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Sample records for 4-helix bundle structure

  1. Cu(l) Luminescence from the Tetranuclear Cu4S4 Cofactor of a Synthetic 4-Helix Bundle

    SciTech Connect

    Kharenko,O.; Kennedy, D.; Demeler, B.; Maroney, M.; Ogawa, M.

    2005-01-01

    The addition of Cu(I) to the random-coil peptide, C16C19-GGY, produces a self-organized, metal-bridged 4-helix bundle which displays an intense room-temperature luminescence at 600 nm. Emission, UV, and CD titrations along with X-ray absorption studies indicate that the luminescent cofactor is likely a Cu{sub 4}S{sub 4} cluster in which each Cu atom is bridged by the side chains of two cysteine residues and has terminal N/O ligation.

  2. Spectroscopic definition of the biferrous and biferric sites of de novo designed 4-helix bundle DFsc peptides: Implications for O2 reactivity of binuclear non-heme iron enzymes

    PubMed Central

    Bell, Caleb B.; Calhoun, Jennifer R.; Bobyr, Elena; Wei, Pin-pin; Hedman, Britt; Hodgson, Keith O.; DeGrado, William F.; Solomon, Edward I.

    2009-01-01

    DFsc is a single chain de novo designed 4-helix bundle peptide that mimics the core protein fold and primary ligand set of various binuclear non-heme iron enzymes. DFsc and the E11D, Y51L and Y18F single amino acid variants have been studied using a combination of near-IR circular dichroism (CD), magnetic circular dichroism (MCD), variable temperature variable field MCD (VTVH MCD) and x-ray absorption (XAS) spectroscopies. The biferrous sites are all weakly antiferromagnetically coupled with μ-1,3 carboxylate bridges and one 4-coordinate and one 5-coordinate Fe, very similar to the active site of Class I ribonucleotide reductase (R2) providing open coordination positions on both irons for dioxygen to bridge. From perturbations of the MCD and VTVH MCD the iron proximal to Y51 can be assigned as the 4-coordinate center and XAS results show that Y51 is not bound to this iron in the reduced state. The two open coordination positions on one iron in the biferrous state would become occupied by dioxygen and Y51 along the O2 reaction coordinate. Subsequent binding of Y51 functions as an internal spectral probe of the O2 reaction and as a proton source that would promote loss of H2O2. Coordination by a ligand that functions as a proton source could be a structural mechanism used by natural binuclear iron enzymes to drive their reactions past peroxo biferric level intermediates. PMID:19090676

  3. Structural Transitions of F-Actin:Espin Bundles

    NASA Astrophysics Data System (ADS)

    Purdy, Kirstin; Bartles, James; Wong, Gerard

    2006-03-01

    Espin is an actin bundling protein involved in the formation of the parallel bundles of filamentous actin in hair cell stereocilia. Mutations in espin are implicated in deafness phenotypes in mice and humans. We present measurements of the F-actin structures induced by wild type and by mutated espin obtained via small angle x-ray scattering and fluorescence microscopy. We found that wild type espin induced a paracrystalline hexagonal array of twisted F-actin, whereas the mutated espin only condensed the F-actin into a nematic-like phase. The possibility of coexisting nematic and bundled actin in mixtures containing both mutant and wild type espins was also investigated.

  4. Increased reliability of nuclear magnetic resonance protein structures by consensus structure bundles.

    PubMed

    Buchner, Lena; Güntert, Peter

    2015-02-03

    Nuclear magnetic resonance (NMR) structures are represented by bundles of conformers calculated from different randomized initial structures using identical experimental input data. The spread among these conformers indicates the precision of the atomic coordinates. However, there is as yet no reliable measure of structural accuracy, i.e., how close NMR conformers are to the "true" structure. Instead, the precision of structure bundles is widely (mis)interpreted as a measure of structural quality. Attempts to increase precision often overestimate accuracy by tight bundles of high precision but much lower accuracy. To overcome this problem, we introduce a protocol for NMR structure determination with the software package CYANA, which produces, like the traditional method, bundles of conformers in agreement with a common set of conformational restraints but with a realistic precision that is, throughout a variety of proteins and NMR data sets, a much better estimate of structural accuracy than the precision of conventional structure bundles.

  5. Enumeration of Secondary Structure Element Bundles

    SciTech Connect

    Brown, William Michael; Faulon, Jean-Loup

    2004-10-26

    A deterministic algorithm for enumeration of transmembrane protein folds is implemented. Using a set of sparse pairwise atomic distance constraints (such as those obtained from chemical cross-linking, FRET, or dipolar EPR experiments), the algorithm performs an exhaustive search of secondary structure element packing conformations distributed throughout the entire conformational space. The end result is a set of distinct protein conformations which can be scored and refined as part of a process designed for computational elucidation of transmembrane protein structures. Algorithm Overview: The ESSEB algorithm works by dividing the conforrnational space of each secondary structure element (SSE) into a set of cells. For each cell there is a representative conformation and for each atom in the SSE for which a distance restraint is available, there is an associated internal error, The internal error for a distance restraint is the maximum distance that the atom, when positioned in any conformation within a cell, can be from the atom in the representative conformation. The algorithm works recursively by positioning one representative conformation of an SSE. AdI distance restraints are checked with a tolerance that includes both the experimental and internal error. If all restraints are satisfied, every representative conformation of the next SSE is checked, otherwise, the program moves on to the next representative conformation of the current SSE. In addition to the distance restraints, other constraints on protein conformation can be enforced. These include the distance of closest approach between SSE axes, a restraint which prevents the crossover of loops connecting adjacent SSEs, and a restriction on the minimum and maximum distances between axis end-points. Any protein conformation satisfying all of the restraints is enumerated for later scoring and possible refinement. Additionally, in order to make run-times feasible, a divide-and-conquer approach is used in which

  6. Structural characterizations and electronic properties of boron nitride nanotube crystalline bundles

    NASA Astrophysics Data System (ADS)

    Zheng, Fawei; Zhou, Gang; Hao, Shaogang; Duan, Wenhui

    2005-09-01

    The structural characterizations and electronic properties of aligned armchair single-walled boron nitride nanotube (BNNT) bundles are theoretically investigated. In the spontaneous bundling process, the cylindrical shapes of bundled BNNTs are preserved all along, whereas their diameters expand, then shrink, and return back to the initial dimensions. Owing to the nonuniform distribution of positive and negative charges among BNNTs, the multipole interaction in bundles is completely dependent upon the chirality of each BNNT and the arrangement of bundled BNNTs. The effect of intertube coupling on the dispersions of BNNT bundles is demonstrated. Our systematical simulations might be helpful for the understanding of potential applications of BNNT bundles in the nanometer manufacturing techniques such as doping, adsorption, and derivative synthesis.

  7. Lexical Bundles in Discourse Structure: A Corpus-Based Study of Classroom Discourse

    ERIC Educational Resources Information Center

    Csomay, Eniko

    2013-01-01

    The present study applies corpus-based methods to document the distributional patterns of previously reported lexical bundle functions as they relate to discourse structure. Specifically, 84 lexical bundles and their discourse functions (Biber "et al." 2004a) were tracked in 1,176 discourse units extracted from the initial phases of 196 university…

  8. Structural reorganization of parallel actin bundles by crosslinking proteins: Incommensurate states of twist

    NASA Astrophysics Data System (ADS)

    Shin, Homin; Grason, Gregory M.

    2010-11-01

    We construct a coarse-grained model of parallel actin bundles crosslinked by compact globular bundling proteins, such as fascin and espin, necessary components of filopodial and mechanosensory bundles. Consistent with structural observations of bundles, we find that the optimal geometry for crosslinking is overtwisted, requiring a coherent structural change of the helical geometry of the filaments. We study the linker-dependent thermodynamic transition of bundled actin filaments from their native state to the overtwisted state and map out the “twist-state” phase diagram in terms of the availability as well as the flexibility of crosslinker proteins. We predict that the transition from the uncrosslinked to fully crosslinked state is highly sensitive to linker flexibility: flexible crosslinking smoothly distorts the twist state of bundled filaments, while rigidly crosslinked bundles undergo a phase transition, rapidly overtwisting filaments over a narrow range of free crosslinker concentrations. Additionally, we predict a rich spectrum of intermediate structures, composed of alternating domains of sparsely bound (untwisted) and strongly bound (overtwisted) filaments. This model reveals that subtle differences in crosslinking agents themselves modify not only the detailed structure of parallel actin bundles, but also the thermodynamic pathway by which they form.

  9. Formation and structural organization of the egg-sperm bundle of the scleractinian coral Montipora capitata

    NASA Astrophysics Data System (ADS)

    Padilla-Gamiño, J. L.; Weatherby, T. M.; Waller, R. G.; Gates, R. D.

    2011-06-01

    The majority of scleractinian corals are hermaphrodites that broadcast spawn their gametes separately or packaged as egg-sperm bundles during spawning events that are timed to the lunar cycle. The egg-sperm bundle is an efficient way of transporting gametes to the ocean surface where fertilization takes place, while minimizing sperm dilution and maximizing the opportunity for gamete encounters during a spawning event. To date, there are few studies that focus on the formation and structure of egg-sperm bundle. This study explores formation, ultrastructure, and longevity of the egg-sperm bundle in Montipora capitata, a major reef building coral in Hawai`i. Our results show that the egg-sperm bundle is formed by a mucus layer secreted by the oocytes. The sperm package is located at the center of each bundle, possibly reflecting the development of male and female gametes in different mesenteries. Once the egg-sperm bundle has reached the ocean surface, it breaks open within 10-35 min, depending on the environmental conditions (i.e., wind, water turbulence). Although the bundle has an ephemeral life span, the formation of an egg-sperm bundle is a fundamental part of the reproductive process that could be strongly influenced by climate change and deterioration of water quality (due to anthropogenic effects) and thus requires further investigation.

  10. Structural implications of Ca2+-dependent actin-bundling function of human EFhd2/Swiprosin-1

    PubMed Central

    Park, Kyoung Ryoung; Kwon, Min-Sung; An, Jun Yop; Lee, Jung-Gyu; Youn, Hyung-Seop; Lee, Youngjin; Kang, Jung Youn; Kim, Tae Gyun; Lim, Jia Jia; Park, Jeong Soon; Lee, Sung Haeng; Song, Woo Keun; Cheong, Hae-Kap; Jun, Chang-Duk; Eom, Soo Hyun

    2016-01-01

    EFhd2/Swiprosin-1 is a cytoskeletal Ca2+-binding protein implicated in Ca2+-dependent cell spreading and migration in epithelial cells. EFhd2 domain architecture includes an N-terminal disordered region, a PxxP motif, two EF-hands, a ligand mimic helix and a C-terminal coiled-coil domain. We reported previously that EFhd2 displays F-actin bundling activity in the presence of Ca2+ and this activity depends on the coiled-coil domain and direct interaction of the EFhd2 core region. However, the molecular mechanism for the regulation of F-actin binding and bundling by EFhd2 is unknown. Here, the Ca2+-bound crystal structure of the EFhd2 core region is presented and structures of mutants defective for Ca2+-binding are also described. These structures and biochemical analyses reveal that the F-actin bundling activity of EFhd2 depends on the structural rigidity of F-actin binding sites conferred by binding of the EF-hands to Ca2+. In the absence of Ca2+, the EFhd2 core region exhibits local conformational flexibility around the EF-hand domain and C-terminal linker, which retains F-actin binding activity but loses the ability to bundle F-actin. In addition, we establish that dimerisation of EFhd2 via the C-terminal coiled-coil domain, which is necessary for F-actin bundling, occurs through the parallel coiled-coil interaction. PMID:27974828

  11. PIV measurement of the vertical cross-flow structure over tube bundles

    NASA Astrophysics Data System (ADS)

    Iwaki, C.; Cheong, K. H.; Monji, H.; Matsui, G.

    Shell and tube heat exchangers are among the most commonly used types of heat exchangers. Shell-side cross-flow in tube bundles has received considerable attention and has been investigated extensively. However, the microscopic flow structure including velocity distribution, wake, and turbulent structure in the tube bundles needs to be determined for more effective designs. Therefore, in this study, in order to clarify the detailed structure of cross-flow in tube bundles with particle image velocimetry (PIV), experiments were conducted using two types of model; in-line and staggered bundles with a pitch-to-diameter ratio of 1.5, containing 20 rows of five 15 mm O.D. tubes in each row. The velocity data in the whole flow field were measured successfully by adjusting the refractive index of the working fluid to that of the tube material. The flow features were characterized in different tube bundles with regards to the velocity vector field, vortex structure, and turbulent intensity.

  12. The role of the tangent bundle for symmetry operations and modulated structures.

    PubMed

    Kocian, Philippe; Schenk, Kurt; Chapuis, Gervais

    2010-05-01

    An equivalence relation on the tangent bundle of a manifold is defined in order to extend a structure (modulated or not) onto it. This extension affords a representation of a structure in any tangent space and that in another tangent space can easily be derived. Euclidean symmetry operations associated with the tangent bundle are generalized and their usefulness for the determination of the intrinsic translation part in helicoidal axes and glide planes is illustrated. Finally, a novel representation of space groups is shown to be independent of any origin point.

  13. Simultaneous single-structure and bundle representation of protein NMR structures in torsion angle space.

    PubMed

    Gottstein, Daniel; Kirchner, Donata K; Güntert, Peter

    2012-04-01

    A method is introduced to represent an ensemble of conformers of a protein by a single structure in torsion angle space that lies closest to the averaged Cartesian coordinates while maintaining perfect covalent geometry and on average equal steric quality and an equally good fit to the experimental (e.g. NMR) data as the individual conformers of the ensemble. The single representative 'regmean structure' is obtained by simulated annealing in torsion angle space with the program CYANA using as input data the experimental restraints, restraints for the atom positions relative to the average Cartesian coordinates, and restraints for the torsion angles relative to the corresponding principal cluster average values of the ensemble. The method was applied to 11 proteins for which NMR structure ensembles are available, and compared to alternative, commonly used simple approaches for selecting a single representative structure, e.g. the structure from the ensemble that best fulfills the experimental and steric restraints, or the structure from the ensemble that has the lowest RMSD value to the average Cartesian coordinates. In all cases our method found a structure in torsion angle space that is significantly closer to the mean coordinates than the alternatives while maintaining the same quality as individual conformers. The method is thus suitable to generate representative single structure representations of protein structure ensembles in torsion angle space. Since in the case of NMR structure calculations with CYANA the single structure is calculated in the same way as the individual conformers except that weak positional and torsion angle restraints are added, we propose to represent new NMR structures by a 'regmean bundle' consisting of the single representative structure as the first conformer and all but one original individual conformers (the original conformer with the highest target function value is discarded in order to keep the number of conformers in the

  14. Two-phase flow interfacial structures in a rod bundle geometry

    NASA Astrophysics Data System (ADS)

    Paranjape, Sidharth S.

    Interfacial structure of air-water two-phase flow in a scaled nuclear reactor rod bundle geometry was studied in this research. Global and local flow regimes were obtained for the rod bundle geometry. Local two-phase flow parameters were measured at various axial locations in order to understand the transport of interfacial structures. A one-dimensional two-group interfacial area transport model was evaluated using the local parameter database. Air-water two-phase flow experiments were performed in an 8 X 8 rod bundle test section to obtain flow regime maps at various axial locations. Area averaged void fraction was measured using parallel plate type impedance void meters. The cumulative probability distribution functions of the signals from the impedance void meters were used along with a self organizing neural network to identify flow regimes. Local flow regime maps revealed the cross-sectional distribution of flow regimes in the bundle. Local parameters that characterize interfacial structure, that is, void fraction alpha, interfacial area concentration, ai, bubble Sauter mean diameter, DSm and bubble velocity, vg were measured using four sensor conductivity probe technique. The local data revealed the distribution of the interfacial structure in the radial direction, as well as its development in the axial direction. In addition to this, the effect of spacer grid on the flow structure at different gas and liquid velocities was revealed by local parameter measurements across the spacer grids. A two-group interfacial area transport equation (IATE) specific to rod bundle geometry was derived. The derivation of two-group IATE required certain assumption on the bubble shapes in the subchannels and the bubbles spanning more than a subchannel. It was found that the geometrical relationship between the volume and the area of a cap bubble distorted by rods was similar to the one derived for a confined channel under a specific geometrical transformation. The one

  15. Euler-Poincaré reduction in principal bundles by a subgroup of the structure group

    NASA Astrophysics Data System (ADS)

    Castrillón López, M.; García, P. L.; Rodrigo, C.

    2013-12-01

    Given a Lagrangian density Lv defined on the 1-jet bundle J1P of a principal G-bundle π:P→M invariant with respect to a subgroup H of G, the reduction of the variational problem defined by Lv to (J1P)/H=C×M(P/H), where C is the bundle of connections in P, is studied. It is shown that the reduced Lagrangian density lv defines a zero order variational problem on connections σ and H-structures s¯ of P with non-holonomic constraints Curv σ=0 and ∇σs¯=0 and set of admissible variations those induced by the infinitesimal gauge transformations in C and P/H. The Euler-Poincaré equations for critical reduced sections are obtained as well as the reconstruction process to the unreduced problem. The corresponding conservation laws and their relationship with the Noether theory are also analyzed. Finally, some instances are studied: the heavy top and affine principal bundles, the main application of which is used for molecular strands.

  16. Methods for modifying monofilaments, bundles of monofilaments, and fibrous structural material

    DOEpatents

    Allen, Charles A.; Argyle, Mark D.; Fox, Robert V.; Ginosar, Daniel M.; Janikowski, Stuart K.; Miller, David L.; Propp, W. Alan; Toth, William J.

    2002-12-17

    The present invention is related to the modifying of substrates such as monofilaments, bundles of monofilaments, and fibrous structural material with a modifying agent. The modifying agent is suspended or dissolved in a supercritical fluid, near-critical fluid, superheated fluid, superheated liquid, or a liquified gas and is deposited by rapidly altering the pressure in a chamber to deposit the modifying material onto the substrate.

  17. Kahler structures on the tangent bundles of rank-one symmetric spaces

    SciTech Connect

    Mykytyuk, I V

    2001-12-31

    For rank-one Riemannian symmetric spaces G/K, dimG/K{>=}3, with semisimple Lie groups G all G-invariant Kahler structures F on subdomains of the symplectic manifolds T(G/K) are constructed. It is shown that this class {l_brace}F{r_brace} of Kahler structures is stable under the reduction procedure. A Lie algebraic method of description of G-invariant Kahler structures on the tangent bundles of symmetric spaces G/K is presented. Related questions of the description of the Lie triple system of the space F{sub 4}/Spin(9) in terms of its spinor structure are also discussed.

  18. Kahler structures on the tangent bundles of rank-one symmetric spaces

    NASA Astrophysics Data System (ADS)

    Mykytyuk, I. V.

    2001-12-01

    For rank-one Riemannian symmetric spaces G/K, \\operatorname{dim}G/K\\geqslant3, with semisimple Lie groups G all G-invariant Kahler structures F on subdomains of the symplectic manifolds T(G/K) are constructed. It is shown that this class \\{F\\} of Kahler structures is stable under the reduction procedure. A Lie algebraic method of description of G-invariant Kahler structures on the tangent bundles of symmetric spaces G/K is presented. Related questions of the description of the Lie triple system of the space F_4/\\operatorname{Spin}(9) in terms of its spinor structure are also discussed.

  19. Geometric principles in the assembly of α-helical bundles.

    PubMed

    Pratap, J V; Luisi, B F; Calladine, C R

    2013-06-28

    α-Helical coiled coils are usually stabilized by hydrophobic interfaces between the two constituent α-helices, in the form of 'knobs-into-holes' packing of non-polar residues arranged in repeating heptad patterns. Here we examine the corresponding 'hydrophobic cores' that stabilize bundles of four α-helices. In particular, we study three different kinds of bundle, involving four α-helices of identical sequence: two pack in a parallel and one in an anti-parallel orientation. We point out that the simplest way of understanding the packing of these 4-helix bundles is to use Crick's original idea that the helices are held together by 'hydrophobic stripes', which are readily visualized on the cylindrical surface lattice of the α-helices; and that the 'helix-crossing angle'--which determines, in particular, whether supercoiling is left- or right-handed--is fixed by the slope of the lattice lines that contain the hydrophobic residues. In our three examples the constituent α-helices have hydrophobic repeat patterns of 7, 11 and 4 residues, respectively; and we associate the different overall conformations with 'knobs-into-holes' packing along the 7-, 11- and 4-start lines, respectively, of the cylindrical surface lattices of the constituent α-helices. For the first two examples, all four interfaces between adjacent helices are geometrically equivalent; but in the third, one of the four interfaces differs significantly from the others. We provide a geometrical explanation for this non-equivalence in terms of two different but equivalent ways of assembling this bundle, which may possibly constitute a bistable molecular 'switch' with a coaxial throw of about 12 Å. The geometrical ideas that we deploy in this paper provide the simplest and clearest description of the structure of helical bundles. In an appendix, we describe briefly a computer program that we have devised in order to search for 'knobs-into-holes' packing between α-helices in proteins.

  20. Multilamellar Structures and Filament Bundles Are Found on the Cell Surface during Bunyavirus Egress

    PubMed Central

    Sanz-Sánchez, Laura; Risco, Cristina

    2013-01-01

    Inside cells, viruses build specialized compartments for replication and morphogenesis. We observed that virus release associates with specific structures found on the surface of mammalian cells. Cultured adherent cells were infected with a bunyavirus and processed for oriented sectioning and transmission electron microscopy. Imaging of cell basal regions showed sophisticated multilamellar structures (MLS) and extracellular filament bundles with attached viruses. Correlative light and electron microscopy confirmed that both MLS and filaments proliferated during the maximum egress of new viruses. MLS dimensions and structure were reminiscent of those reported for the nanostructures on gecko fingertips, which are responsible for the extraordinary attachment capacity of these lizards. As infected cells with MLS were more resistant to detachment than control cells, we propose an adhesive function for these structures, which would compensate for the loss of adherence during release of new virus progeny. PMID:23799021

  1. Structure and vibrational properties of single-wall carbon nanotube bundles under hyprostatic pressure

    NASA Astrophysics Data System (ADS)

    Reich, Stephanie; Thomsen, Christian; Ordejon, Pablo

    2001-03-01

    We investigated experimentally and theoretically the mechanical and vibrational properties of carbon nanotube bundles under high hydrostatic pressure. While Raman spectra excited with blue laser light (2.54 eV) show a uniform shift of the high-energy modes under pressure towards higher frequencies (≈3.8 TPa-1), we find a small splitting of 0.56 TPa-1 when exciting in the red (1.92 eV).(S. Reich, H. Jantoljak, and C. Thomsen, Phys. Rev. B 61), R13 389 (2000); and references therein To investigate this splitting we calculated the relaxed structure of bundles of small nanotubes (d=8 Åunder pressures up to 4 GPa using an LDA pseudopotential structural ab initio method.(D. Sanchez-Portal, P. Ordejón, E. Artacho, and J. M. Soler Int. J. Quant. Chem. 65), 453 (1997). We find that armchair nanotubes show a different strain in axial and circumferential directions. In contrast, zig zag tubes behave uniformly in this respect. We discuss these results in light of the theoretical and experimental pressure dependence of the high energy modes.

  2. X-rays Reveal the Internal Structure of Keratin Bundles in Whole Cells.

    PubMed

    Hémonnot, Clément Y J; Reinhardt, Juliane; Saldanha, Oliva; Patommel, Jens; Graceffa, Rita; Weinhausen, Britta; Burghammer, Manfred; Schroer, Christian G; Köster, Sarah

    2016-03-22

    In recent years, X-ray imaging of biological cells has emerged as a complementary alternative to fluorescence and electron microscopy. Different techniques were established and successfully applied to macromolecular assemblies and structures in cells. However, while the resolution is reaching the nanometer scale, the dose is increasing. It is essential to develop strategies to overcome or reduce radiation damage. Here we approach this intrinsic problem by combing two different X-ray techniques, namely ptychography and nanodiffraction, in one experiment and on the same sample. We acquire low dose ptychography overview images of whole cells at a resolution of 65 nm. We subsequently record high-resolution nanodiffraction data from regions of interest. By comparing images from the two modalities, we can exclude strong effects of radiation damage on the specimen. From the diffraction data we retrieve quantitative structural information from intracellular bundles of keratin intermediate filaments such as a filament radius of 5 nm, hexagonal geometric arrangement with an interfilament distance of 14 nm and bundle diameters on the order of 70 nm. Thus, we present an appealing combined approach to answer a broad range of questions in soft-matter physics, biophysics and biology.

  3. Structure and Mutational Analyses of Escherichia coli ZapD Reveal Charged Residues Involved in FtsZ Filament Bundling

    PubMed Central

    Roach, Elyse J.; Wroblewski, Charles; Seidel, Laura; Berezuk, Alison M.; Brewer, Dyanne; Kimber, Matthew S.

    2016-01-01

    ABSTRACT Bacterial cell division is an essential and highly coordinated process. It requires the polymerization of the tubulin homologue FtsZ to form a dynamic ring (Z-ring) at midcell. Z-ring formation relies on a group of FtsZ-associated proteins (Zap) for stability throughout the process of division. In Escherichia coli, there are currently five Zap proteins (ZapA through ZapE), of which four (ZapA, ZapB, ZapC, and ZapD) are small soluble proteins that act to bind and bundle FtsZ filaments. In particular, ZapD forms a functional dimer and interacts with the C-terminal tail of FtsZ, but little is known about its structure and mechanism of action. Here, we present the crystal structure of Escherichia coli ZapD and show it forms a symmetrical dimer with centrally located α-helices flanked by β-sheet domains. Based on the structure of ZapD and its chemical cross-linking to FtsZ, we targeted nine charged ZapD residues for modification by site-directed mutagenesis. Using in vitro FtsZ sedimentation assays, we show that residues R56, R221, and R225 are important for bundling FtsZ filaments, while transmission electron microscopy revealed that altering these residues results in different FtsZ bundle morphology compared to those of filaments bundled with wild-type ZapD. ZapD residue R116 also showed altered FtsZ bundle morphology but levels of FtsZ bundling similar to that of wild-type ZapD. Together, these results reveal that ZapD residues R116, R221, and R225 likely participate in forming a positively charged binding pocket that is critical for bundling FtsZ filaments. IMPORTANCE Z-ring assembly underpins the formation of the essential cell division complex known as the divisome and is required for recruitment of downstream cell division proteins. ZapD is one of several proteins in E. coli that associates with the Z-ring to promote FtsZ bundling and aids in the overall fitness of the division process. In the present study, we describe the dimeric structure of E. coli

  4. Polycation induced actin bundles.

    PubMed

    Muhlrad, Andras; Grintsevich, Elena E; Reisler, Emil

    2011-04-01

    Three polycations, polylysine, the polyamine spermine and the polycationic protein lysozyme were used to study the formation, structure, ionic strength sensitivity and dissociation of polycation-induced actin bundles. Bundles form fast, simultaneously with the polymerization of MgATP-G-actins, upon the addition of polycations to solutions of actins at low ionic strength conditions. This indicates that nuclei and/or nascent filaments bundle due to attractive, electrostatic effect of polycations and the neutralization of repulsive interactions of negative charges on actin. The attractive forces between the filaments are strong, as shown by the low (in nanomolar range) critical concentration of their bundling at low ionic strength. These bundles are sensitive to ionic strength and disassemble partially in 100 mM NaCl, but both the dissociation and ionic strength sensitivity can be countered by higher polycation concentrations. Cys374 residues of actin monomers residing on neighboring filaments in the bundles can be cross-linked by the short span (5.4Å) MTS-1 (1,1-methanedyl bismethanethiosulfonate) cross-linker, which indicates a tight packing of filaments in the bundles. The interfilament cross-links, which connect monomers located on oppositely oriented filaments, prevent disassembly of bundles at high ionic strength. Cofilin and the polysaccharide polyanion heparin disassemble lysozyme induced actin bundles more effectively than the polylysine-induced bundles. The actin-lysozyme bundles are pathologically significant as both proteins are found in the pulmonary airways of cystic fibrosis patients. Their bundles contribute to the formation of viscous mucus, which is the main cause of breathing difficulties and eventual death in this disorder.

  5. Anatomy of Mandibular Vital Structures. Part I: Mandibular Canal and Inferior Alveolar Neurovascular Bundle in Relation with Dental Implantology

    PubMed Central

    Wang, Hom-Lay; Sabalys, Gintautas

    2010-01-01

    ABSTRACT Objectives It is critical to determine the location and configuration of the mandibular canal and related vital structures during the implant treatment. The purpose of the present study was to review the literature concerning the mandibular canal and inferior alveolar neurovascular bundle anatomical variations related to the implant surgery. Material and Methods Literature was selected through the search of PubMed, Embase and Cochrane electronic databases. The keywords used for search were mandibular canal, inferior alveolar nerve, and inferior alveolar neurovascular bundle. The search was restricted to English language articles, published from 1973 to November 2009. Additionally, a manual search in the major anatomy, dental implant, prosthetic and periodontal journals and books were performed. Results In total, 46 literature sources were obtained and morphological aspects and variations of the anatomy related to implant treatment in posterior mandible were presented as two entities: intraosseous mandibular canal and associated inferior alveolar neurovascular bundle. Conclusions A review of morphological aspects and variations of the anatomy related to mandibular canal and mandibular vital structures are very important especially in implant therapy since inferior alveolar neurovascular bundle exists in different locations and possesses many variations. Individual, gender, age, race, assessing technique used and degree of edentulous alveolar bone atrophy largely influence these variations. It suggests that osteotomies in implant dentistry should not be developed in the posterior mandible until the position of the mandibular canal is established. PMID:24421958

  6. Nanoscale structure and spectroscopic probing of Aβ1-40 fibril bundle formation

    NASA Astrophysics Data System (ADS)

    Psonka-Antonczyk, Katarzyna; Hammarström, Per; Johansson, Leif; Lindgren, Mikael; Stokke, Bjørn Torger; Nilsson, Peter; Nyström, Sofie

    2016-11-01

    Amyloid plaques composed of fibrillar Amyloid-β (Aβ) is a hallmark of Alzheimer’s disease. However, Aβ fibrils are morphologically heterogeneous. Conformation sensitive luminescent conjugated oligothiophenes (LCOs) are versatile tools for monitoring such fibril polymorphism in vivo and in vitro. Biophysical methods applied on in vitro generated Aβ fibrils, stained with LCOs with different binding and fluorescence properties, can be used to characterize the Aβ fibrillation in depth, far beyond that possible for in vivo generated amyloid plaques. In this study, in vitro fibrillation of the Aβ1-40 peptide was monitored by time-lapse transmission electron microscopy, LCO fluorescence and atomic force microscopy. Differences in the LCO binding in combination with nanoscale imaging revealed that spectral variation correlated with fibrils transforming from solitary filaments (Ø 2.5 nm) into higher order bundled structures (Ø 5 nm). These detailed in vitro experiments can be used to derive data that reflects the heterogeneity of in vivo generated Aβ plaques observed by LCO fluorescence. Our work provides new structural basis for targeted drug design and molecular probe development for amyloid imaging.

  7. Nanoscale Structure and Spectroscopic Probing of Aβ1-40 Fibril Bundle Formation

    PubMed Central

    Psonka-Antonczyk, Katarzyna M.; Hammarström, Per; Johansson, Leif B. G.; Lindgren, Mikael; Stokke, Bjørn T.; Nilsson, K. Peter R.; Nyström, Sofie

    2016-01-01

    Amyloid plaques composed of fibrillar Amyloid-β (Aβ) are hallmarks of Alzheimer's disease. However, Aβ fibrils are morphologically heterogeneous. Conformation sensitive luminescent conjugated oligothiophenes (LCOs) are versatile tools for monitoring such fibril polymorphism in vivo and in vitro. Biophysical methods applied on in vitro generated Aβ fibrils, stained with LCOs with different binding and fluorescence properties, can be used to characterize the Aβ fibrillation in depth, far beyond that possible for in vivo generated amyloid plaques. In this study, in vitro fibrillation of the Aβ1-40 peptide was monitored by time-lapse transmission electron microscopy, LCO fluorescence, and atomic force microscopy. Differences in the LCO binding in combination with nanoscale imaging revealed that spectral variation correlated with fibrils transforming from solitary filaments (Ø~2.5 nm) into higher order bundled structures (Ø~5 nm). These detailed in vitro experiments can be used to derive data that reflects the heterogeneity of in vivo generated Aβ plaques observed by LCO fluorescence. Our work provides new structural basis for targeted drug design and molecular probe development for amyloid imaging. PMID:27921029

  8. Structure and Characterization of Vertically Aligned Single-Walled Carbon Nanotube Bundles

    DOE PAGES

    Márquez, Francisco; López, Vicente; Morant, Carmen; ...

    2010-01-01

    Arrmore » ays of vertically aligned single-walled carbon nanotube bundles, SWCNTs, have been synthesized by simple alcohol catalytic chemical vapor deposition process, carried out at 800°C. The formed SWCNTs are organized in small groups perpendicularly aligned and attached to the substrate. These small bundles show a constant diameter of ca. 30 nm and are formed by the adhesion of no more than twenty individual SWCNTs perfectly aligned along their length.« less

  9. Structure and stability of a model three-helix-bundle protein on tailored surfaces.

    PubMed

    Knotts, Thomas A; Rathore, Nitin; de Pablo, Juan J

    2005-11-01

    The interaction of protein molecules with surfaces is important in numerous applications. Theoretical work on protein adsorption has been limited. In particular, it is difficult to obtain quantitative predictions about the structure and stability of proteins on surfaces. In this study, density-of-states-based simulations were performed on a Gō-like model of a three-helix-bundle fragment from protein A (PDB ID: 1bdd). Both mechanical and thermal stability were investigated on neutral and attractive surfaces and compared to that in the absence of a surface. It was found that attaching the peptide to any type of surface decreases its melting temperature by as much as 9 K, depending upon orientation. Calorimetric cooperativity, as measured by van't Hoff to calorimetric enthalpy ratios, similarly decreased. It was also found that the mechanical strength of the peptide attached to surfaces is degraded to varying extents, depending upon the surface type and protein orientation. A comparison of mechanical and thermal stability showed that the two are not synonymous, but occur through different pathways, and that system configurations that are more thermally stable are not always so mechanically.

  10. Study and Test of a New Bundle-Structure Riser Stress Monitoring Sensor Based on FBG

    PubMed Central

    Xu, Jian; Yang, Dexing; Qin, Chuan; Jiang, Yajun; Sheng, Leixiang; Jia, Xiangyun; Bai, Yang; Shen, Xiaohong; Wang, Haiyan; Deng, Xin; Xu, Liangbin; Jiang, Shiquan

    2015-01-01

    To meet the requirements of riser safety monitoring in offshore oil fields, a new Fiber Bragg Grating (FBG)-based bundle-structure riser stress monitoring sensor has been developed. In cooperation with many departments, a 49-day marine test in water depths of 1365 m and 1252 m was completed on the “HYSY-981” ocean oil drilling platform. No welding and pasting were used when the sensor was installed on risers. Therefore, the installation is convenient, reliable and harmless to risers. The continuous, reasonable, time-consistent data obtained indicates that the sensor worked normally under water. In all detailed working conditions, the test results show that the sensor can do well in reflecting stresses and bending moments both in and in magnitude. The measured maximum stress is 132.7 MPa, which is below the allowable stress. In drilling and testing conditions, the average riser stress was 86.6 MPa, which is within the range of the China National Offshore Oil Corporation (CNOOC) mechanical simulation results. PMID:26610517

  11. Study and Test of a New Bundle-Structure Riser Stress Monitoring Sensor Based on FBG.

    PubMed

    Xu, Jian; Yang, Dexing; Qin, Chuan; Jiang, Yajun; Sheng, Leixiang; Jia, Xiangyun; Bai, Yang; Shen, Xiaohong; Wang, Haiyan; Deng, Xin; Xu, Liangbin; Jiang, Shiquan

    2015-11-24

    To meet the requirements of riser safety monitoring in offshore oil fields, a new Fiber Bragg Grating (FBG)-based bundle-structure riser stress monitoring sensor has been developed. In cooperation with many departments, a 49-day marine test in water depths of 1365 m and 1252 m was completed on the "HYSY-981" ocean oil drilling platform. No welding and pasting were used when the sensor was installed on risers. Therefore, the installation is convenient, reliable and harmless to risers. The continuous, reasonable, time-consistent data obtained indicates that the sensor worked normally under water. In all detailed working conditions, the test results show that the sensor can do well in reflecting stresses and bending moments both in and in magnitude. The measured maximum stress is 132.7 MPa, which is below the allowable stress. In drilling and testing conditions, the average riser stress was 86.6 MPa, which is within the range of the China National Offshore Oil Corporation (CNOOC) mechanical simulation results.

  12. Structure of the 34 kDa F-actin-bundling protein ABP34 from Dictyostelium discoideum.

    PubMed

    Kim, Min-Kyu; Kim, Ji-Hye; Kim, Ji-Sun; Kang, Sa-Ouk

    2015-09-01

    The crystal structure of the 34 kDa F-actin-bundling protein ABP34 from Dictyostelium discoideum was solved by Ca(2+)/S-SAD phasing and refined at 1.89 Å resolution. ABP34 is a calcium-regulated actin-binding protein that cross-links actin filaments into bundles. Its in vitro F-actin-binding and F-actin-bundling activities were confirmed by a co-sedimentation assay and transmission electron microscopy. The co-localization of ABP34 with actin in cells was also verified. ABP34 adopts a two-domain structure with an EF-hand-containing N-domain and an actin-binding C-domain, but has no reported overall structural homologues. The EF-hand is occupied by a calcium ion with a pentagonal bipyramidal coordination as in the canonical EF-hand. The C-domain structure resembles a three-helical bundle and superposes well onto the rod-shaped helical structures of some cytoskeletal proteins. Residues 216-244 in the C-domain form part of the strongest actin-binding sites (193-254) and exhibit a conserved sequence with the actin-binding region of α-actinin and ABP120. Furthermore, the second helical region of the C-domain is kinked by a proline break, offering a convex surface towards the solvent area which is implicated in actin binding. The F-actin-binding model suggests that ABP34 binds to the side of the actin filament and residues 216-244 fit into a pocket between actin subdomains -1 and -2 through hydrophobic interactions. These studies provide insights into the calcium coordination in the EF-hand and F-actin-binding site in the C-domain of ABP34, which are associated through interdomain interactions.

  13. Redesigning the hydrophobic core of a four-helix-bundle protein.

    PubMed Central

    Munson, M.; O'Brien, R.; Sturtevant, J. M.; Regan, L.

    1994-01-01

    Rationally redesigned variants of the 4-helix-bundle protein Rop are described. The novel proteins have simplified, repacked, hydrophobic cores and yet reproduce the structure and native-like physical properties of the wild-type protein. The repacked proteins have been characterized thermodynamically and their equilibrium and kinetic thermal and chemical unfolding properties are compared with those of wild-type Rop. The equilibrium stability of the repacked proteins to thermal denaturation is enhanced relative to that of the wild-type protein. The rate of chemically induced folding and unfolding of wild-type Rop is extremely slow when compared with other small proteins. Interestingly, although the repacked proteins are more thermally stable than the wild type, their rates of chemically induced folding and unfolding are greatly increased in comparison to wild type. Perhaps as a consequence of this, their equilibrium stabilities to chemical denaturants are slightly reduced in comparison to the wild type. PMID:7535612

  14. Connections on decorated path space bundles

    NASA Astrophysics Data System (ADS)

    Chatterjee, Saikat; Lahiri, Amitabha; Sengupta, Ambar N.

    2017-02-01

    For a principal bundle P → M equipped with a connection A ¯ , we study an infinite dimensional bundle PA¯ dec P over the space of paths on M, with the points of PA¯ dec P being horizontal paths on P decorated with elements of a second structure group. We construct parallel transport processes on such bundles and study holonomy bundles in this setting.

  15. CFD analyses of flow structures in air-ingress and rod bundle problems

    NASA Astrophysics Data System (ADS)

    Wei, Hong-Chan

    Two topics from nuclear engineering field are included in this dissertation. One study is the air-ingress phenomenon during a loss of coolant accident (LOCA) scenario, and the other is a 5-by-5 bundle assembly with a PWR design. The objectives were to investigate the Kelvin-Helmholtz instability of the gravity-driven stratified flows inside a coaxial pipe and the effects caused by two types of spacers at the downstream of the rod bundle. Richardson extrapolation was used for the grid independent study. The simulation results show good agreements with the experiments. Wavelet analysis and Proper Orthogonal Decomposition (POD) were used to study the flow behaviors and flow patterns. For the air-ingress phenomenon, Brunt-Vaisala frequency, or buoyancy frequency, predicts a frequency of 2.34 Hz; this is confirmed by the dominant frequency of 2.4 Hz obtained from the wavelet analysis between times 1.2 s and 1.85 s. For the rod bundle study, the dominant frequency at the center of the subchannel was determined to be 2.4 Hz with a secondary dominant frequency of 4 Hz and a much minor frequency of 6 Hz. Generally, wavelet analysis has much better performance than POD, in the air-ingress phenomenon, for a strongly transient scenario; they are both appropriate for the rod bundle study. Based on this study, when the fluid pair in a real condition is used, the time which air intrudes into the reactor is predictable.

  16. NMR and XAS reveal an inner-sphere metal binding site in the P4 helix of the metallo-ribozyme ribonuclease P

    PubMed Central

    Koutmou, Kristin S.; Casiano-Negroni, Anette; Getz, Melissa M.; Pazicni, Samuel; Andrews, Andrew J.; Penner-Hahn, James E.; Al-Hashimi, Hashim M.; Fierke, Carol A.

    2010-01-01

    Functionally critical metals interact with RNA through complex coordination schemes that are currently difficult to visualize at the atomic level under solution conditions. Here, we report a new approach that combines NMR and XAS to resolve and characterize metal binding in the most highly conserved P4 helix of ribonuclease P (RNase P), the ribonucleoprotein that catalyzes the divalent metal ion-dependent maturation of the 5′ end of precursor tRNA. Extended X-ray absorption fine structure (EXAFS) spectroscopy reveals that the Zn2+ bound to a P4 helix mimic is six-coordinate, with an average Zn-O/N bond distance of 2.08 Å. The EXAFS data also show intense outer-shell scattering indicating that the zinc ion has inner-shell interactions with one or more RNA ligands. NMR Mn2+ paramagnetic line broadening experiments reveal strong metal localization at residues corresponding to G378 and G379 in B. subtilis RNase P. A new “metal cocktail” chemical shift perturbation strategy involving titrations with , Zn2+, and confirm an inner-sphere metal interaction with residues G378 and G379. These studies present a unique picture of how metals coordinate to the putative RNase P active site in solution, and shed light on the environment of an essential metal ion in RNase P. Our experimental approach presents a general method for identifying and characterizing inner-sphere metal ion binding sites in RNA in solution. PMID:20133747

  17. Nerve guidance conduit with a hybrid structure of a PLGA microfibrous bundle wrapped in a micro/nanostructured membrane.

    PubMed

    Peng, Shih-Wen; Li, Ching-Wen; Chiu, Ing-Ming; Wang, Gou-Jen

    2017-01-01

    Nerve repair in tissue engineering involves the precise construction of a scaffold to guide nerve cell regeneration in the desired direction. However, improvements are needed to facilitate the cell migration/growth rate of nerves in the center of a nerve conduit. In this paper, we propose a nerve guidance conduit with a hybrid structure comprising a microfibrous poly(lactic-co-glycolic acid) (PLGA) bundle wrapped in a micro/nanostructured PLGA membrane. We applied sequential fabrication processes, including photolithography, nano-electroforming, and polydimethylsiloxane casting to manufacture master molds for the repeated production of the PLGA subelements. After demolding it from the master molds, we rolled the microfibrous membrane into a bundle and then wrapped it in the micro/nanostructured membrane to form a nerve-guiding conduit. We used KT98/F1B-GFP cells to estimate the migration rate and guidance ability of the fabricated nerve conduit and found that both elements increased the migration rate 1.6-fold compared with a flat PLGA membrane. We also found that 90% of the cells in the hybrid nano/microstructured membrane grew in the direction of the designed patterns. After 3 days of culturing, the interior of the nerve conduit was filled with cells, and the microfiber bundle was also surrounded by cells. Our conduit cell culture results also demonstrate that the proposed micro/nanohybrid and microfibrous structures can retain their shapes. The proposed hybrid-structured conduit demonstrates a high capability for guiding nerve cells and promoting cell migration, and, as such, is feasible for use in clinical applications.

  18. Nerve guidance conduit with a hybrid structure of a PLGA microfibrous bundle wrapped in a micro/nanostructured membrane

    PubMed Central

    Peng, Shih-Wen; Li, Ching-Wen; Chiu, Ing-Ming; Wang, Gou-Jen

    2017-01-01

    Nerve repair in tissue engineering involves the precise construction of a scaffold to guide nerve cell regeneration in the desired direction. However, improvements are needed to facilitate the cell migration/growth rate of nerves in the center of a nerve conduit. In this paper, we propose a nerve guidance conduit with a hybrid structure comprising a microfibrous poly(lactic-co-glycolic acid) (PLGA) bundle wrapped in a micro/nanostructured PLGA membrane. We applied sequential fabrication processes, including photolithography, nano-electroforming, and polydimethylsiloxane casting to manufacture master molds for the repeated production of the PLGA subelements. After demolding it from the master molds, we rolled the microfibrous membrane into a bundle and then wrapped it in the micro/nanostructured membrane to form a nerve-guiding conduit. We used KT98/F1B-GFP cells to estimate the migration rate and guidance ability of the fabricated nerve conduit and found that both elements increased the migration rate 1.6-fold compared with a flat PLGA membrane. We also found that 90% of the cells in the hybrid nano/microstructured membrane grew in the direction of the designed patterns. After 3 days of culturing, the interior of the nerve conduit was filled with cells, and the microfiber bundle was also surrounded by cells. Our conduit cell culture results also demonstrate that the proposed micro/nanohybrid and microfibrous structures can retain their shapes. The proposed hybrid-structured conduit demonstrates a high capability for guiding nerve cells and promoting cell migration, and, as such, is feasible for use in clinical applications. PMID:28138239

  19. Templated growth of PFO-DBT nanorod bundles by spin coating: effect of spin coating rate on the morphological, structural, and optical properties.

    PubMed

    Fakir, Muhamad Saipul; Supangat, Azzuliani; Sulaiman, Khaulah

    2014-01-01

    In this study, the spin coating of template-assisted method is used to synthesize poly[2,7-(9,9-dioctylfluorene)-alt-4,7-bis(thiophen-2-yl)benzo-2,1,3-thiadiazole] (PFO-DBT) nanorod bundles. The morphological, structural, and optical properties of PFO-DBT nanorod bundles are enhanced by varying the spin coating rate (100, 500, and 1,000 rpm) of the common spin coater. The denser morphological distributions of PFO-DBT nanorod bundles are favorably yielded at the low spin coating rate of 100 rpm, while at high spin coating rate, it is shown otherwise. The auspicious morphologies of highly dense PFO-DBT nanorod bundles are supported by the augmented absorption and photoluminescence.

  20. {{P}}^1 -bundle bases and the prevalence of non-Higgsable structure in 4D F-theory models

    NASA Astrophysics Data System (ADS)

    Halverson, James; Taylor, Washington

    2015-09-01

    We explore a large class of F-theory compactifications to four dimensions. We find evidence that gauge groups that cannot be Higgsed without breaking supersymmetry, often accompanied by associated matter fields, are a ubiquitous feature in the landscape of N=1 4D F-theory constructions. In particular, we study 4D F-theory models that arise from compactification on threefold bases that are {{P}}^1 bundles over certain toric surfaces. These bases are one natural analogue to the minimal models for base surfaces for 6D F-theory compactifications. Of the roughly 100,000 bases that we study, only 80 are weak Fano bases in which there are no automatic singularities on the associated elliptic Calabi-Yau fourfolds, and 98.3% of the bases have geometrically non-Higgsable gauge factors. The {{P}}^1 -bundle threefold bases we analyze contain a wide range of distinct surface topologies that support geometrically non-Higgsable clusters. Many of the bases that we consider contain SU(3) × SU(2) seven-brane clusters for generic values of deformation moduli; we analyze the relative frequency of this combination relative to the other four possible two-factor non-Higgsable product groups, as well as various other features such as geometrically non-Higgsable candidates for dark matter structure and phenomenological (SU(2)-charged) Higgs fields.

  1. Salinity induces membrane structure and lipid changes in maize mesophyll and bundle sheath chloroplasts.

    PubMed

    Omoto, Eiji; Iwasaki, Yugo; Miyake, Hiroshi; Taniguchi, Mitsutaka

    2016-05-01

    The membranes of Zea mays (maize) mesophyll cell (MC) chloroplasts are more vulnerable to salinity stress than are those of bundle sheath cell (BSC) chloroplasts. To clarify the mechanism underlying this difference in salt sensitivity, we monitored changes in the glycerolipid and fatty acid compositions of both types of chloroplast upon exposure to salinity stress. The monogalactosyldiacylglycerol (MGDG) and digalactosyldiacylglycerol (DGDG) contents were higher in MC chloroplasts than in BSC chloroplasts, in both the presence and absence of salt treatment. Under salt conditions, the MGDG level in MC chloroplasts was significantly lower than under normal conditions, while it was unchanged in BSC chloroplasts. In both types of chloroplast, the contents of DGDG, phosphatidylglycerol and phosphatidylinositol remained at the same levels in control and salt-treated plants, whereas sulfoquinovosyldiacylglycerol and phosphatidylcholine were significantly lower and higher, respectively, upon salt treatment. In addition, the fatty acid composition and double bond index of individual lipid classes were changed by salt treatment in both BSC and MC chloroplasts, although these factors had no effect on glycerolipid content. These findings suggest that the difference in salt sensitivity of MC and BSC chloroplast membranes is related to differences in MGDG responses to salinity. Thus, we propose that the low MGDG content and the low sensitivity of MGDG to salinity in BSC chloroplasts render them more tolerant than MC chloroplasts to salinity stress.

  2. Fuel bundle

    SciTech Connect

    Lui, C.K.

    1989-04-04

    This patent describes a method of forming a fuel bundle of a nuclear reactor. The method consists of positioning the fuel rods in the bottom plate, positioning the tie rod in the bottom plate with the key passed through the receptacle to the underside of the bottom plate and, after the tie rod is so positioned, turning the tie rod so that the key is in engagement with the underside of the bottom plate. Thereafter mounting the top plate is mounted in engagement with the fuel rods with the upper end of the tie rod extending through the opening in the top plate and extending above the top plate, and the tie rod is secured to the upper side of sid top plate thus simultaneously securing the key to the underside of the bottom plate.

  3. Isopeptide bonds of the major pilin protein BcpA influence pilus structure and bundle formation on the surface of Bacillus cereus

    SciTech Connect

    Hendrickx, Antoni P.A.; Poor, Catherine B.; Jureller, Justin E.; Budzik, Jonathan M.; He, Chuan; Schneewind, Olaf

    2012-09-05

    Bacillus cereus strains elaborate pili on their surface using a mechanism of sortase-mediated cross-linking of major and minor pilus components. Here we used a combination of electron microscopy and atomic force microscopy to visualize these structures. Pili occur as single, double or higher order assemblies of filaments formed from monomers of the major pilin, BcpA, capped by the minor pilin, BcpB. Previous studies demonstrated that within assembled pili, four domains of BcpA -- CNA{sub 1}, CNA{sub 2}, XNA and CNA{sub 3} -- each acquire intramolecular lysine-asparagine isopeptide bonds formed via catalytic glutamic acid or aspartic acid residues. Here we showed that mutants unable to form the intramolecular isopeptide bonds in the CNA2 or CNA3 domains retain the ability to form pilus bundles. A mutant lacking the CNA{sub 1} isopeptide bond assembled deformed pilin subunits that failed to associate as bundles. X-ray crystallography revealed that the BcpA variant Asp{sup 312}Ala, lacking an aspartyl catalyst, did not generate the isopeptide bond within the jelly-roll structure of XNA. The Asp{sup 312}Ala mutant was also unable to form bundles and promoted the assembly of deformed pili. Thus, structural integrity of the CNA{sub 1} and XNA domains are determinants for the association of pili into higher order bundle structures and determine native pilus structure.

  4. Quantification and cluster analysis of actin cytoskeletal structures in plant cells: role of actin bundling in stomatal movement during diurnal cycles in Arabidopsis guard cells.

    PubMed

    Higaki, Takumi; Kutsuna, Natsumaro; Sano, Toshio; Kondo, Noriaki; Hasezawa, Seiichiro

    2010-01-01

    Manual evaluation of cellular structures is a popular approach in cell biological studies. However, such approaches are laborious and are prone to error, especially when large quantities of image data need to be analyzed. Here, we introduce an image analysis framework that overcomes these limitations by semi-automatic quantification and clustering of cytoskeletal structures. In our framework, cytoskeletal orientation, bundling and density are quantified by measurement of newly-developed, robust metric parameters from microscopic images. Thereafter, the microscopic images are classified without supervision by clustering based on the metric patterns. Clustering allows us to collectively investigate the large number of cytoskeletal structure images without laborious inspection. Application of this framework to images of GFP-actin binding domain 2 (GFP-ABD2)-labeled actin cytoskeletons in Arabidopsis guard cells determined that microfilaments (MFs) are radially oriented and transiently bundled in the process of diurnal stomatal opening. The framework also revealed that the expression of mouse talin GFP-ABD (GFP-mTn) continuously induced MF bundling and suppressed the diurnal patterns of stomatal opening, suggesting that changes in the level of MF bundling are crucial for promoting stomatal opening. These results clearly demonstrate the utility of our image analysis framework.

  5. Proper Cellular Reorganization during Drosophila Spermatid Individualization Depends on Actin Structures Composed of Two Domains, Bundles and Meshwork, That Are Differentially Regulated and Have Different Functions

    PubMed Central

    Noguchi, Tatsuhiko; Lenartowska, Marta; Rogat, Aaron D.; Frank, Deborah J.

    2008-01-01

    During spermatid individualization in Drosophila, actin structures (cones) mediate cellular remodeling that separates the syncytial spermatids into individual cells. These actin cones are composed of two structural domains, a front meshwork and a rear region of parallel bundles. We show here that the two domains form separately in time, are regulated by different sets of actin-associated proteins, can be formed independently, and have different roles. Newly forming cones were composed only of bundles, whereas the meshwork formed later, coincident with the onset of cone movement. Polarized distributions of myosin VI, Arp2/3 complex, and the actin-bundling proteins, singed (fascin) and quail (villin), occurred when movement initiated. When the Arp2/3 complex was absent, meshwork formation was compromised, but surprisingly, the cones still moved. Despite the fact that the cones moved, membrane reorganization and cytoplasmic exclusion were abnormal and individualization failed. In contrast, when profilin, a regulator of actin assembly, was absent, bundle formation was greatly reduced. The meshwork still formed, but no movement occurred. Analysis of this actin structure's formation and participation in cellular reorganization provides insight into how the mechanisms used in cell motility are modified to mediate motile processes within specialized cells. PMID:18353976

  6. Structure of Turbulent Flow in Subchannel of Rod Bundle Downstream of Spacer Grid With Hybrid Flow Mixing Device

    SciTech Connect

    Dong Seok Oh; Wang Kee In; Tae Hyun Chun

    2002-07-01

    An experiment was performed in a wind tunnel to investigate the flow structure in a rod bundle with a hybrid vane grid. The hybrid vane is a flow-mixing device, which consists of two pairs of primary and secondary vanes in a cell. The test section is a rectangular channel (300 mm x 300 mm x 2400 mm) including 3 x 3 rod (75 mm diameter) array with a spacer grid. The pitch to diameter ratio of the rod array is 1.33. The flow structures downstream the grid are measured at Reynolds number of 1.2 X 105 for 35-degree deflecting angle of the hybrid flow-mixing vane. The data are obtained for the distributions of the time mean axial velocity, lateral velocity, and turbulent intensities in 3 component directions over a center subchannel along axial locations and compared with the previous results of split vane grid that has two vanes in a cell. The results show that the mixing efficiency of the hybrid vane grid could be similar with that of the split vane grid because swirl factor of the hybrid vane grid is higher than that of split vane grid and the magnitude of axial turbulent intensity, turbulent diffusion coefficient, and cross flow factor is similar to each other in spite of differences of the vane numbers and shape in a cell between hybrid and split vane grids. (authors)

  7. An energy-based approach to packing the 7-helix bundle of bacteriorhodopsin.

    PubMed Central

    Chou, K. C.; Carlacci, L.; Maggiora, G. M.; Parodi, L. A.; Schulz, M. W.

    1992-01-01

    bundle structure has also been analyzed. Electrostatic interactions favor an antiparallel arrangement among adjacent helices. Nonbonded interactions, however, drive most of the closely packed helices into an arrangement in which the packing angles lie around -160 degrees, a value very near the -154 degrees value computed earlier as the most favorable packing arrangement of two poly(Ala) alpha-helices (Chou, K.-C., Némethy, G., & Scheraga, H.A., 1983, J. Phys. Chem. 87, 2869-2881). The structural features of the 7-helix bundle and their relationship to those found in typical 4-helix bundle proteins are also discussed.(ABSTRACT TRUNCATED AT 400 WORDS) PMID:1304922

  8. Structure and Mechanism of Proton Transport Through the Transmembrane Tetrameric M2 Protein Bundle of the Influenza A Virus

    SciTech Connect

    R Acharya; V Carnevale; G Fiorin; B Levine; A Polishchuk; V Balannick; I Samish; R Lamb; L Pinto; et al.

    2011-12-31

    The M2 proton channel from influenza A virus is an essential protein that mediates transport of protons across the viral envelope. This protein has a single transmembrane helix, which tetramerizes into the active channel. At the heart of the conduction mechanism is the exchange of protons between the His37 imidazole moieties of M2 and waters confined to the M2 bundle interior. Protons are conducted as the total charge of the four His37 side chains passes through 2{sup +} and 3{sup +} with a pK{sub a} near 6. A 1.65 {angstrom} resolution X-ray structure of the transmembrane protein (residues 25-46), crystallized at pH 6.5, reveals a pore that is lined by alternating layers of sidechains and well-ordered water clusters, which offer a pathway for proton conduction. The His37 residues form a box-like structure, bounded on either side by water clusters with well-ordered oxygen atoms at close distance. The conformation of the protein, which is intermediate between structures previously solved at higher and lower pH, suggests a mechanism by which conformational changes might facilitate asymmetric diffusion through the channel in the presence of a proton gradient. Moreover, protons diffusing through the channel need not be localized to a single His37 imidazole, but instead may be delocalized over the entire His-box and associated water clusters. Thus, the new crystal structure provides a possible unification of the discrete site versus continuum conduction models.

  9. Structure of the Newcastle disease virus hemagglutinin-neuraminidase (HN) ectodomain reveals a four-helix bundle stalk

    SciTech Connect

    Yuan, Ping; Swanson, Kurt A.; Leser, George P.; Paterson, Reay G.; Lamb, Robert A.; Jardetzky, Theodore S.

    2014-10-02

    The paramyxovirus hemagglutinin-neuraminidase (HN) protein plays multiple roles in viral entry and egress, including binding to sialic acid receptors, activating the fusion (F) protein to activate membrane fusion and viral entry, and cleaving sialic acid from carbohydrate chains. HN is an oligomeric integral membrane protein consisting of an N-terminal transmembrane domain, a stalk region, and an enzymatically active neuraminidase (NA) domain. Structures of the HN NA domains have been solved previously; however, the structure of the stalk region has remained elusive. The stalk region contains specificity determinants for F interactions and activation, underlying the requirement for homotypic F and HN interactions in viral entry. Mutations of the Newcastle disease virus HN stalk region have been shown to affect both F activation and NA activities, but a structural basis for understanding these dual affects on HN functions has been lacking. Here, we report the structure of the Newcastle disease virus HN ectodomain, revealing dimers of NA domain dimers flanking the N-terminal stalk domain. The stalk forms a parallel tetrameric coiled-coil bundle (4HB) that allows classification of extensive mutational data, providing insight into the functional roles of the stalk region. Mutations that affect both F activation and NA activities map predominantly to the 4HB hydrophobic core, whereas mutations that affect only F-protein activation map primarily to the 4HB surface. Two of four NA domains interact with the 4HB stalk, and residues at this interface in both the stalk and NA domain have been implicated in HN function.

  10. Modulating immunogenic properties of HIV-1 gp41 membrane-proximal external region by destabilizing six-helix bundle structure

    PubMed Central

    Banerjee, Saikat; Shi, Heliang; Habte, Habtom H.; Qin, Yali; Cho, Michael W.

    2016-01-01

    The C-terminal alpha-helix of gp41 membrane-proximal external region (MPER; 671NWFDITNWLWYIK683) encompassing 4E10/10E8 epitopes is an attractive target for HIV-1 vaccine development. We previously reported that gp41-HR1-54Q, a trimeric protein comprised of the MPER in the context of a stable six-helix bundle (6HB), induced strong immune responses against the helix, but antibodies were directed primarily against the non-neutralizing face of the helix. To better target 4E10/10E8 epitopes, we generated four putative fusion intermediates by introducing double point mutations or deletions in the heptad repeat region 1 (HR1) that destabilize 6HB in varying degrees. One variant, HR1-Δ10-54K, elicited antibodies in rabbits that targeted W672, I675 and L679, which are critical for 4E10/10E8 recognition. Overall, the results demonstrated that altering structural parameters of 6HB can influence immunogenic properties of the MPER and antibody targeting. Further exploration of this strategy could allow development of immunogens that could lead to induction of 4E10/10E8-like antibodies. PMID:26803471

  11. Modulating immunogenic properties of HIV-1 gp41 membrane-proximal external region by destabilizing six-helix bundle structure.

    PubMed

    Banerjee, Saikat; Shi, Heliang; Habte, Habtom H; Qin, Yali; Cho, Michael W

    2016-03-01

    The C-terminal alpha-helix of gp41 membrane-proximal external region (MPER; (671)NWFDITNWLWYIK(683)) encompassing 4E10/10E8 epitopes is an attractive target for HIV-1 vaccine development. We previously reported that gp41-HR1-54Q, a trimeric protein comprised of the MPER in the context of a stable six-helix bundle (6HB), induced strong immune responses against the helix, but antibodies were directed primarily against the non-neutralizing face of the helix. To better target 4E10/10E8 epitopes, we generated four putative fusion intermediates by introducing double point mutations or deletions in the heptad repeat region 1 (HR1) that destabilize 6HB in varying degrees. One variant, HR1-∆10-54K, elicited antibodies in rabbits that targeted W672, I675 and L679, which are critical for 4E10/10E8 recognition. Overall, the results demonstrated that altering structural parameters of 6HB can influence immunogenic properties of the MPER and antibody targeting. Further exploration of this strategy could allow development of immunogens that could lead to induction of 4E10/10E8-like antibodies.

  12. Modulating immunogenic properties of HIV-1 gp41 membrane-proximal external region by destabilizing six-helix bundle structure

    SciTech Connect

    Banerjee, Saikat; Shi, Heliang; Habte, Habtom H.; Qin, Yali; Cho, Michael W.

    2016-03-15

    The C-terminal alpha-helix of gp41 membrane-proximal external region (MPER; {sup 671}NWFDITNWLWYIK{sup 683}) encompassing 4E10/10E8 epitopes is an attractive target for HIV-1 vaccine development. We previously reported that gp41-HR1-54Q, a trimeric protein comprised of the MPER in the context of a stable six-helix bundle (6HB), induced strong immune responses against the helix, but antibodies were directed primarily against the non-neutralizing face of the helix. To better target 4E10/10E8 epitopes, we generated four putative fusion intermediates by introducing double point mutations or deletions in the heptad repeat region 1 (HR1) that destabilize 6HB in varying degrees. One variant, HR1-∆10-54K, elicited antibodies in rabbits that targeted W672, I675 and L679, which are critical for 4E10/10E8 recognition. Overall, the results demonstrated that altering structural parameters of 6HB can influence immunogenic properties of the MPER and antibody targeting. Further exploration of this strategy could allow development of immunogens that could lead to induction of 4E10/10E8-like antibodies. - Highlights: • Four gp41 MPER-based immunogens that resemble fusion intermediates were generated. • C-terminal region of MPER that contains 4E10/10E8 epitopes was highly immunogenic. • Altering 6HB structure can influence immunogenic properties of the MPER. • Induced antibodies targeted multiple residues critical for 4E10/10E8 binding. • Development of immunogens based on fusion intermediates is a promising strategy.

  13. Bundle Formation in Biomimetic Hydrogels.

    PubMed

    Jaspers, Maarten; Pape, A C H; Voets, Ilja K; Rowan, Alan E; Portale, Giuseppe; Kouwer, Paul H J

    2016-08-08

    Bundling of single polymer chains is a crucial process in the formation of biopolymer network gels that make up the extracellular matrix and the cytoskeleton. This bundled architecture leads to gels with distinctive properties, including a large-pore-size gel formation at very low concentrations and mechanical responsiveness through nonlinear mechanics, properties that are rarely observed in synthetic hydrogels. Using small-angle X-ray scattering (SAXS), we study the bundle formation and hydrogelation process of polyisocyanide gels, a synthetic material that uniquely mimics the structure and mechanics of biogels. We show how the structure of the material changes at the (thermally induced) gelation point and how factors such as concentration and polymer length determine the architecture, and with that, the mechanical properties. The correlation of the gel mechanics and the structural parameters obtained from SAXS experiments is essential in the design of future (synthetic) mimics of biopolymer networks.

  14. Anatomy of Mandibular Vital Structures. Part II: Mandibular Incisive Canal, Mental Foramen and Associated Neurovascular Bundles in Relation with Dental Implantology

    PubMed Central

    Wang, Hom-Lay; Sabalys, Gintautas

    2010-01-01

    ABSTRACT Objectives The purpose of the present study was to review the literature of how to identify the mental foramen, mandibular incisive canal and associated neurovascular bundles during implant surgery and how to detect and avoid the damage of these vital structures during implant therapy. Material and Methods Literature was selected through a search of PubMed, Embase and Cochrane electronic databases. The keywords used for search were mandibular incisive canal, mental foramen, mental nerve, anterior mental loop. The search was restricted to English language articles, published from 1979 to November 2009. Additionally, a manual search in the major anatomy, dental implant, and periodontal journals and books was performed. Results In total, 47 literature sources were obtained and reviewed. The morphology and variations of the mandibular incisive canal, mental foramen and associated neurovascular bundles were presented as two entities. It suggested that clinicians should carefully assess these vital structures to avoid nerve/artery damage. Conclusions The mandibular incisive canal, mental foramen and associated neurovascular bundles exist in different locations and possess many variations. Individual, gender, age, race, assessing technique used and degree of edentulous alveolar bone atrophy largely influence these variations. It suggests that the clinicians should carefully identify these anatomical landmarks, by analyzing all influencing factors, prior to their implant surgical operation. PMID:24421959

  15. Non-abelian higher gauge theory and categorical bundle

    NASA Astrophysics Data System (ADS)

    Viennot, David

    2016-12-01

    A gauge theory is associated with a principal bundle endowed with a connection permitting to define horizontal lifts of paths. The horizontal lifts of surfaces cannot be defined into a principal bundle structure. An higher gauge theory is an attempt to generalize the bundle structure in order to describe horizontal lifts of surfaces. A such attempt is particularly difficult for the non-abelian case. Some structures have been proposed to realize this goal (twisted bundle, gerbes with connection, bundle gerbe, 2-bundle). Each of them uses a category in place of the total space manifold of the usual principal bundle structure. Some of them replace also the structure group by a category (more precisely a Lie crossed module viewed as a category). But the base space remains still a simple manifold (possibly viewed as a trivial category with only identity arrows). We propose a new principal categorical bundle structure, with a Lie crossed module as structure groupoid, but with a base space belonging to a bigger class of categories (which includes non-trivial categories), that we called affine 2-spaces. We study the geometric structure of the categorical bundles built on these categories (which are a more complicated structure than the 2-bundles) and the connective structures on these bundles. Finally we treat an example interesting for quantum dynamics which is associated with the Bloch wave operator theory.

  16. Implementing sepsis bundles

    PubMed Central

    Jozwiak, Mathieu; Monnet, Xavier

    2016-01-01

    Sepsis bundles represent key elements of care regarding the diagnosis and treatment of patients with septic shock and allow ones to convert complex guidelines into meaningful changes in behavior. Sepsis bundles endorsed the early goal-directed therapy (EGDT) and their implementation resulted in an improved outcome of septic shock patients. They induced more consistent and timely application of evidence-based care and reduced practice variability. These benefits mainly depend on the compliance with sepsis bundles, highlighting the importance of dedicated performance improvement initiatives, such as multifaceted educational programs. Nevertheless, the interest of early goal directed therapy in septic shock patients compared to usual care has recently been questioned, leading to an update of sepsis bundles in 2015. These new sepsis bundles may also exhibit, as the previous bundles, some limits and pitfalls and the effects of their implementation still needs to be evaluated. PMID:27713890

  17. Structural changes in the vascular bundles of light-exposed and shaded spruce needles suffering from Mg deficiency and ozone pollution.

    PubMed

    Boxler-Baldoma, Carmen; Lütz, Cornelius; Heumann, Hans-Günther; Siefermann-Harms, Dorothea

    2006-02-01

    The correlation between structural changes of the vascular bundles and needle yellowing was examined for needles of damaged spruce (Picea abies (L.) Karst.) growing at a Mg-deficient and ozone polluted mountain site in the Central Black Forest (840m a.s.l.). In the previous year's sun-exposed needles, the following sequence of events was observed: (1) rapid needle yellowing, (2) hypertrophy and anomalous divisions of cambium cells, (3) phloem collapse, and, (4) production of atypical xylem tracheids. Under defined shade (reduction of the photosynthetically active photon flux density of the ambient light by 85-90%), the needles remained green, while the phloem collapsed completely within the first 6 weeks of shading; subsequently, a reversal of the collapse was observed. Under both light conditions, the content of Mg not bound to chlorophyll (Mg(free)) was in the range of 0.1 mg g(-1) needle dry matter, and hardly changed throughout the investigation period. After Mg fertilization, the Mg(free) level of the previous year's needles increased to 0.2 mg g(-1) dry matter, the light-exposed needles remained green, and the vascular bundles developed no anomalies. The data show that the rapid needle yellowing of ozone-exposed Mg-deficient needles did not depend on the collapse of the phloem. Mg deficiency played a key role in the development of anomalous vascular bundles under light, and also appears to explain the transient changes in sieve cell structure under shade. The role of Mg deficiency, rather than ozone pollution, in the damage of the sieve cells was confirmed in a long-term ozone exposure experiment with young clonal spruce growing under defined conditions.

  18. Assembly of hair bundles, an amazing problem for cell biology.

    PubMed

    Barr-Gillespie, Peter-G

    2015-08-01

    The hair bundle--the sensory organelle of inner-ear hair cells of vertebrates--exemplifies the ability of a cell to assemble complex, elegant structures. Proper construction of the bundle is required for proper mechanotransduction in response to external forces and to transmit information about sound and movement. Bundles contain tightly controlled numbers of actin-filled stereocilia, which are arranged in defined rows of precise heights. Indeed, many deafness mutations that disable hair-cell cytoskeletal proteins also disrupt bundles. Bundle assembly is a tractable problem in molecular and cellular systems biology; the sequence of structural changes in stereocilia is known, and a modest number of proteins may be involved.

  19. Requirements for contractility in disordered cytoskeletal bundles

    NASA Astrophysics Data System (ADS)

    Lenz, Martin; Gardel, Margaret L.; Dinner, Aaron R.

    2012-03-01

    Actomyosin contractility is essential for biological force generation, and is well understood in highly organized structures such as striated muscle. Additionally, actomyosin bundles devoid of this organization are known to contract both in vivo and in vitro, which cannot be described by standard muscle models. To narrow down the search for possible contraction mechanisms in these systems, we investigate their microscopic symmetries. We show that contractile behavior requires non-identical motors that generate large-enough forces to probe the nonlinear elastic behavior of F-actin. This suggests a role for filament buckling in the contraction of these bundles, consistent with recent experimental results on reconstituted actomyosin bundles.

  20. Multiwalled carbon nanotube reinforced biomimetic bundled gel fibres.

    PubMed

    Kim, Young-Jin; Yamamoto, Seiichiro; Takahashi, Haruko; Sasaki, Naruo; Matsunaga, Yukiko T

    2016-08-19

    This work describes the fabrication and characterization of hydroxypropyl cellulose (HPC)-based biomimetic bundled gel fibres. The bundled gel fibres were reinforced with multiwalled carbon nanotubes (MWCNTs). A phase-separated aqueous solution with MWCNT and HPC was transformed into a bundled fibrous structure after being injected into a co-flow microfluidic device and applying the sheath flow. The resulting MWCNT-bundled gel fibres consist of multiple parallel microfibres. The mechanical and electrical properties of MWCNT-bundled gel fibres were improved and their potential for tissue engineering applications as a cell scaffold was demonstrated.

  1. Mechanism of Interaction Between the General Anesthetic Halothane and a Model Ion Channel Protein, I: Structural Investigations via X-Ray Reflectivity from Langmuir Monolayers

    SciTech Connect

    Strzalka, J.; Liu, J; Tronin, A; Churbanova, I; Johansson, J; Blasie, J

    2009-01-01

    We previously reported the synthesis and structural characterization of a model membrane protein comprised of an amphiphilic 4-helix bundle peptide with a hydrophobic domain based on a synthetic ion channel and a hydrophilic domain with designed cavities for binding the general anesthetic halothane. In this work, we synthesized an improved version of this halothane-binding amphiphilic peptide with only a single cavity and an otherwise identical control peptide with no such cavity, and applied x-ray reflectivity to monolayers of these peptides to probe the distribution of halothane along the length of the core of the 4-helix bundle as a function of the concentration of halothane. At the moderate concentrations achieved in this study, approximately three molecules of halothane were found to be localized within a broad symmetric unimodal distribution centered about the designed cavity. At the lowest concentration achieved, of approximately one molecule per bundle, the halothane distribution became narrower and more peaked due to a component of {approx}19Angstroms width centered about the designed cavity. At higher concentrations, approximately six to seven molecules were found to be uniformly distributed along the length of the bundle, corresponding to approximately one molecule per heptad. Monolayers of the control peptide showed only the latter behavior, namely a uniform distribution along the length of the bundle irrespective of the halothane concentration over this range. The results provide insight into the nature of such weak binding when the dissociation constant is in the mM regime, relevant for clinical applications of anesthesia. They also demonstrate the suitability of both the model system and the experimental technique for additional work on the mechanism of general anesthesia, some of it presented in the companion parts II and III under this title.

  2. Sealed fiber-optic bundle feedthrough

    DOEpatents

    Tanner, Carol E.

    2002-01-01

    A sealed fiber-optic bundle feedthrough by which a multitude of fiber-optic elements may be passed through an opening or port in a wall or structure separating two environments at different pressures or temperatures while maintaining the desired pressure or temperature in each environment. The feedthrough comprises a rigid sleeve of suitable material, a bundle of individual optical fibers, and a resin-based sealing material that bonds the individual optical fibers to each other and to the rigid sleeve.

  3. Structural Alteration in Dermal Vessels and Collagen Bundles following Exposure of Skin Wound to Zeolite–Bentonite Compound

    PubMed Central

    Paydar, Shahram; Noorafshan, Ali; Jahanabadi, Shahram; Mortazavi, Seyed Mohammad Javad; Yahyavi, Seyedeh-Saeedeh; Khoshmohabat, Hadi

    2016-01-01

    Background. This study examines the impact of one-time direct application of haemostatic agent zeolite–bentonite powder to wounded skin on the healing process in rats. Materials and Methods. 24 male Sprague-Dawley rats were randomly allocated into two groups (n = 12): (1) the rats whose wounds were washed only with sterile normal saline (NS-treated) and (2) those treated with zeolite–bentonite compound (ZEO-treated). The wound was circular, full-thickness, and 2 cm in diameter. At the end of the 12th day, six animals from each group were randomly selected and terminated. The remaining rats were terminated after 21 days. Just after scarification, skin samples were excised and sent for stereological evaluation. Results. The results showed a significant difference between the two groups regarding the length density of the blood vessels and diameter of the large and small vessels on the 12th day after the wound was inflicted. Besides, volume density of both the dermis and collagen bundles was reduced by 25% in the ZEO-treated rats in comparison to the NS-treated animals after 21 days. Conclusions. One-time topical usage of zeolite–bentonite haemostatic powder on an animal skin wound might negatively affect the healing process through vasoconstriction and inhibition of neoangiogenesis. PMID:28116221

  4. A compactification of the moduli space of principal Higgs bundles over singular curves

    NASA Astrophysics Data System (ADS)

    Lo Giudice, Alessio; Pustetto, Andrea

    2016-12-01

    A principal Higgs bundle (P , ϕ) over a singular curve X is a pair consisting of a principal bundle P and a morphism ϕ : X →Ad P ⊗ ΩX1. We construct the moduli space of principal Higgs G-bundles over an irreducible singular curve X using the theory of decorated vector bundles. More precisely, given a faithful representation ρ : G → Sl(V) of G, we consider principal Higgs bundles as triples (E , q , φ) , where E is a vector bundle with rk(E) = dim V over the normalization X ˜ of X, q is a parabolic structure on E and φ :Ea,b → L is a morphism of bundles, L being a line bundle and Ea,b ≑(E⊗a) ⊕ b a vector bundle depending on the Higgs field ϕ and on the principal bundle structure.

  5. Phases Hybriding and Hierarchical Structuring of Mesoporous TiO2 Nanowire Bundles for High‐Rate and High‐Capacity Lithium Batteries

    PubMed Central

    Jin, Jun; Huang, Shao‐Zhuan; Liu, Jing; Chen, Li‐Hua; Yu, Yong; Wang, Hong‐En; Grey, Clare P.

    2015-01-01

    A hierarchical mesoporous TiO2 nanowire bundles (HM‐TiO2‐NB) superstructure with amorphous surface and straight nanochannels has been designed and synthesized through a templating method at a low temperature under acidic and wet conditions. The obtained HM‐TiO2‐NB superstructure demonstrates high reversible capacity, excellent cycling performance, and superior rate capability. Most importantly, a self‐improving phenomenon of Li+ insertion capability based on two simultaneous effects, the crystallization of amorphous TiO2 and the formation of Li2Ti2O4 crystalline dots on the surface of TiO2 nanowires, has been clearly revealed through ex situ transmission electron microcopy (TEM), high‐resolution transmission electron microscopy (HRTEM), X‐ray diffraction (XRD), Raman, and X‐ray photoelectron spectroscopy (XPS) techniques during the Li+ insertion process. When discharged for 100 cycles at 1 C, the HM‐TiO2‐NB exhibits a reversible capacity of 174 mA h g−1. Even when the current density is increased to 50 C, a very stable and extraordinarily high reversible capacity of 96 mA h g−1 can be delivered after 50 cycles. Compared to the previously reported results, both the lithium storage capacity and rate capability of our pure TiO2 material without any additives are among the highest values reported. The advanced electrochemical performance of these HM‐TiO2‐NB superstructures is the result of the synergistic effect of hybriding of amorphous and crystalline (anatase/rutile) phases and hierarchically structuring of TiO2 nanowire bundles. Our material could be a very promising anodic material for lithium‐ion batteries. PMID:27708997

  6. The structure of dimeric apolipoprotein A-IV and its mechanism of self-association.

    PubMed

    Deng, Xiaodi; Morris, Jamie; Dressmen, James; Tubb, Matthew R; Tso, Patrick; Jerome, W Gray; Davidson, W Sean; Thompson, Thomas B

    2012-05-09

    Apolipoproteins are key structural elements of lipoproteins and critical mediators of lipid metabolism. Their detergent-like properties allow them to emulsify lipid or exist in a soluble lipid-free form in various states of self-association. Unfortunately, these traits have hampered high-resolution structural studies needed to understand the biogenesis of cardioprotective high-density lipoproteins (HDLs). We derived a crystal structure of the core domain of human apolipoprotein (apo)A-IV, an HDL component and important mediator of lipid absorption. The structure at 2.4 Å depicts two linearly connected 4-helix bundles participating in a helix swapping arrangement that offers a clear explanation for how the protein self-associates as well as clues to the structure of its monomeric form. This also provides a logical basis for antiparallel arrangements recently described for lipid-containing particles. Furthermore, we propose a "swinging door" model for apoA-IV lipid association.

  7. The Structure of Dimeric Apolipoprotein A-IV and Its Mechanism of Self-Association

    SciTech Connect

    Deng, Xiaodi; Morris, Jamie; Dressmen, James; Tubb, Matthew R.; Tso, Patrick; Jerome, W. Gray; Davidson, W. Sean; Thompson, Thomas B.

    2012-08-10

    Apolipoproteins are key structural elements of lipoproteins and critical mediators of lipid metabolism. Their detergent-like properties allow them to emulsify lipid or exist in a soluble lipid-free form in various states of self-association. Unfortunately, these traits have hampered high-resolution structural studies needed to understand the biogenesis of cardioprotective high-density lipoproteins (HDLs). We derived a crystal structure of the core domain of human apolipoprotein (apo)A-IV, an HDL component and important mediator of lipid absorption. The structure at 2.4 {angstrom} depicts two linearly connected 4-helix bundles participating in a helix swapping arrangement that offers a clear explanation for how the protein self-associates as well as clues to the structure of its monomeric form. This also provides a logical basis for antiparallel arrangements recently described for lipid-containing particles. Furthermore, we propose a 'swinging door' model for apoA-IV lipid association.

  8. Structure and function analysis of the CMS/CIN85 protein family identifies actin-bundling properties and heterotypic-complex formation.

    PubMed

    Gaidos, Gabriel; Soni, Shefali; Oswald, Duane J; Toselli, Paul A; Kirsch, Kathrin H

    2007-07-15

    Members of the CMS/CIN85 protein family participate in clathrin-mediated endocytosis and play a crucial role in maintaining the kidney filtration barrier. The CMS protein structure includes three Src homology 3 (SH3) domains and a proline-rich (PR) region that is connected by a 'linker' sequence to a coiled-coil (CC) domain. We show that CMS is a component of special actin-rich adhesion structures--podosomes--and demonstrate specific actin-binding properties of CMS. We have found that the entire C-terminal half of CMS is necessary for efficient binding to filamentous actin (F-actin). CMS and CIN85 can crosslink F-actin into bundles, a function that depends on the PR region and the CC domain. Removal of these domains reduces migration. CMS can also form heterotypic complexes with CIN85. CIN85 is expressed as multiple isoforms that share the CC domain, suggesting that heterotypic interactions with CMS provides a mechanism to regulate CMS binding to F-actin and thus for modulating dynamic rearrangements of the cytoskeleton.

  9. Buckling behavior of individual and bundled microtubules.

    PubMed

    Soheilypour, Mohammad; Peyro, Mohaddeseh; Peter, Stephen J; Mofrad, Mohammad R K

    2015-04-07

    As the major structural constituent of the cytoskeleton, microtubules (MTs) serve a variety of biological functions that range from facilitating organelle transport to maintaining the mechanical integrity of the cell. Neuronal MTs exhibit a distinct configuration, hexagonally packed bundles of MT filaments, interconnected by MT-associated protein (MAP) tau. Building on our previous work on mechanical response of axonal MT bundles under uniaxial tension, this study is focused on exploring the compression scenarios. Intracellular MTs carry a large fraction of the compressive loads sensed by the cell and therefore, like any other column-like structure, are prone to substantial bending and buckling. Various biological activities, e.g., actomyosin contractility and many pathological conditions are driven or followed by bending, looping, and buckling of MT filaments. The coarse-grained model previously developed in our lab has been used to study the mechanical behavior of individual and bundled in vivo MT filaments under uniaxial compression. Both configurations show tip-localized, decaying, and short-wavelength buckling. This behavior highlights the role of the surrounding cytoplasm and MAP tau on MT buckling behavior, which allows MT filaments to bear much larger compressive forces. It is observed that MAP tau interconnections improve this effect by a factor of two. The enhanced ability of MT bundles to damp buckling waves relative to individual MT filaments, may be interpreted as a self-defense mechanism because it helps axonal MTs to endure harsher environments while maintaining their function. The results indicate that MT filaments in a bundle do not buckle simultaneously implying that the applied stress is not equally shared among the MT filaments, that is a consequence of the nonuniform distribution of MAP tau proteins along the bundle length. Furthermore, from a pathological perspective, it is observed that axonal MT bundles are more vulnerable to failure in

  10. Buckling Behavior of Individual and Bundled Microtubules

    PubMed Central

    Soheilypour, Mohammad; Peyro, Mohaddeseh; Peter, Stephen J.; Mofrad, Mohammad R.K.

    2015-01-01

    As the major structural constituent of the cytoskeleton, microtubules (MTs) serve a variety of biological functions that range from facilitating organelle transport to maintaining the mechanical integrity of the cell. Neuronal MTs exhibit a distinct configuration, hexagonally packed bundles of MT filaments, interconnected by MT-associated protein (MAP) tau. Building on our previous work on mechanical response of axonal MT bundles under uniaxial tension, this study is focused on exploring the compression scenarios. Intracellular MTs carry a large fraction of the compressive loads sensed by the cell and therefore, like any other column-like structure, are prone to substantial bending and buckling. Various biological activities, e.g., actomyosin contractility and many pathological conditions are driven or followed by bending, looping, and buckling of MT filaments. The coarse-grained model previously developed in our lab has been used to study the mechanical behavior of individual and bundled in vivo MT filaments under uniaxial compression. Both configurations show tip-localized, decaying, and short-wavelength buckling. This behavior highlights the role of the surrounding cytoplasm and MAP tau on MT buckling behavior, which allows MT filaments to bear much larger compressive forces. It is observed that MAP tau interconnections improve this effect by a factor of two. The enhanced ability of MT bundles to damp buckling waves relative to individual MT filaments, may be interpreted as a self-defense mechanism because it helps axonal MTs to endure harsher environments while maintaining their function. The results indicate that MT filaments in a bundle do not buckle simultaneously implying that the applied stress is not equally shared among the MT filaments, that is a consequence of the nonuniform distribution of MAP tau proteins along the bundle length. Furthermore, from a pathological perspective, it is observed that axonal MT bundles are more vulnerable to failure in

  11. Mechanism of Actin Filament Bundling by Fascin

    SciTech Connect

    Jansen, Silvia; Collins, Agnieszka; Yang, Changsong; Rebowski, Grzegorz; Svitkina, Tatyana; Dominguez, Roberto

    2013-03-07

    Fascin is the main actin filament bundling protein in filopodia. Because of the important role filopodia play in cell migration, fascin is emerging as a major target for cancer drug discovery. However, an understanding of the mechanism of bundle formation by fascin is critically lacking. Fascin consists of four {beta}-trefoil domains. Here, we show that fascin contains two major actin-binding sites, coinciding with regions of high sequence conservation in {beta}-trefoil domains 1 and 3. The site in {beta}-trefoil-1 is located near the binding site of the fascin inhibitor macroketone and comprises residue Ser-39, whose phosphorylation by protein kinase C down-regulates actin bundling and formation of filopodia. The site in {beta}-trefoil-3 is related by pseudo-2-fold symmetry to that in {beta}-trefoil-1. The two sites are {approx}5 nm apart, resulting in a distance between actin filaments in the bundle of {approx}8.1 nm. Residue mutations in both sites disrupt bundle formation in vitro as assessed by co-sedimentation with actin and electron microscopy and severely impair formation of filopodia in cells as determined by rescue experiments in fascin-depleted cells. Mutations of other areas of the fascin surface also affect actin bundling and formation of filopodia albeit to a lesser extent, suggesting that, in addition to the two major actin-binding sites, fascin makes secondary contacts with other filaments in the bundle. In a high resolution crystal structure of fascin, molecules of glycerol and polyethylene glycol are bound in pockets located within the two major actin-binding sites. These molecules could guide the rational design of new anticancer fascin inhibitors.

  12. Structure and Mutagenesis of the Parainfluenza Virus 5 Hemagglutinin-Neuraminidase Stalk Domain Reveals a Four-Helix Bundle and the Role of the Stalk in Fusion Promotion

    SciTech Connect

    Bose, Sayantan; Welch, Brett D.; Kors, Christopher A.; Yuan, Ping; Jardetzky, Theodore S.; Lamb, Robert A.

    2014-10-02

    Paramyxovirus entry into cells requires the fusion protein (F) and a receptor binding protein (hemagglutinin-neuraminidase [HN], H, or G). The multifunctional HN protein of some paramyxoviruses, besides functioning as the receptor (sialic acid) binding protein (hemagglutinin activity) and the receptor-destroying protein (neuraminidase activity), enhances F activity, presumably by lowering the activation energy required for F to mediate fusion of viral and cellular membranes. Before or upon receptor binding by the HN globular head, F is believed to interact with the HN stalk. Unfortunately, until recently none of the receptor binding protein crystal structures have shown electron density for the stalk domain. Parainfluenza virus 5 (PIV5) HN exists as a noncovalent dimer-of-dimers on the surface of cells, linked by a single disulfide bond in the stalk. Here we present the crystal structure of the PIV5-HN stalk domain at a resolution of 2.65 {angstrom}, revealing a four-helix bundle (4HB) with an upper (N-terminal) straight region and a lower (C-terminal) supercoiled part. The hydrophobic core residues are a mix of an 11-mer repeat and a 3- to 4-heptad repeat. To functionally characterize the role of the HN stalk in F interactions and fusion, we designed mutants along the PIV5-HN stalk that are N-glycosylated to physically disrupt F-HN interactions. By extensive study of receptor binding, neuraminidase activity, oligomerization, and fusion-promoting functions of the mutant proteins, we found a correlation between the position of the N-glycosylation mutants on the stalk structure and their neuraminidase activities as well as their abilities to promote fusion.

  13. Structure and mutagenesis of the parainfluenza virus 5 hemagglutinin-neuraminidase stalk domain reveals a four-helix bundle and the role of the stalk in fusion promotion.

    PubMed

    Bose, Sayantan; Welch, Brett D; Kors, Christopher A; Yuan, Ping; Jardetzky, Theodore S; Lamb, Robert A

    2011-12-01

    Paramyxovirus entry into cells requires the fusion protein (F) and a receptor binding protein (hemagglutinin-neuraminidase [HN], H, or G). The multifunctional HN protein of some paramyxoviruses, besides functioning as the receptor (sialic acid) binding protein (hemagglutinin activity) and the receptor-destroying protein (neuraminidase activity), enhances F activity, presumably by lowering the activation energy required for F to mediate fusion of viral and cellular membranes. Before or upon receptor binding by the HN globular head, F is believed to interact with the HN stalk. Unfortunately, until recently none of the receptor binding protein crystal structures have shown electron density for the stalk domain. Parainfluenza virus 5 (PIV5) HN exists as a noncovalent dimer-of-dimers on the surface of cells, linked by a single disulfide bond in the stalk. Here we present the crystal structure of the PIV5-HN stalk domain at a resolution of 2.65 Å, revealing a four-helix bundle (4HB) with an upper (N-terminal) straight region and a lower (C-terminal) supercoiled part. The hydrophobic core residues are a mix of an 11-mer repeat and a 3- to 4-heptad repeat. To functionally characterize the role of the HN stalk in F interactions and fusion, we designed mutants along the PIV5-HN stalk that are N-glycosylated to physically disrupt F-HN interactions. By extensive study of receptor binding, neuraminidase activity, oligomerization, and fusion-promoting functions of the mutant proteins, we found a correlation between the position of the N-glycosylation mutants on the stalk structure and their neuraminidase activities as well as their abilities to promote fusion.

  14. Acentric 2-D Ensembles of D-br-A Electron-Transfer Chromophores via Vectorial Orientation within Amphiphilic n-Helix Bundle Peptides for Photovoltaic Device Applications

    PubMed Central

    Koo, Jaseung; Park, Jaehong; Tronin, Andrey; Zhang, Ruili; Krishnan, Venkata; Strzalka, Joseph; Kuzmenko, Ivan; Fry, H. Christopher; Therien, Michael J.; Blasie, J. Kent

    2012-01-01

    We show that simply designed amphiphilic 4-helix bundle peptides can be utilized to vectorially-orient a linearly-extended Donor-bridge-Acceptor (D-br-A) electron transfer (ET) chromophore within its core. The bundle’s interior is shown to provide a unique solvation environment for the D-br-A assembly not accessible in conventional solvents, and thereby control the magnitudes of both light-induced ET and thermal charge recombination rate constants. The amphiphilicity of the bundle’s exterior was employed to vectorially-orient the peptide-chromophore complex at a liquid-gas interface, and its ends tailored for subsequent covalent attachment to an inorganic surface, via a “directed assembly” approach. Structural data, combined with evaluation of the excited state dynamics exhibited by these peptide-chromophore complexes, demonstrates that densely-packed, acentrically ordered 2-D monolayer ensembles of such complexes at high in-plane chromophore densities approaching 1/200Å2 offer unique potential as active layers in binary heterojucntion photovoltaic devices. PMID:22242787

  15. Bundled monocapillary optics

    DOEpatents

    Hirsch, Gregory

    2002-01-01

    A plurality of glass or metal wires are precisely etched to form the desired shape of the individual channels of the final polycapillary optic. This shape is created by carefully controlling the withdrawal speed of a group of wires from an etchant bath. The etched wires undergo a subsequent operation to create an extremely smooth surface. This surface is coated with a layer of material which is selected to maximize the reflectivity of the radiation being used. This reflective surface may be a single layer of material, or a multilayer coating for optimizing the reflectivity in a narrower wavelength interval. The collection of individual wires is assembled into a close-packed multi-wire bundle, and the wires are bonded together in a manner which preserves the close-pack configuration, irrespective of the local wire diameter. The initial wires are then removed by either a chemical etching procedure or mechanical force. In the case of chemical etching, the bundle is generally segmented by cutting a series of etching slots. Prior to removing the wire, the capillary array is typically bonded to a support substrate. The result of the process is a bundle of precisely oriented radiation-reflecting hollow channels. The capillary optic is used for efficiently collecting and redirecting the radiation from a source of radiation which could be the anode of an x-ray tube, a plasma source, the fluorescent radiation from an electron microprobe, a synchrotron radiation source, a reactor or spallation source of neutrons, or some other source.

  16. Complete bundle moduli reduction in heterotic string compactifications

    NASA Astrophysics Data System (ADS)

    Curio, Gottfried

    2012-05-01

    A major problem in discussing heterotic string models is the stabilisation of the many vector bundle moduli via the superpotential generated by world-sheet instantons. In arXiv:1110.6315 we have discussed the method to make a discrete twist in a large and much discussed class of vector bundles such that the generation number gets new contributions (which can be tuned suitably) and at the same time the space of bundle moduli of the new, twisted bundle is a proper subspace (where the 'new', non-generic twist class exists) of the original bundle moduli space; one thus gets a model, closely related to the original model one started with, but with enhanced flexibility in the generation number and where on the other hand the number of bundle moduli is somewhat reduced. Whereas in the previous paper the emphasis was on examples for the new flexibility in the generation number we here classify and describe explicitly the twists and give the precise reduction formula (for the number of moduli) for SU(5) bundles leading to an SU(5) GUT group in four dimensions. Finally we give various examples where the bundle moduli space is reduced completely: the superpotential for such rigid bundles becomes a function of the complex structure moduli alone (besides the exponential Kahler moduli contribution).

  17. Optimising UAV topographic surveys processed with structure-from-motion: Ground control quality, quantity and bundle adjustment

    NASA Astrophysics Data System (ADS)

    James, Mike R.; Robson, Stuart; d'Oleire-Oltmanns, Sebastian; Niethammer, Uwe

    2016-04-01

    Structure-from-motion (SfM) algorithms are greatly facilitating the production of detailed topographic models based on images collected by unmanned aerial vehicles (UAVs). However, SfM-based software does not generally provide the rigorous photogrammetric analysis required to fully understand survey quality. Consequently, error related to problems in control point data or the distribution of control points can remain undiscovered. Even if these errors are not large in magnitude, they can be systematic, and thus have strong implications for the use of products such as digital elevation models (DEMs) and orthophotos. Here, we develop a Monte Carlo approach to (1) improve the accuracy of products when SfM-based processing is used and (2) reduce the associated field effort by identifying suitable lower density deployments of ground control points. The method highlights over-parameterisation during camera self-calibration and provides enhanced insight into control point performance when rigorous error metrics are not available. Processing was implemented using commonly-used SfM-based software (Agisoft PhotoScan), which we augment with semi-automated and automated GCPs image measurement. We apply the Monte Carlo method to two contrasting case studies - an erosion gully survey (Taurodont, Morocco) carried out with an fixed-wing UAV, and an active landslide survey (Super-Sauze, France), acquired using a manually controlled quadcopter. The results highlight the differences in the control requirements for the two sites, and we explore the implications for future surveys. We illustrate DEM sensitivity to critical processing parameters and show how the use of appropriate parameter values increases DEM repeatability and reduces the spatial variability of error due to processing artefacts.

  18. Optimising UAV topographic surveys processed with structure-from-motion: Ground control quality, quantity and bundle adjustment

    NASA Astrophysics Data System (ADS)

    James, M. R.; Robson, S.; d'Oleire-Oltmanns, S.; Niethammer, U.

    2017-03-01

    Structure-from-motion (SfM) algorithms greatly facilitate the production of detailed topographic models from photographs collected using unmanned aerial vehicles (UAVs). However, the survey quality achieved in published geomorphological studies is highly variable, and sufficient processing details are never provided to understand fully the causes of variability. To address this, we show how survey quality and consistency can be improved through a deeper consideration of the underlying photogrammetric methods. We demonstrate the sensitivity of digital elevation models (DEMs) to processing settings that have not been discussed in the geomorphological literature, yet are a critical part of survey georeferencing, and are responsible for balancing the contributions of tie and control points. We provide a Monte Carlo approach to enable geomorphologists to (1) carefully consider sources of survey error and hence increase the accuracy of SfM-based DEMs and (2) minimise the associated field effort by robust determination of suitable lower-density deployments of ground control. By identifying appropriate processing settings and highlighting photogrammetric issues such as over-parameterisation during camera self-calibration, processing artefacts are reduced and the spatial variability of error minimised. We demonstrate such DEM improvements with a commonly-used SfM-based software (PhotoScan), which we augment with semi-automated and automated identification of ground control points (GCPs) in images, and apply to two contrasting case studies - an erosion gully survey (Taroudant, Morocco) and an active landslide survey (Super-Sauze, France). In the gully survey, refined processing settings eliminated step-like artefacts of up to 50 mm in amplitude, and overall DEM variability with GCP selection improved from 37 to 16 mm. In the much more challenging landslide case study, our processing halved planimetric error to 0.1 m, effectively doubling the frequency at which changes in

  19. Bundling of bacterial flagella

    NASA Astrophysics Data System (ADS)

    Powers, Thomas R.; van Parys, Annemarie J.; Breuer, Kenneth S.

    2002-03-01

    In bacterial chemotaxis, cells such as E. coli drift up chemical gradients by means of a directed random walk. Near the beginning of each step of a walk, the rotating helical flagella which propel the cell form a bundle. Using macroscopic experiments and numerical calculations, we study the viscous flows set up by two rotating helices. Our work illustrates the importance of geometry; for example, left-handed helices rotating counter-clockwise when viewed from the distal ends will inter-penetrate and synchronize when the pitch is shorter than the circumference. When the same helices turn clockwise, they fail to inter-penetrate.

  20. Electron diffraction and microscopy of single-wall carbon nanotube bundles produced by different methods

    NASA Astrophysics Data System (ADS)

    Colomer, J.-F.; Henrard, L.; Lambin, Ph.; van Tendeloo, G.

    2002-05-01

    The atomic structure of single-wall carbon nanotube bundles produced by three different techniques (laser ablation, electric arc discharge and catalytic chemical vapor deposition (CCVD)) has been characterized by electron diffraction and microscopy. Information on the helicity and the lattice packing has been obtained. Concerning the helicity, small bundles produced by CCVD exhibit only one or two tube helicities within a single bundle. The diffraction patterns of laser-ablation produced bundles also present well-defined but more diversified chiralities within a single bundle. By contrast the data acquired on bundles formed by arc discharge show a more diffuse pattern, characteristic of a random chirality dispersion within a single bundle. Concerning the lattice packing, informations are obtained via a detailed study of the equatorial line of the diffraction pattern for bundles produced by the three techniques. This electron diffraction study is completed by high-resolution electron microscopy.

  1. A four-helix bundle stores copper for methane oxidation

    PubMed Central

    Vita, Nicolas; Platsaki, Semeli; Baslé, Arnaud; Allen, Stephen J.; Paterson, Neil G.; Crombie, Andrew T.; Murrell, J. Colin; Waldron, Kevin J.; Dennison, Christopher

    2015-01-01

    Methane-oxidising bacteria (methanotrophs) require large quantities of copper for the membrane-bound (particulate) methane monooxygenase (pMMO)1,2. Certain methanotrophs are also able to switch to using the iron-containing soluble MMO (sMMO) to catalyse methane oxidation, with this switchover regulated by copper3,4. MMOs are Nature’s primary biological mechanism for suppressing atmospheric levels of methane, a potent greenhouse gas. Furthermore, methanotrophs and MMOs have enormous potential in bioremediation and for biotransformations producing bulk and fine chemicals, and in bioenergy, particularly considering increased methane availability from renewable sources and hydraulic fracturing of shale rock5,6. We have discovered and characterised a novel copper storage protein (Csp1) from the methanotroph Methylosinus trichosporium OB3b that is exported from the cytosol, and stores copper for pMMO. Csp1 is a tetramer of 4-helix bundles with each monomer binding up to 13 Cu(I) ions in a previously unseen manner via mainly Cys residues that point into the core of the bundle. Csp1 is the first example of a protein that stores a metal within an established protein-folding motif. This work provides a detailed insight into how methanotrophs accumulate copper for the oxidation of methane. Understanding this process is essential if the wide-ranging biotechnological applications of methanotrophs are to be realised. Cytosolic homologues of Csp1 are present in diverse bacteria thus challenging the dogma that such organisms do not use copper in this location. PMID:26308900

  2. Bundle Security Protocol for ION

    NASA Technical Reports Server (NTRS)

    Burleigh, Scott C.; Birrane, Edward J.; Krupiarz, Christopher

    2011-01-01

    This software implements bundle authentication, conforming to the Delay-Tolerant Networking (DTN) Internet Draft on Bundle Security Protocol (BSP), for the Interplanetary Overlay Network (ION) implementation of DTN. This is the only implementation of BSP that is integrated with ION.

  3. Cable Bundle Wire Derating

    NASA Technical Reports Server (NTRS)

    Lundquist, Ray A.; Leidecker, Henning

    1999-01-01

    The allowable operating currents of electrical wiring when used in the space vacuum environment is predominantly determined by the maximum operating temperature of the wire insulation. For Kapton insulated wire this value is 200 degree C. Guidelines provided in the Goddard Space Flight Center (GSFC) Preferred Parts List (PPL) limit the operating current of wire within vacuum to ensure the maximum insulation temperature is not exceeded. For 20 AWG wire, these operating parameters are: (1) 3.7 amps per wire (2) bundle of 15 or more wires (3) 70 C environment (4) vacuum of 10(exp -5) torr or less To determine the behavior and temperature of electrical wire at different operating conditions, a thermal vacuum test was performed on a representative electrical harness of the Hubble Space Telescope (HST) power distribution system. This paper describes the test and the results.

  4. Cable Bundle Wire Derating

    NASA Technical Reports Server (NTRS)

    Lundquist, Ray A.; Leidecker, Henning

    1998-01-01

    The allowable operating currents of electrical wiring when used in the space vacuum environment is predominantly determined by the maximum operating temperature of the wire insulation. For Kapton insulated wire this value is 200 C. Guidelines provided in the Goddard Space Flight Center (GSFC) Preferred Parts List (PPL) limit the operating current of wire within vacuum to ensure the maximum insulation temperature is not exceeded. For 20 AWG wire, these operating parameters are: (1) 3.7 amps per wire; (2) bundle of 15 or more wires; (3) 70 C environment: and (4) vacuum of 10(exp -5) torr or less. To determine the behavior and temperature of electrical wire at different operating conditions, a thermal vacuum test was performed on a representative electrical harness of the Hubble Space Telescope (HST) power distribution system. This paper describes the test and the results.

  5. Cable Bundle Wire Derating

    NASA Technical Reports Server (NTRS)

    Lundquist, Ray A.; Leidecker, Henning

    1998-01-01

    The allowable operating currents of electrical wiring when used in the space vacuum environment is predominantly determined by the maximum operating temperature of the wire insulation. For Kapton insulated wire this value is 200 C. Guidelines provided in the Goddard Space Flight Center (GSFC) Preferred Parts List (PPL) limit the operating current of wire within vacuum to ensure the maximum insulation temperature is not exceeded. For 20 AWG wire, these operating parameters are: 3.7 amps per wire, bundle of 15 or more wires, 70 C environment, and vacuum of 10(exp -5) torr or less. To determine the behavior and temperature of electrical wire at different operating conditions, a thermal vacuum test was performed on a representative electrical harness of the Hubble Space Telescope (HST) power distribution system. This paper describes the test and the results.

  6. Fiber bundle phase conjugate mirror

    DOEpatents

    Ward, Benjamin G.

    2012-05-01

    An improved method and apparatus for passively conjugating the phases of a distorted wavefronts resulting from optical phase mismatch between elements of a fiber laser array are disclosed. A method for passively conjugating a distorted wavefront comprises the steps of: multiplexing a plurality of probe fibers and a bundle pump fiber in a fiber bundle array; passing the multiplexed output from the fiber bundle array through a collimating lens and into one portion of a non-linear medium; passing the output from a pump collection fiber through a focusing lens and into another portion of the non-linear medium so that the output from the pump collection fiber mixes with the multiplexed output from the fiber bundle; adjusting one or more degrees of freedom of one or more of the fiber bundle array, the collimating lens, the focusing lens, the non-linear medium, or the pump collection fiber to produce a standing wave in the non-linear medium.

  7. Are accessory hearing structures linked to inner ear morphology? Insights from 3D orientation patterns of ciliary bundles in three cichlid species

    PubMed Central

    2014-01-01

    Background Cichlid fishes show considerable diversity in swim bladder morphology. In members of the subfamily Etroplinae, the connection between anterior swim bladder extensions and the inner ears enhances sound transmission and translates into an improved hearing ability. We tested the hypothesis that those swim bladder modifications coincide with differences in inner ear morphology and thus compared Steatocranus tinanti (vestigial swim bladder), Hemichromis guttatus (large swim bladder without extensions), and Etroplus maculatus (intimate connection between swim bladder and inner ears). Methodology and results We applied immunostaining together with confocal imaging and scanning electron microscopy for the investigation of sensory epithelia, and high-resolution, contrast-enhanced microCT imaging for characterizing inner ears in 3D, and evaluated otolith dimensions. Compared to S. tinanti and H. guttatus, inner ears of E. maculatus showed an enlargement of all three maculae, and a particularly large lacinia of the macula utriculi. While our analysis of orientation patterns of ciliary bundles on the three macula types using artificially flattened maculae uncovered rather similar orientation patterns of ciliary bundles, interspecific differences became apparent when illustrating the orientation patterns on the 3D models of the maculae: differences in the shape and curvature of the lacinia of the macula utriculi, and the anterior arm of the macula lagenae resulted in an altered arrangement of ciliary bundles. Conclusions Our results imply that improved audition in E. maculatus is associated not only with swim bladder modifications but also with altered inner ear morphology. However, not all modifications in E. maculatus could be connected to enhanced auditory abilities, and so a potential improvement of the vestibular sense, among others, also needs to be considered. Our study highlights the value of analyzing orientation patterns of ciliary bundles in their intact 3

  8. Modelling packing interactions in parallel helix bundles: pentameric bundles of nicotinic receptor M2 helices.

    PubMed

    Sankararamakrishnan, R; Sansom, M S

    1995-11-01

    The transbilayer pore of the nicotinic acetylcholine receptor (nAChR) is formed by a pentameric bundle of M2 helices. Models of pentameric bundles of M2 helices have been generated using simulated annealing via restrained molecular dynamics. The influence of: (a) the initial C alpha template; and (b) screening of sidechain electrostatic interactions on the geometry of the resultant M2 helix bundles is explored. Parallel M2 helices, in the absence of sidechain electrostatic interactions, pack in accordance with simple ridges-in-grooves considerations. This results in a helix crossing angle of ca. +12 degrees, corresponding to a left-handed coiled coil structure for the bundle as a whole. Tilting of M2 helices away from the central pore axis at their C-termini and/or inclusion of sidechain electrostatic interactions may perturb such ridges-in-grooves packing. In the most extreme cases right-handed coiled coils are formed. An interplay between inter-helix H-bonding and helix bundle geometry is revealed. The effects of changes in electrostatic screening on the dimensions of the pore mouth are described and the significance of these changes in the context of models for the nAChR pore domain is discussed.

  9. Bundle duct interaction studies for fuel assemblies. [LMFBR

    SciTech Connect

    Hsia, H.T.S.; Kaplan, S.

    1981-06-01

    It is known that the wire-wrapped rods and duct in an LMFBR are undergoing a gradual structural distortion from the initially uniform geometry under the combined effects of thermal expansion and irradiation induced swelling and creep. These deformations have a significant effect on flow characteristics, thus causing changes in thermal behavior such as cladding temperature and temperature distribution within a bundle. The temperature distribution may further enhance or retard irradiation induced deformation of the bundle. This report summarizes the results of the continuing effort in investigating the bundle-duct interaction, focusing on the need for the large development plant.

  10. Coupling a sensory hair-cell bundle to cyber clones enhances nonlinear amplification.

    PubMed

    Barral, Jérémie; Dierkes, Kai; Lindner, Benjamin; Jülicher, Frank; Martin, Pascal

    2010-05-04

    The vertebrate ear benefits from nonlinear mechanical amplification to operate over a vast range of sound intensities. The amplificatory process is thought to emerge from active force production by sensory hair cells. The mechano-sensory hair bundle that protrudes from the apical surface of each hair cell can oscillate spontaneously and function as a frequency-selective, nonlinear amplifier. Intrinsic fluctuations, however, jostle the response of a single hair bundle to weak stimuli and seriously limit amplification. Most hair bundles are mechanically coupled by overlying gelatinous structures. Here, we assayed the effects of mechanical coupling on the hair-bundle amplifier by combining dynamic force clamp of a hair bundle from the bullfrog's saccule with real-time stochastic simulations of hair-bundle mechanics. This setup couples the hair bundle to two virtual hair bundles, called cyber clones, and mimics a situation in which the hair bundle is elastically linked to two neighbors with similar characteristics. We found that coupling increased the coherence of spontaneous hair-bundle oscillations. By effectively reducing noise, the synergic interplay between the hair bundle and its cyber clones also enhanced amplification of sinusoidal stimuli. All observed effects of coupling were in quantitative agreement with simulations. We argue that the auditory amplifier relies on hair-bundle cooperation to overcome intrinsic noise limitations and achieve high sensitivity and sharp frequency selectivity.

  11. Evaluating big deal journal bundles

    PubMed Central

    Bergstrom, Theodore C.; Courant, Paul N.; McAfee, R. Preston; Williams, Michael A.

    2014-01-01

    Large commercial publishers sell bundled online subscriptions to their entire list of academic journals at prices significantly lower than the sum of their á la carte prices. Bundle prices differ drastically between institutions, but they are not publicly posted. The data that we have collected enable us to compare the bundle prices charged by commercial publishers with those of nonprofit societies and to examine the types of price discrimination practiced by commercial and nonprofit journal publishers. This information is of interest to economists who study monopolist pricing, librarians interested in making efficient use of library budgets, and scholars who are interested in the availability of the work that they publish. PMID:24979785

  12. Evaluating big deal journal bundles.

    PubMed

    Bergstrom, Theodore C; Courant, Paul N; McAfee, R Preston; Williams, Michael A

    2014-07-01

    Large commercial publishers sell bundled online subscriptions to their entire list of academic journals at prices significantly lower than the sum of their á la carte prices. Bundle prices differ drastically between institutions, but they are not publicly posted. The data that we have collected enable us to compare the bundle prices charged by commercial publishers with those of nonprofit societies and to examine the types of price discrimination practiced by commercial and nonprofit journal publishers. This information is of interest to economists who study monopolist pricing, librarians interested in making efficient use of library budgets, and scholars who are interested in the availability of the work that they publish.

  13. Spontaneous Oscillation by Hair Bundles of the Bullfrog's Sacculus

    PubMed Central

    Martin, Pascal; Bozovic, D.; Choe, Y.; Hudspeth, A. J.

    2007-01-01

    One prominent manifestation of mechanical activity in hair cells is spontaneous otoacoustic emission, the unprovoked emanation of sound by an internal ear. Because active hair-bundle motility probably constitutes the active process of non-mammalian hair cells, we investigated the ability of hair bundles in the bullfrog's sacculus to produce oscillations that might underlie spontaneous otoacoustic emissions. When maintained in the ear's normal ionic milieu, many bundles oscillated spontaneously through distances as great as 80 nm at frequencies of 5-50 Hz. Whole-cell recording disclosed that the positive phase of movement was associated with the opening of transduction channels. Gentamicin, which blocks transduction channels, reversibly arrested oscillation; drugs that affect the cAMP phosphorylation pathway and might influence myosin's activity altered the rate of oscillation. Increasing the Ca2+ concentration rendered oscillations faster and smaller until they were suppressed; lowering the Ca2+ concentration moderately with chelators had the opposite effect. When a bundle was offset with a stimulus fiber, oscillations were transiently suppressed but gradually resumed. Loading a bundle by partial displacement clamping, which simulated the presence of the accessory structures to which a bundle is ordinarily attached, increased the frequency and diminished the magnitude of oscillation. These observations accord with a model in which oscillations arise from the interplay of the hair bundle's negative stiffness with the activity of adaptation motors and with Ca2+-dependent relaxation of gating springs. PMID:12805294

  14. Tube bundle system

    PubMed Central

    Marchewka, W.; Mohamed, K.; Addis, J.; Karnack, F.

    2015-01-01

    A tube bundle system (TBS) is a mechanical system for continuously drawing gas samples through tubes from multiple monitoring points located in an underground coal mine. The gas samples are drawn via vacuum pump to the surface and are typically analyzed for oxygen, methane, carbon dioxide and carbon monoxide. Results of the gas analyses are displayed and recorded for further analysis. Trends in the composition of the mine atmosphere, such as increasing methane or carbon monoxide concentration, can be detected early, permitting rapid intervention that prevents problems, such as a potentially explosive atmosphere behind seals, fire or spontaneous combustion. TBS is a well-developed technology and has been used in coal mines around the world for more than 50 years. Most longwall coal mines in Australia deploy a TBS, usually with 30 to 40 monitoring points as part of their atmospheric monitoring. The primary uses of a TBS are detecting spontaneous combustion and maintaining sealed areas inert. The TBS might also provide mine atmosphere gas composition data after a catastrophe occurs in an underground mine, if the sampling tubes are not damaged. TBSs are not an alternative to statutory gas and ventilation airflow monitoring by electronic sensors or people; rather, they are an option to consider in an overall mine atmosphere monitoring strategy. This paper describes the hardware, software and operation of a TBS and presents one example of typical data from a longwall coal mine PMID:26306052

  15. Correlation of expression of the actin filament-bundling protein espin with stereociliary bundle formation in the developing inner ear.

    PubMed

    Li, Huawei; Liu, Hong; Balt, Steve; Mann, Sabine; Corrales, C Eduardo; Heller, Stefan

    2004-01-01

    The vertebrate hair cell is named for its stereociliary bundle or hair bundle that protrudes from the cell's apical surface. Hair bundles mediate mechanosensitivity, and their highly organized structure plays a critical role in mechanoelectrical transduction and amplification. The prototypical hair bundle is composed of individual stereocilia, 50-300 in number, depending on the animal species and on the type of hair cell. The assembly of stereocilia, in particular, the formation during development of individual rows of stereocilia with descending length, has been analyzed in great morphological detail. Electron microscopic studies have demonstrated that stereocilia are filled with actin filaments that are rigidly cross-linked. The growth of individual rows of stereocilia is associated with the addition of actin filaments and with progressively increasing numbers of cross-bridges between actin filaments. Recently, a mutation in the actin filament-bundling protein espin has been shown to underlie hair bundle degeneration in the deaf jerker mouse, subsequently leading to deafness. Our study was undertaken to investigate the appearance and developmental expression of espin in chicken inner ear sensory epithelia. We found that the onset of espin expression correlates with the initiation and growth of stereocilia bundles in vestibular and cochlear hair cells. Intense espin immunolabeling of stereocilia was colocalized with actin filament staining in all types of hair cells at all developmental stages and in adult animals. Our analysis of espin as a molecular marker for actin filament cross-links in stereocilia is in full accordance with previous morphological studies and implicates espin as an important structural component of hair bundles from initiation of bundle assembly to mature chicken hair cells.

  16. Generalized holomorphic bundles and the B-field action

    NASA Astrophysics Data System (ADS)

    Hitchin, Nigel

    2011-01-01

    On a generalized complex manifold, there is an associated definition of a generalized holomorphic bundle, introduced by Gualtieri. In the case of an ordinary complex structure, this notion yields an object which we call a co-Higgs bundle, and we consider the B-field action of a closed form of type (1,1), both local and global. The effect makes contact with both Nahm's equations and holomorphic gerbes.

  17. Systematic evaluation of bundled SPC water for biomolecular simulations.

    PubMed

    Gopal, Srinivasa M; Kuhn, Alexander B; Schäfer, Lars V

    2015-04-07

    In bundled SPC water models, the relative motion of groups of four water molecules is restrained by distance-dependent potentials. Bundled SPC models have been used in hybrid all-atom/coarse-grained (AA/CG) multiscale simulations, since they enable to couple atomistic SPC water with supra-molecular CG water models that effectively represent more than a single water molecule. In the present work, we systematically validated and critically tested bundled SPC water models as solvent for biomolecular simulations. To that aim, we investigated both thermodynamic and structural properties of various biomolecular systems through molecular dynamics (MD) simulations. Potentials of mean force of dimerization of pairs of amino acid side chains as well as hydration free energies of single side chains obtained with bundled SPC and standard (unrestrained) SPC water agree closely with each other and with experimental data. Decomposition of the hydration free energies into enthalpic and entropic contributions reveals that in bundled SPC, this favorable agreement of the free energies is due to a larger degree of error compensation between hydration enthalpy and entropy. The Ramachandran maps of Ala3, Ala5, and Ala7 peptides are similar in bundled and unrestrained SPC, whereas for the (GS)2 peptide, bundled water leads to a slight overpopulation of extended conformations. Analysis of the end-to-end distance autocorrelation times of the Ala5 and (GS)2 peptides shows that sampling in more viscous bundled SPC water is about two times slower. Pronounced differences between the water models were found for the structure of a coiled-coil dimer, which is instable in bundled SPC but not in standard SPC. In addition, the hydration of the active site of the serine protease α-chymotrypsin depends on the water model. Bundled SPC leads to an increased hydration of the active site region, more hydrogen bonds between water and catalytic triad residues, and a significantly slower exchange of water

  18. Fabrication of electrospun nanofibers bundles

    NASA Astrophysics Data System (ADS)

    Ye, Junjun; Sun, Daoheng

    2007-12-01

    Aligned nanofibers, filament bundle composed of large number of nanofibers have potential applications such as bio-material, composite material etc. A series of electrospinning experiments have been conducted to investigate the electrospinning process,in which some parameters such as polymer solution concentration, bias voltage, distance between spinneret and collector, solution flow rate etc have been setup to do the experiment of nanofibers bundles construction. This work firstly reports electrospun nanofiber bundle through non-uniform electrical field, and nanofibers distributed in different density on electrodes from that between them. Thinner nanofibers bundle with a few numbers of nanofiber is collected for 3 seconds; therefore it's also possible that the addressable single nanofiber could be collected to bridge two electrodes.

  19. Atrio-His bundle tracts.

    PubMed Central

    Brechenmacher, C

    1975-01-01

    The atrio-His bundle tracts are very rare; only two have been found in 687 hearts studied histologically. These tracts have a similar appearance to those of the atrioventricular bundle and form a complete bypass of the atrioventricular node. In their presence the electrocardiogram may show a short or normal PR interval. They may be responsible for some cases of very rapid ventricular response to supraventricular arrhythmias. Images PMID:1191446

  20. Phase Slips in Oscillatory Hair Bundles

    NASA Astrophysics Data System (ADS)

    Roongthumskul, Yuttana; Shlomovitz, Roie; Bruinsma, Robijn; Bozovic, Dolores

    2013-04-01

    Hair cells of the inner ear contain an active amplifier that allows them to detect extremely weak signals. As one of the manifestations of an active process, spontaneous oscillations arise in fluid immersed hair bundles of in vitro preparations of selected auditory and vestibular organs. We measure the phase-locking dynamics of oscillatory bundles exposed to low-amplitude sinusoidal signals, a transition that can be described by a saddle-node bifurcation on an invariant circle. The transition is characterized by the occurrence of phase slips, at a rate that is dependent on the amplitude and detuning of the applied drive. The resultant staircase structure in the phase of the oscillation can be described by the stochastic Adler equation, which reproduces the statistics of phase slip production.

  1. Assembly of mm-scale macrobridges with carbon nanotube bundles

    NASA Astrophysics Data System (ADS)

    Cao, Anyuan; Ajayan, P. M.; Ramanath, G.

    2003-07-01

    We report a chemical vapor deposition method for in situ bridging of mm-scale metal-contact patterns with bundles of multiwalled carbon nanotubes. The nanotube bundles synthesized from a hexane-ferrocene-thiophene mixture have a diameter of <50 μm and lengths up to millimeters, typically consisting of tens to hundreds of aligned nanotubes. These bundles are transported to the downstream end of the furnace, where they are captured by relief patterns of metal-contact tips. We can control the orientation and length of the nanotube bridges by preorganizing the metal tips to receive the bundles. This method is amenable to both scaling up, e.g., to create large-area arrays of nanotubes with contact electrodes, as well as scaling down, e.g., to bridge closely spaced contact structures.

  2. Molecular dynamics simulation of the M2 helices within the nicotinic acetylcholine receptor transmembrane domain: structure and collective motions.

    PubMed

    Hung, Andrew; Tai, Kaihsu; Sansom, Mark S P

    2005-05-01

    Multiple nanosecond duration molecular dynamics simulations were performed on the transmembrane region of the Torpedo nicotinic acetylcholine receptor embedded within a bilayer mimetic octane slab. The M2 helices and M2-M3 loop regions were free to move, whereas the outer (M1, M3, M4) helix bundle was backbone restrained. The M2 helices largely retain their hydrogen-bonding pattern throughout the simulation, with some distortions in the helical end and loop regions. All of the M2 helices exhibit bending motions, with the hinge point in the vicinity of the central hydrophobic gate region (corresponding to residues alphaL251 and alphaV255). The bending motions of the M2 helices lead to a degree of dynamic narrowing of the pore in the region of the proposed hydrophobic gate. Calculations of Born energy profiles for various structures along the simulation trajectory suggest that the conformations of the M2 bundle sampled correspond to a closed conformation of the channel. Principal components analyses of each of the M2 helices, and of the five-helix M2 bundle, reveal concerted motions that may be relevant to channel function. Normal mode analyses using the anisotropic network model reveal collective motions similar to those identified by principal components analyses.

  3. Ultrastructure of the three anterior cruciate ligament bundles.

    PubMed

    Suzuki, Daisuke; Otsubo, Hidenori; Watanabe, Takafumi; Kamiya, Tomoaki; Nagoya, Satoshi; Yamashita, Toshihiko; Shino, Konsei

    2015-10-01

    The anterior cruciate ligament (ACL) can be morphologically separated into not only two, but three bundles: the anteromedial-medial bundle (AM-MB), the anteromedial-lateral bundle (AM-LB), and the posterolateral bundle (PLB). Our hypothesis was that the three bundles differ in their microstructures. The purpose of this study was to clarify the microstructural differences among the three bundles. The normal ACLs of six fresh frozen cadavers were harvested. After the AM-MB, AM-LB, and PLB were identified, their fibril structures were analyzed using a transmission electron microscope. The fibril orientation, distribution pattern, and the mass average diameter of the fibrils (MAD) were compared among the AM-MBs, AM-LBs, and PLBs. The AM-MB and AM-LB fibrils were arranged mostly in the longitudinal direction, while the PLB fibrils were not aligned in a uniform direction. The fibril diameter distribution pattern of AM-MBs showed a bi-modal pattern due to the existence of small-diameter (30-40 nm) and large-diameter fibrils (70-80 nm), while that of the AM-LBs and PLBs had a unimodal pattern with one prominent high peak at a diameter of 50-60 nm. The mean MAD of the AM-MBs (83.2 - 11.2 nm) was significantly larger than that of the PLBs (66.8 - 7.7 nm), while it showed no significant difference compared to that of the AM-LBs (77.6 - 12.3 nm). The three ACL bundles have different ultrastructures. The AM-MB predominantly includes thick, uni-directionally oriented fibrils like tendons, while the PLB consists of thinner, multi-directionally oriented fibrils. The AM-LB shows an intermediate structure between the AM-MB and the PLB.

  4. Procedure for dispersing fiber bundles

    NASA Technical Reports Server (NTRS)

    Padilla, D.

    1974-01-01

    Fiber bundles are dispersed and fibers are cleaned within enclosed container; therefore, safety clothing, masks, and eye protection are not required. Procedure also could be used wherever materials, such as fiberglass or insulation, require dispersion, fluffing, or cleaning. Process could be automated into continuous operation for handling large quantities of fiber.

  5. Subroutine bundls, a fortran IV program to determine schreinemakers bundles

    NASA Astrophysics Data System (ADS)

    Linde, J.; Andrew, A. S.

    Given an entire set of relevant balanced equations, BUNDLS and associated subroutines select all invariant points and order univariant lines around these points. Invariant points are formed by taking every set of m absent phases from each reaction. All revelant univariant lines are ordered around each invariant point by a direct application of the rules of Schreinemakers. The program also calculates true angular values for PT, P-μ x1 or μ y-μ x diagrams.

  6. Reflooding of tight lattice bundles

    SciTech Connect

    Veteau, J.M.; Digonnet, A.; Deruaz, R. . Centre d'Etudes Nucleaires de Grenoble)

    1994-07-01

    Results regarding analytical bottom reflooding experiments in a 37- and a 127-heater rod bundle are presented for two different tight lattices. A comparison between these two geometries and with the standard pressurized water reactor (PWR) array shows a degradation of cooling efficiency when the cross section of the subchannels is decreased. The core heat sinks (guide thimbles and water tubes'') are seen to have a noticeable influence on the overall cooling of the bundle, and it is confirmed that a combined top/bottom injection does not significantly improve cooling efficiency. Calculations with CATHARE 1.3 code adjusted for the standard PWR array are presented (zero heat sinks), but results have to be confirmed over a wider range of parameters.

  7. Mathematical modelling for nanotube bundle oscillators

    NASA Astrophysics Data System (ADS)

    Thamwattana, Ngamta; Cox, Barry J.; Hill, James M.

    2009-07-01

    This paper investigates the mechanics of a gigahertz oscillator comprising a nanotube oscillating within the centre of a uniform concentric ring or bundle of nanotubes. The study is also extended to the oscillation of a fullerene inside a nanotube bundle. In particular, certain fullerene-nanotube bundle oscillators are studied, namely C60-carbon nanotube bundle, C60-boron nitride nanotube bundle, B36N36-carbon nanotube bundle and B36N36-boron nitride nanotube bundle. Using the Lennard-Jones potential and the continuum approach, we obtain a relation between the bundle radius and the radii of the nanotubes forming the bundle, as well as the optimum bundle size which gives rise to the maximum oscillatory frequency for both the fullerene and the nanotube bundle oscillators. While previous studies in this area have been undertaken through molecular dynamics simulations, this paper emphasizes the use of applied mathematical modelling techniques which provides considerable insight into the underlying mechanisms. The paper presents a synopsis of the major results derived in detail by the present authors in [1, 2].

  8. Surgical Management of Neurovascular Bundle in Uterine Fibroid Pseudocapsule

    PubMed Central

    Malvasi, Antonio; Hurst, Brad S.; Tsin, Daniel A.; Davila, Fausto; Dominguez, Guillermo; Dell'edera, Domenico; Cavallotti, Carlo; Negro, Roberto; Gustapane, Sarah; Teigland, Chris M.; Mettler, Liselotte

    2012-01-01

    The uterine fibroid pseudocapsule is a fibro-neurovascular structure surrounding a leiomyoma, separating it from normal peripheral myometrium. The fibroid pseudocapsule is composed of a neurovascular network rich in neurofibers similar to the neurovascular bundle surrounding a prostate. The nerve-sparing radical prostatectomy has several intriguing parallels to myomectomy. It may serve either as a useful model in modern fibroid surgical removal, or it may accelerate our understanding of the role of the fibrovascular bundle and neurotransmitters in the healing and restoration of reproductive potential after intracapsular myomectomy. Surgical innovations, such as laparoscopic or robotic myomectomy applied to the intracapsular technique with magnification of the fibroid pseudocapsule surrounding a leiomyoma, originated from the radical prostatectomy method that highlighted a careful dissection of the neurovascular bundle to preserve sexual functioning after prostatectomy. Gentle uterine leiomyoma detachment from the pseudocapsule neurovascular bundle has allowed a reduction in uterine bleeding and uterine musculature trauma with sparing of the pseudocapsule neuropeptide fibers. This technique has had a favorable impact on functionality in reproduction and has improved fertility outcomes. Further research should determine the role of the myoma pseudocapsule neurovascular bundle in the formation, growth, and pathophysiological consequences of fibroids, including pain, infertility, and reproductive outcomes. PMID:22906340

  9. A statistical model of protein binding in parallel actin bundles

    NASA Astrophysics Data System (ADS)

    Shin, Homin; Grason, Gregory; Purdy Drew, Kirstin; Wong, Gerard

    2010-03-01

    We propose a coarse-grained lattice model of cross-linking proteins in parallel actin bundles. Based on this model that captures the interplay between geometrical frustration of binding and the intrinsic flexibility of filaments and linkers, we predict a unique regular ground-state structure of fully cross-linked bundles. We also discuss the linker-dependent thermodynamic transition of actin filaments from their native state to the overtwisted state and map out the ``twist-state'' phase diagram in terms of linker flexibility as well as the chemical potential. A flexible linker regime exhibits a continuous spectrum of intermediate twist states, while a stiff linker regime only allows for untwisted actin filaments and fully overtwisted bundles. Our predictions compare well with small-angle scattering studies of bundles formed in the presence of two types of reconstituted cross-linking proteins, fascin and espin. Additionally, this study reveals how subtle differences in crosslinking agents themselves may be used by cells to achieve self-organized bundles with dramatically different properties.

  10. Role of the actin bundling protein fascin in growth cone morphogenesis: localization in filopodia and lamellipodia.

    PubMed

    Cohan, C S; Welnhofer, E A; Zhao, L; Matsumura, F; Yamashiro, S

    2001-02-01

    Growth cones at the distal tips of growing nerve axons contain bundles of actin filaments distributed throughout the lamellipodium and that project into filopodia. The regulation of actin bundling by specific actin binding proteins is likely to play an important role in many growth cone behaviors. Although the actin binding protein, fascin, has been localized in growth cones, little information is available on its functional significance. We used the large growth cones of the snail Helisoma to determine whether fascin was involved in temporal changes in actin filaments during growth cone morphogenesis. Fascin localized to radially oriented actin bundles in lamellipodia (ribs) and filopodia. Using a fascin antibody and a GFP fascin construct, we found that fascin incorporated into actin bundles from the beginning of growth cone formation at the cut end of axons. Fascin associated with most of the actin bundle except the proximal 6--12% adjacent to the central domain, which is the region associated with actin disassembly. Later, during growth cone morphogenesis when actin ribs shortened, the proximal fascin-free zone of bundles increased, but fascin was retained in the distal, filopodial portion of bundles. Treatment with tumor promoter 12-O-tetradecanoylphorbol-13-acetate (TPA), which phosphorylates fascin and decreases its affinity for actin, resulted in loss of all actin bundles from growth cones. Our findings suggest that fascin may be particularly important for the linear structure and dynamics of filopodia and for lamellipodial rib dynamics by regulating filament organization in bundles.

  11. Bagger-Witten line bundles on moduli spaces of elliptic curves

    NASA Astrophysics Data System (ADS)

    Gu, Wei; Sharpe, Eric

    2016-12-01

    In this paper, we discuss Bagger-Witten line bundles over moduli spaces of SCFTs. We review how in general they are “fractional” line bundles, not honest line bundles, twisted on triple overlaps. We discuss the special case of moduli spaces of elliptic curves in detail. There, the Bagger-Witten line bundle does not exist as an ordinary line bundle, but rather is necessarily fractional. As a fractional line bundle, it is nontrivial (though torsion) over the uncompactified moduli stack, and its restriction to the interior, excising corners with enhanced stabilizers, is also fractional. It becomes an honest line bundle on a moduli stack defined by a quotient of the upper half plane by a metaplectic group, rather than SL(2, ℤ). We review and compare to results of recent work arguing that well-definedness of the worldsheet metric implies that the Bagger-Witten line bundle admits a flat connection (which includes torsion bundles as special cases), and gives general arguments on the existence of universal structures on moduli spaces of SCFTs, in which superconformal deformation parameters are promoted to nondynamical fields ranging over the SCFT moduli space.

  12. Chern-Simons functional under gauge transformations on flat bundles

    NASA Astrophysics Data System (ADS)

    Byun, Yanghyun; Kim, Joohee

    2017-01-01

    We describe the effect of a gauge transformation on the Chern-Simons functional in a thorough and unifying manner. We use the assumptions that the structure group is compact and connected and, in particular, that the principal bundle is flat. The Chern-Simons functional we consider is the one defined by choosing a flat reference connection. The most critical step in arriving at the main result is to show both the existence and the uniqueness of a cohomology class on the adjoint bundle such that it is the class of the so-called Maurer-Cartan 3-form when restricted to each fiber.

  13. High thermodynamic stability of parametrically designed helical bundles

    SciTech Connect

    Huang, Po -Ssu; Oberdorfer, Gustav; Xu, Chunfu; Pei, Xue Y.; Nannenga, Brent L.; Rogers, Joseph M.; DiMaio, Frank; Gonen, Tamir; Luisi, Ben; Baker, David

    2014-10-24

    Here we describe a procedure for designing proteins with backbones produced by varying the parameters in the Crick coiled coil–generating equations. Combinatorial design calculations identify low-energy sequences for alternative helix supercoil arrangements, and the helices in the lowest-energy arrangements are connected by loop building. We design an antiparallel monomeric untwisted three-helix bundle with 80-residue helices, an antiparallel monomeric right-handed four-helix bundle, and a pentameric parallel left-handed five-helix bundle. The designed proteins are extremely stable (extrapolated ΔGfold > 60 kilocalories per mole), and their crystal structures are close to those of the design models with nearly identical core packing between the helices. The approach enables the custom design of hyperstable proteins with fine-tuned geometries for a wide range of applications.

  14. Magnetic Propulsion of Microswimmers with DNA-Based Flagellar Bundles.

    PubMed

    Maier, Alexander M; Weig, Cornelius; Oswald, Peter; Frey, Erwin; Fischer, Peer; Liedl, Tim

    2016-02-10

    We show that DNA-based self-assembly can serve as a general and flexible tool to construct artificial flagella of several micrometers in length and only tens of nanometers in diameter. By attaching the DNA flagella to biocompatible magnetic microparticles, we provide a proof of concept demonstration of hybrid structures that, when rotated in an external magnetic field, propel by means of a flagellar bundle, similar to self-propelling peritrichous bacteria. Our theoretical analysis predicts that flagellar bundles that possess a length-dependent bending stiffness should exhibit a superior swimming speed compared to swimmers with a single appendage. The DNA self-assembly method permits the realization of these improved flagellar bundles in good agreement with our quantitative model. DNA flagella with well-controlled shape could fundamentally increase the functionality of fully biocompatible nanorobots and extend the scope and complexity of active materials.

  15. Magnetic Propulsion of Microswimmers with DNA-Based Flagellar Bundles

    PubMed Central

    2016-01-01

    We show that DNA-based self-assembly can serve as a general and flexible tool to construct artificial flagella of several micrometers in length and only tens of nanometers in diameter. By attaching the DNA flagella to biocompatible magnetic microparticles, we provide a proof of concept demonstration of hybrid structures that, when rotated in an external magnetic field, propel by means of a flagellar bundle, similar to self-propelling peritrichous bacteria. Our theoretical analysis predicts that flagellar bundles that possess a length-dependent bending stiffness should exhibit a superior swimming speed compared to swimmers with a single appendage. The DNA self-assembly method permits the realization of these improved flagellar bundles in good agreement with our quantitative model. DNA flagella with well-controlled shape could fundamentally increase the functionality of fully biocompatible nanorobots and extend the scope and complexity of active materials. PMID:26821214

  16. High thermodynamic stability of parametrically designed helical bundles

    DOE PAGES

    Huang, Po -Ssu; Oberdorfer, Gustav; Xu, Chunfu; ...

    2014-10-24

    Here we describe a procedure for designing proteins with backbones produced by varying the parameters in the Crick coiled coil–generating equations. Combinatorial design calculations identify low-energy sequences for alternative helix supercoil arrangements, and the helices in the lowest-energy arrangements are connected by loop building. We design an antiparallel monomeric untwisted three-helix bundle with 80-residue helices, an antiparallel monomeric right-handed four-helix bundle, and a pentameric parallel left-handed five-helix bundle. The designed proteins are extremely stable (extrapolated ΔGfold > 60 kilocalories per mole), and their crystal structures are close to those of the design models with nearly identical core packing between themore » helices. The approach enables the custom design of hyperstable proteins with fine-tuned geometries for a wide range of applications.« less

  17. Time-dependent fiber bundles with local load sharing.

    PubMed

    Newman, W I; Phoenix, S L

    2001-02-01

    Fiber bundle models, where fibers have random lifetimes depending on their load histories, are useful tools in explaining time-dependent failure in heterogeneous materials. Such models shed light on diverse phenomena such as fatigue in structural materials and earthquakes in geophysical settings. Various asymptotic and approximate theories have been developed for bundles with various geometries and fiber load-sharing mechanisms, but numerical verification has been hampered by severe computational demands in larger bundles. To gain insight at large size scales, interest has returned to idealized fiber bundle models in 1D. Such simplified models typically assume either equal load sharing (ELS) among survivors, or local load sharing (LLS) where a failed fiber redistributes its load onto its two nearest flanking survivors. Such models can often be solved exactly or asymptotically in increasing bundle size, N, yet still capture the essence of failure in real materials. The present work focuses on 1D bundles under LLS. As in previous works, a fiber has failure rate following a power law in its load level with breakdown exponent rho. Surviving fibers under fixed loads have remaining lifetimes that are independent and exponentially distributed. We develop both new asymptotic theories and new computational algorithms that greatly increase the bundle sizes that can be treated in large replications (e.g., one million fibers in thousands of realizations). In particular we develop an algorithm that adapts several concepts and methods that are well-known among computer scientists, but relatively unknown among physicists, to dramatically increase the computational speed with no attendant loss of accuracy. We consider various regimes of rho that yield drastically different behavior as N increases. For 1/2< or =rho< or =1, ELS and LLS have remarkably similar behavior (they have identical lifetime distributions at rho=1) with approximate Gaussian bundle lifetime statistics and a

  18. Wire bundle formed into grids with minute interstices

    NASA Technical Reports Server (NTRS)

    Todd, H. H.

    1965-01-01

    Deforming the ends of a bundle of closely packed parallel wires to restrict the interstices to substantially uniform and minute dimensions produces grids or filters for ion engines. Porous metal structures made by this process are also used as fuel cell electrodes, diffusion membranes, and catalysts.

  19. Advanced tube-bundle rocket thrust chamber

    NASA Technical Reports Server (NTRS)

    Kazaroff, John M.; Pavli, Albert J.

    1990-01-01

    An advanced rocket thrust chamber for future space application is described along with an improved method of fabrication. Potential benefits of the concept are improved cyclic life, reusability, and performance. Performance improvements are anticipated because of the enhanced heat transfer into the coolant which will enable higher chamber pressure in expander cycle engines. Cyclic life, reusability and reliability improvements are anticipated because of the enhanced structural compliance inherent in the construction. The method of construction involves the forming of the combustion chamber with a tube-bundle of high conductivity copper or copper alloy tubes, and the bonding of these tubes by an electroforming operation. Further, the method of fabrication reduces chamber complexity by incorporating manifolds, jackets, and structural stiffeners while having the potential for thrust chamber cost and weight reduction.

  20. Vertical, Bubbly, Cross-Flow Characteristics over Tube Bundles

    NASA Astrophysics Data System (ADS)

    Iwaki, C.; Cheong, K. H.; Monji, H.; Matsui, G.

    2005-12-01

    Two-phase flow over tube bundles is commonly observed in shell and tube-type heat exchangers. However, only limited amount of data concerning flow pattern and void fraction exists due to the flow complexity and the difficulties in measurement. The detailed flow structure in tube bundles needs to be understood for reliable and effective design. Therefore, the objective of this study was to clarify the two-phase structure of cross-flow in tube bundles by PIV. Experiments were conducted using two types of models, namely in-line and staggered arrays with a pitch-to-diameter ratio of 1.5. Each test section contains 20 rows of five 15 mm O.D. tubes in each row. The experiment’s data were obtained under very low void fraction (α<0.02). Liquid and gas velocity data in the whole flow field were measured successfully by optical filtering and image processing. The structures of bubbly flow in the two different configurations of tube bundles were described in terms of the velocity vector field, turbulence intensity and void fraction.

  1. Solid-state NMR spectroscopy of the HIV gp41 membrane fusion protein supports intermolecular antiparallel β sheet fusion peptide structure in the final six-helix bundle state.

    PubMed

    Sackett, Kelly; Nethercott, Matthew J; Zheng, Zhaoxiong; Weliky, David P

    2014-03-06

    The HIV gp41 protein catalyzes fusion between viral and target cell membranes. Although the ~20-residue N-terminal fusion peptide (FP) region is critical for fusion, the structure of this region is not well characterized in large gp41 constructs that model the gp41 state at different times during fusion. This paper describes solid-state NMR (SSNMR) studies of FP structure in a membrane-associated construct (FP-Hairpin), which likely models the final fusion state thought to be thermostable trimers with six-helix bundle structure in the region C-terminal of the FP. The SSNMR data show that there are populations of FP-Hairpin with either α helical or β sheet FP conformation. For the β sheet population, measurements of intermolecular (13)C-(13)C proximities in the FP are consistent with a significant fraction of intermolecular antiparallel β sheet FP structure with adjacent strand crossing near L7 and F8. There appears to be negligible in-register parallel structure. These findings support assembly of membrane-associated gp41 trimers through interleaving of N-terminal FPs from different trimers. Similar SSNMR data are obtained for FP-Hairpin and a construct containing the 70 N-terminal residues of gp41 (N70), which is a model for part of the putative pre-hairpin intermediate state of gp41. FP assembly may therefore occur at an early fusion stage. On a more fundamental level, similar SSNMR data are obtained for FP-Hairpin and a construct containing the 34 N-terminal gp41 residues (FP34) and support the hypothesis that the FP is an autonomous folding domain.

  2. Defect-driven shape instabilities in cohesive filament bundles

    NASA Astrophysics Data System (ADS)

    Bruss, Isaac; Grason, Gregory

    When defects are incorporated into the lattice of a flexible 2D crystalline membrane, it buckles into a new configuration. Specifically, 5- and 7-fold disclinations produce conical- and saddle-like geometries respectively. For bundles composed of a crystalline array of cohesive flexible filaments, we propose a similar phenomena of defect-induced buckling. This revelation is fueled by a recently discovered mapping between the metric properties of a curved surface, and the inter-filament spacing within a deformed bundle. Using a combination of continuum elasticity theory and numerical simulations, we investigate the effects of defects in the cross section on a bundle's global structure. We find that positive disclinations promote the twisting of filaments around a central axis within the bundle, while negative disclinations promote twisting around two parallel axes simultaneously. Both instabilities are interpreted by means of their equivalent Gaussian curvature, and map appropriately to the the corresponding membrane responses. Additionally, for 5-fold disclinations we uncover a new equilibria structure, torsional wrinkling, with the intriguing ability to focus gradients in filament tilt much like curvature-focusing for the analogous membrane. NSF (CAREER) DMR-0955760.

  3. A comprehensive in-pile test of PWR fuel bundle

    NASA Astrophysics Data System (ADS)

    Kang, Rixin; Zhang, Shucheng; Chen, Dianshan

    1991-02-01

    An in-pile test of PWR fuel bundle has been conducted in HWRR at IAE of China. This paper describes the structure of the test bundle (3 × 3-2), fabrication process and quality control of the fuel rod, irradiation conditions and the main Post Irradiation Examination (PIE) results. The test fuel bundle was irradiated under the PWR operation and water chemistry conditions with an average linear power of 381 W/cm and reached an average burnup of 25010 MWd/tU of the fuel bundle. After the test, destructive and non-destructive examination of the fuel rods was conducted at hot laboratories. The fission gas release was 10.4-23%. The ridge height of cladding was 3 to 8 μm. The hydrogen content of the cladding was 80 to 140 ppm. The fuel stack height was increased by 2.9 to 3.3 mm. The relative irradiation growth was about 0.11 to 0.17% of the fuel rod length. During the irradiation test, no fuel rod failure or other abnormal phenomena had been found by the on-line fuel failure monitoring system of the test loop and water sampling analysis. The structure of the test fuel assembly was left undamaged without twist and detectable deformation.

  4. Fiber-bundle formalism for quantization in curved spaces

    SciTech Connect

    Wyrozumski, T. )

    1990-08-15

    We set up a geometrical formulation of the canonical quantization of a free Klein-Gordon field on a gravitational background. We introduce the notion of the Bogolubov bundle as the principal fiber bundle over the space of all Cauchy surfaces belonging to some fixed foliation of space-time, with the Bogolubov group as the structure group, as a tool in considering local Bogolubov transformations. Sections of the associated complex structure bundle have the meaning of attaching Hilbert spaces to Cauchy surfaces. We single out, as physical, sections defined by the equation of parallel transport on the Bogolubov bundle. The connection is then subjected to a certain nonlinear differential equation. We find a particular solution, which happens to coincide with a formula given by Parker for Robertson-Walker space-times. Finally, we adopt the adiabatic hypothesis as the physical input to the formalism and fix in this way a free parameter in the connection. Concluding, we comment on a possible geometrical interpretation of the regularization of the stress-energy tensor and on generalizations of the formalism toward quantum gravity.

  5. Cyclic hardening in bundled actin networks.

    PubMed

    Schmoller, K M; Fernández, P; Arevalo, R C; Blair, D L; Bausch, A R

    2010-01-01

    Nonlinear deformations can irreversibly alter the mechanical properties of materials. Most soft materials, such as rubber and living tissues, display pronounced softening when cyclically deformed. Here we show that, in contrast, reconstituted networks of crosslinked, bundled actin filaments harden when subject to cyclical shear. As a consequence, they exhibit a mechano-memory where a significant stress barrier is generated at the maximum of the cyclic shear strain. This unique response is crucially determined by the network architecture: at lower crosslinker concentrations networks do not harden, but soften showing the classic Mullins effect known from rubber-like materials. By simultaneously performing macrorheology and confocal microscopy, we show that cyclic shearing results in structural reorganization of the network constituents such that the maximum applied strain is encoded into the network architecture.

  6. Defects in crystalline packings of twisted filament bundles. II. Dislocations and grain boundaries

    NASA Astrophysics Data System (ADS)

    Azadi, Amir; Grason, Gregory M.

    2012-03-01

    Twisted and ropelike assemblies of filamentous molecules are common and vital structural elements in cells and tissues of living organisms. We study the intrinsic frustration occurring in these materials between the two-dimensional organization of filaments in cross section and out-of-plane interfilament twist in bundles. Using nonlinear continuum elasticity theory of columnar materials, we study the favorable coupling of twist-induced stresses to the presence of edge dislocations in the lattice packing of bundles, which leads to a restructuring of the ground-state order of these materials at intermediate twist. The stability of dislocations increases as both the degree of twist and lateral bundle size grow. We show that in ground states of large bundles, multiple dislocations pile up into linear arrays, radial grain boundaries, whose number and length grows with bundle twist, giving rise to a rich class of “polycrystalline” packings.

  7. Topological Defects in Twisted Bundles of Two-Dimensionally Ordered Filaments

    NASA Astrophysics Data System (ADS)

    Grason, Gregory M.

    2010-07-01

    Twisted assemblies of filaments in ropes, cables, and bundles are essential structural elements in both macroscopic materials and living organisms. We develop the unique, nonlinear elastic properties of twisted filament bundles that derive from generic properties of two-dimensional line-ordered materials. Continuum elasticity reveals a formal equivalence between the elastic stresses induced by bundle twist and those induced by the positive curvature in thin, elastic sheets. These geometrically induced stresses are screened by fivefold disclination defects in the lattice packing, and we predict a discrete spectrum of elastic-energy ground states associated with integer numbers of disclinations in cylindrical bundles. Finally, we show that elastic-energy ground states are extremely sensitive to the defect position in the cross section, with off-center disclinations driving the entire bundle to buckle and writhe.

  8. Liquid-like bundles of crosslinked actin filaments contract without motors

    NASA Astrophysics Data System (ADS)

    Weirich, Kimberly

    The actin cytoskeleton is a dynamic, structural material that drives cellular-scale deformations during processes such as cell migration and division. Motor proteins are responsible for actively driving many deformations by buckling and translocating actin filaments. However, there is evidence that deformations, such as the constriction of the actin bundle that drives the separation of cells during division, can occur without motors, mediated instead by crosslinker proteins. How might crosslinkers, independent of motors, drive contraction of a bundle? Using a model system of purified proteins, we show that crosslinkers, analogous to molecular cohesion, create an effective surface tension that induces bundle contraction. Crosslinked short actin filaments form micron-sized spindle-shaped bundles. Similar to tactoid granules found at the isotropic-nematic phase transition in liquid crystals, these bundles coarsen and coalesce like liquid droplets. In contrast, crosslinked long filaments coarsen into a steady state of bundles that are frozen in a solid-like network. Near the liquid-solid boundary, filaments of intermediate length initially form bundles that spontaneously contract into tactoid droplets. Our results, that crosslinked actin bundles are liquid-like with an effective surface tension, provide evidence for a mechanism of motor-independent contractility in biological materials.

  9. Drosophila singed, a fascin homolog, is required for actin bundle formation during oogenesis and bristle extension

    PubMed Central

    1994-01-01

    Drosophila singed mutants were named for their gnarled bristle phenotype but severe alleles are also female sterile. Recently, singed protein was shown to have 35% peptide identity with echinoderm fascin. Fascin is found in actin filament bundles in microvilli of sea urchin eggs and in filopodial extensions in coelomocytes. We show that Drosophila singed is required for actin filament bundle formation in the cytoplasm of nurse cells during oogenesis; in severe mutants, the absence of cytoplasmic actin filament bundles allows nurse cell nuclei to lodge in ring canals and block nurse cell cytoplasm transport. Singed is also required for organized actin filament bundle formation in the cellular extension that forms a bristle; in severe mutants, the small disorganized actin filament bundles lack structural integrity and allow bristles to bend and branch during extension. Singed protein is also expressed in migratory cells of the developing egg chamber and in the socket cell of the developing bristle, but no defect is observed in these cells in singed mutants. Purified, bacterially expressed singed protein bundles actin filaments in vitro with the same stoichiometry reported for purified sea urchin fascin. Singed-saturated actin bundles have a molar ratio of singed/actin of approximately 1:4.3 and a transverse cross-banding pattern of 12 nm seen using electron microscopy. Our results suggest that singed protein is required for actin filament bundle formation and is a Drosophila homolog of echinoderm fascin. PMID:8163553

  10. Are central line bundles and ventilator bundles effective in critically ill neonates and children?

    PubMed

    Smulders, Charlotte A; van Gestel, Josephus P J; Bos, Albert P

    2013-08-01

    Central line-associated bloodstream infections (CLABSI) and ventilator-associated pneumonia (VAP) are common problems in adult, pediatric (PICU) and neonatal (NICU) intensive care unit patients. Care bundles have been developed to prevent these hospital-acquired infections and to provide best possible care. Studies in adults have proven that care bundles contribute to a decrease in CLABSI and VAP rates. The purpose of this literature review was to critically appraise the known evidence of the effectiveness of central line bundles and ventilator bundles in PICU and NICU patients. The number of publications of central line bundles and ventilator bundles in PICU and NICU patients is limited compared to adults. Ten studies in PICU patients demonstrated a significant decrease in the CLABSI or VAP rate after implementation of the bundle. Two studies in neonates demonstrated a reduction in the CLABSI rate after implementation of the central line bundle. No studies on the effectiveness of the ventilator bundle in neonates were found. Bundle elements differed between studies, and their scientific basis was not as robust as in adults. Monitoring of compliance to bundle elements seems required for optimal reduction of CLABSI and VAP. Bundle components that focus on maintenance of a central line probably are important to prevent CLABSI in children.

  11. Crystal structures of MW1337R and lin2004: Representatives of a novel protein family that adopt a four-helical bundle fold

    SciTech Connect

    Kozbial, Piotr; Xu, Qingping; Chiu, Hsiu-Ju; McMullan, Daniel; Krishna, S. Sri; Miller, Mitchell D.; Abdubek, Polat; Acosta, Claire; Astakhova, Tamara; Axelrod, Herbert L.; Carlton, Dennis; Clayton, Thomas; Deller, Marc; Duan, Lian; Elias, Ylva; Elsliger, Marc-André; Feuerhelm, Julie; Grzechnik, Slawomir K.; Hale, Joanna; Han, Gye Won; Jaroszewski, Lukasz; Jin, Kevin K.; Klock, Heath E.; Knuth, Mark W.; Koesema, Eric; Kumar, Abhinav; Marciano, David; Morse, Andrew T.; Murphy, Kevin D.; Nigoghossian, Edward; Okach, Linda; Oommachen, Silvya; Reyes, Ron; Rife, Christopher L.; Spraggon, Glen; Trout, Christina V.; ban den Bedem, Henry; Weekes, Dana; White, Aprilfawn; Wolf, Guenter; Zubieta, Chloe; Hodgson, Keith O.; Wooley, John; Deacon, Ashley M.; Godzik, Adam; Lesley, Scott A.; Wilson, Ian A.

    2009-08-28

    To extend the structural coverage of proteins with unknown functions, we targeted a novel protein family (Pfam accession number PF08807, DUF1798) for which we proposed and determined the structures of two representative members. The MW1337R gene of Staphylococcus aureus subsp. aureus Rosenbach (Wood 46) encodes a protein with a molecular weight of 13.8 kDa (residues 1-116) and a calculated isoelectric point of 5.15. The lin2004 gene of the nonspore-forming bacterium Listeria innocua Clip11262 encodes a protein with a molecular weight of 14.6 kDa (residues 1-121) and a calculated isoelectric point of 5.45. MW1337R and lin2004, as well as their homologs, which, so far, have been found only in Bacillus, Staphylococcus, Listeria, and related genera (Geobacillus, Exiguobacterium, and Oceanobacillus), have unknown functions and are annotated as hypothetical proteins. The genomic contexts of MW1337R and lin2004 are similar and conserved in related species. In prokaryotic genomes, most often, functionally interacting proteins are coded by genes, which are colocated in conserved operons. Proteins from the same operon as MW1337R and lin2004 either have unknown functions (i.e., belong to DUF1273, Pfam accession number PF06908) or are similar to ypsB from Bacillus subtilis. The function of ypsB is unclear, although it has a strong similarity to the N-terminal region of DivIVA, which was characterized as a bifunctional protein with distinct roles during vegetative growth and sporulation. In addition, members of the DUF1273 family display distant sequence similarity with the DprA/Smf protein, which acts downstream of the DNA uptake machinery, possibly in conjunction with RecA. The RecA activities in Bacillus subtilis are modulated by RecU Holliday-junction resolvase. In all analyzed cases, the gene coding for RecU is in the vicinity of MW1337R, lin2004, or their orthologs, but on a different operon located in the complementary DNA strand. Here, we report the crystal structures

  12. Sperm bundle and reproductive organs of carabid beetles tribe Pterostichini (Coleoptera: Carabidae).

    PubMed

    Sasakawa, Kôji

    2007-05-01

    The morphological characteristics of sperm and reproductive organs may offer clues as to how reproductive systems have evolved. In this paper, the morphologies of the sperm and male reproductive organs of carabid beetles in the tribe Pterostichini (Coleoptera: Carabidae) are described, and the morphological associations among characters are examined. All species form sperm bundles in which the head of the sperm was embedded in a rod-shaped structure, i.e., spermatodesm. The spermatodesm shape (left-handed spiral, right-handed spiral, or without conspicuous spiral structure) and the condition of the sperm on the spermatodesm surface (with the tail free-moving or forming a thin, sheetlike structure) vary among species. In all species, the spiral directions of the convoluted seminal vesicles and vasa deferentia are the same on both sides of the body; that is, they show an asymmetric structure. The species in which the sperm bundle and the seminal vesicles both have a spiral structure could be classified into two types, with significant differences in sperm-bundle length between the two types. The species with a sperm-bundle spiral and seminal-vesicle spiral of almost the same diameter have longer sperm bundles than the species with a sperm-bundle spiral and seminal-vesicle tube of almost the same diameter. In the former type, the spiral directions of the sperm bundles and seminal vesicles are inevitably the same, whereas they differ in some species with the later type. Therefore, increased sperm bundle length appears to have been facilitated by the concordance of the sperm bundle's coiling direction with the coiling direction of the seminal vesicle.

  13. Ab initio study of MoS2 nanotube bundles

    NASA Astrophysics Data System (ADS)

    Verstraete, Matthieu; Charlier, Jean-Christophe

    2003-07-01

    Recently, the synthesis of a new phase of MoS2I1/3 stoichiometry was reported [M. Remskar, A. Mrzel, Z. Skraba, A. Jesih, M. Ceh, J. Demšar, P. Stadelmann, F. Lévy, and D. Mihailovic, Science 292, 479 (2001)]. Electron microscope images and diffraction data were interpreted to indicate bundles of sub-nanometer-diameter single-wall MoS2 nanotubes. After experimental characterization, the structure was attributed to an assembly of “armchair” nanotubes with interstitial iodine. Using first-principles total-energy calculations, bundles of MoS2 nanotubes with different topologies and stoichiometries are investigated. All of the systems are strongly metallic. Configurations with “zigzag” structures are found to be more stable energetically than the “armchair” ones, though all of the structures have similar stabilities. After relaxation, there remain several candidates which give a lattice parameter in relative agreement with experiment. Further, spin-polarized calculations indicate that a structure with armchair tubes iodine atoms in their center acquires a very large spontaneous magnetic moment of 12μB, while the other structures are nonmagnetic. Our ab initio calculations show that in most of the other structures, the tubes are very strongly bound together, and that the compounds should be considered as a crystal, rather than as a bundle of tubes in the habitual sense.

  14. Infinitesimal moduli of G2 holonomy manifolds with instanton bundles

    NASA Astrophysics Data System (ADS)

    de la Ossa, Xenia; Larfors, Magdalena; Svanes, Eirik E.

    2016-11-01

    We describe the infinitesimal moduli space of pairs ( Y, V) where Y is a manifold with G 2 holonomy, and V is a vector bundle on Y with an instanton connection. These structures arise in connection to the moduli space of heterotic string compactifications on compact and non-compact seven dimensional spaces, e.g. domain walls. Employing the canonical G 2 cohomology developed by Reyes-Carrión and Fernández and Ugarte, we show that the moduli space decomposes into the sum of the bundle moduli {H}_{{overset{ěe }{d}}_A}^1(Y,End(V)) plus the moduli of the G 2 structure preserving the instanton condition. The latter piece is contained in {H}_{overset{ěe }{d}θ}^1(Y,TY) , and is given by the kernel of a map overset{ěe }{F} which generalises the concept of the Atiyah map for holomorphic bundles on complex manifolds to the case at hand. In fact, the map overset{ěe }{F} is given in terms of the curvature of the bundle and maps {H}_{overset{ěe }{d}θ}^1(Y,TY) into {H}_{{overset{ěe }{d}}_A}^2(Y,End(V)) , and moreover can be used to define a cohomology on an extension bundle of TY by End( V). We comment further on the resemblance with the holomorphic Atiyah algebroid and connect the story to physics, in particular to heterotic compactifications on ( Y, V) when α' = 0.

  15. Effect of temperature on the formation of macroporous ZnO bundles and its application in photocatalysis.

    PubMed

    Muruganandham, M; Chen, I S; Wu, J J

    2009-12-30

    In this article, the effects of temperature on the formation of macroporous zinc oxide bundles and its photocatalytic activity under a variety of experimental conditions were reported. Thermal decomposition of zinc oxalate dihydrate yields hexagonal wurtzite-type ZnO bundles. Increased the decomposition temperatures resulted in decreased time required for bundle formation, with a corresponding increase in nanoparticles agglomeration. ZnO bundle formation was facilitated up to 200 degrees C after complete decomposition of zinc oxalate into ZnO at 400 degrees C in 15 min. However, low temperature (such as 100 degrees C) was not facilitated nanobundle formation, suggesting the importance of temperature on ZnO bundles formation. In addition, nitrogen adsorption experiments confirmed the presence of macroporous structure in the bundles. The photocatalytic decolorization and adsorption of methylene blue dye (MB) on ZnO bundles were investigated under UV light irradiation. The adsorption and decolorization efficiency of macroporous bundles were higher than the fused bundles. In conclusion, ZnO bundles are efficient and easily recyclable photocatalyst.

  16. Delay Tolerant Networking - Bundle Protocol Simulation

    NASA Technical Reports Server (NTRS)

    SeGui, John; Jenning, Esther

    2006-01-01

    In this paper, we report on the addition of MACHETE models needed to support DTN, namely: the Bundle Protocol (BP) model. To illustrate the useof MACHETE with the additional DTN model, we provide an example simulation to benchmark its performance. We demonstrate the use of the DTN protocol and discuss statistics gathered concerning the total time needed to simulate numerous bundle transmissions.

  17. Damping Properties of the Hair Bundle

    NASA Astrophysics Data System (ADS)

    Baumgart, Johannes; Kozlov, Andrei S.; Risler, Thomas; Hudspeth, A. J.

    2011-11-01

    The viscous liquid surrounding a hair bundle dissipates energy and dampens oscillations, which poses a fundamental physical challenge to the high sensitivity and sharp frequency selectivity of hearing. To identify the mechanical forces at play, we constructed a detailed finite-element model of the hair bundle. Based on data from the hair bundle of the bullfrog's sacculus, this model treats the interaction of stereocilia both with the surrounding liquid and with the liquid in the narrow gaps between the individual stereocilia. The investigation revealed that grouping stereocilia in a bundle dramatically reduces the total drag. During hair-bundle deflections, the tip links potentially induce drag by causing small but very dissipative relative motions between stereocilia; this effect is offset by the horizontal top connectors that restrain such relative movements at low frequencies. For higher frequencies the coupling liquid is sufficient to assure that the hair bundle moves as a unit with a low total drag. This work reveals the mechanical characteristics originating from hair-bundle morphology and shows quantitatively how a hair bundle is adapted for sensitive mechanotransduction.

  18. Critical heat flux predictions in rod bundles

    SciTech Connect

    Kao, S.P.; Kazimi, M.S.

    1983-01-01

    The prediction of critical heat flux (CHF) in rod bundles has been studied with both subchannel and bundle-average methods. The correlations of Biasi, Bowring, CISE-4, and Barnett were considered. The General Electric 9-rod bundle CHF data were used in the comparisons. Calculations were performed by the two-fluid subchannel code THERMIT-2. The results indicate that the subchannel method yields more conservative CHF predictions than the bundleaverage method. This is attributed to the two-phase turbulent mixing phenomenon in the bundle, which can be modeled only on a subchannel basis. The results also indicate that the CISE-4 correlation had the smallest error in prediction of transition boiling for both subchannel and bundle-average methods.

  19. Line bundle embeddings for heterotic theories

    NASA Astrophysics Data System (ADS)

    Nibbelin, Stefan Groot; Ruehle, Fabian

    2016-04-01

    In heterotic string theories consistency requires the introduction of a non-trivial vector bundle. This bundle breaks the original ten-dimensional gauge groups E8 × E8 or SO(32) for the supersymmetric heterotic string theories and SO(16) × SO(16) for the non-supersymmetric tachyon-free theory to smaller subgroups. A vast number of MSSM-like models have been constructed up to now, most of which describe the vector bundle as a sum of line bundles. However, there are several different ways of describing these line bundles and their embedding in the ten-dimensional gauge group. We recall and extend these different descriptions and explain how they can be translated into each other.

  20. Investigation of Swirling Flow in Rod Bundle Subchannels Using Computational Fluid Dynamics

    SciTech Connect

    Holloway, Mary V.; Beasley, Donald E.; Conner, Michael E.

    2006-07-01

    The fluid dynamics for turbulent flow through rod bundles representative of those used in pressurized water reactors is examined using computational fluid dynamics (CFD). The rod bundles of the pressurized water reactor examined in this study consist of a square array of parallel rods that are held on a constant pitch by support grids spaced axially along the rod bundle. Split-vane pair support grids are often used to create swirling flow in the rod bundle in an effort to improve the heat transfer characteristics for the rod bundle during both normal operating conditions and in accident condition scenarios. Computational fluid dynamics simulations for a two subchannel portion of the rod bundle were used to model the flow downstream of a split-vane pair support grid. A high quality computational mesh was used to investigate the choice of turbulence model appropriate for the complex swirling flow in the rod bundle subchannels. Results document a central swirling flow structure in each of the subchannels downstream of the split-vane pairs. Strong lateral flows along the surface of the rods, as well as impingement regions of lateral flow on the rods are documented. In addition, regions of lateral flow separation and low axial velocity are documented next to the rods. Results of the CFD are compared to experimental particle image velocimetry (PIV) measurements documenting the lateral flow structures downstream of the split-vane pairs. Good agreement is found between the computational simulation and experimental measurements for locations close to the support grid. (authors)

  1. Dimer model for Tau proteins bound in microtubule bundles

    NASA Astrophysics Data System (ADS)

    Hall, Natalie; Kluber, Alexander; Hayre, N. Robert; Singh, Rajiv; Cox, Daniel

    2013-03-01

    The microtubule associated protein tau is important in nucleating and maintaining microtubule spacing and structure in neuronal axons. Modification of tau is implicated as a later stage process in Alzheimer's disease, but little is known about the structure of tau in microtubule bundles. We present preliminary work on a proposed model for tau dimers in microtubule bundles (dimers are the minimal units since there is one microtubule binding domain per tau). First, a model of tau monomer was created and its characteristics explored using implicit solvent molecular dynamics simulation. Multiple simulations yield a partially collapsed form with separate positively/negatively charged clumps, but which are a factor of two smaller than required by observed microtubule spacing. We argue that this will elongate in dimer form to lower electrostatic energy at a cost of entropic ``spring'' energy. We will present preliminary results on steered molecular dynamics runs on tau dimers to estimate the actual force constant. Supported by US NSF Grant DMR 1207624.

  2. Preliminary report: NIF laser bundle review

    SciTech Connect

    Tietbohl, G.L.; Larson, D.W.; Erlandson, A.C.

    1995-08-31

    As requested in the guidance memo {sup 1}, this committe determined whether there are compelling reasons to recommend a change from the NIF CDR baseline laser. The baseline bundle design based on a tradeoff between cost and technical risk, which is replicated four times to create the required 192 beams. The baseline amplifier design uses bottom loading 1{times}4 slab and flashlamp cassettes for amplifier maintenance and large vacuum enclosures (2.5m high {times} 7m wide in cross-section for each of the two spatial filters in each of the four bundles. The laser beams are arranged in two laser bays configured in a u-shape around the target area. The entire bundle review effort was performed in a very short time (six weeks) and with limited resources (15 personnel part-time). This should be compared to the effort that produced the CDR design (12 months, 50 to 100 personnel). This committee considered three alternate bundle configurations (2{times}2, 4{times}2, and 4{times}4 bundles), and evaluated each bundle against the baseline design using the seven requested issues in the guidance memo: Cost; schedule; performance risk; maintainability/operability; hardware failure cost exposure; activation; and design flexibility. The issues were reviewed to identify differences between each alternate bundle configuration and the baseline.

  3. F actin bundles in Drosophila bristles. I. Two filament cross-links are involved in bundling

    PubMed Central

    1995-01-01

    Transverse sections though Drosophila bristles reveal 7-11 nearly round, plasma membrane-associated bundles of actin filaments. These filaments are hexagonally packed and in a longitudinal section they show a 12-nm periodicity in both the 1.1 and 1.0 views. From earlier studies this periodicity is attributable to cross-links and indicates that the filaments are maximally cross-linked, singed mutants also have 7-11 bundles, but the bundles are smaller, flattened, and the filaments within the bundles are randomly packed (not hexagonal); no periodicity can be detected in longitudinal sections. Another mutant, forked (f36a), also has 7-11 bundles but even though the bundles are very small, the filaments within them are hexagonally packed and display a 12-nm periodicity in longitudinal section. The singed-forked double mutant lacks filament bundles. Thus there are at least two species of cross-links between adjacent actin filaments. Hints of why two species of cross-links are necessary can be gleaned by studying bristle formation. Bristles sprout with only microtubules within them. A little later in development actin filaments appear. At early stages the filaments in the bundles are randomly packed. Later the filaments in the bundles become hexagonally packed and maximally cross-linked. We consider that the forked proteins may be necessary early in development to tie the filaments together in a bundle so that they can be subsequently zippered together by fascin (the singed gene product). PMID:7622563

  4. Validation of fuel bundle mechanical performance code ETOILE with bundle/duct interaction experimental data

    SciTech Connect

    Nakagawa, Masatoshi )

    1993-04-01

    Validation of the ETOILE code through a comparison with experimental bundle/duct interaction (BDI) data is discussed. ETOILE is a newly developed three-dimensional finite element program that uses a new analytical method to predict distortions and mechanical behavior in wire-wrapped-type fuel-pin bundles during irradiation in liquid-metal fast breeder reactor cores. Comparisons between the ETOILE solutions and the experimental data for bundle stiffnesses and minimum pin-to-pin and pin-to-duct clearances under bundle compression suggest that BDI performance can be predicted reasonably well with a suitable choice of friction coefficient and initial spiral wire displacement. Application of the code in the analysis of the mechanical behavior of soft bundles with distributed wireless pins is also presented to demonstrate the effectiveness of this design in reducing the interaction forces between a fuel-pin bundle and a duct wall under bundle compression. Agreement with the experimental data is fairly good for the reduction in bundle stiffness when the configuration is changed from the normal bundle to the soft bundle.

  5. Sperm bundle and reproductive organs of carabid beetles tribe Pterostichini (Coleoptera: Carabidae)

    NASA Astrophysics Data System (ADS)

    Sasakawa, Kôji

    2007-05-01

    The morphological characteristics of sperm and reproductive organs may offer clues as to how reproductive systems have evolved. In this paper, the morphologies of the sperm and male reproductive organs of carabid beetles in the tribe Pterostichini (Coleoptera: Carabidae) are described, and the morphological associations among characters are examined. All species form sperm bundles in which the head of the sperm was embedded in a rod-shaped structure, i.e., spermatodesm. The spermatodesm shape (left-handed spiral, right-handed spiral, or without conspicuous spiral structure) and the condition of the sperm on the spermatodesm surface (with the tail free-moving or forming a thin, sheetlike structure) vary among species. In all species, the spiral directions of the convoluted seminal vesicles and vasa deferentia are the same on both sides of the body; that is, they show an asymmetric structure. The species in which the sperm bundle and the seminal vesicles both have a spiral structure could be classified into two types, with significant differences in sperm-bundle length between the two types. The species with a sperm-bundle spiral and seminal-vesicle spiral of almost the same diameter have longer sperm bundles than the species with a sperm-bundle spiral and seminal-vesicle tube of almost the same diameter. In the former type, the spiral directions of the sperm bundles and seminal vesicles are inevitably the same, whereas they differ in some species with the later type. Therefore, increased sperm bundle length appears to have been facilitated by the concordance of the sperm bundle’s coiling direction with the coiling direction of the seminal vesicle.

  6. Probing the sliding interactions between bundled actin filaments

    NASA Astrophysics Data System (ADS)

    Ward, Andy; Dogic, Zvonimir

    2011-03-01

    Assemblies of filamentous biopolymers are hierarchical materials in which the properties of the overall assemblage are determined by structure and interactions between constituent particles at all hierarchical levels. For example, the overall bending rigidity of a two bundled filaments greatly depends on the bending rigidity of, and the adhesion strength between individual filaments. However, another property of importance is the ability for the filaments to slide freely against one another. Everyday experience indicates that it is much easier to bend a stack of papers in which individual sheets freely slide past each other than the same stack of papers in which all the sheets are irreversibly glued together. Similarly, in filamentous structures the ability for local re-arrangement is of the utmost importance in determining the properties of the structures observed. In order to study this phenomenon we create bundles of biopolymers by inducing attractive interactions between actin filaments via the depletion mechanism. We find that bundles of actin filaments to do not slide freely across one another. In order to characterize these sliding interactions, we perform active experiments using laser tweezers to pull one filament across the other at constant velocity.

  7. Increasing silk fibre strength through heterogeneity of bundled fibrils.

    PubMed

    Cranford, Steven W

    2013-05-06

    Can naturally arising disorder in biological materials be beneficial? Materials scientists are continuously attempting to replicate the exemplary performance of materials such as spider silk, with detailed techniques and assembly procedures. At the same time, a spider does not precisely machine silk-imaging indicates that its fibrils are heterogeneous and irregular in cross section. While past investigations either focused on the building material (e.g. the molecular scale protein sequence and behaviour) or on the ultimate structural component (e.g. silk threads and spider webs), the bundled structure of fibrils that compose spider threads has been frequently overlooked. Herein, I exploit a molecular dynamics-based coarse-grain model to construct a fully three-dimensional fibril bundle, with a length on the order of micrometres. I probe the mechanical behaviour of bundled silk fibrils with variable density of heterogenic protrusions or globules, ranging from ideally homogeneous to a saturated distribution. Subject to stretching, the model indicates that cooperativity is enhanced by contact through low-force deformation and shear 'locking' between globules, increasing shear stress transfer by up to 200 per cent. In effect, introduction of a random and disordered structure can serve to improve mechanical performance. Moreover, addition of globules allows a tuning of free volume, and thus the wettability of silk (with implications for supercontraction). These findings support the ability of silk to maintain near-molecular-level strength at the scale of silk threads, and the mechanism could be easily adopted as a strategy for synthetic fibres.

  8. The myosin X motor is optimized for movement on actin bundles

    PubMed Central

    Ropars, Virginie; Yang, Zhaohui; Isabet, Tatiana; Blanc, Florian; Zhou, Kaifeng; Lin, Tianming; Liu, Xiaoyan; Hissier, Pascale; Samazan, Frédéric; Amigues, Béatrice; Yang, Eric D.; Park, Hyokeun; Pylypenko, Olena; Cecchini, Marco; Sindelar, Charles V.; Sweeney, H. Lee; Houdusse, Anne

    2016-01-01

    Myosin X has features not found in other myosins. Its structure must underlie its unique ability to generate filopodia, which are essential for neuritogenesis, wound healing, cancer metastasis and some pathogenic infections. By determining high-resolution structures of key components of this motor, and characterizing the in vitro behaviour of the native dimer, we identify the features that explain the myosin X dimer behaviour. Single-molecule studies demonstrate that a native myosin X dimer moves on actin bundles with higher velocities and takes larger steps than on single actin filaments. The largest steps on actin bundles are larger than previously reported for artificially dimerized myosin X constructs or any other myosin. Our model and kinetic data explain why these large steps and high velocities can only occur on bundled filaments. Thus, myosin X functions as an antiparallel dimer in cells with a unique geometry optimized for movement on actin bundles. PMID:27580874

  9. Two-dimensional evaluation of 3D needled Cf/SiC composite fiber bundle surface

    NASA Astrophysics Data System (ADS)

    Wei, Jinhua; Lin, Bin; Cao, Xiaoyan; Zhang, Xiaofeng; Fang, Sheng

    2015-11-01

    The variations of fiber bundle surface microstructure have direct influence on the material performance, especially the friction and wear properties. Therefore, fiber bundle is the smallest evaluation unit of Cf/SiC composite surface. However, due to the anisotropy and inhomogeneity of Cf/SiC composite, it is difficult to evaluate the surface characteristics. Researchers think that two-dimensional evaluation is not suitable for the composites surface assessment any more because of its complex composition and varied surface structure. In this paper, a novel method is introduced for the evaluation of 3D needled Cf/SiC composite fiber bundle surface. On the level of Cf/SiC composite fiber bundle surface, two-dimensional evaluation method is adopted, with which the fiber bundle surface quality can be quantitatively evaluated by the two-dimensional surface roughness Ra. As long as the extracted surface profiles averagely distributed on Cf/SiC composite fiber bundle surface, with appropriate sampling length and sampling number, the mean value of Ra can estimate the whole surface roughness, thus reflecting the roughness degree of surface accurately. This study not only benefits the detection of 3D needled Cf/SiC composite fiber bundle surface quality, and lays a foundation on the evaluation of material functional features in further. And it corresponds to the convenient application in engineering practice.

  10. Actin-binding proteins sensitively mediate F-actin bundle stiffness

    NASA Astrophysics Data System (ADS)

    Claessens, Mireille M. A. E.; Bathe, Mark; Frey, Erwin; Bausch, Andreas R.

    2006-09-01

    Bundles of filamentous actin (F-actin) form primary structural components of a broad range of cytoskeletal processes including filopodia, sensory hair cell bristles and microvilli. Actin-binding proteins (ABPs) allow the cell to tailor the dimensions and mechanical properties of the bundles to suit specific biological functions. Therefore, it is important to obtain quantitative knowledge on the effect of ABPs on the mechanical properties of F-actin bundles. Here we measure the bending stiffness of F-actin bundles crosslinked by three ABPs that are ubiquitous in eukaryotes. We observe distinct regimes of bundle bending stiffness that differ by orders of magnitude depending on ABP type, concentration and bundle size. The behaviour observed experimentally is reproduced quantitatively by a molecular-based mechanical model in which ABP shearing competes with F-actin extension/compression. Our results shed new light on the biomechanical function of ABPs and demonstrate how single-molecule properties determine mesoscopic behaviour. The bending mechanics of F-actin fibre bundles are general and have implications for cytoskeletal mechanics and for the rational design of functional materials.

  11. SU(5) heterotic Standard Model bundles

    NASA Astrophysics Data System (ADS)

    Andreas, Björn; Hoffmann, Norbert

    2012-04-01

    We construct a class of stable SU(5) bundles on an elliptically fibered Calabi-Yau threefold with two sections, a variant of the ordinary Weierstrass fibration, which admits a free involution. The bundles are invariant under the involution, solve the topological constraint imposed by the heterotic anomaly equation and give three generations of Standard Model fermions after symmetry breaking by Wilson lines of the intermediate SU(5) GUT-group to the Standard Model gauge group. Among the solutions we find some which can be perturbed to solutions of the Strominger system. Thus these solutions provide a step toward the construction of phenomenologically realistic heterotic flux compactifications via non-Kähler deformations of Calabi-Yau geometries with bundles. This particular class of solutions involves a rank two hidden sector bundle and does not require background fivebranes for anomaly cancellation.

  12. Robust incoherent fiber optic bundle decoder

    NASA Technical Reports Server (NTRS)

    Roberts, Hilary E. (Inventor); DePlachett, Charles P. (Inventor); Deason, Brent E. (Inventor); Pilgrim, Robert A. (Inventor); Sanford, Harold S. (Inventor)

    2003-01-01

    Apparatus and method for calibrating an incoherent fiber optic bundle for use in transmitting visual or infrared coherent images. The apparatus includes a computer, a computer video monitor, an objective lens adjacent to the input end of the bundle, a second lens adjacent the output end of the bundle, and a CCD camera. The camera transmits video data to the monitor to produce an illuminated fiber optic image. The coordinates for the center of each fiber is found through an imaging process and the output fibers coordinates are related to the input fiber coordinates and processed in the computer to produce a mapping lookup-table (LUT) unique to the specific fiber bundle. Remapping of the LUT due to changes in the lens focus, CCD camera, or the addition of an infrared filter is accomplished by a software utility in the computer.

  13. Coupling and elastic loading affect the active response by the inner ear hair cell bundles.

    PubMed

    Strimbu, Clark Elliott; Fredrickson-Hemsing, Lea; Bozovic, Dolores

    2012-01-01

    Active hair bundle motility has been proposed to underlie the amplification mechanism in the auditory endorgans of non-mammals and in the vestibular systems of all vertebrates, and to constitute a crucial component of cochlear amplification in mammals. We used semi-intact in vitro preparations of the bullfrog sacculus to study the effects of elastic mechanical loading on both natively coupled and freely oscillating hair bundles. For the latter, we attached glass fibers of different stiffness to the stereocilia and observed the induced changes in the spontaneous bundle movement. When driven with sinusoidal deflections, hair bundles displayed phase-locked response indicative of an Arnold Tongue, with the frequency selectivity highest at low amplitudes and decreasing under stronger stimulation. A striking broadening of the mode-locked response was seen with increasing stiffness of the load, until approximate impedance matching, where the phase-locked response remained flat over the physiological range of frequencies. When the otolithic membrane was left intact atop the preparation, the natural loading of the bundles likewise decreased their frequency selectivity with respect to that observed in freely oscillating bundles. To probe for signatures of the active process under natural loading and coupling conditions, we applied transient mechanical stimuli to the otolithic membrane. Following the pulses, the underlying bundles displayed active movement in the opposite direction, analogous to the twitches observed in individual cells. Tracking features in the otolithic membrane indicated that it moved in phase with the bundles. Hence, synchronous active motility evoked in the system of coupled hair bundles by external input is sufficient to displace large overlying structures.

  14. Nanostructured Composites: Effective Mechanical Property Determination of Nanotube Bundles

    NASA Technical Reports Server (NTRS)

    Saether, E.; Pipes, R. B.; Frankland, S. J. V.

    2002-01-01

    Carbon nanotubes naturally tend to form crystals in the form of hexagonally packed bundles or ropes that should exhibit a transversely isotropic constitutive behavior. Although the intratube axial stiffness is on the order of 1 TPa due to a strong network of delocalized bonds, the intertube cohesive strength is orders of magnitude less controlled by weak, nonbonding van der Waals interactions. An accurate determination of the effective mechanical properties of nanotube bundles is important to assess potential structural applications such as reinforcement in future composite material systems. A direct method for calculating effective material constants is developed in the present study. The Lennard-Jones potential is used to model the nonbonding cohesive forces. A complete set of transverse moduli are obtained and compared with existing data.

  15. Is It Complete Left Bundle Branch Block? Just Ablate the Right Bundle.

    PubMed

    Ali, Hussam; Lupo, Pierpaolo; Foresti, Sara; De Ambroggi, Guido; Epicoco, Gianluca; Fundaliotis, Angelica; Cappato, Riccardo

    2017-03-01

    Complete left bundle branch block (LBBB) is established according to standard electrocardiographic criteria. However, functional LBBB may be rate-dependent or can perpetuate during tachycardia due to repetitive concealed retrograde penetration of impulses through the contralateral bundle "linking phenomenon." In this brief article, we present two patients with basal complete LBBB in whom ablating the right bundle unmasked the actual antegrade conduction capabilities of the left bundle. These cases highlight intriguing overlap between electrophysiological concepts of complete block, linking, extremely slow, and concealed conduction.

  16. Nursing Care Management: Influence on Bundled Payments.

    PubMed

    Lentz, Shaynie; Luther, Brenda

    Fragmented and uncoordinated care is the third highest driver of U.S. healthcare costs. Although less than 10% of patients experience uncoordinated care, these patients represent 36% of total healthcare costs; care management interaction makes a significant impact on the utilization of healthcare dollars. A literature search was conducted to construct a model of care coordination for elective surgical procedures by collecting best practices for acute, transitions, and post-acute care periods. A case study was used to demonstrate the model developed. Care management defines care coordination as a model of care to address improving patient and caregiver engagement, communication across settings of care, and ultimately improved patient outcomes of care. Nurse-led care coordination in the presurgical, inpatient, and post-acute care settings requires systems change and administrative support to effectively meet the goals of the Affordable Care Act of reducing redundancy and costs while improving the patient experience. Nursing is the lynchpin of care management processes in all settings of care; thus, this model of care coordination for elective surgical admissions can provide nursing care management leaders a comprehensive view of coordinating care for these patient across settings of care during the predetermined time period of care. As bundled payment structures increasingly affect hospital systems, nursing leaders need to be ready to create or improve their care management processes; care coordination is one such process requiring immediate attention.

  17. Modeling of imaging fiber bundles and adapted signal processing for fringe projection

    NASA Astrophysics Data System (ADS)

    Matthias, Steffen; Kästner, Markus; Reithmeier, Eduard

    2016-12-01

    Fringe projection profilometry is an established technique for capturing three-dimensional (3-D)-geometry data with high-point densities in short time. By combining fringe projection with endoscopy techniques, it is possible to perform inline inspection of industrial manufacturing processes. A new fringe projection system is presented, which uses flexible image fiber bundles to achieve versatile positioning of a compact sensor head. When measuring specimens with highly varying reflectivity, such as technical surfaces on tool geometries, measurement errors increase especially due to the crosstalk between individual fibers in the bundle. A detailed analysis of the transmission properties of the utilized fiber bundles is presented. It is shown that aliasing is avoided due to the non-regular grid structure of a bundle. Different techniques are demonstrated to reduce the effect of crosstalk on the phase evaluation. Measurements of highly reflective technical surfaces with different geometrical properties are shown.

  18. Adsorption behavior of ternary mixtures of noble gases inside single-walled carbon nanotube bundles

    NASA Astrophysics Data System (ADS)

    Foroutan, Masumeh; Nasrabadi, Amir Taghavi

    2010-09-01

    In order to study the gas-storage and gas-filtering capability of carbon nanotube (CNT) bundles simultaneously, we considered the adsorption behavior of a ternary mixture of noble gases, including Argon (Ar), Krypton (Kr), and Xenon (Xe), i.e., Ar-Kr-Xe mixture, on (10, 10) single-walled carbon nanotube (SWCNT) bundles. Molecular dynamics (MD) simulations at different temperatures of (75, 100, 150, 200, 250, and 300) K were performed, and adsorption energies, self-diffusion coefficients, activation energies, and radial distribution functions (RDFs) were computed to analyze the thermodynamics, transport and structural properties of the adsorption systems. It is observed that the SWCNT bundles have larger contents of heavier noble gases compared to the lighter ones. This interesting behavior of SWCNT bundles makes them proper candidates for gas-storage and gas molecular-sieving processes.

  19. Creep rupture of fiber bundles: A molecular dynamics investigation

    NASA Astrophysics Data System (ADS)

    Linga, G.; Ballone, P.; Hansen, Alex

    2015-08-01

    The creep deformation and eventual breaking of polymeric samples under a constant tensile load F is investigated by molecular dynamics based on a particle representation of the fiber bundle model. The results of the virtual testing of fibrous samples consisting of 40 000 particles arranged on Nc=400 chains reproduce characteristic stages seen in the experimental investigations of creep in polymeric materials. A logarithmic plot of the bundle lifetime τ versus load F displays a marked curvature, ruling out a simple power-law dependence of τ on F . A power law τ ˜F-4 , however, is recovered at high load. We discuss the role of reversible bond breaking and formation on the eventual fate of the sample and simulate a different type of creep testing, imposing a constant stress rate on the sample up to its breaking point. Our simulations, relying on a coarse-grained representation of the polymer structure, introduce new features into the standard fiber bundle model, such as real-time dynamics, inertia, and entropy, and open the way to more detailed models, aiming at material science aspects of polymeric fibers, investigated within a sound statistical mechanics framework.

  20. Evaluating pulp stiffness from fibre bundles by ultrasound

    NASA Astrophysics Data System (ADS)

    Karppinen, Timo; Montonen, Risto; Määttänen, Marjo; Ekman, Axel; Myllys, Markko; Timonen, Jussi; Hæggström, Edward

    2012-06-01

    A non-destructive ultrasonic tester was developed to measure the stiffness of pulp bundles. The mechanical properties of pulp are important when estimating the behaviour of paper under stress. Currently available pulp tests are tedious and alter the fibres structurally and mechanically. The developed tester employs (933 ± 15) kHz tweezer-like ultrasonic transducers and time-of-flight measurement through (9.0 ± 2.5) mm long and (0.8 ± 0.1) mm thick fibre bundles kept at (19.1 ± 0.4) °C and (62 ± 1)% RH. We determined the stiffness of soft wood pulps produced by three kraft pulping modifications: standard kraft pulp, (5.2 ± 0.4) GPa, prehydrolysis kraft pulp, (4.3 ± 0.4) GPa, and alkali extracted prehydrolysis kraft pulp, (3.3 ± 0.4) GPa. Prehydrolysis and alkali extraction processes mainly lowered the hemicellulose content of the pulps, which essentially decreased the fibre-wall stiffness hence impairing the stiffness of the fibre networks. Our results indicate that the method allows ranking of pulps according to their stiffness determined from bundle-like samples taken at an early phase of the papermaking process.

  1. Determinants of contractile forces generated in disorganized actomyosin bundles.

    PubMed

    Kim, Taeyoon

    2015-04-01

    Actomyosin machinery is a fundamental engine consisting mostly of actin filaments, molecular motors, and passive cross-linkers, generating mechanical forces required for biological processes of non-muscle cells such as cell migration, cytokinesis, and morphogenesis. Although the molecular and physical properties of key elements in the actomyosin machinery have been characterized well, it still remains unclear how macroscopic force buildup and dissipation in actomyosin networks and bundles depend on the microscopic properties of individual cytoskeletal components and their local interactions. To bridge such a gap between macroscopic and microscopic scales, we have developed a three-dimensional computational model of actomyosin bundles clamped to an elastic substrate with minimal components: actin filaments, passive cross-linkers, and active motors. Our model accounts for several key features neglected by previous studies despite their significance for force generation, such as realistic structure and kinetics of the motors. Using the model, we systematically investigated how net tension in actomyosin bundles is governed via interplay between motors and cross-linkers. We demonstrated motors can generate large tension on a bundle in the absence of cross-linkers in a very inefficient, unstable manner. Cross-linkers help motors to generate their maximum potential forces as well as enhance overall connectivity, leading to much higher efficiency and stability. We showed further that the cross-linkers behave as a molecular clutch with tunable friction which has quite distinct effects on net tension depending on their cross-linking angles. We also examined the source of symmetry breaking between tensile and compressive forces during tension generation process and discussed how the length and dynamics of actin filaments and the stiffness of the elastic substrate can affect the generated tension.

  2. The histology of retinal nerve fiber layer bundles and bundle defects.

    PubMed

    Radius, R L; Anderson, D R

    1979-05-01

    The fiber bundle striations recognized clinically in normal monkey eyes appear to be bundles of axons compartmentalized within glial tunnels formed by Müller's-cell processes, when viewed histologically. The dark boundaries that separate individual bundles are the broadened foot endings of these cells near the inner surface of the retina. Within one week after focal retinal photocoagulation, characteristic fundus changes could be seen in experimental eyes. In histologic sections of the involved retina, there was marked cystic degeneration of the retinal nerve fiber layer. Within one month, atrophy of distal axon segments was complete. With the drop-out of damaged axons and thinning of individual fiber bundles, retinal striations became less prominent. The resulting fundus picture in these experimental eyes is similar to fiber bundle defects that can be seen clinically in various neuro-ophthalmic disorders.

  3. Spectral bundles and the DRY-Conjecture

    NASA Astrophysics Data System (ADS)

    Andreas, Björn; Curio, Gottfried

    2012-04-01

    Supersymmetric heterotic string models, built from a Calabi-Yau threefold X endowed with a stable vector bundle V, usually start from a phenomenologically motivated choice of a bundle Vv in the visible sector, the spectral cover construction on an elliptically fibered X being a prominent example. The ensuing anomaly mismatch between c2(Vv) and c2(X), or rather the corresponding differential forms, is often 'solved', on the cohomological level, by including a fivebrane. This leads to the question whether the difference can be alternatively realized by a further stable bundle. The 'DRY'-conjecture of Douglas, Reinbacher and Yau in math.AG/0604597 gives a sufficient condition on cohomology classes on X to be realized as the Chern classes of a stable sheaf. In 1010.1644 [hep-th], we showed that infinitely many classes on X exist for which the conjecture is true. In this note, we give the sufficient condition for the mentioned fivebrane classes to be realized by a further stable bundle in the hidden sector. Using a result obtained in 1011.6246 [hep-th], we show that corresponding bundles exist, thereby confirming this version of the DRY-Conjecture.

  4. Photothermal imaging through coherent infrared bundles

    NASA Astrophysics Data System (ADS)

    Milstein, Yonat; Tepper, Michal; Harrington, James A.; Ben David, Moshe; Gannot, Israel

    2011-03-01

    This study aims to develop a photothermal imaging system through a coherent infrared bundle. This system will be used to determine the oxygenation level of various tissues, suspected malignant tissues in particular. The oxygenation estimation is preformed using a computerized algorithm. In order to evaluate the system, different bundle configurations were used for the determination of the optimal one. Bundle transmittance and the algorithm's estimation ability were measured, measurements were performed using agar phantoms consisting of varying ratios of Methylene Blue and ICG. A bundle consisting of 19 Teflon waveguides with a of 1.1mm was found to be the optimal configuration with an RMS of the error of 9.38%. At a second stage the system was validated on blood samples with varying oxygenation levels and there oxygenation levels were estimated. This stage had an RMS of the error of 10.16% for the oxygenation level estimation for samples with a 50% oxygenation level and higher. Once the basic system was validated successfully on agar phantoms and blood samples a portable system was designed and built in order to fit the system for portable use. The portable system consists of a white light illuminating source followed by filters transmitting certain wavelengths, a transmitting fiber, a thermal imaging bundle and a portable thermal camera. This portable system will be evaluated in order to have an adequate portable system for implementing the method out of the lab.

  5. Effects of oil on boiling of replacement refrigerants flowing normal to a tube bundle -- Part 1: R-123

    SciTech Connect

    Tatara, R.A.; Payvar, P.

    2000-07-01

    Local experimental heat transfer coefficients have been obtained for boiling refrigerant flowing up and across a tube bundle segment representing a full flooded evaporator tube bundle. R-123 data with a structured enhanced boiling tube are available.The refrigerant enters at 15% vapor quality and exits at nearly 100% vapor in order to simulate an actual flooded evaporator bundle. Both heat flux, 2,607 to 10,427 Btu/h{center_dot}ft{sup 2} (8,224 to 32,893 W/m{sup 2}), and oil content, 0--15% (by weight), are varied; the mass flux is not varied independently but set by the heat flux. Local tube and bulk fluid temperatures are measured directly, by thermocouples, to calculate the refrigerant-side heat transfer coefficients. The bundle segment saturation temperature set point (taken at the top of the tube bundle) is 40 F (4.4 C).

  6. The impact of Lean bundles on hospital performance: does size matter?

    PubMed

    Al-Hyari, Khalil; Abu Hammour, Sewar; Abu Zaid, Mohammad Khair Saleem; Haffar, Mohamed

    2016-10-10

    Purpose The purpose of this paper is to study the effect of the implementation of Lean bundles on hospital performance in private hospitals in Jordan and evaluate how much the size of organization can affect the relationship between Lean bundles implementation and hospital performance. Design/methodology/approach The research is considered as quantitative method (descriptive and hypothesis testing). Three statistical techniques were adopted to analyse the data. Structural equation modeling techniques and multi-group analysis were used to examine the research's hypothesis, and to perform the required statistical analysis of the data from the survey. Reliability analysis and confirmatory factor analysis were used to test the construct validity, reliability and measurement loadings that were performed. Findings Lean bundles have been identified as an effective approach that can dramatically improve the organizational performance of private hospitals in Jordan. Main Lean bundles - just in time, human resource management, and total quality management are applicable to large, small and medium hospitals without significant differences in advantages that depend on size. Originality/value According to the researchers' best knowledge, this is the first research that studies the impact of Lean bundles implementation in healthcare sector in Jordan. This research also makes a significant contribution for decision makers in healthcare to increase their awareness of Lean bundles.

  7. Focal loss of actin bundles causes microtubule redistribution and growth cone turning.

    PubMed

    Zhou, Feng-Quan; Waterman-Storer, Clare M; Cohan, Christopher S

    2002-05-27

    It is commonly believed that growth cone turning during pathfinding is initiated by reorganization of actin filaments in response to guidance cues, which then affects microtubule structure to complete the turning process. However, a major unanswered question is how changes in actin cytoskeleton are induced by guidance cues and how these changes are then translated into microtubule rearrangement. Here, we report that local and specific disruption of actin bundles from the growth cone peripheral domain induced repulsive growth cone turning. Meanwhile, dynamic microtubules within the peripheral domain were oriented into areas where actin bundles remained and were lost from areas where actin bundles disappeared. This resulted in directional microtubule extension leading to axon bending and growth cone turning. In addition, this local actin bundle loss coincided with localized growth cone collapse, as well as asymmetrical lamellipodial protrusion. Our results provide direct evidence, for the first time, that regional actin bundle reorganization can steer the growth cone by coordinating actin reorganization with microtubule dynamics. This suggests that actin bundles can be potential targets of signaling pathways downstream of guidance cues, providing a mechanism for coupling changes in leading edge actin with microtubules at the central domain during turning.

  8. Liquefaction of H{sub 2} molecules upon exterior surfaces of carbon nanotube bundles

    SciTech Connect

    Han, Sang Soo; Kang, Jeung Ku; Lee, Hyuck Mo; Duin, Adri C.T. van; Goddard, William A. III

    2005-05-16

    We have used molecular dynamics simulations to investigate interaction of H{sub 2} molecules on the exterior surfaces of carbon nanotubes (CNTs): single and bundle types. At 80 K and 10 MPa, it is found that charge transfer occurs from a low curvature region to a high curvature region of the deformed CNT bundle, which develops charge polarization only on the deformed structure. The long-range electrostatic interactions of polarized charges on the deformed CNT bundle with hydrogen molecules are observed to induce a high local-ordering of H{sub 2} gas that results in hydrogen liquefaction. Our predicted heat of hydrogen liquefaction on the CNT bundle is 97.6 kcal kg{sup -1}. On the other hand, hydrogen liquefaction is not observed in the CNT of a single type. This is because charge polarization is not developed on the single CNT as it is symmetrically deformed under the same pressure. Consequently, the hydrogen storage capacity on the CNT bundle is much higher due to liquefaction than that on the single CNT. Additionally, our results indicate that it would also be possible to liquefy H{sub 2} gas on a more strongly polarized CNT bundle at temperatures higher than 80 K.

  9. A Kinetic Model of Active Extensile Bundles

    NASA Astrophysics Data System (ADS)

    Goldstein, Daniel; Chakraborty, Bulbul; Baskaran, Aparna

    Recent experiments in active filament networks reveal interesting rheological properties (Dan Chen: APS March Meeting 2015 D49.00001). This system consumes ATP to produce an extensile motion in bundles of microtubules. This extension then leads to self generated stresses and spontaneous flows. We propose a minimal model where the activity is modeled by self-extending bundles that are part of a cross linked network. This network can reorganize itself through buckling of extending filaments and merging events that alter the topology of the network. We numerically simulate this minimal kinetic model and examine the emergent rheological properties and determine how stresses are generated by the extensile activity. We will present results that focus on the effects of confinement and network connectivity of the bundles on stress fluctuations and response of an active gel.

  10. Hydrodynamic interaction of bacterial flagella - flagellar bundling

    NASA Astrophysics Data System (ADS)

    Lim, Sookkyung

    2013-11-01

    Flagellar bundling is an important aspect of locomotion in bacteria such as Escherichia coli. To study the hydrodynamic behavior of helical flagella, we present a computational model that is based on the geometry of the bacterial flagellar filament at the micrometer scale. We consider two model flagella, each of which has a rotary motor at its base with the rotation rate of the motor set at 100 Hz. Bundling occurs when both flagella are left-handed helices turning counterclockwise (when viewed from the nonmotor end of the flagellum looking back toward the motor) or when both flagella are right-handed helices turning clockwise. Helical flagella of the other combinations of handedness and rotation direction do not bundle. In this work we use the generalized immersed boundary method combined with the unconstrained Kirchhoff rod theory, which allows us to study the complicated hydrodynamics of flagellar behavior. This is a joint work with Charlie Peskin at NYU. NSF

  11. Contour based object detection using part bundles

    PubMed Central

    Lu, ChengEn; Adluru, Nagesh; Ling, Haibin; Zhu, Guangxi; Latecki, Longin Jan

    2016-01-01

    In this paper we propose a novel framework for contour based object detection from cluttered environments. Given a contour model for a class of objects, it is first decomposed into fragments hierarchically. Then, we group these fragments into part bundles, where a part bundle can contain overlapping fragments. Given a new image with set of edge fragments we develop an efficient voting method using local shape similarity between part bundles and edge fragments that generates high quality candidate part configurations. We then use global shape similarity between the part configurations and the model contour to find optimal configuration. Furthermore, we show that appearance information can be used for improving detection for objects with distinctive texture when model contour does not sufficiently capture deformation of the objects.

  12. Generalized holomorphic structures

    NASA Astrophysics Data System (ADS)

    Wang, Yicao

    2014-12-01

    We define the notion of generalized holomorphic principal bundles and establish that their associated vector bundles of holomorphic representations are generalized holomorphic vector bundles defined by M. Gualtieri. Motivated by our definition, several examples of generalized holomorphic structures are constructed. A reduction theorem of generalized holomorphic structures is also included.

  13. Cortactin Adopts a Globular Conformation and Bundles Actin into Sheets

    SciTech Connect

    Cowieson, Nathan P.; King, Gordon; Cookson, David; Ross, Ian; Huber, Thomas; Hume, David A.; Kobe, Bostjan; Martin, Jennifer L.

    2008-08-21

    Cortactin is a filamentous actin-binding protein that plays a pivotal role in translating environmental signals into coordinated rearrangement of the cytoskeleton. The dynamic reorganization of actin in the cytoskeleton drives processes including changes in cell morphology, cell migration, and phagocytosis. In general, structural proteins of the cytoskeleton bind in the N-terminal region of cortactin and regulatory proteins in the C-terminal region. Previous structural studies have reported an extended conformation for cortactin. It is therefore unclear how cortactin facilitates cross-talk between structural proteins and their regulators. In the study presented here, circular dichroism, chemical cross-linking, and small angle x-ray scattering are used to demonstrate that cortactin adopts a globular conformation, thereby bringing distant parts of the molecule into close proximity. In addition, the actin bundling activity of cortactin is characterized, showing that fully polymerized actin filaments are bundled into sheet-like structures. We present a low resolution structure that suggests how the various domains of cortactin interact to coordinate its array of binding partners at sites of actin branching.

  14. Elevated temperature triggers human respiratory syncytial virus F protein six-helix bundle formation

    SciTech Connect

    Yunus, Abdul S.; Jackson, Trent P.; Crisafi, Katherine; Burimski, Irina; Kilgore, Nicole R.; Zoumplis, Dorian; Allaway, Graham P.; Wild, Carl T.; Salzwedel, Karl

    2010-01-20

    Human respiratory syncytial virus (RSV) is a major cause of severe lower respiratory tract infection in infants, immunocompromised patients, and the elderly. The RSV fusion (F) protein mediates fusion of the viral envelope with the target cell membrane during virus entry and is a primary target for antiviral drug and vaccine development. The F protein contains two heptad repeat regions, HR1 and HR2. Peptides corresponding to these regions form a six-helix bundle structure that is thought to play a critical role in membrane fusion. However, characterization of six-helix bundle formation in native RSV F protein has been hindered by the fact that a trigger for F protein conformational change has yet to be identified. Here we demonstrate that RSV F protein on the surface of infected cells undergoes a conformational change following exposure to elevated temperature, resulting in the formation of the six-helix bundle structure. We first generated and characterized six-helix bundle-specific antibodies raised against recombinant peptides modeling the RSV F protein six-helix bundle structure. We then used these antibodies as probes to monitor RSV F protein six-helix bundle formation in response to a diverse array of potential triggers of conformational changes. We found that exposure of 'membrane-anchored' RSV F protein to elevated temperature (45-55 deg. C) was sufficient to trigger six-helix bundle formation. Antibody binding to the six-helix bundle conformation was detected by both flow cytometry and cell-surface immunoprecipitation of the RSV F protein. None of the other treatments, including interaction with a number of potential receptors, resulted in significant binding by six-helix bundle-specific antibodies. We conclude that native, untriggered RSV F protein exists in a metastable state that can be converted in vitro to the more stable, fusogenic six-helix bundle conformation by an increase in thermal energy. These findings help to better define the mechanism of

  15. Atrial Septopulmonary Bundle of the Posterior Left Atrium Provides a Substrate for Atrial Fibrillation Initiation in a Model of Vagally Mediated Pulmonary Vein Tachycardia of the Structurally Normal Heart

    PubMed Central

    Klos, Matthew; Calvo, David; Yamazaki, Masatoshi; Zlochiver, Sharon; Mironov, Sergey; Cabrera, José-Angel; Sanchez-Quintana, Damian; Jalife, José; Berenfeld, Omer; Kalifa, Jérôme

    2009-01-01

    Background The posterior left atrium (PLA) and pulmonary veins (PVs) have been shown to be critical for atrial fibrillation (AF) initiation. However, the detailed mechanisms of reentry and AF initiation by PV impulses are poorly understood. We hypothesized that PV impulses trigger reentry and AF by undergoing wavebreaks as a result of sink-to-source mismatch at specific PV-PLA transitions along the septopulmonary bundle, where there are changes in thickness and fiber direction. Methods and Results In 7 Langendorff-perfused sheep hearts AF was initiated by a burst of 6 pulses (CL 80 to 150ms) delivered to the left inferior or right superior PV ostium 100 to 150 ms after the sinus impulse in the presence of 0.5 μmol/L acetylcholine. The exposed septal-PLA endocardial area was mapped with high spatio-temporal resolution (DI-4-ANEPPS, 1000-fr/s) during AF initiation. Isochronal maps for each paced beat preceding AF onset were constructed to localize areas of conduction delay and block. Phase movies allowed the determination of the wavebreak sites at the onset of AF. Thereafter, the PLA myocardial wall thickness was quantified by echocardiography, and the fiber direction in the optical field of view was determined after peeling off the endocardium. Finally, isochrone, phase and conduction velocity maps were superimposed on the corresponding anatomic pictures for each of the 28 episodes of AF initiation. The longest delays of the paced PV impulses, as well as the first wavebreak, occurred at those boundaries along the septopulmonary bundle that showed sharp changes in fiber direction and the largest and most abrupt increase in myocardial thickness. Conclusion Waves propagating from the PVs into the PLA originating from a simulated PV tachycardia triggered reentry and vagally mediated AF by breaking at boundaries along the septopulmonary bundle where abrupt changes in thickness and fiber direction resulted in sink-to-source mismatch and low safety for propagation. PMID

  16. Increasing silk fibre strength through heterogeneity of bundled fibrils

    PubMed Central

    Cranford, Steven W.

    2013-01-01

    Can naturally arising disorder in biological materials be beneficial? Materials scientists are continuously attempting to replicate the exemplary performance of materials such as spider silk, with detailed techniques and assembly procedures. At the same time, a spider does not precisely machine silk—imaging indicates that its fibrils are heterogeneous and irregular in cross section. While past investigations either focused on the building material (e.g. the molecular scale protein sequence and behaviour) or on the ultimate structural component (e.g. silk threads and spider webs), the bundled structure of fibrils that compose spider threads has been frequently overlooked. Herein, I exploit a molecular dynamics-based coarse-grain model to construct a fully three-dimensional fibril bundle, with a length on the order of micrometres. I probe the mechanical behaviour of bundled silk fibrils with variable density of heterogenic protrusions or globules, ranging from ideally homogeneous to a saturated distribution. Subject to stretching, the model indicates that cooperativity is enhanced by contact through low-force deformation and shear ‘locking’ between globules, increasing shear stress transfer by up to 200 per cent. In effect, introduction of a random and disordered structure can serve to improve mechanical performance. Moreover, addition of globules allows a tuning of free volume, and thus the wettability of silk (with implications for supercontraction). These findings support the ability of silk to maintain near-molecular-level strength at the scale of silk threads, and the mechanism could be easily adopted as a strategy for synthetic fibres. PMID:23486175

  17. Microtubule bundling and shape transitions: Mechanics, interactions, and self-assemblies

    NASA Astrophysics Data System (ADS)

    Needleman, Daniel Joseph

    Microtubules associate to form bundles in vivo in a wide variety of contexts including the mitotic spindle, neuronal processes, and the cortical array in plant cells. These supramolecular assemblies differ in size and shape, and in their internal structure, but the principles that determine this variation in morphology are not understood. To help elucidate such principals we constructed microtubule bundles in vitro using a variety of bundling agents. We have characterized the structure of these supramolecular assemblies of microtubules from the nanoscale to the mesoscale using synchrotron x-ray scattering and diffraction, video enhanced DIC and fluorescence microscopy, and electron microscopy. In the presence of inert polymers, an osmotic pressure imbalance between the inside and the outside of the microtubules may cause them to buckle to a non-circular cross-section. Depletion effects cause these distorted microtubules to bundle into a lattice with rectangular symmetry. The critical buckling pressure provides a measure of the stiffness of the inter-protofilament bond, and we determined that microtubule associated proteins enhance the strength of this bond, while the chemotherapeutic drug taxol has no effect. Multivalent ions cause microtubules to associate into bundles whose morphology depends on the condensing ion. Tightly packed hexagonal bundles with controllable diameters are observed for large tri-, tetra-, and pentavalent counterions. Unexpectedly, in the presence of small divalent cations, we have discovered a living necklace bundle phase, comprised of dynamical assemblies of MT nematic membranes with linear, branched, and loop topologies. Cations may also cause tubulin to assemble into non-microtubule structures. For example, in the presence of spermine, over time the microtubule bundles transform into a columnar phase of inverted tubules, such that the surface which was facing outside of the microtubules switches to the inside. This rearrangement between

  18. EsxB, a secreted protein from Bacillus anthracis forms two distinct helical bundles

    DOE PAGES

    Fan, Yao; Tan, Kemin; Chhor, Gekleng; ...

    2015-07-03

    The EsxB protein from Bacillus anthracis belongs to the WXG100 family, a group of proteins secreted by a specialized secretion system. We have determined the crystal structures of recombinant EsxB and discovered that the small protein (~10 kDa), comprised of a helix-loop-helix (HLH) hairpin, is capable of associating into two different helical bundles. The two basic quaternary assemblies of EsxB are an antiparallel (AP) dimer and a rarely observed bisecting U (BU) dimer. This structural duality of EsxB is believed to originate from the heptad repeat sequence diversity of the first helix of its HLH hairpin, which allows for twomore » alternative helix packing. The flexibility of EsxB and the ability to form alternative helical bundles underscore the possibility that this protein can serve as an adaptor in secretion and can form hetero-oligomeric helix bundle(s) with other secreted members of the WXG100 family, such as EsxW. The highly conserved WXG motif is located within the loop of the HLH hairpin and is mostly buried within the helix bundle suggesting that its role is mainly structural. The exact functions of the motif, including a proposed role as a secretion signal, remain unknown.« less

  19. Tangent bundle geometry from dynamics: Application to the Kepler problem

    NASA Astrophysics Data System (ADS)

    Cariñena, J. F.; Clemente-Gallardo, J.; Jover-Galtier, J. A.; Marmo, G.

    In this paper, we consider a manifold with a dynamical vector field and enquire about the possible tangent bundle structures which would turn the starting vector field into a second-order one. The analysis is restricted to manifolds which are diffeomorphic with affine spaces. In particular, we consider the problem in connection with conformal vector fields of second-order and apply the procedure to vector fields conformally related with the harmonic oscillator (f-oscillators). We select one which covers the vector field describing the Kepler problem.

  20. Determining the tube bundle streamlining critical parameters using the numerical experiment method

    NASA Astrophysics Data System (ADS)

    Kaplunov, S. M.; Val'es, N. G.; Samolysov, A. V.; Marchevskaya, O. A.

    2015-08-01

    The article is devoted to development and application of mathematical models describing the most dangerous mechanisms through which vibrations are excited in tube bundles and blunt cylindrically shaped structures, and to development of reliable calculation methods for describing these models, which would make it possible to obtain prompt data for designing and subsequent operation of the considered structural elements. For solving such problems, a comprehensive approach is required, which should be based on a combined use of numerical experiments on computers and experimental investigations on full-scale equipment. The authors have developed a procedure for numerically investigating the hydrodynamic forces arising during stalled streamlining and the tube bundle vibrations caused by these forces. The procedure is based on using the developed mathematical model describing fluid-elastic excitation of vibrations in a bundle of elastic tubes placed in external cross flow. The problem of studying fluid-elastic excitation is brought to stability analysis, which is carried out with the assumption about a linear behavior of destabilizing forces for undisturbed state of elastic tubes. A theoretical investigation of the developed mathematical model was carried out, from which the necessary and sufficient condition of system stability has been obtained in terms of system dimensionless parameters (mass, damping, and velocity). An algorithm for numerically determining the matrices of linear hydrodynamic coupling coefficients for particular tube bundles is developed. The validity of the algorithm and the computer programs developed on its basis are checked by comparing the results of test calculations with the bank of known experimental data. A procedure is proposed for determining the matrices of linear hydrodynamic coupling coefficients in bundles having a regular layout of their cross section and a large number of tubes through calculating these matrices for a relatively small

  1. Meromorphic Higgs bundles and related geometries

    NASA Astrophysics Data System (ADS)

    Dalakov, Peter

    2016-11-01

    The present note is mostly a survey on the generalised Hitchin integrable system and moduli spaces of meromorphic G-Higgs bundles. We also fill minor gaps in the existing literature, outline a calculation of the infinitesimal period map and review some related geometries.

  2. Social Bundles: Thinking through the Infant Body

    ERIC Educational Resources Information Center

    Brownlie, Julie; Leith, Valerie M. Sheach

    2011-01-01

    Drawing on a UK research study on immunization, this article investigates parents' understandings of the relationship between themselves, their infants, other bodies, the state, and cultural practices--material and symbolic. The article argues that infant bodies are best thought of as always social bundles, rather than as biobundles made social…

  3. Laughter-induced left bundle branch block.

    PubMed

    Chow, Grant V; Desai, Dipan; Spragg, David D; Zakaria, Sammy

    2012-10-01

    We present the case of a patient with ischemic heart disease and intermittent left bundle branch block, reproducibly induced by laughter. Following treatment of ischemia with successful deployment of a drug-eluting stent, no further episodes of inducible LBBB were seen. Transient ischemia, exacerbated by elevated intrathoracic pressure during laughter, may have contributed to onset of this phenomenon.

  4. Interplanetary Overlay Network Bundle Protocol Implementation

    NASA Technical Reports Server (NTRS)

    Burleigh, Scott C.

    2011-01-01

    The Interplanetary Overlay Network (ION) system's BP package, an implementation of the Delay-Tolerant Networking (DTN) Bundle Protocol (BP) and supporting services, has been specifically designed to be suitable for use on deep-space robotic vehicles. Although the ION BP implementation is unique in its use of zero-copy objects for high performance, and in its use of resource-sensitive rate control, it is fully interoperable with other implementations of the BP specification (Internet RFC 5050). The ION BP implementation is built using the same software infrastructure that underlies the implementation of the CCSDS (Consultative Committee for Space Data Systems) File Delivery Protocol (CFDP) built into the flight software of Deep Impact. It is designed to minimize resource consumption, while maximizing operational robustness. For example, no dynamic allocation of system memory is required. Like all the other ION packages, ION's BP implementation is designed to port readily between Linux and Solaris (for easy development and for ground system operations) and VxWorks (for flight systems operations). The exact same source code is exercised in both environments. Initially included in the ION BP implementations are the following: libraries of functions used in constructing bundle forwarders and convergence-layer (CL) input and output adapters; a simple prototype bundle forwarder and associated CL adapters designed to run over an IPbased local area network; administrative tools for managing a simple DTN infrastructure built from these components; a background daemon process that silently destroys bundles whose time-to-live intervals have expired; a library of functions exposed to applications, enabling them to issue and receive data encapsulated in DTN bundles; and some simple applications that can be used for system checkout and benchmarking.

  5. Computational models of hair cell bundle mechanics: III. 3-D utricular bundles.

    PubMed

    Silber, Joe; Cotton, John; Nam, Jong-Hoon; Peterson, Ellengene H; Grant, Wally

    2004-11-01

    Six utricular hair bundles from a red-eared turtle are modeled using 3-D finite element analysis. The mechanical model includes shear deformable stereocilia, realignment of all forces during force load increments, and tip and lateral link inter-stereocilia connections. Results show that there are two distinct bundle types that can be separated by mechanical bundle stiffness. The more compliant group has fewer total stereocilia and short stereocilia relative to kinocilium height; these cells are located in the medial and lateral extrastriola. The stiff group are located in the striola. They have more stereocilia and long stereocilia relative to kinocilia heights. Tip link tensions show parallel behavior in peripheral columns of the bundle and serial behavior in central columns when the tip link modulus is near or above that of collagen (1x10(9) N/m(2)). This analysis shows that lumped parameter models of single stereocilia columns can show some aspects of bundle mechanics; however, a distributed, 3-D model is needed to explore overall bundle behavior.

  6. Masquerading bundle branch block: a variety of right bundle branch block with left anterior fascicular block.

    PubMed

    Elizari, Marcelo V; Baranchuk, Adrian; Chiale, Pablo A

    2013-01-01

    The so-called 'masquerading' type of right bundle branch block is caused by the simultaneous presence of a high-degree left anterior fascicular block often accompanied with severe left ventricular enlargement and/or fibrotic block in the anterolateral wall of the left ventricle. These conditions tend to reorient the terminal electrical forces of the QRS complex towards the left and upwards, in such a way that the characteristic slurred S wave in lead I becomes smaller or even disappears. In many cases of standard masquerading right bundle branch block, a small Q wave in lead I is present due to the initial forces of the left anterior fascicular block, which are oriented rightwards and inferiorly. However, in some cases, the Q wave in lead I also vanishes, and the mimicking of a left bundle branch block becomes perfect in standard leads. This is commonly associated with an inferior myocardial infarction or severe inferior fibrosis in cardiomyopathies. The typical QRS changes of right bundle branch block may eventually be concealed even in the right precordial leads; under such circumstances, the ECG diagnosis may be mistaken and the right bundle branch block totally missed. The masquerading right bundle branch block carries a poor prognosis, since it always implies the presence of a severe underlying heart disease.

  7. Experimental results of the QUENCH-16 bundle test on air ingress

    SciTech Connect

    Stuckert, J.; Steinbrueck, M.

    2012-07-01

    The out-of-pile bundle experiment QUENCH-16 on air ingress was conducted in the electrically heated 21-rod QUENCH facility at KIT in July 2011. It was performed in the frame of the EC supported LACOMECO program. The test scenario included the oxidation of the Zircaloy-4 claddings in air following a limited pre-oxidation in steam, and involved a long period of oxygen starvation to promote interaction with the nitrogen. The primary aim was to examine the influence of the formed oxide layer structure on bundle coolability and hydrogen release during the terminal flooding phase. QUENCH-16 was thus a companion test to the earlier air ingress experiment, QUENCH-10, which was performed with strongly pre-oxidized bundle. Unlike QUENCH-10, significant temperature escalation and intensive hydrogen release were observed during the reflood phase. Post-test investigations of bundle cross sections reveal residual nitride traces at various elevations. The external part of the oxide scale is of porous structure due to re-oxidation of nitrides during reflood. Relative thick internal oxide scales underneath this porous layer and residual nitrides were formed during reflood. At lower bundle elevations frozen partially oxidized melt was detected, relocated from upper elevations. (authors)

  8. Enhanced Load Transfer in Carbon Nanotube Bundles via Carbon-Ion Bombardment

    NASA Astrophysics Data System (ADS)

    Carpena-Nunez, Jennifer; Hernandez, Jose A.; Siochi, Emilie J.; Kim, Jae-Woo; Fonseca, Luis F.

    2014-03-01

    Carbon Nanotubes (CNTs) are ideal candidates for structural composites due to their high modulus and strength, and low weight and density. However, achieving their exceptional mechanical performance at the macroscale is an ongoing challenge, as individual CNTs within bundles are held together by weak van der Waals forces. The current work aims to address issues related to crosslinking CNTs via carbon-ion irradiation to achieve the mechanical performance promised by CNTs. Samples irradiated with a carbon-ion dose of ~ 1013-1014 cm-2 and kinetic energies ranging from 9-25keV show partial amorphization at the outermost layer of the CNT bundle, as theoretically predicted. Mechanical data collected via in-situ Transmission Electron Microscopy-Atomic Force Microscopy (TEM-AFM) shows an increase in tensile and shear strength for irradiated CNT bundles of ~ 6.6GPa and ~ 100MPa, respectively. The adhesion energy between CNT bundles showed an increase from ~ 0.12-0.48 Jm-2 for pristine CNTs up to ~ 42 Jm-2 for carbon-ion irradiated bundles. In addition, enhanced shear interaction exceeding a strength value of ~ 1GPa was observed when exposed to additional amorphous carbon binding, providing a route for improved adhesion to polymer components used in structural composites. This work was supported by a NASA Space Technology Research Fellowship.

  9. Molecular Basis for the Dual Function of Eps8 on Actin Dynamics: Bundling and Capping

    PubMed Central

    Hazelwood, Larnele; Disanza, Andrea; Liu, HongJun; Perlade, Emilie; Malabarba, Maria Grazia; Pasqualato, Sebastiano; Maiolica, Alessio; Confalonieri, Stefano; Le Clainche, Christophe; Offenhauser, Nina; Block, Jennifer; Rottner, Klemens; Di Fiore, Pier Paolo; Carlier, Marie-France; Volkmann, Niels; Hanein, Dorit; Scita, Giorgio

    2010-01-01

    Actin capping and cross-linking proteins regulate the dynamics and architectures of different cellular protrusions. Eps8 is the founding member of a unique family of capping proteins capable of side-binding and bundling actin filaments. However, the structural basis through which Eps8 exerts these functions remains elusive. Here, we combined biochemical, molecular, and genetic approaches with electron microscopy and image analysis to dissect the molecular mechanism responsible for the distinct activities of Eps8. We propose that bundling activity of Eps8 is mainly mediated by a compact four helix bundle, which is contacting three actin subunits along the filament. The capping activity is mainly mediated by a amphipathic helix that binds within the hydrophobic pocket at the barbed ends of actin blocking further addition of actin monomers. Single-point mutagenesis validated these modes of binding, permitting us to dissect Eps8 capping from bundling activity in vitro. We further showed that the capping and bundling activities of Eps8 can be fully dissected in vivo, demonstrating the physiological relevance of the identified Eps8 structural/functional modules. Eps8 controls actin-based motility through its capping activity, while, as a bundler, is essential for proper intestinal morphogenesis of developing Caenorhabditis elegans. PMID:20532239

  10. Turkish and Native English Academic Writers' Use of Lexical Bundles

    ERIC Educational Resources Information Center

    Öztürk, Yusuf; Köse, Gül Durmusoglu

    2016-01-01

    Lexical bundles such as "on the other hand" and "as a result of" are extremely common and important in academic discourse. The appropriate use of lexical bundles typical of a specific academic discipline is important for writers and the absence of such bundles may not sound fluent and native-like. Recent studies (e.g. Adel…

  11. 76 FR 61365 - Bundled Payments for Care Improvement Initiative

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-10-04

    ... HUMAN SERVICES Centers for Medicare & Medicaid Services Bundled Payments for Care Improvement Initiative.... SUMMARY: This notice extends the deadlines for the submission of the Bundled Payments for Care Improvement.../patient-care-models/bundled-payments-for-care-improvement.html . Application Submission Deadline:...

  12. Lateral Flow Field Behavior Downstream of Mixing Vanes In a Simulated Nuclear Fuel Rod Bundle

    SciTech Connect

    Conner, Michael E.; Smith, L. David III; Holloway, Mary V.; Beasley, Donald E.

    2004-07-01

    To assess the fuel assembly performance of PWR nuclear fuel assemblies, average subchannel flow values are used in design analyses. However, for this highly complex flow, it is known that local conditions around fuel rods vary dependent upon the location of the fuel rod in the fuel assembly and upon the support grid design that maintains the fuel rod pitch. To investigate the local flow in a simulated nuclear fuel rod bundle, a testing technique has been employed to measure the lateral flow field in a 5 x 5 rod bundle. Particle Image Velocimetry was used to measure the lateral flow field downstream of a support grid with mixing vanes for four unique subchannels in the 5 x 5 bundle. The dominant lateral flow structures for each subchannel are compared in this paper including the decay of these flow structures. (authors)

  13. Unfolding four-helix bundles

    NASA Astrophysics Data System (ADS)

    Gray, Harry B.; Winkler, Jay R.; Kozak, John J.

    2011-03-01

    A geometrical model has been developed to describe the early stages of unfolding of cytochromes c‧ and c-b562 . Calculations are based on a step-wise extension of the polypeptide chain subject to the constraint that the spatial relationship among the residues of each triplet is fixed by the native-state crystallographic data. The response of each protein to these structural perturbations allows the evolution of each of the four helices in these two proteins to be differentiated. It is found that the two external helices in c‧ unfold before its two internal helices, whereas exactly the opposite behaviour is demonstrated by c-b562 . Each of these cytochromes has an extended, internal, non-helical ('turning') region that initially lags behind the most labile helix but then, at a certain stage (identified for each cytochrome), unravels before any of the four helices present in the native structure. It is believed that these predictions will be useful in guiding future experimental studies on the unfolding of these two cytochromes.

  14. Prostaglandins temporally regulate cytoplasmic actin bundle formation during Drosophila oogenesis.

    PubMed

    Spracklen, Andrew J; Kelpsch, Daniel J; Chen, Xiang; Spracklen, Cassandra N; Tootle, Tina L

    2014-02-01

    Prostaglandins (PGs)--lipid signals produced downstream of cyclooxygenase (COX) enzymes--regulate actin dynamics in cell culture and platelets, but their roles during development are largely unknown. Here we define a new role for Pxt, the Drosophila COX-like enzyme, in regulating the actin cytoskeleton--temporal restriction of actin remodeling during oogenesis. PGs are required for actin filament bundle formation during stage 10B (S10B). In addition, loss of Pxt results in extensive early actin remodeling, including actin filaments and aggregates, within the posterior nurse cells of S9 follicles; wild-type follicles exhibit similar structures at a low frequency. Hu li tai shao (Hts-RC) and Villin (Quail), an actin bundler, localize to all early actin structures, whereas Enabled (Ena), an actin elongation factor, preferentially localizes to those in pxt mutants. Reduced Ena levels strongly suppress early actin remodeling in pxt mutants. Furthermore, loss of Pxt results in reduced Ena localization to the sites of bundle formation during S10B. Together these data lead to a model in which PGs temporally regulate actin remodeling during Drosophila oogenesis by controlling Ena localization/activity, such that in S9, PG signaling inhibits, whereas at S10B, it promotes Ena-dependent actin remodeling.

  15. Noise alters hair-bundle mechanics at the cochlear apex

    NASA Astrophysics Data System (ADS)

    Strimbu, C. Elliott; Fridberger, Anders

    2015-12-01

    Exposure to loud sounds can lead to both permanent and short term changes in auditory sensitivity. Permanent hearing loss is often associated with gross changes in cochlear morphology including the loss of hair cells and auditory nerve fibers while the mechanisms of short term threshold shifts are much less well understood and may vary at different locations across the cochlea. Previous reports suggest that exposure to loud sounds leads to a decrease in the cochlear microphonic potential and in the stiffness of the organ of Corti. Because the cochlear microphonic reflects changes in the membrane potential of the hair cells, this suggests that hair-bundle motion should be reversibly altered following exposure to loud sounds. Using an in vitro preparation of the guinea pig temporal bone we investigate changes in the micro-mechanical response near the cochlear apex following a brief (up to 10 - 20 minutes) exposure to loud (˜ 120 dB) tones near the best frequency at this location. We use time-resolved confocal imaging to record the motion of outer hair cell bundles before and after acoustic overstimulation. We have also recorded larger-scale structural views of the organ of Corti before and after exposure to the loud sound. Conventional electrophysiological techniques are used measure the cochlear microphonic potential. As has been previously reported, following acoustic overexposure the cochlear microphonic declines in value and typically recovers on the order of 30 - 60 minutes. Hair-bundle trajectories are affected following the loud sound and typically recover on a somewhat faster time scale than the microphonic potential, although the results vary considerably across preparations. Preliminary results also suggest reversible changes in the hair cell's resting potential following the loud sound.

  16. Irreducible vector bundles on some elliptic non-Kahler threefolds

    NASA Astrophysics Data System (ADS)

    Brînzănescu, Vasile; Vuletescu, Victor

    2015-05-01

    We study rank-2 vector bundles on non-Kähler threefolds π : X → B, which are elliptic principal bundles with at least one non-zero Chern class over a complex surface B with no curves. In this case, we prove that every rank-2 irreducible vector bundle on X is a pull-back from B up to a twist by a line bundle. These 2-vector bundles are, via the Kobayashi-Hitchin correspondence, solutions of the Yang-Mills equations on the threefold X.

  17. A Comparison between Clinical Results of Selective Bundle and Double Bundle Anterior Cruciate Ligament Reconstruction

    PubMed Central

    Yoo, Yon-Sik; Song, Si Young; Yang, Cheol Jung; Ha, Jong Mun; Kim, Yoon Sang

    2016-01-01

    Purpose The purpose of this study was to compare the clinical outcomes of arthroscopic anatomical double bundle (DB) anterior cruciate ligament (ACL) reconstruction with either selective anteromedial (AM) or posterolateral (PL) bundle reconstruction while preserving a relatively healthy ACL bundle. Materials and Methods The authors evaluated 98 patients with a mean follow-up of 30.8±4.0 months who had undergone DB or selective bundle ACL reconstructions. Of these, 34 cases underwent DB ACL reconstruction (group A), 34 underwent selective AM bundle reconstruction (group B), and 30 underwent selective PL bundle reconstructions (group C). These groups were compared with respect to Lysholm and International Knee Documentation Committee (IKDC) score, side-to-side differences of anterior laxity measured by KT-2000 arthrometer at 30 lbs, and stress radiography and Lachman and pivot shift test results. Pre- and post-operative data were objectively evaluated using a statistical approach. Results The preoperative anterior instability measured by manual stress radiography at 90° of knee flexion in group A was significantly greater than that in groups B and C (all p<0.001). At last follow-up, mean side-to-side instrumented laxities measured by the KT-2000 and manual stress radiography were significantly improved from preoperative data in all groups (all p<0.001). There were no significant differences between the three groups in anterior instability measured by KT-2000 arthrometer, pivot shift, or functional scores. Conclusion Selective bundle reconstruction in partial ACL tears offers comparable clinical results to DB reconstruction in complete ACL tears. PMID:27401652

  18. Emitters of N-photon bundles.

    PubMed

    Muñoz, C Sánchez; Del Valle, E; Tudela, A González; Müller, K; Lichtmannecker, S; Kaniber, M; Tejedor, C; Finley, J J; Laussy, F P

    2014-07-01

    Controlling the ouput of a light emitter is one of the basic tasks of photonics, with landmarks such as the laser and single-photon sources. The development of quantum applications makes it increasingly important to diversify the available quantum sources. Here, we propose a cavity QED scheme to realize emitters that release their energy in groups, or "bundles" of N photons, for integer N. Close to 100% of two-photon emission and 90% of three-photon emission is shown to be within reach of state of the art samples. The emission can be tuned with system parameters so that the device behaves as a laser or as a N-photon gun. The theoretical formalism to characterize such emitters is developed, with the bundle statistics arising as an extension of the fundamental correlation functions of quantum optics. These emitters will be useful for quantum information processing and for medical applications.

  19. Care bundles reduce readmissions for COPD.

    PubMed

    Matthews, Healther; Tooley, Cathy; Nicholls, Carol; Lindsey-Halls, Anna

    In 2011, the respiratory nursing team at the James Paget University Hospital Foundation Trust were considering introducing a discharge care bundle for patients admitted with an acute exacerbation of chronic obstructive pulmonary disease. At the same time, the trust was asking for applications for Commissioning for Quality and Innovation schemes (CQUINs). These are locally agreed packages of quality improvement goals and indicators, which, if achieved in total, enable the provider to earn its full CQUIN payment. A CQUIN scheme should address the three domains of quality, safety and effectiveness, patient experience and also show innovation. This article discusses how the care bundle was introduced and how, over a 12-month period, it showed tangible results in improving the care pathway for COPD patients as well as reducing readmissions and saving a significant amount of money.

  20. Type IIB flux compactifications on twistor bundles

    NASA Astrophysics Data System (ADS)

    Imaanpur, Ali

    2014-02-01

    We construct a U(1) bundle over N(1,1), usually considered as an SO(3) bundle on CP2, and show that type IIB supergravity can be consistently compactified over it. With the five form flux turned on, there is a solution for which the metric becomes Einstein. We further turn on 3-form fluxes and show that there is a one parameter family of solutions. In particular, there is a limiting solution of large 3-form fluxes for which two U(1) fiber directions of the metric shrink to zero size. We also discuss compactifications over N(1,1) to AdS3. All solutions turn out to be non-supersymmetric.

  1. The Calcium-Dependent Switch Helix of L-Plastin Regulates Actin Bundling

    PubMed Central

    Ishida, Hiroaki; Jensen, Katharine V.; Woodman, Andrew G.; Hyndman, M. Eric; Vogel, Hans J.

    2017-01-01

    L-plastin is a calcium-regulated actin-bundling protein that is expressed in cells of hematopoietic origin and in most metastatic cancer cells. These cell types are mobile and require the constant remodeling of their actin cytoskeleton, where L-plastin bundles filamentous actin. The calcium-dependent regulation of the actin-bundling activity of L-plastin is not well understood. We have used NMR spectroscopy to determine the solution structure of the EF-hand calcium-sensor headpiece domain. Unexpectedly, this domain does not bind directly to the four CH-domains of L-plastin. A novel switch helix is present immediately after the calcium-binding region and it binds tightly to the EF-hand motifs in the presence of calcium. We demonstrate that this switch helix plays a major role during actin-bundling. Moreover a peptide that competitively inhibits the association between the EF-hand motifs and the switch helix was shown to deregulate the actin-bundling activity of L-plastin. Overall, these findings may help to develop new drugs that target the L-plastin headpiece and interfere in the metastatic activity of cancer cells. PMID:28145401

  2. Towards a bimodal proximity sensor for in situ neurovascular bundle detection during dental implant surgery

    PubMed Central

    Weber, Jessie R.; Baribeau, François; Grenier, Paul; Émond, Frédéric; Dubois, Sylvain; Duchesne, François; Girard, Marc; Pope, Timothy; Gallant, Pascal; Mermut, Ozzy; Moghadam, Hassan Ghaderi

    2013-01-01

    Proof of concept results are presented towards an in situ bimodal proximity sensor for neurovascular bundle detection during dental implant surgery using combined near infrared absorption (NIR) and optical coherence tomography (OCT) techniques. These modalities are shown to have different sensitivity to the proximity of optical contrast from neurovascular bundles. NIR AC and DC signals from the pulsing of an artery enable qualitative ranging of the bundle in the millimeter range, with best sensitivity around 0.5-3mm distance in a custom phantom setup. OCT provides structural mapping of the neurovascular bundle at sub-millimeter distances in an ex vivo human jaw bone. Combining the two techniques suggests a novel ranging system for the surgeon that could be implemented in a “smart drill.” The proximity to the neurovascular bundle can be tracked in real time in the range of a few millimeters with NIR signals, after which higher resolution imaging OCT to provide finer ranging in the sub-millimeter distances. PMID:24466473

  3. Uncovering ecosystem service bundles through social preferences.

    PubMed

    Martín-López, Berta; Iniesta-Arandia, Irene; García-Llorente, Marina; Palomo, Ignacio; Casado-Arzuaga, Izaskun; Amo, David García Del; Gómez-Baggethun, Erik; Oteros-Rozas, Elisa; Palacios-Agundez, Igone; Willaarts, Bárbara; González, José A; Santos-Martín, Fernando; Onaindia, Miren; López-Santiago, Cesar; Montes, Carlos

    2012-01-01

    Ecosystem service assessments have increasingly been used to support environmental management policies, mainly based on biophysical and economic indicators. However, few studies have coped with the social-cultural dimension of ecosystem services, despite being considered a research priority. We examined how ecosystem service bundles and trade-offs emerge from diverging social preferences toward ecosystem services delivered by various types of ecosystems in Spain. We conducted 3,379 direct face-to-face questionnaires in eight different case study sites from 2007 to 2011. Overall, 90.5% of the sampled population recognized the ecosystem's capacity to deliver services. Formal studies, environmental behavior, and gender variables influenced the probability of people recognizing the ecosystem's capacity to provide services. The ecosystem services most frequently perceived by people were regulating services; of those, air purification held the greatest importance. However, statistical analysis showed that socio-cultural factors and the conservation management strategy of ecosystems (i.e., National Park, Natural Park, or a non-protected area) have an effect on social preferences toward ecosystem services. Ecosystem service trade-offs and bundles were identified by analyzing social preferences through multivariate analysis (redundancy analysis and hierarchical cluster analysis). We found a clear trade-off among provisioning services (and recreational hunting) versus regulating services and almost all cultural services. We identified three ecosystem service bundles associated with the conservation management strategy and the rural-urban gradient. We conclude that socio-cultural preferences toward ecosystem services can serve as a tool to identify relevant services for people, the factors underlying these social preferences, and emerging ecosystem service bundles and trade-offs.

  4. Uncovering Ecosystem Service Bundles through Social Preferences

    PubMed Central

    Martín-López, Berta; Iniesta-Arandia, Irene; García-Llorente, Marina; Palomo, Ignacio; Casado-Arzuaga, Izaskun; Amo, David García Del; Gómez-Baggethun, Erik; Oteros-Rozas, Elisa; Palacios-Agundez, Igone; Willaarts, Bárbara; González, José A.; Santos-Martín, Fernando; Onaindia, Miren; López-Santiago, Cesar; Montes, Carlos

    2012-01-01

    Ecosystem service assessments have increasingly been used to support environmental management policies, mainly based on biophysical and economic indicators. However, few studies have coped with the social-cultural dimension of ecosystem services, despite being considered a research priority. We examined how ecosystem service bundles and trade-offs emerge from diverging social preferences toward ecosystem services delivered by various types of ecosystems in Spain. We conducted 3,379 direct face-to-face questionnaires in eight different case study sites from 2007 to 2011. Overall, 90.5% of the sampled population recognized the ecosystem’s capacity to deliver services. Formal studies, environmental behavior, and gender variables influenced the probability of people recognizing the ecosystem’s capacity to provide services. The ecosystem services most frequently perceived by people were regulating services; of those, air purification held the greatest importance. However, statistical analysis showed that socio-cultural factors and the conservation management strategy of ecosystems (i.e., National Park, Natural Park, or a non-protected area) have an effect on social preferences toward ecosystem services. Ecosystem service trade-offs and bundles were identified by analyzing social preferences through multivariate analysis (redundancy analysis and hierarchical cluster analysis). We found a clear trade-off among provisioning services (and recreational hunting) versus regulating services and almost all cultural services. We identified three ecosystem service bundles associated with the conservation management strategy and the rural-urban gradient. We conclude that socio-cultural preferences toward ecosystem services can serve as a tool to identify relevant services for people, the factors underlying these social preferences, and emerging ecosystem service bundles and trade-offs. PMID:22720006

  5. Mesophase Behavior in Carbon Fiber Bundles.

    DTIC Science & Technology

    1982-06-01

    Mesophase Coal-tar pitch Mesophase bloating Composite fabrication Mesophase wetting Ccmposite micrography Petroleum pitch 20. Atl RACT (Continue on reve...fiber in petroleum pitch were pyrolyzed under three conditions of constraint. The results confirm a recent report that the mesophase transformation...proceeds differently within a fiber bundle than in bulk pitch . In the early stages of transformation, both pitch and mesophase wet the fiber, and the

  6. Alpha1 LASSO data bundles Lamont, OK

    SciTech Connect

    Gustafson, William Jr; Vogelmann, Andrew; Endo, Satoshi; Toto, Tami; Xiao, Heng; Li, Zhijin; Cheng, Xiaoping; Krishna, Bhargavi

    2016-08-03

    A data bundle is a unified package consisting of LASSO LES input and output, observations, evaluation diagnostics, and model skill scores. LES input includes model configuration information and forcing data. LES output includes profile statistics and full domain fields of cloud and environmental variables. Model evaluation data consists of LES output and ARM observations co-registered on the same grid and sampling frequency. Model performance is quantified by skill scores and diagnostics in terms of cloud and environmental variables.

  7. Cross-Linker Unbinding and Self-Similarity in Bundled Cytoskeletal Networks

    NASA Astrophysics Data System (ADS)

    Lieleg, O.; Bausch, A. R.

    2007-10-01

    The macromechanical properties of purely bundled in vitro actin networks are not only determined by the micromechanical properties of individual bundles but also by molecular unbinding events of the actin-binding protein (ABP) fascin. Under high mechanical load the network elasticity depends on the forced unbinding of individual ABPs in a rate dependent manner. Cross-linker unbinding in combination with the structural self-similarity of the network enables the introduction of a concentration-time superposition principle—broadening the mechanically accessible frequency range over 8 orders of magnitude.

  8. Segmentation of nerve bundles and ganglia in spine MRI using particle filters.

    PubMed

    Dalca, Adrian; Danagoulian, Giovanna; Kikinis, Ron; Schmidt, Ehud; Golland, Polina

    2011-01-01

    Automatic segmentation of spinal nerve bundles that originate within the dural sac and exit the spinal canal is important for diagnosis and surgical planning. The variability in intensity, contrast, shape and direction of nerves seen in high resolution myelographic MR images makes segmentation a challenging task. In this paper, we present an automatic tracking method for nerve segmentation based on particle filters. We develop a novel approach to particle representation and dynamics, based on Bézier splines. Moreover, we introduce a robust image likelihood model that enables delineation of nerve bundles and ganglia from the surrounding anatomical structures. We demonstrate accurate and fast nerve tracking and compare it to expert manual segmentation.

  9. An analytical fiber bundle model for pullout mechanics of root bundles

    NASA Astrophysics Data System (ADS)

    Cohen, D.; Schwarz, M.; Or, D.

    2011-09-01

    Roots in soil contribute to the mechanical stability of slopes. Estimation of root reinforcement is challenging because roots form complex biological networks whose geometrical and mechanical characteristics are difficult to characterize. Here we describe an analytical model that builds on simple root descriptors to estimate root reinforcement. Root bundles are modeled as bundles of heterogeneous fibers pulled along their long axes neglecting root-soil friction. Analytical expressions for the pullout force as a function of displacement are derived. The maximum pullout force and corresponding critical displacement are either derived analytically or computed numerically. Key model inputs are a root diameter distribution (uniform, Weibull, or lognormal) and three empirical power law relations describing tensile strength, elastic modulus, and length of roots as functions of root diameter. When a root bundle with root tips anchored in the soil matrix is pulled by a rigid plate, a unique parameter, ?, that depends only on the exponents of the power law relations, dictates the order in which roots of different diameters break. If ? < 1, small roots break first; if ? > 1, large roots break first. When ? = 1, all fibers break simultaneously, and the maximum tensile force is simply the roots' mean force times the number of roots in the bundle. Based on measurements of root geometry and mechanical properties, the value of ? is less than 1, usually ranging between 0 and 0.7. Thus, small roots always fail first. The model shows how geometrical and mechanical characteristics of roots and root diameter distribution affect the pullout force, its maximum and corresponding displacement. Comparing bundles of roots that have similar mean diameters, a bundle with a narrow variance in root diameter will result in a larger maximum force and a smaller displacement at maximum force than a bundle with a wide diameter distribution. Increasing the mean root diameter of a bundle without

  10. CFD Simulation of the Turbulent Flow and Heat Transfer in a Bare Rod Bundle

    SciTech Connect

    In, W.K.; Shin, C.H.; Oh, D.S.; Chun, T.H.

    2004-07-01

    A computational fluid dynamics(CFD) analysis has been performed to investigate the turbulent flow and heat transfer in a triangular rod bundle with pitch-to-diameter ratios(P/D) of 1.06 and 1.12. The CFD predictions using various turbulence models were compared with the experimental results. Anisotropic turbulence models(nonlinear k - {epsilon} and second-moment closure models) predicted the turbulence-driven secondary flow in the triangular subchannel and the distributions of the time mean velocity and temperature showing a significantly improved agreement with the measurements from the linear standard k - {epsilon} model. The anisotropic turbulence models predicted the turbulence structure for a rod bundle with a large P/D fairly well but could not predict the very high turbulent intensity of the azimuthal velocity observed in the narrow flow region(gap) for a rod bundle with a small P/D. (authors)

  11. Myosin III-mediated cross-linking and stimulation of actin bundling activity of Espin.

    PubMed

    Liu, Haiyang; Li, Jianchao; Raval, Manmeet H; Yao, Ningning; Deng, Xiaoying; Lu, Qing; Nie, Si; Feng, Wei; Wan, Jun; Yengo, Christopher M; Liu, Wei; Zhang, Mingjie

    2016-01-19

    Class III myosins (Myo3) and actin-bundling protein Espin play critical roles in regulating the development and maintenance of stereocilia in vertebrate hair cells, and their defects cause hereditary hearing impairments. Myo3 interacts with Espin1 through its tail homology I motif (THDI), however it is not clear how Myo3 specifically acts through Espin1 to regulate the actin bundle assembly and stabilization. Here we discover that Myo3 THDI contains a pair of repeat sequences capable of independently and strongly binding to the ankyrin repeats of Espin1, revealing an unexpected Myo3-mediated cross-linking mechanism of Espin1. The structures of Myo3 in complex with Espin1 not only elucidate the mechanism of the binding, but also reveal a Myo3-induced release of Espin1 auto-inhibition mechanism. We also provide evidence that Myo3-mediated cross-linking can further promote actin fiber bundling activity of Espin1.

  12. Water-mediated conformational transitions in nicotinic receptor M2 helix bundles: a molecular dynamics study.

    PubMed

    Sankararamakrishnan, R; Sansom, M S

    1995-12-27

    The ion channel of the nicotinic acetylcholine receptor is a water-filled pore formed by five M2 helix segments, one from each subunit. Molecular dynamics simulations on bundles of five M2 alpha 7 helices surrounding a central column of water and with caps of water molecules at either end of the pore have been used to explore the effects of intrapore water on helix packing. Interactions of water molecules with the N-terminal polar sidechains lead to a conformational transition from right- to left-handed supercoils during these stimulations. These studies reveal that the pore formed by the bundle of M2 helices is flexible. A structural role is proposed for water molecules in determining the geometry of bundles of isolated pore-forming helices.

  13. Bundled payment fails to gain a foothold In California: the experience of the IHA bundled payment demonstration.

    PubMed

    Ridgely, M Susan; de Vries, David; Bozic, Kevin J; Hussey, Peter S

    2014-08-01

    To determine whether bundled payment could be an effective payment model for California, the Integrated Healthcare Association convened a group of stakeholders (health plans, hospitals, ambulatory surgery centers, physician organizations, and vendors) to develop, through a consensus process, the methods and means of implementing bundled payment. In spite of a high level of enthusiasm and effort, the pilot did not succeed in its goal to implement bundled payment for orthopedic procedures across multiple payers and hospital-physician partners. An evaluation of the pilot documented a number of barriers, such as administrative burden, state regulatory uncertainty, and disagreements about bundle definition and assumption of risk. Ultimately, few contracts were signed, which resulted in insufficient volume to test hypotheses about the impact of bundled payment on quality and costs. Although bundled payment failed to gain a foothold in California, the evaluation provides lessons for future bundled payment initiatives.

  14. Lexical Bundles and the Construction of an Academic Voice in Business Writing

    ERIC Educational Resources Information Center

    Mhedhbi, Malek

    2014-01-01

    Most previous studies on disciplinary academic writing focused on the structures in research articles or linguistic realizations of each move (Lau, 2004; Hyland, 2000). Few have been conducted to address the interpersonal aspect of disciplinary discourse texts. The purpose of this study was to measure the effect of lexical bundles' (LBs) awareness…

  15. A bundled-stack discotic columnar liquid crystalline phase with inter-stack electronic coupling

    DOE PAGES

    Wang, Bin; Sun, Runkun; Günbaş, Duygu D.; ...

    2015-06-15

    The first compound proving to be capable of forming a bundled-stack discotic columnar liquid crystalline (BSDCLC) phase was designed and synthesized. Finally, the unique perylene anhydride inter-stack interaction was found to be the key to the formation of the BSDCLC structure and inter-stack electronic coupling (ISEC).

  16. A complete right bundle-branch block masking Brugada syndrome: a case

    PubMed Central

    Tomita, Makoto; Kitazawa, Hitoshi; Sato, Masahito; Okabe, Masaaki; Antzelevitch, Charles; Aizawa, Yoshifusa

    2012-01-01

    A 69-year-old man without structural heart disease was admitted for syncope. His electrocardiogram displayed complete right bundle branch (CRBBB). A coved type ST elevation was observed with transient normalization of CRBBB giving rise to a normal QRS. These findings suggest that Brugada syndrome can be masked by CRBBB. PMID:22832153

  17. Modern Methods of Bundle Adjustment on the Gpu

    NASA Astrophysics Data System (ADS)

    Hänsch, R.; Drude, I.; Hellwich, O.

    2016-06-01

    The task to compute 3D reconstructions from large amounts of data has become an active field of research within the last years. Based on an initial estimate provided by structure from motion, bundle adjustment seeks to find a solution that is optimal for all cameras and 3D points. The corresponding nonlinear optimization problem is usually solved by the Levenberg-Marquardt algorithm combined with conjugate gradient descent. While many adaptations and extensions to the classical bundle adjustment approach have been proposed, only few works consider the acceleration potentials of GPU systems. This paper elaborates the possibilities of time and space savings when fitting the implementation strategy to the terms and requirements of realizing a bundler on heterogeneous CPUGPU systems. Instead of focusing on the standard approach of Levenberg-Marquardt optimization alone, nonlinear conjugate gradient descent and alternating resection-intersection are studied as two alternatives. The experiments show that in particular alternating resection-intersection reaches low error rates very fast, but converges to larger error rates than Levenberg-Marquardt. PBA, as one of the current state-of-the-art bundlers, converges slower in 50 % of the test cases and needs 1.5-2 times more memory than the Levenberg- Marquardt implementation.

  18. The helix bundle: A reversible lipid binding motif

    PubMed Central

    Narayanaswami, Vasanthy; Kiss, Robert S.; Weers, Paul M.M.

    2009-01-01

    Apolipoproteins are the protein components of lipoproteins that have the innate ability to inter convert between a lipid-free and a lipid-bound form in a facile manner, a remarkable property conferred by the helix bundle motif. Composed of a series of four or five amphipathic α-helices that fold to form a helix bundle, this motif allows the en face orientation of the hydrophobic faces of the α-helices in the protein interior in the lipid-free state. A conformational switch then permits helix-helix interactions to be substituted by helix-lipid interactions upon lipid binding interaction. This review compares the apolipoprotein high resolution structures and the factors that trigger this switch in insect apolipophorin III and the mammalian apolipoproteins, apolipoprotein E and apolipoprotein A-I, pointing out the commonalities and key differences in the mode of lipid interaction. Further insights into the lipid bound conformation of apolipoproteins are required to fully understand their functional role under physiological conditions. PMID:19770066

  19. Fascial bundles of the infraspinatus fascia: anatomy, function, and clinical considerations.

    PubMed

    Moccia, David; Nackashi, Andrew A; Schilling, Rebecca; Ward, Peter J

    2016-01-01

    The infraspinatus fascia is a tough sheet of connective tissue that covers the infraspinatus fossa of the scapula and the muscle within. Muscle fibers originate from the fossa and fascia and then travel laterally to insert on the greater tubercle of the humerus. Frequently the infraspinatus fascia is quickly removed to appreciate the underlying muscle, but the fascia is an interesting and complex structure in its own right. Despite having a characteristic set of fascial bundles, no contemporary anatomy texts or atlases describe the fascia in detail. The infraspinatus fascia was dissected in detail in 11 shoulders, to characterize the fascial bundles and connections that contribute to it. Thereafter, 70 shoulders were dissected to tabulate the variability of the fascial bundles and connections. Six characteristic features of the infraspinatus fascia were noted: a medial band, an inferior-lateral band, and superior-lateral band of fascia, insertion of the posterior deltoid into the infraspinatus fascia, a transverse connection from the posterior deltoid muscle to the infraspinatus fascia, and a retinacular sheet deep to the deltoid and superficial to the infraspinatus and teres minor muscles. Although other structures of the shoulder are more frequently injured, the infraspinatus fascia is involved in compartment syndromes and the fascial bundles of this structure are certain to impact the biomechanical function of the muscles of the posterior shoulder.

  20. Experience with Designing and Implementing a Bundled Payment Program for Total Hip Replacement

    PubMed Central

    Whitcomb, Winthrop F.; Lagu, Tara; Krushell, Robert J.; Lehman, Andrew P.; Greenbaum, Jordan; McGirr, Joan; Pekow, Penelope S.; Calcasola, Stephanie; Benjamin, Evan; Mayforth, Janice; Lindenauer, Peter K.

    2015-01-01

    Background Bundled payments, also known as episode-based payments, are intended to contain health care costs and promote quality. In 2011 a bundled payment pilot program for total hip replacement was implemented by an integrated health care delivery system in conjunction with a commercial health plan subsidiary. In July 2015 the Centers for Medicare & Medicaid Services (CMS) proposed the Comprehensive Care for Joint Replacement Model to test bundled payment for hip and knee replacement. Methods Stakeholders were identified and a structure for program development and implementation was created. An Oversight Committee provided governance over a Clinical Model Subgroup and a Financial Model Subgroup. Results The pilot program included (1) a clinical model of care encompassing the period from the preoperative evaluation through the third postoperative visit, (2) a pricing model, (3) a program to share savings, and (4) a patient engagement and expectation strategy. Compared to 32 historical controls— patients treated before bundle implementation—45 post-bundle-implementation patients with total hip replacement had a similar length of hospital stay (3.0 versus 3.4 days, p = .24), higher rates of discharge to home or home with services than to a rehabilitation facility (87% versus 63%), similar adjusted median total payments ($22,272 versus $22,567, p = .43), and lower median posthospital payments ($704 versus $1,121, p = .002), and were more likely to receive guideline-consistent care (99% versus 95%, p = .05). Discussion The bundled payment pilot program was associated with similar total costs, decreased posthospital costs, fewer discharges to rehabilitation facilities, and improved quality. Successful implementation of the program hinged on buy-in from stakeholders and close collaboration between stakeholders and the clinical and financial teams. PMID:26289235

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

    USGS Publications Warehouse

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

    2006-01-01

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

  2. Historical dynamics in ecosystem service bundles.

    PubMed

    Renard, Delphine; Rhemtulla, Jeanine M; Bennett, Elena M

    2015-10-27

    Managing multiple ecosystem services (ES), including addressing trade-offs between services and preventing ecological surprises, is among the most pressing areas for sustainability research. These challenges require ES research to go beyond the currently common approach of snapshot studies limited to one or two services at a single point in time. We used a spatiotemporal approach to examine changes in nine ES and their relationships from 1971 to 2006 across 131 municipalities in a mixed-use landscape in Quebec, Canada. We show how an approach that incorporates time and space can improve our understanding of ES dynamics. We found an increase in the provision of most services through time; however, provision of ES was not uniformly enhanced at all locations. Instead, each municipality specialized in providing a bundle (set of positively correlated ES) dominated by just a few services. The trajectory of bundle formation was related to changes in agricultural policy and global trends; local biophysical and socioeconomic characteristics explained the bundles' increasing spatial clustering. Relationships between services varied through time, with some provisioning and cultural services shifting from a trade-off or no relationship in 1971 to an apparent synergistic relationship by 2006. By implementing a spatiotemporal perspective on multiple services, we provide clear evidence of the dynamic nature of ES interactions and contribute to identifying processes and drivers behind these changing relationships. Our study raises questions about using snapshots of ES provision at a single point in time to build our understanding of ES relationships in complex and dynamic social-ecological systems.

  3. The avalanche process of the fiber bundle model with defect

    NASA Astrophysics Data System (ADS)

    Hao, Da-Peng; Tang, Gang; Xia, Hui; Xun, Zhi-Peng; Han, Kui

    2017-04-01

    In order to explore the impacts of defect on the tensile fracture process of materials, the fiber bundle model with defect is constructed based on the classical fiber bundle model. In the fiber bundle model with defect, the two key parameters are the mean size and the density of defects. In both uniform and Weibull threshold distributions, the mean size and density all bring impacts on the threshold distribution of fibers. By means of analytical approximation and numerical simulation, we show that the two key parameters of the model have substantial effects on the failure process of the bundle. From macroscopic view, the defect described by the altering of threshold distribution of fibers will has a significant impact on the mechanical properties of the bundle. While in microscopic scale, the statistical properties of the model are still harmonious with the classical fiber bundle model.

  4. Morphology selection via geometric frustration in chiral filament bundles.

    PubMed

    Hall, Douglas M; Bruss, Isaac R; Barone, Justin R; Grason, Gregory M

    2016-07-01

    In assemblies, the geometric frustration of a locally preferred packing motif leads to anomalous behaviours, from self-limiting growth to defects in the ground state. Here, we demonstrate that geometric frustration selects the equilibrium morphology of cohesive bundles of chiral filaments, an assembly motif critical to a broad range of biological and synthetic nanomaterials. Frustration of inter-filament spacing leads to optimal shapes of self-twisting bundles that break the symmetries of packing and of the underlying inter-filament forces, paralleling a morphological instability in spherical two-dimensional crystals. Equilibrium bundle morphology is controlled by a parameter that characterizes the relative costs of filament bending and the straining of cohesive bonds between filaments. This parameter delineates the boundaries between stable, isotropic cylindrical bundles and anisotropic, twisted-tape bundles. We also show how the mechanical and interaction properties of constituent amyloid fibrils may be extracted from the mesoscale dimensions of the anisotropic bundles that they form.

  5. Synchronization of Spontaneous Active Motility of Hair Cell Bundles

    PubMed Central

    Zhang, Tracy-Ying; Ji, Seung; Bozovic, Dolores

    2015-01-01

    Hair cells of the inner ear exhibit an active process, believed to be crucial for achieving the sensitivity of auditory and vestibular detection. One of the manifestations of the active process is the occurrence of spontaneous hair bundle oscillations in vitro. Hair bundles are coupled by overlying membranes in vivo; hence, explaining the potential role of innate bundle motility in the generation of otoacoustic emissions requires an understanding of the effects of coupling on the active bundle dynamics. We used microbeads to connect small groups of hair cell bundles, using in vitro preparations that maintain their innate oscillations. Our experiments demonstrate robust synchronization of spontaneous oscillations, with either 1:1 or multi-mode phase-locking. The frequency of synchronized oscillation was found to be near the mean of the innate frequencies of individual bundles. Coupling also led to an improved regularity of entrained oscillations, demonstrated by an increase in the quality factor. PMID:26540409

  6. Expansion and Polarity Sorting in Microtubule-Dynein Bundles

    NASA Astrophysics Data System (ADS)

    Zemel, A.; Mogilner, A.

    Interactions of multiple molecular motors with dynamicpolymers, such as actin and microtubules, form the basis for many processes in the cell cytoskeleton. One example is the active `sorting' of microtubule bundles by dynein molecular motors into aster-like arrays of microtubules; in these bundles dynein motors cross-link and slide neighboring microtubules apart. A number of models have been suggested to quantify the active dynamics of cross-linked bundles of polar filaments. In the case of densely packed bundles, however, a major complication arises from the fact that each microtubule interacts with multiple neighboring filaments. To explicitly take these interactions into account we performed detailed computer simulations in which the equations of motion for all microtubules in the bundle were iteratively solved. Our simulations demonstrate the phenomenon of polarity sorting and reveal the variable-rate of the concurrent bundle expansion and its dependence on the nature of the microtubule-motor interactions.

  7. Monopoles and Modifications of Bundles over Elliptic Curves

    NASA Astrophysics Data System (ADS)

    Levin, Andrey M.; Olshanetsky, Mikhail A.; Zotov, Andrei V.

    2009-06-01

    Modifications of bundles over complex curves is an operation that allows one to construct a new bundle from a given one. Modifications can change a topological type of bundle. We describe the topological type in terms of the characteristic classes of the bundle. Being applied to the Higgs bundles modifications establish an equivalence between different classical integrable systems. Following Kapustin and Witten we define the modifications in terms of monopole solutions of the Bogomolny equation. We find the Dirac monopole solution in the case R × (elliptic curve). This solution is a three-dimensional generalization of the Kronecker series. We give two representations for this solution and derive a functional equation for it generalizing the Kronecker results. We use it to define Abelian modifications for bundles of arbitrary rank. We also describe non-Abelian modifications in terms of theta-functions with characteristic.

  8. Cooperativity and Frustration in Protein-Mediated Parallel Actin Bundles

    NASA Astrophysics Data System (ADS)

    Shin, Homin; Drew, Kirstin R. Purdy; Bartles, James R.; Wong, Gerard C. L.; Grason, Gregory M.

    2009-12-01

    We examine the mechanism of bundling of cytoskeletal actin filaments by two representative bundling proteins, fascin and espin. Small-angle x-ray studies show that increased binding from linkers drives a systematic overtwist of actin filaments from their native state, which occurs in a linker-dependent fashion. Fascin bundles actin into a continuous spectrum of intermediate twist states, while espin only allows for untwisted actin filaments and fully overtwisted bundles. Based on a coarse-grained, statistical model of protein binding, we show that the interplay between binding geometry and the intrinsic flexibility of linkers mediates cooperative binding in the bundle. We attribute the respective continuous (discontinuous) bundling mechanisms of fascin (espin) to difference in the stiffness of linker bonds themselves.

  9. Higher order mechanics on graded bundles

    NASA Astrophysics Data System (ADS)

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

    2015-05-01

    In this paper we develop a geometric approach to higher order mechanics on graded bundles in both, the Lagrangian and Hamiltonian formalism, via the recently discovered weighted algebroids. We present the corresponding Tulczyjew triple for this higher order situation and derive in this framework the phase equations from an arbitrary (also singular) Lagrangian or Hamiltonian, as well as the Euler-Lagrange equations. As important examples, we geometrically derive the classical higher order Euler-Lagrange equations and analogous reduced equations for invariant higher order Lagrangians on Lie groupoids.

  10. Heat Transfer Analysis in Wire Bundles for Aerospace Vehicles

    NASA Technical Reports Server (NTRS)

    Rickman, S. L.; Iamello, C. J.

    2016-01-01

    Design of wiring for aerospace vehicles relies on an understanding of "ampacity" which refers to the current carrying capacity of wires, either, individually or in wire bundles. Designers rely on standards to derate allowable current flow to prevent exceedance of wire temperature limits due to resistive heat dissipation within the wires or wire bundles. These standards often add considerable margin and are based on empirical data. Commercial providers are taking an aggressive approach to wire sizing which challenges the conventional wisdom of the established standards. Thermal modelling of wire bundles may offer significant mass reduction in a system if the technique can be generalized to produce reliable temperature predictions for arbitrary bundle configurations. Thermal analysis has been applied to the problem of wire bundles wherein any or all of the wires within the bundle may carry current. Wire bundles present analytical challenges because the heat transfer path from conductors internal to the bundle is tortuous, relying on internal radiation and thermal interface conductance to move the heat from within the bundle to the external jacket where it can be carried away by convective and radiative heat transfer. The problem is further complicated by the dependence of wire electrical resistivity on temperature. Reduced heat transfer out of the bundle leads to higher conductor temperatures and, hence, increased resistive heat dissipation. Development of a generalized wire bundle thermal model is presented and compared with test data. The steady state heat balance for a single wire is derived and extended to the bundle configuration. The generalized model includes the effects of temperature varying resistance, internal radiation and thermal interface conductance, external radiation and temperature varying convective relief from the free surface. The sensitivity of the response to uncertainties in key model parameters is explored using Monte Carlo analysis.

  11. Local load-sharing fiber bundle model in higher dimensions

    NASA Astrophysics Data System (ADS)

    Sinha, Santanu; Kjellstadli, Jonas T.; Hansen, Alex

    2015-08-01

    We consider the local load-sharing fiber bundle model in one to five dimensions. Depending on the breaking threshold distribution of the fibers, there is a transition where the fracture process becomes localized. In the localized phase, the model behaves as the invasion percolation model. The difference between the local load-sharing fiber bundle model and the equal load-sharing fiber bundle model vanishes with increasing dimensionality with the characteristics of a power law.

  12. Robust Mapping of Incoherent Fiber-Optic Bundles

    NASA Technical Reports Server (NTRS)

    Roberts, Harry E.; Deason, Brent E.; DePlachett, Charles P.; Pilgrim, Robert A.; Sanford, Harold S.

    2007-01-01

    A method and apparatus for mapping between the positions of fibers at opposite ends of incoherent fiber-optic bundles have been invented to enable the use of such bundles to transmit images in visible or infrared light. The method is robust in the sense that it provides useful mapping even for a bundle that contains thousands of narrow, irregularly packed fibers, some of which may be defective. In a coherent fiber-optic bundle, the input and output ends of each fiber lie at identical positions in the input and output planes; therefore, the bundle can be used to transmit images without further modification. Unfortunately, the fabrication of coherent fiber-optic bundles is too labor-intensive and expensive for many applications. An incoherent fiber-optic bundle can be fabricated more easily and at lower cost, but it produces a scrambled image because the position of the end of each fiber in the input plane is generally different from the end of the same fiber in the output plane. However, the image transmitted by an incoherent fiber-optic bundle can be unscrambled (or, from a different perspective, decoded) by digital processing of the output image if the mapping between the input and output fiber-end positions is known. Thus, the present invention enables the use of relatively inexpensive fiber-optic bundles to transmit images.

  13. Isothermal microcalorimetry, a tool for probing SWNT bundles.

    PubMed

    Marquis, Renaud; Greco, Carla; Schultz, Patrick; Meunier, Stéphane; Mioskowski, Charles

    2009-11-01

    The bundling state of several dry single-walled carbon nanotube (SWNT) samples is compared using isothermal microcalorimetry (IMC). So as to get different dry samples with various bundling states, the pristine SWNTs were pretreated with a solution of an aromatic amphiphile with or without sonication, washed and dried before being studied by IMC. The bundling state of the different SWNT samples, which was first analyzed by TEM, was then correlated to the obtained IMC data thanks to the interpretation of the observed energy transfer phenomena. From our results, IMC appears to be an interesting technique for the surface probing of dry SWNT samples, and herein for the evaluation of the bundling state.

  14. Pixelation effect removal from fiber bundle probe based optical coherence tomography imaging.

    PubMed

    Han, Jae-Ho; Lee, Junghoon; Kang, Jin U

    2010-03-29

    A method of eliminating pixelization effect from en face optical coherence tomography (OCT) image when a fiber bundle is used as an OCT imaging probe is presented. We have demonstrated that applying a histogram equalization process before performing a weighted-averaged Gaussian smoothing filter to the original lower gray level intensity based image not only removes the structural artifact of the bundle but also enhances the image quality with minimum blurring of object's image features. The measured contrast-to-noise ratio (CNR) for an image of the US Air Force test target was 14.7dB (4.9dB), after (before) image processing. In addition, by performing the spatial frequency analysis based on two-dimensional discrete Fourier transform (2-D DFT), we were able to observe that the periodic intensity peaks induced by the regularly arrayed structure of the fiber bundle can be efficiently suppressed by 41.0dB for the first nearby side lobe as well as to obtain the precise physical spacing information of the fiber grid. The proposed combined method can also be used as a straight forward image processing tool for any imaging system utilizing fiber bundle as a high-resolution imager.

  15. Brownian dynamics simulation of sickle hemoglobin bundle formation

    NASA Astrophysics Data System (ADS)

    Liu, Ya; Gunton, James; Chakrabarti, Amit

    2010-03-01

    The physical properties of biopolymer fibers, such as their stability and degree of aggregation, are implicated in many diseases, including sickle cell anemia. The natural chirality of protofilaments plays a crucial role in the formation of sickle hemoglobin fiber which leads to the permanent blockage of microvessels. We use Brownian dynamics to investigate the kinetics of fiber aggregation. The geometrical helical structure and chirality of the filaments are modeled by anisotropic patch-like interactions. We present the kinetics of fiber formation and study the possibility of a finite critical fiber bundle size. We compare our results with various experimental and theoretical results. This work is supported by grants from the NSF and the G. Harold and Leila Y. Mathers Foundation.

  16. MENT reconstruction and potting comparison of a LMFBR fuel bundle

    SciTech Connect

    Betten, P.R.; Tow, D.M.

    1984-01-01

    Since the advent of computer-assisted-tomography (CAT), the CAT techniques have been rapidly expanded to the nuclear industry. A number of investigators have applied these techniques to reconstruct the fuel bundle configuration inside a subassembly with various degrees of resolution; however, there has been little data available on the accuracy of these reconstructions, and no comparisons have been made with the internal structure of actual irradiated subassemblies. Some efforts have utilized pretest mock-ups to calibrate the CAT algorithms, but the resulting mock-up configurations do not necessarily represent an actual subassembly, so an exact comparison has been lacking. The purpose of this paper is to present the results of a comparison between a CAT reconstruction of an irradiated subassembly and the destructive examination of the same subassembly.

  17. Bundled capillary electrophoresis using microstructured fibres.

    PubMed

    Rogers, Benjamin; Gibson, Graham T T; Oleschuk, Richard D

    2011-01-01

    Joule heating, arising from the electric current passing through the capillary, causes many undesired effects in CE that ultimately result in band broadening. The use of narrow-bore capillaries helps to solve this problem as smaller cross-sectional area results in decreased Joule heating and the rate of heat dissipation is increased by the larger surface-to-volume ratio. Issues arising from such small capillaries, such as poor detection sensitivity, low loading capacity and high flow-induced backpressure (complicating capillary loading) can be avoided by using a bundle of small capillaries operating simultaneously that share buffer reservoirs. Microstructured fibres, originally designed as waveguides in the telecommunication industry, are essentially a bundle of parallel ∼5 μm id channels that extend the length of a fibre having otherwise similar dimensions to conventional CE capillaries. This work presents the use of microstructured fibres for CZE, taking advantage of their relatively high surface-to-volume ratio and the small individual size of each channel to effect highly efficient separations, particularly for dye-labelled peptides.

  18. Confinement-Dependent Friction in Peptide Bundles

    PubMed Central

    Erbaş, Aykut; Netz, Roland R.

    2013-01-01

    Friction within globular proteins or between adhering macromolecules crucially determines the kinetics of protein folding, the formation, and the relaxation of self-assembled molecular systems. One fundamental question is how these friction effects depend on the local environment and in particular on the presence of water. In this model study, we use fully atomistic MD simulations with explicit water to obtain friction forces as a single polyglycine peptide chain is pulled out of a bundle of k adhering parallel polyglycine peptide chains. The whole system is periodically replicated along the peptide axes, so a stationary state at prescribed mean sliding velocity V is achieved. The aggregation number is varied between k = 2 (two peptide chains adhering to each other with plenty of water present at the adhesion sites) and k = 7 (one peptide chain pulled out from a close-packed cylindrical array of six neighboring peptide chains with no water inside the bundle). The friction coefficient per hydrogen bond, extrapolated to the viscous limit of vanishing pulling velocity V → 0, exhibits an increase by five orders of magnitude when going from k = 2 to k = 7. This dramatic confinement-induced friction enhancement we argue to be due to a combination of water depletion and increased hydrogen-bond cooperativity. PMID:23528088

  19. Tangent Bundle Elastica and Computer Vision.

    PubMed

    Ben-Shahar, Ohad; Ben-Yosef, Guy

    2015-01-01

    Visual curve completion, an early visual process that completes the occluded parts between observed boundary fragments (a.k.a. inducers), is a major problem in perceptual organization and a critical step toward higher level visual tasks in both biological and machine vision. Most computational contributions to solving this problem suggest desired perceptual properties that the completed contour should satisfy in the image plane, and then seek the mathematical curves that provide them. Alternatively, few studies (including by the authors) have suggested to frame the problem not in the image plane but rather in the unit tangent bundleR (2) × S(1), the space that abstracts the primary visual cortex, where curve completion allegedly occurs. Combining both schools, here we propose and develop a biologically plausible theory of elastica in the tangent bundle that provides not only perceptually superior completion results but also a rigorous computational prediction that inducer curvatures greatly affects the shape of the completed curve, as indeed indicated by human perception.

  20. Constrained ripple optimization of Tokamak bundle divertors

    SciTech Connect

    Hively, L.M.; Rome, J.A.; Lynch, V.E.; Lyon, J.F.; Fowler, R.H.; Peng, Y-K.M.; Dory, R.A.

    1983-02-01

    Magnetic field ripple from a tokamak bundle divertor is localized to a small toroidal sector and must be treated differently from the usual (distributed) toroidal field (TF) coil ripple. Generally, in a tokamak with an unoptimized divertor design, all of the banana-trapped fast ions are quickly lost due to banana drift diffusion or to trapping between the 1/R variation in absolute value vector B ..xi.. B and local field maxima due to the divertor. A computer code has been written to optimize automatically on-axis ripple subject to these constraints, while varying up to nine design parameters. Optimum configurations have low on-axis ripple (<0.2%) so that, now, most banana-trapped fast ions are confined. Only those ions with banana tips near the outside region (absolute value theta < or equal to 45/sup 0/) are lost. However, because finite-sized TF coils have not been used in this study, the flux bundle is not expanded.

  1. Adaptive Optics Imaging of Healthy and Abnormal Regions of Retinal Nerve Fiber Bundles of Patients With Glaucoma

    PubMed Central

    Chen, Monica F.; Chui, Toco Y. P.; Alhadeff, Paula; Rosen, Richard B.; Ritch, Robert; Dubra, Alfredo; Hood, Donald C.

    2015-01-01

    Purpose. To better understand the nature of glaucomatous damage of the macula, especially the structural changes seen between relatively healthy and clearly abnormal (AB) retinal regions, using an adaptive optics scanning light ophthalmoscope (AO-SLO). Methods. Adaptive optics SLO images and optical coherence tomography (OCT) vertical line scans were obtained on one eye of seven glaucoma patients, with relatively deep local arcuate defects on the 10-2 visual field test in one (six eyes) or both hemifields (one eye). Based on the OCT images, the retinal nerve fiber (RNF) layer was divided into two regions: (1) within normal limits (WNL), relative RNF layer thickness within mean control values ±2 SD; and (2) AB, relative thickness less than −2 SD value. Results. As seen on AO-SLO, the pattern of AB RNF bundles near the border of the WNL and AB regions differed across eyes. There were normal-appearing bundles in the WNL region of all eyes and AB-appearing bundles near the border with the AB region. This region with AB bundles ranged in extent from a few bundles to the entire AB region in the case of one eye. All other eyes had a large AB region without bundles. However, in two of these eyes, a few bundles were seen within this region of otherwise missing bundles. Conclusions. The AO-SLO images revealed details of glaucomatous damage that are difficult, if not impossible, to see with current OCT technology. Adaptive optics SLO may prove useful in following progression in clinical trials, or in disease management, if AO-SLO becomes widely available and easy to use. PMID:25574048

  2. Single-molecule analysis of the microtubule cross-linking protein MAP65-1 reveals a molecular mechanism for contact-angle-dependent microtubule bundling.

    PubMed

    Tulin, Amanda; McClerklin, Sheri; Huang, Yue; Dixit, Ram

    2012-02-22

    Bundling of microtubules (MTs) is critical for the formation of complex MT arrays. In land plants, the interphase cortical MTs form bundles specifically following shallow-angle encounters between them. To investigate how cells select particular MT contact angles for bundling, we used an in vitro reconstitution approach consisting of dynamic MTs and the MT-cross-linking protein MAP65-1. We found that MAP65-1 binds to MTs as monomers and inherently targets antiparallel MTs for bundling. Dwell-time analysis showed that the affinity of MAP65-1 for antiparallel overlapping MTs is about three times higher than its affinity for single MTs and parallel overlapping MTs. We also found that purified MAP65-1 exclusively selects shallow-angle MT encounters for bundling, indicating that this activity is an intrinsic property of MAP65-1. Reconstitution experiments with mutant MAP65-1 proteins with different numbers of spectrin repeats within the N-terminal rod domain showed that the length of the rod domain is a major determinant of the range of MT bundling angles. The length of the rod domain also determined the distance between MTs within a bundle. Together, our data show that the rod domain of MAP65-1 acts both as a spacer and as a structural element that specifies the MT encounter angles that are conducive for bundling.

  3. Bundle brunch reentrant ventricular tachycardia with two distinct conduction patterns in a patient with complete right bundle branch block.

    PubMed

    Enjoji, Yoshihisa; Mizobuchi, Masahiro; Shibata, Kensaku; Ono, Tsuyoshi; Funatsu, Atsushi; Kanbayashi, Daisuke; Kobayashi, Tomoko; Nakamura, Shigeru

    2006-12-01

    We report a rare case of bundle branch reentrant ventricular tachycardia [BBRVT]. A 67-year-old female was admitted for management of wide QRS tachycardia (right bundle branch block [RBBB] and a southwest axis). The mapping procedure revealed the tachycardia circuit consisted of the left anterior fascicle (LAF) as an antegrade, and the right bundle as a retrograde pathway. She presented RBBB during sinus rhythm. LAF ablation changed the tachycardia configuration to a northwest axis and prolonged the cycle length. Left posterior fascicle ablation terminated the tachycardia, and complete atrioventricular block occurred, which showed the unidirectional conduction over the right bundle.

  4. Architecture of helix bundle membrane proteins: an analysis of cytochrome c oxidase from bovine mitochondria.

    PubMed Central

    Wallin, E.; Tsukihara, T.; Yoshikawa, S.; von Heijne, G.; Elofsson, A.

    1997-01-01

    We have analyzed the structure of mitochondrial cytochrome c oxidase in terms of general characteristics thought to be important for describing the architecture of helix bundle membrane proteins. Many aspects of the structure are similar to what has previously been found for the photosynthetic reaction center and bacteriorhodopsin. Our results lead to a considerably more precise general picture of membrane protein architecture than has hitherto been possible to obtain. PMID:9098890

  5. Coherent hollow-core waveguide bundles for thermal imaging.

    PubMed

    Gal, Udi; Harrington, James; Ben-David, Moshe; Bledt, Carlos; Syzonenko, Nicholas; Gannot, Israel

    2010-09-01

    There has been very little work done in the past to extend the wavelength range of fiber image bundles to the IR range. This is due, in part, to the lack of IR transmissive fibers with optical and mechanical properties analogous to the oxide glass fibers currently employed in the visible fiber bundles. Our research is aimed at developing high-resolution hollow-core coherent IR fiber bundles for transendoscopic infrared imaging. We employ the hollow glass waveguide (HGW) technology that was used successfully to make single-HGWs with Ag/AgI thin film coatings to form coherent bundles for IR imaging. We examine the possibility of developing endoscopic systems to capture thermal images using hollow waveguide fiber bundles adjusted to the 8-10?mum spectral range and investigate the applicability of such systems. We carried out a series of measurements in order to characterize the optical properties of the fiber bundles. These included the attenuation, resolution, and temperature response. We developed theoretical models and simulation tools that calculate the light propagation through HGW bundles, and which can be used to calculate the optical properties of the fiber bundles. Finally, the HGW fiber bundles were used to transmit thermal images of various heated objects; the results were compared with simulation results. The experimental results are encouraging, show an improvement in the resolution and thermal response of the HGW fiber bundles, and are consistent with the theoretical results. Nonetheless, additional improvements in the attenuation of the bundles are required in order to be able to use this technology for medical applications.

  6. Incorporating Endmember Variability into Spectral Mixture Analysis Through Endmember Bundles

    NASA Technical Reports Server (NTRS)

    Bateson, C. Ann; Asner, Gregory P.; Wessman, Carol A.

    1998-01-01

    Variation in canopy structure and biochemistry induces a concomitant variation in the top-of-canopy spectral reflectance of a vegetation type. Hence, the use of a single endmember spectrum to track the fractional abundance of a given vegetation cover in a hyperspectral image may result in fractions with considerable error. One solution to the problem of endmember variability is to increase the number of endmembers used in a spectral mixture analysis of the image. For example, there could be several tree endmembers in the analysis because of differences in leaf area index (LAI) and multiple scatterings between leaves and stems. However, it is often difficult in terms of computer or human interaction time to select more than six or seven endmembers and any non-removable noise, as well as the number of uncorrelated bands in the image, limits the number of endmembers that can be discriminated. Moreover, as endmembers proliferate, their interpretation becomes increasingly difficult and often applications simply need the aerial fractions of a few land cover components which comprise most of the scene. In order to incorporate endmember variability into spectral mixture analysis, we propose representing a landscape component type not with one endmember spectrum but with a set or bundle of spectra, each of which is feasible as the spectrum of an instance of the component (e.g., in the case of a tree component, each spectrum could reasonably be the spectral reflectance of a tree canopy). These endmember bundles can be used with nonlinear optimization algorithms to find upper and lower bounds on endmember fractions. This approach to endmember variability naturally evolved from previous work in deriving endmembers from the data itself by fitting a triangle, tetrahedron or, more generally, a simplex to the data cloud reduced in dimension by a principal component analysis. Conceptually, endmember variability could make it difficult to find a simplex that both surrounds the data

  7. Mechanism of Origin of Conduction Disturbances in Aging Human Atrial Bundles: Experimental and Model Study

    PubMed Central

    Spach, Madison S.; Heidlage, J. Francis; Dolber, Paul C.; Barr, Roger C.

    2007-01-01

    BACKGROUND Aging is associated with a significant increase in atrial tachyarrhythmias, especially atrial fibrillation. A macroscopic repolarization gradient created artificially by a stimulus at one site prior to a premature stimulus from a second site is widely considered to be part of the experimental protocol necessary for the initiation of such arrhythmias in the laboratory. How such gradients occur naturally in aging atrial tissue has remained unknown. OBJECTIVE This study was to determine if the pattern of cellular connectivity in aging human atrial bundles produces a mechanism for variable early premature responses. METHODS Extracellular and intracellular potentials were recorded following control and premature stimuli at a single site in aging human atrial bundles. We also measured cellular geometry, the distribution of connexins, and the distribution of collagenous septa. A model of the atrial bundles was constructed based on the morphological results. Action potential propagation and the sodium current were analyzed following premature stimuli in the model. RESULTS Similar extracellular potential waveform responses occurred following early premature stimuli in the aging bundles and in the model. Variable premature conduction patterns were accounted for by the single model of aging atrial structure. A major feature of the model results was that the conduction events and the magnitude of the sodium current at multiple sites were very sensitive to small changes in the location and the timing of premature stimuli. CONCLUSION In aging human atrial bundles stimulated from only a single site, premature stimuli induce variable arrhythmogenic conduction responses. The generation of these responses is greatly enhanced by remodeling of cellular connectivity during aging. The results provide insight into sodium current-structural interactions as a general mechanism of arrhythmogenic atrial responses to premature stimuli. PMID:17275753

  8. Diversity in the organization of elastin bundles and intramembranous muscles in bat wings.

    PubMed

    Cheney, Jorn A; Allen, Justine J; Swartz, Sharon M

    2017-04-01

    Unlike birds and insects, bats fly with wings composed of thin skin that envelops the bones of the forelimb and spans the area between the limbs, digits, and sometimes the tail. This skin is complex and unusual; it is thinner than typical mammalian skin and contains organized bundles of elastin and embedded skeletal muscles. These elements are likely responsible for controlling the shape of the wing during flight and contributing to the aerodynamic capabilities of bats. We examined the arrangement of two macroscopic architectural elements in bat wings, elastin bundles and wing membrane muscles, to assess the diversity in bat wing skin morphology. We characterized the plagiopatagium and dactylopatagium of 130 species from 17 families of bats using cross-polarized light imaging. This method revealed structures with distinctive relative birefringence, heterogeneity of birefringence, variation in size, and degree of branching. We used previously published anatomical studies and tissue histology to identify birefringent structures, and we analyzed their architecture across taxa. Elastin bundles, muscles, neurovasculature, and collagenous fibers are present in all species. Elastin bundles are oriented in a predominantly spanwise or proximodistal direction, and there are five characteristic muscle arrays that occur within the plagiopatagium, far more muscle than typically recognized. These results inform recent functional studies of wing membrane architecture, support the functional hypothesis that elastin bundles aid wing folding and unfolding, and further suggest that all bats may use these architectural elements for flight. All species also possess numerous muscles within the wing membrane, but the architecture of muscle arrays within the plagiopatagium varies among families. To facilitate present and future discussion of these muscle arrays, we refine wing membrane muscle nomenclature in a manner that reflects this morphological diversity. The architecture of the

  9. Incremental Real-Time Bundle Adjustment for Multi-Camera Systems with Points at Infinity

    NASA Astrophysics Data System (ADS)

    Schneider, J.; Läbe, T.; Förstner, W.

    2013-08-01

    This paper presents a concept and first experiments on a keyframe-based incremental bundle adjustment for real-time structure and motion estimation in an unknown scene. In order to avoid periodic batch steps, we use the software iSAM2 for sparse nonlinear incremental optimization, which is highly efficient through incremental variable reordering and fluid relinearization. We adapted the software to allow for (1) multi-view cameras by taking the rigid transformation between the cameras into account, (2) omnidirectional cameras as it can handle arbitrary bundles of rays and (3) scene points at infinity, which improve the estimation of the camera orientation as points at the horizon can be observed over long periods of time. The real-time bundle adjustment refers to sets of keyframes, consisting of frames, one per camera, taken in a synchronized way, that are initiated if a minimal geometric distance to the last keyframe set is exceeded. It uses interest points in the keyframes as observations, which are tracked in the synchronized video streams of the individual cameras and matched across the cameras, if possible. First experiments show the potential of the incremental bundle adjustment w.r.t. time requirements. Our experiments are based on a multi-camera system with four fisheye cameras, which are mounted on a UAV as two stereo pairs, one looking ahead and one looking backwards, providing a large field of view.

  10. Single-pixel phase-corrected fiber bundle endomicroscopy with lensless focussing capability.

    PubMed

    Gordon, George S D; Joseph, James; Bohndiek, Sarah E; Wilkinson, Timothy D

    2015-08-15

    In this paper a novel single-pixel method for coherent imaging through an endoscopic fiber bundle is presented. The use of a single-pixel detector allows greater sensitivity over a wider range of wavelengths, which could have significant applications in endoscopic fluorescence microscopy. First, the principle of lensless focussing at the distal end of a coherent fiber bundle is simulated to examine the impact of pixelation at microscopic scales. Next, an experimental optical correlator system using spatial light modulators (SLMs) is presented. A simple contrast imaging method of characterizing and compensating phase aberrations introduced by fiber bundles is described. Experimental results are then presented showing that our phase compensation method enables characterization of the optical phase profile of individual fiberlets. After applying this correction, early results demonstrating the ability of the system to electronically adjust the focal plane at the distal end of the fiber bundle are presented. The structural similarity index (SSIM) between the simulated image and the experimental focus-adjusted image increases noticeably when the phase correction is applied and the retrieved image is visually recognizable. Strategies to improve image quality are discussed.

  11. Single-pixel phase-corrected fiber bundle endomicroscopy with lensless focussing capability

    PubMed Central

    Gordon, George S.D.; Joseph, James; Bohndiek, Sarah E.; Wilkinson, Timothy D.

    2016-01-01

    In this paper a novel single-pixel method for coherent imaging through an endoscopic fiber bundle is presented. The use of a single-pixel detector allows greater sensitivity over a wider range of wavelengths, which could have significant applications in endoscopic fluorescence microscopy. First, the principle of lensless focussing at the distal end of a coherent fiber bundle is simulated to examine the impact of pixelation at microscopic scales. Next, an experimental optical correlator system using spatial light modulators (SLMs) is presented. A simple contrast imaging method of characterizing and compensating phase aberrations introduced by fiber bundles is described. Experimental results are then presented showing that our phase compensation method enables characterization of the optical phase profile of individual fiberlets. After applying this correction, early results demonstrating the ability of the system to electronically adjust the focal plane at the distal end of the fiber bundle are presented. The structural similarity index (SSIM) between the simulated image and the experimental focus-adjusted image increases noticeably when the phase correction is applied and the retrieved image is visually recognizable. Strategies to improve image quality are discussed. PMID:27279676

  12. Formation of an intricate helical bundle dictates the assembly of the 26S proteasome lid.

    PubMed

    Estrin, Eric; Lopez-Blanco, José Ramón; Chacón, Pablo; Martin, Andreas

    2013-09-03

    The 26S proteasome is the major ATP-dependent protease in eukaryotes and thus involved in regulating a diverse array of vital cellular processes. Three subcomplexes form this massive degradation machine: the lid, the base, and the core. While assembly of base and core has been well-studied, the detailed molecular mechanisms involved in formation of the nine-subunit lid remain largely unknown. Here, we reveal that helices found at the C terminus of each lid subunit form a helical bundle that directs the ordered self-assembly of the lid subcomplex. Furthermore, we use an integrative modeling approach to gain critical insights into the bundle topology and provide an important structural framework for our biochemical data. We show that the helical bundle serves as a hub through which the last-added subunit Rpn12 monitors proper lid assembly before incorporation into the proteasome. Finally, we predict that the assembly of the COP9 signalosome depends on a similar helical bundle.

  13. Lexical Bundles: Facilitating University "Talk" in Group Discussions

    ERIC Educational Resources Information Center

    Heng, Chan Swee; Kashiha, Hadi; Tan, Helen

    2014-01-01

    Group discussion forms an integral language experience for most language learners, providing them with an opportunity to express themselves in a naturalistic setting. Multi-word expressions are commonly used and one of them is lexical bundles. Lexical bundles are types of extended collocations that occur more commonly than we expect; they are…

  14. Amplitude death of coupled hair bundles with stochastic channel noise

    NASA Astrophysics Data System (ADS)

    Kim, Kyung-Joong; Ahn, Kang-Hun

    2014-04-01

    Hair cells conduct auditory transduction in vertebrates. In lower vertebrates such as frogs and turtles, due to the active mechanism in hair cells, hair bundles (stereocilia) can be spontaneously oscillating or quiescent. Recently an amplitude death phenomenon has been proposed [K.-H. Ahn, J. R. Soc. Interface, 10, 20130525 (2013)] as a mechanism for auditory transduction in frog hair-cell bundles, where sudden cessation of the oscillations arises due to the coupling between nonidentical hair bundles. The gating of the ion channel is intrinsically stochastic due to the stochastic nature of the configuration change of the channel. The strength of the noise due to the channel gating can be comparable to the thermal Brownian noise of hair bundles. Thus, we perform stochastic simulations of the elastically coupled hair bundles. In spite of stray noisy fluctuations due to its stochastic dynamics, our simulation shows the transition from collective oscillation to amplitude death as interbundle coupling strength increases. In its stochastic dynamics, the formation of the amplitude death state of coupled hair bundles can be seen as a sudden suppression of the displacement fluctuation of the hair bundles as the coupling strength increases. The enhancement of the signal-to-noise ratio through the amplitude death phenomenon is clearly seen in the stochastic dynamics. Our numerical results demonstrate that the multiple number of transduction channels per hair bundle is an important factor to the amplitude death phenomenon, because the phenomenon may disappear for a small number of transduction channels due to strong gating noise.

  15. As Can Be Seen: Lexical Bundles and Disciplinary Variation

    ERIC Educational Resources Information Center

    Hyland, Ken

    2008-01-01

    An important component of fluent linguistic production is control of the multi-word expressions referred to as clusters, chunks or bundles. These are extended collocations which appear more frequently than expected by chance, helping to shape meanings in specific contexts and contributing to our sense of coherence in a text. Bundles have begun to…

  16. Lexical Bundles in University Spoken and Written Registers

    ERIC Educational Resources Information Center

    Biber, Douglas; Barbieri, Federica

    2007-01-01

    Lexical bundles--recurrent sequences of words--are important building blocks of discourse in spoken and written registers. Previous research has shown that lexical bundles are especially prevalent in university classroom teaching, where they serve three major discourse functions: stance expressions, discourse organizers, and referential…

  17. Sensory transduction: the 'swarm intelligence' of auditory hair bundles.

    PubMed

    Albert, Jörg

    2011-08-23

    In vertebrate hair cells, the hair bundle is responsible for the conversion of mechanical vibrations into electrical signals. In a combined experimental and computational tour de force, a group of researchers now presents a quantitative model that explains how the bundle's specific microarchitecture gives rise to its exquisite mechanosensory properties.

  18. Method of pressure pulse cleaning a tube bundle heat exchanger

    SciTech Connect

    Scharton, T.D.; Taylor, G.B.

    1987-04-07

    A method is described of removing the products of corrosion, oxidation, sedimentation and comparable chemical reactions collectively known as sludge which settle on the bottom of a tube bundle heat exchange and form a pile of sludge. The tube bundle heat exchanger is characterized by a tube bundle heat exchanger wall and a thick metal plate known as a tube sheet near the lower portion of the tube bundle heat exchanger wall's interior surface. The tube sheet serves to support the lower ends of a multiplicity of heat exchanger tubes within the tube bundle heat exchanger. The tube bundle heat exchange wall further comprises a multiplicity of small holes known as hand holes, manways, drain lines and vents, located around its circumference and above the tube sheet. The method is described of removing the pile of sludge which settles on the tube sheet comprising: a. locating at least one air-gun type pressure pulse shock wave source outside the tube bundle heat exchanger so as to be able to introduce pressure pulse shock waves through one or more of the multiplicity of hand holes, manways, drain lines and vents; and b. filling the tube bundle heat exchanger with a liquid to a level above the pile of sludge.

  19. Presenting Lexical Bundles for Explicit Noticing with Schematic Linguistic Representation

    ERIC Educational Resources Information Center

    Thomson, Haidee Elizabeth

    2016-01-01

    Lexical bundles are essential for fluency, but their incompleteness is a stumbling block for learners. In this study, two presentation methods to increase awareness of lexical bundles through explicit noticing are explored and compared with incidental exposure. The three conditions in this study were as follows: noticing with schematic linguistic…

  20. EsxB, a secreted protein from Bacillus anthracis forms two distinct helical bundles

    SciTech Connect

    Fan, Yao; Tan, Kemin; Chhor, Gekleng; Butler, Emily K.; Jedrzejczak, Robert P.; Missiakas, Dominique; Joachimiak, Andrzej

    2015-07-03

    The EsxB protein from Bacillus anthracis belongs to the WXG100 family, a group of proteins secreted by a specialized secretion system. We have determined the crystal structures of recombinant EsxB and discovered that the small protein (~10 kDa), comprised of a helix-loop-helix (HLH) hairpin, is capable of associating into two different helical bundles. The two basic quaternary assemblies of EsxB are an antiparallel (AP) dimer and a rarely observed bisecting U (BU) dimer. This structural duality of EsxB is believed to originate from the heptad repeat sequence diversity of the first helix of its HLH hairpin, which allows for two alternative helix packing. The flexibility of EsxB and the ability to form alternative helical bundles underscore the possibility that this protein can serve as an adaptor in secretion and can form hetero-oligomeric helix bundle(s) with other secreted members of the WXG100 family, such as EsxW. The highly conserved WXG motif is located within the loop of the HLH hairpin and is mostly buried within the helix bundle suggesting that its role is mainly structural. The exact functions of the motif, including a proposed role as a secretion signal, remain unknown.

  1. Extendability of parallel sections in vector bundles

    NASA Astrophysics Data System (ADS)

    Kirschner, Tim

    2016-01-01

    I address the following question: Given a differentiable manifold M, what are the open subsets U of M such that, for all vector bundles E over M and all linear connections ∇ on E, any ∇-parallel section in E defined on U extends to a ∇-parallel section in E defined on M? For simply connected manifolds M (among others) I describe the entirety of all such sets U which are, in addition, the complement of a C1 submanifold, boundary allowed, of M. This delivers a partial positive answer to a problem posed by Antonio J. Di Scala and Gianni Manno (2014). Furthermore, in case M is an open submanifold of Rn, n ≥ 2, I prove that the complement of U in M, not required to be a submanifold now, can have arbitrarily large n-dimensional Lebesgue measure.

  2. Bundled automobile insurance coverage and accidents.

    PubMed

    Li, Chu-Shiu; Liu, Chwen-Chi; Peng, Sheng-Chang

    2013-01-01

    This paper investigates the characteristics of automobile accidents by taking into account two types of automobile insurance coverage: comprehensive vehicle physical damage insurance and voluntary third-party liability insurance. By using a unique data set in the Taiwanese automobile insurance market, we explore the bundled automobile insurance coverage and the occurrence of claims. It is shown that vehicle physical damage insurance is the major automobile coverage and affects the decision to purchase voluntary liability insurance coverage as a complement. Moreover, policyholders with high vehicle physical damage insurance coverage have a significantly higher probability of filing vehicle damage claims, and if they additionally purchase low voluntary liability insurance coverage, their accident claims probability is higher than those who purchase high voluntary liability insurance coverage. Our empirical results reveal that additional automobile insurance coverage information can capture more driver characteristics and driving behaviors to provide useful information for insurers' underwriting policies and to help analyze the occurrence of automobile accidents.

  3. Vision, healing brush, and fiber bundles

    NASA Astrophysics Data System (ADS)

    Georgiev, Todor

    2005-03-01

    The Healing Brush is a tool introduced for the first time in Adobe Photoshop (2002) that removes defects in images by seamless cloning (gradient domain fusion). The Healing Brush algorithms are built on a new mathematical approach that uses Fibre Bundles and Connections to model the representation of images in the visual system. Our mathematical results are derived from first principles of human vision, related to adaptation transforms of von Kries type and Retinex theory. In this paper we present the new result of Healing in arbitrary color space. In addition to supporting image repair and seamless cloning, our approach also produces the exact solution to the problem of high dynamic range compression of17 and can be applied to other image processing algorithms.

  4. On the presence of dendrite bundles in the cerebral cortex of the Madagascan lesser hedgehog tenrec and the red-eared pond turtle.

    PubMed

    Schmolke, C; Künzle, H

    1997-09-01

    In mammals with a well-differentiated neocortex apical dendrites of pyramidal cells form vertical bundles. Little is known about the presence of dendrite bundles in animals with a poorly differentiated cortex. In this paper the presence of dendrite bundles has been investigated in the lesser hedgehog tenrec, Echinops telfairi, a basal insectivore with a very low degree of neocorticalization. In a further step the arrangement of dendrites has been analyzed in the cerebral cortex of the red-eared pond turtle, Pseudemys scripta elegans. Among non-mammalian vertebrates, reptiles have a cerebral cortex that is relatively most comparable with the mammalian one, and the cerebral cortex of turtles shows more structural and functional similarities with the cortex in mammals than those of other reptiles. In the hedgehog tenrec, bundles of apical dendrites are found in all neo-cortical areas, the cingulate and retrosplenial cortices. The shape and arrangement of dendrite bundles are primarily determined by apical dendrites of lamina V pyramids. Apical dendrites originating in laminae III/IV or VI join these bundles, and do not give rise to separate sets of bundles in the supra- and infragranular layers as in other mammals. Center to center distances between bundles determined in the neocortical areas A(2-4) range from 7 to 76 microm, with an average of 32 microm. Area-specific differences are found concerning the length of bundles as well as the number, caliber, branching pattern and packing density of dendrites sharing an individual bundle. In the three-layered entorhinal cortex and the hippocampus dendrite bundles are not observed. In the turtle, no vertical bundles of dendrites are seen either in the medial, dorsomedial or medial part of the dorsal cortex. Only in the lateral part of the dorsal cortex are isolated bundles of apical dendrites originating from groups of perikarya situated below the main level of lamina II detected. Our findings suggest that the presence of

  5. Voltage- and calcium-dependent motility of saccular hair bundles

    NASA Astrophysics Data System (ADS)

    Quiñones, Patricia M.; Meenderink, Sebastiaan W. F.; Bozovic, Dolores

    2015-12-01

    Active bundle motility, which is hypothesized to supply feedback for mechanical amplification of signals, is thought to enhance sensitivity and sharpen tuning in vestibular and auditory organs. To study active hair bundle motility, we combined high-speed camera recordings of bullfrog sacculi, which were mounted in a two-compartment chamber, and voltage-clamp of the hair cell membrane potential. Using this paradigm, we measured three types of bundle motions: 1) spontaneous oscillations which can be analyzed to measure the physiological operating range of the transduction channel; 2) a sustained quasi-static movement of the bundle that depends on membrane potential; and 3) a fast, transient and asymmetric movement that resets the bundle position and depends on changes in the membrane potential. These data support a role for both calcium and voltage in the transduction-channel function.

  6. Historical dynamics in ecosystem service bundles

    PubMed Central

    Renard, Delphine; Rhemtulla, Jeanine M.; Bennett, Elena M.

    2015-01-01

    Managing multiple ecosystem services (ES), including addressing trade-offs between services and preventing ecological surprises, is among the most pressing areas for sustainability research. These challenges require ES research to go beyond the currently common approach of snapshot studies limited to one or two services at a single point in time. We used a spatiotemporal approach to examine changes in nine ES and their relationships from 1971 to 2006 across 131 municipalities in a mixed-use landscape in Quebec, Canada. We show how an approach that incorporates time and space can improve our understanding of ES dynamics. We found an increase in the provision of most services through time; however, provision of ES was not uniformly enhanced at all locations. Instead, each municipality specialized in providing a bundle (set of positively correlated ES) dominated by just a few services. The trajectory of bundle formation was related to changes in agricultural policy and global trends; local biophysical and socioeconomic characteristics explained the bundles’ increasing spatial clustering. Relationships between services varied through time, with some provisioning and cultural services shifting from a trade-off or no relationship in 1971 to an apparent synergistic relationship by 2006. By implementing a spatiotemporal perspective on multiple services, we provide clear evidence of the dynamic nature of ES interactions and contribute to identifying processes and drivers behind these changing relationships. Our study raises questions about using snapshots of ES provision at a single point in time to build our understanding of ES relationships in complex and dynamic social-ecological systems. PMID:26460005

  7. Big things come in bundled packages: implications of bundled payment systems in health care reimbursement reform.

    PubMed

    Delisle, Dennis R

    2013-01-01

    With passage of the Affordable Care Act, the ever-evolving landscape of health care braces for another shift in the reimbursement paradigm. As health care costs continue to rise, providers are pressed to deliver efficient, high-quality care at flat to minimally increasing rates. Inherent systemwide inefficiencies between payers and providers at various clinical settings pose a daunting task for enhancing collaboration and care coordination. A change from Medicare's fee-for-service reimbursement model to bundled payments offers one avenue for resolution. Pilots using such payment models have realized varying degrees of success, leading to the development and upcoming implementation of a bundled payment initiative led by the Center for Medicare and Medicaid Innovation. Delivery integration is critical to ensure high-quality care at affordable costs across the system. Providers and payers able to adapt to the newly proposed models of payment will benefit from achieving cost reductions and improved patient outcomes and realize a competitive advantage.

  8. Probing the sliding interactions between bundled actin filaments

    NASA Astrophysics Data System (ADS)

    Ward, Andy; Dogic, Zvonimir

    2012-02-01

    Assemblies of filamentous biopolymers are hierarchical materials in which the properties of the overall assemblage are determined by structure and interactions between constituent particles at all hierarchical levels. For example, the overall bending rigidity of a two bundled filaments greatly depends on the bending rigidity of, and the adhesion strength between individual filaments. However, another property of importance is the ability for the filaments to slide freely against one another. Everyday experience indicates that it is much easier to bend a stack of papers in which individual sheets freely slide past each other than the same stack of papers in which all the sheets are irreversibly glued together. Similarly, in filamentous structures the ability for local re-arrangement is of the utmost importance in determining the properties of the structures observed. We have developed a method to directly measure the frictional interactions between a pair of aligned filaments in a well-defined and controllable configuration. This enables us to systematically investigate the role of adhesion strength, filament orientation, length, and surface structure.

  9. His bundle recordings in right bundle-branch block coexisting with iatrogenic right ventricular pre-excitation

    PubMed Central

    Castellanos, Agustin; Castillo, Cesar A.

    1972-01-01

    Iatrogenic right ventricular pre-excitation failed to abolish right bundle-branch block in two patients. When `exclusive' His bundle pacing was performed, the QRS complexes, St-V, and St-LVE intervals were similar to the ventricular deflections, H-V, and V-LVE (intervals) recorded during sinus rhythm. `Exclusive' pacing of the ordinary muscle at the right ventricular inflow tract produced a complete left bundle-branch block pattern without abnormal left axis deviation. Pacing of both His bundle and ordinary muscle yielded combination complexes in which the right bundle-branch block pattern persisted. The ventricular activation process was studied in these beats, as well as during the right and left bundle-branch block induced by coupled atrial stimulation. It appeared as if certain areas of the right septal surface behaved, electrophysiologically, as if they belonged to the left ventricle. Impulses emerging from these sites were not propagated to the right ventricular free wall. The latter was activated by the excitation front emerging through the left bundle system. During right bundle-branch block the endocardium of the right ventricular inflow was activated before the peak of the R in V1. Bipolar leads, 1 mm apart (with the possible exception of the ones over the tricuspid valve), were helpful in mapping the spread of activation in the human heart. Images PMID:18610233

  10. BUNDLE - A Novel Furnace for Performing Controlled Directional Solidification Experiments in a Microgravity Environment

    NASA Technical Reports Server (NTRS)

    Carrasquillo, Edgar J.; Griffin, Mark R.; Hammond, Monica S.; Johnson, Martin L.; Grugel, R. N.

    2001-01-01

    indicating uniform axial heat flow. Delineation between the growing dendrites and eutectic structure with the "quenched-in" liquid was sharp, attesting to the efficacy of the helium quench. BUNDLE's conception, development, capability, and adaptability are presented (in view of Flight PI's needs and science requirements) through viewgraphs depicting actual hardware, generated thermal analysis, and micrographs prepared from BUNDLE processed, flight-like samples.

  11. BUNDLE: A Novel Furnace for Performing Controlled Directional Solidification Experiments in a Microgravity Environment

    NASA Technical Reports Server (NTRS)

    Carrasquillo, Edgar J.; Griffin, Mark R.; Hammond, Monica S.; Johnson, Martin L.; Grugel, R. N.

    2000-01-01

    indicating uniform axial heat flow. Delineation between the growing dendrites and eutectic structure with the "quenched-in" liquid was sharp, attesting to the efficacy of the helium quench. BUNDLE's conception, development, capability, and adaptability are presented (in view of Flight PI's needs and science requirements) through viewgraphs depicting actual hardware, generated thermal analysis, and micrographs prepared from BUNDLE processed, flight-like samples.

  12. A categorical equivalence between generalized holonomy maps on a connected manifold and principal connections on bundles over that manifold

    NASA Astrophysics Data System (ADS)

    Rosenstock, Sarita; Weatherall, James Owen

    2016-10-01

    A classic result in the foundations of Yang-Mills theory, due to Barrett [Int. J. Theor. Phys. 30, 1171-1215 (1991)], establishes that given a "generalized" holonomy map from the space of piece-wise smooth, closed curves based at some point of a manifold to a Lie group, there exists a principal bundle with that group as structure group and a principal connection on that bundle such that the holonomy map corresponds to the holonomies of that connection. Barrett also provided one sense in which this "recovery theorem" yields a unique bundle, up to isomorphism. Here we show that something stronger is true: with an appropriate definition of isomorphism between generalized holonomy maps, there is an equivalence of categories between the category whose objects are generalized holonomy maps on a smooth, connected manifold and whose arrows are holonomy isomorphisms, and the category whose objects are principal connections on principal bundles over a smooth, connected manifold. This result clarifies, and somewhat improves upon, the sense of "unique recovery" in Barrett's theorems; it also makes precise a sense in which there is no loss of structure involved in moving from a principal bundle formulation of Yang-Mills theory to a holonomy, or "loop," formulation.

  13. In vivo bioluminescence and reflectance imaging of multiple organs in bioluminescence reporter mice by bundled-fiber-coupled microscopy

    PubMed Central

    Ando, Yoriko; Sakurai, Takashi; Koida, Kowa; Tei, Hajime; Hida, Akiko; Nakao, Kazuki; Natsume, Mistuo; Numano, Rika

    2016-01-01

    Bioluminescence imaging (BLI) is used in biomedical research to monitor biological processes within living organisms. Recently, fiber bundles with high transmittance and density have been developed to detect low light with high resolution. Therefore, we have developed a bundled-fiber-coupled microscope with a highly sensitive cooled-CCD camera that enables the BLI of organs within the mouse body. This is the first report of in vivo BLI of the brain and multiple organs in luciferase-reporter mice using bundled-fiber optics. With reflectance imaging, the structures of blood vessels and organs can be seen clearly with light illumination, and it allowed identification of the structural details of bioluminescence images. This technique can also be applied to clinical diagnostics in a low invasive manner. PMID:27231601

  14. In vivo bioluminescence and reflectance imaging of multiple organs in bioluminescence reporter mice by bundled-fiber-coupled microscopy.

    PubMed

    Ando, Yoriko; Sakurai, Takashi; Koida, Kowa; Tei, Hajime; Hida, Akiko; Nakao, Kazuki; Natsume, Mistuo; Numano, Rika

    2016-03-01

    Bioluminescence imaging (BLI) is used in biomedical research to monitor biological processes within living organisms. Recently, fiber bundles with high transmittance and density have been developed to detect low light with high resolution. Therefore, we have developed a bundled-fiber-coupled microscope with a highly sensitive cooled-CCD camera that enables the BLI of organs within the mouse body. This is the first report of in vivo BLI of the brain and multiple organs in luciferase-reporter mice using bundled-fiber optics. With reflectance imaging, the structures of blood vessels and organs can be seen clearly with light illumination, and it allowed identification of the structural details of bioluminescence images. This technique can also be applied to clinical diagnostics in a low invasive manner.

  15. De novo design of a transmembrane Zn²⁺-transporting four-helix bundle.

    PubMed

    Joh, Nathan H; Wang, Tuo; Bhate, Manasi P; Acharya, Rudresh; Wu, Yibing; Grabe, Michael; Hong, Mei; Grigoryan, Gevorg; DeGrado, William F

    2014-12-19

    The design of functional membrane proteins from first principles represents a grand challenge in chemistry and structural biology. Here, we report the design of a membrane-spanning, four-helical bundle that transports first-row transition metal ions Zn(2+) and Co(2+), but not Ca(2+), across membranes. The conduction path was designed to contain two di-metal binding sites that bind with negative cooperativity. X-ray crystallography and solid-state and solution nuclear magnetic resonance indicate that the overall helical bundle is formed from two tightly interacting pairs of helices, which form individual domains that interact weakly along a more dynamic interface. Vesicle flux experiments show that as Zn(2+) ions diffuse down their concentration gradients, protons are antiported. These experiments illustrate the feasibility of designing membrane proteins with predefined structural and dynamic properties.

  16. A nano-microstructured artificial-hair-cell-type sensor based on topologically graded 3D carbon nanotube bundles

    NASA Astrophysics Data System (ADS)

    Yilmazoglu, O.; Yadav, S.; Cicek, D.; Schneider, J. J.

    2016-09-01

    A design for a unique artificial-hair-cell-type sensor (AHCTS) based entirely on 3D-structured, vertically aligned carbon nanotube (CNT) bundles is introduced. Standard microfabrication techniques were used for the straightforward micro-nano integration of vertically aligned carbon nanotube arrays composed of low-layer multi-walled CNTs (two to six layers). The mechanical properties of the carbon nanotube bundles were intensively characterized with regard to various substrates and CNT morphology, e.g. bundle height. The CNT bundles display excellent flexibility and mechanical stability for lateral bending, showing high tear resistance. The integrated 3D CNT sensor can detect three-dimensional forces using the deflection or compression of a central CNT bundle which changes the contact resistance to the shorter neighboring bundles. The complete sensor system can be fabricated using a single chemical vapor deposition (CVD) process step. Moreover, sophisticated external contacts to the surroundings are not necessary for signal detection. No additional sensors or external bias for signal detection are required. This simplifies the miniaturization and the integration of these nanostructures for future microsystem set-ups. The new nanostructured sensor system exhibits an average sensitivity of 2100 ppm in the linear regime with the relative resistance change per micron (ppm μm-1) of the individual CNT bundle tip deflection. Furthermore, experiments have shown highly sensitive piezoresistive behavior with an electrical resistance decrease of up to ˜11% at 50 μm mechanical deflection. The detection sensitivity is as low as 1 μm of deflection, and thus highly comparable with the tactile hair sensors of insects, having typical thresholds on the order of 30-50 μm. The AHCTS can easily be adapted and applied as a flow, tactile or acceleration sensor as well as a vibration sensor. Potential applications of the latter might come up in artificial cochlear systems. In

  17. Two-state approach to stochastic hair bundle dynamics

    NASA Astrophysics Data System (ADS)

    Clausznitzer, Diana; Lindner, Benjamin; Jülicher, Frank; Martin, Pascal

    2008-04-01

    Hair cells perform the mechanoelectrical transduction of sound signals in the auditory and vestibular systems of vertebrates. The part of the hair cell essential for this transduction is the so-called hair bundle. In vitro experiments on hair cells from the sacculus of the American bullfrog have shown that the hair bundle comprises active elements capable of producing periodic deflections like a relaxation oscillator. Recently, a continuous nonlinear stochastic model of the hair bundle motion [Nadrowski , Proc. Natl. Acad. Sci. U.S.A. 101, 12195 (2004)] has been shown to reproduce the experimental data in stochastic simulations faithfully. Here, we demonstrate that a binary filtering of the hair bundle's deflection (experimental data and continuous hair bundle model) does not change significantly the spectral statistics of the spontaneous as well as the periodically driven hair bundle motion. We map the continuous hair bundle model to the FitzHugh-Nagumo model of neural excitability and discuss the bifurcations between different regimes of the system in terms of the latter model. Linearizing the nullclines and assuming perfect time-scale separation between the variables we can map the FitzHugh-Nagumo system to a simple two-state model in which each of the states corresponds to the two possible values of the binary-filtered hair bundle trajectory. For the two-state model, analytical expressions for the power spectrum and the susceptibility can be calculated [Lindner and Schimansky-Geier, Phys. Rev. E 61, 6103 (2000)] and show the same features as seen in the experimental data as well as in simulations of the continuous hair bundle model.

  18. Dark-field illuminated reflectance fiber bundle endoscopic microscope

    NASA Astrophysics Data System (ADS)

    Liu, Xuan; Huang, Yong; Kang, Jin U.

    2011-04-01

    We propose a reflectance fiber bundle microscope using a dark-field illumination configuration for applications in endoscopic medical imaging and diagnostics. Our experiment results show that dark-field illumination can effectively suppress strong specular reflection from the proximal end of the fiber bundle. We realized a lateral resolution of 4.4 μm using the dark-field illuminated fiber bundle configuration. To demonstrate the feasibility of using the system to study cell morphology, we obtained still and video images of two thyroid cancer cell lines. Our results clearly allow differentiation of different cancer cell types.

  19. Characterization of a space orbited incoherent fiber optic bundle

    NASA Technical Reports Server (NTRS)

    Dewalt, Stephen A.; Taylor, Edward W.

    1993-01-01

    The results of a study performed to determine the effects of adverse space environments on a bundle of over 1800 optical fibers orbited for 69 months are reported. Experimental results are presented on an incoherent fiber optic bundle oriented in low Earth orbit aboard the Long Duration Exposure Facility (LDEF) satellite as part of the Space Environment Effects Experiment (M0006). Measurements were performed to determine if space induced radiation effects changed the fiber bundle characteristics. Data demonstrating the success of light transmitting fibers to withstand the adverse space environment are presented.

  20. Controlled production of aligned-nanotube bundles

    NASA Astrophysics Data System (ADS)

    Terrones, M.; Grobert, N.; Olivares, J.; Zhang, J. P.; Terrones, H.; Kordatos, K.; Hsu, W. K.; Hare, J. P.; Townsend, P. D.; Prassides, K.; Cheetham, A. K.; Kroto, H. W.; Walton, D. R. M.

    1997-07-01

    Carbon nanotubes might be usefully employed in nanometre-scale engineering and electronics. Electrical conductivity measurements on the bulk material, on individual multi-walled and single-walled nanotubes and on bundles of single-walled nanotubes have revealed that they may behave as metallic, insulating or semiconducting nanowires, depending on the method of production-which controls the degree of graphitization, the helicity and the diameter. Measurements of Young's modulus show that single nanotubes are stiffer than commercial carbon fibres. Methods commonly used to generate nanotubes-carbon-arc discharge techniques, catalytic pyrolysis of hydrocarbons and condensed-phase electrolysis-generally suffer from the drawbacks that polyhedral particles are also formed and that the dimensions of the nanotubes are highly variable. Here we describe a method for generating aligned carbon nanotubes by pyrolysis of 2-amino-4,6-dichloro-s-triazine over thin films of a cobalt catalyst patterned on a silica substrate by laser etching. The use of a patterned catalyst apparently encourages the formation of aligned nanotubes. The method offers control over length (up to about 50μm) and fairly uniform diameters (30-50nm), as well as producing nanotubes in high yield, uncontaminated by polyhedral particles.

  1. Concise Care Bundles In Acute Medicine

    PubMed Central

    Kivlin, Jude; Altemimi, Harith

    2015-01-01

    The Queen Elizabeth Hospital in King's Lynn, Norfolk is a 488 bed hospital providing services to approximately 331,000 people across 750 square miles. In 2012 a need was recognised for documentation (pathways) in a practical format to increase usage of national guidelines and facilitate adherence to best practice (gold standards of care) that could be easily version controlled, auditable and provide support in clinical decision-making by junior doctors. BMJ Action Sets[1] fulfilled the brief with expert knowledge, version control and support, though they were deemed too lengthy and unworkable in fast paced settings like the medical assessment unit; they formed the base creation of concise care bundles (CCB). CCB were introduced for 21 clinical presentations and one procedure. Outcomes were fully audited and showed significant improvement in a range of measures, including an increase in completions of CHADVASC score in atrial fibrillation, antibiotics prescribed per protocol in chronic obstructive pulmonary disease (COPD), and Blatchford score recorded for patients presenting with upper gastrointestinal bleed. PMID:26734437

  2. A study of bacterial flagellar bundling.

    PubMed

    Flores, Heather; Lobaton, Edgar; Méndez-Diez, Stefan; Tlupova, Svetlana; Cortez, Ricardo

    2005-01-01

    Certain bacteria, such as Escherichia coli (E. coli) and Salmonella typhimurium (S. typhimurium), use multiple flagella often concentrated at one end of their bodies to induce locomotion. Each flagellum is formed in a left-handed helix and has a motor at the base that rotates the flagellum in a corkscrew motion. We present a computational model of the flagellar motion and their hydrodynamic interaction. The model is based on the equations of Stokes flow to describe the fluid motion. The elasticity of the flagella is modeled with a network of elastic springs while the motor is represented by a torque at the base of each flagellum. The fluid velocity due to the forces is described by regularized Stokeslets and the velocity due to the torques by the associated regularized rotlets. Their expressions are derived. The model is used to analyze the swimming motion of a single flagellum and of a group of three flagella in close proximity to one another. When all flagellar motors rotate counterclockwise, the hydrodynamic interaction can lead to bundling. We present an analysis of the flow surrounding the flagella. When at least one of the motors changes its direction of rotation, the same initial conditions lead to a tumbling behavior characterized by the separation of the flagella, changes in their orientation, and no net swimming motion. The analysis of the flow provides some intuition for these processes.

  3. Effects of oil on boiling of replacement refrigerants flowing normal to a tube bundle -- Part 2: R-134a

    SciTech Connect

    Tatara, R.A.; Payvar, P.

    2000-07-01

    Local, experimental heat transfer coefficients have been obtained for boiling refrigerant flowing up and across a tube bundle segment representing a full flooded evaporator tube bundle. R-134a data with a structured enhanced boiling tube are available. This tube has reentrant cavities designed for higher saturation pressure of refrigerants. The refrigerant enters at 15% vapor quality and exits at nearly 100% vapor in order to simulate an actual evaporator bundle. Both heat flux, 2,607 to 10,427 Btu/h{center_dot}f{sup 2} (8,224 to 32,893 W/m{sup 2}), and oil content, 0--12% (by weight), are varied; the mass flux is not an independent variable but determined by the heat flux. Local tube and bulk fluid temperatures are measured directly, by thermocouples, to calculate the refrigerant-side heat transfer coefficients. The bundle segment saturation temperature setpoint (taken at the top of the tube bundle) is 40 F (4.4 C).

  4. Bundles of Norms About Teen Sex and Pregnancy.

    PubMed

    Mollborn, Stefanie; Sennott, Christie

    2015-09-01

    Teen pregnancy is a cultural battleground in struggles over morality, education, and family. At its heart are norms about teen sex, contraception, pregnancy, and abortion. Analyzing 57 interviews with college students, we found that "bundles" of related norms shaped the messages teens hear. Teens did not think their communities encouraged teen sex or pregnancy, but normative messages differed greatly, with either moral or practical rationalizations. Teens readily identified multiple norms intended to regulate teen sex, contraception, abortion, childbearing, and the sanctioning of teen parents. Beyond influencing teens' behavior, norms shaped teenagers' public portrayals and post hoc justifications of their behavior. Although norm bundles are complex to measure, participants could summarize them succinctly. These bundles and their conflicting behavioral prescriptions create space for human agency in negotiating normative pressures. The norm bundles concept has implications for teen pregnancy prevention policies and can help revitalize social norms for understanding health behaviors.

  5. National Partnership for Maternal Safety: Consensus Bundle on Obstetric Hemorrhage.

    PubMed

    Main, Elliott K; Goffman, Dena; Scavone, Barbara M; Low, Lisa Kane; Bingham, Debra; Fontaine, Patricia L; Gorlin, Jed B; Lagrew, David C; Levy, Barbara S

    2015-07-01

    Hemorrhage is the most frequent cause of severe maternal morbidity and preventable maternal mortality and therefore is an ideal topic for the initial national maternity patient safety bundle. These safety bundles outline critical clinical practices that should be implemented in every maternity unit. They are developed by multidisciplinary work groups of the National Partnership for Maternal Safety under the guidance of the Council on Patient Safety in Women's Health Care. The safety bundle is organized into four domains: Readiness, Recognition and Prevention, Response, and Reporting and System Learning. Although the bundle components may be adapted to meet the resources available in individual facilities, standardization within an institution is strongly encouraged. References contain sample resources and "Potential Best Practices" to assist with implementation.

  6. National Partnership for Maternal Safety Consensus Bundle on Obstetric Hemorrhage.

    PubMed

    Main, Elliott K; Goffman, Dena; Scavone, Barbara M; Low, Lisa Kane; Bingham, Debra; Fontaine, Patricia L; Gorlin, Jed B; Lagrew, David C; Levy, Barbara S

    2015-01-01

    Hemorrhage is the most frequent cause of severe maternal morbidity and preventable maternal mortality and therefore is an ideal topic for the initial national maternity patient safety bundle. These safety bundles outline critical clinical practices that should be implemented in every maternity unit. They are developed by multidisciplinary work groups of the National Partnership for Maternal Safety under the guidance of the Council on Patient Safety in Women's Health Care. The safety bundle is organized into 4 domains: Readiness, Recognition and Prevention, Response, and Reporting and Systems Learning. Although the bundle components may be adapted to meet the resources available in individual facilities, standardization within an institution is strongly encouraged. References contain sample resources and "Potential Best Practices" to assist with implementation.

  7. National Partnership for Maternal Safety: consensus bundle on obstetric hemorrhage.

    PubMed

    Main, Elliott K; Goffman, Dena; Scavone, Barbara M; Low, Lisa Kane; Bingham, Debra; Fontaine, Patricia L; Gorlin, Jed B; Lagrew, David C; Levy, Barbara S

    2015-07-01

    Hemorrhage is the most frequent cause of severe maternal morbidity and preventable maternal mortality and therefore is an ideal topic for the initial national maternity patient safety bundle. These safety bundles outline critical clinical practices that should be implemented in every maternity unit. They are developed by multidisciplinary work groups of the National Partnership for Maternal Safety under the guidance of the Council on Patient Safety in Women's Health Care. The safety bundle is organized into four domains: Readiness, Recognition and Prevention, Response, and Reporting and System Learning. Although the bundle components may be adapted to meet the resources available in individual facilities, standardization within an institution is strongly encouraged. References contain sample resources and "Potential Best Practices" to assist with implementation.

  8. 15. VIEW OF SHINGLES BUNDLED, PLACED ON PALLET, AND READIED ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    15. VIEW OF SHINGLES BUNDLED, PLACED ON PALLET, AND READIED FOR FORKLIFT OPERATOR TO MOVE PALLET OF SHINGLES TO LOADING DOCK - Lester Shingle Mill, 1602 North Eighteenth Street, Sweet Home, Linn County, OR

  9. Performance-based bundled payments: potential benefits and burdens.

    PubMed

    Satin, David J; Miles, Justin

    2009-10-01

    Performance-based bundled payments have emerged as the most recent iteration of pay for performance. These are programs in which providers are paid a single fee for a set of evidenced-based services related to a diagnosis. The payments are typically linked to outcomes as well as other quality measures. This paper reviews two prominent bundled payment programs--PROMETHEUS and ProvenCare--and discusses the potential pitfalls of these approaches.

  10. Coordinated Movement of Vesicles and Actin Bundles during Nerve Growth Revealed by Superresolution Microscopy.

    PubMed

    Nozumi, Motohiro; Nakatsu, Fubito; Katoh, Kaoru; Igarashi, Michihiro

    2017-02-28

    The growth cone is an essential structure for nerve growth. Although its membrane and cytoskeleton are likely to interact coordinately during nerve growth, the mechanisms are unknown due to their close proximity. Here, we used superresolution microscopy to simultaneously observe vesicles and F-actin in growth cones. We identified a novel vesicular generation mechanism that is independent of clathrin and dependent on endophilin-3- and dynamin-1 and that occurs proximal to the leading edge simultaneously with fascin-1-dependent F-actin bundling. In contrast to conventional clathrin-dependent endocytosis, which occurs distal from the leading edge at the basal surfaces of growth cones, this mechanism was distinctly observed at the apical surface using 3D imaging and was involved in mediating axon growth. Reduced endophilin or fascin inhibited this endocytic mechanism. These results suggest that, at the leading edge, vesicles are coordinately generated and transported with actin bundling during nerve growth.

  11. Reflectance imaging by fiber bundle endoscope: Vertical reconstruction by multipositional illumination

    NASA Astrophysics Data System (ADS)

    Ando, Yoriko; Koida, Kowa; Sawahata, Hirohito; Sakurai, Takashi; Natsume, Mitsuo; Kawano, Takeshi; Numano, Rika

    2016-02-01

    Fiber bundles for imaging internal organs with minimum physical damage have been increasingly developed for both basic life sciences and clinical applications. Reflectance imaging is possible using fiber bundles for detecting the intrinsic optical contrast of blood vessels and tissue structure. The placement of an illumination source adjacent to imaging optics causes scattered light from deeper tissue layers to illuminate superficial tissues and results in a reflectance image. However, it does not have focal capacity and lacks depth resolution. In this study, we performed spatial analysis for the vertical reconstruction of in vivo tissues using a multipositional illumination scheme. The observed image corresponded to the "shadow" of a target object. When we manipulated the location of illumination, the shadow moved horizontally depending on the depth of the target. We used this horizontal displacement as a cue and successfully performed the vertical reconstruction of mouse brain blood vessels.

  12. Segmentation of Nerve Bundles and Ganglia in Spine MRI Using Particle Filters

    PubMed Central

    Dalca, Adrian; Danagoulian, Giovanna; Kikinis, Ron; Schmidt, Ehud; Golland, Polina

    2011-01-01

    Automatic segmentation of spinal nerve bundles that originate within the dural sac and exit the spinal canal is important for diagnosis and surgical planning. The variability in intensity, contrast, shape and direction of nerves seen in high resolution myelographic MR images makes segmentation a challenging task. In this paper, we present an automatic tracking method for nerve segmentation based on particle filters. We develop a novel approach to particle representation and dynamics, based on Bézier splines. Moreover, we introduce a robust image likelihood model that enables delineation of nerve bundles and ganglia from the surrounding anatomical structures. We demonstrate accurate and fast nerve tracking and compare it to expert manual segmentation. PMID:22003741

  13. Hydraulic testing of accelerator-production-of-tritium rod bundles

    SciTech Connect

    Spatz, T.L.; Siebe, D.A.

    1999-01-01

    Hydraulic tests have been performed on small pitch-to-diameter-ratio rod bundles using light water (1.7 < P/D < 1.17, and d = 3.175 mm). Flows cover the range from greater-than-nominal Reynolds numbers (fully turbulent) to low-speed laminar flows. Differential pressure measurements were made across the support plates holding the rod bundles, across the rod bundles, and across the entire assembly. Flow rates, temperatures, and gauge pressures also were measured. The data from these hydraulic tests have been compared to correlating literature for tightly pitched rod bundles. The prototypic geometry of these tests did not compare directly to any geometry found in the literature because of the variety of subchannels along the outer wall of the rod bundle. Under that constraint, there was excellent comparison of the rod-bundle friction factor with those factors given in the literature. The results show a large range of the Reynolds number over which the flow is in transition from laminar to turbulent (e.g., 580 < Re{sub Tr} < 13,000). Also presented is the comparison of the overall rung pressure drop to a solution based on hydraulic-resistance handbook calculations.

  14. Tapered fiber bundles for combining high-power diode lasers.

    PubMed

    Kosterin, Andrey; Temyanko, Valery; Fallahi, Mahmoud; Mansuripur, Masud

    2004-07-01

    Tapered fiber bundles are often used to combine the output power of several semiconductor lasers into a multimode optical fiber for the purpose of pumping fiber lasers and amplifiers. It is generally recognized that the brightness of such combiners does not exceed the brightness of the individual input fibers. We report that the brightness of the tapered fibers (and fiber bundles) depends on both the taper ratio and the mode-filling properties of the beams launched into the individual fibers. Brightness, therefore, can be increased by selection of sources that fill a small fraction of the input fiber's modal capacity. As proof of concept, we present the results of measurements on tapered fiber-bundle combiners having a low-output étendue. Under low mode-filling conditions per input multimode fiber (i.e., fraction of filled modes < or =0.29), we report brightness enhancements of 8.0 dB for 19 x 1 bundles, 6.7 dB for 7 x 1 bundles, and 4.0 dB for 3 x 1 combiners. Our measured coupling efficiency variations of approximately 1%-2% among the various fibers in a given bundle confirm the uniformity and quality of the fabricated devices.

  15. Optical system design of subminiature endoscope with imaging fiber bundle

    NASA Astrophysics Data System (ADS)

    Lv, Juan; Xue, Bin; Li, Ting; He, Ying-hong; Ma, Xiao-long; Yan, Xing-tao

    2016-10-01

    A new subminiature endoscope which used for reconnaissance and diagnosis has been designed. This subminiature endoscope is designed based on imaging fiber bundle and consist of the front object lens whose aperture is only 0.5mm, imaging fiber bundle and the post coupling lens. It realized by using subminiature optical systems . The FOV(field of view) and the focal length of the front object lens are 50° and 0.59mm. And the object distance, F number and detected imaging high of the front object lens are 3mm, 6 and 0.5mm. The total number of the imaging fiber bundle are 10000 and it's pixel cell size is 5 μm. The effective aperture of the imaging fiber bundle is 0.46mm. The post coupling lens has a reduction ratio of 1.73. It's object distance and imaging height are 5mm and 0.8mm. The Numerical Aperture (NA) of the front object lens, imaging fiber bundle and the post coupling lens are matching will. The coupling efficiency of the imaging fiber bundle is above 93% and the system's design result can meet the need of the limit resolution of the imaging fiber. This kind of the fiber endoscope has the peculiarity of wide FOV, fine imaging quality, compact configuration, low finished cost and etc. It is meaningful to realize the objective of miniaturization, batch-type production and high imaging quality of the endoscope.

  16. Plantain fibre bundles isolated from Colombian agro-industrial residues.

    PubMed

    Gañán, Piedad; Zuluaga, Robin; Restrepo, Adriana; Labidi, Jalel; Mondragon, Iñaki

    2008-02-01

    Comestible fruit production from Musaceas plants is an important economical activity in developing countries like Colombia. However, it generates a large amount of agro-industrial residues. Some of them are a potential resource of natural fibres, which can be used as reinforcement for composite materials. In this work, a series of commercial plantain (Musa AAB, cv "Dominico Harton") fibre bundles extracted from pseudostem, leaf sheath and rachis agricultural wastes were analyzed. Mechanical decortication and biological retting processes were used during fiber extraction. No significant differences in composition of vascular bundles were observed for both extraction processes. Gross morphological characteristics and mechanical behavior have been evaluated. Conducting tissues with spiral-like arrangement are observed attached to fibre bundles. This fact suggests a big amount of these tissues in commercial plantain plants. Both used extraction methods are not enough to remove them. Pseudostem fibre bundles have higher specific strength and modulus and lower strain at break than leaf sheath and rachis fibre bundles, having values comparable to other lignocellulosic fibres bundles.

  17. Oscillation of carbon molecules inside carbon nanotube bundles.

    PubMed

    Thamwattana, Ngamta; Cox, Barry J; Hill, James M

    2009-04-08

    In this paper, we investigate the mechanics of a nanoscaled gigahertz oscillator comprising a carbon molecule oscillating within the centre of a uniform concentric ring or bundle of carbon nanotubes. Two kinds of oscillating molecules are considered, which are a carbon nanotube and a C(60) fullerene. Using the Lennard-Jones potential and the continuum approach, we obtain a relation between the bundle radius and the radii of the nanotubes forming the bundle, as well as the optimum bundle size which gives rise to the maximum oscillatory frequency for both the nanotube-bundle and the C(60)-bundle oscillators. While previous studies in this area have been undertaken through molecular dynamics simulations, this paper emphasizes the use of applied mathematical modelling techniques, which provides considerable insight into the underlying mechanisms of the nanoscaled oscillators. The paper presents a synopsis of the major results derived in detail by the present authors (Cox et al 2007 Proc. R. Soc. A 464 691-710 and Cox et al 2007 J. Phys. A: Math. Theor. 40 13197-208).

  18. Oscillation of carbon molecules inside carbon nanotube bundles

    NASA Astrophysics Data System (ADS)

    Thamwattana, Ngamta; Cox, Barry J.; Hill, James M.

    2009-04-01

    In this paper, we investigate the mechanics of a nanoscaled gigahertz oscillator comprising a carbon molecule oscillating within the centre of a uniform concentric ring or bundle of carbon nanotubes. Two kinds of oscillating molecules are considered, which are a carbon nanotube and a C60 fullerene. Using the Lennard-Jones potential and the continuum approach, we obtain a relation between the bundle radius and the radii of the nanotubes forming the bundle, as well as the optimum bundle size which gives rise to the maximum oscillatory frequency for both the nanotube-bundle and the C60-bundle oscillators. While previous studies in this area have been undertaken through molecular dynamics simulations, this paper emphasizes the use of applied mathematical modelling techniques, which provides considerable insight into the underlying mechanisms of the nanoscaled oscillators. The paper presents a synopsis of the major results derived in detail by the present authors (Cox et al 2007 Proc. R. Soc. A 464 691-710 and Cox et al 2007 J. Phys. A: Math. Theor. 40 13197-208).

  19. Supramolecular assembly of biological molecules purified from bovine nerve cells: from microtubule bundles and necklaces to neurofilament networks

    NASA Astrophysics Data System (ADS)

    Needleman, Daniel J.; Jones, Jayna B.; Raviv, Uri; Ojeda-Lopez, Miguel A.; Miller, H. P.; Li, Y.; Wilson, L.; Safinya, C. R.

    2005-11-01

    With the completion of the human genome project, the biosciences community is beginning the daunting task of understanding the structures and functions of a large number of interacting biological macromolecules. Examples include the interacting molecules involved in the process of DNA condensation during the cell cycle, and in the formation of bundles and networks of filamentous actin proteins in cell attachment, motility and cytokinesis. In this proceedings paper we present examples of supramolecular assembly based on proteins derived from the vertebrate nerve cell cytoskeleton. The axonal cytoskeleton in vertebrate neurons provides a rich example of bundles and networks of neurofilaments, microtubules (MTs) and filamentous actin, where the nature of the interactions, structures, and structure-function correlations remains poorly understood. We describe synchrotron x-ray diffraction, electron microscopy, and optical imaging data, in reconstituted protein systems purified from bovine central nervous system, which reveal unexpected structures not predicted by current electrostatic theories of polyelectrolyte bundling, including three-dimensional MT bundles and two-dimensional MT necklaces.

  20. Subchannel Analysis with Mechanistic Methods for Thermo-Hydro Dynamics in BWR Fuel Bundles

    SciTech Connect

    Kentaro Imura; Kenji Yoshida; Isao Kataoka; Masanori Naitoh

    2006-07-01

    In order to predict the critical power or void fraction in BWR fuel bundles and the DNB heat flux of PWR fuel assemblies, the boiling transition analysis code called 'CAPE' with mechanistic models has been developed in the IMPACT project by NUPEC. The objective of the CAPE code development is to perform with good accuracy the safety evaluation for a new type or improved fuel bundle design of BWR and PWR without full-scale experiments or any tuning parameters in the analysis code. In this study, the CAPE for BWR was validated by the test analysis for 8 x 8 fuel bundles comparing with the void distribution data of the experimental data, which was carried out under several operational conditions in a BWR. The computations were carried out by changing the operational parameter such as the inlet subcooling, mass flow rate and the power output of the fuel bundles. Resultantly, the thermal equilibrium quality at the outlet ranges from 2% to 25%. From these results, though the predictive accuracy of the analytical results are in close agreement with the experimental data, it was noted that the errors were relatively outstanding in some subchannels, which was surrounded by the heated fuel rods and partially unheated walls, such as an unheated rod, a water rod and a separation wall of the channel box. The reason for this error is thought to be that the cross sectional void distribution was partially distributed in such subchannels surrounded partially by unheated wall, so the multidimensional void distribution structure might be formed in these subchannels. Under such conditions, it is very important to take into consideration the multidimensional structure of the two-phase flow in subchannel, and perhaps improve the estimation or correlations for the distribution parameter, as well as the amount of void exchange between neighboring subchannels. (authors)

  1. Skeletal cubic, lamellar, and ribbon phases of bundled thermotropic bolapolyphiles.

    PubMed

    Liu, Feng; Prehm, Marko; Zeng, Xiangbing; Tschierske, Carsten; Ungar, Goran

    2014-05-14

    A series of T-shaped polyphilic molecules composed of a rigid linear biphenyl core with a polar glycerol group at each end and one swallow-tail semiperfluorinated lateral chain were synthesized and their thermotropic liquid crystalline (LC) phases were investigated by X-ray diffraction, calorimetry, and microscopy. The compounds have a long alkyl spacer between the aromatic core and the fluorinated C(n)F(2n+1) ends, where n = 4, 6, 8, and 10. Upon melting, all compounds start with lamellar LC phases, followed on heating by a rectangular columnar ribbon phase with c2mm symmetry. Unusually, a ribbon is a flat bundle of molecular cores highly aligned parallel to the ribbon axis. On further heating, for n = 8 and 10, this phase is succeeded by a bicontinuous cubic phase with Ia3d symmetry. This is a new variant of the "gyroid" phase, with axially oriented rod-like molecular cores forming the skeleton of the two infinite networks and junctions separated by exactly two molecular lengths. In this tricontinuous core-shell structure (aromatic-aliphatic-perfluoroalkyl), the polar glycerol domains of appreciable size, contained within the skeleton, can be considered as micellar.

  2. Combustor having mixing tube bundle with baffle arrangement for directing fuel

    DOEpatents

    Hughes, Michael John; McConnaughhay, Johnie Franklin

    2016-08-23

    A combustor includes a tube bundle that extends radially across at least a portion of the combustor. The tube bundle includes an upstream surface axially separated from a downstream surface, and a plurality of tubes extend from the upstream surface through the downstream surface to provide fluid communication through the tube bundle. A barrier extends radially inside the tube bundle between the upstream and downstream surfaces, and a baffle extends axially inside the tube bundle between the upstream surface and the barrier.

  3. Numerical modeling of anisotropic fiber bundle behavior in oxygenators.

    PubMed

    Bhavsar, Sonya S; Schmitz-Rode, Thomas; Steinseifer, Ulrich

    2011-11-01

    Prediction of flow patterns through oxygenator fiber bundles can allow shape optimization so that efficient gas exchange occurs with minimal thrombus formation and hemolysis. Computational fluid dynamics (CFD) simulations can be used to predict three-dimensional flow velocities and flow distribution from spatially dependent variables and they allow estimations of erythrocyte residence time within the fiber bundle. This study builds upon previous work to develop an accurate numerical model for oxygenators, which would allow for accelerated iterations in oxygenator shape and diffuser plate design optimization. Hollow fiber flow channels were developed to permit experimental calculation of fluid permeability in two directions: main flow along the hollow fiber and perpendicular to the hollow fibers. Commercial software was used to develop three-dimensional CFD models of the experimental flow channels and an anisotropic porous media model for oxygenators from these experimental results. The oxygenator model was used to predict pressure loss throughout the device, visualize blood distribution within the fiber bundle, and estimate erythrocyte residence time within the bundle. Experimental flow channels measurements produced a streamwise permeability of 1.143e(-8) m(2) and transverse permeability of 2.385e(-9) m(2) . These permeabilities, coupled with previous work with volume porosity, were used to develop the numerical model of anisotropic behavior through porous fiber bundles, which indicated a more uniform flow field throughout the oxygenator. Incorporation of known anisotropic fiber bundle behavior in previous numerical models more accurately represents fluid behavior through an oxygenator fiber bundle. CFD coupled with experimental validation can produce a powerful tool for oxygenator design and development.

  4. Discontinuous bundling transition in semiflexible polymer networks induced by Casimir interactions

    NASA Astrophysics Data System (ADS)

    Kachan, Devin; Müller, Kei W.; Wall, Wolfgang A.; Levine, Alex J.

    2016-09-01

    Fluctuation-induced interactions are an important organizing principle in a variety of soft matter systems. We investigate the role of fluctuation-based or thermal Casimir interactions between cross linkers in a semiflexible network. One finds that, by integrating out the polymer degrees of freedom, there is an attractive logarithmic potential between nearest-neighbor cross linkers in a bundle, with a significantly weaker next-nearest-neighbor interaction. Here we show that a one-dimensional gas of these strongly interacting linkers in equilibrium with a source of unbound ones admits a discontinuous phase transition between a sparsely and a densely bound bundle. This discontinuous transition induced by the long-ranged nature of the Casimir interaction allows for a similarly abrupt structural transition in semiflexible filament networks between a low cross linker density isotropic phase and a higher cross link density bundle network. We support these calculations with the results of finite element Brownian dynamics simulations of semiflexible filaments and transient cross linkers.

  5. Defects in crystalline packings of twisted filament bundles. I. Continuum theory of disclinations

    NASA Astrophysics Data System (ADS)

    Grason, Gregory M.

    2012-03-01

    We develop the theory of the coupling between in-plane order and out-of-plane geometry in twisted, two-dimensionally ordered filament bundles based on the nonlinear continuum elasticity theory of columnar materials. We show that twisted textures of filament backbones necessarily introduce stresses into the cross-sectional packing of bundles and that these stresses are formally equivalent to the geometrically induced stresses generated in thin elastic sheets that are forced to adopt spherical curvature. As in the case of crystalline order on curved membranes, geometrically induced stresses couple elastically to the presence of topological defects in the in-plane order. We derive the effective theory of multiple disclination defects in the cross section of bundle with a fixed twist and show that above a critical degree of twist, one or more fivefold disclinations is favored in the elastic energy ground state. We study the structure and energetics of multidisclination packings based on models of equilibrium and nonequilibrium cross-sectional order.

  6. The universal bundling activity of AtVLN4 in diffusely growing cells.

    PubMed

    Du, Fei; Zhang, Yi; Ren, Haiyun

    2011-09-01

    We recently reported that AtVLN4, a member of villin/gelsolin/fragmin superfamily in Arabidopsis thaliana, participated in root hair growth through its actin bundling activity. To further understand the functions of AtVLN4, we investigated its in vivo expression pattern and roles in diffusely growing cells. Transcription analysis of AtVLN4 and detection of AtVLN 4 promoter-GUS activity consistently indicated that AtVLN4 had a universal expression pattern and was preferentially expressed in vegetative tissues. Observation of actin structures labeled by GFP-fABD2 revealed that there were less actin bundles in many diffusely growing cell types in atvln4-1 seedlings than in wild-type seedlings. Pharmacological studies by treatment with Latrunculin B showed that the actin filaments were much easier to be disrupted in diffusely growing cells of atvln4-1 seedlings. Collectively, these results demonstrate that AtVLN4 has a universal actin bundling activity in diffusely growing cells just like that in the tip growing cell, root hairs.

  7. Myosin III-mediated cross-linking and stimulation of actin bundling activity of Espin

    PubMed Central

    Liu, Haiyang; Li, Jianchao; Raval, Manmeet H; Yao, Ningning; Deng, Xiaoying; Lu, Qing; Nie, Si; Feng, Wei; Wan, Jun; Yengo, Christopher M; Liu, Wei; Zhang, Mingjie

    2016-01-01

    Class III myosins (Myo3) and actin-bundling protein Espin play critical roles in regulating the development and maintenance of stereocilia in vertebrate hair cells, and their defects cause hereditary hearing impairments. Myo3 interacts with Espin1 through its tail homology I motif (THDI), however it is not clear how Myo3 specifically acts through Espin1 to regulate the actin bundle assembly and stabilization. Here we discover that Myo3 THDI contains a pair of repeat sequences capable of independently and strongly binding to the ankyrin repeats of Espin1, revealing an unexpected Myo3-mediated cross-linking mechanism of Espin1. The structures of Myo3 in complex with Espin1 not only elucidate the mechanism of the binding, but also reveal a Myo3-induced release of Espin1 auto-inhibition mechanism. We also provide evidence that Myo3-mediated cross-linking can further promote actin fiber bundling activity of Espin1. DOI: http://dx.doi.org/10.7554/eLife.12856.001 PMID:26785147

  8. Systematic significance of midrib vascular bundles in some Schefflera Spreng (Araliaceae) species

    NASA Astrophysics Data System (ADS)

    Noor-Syaheera, M. Y.; Noraini, T.; Aida-Shafreena, A. P.

    2014-09-01

    Anatomy study was undertaken on midrib vascular bundles of six Schefflera Spreng species, namely as S. obovatilimba, S. borneensis, S.kinabaluensis, S.lineamentorum, S. opacus and S.petiolosa. The genus Schefflera belongs to the family Araliaceae. The objective of this study is to determine variations in the midrib anatomical characteristics that can be used to identify species. Leaves samples were collected from various forest reserves in Sabah and Sarawak, Malaysia., were fixed in AA (Acetic acid: Alcohol, in a ratio of 1:3), the midrib parts then were sectioned using sliding microtome, were stained in Safranin and Alcian blue, been mounted in Eupharal and were observed under light microscope. Findings in this study have shown that all species have complex structure of vascular bundles. Each species has identical arrangement of vascular bundles and can be very useful for species identification. As a conclusion, variation in the midrib anatomical characteristics is outstanding and can has taxonomic value in the genus Schefflera respectively.

  9. Retinal nerve fiber bundle tracing and analysis in human eye by polarization sensitive OCT.

    PubMed

    Sugita, Mitsuro; Pircher, Michael; Zotter, Stefan; Baumann, Bernhard; Roberts, Philipp; Makihira, Tomoyuki; Tomatsu, Nobuhiro; Sato, Makoto; Vass, Clemens; Hitzenberger, Christoph K

    2015-03-01

    We present a new semi-automatic processing method for retinal nerve fiber bundle tracing based on polarization sensitive optical coherence tomography (PS-OCT) data sets. The method for tracing is based on a nerve fiber orientation map that covers the fovea and optic nerve head (ONH) regions. In order to generate the orientation map, two types of information are used: optic axis orientation based on polarization data, and complementary information obtained from nerve fiber layer (NFL) local thickness variation to reveal fiber bundle structures around the fovea. The corresponding two orientation maps are fused into a combined fiber orientation map. En face maps of NFL retardation, thickness, and unit-depth-retardation (UDR, equivalent to birefringence) are transformed into "along-trace" maps by using the obtained traces of the nerve fiber bundles. The method is demonstrated in the eyes of healthy volunteers, and as an example of further analyses utilizing this method, maps illustrating the gradients of NFL retardation, thickness, and UDR are demonstrated.

  10. Holographic fiber bundle system for patterned optogenetic activation of large-scale neuronal networks

    PubMed Central

    Farah, Nairouz; Levinsky, Alexandra; Brosh, Inbar; Kahn, Itamar; Shoham, Shy

    2015-01-01

    Abstract. Optogenetic perturbation has become a fundamental tool in controlling activity in neurons. Used to control activity in cell cultures, slice preparations, anesthetized and awake behaving animals, optical control of cell-type specific activity enables the interrogation of complex systems. A remaining challenge in developing optical control tools is the ability to produce defined light patterns such that power-efficient, precise control of neuronal populations is obtained. Here, we describe a system for patterned stimulation that enables the generation of structured activity in neurons by transmitting optical patterns from computer-generated holograms through an optical fiber bundle. The system couples the optical system to versatile fiber bundle configurations, including coherent or incoherent bundles composed of hundreds of up to several meters long fibers. We describe the components of the system, a method for calibration, and a detailed power efficiency and spatial specificity quantification. Next, we use the system to precisely control single-cell activity as measured by extracellular electrophysiological recordings in ChR2-expressing cortical cell cultures. The described system complements recent descriptions of optical control systems, presenting a system suitable for high-resolution spatiotemporal optical control of wide-area neural networks in vitro and in vivo, yielding a tool for precise neural system interrogation. PMID:26793741

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

    NASA Astrophysics Data System (ADS)

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

    2014-09-01

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

  12. External Verification of the Bundle Adjustment in Photogrammetric Software Using the Damped Bundle Adjustment Toolbox

    NASA Astrophysics Data System (ADS)

    Börlin, Niclas; Grussenmeyer, Pierre

    2016-06-01

    The aim of this paper is to investigate whether the Matlab-based Damped Bundle Adjustment Toolbox (DBAT) can be used to provide independent verification of the BA computation of two popular software—PhotoModeler (PM) and PhotoScan (PS). For frame camera data sets with lens distortion, DBAT is able to reprocess and replicate subsets of PM results with high accuracy. For lens-distortion-free data sets, DBAT can furthermore provide comparative results between PM and PS. Data sets for the discussed projects are available from the authors. The use of an external verification tool such as DBAT will enable users to get an independent verification of the computations of their software. In addition, DBAT can provide computation of quality parameters such as estimated standard deviations, correlation between parameters, etc., something that should be part of best practice for any photogrammetric software. Finally, as the code is free and open-source, users can add computations of their own.

  13. Ecosystem service bundles for analyzing tradeoffs in diverse landscapes.

    PubMed

    Raudsepp-Hearne, C; Peterson, G D; Bennett, E M

    2010-03-16

    A key challenge of ecosystem management is determining how to manage multiple ecosystem services across landscapes. Enhancing important provisioning ecosystem services, such as food and timber, often leads to tradeoffs between regulating and cultural ecosystem services, such as nutrient cycling, flood protection, and tourism. We developed a framework for analyzing the provision of multiple ecosystem services across landscapes and present an empirical demonstration of ecosystem service bundles, sets of services that appear together repeatedly. Ecosystem service bundles were identified by analyzing the spatial patterns of 12 ecosystem services in a mixed-use landscape consisting of 137 municipalities in Quebec, Canada. We identified six types of ecosystem service bundles and were able to link these bundles to areas on the landscape characterized by distinct social-ecological dynamics. Our results show landscape-scale tradeoffs between provisioning and almost all regulating and cultural ecosystem services, and they show that a greater diversity of ecosystem services is positively correlated with the provision of regulating ecosystem services. Ecosystem service-bundle analysis can identify areas on a landscape where ecosystem management has produced exceptionally desirable or undesirable sets of ecosystem services.

  14. Consensus Bundle on Maternal Mental Health: Perinatal Depression and Anxiety.

    PubMed

    Kendig, Susan; Keats, John P; Hoffman, M Camille; Kay, Lisa B; Miller, Emily S; Simas, Tiffany A Moore; Frieder, Ariela; Hackley, Barbara; Indman, Pec; Raines, Christena; Semenuk, Kisha; Wisner, Katherine L; Lemieux, Lauren A

    2017-04-06

    Perinatal mood and anxiety disorders are among the most common mental health conditions encountered by women of reproductive age. When left untreated, perinatal mood and anxiety disorders can have profound adverse effects on women and their children, ranging from increased risk of poor adherence to medical care, exacerbation of medical conditions, loss of interpersonal and financial resources, smoking and substance use, suicide, and infanticide. Perinatal mood and anxiety disorders are associated with increased risks of maternal and infant mortality and morbidity and are recognized as a significant patient safety issue. In 2015, the Council on Patient Safety in Women's Health Care convened an interdisciplinary work group to develop an evidence-based patient safety bundle to address maternal mental health. The focus of this bundle is perinatal mood and anxiety disorders. The bundle is modeled after other bundles released by the Council on Patient Safety in Women's Health Care and provides broad direction for incorporating perinatal mood and anxiety disorder screening, intervention, referral, and follow-up into maternity care practice across health care settings. This commentary provides information to assist with bundle implementation.

  15. Hair-bundle friction from transduction channels' gating forces

    NASA Astrophysics Data System (ADS)

    Bormuth, Volker; Barral, Jérémie; Joanny, Jean-François; Jülicher, Frank; Martin, Pascal

    2015-12-01

    Hearing starts when sound-evoked mechanical vibrations of the hair-cell bundle activate mechanosensitive ion channels, giving birth to an electrical signal. As for any mechanical system, friction impedes movements of the hair bundle and thus constrains the sensitivity and frequency selectivity of auditory transduction. We have shown recently that the opening and closing of the transduction channels produce internal frictional forces that can dominate viscous drag on the micrometer-sized hair bundle and thus provide a major source of damping [2]. We develop here a physical theory of passive hair-bundle mechanics that explains the origin of channel friction. We show that channel friction can be understood quantitatively by coupling the dynamics of the conformational change associated with channel gating to tip-link tension. As a result, varying channel properties affects friction, with faster channels producing smaller friction. The analysis emphasizes the dual role of transduction channels' gating forces, which affect both hair-bundle stiffness and drag. Friction originating from gating of ion channels is a general concept that is relevant to all mechanosensitive channels.

  16. Consensus Bundle on Maternal Mental Health: Perinatal Depression and Anxiety.

    PubMed

    Kendig, Susan; Keats, John P; Hoffman, M Camille; Kay, Lisa B; Miller, Emily S; Moore Simas, Tiffany A; Frieder, Ariela; Hackley, Barbara; Indman, Pec; Raines, Christena; Semenuk, Kisha; Wisner, Katherine L; Lemieux, Lauren A

    Perinatal mood and anxiety disorders are among the most common mental health conditions encountered by women of reproductive age. When left untreated, perinatal mood and anxiety disorders can have profound adverse effects on women and their children, ranging from increased risk of poor adherence to medical care, exacerbation of medical conditions, loss of interpersonal and financial resources, smoking and substance use, suicide, and infanticide. Perinatal mood and anxiety disorders are associated with increased risks of maternal and infant mortality and morbidity and are recognized as a significant patient safety issue. In 2015, the Council on Patient Safety in Women's Health Care convened an interdisciplinary workgroup to develop an evidence-based patient safety bundle to address maternal mental health. The focus of this bundle is perinatal mood and anxiety disorders. The bundle is modeled after other bundles released by the Council on Patient Safety in Women's Health Care and provides broad direction for incorporating perinatal mood and anxiety disorder screening, intervention, referral, and follow-up into maternity care practice across health care settings. This commentary provides information to assist with bundle implementation.

  17. Consensus Bundle on Maternal Mental Health: Perinatal Depression and Anxiety.

    PubMed

    Kendig, Susan; Keats, John P; Hoffman, M Camille; Kay, Lisa B; Miller, Emily S; Moore Simas, Tiffany A; Frieder, Ariela; Hackley, Barbara; Indman, Pec; Raines, Christena; Semenuk, Kisha; Wisner, Katherine L; Lemieux, Lauren A

    2017-03-01

    Perinatal mood and anxiety disorders are among the most common mental health conditions encountered by women of reproductive age. When left untreated, perinatal mood and anxiety disorders can have profound adverse effects on women and their children, ranging from increased risk of poor adherence to medical care, exacerbation of medical conditions, loss of interpersonal and financial resources, smoking and substance use, suicide, and infanticide. Perinatal mood and anxiety disorders are associated with increased risks of maternal and infant mortality and morbidity and are recognized as a significant patient safety issue. In 2015, the Council on Patient Safety in Women's Health Care convened an interdisciplinary workgroup to develop an evidence-based patient safety bundle to address maternal mental health. The focus of this bundle is perinatal mood and anxiety disorders. The bundle is modeled after other bundles released by the Council on Patient Safety in Women's Health Care and provides broad direction for incorporating perinatal mood and anxiety disorder screening, intervention, referral, and follow-up into maternity care practice across health care settings. This commentary provides information to assist with bundle implementation.

  18. Variable recruitment in bundles of miniature pneumatic artificial muscles.

    PubMed

    DeLaHunt, Sylvie A; Pillsbury, Thomas E; Wereley, Norman M

    2016-09-13

    The natural compliance and force generation properties of pneumatic artificial muscles (PAMs) allow them to operate like human muscles in anthropomorphic robotic manipulators. Traditionally, manipulators use a single PAM or multiple PAMs actuated in unison in place of a human muscle. However, these standard manipulators can experience significant efficiency losses when operated outside their target performance ranges at low actuation pressures. This study considers the application of a variable recruitment control strategy to a parallel bundle of miniature PAMs as an attempt to mimic the selective recruitment of motor units in a human muscle. Bundles of miniature PAMs are experimentally characterized, their actuation behavior is modeled, and the efficiency gains and losses associated with the application of a variable recruitment control strategy are assessed. This bio-inspired control strategy allows muscle bundles to operate the fewest miniature PAMs necessary to achieve a desired performance objective, improving the muscle bundle's operating efficiency over larger ranges of force generation and displacement. The study also highlights the need for improved PAM fabrication techniques to facilitate the production of identical miniature PAMs for inclusion in muscle bundles.

  19. Statistical evaluation of fiber bundle imagery of wavelength multiplexing

    NASA Astrophysics Data System (ADS)

    Zhang, Yixin

    1994-09-01

    The effects of the wavelength multiplexing on the quality of an image transferred through a fiber bundle system is discussed by using the information capacity of an imaging system. The image transfer through a conventional fiber bundle can be thought of as a discrete sampling of the illuminance of the image at the entrance and of the bundle by each fiber element. This discrete sampling limits the band width of signals which can be transmitted. Also, the ends of the component fibers form an obtrusive pattern in the received image. Because, in the dispersion fiber bundle system, each fiber integrates the flux falling upon its entrance aperture, the entire picture format dispersion scan is reproduced at the frequency response characteristic of a uniform disk whose diameter is equal to that of the component fibers. Also, the individual fiber ends are thus blurred out and the obtrusive pattern formed by them is destroyed. It is shown, in theory, that the use of a dispersion method makes it possible to reduce the value of the light transmission nonuniformity contrast and to improve the resolution of fiber bundle image system, respectively.

  20. Dynamic response of fiber bundle under transverse impact.

    SciTech Connect

    Lu, Wei-Yang; Song, Bo

    2010-03-01

    There has been a very high demand in developing efficient soft body armors to protect the military and law enforcement personnel from ballistic or explosive attack. As a basic component in the soft body armor, fibers or fiber bundles play a key role in the performance against ballistic impact. In order to study the ballistic-resistant mechanism of the soft body armor, it is desirable to understand the dynamic response of the fiber bundle under transverse impact. Transverse wave speed is one important parameter because a faster transverse wave speed can make the impact energy dissipate more quickly. In this study, we employed split Hopkinson pressure bar (SHPB) to generate constant high-speed impact on a Kevlar fiber bundle in the transverse direction. The deformation of the fiber bundle was photographed with high-speed digital cameras. The transverse wave speeds were experimentally measured at various transverse impact velocities. The experimental results can also be used to quantitatively verify the current analytical models or to develop new models to describe the dynamic response of fiber bundle under transverse impact.

  1. Abnormal cingulum bundle development in autism: a probabilistic tractography study.

    PubMed

    Ikuta, Toshikazu; Shafritz, Keith M; Bregman, Joel; Peters, Bart D; Gruner, Patricia; Malhotra, Anil K; Szeszko, Philip R

    2014-01-30

    There is now considerable evidence that white matter abnormalities play a role in the neurobiology of autism. Little research has been directed, however, at understanding (a) typical white matter development in autism and how this relates to neurocognitive impairments observed in the disorder. In this study we used probabilistic tractography to identify the cingulum bundle in 21 adolescents and young adults with Autism Spectrum Disorder (ASD), and 21 age- and sex-matched healthy volunteers. We investigated group differences in the relationships between age and fractional anisotropy, a putative measure of white matter integrity, within the cingulum bundle. Moreover, in a preliminary investigation, we examined the relationship between cingulum fractional anisotropy and executive functioning using the Behavior Rating Inventory of Executive Function (BRIEF). The ASD participants demonstrated significantly lower fractional anisotropy within the cingulum bundle compared to the typically developing volunteers. There was a significant group-by-age interaction such that the ASD group did not show the typical age-associated increases in fractional anisotropy observed among healthy individuals. Moreover, lower fractional anisotropy within the cingulum bundle was associated with worse BRIEF behavioral regulation index scores in the ASD group. The current findings implicate a dysregulation in cingulum bundle white matter development occurring in late adolescence and early adulthood in ASD, and suggest that greater disturbances in this trajectory are associated with executive dysfunction in ASD.

  2. Ventricular fibrillation associated with complete right bundle branch block

    PubMed Central

    Aizawa, Yoshiyasu; Takatsuki, Seiji; Kimura, Takehiro; Nishiyama, Nobuhiro; Fukumoto, Kotaro; Tanimoto, Yoko; Tanimoto, Kojiro; Miyoshi, Shunichiro; Suzuki, Makoto; Yokoyama, Yasuhiro; Chinushi, Masaomi; Watanabe, Ichiro; Ogawa, Satoshi; Aizawa, Yoshifusa; Antzelevitch, Charles; Fukuda, Keiichi

    2013-01-01

    BACKGROUND A substantial number of patients with idiopathic ventricular fibrillation (IVF) present with no specific electrocardiographic (ECG) findings. OBJECTIVE To evaluate complete right bundle branch block (RBBB) in patients with IVF. METHODS Patients with IVF showing complete RBBB were included in the present study. Structural and primary electrical diseases were excluded, and provocation tests were performed to exclude the presence of spastic angina or Brugada syndrome (BrS). The prevalence of complete RBBB and the clinical and ECG parameters were compared either in patients with IVF who did not show RBBB or in the general population and age and sex comparable controls with RBBB. RESULTS Of 96 patients with IVF, 9 patients were excluded for the presence of BrS. Of 87 patients studied, 10 (11.5%) patients showed complete RBBB. None had structural heart diseases, BrS, or coronary spasms. The mean age was 44 ± 15 years, and 8 of 10 patients were men. Among the ECG parameters, only the QRS duration was different from that of the other patients with IVF who did not show complete RBBB. Ventricular fibrillation recurred in 3:2 in the form of storms, which were well suppressed by isoproterenol. Complete RBBB was found less often in control subjects (1.37%; P < .0001), and the QRS duration was more prolonged in patients with IVF: 139 ± 10 ms vs 150 ± 14 ms (P = .0061). CONCLUSIONS Complete RBBB exists more often in patients with IVF than in controls. A prolonged QRS complex suggests a conduction abnormality. Our findings warrant further investigation of the role of RBBB in the development of arrhythmias in patients with IVF. PMID:23499623

  3. [Ventricular tachycardias originating in the his-purkinje system. Bundle branch reentrant ventricular tachycardias and fascicular ventricular tachycardias].

    PubMed

    Schmidt, Boris; Chun, Kyoung Ryul Julian; Kuck, Karl-Heinz; Ouyang, Feifan

    2009-11-01

    Ventricular tachycardias (VT) associated with the His-Purkinje system may occur in patients with and without organic heart disease. The former may encounter bundle branch reentrant VT, a macroreentrant VT utilizing the specific conduction system. It frequently occurs in patients with preexisting conduction disturbance such as complete left bundle branch block and may be eliminated by catheter ablation of the right bundle branch. After successful ablation, patient's prognosis depends on the presence or absence of structural heart disease.In patients without structural heart disease, VT with right bundle branch block pattern and superior axis, referred to as idiopathic left ventricular tachycardia, is observed. It is a reentrant VT utilizing the posterior left fascicle and the Purkinje network. The two treatment options include antiarrhythmic drug therapy with verapamil or curative catheter ablation.Another form of ventricular arrhythmia originating in the Purkinje network is idiopathic ventricular fibrillation (IVF). Focal triggers from the right and left ventricular Purkinje network induce premature ventricular contractions inducing IVF. This is amenable to catheter ablation leading to a significant reduction in ICD (implantable cardioverter defibrillator) interventions in sudden cardiac death survivors.

  4. The fabrication of vertically aligned and periodically distributed carbon nanotube bundles and periodically porous carbon nanotube films through a combination of laser interference ablation and metal-catalyzed chemical vapor deposition.

    PubMed

    Yuan, Dajun; Lin, Wei; Guo, Rui; Wong, C P; Das, Suman

    2012-06-01

    Scalable fabrication of carbon nanotube (CNT) bundles is essential to future advances in several applications. Here, we report on the development of a simple, two-step method for fabricating vertically aligned and periodically distributed CNT bundles and periodically porous CNT films at the sub-micron scale. The method involves laser interference ablation (LIA) of an iron film followed by CNT growth via iron-catalyzed chemical vapor deposition. CNT bundles with square widths ranging from 0.5 to 1.5 µm in width, and 50-200 µm in length, are grown atop the patterned catalyst over areas spanning 8 cm(2). The CNT bundles exhibit a high degree of control over square width, orientation, uniformity, and periodicity. This simple scalable method of producing well-placed and oriented CNT bundles demonstrates a high application potential for wafer-scale integration of CNT structures into various device applications, including IC interconnects, field emitters, sensors, batteries, and optoelectronics, etc.

  5. Developmental regulation of planar cell polarity and hair-bundle morphogenesis in auditory hair cells: lessons from human and mouse genetics.

    PubMed

    Lu, Xiaowei; Sipe, Conor W

    2016-01-01

    Hearing loss is the most common and costly sensory defect in humans and genetic causes underlie a significant proportion of affected individuals. In mammals, sound is detected by hair cells (HCs) housed in the cochlea of the inner ear, whose function depends on a highly specialized mechanotransduction organelle, the hair bundle. Understanding the factors that regulate the development and functional maturation of the hair bundle is crucial for understanding the pathophysiology of human deafness. Genetic analysis of deafness genes in animal models, together with complementary forward genetic screens and conditional knock-out mutations in essential genes, have provided great insights into the molecular machinery underpinning hair-bundle development and function. In this review, we highlight recent advances in our understanding of hair-bundle morphogenesis, with an emphasis on the molecular pathways governing hair-bundle polarity and orientation. We next discuss the proteins and structural elements important for hair-cell mechanotransduction as well as hair-bundle cohesion and maintenance. In addition, developmental signals thought to regulate tonotopic features of HCs are introduced. Finally, novel approaches that complement classic genetics for studying the molecular etiology of human deafness are presented. WIREs Dev Biol 2016, 5:85-101. doi: 10.1002/wdev.202 For further resources related to this article, please visit the WIREs website.

  6. High-order synchronization of hair cell bundles

    NASA Astrophysics Data System (ADS)

    Levy, Michael; Molzon, Adrian; Lee, Jae-Hyun; Kim, Ji-Wook; Cheon, Jinwoo; Bozovic, Dolores

    2016-12-01

    Auditory and vestibular hair cell bundles exhibit active mechanical oscillations at natural frequencies that are typically lower than the detection range of the corresponding end organs. We explore how these noisy nonlinear oscillators mode-lock to frequencies higher than their internal clocks. A nanomagnetic technique is used to stimulate the bundles without an imposed mechanical load. The evoked response shows regimes of high-order mode-locking. Exploring a broad range of stimulus frequencies and intensities, we observe regions of high-order synchronization, analogous to Arnold Tongues in dynamical systems literature. Significant areas of overlap occur between synchronization regimes, with the bundle intermittently flickering between different winding numbers. We demonstrate how an ensemble of these noisy spontaneous oscillators could be entrained to efficiently detect signals significantly above the characteristic frequencies of the individual cells.

  7. High-order synchronization of hair cell bundles

    PubMed Central

    Levy, Michael; Molzon, Adrian; Lee, Jae-Hyun; Kim, Ji-wook; Cheon, Jinwoo; Bozovic, Dolores

    2016-01-01

    Auditory and vestibular hair cell bundles exhibit active mechanical oscillations at natural frequencies that are typically lower than the detection range of the corresponding end organs. We explore how these noisy nonlinear oscillators mode-lock to frequencies higher than their internal clocks. A nanomagnetic technique is used to stimulate the bundles without an imposed mechanical load. The evoked response shows regimes of high-order mode-locking. Exploring a broad range of stimulus frequencies and intensities, we observe regions of high-order synchronization, analogous to Arnold Tongues in dynamical systems literature. Significant areas of overlap occur between synchronization regimes, with the bundle intermittently flickering between different winding numbers. We demonstrate how an ensemble of these noisy spontaneous oscillators could be entrained to efficiently detect signals significantly above the characteristic frequencies of the individual cells. PMID:27974743

  8. IKKε inhibits PKC to promote Fascin-dependent actin bundling

    PubMed Central

    Ogura, Yosuke; Misaki, Kazuyo; Maeda, Takuya; Kimpara, Akiyo; Yonemura, Shigenobu; Hayashi, Shigeo

    2016-01-01

    Signaling molecules have pleiotropic functions and are activated by various extracellular stimuli. Protein kinase C (PKC) is activated by diverse receptors, and its dysregulation is associated with diseases including cancer. However, how the undesired activation of PKC is prevented during development remains poorly understood. We have previously shown that a protein kinase, IKKε, is active at the growing bristle tip and regulates actin bundle organization during Drosophila bristle morphogenesis. Here, we demonstrate that IKKε regulates the actin bundle localization of a dynamic actin cross-linker, Fascin. IKKε inhibits PKC, thereby protecting Fascin from inhibitory phosphorylation. Excess PKC activation is responsible for the actin bundle defects in IKKε-deficient bristles, whereas PKC is dispensable for bristle morphogenesis in wild-type bristles, indicating that PKC is repressed by IKKε in wild-type bristle cells. These results suggest that IKKε prevents excess activation of PKC during bristle morphogenesis. PMID:27578797

  9. Rheology of semiflexible bundle networks with transient linkers.

    PubMed

    Müller, Kei W; Bruinsma, Robijn F; Lieleg, Oliver; Bausch, Andreas R; Wall, Wolfgang A; Levine, Alex J

    2014-06-13

    We present a theoretical and computational analysis of the rheology of networks made up of bundles of semiflexible filaments bound by transient cross-linkers. Such systems are ubiquitous in the cytoskeleton and can be formed in vitro using filamentous actin and various cross-linkers. We find that their high-frequency rheology is characterized by a scaling behavior that is quite distinct from that of networks of the well-studied single semiflexible filaments. This regime can be understood theoretically in terms of a length-scale-dependent bending modulus for bundles. Next, we observe new dissipative dynamics associated with the shear-induced disruption of the network at intermediate frequencies. Finally, at low frequencies, we encounter a region of non-Newtonian rheology characterized by power-law scaling. This regime is dominated by bundle dissolution and large-scale rearrangements of the network driven by equilibrium thermal fluctuations.

  10. Betti numbers of graded modules and cohomology of vector bundles

    NASA Astrophysics Data System (ADS)

    Eisenbud, David; Schreyer, Frank-Olaf

    2009-07-01

    In the remarkable paper Graded Betti numbers of Cohen-Macaulay modules and the multiplicity conjecture, Mats Boij and Jonas Soederberg conjectured that the Betti table of a Cohen-Macaulay module over a polynomial ring is a positive linear combination of Betti tables of modules with pure resolutions. We prove a strengthened form of their conjectures. Applications include a proof of the Multiplicity Conjecture of Huneke and Srinivasan and a proof of the convexity of a fan naturally associated to the Young lattice. With the same tools we show that the cohomology table of any vector bundle on projective space is a positive rational linear combination of the cohomology tables of what we call supernatural vector bundles. Using this result we give new bounds on the slope of a vector bundle in terms of its cohomology.

  11. System for supporting bundled tube segments within a combustor

    DOEpatents

    Melton, Patrick Benedict

    2016-03-01

    A system for supporting bundled tube segments within a combustor includes an annular sleeve that extends circumferentially and axially within the combustor, a support lug that extends radially inward from the annular sleeve and an annular support frame that is disposed within the annular sleeve. The annular support frame includes an inner ring portion, an outer ring portion and a plurality of spokes that extend radially between the inner and outer ring portions. The inner ring portion, the outer ring portion and the plurality of spokes define an annular array of openings for receiving a respective bundled tube segment. The inner ring portion is connected to each bundled tube segment and the outer ring portion is coupled to the support lug.

  12. Preparation of superhydrophobic poly-p-phenylenebenzobisoxazole (PBO) fiber bundles

    NASA Astrophysics Data System (ADS)

    Jiang, Zai X.; Geng, Lin; Huang, Yu D.

    2011-02-01

    According to the reformed Cassie-Baxter equation, the superhydrophobic phenylenebenzobisoxazole (PBO) fiber bundle boats were fabricated from mimicking the lotus leaf venation using chemical surface modifications and roughness introduction. Water contact angles as high as 152.3° were achieved for PBO fiber bundles. Furthermore, the loading capacities of the superhydrophobic PBO fiber bundle boats were also measured. And the highest loading weight, 8.36 g, was obtained by the boats treated with 2.0 wt.% (heptadecafluoro-1,1,2,2,-tetradecyl)trimethoxysilane (HFTES). The large loading capacities were believed to arise from the air film surrounding the superhydrophobic surfaces of boats. The results of this study presented new applications of artificial hydrophobic surfaces in areas of miniature aquatic devices.

  13. Stable parabolic Higgs bundles as asymptotically stable decorated swamps

    NASA Astrophysics Data System (ADS)

    Beck, Nikolai

    2016-06-01

    Parabolic Higgs bundles can be described in terms of decorated swamps, which we studied in a recent paper. This description induces a notion of stability of parabolic Higgs bundles depending on a parameter, and we construct their moduli space inside the moduli space of decorated swamps. We then introduce asymptotic stability of decorated swamps in order to study the behaviour of the stability condition as one parameter approaches infinity. The main result is the existence of a constant, such that stability with respect to parameters greater than this constant is equivalent to asymptotic stability. This implies boundedness of all decorated swamps which are semistable with respect to some parameter. Finally, we recover the usual stability condition of parabolic Higgs bundles as asymptotic stability.

  14. Cortactin Adopts a Globular Conformation and Bundles Actin into Sheets*S⃞

    PubMed Central

    Cowieson, Nathan P.; King, Gordon; Cookson, David; Ross, Ian; Huber, Thomas; Hume, David A.; Kobe, Bostjan; Martin, Jennifer L.

    2008-01-01

    Cortactin is a filamentous actin-binding protein that plays a pivotal role in translating environmental signals into coordinated rearrangement of the cytoskeleton. The dynamic reorganization of actin in the cytoskeleton drives processes including changes in cell morphology, cell migration, and phagocytosis. In general, structural proteins of the cytoskeleton bind in the N-terminal region of cortactin and regulatory proteins in the C-terminal region. Previous structural studies have reported an extended conformation for cortactin. It is therefore unclear how cortactin facilitates cross-talk between structural proteins and their regulators. In the study presented here, circular dichroism, chemical cross-linking, and small angle x-ray scattering are used to demonstrate that cortactin adopts a globular conformation, thereby bringing distant parts of the molecule into close proximity. In addition, the actin bundling activity of cortactin is characterized, showing that fully polymerized actin filaments are bundled into sheet-like structures. We present a low resolution structure that suggests how the various domains of cortactin interact to coordinate its array of binding partners at sites of actin branching. PMID:18375393

  15. Fiber bundle design for an integrated wearable artificial lung.

    PubMed

    Madhani, Shalv P; Frankowski, Brian J; Federspiel, William J

    2017-02-07

    Mechanical ventilation and ECMO are the only viable treatment options for lung failure patients at the end stage, including ARDS and COPD. These treatments however are associated with high morbidity and mortality due to long wait times for lung transplant. Contemporary clinical literature has shown ambulation improves post-transplant outcomes in lung failure patients. Given this, we are developing the PAAL, a truly wearable artificial lung that allows for ambulation. In this study, we targeted 180 ml/min oxygenation and determined the form factor for a hollow fiber membrane (HFM) bundle for the PAAL.Based on a previously published mass transfer correlation we modeled oxygenation efficiency as a function of fiber bundle diameter. Three benchmark fiber bundles were fabricated to validate the model through in-vitro blood gas exchange at blood flow rates from 1 to 4 L/min according to ASTM standards. We used the model to determine a final design, which was characterized in-vitro through a gas exchange as well as a hemolysis study at 3.5 L/minThe percent difference between model predictions and experiment for the benchmark bundles ranged from 3% to 17.5% at the flowrates tested. Using the model, we predicted a 1.75 inch diameter bundle with 0.65 m surface area would produce 180 ml/min at 3.5 L/min blood flow rate. The oxygenation efficiency was 278 ml/min/m and the Normalized Index of Hemolysis (NIH) was less than 0.05g/100L. Future work involves integrating this bundle into the PAAL for which an experimental prototype is under development in our laboratory.

  16. One-sided ejaculation of echidna sperm bundles.

    PubMed

    Johnston, S D; Smith, B; Pyne, M; Stenzel, D; Holt, W V

    2007-12-01

    We report for the first time an unusual ejaculatory mechanism in the short-beaked echidna in which each side of the bilaterally symmetrical, rosettelike glans penis is used alternately, with the other being shut down. This is unparalleled in mammals but is reminiscent of the use of hemipenes in squamate reptiles, providing further reproductive evidence of a sauropsidian lineage in the Monotremata. Further, we describe the occurrence of motile sperm bundles in ejaculated echidna semen and provide scanning electron micrographs of their morphology. Sperm bundling appears to confer increased sperm motility, which may provide the potential for sperm competition between males.

  17. Dunkl Operators as Covariant Derivatives in a Quantum Principal Bundle

    NASA Astrophysics Data System (ADS)

    Durdevich, Micho; Sontz, Stephen Bruce

    2013-05-01

    A quantum principal bundle is constructed for every Coxeter group acting on a finite-dimensional Euclidean space E, and then a connection is also defined on this bundle. The covariant derivatives associated to this connection are the Dunkl operators, originally introduced as part of a program to generalize harmonic analysis in Euclidean spaces. This gives us a new, geometric way of viewing the Dunkl operators. In particular, we present a new proof of the commutativity of these operators among themselves as a consequence of a geometric property, namely, that the connection has curvature zero.

  18. Asynchrony of the early maturation of white matter bundles in healthy infants: quantitative landmarks revealed noninvasively by diffusion tensor imaging.

    PubMed

    Dubois, Jessica; Dehaene-Lambertz, Ghislaine; Perrin, Muriel; Mangin, Jean-François; Cointepas, Yann; Duchesnay, Edouard; Le Bihan, Denis; Hertz-Pannier, Lucie

    2008-01-01

    Normal cognitive development in infants follows a well-known temporal sequence, which is assumed to be correlated with the structural maturation of underlying functional networks. Postmortem studies and, more recently, structural MR imaging studies have described qualitatively the heterogeneous spatiotemporal progression of white matter myelination. However, in vivo quantification of the maturation phases of fiber bundles is still lacking. We used noninvasive diffusion tensor MR imaging and tractography in twenty-three 1-4-month-old healthy infants to quantify the early maturation of the main cerebral fascicles. A specific maturation model, based on the respective roles of different maturational processes on the diffusion phenomena, was designed to highlight asynchronous maturation across bundles by evaluating the time-course of mean diffusivity and anisotropy changes over the considered developmental period. Using an original approach, a progression of maturation in four relative stages was determined in each tract by estimating the maturation state and speed, from the diffusion indices over the infants group compared with an adults group on one hand, and in each tract compared with the average over bundles on the other hand. Results were coherent with, and extended previous findings in 8 of 11 bundles, showing the anterior limb of the internal capsule and cingulum as the most immature, followed by the optic radiations, arcuate and inferior longitudinal fascicles, then the spinothalamic tract and fornix, and finally the corticospinal tract as the most mature bundle. Thus, this approach provides new quantitative landmarks for further noninvasive research on brain-behavior relationships during normal and abnormal development.

  19. Annexin A2–dependent actin bundling promotes secretory granule docking to the plasma membrane and exocytosis

    PubMed Central

    Gabel, Marion; Delavoie, Franck; Demais, Valérie; Royer, Cathy; Bailly, Yannick; Vitale, Nicolas; Bader, Marie-France

    2015-01-01

    Annexin A2, a calcium-, actin-, and lipid-binding protein involved in exocytosis, mediates the formation of lipid microdomains required for the structural and spatial organization of fusion sites at the plasma membrane. To understand how annexin A2 promotes this membrane remodeling, the involvement of cortical actin filaments in lipid domain organization was investigated. 3D electron tomography showed that cortical actin bundled by annexin A2 connected docked secretory granules to the plasma membrane and contributed to the formation of GM1-enriched lipid microdomains at the exocytotic sites in chromaffin cells. When an annexin A2 mutant with impaired actin filament–bundling activity was expressed, the formation of plasma membrane lipid microdomains and the number of exocytotic events were decreased and the fusion kinetics were slower, whereas the pharmacological activation of the intrinsic actin-bundling activity of endogenous annexin A2 had the opposite effects. Thus, annexin A2–induced actin bundling is apparently essential for generating active exocytotic sites. PMID:26323692

  20. Vulnerability of Protoxylem and Metaxylem Vessels to Embolisms and Radial Refilling in a Vascular Bundle of Maize Leaves

    PubMed Central

    Hwang, Bae Geun; Ryu, Jeongeun; Lee, Sang Joon

    2016-01-01

    Regulation of water flow in an interconnected xylem vessel network enables plants to survive despite challenging environment changes that can cause xylem embolism. In this study, vulnerability to embolisms of xylem vessels and their water-refilling patterns in vascular bundles of maize leaves were experimentally investigated by employing synchrotron X-ray micro-imaging technique. A vascular bundle in maize consisted of a protoxylem vessel with helical thickenings between two metaxylem vessels with single perforation plates and nonuniformly distributed pits. When embolism was artificially induced in excised maize leaves by exposing them to air, protoxylem vessels became less vulnerable to dehydration compared to metaxylem vessels. After supplying water into the embolized vascular bundles, when water-refilling process stopped at the perforation plates in metaxylem vessels, discontinuous radial water influx occurred surprisingly in the adjacent protoxylem vessels. Alternating water refilling pattern in protoxylem and metaxylem vessels exhibited probable correlation between the incidence location and time of water refilling and the structural properties of xylem vessels. These results imply that the maintenance of water transport and modulation of water refilling are affected by hydrodynamic roles of perforation plates and radial connectivity in a xylem vascular bundle network. PMID:27446168

  1. Branes as Stable Holomorphic Line Bundles On the Non-Commutative Torus

    NASA Astrophysics Data System (ADS)

    Grange, Pascal

    2004-10-01

    It was suggested by A. Kapustin that turning on a B-field, and allowing some discrepancy between the left and and right-moving complex structures, must induce an identification of B-branes with holomorphic line bundles on a non-commutative complex torus. The stability condition for the branes is written as a topological identity of non-commutative gauge theory. This identifies stable B-branes with previously proposed non-commutative instanton equations. Consistency of the non-commutative description with complex geometry is examined, using the non-linearities of the Seiberg-Witten map.

  2. Basic Tilted Helix Bundle – A new protein fold in human FKBP25/FKBP3 and HectD1

    SciTech Connect

    Helander, Sara; Montecchio, Meri; Lemak, Alexander; Farès, Christophe; Almlöf, Jonas; Li, Yanjun; Yee, Adelinda; Arrowsmith, Cheryl H.; Dhe-Paganon, Sirano; Sunnerhagen, Maria

    2014-04-25

    Highlights: • We describe the structure of a novel fold in FKBP25 and HectD. • The new fold is named the Basic Tilted Helix Bundle (BTHB) domain. • A conserved basic surface patch is presented, suggesting a functional role. - Abstract: In this paper, we describe the structure of a N-terminal domain motif in nuclear-localized FKBP25{sub 1–73}, a member of the FKBP family, together with the structure of a sequence-related subdomain of the E3 ubiquitin ligase HectD1 that we show belongs to the same fold. This motif adopts a compact 5-helix bundle which we name the Basic Tilted Helix Bundle (BTHB) domain. A positively charged surface patch, structurally centered around the tilted helix H4, is present in both FKBP25 and HectD1 and is conserved in both proteins, suggesting a conserved functional role. We provide detailed comparative analysis of the structures of the two proteins and their sequence similarities, and analysis of the interaction of the proposed FKBP25 binding protein YY1. We suggest that the basic motif in BTHB is involved in the observed DNA binding of FKBP25, and that the function of this domain can be affected by regulatory YY1 binding and/or interactions with adjacent domains.

  3. Get ready: Bundled payments are in your future.

    PubMed

    2015-09-01

    The Centers for Medicare & Medicaid Services' (CMS') mandatory bundled payment pilot project makes clear that the agency intends to reform Medicare reimbursement. Hospitals in 75 geographic areas are required to participate in a five-year pilot project that puts them at risk for the cost of hip and knee replacements from the time of surgery until 90 days after discharge. Already, more than 6,500 providers are participating in the Bundled Payments for Care Improvement project, a voluntary program where participants can choose from 48 clinical episodes and four models. Even if they won't be part of a bundled payments arrangement, case managers need to shift their thinking to prepare for the future of reimbursement by developing close working relationships with post-acute providers, knowing the services and quality delivered by post-acute providers, and being aware of the costs for the entire episode of care. Case managers will not be able to handle all the responsibilities necessary in a bundled payment arrangement if they have large caseloads.

  4. Fission Yeast Scp3 Potentially Maintains Microtubule Orientation through Bundling

    PubMed Central

    Ozaki, Kanako; Chikashige, Yuji; Hiraoka, Yasushi; Matsumoto, Tomohiro

    2015-01-01

    Microtubules play important roles in organelle transport, the maintenance of cell polarity and chromosome segregation and generally form bundles during these processes. The fission yeast gene scp3+ was identified as a multicopy suppressor of the cps3-81 mutant, which is hypersensitive to isopropyl N-3-chlorophenylcarbamate (CIPC), a poison that induces abnormal multipolar spindle formation in higher eukaryotes. In this study, we investigated the function of Scp3 along with the effect of CIPC in the fission yeast Schizosaccharomyces pombe. Microscopic observation revealed that treatment with CIPC, cps3-81 mutation and scp3+ gene deletion disturbed the orientation of microtubules in interphase cells. Overexpression of scp3+ suppressed the abnormal orientation of microtubules by promoting bundling. Functional analysis suggested that Scp3 functions independently from Ase1, a protein largely required for the bundling of the mitotic spindle. A strain lacking the ase1+ gene was more sensitive to CIPC, with the drug affecting the integrity of the mitotic spindle, indicating that CIPC has a mitotic target that has a role redundant with Ase1. These results suggested that multiple systems are independently involved to ensure microtubule orientation by bundling in fission yeast. PMID:25767875

  5. Formation and Dissociation of Sperm Bundles in Monotremes.

    PubMed

    Nixon, Brett; Ecroyd, Heath; Dacheux, Jean-Louis; Dacheux, Francoise; Labas, Valerie; Johnston, Steve D; Jones, Russell C

    2016-10-01

    Because monotremes are the earliest offshoot of the mammalian lineage, the platypus and short-beaked echidna were studied as model animals to assess the origin and biological significance of adaptations considered unique to therian mammals: epididymal sperm maturation and subsequent capacitation. We show that spermatozoa from both species assemble into bundles of approximately 100 cells during passage through the epididymis and that an epididymal protein-secreted protein, acidic, cysteine-rich (osteonectin; SPARC)-is involved in bundle formation. The bundles persisted during incubation in vitro for at least 1 h under conditions that capacitate therian spermatozoa, and then underwent a time-dependent dissociation to release spermatozoa capable of fertilization. Only after this dissociation could the spermatozoa bind to the perivitelline membrane of a hen's egg, display an altered form of motility reminiscent of hyperactivation, and be induced to undergo an acrosome reaction. It is concluded that the development of sperm bundles in the monotreme epididymis mandates that they require a time-dependent process to be capable of fertilizing an ovum. However, because this functional end point was achieved without overt changes in protein tyrosine phosphorylation (a hallmark of capacitation in therians), it is concluded that the process in monotremes is distinctly different from capacitation in therian mammals.

  6. Metabolite Diffusion into Bundle Sheath Cells from C4 Plants

    PubMed Central

    Weiner, Hendrik; Burnell, James N.; Woodrow, Ian E.; Heldt, Hans W.; Hatch, Marshall D.

    1988-01-01

    The present studies provide the first measurements of the resistance to diffusive flux of metabolites between mesophyll and bundle sheath cells of C4 plants. Species examined were Panicum miliaceum, Urochloa panicoides, Atriplex spongiosa, and Zea mays. Diffusive flux of metabolites into isolated bundle sheath cells was monitored by following their metabolic transformation. Evidence was obtained that the observed rapid fluxes occurred via functional plasmodesmata. Diffusion constants were determined from the rate of transformation of limiting concentrations of metabolites via cytosolic enzymes with high potential velocities and favorable equilibrium constants. Values on a leaf chlorophyll basis ranged between 1 and 5 micromoles per minute per milligram of chlorophyll per millimolar gradient depending on the molecular weight of the metabolite and the source of bundle sheath cells. Diffusion of metabolites into these cells was unaffected by a wide variety of compounds including respiratory inhibitors, monovalent and divalent cations, and plant hormones, but it was interrupted by treatments inducing cell plasmolysis. The molecular weight exclusion limit for permeation of compounds into bundle sheath cells was in the range of 850 to 900. These cells provide an ideal system for the quantitative study of plasmodesmatal function. PMID:16666390

  7. Fuel bundle design for enhanced usage of plutonium fuel

    DOEpatents

    Reese, Anthony P.; Stachowski, Russell E.

    1995-01-01

    A nuclear fuel bundle includes a square array of fuel rods each having a concentration of enriched uranium and plutonium. Each rod of an interior array of the rods also has a concentration of gadolinium. The interior array of rods is surrounded by an exterior array of rods void of gadolinium. By this design, usage of plutonium in the nuclear reactor is enhanced.

  8. A Method of Assembling Compact Coherent Fiber-Optic Bundles

    NASA Technical Reports Server (NTRS)

    Martin, Stefan; Liu, Duncan; Levine, Bruce Martin; Shao, Michael; Wallace, James

    2007-01-01

    A method of assembling coherent fiber-optic bundles in which all the fibers are packed together as closely as possible is undergoing development. The method is based, straightforwardly, on the established concept of hexagonal close packing; hence, the development efforts are focused on fixtures and techniques for practical implementation of hexagonal close packing of parallel optical fibers.

  9. Exposure Control Using Adaptive Multi-Stage Item Bundles.

    ERIC Educational Resources Information Center

    Luecht, Richard M.

    This paper presents a multistage adaptive testing test development paradigm that promises to handle content balancing and other test development needs, psychometric reliability concerns, and item exposure. The bundled multistage adaptive testing (BMAT) framework is a modification of the computer-adaptive sequential testing framework introduced by…

  10. Thermal conversion of bundled carbon nanotubes into graphitic ribbons.

    PubMed

    Gutiérrez, H R; Kim, U J; Kim, J P; Eklund, P C

    2005-11-01

    High temperature heat treatment (HTT) of bundled single-walled carbon nanotubes (SWNTs) in vacuum ( approximately 10(-5) Torr) has been found to lead to the formation of two types of graphitic nanoribbons (GNRs), as observed by high-resolution transmission electron microscopy. Purified SWNT bundles were first found to follow two evolutionary steps, as reported previously, that is, tube coalescence (HTT approximately 1400 degrees C) and then massive bond rearrangement (HTT approximately 1600 degrees C), leading to the formation of bundled multiwall nanotubes (MWNTs) with 3-12 shells. At HTT > 1800 degrees C, we find that these MWNTs collapse into multishell GNRs. The first type of GNR we observed is driven by the collapse of diameter-doubled single-wall nanotubes, and their production is terminated at HTT approximately 1600 degrees C when the MWNTs also start to form. We propose that the collapse is driven by van der Waals forces between adjacent tubes in the same bundle. For HTT > 2000 degrees C, the heat-treated material is found to be almost completely in the multishell GNR form.

  11. Hair Cells: Bundles, Tuning, Transduction—A Moderated Discussion

    NASA Astrophysics Data System (ADS)

    Karavitaki, K. Domenica; Ricci, Anthony J.

    2011-11-01

    A discussion moderated by the authors on the topic "Hair Cells: Bundles, Tuning, Transduction" was held on 17 July 2011 at the 11th International Mechanics of Hearing Workshop in Williamstown, Massachusetts. The paper provides an edited transcript of the session.

  12. Masquerading Bundle Branch Block: A Poor Prognostic Sign Revisited

    PubMed Central

    Dhanse, Suheil; Kareem, Hashir; Devasia, Tom

    2016-01-01

    Masquerading bundle branch block is a rare but important finding on the Electrocardiogram (ECG). It is an indication of severe and diffuse conduction system disease and usually indicates poor prognosis. The precordial leads show a Right Bundle Branch Block (RBBB) pattern while the limb leads resemble a Left Bundle Branch Block (LBBB). This finding on an ECG is almost invariably associated with severe underlying heart disease. It is extremely important to be aware of this finding as it is a marker of poor cardiac outcomes. We report the case of a 68-year-old gentleman, who presented with progressive dyspnoea on exertion over three months. ECG showed a broad QRS complex with a RBBB pattern on the precordial leads and a LBBB pattern on the limb leads (suggestive of masquerading bundle branch block). A coronary angiogram revealed severe Triple Vessel Disease (TVD). The patient was scheduled for an early Coronary Artery By-Pass Grafting Surgery. However, his clinical condition deteriorated and he died while awaiting the surgery. PMID:27790494

  13. Product Bundling and Shared Information Goods: A Pricing Exercise

    ERIC Educational Resources Information Center

    Morrison, William G.

    2016-01-01

    In this article, the author describes an exercise in which two pricing problems (product bundling and the sharing of digital information goods) can be understood using the same analytical approach. The exercise allows students to calculate the correct numerical answers with relative ease, while the teaching plan demonstrates the importance of the…

  14. Coolant mixing in LMFBR rod bundles and outlet plenum mixing transients. Progress report

    SciTech Connect

    Todreas, N.E.; Golay, M.W.; Wold, L.

    1981-02-01

    Four tasks are reported on: bundle geometry (wrapped and bare rods), subchannel geometry (bare rods), LMFBR outlet plenum flow mixing, and theoretical determination of local temperature fields in LMFBR fuel rod bundles. (DLC)

  15. 76 FR 53137 - Bundled Payments for Care Improvement Initiative: Request for Applications

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-08-25

    ... HUMAN SERVICES Centers for Medicare & Medicaid Services Bundled Payments for Care Improvement Initiative... of the initial four models under the Bundled Payments for Care Improvement initiative beginning in... described on the CMS Innovation Center Web site...

  16. 75 FR 8353 - Price Index Adjustments for Expenditure Limitations and Lobbyist Bundling Disclosure Threshold

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-02-24

    ... Price Index Adjustments for Expenditure Limitations and Lobbyist Bundling Disclosure Threshold AGENCY: Federal Election Commission. ACTION: Notice of adjustments to expenditure limitations and lobbyist... Commission'') is adjusting certain expenditure limitations and the lobbyist bundling disclosure threshold...

  17. Pressure and Flow Relations in Vascular Bundles of the Tomato Plant

    PubMed Central

    Dimond, A. E.

    1966-01-01

    In the tomato plant water flows through primary xylem in accordance with Poiseuille's law. This relation and the analogy between Poiseuille's and Ohm's law were employed to calculate rates of flow and differences in pressure within vascular bundles when transpiration rates from individual leaves were known. The resistance of vascular bundles to flow was calculated from a modification of Poiseuille's law and from measurements of vessels in all bundles. The rates of flow in all bundles were derived from a set of simultaneous linear equations of flow, written to correspond with the nature of the vascular network. Values of the difference in pressure associated with flow in bundles were derived from resistances and flow rates in individual bundles. These agreed substantially with values observed in a comparable plant. In large bundles, vessels occur in a frequency distribution that is approximately normal with respect either to the logarithms of their radii or to the fourth power of their radii. The largest vessels in a bundle transport most of the water when they are functioning. The tomato plant contains 2 types of vascular bundle. The large bundles of the stem form a network by joining above each node in combinations of 2 at a time. The small bundles of the stem and petiolar bundles are independent of other bundles from their origins at junctions to their termini. The small bundles offer high resistance to flow, whereas the resistance of large bundles is low. The average conductance of large bundles decreases from the base to the apex of the stem. That of small vascular bundles remains low and more or less constant throughout the plant. Only a small difference in pressure is required to maintain flow in large bundles. For lower leaves, the driving pressure required to move water to the base of a petiole is considerably less than that which moves water through petioles. The difference in pressure that maintains flow increases steadily for successively higher nodes

  18. Synchrotron radiation circular dichroism spectroscopy applied to metmyoglobin and a 4-alpha-helix bundle carboprotein.

    PubMed

    Thulstrup, Peter W; Brask, Jesper; Jensen, Knud J; Larsen, Erik

    2005-05-01

    The novel technique, synchrotron radiation-based circular dichroism (SR-CD), has been applied to the study of metmyoglobin and a carboprotein (carbohydrate-based peptide with protein tertiary structure) with 4-alpha-helix bundle structure, as well as a carbopeptide (carbohydrate-based peptide) with a truncated peptide sequence. The use of synchroton radiation (SR) enabled circular dichroism (CD) measurements in the vacuum ultraviolet (VUV) down to 168 nm in D(2)O and 160 nm in 2,2,2-trifluoroethanol (TFE). The band shape in the CD spectra in the low wavelength region was studied, comparing samples with two types of alpha-helical tertiary structure, namely the globin fold and the 4-alpha-helix bundle motif. No significant differences were found between the CD spectra of the alpha-helical samples (metmyoglobin and carboprotein) in D(2)O solution. The use of 2,2,2-TFE (TFE) as solvent clearly alters the VUV CD but the two samples have very similar CD spectra. The solvent-induced denaturing of metmyoglobin in TFE was observed using absorption and CD spectroscopy of the Soret band, with results indicating heme release. The VUV spectrum of TFE-denatured metmyoglobin exhibits dramatic differences in comparison with previous studies of the native enzyme in aqueous solution. The implications of this observation are discussed.

  19. Representing Practice: Practice Models, Patterns, Bundles

    ERIC Educational Resources Information Center

    Falconer, Isobel; Finlay, Janet; Fincher, Sally

    2011-01-01

    This article critiques learning design as a representation for sharing and developing practice, based on synthesis of three projects. Starting with the findings of the Mod4L Models of Practice project, it argues that the technical origins of learning design, and the consequent focus on structure and sequence, limit its usefulness for sharing…

  20. 78 FR 29139 - Medicare Program; Bundled Payments for Care Improvement Model 1 Open Period

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-05-17

    ... participation in Model 1 of the Bundled Payments for Care Improvement initiative. DATES: Model 1 of the Bundled Payments for Care Improvement Deadline: Interested organizations must submit a Model 1 Open Period... regarding Model 1 of the Bundled Payments for Care Improvement initiative. For additional information...

  1. Exploring Differential Bundle Functioning in Mathematics by Gender: The Effect of Hierarchical Modelling

    ERIC Educational Resources Information Center

    Ong, Yoke Mooi; Williams, Julian; Lamprianou, Iasonas

    2013-01-01

    Researchers interested in exploring substantive group differences are increasingly attending to bundles of items (or testlets): the aim is to understand how gender differences, for instance, are explained by differential performances on different types or bundles of items, hence differential bundle functioning (DBF). Some previous work has…

  2. Patient and carer experiences of clinical uncertainty and deterioration, in the face of limited reversibility: A comparative observational study of the AMBER care bundle

    PubMed Central

    Bristowe, Katherine; Carey, Irene; Hopper, Adrian; Shouls, Susanna; Prentice, Wendy; Caulkin, Ruth; Higginson, Irene J; Koffman, Jonathan

    2015-01-01

    Background: Clinical uncertainty is emotionally challenging for patients and carers and creates additional pressures for those clinicians in acute hospitals. The AMBER care bundle was designed to improve care for patients identified as clinically unstable, deteriorating, with limited reversibility and at risk of dying in the next 1–2 months. Aim: To examine the experience of care supported by the AMBER care bundle compared to standard care in the context of clinical uncertainty, deterioration and limited reversibility. Design: A comparative observational mixed-methods study using semi-structured qualitative interviews and a followback survey. Setting/participants: Three large London acute tertiary National Health Service hospitals. Nineteen interviews with 23 patients and carers (10 supported by AMBER care bundle and 9 standard care). Surveys completed by next of kin of 95 deceased patients (59 AMBER care bundle and 36 standard care). Results: The AMBER care bundle was associated with increased frequency of discussions about prognosis between clinicians and patients (χ2 = 4.09, p = 0.04), higher awareness of their prognosis by patients (χ2 = 4.29, p = 0.04) and lower clarity in the information received about their condition (χ2 = 6.26, p = 0.04). Although the consistency and quality of communication were not different between the two groups, those supported by the AMBER care bundle described more unresolved concerns about caring for someone at home. Conclusion: Awareness of prognosis appears to be higher among patients supported by the AMBER care bundle, but in this small study this was not translated into higher quality communication, and information was judged less easy to understand. Adequately powered comparative evaluation is urgently needed. PMID:25829443

  3. Backbone dynamics measurements on leukemia inhibitory factor, a rigid four-helical bundle cytokine.

    PubMed Central

    Yao, S.; Smith, D. K.; Hinds, M. G.; Zhang, J. G.; Nicola, N. A.; Norton, R. S.

    2000-01-01

    The backbone dynamics of the four-helical bundle cytokine leukemia inhibitory factor (LIF) have been investigated using 15N NMR relaxation and amide proton exchange measurements on a murine-human chimera, MH35-LIF. For rapid backbone motions (on a time scale of 10 ps to 100 ns), as probed by 15N relaxation measurements, the dynamics parameters were calculated using the model-free formalism incorporating the model selection approach. The principal components of the inertia tensor of MH35-LIF, as calculated from its NMR structure, were 1:0.98:0.38. The global rotational motion of the molecule was, therefore, assumed to be axially symmetric in the analysis of its relaxation data. This yielded a diffusion anisotropy D(parallel)/D(perpendicular) of 1.31 and an effective correlation time (4D(perpendicular) + 2D(parallel))(-1) of 8.9 ns. The average values of the order parameters (S2) for the four helices, the long interhelical loops, and the N-terminus were 0.91, 0.84, and 0.65, respectively, indicating that LIF is fairly rigid in solution, except at the N-terminus. The S2 values for the long interhelical loops of MH35-LIF were higher than those of their counterparts in short-chain members of the four-helical bundle cytokine family. Residues involved in LIF receptor binding showed no consistent pattern of backbone mobilities, with S2 values ranging from 0.71 to 0.95, but residues contributing to receptor binding site III had relatively lower S2 values, implying higher amplitude motions than for the backbone of sites I and II. In the relatively slow motion regime, backbone amide exchange measurements showed that a number of amides from the helical bundle exchanged extremely slowly, persisting for several months in 2H2O at 37 degrees C. Evidence for local unfolding was considered, and correlations among various structure-related parameters and the backbone amide exchange rates were examined. Both sets of data concur in showing that LIF is one of the most rigid four

  4. Xyloside primed glycosaminoglycans alter hair bundle micromechanical coupling and synaptic transmission: Pharmacokinetics

    SciTech Connect

    Holman, Holly A.; Nguyen, Lynn Y.; Tran, Vy M.; Arungundram, Sailaja; Kalita, Mausam; Kuberan, Balagurunathan; Rabbitt, Richard D.

    2015-12-31

    Glycosaminoglycans (GAGs) are ubiquitous in the inner ear, and disorders altering their structure or production often result in debilitating hearing and balance deficits. The specific mechanisms responsible for loss of hair-cell function are not well understood. We recently reported that introduction of a novel BODIPY conjugated xyloside (BX) into the endolymph primes fluorescent GAGs in vivo [6, 15]. Confocal and two-photon fluorescence imaging revealed rapid turnover and assembly of a glycocalyx enveloping the kinocilia and extending into the cupula, a structure that presumably serves as a mechanical link between the hair bundle and the cupula. Extracellular fluorescence was also observed around the basolateral surface of hair cells and surrounding afferent nerve projections into the crista. Single unit afferent recordings during mechanical hair bundle stimulation revealed temporary interruption of synaptic transmission following BX administration followed by recovery, demonstrating an essential role for GAGs in function of the hair cell synapse. In the present work we present a pharmacokinetic model to quantify the time course of BX primed GAG production and turnover in the ear.

  5. Xyloside primed glycosaminoglycans alter hair bundle micromechanical coupling and synaptic transmission: Pharmacokinetics

    NASA Astrophysics Data System (ADS)

    Holman, Holly A.; Tran, Vy M.; Nguyen, Lynn Y.; Arungundram, Sailaja; Kalita, Mausam; Kuberan, Balagurunathan; Rabbitt, Richard D.

    2015-12-01

    Glycosaminoglycans (GAGs) are ubiquitous in the inner ear, and disorders altering their structure or production often result in debilitating hearing and balance deficits. The specific mechanisms responsible for loss of hair-cell function are not well understood. We recently reported that introduction of a novel BODIPY conjugated xyloside (BX) into the endolymph primes fluorescent GAGs in vivo [6, 15]. Confocal and two-photon fluorescence imaging revealed rapid turnover and assembly of a glycocalyx enveloping the kinocilia and extending into the cupula, a structure that presumably serves as a mechanical link between the hair bundle and the cupula. Extracellular fluorescence was also observed around the basolateral surface of hair cells and surrounding afferent nerve projections into the crista. Single unit afferent recordings during mechanical hair bundle stimulation revealed temporary interruption of synaptic transmission following BX administration followed by recovery, demonstrating an essential role for GAGs in function of the hair cell synapse. In the present work we present a pharmacokinetic model to quantify the time course of BX primed GAG production and turnover in the ear.

  6. Long Circulating Micelles based on Helix Bundle-Forming Peptide-Polymer Conjugates

    NASA Astrophysics Data System (ADS)

    Shu, Jessica; Dong, He; Dube, Nikhil; Seo, Jai Woong; Ma, Yu Fei; Ferrara, Katherine; Xu, Ting

    2012-02-01

    Stable, multi-functional organic nanoparticles that combine long in vivo circulation, the ability to cross vessel walls to reach tumor tissues and controlled disassembly for eventual clearance will have a significant impact in nanomedicine. Although current self-assemblies of amphiphiles provide a versatile platform to generate modular organic nanoparticles, it remains a significant challenge to simultaneously control nanoparticle size in the range of 10-30 nm, enhance particle stability and tailor disassembly within suitable timescales. We have advanced this goal by designing a new family of amphiphiles based on coiled-coil 3-helix bundle forming peptide-polymer conjugates. By attaching a polymer chain to the middle of a helical peptide, the protein tertiary structures are used to position entropic forces of compressed polymer chains comprising the headgroups so as to effectively slow down the subunit desorption rate and enhance the in vivo stability. The resultant monodispersed nanoparticles are composed of subunits, < 4 nm in size, that form highly stable 15-17 nm diameter particles and demonstrate an in vivo circulation half life-time of 28 hrs, minimal accumulation in the liver and spleen and effective urinary clearance. By uniquely combining the configurational entropy of a polymer chain with a common protein structure, i.e. coiled-coil helix bundle, and a lipid core, self-assembled nanoparticles have been engineered with tunable stability and disassembly.

  7. Medical catheters thermally manipulated by fiber optic bundles

    DOEpatents

    Chastagner, Philippe

    1992-01-01

    A maneuverable medical catheter comprising a flexible tube having a functional tip. The catheter is connected to a control source. The functional tip of the catheter carries a plurality of temperature activated elements arranged in parallel and disposed about the functional tip and held in spaced relation at each end. These elements expand when they are heated. A plurality of fiber optic bundles, each bundle having a proximal end attached to the control source and a distal end attached to one of the elements carry light into the elements where the light is absorbed as heat. By varying the optic fiber that is carrying the light and the intensity of the light, the bending of the elements can be controlled and thus the catheter steered. In an alternate embodiment, the catheter carries a medical instrument for gathering a sample of tissue. The instrument may also be deployed and operated by thermal expansion and contraction of its moving parts.

  8. Medical catheters thermally manipulated by fiber optic bundles

    DOEpatents

    Chastagner, P.

    1992-10-06

    A maneuverable medical catheter comprising a flexible tube having a functional tip is described. The catheter is connected to a control source. The functional tip of the catheter carries a plurality of temperature activated elements arranged in parallel and disposed about the functional tip and held in spaced relation at each end. These elements expand when they are heated. A plurality of fiber optic bundles, each bundle having a proximal end attached to the control source and a distal end attached to one of the elements carry light into the elements where the light is absorbed as heat. By varying the optic fiber that is carrying the light and the intensity of the light, the bending of the elements can be controlled and thus the catheter steered. In an alternate embodiment, the catheter carries a medical instrument for gathering a sample of tissue. The instrument may also be deployed and operated by thermal expansion and contraction of its moving parts. 10 figs.

  9. Quantum Turbulence: Vortex Bundle Collapse and Kolmogorov Spectrum

    NASA Astrophysics Data System (ADS)

    Nemirovskii, Sergey K.

    2016-12-01

    The statement of problem is motivated by the idea of modeling the classical turbulence with a set of chaotic quantized vortex filaments in superfluids. Among various arguments supporting the idea of quasi-classic behavior of quantum turbulence, the strongest, probably, is the k dependence of the spectra of energy, E(k)∝ k^{-5/3} obtained in numerical simulations and experiments. At the same time, the mechanism of classical vs. quantum turbulence is not clarified and the source of the k^{-5/3} dependence is unclear. In this work, we concentrated on the nonuniform vortex bundles. This choice is related to the actively discussed question concerning a role of collapses in the vortex dynamics in formation of turbulent spectra. We demonstrate that the nonuniform vortex bundles, which appear in result of nonlinear vortex dynamics, generates an energy spectrum which is close to the Kolmogorov dependence ∝ k^{-5/3}.

  10. Synthesis of bundled tungsten oxide nanowires with controllable morphology

    SciTech Connect

    Sun Shibin Zou Zengda; Min Guanghui

    2009-05-15

    Bundled tungsten oxide nanowires with controllable morphology were synthesized by a simple solvothermal method with tungsten hexachloride (WCl{sub 6}) as precursor and cyclohexanol as solvent. The as-synthesized products were systematically characterized by using scanning electron microscopy, X-ray diffraction and transition electron microscopy. Brunauer-Emmett-Teller gas-sorption measurements were also employed. Accompanied by an apparent drop of specific surface area from 151 m{sup 2} g{sup -1} for the longer nanowires synthesized using a lower concentration of WCl{sub 6} to 106 m{sup 2} g{sup -1} for the shorter nanowires synthesized using a higher concentration of WCl{sub 6}, a dramatically morphological evolution was also observed. With increasing concentration of tungsten hexachloride (WCl{sub 6}) in cyclohexanol, the nanostructured bundles became larger, shorter and straighter, and finally a block-shape product occurred.

  11. Curved Space-Times by Crystallization of Liquid Fiber Bundles

    NASA Astrophysics Data System (ADS)

    Hélein, Frédéric; Vey, Dimitri

    2017-01-01

    Motivated by the search for a Hamiltonian formulation of Einstein equations of gravity which depends in a minimal way on choices of coordinates, nor on a choice of gauge, we develop a multisymplectic formulation on the total space of the principal bundle of orthonormal frames on the 4-dimensional space-time. This leads quite naturally to a new theory which takes place on 10-dimensional manifolds. The fields are pairs of ((α ,ω ),π), where (α ,ω ) is a 1-form with coefficients in the Lie algebra of the Poincaré group and π is an 8-form with coefficients in the dual of this Lie algebra. The dynamical equations derive from a simple variational principle and imply that the 10-dimensional manifold looks locally like the total space of a fiber bundle over a 4-dimensional base manifold. Moreover this base manifold inherits a metric and a connection which are solutions of a system of Einstein-Cartan equations.

  12. Buckling of a fiber bundle embedded in epoxy

    NASA Technical Reports Server (NTRS)

    Hahn, H. T.; Sohi, M. M.

    1986-01-01

    Buckling of a fiber bundle embedded in epoxy resin was studied to gain insight into compressive failure mechanisms in unidirectional composites. The fibers used were E-glass, T300 graphite, T700 graphite, and P75 graphite. These fibers were combined with two different resins: Epon 815/V140 and Epon 828/Z. In both resins the failure mode of the bundle was found to be microbuckling of fibers for the first three types of fibers; however, the high-modulus P75 fibers failed in shear without any sign of microbuckling. The strains at which microbuckling occurred were higher than the compressive failure strains of the corresponding unidirectional composites. In the soft resin, Epon 815/V140, fibers buckled at lower strains than in the stiff resin, Epon 828/Z. The buckling strains and the segment lengths followed the trends predicted for a single filament embedded in an infinite matrix.

  13. CAT reconstruction and potting comparison of a LMFBR fuel bundle

    SciTech Connect

    Betten, P.R.; Tow, D.M.

    1984-04-01

    A standard Liquid Metal Fast Breeder Reactor (LMFBR) subassembly used in the Experimental Breeder Reactor II (EBR-II) was investigated, by remote techniques, for fuel bundle distortion by both nondestructive and destructive methods, and the results from both methods were compared. The non-destructive method employed neutron tomography to reconstruct the locations of fuel elements through the use of a maximum entropy reconstruction algorithm known as MENT. The destructive method consisted of ''potting'' (a technique that embeds and permanently fixes the fuel elements in a solid matrix) the subassembly, and then cutting and polishing the individual sections. The comparison indicated that the tomography reconstruction provided good results in describing the bundle geometry and spacer-wire locations, with the overall resolution being on the order of a spacer-wire diameter. A dimensional consistency check indicated that the element and spacer-wire dimensions were accurately reproduced in the reconstruction.

  14. Cofilin-mediated actin dynamics promotes actin bundle formation during Drosophila bristle development

    PubMed Central

    Wu, Jing; Wang, Heng; Guo, Xuan; Chen, Jiong

    2016-01-01

    The actin bundle is an array of linear actin filaments cross-linked by actin-bundling proteins, but its assembly and dynamics are not as well understood as those of the branched actin network. Here we used the Drosophila bristle as a model system to study actin bundle formation. We found that cofilin, a major actin disassembly factor of the branched actin network, promotes the formation and positioning of actin bundles in the developing bristles. Loss of function of cofilin or AIP1, a cofactor of cofilin, each resulted in increased F-actin levels and severe defects in actin bundle organization, with the defects from cofilin deficiency being more severe. Further analyses revealed that cofilin likely regulates actin bundle formation and positioning by the following means. First, cofilin promotes a large G-actin pool both locally and globally, likely ensuring rapid actin polymerization for bundle initiation and growth. Second, cofilin limits the size of a nonbundled actin-myosin network to regulate the positioning of actin bundles. Third, cofilin prevents incorrect assembly of branched and myosin-associated actin filament into bundles. Together these results demonstrate that the interaction between the dynamic dendritic actin network and the assembling actin bundles is critical for actin bundle formation and needs to be closely regulated. PMID:27385345

  15. Arrays of Bundles of Carbon Nanotubes as Field Emitters

    NASA Technical Reports Server (NTRS)

    Manohara, Harish; Bronkowski, Michael

    2007-01-01

    Experiments have shown that with suitable choices of critical dimensions, planar arrays of bundles of carbon nanotubes (see figure) can serve as high-current-density field emitter (cold-cathode) electron sources. Whereas some hot-cathode electron sources must be operated at supply potentials of thousands of volts, these cold-cathode sources generate comparable current densities when operated at tens of volts. Consequently, arrays of bundles of carbon nanotubes might prove useful as cold-cathode sources in miniature, lightweight electron-beam devices (e.g., nanoklystrons) soon to be developed. Prior to the experiments, all reported efforts to develop carbon-nanotube-based field-emission sources had yielded low current densities from a few hundred microamperes to a few hundred milliamperes per square centimeter. An electrostatic screening effect, in which taller nanotubes screen the shorter ones from participating in field emission, was conjectured to be what restricts the emission of electrons to such low levels. It was further conjectured that the screening effect could be reduced and thus emission levels increased by increasing the spacing between nanotubes to at least by a factor of one to two times the height of the nanotubes. While this change might increase the emission from individual nanotubes, it would decrease the number of nanotubes per unit area and thereby reduce the total possible emission current. Therefore, to maximize the area-averaged current density, it would be necessary to find an optimum combination of nanotube spacing and nanotube height. The present concept of using an array of bundles of nanotubes arises partly from the concept of optimizing the spacing and height of field emitters. It also arises partly from the idea that single nanotubes may have short lifetimes as field emitters, whereas bundles of nanotubes could afford redundancy so that the loss of a single nanotube would not significantly reduce the overall field emission.

  16. Fuel bundle design for enhanced usage of plutonium fuel

    DOEpatents

    Reese, A.P.; Stachowski, R.E.

    1995-08-08

    A nuclear fuel bundle includes a square array of fuel rods each having a concentration of enriched uranium and plutonium. Each rod of an interior array of the rods also has a concentration of gadolinium. The interior array of rods is surrounded by an exterior array of rods void of gadolinium. By this design, usage of plutonium in the nuclear reactor is enhanced. 10 figs.

  17. Image processing for cameras with fiber bundle image relay.

    PubMed

    Olivas, Stephen J; Arianpour, Ashkan; Stamenov, Igor; Morrison, Rick; Stack, Ron A; Johnson, Adam R; Agurok, Ilya P; Ford, Joseph E

    2015-02-10

    Some high-performance imaging systems generate a curved focal surface and so are incompatible with focal plane arrays fabricated by conventional silicon processing. One example is a monocentric lens, which forms a wide field-of-view high-resolution spherical image with a radius equal to the focal length. Optical fiber bundles have been used to couple between this focal surface and planar image sensors. However, such fiber-coupled imaging systems suffer from artifacts due to image sampling and incoherent light transfer by the fiber bundle as well as resampling by the focal plane, resulting in a fixed obscuration pattern. Here, we describe digital image processing techniques to improve image quality in a compact 126° field-of-view, 30 megapixel panoramic imager, where a 12 mm focal length F/1.35 lens made of concentric glass surfaces forms a spherical image surface, which is fiber-coupled to six discrete CMOS focal planes. We characterize the locally space-variant system impulse response at various stages: monocentric lens image formation onto the 2.5 μm pitch fiber bundle, image transfer by the fiber bundle, and sensing by a 1.75 μm pitch backside illuminated color focal plane. We demonstrate methods to mitigate moiré artifacts and local obscuration, correct for sphere to plane mapping distortion and vignetting, and stitch together the image data from discrete sensors into a single panorama. We compare processed images from the prototype to those taken with a 10× larger commercial camera with comparable field-of-view and light collection.

  18. "Bundle Data" Approach at GES DISC Targeting Natural Hazards

    NASA Astrophysics Data System (ADS)

    Shie, C. L.; Shen, S.; Kempler, S. J.

    2015-12-01

    Severe natural phenomena such as hurricane, volcano, blizzard, flood and drought have the potential to cause immeasurable property damages, great socioeconomic impact, and tragic loss of human life. From searching to assessing the "Big", i.e., massive and heterogeneous scientific data (particularly, satellite and model products) in order to investigate those natural hazards, it has, however, become a daunting task for Earth scientists and applications researchers, especially during recent decades. The NASA Goddard Earth Sciences Data and Information Service Center (GES DISC) has served "Big" Earth science data, and the pertinent valuable information and services to the aforementioned users of diverse communities for years. In order to help and guide our users to online readily (i.e., with a minimum effort) acquire their requested data from our enormous resource at GES DISC for studying their targeted hazard/event, we have thus initiated a "Bundle Data" approach in 2014, first targeting the hurricane event/topic. We have recently worked on new topics such as volcano and blizzard. The "bundle data" of a specific hazard/event is basically a sophisticated integrated data package consisting of a series of proper datasets containing a group of relevant ("knowledge-based") data variables readily accessible to users via a system-prearranged table linking those data variables to the proper datasets (URLs). This online approach has been developed by utilizing a few existing data services such as Mirador as search engine; Giovanni for visualization; and OPeNDAP for data access, etc. The online "Data Cookbook" site at GES DISC is the current host for the "bundle data". We are now also planning on developing an "Automated Virtual Collection Framework" that shall eventually accommodate the "bundle data", as well as further improve our management in "Big Data".

  19. The Business of Bundling: Joining Forces on Joint Replacement.

    PubMed

    Kaldy, Joanne

    2016-03-01

    A mandated bundled-payment program for joint replacement is in place in several regions across the country, and practitioners such as pharmacists are still sorting out their roles in this federal initiative. To get involved, pharmacists need to establish connections with area hospitals and physician groups to promote and document their ability to manage medications, reduce and eliminate medication-related problems and rehospitalizations, and work with patients to maximize adherence and improve communication for those undergoing hip and knee replacement.

  20. Topological Aharonov-Bohm Effect and Pseudo-Particle Bundles

    NASA Astrophysics Data System (ADS)

    Payandeh, Farrin

    2016-10-01

    Exploiting a topological approach, we discuss the outstanding Aharonov-Bohm effect and try to explain it in the context of the principal P(M, U(1)) bundle. We show that this could be done by excluding a specific region from the main manifold which acts as the solenoid around which the effect is observed. Moreover, we discuss the impacts of pseudo-particles in this topological approach.

  1. Background independent noncommutative gravity from Fedosov quantization of endomorphism bundle

    NASA Astrophysics Data System (ADS)

    Dobrski, Michał

    2017-04-01

    A model of noncommutative gravity is constructed by means of Fedosov deformation quantization of an endomorphism bundle. The fields describing noncommutativity—symplectic form and symplectic connection—are dynamical, and the resulting theory is coordinate covariant and background independent. Its interpretation in terms of a Seiberg–Witten map is provided. Also, a new action for ordinary (commutative) general relativity is given, which in the present context appears as a commutative limit of noncommutative theory.

  2. Bundle Data Approach at GES DISC Targeting Natural Hazards

    NASA Technical Reports Server (NTRS)

    Shie, Chung-Lin; Shen, Suhung; Kempler, Steven J.

    2015-01-01

    Severe natural phenomena such as hurricane, volcano, blizzard, flood and drought have the potential to cause immeasurable property damages, great socioeconomic impact, and tragic loss of human life. From searching to assessing the Big, i.e., massive and heterogeneous scientific data (particularly, satellite and model products) in order to investigate those natural hazards, it has, however, become a daunting task for Earth scientists and applications researchers, especially during recent decades. The NASA Goddard Earth Sciences Data and Information Service Center (GES DISC) has served Big Earth science data, and the pertinent valuable information and services to the aforementioned users of diverse communities for years. In order to help and guide our users to online readily (i.e., with a minimum effort) acquire their requested data from our enormous resource at GES DISC for studying their targeted hazard event, we have thus initiated a Bundle Data approach in 2014, first targeting the hurricane event topic. We have recently worked on new topics such as volcano and blizzard. The bundle data of a specific hazard event is basically a sophisticated integrated data package consisting of a series of proper datasets containing a group of relevant (knowledge--based) data variables readily accessible to users via a system-prearranged table linking those data variables to the proper datasets (URLs). This online approach has been developed by utilizing a few existing data services such as Mirador as search engine; Giovanni for visualization; and OPeNDAP for data access, etc. The online Data Cookbook site at GES DISC is the current host for the bundle data. We are now also planning on developing an Automated Virtual Collection Framework that shall eventually accommodate the bundle data, as well as further improve our management in Big Data.

  3. Frontostriatal fiber bundle compromise in HIV infection without dementia

    PubMed Central

    Pfefferbaum, Adolf; Rosenbloom, Margaret J.; Rohlfing, Torsten; Kemper, Carol A.; Deresinski, Stanley; Sullivan, Edith V.

    2010-01-01

    Background Quantitative fiber tracking derived from diffusion tensor imaging (DTI) was used to determine whether white matter association, projection, or commissural tracts are affected in nondemented individuals with HIV infection and to identify the regional distribution of sparing and impairment of fiber systems. Methods DTI measured fractional anisotropy and diffusivity, quantified separately for longitudinal (λL) diffusivity (index of axonal injury) and transverse (λT) diffusivity (index of myelin injury), in 11 association and projection white matter tracts and six commissural tracts in 29 men and 13 women with HIV infection and 88 healthy, age-matched controls (42 men and 46 women). Results The total group of HIV-infected individuals had higher diffusivity (principally longitudinal) than controls in the posterior sectors of the corpus callosum, internal and external capsules, and superior cingulate bundles. High longitudinal diffusivity, indicative of axonal compromise, was especially prominent in posterior callosal sectors, fornix, and superior cingulate bundle in HIV with AIDS. Unmedicated patients had notably high transverse diffusivity, indicative of myelin compromise, in the occipital forceps, inferior cingulate bundle, and superior longitudinal fasciculus. Pontocerebellar projection fibers were resistant to HIV effects as were commissural fibers coursing through premotor and sensorimotor callosal sectors. Conclusion This quantitative survey of brain fiber tract integrity indicates that even nondemented HIV patients can have neuroradiological evidence for damage to association and commissural tracts. These abnormalities were vulnerable to exacerbation with AIDS and possibly mitigated by HAART. PMID:19730350

  4. Mass Transport Through Carbon Nanotube-Polystyrene Bundles

    NASA Astrophysics Data System (ADS)

    Lin, Rongzhou; Tran, Tuan

    2016-05-01

    Carbon nanotubes have been widely used as test channels to study nanofluidic transport, which has been found to have distinctive properties compared to transport of fluids in macroscopic channels. A long-standing challenge in the study of mass transport through carbon nanotubes (CNTs) is the determination of flow enhancement. Various experimental investigations have been conducted to measure the flow rate through CNTs, mainly based on either vertically aligned CNT membranes or individual CNTs. Here, we proposed an alternative approach that can be used to quantify the mass transport through CNTs. This is a simple method relying on the use of carbon nanotube-polystyrene bundles, which are made of CNTs pulled out from a vertically aligned CNT array and glued together by polystyrene. We experimentally showed by using fluorescent tagging that the composite bundles allowed measureable and selective mass transport through CNTs. This type of composite bundle may be useful in various CNT research areas as they are simple to fabricate, less likely to form macroscopic cracks, and offer a high density of CNT pores while maintaining the aligned morphology of CNTs.

  5. Medicare's bundling pilot: including post-acute care services.

    PubMed

    Dummit, Laura A

    2011-03-28

    Fee-for-service Medicare, in which a separate payment is made for each service, rewards health care providers for delivering more services, but not necessarily coordinating those services over time or across settings. To help address these concerns, the Patient Protection and Affordable Care Act of 2010 requires Medicare to experiment with making a bundled payment for a hospitalization plus post-acute care, that is, the recuperative or rehabilitative care following a hospital discharge. This bundled payment approach is intended to promote more efficient care across the acute/post-acute episode because the entity that receives the payment has financial incentives to keep episode costs below the payment. Although the entity is expected to control costs through improved care coordination and efficiency, it could stint on care or avoid expensive patients instead. This issue brief focuses on the unique challenges posed by the inclusion of post-acute care services in a payment bundle and special considerations in implementing and evaluating the episode payment approach.

  6. Enhanced boiling heat transfer in horizontal test bundles

    SciTech Connect

    Trewin, R.R.; Jensen, M.K.; Bergles, A.E.

    1994-08-01

    Two-phase flow boiling from bundles of horizontal tubes with smooth and enhanced surfaces has been investigated. Experiments were conducted in pure refrigerant R-113, pure R-11, and mixtures of R-11 and R-113 of approximately 25, 50, and 75% of R-113 by mass. Tests were conducted in two staggered tube bundles consisting of fifteen rows and five columns laid out in equilateral triangular arrays with pitch-to-diameter ratios of 1.17 and 1.5. The enhanced surfaces tested included a knurled surface (Wolverine`s Turbo-B) and a porous surface (Linde`s High Flux). Pool boiling tests were conducted for each surface so that reference values of the heat transfer coefficient could be obtained. Boiling heat transfer experiments in the tube bundles were conducted at pressures of 2 and 6 bar, heat flux values from 5 to 80 kW/m{sup 2}s, and qualities from 0% to 80%, Values of the heat transfer coefficients for the enhanced surfaces were significantly larger than for the smooth tubes and were comparable to the values obtained in pool boiling. It was found that the performance of the enhanced tubes could be predicted using the pool boiling results. The degradation in the smooth tube heat transfer coefficients obtained in fluid mixtures was found to depend on the difference between the molar concentration in the liquid and vapor.

  7. F-actin bundles in Drosophila bristles are assembled from modules composed of short filaments

    PubMed Central

    1996-01-01

    The actin bundles in Drosophila bristles run the length of the bristle cell and are accordingly 65 microns (microchaetes) or 400 microns (macrochaetes) in length, depending on the bristle type. Shortly after completion of bristle elongation in pupae, the actin bundles break down as the bristle surface becomes chitinized. The bundles break down in a bizarre way; it is as if each bundle is sawed transversely into pieces that average 3 microns in length. Disassembly of the actin filaments proceeds at the "sawed" surfaces. In all cases, the cuts in adjacent bundles appear in transverse register. From these images, we suspected that each actin bundle is made up of a series of shorter bundles or modules that are attached end-to-end. With fluorescent phalloidin staining and serial thin sections, we show that the modular design is present in nondegenerating bundles. Decoration of the actin filaments in adjacent bundles in the same bristle with subfragment 1 of myosin reveals that the actin filaments in every module have the same polarity. To study how modules form developmentally, we sectioned newly formed and elongating bristles. At the bristle tip are numerous tiny clusters of 6-10 filaments. These clusters become connected together more basally to form filament bundles that are poorly organized, initially, but with time become maximally cross-linked. Additional filaments are then added to the periphery of these organized bundle modules. All these observations make us aware of a new mechanism for the formation and elongation of actin filament bundles, one in which short bundles are assembled and attached end-to-end to other short bundles, as are the vertical girders between the floors of a skyscraper. PMID:8947552

  8. Electrolytic/fuel cell bundles and systems including a current collector in communication with an electrode thereof

    DOEpatents

    Hawkes, Grant L.; Herring, James S.; Stoots, Carl M.; O& #x27; Brien, James E.

    2013-03-05

    Electrolytic/fuel cell bundles and systems including such bundles include an electrically conductive current collector in communication with an anode or a cathode of each of a plurality of cells. A cross-sectional area of the current collector may vary in a direction generally parallel to a general direction of current flow through the current collector. The current collector may include a porous monolithic structure. At least one cell of the plurality of cells may include a current collector that surrounds an outer electrode of the cell and has at least six substantially planar exterior surfaces. The planar surfaces may extend along a length of the cell, and may abut against a substantially planar surface of a current collector of an adjacent cell. Methods for generating electricity and for performing electrolysis include flowing current through a conductive current collector having a varying cross-sectional area.

  9. Hair cell stereociliary bundle regeneration by espin gene transduction after aminoglycoside damage and hair cell induction by Notch inhibition

    PubMed Central

    Taura, Akiko; Taura, Kojiro; Koyama, Yukinori; Yamamoto, Norio; Nakagawa, Takayuki; Ito, Juichi; Ryan, Allen F.

    2015-01-01

    Once inner ear hair cells (HCs) are damaged by drugs, noise or aging, their apical structures including the stereociliary arrays are frequently the first cellular feature to be lost. While this can be followed by progressive loss of HC somata, a significant number of HC bodies often remain even after stereociliary loss. However, in the absence of stereocilia they are nonfunctional. HCs can sometimes be regenerated by Atoh1 transduction or Notch inhibition, but they also may lack stereociliary bundles. It is therefore important to develop methods for the regeneration of stereocilia, in order to achieve HC functional recovery. Espin is an actin bundling protein known to participate in sterociliary elongation during development. We evaluated stereociliary array regeneration in damaged vestibular sensory epithelia in tissue culture, using viral vector transduction of two espin isoforms. Utricular HCs were damaged with aminoglycosides. The utricles were then treated with a γ-secretase inhibitor, followed by espin or control transduction and histochemistry. While γ-secretase inhibition increased the number of HCs, few had stereociliary arrays. In contrast, 46 hrs after espin1 transduction, a significant increase in hair-bundle-like structures was observed. These were confirmed to be immature stereociliary arrays by scanning electron microscopy. Increased uptake of FM1–43 uptake provided evidence of stereociliary function. Espin4 transduction had no effect. The results demonstrate that espin1 gene therapy can restore stereocilia on damaged or regenerated HCs. PMID:26886463

  10. Hair cell stereociliary bundle regeneration by espin gene transduction after aminoglycoside damage and hair cell induction by Notch inhibition.

    PubMed

    Taura, A; Taura, K; Koyama, Y; Yamamoto, N; Nakagawa, T; Ito, J; Ryan, A F

    2016-05-01

    Once inner ear hair cells (HCs) are damaged by drugs, noise or aging, their apical structures including the stereociliary arrays are frequently the first cellular feature to be lost. Although this can be followed by progressive loss of HC somata, a significant number of HC bodies often remain even after stereociliary loss. However, in the absence of stereocilia they are nonfunctional. HCs can sometimes be regenerated by Atoh1 transduction or Notch inhibition, but they also may lack stereociliary bundles. It is therefore important to develop methods for the regeneration of stereocilia, in order to achieve HC functional recovery. Espin is an actin-bundling protein known to participate in sterociliary elongation during development. We evaluated stereociliary array regeneration in damaged vestibular sensory epithelia in tissue culture, using viral vector transduction of two espin isoforms. Utricular HCs were damaged with aminoglycosides. The utricles were then treated with a γ-secretase inhibitor, followed by espin or control transduction and histochemistry. Although γ-secretase inhibition increased the number of HCs, few had stereociliary arrays. In contrast, 46 h after espin1 transduction, a significant increase in hair-bundle-like structures was observed. These were confirmed to be immature stereociliary arrays by scanning electron microscopy. Increased uptake of FM1-43 uptake provided evidence of stereociliary function. Espin4 transduction had no effect. The results demonstrate that espin1 gene therapy can restore stereocilia on damaged or regenerated HCs.

  11. Relating microstructure to rheology of a bundled and cross-linked F-actin network in vitro

    NASA Astrophysics Data System (ADS)

    Shin, J. H.; Gardel, M. L.; Mahadevan, L.; Matsudaira, P.; Weitz, D. A.

    2004-06-01

    The organization of individual actin filaments into higher-order structures is controlled by actin-binding proteins (ABPs). Although the biological significance of the ABPs is well documented, little is known about how bundling and cross-linking quantitatively affect the microstructure and mechanical properties of actin networks. Here we quantify the effect of the ABP scruin on actin networks by using imaging techniques, cosedimentation assays, multiparticle tracking, and bulk rheology. We show how the structure of the actin network is modified as the scruin concentration is varied, and we correlate these structural changes to variations in the resultant network elasticity.

  12. Rod Bundle Heat Transfer: Steady-State Steam Cooling Experiments

    SciTech Connect

    Spring, J.P.; McLaughlin, D.M.

    2006-07-01

    Through the joint efforts of the Pennsylvania State University and the United States Nuclear Regulatory Commission, an experimental rod bundle heat transfer (RBHT) facility was designed and built. The rod bundle consists of a 7 x 7 square pitch array with spacer grids and geometry similar to that found in a modern pressurized water reactor. From this facility, a series of steady-state steam cooling experiments were performed. The bundle inlet Reynolds number was varied from 1 400 to 30 000 over a pressure range from 1.36 to 4 bars (20 to 60 psia). The bundle inlet steam temperature was controlled to be at saturation for the specified pressure and the fluid exit temperature exceeded 550 deg. C in the highest power tests. One important quantity of interest is the local convective heat transfer coefficient defined in terms of the local bulk mean temperature of the flow, local wall temperature, and heat flux. Steam temperatures were measured at the center of selected subchannels along the length of the bundle by traversing miniaturized thermocouples. Using an analogy between momentum and energy transport, a method was developed for relating the local subchannel centerline temperature measurement to the local bulk mean temperature. Wall temperatures were measured using internal thermocouples strategically placed along the length of each rod and the local wall heat flux was obtained from an inverse conduction program. The local heat transfer coefficient was calculated from the data at each rod thermocouple location. The local heat transfer coefficients calculated for locations where the flow was fully developed were compared against several published correlations. The Weisman and El-Genk correlations were found to agree best with the RBHT steam cooling data, especially over the range of turbulent Reynolds numbers. The effect of spacer grids on the heat transfer enhancement was also determined from instrumentation placed downstream of the spacer grid locations. The local

  13. Nonlinear dynamics of bi-layered graphene sheet, double-walled carbon nanotube and nanotube bundle

    NASA Astrophysics Data System (ADS)

    Gajbhiye, Sachin O.; Singh, S. P.

    2016-05-01

    Due to strong van der Waals (vdW) interactions, the graphene sheets and nanotubes stick to each other and form clusters of these corresponding nanostructures, viz. bi-layered graphene sheet (BLGS), double-walled carbon nanotube (DWCNT) and nanotube bundle (NB) or ropes. This research work is concerned with the study of nonlinear dynamics of BLGS, DWCNT and NB due to nonlinear interlayer vdW forces using multiscale atomistic finite element method. The energy between two adjacent carbon atoms is represented by the multibody interatomic Tersoff-Brenner potential, whereas the nonlinear interlayer vdW forces are represented by Lennard-Jones 6-12 potential function. The equivalent nonlinear material model of carbon-carbon bond is used to model it based on its force-deflection relation. Newmark's algorithm is used to solve the nonlinear matrix equation governing the motion of the BLGS, DWCNT and NB. An impulse and harmonic excitations are used to excite these nanostructures under cantilevered, bridged and clamped boundary conditions. The frequency responses of these nanostructures are computed, and the dominant resonant frequencies are identified. Along with the forced vibration of these structures, the eigenvalue extraction problem of armchair and zigzag NB is also considered. The natural frequencies and corresponding mode shapes are extracted for the different length and boundary conditions of the nanotube bundle.

  14. Large field distributed aperture laser semiactive angle measurement system design with imaging fiber bundles.

    PubMed

    Xu, Chunyun; Cheng, Haobo; Feng, Yunpeng; Jing, Xiaoli

    2016-09-01

    A type of laser semiactive angle measurement system is designed for target detecting and tracking. Only one detector is used to detect target location from four distributed aperture optical systems through a 4×1 imaging fiber bundle. A telecentric optical system in image space is designed to increase the efficiency of imaging fiber bundles. According to the working principle of a four-quadrant (4Q) detector, fiber diamond alignment is adopted between an optical system and a 4Q detector. The structure of the laser semiactive angle measurement system is, we believe, novel. Tolerance analysis is carried out to determine tolerance limits of manufacture and installation errors of the optical system. The performance of the proposed method is identified by computer simulations and experiments. It is demonstrated that the linear region of the system is ±12°, with measurement error of better than 0.2°. In general, this new system can be used with large field of view and high accuracy, providing an efficient, stable, and fast method for angle measurement in practical situations.

  15. Assembly of tobacco mosaic virus into fibrous and macroscopic bundled arrays mediated by surface aniline polymerization.

    SciTech Connect

    Niu, Z.; Bruckman, M.; Li, S.; Lee, A.; Lee, B.; Pingali, S.-V.; Thiyagarajan, P.; Wang, Q.; Univ. of South Carolina

    2007-06-05

    One-dimensional (1D) polyaniline/tobacco mosaic virus (TMV) composite nanofibers and macroscopic bundles of such fibers were generated via a self-assembly process of TMV assisted by in-situ polymerization of polyaniline on the surface of TMV. At near-neutral reaction pH, branched polyaniline formed on the surface of TMV preventing lateral association. Therefore, long 1D nanofibers were observed with high aspect ratios and excellent processibility. At a lower pH, transmission electron microscopy (TEM) analysis revealed that initially long nanofibers were formed which resulted in bundled structures upon long-time reaction, presumably mediated by the hydrophobic interaction because of the polyaniline on the surface of TMV. In-situ time-resolved small-angle X-ray scattering study of TMV at different reaction conditions supported this mechanism. This novel strategy to assemble TMV into 1D and 3D supramolecular composites could be utilized in the fabrication of advanced materials for potential applications including electronics, optics, sensing, and biomedical engineering.

  16. Fractal frontiers of bursts and cracks in a fiber bundle model of creep rupture

    NASA Astrophysics Data System (ADS)

    Danku, Zsuzsa; Kun, Ferenc; Herrmann, Hans J.

    2015-12-01

    We investigate the geometrical structure of breaking bursts generated during the creep rupture of heterogeneous materials. Using a fiber bundle model with localized load sharing we show that bursts are compact geometrical objects; however, their external frontiers have a fractal structure which reflects their growth dynamics. The perimeter fractal dimension of bursts proved to have the universal value 1.25 independent of the external load and of the amount of disorder in the system. We conjecture that according to their geometrical features, breaking bursts fall in the universality class of loop-erased self-avoiding random walks with perimeter fractal dimension 5/4 similar to the avalanches of Abelian sand pile models. The fractal dimension of the growing crack front along which bursts occur proved to increase from 1 to 1.25 as bursts gradually cover the entire front.

  17. New method of making advanced tube-bundle rocket thrust chambers

    NASA Technical Reports Server (NTRS)

    Kazaroff, John M.; Pavli, Albert J.; Malone, Glenn A.

    1990-01-01

    An improved method of fabrication rocket chambers for future space applications is described. Included are fabrication demonstrator and test chambers produced by this method. This concept offers the promise of improved cyclic life, reusability, and performance. The performance is improved because of the enhanced enthalpy extraction. The improved cyclic life, reusability, and reliability is improved because of the structural compliance inherent in the construction. The method of construction involves the forming of the combustion chamber by a tube-bundle of high conductivity copper or copper alloy tubes and the bonding of these tubes by a unique electroforming operation. Furthermore, the method of fabrication reduces chamber complexity by incorporating manifolds, and structural stiffeners while having the potential for thrust chamber cost and weight reduction.

  18. Evidence for involvement of TRPA1 in the detection of vibrations by hair bundle mechanoreceptors in sea anemones.

    PubMed

    Mahoney, Janna L; Graugnard, Erin M; Mire, Patricia; Watson, Glen M

    2011-07-01

    A homolog of TRPA1 was identified in the genome of the anemone, Nematostella vectensis (nv-TRPA1a), and predicted to possess six ankyrin repeat domains at the N-terminus and an ion channel domain near the C-terminus. Transmembrane segments of the ion channel domain are well conserved among several known TRPA1 polypeptides. Inhibitors of TRPA1 including ruthenium red decrease vibration-dependent discharge of nematocysts in N. vectensis and Haliplanella luciae. Activators of TRPA1 including URB-597 and polygodial increase nematocyst discharge in the absence of vibrations. Co-immunoprecipitation yields a band on SDS-PAGE gels at the predicted mass of the nv-TRPA1a polypeptide among other bands. Co-immunoprecipitation performed in the presence of antigenic peptide decreases the yield of this and several other polypeptides. In untreated controls, anti-nv-TRPA1a primarily labels the base of the hair bundle with some labeling also distributed along the length of stereocilia. Tissue immunolabeled in the presence of the antigenic peptide exhibits reduced labeling. Activating chemoreceptors for N-acetylated sugars induce immunolabel to distribute distally in stereocilia. In anemones, activating chemoreceptors for N-acetylated sugars induce hair bundles to elongate among several other structural and functional changes. Taken together, these results are consistent with the possibility that nv-TRPA1a participates in signal transduction of anemone hair bundles.

  19. Photothermal imaging bundle system for estimating tissue oxygen saturation

    NASA Astrophysics Data System (ADS)

    Milstein, Yonat; Allon, Dror M.; Harrington, James; Bledt, Carlos; Gannot, Israel

    2012-01-01

    The objective of this study is to validate a method for the measurement of tissue oxygen saturation level via a thermal imaging bundle in-vitro and in-vivo. The method consists of a thermal imaging system and an algorithm which estimates the compound concentration according to the temperature rise of the tissue. A temperature rise is obtained by illuminating the tissue in the NIR range and is measured using a thermal camera and a coherent thermal imaging bundle for non-invasive transendoscopic use. The system was validated using agar phantoms of varying concentrations of Methylene Blue and ICG as well as blood samples. The algorithm estimated the Methylene Blue relative amount and the results were compared to the real relative amount. The calculated RMS of the error was 5.12%, a satisfying value for this stage. In the blood samples, for oxygenation levels higher than 50% the RMS of the error was 5.79%. Once the system was verified a portable system was built for clinical use, this system was also evaluated on agar phantoms and the RMS of the error was 10.64%. As a result of the encouraging experiments in-vivo, animal trials were performed. The oxygenation levels of mice were decreased and were estimated respectively using our system. The system determined a small decrease in the tissue oxygen saturation of the mice. These results verify the algorithm's and bundle's suitability for the use in a non-invasive system. They provide motivation for performing more complex in-vitro experiments and moving on to clinical trials.

  20. "Bundle" Practices and Ventilator-Associated Events: Not Enough.

    PubMed

    O'Horo, John C; Lan, Haitao; Thongprayoon, Charat; Schenck, Louis; Ahmed, Adil; Dziadzko, Mikhail

    2016-12-01

    OBJECTIVE Ventilator-associated events (VAEs) are nosocomial events correlated with length of stay, costs, and mortality. Current ventilator bundle practices target the older definition of ventilator-associated pneumonia and have not been systematically evaluated for their impact on VAEs. DESIGN Retrospective cohort study. SETTING Tertiary medical center between January 2012 and August 2014. PARTICIPANTS All adult patients ventilated for at least 24 hours at our institution. INTERVENTIONS We conducted univariate analyses for compliance with each element; we focused on VAEs occurring within a 2-day window of failure to meet any ventilator bundle element. We used Cox proportional hazard models to assess the effect of stress ulcer prophylaxis, deep vein thrombosis (DVT) prophylaxis, oral care, and sedation breaks on VAEs. We adjusted models for gender, age, and Acute Physiology and Chronic Health Evaluation (APACHE) III scores. RESULTS Our cohort comprised 2,660 patients with 16,858 ventilator days and 77 VAEs. Adjusting for APACHE score and gender, only oral care was associated with a reduction in the risk of VAE (hazard ratio [HR], 0.44; 95% confidence interval [CI], 0.26-0.77). The DVT prophylaxis and sedation breaks did not show any significant impact on VAEs. Stress ulcer prophylaxis trended toward an increased risk of VAE (HR, 1.59; 95% CI, 1.00-2.56). CONCLUSION Although limited by a low baseline rate of VAEs, existing ventilator bundle practices do not appear to target VAEs well. Oral care is clearly important, but the impact of DVT prophylaxis, sedation breaks, and especially stress ulcer prophylaxis are questionable at best. Infect Control Hosp Epidemiol 2016;1453-1457.

  1. Local Pixel Bundles: Bringing the Pixels to the People

    NASA Astrophysics Data System (ADS)

    Anderson, Jay

    2014-12-01

    The automated galaxy-based alignment software package developed for the Frontier Fields program (hst2galign, see Anderson & Ogaz 2014 and http://www.stsci.edu/hst/campaigns/frontier-fields/) produces a direct mapping from the pixels of the flt frame of each science exposure into a common master frame. We can use these mappings to extract the flt-pixels in the vicinity of a source of interest and package them into a convenient "bundle". In addition to the pixels, this data bundle can also contain "meta" information that will allow users to transform positions from the flt pixels to the reference frame and vice-versa. Since the un-resampled pixels in the flt frames are the only true constraints we have on the astronomical scene, the ability to inter-relate these pixels will enable many high-precision studies, such as: point-source-fitting and deconvolution with accurate PSFs, easy exploration of different image-combining algorithms, and accurate faint-source finding and photometry. The data products introduced in this ISR are a very early attempt to provide the flt-level pixel constraints in a package that is accessible to more than the handful of experts in HST astrometry. The hope is that users in the community might begin using them and will provide feedback as to what information they might want to see in the bundles and what general analysis packages they might find useful. For that reason, this document is somewhat informally written, since I know that it will be modified and updated as the products and tools are optimized.

  2. Bound constrained bundle adjustment for reliable 3D reconstruction

    PubMed Central

    Gong, Yuanzheng; Meng, De; Seibel, Eric J.

    2015-01-01

    Bundle adjustment (BA) is a common estimation algorithm that is widely used in machine vision as the last step in a feature-based three-dimensional (3D) reconstruction algorithm. BA is essentially a non-convex non-linear least-square problem that can simultaneously solve the 3D coordinates of all the feature points describing the scene geometry, as well as the parameters of the camera. The conventional BA takes a parameter either as a fixed value or as an unconstrained variable based on whether the parameter is known or not. In cases where the known parameters are inaccurate but constrained in a range, conventional BA results in an incorrect 3D reconstruction by using these parameters as fixed values. On the other hand, these inaccurate parameters can be treated as unknown variables, but this does not exploit the knowledge of the constraints, and the resulting reconstruction can be erroneous since the BA optimization halts at a dramatically incorrect local minimum due to its non-convexity. In many practical 3D reconstruction applications, unknown variables with range constraints are usually available, such as a measurement with a range of uncertainty or a bounded estimate. Thus to better utilize these pre-known, constrained, but inaccurate parameters, a bound constrained bundle adjustment (BCBA) algorithm is proposed, developed and tested in this study. A scanning fiber endoscope (the camera) is used to capture a sequence of images above a surgery phantom (the object) of known geometry. 3D virtual models are reconstructed based on these images and then compared with the ground truth. The experimental results demonstrate BCBA can achieve a more reliable, rapid, and accurate 3D reconstruction than conventional bundle adjustment. PMID:25969115

  3. The reduction of volume and fiber bundle connections in the hippocampus of EGR3 transgenic schizophrenia rats

    PubMed Central

    Ma, Ensen; Song, Tianbin; Zhang, Hui; Lu, Jie; Wang, Liwen; Zhao, Qichao; Guo, Runcai; Li, Miao; Ma, Guolin; Lu, Guangming; Li, Kefeng

    2015-01-01

    Background and objective There is a growing consensus that schizophrenia is ultimately caused by abnormal communication between spatially disparate brain structures. White matter fasciculi represent the primary infrastructure for long distance communication in the brain. In this study, we aimed to investigate the white matter connection in schizophrenia susceptible brain regions of early growth response factor 3 (EGR3) expressing rats. Methods A rat model of schizophrenia was created by the transfection of the EGR3 gene into rat hippocampus. All animals were placed in a fixation system using a commercial rat-dedicated coil. Schizophrenia susceptible brain regions were scanned using in vivo diffusion tensor magnetic resonance imaging. The volume, quantity, average length of fiber bundles, fractional anisotropy, apparent diffusion coefficient, the relative heterosexual fraction, and volume ratio were collected in the whole brain and schizophrenia related brain areas (the hippocampus, thalamus, and prefrontal lobe). MedINRIA software was used for data processing of diffusion tensor and fiber bundles tracking. The fibronectin in relevant brain regions was also analyzed. Results There was a significant decrease in the volume of the fiber beam through the left hippocampus dentate in the schizophrenia model group in comparison to the control group and the risperidone treatment group (P<0.05). A significant reduction in the volume and number of the fiber bundles was also observed in left prefrontal–left hippocampus, left hippocampus–left thalamus, left prefrontal–left hippocampus–left thalamus areas in the model group (all P<0.05). Conclusion The volume of hippocampus and the number of fiber bundles were reduced in EGR3 transgenic schizophrenia rats, and are the most sensitive indicators in schizophrenia. The diffusion tensor imaging technique plays an important role in the evaluation of patients with schizophrenia. PMID:26170675

  4. Heterotic non-Kähler geometries via polystable bundles on Calabi-Yau threefolds

    NASA Astrophysics Data System (ADS)

    Andreas, Björn; Garcia-Fernandez, Mario

    2012-02-01

    In arXiv:1008.1018 it is shown that a given stable vector bundle V on a Calabi-Yau threefold X which satisfies c2(X)=c2(V) can be deformed to a solution of the Strominger system and the equations of motion of heterotic string theory. In this note we extend this result to the polystable case and construct explicit examples of polystable bundles on elliptically fibered Calabi-Yau threefolds where it applies. The polystable bundle is given by a spectral cover bundle, for the visible sector, and a suitably chosen bundle, for the hidden sector. This provides a new class of heterotic flux compactifications via non-Kähler deformation of Calabi-Yau geometries with polystable bundles. As an application, we obtain examples of non-Kähler deformations of some three generation GUT models.

  5. Synthesis and Self-Assembly of Bundle-Forming α-Helical Peptide-Dendron Hybrids.

    PubMed

    Marine, Jeannette E; Song, Shuang; Liang, Xiaoli; Rudick, Jonathan G

    2016-01-11

    Dendronized helix bundle assemblies combine the sequence diversity and folding properties of proteins with the tailored physical properties of dendrimers. Assembly of peptide-dendron hybrids into α-helical bundles encapsulates the helix bundle motif in a dendritic sheath that will allow the functional, protein-like domain to be transplanted to nonbiological environments. A bioorthogonal graft-to synthetic strategy for preparing helix bundle-forming peptide-dendron hybrids is described herein for hybrids 1a, 1b, and 2. Titration experiments monitored by circular dichroism spectroscopy support our self-assembly model for how the peptide-dendron hybrids self-assemble into α-helical bundles with the dendrons on outside of the bundle.

  6. Synthesis and Self-Assembly of Bundle-Forming α-Helical Peptide–Dendron Hybrids

    PubMed Central

    Marine, Jeannette E.; Song, Shuang; Liang, Xiaoli; Rudick, Jonathan G.

    2015-01-01

    Dendronized helix bundle assemblies combine the sequence diversity and folding properties of proteins with the tailored physical properties of dendrimers. Assembly of peptide-dendron hybrids into α-helical bundles encapsulates the helix bundle motif in a dendritic sheath that will allow the functional, protein-like domain to be transplanted to non-biological environments. A bioorthogonal graft-to synthetic strategy for preparing helix bundle-forming peptide-dendron hybrids is described herein for hybrids 1a, 1b, and 2. Titration experiments monitored by circular dichroism spectroscopy support our self-assembly model for how the peptide-dendron hybrids self-assemble into α-helical bundles with the dendrons on outside of the bundle. PMID:26674475

  7. Maximum allowable heat flux for a submerged horizontal tube bundle

    SciTech Connect

    McEligot, D.M.

    1995-08-14

    For application to industrial heating of large pools by immersed heat exchangers, the socalled maximum allowable (or {open_quotes}critical{close_quotes}) heat flux is studied for unconfined tube bundles aligned horizontally in a pool without forced flow. In general, we are considering boiling after the pool reaches its saturation temperature rather than sub-cooled pool boiling which should occur during early stages of transient operation. A combination of literature review and simple approximate analysis has been used. To date our main conclusion is that estimates of q inch chf are highly uncertain for this configuration.

  8. Cotangent bundle reduction and Poincaré-Birkhoff normal forms

    NASA Astrophysics Data System (ADS)

    Çiftçi, Ünver; Waalkens, Holger; Broer, Henk W.

    2014-02-01

    In this paper we study a systematic and natural construction of canonical coordinates for the reduced space of a cotangent bundle with a free Lie group action. The canonical coordinates enable us to compute Poincaré-Birkhoff normal forms of relative equilibria using standard algorithms. The case of simple mechanical systems with symmetries is studied in detail. As examples we compute Poincaré-Birkhoff normal forms for a Lagrangian equilateral triangle configuration of a three-body system with a Morse-type potential and the stretched-out configuration of a double spherical pendulum.

  9. Solutions of the Strominger System via Stable Bundles on Calabi-Yau Threefolds

    NASA Astrophysics Data System (ADS)

    Andreas, Björn; Garcia-Fernandez, Mario

    2012-10-01

    We prove that a given Calabi-Yau threefold with a stable holomorphic vector bundle can be perturbed to a solution of the Strominger system provided that the second Chern class of the vector bundle is equal to the second Chern class of the tangent bundle. If the Calabi-Yau threefold has strict SU(3) holonomy then the equations of motion derived from the heterotic string effective action are also satisfied by the solutions we obtain.

  10. Analysis of multimode fiber bundles for endoscopic spectral-domain optical coherence tomography

    PubMed Central

    Risi, Matthew D.; Makhlouf, Houssine; Rouse, Andrew R.; Gmitro, Arthur F.

    2016-01-01

    A theoretical analysis of the use of a fiber bundle in spectral-domain optical coherence tomography (OCT) systems is presented. The fiber bundle enables a flexible endoscopic design and provides fast, parallelized acquisition of the OCT data. However, the multimode characteristic of the fibers in the fiber bundle affects the depth sensitivity of the imaging system. A description of light interference in a multimode fiber is presented along with numerical simulations and experimental studies to illustrate the theoretical analysis. PMID:25967012

  11. Sperm competition promotes diversity of sperm bundles in Ohomopterus ground beetles

    NASA Astrophysics Data System (ADS)

    Takami, Yasuoki; Sota, Teiji

    2007-07-01

    Diversification of sperm morphology has been investigated in the context of sperm competition, but the adaptive significance of sperm bundles is still unclear. In analyzing 10 taxa of the genus Carabus subgenus Ohomopterus and one related Carabus ground beetles, we found that dimorphic sperm bundles occurred in most species with varied degrees of bimodality, whereas sperm were generally monomorphic. Comparative analyses with phylogenetically independent contrasts revealed that the sizes of large and small sperm bundles evolved more rapidly than, and were not correlated with, the length of sperm, suggesting more intense selection on sperm bundle sizes and their independent responses to different evolutionary forces. The size of large sperm bundles was positively correlated with male genital morphology (pertinent to displacement of rival spermatophores) and postcopulatory guarding duration as well as male body length, suggesting that larger sperm bundles have been favored when the risk of spermatophore displacement is high. Larger sperm bundles may be advantageous because of their ability to migrate more rapidly into the spermatheca. In contrast, no clear association was detected between the small sperm bundle size and mating traits despite its rapid diversification. The present study provides the first record of heteromorphic sperm bundles, the diversity of which may be promoted by sperm competition.

  12. Significance of the resting angles of hair-cell bundles for Hopf bifurcation criticality

    NASA Astrophysics Data System (ADS)

    Kim, Kyung-Joong; Ahn, Kang-Hun

    2016-08-01

    We investigate the significance of the inclined angle of a hair bundle at equilibrium. We find that, while the angle gives a geometrical conversion factor between the bundle deflection and the ion channel displacement, it also controls the dynamics of the bundle. We show that a Hopf bifurcation, which enhances sensitivity, can be driven by the geometrical factor. However, existing experimental data indicate that mammalian auditory hair-cell bundles are located far away from the Hopf bifurcation point, suggesting that the high sensitivity of mammalian hearing might come from other mechanisms.

  13. Geometry of moduli stacks of (k , l) -stable vector bundles over algebraic curves

    NASA Astrophysics Data System (ADS)

    Mata-Gutiérrez, O.; Neumann, Frank

    2017-01-01

    We study the geometry of the moduli stack of vector bundles of fixed rank and degree over an algebraic curve by introducing a filtration made of open substacks build from (k , l) -stable vector bundles. The concept of (k , l) -stability was introduced by Narasimhan and Ramanan to study the geometry of the coarse moduli space of stable bundles. We will exhibit the stacky picture and analyse the geometric and cohomological properties of the moduli stacks of (k , l) -stable vector bundles. For particular pairs (k , l) of integers we also show that these moduli stacks admit coarse moduli spaces and we discuss their interplay.

  14. Bundles over nearly-Kahler homogeneous spaces in heterotic string theory

    NASA Astrophysics Data System (ADS)

    Klaput, Michael; Lukas, Andre; Matti, Cyril

    2011-09-01

    We construct heterotic vacua based on six-dimensional nearly-Kahler homogeneous manifolds and non-trivial vector bundles thereon. Our examples are based on three specific group coset spaces. It is shown how to construct line bundles over these spaces, compute their properties and build up vector bundles consistent with supersymmetry and anomaly cancelation. It turns out that the most interesting coset is SU(3)/U(1)2. This space supports a large number of vector bundles which lead to consistent heterotic vacua, some of them with three chiral families.

  15. Purification and alignment of arc-synthesis single-walled carbon nanotube bundles

    NASA Astrophysics Data System (ADS)

    Huang, Houjin; Kajiura, Hisashi; Yamada, Atsuo; Ata, Masafumi

    2002-04-01

    We report here a scalable method for purification and alignment of single-walled carbon nanotubes (SWNT) in an aqueous solution. Arc-synthesis soot containing SWNTs is first treated with a concentrated nitric acid. After removal of most of the impurities and water, macroscopic and well-aligned SWNT bundles up to several centimeters long are formed in a rotary evaporator. Alignment of the SWNT bundles is ascribed to the liquid flow induced by rotary evaporation and van der Waals interactions among the bundles. The aligned SWNT bundles are further purified by ultrasonic Soxhlet extraction and annealing.

  16. Redesign and replacement of Connecticut Yankee moisture separator/reheater (MSR) tube bundles

    SciTech Connect

    Gibson, J.N.

    1981-01-01

    This paper describes the various aspects of the tube bundle redesign and replacement coordinated by Northeast Utilities Service Company for the Connecticut Yankee Atomic Power Company during the plant's 1980 refueling outage. The main objective of the replacement was to improve the operating reliability along with secondary plant chemistry through the use of new bundle design and tube material. The considerations leading to the selection of material and design of the new bundles, the highlights of fabrication and bundle change-out, and the eddy current test experience and performance monitoring techniques and results are presented. 6 refs.

  17. Sperm competition promotes diversity of sperm bundles in Ohomopterus ground beetles.

    PubMed

    Takami, Yasuoki; Sota, Teiji

    2007-07-01

    Diversification of sperm morphology has been investigated in the context of sperm competition, but the adaptive significance of sperm bundles is still unclear. In analyzing 10 taxa of the genus Carabus subgenus Ohomopterus and one related Carabus ground beetles, we found that dimorphic sperm bundles occurred in most species with varied degrees of bimodality, whereas sperm were generally monomorphic. Comparative analyses with phylogenetically independent contrasts revealed that the sizes of large and small sperm bundles evolved more rapidly than, and were not correlated with, the length of sperm, suggesting more intense selection on sperm bundle sizes and their independent responses to different evolutionary forces. The size of large sperm bundles was positively correlated with male genital morphology (pertinent to displacement of rival spermatophores) and postcopulatory guarding duration as well as male body length, suggesting that larger sperm bundles have been favored when the risk of spermatophore displacement is high. Larger sperm bundles may be advantageous because of their ability to migrate more rapidly into the spermatheca. In contrast, no clear association was detected between the small sperm bundle size and mating traits despite its rapid diversification. The present study provides the first record of heteromorphic sperm bundles, the diversity of which may be promoted by sperm competition.

  18. A single charge in the actin binding domain of fascin can independently tune the linear and non-linear response of an actin bundle network.

    PubMed

    Maier, M; Müller, K W; Heussinger, C; Köhler, S; Wall, W A; Bausch, A R; Lieleg, O

    2015-05-01

    Actin binding proteins (ABPs) not only set the structure of actin filament assemblies but also mediate the frequency-dependent viscoelastic moduli of cross-linked and bundled actin networks. Point mutations in the actin binding domain of those ABPs can tune the association and dissociation dynamics of the actin/ABP bond and thus modulate the network mechanics both in the linear and non-linear response regime. We here demonstrate how the exchange of a single charged amino acid in the actin binding domain of the ABP fascin triggers such a modulation of the network rheology. Whereas the overall structure of the bundle networks is conserved, the transition point from strain-hardening to strain-weakening sensitively depends on the cross-linker off-rate and the applied shear rate. Our experimental results are consistent both with numerical simulations of a cross-linked bundle network and a theoretical description of the bundle network mechanics which is based on non-affine bending deformations and force-dependent cross-link dynamics.

  19. Predicting stability of alpha-helical, orthogonal-bundle proteins on surfaces

    NASA Astrophysics Data System (ADS)

    Wei, Shuai; Knotts, Thomas A.

    2010-09-01

    The interaction of proteins with surfaces is a key phenomenon in many applications, but current understanding of the biophysics involved is lacking. At present, rational design of such emerging technologies is difficult as no methods or theories exist that correctly predict how surfaces influence protein behavior. Using molecular simulation and a coarse-grain model, this study illustrates for the first time that stability of proteins on surfaces can be correlated with tertiary structural elements for alpha-helical, orthogonal-bundle proteins. Results show that several factors contribute to stability on surfaces including the nature of the loop region where the tether is placed and the ability of the protein to freely rotate on the surface. A thermodynamic analysis demonstrates that surfaces stabilize proteins entropically and that any destabilization is an enthalpic effect. Moreover, the entropic effects are concentrated on the unfolded state of the protein while the ethalpic effects are focused on the folded state.

  20. Predicting stability of alpha-helical, orthogonal-bundle proteins on surfaces.

    PubMed

    Wei, Shuai; Knotts, Thomas A

    2010-09-21

    The interaction of proteins with surfaces is a key phenomenon in many applications, but current understanding of the biophysics involved is lacking. At present, rational design of such emerging technologies is difficult as no methods or theories exist that correctly predict how surfaces influence protein behavior. Using molecular simulation and a coarse-grain model, this study illustrates for the first time that stability of proteins on surfaces can be correlated with tertiary structural elements for alpha-helical, orthogonal-bundle proteins. Results show that several factors contribute to stability on surfaces including the nature of the loop region where the tether is placed and the ability of the protein to freely rotate on the surface. A thermodynamic analysis demonstrates that surfaces stabilize proteins entropically and that any destabilization is an enthalpic effect. Moreover, the entropic effects are concentrated on the unfolded state of the protein while the ethalpic effects are focused on the folded state.

  1. A four-helix bundle stores copper for methane oxidation.

    PubMed

    Vita, Nicolas; Platsaki, Semeli; Baslé, Arnaud; Allen, Stephen J; Paterson, Neil G; Crombie, Andrew T; Murrell, J Colin; Waldron, Kevin J; Dennison, Christopher

    2015-09-03

    Methane-oxidizing bacteria (methanotrophs) require large quantities of copper for the membrane-bound (particulate) methane monooxygenase. Certain methanotrophs are also able to switch to using the iron-containing soluble methane monooxygenase to catalyse methane oxidation, with this switchover regulated by copper. Methane monooxygenases are nature's primary biological mechanism for suppressing atmospheric levels of methane, a potent greenhouse gas. Furthermore, methanotrophs and methane monooxygenases have enormous potential in bioremediation and for biotransformations producing bulk and fine chemicals, and in bioenergy, particularly considering increased methane availability from renewable sources and hydraulic fracturing of shale rock. Here we discover and characterize a novel copper storage protein (Csp1) from the methanotroph Methylosinus trichosporium OB3b that is exported from the cytosol, and stores copper for particulate methane monooxygenase. Csp1 is a tetramer of four-helix bundles with each monomer binding up to 13 Cu(I) ions in a previously unseen manner via mainly Cys residues that point into the core of the bundle. Csp1 is the first example of a protein that stores a metal within an established protein-folding motif. This work provides a detailed insight into how methanotrophs accumulate copper for the oxidation of methane. Understanding this process is essential if the wide-ranging biotechnological applications of methanotrophs are to be realized. Cytosolic homologues of Csp1 are present in diverse bacteria, thus challenging the dogma that such organisms do not use copper in this location.

  2. Faster and improved microchip electrophoresis using a capillary bundle.

    PubMed

    Sun, Yi; Kwok, Yien Chian; Nguyen, Nam Trung

    2007-12-01

    Joule heating generated in CE microchips is known to affect temperature gradient, electrophoretic mobility, diffusion of analytes, and ultimately the efficiency and reproducibility of the separation. One way of reducing the effect of Joule heating is to decrease the cross-section area of microchannels. Currently, due to the limit of fabrication technique and detection apparatus, the typical dimensions of CE microchannels are in the range of 50-200 microm. In this paper, we propose a novel approach of performing microchip CE in a bundle of extremely narrow channels by using photonic crystal fiber (PCF) as separation column. The PCF was simply encapsulated in a poly(methyl methacrylate) (PMMA) microchannel right after a T-shaped injector. CE was simultaneously but independently carried out in 54 narrow capillaries, each capillary with diameter of 3.7 microm. The capillary bundle could sustain high electric field strength up to 1000 V/cm due to efficient heat dissipation, thus faster and enhanced separation was attained.

  3. Contrast limiting factors of optical fiber bundles for flexible endoscopy

    NASA Astrophysics Data System (ADS)

    Ortega-Quijano, N.; Arce-Diego, J. L.; Fanjul-Vélez, F.

    2008-11-01

    Medical endoscopy constitutes a basic device for the development of minimally invasive procedures for a wide range of medical applications, involving diagnosis, treatment and surgery, as well as biopsy sampling. Its minimally invasive nature results in no surgery, or only small incisions, which involves a minimal hospitalization time. The medical relevance of endoscopes relies on the fact that they are one of the most effective means of early stages of cancer diagnosis, with the subsequent improvement in the patient's quality of life. Flexible endoscopy by means of coherent optical fiber bundles shows both flexibility and a high active area. However, the parallel arrangement of the fibers within the bundle produces interference phenomena between them, which results in optical crosstalk. As a consequence, there is a power exchange between contiguous fibers, producing a worsening in the contrast of the image. In this work, this quality limiting factor is deeply studied. We quantitatively analyze crosstalk, performing several studies that show the limitations imposed to the endoscopic system. Finally, we propose some solutions by an analytical method to accurately determine the appropriate optical fibers for each particular design. The method is also applied to endoscopic OCT.

  4. Influence of fiber packing structure on permeability

    NASA Technical Reports Server (NTRS)

    Cai, Zhong; Berdichevsky, Alexander L.

    1993-01-01

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

  5. Principal fiber bundle description of number scaling for scalars and vectors: application to gauge theory

    NASA Astrophysics Data System (ADS)

    Benioff, Paul

    2015-05-01

    The purpose of this paper is to put the description of number scaling and its effects on physics and geometry on a firmer foundation, and to make it more understandable. A main point is that two different concepts, number and number value are combined in the usual representations of number structures. This is valid as long as just one structure of each number type is being considered. It is not valid when different structures of each number type are being considered. Elements of base sets of number structures, considered by themselves, have no meaning. They acquire meaning or value as elements of a number structure. Fiber bundles over a space or space time manifold, M, are described. The fiber consists of a collection of many real or complex number structures and vector space structures. The structures are parameterized by a real or complex scaling factor, s. A vector space at a fiber level, s, has, as scalars, real or complex number structures at the same level. Connections are described that relate scalar and vector space structures at both neighbor M locations and at neighbor scaling levels. Scalar and vector structure valued fields are described and covariant derivatives of these fields are obtained. Two complex vector fields, each with one real and one imaginary field, appear, with one complex field associated with positions in M and the other with position dependent scaling factors. A derivation of the covariant derivative for scalar and vector valued fields gives the same vector fields. The derivation shows that the complex vector field associated with scaling fiber levels is the gradient of a complex scalar field. Use of these results in gauge theory shows that the imaginary part of the vector field associated with M positions acts like the electromagnetic field. The physical relevance of the other three fields, if any, is not known.

  6. "The Purpose of This Study Is to": Connecting Lexical Bundles and Moves in Research Article Introductions

    ERIC Educational Resources Information Center

    Cortes, Viviana

    2013-01-01

    This article presents a group of lexical bundles identified in a corpus of research article introductions as the first step in the analysis of these expressions in the different sections of the research article. A one-million word corpus of research article introductions from various disciplines was compiled and the lexical bundles identified in…

  7. Bundled Slash: A Potential New Biomass Resource for Fuels and Chemicals

    NASA Astrophysics Data System (ADS)

    Steele, Philip H.; Mitchell, Brian K.; Cooper, Jerome E.; Arora, S.

    Postharvest residues for southern pine species have not previously been quantified to compare volumes produced from both thinnings and clearcut volumes. A John Deere 1490 Slash Bundler bundled postharvest residues following a first thinning of a 14-year-old stand, a second thinning of a 25-year-old stand, and a clearcut of a naturally regenerated mature stand of 54 years of age. Regardless of stand type, nearly one-fifth of merchantable volume harvested was collected as postharvest residue. Initial bundle moisture contents were 127.3, 81.1, and 49.4% dry basis (db) for the first and second thinnings and mature stands, respectively. Bundle needles content was found to significantly influence the relative moisture contents of the bundles by stand type due to the high moisture content of needles compared to other bundle components. Bundles were stored outside and exposed to very hot and dry conditions and dried very rapidly to lowest moisture contents of 22.8, 14.5, and 13.5% (db) for first and second thinnings and mature stands, respectively. Response to moderating temperatures and higher precipitation resulted in rapid moisture content increase to 69.9, 46.2, and 38.1% (db) for the first and second thinnings and mature stand bundles by the end of the study. Temperature and precipitation and bundle percentage needles content all significantly influenced the rapid moisture content variations observed over the study periods.

  8. On the existence of stable bundles with prescribed Chern classes on Calabi-Yau threefolds

    NASA Astrophysics Data System (ADS)

    Andreas, Björn; Curio, Gottfried

    2014-02-01

    We prove a case of the conjecture of Douglas, Reinbacher and Yau about the existence of stable vector bundles with prescribed Chern classes on a Calabi-Yau threefold. For this purpose we prove the existence of certain stable vector bundle extensions over elliptically fibered Calabi-Yau threefolds.

  9. Bundled slash: a potential new biomass resource for fuels and chemicals.

    PubMed

    Steele, Philip H; Mitchell, Brian K; Cooper, Jerome E; Arora, S

    2008-03-01

    Postharvest residues for southern pine species have not previously been quantified to compare volumes produced from both thinnings and clearcut volumes. A John Deere 1490 Slash Bundler bundled postharvest residues following a first thinning of a 14-year-old stand, a second thinning of a 25-year-old stand, and a clearcut of a naturally regenerated mature stand of 54 years of age. Regardless of stand type, nearly one-fifth of merchantable volume harvested was collected as postharvest residue. Initial bundle moisture contents were 127.3, 81.1, and 49.4% dry basis (db) for the first and second thinnings and mature stands, respectively. Bundle needles content was found to significantly influence the relative moisture contents of the bundles by stand type due to the high moisture content of needles compared to other bundle components. Bundles were stored outside and exposed to very hot and dry conditions and dried very rapidly to lowest moisture contents of 22.8, 14.5, and 13.5% (db) for first and second thinnings and mature stands, respectively. Response to moderating temperatures and higher precipitation resulted in rapid moisture content increase to 69.9, 46.2, and 38.1% (db) for the first and second thinnings and mature stand bundles by the end of the study. Temperature and precipitation and bundle percentage needles content all significantly influenced the rapid moisture content variations observed over the study periods.

  10. Overhead electric power transmission line jumpering system for bundles of five or more subconductors

    DOEpatents

    Winkelman, Paul F.

    1982-01-01

    Jumpering of electric power transmission lines at a dead end tower. Two transmission line conductor bundles each contain five or more spaced apart subconductors (5) arranged in the shape of a cylinder having a circular cross section. The ends of each bundle of subconductors are attached with insulators to a dead end tower (1). Jumpering allows the electric current to flow between the two bundles of subconductors using jumper buses, internal jumper conductors, and external jumper conductors. One or more current collecting jumper buses (37) are located inside each bundle of subconductors with each jumper bus being attached to the end of a subconductor. Small-diameter internal jumper conductors (33) are located in the inherently electrically shielded area inside each bundle of subconductors with each subconductor (except ones having an attached jumper bus) having one internal jumper conductor connected between that subconductor's end and a jumper bus. Large-diameter external jumper conductors (9) are located outside each bundle of subconductors with one or more external jumper conductors being connected between the jumper buses in one bundle of subconductors and the jumper buses in the other bundle.

  11. 47 CFR 76.1514 - Bundling of video and local exchange services.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 47 Telecommunication 4 2010-10-01 2010-10-01 false Bundling of video and local exchange services... RADIO SERVICES MULTICHANNEL VIDEO AND CABLE TELEVISION SERVICE Open Video Systems § 76.1514 Bundling of video and local exchange services. An open video system operator may offer video and local...

  12. 47 CFR 76.1514 - Bundling of video and local exchange services.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 47 Telecommunication 4 2012-10-01 2012-10-01 false Bundling of video and local exchange services... RADIO SERVICES MULTICHANNEL VIDEO AND CABLE TELEVISION SERVICE Open Video Systems § 76.1514 Bundling of video and local exchange services. An open video system operator may offer video and local...

  13. 47 CFR 76.1514 - Bundling of video and local exchange services.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 47 Telecommunication 4 2014-10-01 2014-10-01 false Bundling of video and local exchange services... RADIO SERVICES MULTICHANNEL VIDEO AND CABLE TELEVISION SERVICE Open Video Systems § 76.1514 Bundling of video and local exchange services. An open video system operator may offer video and local...

  14. 47 CFR 76.1514 - Bundling of video and local exchange services.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 47 Telecommunication 4 2013-10-01 2013-10-01 false Bundling of video and local exchange services... RADIO SERVICES MULTICHANNEL VIDEO AND CABLE TELEVISION SERVICE Open Video Systems § 76.1514 Bundling of video and local exchange services. An open video system operator may offer video and local...

  15. 47 CFR 76.1514 - Bundling of video and local exchange services.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 47 Telecommunication 4 2011-10-01 2011-10-01 false Bundling of video and local exchange services... RADIO SERVICES MULTICHANNEL VIDEO AND CABLE TELEVISION SERVICE Open Video Systems § 76.1514 Bundling of video and local exchange services. An open video system operator may offer video and local...

  16. Nucleate Boiling Characteristics of R-113 in a Small Enhanced Tube Bundle

    DTIC Science & Technology

    1991-09-26

    kettle reboilers and full bundle boilers. The difference is described in detail in Payvar [Ref. 5]. To summarize, in the kettle type reboiler the...Liquid levels", BuilleinJME, Vol. 10, p.3 2 8 . 5. Payvar , P., "Analysis of Performance of Full Bundle Submerged Boilers," ASME HMII , Vol. 44, pp. 11

  17. Bundled payment: hospitals see the advantages, but face big challenges too.

    PubMed

    Burns, Joseph

    2013-04-01

    What you need to know about bundled payment. While most hospital leaders see the advantages of moving to bundled payments for an episode of care, many are unprepared either for the mindset or the mechanics required to implement the emerging reimbursement model. Here the concers and possible strategies you should consider.

  18. A retracting wire knife for cutting fiber bundles and making sheet lesions of brain tissue.

    PubMed

    Shibata, M; Russell, I S

    1979-07-01

    A retracting knife which has two cutting wires for the transection of fiber bundles is described. The knife holds the fiber bundles of the stria terminalis between the two cutting wires and transects them by a shearing movement as the wires close. In addition, the feasability of such a knife producing a sheet lesion around the n. caudatus is also described.

  19. Vestibular Deprivation and the Development of Dendrite Bundles in the Rat

    PubMed Central

    Geisler, Hildegard C.; IJkema-Paassen, Jos; Westerga, Johan; Gramsbergen, Albert

    2000-01-01

    Motoneuronal pools of muscles that subserve postural tasks contain dendrite bundles. We investigated in the rat the development of these bundles in the pools of the long back muscles and related this to postural development. Motoneurons and their dendrites were retrogradely labeled by injecting unconjugated cholera toxin subunit B (CTB) into the muscles of 54 normal rats from birth until adulthood and into 18 rats that were vestibularly deprived from the 5th postnatal day (P5). Dendrite bundles coursing in a transverse direction already occurred at P1. From P4, the first longitudinal bundles could be observed, but the major spurt in development occurred between P6 and P9, when conspicuous bundles developed coursing in rostro-caudal and tranverse directions. This is the age when rats become able to stand freely and walk a few steps. Around P20, the dendrite bundles attained their adult characteristics. Vestibular deprivation by plugging both semicircular horizontal canals did not lead to a retarded development of dendrite bundles nor to a changed morphology. This finding is remarkable, as behavioral analysis showed a delay in postural development by about 3 days. We hypothesize that dendrite bundles in the pools of the long back muscles function to synchronize the motoneurons in different spinal cord segments. PMID:11147461

  20. A bundle strategy including patient hand hygiene to decrease clostridium difficile infections.

    PubMed

    Pokrywka, Marian; Feigel, Jody; Douglas, Barbara; Grossberger, Susan; Hensler, Amelia; Hensler, Amelia; Weber, David

    2014-01-01

    Prevention strategies for Clostridium difficile infection traditionally have addressed barrier precautions, environmental disinfection, and health care worker hand hygiene. When applied as a bundle, this approach has been used widely as an evidence-based strategy to prevent hospital-acquired C. difficile infection. Expanding the bundle to include patient hand hygiene is a nurse-driven approach to prevent C. difficile transmission.

  1. Assessing the Effect of Language Demand in Bundles of Math Word Problems

    ERIC Educational Resources Information Center

    Banks, Kathleen; Jeddeeni, Ahmad; Walker, Cindy M.

    2016-01-01

    Differential bundle functioning (DBF) analyses were conducted to determine whether seventh and eighth grade second language learners (SLLs) had lower probabilities of answering bundles of math word problems correctly that had heavy language demands, when compared to non-SLLs of equal math proficiency. Math word problems on each of four test forms…

  2. Textbook-Bundled Metacognitive Tools: A Study of LearnSmart's Efficacy in General Chemistry

    ERIC Educational Resources Information Center

    Thadani, Vandana; Bouvier-Brown, Nicole C.

    2016-01-01

    College textbook publishers increasingly bundle sophisticated technology-based study tools with their texts. These tools appear promising, but empirical work on their efficacy is needed. We examined whether LearnSmart, a study tool bundled with McGraw-Hill's textbook "Chemistry" (Chang & Goldsby, 2013), improved learning in an…

  3. Characterization of midrib vascular bundles of selected medicinal species in Rubiaceae

    NASA Astrophysics Data System (ADS)

    Nurul-Syahirah, M.; Noraini, T.; Latiff, A.

    2016-11-01

    An anatomical study was carried out on mature leaves of five selected medicinal species of Rubiaceae from Peninsular Malaysia. The chosen medicinal species were Aidia densiflora, Aidia racemosa, Chasallia chartacea, Hedyotis auricularia and Ixora grandifolia. The objective of this study is to determine the taxonomic value of midrib anatomical characteristics. Leaves samples were collected from Taman Paku Pakis, Universiti Kebangsaan Malaysia, Bangi, Selangor and Kledang Saiong Forest Reserve, Perak, Malaysia. Leaves samples then were fixed in spirit and acetic acid (3:1), the midrib parts then were sectioned using sliding microtome, cleared using Clorox, stained in Safranin and Alcian blue, mounted in Euparal and were observed under light microscope. Findings in this study have shown all species have collateral bundles. The midrib vascular bundles characteristics that can be used as tool to differentiate between species or genus are vascular bundles system (opened or closed), shape and arrangement of main vascular bundles, presence of both additional and medullary vascular bundles, position of additional vascular bundles, shape of medullary vascular bundles, presence of sclerenchyma cells ensheathed the vascular bundles. As a conclusion, midrib anatomical characteristics can be used to identify and discriminate medicinal plants species studied in the Rubiaceae.

  4. The MIMIC Model as a Tool for Differential Bundle Functioning Detection

    ERIC Educational Resources Information Center

    Finch, W. Holmes

    2012-01-01

    Increasingly, researchers interested in identifying potentially biased test items are encouraged to use a confirmatory, rather than exploratory, approach. One such method for confirmatory testing is rooted in differential bundle functioning (DBF), where hypotheses regarding potential differential item functioning (DIF) for sets of items (bundles)…

  5. Unwrapping the Bundle: An Examination of Research Libraries and the "Big Deal"

    ERIC Educational Resources Information Center

    Strieb, Karla L.; Blixrud, Julia C.

    2014-01-01

    This study presents and analyzes the findings of a 2012 survey of member libraries belonging to the Association of Research Libraries (ARL) about publishers' large journal bundles and compares the results to earlier surveys. The data illuminate five research questions: market penetration, journal bundle construction, collection format shifts,…

  6. 48 CFR 7.107 - Additional requirements for acquisitions involving bundling.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... the agency must conduct market research to determine whether bundling is necessary and justified (15 U.S.C. 644(e)(2)). Market research may indicate that bundling is necessary and justified if an agency... if a cost comparison analysis will be performed in accordance with OMB Circular A-76....

  7. Active hair-bundle motility harnesses noise to operate near an optimum of mechanosensitivity.

    PubMed

    Nadrowski, Björn; Martin, Pascal; Jülicher, Frank

    2004-08-17

    The ear relies on nonlinear amplification to enhance its sensitivity and frequency selectivity to oscillatory mechanical stimuli. It has been suggested that this active process results from the operation of dynamical systems that operate in the vicinity of an oscillatory instability, a Hopf bifurcation. In the bullfrog's sacculus, a hair cell can display spontaneous oscillations of its mechanosensory hair bundle. The behavior of an oscillatory hair bundle resembles that of a critical oscillator. We present here a theoretical description of the effects of intrinsic noise on active hair-bundle motility. An oscillatory instability can result from the interplay between a region of negative stiffness in the bundle's force-displacement relation and the Ca(2+)-regulated activity of molecular motors. We calculate a state diagram that describes the possible dynamical states of the hair bundle in the absence of fluctuations. Taking into account thermal fluctuations, the stochastic nature of transduction channels' gating, and of the forces generated by molecular motors, we discuss conditions that yield a response function and spontaneous noisy movements of the hair bundle in quantitative agreement with previously published experiments. We find that the magnitude of the fluctuations resulting from the active processes that mediate mechanical amplification remains just below that of thermal fluctuations. Fluctuations destroy the phase coherence of spontaneous oscillations and restrict the bundle's sensitivity as well as frequency selectivity to small oscillatory stimuli. We show, however, that a hair bundle studied experimentally operates near an optimum of mechanosensitivity in our state diagram.

  8. Parallel helix bundles and ion channels: molecular modeling via simulated annealing and restrained molecular dynamics.

    PubMed Central

    Kerr, I D; Sankararamakrishnan, R; Smart, O S; Sansom, M S

    1994-01-01

    A parallel bundle of transmembrane (TM) alpha-helices surrounding a central pore is present in several classes of ion channel, including the nicotinic acetylcholine receptor (nAChR). We have modeled bundles of hydrophobic and of amphipathic helices using simulated annealing via restrained molecular dynamics. Bundles of Ala20 helices, with N = 4, 5, or 6 helices/bundle were generated. For all three N values the helices formed left-handed coiled coils, with pitches ranging from 160 A (N = 4) to 240 A (N = 6). Pore radius profiles revealed constrictions at residues 3, 6, 10, 13, and 17. A left-handed coiled coil and a similar pattern of pore constrictions were observed for N = 5 bundles of Leu20. In contrast, N = 5 bundles of Ile20 formed right-handed coiled coils, reflecting loosened packing of helices containing beta-branched side chains. Bundles formed by each of two classes of amphipathic helices were examined: (a) M2a, M2b, and M2c derived from sequences of M2 helices of nAChR; and (b) (LSSLLSL)3, a synthetic channel-forming peptide. Both classes of amphipathic helix formed left-handed coiled coils. For (LSSLLSL)3 the pitch of the coil increased as N increased from 4 to 6. The M2c N = 5 helix bundle is discussed in the context of possible models of the pore domain of nAChR. Images FIGURE 1 FIGURE 3 PMID:7529585

  9. Lexical bundles in an advanced INTOCSU writing class and engineering texts: A functional analysis

    NASA Astrophysics Data System (ADS)

    Alquraishi, Mohammed Abdulrahman

    The purpose of this study is to investigate the functions of lexical bundles in two corpora: a corpus of engineering academic texts and a corpus of IEP advanced writing class texts. This study is concerned with the nature of formulaic language in Pathway IEPs and engineering texts, and whether those types of texts show similar or distinctive formulaic functions. Moreover, the study looked into lexical bundles found in an engineering 1.26 million-word corpus and an ESL 65000-word corpus using a concordancing program. The study then analyzed the functions of those lexical bundles and compared them statistically using chi-square tests. Additionally, the results of this investigation showed 236 unique frequent lexical bundles in the engineering corpus and 37 bundles in the pathway corpus. Also, the study identified several differences between the density and functions of lexical bundles in the two corpora. These differences were evident in the distribution of functions of lexical bundles and the minimal overlap of lexical bundles found in the two corpora. The results of this study call for more attention to formulaic language at ESP and EAP programs.

  10. A Clinical and Follow-up Study of Right and Left Bundle Branch Block

    DTIC Science & Technology

    1974-09-03

    I’SAFSAM) The pur- pose of the study was to group subjects with bundle branch block into various fascicular combinations and to compare and...and left bundle branch block with no clinically apparent cardiovascular disease have revealed a mild diffuse abnormality of the ventricular

  11. CRP2, a new invadopodia actin bundling factor critically promotes breast cancer cell invasion and metastasis

    PubMed Central

    Dieterle, Monika; Moreau, Flora; Al Absi, Antoun; Steinmetz, André; Oudin, Anaïs; Berchem, Guy; Janji, Bassam; Thomas, Clément

    2016-01-01

    A critical process underlying cancer metastasis is the acquisition by tumor cells of an invasive phenotype. At the subcellular level, invasion is facilitated by actin-rich protrusions termed invadopodia, which direct extracellular matrix (ECM) degradation. Here, we report the identification of a new cytoskeletal component of breast cancer cell invadopodia, namely cysteine-rich protein 2 (CRP2). We found that CRP2 was not or only weakly expressed in epithelial breast cancer cells whereas it was up-regulated in mesenchymal/invasive breast cancer cells. In addition, high expression of the CRP2 encoding gene CSRP2 was associated with significantly increased risk of metastasis in basal-like breast cancer patients. CRP2 knockdown significantly reduced the invasive potential of aggressive breast cancer cells, whereas it did not impair 2D cell migration. In keeping with this, CRP2-depleted breast cancer cells exhibited a reduced capacity to promote ECM degradation, and to secrete and express MMP-9, a matrix metalloproteinase repeatedly associated with cancer progression and metastasis. In turn, ectopic expression of CRP2 in weakly invasive cells was sufficient to stimulate cell invasion. Both GFP-fused and endogenous CRP2 localized to the extended actin core of invadopodia, a structure primarily made of actin bundles. Purified recombinant CRP2 autonomously crosslinked actin filaments into thick bundles, suggesting that CRP2 contributes to the formation/maintenance of the actin core. Finally, CRP2 depletion significantly reduced the incidence of lung metastatic lesions in two xenograft mouse models of breast cancer. Collectively, our data identify CRP2 as a new cytoskeletal component of invadopodia that critically promotes breast cancer cell invasion and metastasis. PMID:26883198

  12. Formation of a Double Diamond Cubic Phase by Thermotropic Liquid Crystalline Self‐Assembly of Bundled Bolaamphiphiles

    PubMed Central

    Zeng, Xiangbing; Prehm, Marko

    2016-01-01

    Abstract A quaternary amphiphile with swallow‐tail side groups displays a new bicontinuous thermotropic cubic phase with symmetry Pn 3‾ m and formed by two interpenetrating networks where cylindrical segments are linked by H bonds at tetrahedral junctions. Each network segment contains two bundles, each containing 12 rod‐like mesogens, lying along the segment axis. This assembly leads to the first thermotropic structure of the “double diamond” type. A quantitative geometric model is proposed to explain the occurrence of this rare phase. PMID:27270840

  13. The electrochemical properties of bundles of single-walled nanotubes

    SciTech Connect

    Zawodzinski, T.A. Jr.; Haridoss, P.; Uribe, F.A.

    1998-12-31

    This is the final report of a Laboratory Directed Research and Development (LDRD) project at Los Alamos National Laboratory (LANL). The authors studied electrochemical properties of single-walled fullerene nanotube bundles. The materials exhibited a highly anisotropic conductivity. Electrochemical cycling in solutions of alkyl ammonium salts in propylene carbonate revealed that the nanotubes are stable to at least {+-}1.5 V and have a fairly high accessible surface area. Double-layer charging currents of approximately 30 farads per gram were observed. This is on the same order of magnitude, though somewhat lower, than state-of-the-art values for ultra-capacitor materials. Electrochemical insertion of lithium was attempted. Though several features were observed in a slow cyclic voltammetric scan, these features were not reversible, indicating little reversible insertion. Several possible reasons for this behavior are discussed.

  14. Cap assembly for a bundled tube fuel injector

    SciTech Connect

    LeBegue, Jeffrey Scott; Melton, Patrick Benedict; Westmoreland, III, James Harold; Flanagan, James Scott

    2016-04-26

    A cap assembly for a bundled tube fuel injector includes an impingement plate and an aft plate that is disposed downstream from the impingement plate. The aft plate includes a forward side that is axially separated from an aft side. A tube passage extends through the impingement plate and the aft plate. A tube sleeve extends through the impingement plate within the tube passage towards the aft plate. The tube sleeve includes a flange at a forward end and an aft end that is axially separated from the forward end. A retention plate is positioned upstream from the impingement plate. A spring is disposed between the retention plate and the flange. The spring provides a force so as to maintain contact between at least a portion of the aft end of the tube sleeve and the forward side of the aft plate.

  15. Liquid behavior of cross-linked actin bundles.

    PubMed

    Weirich, Kimberly L; Banerjee, Shiladitya; Dasbiswas, Kinjal; Witten, Thomas A; Vaikuntanathan, Suriyanarayanan; Gardel, Margaret L

    2017-02-28

    The actin cytoskeleton is a critical regulator of cytoplasmic architecture and mechanics, essential in a myriad of physiological processes. Here we demonstrate a liquid phase of actin filaments in the presence of the physiological cross-linker, filamin. Filamin condenses short actin filaments into spindle-shaped droplets, or tactoids, with shape dynamics consistent with a continuum model of anisotropic liquids. We find that cross-linker density controls the droplet shape and deformation timescales, consistent with a variable interfacial tension and viscosity. Near the liquid-solid transition, cross-linked actin bundles show behaviors reminiscent of fluid threads, including capillary instabilities and contraction. These data reveal a liquid droplet phase of actin, demixed from the surrounding solution and dominated by interfacial tension. These results suggest a mechanism to control organization, morphology, and dynamics of the actin cytoskeleton.

  16. Rare Manifestation of Digoxin Toxicity: Right Bundle Branch Block

    PubMed Central

    Gill, Dalvir; Zaidi, Samana

    2016-01-01

    A 76-year-old female, with medical history significant for systolic congestive heart failure, who presented to the emergency department with lethargy and abdominal pain with diarrhea for the past 3 weeks. Due to hypotension, the patient received multiple boluses of isotonic saline and was started on norepinephrine. Laboratories were significant for severe digoxin toxicity (29 ng/mL), in setting of acute kidney injury. Electrocardiogram (EKG) revealed a new right bundle branch block (RBBB). She was given Digibind and her repeat digoxin level was 20 ng/mL. Repeat EKG showed resolved RBBB. This case identifies that patients with digoxin toxicity are at risk for RBBB. This is a rare finding and is not commonly recognized. Emergency medicine physicians are often the first to encounter patients with digoxin toxicity and need to be aware of such EKG findings. PMID:28104974

  17. Superconductivity in bundles of double-wall carbon nanotubes.

    PubMed

    Shi, Wu; Wang, Zhe; Zhang, Qiucen; Zheng, Yuan; Ieong, Chao; He, Mingquan; Lortz, Rolf; Cai, Yuan; Wang, Ning; Zhang, Ting; Zhang, Haijing; Tang, Zikang; Sheng, Ping; Muramatsu, Hiroyuki; Kim, Yoong Ahm; Endo, Morinobu; Araujo, Paulo T; Dresselhaus, Mildred S

    2012-01-01

    We present electrical and thermal specific heat measurements that show superconductivity in double-wall carbon nanotube (DWCNT) bundles. Clear evidence, comprising a resistance drop as a function of temperature, magnetoresistance and differential resistance signature of the supercurrent, suggest an intrinsic superconducting transition below 6.8 K for one particular sample. Additional electrical data not only confirm the existence of superconductivity, but also indicate the T(c) distribution that can arise from the diversity in the diameter and chirality of the DWCNTs. A broad superconducting anomaly is observed in the specific heat of a bulk DWCNT sample, which yields a T(c) distribution that correlates well with the range of the distribution obtained from the electrical data. As quasi one dimensionality of the DWCNTs dictates the existence of electronic density of state peaks, confirmation of superconductivity in this material system opens the exciting possibility of tuning the T(c) through the application of a gate voltage.

  18. Gas flow and thermal mixing in a helically wound tube bundle

    SciTech Connect

    Chiger, H.D.

    1980-07-01

    The thermal dissipation of a hot gas streak flowing across a segment of a helically wound tube bundle and the bypass flow streaming between the tubes and the bundle wall were investigated experimentally in the range of 8000 < Re < 50,000. Two different modes of creating a hot streak were employed. A planar hot streak was (1) injected at the entrance to the tube bundle and (2) generated by electrically heating several tubes past the bundle inlet. In the first case the mixing occurs in a region of lower turbulence since it occurs near the bundle inlet. In the second case the mixing occurs in a region of higher turbulence since the flow has already passed over several tube rows before the hot streak is generated.

  19. Numerical Hermitian Yang-Mills connections and vector bundle stability in heterotic theories

    NASA Astrophysics Data System (ADS)

    Anderson, Lara B.; Braun, Volker; Karp, Robert L.; Ovrut, Burt A.

    2010-06-01

    A numerical algorithm is presented for explicitly computing the gauge connection on slope-stable holomorphic vector bundles on Calabi-Yau manifolds. To illustrate this algorithm, we calculate the connections on stable monad bundles defined on the K3 twofold and Quintic threefold. An error measure is introduced to determine how closely our algorithmic connection approximates a solution to the Hermitian Yang-Mills equations. We then extend our results by investigating the behavior of non slope-stable bundles. In a variety of examples, it is shown that the failure of these bundles to satisfy the Hermitian Yang-Mills equations, including field-strength singularities, can be accurately reproduced numerically. These results make it possible to numerically determine whether or not a vector bundle is slope-stable, thus providing an important new tool in the exploration of heterotic vacua.

  20. The dual specificity phosphatase Cdc14B bundles and stabilizes microtubules

    SciTech Connect

    Plumley, Hyekyung; Liu, Yie; Gomez, Marla V; Wang, Yisong

    2005-01-01

    The Cdc14 dual-specificity phosphatases regulate key events in the eukaryotic cell cycle. However, little is known about the function of mammalian CDC14B family members. Here, we demonstrate that subcellular localization of CDC14B protein is cell cycle regulated. CDC14B can bind, bundle, and stabilize microtubules in vitro independently of its catalytic activity. Basic amino acid residues within the nucleolar targeting domain are important for both retaining CDC14B in the nucleolus and preventing microtubule bundling. Overexpression of CDC14B resulted in the formation of cytoplasmic CDC14B and microtubule bundles in interphase cells. These microtubule bundles were resistant to microtubule depolymerization reagents and enriched in acetylated -tubulin. Expression of cytoplasmic forms of CDC14B impaired microtubule nucleation from the microtubule organization center. CDC14B is thus a novel microtubule-bundling and -stabilizing protein, whose regulated subcellular localization may help modulate spindle and microtubule dynamics in mitosis.

  1. Ordered bundles of infrared-transmitting AgClBr fibers: optical characterization of individual fibers.

    PubMed

    Rave, E; Nagli, L; Katzir, A

    2000-09-01

    Silver halide (AgCl(x) Br(1-x)) crystals were extruded to form polycrystalline fibers that are highly transparent in the spectral range 3-30 mum. Ordered bundles consisting of as many as 9000 fibers were fabricated by multiple extrusion steps. The transmission loss of an individual fiber in the 100-fiber bundles was 0.12 dB/cm, and the cross talk between neighboring fibers in the 900-fiber bundles was 25%. Thermal images of bodies at room temperature have been transmitted through the bundles. Such ordered bundles provide a solution for the problem of thermal imaging in regions where there is no line of sight between a thermal camera and a warm object.

  2. Photoacoustic imaging by using a bundle of thin hollow-optical fibers

    NASA Astrophysics Data System (ADS)

    Seki, A.; Iwai, K.; Katagiri, T.; Matsuura, Y.

    2016-03-01

    We propose a photoacoustic imaging system composed of a flexible bundle of thin hollow-optical fibers that enables endoscopic diagnosis. The hollow-fiber bundle involves 37 fibers with an inner diameter of 100 μm and the total diameter of the bundle is 1.2 mm. A laser beam for photoacoustic excitation is scanned at the input end of fiber bundle and therefore, no scanning mechanism is necessary at the distal end. In addition, owing to the small numerical aperture of hollow optical fibers, a high resolution image is obtained without using a micro-lens array at the end. By using the fiber bundle probe, photoacoustic imaging of blood vessels in the ovarian membrane of fish were successfully obtained with a laser fluence of around 2.8 mJ/cm2.

  3. Load sharing in the growth of bundled biopolymers

    NASA Astrophysics Data System (ADS)

    Wang, Ruizhe; Carlsson, A. E.

    2014-11-01

    To elucidate the nature of load sharing in the growth of multiple biopolymers, we perform stochastic simulations of the growth of biopolymer bundles against obstacles under a broad range of conditions and varying assumptions. The obstacle motion due to thermal fluctuations is treated explicitly. We assume the ‘perfect Brownian ratchet’ model, in which the polymerization rate equals the free-filament rate as soon as the filament-obstacle distance exceeds the monomer size. Accurate closed-form formulas are obtained for the case of a rapidly moving obstacle. We find the following: (1) load sharing is usually sub-perfect in the sense that polymerization is slower than for a single filament carrying the same average force; (2) the sub-perfect behavior becomes significant at a total force proportional to the logarithm or the square root of the number of filaments, depending on the alignment of the filaments; (3) for the special case of slow barrier diffusion and low opposing force, an enhanced obstacle velocity for an increasing number of filaments is possible; (4) the obstacle velocity is very sensitive to the alignment of the filaments in the bundle, with a staggered alignment being an order of magnitude faster than an unstaggered one at forces of only 0.5 pN per filament for 20 filaments; (5) for large numbers of filaments, the power is maximized at a force well below 1 pN per filament; (6) for intermediate values of the obstacle diffusion coefficient, the shape of the force velocity relation is very similar to that for rapid obstacle diffusion.

  4. Compressive nonlinearity in the hair bundle's active response to mechanical stimulation.

    PubMed

    Martin, P; Hudspeth, A J

    2001-12-04

    The auditory system's ability to interpret sounds over a wide range of amplitudes rests on the nonlinear responsiveness of the ear. Whether measured by basilar-membrane vibration, nerve-fiber activity, or perceived loudness, the ear is most sensitive to small signals and grows progressively less responsive as stimulation becomes stronger. Seeking a correlate of this behavior at the level of mechanoelectrical transduction, we examined the responses of hair bundles to direct mechanical stimulation. As reported by the motion of an attached glass fiber, an active hair bundle from the bullfrog's sacculus oscillates spontaneously. Sinusoidal movement of the fiber's base by as little as +/-1 nm, corresponding to the application at the bundle's top of a force of +/-0.3 pN, causes detectable phase-locking of the bundle's oscillations to the stimulus. Although entrainment increases as the stimulus grows, the amplitude of the hair-bundle movement does not rise until phase-locking is nearly complete. A bundle is most sensitive to stimulation at its frequency of spontaneous oscillation. Far from that frequency, the sensitivity of an active hair bundle resembles that of a passive bundle. Over most of its range, an active hair bundle's response grows as the one-third power of the stimulus amplitude; the bundle's sensitivity declines accordingly in proportion to the negative two-thirds power of the excitation. This scaling behavior, also found in the response of the mammalian basilar membrane to sound, signals the operation of an amplificatory process at the brink of an oscillatory instability, a Hopf bifurcation.

  5. MRI depiction and 3D visualization of three anterior cruciate ligament bundles.

    PubMed

    Otsubo, H; Akatsuka, Y; Takashima, H; Suzuki, T; Suzuki, D; Kamiya, T; Ikeda, Y; Matsumura, T; Yamashita, T; Shino, K

    2017-03-01

    The anterior cruciate ligament (ACL) is divided into three fiber bundles (AM-M: anteromedial-medial, AM-L: anteromedial-lateral, PL: posterolateral). We attempted to depict the three bundles of the human ACL on MRI images and to obtain 3-dimensional visualization of them. Twenty-four knees of healthy volunteers (14 males, 10 females) were scanned by 3T-MRI using the fat suppression 3D coherent oscillatory state acquisition for the manipulation of imaging contrast (FS 3D-COSMIC). The scanned images were reconstructed after the isotropic voxel data, which allows the images to be reconstructed in any plane, was acquired. We conducted statistical examination on the identification rate of the three ACL bundles by 2D planes. Segmentation and 3D visualization of the fiber bundles using volume rendering were performed. The triple-bundle ACL was best depicted in the oblique axial plane. While the AM-M and AM-L bundles were clearly depicted in all cases, the PL bundle was not clearly visualized in two knees (8%). Therefore, the three ACL bundles were depicted in 22 knees (92%). The results of 3D visualization of the fiber arrangement agreed well with macroscopic findings of previous anatomical studies. 3T-MRI and the isotropic voxel data from FS 3D-COSMIC made it possible to demonstrate the identifiable depiction of three ACL bundles in nearly all cases. 3D visualization of the bundles could be a useful tool to understand the ACL fiber arrangement. Clin. Anat. 30:276-283, 2017. 2016 The Authors. Clinical Anatomy published by Wiley Periodicals, Inc. on behalf of American Association of Clinical Anatomists.

  6. Coolant mixing in LMFBR rod bundles and outlet plenum mixing transients. Progress report, March 1, 1980-May 31, 1980

    SciTech Connect

    Todreas, N.E.; Golay, M.W.; Wolf, L.

    1980-01-01

    Experimental and theoretical work is reported on four tasks: bundle geometry (wrapped and bare rods), subchannel geometry (bare rods), LMFBR outlet plenum flow mixing, and theoretical local temperature files in LMFBR fuel rod bundles. (DLC)

  7. Coolant mixing in LMFBR rod bundles and outlet plenum mixing transients. Progress report, September 1, 1980-November 30, 1980

    SciTech Connect

    Todreas, N.E.; Golay, M.W.; Wolf, L.

    1981-02-01

    Four tasks are reported: bundle geometry (wrapped and bare rods), subchannel geometry (bare rods), subchannel geometry (bare rods), LMFBR outlet plenum flow mixing, and theoretical determination of local temperature fields in LMFBR fuel rod bundles. (DLC)

  8. Methods for implantation of micro-wire bundles and optimization of single/multiunit recordings from human mesial temporal lobe

    PubMed Central

    Misra, A; Burke, JF; Ramayya, A; Jacobs, J; Sperling, MR; Moxon, KA; Kahana, MJ; Evans, JJ; Sharan, AD

    2014-01-01

    Objective The authors report methods developed for the implantation of micro-wire bundles into mesial temporal lobe structures and subsequent single neuron recording in epileptic patients undergoing in-patient diagnostic monitoring. This is done with the intention of lowering the perceived barriers to routine single neuron recording from deep brain structures in the clinical setting. Approach Over a 15 month period, 11 patients were implanted with platinum micro-wire bundles into mesial temporal structures. Protocols were developed for A) monitoring electrode integrity through impedance testing, B) ensuring continuous 24-7 recording, C) localizing micro-wire position and “splay” pattern and D) monitoring grounding and referencing to maintain the quality of recordings. Main Result Five common modes of failure were identified: 1) broken micro-wires from acute tensile force, 2) broken micro-wires from cyclic fatigue at stress points, 3) poor in-vivo micro-electrode separation, 4) motion artifact and 5) deteriorating ground connection and subsequent drop in common mode noise rejection. Single neurons have been observed up to 14 days post implantation and on 40% of micro-wires. Significance Long-term success requires detailed review of each implant by both the clinical and research teams to identify failure modes, and appropriate refinement of techniques while moving forward. This approach leads to reliable unit recordings without prolonging operative times, which will help increase the availability and clinical viability of human single neuron data. PMID:24608589

  9. Existence of automaticity in anomalous bundle of Wolff-Parkinson-White syndrome.

    PubMed Central

    Przybylski, J; Chiale, P A; Halpern, M S; Lázzari, J O; Elizari, M V; Rosenbaum, M B

    1978-01-01

    Escape beats probably arising from the anomalous bundle were documented in 2 patients with the Wolff-Parkinson-White (WPW) syndrome. A third patient, in whom complete AV block developed both in the anomalous bundle and the normal pathway, showed the occurrence of escape beats (an escape-bigeminy pattern), as well as a regular idioventricular rhythm arising from the anomalous bundle. Phase 4 block in the anomalous bundle occurred in 7 other patients, in 4 of them spontaneously and in 3 only after the administration of ajmaline or amiodarone. Only 4 of 14 fully investigated patients (out of a total number of 23) showed absence of both escape beats and phase 4 block. The escape beats were considered as direct evidence, and the phase 4 block as indirect evidence, for the existence of automaticity in the anomalous bundle. Such evidence supports the view that the anomalous bundle, like the His bundle-branch system, may be composed of specialised tissue endowed with the property of automaticity. PMID:656241

  10. Transduction channels’ gating can control friction on vibrating hair-cell bundles in the ear

    PubMed Central

    Bormuth, Volker; Barral, Jérémie; Joanny, Jean-François; Jülicher, Frank; Martin, Pascal

    2014-01-01

    Hearing starts when sound-evoked mechanical vibrations of the hair-cell bundle activate mechanosensitive ion channels, giving birth to an electrical signal. As for any mechanical system, friction impedes movements of the hair bundle and thus constrains the sensitivity and frequency selectivity of auditory transduction. Friction is generally thought to result mainly from viscous drag by the surrounding fluid. We demonstrate here that the opening and closing of the transduction channels produce internal frictional forces that can dominate viscous drag on the micrometer-sized hair bundle. We characterized friction by analyzing hysteresis in the force–displacement relation of single hair-cell bundles in response to periodic triangular stimuli. For bundle velocities high enough to outrun adaptation, we found that frictional forces were maximal within the narrow region of deflections that elicited significant channel gating, plummeted upon application of a channel blocker, and displayed a sublinear growth for increasing bundle velocity. At low velocity, the slope of the relation between the frictional force and velocity was nearly fivefold larger than the hydrodynamic friction coefficient that was measured when the transduction machinery was decoupled from bundle motion by severing tip links. A theoretical analysis reveals that channel friction arises from coupling the dynamics of the conformational change associated with channel gating to tip-link tension. Varying channel properties affects friction, with faster channels producing smaller friction. We propose that this intrinsic source of friction may contribute to the process that sets the hair cell’s characteristic frequency of responsiveness. PMID:24799674

  11. Comparative effects of ajmaline on intermittent bundle branch block and the Wolff-Parkinson-White syndrome.

    PubMed

    Chiale, P A; Przybylski, J; Halpern, M S; Lazzari, J O; Elizari, M V; Rosenbaum, M B

    1977-05-04

    Phase 4 or phase 3 block or both occurred in the His bundle branch system of 11 patients with intermittent bundle branch block and in the anomalous bundle of 6 of 46 patients with the Wolff-Parkinson-White syndrome (13%). Administration of a single dose of ajmaline (50 mg intravenously) in these patients caused a similar response: expansion of the range of phase 3 and phase 4 block at the expense of the intermediate normal conduction range and total interruption of conduction in the affected fascicle when the effect of the drug was maximal. The great similarity in physiologic behavior and pharmacologic response in these groups of patients suggests that the anomalous bundle was probably diseased or abnormal in the six patients with Wolff-Parkinson-White conduction. In addition, ajmaline caused the first appearance of phase 4 or phase 3 block, or both, but not total interruption of conduction in 26 of the 46 patients with Wolff-Parkinson-White conduction (56.5%). Ajmaline does not cause fascicular block in normal subjects; thus this finding suggests either that the anomalous bundle is diseased or that the safety margin for conduction in the anomalous bundle is much narrower than in the bundle branch system. The conduction-depressing action of ajmaline may be greater at relatively rapid or relatively slow rates of stimulation, and smaller or absent at intermediate rates.

  12. Performance of a Novel PMMA Polymer Imaging Bundle for Field Acquisition and Wavefront Sensing

    NASA Astrophysics Data System (ADS)

    Richards, S. N.; Leon-Saval, S.; Goodwin, M.; Zheng, J.; Lawrence, J. S.; Bryant, J. J.; Bland-Hawthorn, J.; Norris, B.; Cvetojevic, N.; Argyros, A.

    2017-01-01

    Imaging bundles provide a convenient way to translate a spatially coherent image, yet conventional imaging bundles made from silica fibre optics typically remain expensive with large losses due to poor filling factors ( 40%). We present the characterisation of a novel polymer imaging bundle made from poly(methyl methacrylate) (PMMA) that is considerably cheaper and a better alternative to silica imaging bundles over short distances ( 1 m; from the middle to the edge of a telescope's focal plane). The large increase in filling factor (92% for the polymer imaging bundle) outweighs the large increase in optical attenuation from using PMMA (1 dB/m) instead of silica (10-3 dB/m). We present and discuss current and possible future multi-object applications of the polymer imaging bundle in the context of astronomical instrumentation including: field acquisition, guiding, wavefront sensing, narrow-band imaging, aperture masking, and speckle imaging. The use of PMMA limits its use in low-light applications (e.g., imaging of galaxies); however, it is possible to fabricate polymer imaging bundles from a range of polymers that are better suited to the desired science.

  13. Optical design of endoscopic shape-tracker using quantum dots embedded in fiber bundles

    NASA Astrophysics Data System (ADS)

    Eisenstein, Jessica; Gavalis, Robb; Wong, Peter Y.; Cao, Caroline G. L.

    2009-08-01

    Colonoscopy is the current gold standard for colon cancer screening and diagnosis. However, the near-blind navigation process employed during colonoscopy results in endoscopist disorientation and scope looping, leading to missed detection of tumors, incorrect localization, and pain for the patient. A fiber optic bend sensor, which would fit into the working channel of a colonoscope, is developed to aid navigation through the colon during colonoscopy. The bend sensor is comprised of a bundle of seven fibers doped with quantum dots (QDs). Each fiber within the bundle contains a unique region made up of three zones with differently-colored QDs, spaced 120° apart circumferentially on the fiber. During bending at the QD region, light lost from the fiber's core is coupled into one of the QD zones, inducing fluorescence of the corresponding color whose intensity is proportional to the degree of bending. A complementary metal oxide semiconductor camera is used to obtain an image of the fluorescing end faces of the fiber bundle. The location of the fiber within the bundle, the color of fluorescence, and the fluorescence intensity are used to determine the bundle's bending location, direction, and degree of curvature, respectively. Preliminary results obtained using a single fiber with three QD zones and a seven-fiber bundle containing one active fiber with two QDs (180° apart) demonstrate the feasibility of the concept. Further developments on fiber orientation during bundling and the design of a graphical user interface to communicate bending information are also discussed.

  14. Education alone is not enough in ventilator associated pneumonia care bundle compliance

    PubMed Central

    Hamishehkar, Hadi; Vahidinezhad, Mahdi; Mashayekhi, Simin Ozar; Asgharian, Parina; Hassankhani, Hadi; Mahmoodpoor, Ata

    2014-01-01

    Objective: Ventilator-associated pneumonia (VAP) described as a secondary and preventable consequence in mechanically ventilated patients, emerges 48 h or more after patients intubation. Considering the high morbidity and mortality rate of VAP and the fact that VAP is preventable, it seemed necessary to evaluate care bundle compliance rate and effect of education on its improvement. Methods: This observational study was conducted on 10 Intensive Care Units (ICUs) of four university affiliated hospitals in three steps. In the first step, VAP care bundle compliance including head of bed (HOB) elevation, endotracheal cuff pressure (ETCP), mouthwash time, utilizing close suction systems, subglottic secretion drainage, type of suction package, and hand wash before suctioning was evaluated. In the second and third steps, ICU staffs were trained and its effect on VAP care bundle compliance was investigated. Finally, an inquiry from nurses was conducted to evaluate the obtained results. Findings: A total of 552 checklists consisting of 294 observations in the pre-education group and 258 observations in the posteducation group were filled. Mean VAP care bundle compliance in pre-education and posteducation stages was 36.5% and 41.2%, respectively (P > 0.05). Except for patients' mouth washing, there were no improvement in HOB elevation (>30°), hand washing and ETCP after education. Based on the results of questionnaire received from nurses at the end of study, more than 90% of nurses believed that lack of rigid monitoring of VAP care bundle is a main reason of low adherence for VAP care bundle compliance. Conclusion: The adherence to VAP care bundle was inappropriate. Education seems to be ineffective on improving VAP care bundle compliance. Frequent recall of the necessity of the VAP care bundle and the continuous supervision of ICU staffs is highly recommended. PMID:25114937

  15. Analytical Deriving of the Field Capacity through Soil Bundle Model

    NASA Astrophysics Data System (ADS)

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

    2015-12-01

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

  16. Understanding Peptide Oligomeric State in Langmuir Monolayers of Amphiphilic 3-Helix Bundle-Forming Peptide-PEG Conjugates

    PubMed Central

    Shu, Jessica Y.; Xu, Ting

    2016-01-01

    Coiled-coil peptide–polymer conjugates are an emerging class of biomaterials. Fundamental understanding of the coiled-coil oligomeric state and assembly process of these hybrid building blocks is necessary to exert control over their assembly into well-defined structures. Here, we studied the effect of peptide structure and PEGylation on the self-assembly process and oligomeric state of a Langmuir monolayer of amphiphilic coiled-coil peptide–polymer conjugates using X-ray reflectivity (XR) and grazing-incidence X-ray diffraction (GIXD). Our results show that the oligomeric state of PEGylated amphiphiles based on 3-helix bundle-forming peptide is surface pressure dependent, a mixture of dimers and trimers was formed at intermediate surface pressure but transitions into trimers completely upon increasing surface pressure. Moreover, the interhelical distance within the coiled-coil bundle of 3-helix peptide-PEG conjugate amphiphiles was not perturbed under high surface pressure. Present studies provide valuable insights into the self-assembly process of hybrid peptide–polymer conjugates and guidance to develop biomaterials with controlled multivalency of ligand presentation. PMID:27784156

  17. All-optical photoacoustic imaging system using fiber ultrasound probe and hollow optical fiber bundle.

    PubMed

    Miida, Yusuke; Matsuura, Yuji

    2013-09-23

    An all-optical 3D photoacoustic imaging probe that consists of an optical fiber probe for ultrasound detection and a bundle of hollow optical fibers for excitation of photoacoustic waves was developed. The fiber probe for ultrasound is based on a single-mode optical fiber with a thin polymer film attached to the output end surface that works as a Fabry Perot etalon. The input end of the hollow fiber bundle is aligned so that each fiber in the bundle is sequentially excited. A thin and flexible probe can be obtained because the probe system does not have a scanning mechanism at the distal end.

  18. Subchannel thermal-hydraulic modeling of an APT tungsten target rod bundle

    SciTech Connect

    Hamm, L.L.; Shadday, M.A. Jr.

    1997-09-01

    The planned target for the Accelerator Production of Tritium (APT) neutron source consists of an array of tungsten rod bundles through which D{sub 2}O coolant flows axially. Here, a scoping analysis of flow through an APT target rod bundle was conducted to demonstrate that lateral cross-flows are important, and therefore subchannel modeling is necessary to accurately predict thermal-hydraulic behavior under boiling conditions. A local reactor assembly code, FLOWTRAN, was modified to model axial flow along the rod bundle as flow through three concentric heated annular passages.

  19. Laboratory manual for static pressure drop experiments in LMFBR wire wrapped rod bundles

    SciTech Connect

    Burns, K.J.; Todreas, N.E.

    1980-07-01

    Purpose of this experiment is to determine both interior and edge subchannel axial pressure drops for a range of Reynolds numbers. The subchannel static pressure drop is used to calculate subchannel and bundle average friction factors, which can be used to verify existing friction factor correlations. The correlations for subchannel friction factors are used as input to computer codes which solve the coupled energy, continuity, and momentum equations, and are also used to develop flow split correlations which are needed as input to codes which solve only the energy equation. The bundle average friction factor is used to calculate the overall bundle pressure drop, which determines the required pumping power.

  20. Atmospheric effects in the intensity of muon bundles and geometrical mechanism of their formation

    NASA Astrophysics Data System (ADS)

    Kokoulin, R. P.; Bogdanov, A. G.; Dmitrieva, A. N.; Romanenkova, E. V.; Shutenko, V. V.; Yurina, E. A.

    2016-02-01

    Temporal changes in the intensity of muon bundles produced as a result of interactions of primary cosmic ray particles with energies of the order of 1015 eV and detected at the ground level are analyzed. Seasonal variations, barometric and temperature effects, and correlations with the altitudes of various levels of residual pressure are considered. It is shown that muon bundle intensity variations are well explained in frame of a simple mechanism related with changes of the muon lateral distribution function at the observation level caused by geometrical changes of the effective altitude of the formation of the bundles.

  1. [Bundle of His tachycardia and chronic reciprocating rhythm: rare forms of prenatal tachycardia].

    PubMed

    Lupoglazoff, J M; Denjoy, I; Magnier, S; Oury, J F; Blot, P; Casasoprana, A; Azancot, A

    2000-05-01

    In cases of permanent tachycardia, ante-natal diagnosis of chronic reciprocating rhythms with long RP' intervals or His bundle tachycardias is difficult. The authors report two cases of permanent foetal tachycardia with 1/1 atrioventricular conduction. In one case, the tachycardia rate was 170/min with anasarca treated by amiodarone in view of a family history of His bundle tachycardia. In the other case, the tachycardia rate was 200/min but with no signs of cardiac failure and was, therefore, not treated. The ECG at birth confirmed the diagnosis of His bundle tachycardia in the first case and identified a chronic reciprocating rhythm in the other.

  2. AC losses in perpendicular external magnetic fields in ring bundle barrier multifilamentary BSCCO(2223) tapes with a central resistive barrier

    NASA Astrophysics Data System (ADS)

    Eckelmann, H.; Krelaus, J.; Nast, R.; Goldacker, W.

    2001-06-01

    For the most common AC frequencies, the main components of the AC losses in multifilamentary Bi(2223) tapes are caused by both hysteresis and coupling losses. These losses can be reduced by increasing the matrix resistivity, applying a twist to the filaments and by the use of a conductor design optimised for a practical application. In the ring bundle barrier (RBB) conductor design we have bundles of filaments which are twisted around a central resistive core. The RBB structure was prepared via the powder in tube assemble and react (PITAR) route . In these tapes six bundles of seven filaments are twisted around a resistive layer of a mixture of 50% SrCO 3 and 50% SrZrO 3 in the centre of the tape. A series of tapes with twist lengths down to 3.4 mm was prepared. We present the measured AC losses of these tapes in external perpendicular magnetic fields. By using existing models, a description of the losses in the low Ḃ range was possible, leading to a separation into hysteresis, eddy current and coupling current losses. The frequency dependent loss contribution is dominated by the coupling current losses, from which the coupling current decay time constant, the effective permeability, the matrix resistivity and the critical Ḃc for filament coupling were extracted. In tapes with a twist length below 5 mm the typical loss behaviour for decoupled filaments is observed at frequencies up to 500 Hz. Compared to the untwisted tapes, a loss reduction of up to 70% for low field amplitudes (below 10 mT) was achieved.

  3. RBA: Reduced Bundle Adjustment for oblique aerial photogrammetry

    NASA Astrophysics Data System (ADS)

    Sun, Yanbiao; Sun, Huabo; Yan, Lei; Fan, Shiyue; Chen, Rui

    2016-11-01

    This study proposes an efficient Bundle Adjustment (BA) model for oblique aerial photogrammetry to reduce the number of unknown parameters and the dimensions of a non-linear optimization problem. Instead of serving as independent exterior orientations, oblique camera poses are parameterized with nadir camera poses and constant relative poses between oblique and nadir cameras. New observation functions are created with image points as a function of the nadir pose and the relative pose parameters. With these observation functions, the problem of BA is defined as finding optimal unknown parameters by minimizing the total difference between estimated and observed image points. A Gauss-Newton optimization method is utilized to provide a solution for this least-square problem with a reduced normal equation, which plays a very critical role in the convergence and efficiency of BA. Compared with traditional BA methods, the number of unknown parameters and the dimension of the normal equations decrease, this approach dramatically reduces the computational complexity and memory cost especially for large-scale scenarios with a number of oblique images. Four synthetic datasets and a real dataset were used to check the validation and the accuracy of the proposed method. The accuracy of the proposed method is very close to that of the traditional BA method, but the efficiency can be significantly improved by the proposed method. For very large-scale scenarios, the proposed method can still address the limitation of memory and orientate all images captured by an oblique aerial multi-camera system.

  4. Bundled-Optode Method in Functional Near-Infrared Spectroscopy

    PubMed Central

    Nguyen, Hoang-Dung; Hong, Keum-Shik; Shin, Yong-Il

    2016-01-01

    In this paper, a theory for detection of the absolute concentrations of oxy-hemoglobin (HbO) and deoxy-hemoglobin (HbR) from hemodynamic responses using a bundled-optode configuration in functional near-infrared spectroscopy (fNIRS) is proposed. The proposed method is then applied to the identification of two fingers (i.e., little and thumb) during their flexion and extension. This experiment involves a continuous-wave-type dual-wavelength (760 and 830 nm) fNIRS and five healthy male subjects. The active brain locations of two finger movements are identified based on the analysis of the t- and p-values of the averaged HbOs, which are quite distinctive. Our experimental results, furthermore, revealed that the hemodynamic responses of two-finger movements are different: The mean, peak, and time-to-peak of little finger movements are higher than those of thumb movements. It is noteworthy that the developed method can be extended to 3-dimensional fNIRS imaging. PMID:27788178

  5. Neurovascular Bundle Decompression without Excessive Dissection for Tarsal Tunnel Syndrome

    PubMed Central

    KIM, Kyongsong; ISU, Toyohiko; MORIMOTO, Daijiro; SASAMORI, Toru; SUGAWARA, Atsushi; CHIBA, Yasuhiro; ISOBE, Masahiro; KOBAYASHI, Shiro; MORITA, Akio

    2014-01-01

    Tarsal tunnel syndrome (TTS) is an entrapment neuropathy of the posterior tibial nerve and its branches in the tarsal tunnel. We present our less invasive surgical treatment of TTS in 69 patients (116 feet) and their clinical outcomes. The mean follow-up period was 64.6 months. With the patient under local anesthesia we use a microscope to perform sharp dissection of the flexor retinaculum and remove the connective tissues surrounding the posterior tibial nerve and vessels. To prevent postoperative adhesion and delayed neuropathy, decompression is performed to achieve symptom improvement without excessive dissection. Decompression is considered complete when the patient reports intraoperative symptom abatement and arterial pulsation is sufficient. The sensation of numbness and/or pain and of foreign substance adhesion was reduced in 92% and 95% of our patients, respectively. In self-assessments, 47 patients (68%) reported the treatment outcome as satisfactory, 15 (22%) as acceptable, and 7 (10%) were dissatisfied. Of 116 feet, 4 (3%) required re-operation, initial decompression was insufficient in 2 feet and further decompression was performed; in the other 2 feet improvement was achieved by decompression of the distal tarsal tunnel. Our surgical method involves neurovascular bundle decompression to obtain sufficient arterial pulsation. As we use local anesthesia, we can confirm symptom improvement intraoperatively, thereby avoiding unnecessary excessive dissection. Our method is simple, safe, and without detailed nerve dissection and it prevents postoperative adhesion. PMID:25367582

  6. Neurovascular bundle decompression without excessive dissection for tarsal tunnel syndrome.

    PubMed

    Kim, Kyongsong; Isu, Toyohiko; Morimoto, Daijiro; Sasamori, Toru; Sugawara, Atsushi; Chiba, Yasuhiro; Isobe, Masahiro; Kobayashi, Shiro; Morita, Akio

    2014-01-01

    Tarsal tunnel syndrome (TTS) is an entrapment neuropathy of the posterior tibial nerve and its branches in the tarsal tunnel. We present our less invasive surgical treatment of TTS in 69 patients (116 feet) and their clinical outcomes. The mean follow-up period was 64.6 months. With the patient under local anesthesia we use a microscope to perform sharp dissection of the flexor retinaculum and remove the connective tissues surrounding the posterior tibial nerve and vessels. To prevent postoperative adhesion and delayed neuropathy, decompression is performed to achieve symptom improvement without excessive dissection. Decompression is considered complete when the patient reports intraoperative symptom abatement and arterial pulsation is sufficient. The sensation of numbness and/or pain and of foreign substance adhesion was reduced in 92% and 95% of our patients, respectively. In self-assessments, 47 patients (68%) reported the treatment outcome as satisfactory, 15 (22%) as acceptable, and 7 (10%) were dissatisfied. Of 116 feet, 4 (3%) required re-operation, initial decompression was insufficient in 2 feet and further decompression was performed; in the other 2 feet improvement was achieved by decompression of the distal tarsal tunnel. Our surgical method involves neurovascular bundle decompression to obtain sufficient arterial pulsation. As we use local anesthesia, we can confirm symptom improvement intraoperatively, thereby avoiding unnecessary excessive dissection. Our method is simple, safe, and without detailed nerve dissection and it prevents postoperative adhesion.

  7. Tube bundle system: for monitoring of coal mine atmosphere.

    PubMed

    Zipf, R Karl; Marchewka, W; Mohamed, K; Addis, J; Karnack, F

    2013-05-01

    A tube bundle system (TBS) is a mechanical system for continuously drawing gas samples through tubes from multiple monitoring points located in an underground coal mine. The gas samples are drawn via vacuum pump to the surface and are typically analyzed for oxygen, methane, carbon dioxide and carbon monoxide. Results of the gas analyses are displayed and recorded for further analysis. Trends in the composition of the mine atmosphere, such as increasing methane or carbon monoxide concentration, can be detected early, permitting rapid intervention that prevents problems, such as a potentially explosive atmosphere behind seals, fire or spontaneous combustion. TBS is a well-developed technology and has been used in coal mines around the world for more than 50 years. Most longwall coal mines in Australia deploy a TBS, usually with 30 to 40 monitoring points as part of their atmospheric monitoring. The primary uses of a TBS are detecting spontaneous combustion and maintaining sealed areas inert. The TBS might also provide mine atmosphere gas composition data after a catastrophe occurs in an underground mine, if the sampling tubes are not damaged. TBSs are not an alternative to statutory gas and ventilation airflow monitoring by electronic sensors or people; rather, they are an option to consider in an overall mine atmosphere monitoring strategy. This paper describes the hardware, software and operation of a TBS and presents one example of typical data from a longwall coal mine.

  8. The left bundle branch block revised with novel imaging modalities

    PubMed Central

    van Dijk, J.; Mannaerts, H.F.J.; Germans, T.; Hauer, H.A.; Knaapen, P.; Visser, C.A.; Kamp, O.

    2006-01-01

    Left bundle branch block (LBBB) is related to abnormal cardiac conduction and mechanical asynchrony and is associated with hypertension and coronary artery disease. Improved evaluation of left ventricular (LV) mechanical asynchrony is needed, because of the increasing number of patients with LBBB and heart failure. In this paper, we describe tissue Doppler imaging (TDI), strain (rate) imaging and tissue tracking in LBBB patients. A variety of patterns of mechanical activation can be observed in LBBB patients. A recent development, referred to as tissue synchronisation imaging, colour codes TDI time-to-peak systolic velocities of segments and displays mechanical asynchrony. Furthermore, real-time 3D echocardiography provides new regional information about mechanical asynchrony. Contained in an LV model and projected on a bull's eye plot, this modality helps to display the spatial distribution of mechanical asynchrony. Finally, segmental time-to-peak circumferential strain curves, produced by cardiac magnetic resonance imaging, provide additional quantification of LV mechanical asynchrony. Effects of LBBB on regional and global cardiac function are impressive, myocardial involvement seems to play a role and with the help of these novel imaging modalities, new insights continue to develop. ImagesFigure 1Figure 2Figure 3Figure 4Figure 5Figure 6Figure 7 PMID:25696572

  9. Temperature response of bundle-sheath conductance in maize leaves

    PubMed Central

    Yin, Xinyou; van der Putten, Peter E.L.; Driever, Steven M.; Struik, Paul C.

    2016-01-01

    A small bundle-sheath conductance (g bs) is essential for the C4 CO2-concentrating mechanism to suppress photorespiration effectively. To predict the productivity of C4 crops accurately under global warming, it is necessary to examine whether and how g bs responds to temperature. We investigated the temperature response of g bs in maize by fitting a C4 photosynthesis model to combined gas exchange and chlorophyll fluorescence measurements of irradiance and CO2 response curves at 21% and 2% O2 within the range of 13.5–39 °C. The analysis was based on reported kinetic constants of C4 Rubisco and phosphoenolpyruvate carboxylase and temperature responses of C3 mesophyll conductance (g m). The estimates of g bs varied greatly with leaf temperature. The temperature response of g bs was well described by the peaked Arrhenius equation, with the optimum temperature being ~34 °C. The assumed temperature responses of g m had only a slight impact on the temperature response of g bs. In contrast, using extreme values of some enzyme kinetic constants changed the shape of the response, from the peaked optimum response to the non-peaked Arrhenius pattern. Further studies are needed to confirm such an Arrhenius response pattern from independent measurement techniques and to assess whether it is common across C4 species. PMID:26969744

  10. Oscillatory characteristics of carbon nanotubes inside carbon nanotube bundles

    NASA Astrophysics Data System (ADS)

    Ansari, R.; Alipour, A.; Sadeghi, F.

    2012-12-01

    This article presents a comprehensive study on the mechanics of carbon nanotubes (CNTs) oscillating in CNT bundles. Using the continuum approximation along with Lennard-Jones (LJ) potential function, new semi-analytical expressions in terms of double integrals are presented to evaluate van der Waals (vdW) potential energy and interaction force upon which the equation of motion is directly solved. The obtained potential expression enables one to arrive at a new semi-analytical formula for the exact evaluation of oscillation frequency. Also, an algebraic frequency formula is extracted on the basis of the simplifying assumption of constant vdW force. Based on the present expressions, a thorough study on various aspects of operating frequencies under different system parameters is given, which permits fresh insight into the problem. The strong dependence of oscillation frequency on system parameters, such as the extrusion distance and initial velocity of the core as initial conditions for the motion is indicated. Interestingly, a specific initial velocity is found at which the oscillation frequency is independent of the core length. In addition, a relation between this specific initial velocity and the escape velocity is disclosed.

  11. Corrosion of Palo Verde 2 upper bundle steam generator tubing

    SciTech Connect

    Magee, T.P.; Molkenthin, J.P.; Hall, J.F.; Melton, M.A.; Sachs, D.E.; Sweeney, K.M.; Begley, J.

    1995-12-31

    Palo Verde Unit-2 (PV-2) has experienced degradation in the upper bundle region of some of its Alloy 600 steam generator (SG) tubes. Arizona Public Service (APS) initiated several mitigating actions, including a 1994 chemical cleaning to remove tube deposits. Eddy current tests (ECT) conducted after chemical cleaning showed an increase in the number of indications. To detail the bend region indications, APS elected to remove the hot leg bend portion of 21 tubes for laboratory examination. The examination showed that the degradation mode was outside diameter initiated intergranular attack (IGA) and intergranular stress corrosion cracking (IGSCC). The most severe corrosion occurred beneath ridge-like deposits, although shallow IGA was discovered on large areas of free-span tubing. In some cases, degradation was associated with scratches or gouges on the tubes. Some wear was apparently caused by periodic tube-to-tube contact. Degradation was found in tubing with both poor and partial correspondence between grain boundaries and carbides. The chemical conditions that caused the tube degradation were likely neutral to alkaline solutions containing residual sulfur (sulfide) species. The burst strength of all tubes tested significantly exceeded Regulatory Guide 1.121 requirements. These results confirmed past PV-2 tube corrosion examination results.

  12. Bundle-forming pilus retraction enhances enteropathogenic Escherichia coli infectivity

    PubMed Central

    Zahavi, Eitan E.; Lieberman, Joshua A.; Donnenberg, Michael S.; Nitzan, Mor; Baruch, Kobi; Rosenshine, Ilan; Turner, Jerrold R.; Melamed-Book, Naomi; Feinstein, Naomi; Zlotkin-Rivkin, Efrat; Aroeti, Benjamin

    2011-01-01

    Enteropathogenic Escherichia coli (EPEC) is an important human pathogen that causes acute infantile diarrhea. The type IV bundle-forming pili (BFP) of typical EPEC strains are dynamic fibrillar organelles that can extend out and retract into the bacterium. The bfpF gene encodes for BfpF, a protein that promotes pili retraction. The BFP are involved in bacterial autoaggregation and in mediating the initial adherence of the bacterium with its host cell. Importantly, BFP retraction is implicated in virulence in experimental human infection. How pili retraction contributes to EPEC pathogenesis at the cellular level remains largely obscure, however. In this study, an effort has been made to address this question using engineered EPEC strains with induced BFP retraction capacity. We show that the retraction is important for tight-junction disruption and, to a lesser extent, actin-rich pedestal formation by promoting efficient translocation of bacterial protein effectors into the host cells. A model is proposed whereby BFP retraction permits closer apposition between the bacterial and the host cell surfaces, thus enabling timely and effective introduction of bacterial effectors into the host cell via the type III secretion apparatus. Our studies hence suggest novel insights into the involvement of pili retraction in EPEC pathogenesis. PMID:21613538

  13. Multiple site-specific infrared dichroism of CD3-zeta, a transmembrane helix bundle.

    PubMed

    Torres, Jaume; Briggs, John A G; Arkin, Isaiah T

    2002-02-15

    The structure of the transmembrane domain of CD3-zeta a component of the T-cell receptor involved in signal transduction, has been studied in its native state (a lipid bilayer) by multiple site-specific infrared dichroism. For the first time, the transmembrane domain has been labelled at multiple positions along the sequence, representing a total of 11 samples, each labelled at a different residue with an isotopically modified carbonyl group, (13)C [double bond] (18)O. A strategy is outlined that, based on the above data, can yield the rotational orientation and the local helix tilt for each labelled residue, giving a detailed description of helix geometry. The results obtained indicate that the transmembrane segment is in an alpha-helical conformation throughout, with an average helix tilt of 12 degrees. The N-terminal side of the helix is more tilted than the C-terminal. In an accompanying paper we describe the implementation of the infrared data in a model-building study of the CD3-zeta transmembrane complex. The model obtained is entirely consistent with results based on evolutionary conservation data. Taken together, this study represents the first step towards elucidation of the backbone structure of a transmembrane alpha-helical bundle by infrared spectroscopy.

  14. Folding of a model three-helix bundle protein: a thermodynamic and kinetic analysis.

    PubMed

    Zhou, Y; Karplus, M

    1999-11-05

    The kinetics and thermodynamics of an off-lattice model for a three-helix bundle protein are investigated as a function of a bias gap parameter that determines the energy difference between native and non-native contacts. A simple dihedral potential is used to introduce the tendency to form right-handed helices. For each value of the bias parameter, 100 trajectories of up to one microsecond are performed. Such statistically valid sampling of the kinetics is made possible by the use of the discrete molecular dynamics method with square-well interactions. This permits much faster simulations for off-lattice models than do continuous potentials. It is found that major folding pathways can be defined, although ensembles with considerable structural variation are involved. The large gap models generally fold faster than those with a smaller gap. For the large gap models, the kinetic intermediates are non-obligatory, while both obligatory and non-obligatory intermediates are present for small gap models. Certain large gap intermediates have a two-helix microdomain with one helix extended outward (as in domain-swapped dimers); the small gap intermediates have more diverse structures. The importance of studying the kinetic, as well as the thermodynamics, of folding for an understanding of the mechanism is discussed and the relation between kinetic and equilibrium intermediates is examined. It is found that the behavior of this model system has aspects that encompass both the "new" view and the "old" view of protein folding.

  15. Strategies and tactics for successful implementation of bundled payments: bundled payment for care improvement at a large, urban, academic medical center.

    PubMed

    Iorio, Richard

    2015-03-01

    As health care reform continues to evolve, there will need to be an emphasis on generating value, quality improvement, and cost control. In 2011, the Centers for Medicare and Medicaid Services (CMS) initiated a new Bundled Payment for Care Improvement initiative. Early results from this CMS bundled payment initiative at an urban, tertiary, academic medical center demonstrate decreased length of stay and increased discharge to home, with decreasing readmission rates, which can result in cost-savings without compromise of the quality of care. Changes in care coordination, clinical care pathways, and evidence-based protocols are the key to improving the quality metrics and cost effectiveness within the implementation of the bundled payment for care initiative, thus bringing increased value to our total joint arthroplasty patients.

  16. 77 FR 9925 - Price Index Adjustments for Expenditure Limitations and Lobbyist Bundling Disclosure Threshold

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-02-21

    ... From the Federal Register Online via the Government Publishing Office FEDERAL ELECTION COMMISSION...: Federal Election Commission. ACTION: Notice of adjustments to expenditure limitations and lobbyist bundling disclosure threshold. SUMMARY: As mandated by provisions of the Federal Election Campaign Act...

  17. Unmasking of left free wall ventricular preexcitation by His bundle ablation.

    PubMed Central

    Visman, A G; Hauer, R N; Robles de Medina, E O

    1993-01-01

    His bundle ablation was performed in a 48 year old man with drug refractory orthodromic atrioventricular reentrant tachycardia and paroxysmal atrial fibrillation. Reentry was caused by a left free wall concealed accessory pathway. Interruption of the His bundle by low energy direct current shock (25 J) was quickly followed by anterograde conduction via the accessory pathway, with various forms of advanced block. The combined effect of unfavourable anterograde conduction (prolonged anterograde effective refractory period and decremental conduction), the left lateral location of the accessory pathway and intra-atrial conduction delay on one side, and normal conduction via the atrioventricular node and His bundle with retrograde concealed conduction into the accessory pathway on the other side resulted in masking of the anterograde conduction capability of the anomalous pathway. This observation does not seem to invalidate the choice of His bundle ablation in similar cases. PMID:8518069

  18. Fabrication of a 10-m-length IR imaging bundle from arsenic trisulfide glass fibers

    NASA Astrophysics Data System (ADS)

    Hilton, Albert R., Sr.; McCord, James; Whaley, Glen; Loretz, Thomas J.; Modlin, Paul

    1999-04-01

    Amorphous Materials (AMI) has been engaged for several years in developing a process suitable for forming coherent imaging bundles from small diameter chalcogenide glass fibers. Currently, in a SBIR II program funded by the Navy Air Warfare Center at Patuxent River, Md., efforts are directed towards forming a bundle 10 meters in length from arsenic trisulfide glass fibers using the stacked ribbon method. A drum 10 meters in circumference was constructed on which to wind the ribbons. The fiber core diameter goal is 50 micrometer. The bundle will be 7 mm square with an active fiber area greater than 50% and an overall transmission goal of 50%. Anti-reflection coatings on both ends are provided using the AMI coating facility. A unique method of forming imaging bundles will be discussed. Images formed during evaluation will be shown.

  19. Dressed elliptic genus of heterotic compactifications with torsion and general bundles

    NASA Astrophysics Data System (ADS)

    Israël, Dan; Sarkis, Matthieu

    2016-08-01

    We define and compute the dressed elliptic genus of {N}=2 heterotic compactifications with torsion that are principal two-torus bundles over a K3 surface. We consider a large class of gauge bundles compatible with supersymmetry, consisting of a stable holomorphic vector bundle over the base together with an Abelian bundle over the total space, generalizing the computation previously done by the authors in the absence of the latter. Starting from a (0,2) gauged linear sigma-model with torsion we use supersymmetric localization to obtain the result. We provide also a mathematical definition of the dressed elliptic genus as a modified Euler characteristic and prove that both expressions agree for hypersurfaces in weighted projective spaces. Finally we show that it admits a natural decomposition in terms of {N}=4 superconformal characters, that may be useful to investigate moonshine phenomena for this wide class of {N}=2 vacua, that includes K3 × T 2 compactifications as special cases.

  20. Microcrystalline sodium tungsten bronze nanowire bundles as efficient visible light-responsive photocatalysts.

    PubMed

    Wang, Lei; Zhan, Jinhua; Fan, Weiliu; Cui, Guanwei; Sun, Honggang; Zhuo, Linhai; Zhao, Xian; Tang, Bo

    2010-12-14

    Microcrystalline sodium tungsten bronze nanowire bundles were obtained via a facile hydrothermal synthesis, and were applied in water purification as visible-light-driven photocatalysts for the first time.