Science.gov

Sample records for ribbon modulates apical

  1. Compact multiwavelength transmitter module for multimode fiber optic ribbon cable

    DOEpatents

    Deri, Robert J.; Pocha, Michael D.; Larson, Michael C.; Garrett, Henry E.

    2002-01-01

    A compact multiwavelength transmitter module for multimode fiber optic ribbon cable, which couples light from an M.times.N array of emitters onto N fibers, where the M wavelength may be distributed across two or more vertical-cavity surface-emitting laser (VCSEL) chips, and combining emitters and multiplexer into a compact package that is compatible with placement on a printed circuit board. A key feature is bringing together two emitter arrays fabricated on different substrates--each array designed for a different wavelength--into close physical proximity. Another key feature is to compactly and efficiently combine the light from two or more clusters of optical emitters, each in a different wavelength band, into a fiber ribbon.

  2. Spectral Modulation of the IBEX Ribbon Flux by the Dynamic Draping of the Interstellar Medium over the Heliosphere

    NASA Astrophysics Data System (ADS)

    Funsten, H. O.; Pittman, K. T.; Frisch, P. C.; Heerikhuisen, J.; Janzen, P. H.; McComas, D. J.; Reisenfeld, D. B.; Schwadron, N.; Zirnstein, E.

    2015-12-01

    The bright energetic neutral atom (ENA) emission in the circular ribbon observed by the Interstellar Boundary Explorer (IBEX) ribbon is a key ordering parameter of the interaction region between the heliosphere and the insterstellar medium. The ribbon is hypothesized to result from the condition in which the interstellar magnetic field, which is draped over the heliosphere and is the emission location in the "secondary" reibbon hypothesis, is oriented perpendicular to the line-of-sight view from IBEX. Here, we consider the relative motion of the draped magnetic field line for modulating ribbon intensity. Using the 0.7 keV and 1.1 keV ENA maps from the IBEX-Hi instrument, we find that this relative motion may significantly contribute to the variation of ribbon flux around the ribbon. We discuss the implications of this relative motion on our understanding the global structure and dynamics of the heliosphere-insterstellar medium interaction.

  3. SUPPRESSOR OF APICAL DOMINANCE1 of Sporisorium reilianum Modulates Inflorescence Branching Architecture in Maize and Arabidopsis.

    PubMed

    Ghareeb, Hassan; Drechsler, Frank; Löfke, Christian; Teichmann, Thomas; Schirawski, Jan

    2015-12-01

    The biotrophic fungus Sporisorium reilianum causes head smut of maize (Zea mays) after systemic plant colonization. Symptoms include the formation of multiple female inflorescences at subapical nodes of the stalk because of loss of apical dominance. By deletion analysis of cluster 19-1, the largest genomic divergence cluster in S. reilianum, we identified a secreted fungal effector responsible for S. reilianum-induced loss of apical dominance, which we named SUPPRESSOR OF APICAL DOMINANCE1 (SAD1). SAD1 transcript levels were highly up-regulated during biotrophic fungal growth in all infected plant tissues. SAD1-green fluorescent protein fusion proteins expressed by recombinant S. reilianum localized to the extracellular hyphal space. Transgenic Arabidopsis (Arabidopsis thaliana)-expressing green fluorescent protein-SAD1 displayed an increased number of secondary rosette-leaf branches. This suggests that SAD1 manipulates inflorescence branching architecture in maize and Arabidopsis through a conserved pathway. Using a yeast (Saccharomyces cerevisiae) two-hybrid library of S. reilianum-infected maize tissues, we identified potential plant interaction partners that had a predicted function in ubiquitination, signaling, and nuclear processes. Presence of SAD1 led to an increase of the transcript levels of the auxin transporter PIN-FORMED1 in the root and a reduction of the branching regulator TEOSINTE BRANCHED1 in the stalk. This indicates a role of SAD1 in regulation of apical dominance by modulation of branching through increasing transcript levels of the auxin transporter PIN1 and derepression of bud outgrowth. PMID:26511912

  4. SUPPRESSOR OF APICAL DOMINANCE1 of Sporisorium reilianum Modulates Inflorescence Branching Architecture in Maize and Arabidopsis.

    PubMed

    Ghareeb, Hassan; Drechsler, Frank; Löfke, Christian; Teichmann, Thomas; Schirawski, Jan

    2015-12-01

    The biotrophic fungus Sporisorium reilianum causes head smut of maize (Zea mays) after systemic plant colonization. Symptoms include the formation of multiple female inflorescences at subapical nodes of the stalk because of loss of apical dominance. By deletion analysis of cluster 19-1, the largest genomic divergence cluster in S. reilianum, we identified a secreted fungal effector responsible for S. reilianum-induced loss of apical dominance, which we named SUPPRESSOR OF APICAL DOMINANCE1 (SAD1). SAD1 transcript levels were highly up-regulated during biotrophic fungal growth in all infected plant tissues. SAD1-green fluorescent protein fusion proteins expressed by recombinant S. reilianum localized to the extracellular hyphal space. Transgenic Arabidopsis (Arabidopsis thaliana)-expressing green fluorescent protein-SAD1 displayed an increased number of secondary rosette-leaf branches. This suggests that SAD1 manipulates inflorescence branching architecture in maize and Arabidopsis through a conserved pathway. Using a yeast (Saccharomyces cerevisiae) two-hybrid library of S. reilianum-infected maize tissues, we identified potential plant interaction partners that had a predicted function in ubiquitination, signaling, and nuclear processes. Presence of SAD1 led to an increase of the transcript levels of the auxin transporter PIN-FORMED1 in the root and a reduction of the branching regulator TEOSINTE BRANCHED1 in the stalk. This indicates a role of SAD1 in regulation of apical dominance by modulation of branching through increasing transcript levels of the auxin transporter PIN1 and derepression of bud outgrowth.

  5. Ribbon plastic optical fiber linked optical transmitter and receiver modules featuring a high alignment tolerance.

    PubMed

    Lee, Hak-Soon; Park, Jun-Young; Cha, Sang-Mo; Lee, Sang-Shin; Hwang, Gyo-Sun; Son, Yung-Sung

    2011-02-28

    Ribbon plastic optical fiber (POF) linked four-channel optical transmitter (Tx) and receiver (Rx) modules have been proposed and realized featuring an excellent alignment tolerance. The two modules share a common configuration involving an optical sub-assembly (OSA) with vertical cavity surface emitting lasers (VCSELs)/photodetectors (PDs), and their driver ICs, which are integrated onto a single printed circuit board (PCB) substrate. The OSA includes an alignment structure, a beam router and a fiber guide, which were produced by using plastic injection molding. We have accomplished a fully passive alignment between the VCSELs/PDs and the ribbon POF by taking advantage of the alignment structure that serves as a reference during the alignment of the constituent parts of the OSA. The electrical link, which largely determines the operation speed, has been remarkably shortened, due to a direct wire-bonding between the VCSELs/PDs and the driver circuits. The light sources and the detectors can be individually positioned, thereby overcoming the pitch limitations of the ribbon POF, which is made up of perfluorinated graded-index (GI) POF with a 62.5 μm core diameter. The overall alignment tolerance was first assessed by observing the optical coupling efficiency in terms of VCSEL/PD misalignment. The horizontal and vertical 3-dB alignment tolerances were about 20 μm and 150 μm for the Tx and 50 μm and over 200 μm for the Rx, respectively. The VCSEL-to-POF coupling loss for the Tx and the POF-to-PD loss for the Rx were 3.25 dB and 1.35 dB at a wavelength of 850 nm, respectively. Subsequently, a high-speed signal at 3.2 Gb/s was satisfactorily delivered via the Tx and Rx modules over a temperature range of -30 to 70°C with no significant errors; the channel crosstalk was below -30 dB. Finally, the performance of the prepared modules was verified by transmitting a 1080p HDMI video supplied by a Bluelay player to an LCD TV.

  6. Ribbon crystals.

    PubMed

    Bohr, Jakob; Markvorsen, Steen

    2013-01-01

    A repetitive crystal-like pattern is spontaneously formed upon the twisting of straight ribbons. The pattern is akin to a tessellation with isosceles triangles, and it can easily be demonstrated with ribbons cut from an overhead transparency. We give a general description of developable ribbons using a ruled procedure where ribbons are uniquely described by two generating functions. This construction defines a differentiable frame, the ribbon frame, which does not have singular points, whereby we avoid the shortcomings of the Frenet-Serret frame. The observed spontaneous pattern is modeled using planar triangles and cylindrical arcs, and the ribbon structure is shown to arise from a maximization of the end-to-end length of the ribbon, i.e. from an optimal use of ribbon length. The phenomenon is discussed in the perspectives of incompatible intrinsic geometries and of the emergence of long-range order.

  7. Ribbon Crystals

    PubMed Central

    Bohr, Jakob; Markvorsen, Steen

    2013-01-01

    A repetitive crystal-like pattern is spontaneously formed upon the twisting of straight ribbons. The pattern is akin to a tessellation with isosceles triangles, and it can easily be demonstrated with ribbons cut from an overhead transparency. We give a general description of developable ribbons using a ruled procedure where ribbons are uniquely described by two generating functions. This construction defines a differentiable frame, the ribbon frame, which does not have singular points, whereby we avoid the shortcomings of the Frenet–Serret frame. The observed spontaneous pattern is modeled using planar triangles and cylindrical arcs, and the ribbon structure is shown to arise from a maximization of the end-to-end length of the ribbon, i.e. from an optimal use of ribbon length. The phenomenon is discussed in the perspectives of incompatible intrinsic geometries and of the emergence of long-range order. PMID:24098360

  8. SUPPRESSOR OF APICAL DOMINANCE1 of Sporisorium reilianum Modulates Inflorescence Branching Architecture in Maize and Arabidopsis1[OPEN

    PubMed Central

    Ghareeb, Hassan; Löfke, Christian; Teichmann, Thomas; Schirawski, Jan

    2015-01-01

    The biotrophic fungus Sporisorium reilianum causes head smut of maize (Zea mays) after systemic plant colonization. Symptoms include the formation of multiple female inflorescences at subapical nodes of the stalk because of loss of apical dominance. By deletion analysis of cluster 19-1, the largest genomic divergence cluster in S. reilianum, we identified a secreted fungal effector responsible for S. reilianum-induced loss of apical dominance, which we named SUPPRESSOR OF APICAL DOMINANCE1 (SAD1). SAD1 transcript levels were highly up-regulated during biotrophic fungal growth in all infected plant tissues. SAD1-green fluorescent protein fusion proteins expressed by recombinant S. reilianum localized to the extracellular hyphal space. Transgenic Arabidopsis (Arabidopsis thaliana)-expressing green fluorescent protein-SAD1 displayed an increased number of secondary rosette-leaf branches. This suggests that SAD1 manipulates inflorescence branching architecture in maize and Arabidopsis through a conserved pathway. Using a yeast (Saccharomyces cerevisiae) two-hybrid library of S. reilianum-infected maize tissues, we identified potential plant interaction partners that had a predicted function in ubiquitination, signaling, and nuclear processes. Presence of SAD1 led to an increase of the transcript levels of the auxin transporter PIN-FORMED1 in the root and a reduction of the branching regulator TEOSINTE BRANCHED1 in the stalk. This indicates a role of SAD1 in regulation of apical dominance by modulation of branching through increasing transcript levels of the auxin transporter PIN1 and derepression of bud outgrowth. PMID:26511912

  9. Laser Micro Welding for Ribbon Bonding

    NASA Astrophysics Data System (ADS)

    Mehlmann, Benjamin; Gehlen, Elmar; Olowinsky, Alexander; Gillner, Arnold

    Laser ribbon bonding is a new field of application for laser micro welding in the electronics industry especially in the area of power electronics. Traditional ribbon bonding is conducted by using ultrasonic welding to create the bond between the aluminum or copper ribbon and a conductive surface. By adapting an ultrasonic ribbon bonder and equipping it with a fiber laser, a galvanometric scanner and a beam focusing and delivery system, a new technology for ribbon bonding is created. The presented work includes test results of the welding of copper ribbons with a thickness of 300 μm to DCB-substrates and the system design of the "laser bonder". For the laser welding of the ribbons spatial power modulation is being used and the effect of this approach on the welded ribbons is presented. The work concludes with advantages and limits of the technology especially concerning the applications compared to ultrasonic bonding.

  10. Differential regulation of the Hippo pathway by adherens junctions and apical-basal cell polarity modules.

    PubMed

    Yang, Chih-Chao; Graves, Hillary K; Moya, Ivan M; Tao, Chunyao; Hamaratoglu, Fisun; Gladden, Andrew B; Halder, Georg

    2015-02-10

    Adherens junctions (AJs) and cell polarity complexes are key players in the establishment and maintenance of apical-basal cell polarity. Loss of AJs or basolateral polarity components promotes tumor formation and metastasis. Recent studies in vertebrate models show that loss of AJs or loss of the basolateral component Scribble (Scrib) cause deregulation of the Hippo tumor suppressor pathway and hyperactivation of its downstream effectors Yes-associated protein (YAP) and Transcriptional coactivator with PDZ-binding motif (TAZ). However, whether AJs and Scrib act through the same or independent mechanisms to regulate Hippo pathway activity is not known. Here, we dissect how disruption of AJs or loss of basolateral components affect the activity of the Drosophila YAP homolog Yorkie (Yki) during imaginal disc development. Surprisingly, disruption of AJs and loss of basolateral proteins produced very different effects on Yki activity. Yki activity was cell-autonomously decreased but non-cell-autonomously elevated in tissues where the AJ components E-cadherin (E-cad) or α-catenin (α-cat) were knocked down. In contrast, scrib knockdown caused a predominantly cell-autonomous activation of Yki. Moreover, disruption of AJs or basolateral proteins had different effects on cell polarity and tissue size. Simultaneous knockdown of α-cat and scrib induced both cell-autonomous and non-cell-autonomous Yki activity. In mammalian cells, knockdown of E-cad or α-cat caused nuclear accumulation and activation of YAP without overt effects on Scrib localization and vice versa. Therefore, our results indicate the existence of multiple, genetically separable inputs from AJs and cell polarity complexes into Yki/YAP regulation.

  11. Modulation of iridovirus-induced apoptosis by endocytosis, early expression, JNK, and apical caspase

    SciTech Connect

    Chitnis, Nilesh S.; D'Costa, Susan M.; Paul, Eric R.; Bilimoria, Shaen L.

    2008-01-20

    Chilo iridescent virus (CIV) is the type species for the family Iridoviridae, which are large, isometric, cytoplasmic dsDNA viruses. We examined the mechanism of apoptosis induction by CIV. High CIV doses (CIV{sub XS}; 400 {mu}g/ml), UV-irradiated virus (CIV{sub UV}; 10 {mu}g/ml) and CVPE (CIV protein extract; 10 {mu}g/ml) induced apoptosis in 60% of treated Choristoneura fumiferana (IPRI-CF-124T) cells. Normal doses of infectious CIV (10 {mu}g/ml) induced apoptosis in only 10% of C. fumiferana (CF) cells. Apoptosis was inhibited by Z-IETD-FMK, an apical caspase inhibitor, indicating that CIV-induced apoptosis requires caspase activity. The putative caspase in CF cells was designated Cf-caspase-i. CIV{sub UV} or CVPE enhanced Cf-caspase-i activity by 80% at 24 h relative to mock-treated cells. Since the MAP kinase pathway induces or inhibits apoptosis depending on the context, we used JNK inhibitor SP600125 and demonstrated drastic suppression of CVPE-induced apoptosis. Thus, the JNK signaling pathway is significant for apoptosis in this system. Virus interaction with the cell surface was not sufficient for apoptosis since CIV{sub UV} particles bound to polysterene beads failed to induce apoptosis. Endocytosis inhibitors (bafilomycin or ammonium chloride) negated apoptosis induction by CIV{sub UV}, CIV{sub XS} or CVPE indicating that entry through this mode is required. Given the weak apoptotic response to infectious CIV, we postulated that viral gene expression inhibited apoptosis. CIV infection of cells pretreated with cycloheximide induced apoptosis in 69% of the cells compared to 10% in normal infections. Furthermore, blocking viral DNA replication with aphidicolin or phosphonoacetic acid suppressed apoptosis and Cf-caspase-i activity, indicating that early viral expression is necessary for inhibition of apoptosis, and de novo synthesis of viral proteins is not required for induction. We show for the first time that, in a member of the family Iridoviridae

  12. Innovative Approaches to Low-Cost Module Manufacturing of String Ribbon Si PV Modules; Final Subcontract Report, March 2002 - January 2005

    SciTech Connect

    Hanoka, J. I.

    2005-10-01

    As a result of this work, Evergreen Solar, Inc., is now poised to take String Ribbon technology to new heights. In the ribbon growth area, Project Gemini-the growth of dual ribbons from a single crucible-has reached or exceeded all the manufacturing goals set for it. This project grew from an R&D concept to a production pilot phase and finally to a full production phase, all within the span of this subcontract. A major aspect of the overall effort was the introduction of controls and instrumentation as in-line diagnostic tools. In the ribbon production area, the result has been a 12% increase in yields, a 10% increase in machine uptime, and the flattest ribbon ever grown at Evergreen. In the cell area, advances in process development and robotic handling of Gemini wafers have contributed, along with the advances in crystal growth, to a yield improvement of 6%. Particularly noteworthy in the cell area was the refinement of the no-etch process whereby the as-grown ribbon surface could be controlled sufficiently to allow this process to succeed as well as it has. This process obviates any need for wet chemistry or etching between ribbon growth and diffusion.

  13. Matrix Metalloproteinase Expression in Teeth with Apical Periodontitis Is Differentially Modulated by the Modality of Root Canal Treatment

    PubMed Central

    Paula-Silva, Francisco Wanderley Garcia; da Silva, Léa Assed Bezerra; Kapila, Yvonne Lorraine

    2009-01-01

    Objectives To investigate the expression of matrix metalloproteinases (MMPs) in apical periodontitis and during the periapical healing phase following root canal treatment. Methods Apical periodontitis was induced in dog teeth and root canal treatment was performed in a single visit or using an additional calcium hydroxide root canal dressing. One hundred and eighty days following treatment the presence of inflammation was examined and tissues were stained to detect bacteria. Bacterial status was correlated to the degree of tissue organization, and to further investigate molecules involved in this process, tissues were stained for MMP-1, MMP-2, MMP-8, and MMP-9. Data were analyzed using one-way ANOVA followed by Tukey test or Kruskal-Wallis followed by Dunn. Results Teeth with apical periodontitis that had root canal therapy performed in a single visit presented an intense inflammatory cell infiltrate. Periapical tissue was extremely disorganized, and this was correlated with the presence of bacteria. Higher MMP expression was evident, similar to teeth with untreated apical periodontitis. In contrast, teeth with apical periodontitis submitted to root canal treatment using calcium hydroxide presented a lower inflammatory cell infiltrate. This group had a moderately organized connective tissue, a lower prevalence of bacteria, and a lower number of MMP-positive cells, similar to healthy teeth submitted to treatment. Conclusion Teeth treated with calcium hydroxide root canal dressing exhibited a lower percentage of bacterial contamination, a lower MMP expression, and a more organized ECM, unlike those treated in a single visit. This suggests that calcium hydroxide may be beneficial in tissue repair processes. PMID:20113780

  14. Growth and characterization of string ribbon

    SciTech Connect

    Hanoka, J.I.; Behnin, B.; Michel, J.; Symko, M.; Sopori, B.L.

    1995-08-01

    Evergreen Solar, a new photovoltaics company, makes solar cells and modules based on String Ribbon. String Ribbon is a silicon sheet growth method wherein two high temperature strings are pulled through a shallow melt of silicon and a crystalline silicon sheet then grows between the two strings. The strings serve to stabilize the edges of the growing silicon sheet. The growth process is primarily meniscus controlled and, compared to other silicon ribbon growth methods such as d-web and EFG, relatively insensitive to temperature fluctuations as great as {+-}10{degrees}C. Growth speed is about 2 cm/minute.

  15. TWISTED RIBBON FUEL ELEMENT

    DOEpatents

    Breden, C.R.; Schultz, A.B.

    1961-06-01

    A reactor core formed of bundles of parallel fuel elements in the form of ribbons is patented. The fuel ribbons are twisted about their axes so as to have contact with one another at regions spaced lengthwise of the ribbons and to be out of contact with one another at locations between these spaced regions. The contact between the ribbons is sufficient to allow them to be held together in a stable bundle in a containing tube without intermediate support, while permitting enough space between the ribbon for coolant flowing.

  16. Noise exposure modulates cochlear inner hair cell ribbon volumes, correlating with changes in auditory measures in the FVB/nJ mouse

    PubMed Central

    Paquette, Stephen T.; Gilels, Felicia; White, Patricia M.

    2016-01-01

    Cochlear neuropathy resulting from unsafe noise exposure is a life altering condition that affects many people. This hearing dysfunction follows a conserved mechanism where inner hair cell synapses are lost, termed cochlear synaptopathy. Here we investigate cochlear synaptopathy in the FVB/nJ mouse strain as a prelude for the investigation of candidate genetic mutations for noise damage susceptibility. We used measurements of auditory brainstem response (ABR) and distortion product otoacoustic emissions (DPOAE) to assess hearing recovery in FVB/nJ mice exposed to two different noise levels. We also utilized confocal fluorescence microscopy in mapped whole mount cochlear tissue, in conjunction with deconvolution and three-dimensional modeling, to analyze numbers, volumes and positions of paired synaptic components. We find evidence for significant synapse reorganization in response to both synaptopathic and sub-synaptopathic noise exposures in FVB/nJ. Specifically, we find that the modulation in volume of very small synaptic ribbons correlates with the presence of reduced ABR peak one amplitudes in both levels of noise exposures. These experiments define the use of FVB/nJ mice for further genetic investigations into the mechanisms of noise damage. They further suggest that in the cochlea, neuronal-inner hair cell connections may dynamically reshape as part of the noise response. PMID:27162161

  17. Comparison of output power for solar cells with standard and structured ribbons

    NASA Astrophysics Data System (ADS)

    Muehleisen, Wolfgang; Neumaier, Lukas; Hirschl, Christina; Maier, Thomas; Schwark, Michael; Seufzer, Siegfried; Battistutti, Rene; Pedevilla, Mathias; Scheurer, Jög; Lorenz, Robert

    2016-07-01

    The optical loss due to the busbar grid and soldered interconnector ribbons on a three busbar standard multicrystalline silicon solar cell's front side is at 2.3%. One way to reduce this optical loss on cell level and in a photovoltaic (PV) module is to use deep structured ribbons as cell connectors. The standard soldered, flat ribbon is replaced with a glued, multiple structured ribbon. The investigation of shiny soldered flat ribbons and multiple structured ribbons in single-cell mini modules demonstrates the light angle dependency and the benefit for the structured alternative. Additional yield measurements for conventional photovoltaic modules with soldered flat and glued multiple structured ribbons technologies were studied under laboratory conditions as well as in outdoor measurements. The simulations and the experimental findings confirmed that the new structured ribbon design increases the short circuit current and the yield by about 2%.

  18. Ribbon-to-fiber transformation in the process of spinning of carbon-nanotube dispersion.

    PubMed

    Kornev, Konstantin G; Callegari, Gerardo; Kuppler, John; Ruetsch, Sigrid; Neimark, Alexander V

    2006-11-01

    We describe a phenomenon of ribbon-to-fiber transformation observed in the process of spinning of single wall carbon nanotubes dispersed in polymer solutions. In the process of spinning, a gel-like ribbon comprised of nanotube bundles bound by polymer is withdrawn from a solvent bath. We show that upon crossing the liquid-air interface, the ribbon may either retain its flat shape or fold into a compact hairlike fiber. The ribbon-to-fiber transformation is caused by the capillary action of the liquid meniscus embracing the ribbon. Only sufficiently stiff ribbons can withhold the capillary compression. The critical conditions of folding, as well as the number of folds in the contractive ribbon, depend on the ribbon width, its flexural rigidity, and the solvent surface tension. We show that the ribbon rigidity can be efficiently modulated by varying the solvent composition, allowing us to control the pore structure of carbon-nanotube fibers. PMID:17155588

  19. Blue Ribbon Panel Report

    Cancer.gov

    An NCI Cancer Currents blog by the NCI acting director thanking the cancer community for contributing to the Cancer Moonshot Blue Ribbon Panel report, which was presented to the National Cancer Advisory Board on September 7.

  20. The Ribbon Laser

    SciTech Connect

    Feit, M D; Beach, R J; Brasure, L D; Payne, S A; Page, R H; Wilcox, R

    2001-04-18

    A new scalable fiber laser approach is described and modeled, based on phase-locking multiple gain cores in an antiguided structure. In essence, the waveguide is comprised of a periodic sequence of gain-loaded and no-gain segments having uniform refractive index (referred to as the ''ribbon'') encapsulated within a reduced index cladding region. Our calculations reveal that the constant index profile within the ribbon structure provides optimal mode discrimination; the refractive index must be constant within {+-}0.001 to ensure single-mode operation for a 5-core design. Periodic variation in refractive index and gain of the ribbon laser lead to the emergence of a photonic bandgap, in analogy to so-called ''holey fibers''. Our constant index design, together with the periodic gain profile, may be described as a photonic metal.

  1. Antiguided fiber ribbon laser

    DOEpatents

    Wilcox, Russel B.; Page, Ralph H.; Beach, Raymond J.; Feit, Michael D.; Payne, Stephen A.

    2003-05-27

    The invention is a ribbon of an optical material with a plurality of cores that run along its length. The plurality of cores includes lasing impurity doped cores in an alternating spaced arrangement with index-modifying impurity doped cores. The ribbon comprises an index of refraction that is substantially equal to or greater than the indices of refraction of said array of lasing impurity doped cores. Index-increasing impurity doped cores promote antiguiding and leaky modes which provide more robust single "supermode" operation.

  2. Apical Dominance in Plants

    ERIC Educational Resources Information Center

    Tucker, D. J.

    1974-01-01

    Describes a tentative hypothesis for the control of plant branching (apical dominance). Explores the mechanism by which apical buds inhibit the growth of axillary buds on the same shoot. Presents an up-to-date picture of the problem and gives economic implications of the study. (BR)

  3. Crystallization of Silicon Ribbons

    NASA Technical Reports Server (NTRS)

    Leipold, M. H.

    1984-01-01

    Purity constraints for reasonable solar-cell efficiency require that silicon-ribbon growth for photovoltaics occur in a regime in which constitutional supercooling or other compositional effects on the crystallization front are not important. A major consideration in the fundamentals of crystallization is the removal of the latent heat of fusion. The direction of removal, compared with the growth direction, has a major influence on the crystallization rate and the development of localized stresses. The detailed shape of the crystallization front appears to have two forms: that required for dendritic-web growth, and that occurring in all others. After the removal of the latent heat of fusion, the thermal-mechanical behavior of all ribbons appears similar within the constraints of the exothermal gradient. The technological constraints in achieving the required thermal and mechanical conditions vary widely among the growth processes.

  4. Stress analysis of ribbon parachutes

    NASA Technical Reports Server (NTRS)

    Reynolds, D. T.; Mullins, W. M.

    1975-01-01

    An analytical method has been developed for determining the internal load distribution for ribbon parachutes subjected to known riser and aerodynamic forces. Finite elements with non-linear elastic properties represent the parachute structure. This method is an extension of the analysis previously developed by the authors and implemented in the digital computer program CANO. The present analysis accounts for the effect of vertical ribbons in the solution for canopy shape and stress distribution. Parametric results are presented which relate the canopy stress distribution to such factors as vertical ribbon strength, number of gores, and gore shape in a ribbon parachute.

  5. Process Makes Thermoplastic Prepreg Ribbon

    NASA Technical Reports Server (NTRS)

    Wilson, Maywood L.; Johnson, Gary S.

    1995-01-01

    Manufacturing process produces ribbon of composite material (prepreg) consisting of continuous lengthwise fibers impregnated with thermoplastic resin. Ribbon can later be cut into sheets of required sizes and shapes, stacked, then heated under pressure to form composite-material structural components. Process accommodates variety of thermoplastic resins and variety of fibers.

  6. Neuraminidase Ribbon Diagram

    NASA Technical Reports Server (NTRS)

    2004-01-01

    Ribbons is a program developed at UAB used worldwide to graphically depict complicated protein structures in a simplified format. The program uses sophisticated computer systems to understand the implications of protein structures. The Influenza virus remains a major causative agent for a large number of deaths among the elderly and young children and huge economic losses due to illness. Finding a cure will have a general impact both on the basic research of viral pathologists of fast evolving infectious agents and clinical treatment of influenza virus infection. The reproduction process of all strains of influenza are dependent on the same enzyme neuraminidase. Shown here is a segmented representation of the neuraminidase inhibitor compound sitting inside a cave-like contour of the neuraminidase enzyme surface. This cave-like formation present in every neuraminidase enzyme is the active site crucial to the flu's ability to infect. The space-grown crystals of neuraminidase have provided significant new details about the three-dimensional characteristics of this active site thus allowing researchers to design drugs that fit tighter into the site. Principal Investigator: Dr. Larry DeLucas

  7. Profiles of the Ribbon: Systematic ENA Flux Features Within and Beyond the Central Ribbon

    NASA Astrophysics Data System (ADS)

    Funsten, H. O.; Demajistre, R.; Frisch, P. C.; Fuselier, S.; Janzen, P. H.; Livadiotis, G.; McComas, D. J.; Pittman, K. T.; Reisenfeld, D. B.; Schwadron, N.

    2014-12-01

    The ribbon of enhanced energetic neutral atom (ENA) flux is the most prominent feature of outer heliospheric ENA emission as observed by the Interstellar Boundary Explorer (IBEX). Here, we study the systematic variation of ENA flux in the ribbon and in its vicinity as a function of angle from the ribbon center at ecliptic (219°, 40°) as projected in the sky. We find that the ENA emission on the interior of the ribbon (between the ribbon and the ribbon center) is correlated with the emission brightness of the ribbon peak, whereas ENA emission on the exterior of the ribbon (between the ribbon and the antipode of the ribbon center) is not correlated with ribbon brightness. The ribbon flux falls to zero beyond a great circle in the sky at 90º from the ribbon center and is thus constrained to a hemisphere of emission that is centered on the ribbon center. These results are consistent with the "secondary" emission process of ribbon formation in the outer heliosheath [Heerikhuisen et al., 2010; McComas and Schwadron, 2013]. We additionally deconvolve the IBEX point spread function from analytical fits to the ribbon shape. We find that the ribbon peak is approximately 5% brighter than observations that do not consider the PSF. We also find a wide but consistent variation of ribbon widths, with the full width at half maximum ranging from 14º and 34º for 0.7-2.7 keV. At 4.3 keV the ribbon is consistently wider, with a 24º minimum ribbon width. We discuss the implications of the sharpness of the ribbon peak for observations of the Interstellar Mapping and Acceleration Probe (IMAP).

  8. Temporal variation of the IBEX Ribbon

    NASA Astrophysics Data System (ADS)

    Janzen, P. H.

    2015-12-01

    We present a study of the time variation over half a solar cycle of the ENA flux composing the IBEX Ribbon, with the goal of determining how closely the Ribbon's temporal variation matches that of the adjacent globally distributed ENA flux (GDF). A high degree of similarity implies that the Ribbon flux originates in the same heliospheric regions as the GDF, presumably the inner heliosheath. If the Ribbon flux shows a separate time history, then it likely originates elsewhere, possibly in the outer heliosheath or beyond. Determining the source region places strong constraints on Ribbon formation theories. Prior Ribbon studies have either treated the Ribbon and the GDF as static over the mission, or have not attempted to separate the GDF from the Ribbon when looking at time variation.

  9. Melt dumping in string stabilized ribbon growth

    DOEpatents

    Sachs, Emanuel M.

    1986-12-09

    A method and apparatus for stabilizing the edge positions of a ribbon drawn from a melt includes the use of wettable strings drawn in parallel up through the melt surface, the ribbon being grown between the strings. A furnace and various features of the crucible used therein permit continuous automatic growth of flat ribbons without close temperature control or the need for visual inspection.

  10. A spiraled niobium tin superconductive ribbon

    NASA Technical Reports Server (NTRS)

    Coles, W. D.

    1973-01-01

    Copper film is vapor-deposited on clean ribbon and sprayed with photosensitive etch-resistant material. Photographic film masks are placed on ribbon and exposed to ultraviolet light. Etchant removes copper and exposure to oxidizing atmosphere forms niobium oxide. Photosensitive material is removed and ribbon is immersed in molten temperatures.

  11. Asymmetric Die Grows Purer Silicon Ribbon

    NASA Technical Reports Server (NTRS)

    Kalejs, J. P.; Chalmers, B.; Surek, T.

    1983-01-01

    Concentration of carbide impurities in silicon ribbon is reduced by growing crystalline ribbon with die one wall higher than other. Height difference controls shape of meniscus at liquid/crystal interface and concentrates silicon carbide impurity near one of broad faces. Opposite face is left with above-average purity. Significantly improves efficiency of solar cells made from ribbon.

  12. A Review of Timeout Ribbons

    ERIC Educational Resources Information Center

    Kostewicz, Douglas E.

    2010-01-01

    Researchers and practitioners often employ timeout procedures to manage inappropriate classroom behavior. When implemented inappropriately, however, timeout can result in dangerous situations and have received increased scrutiny (i.e., seclusion). The timeout ribbon procedure can prevent some of the dangerous situations associated with other forms…

  13. Protein composition of immunoprecipitated synaptic ribbons

    PubMed Central

    Kantardzhieva, A.; Peppi, M.; Lane, W.S.; Sewell, W.F.

    2012-01-01

    The synaptic ribbon is an electron-dense structure found in hair cells and photoreceptors. The ribbon is surrounded by neurotransmitter-filled vesicles and considered to play a role in vesicle release. We generated an objective, quantitative analysis of the protein composition of the ribbon complex using a mass spectrometry-based proteomics analysis. Our use of affinity-purified ribbons and control IgG immunoprecipitations ensure that the identified proteins are indeed associated with the ribbon complex. The use of mouse tissue, where the proteome is complete, generated a comprehensive analysis of the candidates. We identified 30 proteins (comprising 56 isoforms and subunits) associated with the ribbon complex. The ribbon complex primarily comprises proteins found in conventional synapses, which we categorized into 6 functional groups: vesicle handling (38.5%), scaffold (7.3%), cytoskeletal molecules (20.6%), phosphorylation enzymes (10.6%), molecular chaperones (8.2%), and transmembrane proteins from the presynaptic membrane firmly attached to the ribbon (11.3%). The 3 CtBP isoforms represent the major protein in the ribbon whether calculated by molar amount (30%) or by mass (20%). The relatively high quantity of phosphorylation enzymes suggests a very active and regulated structure. The ribbon appears to comprise a concentrated cluster of proteins dealing with vesicle creation, retention and distribution, and consequent exocytosis. PMID:22103298

  14. TOPICAL REVIEW: New crystalline silicon ribbon materials for photovoltaics

    NASA Astrophysics Data System (ADS)

    Hahn, G.; Schönecker, A.

    2004-12-01

    The objective of this article is to review, in relation to photovoltaic applications, the current status of crystalline silicon ribbon technologies as an alternative to technologies based on wafers originating from ingots. Increased wafer demand, the foreseeable silicon feedstock shortage, and the need for a substantial module cost reduction are the main issues that must be faced in the booming photovoltaic market. Ribbon technologies make excellent use of silicon, as wafers are crystallized directly from the melt at the desired thickness and no kerf losses occur. Therefore, they offer a high potential for significantly reducing photovoltaic electricity costs as compared to technology based on wafers cut from ingots. However, the defect structure present in the ribbon silicon wafers can limit material quality and cell efficiency. We will review the most successful of the ribbon techniques already used in large scale production or currently in the pilot demonstration phase, with special emphasis on the defects incorporated during crystal growth. Because of the inhomogeneous distribution of defects, mapped characterization techniques have to be applied. Al and P gettering studies give an insight into the complex interaction of defects in the multicrystalline materials as the gettering efficiency is influenced by the state of the chemical bonding of the metal atoms. The most important technique for improvement of carrier lifetimes is hydrogenation, whose kinetics are strongly influenced by oxygen and carbon concentrations present in the material. The best cell efficiencies for laboratory-type (17%-18% cell area: 4 cm2) as well as industrial-type (15%-16% cell area: {\\ge } 80~{\\mathrm {cm^{2}}} ) ribbon silicon solar cells are in the same range as for standard wafers cut from ingots. A substantial cost reduction therefore seems achievable, although the most promising techniques need to be improved.

  15. Twisted, multifilament Nb3Sn superconductive ribbon

    NASA Technical Reports Server (NTRS)

    Coles, W. D.

    1972-01-01

    An experimental study of superconductor stabilization has resulted in the successful application of the concepts of filamentary structure and conductor twist to Nb3Sn ribbon. The Nb3Sn is formed in parallel, helical paths, which are continuous around the ribbon. Short lengths (12-18cm) of 1.27 cm wide superconductive ribbon were produced. The filamentary and twist characteristics are incorporated in the ribbon by means of an inert mask formed on the ribbon surface early in the fabrication process. Diffusion reaction of the niobium and tin is prevented at the filament boundaries. Described are the conductor methods of fabrication, and test results obtained. The technology required to adapt the processes for the production of long lengths of ribbon is available.

  16. Chirality effect in disordered graphene ribbon junctions

    NASA Astrophysics Data System (ADS)

    Long, Wen

    2012-05-01

    We investigate the influence of edge chirality on the electronic transport in clean or disordered graphene ribbon junctions. By using the tight-binding model and the Landauer-Büttiker formalism, the junction conductance is obtained. In the clean sample, the zero-magnetic-field junction conductance is strongly chirality-dependent in both unipolar and bipolar ribbons, whereas the high-magnetic-field conductance is either chirality-independent in the unipolar or chirality-dependent in the bipolar ribbon. Furthermore, we study the disordered sample in the presence of magnetic field and find that the junction conductance is always chirality-insensitive for both unipolar and bipolar ribbons with adequate disorders. In addition, the disorder-induced conductance plateaus can exist in all chiral bipolar ribbons provided the disorder strength is moderate. These results suggest that we can neglect the effect of edge chirality in fabricating electronic devices based on the magnetotransport in a disordered graphene ribbon.

  17. Ribbon NAPL sampler. Innovative Technology Summary Report

    SciTech Connect

    2000-04-01

    The FLUTE Hydrophobic Flexible Membrane is a sampling device that provides detailed delineation of Dense Nonaqueous Phase Liquids (DNAPL) in a borehole. It is deployed via a reusable nylon liner, with a hydrophobic ribbon impregnated with dye, that when converted into a borehole creates a tight contact with the walls of the borehole. When deployed, the ribbon will absorb the DNAPL that is in contact with the membrane causing a color change in the dye. Upon removal, the membrane is turned inside out and the ribbon is retrieved into the membrane. The ribbon is then removed and examined. The presence of DNAPL is indicated by brilliant red marks on the hydrophobic ribbon. Sections of ribbon can also be sent for laboratory analysis to identify the specific NAPL compounds that are present.

  18. Geothermal Technologies Program Blue Ribbon Panel Recommendations

    SciTech Connect

    none,

    2011-06-17

    The Geothermal Technologies Program assembled a geothermal Blue Ribbon Panel on March 22-23, 2011 in Albuquerque, New Mexico for a guided discussion on the future of geothermal energy in the United States and the role of the DOE Program. The Geothermal Blue Ribbon Panel Report captures the discussions and recommendations of the experts. An addendum is available here: http://www.eere.energy.gov/geothermal/pdfs/gtp_blue_ribbon_panel_report_addendum10-2011.pdf

  19. Processed-induced defects in EFG ribbons

    NASA Technical Reports Server (NTRS)

    Cunningham, B.; Ast, D. G.

    1982-01-01

    The defect structure of processed edge defined film-fed growth (EFG) silicon ribbons was studied using a variety of electron microscopic techniques. Comparison between the present results and previous studies on as-grown ribbons has shown that solar cell processing introduces additional defects into the ribbons. The creation of point defects during high temperature phosphorus diffusion induces dislocation climb, resulting in the formation of dislocation helices in the diffused layer.

  20. Evaluation of Dynamic Mechanical Loading as an Accelerated Test Method for Ribbon Fatigue: Preprint

    SciTech Connect

    Bosco, N.; Silverman, T. J.; Wohlgemuth, J.; Kurtz, S.; Inoue, M.; Sakurai, K.; Shinoda, T.; Zenkoh, H.; Hirota, K.; Miyashita, M.; Tadanori, T.; Suzuki, S.

    2015-04-07

    Dynamic Mechanical Loading (DML) of photovoltaic modules is explored as a route to quickly fatigue copper interconnect ribbons. Results indicate that most of the interconnect ribbons may be strained through module mechanical loading to a level that will result in failure in a few hundred to thousands of cycles. Considering the speed at which DML may be applied, this translates into a few hours o testing. To evaluate the equivalence of DML to thermal cycling, parallel tests were conducted with thermal cycling. Preliminary analysis suggests that one +/-1 kPa DML cycle is roughly equivalent to one standard accelerated thermal cycle and approximately 175 of these cycles are equivalent to a 25-year exposure in Golden Colorado for the mechanism of module ribbon fatigue.

  1. Evaluation of Dynamic Mechanical Loading as an Accelerated Test Method for Ribbon Fatigue

    SciTech Connect

    Bosco, Nick; Silverman, Timothy J.; Wohlgemuth, John; Kurtz, Sarah; Inoue, Masanao; Sakurai, Keiichiro; Shioda, Tsuyoshi; Zenkoh, Hirofumi; Hirota, Kusato; Miyashita, Masanori; Tadanori, Tanahashi; Suzuki, Soh; Chen, Yifeng; Verlinden, Pierre J.

    2014-12-31

    Dynamic Mechanical Loading (DML) of photovoltaic modules is explored as a route to quickly fatigue copper interconnect ribbons. Results indicate that most of the interconnect ribbons may be strained through module mechanical loading to a level that will result in failure in a few hundred to thousands of cycles. Considering the speed at which DML may be applied, this translates into a few hours of testing. To evaluate the equivalence of DML to thermal cycling, parallel tests were conducted with thermal cycling. Preliminary analysis suggests that one +/-1 kPa DML cycle is roughly equivalent to one standard accelerated thermal cycle and approximately 175 of these cycles are equivalent to a 25-year exposure in Golden Colorado for the mechanism of module ribbon fatigue.

  2. 27 CFR 9.182 - Ribbon Ridge.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ...) Approved Maps. The appropriate maps used to determine the boundaries of the Ribbon Ridge viticultural area are the following two United States Geological Survey (USGS), 1:24,000 scale, topographical maps (7.5..., Oregon, 1956, revised 1993. (c) Boundary. The Ribbon Ridge viticultural area is located in...

  3. Preventing Freezeup in Silicon Ribbon Growth

    NASA Technical Reports Server (NTRS)

    Mackintosh, B.

    1983-01-01

    Carefully-shaped heat conductor helps control thermal gradients crucial to growth of single-crystal silicon sheets for solar cells. Ends of die through which silicon sheet is drawn as ribbon from molten silicon. Profiled heat extractor prevents ribbon ends from solidifying prematurely and breaking.

  4. Contoured Orifice for Silicon-Ribbon Die

    NASA Technical Reports Server (NTRS)

    Mackintosh, B. H.

    1985-01-01

    Die configuration encourages purity and stable growth. Contour of die orifice changes near ribbon edges. As result, silicon ribbon has nearly constant width and little carbon contamination. Die part of furnace being developed to produce high-quality, low-cost material for solar cells.

  5. Helicoids, wrinkles, and loops in twisted ribbons.

    PubMed

    Chopin, Julien; Kudrolli, Arshad

    2013-10-25

    We investigate the instabilities of a flat elastic ribbon subject to twist under tension and develop an integrated phase diagram of the observed shapes and transitions. We find that the primary buckling mode switches from being localized longitudinally along the length of the ribbon to transverse above a triple point characterized by a crossover tension that scales with ribbon elasticity and aspect ratio. Far from threshold, the longitudinally buckled ribbon evolves continuously into a self-creased helicoid with focusing of the curvature along the triangular edges. Further twist causes an anomalous transition to loops compared with rods due to the self-rigidity induced by the creases. When the ribbon is twisted under high tension, transverse wrinkles are observed due to the development of compressive stresses with higher harmonics for greater width-to-length ratios. Our results can be used to develop functional structures using a wide range of elastic materials and length scales.

  6. Method for horizontally growing ribbon crystal

    NASA Technical Reports Server (NTRS)

    Kudo, B.

    1980-01-01

    A high speed method for forming ribbon crystal of desired width and thickness is characterized by drawing out the ribbon through a space whose distance is 5.7 times that of the thickness of the grown ribbon. The ribbon is drawn out between the molten body of the lower surface and the tip of the upper surface of the seed crystal and growing crystal. The ribbon growing at the tip of the seed crystal is drawn out horizontally and centrifugally by controlling the amount of cooling and heating. The temperature is maintained about equal to the upper surface of the outlets from which the molten substance is drawn, at least in certain portions of the crucible rim, the rim is elevated to prevent dropping of the molten raw material.

  7. Web-dendritic ribbon growth

    NASA Technical Reports Server (NTRS)

    Hilborn, R. B., Jr.; Faust, J. W., Jr.

    1976-01-01

    A web furnace was constructed for pulling dendritic-web samples. The effect of changes in the furnace thermal geometry on the growth of dendritic-web was studied. Several attempts were made to grow primitive dendrites for use as the dendritic seed crystals for web growth and to determine the optimum twin spacing in the dendritic seed crystal for web growth. Mathematical models and computer programs were used to determine the thermal geometries in the susceptor, crucible melt, meniscus, and web. Several geometries were determined for particular furnace geometries and growth conditions. The information obtained was used in conjunction with results from the experimental growth investigations in order to achieve proper conditions for sustained pulling of two dendrite web ribbons. In addition, the facilities for obtaining the following data were constructed: twin spacing, dislocation density, web geometry, resistivity, majority charge carrier type, and minority carrier lifetime.

  8. Carbon nanotube fiber spun from wetted ribbon

    SciTech Connect

    Zhu, Yuntian T; Arendt, Paul; Zhang, Xiefei; Li, Qingwen; Fu, Lei; Zheng, Lianxi

    2014-04-29

    A fiber of carbon nanotubes was prepared by a wet-spinning method involving drawing carbon nanotubes away from a substantially aligned, supported array of carbon nanotubes to form a ribbon, wetting the ribbon with a liquid, and spinning a fiber from the wetted ribbon. The liquid can be a polymer solution and after forming the fiber, the polymer can be cured. The resulting fiber has a higher tensile strength and higher conductivity compared to dry-spun fibers and to wet-spun fibers prepared by other methods.

  9. Apical transportation: two assessment methods.

    PubMed

    López, Fernanda Ullmann; Travessas, Juliana Andréa Corrêa; Fachin, Elaine; Fontanella, Vania; Grecca, Fabiana

    2009-08-01

    Root canal transportation can lead to treatment failure. A large number of methodologies for assessing root canal preparation have been tried in the past. This study compared two methods for apical transportation measurement: digitised images of longitudinal root sections and radiographs. Sixty upper molar mesiobuccal root canals prepared for endodontic treatment were assessed. The results did not demonstrate statistically significant differences between the two imaging methods used to evaluate root canal transportation. The two methods were proven to be equally reliable. PMID:19703081

  10. Method of growing a ribbon crystal particularly suited for facilitating automated control of ribbon width

    NASA Technical Reports Server (NTRS)

    Ciszek, T. F. (Inventor)

    1980-01-01

    A method of growing a ribbon crystal is described wherein a meniscus of molten semiconductor material attached to vertical movable seed is lifted at a rate substantially equal to the rate at which the meniscus freezes. The method is characterized by the steps of continuously sensing the brightness of the growth region of the ribbon in selected areas across the ribbon width for detecting changes in the intensity of the brightness of the selected areas, and modifying the temperature of the meniscus and pulling speed in response to changes detected in the intensity for controlling the geometry of the ribbon.

  11. 27 CFR 9.182 - Ribbon Ridge.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ..., Oregon, 1956, revised 1993. (c) Boundary. The Ribbon Ridge viticultural area is located in northern... Quadrangle map at the intersection of a light-duty road known locally as Albertson Road and Dopp Road...

  12. 27 CFR 9.182 - Ribbon Ridge.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ..., Oregon, 1956, revised 1993. (c) Boundary. The Ribbon Ridge viticultural area is located in northern... Quadrangle map at the intersection of a light-duty road known locally as Albertson Road and Dopp Road...

  13. 27 CFR 9.182 - Ribbon Ridge.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ..., Oregon, 1956, revised 1993. (c) Boundary. The Ribbon Ridge viticultural area is located in northern... Quadrangle map at the intersection of a light-duty road known locally as Albertson Road and Dopp Road...

  14. 27 CFR 9.182 - Ribbon Ridge.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ..., Oregon, 1956, revised 1993. (c) Boundary. The Ribbon Ridge viticultural area is located in northern... Quadrangle map at the intersection of a light-duty road known locally as Albertson Road and Dopp Road...

  15. Hydro Impact Basin Ribbon-Cutting Ceremony

    NASA Video Gallery

    August 9, 2011 -- Ribbon-cutting ceremony for the Hydro Impact Basin at NASA's Langley Research Center in Hampton, Va. The HIB expands NASA's capability to test and certify future spacecraft for wa...

  16. Blue Ribbon Commission Tour of Hanford Site

    SciTech Connect

    Paul Saueressig

    2010-07-14

    The Blue Ribbon Commission on America's Nuclear Future toured the Department of Energy's Hanford Site on July 14, 2010. Commission members, invited guests, and members of the public visited facilities that store high-level, radioactive waste.

  17. Blue Ribbon Commission Tour of Hanford Site

    ScienceCinema

    Paul Saueressig

    2016-07-12

    The Blue Ribbon Commission on America's Nuclear Future toured the Department of Energy's Hanford Site on July 14, 2010. Commission members, invited guests, and members of the public visited facilities that store high-level, radioactive waste.

  18. Computer design code for conical ribbon parachutes

    SciTech Connect

    Waye, D.E.

    1986-01-01

    An interactive computer design code has been developed to aid in the design of conical ribbon parachutes. The program is written to include single conical and polyconical parachute designs. The code determines the pattern length, vent diameter, radial length, ribbon top and bottom lengths, and geometric local and average porosity for the designer with inputs of constructed diameter, ribbon widths, ribbon spacings, radial width, and number of gores. The gores are designed with one mini-radial in the center with an option for the addition of two outer mini-radials. The output provides all of the dimensions necessary for the construction of the parachute. These results could also be used as input into other computer codes used to predict parachute loads.

  19. Ribbon cutting opens new ELV offices

    NASA Technical Reports Server (NTRS)

    2000-01-01

    Center Director Roy Bridges welcomes the audience to a ribbon- cutting ceremony at the E&O Building at KSC. Home for NASA's unmanned missions since 1964, the building has been renovated to house the Expendable Launch Vehicle Program.

  20. LISM Inhomogeneities and the IBEX Ribbon

    NASA Astrophysics Data System (ADS)

    Sylla, Adama; Fichtner, Horst

    2016-04-01

    The Energetic Neutral Atom (ENA) full-sky maps obtained with the Interstellar Boundary Explorer (IBEX) show an unexpected bright narrow band of increased intensity. This so-called ENA ribbon results from charge exchange of interstellar neutral atoms with protons in the inner heliosheath and/or beyond. According to a recent hypothesis this ribbon may be related to a neutral density enhancement, a so-called H-wave, in the local interstellar medium. It is shown on the basis of an analytical model of the principal large-scale heliospheric structure that this scenario for the ribbon formation is consistent with the observed location of the ribbon in the full-sky maps at all energies detected with high-energy sensor IBEX-Hi.

  1. On the Geometry of the IBEX Ribbon

    NASA Astrophysics Data System (ADS)

    Sylla, Adama; Fichtner, Horst

    2015-10-01

    The Energetic Neutral Atom (ENA) full-sky maps obtained with the Interstellar Boundary Explorer (IBEX) show an unexpected bright narrow band of increased intensity. This so-called ENA ribbon results from charge exchange of interstellar neutral atoms with protons in the outer heliosphere or beyond. Among other hypotheses it has been argued that this ribbon may be related to a neutral density enhancement, or H-wave, in the local interstellar medium. Here we quantitatively demonstrate, on the basis of an analytical model of the principal large-scale heliospheric structure, that this scenario for the ribbon formation leads to results that are fully consistent with the observed location of the ribbon in the full-sky maps at all energies detected with high-energy sensor IBEX-Hi.

  2. NAPL Characterization Using the Ribbon NAPL Sampler

    SciTech Connect

    Riha, B.D.

    1999-12-01

    The Ribbon NAPL Sampler (RNS) is a direct sampling device that can provide detailed depth discrete mapping of Non Aqueous Phase Liquids (NAPLs - liquid solvents and/or petroleum products) in a borehole.

  3. Blue Ribbon Panel Report Cover Letter

    Cancer.gov

    The letter from NCI Acting Director Douglas R. Lowy, M.D., to Vice President Biden that accompanied the Blue Ribbon Panel final report, thanking the Vice President for his commitment to and leadership of the Cancer Moonshot.

  4. Blue Ribbon Panel 2016 Video Playlist

    Cancer.gov

    Blue Ribbon Panel members discuss recommendations from the panel report that was presented to the National Cancer Advisory Board. The playlist includes an overview video and 10 videos on the specific recommendations.

  5. Blue Ribbon Panel Report - BRP - Cancer Moonshot

    Cancer.gov

    The Blue Ribbon Panel Report outlines 10 recommendations to accelerate progress against cancer. The panel was established to ensure that the Cancer Moonshot's approaches are grounded in the best science.

  6. Stripe states in photonic honeycomb ribbon

    PubMed Central

    Park, Sul-Ah; Son, Young-Woo; Ahn, Kang-Hun

    2015-01-01

    We reveal new stripe states in deformed hexagonal array of photonic wave guides when the array is terminated to have a ribbon-shaped geometry. Unlike the well-known zero energy edge modes of honeycomb ribbon, the new one-dimensional states are shown to originate from high-energy saddle-shaped photonic bands of the ribbon's two-dimensional counterpart. We find that the strain field deforming the ribbon generates pseudo-electric fields in contrast to pseudo-magnetic fields in other hexagonal crystals. Thus, the stripe states experience Bloch oscillation without any actual electric field so that the spatial distributions of stripes have a singular dependence on the strength of the field. The resulting stripe states are located inside the bulk and their positions depend on their energies. PMID:27547090

  7. Defect structure of EFG silicon ribbon

    NASA Technical Reports Server (NTRS)

    Strunk, H.; Cunningham, B.; Ast, D.

    1980-01-01

    The defect structure of EFG ribbons was studied using EBIC, TEM and HVEM. By imaging the same areas in EBIC and HVEM, a direct correlation between the crystallographic nature of defects and their electrical properties was obtained. (1) Partial dislocations at coherent twin boundaries may or may not be electrically active. Since no microprecipitates were observed at these dislocations it is likely that the different electrical activity is a consequence of the different dislocation core structures. (2) 2nd order twin joins were observed which followed the same direction as the coherent first order twins normally associated with EFG ribbons. These 2nd order twin joins are in all cases strongly electrically active. EFG ribbons contain high concentrations of carbon. Since no evidence of precipitation was found with TEM it is suggested that the carbon may be incorporated into the higher order twin boundaries now known to exist in EFG ribbons.

  8. Pressure distributions on parachute ribbon shapes

    SciTech Connect

    Henfling, J.F.; Purvis, J.W.

    1984-01-01

    Pressure distributions across the surface of parachute ribbons in a low-speed flow were measured. The data were taken at five chordwise points and several spanwise stations using flexible pressure tubes sewn to the ribbons. The measured data indicate that angle-of-attack and curvature both have significant effects on the pressure loading distribution, and that an assumption of constant pressure loading may give large errors in shape and stress prediction methods.

  9. Relation between strings and ribbon knots

    NASA Astrophysics Data System (ADS)

    Ahmed, E.; El-Rifai, E. A.; Abdellatif, R. A.

    1991-02-01

    A ribbon knot can be represented as the propagation of an open string in (Euclidean) space-time. By imposing physical conditions plus an ansatz on the string scattering amplitude, we get invariant polynomials of ribbon knots which correspond to Jones and Wadati et al. polynomials for ordinary knots. Motivated by the string scattering vertices, we derive an algebra which is a generalization of Hecke and Murakami-Birman-Wenzel (BMW) algebras of knots.

  10. SPECTROSCOPIC OBSERVATIONS OF AN EVOLVING FLARE RIBBON SUBSTRUCTURE SUGGESTING ORIGIN IN CURRENT SHEET WAVES

    SciTech Connect

    Brannon, S. R.; Longcope, D. W.; Qiu, J.

    2015-09-01

    We present imaging and spectroscopic observations from the Interface Region Imaging Spectrograph of the evolution of the flare ribbon in the SOL2014-04-18T13:03 M-class flare event, at high spatial resolution and time cadence. These observations reveal small-scale substructure within the ribbon, which manifests as coherent quasi-periodic oscillations in both position and Doppler velocities. We consider various alternative explanations for these oscillations, including modulation of chromospheric evaporation flows. Among these, we find the best support for some form of wave localized to the coronal current sheet, such as a tearing mode or Kelvin–Helmholtz instability.

  11. Electronically tunable extraordinary optical transmission in graphene plasmonic ribbons coupled to subwavelength metallic slit arrays

    NASA Astrophysics Data System (ADS)

    Kim, Seyoon; Jang, Min Seok; Brar, Victor W.; Tolstova, Yulia; Mauser, Kelly W.; Atwater, Harry A.

    2016-08-01

    Subwavelength metallic slit arrays have been shown to exhibit extraordinary optical transmission, whereby tunnelling surface plasmonic waves constructively interfere to create large forward light propagation. The intricate balancing needed for this interference to occur allows for resonant transmission to be highly sensitive to changes in the environment. Here we demonstrate that extraordinary optical transmission resonance can be coupled to electrostatically tunable graphene plasmonic ribbons to create electrostatic modulation of mid-infrared light. Absorption in graphene plasmonic ribbons situated inside metallic slits can efficiently block the coupling channel for resonant transmission, leading to a suppression of transmission. Full-wave simulations predict a transmission modulation of 95.7% via this mechanism. Experimental measurements reveal a modulation efficiency of 28.6% in transmission at 1,397 cm-1, corresponding to a 2.67-fold improvement over transmission without a metallic slit array. This work paves the way for enhancing light modulation in graphene plasmonics by employing noble metal plasmonic structures.

  12. Electric gating induced bandgaps and enhanced Seebeck effect in zigzag bilayer graphene ribbons

    NASA Astrophysics Data System (ADS)

    Vu, Thanh-Tra; Tran, Van-Truong

    2016-08-01

    We theoretically investigate the effect of a transverse electric field generated by side gates and a vertical electric field generated by top/back gates on energy bands and transport properties of zigzag bilayer graphene ribbons (Bernal stacking). Using atomistic tight binding calculations and Green’s function formalism we demonstrate that a bandgap is opened when either field is applied and even enlarged under simultaneous influence of the two fields. Interestingly, although vertical electric fields are widely used to control the bandgap in bilayer graphene, here we show that transverse fields exhibit a more positive effect in terms of modulating a larger range of bandgap and retaining good electrical conductance. The Seebeck effect is also demonstrated to be enhanced strongly—by about 13 times for a zigzag bilayer graphene ribbon with 16 chain lines. These results may motivate new designs of devices made of bilayer graphene ribbons using electric gates.

  13. Onset coding is degraded in auditory nerve fibers from mutant mice lacking synaptic ribbons

    PubMed Central

    Buran, B.N.; Strenzke, N.; Neef, A.; Gundelfinger, E.D.; Moser, T.; Liberman, M.C.

    2010-01-01

    Synaptic ribbons, found at the pre-synaptic membrane of sensory cells in both ear and eye, have been implicated in the vesicle-pool dynamics of synaptic transmission. To elucidate ribbon function, we characterized the response properties of single auditory nerve fibers in mice lacking Bassoon, a scaffolding protein involved in anchoring ribbons to the membrane. In Bassoon mutants, immunohistochemistry showed fewer than 3% of the hair cells’ afferent synapses retained anchored ribbons. Auditory nerve fibers from mutants had normal threshold, dynamic range and post-onset adaptation in response to tone bursts, and they were able to phase-lock with normal precision to amplitude-modulated tones. However, spontaneous and sound-evoked discharge rates were reduced, and the reliability of spikes, particularly at stimulus onset, was significantly degraded as shown by an increased variance of first-spike latencies. Modeling based on in vitro studies of normal and mutant hair cells links these findings to reduced release rates at the synapse. The degradation of response reliability in these mutants suggests that the ribbon and/or bassoon normally facilitate high rates of exocytosis and that its absence significantly compromises the temporal resolving power of the auditory system. PMID:20519533

  14. Onset coding is degraded in auditory nerve fibers from mutant mice lacking synaptic ribbons.

    PubMed

    Buran, Bradley N; Strenzke, Nicola; Neef, Andreas; Gundelfinger, Eckart D; Moser, Tobias; Liberman, M Charles

    2010-06-01

    Synaptic ribbons, found at the presynaptic membrane of sensory cells in both ear and eye, have been implicated in the vesicle-pool dynamics of synaptic transmission. To elucidate ribbon function, we characterized the response properties of single auditory nerve fibers in mice lacking Bassoon, a scaffolding protein involved in anchoring ribbons to the membrane. In bassoon mutants, immunohistochemistry showed that fewer than 3% of the hair cells' afferent synapses retained anchored ribbons. Auditory nerve fibers from mutants had normal threshold, dynamic range, and postonset adaptation in response to tone bursts, and they were able to phase lock with normal precision to amplitude-modulated tones. However, spontaneous and sound-evoked discharge rates were reduced, and the reliability of spikes, particularly at stimulus onset, was significantly degraded as shown by an increased variance of first-spike latencies. Modeling based on in vitro studies of normal and mutant hair cells links these findings to reduced release rates at the synapse. The degradation of response reliability in these mutants suggests that the ribbon and/or Bassoon normally facilitate high rates of exocytosis and that its absence significantly compromises the temporal resolving power of the auditory system.

  15. Acute destruction of the synaptic ribbon reveals a role for the ribbon in vesicle priming

    PubMed Central

    Snellman, Josefin; Mehta, Bhupesh; Babai, Norbert; Bartoletti, Theodore M.; Akmentin, Wendy; Francis, Adam; Matthews, Gary; Thoreson, Wallace; Zenisek, David

    2011-01-01

    In vision, balance, and hearing, sensory receptor cells translate sensory stimuli into electrical signals whose amplitude is graded with stimulus intensity. The output synapses of these sensory neurons must provide fast signaling to follow rapidly changing stimuli, while also transmitting graded information covering a wide range of stimulus intensity and sustained for long time periods. To meet these demands, specialized machinery for transmitter release—the synaptic ribbon—has evolved at the synaptic outputs of these neurons. Here we show that acute disruption of synaptic ribbons by photodamage to the ribbon dramatically reduces both sustained and transient components of neurotransmitter release in mouse bipolar cells and salamander cones, without affecting the ultrastructure of the ribbon or its ability to localize synaptic vesicles to the active zone. Our results indicate that ribbons mediate slow as well as fast signaling at sensory synapses, and support an additional role for the synaptic ribbon in priming vesicles for exocytosis at active zones. PMID:21785435

  16. Thermoplastic Ribbon-Ply Bonding Model

    NASA Technical Reports Server (NTRS)

    Hinkley, Jeffrey A.; Marchello, Joseph M.; Messier, Bernadette C.

    1996-01-01

    The aim of the present work was to identify key variables in rapid weldbonding of thermoplastic tow (ribbon) and their relationship to matrix polymer properties and to ribbon microstructure. Theoretical models for viscosity, establishment of ply-ply contact, instantaneous (Velcro) bonding, molecular interdiffusion (healing), void growth suppression, and gap filling were reviewed and synthesized. Consideration of the theoretical bonding mechanisms and length scales and of the experimental weld/peel data allow the prediction of such quantities as the time and pressure required to achieve good contact between a ribbon and a flat substrate, the time dependence of bond strength, pressures needed to prevent void growth from dissolved moisture and conditions for filling gaps and smoothing overlaps.

  17. Ballistic thermal conductance of graphene ribbons.

    PubMed

    Muñoz, Enrique; Lu, Jianxin; Yakobson, Boris I

    2010-05-12

    An elastic-shell-based theory for calculating the thermal conductance of graphene ribbons of arbitrary width w is presented. The analysis of vibrational modes of a continuum thin plate leads to a general equation for ballistic conductance sigma. At low temperature, it yields a power law sigma approximately T(beta), where the exponent beta varies with the ribbon width w from beta = 1 for a narrow ribbon (sigma approximately T, as a four-channel quantum wire) to beta = (3)/(2) (sigma approximately wT(3/2)) in the limit of wider graphene sheets. The ballistic results can be augmented by the phenomenological value of a phonon mean free path to account for scattering and agree well with the reported experimental observations. PMID:20402531

  18. The bridge-region of the Ku superfamily is an atypical zinc ribbon domain

    PubMed Central

    Krishna, S. Sri; Aravind, L.

    2010-01-01

    Members of the Ku superfamily are DNA-end-binding proteins involved in non-homologous end-joining (NHEJ) DNA repair. The published crystal structure of human Ku-DNA complex reveals a heterodimer that forms a ring around dsDNA by means of the Ku core modules. These modules contain a highly conserved seven-stranded β-barrel, which in turn contains an insertion, termed the bridge-region, between its second and third β-strands. The bridge-region adopts an unusual β-strand-rich structure critical for dsDNA-binding and Ku function, but its provenance remains unclear. Here, we demonstrate that the bridge-region of Ku is a novel member of the diverse Zn-ribbon fold group. Sequence analysis reveals that Ku from several Gram-positive bacteria and bacteriophages retain metal-chelating motifs, whereas they have been lost in the versions from most other organisms. Structural comparisons suggest that the Zn-ribbon from Ku bridge-region is the first example of a circularly permuted, segment-swapped Zn-ribbon. This finding helps explain how Ku is likely to bind DNA as an obligate dimer. Further, we hypothesize that retention of the unusual conformation of the turns of the Zn-ribbons, despite loss of the Zn-binding sites, provides clues regarding the mechanism by which the Ku bridge-regions sense the DNA state. PMID:20580930

  19. Ribbon rod for use in oil well apparatus

    SciTech Connect

    Tanner, C.J.; Bender, R.E.; Simson, A.K.; McCutchen, H. Jr.

    1986-01-07

    This patent describes a ribbon rod for use in oil well tubing as a replacement for a conventional steel sucker rod. The ribbon rod consists of: an elongated ribbon having a core of relatively stiff material that still has a degree of flexibility such that the ribbon is capable of being wound onto and dispensed from a rotatable reel and can support the weight of oil pumping apparatus attached to a downhole portion of the ribbon, the ribbon core having opposed side surfaces and relatively narrow end surfaces joining the side surfaces; a ply of fabric overlying the side surfaces to provide transverse strength to the ribbon rod; and corner tows extending over the end surfaces to provide damage resistance to the ribbon as it is raised and lowered in the oil well tubing.

  20. Low-loss terahertz ribbon waveguides.

    PubMed

    Yeh, Cavour; Shimabukuro, Fred; Siegel, Peter H

    2005-10-01

    The submillimeter wave or terahertz (THz) band (1 mm-100 microm) is one of the last unexplored frontiers in the electromagnetic spectrum. A major stumbling block hampering instrument deployment in this frequency regime is the lack of a low-loss guiding structure equivalent to the optical fiber that is so prevalent at the visible wavelengths. The presence of strong inherent vibrational absorption bands in solids and the high skin-depth losses of conductors make the traditional microstripline circuits, conventional dielectric lines, or metallic waveguides, which are common at microwave frequencies, much too lossy to be used in the THz bands. Even the modern surface plasmon polariton waveguides are much too lossy for long-distance transmission in the THz bands. We describe a concept for overcoming this drawback and describe a new family of ultra-low-loss ribbon-based guide structures and matching components for propagating single-mode THz signals. For straight runs this ribbon-based waveguide can provide an attenuation constant that is more than 100 times less than that of a conventional dielectric or metallic waveguide. Problems dealing with efficient coupling of power into and out of the ribbon guide, achieving low-loss bends and branches, and forming THz circuit elements are discussed in detail. One notes that active circuit elements can be integrated directly onto the ribbon structure (when it is made with semiconductor material) and that the absence of metallic structures in the ribbon guide provides the possibility of high-power carrying capability. It thus appears that this ribbon-based dielectric waveguide and associated components can be used as fundamental building blocks for a new generation of ultra-high-speed electronic integrated circuits or THz interconnects.

  1. Low-loss terahertz ribbon waveguides

    NASA Astrophysics Data System (ADS)

    Yeh, Cavour; Shimabukuro, Fred; Siegel, Peter H.

    2005-10-01

    The submillimeter wave or terahertz (THz) band (1 mm-100 µm) is one of the last unexplored frontiers in the electromagnetic spectrum. A major stumbling block hampering instrument deployment in this frequency regime is the lack of a low-loss guiding structure equivalent to the optical fiber that is so prevalent at the visible wavelengths. The presence of strong inherent vibrational absorption bands in solids and the high skin-depth losses of conductors make the traditional microstripline circuits, conventional dielectric lines, or metallic waveguides, which are common at microwave frequencies, much too lossy to be used in the THz bands. Even the modern surface plasmon polariton waveguides are much too lossy for long-distance transmission in the THz bands. We describe a concept for overcoming this drawback and describe a new family of ultra-low-loss ribbon-based guide structures and matching components for propagating single-mode THz signals. For straight runs this ribbon-based waveguide can provide an attenuation constant that is more than 100 times less than that of a conventional dielectric or metallic waveguide. Problems dealing with efficient coupling of power into and out of the ribbon guide, achieving low-loss bends and branches, and forming THz circuit elements are discussed in detail. One notes that active circuit elements can be integrated directly onto the ribbon structure (when it is made with semiconductor material) and that the absence of metallic structures in the ribbon guide provides the possibility of high-power carrying capability. It thus appears that this ribbon-based dielectric waveguide and associated components can be used as fundamental building blocks for a new generation of ultra-high-speed electronic integrated circuits or THz interconnects.

  2. CIRCULAR RIBBON FLARES AND HOMOLOGOUS JETS

    SciTech Connect

    Wang Haimin; Liu Chang

    2012-12-01

    Solar flare emissions in the chromosphere often appear as elongated ribbons on both sides of the magnetic polarity inversion line (PIL), which has been regarded as evidence of a typical configuration of magnetic reconnection. However, flares having a circular ribbon have rarely been reported, although it is expected in the fan-spine magnetic topology involving reconnection at a three-dimensional (3D) coronal null point. We present five circular ribbon flares with associated surges, using high-resolution and high-cadence H{alpha} blue wing observations obtained from the recently digitized films of Big Bear Solar Observatory. In all the events, a central parasitic magnetic field is encompassed by the opposite polarity, forming a circular PIL traced by filament material. Consequently, a flare kernel at the center is surrounded by a circular flare ribbon. The four homologous jet-related flares on 1991 March 17 and 18 are of particular interest, as (1) the circular ribbons brighten sequentially, with cospatial surges, rather than simultaneously, (2) the central flare kernels show an intriguing 'round-trip' motion and become elongated, and (3) remote brightenings occur at a region with the same magnetic polarity as the central parasitic field and are co-temporal with a separate phase of flare emissions. In another flare on 1991 February 25, the circular flare emission and surge activity occur successively, and the event could be associated with magnetic flux cancellation across the circular PIL. We discuss the implications of these observations combining circular flare ribbons, homologous jets, and remote brightenings for understanding the dynamics of 3D magnetic restructuring.

  3. Conductance quantization in strongly disordered graphene ribbons

    NASA Astrophysics Data System (ADS)

    Ihnatsenka, S.; Kirczenow, G.

    2009-11-01

    We present numerical studies of conduction in graphene nanoribbons with different types of disorder. We find that even when defect scattering depresses the conductance to values two orders of magnitude lower than 2e2/h , equally spaced conductance plateaus occur at moderately low temperatures due to enhanced electron backscattering near subband edge energies if bulk vacancies are present in the ribbon. This work accounts quantitatively for the surprising conductance quantization observed by Lin [Phys. Rev. B 78, 161409(R) (2008)] in ribbons with such low conductances.

  4. Steady state stresses in ribbon parachute canopies

    NASA Technical Reports Server (NTRS)

    Garrard, W. L.; Wu, K. Y.; Muramoto, K. K.

    1984-01-01

    An experimental study of the steady state stresses in model ribbon parachute canopies is presented. The distribution of circumferential stress was measured in the horizontal ribbons of two parachutes using Omega sensors. Canopy pressure distributions and overall drag were also measured. Testing was conducted in the University of Minnesota Low-Speed Wind Tunnel at dynamic pressures ranging from 1.0 to 1.5 inches of water. The stresses in the parachute canopies were calculated using the parachute structural analysis code, CANO. It was found that the general shape of the measured and calculated stress distributions was fairly similar; however, the measured stresses were somewhat less than the calculated stresses.

  5. Genetic Predisposition to Persistent Apical Periodontitis

    PubMed Central

    Morsani, Jussara M.; Aminoshariae, Anita; Han, Yiping Weng; Montagnese, Thomas A.; Mickel, Andre

    2013-01-01

    Introduction The proinflammatory cytokine interleukin (IL)-1 is a key regulator of host responses to microbial infection and a major modulator of extracellular matrix catabolism and bone resorption. Allele2 of IL-1b is associated with a four-fold increase in IL-1β production. The aim of this case-control study was to evaluate the gene polymorphism of IL-1β in the pathogenesis of endodontic failure. We hypothesized that the gene polymorphism (allele2 of IL-1β) would influence host response and enhance inflammatory reactions predisposing to persistent apical periodontitis (PAP). Materials and Methods Subjects with at least 1 year of follow-up after root canal therapy (RCT) were recalled. Inclusion and exclusion criteria were applied, and 34 subjects with signs/symptoms of PAP with otherwise acceptable RCT were included. Sixty-one controls showed healing with acceptable RCT. Genomic DNA from buccal mucosa was amplified by polymerase chain reaction followed by restriction fragment length polymorphism to distinguish the alleles of IL-1β gene polymorphism. Results A significant difference in the distribution of the polymorphic genotype among cases (70.6%) and controls (24.6%) (P < .001, Pearson χ2) was shown. Conclusions These findings suggest that specific genetic markers associated with increased IL-1β production may contribute to increased susceptibility to PAP. PMID:21419289

  6. 7 CFR 1217.2 - Blue Ribbon Commission or BRC.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 7 Agriculture 10 2013-01-01 2013-01-01 false Blue Ribbon Commission or BRC. 1217.2 Section 1217.2... Education, and Industry Information Order Definitions § 1217.2 Blue Ribbon Commission or BRC. Blue Ribbon Commission or BRC means the 21-member committee representing businesses that manufacture softwood lumber...

  7. 7 CFR 1217.2 - Blue Ribbon Commission or BRC.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 7 Agriculture 10 2012-01-01 2012-01-01 false Blue Ribbon Commission or BRC. 1217.2 Section 1217.2... Education, and Industry Information Order Definitions § 1217.2 Blue Ribbon Commission or BRC. Blue Ribbon Commission or BRC means the 21-member committee representing businesses that manufacture softwood lumber...

  8. 7 CFR 1217.2 - Blue Ribbon Commission or BRC.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 7 Agriculture 10 2014-01-01 2014-01-01 false Blue Ribbon Commission or BRC. 1217.2 Section 1217.2... Education, and Industry Information Order Definitions § 1217.2 Blue Ribbon Commission or BRC. Blue Ribbon Commission or BRC means the 21-member committee representing businesses that manufacture softwood lumber...

  9. Direct Observation of Morphological Tranformation from Twisted Ribbons into Helical Ribbons

    SciTech Connect

    Pashuck, E.Thomas; Stupp, Samuel I.

    2010-07-01

    We report on the direct observation of a nanostructural transformation from a twisted ribbon to a helical ribbon in supramolecular assemblies of peptide amphiphiles. Using cryogenic electron microscopy, a peptide amphiphile molecule containing aromatic residues was found to first assemble into short twisted ribbons in the time range of seconds, which then elongate in the time scale of minutes, and finally transform into helical ribbons over the course of weeks. By synthesizing an analogous molecule without the aromatic side groups, it was found that a cylindrical nanostructure is formed that does not undergo any transitions during the same time period. The study of metastable states in peptide aggregation can contribute to our understanding of amyloid-related diseases, such as Alzheimer's disease.

  10. Ribbon cutting opens new ELV offices

    NASA Technical Reports Server (NTRS)

    2000-01-01

    Bobby Bruckner, manager, ELV and Payload Carrier Programs, speaks at the ribbon-cutting ceremony of the E&O Building at KSC. Home for NASA's unmanned missions since 1964, the building has been renovated to house the Expendable Launch Vehicle Program.

  11. Practices of Blue Ribbon Catholic Schools, 2001.

    ERIC Educational Resources Information Center

    Kealey, Robert J., Comp.

    For almost 20 years, the U.S. Department of Education has invited schools to seek the Blue Ribbon School Award. A large number of Catholic schools have received this award. For this publication, the Department of Elementary Schools Executive Committee requested principals of awarded schools to write a short article on an exemplary school program…

  12. Defect characterization of silicon dendritic web ribbons

    NASA Technical Reports Server (NTRS)

    Cheng, L. J.

    1985-01-01

    Progress made in the study of defect characterization of silicon dendritic web ribbon is presented. Chemical etching is used combined with optical microscopy, as well as the electron beam induced current (EBIC) technique. Thermal annealing effect on carrier lifetime is examined.

  13. Paramagnetic colloidal ribbons in a precessing magnetic field

    NASA Astrophysics Data System (ADS)

    Alvarez-Nodarse, R.; Quintero, N. R.; Mertens, F. G.; Casic, N.; Fischer, Th. M.

    2015-03-01

    We investigate the dynamics of a kink in a damped parametrically driven nonlinear Klein-Gordon equation. We show by using a method of averaging that, in the high-frequency limit, the kink moves in an effective potential and is driven by an effective constant force. We demonstrate that the shape of the solitary wave can be controlled via the frequency and the eccentricity of the modulation. This is in accordance with the experimental results reported in a recent paper [Casic et al., Phys. Rev. Lett. 110, 168302 (2013), 10.1103/PhysRevLett.110.168302], where the dynamic self-assembly and propulsion of a ribbon formed from paramagnetic colloids in a time-dependent magnetic field has been studied.

  14. Paramagnetic colloidal ribbons in a precessing magnetic field.

    PubMed

    Alvarez-Nodarse, R; Quintero, N R; Mertens, F G; Casic, N; Fischer, Th M

    2015-03-01

    We investigate the dynamics of a kink in a damped parametrically driven nonlinear Klein-Gordon equation. We show by using a method of averaging that, in the high-frequency limit, the kink moves in an effective potential and is driven by an effective constant force. We demonstrate that the shape of the solitary wave can be controlled via the frequency and the eccentricity of the modulation. This is in accordance with the experimental results reported in a recent paper [Casic et al., Phys. Rev. Lett. 110, 168302 (2013)], where the dynamic self-assembly and propulsion of a ribbon formed from paramagnetic colloids in a time-dependent magnetic field has been studied.

  15. Subscale Test Program for the Orion Conical Ribbon Drogue Parachute

    NASA Technical Reports Server (NTRS)

    Sengupta, Anita; Stuart, Phil; Machin, Ricardo; Bourland, Gary; Schwing, Allen; Longmire, Ellen; Henning, Elsa; Sinclair, Rob

    2011-01-01

    A subscale wind tunnel test program for Orion's conical ribbon drogue parachute is under development. The desired goals of the program are to quantify aerodynamic performance of the parachute in the wake of the entry vehicle, including understanding of the coupling of the parachute and command module dynamics, and an improved understanding of the load distribution within the textile elements of the parachute. The test program is ten percent of full scale conducted in a 3x2.1 m (10x7 ft) closed loop subsonic wind tunnel. The subscale test program is uniquely suited to probing the aerodynamic and structural environment in both a quantitative and qualitative manner. Non-intrusive diagnostics, including Particle Image Velocimetry for wake velocity surveys, high speed pressure transducers for canopy pressure distribution, and a high speed photogrammetric reconstruction, will be used to quantify the parachute's performance.

  16. Surgical treatments for vaginal apical prolapse

    PubMed Central

    Kong, Mi Kyung

    2016-01-01

    Pelvic organ prolapse is a common condition, occurring in up to 11% of women in the United States. Often, pelvic organ prolapse recurs after surgery; when it recurs after hysterectomy, it frequently presents as vaginal apical prolapse. There are many different surgical treatments for vaginal apical prolapse; among them, abdominal sacral colpopexy is considered the gold standard. However, recent data reveal that other surgical procedures also result in good outcome. This review discusses the various surgical treatments for vaginal apical prolapse including their risks and benefits. PMID:27462591

  17. Innervation regulates synaptic ribbons in lateral line mechanosensory hair cells.

    PubMed

    Suli, Arminda; Pujol, Remy; Cunningham, Dale E; Hailey, Dale W; Prendergast, Andrew; Rubel, Edwin W; Raible, David W

    2016-06-01

    Failure to form proper synapses in mechanosensory hair cells, the sensory cells responsible for hearing and balance, leads to deafness and balance disorders. Ribbons are electron-dense structures that tether synaptic vesicles to the presynaptic zone of mechanosensory hair cells where they are juxtaposed with the post-synaptic endings of afferent fibers. They are initially formed throughout the cytoplasm, and, as cells mature, ribbons translocate to the basolateral membrane of hair cells to form functional synapses. We have examined the effect of post-synaptic elements on ribbon formation and maintenance in the zebrafish lateral line system by observing mutants that lack hair cell innervation, wild-type larvae whose nerves have been transected and ribbons in regenerating hair cells. Our results demonstrate that innervation is not required for initial ribbon formation but suggest that it is crucial for regulating the number, size and localization of ribbons in maturing hair cells, and for ribbon maintenance at the mature synapse.

  18. Process and apparatus for growing a crystal ribbon

    NASA Technical Reports Server (NTRS)

    Thornhill, J. W. (Inventor)

    1984-01-01

    A process and apparatus is disclosed for growing a crystal ribbon of a substance of theoretically infinite length from a melt of the substance. A pair of fixedly positioned edge defining members are partially submerged into the melt so as to break the surface of the melt at a predetermined distance from one another. The edge defining members are wettable by the melt and the predetermined distance substantially corresponds to the width of the crystal ribbon to be grown. The crystal ribbon is grown by contacting the surface of the melt with a seed ribbon between the edge defining members whereby a meniscus of the melt is established on the seed ribbon. The meniscus is stabilized by the meniscus of the melt on the edge defining members. Pulling the seed crystal ribbon away from the melt results in continuous growth of the crystal ribbon.

  19. Innervation regulates synaptic ribbons in lateral line mechanosensory hair cells.

    PubMed

    Suli, Arminda; Pujol, Remy; Cunningham, Dale E; Hailey, Dale W; Prendergast, Andrew; Rubel, Edwin W; Raible, David W

    2016-06-01

    Failure to form proper synapses in mechanosensory hair cells, the sensory cells responsible for hearing and balance, leads to deafness and balance disorders. Ribbons are electron-dense structures that tether synaptic vesicles to the presynaptic zone of mechanosensory hair cells where they are juxtaposed with the post-synaptic endings of afferent fibers. They are initially formed throughout the cytoplasm, and, as cells mature, ribbons translocate to the basolateral membrane of hair cells to form functional synapses. We have examined the effect of post-synaptic elements on ribbon formation and maintenance in the zebrafish lateral line system by observing mutants that lack hair cell innervation, wild-type larvae whose nerves have been transected and ribbons in regenerating hair cells. Our results demonstrate that innervation is not required for initial ribbon formation but suggest that it is crucial for regulating the number, size and localization of ribbons in maturing hair cells, and for ribbon maintenance at the mature synapse. PMID:27103160

  20. CORROSION STUDY OF AMORPHOUS METAL RIBBONS

    SciTech Connect

    Lian, T; Day, S D; Farmer, J C

    2006-07-31

    Corrosion costs the Department of Defense billions of dollars every year, with an immense quantity of material in various structures undergoing corrosion. For example, in addition to fluid and seawater piping, ballast tanks, and propulsions systems, approximately 345 million square feet of structure aboard naval ships and crafts require costly corrosion control measures. The use of advanced corrosion-resistant materials to prevent the continuous degradation of this massive surface area would be extremely beneficial. The potential advantages of amorphous metals have been recognized for some time [Latanison 1985]. Iron-based corrosion-resistant, amorphous-metal coatings under development may prove important for maritime applications [Farmer et al. 2005]. Such materials could also be used to coat the entire outer surface of containers for the transportation and long-term storage of spent nuclear fuel, or to protect welds and heat affected zones, thereby preventing exposure to environments that might cause stress corrosion cracking [Farmer et al. 1991, 2000a, 2000b]. In the future, it may be possible to substitute such high-performance iron-based materials for more-expensive nickel-based alloys, thereby enabling cost savings in a wide variety of industrial applications. It should be noted that thermal-spray ceramic coatings have also been investigated for such applications [Haslam et al. 2005]. This report focuses on the corrosion resistance of iron-based melt-spun amorphous metal ribbons. Melt-Spun ribbon is made by rapid solidification--a stream of molten metal is dropped onto a spinning copper wheel, a process that enables the manufacture of amorphous metals which are unable to be manufactured by conventional cold or hot rolling techniques. The study of melt-spun ribbon allows quick evaluation of amorphous metals corrosion resistance. The melt-spun ribbons included in this study are DAR40, SAM7, and SAM8, SAM1X series, and SAM2X series. The SAM1X series ribbons have

  1. Advanced Pointing Imaging Camera (APIC) Concept

    NASA Astrophysics Data System (ADS)

    Park, R. S.; Bills, B. G.; Jorgensen, J.; Jun, I.; Maki, J. N.; McEwen, A. S.; Riedel, E.; Walch, M.; Watkins, M. M.

    2016-10-01

    The Advanced Pointing Imaging Camera (APIC) concept is envisioned as an integrated system, with optical bench and flight-proven components, designed for deep-space planetary missions with 2-DOF control capability.

  2. Mobility and Turnover of Vesicles at the Synaptic Ribbon

    PubMed Central

    LoGiudice, Lisamarie; Sterling, Peter; Matthews, Gary

    2008-01-01

    Ribbon synapses release neurotransmitter continuously at high rates, and the ribbons tether a large pool of synaptic vesicles. To determine if the tethered vesicles are actually released, we tracked vesicles labeled with FM4-64 dye in mouse retinal bipolar cell terminals whose ribbons had been labeled with a fluorescent peptide. We photobleached vesicles in regions with ribbons and without them and then followed recovery of fluorescence as bleached regions were repopulated by labeled vesicles. In the resting terminal, fluorescence recovered by ~50% in non-ribbon regions, but by only ~20% at ribbons. Thus, at rest, vesicles associated with ribbons cannot exchange freely with cytoplasmic vesicles. Depolarization stimulated vesicle turnover at ribbons as bleached, immobile vesicles were released by exocytosis and were then replaced by fluorescent vesicles from the cytoplasm, producing a further increase in fluorescence specifically at the ribbon location. We conclude that vesicles immobilized at synaptic ribbons participate in the readily releasable pool that is tapped rapidly during depolarization. PMID:18354018

  3. Edge Stabilized Ribbon (ESR); Stress, Dislocation Density and Electronic Performance

    NASA Technical Reports Server (NTRS)

    Sachs, E. M.

    1984-01-01

    The edge stabilized ribbon (ESR) silicon ribbon was grown in widths of 1, 2.2 and 4.0 inches at speeds ranging from .6 to 7 in/min, which result in ribbon thicknesses of 5 to 400 microns. One of the primary problems remaining in ESR growth is that of thermally induced mechanical stresses. This problem is manifested as ribbon with a high degree of residual stress or as ribbon with buckled ribbon. Thermal stresses result in a high dislocation density in the grown material, resulting in compromised electronic performance. Improvements in ribbon flatness were accomplished by modification of the ribbon cooling profile. Ribbon flatness and other experimental observations of ESR ribbon are discussed. Laser scanner measurements show a good correlation between diffusion length and dislocation density which indicates that the high dislocation densities are the primary cause of the poor current performance of ESR materials. Dislocation densities were reduced and improved electronic performance resulted. Laser scanner data on new and old material are presented.

  4. Local effects of apical oxygen on superconductivity in high-Tc cuprates

    NASA Astrophysics Data System (ADS)

    Mori, Michiyasu; Tohyama, Takami; Maekawa, Sadamichi

    2008-03-01

    The superconducting critical temperature (Tc) of high- Tc cuprates widely distributes among various series of crystal structures, even if the doping rate is optimized in the CuO2 planes. In addition, the Tc is enhanced by applying pressure[1]. These material- and pressure dependences have meaningful correlation with an energy difference of oxygen sites in an apical site and in the CuO2 plane (VA)[2]. On the other hand, Slezak et al. has found that locally modulated gap energy has anti-correlation with a distance between a Cu- and an apical O-sites, i.e., the larger distance is related to the smaller gap energy[3]. We study such a local effect of apical oxygen on superconductivity by calculating the Madelung potential. In particular, we focus on a local variation of VA, whose value approximately corresponds to stability of the Zhang- Rice singlet state[2]. It is found that, on neighboring sites of apical sites close to Cu sites, VA are locally enhanced compared to other sites. To estimate the gap energy, we propose a toy model like a BCS mean field Hamiltonian with an additional degree of freedom, which describes a role of apical oxygen. We will discuss an anti-correlation between the gap energy and the position of apical oxygen. [1] N. Tanahashi et al: Jpn. J. Appl. Phys. 28, L762 (1989). [2] Y. Ohta, T. Tohyama, and S. Maekawa: Phys. Rev. B 43, 2968 (1991). [3] J. Slezak, PhD thesis.

  5. Pseudo ribbon metal ion beam source

    SciTech Connect

    Stepanov, Igor B. Ryabchikov, Alexander I.; Sivin, Denis O.; Verigin, Dan A.

    2014-02-15

    The paper describes high broad metal ion source based on dc macroparticle filtered vacuum arc plasma generation with the dc ion-beam extraction. The possibility of formation of pseudo ribbon beam of metal ions with the parameters: ion beam length 0.6 m, ion current up to 0.2 A, accelerating voltage 40 kV, and ion energy up to 160 kV has been demonstrated. The pseudo ribbon ion beam is formed from dc vacuum arc plasma. The results of investigation of the vacuum arc evaporator ion-emission properties are presented. The influence of magnetic field strength near the cathode surface on the arc spot movement and ion-emission properties of vacuum-arc discharge for different cathode materials are determined. It was shown that vacuum-arc discharge stability can be reached when the magnetic field strength ranges from 40 to 70 G on the cathode surface.

  6. Spikes and ribbon synapses in early vision.

    PubMed

    Baden, Tom; Euler, Thomas; Weckström, Matti; Lagnado, Leon

    2013-08-01

    Image processing begins in the retina, where neurons respond with graded voltage changes that must be converted into spikes. This conversion from 'analog' to 'digital' coding is a fundamental transformation carried out by the visual system, but the mechanisms are still not well understood. Recent work demonstrates that, in vertebrates, graded-to-spiking conversion of the visual signal begins in the axonal system of bipolar cells (BCs), which transmit visual information through ribbon-type synapses specialized for responding to graded voltage signals. Here, we explore the evidence for and against the idea that ribbon synapses also transmit digital information. We then discuss the potential costs and benefits of digitization at different stages of visual pathways in vertebrates and invertebrates. PMID:23706152

  7. Machining of Silicon-Ribbon-Forming Dies

    NASA Technical Reports Server (NTRS)

    Menna, A. A.

    1985-01-01

    Carbon extension for dies used in forming silicon ribbon crystals machined precisely with help of special tool. Die extension has edges beveled toward narrow flats at top, with slot precisely oriented and centered between flats and bevels. Cutting tool assembled from standard angle cutter and circular saw or saws. Angle cutters cuts bevels while slot saw cuts slot between them. In alternative version, custom-ground edges or additional circular saws also cut flats simultaneously.

  8. The timeout ribbon: a nonexclusionary timeout procedure.

    PubMed Central

    Foxx, R M; Shapiro, S T

    1978-01-01

    Recently, the use of timeout rooms has been questioned by various agencies, and some have adopted policies that prohibit or greatly restrict exclusionary timeout. The present study developed a timeout procedure that did not require removal of the misbehaver from the learning environment. The procedure was applied to the disruptive behaviors of five severely retarded children in an institutional special-education classroom. An observer prompted all teacher behaviors related to the procedures to assure their precise implementation. After baseline, a reinforcement-only condition was implemented. Each child was given a different colored ribbon to wear as a tie and received edibles and praise every few minutes for good behavior and for wearing the ribbon. When timeout was added, a child's ribbon was removed for any instance of misbehavior and teacher attention and participation in activities ceased for three minutes or until the misbehavior stopped. Reinforcement continued at other times for appropriate behavior. An ABCBC reversal design was used to demonstrate control of the behavior by the conditions applied. On average, the children misbehaved 42% and 32% of the time during the baseline and reinforcement conditions respectively but only 6% of the time during the timeout conditions. A followup probe during the new school year revealed that the teacher was able to conduct the procedure independently and that the children's disruptive behaviors were maintained at low levels. The practicality and acceptability of the procedure were supported further by the successful implementation of the procedure by a teacher in another state and by responses to a questionnaire given to 40 mental health professionals. The ribbon procedure appears to be a viable form of timeout, provided that disruptive behaviors during timeout can be tolerated within the setting, or a backup procedure such as exclusionary timeout can be tolerated within the setting, or a backup procedure such as

  9. Functional maturation of the exocytotic machinery at gerbil hair cell ribbon synapses.

    PubMed

    Johnson, Stuart L; Franz, Christoph; Knipper, Marlies; Marcotti, Walter

    2009-04-15

    Auditory afferent fibre activity in mammals relies on neurotransmission at hair cell ribbon synapses. Developmental changes in the Ca(2+) sensitivity of the synaptic machinery allow inner hair cells (IHCs), the primary auditory receptors, to encode Ca(2+) action potentials (APs) during pre-hearing stages and graded receptor potentials in adult animals. However, little is known about the time course of these changes or whether the kinetic properties of exocytosis differ as a function of IHC position along the immature cochlea. Furthermore, the role of afferent transmission in outer hair cells (OHCs) is not understood. Calcium currents and exocytosis (measured as membrane capacitance changes: DeltaC(m)) were measured with whole-cell recordings from immature gerbil hair cells using near-physiological conditions. The kinetics, vesicle pool depletion and Ca(2+) coupling of exocytosis were similar in apical and basal immature IHCs. This could indicate that possible differences in AP activity along the immature cochlea do not require synaptic specialization. Neurotransmission in IHCs became mature from postnatal day 20 (P20), although changes in its Ca(2+) dependence occurred at P9-P12 in basal and P12-P15 in apical cells. OHCs showed a smaller DeltaC(m) than IHCs that was reflected by fewer active zones in OHCs. Otoferlin, the proposed Ca(2+) sensor in cochlear hair cells, was similarly distributed in both cell types despite the high-order exocytotic Ca(2+) dependence in IHCs and the near-linear relation in OHCs. The results presented here provide a comprehensive study of the function and development of hair cell ribbon synapses. PMID:19237422

  10. Silicon ribbon growth by a capillary action shaping technique

    NASA Technical Reports Server (NTRS)

    Schwuttke, G. H.; Schwuttke, G. H.; Ciszek, T. F.; Kran, A.

    1977-01-01

    Substantial improvements in ribbon surface quality are achieved with a higher melt meniscus than that attainable with the film-fed (EFG) growth technique. A capillary action shaping method is described in which meniscus shaping for the desired ribbon geometry occurs at the vertex of a wettable die. As ribbon growth depletes the melt meniscus, capillary action supplies replacement material. Topics discussed cover experimental apparatus and growth procedures; die materials investigations, fabrication and evaluation; process development for 25 mm, 38 mm, 50 mm and 100 mm silicon ribbons; and long grain direct solidification of silicon. Methods for the structural and electrical characterization of cast silicon ribbons are assessed as well as silicon ribbon technology for the 1978 to 1986 period.

  11. Faceted ceramic fibers, tapes or ribbons and epitaxial devices therefrom

    SciTech Connect

    Goyal, Amit

    2013-07-09

    A crystalline article includes a single-crystal ceramic fiber, tape or ribbon. The fiber, tape or ribbon has at least one crystallographic facet along its length, which is generally at least one meter long. In the case of sapphire, the facets are R-plane, M-plane, C-plane or A-plane facets. Epitaxial articles, including superconducting articles, can be formed on the fiber, tape or ribbon.

  12. Faceted ceramic fibers, tapes or ribbons and epitaxial devices therefrom

    SciTech Connect

    Goyal, Amit

    2012-07-24

    A crystalline article includes a single-crystal ceramic fiber, tape or ribbon. The fiber, tape or ribbon has at least one crystallographic facet along its length, which is generally at least one meter long. In the case of sapphire, the facets are R-plane, M-plane, C-plane or A-plane facets. Epitaxial articles, including superconducting articles, can be formed on the fiber, tape or ribbon.

  13. Structural defect characterization of silicon dendritic web ribbons

    NASA Technical Reports Server (NTRS)

    Cheng, L. J.

    1985-01-01

    An EBIC study of the cross section of silicon dendritic web ribbon has revealed that recombination-active structural defects are mainly concentrated in the inner part of the ribbon, particularly at and near the twin plane, whereas the material near the surface has significantly fewer defects. An analysis of the distribution of etch pits due to slip dislocations created by shear stress indicates that a minimum in the dislocation density is frequently observed in the ribbon adjacent to the dendrite.

  14. Growth and development of the root apical meristem.

    PubMed

    Perilli, Serena; Di Mambro, Riccardo; Sabatini, Sabrina

    2012-02-01

    A key question in plant developmental biology is how cell division and cell differentiation are balanced to modulate organ growth and shape organ size. In recent years, several advances have been made in understanding how this balance is achieved during root development. In the Arabidopsis root meristem, stem cells in the apical region of the meristem self-renew and produce daughter cells that differentiate in the distal meristem transition zone. Several factors have been implicated in controlling the different functional zones of the root meristem to modulate root growth; among these, plant hormones have been shown to play a main role. In this review, we summarize recent findings regarding the role of hormone signaling and transcriptional networks in regulating root development.

  15. Apical root resorption in orthodontically treated adults.

    PubMed

    Baumrind, S; Korn, E L; Boyd, R L

    1996-09-01

    This study analyzed the relationship in orthodontically treated adults between upper central incisor displacement measured on lateral cephalograms and apical root resorption measured on anterior periapical x-ray films. A multiple linear regression examined incisor displacements in four directions (retraction, advancement, intrusion, and extrusion) as independent variables, attempting to account for observed differences in the dependent variable, resorption. Mean apical resorption was 1.36 mm (sd +/- 1.46, n = 73). Mean horizontal displacement of the apex was -0.83 mm (sd +/- 1.74, n = 67); mean vertical displacement was 0.19 mm (sd +/- 1.48, n = 67). The regression coefficients for the intercept and for retraction were highly significant; those for extrusion, intrusion, and advancement were not. At the 95% confidence level, an average of 0.99 mm (se = +/- 0.34) of resorption was implied in the absence of root displacement and an average of 0.49 mm (se = +/- 0.14) of resorption was implied per millimeter of retraction. R2 for all four directional displacement variables (DDVs) taken together was only 0.20, which implied that only a relatively small portion of the observed apical resorption could be accounted for by tooth displacement alone. In a secondary set of univariate analyses, the associations between apical resorption and each of 14 additional treatment-related variables were examined. Only Gender, Elapsed Time, and Total Apical Displacement displayed statistically significant associations with apical resorption. Additional multiple regressions were then performed in which the data for each of these three statistically significant variables were considered separately, with the data for the four directional displacement variables. The addition of information on Elapsed Time or Total Apical Displacement did not explain a significant additional portion of the variability in apical resorption. On the other hand, the addition of information on Gender to the

  16. Microbiology and Treatment of Acute Apical Abscesses

    PubMed Central

    Rôças, Isabela N.

    2013-01-01

    SUMMARY Acute apical abscess is the most common form of dental abscess and is caused by infection of the root canal of the tooth. It is usually localized intraorally, but in some cases the apical abscess may spread and result in severe complications or even mortality. The reasons why dental root canal infections can become symptomatic and evolve to severe spreading and sometimes life-threatening abscesses remain elusive. Studies using culture and advanced molecular microbiology methods for microbial identification in apical abscesses have demonstrated a multispecies community conspicuously dominated by anaerobic bacteria. Species/phylotypes commonly found in these infections belong to the genera Fusobacterium, Parvimonas, Prevotella, Porphyromonas, Dialister, Streptococcus, and Treponema. Advances in DNA sequencing technologies and computational biology have substantially enhanced the knowledge of the microbiota associated with acute apical abscesses and shed some light on the etiopathogeny of this disease. Species richness and abundance and the resulting network of interactions among community members may affect the collective pathogenicity and contribute to the development of acute infections. Disease modifiers, including transient or permanent host-related factors, may also influence the development and severity of acute abscesses. This review focuses on the current evidence about the etiology and treatment of acute apical abscesses and how the process is influenced by host-related factors and proposes future directions in research, diagnosis, and therapeutic approaches to deal with this disease. PMID:23554416

  17. Apical domain polarization localizes actin-myosin activity to drive ratchet-like apical constriction.

    PubMed

    Mason, Frank M; Tworoger, Michael; Martin, Adam C

    2013-08-01

    Apical constriction promotes epithelia folding, which changes tissue architecture. During Drosophila gastrulation, mesoderm cells exhibit repeated contractile pulses that are stabilized such that cells apically constrict like a ratchet. The transcription factor Twist is required to stabilize cell shape. However, it is unknown how Twist spatially coordinates downstream signals to prevent cell relaxation. We find that during constriction, Rho-associated kinase (Rok) is polarized to the middle of the apical domain (medioapical cortex), separate from adherens junctions. Rok recruits or stabilizes medioapical myosin II (Myo-II), which contracts dynamic medioapical actin cables. The formin Diaphanous mediates apical actin assembly to suppress medioapical E-cadherin localization and form stable connections between the medioapical contractile network and adherens junctions. Twist is not required for apical Rok recruitment, but instead polarizes Rok medioapically. Therefore, Twist establishes radial cell polarity of Rok/Myo-II and E-cadherin and promotes medioapical actin assembly in mesoderm cells to stabilize cell shape fluctuations.

  18. Silicon ribbon growth by a capillary action shaping technique

    NASA Technical Reports Server (NTRS)

    Schwuttke, G. H.; Ciszek, T. F.; Kran, A.; Yang, K.

    1977-01-01

    The crystal-growth method under investigation is a capillary action shaping technique. Meniscus shaping for the desired ribbon geometry occurs at the vertex of a wettable dye. As ribbon growth depletes the melt meniscus, capillary action supplies replacement material. The configuration of the technique used in our initial studies is shown. The crystal-growth method has been applied to silicon ribbons it was found that substantial improvements in ribbon surface quality could be achieved with a higher melt meniscus than that attainable with the EFG technique.

  19. Pseudo-phase Diagram of Cholesterol-Rich Filamentous, Helical Ribbon, and Crystal Microstructures

    NASA Astrophysics Data System (ADS)

    Miroshnikova, Y. A.; Elsenbeck, M.; Ou, Guanqing; Zastavker, Y. V.; Kashuri, K.; Iannacchione, G. S.

    2009-03-01

    Optical and calorimetric techniques are employed to study temperature and concentration dependence of three self-assembled microstructure types formed in Chemically Defined Lipid Concentrate (CDLC): filaments, helical ribbons, and crystals. CDLC consists of cholesterol, bilayer-forming amphiphiles, and micelle-forming amphiphiles in water, and is considered to be a model system for cholesterol crystallization in gallbladder bile. Phase contrast and DIC microscopy indicate the presence of all three microstructure types in all samples studied. Optically observed structural evolution indicates that filaments first bend to form helical ribbons followed by clustering and ``straightening'' of these structures into short and increasingly thickening filaments that dissolve with increasing temperature. Complementary calorimetric studies (differential-scanning and modulation) reveal thermal signatures that correspond to this observed structural evolution, which occurs throughout a large region of metastable chemical coexistence. These results suggest that a pseudo-phase diagram for the microstructures formed in CDLC may be developed to explain the observed behavior of the system.

  20. Dry Ribbon for Heated Head Automated Fiber Placement

    NASA Technical Reports Server (NTRS)

    Hulcher, A. Bruce; Marchello, Joseph M.; Hinkley, Jeffrey A.; Johnston, Norman J.; Lamontia, Mark A.

    2000-01-01

    Ply-by-ply in situ processes involving automated heated head deposition are being developed for fabrication of high performance, high temperature composite structures from low volatile content polymer matrices. This technology requires (1) dry carbon fiber towpreg, (2) consolidation of towpreg to quality, placement-grade unidirectional ribbon or tape, and (3) rapid, in situ, accurate, ply-by-ply robotic placement and consolidation of this material to fabricate a composite structure. In this study, the physical properties of a candidate thermoplastic ribbon, PIXA/IM7, were evaluated and screened for suitability in robotic placement. Specifically, towpreg was prepared from PIXA powder. Various conditions (temperatures) were used to convert the powder-coated towpreg to ribbons with varying degrees of processability. Ribbon within preset specifications was fabricated at 3 temperatures: 390, 400 and 410 C. Ribbon was also produced out-of-spec by purposely overheating the material to a processing temperature of 450 C. Automated placement equipment at Cincinnati Milacron and NASA Langley was used to fabricate laminates from these experimental ribbons. Ribbons were placed at 405 and 450 C by both sets of equipment. Double cantilever beam and wedge peel tests were used to determine the quality of the laminates and, especially, the interlaminar bond formed during the placement process. Ribbon made under conditions expected to be non-optimal (overheated) resulted in poor placeability and composites with weak interlaminar bond strengths, regardless of placement conditions. Ribbon made under conditions expected to be ideal showed good processability and produced well-consolidated laminates. Results were consistent from machine to machine and demonstrated the importance of ribbon quality in heated-head placement of dry material forms. Preliminary screening criteria for the development and evaluation of ribbon from new matrix materials were validated.

  1. Ribbon cutting opens new ELV offices

    NASA Technical Reports Server (NTRS)

    2000-01-01

    The audience applauds and enjoys the official opening of the E&O Building as the new site of the Expendable Launch Vehicle Program. Home for NASA's unmanned missions since 1964, the building has been renovated to house the ELV Program. Cutting the ribbon for the event were Deputy Manager of the ELV and Payload Carrier Programs, Steve Francois; Director of ELV Launch Services, Michael Benik; Center Director Roy Bridges; Manager of the ELV and Payload Carrier Programs, Bobby Bruckner; and Senior Manager of the Boeing ELV Program Support office, Jim Schofield.

  2. THE BALLISTICS OF A RIBBON COMPOSITE

    SciTech Connect

    Larcombe, J.; Morley, M.; Earp, S.; Proud, W. G.; Fray, A. J.; French, M. A.

    2009-12-28

    The impact behaviour of composites is of great importance in the field of aerospace and vehicle protection. The combination of formability, lightness and strength make composite systems attractive compared to equivalent monolithic systems. However, their use as optical components has been hampered by their lack of transparency. Transparency is strongly affected by refractive index differences in the materials that form the composite. In this study a number of ribbon-based composites were produced. The impact velocity, sample deformation during the impact process and residual impactor velocity were measured. This allowed comparison between the materials ballistic efficiency. The materials are then compared to other transparent systems.

  3. Alterations of the apical junctional complex and actin cytoskeleton and their role in colorectal cancer progression

    PubMed Central

    Gehren, Adriana Sartorio; Rocha, Murilo Ramos; de Souza, Waldemir Fernandes; Morgado-Díaz, José Andrés

    2015-01-01

    Colorectal cancer represents the fourth highest mortality rate among cancer types worldwide. An understanding of the molecular mechanisms that regulate their progression can prevents or reduces mortality due to this disease. Epithelial cells present an apical junctional complex connected to the actin cytoskeleton, which maintains the dynamic properties of this complex, tissue architecture and cell homeostasis. Several studies have indicated that apical junctional complex alterations and actin cytoskeleton disorganization play a critical role in epithelial cancer progression. However, few studies have examined the existence of an interrelation between these 2 components, particularly in colorectal cancer. This review discusses the recent progress toward elucidating the role of alterations of apical junctional complex constituents and of modifications of actin cytoskeleton organization and discusses how these events are interlinked to modulate cellular responses related to colorectal cancer progression toward successful metastasis. PMID:26451338

  4. Sheet silicon cell/module technology

    NASA Technical Reports Server (NTRS)

    Morrison, A. D.

    1983-01-01

    The cost involved in the performance of the standard operations for the manufacture of silicon wafers is insignificant in the case of space photovoltaics applications. It is, however, a decisive factor with respect to terrestrial applications of silicon photovoltaic devices. In 1975, a program was, therefore, begun to develop low cost silicon solar arrays for terrestrial applications. The goal was silicon-based photovoltaic (PV) modules ready for installation at a selling price of $0.50/watt (1975 dollars). Sheet and ribbon silicon growth held out the promise of reduced cost through continuous operation, high material throughput, high material utilization efficiency, and a product whose shape lent itself to the assembly of high packing density modules. Attention is given to ribbon growth technologies, sheet technology generic problems, and ribbon cell and module technology status. It is concluded that the potential for crystalline ribbon silicon appears to be better today than ever before.

  5. Study of growth of single crystal ribbon in space

    NASA Technical Reports Server (NTRS)

    Wood, V. E.; Markworth, A. J.

    1975-01-01

    The technical feasibility is studied of growing single-crystal silicon ribbon in the space environment. Procedures are described for calculating the electromagnetic fields produced in a silicon ribbon by an rf shaping coil. The forces on the ribbon and the degree of shaping to be expected are determined. The expected steady-state temperature distribution in the ribbon is calculated in the one-dimensional approximation. Calculations on simplified models indicate, that lack of flatness of the shaped ribbon and excessive heating of the melt by the eddy currents induced by the shaping fields may pose problems. An analysis of the relative effects of various kinds of forces other than electromagnetic showed that in the space environment capillarity forces would dominate, and that the shape of the melt is thus principally determined by the shape of any solids with which it comes in contact. This suggests that ribbon may be produced simply by drawing between parallel wires. A concept is developed for a process of off-angle growth, in which the ribbon is pulled at an angle to the solidification front. Such a process promises to offer increased growth rate, better homogeneity, and thinner ribbon.

  6. Development of a process for producing ribbon shaped boron filaments

    NASA Technical Reports Server (NTRS)

    Basche, M.; Jacob, B.

    1973-01-01

    A ribbon-shaped boron filament with a tensile strength of 138 KN/sq cm (200 ksi) was investigated. The investigation was carried out using both carbon and tungsten as substrate materials. No satisfactory results were obtained utilizing uncoated, copper-plated or silicon carbide coated tungsten ribbon substrates. Carbon ribbon substrates were prepared by pyrolysis of stretched polyimide tape. A severe deposition gradient occurred in all dc reactor experiments due to convective cooling at the edge of the substrate that resulted in a weak, nonuniform filament. RF heating, however, completely eliminated this gradient problem and a 90 cm (35.5 in.) long boron ribbon was produced at .85 cm/sec (100 ft/hr) using a frequency of 40.68 megahertz. This boron ribbon, however, exhibited a light-bulb effect during deposition to 59 KN/sq cm (85.7 ksi) were obtained from this ribbon. Several silicon carbide ribbon shaped filaments were also produced during this investigation by decomposition of CH3SiHCl2 onto carbon substrates. Contrary to the boron work, silicon carbide ribbon was readily prepared in dc static reactors. A very uniform and smooth deposition was obtained with strengths up to 71.1 KN/sq cm (103.5 ksi).

  7. Pathogenesis of Apical Periodontitis: a Literature Review

    PubMed Central

    Lodiene, Greta; Maciulskiene, Vita

    2011-01-01

    ABSTRACT Objectives This review article discusses the host response in apical periodontitis with the main focus on cytokines, produced under this pathological condition and contributing to the degradation of periradicular tissues. The pace of research in this field has greatly accelerated in the last decade. Here we provide an analysis of studies published in this area during this period. Material and methods Literature was selected through a search of PubMed electronic database. The keywords used for search were pathogenesis of apical periodontitis cytokines, periapical granuloma cytokines, inflammatory infiltrate apical periodontitis. The search was restricted to English language articles, published from 1999 to December 2010. Additionally, a manual search in the cytokine production, cytokine functions and periapical tissue destruction in the journals and books was performed. Results In total, 97 literature sources were obtained and reviewed. The topics covered in this article include cellular composition of an inflammatory infiltrate in the periapical lesions, mechanisms of the formation of the innate and specific immune response. Studies which investigated cytokine secretion and functions were identified and cellular and molecular interactions in the course of apical periodontitis described. Conclusions The abundance and interactions of various inflammatory and anti-inflammatory molecules can influence and alter the state and progression of the disease. Therefore, periapical inflammatory response offers a model, suited for the study of many facets of pathogenesis, biocompatibility of different materials to periapical tissues and development of novel treatment methods, based on the regulation of cytokines expression PMID:24421998

  8. Role of PIN-mediated auxin efflux in apical hook development of Arabidopsis thaliana.

    PubMed

    Zádníková, Petra; Petrásek, Jan; Marhavy, Peter; Raz, Vered; Vandenbussche, Filip; Ding, Zhaojun; Schwarzerová, Katerina; Morita, Miyo T; Tasaka, Masao; Hejátko, Jan; Van Der Straeten, Dominique; Friml, Jirí; Benková, Eva

    2010-02-01

    The apical hook of dark-grown Arabidopsis seedlings is a simple structure that develops soon after germination to protect the meristem tissues during emergence through the soil and that opens upon exposure to light. Differential growth at the apical hook proceeds in three sequential steps that are regulated by multiple hormones, principally auxin and ethylene. We show that the progress of the apical hook through these developmental phases depends on the dynamic, asymmetric distribution of auxin, which is regulated by auxin efflux carriers of the PIN family. Several PIN proteins exhibited specific, partially overlapping spatial and temporal expression patterns, and their subcellular localization suggested auxin fluxes during hook development. Genetic manipulation of individual PIN activities interfered with different stages of hook development, implying that specific combinations of PIN genes are required for progress of the apical hook through the developmental phases. Furthermore, ethylene might modulate apical hook development by prolonging the formation phase and strongly suppressing the maintenance phase. This ethylene effect is in part mediated by regulation of PIN-dependent auxin efflux and auxin signaling.

  9. Hierarchy of hormone action controlling apical hook development in Arabidopsis.

    PubMed

    Gallego-Bartolomé, Javier; Arana, María V; Vandenbussche, Filip; Zádníková, Petra; Minguet, Eugenio G; Guardiola, Vicente; Van Der Straeten, Dominique; Benkova, Eva; Alabadí, David; Blázquez, Miguel A

    2011-08-01

    The apical hook develops in the upper part of the hypocotyl when seeds buried in the soil germinate, and serves to protect cotyledons and the shoot apical meristem from possible damage caused by pushing through the soil. The curvature is formed through differential cell growth that occurs at the two opposite sides of the hypocotyl, and it is established by a gradient of auxin activity and refined by the coordinated action of auxin and ethylene. Here we show that gibberellins (GAs) promote hook development through the transcriptional regulation of several genes of the ethylene and auxin pathways in Arabidopsis. The level of GA activity determines the speed of hook formation and the extent of the curvature during the formation phase independently of ethylene, probably by modulating auxin transport and response through HLS1, PIN3, and PIN7. Moreover, GAs cooperate with ethylene in preventing hook opening, in part through the induction of ethylene production mediated by ACS5/ETO2 and ACS8.

  10. Electrostatics-Driven Hierarchical Buckling of Charged Flexible Ribbons

    NASA Astrophysics Data System (ADS)

    Yao, Zhenwei; Olvera de la Cruz, Monica

    2016-04-01

    We investigate the rich morphologies of an electrically charged flexible ribbon, which is a prototype for many beltlike structures in biology and nanomaterials. Long-range electrostatic repulsion is found to govern the hierarchical buckling of the ribbon from its initially flat shape to its undulated and out-of-plane twisted conformations. In this process, the screening length is the key controlling parameter, suggesting that a convenient way to manipulate the ribbon morphology is simply to change the salt concentration. We find that these shapes originate from the geometric effect of the electrostatic interaction, which fundamentally changes the metric over the ribbon surface. We also identify the basic modes by which the ribbon reshapes itself in order to lower the energy. The geometric effect of the physical interaction revealed in this Letter has implications for the shape design of extensive ribbonlike materials in nano- and biomaterials.

  11. Guidance system for low angle silicon ribbon growth

    DOEpatents

    Jewett, David N.; Bates, Herbert E.; Milstein, Joseph B.

    1986-07-08

    In a low angle silicon sheet growth process, a puller mechanism advances a seed crystal and solidified ribbon from a cooled growth zone in a melt at a low angle with respect to the horizontal. The ribbon is supported on a ramp adjacent the puller mechanism. Variations in the vertical position of the ribbon with respect to the ramp are isolated from the growth end of the ribbon by (1) growing the ribbon so that it is extremely thin, preferably less than 0.7 mm, (2) maintaining a large growth zone, preferably one whose length is at least 5.0 cm, and (3) spacing the ramp from the growth zone by at least 15 cm.

  12. Twisted Ribbons: Theory, Experiment and Applications

    NASA Astrophysics Data System (ADS)

    Chopin, Julien; Davidovitch, Benjamin; Silva, Flavio A.; Toledo Filho, Romildo D.; Kudrolli, Arshad

    2014-03-01

    We investigate, experimentally and theoretically, the buckling and wrinkling instabilities of a pre-stretched ribbon upon twisting and propose strategies for the fabrication of structured yarns. Our experiment consists in a thin elastic sheet in the form of a ribbon which is initially stretched by a fixed load and then subjected to a twist by rotating the ends through a prescribed angle. We show that a wide variety of shapes and instabilities can be obtained by simply varying the applied twist and tension. The observed structures which include helicoids with and without longitudinal and transverse wrinkles, and spontaneous creases, can be organized in a phase diagram with the tension and twist angle as control parameters [J. Chopin and A. Kudrolli, PRL (2013)]. Using a far-from-threshold analysis and a slender body approximation, we provide a comprehensive understanding of the longitudinal and transverse instabilities and show that several regimes emerge depending on subtle combinations of loading and geometrical parameters. Further, we show that the wrinkling instabilities can be manipulated to fabricate structured yarns which may be used to encapsulate amorphous materials or serve as efficient reinforcements for cement-based composites. COPPETEC / CNPq - Science Without Border Program

  13. The Impact of Apical Patency in the Success of Endodontic Treatment of Necrotic Teeth with Apical Periodontitis: A Brief Review

    PubMed Central

    Machado, Ricardo; Ferrari, Carlos Henrique; Back, Eduardo; Comparin, Daniel; Tomazinho, Luiz Fernando; Vansan, Luiz Pascoal

    2016-01-01

    Accumulation of soft tissue or dentinal remnants in the apical region is a common event that can cause blockage of root canals. This event can be avoided if apical patency is performed during the root canal shaping procedures. However, there is no consensus on the role of apical patency in relation to the success of endodontic treatment of necrotic teeth with apical periodontitis. Therefore, the purpose of this paper was to conduct a brief review on the role of apical patency in guaranteeing the success of endodontic treatments of necrotic teeth with apical periodontitis considering two other key points; the root canal anatomy and microbiology. PMID:26843880

  14. Electronically tunable extraordinary optical transmission in graphene plasmonic ribbons coupled to subwavelength metallic slit arrays.

    PubMed

    Kim, Seyoon; Jang, Min Seok; Brar, Victor W; Tolstova, Yulia; Mauser, Kelly W; Atwater, Harry A

    2016-01-01

    Subwavelength metallic slit arrays have been shown to exhibit extraordinary optical transmission, whereby tunnelling surface plasmonic waves constructively interfere to create large forward light propagation. The intricate balancing needed for this interference to occur allows for resonant transmission to be highly sensitive to changes in the environment. Here we demonstrate that extraordinary optical transmission resonance can be coupled to electrostatically tunable graphene plasmonic ribbons to create electrostatic modulation of mid-infrared light. Absorption in graphene plasmonic ribbons situated inside metallic slits can efficiently block the coupling channel for resonant transmission, leading to a suppression of transmission. Full-wave simulations predict a transmission modulation of 95.7% via this mechanism. Experimental measurements reveal a modulation efficiency of 28.6% in transmission at 1,397 cm(-1), corresponding to a 2.67-fold improvement over transmission without a metallic slit array. This work paves the way for enhancing light modulation in graphene plasmonics by employing noble metal plasmonic structures. PMID:27499258

  15. Electronically tunable extraordinary optical transmission in graphene plasmonic ribbons coupled to subwavelength metallic slit arrays

    PubMed Central

    Kim, Seyoon; Jang, Min Seok; Brar, Victor W.; Tolstova, Yulia; Mauser, Kelly W.; Atwater, Harry A.

    2016-01-01

    Subwavelength metallic slit arrays have been shown to exhibit extraordinary optical transmission, whereby tunnelling surface plasmonic waves constructively interfere to create large forward light propagation. The intricate balancing needed for this interference to occur allows for resonant transmission to be highly sensitive to changes in the environment. Here we demonstrate that extraordinary optical transmission resonance can be coupled to electrostatically tunable graphene plasmonic ribbons to create electrostatic modulation of mid-infrared light. Absorption in graphene plasmonic ribbons situated inside metallic slits can efficiently block the coupling channel for resonant transmission, leading to a suppression of transmission. Full-wave simulations predict a transmission modulation of 95.7% via this mechanism. Experimental measurements reveal a modulation efficiency of 28.6% in transmission at 1,397 cm−1, corresponding to a 2.67-fold improvement over transmission without a metallic slit array. This work paves the way for enhancing light modulation in graphene plasmonics by employing noble metal plasmonic structures. PMID:27499258

  16. Electronically tunable extraordinary optical transmission in graphene plasmonic ribbons coupled to subwavelength metallic slit arrays

    DOE PAGESBeta

    Kim, Seyoon; Jang, Min Seok; Brar, Victor W.; Tolstova, Yulia; Mauser, Kelly W.; Atwater, Harry A.

    2016-08-08

    In this paper, subwavelength metallic slit arrays have been shown to exhibit extraordinary optical transmission, whereby tunneling surface plasmonic waves constructively interfere to create large forward light propagation. The intricate balancing needed for this interference to occur allows for resonant transmission to be highly sensitive to changes in the environment. Here we demonstrate that extraordinary optical transmission resonance can be coupled to electrostatically tunable graphene plasmonic ribbons to create electrostatic modulation of mid-infrared light. Absorption in graphene plasmonic ribbons situated inside metallic slits can efficiently block the coupling channel for resonant transmission, leading to a suppression of transmission. Full-wave simulationsmore » predict a transmission modulation of 95.7% via this mechanism. Experimental measurements reveal a modulation efficiency of 28.6% in transmission at 1,397 cm–1, corresponding to a 2.67-fold improvement over transmission without a metallic slit array. This work paves the way for enhancing light modulation in graphene plasmonics by employing noble metal plasmonic structures.« less

  17. Microbiome in the Apical Root Canal System of Teeth with Post-Treatment Apical Periodontitis

    PubMed Central

    Siqueira, José F.; Antunes, Henrique S.; Rôças, Isabela N.; Rachid, Caio T. C. C.

    2016-01-01

    Introduction Bacteria present in the apical root canal system are directly involved with the pathogenesis of post-treatment apical periodontitis. This study used a next-generation sequencing approach to identify the bacterial taxa occurring in cryopulverized apical root samples from root canal-treated teeth with post-treatment disease. Methods Apical root specimens obtained during periradicular surgery of ten adequately treated teeth with persistent apical periodontitis were cryogenically ground. DNA was extracted from the powder and the microbiome was characterized on the basis of the V4 hypervariable region of the 16S rRNA gene by using paired-end sequencing on Illumina MiSeq device. Results All samples were positive for the presence of bacterial DNA. Bacterial taxa were mapped to 11 phyla and 103 genera composed by 538 distinct operational taxonomic units (OTUs) at 3% of dissimilarity. Over 85% of the sequences belonged to 4 phyla: Proteobacteria, Firmicutes, Fusobacteria and Actinobacteria. In general, these 4 phyla accounted for approximately 80% of the distinct OTUs found in the apical root samples. Proteobacteria was the most abundant phylum in 6/10 samples. Fourteen genera had representatives identified in all cases. Overall, the genera Fusobacterium and Pseudomonas were the most dominant. Enterococcus was found in 4 cases, always in relatively low abundance. Conclusions This study showed a highly complex bacterial community in the apical root canal system of adequately treated teeth with persistent apical periodontitis. This suggests that this disease is characterized by multispecies bacterial communities and has a heterogeneous etiology, because the community composition largely varied from case to case. PMID:27689802

  18. The ribbon continent of northwestern South America

    NASA Astrophysics Data System (ADS)

    Altamira-Areyan, Armando

    The tectonic structure of the Plate Boundary Zone (PBZ) between the Caribbean Plate (CARIB) and the South American Plate (SOAM) is interpreted using models that require CARIB motion from the Pacific into the Atlantic. Those models can be subdivided into: (1) those in which the island arc rocks that are now in the CARIB-SOAM PBZ have collided with the northern South America margin, either obliquely or directly during the Cretaceous or during the Cenozoic, and (2) those in which the island arc rocks now in the CARIB-SOAM PBZ collided with the west coast of South America during the Cretaceous and were transferred to the northern margin by transform motion during the Cenozoic. Magnetic anomalies were first rotated in the Central and South Atlantic, holding Africa fixed to establish how much NOAM had converged on SOAM during the Cenozoic. WSW convergence was discovered to have been accommodated in the northern boundary of the CARIB. There is no evidence of convergence in the form of Cenozoic island arc igneous rocks on the north coast of South America. Those results are consistent only with models of Class (2) that call for transform movement of material that had collided with the west coast of South America along the CARIB-SOAM PBZ on the northern margin of South America. 40Ar/39Ar ages of island arc rocks from northern Venezuela were found to be older than ca 70 Ma, which is consistent with a requirement of models of Class (2) that those rocks are from an island arc which collided with the west coast of South America during Cretaceous times. Testing that conclusion using data from Ecuador, Colombia, Venezuela, the Netherlands Antilles, Trinidad and Tobago has led to the construction of a new ribbon continent model of the northwestern Cordillera of South America. Because the part of the ribbon continent on the north coast of South America has been experiencing substantial deformation in the Maracaibo block during the past 10 m.y., structures in that body have had to be

  19. Ribbon curling via stress relaxation in thin polymer films

    PubMed Central

    Prior, Chris; Moussou, Julien; Chakrabarti, Buddhapriya

    2016-01-01

    The procedure of curling a ribbon by running it over a sharp blade is commonly used when wrapping presents. Despite its ubiquity, a quantitative explanation of this everyday phenomenon is still lacking. We address this using experiment and theory, examining the dependence of ribbon curvature on blade curvature, the longitudinal load imposed on the ribbon, and the speed of pulling. Experiments in which a ribbon is drawn steadily over a blade under a fixed load show that the ribbon curvature is generated over a restricted range of loads, the curvature/load relationship can be nonmonotonic, and faster pulling (under a constant imposed load) results in less tightly curled ribbons. We develop a theoretical model that captures these features, building on the concept that the ribbon under the imposed deformation undergoes differential plastic stretching across its thickness, resulting in a permanently curved shape. The model identifies factors that optimize curling and clarifies the physical mechanisms underlying the ribbon’s nonlinear response to an apparently simple deformation. PMID:26831118

  20. Observations and Numerical Modeling of the Jovian Ribbon

    NASA Technical Reports Server (NTRS)

    Cosentino, R. G.; Simon, A.; Morales-Juberias, R.; Sayanagi, K. M.

    2015-01-01

    Multiple wavelength observations made by the Hubble Space Telescope in early 2007 show the presence of a wavy, high-contrast feature in Jupiter's atmosphere near 30 degrees North. The "Jovian Ribbon," best seen at 410 nanometers, irregularly undulates in latitude and is time-variable in appearance. A meridional intensity gradient algorithm was applied to the observations to track the Ribbon's contour. Spectral analysis of the contour revealed that the Ribbon's structure is a combination of several wavenumbers ranging from k equals 8-40. The Ribbon is a dynamic structure that has been observed to have spectral power for dominant wavenumbers which vary over a time period of one month. The presence of the Ribbon correlates with periods when the velocity of the westward jet at the same location is highest. We conducted numerical simulations to investigate the stability of westward jets of varying speed, vertical shear, and background static stability to different perturbations. A Ribbon-like morphology was best reproduced with a 35 per millisecond westward jet that decreases in amplitude for pressures greater than 700 hectopascals and a background static stability of N equals 0.005 per second perturbed by heat pulses constrained to latitudes south of 30 degrees North. Additionally, the simulated feature had wavenumbers that qualitatively matched observations and evolved throughout the simulation reproducing the Jovian Ribbon's dynamic structure.

  1. Growth of a single crystal ribbon in space

    NASA Technical Reports Server (NTRS)

    Padovani, F. A.; Voltmer, F. W.

    1973-01-01

    Three critical technological areas associated with adapting the method of pulling signal crystal silicon ribbon to a space environment were investigated. Basic parameters such as the magnitude of the forces required and the coupling between thermal and force are discussed. The design of a ribbon puller is described, and the problems encountered are also discussed. The force fields in the vicinity of a coil were characterized and results of attempts to pull ribbon are described. The results of the one experiment to grow a conventional float zone crystal in an external static magnetic field are presented.

  2. Mass fusion splicing machine for ribbon-type optical fibers

    NASA Astrophysics Data System (ADS)

    Osaka, K.; Yanagi, T.; Asano, Y.

    1986-11-01

    A mass fusion splicer was designed and manufactured. Using this splicer, mass fusion splicing of optical fiber ribbons was investigated. Ten-fiber ribbon tapes were cut and spliced at an average loss of 0.08 dB for GI and 0.24 dB for SM. They were reinforced by heat-shrinkable tubes with EVA adhesive improved for ribbon tape. An average tensile strength until break was about 3.2 kg soon after splice and about 8.3 kg after reinforcement.

  3. Silicon ribbon growth by a capillary action shaping technique

    NASA Technical Reports Server (NTRS)

    Schwuttke, G. H.; Ciszek, T. F.; Kran, A.

    1976-01-01

    The crystal growth method described is a capillary action shaping technique. Meniscus shaping for the desired ribbon geometry occurs at the vertex of a wettable die. As ribbon growth depletes the melt meniscus, capillary action supplies replacement material. A capillary die is so designed that the bounding edges of the die top are not parallel or concentric with the growing ribbon. The new dies allow a higher melt meniscus with concomitant improvements in surface smoothness and freedom from SiC surface particles, which can degrade perfection.

  4. Transmittance characteristics and tunable sensor performances of plasmonic graphene ribbons

    NASA Astrophysics Data System (ADS)

    Yan, Xin; Yuan, Lin; Wang, Yueke; Sang, Tian; Yang, Guofeng

    2016-08-01

    We investigate the transmittance characteristics of graphene ribbons numerically. It is found that the transmission dips originate from the transverse and longitudinal resonances of edge graphene plasmon modes, supported by the graphene ribbon resonator. The environmental refractive index changes are detected by measuring the resulting spectral shifts of the resonant transmission dip, so the graphene ribbons can be applied to plasmonic sensor in infrared. Simulation results show that sensing performances for each resonant mode are similar, and figure of merit can be up to 6. Beside, thanks to the tunable permittivity of graphene by bias voltages, the transmittance spectra and sensor performances can be easily tuned.

  5. Inflammatory Myofibroblastic Tumor Mimicking Apical Periodontitis.

    PubMed

    Adachi, Makoto; Kiho, Kazuki; Sekine, Genta; Ohta, Takahisa; Matsubara, Makoto; Yoshida, Takakazu; Katsumata, Akitoshi; Tanuma, Jun-ichi; Sumitomo, Shinichiro

    2015-12-01

    Inflammatory myofibroblastic tumors (IMTs) are rare. IMTs of the head and neck occur in all age groups, from neonates to old age, with the highest incidence occurring in childhood and early adulthood. An IMT has been defined as a histologically distinctive lesion of uncertain behavior. This article describes an unusual case of IMT mimicking apical periodontitis in the mandible of a 42-year-old man. At first presentation, the patient showed spontaneous pain and percussion pain at teeth #28 to 30, which continued after initial endodontic treatment. Panoramic radiography revealed a radiolucent lesion at the site. Cone-beam computed tomographic imaging showed osteolytic lesions, suggesting an aggressive neoplasm requiring incisional biopsy. Histopathological examination indicated an IMT. The lesion was removed en bloc under general anesthesia, and the patient manifested no clinical evidence of recurrence for 24 months. Lesions of nonendodontic origin should be included in the differential diagnosis of apical periodontitis. Every available diagnostic tool should be used to confirm the diagnosis. Cone-beam computed tomographic imaging is very helpful for differential diagnosis in IMTs mimicking apical periodontitis. PMID:26602450

  6. Magnetocaloric effect in ribbon samples of Heusler alloys Ni-Mn-M (M=In,Sn)

    NASA Astrophysics Data System (ADS)

    Aliev, A. M.; Batdalov, A. B.; Kamilov, I. K.; Koledov, V. V.; Shavrov, V. G.; Buchelnikov, V. D.; García, J.; Prida, V. M.; Hernando, B.

    2010-11-01

    Direct measurements of the magnetocaloric effect in samples of rapidly quenched ribbons of Mn50Ni40In10 and Ni50Mn37Sn13 Heusler alloys with potential applications in magnetic refrigeration technology are carried out. The measurements were made by a precise method based on the measurement of the oscillation amplitude of the temperature in the sample while is subjected to a modulated magnetic field. In the studied compositions both direct and inverse magnetocaloric effects associated with magnetic (paramagnet-ferromagnet-antiferromagnet) and structural (austenite-martensite) phase transitions are found. Additional inverse magnetocaloric effects of small value are observed around the ferromagnetic transitions.

  7. Architecture of apical dendrites in the murine neocortex: dual apical dendritic systems.

    PubMed

    Escobar, M I; Pimienta, H; Caviness, V S; Jacobson, M; Crandall, J E; Kosik, K S

    1986-04-01

    A monoclonal antibody (5F9) against microtubule-associated protein 2 is a selective and sensitive marker for neocortical dendrites in the mouse. The marker stains all dendrites. It affords a particularly comprehensive picture of the patterns of arrangements of apical dendrites which are most intensely stained with this antibody. Dual systems of apical dendrites arise from the polymorphic neurons of layer VI, on the one hand, and the pyramidal neurons of layers II-V, on the other. Terminal arborization of the former is concentrated principally at the interface of layers V and IV, while that of the latter is in the molecular layer. Apical dendrites of both systems are grouped into fascicles. In supragranular layers and in upper layer VI-lower layer V, where apical dendrites are most abundant, the fascicles coalesce into septa. These generate a honeycomb-like pattern, subdividing these cortical levels into columnar spaces of approximately 20-40 micron diameter. At the level of layer IV, where the number of apical dendrites is greatly reduced, the fascicles are isolated bundles. These bundles have the form of circular, elliptical or rectangular columns in the primary somatosensory, temporal and frontal regions, respectively. Those in the barrel field are preferentially concentrated in the sides of barrels and the interbarrel septa. The configurations of the dendritic fascicles, particularly the midcortical bundles, may conform to the spatial configuration of investing axons of interneurons.

  8. Silicon ribbon growth by a capillary action shaping technique

    NASA Technical Reports Server (NTRS)

    Schwuttke, G. H.; Ciszek, T. F.; Kran, A.

    1976-01-01

    The technique of silicon ribbon growth by the capillary action shaping is assessed for applicability to photovoltaic power device material. Ribbons 25 mm in width and up to 0.5 m in length have been grown from SiC dies, and some new characteristics of growth from such dies have been identified. Thermal modifiers have been studied, and systems were developed which reduce the frozen-in stress un silicon ribbons and improve the thickness uniformity of the ribbons. Preliminary spreading resistance measurements indicate that neither surface striations nor twin boundaries give rise to appreciable resistivity variations, but that large-angle grain boundaries cause local resistivity increases of up to 200%.

  9. String stabilized ribbon growth a method for seeding same

    DOEpatents

    Sachs, Emanuel M.

    1987-08-25

    This invention is a method of initiating or seeding the growth of a crystalline or polycrystalline ribbon by the String Stabilized Ribbon Growth Method. The method for seeding the crystal growth comprises contacting a melt surface with a seed and two strings used in edge stabilization. The wetted strings attach to the wetted seed as a result of the freezing of the liquid melt. Upon drawing the seed, which is attached to the strings, away from the melt surface a melt liquid meniscus, a seed junction, and a growth interface forms. Further pulling of the attached seed causes a crystal ribbon to grow at the growth interface. The boundaries of the growing ribbon are: at the top the seed junction, at the bottom the freezing boundary of the melt liquid meniscus, and at the edges frozen-in strings.

  10. Loss of Llgl1 in retinal neuroepithelia reveals links between apical domain size, Notch activity and neurogenesis

    PubMed Central

    Clark, Brian S.; Cui, Shuang; Miesfeld, Joel B.; Klezovitch, Olga; Vasioukhin, Valeri; Link, Brian A.

    2012-01-01

    To gain insights into the cellular mechanisms of neurogenesis, we analyzed retinal neuroepithelia deficient for Llgl1, a protein implicated in apicobasal cell polarity, asymmetric cell division, cell shape and cell cycle exit. We found that vertebrate retinal neuroepithelia deficient for Llgl1 retained overt apicobasal polarity, but had expanded apical domains. Llgl1 retinal progenitors also had increased Notch activity and reduced rates of neurogenesis. Blocking Notch function by depleting Rbpj restored normal neurogenesis. Experimental expansion of the apical domain, through inhibition of Shroom3, also increased Notch activity and reduced neurogenesis. Significantly, in wild-type retina, neurogenic retinal progenitors had smaller apical domains compared with proliferative neuroepithelia. As nuclear position during interkinetic nuclear migration (IKNM) has been previously linked with cell cycle exit, we analyzed this phenomenon in cells depleted of Llgl1. We found that although IKNM was normal, the relationship between nuclear position and neurogenesis was shifted away from the apical surface, consistent with increased pro-proliferative and/or anti-neurogenic signals associated with the apical domain. These data, in conjunction with other findings, suggest that, in retinal neuroepithelia, the size of the apical domain modulates the strength of polarized signals that influence neurogenesis. PMID:22492354

  11. Distance to the IBEX Ribbon Source Inferred from Parallax

    NASA Astrophysics Data System (ADS)

    Swaczyna, P.; Bzowski, M.; Christian, E. R.; Funsten, H. O.; McComas, D. J.; Schwadron, N. A.

    2016-06-01

    Maps of energetic neutral atom (ENA) fluxes obtained from observations made by the Interstellar Boundary Explorer (IBEX) revealed a bright structure extending over the sky, subsequently dubbed the IBEX ribbon. The ribbon had not been expected from the existing models and theories prior to IBEX, and a number of mechanisms have since been proposed to explain the observations. In these mechanisms, the observed ENAs emerge from source plasmas located at different distances from the Sun. Since each part of the sky is observed by IBEX twice during the year from opposite sides of the Sun, the apparent position of the ribbon as observed in the sky is shifted due to parallax. To determine the ribbon’s parallax, we found the precise location of the maximum signal of the ribbon observed in each orbital arc. The apparent positions obtained were subsequently corrected for the Compton-Getting effect, gravitational deflection, and radiation pressure. Finally, we selected a part of the ribbon where its position is similar in the different IBEX energy passbands. We compared the apparent positions obtained from the viewing locations on the opposite sides of the Sun, and found that they are shifted by a parallax angle of 0.°41 ± 0.°15, which corresponds to a distance of {140}-38+84 AU. This finding supports models of the ribbon with the source located just outside the heliopause.

  12. SECONDARY FLARE RIBBONS OBSERVED BY THE SOLAR DYNAMICS OBSERVATORY

    SciTech Connect

    Zhang, Jun; Li, Ting; Yang, Shuhong E-mail: liting@nao.cas.cn

    2014-02-20

    Using the observations from the Atmospheric Imaging Assembly (AIA) and the Helioseismic and Magnetic Imager on board the Solar Dynamics Observatory, we statistically investigate the flare ribbons (FRs) of 19 X-class flares of the 24th solar cycle from 2010 June to 2013 August. Of these 19 flares, the source regions of 16 can be observed by AIA and the FRs of each flare are well detected, and 11 of the 16 display multiple ribbons. Based on the ribbon brightness and the relationship between the ribbons and post-flare loops, we divide the multiple ribbons into two types: normal FRs, which are connected by post-flare loops and have been extensively investigated, and secondary flare ribbons (SFRs), which are weaker than the FRs, not connected by post-flare loops, and always have a short lifetime. Of the 11 SFRs, 10 appear simultaneously with the FRs, and none of them have post-flare loops. The last one, on the other hand, appears 80 minutes later than the FR, lasts almost two hours, and also has no post-flare loops detected. We suggest that the magnetic reconnection associated with this SFR is triggered by the blast wave that results from the main flare. These observations imply that in some flare processes, more than two sets of magnetic loops or more than twice the number of magnetic reconnections are involved.

  13. FINE STRUCTURE OF FLARE RIBBONS AND EVOLUTION OF ELECTRIC CURRENTS

    SciTech Connect

    Sharykin, I. N.; Kosovichev, A. G.

    2014-06-10

    Emission of solar flares across the electromagnetic spectrum is often observed in the form of two expanding ribbons. The standard flare model explains flare ribbons as footpoints of magnetic arcades, emitting due to interaction of energetic particles with the chromospheric plasma. However, the physics of this interaction and properties of the accelerated particles are still unknown. We present results of multiwavelength observations of the C2.1 flare of 2013 August 15, observed with the New Solar Telescope of the Big Bear Solar Observatory, and the Solar Dynamics Observatory, GOES, and Fermi spacecraft. The observations reveal previously unresolved sub-arcsecond structure of flare ribbons in regions of strong magnetic field consisting from numerous small-scale bright knots. We observe a red-blue asymmetry of H{sub α} flare ribbons with a width as small as ∼100 km. We discuss the relationship between the ribbons and vertical electric currents estimated from vector magnetograms, and show that Joule heating can be responsible for energization of H{sub α} knots in the ribbons.

  14. Ferromagnetism in graphene nanoribbons: split versus oxidative unzipped ribbons.

    PubMed

    Rao, S S; Jammalamadaka, S Narayana; Stesmans, A; Moshchalkov, V V; van Tol, J; Kosynkin, D V; Higginbotham-Duque, A; Tour, J M

    2012-03-14

    Two types of graphene nanoribbons: (a) potassium-split graphene nanoribbons (GNRs), and (b) oxidative unzipped and chemically converted graphene nanoribbons (CCGNRs) were investigated for their magnetic properties using the combination of static magnetization and electron spin resonance measurements. The two types of ribbons possess remarkably different magnetic properties. While a low-temperature ferromagnet-like feature is observed in both types of ribbons, such room-temperature feature persists only in potassium-split ribbons. The GNRs show negative exchange bias, but the CCGNRs exhibit a "positive exchange bias". Electron spin resonance measurements suggest that the carbon-related defects may be responsible for the observed magnetic behavior in both types of ribbons. Furthermore, information on the proton hyperfine coupling strength has been obtained from hyperfine sublevel correlation experiments performed on the GNRs. Electron spin resonance finds no evidence for the presence of potassium (cluster) related signals, pointing to the intrinsic magnetic nature of the ribbons. Our combined experimental results may indicate the coexistence of ferromagnetic clusters with antiferromagnetic regions leading to disordered magnetic phase. We discuss the possible origin of the observed contrast in the magnetic behaviors of the two types of ribbons studied.

  15. MicroRNAs as key regulators of GTPase-mediated apical actin reorganization in multiciliated epithelia

    PubMed Central

    Mercey, Olivier; Kodjabachian, Laurent; Barbry, Pascal; Marcet, Brice

    2016-01-01

    ABSTRACT Multiciliated cells (MCCs), which are present in specialized vertebrate tissues such as mucociliary epithelia, project hundreds of motile cilia from their apical membrane. Coordinated ciliary beating in MCCs contributes to fluid propulsion in several biological processes. In a previous work, we demonstrated that microRNAs of the miR-34/449 family act as new conserved regulators of MCC differentiation by specifically repressing cell cycle genes and the Notch pathway. Recently, we have shown that miR-34/449 also modulate small GTPase pathways to promote, in a later stage of differentiation, the assembly of the apical actin network, a prerequisite for proper anchoring of centrioles-derived neo-synthesized basal bodies. We characterized several miR-34/449 targets related to small GTPase pathways including R-Ras, which represents a key and conserved regulator during MCC differentiation. Direct RRAS repression by miR-34/449 is necessary for apical actin meshwork assembly, notably by allowing the apical relocalization of the actin binding protein Filamin-A near basal bodies. Our studies establish miR-34/449 as central players that orchestrate several steps of MCC differentiation program by regulating distinct signaling pathways. PMID:27144998

  16. Targeted Proteomic Quantitation of the Absolute Expression and Turnover of Cystic Fibrosis Transmembrane Conductance Regulator in the Apical Plasma Membrane

    PubMed Central

    2015-01-01

    Deficient chloride transport through cystic fibrosis (CF) transmembrane conductance regulator (CFTR) causes lethal complications in CF patients. CF is the most common autosomal recessive genetic disease, which is caused by mutations in the CFTR gene; thus, CFTR mutants can serve as primary targets for drugs to modulate and rescue the ion channel’s function. The first step of drug modulation is to increase the expression of CFTR in the apical plasma membrane (PM); thus, accurate measurement of CFTR in the PM is desired. This work reports a tandem enrichment strategy to prepare PM CFTR and uses a stable isotope labeled CFTR sample as the quantitation reference to measure the absolute amount of apical PM expression of CFTR in CFBE 41o- cells. It was found that CFBE 41o- cells expressing wild-type CFTR (wtCFTR), when cultured on plates, had 2.9 ng of the protein in the apical PM per million cells; this represented 10% of the total CFTR found in the cells. When these cells were polarized on filters, the apical PM expression of CFTR increased to 14%. Turnover of CFTR in the apical PM of baby hamster kidney cells overexpressing wtCFTR (BHK-wtCFTR) was also quantified by targeted proteomics based on multiple reaction monitoring mass spectrometry; wtCFTR had a half-life of 29.0 ± 2.5 h in the apical PM. This represents the first direct measurement of CFTR turnover using stable isotopes. The absolute quantitation and turnover measurements of CFTR in the apical PM can significantly facilitate understanding the disease mechanism of CF and thus the development of new disease-modifying drugs. Absolute CFTR quantitation allows for direct result comparisons among analyses, analysts, and laboratories and will greatly amplify the overall outcome of CF research and therapy. PMID:25227318

  17. Dopamine Induces LTP Differentially in Apical and Basal Dendrites through BDNF and Voltage-Dependent Calcium Channels

    ERIC Educational Resources Information Center

    Navakkode, Sheeja; Sajikumar, Sreedharan; Korte, Martin; Soong, Tuck Wah

    2012-01-01

    The dopaminergic modulation of long-term potentiation (LTP) has been studied well, but the mechanism by which dopamine induces LTP (DA-LTP) in CA1 pyramidal neurons is unknown. Here, we report that DA-LTP in basal dendrites is dependent while in apical dendrites it is independent of activation of L-type voltage-gated calcium channels (VDCC).…

  18. Calcium regulates vesicle replenishment at the cone ribbon synapse.

    PubMed

    Babai, Norbert; Bartoletti, Theodore M; Thoreson, Wallace B

    2010-11-24

    Cones release glutamate-filled vesicles continuously in darkness, and changing illumination modulates this release. Because sustained release in darkness is governed by vesicle replenishment rates, we analyzed how cone membrane potential regulates replenishment. Synaptic release from cones was measured by recording postsynaptic currents in Ambystoma tigrinum horizontal or OFF bipolar cells evoked by depolarization of simultaneously voltage-clamped cones. We measured replenishment after attaining a steady state between vesicle release and replenishment using trains of test pulses. Increasing Ca(2+) currents (I(Ca)) by changing the test step from -30 to -10 mV increased replenishment. Lengthening -30 mV test pulses to match the Ca(2+) influx during 25 ms test pulses to -10 mV produced similar replenishment rates. Reducing Ca(2+) driving force by using test steps to +30 mV slowed replenishment. Using UV flashes to reverse inhibition of I(Ca) by nifedipine accelerated replenishment. Increasing [Ca(2+)](i) by flash photolysis of caged Ca(2+) also accelerated replenishment. Replenishment, but not the initial burst of release, was enhanced by using an intracellular Ca(2+) buffer of 0.5 mm EGTA rather than 5 mm EGTA, and diminished by 1 mm BAPTA. This suggests that although release and replenishment exhibited similar Ca(2+) dependencies, release sites are <200 nm from Ca(2+) channels but replenishment sites are >200 nm away. Membrane potential thus regulates replenishment by controlling Ca(2+) influx, principally by effects on replenishment mechanisms but also by altering releasable pool size. This in turn provides a mechanism for converting changes in light intensity into changes in sustained release at the cone ribbon synapse. PMID:21106825

  19. Waste minimization assessment for a manufacturer of paper rolls, ink rolls, ink ribbons, and magnetic and thermal transfer ribbon. Environmental research brief

    SciTech Connect

    Jendrucko, R.J.; Hurst, B.T.; Looby, G.P.

    1995-04-01

    The WMAC team at the University of Tennessee performed an assessment at a plant that manufactures paper rolls, ink rolls, ink ribbons, and magnetic and thermal transfer ribbon. The assessment team`s report, detailing findings and recommendations, indicated that the plant generates a great deal of hazardous waste in the coating operations of the magnetic and thermal transfer ribbon production and in the clean-up of production equipment. The greatest cost saving opportunity recommended to the plant involved the reuse of tracer ribbon in the ink ribbon production line in order to reduce raw material purchase costs.

  20. Pak3 regulates apical-basal polarity in migrating border cells during Drosophila oogenesis.

    PubMed

    Felix, Martina; Chayengia, Mrinal; Ghosh, Ritabrata; Sharma, Aditi; Prasad, Mohit

    2015-11-01

    Group cell migration is a highly coordinated process that is involved in a number of physiological events such as morphogenesis, wound healing and tumor metastasis. Unlike single cells, collectively moving cells are physically attached to each other and retain some degree of apical-basal polarity during the migratory phase. Although much is known about direction sensing, how polarity is regulated in multicellular movement remains unclear. Here we report the role of the protein kinase Pak3 in maintaining apical-basal polarity in migrating border cell clusters during Drosophila oogenesis. Pak3 is enriched in border cells and downregulation of its function impedes border cell movement. Time-lapse imaging suggests that Pak3 affects protrusive behavior of the border cell cluster, specifically regulating the stability and directionality of protrusions. Pak3 functions downstream of guidance receptor signaling to regulate the level and distribution of F-actin in migrating border cells. We also provide evidence that Pak3 genetically interacts with the lateral polarity marker Scribble and that it regulates JNK signaling in the moving border cells. Since Pak3 depletion results in mislocalization of several apical-basal polarity markers and overexpression of Jra rescues the polarity of the Pak3-depleted cluster, we propose that Pak3 functions through JNK signaling to modulate apical-basal polarity of the migrating border cell cluster. We also observe loss of apical-basal polarity in Rac1-depleted border cell clusters, suggesting that guidance receptor signaling functions through Rac GTPase and Pak3 to regulate the overall polarity of the cluster and mediate efficient collective movement of the border cells to the oocyte boundary.

  1. Curling and rolling dynamics of naturally curved ribbons.

    PubMed

    Arriagada, Octavio Albarrán; Massiera, Gladys; Abkarian, Manouk

    2014-05-01

    When a straight rod is bent and suddenly released on one end, a burst of dispersive flexural waves propagates down the material as predicted by linear beam theories. However, we show that for ribbons with a longitudinal natural radius of curvature a0, geometrical constraints lead to strain localization which controls the dynamics. This localized region of deformation selects a specific curling deformation front which travels down the ribbon when initially flattened and released. Performing experiments on different ribbons, in air and in water, we show that initially, on length scales on the order of a0, the curling front moves as a power law of time with an exponent ranging from 0.5 to 2 for increasing values of the ribbons' width. At longer time scales, the material wraps itself at a constant speed Vr into a roll of radius R ≠ a0. The relationship between Vr and R is calculated by a balance between kinetic, elastic and gravitational energy and both internal and external powers dissipated. When gravity and drag are negligible, we observe that a0/R reaches a limiting value of 0.48 that we predict by solving the Elastica on the curled ribbon considering the centrifugal forces due to rotation. The solution we propose represents a solitary traveling curvature wave which is reminiscent to propagating instabilities in mechanics.

  2. The Local Interstellar Magnetic Field Determined from the IBEX Ribbon

    NASA Astrophysics Data System (ADS)

    Zirnstein, E.; Funsten, H. O.; Heerikhuisen, J.; Livadiotis, G.; McComas, D. J.; Pogorelov, N. V.

    2015-12-01

    As the solar wind plasma flows away from the Sun, it eventually collides with the local interstellar medium, creating the heliosphere. Neutral atoms from interstellar space travel inside the heliosphere and charge-exchange with the solar wind plasma, creating energetic neutral atoms (ENAs). Some of these ENAs travel outside the heliosphere, undergo two charge-exchange events, and travel back inside the heliosphere towards Earth, with the strongest intensity in directions perpendicular to the interstellar magnetic field (IMF). It is widely believed that this process generates the "ribbon" of enhanced ENA intensity observed by the Interstellar Boundary Explorer (IBEX), and has been shown to explain many key features of the observations. IBEX observations of the ribbon are composed of a complex, line-of-sight integration of ENAs that come from different distances beyond the heliopause, and thus the ENAs detected by IBEX over a wide range of energies are uniquely coupled to the IMF draped around the heliosphere. We present a detailed analysis of the IBEX ribbon measurements using 3D simulations of the heliosphere and computations of the ribbon flux at Earth based on IBEX capabilities, and derive the magnitude and direction of the IMF required to reproduce the position of the IBEX ribbon in the sky. These results have potentially large implications for our understanding of the solar-interstellar environment.

  3. Anomalous size dependence of the thermal conductivity of graphene ribbons.

    PubMed

    Nika, Denis L; Askerov, Artur S; Balandin, Alexander A

    2012-06-13

    We investigated the thermal conductivity K of graphene ribbons and graphite slabs as the function of their lateral dimensions. Our theoretical model considered the anharmonic three-phonon processes to the second-order and included the angle-dependent phonon scattering from the ribbon edges. It was found that the long mean free path of the long-wavelength acoustic phonons in graphene can lead to an unusual nonmonotonic dependence of the thermal conductivity on the length L of a ribbon. The effect is pronounced for the ribbons with the smooth edges (specularity parameter p > 0.5). Our results also suggest that, contrary to what was previously thought, the bulk-like three-dimensional phonons in graphite make a rather substantial contribution to its in-plane thermal conductivity. The Umklapp-limited thermal conductivity of graphite slabs scales, for L below ∼30 μm, as log(L), while for larger L, the thermal conductivity approaches a finite value following the dependence K(0) - A × L(-1/2), where K(0) and A are parameters independent of the length. Our theoretical results clarify the scaling of the phonon thermal conductivity with the lateral sizes in graphene and graphite. The revealed anomalous dependence K(L) for the micrometer-size graphene ribbons can account for some of the discrepancy in reported experimental data for graphene.

  4. Curling and rolling dynamics of naturally curved ribbons.

    PubMed

    Arriagada, Octavio Albarrán; Massiera, Gladys; Abkarian, Manouk

    2014-05-01

    When a straight rod is bent and suddenly released on one end, a burst of dispersive flexural waves propagates down the material as predicted by linear beam theories. However, we show that for ribbons with a longitudinal natural radius of curvature a0, geometrical constraints lead to strain localization which controls the dynamics. This localized region of deformation selects a specific curling deformation front which travels down the ribbon when initially flattened and released. Performing experiments on different ribbons, in air and in water, we show that initially, on length scales on the order of a0, the curling front moves as a power law of time with an exponent ranging from 0.5 to 2 for increasing values of the ribbons' width. At longer time scales, the material wraps itself at a constant speed Vr into a roll of radius R ≠ a0. The relationship between Vr and R is calculated by a balance between kinetic, elastic and gravitational energy and both internal and external powers dissipated. When gravity and drag are negligible, we observe that a0/R reaches a limiting value of 0.48 that we predict by solving the Elastica on the curled ribbon considering the centrifugal forces due to rotation. The solution we propose represents a solitary traveling curvature wave which is reminiscent to propagating instabilities in mechanics. PMID:24695463

  5. Ribbon storage techniques for liquid chromatography: mass spectrometry

    SciTech Connect

    Smith, R.D.; Johnson, A.L.

    1981-06-01

    A new liquid chromatography-mass spectrometry (LC-MS) has been developed which allows semipermanent storage of the chromatographically separated material on a moving ribbon permitting multiple temperature analyses of a single LC separation. The new interface removes the major disadvantage of conventional moving ribbon devices by allowing analysis of a single LC separation at several different temperatures. Reconstructed ion chromatograms for the molecular ions in a standard mixture of benzopyrene, chrysene, carbazole, 7 amino-4-hydroxyquinoline, 5-hydroxyquinoline, 5-aminoquinoline, 5-hydroxy indole, and o-cresol are presented. The results are for a single injection and two passes of the separated material through desorption region at 195/sup 0/C and 285/sup 0/C. Reconstructed ion chromatograms are also presented for eight typical ions in an analysis of a biomass product for a single injection at three different ribbon passes through the flash heater.

  6. Piezoelectric ribbons printed onto rubber for flexible energy conversion.

    PubMed

    Qi, Yi; Jafferis, Noah T; Lyons, Kenneth; Lee, Christine M; Ahmad, Habib; McAlpine, Michael C

    2010-02-10

    The development of a method for integrating highly efficient energy conversion materials onto stretchable, biocompatible rubbers could yield breakthroughs in implantable or wearable energy harvesting systems. Being electromechanically coupled, piezoelectric crystals represent a particularly interesting subset of smart materials that function as sensors/actuators, bioMEMS devices, and energy converters. Yet, the crystallization of these materials generally requires high temperatures for maximally efficient performance, rendering them incompatible with temperature-sensitive plastics and rubbers. Here, we overcome these limitations by presenting a scalable and parallel process for transferring crystalline piezoelectric nanothick ribbons of lead zirconate titanate from host substrates onto flexible rubbers over macroscopic areas. Fundamental characterization of the ribbons by piezo-force microscopy indicates that their electromechanical energy conversion metrics are among the highest reported on a flexible medium. The excellent performance of the piezo-ribbon assemblies coupled with stretchable, biocompatible rubber may enable a host of exciting avenues in fundamental research and novel applications.

  7. Ribbon channel plate rotating drum DNA sequencing device.

    PubMed

    Douthart, R J; Welt, M; Walling, L

    1996-01-01

    A new design DNA sequencing electrophoresis device is described. The device, called the ribbon channeled plate rotating drum (rprd), consists of two major components, the plate assembly and the drum assembly. The plate assembly contains a machined or etched plate of individual micro-channels called the ribbon channeled plate. The ribbon channeled plate and other components of the plate assembly combine the advantages of thin gels and capillary arrays in a single unit with few of the disadvantages. The other major component of rprd is the drum assembly, which facilitates direct blotting onto deposition membranes affixed to a large plastic drum. The drum with attached membrane and deposited electrophoretically resolved ladders is easily moved to special units facilitating downstream processing and detection. The drum unit, although versatile, is specifically designed to be used with multiplex sequencing. PMID:8907517

  8. From Cylindrical to Stretching Ridges and Wrinkles in Twisted Ribbons

    NASA Astrophysics Data System (ADS)

    Pham Dinh, Huy; Démery, Vincent; Davidovitch, Benny; Brau, Fabian; Damman, Pascal

    2016-09-01

    Twisted ribbons under tension exhibit a remarkably rich morphology, from smooth and wrinkled helicoids, to cylindrical or faceted patterns. This complexity emanates from the instability of the natural, helicoidal symmetry of the system, which generates both longitudinal and transverse stresses, thereby leading to buckling of the ribbon. Here, we focus on the tessellation patterns made of triangular facets. Our experimental observations are described within an "asymptotic isometry" approach that brings together geometry and elasticity. The geometry consists of parametrized families of surfaces, isometric to the undeformed ribbon in the singular limit of vanishing thickness and tensile load. The energy, whose minimization selects the favored structure among those families, is governed by the tensile work and bending cost of the pattern. This framework describes the coexistence lines in a morphological phase diagram, and determines the domain of existence of faceted structures.

  9. Development of new ribbons and webbings for high performance parachutes

    SciTech Connect

    Ericksen, R.H.; Johnson, D.W.; Guess, T.R.

    1984-01-01

    Development of a 46 ft ribbon parachute required design of new and improved narrow fabrics. These included a lightweight, low porosity, 550 lb reinforced selvage nylon ribbon; a low porosity 1000 lb nylon ribbon; and a 2400 lb Kevlar webbing. Tensile elongation, lateral contraction, and other mechanical properties were measured as a function of load at room and elevated temperature to evaluate the fabrics and determine possible sources of parachute porosity variation. The property changes were too small to cause the parachute porosity to change significantly during deployment. Broken fill yarns observed in some Kevlar suspension line webbing after parachute deployment led to high rate loading tests to investigate conditions that might cause fill breakage. It was shown that fill damage did not reduce the strength of Kevlar suspension lines.

  10. Let's twist again: elasto-capillary assembly of parallel ribbons.

    PubMed

    Legrain, Antoine; Berenschot, Erwin J W; Abelmann, Leon; Bico, José; Tas, Niels R

    2016-09-14

    We show the self-assembly through twisting and bending of side by side ribbons under the action of capillary forces. Micro-ribbons made of silicon nitride are batch assembled at the wafer scale. We study their assembly as a function of their dimensions and separating distance. Model experiments are carried out at the macroscopic scale where the tension in ribbons can easily be tuned. The process is modeled considering the competition between capillary, elastic and tension forces. Theory shows a good agreement for macroscale assemblies, while the accuracy is within 30% at the micrometer scale. This simple self-assembly technique yields highly symmetric and controllable structures which could be used for batch fabrication of functional 3D micro-structures. PMID:27501147

  11. Molecular mechanisms responsible for formation of Golgi ribbon.

    PubMed

    Mironov, Alexander A; Beznoussenko, Galina V

    2011-01-01

    The formation of the Golgi ribbon takes place in protists and metazoans. It is especially prominent in mammalian cells during interphase. Golgi ribbon formation represents an orchestrated sequence of events based not only on different molecular mechanisms but also on discrete cellular functions. Mechanisms responsible for the generation of the Golgi ribbon include Golgi centralization, cis- and trans-Golgins, molecular machines responsible for the fusion of cargo domains with cisternal rims, and several other less studied factors. Here, we substantiate the hypothesis that cis-Golgins function mostly not as tethering factors, but are responsible for the attachment of the cis-most cisternae to the medial Golgi stacks, whereas trans-Golgins are responsible for the attachment of the trans-most cisterna to the medial Golgi stacks. This hypothesis is tested analyzing predictions derived from it and related to molecular mechanisms responsible for mitotic fragmentation of Golgi stacks.

  12. A Magnetic Ribbon Model for Star-forming Filaments

    NASA Astrophysics Data System (ADS)

    Auddy, Sayantan; Basu, Shantanu; Kudoh, Takahiro

    2016-11-01

    We develop a magnetic ribbon model for molecular cloud filaments. These result from turbulent compression in a molecular cloud in which the background magnetic field sets a preferred direction. We argue that this is a natural model for filaments and is based on the interplay between turbulence, strong magnetic fields, and gravitationally driven ambipolar diffusion, rather than pure gravity and thermal pressure. An analytic model for the formation of magnetic ribbons that is based on numerical simulations is used to derive a lateral width of a magnetic ribbon. This differs from the thickness along the magnetic field direction, which is essentially the Jeans scale. We use our model to calculate a synthetic observed relation between apparent width in projection versus observed column density. The relationship is relatively flat, similar to observations, and unlike the simple expectation based on a Jeans length argument.

  13. From Cylindrical to Stretching Ridges and Wrinkles in Twisted Ribbons.

    PubMed

    Pham Dinh, Huy; Démery, Vincent; Davidovitch, Benny; Brau, Fabian; Damman, Pascal

    2016-09-01

    Twisted ribbons under tension exhibit a remarkably rich morphology, from smooth and wrinkled helicoids, to cylindrical or faceted patterns. This complexity emanates from the instability of the natural, helicoidal symmetry of the system, which generates both longitudinal and transverse stresses, thereby leading to buckling of the ribbon. Here, we focus on the tessellation patterns made of triangular facets. Our experimental observations are described within an "asymptotic isometry" approach that brings together geometry and elasticity. The geometry consists of parametrized families of surfaces, isometric to the undeformed ribbon in the singular limit of vanishing thickness and tensile load. The energy, whose minimization selects the favored structure among those families, is governed by the tensile work and bending cost of the pattern. This framework describes the coexistence lines in a morphological phase diagram, and determines the domain of existence of faceted structures. PMID:27636477

  14. Mouse cystic fibrosis transmembrane conductance regulator forms cAMP-PKA-regulated apical chloride channels in cortical collecting duct.

    PubMed

    Lu, Ming; Dong, Ke; Egan, Marie E; Giebisch, Gerhard H; Boulpaep, Emile L; Hebert, Steven C

    2010-03-30

    The cystic fibrosis transmembrane conductance regulator (CFTR) is expressed in many segments of the mammalian nephron, where it may interact with and modulate the activity of a variety of apical membrane proteins, including the renal outer medullary potassium (ROMK) K(+) channel. However, the expression of CFTR in apical cell membranes or its function as a Cl(-) channel in native renal epithelia has not been demonstrated. Here, we establish that CFTR forms protein kinase A (PKA)-activated Cl(-) channels in the apical membrane of principal cells from the cortical collecting duct obtained from mice. These Cl(-) channels were observed in cell-attached apical patches of principal cells after stimulation by forskolin/3-isobutyl-1-methylxanthine. Quiescent Cl(-) channels were present in patches excised from untreated tubules because they could be activated after exposure to Mg-ATP and the catalytic subunit of PKA. The single-channel conductance, kinetics, and anion selectivity of these Cl(-) channels were the same as those of recombinant mouse CFTR channels expressed in Xenopus laevis oocytes. The CFTR-specific closed-channel blocker CFTR(inh)-172 abolished apical Cl(-) channel activity in excised patches. Moreover, apical Cl(-) channel activity was completely absent in principal cells from transgenic mice expressing the DeltaF508 CFTR mutation but was present and unaltered in ROMK-null mice. We discuss the physiologic implications of open CFTR Cl(-) channels on salt handling by the collecting duct and on the functional CFTR-ROMK interactions in modulating the metabolic ATP-sensing of ROMK. PMID:20231442

  15. The apical polarity protein network in Drosophila epithelial cells: regulation of polarity, junctions, morphogenesis, cell growth, and survival.

    PubMed

    Tepass, Ulrich

    2012-01-01

    Epithelial tissue formation and function requires the apical-basal polarization of individual epithelial cells. Apical polarity regulators (APRs) are an evolutionarily conserved group of key factors that govern polarity and several other aspects of epithelial differentiation. APRs compose a diverse set of molecules including a transmembrane protein (Crumbs), a serine/threonine kinase (aPKC), a lipid phosphatase (PTEN), a small GTPase (Cdc42), FERM domain proteins (Moesin, Yurt), and several adaptor or scaffolding proteins (Bazooka/Par3, Par6, Stardust, Patj). These proteins form a dynamic cooperative network that is engaged in negative-feedback regulation with basolateral polarity factors to set up the epithelial apical-basal axis. APRs support the formation of the apical junctional complex and the segregation of the junctional domain from the apical membrane. It is becoming increasingly clear that APRs interact with the cytoskeleton and vesicle trafficking machinery, regulate morphogenesis, and modulate epithelial cell growth and survival. Not surprisingly, APRs have multiple fundamental links to human diseases such as cancer and blindness.

  16. CLIC4 regulates apical exocytosis and renal tube luminogenesis through retromer- and actin-mediated endocytic trafficking

    PubMed Central

    Chou, Szu-Yi; Hsu, Kuo-Shun; Otsu, Wataru; Hsu, Ya-Chu; Luo, Yun-Cin; Yeh, Celine; Shehab, Syed S.; Chen, Jie; Shieh, Vincent; He, Guo-an; Marean, Michael B.; Felsen, Diane; Ding, Aihao; Poppas, Dix P.; Chuang, Jen-Zen; Sung, Ching-Hwa

    2016-01-01

    Chloride intracellular channel 4 (CLIC4) is a mammalian homologue of EXC-4 whose mutation is associated with cystic excretory canals in nematodes. Here we show that CLIC4-null mouse embryos exhibit impaired renal tubulogenesis. In both developing and developed kidneys, CLIC4 is specifically enriched in the proximal tubule epithelial cells, in which CLIC4 is important for luminal delivery, microvillus morphogenesis, and endolysosomal biogenesis. Adult CLIC4-null proximal tubules display aberrant dilation. In MDCK 3D cultures, CLIC4 is expressed on early endosome, recycling endosome and apical transport carriers before reaching its steady-state apical membrane localization in mature lumen. CLIC4 suppression causes impaired apical vesicle coalescence and central lumen formation, a phenotype that can be rescued by Rab8 and Cdc42. Furthermore, we show that retromer- and branched actin-mediated trafficking on early endosome regulates apical delivery during early luminogenesis. CLIC4 selectively modulates retromer-mediated apical transport by negatively regulating the formation of branched actin on early endosomes. PMID:26786190

  17. Optical Möbius strips and twisted ribbon cloaks.

    PubMed

    Freund, Isaac

    2014-02-15

    Optical Möbius strips that surround points of circular polarization, C points, in a generic three-dimensional optical field are cloaked by lines of twisted ribbons attached to the C points. When cloaking occurs, the observable signed twist index that counts the number of half-twists (one or three), and also measures the handedness (right or left), of a generic Möbius strip is determined by the twisted ribbon cloaks. Although some cloaks can be detached, they can never all be removed.

  18. Full-mesh optical backplane with standard MM fiber ribbons

    NASA Astrophysics Data System (ADS)

    Ferrario, M.; Coviello, D.; Boffi, P.; Martinelli, M.; Basile, V.; Fassi, I.; Falcucci, M.; Renghini, C.; Scalmati, Paolo

    2016-03-01

    A new optical backplane solution is proposed for high-capacity ICT apparatus. A modular, scalable and full-mesh bandwidth-upgradable optical interconnection between optoelectronic boards is guaranteed thanks to an optimized layout of standard MM 12-fiber ribbons which divides the overall backplane into several independent optical sub-circuits. The novel automated assembly procedure of fiber ribbons inside sub-circuits with a robotic work-cell is described. System validation of the optical backplane performed with commercially available MM 12-fiber transceivers @10Gb/s proved the feasibility of the proposed solution for future optical interconnections with terabit overall capacity.

  19. Hydrostatic extrusion of Cu-Ag melt spun ribbon

    DOEpatents

    Hill, Mary Ann; Bingert, John F.; Bingert, Sherri A.; Thoma, Dan J.

    1998-01-01

    The present invention provides a method of producing high-strength and high-conductance copper and silver materials comprising the steps of combining a predetermined ratio of the copper with the silver to produce a composite material, and melt spinning the composite material to produce a ribbon of copper and silver. The ribbon of copper and silver is heated in a hydrogen atmosphere, and thereafter die pressed into a slug. The slug then is placed into a high-purity copper vessel and the vessel is sealed with an electron beam. The vessel and slug then are extruded into wire form using a cold hydrostatic extrusion process.

  20. Hydrostatic extrusion of Cu-Ag melt spun ribbon

    DOEpatents

    Hill, M.A.; Bingert, J.F.; Bingert, S.A.; Thoma, D.J.

    1998-09-08

    The present invention provides a method of producing high-strength and high-conductance copper and silver materials comprising the steps of combining a predetermined ratio of the copper with the silver to produce a composite material, and melt spinning the composite material to produce a ribbon of copper and silver. The ribbon of copper and silver is heated in a hydrogen atmosphere, and thereafter die pressed into a slug. The slug then is placed into a high-purity copper vessel and the vessel is sealed with an electron beam. The vessel and slug then are extruded into wire form using a cold hydrostatic extrusion process. 5 figs.

  1. Okadaic acid disrupts synaptic vesicle trafficking in a ribbon-type synapse

    PubMed Central

    Guatimosim, Cristina; Hull, Court; von Gersdorff, Henrique; Prado, Marco A. M.

    2013-01-01

    Protein phosphorylation plays an essential role in regulating synaptic transmission and plasticity. However, regulation of vesicle trafficking towards and away from the plasma membrane is poorly understood. Furthermore, the extent to which phosphorylation modulates ribbon-type synapses is unknown. Using the phosphatase inhibitor okadaic acid (OA), we investigated the influence of persistent phosphorylation on vesicle cycling in goldfish bipolar cells. We followed uptake of FM1-43 during vesicle recycling in control and OA-treated cells. FM1-43 fluorescence spread to the center of control synaptic terminals after depolarization elicited Ca2+ influx. However, OA (1–50 nM) impaired this spatial spread of FM1-43 in a dose-dependent manner. Capacitance measurements revealed that OA (50 nM) did not modify either the amount or kinetics of exocytosis and endocytosis evoked by depolarizing pulses. The extremely low concentrations of OA (1–5 nM) sufficient to observe the inhibition of vesicle mobility implicate phosphatase 2A (PP2A) as a major regulator of vesicle trafficking after endocytosis. These results contrast with those at the neuromuscular junction where OA enhances lateral movement of vesicles between distinct vesicle clusters. Thus, our results suggest that phosphatases regulate vesicle translocation at ribbon synapses in a different manner than conventional active zones. PMID:12358752

  2. Optical and Calorimetric Studies of Cholesterol-Rich Filamentous, Helical Ribbon and Crystal Microstructures (abstract)

    NASA Astrophysics Data System (ADS)

    Miroshnikova, Y. A.; Elsenbeck, M.; Kashuri, K.; Iannacchione, G. S.; Zastavker, Y. V.

    2009-04-01

    Formation of biological self-assemblies at all scales is a focus of studies in fields ranging from biology to physics to biomimetics. Understanding the physico-chemical properties of these self-assemblies may lead to the design of bio-inspired structures and technological applications. Here we examine self-assembled filamentous, helical ribbon, and crystal microstructures formed in chemically defined lipid concentrate (CDLC), a model system for cholesterol crystallization in gallbladder bile. CDLC consists of cholesterol, bilayer-forming amphiphiles, micelle-forming amphiphiles, and water. Phase contrast and differential interference contrast (DIC) microscopy indicate the presence of three microstructure types in all samples studied, and allow for an investigation of the structures' unique geometries. Additionally, confocal microscopy is used for qualitative assessment of surface and internal composition. To complement optical observations, calorimetric (differential-scanning and modulation) experiments, provide the basis for an in-depth understanding of collective and individual thermal behavior. Observed ``transition'' features indicate clustering and ``straightening'' of helical ribbons into short, increasingly thickening, filaments that dissolve with increasing temperature. These results suggest that all microstructures formed in CDLC may coexist in a metastable chemical equilibrium. Further investigation of the CDLC thermal profile should uncover the process of cholesterol crystallization as well as the unique design and function of microstructures formed in this system.

  3. Optical and Calorimetric Studies of Cholesterol-Rich Filamentous, Helical Ribbon and Crystal Microstructures

    SciTech Connect

    Miroshnikova, Y. A.; Elsenbeck, M.; Zastavker, Y. V.; Kashuri, K; Iannacchione, G. S.

    2009-04-19

    Formation of biological self-assemblies at all scales is a focus of studies in fields ranging from biology to physics to biomimetics. Understanding the physico-chemical properties of these self-assemblies may lead to the design of bio-inspired structures and technological applications. Here we examine self-assembled filamentous, helical ribbon, and crystal microstructures formed in chemically defined lipid concentrate (CDLC), a model system for cholesterol crystallization in gallbladder bile. CDLC consists of cholesterol, bilayer-forming amphiphiles, micelle-forming amphiphiles, and water. Phase contrast and differential interference contrast (DIC) microscopy indicate the presence of three microstructure types in all samples studied, and allow for an investigation of the structures' unique geometries. Additionally, confocal microscopy is used for qualitative assessment of surface and internal composition. To complement optical observations, calorimetric (differential-scanning and modulation) experiments, provide the basis for an in-depth understanding of collective and individual thermal behavior. Observed ''transition'' features indicate clustering and ''straightening'' of helical ribbons into short, increasingly thickening, filaments that dissolve with increasing temperature. These results suggest that all microstructures formed in CDLC may coexist in a metastable chemical equilibrium. Further investigation of the CDLC thermal profile should uncover the process of cholesterol crystallization as well as the unique design and function of microstructures formed in this system.

  4. CFD simulation of the laminar flow in stirred tanks generated by double helical ribbons and double helical screw ribbons impellers

    NASA Astrophysics Data System (ADS)

    Driss, Zied; Karray, Sarhan; Kchaou, Hedi; Abid, Mohamed Salah

    2011-12-01

    In this paper, the mixing performance of double helical ribbons and double helical screw ribbons impellers mounted on stirred tanks is numerical investigated. The computer simulations are conducted within a specific computational fluid dynamic (CFD) code, based on resolution of the Naviers-Stokes equations in the laminar flow with a finite volume discretization. The field velocity and the viscous dissipation rate are presented in different vessel planes. The global characteristics and the power consumption of these impellers are also studied. The numerical results showed that the velocity field is more active with the double helical screw ribbons impeller. In this case, the effectiveness of the viscous dissipation and the pumping flow has been obviously noted. Also, the pumping and the energy efficiency reach the highest values at the same Reynolds number. The good agreement between the numerical results and the experimental data quietly confirmed the analysed method.

  5. A new tool based on two micromanipulators facilitates the handling of ultrathin cryosection ribbons.

    PubMed

    Studer, Daniel; Klein, Alycia; Iacovache, Ioan; Gnaegi, Helmut; Zuber, Benoît

    2014-01-01

    A close to native structure of bulk biological specimens can be imaged by cryo-electron microscopy of vitreous sections (CEMOVIS). In some cases structural information can be combined with X-ray data leading to atomic resolution in situ. However, CEMOVIS is not routinely used. The two critical steps consist of producing a frozen section ribbon of a few millimeters in length and transferring the ribbon onto an electron microscopy grid. During these steps, the first sections of the ribbon are wrapped around an eyelash (unwrapping is frequent). When a ribbon is sufficiently attached to the eyelash, the operator must guide the nascent ribbon. Steady hands are required. Shaking or overstretching may break the ribbon. In turn, the ribbon immediately wraps around itself or flies away and thereby becomes unusable. Micromanipulators for eyelashes and grids as well as ionizers to attach section ribbons to grids were proposed. The rate of successful ribbon collection, however, remained low for most operators. Here we present a setup composed of two micromanipulators. One of the micromanipulators guides an electrically conductive fiber to which the ribbon sticks with unprecedented efficiency in comparison to a not conductive eyelash. The second micromanipulator positions the grid beneath the newly formed section ribbon and with the help of an ionizer the ribbon is attached to the grid. Although manipulations are greatly facilitated, sectioning artifacts remain but the likelihood to investigate high quality sections is significantly increased due to the large number of sections that can be produced with the reported tool.

  6. 16 CFR 1511.6 - Ribbons, strings, cords, or other attachments.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 16 Commercial Practices 2 2011-01-01 2011-01-01 false Ribbons, strings, cords, or other... SUBSTANCES ACT REGULATIONS REQUIREMENTS FOR PACIFIERS § 1511.6 Ribbons, strings, cords, or other attachments. A pacifier shall not be sold or distributed with any ribbon, string, cord, chain, twine,...

  7. 16 CFR 1511.6 - Ribbons, strings, cords, or other attachments.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 16 Commercial Practices 2 2013-01-01 2013-01-01 false Ribbons, strings, cords, or other... SUBSTANCES ACT REGULATIONS REQUIREMENTS FOR PACIFIERS § 1511.6 Ribbons, strings, cords, or other attachments. A pacifier shall not be sold or distributed with any ribbon, string, cord, chain, twine,...

  8. 16 CFR 1511.6 - Ribbons, strings, cords, or other attachments.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 16 Commercial Practices 2 2014-01-01 2014-01-01 false Ribbons, strings, cords, or other... SUBSTANCES ACT REGULATIONS REQUIREMENTS FOR PACIFIERS § 1511.6 Ribbons, strings, cords, or other attachments. A pacifier shall not be sold or distributed with any ribbon, string, cord, chain, twine,...

  9. 16 CFR 1511.6 - Ribbons, strings, cords, or other attachments.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 16 Commercial Practices 2 2012-01-01 2012-01-01 false Ribbons, strings, cords, or other... SUBSTANCES ACT REGULATIONS REQUIREMENTS FOR PACIFIERS § 1511.6 Ribbons, strings, cords, or other attachments. A pacifier shall not be sold or distributed with any ribbon, string, cord, chain, twine,...

  10. Efficacy of Biodentine as an Apical Plug in Nonvital Permanent Teeth with Open Apices: An In Vitro Study.

    PubMed

    Bani, Mehmet; Sungurtekin-Ekçi, Elif; Odabaş, Mesut Enes

    2015-01-01

    The aim of this study was to evaluate the apical microleakage of Biodentine and MTA orthograde apical plugs and to compare the effect of thickness of these biomaterials on their sealing ability. A total of eighty maxillary anterior teeth were used. The apices were removed by cutting with a diamond disc (Jota, Germany) 2 mm from the apical root end in an attempt to standardize the working length of all specimens to 15 ± 1 mm. Both materials were placed in 1-4 mm thickness as apical plugs root canal. Root canal leakage was evaluated by the fluid filtration technique. One-way ANOVA was used in order to determine normality of dispersal distribution of parameters; thereafter, results were analyzed by Kolmogorov-Smirnov test. Overall, between microleakage values of MTA and Biodentine regardless of apical plug thickness, no difference was observed. In terms of plug thickness, a statistically significant difference was observed between the subgroups of MTA and Biodentine (p < 0.05). The apical sealing ability of Biodentine was comparable to MTA at any apical plug thickness. PMID:26436090

  11. Efficacy of Biodentine as an Apical Plug in Nonvital Permanent Teeth with Open Apices: An In Vitro Study

    PubMed Central

    Bani, Mehmet; Sungurtekin-Ekçi, Elif; Odabaş, Mesut Enes

    2015-01-01

    The aim of this study was to evaluate the apical microleakage of Biodentine and MTA orthograde apical plugs and to compare the effect of thickness of these biomaterials on their sealing ability. A total of eighty maxillary anterior teeth were used. The apices were removed by cutting with a diamond disc (Jota, Germany) 2 mm from the apical root end in an attempt to standardize the working length of all specimens to 15 ± 1 mm. Both materials were placed in 1–4 mm thickness as apical plugs root canal. Root canal leakage was evaluated by the fluid filtration technique. One-way ANOVA was used in order to determine normality of dispersal distribution of parameters; thereafter, results were analyzed by Kolmogorov-Smirnov test. Overall, between microleakage values of MTA and Biodentine regardless of apical plug thickness, no difference was observed. In terms of plug thickness, a statistically significant difference was observed between the subgroups of MTA and Biodentine (p < 0.05). The apical sealing ability of Biodentine was comparable to MTA at any apical plug thickness. PMID:26436090

  12. Properties of Ribbon and Non-Ribbon Release from Rod Photoreceptors Revealed by Visualizing Individual Synaptic Vesicles

    PubMed Central

    Chen, Minghui; Van Hook, Matthew J.; Zenisek, David

    2013-01-01

    Vesicle release from rod photoreceptors is regulated by Ca2+ entry through L-type channels located near synaptic ribbons. We characterized sites and kinetics of vesicle release in salamander rods by using total internal reflection fluorescence microscopy to visualize fusion of individual synaptic vesicles. A small number of vesicles were loaded by brief incubation with FM1–43 or a dextran-conjugated, pH-sensitive form of rhodamine, pHrodo. Labeled organelles matched the diffraction-limited size of fluorescent microspheres and disappeared rapidly during stimulation. Consistent with fusion, depolarization-evoked vesicle disappearance paralleled electrophysiological release kinetics and was blocked by inhibiting Ca2+ influx. Rods maintained tonic release at resting membrane potentials near those in darkness, causing depletion of membrane-associated vesicles unless Ca2+ entry was inhibited. This depletion of release sites implies that sustained release may be rate limited by vesicle delivery. During depolarizing stimulation, newly appearing vesicles approached the membrane at ∼800 nm/s, where they paused for ∼60 ms before fusion. With fusion, vesicles advanced ∼18 nm closer to the membrane. Release events were concentrated near ribbons, but lengthy depolarization also triggered release from more distant non-ribbon sites. Consistent with greater contributions from non-ribbon sites during lengthier depolarization, damaging the ribbon by fluorophore-assisted laser inactivation (FALI) of Ribeye caused only weak inhibition of exocytotic capacitance increases evoked by 200-ms depolarizing test steps, whereas FALI more strongly inhibited capacitance increases evoked by 25 ms steps. Amplifying release by use of non-ribbon sites when rods are depolarized in darkness may improve detection of decrements in release when they hyperpolarize to light. PMID:23365244

  13. Graphene: powder, flakes, ribbons, and sheets.

    PubMed

    James, Dustin K; Tour, James M

    2013-10-15

    Graphene's unique physical and electrical properties (high tensile strength, Young's modulus, electron mobility, and thermal conductivity) have led to its nickname of "super carbon." Graphene research involves the study of several different physical forms of the material: powders, flakes, ribbons, and sheets and others not yet named or imagined. Within those forms, graphene can include a single layer, two layers, or ≤10 sheets of sp² carbon atoms. The chemistry and applications available with graphene depend on both the physical form of the graphene and the number of layers in the material. Therefore the available permutations of graphene are numerous, and we will discuss a subset of this work, covering some of our research on the synthesis and use of many of the different physical and layered forms of graphene. Initially, we worked with commercially available graphite, with which we extended diazonium chemistry developed to functionalize single-walled carbon nanotubes to produce graphitic materials. These structures were soluble in common organic solvents and were better dispersed in composites. We developed an improved synthesis of graphene oxide (GO) and explored how the workup protocol for the synthesis of GO can change the electronic structure and chemical functionality of the GO product. We also developed a method to remove graphene layers one-by-one from flakes. These powders and sheets of GO can serve as fluid loss prevention additives in drilling fluids for the oil industry. Graphene nanoribbons (GNRs) combine small width with long length, producing valuable electronic and physical properties. We developed two complementary syntheses of GNRs from multiwalled carbon nanotubes: one simple oxidative method that produces GNRs with some defects and one reductive method that produces GNRs that are less defective and more electrically conductive. These GNRs can be used in low-loss, high permittivity composites, as conductive reinforcement coatings on Kevlar

  14. Graphene: powder, flakes, ribbons, and sheets.

    PubMed

    James, Dustin K; Tour, James M

    2013-10-15

    Graphene's unique physical and electrical properties (high tensile strength, Young's modulus, electron mobility, and thermal conductivity) have led to its nickname of "super carbon." Graphene research involves the study of several different physical forms of the material: powders, flakes, ribbons, and sheets and others not yet named or imagined. Within those forms, graphene can include a single layer, two layers, or ≤10 sheets of sp² carbon atoms. The chemistry and applications available with graphene depend on both the physical form of the graphene and the number of layers in the material. Therefore the available permutations of graphene are numerous, and we will discuss a subset of this work, covering some of our research on the synthesis and use of many of the different physical and layered forms of graphene. Initially, we worked with commercially available graphite, with which we extended diazonium chemistry developed to functionalize single-walled carbon nanotubes to produce graphitic materials. These structures were soluble in common organic solvents and were better dispersed in composites. We developed an improved synthesis of graphene oxide (GO) and explored how the workup protocol for the synthesis of GO can change the electronic structure and chemical functionality of the GO product. We also developed a method to remove graphene layers one-by-one from flakes. These powders and sheets of GO can serve as fluid loss prevention additives in drilling fluids for the oil industry. Graphene nanoribbons (GNRs) combine small width with long length, producing valuable electronic and physical properties. We developed two complementary syntheses of GNRs from multiwalled carbon nanotubes: one simple oxidative method that produces GNRs with some defects and one reductive method that produces GNRs that are less defective and more electrically conductive. These GNRs can be used in low-loss, high permittivity composites, as conductive reinforcement coatings on Kevlar

  15. Apical surgery: A review of current techniques and outcome

    PubMed Central

    von Arx, Thomas

    2010-01-01

    Apical surgery is considered a standard oral surgical procedure. It is often a last resort to surgically maintain a tooth with a periapical lesion that cannot be managed with conventional endodontic (re-)treatment. The main goal of apical surgery is to prevent bacterial leakage from the root-canal system into the periradicular tissues by placing a tight root-end filling following root-end resection. Clinicians are advised to utilize a surgical microscope to perform apical surgery to benefit from magnification and illumination. In addition, the application of microsurgical techniques in apical surgery, i.e., gentle incision and flap elevation, production of a small osteotomy, and the use of sonic- or ultrasonic driven microtips, will result in less trauma to the patient and faster postsurgical healing. A major step in apical surgery is to identify possible leakage areas at the cut root face and subsequently to ensure adequate root-end filling. Only a tight and persistent apical obturation will allow periapical healing with good long-term prognosis. The present paper describes current indications, techniques and outcome of apical surgery. PMID:24151412

  16. Effect of gravity on apical dominance in Pharbitis nil.

    PubMed

    Kitazawa, Daisuke; Fujii, Nobuharu; Suge, Hiroshi; Takahashi, Hideyuki

    2003-10-01

    When the upper part of main shoot of morning glory (Pharbitis nil) is gently bent down, lateral bud on the bending region is released from apical dominance and starts to elongate. But, clinorotating the bending shoots prevents the release of the lateral bud from apical dominance. These results suggest that gravity affects apical dominance in morning glory. Here we verified the gravity-regulated apical dominance by using a weeping morning glory defective in gravitropic response due to abnormal differentiation of endodermis. That is, bending main shoot of the weeping morning glory hardly caused the lateral bud to elongate. In addition, decapitation of apical bud released the lateral bud from apical dominance, and exogenous auxin applied to the cut surface of the decapitated stem was inhibitory to the outgrowth of the lateral bud in the wild type. However, the effect of auxin was much less in the weeping morning glory. Thus, apical dominance of the weeping morning glory was weaker and less influenced by gravity than that of the wild type, which could occur due to abnormal differentiation of endodermis required for graviperception.

  17. Improved method of edge coating flat ribbon wire

    NASA Technical Reports Server (NTRS)

    1966-01-01

    Method to coat the edges of flat ribbon wire is devised by using enamel with modified flow properties due to addition of 2 to 4 percent silicon. Conventional coating procedes several edge coatings to minimize oxidation and additional conventional coats are applied after edge coating to build up thickness.

  18. SPATIAL RETENTION OF IONS PRODUCING THE IBEX RIBBON

    SciTech Connect

    Schwadron, N. A.; McComas, D. J.

    2013-02-10

    The ribbon observed by the Interstellar Boundary Explorer (IBEX) mission is a narrow, {approx}20 Degree-Sign wide feature that stretches across much of the sky in the global flux of energetic neutral atoms from the outer heliosphere. The ribbon remains an enigma despite its persistence after 3 years of IBEX observations and after almost a dozen theories that attempt to explain it. While each theory that has been posed has its strengths, each one also contradicts IBEX observations or demonstrates significant flaws in internal consistency. Here, we present a new theory that is different than any of the existing ideas and yet accounts for many of the key observations. We argue that the ribbon could be produced by a spatial region in the local interstellar medium where newly ionized atoms are temporarily contained through increased rates of scattering by locally generated waves in the electromagnetic fields. The particles in the ribbon are created predominantly from neutralized solar wind and neutralized pickup ions from inside the solar wind termination shock.

  19. 38 CFR 21.9700 - Yellow Ribbon Program.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 38 Pensions, Bonuses, and Veterans' Relief 2 2012-07-01 2012-07-01 false Yellow Ribbon Program. 21.9700 Section 21.9700 Pensions, Bonuses, and Veterans' Relief DEPARTMENT OF VETERANS AFFAIRS (CONTINUED) VOCATIONAL REHABILITATION AND EDUCATION Post-9/11 GI Bill Payments-Educational Assistance § 21.9700...

  20. 38 CFR 21.9700 - Yellow Ribbon Program.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 38 Pensions, Bonuses, and Veterans' Relief 2 2011-07-01 2011-07-01 false Yellow Ribbon Program. 21.9700 Section 21.9700 Pensions, Bonuses, and Veterans' Relief DEPARTMENT OF VETERANS AFFAIRS (CONTINUED) VOCATIONAL REHABILITATION AND EDUCATION Post-9/11 GI Bill Payments-Educational Assistance § 21.9700...

  1. 38 CFR 21.9700 - Yellow Ribbon Program.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 38 Pensions, Bonuses, and Veterans' Relief 2 2014-07-01 2014-07-01 false Yellow Ribbon Program. 21.9700 Section 21.9700 Pensions, Bonuses, and Veterans' Relief DEPARTMENT OF VETERANS AFFAIRS (CONTINUED) VOCATIONAL REHABILITATION AND EDUCATION Post-9/11 GI Bill Payments-Educational Assistance § 21.9700...

  2. 38 CFR 21.9700 - Yellow Ribbon Program.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 38 Pensions, Bonuses, and Veterans' Relief 2 2013-07-01 2013-07-01 false Yellow Ribbon Program. 21.9700 Section 21.9700 Pensions, Bonuses, and Veterans' Relief DEPARTMENT OF VETERANS AFFAIRS (CONTINUED) VOCATIONAL REHABILITATION AND EDUCATION Post-9/11 GI Bill Payments-Educational Assistance § 21.9700...

  3. Observations and Numerical Modeling of the Jovian Ribbon

    NASA Astrophysics Data System (ADS)

    Cosentino, R. G.; Simon, A.; Morales-Juberias, R.; Sayanagi, K. M.

    2015-09-01

    Multiple wavelength observations made by the Hubble Space Telescope in early 2007 show the presence of a wavy, high-contrast feature in Jupiter’s atmosphere near 30°N. The “Jovian Ribbon,” best seen at 410 nm, irregularly undulates in latitude and is time-variable in appearance. A meridional intensity gradient algorithm was applied to the observations to track the Ribbon’s contour. Spectral analysis of the contour revealed that the Ribbon’s structure is a combination of several wavenumbers ranging from k = 8–40. The Ribbon is a dynamic structure that has been observed to have spectral power for dominant wavenumbers which vary over a time period of one month. The presence of the Ribbon correlates with periods when the velocity of the westward jet at the same location is highest. We conducted numerical simulations to investigate the stability of westward jets of varying speed, vertical shear, and background static stability to different perturbations. A Ribbon-like morphology was best reproduced with a 35 ms‑1 westward jet that decreases in amplitude for pressures greater than 700 hPa and a background static stability of N = 0.005 s‑1 perturbed by heat pulses constrained to latitudes south of 30°N. Additionally, the simulated feature had wavenumbers that qualitatively matched observations and evolved throughout the simulation reproducing the Jovian Ribbon’s dynamic structure.

  4. 75 FR 36647 - Blue Ribbon Commission on America's Nuclear Future

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-06-28

    ...This notice announces an open meeting of the Blue Ribbon Commission on America's Nuclear Future (the Commission). The Commission was organized pursuant to the Federal Advisory Committee Act (Pub. L. 92-463, 86 Stat. 770) (the Act). This notice is provided in accordance with the...

  5. 75 FR 67958 - Blue Ribbon Commission on America's Nuclear Future

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-11-04

    ... Ribbon Commission on America's Nuclear Future AGENCY: Office of Nuclear Energy, Department of Energy... CommissionDFO@nuclear.energy.gov . Additional information will be available at http://www.brc.gov... cycle policies that have been established by other leading nuclear energy nations. The Commission...

  6. 76 FR 2891 - Blue Ribbon Commission on America's Nuclear Future

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-01-18

    ... Ribbon Commission on America's Nuclear Future AGENCY: Office of Nuclear Energy, Department of Energy...-4243 or facsimile (202) 586- 0544; e-mail CommissionDFO@nuclear.energy.gov . Additional information... and nuclear waste. The Commission is scheduled to submit a draft report to the Secretary of Energy...

  7. 76 FR 1608 - Blue Ribbon Commission on America's Nuclear Future

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-01-11

    ... Ribbon Commission on America's Nuclear Future AGENCY: Department of Energy, Office of Nuclear Energy... and nuclear waste. The Commission is scheduled to submit a draft report to the Secretary of Energy by... to CommissionDFO@nuclear.energy.gov , or post comments on the Commission Web site at...

  8. 75 FR 25850 - Blue Ribbon Commission on America's Nuclear Future

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-05-10

    ... Ribbon Commission on America's Nuclear Future AGENCY: Department of Energy, Office of Nuclear Energy...- 0544; e-mail CommissionDFO@nuclear.energy.gov . Additional information may also be available at http... to CommissionDFO@nuclear.energy.gov , or post comments on the Commission Web site at...

  9. 76 FR 4646 - Blue Ribbon Commission on America's Nuclear Future

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-01-26

    ... Ribbon Commission on America's Nuclear Future AGENCY: Department of Energy, Office of Nuclear Energy... facsimile (202) 586- 0544; e-mail CommissionDFO@nuclear.energy.gov . Additional information will be... to CommissionDFO@nuclear.energy.gov , or post comments on the Commission Web site at...

  10. 75 FR 13757 - Blue Ribbon Commission on America's Nuclear Future

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-03-23

    ... From the Federal Register Online via the Government Publishing Office DEPARTMENT OF ENERGY Blue Ribbon Commission on America's Nuclear Future AGENCY: Department of Energy, Office of Nuclear Energy.... Department of Energy 1000 Independence Avenue, SW., Washington DC 20585, or e-mail...

  11. 76 FR 1607 - Blue Ribbon Commission on America's Nuclear Future

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-01-11

    ... Ribbon Commission on America's Nuclear Future AGENCY: Department of Energy, Office of Nuclear Energy...) 586-4243 or facsimile (202) 586- 0544; e-mail CommissionDFO@nuclear.energy.gov . Additional.... Department of Energy, 1000 Independence Avenue, SW., Washington, DC 20585, e-mail to...

  12. 75 FR 10791 - Blue Ribbon Commission on America's Nuclear Future

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-03-09

    ... Ribbon Commission on America's Nuclear Future AGENCY: Department of Energy, Office of Nuclear Energy...-4243 or facsimile (202) 586- 0544; e-mail CommissionDFO@nuclear.energy.gov . SUPPLEMENTARY INFORMATION... knowledge of issues pertaining to nuclear energy. Purpose of the Meeting: Inform the Commission...

  13. Extrusion of metal oxide superconducting wire, tube or ribbon

    DOEpatents

    Dusek, Joseph T.

    1993-01-01

    A process for extruding a superconducting metal oxide composition YBa.sub.2 Cu.sub.3 O.sub.7-x provides a wire (tube or ribbon) having a cohesive mass and a degree of flexibility together with enhanced electrical properties. Wire diameters in the range of 6-85 mils have been produced with smaller wires on the order of 10 mils in diameter exhibiting enhanced flexibility for forming braided, or multistrand, configurations for greater current carrying capacity. The composition for extrusion contains a polymeric binder to provide a cohesive mass to bind the particles together during the extrusion process with the binder subsequently removed at lower temperatures during sintering. The composition for extrusion further includes a deflocculent, an organic plasticizer and a solvent which also are subsequently removed during sintering. Electrically conductive tubing with an inner diameter of 52 mil and an outer diameter of 87-355 mil has also been produced. Flat ribbons have been produced in the range of 10-125 mil thick by 100-500 mil wide. The superconducting wire, tube or ribbon may include an outer ceramic insulating sheath co-extruded with the wire, tubing or ribbon.

  14. 75 FR 81592 - Blue Ribbon Commission on America's Nuclear Future

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-12-28

    ..., processing, and disposal of civilian and defense spent nuclear fuel and nuclear waste. The Commission is... Ribbon Commission on America's Nuclear Future AGENCY: Department of Energy, Office of Nuclear Energy... Commission on America's Nuclear Future (the Commission). The Commission was organized pursuant to the...

  15. 4. DETAIL OF NAME AND RIBBON BOARDS ON PORT SIDE. ...

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

    4. DETAIL OF NAME AND RIBBON BOARDS ON PORT SIDE. NAME BOARD WAS REMOVED AT TIME OF DECOMMISSIONING. PHOTOGRAPHER TEMPORARILY REATTACHED THE NAME BOARD. - U.S. Coast Guard Cutter WHITE LUPINE, U.S. Coast Guard Station Rockland, east end of Tillson Avenue, Rockland, Knox County, ME

  16. Effects of parachute-ribbon surface treatments on tensile strength

    SciTech Connect

    Auerbach, I.; Whinery, L.D.; Johnson, D.W.; Mead, K.E.; Sheldon, D.D.

    1986-01-01

    Routine quality-assurance evaluations of nylon ribbons used on test-deployed parachutes revealed tensile-strength degradation had occurred in some of the ribbons. The degradation occurred exclusively in some of the noncritical skirt ribbons with stenciled blue-ink identification markings. Although the strength loss was excessive, the reliability of the parachute was not affected. These results motivated an accelerated-aging study of the effects on tensile strength of not only the inks but also of the sizing chemicals that are used to coat fabrics in parachute construction. Nylon ribbons and Kevlar webbing were treated with these materials and stored both under ambient conditions and at 60/sup 0/C (140/sup 0/F) for periods of time up to eight months. Small increases in strength developed under ambient conditions whereas small decreases developed at elevated temperatures. Samples stored in glass degraded more than those stored in stainless steel. None of these laboratory results correlated with those obtained from parachutes. Possible explanations for the lack of a correlation are provided in this paper. Additional studies are in progress.

  17. Extrusion of metal oxide superconducting wire, tube or ribbon

    DOEpatents

    Dusek, Joseph T.

    1993-10-05

    A process for extruding a superconducting metal oxide composition YBa.sub.2 Cu.sub.3 O.sub.7-x provides a wire (tube or ribbon) having a cohesive mass and a degree of flexibility together with enhanced electrical properties. Wire diameters in the range of 6-85 mils have been produced with smaller wires on the order of 10 mils in diameter exhibiting enhanced flexibility for forming braided, or multistrand, configurations for greater current carrying capacity. The composition for extrusion contains a polymeric binder to provide a cohesive mass to bind the particles together during the extrusion process with the binder subsequently removed at lower temperatures during sintering. The composition for extrusion further includes a deflocculent, an organic plasticizer and a solvent which also are subsequently removed during sintering. Electrically conductive tubing with an inner diameter of 52 mil and an outer diameter of 87-355 mil has also been produced. Flat ribbons have been produced in the range of 10-125 mil thick by 100-500 mil wide. The superconducting wire, tube or ribbon may include an outer ceramic insulating sheath co-extruded with the wire, tubing or ribbon.

  18. Hypercompliant Apical Membranes of Bladder Umbrella Cells

    PubMed Central

    Mathai, John C.; Zhou, Enhua H.; Yu, Weiqun; Kim, Jae Hun; Zhou, Ge; Liao, Yi; Sun, Tung-Tien; Fredberg, Jeffrey J.; Zeidel, Mark L.

    2014-01-01

    Urinary bladder undergoes dramatic volume changes during filling and voiding cycles. In the bladder the luminal surface of terminally differentiated urothelial umbrella cells is almost completely covered by plaques. These plaques (500 to 1000 nm) are made of a family of proteins called uroplakins that are known to form a tight barrier to prevent leakage of water and solutes. Electron micrographs from previous studies show these plaques to be interconnected by hinge regions to form structures that appear rigid, but these same structures must accommodate large changes in cell shape during voiding and filling cycles. To resolve this paradox, we measured the stiffness of the intact, living urothelial apical membrane and found it to be highly deformable, even more so than the red blood cell membrane. The intermediate cells underlying the umbrella cells do not have uroplakins but their membranes are an order of magnitude stiffer. Using uroplakin knockout mouse models we show that cell compliance is conferred by uroplakins. This hypercompliance may be essential for the maintenance of barrier function under dramatic cell deformation during filling and voiding of the bladder. PMID:25229135

  19. Apical control of conidiation in Aspergillus nidulans.

    PubMed

    Oiartzabal-Arano, Elixabet; Perez-de-Nanclares-Arregi, Elixabet; Espeso, Eduardo A; Etxebeste, Oier

    2016-05-01

    The infection cycle of filamentous fungi consists of two main stages: invasion (growth) and dispersion (development). After the deposition of a spore on a host, germination, polar extension and branching of vegetative cells called hyphae allow a fast and efficient invasion. Under suboptimal conditions, genetic reprogramming of hyphae results in the generation of asexual spores, allowing dissemination to new hosts and the beginning of a new infection cycle. In the model filamentous fungus Aspergillus nidulans, asexual development or conidiation is induced by the upstream developmental activation (UDA) pathway. UDA proteins transduce signals from the tip, the polarity site of hyphae, to nuclei, where developmental programs are transcriptionally activated. The present review summarizes the current knowledge on this tip-to-nucleus communication mechanism, emphasizing its dependence on hyphal polarity. Future approaches to the topic will also be suggested, as stimulating elements contributing to the understanding of how apical signals are coupled with the transcriptional control of development and pathogenesis in filamentous fungi. PMID:26782172

  20. The status of silicon ribbon growth technology for high-efficiency silicon solar cells

    NASA Technical Reports Server (NTRS)

    Ciszek, T. F.

    1985-01-01

    More than a dozen methods have been applied to the growth of silicon ribbons, beginning as early as 1963. The ribbon geometry has been particularly intriguing for photovoltaic applications, because it might provide large area, damage free, nearly continuous substrates without the material loss or cost of ingot wafering. In general, the efficiency of silicon ribbon solar cells has been lower than that of ingot cells. The status of some ribbon growth techniques that have achieved laboratory efficiencies greater than 13.5% are reviewed, i.e., edge-defined, film-fed growth (EFG), edge-supported pulling (ESP), ribbon against a drop (RAD), and dendritic web growth (web).

  1. Nucleation and growth of crystalline ribbons in diastereomeric ephedrine cyclic phosphoric acid systems

    NASA Astrophysics Data System (ADS)

    Loh, Joanne S. C.; van Enckevort, Willem J. P.; Vlieg, Elias

    2004-05-01

    In an attempt to understand the fast formation of diastereomerically enriched crystals in a Dutch resolution system, the nucleation and growth behaviour of such a system was investigated by in situ optical microscopy. Nucleation was observed to follow two pathways: nuclei crystal formation and ribbon formation. The shape of these ribbons (flat, helical or twisted) was dependent on the composition of the system. Hindrance during growth of the ribbons was observed to result in cleavage of the ribbons, creating new crystals. After continued growth, the ribbons develop into needles. This is most likely caused by the introduction of defects and not by a change in crystal polymorph.

  2. Study of phase transformation and crystal structure for 1D carbon-modified titania ribbons

    SciTech Connect

    Zhou, Lihui Zhang, Fang; Li, Jinxia

    2014-02-15

    One-dimensional hydrogen titanate ribbons were successfully prepared with hydrothermal reaction in a highly basic solution. A series of one-dimensional carbon-modified TiO{sub 2} ribbons were prepared via calcination of the mixture of hydrogen titanate ribbons and sucrose solution under N{sub 2} flow at different temperatures. The phase transformation process of hydrogen titanate ribbons was investigated by in-situ X-ray diffraction at various temperatures. Besides, one-dimensional carbon-modified TiO{sub 2} ribbons calcined at different temperatures were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, nitrogen adsorption isotherms, diffuse reflectance ultraviolet–visible spectroscopy, and so on. Carbon-modified TiO{sub 2} ribbons showed one-dimensional ribbon crystal structure and various crystal phases of TiO{sub 2}. After being modified with carbon, a layer of uniform carbon film was coated on the surface of TiO{sub 2} ribbons, which improved their adsorption capacity for methyl orange as a model organic pollutant. One-dimensional carbon-modified TiO{sub 2} ribbons also exhibited enhanced visible-light absorbance with the increase of calcination temperatures. - Highlights: • The synthesis of 1D carbon-modified TiO{sub 2} ribbons. • The phase transformation of 1D carbon-modified TiO{sub 2} ribbons. • 1D carbon-modified TiO{sub 2} exhibites enhanced visible-light absorbance.

  3. Blue Ribbon Commissions and Higher Education: Changing Academe from the Outside. ASHE-ERIC Higher Education Report No. 2, 1986.

    ERIC Educational Resources Information Center

    Johnson, Janet Rogers-Clarke; Marcus, Laurence R.

    Blue ribbon commissions in the United States from 1965-1983 are reviewed, and two commissions are covered in-depth. Attention is directed to: nationally-oriented blue-ribbon commissions, state-level commissions, blue ribbon commissions on campus, and factors that make commissions effective. For purposes of the study, a blue ribbon commission was…

  4. Coordinated regulation of apical hook development by gibberellins and ethylene in etiolated Arabidopsis seedlings

    PubMed Central

    An, Fengying; Zhang, Xing; Zhu, Ziqiang; Ji, Yusi; He, Wenrong; Jiang, Zhiqiang; Li, Mingzhe; Guo, Hongwei

    2012-01-01

    Dark-grown Arabidopsis seedlings develop an apical hook when germinating in soil, which protects the cotyledons and apical meristematic tissues when protruding through the soil. Several hormones are reported to distinctly modulate this process. Previous studies have shown that ethylene and gibberellins (GAs) coordinately regulate the hook development, although the underlying molecular mechanism is largely unknown. Here we showed that GA3 enhanced while paclobutrazol repressed ethylene- and EIN3-overexpression (EIN3ox)-induced hook curvature, and della mutant exhibited exaggerated hook curvature, which required an intact ethylene signaling pathway. Genetic study revealed that GA-enhanced hook development was dependent on HOOKLESS 1 (HLS1), a central regulator mediating the input of the multiple signaling pathways during apical hook development. We further found that GA3 induced (and DELLA proteins repressed) HLS1 expression in an ETHYLENE INSENSITIVE 3/EIN3-LIKE 1 (EIN3/EIL1)-dependent manner, whereby EIN3/EIL1 activated HLS1 transcription by directly binding to its promoter. Additionally, DELLA proteins were found to interact with the DNA-binding domains of EIN3/EIL1 and repress EIN3/EIL1-regulated HLS1 expression. Treatment with naphthylphthalamic acid, a polar auxin transport inhibitor, repressed the constitutively exaggerated hook curvature of EIN3ox line and della mutant, supporting that auxin functions downstream of the ethylene and GA pathways in hook development. Taken together, our results identify EIN3/EIL1 as a new class of DELLA-associated transcription factors and demonstrate that GA promotes apical hook formation in cooperation with ethylene partly by inducing the expression of HLS1 via derepression of EIN3/EIL1 functions. PMID:22349459

  5. Localization of apical sushi protein in Plasmodium falciparum merozoites.

    PubMed

    Srivastava, Anand; Singh, Shailja; Dhawan, Shikha; Mahmood Alam, M; Mohmmed, Asif; Chitnis, Chetan E

    2010-11-01

    Plasmodium falciparum belongs to the Apicomplexan group of parasites and is characterised by presence of specialized secretory organelles at the apical end. These apical organelles, referred to as microneme and rhoptries, contain proteins that play important roles during host cell invasion by mediating specific functions such as initial attachment, apical reorientation and junction formation. Recently, a protein referred to as P. falciparum apical sushi protein (PfASP), which is expressed at late schizont stage, was localized to micronemes of P. falciparum merozoites. In the present study, we have used indirect immunofluorescence assays and immunoelectron microscopy to demonstrate that PfASP is localized in the neck of rhoptries and not in micronemes as previously described.

  6. Apical constriction and epithelial invagination are regulated by BMP activity

    PubMed Central

    Jidigam, Vijay K.; Srinivasan, Raghuraman C.; Patthey, Cedric; Gunhaga, Lena

    2015-01-01

    ABSTRACT Epithelial invagination is a morphological process in which flat cell sheets transform into three-dimensional structures through bending of the tissue. It is accompanied by apical constriction, in which the apical cell surface is reduced in relation to the basal cell surface. Although much is known about the intra-cellular molecular machinery driving apical constriction and epithelial invagination, information of how extra-cellular signals affect these processes remains insufficient. In this study we have established several in vivo assays of placodal invagination to explore whether the external signal BMP regulates processes connected to epithelial invagination. By inhibiting BMP activity in prospective cranial placodes, we provide evidence that BMP signals are required for RhoA and F-actin rearrangements, apical constriction, cell elongation and epithelial invagination. The failure of placode invagination after BMP inhibition appears to be a direct consequence of disrupted apical accumulation of RhoA and F-actin, rather than changes in cell death or proliferation. In addition, our results show that epithelial invagination and acquisition of placode-specific identities are two distinct and separable developmental processes. In summary, our results provide evidence that BMP signals promote epithelial invagination by acting upstream of the intracellular molecular machinery that drives apical constriction and cell elongation. PMID:26621830

  7. Haemostatic agents in apical surgery. A systematic review

    PubMed Central

    Clé-Ovejero, Adrià

    2016-01-01

    Background Blood presence in apical surgery can prevent the correct vision of the surgical field, change the physical properties of filling materials and reduce their sealing ability. Objetive To describe which are the most effective and safest haemostatic agents to control bleeding in patients undergoing apical surgery. Material and Methods TWe carried out a systematic review, using Medline and Cochrane Library databases, of human clinical studies published in the last 10 years. Results The agents that proved more effective in bleeding control were calcium sulphate (100%) and collagen plus epinephrine (92.9%) followed by ferric sulphate (60%), gauze packing (30%) and collagen (16.7%). When using aluminium chloride (Expasyl®), over 90% of the apical lesions improved, but this agent seemed to increase swelling. Epinephrine with collagen did not significantly raise either blood pressure or heart rate. Conclusions Despite the use of several haemostatic materials in apical surgery, there is little evidence on their effectiveness and safety. The most effective haemostatic agents were calcium sulphate and epinephrine plus collagen. Epinephrine plus collagen did not seem to significantly raise blood pressure or heart rate during surgery. Aluminium chloride did not increase postoperative pain but could slightly increase postoperative swelling. Randomized clinical trials are needed to assess the haemostatic effectiveness and adverse effects of haemostatic materials in apical surgery. Key words:Haemostasis, apical surgery. PMID:27475689

  8. Molecular dissection of the photoreceptor ribbon synapse: physical interaction of Bassoon and RIBEYE is essential for the assembly of the ribbon complex.

    PubMed

    tom Dieck, Susanne; Altrock, Wilko D; Kessels, Michael M; Qualmann, Britta; Regus, Hanna; Brauner, Dana; Fejtová, Anna; Bracko, Oliver; Gundelfinger, Eckart D; Brandstätter, Johann H

    2005-02-28

    The ribbon complex of retinal photoreceptor synapses represents a specialization of the cytomatrix at the active zone (CAZ) present at conventional synapses. In mice deficient for the CAZ protein Bassoon, ribbons are not anchored to the presynaptic membrane but float freely in the cytoplasm. Exploiting this phenotype, we dissected the molecular structure of the photoreceptor ribbon complex. Identifiable CAZ proteins segregate into two compartments at the ribbon: a ribbon-associated compartment including Piccolo, RIBEYE, CtBP1/BARS, RIM1, and the motor protein KIF3A, and an active zone compartment including RIM2, Munc13-1, a Ca2+ channel alpha1 subunit, and ERC2/CAST1. A direct interaction between the ribbon-specific protein RIBEYE and Bassoon seems to link the two compartments and is responsible for the physical integrity of the photoreceptor ribbon complex. Finally, we found the RIBEYE homologue CtBP1 at ribbon and conventional synapses, suggesting a novel role for the CtBP/BARS family in the molecular assembly and function of central nervous system synapses.

  9. The circularity and stability of the IBEX energetic neutral atom (ENA) ribbon

    SciTech Connect

    Funsten, Herbert O

    2010-09-07

    The first sky map of energetic neutral atoms (ENAs) from the outer heliosphere measured from the Interstellar Boundary Explorer revealed the ribbon, a remarkable circular arc of enhanced ENA emission [McComas, et all, 2009] narrow in width [Fuselier, et all, 2009] and centered at ecliptic coordinate ({lambda},{beta}) = (221{sup o},39{sup o}) [Funsten et al., 2009]. The ribbon is a key signature for understanding the interaction of the heliosphere and the interstellar cloud through which we are moving [McComas, et al., 2009; Schwadron et al., 2010]. At each energy passband of the IBEX-Hi neutral atom imager, we compare the circular metrics of the ribbon in the different ENA sky maps, including the ribbon center, opening angle from the ribbon center to the ribbon, and ribbon circularity. The values of these parameters do not systematically change between maps within statistical uncertainty, suggesting that the dynamics that govern the ribbon structure do not vary on a global scale over the time frame of the maps. Assuming the ribbon ENAs of all energies originate from the same source, the time of travel of lower energy ENAs is nearly twice that of higher energy ENAs measured by IBEX. Thus, because the lower energy ions are characteristic of the ribbon structure earlier in time than the higher energy ions, we infer that this stability extends over a longer time period than that used to acquire the maps.

  10. A novel use of friability testing for characterising ribbon milling behaviour.

    PubMed

    Schiano, Serena; Wu, Chuan-Yu; Mirtic, Andreja; Reynolds, Gavin

    2016-07-01

    Dry granulation using roll compaction (DGRC) has been increasingly adopted in the pharmaceutical industry due to its unique advantage of not requiring liquid binder and a subsequent drying process. However the DGRC process presents also some challenges, in particular, a high fine fraction generated during the milling stage significantly limits its application. Although the fines produced can be recycled in practice, it may lead to poor content uniformity of the final product. At present there is a lack of mechanistic understanding of milling of roll compacted ribbons. For instance, it is not clear how fines are generated, what are the dominant mechanisms and controlling attributes and whether any measurement technique can be used to characterise ribbon milling behaviour. Therefore, the aim of this paper was to assess whether ribbon milling behaviour can be assessed using some characterisation methods. For this purpose, friability was evaluated for ribbons made of microcrystalline cellulose (MCC) powders using a friability tester that was originally developed for characterising the tendency of pharmaceutical tablets to generate small pieces while being abraded. Granules were also produced by milling of the ribbons and their size distributions were measured. The correlation between the fine fraction of the granules with ribbon friability was then explored. It was found that there was a strong correlation between ribbon friability and the fine fraction of granules generated during milling. This implies that friability tests can be performed to characterise ribbon milling behaviour, and ribbon friability provides a good indication of the fraction of fines generated during ribbon milling. PMID:27045469

  11. Effect of apical clearing technique on the treatment outcome of teeth with asymptomatic apical periodontitis: A randomized clinical trial

    PubMed Central

    Mittal, Priya; Logani, Ajay; Shah, Naseem; Pandey, R. M.

    2016-01-01

    Aim: This study aims to compare the periapical healing of teeth with asymptomatic apical periodontitis treated either by conventional apical preparation (CAP) or apical clearing technique (ACT). Materials and Methods: Twenty subjects with bilateral nonvital similar teeth exhibiting comparable periapical index (PAI) score were enrolled and randomly allocated. Group I (CAP, n = 20): Apical preparation three sizes greater (master apical file [MAF]) than the first binding file at the established working length. Group II (ACT, n = 20): Apical preparation three sizes greater than the MAF that was followed by dry reaming. Root canal therapy was accomplished in single-visit for all the teeth. They were pursued radiographically at 3, 6, 9 and 12 months. Pre- and post-treatment PAI scores were compared. To ascertain the proportion of healed teeth between the two groups, McNemar Chi-square test was applied. Results: At 3, 6, and 9 months’ time interval the proportion of healed teeth for Group II (ACT) was greater in comparison to Group I (CAP) (P < 0.05). However, at 12 months follow-up period this difference was not significant (P = 0.08). Conclusion: ACT enhanced the healing kinetics. However, the long-term (12 months) radiographic outcome was similar for either technique. PMID:27656054

  12. Effect of apical clearing technique on the treatment outcome of teeth with asymptomatic apical periodontitis: A randomized clinical trial

    PubMed Central

    Mittal, Priya; Logani, Ajay; Shah, Naseem; Pandey, R. M.

    2016-01-01

    Aim: This study aims to compare the periapical healing of teeth with asymptomatic apical periodontitis treated either by conventional apical preparation (CAP) or apical clearing technique (ACT). Materials and Methods: Twenty subjects with bilateral nonvital similar teeth exhibiting comparable periapical index (PAI) score were enrolled and randomly allocated. Group I (CAP, n = 20): Apical preparation three sizes greater (master apical file [MAF]) than the first binding file at the established working length. Group II (ACT, n = 20): Apical preparation three sizes greater than the MAF that was followed by dry reaming. Root canal therapy was accomplished in single-visit for all the teeth. They were pursued radiographically at 3, 6, 9 and 12 months. Pre- and post-treatment PAI scores were compared. To ascertain the proportion of healed teeth between the two groups, McNemar Chi-square test was applied. Results: At 3, 6, and 9 months’ time interval the proportion of healed teeth for Group II (ACT) was greater in comparison to Group I (CAP) (P < 0.05). However, at 12 months follow-up period this difference was not significant (P = 0.08). Conclusion: ACT enhanced the healing kinetics. However, the long-term (12 months) radiographic outcome was similar for either technique.

  13. Differentiation of Apical Bud Cells in a Newly Developed Apical Bud Transplantation Model Using GFP Transgenic Mice as Donor

    PubMed Central

    Sakagami, Ryuji; Yoshinaga, Yasunori; Okamura, Kazuhiko

    2016-01-01

    Rodent mandibular incisors have a unique anatomical structure that allows teeth to grow throughout the lifetime of the rodent. This report presents a novel transplantation technique for studying the apical bud differentiation of rodent mandibular incisors. Incisal apical end tissue with green fluorescent protein from transgenic mouse was transplanted to wild type mice, and the development of the transplanted cells were immunohistologically observed for 12 weeks after the transplantation. Results indicate that the green fluorescent apical end tissue replaced the original tissue, and cells from the apical bud differentiated and extended toward the incisal edge direction. The immunostaining with podoplanin also showed that the characteristics of the green fluorescent tissue were identical to those of the original. The green fluorescent cells were only found in the labial side of the incisor up to 4 weeks. After 12 weeks, however, they were also found in the lingual side. Here the green fluorescent cementocyte-like cells were only present in the cementum close to the dentin surface. This study suggests that some of the cells that form the cellular cementum come from the apical tissue including the apical bud in rodent incisors. PMID:26978064

  14. Terahertz wavefront control by tunable metasurface made of graphene ribbons

    SciTech Connect

    Yatooshi, Takumi; Ishikawa, Atsushi Tsuruta, Kenji

    2015-08-03

    We propose a tunable metasurface consisting of an array of graphene ribbons on a silver mirror with a SiO{sub 2} gap layer to control reflected wavefront at terahertz frequencies. The graphene ribbons exhibit localized plasmon resonances depending on their Fermi levels to introduce abrupt phase shifts along the metasurface. With interference of the Fabry-Perot resonances in the SiO{sub 2} layer, phase shift through the system is largely accumulated, covering the 0-to-2π range for full control of the wavefront. Numerical simulations prove that wide-angle beam steering up to 53° with a high reflection efficiency of 60% is achieved at 5 THz within a switching time shorter than 0.6 ps.

  15. Hooked Flare Ribbons and Flux-rope-related QSL Footprints

    NASA Astrophysics Data System (ADS)

    Zhao, Jie; Gilchrist, Stuart A.; Aulanier, Guillaume; Schmieder, Brigitte; Pariat, Etienne; Li, Hui

    2016-05-01

    We studied the magnetic topology of active region 12158 on 2014 September 10 and compared it with the observations before and early in the flare that begins at 17:21 UT (SOL2014-09-10T17:45:00). Our results show that the sigmoidal structure and flare ribbons of this active region observed by the Solar Dynamics Observatory/Atmospheric Imaging Assembly can be well reproduced from a Grad–Rubin nonlinear force-free field extrapolation method. Various inverse-S- and inverse-J-shaped magnetic field lines, which surround a coronal flux rope, coincide with the sigmoid as observed in different extreme-ultraviolet wavelengths, including its multithreaded curved ends. Also, the observed distribution of surface currents in the magnetic polarity where it was not prescribed is well reproduced. This validates our numerical implementation and setup of the Grad–Rubin method. The modeled double inverse-J-shaped quasi-separatrix layer (QSL) footprints match the observed flare ribbons during the rising phase of the flare, including their hooked parts. The spiral-like shape of the latter may be related to a complex pre-eruptive flux rope with more than one turn of twist, as obtained in the model. These ribbon-associated flux-rope QSL footprints are consistent with the new standard flare model in 3D, with the presence of a hyperbolic flux tube located below an inverse-teardrop-shaped coronal QSL. This is a new step forward forecasting the locations of reconnection and ribbons in solar flares and the geometrical properties of eruptive flux ropes.

  16. EBIC and HVTEM studies of RTR silicon ribbon

    NASA Technical Reports Server (NTRS)

    Cunningham, B.; Strunk, H.; Ast, D.

    1981-01-01

    The defect structure of RTR ribbon #6-731, run 803 was studied. Prior to laser recrystallization the defect structure consists of closely spaced twin and grain boundaries. Precipitation of impurities occurs after laser recrystallization. The observation of electrically active defects in EBIC was correlated with HVTEM studies. Pairs of electrically active defects in twin boundaries are due to stacking faults connecting the twin boundaries.

  17. Method and apparatus for drawing monocrystalline ribbon from a melt

    DOEpatents

    Ciszek, Theodore F.; Schwuttke, Guenter H.

    1981-11-10

    A method and apparatus for drawing a monocrystalline ribbon or web from a melt comprising utilizing a shaping die including at least two elements spaced one from the other each having a portion thereof located below the level of the melt and another portion located above the level of the melt a distance sufficient to form a raised meniscus of melt about the corresponding element.

  18. Color and shape changing polymeric ribbons and sheets

    DOEpatents

    Stevens, Raymond C.; Cheng, Quan; Song, Jie

    2006-05-23

    The present invention herein provides the design, synthesis and characterization of compositions comprising asymmetric bolaamphiphilic lipids that form extended polymeric ribbons and wide sheets. These compositions may be doped, or interspersed, with various compounds to fine-tune the fluidity and rigidity of the bolaamphiphilic lipid composition, and promote other morphologies of the composition, including fluid vesicles and truncated flat sheets. Upon an increase in pH these compositions undergo a calorimetric and morphological transformation.

  19. Ribbon-cutting ceremony occurs at grand opening of new International Space Station Center at KSC

    NASA Technical Reports Server (NTRS)

    1998-01-01

    Celebrating the official opening of the new International Space Station (ISS) Center at Kennedy Space Center are, left to right, James Ball, chief, NASA Public Services, KSC; KSC Director Roy D. Bridges Jr.; Hugh Harris, director, NASA Public Affairs, KSC; and Rick Abramson, president and chief operating officer, Delaware North Parks Services of Spaceport Inc. Center Director Bridges cuts the ribbon to the new tour attraction where full-scale mockups of station modules, through which visitors can walk, are on display. These include the Habitation Unit, where station crew members will live, sleep, and work; a Laboratory Module; and the Pressurized Logistics Module, where racks and supplies will be transported back and forth from KSC to space. Guests also can take an elevated walkway to a gallery overlooking the work are where actual ISS hardware is prepared for flight into space. This new tour site, in addition to a new Launch Complex 39 Observation Gantry, are part of a comprehensive effort by NASA and Delaware North to expand and improve the KSC public tour and visitor facilities.

  20. aPKC Inhibition by Par3 CR3 Flanking Regions Controls Substrate Access and Underpins Apical-Junctional Polarization.

    PubMed

    Soriano, Erika V; Ivanova, Marina E; Fletcher, Georgina; Riou, Philippe; Knowles, Philip P; Barnouin, Karin; Purkiss, Andrew; Kostelecky, Brenda; Saiu, Peter; Linch, Mark; Elbediwy, Ahmed; Kjær, Svend; O'Reilly, Nicola; Snijders, Ambrosius P; Parker, Peter J; Thompson, Barry J; McDonald, Neil Q

    2016-08-22

    Atypical protein kinase C (aPKC) is a key apical-basal polarity determinant and Par complex component. It is recruited by Par3/Baz (Bazooka in Drosophila) into epithelial apical domains through high-affinity interaction. Paradoxically, aPKC also phosphorylates Par3/Baz, provoking its relocalization to adherens junctions (AJs). We show that Par3 conserved region 3 (CR3) forms a tight inhibitory complex with a primed aPKC kinase domain, blocking substrate access. A CR3 motif flanking its PKC consensus site disrupts the aPKC kinase N lobe, separating P-loop/αB/αC contacts. A second CR3 motif provides a high-affinity anchor. Mutation of either motif switches CR3 to an efficient in vitro substrate by exposing its phospho-acceptor site. In vivo, mutation of either CR3 motif alters Par3/Baz localization from apical to AJs. Our results reveal how Par3/Baz CR3 can antagonize aPKC in stable apical Par complexes and suggests that modulation of CR3 inhibitory arms or opposing aPKC pockets would perturb the interaction, promoting Par3/Baz phosphorylation. PMID:27554858

  1. Explosive Chromospheric Evaporation in a Circular-ribbon Flare

    NASA Astrophysics Data System (ADS)

    Zhang, Q. M.; Li, D.; Ning, Z. J.; Su, Y. N.; Ji, H. S.; Guo, Y.

    2016-08-01

    In this paper, we report our multiwavelength observations of the C4.2 circular-ribbon flare in active region (AR) 12434 on 2015 October 16. The short-lived flare was associated with positive magnetic polarities and a negative polarity inside, as revealed by the photospheric line-of-sight magnetograms. Such a magnetic pattern is strongly indicative of a magnetic null point and spine-fan configuration in the corona. The flare was triggered by the eruption of a mini-filament residing in the AR, which produced the inner flare ribbon (IFR) and the southern part of a closed circular flare ribbon (CFR). When the eruptive filament reached the null point, it triggered null point magnetic reconnection with the ambient open field and generated the bright CFR and a blowout jet. Raster observations of the Interface Region Imaging Spectrograph show plasma upflow at speeds of 35-120 km s-1 in the Fe xxi λ1354.09 line ({log}T≈ 7.05) and downflow at speeds of 10-60 km s-1 in the Si iv λ1393.77 line ({log}T≈ 4.8) at certain locations of the CFR and IFR during the impulsive phase of the flare, indicating explosive chromospheric evaporation. Coincidence of the single hard X-ray source at 12-25 keV with the IFR and calculation based on the thick-target model suggest that the explosive evaporation was most probably driven by nonthermal electrons.

  2. Magnetoimpedance of cobalt-based amorphous ribbons/polymer composites

    NASA Astrophysics Data System (ADS)

    Semirov, A. V.; Derevyanko, M. S.; Bukreev, D. A.; Moiseev, A. A.; Kudryavtsev, V. O.; Safronov, A. P.

    2016-10-01

    The combined influence of the temperature, the elastic tensile stress and the external magnetic field on the total impedance and impedance components were studied for rapidly quenched amorphous Co75Fe5Si4B16 ribbons. Both as-cast amorphous ribbons and Co75Fe5Si4B16/polymer amorphous ribbon based composites were considered. Following polymer coverings were studied: modified rubber solution in o-xylene, solution of butyl methacrylate and methacrylic acid copolymer in isopropanol and solution of polymethylphenylsiloxane resin in toluene. All selected composites showed very good adhesion of the coverings and allowed to provide temperature measurements from 163 K up to 383 K under the applied deforming tensile force up to 30 N. The dependence of the modulus of the impedance and its components on the external magnetic field was influenced by the elastic tensile stresses and was affected by the temperature of the samples. It was shown that maximal sensitivity of the impedance and its components to the external magnetic field was observed at minimal temperature and maximal deforming force depended on the frequency of an alternating current.

  3. MSRC-based defective nanocrystalline soft magnetic ribbon detection

    NASA Astrophysics Data System (ADS)

    He, Zaixing; Zhao, Xinyue

    2015-09-01

    The traditional manual inspection of nanocrystalline soft magnetic materials based on metallographic samples is a time-consuming and somewhat unreliable task. It is also difficult to achieve high accuracy by simply adopting existing automatic signal processing methods as an alternative. To address the issue, a novel automatic microscopic defect recognition method for nanocrystalline soft magnetic ribbon using high-resolution optical microscopic images is proposed. The target problem is viewed as a pattern recognition problem, in which images are classified as non-defective and defective. An effective and highly efficient random feature is used to describe the structures of the nanocrystalline soft magnetic ribbons. Then the extracted features are used to recognize defects via a modified sparse representation-based classifier (MSRC). In the experiment, two well-known features, LBP (local binary pattern) and PCA (principal component analysis), and different classifiers, SVM (support vector machine) and SRC (sparse representation classifier), are compared. The experimental results demonstrate that the proposed method can provide low error rates in recognizing ribbon defects.

  4. Apical branching in a temperature sensitive mutant of Aspergillus niger.

    PubMed

    Reynaga-Peña, C G; Bartnicki-Garcia, S

    1997-12-01

    An apical branching, temperature-sensitive, mutant of Aspergillus niger (ramosa-1) was isolated by UV mutagenesis. Ramosa-1 has a wild type morphology at 23 degrees C, but branches apically when shifted to 34 degrees C. The cytological events leading to apical branching were recorded by video-enhanced phase contrast microscopy. The first event was a momentary, localized, cytoplasmic contraction lasting approximately 1 s. This contraction was seen as a sudden unidirectional movement of visible organelles (mitochondria, spheroid bodies) toward the hyphal apex. During the contraction, there was a transitory sharp increase in refractive index in a localized area of cytoplasm in the apex or subapex of the cell. Within 5 s, the Spitzenkörper retracted from its normal position next to the apical pole and disappeared from view 20 to 50 s later. Hyphal elongation rate diminished sharply, and the typical distribution of organelles at the hyphal tip was disturbed. After 210-240 s, organelle distribution returned to normal, polarized growth resumed, but instead of one Spitzenkörper two new Spitzenkörper appeared, each giving rise to an apical branch. The second branch Spitzenkörper appeared with a 60- to 100-s delay. We did not observe the original Spitzenkörper dividing in two; instead, the new Spitzenkörper arose de novo from vesicle clouds that formed in the apical region next to the future site of branch emergence. In all instances that we examined, the dislocation and disappearance of the Spitzenkörper was preceded by cytoplasmic contractions. We therefore suspect the existence of an intimate connection between the cytoskeletal network and the Spitzenkörper. Accordingly, we propose that the apical branching phenotype in ramosa-1 is triggered by a molecular event that induces a transient alteration in cytoskeleton organization.

  5. A quantitative correlation of the effect of density distributions in roller-compacted ribbons on the mechanical properties of tablets using ultrasonics and X-ray tomography.

    PubMed

    Akseli, Ilgaz; Iyer, Srinivas; Lee, Hwahsiung P; Cuitiño, Alberto M

    2011-09-01

    Enabling the paradigm of quality by design requires the ability to quantitatively correlate material properties and process variables to measureable product performance attributes. In this study, we show how heterogeneities in compacted ribbon densities quantitatively correlate to tablet mechanical properties. These density variations, which have been purposely modulated by internal and external lubrications, are characterized longitudinally and transversally by nondestructive ultrasonic and X-ray micro-computed tomography measurements. Subsequently, different transversal regions of the compacted ribbon are milled under the same conditions, and granules with nominally the same particle size distribution are utilized to manufacture cylindrical tablets, whose mechanical properties are further analyzed by ultrasonic measurements. We consider three different ribbon conditions: no lubrication (case 1); lubricated powder (case 2); and lubricated tooling (hopper, side sealing plates, feed screws, and rolls) (case 3). This study quantitatively reveals that variation in local densities in ribbons (for case 1) and process conditions (i.e., internal case 2 and external lubrication case 3) during roller compaction significantly affect the mechanical properties of tablets even for granules with the same particle size distribution. For case 1, the mechanical properties of tablets depend on the spatial location where granules are produced. For cases 2 and 3, the ribbon density homogeneity was improved by the use of a lubricant. It is demonstrated that the mechanical performances of tablets are decreased due to applied lubricant and work-hardening phenomenon. Moreover, we extended our study to correlate the speed of sound to the tensile strength of the tablet. It is found that the speed of sound increases with the tensile strength for the tested tablets.

  6. A quantitative correlation of the effect of density distributions in roller-compacted ribbons on the mechanical properties of tablets using ultrasonics and X-ray tomography.

    PubMed

    Akseli, Ilgaz; Iyer, Srinivas; Lee, Hwahsiung P; Cuitiño, Alberto M

    2011-09-01

    Enabling the paradigm of quality by design requires the ability to quantitatively correlate material properties and process variables to measureable product performance attributes. In this study, we show how heterogeneities in compacted ribbon densities quantitatively correlate to tablet mechanical properties. These density variations, which have been purposely modulated by internal and external lubrications, are characterized longitudinally and transversally by nondestructive ultrasonic and X-ray micro-computed tomography measurements. Subsequently, different transversal regions of the compacted ribbon are milled under the same conditions, and granules with nominally the same particle size distribution are utilized to manufacture cylindrical tablets, whose mechanical properties are further analyzed by ultrasonic measurements. We consider three different ribbon conditions: no lubrication (case 1); lubricated powder (case 2); and lubricated tooling (hopper, side sealing plates, feed screws, and rolls) (case 3). This study quantitatively reveals that variation in local densities in ribbons (for case 1) and process conditions (i.e., internal case 2 and external lubrication case 3) during roller compaction significantly affect the mechanical properties of tablets even for granules with the same particle size distribution. For case 1, the mechanical properties of tablets depend on the spatial location where granules are produced. For cases 2 and 3, the ribbon density homogeneity was improved by the use of a lubricant. It is demonstrated that the mechanical performances of tablets are decreased due to applied lubricant and work-hardening phenomenon. Moreover, we extended our study to correlate the speed of sound to the tensile strength of the tablet. It is found that the speed of sound increases with the tensile strength for the tested tablets. PMID:21710336

  7. The ENA Ribbon and the ISN Flow as Key Tools for the ISM-Heliosphere Interaction - Open Questions, the Need for Future Observations with IBEX and IMAP

    NASA Astrophysics Data System (ADS)

    Moebius, E.; Bzowski, M.; Frisch, P. C.; Funsten, H. O.; Fuselier, S.; Kucharek, H.; McComas, D. J.; Schwadron, N.; Wimmer-Schweingruber, R. F.; Wurz, P.; Zank, G. P.

    2014-12-01

    The unexpected ribbon in the IBEX energetic neutral atom (ENA) maps is still far from understood. According to most models, the interstellar magnetic field (BISM) controls its location and shape, with the direction in agreement with the termination shock (TS) asymmetry found by the Voyagers, the deflection of the interstellar neutral (ISN) flow, and the high energy cosmic ray anisotropy. With direct ISN flow velocity vector VISM and temperature observations, along with secondary neutrals, most likely from the outer heliosheath, IBEX also probes the conditions and interaction outside the heliospheric boundary. Precise knowledge of the ISN flow direction is key, because small differences have substantial leverage on the VISM-BISM plane, which controls the large-scale heliosphere structure. For quantitative tools, the ribbon formation must be understood and the ISN flow parameters must be further refined. IBEX maps show that the latitudinal ribbon structure carries the imprint of fast and slow solar wind (SW). These results support models that involve charge exchange with the SW, currently in two renditions: secondary ENAs from neutral SW reaching into the outer heliosheath and reflection of SW at the TS. In the TS model, the ribbon distance maps the TS, and reactions to changing SW at 1 AU follow within 1 - 2 years. In the secondary ENA model, ribbon ENAs provide an energy-dependent spatio-temporal probe of the outer heliosheath over several years after SW changes at 1 AU. Therefore, observations over a full solar cycle with IBEX, probing the ribbon depth with SW modulation, are key to its understanding. Likewise, expanding the successful variation of the IBEX pointing strategy over times with varying ionization rates will refine the ISN flow vector. The capabilities of the Interstellar Mapping and Acceleration Probe (IMAP), which has highest priority in the recent NRC Heliophysics Decadal Survey, are needed to probe the spatio-temporal fine-structure of the ribbon

  8. Symmetry breaking induced excitations of dark plasmonic modes in multilayer graphene ribbons.

    PubMed

    Dai, Y Y; Chen, A; Xia, Y Y; Han, D Z; Liu, X H; Shi, L; Zi, J

    2016-09-01

    Multilayer graphene can support multiple plasmon bands. If structured into graphene ribbons, they can support multiple localized plasmonic modes with interesting optical properties. However, not all such plasmonic modes can be excited directly due to the constrains of the structural symmetry. We show by numerical simulations that by breaking the symmetry all plasmonic modes can be excited. We discuss the general principles and properties of two-layer graphene ribbons and then extend to multilayer graphene ribbons. In multilayer graphene ribbons with different ribbon widths, a tunable broadband absorption can be attained due to the excitations of all plasmonic modes. Our results suggest that these symmetry-broken multilayer graphene ribbons could offer more degrees of freedom in designing photonic devices. PMID:27607610

  9. A precision technique for mounting scintillating fiber ribbons for charged particle tracking

    SciTech Connect

    Carabello, S.; Gau, D.; Howell, B.; Koltick, D.; Pischalnikov, Y.; Michael, D.

    1996-06-01

    The authors have undertaken a research program to develop a Scintillating Fiber charged particle Tracking (SFT) detector for the D0 upgrade experiment at FNAL. They have developed a construction method utilizing scintillating fibers first accurately formed into ribbons, then precisely locating these ribbons on the inside and outside of a lightweight cylindrical base. A Coordinate Measuring Machine (CMM) is used to control each step of the ribbon mounting procedure. Ribbons 2m long, containing 255 fibers each have been placed on composite structures with accuracy {approximately}20 {micro}m. The technique for producing highly accurate fiber ribbons and the method of precision placement of ribbons are presented. The spatial calibration of a charged particle tracker using the CMM measurements are discussed.

  10. Global Ca2+ Signaling Drives Ribbon-Independent Synaptic Transmission at Rod Bipolar Cell Synapses

    PubMed Central

    Mehta, Bhupesh; Ke, Jiang-Bin; Zhang, Lei; Baden, Alexander D.; Markowitz, Alexander L.; Nayak, Subhashree; Briggman, Kevin L.

    2014-01-01

    Ribbon-type presynaptic active zones are a hallmark of excitatory retinal synapses, and the ribbon organelle is thought to serve as the organizing point of the presynaptic active zone. Imaging of exocytosis from isolated retinal neurons, however, has revealed ectopic release (i.e., release away from ribbons) in significant quantities. Here, we demonstrate in an in vitro mouse retinal slice preparation that ribbon-independent release from rod bipolar cells activates postsynaptic AMPARs on AII amacrine cells. This form of release appears to draw on a unique, ribbon-independent, vesicle pool. Experimental, anatomical, and computational analyses indicate that it is elicited by a significant, global elevation of intraterminal [Ca2+] arising following local buffer saturation. Our observations support the conclusion that ribbon-independent release provides a read-out of the average behavior of all of the active zones in a rod bipolar cell's terminal. PMID:24790194

  11. Highly efficient active optical interconnect incorporating a partially chlorinated ribbon POF in conjunction with a visible VCSEL.

    PubMed

    Lee, Hak-Soon; Lee, Sang-Shin; Kim, Bong-Seok; Son, Yung-Sung

    2014-05-19

    A low-loss 4-ch active optical interconnect (AOI) enabling passive alignment was proposed and built resorting to a transmitter (Tx) incorporating a red 680-nm VCSEL, which is linked to a receiver (Rx) module via a partially chlorinated ribbon POF. The POF was observed to exhibit an extremely low loss of ~0.24 dB/m at λ = 680 nm, in comparison to ~1.29 dB/m at λ = 850 nm, and a large numerical aperture of ~0.42. Both the Tx and Rx, which taps into a beam router based on collimated beam optics involving a pair of spherical lenses, were meant to be substantially alignment tolerant and compact. The achieved tolerance for the constructed modules was beyond 40 μm in terms of the positioning of VCSEL and photodetector. The proposed AOI was completed by linking the Tx with the Rx via a 3-m long ribbon POF, incurring a transmission loss of as small as 3.2 dB. The AOI was practically assessed in terms of a high-speed data transmission over a wide range of temperatures and then exploited to convey full HD video signals.

  12. Orientation dependence of defect structure in EFG silicon ribbons. [Edge-defined Film-fed Growth

    NASA Technical Reports Server (NTRS)

    Garone, L. C.; Rao, C. V. H.; Morrison, A. D.; Surek, T.; Ravi, K. V.

    1976-01-01

    Sustained growth of long lengths of silicon ribbons by the edge-defined film-fed growth (EFG) technique is shown to result in the attainment of an 'equilibrium' defect structure and orientation by the crystals. The structure consists of parallel defect boundaries parallel to the edges of the ribbon with a specific ribbon orientation. The influence of seed orientation on the attainment of this structure has been examined.

  13. CIRCULARITY OF THE INTERSTELLAR BOUNDARY EXPLORER RIBBON OF ENHANCED ENERGETIC NEUTRAL ATOM (ENA) FLUX

    SciTech Connect

    Funsten, H. O.; Higdon, D. M.; Larsen, B. A.; Möbius, E. E-mail: dhigdon@lanl.gov; and others

    2013-10-10

    As a sharp feature in the sky, the ribbon of enhanced energetic neutral atom (ENA) flux observed by the Interstellar Boundary Explorer (IBEX) mission is a key signature for understanding the interaction of the heliosphere and the interstellar medium through which we are moving. Over five nominal IBEX energy passbands (0.7, 1.1, 1.7, 2.7, and 4.3 keV), the ribbon is extraordinarily circular, with a peak location centered at ecliptic (λ{sub RC}, β{sub RC}) = (219.°2 ± 1.°3, 39.°9 ± 2.°3) and a half cone angle of φ{sub C} = 74.°5 ± 2.°0. A slight elongation of the ribbon, generally perpendicular to the ribbon center-heliospheric nose vector and with eccentricity ∼0.3, is observed over all energies. At 4.3 keV, the ribbon is slightly larger and displaced relative to lower energies. For all ENA energies, a slice of the ribbon flux peak perpendicular to the circular arc is asymmetric and systematically skewed toward the ribbon center. We derive a spatial coherence parameter δ{sub C} ≤ 0.014 that characterizes the spatial uniformity of the ribbon over its extent in the sky and is a key constraint for understanding the underlying processes and structure governing the ribbon ENA emission.

  14. Development of a process for producing ribbon shaped filaments. [production of silicon carbide filaments

    NASA Technical Reports Server (NTRS)

    Debolt, H. E.; Krukonis, V. J.

    1973-01-01

    Silicon carbide (SiC) ribbon filaments were produced on a carbon ribbon substrate, about 1500 microns (60 mils) wide and 100 microns (4 mils) thick in lengths up to 2 meters (6 ft), and with tensile strengths up to 142 KN/cm sq (206 Ksi). During the course of the study, ribbon filaments of boron were also produced on the carbon ribbon substrate; the boron ribbon produced was extremely fragile. The tensile strength of the SiC ribbon was limited by large growths or flaws caused by anomalies at the substrate surface; these anomalies were either foreign dirt or substrate imperfections or both. Related work carried out on round 100 micron (4 mils) diameter SiC filaments on a 33 micron (1.3 mil) diameter, very smooth carbon monofilament substrate has shown that tensile strengths as high as 551 KN/cm sq (800 Ksi) are obtainable with the SiC-carbon round substrate combination, and indicates that if the ribbon substrate surface and ribbon deposition process can be improved similar strengths can be realizable. Cost analysis shows that 100 micron x 5-10 micron SiC ribbon can be very low cost reinforcement material.

  15. Cryopreservation of Pelargonium apices by droplet-vitrification.

    PubMed

    Gallard, Anthony; Panis, Bart; Dorion, Nöelle; Swennen, Rony; Grapin, Agnès

    2008-01-01

    The droplet-vitrification method was adapted to Pelargonium apices by optimizing the duration of the loading solution (LS) as well as the plant vitrification solution 2 (PVS2). The excised apices were dehydrated in two steps (20 min in LS and 15 min in PVS2) and then immersed directly in liquid nitrogen (LN). After thawing and unloading in the recovery solution at room temperature for 15 min, apices were plated onto semi-solid Murashige and Skoog medium. This simple protocol without any pretreatment was successfully applied to eight cultivars with a survival level ranging between 55.6 - 96.2 percent and a regrowth level between 9.1 and 70.6 percent. These results prove the feasibility of the long-term storage of Pelargonium germplasm through cryopreservation.

  16. Single Step Endodontic Management of Immature Apices using MTA

    PubMed Central

    Mishra, SK; Kumar, Ashok; Garg, Amit Kumar; Jindal, MK; Juneja, Harish

    2011-01-01

    Aim To examine the clinical and radiographic appearance of teeth with immature apices that were treated by single step procedure using mineral trioxide aggregate (MTA). Summary Creation of a physiological hard tissue barrier with calcium hydroxide in a nonvital tooth although quite predictable has certain limitations, such as the very long duration of the treatment spread over multiple visits and increased risk of root fracture. Plugging the root canal end with MTA has been advocated as an alternative treatment modality for open apices. The technique has been proven to be successful in many recently reported cases. The cases reported here present the successful treatment of two traumatized maxillary central incisors with open apices and periapical lesions using MTA. In this case report, MTA has been used to create a hard tissue barrier after disinfection of the root canal.

  17. Single Step Endodontic Management of Immature Apices using MTA

    PubMed Central

    Mishra, SK; Kumar, Ashok; Garg, Amit Kumar; Jindal, MK; Juneja, Harish

    2011-01-01

    Aim To examine the clinical and radiographic appearance of teeth with immature apices that were treated by single step procedure using mineral trioxide aggregate (MTA). Summary Creation of a physiological hard tissue barrier with calcium hydroxide in a nonvital tooth although quite predictable has certain limitations, such as the very long duration of the treatment spread over multiple visits and increased risk of root fracture. Plugging the root canal end with MTA has been advocated as an alternative treatment modality for open apices. The technique has been proven to be successful in many recently reported cases. The cases reported here present the successful treatment of two traumatized maxillary central incisors with open apices and periapical lesions using MTA. In this case report, MTA has been used to create a hard tissue barrier after disinfection of the root canal. PMID:27678239

  18. Transient apical breakdown following subluxation injury: a case report.

    PubMed

    Boyd, K S

    1995-02-01

    Transient apical breakdown has been reported to occur in cases in which a periapical radiolucency develops and resolves without treatment following luxation injury. Diagnostic errors are inevitable if periapical breakdown is used as the sole criterion or as an overriding criterion in the decision to initiate root canal treatment. A clinical case report is presented in which transient apical breakdown occurred after a subluxation injury. The threshold to sensitivity tests increased yet sensitivity remained positive with the appearance of the periapical radiolucency. The decision was made not to initiate root canal treatment in spite of the radiographic appearance periapically. At the 10-month recall the tooth remained responsive to sensitivity tests and the apical radiolucency had disappeared.

  19. Apical potassium channels in the rat connecting tubule.

    PubMed

    Frindt, Gustavo; Palmer, Lawrence G

    2004-11-01

    Apical membrane K channels in the rat connecting tubule (CNT) were studied using the patch-clamp technique. Tubules were isolated from the cortical labyrinth of the kidney and split open to provide access to the apical membrane. Cell-attached patches were formed on presumed principal and/or connecting tubule cells. The major channel type observed had a single-channel conductance of 52 pS, high open probability and kinetics that were only weakly dependent on voltage. These correspond closely to the "SK"-type channels in the cortical collecting duct, identified with the ROMK (Kir1.1) gene product. A second channel type, which was less frequently observed, mediated larger currents and was strongly activated by depolarization of the apical membrane voltage. These were identified as BK or maxi-K channels. The density of active SK channels revealed a high degree of clustering. Although heterogeneity of tubules or of cell types within a tubule could not be excluded, the major factor underlying the distribution appeared to be the presence of channel clusters on the membrane of individual cells. The overall density of channels was higher than that previously found in the cortical collecting tubule (CCT). In contrast to results in the CCT, we did not detect an increase in the overall density of SK channels in the apical membrane after feeding the animals a high-K diet. However, the activity of amiloride-sensitive Na channels was undetectable under control conditions but was increased after both 1 day (90 +/- 24 pA/cell) or 7 days (385 +/- 82 pA/cell) of K loading. Thus one important factor leading to an increased K secretion in the CNT in response to increased dietary K is an increased apical Na conductance, leading to depolarization of the apical membrane voltage and an increased driving force for K movement out into the tubular lumen. PMID:15280155

  20. Dental Apical Papilla as Therapy for Spinal Cord Injury.

    PubMed

    De Berdt, P; Vanacker, J; Ucakar, B; Elens, L; Diogenes, A; Leprince, J G; Deumens, R; des Rieux, A

    2015-11-01

    Stem cells of the apical papilla (SCAP) represent great promise regarding treatment of neural tissue damage, such as spinal cord injury (SCI). They derive from the neural crest, express numerous neurogenic markers, and mediate neurite outgrowth and axonal targeting. The goal of the present work was to investigate for the first time their potential to promote motor recovery after SCI in a rat hemisection model when delivered in their original stem cell niche-that is, by transplantation of the human apical papilla tissue itself into the lesion. Control groups consisted of animals subjected to laminectomy only (shams) and to lesion either untreated or injected with a fibrin hydrogel with or without human SCAP. Basso-Beattie-Bresnahan locomotor scores at 1 and 3 d postsurgery confirmed early functional decline in all SCI groups. This significant impairment was reversed, as seen in CatWalk analyses, after transplantation of apical papilla into the injured spinal cord wound, whereas the other groups demonstrated persistent functional impairment. Moreover, tactile allodynia did not develop as an unwanted side effect in any of the groups, even though the SCAP hydrogel group showed higher expression of the microglial marker Iba-1, which has been frequently associated with allodynia. Notably, the apical papilla transplant group presented with reduced Iba-1 expression level. Masson trichrome and human mitochondria staining showed the preservation of the apical papilla integrity and the presence of numerous human cells, while human cells could no longer be detected in the SCAP hydrogel group at the 6-wk postsurgery time point. Altogether, our data suggest that the transplantation of a human apical papilla at the lesion site improves gait in spinally injured rats and reduces glial reactivity. It also underlines the potential interest for the application of delivering SCAP in their original niche, as compared with use of a fibrin hydrogel.

  1. Multiple idiopathic external apical root resorption: A rare case report

    PubMed Central

    Bansal, Parul; Nikhil, Vineeta; Kapur, Sonali

    2015-01-01

    Multiple idiopathic external apical root resorption (MIEARR) is a relatively rare condition affecting multiple teeth in a dentition. As the condition is nonsymptomatic, a case is usually detected as an incidental radiographic finding. However, it may cause pain and mobility in severe cases. It is sometimes self-limiting or sometimes may progress to tooth loss. This paper presents a case of external apical root resorption involving multiple teeth in which etiology was not identified, so idiopathic root resorption was considered as a diagnosis of exclusion. PMID:25657532

  2. Transmittance characteristics of plasmonic graphene ribbons with a wing

    NASA Astrophysics Data System (ADS)

    Yuan, Lin; Yan, Xin; Wang, Yueke; Sang, Tian; Yang, Guofeng

    2016-09-01

    We numerically investigate the transmittance characteristics of graphene ribbons with a wing by the finite element method. By determining the dispersion relation of edge graphene plasmon (EGP) modes and analyzing the mode distributions, it is considered that the transmission dips originate from the resonances of three EGP modes, namely, the symmetrical EGPs, antisymmetrical EGPs, and EGPs of a semi-infinite sheet. By changing the width and length of the wing, it was further confirmed that transmission dips originate from the EGP modes. Owing to the tunable permittivity of graphene by adjusting the gate voltage, the transmittance dips can be easily tuned.

  3. [Nonsurgical retreatment in a case of a radiolucent apical lesion].

    PubMed

    Vicente Gómez, A; Rodríguez Ponce, A

    1989-01-01

    We present a case of failure that was helpful solved without surgical endodontic treatment. We don't achieve clinical success besides endodontic treatment was twice remade. Finally we decided to put a temporary filling with calcium hydroxide and wait until apical radiolucency disappear and complete our treatment with gutta-percha, sealer and lateral condensation.

  4. Brefeldin A inhibition of apical Na+ channels in epithelia.

    PubMed

    Fisher, R S; Grillo, F G; Sariban-Sohraby, S

    1996-01-01

    Brefeldin A (BFA) is used to probe trafficking of proteins through the central vacuolar system (CVS) in a variety of cells. Transepithelial Na+ transport by high-resistance epithelia, such as A6 cultured cells, is inhibited by BFA. Apical Na+ channels, as well as basolateral pumps and K+ channels, are complex proteins that probably traverse the CVS for routing to the plasma membrane. BFA (5 micrograms/ml) decreases transepithelial Na+ current near zero and increases resistance reversibly after 4 h. Longer exposures are toxic. When tissues were treated for 20 h with 0.2 microgram/ml BFA, Na+ transport also was reversibly inhibited. Using noise analysis, we found that BFA drastically reduced apical Na+ channel density. The increase in single channel current was consistent with cell hyperpolarization. After apical permeabilization with nystatin, changes in transepithelial current reflect changes in basolateral membrane transport. Transport at this membrane was inhibited by ouabain and cycloheximide, but not by BFA. After BFA, aldosterone was ineffective, suggesting that an intact CVS is required for stimulation by this hormone. Thus BFA inhibition of Na+ transport is localized at the apical membrane. Implications for channel turnover as a mechanism for regulating the Na+ transport rate are discussed.

  5. Chapter Four - Shoot apical meristem form and function. In:

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The shoot apical meristem (SAM) generates above-ground aerial organs throughout the lifespan of higher plants. In order to fulfill this function, the meristem must maintain a balance between the self-renewal of a reservoir of central stem cells and organ initiation from peripheral cells. The activit...

  6. [Nonsurgical retreatment in a case of a radiolucent apical lesion].

    PubMed

    Vicente Gómez, A; Rodríguez Ponce, A

    1989-01-01

    We present a case of failure that was helpful solved without surgical endodontic treatment. We don't achieve clinical success besides endodontic treatment was twice remade. Finally we decided to put a temporary filling with calcium hydroxide and wait until apical radiolucency disappear and complete our treatment with gutta-percha, sealer and lateral condensation. PMID:2640036

  7. Echocardiographic assessment of takotsubo cardiomyopathy: beyond apical ballooning.

    PubMed

    Okura, Hiroyuki

    2016-03-01

    It has been >25 years since the first report of the takotsubo cardiomyopathy (TC). Although left ventriculography was originally used to depict its typical and impressive wall motion abnormality mimicking "takotsubo", or octopus pot, echocardiography plays a pivotal role in detecting not only its left ventricular (LV) wall motion abnormality, apical ballooning, but also various other findings. First of all, apical ballooning is not an essential finding for TC anymore. Mid-ventricular LV asynergy with or without apical involvement is a basic pattern of the LV wall motion abnormality. Distribution and time course of the asynergy may be best detected by echocardiography and echo provides useful information to differentiate between TC and acute coronary syndrome or acute myocarditis. In addition to the wall motion assessment, echo detects complications of TC such as systolic anterior motion of the mitral leaflet with or without LV outflow obstruction, mitral regurgitation, LV thrombus, right ventricular (RV) involvement. In particular, RV involvement is not an uncommon finding and is associated with worse short-term as well as long-term prognosis. Finally, coronary flow measurements and speckle tracking by echo may offer additional and useful information about pathophysiology and prognosis of TC. In conclusion, echocardiography is a standard imaging modality for detecting various dynamic findings beyond apical ballooning in patients with TC. PMID:26694809

  8. AKAP220 manages apical actin networks that coordinate aquaporin-2 location and renal water reabsorption.

    PubMed

    Whiting, Jennifer L; Ogier, Leah; Forbush, Katherine A; Bucko, Paula; Gopalan, Janani; Seternes, Ole-Morten; Langeberg, Lorene K; Scott, John D

    2016-07-26

    Filtration through the kidney eliminates toxins, manages electrolyte balance, and controls water homeostasis. Reabsorption of water from the luminal fluid of the nephron occurs through aquaporin-2 (AQP2) water pores in principal cells that line the kidney-collecting duct. This vital process is impeded by formation of an "actin barrier" that obstructs the passive transit of AQP2 to the plasma membrane. Bidirectional control of AQP2 trafficking is managed by hormones and signaling enzymes. We have discovered that vasopressin-independent facets of this homeostatic mechanism are under the control of A-Kinase Anchoring Protein 220 (AKAP220; product of the Akap11 gene). CRISPR/Cas9 gene editing and imaging approaches show that loss of AKAP220 disrupts apical actin networks in organoid cultures. Similar defects are evident in tissue sections from AKAP220-KO mice. Biochemical analysis of AKAP220-null kidney extracts detected reduced levels of active RhoA GTPase, a well-known modulator of the actin cytoskeleton. Fluorescent imaging of kidney sections from these genetically modified mice revealed that RhoA and AQP2 accumulate at the apical surface of the collecting duct. Consequently, these animals are unable to appropriately dilute urine in response to overhydration. We propose that membrane-proximal signaling complexes constrained by AKAP220 impact the actin barrier dynamics and AQP2 trafficking to ensure water homeostasis. PMID:27402760

  9. Safety Changes in Blue Ribbon Schools since the Attack on Columbine High School

    ERIC Educational Resources Information Center

    Gust, Joseph

    2009-01-01

    Measuring school success using a variety of tools is commonplace in America. For many years, one standard measurement of a school's success was The Blue Ribbon Award from 1982 through 2002. This award quantified success based on schools achieving successful outcomes in a variety of areas with specific criteria. Blue Ribbon award winning schools…

  10. Perceptions of Factors Affecting the Relative Effectiveness of Temporary Blue Ribbon State Commissions.

    ERIC Educational Resources Information Center

    Johnson, Janet Rogers-Clarke

    Elements in the composition and process of higher education blue ribbon commissions that influence their effectiveness were studied. Blue ribbon commissions, which have been used as one type of statewide planning strategy, are defined here as commissions with (1) a predetermined life span; (2) authority established by the legislature and/or the…

  11. 76 FR 38648 - Availability of the Geothermal Technologies Program Blue Ribbon Panel Report and Request for...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-07-01

    ...The Department of Energy's (DOE) Office of Energy Efficiency and Renewable Energy (EERE) Geothermal Technologies Program (the Program) assembled a geothermal Blue Ribbon Panel (the Panel) on March 22/23, 2011 in Albuquerque, New Mexico for a guided discussion on the future of geothermal energy in the United States and the role of the DOE Program. The Geothermal Blue Ribbon Panel Report......

  12. 77 FR 20852 - U.S. Antarctic Program Blue Ribbon Panel Review; Notice of Meeting

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-04-06

    ... the Antarctic Treaty. Agenda: Present the Panel with additional programmatic information related to... U.S. Antarctic Program Blue Ribbon Panel Review; Notice of Meeting In accordance with Federal... following meeting: Name: U.S. Antarctic Program Blue Ribbon Panel Review, 76826. Date/Time: April 20,...

  13. 77 FR 9707 - U.S. Antarctic Program Blue Ribbon Panel Review; Notice of Meeting

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-02-17

    ..., innovative, affordable, sustainable, and consistent with the Antarctic Treaty. Agenda: Present the Panel with... U.S. Antarctic Program Blue Ribbon Panel Review; Notice of Meeting In accordance with Federal... following meeting: Name: U.S. Antarctic Program Blue Ribbon Panel Review, 76826. Date/Time: March 5, 2012,...

  14. 76 FR 63329 - U.S. Antarctic Program Blue Ribbon Panel Review; Notice of Meeting

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-10-12

    ... the Antarctic Treaty. Agenda: First meeting of the Panel to present the Panel with an overview of... U.S. Antarctic Program Blue Ribbon Panel Review; Notice of Meeting In accordance with Federal... following meeting: Name: U.S. Antarctic Program Blue Ribbon Panel Review (76826). Date/Time: November...

  15. 77 FR 1743 - U.S. Antarctic Program Blue Ribbon Panel; Notice of Meeting

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-01-11

    ... sound, safe, innovative, affordable, sustainable, and consistent with the Antarctic Treaty. Agenda... U.S. Antarctic Program Blue Ribbon Panel; Notice of Meeting In accordance with Federal Advisory...: Name: U.S. Antarctic Program Blue Ribbon Panel Review, 76826. Date/Time: January 24, 2012, 8 a.m. to...

  16. Evidence for synergistic and complementary roles of Bassoon and darkness in organizing the ribbon synapse.

    PubMed

    Spiwoks-Becker, I; Lamberti, R; Tom Dieck, S; Spessert, R

    2013-04-16

    Ribbon synapses are tonically active high-throughput synapses. The performance of the ribbon synapse is accomplished by a specialization of the cytomatrix at the active zone (CAZ) referred to as the synaptic ribbon (SR). Progress in our understanding of the structure-function relationship at the ribbon synapse has come from observations that, in photoreceptors lacking a full-size scaffolding protein Bassoon (Bsn(ΔEx4/5)), dissociation of SRs coincides with perturbed signal transfer. The aim of the present study has been to elaborate the role of Bassoon as a structural organizer of the ribbon synapse and to differentiate it with regard to the ambient lighting conditions. The ultrastructure of retinal ribbon synapses has been compared between wild-type (Wt) and Bsn(ΔEx4/5) mice adapted to light (low activity) and darkness (high activity). The results obtained suggest that Bassoon and environmental illumination synergistically and complementarily act as organizers of the ribbon synapse. Thus, light-dependent and Bassoon-independent regulation involves initial SR tethering to the membrane and a basic shape transition of ribbon material from spherical to rod-like, since darkness induces these features in Bsn(ΔEx4/5) rod spherules. However, the tight anchorage of the SR via an arciform density and the proper assembly of SRs to the full-sized horseshoe-shaped complex depend on Bassoon, as these steps fail in Bsn(ΔEx4/5) rod spherules.

  17. The Impact of Leadership Behaviors of Blue Ribbon Catholic School Principals on School Culture

    ERIC Educational Resources Information Center

    Cardarelli, Rosaline

    2014-01-01

    The purpose of this study was to conduct an analysis of six successful Blue Ribbon Catholic schools to determine the relationship between principal's leadership behaviors, teacher's perceptions of principals and resulting school culture within six successful Blue Ribbon schools. A mixed methods approach for analysis was used through both…

  18. Fluid-Structure Interaction Study on a Pre-Buckled Deformable Flat Ribbon

    NASA Astrophysics Data System (ADS)

    Fovargue, Lauren; Shams, Ehsan; Watterson, Amy; Corson, Dave; Filardo, Benjamin; Zimmerman, Daniel; Shan, Bob; Oberai, Assad

    2015-11-01

    A Fluid-Structure Interaction study is conducted for the flow over a deformable flat ribbon. This mechanism, which is called ribbon frond, maybe used as a device for pumping water and/or harvesting energy in rivers. We use a lower dimensional mathematical model, which represents the ribbon as a pre-buckled structure. The surface forces from the fluid flow, dictate the deformation of the ribbon, and the ribbon in turn imposes boundary conditions for the incompressible Navier-Stokes equations. The mesh motion is handled using an Arbitrary Lagrangian-Eulerian (ALE) scheme and the fluid-structure coupling is handled by iterating over the staggered governing equations for the structure, the fluid and the mesh. Simulations are conducted at three different free stream velocities. The results, including the frequency of oscillations, show agreement with experimental data. The vortical structures near the surface of the ribbon and its deformation are highly correlated. It is observed that the ribbon motion exhibits deviation from a harmonic motion, especially at lower free stream velocities. The behavior of the ribbon is compared to swimming animals, such as eels, in order to better understand its performance. The authors acknowledge support from ONR SBIR Phase II, contract No. N0001412C0604 and USDA, NIFA SBIR Phase I, contract No. 2013-33610-20836 and NYSERDA PON 2569, contract No. 30364.

  19. 76 FR 46325 - Agency Information Collection Activities: Proposed Collection; Comments Requested: Red Ribbon...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-08-02

    ...: Red Ribbon Week Patch DEA Form 316 and 316A ACTION: 30-Day Notice of Information Collection under... Participate and Red Ribbon Week Patch Activity Report. (3) Agency form number, if any, and the applicable... the information from Boy/Girl Scout Troop Leaders that express an interest in participating in DEA...

  20. Hydrogen passivation of defects and rapid thermal processing for high-efficiency silicon ribbon solar cells

    NASA Astrophysics Data System (ADS)

    Jeong, Ji-Weon

    2002-01-01

    The use of photovoltaic (PV) system offers a unique opportunity to solve the energy and the environmental problems simultaneously because solar energy is free and can be directly converted into electrical energy by solar cells without any undesirable impact on the environment. In spite of the many advantages, PV still accounts for less than 0.05% of the current U.S. energy portfolio. This is mainly because PV is 2-4 times more expensive than traditional energy sources. PV modules should cost about $1/W to produce electricity at a rate of 6¢/kWh and to compete with fossil fuels. Since Si material accounts for ˜40% of the cost of current Si PV modules, the use of low-cost Si substrate is critical for cost reduction. Edge-defined film-fed grown (EFG) Si ribbon is the focus as substrate materials for this research because it is one of the most promising for low-cost PV. However, as-grown EFG Si has a lot of impurities and crystal defects resulted from the Si feedstock and its growth system, which reduce the bulk lifetime of less than 3 ms. In this research, first, the requirements for achieving 16% efficiency have been established using computer model simulations. To improve the bulk lifetime, manufacturable P and Al gettering techniques are developed to remove the lifetime-killing impurities from the active to inactive device regions. PECVD SiN-induced hydrogen defect passivation is investigated and maximized through the fundamental understanding of the role of Al, the impact of RTP firing, and the difference between two PECVD SiN films. For low-cost contact formation, a novel RTP firing process is developed for high-quality screen-printed contacts and Al-BSF. Finally, a complete process sequence that involves the optimal conditions for defect passivation and contacts is developed to produce ˜16% efficiency on screen-printed EFG Si solar cells, which is the highest efficiency for any screen-printed Si ribbon solar cells to date.

  1. Compact, low-crosstalk, WDM filter elements for multimode ribbon fiber data links

    SciTech Connect

    Patel, R. R.; Garrett, H. H.; Emanuel, M. A.; Larson, M. C.; Pocha, M. D.; Krol, D. M.; Deri, R. J.; Lowry, M. E.

    1999-01-01

    We have been developing the optical components for a source-routed wavelength division multiplexed (WDM) computer interconnect fabric that uses multi-mode fiber ribbon cable as the transmission medium. We are developing wavelength selectable VCSEL transmitters, interference filters, and a compact broadcast element. Here we report on key results from our interference filter development activities. Our WDM filter approach is based upon post-market machining of the commercially available molded plastic "MT" fiber ribbon connector. We use III-IV semiconductors grown by MBE or MOCVD as the filter materials. The high indices of our thin film materials enable us to use multimode fiber and maintain narrow passbands without the need for micro-optics. We have fabricated both 2-port and 3-port devices based upon this approach. Our current work focuses on 2-port WDM filters suitable for a broadcast and select architecture. Our single-cavity Fabry- Perot (FP) filters have demonstrated insertion losses of < 2 dB for 4 nm passbands. The maximum crosstalk suppression for the single-cavity FP filters is 18dB To improve crosstalk suppression beyond that attainable with the Lorentzian lineshapes of the single-cavity FP we have investigated some multiple-cavity Fabry-Perot (MC-FP) designs which have a spectral response with a flatter top and sharper passband edges. Filter passband edge sharpness can be quantified by the ratio of the filter 3 dB bandwidth to 18 dB bandwidth This ratio is 0.48 for our multi-cavity filter, three times sharper than the single-cavity FP devices. This device provides a 5 nm tolerance window for component wavelength variations (at 1 dB excess loss) and is suitable for 10 nm channel spacing with 23 dB crosstalk suppression between adjacent channels. The average insertion loss for the MC-l? devices is 1.6 dB. (Average of insertion losses for the 12 fibers in a filter module.) Our current MC-FP filters have a 3-dB width of 7.6nm. Fiber to fiber center

  2. Electronic properties and mechanical strength of β-phosphorene nano-ribbons

    NASA Astrophysics Data System (ADS)

    Swaroop, Ram; Bhatia, Pradeep; Kumar, Ashok

    2016-05-01

    We have performed first principles calculations to find out the effect of mechanical strain on the electronic properties of zig-zag edged nano ribbons of β-phosphorene. It is found that electronic band-gap get opened-up to 2.61 eV by passivation of the edges of ribbons. Similarly, the mechanical strength is found to be increase from 1.75 GPa to 2.65 GPa on going from unpassivated nano ribbons to passivated ones along with the 2% increase in ultimate tensile strain. The band-gap value of passivated ribbon gets decreased to 0.43 eV on applying strain up to which the ribbon does not break. These tunable properties of β-phospherene with passivation with H-atom and applying mechanical strain offer its use in tunable nano electronics.

  3. Width and variation of the ENA flux ribbon observed by the Interstellar Boundary Explorer.

    PubMed

    Fuselier, S A; Allegrini, F; Funsten, H O; Ghielmetti, A G; Heirtzler, D; Kucharek, H; Lennartsson, O W; McComas, D J; Möbius, E; Moore, T E; Petrinec, S M; Saul, L A; Scheer, J A; Schwadron, N; Wurz, P

    2009-11-13

    The dominant feature in Interstellar Boundary Explorer (IBEX) sky maps of heliospheric energetic neutral atom (ENA) flux is a ribbon of enhanced flux that extends over a broad range of ecliptic latitudes and longitudes. It is narrow (approximately 20 degrees average width) but long (extending over 300 degrees in the sky) and is observed at energies from 0.2 to 6 kilo-electron volts. We demonstrate that the flux in the ribbon is a factor of 2 to 3 times higher than that of the more diffuse, globally distributed heliospheric ENA flux. The ribbon is most pronounced at approximately 1 kilo-electron volt. The average width of the ribbon is nearly constant, independent of energy. The ribbon is likely the result of an enhancement in the combined solar wind and pickup ion populations in the heliosheath.

  4. On the temperature dependent magnetic properties of as-spun Mn-Bi ribbons

    NASA Astrophysics Data System (ADS)

    Kavita, S.; Seelam, U. M. R.; Prabhu, D.; Gopalan, R.

    2015-03-01

    The structural and magnetic properties of melt-spun ribbons with nominal composition of Mn55Bi45 were investigated using X-ray diffraction, transmission electron microscopy and magnetometer measurements. A large coercivity (Hc) of 0.8 T was observed in the as-spun ribbons. Microstructure reveals the presence of Mn-Bi nanoparticles in the as-spun ribbons. Coercivity was found to increase with increasing temperature with a maximum coercivity of 1.4 T at T=503 K in the as-spun ribbons. Heat treatment of the as-spun ribbons resulted in the increase of LTP MnBi phase. Spin reorientation transition (TSR) was observed around 100 K.

  5. Structure suggests function: the case for synaptic ribbons as exocytotic nanomachines.

    PubMed

    Lenzi, D; von Gersdorff, H

    2001-09-01

    Synaptic ribbons, the organelles identified in electron micrographs of the sensory synapses involved in vision, hearing, and balance, have long been hypothesized to play an important role in regulating presynaptic function because they associate with synaptic vesicles at the active zone. Their physiology and molecular composition have, however, remained largely unknown. Recently, a series of elegant studies spurred by technical innovation have finally begun to shed light on the ultrastructure and function of ribbon synapses. Electrical capacitance measurements have provided sub-millisecond resolution of exocytosis, evanescent-wave microscopy has filmed the fusion of single 30 nm synaptic vesicles, electron tomography has revealed the 3D architecture of the synapse, and molecular cloning has begun to identify the proteins that make up ribbons. These results are consistent with the ribbon serving as a vesicle "conveyor belt" to resupply the active zone, and with the suggestion that ribbon and conventional chemical synapses have much in common.

  6. Mena–GRASP65 interaction couples actin polymerization to Golgi ribbon linking

    PubMed Central

    Tang, Danming; Zhang, Xiaoyan; Huang, Shijiao; Yuan, Hebao; Li, Jie; Wang, Yanzhuang

    2016-01-01

    In mammalian cells, the Golgi reassembly stacking protein 65 (GRASP65) has been implicated in both Golgi stacking and ribbon linking by forming trans-oligomers through the N-terminal GRASP domain. Because the GRASP domain is globular and relatively small, but the gaps between stacks are large and heterogeneous, it remains puzzling how GRASP65 physically links Golgi stacks into a ribbon. To explore the possibility that other proteins may help GRASP65 in ribbon linking, we used biochemical methods and identified the actin elongation factor Mena as a novel GRASP65-binding protein. Mena is recruited onto the Golgi membranes through interaction with GRASP65. Depleting Mena or disrupting actin polymerization resulted in Golgi fragmentation. In cells, Mena and actin were required for Golgi ribbon formation after nocodazole washout; in vitro, Mena and microfilaments enhanced GRASP65 oligomerization and Golgi membrane fusion. Thus Mena interacts with GRASP65 to promote local actin polymerization, which facilitates Golgi ribbon linking. PMID:26538023

  7. The presynaptic active zone protein bassoon is essential for photoreceptor ribbon synapse formation in the retina.

    PubMed

    Dick, Oliver; tom Dieck, Susanne; Altrock, Wilko Detlef; Ammermüller, Josef; Weiler, Reto; Garner, Craig Curtis; Gundelfinger, Eckart Dieter; Brandstätter, Johann Helmut

    2003-03-01

    The photoreceptor ribbon synapse is a highly specialized glutamatergic synapse designed for the continuous flow of synaptic vesicles to the neurotransmitter release site. The molecular mechanisms underlying ribbon synapse formation are poorly understood. We have investigated the role of the presynaptic cytomatrix protein Bassoon, a major component of the photoreceptor ribbon, in a mouse retina deficient of functional Bassoon protein. Photoreceptor ribbons lacking Bassoon are not anchored to the presynaptic active zones. This results in an impaired photoreceptor synaptic transmission, an abnormal dendritic branching of neurons postsynaptic to photoreceptors, and the formation of ectopic synapses. These findings suggest a critical role of Bassoon in the formation and the function of photoreceptor ribbon synapses of the mammalian retina.

  8. Spatial confinement of the IBEX Ribbon: A dominant turbulence mechanism

    SciTech Connect

    Isenberg, Philip A.

    2014-05-20

    The narrow ribbon of enhanced energetic neutral atom flux observed by the Interstellar Boundary Explorer spacecraft has prompted numerous ideas to explain its structure and properties. One of these ideas is the 'neutral solar wind' scenario, which identifies the source particles as pickup protons in the local interstellar medium originating in solar wind charge-exchange interactions. This scenario has been thought to require unrealistically weak pitch-angle scattering of the pickup protons to explain the narrow structure. Recently, Schwadron and McComas suggested that this structure could result from a spatial retention of the pickup protons, rather than from a restricted pitch-angle distribution. Here, we present a physically motivated, quantitative mechanism to produce such a spatial configuration. This mechanism is based on the 'dominant turbulence' assumption, which can be applied where the production of new pickup protons is slow, and has been used to successfully explain the level of turbulent heating observed in the outer solar wind. This formalism predicts a pickup isotropization process which adds or subtracts energy from the ambient turbulent fluctuations, depending on the initial pitch angle of the pickup protons. We show that a simple model of this process can yield a ribbon structure in qualitative agreement with the observations. The results of this simple model are not yet quantitatively satisfactory, but we suggest several improvements which may reduce the quantitative discrepancy.

  9. GPU-accelerated visualization of protein dynamics in ribbon mode

    NASA Astrophysics Data System (ADS)

    Wahle, Manuel; Birmanns, Stefan

    2011-01-01

    Proteins are biomolecules present in living organisms and essential for carrying out vital functions. Inherent to their functioning is folding into different spatial conformations, and to understand these processes, it is crucial to visually explore the structural changes. In recent years, significant advancements in experimental techniques and novel algorithms for post-processing of protein data have routinely revealed static and dynamic structures of increasing sizes. In turn, interactive visualization of the systems and their transitions became more challenging. Therefore, much research for the efficient display of protein dynamics has been done, with the focus being space filling models, but for the important class of abstract ribbon or cartoon representations, there exist only few methods for an efficient rendering. Yet, these models are of high interest to scientists, as they provide a compact and concise description of the structure elements along the protein main chain. In this work, a method was developed to speed up ribbon and cartoon visualizations. Separating two phases in the calculation of geometry allows to offload computational work from the CPU to the GPU. The first phase consists of computing a smooth curve along the protein's main chain on the CPU. In the second phase, conducted independently by the GPU, vertices along that curve are moved to set up the final geometrical representation of the molecule.

  10. Experimental and numerical investigation of the horizontal ribbon growth process

    NASA Astrophysics Data System (ADS)

    Helenbrook, Brian T.; Kellerman, Peter; Carlson, Frederick; Desai, Nandish; Sun, Dawei

    2016-11-01

    Experimental and numerical results are presented on the process of horizontal ribbon growth (HRG) of single-crystal silicon. Experimental data on the leading edge position of the growth front as a function of pull speed is compared to model predictions with and without solidification kinetic effects. Without kinetics, the numerical results predict leading edge positions which are completely different than that observed in the experiment. With kinetics, the leading edge position is predicted typically within 1 mm and the change in position with pull speed also is well predicted. Conclusions from the kinetic model are that the growth occurs through a faceted process where the leading edge is a {111} facet that requires significant supercooling to maintain the growth. An outcome of the model is that the leading edge position versus pull speed response shows a turning point beyond which there are no steady growth solutions. This is consistent with all previously reported experiments on this process, which have reported maximum attainable pull-speeds. These results directly contradict previous conclusions from the "wedge" model of horizontal ribbon growth, which predicts that a large area wedge-shaped growth region exists and that increasing pull speeds simply result in a narrower wedge angle.

  11. Numerical Simulations of a Jovian Ribbon-like Feature

    NASA Astrophysics Data System (ADS)

    Morales-Juberias, R.; Simon-Miller, A. A.; Dowling, T. E.; Sayanagi, K. M.; Choi, D. S.

    2013-12-01

    HST observations show the presence of a Ribbon like feature in Jupiter's atmosphere at ≈ 30 degrees North. The presence of this feature seems to correlate with periods when the jet amplitude velocities are highest. Studies of motions can help to determine the nature of the feature. Its detailed structure will be studied using Hubble data at multiple wavelengths and it may be possible to reprocess the long global movies of the Voyager era to study motions at this latitude. Preliminary model results without forcing show that the morphology of the produced instabilities is dependent on the conditions of the background flow and static stability of the atmosphere. Different forcing terms will be used to study the variable nature of this feature. We use numerical simulations to investigate the instabilities produced by different kinds of forcing on the westward jet centered at ≈ 30 degrees North in Jupiter's atmosphere as well as in its two flanking eastward jets to the north and south. Our goal is to understand how the background flow and static stability of the atmosphere affect the ability of the model to reproduce the Ribbon-like cloud pattern observed in Hubble Space Telescope (HST) images of that latitude taken in support of the 2007 New Horizons Jupiter flyby.

  12. Intracellular calcium stores drive slow non-ribbon vesicle release from rod photoreceptors

    PubMed Central

    Chen, Minghui; Križaj, David; Thoreson, Wallace B.

    2014-01-01

    Rods are capable of greater slow release than cones contributing to overall slower release kinetics. Slow release in rods involves Ca2+-induced Ca2+ release (CICR). By impairing release from ribbons, we found that unlike cones where release occurs entirely at ribbon-style active zones, slow release from rods occurs mostly at ectopic, non-ribbon sites. To investigate the role of CICR in ribbon and non-ribbon release from rods, we used total internal reflection fluorescence microscopy as a tool for visualizing terminals of isolated rods loaded with fluorescent Ca2+ indicator dyes and synaptic vesicles loaded with dextran-conjugated pH-sensitive rhodamine. We found that rather than simply facilitating release, activation of CICR by ryanodine triggered release directly in rods, independent of plasma membrane Ca2+ channel activation. Ryanodine-evoked release occurred mostly at non-ribbon sites and release evoked by sustained depolarization at non-ribbon sites was mostly due to CICR. Unlike release at ribbon-style active zones, non-ribbon release did not occur at fixed locations. Fluorescence recovery after photobleaching of endoplasmic reticulum (ER)-tracker dye in rod terminals showed that ER extends continuously from synapse to soma. Release of Ca2+ from terminal ER by lengthy depolarization did not significantly deplete Ca2+ from ER in the perikaryon. Collectively, these results indicate that CICR-triggered release at non-ribbon sites is a major mechanism for maintaining vesicle release from rods and that CICR in terminals may be sustained by diffusion of Ca2+ through ER from other parts of the cell. PMID:24550779

  13. An unusual ST-segment elevation: apical hypertrophic cardiomyopathy shows the ace up its sleeve.

    PubMed

    de Santis, Francesco; Pergolini, Amedeo; Zampi, Giordano; Pero, Gaetano; Pino, Paolo Giuseppe; Minardi, Giovanni

    2013-01-01

    Apical hypertrophic cardiomyopathy is part of the broad clinical and morphologic spectrum of hypertrophic cardiomyopathy. We report a patient with electrocardiographic abnormalities in whom acute coronary syndrome was excluded and apical hypertrophic cardiomyopathy was demonstrated by careful differential diagnosis.

  14. Dense optical-electrical interface module

    SciTech Connect

    Paul Chang

    2000-12-21

    The DOIM (Dense Optical-electrical Interface Modules) is a custom-designed optical data transmission module employed in the upgrade of Silicon Vertex Detector of CDF experiment at Fermilab. Each DOIM module consists of a transmitter (TX) converting electrical differential input signals to optical outputs, a middle segment of jacketed fiber ribbon cable, and a receiver (RX) which senses the light inputs and converts them back to electrical signals. The targeted operational frequency is 53 MHz, and higher rate is achievable. This article outlines the design goals, implementation methods, production test results, and radiation hardness tests of these modules.

  15. Reproducibility of Echocardiograph-Derived Multilevel Left Ventricular Apical Twist Mechanics.

    PubMed

    Stewart, Glenn M; Yamada, Akira; Kavanagh, Justin J; Haseler, Luke J; Chan, Jonathan; Sabapathy, Surendran

    2016-02-01

    Left ventricular (LV) twist mechanics are routinely assessed via echocardiography in clinical and research trials investigating the function of obliquely oriented myocardial fibers. However, echocardiograph-derived measures of LV twist may be compromised by nonstandardized acquisition of the apical image. This study examined the reproducibility of echocardiograph-derived parameters of apical twist mechanics at multiple levels of the apical myocardium. Two sets of 2D LV parasternal short-axis images were obtained in 30 healthy subjects (24 men; 19-57 year) via echocardiography. Images were acquired immediately distal to the papillary muscles (apical image 1), immediately above the point of LV cavity obliteration at end systole (apical image 3), and midway between apical image 1 and apical image 3 (apical image 2). Repeat scans were performed within 1 hour, and twist mechanics (rotation and rotation rate) were calculated via frame-by-frame tracking of natural acoustic echocardiographic markers (speckle tracking). The magnitude of apical rotation increased progressively toward the apex (apical image 1: 4.2 ± 2.1°, apical image 2: 7.2 ± 3.9°, apical image 3: 11.8 ± 4.6°). apical images 1, 2, and 3 each had moderate to good correlations between repeat scans (ICC: 0.531-0.856). When apical images 1, 2, and 3 were averaged, rotation was 7.7 ± 2.7° and between-scan correlation was excellent (ICC: 0.910). Similar results were observed for systolic and diastolic rotation rates. Averaging multiple standardized apical images, tending progressively toward the apex, generated the most reproducible rotation indices and may be optimal for the assessment of LV twist mechanics across therapeutic, interventional, and research studies; however, care should be taken given the influence of acquisition level on the magnitude of apical rotation.

  16. Patterned Anchorage to the Apical Extracellular Matrix Defines Tissue Shape in the Developing Appendages of Drosophila.

    PubMed

    Ray, Robert P; Matamoro-Vidal, Alexis; Ribeiro, Paulo S; Tapon, Nic; Houle, David; Salazar-Ciudad, Isaac; Thompson, Barry J

    2015-08-10

    How tissues acquire their characteristic shape is a fundamental unresolved question in biology. While genes have been characterized that control local mechanical forces to elongate epithelial tissues, genes controlling global forces in epithelia have yet to be identified. Here, we describe a genetic pathway that shapes appendages in Drosophila by defining the pattern of global tensile forces in the tissue. In the appendages, shape arises from tension generated by cell constriction and localized anchorage of the epithelium to the cuticle via the apical extracellular-matrix protein Dumpy (Dp). Altering Dp expression in the developing wing results in predictable changes in wing shape that can be simulated by a computational model that incorporates only tissue contraction and localized anchorage. Three other wing shape genes, narrow, tapered, and lanceolate, encode components of a pathway that modulates Dp distribution in the wing to refine the global force pattern and thus wing shape.

  17. Patterned Anchorage to the Apical Extracellular Matrix Defines Tissue Shape in the Developing Appendages of Drosophila

    PubMed Central

    Ray, Robert P.; Matamoro-Vidal, Alexis; Ribeiro, Paulo S.; Tapon, Nic; Houle, David; Salazar-Ciudad, Isaac; Thompson, Barry J.

    2015-01-01

    Summary How tissues acquire their characteristic shape is a fundamental unresolved question in biology. While genes have been characterized that control local mechanical forces to elongate epithelial tissues, genes controlling global forces in epithelia have yet to be identified. Here, we describe a genetic pathway that shapes appendages in Drosophila by defining the pattern of global tensile forces in the tissue. In the appendages, shape arises from tension generated by cell constriction and localized anchorage of the epithelium to the cuticle via the apical extracellular-matrix protein Dumpy (Dp). Altering Dp expression in the developing wing results in predictable changes in wing shape that can be simulated by a computational model that incorporates only tissue contraction and localized anchorage. Three other wing shape genes, narrow, tapered, and lanceolate, encode components of a pathway that modulates Dp distribution in the wing to refine the global force pattern and thus wing shape. PMID:26190146

  18. Apical organs in echinoderm larvae: insights into larval evolution in the Ambulacraria.

    PubMed

    Byrne, Maria; Nakajima, Yoko; Chee, Francis C; Burke, Robert D

    2007-01-01

    The anatomy and cellular organization of serotonergic neurons in the echinoderm apical organ exhibits class-specific features in dipleurula-type (auricularia, bipinnaria) and pluteus-type (ophiopluteus, echinopluteus) larvae. The apical organ forms in association with anterior ciliary structures. Apical organs in dipleurula-type larvae are more similar to each other than to those in either of the pluteus forms. In asteroid bipinnaria and holothuroid auricularia the apical organ spans ciliary band sectors that traverse the anterior-most end of the larvae. The asteroid apical organ also has prominent bilateral ganglia that connect with an apical network of neurites. The simple apical organ of the auricularia is similar to that in the hemichordate tornaria larva. Apical organs in pluteus forms differ markedly. The echinopluteus apical organ is a single structure on the oral hood between the larval arms comprised of two groups of cells joined by a commissure and its cell bodies do not reside in the ciliary band. Ophioplutei have a pair of lateral ganglia associated with the ciliary band of larval arms that may be the ophiuroid apical organ. Comparative anatomy of the serotonergic nervous systems in the dipleurula-type larvae of the Ambulacraria (Echinodermata+Hemichordata) suggests that the apical organ of this deuterostome clade originated as a simple bilaterally symmetric nerve plexus spanning ciliary band sectors at the anterior end of the larva. From this structure, the apical organ has been independently modified in association with the evolution of class-specific larval forms. PMID:17845515

  19. Implantation of a left ventricular assist device in patients with a complex apical anatomy.

    PubMed

    Palmen, Meindert; Verwey, Harriette F; Haeck, Marlieke L A; Holman, Eduard R; Schalij, Martin J; Klautz, Robert J M

    2012-12-01

    Implantation of a left ventricular assist device can be challenging in patients with an altered apical anatomy after cardiac surgery or as the result of the presence of a calcified apical aneurysm. In this paper we present 2 cases with a challenging apical anatomy and introduce a new surgical technique facilitating left ventricular assist device implantation in these patients.

  20. Mid-ventricular obstructive hypertrophic cardiomyopathy with an apical aneurysm caused by vasospastic angina.

    PubMed

    Kiyooka, Takahiko; Satoh, Yasuhiro

    2014-03-20

    Mid-ventricular obstructive hypertrophic cardiomyopathy (MVOHCM) is a rare form of cardiomyopathy, characterized by the presence of a pressure gradient between the left ventricular basal and apical chambers and is frequently associated with an apical aneurysm. However, the exact cause of this aneurysm remains unknown. We here describe a patient with MVOHCM in whom the apical aneurysm may be caused by vasospastic angina.

  1. Apical organs in echinoderm larvae: insights into larval evolution in the Ambulacraria.

    PubMed

    Byrne, Maria; Nakajima, Yoko; Chee, Francis C; Burke, Robert D

    2007-01-01

    The anatomy and cellular organization of serotonergic neurons in the echinoderm apical organ exhibits class-specific features in dipleurula-type (auricularia, bipinnaria) and pluteus-type (ophiopluteus, echinopluteus) larvae. The apical organ forms in association with anterior ciliary structures. Apical organs in dipleurula-type larvae are more similar to each other than to those in either of the pluteus forms. In asteroid bipinnaria and holothuroid auricularia the apical organ spans ciliary band sectors that traverse the anterior-most end of the larvae. The asteroid apical organ also has prominent bilateral ganglia that connect with an apical network of neurites. The simple apical organ of the auricularia is similar to that in the hemichordate tornaria larva. Apical organs in pluteus forms differ markedly. The echinopluteus apical organ is a single structure on the oral hood between the larval arms comprised of two groups of cells joined by a commissure and its cell bodies do not reside in the ciliary band. Ophioplutei have a pair of lateral ganglia associated with the ciliary band of larval arms that may be the ophiuroid apical organ. Comparative anatomy of the serotonergic nervous systems in the dipleurula-type larvae of the Ambulacraria (Echinodermata+Hemichordata) suggests that the apical organ of this deuterostome clade originated as a simple bilaterally symmetric nerve plexus spanning ciliary band sectors at the anterior end of the larva. From this structure, the apical organ has been independently modified in association with the evolution of class-specific larval forms.

  2. Transient apical dyskinesia with a pacemaker: Electrocardiographic features.

    PubMed

    Núñez-Gil, Iván J; Feltes, Gisela I; Mejía-Rentería, Hernán D; Biagioni, Corina; De Agustín, J Alberto; Vivas, David; Fernández-Ortiz, Antonio

    2015-04-01

    Transient apical dyskinesia syndromes present features similar to acute coronary syndromes, but with normal coronary arteries and rapid complete resolution of wall motion alterations. We report the case of a 73-year-old woman who was admitted to hospital because of typical chest pain at rest after her brother's death. She had had a pacemaker implanted in 2001. Troponin levels were elevated and apical hypokinesia was shown by ventriculography and echocardiography, with normal coronary arteries. Evolving ECG alterations were observed in spite of the continued pacing rhythm. All these alterations were fully resolved after discharge. This case shows that, even in the presence of a pacemaker, evolving ECG alterations can be observed in Takotsubo syndrome.

  3. Transient apical dyskinesia with a pacemaker: Electrocardiographic features.

    PubMed

    Núñez-Gil, Iván J; Feltes, Gisela I; Mejía-Rentería, Hernán D; Biagioni, Corina; De Agustín, J Alberto; Vivas, David; Fernández-Ortiz, Antonio

    2015-04-01

    Transient apical dyskinesia syndromes present features similar to acute coronary syndromes, but with normal coronary arteries and rapid complete resolution of wall motion alterations. We report the case of a 73-year-old woman who was admitted to hospital because of typical chest pain at rest after her brother's death. She had had a pacemaker implanted in 2001. Troponin levels were elevated and apical hypokinesia was shown by ventriculography and echocardiography, with normal coronary arteries. Evolving ECG alterations were observed in spite of the continued pacing rhythm. All these alterations were fully resolved after discharge. This case shows that, even in the presence of a pacemaker, evolving ECG alterations can be observed in Takotsubo syndrome. PMID:25840647

  4. [An endodontic ultrasonic system for apical endodontic surgery].

    PubMed

    de Lange, I; Putters, T; Baas, E M; van Ingen, J M

    2009-09-01

    Apical endodontic surgery is applied frequently following a failed conventional endodontic treatment. The apical preparation can be carried out conventionally using a round bur or using an endodontic ultrasonic system. The purpose of this study was to compare the outcome of the 2 treatment options by a randomized prospective clinical study. Patients (n=399) were at random allocated to treatment using a conventional round bur or using an ultrasonic system (P-max Newtron) according to a for the rest similar treatment protocol. One year post treatment, the treatment outcomes were determined by 2 oral and maxillofacial surgeons, blinded for the treatment option. Adequate follow-up data were obtained from 290 patients. The overall success rate was 71% in the patients treated conventionally and 81% in the patients treated using the ultrasonic system. In molar teeth, the difference in success rate was statistically significant. PMID:19791493

  5. Pathogenesis of apical periodontitis and the causes of endodontic failures.

    PubMed

    Nair, P N R

    2004-01-01

    Apical periodontitis is a sequel to endodontic infection and manifests itself as the host defense response to microbial challenge emanating from the root canal system. It is viewed as a dynamic encounter between microbial factors and host defenses at the interface between infected radicular pulp and periodontal ligament that results in local inflammation, resorption of hard tissues, destruction of other periapical tissues, and eventual formation of various histopathological categories of apical periodontitis, commonly referred to as periapical lesions. The treatment of apical periodontitis, as a disease of root canal infection, consists of eradicating microbes or substantially reducing the microbial load from the root canal and preventing re-infection by orthograde root filling. The treatment has a remarkably high degree of success. Nevertheless, endodontic treatment can fail. Most failures occur when treatment procedures, mostly of a technical nature, have not reached a satisfactory standard for the control and elimination of infection. Even when the highest standards and the most careful procedures are followed, failures still occur. This is because there are root canal regions that cannot be cleaned and obturated with existing equipments, materials, and techniques, and thus, infection can persist. In very rare cases, there are also factors located within the inflamed periapical tissue that can interfere with post-treatment healing of the lesion. The data on the biological causes of endodontic failures are recent and scattered in various journals. This communication is meant to provide a comprehensive overview of the etio-pathogenesis of apical periodontitis and the causes of failed endodontic treatments that can be visualized in radiographs as asymptomatic post-treatment periapical radiolucencies. PMID:15574679

  6. SYMMETRY OF THE IBEX RIBBON OF ENHANCED ENERGETIC NEUTRAL ATOM (ENA) FLUX

    SciTech Connect

    Funsten, H. O.; Cai, D. M.; Higdon, D. M.; Larsen, B. A. E-mail: dmc@lanl.gov E-mail: balarsen@lanl.gov; and others

    2015-01-20

    The circular ribbon of enhanced energetic neutral atom (ENA) emission observed by the Interstellar Boundary Explorer (IBEX) mission remains a critical signature for understanding the interaction between the heliosphere and the interstellar medium. We study the symmetry of the ribbon flux and find strong, spectrally dependent reflection symmetry throughout the energy range 0.7-4.3 keV. The distribution of ENA flux around the ribbon is predominantly unimodal at 0.7 and 1.1 keV, distinctly bimodal at 2.7 and 4.3 keV, and a mixture of both at 1.7 keV. The bimodal flux distribution consists of partially opposing bilateral flux lobes, located at highest and lowest heliographic latitude extents of the ribbon. The vector between the ribbon center and heliospheric nose (which defines the so-called BV plane) appears to play an organizing role in the spectral dependence of the symmetry axis locations as well as asymmetric contributions to the ribbon flux. The symmetry planes at 2.7 and 4.3 keV, derived by projecting the symmetry axes to a great circle in the sky, are equivalent to tilting the heliographic equatorial plane to the ribbon center, suggesting a global heliospheric ordering. The presence and energy dependence of symmetric unilateral and bilateral flux distributions suggest strong spectral filtration from processes encountered by an ion along its journey from the source plasma to its eventual detection at IBEX.

  7. Symmetry of the IBEX Ribbon of Enhanced Energetic Neutral Atom (ENA) Flux

    NASA Astrophysics Data System (ADS)

    Funsten, H. O.; Bzowski, M.; Cai, D. M.; Dayeh, M.; DeMajistre, R.; Frisch, P. C.; Heerikhuisen, J.; Higdon, D. M.; Janzen, P.; Larsen, B. A.; Livadiotis, G.; McComas, D. J.; Möbius, E.; Reese, C. S.; Roelof, E. C.; Reisenfeld, D. B.; Schwadron, N. A.; Zirnstein, E. J.

    2015-01-01

    The circular ribbon of enhanced energetic neutral atom (ENA) emission observed by the Interstellar Boundary Explorer (IBEX) mission remains a critical signature for understanding the interaction between the heliosphere and the interstellar medium. We study the symmetry of the ribbon flux and find strong, spectrally dependent reflection symmetry throughout the energy range 0.7-4.3 keV. The distribution of ENA flux around the ribbon is predominantly unimodal at 0.7 and 1.1 keV, distinctly bimodal at 2.7 and 4.3 keV, and a mixture of both at 1.7 keV. The bimodal flux distribution consists of partially opposing bilateral flux lobes, located at highest and lowest heliographic latitude extents of the ribbon. The vector between the ribbon center and heliospheric nose (which defines the so-called BV plane) appears to play an organizing role in the spectral dependence of the symmetry axis locations as well as asymmetric contributions to the ribbon flux. The symmetry planes at 2.7 and 4.3 keV, derived by projecting the symmetry axes to a great circle in the sky, are equivalent to tilting the heliographic equatorial plane to the ribbon center, suggesting a global heliospheric ordering. The presence and energy dependence of symmetric unilateral and bilateral flux distributions suggest strong spectral filtration from processes encountered by an ion along its journey from the source plasma to its eventual detection at IBEX.

  8. Enlargement of the apical gap after laser root resection

    NASA Astrophysics Data System (ADS)

    Mello, Guilherme P. S.; Paradella, Thais C.; Munin, Egberto; Mello, Jose B.; Pacheco, Marcos T. T.

    2000-11-01

    An apical filling material should establish, as perfect as possible, the hermetic sealing of an apical cavity. However, a gap is formed between the filling material (gutta-percha) and the root canal wall. The egress of irritants into the root canal system to the periapical tissues is considered the principal cause of fails in apicoectomy and retro-filling, being assumed that irritants penetrate mainly through the gap located between the gutta-percha and the dentin. In this paper, we report the observation of an enlargement of the apical gap, after laser apicoectomy, comparing to conventional apicoectomy. The samples were divided into groups, and the conventional apicoectomy group, together with the Er:YAG laser group (400 mJ/10 Hz) produced both similar results, being the gap unaltered. On the other hand, the samples that were irradiated with the Er:YAG laser, followed by Nd:YAG laser irradiation (1.5 W/10 Hz) presented a larger gap, conclusions that were drawn from Scanning Electronic Microscope analysis. The enlargement of the gap was due to the fusion of the dentin on the border, close to the gutta-percha. This pronounced behavior might have been caused by the surface discontinuity, imposing a non-homogeneous condition, in relation to heat propagation, existing many clinical applications of these observations.

  9. Apical Periodontitis - Is It Accountable for Cardiovascular Diseases?

    PubMed Central

    Chaman, Chandrakar

    2016-01-01

    The aim of this review was to assess the relationship between apical periodontitis and cardiovascular diseases and the predictive factors regarding this association. Cross sectional and observational studies have been included, which are mostly retrospective. A comprehensive search was performed in the Systematic Electronic Databases, PUBMED and MEDLINE from 1919 till September 2014. Articles were also hand searched. From 86 studies identified, all were read and 58 articles which were relevant were included in the text. Some articles were excluded because they were pertaining to periodontology and other systemic disorders. Some were solely animal studies and were thus excluded. Our results suggest an independent association between cardiovascular diseases and apical periodontitis. A causal relationship could not be established since weak parameters of risk have been assessed in the studies, population taken is difficult to compare and other confounding factors have not been ruled out. Only a more focused and better instituted scientific research can determine this association. Establishing a cause and effect relationship between apical periodontitis and cardiovascular diseases can affect the course of treatment of cardiovascular diseases. It is not only of interest from the scientific point of view but also from public health perspective. PMID:27656588

  10. An Apical-Membrane Chloride Channel in Human Tracheal Epithelium

    NASA Astrophysics Data System (ADS)

    Welsh, Michael J.

    1986-06-01

    The mechanism of chloride transport by airway epithelia has been of substantial interest because airway and sweat gland-duct epithelia are chloride-impermeable in cystic fibrosis. The decreased chloride permeability prevents normal secretion by the airway epithelium, thereby interfering with mucociliary clearance and contributing to the morbidity and mortality of the disease. Because chloride secretion depends on and is regulated by chloride conductance in the apical cell membrane, the patch-clamp technique was used to directly examine single-channel currents in primary cultures of human tracheal epithelium. The cells contained an anion-selective channel that was not strongly voltage-gated or regulated by calcium in cell-free patches. The channel was also blocked by analogs of carboxylic acid that decrease apical chloride conductance in intact epithelia. When attached to the cell, the channel was activated by isoproterenol, although the channel was also observed to open spontaneously. However, in some cases, the channel was only observed after the patch was excised from the cell. These results suggest that this channel is responsible for the apical chloride conductance in airway epithelia.

  11. Apical Periodontitis - Is It Accountable for Cardiovascular Diseases?

    PubMed

    Garg, Paridhi; Chaman, Chandrakar

    2016-08-01

    The aim of this review was to assess the relationship between apical periodontitis and cardiovascular diseases and the predictive factors regarding this association. Cross sectional and observational studies have been included, which are mostly retrospective. A comprehensive search was performed in the Systematic Electronic Databases, PUBMED and MEDLINE from 1919 till September 2014. Articles were also hand searched. From 86 studies identified, all were read and 58 articles which were relevant were included in the text. Some articles were excluded because they were pertaining to periodontology and other systemic disorders. Some were solely animal studies and were thus excluded. Our results suggest an independent association between cardiovascular diseases and apical periodontitis. A causal relationship could not be established since weak parameters of risk have been assessed in the studies, population taken is difficult to compare and other confounding factors have not been ruled out. Only a more focused and better instituted scientific research can determine this association. Establishing a cause and effect relationship between apical periodontitis and cardiovascular diseases can affect the course of treatment of cardiovascular diseases. It is not only of interest from the scientific point of view but also from public health perspective. PMID:27656588

  12. Ontogenetic contingency of tolerance mechanisms in response to apical damage

    PubMed Central

    Gruntman, Michal; Novoplansky, Ariel

    2011-01-01

    Background and Aims Plants are able to tolerate tissue loss through vigorous branching which is often triggered by release from apical dominance and activation of lateral meristems. However, damage-induced branching might not be a mere physiological outcome of released apical dominance, but an adaptive response to environmental signals, such as damage timing and intensity. Here, branching responses to both factors were examined in the annual plant Medicago truncatula. Methods Branching patterns and allocation to reproductive traits were examined in response to variable clipping intensities and timings in M. truncatula plants from two populations that vary in the onset of reproduction. Phenotypic selection analysis was used to evaluate the strength and direction of selection on branching under the damage treatments. Key Results Plants of both populations exhibited an ontogenetic shift in tolerance mechanisms: while early damage induced greater meristem activation, late damage elicited investment in late-determined traits, including mean pod and seed biomass, and supported greater germination rates. Severe damage mostly elicited simultaneous development of multiple-order lateral branches, but this response was limited to early damage. Selection analyses revealed positive directional selection on branching in plants under early- compared with late- or no-damage treatments. Conclusions The results demonstrate that damage-induced meristem activation is an adaptive response that could be modified according to the plant's developmental stage, severity of tissue loss and their interaction, stressing the importance of considering these effects when studying plastic responses to apical damage. PMID:21873259

  13. Thin-ribbon tapered coupler for dielectric waveguides

    NASA Technical Reports Server (NTRS)

    Yeh, C.; Otoshi, T. Y.; Shimabukuro, F. I.

    1994-01-01

    A recent discovery shows that a high-dielectric constant, low-loss, solid material can be made into a ribbon-like waveguide structure to yield an attenuation constant of less than 0.02 dB/m for single-mode guidance of millimeter/submillimeter waves. One of the crucial components that must be invented in order to guarantee the low-loss utilization of this dielectric-waveguide guiding system is the excitation coupler. The traditional tapered-to-a-point coupler for a dielectric rod waveguide fails when the dielectric constant of the dielectric waveguide is large. This article presents a new way to design a low-loss coupler for a high- or low-dielectric constant dielectric waveguide for millimeter or submillimeter waves.

  14. Nanoscale phase change memory with graphene ribbon electrodes

    NASA Astrophysics Data System (ADS)

    Behnam, Ashkan; Xiong, Feng; Cappelli, Andrea; Wang, Ning C.; Carrion, Enrique A.; Hong, Sungduk; Dai, Yuan; Lyons, Austin S.; Chow, Edmond K.; Piccinini, Enrico; Jacoboni, Carlo; Pop, Eric

    2015-09-01

    Phase change memory (PCM) devices are known to reduce in power consumption as the bit volume and contact area of their electrodes are scaled down. Here, we demonstrate two types of low-power PCM devices with lateral graphene ribbon electrodes: one in which the graphene is patterned into narrow nanoribbons and the other where the phase change material is patterned into nanoribbons. The sharp graphene "edge" contacts enable switching with threshold voltages as low as ˜3 V, low programming currents (<1 μA SET and <10 μA RESET) and OFF/ON resistance ratios >100. Large-scale fabrication with graphene grown by chemical vapor deposition also enables the study of heterogeneous integration and that of variability for such nanomaterials and devices.

  15. The generation of proton beams in two-ribbon flares

    NASA Technical Reports Server (NTRS)

    Martens, P. C. H.

    1988-01-01

    It is shown that, in the current sheet at the top of the arcade of postflare loops in a two-ribbon solar flare, particle beams are generated by direct electric-field acceleration. The acceleration process is completely collisionless and is limited only by the gyromotion along the component of the magnetic field perpendicular to the sheet. This mechanism is similar to the particle acceleration in the geomagnetic tail. Neutral beams emanate from the sheet with almost zero pitch angle, making protons the main carriers of the beam energy. Approximately 10 to the 35th protons/sec are generated with a typical energy of 200 keV. Their energy distribution is a single power law, with an upper and lower energy cut-off. Such a population is capable of simultaneously generating the observed impulsive-phase hard X-rays and the gamma rays.

  16. Tracking unstable periodic orbits in a bronze ribbon experiment

    NASA Astrophysics Data System (ADS)

    Dressler, U.; Ritz, T.; Schenck Zu Schweinsberg, A.; Doerner, R.; Hübinger, B.; Martienssen, W.

    1995-03-01

    We demonstrate the tracking of an unstable periodic orbit (UPO) in a bronze ribbon experiment. The stabilization of the UPO at each tracking step is performed via the local control method, a variant of the Ott-Grebogi-Yorke [Phys. Rev. Lett. 64, 1196 (1990)] feedback control method. Starting with feedback control vectors extracted from the analysis of the experimental data at each tracking step, we redetermine the location of the UPO using an adaptive orbit correction that exploits the applied control signal and the actual trajectory of the system. Doing so, the unstable periodic orbit can be tracked into a parameter regime where the chaotic attractor has long ago lost its stability and another periodic orbit has become stable.

  17. Semiconducor wires and ribbons for high performance flexible electronics.

    SciTech Connect

    Sun, Y.; Baca, A. J.; Ahn, J.-H.; Meitl, M.; Menard, E.; Kim, H.-S; Choi, W.; Kim, D.-H; Huang, Y.; Rogers, J. A.; Center for Nanoscale Materials; Univ. of Illinois

    2008-01-01

    This article reviews the properties, fabrication and assembly of inorganic semiconductor materials that can be used as active building blocks to form high-performance transistors and circuits for flexible and bendable large-area electronics. Obtaining high performance on low temperature polymeric substrates represents a technical challenge for macroelectronics. Therefore, the fabrication of high quality inorganic materials in the form of wires, ribbons, membranes, sheets, and bars formed by bottom-up and top-down approaches, and the assembly strategies used to deposit these thin films onto plastic substrates will be emphasized. Substantial progress has been made in creating inorganic semiconducting materials that are stretchable and bendable, and the description of the mechanics of these form factors will be presented, including circuits in three-dimensional layouts. Finally, future directions and promising areas of research will be described.

  18. Lithologic, structural, and geomorphic controls on ribbon forest patterns in a glaciated mountain environment

    NASA Astrophysics Data System (ADS)

    Butler, David R.; Malanson, George P.; Bekker, Matthew F.; Resler, Lynn M.

    2003-09-01

    So-called "ribbon forests" have been attributed to snowdrift patterns and fire history without reference to geomorphology [Vegetatio 19 (1969) 192.]. This paper illustrates how site conditions of geomorphology and geology explain the origin of ribbon forests. In Glacier National Park, MT (USA), regional tectonic uplift associated with the Laramide Orogeny produced structural features that amplify lithologic differences. Pleistocene glaciation scoured deeply along the strike of bedding planes, highlighting this pattern and in some cases producing fine-scale parallel finger lakes between forested ribbon strips. Twelve ribbon forest sites on both sides of the Continental Divide were closely studied on stereoscopic aerial photographs, and several of these sites were examined in the field or from helicopter overflights. In all cases, geologic and geomorphic conditions explain the location and distribution of the ribbon forests. Change-detection of the distribution of trees versus nontree-covered surfaces in an area of ribbon forest on Flattop Mountain, a complex uplifted synclinal structure, was undertaken using panchromatic, low-altitude aerial photographs from 1966 to 1991. Areas changed from forest to meadow and from meadow to forest in roughly equal amounts in a generally random spatial pattern. No evidence was seen to suggest that the creation of one ribbon eventually created another downwind, as suggested by Billings. Aerial photograph interpretation, field examination and soils analyses of forest ribbons and adjacent unforested meadows clearly illustrated that trees occupy higher, parallel to subparallel, well-drained sites where the spatial pattern is in turn a distinct reflection of the spatial pattern of structure and stratigraphy. Meadows occupy topographically lower positions between ridges where erosion along bedding plane strike was concentrated. Topography sets conditions that allow tree growth in certain locations while precluding it in immediately

  19. The Disease Protein Tulp1 Is Essential for Periactive Zone Endocytosis in Photoreceptor Ribbon Synapses

    PubMed Central

    Wahl, Silke; Magupalli, Venkat Giri; Dembla, Mayur; Katiyar, Rashmi; Schwarz, Karin; Köblitz, Louise; Alpadi, Kannan; Krause, Elmar; Rettig, Jens; Sung, Ching-Hwa; Goldberg, Andrew F. X.

    2016-01-01

    Mutations in the Tulp1 gene cause severe, early-onset retinitis pigmentosa (RP14) in humans. In the retina, Tulp1 is mainly expressed in photoreceptors that use ribbon synapses to communicate with the inner retina. In the present study, we demonstrate that Tulp1 is highly enriched in the periactive zone of photoreceptor presynaptic terminals where Tulp1 colocalizes with major endocytic proteins close to the synaptic ribbon. Analyses of Tulp1 knock-out mice demonstrate that Tulp1 is essential to keep endocytic proteins enriched at the periactive zone and to maintain high levels of endocytic activity close to the synaptic ribbon. Moreover, we have discovered a novel interaction between Tulp1 and the synaptic ribbon protein RIBEYE, which is important to maintain synaptic ribbon integrity. The current findings suggest a new model for Tulp1-mediated localization of the endocytic machinery at the periactive zone of ribbon synapses and offer a new rationale and mechanism for vision loss associated with genetic defects in Tulp1. SIGNIFICANCE STATEMENT Mutations in the Tulp1 gene cause severe, early-onset retinitis pigmentosa (RP14) and Leber congenital amaurosis (LCA15) in human patients. In this study, we discovered that the phosphoinositol-4,5-bisphosphate-binding protein Tulp1 is essential for the structural and functional organization of the periactive zone in photoreceptor synapses. Using Tulp1 knock-out mice, we found that Tulp1 is required to enrich major endocytic proteins at the periactive zone next to the synaptic ribbon. We demonstrate that Tulp1 is needed to promote endocytic vesicle retrieval at the periactive zone. Moreover, we discovered a novel interaction between Tulp1 and the synaptic ribbon protein RIBEYE. This newly discovered disease-sensitive interaction provides a molecular model for the control of endocytosis close to the synaptic ribbon. PMID:26911694

  20. Magnetostriction measurements of amorphous ribbons and thin films

    NASA Astrophysics Data System (ADS)

    Ouyang, Chien

    The theme of the present work is to measure the saturation magnetostriction constants of amorphous ribbons and thin films. The saturation magnetostriction constants of amorphous ribbons, and thin films of Cosb{39}Nisb{31}Fesb8Sisb8Bsb{14}, CoZrY, and CoZrTb have been measured either by the Small Angle Magnetization Rotation (SAMR) method or by the initial susceptibility method. The SAMR method is used for the soft materials. It is found that the amorphous Cosb{39}Nisb{31}Fesb8Sisb8Bsb{14} prepared by ion beam deposition from an alloy target shows very soft magnetic properties and has a very small negative saturation magnetostriction, lambdasb{s}, of about {-}1×10sp{-7}. Sputtered films of CoZrTb show a strong perpendicular anisotropy when the Tb content is high. We have found that the SAMR method can be applied to CoZrTb films when the Tb content is low. The saturation magnetostriction constant of a sputtered film of Cosb{78.4}Zrsb{20.8}Tbsb{0.8} is 2×10sp{-6}. When the material is not magnetically soft or has a strong perpendicular anisotropy, the initial susceptibility method is used. The saturation magnetostriction constants of amorphous Cosb{77.2}Zrsb{20.4}Tbsb{2.4} and Cosb{72.2}Zrsb{14.6}Ysb{13.2} thin films are 6×10sp{-6}, and (2{˜}6)×10sp{-7}, respectively. The two methods, the SAMR and the initial susceptibility, utilize the same measurement setup making it a very convenient technique which is applicable for a range of materials.

  1. Utilization of multiwalled boron nitride nanotubes for the reinforcement of lightweight aluminum ribbons

    PubMed Central

    2013-01-01

    Multiwalled boron nitride nanotubes (BNNTs) have very attractive mechanical and thermal properties, e.g., elasticity, tensile strength, and high resistance to oxidation, and may be considered as ideal reinforcing agents in lightweight metal matrix composites. Herein, for the first time, Al-BNNT ribbons with various BNNT contents (up to 3 wt.%) were fabricated via melt spinning in an argon atmosphere. BNNTs were randomly dispersed within a microcrystalline Al matrix under ribbon casting and led to more than doubling of room-temperature ultimate tensile strength of the composites compared to pure Al ribbons produced at the similar conditions. PMID:23279813

  2. Utilization of multiwalled boron nitride nanotubes for the reinforcement of lightweight aluminum ribbons.

    PubMed

    Yamaguchi, Maho; Pakdel, Amir; Zhi, Chunyi; Bando, Yoshio; Tang, Dai-Ming; Faerstein, Konstantin; Shtansky, Dmitry; Golberg, Dmitri

    2013-01-01

    Multiwalled boron nitride nanotubes (BNNTs) have very attractive mechanical and thermal properties, e.g., elasticity, tensile strength, and high resistance to oxidation, and may be considered as ideal reinforcing agents in lightweight metal matrix composites. Herein, for the first time, Al-BNNT ribbons with various BNNT contents (up to 3 wt.%) were fabricated via melt spinning in an argon atmosphere. BNNTs were randomly dispersed within a microcrystalline Al matrix under ribbon casting and led to more than doubling of room-temperature ultimate tensile strength of the composites compared to pure Al ribbons produced at the similar conditions. PMID:23279813

  3. Utilization of multiwalled boron nitride nanotubes for the reinforcement of lightweight aluminum ribbons.

    PubMed

    Yamaguchi, Maho; Pakdel, Amir; Zhi, Chunyi; Bando, Yoshio; Tang, Dai-Ming; Faerstein, Konstantin; Shtansky, Dmitry; Golberg, Dmitri

    2013-01-02

    Multiwalled boron nitride nanotubes (BNNTs) have very attractive mechanical and thermal properties, e.g., elasticity, tensile strength, and high resistance to oxidation, and may be considered as ideal reinforcing agents in lightweight metal matrix composites. Herein, for the first time, Al-BNNT ribbons with various BNNT contents (up to 3 wt.%) were fabricated via melt spinning in an argon atmosphere. BNNTs were randomly dispersed within a microcrystalline Al matrix under ribbon casting and led to more than doubling of room-temperature ultimate tensile strength of the composites compared to pure Al ribbons produced at the similar conditions.

  4. Electronic ferroelectricity in carbon-based systems: from reality of organic conductors to promises of polymers and graphene nano-ribbons

    NASA Astrophysics Data System (ADS)

    Kirova, Natasha; Brazovskii, Serguei

    2014-03-01

    Ferroelectricity is a rising demand in fundamental and applied solid state physics. Ferroelectrics are used in microelectronics as active gate materials, in capacitors, electro-optical-acoustic modulators, etc. There is a particular demand for plastic ferroelectrics, e.g. as a sensor for acoustic imaging in medicine and beyond, in shapeable capacitors, etc. Microscopic mechanisms of ferroelectric polarization in traditional materials are typically ionic. In this talk we discuss the electronic ferroelectrics - carbon-based materials: organic crystals, conducting polymers and graphene nano-ribbons. The motion of walls, separating domains with opposite electric polarisation, can be influenced and manipulated by terahertz and infra-red range optics.

  5. Ribbon networks for modeling navigable paths of autonomous agents in virtual environments.

    PubMed

    Willemsen, Peter; Kearney, Joseph K; Wang, Hongling

    2006-01-01

    This paper presents the Environment Description Framework (EDF) for modeling complex networks of intersecting roads and pathways in virtual environments. EDF represents information about the layout of streets and sidewalks, the rules that govern behavior on roads and walkways, and the locations of agents with respect to navigable structures. The framework serves as the substrate on which behavior programs for autonomous vehicles and pedestrians are built. Pathways are modeled as ribbons in space. The ribbon structure provides a natural coordinate frame for defining the local geometry of navigable surfaces. EDF includes a powerful runtime interface supported by robust and efficient code for locating objects on the ribbon network, for mapping between Cartesian and ribbon coordinates, and for determining behavioral constraints imposed by the environment.

  6. Light-controlled self-assembly of semiconductor nanoparticles into twisted ribbons.

    PubMed

    Srivastava, Sudhanshu; Santos, Aaron; Critchley, Kevin; Kim, Ki-Sub; Podsiadlo, Paul; Sun, Kai; Lee, Jaebeom; Xu, Chuanlai; Lilly, G Daniel; Glotzer, Sharon C; Kotov, Nicholas A

    2010-03-12

    The collective properties of nanoparticles manifest in their ability to self-organize into complex microscale structures. Slow oxidation of tellurium ions in cadmium telluride (CdTe) nanoparticles results in the assembly of 1- to 4-micrometer-long flat ribbons made of several layers of individual cadmium sulfide (CdS)/CdTe nanocrystals. Twisting of the ribbons with an equal distribution of left and right helices was induced by illumination with visible light. The pitch lengths (250 to 1500 nanometers) varied with illumination dose, and the twisting was associated with the relief of mechanical shear stress in assembled ribbons caused by photooxidation of CdS. Unusual shapes of multiparticle assemblies, such as ellipsoidal clouds, dog-bone agglomerates, and ribbon bunches, were observed as intermediate stages. Computer simulations revealed that the balance between attraction and electrostatic repulsion determines the resulting geometry and dimensionality of the nanoparticle assemblies.

  7. 77 FR 72825 - Narrow Woven Ribbons With Woven Selvedge From Taiwan: Final Results of Antidumping Duty...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-12-06

    ... International Trade Administration Narrow Woven Ribbons With Woven Selvedge From Taiwan: Final Results of Antidumping Duty Administrative Review; 2010-2011 AGENCY: Import Administration, International Trade... Administration, International Trade Administration, U.S. Department of Commerce, 14th Street and...

  8. 16 CFR 1511.6 - Ribbons, strings, cords, or other attachments.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... attachments. 1511.6 Section 1511.6 Commercial Practices CONSUMER PRODUCT SAFETY COMMISSION FEDERAL HAZARDOUS SUBSTANCES ACT REGULATIONS REQUIREMENTS FOR PACIFIERS § 1511.6 Ribbons, strings, cords, or other attachments..., yarn or similar attachments....

  9. The cytomatrix protein bassoon contributes to fast transmission at conventional and ribbon synapses.

    PubMed

    Joselevitch, Christina; Zenisek, David

    2010-11-18

    The presynaptic active zone contains a complex web of proteins involved in synaptic transmission. In this issue of Neuron, two articles show evidence that one of these proteins, Bassoon, coordinates multiple functions in a conventional and ribbon-type synapse.

  10. Microstructural analysis of the crystallization of silicon ribbons produced by the RGS process

    SciTech Connect

    Steinbach, I.; Hoefs, H.U.

    1997-12-31

    The microstructural evolution of multicrystalline silicon ribbons produced by the RGS process (Ribbon Growth on Substrate) is analyzed by numerical simulation. The crystallization model takes into account the faceted growth structure of silicon, thermal supercooling in front of the crystallization front and nucleation dependent on the thermal supercooling. The thermal conditions for the crystallization of the ribbon are taken from a macroscopic finite element simulation of the RGS process, as it is realized at Bayer AG, Germany. Different crystallization morphologies--single crystal, columnar multicrystal or dendritic--are discussed in their dependence on the process and nucleation conditions. The numerical results are compared to morphologies of silicon ribbons, grown on the pilot plant of Bayer AG, Germany.

  11. Effect of heat treatment on the bulk diffusion length of EFG ribbon silicon

    NASA Astrophysics Data System (ADS)

    Ho, C. T.; Moeller, G.; Mathias, J. D.

    1983-03-01

    The effect of thermal anneal on the bulk minority carrier diffusion length L(n) of Edge-defined Film-fed Growth ribbon silicon has been investigated. Statistical distributions of L(n) were gathered after the thermally treated ribbons were fabricated into solor cells by a cold junction formation method (ion implant and pulsed electron beam anneal). The measurements were made by using a bifurcated optical guide arrangement which was specifically designed for ribbon samples with variable surface reflectance. The experimental results indicated that, after a medium temperature (800 C) thermal anneal in a neutral ambient, the form of the L(n) distribution changed in an overall degradation in the average value. With the same thermal anneal in a gettering ambient, the distribution also altered, but with an overall improvement. The observations are discussed in terms of the interaction of metallic impurities with the local structural and chemical defects contained in the ribbons.

  12. Use of the timeout ribbon procedure during community-based instruction.

    PubMed

    Alberto, Paul; Heflin, L Juane; Andrews, Donna

    2002-04-01

    Involvement in community-based instruction can be adversely affected when students engage in behavior that interferes with participation in instruction. A multiple probe across settings design with an embedded reversal was used to investigate the effectiveness of the nonseclusionary timeout ribbon procedure for two middle-school students with moderate mental retardation in community and school settings. An athletic wristband served as the timeout ribbon, which functioned as the stimulus for the availability of reinforcement. When the student was wearing the wristband, he could earn reinforcers. On occurrence of inappropriate behavior, the wristband was removed and the student was placed in nonseclusionary timeout. Implementation of the timeout ribbon procedure resulted in target behaviors reduced to zero occurrences for both youths. This was maintained at a 2-week follow-up, even as the reinforcement schedule was thinned. The timeout ribbon procedure provided an efficient, effective, and socially valid means of supporting positive behavior across settings for these students.

  13. Using Two-Ribbon Flare Observations and MHD Simulations to Constrain Flare Properties

    NASA Astrophysics Data System (ADS)

    Kazachenko, Maria D.; Lynch, Benjamin J.; Welsch, Brian

    2016-05-01

    Flare ribbons are emission structures that are frequently observed during flares in transition-region and chromospheric radiation. These typically straddle a polarity inversion line (PIL) of the radial magnetic field at the photosphere, and move apart as the flare progresses. The ribbon flux - the amount of unsigned photospheric magnetic flux swept out by flare ribbons - is thought to be related to the amount coronal magnetic reconnection, and hence provides a key diagnostic tool for understanding the physical processes at work in flares and CMEs. Previous measurements of the magnetic flux swept out by flare ribbons required time-consuming co-alignment between magnetograph and intensity data from different instruments, explaining why those studies only analyzed, at most, a few events. The launch of the Helioseismic and Magnetic Imager (HMI) and the Atmospheric Imaging Assembly (AIA), both aboard the Solar Dynamics Observatory (SDO), presented a rare opportunity to compile a much larger sample of flare-ribbon events than could readily be assembled before. We created a dataset of 363 events of both flare ribbon positions and fluxes, as a function of time, for all C9.-class and greater flares within 45 degrees of disk center observed by SDO from June 2010 till April 2015. For this purpose, we used vector magnetograms (2D magnetic field maps) from HMI and UV images from AIA. A critical problem with using unprocessed AIA data is the existence of spurious intensities in AIA data associated with strong flare emission, most notably "blooming" (spurious smearing of saturated signal into neighboring pixels, often in streaks). To overcome this difficulty, we have developed an algorithmic procedure that effectively excludes artifacts like blooming. We present our database and compare statistical properties of flare ribbons, e.g. evolutions of ribbon reconnection fluxes, reconnection flux rates and vertical currents with the properties from MHD simulations.

  14. New concepts on the interfacial friction behavior between flat steel ribbon layers

    SciTech Connect

    Zheng, J.; Zhu, G.

    1995-11-01

    Flat steel ribbon wound pressure vessels are widely used in chemical, petrochemical, and other industries. However, no satisfactory theoretical formulae are available to estimate the additional strengthening induced by the friction between the layers. Effective normal stress in the ribbon wide direction and shear stress are new concepts for describing such strengthening effect. These concepts are analyzed further to obtain expressions for both axial and circumferential bursting pressure, and stresses of the vessel. Comparison with one set of experimental results shows excellent agreement.

  15. Recombination-active defects in silicon ribbon and polycrystalline solar cells

    NASA Technical Reports Server (NTRS)

    Cheng, L. J.

    1984-01-01

    This paper reports results from a study of recombination-active structural defects in silicon ribbon and polycrystalline solar cells using the electron beam induced current (EBIC) technique in a scanning electron microscope. It is demonstrated that low temperature EBIC measurements can reveal a range of defects that are not observable at room temperature, including slip dislocations in silicon dendritic web ribbons as well as decorated twin boundaries and dislocation complexes in cast polycrystalline silicon solar cell materials.

  16. The application of terahertz pulsed imaging in characterising density distribution of roll-compacted ribbons.

    PubMed

    Zhang, Jianyi; Pei, Chunlei; Schiano, Serena; Heaps, David; Wu, Chuan-Yu

    2016-09-01

    Roll compaction is a commonly used dry granulation process in pharmaceutical, fine chemical and agrochemical industries for materials sensitive to heat or moisture. The ribbon density distribution plays an important role in controlling properties of granules (e.g. granule size distribution, porosity and strength). Accurate characterisation of ribbon density distribution is critical in process control and quality assurance. The terahertz imaging system has a great application potential in achieving this as the terahertz radiation has the ability to penetrate most of the pharmaceutical excipients and the refractive index reflects variations in density and chemical compositions. The aim of this study is to explore whether terahertz pulse imaging is a feasible technique for quantifying ribbon density distribution. Ribbons were made of two grades of microcrystalline cellulose (MCC), Avicel PH102 and DG, using a roll compactor at various process conditions and the ribbon density variation was investigated using terahertz imaging and section methods. The density variations obtained from both methods were compared to explore the reliability and accuracy of the terahertz imaging system. An average refractive index is calculated from the refractive index values in the frequency range between 0.5 and 1.5THz. It is shown that the refractive index gradually decreases from the middle of the ribbon towards to the edges. Variations of density distribution across the width of the ribbons are also obtained using both the section method and the terahertz imaging system. It is found that the terahertz imaging results are in excellent agreement with that obtained using the section method, demonstrating that terahertz imaging is a feasible and rapid tool to characterise ribbon density distributions. PMID:26826401

  17. Reefing of Quarter Spherical Ribbon Parachutes Used in the Ares I First Stage Deceleration System

    NASA Technical Reports Server (NTRS)

    Schmidt, Jason R.; McFadden, Peter G.

    2009-01-01

    This paper introduces the parachutes that have been drop tested in support of the Ares I first stage deceleration system development. The results of the tests show that the reefing ratios for these quarter spherical ribbon parachutes provide the same reefed drag area as historical conical ribbon parachutes. Two sources are investigated for properly normalizing the parachutes relative to their suspension line length, and one is found to be superior.

  18. Means for growing ribbon crystals without subjecting the crystals to thermal shock-induced strains

    NASA Technical Reports Server (NTRS)

    Berkman, S.; Kim, K. M.; Temple, H. E. (Inventor)

    1980-01-01

    A susceptor particularly suited for use in growing a ribbon crystal employing edge defined film fed growth techniques is described. The susceptor includes a die through which a melt is drawn for forming a crystal ribbon. This is combined with a coolant delivery system characterized by a pair of jets for directing a stream of fluid coolant along a path extended to impinge on the susceptor in close proximity with the die in nonincident relation with the crystal being grown.

  19. On the way to fullerenes: Molecular dynamics study of the curling and closure of graphitic ribbons

    SciTech Connect

    Robertson, D.H.; Brenner, D.W.; White, C.T.

    1992-07-23

    The short-time behavior of isolated graphitic ribbons is simulated at high temperature using a model hydrocarbon potential. These ribbons show large instantaneous deviations from planarity that often result in the formation of open-ended hollow carbon structures representing good fullerene precursors. While confirming the importance of pentagon formation in the production of these precursors, these results also point to the central role of relatively high temperatures in these processes. 20 refs., 4 figs., 1 tab.

  20. The application of terahertz pulsed imaging in characterising density distribution of roll-compacted ribbons.

    PubMed

    Zhang, Jianyi; Pei, Chunlei; Schiano, Serena; Heaps, David; Wu, Chuan-Yu

    2016-09-01

    Roll compaction is a commonly used dry granulation process in pharmaceutical, fine chemical and agrochemical industries for materials sensitive to heat or moisture. The ribbon density distribution plays an important role in controlling properties of granules (e.g. granule size distribution, porosity and strength). Accurate characterisation of ribbon density distribution is critical in process control and quality assurance. The terahertz imaging system has a great application potential in achieving this as the terahertz radiation has the ability to penetrate most of the pharmaceutical excipients and the refractive index reflects variations in density and chemical compositions. The aim of this study is to explore whether terahertz pulse imaging is a feasible technique for quantifying ribbon density distribution. Ribbons were made of two grades of microcrystalline cellulose (MCC), Avicel PH102 and DG, using a roll compactor at various process conditions and the ribbon density variation was investigated using terahertz imaging and section methods. The density variations obtained from both methods were compared to explore the reliability and accuracy of the terahertz imaging system. An average refractive index is calculated from the refractive index values in the frequency range between 0.5 and 1.5THz. It is shown that the refractive index gradually decreases from the middle of the ribbon towards to the edges. Variations of density distribution across the width of the ribbons are also obtained using both the section method and the terahertz imaging system. It is found that the terahertz imaging results are in excellent agreement with that obtained using the section method, demonstrating that terahertz imaging is a feasible and rapid tool to characterise ribbon density distributions.

  1. Topological end states due to inhomogeneous strains in wrinkled semiconducting ribbons

    NASA Astrophysics Data System (ADS)

    Pandey, Sudhakar; Ortix, Carmine

    2016-05-01

    We show that curvature-induced inhomogeneous strain distributions in nanoscale buckled semiconducting ribbons lead to the existence of end states which are topologically protected by inversion symmetry. These end-state doublets, corresponding to the so-called Maue-Shockley states, are robust against weak disorder. By identifying and calculating the corresponding topological invariants, we further show that a buckled semiconducting ribbon undergoes topological phase transitions between trivial and nontrivial insulating phases by varying its real-space geometry.

  2. SEPARATION OF THE RIBBON FROM GLOBALLY DISTRIBUTED ENERGETIC NEUTRAL ATOM FLUX USING THE FIRST FIVE YEARS OF IBEX OBSERVATIONS

    SciTech Connect

    Schwadron, N. A.; Moebius, E.; Kucharek, H.; Lee, M. A.; Fairchild, K.; Fuselier, S. A.; McComas, D. J.; Allegrini, F.; Dayeh, M.; Livadiotis, G.; Reno, M.; Funsten, H. O.; Janzen, P.; Reisenfeld, D.; Bzowski, M.; Sokół, J. M.; Kubiak, M. A.; Christian, E. R.; DeMajistre, R.; Frisch, P.; and others

    2014-11-01

    The Interstellar Boundary Explorer (IBEX) observes the IBEX ribbon, which stretches across much of the sky observed in energetic neutral atoms (ENAs). The ribbon covers a narrow (∼20°-50°) region that is believed to be roughly perpendicular to the interstellar magnetic field. Superimposed on the IBEX ribbon is the globally distributed flux that is controlled by the processes and properties of the heliosheath. This is a second study that utilizes a previously developed technique to separate ENA emissions in the ribbon from the globally distributed flux. A transparency mask is applied over the ribbon and regions of high emissions. We then solve for the globally distributed flux using an interpolation scheme. Previously, ribbon separation techniques were applied to the first year of IBEX-Hi data at and above 0.71 keV. Here we extend the separation analysis down to 0.2 keV and to five years of IBEX data enabling first maps of the ribbon and the globally distributed flux across the full sky of ENA emissions. Our analysis shows the broadening of the ribbon peak at energies below 0.71 keV and demonstrates the apparent deformation of the ribbon in the nose and heliotail. We show global asymmetries of the heliosheath, including both deflection of the heliotail and differing widths of the lobes, in context of the direction, draping, and compression of the heliospheric magnetic field. We discuss implications of the ribbon maps for the wide array of concepts that attempt to explain the ribbon's origin. Thus, we present the five-year separation of the IBEX ribbon from the globally distributed flux in preparation for a formal IBEX data release of ribbon and globally distributed flux maps to the heliophysics community.

  3. Separation of the Ribbon from Globally Distributed Energetic Neutral Atom Flux Using the First Five Years of IBEX Observations

    NASA Astrophysics Data System (ADS)

    Schwadron, N. A.; Moebius, E.; Fuselier, S. A.; McComas, D. J.; Funsten, H. O.; Janzen, P.; Reisenfeld, D.; Kucharek, H.; Lee, M. A.; Fairchild, K.; Allegrini, F.; Dayeh, M.; Livadiotis, G.; Reno, M.; Bzowski, M.; Sokół, J. M.; Kubiak, M. A.; Christian, E. R.; DeMajistre, R.; Frisch, P.; Galli, A.; Wurz, P.; Gruntman, M.

    2014-11-01

    The Interstellar Boundary Explorer (IBEX) observes the IBEX ribbon, which stretches across much of the sky observed in energetic neutral atoms (ENAs). The ribbon covers a narrow (~20°-50°) region that is believed to be roughly perpendicular to the interstellar magnetic field. Superimposed on the IBEX ribbon is the globally distributed flux that is controlled by the processes and properties of the heliosheath. This is a second study that utilizes a previously developed technique to separate ENA emissions in the ribbon from the globally distributed flux. A transparency mask is applied over the ribbon and regions of high emissions. We then solve for the globally distributed flux using an interpolation scheme. Previously, ribbon separation techniques were applied to the first year of IBEX-Hi data at and above 0.71 keV. Here we extend the separation analysis down to 0.2 keV and to five years of IBEX data enabling first maps of the ribbon and the globally distributed flux across the full sky of ENA emissions. Our analysis shows the broadening of the ribbon peak at energies below 0.71 keV and demonstrates the apparent deformation of the ribbon in the nose and heliotail. We show global asymmetries of the heliosheath, including both deflection of the heliotail and differing widths of the lobes, in context of the direction, draping, and compression of the heliospheric magnetic field. We discuss implications of the ribbon maps for the wide array of concepts that attempt to explain the ribbon's origin. Thus, we present the five-year separation of the IBEX ribbon from the globally distributed flux in preparation for a formal IBEX data release of ribbon and globally distributed flux maps to the heliophysics community.

  4. Protein tyrosine phosphatase σ targets apical junction complex proteins in the intestine and regulates epithelial permeability.

    PubMed

    Murchie, Ryan; Guo, Cong-Hui; Persaud, Avinash; Muise, Aleixo; Rotin, Daniela

    2014-01-14

    Protein tyrosine phosphatase (PTP)σ (PTPRS) was shown previously to be associated with susceptibility to inflammatory bowel disease (IBD). PTPσ(-/-) mice exhibit an IBD-like phenotype in the intestine and show increased susceptibility to acute models of murine colitis. However, the function of PTPσ in the intestine is uncharacterized. Here, we show an intestinal epithelial barrier defect in the PTPσ(-/-) mouse, demonstrated by a decrease in transepithelial resistance and a leaky intestinal epithelium that was determined by in vivo tracer analysis. Increased tyrosine phosphorylation was observed at the plasma membrane of epithelial cells lining the crypts of the small bowel and colon of the PTPσ(-/-) mouse, suggesting the presence of PTPσ substrates in these regions. Using mass spectrometry, we identified several putative PTPσ intestinal substrates that were hyper-tyrosine-phosphorylated in the PTPσ(-/-) mice relative to wild type. Among these were proteins that form or regulate the apical junction complex, including ezrin. We show that ezrin binds to and is dephosphorylated by PTPσ in vitro, suggesting it is a direct PTPσ substrate, and identified ezrin-Y353/Y145 as important sites targeted by PTPσ. Moreover, subcellular localization of the ezrin phosphomimetic Y353E or Y145 mutants were disrupted in colonic Caco-2 cells, similar to ezrin mislocalization in the colon of PTPσ(-/-) mice following induction of colitis. Our results suggest that PTPσ is a positive regulator of intestinal epithelial barrier, which mediates its effects by modulating epithelial cell adhesion through targeting of apical junction complex-associated proteins (including ezrin), a process impaired in IBD.

  5. Apical Na+ permeability of frog skin during serosal Cl- replacement.

    PubMed

    Leibowich, S; DeLong, J; Civan, M M

    1988-05-01

    Gluconate substitution for serosal Cl- reduces the transepithelial short-circuit current (Isc) and depolarizes short-circuited frog skins. These effects could result either from inhibition of basolateral K+ conductance, or from two actions to inhibit both apical Na+ permeability (PapNa) and basolateral pump activity. We have addressed this question by studying whole-and split-thickness frog skins. Intracellular Na+ concentration (CcNa) and PapNa have been monitored by measuring the current-voltage relationship for apical Na+ entry. This analysis was conducted by applying trains of voltage pulses, with pulse durations of 16 to 32 msec. Estimates of PapNa and CcNa were not detectably dependent on pulse duration over the range 16 to 80 msec. Serosal Cl- replacement uniformly depolarized short-circuited tissues. The depolarization was associated with inhibition of Isc across each split skin, but only occasionally across the whole-thickness preparations. This difference may reflect the better ionic exchange between the bulk medium and the extracellular fluid in contact with the basolateral membranes, following removal of the underlying dermis in the split-skin preparations. PapNa was either unchanged or increased, and CcNa either unchanged or reduced after the anionic replacement. These data are incompatible with the concept that serosal Cl- replacement inhibits PapNa and Na,K-pump activity. Gluconate substitution likely reduces cell volume, triggering inhibition of the basolateral K+ channels, consistent with the data and conclusions of S.A. Lewis, A.G. Butt, M.J. Bowler, J.P. Leader and A.D.C. Macknight (J. Membrane Biol. 83:119-137, 1985) for toad bladder. The resulting depolarization reduces the electrical force favoring apical Na+ entry. The volume-conductance coupling serves to conserve volume by reducing K+ solute loss. Its molecular basis remains to be identified.

  6. SEM investigation of Er:YAG laser apical preparation

    NASA Astrophysics Data System (ADS)

    Bǎlǎbuc, Cosmin; Todea, Carmen; Locovei, Cosmin; RǎduÅ£ǎ, Aurel

    2016-03-01

    Endodontic surgery involves the incision and flap elevation, the access to the root tip, its resection, the cavity retrograde preparation and filling it with biocompatible material that provides a good seal of the apex[1]. Apicoectomy is compulsory in endodontic surgery. The final stage involves the root retropreparation and the carrying out of the retrograde obturation. In order to perform the retrograde preparation the endodontist can use various tools such as lowspeed conventional handpieces, sonic and ultrasonic equipment. The ideal depth of the preparation should be 3 mm, exceeding this value may affect the long-term success of the obturation [2]. Resection at the depth of 3 mm reduces apical ramifications by 98% and lateral root canals by 93%. The ultrasonic retropreparation has numerous advantages compared to the dental drill. Firstly, the cavity will be in the axis of the tooth which implies a minimum destruction of the root canal morphology. The preparations are precise, and the cutting pattern is perpendicular to the long axis of the root, the advantage being the reduction in the number of dentinal tubules exposed at the resected area [3]. Therefore, the retrograde filling is the procedure when an inert and non-toxic material is compacted in the apically created cavity.[4,5]. The Er:YAG laser is the most common wavelength indicated for dental hard tissue preparation. Its natural selectivity offers a significant advantage compared to the conventional hard tissue preparation [6-9].The purpose of this in vitro study was to investigate the quality of Er:YAG laser apical third preparation using Scanning Electron Microscopy (SEM), in comparison with the conventional ultrasonic method.

  7. MK571 inhibits phase-2 conjugation of flavonols by Caco-2/TC7 cells, but does not specifically inhibit their apical efflux☆

    PubMed Central

    Barrington, Robert D.; Needs, Paul W.; Williamson, Gary; Kroon, Paul A.

    2015-01-01

    MK571 is a multidrug resistance protein-2 (ABCC2, Mrp2) inhibitor and has been widely used to demonstrate the role of Mrp2 in the cellular efflux of drugs, xenobiotics and their conjugates. Numerous reports have described modulation of Caco-2 cellular efflux and transport of flavonoids in the presence of MK571. Since flavonoids are efficiently conjugated by Caco-2/TC7 cells, we investigated the effects of MK571 on the efflux of flavonoid conjugates. The flavonol aglycones kaempferol, quercetin and galangin were efficiently taken up, conjugated and effluxed by Caco-2/TC7 cells. Apically-applied MK571 caused significant reductions in both the apical and basolateral efflux of flavonol conjugates from Caco-2/TC7 monolayers. MK571 did not significantly alter the apical:basolateral efflux ratio for flavonol conjugates, however, which is not consistent with MK571 specifically inhibiting only apical Mrp2. Since MK571 decreased the total amounts of conjugates formed, and increased cellular flavonol aglycone concentrations, we explored the possibility that MK571 also inhibits phase-2 conjugation of flavonols. MK571 dose-dependently inhibited the intracellular biosynthesis of all flavonol glucuronides and sulphates by Caco-2 cells. MK571 significantly inhibited phase-2 conjugation of kaempferol by cell-free extracts of Caco-2, and production of kaempferol-4′-O-glucuronide was competitively inhibited. These data show that MK571, in addition to inhibiting MRP2, is a potential inhibitor of enterocyte phase-2 conjugation. PMID:25801004

  8. On the effect of cooling rate during melt spinning of FINEMET ribbons.

    PubMed

    Gheiratmand, Tayebeh; Hosseini, Hamid Reza Madaah; Davami, Parviz; Ostadhossein, Fatemeh; Song, Min; Gjoka, Margaritis

    2013-08-21

    The effect of quenching wheel speed on the structure and Curie temperature of Fe73.5Si13.5B9Nb3Cu1 alloy has been investigated using X-ray diffraction, differential scanning calorimetry, transition electron microscopy and a SQUID magnetometer. Ribbons were melt-spun at different wheel speeds and then were annealed to nucleate nano crystals embedded in the amorphous matrix. The results indicated that the thickness of the ribbons was inversely proportional to the wheel speed following the power law of the type t∝V(s)(-1.231). DSC and XRD results showed that at higher wheel speeds the greater potential energy triggers the formation of Fe (Si) crystallites and thus, increases the crystallinity. TEM observations confirmed the presence of an α-Fe (Si) phase with ∼11 nm crystallite size in the amorphous matrix of annealed ribbons. Special emphasis was placed on the effect of the quenching wheel speed on the Curie temperature during the measurements. To this end, the magnetization variations versus temperature were studied before and after annealing. It was found that increasing the wheel speed results in the reduction of the Curie temperature in as-spun ribbons. Moreover, the Curie temperature of the intergranular amorphous region in the annealed ribbons was at least 80 °C higher than that of corresponding amorphous phase in as-spun ribbons due to exchange interaction penetration of the adjacent Fe (Si) crystallites and relaxation processes.

  9. Fully coupled, dynamic model of a magnetostrictive amorphous ribbon and its validation

    SciTech Connect

    Bergmair, Bernhard Huber, Thomas; Bruckner, Florian; Vogler, Christoph; Fuger, Markus; Suess, Dieter

    2014-01-14

    Magnetostrictive amorphous ribbons are widely used in electronic article surveillance as well as for magnetoelastic sensors. Both applications utilize the fact that the ribbons' resonant frequency can be read out remotely by applying external magnetic AC fields. This paper proposes a magnetomechanical model to simulate the dynamics of such ribbons. The goal was to only use general material properties as input parameters, which are usually denoted in the data sheet of amorphous metals. Thus, only the magnetization curve at zero stress has to be gained via measurement. The magnetization under stress is calculated thereof. The equation of motion for a longitudinally oscillating ribbon is derived and coupled to Maxwell's equations for magnetostatics. The fully coupled initial value problem is solved simultaneously by a finite difference approach. The model is validated by comparing calculated and measured resonant frequencies of various amorphous ribbons, which turned out to be in good agreement. When slightly adapting single material properties from the data sheet, the match is almost perfect. The model is then used to calculate the local magnetic and mechanical properties inside static and vibrating ribbons. These local distributions can be directly linked to the field dependence of the resonant frequency and its higher harmonics.

  10. The Energy-Dependent Position of the IBEX Ribbon Due to the Solar Wind Structure

    NASA Astrophysics Data System (ADS)

    Swaczyna, Paweł; Bzowski, Maciej; Sokół, Justyna M.

    2016-08-01

    Observations of energetic neutral atoms (ENAs) allow for remote studies of the condition of plasma in the heliosphere and the neighboring local interstellar medium. The first results from the Interstellar Boundary Explorer (IBEX) revealed an arc-like enhancement of the ENA intensity in the sky, known as the ribbon. The ribbon was not expected from the heliospheric models prior to the launch of IBEX. One proposed explanation for the ribbon is the mechanism of secondary ENA emission. The ribbon reveals energy-dependent structure in the relative intensity along its circumference and in its position. That is, the geometric center of the ribbon varies systematically by about 10° in the energy range 0.7-4.3 keV. Here, we show by analytical modeling that this effect is a consequence of the helio-latitudinal structure of the solar wind reflected in the secondary ENAs. Along with a recently measured distance to the ribbon’s source just beyond the heliopause, our findings support the connection of the ribbon with the local interstellar magnetic field by the mechanism of secondary ENA emission. However, the magnitude of the center shift in the highest IBEX energy channel is much larger in the observations than expected from the modeling. This may be due to another, not currently recognized, process of ENA generation.

  11. The Energy-Dependent Position of the IBEX Ribbon Due to the Solar Wind Structure

    NASA Astrophysics Data System (ADS)

    Swaczyna, Paweł; Bzowski, Maciej; Sokół, Justyna M.

    2016-08-01

    Observations of energetic neutral atoms (ENAs) allow for remote studies of the condition of plasma in the heliosphere and the neighboring local interstellar medium. The first results from the Interstellar Boundary Explorer (IBEX) revealed an arc-like enhancement of the ENA intensity in the sky, known as the ribbon. The ribbon was not expected from the heliospheric models prior to the launch of IBEX. One proposed explanation for the ribbon is the mechanism of secondary ENA emission. The ribbon reveals energy-dependent structure in the relative intensity along its circumference and in its position. That is, the geometric center of the ribbon varies systematically by about 10° in the energy range 0.7–4.3 keV. Here, we show by analytical modeling that this effect is a consequence of the helio-latitudinal structure of the solar wind reflected in the secondary ENAs. Along with a recently measured distance to the ribbon’s source just beyond the heliopause, our findings support the connection of the ribbon with the local interstellar magnetic field by the mechanism of secondary ENA emission. However, the magnitude of the center shift in the highest IBEX energy channel is much larger in the observations than expected from the modeling. This may be due to another, not currently recognized, process of ENA generation.

  12. A lady with a broken heart: Apical ballooning syndrome.

    PubMed

    Rush, C; Ntsekhe, M

    2015-05-01

    Severe chest pain afteran emotional argumentresulted in the admissionof a healthy 72-year-oldwoman. She was haemodynamicallycompromised, with anelectrocardiogram (ECG) demonstratinganterior ST-depression and T-wave inversions(Fig. 1). Her 6-hour troponin T levelwas 132 ng/L. Cardiac catheterisationrevealed unobstructed coronary arteriesand a reduced left ventricular ejectionfraction (LVEF) of <35%, with basalhyperkinesia and apical segment ballooning(Figs 2 - 5). She was discharged home after3 days of supportive therapy. At 3 monthsshe was asymptomatic, with an equilibriumradionuclide angiography scan revealing anormal heart with an LVEF of 73%. PMID:26242680

  13. Capillary origami: superhydrophobic ribbon surfaces and liquid marbles

    PubMed Central

    Newton, Michael I; Shirtcliffe, Neil J; Geraldi, Nicasio R

    2011-01-01

    Summary In the wetting of a solid by a liquid it is often assumed that the substrate is rigid. However, for an elastic substrate the rigidity depends on the cube of its thickness and so reduces rapidly as the substrate becomes thinner as it approaches becoming a thin sheet. In such circumstances, it has been shown that the capillary forces caused by a contacting droplet of a liquid can shape the solid rather than the solid shaping the liquid. A substrate can be bent and folded as a (pinned) droplet evaporates or even instantaneously and spontaneously wrapped on contact with a droplet. When this effect is used to create three dimensional shapes from initially flat sheets, the effect is called capillary origami or droplet wrapping. In this work, we consider how the conditions for the spontaneous, capillary induced, folding of a thin ribbon substrate might be altered by a rigid surface structure that, for a rigid substrate, would be expected to create Cassie–Baxter and Wenzel effects. For smooth thin substrates, droplet wrapping can occur for all liquids, including those for which the Young’s law contact angle (defined by the interfacial tensions) is greater than 90° and which would therefore normally be considered relatively hydrophobic. However, consideration of the balance between bending and interfacial energies suggests that the tendency for droplet wrapping can be suppressed for some liquids by providing the flexible solid surface with a rigid topographic structure. In general, it is known that when a liquid interacts with such a structure it can either fully penetrate the structure (the Wenzel case) or it can bridge between the asperities of the structure (the Cassie–Baxter case). In this report, we show theoretically that droplet wrapping should occur with both types of solid–liquid contact. We also derive a condition for the transition between the Cassie–Baxter and Wenzel type droplet wrapping and relate it to the same transition condition known to

  14. The ribbon-cutting ceremony unveils the reactivated altitude chamber inside the O&C high bay

    NASA Technical Reports Server (NTRS)

    1999-01-01

    Cutting a red ribbon for the unveiling of a newly renovated altitude chamber are (left to right) Tommy Mack, project manager, NASA; Steve Francois, director, Space Station and Shuttle Payloads; Sterling Walker, director, Engineering Development; Roy Bridges, director, Kennedy Space Center; Jay Greene, International Space Station manager for Technical; Michael Terry, project manager, Boeing; and Terry Smith, director of Engineering, Boeing Space Coast Operations. The chamber was reactivated, after a 24-year hiatus, to perform leak tests on International Space Station pressurized modules at the launch site. Originally, two chambers were built to test the Apollo command and lunar service modules. They were last used in 1975 during the Apollo-Soyuz Test Project. After installation of new vacuum pumping equipment and controls, a new control room, and a new rotation handling fixture, the chamber again became operational in February 1999. The chamber, which is 33 feet in diameter and 50 feet tall, is constructed of stainless steel. The first module that will be tested for leaks is the U.S. Laboratory. No date has been determined for the test.

  15. Connective Auxin Transport in the Shoot Facilitates Communication between Shoot Apices

    PubMed Central

    Bennett, Tom; Hines, Geneviève; van Rongen, Martin; Sawchuk, Megan G.; Scarpella, Enrico; Ljung, Karin

    2016-01-01

    The bulk polar movement of the plant signaling molecule auxin through the stem is a long-recognized but poorly understood phenomenon. Here we show that the highly polar, high conductance polar auxin transport stream (PATS) is only part of a multimodal auxin transport network in the stem. The dynamics of auxin movement through stems are inconsistent with a single polar transport regime and instead suggest widespread low conductance, less polar auxin transport in the stem, which we term connective auxin transport (CAT). The bidirectional movement of auxin between the PATS and the surrounding tissues, mediated by CAT, can explain the complex auxin transport kinetics we observe. We show that the auxin efflux carriers PIN3, PIN4, and PIN7 are major contributors to this auxin transport connectivity and that their activity is important for communication between shoot apices in the regulation of shoot branching. We propose that the PATS provides a long-range, consolidated stream of information throughout the plant, while CAT acts locally, allowing tissues to modulate and be modulated by information in the PATS. PMID:27119525

  16. Connective Auxin Transport in the Shoot Facilitates Communication between Shoot Apices.

    PubMed

    Bennett, Tom; Hines, Geneviève; van Rongen, Martin; Waldie, Tanya; Sawchuk, Megan G; Scarpella, Enrico; Ljung, Karin; Leyser, Ottoline

    2016-04-01

    The bulk polar movement of the plant signaling molecule auxin through the stem is a long-recognized but poorly understood phenomenon. Here we show that the highly polar, high conductance polar auxin transport stream (PATS) is only part of a multimodal auxin transport network in the stem. The dynamics of auxin movement through stems are inconsistent with a single polar transport regime and instead suggest widespread low conductance, less polar auxin transport in the stem, which we term connective auxin transport (CAT). The bidirectional movement of auxin between the PATS and the surrounding tissues, mediated by CAT, can explain the complex auxin transport kinetics we observe. We show that the auxin efflux carriers PIN3, PIN4, and PIN7 are major contributors to this auxin transport connectivity and that their activity is important for communication between shoot apices in the regulation of shoot branching. We propose that the PATS provides a long-range, consolidated stream of information throughout the plant, while CAT acts locally, allowing tissues to modulate and be modulated by information in the PATS.

  17. Connective Auxin Transport in the Shoot Facilitates Communication between Shoot Apices.

    PubMed

    Bennett, Tom; Hines, Geneviève; van Rongen, Martin; Waldie, Tanya; Sawchuk, Megan G; Scarpella, Enrico; Ljung, Karin; Leyser, Ottoline

    2016-04-01

    The bulk polar movement of the plant signaling molecule auxin through the stem is a long-recognized but poorly understood phenomenon. Here we show that the highly polar, high conductance polar auxin transport stream (PATS) is only part of a multimodal auxin transport network in the stem. The dynamics of auxin movement through stems are inconsistent with a single polar transport regime and instead suggest widespread low conductance, less polar auxin transport in the stem, which we term connective auxin transport (CAT). The bidirectional movement of auxin between the PATS and the surrounding tissues, mediated by CAT, can explain the complex auxin transport kinetics we observe. We show that the auxin efflux carriers PIN3, PIN4, and PIN7 are major contributors to this auxin transport connectivity and that their activity is important for communication between shoot apices in the regulation of shoot branching. We propose that the PATS provides a long-range, consolidated stream of information throughout the plant, while CAT acts locally, allowing tissues to modulate and be modulated by information in the PATS. PMID:27119525

  18. Larval body patterning and apical organs are conserved in animal evolution

    PubMed Central

    2014-01-01

    Background Planktonic ciliated larvae are characteristic for the life cycle of marine invertebrates. Their most prominent feature is the apical organ harboring sensory cells and neurons of largely undetermined function. An elucidation of the relationships between various forms of primary larvae and apical organs is key to understanding the evolution of animal life cycles. These relationships have remained enigmatic due to the scarcity of comparative molecular data. Results To compare apical organs and larval body patterning, we have studied regionalization of the episphere, the upper hemisphere of the trochophore larva of the marine annelid Platynereis dumerilii. We examined the spatial distribution of transcription factors and of Wnt signaling components previously implicated in anterior neural development. Pharmacological activation of Wnt signaling with Gsk3β antagonists abolishes expression of apical markers, consistent with a repressive role of Wnt signaling in the specification of apical tissue. We refer to this Wnt-sensitive, six3- and foxq2-expressing part of the episphere as the ‘apical plate’. We also unraveled a molecular signature of the apical organ - devoid of six3 but expressing foxj, irx, nkx3 and hox - that is shared with other marine phyla including cnidarians. Finally, we characterized the cell types that form part of the apical organ by profiling by image registration, which allows parallel expression profiling of multiple cells. Besides the hox-expressing apical tuft cells, this revealed the presence of putative light- and mechanosensory as well as multiple peptidergic cell types that we compared to apical organ cell types of other animal phyla. Conclusions The similar formation of a six3+, foxq2+ apical plate, sensitive to Wnt activity and with an apical tuft in its six3-free center, is most parsimoniously explained by evolutionary conservation. We propose that a simple apical organ - comprising an apical tuft and a basal plexus

  19. Laser-zone growth in a Ribbon-To-Ribbon (RTR) process, silicon sheet growth development for the large area silicon sheet task of the low cost silicon solar array project

    NASA Technical Reports Server (NTRS)

    Gurtler, R. W.; Baghdadi, A.

    1976-01-01

    The objective of this research is to fully investigate the Ribbon-To-Ribbon (R-T-R) approach to silicon ribbon growth. Initial work has concentrated on modification and characterization of an existing R-T-R apparatus. In addition, equipment for auxiliary heating of the melt is being evaluated and acquired. Modification of the remote viewing system and mechanical staging are nearly complete. Characterization of the laser and other components is in progress and several auxiliary heating techniques are being investigated.

  20. Perversions driven spontaneous symmetry breaking in heterogeneous elastic ribbons

    NASA Astrophysics Data System (ADS)

    Liu, Shuangping; Yao, Zhenwei; Olvera de La Cruz, Monica

    2015-03-01

    Perversion structures in an otherwise uniform helical structure are associated with several important concepts in fundamental physics and materials science, including the spontaneous symmetry breaking and the elastic buckling. They also have strong connections with biological motifs (e.g., bacteria shapes and plant tendrils) and have potential applications in micro-muscles and soft robotics. In this work, using a three-dimensional elastomeric bi-stripe model, we investigate the properties of perversions that are independent of the specific ribbon shapes. Several intrinsic features of perversions are revealed, including the spontaneous condensation of energy as well as the distinct energy transfer modes within the perversion region. These properties of perversions associated with the storage of elastic energies can be exploited in the design of actuator devices. We thank the financial support from the U.S. Department of Commerce, National Institute of Standards and Technology, the Office of the Director of Defense Research and Engineering (DDR&E) and the Air Force Office of Scientific Research.

  1. Thermocapillary Technique for Shaping and Fabricating Optical Ribbon Waveguides

    NASA Astrophysics Data System (ADS)

    Fiedler, Kevin; Troian, Sandra

    The demand for ever increasing bandwidth and higher speed communication has ushered the next generation optoelectronic integrated circuits which directly incorporate polymer optical waveguide devices. Polymer melts are very versatile materials which have been successfully cast into planar single- and multimode waveguides using techniques such as embossing, photolithography and direct laser writing. In this talk, we describe a novel thermocapillary patterning method for fabricating waveguides in which the free surface of an ultrathin molten polymer film is exposed to a spatially inhomogeneous temperature field via thermal conduction from a nearby cooled mask pattern held in close proximity. The ensuring surface temperature distribution is purposely designed to pool liquid selectively into ribbon shapes suitable for optical waveguiding, but with rounded and not rectangular cross sectional areas due to capillary forces. The solidified waveguide patterns which result from this non-contact one step procedure exhibit ultrasmooth interfaces suitable for demanding optoelectronic applications. To complement these studies, we have also conducted finite element simulations for quantifying the influence of non-rectangular cross-sectional shapes on mode propagation and losses. Kf gratefully acknowledges support from a NASA Space Technology Research Fellowship.

  2. Growth and Detachment of 5 Helix DNA Ribbons.

    PubMed

    Bashar, Saima; Hwang, Si Un; Lee, Junwye; Amin, Rashid; Dugasani, Sreekantha Reddy; Ha, Tai Hwan; Park, Sung Ha

    2016-04-01

    We report on the concentration-dependent surface-assisted growth and time-temperature-dependent detachment of one-dimensional 5 helix DNA ribbons (5HR) on a mica substrate. The growth coverage ratio was determined by varying the concentration of the 5HR strands in a test tube, and the detachment rate of 5HR on mica was determined by varying the incubation time at a fixed temperature on a heat block. The topological changes in the concentration-dependent attachment and the time-temperature-dependent detachment for 5HR on mica were observed via atomic force microscopy. The observations indicate that 5HR started to grow on mica at ~10 nM and provided full coverage at ~50 nM. In contrast, 5HR at 65 °C started to detach from mica after 5 min and was completely removed after 10 min. The growth and detachment coverage show a sinusoidal variation in the growth ratio and a linear variation with a rate of detachment of 20%/min, respectively. The physical parameters that control the stability of the DNA structures on a given substrate should be studied to successfully integrate DNA structures for physical and chemical applications. PMID:27451775

  3. Geometry controls conformation of graphene sheets: membranes, ribbons, and scrolls.

    PubMed

    Xu, Zhiping; Buehler, Markus J

    2010-07-27

    Graphene features a two-dimensional structure, where applications from electronic building blocks to reinforced composites are emerging, enabled through the utilization of its intriguing electrical, mechanical, and thermal properties. These properties are controlled by the structural makeup of graphene, which is known to display multiple morphologies that change under thermal fluctuations and variations of its geometry. However, as of now, a systematic understanding of the relationship between the conformation of graphene and its geometry remains unknown, preventing rational bottom-up design of materials, structures, and devices. Here, we present a conformational phase diagram for rectangular graphene sheets, defined by their geometry (size and aspect ratio), boundary conditions, and the environmental conditions such as supporting substrates and chemical modifications, as well as changes in temperature. We discover the occurrence of three major structural arrangements in membrane, ribbon, and scroll phases as the aspect ratio of the graphene nanoribbon increases. A theoretical and computational analysis of governing mechanisms for each conformation is provided. PMID:20597529

  4. Shape selection and multi-stability in helical ribbons

    NASA Astrophysics Data System (ADS)

    Guo, Q.; Mehta, A. K.; Grover, M. A.; Chen, W.; Lynn, D. G.; Chen, Z.

    2014-05-01

    Helical structures, almost ubiquitous in biological systems, have inspired the design and manufacturing of helical devices with applications in nanoelecromechanical systems, morphing structures, optoelectronics, micro-robotics, and drug delivery devices. Meanwhile, multi-stable structures, represented by the Venus flytrap and slap bracelet, have attracted increasing attention due to their applications in making artificial muscles, bio-inspired robots, deployable aerospace components, and energy harvesting devices. Here we show that the mechanical anisotropy pertinent to helical deformation, together with geometric nonlinearity associated with multi-stability, can lead to a selection principle of the geometric shape and multi-stability in spontaneous helical ribbons. Simple table-top experiments were also performed to illustrate the working principle. Our work will promote understanding of spontaneous curling, twisting, wrinkling of thin objects, and their instabilities. The proposed theoretical framework can also serve as a tool for developing functional structures and devices featuring tunable, morphing geometries and smart actuation mechanisms that can be applied in a spectrum of areas.

  5. Ballistic to diffusive crossover of heat flow in graphene ribbons.

    PubMed

    Bae, Myung-Ho; Li, Zuanyi; Aksamija, Zlatan; Martin, Pierre N; Xiong, Feng; Ong, Zhun-Yong; Knezevic, Irena; Pop, Eric

    2013-01-01

    Heat flow in nanomaterials is an important area of study, with both fundamental and technological implications. However, little is known about heat flow in two-dimensional devices or interconnects with dimensions comparable to the phonon mean free path. Here we find that short, quarter-micron graphene samples reach ~35% of the ballistic thermal conductance limit up to room temperature, enabled by the relatively large phonon mean free path (~100 nm) in substrate-supported graphene. In contrast, patterning similar samples into nanoribbons leads to a diffusive heat-flow regime that is controlled by ribbon width and edge disorder. In the edge-controlled regime, the graphene nanoribbon thermal conductivity scales with width approximately as ~W(1.8)(0.3), being about 100 W m(-1) K(-1) in 65-nm-wide graphene nanoribbons, at room temperature. These results show how manipulation of two-dimensional device dimensions and edges can be used to achieve full control of their heat-carrying properties, approaching fundamentally limited upper or lower bounds. PMID:23591901

  6. Actin Filaments Regulate Exocytosis at the Hair Cell Ribbon Synapse.

    PubMed

    Guillet, Marie; Sendin, Gaston; Bourien, Jérôme; Puel, Jean-Luc; Nouvian, Régis

    2016-01-20

    Exocytosis at the inner hair cell ribbon synapse is achieved through the functional coupling between calcium channels and glutamate-filled synaptic vesicles. Using membrane capacitance measurements, we investigated whether the actin network regulates the exocytosis of synaptic vesicles at the mouse auditory hair cell. Our results suggest that actin network disruption increases exocytosis and that actin filaments may spatially organize a subfraction of synaptic vesicles with respect to the calcium channels. Significance statement: Inner hair cells (IHCs), the auditory sensory cells of the cochlea, release glutamate onto the afferent auditory nerve fibers to encode sound stimulation. To achieve this task, the IHC relies on the recruitment of glutamate-filled vesicles that can be located in close vicinity to the calcium channels or more remotely from them. The molecular determinants responsible for organizing these vesicle pools are not fully identified. Using pharmacological tools in combination with membrane capacitance measurements, we show that actin filament disruption increases exocytosis in IHCs and that actin filaments most likely position a fraction of vesicles away from the calcium channels. PMID:26791198

  7. Magnetic field driving gradient effects on the microstructure in amorphous-nanocrystalline cobalt alloy ribbons

    NASA Astrophysics Data System (ADS)

    Tang, Zhaowei; Song, Yujun; Sun, Qiangqiang; Zhang, Tao; Jiang, Yanwei

    2012-01-01

    Field effects on the early crystallization of Co-rich amorphous ribbons (Co68.15Fe4.35Si12.5B15, atomic%) performed at 450 °C for 30 minutes in an applied 10 Oe longitudinal or transverse external magnetic field are investigated by comparing with the as-spun and annealed samples in zero applied magnetic field. Results indicate that the crystallization on the surface skin of the ribbon differs from that of the middle section due to the combined effects from the field direction and the defects or stress characteristics across the ribbons. In particular, the ribbons annealed under a transverse field exhibit an extremely distinct graded microstructure across the ribbon, which features amorphous-phased skin layers (top and bottom) of about 4-5 μm thickness and a middle amorphous-nanocrystalline composite layer about 10-12 μm thick, with the nanograins of 434 +/- 99 nm dispersing in the amorphous matrix.Field effects on the early crystallization of Co-rich amorphous ribbons (Co68.15Fe4.35Si12.5B15, atomic%) performed at 450 °C for 30 minutes in an applied 10 Oe longitudinal or transverse external magnetic field are investigated by comparing with the as-spun and annealed samples in zero applied magnetic field. Results indicate that the crystallization on the surface skin of the ribbon differs from that of the middle section due to the combined effects from the field direction and the defects or stress characteristics across the ribbons. In particular, the ribbons annealed under a transverse field exhibit an extremely distinct graded microstructure across the ribbon, which features amorphous-phased skin layers (top and bottom) of about 4-5 μm thickness and a middle amorphous-nanocrystalline composite layer about 10-12 μm thick, with the nanograins of 434 +/- 99 nm dispersing in the amorphous matrix. Electronic supplementary information (ESI) available. See DOI: 10.1039/c1nr10968e

  8. THE NATURE OF FLARE RIBBONS IN CORONAL NULL-POINT TOPOLOGY

    SciTech Connect

    Masson, S.; Aulanier, G.; Pariat, E.; Schrijver, C. J.

    2009-07-20

    Flare ribbons are commonly attributed to the low-altitude impact, along the footprints of separatrices or quasi-separatrix layers (QSLs), of particle beams accelerated through magnetic reconnection. If reconnection occurs at a three-dimensional coronal magnetic null point, the footprint of the dome-shaped fan surface would map a closed circular ribbon. This paper addresses the following issues: does the entire circular ribbon brighten simultaneously, as expected because all fan field lines pass through the null point? And since the spine separatrices are singular field lines, do spine-related ribbons look like compact kernels? What can we learn from these observations about current sheet formation and magnetic reconnection in a null-point topology? The present study addresses these questions by analyzing Transition Region and Coronal Explorer and Solar and Heliospheric Observatory/Michelson Doppler Imager observations of a confined flare presenting a circular ribbon. Using a potential field extrapolation, we linked the circular shape of the ribbon with the photospheric mapping of the fan field lines originating from a coronal null point. Observations show that the flare ribbon outlining the fan lines brightens sequentially along the counterclockwise direction and that the spine-related ribbons are elongated. Using the potential field extrapolation as initial condition, we conduct a low-{beta} resistive magnetohydrodynamics simulation of this observed event. We drive the coronal evolution by line-tied diverging boundary motions, so as to emulate the observed photospheric flow pattern associated with some magnetic flux emergence. The numerical analysis allows us to explain several observed features of the confined flare. The vorticity induced in the fan by the prescribed motions causes the spines to tear apart along the fan. This leads to formation of a thin current sheet and induces null-point reconnection. We also find that the null point and its associated

  9. Effect of masticatory cycles on apical leakage of obturated teeth.

    PubMed

    Esber, S; Blum, J Y; Chazel, J C; Parahy, E

    1998-05-01

    This study investigated the effect of apical leakage due to masticatory cycles on root canal treatment. Twenty upper maxillary molars were first obturated using the warm vertical compaction technique. Four maxillary casts were then built, with each holding four of the sample molars. The molars were embedded in resin with the roots separated from the resin by means of a light silicon. The four remaining teeth served as controls and were not submitted to occlusal forces. A mechanical device to simulate masticatory cycles subjected the teeth to 0.5 x 10(6) cycles (group A), 10(6) cycles (group B), 2 x 10(6) cycles (group C), and 3 x 10(6) cycles (group D); the control was group E. The roots were placed in 2% methylene blue dye solution for 72 h and then sectioned longitudinally so that dye penetration could be measured. The mean values of dye penetration were: 3.70 +/- 0.69 mm, group A; 5.00 +/- 1.14 mm, group B; 6.00 +/- 1.01 mm, group C; 7.23 +/- 0.66 mm, group D; and 2.74 +/- 0.75 mm, group E. The value of dye penetration increased in correlation with the number of masticatory cycles. This in vitro study suggests the significant effect of masticatory loads on apical leakage. PMID:9641106

  10. Torsional deformity of apical vertebra in adolescent idiopathic scoliosis.

    PubMed

    Kotwicki, Tomasz; Napiontek, Marek

    2002-01-01

    CT scans of structural thoracic idiopathic scoliosis were reviewed in nine patients admitted to our department for scoliosis surgery. The apical vertebra scans were chosen and the following parameters were evaluated: 1) alpha angle formed by the axis of vertebra and the axis of spinous process 2) beta concave and beta convex angle between the spinous process and the left and right transverse process, respectively, 3) gamma concave and gamma convex angle between the axis of vertebra and the left and right transverse process, respectively, 4) the rotation angle to the sagittal plane. The constant deviation of the spinous process towards the convex side of the curve was observed. The vertebral body itself was distorted towards the concavity of the curve. The angle between the spinous process and the transverse process was smaller on the convex side of the curve. The torsional, intravertebral deformity of the apical vertebra was a factor acting in the direction opposite to the rotation, in the sense to reduce the deformity of the spine in idiopathic scoliosis. PMID:15456062

  11. A Comparison of Teachers' Perceptions of Principal Effectiveness in National Blue Ribbon Schools and Matched Sets of Selected Non-Blue Ribbon Schools in Pennsylvania

    ERIC Educational Resources Information Center

    Giffing, Ryan Robert

    2010-01-01

    With a focus on leadership, this study examines the leadership characteristics of principals in schools that are recognized as National Blue Ribbon Schools by the United States Department of Education. This mixed methodology study utilizes the causal comparative method to compare what teachers consider to be effective leadership characteristics of…

  12. SEPARATION OF THE INTERSTELLAR BOUNDARY EXPLORER RIBBON FROM GLOBALLY DISTRIBUTED ENERGETIC NEUTRAL ATOM FLUX

    SciTech Connect

    Schwadron, N. A.; Kucharek, H.; Moebius, E. E-mail: harald.kucharek@unh.edu

    2011-04-10

    The Interstellar Boundary Explorer (IBEX) observes a remarkable feature, the IBEX ribbon, which has energetic neutral atom (ENA) flux over a narrow region {approx}20{sup 0} wide, a factor of 2-3 higher than the more globally distributed ENA flux. Here, we separate ENA emissions in the ribbon from the distributed flux by applying a transparency mask over the ribbon and regions of high emissions, and then solve for the distributed flux using an interpolation scheme. Our analysis shows that the energy spectrum and spatial distribution of the ribbon are distinct from the surrounding globally distributed flux. The ribbon energy spectrum shows a knee between {approx}1 and 4 keV, and the angular distribution is approximately independent of energy. In contrast, the distributed flux does not show a clear knee and more closely conforms to a power law over much of the sky. Consistent with previous analyses, the slope of the power law steepens from the nose to tail, suggesting a weaker termination shock toward the tail as compared to the nose. The knee in the energy spectrum of the ribbon suggests that its source plasma population is generated via a distinct physical process. Both the slope in the energy distribution of the distributed flux and the knee in the energy distribution of the ribbon are ordered by latitude. The heliotail may be identified in maps of globally distributed flux as a broad region of low flux centered {approx}44{sup 0}W of the interstellar downwind direction, suggesting heliotail deflection by the interstellar magnetic field.

  13. ILQINS hexapeptide, identified in lysozyme left-handed helical ribbons and nanotubes, forms right-handed helical ribbons and crystals.

    PubMed

    Lara, Cecile; Reynolds, Nicholas P; Berryman, Joshua T; Xu, Anqiu; Zhang, Afang; Mezzenga, Raffaele

    2014-03-26

    Amyloid fibrils are implicated in over 20 neurodegenerative diseases. The mechanisms of fibril structuring and formation are not only of medical and biological importance but are also relevant for material science and nanotechnologies due to the unique structural and physical properties of amyloids. We previously found that hen egg white lysozyme, homologous to the disease-related human lysozyme, can form left-handed giant ribbons, closing into nanotubes. By using matrix-assisted laser desorption ionization mass spectrometry analysis, we here identify a key component of such structures: the ILQINS hexapeptide. By combining atomic force microscopy and circular dichorism, we find that this fragment, synthesized by solid-phase peptide synthesis, also forms fibrillar structures in water at pH 2. However, all fibrillar structures formed possess an unexpected right-handed twist, a rare chirality within the corpus of amyloid experimental observations. We confirm by small- and wide-angle X-ray scattering and molecular dynamics simulations that these fibrils are composed of conventional left-handed β-sheets, but that packing stresses between adjacent sheets create this twist of unusual handedness. We also show that the right-handed fibrils represent a metastable state toward β-sheet-based microcrystals formation.

  14. Type B Phosphatidylinositol-4-Phosphate 5-Kinases Mediate Arabidopsis and Nicotiana tabacum Pollen Tube Growth by Regulating Apical Pectin Secretion[W

    PubMed Central

    Ischebeck, Till; Stenzel, Irene; Heilmann, Ingo

    2008-01-01

    Phosphatidylinositol-4,5-bisphosphate [PtdIns(4,5)P2] occurs in the apical plasma membrane of growing pollen tubes. Because enzymes responsible for PtdIns(4,5)P2 production at that location are uncharacterized, functions of PtdIns(4,5)P2 in pollen tube tip growth are unresolved. Two candidate genes encoding pollen-expressed Arabidopsis thaliana phosphatidylinositol-4-phosphate 5-kinases (PI4P 5-kinases) of Arabidopsis subfamily B were identified (PIP5K4 and PIP5K5), and their recombinant proteins were characterized as being PI4P 5-kinases. Pollen of T-DNA insertion lines deficient in both PIP5K4 and PIP5K5 exhibited reduced pollen germination and defects in pollen tube elongation. Fluorescence-tagged PIP5K4 and PIP5K5 localized to an apical plasma membrane microdomain in Arabidopsis and tobacco (Nicotiana tabacum) pollen tubes, and overexpression of either PIP5K4 or PIP5K5 triggered multiple tip branching events. Further studies using the tobacco system revealed that overexpression caused massive apical pectin deposition accompanied by plasma membrane invaginations. By contrast, callose deposition and cytoskeletal structures were unaltered in the overexpressors. Morphological effects depended on PtdIns(4,5)P2 production, as an inactive enzyme variant did not produce any effects. The data indicate that excessive PtdIns(4,5)P2 production by type B PI4P 5-kinases disturbs the balance of membrane trafficking and apical pectin deposition. Polar tip growth of pollen tubes may thus be modulated by PtdIns(4,5)P2 via regulatory effects on membrane trafficking and/or apical pectin deposition. PMID:19060112

  15. Myocardial edema in Takotsubo syndrome mimicking apical hypertrophic cardiomyopathy: An insight into diagnosis by cardiovascular magnetic resonance.

    PubMed

    Izgi, Cemil; Ray, Sanjoy; Nyktari, Evangelia; Alpendurada, Francisco; Lyon, Alexander R; Rathore, Sudhir; Baksi, Arun John

    2015-01-01

    Myocardial edema is one of the characteristic features in the pathogenesis of Takotsubo syndrome. We report a middle aged man who presented with typical clinical and echocardiographic features of apical variant of Takotsubo syndrome. However, a cardiovascular magnetic resonance study performed 10 days after presentation did not show any apical 'ballooning' but revealed features of an apical hypertrophic cardiomyopathy on cine images. Tissue characterization with T2 weighted images proved severe edema as the cause of significantly increased apical wall thickness. A follow-up cardiovascular magnetic resonance study was performed 5 months later which showed that edema, wall thickening and the appearance of apical hypertrophic cardiomyopathy all resolved, confirming Takotsubo syndrome as the cause of the initial appearance. As the affected myocardium most commonly involves the apical segments, an edema induced increase in apical wall thickness may lead to appearances of an apical hypertrophic cardiomyopathy rather than apical ballooning in the acute to subacute phase of Takotsubo syndrome.

  16. Receptor-mediated transcytosis of IgA in MDCK cells is via apical recycling endosomes

    PubMed Central

    1994-01-01

    Classically, the polymeric immunoglobulin receptor and its ligand, IgA, are thought to be sorted from basolateral early endosomes into transcytotic vesicles that directly fuse with the apical plasma membrane. In contrast, we have found that in MDCK cells IgA is delivered from basolateral endosomes to apical endosomes and only then to the apical cell surface. When internalized from the basolateral surface of MDCK cells IgA is found to accumulate under the apical plasma membrane in a compartment that is accessible to two apically added membrane markers: anti-secretory component Fab fragments, and avidin internalized from the biotinylated apical pole of the cell. This accumulation occurs in the presence of apical trypsin, which prevents internalization of the ligand from the apical cell surface. Using a modification of the diaminobenzidine density-shift assay, we estimate that approximately 80% of basolaterally internalized IgA resides in the apical endosomal compartment. In addition, approximately 50% of basolaterally internalized transferrin, a basolateral recycling protein, has access to this apical endosomal compartment and is efficiently recycled back to the basolateral surface. Microtubules are required for the organization of the apical endosomal compartment and it is dispersed in nocodazole-treated cells. Moreover, this compartment is largely inaccessible to fluid-phase markers added to either pole of the cell, and therefore seems analogous to the recycling endosome described in nonpolarized cells. We propose a model in which transcytosis is not a specialized pathway that uses unique transcytotic vesicles, but rather combines portions of pathways used by non- transcytosing molecules. PMID:8138576

  17. Congenital left ventricular apical aneurysm presenting as ventricular tachycardia.

    PubMed

    Amado, José; Marques, Nuno; Candeias, Rui; Gago, Paula; de Jesus, Ilídio

    2016-10-01

    The authors present the case of a 34-year-old male patient seen in our department due to palpitations. On the electrocardiogram monomorphic ventricular tachycardia (VT) was documented, treated successfully with amiodarone. The subsequent study revealed a normal echocardiogram and an apical aneurysm of the left ventricle on magnetic resonance imaging, confirmed by computed tomography coronary angiography that also excluded coronary disease. He underwent an electrophysiological study to determine the origin of the VT and to perform catheter ablation using electroanatomical mapping. VT was induced and radiofrequency applications were performed in the left ventricular aneurysm area. VT was no longer inducible, with acute success. Despite this it was decided to implant a subcutaneous implantable cardioverter-defibrillator (ICD). Eight months after the ablation the patient was admitted again due to VT, treated by the ICD.

  18. Emergence of an Apical Epithelial Cell Surface In Vivo.

    PubMed

    Sedzinski, Jakub; Hannezo, Edouard; Tu, Fan; Biro, Maté; Wallingford, John B

    2016-01-11

    Epithelial sheets are crucial components of all metazoan animals, enclosing organs and protecting the animal from its environment. Epithelial homeostasis poses unique challenges, as addition of new cells and loss of old cells must be achieved without disrupting the fluid-tight barrier and apicobasal polarity of the epithelium. Several studies have identified cell biological mechanisms underlying extrusion of cells from epithelia, but far less is known of the converse mechanism by which new cells are added. Here, we combine molecular, pharmacological, and laser-dissection experiments with theoretical modeling to characterize forces driving emergence of an apical surface as single nascent cells are added to a vertebrate epithelium in vivo. We find that this process involves the interplay between cell-autonomous actin-generated pushing forces in the emerging cell and mechanical properties of neighboring cells. Our findings define the forces driving this cell behavior, contributing to a more comprehensive understanding of epithelial homeostasis.

  19. Cryopreservation of Galanthus elwesii Hook. apical meristems by droplet vitrification.

    PubMed

    Maslanka, M; Panis, B; Bach, A

    2013-01-01

    The aim of this study was to develop an efficient cryopreservation protocol for the geophyte giant snowdrop (Galanthus elwesii Hook.) that guarantees a high rate of survival and plant regeneration after cryopreservation. The excised apical meristems were obtained from cultures of in vitro grown bulb scales. Using a vitrification procedure and optimizing the duration of the exposure to the loading solution (LS), meristem post-rewarm survival rates higher than 90 percent were achieved. Also regrowth percentages were very high, ranging from 87 to 91 percent. After optimizing the time of exposure to the plant vitrification solution (PVS2), the survival rate was between 83 and 97 percent. During post-rewarm regeneration, good growth recovery was as high as 76 percent; however, hyperhydration and callusing were also observed. The results demonstrate that cryopreservation of Galanthus elwesii germplasm seems to be feasible.

  20. Oscillation frequencies of plant stems with apical loads.

    PubMed

    Spatz, H C; Zebrowski, J

    2001-12-01

    The frequency of free oscillations of plant stems with apical loads, as found in some cereals, is different depending on whether the stems are oriented vertically or horizontally. Neglecting the stem's own weight the differential equations describing the oscillation can be solved for both cases, although in the vertical orientation only for a limited set of conditions including constant bending stiffness along the stem. Comparison with experimental data shows that the difference between the oscillation frequencies in vertical and horizontal orientations can be attributed to the fact that in the vertical orientation the top load due to gravity induces a bending moment varying with the oscillation, while in the horizontal case this bending moment is nearly constant.

  1. Case of cheilitis granulomatosa associated with apical periodontitis.

    PubMed

    Kawakami, Tomoko; Fukai, Kazuyoshi; Sowa, Junko; Ishii, Masamitsu; Teramae, Hiroyuki; Kanazawa, Koutetsu

    2008-02-01

    The etiology of cheilitis granulomatosa is unknown. In some cases, rapid improvement and/or complete elimination of swelling of the lips after dental treatment has been reported. Here, we describe another case of improvement following dental treatment. A 57-year-old woman had developed asymptomatic swelling of the lower lip 2 months previously. Histological examination revealed non-caseous giant cell granulomas. Neither facial nerve palsy nor fissuring of the tongue was present. Patch testing for metal allergy revealed only mild irritation to zinc ion. Although topical corticosteroid ointment and oral tranilast for 4 months were ineffective, rapid and remarkable improvement of the swelling was noted soon after treatment of two lesions of apical periodontitis. Thorough examination for foci of infection is necessary when treating a patient with cheilitis granulomatosa. PMID:18271809

  2. Web-dendritic growth. [single crystal silicon ribbons for solar cells

    NASA Technical Reports Server (NTRS)

    Hilborn, R. B.; Faust, J. W., Jr.; Rhodes, C.

    1977-01-01

    The effects of various machine design parameters on the growth of web dendritic silicon ribbon were investigated. Ribbons were grown up to lengths of one meter, with widths increasing linearly up to one cm at the point of termination of growth. Thermal data were collected and evaluated for actual seeding and growth with variations in parameters affecting heat loss. It was found that for suitable growth, the mechanical system should be very rigid and stable, and the tolerances and specifications of the quartz crucibles must be far tighter than normal quartz tolerances. The widening rates of the ribbons were found to be a function of the temperature gradient rather than the temperature differences alone. A twin spacing in the seed of 3 microns to 2 microns was found to be unfavorable for growth; whereas spacing of 0.9 microns to 2 microns and 8 microns to 2 microns were favorable. Thermal modeling studies of the effects of furnace design parameters on the temperature distributions in melt and the growth of the dendritic web ribbon showed that the pull rate of the ribbon is strongly dependent on the temperature of the top thermal shield, the spacing between this shield and the melt, and the thickness of the growing web.

  3. Disconnecting the Golgi ribbon from the centrosome prevents directional cell migration and ciliogenesis

    PubMed Central

    Hurtado, Lidia; Caballero, Cristina; Gavilan, Maria P.; Cardenas, Jesus; Bornens, Michel

    2011-01-01

    Mammalian cells exhibit a frequent pericentrosomal Golgi ribbon organization. In this paper, we show that two AKAP450 N-terminal fragments, both containing the Golgi-binding GM130-interacting domain of AKAP450, dissociated endogenous AKAP450 from the Golgi and inhibited microtubule (MT) nucleation at the Golgi without interfering with centrosomal activity. These two fragments had, however, strikingly different effects on both Golgi apparatus (GA) integrity and positioning, whereas the short fragment induced GA circularization and ribbon fragmentation, the large construct that encompasses an additional p150glued/MT-binding domain induced separation of the Golgi ribbon from the centrosome. These distinct phenotypes arose by specific interference of each fragment with either Golgi-dependent or centrosome-dependent stages of Golgi assembly. We could thus demonstrate that breaking the polarity axis by perturbing GA positioning has a more dramatic effect on directional cell migration than disrupting the Golgi ribbon. Both features, however, were required for ciliogenesis. We thus identified AKAP450 as a key determinant of pericentrosomal Golgi ribbon integrity, positioning, and function in mammalian cells. PMID:21606206

  4. Application of fly ash as a catalyst for synthesis of carbon nanotube ribbons.

    PubMed

    Nath, Dilip C D; Sahajwalla, Veena

    2011-08-30

    The larger diameter-based carbon nanotube (CNT) ropes and ribbons are currently synthesized by catalytic decomposition of hydrocarbons with transition metal-based catalysts e.g., Co, Ni, Fe and Mo at 1100-1200°C, using chemical vapour deposition (CVD) and electric arc methods. We produced CNT ribbons by fly ash (FA) catalyzed pyrolysis of a composite film of poly (vinyl alcohol) (PVA) with FA at 500°C for 10min under a nitrogen flow of 2L/min. Different geometrical structures, e.g.; knotted and twisted, U- and spiral-shaped CNT ribbons were observed in the images of scanning and transmission electron microscopy. The widths of the CNT ribbons measured varied in the ranges 18-80nm. X-ray photoelectron spectroscopy analysis showed five types of carbon binding peaks, C-C/C-H (∼77%), C-O-H (∼9%), -C-O-C (∼5%), C=O (∼5%) and -O-C=O (∼3%). The ratio of intensities of G and D bands, IG/ID was 1.61 analysed by Raman Spectroscopy. CNT ribbons grown on the surface of FA have potential for the fabrication of high-strength composite materials with polymer and metal.

  5. Differential expression of the presynaptic cytomatrix protein bassoon among ribbon synapses in the mammalian retina.

    PubMed

    Brandstätter, J H; Fletcher, E L; Garner, C C; Gundelfinger, E D; Wässle, H

    1999-10-01

    Bassoon is a 420-kDa presynaptic protein which is highly concentrated at the active zones of nerve terminals of conventional synapses, both excitatory glutamatergic and inhibitory GABAergic, in rat brain. It is thought to be involved in the organization of the cytomatrix at the site of neurotransmitter release. In the retina, there are two structurally and functionally distinct types of synapses: ribbon and conventional synapses. Antibodies against bassoon were applied to sections of rat and rabbit retina. Strong punctate immunofluorescence was found in the outer and inner plexiform layers. Using pre- and post-embedding immunostaining and electron microscopy, bassoon was localized in the outer plexiform layer at ribbon synapses formed by rods and cones but was absent from basal synaptic contacts formed by cones. In the inner plexiform layer a different picture emerged. As in the brain, bassoon was found at conventional inhibitory GABAergic synapses, made by amacrine cells, but it was absent from the bipolar cell ribbon synapses. These data demonstrate differences in the molecular composition of the presynaptic apparatuses of outer and inner plexiform layer ribbon synapses. Thus, differential equipment with cytomatrix proteins may account for the functional differences observed between the two types of ribbon synapses in the retina.

  6. Fabrication and analysis of high-efficiency String Ribbon Si solar cells

    NASA Astrophysics Data System (ADS)

    Nakayashiki, Kenta; Rousaville, Brian; Yelundur, Vijay; Kim, Dong Seop; Rohatgi, Ajeet; Clark-Phelps, Robert; Hanoka, Jack I.

    2006-07-01

    This paper reports on the solar cell efficiencies of 18.3% and 16.8% (both 4 cm 2) achieved on String Ribbon Si material using photolithography-defined and screen-printed front grid contacts, respectively, reinforcing the potential of String Ribbon Si for high-performance industrial cells. Rapid co-firing of screen-printed Al on the rear and low-frequency plasma-enhanced chemical vapor deposited single-layer SiN x antireflection coating on the front in a rapid thermal processing unit was combined to enhance the as-grown minority carrier lifetime of 2-3 μs to 91 μs in processed String Ribbon Si cells. The performance of the best screen- printed String Ribbon Si cell (16.8%) was comparable to the 17.0% efficient planar float-zone (FZ) Si cell, which was processed simultaneously in the same run. However, the average performance of String Ribbon Si cells was 0.9%-1.4% lower in absolute efficiency relative to the FZ Si cells. Detailed characterization and analysis revealed that this is due to the presence of distributed electrically active defects, which could not be fully passivated, in spite of very effective defect hydrogenation during the cell processing.

  7. Scalable and Direct Growth of Graphene Micro Ribbons on Dielectric Substrates

    PubMed Central

    Wang, Debin; Tian, He; Yang, Yi; Xie, Dan; Ren, Tian-Ling; Zhang, Yuegang

    2013-01-01

    Here we report on a scalable and direct growth of graphene micro ribbons on SiO2 dielectric substrates using a low temperature chemical vapor deposition. Due to the fast annealing at low temperature and dewetting of Ni, continuous few-layer graphene micro ribbons grow directly on bare dielectric substrates through Ni assisted catalytic decomposition of hydrocarbon precursors. These high quality graphene micro ribbons exhibit low sheet resistance of ~700 Ω −2100 Ω, high on/off current ratio of ~3, and high carrier mobility of ~655 cm2V−1s−1 at room temperature, all of which have shown significant improvement over other lithography patterned CVD graphene micro ribbons. This direct approach can in principle form graphene ribbons of any arbitrary sizes and geometries. It allows for a feasible methodology towards better integration with semiconductor materials for interconnect electronics and scalable production for graphene based electronic and optoelectronic applications where the electrical gating is the key enabling factor. PMID:23443152

  8. Oral microbiota species in acute apical endodontic abscesses

    PubMed Central

    George, Noelle; Flamiatos, Erin; Kawasaki, Kellie; Kim, Namgu; Carriere, Charles; Phan, Brian; Joseph, Raphael; Strauss, Shay; Kohli, Richie; Choi, Dongseok; Craig Baumgartner, J.; Sedgley, Christine; Maier, Tom; Machida, Curtis A.

    2016-01-01

    Background and objectives Acute apical abscesses are serious endodontic diseases resulting from pulpal infection with opportunistic oral microorganisms. The objective of this study was to identify and compare the oral microbiota in patients (N=18) exhibiting acute apical abscesses, originating from the demographic region in Portland, Oregon. The study hypothesis is that abscesses obtained from this demographic region may contain unique microorganisms not identified in specimens from other regions. Design Endodontic abscesses were sampled from patients at the Oregon Health & Science University (OHSU) School of Dentistry. DNA from abscess specimens was subjected to polymerase chain reaction amplification using 16S rRNA gene-specific primers and Cy3-dCTP labeling. Labeled DNA was then applied to microbial microarrays (280 species) generated by the Human Oral Microbial Identification Microarray Laboratory (Forsyth Institute, Cambridge, MA). Results The most prevalent microorganisms, found across multiple abscess specimens, include Fusobacterium nucleatum, Parvimonas micra, Megasphaera species clone CS025, Prevotella multisaccharivorax, Atopobium rimae, and Porphyromonas endodontalis. The most abundant microorganisms, found in highest numbers within individual abscesses, include F. nucleatum, P. micra, Streptococcus Cluster III, Solobacterium moorei, Streptococcus constellatus, and Porphyromonas endodontalis. Strong bacterial associations were identified between Prevotella multisaccharivorax, Acidaminococcaceae species clone DM071, Megasphaera species clone CS025, Actinomyces species clone EP053, and Streptococcus cristatus (all with Spearman coefficients >0.9). Conclusions Cultivable and uncultivable bacterial species have been identified in endodontic abscesses obtained from the Portland, Oregon demographic region, and taxa identifications correlated well with other published studies, with the exception of Treponema and Streptococcus cristae, which were not commonly

  9. Dlg5 maintains apical polarity by promoting membrane localization of Crumbs during Drosophila oogenesis

    PubMed Central

    Luo, Jun; Wang, Heng; Kang, Di; Guo, Xuan; Wan, Ping; Wang, Dou; Chen, Jiong

    2016-01-01

    Apical-basal polarity plays critical roles in the functions of epithelial tissues. However, the mechanisms of epithelial polarity establishment and maintenance remain to be fully elucidated. Here we show that the membrane-associated guanylate kinase (MAGUK) family protein Dlg5 is required for the maintenance of apical polarity of follicle epithelium during Drosophila oogenesis. Dlg5 localizes at the apical membrane and adherens junction (AJ) of follicle epithelium in early stage egg chambers. Specifically, we demonstrate that the major function of Dlg5 is to promote apical membrane localization of Crumbs, since overexpression of Crumbs but not other major apical or AJ components could rescue epithelial polarity defects resulted from loss of Dlg5. Furthermore, we performed a structure-function analysis of Dlg5 and found that the C-terminal PDZ3 and PDZ4 domains are required for all Dlg5’s functions as well as its ability to localize to apical membrane. The N-terminal coiled-coil motif could be individually targeted to the apical membrane, while the central linker region could be targeted to AJ. Lastly, the MAGUK core domains of PDZ4-SH3-GUK could be individually targeted to apical, AJ and basolateral membranes. PMID:27211898

  10. Lulu Regulates Shroom-Induced Apical Constriction during Neural Tube Closure

    PubMed Central

    Chu, Chih-Wen; Gerstenzang, Emma; Ossipova, Olga; Sokol, Sergei Y.

    2013-01-01

    Apical constriction is an essential cell behavior during neural tube closure, but its underlying mechanisms are not fully understood. Lulu, or EPB4.1l5, is a FERM domain protein that has been implicated in apical constriction and actomyosin contractility in mouse embryos and cultured cells. Interference with the function of Lulu in Xenopus embryos by a specific antisense morpholino oligonucleotide or a carboxy-terminal fragment of Lulu impaired apical constriction during neural plate hinge formation. This effect was likely due to lack of actomyosin contractility in superficial neuroectodermal cells. By contrast, overexpression of Lulu RNA in embryonic ectoderm cells triggered ectopic apico-basal elongation and apical constriction, accompanied by the apical recruitment of F-actin. Depletion of endogenous Lulu disrupted the localization and activity of Shroom3, a PDZ-containing actin-binding protein that has also been implicated in apical constriction. Furthermore, Lulu and Shroom3 RNAs cooperated in triggering ectopic apical constriction in embryonic ectoderm. Our findings reveal that Lulu is essential for Shroom3-dependent apical constriction during vertebrate neural tube closure. PMID:24282618

  11. Arabidopsis FIM5 decorates apical actin filaments and regulates their organization in the pollen tube

    PubMed Central

    Zhang, Meng; Zhang, Ruihui; Qu, Xiaolu; Huang, Shanjin

    2016-01-01

    The actin cytoskeleton is increasingly recognized as a major regulator of pollen tube growth. Actin filaments have distinct distribution patterns and dynamic properties within different regions of the pollen tube. Apical actin filaments are highly dynamic and crucial for pollen tube growth. However, how apical actin filaments are generated and properly constructed remains an open question. Here we showed that Arabidopsis fimbrin5 (FIM5) decorates filamentous structures throughout the entire tube but is apically concentrated. Apical actin structures are disorganized to different degrees in the pollen tubes of fim5 loss-of-function mutants. Further observations suggest that apical actin structures are not constructed properly because apical actin filaments cannot be maintained at the cortex of fim5 pollen tubes. Actin filaments appeared to be more curved in fim5 pollen tubes and this was confirmed by measurements showing that the convolutedness and the rate of change of convolutedness of actin filaments was significantly increased in fim5 pollen tubes. This suggests that the rigidity of the actin filaments may be compromised in fim5 pollen tubes. Further, the apical cell wall composition is altered, implying that tip-directed vesicle trafficking events are impaired in fim5 pollen tubes. Thus, we found that FIM5 decorates apical actin filaments and regulates their organization in order to drive polarized pollen tube growth. PMID:27117336

  12. The articulatory and acoustical characteristics of the ``apical vowels'' in Beijing Mandarin

    NASA Astrophysics Data System (ADS)

    Lee, Wai-Sum

    2005-09-01

    The study investigates the articulatory and acoustical characteristics of the two so-called ``apical vowels'' in Beijing Mandarin, which have been referred to as ``apical anterior vowel'' and ``apical posterior vowel'' by the linguists in China. The ``apical posterior vowel'' has also been described as a retroflex. The results of an EMA (electromagnetic articulograph) analysis show that both vowels are apical, with the tip of tongue approaching the alveolar region for the ``anterior vowel'' and the postalveolar region for the ``posterior vowel.'' The ``posterior vowel'' is pharyngealized, as the body of tongue in particular the posterodorsal portion is pulled backward toward the pharynx. Acoustical data obtained using the CSL4400 speech analysis software show that the two ``apical vowels'' have similar F1 value. The F2 value is slightly larger for the ``posterior vowel'' than ``anterior vowel.'' Thus, the correlation between a larger F2 and the advanced tongue position is not applicable to these ``apical vowels.'' The main difference between the two ``apical vowels'' is in F3, where the value is much smaller for the ``posterior vowel'' than ``anterior vowel.'' It is assumed that the smaller F3 value for the ``posterior vowel'' is due to pharyngealization.

  13. The eternal tooth germ is formed at the apical end of continuously growing teeth.

    PubMed

    Ohshima, Hayato; Nakasone, Naohiro; Hashimoto, Emi; Sakai, Hideo; Nakakura-Ohshima, Kuniko; Harada, Hidemitsu

    2005-02-01

    Rodent incisors are known to be continuously growing teeth that are maintained by both the cell-proliferation at the apical end and the attrition of the incisal edge. This type of tooth had a special epithelial structure for the maintenance of stem cells, showing the bulbous epithelial protrusion at the apical end. The morphological transition of the epithelial-mesenchymal compartment by serial transverse sections of the apical end toward the incisal direction is likely to reflect the development of the tooth germ in the prenatal stage. Based on the present histological and previous molecular biological studies, the special structure at the apical end is obviously different from the cervical loop giving rise to Hertwig's epithelial root sheath (HERS), in human, mouse and rat molar tooth germs. Hence, we propose a new concept that the eternal tooth bud producing various dental progeny is formed at the apical end of continuously growing teeth, and a new term "apical bud" for indicating this specialized epithelial structure. Furthermore, BrdU labelling analysis suggested that the guinea-pig molars, which were continuously growing teeth, also possessed plural specific proliferative regions and "apical bud" at the apical end. PMID:15721143

  14. Localized surface plasmon resonances in graphene ribbon arrays for sensing of dielectric environment at infrared frequencies

    NASA Astrophysics Data System (ADS)

    Vasić, Borislav; Isić, Goran; Gajić, Radoš

    2013-01-01

    High confinement of surface plasmon polaritons in graphene at infrared frequencies enhances the light-matter interaction and can be used for the sensing of the environment. The considered sensing platform consists of parallel graphene ribbons which enables efficient coupling of an electromagnetic field into localized surface plasmons. Changes in the environment are then detected by measuring the resulting frequency shifts of the plasmonic resonances. It is shown that the graphene ribbons have the sensitivity comparable to the sensitivity of noble metal nanoparticles at visible frequencies, which enable sensing of only several nanometers thick films at wavelengths around ten microns. At the same time, the tunability of graphene plasmons enables a design of broadband substrates for surface enhanced infrared absorption of thin films. By changing the Fermi level in graphene, the plasmonic resonance of graphene ribbons can be adjusted to desired vibrational mode which facilitates detection of multiple absorption bands.

  15. Quasi one-dimensional lead ribbons on the Si(110) surface

    NASA Astrophysics Data System (ADS)

    Kopciuszyński, M.; Zdyb, R.; Nita, P.; Dachniewicz, M.; Dyniec, P.

    2016-06-01

    The crystallographic structure of quasi one-dimensional lead ribbons prepared on Si(110) surface is investigated with reflection high energy electron diffraction and scanning tunneling microscopy. Deposition of 2.6 monolayers of lead with subsequent annealing at 260 °C results in the formation of anisotropic metallic structures ordered over macroscopic area. The lead ribbons grow along [ 1 bar 10 ] which is a unique direction for this surface and form a single domain system contrary to pristine Si(110)-(16 × 2) or (7 × 2)-Pb reconstructions that extend along equivalent < 11 2 bar > directions. Diffraction and STM experiments reveal the 16.3 Å periodicity along the [001] direction and multilevel structure of the ribbons.

  16. Space-efficient fiber ribbon composed of reduced-cladding single-mode fibers

    NASA Astrophysics Data System (ADS)

    Chang, J. H.; Bae, S. H.; Kim, Hoon; Ouh, C. H.; Jung, C. H.; Cho, H. S.; Chung, Y. C.

    2016-09-01

    We develop a space-efficient single-mode fiber (SMF) having a cladding diameter of only 82 μm. This SMF has the depressed-cladding index profile and its mode-field diameter, cutoff wavelength, and macro bending loss are designed to be similar to those of the conventional step-index SMF. We fabricate this reduced-cladding SMF and measure its optical and mechanical characteristics. The results show that this fiber satisfies major specifications of the ITU-T G.654 recommendations. We also fabricate a fiber ribbon by using twelve of these reduced-cladding SMFs. Compared to a commercial fiber ribbon made of twelve standard SMFs having 125-μm cladding diameter, this fiber ribbon can improve the spatial efficiency by ∼75%.

  17. EBIC/TEM investigations of defects in solar silicon ribbon materials

    NASA Technical Reports Server (NTRS)

    Ast, D. G.

    1981-01-01

    Transmission electron microscopy was used to investigate the defect structure of edge defined film growth (EFG) material, web dentritic ribbons (WEB), and ribbon to ribbon recrystallized material (RTR). The most common defects in all these materials are coherent first order twin boundaries. These coherent twins can be very thin, a few atomic layers. Bundles of the twins which contain odd numbers of twins will in optical images appear as a seemingly single first twin boundary. First-order coherent twin boundaries are not electrically active, except at locations where they contain intrinsic (grain boundary) dislocations. These dislocations take up small deviations from the ideal twin relation and play the same role in twin boundaries as conventional and play the some role in twin boundaries as conventional edge and screw dislocations in small angle tilt and twist boundaries.

  18. Active zone protein CAST is a component of conventional and ribbon synapses in mouse retina.

    PubMed

    Deguchi-Tawarada, Maki; Inoue, Eiji; Takao-Rikitsu, Etsuko; Inoue, Marie; Kitajima, Isao; Ohtsuka, Toshihisa; Takai, Yoshimi

    2006-04-01

    CAST is a novel cytomatrix at the active zone (CAZ)-associated protein. In conventional brain synapses, CAST forms a large molecular complex with other CAZ proteins, including RIM, Munc13-1, Bassoon, and Piccolo. Here we investigated the distribution of CAST and its structurally related protein, ELKS, in mouse retina. Immunofluorescence analyses revealed that CAST and ELKS showed punctate signals in the outer and inner plexiform layers of the retina that were well-colocalized with those of Bassoon and RIM. Both proteins were found presynaptically at glutamatergic ribbon synapses, and at conventional GABAergic and glycinergic synapses. Moreover, immunoelectron microscopy revealed that CAST, like Bassoon and RIM, localized at the base of synaptic ribbons, whereas ELKS localized around the ribbons. Both proteins also localized in the vicinity of the presynaptic plasma membrane of conventional synapses in the retina. These results indicated that CAST and ELKS were novel components of the presynaptic apparatus of mouse retina.

  19. Properties of Ni-based amorphous ribbons consolidated by high pressure torsion

    NASA Astrophysics Data System (ADS)

    Czeppe, T.; Korznikova, G. F.; Ochin, P.; Korznikov, A. V.; Chinh, N. Q.; Sypień, A.

    2008-02-01

    Two amorphous ribbons, of compositions (Ni56Cu2)Zr18Ti16Al3Si5 and (Ni36Cu23)Zr18Ti14Al5Si4, were subdued to the similar process of cold consolidation by the high pressure torsion (HPT) method. The first ribbon, that revealed higher thermal stability of the amorphous phase, higher GFA and better mechanical properties like tensile strength, Young modulus and hardness, partially crystallized in the HPT process. The second ribbon, revealing lower Tg and Tx temperatures, tensile strength and hardness, could be consolidated preserving amorphous structure. Such result suggests that the thermal stability against crystallization was not responsible for the preservation of the amorphous phase in the cold consolidation by the HPT. It rather seemed that a proper relation of the undercooled liquid temperature range to the local temperature increase during consolidation is suggested and it was a decisive parameter.

  20. Floating Silicon Method single crystal ribbon - observations and proposed limit cycle theory

    NASA Astrophysics Data System (ADS)

    Kellerman, Peter; Kernan, Brian; Helenbrook, Brian T.; Sun, Dawei; Sinclair, Frank; Carlson, Frederick

    2016-10-01

    In the Floating Silicon Method (FSM), a single-crystal Si ribbon is grown while floating on the surface of a Si melt. In this paper, we describe the phenomenology of FSM, including the observation of approximately regularly spaced "facet lines" on the ribbon surface whose orientation aligns with (111) crystal planes. Sb demarcation experiments sectioned through the thickness of the ribbon reveal that the solid/melt interface consists of dual (111) planes and that the leading edge facet growth is saccadic in nature, rather than steady-state. To explain this behavior, we propose a heuristic solidification limit cycle theory, using a continuum level of description with anisotropic kinetics as developed by others, and generalizing the interface kinetics to include a roughening transition as well as a re-faceting mechanism that involves curvature and the Gibbs-Thomson effect.

  1. Edge plasmons and cut-off behavior of graphene nano-ribbon waveguides

    NASA Astrophysics Data System (ADS)

    Hou, Haowen; Teng, Jinghua; Palacios, Tomás; Chua, Soojin

    2016-07-01

    Graphene nano-ribbon waveguides with ultra-short plasmon wavelength are a promising candidate for nanoscale photonic applications. Graphene edge plasmons are the fundamental and lowest losses mode. Through finite element method, edge plasmons show large effective refractive index and strong field confinement on nanoscale ribbons. The edge plasmons follow a k1/2 dispersion relation. The wavelengths of the edge plasmons and center plasmons differ by a fixed factor. The width of edge plasmon is inversely proportional to wave vector of edge plasmon kedge. Edge defects associate with graphene nano-ribbon induce extra losses and reduce the propagation length. Cut-off width of edge plasmons reduces with increasing frequency. Cut-off width of center plasmon is enlarged by edge component but the enlargement effect diminishing with the increase of kedge. The results are important for the application of graphene plasmon towards ultra-compact photonic devices.

  2. Myosin 1b Regulates Amino Acid Transport by Associating Transporters with the Apical Plasma Membrane of Kidney Cells

    PubMed Central

    Komaba, Shigeru; Coluccio, Lynne M.

    2015-01-01

    Amino acid transporters (AATers) in the brush border of the apical plasma membrane (APM) of renal proximal tubule (PT) cells mediate amino acid transport (AAT). We found that the membrane-associated class I myosin myosin 1b (Myo1b) localized at the apical brush border membrane of PTs. In opossum kidney (OK) 3B/2 epithelial cells, which are derived from PTs, expressed rat Myo1b-GFP colocalized in patched microvilli with expressed mouse V5-tagged SIT1 (SIT1-V5), which mediates neutral amino acid transport in OK cells. Lentivirus-mediated delivery of opossum Myo1b-specific shRNA resulted in knockdown (kd) of Myo1b expression, less SIT1-V5 at the APM as determined by localization studies, and a decrease in neutral AAT as determined by radioactive uptake assays. Myo1b kd had no effect on Pi transport or noticeable change in microvilli structure as determined by rhodamine phalloidin staining. The studies are the first to define a physiological role for Myo1b, that of regulating renal AAT by modulating the association of AATers with the APM. PMID:26361046

  3. Amiloride‐sensitive fluid resorption in NCI‐H441 lung epithelia depends on an apical Cl− conductance

    PubMed Central

    Korbmacher, Jonas P.; Michel, Christiane; Neubauer, Daniel; Thompson, Kristin; Mizaikoff, Boris; Frick, Manfred; Dietl, Paul; Wittekindt, Oliver H.

    2014-01-01

    Abstract Proper apical airway surface hydration is essential to maintain lung function. This hydration depends on well‐balanced water resorption and secretion. The mechanisms involved in resorption are still a matter of debate, especially as the measurement of transepithelial water transport remains challenging. In this study, we combined classical short circuit current (ISC) measurements with a novel D2O dilution method to correlate ion and water transport in order to reveal basic transport mechanisms in lung epithelia. D2O dilution method enabled precise analysis of water resorption with an unprecedented resolution. NCI‐H441 cells cultured at an air–liquid interface resorbed water at a rate of 1.5 ± 0.4 μL/(h cm2). Water resorption and ISC were reduced by almost 80% in the presence of the bulk Cl− channel inhibitor 5‐nitro‐2‐(3‐phenylpropylamino)benzoic acid (NPPB) or amiloride, a specific inhibitor of epithelial sodium channel (ENaC). However, water resorption and ISC were only moderately affected by forskolin or cystic fibrosis transmembrane regulator (CFTR) channel inhibitors (CFTRinh‐172 and glybenclamide). In line with previous studies, we demonstrate that water resorption depends on ENaC, and CFTR channels have only a minor but probably modulating effect on water resorption. However, the major ENaC‐mediated water resorption depends on an apical non‐CFTR Cl− conductance. PMID:24744880

  4. Myosin 1b Regulates Amino Acid Transport by Associating Transporters with the Apical Plasma Membrane of Kidney Cells.

    PubMed

    Komaba, Shigeru; Coluccio, Lynne M

    2015-01-01

    Amino acid transporters (AATers) in the brush border of the apical plasma membrane (APM) of renal proximal tubule (PT) cells mediate amino acid transport (AAT). We found that the membrane-associated class I myosin myosin 1b (Myo1b) localized at the apical brush border membrane of PTs. In opossum kidney (OK) 3B/2 epithelial cells, which are derived from PTs, expressed rat Myo1b-GFP colocalized in patched microvilli with expressed mouse V5-tagged SIT1 (SIT1-V5), which mediates neutral amino acid transport in OK cells. Lentivirus-mediated delivery of opossum Myo1b-specific shRNA resulted in knockdown (kd) of Myo1b expression, less SIT1-V5 at the APM as determined by localization studies, and a decrease in neutral AAT as determined by radioactive uptake assays. Myo1b kd had no effect on Pi transport or noticeable change in microvilli structure as determined by rhodamine phalloidin staining. The studies are the first to define a physiological role for Myo1b, that of regulating renal AAT by modulating the association of AATers with the APM. PMID:26361046

  5. Glyphosate effects on the gene expression of the apical bud in soybean (Glycine max).

    PubMed

    Jiang, Ling-Xue; Jin, Long-Guo; Guo, Yong; Tao, Bo; Qiu, Li-Juan

    2013-08-01

    Glyphosate is a broad spectrum, non-selective herbicide which has been widely used for weed control. Much work has focused on elucidating the high accumulation of glyphosate in shoot apical bud (shoot apex). However, to date little is known about the molecular mechanisms of the sensitivity of shoot apical bud to glyphosate. Global gene expression profiling of the soybean apical bud response to glyphosate treatment was performed in this study. The results revealed that the glyphosate inhibited tryptophan biosynthesis of the shikimic acid pathway in the soybean apical bud, which was the target site of glyphosate. Glyphosate inhibited the expression of most of the target herbicide site genes. The promoter sequence analysis of key target genes revealed that light responsive elements were important regulators in glyphosate induction. These results will facilitate further studies of cloning genes and molecular mechanisms of glyphosate on soybean shoot apical bud.

  6. Apical Hypertrophic Cardiomyopathy: The Ace-of-Spades as the Disease Card

    PubMed Central

    Diaconu, Camelia C.; Dumitru, Nicoleta; Fruntelata, Ana G.; Lacau, Smarandita; Bartos, Daniela

    2015-01-01

    Apical cardiac hypertrophy (Yamaguchi syndrome) is a relatively rare form of hypertrophic cardiomyopathy. A 67-year-old woman presented with exertional angina and moderate dyspnea. Her electrocardiogram showed sinus rhythm, flattened T waves in the limb leads and a strain pattern in the V2-V6 leads. Echocardiographic examination showed that apical wall thickness of the left ventricle (LV) was 19 mm. Coronary angiography was normal, but left ventriculography revealed a spade-like shaped LV cavity, typical for apical cardiac hypertrophy. The diagnostic criteria for apical cardiac hypertrophy are: 1) asymmetric LV hypertrophy - predominantly at the apex of the ventricle; 2) LV wall thickness of 15 mm or more during diastole; and 3) apical to posterior wall thickness ratio of 1.5 or more determined by 2-dimensional echocardiography or cardiac magnetic resonance imaging. Although relatively rare, Yamaguchi syndrome must enter into the differential diagnosis of patients presenting with exertional angina pectoris. PMID:27122852

  7. Suppression of amyloid fibrils using the GroEL apical domain.

    PubMed

    Ojha, Bimlesh; Fukui, Naoya; Hongo, Kunihiro; Mizobata, Tomohiro; Kawata, Yasushi

    2016-08-04

    In E. coli cells, rescue of non-native proteins and promotion of native state structure is assisted by the chaperonin GroEL. An important key to this activity lies in the structure of the apical domain of GroEL (GroEL-AD) (residue 191-376), which recognizes and binds non-native protein molecules through hydrophobic interactions. In this study, we investigated the effects of GroEL-AD on the aggregation of various client proteins (α-Synuclein, Aβ42, and GroES) that lead to the formation of distinct protein fibrils in vitro. We found that GroEL-AD effectively inhibited the fibril formation of these three proteins when added at concentrations above a critical threshold; the specific ratio differed for each client protein, reflecting the relative affinities. The effect of GroEL-AD in all three cases was to decrease the concentration of aggregate-forming unfolded client protein or its early intermediates in solution, thereby preventing aggregation and fibrillation. Binding affinity assays revealed some differences in the binding mechanisms of GroEL-AD toward each client. Our findings suggest a possible applicability of this minimal functioning derivative of the chaperonins (the "minichaperones") as protein fibrillation modulators and detectors.

  8. Suppression of amyloid fibrils using the GroEL apical domain

    PubMed Central

    Ojha, Bimlesh; Fukui, Naoya; Hongo, Kunihiro; Mizobata, Tomohiro; Kawata, Yasushi

    2016-01-01

    In E. coli cells, rescue of non-native proteins and promotion of native state structure is assisted by the chaperonin GroEL. An important key to this activity lies in the structure of the apical domain of GroEL (GroEL-AD) (residue 191–376), which recognizes and binds non-native protein molecules through hydrophobic interactions. In this study, we investigated the effects of GroEL-AD on the aggregation of various client proteins (α-Synuclein, Aβ42, and GroES) that lead to the formation of distinct protein fibrils in vitro. We found that GroEL-AD effectively inhibited the fibril formation of these three proteins when added at concentrations above a critical threshold; the specific ratio differed for each client protein, reflecting the relative affinities. The effect of GroEL-AD in all three cases was to decrease the concentration of aggregate-forming unfolded client protein or its early intermediates in solution, thereby preventing aggregation and fibrillation. Binding affinity assays revealed some differences in the binding mechanisms of GroEL-AD toward each client. Our findings suggest a possible applicability of this minimal functioning derivative of the chaperonins (the “minichaperones”) as protein fibrillation modulators and detectors. PMID:27488469

  9. Laser-zone growth in a Ribbon-To-Ribbon (RTR) process silicon sheet growth development for the large area silicon sheet task of the low cost silicon solar array project

    NASA Technical Reports Server (NTRS)

    Gurtler, R. W.; Baghdadi, A.; Wise, J.; Ellis, R. J.

    1977-01-01

    The Ribbon-to-Ribbon (RTR) approach to silicon ribbon growth was investigated. An existing RTR apparatus, RTR#1, was upgraded to allow for 5 cm wide ribbon growth with a finite stroke length of at least 15 cm. A second RTR apparatus, RTR#2, was designed, built, and operated which utilizes continuous feed mechanisms and allows continuous growth of 7.5 cm wide ribbons. RTR#2 includes development and utilization of advanced beam scanning (or shaping), high power lasers, and thermal profile modification elements to attain maximum growth velocities (with a design goal of 18 cm/min). Materials studies, process development, and thermal analyses are also described. Residual stresses and dislocation densities were minimized through theoretical and experimental efforts towards optimization of thermal profiles. Growth runs were performed on RTR#2 and solar cells were fabricated which demonstrated efficiencies greater than 10%.

  10. Zebrafish Cacna1fa is required for cone photoreceptor function and synaptic ribbon formation

    PubMed Central

    Jia, Sujuan; Muto, Akira; Orisme, Wilda; Henson, Hannah E.; Parupalli, Chaithanyarani; Ju, Bensheng; Baier, Herwig; Taylor, Michael R.

    2014-01-01

    Mutations in the human CACNA1F gene cause incomplete congenital stationary night blindness type 2 (CSNB2), a non-progressive, clinically heterogeneous retinal disorder. However, the molecular mechanisms underlying CSNB2 have not been fully explored. Here, we describe the positional cloning of a blind zebrafish mutant, wait until dark (wud), which encodes a zebrafish homolog of human CACNA1F. We identified two zebrafish cacna1f paralogs and showed that the cacna1fa transcript (the gene mutated in wud) is expressed exclusively in the photoreceptor layer. We demonstrated that Cacna1fa localizes at the photoreceptor synapse and is absent from wud mutants. Electroretinograms revealed abnormal cone photoreceptor responses from wud mutants, indicating a defect in synaptic transmission. Although there are no obvious morphological differences, we found that wud mutants lacked synaptic ribbons and that wud is essential for the development of synaptic ribbons. We found that Ribeye, the most prominent synaptic ribbon protein, was less abundant and mislocalized in adult wud mutants. In addition to cloning wud, we identified synaptojanin 1 (synj1) as the defective gene in slacker (slak), a blind mutant with floating synaptic ribbons. We determined that Cacna1fa was expressed in slak photoreceptors and that Synj1 was initially expressed wud photoreceptors, but was absent by 5 days postfertilization. Collectively, our data demonstrate that Cacna1fa is essential for cone photoreceptor function and synaptic ribbon formation and reveal a previously unknown yet critical role of L-type voltage-dependent calcium channels in the expression and/or distribution of synaptic ribbon proteins, providing a new model to study the clinical variability in human CSNB2 patients. PMID:24419318

  11. 78 FR 41371 - Endangered and Threatened Wildlife; Determination on Whether To List the Ribbon Seal as a...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-07-10

    ... March 28, 2008, we published a 90-day finding (73 FR 16617) in which we determined that the petition... that listing of the ribbon seal was not warranted (73 FR 79822). On September 3, 2009, CBD and...) that we completed subsequent to the ribbon seal status review (75 FR 65239, October 22, 2010; 77...

  12. 76 FR 61719 - Notice of a meeting of a working group of the NIH Blue Ribbon Panel

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-10-05

    ... HUMAN SERVICES National Institutes of Health Notice of a meeting of a working group of the NIH Blue Ribbon Panel The purpose of this notice is to inform the public about a meeting of the NIH Blue Ribbon... Regency Bethesda, 7400 Wisconsin Avenue, Bethesda, MD 20814 from approximately 8:30 a.m. to 4:30 p.m....

  13. Observations of an X-shaped Ribbon Flare in the Sun and Its Three-dimensional Magnetic Reconnection

    NASA Astrophysics Data System (ADS)

    Li, Y.; Qiu, J.; Longcope, D. W.; Ding, M. D.; Yang, K.

    2016-05-01

    We report evolution of an atypical X-shaped flare ribbon that provides novel observational evidence of three-dimensional (3D) magnetic reconnection at a separator. The flare occurred on 2014 November 9. High-resolution slit-jaw 1330 Å images from the Interface Region Imaging Spectrograph reveal four chromospheric flare ribbons that converge and form an X-shape. Flare brightening in the upper chromosphere spreads along the ribbons toward the center of the “X” (the X-point), and then spreads outward in a direction more perpendicular to the ribbons. These four ribbons are located in a quadrupolar magnetic field. Reconstruction of magnetic topology in the active region suggests the presence of a separator connecting to the X-point outlined by the ribbons. The inward motion of flare ribbons in the early stage therefore indicates 3D magnetic reconnection between two sets of non-coplanar loops that approach laterally, and reconnection proceeds downward along a section of vertical current sheet. Coronal loops are also observed by the Atmospheric Imaging Assembly on board the Solar Dynamics Observatory confirming the reconnection morphology illustrated by ribbon evolution.

  14. U.S. Department of Education 2008 No Child Left Behind -- Blue Ribbon Schools Program: Statistical Summary of National Participation

    ERIC Educational Resources Information Center

    US Department of Education, 2008

    2008-01-01

    The No Child Left Behind Blue Ribbon Schools Program honors public and private K-12 schools that are either academically superior in their state or that demonstrate dramatic gains in student achievement. This document includes 2008 statistical information for public and private blue ribbon schools for 45 states. In addition to summarized totals,…

  15. Ribbon thickness dependence of the Magnetic Alloy core characteristics in the accelerating frequency region of the J-PARC synchrotrons

    NASA Astrophysics Data System (ADS)

    Nomura, M.; Shimada, T.; Tamura, F.; Yamamoto, M.; Hara, K.; Hasegawa, K.; Ohmori, C.; Takata, K.; Toda, M.; Yoshii, M.; Schnase, A.

    2014-06-01

    We employ Magnetic Alloy (MA) core loaded RF cavities for the J-PARC synchrotrons to achieve a high field gradient. The MA core has a laminated structure of 18 μm thick ribbon layers. We have been developing high shunt impedance MA cores to prepare for an increase of beam power. At low frequencies, it is well known that the eddy current loss in the ribbon is proportional to the square of the ribbon thickness. The MA core shunt impedance can be increased by using thinner ribbons. On the other hand, at high frequencies, the MA core magnetic characteristics are largely different from low frequencies. Using thinner ribbons might be effective to increase the MA core shunt impedance in the accelerating frequency region of the J-PARC synchrotrons. We reviewed the theoretical calculations of the ribbon thickness dependence of the MA core magnetic characteristics and we derived the ribbon thickness dependence from measured data. The measured data show that the MA core shunt impedance is inversely proportional to the ribbon thickness in the accelerating frequency region of the J-PARC synchrotrons, which is consistent with our calculations.

  16. Apical Ca2+-activated potassium channels in mouse parotid acinar cells.

    PubMed

    Almassy, Janos; Won, Jong Hak; Begenisich, Ted B; Yule, David I

    2012-02-01

    Ca(2+) activation of Cl and K channels is a key event underlying stimulated fluid secretion from parotid salivary glands. Cl channels are exclusively present on the apical plasma membrane (PM), whereas the localization of K channels has not been established. Mathematical models have suggested that localization of some K channels to the apical PM is optimum for fluid secretion. A combination of whole cell electrophysiology and temporally resolved digital imaging with local manipulation of intracellular [Ca(2+)] was used to investigate if Ca(2+)-activated K channels are present in the apical PM of parotid acinar cells. Initial experiments established Ca(2+)-buffering conditions that produced brief, localized increases in [Ca(2+)] after focal laser photolysis of caged Ca(2+). Conditions were used to isolate K(+) and Cl(-) conductances. Photolysis at the apical PM resulted in a robust increase in K(+) and Cl(-) currents. A localized reduction in [Ca(2+)] at the apical PM after photolysis of Diazo-2, a caged Ca(2+) chelator, resulted in a decrease in both K(+) and Cl(-) currents. The K(+) currents evoked by apical photolysis were partially blocked by both paxilline and TRAM-34, specific blockers of large-conductance "maxi-K" (BK) and intermediate K (IK), respectively, and almost abolished by incubation with both antagonists. Apical TRAM-34-sensitive K(+) currents were also observed in BK-null parotid acini. In contrast, when the [Ca(2+)] was increased at the basal or lateral PM, no increase in either K(+) or Cl(-) currents was evoked. These data provide strong evidence that K and Cl channels are similarly distributed in the apical PM. Furthermore, both IK and BK channels are present in this domain, and the density of these channels appears higher in the apical versus basolateral PM. Collectively, this study provides support for a model in which fluid secretion is optimized after expression of K channels specifically in the apical PM.

  17. Space Flight Qualification on a Multi-Fiber Ribbon Cable and Array Connector Assembly

    NASA Technical Reports Server (NTRS)

    Xiaodan, Linda Jin; Ott, Melanie N.; LaRocca, Frank V.; Baker, Ronald M.; Keeler, Bianca E. N.; Friedberg, Patricia R.; Chuska, Richard F.; Malenab, Mary C.; Macmurphy, Shawn L.

    2006-01-01

    NASA's Goddard Space Flight Center (GSFC) cooperatively with Sandia National Laboratories completed a series of tests on three separate configurations of multi-fiber ribbon cable and MTP connector assemblies. These tests simulate the aging process of components during launch and long-term space environmental exposure. The multi-fiber ribbon cable assembly was constructed of non-outgassing materials, with radiation-hardened, graded index 100/140-micron optical fiber. The results of this characterization presented here include vibration testing, thermal vacuum monitoring, and extended radiation exposure testing data.

  18. Broadband single-layered graphene absorber using periodic arrays of graphene ribbons with gradient width

    NASA Astrophysics Data System (ADS)

    Zhihong, Zhu; Chucai, Guo; Jianfa, Zhang; Ken, Liu; Xiaodong, Yuan; Shiqiao, Qin

    2015-01-01

    We demonstrate that a broadband single-layered graphene absorber can be obtained in the THz range using periodic arrays of chemically doped graphene ribbons with gradient width, supported on a dielectric film placed on a thick piece of metal. The working bandwidth of 90% absorption for this structure is as high as 1.3 THz with a central frequency of 3 THz. The broadband operation mechanism is a result of the varying continuous plasmon resonances occurring in graphene ribbons with gradient width. The operation wavelength can be expanded to the far-infrared range.

  19. Role of intracellular calcium stores in hair-cell ribbon synapse

    PubMed Central

    Castellano-Muñoz, Manuel; Ricci, Anthony J.

    2014-01-01

    Intracellular calcium stores control many neuronal functions such as excitability, gene expression, synaptic plasticity, and synaptic release. Although the existence of calcium stores along with calcium-induced calcium release (CICR) has been demonstrated in conventional and ribbon synapses, functional significance and the cellular mechanisms underlying this role remains unclear. This review summarizes recent experimental evidence identifying contribution of CICR to synaptic transmission and synaptic plasticity in the CNS, retina and inner ear. In addition, the potential role of CICR in the recruitment of vesicles to releasable pools in hair-cell ribbon synapses will be specifically discussed. PMID:24971053

  20. Multiple EFG silicon ribbon technology as the basis for manufacturing low-cost terrestrial solar cells. [Epitaxial Film Growth

    NASA Technical Reports Server (NTRS)

    Mackintosh, B.; Kalejs, J. P.; Ho, C. T.; Wald, F. V.

    1981-01-01

    Mackintosh et al. (1978) have reported on the development of a multiple ribbon furnace based on the 'edge defined film fed growth' (EFG) process for the fabrication of silicon ribbon. It has been demonstrated that this technology can meet the requirements for a silicon substrate material to be used in the manufacture of solar panels which can meet requirements regarding a selling price of $0.70/Wp when certain goals in terms of throughput and quality are achieved. These goals for the multiple ribbon technology using 10 cm wide ribbon require simultaneous growth of 12 ribbons by one operator at average speeds of 4 to 4.5 cm/min, and 13% efficient solar cells. A description is presented of the progress made toward achieving these goals. It is concluded that the required performance levels have now been achieved. The separate aspects of technology must now be integrated into a single prototype furnace.

  1. Large Area Silicon Sheet by EFG. [quality control and productivity of edge-defined film-fed growth of ribbons

    NASA Technical Reports Server (NTRS)

    1979-01-01

    Influences on ribbon quality which might be caused by various materials of construction which are used in the growth furnace were assessed. At the present level of ribbon quality, which has produced 8.5% to 9.5% efficient solar cells, no particular influence of any furnace part was detected. The experiments led to the suspicion that the general environment and the somewhat unoptimized materials handling procedures might be responsible for the current variations in ribbon quality and that, therefore, continuous work with this furnace under rather more stringent environmental conditions and operating procedures could perhaps improve materials quality to some extent. The work on the multiple furnace was continued with two multiple growth runs being performed. In these runs, the melt replenishment system performed poorly and extensive modifications to it were designed to make reliable melt feeding for five ribbon growth possible. Additional characterization techniques for wide ribbons, stress measurements, and growth dynamics experiments are reported.

  2. Overexpression of Guanylate Cyclase Activating Protein 2 in Rod Photoreceptors In Vivo Leads to Morphological Changes at the Synaptic Ribbon

    PubMed Central

    López-Begines, Santiago; Fernández-Sánchez, Laura; Cuenca, Nicolás; Llorens, Jordi; de la Villa, Pedro; Méndez, Ana

    2012-01-01

    Guanylate cyclase activating proteins are EF-hand containing proteins that confer calcium sensitivity to retinal guanylate cyclase at the outer segment discs of photoreceptor cells. By making the rate of cGMP synthesis dependent on the free intracellular calcium levels set by illumination, GCAPs play a fundamental role in the recovery of the light response and light adaptation. The main isoforms GCAP1 and GCAP2 also localize to the synaptic terminal, where their function is not known. Based on the reported interaction of GCAP2 with Ribeye, the major component of synaptic ribbons, it was proposed that GCAP2 could mediate the synaptic ribbon dynamic changes that happen in response to light. We here present a thorough ultrastructural analysis of rod synaptic terminals in loss-of-function (GCAP1/GCAP2 double knockout) and gain-of-function (transgenic overexpression) mouse models of GCAP2. Rod synaptic ribbons in GCAPs−/− mice did not differ from wildtype ribbons when mice were raised in constant darkness, indicating that GCAPs are not required for ribbon early assembly or maturation. Transgenic overexpression of GCAP2 in rods led to a shortening of synaptic ribbons, and to a higher than normal percentage of club-shaped and spherical ribbon morphologies. Restoration of GCAP2 expression in the GCAPs−/− background (GCAP2 expression in the absence of endogenous GCAP1) had the striking result of shortening ribbon length to a much higher degree than overexpression of GCAP2 in the wildtype background, as well as reducing the thickness of the outer plexiform layer without affecting the number of rod photoreceptor cells. These results indicate that preservation of the GCAP1 to GCAP2 relative levels is relevant for maintaining the integrity of the synaptic terminal. Our demonstration of GCAP2 immunolocalization at synaptic ribbons at the ultrastructural level would support a role of GCAPs at mediating the effect of light on morphological remodeling changes of synaptic

  3. The use of regenerative techniques in apical surgery: A literature review

    PubMed Central

    von Arx, Thomas; AlSaeed, Mohammed

    2011-01-01

    Apical surgery has become a standard of care for tooth maintenance if conventional endodontic retreatment is not possible or associated with risks. However, in certain situations, the outcome of apical surgery may be compromised due to the extent or location of the periapical or periradicular lesions. The present review article including clinical and experimental studies reports and discusses the outcome of regenerative techniques (RT) in conjunction with apical surgery, with regard to the type of periradicular lesions: Apical lesions The majority of studies have shown no benefit for healing in test sites treated with RT compared to control sites treated without RT. The use of a radio-opaque bone filler/substitute may even compound the radiographic interpretation of periapical healing. Currently, the use of RT for lesions <10 mm limited to the apical area is not warranted. Through-and-through lesions All reviewed studies demonstrated a better outcome for test sites with RT compared to the control sites without RT; hence the use of RT for treatment of tunnel lesions in apical surgery is recommended. Apico-marginal lesions All clinical studies assessed cohorts without controls, and, therefore, no firm conclusion about the benefit of RT for treatment of apico-marginal lesions in conjunction with apical surgery can be drawn. However, the experimental animal studies have shown that healing of teeth with apico-marginal lesions appears to benefit from RT. PMID:24151420

  4. The fast-recycling receptor Megalin defines the apical recycling pathway of epithelial cells.

    PubMed

    Perez Bay, Andres E; Schreiner, Ryan; Benedicto, Ignacio; Paz Marzolo, Maria; Banfelder, Jason; Weinstein, Alan M; Rodriguez-Boulan, Enrique J

    2016-01-01

    The basolateral recycling and transcytotic pathways of epithelial cells were previously defined using markers such as transferrin (TfR) and polymeric IgA (pIgR) receptors. In contrast, our knowledge of the apical recycling pathway remains fragmentary. Here we utilize quantitative live-imaging and mathematical modelling to outline the recycling pathway of Megalin (LRP-2), an apical receptor with key developmental and renal functions, in MDCK cells. We show that, like TfR, Megalin is a long-lived and fast-recycling receptor. Megalin enters polarized MDCK cells through segregated apical sorting endosomes and subsequently intersects the TfR and pIgR pathways at a perinuclear Rab11-negative compartment termed common recycling endosomes (CRE). Whereas TfR recycles to the basolateral membrane from CRE, Megalin, like pIgR, traffics to subapical Rab11-positive apical recycling endosomes (ARE) and reaches the apical membrane in a microtubule- and Rab11-dependent manner. Hence, Megalin defines the apical recycling pathway of epithelia, with CRE as its apical sorting station.

  5. The fast-recycling receptor Megalin defines the apical recycling pathway of epithelial cells.

    PubMed

    Perez Bay, Andres E; Schreiner, Ryan; Benedicto, Ignacio; Paz Marzolo, Maria; Banfelder, Jason; Weinstein, Alan M; Rodriguez-Boulan, Enrique J

    2016-01-01

    The basolateral recycling and transcytotic pathways of epithelial cells were previously defined using markers such as transferrin (TfR) and polymeric IgA (pIgR) receptors. In contrast, our knowledge of the apical recycling pathway remains fragmentary. Here we utilize quantitative live-imaging and mathematical modelling to outline the recycling pathway of Megalin (LRP-2), an apical receptor with key developmental and renal functions, in MDCK cells. We show that, like TfR, Megalin is a long-lived and fast-recycling receptor. Megalin enters polarized MDCK cells through segregated apical sorting endosomes and subsequently intersects the TfR and pIgR pathways at a perinuclear Rab11-negative compartment termed common recycling endosomes (CRE). Whereas TfR recycles to the basolateral membrane from CRE, Megalin, like pIgR, traffics to subapical Rab11-positive apical recycling endosomes (ARE) and reaches the apical membrane in a microtubule- and Rab11-dependent manner. Hence, Megalin defines the apical recycling pathway of epithelia, with CRE as its apical sorting station. PMID:27180806

  6. Apical constriction initiates new bud formation during monopodial branching of the embryonic chicken lung.

    PubMed

    Kim, Hye Young; Varner, Victor D; Nelson, Celeste M

    2013-08-01

    Branching morphogenesis sculpts the airway epithelium of the lung into a tree-like structure to conduct air and promote gas exchange after birth. In the avian lung, a series of buds emerges from the dorsal surface of the primary bronchus via monopodial branching to form the conducting airways; anatomically, these buds are similar to those formed by domain branching in the mammalian lung. Here, we show that monopodial branching is initiated by apical constriction of the airway epithelium, and not by differential cell proliferation, using computational modeling and quantitative imaging of embryonic chicken lung explants. Both filamentous actin and phosphorylated myosin light chain were enriched at the apical surface of the airway epithelium during monopodial branching. Consistently, inhibiting actomyosin contractility prevented apical constriction and blocked branch initiation. Although cell proliferation was enhanced along the dorsal and ventral aspects of the primary bronchus, especially before branch formation, inhibiting proliferation had no effect on the initiation of branches. To test whether the physical forces from apical constriction alone are sufficient to drive the formation of new buds, we constructed a nonlinear, three-dimensional finite element model of the airway epithelium and used it to simulate apical constriction and proliferation in the primary bronchus. Our results suggest that, consistent with the experimental results, apical constriction is sufficient to drive the early stages of monopodial branching whereas cell proliferation is dispensable. We propose that initial folding of the airway epithelium is driven primarily by apical constriction during monopodial branching of the avian lung.

  7. The fast-recycling receptor Megalin defines the apical recycling pathway of epithelial cells

    PubMed Central

    Perez Bay, Andres E.; Schreiner, Ryan; Benedicto, Ignacio; Paz Marzolo, Maria; Banfelder, Jason; Weinstein, Alan M.; Rodriguez-Boulan, Enrique J.

    2016-01-01

    The basolateral recycling and transcytotic pathways of epithelial cells were previously defined using markers such as transferrin (TfR) and polymeric IgA (pIgR) receptors. In contrast, our knowledge of the apical recycling pathway remains fragmentary. Here we utilize quantitative live-imaging and mathematical modelling to outline the recycling pathway of Megalin (LRP-2), an apical receptor with key developmental and renal functions, in MDCK cells. We show that, like TfR, Megalin is a long-lived and fast-recycling receptor. Megalin enters polarized MDCK cells through segregated apical sorting endosomes and subsequently intersects the TfR and pIgR pathways at a perinuclear Rab11-negative compartment termed common recycling endosomes (CRE). Whereas TfR recycles to the basolateral membrane from CRE, Megalin, like pIgR, traffics to subapical Rab11-positive apical recycling endosomes (ARE) and reaches the apical membrane in a microtubule- and Rab11-dependent manner. Hence, Megalin defines the apical recycling pathway of epithelia, with CRE as its apical sorting station. PMID:27180806

  8. Annexin XIIIb Associates with Lipid Microdomains to Function in Apical Delivery

    PubMed Central

    Lafont, Frank; Lecat, Sandra; Verkade, Paul; Simons, Kai

    1998-01-01

    A member of the annexin XIII sub-family, annexin XIIIb, has been implicated in the apical exocytosis of epithelial kidney cells. Annexins are phospholipid-binding proteins that have been suggested to be involved in membrane trafficking events although their actual physiological function remains open. Unlike the other annexins, annexin XIIIs are myristoylated. Here, we show by immunoelectron microscopy that annexin XIIIb is localized to the trans-Golgi network (TGN), vesicular carriers and the apical cell surface. Polarized apical sorting involves clustering of apical proteins into dynamic sphingolipid-cholesterol rafts. We now provide evidence for the raft association of annexin XIIIb. Using in vitro assays and either myristoylated or unmyristoylated recombinant annexin XIIIb, we demonstrate that annexin XIIIb in its native myristoylated form stimulates specifically apical transport whereas the unmyristoylated form inhibits this route. Moreover, we show that formation of apical carriers from the TGN is inhibited by an anti-annexin XIIIb antibody whereas it is stimulated by myristoylated recombinant annexin XIIIb. These results suggest that annexin XIIIb directly participates in apical delivery. PMID:9744874

  9. Apical constriction initiates new bud formation during monopodial branching of the embryonic chicken lung

    PubMed Central

    Kim, Hye Young; Varner, Victor D.; Nelson, Celeste M.

    2013-01-01

    Branching morphogenesis sculpts the airway epithelium of the lung into a tree-like structure to conduct air and promote gas exchange after birth. In the avian lung, a series of buds emerges from the dorsal surface of the primary bronchus via monopodial branching to form the conducting airways; anatomically, these buds are similar to those formed by domain branching in the mammalian lung. Here, we show that monopodial branching is initiated by apical constriction of the airway epithelium, and not by differential cell proliferation, using computational modeling and quantitative imaging of embryonic chicken lung explants. Both filamentous actin and phosphorylated myosin light chain were enriched at the apical surface of the airway epithelium during monopodial branching. Consistently, inhibiting actomyosin contractility prevented apical constriction and blocked branch initiation. Although cell proliferation was enhanced along the dorsal and ventral aspects of the primary bronchus, especially before branch formation, inhibiting proliferation had no effect on the initiation of branches. To test whether the physical forces from apical constriction alone are sufficient to drive the formation of new buds, we constructed a nonlinear, three-dimensional finite element model of the airway epithelium and used it to simulate apical constriction and proliferation in the primary bronchus. Our results suggest that, consistent with the experimental results, apical constriction is sufficient to drive the early stages of monopodial branching whereas cell proliferation is dispensable. We propose that initial folding of the airway epithelium is driven primarily by apical constriction during monopodial branching of the avian lung. PMID:23824575

  10. Profilin Regulates Apical Actin Polymerization to Control Polarized Pollen Tube Growth.

    PubMed

    Liu, Xiaonan; Qu, Xiaolu; Jiang, Yuxiang; Chang, Ming; Zhang, Ruihui; Wu, Youjun; Fu, Ying; Huang, Shanjin

    2015-12-01

    Pollen tube growth is an essential step during flowering plant reproduction, whose growth depends on a population of dynamic apical actin filaments. Apical actin filaments were thought to be involved in the regulation of vesicle fusion and targeting in the pollen tube. However, the molecular mechanisms that regulate the construction of apical actin structures in the pollen tube remain largely unclear. Here, we identify profilin as an important player in the regulation of actin polymerization at the apical membrane in the pollen tube. Downregulation of profilin decreased the amount of filamentous actin and induced disorganization of apical actin filaments, and reduced tip-directed vesicle transport and accumulation in the pollen tube. Direct visualization of actin dynamics revealed that the elongation of actin filaments originating at the apical membrane decreased in profilin mutant pollen tubes. Mutant profilin that is defective in binding poly-L-proline only partially rescues the actin polymerization defect in profilin mutant pollen tubes, although it fully rescues the actin turnover phenotype. We propose that profilin controls the construction of actin structures at the pollen tube tip, presumably by favoring formin-mediated actin polymerization at the apical membrane.

  11. Emergence of an Apical Epithelial Cell Surface In Vivo.

    PubMed

    Sedzinski, Jakub; Hannezo, Edouard; Tu, Fan; Biro, Maté; Wallingford, John B

    2016-01-11

    Epithelial sheets are crucial components of all metazoan animals, enclosing organs and protecting the animal from its environment. Epithelial homeostasis poses unique challenges, as addition of new cells and loss of old cells must be achieved without disrupting the fluid-tight barrier and apicobasal polarity of the epithelium. Several studies have identified cell biological mechanisms underlying extrusion of cells from epithelia, but far less is known of the converse mechanism by which new cells are added. Here, we combine molecular, pharmacological, and laser-dissection experiments with theoretical modeling to characterize forces driving emergence of an apical surface as single nascent cells are added to a vertebrate epithelium in vivo. We find that this process involves the interplay between cell-autonomous actin-generated pushing forces in the emerging cell and mechanical properties of neighboring cells. Our findings define the forces driving this cell behavior, contributing to a more comprehensive understanding of epithelial homeostasis. PMID:26766441

  12. Sulfate transport in apical membrane vesicles isolated from tracheal epithelium

    SciTech Connect

    Elgavish, A.; DiBona, D.R.; Norton, P.; Meezan, E.

    1987-09-01

    Sulfate uptake in apical membrane vesicles isolated from bovine tracheal epithelium is shown to occur into an osmotically sensitive intravesicular space, via a carrier-mediated system. This conclusion is based on three lines of evidence: 1) saturation kinetics: 2) substrate specificity; and 3) inhibition by the anion transport inhibitors SITS and DIDS. The affinity of the transport system is highest in low ionic strength media and decreases in the presence of gluconate. Chloride appears to cis-inhibit sulfate uptake and to trans-stimulate sulfate efflux. Cis-inhibition and trans-stimulation studies with a variety of anions indicate that this exchange system may be shared by HCO/sub 3//sup -/, S/sub 2/O/sub 3//sup 2 -/, SeO/sub 4//sup 2 -/, and MoO/sub 4//sup 2 -/ but not by H/sub 2/PO/sub 4//sup -/ or HAsO/sub 4//sup 2/. Studies indicate that protons may play two distinct roles in sulfate transport in this system. These studies show that the carrier-mediated system can function in the absence of chloride. The overshoot observed in the presence of a proton gradient indicates that under those conditions the mechanism of transport may be a SO/sub 4//sup 2 -/-OH/sup -/ exchange.

  13. Structural development and energy dissipation in simulated silicon apices.

    PubMed

    Jarvis, Samuel Paul; Kantorovich, Lev; Moriarty, Philip

    2013-12-20

    In this paper we examine the stability of silicon tip apices by using density functional theory (DFT) calculations. We find that some tip structures - modelled as small, simple clusters - show variations in stability during manipulation dependent on their orientation with respect to the sample surface. Moreover, we observe that unstable structures can be revealed by a characteristic hysteretic behaviour present in the F(z) curves that were calculated with DFT, which corresponds to a tip-induced dissipation of hundreds of millielectronvolts resulting from reversible structural deformations. Additionally, in order to model the structural evolution of the tip apex within a low temperature NC-AFM experiment, we simulated a repeated tip-surface indentation until the tip structure converged to a stable termination and the characteristic hysteretic behaviour was no longer observed. Our calculations suggest that varying just a single rotational degree of freedom can have as measurable an impact on the tip-surface interaction as a completely different tip structure.

  14. Takotsubo syndrome (or apical ballooning syndrome) secondary to Zolmitriptan.

    PubMed

    Garg, Jalaj; Aronow, Wilbert S; Devabhaktuni, Srikala; Ahmad, Hasan

    2015-01-01

    Takotsubo syndrome (TS), also known as broken heart syndrome, is characterized by left ventricle apical ballooning with elevated cardiac biomarkers and electrocardiographic changes suggestive of an acute coronary syndrome (ie, ST-segment elevation, T wave inversions, and pathologic Q waves). We report a case of 54-year-old woman with medical history of mitral valve prolapse and migraines, who was admitted to the hospital for substernal chest pain and electrocardiogram demonstrated 1/2 mm ST-segment elevation in leads II, III, aVF, V5, and V6 and positive troponin I. Emergent coronary angiogram revealed normal coronary arteries with moderately reduced left ventricular ejection fraction with wall motion abnormalities consistent with TS. Detailed history obtained retrospectively revealed that the patient took zolmitriptan sparingly only when she had migraines. But before this event, she was taking zolmitriptan 2-3 times daily for several days because of a persistent migraine headache. She otherwise reported that she is quite active, rides horses, and does show jumping without any limitations in her physical activity. There was no evidence of any recent stress or status migrainosus. Extensive literature search revealed multiple cases of coronary artery vasospasm secondary to zolmitriptan, but none of the cases were associated with TS. PMID:24100257

  15. Pathological studies of cheek teeth apical infections in the horse: 5. Aetiopathological findings in 57 apically infected maxillary cheek teeth and histological and ultrastructural findings.

    PubMed

    Dacre, Ian; Kempson, S; Dixon, P M

    2008-12-01

    Examination of 57 apically infected maxillary cheek teeth (CT) showed one or more viable pulps and minimal apical calcified tissue changes present in recently infected CT. With chronic infections, pulps were necrotic or absent, pulp horns were filled with food if occlusal pulpar exposure was present, and gross caries of dentine was occasionally present. With chronic infections, the apical changes varied from gross destructive changes in some teeth, to extensive proliferative calcified apical changes in others. Infundibular caries was believed to cause apical infection in just 16% of infected (maxillary) CT, anachoretic infection in 51%, periodontal spread in 12%, fractures and fissures in 9%, dysplasia in 5% and miscellaneous or undiagnosed causes in 7%. Histology showed viable pulp and absence of circumpulpar dentinal changes in some recently infected CT, but chronically infected teeth had loss of predentine and progressive destruction of the circumpulpar secondary, and even primary dentine, with bacteria identified within the dentinal tubules surrounding infected pulps. Tertiary dentine deposition was rarely detected. Scanning and transmission electron microscopy confirmed these histological findings and showed extensive destructive changes, especially to the dentinal architecture surrounding the pulp chambers of some infected teeth. PMID:19022689

  16. Core-glycosylated mucin-like repeats from MUC1 are an apical targeting signal.

    PubMed

    Kinlough, Carol L; Poland, Paul A; Gendler, Sandra J; Mattila, Polly E; Mo, Di; Weisz, Ora A; Hughey, Rebecca P

    2011-11-11

    MUC1 is efficiently delivered to the apical surface of polarized Madin-Darby canine kidney (MDCK) cells by transit through apical recycling endosomes, a route associated with delivery of apical proteins with glycan-dependent targeting signals. However, a role for glycans in MUC1 sorting has not been established. A key feature of MUC1 is a heavily O-glycosylated mucin-like domain with a variable number of nearly perfect tandem repeats and adjacent imperfect repeats. Metabolic labeling, cell surface biotinylation, immobilized lectins, and confocal immunofluorescence microscopy were used to characterize the polarized delivery of MUC1 mutants and chimeras in MDCK cells to identify the apical targeting signal. Both the interleukin-2 receptor α subunit (Tac) and a chimera where the Tac ectodomain replaced that of MUC1 were delivered primarily to the basolateral surface. Attachment of the MUC1 mucin-like domain to the N terminus of Tac enhanced apical but not basolateral delivery when compared with Tac. Conversely, deletions within the mucin-like domain in MUC1 reduced apical but not basolateral delivery when compared with MUC1. In pull-down assays with lectins, we found a notable difference in the presence of core 1 O-glycans, but not poly-N-acetyllactosamine, in apically targeted MUC1 and chimeras when compared with Tac. Consistent with these data, we found no effect on MUC1 targeting when galectin-3, with preference for poly-N-acetyllactosamine, was depleted from polarized MDCK cells. However, we did block the apical targeting activity of the mucin-like repeats when we overexpressed CMP-Neu5Ac:GalNAc-Rα2,6-sialyltransferase-1 to block core O-glycan synthesis. The cumulative data indicate that the core-glycosylated mucin-like repeats of MUC1 constitute an apical targeting signal. PMID:21937430

  17. Molecular characterization of the apical organ of the anthozoan Nematostella vectensis

    PubMed Central

    Sinigaglia, Chiara; Busengdal, Henriette; Lerner, Avi; Oliveri, Paola; Rentzsch, Fabian

    2015-01-01

    Apical organs are sensory structures present in many marine invertebrate larvae where they are considered to be involved in their settlement, metamorphosis and locomotion. In bilaterians they are characterised by a tuft of long cilia and receptor cells and they are associated with groups of neurons, but their relatively low morphological complexity and dispersed phylogenetic distribution have left their evolutionary relationship unresolved. Moreover, since apical organs are not present in the standard model organisms, their development and function are not well understood. To provide a foundation for a better understanding of this structure we have characterised the molecular composition of the apical organ of the sea anemone Nematostella vectensis. In a microarray-based comparison of the gene expression profiles of planulae with either a wildtype or an experimentally expanded apical organ, we identified 78 evolutionarily conserved genes, which are predominantly or specifically expressed in the apical organ of Nematostella. This gene set comprises signalling molecules, transcription factors, structural and metabolic genes. The majority of these genes, including several conserved, but previously uncharacterized ones, are potentially involved in different aspects of the development or function of the long cilia of the apical organ. To demonstrate the utility of this gene set for comparative analyses, we further analysed the expression of a subset of previously uncharacterized putative orthologs in sea urchin larvae and detected expression for twelve out of eighteen of them in the apical domain. Our study provides a molecular characterization of the apical organ of Nematostella and represents an informative tool for future studies addressing the development, function and evolutionary history of apical organ cells. PMID:25478911

  18. Molecular characterization of the apical organ of the anthozoan Nematostella vectensis.

    PubMed

    Sinigaglia, Chiara; Busengdal, Henriette; Lerner, Avi; Oliveri, Paola; Rentzsch, Fabian

    2015-02-01

    Apical organs are sensory structures present in many marine invertebrate larvae where they are considered to be involved in their settlement, metamorphosis and locomotion. In bilaterians they are characterised by a tuft of long cilia and receptor cells and they are associated with groups of neurons, but their relatively low morphological complexity and dispersed phylogenetic distribution have left their evolutionary relationship unresolved. Moreover, since apical organs are not present in the standard model organisms, their development and function are not well understood. To provide a foundation for a better understanding of this structure we have characterised the molecular composition of the apical organ of the sea anemone Nematostella vectensis. In a microarray-based comparison of the gene expression profiles of planulae with either a wildtype or an experimentally expanded apical organ, we identified 78 evolutionarily conserved genes, which are predominantly or specifically expressed in the apical organ of Nematostella. This gene set comprises signalling molecules, transcription factors, structural and metabolic genes. The majority of these genes, including several conserved, but previously uncharacterized ones, are potentially involved in different aspects of the development or function of the long cilia of the apical organ. To demonstrate the utility of this gene set for comparative analyses, we further analysed the expression of a subset of previously uncharacterized putative orthologs in sea urchin larvae and detected expression for twelve out of eighteen of them in the apical domain. Our study provides a molecular characterization of the apical organ of Nematostella and represents an informative tool for future studies addressing the development, function and evolutionary history of apical organ cells.

  19. Anisotropic hot deformed magnets prepared from Zn-coated MRE-Fe-B ribbon powder

    SciTech Connect

    Tang, W; Zhou, L; Sun, K W; Dennis, K W; Kramer, M J; Anderson, I E; McCallum, R W

    2014-05-07

    Milled melt-spun ribbon flake of MRE-Fe-B coated with Zn coating using a vapor transport technique was found to have significant increase in coercivity without degrading the magnetization when the Zn thickness and heat treatment were optimized. Magnetic measurements show that 0.5–1 wt. % Zn coating increases the coercivity about 1 kOe over the initial ribbon powder. After vacuum hot deformation (VHD), the VHD magnet with Zn coating of 0.5 wt. % results in a nearly 3 kOe higher coercivity than an un-coated alloy magnet. An optimized VHD magnet with 0.5 wt. % Zn coating obtains a coercivity of 11.2 kOe and (BH)max of 23.0 MGOe, respectively. SEM and TEM microstructures analysis demonstrates that the Zn coating on the surface of ribbon powder has diffused along the intergranular boundaries after the ribbon powder was annealed at 750 °C for 30 min or was hot deformed at 700–750 °C.

  20. The Ribbon Workers as Popular Educators: (Re)-Presenting the Colours of the Crusades

    ERIC Educational Resources Information Center

    Lander, Dorothy A.

    2005-01-01

    The educational aim of this genealogical study of ribbon workers as popular educators is to expose activist and voluntary organisations, not only as generative sites of learning, but also as sites of habituated learning and stereotypical colour assumptions. This study urges popular educators and activists to reflect critically on the popular…

  1. Reefing of Quarter Spherical Ribbon Parachutes used in the Ares I First Stage Deceleration Subsystem

    NASA Technical Reports Server (NTRS)

    Schmidt, Jason R.; McFadden, Peter G.

    2009-01-01

    Normalizing drop test reefed drag area for suspension line length with data from Wolf allows best match of test results with Knacke reefing ratio curve. Various sizes and porosities of quarter spherical ribbon parachutes were tested. All appear to fit the published reefing ratio curve-quarter spherical parachutes match.

  2. Tying the Yellow Ribbon: How School Psychologists and Educators Can Support Military Families

    ERIC Educational Resources Information Center

    Anweiler, Justin

    2008-01-01

    Tying a yellow ribbon around the tree in one's front yard or placing a magnet on one's car is more than just a show of support. It is a promise to American military around the world that one is ready and able to support them in their time of need just as they have supported the country. Educators, including school psychologists, are especially…

  3. Complementary halogen and hydrogen bonding: sulfur...iodine interactions and thioamide ribbons.

    PubMed

    Arman, Hadi D; Gieseking, Rebecca L; Hanks, Timothy W; Pennington, William T

    2010-03-21

    Complementary halogen bonding and hydrogen bonding coexist in co-crystals of organoiodines with molecules containing the thioamide functionality. Thiourea.organoiodine co-crystals are shown to exhibit a remarkably reliable synthon with complementary N-H...S ribbons and S...I interactions.

  4. 75 FR 65465 - Blue Ribbon Commission on America's Nuclear Future, Disposal Subcommittee

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-10-25

    ...This notice announces an open meeting of the Disposal Subcommittee. The Disposal Subcommittee is a subcommittee of the Blue Ribbon Commission on America's Nuclear Future (the Commission). The establishment of subcommittees is authorized in the Commission's charter. The Commission was organized pursuant to the Federal Advisory Committee Act (Pub. L. No. 92-463, 86 Stat. 770) (the Act). This......

  5. 75 FR 36648 - Blue Ribbon Commission on America's Nuclear Future, Disposal Subcommittee

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-06-28

    ... Ribbon Commission on America's Nuclear Future, Disposal Subcommittee AGENCY: Department of Energy, Office of Nuclear Energy. ACTION: Notice of open meeting correction. On June 21, 2010, the Department of Energy published a notice announcing an open meeting of the Disposal Subcommittee, 75 FR 35000, on July...

  6. 75 FR 36648 - Blue Ribbon Commission on America's Nuclear Future, Reactor and Fuel Cycle Technologies Subcommittee

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-06-28

    ... From the Federal Register Online via the Government Publishing Office DEPARTMENT OF ENERGY Blue Ribbon Commission on America's Nuclear Future, Reactor and Fuel Cycle Technologies Subcommittee AGENCY: Office of Nuclear Energy, DOE. ACTION: Notice of open meeting correction. On June 21, 2010,...

  7. 75 FR 51247 - Blue Ribbon Commission on America's Nuclear Future, Disposal Subcommittee

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-08-19

    ... Ribbon Commission on America's Nuclear Future, Disposal Subcommittee AGENCY: Department of Energy, Office of Nuclear Energy. ACTION: Notice of open meeting. SUMMARY: This notice announces an open meeting of... (202) 586- 0544; e-mail CommissionDFO@nuclear.energy.gov . Additional information will be available...

  8. 75 FR 35000 - Blue Ribbon Commission on America's Nuclear Future, Disposal Subcommittee

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-06-21

    ... Ribbon Commission on America's Nuclear Future, Disposal Subcommittee AGENCY: Department of Energy, Office of Nuclear Energy. ACTION: Notice of Open Meeting. SUMMARY: This notice announces an open meeting of... (202) 586-4243 or facsimile (202) 586- 0544; e-mail CommissionDFO@nuclear.energy.gov ....

  9. In vivo knockdown of Piccolino disrupts presynaptic ribbon morphology in mouse photoreceptor synapses

    PubMed Central

    Regus-Leidig, Hanna; Fuchs, Michaela; Löhner, Martina; Leist, Sarah R.; Leal-Ortiz, Sergio; Chiodo, Vince A.; Hauswirth, William W.; Garner, Craig C.; Brandstätter, Johann H.

    2014-01-01

    Piccolo is the largest known cytomatrix protein at active zones of chemical synapses. A growing number of studies on conventional chemical synapses assign Piccolo a role in the recruitment and integration of molecules relevant for both endo- and exocytosis of synaptic vesicles, the dynamic assembly of presynaptic F-actin, as well as the proteostasis of presynaptic proteins, yet a direct function in the structural organization of the active zone has not been uncovered in part due to the expression of multiple alternatively spliced isoforms. We recently identified Piccolino, a Piccolo splice variant specifically expressed in sensory ribbon synapses of the eye and ear. Here we down regulated Piccolino in vivo via an adeno-associated virus-based RNA interference approach and explored the impact on the presynaptic structure of mouse photoreceptor ribbon synapses. Detailed immunocytochemical light and electron microscopical analysis of Piccolino knockdown in photoreceptors revealed a hitherto undescribed photoreceptor ribbon synaptic phenotype with striking morphological changes of synaptic ribbon ultrastructure. PMID:25232303

  10. ATRF Ribbon-Cutting Ceremony Coincides with Chamber of Commerce Centennial Gala | Poster

    Cancer.gov

    By Frank Blanchard, Staff Writer U.S. Rep. Roscoe Bartlett, NCI Deputy Director for Management John Czajkowski, and SAIC Corporate Chief Executive Officer (CEO) John Jumper were joined by representatives of the Frederick County Chamber of Commerce in cutting the ribbon for the National Cancer Institute’s Advanced Technology Research Facility (ATRF).

  11. Alteration of in vivo cellulose ribbon assembly by carboxymethylcellulose and other cellulose derivatives

    PubMed Central

    1982-01-01

    In vivo cellulose ribbon assembly by the Gram-negative bacterium Acetobacter xylinum can be altered by incubation in carboxymethylcellulose (CMC), a negatively charged water-soluble cellulose derivative, and also by incubation in a variety of neutral, water-soluble cellulose derivatives. In the presence of all of these substituted celluloses, normal fasciation of microfibril bundles to form the typical twisting ribbon is prevented. Alteration of ribbon assembly is most extensive in the presence of CMC, which often induces synthesis of separate, intertwining bundles of microfibrils. Freeze- etch preparations of the bacterial outer membrane suggest that particles that are thought to be associated with cellulose synthesis or extrusion may be specifically organized to mediate synthesis of microfibril bundles. These data support the previous hypothesis that the cellulose ribbon of A. xylinum is formed by a hierarchical, cell- directed, self-assembly process. The relationship of these results to the regulation of cellulose microfibril size and wall extensibility in plant cell walls is discussed. PMID:6889605

  12. Ribbon-cutting officially opens Consolidated Support Operations Center at CCAS

    NASA Technical Reports Server (NTRS)

    1999-01-01

    Cutting the ribbon at a ceremony for the opening of the Consolidated Support Operations Center at ROCC, Cape Canaveral Air Station, are (left to right) William P. Hickman, program manager, Space Gateway Support; Ed Gormel, executive director, JPMO; Barbara White, supervisor, Mission Support; KSC Center Director Roy Bridges, and Lt Col Steve Vuresky, USAF.

  13. The origins of quantum interference and uncertainty broadening. A linear ribbon model approach

    SciTech Connect

    Tang, J.

    1996-02-01

    As an alternative to the orthodox Schroedinger wave mechanics or Heisenberg matrix mechanics approach, a simple linear ribbon model for quantum theory is presented. A different perspective and better physical insights into the origins of quantum interference and the mechanisms for uncertainty broadening are offered. Quantum interference in the atomic scale and superconducting behaviour in the macroscopic scale are compared.

  14. Treatment with Piribedil and Memantine Reduces Noise-Induced Loss of Inner Hair Cell Synaptic Ribbons

    PubMed Central

    Altschuler, Richard A.; Wys, Noel; Prieskorn, Diane; Martin, Cathy; DeRemer, Susan; Bledsoe, Sanford; Miller, Josef M.

    2016-01-01

    Noise overstimulation can induce loss of synaptic ribbons associated with loss of Inner Hair Cell – Auditory Nerve synaptic connections. This study examined if systemic administration of Piribedil, a dopamine agonist that reduces the sound evoked auditory nerve compound action potential and/or Memantine, an NMDA receptor open channel blocker, would reduce noise-induced loss of Inner Hair Cell ribbons. Rats received systemic Memantine and/or Piribedil for 3 days before and 3 days after a 3 hour 4 kHz octave band noise at 117 dB (SPL). At 21 days following the noise there was a 26% and 38% loss of synaptic ribbons in regions 5.5 and 6.5 mm from apex, respectively, elevations in 4-, 8- and 20 kHz tonal ABR thresholds and reduced dynamic output at higher intensities of stimulation. Combined treatment with Piribedil and Memantine produced a significant reduction in the noise-induced loss of ribbons in both regions and changes in ABR sensitivity and dynamic responsiveness. Piribedil alone gave significant reduction in only the 5.5 mm region and Memantine alone did not reach significance in either region. Results identify treatments that could prevent the hearing loss and hearing disorders that result from noise-induced loss of Inner Hair Cell – Auditory Nerve synaptic connections. PMID:27686418

  15. 75 FR 53686 - Blue Ribbon Commission on America's Nuclear Future, Transportation and Storage Subcommittee

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-09-01

    ... spent nuclear fuel and nuclear waste. The Co-chairs of the Commission requested the formation of the T&S... Ribbon Commission on America's Nuclear Future, Transportation and Storage Subcommittee AGENCY: Department of Energy, Office of Nuclear Energy. ACTION: Notice of open meeting. SUMMARY: This notice...

  16. 75 FR 45608 - Blue Ribbon Commission on America's Nuclear Future, Transportation and Storage Subcommittee

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-08-03

    ..., processing, and disposal of civilian and defense spent nuclear fuel and nuclear waste. The Co-chairs of the... the way in which it is storing used nuclear fuel and high level waste while one or more final disposal... Ribbon Commission on America's Nuclear Future, Transportation and Storage Subcommittee AGENCY:...

  17. 75 FR 64720 - Blue Ribbon Commission on America's Nuclear Future, Transportation and Storage Subcommittee

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-10-20

    ... spent nuclear fuel and nuclear waste. The Co-chairs of the Commission requested the formation of the T&S... Ribbon Commission on America's Nuclear Future, Transportation and Storage Subcommittee AGENCY: Office of Nuclear Energy, Department of Energy. ACTION: Notice of Open Meeting. SUMMARY: This notice announces...

  18. Solar-grade silicon substrates by a powder-to-ribbon process

    NASA Astrophysics Data System (ADS)

    Norman, C. E.; Absi, E. M.; Thomas, R. E.

    1985-06-01

    A new technique for producing silicon ribbons for solar-cell substrates is described. The process begins with inexpensive, 98 percent pure silicon that is crushed and acid leached to raise the purity to 99.9 percent. This powder is spread on a graphite plate and electron-beam annealed to form a flat, self-supporting 'preribbon'. After removal of the graphite and unmelted powder, the preribbon is given a second electron-beam scan that recrystallizes the silicon into a smooth polycrystalline ribbon. This zone melting further improves the purity to over 99.99 percent. Ribbons 0.4 mm thick and up to 16 mm wide were produced in this initial work. The ribbons are p-type, 0.07 ohm-cm and have long crystals about 1 mm wide. Electron-diffusion lengths of 20-30 microns were measured. Calculations indicate that solar-cell efficiencies up to 13 percent should be possible. If the process can be scaled up and automated, the cost of volume production could be as low as 43 cents/W. It is concluded that the process has the potential for achieving low-cost 'solar-grade' substrates and has advantages over other processes. Further work is planned.

  19. The electro-mechanical responses of suspended graphene ribbons for electrostatic discharge applications

    NASA Astrophysics Data System (ADS)

    Zhang, Wei; Ma, Rui; Chen, Qi; Xia, Ming; Ng, Jimmy; Wang, Albert; Xie, Ya-Hong

    2016-04-01

    This work presents a suspended graphene ribbon device for electrostatic discharge (ESD) applications. The device structure was proposed and fabricated after careful design considerations. Compared to the conventional ESD devices such as diodes, bipolar junction transistors, and metal-oxide-semiconductor field effect transistors, the proposed device structure is believed to render several advantages including zero leakage, low parasitic effects, fast response, and high critical current density. A process flow was developed for higher yield and reliability of the suspended graphene ribbons. Direct current (DC) and transmission-line pulse (TLP) measurements were carried out to investigate the switching behavior of the device, which is crucial for ESD operation. DC measurements with a different configuration were used to assess the mechanical shape evolution of the graphene ribbon upon biasing. Finite Element Simulations were conducted and agreed well with the experimental results. Furthermore, the current carrying capability of non-suspended graphene ribbons was tested using TLP. It was found that the critical current density of graphene is higher than that of copper wires widely used as interconnects in integrated circuits (ICs).

  20. 75 FR 66766 - NIAID Blue Ribbon Panel Meeting on Adjuvant Discovery and Development

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-10-29

    ... knowledge and capabilities, and defines NIAID's goals for the continued discovery, development and... HUMAN SERVICES NIAID Blue Ribbon Panel Meeting on Adjuvant Discovery and Development Notice is hereby... discovery, development and clinical evaluation of adjuvants for use with preventive vaccines. NIAID...

  1. A Lasting Legacy: Recommendations of the New England Governors Blue Ribbon Commission on Land Conservation

    ERIC Educational Resources Information Center

    Barringer, Richard

    2010-01-01

    In September 2008, New England's governors established a blue-ribbon Commission on Land Conservation to identify the most urgent land-conservation issues facing New England today and provide recommendations to the governors in September 2009. New England faces profound threats to its land and natural-resource base. As the nation urbanizes further,…

  2. 78 FR 29703 - Narrow Woven Ribbons With Woven Selvedge From Taiwan: Preliminary Results of Antidumping Duty...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-05-21

    ... Determination of Sales at Less than Fair Value: Narrow Woven Ribbons with Woven Selvedge from Taiwan, 75 FR... questionnaire. As a result, we have preliminarily assigned these companies a margin based on adverse facts... preliminary results, we have relied on facts available and, because the respondents did not act to the best...

  3. Bleu Ribbon Chocolates: How Can Small Businesses Adapt to a Changing Environment?

    ERIC Educational Resources Information Center

    Deeter-Schmelz, Dawn R.; Ramsey, Rosemary P.; Gassenheimer, Jule B.

    2011-01-01

    Bleu Ribbon Chocolates is a small regional manufacturer of high-quality chocolate that sells its products via trade accounts, corporate-owned stores, and online/mail. Historically, the company has not engaged in strategic planning, as demand was greater than manufacturing capabilities. The trend toward healthier foods and the poor economy,…

  4. 76 FR 77467 - Endangered and Threatened Species; Initiation of Status Review for Ribbon Seal

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-12-13

    ... finding (73 FR 16617) in which we determined that the petition presented substantial information... FR 79822). In this finding we concluded that although ribbon seal population abundance is likely to... (75 FR 65239, October 22, 2010; 75 FR 77476 and 75 FR 77496, December 10, 2010). In consideration...

  5. 77 FR 32938 - Narrow Woven Ribbons With Woven Selvedge From Taiwan: Preliminary Results of Antidumping Duty...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-06-04

    ... China: Antidumping Duty Orders, 75 FR 53632 (Sept. 1, 2010), as amended in Narrow Woven Ribbons With Woven Selvedge From Taiwan and the People's Republic of China: Amended Antidumping Duty Orders, 75 FR... Investigation; Opportunity To Request Administrative Review, 76 FR 54735, 54736 (Sept. 2, 2011). \\3\\...

  6. Obturating teeth with wide open apices using mineral trioxide aggregate: a case report.

    PubMed

    Levenstein, H

    2002-07-01

    The conventional approach in handling a tooth with a wide open apex requiring endodontic treatment is by means of a procedure called apexification. The objective of treatment is to introduce calcium hydroxide mixed with sterile water or local anaesthetic into the root canal to create a hard-tissue-like formation or an apical plug to prevent extrusion of filling materials during obturation of teeth with wide open apices. This procedure may take anything from 6 months to 2 years. In 1999 a new material called mineral trioxide aggregate (MTA) was introduced to the dental profession for clinical use which has the ability to create an apical plug within a few weeks.

  7. Highly Automated Module Production Incorporating Advanced Light Management

    SciTech Connect

    Perelli-Minetti, Michael; Roof, Kyle

    2015-08-11

    The objective was to enable a high volume, cost effective solution for increasing the amount of light captured by PV modules through utilization of an advanced Light Re-directing Film and to follow a phased approach to develop and implement this new technology in order to achieve an expected power gain of up to 12 watts per module. Full size PV modules were manufactured using a new Light Redirecting Film (LRF) material applied to two different areas of PV modules in order to increase the amount of light captured by the modules. One configuration involved applying thin strips of LRF film over the tabbing ribbon on the cells in order to redirect the light that is normally absorbed by the tabbing ribbon to the active areas of the cells. A second configuration involved applying thin strips of LRF film over the white spaces between cells within a module in order to capture some of the light that is normally reflected from the white areas back through the front glass of the modules. Significant power increases of 1.4% (3.9 watts) and 1.0% (3.2 watts), respectively, compared to standard PV modules were measured under standard test conditions. The performance of PV modules with LRF applied to the tabbing ribbon was modeled. The results showed that the power increase provided by LRF depended greatly on the angle of incident light with the optimum performance only occurring when the light was within a narrow range of being perpendicular to the solar module. The modeling showed that most of the performance gain would be lost when the angle of incident light was greater than 28 degrees off axis. This effect made the orientation of modules with LRF applied to tabbing ribbons very important as modules mounted in “portrait” mode were predicted to provide little to no power gain from LRF under real world conditions. Based on these results, modules with LRF on tabbing ribbons would have to be mounted in “landscape” mode to realize a performance advantage. In addition

  8. Evolution of the Topology, Electric Currents, and Ribbons during an X-class Flare

    NASA Astrophysics Data System (ADS)

    Savcheva, Antonia; Janvier, Miho; Pariat, Etienne

    2016-05-01

    The standard model for eruptive flares has in the past few years been extended to 3D. It predicts typical J-shaped photospheric footprints of the coronal current layer, forming at similar locations as the Quasi-Separatrix Layers (QSLs). We study the evolution of the photospheric traces of the current density and the flare ribbons observed with SDO. We aim at comparing their morphology and their time evolution, before and during the flare, with the topological features found in a magnetic field model. For this purpose we investigate the photospheric current evolution during the 6 Sep 2011 X-class flare occurring in AR11283 from observational data of the magnetic field obtained with HMI. This evolution is compared with that of the flare ribbons observed with AIA. We also compare the observed electric current density and the flare ribbon morphology with that of the QSLs computed from magnetic field models obtained from the the flux rope insertion method. Both the NLFFF and the unstable (eruptive) model show the presence of a fan-spine configuration of overlying field lines, due to the presence of a parasitic polarity, embedding in elongated flux rope that appears in the observations as two parts of a filament. The magnetofrictional evolution of the unstable model tells a consistent story of the filament eruption in which topology plays an important role. The photospheric QSL traces of the fan configuration appear as an elongated flare ribbon that encircles the J-shaped ribbons related to the filament ejection. The QSLs, evolved via a magnetofrictional method, also show similar morphology and evolution as both the current ribbons and the EUV flare ribbons obtained at several times during the flare. For the first time, we propose a combined analysis of the photospheric traces of an eruptive flare, in a complex topology, with direct measurements of electric currents and QSLs from observational data and a magnetic field model. The results obtained by two independent

  9. Hard magnetic property enhancement of Co{sub 7}Hf-based ribbons by boron doping

    SciTech Connect

    Chang, H. W.; Liao, M. C.; Shih, C. W.; Chang, W. C.; Yang, C. C.; Hsiao, C. H.; Ouyang, H.

    2014-11-10

    Hard magnetic property enhancement of melt spun Co{sub 88}Hf{sub 12} ribbons by boron doping is demonstrated. B-doping could not only remarkably enhance the magnetic properties from energy product ((BH){sub max}) of 2.6 MGOe and intrinsic coercivity ({sub i}H{sub c}) of 1.5 kOe for B-free Co{sub 88}Hf{sub 12} ribbons to (BH){sub max} = 7.7 MGOe and {sub i}H{sub c} = 3.1 kOe for Co{sub 85}Hf{sub 12}B{sub 3} ribbons but also improve the Curie temperature (T{sub C}) of 7:1 phase. The (BH){sub max} value achieved in Co{sub 85}Hf{sub 12}B{sub 3} ribbons is the highest in Co-Hf alloy ribbons ever reported, which is about 15% higher than that of Co{sub 11}Hf{sub 2}B ribbons spun at 16 m/s [M. A. McGuire, O. Rios, N. J. Ghimire, and M. Koehler, Appl. Phys. Lett. 101, 202401 (2012)]. The structural analysis confirms that B enters the orthorhombic Co{sub 7}Hf (7:1) crystal structure as interstitial atoms, forming Co{sub 7}HfB{sub x}, in the as-spun state. Yet B may diffuse out from the 7:1 phase after post-annealing, leading to the reduction of Curie temperature and the magnetic properties. The uniformly refined microstructure with B-doping results in high remanence (B{sub r}) and improves the squareness of demagnetization curve. The formation of interstitial-atom-modified Co{sub 7}HfB{sub x} phase and the microstructure refinement are the main reasons to give rise to the enhancement of hard magnetic properties in the B-containing Co{sub 7}Hf-based ribbons.

  10. A CIRCULAR-RIBBON SOLAR FLARE FOLLOWING AN ASYMMETRIC FILAMENT ERUPTION

    SciTech Connect

    Liu, Chang; Deng, Na; Lee, Jeongwoo; Wang, Haimin; Liu, Rui; Pariat, Étienne; Wiegelmann, Thomas; Liu, Yang; Kleint, Lucia

    2015-10-20

    The dynamic properties of flare ribbons and the often associated filament eruptions can provide crucial information on the flaring coronal magnetic field. This Letter analyzes the GOES-class X1.0 flare on 2014 March 29 (SOL2014-03-29T17:48), in which we found an asymmetric eruption of a sigmoidal filament and an ensuing circular flare ribbon. Initially both EUV images and a preflare nonlinear force-free field model show that the filament is embedded in magnetic fields with a fan-spine-like structure. In the first phase, which is defined by a weak but still increasing X-ray emission, the western portion of the sigmoidal filament arches upward and then remains quasi-static for about five minutes. The western fan-like and the outer spine-like fields display an ascending motion, and several associated ribbons begin to brighten. Also found is a bright EUV flow that streams down along the eastern fan-like field. In the second phase that includes the main peak of hard X-ray (HXR) emission, the filament erupts, leaving behind two major HXR sources formed around its central dip portion and a circular ribbon brightened sequentially. The expanding western fan-like field interacts intensively with the outer spine-like field, as clearly seen in running difference EUV images. We discuss these observations in favor of a scenario where the asymmetric eruption of the sigmoidal filament is initiated due to an MHD instability and further facilitated by reconnection at a quasi-null in corona; the latter is in turn enhanced by the filament eruption and subsequently produces the circular flare ribbon.

  11. Rings and ribbons in protein structures: Characterization using helical parameters and Ramachandran plots for repeating dipeptides.

    PubMed

    Hayward, Steven; Leader, David P; Al-Shubailly, Fawzia; Milner-White, E James

    2014-02-01

    Helical parameters displayed on a Ramachandran plot allow peptide structures with successive residues having identical main chain conformations to be studied. We investigate repeating dipeptide main chain conformations and present Ramachandran plots encompassing the range of possible structures. Repeating dipeptides fall into the categories: rings, ribbons, and helices. Partial rings occur in the form of "nests" and "catgrips"; many nests are bridged by an oxygen atom hydrogen bonding to the main chain NH groups of alternate residues, an interaction optimized by the ring structure of the nest. A novel recurring feature is identified that we name unpleated β, often situated at the ends of a β-sheet strand. Some are partial rings causing the polypeptide to curve gently away from the sheet; some are straight. They lack β-pleat and almost all incorporate a glycine. An example is the first glycine in the GxxxxGK motif of P-loop proteins. Ribbons in repeating dipeptides can be either flat, as seen in repeated type II and type II' β-turns, or twisted, as in multiple type I and type I' β-turns. Hexa- and octa-peptides in such twisted ribbons occur frequently in proteins, predominantly with type I β-turns, and are the same as the "β-bend ribbons" hitherto identified only in short peptides. One is seen in the GTPase-activating protein for Rho in the active, but not the inactive, form of the enzyme. It forms a β-bend ribbon, which incorporates the catalytic arginine, allowing its side chain guanidino group to approach the active site and enhance enzyme activity.

  12. Ribbon Surface Pressure and Wake Velocity Data for the Experimental Validation of a Vortex-Based Parachute Inflation Code

    SciTech Connect

    MCBRIDE,DONALD DEAN; CLARK JR,EDWARD LEE; HENFLING,JOHN F.

    2001-06-01

    An experiment to measure surface pressure data on a series of three stainless steel simulated parachute ribbons was conducted. During the first phase of the test, unsteady pressure measurements were made on the windward and leeward sides of the ribbons to determine the statistical properties of the surface pressures. Particle Image Velocimetry (PIV) measurements were simultaneously made to establish the velocity field in the wake of the ribbons and its correlation with the pressure measurements. In the second phase of the test, steady-state pressure measurements were made to establish the pressure distributions. In the third phase, the stainless steel ribbons were replaced with nylon ribbons and PIV measurements were made in the wake. A detailed error analysis indicates that the accuracy of the pressure measurements was very good. However, an anomaly in the flow field caused the wake behind the stainless steel ribbons to establish itself in a stable manner on one side of the model. This same stability was not present for the nylon ribbon model although an average of the wake velocity data indicated an apparent 2{degree} upwash in the wind tunnel flow field. Since flow angularity upstream of the model was not measured, the use of the data for code validation is not recommended without a second experiment to establish that upstream boundary condition.

  13. Absence of functional active zone protein Bassoon affects assembly and transport of ribbon precursors during early steps of photoreceptor synaptogenesis.

    PubMed

    Regus-Leidig, Hanna; tom Dieck, Susanne; Brandstätter, Johann Helmut

    2010-06-01

    The retinal photoreceptor ribbon synapse is a structurally and functionally unique type of chemical synapse, specialized for tonic release of neurotransmitter in the dark. It is characterized by the presynaptic ribbon, an electron-dense organelle at the active zone, which is covered by hundreds of synaptic vesicles. Recently we showed that photoreceptor ribbon complexes are assembled from non-membranous, spherical densities--the precursor spheres--during the first two postnatal weeks of photoreceptor synaptogenesis. A core component of the precursor spheres and a key player in attaching the ribbon to the active zone is the presynaptic cytomatrix protein Bassoon. In this study, we examined in a comprehensive light and electron microscopic analysis whether Bassoon plays a role in the formation of the precursor spheres using Bassoon mutant mice lacking functional Bassoon. We report that developing Bassoon mutant photoreceptors contain fewer and smaller precursor spheres and that transport of precursor spheres to nascent synapses is delayed compared to wild-type controls. Moreover, western blot analyses of homogenates from postnatal day 0 (P0) to P14 Bassoon mutant retinae exhibit lower RIBEYE and Piccolo protein levels compared to the wild type, indicating elevated protein degradation in the absence of Bassoon. Our findings reveal a novel function of Bassoon in the early formation and delivery of precursor spheres to nascent ribbon synaptic sites in addition to its known role in ribbon anchoring during later stages of photoreceptor ribbon synaptogenesis.

  14. Surface valence transformation during thermal activation and hydrogenation thermodynamics of Mg-Ni-Y melt-spun ribbons

    NASA Astrophysics Data System (ADS)

    Zhang, Tiebang; Song, Wenjie; Kou, Hongchao; Li, Jinshan

    2016-05-01

    In this work, phase compositions and chemical valence states on the surface and subsurface of Mg67Ni33-xYx (x = 0, 1, 3, 6) ribbons during thermal activation have been investigated by X-ray photoelectron spectroscopy (XPS). The results indicate that the surface contaminants of melt-spun ribbons are mainly MgO, NiO, Y2O3 and organics. The oxides/hydroxides of Mg67Ni33-xYx (x = 0, 1, 3, 6) melt-spun ribbons are removed from the surface during thermal activation. Surface chemical valence firstly transforms from oxidized state to the metallic one during thermal activation, which accounts for hydrogenation of Mg67Ni33-xYx melt-spun ribbons. Hydrogen absorption capacities of Mg67Ni33-xYx (x = 0, 1, 3, 6) melt-spun ribbons are enhanced with the increase of cycle numbers during thermal activation. Hydrogenation thermodynamics of activated Mg67Ni33-xYx (x = 0, 1, 3, 6) melt-spun ribbons have been also compared and correlated with the surface valence transformation. The obtained enthalpy of hydride formation is -55.5, -50.5, -46.9 and -48.6 kJ/mol for Mg67Ni33-xYx melt-spun ribbons with x = 0, 1, 3 and 6, respectively.

  15. Effects of solar wind speed on the secondary energetic neutral source of the Interstellar Boundary Explorer ribbon

    NASA Astrophysics Data System (ADS)

    Zirnstein, E. J.; Funsten, H. O.; Heerikhuisen, J.; McComas, D. J.

    2016-02-01

    The Interstellar Boundary EXplorer (IBEX) ribbon is an intense energetic neutral atom (ENA) emission feature encircling the sky, spanning energies ≤0.5-6 keV. The ribbon may be produced by the "secondary ENA" mechanism, where ENAs emitted from a source plasma population inside the heliosphere propagate outside the heliopause, undergo two charge-exchange events, and become secondary ENAs that may be directed back toward Earth and detected by IBEX. In this scenario, the source plasma population is governed by the interaction of the solar wind (SW) with the interstellar medium and is thus sensitive to the global SW properties. Moreover, this scenario predicts that the distance to the source of secondary ENAs depends on the ENA energy and SW speed, which in turn may affect the shape of the ribbon. In this paper, we use a computational model of the heliosphere with simplified SW boundary conditions to analyze the influence of ENA energy and SW speed, independent of time and latitude, on the global spatial and geometric properties of the ribbon. We find a strong dependence of the simulated ribbon energy spectrum and spatial symmetry on SW speed and ENA energy, and only a slight dependence on ribbon geometry. Our results suggest a significant number of primary ENAs from the inner heliosheath may contribute to the pickup ion source population outside the heliopause, depending on the ENA energy and SW speed. The lack of variation in the simulated ribbon center as a function of ENA energy and SW speed, in contrast to the observations, implies that the asymmetry of the SW plays an important role in determining the position of the ribbon. Comparisons to the IBEX data also signify the ribbon's dependence on the properties of the local interstellar medium, particularly the interstellar magnetic field.

  16. Genetic Control of Maize Shoot Apical Meristem Architecture

    PubMed Central

    Thompson, Addie M.; Crants, James; Schnable, Patrick S.; Yu, Jianming; Timmermans, Marja C. P.; Springer, Nathan M.; Scanlon, Michael J.; Muehlbauer, Gary J.

    2014-01-01

    The shoot apical meristem contains a pool of undifferentiated stem cells and generates all above-ground organs of the plant. During vegetative growth, cells differentiate from the meristem to initiate leaves while the pool of meristematic cells is preserved; this balance is determined in part by genetic regulatory mechanisms. To assess vegetative meristem growth and genetic control in Zea mays, we investigated its morphology at multiple time points and identified three stages of growth. We measured meristem height, width, plastochron internode length, and associated traits from 86 individuals of the intermated B73 × Mo17 recombinant inbred line population. For meristem height-related traits, the parents exhibited markedly different phenotypes, with B73 being very tall, Mo17 short, and the population distributed between. In the outer cell layer, differences appeared to be related to number of cells rather than cell size. In contrast, B73 and Mo17 were similar in meristem width traits and plastochron internode length, with transgressive segregation in the population. Multiple loci (6−9 for each trait) were mapped, indicating meristem architecture is controlled by many regions; none of these coincided with previously described mutants impacting meristem development. Major loci for height and width explaining 16% and 19% of the variation were identified on chromosomes 5 and 8, respectively. Significant loci for related traits frequently coincided, whereas those for unrelated traits did not overlap. With the use of three near-isogenic lines, a locus explaining 16% of the parental variation in meristem height was validated. Published expression data were leveraged to identify candidate genes in significant regions. PMID:24855316

  17. Investigation of easy axis orientation of Nd-Fe-B melt-spun ribbons produced by hot rolling and influence of Ti-C addition

    SciTech Connect

    Takezawa, M.; Nakanishi, Y.; Morimoto, Y.; Yamasaki, J.; Yagi, M.

    2012-04-01

    The c-axis orientation of Nd-Fe-B melt-spun ribbons caused by hot rolling and the influence of Ti-C addition were investigated. A small roll was placed on a steel wheel near a quartz tube in such a manner that the melt-spun ribbons were hot rolled immediately after quenching. X-ray diffraction patterns measured on both surfaces of the Nd-Fe-B-Ti ribbon indicate that the c-axis is oriented normal to the ribbon plane. The domain pattern of the Nd-Fe-B-Ti-C ribbon was observed with a Kerr microscope. Most of the grains exhibit a maze domain configuration, indicating that the c-axis is oriented normal to the ribbon plane. Furthermore, it was demonstrated that hot rolling and the addition of Ti-C promote c-axis orientation and high coercivity of Nd-Fe-B melt-spun ribbons.

  18. Characterization of actin microfilaments at the apical pole of thyroid cells.

    PubMed

    Gabrion, J; Travers, F; Benyamin, Y; Sentein, P; Van Thoai, N

    1980-01-01

    In thyroid cells (rat or hog), actin has been detected by immunofluorescence with an antiactin antibody and, in electron microscopy by decoration "in situ" with heavy meromyosin. The antibody as the heavy meromyosin method have shown that actin microfilaments are especially localized at the apical pole of the cells, in a region where thin filaments are usually observed by conventional methods of electron microscopy. These microfilaments are attached to the apical membrane at the ends of the microvilli and form dense bundles at their cores. They are polarized towards the interior of the cell. Decorated filaments are also organized in a clear network, parallel to the apical membrane; they are associated with microvillar bundles, but also with small apical vesicles and lateral membranes, in tight or gap junctions.

  19. Isolation of gibberellin A8-glucoside from shoot apices of Althaea rosea.

    PubMed

    Harada, H; Yokota, T

    1970-03-01

    Gibberellin A8-glucoside has been isolated from shoot apices of Althaea rosea. It showed a weak growth-promoting activity on rice seedlings and oat mesocotyl sections but did not induce germination of lettuce seeds in darkness.

  20. Apical constriction: themes and variations on a cellular mechanism driving morphogenesis

    PubMed Central

    Martin, Adam C.; Goldstein, Bob

    2014-01-01

    Apical constriction is a cell shape change that promotes tissue remodeling in a variety of homeostatic and developmental contexts, including gastrulation in many organisms and neural tube formation in vertebrates. In recent years, progress has been made towards understanding how the distinct cell biological processes that together drive apical constriction are coordinated. These processes include the contraction of actin-myosin networks, which generates force, and the attachment of actin networks to cell-cell junctions, which allows forces to be transmitted between cells. Different cell types regulate contractility and adhesion in unique ways, resulting in apical constriction with varying dynamics and subcellular organizations, as well as a variety of resulting tissue shape changes. Understanding both the common themes and the variations in apical constriction mechanisms promises to provide insight into the mechanics that underlie tissue morphogenesis. PMID:24803648

  1. Isolated Left Ventricular Apical Hypoplasia: Reporting a Case With Mild Manifestations and Different Echocardiography Features

    PubMed Central

    Mirdamadi, Ahmad; Ashrafi, Samira

    2016-01-01

    Introduction Isolated left ventricular apical hypoplasia is an unusual type of cardiomyopathy that presents with different clinical manifestations according to the age of the disease, ranging from no symptoms in children to congestive heart failure, pulmonary edema, or even malignant tachycardia in adults. To our knowledge, only a few cases of isolated left ventricular apical hypoplasia have been reported in Asian adults. Case Presentation Herein, we described an adult case of isolated left ventricular apical hypoplasia referred to our heart center in Isfahan, Iran in 2015 with a complaint of mild dyspnea with the absence of obvious fatty tissue in the heart’s apex and an absence of any shunt, which are common findings in patients with this phenomenon. Conclusions Patients faced with isolated left ventricular apical hypoplasia should be monitored by echocardiography because of this disease’s possible progressive trend to life-threatening consequences. PMID:27800175

  2. EVALUATION OF THE APICAL INFILTRATION AFTER ROOT CANAL DISRUPTION AND OBTURATION

    PubMed Central

    Gomes, João Eduardo; Hopp, Renato Nicolás; Bernabé, Pedro Felício Estrada; Nery, Mauro Juvenal; Otoboni, José Arlindo; Dezan, Elói

    2008-01-01

    The aim of this study was to evaluate two root canal filling techniques used in teeth that had their apical foramen disrupted and compare the apical infiltration with an ideal clinical situation. Twenty-seven freshly extracted single-rooted teeth were selected and radiographed to confirm the existence of a single and straight root canal. The crowns were removed at a mean distance of 11 mm from the apex. The teeth had the root canals instrumented and were randomly assigned to 3 groups (n=9): ND group - root canals were filled using the lateral compaction technique and no disruption was performed; DRF group - the apical constriction was disrupted by advancing a #40 K-file 1 mm beyond the original working length, the canals were reinstrumented to create an apical ledge at 1 mm from the apical foramen and were obturated with a master gutta-percha cone with same size as the last file used for reinstrumentation; DF group - the teeth had the apical constriction disrupted and the canals were obturated with a master gutta-percha cone that fit at 1 mm from the apex. The teeth were submitted to dye leakage test with Rhodamine B for 7 days, using vaccum on the initial 5 min. The teeth were sectioned longitudinally and the leakage was measured in a linear fashion from apex to crown. There was no statistically significant difference (p>0.05) between the groups that had the apical foramen disrupted (DF, DRF), but significant difference was found between the disrupted groups and the non-disrupted one (p<0.01). In conclusion, none of the evaluated techniques was able to prevent apical infiltration, so working length so the working length determination has to be established and maintained carefully. PMID:19089232

  3. Light and nitrogen nutrition regulate apical control in Rosa hybrida L.

    PubMed

    Furet, Pierre-Maxime; Lothier, Jérémy; Demotes-Mainard, Sabine; Travier, Sandrine; Henry, Clémence; Guérin, Vincent; Vian, Alain

    2014-03-01

    Apical control is defined as the inhibition of basal axillary bud outgrowth by an upper actively growing axillary axis, whose regulation is poorly understood yet differs markedly from the better-known apical dominance. We studied the regulation of apical control by environmental factors in decapitated Rosa hybrida in order to remove the apical hormonal influence and nutrient sink. In this plant model, all the buds along the main axis have a similar morphology and are able to burst in vitro. We concentrated on the involvement of light intensity and nitrate nutrition on bud break and axillary bud elongation in the primary axis pruned above the fifth leaf of each rose bush. We observed that apical control took place in low light (92 μmol m(-2)s(-1)), where only the 2-apical buds grew out, both in low (0.25 mM) and high (12.25 mM) nitrate. In contrast, in high light (453 μmol m(-2)s(-1)), the apical control only operates in low nitrate while all the buds along the stem grew out when the plant was supplied with a high level of nitrate. We found a decreasing photosynthetic activity from the top to the base of the plant concomitant with a light gradient along the stem. The quantity of sucrose, fructose, glucose and starch are higher in high light conditions in leaves and stem. The expression of the sucrose transporter RhSUC2 was higher in internodes and buds in this lighting condition, suggesting an increased capacity for sucrose transport. We propose that light intensity and nitrogen availability both contribute to the establishment of apical control.

  4. Cochlear outer hair cells undergo an apical circumference remodeling constrained by the hair bundle shape.

    PubMed

    Etournay, Raphaël; Lepelletier, Léa; Boutet de Monvel, Jacques; Michel, Vincent; Cayet, Nadège; Leibovici, Michel; Weil, Dominique; Foucher, Isabelle; Hardelin, Jean-Pierre; Petit, Christine

    2010-04-01

    Epithelial cells acquire diverse shapes relating to their different functions. This is particularly relevant for the cochlear outer hair cells (OHCs), whose apical and basolateral shapes accommodate the functioning of these cells as mechano-electrical and electromechanical transducers, respectively. We uncovered a circumferential shape transition of the apical junctional complex (AJC) of OHCs, which occurs during the early postnatal period in the mouse, prior to hearing onset. Geometric analysis of the OHC apical circumference using immunostaining of the AJC protein ZO1 and Fourier-interpolated contour detection characterizes this transition as a switch from a rounded-hexagon to a non-convex circumference delineating two lateral lobes at the neural side of the cell, with a negative curvature in between. This shape tightly correlates with the 'V'-configuration of the OHC hair bundle, the apical mechanosensitive organelle that converts sound-evoked vibrations into variations in cell membrane potential. The OHC apical circumference remodeling failed or was incomplete in all the mouse mutants affected in hair bundle morphogenesis that we tested. During the normal shape transition, myosin VIIa and myosin II (A and B isoforms) displayed polarized redistributions into and out of the developing lobes, respectively, while Shroom2 and F-actin transiently accumulated in the lobes. Defects in these redistributions were observed in the mutants, paralleling their apical circumference abnormalities. Our results point to a pivotal role for actomyosin cytoskeleton tensions in the reshaping of the OHC apical circumference. We propose that this remodeling contributes to optimize the mechanical coupling between the basal and apical poles of mature OHCs.

  5. Isotropic actomyosin dynamics promote organization of the apical cell cortex in epithelial cells

    PubMed Central

    Klingner, Christoph; Cherian, Anoop V.; Fels, Johannes; Diesinger, Philipp M.; Aufschnaiter, Roland; Maghelli, Nicola; Keil, Thomas; Beck, Gisela; Tolić-Nørrelykke, Iva M.; Bathe, Mark

    2014-01-01

    Although cortical actin plays an important role in cellular mechanics and morphogenesis, there is surprisingly little information on cortex organization at the apical surface of cells. In this paper, we characterize organization and dynamics of microvilli (MV) and a previously unappreciated actomyosin network at the apical surface of Madin–Darby canine kidney cells. In contrast to short and static MV in confluent cells, the apical surfaces of nonconfluent epithelial cells (ECs) form highly dynamic protrusions, which are often oriented along the plane of the membrane. These dynamic MV exhibit complex and spatially correlated reorganization, which is dependent on myosin II activity. Surprisingly, myosin II is organized into an extensive network of filaments spanning the entire apical membrane in nonconfluent ECs. Dynamic MV, myosin filaments, and their associated actin filaments form an interconnected, prestressed network. Interestingly, this network regulates lateral mobility of apical membrane probes such as integrins or epidermal growth factor receptors, suggesting that coordinated actomyosin dynamics contributes to apical cell membrane organization. PMID:25313407

  6. Proliferative effects of apical, but not basal, matrix metalloproteinase-7 activity in polarized MDCK cells

    SciTech Connect

    Harrell, Permila C.; McCawley, Lisa J.; Fingleton, Barbara; McIntyre, J. Oliver; Matrisian, Lynn M. . E-mail: lynn.matrisian@vanderbilt.edu

    2005-02-15

    Matrix metalloproteinase-7 (MMP-7) is primarily expressed in glandular epithelium. Therefore, its mechanism of action may be influenced by its regulated vectorial release to either the apical and/or basolateral compartments, where it would act on its various substrates. To gain a better understanding of where MMP-7 is released in polarized epithelium, we have analyzed its pattern of secretion in polarized MDCK cells expressing stably transfected human MMP-7 (MDCK-MMP-7), and HCA-7 and Caco2 human colon cancer cell lines. In all cell lines, latent MMP-7 was secreted to both cellular compartments, but was 1.5- to 3-fold more abundant in the basolateral compartment as compared to the apical. However, studies in the MDCK system demonstrated that MMP-7 activity was 2-fold greater in the apical compartment of MDCK-MMP-7{sup HIGH}-polarized monolayers, which suggests the apical co-release of an MMP-7 activator. In functional assays, MMP-7 over-expression increased cell saturation density as a result of increased cell proliferation with no effect on apoptosis. Apical MMP-7 activity was shown to be responsible for the proliferative effect, which occurred, as demonstrated by media transfer experiments, through cleavage of an apical substrate and not through the generation of a soluble factor. Taken together, our findings demonstrate the importance of MMP-7 secretion in relation to its mechanism of action when expressed in a polarized epithelium.

  7. Clathrin and AP-1 regulate apical polarity and lumen formation during C. elegans tubulogenesis

    PubMed Central

    Zhang, Hongjie; Kim, Ahlee; Abraham, Nessy; Khan, Liakot A.; Hall, David H.; Fleming, John T.; Gobel, Verena

    2012-01-01

    Clathrin coats vesicles in all eukaryotic cells and has a well-defined role in endocytosis, moving molecules away from the plasma membrane. Its function on routes towards the plasma membrane was only recently appreciated and is thought to be limited to basolateral transport. Here, an unbiased RNAi-based tubulogenesis screen identifies a role of clathrin (CHC-1) and its AP-1 adaptor in apical polarity during de novo lumenal membrane biogenesis in the C. elegans intestine. We show that CHC-1/AP-1-mediated polarized transport intersects with a sphingolipid-dependent apical sorting process. Depleting each presumed trafficking component mislocalizes the same set of apical membrane molecules basolaterally, including the polarity regulator PAR-6, and generates ectopic lateral lumens. GFP::CHC-1 and BODIPY-ceramide vesicles associate perinuclearly and assemble asymmetrically at polarized plasma membrane domains in a co-dependent and AP-1-dependent manner. Based on these findings, we propose a trafficking pathway for apical membrane polarity and lumen morphogenesis that implies: (1) a clathrin/AP-1 function on an apically directed transport route; and (2) the convergence of this route with a sphingolipid-dependent apical trafficking path. PMID:22535410

  8. aPKC Phosphorylation of Bazooka Defines the Apical/Lateral Border in Drosophila Epithelial Cells

    PubMed Central

    Morais-de-Sá, Eurico; Mirouse, Vincent; St Johnston, Daniel

    2010-01-01

    Summary Bazooka (PAR-3), PAR-6, and aPKC form a complex that plays a key role in the polarization of many cell types. In epithelial cells, however, Bazooka localizes below PAR-6 and aPKC at the apical/lateral junction. Here, we show that Baz is excluded from the apical aPKC domain in epithelia by aPKC phosphorylation, which disrupts the Baz/aPKC interaction. Removal of Baz from the complex is epithelial-specific because it also requires the Crumbs complex, which prevents the Baz/PAR-6 interaction. In the absence of Crumbs or aPKC phosphorylation of Baz, mislocalized Baz recruits adherens junction components apically, leading to a loss of the apical domain and an expansion of lateral. Thus, apical exclusion of Baz by Crumbs and aPKC defines the apical/lateral border. Although Baz acts as an aPKC targeting and specificity factor in nonepithelial cells, our results reveal that it performs a complementary function in positioning the adherens junction in epithelia. PMID:20434988

  9. Vangl2 cooperates with Rab11 and Myosin V to regulate apical constriction during vertebrate gastrulation

    PubMed Central

    Ossipova, Olga; Chuykin, Ilya; Chu, Chih-Wen; Sokol, Sergei Y.

    2015-01-01

    Core planar cell polarity (PCP) proteins are well known to regulate polarity in Drosophila and vertebrate epithelia; however, their functions in vertebrate morphogenesis remain poorly understood. In this study, we describe a role for PCP signaling in the process of apical constriction during Xenopus gastrulation. The core PCP protein Vangl2 is detected at the apical surfaces of cells at the blastopore lip, and it functions during blastopore formation and closure. Further experiments show that Vangl2, as well as Daam1 and Rho-associated kinase (Rock), regulate apical constriction of bottle cells at the blastopore and ectopic constriction of ectoderm cells triggered by the actin-binding protein Shroom3. At the blastopore lip, Vangl2 is required for the apical accumulation of the recycling endosome marker Rab11. We also show that Rab11 and the associated motor protein Myosin V play essential roles in both endogenous and ectopic apical constriction, and might be involved in Vangl2 trafficking to the cell surface. Overexpression of Rab11 RNA was sufficient to partly restore normal blastopore formation in Vangl2-deficient embryos. These observations suggest that Vangl2 affects Rab11 to regulate apical constriction during blastopore formation. PMID:25480917

  10. Defective calmodulin-dependent rapid apical endocytosis in zebrafish sensory hair cell mutants.

    PubMed

    Seiler, C; Nicolson, T

    1999-11-15

    Vertebrate mechanosensory hair cells contain a narrow "pericuticular" zone which is densely populated with small vesicles between the cuticular plate and cellular junctions near the apical surface. The presence of many cytoplasmic vesicles suggests that the apical surface of hair cells has a high turnover rate. The significance of intense membrane trafficking at the apical surface is not known. Using a marker of endocytosis, the styryl dye FM1-43, this report shows that rapid apical endocytosis in zebrafish lateral line sensory hair cells is calcium and calmodulin dependent and is partially blocked by the presence of amiloride and dihydrostreptomycin, known inhibitors of mechanotransduction channels. As seen in lateral line hair cells, sensory hair cells within the larval otic capsule also exhibit rapid apical endocytosis. Defects in internalization of the dye in both lateral line and inner ear hair cells were found in five zebrafish auditory/vestibular mutants: sputnik, mariner, orbiter, mercury, and skylab. In addition, lateral line hair cells in these mutants were not sensitive to prolonged exposure to streptomycin, which is toxic to hair cells. The presence of endocytic defects in the majority of zebrafish mechanosensory mutants points to a important role of apical endocytosis in hair cell function. PMID:10526320

  11. Laser-zone growth in a Ribbon-To-Ribbon (RTR) process. Silicon sheet growth development for the large area sheet task of the low-cost solar array project

    NASA Technical Reports Server (NTRS)

    Baghdadi, A.; Gurtler, R. W.; Legge, R.; Sopori, B.; Ellis, R. J.

    1978-01-01

    A new calculation of the effects of thermal stresses during growth on silicon ribbon quality is reported. Thermal stress distributions are computed for ribbon growth under a variety of temperature profiles. A growth rate of 55 cu cm/min with a single ribbon was achieved. The growth of RTR ribbon with a fairly uniform parallel dendritic structure was demonstrated. Results with two approaches were obtained for reducing the Mo impurity level in polycrystalline feedstock. Coating the Mo substrate with Si3N4 does not effect thermal shear separation of the polyribbon; this process shows promise of improving cell efficiency and also increasing the useful life of the molybdenum substrate. A number of solar cells were fabricated on RTR silicon grown from CVD feedstock.

  12. Automated solar module assembly line

    NASA Technical Reports Server (NTRS)

    Bycer, M.

    1980-01-01

    The solar module assembly machine which Kulicke and Soffa delivered under this contract is a cell tabbing and stringing machine, and capable of handling a variety of cells and assembling strings up to 4 feet long which then can be placed into a module array up to 2 feet by 4 feet in a series of parallel arrangement, and in a straight or interdigitated array format. The machine cycle is 5 seconds per solar cell. This machine is primarily adapted to 3 inch diameter round cells with two tabs between cells. Pulsed heat is used as the bond technique for solar cell interconnects. The solar module assembly machine unloads solar cells from a cassette, automatically orients them, applies flux and solders interconnect ribbons onto the cells. It then inverts the tabbed cells, connects them into cell strings, and delivers them into a module array format using a track mounted vacuum lance, from which they are taken to test and cleaning benches prior to final encapsulation into finished solar modules. Throughout the machine the solar cell is handled very carefully, and any contact with the collector side of the cell is avoided or minimized.

  13. Visualization and prediction of porosity in roller compacted ribbons with near-infrared chemical imaging (NIR-CI).

    PubMed

    Khorasani, M; Amigo, J M; Sonnergaard, J; Olsen, P; Bertelsen, P; Rantanen, J

    2015-05-10

    The porosity of roller compacted ribbon is recognized as an important critical quality attribute which has a huge impact on the final product quality. The purpose of this study was to investigate the use of near-infrared chemical imaging (NIR-CI) for porosity estimation of ribbons produced at different roll pressures. Two off-line methods were utilized as reference methods. The relatively fast method (oil absorption) was comparable with the more time-consuming mercury intrusion method (R(2)=0.98). Therefore, the oil method was selected as the reference off line method. It was confirmed by both reference methods that ribbons compressed at a higher pressure resulted in a lower mean porosity. Using NIR-CI in combination with multivariate data analysis it was possible to visualize and predict the porosity distribution of the ribbons. This approach is considered important for process monitoring and control of continuously operating roller compaction line. PMID:25746502

  14. 78 FR 26614 - Narrow Woven Ribbon With Woven Selvedge From the People's Republic of China: Rescission of...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-05-07

    ... International Trade Administration Narrow Woven Ribbon With Woven Selvedge From the People's Republic of China: Rescission of Antidumping Duty Administrative Review; 2011-2012 AGENCY: Import Administration, International... Robert Bolling, AD/ CVD Operations, Office 4, Import Administration, International Trade...

  15. 78 FR 14963 - Narrow Woven Ribbons With Woven Selvedge From Taiwan: Rescission, in Part, of Antidumping Duty...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-03-08

    ... International Trade Administration Narrow Woven Ribbons With Woven Selvedge From Taiwan: Rescission, in Part, of Antidumping Duty Administrative Review AGENCY: Import Administration, International Trade Administration... Eastwood or David Crespo, AD/CVD Operations, Office 2, Import Administration, International...

  16. Large magnetoresistance in highly textured Mn44.7Ni43.5Sn11.8 melt spun ribbons

    NASA Astrophysics Data System (ADS)

    Chen, Fenghua; Huang, Qingxue; Jiang, Zhengyi; Xuan, Haicheng; Zhang, Mingang; Xu, Xiaohong; Zhao, Jingwei

    2016-05-01

    Highly textured Heusler alloy Mn44.7Ni43.5Sn11.8 ribbons were prepared by melt spinning. The magnetoresistance (MR) properties were evaluated by the magnetic field perpendicular to the ribbon surface with the field up to 30 kOe. A large MR (about 25%) with a lower magnetic field (10 kOe) was obtained at 276 K. Due to the rapid solidification. The ribbons with a specific texture can get a large MR twice than polycrystalline alloys at the same magnetic field. The highly textured Mn-Ni-Sn melt spun ribbons may be broadly applied in magnetic memory and as temperature and magnetic sensors as well.

  17. Illustration of the development of bacterial cellulose bundles/ribbons by Gluconacetobacter xylinus via atomic force microscopy.

    PubMed

    Zhang, Kai

    2013-05-01

    The development of bacterial cellulose (BC) fibrils biosynthesized by Gluconacetobacter xylinus was investigated using atomic force microscopy (AFM). After various incubation times at 30 °C, both the length of BC fibrils and their average diameters increased significantly. After the first 2-h incubation, not only single BC microfibrils with an average diameter of 5.8 ± 0.7 nm were biosynthesized but single microfibrils also began to bind with each other forming bundles. After longer incubation times of 6 h, 16 h, and 48 h, only BC bundles and ribbons or even only ribbons were detectable. The development of BC fibrils and the formation of BC bundles/ribbons along with the biosynthesis time were illustrated using AFM. Furthermore, single BC fibrils were twisted in a right-handed manner. The twisting of BC fibrils possibly promoted the formation of bigger ribbons.

  18. Structure of FitAB from Neisseria gonorrhoeae bound to DNA reveals a tetramer of toxin-antitoxin heterodimers containing pin domains and ribbon-helix-helix motifs.

    PubMed

    Mattison, Kirsten; Wilbur, J Scott; So, Magdalene; Brennan, Richard G

    2006-12-01

    Neisseria gonorrhoeae is a sexually transmitted pathogen that initiates infections in humans by adhering to the mucosal epithelium of the urogenital tract. The bacterium then enters the apical region of the cell and traffics across the cell to exit into the subepithelial matrix. Mutations in the fast intracellular trafficking (fitAB) locus cause the bacteria to transit a polarized epithelial monolayer more quickly than the wild-type parent and to replicate within cells at an accelerated rate. Here, we describe the crystal structure of the toxin-antitoxin heterodimer, FitAB, bound to a high affinity 36-bp DNA fragment from the fitAB promoter. FitA, the antitoxin, binds DNA through its ribbon-helix-helix motif and is tethered to FitB, the toxin, to form a heterodimer by the insertion of a four turn alpha-helix into an extensive FitB hydrophobic pocket. FitB is composed of a PIN (PilT N terminus) domain, with a central, twisted, 5-stranded parallel beta-sheet that is open on one side and flanked by five alpha-helices. FitB in the context of the FitAB complex does not display nuclease activity against tested PIN substrates. The FitAB complex points to the mechanism by which antitoxins with RHH motifs can block the activity of toxins with PIN domains. Interactions between two FitB molecules result in the formation of a tetramer of FitAB heterodimers, which binds to the 36-bp DNA fragment and provides an explanation for how FitB enhances the DNA binding affinity of FitA. PMID:16982615

  19. Release of Apical Dominance in Potato Tuber Is Accompanied by Programmed Cell Death in the Apical Bud Meristem[C][W

    PubMed Central

    Teper-Bamnolker, Paula; Buskila, Yossi; Lopesco, Yael; Ben-Dor, Shifra; Saad, Inbal; Holdengreber, Vered; Belausov, Eduard; Zemach, Hanita; Ori, Naomi; Lers, Amnon; Eshel, Dani

    2012-01-01

    Potato (Solanum tuberosum) tuber, a swollen underground stem, is used as a model system for the study of dormancy release and sprouting. Natural dormancy release, at room temperature, is initiated by tuber apical bud meristem (TAB-meristem) sprouting characterized by apical dominance (AD). Dormancy is shortened by treatments such as bromoethane (BE), which mimics the phenotype of dormancy release in cold storage by inducing early sprouting of several buds simultaneously. We studied the mechanisms governing TAB-meristem dominance release. TAB-meristem decapitation resulted in the development of increasing numbers of axillary buds with time in storage, suggesting the need for autonomous dormancy release of each bud prior to control by the apical bud. Hallmarks of programmed cell death (PCD) were identified in the TAB-meristems during normal growth, and these were more extensive when AD was lost following either extended cold storage or BE treatment. Hallmarks included DNA fragmentation, induced gene expression of vacuolar processing enzyme1 (VPE1), and elevated VPE activity. VPE1 protein was semipurified from BE-treated apical buds, and its endogenous activity was fully inhibited by a cysteinyl aspartate-specific protease-1-specific inhibitor N-Acetyl-Tyr-Val-Ala-Asp-CHO (Ac-YVAD-CHO). Transmission electron microscopy further revealed PCD-related structural alterations in the TAB-meristem of BE-treated tubers: a knob-like body in the vacuole, development of cytoplasmic vesicles, and budding-like nuclear segmentations. Treatment of tubers with BE and then VPE inhibitor induced faster growth and recovered AD in detached and nondetached apical buds, respectively. We hypothesize that PCD occurrence is associated with the weakening of tuber AD, allowing early sprouting of mature lateral buds. PMID:22362870

  20. Data Set of Flare-Ribbon Reconnected Magnetic Fluxes: A Critical Tool for Understanding Solar Flares and Eruptions

    NASA Astrophysics Data System (ADS)

    Kazachenko, M.; Lynch, B. J.; Welsch, B. T.

    2015-12-01

    Flare ribbons are emission structures that are frequently observed during flares in transition-region and chromospheric radiation. These typically straddle a polarity inversion line (PIL) of the radial magnetic field at the photosphere, and move apart as the flare progresses. The ribbon flux - the amount of unsigned photospheric magnetic flux swept out by flare ribbons - is thought to be related to the amount coronal magnetic reconnection, and hence provides a key diagnostic tool for understanding the physical processes at work in flares and CMEs. Previous measurements of the magnetic flux swept out by flare ribbons required time-consuming co-alignment between magnetograph and intensity data from different instruments, explaining why those studies only analyzed, at most, a few events. The launch of the Helioseismic and Magnetic Imager (HMI) and the Atmospheric Imaging Assembly (AIA), both aboard the Solar Dynamics Observatory (SDO), presented a rare opportunity to compile a much larger sample of flare-ribbon events than could readily be assembled before. We created a dataset of 141 events of both flare ribbon positions and fluxes, as a function of time, for all C9.-class and greater flares within 45 degrees of disk center observed by SDO from January 2013 till April 2015. For this purpose, we used vector magnetograms (2D magnetic field maps) from HMI and UV images from AIA. A critical problem with using unprocessed AIA data is the existence of spurious intensities in AIA data associated with strong flare emission, most notably "blooming" (spurious smearing of saturated signal into neighboring pixels, often in streaks). To overcome this difficulty, we have developed an algorithmic procedure that effectively excludes artifacts like blooming. We present our database and compare statistical properties of flare ribbons, e.g. evolutions of ribbon reconnection fluxes and reconnection flux rates, with the properties from theoretical models.