharmacokinetic diffuse fluorescence tomography: two-dimensional simulative and experimental validations.

    PubMed

    Wang, Xin; Zhang, Yanqi; Zhang, Limin; Li, Jiao; Zhou, Zhongxing; Zhao, Huijuan; Gao, Feng

    2016-04-30

    We present a generalized strategy for direct reconstruction in pharmacokinetic diffuse fluorescence tomography (DFT) with CT-analogous scanning mode, which can accomplish one-step reconstruction of the indocyanine-green pharmacokinetic-rate images within in vivo small animals by incorporating the compartmental kinetic model into an adaptive extended Kalman filtering scheme and using an instantaneous sampling dataset. This scheme, compared with the established indirect and direct methods, eliminates the interim error of the DFT inversion and relaxes the expensive requirement of the instrument for obtaining highly time-resolved date-sets of complete 360 deg projections. The scheme is validated by two-dimensional simulations for the two-compartment model and pilot phantom experiments for the one-compartment model, suggesting that the proposed method can estimate the compartmental concentrations and the pharmacokinetic-rates simultaneously with a fair quantitative and localization accuracy, and is well suitable for cost-effective and dense-sampling instrumentation based on the highly-sensitive photon counting technique. PMID:27093958

  7. A multi-directional backlight for a wide-angle, glasses-free three-dimensional display.

    PubMed

    Fattal, David; Peng, Zhen; Tran, Tho; Vo, Sonny; Fiorentino, Marco; Brug, Jim; Beausoleil, Raymond G

    2013-03-21

    Multiview three-dimensional (3D) displays can project the correct perspectives of a 3D image in many spatial directions simultaneously. They provide a 3D stereoscopic experience to many viewers at the same time with full motion parallax and do not require special glasses or eye tracking. None of the leading multiview 3D solutions is particularly well suited to mobile devices (watches, mobile phones or tablets), which require the combination of a thin, portable form factor, a high spatial resolution and a wide full-parallax view zone (for short viewing distance from potentially steep angles). Here we introduce a multi-directional diffractive backlight technology that permits the rendering of high-resolution, full-parallax 3D images in a very wide view zone (up to 180 degrees in principle) at an observation distance of up to a metre. The key to our design is a guided-wave illumination technique based on light-emitting diodes that produces wide-angle multiview images in colour from a thin planar transparent lightguide. Pixels associated with different views or colours are spatially multiplexed and can be independently addressed and modulated at video rate using an external shutter plane. To illustrate the capabilities of this technology, we use simple ink masks or a high-resolution commercial liquid-crystal display unit to demonstrate passive and active (30 frames per second) modulation of a 64-view backlight, producing 3D images with a spatial resolution of 88 pixels per inch and full-motion parallax in an unprecedented view zone of 90 degrees. We also present several transparent hand-held prototypes showing animated sequences of up to six different 200-view images at a resolution of 127 pixels per inch. PMID:23518562

  8. Three-dimensional construction and omni-directional rolling analysis of a novel frame-like lattice modular robot

    NASA Astrophysics Data System (ADS)

    Ding, Wan; Wu, Jianxu; Yao, Yan'an

    2015-07-01

    Lattice modular robots possess diversity actuation methods, such as electric telescopic rod, gear rack, magnet, robot arm, etc. The researches on lattice modular robots mainly focus on their hardware descriptions and reconfiguration algorithms. Meanwhile, their design architectures and actuation methods perform slow telescopic and moving speeds, relative low actuation force verse weight ratio, and without internal space to carry objects. To improve the mechanical performance and reveal the locomotion and reconfiguration binary essences of the lattice modular robots, a novel cube-shaped, frame-like, pneumatic-based reconfigurable robot module called pneumatic expandable cube(PE-Cube) is proposed. The three-dimensional(3D) expanding construction and omni-directional rolling analysis of the constructed robots are the main focuses. The PE-Cube with three degrees of freedom(DoFs) is assembled by replacing the twelve edges of a cube with pneumatic cylinders. The proposed symmetric construction condition makes the constructed robots possess the same properties in each supporting state, and a binary control strategy cooperated with binary actuator(pneumatic cylinder) is directly adopted to control the PE-Cube. Taking an eight PE-Cube modules' construction as example, its dynamic rolling simulation, static rolling condition, and turning gait are illustrated and discussed. To testify telescopic synchronization, respond speed, locomotion feasibility, and repeatability and reliability of hardware system, an experimental pneumatic-based robotic system is built and the rolling and turning experiments of the eight PE-Cube modules' construction are carried out. As an extension, the locomotion feasibility of a thirty-two PE-Cube modules' construction is analyzed and proved, including dynamic rolling simulation, static rolling condition, and dynamic analysis in free tipping process. The proposed PE-Cube module, construction method, and locomotion analysis enrich the family of the

  9. Electrochemically Functionalized Seamless Three-Dimensional Graphene-Carbon Nanotube Hybrid for Direct Electron Transfer of Glucose Oxidase and Bioelectrocatalysis.

    PubMed

    Terse-Thakoor, Trupti; Komori, Kikuo; Ramnani, Pankaj; Lee, Ilkeun; Mulchandani, Ashok

    2015-12-01

    Three-dimensional seamless chemical vapor deposition (CVD) grown graphene-carbon nanotubes (G-CNT) hybrid film has been studied for its potential in achieving direct electron transfer (DET) of glucose oxidase (GOx) and its bioelectrocatalytic activity in glucose detection. A two-step CVD method was employed for the synthesis of seamless G-CNT hybrid film where CNTs are grown on already grown graphene film on copper foil using iron as a catalyst. Physical characterization using SEM and TEM show uniform dense coverage of multiwall carbon nanotubes (MWCNT) grown directly on graphene with seamless contacts. The G-CNT hybrid film was electrochemically modified to introduce oxygenated functional groups for DET favorable immobilization of GOx. Pristine and electrochemically functionalized G-CNT film was characterized by electrochemical impedance spectroscopy (EIS), cyclic voltammetry, X-ray photoelectron-spectroscopy, and Raman spectroscopy. The DET between GOx and electrochemically oxidized G-CNT electrode was studied using cyclic voltammetry which showed a pair of well-defined and quasi-reversible redox peaks with a formal potential of -459 mV at pH 7 corresponding to the redox site of GOx. The constructed electrode detected glucose concentration over the clinically relevant range of 2-8 mM with the highest sensitivity of 19.31 μA/mM/cm(2) compared to reported composite hybrid electrodes of graphene oxide and CNTs. Electrochemically functionalized CVD grown seamless G-CNT structure used in this work has potential to be used for development of artificial mediatorless redox enzyme based biosensors and biofuel cells. PMID:26551320

  10. Bearing Abilities and Progressive Damage Analysis of Three Dimensional Four-Directional Braided Composites with Cut-Edge

    NASA Astrophysics Data System (ADS)

    Lei, Bing; Liu, Zhenguo; Ya, Jixuan; Wang, Yibo; Li, Xiaokang

    2016-04-01

    Cut-edge is a kind of damage for the three-dimensional four-directional (3D4d) braided composites which is inevitable because of machining to meet requisite shape and working in the abominable environment. The longitudinal tensile experiment of the 3D4d braided composites with different braiding angles between cut-edge and the ones without cut-edge was conducted. Then representative volume cell (RVC) with interface zones was established to analyze the tensile properties through the fracture and damage mechanics. The periodic boundary conditions under the cut-edge and uncut-edge conditions were imposed to simulate the failure mechanism. Stress-strain distribution and the damage evolution nephogram in cut-edge condition were conducted. Numerical results were coincident with the experimental results. Finally the variation of cut-edge effect with the specimen thickness was simulated by superimposing inner cells. The consequence showed that thickness increase can effectively reduce cut-edge influence on longitudinal strength for 3D4d braided composites. Cut-edge simulation of braided composites has guiding significance on the actual engineering application.