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Sample records for linker-assisted filament aggregation

  1. Atomic Force Microscopy Imaging of Filamentous Aggregates from an N-Terminal Peptide Fragment of Barnase

    NASA Astrophysics Data System (ADS)

    Shibata-Seki, Teiko; Masai, Junji; Yoshida, Kenji; Sato, Kazuki; Yanagawa, Hiroshi

    1993-06-01

    This paper reports the atomic force microscopy (AFM) imaging of filamentous aggregates derived from an N-terminal peptide fragment of barnase, a ribonuclease from Bacillus amyloliquefaciens. The sample was deposited on a freshly cleaved mica surface and observed in ambient conditions. The overall shapes of the filamentous structures imaged with two different kinds of AFMs were similar to those obtained with a transmission electron microscope (TEM), except that the filaments in AFM images were broader than those in TEM images. This broadening phenomenon characteristic of AFM images was explained in terms of the convolution-type distortion of the specimen diameter by the scanning-tip apex.

  2. Expression of Cardamom mosaic virus coat protein in Escherichia coli and its assembly into filamentous aggregates.

    PubMed

    Jacob, Thomas; Usha, R

    2002-06-01

    Cardamom mosaic virus (CdMV), a member of the genus Macluravirus of Potyviridae, causes a mosaic disease in cardamom. A polyclonal antiserum was raised against the purified virus and IgG was prepared. Electron microscopic studies on the purified virus showed flexuous filamentous particles of approximately 800 nm in length, typical of members of Potyviridae. The coat protein (CP) encoding sequence of the virus was expressed in Escherichia coli and the protein purified by affinity chromatography under denaturing conditions. The viral nature of the expressed CP was confirmed by positive reaction with anti CdMV IgG in a Western blot. The expressed CP aggregated irreversibly upon renaturation at concentrations above 0.07 mg/ml. The expression of the CP led to the formation of filamentous aggregates in E. coli as observed by immuno-gold electron microscopy. The filamentous aggregates were of 100-150 nm in length. Immuno-capture RT-PCR confirmed the absence of coat protein mRNA in the filamentous aggregates. Deletion mutations, which were expected to inhibit virus assembly, were introduced in the core region of the coat protein. However, these mutations did not improve the solubility of the CP in non-denaturing buffers.

  3. Metal ion-induced lateral aggregation of filamentous viruses fd and M13.

    PubMed Central

    Tang, Jay X; Janmey, Paul A; Lyubartsev, Alexander; Nordenskiöld, Lars

    2002-01-01

    We report a detailed comparison between calculations of inter-filament interactions based on Monte-Carlo simulations and experimental features of lateral aggregation of bacteriophages fd and M13 induced by a number of divalent metal ions. The general findings are consistent with the polyelectrolyte nature of the virus filaments and confirm that the solution electrostatics account for most of the experimental features observed. One particularly interesting discovery is resolubilization for bundles of either fd or M13 viruses when the concentration of the bundle-inducing metal ion Mg(2+) or Ca(2+) is increased to large (>100 mM) values. In the range of Mg(2+) or Ca(2+) concentrations where large bundles of the virus filaments are formed, the optimal attractive interaction energy between the virus filaments is estimated to be on the order of 0.01 kT per net charge on the virus surface when a recent analytical prediction to the experimentally defined conditions of resolubilization is applied. We also observed qualitatively distinct behavior between the alkali-earth metal ions and the divalent transition metal ions in their action on the charged viruses. The understanding of metal ions-induced reversible aggregation based on solution electrostatics may lead to potential applications in molecular biology and medicine. PMID:12080143

  4. The specificity of the interaction between αB-crystallin and desmin filaments and its impact on filament aggregation and cell viability

    PubMed Central

    Elliott, Jayne L.; Der Perng, Ming; Prescott, Alan R.; Jansen, Karin A.; Koenderink, Gijsje H.; Quinlan, Roy A.

    2013-01-01

    CRYAB (αB-crystallin) is expressed in many tissues and yet the R120G mutation in CRYAB causes tissue-specific pathologies, namely cardiomyopathy and cataract. Here, we present evidence to demonstrate that there is a specific functional interaction of CRYAB with desmin intermediate filaments that predisposes myocytes to disease caused by the R120G mutation. We use a variety of biochemical and biophysical techniques to show that plant, animal and ascidian small heat-shock proteins (sHSPs) can interact with intermediate filaments. Nevertheless, the mutation R120G in CRYAB does specifically change that interaction when compared with equivalent substitutions in HSP27 (R140G) and into the Caenorhabditis elegans HSP16.2 (R95G). By transient transfection, we show that R120G CRYAB specifically promotes intermediate filament aggregation in MCF7 cells. The transient transfection of R120G CRYAB alone has no significant effect upon cell viability, although bundling of the endogenous intermediate filament network occurs and the mitochondria are concentrated into the perinuclear region. The combination of R120G CRYAB co-transfected with wild-type desmin, however, causes a significant reduction in cell viability. Therefore, we suggest that while there is an innate ability of sHSPs to interact with and to bind to intermediate filaments, it is the specific combination of desmin and CRYAB that compromises cell viability and this is potentially the key to the muscle pathology caused by the R120G CRYAB. PMID:23530264

  5. Linker-assisted immunoassay and liquid chromatography/mass spectrometry for the analysis of glyphosate

    USGS Publications Warehouse

    Lee, E.A.; Zimmerman, L.R.; Bhullar, B.S.; Thurman, E.M.

    2002-01-01

    A novel, sensitive, linker-assisted enzyme-linked immunosorbent assay (L'ELISA) was compared to on-line solidphase extraction (SPE) with high-performance liquid chromatography/mass spectrometry (HPLC/MS) for the analysis of glyphosate in surface water and groundwater samples. The L'ELISA used succinic anhydride to derivatize glyphosate, which mimics the epitotic attachment of glyphosate to horseradish peroxidase hapten. Thus, L'ELISA recognized the derivatized glyphosate more effectively (detection limit of 0.1 μg/L) and with increased sensitivity (10-100 times) over conventional ELISA and showed the potential for other applications. The precision and accuracy of L'ELISA then was compared with on-line SPE/HPLC/MS, which detected glyphosate and its degradate derivatized with 9-fluorenylmethyl chloroformate using negative-ion electrospray (detection limit 0.1 μg/L, relative standard deviation ±15%). Derivatization efficiency and matrix effects were minimized by adding an isotope-labeled glyphosate (2-13C15N). The accuracy of L'ELISA gave a false positive rate of 18% between 0.1 and 1.0 μg/L and a false positive rate of only 1% above 1.0 μg/L. The relative standard deviation was ±20%. The correlation of L'ELISA and HPLC/MS for 66 surface water and groundwater samples was 0.97 with a slope of 1.28, with many detections of glyphosate and its degradate in surface water but not in groundwater.

  6. Aggregation of endosomal-vacuolar compartments in the Aovps24-deleted strain in the filamentous fungus Aspergillus oryzae

    SciTech Connect

    Tatsumi, Akinori; Shoji, Jun-ya; Kikuma, Takashi; Arioka, Manabu; Kitamoto, Katsuhiko

    2007-10-19

    Previously, we found that deletion of Aovps24, an ortholog of Saccharomyces cerevisiae VPS24, that encodes an ESCRT (endosomal sorting complex required for transport)-III component required for late endosomal function results in fragmented and aggregated vacuoles. Although defective late endosomal function is likely responsible for this phenotype, critical lack of our knowledge on late endosomes in filamentous fungi prevented us from further characterization. In this study, we identified late endosomes of Aspergillus oryzae, by expressing a series of fusion proteins of fluorescent proteins with orthologs of late endosomal proteins. Using these fusion proteins as markers, we observed late endosomes in the wild type strain and the Aovps24 disruptant and demonstrated that late endosomes are aberrantly aggregated in the Aovps24 disruptant. Moreover, we revealed that the aggregated late endosomes have features of vacuoles as well. As deletion of another ESCRT-III component-encoding gene, Aovps2, resulted in similar phenotypes to that in the Aovps24 disruptant, phenotypes of the Aovps24 disruptant are probably due to defective late endosomal function.

  7. Kinetic heterogeneity of F-actin polymers. Further evidence that the elongation reaction may occur through condensation of the actin filaments with small aggregates.

    PubMed Central

    Grazi, E; Magri, E

    1987-01-01

    We have shown that F-actin, polymerized in 50 mM-KCl at 20 degrees C and pH 8.0, can be resolved by centrifugation into two polymer populations, which differ morphologically as well as kinetically. The first population represents about 10% of the overall polymer and is composed of small amorphous aggregates. It rapidly exchanges the bound nucleotide with free ATP in the medium, either directly or through the monomers. The second population is composed of long actin filaments. These are labelled by free ATP in the medium only through condensation with labelled small amorphous aggregates. Images Fig. 1. PMID:3435480

  8. Fetal akinesia caused by a novel actin filament aggregate myopathy skeletal muscle actin gene (ACTA1) mutation.

    PubMed

    Stenzel, Werner; Prokop, Stefan; Kress, Wolfram; Huppmann, Stephanie; Loui, Andrea; Sarioglu, Nanette M E; Laing, Nigel G; Sparrow, John C; Heppner, Frank L; Goebel, Hans H

    2010-08-01

    We report a female newborn, diagnosed with fetal akinesia in utero, who died one hour after birth. Post-mortem muscle biopsy demonstrated actin-filament myopathy based on immunolabelling for sarcomeric actin, and large areas of filaments, without rod formation, ultrastructurally. Analysis of DNA extracted from the muscle disclosed a novel de novo heterozygous c.44G>A, GGC>GAC, 'p.Gly15Asp' mutation in the ACTA1 gene. Analysis of the location of the mutated amino-acid in the actin molecule suggests the mutation most likely causes abnormal nucleotide binding, and consequent pathological actin polymerization. This case emphasizes the association of fetal akinesia with actin-filament myopathy.

  9. The cytokeratin filament-aggregating protein filaggrin is the target of the so-called "antikeratin antibodies," autoantibodies specific for rheumatoid arthritis.

    PubMed Central

    Simon, M; Girbal, E; Sebbag, M; Gomès-Daudrix, V; Vincent, C; Salama, G; Serre, G

    1993-01-01

    In rheumatoid arthritis (RA), the high diagnostic value of serum antibodies to the stratum corneum of rat esophagus epithelium has been widely reported. These so-called "antikeratin antibodies," detected by indirect immunofluorescence, were found to be autoantibodies since they also labeled human epidermis. Despite their name, the actual target of these autoantibodies was not known. In this study, a 40-kD protein (designated as 40K), extracted from human epidermis and specifically immunodetected by 75% of RA sera, was purified and identified as a neutral/acidic isoform of basic filaggrin, a cytokeratin filament-aggregating protein, by peptide mapping studies and by the following evidences: (a) mAbs specific for filaggrin reacted with the 40K protein; (b) the autoantibodies, affinity-purified from RA sera on the 40K protein, immunodetected purified filaggrin; (c) the reactivity of RA sera to the 40K protein was abolished after immunoadsorption with purified filaggrin; (d) the 40K protein and filaggrin had similar amino acid compositions. Furthermore, autoantibodies against the 40K protein and the so-called "antikeratin antibodies" were shown, by immunoadsorption experiments, to be largely the same. The identification of filaggrin as a RA-specific autoantigen could contribute to the understanding of the pathogenesis of this disease and, ultimately, to the development of methods for preventing the autoimmune response. Images PMID:7690781

  10. Chaperonin filaments: The archael cytoskeleton

    SciTech Connect

    Trent, J.D.; Kagawa, H.K.; Yaoi, Takuro; Olle, E.; Zaluzec, N.J.

    1997-08-01

    Chaperonins are multi-subunit double-ring complexed composed of 60-kDa proteins that are believed to mediate protein folding in vivo. The chaperonins in the hyperthermophilic archaeon Sulfolobus shibatae are composed of the organism`s two most abundant proteins, which represent 4% of its total protein and have an intracellular concentration of {ge} 3.0 mg/ml. At concentrations of 1.0 mg/ml, purified chaperonin proteins aggregate to form ordered filaments. Filament formation, which requires Mg{sup ++} and nucleotide binding (not hydrolysis), occurs at physiological temperatures under conditions suggesting filaments may exist in vivo. If the estimated 4,600 chaperonins per cell, formed filaments in vivo, they could create a matrix of filaments that would span the diameter of an average S. shibatae cell 100 times. Direct observations of unfixed, minimally treated cells by intermediate voltage electron microscopy (300 kV) revealed an intracellular network of filaments that resembles chaperonin filaments produced in vitro. The hypothesis that the intracellular network contains chaperonins is supported by immunogold analyses. The authors propose that chaperonin activity may be regulated in vivo by filament formation and that chaperonin filaments may serve a cytoskeleton-like function in archaea and perhaps in other prokaryotes.

  11. The Many Fates of Retracting Newtonian Filaments

    NASA Astrophysics Data System (ADS)

    Anthony, Christopher; Thete, Sumeet; Harris, Michael; Basaran, Osman

    2016-11-01

    The retraction of Newtonian filaments plays a central role in applications as diverse as inkjet printing and atomization where formation of satellite droplets is undesirable. In order to avoid satellite drop production, filaments formed after drop, jet, or sheet breakup should contract to spheres without undergoing further pinch-off. Therefore, it is important to understand all of the dynamical responses that can arise during filament recoil. To accomplish this goal, we use high accuracy simulations to analyze the retraction of Newtonian filaments in a passive ambient fluid. Previously, Notz and Basaran described the fate of low-viscosity filaments. More recent works by Hoepffner and Pare on intermediate viscosity filaments and by Lohse et al. on high viscosity filaments have greatly enhanced our understanding of filament recoil. Unfortunately, taking all of these works in aggregate does not provide a comprehensive picture of filament dynamics. Here, we overcome the deficiencies of these earlier studies to provide a comprehensive analysis of filament recoil and arrive at a complete phase diagram of the system response. While doing so, we also uncover a new mode of filament breakup that has been missed by earlier investigators.

  12. Dynamics of heteromolecular filament formation

    NASA Astrophysics Data System (ADS)

    Dear, Alexander J.; Michaels, Thomas C. T.; Knowles, Tuomas P. J.

    2016-11-01

    The self-assembly of molecular building blocks into linear filaments is a common form of self-organization in nature and underlies the formation of supra-molecular polymers in a variety of contexts, including in both functional and aberrant biology. To date, attention has focused mainly on homomolecular assembly phenomena; however, it has recently become apparent that heteromolecular assemblies can be common, and, for instance, pathological protein filaments such as amyloid aggregates form in vivo in environments supporting copolymerization. Here, we present a general kinetic scheme for heteromolecular filament formation and derive closed-form analytical expressions that describe the dynamics of such systems. Our results reveal the existence of a demixing transition time controlled by the relative rates of depletion of the different aggregating species, after which predominantly homomolecular polymers are formed even when the initial solution is heteromolecular. Furthermore, these results may be applied to the analysis of experimental kinetic data on the aggregation of mixtures of proteins, to determine which fundamental reaction steps occur between unlike proteins, and to provide accurate estimates of their rate constants.

  13. Collaborative protein filaments.

    PubMed

    Ghosal, Debnath; Löwe, Jan

    2015-09-14

    It is now well established that prokaryotic cells assemble diverse proteins into dynamic cytoskeletal filaments that perform essential cellular functions. Although most of the filaments assemble on their own to form higher order structures, growing evidence suggests that there are a number of prokaryotic proteins that polymerise only in the presence of a matrix such as DNA, lipid membrane or even another filament. Matrix-assisted filament systems are frequently nucleotide dependent and cytomotive but rarely considered as part of the bacterial cytoskeleton. Here, we categorise this family of filament-forming systems as collaborative filaments and introduce a simple nomenclature. Collaborative filaments are frequent in both eukaryotes and prokaryotes and are involved in vital cellular processes including chromosome segregation, DNA repair and maintenance, gene silencing and cytokinesis to mention a few. In this review, we highlight common principles underlying collaborative filaments and correlate these with known functions.

  14. Filamentation in Laser Wakefields

    NASA Astrophysics Data System (ADS)

    Los, Eva; Trines, Raoul; Silva, Luis; Bingham, Robert

    2016-10-01

    Laser filamentation instability is observed in plasma wakefields with sub-critical densities, and in high density inertial fusion plasmas. This leads to non-uniform acceleration or compression respectively. Here, we present simulation results on laser filamentation in plasma wakefields. The 2-D simulations are carried out using the particle-in-cell code Osiris. The filament intensity was found to increase exponentially before saturating. The maximum amplitude to which the highest intensity filament grew for a specific set of parameters was also recorded, and plotted against a corresponding parameter value. Clear, positively correlated linear trends were established between plasma density, transverse wavenumber k, laser pulse amplitude and maximum filament amplitude. Plasma density and maximum filament amplitude also showed a positive correlation, which saturated after a certain plasma density. Pulse duration and interaction length did not affect either filament intensity or transverse k value in a predictable manner. There was no discernible trend between pulse amplitude and filament width.

  15. Filament Eruption Onset

    NASA Technical Reports Server (NTRS)

    Sterling, Alphonse C.; Moore, Ronald L.

    2011-01-01

    We have been investigating filament eruptions in recent years. Use filament eruptions as markers of the coronal field evolution. Data from SoHO, Yohkoh, TRACE, Hinode, and other sources. We and others have observed: (1)Filaments often show slow rise, followed by fast rise, (2) Brightenings, preflares, microflares during slow rise (3) Magnetic evolution in hours prior to eruption onset. We investigated What do Hinode and SDO show for filament eruptions?

  16. Physical principles of filamentous protein self-assembly kinetics

    NASA Astrophysics Data System (ADS)

    Michaels, Thomas C. T.; Liu, Lucie X.; Meisl, Georg; Knowles, Tuomas P. J.

    2017-04-01

    The polymerization of proteins and peptides into filamentous supramolecular structures is an elementary form of self-organization of key importance to the functioning biological systems, as in the case of actin biofilaments that compose the cellular cytoskeleton. Aberrant filamentous protein self-assembly, however, is associated with undesired effects and severe clinical disorders, such as Alzheimer’s and Parkinson’s diseases, which, at the molecular level, are associated with the formation of certain forms of filamentous protein aggregates known as amyloids. Moreover, due to their unique physicochemical properties, protein filaments are finding extensive applications as biomaterials for nanotechnology. With all these different factors at play, the field of filamentous protein self-assembly has experienced tremendous activity in recent years. A key question in this area has been to elucidate the microscopic mechanisms through which filamentous aggregates emerge from dispersed proteins with the goal of uncovering the underlying physical principles. With the latest developments in the mathematical modeling of protein aggregation kinetics as well as the improvement of the available experimental techniques it is now possible to tackle many of these complex systems and carry out detailed analyses of the underlying microscopic steps involved in protein filament formation. In this paper, we review some classical and modern kinetic theories of protein filament formation, highlighting their use as a general strategy for quantifying the molecular-level mechanisms and transition states involved in these processes.

  17. Physical principles of filamentous protein self-assembly kinetics.

    PubMed

    Michaels, Thomas; Liu, Xiaoxuan; Meisl, Georg; Knowles, Tuomas P J

    2017-02-07

    The polymerization of proteins and peptides into filamentous supramolecular structures is an elementary form of self-organization of key importance to the functioning biological systems, as in the case of actin biofilaments that compose the cellular cytoskeleton. Aberrant filamentous protein self-assembly, however, is associated with undesired effects and severe clinical disorders, such as Alzheimer's and Parkinson's diseases, which, at the molecular level, are associated with the formation of certain forms of filamentous protein aggregates known as amyloids. Moreover, due to their unique physicochemical properties, protein filaments are finding extensive applications as biomaterials for nanotechnology. With all these different factors at play, the field of filamentous protein self-assembly has experienced tremendous activity in recent years. A key question in this area has been to elucidate the microscopic mechanisms through which filamentous aggregates emerge from dispersed proteins with the goal of uncovering the underlying physical principles. With the latest developments in the mathematical modeling of protein aggregation kinetics as well as the improvement of the available experimental techniques it is now possible to tackle many of these complex systems and carry out detailed analyses of the underlying microscopic steps involved in protein filament formation. In this paper, we review some classical and modern kinetic theories of protein filament formation, highlighting their use as a general strategy for quantifying the molecular-level mechanisms and transition states involved in these processes.

  18. Special issue on filamentation

    NASA Astrophysics Data System (ADS)

    Li, Ruxin; Milchberg, Howard; Mysyrowicz, André

    2014-05-01

    Journal of Physics B: Atomic, Molecular and Optical Physics is delighted to announce a forthcoming special issue on filamentation, to appear in the spring of 2015, and invites you to submit a paper. This special issue will attempt to give an overview of the present status of this field in order to create synergies and foster future developments. The issue is open to papers on the following issues: Theoretical advances on filamentation. Self-focusing and collapse. Filamentation in various media. Pulse self-compression and ultrafast processes in filaments. Molecular alignment and rotation. Filamentation tailoring. Interaction between filaments. Filament weather and pollution control. Filament induced condensation and precipitation. Terahertz science with filaments. Lasing in filaments. Filament induced molecular excitation and reaction. Electric discharge and plasma. Cross-disciplinary applications. Novel concepts related to these topics are particularly welcome. Please submit your article by 1 October 2014 (expected web publication: spring 2015) using our website http://mc04.manuscriptcentral.com/jphysb-iop. Submissions received after this date will be considered for the journal, but may not be included in the special issue. The issue will be edited by Ruxin Li, Howard Milchberg and André Mysyrowicz.

  19. Large-Scale Patterns of Filament Channels and Filaments

    NASA Astrophysics Data System (ADS)

    Mackay, Duncan

    2016-07-01

    In this review the properties and large-scale patterns of filament channels and filaments will be considered. Initially, the global formation locations of filament channels and filaments are discussed, along with their hemispheric pattern. Next, observations of the formation of filament channels and filaments are described where two opposing views are considered. Finally, the wide range of models that have been constructed to consider the formation of filament channels and filaments over long time-scales are described, along with the origin of the hemispheric pattern of filaments.

  20. Tungsten Filament Fire

    ERIC Educational Resources Information Center

    Ruiz, Michael J.; Perkins, James

    2016-01-01

    We safely remove the outer glass bulb from an incandescent lamp and burn up the tungsten filament after the glass is removed. This demonstration dramatically illustrates the necessity of a vacuum or inert gas for the environment surrounding the tungsten filament inside the bulb. Our approach has added historical importance since the incandescent…

  1. Tungsten filament fire

    NASA Astrophysics Data System (ADS)

    Ruiz, Michael J.; Perkins, James

    2016-05-01

    We safely remove the outer glass bulb from an incandescent lamp and burn up the tungsten filament after the glass is removed. This demonstration dramatically illustrates the necessity of a vacuum or inert gas for the environment surrounding the tungsten filament inside the bulb. Our approach has added historical importance since the incandescent light bulb is being replaced by compact fluorescent and LED lamps.

  2. PDGF induces reorganization of vimentin filaments.

    PubMed

    Valgeirsdóttir, S; Claesson-Welsh, L; Bongcam-Rudloff, E; Hellman, U; Westermark, B; Heldin, C H

    1998-07-30

    In this study we demonstrate that stimulation with platelet-derived growth factor (PDGF) leads to a marked reorganization of the vimentin filaments in porcine aortic endothelial (PAE) cells ectopically expressing the PDGF beta-receptor. Within 20 minutes after stimulation, the well-spread fine fibrillar vimentin was reorganized as the filaments aggregated into a dense coil around the nucleus. The solubility of vimentin upon Nonidet-P40-extraction of cells decreased considerably after PDGF stimulation, indicating that PDGF caused a redistribution of vimentin to a less soluble compartment. In addition, an increased tyrosine phosphorylation of vimentin was observed. The redistribution of vimentin was not a direct consequence of its tyrosine phosphorylation, since treatment of cells with an inhibitor for the cytoplasmic tyrosine kinase Src, attenuated phosphorylation but not redistribution of vimentin. These changes in the distribution of vimentin occurred in conjunction with reorganization of actin filaments. In PAE cells expressing a Y740/751F mutant receptor that is unable to bind and activate phosphatidylinositol 3'-kinase (PI3-kinase), the distribution of vimentin was virtually unaffected by PDGF stimulation. Thus, PI3-kinase is important for vimentin reorganization, in addition to its previously demonstrated role in actin reorganization. The small GTPase Rac has previously been shown to be involved downstream of PI3-kinase in the reorganization of actin filaments. In PAE cells overexpressing dominant negative Rac1 (N17Rac1), no change in the fine fibrillar vimentin network was seen after PDGF-BB stimulation, whereas in PAE cells overexpressing constitutively active Rac1 (V12Rac1), there was a dramatic change in vimentin filament organization independent of PDGF stimulation. These data indicate that PDGF causes a reorganization of microfilaments as well as intermediate filaments in its target cells and suggest an important role for Rac downstream of PI3-kinase in

  3. Coexistence of two types of metal filaments in oxide memristors

    NASA Astrophysics Data System (ADS)

    Xu, D.; Shangguan, X. N.; Wang, S. M.; Cao, H. T.; Liang, L. Y.; Zhang, H. L.; Gao, J. H.; Long, W. M.; Wang, J. R.; Zhuge, F.

    2017-02-01

    One generally considers the conducting filament in ZnO-based valence change memristors (VCMs) as an aggregation of oxygen vacancies. Recently, the transmission electron microscopy observation showed the filament is composed of a Zn-dominated ZnOx. In this study, careful analysis of the temperature dependence of the ON state resistance demonstrates that the formation/rupture of a Zn filament is responsible for the resistive switching in ZnO VCMs. Cu/ZnO/Pt memristive devices can be operated in both VCM and ECM (electrochemical metallization memristor) modes by forming different metal filaments including Cu, Zn and a coexistence of these two filaments. The device operation can be reversibly switched between ECM and VCM modes. The dual mode operation capability of Cu/ZnO/Pt provides a wide choice of select devices for constructing memristive crossbar architectures.

  4. Deletions in epidermal keratins leading to alterations in filament organization in vivo and in intermediate filament assembly in vitro

    PubMed Central

    1990-01-01

    To investigate the sequences important for assembly of keratins into 10- nm filaments, we used a combined approach of (a) transfection of mutant keratin cDNAs into epithelial cells in vivo, and (b) in vitro assembly of mutant and wild-type keratins. Keratin K14 mutants missing the nonhelical carboxy- and amino-terminal domains not only integrated without perturbation into endogenous keratin filament networks in vivo, but they also formed 10-nm filaments with K5 in vitro. Surprisingly, keratin mutants missing the highly conserved L L E G E sequence, common to all intermediate filament proteins and found at the carboxy end of the alpha-helical rod domain, also assembled into filaments with only a somewhat reduced efficiency. Even a carboxy K14 mutant missing approximately 10% of the rod assembled into filaments, although in this case filaments aggregated significantly. Despite the ability of these mutants to form filaments in vitro, they often perturbed keratin filament organization in vivo. In contrast, small truncations in the amino-terminal end of the rod domain more severely disrupted the filament assembly process in vitro as well as in vivo, and in particular restricted elongation. For both carboxy and amino rod deletions, the more extensive the deletion, the more severe the phenotype. Surprisingly, while elongation could be almost quantitatively blocked with large mutations, tetramer formation and higher ordered lateral interactions still occurred. Collectively, our in vitro data (a) provide a molecular basis for the dominance of our mutants in vivo, (b) offer new insights as to why different mutants may generate different phenotypes in vivo, and (c) delineate the limit sequences necessary for K14 to both incorporate properly into a preexisting keratin filament network in vivo and assemble efficiently into 10-nm keratin filaments in vitro. PMID:1702787

  5. Snake Filament Eruption

    NASA Video Gallery

    A very long solar filament that had been snaking around the Sun erupted on Dec. 6, 2010 with a flourish. NASA's Solar Dynamics Observatory (SDO) caught the action in dramatic detail in extreme ultr...

  6. Isolation and preliminary characterization of 10-nm filaments from baby hamster kidney (BHK-21) cells.

    PubMed Central

    Starger, J M; Goldman, R D

    1977-01-01

    A procedure for isolating 10-nm filaments as juxtanuclear caps from normal and colchicine-treated BHK-21 cells is described. These aggregates of 10-nm filaments retain their birefringence and their structural integrity. The major proteins comprising the filament preparations can be resolved as two bands on sodium dodecyl sulfate gels, corresponding to approximate molecular weights of 54,000 and 55,000. Images PMID:329284

  7. Construction aggregates

    USGS Publications Warehouse

    Tepordei, V.V.

    1995-01-01

    Part of the 1994 Industrial Minerals Review. The production, consumption, and applications of construction aggregates are reviewed. In 1994, the production of construction aggregates, which includes crushed stone and construction sand and gravel combined, increased 7.7 percent to 2.14 Gt compared with the previous year. These record production levels are mostly a result of funding for highway construction work provided by the Intermodal Surface Transportation Efficiency Act of 1991. Demand is expected to increase for construction aggregates in 1995.

  8. Characterization of HI Filaments

    NASA Astrophysics Data System (ADS)

    Lubar, Emily; Verschuur, Gerrit L.

    2017-01-01

    We characterized the properties of dramatic interstellar HI filaments to learn more about the dynamics and structure of such features. Using Gauss fitting software, we searched the Effelsburg-Bonn HI Survey data for indications of a simple twisting (toroidal) motion across these filaments. Instead, we found that the structure was more complicated than expected. Apparent angular widths of several filaments were measured using the Galactic Arecibo L-band Feed Array HI (GALFA-HI), Bonn, and Leident/Argentine/Bonn (LAB) surveys. Based on filament widths and other parameters, we conclude that magnetism is the dominant force opposing internal motion and maintaining the structure of these filaments. The apparent width as a function of beam width closely follows a relationship reported in 1993 for HI features in general. They tend to subtend an angle two times the beam width, suggesting that the features remain unresolved.The Arecibo Observatory is operated by SRI International under a cooperative agreement with the National Science Foundation (AST-1100968), and in alliance with Ana G. Méndez-Universidad Metropolitana, and the Universities Space Research Association. The Arecibo Observatory REU is funded under grant AST-1559849 to Universidad Metropolitana.

  9. Salt-induced aggregation of stiff polyelectrolytes.

    PubMed

    Fazli, Hossein; Mohammadinejad, Sarah; Golestanian, Ramin

    2009-10-21

    Molecular dynamics simulation techniques are used to study the process of aggregation of highly charged stiff polyelectrolytes due to the presence of multivalent salt. The dominant kinetic mode of aggregation is found to be the case of one end of one polyelectrolyte meeting others at right angles, and the kinetic pathway to bundle formation is found to be similar to that of flocculation dynamics of colloids as described by Smoluchowski. The aggregation process is found to favor the formation of finite bundles of 10-11 filaments at long times. Comparing the distribution of the cluster sizes with the Smoluchowski formula suggests that the energy barrier for the aggregation process is negligible. Also, the formation of long-lived metastable structures with similarities to the raft-like structures of actin filaments is observed within a range of salt concentration.

  10. Filamentous Influenza Viruses

    PubMed Central

    Badham, Matthew D.; Rossman, Jeremy S.

    2016-01-01

    Influenza A virus is a pathogen of global medical importance causing significant health and socio-economic costs every year. Influenza virus is an unusual pathogen in that it is pleomorphic, capable of forming virions ranging in shape from spherical to filamentous. Despite decades of research on the influenza virus, much remains unknown about the formation of filamentous influenza viruses and their role in the viral replication cycle. Here, we discuss what is known about influenza virus assembly and budding, focusing on the viral and host factors that are involved in the determination of viral morphology. Whilst the biological function of the filamentous morphology remains unknown, recent results suggest a role in facilitating viral spread in vivo. We discuss these results and speculate on the consequences of viral morphology during influenza virus infection of the human respiratory tract. PMID:28042529

  11. Aerogel-supported filament

    DOEpatents

    Wuest, C.R.; Tillotson, T.M.; Johnson, C.V. III

    1995-05-16

    The present invention is a thin filament embedded in a low density aerogel for use in radiation detection instruments and incandescent lamps. The aerogel provides a supportive matrix that is thermally and electrically nonconductive, mechanically strong, highly porous, gas-permeable, and transparent to ionizing radiation over short distances. A low density, open-cell aerogel is cast around a fine filament or wire, which allows the wire to be positioned with little or no tension and keeps the wire in place in the event of breakage. The aerogel support reduces the stresses on the wire caused by vibrational, gravitational, electrical, and mechanical forces. 6 Figs.

  12. Aerogel-supported filament

    DOEpatents

    Wuest, Craig R.; Tillotson, Thomas M.; Johnson, III, Coleman V.

    1995-01-01

    The present invention is a thin filament embedded in a low density aerogel for use in radiation detection instruments and incandescent lamps. The aerogel provides a supportive matrix that is thermally and electrically nonconductive, mechanically strong, highly porous, gas-permeable, and transparent to ionizing radiation over short distances. A low density, open-cell aerogel is cast around a fine filament or wire, which allows the wire to be positioned with little or no tension and keeps the wire in place in the event of breakage. The aerogel support reduces the stresses on the wire caused by vibrational, gravitational, electrical, and mechanical forces.

  13. Branching of keratin intermediate filaments.

    PubMed

    Nafeey, Soufi; Martin, Ines; Felder, Tatiana; Walther, Paul; Felder, Edward

    2016-06-01

    Keratin intermediate filaments (IFs) are crucial to maintain mechanical stability in epithelial cells. Since little is known about the network architecture that provides this stiffness and especially about branching properties of filaments, we addressed this question with different electron microscopic (EM) methods. Using EM tomography of high pressure frozen keratinocytes, we investigated the course of several filaments in a branching of a filament bundle. Moreover we found several putative bifurcations in individual filaments. To verify our observation we also visualized the keratin network in detergent extracted keratinocytes with scanning EM. Here bifurcations of individual filaments could unambiguously be identified additionally to bundle branchings. Interestingly, identical filament bifurcations were also found in purified keratin 8/18 filaments expressed in Escherichia coli which were reassembled in vitro. This excludes that an accessory protein contributes to the branch formation. Measurements of the filament cross sectional areas showed various ratios between the three bifurcation arms. This demonstrates that intermediate filament furcation is very different from actin furcation where an entire new filament is attached to an existing filament. Instead, the architecture of intermediate filament bifurcations is less predetermined and hence consistent with the general concept of IF formation.

  14. Electrical contact resistance in filaments

    NASA Astrophysics Data System (ADS)

    Wu, Xiang-Fa; Zhou, Zhengping; Zhou, Wang-Min

    2012-05-01

    Electrical contact resistance (ECR) influences the electrochemical performance of porous electrodes made of stacked discrete materials (e.g., carbon nanotubes, nanofibers, etc.) for use in supercapacitors and rechargeable batteries. This study establishes a simple elasticity-conductivity model for the ECR of filaments in adhesive contact. The elastic deformation and size of electrical contact zone of the filaments are determined by using an adhesive contact model of filaments, and the ECR of adhesive filaments is obtained in explicit form. Dependencies of the ECR upon the filament geometries, surface energy, and elasticity are examined.

  15. Solid friction between soft filaments.

    PubMed

    Ward, Andrew; Hilitski, Feodor; Schwenger, Walter; Welch, David; Lau, A W C; Vitelli, Vincenzo; Mahadevan, L; Dogic, Zvonimir

    2015-06-01

    Any macroscopic deformation of a filamentous bundle is necessarily accompanied by local sliding and/or stretching of the constituent filaments. Yet the nature of the sliding friction between two aligned filaments interacting through multiple contacts remains largely unexplored. Here, by directly measuring the sliding forces between two bundled F-actin filaments, we show that these frictional forces are unexpectedly large, scale logarithmically with sliding velocity as in solid-like friction, and exhibit complex dependence on the filaments' overlap length. We also show that a reduction of the frictional force by orders of magnitude, associated with a transition from solid-like friction to Stokes's drag, can be induced by coating F-actin with polymeric brushes. Furthermore, we observe similar transitions in filamentous microtubules and bacterial flagella. Our findings demonstrate how altering a filament's elasticity, structure and interactions can be used to engineer interfilament friction and thus tune the properties of fibrous composite materials.

  16. RecA-ssDNA filaments supercoil in the presence of single-stranded DNA-binding protein

    SciTech Connect

    Shi Weixian; Larson, Ronald G. . E-mail: rlarson@umich.edu

    2007-06-08

    Using atomic force microscopy (AFM), we find that RecA-single-stranded DNA (RecA-ssDNA) filaments, in the presence of single-stranded DNA-binding (SSB) protein, organize into left-handed bundles, which differ from the previously reported disordered aggregates formed when SSB is excluded from the reaction. In addition, we see both left- and right-handedness on bundles of two filaments. These two-filament supercoils, individual filaments, and other smaller bundles further organize into more complicated bundles, showing overall left-handedness which cannot be explained by earlier arguments that presumed supercoiling is absent in RecA-ssDNA filaments. This novel finding and our previous results regarding supercoiling of RecA-double-stranded DNA (RecA-dsDNA) filaments are, however, consistent with each other and can possibly be explained by the intrinsic tendency of RecA-DNA filaments, in their fully coated form, to order themselves into helical bundles, independent of the DNA inside the filaments (ssDNA or dsDNA). RecA-RecA interactions may dominate the bundling process, while the original conformation of DNA inside filaments and other factors (mechanical properties of filaments, concentration of filaments, and Mg{sup 2+} concentration) could contribute to the variation in the appearance and pitch of supercoils. The tendency of RecA-DNA filaments to form ordered supercoils and their presence during strand exchange suggest a possible biological importance of supercoiled filaments.

  17. Complex Flare Dynamics Initiated by a Filament-Filament Interaction

    NASA Astrophysics Data System (ADS)

    Zhu, Chunming; Liu, Rui; Alexander, David; Sun, Xudong; McAteer, James

    2015-04-01

    We report on a filament eruption that led to a relatively rare filament-filament interaction event. The filaments were located at different heights above the same segment of a circular polarity inversion line (PIL) around a condensed leading sunspot. The onset of the eruption of the lower of the two filaments was accompanied by a simultaneous descent of the upper filament resulting in a convergence and direct interaction of the two filaments. The interaction led to the subsequent merger of the filaments into a single magnetically complex structure that erupted to create a large solar flare and an array of complex dynamical activity. A hard X-ray coronal source and an associated enhancement of hot plasma are observed at the interface between the two interacting filaments. These phenomena are related to the production of a small C flare and the subsequent development of a much stronger M flare. Magnetic loop shrinkage and descending dark voids were observed at different locations as part of the large flare energy release giving us a unique insight into these dynamic flare phenomena.

  18. Filament wound structure and method

    DOEpatents

    Dritt, William S.; Gerth, Howard L.; Knight, Jr., Charles E.; Pardue, Robert M.

    1977-01-01

    The present invention relates to a filament wound spherical structure comprising a plurality of filament band sets disposed about the surface of a mandrel with each band of each set formed of a continuous filament circumferentially wound about the mandrel a selected number of circuits and with each circuit of filament being wound parallel to and contiguous with an immediate previously wound circuit. Each filament band in each band set is wound at the same helix angle from the axis of revolution of the mandrel and all of the bands of each set are uniformly distributed about the mandrel circumference. The pole-to-equator wall thickness taper associated with each band set, as several contiguous band sets are wound about the mandrel starting at the poles, is accumulative as the band sets are nested to provide a complete filament wound sphere of essentially uniform thickness.

  19. Predicting Solar Filament Eruptions with HEK Filament Metadata

    NASA Astrophysics Data System (ADS)

    Aggarwal, A.; Reeves, K.; Schanche, N.

    2015-12-01

    Solar filaments are cool, dark channels of partially-ionized plasma that lie above the chromosphere. Their structure follows the neutral line between local regions of opposite magnetic polarity. Previous research (e.g. Schmieder et al. 2013) has shown a positive correlation (80%) between the occurrence of filament eruptions and coronal mass ejections (CME's). If certain filament properties, such as length, chirality, and tilt, indicate a tendency towards filament eruptions, one may be able to further predict an oncoming CME. Towards this end, we present a novel algorithm based on spatiotemporal analysis that systematically correlates filament eruptions documented in the Heliophysics Event Knowledgebase (HEK) with HEK filaments that have been grouped together using a tracking algorithm developed at Georgia State University (e.g. Kempton et al. 2014). We also find filament tracks that are not correlated with eruptions to form a null data set in a similar fashion. Finally, we compare the metadata from erupting and non-erupting filament tracks to discover which filament properties may present signs of an eruption onset. Through statistical methods such as the two-sample Kolmogorov-Smirnov test and Random Forest Classifier, we find that a filament that is increasing in length or changing in tilt with respect to the equator may be a useful gauge to predict a filament eruption. However, the average values of length and tilt for both datasets follow similar distributions, leading us to conclude that these parameters do not indicate an eruption event. This work is supported by the NSF-REU solar physics program at SAO, grant number AGS-1263241, and NSF DIBBS grant number ACI-1443061.

  20. Tau Isoform Composition Influences Rate and Extent of Filament Formation*

    PubMed Central

    Zhong, Qi; Congdon, Erin E.; Nagaraja, Haikady N.; Kuret, Jeff

    2012-01-01

    The risk of developing tauopathic neurodegenerative disease depends in part on the levels and composition of six naturally occurring Tau isoforms in human brain. These proteins, which form filamentous aggregates in disease, vary only by the presence or absence of three inserts encoded by alternatively spliced exons 2, 3, and 10 of the Tau gene (MAPT). To determine the contribution of alternatively spliced segments to Tau aggregation propensity, the aggregation kinetics of six unmodified, recombinant human Tau isoforms were examined in vitro using electron microscopy assay methods. Aggregation propensity was then compared at the level of elementary rate constants for nucleation and extension phases. We found that all three alternatively spliced segments modulated Tau aggregation but through differing kinetic mechanisms that could synergize or compete depending on sequence context. Overall, segments encoded by exons 2 and 10 promoted aggregation, whereas the segment encoded by exon 3 depressed it with its efficacy dependent on the presence or absence of a fourth microtubule binding repeat. In general, aggregation propensity correlated with genetic risk reported for multiple tauopathies, implicating aggregation as one candidate mechanism rationalizing the correlation between Tau expression patterns and disease. PMID:22539343

  1. Current filamentation model for the Weibel/Filamentation instabilities

    NASA Astrophysics Data System (ADS)

    Ryu, Chang-Mo; Huynh, Cong Tuan; Kim, Chul Min

    2016-10-01

    A current filamentaion model for a nonrelativistic plasma with e +/e- beam has been presented together with PIC simulations, which can explain the mangetic field enhancement during the Weibel/ Filamentation instabilities. This filament model assumes the Hammer-Rostoker equilibrium. In addition, this model predicts preferential acceleration/deceleration for electron-ion plasmas depending on the injected beam to be e +/e-.

  2. Population balance modeling of the conidial aggregation of Aspergillus niger.

    PubMed

    Lin, P-J; Grimm, L H; Wulkow, M; Hempel, D C; Krull, R

    2008-02-01

    Numerous biotechnological production processes are based on the submerse cultivation of filamentous fungi. Process design, however, is often hampered by the complex growth pattern of these organisms. In the morphologic development of coagulating filamentous fungi, like Aspergillus niger, conidial aggregation is the first step of filamentous morphogenesis. For a proper description of this phenomenon it is necessary to characterize conidial populations. Kinetic studies performed with an in-line particle size analyzer suggested that two distinct aggregation steps have to be considered. The first step of conidial aggregation starts immediately after inoculation. Both the rate constants of formation and disintegration of aggregates have been determined by measuring the concentration of conidia at the beginning of the cultivation and the concentration of particles at steady state during the first hours of cultivation. In contrast to the first aggregation step, where the collision of conidia is presumed to be responsible for the process, the second aggregation step is thought to be initiated by germination of conidia. Growing hyphae provide additional surface for the attachment of non- germinated conidia, which leads to a strong decrease in particle concentration. The specific hyphal length growth rate and the ratio of particle concentration to the growing adhesion hyphal surface are decisive matters of the second aggregation step. Both aggregation steps can be described by population dynamics and simulated using the program package PARSIVAL (PARticle SIze eVALution) for the treatment of general particle population balances.

  3. Construction aggregates

    USGS Publications Warehouse

    Nelson, T.I.; Bolen, W.P.

    2007-01-01

    Construction aggregates, primarily stone, sand and gravel, are recovered from widespread naturally occurring mineral deposits and processed for use primarily in the construction industry. They are mined, crushed, sorted by size and sold loose or combined with portland cement or asphaltic cement to make concrete products to build roads, houses, buildings, and other structures. Much smaller quantities are used in agriculture, cement manufacture, chemical and metallurgical processes, glass production and many other products.

  4. Construction aggregates

    USGS Publications Warehouse

    Tepordei, V.V.

    1996-01-01

    Part of the Annual Commodities Review 1995. Production of construction aggregates such as crushed stone and construction sand and gravel showed a marginal increase in 1995. Most of the 1995 increases were due to funding for highway construction work. The major areas of concern to the industry included issues relating to wetlands classification and the classification of crystalline silica as a probable human carcinogen. Despite this, an increase in demand is anticipated for 1996.

  5. Metabolomics protocols for filamentous fungi.

    PubMed

    Gummer, Joel P A; Krill, Christian; Du Fall, Lauren; Waters, Ormonde D C; Trengove, Robert D; Oliver, Richard P; Solomon, Peter S

    2012-01-01

    Proteomics and transcriptomics are established functional genomics tools commonly used to study filamentous fungi. Metabolomics has recently emerged as another option to complement existing techniques and provide detailed information on metabolic regulation and secondary metabolism. Here, we describe broad generic protocols that can be used to undertake metabolomics studies in filamentous fungi.

  6. Surface manipulation of protein filaments

    NASA Astrophysics Data System (ADS)

    Kreplak, Laurent; Staple, Douglas; Loparic, Marko; Kreuzer, Hans-Juergen

    2009-03-01

    Within mammalian tissues, cells move by actively remodeling a dense network of collagen fibrils. In order to study this situation, we analyze the force response of two types of filamentous protein structures, desmin intermediate filaments 12 nm in diameter and collagen fibrils 80 nm in diameter. Both types of filaments were adsorbed at a solid-liquid interface and locally moved with an AFM tip at constant velocity against surface friction in the interfacial plane. In the case of collagen fibrils, that have an extensibility below 30% extension, we observed that microns long fibrils could be moved by the tip and deformed into shapes that could not be explain by the linear elastic theory for a stiff rod. In the case of desmin filaments that can be stretched up to 3.5 times there length, we observed local stretching of the filaments and discreet steps in the torsional force measured with the cantilever. In order to describe both types of filaments' behaviors, we described the protein filaments as a chain of beads of mass m linked together by a mass-less polymer linker. By solving the Newtonian equations of motions for the coupled beads in the presence of a point load and a viscous drag due to the surface-filament interactions we were able to reproduced our experimental data and extract information on friction.

  7. Magnetic Fields in Massive Filaments

    NASA Astrophysics Data System (ADS)

    Pillai, Thushara

    Magnetic fields pervade galaxies, shaping them from the largest scales to the smallest star forming scales. A firm understanding of their role is crucial to our understanding of the physics of ISM. A dominant phase of the ISM that has received considerable attention is that of filaments which are ubiquitous and dominate the mass reservoir in molecular clouds. Enormous progress has been made recently towards understanding filament properties. The next major step should be to understand the role of magnetic fields in filaments. We propose to take advantage of HAWC+ dust emission polarimeter now available on SOFIA to launch a pilot polarization study towards three major classes of filaments: (i) Pristine (ii) Hub-Filament systems and (iii) Perturbed. HAWC+ will trace the connection between the star forming cores and the filaments enveloping them. By covering a vast range in parameter space from quiescent to active filaments, we will be constraining the initial conditions prior to star formation, during star formation and after star formation (feedback from newly formed stars on their parent clouds.) The interpretation of observations will be supported by extensive custom-made numerical simulations of magnetized clouds and subsequent dust radiative transfer with various grain alignment mechanisms, as provided by collaborators. Combined, these observations will provide the first panoramic view of the magnetized nature of massive filaments in the ISM.

  8. Magnetic Fields in Massive Filaments

    NASA Astrophysics Data System (ADS)

    Pillai, G. S. Thushara

    2015-10-01

    Magnetic fields pervade galaxies, shaping them from the largest scales to the smallest star forming scales. A firm understanding of their role is crucial to our understanding of the physics of ISM. A dominant phase of the ISM that has received considerable attention is that of filaments which are ubiquitous and dominate the mass reservoir in molecular clouds. Enormous progress has been made recently towards understanding filament properties. The next major step should be to understand the role of magnetic fields in filaments. We propose to take advantage of HAWC+ dust emission polarimeter now available on SOFIA to launch a pilot polarization study towards three major classes of filaments: (i) Pristine (ii) Hub-Filament systems and (iii) Perturbed. HAWC+ will trace the connection between the star forming cores and the filaments enveloping them. By covering a vast range in parameter space from quiescent to active filaments, we will be constraining the initial conditions prior to star formation, during star formation and after star formation (feedback from newly formed stars on their parent clouds.) The interpretation of observations will be supported by extensive custom--made numerical simulations of magnetized clouds and subsequent dust radiative transfer with various grain alignment mechanisms, as provided by collaborators. Combined, these observations will provide the first panoramic view of the magnetized nature of massive filaments in the ISM.

  9. Filamentation in tokamaks

    SciTech Connect

    Cardozo, N.J.; Barth, C.J.; Chu, C.C.; Lok, J.; Montvai, A.; Oomens, A.A.; Peters, M.; Pijper, F.J.; de Rover, M.; Schueller, F.C.; Steenbakkers, M.F.; RTP team

    1995-09-01

    The relevance of a nest of toroidal flux surfaces as a paradigm of the magnetic topology of a tokamak plasma is challenged. High resolution Thomson scattering measurements of electron temperature and density in RTP show several hot filaments in the plasma center and sharp gradients near the sawtooth inversion radius and structures outside the sawtooth region under central ECH. In ohmic plasmas, too, the pressure and temperature profiles show significant bumps. These measurements give evidence of a complex magnetic topology. Transport in a medium with spatially strongly varying diffusivity is considered. It is shown that macroscopic transport is determined by the microscopic structure: a transport theory must predict this structure and the diffusivity in the insulating regions, while the {open_quote}turbulent{close_quote} diffusivity is irrelevant. A numerical approach to equilibria with broken surfaces is presented. {copyright} {ital 1995 American Institute of Physics.}

  10. Solid friction between soft filaments

    NASA Astrophysics Data System (ADS)

    Ward, Andrew; Hilitski, Feodor; Schwenger, Walter; Welch, David; Lau, A. W. C.; Vitelli, Vincenzo; Mahadevan, L.; Dogic, Zvonimir

    2015-06-01

    Any macroscopic deformation of a filamentous bundle is necessarily accompanied by local sliding and/or stretching of the constituent filaments. Yet the nature of the sliding friction between two aligned filaments interacting through multiple contacts remains largely unexplored. Here, by directly measuring the sliding forces between two bundled F-actin filaments, we show that these frictional forces are unexpectedly large, scale logarithmically with sliding velocity as in solid-like friction, and exhibit complex dependence on the filaments’ overlap length. We also show that a reduction of the frictional force by orders of magnitude, associated with a transition from solid-like friction to Stokes’s drag, can be induced by coating F-actin with polymeric brushes. Furthermore, we observe similar transitions in filamentous microtubules and bacterial flagella. Our findings demonstrate how altering a filament’s elasticity, structure and interactions can be used to engineer interfilament friction and thus tune the properties of fibrous composite materials.

  11. Solid friction between soft filaments

    SciTech Connect

    Ward, Andrew; Hilitski, Feodor; Schwenger, Walter; Welch, David; Lau, A. W. C.; Vitelli, Vincenzo; Mahadevan, L.; Dogic, Zvonimir

    2015-03-02

    Any macroscopic deformation of a filamentous bundle is necessarily accompanied by local sliding and/or stretching of the constituent filaments. Yet the nature of the sliding friction between two aligned filaments interacting through multiple contacts remains largely unexplored. Here, by directly measuring the sliding forces between two bundled F-actin filaments, we show that these frictional forces are unexpectedly large, scale logarithmically with sliding velocity as in solid-like friction, and exhibit complex dependence on the filaments’ overlap length. We also show that a reduction of the frictional force by orders of magnitude, associated with a transition from solid-like friction to Stokes’s drag, can be induced by coating F-actin with polymeric brushes. Furthermore, we observe similar transitions in filamentous microtubules and bacterial flagella. In conclusion, our findings demonstrate how altering a filament’s elasticity, structure and interactions can be used to engineer interfilament friction and thus tune the properties of fibrous composite materials.

  12. Improvement of the intersection method for the quantification of filamentous organisms: basis and practice for bulking and foaming bioindication purposes.

    PubMed

    Salvadó, Humbert

    2016-09-01

    Bulking and foaming phenomena in activated sludge wastewater treatment plants are in most cases related to the abundance of filamentous microorganisms. Quantifying these microorganisms should be a preliminary stage in their control. In this paper, the simplicity of quantifying them based on the intersection method is demonstrated, by redescribing the theory and applying a new improved protocol; new data of interest are also provided. The improved method allows us to use it with stained smears, including epifluorescence techniques. The error that could be made, when considering the distribution of filamentous bacteria in fresh microscope preparations in two dimensions rather than three is negligible. The effect of the different types of filamentous microorganisms on the settleability was also studied. The effect of the total extended filament length on the sludge settleability was shown to depend on the type of filamentous organism and how it aggregates. When these groups of filamentous organisms are found in small aggregations and there is an increase in the number of filamentous organisms, the sludge volume index (SVI) increases proportionally to the filament length. However, when aggregation increases, the impact on the SVI is significantly lower.

  13. Cinnamon extract inhibits tau aggregation associated with Alzheimer’s Disease in vitro

    Technology Transfer Automated Retrieval System (TEKTRAN)

    An aqueous extract of Ceylon cinnamon (C. zeylanicum) was found to inhibit tau aggregation and filament formation, hallmarks of Alzheimer’s disease (AD) in vitro using brain cells taken from patients who died with AD. The extract also promoted complete disassembly of recombinant tau filaments, and ...

  14. Perturbation growth in accreting filaments

    NASA Astrophysics Data System (ADS)

    Clarke, S. D.; Whitworth, A. P.; Hubber, D. A.

    2016-05-01

    We use smoothed particle hydrodynamic simulations to investigate the growth of perturbations in infinitely long filaments as they form and grow by accretion. The growth of these perturbations leads to filament fragmentation and the formation of cores. Most previous work on this subject has been confined to the growth and fragmentation of equilibrium filaments and has found that there exists a preferential fragmentation length-scale which is roughly four times the filament's diameter. Our results show a more complicated dispersion relation with a series of peaks linking perturbation wavelength and growth rate. These are due to gravo-acoustic oscillations along the longitudinal axis during the sub-critical phase of growth. The positions of the peaks in growth rate have a strong dependence on both the mass accretion rate onto the filament and the temperature of the gas. When seeded with a multiwavelength density power spectrum, there exists a clear preferred core separation equal to the largest peak in the dispersion relation. Our results allow one to estimate a minimum age for a filament which is breaking up into regularly spaced fragments, as well as an average accretion rate. We apply the model to observations of filaments in Taurus by Tafalla & Hacar and find accretion rates consistent with those estimated by Palmeirim et al.

  15. Metabolic regulation via enzyme filamentation

    PubMed Central

    Aughey, Gabriel N.; Liu, Ji-Long

    2016-01-01

    Abstract Determining the mechanisms of enzymatic regulation is central to the study of cellular metabolism. Regulation of enzyme activity via polymerization-mediated strategies has been shown to be widespread, and plays a vital role in mediating cellular homeostasis. In this review, we begin with an overview of the filamentation of CTP synthase, which forms filamentous structures termed cytoophidia. We then highlight other important examples of the phenomenon. Moreover, we discuss recent data relating to the regulation of enzyme activity by compartmentalization into cytoophidia. Finally, we hypothesize potential roles for enzyme filament formation in the regulation of metabolism, development and disease. PMID:27098510

  16. Merging of Filaments in a Dual-Filament System

    NASA Astrophysics Data System (ADS)

    Mikurda, K.; Martin, S. F.

    2006-08-01

    Introduction: The dual filament system merges to form one extended filament. Methods: The filaments were observed at Helio Research at multiple wavelengths around Hα using a tunable filter and a narrow band Fabry-Perot etalon as part of the Joint Observing Campaign (JOP 178). These observations are used to create two-dimensional Dopplergrams. The Hα images are compared with data taken onboard the SOHO (Solar and Heliospheric Observatory) spacecraft (EIT at 304 A and LASCO C2). The GONG magnetograms provide the information on photospheric magnetic fields. Results and Discussion: The filaments were observed on the solar disk between October 10 and 16, 2004. We compare the morphology of the filament system in Hα and He II line at 304 A and discuss its evolution. We investigate the photospheric magnetic flux cancellation rate during the merging process. There is no clear evidence of an eruption associated with the merging of the filaments from either EIT or LASCO in contrary to some previous findings.

  17. Collisions of Vortex Filament Pairs

    NASA Astrophysics Data System (ADS)

    Banica, Valeria; Faou, Erwan; Miot, Evelyne

    2014-12-01

    We consider the problem of collisions of vortex filaments for a model introduced by Klein et al. (J Fluid Mech 288:201-248, 1995) and Zakharov (Sov Phys Usp 31(7):672-674, 1988, Lect. Notes Phys 536:369-385, 1999) to describe the interaction of almost parallel vortex filaments in three-dimensional fluids. Since the results of Crow (AIAA J 8:2172-2179, 1970) examples of collisions are searched as perturbations of antiparallel translating pairs of filaments, with initial perturbations related to the unstable mode of the linearized problem; most results are numerical calculations. In this article, we first consider a related model for the evolution of pairs of filaments, and we display another type of initial perturbation leading to collision in finite time. Moreover, we give numerical evidence that it also leads to collision through the initial model. We finally study the self-similar solutions of the model.

  18. Electron emitting filaments for electron discharge devices

    DOEpatents

    Leung, Ka-Ngo; Pincosy, Philip A.; Ehlers, Kenneth W.

    1988-01-01

    Electrons are copiously emitted by a device comprising a loop-shaped filament made of lanthanum hexaboride. The filament is directly heated by an electrical current produced along the filament by a power supply connected to the terminal legs of the filament. To produce a filament, a diamond saw or the like is used to cut a slice from a bar made of lanthanum hexaboride. The diamond saw is then used to cut the slice into the shape of a loop which may be generally rectangular, U-shaped, hairpin-shaped, zigzag-shaped, or generally circular. The filaments provide high electron emission at a relatively low operating temperature, such as 1600.degree. C. To achieve uniform heating, the filament is formed with a cross section which is tapered between the opposite ends of the filament to compensate for non-uniform current distribution along the filament due to the emission of electrons from the filament.

  19. Electron emitting filaments for electron discharge devices

    DOEpatents

    Leung, K.N.; Pincosy, P.A.; Ehlers, K.W.

    1983-06-10

    Electrons are copiously emitted by a device comprising a loop-shaped filament made of lanthanum hexaboride. The filament is directly heated by an electrical current produced along the filament by a power supply connected to the terminal legs of the filament. To produce a filament, a diamond saw or the like is used to cut a slice from a bar made of lanthanum hexaboride. The diamond saw is then used to cut the slice into the shape of a loop which may be generally rectangular, U-shaped, hairpin-shaped, zigzag-shaped, or generally circular. The filaments provide high electron emission at a relatively low operating temperature, such as 1600/sup 0/C. To achieve uniform heating, the filament is formed with a cross section which is tapered between the opposite ends of the filament to compensate for nonuniform current distribution along the filament due to the emission of electrons from the filament.

  20. Kinetic studies on the aggregation of Aspergillus niger conidia.

    PubMed

    Grimm, L H; Kelly, S; Hengstler, J; Göbel, A; Krull, R; Hempel, D C

    2004-07-20

    Morphology has a crucial effect on productivity and the supply of substrate for cultures of filamentous fungi. However, cultivation parameters leading to the desired morphology are often chosen empirically as the mechanisms governing the processes involved are usually unknown. For coagulating microorganisms like Aspergillus niger the morphological development is considered to start with the aggregation of conidia right after inoculation. To elucidate the mechanism of this process, kinetic studies were carried out using an in-line particle size analyzer. Based on the data obtained from these experiments a model for conidial aggregation is proposed in this article. It consists of two separate aggregation steps. The first one takes place immediately after inoculation, but only leads to a small decrease of total particle concentration. Most suspended conidia aggregate after a second aggregation step triggered by germination and hyphal growth. Aggregation velocity of this second phase is linearly dependent on the particle growth rate.

  1. Boolean gates on actin filaments

    NASA Astrophysics Data System (ADS)

    Siccardi, Stefano; Tuszynski, Jack A.; Adamatzky, Andrew

    2016-01-01

    Actin is a globular protein which forms long polar filaments in the eukaryotic cytoskeleton. Actin networks play a key role in cell mechanics and cell motility. They have also been implicated in information transmission and processing, memory and learning in neuronal cells. The actin filaments have been shown to support propagation of voltage pulses. Here we apply a coupled nonlinear transmission line model of actin filaments to study interactions between voltage pulses. To represent digital information we assign a logical TRUTH value to the presence of a voltage pulse in a given location of the actin filament, and FALSE to the pulse's absence, so that information flows along the filament with pulse transmission. When two pulses, representing Boolean values of input variables, interact, then they can facilitate or inhibit further propagation of each other. We explore this phenomenon to construct Boolean logical gates and a one-bit half-adder with interacting voltage pulses. We discuss implications of these findings on cellular process and technological applications.

  2. Solid friction between soft filaments

    DOE PAGES

    Ward, Andrew; Hilitski, Feodor; Schwenger, Walter; ...

    2015-03-02

    Any macroscopic deformation of a filamentous bundle is necessarily accompanied by local sliding and/or stretching of the constituent filaments. Yet the nature of the sliding friction between two aligned filaments interacting through multiple contacts remains largely unexplored. Here, by directly measuring the sliding forces between two bundled F-actin filaments, we show that these frictional forces are unexpectedly large, scale logarithmically with sliding velocity as in solid-like friction, and exhibit complex dependence on the filaments’ overlap length. We also show that a reduction of the frictional force by orders of magnitude, associated with a transition from solid-like friction to Stokes’s drag,more » can be induced by coating F-actin with polymeric brushes. Furthermore, we observe similar transitions in filamentous microtubules and bacterial flagella. In conclusion, our findings demonstrate how altering a filament’s elasticity, structure and interactions can be used to engineer interfilament friction and thus tune the properties of fibrous composite materials.« less

  3. Solid friction between soft filaments

    PubMed Central

    Ward, Andrew; Hilitski, Feodor; Schwenger, Walter; Welch, David; Lau, A.W. C.; Vitelli, Vincenzo; Mahadevan, L.; Dogic, Zvonimir

    2015-01-01

    Any macroscopic deformation of a filamentous bundle is necessarily accompanied by local sliding and/or stretching of the constituent filaments1,2. Yet the nature of the sliding friction between two aligned filaments interacting through multiple contacts remains largely unexplored. Here, by directly measuring the sliding forces between two bundled F-actin filaments, we show that these frictional forces are unexpectedly large, scale logarithmically with sliding velocity as in solid-like friction, and exhibit complex dependence on the filaments’ overlap length. We also show that a reduction of the frictional force by orders of magnitude, associated with a transition from solid-like friction to Stokes’s drag, can be induced by coating F-actin with polymeric brushes. Furthermore, we observe similar transitions in filamentous microtubules and bacterial flagella. Our findings demonstrate how altering a filament’s elasticity, structure and interactions can be used to engineer interfilament friction and thus tune the properties of fibrous composite materials. PMID:25730393

  4. The filamentous fungal pellet and forces driving its formation.

    PubMed

    Zhang, Jianguo; Zhang, Jining

    2016-12-01

    Filamentous fungi play an important role not only in the bio-manufacturing of value-added products, but also in bioenergy and environmental research. The bioprocess manipulation of filamentous fungi is more difficult than that of other microbial species because of their different pellet morphologies and the presence of tangled mycelia under different cultivation conditions. Fungal pellets, which have the advantages of harvest ease, low fermentation broth viscosity and high yield of some proteins, have been used for a long time. Many attempts have been made to establish the relationship between pellet and product yield using quantitative approaches. Fungal pellet formation is attributed to the combination of electrostatic interactions, hydrophobicity and specific interactions from spore wall components. Electrostatic interactions result from van der Waals forces and negative charge repulsion from carboxyl groups in the spore wall structure. Electrostatic interactions are also affected by counter-ions (cations) and the physiologic conditions of spores that modify the carboxyl groups. Fungal aggregates are promoted by the hydrophobicity generated by hydrophobins, which form a hydrophobic coat that covers the spore. The specific interactions of spore wall components contribute to spore aggregation through salt bridging. A model of spore aggregation was proposed based on these forces. Additionally, some challenges were addressed, including the limitations of research techniques, the quantitative determination of forces and the complex information of biological systems, to clarify the mechanism of fungal pellet formation.

  5. Self-assembly of a filament by curvature-inducing proteins

    NASA Astrophysics Data System (ADS)

    Kwiecinski, James; Chapman, S. Jonathan; Goriely, Alain

    2017-04-01

    We explore a simplified macroscopic model of membrane shaping by means of curvature-sensing BAR proteins. Equations describing the interplay between the shape of a freely floating filament in a fluid and the adhesion kinetics of proteins are derived from mechanical principles. The constant curvature solutions that arise from this system are studied using weakly nonlinear analysis. We show that the stability of the filament's shape is completely characterized by the parameters associated with protein recruitment and establish that in the bistable regime, proteins aggregate on the filament forming regions of high and low curvatures. This pattern formation is then followed by phase-coarsening that resolves on a time-scale dependent on protein diffusion and drift across the filament, which contend to smooth and maintain the pattern respectively. The model is generalized for multiple species of BAR proteins and we show that the stability of the assembled shape is determined by a competition between proteins attaching on opposing sides.

  6. Intermediate filaments in nervous tissues

    PubMed Central

    Liem, RKH; Yen, S; Salomon, GD; Shelanski, ML

    1978-01-01

    Intermediate filaments have been isolated from rabbit intradural spinal nerve roots by the axonal flotation method. This method was modified to avoid exposure of axons to low ionic strength medium. The purified filaments are morphologically 75-80 percent pure. The gel electrophoretogram shows four major bands migrating at 200,000, 145,000, 68,000, and 60,000 daltons, respectively. A similar preparation from rabbit brain shows four major polypeptides with mol wt of 200,000 145,000, 68,000, and 51,000 daltons. These results indicate that the neurofilament is composed of a triplet of polypepetides with mol wt of 200,000, 145,000, and 68,000 daltons. The 51,000-dalton band that appears in brain filament preparations as the major polypeptide seems to be of glial origin. The significance of the 60,000- dalton band in the nerve root filament preparation is unclear at this time. Antibodies raised against two of the triplet proteins isolated from calf brain localize by immunofluorescence to neurons in central and peripheral nerve. On the other hand, an antibody to the 51,000-dalton polypeptide gives only glial staining in the brain, and very weak peripheral nerve staining. Prolonged exposure of axons to low ionic strength medium solubilizes almost all of the triplet polypeptides, leaving behind only the 51,000- dalton component. This would indicate that the neurofilament is soluble at low ionic strength, whereas the glial filament is not. These results indicate that neurofilaments and glial filaments are composed of different polypeptides and have different solubility characteristics. PMID:83322

  7. Graphite filament wound pressure vessels

    NASA Technical Reports Server (NTRS)

    Feldman, A.; Damico, J. J.

    1972-01-01

    Filament wound NOL rings, 4-inch and 8-inch diameter closed-end vessels involving three epoxy resin systems and three graphite fibers were tested to develop property data and fabrication technology for filament wound graphite/epoxy pressure vessels. Vessels were subjected to single-cycle burst tests at room temperature. Manufacturing parameters were established for tooling, winding, and curing that resulted in the development of a pressure/vessel performance factor (pressure x volume/weight) or more than 900,000 in. for an oblate spheroid specimen.

  8. Beam distribution function after filamentation

    SciTech Connect

    Raubenheimer, T.O.; Decker, F.J.; Seeman, J.T.

    1995-05-01

    In this paper, the authors calculate the beam distribution function after filamentation (phase-mixing) of a focusing mismatch. This distribution is relevant when interpreting beam measurements and sources of emittance dilution in linear colliders. It is also important when considering methods of diluting the phase space density, which may be required for the machine protection system in future linear colliders, and it is important when studying effects of trapped ions which filament in the electron beam potential. Finally, the resulting distribution is compared with measured beam distributions from the SLAC linac.

  9. Virtual filaments that mimic conventional light bulb filaments

    NASA Astrophysics Data System (ADS)

    Chaves, Julio; Munoz, Fernando; Minano, Juan Carlos; Benitez, Pablo; Parkyn, Bill; Falicoff, Waqidi; Sun, Yupin

    2004-09-01

    Conventional incandescent light bulbs have a wire filament acting as an extended light source with nearly constant intensity throughout its quasi-spherical emission pattern. Here we present a novel family of optical devices that make use of commercially available Lambertian or near-Lambertian LED light sources, in conjunction with tailored optical element bonded to the top surface of the LED. These hybrid devices can emulate the output of traditional incandescent filaments, or can be designed to produce a wide range of light output beam patterns. We call these new devices Virtual Filaments, as they can be designed to appear the same as an incandescent filament, with a similar light output pattern, and having a similar focal position above the base. These new lamps can then be used in the same applications as those they replace, thus eliminating the need to redesign or replace the original luminaire. We present several possible optical designs that can be used with a number of standard LEDs to replace standard incandescent bulbs. In one example we show a design that provides an output with near-uniform intensity across a full beam angle of 300 degrees, from a focal position 20 mm above an LED. Other major advantages of these new devices include their ability to be given sharp cutoffs, to homogenize non-uniform LED light sources and to color-mix the output of RGB LEDs.

  10. Star-forming Filament Models

    NASA Astrophysics Data System (ADS)

    Myers, Philip C.

    2017-03-01

    New models of star-forming filamentary clouds are presented in order to quantify their properties and to predict their evolution. These 2D axisymmetric models describe filaments that have no core, one low-mass core, and one cluster-forming core. They are based on Plummer-like cylinders and spheroids that are bounded by a constant-density surface of finite extent. In contrast to 1D Plummer-like models, they have specific values of length and mass, they approximate observed column density maps, and their distributions of column density (N-pdfs) are pole-free. Each model can estimate the star-forming potential of a core-filament system by identifying the zone of gas dense enough to form low-mass stars and by counting the number of enclosed thermal Jeans masses. This analysis suggests that the Musca central filament may be near the start of its star-forming life, with enough dense gas to make its first ∼3 protostars, while the Coronet filament is near the midpoint of its star formation, with enough dense gas to add ∼8 protostars to its ∼20 known stars. In contrast, L43 appears to be near the end of its star-forming life, since it lacks enough dense gas to add any new protostars to the two young stellar objectsalready known.

  11. METHOD OF MAKING TUNGSTEN FILAMENTS

    DOEpatents

    Frazer, J.W.

    1962-12-18

    A method of making tungsten filaments is described in which the tungsten is completely free of isotope impurities in the range of masses 234 to 245 for use in mass spectrometers. The filament comprises a tantalum core generally less than 1 mil in diameter having a coating of potassium-free tantalum-diffused tungsten molecularly bonded thereto. In the preferred process of manufacture a short, thin tantalum filament is first mounted between terminal posts mounted in insulated relation through a backing plate. The tungsten is most conveniently vapor plated onto the tantalum by a tungsten carbonyl vapor decomposition method having a critical step because of the tendency of the tantalum to volatilize at the temperature of operntion of the filament. The preferred recipe comprises volatilizing tantalum by resistance henting until the current drops by about 40%, cutting the voltage back to build up the tungsten, and then gradually building the temperature back up to balance the rate of tungsten deposition with the rate of tantalum volatilization. (AEC)

  12. SDO Sees a Dark Filament Circle

    NASA Video Gallery

    A dark, almost circular filament broke away from the sun in a gauzy, feathery swirl, on Nov. 15, 2015, in this video from NASA’s Solar Dynamics Observatory. This filament eruption was followed by a...

  13. SDO Watches Giant Filament on the Sun

    NASA Video Gallery

    A snaking, extended filament of solar material currently lies on the front of the sun-- some 1 million miles across from end to end. Filaments are clouds of solar material suspended above the sun b...

  14. Role of Intermediate Filaments in Vesicular Traffic

    PubMed Central

    Margiotta, Azzurra; Bucci, Cecilia

    2016-01-01

    Intermediate filaments are an important component of the cellular cytoskeleton. The first established role attributed to intermediate filaments was the mechanical support to cells. However, it is now clear that intermediate filaments have many different roles affecting a variety of other biological functions, such as the organization of microtubules and microfilaments, the regulation of nuclear structure and activity, the control of cell cycle and the regulation of signal transduction pathways. Furthermore, a number of intermediate filament proteins have been involved in the acquisition of tumorigenic properties. Over the last years, a strong involvement of intermediate filament proteins in the regulation of several aspects of intracellular trafficking has strongly emerged. Here, we review the functions of intermediate filaments proteins focusing mainly on the recent knowledge gained from the discovery that intermediate filaments associate with key proteins of the vesicular membrane transport machinery. In particular, we analyze the current understanding of the contribution of intermediate filaments to the endocytic pathway. PMID:27120621

  15. Filament Winding Of Carbon/Carbon Structures

    NASA Technical Reports Server (NTRS)

    Jacoy, Paul J.; Schmitigal, Wesley P.; Phillips, Wayne M.

    1991-01-01

    Improved method of winding carbon filaments for carbon/carbon composite structures less costly and labor-intensive, also produces more consistent results. Involves use of roller squeegee to ensure filaments continuously wet with resin during winding. Also involves control of spacing and resin contents of plies to obtain strong bonds between carbon filaments and carbon matrices. Lends itself to full automation and involves use of filaments and matrix-precursor resins in their simplest forms, thereby reducing costs.

  16. Dynamics of Filaments of Scroll Waves

    NASA Astrophysics Data System (ADS)

    Biktashev, Vadim N.; Biktasheva, Irina V.

    The following sections are included: * A Brief History and Motivation * Wave-Particle Duality of Spiral Waves * Perturbative Dynamics of Scrolls, and Tension of Filaments * Scroll Wave Turbulence * Rigidity of Scroll Filaments: Pinning and Buckling * Filament Statics, Geodesic Principle and Snell's Law * References

  17. Remote electrical arc suppression by laser filamentation.

    PubMed

    Schubert, Elise; Mongin, Denis; Kasparian, Jérôme; Wolf, Jean-Pierre

    2015-11-02

    We investigate the interaction of narrow plasma channels formed in the filamentation of ultrashort laser pulses, with a DC high voltage. The laser filaments prevent electrical arcs by triggering corona that neutralize the high-voltage electrodes. This phenomenon, that relies on the electric field modulation and free electron release around the filament, opens new prospects to lightning and over-voltage mitigation.

  18. 14-3-3ζ Mediates Tau Aggregation in Human Neuroblastoma M17 Cells.

    PubMed

    Li, Tong; Paudel, Hemant K

    2016-01-01

    Microtubule-associated protein tau is the major component of paired helical filaments (PHFs) associated with the neuropathology of Alzheimer's disease (AD). Tau in the normal brain binds and stabilizes microtubules. Tau isolated from PHFs is hyperphosphorylated, which prevents it from binding to microtubules. Tau phosphorylation has been suggested to be involved in the development of NFT pathology in the AD brain. Recently, we showed that 14-3-3ζ is bound to tau in the PHFs and when incubated in vitro with 14-3-3ζ, tau formed amorphous aggregates, single-stranded straight filaments, double stranded ribbon-like filaments and PHF-like filaments that displayed close resemblance with corresponding ultrastructures of AD brain. Surprisingly however, phosphorylated and non-phosphorylated tau aggregated in a similar manner, indicating that tau phosphorylation does not affect in vitro tau aggregation (Qureshi et al (2013) Biochemistry 52, 6445-6455). In this study, we have examined the role of tau phosphorylation in tau aggregation in cellular level. We have found that in human M17 neuroblastoma cells, tau phosphorylation by GSK3β or PKA does not cause tau aggregation, but promotes 14-3-3ζ-induced tau aggregation by destabilizing microtubules. Microtubule disrupting drugs also promoted 14-3-3ζ-induced tau aggregation without changing tau phosphorylation in M17 cell. In vitro, when incubated with 14-3-3ζ and microtubules, nonphosphorylated tau bound to microtubules and did not aggregate. Phosphorylated tau on the other hand did not bind to microtubules and aggregated. Our data indicate that microtubule-bound tau is resistant to 14-3-3ζ-induced tau aggregation and suggest that tau phosphorylation promotes tau aggregation in the brain by detaching tau from microtubules and thus making it accessible to 14-3-3ζ.

  19. 14-3-3ζ Mediates Tau Aggregation in Human Neuroblastoma M17 Cells

    PubMed Central

    Li, Tong; Paudel, Hemant K.

    2016-01-01

    Microtubule-associated protein tau is the major component of paired helical filaments (PHFs) associated with the neuropathology of Alzheimer’s disease (AD). Tau in the normal brain binds and stabilizes microtubules. Tau isolated from PHFs is hyperphosphorylated, which prevents it from binding to microtubules. Tau phosphorylation has been suggested to be involved in the development of NFT pathology in the AD brain. Recently, we showed that 14-3-3ζ is bound to tau in the PHFs and when incubated in vitro with 14-3-3ζ, tau formed amorphous aggregates, single-stranded straight filaments, double stranded ribbon-like filaments and PHF-like filaments that displayed close resemblance with corresponding ultrastructures of AD brain. Surprisingly however, phosphorylated and non-phosphorylated tau aggregated in a similar manner, indicating that tau phosphorylation does not affect in vitro tau aggregation (Qureshi et al (2013) Biochemistry 52, 6445–6455). In this study, we have examined the role of tau phosphorylation in tau aggregation in cellular level. We have found that in human M17 neuroblastoma cells, tau phosphorylation by GSK3β or PKA does not cause tau aggregation, but promotes 14-3-3ζ-induced tau aggregation by destabilizing microtubules. Microtubule disrupting drugs also promoted 14-3-3ζ-induced tau aggregation without changing tau phosphorylation in M17 cell. In vitro, when incubated with 14-3-3ζ and microtubules, nonphosphorylated tau bound to microtubules and did not aggregate. Phosphorylated tau on the other hand did not bind to microtubules and aggregated. Our data indicate that microtubule-bound tau is resistant to 14-3-3ζ-induced tau aggregation and suggest that tau phosphorylation promotes tau aggregation in the brain by detaching tau from microtubules and thus making it accessible to 14-3-3ζ. PMID:27548710

  20. Characterization of paired helical filaments by scanning transmission electron microscopy.

    PubMed

    Ksiezak-Reding, Hanna; Wall, Joseph S

    2005-07-01

    Paired helical filaments (PHFs) are abnormal twisted filaments composed of hyperphosphorylated tau protein. They are found in Alzheimer's disease and other neurodegenerative disorders designated as tauopathies. They are a major component of intracellular inclusions known as neurofibrillary tangles (NFTs). The objective of this review is to summarize various structural studies of PHFs in which using scanning transmission electron microscopy (STEM) has been particularly informative. STEM provides shape and mass per unit length measurements important for studying ultrastructural aspects of filaments. These include quantitative comparisons between dispersed and aggregated populations of PHFs as well as comparative studies of PHFs in Alzheimer's disease and other neurodegenerative disorders. Other approaches are also discussed if relevant or complementary to studies using STEM, e.g., application of a novel staining reagent, Nanovan. Our understanding of the PHF structure and the development of PHFs into NFTs is presented from a historical perspective. Others goals are to describe the biochemical and ultrastructural complexity of authentic PHFs, to assess similarities between authentic and synthetic PHFs, and to discuss recent advances in PHF modeling.

  1. Filamentation as primitive growth mode?

    NASA Astrophysics Data System (ADS)

    Bigan, Erwan; Steyaert, Jean-Marc; Douady, Stéphane

    2015-12-01

    Osmotic pressure influences cellular shape. In a growing cell, chemical reactions and dilution induce changes in osmolarity, which in turn influence the cellular shape. Using a protocell model relying upon random conservative chemical reaction networks with arbitrary stoichiometry, we find that when the membrane is so flexible that its shape adjusts itself quasi-instantaneously to balance the osmotic pressure, the protocell either grows filamentous or fails to grow. This behavior is consistent with a mathematical proof. This suggests that filamentation may be a primitive growth mode resulting from the simple physical property of balanced osmotic pressure. We also find that growth is favored if some chemical species are only present inside the protocell, but not in the outside growth medium. Such an insulation requires specific chemical schemes. Modern evolved cells such as E. coli meet these requirements through active transport mechanisms such as the phosphotransferase system.

  2. Picosecond laser filamentation in air

    NASA Astrophysics Data System (ADS)

    Schmitt-Sody, Andreas; Kurz, Heiko G.; Bergé, Luc; Skupin, Stefan; Polynkin, Pavel

    2016-09-01

    The propagation of intense picosecond laser pulses in air in the presence of strong nonlinear self-action effects and air ionization is investigated experimentally and numerically. The model used for numerical analysis is based on the nonlinear propagator for the optical field coupled to the rate equations for the production of various ionic species and plasma temperature. Our results show that the phenomenon of plasma-driven intensity clamping, which has been paramount in femtosecond laser filamentation, holds for picosecond pulses. Furthermore, the temporal pulse distortions in the picosecond regime are limited and the pulse fluence is also clamped. In focused propagation geometry, a unique feature of picosecond filamentation is the production of a broad, fully ionized air channel, continuous both longitudinally and transversely, which may be instrumental for many applications including laser-guided electrical breakdown of air, channeling microwave beams and air lasing.

  3. The stability of viscous liquid filaments

    NASA Astrophysics Data System (ADS)

    Driessen, Theo; Jeurissen, Roger; Wijshoff, Herman; Lohse, Detlef

    2012-11-01

    The stability of liquid filaments is relevant both in industrial applications, such as inkjet printing and atomization, and in nature, where the stability of filaments has a large influence on the final drop size distribution of rain droplets and waterfalls. The liquid filament may either stably collapse into a single droplet, or break up into multiple droplets. Which scenario is realized depends on the viscosity and the aspect ratio of the filament. Here we study the collapse of an axisymmetric liquid filament is analytically and with a numerical model. We find that a long, high viscous filament can only break up due to the Rayleigh-Plateau instability, whereas a low viscous filament can break up due to end-pinching. The theory shows quantitative agreement with recent experimental findings by Castréjon-Pita et al., PRL 108, 074506 (2012).

  4. Microwave processing of ceramic oxide filaments

    SciTech Connect

    Vogt, G.J.; Katz, J.D.

    1995-05-01

    The objective of the microwave filament processing project is to develop microwave techniques at 2.45 GHZ to manufacture continuous ceramic oxide filaments. Microwave processing uses the volumetric absorption of microwave power in oxide filament tows to drive off process solvents, to burn out organic binders, and to sinter the dried fibers to produce flexible, high-strength ceramic filaments. The technical goal is to advance filament processing technology by microwave heating more rapidly with less energy and at a lower cost than conventional processing, but with the same quality as conventional processing. The manufacturing goal is to collaborate with the 3M Company, a US manufacturer of ceramic oxide filaments, to evaluate the technology using a prototype filament system and to transfer the microwave technology to the 3M Company.

  5. PARTIAL SLINGSHOT RECONNECTION BETWEEN TWO FILAMENTS

    SciTech Connect

    Jiang, Yunchun; Hong, Junchao; Yang, Jiayan; Bi, Yi; Zheng, Ruisheng; Yang, Bo; Li, Haidong; Yang, Dan

    2013-02-10

    We present a rare observation of an interaction between two filaments around AR 11358 and AR 11361 on 2011 December 3 that is strongly suggestive of the occurrence of slingshot reconnection. A small elbow-shaped active-region filament (F12) underwent a failed eruption that brought it into contact with a nearby larger, thicker filament (F34). Accompanied by the appearance of complicated internal structures below the erupting F12, its two legs separated away from each other and then connected into F34. This process led the filaments to change their connectivity to form two newly linked filaments, and one of them showed a clear inverse {gamma}-shape. However, the alteration in the filament connectivity was imperfect since F34 is discernible after the eruption. These observations can be interpreted as a partial slingshot reconnection between two filaments that had unequal axial magnetic flux.

  6. Dynamics of 3D isolated thermal filaments

    NASA Astrophysics Data System (ADS)

    Walkden, N. R.; Easy, L.; Militello, F.; Omotani, J. T.

    2016-11-01

    Simulations have been carried out to establish how electron thermal physics, introduced in the form of a dynamic electron temperature, affects isolated filament motion and dynamics in 3D. It is found that thermal effects impact filament motion in two major ways when the pressure perturbation within the filament is supported primarily through a temperature increase as opposed to density: they lead to a strong increase in filament propagation in the bi-normal direction and a significant decrease in net radial propagation. Both effects arise from the temperature dependence of the sheath current which leads to a non-uniform floating potential, with the latter effect supplemented by faster pressure loss. The reduction in radial velocity can only occur when the filament cross-section loses angular symmetry. The behaviour is observed across different filament sizes and suggests that filaments with much larger temperature perturbations than density perturbations are more strongly confined to the near SOL region.

  7. Mechanics of vimentin intermediate filaments

    NASA Technical Reports Server (NTRS)

    Wang, Ning; Stamenovic, Dimitrijie

    2002-01-01

    It is increasingly evident that the cytoskeleton of living cells plays important roles in mechanical and biological functions of the cells. Here we focus on the contribution of intermediate filaments (IFs) to the mechanical behaviors of living cells. Vimentin, a major structural component of IFs in many cell types, is shown to play an important role in vital mechanical and biological functions such as cell contractility, migration, stiffness, stiffening, and proliferation.

  8. Filament wound rocket motor chambers

    NASA Technical Reports Server (NTRS)

    1976-01-01

    The design, analysis, fabrication and testing of a Kevlar-49/HBRF-55A filament wound chamber is reported. The chamber was fabricated and successfully tested to 80% of the design burst pressure. Results of the data reduction and analysis from the hydrotest indicate that the chamber design and fabrication techniques used for the chamber were adequate and the chamber should perform adequately in a static test.

  9. Temperature of a lightbulb filament

    NASA Astrophysics Data System (ADS)

    Denardo, Bruce

    2002-02-01

    A standard problem in introductory physics books is to use the temperature coefficient of resistivity to calculate the operating temperature of an incandescent lightbulb filament or heating wire. This assumes a linear variation of resistivity with temperature, which is shown to be significantly incorrect for a 120-V 60-W lightbulb. A discussion of this error can be included with a lecture calculation of the temperature.

  10. Lighting the universe with filaments.

    PubMed

    Gao, Liang; Theuns, Tom

    2007-09-14

    The first stars in the universe form when chemically pristine gas heats as it falls into dark-matter potential wells, cools radiatively because of the formation of molecular hydrogen, and becomes self-gravitating. Using supercomputer simulations, we demonstrated that the stars' properties depend critically on the currently unknown nature of the dark matter. If the dark-matter particles have intrinsic velocities that wipe out small-scale structure, then the first stars form in filaments with lengths on the order of the free-streaming scale, which can be approximately 10(20) meters (approximately 3 kiloparsecs, corresponding to a baryonic mass of approximately 10(7) solar masses) for realistic "warm dark matter" candidates. Fragmentation of the filaments forms stars with a range of masses, which may explain the observed peculiar element abundance pattern of extremely metal-poor stars, whereas coalescence of fragments and stars during the filament's ultimate collapse may seed the supermassive black holes that lurk in the centers of most massive galaxies.

  11. Aluminum modifies the viscosity of filamentous actin solutions as measured by optical displacement microviscometry.

    PubMed

    Arnoys, E J; Schindler, M

    2000-01-01

    A microtechnique has been developed that is capable of measuring the viscosity of filamentous actin (F-actin) solutions. This method, called optical displacement microviscometry (ODM), was utilized to determine the changes in viscosity of solutions of rabbit muscle, human platelet, and maize pollen actin when measured in the absence and presence of aluminum. Measurements demonstrated that the viscosity of the different actin solutions decreased with aluminum concentration. In contrast, increases in viscosity were observed when aluminum was added to F-actin solutions containing filamin (chicken gizzard), a protein that bundles actin filaments. Confocal fluorescence imaging of pure actin solutions in the presence of aluminum showed a disrupted actin network composed of fragmented actin filaments in the form of small aggregates. In contrast, in the presence of filamin, aluminum promoted the formation of thicker actin filaments. These measurements demonstrate that aluminum can affect actin filaments differentially depending on the presence of an actin-binding protein. In addition, a strong correlation is observed between the changes in viscosity as measured by ODM and the thickness and assembled state of bundles of actin filaments.

  12. In vivo formation steps of the hard alpha-keratin intermediate filament along a hair follicle: evidence for structural polymorphism.

    PubMed

    Rafik, Mériem Er; Briki, Fatma; Burghammer, Manfred; Doucet, Jean

    2006-04-01

    Several aspects of the intermediate filaments' molecular architecture remain mysterious despite decades of study. The growth process and the final architecture may depend on the physical, chemical, and biochemical environment. Aiming at clarifying this issue, we have revisited the structure of the human hair follicle by means of X-ray microdiffraction. We conclude that the histology-based growth zones along the follicle are correlated to the fine architecture of the filaments deduced from X-ray microdiffraction. Our analysis reveals the existence of two major polymorph intermediate filament architectures. Just above the bulb, the filaments are characterized by a diameter of 100 Angstroms and a low-density core. The following zone upwards is characterized by the lateral aggregation of the filaments into a compact network of filaments, by a contraction of their diameter (to 75 Angstroms) and by the setting up of a long-range longitudinal ordering. In the upper zone, the small structural change associated with the tissue hardening likely concerns the terminal domains. The architecture of the intermediate filament in the upper zones could be specific to hard alpha-keratin whilst the other architecture found in the lower zone could be representative for intermediate filaments in a different environment.

  13. Thermodynamics of Protein Aggregation

    NASA Astrophysics Data System (ADS)

    Osborne, Kenneth L.; Barz, Bogdan; Bachmann, Michael; Strodel, Birgit

    Amyloid protein aggregation characterizes many neurodegenerative disorders, including Alzheimer's, Parkinson's, and Creutz- feldt-Jakob disease. Evidence suggests that amyloid aggregates may share similar aggregation pathways, implying simulation of full-length amyloid proteins is not necessary for understanding amyloid formation. In this study we simulate GNNQQNY, the N-terminal prion-determining domain of the yeast protein Sup35 to investigate the thermodynamics of structural transitions during aggregation. We use a coarse-grained model with replica-exchange molecular dynamics to investigate the association of 3-, 6-, and 12-chain GNNQQNY systems and we determine the aggregation pathway by studying aggregation states of GN- NQQNY. We find that the aggregation of the hydrophilic GNNQQNY sequence is mainly driven by H-bond formation, leading to the formation of /3-sheets from the very beginning of the assembly process. Condensation (aggregation) and ordering take place simultaneously, which is underpinned by the occurrence of a single heat capacity peak only.

  14. Aggregate-prone desmin mutations impair mitochondrial calcium uptake in primary myotubes.

    PubMed

    Smolina, Natalia; Bruton, Joseph; Sjoberg, Gunnar; Kostareva, Anna; Sejersen, Thomas

    2014-10-01

    Desmin, being a major intermediate filament of mature muscle cell, interacts with mitochondria within the cell and participates in mitochondria proper localization. The goal of the present study was to assess the effect of aggregate-prone and non-aggregate-prone desmin mutations on mitochondrial calcium uptake. Primary murine satellite cells were transduced with lentiviruses carrying desmin in wild type or mutant form, and were induced to differentiate into myotubes. Four mutations resulting in different degree of desmin aggregates formation were analyzed. Tail domain mutation Asp399Tyr has the mildest impact on desmin filament polymerization, rod domain mutation Ala357Pro causes formation of large aggregates composed of filamentous material, and Leu345Pro and Leu370Pro are considered to be the most severest in their impact on desmin polymerization and structure. For mitochondrial calcium measurement cells were loaded with rhod 2-AM. We found that aggregate-prone mutations significantly decreased [Ca(2+)]mit, whereas non-aggregate-prone mutations did not decrease [Ca(2+)]mit. Moreover aggregate-prone desmin mutations resulted in increased resting cytosolic [Ca(2+)]. However this increase was not accompanied by any alterations in sarcoplasmic reticulum calcium release. We suggest that the observed decline in [Ca(2+)]mit was due to desmin aggregate accumulation resulting in the loss of desmin mitochondria interactions.

  15. Dynamics of Contracting Asymmetric Viscoelastic Filaments

    NASA Astrophysics Data System (ADS)

    Anthony, Christopher; Thete, Sumeet; Appathurai, Santosh; Bhat, Pradeep; Basaran, Osman; Harris, Michael

    2013-11-01

    In ink-jet printing and atomization, slender filaments are routinely formed. Such filaments either contract to form a single drop or breakup into multiple drops, e.g. by end pinching. Beginning with papers by Schulkes (1996) and Notz & Basaran (2004), past studies have focused exclusively on the contraction dynamics of Newtonian filaments. Also in these studies, initial filament shapes are taken to be long cylinders terminated by two identical spherical caps (symmetric filaments). In emerging applications, e.g. ink-jet printing of complex fluids, the filaments are viscoelastic (VE) fluids. Moreover, older experiments by Notz et al. (2001) and more recent ones by Castrejón-Pita et al. (2012) show that initial filament shapes resemble long, tapered cylinders terminated by hemispherical caps of unequal radii (asymmetric filaments). Therefore, we analyze the contraction dynamics of both asymmetric and symmetric filaments of VE fluids using the Giesekus model. Rather than solving the full set of equations governing the problem, we take advantage of filament slenderness and solve a much simpler set of 1D equations (Eggers, 1997). We then use a finite element method with Streamline Upwind/Petrov Galerkin (SUPG) formulation (Brooks & Hughes, 1982) to solve the reduced equations.

  16. Actin filament curvature biases branching direction

    NASA Astrophysics Data System (ADS)

    Wang, Evan; Risca, Viviana; Chaudhuri, Ovijit; Chia, Jia-Jun; Geissler, Phillip; Fletcher, Daniel

    2012-02-01

    Actin filaments are key components of the cellular machinery, vital for a wide range of processes ranging from cell motility to endocytosis. Actin filaments can branch, and essential in this process is a protein complex known as the Arp2/3 complex, which nucleate new ``daughter'' filaments from pre-existing ``mother'' filaments by attaching itself to the mother filament. Though much progress has been made in understanding the Arp2/3-actin junction, some very interesting questions remain. In particular, F-actin is a dynamic polymer that undergoes a wide range of fluctuations. Prior studies of the Arp2/3-actin junction provides a very static notion of Arp2/3 binding. The question we ask is how differently does the Arp2/3 complex interact with a straight filament compared to a bent filament? In this study, we used Monte Carlo simulations of a surface-tethered worm-like chain to explore possible mechanisms underlying the experimental observation that there exists preferential branch formation by the Arp2/3 complex on the convex face of a curved filament. We show that a fluctuation gating model in which Arp2/3 binding to the actin filament is dependent upon a rare high-local-curvature shape fluctuation of the filament is consistent with the experimental data.

  17. Chirality and Magnetic Configurations of Solar Filaments

    NASA Astrophysics Data System (ADS)

    Ouyang, Y.; Zhou, Y. H.; Chen, P. F.; Fang, C.

    2017-01-01

    It has been revealed that the magnetic topology in the solar atmosphere displays hemispheric preference, i.e., helicity is mainly negative/positive in the northern/southern hemispheres, respectively. However, the strength of the hemispheric rule and its cyclic variation are controversial. In this paper, we apply a new method based on the filament drainage to 571 erupting filaments from 2010 May to 2015 December in order to determine the filament chirality and its hemispheric preference. It is found that 91.6% of our sample of erupting filaments follows the hemispheric rule of helicity sign. It is also found that the strength of the hemispheric preference of the quiescent filaments decreases slightly from ∼97% in the rising phase to ∼85% in the declining phase of solar cycle 24, whereas the strength of the intermediate filaments keeps a high value around 96 ± 4% at all times. Only the active-region filaments show significant variations. Their strength of the hemispheric rule rises from ∼63% to ∼95% in the rising phase, and keeps a high value of 82% ± 5% during the declining phase. Furthermore, during a half-year period around the solar maximum, their hemispheric preference totally vanishes. Additionally, we also diagnose the magnetic configurations of the filaments based on our indirect method and find that in our sample of erupting events, 89% are inverse-polarity filaments with a flux rope magnetic configuration, whereas 11% are normal-polarity filaments with a sheared arcade configuration.

  18. Photospheric flows around a quiescent filament

    NASA Astrophysics Data System (ADS)

    Rondi, S.; Roudier, Th.; Molodij, G.; Bommier, V.; Keil, S.; Sütterlin, P.; Malherbe, J. M.; Meunier, N.; Schmieder, B.; Maloney, P.

    2007-06-01

    Context: The horizontal photospheric flows below and around a filament are one of the components in the formation and evolution of filaments. Few studies exist because they require multiwalength time sequences at high spatial resolution. Aims: Our objective is to measure the horizontal photospheric flows associated with the evolution and eruption of a filament. Methods: We present observations obtained in 2004 during the international JOP 178 campaign which involved eleven instruments both in space and at ground based observatories. We use TRACE WL, DOT and DST observation to derive flow maps which are then coaligned with intensity images and with the vector magnetic field map obtained with THEMIS/MTR. Results: Several supergranulation cells cross the Polarity Inversion Line (PIL) and can transport magnetic flux through the PIL, in particular parasitic polarities. We present a detailed example of the formation of a secondary magnetic dip at the location of a filament footpoint. Large-scale converging flows, which could exist along the filament channel and contribute to its formation, are not observed. Before the filament's eruptive phase, we observe both parasitic and normal polarities being swept by a continuously diverging horizontal flow located in the filament gap. The disappearance of the filament initiates in this gap. Such purely horizontal motions could lead to destabilization of the filament and could trigger the sudden filament disappearance.

  19. Diagnosis of femtosecond plasma filament by channeling microwaves along the filament

    SciTech Connect

    Alshershby, Mostafa; Ren, Yu; Qin, Jiang; Hao, Zuoqiang; Lin, Jingquan

    2013-05-20

    We introduce a simple, fast, and non-intrusive experimental method to obtain the basic parameters of femtosecond laser-generated plasma filament. The method is based on the channeling of microwaves along both a plasma filament and a well-defined conducting wire. By comparing the detected microwaves that propagate along the plasma filament and a copper wire with known conductivity and spatial dimension, the basic parameters of the plasma filament can be easily obtained. As a result of the possibility of channeling microwave radiation along the plasma filament, we were then able to obtain the plasma density distribution along the filament length.

  20. A penny-shaped crack in a filament reinforced matrix. 1: The filament model

    NASA Technical Reports Server (NTRS)

    Erdogan, F.; Pacella, A. H.

    1973-01-01

    The electrostatic problem of a penny-shaped crack in an elastic matrix which reinforced by filaments or fibers perpendicular to the plane of the crack was studied. The elastic filament model was developed for application to evaluation studies of the stress intensity factor along the periphery of the crack, the stresses in the filaments or fibers, and the interface shear between the matrix and the filaments or fibers. The requirements expected of the model are a sufficiently accurate representation of the filament and applicability to the interaction problems involving a cracked elastic continuum with multi-filament reinforcements. The technique for developing the model and numerical examples of it are shown.

  1. Diagnosis of femtosecond plasma filament by channeling microwaves along the filament

    NASA Astrophysics Data System (ADS)

    Alshershby, Mostafa; Ren, Yu; Qin, Jiang; Hao, Zuoqiang; Lin, Jingquan

    2013-05-01

    We introduce a simple, fast, and non-intrusive experimental method to obtain the basic parameters of femtosecond laser-generated plasma filament. The method is based on the channeling of microwaves along both a plasma filament and a well-defined conducting wire. By comparing the detected microwaves that propagate along the plasma filament and a copper wire with known conductivity and spatial dimension, the basic parameters of the plasma filament can be easily obtained. As a result of the possibility of channeling microwave radiation along the plasma filament, we were then able to obtain the plasma density distribution along the filament length.

  2. On mean type aggregation.

    PubMed

    Yager, R R

    1996-01-01

    We introduce and define the concept of mean aggregation of a collection of n numbers. We point out that the lack of associativity of this operation compounds the problem of the extending mean of n numbers to n+1 numbers. The closely related concepts of self identity and the centering property are introduced as one imperative for extending mean aggregation operators. The problem of weighted mean aggregation is studied. A new concept of prioritized mean aggregation is then introduced. We next show that the technique of selecting an element based upon the performance of a random experiment can be considered as a mean aggregation operation.

  3. Femtosecond Laser Filamentation for Atmospheric Sensing

    PubMed Central

    Xu, Huai Liang; Chin, See Leang

    2011-01-01

    Powerful femtosecond laser pulses propagating in transparent materials result in the formation of self-guided structures called filaments. Such filamentation in air can be controlled to occur at a distance as far as a few kilometers, making it ideally suited for remote sensing of pollutants in the atmosphere. On the one hand, the high intensity inside the filaments can induce the fragmentation of all matters in the path of filaments, resulting in the emission of characteristic fluorescence spectra (fingerprints) from the excited fragments, which can be used for the identification of various substances including chemical and biological species. On the other hand, along with the femtosecond laser filamentation, white-light supercontinuum emission in the infrared to UV range is generated, which can be used as an ideal light source for absorption Lidar. In this paper, we present an overview of recent progress concerning remote sensing of the atmosphere using femtosecond laser filamentation. PMID:22346566

  4. Self-Organization of Treadmilling Filaments

    NASA Astrophysics Data System (ADS)

    Doubrovinski, K.; Kruse, K.

    2007-11-01

    The cytoskeleton is an active network of polar filaments. The activity can lead to the polymerization of filaments at one end and depolymerization at the other. This phenomenon is called treadmilling and is essential for many cellular processes, in particular, the crawling of cells on a substrate. We develop a microscopic theoretical framework for describing systems of treadmilling filaments. We show that such systems can self-organize into structures observed in cell fragments, in particular, asters and moving spots.

  5. Motion, decay and merging of vortex filaments

    NASA Technical Reports Server (NTRS)

    Liu, C. H.; Ting, L.

    1988-01-01

    The asymptotic solutions of Navier-Stokes equations for vortex filaments of finite strength with small effective vortical cores are summarized. Emphases are placed on the physical meaning and the practical limit to the applicability of the asymptotic solution. Finite-difference solutions of Navier-Stokes equations for the merging of the filament(s) are described. It is focused on the development of the approximate boundary conditions for the computational domain.

  6. Studies on UV filaments in air

    SciTech Connect

    Schwarz, J.; Rambo, P.; Diels, J.C.; Luk, T.S.; Bernstein, A.C.; Cameron, S.M.

    2000-01-05

    UV filaments in air have been examined on the basis of the diameter and length of the filament, the generation of new spectral components, and the ionization by multiphoton processes. There have been numerous observations of filaments at 800 nm. The general perception is that, above a critical power, the beam focuses because nonlinear self-lensing overcomes diffraction. The self-focusing proceeds until an opposing higher order nonlinearity forms a stable balance.

  7. Solubilization and fractionation of paired helical filaments.

    PubMed

    González, P J; Correas, I; Avila, J

    1992-09-01

    Paired helical filaments isolated from brains of two different patients with Alzheimer's disease were extensively treated with the ionic detergent, sodium dodecyl sulphate. Filaments were solubilized at different extents, depending on the brain examined, thus suggesting the existence of two types of paired helical filaments: sodium dodecyl sulphate-soluble and insoluble filaments. In the first case, the number of structures resembling paired helical filaments greatly decreased after the detergent treatment, as observed by electron microscopy. Simultaneously, a decrease in the amount of sedimentable protein was also observed upon centrifugation of the sodium dodecyl sulfate-treated paired helical filaments. A sodium dodecyl sulphate-soluble fraction was isolated as a supernatant after low-speed centrifugation of the sodium dodecyl sulphate-treated paired helical filaments. The addition of the non-ionic detergent Nonidet-P40 to this fraction resulted in the formation of paired helical filament-like structures. When the sodium dodecyl sulphate-soluble fraction was further fractionated by high-speed centrifugation, three subfractions were observed: a supernatant, a pellet and a thin layer between these two subfractions. No paired helical filaments were observed in any of these subfractions, even after addition of Nonidet P-40. However, when they were mixed back together, the treatment with Nonidet P-40 resulted in the visualization of paired helical filament-like structures. These results suggest that at least two different components are needed for the reconstitution of paired helical filaments as determined by electron microscopy. The method described here may allow the study of the components involved in the formation of paired helical filaments and the identification of possible factors capable of blocking this process.

  8. Deep coronal hole associated with quiescent filament

    NASA Astrophysics Data System (ADS)

    Kesumaningrum, Rasdewita; Herdiwidjaya, Dhani

    2014-03-01

    We present a study of the morphology of quiescent filament observed by H-alpha Solar Telescope at Bosscha Observatory in association with coronal hole observed by Atmospheric Imaging Assembly (AIA) instrument in 193 Å from Solar Dynamics Observatory. H-alpha images were processed by imaging softwares, namely Iris 5.59 and ImageJ, to enhance the signal to noise ratio and to identify the filament features associated with coronal hole. For images observed on October 12, 2011, November 14, 2011 and January 2, 2012, we identified distinct features of coronal holes above the quiescent filaments. This associated coronal holes have filament-like morphology with a thick long thread as it's `spine', defined as Deep Coronal Hole. Because of strong magnetic field of sunspot, these filaments and coronal holes emerged far from active region and lasted for several days. It is interesting as for segmented filament, deep coronal holes above the filaments lasted for a quite long period of time and merged. This association between filament and deep coronal hole can be explained by filament magnetic loop.

  9. Hydrodynamic interactions between nearby slender filaments

    NASA Astrophysics Data System (ADS)

    Man, Yi; Koens, Lyndon; Lauga, Eric

    2016-10-01

    Cellular biology abound with filaments interacting through fluids, from intracellular microtubules, to rotating flagella and beating cilia. While previous work has demonstrated the complexity of capturing nonlocal hydrodynamic interactions between moving filaments, the problem remains difficult theoretically. We show here that when filaments are closer to each other than their relevant length scale, the integration of hydrodynamic interactions can be approximately carried out analytically. This leads to a set of simplified local equations, illustrated on a simple model of two interacting filaments, which can be used to tackle theoretically a range of problems in biology and physics.

  10. Myosin filament structure in vertebrate smooth muscle

    PubMed Central

    1996-01-01

    The in vivo structure of the myosin filaments in vertebrate smooth muscle is unknown. Evidence from purified smooth muscle myosin and from some studies of intact smooth muscle suggests that they may have a nonhelical, side-polar arrangement of crossbridges. However, the bipolar, helical structure characteristic of myosin filaments in striated muscle has not been disproved for smooth muscle. We have used EM to investigate this question in a functionally diverse group of smooth muscles (from the vascular, gastrointestinal, reproductive, and visual systems) from mammalian, amphibian, and avian species. Intact muscle under physiological conditions, rapidly frozen and then freeze substituted, shows many myosin filaments with a square backbone in transverse profile. Transverse sections of fixed, chemically skinned muscles also show square backbones and, in addition, reveal projections (crossbridges) on only two opposite sides of the square. Filaments gently isolated from skinned smooth muscles and observed by negative staining show crossbridges with a 14.5-nm repeat projecting in opposite directions on opposite sides of the filament. Such filaments subjected to low ionic strength conditions show bare filament ends and an antiparallel arrangement of myosin tails along the length of the filament. All of these observations are consistent with a side-polar structure and argue against a bipolar, helical crossbridge arrangement. We conclude that myosin filaments in all smooth muscles, regardless of function, are likely to be side-polar. Such a structure could be an important factor in the ability of smooth muscles to contract by large amounts. PMID:8698822

  11. Probing the Physical Structures of Dense Filaments

    NASA Astrophysics Data System (ADS)

    Li, Di

    2015-08-01

    Filament is a common feature in cosmological structures of various scales, ranging from dark matter cosmic web, galaxy clusters, inter-galactic gas flows, to Galactic ISM clouds. Even within cold dense molecular cores, filaments have been detected. Theories and simulations with (or without) different combination of physical principles, including gravity, thermal balance, turbulence, and magnetic field, can reproduce intriguing images of filaments. The ubiquity of filaments and the similarity in simulated ones make physical parameters, beyond dust column density, a necessity for understanding filament evolution. I report three projects attempting to measure physical parameters of filaments. We derive the volume density of a dense Taurus filament based on several cyanoacetylene transitions observed by GBT and ART. We measure the gas temperature of the OMC 2-3 filament based on combined GBT+VLA ammonia images. We also measured the sub-millimeter polarization vectors along OMC3. These filaments were found to be likely a cylinder-type structure, without dynamic heating, and likely accreting mass along the magnetic field lines.

  12. Kinetics of spontaneous filament nucleation via oligomers: Insights from theory and simulation

    NASA Astrophysics Data System (ADS)

    Šarić, Andela; Michaels, Thomas C. T.; Zaccone, Alessio; Knowles, Tuomas P. J.; Frenkel, Daan

    2016-12-01

    Nucleation processes are at the heart of a large number of phenomena, from cloud formation to protein crystallization. A recently emerging area where nucleation is highly relevant is the initiation of filamentous protein self-assembly, a process that has broad implications in many research areas ranging from medicine to nanotechnology. As such, spontaneous nucleation of protein fibrils has received much attention in recent years with many theoretical and experimental studies focussing on the underlying physical principles. In this paper we make a step forward in this direction and explore the early time behaviour of filamentous protein growth in the context of nucleation theory. We first provide an overview of the thermodynamics and kinetics of spontaneous nucleation of protein filaments in the presence of one relevant degree of freedom, namely the cluster size. In this case, we review how key kinetic observables, such as the reaction order of spontaneous nucleation, are directly related to the physical size of the critical nucleus. We then focus on the increasingly prominent case of filament nucleation that includes a conformational conversion of the nucleating building-block as an additional slow step in the nucleation process. Using computer simulations, we study the concentration dependence of the nucleation rate. We find that, under these circumstances, the reaction order of spontaneous nucleation with respect to the free monomer does no longer relate to the overall physical size of the nucleating aggregate but rather to the portion of the aggregate that actively participates in the conformational conversion. Our results thus provide a novel interpretation of the common kinetic descriptors of protein filament formation, including the reaction order of the nucleation step or the scaling exponent of lag times, and put into perspective current theoretical descriptions of protein aggregation.

  13. The Tumor Inhibitor and Antiangiogenic Agent Withaferin A Targets the Intermediate Filament Protein Vimentin

    PubMed Central

    Bargagna-Mohan, Paola; Hamza, Adel; Kim, Yang-eon; Ho, Yik Khuan (Abby); Mor-Vaknin, Nirit; Wendschlag, Nicole; Liu, Junjun; Evans, Robert M.; Markovitz, David M.; Zhan, Chang-Guo; Kim, Kyung Bo; Mohan, Royce

    2011-01-01

    SUMMARY The natural product withaferin A (WFA) exhibits antitumor and antiangiogenesis activity in vivo, which results from this drug’s potent growth inhibitory activities. Here, we show that WFA binds to the intermediate filament (IF) protein, vimentin, by covalently modifying its cysteine residue, which is present in the highly conserved α-helical coiled coil 2B domain. WFA induces vimentin filaments to aggregate in vitro, an activity manifested in vivo as punctate cytoplasmic aggregates that colocalize vimentin and F-actin. WFA’s potent dominant-negative effect on F-actin requires vimentin expression and induces apoptosis. Finally, we show that WFA-induced inhibition of capillary growth in a mouse model of corneal neovascularization is compromised in vimentin-deficient mice. These findings identify WFA as a chemical genetic probe of IF functions, and illuminate a potential molecular target for withanolide-based therapeutics for treating angioproliferative and malignant diseases. PMID:17584610

  14. The WSRT virgo filament survey

    NASA Astrophysics Data System (ADS)

    Popping, A.; Braun, R.

    2007-02-01

    In the last few years, the realization has emerged that the universal baryons are almost equally distributed by mass in three components: (1) galactic concentrations, (2) a warm-hot intergalactic medium (WHIM) and (3) a diffuse intergalactic medium. These three components are predicted by hydrodynamical simulations and are probed by QSO absorption lines. To observe the WHIM in neutral hydrogen, observations are needed which are deeper than log( NHI) = 18. The WHIM should appear as a Cosmic Web, underlying the galaxies with higher column densities. We have used the WSRT to simulate a filled aperture by observing at very high hour angles, to reach very high column density sensitivity. To achieve even higher image fidelity, an accurate model of the WSRT primary beam was developed. This will be used in the joint deconvolution of the observations. To get a good overview of the distribution and kinematics of the Cosmic Web, a deep survey of 1500 square degrees of sky was undertaken, containing the galaxy filament extending between the Local Group and the Virgo Cluster. The auto-correlation data have been reduced and has an RMS of Δ NHI = 4.2 × 10 16 cm -2 over 20 km s -1. Several sources have been tentatively detected, which were previously unknown, as well as an indication for diffuse intergalactic filaments.

  15. Filamentation with nonlinear Bessel vortices.

    PubMed

    Jukna, V; Milián, C; Xie, C; Itina, T; Dudley, J; Courvoisier, F; Couairon, A

    2014-10-20

    We present a new type of ring-shaped filaments featured by stationary nonlinear high-order Bessel solutions to the laser beam propagation equation. Two different regimes are identified by direct numerical simulations of the nonlinear propagation of axicon focused Gaussian beams carrying helicity in a Kerr medium with multiphoton absorption: the stable nonlinear propagation regime corresponds to a slow beam reshaping into one of the stationary nonlinear high-order Bessel solutions, called nonlinear Bessel vortices. The region of existence of nonlinear Bessel vortices is found semi-analytically. The influence of the Kerr nonlinearity and nonlinear losses on the beam shape is presented. Direct numerical simulations highlight the role of attractors played by nonlinear Bessel vortices in the stable propagation regime. Large input powers or small cone angles lead to the unstable propagation regime where nonlinear Bessel vortices break up into an helical multiple filament pattern or a more irregular structure. Nonlinear Bessel vortices are shown to be sufficiently intense to generate a ring-shaped filamentary ionized channel in the medium which is foreseen as opening the way to novel applications in laser material processing of transparent dielectrics.

  16. Intermediate Filaments: Structure and Assembly.

    PubMed

    Herrmann, Harald; Aebi, Ueli

    2016-11-01

    Proteins of the intermediate filament (IF) supergene family are ubiquitous structural components that comprise, in a cell type-specific manner, the cytoskeleton proper in animal tissues. All IF proteins show a distinctly organized, extended α-helical conformation prone to form two-stranded coiled coils, which are the basic building blocks of these highly flexible, stress-resistant cytoskeletal filaments. IF proteins are highly charged, thus representing versatile polyampholytes with multiple functions. Taking vimentin, keratins, and the nuclear lamins as our prime examples, we present an overview of their molecular and structural parameters. These, in turn, document the ability of IF proteins to form distinct, highly diverse supramolecular assemblies and biomaterials found, for example, at the inner nuclear membrane, throughout the cytoplasm, and in highly complex extracellular appendages, such as hair and nails, of vertebrate organisms. Ultimately, our aim is to set the stage for a more rational understanding of the immediate effects that missense mutations in IF genes have on cellular functions and for their far-reaching impact on the development of the numerous IF diseases caused by them.

  17. Mutation-Specific Effects on Thin Filament Length in Thin Filament Myopathy

    PubMed Central

    de Winter, Josine M.; Joureau, Barbara; Lee, Eun-Jeong; Kiss, Balázs; Yuen, Michaela; Gupta, Vandana A.; Pappas, Christopher T.; Gregorio, Carol C.; Stienen, Ger J. M.; Edvardson, Simon; Wallgren-Pettersson, Carina; Lehtokari, Vilma-Lotta; Pelin, Katarina; Malfatti, Edoardo; Romero, Norma B.; van Engelen, Baziel G.; Voermans, Nicol C.; Donkervoort, Sandra; Bönnemann, C. G.; Clarke, Nigel F.; Beggs, Alan H.; Granzier, Henk; Ottenheijm, Coen A. C.

    2016-01-01

    Objective Thin filament myopathies are among the most common nondystrophic congenital muscular disorders, and are caused by mutations in genes encoding proteins that are associated with the skeletal muscle thin filament. Mechanisms underlying muscle weakness are poorly understood, but might involve the length of the thin filament, an important determinant of force generation. Methods We investigated the sarcomere length-dependence of force, a functional assay that provides insights into the contractile strength of muscle fibers as well as the length of the thin filaments, in muscle fibers from 51 patients with thin filament myopathy caused by mutations in NEB, ACTA1, TPM2, TPM3, TNNT1, KBTBD13, KLHL40, and KLHL41. Results Lower force generation was observed in muscle fibers from patients of all genotypes. In a subset of patients who harbor mutations in NEB and ACTA1, the lower force was associated with downward shifted force–sarcomere length relations, indicative of shorter thin filaments. Confocal microscopy confirmed shorter thin filaments in muscle fibers of these patients. A conditional Neb knockout mouse model, which recapitulates thin filament myopathy, revealed a compensatory mechanism; the lower force generation that was associated with shorter thin filaments was compensated for by increasing the number of sarcomeres in series. This allowed muscle fibers to operate at a shorter sarcomere length and maintain optimal thin–thick filament overlap. Interpretation These findings might provide a novel direction for the development of therapeutic strategies for thin filament myopathy patients with shortened thin filament lengths. PMID:27074222

  18. Growth of filaments and saturation of the filamentation instability

    SciTech Connect

    Gedalin, M.; Medvedev, M.; Spitkovsky, A.; Krasnoselskikh, V.; Vaivads, A.; Perri, S.

    2010-03-15

    The filamentation instability of counterstreaming beams is a nonresonant hydrodynamic-type instability whose growth rate is a smooth function of the wavelength (scale). As a result, perturbations with all unstable wavelengths develop, and the growth saturates due to the saturation of available current. For a given scale, the magnetic field at saturation is proportional to the scale. As a result, the instability develops in a nearly linear regime, where the unstable modes stop growing as soon as the saturation of the corresponding wavelength is reached. At each moment there exists a dominant scale of the magnetic field which is the scale that reached saturation at this particular time. The smaller scales do not disappear and can be easily distinguished in the current structure. The overall growth of the instability stops when the loss of the streaming ion energy because of deceleration is comparable to the initial ion energy.

  19. A Statistical Study of Solar Filament Eruptions

    NASA Astrophysics Data System (ADS)

    Schanche, Nicole; Aggarwal, Ashna; Reeves, Kathy; Kempton, Dustin James; Angryk, Rafal

    2016-05-01

    Solar filaments are cool, dark channels of partially-ionized plasma that lie above the chromosphere. Their structure follows the neutral line between local regions of opposite magnetic polarity. Previous research (e.g. Schmieder et al. 2013, McCauley et al. 2015) has shown a positive correlation (70-80%) between the occurrence of filament eruptions and coronal mass ejections (CME’s). In this study, we attempt to use properties of the filament in order to predict whether or not a given filament will erupt. This prediction would help to better predict the occurrence of an oncoming CME. To track the evolution of a filament over time, a spatio-temporal algorithm that groups separate filament instances from the Heliophysics Event Knowledgebase (HEK) into filament tracks was developed. Filament features from the HEK metadata, such as length, chirality, and tilt are then combined with other physical features, such as the overlying decay index for two sets of filaments tracks - those that erupt and those that remain bound. Using statistical methods such as the Kolmogrov-Smirnov test and a Random Forest Classifier, we determine the effectiveness of the combined features in prediction. We conclude that there is significant overlap between the properties of filaments that erupt and those that do not, leading to predictions only ~5-10% above chance. However, the changes in features, such as a change in the filament's length over time, were determined to have the highest predictive power. We discuss the possible physical connections with the change in these features."This project has been supported by funding from the Division of Advanced Cyberinfrastructure within the Directorate for Computer and Information Science and Engineering, the Division of Astronomical Sciences within the Directorate for Mathematical and Physical Sciences, and the Division of Atmospheric and Geospace Sciences within the Directorate for Geosciences, under NSF award #1443061.”

  20. Bundle formation of smooth muscle desmin intermediate filaments by calponin and its binding site on the desmin molecule.

    PubMed

    Fujii, T; Takagi, H; Arimoto, M; Ootani, H; Ueeda, T

    2000-03-01

    Smooth muscle basic calponin, a major actin-, tropomyosin-, and calmodulin-binding protein, has been examined for its ability to interact with desmin intermediate filaments from smooth muscle cells using sedimentation analysis, turbidity changes, chemical cross-linking, matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI TOF/MS), and electron microscopic observations. Calponin interacted with desmin intermediate filaments in a concentration-dependent manner in vitro. The binding of calponin to desmin produced dense aggregates at 30 degrees C. The dense aggregates were observed by electron microscopy to be composed of large anisotropic bundles of desmin filaments, indicating that calponin forms bundles of desmin filaments. The addition of calmodulin or S100 to the mixture of calponin and desmin caused the removal of calponin from the desmin filaments and inhibited bundle formation in the presence of Ca(2+), but not in the presence of EGTA. Calponin-related proteins including G-actin, tropomyosin, and SM22, had little effect on the binding of calponin to desmin filaments, whereas tubulin weakly inhibited the binding. Desmin had little influence on the calponin-actin and calponin-tubulin interactions using the zero-length cross-linker, EDC. Domain mapping with chymotryptic digestion showed that the binding site of calponin resides within the central a-helical rod domain of the desmin molecule. The chemical cross-linked products of calponin and synthetic peptides (TQ27, TNEKVELQELNDRFANYIEKVRFLEQQ; EE24, EEELRELRRQVDALTGQRARVEVE) derived from the rod domain were detected by MALDI TOF/MS. Furthermore, the calponin-desmin interaction was significantly inhibited by the addition of EE24, but only slightly by TQ27. These results suggest that calponin may act as a cross-linking protein between desmin filaments as well as among intermediate filaments, microfilaments and microtubules in smooth muscle cells.

  1. Stability and gelation behavior of bovine serum albumin pre-aggregates in the presence of calcium chloride.

    PubMed

    Wu, Hua; Arosio, Paolo; Podolskaya, Olga Gennadievna; Wei, Dan; Morbidelli, Massimo

    2012-04-14

    We study, using wide-angle and small-angle light scattering techniques, the stability and aggregation/gelation behaviors of denatured filamentous bovine serum albumin pre-aggregates (BSA-PAs), induced by CaCl(2). It is observed that transparent filamentous gels can be formed not only at low CaCl(2) concentrations but also at high CaCl(2) concentrations, while turbid gels are obtained at intermediate CaCl(2) concentrations. Although the filamentous gels at low CaCl(2) concentrations and the turbid gels at intermediate CaCl(2) concentrations are consistent with the literature observations, the filamentous gels at high CaCl(2) concentrations have to be explained by different mechanisms. The latter is attributed to the repulsive hydration interactions originating from increased surface dipoles generated by counterion binding. Since such surface dipole-induced hydration is very short-range and occurs mainly on charged or polar patches of proteins (thus protected from aggregation), the aggregation of the filamentous BSA-PAs at hydrophobic patches at the two ends is still possible, leading to formation of the filamentous gels.

  2. A First Approach to Filament Dynamics

    ERIC Educational Resources Information Center

    Silva, P. E. S.; de Abreu, F. Vistulo; Simoes, R.; Dias, R. G.

    2010-01-01

    Modelling elastic filament dynamics is a topic of high interest due to the wide range of applications. However, it has reached a high level of complexity in the literature, making it unaccessible to a beginner. In this paper we explain the main steps involved in the computational modelling of the dynamics of an elastic filament. We first derive…

  3. Filament-induced laser machining (FILM)

    NASA Astrophysics Data System (ADS)

    Kiselev, D.; Woeste, L.; Wolf, J.-P.

    2010-09-01

    Laser filamentation provides high intensity plasma strings of micrometric diameters and lengths of tens of centimeters. We demonstrate that these filaments can be used for remotely drilling and cutting metals and biological materials such as flesh and bones. Since no tight focusing is needed, complex 3D shapes can be machined without any adjustment of the laser while processing.

  4. One Half Million Mile Solar Filament

    NASA Video Gallery

    NASA’s Solar Dynamics Observatory (SDO) captures a very long, whip-like solar filament extending over half a million miles in a long arc above the sun’s surface. Filaments are cooler clouds of ...

  5. Radial Infall onto a Massive Molecular Filament

    NASA Astrophysics Data System (ADS)

    Battersby, Cara; Myers, Philip C.; Shirley, Yancy L.; Keto, Eric; Kirk, Helen

    The newly discovered Massive Molecular Filament (MMF) G32.02+0.05 (~ 70 pc long, 105 M⊙) has been shaped and compressed by older generations of massive stars. The similarity of this filament in physical structure (density profile, temperature) to much smaller star-forming filaments, suggests that the mechanism to form such filaments may be a universal process. The densest portion of the filament, apparent as an Infrared Dark Cloud (IRDC) shows a range of massive star formation signatures throughout. We investigate the kinematics in this filament and find widespread inverse P cygni asymmetric line profiles. These line asymmetries are interpreted as a signature of large-scale radial collapse. Using line asymmetries observed with optically thick HCO+ (1-0) and optically thin H13CO+ (1-0) across a range of massive star forming regions in the filament, we estimate the global radial infall rate of the filament to range from a few 100 to a few 1000 M⊙ Myr-1 pc-1. At its current infall rate the densest portions of the cloud will more than double their current mass within a Myr.

  6. Kinetics of filamentous phage assembly

    NASA Astrophysics Data System (ADS)

    Ploss, Martin; Kuhn, Andreas

    2010-12-01

    Filamentous phages release their progeny particles by a secretory process without lysing the bacterial cell. By this process about 6 viral particles per min are secreted from each cell. We show here that when the major coat protein (gp8) is provided from a plasmid we observe a phage progeny production rate depending on the induction of gp8 by IPTG. We also show that a transfection of Escherichia coli lacking F-pili is observed using a mutant of M13 that carries an ampicillin resistance gene, and phage particles are secreted in the absence of an F-plasmid. Extruding phage was visualized by atomic force microscopy (AFM) and by transmission electron microscopy (TEM) using gold-labeled antibodies to the major coat protein.

  7. Particles trajectories in magnetic filaments

    SciTech Connect

    Bret, A.

    2015-07-15

    The motion of a particle in a spatially harmonic magnetic field is a basic problem involved, for example, in the mechanism of formation of a collisionless shock. In such settings, it is generally reasoned that particles entering a Weibel generated turbulence are trapped inside it, provided their Larmor radius in the peak field is smaller than the field coherence length. The goal of this work is to put this heuristic conclusion on firm ground by studying, both analytically and numerically, such motion. A toy model is analyzed, consisting of a relativistic particle entering a region of space occupied by a spatially harmonic field. The particle penetrates the magnetic structure in a direction aligned with the magnetic filaments. Although the conclusions are not trivial, the main result is confirmed.

  8. Natural colorants from filamentous fungi.

    PubMed

    Torres, Fábio Aurélio Esteves; Zaccarim, Bruna Regina; de Lencastre Novaes, Letícia Celia; Jozala, Angela Faustino; Dos Santos, Carolina Alves; Teixeira, Maria Francisca Simas; Santos-Ebinuma, Valéria Carvalho

    2016-03-01

    In the last years, there is a trend towards the replacement of synthetic colorants by natural ones, mainly due to the increase of consumer demand for natural products. The natural colorants are used to enhance the appearance of pharmaceutical products, food, and different materials, making them preferable or attractive. This review intends to provide and describe a comprehensive overview of the history of colorants, from prehistory to modern time, of their market and their applications, as well as of the most important aspects of the fermentation process to obtain natural colorants. Focus is given to colorants produced by filamentous fungal species, aiming to demonstrate the importance of these microorganisms and biocompounds, highlighting the production performance to get high yields and the aspects of conclusion that should be taken into consideration in future studies about natural colorants.

  9. INTERMEDIATE FILAMENTS IN SMOOTH MUSCLE

    PubMed Central

    Tang, Dale D.

    2008-01-01

    The intermediate filament (IF) network is one of the three cytoskeletal systems in smooth muscle. The type III IF proteins vimentin and desmin are major constituents of the network in smooth muscle cells and tissues. Lack of vimentin or desmin impairs contractile ability of various smooth muscle preparations, implying their important role for smooth muscle force development. The IF framework has long been viewed as a fixed cytostructure that solely provides mechanical integrity for the cell. However, recent studies suggest that the IF cytoskeleton is dynamic in mammalian cells in response to various external stimulation. In this review, the structure and biological properties of IF proteins in smooth muscle are summarized. The role of IF proteins in the modulation of smooth muscle force development and redistribution/translocation of signaling partners (such as p130 Crk-associated substrate, CAS) is depicted. This review also summarizes our latest understanding on how the IF network may be regulated in smooth muscle. PMID:18256275

  10. Enigmatic reticulated filaments in subsurface granite.

    PubMed

    Miller, A Z; Hernández-Mariné, M; Jurado, V; Dionísio, A; Barquinha, P; Fortunato, E; Afonso, M J; Chaminé, H I; Saiz-Jimenez, C

    2012-12-01

    In the last few years, geomicrobiologists have focused their researches on the nature and origin of enigmatic reticulated filaments reported in modern and fossil samples from limestone caves and basalt lava tubes. Researchers have posed questions on these filaments concerning their nature, origin, chemistry, morphology, mode of formation and growth. A tentative microbial origin has been elusive since these filaments are found as hollow tubular sheaths and could not be affiliated to any known microorganism. We describe the presence of similar structures in a 16th century granite tunnel in Porto, Northwest Portugal. The reticulated filaments we identify exhibit fine geometry surface ornamentation formed by cross-linked Mn-rich nanofibres, surrounded by a large amount of extracellular polymeric substances. Within these Mn-rich filaments we report for the first time the occurrence of microbial cells.

  11. Epithelial Intermediate Filaments: Guardians against Microbial Infection?

    PubMed Central

    Geisler, Florian; Leube, Rudolf E.

    2016-01-01

    Intermediate filaments are abundant cytoskeletal components of epithelial tissues. They have been implicated in overall stress protection. A hitherto poorly investigated area of research is the function of intermediate filaments as a barrier to microbial infection. This review summarizes the accumulating knowledge about this interaction. It first emphasizes the unique spatial organization of the keratin intermediate filament cytoskeleton in different epithelial tissues to protect the organism against microbial insults. We then present examples of direct interaction between viral, bacterial, and parasitic proteins and the intermediate filament system and describe how this affects the microbe-host interaction by modulating the epithelial cytoskeleton, the progression of infection, and host response. These observations not only provide novel insights into the dynamics and function of intermediate filaments but also indicate future avenues to combat microbial infection. PMID:27355965

  12. Quantifying protein diffusion and capture on filaments.

    PubMed

    Reithmann, Emanuel; Reese, Louis; Frey, Erwin

    2015-02-17

    The functional relevance of regulating proteins is often limited to specific binding sites such as the ends of microtubules or actin-filaments. A localization of proteins on these functional sites is of great importance. We present a quantitative theory for a diffusion and capture process, where proteins diffuse on a filament and stop diffusing when reaching the filament's end. It is found that end-association after one-dimensional diffusion is the main source for tip-localization of such proteins. As a consequence, diffusion and capture is highly efficient in enhancing the reaction velocity of enzymatic reactions, where proteins and filament ends are to each other as enzyme and substrate. We show that the reaction velocity can effectively be described within a Michaelis-Menten framework. Together, one-dimensional diffusion and capture beats the (three-dimensional) Smoluchowski diffusion limit for the rate of protein association to filament ends.

  13. Lamp automatically switches to new filament on burnout

    NASA Technical Reports Server (NTRS)

    Ingle, W. B.

    1966-01-01

    Lamp with primary and secondary filaments has a means for automatic switching to the secondary filament at primary filament burnout. Lamp failures and resultant expenses during oscillograph printing are appreciably reduced.

  14. The invertebrate myosin filament: subfilament arrangement of the solid filaments of insect flight muscles.

    PubMed Central

    Beinbrech, G; Ashton, F T; Pepe, F A

    1992-01-01

    Transverse sections (approximately 140 nm thick) of solid myosin filaments of the flight muscles of the fleshfly, Phormia terrae-novae, the honey bee, Apis mellifica, and the waterbug, Lethocerus uhleri, were photographed in a JEM model 200A electron microscope at 200 kV. The images were digitized and computer processed by rotational filtering. In each of these filaments it was found that the symmetry of the core and the wall was not the same. The power spectra of the images showed sixfold symmetry for the wall and threefold symmetry for the core of the filaments. The images of the filaments in each muscle were superimposed according to the sixfold center of the wall. These averaged images for all three muscles showed six pairs of subunits in the wall similar to those found in the wall of tubular filaments. From serial sections of the fleshfly filaments, we conclude that the subunits in the wall of the filaments represent subfilaments essentially parallel to the long axis of the filament. In each muscle there are additional subunits in the core, closely related to the subunits in the wall. Evaluation of serial sections through fleshfly filaments suggests that the relationship of the three subunits observed in the core to those in the wall varies along the length of the filaments. In waterbug filaments there are three dense and three less dense subunits for a total of six all closely related to the wall. Bee filaments have three subunits related to the wall and three subunits located eccentrically in the core of the filaments. The presence of core subunits can be related to the paramyosin content of the filaments. Images FIGURE 1 FIGURE 3 FIGURE 4 FIGURE 5 FIGURE 7 FIGURE 9 FIGURE 12 PMID:1617135

  15. Aggregations in Flatworms.

    ERIC Educational Resources Information Center

    Liffen, C. L.; Hunter, M.

    1980-01-01

    Described is a school project to investigate aggregations in flatworms which may be influenced by light intensity, temperature, and some form of chemical stimulus released by already aggregating flatworms. Such investigations could be adopted to suit many educational levels of science laboratory activities. (DS)

  16. Unbonded Aggregate Surface Roads

    DTIC Science & Technology

    2006-12-01

    are sufficiently angular and rough in texture, thus ensuring mixture stability. A popular asphalt mixture design method called Superpave Level 1...would not pass either of the Superpave aggregate requirements. Table 18 Additional Characteristics for the Fine Fraction Abbreviated Common Name...CBR values when compacted wet of optimum. This is likely attributable to their relatively high permeabilities . For soaked CBR tests, the aggregates

  17. Erosion of dust aggregates

    NASA Astrophysics Data System (ADS)

    Seizinger, A.; Krijt, S.; Kley, W.

    2013-12-01

    Aims: The aim of this work is to gain a deeper insight into how much different aggregate types are affected by erosion. Especially, it is important to study the influence of the velocity of the impacting projectiles. We also want to provide models for dust growth in protoplanetary disks with simple recipes to account for erosion effects. Methods: To study the erosion of dust aggregates we employed a molecular dynamics approach that features a detailed micro-physical model of the interaction of spherical grains. For the first time, the model has been extended by introducing a new visco-elastic damping force, which requires a proper calibration. Afterwards, different sample generation methods were used to cover a wide range of aggregate types. Results: The visco-elastic damping force introduced in this work turns out to be crucial to reproduce results obtained from laboratory experiments. After proper calibration, we find that erosion occurs for impact velocities of 5 ms-1 and above. Though fractal aggregates as formed during the first growth phase are most susceptible to erosion, we observe erosion of aggregates with rather compact surfaces as well. Conclusions: We find that bombarding a larger target aggregate with small projectiles results in erosion for impact velocities as low as a few ms-1. More compact aggregates suffer less from erosion. With increasing projectile size the transition from accretion to erosion is shifted to higher velocities. This allows larger bodies to grow through high velocity collisions with smaller aggregates.

  18. Unwinding motion of a twisted active region filament

    SciTech Connect

    Yan, X. L.; Xue, Z. K.; Kong, D. F.; Liu, J. H.; Xu, C. L.

    2014-12-10

    To better understand the structures of active region filaments and the eruption process, we study an active region filament eruption in active region NOAA 11082 in detail on 2010 June 22. Before the filament eruption, the opposite unidirectional material flows appeared in succession along the spine of the filament. The rising of the filament triggered two B-class flares at the upper part of the filament. As the bright material was injected into the filament from the sites of the flares, the filament exhibited a rapid uplift accompanying the counterclockwise rotation of the filament body. From the expansion of the filament, we can see that the filament consisted of twisted magnetic field lines. The total twist of the filament is at least 5π obtained by using a time slice method. According to the morphology change during the filament eruption, it is found that the active region filament was a twisted flux rope and its unwinding motion was like a solar tornado. We also find that there was a continuous magnetic helicity injection before and during the filament eruption. It is confirmed that magnetic helicity can be transferred from the photosphere to the filament. Using the extrapolated potential fields, the average decay index of the background magnetic fields over the filament is 0.91. Consequently, these findings imply that the mechanism of solar filament eruption could be due to the kink instability and magnetic helicity accumulation.

  19. The Hydrodynamic Stability of Gaseous Cosmic Filaments

    NASA Astrophysics Data System (ADS)

    Birnboim, Yuval; Padnos, Dan; Zinger, Elad

    2016-11-01

    Virial shocks at the edges of cosmic-web structures are a clear prediction of standard structure formation theories. We derive a criterion for the stability of the post-shock gas and of the virial shock itself in spherical, filamentary, and planar infall geometries. When gas cooling is important, we find that shocks become unstable, and gas flows uninterrupted toward the center of the respective halo, filament, or sheet. For filaments, we impose this criterion on self-similar infall solutions. We find that instability is expected for filament masses between 1011 and 1013 {M}⊙ Mpc-1. Using a simplified toy model, we then show that these filaments will likely feed halos with 1010 M ⊙ ≲ M halo ≲ 1013 M ⊙ at redshift z = 3, as well as 1012 M ⊙ ≲ M halo ≲ 1015 M ⊙ at z = 0. The instability will affect the survivability of the filaments as they penetrate gaseous halos in a non-trivial way. Additionally, smaller halos accreting onto non-stable filaments will not be subject to ram pressure inside the filaments. The instreaming gas will continue toward the center and stop either once its angular momentum balances the gravitational attraction, or when its density becomes so high that it becomes self-shielded to radiation.

  20. Thermal and Chemical Evolution of Collapsing Filaments

    SciTech Connect

    Gray, William J.; Scannapieco, Evan

    2013-01-15

    Intergalactic filaments form the foundation of the cosmic web that connect galaxies together, and provide an important reservoir of gas for galaxy growth and accretion. Here we present very high resolution two-dimensional simulations of the thermal and chemical evolution of such filaments, making use of a 32 species chemistry network that tracks the evolution of key molecules formed from hydrogen, oxygen, and carbon. We study the evolution of filaments over a wide range of parameters including the initial density, initial temperature, strength of the dissociating UV background, and metallicity. In low-redshift, Z ≈ 0.1Z filaments, the evolution is determined completely by the initial cooling time. If this is sufficiently short, the center of the filament always collapses to form dense, cold core containing a substantial fraction of molecules. In high-redshift, Z = 10-3Z filaments, the collapse proceeds much more slowly. This is due mostly to the lower initial temperatures, which leads to a much more modest increase in density before the atomic cooling limit is reached, making subsequent molecular cooling much less efficient. Finally, we study how the gravitational potential from a nearby dwarf galaxy affects the collapse of the filament and compare this to NGC 5253, a nearby starbusting dwarf galaxy thought to be fueled by the accretion of filament gas. In contrast to our fiducial case, a substantial density peak forms at the center of the potential. This peak evolves faster than the rest of the filament due to the increased rate at which chemical species form and cooling occur. We find that we achieve similar accretion rates as NGC 5253, but our two-dimensional simulations do not recover the formation of the giant molecular clouds that are seen in radio observations.

  1. Automatic filament warm-up controller

    NASA Technical Reports Server (NTRS)

    Mccluskey, J.; Daeges, J.

    1979-01-01

    As part of the unattended operations objective of the Deep Space Network deep space stations, this filament controller serves as a step between manual operation of the station and complete computer control. Formerly, the operator was required to devote five to fifteen minutes of his time just to properly warm up the filaments on the klystrons of the high power transmitters. The filament controller reduces the operator's duty to a one-step command and is future-compatible with various forms of computer control.

  2. Optical rogue wave statistics in laser filamentation.

    PubMed

    Kasparian, Jérôme; Béjot, Pierre; Wolf, Jean-Pierre; Dudley, John M

    2009-07-06

    We experimentally observed optical rogue wave statistics during high power femtosecond pulse filamentation in air. We characterized wavelength-dependent intensity fluctuations across 300 nm broadband filament spectra generated by pulses with several times the critical power for filamentation. We show how the statistics vary from a near-Gaussian distribution in the vicinity of the pump to a long tailed "L-shaped" distribution at the short wavelength and long wavelength edges. The results are interpreted in terms of pump noise transfer via self-phase modulation.

  3. System Applies Polymer Powder To Filament Tow

    NASA Technical Reports Server (NTRS)

    Baucom, Robert M.; Snoha, John J.; Marchello, Joseph M.

    1993-01-01

    Polymer powder applied uniformly and in continuous manner. Powder-coating system applies dry polymer powder to continuous fiber tow. Unique filament-spreading technique, combined with precise control of tension on fibers in system, ensures uniform application of polymer powder to web of spread filaments. Fiber tows impregnated with dry polymer powders ("towpregs") produced for preform-weaving and composite-material-molding applications. System and process valuable to prepreg industry, for production of flexible filament-windable tows and high-temperature polymer prepregs.

  4. Charged Dust Aggregate Interactions

    NASA Astrophysics Data System (ADS)

    Matthews, Lorin; Hyde, Truell

    2015-11-01

    A proper understanding of the behavior of dust particle aggregates immersed in a complex plasma first requires a knowledge of the basic properties of the system. Among the most important of these are the net electrostatic charge and higher multipole moments on the dust aggregate as well as the manner in which the aggregate interacts with the local electrostatic fields. The formation of elongated, fractal-like aggregates levitating in the sheath electric field of a weakly ionized RF generated plasma discharge has recently been observed experimentally. The resulting data has shown that as aggregates approach one another, they can both accelerate and rotate. At equilibrium, aggregates are observed to levitate with regular spacing, rotating about their long axis aligned parallel to the sheath electric field. Since gas drag tends to slow any such rotation, energy must be constantly fed into the system in order to sustain it. A numerical model designed to analyze this motion provides both the electrostatic charge and higher multipole moments of the aggregate while including the forces due to thermophoresis, neutral gas drag, and the ion wakefield. This model will be used to investigate the ambient conditions leading to the observed interactions. This research is funded by NSF Grant 1414523.

  5. Filament overwrapped motor case technology

    NASA Astrophysics Data System (ADS)

    Compton, Joel P.

    1993-11-01

    Atlantic Research Corporation (ARC) joined with the French Societe Europeenne de Propulsion (SEP) to develop and deliver to the U.S. Navy a small quantity of composite filament wound rocket motors to demonstrate a manufacturing technique that was being applied at the two companies. It was perceived that the manufacturing technique could produce motors that would be light in weight, inexpensive to produce, and that had a good chance of meeting insensitive munitions (IM) requirements that were being formulated by the Navy in the early 1980s. Under subcontract to ARC, SEP designed, tested, and delivered 2.75-inch rocket motors to the U.S. Navy for IM tests that were conducted in 1989 at China Lake, California. The program was one of the first to be founded by Nunn Amendment money. The Government-to-Government program was sponsored by the Naval Air Systems Command and was monitored by the Naval Surface Warfare Center, Indian Head (NSWC-IH), Maryland. The motor propellant that was employed was a new, extruded composite formulation that was under development at the Naval Surface Warfare Center. The following paper describes the highlights of the program and gives the results of structural and ballistic static tests and insensitive munitions tests that were conducted on demonstration motors.

  6. Aggregate and the environment

    USGS Publications Warehouse

    Langer, William H.; Drew, Lawrence J.; Sachs, J.S.

    2004-01-01

    This book is designed to help you understand our aggregate resources-their importance, where they come from, how they are processed for our use, the environmental concerns related to their mining and processing, how those concerns are addressed, and the policies and regulations designed to safeguard workers, neighbors, and the environment from the negative impacts of aggregate mining. We hope this understanding will help prepare you to be involved in decisions that need to be made-individually and as a society-to be good stewards of our aggregate resources and our living planet.

  7. Thioredoxin is required for filamentous phage assembly.

    PubMed Central

    Russel, M; Model, P

    1985-01-01

    Sequence comparisons show that the fip gene product of Escherichia coli, which is required for filamentous phage assembly, is thioredoxin. Thioredoxin serves as a cofactor for reductive processes in many cell types and is a constituent of phage T7 DNA polymerase. The fip-1 mutation makes filamentous phage and T7 growth temperature sensitive in cells that carry it. The lesion lies within a highly conserved thioredoxin active site. Thioredoxin reductase (NADPH), as well as thioredoxin, is required for efficient filamentous phage production. Mutant phages defective in phage gene I are particularly sensitive to perturbations in the fip-thioredoxin system. A speculative model is presented in which thioredoxin reductase, thioredoxin, and the gene I protein interact to drive an engine for filamentous phage assembly. Images PMID:3881756

  8. Physical properties of cytoplasmic intermediate filaments.

    PubMed

    Block, Johanna; Schroeder, Viktor; Pawelzyk, Paul; Willenbacher, Norbert; Köster, Sarah

    2015-11-01

    Intermediate filaments (IFs) constitute a sophisticated filament system in the cytoplasm of eukaryotes. They form bundles and networks with adapted viscoelastic properties and are strongly interconnected with the other filament types, microfilaments and microtubules. IFs are cell type specific and apart from biochemical functions, they act as mechanical entities to provide stability and resilience to cells and tissues. We review the physical properties of these abundant structural proteins including both in vitro studies and cell experiments. IFs are hierarchical structures and their physical properties seem to a large part be encoded in the very specific architecture of the biopolymers. Thus, we begin our review by presenting the assembly mechanism, followed by the mechanical properties of individual filaments, network and structure formation due to electrostatic interactions, and eventually the mechanics of in vitro and cellular networks. This article is part of a Special Issue entitled: Mechanobiology.

  9. Viscosity of Sheared Helical filament Suspensions

    NASA Astrophysics Data System (ADS)

    Sartucci, Matthew; Urbach, Jeff; Blair, Dan; Schwenger, Walter

    The viscosity of suspensions can be dramatically affected by high aspect ratio particles. Understanding these systems provides insight into key biological functions and can be manipulated for many technological applications. In this talk, the viscosity as a function of shear rate of suspensions of helical filaments is compared to that of suspensions of straight rod-like filaments. Our goal is to determine the impact of filament geometry on low volume fraction colloidal suspensions in order to identify strategies for altering viscosity with minimal volume fraction. In this research, the detached flagella of the bacteria Salmonella Typhimurium are used as a model system of helical filaments and compared to mutated straight flagella of the Salmonella. We compare rheological measurements of the suspension viscosity in response to shear flow and use a combination of the rheology and fluorescence microscopy to identify the microstructural changes responsible for the observed rheological response.

  10. Tunnel ionization, population trapping, filamentation and applications

    NASA Astrophysics Data System (ADS)

    Leang Chin, See; Xu, Huailiang

    2016-11-01

    The advances in femtosecond Ti-sapphire laser technology have led to the discovery of a profusion of new physics. This review starts with a brief historical account of the experimental realization of tunnel ionization, followed by high harmonic generation and the prediction of attosecond pulses. Then, the unique phenomenon of dynamic population trapping during the ionization of atoms and molecules in intense laser fields is introduced. One of the consequences of population trapping in the highly excited states is the neutral dissociation into simple molecular fragments which fluoresce. Such fluorescence could be amplified in femtosecond laser filamentation in gases. The experimental observations of filament-induced fluorescence and lasing in the atmosphere and combustion flames are given. Excitation of molecular rotational wave packets (molecular alignment) and their relaxation and revival in a gas filament are described. Furthermore, filament-induced condensation and precipitation inside a cloud chamber is explained. Lastly, a summary and future outlook is given.

  11. Huge Filament Rises From Sun's Northern Hemisphere

    NASA Video Gallery

    On August 1, 2010 following a C3-class solar flare from sunspot 1092, an enormous magnetic filament stretching across the sun's northern hemisphere erupted. This 304 angstrom video shows that filam...

  12. Filament-wound, fiberglass cryogenic tank supports

    NASA Technical Reports Server (NTRS)

    Carter, J. S.; Timberlake, T. E.

    1971-01-01

    The design, fabrication, and testing of filament-wound, fiberglass cryogenic tank supports for a LH2 tank, a LF2/FLOX tank and a CH4 tank. These supports consist of filament-wound fiberglass tubes with titanium end fittings. These units were satisfactorily tested at cryogenic temperatures, thereby offering a design that can be reliably and economically produced in large or small quantities. The basic design concept is applicable to any situation where strong, lightweight axial load members are desired.

  13. A Robust Actin Filaments Image Analysis Framework

    PubMed Central

    Alioscha-Perez, Mitchel; Benadiba, Carine; Goossens, Katty; Kasas, Sandor; Dietler, Giovanni; Willaert, Ronnie; Sahli, Hichem

    2016-01-01

    The cytoskeleton is a highly dynamical protein network that plays a central role in numerous cellular physiological processes, and is traditionally divided into three components according to its chemical composition, i.e. actin, tubulin and intermediate filament cytoskeletons. Understanding the cytoskeleton dynamics is of prime importance to unveil mechanisms involved in cell adaptation to any stress type. Fluorescence imaging of cytoskeleton structures allows analyzing the impact of mechanical stimulation in the cytoskeleton, but it also imposes additional challenges in the image processing stage, such as the presence of imaging-related artifacts and heavy blurring introduced by (high-throughput) automated scans. However, although there exists a considerable number of image-based analytical tools to address the image processing and analysis, most of them are unfit to cope with the aforementioned challenges. Filamentous structures in images can be considered as a piecewise composition of quasi-straight segments (at least in some finer or coarser scale). Based on this observation, we propose a three-steps actin filaments extraction methodology: (i) first the input image is decomposed into a ‘cartoon’ part corresponding to the filament structures in the image, and a noise/texture part, (ii) on the ‘cartoon’ image, we apply a multi-scale line detector coupled with a (iii) quasi-straight filaments merging algorithm for fiber extraction. The proposed robust actin filaments image analysis framework allows extracting individual filaments in the presence of noise, artifacts and heavy blurring. Moreover, it provides numerous parameters such as filaments orientation, position and length, useful for further analysis. Cell image decomposition is relatively under-exploited in biological images processing, and our study shows the benefits it provides when addressing such tasks. Experimental validation was conducted using publicly available datasets, and in osteoblasts

  14. Making Linked, Wound-Filament Bands

    NASA Technical Reports Server (NTRS)

    Bamford, Robert M.; Stephens, James B.

    1987-01-01

    Chains produced by use of rotating mandrel. Mandrel and locating and driving disks assembled around first band. Mandrel and band then mounted in respective positions on filament-winding machine. Second band linked to first by winding filament around first band on rotating mandrel. Short chains made this way have variety of uses; example, thermal isolators, each consisting of two linked bands of insulating material, used to support two separated insulating sheilds surrounding container of liquid helium.

  15. Flux Cancellation Leading to CME Filament Eruptions

    NASA Technical Reports Server (NTRS)

    Popescu, Roxana M.; Panesar, Navdeep K.; Sterling, Alphonse C.; Moore, Ronald L.

    2016-01-01

    Solar filaments are strands of relatively cool, dense plasma magnetically suspended in the lower density hotter solar corona. They trace magnetic polarity inversion lines (PILs) in the photosphere below, and are supported against gravity at heights of up to approx.100 Mm above the chromosphere by the magnetic field in and around them. This field erupts when it is rendered unstable, often by magnetic flux cancellation or emergence at or near the PIL. We have studied the evolution of photospheric magnetic flux leading to ten observed filament eruptions. Specifically, we look for gradual magnetic changes in the neighborhood of the PIL prior to and during eruption. We use Extreme Ultraviolet (EUV) images from the Atmospheric Imaging Assembly (AIA), and magnetograms from the Helioseismic and Magnetic Imager (HMI), both on board the Solar Dynamics Observatory (SDO), to study filament eruptions and their photospheric magnetic fields. We examine whether flux cancellation or/and emergence leads to filament eruptions. We find that continuous flux cancellation was present at the PIL for many hours prior to each eruption. We present two CME-producing eruptions in detail and find the following: (a) the pre-eruption filament-holding core field is highly sheared and appears in the shape of a sigmoid above the PIL; (b) at the start of the eruption the opposite arms of the sigmoid reconnect in the middle above the site of (tether-cutting) flux cancellation at the PIL; (c) the filaments first show a slow-rise, followed by a fast-rise as they erupt. We conclude that these two filament eruptions result from flux cancellation in the middle of the sheared field, and thereafter evolve in agreement with the standard model for a CME/flare filament eruption from a closed bipolar magnetic field [flux cancellation (van Ballegooijen and Martens 1989 and Moore and Roumelrotis 1992) and runaway tether-cutting (Moore et. al 2001)].

  16. Intense EM filamentation in relativistic hot plasmas

    NASA Astrophysics Data System (ADS)

    Hu, Qiang-Lin; Chen, Zhong-Ping; Mahajan, Swadesh M.

    2017-03-01

    Through 2D particle-in-cell (PIC) simulations, we demonstrate that the nature of filamentation of a high intensity electromagnetic (EM) pulse propagating in an underdense plasma, is profoundly affected at relativistically high temperatures. The "relativistic" filaments are sharper, are dramatically extended (along the direction of propagation), and live much longer than their lower temperature counterparts. The thermally boosted electron inertia is invoked to understand this very interesting and powerful phenomenon.

  17. Marine aggregate dynamics

    NASA Astrophysics Data System (ADS)

    The direction and scope of the Office of Naval Research's Marine Aggregate Dynamics Accelerated Research Initiative will be the topic of an open-house style meeting February 14, 7:30-10:00 P.M. in Ballroom D of the Hyatt Regency New Orleans at the Louisiana Superdome. This meeting is scheduled during the AGU/American Society of Limnology and Oceanography Ocean Sciences Meeting February 12-16 in New Orleans.The critical focus of the ARI is the measurement and modeling of the dynamics of the biological, physical, chemical and molecular processes that drive aggregation and produce aggregates. This new ARI will provide funding in Fiscal Years 1991-1995 to identify and quantify mechanisms that determine the distribution, abundance and size spectrum of aggregated particulate matter in the ocean.

  18. Protein Colloidal Aggregation Project

    NASA Technical Reports Server (NTRS)

    Oliva-Buisson, Yvette J. (Compiler)

    2014-01-01

    To investigate the pathways and kinetics of protein aggregation to allow accurate predictive modeling of the process and evaluation of potential inhibitors to prevalent diseases including cataract formation, chronic traumatic encephalopathy, Alzheimer's Disease, Parkinson's Disease and others.

  19. Aggregation and Averaging.

    ERIC Educational Resources Information Center

    Siegel, Irving H.

    The arithmetic processes of aggregation and averaging are basic to quantitative investigations of employment, unemployment, and related concepts. In explaining these concepts, this report stresses need for accuracy and consistency in measurements, and describes tools for analyzing alternative measures. (BH)

  20. Discovery of a pre-existing molecular filament associated with supernova remnant G127.1+0.5

    SciTech Connect

    Zhou, Xin; Yang, Ji; Fang, Min; Su, Yang

    2014-08-20

    We performed millimeter observations in CO lines toward the supernova remnant (SNR) G127.1+0.5. We found a molecular filament at 4-13 km s{sup –1} consisting of two distinct parts: a straight part coming out of the remnant region and a curved part in the remnant region. The curved part is coincides well with the bright SNR shell detected in 1420 MHz radio continuum and mid-infrared observations in the northeastern region. In addition, redshifted line wing broadening is found only in the curved part of the molecular filament, which indicates a physical interaction. These provide strong evidences, for the first time, to confirm the association between an SNR and a pre-existing long molecular filament. Multi-band observations in the northeastern remnant shell could be explained by the interaction between the remnant shock and the dense molecular filament. RADEX radiative transfer modeling of the quiet and shocked components yield physical conditions consistent with the passage of a non-dissociative J-type shock. We argue that the curved part of the filament is fully engulfed by the remnant's forward shock. A spatial correlation between aggregated young stellar objects (YSOs) and the adjacent molecular filament close to the SNR is also found, which could be related to the progenitor's activity.

  1. Filaments in the Lupus molecular clouds

    NASA Astrophysics Data System (ADS)

    Benedettini, M.; Schisano, E.; Pezzuto, S.; Elia, D.; André, P.; Könyves, V.; Schneider, N.; Tremblin, P.; Arzoumanian, D.; di Giorgio, A. M.; Di Francesco, J.; Hill, T.; Molinari, S.; Motte, F.; Nguyen-Luong, Q.; Palmeirim, P.; Rivera-Ingraham, A.; Roy, A.; Rygl, K. L. J.; Spinoglio, L.; Ward-Thompson, D.; White, G. J.

    2015-10-01

    We have studied the filaments extracted from the column density maps of the nearby Lupus 1, 3, and 4 molecular clouds, derived from photometric maps observed with the Herschel satellite. Filaments in the Lupus clouds have quite low column densities, with a median value of ˜1.5 × 1021 cm-2 and most have masses per unit length lower than the maximum critical value for radial gravitational collapse. Indeed, no evidence of filament contraction has been seen in the gas kinematics. We find that some filaments, that on average are thermally subcritical, contain dense cores that may eventually form stars. This is an indication that in the low column density regime, the critical condition for the formation of stars may be reached only locally and this condition is not a global property of the filament. Finally, in Lupus we find multiple observational evidences of the key role that the magnetic field plays in forming filaments, and determining their confinement and dynamical evolution.

  2. Hydrodynamic interactions between two semiflexible inextensible filaments in Stokes flow.

    PubMed

    Young, Y-N

    2009-04-01

    Hydrodynamic interactions between two semiflexible inextensible filaments are shown to have a significant impact on filament buckling and their subsequent motion in Stokesian fluids. In linear shear flow, hydrodynamic interactions lead to filament shear dispersion that depends on the filament aspect ratio and the initial filament separation. In linear extensional flow, hydrodynamic interactions lead to complex filament dynamics around the stagnation point. These results suggest that hydrodynamic interactions need to be taken into account to determine the self-diffusion of non-Brownian semiflexible filaments in a cellular flow [Y.-N. Young and M. J. Shelley, Phys. Rev. Lett. 99, 058303 (2007)].

  3. Otomycosis due to filamentous fungi.

    PubMed

    García-Agudo, Lidia; Aznar-Marín, Pilar; Galán-Sánchez, Fátima; García-Martos, Pedro; Marín-Casanova, Pilar; Rodríguez-Iglesias, Manuel

    2011-10-01

    Otomycosis is common throughout the world but barely studied in Spain. Our objective was to determine the microbiological and epidemiological characteristics of this pathology in Cadiz (Spain) between 2005 and 2010. Samples from patients with suspicion of otomycosis underwent a direct microscopic examination and culture on different media for fungi and bacteria. Mycological cultures were incubated at 30°C for at least seven days. Identification of fungi was based on colonial morphology and microscopic examination of fungal structure. From a total of 2,633 samples, microbial growth was present in 1,375 (52.2%) and fungal isolation in 390 (28.4%). We identified 228 yeasts and 184 filamentous fungi (13.4% of positive cultures and 47.2% of otomycosis), associated with yeasts in 22 cases (5.6%). The most frequent species were Aspergillus flavus (42.4%), A. niger (35.9%), A. fumigatus (12.5%), A. candidus (7.1%), A. terreus (1.6%), and Paecilomyces variotii (0.5%). Infection was predominant in men (54.9%) and patients beyond 55 years old (46.8%). The most common clinical symptoms were itching (98.9%), otalgia (59.3%), and hypoacusis (56.0%). Fall season reported the lowest number of cases (20.1%). Incidence of otomycosis and fungi producing otomycosis vary within the distinct geographical areas. In Cadiz, this infection is endemic due to warm temperatures, high humidity, sea bathing, and wind, which contributes to disseminate the conidia. Despite Aspergillus niger has been reported as the main causative agent, A. flavus is predominant in Cadiz. Although infection is usually detected in warm months, we observed a homogeneous occurrence of otomycosis in almost all the seasons.

  4. Bifunctional bridging linker-assisted synthesis and characterization of TiO2/Au nanocomposites

    NASA Astrophysics Data System (ADS)

    Žunič, Vojka; Kurtjak, Mario; Suvorov, Danilo

    2016-11-01

    Using a simple organic bifunctional bridging linker, titanium dioxide (TiO2) nanoparticles were coupled with the Au nanoparticles to form TiO2/Au nanocomposites with a variety of Au loadings. This organic bifunctional linker, meso-2,3-dimercaptosuccinic acid, contains two types of functional groups: (i) the carboxyl group, which enables binding to the TiO2, and (ii) the thiol group, which enables binding to the Au. In addition, the organic bifunctional linker acts as a stabilizing agent to prevent the agglomeration and growth of the Au particles, resulting in the formation of highly dispersed Au nanoparticles. To form the TiO2/Au nanocomposites in a simple way, we deliberately applied a synthetic method that simultaneously ensures: (i) the capping of the Au nanoparticles and (ii) the binding of different amounts of Au to the TiO2. The TiO2/Au nanocomposites formed with this method show enhanced UV and Vis photocatalytic activities when compared to the pure TiO2 nanopowders.

  5. Fibronectin Aggregation and Assembly

    PubMed Central

    Ohashi, Tomoo; Erickson, Harold P.

    2011-01-01

    The mechanism of fibronectin (FN) assembly and the self-association sites are still unclear and contradictory, although the N-terminal 70-kDa region (I1–9) is commonly accepted as one of the assembly sites. We previously found that I1–9 binds to superfibronectin, which is an artificial FN aggregate induced by anastellin. In the present study, we found that I1–9 bound to the aggregate formed by anastellin and a small FN fragment, III1–2. An engineered disulfide bond in III2, which stabilizes folding, inhibited aggregation, but a disulfide bond in III1 did not. A gelatin precipitation assay showed that I1–9 did not interact with anastellin, III1, III2, III1–2, or several III1–2 mutants including III1–2KADA. (In contrast to previous studies, we found that the III1–2KADA mutant was identical in conformation to wild-type III1–2.) Because I1–9 only bound to the aggregate and the unfolding of III2 played a role in aggregation, we generated a III2 domain that was destabilized by deletion of the G strand. This mutant bound I1–9 as shown by the gelatin precipitation assay and fluorescence resonance energy transfer analysis, and it inhibited FN matrix assembly when added to cell culture. Next, we introduced disulfide mutations into full-length FN. Three disulfide locks in III2, III3, and III11 were required to dramatically reduce anastellin-induced aggregation. When we tested the disulfide mutants in cell culture, only the disulfide bond in III2 reduced the FN matrix. These results suggest that the unfolding of III2 is one of the key factors for FN aggregation and assembly. PMID:21949131

  6. Morphology of Filamentous Fungi: Linking Cellular Biology to Process Engineering Using Aspergillus niger

    NASA Astrophysics Data System (ADS)

    Krull, Rainer; Cordes, Christiana; Horn, Harald; Kampen, Ingo; Kwade, Arno; Neu, Thomas R.; Nörtemann, Bernd

    In various biotechnological processes, filamentous fungi, e.g. Aspergillus niger, are widely applied for the production of high value-added products due to their secretion efficiency. There is, however, a tangled relationship between the morphology of these microorganisms, the transport phenomena and the related productivity. The morphological characteristics vary between freely dispersed mycelia and distinct pellets of aggregated biomass. Hence, advantages and disadvantages for mycel or pellet cultivation have to be balanced out carefully. Due to this inadequate understanding of morphogenesis of filamentous microorganisms, fungal morphology, along with reproducibility of inocula of the same quality, is often a bottleneck of productivity in industrial production. To obtain an optimisation of the production process it is of great importance to gain a better understanding of the molecular and cell biology of these microorganisms as well as the approaches in biochemical engineering and particle technique, in particular to characterise the interactions between the growth conditions, cell morphology, spore-hyphae-interactions and product formation. Advances in particle and image analysis techniques as well as micromechanical devices and their applications to fungal cultivations have made available quantitative morphological data on filamentous cells. This chapter provides the ambitious aspects of this line of action, focussing on the control and characterisation of the morphology, the transport gradients and the approaches to understand the metabolism of filamentous fungi. Based on these data, bottlenecks in the morphogenesis of A. niger within the complex production pathways from gene to product should be identified and this may improve the production yield.

  7. Morphology of filamentous fungi: linking cellular biology to process engineering using Aspergillus niger.

    PubMed

    Krull, Rainer; Cordes, Christiana; Horn, Harald; Kampen, Ingo; Kwade, Arno; Neu, Thomas R; Nörtemann, Bernd

    2010-01-01

    In various biotechnological processes, filamentous fungi, e.g. Aspergillus niger, are widely applied for the production of high value-added products due to their secretion efficiency. There is, however, a tangled relationship between the morphology of these microorganisms, the transport phenomena and the related productivity. The morphological characteristics vary between freely dispersed mycelia and distinct pellets of aggregated biomass. Hence, advantages and disadvantages for mycel or pellet cultivation have to be balanced out carefully. Due to this inadequate understanding of morphogenesis of filamentous microorganisms, fungal morphology, along with reproducibility of inocula of the same quality, is often a bottleneck of productivity in industrial production. To obtain an optimisation of the production process it is of great importance to gain a better understanding of the molecular and cell biology of these microorganisms as well as the approaches in biochemical engineering and particle technique, in particular to characterise the interactions between the growth conditions, cell morphology, spore-hyphae-interactions and product formation. Advances in particle and image analysis techniques as well as micromechanical devices and their applications to fungal cultivations have made available quantitative morphological data on filamentous cells. This chapter provides the ambitious aspects of this line of action, focussing on the control and characterisation of the morphology, the transport gradients and the approaches to understand the metabolism of filamentous fungi. Based on these data, bottlenecks in the morphogenesis of A. niger within the complex production pathways from gene to product should be identified and this may improve the production yield.

  8. Structural basis for the prion-like MAVS filaments in antiviral innate immunity

    PubMed Central

    Xu, Hui; He, Xiaojing; Zheng, Hui; Huang, Lily J; Hou, Fajian; Yu, Zhiheng; de la Cruz, Michael Jason; Borkowski, Brian; Zhang, Xuewu; Chen, Zhijian J; Jiang, Qiu-Xing

    2014-01-01

    Mitochondrial antiviral signaling (MAVS) protein is required for innate immune responses against RNA viruses. In virus-infected cells MAVS forms prion-like aggregates to activate antiviral signaling cascades, but the underlying structural mechanism is unknown. Here we report cryo-electron microscopic structures of the helical filaments formed by both the N-terminal caspase activation and recruitment domain (CARD) of MAVS and a truncated MAVS lacking part of the proline-rich region and the C-terminal transmembrane domain. Both structures are left-handed three-stranded helical filaments, revealing specific interfaces between individual CARD subunits that are dictated by electrostatic interactions between neighboring strands and hydrophobic interactions within each strand. Point mutations at multiple locations of these two interfaces impaired filament formation and antiviral signaling. Super-resolution imaging of virus-infected cells revealed rod-shaped MAVS clusters on mitochondria. These results elucidate the structural mechanism of MAVS polymerization, and explain how an α-helical domain uses distinct chemical interactions to form self-perpetuating filaments. DOI: http://dx.doi.org/10.7554/eLife.01489.001 PMID:24569476

  9. Structural basis for the prion-like MAVS filaments in antiviral innate immunity.

    PubMed

    Xu, Hui; He, Xiaojing; Zheng, Hui; Huang, Lily J; Hou, Fajian; Yu, Zhiheng; de la Cruz, Michael Jason; Borkowski, Brian; Zhang, Xuewu; Chen, Zhijian J; Jiang, Qiu-Xing

    2014-01-01

    Mitochondrial antiviral signaling (MAVS) protein is required for innate immune responses against RNA viruses. In virus-infected cells MAVS forms prion-like aggregates to activate antiviral signaling cascades, but the underlying structural mechanism is unknown. Here we report cryo-electron microscopic structures of the helical filaments formed by both the N-terminal caspase activation and recruitment domain (CARD) of MAVS and a truncated MAVS lacking part of the proline-rich region and the C-terminal transmembrane domain. Both structures are left-handed three-stranded helical filaments, revealing specific interfaces between individual CARD subunits that are dictated by electrostatic interactions between neighboring strands and hydrophobic interactions within each strand. Point mutations at multiple locations of these two interfaces impaired filament formation and antiviral signaling. Super-resolution imaging of virus-infected cells revealed rod-shaped MAVS clusters on mitochondria. These results elucidate the structural mechanism of MAVS polymerization, and explain how an α-helical domain uses distinct chemical interactions to form self-perpetuating filaments. DOI: http://dx.doi.org/10.7554/eLife.01489.001.

  10. A potential role for the COOH-terminal domain in the lateral packing of type III intermediate filaments

    PubMed Central

    1991-01-01

    To identify sites of self-association in type III intermediate filament (IF) proteins, we have taken an "anti-idiotypic antibody" approach. A mAb (anti-Ct), recognizing a similar feature near the end of the rod domain of vimentin, desmin, and peripherin (epsilon site or epsilon epitope), was characterized. Anti-idiotypic antibodies, generated by immunizing rabbits with purified anti-Ct, recognize a site (presumably "complementary" to the epsilon epitope) common among vimentin, desmin, and peripherin (beta site or beta epitope). The beta epitope is represented in a synthetic peptide (PII) modeled after the 30 COOH- terminal residues of peripherin, as seen by comparative immunoblotting assays. Consistent with the idea of an association between the epsilon and the beta site, PII binds in vitro to intact IF proteins and fragments containing the epsilon epitope, but not to IF proteins that do not react with anti-Ct. Microinjection experiments conducted in vivo and filament reconstitution assays carried out in vitro further demonstrate that "uncoupling" of this site-specific association (by competition with PII or anti-Ct) interferes with normal IF architecture, resulting in the formation of filaments and filament bundles with diameters much greater than that of the normal IFs. These thick fibers are very similar to the ones observed previously when a derivative of desmin missing 27 COOH-terminal residues was assembled in vitro (Kaufmann, E., K. Weber, and N. Geisler. 1985. J. Mol. Biol. 185:733-742). As a molecular explanation, we propose here that the epsilon and the beta sites of type III IF proteins are "complementary" and associate during filament assembly. As a result of this association, we further postulate the formation of a surface-exposed "loop" or "hairpin" structure that may sterically prevent inappropriate filament-filament aggregation and regulate filament thickness. PMID:1714461

  11. Actomyosin contraction, aggregation and traveling waves in a treadmilling actin array

    NASA Astrophysics Data System (ADS)

    Oelz, Dietmar; Mogilner, Alex

    2016-04-01

    We use perturbation theory to derive a continuum model for the dynamic actomyosin bundle/ring in the regime of very strong crosslinking. Actin treadmilling is essential for contraction. Linear stability analysis and numerical solutions of the model equations reveal that when the actin treadmilling is very slow, actin and myosin aggregate into equidistantly spaced peaks. When treadmilling is significant, actin filament of one polarity are distributed evenly, while filaments of the opposite polarity develop a shock wave moving with the treadmilling velocity. Myosin aggregates into a sharp peak surfing the crest of the actin wave. Any actomyosin aggregation diminishes contractile stress. The easiest way to maintain higher contraction is to upregulate the actomyosin turnover which destabilizes nontrivial patterns and stabilizes the homogeneous actomyosin distributions. We discuss the model's implications for the experiment.

  12. Relationship of Species-Specific Filament Levels to Filamentous Bulking in Activated Sludge

    PubMed Central

    Liao, Jiangying; Lou, Inchio; de los Reyes, Francis L.

    2004-01-01

    To examine the relationship between activated-sludge bulking and levels of specific filamentous bacteria, we developed a statistics-based quantification method for estimating the biomass levels of specific filaments using 16S rRNA-targeted fluorescent in situ hybridization (FISH) probes. The results of quantitative FISH for the filament Sphaerotilus natans were similar to the results of quantitative membrane hybridization in a sample from a full-scale wastewater treatment plant. Laboratory-scale reactors were operated under different flow conditions to develop bulking and nonbulking sludge and were bioaugmented with S. natans cells to stimulate bulking. Instead of S. natans, the filament Eikelboom type 1851 became dominant in the reactors. Levels of type 1851 filaments extending out of the flocs correlated strongly with the sludge volume index, and extended filament lengths of approximately 6 × 108 μm ml−1 resulted in bulking in laboratory-scale and full-scale activated-sludge samples. Quantitative FISH showed that high levels of filaments occurred inside the flocs in nonbulking sludge, supporting the “substrate diffusion limitation” hypothesis for bulking. The approach will allow the monitoring of incremental improvements in bulking control methods and the delineation of the operational conditions that lead to bulking due to specific filaments. PMID:15066840

  13. Filament Eruption without Coronal Mass Ejection

    NASA Technical Reports Server (NTRS)

    Choudhary, Debi Prasad; Moore, Ronald L.

    2003-01-01

    We report characteristics of quiescent filament eruptions that were not associated with coronal mass ejections (CMEs). We examined 12 quiescent filament eruptions, each of which was located far from disk center (20.7 R(sub sun)) in diffuse remnant magnetic fields of decayed active regions, was well observed in full-disk movies in Ha and Fe XI, and had good coronagraph coverage. Of the 12 events, 9 were associated with CMEs and 3 were not. Even though the two kinds of eruption were indistinguishable in their magnetic setting and in the eruptive motion of the filament in the Ha movies, each of the CME-producing eruptions produced a two-ribbon flare in Ha and a coronal arcade and/or two-ribbon flare in Fe XII, and each of the non-CME-producing eruptions did not. From this result, and the appearance of the eruptive motion in the Fe XII movies, we conclude that the non-CME-associated filament eruptions are confined eruptions like the confined filament eruptions in active regions.

  14. Interaction and merging of two sinistral filaments

    SciTech Connect

    Jiang, Yunchun; Yang, Jiayan; Liu, Yu; Li, Haidong; Wang, Haimin; Ji, Haisheng; Li, Jianping

    2014-09-20

    In this paper, we report the interaction and subsequent merging of two sinistral filaments (F1 and F2) occurring at the boundary of AR 9720 on 2001 December 6. The two filaments were close and nearly perpendicular to each other. The interaction occurred after F1 was erupted and the eruption was impeded by a more extended filament channel (FC) standing in the way, in which F2 was embedded. The erupted material ran into FC along its axis, causing F1 and F2 to merge into a single structure that subsequently underwent a large-amplitude to-and-fro motion. A significant plasma heating process was observed in the merging process, making the mixed material largely disappear from the Hα passband, but appear in Extreme Ultraviolet Telescope 195 Å images for a while. These observations can serve as strong evidence of merging reconnection between the two colliding magnetic structures. A new sinistral filament was formed along FC after the cooling of the merged and heated material. No coronal mass ejection was observed to be associated with the event; though, the eruption was accompanied by a two-ribbon flare with a separation motion, indicating that the eruption had failed. This event shows that, in addition to overlying magnetic fields, such an interaction is an effective restraint to make a filament eruption fail in this way.

  15. Paired helical filaments from Alzheimer disease brain induce intracellular accumulation of Tau protein in aggresomes.

    PubMed

    Santa-Maria, Ismael; Varghese, Merina; Ksiezak-Reding, Hanna; Dzhun, Anastasiya; Wang, Jun; Pasinetti, Giulio M

    2012-06-08

    Abnormal folding of tau protein leads to the generation of paired helical filaments (PHFs) and neurofibrillary tangles, a key neuropathological feature in Alzheimer disease and tauopathies. A specific anatomical pattern of pathological changes developing in the brain suggests that once tau pathology is initiated it propagates between neighboring neuronal cells, possibly spreading along the axonal network. We studied whether PHFs released from degenerating neurons could be taken up by surrounding cells and promote spreading of tau pathology. Neuronal and non-neuronal cells overexpressing green fluorescent protein-tagged tau (GFP-Tau) were treated with isolated fractions of human Alzheimer disease-derived PHFs for 24 h. We found that cells internalized PHFs through an endocytic mechanism and developed intracellular GFP-Tau aggregates with attributes of aggresomes. This was particularly evident by the perinuclear localization of aggregates and redistribution of the vimentin intermediate filament network and retrograde motor protein dynein. Furthermore, the content of Sarkosyl-insoluble tau, a measure of abnormal tau aggregation, increased 3-fold in PHF-treated cells. An exosome-related mechanism did not appear to be involved in the release of GFP-Tau from untreated cells. The evidence that cells can internalize PHFs, leading to formation of aggresome-like bodies, opens new therapeutic avenues to prevent propagation and spreading of tau pathology.

  16. Paired Helical Filaments from Alzheimer Disease Brain Induce Intracellular Accumulation of Tau Protein in Aggresomes*

    PubMed Central

    Santa-Maria, Ismael; Varghese, Merina; Ksiȩżak-Reding, Hanna; Dzhun, Anastasiya; Wang, Jun; Pasinetti, Giulio M.

    2012-01-01

    Abnormal folding of tau protein leads to the generation of paired helical filaments (PHFs) and neurofibrillary tangles, a key neuropathological feature in Alzheimer disease and tauopathies. A specific anatomical pattern of pathological changes developing in the brain suggests that once tau pathology is initiated it propagates between neighboring neuronal cells, possibly spreading along the axonal network. We studied whether PHFs released from degenerating neurons could be taken up by surrounding cells and promote spreading of tau pathology. Neuronal and non-neuronal cells overexpressing green fluorescent protein-tagged tau (GFP-Tau) were treated with isolated fractions of human Alzheimer disease-derived PHFs for 24 h. We found that cells internalized PHFs through an endocytic mechanism and developed intracellular GFP-Tau aggregates with attributes of aggresomes. This was particularly evident by the perinuclear localization of aggregates and redistribution of the vimentin intermediate filament network and retrograde motor protein dynein. Furthermore, the content of Sarkosyl-insoluble tau, a measure of abnormal tau aggregation, increased 3-fold in PHF-treated cells. An exosome-related mechanism did not appear to be involved in the release of GFP-Tau from untreated cells. The evidence that cells can internalize PHFs, leading to formation of aggresome-like bodies, opens new therapeutic avenues to prevent propagation and spreading of tau pathology. PMID:22496370

  17. Void galaxy properties depending on void filament straightness

    NASA Astrophysics Data System (ADS)

    Shim, Junsup; Lee, Jounghun; Hoyle, Fiona

    2015-08-01

    We investigate the properties of galaxies belonging to the filaments in cosmic void regions, using the void catalogue constructed by Pan et al. (2012) from the SDSS DR7. To identify galaxy filaments within a void, voids with 30 or more galaxies are selected as a sample. We identify 3172 filaments in 1055 voids by applying the filament finding algorithm utilizing minimal spanning tree (MST) which is an unique linear pattern into which connects all the galaxies in a void. We study the correlations between galaxy properties and the specific size of filament which quantifies the degree of the filament straightness. For example, the average magnitude and the magnitude of the faintest galaxy in filament decrease as the straightness of the filament increases. We also find that the correlations become stronger in rich filaments with many member galaxies than in poor ones. We discuss a physical explanation to our findings and their cosmological implications.

  18. Terahertz waves radiated from two noncollinear femtosecond plasma filaments

    SciTech Connect

    Du, Hai-Wei; Hoshina, Hiromichi; Otani, Chiko; Midorikawa, Katsumi

    2015-11-23

    Terahertz (THz) waves radiated from two noncollinear femtosecond plasma filaments with a crossing angle of 25° are investigated. The irradiated THz waves from the crossing filaments show a small THz pulse after the main THz pulse, which was not observed in those from single-filament scheme. Since the position of the small THz pulse changes with the time-delay of two filaments, this phenomenon can be explained by a model in which the small THz pulse is from the second filament. The denser plasma in the overlap region of the filaments changes the movement of space charges in the plasma, thereby changing the angular distribution of THz radiation. As a result, this schematic induces some THz wave from the second filament to propagate along the path of the THz wave from the first filament. Thus, this schematic alters the direction of the THz radiation from the filamentation, which can be used in THz wave remote sensing.

  19. Technology meets aggregate

    SciTech Connect

    Wilson, C.; Swan, C.

    2007-07-01

    New technology carried out at Tufts University and the University of Massachusetts on synthetic lightweight aggregate has created material from various qualities of fly ash from coal-fired power plants for use in different engineered applications. In pilot scale manufacturing tests an 'SLA' containing 80% fly ash and 20% mixed plastic waste from packaging was produced by 'dry blending' mixed plastic with high carbon fly ash. A trial run was completed to produce concrete masonry unit (CMU) blocks at a full-scale facility. It has been shown that SLA can be used as a partial substitution of a traditional stone aggregate in hot asphalt mix. 1 fig., 2 photos.

  20. Filament velocity scaling laws for warm ions

    SciTech Connect

    Manz, P.; Carralero, D.; Birkenmeier, G.; Müller, H. W.; Scott, B. D.; Müller, S. H.; Fuchert, G.; Stroth, U.

    2013-10-15

    The dynamics of filaments or blobs in the scrape-off layer of magnetic fusion devices are studied by magnitude estimates of a comprehensive drift-interchange-Alfvén fluid model. The standard blob models are reproduced in the cold ion case. Even though usually neglected, in the scrape-off layer, the ion temperature can exceed the electron temperature by an order of magnitude. The ion pressure affects the dynamics of filaments amongst others by adding up to the interchange drive and the polarisation current. It is shown how both effects modify the scaling laws for filament velocity in dependence of its size. Simplifications for experimentally relevant limit regimes are given. These are the sheath dissipation, collisional, and electromagnetic regime.

  1. SOLAR MAGNETIZED 'TORNADOES': RELATION TO FILAMENTS

    SciTech Connect

    Su Yang; Veronig, Astrid; Temmer, Manuela; Wang Tongjiang; Gan Weiqun

    2012-09-10

    Solar magnetized 'tornadoes', a phenomenon discovered in the solar atmosphere, appear as tornado-like structures in the corona but are rooted in the photosphere. Like other solar phenomena, solar tornadoes are a feature of magnetized plasma and therefore differ distinctly from terrestrial tornadoes. Here we report the first analysis of solar 'tornadoes' (two papers which focused on different aspects of solar tornadoes were published in the Astrophysical Journal Letters and Nature, respectively, during the revision of this Letter). A detailed case study of two events indicates that they are rotating vertical magnetic structures probably driven by underlying vortex flows in the photosphere. They usually exist as a group and are related to filaments/prominences, another important solar phenomenon whose formation and eruption are still mysteries. Solar tornadoes may play a distinct role in the supply of mass and twists to filaments. These findings could lead to a new explanation of filament formation and eruption.

  2. Random bursts determine dynamics of active filaments.

    PubMed

    Weber, Christoph A; Suzuki, Ryo; Schaller, Volker; Aranson, Igor S; Bausch, Andreas R; Frey, Erwin

    2015-08-25

    Constituents of living or synthetic active matter have access to a local energy supply that serves to keep the system out of thermal equilibrium. The statistical properties of such fluctuating active systems differ from those of their equilibrium counterparts. Using the actin filament gliding assay as a model, we studied how nonthermal distributions emerge in active matter. We found that the basic mechanism involves the interplay between local and random injection of energy, acting as an analog of a thermal heat bath, and nonequilibrium energy dissipation processes associated with sudden jump-like changes in the system's dynamic variables. We show here how such a mechanism leads to a nonthermal distribution of filament curvatures with a non-Gaussian shape. The experimental curvature statistics and filament relaxation dynamics are reproduced quantitatively by stochastic computer simulations and a simple kinetic model.

  3. Random bursts determine dynamics of active filaments

    PubMed Central

    Weber, Christoph A.; Suzuki, Ryo; Schaller, Volker; Aranson, Igor S.; Bausch, Andreas R.; Frey, Erwin

    2015-01-01

    Constituents of living or synthetic active matter have access to a local energy supply that serves to keep the system out of thermal equilibrium. The statistical properties of such fluctuating active systems differ from those of their equilibrium counterparts. Using the actin filament gliding assay as a model, we studied how nonthermal distributions emerge in active matter. We found that the basic mechanism involves the interplay between local and random injection of energy, acting as an analog of a thermal heat bath, and nonequilibrium energy dissipation processes associated with sudden jump-like changes in the system’s dynamic variables. We show here how such a mechanism leads to a nonthermal distribution of filament curvatures with a non-Gaussian shape. The experimental curvature statistics and filament relaxation dynamics are reproduced quantitatively by stochastic computer simulations and a simple kinetic model. PMID:26261319

  4. Spatiotemporal rogue events in optical multiple filamentation.

    PubMed

    Birkholz, Simon; Nibbering, Erik T J; Brée, Carsten; Skupin, Stefan; Demircan, Ayhan; Genty, Goëry; Steinmeyer, Günter

    2013-12-13

    The transient appearance of bright spots in the beam profile of optical filaments formed in xenon is experimentally investigated. Fluence profiles are recorded with high-speed optical cameras at the kilohertz repetition rate of the laser source. A statistical analysis reveals a thresholdlike appearance of heavy-tailed fluence distributions together with the transition from single to multiple filamentation. The multifilament scenario exhibits near-exponential probability density functions, with extreme events exceeding the significant wave height by more than a factor of 10. The extreme events are isolated in space and in time. The macroscopic origin of these experimentally observed heavy-tail statistics is shown to be local refractive index variations inside the nonlinear medium, induced by multiphoton absorption and subsequent plasma thermalization. Microscopically, mergers between filament strings appear to play a decisive role in the observed rogue wave statistics.

  5. Structure of Flexible Filamentous Plant Viruses

    SciTech Connect

    Kendall, Amy; McDonald, Michele; Bian, Wen; Bowles, Timothy; Baumgarten, Sarah C.; Shi, Jian; Stewart, Phoebe L.; Bullitt, Esther; Gore, David; Irving, Thomas C.; Havens, Wendy M.; Ghabrial, Said A.; Wall, Joseph S.; Stubbs, Gerald

    2008-10-23

    Flexible filamentous viruses make up a large fraction of the known plant viruses, but in comparison with those of other viruses, very little is known about their structures. We have used fiber diffraction, cryo-electron microscopy, and scanning transmission electron microscopy to determine the symmetry of a potyvirus, soybean mosaic virus; to confirm the symmetry of a potexvirus, potato virus X; and to determine the low-resolution structures of both viruses. We conclude that these viruses and, by implication, most or all flexible filamentous plant viruses share a common coat protein fold and helical symmetry, with slightly less than 9 subunits per helical turn.

  6. Infrared Radiation Filament And Metnod Of Manufacture

    DOEpatents

    Johnson, Edward A.

    1998-11-17

    An improved IR radiation source is provided by the invention. A radiation filament has a textured surface produced by seeded ion bombardment of a metal foil which is cut to a serpentine shape and mounted in a windowed housing. Specific ion bombardment texturing techniques tune the surface to maximize emissions in the desired wavelength range and to limit emissions outside that narrow range, particularly at longer wavelengths. A combination of filament surface texture, thickness, material, shape and power circuit feedback control produce wavelength controlled and efficient radiation at much lower power requirements than devices of the prior art.

  7. Carbon nanotube filaments in household light bulbs

    NASA Astrophysics Data System (ADS)

    Wei, Jinquan; Zhu, Hongwei; Wu, Dehai; Wei, Bingqing

    2004-06-01

    Household light bulbs made from macroscopic single-walled and double-walled carbon nanotube filaments were fabricated and tested. The nanotube bulbs are found to possess several interesting features when compared to a conventional tungsten filament in safelight (36 V, 40 W), such as lower threshold voltage for light emission and higher brightness at high voltages. Electrically induced excited peaks at 407, 417, 655 nm were identified to be an intrinsic property of nanotubes and these peaks are observed to become stronger in the light emission spectra at high temperatures which cannot be explained easily with the concept of blackbody emission.

  8. Structure of flexible filamentous plant viruses.

    PubMed

    Kendall, Amy; McDonald, Michele; Bian, Wen; Bowles, Timothy; Baumgarten, Sarah C; Shi, Jian; Stewart, Phoebe L; Bullitt, Esther; Gore, David; Irving, Thomas C; Havens, Wendy M; Ghabrial, Said A; Wall, Joseph S; Stubbs, Gerald

    2008-10-01

    Flexible filamentous viruses make up a large fraction of the known plant viruses, but in comparison with those of other viruses, very little is known about their structures. We have used fiber diffraction, cryo-electron microscopy, and scanning transmission electron microscopy to determine the symmetry of a potyvirus, soybean mosaic virus; to confirm the symmetry of a potexvirus, potato virus X; and to determine the low-resolution structures of both viruses. We conclude that these viruses and, by implication, most or all flexible filamentous plant viruses share a common coat protein fold and helical symmetry, with slightly less than 9 subunits per helical turn.

  9. Integration of hydrodynamic interactions between filaments

    NASA Astrophysics Data System (ADS)

    Man, Yi; Lauga, Eric

    2015-11-01

    In many biological situations, slender filaments interact through a viscous fluid, and these hydrodynamic interactions play a crucial cellular role. Examples include the ability of peritrichous bacteria to bundle their flagella or the generation of metachronal waves in cilia arrays. In most cases of interest, three distinct length scales characterize the filaments, their typical thickness a, relative distance h, and length L, which are asymptotically separated as a << h << L . In this talk, we demonstrate how to analytically develop a long-wavelength integration of hydrodynamic singularities in this biologically-relevant limit.

  10. Filament winding - Waking the sleeping giant

    NASA Technical Reports Server (NTRS)

    Freeman, W. T., Jr.; Stein, B. A.

    1985-01-01

    The use of filament winding (FW) in the production of aerospace composite structures is examined. The FW process applies spools of fiber and prepreg tow or prepreg tape to a male mandrel; the process is more efficient and cost effective than metallic construction. The fibers used in FW and the curing process are explained. The reduced storage and fabrication costs that result from FW are discussed. The use of FW to produce a filament-wound case for a solid rocket motor and the substructure and skin of an aircraft fuselage are described. Areas which require further development in order to expand the use of FW are listed and discussed.

  11. Aggregates, broccoli and cauliflower

    NASA Astrophysics Data System (ADS)

    Grey, Francois; Kjems, Jørgen K.

    1989-09-01

    Naturally grown structures with fractal characters like broccoli and cauliflower are discussed and compared with DLA-type aggregates. It is suggested that the branching density can be used to characterize the growth process and an experimental method to determine this parameter is proposed.

  12. Interaction of Two Filaments in a Long Filament Channel Associated with Twin Coronal Mass Ejections

    NASA Astrophysics Data System (ADS)

    Zheng, Ruisheng; Zhang, Qingmin; Chen, Yao; Wang, Bing; Du, Guohui; Li, Chuanyang; Yang, Kai

    2017-02-01

    Using the high-quality observations of the Solar Dynamics Observatory, we present the interaction of two filaments (F1 and F2) in a long filament channel associated with twin coronal mass ejections (CMEs) on 2016 January 26. Before the eruption, a sequence of rapid cancellation and emergence of the magnetic flux has been observed, which likely triggered the ascending of the west filament (F1). The east footpoints of rising F1 moved toward the east far end of the filament channel, accompanied by post-eruption loops and flare ribbons. This likely indicated a large-scale eruption involving the long filament channel, which resulted from the interaction between F1 and the east filament (F2). Some bright plasma flew over F2, and F2 stayed at rest during the eruption, likely due to the confinement of its overlying lower magnetic field. Interestingly, the impulsive F1 pushed its overlying magnetic arcades to form the first CME, and F1 finally evolved into the second CME after the collision with the nearby coronal hole. We suggest that the interaction of F1 and the overlying magnetic field of F2 led to the merging reconnection that forms a longer eruptive filament loop. Our results also provide a possible picture of the origin of twin CMEs and show that the large-scale magnetic topology of the coronal hole is important for the eventual propagation direction of CMEs.

  13. Molecular Level Insights into Thermally Induced [alpha]-Chymotrypsinogen A Amyloid Aggregation Mechanism and Semiflexible Protofibril Morphology

    SciTech Connect

    Zhang, Aming; Jordan, Jacob L.; Ivanova, Magdalena I.; Weiss, IV., William F.; Roberts, Christopher J.; Fernandez, Erik J.

    2010-12-07

    Understanding nonnative protein aggregation is critical not only to a number of amyloidosis disorders but also for the development of effective and safe biopharmaceuticals. In a series of previous studies [Weiss et al. (2007) Biophys. J. 93, 4392-4403; Andrews et al. (2007) Biochemistry 46, 7558-7571; Andrews et al. (2008) Biochemistry 47, 2397-2403], {alpha}-chymotrypsinogen A (aCgn) and bovine granulocyte colony stimulating factor (bG-CSF) have been shown to exhibit the kinetic and morphological features of other nonnative aggregating proteins at low pH and ionic strength. In this study, we investigated the structural mechanism of aCgn aggregation. The resultant aCgn aggregates were found to be soluble and exhibited semiflexible filamentous aggregate morphology under transmission electron microscopy. In addition, the filamentous aggregates were demonstrated to possess amyloid characteristics by both Congo red binding and X-ray diffraction. Peptide level hydrogen exchange (HX) analysis suggested that a buried native {beta}-sheet comprised of three peptide segments (39-46, 51-64, and 106-114) reorganizes into the cross-{beta} amyloid core of aCgn aggregates and that at least 50% of the sequence adopts a disordered structure in the aggregates. Furthermore, the equimolar, bimodal HX labeling distribution observed for three reported peptides (65-102, 160-180, and 229-245) suggested a heterogeneous assembly of two molecular conformations in aCgn aggregates. This demonstrates that extended {beta}-sheet interactions typical of the amyloid are sufficiently strong that a relatively small fraction of polypeptide sequence can drive formation of filamentous aggregates even under conditions favoring colloidal stability.

  14. Comparative studies on the structure and aggregative properties of the myosin molecule. III. The in vitro aggregative properties of the lobster myosin molecule.

    PubMed

    Siemankowski, R F; Zobel, C R

    1976-02-20

    The solubility of rabbit skeletal and lobster abdominal muscle myosin has been studied in monovalent salt solutions as a function of pH (over the range 4.75 to 8.5) and ionic strength (50-500 mM). Rabbit skeletal muscle myosin was found to precipitate over a narrower pH range than the lobster abdominal muscle myosin but at equivalent pH values and ionic strengths the former exhibited greater solubility. Comparison of the solubility of rabbit myosin, per se with that of light meromyosin and lobster myosin with its equivalent proteolytically produced fragment (fraction B1) showed that both rod fragments were more soluble than their parent molecules. Under conditions of low solubility (low ionic strength and pH) the quantitiy of protein in solution remained essentially constant with increasing total protein, thus suggesting that the aggregation phenomenon is of a phase transition type. Examination of the aggregates by electron microscopy revealed that rabbit myosin formed classical, elongate, spindle-shaped filaments similar to those previously observed by others. In contrast lobster myosin only formed short, dumbbell-shaped filaments 0.2-0.3 mum long. Consideration of the pH ranges over which aggregation occurred suggests that protonation of histidine residues may be involved in rabbit myosin filament formation while for lobster myosin, aggregation may involve protonation of epsilon-amino or guanidino groups. The possible relationship between the distribution of these groups along the rod portion of the myosin molecule and the formation of elongate filaments has been explored.

  15. Intermediate filaments: a role in epithelial polarity

    PubMed Central

    Oriolo, Andrea S.; Wald, Flavia A.; Ramsauer, Victoria P.; Salas, Pedro J.I.

    2007-01-01

    Intermediate filaments have long been considered mechanical components of the cell that provide resistance to deformation stress. Practical experimental problems, including insolubility, lack of good pharmacological antagonists, and the paucity of powerful genetic models, have handicapped the research of other functions. In single-layered epithelial cells, keratin intermediate filaments are cortical, either apically polarized or apico-lateral. This review analyzes phenotypes of genetic manipulations of simple epithelial cell keratins in mice and C. elegans that strongly suggest a role of keratins in apico-basal polarization and membrane traffic. Published evidence that intermediate filaments can act as scaffolds for proteins involved in membrane traffic and signaling is also discussed. Such a scaffolding function would generate a highly polarized compartment within the cytoplasm of simple epithelial cells. While in most cases mechanistic explanations for the keratin-null or overexpression phenotypes are still missing, it is hoped investigators will be encouraged to study these as yet poorly understood functions of intermediate filaments. PMID:17425955

  16. Helicity within the vortex filament model

    PubMed Central

    Hänninen, R.; Hietala, N.; Salman, H.

    2016-01-01

    Kinetic helicity is one of the invariants of the Euler equations that is associated with the topology of vortex lines within the fluid. In superfluids, the vorticity is concentrated along vortex filaments. In this setting, helicity would be expected to acquire its simplest form. However, the lack of a core structure for vortex filaments appears to result in a helicity that does not retain its key attribute as a quadratic invariant. By defining a spanwise vector to the vortex through the use of a Seifert framing, we are able to introduce twist and henceforth recover the key properties of helicity. We present several examples for calculating internal twist to illustrate why the centreline helicity alone will lead to ambiguous results if a twist contribution is not introduced. Our choice of the spanwise vector can be expressed in terms of the tangential component of velocity along the filament. Since the tangential velocity does not alter the configuration of the vortex at later times, we are able to recover a similar equation for the internal twist angle to that of classical vortex tubes. Our results allow us to explain how a quasi-classical limit of helicity emerges from helicity considerations for individual superfluid vortex filaments. PMID:27883029

  17. Light sources based on semiconductor current filaments

    DOEpatents

    Zutavern, Fred J.; Loubriel, Guillermo M.; Buttram, Malcolm T.; Mar, Alan; Helgeson, Wesley D.; O'Malley, Martin W.; Hjalmarson, Harold P.; Baca, Albert G.; Chow, Weng W.; Vawter, G. Allen

    2003-01-01

    The present invention provides a new type of semiconductor light source that can produce a high peak power output and is not injection, e-beam, or optically pumped. The present invention is capable of producing high quality coherent or incoherent optical emission. The present invention is based on current filaments, unlike conventional semiconductor lasers that are based on p-n junctions. The present invention provides a light source formed by an electron-hole plasma inside a current filament. The electron-hole plasma can be several hundred microns in diameter and several centimeters long. A current filament can be initiated optically or with an e-beam, but can be pumped electrically across a large insulating region. A current filament can be produced in high gain photoconductive semiconductor switches. The light source provided by the present invention has a potentially large volume and therefore a potentially large energy per pulse or peak power available from a single (coherent) semiconductor laser. Like other semiconductor lasers, these light sources will emit radiation at the wavelength near the bandgap energy (for GaAs 875 nm or near infra red). Immediate potential applications of the present invention include high energy, short pulse, compact, low cost lasers and other incoherent light sources.

  18. SRM filament wound case resin characterization studies

    NASA Technical Reports Server (NTRS)

    Chou, L. W.

    1985-01-01

    The amine cured epoxy wet winding resin used in fabrication of the SRM filament wound case is analyzed. High pressure liquid chromatography (HPSC) is utilized extensively to study lot-to-lot variation in both resin and curing agent. The validity of quantitative hplc methodology currently under development in-process resin/catalyst assay is assessed.

  19. Using Drosophila for Studies of Intermediate Filaments.

    PubMed

    Bohnekamp, Jens; Cryderman, Diane E; Thiemann, Dylan A; Magin, Thomas M; Wallrath, Lori L

    2016-01-01

    Drosophila melanogaster is a useful organism for determining protein function and modeling human disease. Drosophila offers a rapid generation time and an abundance of genomic resources and genetic tools. Conservation in protein structure, signaling pathways, and developmental processes make studies performed in Drosophila relevant to other species, including humans. Drosophila models have been generated for neurodegenerative diseases, muscular dystrophy, cancer, and many other disorders. Recently, intermediate filament protein diseases have been modeled in Drosophila. These models have revealed novel mechanisms of pathology, illuminated potential new routes of therapy, and make whole organism compound screens feasible. The goal of this chapter is to outline steps to study intermediate filament function and model intermediate filament-associated diseases in Drosophila. The steps are general and can be applied to study the function of almost any protein. The protocols outlined here are for both the novice and experienced Drosophila researcher, allowing the rich developmental and cell biology that Drosophila offers to be applied to studies of intermediate filaments.

  20. Self-assembly of Artificial Actin Filaments

    NASA Astrophysics Data System (ADS)

    Grosenick, Christopher; Cheng, Shengfeng

    Actin Filaments are long, double-helical biopolymers that make up the cytoskeleton along with microtubules and intermediate filaments. In order to further understand the self-assembly process of these biopolymers, a model to recreate actin filament geometry was developed. A monomer in the shape of a bent rod with vertical and lateral binding sites was designed to assemble into single or double helices. With Molecular Dynamics simulations, a variety of phases were observed to form by varying the strength of the binding sites. Ignoring lateral binding sites, we have found a narrow range of binding strengths that lead to long single helices via various growth pathways. When lateral binding strength is introduced, double helices begin to form. These double helices self-assemble into substantially more stable structures than their single helix counterparts. We have found double helices to form long filaments at about half the vertical binding strength of single helices. Surprisingly, we have found that triple helices occasionally form, indicating the importance of structural regulation in the self-assembly of biopolymers.

  1. Helicity within the vortex filament model

    NASA Astrophysics Data System (ADS)

    Hänninen, R.; Hietala, N.; Salman, H.

    2016-11-01

    Kinetic helicity is one of the invariants of the Euler equations that is associated with the topology of vortex lines within the fluid. In superfluids, the vorticity is concentrated along vortex filaments. In this setting, helicity would be expected to acquire its simplest form. However, the lack of a core structure for vortex filaments appears to result in a helicity that does not retain its key attribute as a quadratic invariant. By defining a spanwise vector to the vortex through the use of a Seifert framing, we are able to introduce twist and henceforth recover the key properties of helicity. We present several examples for calculating internal twist to illustrate why the centreline helicity alone will lead to ambiguous results if a twist contribution is not introduced. Our choice of the spanwise vector can be expressed in terms of the tangential component of velocity along the filament. Since the tangential velocity does not alter the configuration of the vortex at later times, we are able to recover a similar equation for the internal twist angle to that of classical vortex tubes. Our results allow us to explain how a quasi-classical limit of helicity emerges from helicity considerations for individual superfluid vortex filaments.

  2. The Apis mellifera filamentous virus genome

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A complete reference genome of the Apis mellifera Filamentous virus (AmFV) was determined using Illumina Hiseq sequencing. The AmFV genome is a double strand DNA molecule of approximately 498’500 nucleotides with a GC content of 50.8%. It encompasses 251 non overlapping open reading frames (ORFs), e...

  3. FILAMENT CHANNEL FORMATION VIA MAGNETIC HELICITY CONDENSATION

    SciTech Connect

    Knizhnik, K. J.; Antiochos, S. K.; DeVore, C. R.

    2015-08-20

    A major unexplained feature of the solar atmosphere is the accumulation of magnetic shear in the form of filament channels at photospheric polarity inversion lines (PILs). In addition to free energy, this shear represents magnetic helicity, which is conserved under reconnection. In this paper we address the problem of filament channel formation and show how filaments acquire their shear and magnetic helicity. The results of three-dimensional (3D) simulations using the Adaptively Refined Magnetohydrodynamics Solver are presented. Our findings support the model of filament channel formation by magnetic helicity condensation that was developed by Antiochos. We consider the small-scale photospheric twisting of a quasi-potential flux system that is bounded by a PIL and contains a coronal hole (CH). The magnetic helicity injected by the small-scale photospheric motions is shown to inverse cascade up to the largest allowable scales that define the closed flux system: the PIL and the CH. This process produces field lines that are both sheared and smooth, and are sheared in opposite senses at the PIL and the CH. The accumulated helicity and shear flux are shown to be in excellent quantitative agreement with the helicity condensation model. We present a detailed analysis of the simulations, including comparisons of our analytical and numerical results, and discuss their implications for observations.

  4. Dynamics of protein aggregation and oligomer formation governed by secondary nucleation

    NASA Astrophysics Data System (ADS)

    Michaels, Thomas C. T.; Lazell, Hamish W.; Arosio, Paolo; Knowles, Tuomas P. J.

    2015-08-01

    The formation of aggregates in many protein systems can be significantly accelerated by secondary nucleation, a process where existing assemblies catalyse the nucleation of new species. In particular, secondary nucleation has emerged as a central process controlling the proliferation of many filamentous protein structures, including molecular species related to diseases such as sickle cell anemia and a range of neurodegenerative conditions. Increasing evidence suggests that the physical size of protein filaments plays a key role in determining their potential for deleterious interactions with living cells, with smaller aggregates of misfolded proteins, oligomers, being particularly toxic. It is thus crucial to progress towards an understanding of the factors that control the sizes of protein aggregates. However, the influence of secondary nucleation on the time evolution of aggregate size distributions has been challenging to quantify. This difficulty originates in large part from the fact that secondary nucleation couples the dynamics of species distant in size space. Here, we approach this problem by presenting an analytical treatment of the master equation describing the growth kinetics of linear protein structures proliferating through secondary nucleation and provide closed-form expressions for the temporal evolution of the resulting aggregate size distribution. We show how the availability of analytical solutions for the full filament distribution allows us to identify the key physical parameters that control the sizes of growing protein filaments. Furthermore, we use these results to probe the dynamics of the populations of small oligomeric species as they are formed through secondary nucleation and discuss the implications of our work for understanding the factors that promote or curtail the production of these species with a potentially high deleterious biological activity.

  5. Dynamics of protein aggregation and oligomer formation governed by secondary nucleation

    SciTech Connect

    Michaels, Thomas C. T. Lazell, Hamish W.; Arosio, Paolo; Knowles, Tuomas P. J.

    2015-08-07

    The formation of aggregates in many protein systems can be significantly accelerated by secondary nucleation, a process where existing assemblies catalyse the nucleation of new species. In particular, secondary nucleation has emerged as a central process controlling the proliferation of many filamentous protein structures, including molecular species related to diseases such as sickle cell anemia and a range of neurodegenerative conditions. Increasing evidence suggests that the physical size of protein filaments plays a key role in determining their potential for deleterious interactions with living cells, with smaller aggregates of misfolded proteins, oligomers, being particularly toxic. It is thus crucial to progress towards an understanding of the factors that control the sizes of protein aggregates. However, the influence of secondary nucleation on the time evolution of aggregate size distributions has been challenging to quantify. This difficulty originates in large part from the fact that secondary nucleation couples the dynamics of species distant in size space. Here, we approach this problem by presenting an analytical treatment of the master equation describing the growth kinetics of linear protein structures proliferating through secondary nucleation and provide closed-form expressions for the temporal evolution of the resulting aggregate size distribution. We show how the availability of analytical solutions for the full filament distribution allows us to identify the key physical parameters that control the sizes of growing protein filaments. Furthermore, we use these results to probe the dynamics of the populations of small oligomeric species as they are formed through secondary nucleation and discuss the implications of our work for understanding the factors that promote or curtail the production of these species with a potentially high deleterious biological activity.

  6. Dynamics of filament formation in a Kerr medium

    SciTech Connect

    Centurion, Martin; Pu Ye; Tsang, Mankei; Psaltis, Demetri

    2005-06-15

    We have studied the large-scale beam breakup and filamentation of femtosecond pulses in a Kerr medium. We have experimentally monitored the formation of stable light filaments, conical emission, and interactions between filaments. Three major stages lead to the formation of stable light filaments: First the beam breaks up into a pattern of connected lines (constellation), then filaments form on the constellations, and finally the filaments release a fraction of their energy through conical emission. We observed a phase transition to a faster filamentation rate at the onset of conical emission. We attribute this to the interaction of conical emissions with the constellation which creates additional filaments. Numerical simulations show good agreement with the experimental results.

  7. Mechanical Heterogeneity Favors Fragmentation of Strained Actin Filaments

    PubMed Central

    De La Cruz, Enrique M.; Martiel, Jean-Louis; Blanchoin, Laurent

    2015-01-01

    We present a general model of actin filament deformation and fragmentation in response to compressive forces. The elastic free energy density along filaments is determined by their shape and mechanical properties, which were modeled in terms of bending, twisting, and twist-bend coupling elasticities. The elastic energy stored in filament deformation (i.e., strain) tilts the fragmentation-annealing reaction free-energy profile to favor fragmentation. The energy gradient introduces a local shear force that accelerates filament intersubunit bond rupture. The severing protein, cofilin, renders filaments more compliant in bending and twisting. As a result, filaments that are partially decorated with cofilin are mechanically heterogeneous (i.e., nonuniform) and display asymmetric shape deformations and energy profiles distinct from mechanically homogenous (i.e., uniform), bare actin, or saturated cofilactin filaments. The local buckling strain depends on the relative size of the compliant segment as well as the bending and twisting rigidities of flanking regions. Filaments with a single bare/cofilin-decorated boundary localize energy and force adjacent to the boundary, within the compliant cofilactin segment. Filaments with small cofilin clusters were predicted to fragment within the compliant cofilactin rather than at boundaries. Neglecting contributions from twist-bend coupling elasticity underestimates the energy density and gradients along filaments, and thus the net effects of filament strain to fragmentation. Spatial confinement causes compliant cofilactin segments and filaments to adopt higher deformation modes and store more elastic energy, thereby promoting fragmentation. The theory and simulations presented here establish a quantitative relationship between actin filament fragmentation thermodynamics and elasticity, and reveal how local discontinuities in filament mechanical properties introduced by regulatory proteins can modulate both the severing efficiency

  8. Tracking protein aggregate interactions

    PubMed Central

    Bartz, Jason C; Nilsson, K Peter R

    2011-01-01

    Amyloid fibrils share a structural motif consisting of highly ordered β-sheets aligned perpendicular to the fibril axis.1, 2 At each fibril end, β-sheets provide a template for recruiting and converting monomers.3 Different amyloid fibrils often co-occur in the same individual, yet whether a protein aggregate aids or inhibits the assembly of a heterologous protein is unclear. In prion disease, diverse prion aggregate structures, known as strains, are thought to be the basis of disparate disease phenotypes in the same species expressing identical prion protein sequences.4–7 Here we explore the interactions reported to occur when two distinct prion strains occur together in the central nervous system. PMID:21597336

  9. Zooplankton Aggregations Near Sills

    DTIC Science & Technology

    2003-09-30

    frequency echo-sounder system. This data were supplemented with multi-net (BIONESS) trawls, bongo nets, and otter trawls (operated by D. Mackas and group...side. The general composition of the zooplankton aggregations can be deduced from the relative levels of the three echo-sounder frequencies; krill ...Nov. 20th, 2002. Krill layer is evident at 66 – 90 m, coincident with BIONESS trawl through the region. 3 Figure 2 shows a comparison between

  10. Filamentary structures in dense plasma focus: Current filaments or vortex filaments?

    SciTech Connect

    Soto, Leopoldo Pavez, Cristian; Moreno, José; Castillo, Fermin; Veloso, Felipe; Auluck, S. K. H.

    2014-07-15

    Recent observations of an azimuthally distributed array of sub-millimeter size sources of fusion protons and correlation between extreme ultraviolet (XUV) images of filaments with neutron yield in PF-1000 plasma focus have re-kindled interest in their significance. These filaments have been described variously in literature as current filaments and vortex filaments, with very little experimental evidence in support of either nomenclature. This paper provides, for the first time, experimental observations of filaments on a table-top plasma focus device using three techniques: framing photography of visible self-luminosity from the plasma, schlieren photography, and interferometry. Quantitative evaluation of density profile of filaments from interferometry reveals that their radius closely agrees with the collision-less ion skin depth. This is a signature of relaxed state of a Hall fluid, which has significant mass flow with equipartition between kinetic and magnetic energy, supporting the “vortex filament” description. This interpretation is consistent with empirical evidence of an efficient energy concentration mechanism inferred from nuclear reaction yields.

  11. Solar Filament Material Oscillations and Drainage before Eruption

    NASA Astrophysics Data System (ADS)

    Bi, Yi; Jiang, Yunchun; Yang, Jiayan; Hong, Junchao; Li, Haidong; Yang, Dan; Yang, Bo

    2014-08-01

    Both large-amplitude longitudinal (LAL) oscillations and material drainage in a solar filament are associated with the flow of material along the filament axis, often followed by an eruption. However, the relationship between these two motions and a subsequent eruption event is poorly understood. We analyze a filament eruption using EUV imaging data captured by the Atmospheric Imaging Array on board the Solar Dynamics Observatory and the Hα images from the Global Oscillation Network Group. Hours before the eruption, the filament was activated, with one of its legs undergoing a slow rising motion. The asymmetric activation inclined the filament relative to the solar surface. After the active phase, LAL oscillations were observed in the inclined filament. The oscillation period increased slightly over time, which may suggest that the magnetic fields supporting the filament evolve to be flatter during the slow rising phase. After the oscillations, a significant amount of filament material was drained toward one filament endpoint, followed immediately by the violent eruption of the filament. The material drainage may further support the change in magnetic topology prior to the eruption. Moreover, we suggest that the filament material drainage could play a role in the transition from a slow to a fast rise of the erupting filament.

  12. FilTER: Filament Trait-Evalutated Reconstruction

    NASA Astrophysics Data System (ADS)

    Panopoulou, G. V.; Tassis, K.; Goldsmith, P. F.; Heyer, M. H.

    2016-02-01

    FilTER (Filament Trait-Evaluated Reconstruction) post-processes output from DisPerSE (ascl:1302.015 ) to produce a set of filaments that are well-defined and have measured properties (e.g. width), then cuts the profiles, fits and assesses them to reconstruct new filaments according to defined criteria.

  13. Proteins aggregation and human diseases

    NASA Astrophysics Data System (ADS)

    Hu, Chin-Kun

    2015-04-01

    Many human diseases and the death of most supercentenarians are related to protein aggregation. Neurodegenerative diseases include Alzheimer's disease (AD), Huntington's disease (HD), Parkinson's disease (PD), frontotemporallobar degeneration, etc. Such diseases are due to progressive loss of structure or function of neurons caused by protein aggregation. For example, AD is considered to be related to aggregation of Aβ40 (peptide with 40 amino acids) and Aβ42 (peptide with 42 amino acids) and HD is considered to be related to aggregation of polyQ (polyglutamine) peptides. In this paper, we briefly review our recent discovery of key factors for protein aggregation. We used a lattice model to study the aggregation rates of proteins and found that the probability for a protein sequence to appear in the conformation of the aggregated state can be used to determine the temperature at which proteins can aggregate most quickly. We used molecular dynamics and simple models of polymer chains to study relaxation and aggregation of proteins under various conditions and found that when the bending-angle dependent and torsion-angle dependent interactions are zero or very small, then protein chains tend to aggregate at lower temperatures. All atom models were used to identify a key peptide chain for the aggregation of insulin chains and to find that two polyQ chains prefer anti-parallel conformation. It is pointed out that in many cases, protein aggregation does not result from protein mis-folding. A potential drug from Chinese medicine was found for Alzheimer's disease.

  14. Production, characterization, and modeling of mineral filled polypropylene filaments

    NASA Astrophysics Data System (ADS)

    George, Brian Robert

    1999-11-01

    This research produced mineral filled polypropylene filaments using a variety of fillers, characterized these filaments, and attempted to model their mechanical properties with current composite models. Also, these filaments were compared with bone to determine if they are suitable for modeling the mechanical properties of bone. Fillers used consist of wollastonite, talc, calcium carbonate, titanium dioxide, and hydroxyapatite. Fillers and polypropylene chips were combined and extruded into rods with the use of a mixer. The rods were chipped up and then formed into filaments through melt extrusion utilizing a piston extruder. Filaments with volume fractions of filler of 0.05, 0.10, 0.15, and 0.20 were produced. Additionally, some methods of trying to improve the properties of these filaments were attempted, but did not result in any significant property improvements. The fillers and filaments were visually characterized with a scanning electron microscope. Cross-sections, filament outer surfaces, fracture surfaces, and longitudinal cut open surfaces were viewed in this manner. Those filaments with anisotropic filler had some oriented filler particles, while all filaments suffered from poor adhesion between the polypropylene and the filler as well as agglomerations of filler particles. Twenty specimens of each filament were tensile tested and the average tenacity, strain, and modulus were calculated. Filaments containing talc, talc and wollastonite, titanium dioxide, or hydroxyapatite suffered from a drastic transition from ductile to brittle with the addition of 0.05 volume fraction of filler. This is evidenced by the sharp decrease in strain at this volume fraction of filler when compared to the strain of the unfilled polypropylene filament. Additionally, these same filaments suffered a sharp decrease in tenacity at the same volume fraction. These instant decreases are attributed to the agglomerations of filler in the filament. Generally, the modulus of the

  15. Soluble and filamentous proteins in Arabidopsis sieve elements.

    PubMed

    Batailler, Brigitte; Lemaître, Thomas; Vilaine, Françoise; Sanchez, Christian; Renard, Denis; Cayla, Thibaud; Beneteau, Julie; Dinant, Sylvie

    2012-07-01

    Phloem sieve elements are highly differentiated cells involved in the long-distance transport of photoassimilates. These cells contain both aggregated phloem-proteins (P-proteins) and soluble proteins, which are also translocated by mass flow. We used liquid chromatography-tandem mass spectrometry (LC-MS/MS) to carry out a proteomic survey of the phloem exudate of Arabidopsis thaliana, collected by the ethylenediaminetetraacetic acid (EDTA)-facilitated method. We identified 287 proteins, a large proportion of which were enzymes involved in the metabolic precursor generation and amino acid synthesis, suggesting that sieve tubes display high levels of metabolic activity. RNA-binding proteins, defence proteins and lectins were also found. No putative P-proteins were detected in the EDTA-exudate fraction, indicating a lack of long-distance translocation of such proteins in Arabidopsis. In parallel, we investigated the organization of P-proteins, by high-resolution transmission electron microscopy, and the localization of the phloem lectin PP2, a putative P-protein component, by immunolocalization with antibodies against PP2-A1. Transmission electron microscopy observations of P-proteins revealed bundles of filaments resembling strings of beads. PP2-A1 was found weakly associated with these structures in the sieve elements and bound to plastids. These observations suggest that PP2-A1 is anchored to P-proteins and organelles rather than being a structural component of P-proteins.

  16. Driven transport on open filaments with interfilament switching processes

    NASA Astrophysics Data System (ADS)

    Ghosh, Subhadip; Pagonabarraga, Ignacio; Muhuri, Sudipto

    2017-02-01

    We study a two-filament driven lattice gas model with oppositely directed species of particles moving on two parallel filaments with filament-switching processes and particle inflow and outflow at filament ends. The filament-switching process is correlated with the occupation number of the adjacent site such that particles switch filaments with finite probability only when oppositely directed particles meet on the same filament. This model mimics some of the coarse-grained features observed in context of microtubule-(MT) based intracellular transport, wherein cellular cargo loaded and off-loaded at filament ends are transported on multiple parallel MT filaments and can switch between the parallel microtubule filaments. We focus on a regime where the filaments are weakly coupled, such that filament-switching rate of particles scale inversely as the length of the filament. We find that the interplay of (off-) loading processes at the boundaries and the filament-switching process of particles leads to some distinctive features of the system. These features includes occurrence of a variety of phases in the system with inhomogeneous density profiles including localized density shocks, density difference across the filaments, and bidirectional current flows in the system. We analyze the system by developing a mean field (MF) theory and comparing the results obtained from the MF theory with the Monte Carlo (MC) simulations of the dynamics of the system. We find that the steady-state density and current profiles of particles and the phase diagram obtained within the MF picture matches quite well with MC simulation results. These findings maybe useful for studying multifilament intracellular transport.

  17. Micromachined hot-filament vacuum devices

    NASA Astrophysics Data System (ADS)

    Williams, Kirt Reed

    We describe investigations on micromachined hot-filament vacuum devices, which are electronic devices made by micromachining an ohmically heated tungsten filament that acts as a source of blackbody-like radiation or of free electrons. The freestanding filaments, which are typically 200-500 μm long, 5-20 μm wide, and 0.7- 2.3 μm thick, are suspended over a cavity etched into a silicon substrate. When the hot filament is used as a source of radiation (visible or infrared), the device is a 'microlamp.' When used as the source of thermionically emitted electrons, circuit devices such as diodes and triodes can be made. The thermionically emitting devices have also been characterized as magnetic-field sensors and ionization pressure sensors (ion gauges). We have designed, modeled, fabricated, and tested all of the aforementioned devices. We discuss at length the modeling of ohmic heating, thermionic emission, and electron flow through our devices. We describe the design and fabrication of vacuum-sealed and unsealed devices (which must be operated in a vacuum chamber). During the design of the device-fabrication processes, we developed a low-stress sputtered-tungsten- deposition method. We have also measured etch rates for more than 300 combinations of materials and etches used in micromachining and describe 20 sources of wet-and plasma-etch-rate variation. We describe the microscale optical pyrometry technique used to measure hot-filament temperature. Lifetimes of 10 hours at 2200 K and 1 hour at 3000 K are typical. Anode current in the vacuum diodes varies with filament temperature, with 50 μA being a representative value. Common-cathode triode circuits with small-signal voltage gains on the order of 2 to 3 have been made. The magnetic-field sensors are based on the Lorentz-force steering of electrons to a pair of anodes in a symmetrical device. The micro ion gauges are a planar version of the macroscopic devices, with about 10-6 times their volume. They have a

  18. The intermediate-sized filaments in rat kangaroo PtK2 cells. I. Morphology in situ.

    PubMed

    Franke, W W; Grund, C; Osborn, M; Weber, K

    1978-08-01

    The system of the intermediate-sized filaments (IF) of rat kangaroo PtK2 cells which can be specifically demonstrated by immunofluorescence microscopy using certain rabbit autoantibodies and guinea pig antibodies against bovine hoof prekeratin has been studied by electron microscopy. The characteristic ornamental, curved arrays of this system are shown after fixation in situ in both thin sections and whole-cell-preparations to represent bundles of 6 to 11 nm thick filaments extending through the whole cytoplasm, although in some cells they appear to be enriched in the perinuclear region. While many individual IF are recognized in the cytoplasm the tendency of such filaments to aggregate laterally into bundles is one of their prominent features. Among such bundle formations one form that consists of tightly packed IF cemented together in a dense osmiophilic matrix is especially conspicious. The appearance and mode of arrangement of the IF is not significantly altered in cells treated with colcemid and/or cytochalasin B. Spatial relationships of IF with microfilament-containing cables and microtubules as well as with membranous structures are also described. IF are heterogeneous in width and reveal an unstained, apparently hollow core, indicative of a tubular organization. Many IF show small, sometimes periodically arranged lateral projections which seem to be involved in IF cross-linking. Associations with polyribosomes are common. The changes in the IF system during mitosis have also been examined. The structural details of the IF as well as their possible role as cytoskeletal elements involved in the control of cell shape and cytoplasmic architecture are discussed in relation to data on various intermediate-sized filaments from other cell types. The close similarity of the IF of PtK2 cells to aggregates of prekeratin filaments is emphasized. It is suggested that PtK2 cells represent an epithelial cell line growing in a state of balanced semi-keratinization.

  19. The structures, mass motions and footpoints of solar filaments

    NASA Astrophysics Data System (ADS)

    Venkataramanasastry, Aparna

    This thesis focuses on identifying the mechanism by which solar filaments acquire mass. Some of the speculations for how a filament gets its mass are 1) injection of mass from the chromosphere into the filament structure, and 2) condensation of mass from the corona into the region of the filament channel. Mass motion at the footpoints of the filaments is studied to detect mass entering and leaving the filament body. The magnetic properties of the footpoints of the filaments are also studied. Recommendations are drawn by comparing observational properties obtained in this study with the features used in some of the previously developed models. The datasets used for this study are high-resolution image sets of centerline and Doppler wings of Halpha, obtained using the Dutch Open Telescope (DOT). The data were obtained on Oct 30, 2010. The data set contains three filaments in an active region in the northern hemisphere of the Sun. The images in each wavelength are aligned and made into movies to find the footpoints of the filaments through which the mass goes into and comes out of the filaments from and to the chromosphere, respectively. The magnetic properties of the footpoints are studied by overlaying the magnetogram images with the DOT images by using full-disk Halpha images for matching the features in the two. Of the three filaments, one of the filaments is observed to be stable throughout the duration of the observations; another filament erupts after about two hours of the beginning of observations; and the third filament is in its early stages of formation. The ends of the stable filament are clearly observed whereas the ends of the erupting filament and the forming filament are observed clearly intermittently during the duration of the observations. The animations of the region near the ends of filament 1 reveal definite injection and draining of mass via the footpoints into and out of the filament. The mass motion into and out of the filaments are observed

  20. Validation of a new image analysis procedure for quantifying filamentous bacteria in activated sludge.

    PubMed

    Liwarska-Bizukojc, Ewa; Bizukojc, Marcin; Andrzejczak, Olga

    2014-01-01

    Quantification of filamentous bacteria in activated sludge systems can be made by manual counting under a microscope or by the application of various automated image analysis procedures. The latter has been significantly developed in the last two decades. In this work a new method based upon automated image analysis techniques was elaborated and presented. It consisted of three stages: (a) Neisser staining, (b) grabbing of microscopic images, and (c) digital image processing and analysis. This automated image analysis procedure possessed the features of novelty. It simultaneously delivered data about aggregates and filaments in an individual calculation routine, which is seldom met in the procedures described in the literature so far. What is more important, the macroprogram performing image processing and calculation of morphological parameters was written in the same software which was used for grabbing of images. Previously published procedures required using two different types of software, one for image grabbing and another one for image processing and analysis. Application of this new procedure for the quantification of filamentous bacteria in the full-scale as well as laboratory activated sludge systems proved that it was simple, fast and delivered reliable results.

  1. A Comparison Study of an Active Region Eruptive Filament and a Neighboring Non-Eruptive Filament

    NASA Astrophysics Data System (ADS)

    Wu, S. T.; Jiang, C.; Feng, X. S.; Hu, Q.

    2014-12-01

    We perform a comparison study of an eruptive filament in the core region of AR 11283 and a nearby non-eruptive filament. The coronal magnetic field supporting these two filaments is extrapolated using our data-driven CESE-MHD-NLFFF code (Jiang et al. 2013, Jiang etal. 2014), which presents two magnetic flux ropes (FRs) in the same extrapolation box. The eruptive FR contains a bald-patch separatrix surface (BPSS) spatially co-aligned very well with a pre-eruption EUV sigmoid, which is consistent with the BPSS model for the coronal sigmoids. The numerically reproduced magnetic dips of the FRs match observations of the filaments strikingly well, which supports strongly the FR-dip model for filaments. The FR that supports the AR eruptive filament is much smaller (with a length of 3 Mm) compared with the large-scale FR holding the quiescent filament (with a length of 30 Mm). But the AR eruptive FR contains most of the magnetic free energy in the extrapolation box and holds a much higher magnetic energy density than the quiescent FR, because it resides along the main polarity inversion line (PIL) around sunspots with strong magnetic shear. Both the FRs are weakly twisted and cannot trigger kink instability. The AR eruptive FR is unstable because its axis reaches above a critical height for torus instability (TI), at which the overlying closed arcades can no longer confine the FR stably. To the contrary, the quiescent FR is firmly held down by its overlying field, as its axis apex is far below the TI threshold height. (This work is partially supported by NSF AGS-1153323 and 1062050)

  2. The influence of erythrocyte aggregation on induced platelet aggregation.

    PubMed

    Ott, C; Lardi, E; Schulzki, T; Reinhart, W H

    2010-01-01

    Red blood cells (RBCs) affect platelet aggregation in flowing blood (primary hemostasis). We tested the hypothesis that RBC aggregation could influence platelet aggregation. RBC aggregation was altered in vitro by: (i) changing plasma aggregatory properties with 3.7 g% dextran 40 (D40), 3.0 g% dextran 70 (D70) or 1.55 g% dextran 500 (D500); (ii) changing RBC aggregatory properties by incubating RBCs in 50 mU/ml neuraminidase for 60 min (reduction of the surface sialic acid content, thus reducing electrostatic repulsion) and subsequent RBC resuspension in platelet rich plasma (PRP) containing 1 g% dextran 70. RBC aggregation was assessed with the sedimentation rate (ESR). Platelet aggregation was measured: (i) in flowing whole blood with a platelet function analyzer PFA-100(R), which simulates in vivo conditions with RBCs flowing in the center and platelets along the wall, where they adhere to collagen and aggregate; and (ii) in a Chrono-log 700 Aggregometer, which measures changes of impedance by platelet aggregation in whole blood or changes in light transmission in PRP. We found that RBC aggregation increased with increasing molecular weight of dextran (ESR: 4 +/- 3 mm/h, 34 +/- 14 mm/h and 89 +/- 23 mm/hfor D40, D70 and D500, respectively, p < 0.0001) and with neuraminidase-treated RBCs (76 +/- 27 mm/h vs 27 +/- 8 mm/h, respectively, p < 0.0001). Platelet aggregation measured in whole blood under flow conditions (PFA-100) and without flow (Chronolog Aggregometer) was not affected by RBC aggregation. Our data suggest that RBC aggregation does not affect platelet aggregation in vitro and plays no role in primary hemostasis.

  3. Experiments on the Propagation of Plasma Filaments

    SciTech Connect

    Katz, Noam; Egedal, Jan; Fox, Will; Le, Ari; Porkolab, Miklos

    2008-07-04

    We investigate experimentally the motion and structure of isolated plasma filaments propagating through neutral gas. Plasma filaments, or 'blobs,' arise from turbulent fluctuations in a range of plasmas. Our experimental geometry is toroidally symmetric, and the blobs expand to a larger major radius under the influence of a vertical electric field. The electric field, which is caused by {nabla}B and curvature drifts in a 1/R magnetic field, is limited by collisional damping on the neutral gas. The blob's electrostatic potential structure and the resulting ExB flow field give rise to a vortex pair and a mushroom shape, which are consistent with nonlinear plasma simulations. We observe experimentally this characteristic mushroom shape for the first time. We also find that the blob propagation velocity is inversely proportional to the neutral density and decreases with time as the blob cools.

  4. SWAYING THREADS OF A SOLAR FILAMENT

    SciTech Connect

    Lin, Y.; Engvold, O.; Langangen, Oe.; Rouppe van der Voort, L. H. M.; Soler, R.; Ballester, J. L.; Oliver, R.

    2009-10-10

    From recent high-resolution observations obtained with the Swedish 1 m Solar Telescope in La Palma, we detect swaying motions of individual filament threads in the plane of the sky. The oscillatory characters of these motions are comparable with oscillatory Doppler signals obtained from corresponding filament threads. Simultaneous recordings of motions in the line of sight and in the plane of the sky give information about the orientation of the oscillatory plane. These oscillations are interpreted in the context of the magnetohydrodynamic (MHD) theory. Kink MHD waves supported by the thread body are proposed as an explanation of the observed thread oscillations. On the basis of this interpretation and by means of seismological arguments, we give an estimation of the thread Alfven speed and magnetic field strength by means of seismological arguments.

  5. Statistical study of solar filaments since 1919

    NASA Astrophysics Data System (ADS)

    Aboudarham, Jean

    2016-04-01

    Science board of Paris Observatory funded the data capture of tables associated with Meudon synoptic maps of Solar activity, which were published for observations ranging from 1919 to 1992. The EU HELIO project developed automatic recognition codes, especially concerning filaments based on observations between 1996 en 2014 (and soon, up to now). We plan to fill the gap between the two catalogues in the short term. But it is already possible to study filaments behavior over quite long periods of time. We present here the first series of results obtained from this analysis which give some clue about the way Solar activity behaves in various parts of the cycle, and about the way if depends on the hemisphere where activity occurs. This information could then be correlated with events catalogues (e.g. flares, CMEs, …) in order to link those phenomena with concrete Solar activity.

  6. Online Catalog for Filament-Sigmoid Correlation

    NASA Astrophysics Data System (ADS)

    Merriot, Ivy; Pevtsov, A.; Martens, P.

    2007-05-01

    A new online catalog correlating H-alpha filaments with SXT sigmoids gives researchers, teachers and pre-college students the ability to access digital H-alpha images online that were previously available only at the physical location of the NSO at Sunspot, NM. This web-based catalog correlates SOHO's SXT sigmoids from 1993-1998 as described in a non-online catalog created by Zach Blehm under the direction of Richard Canfield, MSU-Bozeman, with H-alpha filament activity as described by Ivy Merriot under the direction of Alexei Pevtsov, NSO, and Petrus Martens, MSU-Bozeman. The H-alpha images were digitized from film archives of the Flare Patrol Telescope at Sunspot, NM. Use of the online catalog will be demonstrated at the poster site with critical comments encouraged.

  7. Merging and energy exchange between optical filaments

    NASA Astrophysics Data System (ADS)

    Georgieva, D. A.; Kovachev, L. M.

    2015-10-01

    We investigate nonlinear interaction between collinear femtosecond laser pulses with power slightly above the critical for self-focusing Pcr trough the processes of cross-phase modulation (CPM) and degenerate four-photon parametric mixing (FPPM). When there is no initial phase difference between the pulses we observe attraction between pulses due to CPM. The final result is merging between the pulses in a single filament with higher power. By method of moments it is found that the attraction depends on the distance between the pulses and has potential character. In the second case we study energy exchange between filaments. This process is described through FPPM scheme and requests initial phase difference between the waves.

  8. How eukaryotic filamentous pathogens evade plant recognition.

    PubMed

    Oliveira-Garcia, Ely; Valent, Barbara

    2015-08-01

    Plant pathogenic fungi and oomycetes employ sophisticated mechanisms for evading host recognition. After host penetration, many fungi and oomycetes establish a biotrophic interaction. It is assumed that different strategies employed by these pathogens to avoid triggering host defence responses, including establishment of biotrophic interfacial layers between the pathogen and host, masking of invading hyphae and active suppression of host defence mechanisms, are essential for a biotrophic parasitic lifestyle. During the infection process, filamentous plant pathogens secrete various effectors, which are hypothesized to be involved in facilitating effective host infection. Live-cell imaging of fungi and oomycetes secreting fluorescently labeled effector proteins as well as functional characterization of the components of biotrophic interfaces have led to the recent progress in understanding how eukaryotic filamentous pathogens evade plant recognition.

  9. Morgellons disease: a filamentous borrelial dermatitis

    PubMed Central

    Middelveen, Marianne J; Stricker, Raphael B

    2016-01-01

    Morgellons disease (MD) is a dermopathy characterized by multicolored filaments that lie under, are embedded in, or project from skin. Although MD was initially considered to be a delusional disorder, recent studies have demonstrated that the dermopathy is associated with tickborne infection, that the filaments are composed of keratin and collagen, and that they result from proliferation of keratinocytes and fibroblasts in epithelial tissue. Culture, histopathological and molecular evidence of spirochetal infection associated with MD has been presented in several published studies using a variety of techniques. Spirochetes genetically identified as Borrelia burgdorferi sensu stricto predominate as the infective agent in most of the Morgellons skin specimens studied so far. Other species of Borrelia including Borrelia garinii, Borrelia miyamotoi, and Borrelia hermsii have also been detected in skin specimens taken from MD patients. The optimal treatment for MD remains to be determined. PMID:27789971

  10. Morgellons disease: a filamentous borrelial dermatitis.

    PubMed

    Middelveen, Marianne J; Stricker, Raphael B

    2016-01-01

    Morgellons disease (MD) is a dermopathy characterized by multicolored filaments that lie under, are embedded in, or project from skin. Although MD was initially considered to be a delusional disorder, recent studies have demonstrated that the dermopathy is associated with tickborne infection, that the filaments are composed of keratin and collagen, and that they result from proliferation of keratinocytes and fibroblasts in epithelial tissue. Culture, histopathological and molecular evidence of spirochetal infection associated with MD has been presented in several published studies using a variety of techniques. Spirochetes genetically identified as Borrelia burgdorferi sensu stricto predominate as the infective agent in most of the Morgellons skin specimens studied so far. Other species of Borrelia including Borrelia garinii, Borrelia miyamotoi, and Borrelia hermsii have also been detected in skin specimens taken from MD patients. The optimal treatment for MD remains to be determined.

  11. In situ ellipsometric study of surface immobilization of flagellar filaments

    NASA Astrophysics Data System (ADS)

    Kurunczi, S.; Németh, A.; Hülber, T.; Kozma, P.; Petrik, P.; Jankovics, H.; Sebestyén, A.; Vonderviszt, F.; Fried, M.; Bársony, I.

    2010-10-01

    Protein filaments composed of thousands of subunits are promising candidates as sensing elements in biosensors. In this work in situ spectroscopic ellipsometry is applied to monitor the surface immobilization of flagellar filaments. This study is the first step towards the development of layers of filamentous receptors for sensor applications. Surface activation is performed using silanization and a subsequent glutaraldehyde crosslinking. Structure of the flagellar filament layers immobilized on activated and non-activated Si wafer substrates is determined using a two-layer effective medium model that accounted for the vertical density distribution of flagellar filaments with lengths of 300-1500 nm bound to the surface. The formation of the first interface layer can be explained by the multipoint covalent attachment of the filaments, while the second layer is mainly composed of tail pinned filaments floating upwards with the free parts. As confirmed by atomic force microscopy, covalent immobilization resulted in an increased surface density compared to absorption.

  12. Ultraminiature broadband light source with spiral shaped filament

    NASA Technical Reports Server (NTRS)

    Tuma, Margaret L. (Inventor); Collura, Joseph S. (Inventor); Helvajian, Henry (Inventor); Pocha, Michael D. (Inventor); Meyer, Glenn A. (Inventor); McConaghy, Charles F. (Inventor); Olsen, Barry L. (Inventor); Hansen, William W (Inventor)

    2012-01-01

    An ultraminiature light source using a double-spiral shaped tungsten filament includes end contact portions which are separated to allow for radial and length-wise unwinding of the spiral. The double-spiral filament is spaced relatively far apart at the end portions thereof so that contact between portions of the filament upon expansion is avoided. The light source is made by fabricating a double-spiral ultraminiature tungsten filament from tungsten foil and housing the filament in a ceramic package having a reflective bottom and a well wherein the filament is suspended. A vacuum furnace brazing process attaches the filament to contacts of the ceramic package. Finally, a cover with a transparent window is attached onto the top of the ceramic package by solder reflow in a second vacuum furnace process to form a complete hermetically sealed package.

  13. COMPLEX FLARE DYNAMICS INITIATED BY A FILAMENT–FILAMENT INTERACTION

    SciTech Connect

    Zhu, Chunming; McAteer, R. T. James; Liu, Rui; Alexander, David; Sun, Xudong

    2015-11-01

    We report on an eruption involving a relatively rare filament–filament interaction on 2013 June 21, observed by SDO and STEREO-B. The two filaments were separated in height with a “double-decker” configuration. The eruption of the lower filament began simultaneously with a descent of the upper filament, resulting in a convergence and direct interaction of the two filaments. The interaction was accompanied by the heating of surrounding plasma and an apparent crossing of a loop-like structure through the upper filament. The subsequent coalescence of the filaments drove a bright front ahead of the erupting structures. The whole process was associated with a C3.0 flare followed immediately by an M2.9 flare. Shrinking loops and descending dark voids were observed during the M2.9 flare at different locations above a C-shaped flare arcade as part of the energy release, giving us unique insight into the flare dynamics.

  14. Transition from linear- to nonlinear-focusing regime in filamentation

    PubMed Central

    Lim, Khan; Durand, Magali; Baudelet, Matthieu; Richardson, Martin

    2014-01-01

    Laser filamentation in gases is often carried out in the laboratory with focusing optics to better stabilize the filament, whereas real-world applications of filaments frequently involve collimated or near-collimated beams. It is well documented that geometrical focusing can alter the properties of laser filaments and, consequently, a transition between a collimated and a strongly focused filament is expected. Nevertheless, this transition point has not been identified. Here, we propose an analytical method to determine the transition, and show that it corresponds to an actual shift in the balance of physical mechanisms governing filamentation. In high-NA conditions, filamentation is primarily governed by geometrical focusing and plasma effects, while the Kerr nonlinearity plays a more significant role as NA decreases. We find the transition between the two regimes to be relatively insensitive to the intrinsic laser parameters, and our analysis agrees well with a wide range of parameters found in published literature. PMID:25434678

  15. The Dark Matter filament between Abell 222/223

    NASA Astrophysics Data System (ADS)

    Dietrich, Jörg P.; Werner, Norbert; Clowe, Douglas; Finoguenov, Alexis; Kitching, Tom; Miller, Lance; Simionescu, Aurora

    2016-10-01

    Weak lensing detections and measurements of filaments have been elusive for a long time. The reason is that the low density contrast of filaments generally pushes the weak lensing signal to unobservably low scales. To nevertheless map the dark matter in filaments exquisite data and unusual systems are necessary. SuprimeCam observations of the supercluster system Abell 222/223 provided the required combination of excellent seeing images and a fortuitous alignment of the filament with the line-of-sight. This boosted the lensing signal to a detectable level and led to the first weak lensing mass measurement of a large-scale structure filament. The filament connecting Abell 222 and Abell 223 is now the only one traced by the galaxy distribution, dark matter, and X-ray emission from the hottest phase of the warm-hot intergalactic medium. The combination of these data allows us to put the first constraints on the hot gas fraction in filaments.

  16. Structure of Viral Aggregates

    NASA Astrophysics Data System (ADS)

    Barr, Stephen; Luijten, Erik

    2010-03-01

    The aggregation of virus particles is a particular form of colloidal self-assembly, since viruses of a give type are monodisperse and have identical, anisotropic surface charge distributions. In small-angle X-ray scattering experiments, the Qbeta virus was found to organize in different crystal structures in the presence of divalent salt and non-adsorbing polymer. Since a simple isotropic potential cannot explain the occurrence of all observed phases, we employ computer simulations to investigate how the surface charge distribution affects the virus interactions. Using a detailed model of the virus particle, we find an asymmetric ion distribution around the virus which gives rise to the different phases observed.

  17. [Elimination of microscopic filamentous fungi with disinfectants].

    PubMed

    Laciaková, A; Laciak, V

    1994-01-01

    The antifungal effectivity of three single-component (Persteril, Septonex, Glutaraldehyd) and of three combined (Persteril+Septonex, Pesteril+Glutaraldehyd, Glutaraldehyd+Septonex) commercially available disinfectants was monitored by the diffuse method on five fen of the microscopic filamentous fungi Aspergillus alternata, Aspergillus niger, Mucor fragillis, Fusarium moniliforme, Penicillium glabrum. The highest antifungal activity was observed in 2% Persteril while 2% Persteril + 1% Septonex were the most effective among the combined disinfectants. M. fragilis was the most resistant strain.

  18. Plasma filamentation in the Rijnhuizen tokamak RTP

    SciTech Connect

    Lopes Cardozo, N.J.; Schueller, F.C.; Barth, C.J.; Chu, C.C.; Pijper, F.J.; Lok, J.; Oomens, A.A.M. )

    1994-07-11

    Evidence for small scale magnetic structures in the Rijnhuizen tokamak RTP is presented. These are manifest through steps and peaks in the electron temperature and pressure, measured with multiposition Thomson scattering. During central electron cyclotron heating, several filaments of high pressure are found in the power deposition region. They live hundreds of microseconds. Near the sawtooth inversion radius a step'' in the temperature profile occurs. Further out, quasiperiodic structures are observed, in both Ohmic and heated discharges.

  19. Cold Milky Way HI Gas in Filaments

    NASA Astrophysics Data System (ADS)

    Kalberla, P. M. W.; Kerp, J.; Haud, U.; Winkel, B.; Ben Bekhti, N.; Flöer, L.; Lenz, D.

    2016-04-01

    We investigate data from the Galactic Effelsberg-Bonn H i Survey, supplemented with data from the third release of the Galactic All Sky Survey (GASS III) observed at Parkes. We explore the all-sky distribution of the local Galactic H i gas with | {v}{{LSR}}| \\lt 25 km s-1 on angular scales of 11‧-16‧. Unsharp masking is applied to extract small-scale features. We find cold filaments that are aligned with polarized dust emission and conclude that the cold neutral medium (CNM) is mostly organized in sheets that are, because of projection effects, observed as filaments. These filaments are associated with dust ridges, aligned with the magnetic field measured on the structures by Planck at 353 GHz. The CNM above latitudes | b| \\gt 20^\\circ is described by a log-normal distribution, with a median Doppler temperature TD = 223 K, derived from observed line widths that include turbulent contributions. The median neutral hydrogen (H i) column density is NH i ≃ 1019.1 cm-2. These CNM structures are embedded within a warm neutral medium with NH i ≃ 1020 cm-2. Assuming an average distance of 100 pc, we derive for the CNM sheets a thickness of ≲0.3 pc. Adopting a magnetic field strength of Btot = (6.0 ± 1.8) μG, proposed by Heiles & Troland, and assuming that the CNM filaments are confined by magnetic pressure, we estimate a thickness of 0.09 pc. Correspondingly, the median volume density is in the range 14 ≲ n ≲ 47 cm-3. The authors thank the Deutsche Forschungsgemeinschaft (DFG) for support under grant numbers KE757/11-1, KE757/7-3, KE757/7-2, KE757/7-1, and BE4823/1-1.

  20. Impact damage in filament wound composite bottles

    NASA Technical Reports Server (NTRS)

    Highsmith, Alton L.

    1993-01-01

    Increasingly, composite materials are being used in advanced structural applications because of the significant weight savings they offer when compared to more traditional engineering materials. The higher cost of composites must be offset by the increased performance that results from reduced structural weight if these new materials are to be used effectively. At present, there is considerable interest in fabricating solid rocket motor cases out of composite materials, and capitalizing on the reduced structural weight to increase rocket performance. However, one of the difficulties that arises when composite materials are used is that composites can develop significant amounts of internal damage during low velocity impacts. Such low velocity impacts may be encountered in routine handling of a structural component like a rocket motor case. The ability to assess the reduction in structural integrity of composite motor cases that experience accidental impacts is essential if composite rocket motor cases are to be certified for manned flight. While experimental studies of the post-impact performance of filament wound composite motor cases haven been proven performed (2,3), scaling impact data from small specimens to full scale structures has proven difficult. If such a scaling methodology is to be achieved, an increased understanding of the damage processes which influence residual strength is required. The study described herein was part of an ongoing investigation of damage development and reduction of tensile strength in filament wound composites subjected to low velocity impacts. The present study, which focused on documenting the damage that develops in filament wound composites as a result of such impacts, included two distinct tasks. The first task was to experimentally assess impact damage in small, filament wound pressure bottles using x-ray radiography. The second task was to study the feasibility of using digital image processing techniques to assist in

  1. Cellular Models of Aggregation-dependent Template-directed Proteolysis to Characterize Tau Aggregation Inhibitors for Treatment of Alzheimer Disease.

    PubMed

    Harrington, Charles R; Storey, John M D; Clunas, Scott; Harrington, Kathleen A; Horsley, David; Ishaq, Ahtsham; Kemp, Steven J; Larch, Christopher P; Marshall, Colin; Nicoll, Sarah L; Rickard, Janet E; Simpson, Michael; Sinclair, James P; Storey, Lynda J; Wischik, Claude M

    2015-04-24

    Alzheimer disease (AD) is a degenerative tauopathy characterized by aggregation of Tau protein through the repeat domain to form intraneuronal paired helical filaments (PHFs). We report two cell models in which we control the inherent toxicity of the core Tau fragment. These models demonstrate the properties of prion-like recruitment of full-length Tau into an aggregation pathway in which template-directed, endogenous truncation propagates aggregation through the core Tau binding domain. We use these in combination with dissolution of native PHFs to quantify the activity of Tau aggregation inhibitors (TAIs). We report the synthesis of novel stable crystalline leucomethylthioninium salts (LMTX®), which overcome the pharmacokinetic limitations of methylthioninium chloride. LMTX®, as either a dihydromesylate or a dihydrobromide salt, retains TAI activity in vitro and disrupts PHFs isolated from AD brain tissues at 0.16 μM. The Ki value for intracellular TAI activity, which we have been able to determine for the first time, is 0.12 μM. These values are close to the steady state trough brain concentration of methylthioninium ion (0.18 μM) that is required to arrest progression of AD on clinical and imaging end points and the minimum brain concentration (0.13 μM) required to reverse behavioral deficits and pathology in Tau transgenic mice.

  2. Contraction dynamics of planar liquid filaments

    NASA Astrophysics Data System (ADS)

    Devlin, Nicole; Sambath, Krishnaraj; Harris, Michael; Basaran, Osman

    2012-11-01

    Thin liquid sheets are ubiquitous in nature and urban landscapes, e.g. waterfalls, and industry, e.g. in various atomizers where sheets of liquid emanate from a nozzle or off a solid surface. These liquid sheets contract due to surface tension and may or may not break into smaller fragments depending on physical properties and flow conditions. The cross-section of a liquid sheet in a plane perpendicular to the main flow direction is a planar or 2D filament. Here, we study the contraction dynamics of an idealized 2D filament of an incompressible Newtonian fluid the initial shape of which is a rectangle terminated by two identical semi-circles. The dynamics are analyzed by solving the full 2D Navier-Stokes system and a1D, slender-jet approximation to it by a numerical technique based on the Galerkin finite element method. Simulation results are summarized by means of a phase diagram in the space of Reynolds number and initial filament aspect ratio. The talk will conclude with a discussion of the different modes of contraction and a critique of the capabilities and limitations of the 1D model.

  3. Experimental Study of the Current Filamentation Instability

    NASA Astrophysics Data System (ADS)

    Allen, Brian; Muggli, Patric; Silva, Luis O.; Martins, Joana; Yakimenko, Vitaly; Fedurin, Mikhail; Kusche, Karl; Babzien, Marcus; Huang, Chengkun; Mori, Warren

    2012-10-01

    The Current Filamentation Instability (CFI) is of central importance for the propagation of relativistic electron beams in plasmas. CFI has potential relevance to astrophysics, afterglow of gamma ray bursts, inertial confinement fusion, energy transport in the fast-igniter concept, and places an upper limit on the plasma density and accelerating gradient in PWFA's. An experimental study at the Accelerator Test Facility at Brookhaven National Laboratory with the 60MeV e^- beam and cm length plasma. The experiment included the systematic study and characterization of the instability as a function of the beam charge and plasma density. The transverse beam profile is measured directly at the plasma exit using OTR. Experimental results show the transition from plasma focusing to CFI near kpσr=1 characterized by the appearance of multiple (1-5) beam filaments and scaling of the transverse filament size with the plasma skin depth. Suppression of the instability is seen by lowering the growth rate of the instability by reducing the beam charge. The experimental results are in excellent agreement with theory and simulations and we present and discuss simulation and experimental results.

  4. Interplanetary shocks preceded by solar filament eruptions

    NASA Technical Reports Server (NTRS)

    Cane, H. V.; Kahler, S. W.; Sheeley, N. R., Jr.

    1986-01-01

    The solar and interplanetary characteristics of six interplanetary shock and energetic particle events associated with the eruptions of solar filaments lying outside active regions are discussed. The events are characterized by the familiar double-ribbon H-alpha brightenings observed with large flares, but only very weak soft X-ray and microwave bursts. Both impulsive phases and metric type II bursts are absent in all six events. The energetic particles observed near the earth appear to be accelerated predominantly in the interplanetary shocks. The interplanetary shock speeds are lower and the longitudinal extents considerably less than those of flare-associated shocks. Three of the events were associated with unusual enhancements of singly-ionized helium in the solar wind following the shocks. These enhancements appear to be direct detections of the cool filament material expelled from the corona. It is suggested that these events are part of a spectrum of solar eruptive events which include both weaker events and the large flares. Despite their unimpressive and unreported solar signatures, the quiescent filament eruptions can result in substantial space and geophysical disturbances.

  5. Hot filament CVD of boron nitride films

    DOEpatents

    Rye, Robert R.

    1992-01-01

    Using a hot filament (.apprxeq.1400.degree. C.) to activate borazine (B.sub.3 N.sub.3 H.sub.6) molecules for subsequent reaction with a direct line-of-sight substrate, transparent boron ntiride films as thick as 25,000 angstroms are grown for a substrate temperature as low as 100.degree. C. The minimum temperature is determined by radiative heating from the adjacent hot filament. The low temperature BN films show no indication of crystallinity with X-ray diffraction (XRD). X-ray photoelectron spectra (XPS) show the films to have a B:N ratio of 0.97:1 with no other XPS detectable impurities above the 0.5% level. Both Raman and infrared (IR) spectroscopy are characteristic of h-BN with small amounts of hydrogen detected as N-H and B-H bands in the IR spectrum. An important feature of this method is the separation and localization of the thermal activation step at the hot filament from the surface reaction and film growth steps at the substrate surface. This allows both higher temperature thermal activation and lower temperature film growth.

  6. Plasma flows in microscopic temperature filaments

    NASA Astrophysics Data System (ADS)

    Maggs, J. E.; Morales, G. J.

    2000-10-01

    We report on measurements of plasma flows in temperature filaments of radial size less than the electron skin depth. The temperature filaments are created by injecting a small electron beam at low voltages into a large magnetized plasma column in the LAPD plasma device at UCLA. The flows are measured using a small double sided Langmuir probe (or Mach probe). Three cases are investigated. The first case is a study of plasma flow under conditions of classical heat transport (A.T. Burke, J.E. Maggs, and G.J. Morales, Phys. Plasmas 7, 544 (2000)) (i.e., transport due to Coulomb collisions) and the transition to non-classical conditions (A.T. Burke, J.E. Maggs, and G.J. Morales, Phys. Plasmas 7, 1397 (2000)) in a temperature filament created in the afterglow plasma. The second case is a beam injected during the discharge plasma at voltages comparable to the plasma discharge voltage. In this case radially outward propagating temperature fluctuations are observed to emanate from the beam heated region. The third case is a beam injected in the edge region of the plasma during the discharge. Reductions in the axial transport of heat are observed apparently due to the large pre-existing fluctuations that naturally occur at the plasma edge.

  7. Mechanical properties of intermediate filament proteins

    PubMed Central

    Charrier, Elisabeth E.; Janmey, Paul A.

    2016-01-01

    Purified intermediate filament proteins can be reassembled in vitro to produce polymers closely resembling those found in cells, and these filament form viscoelastic gels. The crosslinks holding IFs together in the network include specific bonds between polypeptides extending from the filament surface and ionic interactions mediated by divalent cations. IF networks exhibit striking non-linear elasticity with stiffness, as quantified by shear modulus, increasing an order of magnitude as the networks are deformed to large stains resembling those that soft tissues undergo in vivo. Individual Ifs can be stretched to more than 2 or 3 times their resting length without breaking. At least ten different rheometric methods have been used to quantify the viscoelasticity of IF networks over a wide range of timescales and strain magnitudes. The mechanical roles of different classes of IF on mesenchymal and epithelial cells in culture have also been studied by an even wider range of microrheological methods. These studies have documented the effects on cell mechanics when IFs are genetically or pharmacologically disrupted or when normal or mutant IF proteins are exogenously expressed in cells. Consistent with in vitro rheology, the mechanical role of IFs is more apparent as cells are subjected to larger and more frequent deformations. PMID:26795466

  8. RNA interference Pathways in Filamentous Fungi

    PubMed Central

    Liu, Yi

    2015-01-01

    RNA interference is a conserved eukaryotic homology-dependent post-transcriptional gene silencing mechanism. The filamentous fungus Neurospora crassa is one of the first organisms used for RNAi studies. Quelling and Meiotic Silencing by Unpaired DNA (MSUD) are two RNAi related phenomena discovered in Neurospora and their characterizations have contributed significantly to our understanding of RNAi mechanisms in eukaryotes. More recently, a type of DNA damage-induced small RNA, microRNA-like small RNAs and Dicer-independent small silencing RNAs have been discovered in Neurospora crassa which can regulate gene expression. In addition, there are at least six different pathways responsible for the production of these small RNAs, indicating that this fungus is an important model system to study small RNA function and biogenesis. The RNAi studies in other filamentous fungi such as Cryphonectria paracitica and Aspergillus provide evidences that RNAi plays an important role in antiviral defense and RNAi mechanism is widely conserved in filamentous fungi, and RNAi has been commonly used as an efficient tool for studying the gene function. The discovery of the endogenous small RNAs from M. circinelloides further indicates the richness and complex of the RNAi field in eukaryotes. PMID:20680389

  9. Oscillating Filaments. I. Oscillation and Geometrical Fragmentation

    NASA Astrophysics Data System (ADS)

    Gritschneder, Matthias; Heigl, Stefan; Burkert, Andreas

    2017-01-01

    We study the stability of filaments in equilibrium between gravity and internal as well as external pressure using the grid-based AMR code RAMSES. A homogeneous, straight cylinder below a critical line mass is marginally stable. However, if the cylinder is bent, such as with a slight sinusoidal perturbation, an otherwise stable configuration starts to oscillate, is triggered into fragmentation, and collapses. This previously unstudied behavior allows a filament to fragment at any given scale, as long as it has slight bends. We call this process “geometrical fragmentation.” In our realization, the spacing between the cores matches the wavelength of the sinusoidal perturbation, whereas up to now, filaments were thought to be only fragmenting on the characteristic scale set by the mass-to-line ratio. Using first principles, we derive the oscillation period as well as the collapse timescale analytically. To enable a direct comparison with observations, we study the line-of-sight velocity for different inclinations. We show that the overall oscillation pattern can hide the infall signature of cores.

  10. Onset of re-epithelialization after skin injury correlates with a reorganization of keratin filaments in wound edge keratinocytes: defining a potential role for keratin 16

    PubMed Central

    1996-01-01

    Injury to stratified epithelia causes a strong induction of keratins 6 (K6) and 16 (K16) in post-mitotic keratinocytes located at the wound edge. We show that induction of K6 and K16 occurs within 6 h after injury to human epidermis. Their subsequent accumulation in keratinocytes correlates with the profound reorganization of keratin filaments from a pan-cytoplasmic distribution to one in which filaments are aggregated in a juxtanuclear location, opposite to the direction of cell migration. This filament reorganization coincides with additional cytoarchitectural changes and the onset of re-epithelialization after 18 h post-injury. By following the assembly of K6 and K16 in vitro and in cultured cells, we find that relative to K5 and K14, a well- characterized keratin pair that is constitutively expressed in epidermis, K6 and K16 polymerize into short 10-nm filaments that accumulate near the nucleus, a property arising from K16. Forced expression of human K16 in skin keratinocytes of transgenic mice causes a retraction of keratin filaments from the cell periphery, often in a polarized fashion. These results imply that K16 may not have a primary structural function akin to epidermal keratins. Rather, they suggest that in the context of epidermal wound healing, the function of K16 could be to promote a reorganization of the cytoplasmic array of keratin filaments, an event that precedes the onset of keratinocyte migration into the wound site. PMID:8636216

  11. Holographic characterization of protein aggregates

    NASA Astrophysics Data System (ADS)

    Wang, Chen; Zhong, Xiao; Ruffner, David; Stutt, Alexandra; Philips, Laura; Ward, Michael; Grier, David

    Holographic characterization directly measures the size distribution of subvisible protein aggregates in suspension and offers insights into their morphology. Based on holographic video microscopy, this analytical technique records and interprets holograms of individual aggregates in protein solutions as they flow down a microfluidic channel, without requiring labeling or other exceptional sample preparation. The hologram of an individual protein aggregate is analyzed in real time with the Lorenz-Mie theory of light scattering to measure that aggregate's size and optical properties. Detecting, counting and characterizing subvisible aggregates proceeds fast enough for time-resolved studies, and lends itself to tracking trends in protein aggregation arising from changing environmental factors. No other analytical technique provides such a wealth of particle-resolved characterization data in situ. Holographic characterization promises accelerated development of therapeutic protein formulations, improved process control during manufacturing, and streamlined quality assurance during storage and at the point of use. Mrsec and MRI program of the NSF, Spheryx Inc.

  12. Kinetic and hydrodynamic models of chemotactic aggregation

    NASA Astrophysics Data System (ADS)

    Chavanis, Pierre-Henri; Sire, Clément

    2007-10-01

    We derive general kinetic and hydrodynamic models of chemotactic aggregation that describe certain features of the morphogenesis of biological colonies (like bacteria, amoebae, endothelial cells or social insects). Starting from a stochastic model defined in terms of N coupled Langevin equations, we derive a nonlinear mean-field Fokker-Planck equation governing the evolution of the distribution function of the system in phase space. By taking the successive moments of this kinetic equation and using a local thermodynamic equilibrium condition, we derive a set of hydrodynamic equations involving a damping term. In the limit of small frictions, we obtain a hyperbolic model describing the formation of network patterns (filaments) and in the limit of strong frictions we obtain a parabolic model which is a generalization of the standard Keller-Segel model describing the formation of clusters (clumps). Our approach connects and generalizes several models introduced in the chemotactic literature. We discuss the analogy between bacterial colonies and self-gravitating systems and between the chemotactic collapse and the gravitational collapse (Jeans instability). We also show that the basic equations of chemotaxis are similar to nonlinear mean-field Fokker-Planck equations so that a notion of effective generalized thermodynamics can be developed.

  13. Plasma Brightenings in a Failed Solar Filament Eruption

    NASA Astrophysics Data System (ADS)

    Li, Y.; Ding, M. D.

    2017-03-01

    Failed filament eruptions are solar eruptions that are not associated with coronal mass ejections. In a failed filament eruption, the filament materials usually show some ascending and falling motions as well as generating bright EUV emissions. Here we report a failed filament eruption (SOL2016-07-22) that occurred in a quiet-Sun region observed by the Atmospheric Imaging Assembly on board the Solar Dynamics Observatory. In this event, the filament spreads out but gets confined by the surrounding magnetic field. When interacting with the ambient magnetic field, the filament material brightens up and flows along the magnetic field lines through the corona to the chromosphere. We find that some materials slide down along the lifting magnetic structure containing the filament and impact the chromosphere, and through kinetic energy dissipation, cause two ribbon-like brightenings in a wide temperature range. There is evidence suggesting that magnetic reconnection occurs between the filament magnetic structure and the surrounding magnetic fields where filament plasma is heated to coronal temperatures. In addition, thread-like brightenings show up on top of the erupting magnetic fields at low temperatures, which might be produced by an energy imbalance from a fast drop of radiative cooling due to plasma rarefaction. Thus, this single event of a failed filament eruption shows the existence of a variety of plasma brightenings that may be caused by completely different heating mechanisms.

  14. Patterns of molecular motors that guide and sort filaments.

    PubMed

    Rupp, Beat; Nédélec, François

    2012-11-21

    Molecular motors can be immobilized to transport filaments and loads that are attached to these filaments inside a nano-device. However, if motors are distributed uniformly over a flat surface, the motility is undirected, and the filaments move equally in all directions. For many applications it is important to control the direction in which the filaments move, and two strategies have been explored to achieve this: applying external forces and confining the filaments inside channels. In this article, we discuss a third strategy in which the topography of the sample remains flat, but the motors are distributed non-uniformly over the surface. Systems of filaments and patterned molecular motors were simulated using a stochastic engine that included Brownian motion and filament bending elasticity. Using an evolutionary algorithm, patterns were optimized for their capacity to precisely control the paths of the filaments. We identified patterns of motors that could either direct the filaments in a particular direction, or separate short and long filaments. These functionalities already exceed what has been achieved with confinement. The patterns are composed of one or two types of motors positioned in lines or along arcs and should be easy to manufacture. Finally, these patterns can be easily combined into larger designs, allowing one to precisely control the motion of microscopic objects inside a device.

  15. Tropomyosin - master regulator of actin filament function in the cytoskeleton.

    PubMed

    Gunning, Peter W; Hardeman, Edna C; Lappalainen, Pekka; Mulvihill, Daniel P

    2015-08-15

    Tropomyosin (Tpm) isoforms are the master regulators of the functions of individual actin filaments in fungi and metazoans. Tpms are coiled-coil parallel dimers that form a head-to-tail polymer along the length of actin filaments. Yeast only has two Tpm isoforms, whereas mammals have over 40. Each cytoskeletal actin filament contains a homopolymer of Tpm homodimers, resulting in a filament of uniform Tpm composition along its length. Evidence for this 'master regulator' role is based on four core sets of observation. First, spatially and functionally distinct actin filaments contain different Tpm isoforms, and recent data suggest that members of the formin family of actin filament nucleators can specify which Tpm isoform is added to the growing actin filament. Second, Tpms regulate whole-organism physiology in terms of morphogenesis, cell proliferation, vesicle trafficking, biomechanics, glucose metabolism and organ size in an isoform-specific manner. Third, Tpms achieve these functional outputs by regulating the interaction of actin filaments with myosin motors and actin-binding proteins in an isoform-specific manner. Last, the assembly of complex structures, such as stress fibers and podosomes involves the collaboration of multiple types of actin filament specified by their Tpm composition. This allows the cell to specify actin filament function in time and space by simply specifying their Tpm isoform composition.

  16. Disruption of the keratin filament network during epithelial cell division.

    PubMed Central

    Lane, E B; Goodman, S L; Trejdosiewicz, L K

    1982-01-01

    The behaviour of keratin filaments during cell division was examined in a wide range of epithelial lines from several species. Almost half of them show keratin disruption as described previously: by immunofluorescence, filaments are replaced during mitosis by a 'speckled' pattern of discrete cytoplasmic dots. In the electron microscope these ' speckles ' are seen as granules around the cell periphery, just below the actin cortical mesh, with no detectable 10 nm filament structure inside them and no keratin filament bundles in the rest of the cytoplasm. A time course of the filament reorganization was constructed from double immunofluorescence data; filaments are disrupted in prophase, and the filament network is intact again by cytokinesis. The phenomenon is restricted to cells rich in keratin filaments, such as keratinocytes; it is unrelated to the co-existence of vimentin in many of these cells, and vimentin is generally maintained as filaments while the keratin is restructured. Some resistance to the effect may be conferred by an extended cycle time. Filament reorganization takes place within minutes, so that a reversible mechanism seems more likely than one involving de novo protein synthesis, at this metabolically quiet stage of the cell cycle. Images Fig. 1. Fig. 2. Fig. 3. Fig. 4. Fig. 5. Fig. 6. PMID:6202508

  17. Microwave processing of ceramic oxide filaments. Annual report, FY1997

    SciTech Connect

    Vogt, G.J.

    1998-12-31

    The objective of the microwave filament processing project is to develop microwave techniques to manufacture continuous ceramic oxide filaments. Microwave processing uses the volumetric absorption of microwave power in oxide filament tows to drive off process solvents, to burn out organic binders, and to sinter the dried fibers to produce flexible, high-strength ceramic filaments. The technical goal is to advance filament processing technology by microwave heating more rapidly with less energy and at a lower cost than conventional processing, but with the same quality as conventional processing. The manufacturing goal is to collaborate with the 3M Company, a US manufacturer of ceramic oxide filaments, to evaluate the technology using a prototype filament system and to transfer the microwave technology to the 3M Company. Continuous ceramic filaments are a principal component in many advanced high temperature materials like continuous fiber ceramic composites (CFCC) and woven ceramic textiles. The use of continuous ceramic filaments in CFCC radiant burners, gas turbines, waste incineration, and hot gas filters in U.S. industry and power generation is estimated to save at least 2.16 quad/yr by year 2010 with energy cost savings of at least $8.1 billion. By year 2010, continuous ceramic filaments and CFCC`s have the potential to abate pollution emissions by 917,000 tons annually of nitrous oxide and 118 million tons annually of carbon dioxide (DOE Report OR-2002, February, 1994).

  18. Filamentous structures in skeletal muscle: anchors for the subsarcolemmal space.

    PubMed

    Khairani, Astrid Feinisa; Tajika, Yuki; Takahashi, Maiko; Ueno, Hitoshi; Murakami, Tohru; Soenggono, Arifin; Yorifuji, Hiroshi

    2015-03-01

    In skeletal muscle fibers, intermediate filaments and actin filaments provide structural support to the myofibrils and the sarcolemma. For many years, it was poorly understood from ultrastructural observations that how these filamentous structures were kept anchored. The present study was conducted to determine the architecture of filamentous anchoring structures in the subsarcolemmal space and the intermyofibrils. The diaphragms (Dp) of adult wild type and mdx mice (mdx is a model for Duchenne muscular dystrophy) were subjected to tension applied perpendicular to the long axis of the muscle fibers, with or without treatment with 1% Triton X-100 or 0.03% saponin. These experiments were conducted to confirm the presence and integrity of the filamentous anchoring structures. Transmission electron microscopy revealed that these structures provide firm transverse connections between the sarcolemma and peripheral myofibrils. Most of the filamentous structures appeared to be inserted into subsarcolemmal densities, forming anchoring connections between the sarcolemma and peripheral myofibrils. In some cases, actin filaments were found to run longitudinally in the subsarcolemmal space to connect to the sarcolemma or in some cases to connect to the intermyofibrils as elongated thin filaments. These filamentous anchoring structures were less common in the mdx Dp. Our data suggest that the transverse and longitudinal filamentous structures form an anchoring system in the subsarcolemmal space and the intermyofibrils.

  19. Geometry of flexible filament cohesion: Better contact through twist?

    NASA Astrophysics Data System (ADS)

    Cajamarca, Luis; Grason, Gregory M.

    2014-11-01

    Cohesive interactions between filamentous molecules have broad implications for a range of biological and synthetic materials. While long-standing theoretical approaches have addressed the problem of inter-filament forces from the limit of infinitely rigid rods, the ability of flexible filaments to deform intra-filament shape in response to changes in inter-filament geometry has a profound affect on the nature of cohesive interactions. In this paper, we study two theoretical models of inter-filament cohesion in the opposite limit, in which filaments are sufficiently flexible to maintain cohesive contact along their contours, and address, in particular, the role played by helical-interfilament geometry in defining interactions. Specifically, we study models of featureless, tubular filaments interacting via: (1) pair-wise Lennard-Jones (LJ) interactions between surface elements and (2) depletion-induced filament binding stabilized by electrostatic surface repulsion. Analysis of these models reveals a universal preference for cohesive filament interactions for non-zero helical skew, and further, that in the asymptotic limit of vanishing interaction range relative to filament diameter, the skew-dependence of cohesion approaches a geometrically defined limit described purely by the close-packing geometry of twisted tubular filaments. We further analyze non-universal features of the skew-dependence of cohesion at small-twist for both potentials, and argue that in the LJ model the pair-wise surface attraction generically destabilizes parallel filaments, while in the second model, pair-wise electrostatic repulsion in combination with non-pairwise additivity of depletion leads to a meta-stable parallel state.

  20. Fractal structure of asphaltene aggregates.

    PubMed

    Rahmani, Nazmul H G; Dabros, Tadeusz; Masliyah, Jacob H

    2005-05-15

    A photographic technique coupled with image analysis was used to measure the size and fractal dimension of asphaltene aggregates formed in toluene-heptane solvent mixtures. First, asphaltene aggregates were examined in a Couette device and the fractal-like aggregate structures were quantified using boundary fractal dimension. The evolution of the floc structure with time was monitored. The relative rates of shear-induced aggregation and fragmentation/restructuring determine the steady-state floc structure. The average floc structure became more compact or more organized as the floc size distribution attained steady state. Moreover, the higher the shear rate is, the more compact the floc structure is at steady state. Second, the fractal dimensions of asphaltene aggregates were also determined in a free-settling test. The experimentally determined terminal settling velocities and characteristic lengths of the aggregates were utilized to estimate the 2D and 3D fractal dimensions. The size-density fractal dimension (D(3)) of the asphaltene aggregates was estimated to be in the range from 1.06 to 1.41. This relatively low fractal dimension suggests that the asphaltene aggregates are highly porous and very tenuous. The aggregates have a structure with extremely low space-filling capacity.

  1. Aggregation dynamics of rigid polyelectrolytes

    NASA Astrophysics Data System (ADS)

    Tom, Anvy Moly; Rajesh, R.; Vemparala, Satyavani

    2016-01-01

    Similarly charged polyelectrolytes are known to attract each other and aggregate into bundles when the charge density of the polymers exceeds a critical value that depends on the valency of the counterions. The dynamics of aggregation of such rigid polyelectrolytes are studied using large scale molecular dynamics simulations. We find that the morphology of the aggregates depends on the value of the charge density of the polymers. For values close to the critical value, the shape of the aggregates is cylindrical with height equal to the length of a single polyelectrolyte chain. However, for larger values of charge, the linear extent of the aggregates increases as more and more polymers aggregate. In both the cases, we show that the number of aggregates decrease with time as power laws with exponents that are not numerically distinguishable from each other and are independent of charge density of the polymers, valency of the counterions, density, and length of the polyelectrolyte chain. We model the aggregation dynamics using the Smoluchowski coagulation equation with kernels determined from the molecular dynamics simulations and justify the numerically obtained value of the exponent. Our results suggest that once counterions condense, effective interactions between polyelectrolyte chains short-ranged and the aggregation of polyelectrolytes are diffusion-limited.

  2. Filament Eruptions, Jets, and Space Weather

    NASA Technical Reports Server (NTRS)

    Moore, Ronald; Sterling, Alphonse; Robe, Nick; Falconer, David; Cirtain, Jonathan

    2013-01-01

    Previously, from chromospheric H alpha and coronal X-ray movies of the Sun's polar coronal holes, it was found that nearly all coronal jets (greater than 90%) are one or the other of two roughly equally common different kinds, different in how they erupt: standard jets and blowout jets (Yamauchi et al 2004, Apl, 605, 5ll: Moore et all 2010, Apj, 720, 757). Here, from inspection of SDO/AIA He II 304 A movies of 54 polar x-ray jets observed in Hinode/XRT movies, we report, as Moore et al (2010) anticipated, that (1) most standard x-ray jets (greater than 80%) show no ejected plasma that is cool enough (T is less than or approximately 10(exp 5K) to be seen in the He II 304 A movies; (2) nearly all blownout X-ray jets (greater than 90%) show obvious ejection of such cool plasma; (3) whereas when cool plasma is ejected in standard X-ray jets, it shows no lateral expansion, the cool plasma ejected in blowout X-ray jets shows strong lateral expansion; and (4) in many blowout X-ray jets, the cool plasma ejection displays the erupting-magnetic-rope form of clasic filament eruptions and is thereby seen to be a miniature filament eruption. The XRT movies also showed most blowout X-ray jets to be larger and brighter, and hence to apparently have more energy, than most standard X-ray jets. These observations (1) confirm the dichotomy of coronal jets, (2) agree with the Shibata model for standard jets, and (3) support the conclusion of Moore et al (2010) that in blowout jets the magnetic-arch base of the jet erupts in the manner of the much larger magnetic arcades in which the core field, the field rooted along the arcade's polarity inversion line, is sheared and twisted (sigmoid), often carries a cool-plasma filament, and erupts to blowout the arcade, producing a CME. From Hinode/SOT Ca II movies of the polar limb, Sterling et al (2010, ApJ, 714, L1) found that chromospheric Type-II spicules show a dichotomy of eruption dynamics similar to that found here for the cool

  3. Overextended sarcomeres regain filament overlap following stretch.

    PubMed

    Panchangam, Appaji; Herzog, Walter

    2012-09-21

    Sarcomere overextension has been widely implicated in stretch-induced muscle injury. Yet, sarcomere overextensions are typically inferred based on indirect evidence obtained in muscle and fibre preparations, where individual sarcomeres cannot be observed during dynamic contractions. Therefore, it remains unclear whether sarcomere overextensions are permanent following injury-inducing stretch-shortening cycles, and thus, if they can explain stretch-induced force loss. We tested the hypothesis that overextended sarcomeres can regain filament overlap in isolated myofibrils from rabbit psoas muscles. Maximally activated myofibrils (n=13) were stretched from an average sarcomere length of 2.6±0.04μm by 0.9μm sarcomere(-1) at a speed of 0.1μm sarcomere(-1)s(-1) and immediately returned to the starting lengths at the same speed (sarcomere strain=34.1±2.3%). Myofibrils were then allowed to contract isometrically at the starting lengths (2.6μm) for ∼30s before relaxing. Force and individual sarcomere lengths were measured continuously. Out of the 182 sarcomeres, 35 sarcomeres were overextended at the peak of stretch, out of which 26 regained filament overlap in the shortening phase while 9 (∼5%) remained overextended. About 35% of the sarcomeres with initial lengths on the descending limb of the force-length relationship and ∼2% of the sarcomeres with shorter initial lengths were overextended. These findings provide first ever direct evidence that overextended sarcomeres can regain filament overlap in the shortening phase following stretch, and that the likelihood of overextension is higher for sarcomeres residing initially on the descending limb.

  4. Mechanism of Actin Filament Bundling by Fascin

    SciTech Connect

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

    2013-03-07

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

  5. Growth and Division of Filamentous Forms of Escherichia coli.

    PubMed

    Adler, H I; Hardigree, A A

    1965-07-01

    Adler, Howard I. (Oak Ridge National Laboratory, Oak Ridge, Tenn.), and Alice A. Hardigree. Growth and division of filamentous forms of Escherichia coli. J. Bacteriol. 90:223-226. 1965.-Cells of certain mutant strains of Escherichia coli grow into long multinucleate filaments after exposure to radiation. Deoxyribonucleic acid, ribonucleic acid, and protein synthesis proceed, but cytokinesis does not occur. Cytokinesis (cross-septation) can be initiated by exposure of the filaments to pantoyl lactone or a temperature of 42 C. If growing filaments are treated with mitomycin C, nuclear division does not occur, and nuclear material is confined to the central region of the filament. Cytokinesis cannot be induced in mitomycin C-treated filaments by pantoyl lactone or treatment at 42 C.

  6. A FILAMENT ERUPTION ON 2010 OCTOBER 21 FROM THREE VIEWPOINTS

    SciTech Connect

    Filippov, Boris

    2013-08-10

    A filament eruption on 2010 October 21 observed from three different viewpoints by the Solar Terrestrial Relations Observatory and the Solar Dynamic Observatory is analyzed by also invoking data from the Solar and Heliospheric Observatory and the Kanzelhoehe Solar Observatory. The position of the filament just before the eruption at the central meridian not far from the center of the solar disk was favorable for photospheric magnetic field measurements in the area below the filament. Because of this, we were able to calculate with high precision the distribution of the coronal potential magnetic field near the filament. We found that the filament began to erupt when it approached the height in the corona where the magnetic field decay index was greater than 1. We also determined that during the initial stage of the eruption the filament moved along the magnetic neutral surface.

  7. Order and disorder in intermediate filament proteins.

    PubMed

    Kornreich, Micha; Avinery, Ram; Malka-Gibor, Eti; Laser-Azogui, Adi; Beck, Roy

    2015-09-14

    Intermediate filaments (IFs), important components of the cytoskeleton, provide a versatile, tunable network of self-assembled proteins. IF proteins contain three distinct domains: an α-helical structured rod domain, flanked by intrinsically disordered head and tail domains. Recent studies demonstrated the functional importance of the disordered domains, which differ in length and amino-acid sequence among the 70 different human IF genes. Here, we investigate the biophysical properties of the disordered domains, and review recent findings on the interactions between them. Our analysis highlights key components governing IF functional roles in the cytoskeleton, where the intrinsically disordered domains dictate protein-protein interactions, supramolecular assembly, and macro-scale order.

  8. Filament winding cylinders. I - Process model

    NASA Technical Reports Server (NTRS)

    Lee, Soo-Yong; Springer, George S.

    1990-01-01

    A model was developed which describes the filament winding process of composite cylinders. The model relates the significant process variables such as winding speed, fiber tension, and applied temperature to the thermal, chemical and mechanical behavior of the composite cylinder and the mandrel. Based on the model, a user friendly code was written which can be used to calculate (1) the temperature in the cylinder and the mandrel, (2) the degree of cure and viscosity in the cylinder, (3) the fiber tensions and fiber positions, (4) the stresses and strains in the cylinder and in the mandrel, and (5) the void diameters in the cylinder.

  9. Spatiotemporal rogue events in femtosecond filamentation

    SciTech Connect

    Majus, D.; Jukna, V.; Valiulis, G.; Dubietis, A.; Faccio, D.

    2011-02-15

    We present experimental and numerical investigations of optical extreme (rogue) event statistics recorded in the regime of femtosecond pulse filamentation in water. In the spectral domain, the extreme events manifest themselves as either large or small extremes of the spectral intensity, justified by right- or left-tailed statistical distributions, respectively. In the time domain, the observed extreme events are associated with pulse splitting and energy redistribution in space and therefore are exquisitely linked to three-dimensional, spatiotemporal dynamics and formation of the X waves.

  10. Folding of viscous sheets and filaments

    NASA Astrophysics Data System (ADS)

    Skorobogatiy, M.; Mahadevan, L.

    2000-12-01

    We consider the nonlinear folding behavior of a viscous filament or a sheet under the influence of an external force such as gravity. Everyday examples of this phenomenon are provided by the periodic folding of a sheet of honey as it impinges on toast, or the folding of a stream of shampoo as it falls on one's hand. To understand the evolution of a fold, we formulate and solve a free-boundary problem for the phenomenon, give scaling laws for the size of the folds and the frequency with which they are laid out, and verify these experimentally.

  11. Forces at individual pseudopod-filament adhesive contacts

    NASA Astrophysics Data System (ADS)

    Paneru, Govind; Thapa, Prem S.; McBride, Sean P.; Moore-Nichols, David; Law, Bruce M.; Flanders, Bret N.

    2011-08-01

    On-chip cellular force sensors are fabricated from cantilever poly(3,4-ethylene dioxythiophene) filaments that visibly deflect under forces exerted at individual pseudopod-filament adhesive contacts. The shape of the deflected filaments and their ˜3 nN/μm spring constants are predicted by cantilever rod theory. Pulling forces exerted by Dictyostelium discoideum cells at these contacts are observed to reach ˜20 nN without breaking the contact.

  12. Numerical simulations of a filament in a flowing soap film

    NASA Astrophysics Data System (ADS)

    Farnell, D. J. J.; David, T.; Barton, D. C.

    2004-01-01

    Experiments concerning the properties of soap films have recently been carried out and these systems have been proposed as experimental versions of theoretical two-dimensional liquids. A silk filament introduced into a flowing soap film, was seen to demonstrate various stable modes, and these were, namely, a mode in which the filament oscillates and one in which the filament is stationary and aligns with the flow of the liquid. The system could be forced from the oscillatory mode into the non- oscillatory mode by varying the length of the filament. In this article we use numerical and computational techniques in order to simulate the strongly coupled behaviour of the filament and the fluid. Preliminary results are presented for the specific case in which the filament is seen to oscillate continuously for the duration of our simulation. We also find that the filament oscillations are strongly suppressed when we reduce the effective length of the filament. We believe that these results are reminiscent of the different oscillatory and non-oscillatory modes observed in experiment. The numerical solutions show that, in contrast to experiment, vortices are created at the leading edge of the filament and are preferentially grown in the curvature of the filament and are eventually released from the trailing edge of the filament. In a similar manner to oscillating hydrofoils, it seems that the oscillating filaments are in a minimal energy state, extracting sufficient energy from the fluid to oscillate. In comparing numerical and experimental results it is possible that the soap film does have an effect on the fluid flow especially in the boundary layer where surface tension forces are large.

  13. Characterization of osmotically induced filaments of Salmonella enterica.

    PubMed

    Pratt, Zachary L; Chen, Bingming; Czuprynski, Charles J; Wong, Amy C L; Kaspar, Charles W

    2012-09-01

    Salmonella enterica forms aseptate filaments with multiple nucleoids when cultured in hyperosmotic conditions. These osmotic-induced filaments are viable and form single colonies on agar plates even though they contain multiple genomes and have the potential to divide into multiple daughter cells. Introducing filaments that are formed during osmotic stress into culture conditions without additional humectants results in the formation of septa and their division into individual cells, which could present challenges to retrospective analyses of infectious dose and risk assessments. We sought to characterize the underlying mechanisms of osmotic-induced filament formation. The concentration of proteins and chromosomal DNA in filaments and control cells was similar when standardized by biomass. Furthermore, penicillin-binding proteins in the membrane of salmonellae were active in vitro. The activity of penicillin-binding protein 2 was greater in filaments than in control cells, suggesting that it may have a role in osmotic-induced filament formation. Filaments contained more ATP than did control cells in standardized cell suspensions, though the levels of two F(0)F(1)-ATP synthase subunits were reduced. Furthermore, filaments could septate and divide within 8 h in 0.2 × Luria-Bertani broth at 23°C, while nonfilamentous control cells did not replicate. Based upon the ability of filaments to septate and divide in this diluted broth, a method was developed to enumerate by plate count the number of individual, viable cells within a population of filaments. This method could aid in retrospective analyses of infectious dose of filamented salmonellae.

  14. Multiple filamentation of supercritical UV laser beam in atmospheric air

    NASA Astrophysics Data System (ADS)

    Zvorykin, V. D.; Ionin, A. A.; Levchenko, A. O.; Seleznev, L. V.; Shutov, A. V.; Sinitsyn, D. V.; Smetanin, I. V.; Ustinovskii, N. N.

    2015-07-01

    Multiple filamentation of subpicosecond UV pulses with peak power up to 0.2 TW was investigated at the Ti:Sapphire/KrF GARPUN-MTW laser facility in the direct amplification scheme. Filamentation arose in the initial preamplifier stage when peak power exceeded the critical value of 0.1 GW. The filamentation pattern was well reproducible for repetitive pulses in time scales from nanoseconds to several minutes.

  15. Ecological and morphological profile of floating spherical Cladophora socialis aggregations in central Thailand.

    PubMed

    Tsutsui, Isao; Miyoshi, Tatsuo; Sukchai, Halethichanok; Pinphoo, Piyarat; Aue-Umneoy, Dusit; Meeanan, Chonlada; Songphatkaew, Jaruwan; Klomkling, Sirimas; Yamaguchi, Iori; Ganmanee, Monthon; Sudo, Hiroyuki; Hamano, Kaoru

    2015-01-01

    The unique beauty of spherical aggregation forming algae has attracted much attention from both the scientific and lay communities. Several aegagropilous seaweeds have been identified to date, including the plants of genus Cladophora and Chaetomorpha. However, this phenomenon remains poorly understood. In July 2013, a mass occurrence of spherical Cladophora aggregations was observed in a salt field reservoir in Central Thailand. The aims of the present study were to describe the habitat of the spherical aggregations and confirm the species. We performed a field survey, internal and external morphological observations, pyrenoid ultrastructure observations, and molecular sequence analysis. Floating spherical Cladophora aggregations (1-8 cm in diameter) were observed in an area ~560 m2, on the downwind side of the reservoir where there was water movement. Individual filaments in the aggregations were entangled in each other; consequently, branches growing in different directions were observed within a clump. We suggest that water movement and morphological characteristics promote the formation of spherical aggregations in this species. The molecular sequencing results revealed that the study species was highly homologous to both C. socialis and C. coelothrix. However, the diameter of the apical cells in the study species was less than that of C. coelothrix. The pyrenoid ultrastructure was more consistent with that of C. socialis. We conclude that the study species is C. socialis. This first record of spherical aggregations in this species advances our understanding of these formations. However, further detailed physical measurements are required to fully elucidate the mechanism behind these spherical formations.

  16. Ecological and Morphological Profile of Floating Spherical Cladophora socialis Aggregations in Central Thailand

    PubMed Central

    Tsutsui, Isao; Miyoshi, Tatsuo; Sukchai, Halethichanok; Pinphoo, Piyarat; Aue-umneoy, Dusit; Meeanan, Chonlada; Songphatkaew, Jaruwan; Klomkling, Sirimas; Yamaguchi, Iori; Ganmanee, Monthon; Sudo, Hiroyuki; Hamano, Kaoru

    2015-01-01

    The unique beauty of spherical aggregation forming algae has attracted much attention from both the scientific and lay communities. Several aegagropilous seaweeds have been identified to date, including the plants of genus Cladophora and Chaetomorpha. However, this phenomenon remains poorly understood. In July 2013, a mass occurrence of spherical Cladophora aggregations was observed in a salt field reservoir in Central Thailand. The aims of the present study were to describe the habitat of the spherical aggregations and confirm the species. We performed a field survey, internal and external morphological observations, pyrenoid ultrastructure observations, and molecular sequence analysis. Floating spherical Cladophora aggregations (1–8 cm in diameter) were observed in an area ~560 m2, on the downwind side of the reservoir where there was water movement. Individual filaments in the aggregations were entangled in each other; consequently, branches growing in different directions were observed within a clump. We suggest that water movement and morphological characteristics promote the formation of spherical aggregations in this species. The molecular sequencing results revealed that the study species was highly homologous to both C. socialis and C. coelothrix. However, the diameter of the apical cells in the study species was less than that of C. coelothrix. The pyrenoid ultrastructure was more consistent with that of C. socialis. We conclude that the study species is C. socialis. This first record of spherical aggregations in this species advances our understanding of these formations. However, further detailed physical measurements are required to fully elucidate the mechanism behind these spherical formations. PMID:25898393

  17. Bundling of actin filaments by elongation factor 1 alpha inhibits polymerization at filament ends

    PubMed Central

    1996-01-01

    Elongation factor 1 alpha (EF1 alpha) is an abundant protein that binds aminoacyl-tRNA and ribosomes in a GTP-dependent manner. EF1 alpha also interacts with the cytoskeleton by binding and bundling actin filaments and microtubules. In this report, the effect of purified EF1 alpha on actin polymerization and depolymerization is examined. At molar ratios present in the cytosol, EF1 alpha significantly blocks both polymerization and depolymerization of actin filaments and increases the final extent of actin polymer, while at high molar ratios to actin, EF1 alpha nucleates actin polymerization. Although EF1 alpha binds actin monomer, this monomer-binding activity does not explain the effects of EF1 alpha on actin polymerization at physiological molar ratios. The mechanism for the inhibition of polymerization is related to the actin-bundling activity of EF1 alpha. Both ends of the actin filament are inhibited for polymerization and both bundling and the inhibition of actin polymerization are affected by pH within the same physiological range; at high pH both bundling and the inhibition of actin polymerization are reduced. Additionally, it is seen that the binding of aminoacyl-tRNA to EF1 alpha releases EF1 alpha's inhibiting effect on actin polymerization. These data demonstrate that EF1 alpha can alter the assembly of F-actin, a filamentous scaffold on which non- membrane-associated protein translation may be occurring in vivo. PMID:8947553

  18. Topics in Probabilistic Judgment Aggregation

    ERIC Educational Resources Information Center

    Wang, Guanchun

    2011-01-01

    This dissertation is a compilation of several studies that are united by their relevance to probabilistic judgment aggregation. In the face of complex and uncertain events, panels of judges are frequently consulted to provide probabilistic forecasts, and aggregation of such estimates in groups often yield better results than could have been made…

  19. Mineral of the month: aggregates

    USGS Publications Warehouse

    Tepordei, Valentin V.

    2005-01-01

    Natural aggregates, consisting of crushed stone, and sand and gravel, are a major contributor to economic health, and have an amazing variety of uses. Aggregates are among the most abundant mineral resources and are major basic raw materials used by construction, agriculture and other industries that employ complex chemical and metallurgical processes.

  20. An invertebrate smooth muscle with striated muscle myosin filaments

    PubMed Central

    Sulbarán, Guidenn; Alamo, Lorenzo; Pinto, Antonio; Márquez, Gustavo; Méndez, Franklin; Padrón, Raúl; Craig, Roger

    2015-01-01

    Muscle tissues are classically divided into two major types, depending on the presence or absence of striations. In striated muscles, the actin filaments are anchored at Z-lines and the myosin and actin filaments are in register, whereas in smooth muscles, the actin filaments are attached to dense bodies and the myosin and actin filaments are out of register. The structure of the filaments in smooth muscles is also different from that in striated muscles. Here we have studied the structure of myosin filaments from the smooth muscles of the human parasite Schistosoma mansoni. We find, surprisingly, that they are indistinguishable from those in an arthropod striated muscle. This structural similarity is supported by sequence comparison between the schistosome myosin II heavy chain and known striated muscle myosins. In contrast, the actin filaments of schistosomes are similar to those of smooth muscles, lacking troponin-dependent regulation. We conclude that schistosome muscles are hybrids, containing striated muscle-like myosin filaments and smooth muscle-like actin filaments in a smooth muscle architecture. This surprising finding has broad significance for understanding how muscles are built and how they evolved, and challenges the paradigm that smooth and striated muscles always have distinctly different components. PMID:26443857

  1. An invertebrate smooth muscle with striated muscle myosin filaments.

    PubMed

    Sulbarán, Guidenn; Alamo, Lorenzo; Pinto, Antonio; Márquez, Gustavo; Méndez, Franklin; Padrón, Raúl; Craig, Roger

    2015-10-20

    Muscle tissues are classically divided into two major types, depending on the presence or absence of striations. In striated muscles, the actin filaments are anchored at Z-lines and the myosin and actin filaments are in register, whereas in smooth muscles, the actin filaments are attached to dense bodies and the myosin and actin filaments are out of register. The structure of the filaments in smooth muscles is also different from that in striated muscles. Here we have studied the structure of myosin filaments from the smooth muscles of the human parasite Schistosoma mansoni. We find, surprisingly, that they are indistinguishable from those in an arthropod striated muscle. This structural similarity is supported by sequence comparison between the schistosome myosin II heavy chain and known striated muscle myosins. In contrast, the actin filaments of schistosomes are similar to those of smooth muscles, lacking troponin-dependent regulation. We conclude that schistosome muscles are hybrids, containing striated muscle-like myosin filaments and smooth muscle-like actin filaments in a smooth muscle architecture. This surprising finding has broad significance for understanding how muscles are built and how they evolved, and challenges the paradigm that smooth and striated muscles always have distinctly different components.

  2. Defects on semiflexible filaments: Kinks and twist kinks

    NASA Astrophysics Data System (ADS)

    Lee, Nam-Kyung; Johner, Albert

    2016-04-01

    Due to local interactions with ligands or to global constraints, semiflexible filaments can exhibit localized defects. We focus on filaments laying flat on a surface. The two lowest order singularities are addressed: discontinuities of the orientation, which are called kink, and discontinuities of the curvature. The latter are called twist kinks in flattened helical filaments where they can form spontaneously. We calculate the partition functions for a given defect fugacity and discuss some often measured quantities like the correlation of the orientation along the filament.

  3. Hollow cylindrical plasma filament waveguide with discontinuous finite thickness cladding

    SciTech Connect

    Alshershby, Mostafa; Hao Zuoqiang; Lin Jingquan

    2013-01-15

    We have explored here a hollow cylindrical laser plasma multifilament waveguide with discontinuous finite thickness cladding, in which the separation between individual filaments is in the range of several millimeters and the waveguide cladding thickness is in the order of the microwave penetration depth. Such parameters give a closer representation of a realistic laser filament waveguide sustained by a long stable propagation of femtosecond (fs) laser pulses. We report how the waveguide losses depend on structural parameters like normalized plasma filament spacing, filament to filament distance or pitch, normal spatial frequency, and radius of the plasma filament. We found that for typical plasma parameters, the proposed waveguide can support guided modes of microwaves in extremely high frequency even with a cladding consisting of only one ring of plasma filaments. The loss of the microwave radiation is mainly caused by tunneling through the discontinuous finite cladding, i.e., confinement loss, and is weakly dependent on the plasma absorption. In addition, the analysis indicates that the propagation loss is fairly large compared with the loss of a plasma waveguide with a continuous infinite thickness cladding, while they are comparable when using a cladding contains more than one ring. Compared to free space propagation, this waveguide still presents a superior microwave transmission to some distance in the order of the filamentation length; thus, the laser plasma filaments waveguide may be a potential channel for transporting pulsed-modulated microwaves if ensuring a long and stable propagation of fs laser pulses.

  4. Dynamics of stellar filaments in f(G) gravity

    NASA Astrophysics Data System (ADS)

    Sharif, M.; Fatima, H. Ismat

    2017-03-01

    We discuss the dynamics of stellar filaments with cylindrical symmetry in the context of f( G) gravity. For this purpose, we consider the modified gravity coupled with a dissipative anisotropic fluid and construct scalar functions through orthogonal splitting of the Riemann tensor. We formulate the set of equations governing the evolution and structure of stellar filaments in terms of these scalars. Finally, we discuss all static solutions for cylindrical filaments with anisotropy as well as isotropy and conclude that stellar filaments are necessarily inhomogeneous in this gravity.

  5. Spatial evolution of filaments in broad area diode laser amplifiers

    NASA Astrophysics Data System (ADS)

    Lang, Robert J.; Mehuys, David; Hardy, Amos; Dzurko, Ken M.; Welch, David F.

    1993-03-01

    We report a numerical model that demonstrates the evolution of a uniform array of filaments from random fluctuations in the input of a single-pass semiconductor laser amplifier. We also report the first direct experimental observation of the spatial evolution of filaments in a broad area active grating semiconductor laser amplifier. The observed filamentation shows good agreement with the numerical model. This agreement suggests that such filaments may result from the unstable growth of microscopic fluctuations in the input and/or nonuniformities within the amplifier.

  6. Phenotypic Diversity of Multicellular Filamentation in Oral Streptococci

    PubMed Central

    Thurnheer, Thomas; Bagheri, Homayoun C.; Belibasakis, Georgios N.

    2013-01-01

    Filamentous multicellular bacteria are among the most ancient multicellular organisms. They inhabit a great variety of environments and are present in the human body, including the oral cavity. Beside the selective advantages related to the larger size achieved through filamentation, the development of multicellular bacteria can be also driven by simple ecological factors such as birth and death rates at the cellular level. In order to extend earlier results obtained in aquatic species, we investigate the filamentation process of four different strains of oral streptococci, namely S. mutans, S. salivarius, S. oralis and S. anginosus. The results indicate differences in the capacities of different streptococcus species to form filaments, manifested in terms of length and the time-scale of filament elongation. The filamentation pattern of these oral streptococci resembles that of aquatic bacteria, whereby filaments reach a peak length during exponential growth and become short when the population reaches a steady state. Hence, this study validates that multicellularity can be an emergent property of filamentous bacteria of different ecological niches, and that phenotypic differences in filamentation can occur within species of the same genus, in this case oral streptococci. Moreover, given the role that specific oral streptococci can play in the etiology of oral diseases, these results can possibly open new perspectives in the study of the virulence properties of these species. PMID:24086713

  7. Improving the electrochemical performance of carbon filaments by solvent cleansing

    SciTech Connect

    Shui, X.; Chung, D.D.L.; Frysz, C.A.

    1995-12-31

    Found inherent in the submicron-diameter vapor-grown carbon filament fabrication process was a tarry residue, which comprised polyaromatic hydrocarbons. Cyclic voltammetry conducted using carbon working electrodes and an iron cyanide electrolyte showed that the residue harmed the electrochemical performance. Removal of the residue from the filaments using a solvent resulted in increases in the electron transfer rate (to values as high as 0.2 cm/s) and reversibility of the iron cyanide redox species, increase in the packing density and decrease in the filament-filament contact electrical resistivity.

  8. The interaction of a magnetohydrodynamical shock with a filament

    NASA Astrophysics Data System (ADS)

    Goldsmith, K. J. A.; Pittard, J. M.

    2016-09-01

    We present 3D magnetohydrodynamic numerical simulations of the adiabatic interaction of a shock with a dense, filamentary cloud. We investigate the effects of various filament lengths and orientations on the interaction using different orientations of the magnetic field, and vary the Mach number of the shock, the density contrast of the filament χ, and the plasma beta, in order to determine their effect on the evolution and lifetime of the filament. We find that in a parallel magnetic field filaments have longer lifetimes if they are orientated more `broadside' to the shock front, and that an increase in χ hastens the destruction of the cloud, in terms of the modified cloud-crushing time-scale, tcs. The combination of a mild shock and a perpendicular or oblique field provides the best condition for extending the life of the filament, with some filaments able to survive almost indefinitely since they are cocooned by the magnetic field. A high value for χ does not initiate large turbulent instabilities in either the perpendicular or oblique field cases but rather draws the filament out into long tendrils which may eventually fragment. In addition, flux ropes are only formed in parallel magnetic fields. The length of the filament is, however, not as important for the evolution and destruction of a filament.

  9. Plasma temperature clamping in filamentation laser induced breakdown spectroscopy

    SciTech Connect

    Harilal, Sivanandan S.; Yeak, J.; Phillips, Mark C.

    2015-10-19

    Ultrafast laser filament induced breakdown spectroscopy is a very promising method for remote material detection. We present characteristics of plasmas generated in a metal target by laser filaments in air. Our measurements show that the temperature of the ablation plasma is clamped along the filamentation channel due to intensity clamping in a filament. Nevertheless, significant changes in radiation intensity are noticeable, and this is essentially due to variation in the number density of emitting atoms. The present results also partly explains the reason for the occurrence of atomic plume during fs LIBS in air compared to long-pulse ns LIBS.

  10. Energy transfer between laser filaments in liquid methanol.

    PubMed

    Strycker, B D; Springer, M; Trendafilova, C; Hua, X; Zhi, M; Kolomenskii, A A; Schroeder, H; Strohaber, J; Schuessler, H A; Kattawar, G W; Sokolov, A V

    2012-01-01

    We demonstrate energy exchange between two filament-forming femtosecond laser beams in liquid methanol. Our results are consistent with those of previous works documenting coupling between filaments in air; in addition, we identify an unreported phenomenon in which the direction of energy exchange oscillates at increments in the relative pulse delay equal to an optical period (2.6 fs). Energy transfer from one filament to another may be used in remote sensing and spectroscopic applications utilizing femtosecond laser filaments in water and air.

  11. C IV Doppler shifts observed in active region filaments

    NASA Technical Reports Server (NTRS)

    Klimchuk, J. A.

    1986-01-01

    The Doppler shift properties of 21 active region filaments were studied using C IV Dopplergram data. Most are associated with corridors of weak magnetic field that separate opposite polarity strong fields seen in photospheric magnetograms. A majority of the filaments are relatively blue shifted, although several lie very close to the dividing lines between blue and red shift. Only one filament in the samples is clearly red shifted. A new calibration procedure for Dopplergrams indicates that sizable zero point offsets are often required. The center-to-limb behavior of the resulting absolute Doppler shifts suggests that filament flows are usually quite small. It is possible that they vanish.

  12. Filament shape versus coronal potential magnetic field structure

    NASA Astrophysics Data System (ADS)

    Filippov, B.

    2016-01-01

    Solar filament shape in projection on disc depends on the structure of the coronal magnetic field. We calculate the position of polarity inversion lines (PILs) of coronal potential magnetic field at different heights above the photosphere, which compose the magnetic neutral surface, and compare with them the distribution of the filament material in Hα chromospheric images. We found that the most of the filament material is enclosed between two PILs, one at a lower height close to the chromosphere and one at a higher level, which can be considered as a height of the filament spine. Observations of the same filament on the limb by the Solar Terrestrial Relations Observatory spacecraft confirm that the height of the spine is really very close to the value obtained from the PIL and filament border matching. Such matching can be used for filament height estimations in on-disc observations. Filament barbs are housed within protruding sections of the low-level PIL. On the base of simple model, we show that the similarity of the neutral surfaces in potential and non-potential fields with the same sub-photospheric sources is the reason for the found tendency for the filament material to gather near the potential-field neutral surface.

  13. Material Supply and Magnetic Configuration of an Active Region Filament

    NASA Astrophysics Data System (ADS)

    Zou, P.; Fang, C.; Chen, P. F.; Yang, K.; Hao, Q.; Cao, Wenda

    2016-11-01

    It is important to study the fine structures of solar filaments with high-resolution observations, since it can help us understand the magnetic and thermal structures of the filaments and their dynamics. In this paper, we study a newly formed filament located inside the active region NOAA 11762, which was observed by the 1.6 m New Solar Telescope at Big Bear Solar Observatory from 16:40:19 UT to 17:07:58 UT on 2013 June 5. As revealed by the Hα filtergrams, cool material is seen to be injected into the filament spine with a speed of 5-10 km s-1. At the source of the injection, brightenings are identified in the chromosphere, which are accompanied by magnetic cancellation in the photosphere, implying the importance of magnetic reconnection in replenishing the filament with plasmas from the lower atmosphere. Counter-streamings are detected near one endpoint of the filament, with the plane-of-the-sky speed being 7-9 km s-1 in the Hα red-wing filtergrams and 9-25 km s-1 in the blue-wing filtergrams. The observations are indicative that this active region filament is supported by a sheared arcade without magnetic dips, and the counter-streamings are due to unidirectional flows with alternative directions, rather than due to the longitudinal oscillations of filament threads as in many other filaments.

  14. Molecular aggregation of humic substances

    USGS Publications Warehouse

    Wershaw, R. L.

    1999-01-01

    Humic substances (HS) form molecular aggregates in solution and on mineral surfaces. Elucidation of the mechanism of formation of these aggregates is important for an understanding of the interactions of HS in soils arid natural waters. The HS are formed mainly by enzymatic depolymerization and oxidation of plant biopolymers. These reactions transform the aromatic and lipid plant components into amphiphilic molecules, that is, molecules that consist of separate hydrophobic (nonpolar) and hydrophilic (polar) parts. The nonpolar parts of the molecules are composed of relatively unaltered segments of plant polymers and the polar parts of carboxylic acid groups. These amphiphiles form membrane-like aggregates on mineral surfaces and micelle-like aggregates in solution. The exterior surfaces of these aggregates are hydrophilic, and the interiors constitute separate hydrophobic liquid-like phases.

  15. Premature red blood cells have decreased aggregation and enhanced aggregability.

    PubMed

    Arbell, D; Orkin, B; Bar-Oz, B; Barshtein, G; Yedgar, S

    2008-06-01

    Preterm infants are highly susceptible to ischemic damage. This damage is most obvious in the brain, retina, and gastrointestinal tract. Studies focusing on the rheological properties of premature red blood cells (pRBCs) have consistently shown minimal or no RBC aggregation. Previously, measurements of pRBC aggregation kinetics indicated that specific plasma properties are responsible for the decreased RBC aggregation observed in the neonates, but that their specific RBC properties do not affect it. However, the strength of interaction in the pRBC aggregates as a function of medium composition has not been tested. In our previous research, we described clinically relevant parameters, that is, the aggregate resistance to disaggregation by flow. With the help of a cell flow property analyzer (CFA), we can monitor RBC aggregation by direct visualization of its dynamics during flow. We used the CFA to examine pRBC (from 9 premature babies) in the natural plasma and in PBS buffer supplemented with dextran (500 kDa) to distinguish between RBC intrinsic-cellular and plasma factors. pRBCs suspended in the native plasma showed minimal or no aggregation in comparison to normal adult RBC. When we transferred pRBCs from the same sample to the dextran solution, enhanced resistance to disaggregation by flow was apparent.

  16. Filamentation and supercontinuum generation in lanthanum glass

    NASA Astrophysics Data System (ADS)

    Yang, Yuxia; Liao, Meisong; Li, Xia; Bi, Wanjun; Ohishi, Yasutake; Cheng, Tonglei; Fang, Yongzheng; Zhao, Guoying; Gao, Weiqing

    2017-01-01

    A broadband supercontinuum (SC) covering 400-2800 nm in a 20 dB dynamic range is reported in a piece of highly nonlinear, low-dispersion bulk lanthanum glass without employing any lens to focus the pump pulse. The spectrum width obtained in this study is broader than the maximum spectrum width obtained in silica photonic crystal fibers. The filaments and bright conical visible emission patterns of the SC are analyzed. Under optimum pump conditions, an SC conversion efficiency of 75% is obtained. The SC conversion efficiency is confirmed to be stable. Additionally, the relationship between the input peak intensity and the output beam radius is elucidated by simulating the propagation of a Gaussian beam in the bulk lanthanum glass. A 0.20 mm stable laser beam radius at the end of the propagation domain is demonstrated in a certain input peak intensity range. This small value of the beam radius indicates that most of the output power is localized over a small region because of the Kerr focusing effect despite the existence of conical emission in the SC generation by filamentation. The findings of this study are of significance for the development of ultra-broadband SC sources based on bulk glasses and high peak power lasers.

  17. Solar filament eruptions and energetic particle events

    NASA Technical Reports Server (NTRS)

    Kahler, S. W.; Cliver, E. W.; Cane, H. V.; Mcguire, R. E.; Stone, R. G.

    1986-01-01

    The 1981 December 5 solar filament eruption that is associated with an energetic (E greater than 50 MeV) particle event observed at 1 AU. The eruption was photographed in H-alpha and was observed by the Solwind whitelight coronagraph on P78-1. It occurred well away from any solar active region and was not associated with an impulsive microwave burst, indicating that magnetic complexity and a detectable impulsive phase are not required for the production of a solar energetic particle (SEP) event. No metric type II or IV emission was observed, but an associated interplanetary type II burst was detected by the low-frequency radio experiment on ISEE 3. The December 5 and two other SEP events lacking evidence for low coronal shocks had unusually steep energy spectra (gamma greater than 3.5). In terms of shock acceleration, this suggests that shocks formed relatively high in the corona may produce steeper energy spectra than those formed at lower altitudes. It is noted that the filament itself maybe one source of the ions accelerated to high energies, since it is the only plausible coronal source of the He(+) ions observed in SEP events.

  18. Compressive testing of filament-wound cylinders

    NASA Technical Reports Server (NTRS)

    Jensen, David W.; Hipp, Patrick A.

    1991-01-01

    An experimental investigation has been conducted on the compressive buckling and failure of filament-wound circular cylinders. This investigation identifies one of the relationships between structural performance and scale, as well as some of the causes of reduced structural performance in large-scale structures. It is hypothesized that this effect is related to two conditions: first, the number of fiber tow undulations; and second, the percentage of weak interfaces within the structure. The effect of winding pattern and the resulting location of the fiber undulations were studied by varying the winding parameters. Three types of cylinders were manufactured from Amoco T650-35/1908 graphite/epoxy preimpregnated tow with different winding sequences (0/+/-60)s, (+/-30/90)s, and (90/+/-30)s. The (90/+/-30)s cylinders were manufactured with two different winding patterns (distributed and classical) and radius-to-thickness ratios (15 and 55). All cylinders were loaded in compression to failure. Comparisons of the compressive strength and failure modes demonstrate the relationship between the winding parameters, scale, and structural performance of filament-wound composite cylinders.

  19. Filament-Prominence-Cme Magnetic Evolution Study

    NASA Astrophysics Data System (ADS)

    Bagala', L. G.; Mandrini, C. H.; Fernandez Borda, R.; de Pontieu, B.; Rovira, M. G.; Rank, G.

    1999-10-01

    The first results of the SOHO Joint Observation Program JOP 99 are outlined. JOP 99 involve several SOHO instruments (CDS, LASCO, MDI), together with TRACE, and two new ground-based instruments: HASTA (Hα Solar Telescope for Argentina) and MICA (Mirror Coronagraph for Argentina). The proposed program have a new motivation in taking advantage of the capabilities of the TRACE instrument, together with our experience in magnetic reconnection. The objective here is focused on the investigation of the conditions of the eruption of a prominence, often associated with the CME. JOP 99 is running at the moment that this abstract is submitted. It is a 5-days study of the filament/prominence, with 3-4 days observing the disk and 1-2 days observing the limb. While on disk, we will look for the eruption signatures in two ways: by studying the physical conditions in the filament and its surroundings (densities, temperature, abundances), and by looking at the magnetic topology changes. While at the limb, we will wait with luck for an eruption. If it does happen, LASCO and MICA observations will study if there exists an associated CME.

  20. Characterising Radio Emissions in Cosmic Filaments

    NASA Astrophysics Data System (ADS)

    Miller, R. O.

    2014-02-01

    A growing number of radio studies probe galaxy clusters into the low-power regime in which star formation is the dominant source of radio emission. However, at the time of writing no comparably deep observations have focused exclusively on the radio populations of cosmic filaments. This thesis describes the ATCA 2.1 GHz observations and subsequent analysis of two such regions - labelled Zone 1 (between clusters A3158 and A3125/A3128) and Zone 2 (between A3135 and A3145) - in the Horologium-Reticulum Supercluster (HRS). Source count profiles of both populations are discussed and a radio luminosity function for Zone 1 is generated. While the source counts of Zone 2 appear to be consistent with expected values, Zone 1 exhibits an excess of counts across a wide flux range (1 mJy< S_1.4 < 200 mJy). An excess in radio activity at the lower extent of this range (log P_1.4 < 22.5; within the SF-dominated regime) is also suggested by the radio luminosity function for that region, and brief colour analysis suggests that such an excess is indeed predominantly associated with a starforming population. The differences between the two filamentary zones is attributed to cosmic variation. The regions are both small (~ 1 degree square), and are significantly separated in the HRS. Further radio observations of filaments are required and the results combined into a larger sample size in order to arrive at a generalised model filamentary population.

  1. Mechanical Properties of Doubly Stabilized Microtubule Filaments

    PubMed Central

    Hawkins, Taviare L.; Sept, David; Mogessie, Binyam; Straube, Anne; Ross, Jennifer L.

    2013-01-01

    Microtubules are cytoskeletal filaments responsible for cell morphology and intracellular organization. Their dynamical and mechanical properties are regulated through the nucleotide state of the tubulin dimers and the binding of drugs and/or microtubule-associated proteins. Interestingly, microtubule-stabilizing factors have differential effects on microtubule mechanics, but whether stabilizers have cumulative effects on mechanics or whether one effect dominates another is not clear. This is especially important for the chemotherapeutic drug Taxol, an important anticancer agent and the only known stabilizer that reduces the rigidity of microtubules. First, we ask whether Taxol will combine additively with another stabilizer or whether one stabilizer will dominate another. We call microtubules in the presence of Taxol and another stabilizer, doubly stabilized. Second, since Taxol is often added to a number of cell types for therapeutic purposes, it is important from a biomedical perspective to understand how Taxol added to these systems affects the mechanical properties in treated cells. To address these questions, we use the method of freely fluctuating filaments with our recently developed analysis technique of bootstrapping to determine the distribution of persistence lengths of a large population of microtubules treated with different stabilizers, including Taxol, guanosine-5′ [(α, β)-methyleno] triphosphate, guanosine-5′-O-(3-thiotriphosphate), tau, and MAP4. We find that combinations of these stabilizers have novel effects on the mechanical properties of microtubules. PMID:23561528

  2. The Golgi apparatus: insights from filamentous fungi.

    PubMed

    Pantazopoulou, Areti

    2016-01-01

    Cargo passage through the Golgi, albeit an undoubtedly essential cellular function, is a mechanistically unresolved and much debated process. Although the main molecular players are conserved, diversification of the Golgi among different eukaryotic lineages is providing us with tools to resolve standing controversies. During the past decade the Golgi apparatus of model filamentous fungi, mainly Aspergillus nidulans, has been intensively studied. Here an overview of the most important findings in the field is provided. Golgi architecture and dynamics, as well as the novel cell biology tools that were developed in filamentous fungi in these studies, are addressed. An emphasis is placed on the central role the Golgi has as a crossroads in the endocytic and secretory-traffic pathways in hyphae. Finally the major advances that the A. nidulans Golgi biology has yielded so far regarding our understanding of key Golgi regulators, such as the Rab GTPases RabC(Rab6) and RabE(Rab11), the oligomeric transport protein particle, TRAPPII, and the Golgi guanine nucleotide exchange factors of Arf1, GeaA(GBF1/Gea1) and HypB(BIG/Sec7), are highlighted.

  3. Mechanical properties of doubly stabilized microtubule filaments.

    PubMed

    Hawkins, Taviare L; Sept, David; Mogessie, Binyam; Straube, Anne; Ross, Jennifer L

    2013-04-02

    Microtubules are cytoskeletal filaments responsible for cell morphology and intracellular organization. Their dynamical and mechanical properties are regulated through the nucleotide state of the tubulin dimers and the binding of drugs and/or microtubule-associated proteins. Interestingly, microtubule-stabilizing factors have differential effects on microtubule mechanics, but whether stabilizers have cumulative effects on mechanics or whether one effect dominates another is not clear. This is especially important for the chemotherapeutic drug Taxol, an important anticancer agent and the only known stabilizer that reduces the rigidity of microtubules. First, we ask whether Taxol will combine additively with another stabilizer or whether one stabilizer will dominate another. We call microtubules in the presence of Taxol and another stabilizer, doubly stabilized. Second, since Taxol is often added to a number of cell types for therapeutic purposes, it is important from a biomedical perspective to understand how Taxol added to these systems affects the mechanical properties in treated cells. To address these questions, we use the method of freely fluctuating filaments with our recently developed analysis technique of bootstrapping to determine the distribution of persistence lengths of a large population of microtubules treated with different stabilizers, including Taxol, guanosine-5' [(α, β)-methyleno] triphosphate, guanosine-5'-O-(3-thiotriphosphate), tau, and MAP4. We find that combinations of these stabilizers have novel effects on the mechanical properties of microtubules.

  4. Composition, Buoyancy Regulation and Fate of Ice Algal Aggregates in the Central Arctic Ocean

    PubMed Central

    Fernández-Méndez, Mar; Wenzhöfer, Frank; Peeken, Ilka; Sørensen, Heidi L.; Glud, Ronnie N.; Boetius, Antje

    2014-01-01

    Sea-ice diatoms are known to accumulate in large aggregates in and under sea ice and in melt ponds. There is recent evidence from the Arctic that such aggregates can contribute substantially to particle export when sinking from the ice. The role and regulation of microbial aggregation in the highly seasonal, nutrient- and light-limited Arctic sea-ice ecosystem is not well understood. To elucidate the mechanisms controlling the formation and export of algal aggregates from sea ice, we investigated samples taken in late summer 2011 and 2012, during two cruises to the Eurasian Basin of the Central Arctic Ocean. Spherical aggregates densely packed with pennate diatoms, as well as filamentous aggregates formed by Melosira arctica showed sign of different stages of degradation and physiological stoichiometries, with carbon to chlorophyll a ratios ranging from 110 to 66700, and carbon to nitrogen molar ratios of 8–35 and 9–40, respectively. Sub-ice algal aggregate densities ranged between 1 and 17 aggregates m−2, maintaining an estimated net primary production of 0.4–40 mg C m−2 d−1, and accounted for 3–80% of total phototrophic biomass and up to 94% of local net primary production. A potential factor controlling the buoyancy of the aggregates was light intensity, regulating photosynthetic oxygen production and the amount of gas bubbles trapped within the mucous matrix, even at low ambient nutrient concentrations. Our data-set was used to evaluate the distribution and importance of Arctic algal aggregates as carbon source for pelagic and benthic communities. PMID:25208058

  5. Composition, buoyancy regulation and fate of ice algal aggregates in the Central Arctic Ocean.

    PubMed

    Fernández-Méndez, Mar; Wenzhöfer, Frank; Peeken, Ilka; Sørensen, Heidi L; Glud, Ronnie N; Boetius, Antje

    2014-01-01

    Sea-ice diatoms are known to accumulate in large aggregates in and under sea ice and in melt ponds. There is recent evidence from the Arctic that such aggregates can contribute substantially to particle export when sinking from the ice. The role and regulation of microbial aggregation in the highly seasonal, nutrient- and light-limited Arctic sea-ice ecosystem is not well understood. To elucidate the mechanisms controlling the formation and export of algal aggregates from sea ice, we investigated samples taken in late summer 2011 and 2012, during two cruises to the Eurasian Basin of the Central Arctic Ocean. Spherical aggregates densely packed with pennate diatoms, as well as filamentous aggregates formed by Melosira arctica showed sign of different stages of degradation and physiological stoichiometries, with carbon to chlorophyll a ratios ranging from 110 to 66700, and carbon to nitrogen molar ratios of 8-35 and 9-40, respectively. Sub-ice algal aggregate densities ranged between 1 and 17 aggregates m(-2), maintaining an estimated net primary production of 0.4-40 mg C m(-2) d(-1), and accounted for 3-80% of total phototrophic biomass and up to 94% of local net primary production. A potential factor controlling the buoyancy of the aggregates was light intensity, regulating photosynthetic oxygen production and the amount of gas bubbles trapped within the mucous matrix, even at low ambient nutrient concentrations. Our data-set was used to evaluate the distribution and importance of Arctic algal aggregates as carbon source for pelagic and benthic communities.

  6. Evidence for a Structural Requirement for the Aggregation of Platelets by Collagen

    PubMed Central

    Jaffe, Russell; Deykin, Daniel

    1974-01-01

    This study investigates whether soluble collagen can initiate platelet aggregation or whether a higher degree of polymerization is required. Purified rat skin collagen was prepared in four states. Soluble monomeric collagen, containing 2 μM calcium chloride, was maintained at 4°C until use. A previously uncharacterized form of collagen, soluble microfibrillar collagen, was prepared from monomeric collagen containing calcium chloride by allowing it to polymerize at 23°C. Viscometric and electron microscopic characterization of microfibrillar collagen indicated polymerization to ordered native filaments. Particulate native macrofibrillar collagen was prepared from monomeric collagen by allowing it to polymerize at 37°C in the absence of calcium. Particulate collagen, in which the fibers were randomly associated, was prepared by salt precipitation of calcium-free monomeric collagen. Microfibrillar and native macrofibrillar collagen initiated platelet aggregation, with a lag phase of approximately 60 s. Monomeric collagen initiated aggregation with a lag phase of approximately 180 s. The duration of the lag phase for platelet aggregation initiated by monomeric collagen was independent of the dose. Salt-precipitated particulate collagen did not initiate platelet aggregation. Agents which prolong the transition from monomeric collagen to fibrillar collagen (urea, arginine) retarded or prevented the aggregation of platelets by monomeric collagen. Sodium borohydride, which stabilizes the intraand intermolecular cross-links of collagen did not affect platelet aggregation. Penicillamine, which displaces the intermolecular cross-links and binds the intramolecular cross-links of collagen, did not prevent platelet aggregation. The data suggest that an architectural requirement exists for the initiation of self-perpetuating platelet aggregation; that tropocollagen units do not fulfill this requirement; that a soluble collagen preparation, microfibrillar collagen, contains

  7. Orthogonal flexible Rydberg aggregates

    NASA Astrophysics Data System (ADS)

    Leonhardt, K.; Wüster, S.; Rost, J. M.

    2016-02-01

    We study the link between atomic motion and exciton transport in flexible Rydberg aggregates, assemblies of highly excited light alkali-metal atoms, for which motion due to dipole-dipole interaction becomes relevant. In two one-dimensional atom chains crossing at a right angle adiabatic exciton transport is affected by a conical intersection of excitonic energy surfaces, which induces controllable nonadiabatic effects. A joint exciton-motion pulse that is initially governed by a single energy surface is coherently split into two modes after crossing the intersection. The modes induce strongly different atomic motion, leading to clear signatures of nonadiabatic effects in atomic density profiles. We have shown how this scenario can be exploited as an exciton switch, controlling direction and coherence properties of the joint pulse on the second of the chains [K. Leonhardt et al., Phys. Rev. Lett. 113, 223001 (2014), 10.1103/PhysRevLett.113.223001]. In this article we discuss the underlying complex dynamics in detail, characterize the switch, and derive our isotropic interaction model from a realistic anisotropic one with the addition of a magnetic bias field.

  8. Neuronal intranuclear inclusions are ultrastructurally and immunologically distinct from cytoplasmic inclusions of neuronal intermediate filament inclusion disease.

    PubMed

    Mosaheb, Sabrina; Thorpe, Julian R; Hashemzadeh-Bonehi, Lida; Bigio, Eileen H; Gearing, Marla; Cairns, Nigel J

    2005-10-01

    Abnormal neuronal cytoplasmic inclusions (NCIs) containing aggregates of alpha-internexin and the neurofilament (NF) subunits, NF-H, NF-M, and NF-L, are the signature lesions of neuronal intermediate filament (IF) inclusion disease (NIFID). The disease has a clinically heterogeneous phenotype, including frontotemporal dementia, pyramidal and extrapyramidal signs presenting at a young age. NCIs are variably ubiquitinated and about half of cases also have neuronal intranuclear inclusions (NIIs), which are also ubiquitinated. NIIs have been described in polyglutamine-repeat expansion diseases, where they are strongly ubiquitin immunoreactive. The fine structure of NIIs of NIFID has not previously been described. Therefore, to determine the ultrastructure of NIIs, immunoelectron microscopy was undertaken on NIFID cases and normal aged control brains. Our results indicate that the NIIs of NIFID are strongly ubiquitin immunoreactive. However, unlike NCIs which contain ubiquitin, alpha-internexin and NF epitopes, NIIs contain neither epitopes of alpha-internexin nor NF subunits. Neither NIIs nor NCIs were recognised by antibodies to expanded polyglutamine repeats. The NII of NIFID lacks a limiting membrane and contains straight filaments of 20 nm mean width (range 11-35 nm), while NCIs contain filaments with a mean width of 10 nm (range 5-18 nm; t-test, P<0.001). Biochemistry revealed no differences in neuronal IF protein mobilities between NIFID and normal brain tissue. Therefore, NIIs of NIFID contain filaments morphologically and immunologically distinct from those of NCIs, and both types of inclusion lack expanded polyglutamine tracts of the triplet-repeat expansion diseases. These observations indicate that abnormal protein aggregation follows separate pathways in different neuronal compartments of NIFID.

  9. Abnormal intermediate filament organization alters mitochondrial motility in giant axonal neuropathy fibroblasts

    PubMed Central

    Lowery, Jason; Jain, Nikhil; Kuczmarski, Edward R.; Mahammad, Saleemulla; Goldman, Anne; Gelfand, Vladimir I.; Opal, Puneet; Goldman, Robert D.

    2016-01-01

    Giant axonal neuropathy (GAN) is a rare disease caused by mutations in the GAN gene, which encodes gigaxonin, an E3 ligase adapter that targets intermediate filament (IF) proteins for degradation in numerous cell types, including neurons and fibroblasts. The cellular hallmark of GAN pathology is the formation of large aggregates and bundles of IFs. In this study, we show that both the distribution and motility of mitochondria are altered in GAN fibroblasts and this is attributable to their association with vimentin IF aggregates and bundles. Transient expression of wild-type gigaxonin in GAN fibroblasts reduces the number of IF aggregates and bundles, restoring mitochondrial motility. Conversely, silencing the expression of gigaxonin in control fibroblasts leads to changes in IF organization similar to that of GAN patient fibroblasts and a coincident loss of mitochondrial motility. The inhibition of mitochondrial motility in GAN fibroblasts is not due to a global inhibition of organelle translocation, as lysosome motility is normal. Our findings demonstrate that it is the pathological changes in IF organization that cause the loss of mitochondrial motility. PMID:26700320

  10. Abnormal intermediate filament organization alters mitochondrial motility in giant axonal neuropathy fibroblasts.

    PubMed

    Lowery, Jason; Jain, Nikhil; Kuczmarski, Edward R; Mahammad, Saleemulla; Goldman, Anne; Gelfand, Vladimir I; Opal, Puneet; Goldman, Robert D

    2016-02-15

    Giant axonal neuropathy (GAN) is a rare disease caused by mutations in the GAN gene, which encodes gigaxonin, an E3 ligase adapter that targets intermediate filament (IF) proteins for degradation in numerous cell types, including neurons and fibroblasts. The cellular hallmark of GAN pathology is the formation of large aggregates and bundles of IFs. In this study, we show that both the distribution and motility of mitochondria are altered in GAN fibroblasts and this is attributable to their association with vimentin IF aggregates and bundles. Transient expression of wild-type gigaxonin in GAN fibroblasts reduces the number of IF aggregates and bundles, restoring mitochondrial motility. Conversely, silencing the expression of gigaxonin in control fibroblasts leads to changes in IF organization similar to that of GAN patient fibroblasts and a coincident loss of mitochondrial motility. The inhibition of mitochondrial motility in GAN fibroblasts is not due to a global inhibition of organelle translocation, as lysosome motility is normal. Our findings demonstrate that it is the pathological changes in IF organization that cause the loss of mitochondrial motility.

  11. Seeking sunlight: rapid phototactic motility of filamentous mat-forming cyanobacteria optimize photosynthesis and enhance carbon burial in Lake Huron’s submerged sinkholes

    PubMed Central

    Biddanda, Bopaiah A.; McMillan, Adam C.; Long, Stephen A.; Snider, Michael J.; Weinke, Anthony D.

    2015-01-01

    We studied the motility of filamentous mat-forming cyanobacteria consisting primarily of Oscillatoria-like cells growing under low-light, low-oxygen, and high-sulfur conditions in Lake Huron’s submerged sinkholes using in situ observations, in vitro measurements and time-lapse microscopy. Gliding movement of the cyanobacterial trichomes (100–10,000 μm long filaments, composed of cells ∼10 μm wide and ∼3 μm tall) revealed individual as well as group-coordinated motility. When placed in a petri dish and dispersed in ground water from the sinkhole, filaments re-aggregated into defined colonies within minutes, then dispersed again. Speed of individual filaments increased with temperature from ∼50 μm min-1 or ∼15 body lengths min-1 at 10°C to ∼215 μm min-1 or ∼70 body lengths min-1 at 35°C – rates that are rapid relative to non-flagellated/ciliated microbes. Filaments exhibited precise and coordinated positive phototaxis toward pinpoints of light and congregated under the light of foil cutouts. Such light-responsive clusters showed an increase in photosynthetic yield – suggesting phototactic motility aids in light acquisition as well as photosynthesis. Once light source was removed, filaments slowly spread out evenly and re-aggregated, demonstrating coordinated movement through inter-filament communication regardless of light. Pebbles and pieces of broken shells placed upon intact mat were quickly covered by vertically motile filaments within hours and became fully buried in the anoxic sediments over 3–4 diurnal cycles – likely facilitating the preservation of falling debris. Coordinated horizontal and vertical filament motility optimize mat cohesion and dynamics, photosynthetic efficiency and sedimentary carbon burial in modern-day sinkhole habitats that resemble the shallow seas in Earth’s early history. Analogous cyanobacterial motility may have played a key role in the oxygenation of the planet by optimizing photosynthesis while

  12. Kinetics of Aggregation with Choice

    DOE PAGES

    Ben-Naim, Eli; Krapivsky, Paul

    2016-12-01

    Here we generalize the ordinary aggregation process to allow for choice. In ordinary aggregation, two random clusters merge and form a larger aggregate. In our implementation of choice, a target cluster and two candidate clusters are randomly selected and the target cluster merges with the larger of the two candidate clusters.We study the long-time asymptotic behavior and find that as in ordinary aggregation, the size density adheres to the standard scaling form. However, aggregation with choice exhibits a number of different features. First, the density of the smallest clusters exhibits anomalous scaling. Second, both the small-size and the large-size tailsmore » of the density are overpopulated, at the expense of the density of moderate-size clusters. Finally, we also study the complementary case where the smaller candidate cluster participates in the aggregation process and find an abundance of moderate clusters at the expense of small and large clusters. Additionally, we investigate aggregation processes with choice among multiple candidate clusters and a symmetric implementation where the choice is between two pairs of clusters.« less

  13. Kinetics of Aggregation with Choice

    SciTech Connect

    Ben-Naim, Eli; Krapivsky, Paul

    2016-12-01

    Here we generalize the ordinary aggregation process to allow for choice. In ordinary aggregation, two random clusters merge and form a larger aggregate. In our implementation of choice, a target cluster and two candidate clusters are randomly selected and the target cluster merges with the larger of the two candidate clusters.We study the long-time asymptotic behavior and find that as in ordinary aggregation, the size density adheres to the standard scaling form. However, aggregation with choice exhibits a number of different features. First, the density of the smallest clusters exhibits anomalous scaling. Second, both the small-size and the large-size tails of the density are overpopulated, at the expense of the density of moderate-size clusters. Finally, we also study the complementary case where the smaller candidate cluster participates in the aggregation process and find an abundance of moderate clusters at the expense of small and large clusters. Additionally, we investigate aggregation processes with choice among multiple candidate clusters and a symmetric implementation where the choice is between two pairs of clusters.

  14. Heterologous protein production by filamentous fungi.

    PubMed

    Jeenes, D J; Mackenzie, D A; Roberts, I N; Archer, D B

    1991-01-01

    There are clearly many facets to successful production of heterologous proteins from filamentous fungi. The objectives are to exploit the natural ability of some species to secrete high levels of protein. The heterologous target proteins produced in a fungal host must be acceptable to the public and be economic to produce, i.e. the targets must be authentic (in structure and activity) and be produced in high yield to necessary levels of purity. The appearance of heterologous products from fungi on the market is testament to some success but, equally, there are considerable limitations in our ability to produce desired yields of many target proteins. We endorse the view of van den Hondel, Punt and van Gorcom (1991) that for the commercial production of heterologous proteins from filamentous fungi more information is required on transcriptional control, introns, mRNA stability and processing, translational efficiency, protein secretion, glycosylation and proteolysis. In addition, there is scope for yield improvement based on a better understanding of the physiology of growth/product secretion coupled to appropriate bioreactor operation. The authenticity of product is an aspect which will assume increasing importance, particularly for therapeutic proteins. The level at which the structures and functional activity of heterologous proteins are assessed will ultimately be determined by legislation. The analytical methods currently available are not always sufficient, for example, to reveal folded structures, and most proteins are not amenable to analysis by two-dimensional NMR. The authenticity of target heterologous proteins will also need to be assessed in relation to the glycosylation level and pattern. This is not easily done and explains the paucity of detailed information published to date on glycosylation of fungal proteins. Novel engineered proteins are already being produced from filamentous fungi where expression is an aid to investigation of structure

  15. Fractal aggregates in Titan's atmosphere

    NASA Astrophysics Data System (ADS)

    Cabane, M.; Rannou, P.; Chassefiere, E.; Israel, G.

    1993-04-01

    The cluster structure of Titan's atmosphere was modeled by using an Eulerian microphysical model with the specific formulation of microphysical laws applying to fractal particles. The growth of aggregates in the settling phase was treated by introducing the fractal dimension as a parameter of the model. The model was used to obtain a vertical distribution of size and number density of the aggregates for different production altitudes. Results confirm previous estimates of the formation altitude of photochemical aerosols. The vertical profile of the effective radius of aggregates was calculated as a function of the visible optical depth.

  16. From Aβ Filament to Fibril: Molecular Mechanism of Surface-Activated Secondary Nucleation from All-Atom MD Simulations.

    PubMed

    Schwierz, Nadine; Frost, Christina V; Geissler, Phillip L; Zacharias, Martin

    2017-02-02

    Secondary nucleation pathways in which existing amyloid fibrils catalyze the formation of new aggregates and neurotoxic oligomers are of immediate importance for the onset and progression of Alzheimer's disease. Here, we apply extensive all-atom molecular dynamics simulations in explicit water to study surface-activated secondary nucleation pathways at the extended lateral β-sheet surface of a preformed Aβ9-40 filament. Calculation of free-energy profiles allows us to determine binding free energies and conformational intermediates for nucleation complexes consisting of 1-4 Aβ peptides. In addition, we combine the free-energy profiles with position-dependent diffusion profiles to extract complementary kinetic information and macroscopic growth rates. Single monomers bind to the β-sheet surface in a disordered, hydrophobically collapsed conformation, whereas dimers and larger oligomers can retain a cross-β conformation resembling a more ordered fibril structure. The association processes during secondary nucleation follow a dock/lock mechanism consisting of a fast initial encounter phase (docking) and a slow structural rearrangement phase (locking). The major driving forces for surface-activated secondary nucleation are the release of a large number of hydration water molecules and the formation of hydrophobic interface contacts, the latter being in contrast to the elongation process at filament tips, which is dominated by the formation of stable and highly specific interface hydrogen bonds. The calculated binding free energies and the association rates for the attachment of Aβ monomers and oligomers to the extended lateral β-sheet surface of the filament seed are higher compared to those for elongation at the filament tips, indicating that secondary nucleation pathways can become important once a critical concentration of filaments has formed.

  17. Reduced receptor aggregation and altered cytoskeleton in cultured myocytes after space-flight

    NASA Technical Reports Server (NTRS)

    Gruener, R.; Roberts, R.; Reitstetter, R.

    1994-01-01

    We carried out parallel experiments first on the slow clinostat and then in space-flight to examine the effects of altered gravity on the aggregation of the nicotinic acetylcholine receptors and the structure of the cytoskeleton in cultured Xenopus embryonic muscle cells. By examining the concordance between results from space flight and the clinostat, we tested whether the slow clinostat is a relevant simulation paradigm. Space-flown cells showed marked changes in the distribution and organization of actin filaments and had a reduced incidence of acetylcholine receptor aggregates at the site of contact with polystyrene beads. Similar effects were found after clinostat rotation. The sensitivity of synaptic receptor aggregation and cytoskeletal morphology suggests that in the microgravity of space cell behavior may be importantly altered.

  18. Localizing and extracting filament distributions from microscopy images.

    PubMed

    Basu, S; Liu, C; Rohde, G K

    2015-04-01

    Detailed quantitative measurements of biological filament networks represent a crucial step in understanding architecture and structure of cells and tissues, which in turn explain important biological events such as wound healing and cancer metastases. Microscopic images of biological specimens marked for different structural proteins constitute an important source for observing and measuring meaningful parameters of biological networks. Unfortunately, current efforts at quantitative estimation of architecture and orientation of biological filament networks from microscopy images are predominantly limited to visual estimation and indirect experimental inference. Here, we describe a new method for localizing and extracting filament distributions from 2D microscopy images of different modalities. The method combines a filter-based detection of pixels likely to contain a filament with a constrained reverse diffusion-based approach for localizing the filaments centrelines. We show with qualitative and quantitative experiments, using both simulated and real data, that the new method can provide more accurate centreline estimates of filament in comparison to other approaches currently available. In addition, we show the algorithm is more robust with respect to variations in the initial filter-based filament detection step often used. We demonstrate the application of the method in extracting quantitative parameters from confocal microscopy images of actin filaments and atomic force microscopy images of DNA fragments.

  19. Method for simultaneously coating a plurality of filaments

    DOEpatents

    Miller, P.A.; Pochan, P.D.; Siegal, M.P.; Dominguez, F.

    1995-07-11

    Methods and apparatuses are disclosed for coating materials, and the products and compositions produced thereby. Substances, such as diamond or diamond-like carbon, are deposited onto materials, such as a filament or a plurality of filaments simultaneously, using one or more cylindrical, inductively coupled, resonator plasma reactors. 3 figs.

  20. Calibration and Temperature Profile of a Tungsten Filament Lamp

    ERIC Educational Resources Information Center

    de Izarra, Charles; Gitton, Jean-Michel

    2010-01-01

    The goal of this work proposed for undergraduate students and teachers is the calibration of a tungsten filament lamp from electric measurements that are both simple and precise, allowing to determine the temperature of tungsten filament as a function of the current intensity. This calibration procedure was first applied to a conventional filament…

  1. Association of actin filaments with axonal microtubule tracts.

    PubMed

    Bearer, E L; Reese, T S

    1999-02-01

    Axoplasmic organelles move on actin as well as microtubules in vitro and axons contain a large amount of actin, but little is known about the organization and distribution of actin filaments within the axon. Here we undertake to define the relationship of the microtubule bundles typically found in axons to actin filaments by applying three microscopic techniques: laser-scanning confocal microscopy of immuno-labeled squid axoplasm; electronmicroscopy of conventionally prepared thin sections; and electronmicroscopy of touch preparations-a thin layer of axoplasm transferred to a specimen grid and negatively stained. Light microscopy shows that longitudinal actin filaments are abundant and usually coincide with longitudinal microtubule bundles. Electron microscopy shows that microfilaments are interwoven with the longitudinal bundles of microtubules. These bundles maintain their integrity when neurofilaments are extracted. Some, though not all microfilaments decorate with the S1 fragment of myosin, and some also act as nucleation sites for polymerization of exogenous actin, and hence are definitively identified as actin filaments. These actin filaments range in minimum length from 0.5 to 1.5 microm with some at least as long as 3.5 microm. We conclude that the microtubule-based tracks for fast organelle transport also include actin filaments. These actin filaments are sufficiently long and abundant to be ancillary or supportive of fast transport along microtubules within bundles, or to extend transport outside of the bundle. These actin filaments could also be essential for maintaining the structural integrity of the microtubule bundles.

  2. Dynamics of a vortex filament in a stratified medium

    SciTech Connect

    Popov, P. V.; Romanov, A. S.; Chukbar, K. V.

    2009-03-15

    The behavior of a vortex filament in a perfectly conducting stratified medium is analyzed. It is shown that the equation describing oscillations of a straight filament is linear, but becomes substantially non-linear with increasing inclination angle. Effects related to the finite radius of the vortex core are considered, and dispersion relations for linear oscillations of a vortex column are derived.

  3. Unlined Reuseable Filament Wound Composite Cryogenic Tank Testing

    NASA Technical Reports Server (NTRS)

    Murphy, A. W.; Lake, R. E.; Wilkerson, C.

    1999-01-01

    An unlined reusable filament wound composite cryogenic tank was tested at the Marshall Space Flight Center using LH2 cryogen and pressurization to 320 psig. The tank was fabricated by Phillips Laboratory and Wilson Composite Group, Inc., using an EnTec five-axis filament winder and sand mandrels. The material used was IM7/977-2 (graphite/epoxy).

  4. Verifying Stiffness Parameters Of Filament-Wound Cylinders

    NASA Technical Reports Server (NTRS)

    Verderaime, V.; Rheinfurth, M.

    1994-01-01

    Predicted engineering stiffness parameters of filament-wound composite-material cylinders verified with respect to experimental data, by use of equations developed straightforwardly from applicable formulation of Hooke's law. Equations derived in engineering study of filament-wound rocket-motor cases, also applicable to other cylindrical pressure vessels made of orthotropic materials.

  5. Filament-wound spar shell graphite/epoxy fan blades

    NASA Technical Reports Server (NTRS)

    Yao, S.

    1976-01-01

    The methodology for fabrication of wet filament wound spar shell fan blades is presented. All principal structural elements were filament wound, assembled, formed, bonded and co-cured in a female mold. A pair of blades were fabricated as one integral unit and parted into two after curing.

  6. Method for simultaneously coating a plurality of filaments

    DOEpatents

    Miller, Paul A.; Pochan, Paul D.; Siegal, Michael P.; Dominguez, Frank

    1995-01-01

    Methods and apparatuses for coating materials, and the products and compositions produced thereby. Substances, such as diamond or diamond-like carbon, are deposited onto materials, such as a filament or a plurality of filaments simultaneously, using one or more cylindrical, inductively coupled, resonator plasma reactors.

  7. Probing the sliding interactions between bundled actin filaments

    NASA Astrophysics Data System (ADS)

    Ward, Andy; Dogic, Zvonimir

    2011-03-01

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

  8. Dissection of Filamentous Growth by Transposon Mutagenesis in Saccharomyces Cerevisiae

    PubMed Central

    Mosch, H. U.; Fink, G. R.

    1997-01-01

    Diploid Saccharomyces cerevisiae strains starved for nitrogen undergo a developmental transition from growth as single yeast form (YF) cells to a multicellular form consisting of filaments of pseudohyphal (PH) cells. Filamentous growth is regulated by an evolutionarily conserved signaling pathway that includes the small GTP-binding proteins Ras2p and Cdc42p, the protein kinases Ste20p, Ste11p and Ste7p, and the transcription factor Ste12p. Here, we designed a genetic screen for mutant strains defective for filamentous growth (dfg) to identify novel targets of the filamentation signaling pathway, and we thereby identified 16 different genes, CDC39, STE12, TEC1, WHI3, NAB1, DBR1, CDC55, SRV2, TPM1, SPA2, BNI1, DFG5, DFG9, DFG10, BUD8 and DFG16, mutations that block filamentous growth. Phenotypic analysis of dfg mutant strains genetically dissects filamentous growth into the cellular processes of signal transduction, bud site selection, cell morphogenesis and invasive growth. Epistasis tests between dfg mutant alleles and dominant activated alleles of the RAS2 and STE11 genes, RAS2(Val19) and STE11-4, respectively, identify putative targets for the filamentation signaling pathway. Several of the genes described here have homologues in filamentous fungi, where they also regulate fungal development. PMID:9055077

  9. Process for the production of superconductor containing filaments

    SciTech Connect

    Tuominen, Olli P.; Hoyt, Matthew B.; Mitchell, David F.; Morgan, Carol W.; Roberts, Clyde Gordon; Tyler, Robert A.

    2002-01-01

    Superconductor containing filaments having embedments of superconducting material surrounded by a rayon matrix are formed by preparing a liquid suspension which contains at least 10 weight percent superconducting material; forming a multicomponent filament having a core of the suspension and a viscose sheath which contains cellulose xanthate; and thereafter, regenerating cellulose from the cellulose xanthate to form a rayon matrix.

  10. Myosin filament 3D structure in mammalian cardiac muscle☆

    PubMed Central

    AL-Khayat, Hind A.; Morris, Edward P.; Kensler, Robert W.; Squire, John M.

    2008-01-01

    A number of cardiac myopathies (e.g. familial hypertrophic cardiomyopathy and dilated cardiomyopathy) are linked to mutations in cardiac muscle myosin filament proteins, including myosin and myosin binding protein C (MyBP-C). To understand the myopathies it is necessary to know the normal 3D structure of these filaments. We have carried out 3D single particle analysis of electron micrograph images of negatively stained isolated myosin filaments from rabbit cardiac muscle. Single filament images were aligned and divided into segments about 2 × 430 Å long, each of which was treated as an independent ‘particle’. The resulting 40 Å resolution 3D reconstruction showed both axial and azimuthal (no radial) myosin head perturbations within the 430 Å repeat, with successive crown rotations of approximately 60°, 60° and 0°, rather than the regular 40° for an unperturbed helix. However, it is shown that the projecting density peaks appear to start at low radius from origins closer to those expected for an unperturbed helical filament, and that the azimuthal perturbation especially increases with radius. The head arrangements in rabbit cardiac myosin filaments are very similar to those in fish skeletal muscle myosin filaments, suggesting a possible general structural theme for myosin filaments in all vertebrate striated muscles (skeletal and cardiac). PMID:18472277

  11. GALAXY SPIN ALIGNMENT IN FILAMENTS AND SHEETS: OBSERVATIONAL EVIDENCE

    SciTech Connect

    Tempel, Elmo; Libeskind, Noam I. E-mail: nlibeskind@aip.de

    2013-10-01

    The properties of galaxies are known to be affected by their environment. One important question is how their angular momentum reflects the surrounding cosmic web. We use the Sloan Digital Sky Survey to investigate the spin axes of spiral and elliptical galaxies relative to their surrounding filament/sheet orientations. To detect filaments, a marked point process with interactions (the {sup B}isous model{sup )} is used. Sheets are found by detecting 'flattened' filaments. The minor axes of ellipticals are found to be preferentially perpendicular to hosting filaments. A weak correlation is found with sheets. These findings are consistent with the notion that elliptical galaxies formed via mergers, which predominantly occurred along the filaments. The spin axis of spiral galaxies is found to align with the host filament, with no correlation between spiral spin and sheet normal. When examined as a function of distance from the filament axis, a much stronger correlation is found in the outer parts, suggesting that the alignment is driven by the laminar infall of gas from sheets to filaments. When compared with numerical simulations, our results suggest that the connection between dark matter halo and galaxy spin is not straightforward. Our results provide an important input to the understanding of how galaxies acquire their angular momentum.

  12. A catalytic oligomeric motor that walks along a filament track

    SciTech Connect

    Huang, Mu-Jie Kapral, Raymond

    2015-06-28

    Most biological motors in the cell execute chemically powered conformational changes as they walk on biopolymer filaments in order to carry out directed transport functions. Synthetic motors that operate in a similar manner are being studied since they have the potential to perform similar tasks in a variety of applications. In this paper, a synthetic nanomotor that moves along a filament track, without invoking motor conformational changes, is constructed and its properties are studied in detail. The motor is an oligomer comprising three linked beads with specific binding properties. The filament track is a stiff polymer chain, also described by a linear chain of linked coarse-grained molecular groups modeled as beads. Reactions on the filament that are catalyzed by a motor bead and use fuel in the environment, in conjunction within the binding affinities of the motor beads to the filament beads, lead to directed motion. The system operates out of equilibrium due to the state of the filament and supply of fuel. The motor, filament, and surrounding medium are all described at microscopic level that permits a full analysis of the motor motion. A stochastic model that captures the main trends seen in the simulations is also presented. The results of this study point to some of the key features that could be used to construct nanomotors that undergo biased walks powered by chemical reactions on filaments.

  13. In Sup35p filaments (the [PSI+] prion), the globular C-terminal domains are widely offset from the amyloid fibril backbone

    SciTech Connect

    Baxa, U.; Wall, J.; Keller, P. W.; Cheng, N.; Steven, A. C.

    2011-01-01

    In yeast cells infected with the [PSI+] prion, Sup35p forms aggregates and its activity in translation termination is downregulated. Transfection experiments have shown that Sup35p filaments assembled in vitro are infectious, suggesting that they reproduce or closely resemble the prion. We have used several EM techniques to study the molecular architecture of filaments, seeking clues as to the mechanism of downregulation. Sup35p has an N-terminal 'prion' domain; a highly charged middle (M-)domain; and a C-terminal domain with the translation termination activity. By negative staining, cryo-EM and scanning transmission EM (STEM), filaments of full-length Sup35p show a thin backbone fibril surrounded by a diffuse 65-nm-wide cloud of globular C-domains. In diameter ({approx}8 nm) and appearance, the backbones resemble amyloid fibrils of N-domains alone. STEM mass-per-unit-length data yield -1 subunit per 0.47 nm for N-fibrils, NM-filaments and Sup35p filaments, further supporting the fibril backbone model. The 30 nm radial span of decorating C-domains indicates that the M-domains assume highly extended conformations, offering an explanation for the residual Sup35p activity in infected cells, whereby the C-domains remain free enough to interact with ribosomes.

  14. Energetic protons from a disappearing solar filament

    NASA Technical Reports Server (NTRS)

    Kahler, S. W.; Cliver, E. W.; Cane, H. V.; Mcguire, R. E.; Stone, R. G.; Sheeley, N. R., Jr.

    1985-01-01

    A solar energetic (E 50 MeV) particle (SEP) event observed at 1 AU began about 15000 UT on 1981 December 5. This event was associated with a fast coronal mass ejection observed with the Solwind coronagraph on the P78-1 satellite. No metric type 2 or type 4 burst was observed, but a weak interplanetary type 2 burst was observed with the low frequency radio experiment on the International Sun-Earth Explorer-3 satellite. The mass ejection was associated with the eruption of a large solar quiescent filament which lay well away from any active regions. The eruption resulted in an H alpha double ribbon structure which straddled the magnetic inversion line. No impulsive phase was obvious in either the H alpha or the microwave observations. This event indicates that neither a detectable impulsive phase nor a strong or complex magnetic field is necessary for the production of energetic ions.

  15. Filament wound data base development, revision 1

    NASA Technical Reports Server (NTRS)

    Sharp, R. Scott; Braddock, William F.

    1985-01-01

    The objective was to update the present Space Shuttle Solid Rocket Booster (SRB) baseline reentry aerodynamic data base and to develop a new reentry data base for the filament wound case SRB along with individual protuberance increments. Lockheed's procedures for performing these tasks are discussed. Free fall of the SRBs after separation from the Space Shuttle Launch Vehicle is completely uncontrolled. However, the SRBs must decelerate to a velocity and attitude that is suitable for parachute deployment. To determine the SRB reentry trajectory parameters, including the rate of deceleration and attitude history during free-fall, engineers at Marshall Space Flight Center are using a six-degree-of-freedom computer program to predict dynamic behavior. Static stability aerodynamic coefficients are part of the information required for input into this computer program. Lockheed analyzed the existing reentry aerodynamic data tape (Data Tape 5) for the current steel case SRB. This analysis resulted in the development of Data Tape 7.

  16. Validation of the filament winding process model

    NASA Technical Reports Server (NTRS)

    Calius, Emilo P.; Springer, George S.; Wilson, Brian A.; Hanson, R. Scott

    1987-01-01

    Tests were performed toward validating the WIND model developed previously for simulating the filament winding of composite cylinders. In these tests two 24 in. long, 8 in. diam and 0.285 in. thick cylinders, made of IM-6G fibers and HBRF-55 resin, were wound at + or - 45 deg angle on steel mandrels. The temperatures on the inner and outer surfaces and inside the composite cylinders were recorded during oven cure. The temperatures inside the cylinders were also calculated by the WIND model. The measured and calculated temperatures were then compared. In addition, the degree of cure and resin viscosity distributions inside the cylinders were calculated for the conditions which existed in the tests.

  17. Cryogenic glass-filament-wound tank evaluation

    NASA Technical Reports Server (NTRS)

    Morris, E. E.; Landes, R. E.

    1971-01-01

    High-pressure glass-filament-wound fluid storage vessels with thin aluminum liners were designed, fabricated, and tested at ambient and cryogenic temperatures which demonstrated the feasibility of producing such vessels as well as high performance and light weight. Significant developments and advancements were made in solving problems associated with the thin metal liners in the tanks, including liner bonding to the overwrap and high strain magnification at the vessel polar bosses. The vessels had very high burst strengths, and failed in cyclic fatigue tests by local liner fracture and leakage without structural failure of the composite tank wall. The weight of the tanks was only 40 to 55% of comparable 2219-T87 aluminum and Inconel 718 tanks.

  18. Engineering of filamentous bacteriophage for protein sensing

    NASA Astrophysics Data System (ADS)

    Brasino, Michael

    Methods of high throughput, sensitive and cost effective quantification of proteins enables personalized medicine by allowing healthcare professionals to better monitor patient condition and response to treatment. My doctoral research has attempted to advance these methods through the use of filamentous bacteriophage (phage). These bacterial viruses are particularly amenable to both genetic and chemical engineering and can be produced efficiently in large amounts. Here, I discuss several strategies for modifying phage for use in protein sensing assays. These include the expression of bio-orthogonal conjugation handles on the phage coat, the incorporation of specific recognition sequences within the phage genome, and the creation of antibody-phage conjugates via a photo-crosslinking non-canonical amino acid. The physical and chemical characterization of these engineered phage and the results of their use in modified protein sensing assays will be presented.

  19. Bending artificial muscle from nylon filaments

    NASA Astrophysics Data System (ADS)

    Mirvakili, Seyed M.; Hunter, Ian W.

    2016-04-01

    Highly oriented nylon and polyethylene fibers shrink in length and expand in diameter when heated. Using this property, in this work, for the first time we are introducing a type of bending artificial muscle from nylon filaments such as fishing line. Reversible radius of curvature of 0.23 mm-1 was achieved with maximum reversible bending amplitude of 115 mm for the nylon bending actuator. Peak force of up to 2040 mN was measured with a catch-state force of up to 40% of the active force. A 3 dB roll-off frequency of around 0.7 Hz was observed in the frequency response of the bending actuator in water.

  20. Persistent nuclear actin filaments inhibit transcription by RNA polymerase II.

    PubMed

    Serebryannyy, Leonid A; Parilla, Megan; Annibale, Paolo; Cruz, Christina M; Laster, Kyle; Gratton, Enrico; Kudryashov, Dmitri; Kosak, Steven T; Gottardi, Cara J; de Lanerolle, Primal

    2016-09-15

    Actin is abundant in the nucleus and it is clear that nuclear actin has important functions. However, mystery surrounds the absence of classical actin filaments in the nucleus. To address this question, we investigated how polymerizing nuclear actin into persistent nuclear actin filaments affected transcription by RNA polymerase II. Nuclear filaments impaired nuclear actin dynamics by polymerizing and sequestering nuclear actin. Polymerizing actin into stable nuclear filaments disrupted the interaction of actin with RNA polymerase II and correlated with impaired RNA polymerase II localization, dynamics, gene recruitment, and reduced global transcription and cell proliferation. Polymerizing and crosslinking nuclear actin in vitro similarly disrupted the actin-RNA-polymerase-II interaction and inhibited transcription. These data rationalize the general absence of stable actin filaments in mammalian somatic nuclei. They also suggest a dynamic pool of nuclear actin is required for the proper localization and activity of RNA polymerase II.

  1. Beam wandering of femtosecond laser filament in air.

    PubMed

    Yang, Jing; Zeng, Tao; Lin, Lie; Liu, Weiwei

    2015-10-05

    The spatial wandering of a femtosecond laser filament caused by the filament heating effect in air has been studied. An empirical formula has also been derived from the classical Karman turbulence model, which determines quantitatively the displacement of the beam center as a function of the propagation distance and the effective turbulence structure constant. After fitting the experimental data with this formula, the effective turbulence structure constant has been estimated for a single filament generated in laboratory environment. With this result, one may be able to estimate quantitatively the displacement of a filament over long distance propagation and interpret the practical performance of the experiments assisted by femtosecond laser filamentation, such as remote air lasing, pulse compression, high order harmonic generation (HHG), etc.

  2. Sedimentation of slender elastic filaments in a viscous liquid

    NASA Astrophysics Data System (ADS)

    Raspa, Veronica; Lindner, Anke; Du Roure, Olivia; Duprat, Camille

    2016-11-01

    We explore experimentally the dynamics of slender flexible filaments sedimenting in a viscous fluid at low Reynolds number. The observed deformations and dynamics result from a balance between viscous, elastic and gravitational forces on the slender body and thus are characterized by a dimensionless elasto-gravity number. We present measurements of the filaments stationary shape, velocities and trajectories for different initial conditions and filament characteristics (i.e: density, bending rigidity, size). In particular, we observe bending and reorientation of the filament, and investigate the conditions under which the filament can buckle. The introduction of elasticity broadens the spectrum of accessible sedimentation stationary states, compared to those appearing for their rigid counterparts where nor bending or buckling are allowed.

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

    PubMed

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

    2016-07-01

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

  4. Conduction in alumina with atomic scale copper filaments

    SciTech Connect

    Xu, Xu; Liu, Jie; Anantram, M. P.

    2014-10-28

    The conductance of atomic scale filaments with three and seven Cu atoms in α-alumina are calculated using ab initio density functional theory. We find that the filament with 3 Cu atoms is sufficient to increase the conductance of 1.3 nm thick alumina film by more than 10{sup 3} times in linear response. As the applied voltage increases, the current quickly saturates and differential resistance becomes negative. Compared to the filament with three Cu atoms, while the conductance of the filament with seven Cu atoms is comparable in linear response, they carry as much as twenty times larger current at large biases. The electron transport is analyzed based on local density of states, and the negative differential resistance in the seven Cu filaments occurs due to their narrow bandwidth.

  5. Propagation of radio frequency waves through density filaments

    SciTech Connect

    Ram, Abhay K.; Hizanidis, Kyriakos

    2015-12-10

    In tokamak fusion plasmas, coherent fluctuations in the form of blobs or filaments are routinely observed in the scrape-off layer. In this paper we develop an analytical formalism for the scattering of radio frequency waves by filaments which are cylindrical with their major axis aligned along the toroidal magnetic field lines. Since the magnitude of the ratio of the density inside the filaments to the background density is generally of order 1, the geometric optics approximation cannot be used to describe the scattering. A full-wave model is formulated which assumes that the plasma is cold and that the plasma in the cylindrical filament has uniform density. The background plasma, in which the filament is present, is also assumed to be cold and uniform. The theoretical framework applies to the scattering of any plasma wave.

  6. Filamentous bacteriophage: biology, phage display and nanotechnology applications.

    PubMed

    Rakonjac, Jasna; Bennett, Nicholas J; Spagnuolo, Julian; Gagic, Dragana; Russel, Marjorie

    2011-01-01

    Filamentous bacteriophage, long and thin filaments that are secreted from the host cells without killing them, have been an antithesis to the standard view of head-and-tail bacterial killing machines. Episomally replicating filamentous phage Ff of Escherichia coli provide the majority of information about the principles and mechanisms of filamentous phage infection, episomal replication and assembly. Chromosomally- integrated "temperate" filamentous phage have complex replication and integration, which are currently under active investigation. The latter are directly or indirectly implicated in diseases caused by bacterial pathogens Vibrio cholerae, Pseudomonas aeruginosa and Neisseria meningitidis. In the first half of the review, both the Ff and temperate phage are described and compared. A large section of the review is devoted to an overview of phage display technology and its applications in nanotechnology.

  7. Ubiquitination and filamentous structure of cytidine triphosphate synthase

    PubMed Central

    Pai, Li-Mei; Wang, Pei-Yu; Lin, Wei-Cheng; Chakraborty, Archan; Yeh, Chau-Ting; Lin, Yu-Hung

    2016-01-01

    ABSTRACT Living organisms respond to nutrient availability by regulating the activity of metabolic enzymes. Therefore, the reversible post-translational modification of an enzyme is a common regulatory mechanism for energy conservation. Recently, cytidine-5′-triphosphate (CTP) synthase was discovered to form a filamentous structure that is evolutionarily conserved from flies to humans. Interestingly, induction of the formation of CTP synthase filament is responsive to starvation or glutamine depletion. However, the biological roles of this structure remain elusive. We have recently shown that ubiquitination regulates CTP synthase activity by promoting filament formation in Drosophila ovaries during endocycles. Intriguingly, although the ubiquitination process was required for filament formation induced by glutamine depletion, CTP synthase ubiquitination was found to be inversely correlated with filament formation in Drosophila and human cell lines. In this article, we discuss the putative dual roles of ubiquitination, as well as its physiological implications, in the regulation of CTP synthase structure. PMID:27116391

  8. Filament capturing with the multimaterial moment-of-fluid method*

    SciTech Connect

    Jemison, Matthew; Sussman, Mark; Shashkov, Mikhail

    2015-01-15

    A novel method for capturing two-dimensional, thin, under-resolved material configurations, known as “filaments,” is presented in the context of interface reconstruction. This technique uses a partitioning procedure to detect disconnected regions of material in the advective preimage of a cell (indicative of a filament) and makes use of the existing functionality of the Multimaterial Moment-of-Fluid interface reconstruction method to accurately capture the under-resolved feature, while exactly conserving volume. An algorithm for Adaptive Mesh Refinement in the presence of filaments is developed so that refinement is introduced only near the tips of filaments and where the Moment-of-Fluid reconstruction error is still large. Comparison to the standard Moment-of-Fluid method is made. As a result, it is demonstrated that using filament capturing at a given resolution yields gains in accuracy comparable to introducing an additional level of mesh refinement at significantly lower cost.

  9. Intermediate Filaments and Polarization in the Intestinal Epithelium

    PubMed Central

    Coch, Richard A.; Leube, Rudolf E.

    2016-01-01

    The cytoplasmic intermediate filament cytoskeleton provides a tissue-specific three-dimensional scaffolding with unique context-dependent organizational features. This is particularly apparent in the intestinal epithelium, in which the intermediate filament network is localized below the apical terminal web region and is anchored to the apical junction complex. This arrangement is conserved from the nematode Caenorhabditis elegans to humans. The review summarizes compositional, morphological and functional features of the polarized intermediate filament cytoskeleton in intestinal cells of nematodes and mammals. We emphasize the cross talk of intermediate filaments with the actin- and tubulin-based cytoskeleton. Possible links of the intermediate filament system to the distribution of apical membrane proteins and the cell polarity complex are highlighted. Finally, we discuss how these properties relate to the establishment and maintenance of polarity in the intestine. PMID:27429003

  10. Propagation of radio frequency waves through density filaments

    NASA Astrophysics Data System (ADS)

    Ram, Abhay K.; Hizanidis, Kyriakos

    2015-12-01

    In tokamak fusion plasmas, coherent fluctuations in the form of blobs or filaments are routinely observed in the scrape-off layer. In this paper we develop an analytical formalism for the scattering of radio frequency waves by filaments which are cylindrical with their major axis aligned along the toroidal magnetic field lines. Since the magnitude of the ratio of the density inside the filaments to the background density is generally of order 1, the geometric optics approximation cannot be used to describe the scattering. A full-wave model is formulated which assumes that the plasma is cold and that the plasma in the cylindrical filament has uniform density. The background plasma, in which the filament is present, is also assumed to be cold and uniform. The theoretical framework applies to the scattering of any plasma wave.

  11. Sedimentary Biosignatures of Social Organization in Cone-Forming Filamentous Bacteria

    NASA Astrophysics Data System (ADS)

    Tice, M. M.; Gong, J.; Zeng, Z.; Sneed, J.; Wehner, M.; Sparks, D. W.

    2013-12-01

    Conical mats consisting of centimeter-scale steep-sided cones growing above flat basal films form some of the most distinctive fossil microbial communities in the geologic record. Cones have been hypothesized to form by the initially random motion of filamentous bacteria into small tangled clumps followed by the phototactic motion of the same bacteria up resulting slopes. More recent models of cone development suggest that they form in response to growth in stagnant fluids where diffusion limits exchange of nutrients and wastes with the environment. Determining the biological and environmental factors that promote cone formation will be important for interpreting the geological record of fossil mats and stromatolites, on Earth and potentially on Mars. Here we report the results of new experiments demonstrating complex social organization of cone-forming communities and a novel biosignature of the growth of such communities on sandy sediments, as well as detection of that biosignature in 3.2 Ga fossil mats of the Moodies Group (Barberton greenstone belt, South Africa). In order to investigate the processes involved in cone formation, we grew cultures of a filamentous cyanobacterium originally isolated from tufted cones in Yellowstone National Park, Montana, U.S.A. (Leptolyngbya sp. Y-WT-2000 Cl 1). During early mat development, filaments coat sand grain surfaces and aggregate into ~100-μm-long tufts, or mutually aligned bundles of filaments. Tufts are highly motile, bridging sand grains and merging to form larger tufts. After 10-14 days of growth, tufts aggregate during the early morning into centers composed of many tufts that wave vertically and along the sand surface. Centers move across the sediment surface during the middle of the day and merge along bridging tufts. These bridges transmit force to the underlying sediment and are capable of rolling sand grains. At this stage, mats are composed of small mobile centers that disperse along streams of co

  12. Surface fractals in liposome aggregation.

    PubMed

    Roldán-Vargas, Sándalo; Barnadas-Rodríguez, Ramon; Quesada-Pérez, Manuel; Estelrich, Joan; Callejas-Fernández, José

    2009-01-01

    In this work, the aggregation of charged liposomes induced by magnesium is investigated. Static and dynamic light scattering, Fourier-transform infrared spectroscopy, and cryotransmission electron microscopy are used as experimental techniques. In particular, multiple intracluster scattering is reduced to a negligible amount using a cross-correlation light scattering scheme. The analysis of the cluster structure, probed by means of static light scattering, reveals an evolution from surface fractals to mass fractals with increasing magnesium concentration. Cryotransmission electron microscopy micrographs of the aggregates are consistent with this interpretation. In addition, a comparative analysis of these results with those previously reported in the presence of calcium suggests that the different hydration energy between lipid vesicles when these divalent cations are present plays a fundamental role in the cluster morphology. This suggestion is also supported by infrared spectroscopy data. The kinetics of the aggregation processes is also analyzed through the time evolution of the mean diffusion coefficient of the aggregates.

  13. Cell aggregation: Packing soft grains

    NASA Astrophysics Data System (ADS)

    Åström, J. A.; Karttunen, M.

    2006-06-01

    Cellular aggregates may be considered as collections of membrane enclosed units with a pressure difference between the internal and external liquid phases. Cells are kept together by membrane adhesion and/or confined space compression. Pattern formation and, in particular, intercellular spacing have important roles in controlling solvent diffusion within such aggregates. A physical approach is used to study generic aspects of cellular packings in a confined space. Average material properties are derived from the free energy. The appearance of penetrating intercellular void channels is found to be critically governed by the cell wall adhesion mechanisms during the formation of dense aggregates. A fully relaxed aggregate efficiently hinders solvent diffusion at high hydrostatic pressures, while a small fraction (˜0.1) of adhesion related packing frustration is sufficient for breaking such a blockage even at high a pressure.

  14. Contractile properties of thin (actin) filament-reconstituted muscle fibers.

    PubMed

    Ishiwata, S; Funatsu, T; Fujita, H

    1998-01-01

    Selective removal and reconstitution of the components of muscle fibers (fibrils) is a useful means of examining the molecular mechanism underlying the formation of the contractile apparatus. In addition, this approach is powerful for examining the structure-function relationship of a specific component of the contractile system. In previous studies, we have achieved the partial structural and functional reconstitution of thin filaments in the skeletal contractile apparatus and full reconstitution in the cardiac contractile apparatus. First, all thin filaments other than short fragments at the Z line were removed by treatment with plasma gelsolin, an actin filament-severing protein. Under these conditions, no active tension could be generated. By incorporating exogenous actin into these thin filament-free fibers, actin filaments were reconstituted by polymerization on the short actin fragments remaining at the Z line, and active tension, which was insensitive to Ca2+, was restored. The active tension after the reconstitution of thin filaments reached as high as 30% of the original level in skeletal muscle, while it reached 140% in cardiac muscle. The augmentation of tension in cardiac muscle is mainly attributable to the elongation of reconstituted filaments, longer than the average length of thin filaments in an intact muscle. These results indicate that a muscle contractile apparatus with a high order structure and function can be constructed by the self-assembly of constituent proteins. Recently, we applied this reconstitution system to the study of the mechanism of spontaneous oscillatory contraction (SPOC) in thin (actin) filament-reconstituted cardiac muscle fibers. As a result, we found that SPOC occurs even in regulatory protein-free actin filament-reconstituted fibers (Fujita & Ishiwata, manuscript submitted), although the SPOC conditions were slightly different from the standard SPOC conditions. This result strongly suggests that spontaneous oscillation

  15. Aggregate breakdown of nanoparticulate titania

    NASA Astrophysics Data System (ADS)

    Venugopal, Navin

    Six nanosized titanium dioxide powders synthesized from a sulfate process were investigated. The targeted end-use of this powder was for a de-NOx catalyst honeycomb monolith. Alteration of synthesis parameters had resulted principally in differences in soluble ion level and specific surface area of the powders. The goal of this investigation was to understand the role of synthesis parameters in the aggregation behavior of these powders. Investigation via scanning electron microscopy of the powders revealed three different aggregation iterations at specific length scales. Secondary and higher order aggregate strength was investigated via oscillatory stress rheometry as a means of simulating shear conditions encountered during extrusion. G' and G'' were measured as a function of the applied oscillatory stress. Oscillatory rheometry indicated a strong variation as a function of the sulfate level of the particles in the viscoelastic yield strengths. Powder yield stresses ranged from 3.0 Pa to 24.0 Pa of oscillatory stress. Compaction curves to 750 MPa found strong similarities in extrapolated yield point of stage I and II compaction for each of the powders (at approximately 500 MPa) suggesting that the variation in sulfate was greatest above the primary aggregate level. Scanning electron microscopy of samples at different states of shear in oscillatory rheometry confirmed the variation in the linear elastic region and the viscous flow regime. A technique of this investigation was to approach aggregation via a novel perspective: aggregates are distinguished as being loose open structures that are highly disordered and stochastic in nature. The methodology used was to investigate the shear stresses required to rupture the various aggregation stages encountered and investigate the attempt to realign the now free-flowing constituents comprising the aggregate into a denser configuration. Mercury porosimetry was utilized to measure the pore size of the compact resulting from

  16. Organization of an actin filament-membrane complex. Filament polarity and membrane attachment in the microvilli of intestinal epithelial cells

    PubMed Central

    1975-01-01

    The association of actin filaments with membranes is now recognized as an important parameter in the motility of nonmuscle cells. We have investigated the organization of one of the most extensive and highly ordered actin filament-membrane complexes in nature, the brush border of intestinal epithelial cells. Through the analysis of isolated, demembranated brush borders decorated with the myosin subfragment, S1, we have determined that all the microvillar actin filaments have the same polarity. The S1 arrowhead complexes point away from the site of attachment of actin filaments at the apical tip of the microvillar membrane. In addition to the end-on attachment of actin filaments at the tip of the microvillus, these filaments are also connected to the plasma membrane all along their lengths by periodic (33 nm) cross bridges. These bridges were best observed in isolated brush borders incubated in high concentrations of Mg++. Their visibility is attributed to the induction of actin paracrystals in the filament bundles of the microvilli. Finally, we present evidence for the presence of myosinlike filaments in the terminal web region of the brush border. A model for the functional organization of actin and myosin in the brush border is presented. PMID:1202021

  17. The intermediate-sized filaments in rat kangaroo PtK2 cells. II. Structure and composition of isolated filaments.

    PubMed

    Franke, W W; Schmid, E; Osborn, M; Weber, K

    1978-08-01

    When cultured cells of the rat kangaroo cell line PtK2 grown on plastic or glass surfaces are lysed and extracted with combinations of low and high salt buffers and the non-ionic detergent Triton X-100 cytoskeletal preparations are obtained that show an enrichment of 6 to 11 nm thick filaments. The arrays of these filaments have been examined by various light and electron microscopic techniques, including ultrathin sectioning, whole mount transmission electron microscopy, negative staining, and indirect immunofluorescence microscopy. In addition, 6 to 11 nm filaments isolated from these cells with similar extraction procedures and with centrifugation techniques have been examined by electron microscopy. The arrays of these isolated intermediate-sized filaments, their ultrastructure and their specific decoration by certain antibodies present in normal rabbit sera as well as by guinea pig antibodies against purified bovine prekeratin is demonstrated. When preparations enriched in these intermediate-sized filaments are examined by SDS-polyacrylamide gel electrophoresis a corresponding enrichment of three polypeptide bands with apparent molecular weights of about 45 000, 52 000 and 58 000 (the latter component sometimes appears split into two bands) is observed, besides some residual actin and a few high molecular weight bands. The morphology of the isolated filaments, their immunological reaction with antibodies decorating prekeratin-containing structures, and the sizes of their constitutive polypeptides suggest that these filaments are closely related to prekeratin-containing filaments observed in a variety of epithelial cells.

  18. NRG1, a repressor of filamentous growth in C.albicans, is down-regulated during filament induction

    PubMed Central

    Braun, Burkhard R.; Kadosh, David; Johnson, Alexander D.

    2001-01-01

    In response to a variety of external signals, the fungal pathogen Candida albicans undergoes a transition between ellipsoidal single cells (blastospores) and filaments composed of elongated cells attached end-to-end. Here we identify a DNA-binding protein, Nrg1, that represses filamentous growth in Candida probably by acting through the co-repressor Tup1. nrg1 mutant cells are predominantly filamentous under non-filament-inducing conditions and their colony morphology resembles that of tup1 mutants. We also identify two filament-specific genes, ECE1 and HWP1, whose transcription is repressed by Nrg1 under non-inducing conditions. These genes constitute a subset of those under Tup1 control, providing further evidence that Nrg1 acts by recruiting Tup1 to target genes. We show that growth in serum at 37°C, a potent inducer of filamentous growth, causes a reduction of NRG1 mRNA, suggesting that filamentous growth is induced by the down-regulation of NRG1. Consistent with this idea, expression of NRG1 from a non-regulated promoter partially blocks the induction of filamentous growth. PMID:11532939

  19. Lamin aggregation is an early sensor of porphyria-induced liver injury.

    PubMed

    Singla, Amika; Griggs, Nicholas W; Kwan, Raymond; Snider, Natasha T; Maitra, Dhiman; Ernst, Stephen A; Herrmann, Harald; Omary, M Bishr

    2013-07-15

    Oxidative liver injury during steatohepatitis results in aggregation and transglutaminase-2 (TG2)-mediated crosslinking of the keratin cytoplasmic intermediate filament proteins (IFs) to form Mallory-Denk body (MDB) inclusions. The effect of liver injury on lamin nuclear IFs is unknown, though lamin mutations in several human diseases result in lamin disorganization and nuclear shape changes. We tested the hypothesis that lamins undergo aggregation during oxidative liver injury using two MDB mouse models: (i) mice fed the porphyrinogenic drug 3,5-diethoxycarbonyl-1,4-dihydrocollidine (DDC) and (ii) mice that harbor a mutation in ferrochelatase (fch), which converts protoporphyrin IX to heme. Dramatic aggregation of lamin A/C and B1 was noted in the livers of both models in association with changes in lamin organization and nuclear shape, as determined by immunostaining and electron microscopy. The lamin aggregates sequester other nuclear proteins including transcription factors and ribosomal and nuclear pore components into high molecular weight complexes, as determined by mass-spectrometry and confirmed biochemically. Lamin aggregate formation is rapid and precedes keratin aggregation in fch livers, and is seen in liver explants of patients with alcoholic cirrhosis. Exposure of cultured cells to DDC, protoporphyrin IX or N-methyl-protoporphyrin, or incubation of purified lamins with protoporphyrin IX, also results in lamin aggregation. In contrast, lamin aggregation is ameliorated by TG2 inhibition. Therefore, lamin aggregation is an early sensor of porphyria-associated liver injury and might serve to buffer oxidative stress. The nuclear shape and lamin defects associated with porphyria phenocopy the changes seen in laminopathies and could result in transcriptional alterations due to sequestration of nuclear proteins.

  20. Influence of mechanical stress and surface interaction on the aggregation of Aspergillus niger conidia.

    PubMed

    Grimm, L H; Kelly, S; Völkerding, I I; Krull, R; Hempel, D C

    2005-12-30

    Productivity of fungal cultures is closely linked with their morphologic development. Morphogenesis of coagulating filamentous fungi, like Aspergillus niger, starts with aggregation of conidia, also denominated as spores. Several parameters are presumed to control this event, but little is known about their mode of action. Rational process optimization requires models that mirror the underlying reaction mechanisms. An approach in this regard is suggested and supported by experimental data. Aggregation kinetics was examined for the first 15 h of cultivation under different cultivation conditions. Mechanical stress was considered as well as pH-dependent surface interaction. Deliberations were based on a two-step aggregation mechanism. The first aggregation step is only affected by the pH-value, not by the fluid dynamic conditions in the bioreactor. The second aggregation step, in contrast, depends on the pH-value as well as on agitation and aeration induced power input. For the given experimental set-up, agitation had much more influence than aeration. In addition, hyphal growth rate was determined to be the driving force for the second aggregation step.

  1. Hsp70 and antifibrillogenic peptides promote degradation and inhibit intracellular aggregation of amyloidogenic light chains.

    SciTech Connect

    Dul, J. L.; Davis, D. P.; Williamson, E. K.; Stevens, F. J.; Argon, Y.; Univ. of Chicago

    2001-02-19

    In light chain (LC) amyloidosis an immunoglobulin LC assembles into fibrils that are deposited in various tissues. Little is known about how these fibrils form in vivo. We previously showed that a known amyloidogenic LC, SMA, can give rise to amyloid fibrils in vitro when a segment of one of its {beta} sheets undergoes a conformational change, exposing an Hsp70 binding site. To examine SMA aggregation in vivo, we expressed it and its wild-type counterpart, LEN, in COS cells. While LEN is rapidly oxidized and subsequently secreted, newly synthesized SMA remains in the reduced state. Most SMA molecules are dislocated out of the ER into the cytosol, where they are ubiquitinylated and degraded by proteasomes. A parallel pathway for molecules that are not degraded is condensation into perinuclear aggresomes that are surrounded by vimentin-containing intermediate filaments and are dependent upon intact microtubules. Inhibition of proteasome activity shifts the balance toward aggresome formation. Intracellular aggregation is decreased and targeting to proteasomes improved by overexpression of the cytosolic chaperone Hsp70. Importantly, transduction into the cell of an Hsp70 target peptide, derived from the LC sequence, also reduces aggresome formation and increases SMA degradation. These results demonstrate that an amyloidogenic LC can aggregate intracellularly despite the common presentation of extracellular aggregates, and that a similar molecular surface mediates both in vitro fibril formation and in vivo aggregation. Furthermore, rationally designed peptides can be used to suppress this aggregation and may provide a feasible therapeutic approach.

  2. Glycation precedes lens crystallin aggregation

    SciTech Connect

    Swamy, M.S.; Perry, R.E.; Abraham, E.C.

    1987-05-01

    Non-enzymatic glycosylation (glycation) seems to have the potential to alter the structure of crystallins and make them susceptible to thiol oxidation leading to disulfide-linked high molecular weight (HMW) aggregate formation. They used streptozotocin diabetic rats during precataract and cataract stages and long-term cell-free glycation of bovine lens crystallins to study the relationship between glycation and lens crystallin aggregation. HMW aggregates and other protein components of the water-soluble (WS) and urea-soluble (US) fractions were separated by molecular sieve high performance liquid chromatography. Glycation was estimated by both (/sup 3/H)NaBH/sub 4/ reduction and phenylboronate agarose affinity chromatography. Levels of total glycated protein (GP) in the US fractions were about 2-fold higher than in the WS fractions and there was a linear increase in GP in both WS and US fractions. This increase was parallelled by a corresponding increase in HMW aggregates. Total GP extracted by the affinity method from the US fraction showed a predominance of HMW aggregates and vice versa. Cell-free glycation studies with bovine crystallins confirmed the results of the animals studies. Increasing glycation caused a corresponding increase in protein insolubilization and the insoluble fraction thus formed also contained more glycated protein. It appears that lens protein glycation, HMW aggregate formation, and protein insolubilization are interrelated.

  3. Model for amorphous aggregation processes

    NASA Astrophysics Data System (ADS)

    Stranks, Samuel D.; Ecroyd, Heath; van Sluyter, Steven; Waters, Elizabeth J.; Carver, John A.; von Smekal, Lorenz

    2009-11-01

    The amorphous aggregation of proteins is associated with many phenomena, ranging from the formation of protein wine haze to the development of cataract in the eye lens and the precipitation of recombinant proteins during their expression and purification. While much literature exists describing models for linear protein aggregation, such as amyloid fibril formation, there are few reports of models which address amorphous aggregation. Here, we propose a model to describe the amorphous aggregation of proteins which is also more widely applicable to other situations where a similar process occurs, such as in the formation of colloids and nanoclusters. As first applications of the model, we have tested it against experimental turbidimetry data of three proteins relevant to the wine industry and biochemistry, namely, thaumatin, a thaumatinlike protein, and α -lactalbumin. The model is very robust and describes amorphous experimental data to a high degree of accuracy. Details about the aggregation process, such as shape parameters of the aggregates and rate constants, can also be extracted.

  4. O-GlcNAcylation determines the solubility, filament organization, and stability of keratins 8 and 18.

    PubMed

    Srikanth, Budnar; Vaidya, Milind M; Kalraiya, Rajiv D

    2010-10-29

    Keratins 8 and 18 (K8/18) are intermediate filament proteins expressed specifically in simple epithelial tissues. Dynamic equilibrium of these phosphoglycoproteins in the soluble and filament pool is an important determinant of their cellular functions, and it is known to be regulated by site-specific phosphorylation. However, little is known about the role of dynamic O-GlcNAcylation on this keratin pair. Here, by comparing immortalized (Chang) and transformed hepatocyte (HepG2) cell lines, we have demonstrated that O-GlcNAcylation of K8/18 exhibits a positive correlation with their solubility (Nonidet P-40 extractability). Heat stress, which increases K8/18 solubility, resulted in a simultaneous increase in O-GlcNAc on these proteins. Conversely, increasing O-GlcNAc levels were associated with a concurrent increase in their solubility. This was also associated with a notable decrease in total cellular levels of K8/18. Unaltered levels of transcripts and the reduced half-life of K8 and K18 indicated their decreased stability on increasing O-GlcNAcylation. On the contrary, the K18 glycosylation mutant (K18 S29A/S30A/S48A) was notably more stable than the wild type K18 in Chang cells. The K18-O-GlcNAc mutant accumulated as aggregates upon stable expression, which possibly altered endogenous filament architecture. These results strongly indicate the involvement of O-GlcNAc on K8/18 in regulating their solubility and stability, which may have a bearing on the functions of these keratins.

  5. Ultrastructural alterations of Alzheimer's disease paired helical filaments by grape seed-derived polyphenols.

    PubMed

    Ksiezak-Reding, Hanna; Ho, Lap; Santa-Maria, Ismael; Diaz-Ruiz, Carmen; Wang, Jun; Pasinetti, Giulio Maria

    2012-07-01

    Abnormal folding of the microtubule-associated protein tau leads to aggregation of tau into paired helical filaments (PHFs) and neurofibrillary tangles, the major hallmark of Alzheimer's disease (AD). We have recently shown that grape seed polyphenol extract (GSPE) reduces tau pathology in the TMHT mouse model of tauopathy (Wang et al., 2010). In the present studies we assessed the impact of GSPE exposure on the ultrastructure of PHFs isolated from Alzheimer's disease brain. Transmission electron microscopy revealed that GSPE induced profound dose- and time-dependent alterations in the morphology of PHFs with partial disintegration of filaments. Filaments showed ∼2-fold enlargement in width and displayed numerous protrusions and splayed ends consistent with unfolding of tau and diminished structural stability. In addition, GSPE induced a reduction in immunogold labeling with antibodies against the C-terminal half (12E8, PHF-1) and the middle region of tau (AT8, Tau5, pSer214 tau, and AT180) but not the C-terminal end (Tau46). In comparison, labeling of N-terminus (Alz50) was enhanced. It is unlikely that alterations in immunogold labeling were due to biochemical alterations, e.g., protein phosphatase or proteolytic activities potentially stimulated by GSPE, because western blotting studies have shown the preservation of full length polypeptides of tau and their phospho-epitopes in GSPE-treated samples. The GSPE mechanism may include a noncovalent interaction of polyphenols with proline residues in the proline-rich domain of tau, with Pin1 sites at P213 and P232 most seriously affected as judged by suppression of labeling. Collectively, our results suggest that GSPE has a significant potential for therapeutic development by neutralizing phospho-epitopes and disrupting fibrillary conformation leading to disintegration of PHFs.

  6. Ash Aggregates in Proximal Settings

    NASA Astrophysics Data System (ADS)

    Porritt, L. A.; Russell, K.

    2012-12-01

    Ash aggregates are thought to have formed within and been deposited by the eruption column and plume and dilute density currents and their associated ash clouds. Moist, turbulent ash clouds are considered critical to ash aggregate formation by facilitating both collision and adhesion of particles. Consequently, they are most commonly found in distal deposits. Proximal deposits containing ash aggregates are less commonly observed but do occur. Here we describe two occurrences of vent proximal ash aggregate-rich deposits; the first within a kimberlite pipe where coated ash pellets and accretionary lapilli are found within the intra-vent sequence; and the second in a glaciovolcanic setting where cored pellets (armoured lapilli) occur within <1 km of the vent. The deposits within the A418 pipe, Diavik Diamond Mine, Canada, are the residual deposits within the conduit and vent of the volcano and are characterised by an abundance of ash aggregates. Coated ash pellets are dominant but are followed in abundance by ash pellets, accretionary lapilli and rare cored pellets. The coated ash pellets typically range from 1 - 5 mm in diameter and have core to rim ratios of approximately 10:1. The formation and preservation of these aggregates elucidates the style and nature of the explosive phase of kimberlite eruption at A418 (and other pipes?). First, these pyroclasts dictate the intensity of the kimberlite eruption; it must be energetic enough to cause intense fragmentation of the kimberlite to produce a substantial volume of very fine ash (<62 μm). Secondly, the ash aggregates indicate the involvement of moisture coupled with the presence of dilute expanded eruption clouds. The structure and distribution of these deposits throughout the kimberlite conduit demand that aggregation and deposition operate entirely within the confines of the vent; this indicates that aggregation is a rapid process. Ash aggregates within glaciovolcanic sequences are also rarely documented. The

  7. Kelch Domain of Gigaxonin Interacts with Intermediate Filament Proteins Affected in Giant Axonal Neuropathy

    PubMed Central

    Johnson-Kerner, Bethany L.; Garcia Diaz, Alejandro; Ekins, Sean; Wichterle, Hynek

    2015-01-01

    Patients with giant axonal neuropathy (GAN) show progressive loss of motor and sensory function starting in childhood and typically live for less than 30 years. GAN is caused by autosomal recessive mutations leading to low levels of gigaxonin (GIG), a ubiquitously-expressed BTB/Kelch cytoplasmic protein believed to be an E3 ligase substrate adaptor. GAN pathology is characterized by aggregates of intermediate filaments (IFs) in multiple tissues. To delineate the molecular pathway between GIG deficiency and IF pathology, we undertook a proteomic screen to identify the normal binding partners of GIG. Prominent among them were several classes of IFs, including the neurofilament subunits whose accumulation leads to the axonal swellings for which GAN is named. We showed these interactions were dependent on the Kelch domain of GIG. Furthermore, we identified the E3 ligase MYCBP2 and the heat shock proteins HSP90AA1/AB1 as interactors with the BTB domain that may result in the ubiquitination and subsequent degradation of intermediate filaments. Our open-ended proteomic screen provides support to GIG’s role as an adaptor protein, linking IF proteins through its Kelch domain to the ubiquitin pathway proteins via its BTB domain, and points to future approaches for reversing the phenotype in human patients. PMID:26460568

  8. O-GlcNAcylation modulates the self-aggregation ability of the fourth microtubule-binding repeat of tau

    SciTech Connect

    Yu, C.-H.; Si Tong; Wu Weihui; Hu Jia; Du Jintang; Zhao Yufen; Li Yanmei

    2008-10-10

    In Alzheimer's disease (AD), tau protein is abnormally hyperphosphorylated and aggregated into paired helical filaments (PHFs). It was discovered recently that tau is also O-GlcNAcylated in human brains. And O-GlcNAcylation may regulate phosphorylation of tau in a site-specific manner. In this work, we focused on the fourth microtubule-binding repeat (R4) of tau, which has an O-GlcNAcylation site-Ser356. The aggregation behavior of this repeat and its O-GlcNAcylated form was investigated by turbidity, precipitation assay and electron microscopy. In addition, conformations of these two peptides were analyzed with circular dichroism (CD). Our results revealed that O-GlcNAcylation at Ser356 could greatly slow down the aggregation speed of R4 peptide. This modulation of O-GlcNAcylation on tau aggregation implies a new perspective of tau pathology.

  9. Labile aggregation stimulating substance, free fatty acids, and platelet aggregation.

    PubMed

    Gerrard, J M; White, J G; Krivit, W

    1976-01-01

    Labile aggregation stimulating substance (LASS), an intermediate produced during platelet biosynthesis of PGE2 and PGF2alpha, acts as a physiologic intercellular messenger to promote platelet aggregation and the release reaction. The activity is formed by intact cells after physiologic stimulation or can be generated from platelet membrane fractions after combination with arachidonate. In the present investigation, small amounts of polyunsaturated fatty acids added to an incubation mixture of platelet microsomes and arachidonate were found to significantly inhibit subsequent platelet aggregation. Saturated and mono-unsaturated fatty acids in the same concentrations were without effect. However, in higher concentrations mono-unsaturated fatty acids were found to be inhibitory and stearic acid was found to enhance subsequent platelet aggregation. The inhibition caused by the polyunsaturated fatty acid, linoleate, was shown to be the result of an effect on the production of LASS through an interaction with the platelet enzyme responsible for conversion of arachidonate to LASS. In contrast, stearic acid was found to enhance platelet aggregation by acting on the platelets and not directly on LASS production. The results suggest that small changes in the fatty acid composition of platelet phospholipids could significantly influence platelet reactivity.

  10. The effective resistance between twisted superconducting filaments in tapes

    NASA Astrophysics Data System (ADS)

    Takács, S.; Iwakuma, M.; Funaki, K.

    2001-05-01

    We consider two mechanisms, which influence the effective resistance between crossing strands on flat cables or filaments in twisted tapes. The one-layer classical Rutherford-type cable and the tapes with twisted BSCCO filaments in silver matrix are taken as analogous cases. The amount of the matrix between strands or filaments increases the effective conductance compared with the direct current paths (determined by the touching area of the filaments). The increase factor is about two and can easily be suppressed by other effects, like the contact resistance between the superconductor and the matrix. The second mechanism is due to the existence of induced voltage between any points of crossing filaments. This leads to an additional effective conductance, proportional to the square of the total number of filaments. Both effects are not very important for isotropic superconductors, but due to the strong anisotropy of critical parameters they can dominate for high temperature superconductors. The first one may partially compensate the influence of the usually weaker critical current density perpendicular to the tape. The contribution due to the second effect can explain the higher resistivity of the matrix in BSCCO tapes compared with pure silver. It seems that to obtain low AC coupling losses in BSCCO tapes, structures with small filament number are required.

  11. Plethora of transitions during breakup of liquid filaments

    PubMed Central

    Castrejón-Pita, José Rafael; Castrejón-Pita, Alfonso Arturo; Thete, Sumeet Suresh; Sambath, Krishnaraj; Hutchings, Ian M.; Hinch, John; Lister, John R.; Basaran, Osman A.

    2015-01-01

    Thinning and breakup of liquid filaments are central to dripping of leaky faucets, inkjet drop formation, and raindrop fragmentation. As the filament radius decreases, curvature and capillary pressure, both inversely proportional to radius, increase and fluid is expelled with increasing velocity from the neck. As the neck radius vanishes, the governing equations become singular and the filament breaks. In slightly viscous liquids, thinning initially occurs in an inertial regime where inertial and capillary forces balance. By contrast, in highly viscous liquids, initial thinning occurs in a viscous regime where viscous and capillary forces balance. As the filament thins, viscous forces in the former case and inertial forces in the latter become important, and theory shows that the filament approaches breakup in the final inertial–viscous regime where all three forces balance. However, previous simulations and experiments reveal that transition from an initial to the final regime either occurs at a value of filament radius well below that predicted by theory or is not observed. Here, we perform new simulations and experiments, and show that a thinning filament unexpectedly passes through a number of intermediate transient regimes, thereby delaying onset of the inertial–viscous regime. The new findings have practical implications regarding formation of undesirable satellite droplets and also raise the question as to whether similar dynamical transitions arise in other free-surface flows such as coalescence that also exhibit singularities. PMID:25825761

  12. Regulation of actin filament length in erythrocytes and striated muscle.

    PubMed

    Fowler, V M

    1996-02-01

    Actin filaments polymerize in vitro to lengths which display an exponential distribution, yet in many highly differentiated cells they can be precisely maintained at uniform lengths in elaborate supramolecular structures. Recent results obtained using two classic model systems, the erythrocyte membrane cytoskeleton and the striated muscle sarcomere, reveal surprising similarities and instructive differences in the molecules and mechanisms responsible for determining and maintaining actin filament lengths in these two systems. Tropomodulin caps the slow-growing, pointed filament ends in muscle and in erythrocytes. CapZ caps the fast-growing, barbed filament ends in striated muscle, whereas a newly discovered barbed end capping protein, adducin, may cap the barbed filament ends in erythrocytes. The mechanisms responsible for specifying the characteristic filament lengths in these systems are more elusive and may include strict control of the relative amounts of actin filament capping proteins and side-binding proteins, molecular templates (e.g. tropomyosin and nebulin) and/or verniers (e.g. tropomyosin).

  13. Structural changes accompanying phosphorylation of tarantula muscle myosin filaments

    PubMed Central

    1987-01-01

    Electron microscopy has been used to study the structural changes that occur in the myosin filaments of tarantula striated muscle when they are phosphorylated. Myosin filaments in muscle homogenates maintained in relaxing conditions (ATP, EGTA) are found to have nonphosphorylated regulatory light chains as shown by urea/glycerol gel electrophoresis and [32P]phosphate autoradiography. Negative staining reveals an ordered, helical arrangement of crossbridges in these filaments, in which the heads from axially neighboring myosin molecules appear to interact with each other. When the free Ca2+ concentration in a homogenate is raised to 10(-4) M, or when a Ca2+-insensitive myosin light chain kinase is added at low Ca2+ (10(-8) M), the regulatory light chains of myosin become rapidly phosphorylated. Phosphorylation is accompanied by potentiation of the actin activation of the myosin Mg- ATPase activity and by loss of order of the helical crossbridge arrangement characteristic of the relaxed filament. We suggest that in the relaxed state, when the regulatory light chains are not phosphorylated, the myosin heads are held down on the filament backbone by head-head interactions or by interactions of the heads with the filament backbone. Phosphorylation of the light chains may alter these interactions so that the crossbridges become more loosely associated with the filament backbone giving rise to the observed changes and facilitating crossbridge interaction with actin. PMID:2958483

  14. Probing the sliding interactions between bundled actin filaments

    NASA Astrophysics Data System (ADS)

    Ward, Andy; Dogic, Zvonimir

    2012-02-01

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

  15. Mechanism of interaction of Dictyostelium severin with actin filaments

    PubMed Central

    1982-01-01

    Severin, a 40,000-dalton protein from Dictyostelium that disassembles actin filaments in a Ca2+ -dependent manner, was purified 500-fold to greater than 99% homogeneity by modifications of the procedure reported by Brown, Yamamoto, and Spudich (1982. J. Cell Biol. 93:205-210). Severin has a Stokes radius of 29 A and consists of a single polypeptide chain. It contains a single methionyl and five cysteinyl residues. We studied the action of severin on actin filaments by electron microscopy, viscometry, sedimentation, nanosecond emission anisotropy, and fluorescence energy transfer spectroscopy. Nanosecond emission anisotropy of fluoresence-labeled severin shows that this protein changes its conformation on binding Ca2+. Actin filaments are rapidly fragmented on addition of severin and Ca2+, but severin does not interact with actin filaments in the absence of Ca2+. Fluorescence energy transfer measurements indicate that fragmentation of actin filaments by severin leads to a partial depolymerization (t1/2 approximately equal to 30 s). Depolymerization is followed by exchange of a limited number of subunits in the filament fragments with the disassembled actin pool (t1/2 approximately equal to 5 min). Disassembly and exchange are probably restricted to the ends of the filament fragments since only a few subunits in each fragment participate in the disassembly or exchange process. Steady state hydrolysis of ATP by actin in the presence of Ca2+-severin is maximal at an actin: severin molar ratio of approximately 10:1, which further supports the inference that subunit exchange is limited to the ends of actin filaments. The observation of sequential depolymerization and subunit exchange following the fragmentation of actin by severin suggests that severin may regulate site-specific disassembly and turnover of actin filament arrays in vivo. PMID:6897549

  16. A study of short wave instability on vortex filaments

    SciTech Connect

    Wang, Hong Yun

    1996-12-01

    The numerical stability and accuracy of the vortex method are studied. The effect of the ordinary differential equations (ODE) solver and of the time step on the numerical stability is analyzed. Various ODE solvers are compared and a best performer is chosen. A new constraint on the time step based on numerical stability is proposed and verified in numerical simulations. It is shown through numerical examples that empirical rules for selecting the spatial discretization obtained in simple test problems may not be extended to more general problems. The thin tube vortex filament method is applied to the problem of Widnall's instability on vortex rings. Numerical results different from previous calculations are presented and the source of the discrepancies is explained. The long time behavior of the unstable mode on thin vortex rings is simulated and analyzed. The short wave instability on vortex filaments is investigated both theoretically and numerically. It is shown that the short wave instability always occurs on co-rotating vortex filaments of fixed core structure. Furthermore when they are close to each other, vortex filaments produce short wave unstable modes which lead to wild stretching and folding. However, when the inter-filament distance is large in comparison with the core size of the filaments, unstable modes are bounded by a small fraction of the core size and the vortex filaments do not create hairpins nor wild stretching. These findings may explain the smooth behavior of the superfluid vortices. The formation of hairpin structures on numerical vortex filaments is investigated. It is shown that the formation of hairpin structures is independent of the ODE solver, of the time step and of other numerical parameters. The hairpin structures are primarily caused by short wave instability on co-rotating vortex filaments.

  17. Force Generation, Polymerization Dynamics and Nucleation of Actin Filaments

    NASA Astrophysics Data System (ADS)

    Wang, Ruizhe

    We study force generation and actin filament dynamics using stochastic and deterministic methods. First, we treat force generation of bundled actin filaments by polymerization via molecular-level stochastic simulations. In the widely-used Brownian Ratchet model, actin filaments grow freely whenever the tip-obstacle gap created by thermal fluctuation exceeds the monomer size. We name this model the Perfect Brownian Ratchet (PBR) model. In the PBR model, actin monomer diffusion is treated implicitly. We perform a series of simulations based on the PBR, in which obstacle motion is treated explicitly; in most previous studies, obstacle motion has been treated implicitly. We find that the cooperativity of filaments is generally weak in the PBR model, meaning that more filaments would grow more slowly given the same force per filament. Closed-form formulas are also developed, which match the simulation results. These portable and accurate formulas provide guidance for experiments and upper and lower bounds for theoretical analyses. We also studied a variation of the PBR, called the Diffusing Brownian Ratchet (DBR) model, in which both actin monomer and obstacle diffusion are treated explicitly. We find that the growth rate of multiple filaments is even lower, compared with that in PBR. This finding challenges the widely-accepted PBR assumption and suggests that pushing the study of actin dynamics down to the sub-nanometer level yields new insights. We subsequently used a rate equation approach to model the effect of local depletion of actin monomers on the nucleation of actin filaments on biomimetic beads, and how the effect is regulated by capping protein (CP). We find that near the bead surface, a higher CP concentration increases local actin concentration, which leads to an enhanced activities of actin filaments' nucleation. Our model analysis matches the experimental results and lends support to an important but undervalued hypothesis proposed by Carlier and

  18. Large-scale filaments associated with Milky Way spiral arms

    NASA Astrophysics Data System (ADS)

    Wang, Ke; Testi, Leonardo; Ginsburg, Adam; Walmsley, C. Malcolm; Molinari, Sergio; Schisano, Eugenio

    2015-07-01

    The ubiquity of filamentary structure at various scales throughout the Galaxy has triggered a renewed interest in their formation, evolution, and role in star formation. The largest filaments can reach up to Galactic scale as part of the spiral arm structure. However, such large-scale filaments are hard to identify systematically due to limitations in identifying methodology (i.e. as extinction features). We present a new approach to directly search for the largest, coldest, and densest filaments in the Galaxy, making use of sensitive Herschel Hi-GAL (Herschel Infrared Galactic Plane Survey) data complemented by spectral line cubes. We present a sample of the nine most prominent Herschel filaments, including six identified from a pilot search field plus three from outside the field. These filaments measure 37-99 pc long and 0.6-3.0 pc wide with masses (0.5-8.3) × 104 M⊙, and beam-averaged (28 arcsec, or 0.4-0.7 pc) peak H2 column densities of (1.7-9.3)× 1022 cm- 2. The bulk of the filaments are relatively cold (17-21 K), while some local clumps have a dust temperature up to 25-47 K. All the filaments are located within ≲60 pc from the Galactic mid-plane. Comparing the filaments to a recent spiral arm model incorporating the latest parallax measurements, we find that 7/9 of them reside within arms, but most are close to arm edges. These filaments are comparable in length to the Galactic scaleheight and therefore are not simply part of a grander turbulent cascade.

  19. Formation of interstellar filaments: the role of magnetic fields

    NASA Astrophysics Data System (ADS)

    Ntormousi, Evangelia; Hennebelle, Patrick

    2014-07-01

    The filamentary structure of interstellar matter and its potential link to star formation has been brought back into focus recently by high resolution observational surveys. The densest of these filaments host pre-stellar and star forming cores, so explaining their properties is tightly correlated to revealing the initial conditions for star formation. To that end, in this work we employ high-resolution, 3D MHD simulations performed with the AMR code RAMSES to investigate two filament formation mechanisms: turbulence and sheet fragmentation. The first series of simulations has as a particular aim to address the origin of the characteristic filament thickness found in observations. Starting from the hypothesis that diffusive processes are responsible, our numerical experiments consist of (driven or decaying) ideal and non-ideal MHD turbulence, at a resolution that greatly exceeds the reported 0.1pc thickness. The comparison points to ion-neutral friction as an excellent candidate for setting a characteristic scale. In this picture dense filaments are the diffusive end of the turbulent cascade, an interpretation with important implications for our understanding of the dynamical behavior of the ISM. A second series of simulations investigates filament formation by the fragmentation of supershells, a scenario inspired by the analytical work of Nagai (1998). We find a striking difference between hydrodynamical and MHD runs as in the first case the sheets fragment into small cores, while in the latter they produce large filaments. In addition though, we see that low-density filaments preferentially form along the dominant component of the magnetic field. In this scenario filaments are prominent features in the ISM, but their fate is still determined by the local magnetic field. A detailed comparison of the filament properties between the two runs is work in progress and will reveal the physical mechanisms responsible for shaping the ISM and setting the initial conditions

  20. Self-folding and aggregation of amyloid nanofibrils

    NASA Astrophysics Data System (ADS)

    Paparcone, Raffaella; Cranford, Steven W.; Buehler, Markus J.

    2011-04-01

    Amyloids are highly organized protein filaments, rich in β-sheet secondary structures that self-assemble to form dense plaques in brain tissues affected by severe neurodegenerative disorders (e.g. Alzheimer's Disease). Identified as natural functional materials in bacteria, in addition to their remarkable mechanical properties, amyloids have also been proposed as a platform for novel biomaterials in nanotechnology applications including nanowires, liquid crystals, scaffolds and thin films. Despite recent progress in understanding amyloid structure and behavior, the latent self-assembly mechanism and the underlying adhesion forces that drive the aggregation process remain poorly understood. On the basis of previous full atomistic simulations, here we report a simple coarse-grain model to analyze the competition between adhesive forces and elastic deformation of amyloid fibrils. We use simple model system to investigate self-assembly mechanisms of fibrils, focused on the formation of self-folded nanorackets and nanorings, and thereby address a critical issue in linking the biochemical (Angstrom) to micrometre scales relevant for larger-scale states of functional amyloid materials. We investigate the effect of varying the interfibril adhesion energy on the structure and stability of self-folded nanorackets and nanorings and demonstrate that these aggregated amyloid fibrils are stable in such states even when the fibril-fibril interaction is relatively weak, given that the constituting amyloid fibril length exceeds a critical fibril length-scale of several hundred nanometres. We further present a simple approach to directly determine the interfibril adhesion strength from geometric measures. In addition to providing insight into the physics of aggregation of amyloid fibrils our model enables the analysis of large-scale amyloid plaques and presents a new method for the estimation and engineering of the adhesive forces responsible of the self-assembly process of

  1. Self-folding and aggregation of amyloid nanofibrils.

    PubMed

    Paparcone, Raffaella; Cranford, Steven W; Buehler, Markus J

    2011-04-01

    Amyloids are highly organized protein filaments, rich in β-sheet secondary structures that self-assemble to form dense plaques in brain tissues affected by severe neurodegenerative disorders (e.g. Alzheimer's Disease). Identified as natural functional materials in bacteria, in addition to their remarkable mechanical properties, amyloids have also been proposed as a platform for novel biomaterials in nanotechnology applications including nanowires, liquid crystals, scaffolds and thin films. Despite recent progress in understanding amyloid structure and behavior, the latent self-assembly mechanism and the underlying adhesion forces that drive the aggregation process remain poorly understood. On the basis of previous full atomistic simulations, here we report a simple coarse-grain model to analyze the competition between adhesive forces and elastic deformation of amyloid fibrils. We use simple model system to investigate self-assembly mechanisms of fibrils, focused on the formation of self-folded nanorackets and nanorings, and thereby address a critical issue in linking the biochemical (Angstrom) to micrometre scales relevant for larger-scale states of functional amyloid materials. We investigate the effect of varying the interfibril adhesion energy on the structure and stability of self-folded nanorackets and nanorings and demonstrate that these aggregated amyloid fibrils are stable in such states even when the fibril-fibril interaction is relatively weak, given that the constituting amyloid fibril length exceeds a critical fibril length-scale of several hundred nanometres. We further present a simple approach to directly determine the interfibril adhesion strength from geometric measures. In addition to providing insight into the physics of aggregation of amyloid fibrils our model enables the analysis of large-scale amyloid plaques and presents a new method for the estimation and engineering of the adhesive forces responsible of the self-assembly process of amyloid

  2. Organic Acid Production by Filamentous Fungi

    SciTech Connect

    Magnuson, Jon K.; Lasure, Linda L.

    2004-05-03

    Many of the commercial production processes for organic acids are excellent examples of fungal biotechnology. However, unlike penicillin, the organic acids have had a less visible impact on human well-being. Indeed, organic acid fermentations are often not even identified as fungal bioprocesses, having been overshadowed by the successful deployment of the β-lactam processes. Yet, in terms of productivity, fungal organic acid processes may be the best examples of all. For example, commercial processes using Aspergillus niger in aerated stirred-tank-reactors can convert glucose to citric acid with greater than 80% efficiency and at final concentrations in hundreds of grams per liter. Surprisingly, this phenomenal productivity has been the object of relatively few research programs. Perhaps a greater understanding of this extraordinary capacity of filamentous fungi to produce organic acids in high concentrations will allow greater exploitation of these organisms via application of new knowledge in this era of genomics-based biotechnology. In this chapter, we will explore the biochemistry and modern genetic aspects of the current and potential commercial processes for making organic acids. The organisms involved, with a few exceptions, are filamentous fungi, and this review is limited to that group. Although yeasts including Saccharomyces cerevisiae, species of Rhodotorula, Pichia, and Hansenula are important organisms in fungal biotechnology, they have not been significant for commercial organic acid production, with one exception. The yeast, Yarrowia lipolytica, and related yeast species, may be in use commercially to produce citric acid (Lopez-Garcia, 2002). Furthermore, in the near future engineered yeasts may provide new commercial processes to make lactic acid (Porro, Bianchi, Ranzi, Frontali, Vai, Winkler, & Alberghina, 2002). This chapter is divided into two parts. The first contains a review of the commercial aspects of current and potential large

  3. HIERARCHICAL FRAGMENTATION OF THE ORION MOLECULAR FILAMENTS

    SciTech Connect

    Takahashi, Satoko; Ho, Paul T. P.; Su, Yu-Nung; Teixeira, Paula S.; Zapata, Luis A.

    2013-01-20

    We present a high angular resolution map of the 850 {mu}m continuum emission of the Orion Molecular Cloud-3 (OMC 3) obtained with the Submillimeter Array (SMA); the map is a mosaic of 85 pointings covering an approximate area of 6.'5 Multiplication-Sign 2.'0 (0.88 Multiplication-Sign 0.27 pc). We detect 12 spatially resolved continuum sources, each with an H{sub 2} mass between 0.3-5.7 M {sub Sun} and a projected source size between 1400-8200 AU. All the detected sources are on the filamentary main ridge (n{sub H{sub 2}}{>=}10{sup 6} cm{sup -3}), and analysis based on the Jeans theorem suggests that they are most likely gravitationally unstable. Comparison of multi-wavelength data sets indicates that of the continuum sources, 6/12 (50%) are associated with molecular outflows, 8/12 (67%) are associated with infrared sources, and 3/12 (25%) are associated with ionized jets. The evolutionary status of these sources ranges from prestellar cores to protostar phase, confirming that OMC-3 is an active region with ongoing embedded star formation. We detect quasi-periodical separations between the OMC-3 sources of Almost-Equal-To 17''/0.035 pc. This spatial distribution is part of a large hierarchical structure that also includes fragmentation scales of giant molecular cloud ( Almost-Equal-To 35 pc), large-scale clumps ( Almost-Equal-To 1.3 pc), and small-scale clumps ( Almost-Equal-To 0.3 pc), suggesting that hierarchical fragmentation operates within the Orion A molecular cloud. The fragmentation spacings are roughly consistent with the thermal fragmentation length in large-scale clumps, while for small-scale cores it is smaller than the local fragmentation length. These smaller spacings observed with the SMA can be explained by either a helical magnetic field, cloud rotation, or/and global filament collapse. Finally, possible evidence for sequential fragmentation is suggested in the northern part of the OMC-3 filament.

  4. Footpoint detection and mass-motion in chromospheric filaments

    NASA Astrophysics Data System (ADS)

    V, Aparna; Hardersen, P. S.; Martin, S. F.

    2013-07-01

    A quiescent region on the Sun containing three filaments is used to study the properties of mass motion. This study determines if the footpoints or end-points of the filaments are the locations from where mass gets injected into the filaments. Several hypotheses have been put forth in the past to determine how a filament acquires mass. Trapping of coronal mass in the filament channel due to condensation (Martin, 1996) and injection of mass into the filaments during magnetic reconnection (Priest, et al., 1995) are some of the speculations. This study looks for indications for injection of mass via chromospheric footpoints. The data consists of blue (Hα-0.5 Å) and red (Hα+0.5 Å) wing high resolution Hα images of the W29N37 region of the Sun taken on Oct 30, 2010, from 1200 - 1600 UT. The Dutch Open Telescope was used to obtain the data. The images are aligned and animated to see Doppler motion in the fibrils. Smaller fibrils merge to form longer ones; barbs appear and disappear in one of the long filaments and is seen moving along the length of the filament. A region with no typical filament-like absorption feature is observed to be continuously receiving mass. Fibrils appear to be converging from opposite sides along what appears to be a neutral line; mass motion is seen in these fibrils as well. An eruption occurs in a region of fibrils lumped together at the end of the first hour (1300 UT) followed by plage brightening at 1430 UT near one of the filament regions. Helioviewer (Panasenco, et al., 2011) is used for aligning the images; GIMP is used for precision alignment and animation. Each frame in the sequence is studied carefully to note changes in the filament regions. The footpoints of the filaments are determined by the changes observed in the position of the filament ‘legs’ in each frame. Variations in the magnetic polarity corresponding to changes observed in the chromosphere are analyzed using HMI magnetograms. Bright and dark points on the

  5. Spin-Glass Model Governs Laser Multiple Filamentation.

    PubMed

    Ettoumi, W; Kasparian, J; Wolf, J-P

    2015-07-17

    We show that multiple filamentation patterns in high-power laser beams can be described by means of two statistical physics concepts, namely, self-similarity of the patterns over two nested scales and nearest-neighbor interactions of classical rotators. The resulting lattice spin model perfectly reproduces the evolution of intense laser pulses as simulated by the nonlinear Schrödinger equation, shedding new light on multiple filamentation. As a side benefit, this approach drastically reduces the computing time by 2 orders of magnitude as compared to the standard simulation methods of laser filamentation.

  6. Structural design criteria for filament-wound composite shells

    NASA Technical Reports Server (NTRS)

    Hahn, H. T.; Jensen, D. W.; Claus, S. J.; Pai, S. P.; Hipp, P. A.

    1994-01-01

    Advanced composite cylinders, manufactured by filament winding, provide a cost effective solution to many present structural applications; however, the compressive performance of filament-wound cylinders is lower than comparable shells fabricated from unidirectional tape. The objective of this study was to determine the cause of this reduction in thin filament-wound cylinders by relating the manufacturing procedures to the quality of the cylinder and to its compressive performance. The experiments on cylinder buckling were complemented by eigenvalue buckling analysis using a detailed geometric model in a finite element analysis. The applicability of classical buckling analyses was also investigated as a design tool.

  7. NSTX Filament Preionization and Glow Discharge Cleaning Systems

    SciTech Connect

    Kugel, H. W.; Blanchard, W.; D'Amico, G.; Gernhardt, R.; Provost, T.

    1999-11-01

    Initial NSTX GDC experiments were performed with one moveable anode and a biased filament preionization system that allowed D2 and He Glow Discharge breakdowns at the actual operating pressure, voltage and current. The biased filament system was also operated continuously during ohmic operations, and used to reduce volt-sec consumption for February 1999 plasma discharges up to 280 KA. An upgraded system has been installed with 2 fixed wall anodes and 3 biased filaments; 2 on the mid-plane and one in the divertor region; all separately controllable remotely using a PLC system. Recent applications include assisting in preionization for 800 KA plasma discharges.

  8. Fractal Aggregates in Tennis Ball Systems

    ERIC Educational Resources Information Center

    Sabin, J.; Bandin, M.; Prieto, G.; Sarmiento, F.

    2009-01-01

    We present a new practical exercise to explain the mechanisms of aggregation of some colloids which are otherwise not easy to understand. We have used tennis balls to simulate, in a visual way, the aggregation of colloids under reaction-limited colloid aggregation (RLCA) and diffusion-limited colloid aggregation (DLCA) regimes. We have used the…

  9. Thermodynamic modeling of asphaltene aggregation.

    PubMed

    Rogel, E

    2004-02-03

    A new molecular thermodynamic model for the description of the aggregation behavior of asphaltenes in different solvents is presented. This new model is relatively simple and strictly predictive and does not use any experimental information from asphaltene solutions. In this model, asphaltene aggregates are described as composed of an aromatic core formed by stacked aromatic sheets surrounded by aliphatic chains. The proposed model qualitatively predicts the asphaltene aggregation behavior in a series of different solvents. In particular, the experimental trends observed for the variation of aggregate size with (1) asphaltene molecular characteristics (condensation index, aromaticity, and chain length), (2) asphaltene concentration, (3) solvent characteristics, and (4) temperature have been successfully reproduced by the proposed model. The model also provides a plausible explanation for the existence or absence of a critical micelle concentration (cmc) for asphaltene solutions. Specifically, the model predicted that the asphaltenes with low aromaticities and low aromatic condensations do not exhibit cmc behavior. Finally, the obtained results clearly support the classical model for asphaltene aggregates.

  10. Spatial aggregation: Language and applications

    SciTech Connect

    Bailey-Kellogg, C.; Zhao, F.; Yip, K.

    1996-12-31

    Spatial aggregation is a framework for organizing computations around image-like, analogue representations of physical processes in data interpretation and control tasks. It conceptualizes common computational structures in a class of implemented problem solvers for difficult scientific and engineering problems. It comprises a mechanism, a language, and a programming style. The spatial aggregation mechanism transforms a numerical input field to successively higher-level descriptions by applying a small, identical set of operators to each layer given a metric, neighborhood relation and equivalence relation. This paper describes the spatial aggregation language and its applications. The spatial aggregation language provides two abstract data types - neighborhood graph and field - and a set of interface operators for constructing the transformations of the field, together with a library of component implementations from which a user can mix-and-match and specialize for a particular application. The language allows users to isolate and express important computational ideas in different problem domains while hiding low-level details. We illustrate the use of the language with examples ranging from trajectory grouping in dynamics interpretation to region growing in image analysis. Programs for these different task domains can be written in a modular, concise fashion in the spatial aggregation language.

  11. Leaching behaviour of synthetic aggregates.

    PubMed

    van der Sloot, H A; Hoede, D; Cresswell, D J; Barton, J R

    2001-01-01

    In the framework of EU project "Utilising innovative kiln technology to recycle waste into synthetic aggregate" (BRST-CT98-5234), the leaching behaviour of synthetic aggregates has been studied to assess its environmental compatibility in the various stages of its use. Since the conditions are very different for the different uses, the assessment calls for a variety of different leaching conditions. The pH dependence test is used to cover important differences in pH environment to which the materials are exposed to as well as for an assessment of the buffering capacity of the material. Synthetic aggregate features a low buffer capacity, which makes it sensitive to externally imposed pH conditions. Utilisation and storage exposed to acidic conditions needs to be avoided. The results of the pH dependence test and column leaching test are mutually consistent. The CEN TC 154 method appears to provide systematically low values due to the arbitrary selection of test conditions. Synthetic aggregate studied to date will not adversely affect the concrete in its service life. The main issue for aggregate use is the recycling and the "end of life" condition, when the material becomes construction debris. Not metals, but oxyanions, such as Cr VI and Mo are most relevant under these conditions. A concise test has been applied to assess crucial aspects of leaching for different production mixes.

  12. Novel insights into amylin aggregation

    PubMed Central

    Pillay, Karen; Govender, Patrick

    2014-01-01

    Amylin is a peptide that aggregates into species that are toxic to pancreatic beta cells, leading to type II diabetes. This study has for the first time quantified amylin association and dissociation kinetics (association constant (ka) = 28.7 ± 5.1 L mol−1 s−1 and dissociation constant (kd) = 2.8 ± 0.6 ×10−4 s−1) using surface plasmon resonance (SPR). Thus far, techniques used for the sizing of amylin aggregates do not cater for the real-time monitoring of unconstrained amylin in solution. In this regard we evaluated recently innovated nanoparticle tracking analysis (NTA). In addition, both SPR and NTA were used to study the effect of previously synthesized amylin derivatives on amylin aggregation and to evaluate their potential as a cell-free system for screening potential inhibitors of amylin-mediated cytotoxicity. Results obtained from NTA highlighted a predominance of 100–300 nm amylin aggregates and correlation to previously published cytotoxicity results suggests the toxic species of amylin to be 200–300 nm in size. The results seem to indicate that NTA has potential as a new technique to monitor the aggregation potential of amyloid peptides in solution and also to screen potential inhibitors of amylin-mediated cytotoxicity. PMID:26019498

  13. Aggregated Recommendation through Random Forests

    PubMed Central

    2014-01-01

    Aggregated recommendation refers to the process of suggesting one kind of items to a group of users. Compared to user-oriented or item-oriented approaches, it is more general and, therefore, more appropriate for cold-start recommendation. In this paper, we propose a random forest approach to create aggregated recommender systems. The approach is used to predict the rating of a group of users to a kind of items. In the preprocessing stage, we merge user, item, and rating information to construct an aggregated decision table, where rating information serves as the decision attribute. We also model the data conversion process corresponding to the new user, new item, and both new problems. In the training stage, a forest is built for the aggregated training set, where each leaf is assigned a distribution of discrete rating. In the testing stage, we present four predicting approaches to compute evaluation values based on the distribution of each tree. Experiments results on the well-known MovieLens dataset show that the aggregated approach maintains an acceptable level of accuracy. PMID:25180204

  14. Biofilm assembly becomes crystal clear – filamentous bacteriophage organize the Pseudomonas aeruginosa biofilm matrix into a liquid crystal

    PubMed Central

    Secor, Patrick R.; Jennings, Laura K.; Michaels, Lia A.; Sweere, Johanna M.; Singh, Pradeep K.; Parks, William C.; Bollyky, Paul L.

    2015-01-01

    Pseudomonas aeruginosa is an opportunistic bacterial pathogen associated with many types of chronic infection. At sites of chronic infection, such as the airways of people with cystic fibrosis (CF), P. aeruginosa forms biofilm-like aggregates. These are clusters of bacterial cells encased in a polymer-rich matrix that shields bacteria from environmental stresses and antibiotic treatment. When P. aeruginosa forms a biofilm, large amounts of filamentous Pf bacteriophage (phage) are produced. Unlike most phage that typically lyse and kill their bacterial hosts, filamentous phage of the genus Inovirus, which includes Pf phage, often do not, and instead are continuously extruded from the bacteria. Here, we discuss the implications of the accumulation of filamentous Pf phage in the biofilm matrix, where they interact with matrix polymers to organize the biofilm into a highly ordered liquid crystal. This structural configuration promotes bacterial adhesion, desiccation survival, and antibiotic tolerance – all features typically associated with biofilms. We propose that Pf phage make structural contributions to P. aeruginosa biofilms and that this constitutes a novel form of symbiosis between bacteria and bacteriophage.

  15. Characterization of erythrose reductases from filamentous fungi

    PubMed Central

    2013-01-01

    Proteins with putative erythrose reductase activity have been identified in the filamentous fungi Trichoderma reesei, Aspergillus niger, and Fusarium graminearum by in silico analysis. The proteins found in T. reesei and A. niger had earlier been characterized as glycerol dehydrogenase and aldehyde reductase, respectively. Corresponding genes from all three fungi were cloned, heterologously expressed in Escherichia coli, and purified. Subsequently, they were used to establish optimal enzyme assay conditions. All three enzymes strictly require NADPH as cofactor, whereas with NADH no activity could be observed. The enzymatic characterization of the three enzymes using ten substrates revealed high substrate specificity and activity with D-erythrose and D-threose. The enzymes from T. reesei and A. niger herein showed comparable activities, whereas the one from F. graminearum reached only about a tenth of it for all tested substrates. In order to proof in vivo the proposed enzyme function, we overexpressed the erythrose reductase-encoding gene in T. reesei. An increased production of erythritol by the recombinant strain compared to the parental strain could be detected. PMID:23924507

  16. Equilibrium theory for braided elastic filaments

    NASA Astrophysics Data System (ADS)

    van der Heijden, Gert

    Motivated by supercoiling of DNA and other filamentous structures, we formulate a theory for equilibria of 2-braids, i.e., structures formed by two elastic rods winding around each other in continuous contact and subject to a local interstrand interaction. Unlike in previous work no assumption is made on the shape of the contact curve. Rather, this shape is found as part of the solution. The theory is developed in terms of a moving frame of directors attached to one of the strands with one of the directors pointing to the position of the other strand. The constant-distance constraint is automatically satisfied by the introduction of what we call braid strains. The price we pay is that the potential energy involves arclength derivatives of these strains, thus giving rise to a second-order variational problem. The Euler-Lagrange equations for this problem give balance equations for the overall braid force and moment referred to the moving frame as well as differential equations that can be interpreted as effective constitutive relations encoding the effect that the second strand has on the first as the braid deforms under the action of end loads. Simple analytical cases are discussed first and used as starting solutions in parameter continuation studies to compute classes of both open and closed (linked or knotted) braid solutions.

  17. The Apis mellifera Filamentous Virus Genome.

    PubMed

    Gauthier, Laurent; Cornman, Scott; Hartmann, Ulrike; Cousserans, François; Evans, Jay D; de Miranda, Joachim R; Neumann, Peter

    2015-07-09

    A complete reference genome of the Apis mellifera Filamentous virus (AmFV) was determined using Illumina Hiseq sequencing. The AmFV genome is a double stranded DNA molecule of approximately 498,500 nucleotides with a GC content of 50.8%. It encompasses 247 non-overlapping open reading frames (ORFs), equally distributed on both strands, which cover 65% of the genome. While most of the ORFs lacked threshold sequence alignments to reference protein databases, twenty-eight were found to display significant homologies with proteins present in other large double stranded DNA viruses. Remarkably, 13 ORFs had strong similarity with typical baculovirus domains such as PIFs (per os infectivity factor genes: pif-1, pif-2, pif-3 and p74) and BRO (Baculovirus Repeated Open Reading Frame). The putative AmFV DNA polymerase is of type B, but is only distantly related to those of the baculoviruses. The ORFs encoding proteins involved in nucleotide metabolism had the highest percent identity to viral proteins in GenBank. Other notable features include the presence of several collagen-like, chitin-binding, kinesin and pacifastin domains. Due to the large size of the AmFV genome and the inconsistent affiliation with other large double stranded DNA virus families infecting invertebrates, AmFV may belong to a new virus family.

  18. Molecular phylogeny of metazoan intermediate filament proteins.

    PubMed

    Erber, A; Riemer, D; Bovenschulte, M; Weber, K

    1998-12-01

    We have cloned cytoplasmic intermediate filament (IF) proteins from a large number of invertebrate phyla using cDNA probes, the monoclonal antibody IFA, peptide sequence information, and various RT-PCR procedures. Novel IF protein sequences reported here include the urochordata and nine protostomic phyla, i.e., Annelida, Brachiopoda, Chaetognatha, Echiura, Nematomorpha, Nemertea, Platyhelminthes, Phoronida, and Sipuncula. Taken together with the wealth of data on IF proteins of vertebrates and the results on IF proteins of Cephalochordata, Mollusca, Annelida, and Nematoda, two IF prototypes emerge. The L-type, which includes 35 sequences from 11 protostomic phyla, shares with the nuclear lamins the long version of the coil 1b subdomain and, in most cases, a homology segment of some 120 residues in the carboxyterminal tail domain. The S-type, which includes all four subfamilies (types I to IV) of vertebrate IF proteins, lacks 42 residues in the coil 1b subdomain and the carboxyterminal lamin homology segment. Since IF proteins from all three phyla of the chordates have the 42-residue deletion, this deletion arose in a progenitor prior to the divergence of the chordates into the urochordate, cephalochordate, and vertebrate lineages, possibly already at the origin of the deuterostomic branch. Four phyla recently placed into the protostomia on grounds of their 18S rDNA sequences (Brachiopoda, Nemertea, Phoronida, and Platyhelminthes) show IF proteins of the L-type and fit by sequence identity criteria into the lophotrochozoic branch of the protostomia.

  19. Tubular filamentation for laser material processing

    PubMed Central

    Xie, Chen; Jukna, Vytautas; Milián, Carles; Giust, Remo; Ouadghiri-Idrissi, Ismail; Itina, Tatiana; Dudley, John M.; Couairon, Arnaud; Courvoisier, Francois

    2015-01-01

    An open challenge in the important field of femtosecond laser material processing is the controlled internal structuring of dielectric materials. Although the availability of high energy high repetition rate femtosecond lasers has led to many advances in this field, writing structures within transparent dielectrics at intensities exceeding 1013 W/cm2 has remained difficult as it is associated with significant nonlinear spatial distortion. This letter reports the existence of a new propagation regime for femtosecond pulses at high power that overcomes this challenge, associated with the generation of a hollow uniform and intense light tube that remains propagation invariant even at intensities associated with dense plasma formation. This regime is seeded from higher order nondiffracting Bessel beams, which carry an optical vortex charge. Numerical simulations are quantitatively confirmed by experiments where a novel experimental approach allows direct imaging of the 3D fluence distribution within transparent solids. We also analyze the transitions to other propagation regimes in near and far fields. We demonstrate how the generation of plasma in this tubular geometry can lead to applications in ultrafast laser material processing in terms of single shot index writing, and discuss how it opens important perspectives for material compression and filamentation guiding in atmosphere. PMID:25753215

  20. Processing parameters for thermoplastic filament winding

    NASA Astrophysics Data System (ADS)

    Colton, J.; Leach, D.

    The consolidation pressure and winding speed for thermoplastic filament winding were studied. Thermoplastic composite parts were manufactured from tape prepreg (APC-2); powder-coated, semiconsolidated towpreg; and commingled fiber towpeg. The material used was carbon fiber (AS-4) (60 vol pct) in a PEEK matrix. The parts made were open-ended cylinders of the three materials, 177.8 mmID, 228.6 mm long, 17 plies thick with a 0 deg lay-up angle; and rings, 50 plies of APC-2 thick, 6.35 mm wide (one strip wide), 177.8 mm ID, and a lay-up of 0 deg. Their quality was determined by surface finish and void percentage. The tubes made from APC-2 appeared to have the best quality of the three prepregs. For the rings, the speed of lay down had a significant effect on both the final width of the parts and on the percentage of voids. The pressure of the roller had a significant effect on the final widths at a 99 percent confidence level, but only a significant effect on the percentage of voids at a 95 percent confidence level.

  1. Customer Aggregation: An Opportunity for Green Power?

    SciTech Connect

    Holt, E.; Bird, L.

    2001-02-26

    We undertook research into the experience of aggregation groups to determine whether customer aggregation offers an opportunity to bring green power choices to more customers. The objectives of this report, therefore, are to (1) identify the different types of aggregation that are occurring today, (2) learn whether aggregation offers an opportunity to advance sales of green power, and (3) share these concepts and approaches with potential aggregators and green power advocates.

  2. Equilibrium structure of ferrofluid aggregates.

    PubMed

    Yoon, Mina; Tománek, David

    2010-11-17

    We study the equilibrium structure of large but finite aggregates of magnetic dipoles, representing a colloidal suspension of magnetite particles in a ferrofluid. With increasing system size, the structural motif evolves from chains and rings to multi-chain and multi-ring assemblies. Very large systems form single- and multi-wall coils, tubes and scrolls. These structural changes result from a competition between various energy terms, which can be approximated analytically within a continuum model. We also study the effect of external parameters such as magnetic field on the relative stability of these structures. Our results may give insight into experimental data obtained during solidification of ferrofluid aggregates at temperatures where thermal fluctuations become negligible in comparison to inter-particle interactions. These data may also help to experimentally control the aggregation of magnetic particles.

  3. Equilibrium structure of ferrofluid aggregates

    SciTech Connect

    Yoon, Mina; Tomanek, David

    2010-01-01

    We study the equilibrium structure of large but finite aggregates of magnetic dipoles, representing a colloidal suspension of magnetite particles in a ferrofluid. With increasing system size, the structural motif evolves from chains and rings to multi-chain and multi-ring assemblies. Very large systems form single- and multi-wall coils, tubes and scrolls. These structural changes result from a competition between various energy terms, which can be approximated analytically within a continuum model. We also study the effect of external parameters such as magnetic field on the relative stability of these structures. Our results may give insight into experimental data obtained during solidification of ferrofluid aggregates at temperatures where thermal fluctuations become negligible in comparison to inter-particle interactions. These data may also help to experimentally control the aggregation of magnetic particles.

  4. Distribution of algal aggregates under summer sea ice in the Central Arctic.

    PubMed

    Katlein, Christian; Fernández-Méndez, Mar; Wenzhöfer, Frank; Nicolaus, Marcel

    The sea ice cover of the Arctic Ocean has changed dramatically in the last decades, and the resulting consequences for the sea-ice-associated ecosystem remain difficult to assess. Algal aggregates underneath sea ice are of great importance for the ice-associated ecosystem and the pelagic-benthic coupling. However, the frequency and distribution of their occurrence is not well quantified. During the IceArc expedition (ARK-27/3) of RV Polarstern in late summer 2012, we observed different types of algal aggregates floating underneath various ice types in the Central Arctic basins. We investigated the spatial distribution of ice algal aggregates and quantified their biomass, using under-ice image surveys obtained by an upward-looking camera on a remotely operated vehicle. On basin scale, filamentous aggregates of Melosira arctica are more frequently found in the inner part of the Central Arctic pack ice, while rounded aggregates mainly formed by pennate diatoms are found closer to the ice edge, under melting sea ice. On the scale of an ice floe, the distribution of algal aggregates in late summer is mainly regulated by the topography of the ice underside, with aggregates accumulating in dome-shaped structures and at the edges of pressure ridges. The average biomass of the aggregates from our sites and season was 0.1-6.0 mg C m(-2). However, depending on the approach used, differences in orders of magnitude for biomass estimates may occur. This highlights the difficulties of upscaling observations and comparing results from surveys conducted using different methods or on different spatial scales.

  5. A specialist's audit of aggregated occurrence records: An 'aggregator's' perspective.

    PubMed

    Belbin, Lee; Daly, Joanne; Hirsch, Tim; Hobern, Donald; Salle, John La

    2013-01-01

    A recent ZooKeys' paper (Mesibov, 2013: http://www.pensoft.net/journal_home_page.php?journal_id=1&page=article&SESID=df7bcb35b02603283dcb83ee0e0af0c9&type=show&article_id=5111) has highlighted data quality issues in aggregated data sets, but did not provide a realistic way to address these issues. This paper provides an aggregator's perspective including ways that the whole community can help to address data quality issues. The establishment of GBIF and national nodes (national aggregators) such as the Atlas of Living Australia (ALA) have integrated and exposed a huge diversity of biological observations along with many associated issues. Much of the admirable work by Mesibov (2013) was enabled by having the data exposed. Data quality, one of the highest priorities for GBIF, the national nodes and other aggregators, depends on both automatic methods and community experts to detect and correct data issues. Not all issues can however be automatically detected or corrected, so community assistance is needed to help improve the quality of exposed biological data. We do need to improve the infrastructure and associated processes to more easily identify data issues and document all changes to ensure a full record is permanently and publicly available.

  6. Environmentalism and natural aggregate mining

    USGS Publications Warehouse

    Drew, L.J.; Langer, W.H.; Sachs, J.S.

    2002-01-01

    Sustaining a developed economy and expanding a developing one require the use of large volumes of natural aggregate. Almost all human activity (commercial, recreational, or leisure) is transacted in or on facilities constructed from natural aggregate. In our urban and suburban worlds, we are almost totally dependent on supplies of water collected behind dams and transported through aqueducts made from concrete. Natural aggregate is essential to the facilities that produce energy-hydroelectric dams and coal-fired powerplants. Ironically, the utility created for mankind by the use of natural aggregate is rarely compared favorably with the environmental impacts of mining it. Instead, the empty quarries and pits are seen as large negative environmental consequences. At the root of this disassociation is the philosophy of environmentalism, which flavors our perceptions of the excavation, processing, and distribution of natural aggregate. The two end-member ideas in this philosophy are ecocentrism and anthropocentrism. Ecocentrism takes the position that the natural world is a organism whose arteries are the rivers-their flow must not be altered. The soil is another vital organ and must not be covered with concrete and asphalt. The motto of the ecocentrist is "man must live more lightly on the land." The anthropocentrist wants clean water and air and an uncluttered landscape for human use. Mining is allowed and even encouraged, but dust and noise from quarry and pit operations must be minimized. The large volume of truck traffic is viewed as a real menace to human life and should be regulated and isolated. The environmental problems that the producers of natural aggregate (crushed stone and sand and gravel) face today are mostly difficult social and political concerns associated with the large holes dug in the ground and the large volume of heavy truck traffic associated with quarry and pit operations. These concerns have increased in recent years as society's demand for

  7. Hydrodynamic behavior of fractal aggregates

    NASA Astrophysics Data System (ADS)

    Wiltzius, Pierre

    1987-02-01

    Measurements of the radius of gyration RG and the hydrodynamic radius RH of colloidal silica aggregates are reported. These aggregates have fractal geometry and RH is proportional to RG for 500 Å<=RH<=7000 Å, with a ratio RH/RG=0.72+/-0.02. The results are compared with predictions for macromolecules of various shapes. The proportionality of the two radii can be understood with use of the pair correlation function of fractal objects and hydrodynamic interactions on the Oseen level. The value of the ratio remains to be explained.

  8. Filamentous Phages As a Model System in Soft Matter Physics

    PubMed Central

    Dogic, Zvonimir

    2016-01-01

    Filamentous phages have unique physical properties, such as uniform particle lengths, that are not found in other model systems of rod-like colloidal particles. Consequently, suspensions of such phages provided powerful model systems that have advanced our understanding of soft matter physics in general and liquid crystals in particular. We described some of these advances. In particular we briefly summarize how suspensions of filamentous phages have provided valuable insight into the field of colloidal liquid crystals. We also describe recent experiments on filamentous phages that have elucidated a robust pathway for assembly of 2D membrane-like materials. Finally, we outline unique structural properties of filamentous phages that have so far remained largely unexplored yet have the potential to further advance soft matter physics and material science. PMID:27446051

  9. Filamentation instability of magnetosonic waves in the solar wind environment

    NASA Technical Reports Server (NTRS)

    Kuo, S. P.; Lee, M. C.

    1989-01-01

    Intense magnetosonic waves, originally propagating at the right angle with the interplanetary magnetic field, can excite a purely growing mode along the interplanetary magnetic field together with two symmetric magnetosonic sidebands propagating obliquely across the magnetic field. This instability process leads to the filamentation of the magnetosonic pump waves. These two excited magnetosonic sideband modes propagate together perpendicularly across the magnetic field and, meanwhile, form a standing wave pattern along the magnetic field. The thresholds of this filamentation instability can be exceeded in the solar wind environment. It is predicted that the density fluctuations produced by the filamentation instability along the interplanetary magnetic field have wavelengths greater than, at least, a few earth radii. The polarization of the obliquely propagating magnetosonic waves excited by the filamentation instability is determined by the characteristics of the magnetosonic pump waves and the environmental plasmas.

  10. Collective alignment of polar filaments by molecular motors.

    PubMed

    Ziebert, F; Vershinin, M; Gross, S P; Aranson, I S

    2009-04-01

    We study the alignment of polar biofilaments, such as microtubules and actin, subject to the action of multiple molecular motors attached simultaneously to more than one filament. Focusing on a paradigm model of only two filaments interacting with multiple motors, we were able to investigate in detail the alignment dynamics. While almost no alignment occurs in the case of a single motor, the filaments become rapidly aligned due to the collective action of the motors. Our analysis shows that the alignment time is governed by the number of bound motors and the magnitude of the motors' stepping fluctuations. We predict that the time scale of alignment is in the order of seconds, much faster than that reported for passive crosslink-induced bundling. In vitro experiments on the alignment of microtubules by multiple-motor covered beads are in qualitative agreement. We also discuss another mode of fast alignment of filaments, namely the cooperation between motors and passive crosslinks.

  11. Evaluation of filamentous green algae as feedstocks for biofuel production.

    PubMed

    Zhang, Wei; Zhao, Yonggang; Cui, Binjie; Wang, Hui; Liu, Tianzhong

    2016-11-01

    Compared with unicellular microalgae, filamentous algae have high resistance to grazer-predation and low-cost recovery in large-scale production. Green algae, as the most diverse group of algae, included numerous filamentous genera and species. In this study, records of filamentous genera and species in green algae were firstly censused and classified. Then, seven filamentous strains subordinated in different genera were cultivated in bubbled-column to investigate their growth rate and energy molecular (lipid and starch) capacity. Four strains including Stigeoclonium sp., Oedogonium nodulosum, Hormidium sp. and Zygnema extenue were screened out due to their robust growth. And they all could accumulate triacylglycerols and starch in their biomass, but with different capacity. After nitrogen starvation, Hormidium sp. and Oedogonium nodulosum respectively exhibited high capacity of lipid (45.38% in dry weight) and starch (46.19% in dry weight) accumulation, which could be of high potential as feedstocks for biodiesel and bioethanol production.

  12. Filamentous Phages As a Model System in Soft Matter Physics.

    PubMed

    Dogic, Zvonimir

    2016-01-01

    Filamentous phages have unique physical properties, such as uniform particle lengths, that are not found in other model systems of rod-like colloidal particles. Consequently, suspensions of such phages provided powerful model systems that have advanced our understanding of soft matter physics in general and liquid crystals in particular. We described some of these advances. In particular we briefly summarize how suspensions of filamentous phages have provided valuable insight into the field of colloidal liquid crystals. We also describe recent experiments on filamentous phages that have elucidated a robust pathway for assembly of 2D membrane-like materials. Finally, we outline unique structural properties of filamentous phages that have so far remained largely unexplored yet have the potential to further advance soft matter physics and material science.

  13. Slow X-ray bursts and flares with filament disruption

    NASA Technical Reports Server (NTRS)

    Roy, J.-R.; Tang, F.

    1975-01-01

    The data from OGO-5 and OSO-7 X-ray experiments have been compared with optical data from six chromospheric flares with filament disruption associated with slow thermal X-ray bursts. Filament activation accompanied by a slight X-ray enhancement precedes the first evidence of H-alpha flare by a few minutes. Rapid increase of the soft X-ray flux accompanies the phase of fastest expansion of the filament. Plateau or slow decay phases in the X-ray flux are associated with slowing and termination of filament expansion. The soft X-ray flux increases as F approaches (A + Bh)h, where h is the height of the disrupted prominence at any given time and A and B are constants. We suggest that the soft X-ray emission originates from a growing shell of roughly constant thickness of high-temperature plasma due to the compression of the coronal gas by the expanding prominence.

  14. Desmin filaments studied by quasi-elastic light scattering.

    PubMed Central

    Hohenadl, M; Storz, T; Kirpal, H; Kroy, K; Merkel, R

    1999-01-01

    We studied polymers of desmin, a muscle-specific type III intermediate filament protein, using quasi-elastic light scattering. Desmin was purified from chicken gizzard. Polymerization was induced either by 2 mM MgCl(2) or 150 mM NaCl. The polymer solutions were in the semidilute regime. We concluded that the persistence length of the filaments is between 0.1 and 1 microm. In all cases, we found a hydrodynamic diameter of desmin filaments of 16-18 nm. The filament dynamics exhibits a characteristic frequency in the sense that correlation functions measured on one sample but at different scattering vectors collapse onto a single master curve when time is normalized by the experimentally determined initial decay rate. PMID:10512839

  15. Manufacturing developments of filament winding for thermoplastic composites

    NASA Astrophysics Data System (ADS)

    Kimura, Minoru; Saigoku, Haruyoshi; Tsuchiya, Kiyoshi; Ishikawa, Takashi

    Thermoplastic composite materials for aerospace structures are examined. A forming method for filament windings is described, and the hot pressing technology is discussed. The test results are given, and the nondestructive inspection of fracture surfaces is considered.

  16. Method for preparing metallated filament-wound structures

    DOEpatents

    Peterson, George R.

    1979-01-01

    Metallated graphite filament-wound structures are prepared by coating a continuous multi-filament carbon yarn with a metal carbide, impregnating the carbide coated yarn with a polymerizable carbon precursor, winding the resulting filament about a mandrel, partially curing the impregnation in air, subjecting the wound composite to heat and pressure to cure the carbon precursor, and thereafter heating the composite in a sizing die at a pressure loading of at least 1000 psi for graphitizing the carbonaceous material in the composite. The carbide in the composite coalesces into rod-like shapes which are disposed in an end-to-end relationship parallel with the filaments to provide resistance to erosion in abrasive laden atmospheres.

  17. Numerical studies of motion and decay of vortex filaments

    NASA Technical Reports Server (NTRS)

    Liu, C. H.; Tavantzis, J.; Ting, L.

    1986-01-01

    A computational code is developed for the integro-differential equations governing the motion of the centerlines of vortex filaments submerged in a background potential flow. These equations, which are derived from the method of matched asymptotic analysis, include the effect of decaying large-magnitude circumferential and axial velocity components in the vortical cores. Numerical examples are presented to assess the effect of large axial velocity and of nonsimilar initial profiles in vortical cores. The initial configurations of the filaments are chosen so as to fulfill the basic assumption of asymptotic analysis, which is the effective vortical core size is much smaller than all other length scales in the flowfield, e.g., the radius of curvature and interfilament distance. The computations are continued until the basic assumption is no longer valid, that is, when the merging or intersection of filaments have begun. Various types of local or global merging or intersection of filaments are classified and demonstrated by numerical examples.

  18. Apparatus for coating and impregnating filament with resin

    DOEpatents

    Robinson, S.C.; Pollard, R.E.

    1986-12-17

    The present invention is directed to an apparatus for evenly coating and impregnating a filament with binder material. Dimension control and repeatability of the coating and impregnating characteristics are obtained with the apparatus.

  19. Eruptive filament of May 31, 1997, observed by SOHO.

    NASA Astrophysics Data System (ADS)

    Schmieder, B.; Heinzel, P.; Vial, J.-C.; Delaboudinière, J.-P.; Delannée, C.

    In the frame of the SUMER/CDS Joint Programme (JOP 17) the authors have detected the four Lyman lines in an erupting filament. The strong self-absorption in these lines, already reported for quiescent filaments, is still present in this highly dynamical event, but the authors observe a significant red asymmetry in the intensities of the two peaks. They ascribe it to an upward bulk motion of the filament, which they can actually see on a series of EIT images taken in the Fe XII line. Both sets of observations can lead to a determination of the velocity vector. The Doppler velocities are also derived from other lines detected by SUMER/CDS and can be correlated with the observations of the Pic-du-Midi MSDP obtained for this event. The filament eruption was also well observed by other GBO instruments in the Hα line (Meudon and Ondřejov).

  20. Filamentation of Focused and Collimated Laser Beams in Liquids

    NASA Astrophysics Data System (ADS)

    Apeksimov, D. V.; Bukin, O. A.; Golik, S. S.; Zemlyanov, A. A.; Kabanov, A. M.; Kuchinskaya, O. I.; Matvienko, G. G.; Oshlakov, V. K.; Petrov, A. V.; Sokolova, E. B.; Khoroshaeva, E. E.

    2015-05-01

    Experimental results of investigations into the transformation of the spectral and spatial characteristics of femtosecond collimated and focused Ti:Sa -laser beams with wavelengths of 800 and 400 nm upon filamentation in continuous liquid media are presented. It is shown that broadening of the laser pulse spectrum due to phase self-modulation in the medium with a cubic nonlinearity depends on the pulse power and beam diameter. Dependences of the number of filaments, width of laser radiation spectrum, nonlinear focusing distance, and diameter of the filamentation region on the laser pulse power are measured. The existence of a relative power interval in which the explosive growth of the number of filaments occurs, is established.

  1. Filamentation of focused and collimated laser beams in liquids

    NASA Astrophysics Data System (ADS)

    Apeksimov, D. V.; Bukin, O. A.; Golik, S. S.; Zemlyanov, A. A.; Kabanov, A. M.; Kuchinskaya, O. I.; Matvienko, G. G.; Oshlakov, V. K.; Petrov, A. V.; Sokolova, E. B.; Khoroshaeva, E. E.

    2015-11-01

    Experimental results of investigations into the transformation of the spectral and spatial characteristics of femtosecond collimated and focused Ti:Sapphire-laser beams with wavelengths of 800 and 400 nm upon filamentation in continuous liquid media are presented. It is shown that broadening of the laser pulse spectrum due to phase self-modulation in the medium with a cubic nonlinearity depends on the pulse power and beam diameter. Dependences of the number of filaments, width of laser radiation spectrum, nonlinear focusing distance, and diameter of the filamentation region on the laser pulse power are measured. The existence of a relative power interval in which the explosive growth of the number of filaments occurs, is established.

  2. MASS COMPOSITION IN PRE-ERUPTION QUIET SUN FILAMENTS

    SciTech Connect

    Kilper, Gary; Gilbert, Holly; Alexander, David

    2009-10-10

    Filament eruptions are extremely important phenomena due to their association with coronal mass ejections and their effects on space weather. Little is known about the filament mass and composition in the eruption process, since most of the related research has concentrated on the evolution and disruption of the magnetic field. Following up on our previous work, we present here an analysis of nineteen quiet Sun filament eruptions observed by Mauna Loa Solar Observatory in Halpha and He I 10830 A that has identified a compositional precursor common to all of these eruptions. There is a combined trend of an apparent increase in the homogenization of the filament mass composition, with concurrent increases in absorption in Halpha and He I and in the level of activity, all starting at least one day prior to eruption. This finding suggests that a prolonged period of mass motions, compositional mixing, and possibly even extensive mass loading is occurring during the build up of these eruptions.

  3. Solar Filament Eruption, Solar Tsunami - Close-up

    NASA Video Gallery

    Close-up of magnetic solar filament erupting during the early hours of February 24, 2012. Notice closer to the surface the solar atmosphere splits and waves of solar material fan out in opposite di...

  4. Elastic response of filamentous networks with compliant crosslinks.

    PubMed

    Sharma, A; Sheinman, M; Heidemann, K M; MacKintosh, F C

    2013-11-01

    Experiments have shown that elasticity of disordered filamentous networks with compliant crosslinks is very different from networks with rigid crosslinks. Here, we model and analyze filamentous networks as a collection of randomly oriented rigid filaments connected to each other by flexible crosslinks that are modeled as wormlike chains. For relatively large extensions we allow for enthalpic stretching of crosslink backbones. We show that for sufficiently high crosslink density, the network linear elastic response is affine on the scale of the filaments' length. The nonlinear regime can become highly nonaffine and is characterized by a divergence of the elastic modulus at finite strain. In contrast to the prior predictions, we do not find an asymptotic regime in which the differential elastic modulus scales linearly with the stress, although an approximate linear dependence can be seen in a transition from entropic to enthalpic regimes. We discuss our results in light of recent experiments.

  5. Broken Detailed Balance of Filament Dynamics in Active Networks

    NASA Astrophysics Data System (ADS)

    Gladrow, J.; Fakhri, N.; MacKintosh, F. C.; Schmidt, C. F.; Broedersz, C. P.

    2016-06-01

    Myosin motor proteins drive vigorous steady-state fluctuations in the actin cytoskeleton of cells. Endogenous embedded semiflexible filaments such as microtubules, or added filaments such as single-walled carbon nanotubes are used as novel tools to noninvasively track equilibrium and nonequilibrium fluctuations in such biopolymer networks. Here, we analytically calculate shape fluctuations of semiflexible probe filaments in a viscoelastic environment, driven out of equilibrium by motor activity. Transverse bending fluctuations of the probe filaments can be decomposed into dynamic normal modes. We find that these modes no longer evolve independently under nonequilibrium driving. This effective mode coupling results in nonzero circulatory currents in a conformational phase space, reflecting a violation of detailed balance. We present predictions for the characteristic frequencies associated with these currents and investigate how the temporal signatures of motor activity determine mode correlations, which we find to be consistent with recent experiments on microtubules embedded in cytoskeletal networks.

  6. Biofilms from a Brazilian water distribution system include filamentous fungi.

    PubMed

    Siqueira, V M; Oliveira, H M B; Santos, C; Paterson, R R M; Gusmão, N B; Lima, N

    2013-03-01

    Filamentous fungi in drinking water can block water pipes, can cause organoleptic biodeterioration, and are a source of pathogens. There are increasing reports of the involvement of the organisms in biofilms. This present study describes a sampling device that can be inserted directly into pipes within water distribution systems, allowing biofilm formation in situ. Calcofluor White M2R staining and fluorescent in situ hybridization with morphological analyses using epifluorescent microscopy were used to analyse biofilms for filamentous fungi, permitting direct observation of the fungi. DAPI (4',6-diamidino-2-phenylindole) was applied to detect bacteria. Filamentous fungi were detected in biofilms after 6 months on coupons exposed to raw water, decanted water and at the entrance of the water distribution system. Algae, yeast, and bacteria were also observed. The role of filamentous fungi requires further investigations.

  7. Measurement and control of plasma oscillations in femtosecond filaments.

    PubMed

    Zhou, B; Houard, A; Liu, Y; Prade, B; Mysyrowicz, A; Couairon, A; Mora, P; Smeenk, C; Arissian, L; Corkum, P

    2011-06-24

    The short-lived longitudinal plasma oscillations generated during filamentation in argon and nitrogen gas are measured with a specially designed current monitor. The magnitude and initial direction of the corresponding currents depend sensitively on laser polarization and nature of the gas. The results are interpreted as resulting from the competition between two forces acting on free electrons born during the filamentation process: the Lorentz laser force and a Coulomb wake force resulting from a lateral expansion of the plasma.

  8. Measurement and Control of Plasma Oscillations in Femtosecond Filaments

    SciTech Connect

    Zhou, B.; Houard, A.; Liu, Y.; Prade, B.; Mysyrowicz, A.; Couairon, A.; Mora, P.; Smeenk, C.; Arissian, L.; Corkum, P.

    2011-06-24

    The short-lived longitudinal plasma oscillations generated during filamentation in argon and nitrogen gas are measured with a specially designed current monitor. The magnitude and initial direction of the corresponding currents depend sensitively on laser polarization and nature of the gas. The results are interpreted as resulting from the competition between two forces acting on free electrons born during the filamentation process: the Lorentz laser force and a Coulomb wake force resulting from a lateral expansion of the plasma.

  9. Fungal Surface and Innate Immune Recognition of Filamentous Fungi

    PubMed Central

    Figueiredo, Rodrigo T.; Carneiro, Leticia A. M.; Bozza, Marcelo T.

    2011-01-01

    The innate immune system performs specific detection of molecules from infectious agents through pattern recognition receptors. This recognition triggers inflammatory responses and activation of microbicidal mechanisms by leukocytes. Infections caused by filamentous fungi have increased in incidence and represent an important cause of mortality and morbidity especially in individuals with immunosuppression. This review will discuss the innate immune recognition of filamentous fungi molecules and its importance to infection control and disease. PMID:22194732

  10. Filamentation of a relativistic short pulse laser in a plasma

    NASA Astrophysics Data System (ADS)

    Kumar, Naveen; Tripathi, V. K.; Sawhney, B. K.

    2006-06-01

    An intense short pulse laser propagating through a plasma undergoes filamentation instability under the combined effects of relativistic mass variation and ponderomotive force-induced electron density depression. These two nonlinearities superimpose each other. In a tenuous plasma, the filament size scales as {\\sim}( c / \\omega _p\\; a_0 ) \\sqrt 2 \\gamma _0^{1/2} , where ω p is the plasma frequency, a0 is the normalized laser amplitude and γ 0 is the relativistic gamma factor.

  11. 7-forming, superconducting filaments through bicomponent dry spinning

    DOEpatents

    Tuominen, Olli P.; Morgan, Carol W.; Burlone, Dominick A.; Blankenship, Keith V.

    2001-01-01

    Fibers which contain potentially superconducting material are dry spun by the steps of preparing a suspension of potentially superconducting powder in a thickened solvent; preparing a solution of fiber-forming polymer; supplying the suspension and the solution to a spinning apparatus; in the spinning apparatus, arranging the solution and the suspension in a bicomponent arrangement; extruding the arranged solution and suspension from a spinneret as a bicomponent filament; and removing the solvent from the filament.

  12. Physics and applications of atmospheric nonlinear optics and filamentation.

    PubMed

    Kasparian, Jérôme; Wolf, Jean-Pierre

    2008-01-07

    We review the properties and applications of ultrashort laser pulses in the atmosphere, with a particular focus on filamentation. Filamentation is a non-linear propagation regime specific of ultrashort and ultraintense laser pulses in the atmosphere. Typical applications include remote sensing of atmospheric gases and aerosols, lightning control, laser-induced spectroscopy, coherent anti-stokes Raman scattering, and the generation of sub-THz radiation.

  13. Filamentation in Air with Ultrashort Mid-Infrared Pulses

    DTIC Science & Technology

    2011-05-09

    Filamentation in air with ultrashort mid-infrared pulses Bonggu Shim,1,2 Samuel E. Schrauth,1 and Alexander L. Gaeta1,3 1School of Applied and...filamentation of ultrashort laser pulses in air in the mid-infrared regime under conditions in which the group-velocity dispersion (GVD) is anomalous. When a...and propagates several times its diffraction length. Compared with temporal self-compression in gases due to plasma formation and pulse splitting in the

  14. KAO and AAT observations of the Galactic Center filaments

    NASA Technical Reports Server (NTRS)

    Erickson, Edwin F.; Colgan, Sean W. J.; Simpson, Janet P.; Rubin, Robert H.; Haas, Michael R.; Morris, M.; Cotera, A. S.; Allen, David A.; Burton, Michael G.

    1995-01-01

    We have used the Kuiper Airborne Observatory (KAO) and the Anglo-Australian Telescope (AAT) to investigate the nature of the filamentary radio emission from the Galactic center region. KAO observations of the FIR line and continuum emission from the radio peak G0.095+0.012 and the E2 thermal radio filament northeast of the Galactic center can be produced by numerous nearby stars with T(sub eff) approx. 35,000 K; these can account for both the FIR luminosity and the excitation of the gas. Much of the FIR continuum and most of the strong (Si II) (34.8 micron) line emission are probably produced in the ionized gas of the filament. The FIR (O III) 52 and 88 micron lines imply an electron density of a few hundred; when compared with the radio emission measure, this implies the filament is roughly tubular or somewhat flattened in the plane of the sky. The (O III) and (S III) lines show higher excitation associated with the filament, and suggest that exciting stars may be located within the filaments and/or southeast of the E2 filament. AAT observations in the near infrared (NIR) in fact reveal a nearby cluster of hot stars southeast of the E2 filament. Additional hot stars, not identifiable from their NIR spectra, are likely to be present. These stars and those in the cluster can plausibly produce the observed radio and FIR emission in the region. The morphology of the filament is not explained by existing information however.

  15. Clamped-filament elongation model for actin-based motors.

    PubMed Central

    Dickinson, Richard B; Purich, Daniel L

    2002-01-01

    Although actin-based motility drives cell crawling and intracellular locomotion of organelles and certain pathogens, the underlying mechanism of force generation remains a mystery. Recent experiments demonstrated that Listeria exhibit episodes of 5.4-nm stepwise motion corresponding to the periodicity of the actin filament subunits, and extremely small positional fluctuations during the intermittent pauses [S. C. Kuo and J. L. McGrath. 2000. Nature. 407:1026-1029]. These findings suggest that motile bacteria remain firmly bound to actin filament ends as they elongate, a behavior that appears to rule out previous models for actin-based motility. We propose and analyze a new mechanochemical model (called the "Lock, Load & Fire" mechanism) for force generation by means of affinity-modulated, clamped-filament elongation. During the locking step, the filament's terminal ATP-containing subunit binds tightly to a clamp situated on the surface of a motile object; in the loading step, actin.ATP monomer(s) bind to the filament end, an event that triggers the firing step, wherein ATP hydrolysis on the clamped subunit attenuates the filament's affinity for the clamp. This last step initiates translocation of the new ATP-containing terminus to the clamp, whereupon another cycle begins anew. This model explains how surface-tethered filaments can grow while exerting flexural or tensile force on the motile surface. Moreover, stochastic simulations of the model reproduce the signature motions of Listeria. This elongation motor, which we term actoclampin, exploits actin's intrinsic ATPase activity to provide a simple, high-fidelity enzymatic reaction cycle for force production that does not require elongating filaments to dissociate from the motile surface. This mechanism may operate whenever actin polymerization is called upon to generate the forces that drive cell crawling or intracellular organelle motility. PMID:11806905

  16. Filamentational instability of partially coherent femtosecond optical pulses in air.

    PubMed

    Marklund, M; Shukla, P K

    2006-06-15

    The filamentational instability of spatially broadband femtosecond optical pulses in air is investigated by means of a kinetic wave equation for spatially incoherent photons. An explicit expression for the spatial amplification rate is derived and analyzed. It is found that the spatial spectral broadening of the pulse can lead to stabilization of the filamentation instability. Thus optical smoothing techniques could optimize current applications of ultrashort laser pulses, such as atmospheric remote sensing.

  17. Observations of a Filament in the North Ecliptic Pole Supercluster

    NASA Technical Reports Server (NTRS)

    Henry, Joseph Henry

    2005-01-01

    Our work on the ROSAT All-Sky Survey at the North Ecliptic Pole has increased from 7 to 21 the group and cluster membership of a previously known supercluster there, revealing a particularly striking example of a filament. We obtained observations of two clusters in this filament to elucidate its dynamics. However, these observations were severely compromised by flares: less than 20% of the requested time survived screening. Consequently the data were inadequate for the project.

  18. Sub-Micron Carbon Filaments for Optical Applications

    DTIC Science & Technology

    1987-11-01

    research at this stage, t grow straight, submicroii, high aspect ratio filaments, has not yet bet achievcd. A ,ariety of groi .-th conditions have bee...however, produced very little filament groi .-th and quilt a lot of carbon deposits on the reactor walls. The deposits ranged from .ell.uwish-brown...arranged across the fiber section varies considerably from one fiber type to another. Ex- PAIN fibers are characteristically disordered in this section

  19. Multiple filamentation of collimated beams Ti:Sapphire-laser in water

    NASA Astrophysics Data System (ADS)

    Apeksimov, D. V.; Bukin, O. A.; Golik, S. S.; Zemlyanov, A. A.; Kabanov, A. M.; Kuchinskaya, O. I.; Mayor, A. V.; Matvienko, G. G.; Oshlakov, V. K.; Petrov, A. V.; Sokolova, E. B.; Horoshaeva, E. E.

    2014-11-01

    The results of experimental studies of filamentation of femtosecond laser pulses in water is presented. Measured the number of filaments, the spectral width of the laser radiation, nonlinear focusing distance, the diameter of the field of filamentation power laser pulses. Noted the existence of plot on the scale of the relative power in passing which the explosive growth in the number of filaments.

  20. Optical spectroscopy using gas-phase femtosecond laser filamentation.

    PubMed

    Odhner, Johanan; Levis, Robert

    2014-01-01

    Femtosecond laser filamentation occurs as a dynamic balance between the self-focusing and plasma defocusing of a laser pulse to produce ultrashort radiation as brief as a few optical cycles. This unique source has many properties that make it attractive as a nonlinear optical tool for spectroscopy, such as propagation at high intensities over extended distances, self-shortening, white-light generation, and the formation of an underdense plasma. The plasma channel that constitutes a single filament and whose position in space can be controlled by its input parameters can span meters-long distances, whereas multifilamentation of a laser beam can be sustained up to hundreds of meters in the atmosphere. In this review, we briefly summarize the current understanding and use of laser filaments for spectroscopic investigations of molecules. A theoretical framework of filamentation is presented, along with recent experimental evidence supporting the established understanding of filamentation. Investigations carried out on vibrational and rotational spectroscopy, filament-induced breakdown, fluorescence spectroscopy, and backward lasing are discussed.

  1. Atomic View of Filament Growth in Electrochemical Memristive Elements

    PubMed Central

    Lv, Hangbing; Xu, Xiaoxin; Sun, Pengxiao; Liu, Hongtao; Luo, Qing; Liu, Qi; Banerjee, Writam; Sun, Haitao; Long, Shibing; Li, Ling; Liu, Ming

    2015-01-01

    Memristive devices, with a fusion of memory and logic functions, provide good opportunities for configuring new concepts computing. However, progress towards paradigm evolution has been delayed due to the limited understanding of the underlying operating mechanism. The stochastic nature and fast growth of localized conductive filament bring difficulties to capture the detailed information on its growth kinetics. In this work, refined programming scheme with real-time current regulation was proposed to study the detailed information on the filament growth. By such, discrete tunneling and quantized conduction were observed. The filament was found to grow with a unit length, matching with the hopping conduction of Cu ions between interstitial sites of HfO2 lattice. The physical nature of the formed filament was characterized by high resolution transmission electron microscopy. Copper rich conical filament with decreasing concentration from center to edge was identified. Based on these results, a clear picture of filament growth from atomic view could be drawn to account for the resistance modulation of oxide electrolyte based electrochemical memristive elements. PMID:26293982

  2. Real-Time Imaging of Fluorescent Flagellar Filaments

    NASA Astrophysics Data System (ADS)

    Ryu, William

    2003-03-01

    Bacteria swim by rotating flagellar filaments that are several micrometers long, but only about 18 nm in diameter. The filaments can exist in different polymorphic forms, having distinct values of curvature and twist. Rotation rates are on the order of 100 Hz. In the past, the motion of individual filaments has been visualized by dark-field or differential-interference-contrast microscopy, methods hampered by intense scattering from the cell body or shallow depth of field, respectively. We have found a simple procedure for fluorescently labeling cells and filaments that allows recording their motion in real time with an inexpensive video camera and an ordinary fluorescence microscope with mercury-arc or strobed laser illumination. We report our initial findings with cells of Escherichia coli. Tumbles (events that enable swimming cells to alter course) are remarkably varied. Not every filament on a cell needs to change its direction of rotation: different filaments can change directions at different times, and a tumble can result from the change in direction of only one. Polymorphic transformations tend to occur in the sequence normal, semicoiled, curly 1, with changes in the direction of movement of the cell body correlated with transformations to the semicoiled form.

  3. Actin filaments as dynamic reservoirs for Drp1 recruitment

    PubMed Central

    Hatch, Anna L.; Ji, Wei-Ke; Merrill, Ronald A.; Strack, Stefan; Higgs, Henry N.

    2016-01-01

    Drp1 is a dynamin-family GTPase recruited to mitochondria and peroxisomes, where it oligomerizes and drives membrane fission. Regulation of mitochondrial Drp1 recruitment is not fully understood. We previously showed that Drp1 binds actin filaments directly, and actin polymerization is necessary for mitochondrial Drp1 oligomerization in mammals. Here we show the Drp1/actin interaction displays unusual properties that are influenced by several factors. At saturation, only a fraction Drp1 binds actin filaments, and the off-rate of actin-bound Drp1 is significantly increased by unbound Drp1. GDP and GTP accelerate and decelerate Drp1/actin binding dynamics, respectively. Actin has a biphasic effect on Drp1 GTP hydrolysis, increasing at low actin:Drp1 ratio but returning to baseline at high ratio. Drp1 also bundles filaments. Bundles have reduced dynamics but follow the same trends as single filaments. Drp1 preferentially incorporates into bundles at higher ionic strength. We measure Drp1 concentration to be ∼0.5 μM in U2OS cell cytosol, suggesting the actin-binding affinity measured here (Kd = 0.6 μM) is in the physiologically relevant range. The ability of Drp1 to bind actin filaments in a highly dynamic manner provides potential for actin filaments to serve as reservoirs of oligomerization-competent Drp1 that can be accessed for mitochondrial fission. PMID:27559132

  4. Force-Velocity Measurements of a Few Growing Actin Filaments

    PubMed Central

    Brangbour, Coraline; du Roure, Olivia; Helfer, Emmanuèle; Démoulin, Damien; Mazurier, Alexis; Fermigier, Marc; Carlier, Marie-France; Bibette, Jérôme; Baudry, Jean

    2011-01-01

    The polymerization of actin in filaments generates forces that play a pivotal role in many cellular processes. We introduce a novel technique to determine the force-velocity relation when a few independent anchored filaments grow between magnetic colloidal particles. When a magnetic field is applied, the colloidal particles assemble into chains under controlled loading or spacing. As the filaments elongate, the beads separate, allowing the force-velocity curve to be precisely measured. In the widely accepted Brownian ratchet model, the transduced force is associated with the slowing down of the on-rate polymerization. Unexpectedly, in our experiments, filaments are shown to grow at the same rate as when they are free in solution. However, as they elongate, filaments are more confined in the interspace between beads. Higher repulsive forces result from this higher confinement, which is associated with a lower entropy. In this mechanism, the production of force is not controlled by the polymerization rate, but is a consequence of the restriction of filaments' orientational fluctuations at their attachment point. PMID:21541364

  5. Evolution of filamentous bacteria during urban wastewater treatment by MBR.

    PubMed

    Parada-Albarracín, J A; Marin, E; Pérez, J I; Moreno, B; Gómez, M A

    2012-01-01

    Evolution of filamentous bacteria in two full-scale experimental MBR systems (microfiltration and ultrafiltration) was studied during two years. Sludge Retention Time (SRT) and Hydraulic Retention Time (HRT) were modified and acted as variables, together with temperature and variation in loading. With SRT values between 20 and 35 d and HRT between 31 and 40 h, both MBR systems presented a high density of filamentous bacteria, according to the Filamentous Index (FI) and Simplified Technique of Filamentous Count (STFC). Highest density was achieved when contaminant loads were high and temperature was low. However, the elevated presence of filamentous bacteria did not affect the quality of effluent or the permeability of the membranes. Nocardioform bacteria showed a high degree of adaptation to the characteristics of the system. Predominance of Nocardioforms gave rise to isolated episodes of massive growth at temperatures between 15 and 20°C, which in turn caused episodes of intense foaming whose most significant consequence was a loss in biomass, leading to a slight increase in transmembrane pressure. In the light of these results, FI and STFC should not be considered as suitable tools for predicting operational problems deriving from filamentous bacteria in MBR systems, which could be prevented through identification.

  6. Mid-infrared laser filaments in the atmosphere.

    PubMed

    Mitrofanov, A V; Voronin, A A; Sidorov-Biryukov, D A; Pugžlys, A; Stepanov, E A; Andriukaitis, G; Flöry, T; Ališauskas, S; Fedotov, A B; Baltuška, A; Zheltikov, A M

    2015-02-17

    Filamentation of ultrashort laser pulses in the atmosphere offers unique opportunities for long-range transmission of high-power laser radiation and standoff detection. With the critical power of self-focusing scaling as the laser wavelength squared, the quest for longer-wavelength drivers, which would radically increase the peak power and, hence, the laser energy in a single filament, has been ongoing over two decades, during which time the available laser sources limited filamentation experiments in the atmosphere to the near-infrared and visible ranges. Here, we demonstrate filamentation of ultrashort mid-infrared pulses in the atmosphere for the first time. We show that, with the spectrum of a femtosecond laser driver centered at 3.9 μm, right at the edge of the atmospheric transmission window, radiation energies above 20 mJ and peak powers in excess of 200 GW can be transmitted through the atmosphere in a single filament. Our studies reveal unique properties of mid-infrared filaments, where the generation of powerful mid-infrared supercontinuum is accompanied by unusual scenarios of optical harmonic generation, giving rise to remarkably broad radiation spectra, stretching from the visible to the mid-infrared.

  7. Mid-infrared laser filaments in the atmosphere

    PubMed Central

    Mitrofanov, A. V.; Voronin, A. A.; Sidorov-Biryukov, D. A.; Pugžlys, A.; Stepanov, E. A.; Andriukaitis, G.; Flöry, T.; Ališauskas, S.; Fedotov, A. B.; Baltuška, A.; Zheltikov, A. M.

    2015-01-01

    Filamentation of ultrashort laser pulses in the atmosphere offers unique opportunities for long-range transmission of high-power laser radiation and standoff detection. With the critical power of self-focusing scaling as the laser wavelength squared, the quest for longer-wavelength drivers, which would radically increase the peak power and, hence, the laser energy in a single filament, has been ongoing over two decades, during which time the available laser sources limited filamentation experiments in the atmosphere to the near-infrared and visible ranges. Here, we demonstrate filamentation of ultrashort mid-infrared pulses in the atmosphere for the first time. We show that, with the spectrum of a femtosecond laser driver centered at 3.9 μm, right at the edge of the atmospheric transmission window, radiation energies above 20 mJ and peak powers in excess of 200 GW can be transmitted through the atmosphere in a single filament. Our studies reveal unique properties of mid-infrared filaments, where the generation of powerful mid-infrared supercontinuum is accompanied by unusual scenarios of optical harmonic generation, giving rise to remarkably broad radiation spectra, stretching from the visible to the mid-infrared. PMID:25687621

  8. Filament eruptions and the impulsive phase of solar flares

    NASA Technical Reports Server (NTRS)

    Kahler, S. W.; Moore, R. L.; Kane, S. R.; Zirin, H.

    1988-01-01

    Filament motion during the onset of the solar flare impulsive phase is examined. The impulsive phase onset is established from profiles of about 30 keV X-ray fluxes and the rapid flare brightenings characteristic of the H-alpha flash phase. The filament motion begins several minutes before the impulsive or flash phase of the flare. No new accleration is observed in the motion of the filament during the onset of the impulsive phase for at least two of the four flares. The most common H-alpha brightenings associated with the impulsive phase lie near the magnetic inversion line roughly centered under the erupting filament. Filament speeds at the onset of the impulsive or flash phase lie in the range 30-180 km/s. These characteristics indicate that the filament eruption is not driven by the flare plasma pressure, but instead marks an eruption of magnetic field driven by a global MHD instability of the field configuration in the region of the flare.

  9. Cofilin cooperates with fascin to disassemble filopodial actin filaments

    PubMed Central

    Breitsprecher, Dennis; Koestler, Stefan A.; Chizhov, Igor; Nemethova, Maria; Mueller, Jan; Goode, Bruce L.; Small, J. Victor; Rottner, Klemens; Faix, Jan

    2011-01-01

    Cells use a large repertoire of proteins to remodel the actin cytoskeleton. Depending on the proteins involved, F-actin is organized in specialized protrusions such as lamellipodia or filopodia, which serve diverse functions in cell migration and sensing. Although factors responsible for directed filament assembly in filopodia have been extensively characterized, the mechanisms of filament disassembly in these structures are mostly unknown. We investigated how the actin-depolymerizing factor cofilin-1 affects the dynamics of fascincrosslinked actin filaments in vitro and in live cells. By multicolor total internal reflection fluorescence microscopy and fluorimetric assays, we found that cofilin-mediated severing is enhanced in fascin-crosslinked bundles compared with isolated filaments, and that fascin and cofilin act synergistically in filament severing. Immunolabeling experiments demonstrated for the first time that besides its known localization in lamellipodia and membrane ruffles, endogenous cofilin can also accumulate in the tips and shafts of filopodia. Live-cell imaging of fluorescently tagged proteins revealed that cofilin is specifically targeted to filopodia upon stalling of protrusion and during their retraction. Subsequent electron tomography established filopodial actin filament and/or bundle fragmentation to precisely correlate with cofilin accumulation. These results identify a new mechanism of filopodium disassembly involving both fascin and cofilin. PMID:21940796

  10. Real-Time Imaging of Fluorescent Flagellar Filaments

    PubMed Central

    Turner, Linda; Ryu, William S.; Berg, Howard C.

    2000-01-01

    Bacteria swim by rotating flagellar filaments that are several micrometers long, but only about 20 nm in diameter. The filaments can exist in different polymorphic forms, having distinct values of curvature and twist. Rotation rates are on the order of 100 Hz. In the past, the motion of individual filaments has been visualized by dark-field or differential-interference-contrast microscopy, methods hampered by intense scattering from the cell body or shallow depth of field, respectively. We have found a simple procedure for fluorescently labeling cells and filaments that allows recording their motion in real time with an inexpensive video camera and an ordinary fluorescence microscope with mercury-arc or strobed laser illumination. We report our initial findings with cells of Escherichia coli. Tumbles (events that enable swimming cells to alter course) are remarkably varied. Not every filament on a cell needs to change its direction of rotation: different filaments can change directions at different times, and a tumble can result from the change in direction of only one. Polymorphic transformations tend to occur in the sequence normal, semicoiled, curly 1, with changes in the direction of movement of the cell body correlated with transformations to the semicoiled form. PMID:10781548

  11. Photospheric flows around a quiescent filament and CALAS first results .

    NASA Astrophysics Data System (ADS)

    Rondi, S.; Roudier, Th.; Molodij, G.; Bommier, V.; Malherbe, J. M.; Schmieder, B.; Meunier, N.; Rieutord, M.; Beigbeder., F.

    The horizontal photospheric flows below and around a filament are one of the components in the formation and evolution of filaments. Few studies have been done so far because this requires multiwalength time sequences with high spatial resolution. We present observations obtained in 2004 during the international JOP 178 campaign in which eleven instruments were involved, from space and ground based observatories. Several supergranulation cells are crossing the Polarity Inversion Line (PIL) allowing the transport of magnetic flux through the PIL, in particular the parasitic polarities. Before the filament eruptive phase, parasitic and normal polarities are swept by a continuous diverging horizontal flow located in the filament gap where the disappearance of the filament starts. In the future, observations at high spatial resolution on a large field-of-view would be very useful to study filaments, as they are very large structures. We also present the first images obtained with the use of our new 14 MPixel camera CALAS (CAmera for the LArge Scales of the Solar Surface) (10 arcmin× 6.7 arcmin) . These are the first large-scale and high-resolution images of the solar surface ever made.

  12. Geometrical and Mechanical Properties Control Actin Filament Organization

    PubMed Central

    Ennomani, Hajer; Théry, Manuel; Nedelec, Francois; Blanchoin, Laurent

    2015-01-01

    The different actin structures governing eukaryotic cell shape and movement are not only determined by the properties of the actin filaments and associated proteins, but also by geometrical constraints. We recently demonstrated that limiting nucleation to specific regions was sufficient to obtain actin networks with different organization. To further investigate how spatially constrained actin nucleation determines the emergent actin organization, we performed detailed simulations of the actin filament system using Cytosim. We first calibrated the steric interaction between filaments, by matching, in simulations and experiments, the bundled actin organization observed with a rectangular bar of nucleating factor. We then studied the overall organization of actin filaments generated by more complex pattern geometries used experimentally. We found that the fraction of parallel versus antiparallel bundles is determined by the mechanical properties of actin filament or bundles and the efficiency of nucleation. Thus nucleation geometry, actin filaments local interactions, bundle rigidity, and nucleation efficiency are the key parameters controlling the emergent actin architecture. We finally simulated more complex nucleation patterns and performed the corresponding experiments to confirm the predictive capabilities of the model. PMID:26016478

  13. Geometrical and mechanical properties control actin filament organization.

    PubMed

    Letort, Gaëlle; Politi, Antonio Z; Ennomani, Hajer; Théry, Manuel; Nedelec, Francois; Blanchoin, Laurent

    2015-05-01

    The different actin structures governing eukaryotic cell shape and movement are not only determined by the properties of the actin filaments and associated proteins, but also by geometrical constraints. We recently demonstrated that limiting nucleation to specific regions was sufficient to obtain actin networks with different organization. To further investigate how spatially constrained actin nucleation determines the emergent actin organization, we performed detailed simulations of the actin filament system using Cytosim. We first calibrated the steric interaction between filaments, by matching, in simulations and experiments, the bundled actin organization observed with a rectangular bar of nucleating factor. We then studied the overall organization of actin filaments generated by more complex pattern geometries used experimentally. We found that the fraction of parallel versus antiparallel bundles is determined by the mechanical properties of actin filament or bundles and the efficiency of nucleation. Thus nucleation geometry, actin filaments local interactions, bundle rigidity, and nucleation efficiency are the key parameters controlling the emergent actin architecture. We finally simulated more complex nucleation patterns and performed the corresponding experiments to confirm the predictive capabilities of the model.

  14. Human myocytes are protected from titin aggregation-induced stiffening by small heat shock proteins

    PubMed Central

    Kötter, Sebastian; Unger, Andreas; Hamdani, Nazha; Lang, Patrick; Vorgerd, Matthias; Nagel-Steger, Luitgard

    2014-01-01

    In myocytes, small heat shock proteins (sHSPs) are preferentially translocated under stress to the sarcomeres. The functional implications of this translocation are poorly understood. We show here that HSP27 and αB-crystallin associated with immunoglobulin-like (Ig) domain-containing regions, but not the disordered PEVK domain (titin region rich in proline, glutamate, valine, and lysine), of the titin springs. In sarcomeres, sHSP binding to titin was actin filament independent and promoted by factors that increased titin Ig unfolding, including sarcomere stretch and the expression of stiff titin isoforms. Titin spring elements behaved predominantly as monomers in vitro. However, unfolded Ig segments aggregated, preferentially under acidic conditions, and αB-crystallin prevented this aggregation. Disordered regions did not aggregate. Promoting titin Ig unfolding in cardiomyocytes caused elevated stiffness under acidic stress, but HSP27 or αB-crystallin suppressed this stiffening. In diseased human muscle and heart, both sHSPs associated with the titin springs, in contrast to the cytosolic/Z-disk localization seen in healthy muscle/heart. We conclude that aggregation of unfolded titin Ig domains stiffens myocytes and that sHSPs translocate to these domains to prevent this aggregation. PMID:24421331

  15. Early Archean (approximately 3.4 Ga) prokaryotic filaments from cherts of the apex basalt, Western Australia: The oldest cellularly preserved microfossils now known

    NASA Technical Reports Server (NTRS)

    Schopf, J. W.

    1991-01-01

    In comparison with that known from later geologic time, the Archean fossil record is miniscule: although literally hundreds of Proterozoic formations, containing more that 2800 occurrences of bona fide microfossils are now known, fewer than 30 units containing some 43 categories of putative microfossils (the vast majority of which are of questionable authenticity) have been reported from the Archean. Among the oldest known fossils are Early Archean filaments reported from cherts of the Towers Formation and the Apex Basalt of the 3.3-3.6 Ga-old Warrawoona Group of Western Australia. The paleobiologic significance of the Towers Formation microstructures is open to question: thin aggregated filaments are properly regarded as dubiomicrofossils (perhaps biogenic, but perhaps not); therefore, they cannot be regarded as firm evidence of Archean life. Although authentic, filamentous microfossiles were reported from a second Towers Formation locality, because the precise layer containing the fossiliferous cherts was not relocated, this discovery can neither be reconfirmed by the original collector nor confirmed independently by other investigators. Discovery of microfossils in bedded cherts of the Apex Basalt, the stratigraphic unit immediately overlying the Towers Formation, obviates the difficulties stored above. The cellularly preserved filaments of the Apex Basalt meet all of the criteria required of a bona fide Archean microfossils. Recent studies indicate that the Apex assemblage includes at least six morphotypes of uniseriate filaments, composed of barrel-shaped, discoidal, or quadrate cells and exhibiting rounded or conical terminal cells and medial bifurcated and paired half-cells that reflect the occurrence of prokaryotic binary cell division. Interestingly, the majority of these morphotypes are morphologically more similar to extant cyanobacteria than to modern filamentous bacteria. Prokaryotes seem clearly to have been hypobradytelic, and the evidence suggests

  16. Scalability of Localized Arc Filament Plasma Actuators

    NASA Technical Reports Server (NTRS)

    Brown, Clifford A.

    2008-01-01

    Temporal flow control of a jet has been widely studied in the past to enhance jet mixing or reduce jet noise. Most of this research, however, has been done using small diameter low Reynolds number jets that often have little resemblance to the much larger jets common in real world applications because the flow actuators available lacked either the power or bandwidth to sufficiently impact these larger higher energy jets. The Localized Arc Filament Plasma Actuators (LAFPA), developed at the Ohio State University (OSU), have demonstrated the ability to impact a small high speed jet in experiments conducted at OSU and the power to perturb a larger high Reynolds number jet in experiments conducted at the NASA Glenn Research Center. However, the response measured in the large-scale experiments was significantly reduced for the same number of actuators compared to the jet response found in the small-scale experiments. A computational study has been initiated to simulate the LAFPA system with additional actuators on a large-scale jet to determine the number of actuators required to achieve the same desired response for a given jet diameter. Central to this computational study is a model for the LAFPA that both accurately represents the physics of the actuator and can be implemented into a computational fluid dynamics solver. One possible model, based on pressure waves created by the rapid localized heating that occurs at the actuator, is investigated using simplified axisymmetric simulations. The results of these simulations will be used to determine the validity of the model before more realistic and time consuming three-dimensional simulations are conducted to ultimately determine the scalability of the LAFPA system.

  17. Experimental study of infrared filaments under different initial conditions

    NASA Astrophysics Data System (ADS)

    Mirell, Daniel Joseph

    In 1964, four years after the first working laser was constructed, long skinny damage tracks and fluorescence trails were seen inside of certain transparent media that were excited by intense light pulses [1]. What was so remarkable about these features was the narrowness of the spatial profile and their long propagation length in the beam in concert with the very high intensity of the light that would be necessary to produce them. A purely linear model of light propagation through such media was insufficient to explain the results of these experiments and hence a new area of nonlinear optics, latex coined filamentation (to describe the length, slimness, and intensity of the light field), was born. Filament studies begin with a medium that has a nonlinear index of refraction, n¯2, that interacts with an intense beam of light so as to cause it to self-focus. The n¯2 of liquid and solid transparent media is much higher than the n¯ 2 of gases and therefore a much higher intensity of laser source would need to be invented to begin the study of filaments in air. With the advent of the Ti-Sapphire Kerr-lens modelocked laser [2], working in combination with the development of the chirped pulse amplifier system in the mid-1990's, light intensities sufficient to produce filaments in air was realized. Since that time much experimental and theoretical work has been done to better understand some of the additional complexities that arise specifically in the filamentation of light in air using several different wavelengths (UV to IR) and pulsewidths (femto- to pico-seconds). Many theoretical models exist each with a different emphasis on the various physical mechanisms that may produce the features experimentally observed in filaments. The experimental work has sought to give the theoretician better data on some of the properties of filaments such as the: (a) spatial and temporal structure of the beam and of the produced plasma (that arises due to the high intensity light

  18. Filament fragmentation in high-mass star formation

    NASA Astrophysics Data System (ADS)

    Beuther, H.; Ragan, S. E.; Johnston, K.; Henning, Th.; Hacar, A.; Kainulainen, J. T.

    2015-12-01

    Context. Filamentary structures in the interstellar medium are crucial ingredients of the star formation process. They fragment to form individual star-forming cores, and at the same time they may also funnel gas toward the central gas cores, providing an additional gas reservoir. Aims: We want to resolve the length scales for filament formation and fragmentation (resolution ≤0.1 pc), in particular the Jeans length and cylinder fragmentation scale. Methods: We have observed the prototypical high-mass star-forming filament IRDC 18223 with the Plateau de Bure Interferometer (PdBI) in the 3.2 mm continuum and N2H+(1-0) line emission in a ten-field mosaic at a spatial resolution of ~ 4'' (~14 000 au). Results: The dust continuum emission resolves the filament into a chain of at least 12 relatively regularly spaced cores. The mean separation between cores is ~0.40(± 0.18) pc. While this is approximately consistent with the fragmentation of an infinite, isothermal, and gravitationally bound gas cylinder, a high mass-to-length ratio of M/l ≈ 1000 M⊙ pc-1 requires additional turbulent and/or magnetic support against radial collapse of the filament. The N2H+(1-0) data reveal a velocity gradient perpendicular to the main filament. Although rotation of the filament cannot be excluded, the data are also consistent with the main filament being comprised of several velocity-coherent subfilaments. Furthermore, this velocity gradient perpendicular to the filament resembles results toward Serpens south that are interpreted as signatures of filament formation within magnetized and turbulent sheet-like structures. Lower-density gas tracers ([CI] and C18O) reveal a similar red- and blueshifted velocity structure on scales around 60'' east and west of the filament. This may tentatively be interpreted as a signature of the large-scale cloud and the smaller scale filament being kinematically coupled. We do not identify a velocity gradient along the axis of the filament. This may

  19. Studies on recycled aggregates-based concrete.

    PubMed

    Rakshvir, Major; Barai, Sudhirkumar V

    2006-06-01

    Reduced extraction of raw materials, reduced transportation cost, improved profits, reduced environmental impact and fast-depleting reserves of conventional natural aggregates has necessitated the use of recycling, in order to be able to conserve conventional natural aggregate. In this study various physical and mechanical properties of recycled concrete aggregates were examined. Recycled concrete aggregates are different from natural aggregates and concrete made from them has specific properties. The percentages of recycled concrete aggregates were varied and it was observed that properties such as compressive strength showed a decrease of up to 10% as the percentage of recycled concrete aggregates increased. Water absorption of recycled aggregates was found to be greater than natural aggregates, and this needs to be compensated during mix design.

  20. Mesoscale Simulation of Asphaltene Aggregation.

    PubMed

    Wang, Jiang; Ferguson, Andrew L

    2016-08-18

    Asphaltenes constitute a heavy aromatic crude oil fraction with a propensity to aggregate and precipitate out of solution during petroleum processing. Aggregation is thought to proceed according to the Yen-Mullins hierarchy, but the molecular mechanisms underlying mesoscopic assembly remain poorly understood. By combining coarse-grained molecular models parametrized using all-atom data with high-performance GPU hardware, we have performed molecular dynamics simulations of the aggregation of hundreds of asphaltenes over microsecond time scales. Our simulations reveal a hierarchical self-assembly mechanism consistent with the Yen-Mullins model, but the details are sensitive and depend on asphaltene chemistry and environment. At low concentrations asphaltenes exist predominantly as dispersed monomers. Upon increasing concentration, we first observe parallel stacking into 1D rod-like nanoaggregates, followed by the formation of clusters of nanoaggregates associated by offset, T-shaped, and edge-edge stacking. Asphaltenes possessing long aliphatic side chains cannot form nanoaggregate clusters due to steric repulsions between their aliphatic coronae. At very high concentrations, we observe a porous percolating network of rod-like nanoaggregates suspended in a sea of interpenetrating aliphatic side chains with a fractal dimension of ∼2. The lifetime of the rod-like aggregates is described by an exponential distribution reflecting a dynamic equilibrium between coagulation and fragmentation.

  1. RAGG - R EPISODIC AGGREGATION PACKAGE

    EPA Science Inventory

    The RAGG package is an R implementation of the CMAQ episodic model aggregation method developed by Constella Group and the Environmental Protection Agency. RAGG is a tool to provide climatological seasonal and annual deposition of sulphur and nitrogen for multimedia management. ...

  2. Sequence-dependent internalization of aggregating peptides.

    PubMed

    Couceiro, José R; Gallardo, Rodrigo; De Smet, Frederik; De Baets, Greet; Baatsen, Pieter; Annaert, Wim; Roose, Kenny; Saelens, Xavier; Schymkowitz, Joost; Rousseau, Frederic

    2015-01-02

    Recently, a number of aggregation disease polypeptides have been shown to spread from cell to cell, thereby displaying prionoid behavior. Studying aggregate internalization, however, is often hampered by the complex kinetics of the aggregation process, resulting in the concomitant uptake of aggregates of different sizes by competing mechanisms, which makes it difficult to isolate pathway-specific responses to aggregates. We designed synthetic aggregating peptides bearing different aggregation propensities with the aim of producing modes of uptake that are sufficiently distinct to differentially analyze the cellular response to internalization. We found that small acidic aggregates (≤500 nm in diameter) were taken up by nonspecific endocytosis as part of the fluid phase and traveled through the endosomal compartment to lysosomes. By contrast, bigger basic aggregates (>1 μm) were taken up through a mechanism dependent on cytoskeletal reorganization and membrane remodeling with the morphological hallmarks of phagocytosis. Importantly, the properties of these aggregates determined not only the mechanism of internalization but also the involvement of the proteostatic machinery (the assembly of interconnected networks that control the biogenesis, folding, trafficking, and degradation of proteins) in the process; whereas the internalization of small acidic aggregates is HSF1-independent, the uptake of larger basic aggregates was HSF1-dependent, requiring Hsp70. Our results show that the biophysical properties of aggregates determine both their mechanism of internalization and proteostatic response. It remains to be seen whether these differences in cellular response contribute to the particular role of specific aggregated proteins in disease.

  3. Theory of electron current filamentation instability and ion density filamentation in the early development of a DPF discharge

    SciTech Connect

    Guillory, J.; Rose, D. V.; Lerner, E. J.

    2009-01-21

    Two-dimensional simulations of the initial stages of plasma formation in a dense plasma focus show the formation, in a few tens of nanoseconds, of a dense layer of plasma (n{sub e}{approx}10{sup 18} cm{sup -3},T{sub e}{approx}3 eV) in a thin layer surrounding the insulator-covered central anode of the focus device, and carrying axially-directed current at rather high current density.Earlier work on the filamentation of dense cathode plasma in high-power diodes seems to indicate that the anode plasma current layer in a dense plasma focus (DPF) device could be subject to the same instability, creating a growth of axially-directed filaments in the current density. The growth rate for resistive-thermal-driven filamentation, e.g. at 30 torr and {approx}3 eV electron temperature, exceeds the that due to non-thermal current (JxB) driving, and is determined by electron dynamics, so its evolution is quicker than the response-time of the ions.Nonetheless, with such a growing current-density perturbation as a seed and its increasing rippling of the azimuthal magnetic field as a driver, the ions will eventually take part in the azimuthal bunching, forming filaments in the ion density as well. The resistive-thermal-driven filamentation fields thus serve to 'hurry-up' the development of ion density filamentation, as shown approximately in the work presented here. This theory predicts, for light ions, a relatively early ({<=}250 ns) development of visible filaments along the anode, perhaps even before the main rundown phase of the focus plasma motion, and these filaments may persist during the 'liftoff' phase of the current layer to form the rundown phase of the plasma front. This work is supported by Larwenceville Plasma Physics.

  4. Giant quiescent solar filament observed with high-resolution spectroscopy

    NASA Astrophysics Data System (ADS)

    Kuckein, C.; Verma, M.; Denker, C.

    2016-05-01

    Aims: An extremely large filament was studied in various layers of the solar atmosphere. The inferred physical parameters and the morphological aspects are compared with smaller quiescent filaments. Methods: A giant quiet-Sun filament was observed with the high-resolution Echelle spectrograph at the Vacuum Tower Telescope at Observatorio del Teide, Tenerife, Spain, on 2011 November 15. A mosaic of spectra (ten maps of 100″ × 182″) was recorded simultaneously in the chromospheric absorption lines Hα and Na i D2. Physical parameters of the filament plasma were derived using cloud model (CM) inversions and line core fits. The spectra were complemented with full-disk filtergrams (He i λ10830 Å, Hα, and Ca ii K) of the Chromospheric Telescope (ChroTel) and full-disk magnetograms of the Helioseismic and Magnetic Imager (HMI). Results: The filament had extremely large linear dimensions (~817 arcsec), which corresponds to about 658 Mm along a great circle on the solar surface. A total amount of 175119 Hα contrast profiles were inverted using the CM approach. The inferred mean line-of-sight (LOS) velocity, Doppler width, and source function were similar to previous works of smaller quiescent filaments. However, the derived optical thickness was higher. LOS velocity trends inferred from the Hα line core fits were in accord but weaker than those obtained with CM inversions. Signatures of counter-streaming flows were detected in the filament. The largest brightening conglomerates in the line core of Na i D2 coincided well with small-scale magnetic fields as seen by HMI. Mixed magnetic polarities were detected close to the ends of barbs. The computation of photospheric horizontal flows based on HMI magnetograms revealed flow kernels with a size of 5-8 Mm and velocities of 0.30-0.45 km s-1 at the ends of the filament. Conclusions: The physical properties of extremely large filaments are similar to their smaller counterparts, except for the optical thickness, which in

  5. Supergranular-scale magnetic flux emergence beneath an unstable filament

    NASA Astrophysics Data System (ADS)

    Palacios, J.; Cid, C.; Guerrero, A.; Saiz, E.; Cerrato, Y.

    2015-11-01

    Aims: Here we report evidence of a large solar filament eruption on 2013, September 29. This smooth eruption, which passed without any previous flare, formed after a two-ribbon flare and a coronal mass ejection towards Earth. The coronal mass ejection generated a moderate geomagnetic storm on 2013, October 2 with very serious localized effects. The whole event passed unnoticed to flare-warning systems. Methods: We have conducted multi-wavelength analyses of the Solar Dynamics Observatory through Atmospheric Imaging Assembly (AIA) and Helioseismic and Magnetic Imager (HMI) data. The AIA data on 304, 193, 211, and 94 Å sample the transition region and the corona, respectively, while HMI provides photospheric magnetograms, continuum, and linear polarization data, in addition to the fully inverted data provided by HMI. Results: This flux emergence happened very close to a filament barb that was very active in mass motion, as seen in 304 Å images. The observed flux emergence exhibited hectogauss values. The flux emergence extent appeared just beneath the filament, and the filament rose during the following hours. The emergence acquired a size of 33'' in ~12 h, about ~0.16 km s-1. The rate of signed magnetic flux is around 2 × 1017 Mx min-1 for each polarity. We have also studied the eruption speed, size, and dynamics. The mean velocity of the rising filament during the ~40 min previous to the flare is 115 ± 5 km s-1, and the subsequent acceleration in this period is 0.049 ± 0.001 km s-2. Conclusions: We have observed a supergranular-sized emergence close to a large filament in the boundary of the active region NOAA11850. Filament dynamics and magnetogram results suggest that the magnetic flux emergence takes place in the photospheric level below the filament. Reconnection occurs underneath the filament between the dipped lines that support the filament and the supergranular emergence. The very smooth ascent is probably caused by this emergence and torus instability

  6. Application of Filament Winding to Cannon and Cannon Components. Part 3. Summary Report

    DTIC Science & Technology

    1976-10-01

    filament volume ratio. There are many filaments that can be used in a composite gun tube. The ultimate strength, density, specific strength, specific ... specific strength indicates the merit of the material, with the largest value considered the best. Values from Table 1 reflect filament properties only...theoretical residual stresses B-B obtained during the filament winding process. These stresses are produced by a constant filament winding tension

  7. Role of streams in myxobacteria aggregate formation

    NASA Astrophysics Data System (ADS)

    Kiskowski, Maria A.; Jiang, Yi; Alber, Mark S.

    2004-10-01

    Cell contact, movement and directionality are important factors in biological development (morphogenesis), and myxobacteria are a model system for studying cell-cell interaction and cell organization preceding differentiation. When starved, thousands of myxobacteria cells align, stream and form aggregates which later develop into round, non-motile spores. Canonically, cell aggregation has been attributed to attractive chemotaxis, a long range interaction, but there is growing evidence that myxobacteria organization depends on contact-mediated cell-cell communication. We present a discrete stochastic model based on contact-mediated signaling that suggests an explanation for the initialization of early aggregates, aggregation dynamics and final aggregate distribution. Our model qualitatively reproduces the unique structures of myxobacteria aggregates and detailed stages which occur during myxobacteria aggregation: first, aggregates initialize in random positions and cells join aggregates by random walk; second, cells redistribute by moving within transient streams connecting aggregates. Streams play a critical role in final aggregate size distribution by redistributing cells among fewer, larger aggregates. The mechanism by which streams redistribute cells depends on aggregate sizes and is enhanced by noise. Our model predicts that with increased internal noise, more streams would form and streams would last longer. Simulation results suggest a series of new experiments.

  8. Attractive interactions among intermediate filaments determine network mechanics in vitro.

    PubMed

    Pawelzyk, Paul; Mücke, Norbert; Herrmann, Harald; Willenbacher, Norbert

    2014-01-01

    Mechanical and structural properties of K8/K18 and vimentin intermediate filament (IF) networks have been investigated using bulk mechanical rheometry and optical microrheology including diffusing wave spectroscopy and multiple particle tracking. A high elastic modulus G0 at low protein concentration c, a weak concentration dependency of G0 (G0 ∼ c(0.5 ± 0.1)) and pronounced strain stiffening are found for these systems even without external crossbridgers. Strong attractive interactions among filaments are required to maintain these characteristic mechanical features, which have also been reported for various other IF networks. Filament assembly, the persistence length of the filaments and the network mesh size remain essentially unaffected when a nonionic surfactant is added, but strain stiffening is completely suppressed, G0 drops by orders of magnitude and exhibits a scaling G0 ∼ c(1.9 ± 0.2) in agreement with microrheological measurements and as expected for entangled networks of semi-flexible polymers. Tailless K8Δ/K18ΔT and various other tailless filament networks do not exhibit strain stiffening, but still show high G0 values. Therefore, two binding sites are proposed to exist in IF networks. A weaker one mediated by hydrophobic amino acid clusters in the central rod prevents stretched filaments between adjacent cross-links from thermal equilibration and thus provides the high G0 values. Another strong one facilitating strain stiffening is located in the tail domain with its high fraction of hydrophobic amino acid sequences. Strain stiffening is less pronounced for vimentin than for K8/K18 due to electrostatic repulsion forces partly compensating the strong attraction at filament contact points.

  9. MESSENGER Observations of Cusp Plasma Filaments at Mercury

    NASA Astrophysics Data System (ADS)

    Poh, G. K.; Slavin, J. A.; DiBraccio, G. A.; Jia, X.; Raines, J. M.; Imber, S. M.; Anderson, B. J.; Korth, H.; Gershman, D. J.; Zurbuchen, T.; McNutt, R. L., Jr.; Solomon, S. C.

    2014-12-01

    At Mercury, MESSENGER has documented ~1-2-s-long reductions in the dayside magnetospheric magnetic field with amplitudes up to 90% of the ambient intensity. These field reductions which we have termed cusp filaments are observed from just poleward of the magnetospheric cusp to mid-latitudes. During these events, MESSENGER's Fast Imaging Plasma Spectrometer (FIPS) measured H+ ions with magnetosheath-like energies. Minimum variance analysis of the Magnetometer (MAG) data indicates that the filaments are simple two dimensional flux tubes filled with magnetosheath plasma that has a diamagnetic effect on the local background field. Here we analyze 139 filaments identified in 3 years of MESSENGER magnetic field and plasma data to determine the physical properties of these structures. Our results indicate that cusp filaments are common phenomena for all solar wind conditions. They occur over a range of magnetic latitudes from ~50 to 80oN, with durations of ~0.1-2.5s and magnetic field decreases of ~50-300 nT. If the filaments are associated with flux transfer events (FTEs) and move over the spacecraft at speeds comparable to the flank magnetosheath flow speed of 300 km/s, then these filaments have dimensions of ~30-750 km, which is larger than the gyro-radius of a 1 keV H+ ion, i.e., ~ 23 km. Correlation analyses show no obvious dependence of the duration or magnitude of the diamagnetic decrease on magnetic latitude. Overall, the MAG and FIPS observations analyzed here appear consistent with an origin for cusp plasma filaments by the inflow of magnetosheath plasma associated with the localized magnetopause reconnection process that produces FTEs. Further analysis will be required to confirm this hypothesis.

  10. Reaction-diffusion-advection approach to spatially localized treadmilling aggregates of molecular motors

    NASA Astrophysics Data System (ADS)

    Yochelis, Arik; Bar-On, Tomer; Gov, Nir S.

    2016-04-01

    Unconventional myosins belong to a class of molecular motors that walk processively inside cellular protrusions towards the tips, on top of actin filament. Surprisingly, in addition, they also form retrograde moving self-organized aggregates. The qualitative properties of these aggregates are recapitulated by a mass conserving reaction-diffusion-advection model and admit two distinct families of modes: traveling waves and pulse trains. Unlike the traveling waves that are generated by a linear instability, pulses are nonlinear structures that propagate on top of linearly stable uniform backgrounds. Asymptotic analysis of isolated pulses via a simplified reaction-diffusion-advection variant on large periodic domains, allows to draw qualitative trends for pulse properties, such as the amplitude, width, and propagation speed. The results agree well with numerical integrations and are related to available empirical observations.

  11. Oligomeric baroeffect and gas aggregation states

    NASA Technical Reports Server (NTRS)

    Noever, David A.

    1992-01-01

    The baroeffect is analyzed to include a gas that aggregates into higher-order polymers or oligomers. The resulting pressure change is found to vary independently of the molecular weight of the gas components and to depend only on the aggregation or oligomeric order of the gas. With increasing aggregation, diffusive slip velocities are found to increase. The calculations are extended to include general counterdiffusion of two distinct aggregation states (k-, j-mer) for the gas, and the pressure change is derived as a function that is independent of both molecular weight and the absolute aggregation. The only parameter that determines the baroeffect is the ratio of aggregated states, beta = k/j. For gases that reversibly aggregate, possible oscillatory behavior and complex dynamics for pressure are discussed. Gas aggregation may play a role for low-temperature crystal-growth conditions in which vapor concentrations of one (or more) species are high.

  12. Virus-induced aggregates in infected cells.

    PubMed

    Moshe, Adi; Gorovits, Rena

    2012-10-17

    During infection, many viruses induce cellular remodeling, resulting in the formation of insoluble aggregates/inclusions, usually containing viral structural proteins. Identification of aggregates has become a useful diagnostic tool for certain viral infections. There is wide variety of viral aggregates, which differ by their location, size, content and putative function. The role of aggregation in the context of a specific virus is often poorly understood, especially in the case of plant viruses. The aggregates are utilized by viruses to house a large complex of proteins of both viral and host origin to promote virus replication, translation, intra- and intercellular transportation. Aggregated structures may protect viral functional complexes from the cellular degradation machinery. Alternatively, the activation of host defense mechanisms may involve sequestration of virus components in aggregates, followed by their neutralization as toxic for the host cell. The diversity of virus-induced aggregates in mammalian and plant cells is the subject of this review.

  13. Protein aggregation in salt solutions

    PubMed Central

    Kastelic, Miha; Kalyuzhnyi, Yurij V.; Hribar-Lee, Barbara; Dill, Ken A.; Vlachy, Vojko

    2015-01-01

    Protein aggregation is broadly important in diseases and in formulations of biological drugs. Here, we develop a theoretical model for reversible protein–protein aggregation in salt solutions. We treat proteins as hard spheres having square-well-energy binding sites, using Wertheim’s thermodynamic perturbation theory. The necessary condition required for such modeling to be realistic is that proteins in solution during the experiment remain in their compact form. Within this limitation our model gives accurate liquid–liquid coexistence curves for lysozyme and γ IIIa-crystallin solutions in respective buffers. It provides good fits to the cloud-point curves of lysozyme in buffer–salt mixtures as a function of the type and concentration of salt. It than predicts full coexistence curves, osmotic compressibilities, and second virial coefficients under such conditions. This treatment may also be relevant to protein crystallization. PMID:25964322

  14. Decay of helical Kelvin waves on a quantum vortex filament

    SciTech Connect

    Van Gorder, Robert A.

    2014-07-15

    We study the dynamics of helical Kelvin waves moving along a quantum vortex filament driven by a normal fluid flow. We employ the vector form of the quantum local induction approximation (LIA) due to Schwarz. For an isolated filament, this is an adequate approximation to the full Hall-Vinen-Bekarevich-Khalatnikov dynamics. The motion of such Kelvin waves is both translational (along the quantum vortex filament) and rotational (in the plane orthogonal to the reference axis). We first present an exact closed form solution for the motion of these Kelvin waves in the case of a constant amplitude helix. Such solutions exist for a critical wave number and correspond exactly to the Donnelly-Glaberson instability, so perturbations of such solutions either decay to line filaments or blow-up. This leads us to consider helical Kelvin waves which decay to line filaments. Unlike in the case of constant amplitude helical solutions, the dynamics are much more complicated for the decaying helical waves, owing to the fact that the rate of decay of the helical perturbations along the vortex filament is not constant in time. We give an analytical and numerical description of the motion of decaying helical Kelvin waves, from which we are able to ascertain the influence of the physical parameters on the decay, translational motion along the filament, and rotational motion, of these waves (all of which depend nonlinearly on time). One interesting finding is that the helical Kelvin waves do not decay uniformly. Rather, such waves decay slowly for small time scales, and more rapidly for large time scales. The rotational and translational velocity of the Kelvin waves depend strongly on this rate of decay, and we find that the speed of propagation of a helical Kelvin wave along a quantum filament is large for small time while the wave asymptotically slows as it decays. The rotational velocity of such Kelvin waves along the filament will increase over time, asymptotically reaching a finite

  15. Investigating the global collapse of filaments using smoothed particle hydrodynamics

    NASA Astrophysics Data System (ADS)

    Clarke, S. D.; Whitworth, A. P.

    2015-05-01

    We use smoothed particle hydrodynamic simulations of cold, uniform density, self-gravitating filaments, to investigate their longitudinal collapse time-scales; these time-scales are important because they determine the time available for a filament to fragment into cores. A filament is initially characterized by its line-mass, μO, its radius, RO (or equivalently its density ρ O= μ O/π RO^2), and its aspect ratio, AO (≡ZO/RO, where ZO is its half-length). The gas is only allowed to contract longitudinally, i.e. parallel to the symmetry axis of the filament (the z-axis). Pon et al. (2012) have considered the global dynamics of such filaments analytically. They conclude that short filaments (AO ≲ 5) collapse along the z-axis more-or-less homologously, on a time-scale tHOM ˜ 0.44 AO (GρO)-1/2; in contrast, longer filaments (AO ≳ 5) undergo end-dominated collapse, i.e. two dense clumps form at the ends of the filament and converge on the centre sweeping up mass as they go, on a time-scale t_{END} ˜ 0.98 AO^{1/2} (Gρ O)^{-1/2}. Our simulations do not corroborate these predictions. First, for all AO ≳ 2, the collapse time satisfies a single equation t_{COL}˜ (0.49+0.26AO)(Gρ O)^{-1/2}, which for large AO is much longer than the Pon et al. prediction. Secondly, for all AO ≳ 2, the collapse is end-dominated. Thirdly, before being swept up, the gas immediately ahead of an end-clump is actually accelerated outwards by the gravitational attraction of the approaching clump, resulting in a significant ram pressure. For high aspect ratio filaments, the end-clumps approach an asymptotic inward speed, due to the fact that they are doing work both accelerating and compressing the gas they sweep up. Pon et al. appear to have neglected the outward acceleration and its consequences.

  16. Dynamic Star Formation in the Massive DR21 Filament

    SciTech Connect

    Schneider, N.; Csengeri, T.; Bontemps, S.; Motte, F.; Simon, R.; Hennebelle, P.; Federrath, C.; Klessen, R.; /ZAH, Heidelberg /KIPAC, Menlo Park

    2010-08-25

    The formation of massive stars is a highly complex process in which it is unclear whether the star-forming gas is in global gravitational collapse or an equilibrium state supported by turbulence and/or magnetic fields. By studying one of the most massive and dense star-forming regions in the Galaxy at a distance of less than 3 kpc, i.e. the filament containing the well-known sources DR21 and DR21(OH), we attempt to obtain observational evidence to help us to discriminate between these two views. We use molecular line data from our {sup 13}CO 1 {yields} 0, CS 2 {yields} 1, and N{sub 2}H{sup +} 1 {yields} 0 survey of the Cygnus X region obtained with the FCRAO and CO, CS, HCO{sup +}, N{sub 2}H{sup +}, and H{sub 2}CO data obtained with the IRAM 30m telescope. We observe a complex velocity field and velocity dispersion in the DR21 filament in which regions of the highest column-density, i.e., dense cores, have a lower velocity dispersion than the surrounding gas and velocity gradients that are not (only) due to rotation. Infall signatures in optically thick line profiles of HCO{sup +} and {sup 12}CO are observed along and across the whole DR21 filament. By modelling the observed spectra, we obtain a typical infall speed of {approx}0.6 km s{sup -1} and mass accretion rates of the order of a few 10{sup -3} M{sub {circle_dot}} yr{sup -1} for the two main clumps constituting the filament. These massive clumps (4900 and 3300 M{sub {circle_dot}} at densities of around 10{sup 5} cm{sup -3} within 1 pc diameter) are both gravitationally contracting. The more massive of the clumps, DR21(OH), is connected to a sub-filament, apparently 'falling' onto the clump. This filament runs parallel to the magnetic field. Conclusions. All observed kinematic features in the DR21 filament (velocity field, velocity dispersion, and infall), its filamentary morphology, and the existence of (a) sub-filament(s) can be explained if the DR21 filament was formed by the convergence of flows on large

  17. A comparison study of a solar active-region eruptive filament and a neighboring non-eruptive filament

    NASA Astrophysics Data System (ADS)

    Jiang, Chao-Wei; Wu, Shi-Tsan; Feng, Xue-Shang; Hu, Qiang

    2016-01-01

    Solar active region (AR) 11283 is a very magnetically complex region and it has produced many eruptions. However, there exists a non-eruptive filament in the plage region just next to an eruptive one in the AR, which gives us an opportunity to perform a comparison analysis of these two filaments. The coronal magnetic field extrapolated using our CESE-MHD-NLFFF code reveals that two magnetic flux ropes (MFRs) exist in the same extrapolation box supporting these two filaments, respectively. Analysis of the magnetic field shows that the eruptive MFR contains a bald-patch separatrix surface (BPSS) cospatial very well with a pre-eruptive EUV sigmoid, which is consistent with the BPSS model for coronal sigmoids. The magnetic dips of the non-eruptive MFRs match Hα observation of the non-eruptive filament strikingly well, which strongly supports the MFR-dip model for filaments. Compared with the non-eruptive MFR/filament (with a length of about 200 Mm), the eruptive MFR/filament is much smaller (with a length of about 20 Mm), but it contains most of the magnetic free energy in the extrapolation box and holds a much higher free energy density than the non-eruptive one. Both the MFRs are weakly twisted and cannot trigger kink instability. The AR eruptive MFR is unstable because its axis reaches above a critical height for torus instability, at which the overlying closed arcades can no longer confine the MFR stably. On the contrary, the quiescent MFR is very firmly held by its overlying field, as its axis apex is far below the torus-instability threshold height. Overall, this comparison investigation supports that an MFR can exist prior to eruption and the ideal MHD instability can trigger an MFR eruption.

  18. Magnetic Fields in the Massive Dense Cores of the DR21 Filament: Weakly Magnetized Cores in a Strongly Magnetized Filament

    NASA Astrophysics Data System (ADS)

    Ching, Tao-Chung; Lai, Shih-Ping; Zhang, Qizhou; Girart, Josep M.; Qiu, Keping; Liu, Hauyu B.

    2017-04-01

    We present Submillimeter Array 880 μm dust polarization observations of six massive dense cores in the DR21 filament. The dust polarization shows complex magnetic field structures in the massive dense cores with sizes of 0.1 pc, in contrast to the ordered magnetic fields of the parsec-scale filament. The major axes of the massive dense cores appear to be aligned either parallel or perpendicular to the magnetic fields of the filament, indicating that the parsec-scale magnetic fields play an important role in the formation of the massive dense cores. However, the correlation between the major axes of the cores and the magnetic fields of the cores is less significant, suggesting that during the core formation, the magnetic fields below 0.1 pc scales become less important than the magnetic fields above 0.1 pc scales in supporting a core against gravity. Our analysis of the angular dispersion functions of the observed polarization segments yields a plane-of-sky magnetic field strength of 0.4–1.7 mG for the massive dense cores. We estimate the kinematic, magnetic, and gravitational virial parameters of the filament and the cores. The virial parameters show that the gravitational energy in the filament dominates magnetic and kinematic energies, while the kinematic energy dominates in the cores. Our work suggests that although magnetic fields may play an important role in a collapsing filament, the kinematics arising from gravitational collapse must become more important than magnetic fields during the evolution from filaments to massive dense cores.

  19. A filament of dark matter between two clusters of galaxies.

    PubMed

    Dietrich, Jörg P; Werner, Norbert; Clowe, Douglas; Finoguenov, Alexis; Kitching, Tom; Miller, Lance; Simionescu, Aurora

    2012-07-12

    It is a firm prediction of the concordance cold-dark-matter cosmological model that galaxy clusters occur at the intersection of large-scale structure filaments. The thread-like structure of this 'cosmic web' has been traced by galaxy redshift surveys for decades. More recently, the warm–hot intergalactic medium (a sparse plasma with temperatures of 10(5) kelvin to 10(7) kelvin) residing in low-redshift filaments has been observed in emission and absorption. However, a reliable direct detection of the underlying dark-matter skeleton, which should contain more than half of all matter, has remained elusive, because earlier candidates for such detections were either falsified or suffered from low signal-to-noise ratios and unphysical misalignments of dark and luminous matter. Here we report the detection of a dark-matter filament connecting the two main components of the Abell 222/223 supercluster system from its weak gravitational lensing signal, both in a non-parametric mass reconstruction and in parametric model fits. This filament is coincident with an overdensity of galaxies and diffuse, soft-X-ray emission, and contributes a mass comparable to that of an additional galaxy cluster to the total mass of the supercluster. By combining this result with X-ray observations, we can place an upper limit of 0.09 on the hot gas fraction (the mass of X-ray-emitting gas divided by the total mass) in the filament.

  20. Semiflexible filament networks viewed as fluctuating beam frames

    NASA Astrophysics Data System (ADS)

    Su, Tianxiang; Purohit, Prashant

    2012-02-01

    We present a new method combining structural and statistical mechanics to study the entropic elasticity of semiflexible filament networks. We view a filament network as a frame structure and use structural mechanics to determine its static equilibrium configuration under applied loads in the first step. To account for thermal motion around this static equilibrium state, we then approximate the potential energy of the deformed frame structure up to the second order in kinematic variables and obtaina deformation-dependent stiffness matrix characterizing the flexibility of the network. Using statistical mechanics, we then evaluate the partition function, free energy and thermo-mechanical properties of the network in terms of the stiffness matrix. We show that penalty methods commonly used in finite elements to account for constraints, are applicable even when statistical and structural mechanics are combined in our method. We apply our framework to understand the expansion, shear, uniaxial tension and compression behavior of some simple filament networks. We are able to capture the stress-stiffening behavior due to filament reorientation and stretching out of thermal fluctuations, as well as the reversible stress-softening behavior due to filament buckling.

  1. Filament capturing with the multimaterial moment-of-fluid method*

    DOE PAGES

    Jemison, Matthew; Sussman, Mark; Shashkov, Mikhail

    2015-01-15

    A novel method for capturing two-dimensional, thin, under-resolved material configurations, known as “filaments,” is presented in the context of interface reconstruction. This technique uses a partitioning procedure to detect disconnected regions of material in the advective preimage of a cell (indicative of a filament) and makes use of the existing functionality of the Multimaterial Moment-of-Fluid interface reconstruction method to accurately capture the under-resolved feature, while exactly conserving volume. An algorithm for Adaptive Mesh Refinement in the presence of filaments is developed so that refinement is introduced only near the tips of filaments and where the Moment-of-Fluid reconstruction error is stillmore » large. Comparison to the standard Moment-of-Fluid method is made. As a result, it is demonstrated that using filament capturing at a given resolution yields gains in accuracy comparable to introducing an additional level of mesh refinement at significantly lower cost.« less

  2. High-Resolution Observations of a Filament showing Activated Barb

    NASA Astrophysics Data System (ADS)

    Joshi, Anand; Martin, Sara F.; Mathew, Shibu; Srivastava, Nandita

    2012-07-01

    Analysis of a filament showing an activated barb using observations from the Dutch Open Telescope (DOT) on 2010 August 20 are presented. The DOT takes Doppler images in Hα, among other wavelengths, in a region about 110 × 110 arcsec^{2} in area, at a cadence of 30~seconds. The offline image restoration technique of speckle reconstruction is applied to obtain diffraction limited images. The filament developed a new barb in 10~minutes, which disappeared within the next 35~minutes. Such a rapid formation and disappearance of a filament barb is unusual, and has not been reported earlier. Line-of-sight velocity maps were constructed from the Doppler images of the target filament. We observe flows in the filament spine towards the barb location prior to its formation, and flows in the barb towards the spine during its disappearance. Photospheric magnetograms from Heliospheric Magnetic Imager on board the Solar Dynamics Observatory, at a cadence of 45~seconds, were used to determine the changes in magnetic flux in the region surrounding the barb location. The variation of magnetic flux in this duration supports the view that barbs are rooted in minor magnetic polarity. Our analysis shows that barbs can be short-lived and formation and disappearance of the barb was associated with cancellation of magnetic flux.

  3. Rapid Formation and Disappearance of a Filament Barb

    NASA Astrophysics Data System (ADS)

    Joshi, Anand D.; Srivastava, Nandita; Mathew, Shibu K.; Martin, Sara F.

    2013-11-01

    We present observations of an activated quiescent filament obtained in Hα from the high-resolution Dutch Open Telescope (DOT) on 20 August 2010. The filament developed a barb in 10 min, which disappeared within the next 35 min. A data set from the DOT spanning 2 h was used to analyse this event. Line-of-sight velocity maps were constructed from the Doppler images, which reveal flows in filament spine during this period. Photospheric magnetograms were used from the Helioseismic and Magnetic Imager (HMI) on board the Solar Dynamics Observatory (SDO) to determine the changes in magnetic flux in the region surrounding the barb location. The analysis shows flows in the filament spine towards the barb location preceding its formation, and flows in the barb towards the spine during its disappearance. Magnetograms reveal patches of minority polarity flux close to the end of the barb at its greatest elongation. The flows in the spine and barbs are along numerous threads that compose these typical filament structures. The flows are consistent with field-aligned threads and demonstrate that the replacement time of the mass in barbs, and by inference, in the spine is very rapid.

  4. Filament winding S-glass/polyimide resin composite processing studies

    NASA Technical Reports Server (NTRS)

    Vaughan, R. W.; Jones, R. J.

    1974-01-01

    The work performed in selecting a TRW A-type polyimide resin that would be suitable for fabrication of filament wound reinforced plastic structures is described. Several different formulations were evaluated after which the P105AC formulation was selected as the most promising. Procedures then were developed for preparing P105AC/S-glass roving prepreg and for fabricating filament wound structural composites. Composites were fabricated and then tested in order to obtain tensile and shear strength information. Small, closed-end cylindrical pressure vessels then were fabricated using a stainless steel liner and end fittings with a P105AC/S-glass polar wound overwrap. These pressure vessels were cured in an air circulating oven without augmented pressure. It is concluded that the P105AC resin system is suitable for filament winding; that low void content, high strength composites are obtained by the filament winding process; and that augmented pressure is not required to effect the fabrication of filament wound P105AC composites.

  5. 3D motion analysis of keratin filaments in living cells

    NASA Astrophysics Data System (ADS)

    Herberich, Gerlind; Windoffer, Reinhard; Leube, Rudolf; Aach, Til

    2010-03-01

    We present a novel and efficient approach for 3D motion estimation of keratin intermediate filaments in vitro. Keratin filaments are elastic cables forming a complex scaffolding within epithelial cells. To understand the mechanisms of filament formation and network organisation under physiological and pathological conditions, quantitative measurements of dynamic network alterations are essential. Therefore we acquired time-lapse series of 3D images using a confocal laser scanning microscope. Based on these image series, we show that a dense vector field can be computed such that the displacements from one frame to the next can be determined. Our method is based on a two-step registration process: First, a rigid pre-registration is applied in order to compensate for possible global cell movement. This step enables the subsequent nonrigid registration to capture only the sought local deformations of the filaments. As the transformation model of the deformable registration algorithm is based on Free Form Deformations, it is well suited for modeling filament network dynamics. The optimization is performed using efficient linear programming techniques such that the huge amount of image data of a time series can be efficiently processed. The evaluation of our results illustrates the potential of our approach.

  6. Early Hinode Observations of a Solar Filament Eruption

    NASA Technical Reports Server (NTRS)

    Sterling, Alphonse C.; Moore, Ronald L.

    2007-01-01

    We use Hinode X-Ray Telescope (XRT) and Solar Optical Telescope (SOT) filtergraph (FG) Stokes-V magnetogram observations to study the early onset of a solar eruption that includes an erupting filament that we observe in TRACE EUV images; this is one of the first filament eruptions seen with Hinode. The filament undergoes a slow rise for at least 30 min prior to its fast eruption and strong soft X-ray flaring, and the new Hinode data elucidate the physical processes occurring during the slow-rise period: During the slow-rise phase, a soft X-ray (SXR) sigmoid forms from apparent reconnection low in the sheared core field traced by the filament, and there is a low-level intensity peak in both EUV and SXRs during the slow rise. The SOT data show that magnetic flux cancellation occurs along the neutral line of the filament in the hours before eruption, and this likely caused the low-lying reconnection that produced the microflaring and the slow rise leading up to the eruption.

  7. Ack kinase regulates CTP synthase filaments during Drosophila oogenesis.

    PubMed

    Strochlic, Todd I; Stavrides, Kevin P; Thomas, Sam V; Nicolas, Emmanuelle; O'Reilly, Alana M; Peterson, Jeffrey R

    2014-11-01

    The enzyme CTP synthase (CTPS) dynamically assembles into macromolecular filaments in bacteria, yeast, Drosophila, and mammalian cells, but the role of this morphological reorganization in regulating CTPS activity is controversial. During Drosophila oogenesis, CTPS filaments are transiently apparent in ovarian germline cells during a period of intense genomic endoreplication and stockpiling of ribosomal RNA. Here, we demonstrate that CTPS filaments are catalytically active and that their assembly is regulated by the non-receptor tyrosine kinase DAck, the Drosophila homologue of mammalian Ack1 (activated cdc42-associated kinase 1), which we find also localizes to CTPS filaments. Egg chambers from flies deficient in DAck or lacking DAck catalytic activity exhibit disrupted CTPS filament architecture and morphological defects that correlate with reduced fertility. Furthermore, ovaries from these flies exhibit reduced levels of total RNA, suggesting that DAck may regulate CTP synthase activity. These findings highlight an unexpected function for DAck and provide insight into a novel pathway for the developmental control of an essential metabolic pathway governing nucleotide biosynthesis.

  8. Type-III secretion filaments as scaffolds for inorganic nanostructures

    PubMed Central

    Azam, Anum; Tullman-Ercek, Danielle

    2016-01-01

    Nanostructured materials exhibit unique magnetic, electrical and catalytic properties. These characteristics are determined by the chemical composition, size and shape of the nanostructured components, which are challenging to modulate on such small size scales and to interface with living cells. To address this problem, we are using a self-assembling filament protein, PrgI, as a scaffold for bottom-up inorganic nanostructure synthesis. PrgI is a small protein (80 amino acids) that oligomerizes to form the type-III secretion system needle of Salmonella enterica. We demonstrate that purified PrgI monomers also spontaneously self-assemble into long filaments and that high-affinity peptide tags specific for attachment to functionalized particles can be integrated into the N-terminal region of PrgI. The resulting filaments selectively bind to gold, whether the filaments are assembled in vitro, sheared from cells or remain attached to live S. enterica cell membranes. Chemical reduction of the gold-modified PrgI variants results in structures that are several micrometres in length and which incorporate a contiguous gold surface. Mutant strains with genomically incorporated metal-binding tags retain the secretion phenotype. We anticipate that self-assembled, cell-tethered protein/metal filamentous structures have applications in sensing and energy transduction in vivo. PMID:26763334

  9. Rational design of MMP degradable peptide-based supramolecular filaments.

    PubMed

    Lin, Yi-An; Ou, Yu-Chuan; Cheetham, Andrew G; Cui, Honggang

    2014-04-14

    One-dimensional nanostructures formed by self-assembly of small molecule peptides have been extensively explored for use as biomaterials in various biomedical contexts. However, unlike individual peptides that can be designed to be specifically degradable by enzymes/proteases of interest, their self-assembled nanostructures, particularly those rich in β-sheets, are generally resistant to enzymatic degradation because the specific cleavage sites are often embedded inside the nanostructures. We report here on the rational design of β-sheet rich supramolecular filaments that can specifically dissociate into less stable micellar assemblies and monomers upon treatment with matrix metalloproteases-2 (MMP-2). Through linkage of an oligoproline segment to an amyloid-derived peptide sequence, we first synthesized an amphiphilic peptide that can undergo a rapid morphological transition in response to pH variations. We then used MMP-2 specific peptide substrates as multivalent cross-linkers to covalently fix the amyloid-like filaments in the self-assembled state at pH 4.5. Our results show that the cross-linked filaments are stable at pH 7.5 but gradually break down into much shorter filaments upon cleavage of the peptidic cross-linkers by MMP-2. We believe that the reported work presents a new design platform for the creation of amyloid-like supramolecular filaments responsive to enzymatic degradation.

  10. Manipulation of flow around bluff bodies by flexible slender filaments

    NASA Astrophysics Data System (ADS)

    Omidyeganeh, Mohammad; Pinelli, Alfredo

    2016-11-01

    Manipulation of bluff bodies wakes to control the intensity of fluid forces and the induced solid vibrations is of paramount importance. A biomimetic passive control based on the use of flexible slender appendages protruding from the body into the separated region has shown promising achievements in drag reduction and moderating force fluctuations. The present research aimed at understating and optimizing the physical properties and the arrangement of elongated flexible filaments to delay the 3D transition of the wake in terms of Reynolds number, mean drag reduction, and mitigation of the force fluctuations. The numerical campaign unveiled the role of flexural stiffness of the filaments: matching the natural frequency with the vortex shedding frequency enhances the mixing at the lee side. However, softer filaments (i.e. larger time scales) lock-in on either side of mid plane breaking the symmetry of the flow field (inducing a net lift force). In addition to 2D effects, the presence of filaments can interfere with the 3D bifurcation process resulting in a delay of the spanwise destabilization of the wake. The most effective parameter for this transitional interference is the spacing between filaments that should be smaller than the wavelength of the dominant 3D unstable mode.

  11. Rotor Vortex Filaments: Living on the Slipstream's Edge

    NASA Technical Reports Server (NTRS)

    Young, Larry A.

    1997-01-01

    The purpose of this paper is to gain a better understanding of rotor wake evolution in hover and axial flow by deriving an analytical solution for the time dependent behavior of vortex filament circulation and core size. This solution is applicable only for vortex filaments in the rotor far-wake. A primarily inviscid vortex/shear layer interaction (where the slipstream boundary is modeled as a shear layer) has been identified in this analytical treatment. This vortex/shear layer interaction results in decreasing, vortex filament circulation and core size with time. The inviscid vortex/shear layer interaction is shown, in a first-order treatment, to be of greater magnitude than viscous diffusion effects. The rate of contraction, and ultimate collapse, of the vortex filament core is found to be directly proportional to the rotor inflow velocity. This new insight into vortex filament decay promises to help reconcile several disparate observations made in the literature and will, hopefully, promote new advances in theoretical modeling of rotor wakes.

  12. Aggregation of Heterogeneously Charged Colloids.

    PubMed

    Dempster, Joshua M; Olvera de la Cruz, Monica

    2016-06-28

    Patchy colloids are attractive as programmable building blocks for metamaterials. Inverse patchy colloids, in which a charged surface is decorated with patches of the opposite charge, are additionally noteworthy as models for heterogeneously charged biological materials such as proteins. We study the phases and aggregation behavior of a single charged patch in an oppositely charged colloid with a single-site model. This single-patch inverse patchy colloid model shows a large number of phases when varying patch size. For large patch sizes we find ferroelectric crystals, while small patch sizes produce cross-linked gels. Intermediate values produce monodisperse clusters and unusual worm structures that preserve finite ratios of area to volume. The polarization observed at large patch sizes is robust under extreme disorder in patch size and shape. We examine phase-temperature dependence and coexistence curves and find that large patch sizes produce polarized liquids, in contrast to mean-field predictions. Finally, we introduce small numbers of unpatched charged colloids. These can either suppress or encourage aggregation depending on their concentration and the size of the patches on the patched colloids. These effects can be exploited to control aggregation and to measure effective patch size.

  13. Antioxidant Treatment and Induction of Autophagy Cooperate to Reduce Desmin Aggregation in a Cellular Model of Desminopathy

    PubMed Central

    Cabet, Eva; Batonnet-Pichon, Sabrina; Delort, Florence; Gausserès, Blandine; Vicart, Patrick; Lilienbaum, Alain

    2015-01-01

    Desminopathies, a subgroup of myofibrillar myopathies (MFMs), the progressive muscular diseases characterized by the accumulation of granulofilamentous desmin-positive aggregates, result from mutations in the desmin gene (DES), encoding a muscle-specific intermediate filament. Desminopathies often lead to severe disability and premature death from cardiac and/or respiratory failure; no specific treatment is currently available. To identify drug-targetable pathophysiological pathways, we performed pharmacological studies in C2C12 myoblastic cells expressing mutant DES. We found that inhibition of the Rac1 pathway (a G protein signaling pathway involved in diverse cellular processes), antioxidant treatment, and stimulation of macroautophagy reduced protein aggregation by up to 75% in this model. Further, a combination of two or three of these treatments was more effective than any of them alone. These results pave the way towards the development of the first treatments for desminopathies and are potentially applicable to other muscle or brain diseases associated with abnormal protein aggregation. PMID:26333167

  14. 24 CFR 58.32 - Project aggregation.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 24 Housing and Urban Development 1 2010-04-01 2010-04-01 false Project aggregation. 58.32 Section... Environmental Review Process: Documentation, Range of Activities, Project Aggregation and Classification § 58.32 Project aggregation. (a) A responsible entity must group together and evaluate as a single project...

  15. 24 CFR 58.32 - Project aggregation.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 24 Housing and Urban Development 1 2012-04-01 2012-04-01 false Project aggregation. 58.32 Section... Environmental Review Process: Documentation, Range of Activities, Project Aggregation and Classification § 58.32 Project aggregation. (a) A responsible entity must group together and evaluate as a single project...

  16. 24 CFR 58.32 - Project aggregation.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 24 Housing and Urban Development 1 2011-04-01 2011-04-01 false Project aggregation. 58.32 Section... Environmental Review Process: Documentation, Range of Activities, Project Aggregation and Classification § 58.32 Project aggregation. (a) A responsible entity must group together and evaluate as a single project...

  17. 24 CFR 58.32 - Project aggregation.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 24 Housing and Urban Development 1 2014-04-01 2014-04-01 false Project aggregation. 58.32 Section... Environmental Review Process: Documentation, Range of Activities, Project Aggregation and Classification § 58.32 Project aggregation. (a) A responsible entity must group together and evaluate as a single project...

  18. Mineral resource of the month: aggregates

    USGS Publications Warehouse

    Willett, Jason C.

    2012-01-01

    Crushed stone and construction sand and gravel, the two major types of natural aggregates, are among the most abundant and accessible natural resources on the planet. The earliest civilizations used aggregates for various purposes, mainly construction. Today aggregates provide the basic raw materials for the foundation of modern society.

  19. 78 FR 68945 - Aggregation of Positions

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-11-15

    ... the aggregation provisions of part 150 of the Commission's regulations that are substantially similar... modifications proposed here to the aggregation provisions of part 150 would apply to the position limits regimes... position limits because it believes that these proposed amendments regarding aggregation of...

  20. Characterization of an integrally wound tungsten and aluminum filament for physical vapor deposition

    NASA Astrophysics Data System (ADS)

    Goble, William; Ortiz, Ricardo

    2016-07-01

    As part of the effort to increase the reliability of the MMT Observatory (MMTO) 6.5m Primary Mirror Coating System, the specified filament has changed from a configuration in which the aluminum charge is hand wound around a tungsten filament to a configuration in which the aluminum is integrally wound with the tungsten at the time of filament manufacture. In the MMTO configuration, this filament consists of the three strands of tungsten wire and one strand of aluminum wire. In preparation of a full system test utilizing two hundred filaments fired simultaneously, an extensive testing program was undertaken to characterize these filaments using a four filament configuration in the MMTO small coating chamber (0.5m) and then a forty filament configuration in the University of Arizona Steward Observatory coating chamber (2m). The testing using the smaller coating chambers has shown these filaments provide very predicable coatings from test to test, and with the proper heating profile, these filaments greatly reduce the likelihood of aluminum drips. The initial filament design was modified during the course of testing by shortening the unwound filament length to closer match the aluminum load required in the MMTO coating chamber. This change increased the aluminum deposition rates without increasing the power delivered of the filament power supplies (commercial welders). Filament power levels measured at the vacuum chamber feed throughs, currents, and deposition rates from multiple coating tests, including a full system test, are presented.