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Sample records for massive dr21 filament

  1. 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

  2. The role of low-mass star clusters in forming the massive stars in DR 21

    NASA Astrophysics Data System (ADS)

    Rivilla, V. M.; Jiménez-Serra, I.; Martín-Pintado, J.; Sanz-Forcada, J.

    2014-01-01

    We have studied the young low-mass pre-main sequence (PMS) stellar population associated with the massive star-forming region DR 21 by using archival X-ray Chandra observations and by complementing them with existing optical and infrared (IR) surveys. The Chandra observations have revealed for the first time a new highly extincted population of PMS low-mass stars previously missed in observations at other wavelengths. The X-ray population exhibits three main stellar density peaks, coincident with the massive star-forming regions, being the DR 21 core the main peak. The cross-correlated X-ray/IR sample exhibits a radial `Spokes-like' stellar filamentary structure that extends from the DR 21 core towards the northeast. The near-IR data reveal a centrally peaked structure for the extinction, which exhibits its maximum in the DR 21 core and gradually decreases with the distance to the N-S cloud axis and to the cluster centre. We find evidence of a global mass segregation in the full low-mass stellar cluster, and of a stellar age segregation, with the youngest stars still embedded in the N-S cloud, and more evolved stars more spatially distributed. The results are consistent with the scenario where an elongated overall potential well created by the full low-mass stellar cluster funnels gas through filaments feeding stellar formation. Besides the full gravitational well, smaller scale local potential wells created by dense stellar sub-clusters of low-mass stars are privileged in the competition for the gas of the common reservoir, allowing the formation of massive stars. We also discuss the possibility that a stellar collision in the very dense stellar cluster revealed by Chandra in the DR 21 core is the origin of the large-scale and highly energetic outflow arising from this region.

  3. The spine of the swan: a Herschel study of the DR21 ridge and filaments in Cygnus X

    NASA Astrophysics Data System (ADS)

    Hennemann, M.; Motte, F.; Schneider, N.; Didelon, P.; Hill, T.; Arzoumanian, D.; Bontemps, S.; Csengeri, T.; André, Ph.; Konyves, V.; Louvet, F.; Marston, A.; Men'shchikov, A.; Minier, V.; Nguyen Luong, Q.; Palmeirim, P.; Peretto, N.; Sauvage, M.; Zavagno, A.; Anderson, L. D.; Bernard, J.-Ph.; Di Francesco, J.; Elia, D.; Li, J. Z.; Martin, P. G.; Molinari, S.; Pezzuto, S.; Russeil, D.; Rygl, K. L. J.; Schisano, E.; Spinoglio, L.; Sousbie, T.; Ward-Thompson, D.; White, G. J.

    2012-07-01

    In order to characterise the cloud structures responsible for the formation of high-mass stars, we present Herschel observations of the DR21 environment. Maps of the column density and dust temperature unveil the structure of the DR21 ridge and several connected filaments. The ridge has column densities higher than 1023 cm-2 over a region of 2.3 pc2. It shows substructured column density profiles and branches into two major filaments in the north. The masses in the filaments range between 130 and 1400 M⊙, whereas the mass in the ridge is 15 000 M⊙. The accretion of these filaments onto the DR21 ridge, suggested by a previous molecular line study, could provide a continuous mass inflow to the ridge. In contrast to the striations seen in, e.g., the Taurus region, these filaments are gravitationally unstable and form cores and protostars. These coresformed in the filaments potentially fall into the ridge. Both inflow and collisions of cores could be important to drive the observed high-mass star formation. The evolutionary gradient of star formation running from DR21 in the south to the northern branching is traced by decreasing dust temperature. This evolution and the ridge structure can be explained by two main filamentary components of the ridge that merged first in the south. Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA (Pilbratt et al. 2010).Appendices are available in electronic form at http://www.aanda.org

  4. Sulfur-bearing molecules observed in the massive star-forming regions, DR21(OH) and G33.92+0.11

    NASA Astrophysics Data System (ADS)

    Minh, Y. C.

    2016-07-01

    Recent high sensitive and high angular resolution observations are providing unprecedented amount of chemical data, especially, on the massive star-forming regions. It will greatly extend our understandings on the complicated star formation process, if we can digest those huge amount of information. We discuss here on the properties of the sulfurbearing species observed with high angular resolutions toward two massive star-forming regions, DR21(OH) and G33.92+0.11. H2S may not exist as a solid form in the grain mantles, but OCS is believed to be one of major solid sulfur species, as suggested before. In addition, the bipolar-like outflow of the H2CS emission observed in DR21(OH) may suggest that H2CS is also one of solid sulfur species on the grain mantles. Depending on the chemical environment, the competition between hydrogenation and oxidization on the grain surface may lead to formation of specific solid forms to dominate, which could be either H2CS or OCS. SO and SO2 are often observed to be associated with ionized gas, such as the UC HII regions. These species seem to be formed in the high temperature turbulent gas in a later stage of star formation after the hot core phase. Fractional abundances of these sulfur-bearing species appear to be consistent to a certain extent in several star-forming regions. The physical and chemical evolution of massive star formation seems to pass through very similar stages in most star-forming regions. Consequently, it may indicate that there exists a consistent and coherent pattern of processes experienced by the massive star formation, in spite of the large variations in small scale locational differences.

  5. Star Formation in the DR21 Region (B)

    NASA Technical Reports Server (NTRS)

    2004-01-01

    , depicted in green, can be seen surrounding the DR21 region.

    The red filaments stretching across this image denote the presence of polycyclic aromatic hydrocarbons. These organic molecules, comprised of carbon and hydrogen, are excited by surrounding interstellar radiation and become luminescent at wavelengths near 8.0 microns. The complex pattern of filaments is caused by an intricate combination of radiation pressure, gravity and magnetic fields. The result is a tapestry in which winds, outflows and turbulence move and shape the interstellar medium.

    To the lower left of the mosaic is a large bubble of gas and dust, which may represent the remnants of a past generation of stars.

    The lower panel shows a 24-micron image mosaic, obtained with the Multiband Imaging Photometer aboard Spitzer (MIPS). This image maps the cooler infrared emission from interstellar dust found throughout the interstellar medium. The DR21 complex is clearly seen near the center of the strip, which covers about twice the area of the IRAC image.

    Perhaps the most fascinating feature in this image is a long and shadowy linear filament extending towards the 10 o'clock position of DR21. This jet of cold and dense gas, nearly 50 light-years in extent, appears in silhouette against a warmer background. This filament is too long and massive to be a stellar jet and may have formed from a pre-existing molecular cloud core sculpted by DR21's strong winds. Regardless of its true nature, this jet and the numerous other arcs and wisps of cool dust signify the interstellar turbulence normally unseen by the human eye.

  6. Star Formation in the DR21 Region (A)

    NASA Technical Reports Server (NTRS)

    2004-01-01

    [figure removed for brevity, see original site] Annotated mosaic

    Hidden behind a shroud of dust in the constellation Cygnus is a stellar nursery called DR21, which is giving birth to some of the most massive stars in our galaxy. Visible light images reveal no trace of this interstellar cauldron because of heavy dust obscuration. In fact, visible light is attenuated in DR21 by a factor of more than 10,000,000,000,000,000,000,000,000,000,000,000,000,000 (ten thousand trillion heptillion).

    New images from NASA's Spitzer Space Telescope allow us to peek behind the cosmic veil and pinpoint one of the most massive natal stars yet seen in our Milky Way galaxy. The never-before-seen star is 100,000 times as bright as the Sun. Also revealed for the first time is a powerful outflow of hot gas emanating from this star and bursting through a giant molecular cloud.

    The colorful image (top panel) is a large-scale composite mosaic assembled from data collected at a variety of different wavelengths. Views at visible wavelengths appear blue, near-infrared light is depicted as green, and mid-infrared data from the InfraRed Array Camera (IRAC) aboard NASA's Spitzer Space Telescope is portrayed as red. The result is a contrast between structures seen in visible light (blue) and those observed in the infrared (yellow and red). A quick glance shows that most of the action in this image is revealed to the unique eyes of Spitzer. The image covers an area about two times that of a full moon.

    Each of the constituent images is shown below the large mosaic. The Digital Sky Survey (DSS) image (lower left) provides a familiar view of deep space, with stars scattered around a dark field. The reddish hue is from gas heated by foreground stars in this region. This fluorescence fades away in the near-infrared Two-Micron All-Sky Survey (2MASS) image (lower center), but other features start to appear through the obscuring clouds of dust, now increasingly transparent. Many more

  7. A 10,000 YEAR OLD EXPLOSION IN DR21

    SciTech Connect

    Zapata, Luis A.; Perez-Goytia, Nadia; Rodriguez, Luis F.; Loinard, Laurent; Schmid-Burgk, Johannes; Ho, Paul T. P.; Cruz-Gonzalez, Irene

    2013-03-10

    Sensitive high angular resolution ({approx}2'') CO(2-1) line observations made with the Submillimeter Array of the flow emanating from the high-mass star-forming region DR21 located in the Cygnus X molecular cloud are presented. These new interferometric observations indicate that this well known enigmatic outflow appears to have been produced by an explosive event that took place about 10,000 years ago, and that might be related to the disintegration of a massive stellar system such as the one that occurred in Orion Becklin-Neugebauer/Kleinman-Low 500 years ago, but about 20 times more energetic. This result therefore argues in favor of the idea that the disintegration of young stellar systems perhaps is a frequent phenomenon present during the formation of massive stars. However, many more theoretical and observational studies are still needed to confirm our hypothesis.

  8. High-Velocity HCO Emission Associated with the DR21 Molecular Outflow

    NASA Astrophysics Data System (ADS)

    Garden, R. P.; Carlstrom, J. E.

    1996-03-01

    The spatial and velocity distribution of HCO(+) J = 1-0 line emission from the DR 21 young stellar outflow is investigated with the Hat Creek millimeter interferometer. It is argued that the HCO(+) emission arises from two spatially distinct components: low-velocity clumps bordering the central DR 21 compact H II region, and extended high-velocity gas associated with the DR 21 outflow lobes. The high-velocity HCO(+) emission associated with the outflow lobes exhibits a remarkable spatial correlation with the distribution of shock-excited H2 line emission and is most likely formed by the compression and acceleration of ambient gas on interaction with a powerful young stellar wind. It is argued that the observed spatial correlation between HCO(+) and H2 line emission results from two interrelated effects: a small enhancement in the fractional abundance of HCO(+) in the shocked gas, and the more favorable conditions for excitation of the HCO(+) ion in the warm dense gas that comprises the outflow lobes. It is suggested that the DR 21 outflow source is one of the largest, most massive and energetic young stellar outflows discovered to date.

  9. DR21(OH) - a high-mass star cluster in formation observed with Herschel-HIFI, and the IRAM PdBI

    NASA Astrophysics Data System (ADS)

    Bontemps, S.; Csengeri, T.; Herpin, F.; Schneider, N.; Motte, F.; Chavarria, L.; Baudry, A.

    2011-05-01

    With 7000 M_⊙ inside a radius of 0.3 pc, DR21(OH) is the most massive nearby sub-parsec size scale clump at less than 3 kpc from Sun (Motte et al. 2007, A&A 476, 1243). With a size similar to the Orion Nebula Cluster (ONC), it has the potential to form a 3 times more massive cluster than the ONC. It already contains a hot core/HCHII region (Araya et al. 2009, ApJ 698, 1321), as well as at least 2 class 0 like massive protostars (Bontemps et al. 2010, A&A 524, 18). It is also the possible location of the impact of a flow of material from a large scale filament detected in CS/N2H+ by Schneider et al. (2010, A&A 520, 49) falling on the clump. Using the IRAM PdBI we have resolved out the complex structure of the region both in the dust continuum and in several molecular lines (N2H+, CH3CN, H2CO, HC3N) and have found that it is actually governed by supersonic flows (see Csengeri et al. 2011, A&A 527, 135). Using the HIFI instrument, and as part of the WISH guaranteed time key program, we have observed DR21(OH) in more than 10 transitions of water and isotopologues which have all been detected with complex line profiles which are tracing the kinematics in the inner regions of the proto-cluster. From these high resolution observations and new water observations we will discuss the origin of water emission in high-mass protostellar objects and will use these results to further contrain the origin of high-mass stars and accompanying clusters. This detailed investigation will also serve to discuss the origin of water emission from other Herschel-HIFI observations of (more distant) high-mass protostars.

  10. Colliding filaments and a massive dense core in the Cygnus OB 7 molecular cloud

    SciTech Connect

    Dobashi, Kazuhito; Shimoikura, Tomomi; Akisato, Ko; Ohashi, Kenjiro; Nakagomi, Keisuke; Matsumoto, Tomoaki; Saito, Hiro

    2014-12-10

    We report the results of molecular line observations carried out toward a massive dense core in the Cyg OB 7 molecular cloud. The core has an extraordinarily large mass (∼1.1 × 10{sup 4} M {sub ☉}) and size (∼2 × 5 pc{sup 2}), but there is no massive young star forming therein. We observed this core in various molecular lines such as C{sup 18}O(J = 1-0) using the 45 m telescope at Nobeyama Radio Observatory. We find that the core has an elongated morphology consisting of several filaments and core-like structures. The filaments are massive (10{sup 2}-10{sup 3} M {sub ☉}), and they are apparently colliding with one another. Some candidates for young stellar objects are distributed around their intersection, suggesting that the collisions of the filaments may have influenced their formation. To understand the formation and evolution of such colliding filaments, we performed numerical simulations using the adaptive mesh refinement technique, adopting the observed core parameters (the mass and size) as the initial conditions. The results indicate that the filaments are formed as seen in other earlier simulations for small cores in the literature, but we could not reproduce the collisions of the filaments simply by assuming a large initial mass and size. We find that collisions of the filaments occur only when there is a large velocity gradient in the initial core, in a sense compressing it. We suggest that the observed core was actually compressed by an external effect, e.g., shocks from nearby supernova remnants, including HB 21 which has been suggested to be interacting with the Cyg OB 7 molecular cloud.

  11. FROM DUSTY FILAMENTS TO MASSIVE STARS: THE CASE OF NGC 7538 S

    SciTech Connect

    Naranjo-Romero, Raul; Zapata, Luis A.; Vazquez-Semadeni, Enrique; Takahashi, Satoko; Palau, Aina; Schilke, Peter

    2012-09-20

    We report on high-sensitivity and high angular resolution archival Submillimeter Array observations of the large ({approx}15,000 AU) putative circumstellar disk associated with the O-type protostar NGC 7538 S. Observations of the continuum resolve this putative circumstellar disk into five compact sources, with sizes {approx}3000 AU and masses {approx}10 M{sub Sun }. This confirms the results of recent millimeter observations made with CARMA/BIMA toward this object. However, we find that most of these compact sources eject collimated bipolar outflows, revealed by our silicon monoxide (SiO J = 5-4) observations, and confirm that these sources have a (proto)stellar nature. All outflows are perpendicular to the large and rotating dusty structure. We propose therefore that, rather than being a single massive circumstellar disk, NGC 7538 S could instead be a large and massive contracting or rotating filament that is fragmenting at scales of 0.1-0.01 pc to form several B-type stars, via the standard process involving outflows and disks. As in recent high spatial resolution studies of dusty filaments, our observations also suggest that thermal pressure does not seem to be sufficient to support the filament, so that either additional support needs to be invoked or else the filament must be in the process of collapsing. A smoothed particle hydrodynamics numerical simulation of the formation of a molecular cloud by converging warm neutral medium flows produces contracting filaments whose dimensions and spacings between the stars forming within them, as well as their column densities, strongly resemble those observed in the filament reported here.

  12. The Structure and Environmental Impacts of Protostellar Outflows in DR 21 and Orion

    NASA Astrophysics Data System (ADS)

    Wiseman, J. J.; Ho, P. T. P.; Brown, R.

    1997-12-01

    Regions of high-mass star formation are considerably more complicated than their low-mass counterparts. Recent HST NICMOS images of Orion-KL (Thompson et al. 1997) as well as sensitive ground-based infrared images of H_2 shock emission in the Orion outflow region (Chrysostomou et al. 1997, McCaughrean & Mac Low 1997, Schild et al. 1997) reveal intricate clumpy shock structures extending in nearly all radial directions from the source. The one radial direction in which the shock emission is particularly diminished is to the northeast, and it is precisely here that a molecular gas filament is present and highly heated, as though blocking the path of outflowing material from Orion-KL. We present our latest NH_3 (1,1), (2,2), and (3,3) VLA MEM mosaics of the Orion-KL region. We present evidence from temperature and chemical excitation gradients that the molecular gas cores along the filament extending to the northeast of Orion-KL are strongly heated by impacts from protostellar ejecta. These effects are seen in the core ``CS1'' 30'' northeast of IRc2 and also in cores at least twice as distant (1.5 pc). The DR 21 outflow region is also quite complex, with multiple molecular outflows extending from a multiple-component HII region. We present sensitive VLA maps of hydrogen recombination line emission, and we report the detection of bipolar ionized gas within the molecular outflow lobes. This detection gives observational evidence for the initial ionized inner structure of high mass protostellar outflows. Chrysostomou, A. et al. 1997, MNRAS, 289, 605 McCaughrean, M., & Mac Low, M.-M. 1997, AJ, 113, 391 Schild, H., Miller, S., & Tennyson, J. 1997, A&A, 319, 1037 Thompson, R., Rieke, M., Schneider, G., Stolovy, S., Erickson, E., & Axon, D. 1997, STSCI Early Release Observation PRC97-13

  13. CONVERGENT FLOWS AND LOW-VELOCITY SHOCKS IN DR21(OH)

    SciTech Connect

    Csengeri, T.; Bontemps, S.; Hora, J. L.

    2011-10-10

    DR21(OH) is a pc-scale massive, {approx}7000 M{sub sun} clump hosting three massive dense cores (MDCs) at an early stage of their evolution. We present a high angular resolution mosaic, covering {approx}70'' x 100'', with the IRAM Plateau de Bure Interferometer at 3 mm to trace the dust continuum emission and the N{sub 2}H{sup +} (J = 1-0) and CH{sub 3}CN (J = 5-4) molecular emission. The cold, dense gas traced by the compact emission in N{sub 2}H{sup +} is associated with the three MDCs and shows several velocity components toward each MDC. These velocity components reveal local shears in the velocity fields which are best interpreted as convergent flows. Moreover, we report the detection of weak extended emission from CH{sub 3}CN at the position of the N{sub 2}H{sup +} velocity shears. We propose that this extended CH{sub 3}CN emission is tracing warm gas associated with the low-velocity shocks expected at the location of convergence of the flows where velocity shears are observed. This is the first detection of low-velocity shocks associated with small (subparsec) scale convergent flows which are proposed to be at the origin of the densest structures and of the formation of (high-mass) stars. In addition, we propose that MDCs may be active sites of star formation for more than a crossing time as they continuously receive material from larger scale flows as suggested by the global picture of dynamical, gravity-driven evolution of massive clumps which is favored by the present observations.

  14. FROM THE CONVERGENCE OF FILAMENTS TO DISK-OUTFLOW ACCRETION: MASSIVE STAR FORMATION IN W33A

    SciTech Connect

    Galvan-Madrid, Roberto; Zhang Qizhou; Keto, Eric; Ho, Paul T. P.; Pineda, Jaime E.; Zapata, Luis A.; RodrIguez, Luis F.; Vazquez-Semadeni, Enrique

    2010-12-10

    Interferometric observations of the W33A massive star formation region, performed with the Submillimeter Array and the Very Large Array at resolutions from 5'' (0.1 pc) to 0.''5 (0.01 pc), are presented. Our three main findings are: (1) parsec-scale, filamentary structures of cold molecular gas are detected. Two filaments at different velocities intersect in the zone where the star formation is occurring. This is consistent with triggering of the star formation activity by the convergence of such filaments, as predicted by numerical simulations of star formation initiated by converging flows. (2) The two dusty cores (MM1 and MM2) at the intersection of the filaments are found to be at different evolutionary stages, and each of them is resolved into multiple condensations. MM1 and MM2 have markedly different temperatures, continuum spectral indices, molecular-line spectra, and masses of both stars and gas. (3) The dynamics of the 'hot-core' MM1 indicates the presence of a rotating disk in its center (MM1-Main) around a faint free-free source. The stellar mass is estimated to be {approx}10 M{sub sun}. A massive molecular outflow is observed along the rotation axis of the disk.

  15. Massive Quiescent Cores in Orion. VI. The Internal Structures and a Candidate of Transiting Core in NGC 2024 Filament

    NASA Astrophysics Data System (ADS)

    Ren, Zhiyuan; Li, Di

    2016-06-01

    We present a multiwavelength observational study of the NGC 2024 filament using infrared to submillimeter continuum and the {{NH}}3 (1,1) and (2,2) inversion transitions centered on FIR-3, the most massive core therein. FIR-3 is found to have no significant infrared point sources in the Spitzer/IRAC bands. But the {{NH}}3 kinetic temperature map shows a peak value at the core center with {T}{{k}}=25 K, which is significantly higher than the surrounding level ({T}{{k}}\\quad = 15–19 K). Such internal heating signature without an infrared source suggests an ongoing core collapse possibly at a transition stage from first hydrostatic core (FHSC) to protostar. The eight dense cores in the filament have dust temperatures between 17.5 and 22 K. They are much cooler than the hot ridge ({T}{{d}}∼ 55 K) around the central heating star IRS-2b. Comparison with a dust heating model suggests that the filament should have a distance of 3–5 pc from IRS-2b. This value is much larger than the spatial extent of the hot ridge, suggesting that the filament is spatially separated from the hot region along the line of sight.

  16. Absorption filaments toward the massive clump G0.253+0.016

    SciTech Connect

    Bally, John; Rathborne, J. M.; Bressert, E.; Contreras, Y. E-mail: ebressert@gmail.com; and others

    2014-11-01

    ALMA HCO{sup +} observations of the infrared dark cloud G0.253+0.016 located in the central molecular zone of the Galaxy are presented. The 89 GHz emission is area-filling, optically thick, and sub-thermally excited. Two types of filaments are seen in absorption against the HCO{sup +} emission. Broad-line absorption filaments (BLAs) have widths of less than a few arcseconds (0.07-0.14 pc), lengths of 30-50 arcsec (1.2-1.8 pc), and absorption profiles extending over a velocity range larger than 20 km s{sup –1}. The BLAs are nearly parallel to the nearby G0.18 non-thermal filaments and may trace HCO{sup +} molecules gyrating about highly ordered magnetic fields located in front of G0.253+0.016 or edge-on sheets formed behind supersonic shocks propagating orthogonal to our line of sight in the foreground. Narrow-line absorption filaments (NLAs) have line widths less than 20 km s{sup –1}. Some NLAs are also seen in absorption in other species with high optical depth, such as HCN, and occasionally in emission where the background is faint. The NLAs, which also trace low-density, sub-thermally excited HCO{sup +} molecules, are mostly seen on the blueshifted side of the emission from G0.253+0.016. If associated with the surface of G0.253+0.016, the kinematics of the NLAs indicate that the cloud surface is expanding. The decompression of entrained, milli-Gauss magnetic fields may be responsible for the re-expansion of the surface layers of G0.253+0.016 as it recedes from the Galactic center following a close encounter with Sgr A.

  17. Characterizing Interstellar Ammonia Masers in the Galactic Star Forming Region DR21(OH)

    NASA Astrophysics Data System (ADS)

    Fagan, Amanda J.; Hoffman, Ian M.

    2015-01-01

    Using the Green Bank Telescope, we observed the (J,K)=(10,6), (11,6), (12,6), and (8,3) transitions of ammonia in DR21(OH). We detected neither emission nor absorption, with an upper limit of 3σ=0.11 Jy. From observations in 1984, DR21(OH) is known to have a (9,6) maser. There are three suggested possibilities for maser emission at higher rotational levels of ammonia: (1) there could be a maser in the adjacent (10,6) level, (2) there could be a maser in alternating levels, including (11,6), or (3) there could be no pumping above (9,6). NGC 7538 is known to have both a (9,6) and (10,6) maser, with a flux density ratio of 4.83:1, and no maser in either (11,6) or (12,6). If the excitation conditions in DR21(OH) are the same as in NGC 7538, a (10,6) maser with a flux density of 0.15 Jy would be expected in DR21(OH) but is not observed. Other possibilities are also discussed in detail.This work is supported by Wittenberg University through the Physics Department.

  18. THE HERSCHEL FILAMENT: A SIGNATURE OF THE ENVIRONMENTAL DRIVERS OF GALAXY EVOLUTION DURING THE ASSEMBLY OF MASSIVE CLUSTERS AT z = 0.9

    SciTech Connect

    Coppin, K. E. K.; Geach, J. E.; Webb, T. M. A.; Faloon, A.; O'Donnell, D.; Yan, R.; Ouellette, N.; Egami, E.; Ellingson, E.; Gilbank, D.; Hicks, A.; Barrientos, L. F.; Yee, H. K. C.; Gladders, M.

    2012-04-20

    We have discovered a 2.5 Mpc (projected) long filament of infrared-bright galaxies connecting two of the three {approx}5 Multiplication-Sign 10{sup 14} M{sub Sun} clusters making up the RCS 2319+00 supercluster at z = 0.9. The filament is revealed in a deep Herschel Spectral and Photometric Imaging REceiver (SPIRE) map that shows 250-500 {mu}m emission associated with a spectroscopically identified filament of galaxies spanning two X-ray bright cluster cores. We estimate that the total (8-1000 {mu}m) infrared luminosity of the filament is L{sub IR} {approx_equal} 5 Multiplication-Sign 10{sup 12} L{sub Sun }, which, if due to star formation alone, corresponds to a total SFR {approx_equal} 900 M{sub Sun} yr{sup -1}. We are witnessing the scene of the buildup of a >10{sup 15} M{sub Sun} cluster of galaxies, seen prior to the merging of three massive components, each of which already contains a population of red, passive galaxies that formed at z > 2. The infrared filament demonstrates that significant stellar mass assembly is taking place in the moderate density, dynamically active circumcluster environments of the most massive clusters at high redshift, and this activity is concomitant with the hierarchical buildup of large-scale structure.

  19. VERY LARGE ARRAY DETECTION OF THE 36 GHz ZEEMAN EFFECT IN DR21W REVISITED

    SciTech Connect

    Momjian, Emmanuel; Sjouwerman, Lorant O.; Fish, Vincent L.

    2012-09-20

    We report on the observation of the 36 GHz methanol maser line in the star-forming region DR21W to accurately measure the Zeeman effect. The Zeeman signature reported by Fish et al. became suspicious after an instrumental effect was discovered in the early days of the commissioning of the Very Large Array Wide-band Digital Architecture correlator. We conclude that the previously reported magnetic field strength of 58 mG (1.7 Hz mG{sup -1}/z) is instrumental in nature and thus incorrect. With the improved performance of the array, we now deduce a 3{sigma} limit of -4.7 to +0.4 mG (1.7 Hz mG{sup -1}/z) for the line-of-sight component of the magnetic field strength in DR21W.

  20. The cometary H II regions of DR 21: Bow shocks or champagne flows or both?

    NASA Astrophysics Data System (ADS)

    Immer, K.; Cyganowski, C.; Reid, M. J.; Menten, K. M.

    2014-03-01

    We present deep Very Large Array H66α radio recombination line (RRL) observations of the two cometary H II regions in DR 21. With these sensitive data, we test the "hybrid" bow shock/champagne flow model previously proposed for the DR 21 H II regions. The ionized gas down the tail of the southern H II region is redshifted by up to ~30 km s-1 with respect to the ambient molecular gas, as expected in the hybrid scenario. The RRL velocity structure, however, reveals the presence of two velocity components in both the northern and southern H II regions. This suggests that the ionized gas is flowing along cone-like shells, swept-up by stellar winds. The observed velocity structure of the well-resolved southern H II region is most consistent with a picture that combines a stellar wind with stellar motion (as in bow shock models) along a density gradient (as in champagne flow models). The direction of the implied density gradient is consistent with that suggested by maps of dust continuum and molecular line emission in the DR 21 region. The image cubes are only available as a FITS file at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/563/A39Table 2, Fig. 4, and Appendices A and B are available in electronic form at http://www.aanda.org

  1. A weak lensing mass reconstruction of the large-scale filament feeding the massive galaxy cluster MACS J0717.5+3745

    NASA Astrophysics Data System (ADS)

    Jauzac, Mathilde; Jullo, Eric; Kneib, Jean-Paul; Ebeling, Harald; Leauthaud, Alexie; Ma, Cheng-Jiun; Limousin, Marceau; Massey, Richard; Richard, Johan

    2012-11-01

    We report the first weak lensing detection of a large-scale filament funnelling matter on to the core of the massive galaxy cluster MACS J0717.5+3745. Our analysis is based on a mosaic of 18 multipassband images obtained with the Advanced Camera for Surveys aboard the Hubble Space Telescope, covering an area of ˜10 × 20 arcmin2. We use a weak lensing pipeline developed for the Cosmic Evolution Survey, modified for the analysis of galaxy clusters, to produce a weak lensing catalogue. A mass map is then computed by applying a weak gravitational lensing multiscale reconstruction technique designed to describe irregular mass distributions such as the one investigated here. We test the resulting mass map by comparing the mass distribution inferred for the cluster core with the one derived from strong lensing constraints and find excellent agreement. Our analysis detects the MACS J0717.5+3745 filament within the 3σ detection contour of the lensing mass reconstruction, and underlines the importance of filaments for theoretical and numerical models of the mass distribution in the cosmic web. We measure the filament's projected length as ˜4.5 h74-1 Mpc, and its mean density as (2.92 ± 0.66) × 108 h74 M⊙ kpc-2. Combined with the redshift distribution of galaxies obtained after an extensive spectroscopic follow-up in the area, we can rule out any projection effect resulting from the chance alignment on the sky of unrelated galaxy group-scale structures. Assuming plausible constraints concerning the structure's geometry based on its galaxy velocity field, we construct a three-dimensional (3D) model of the large-scale filament. Within this framework, we derive the 3D length of the filament to be 18 h74-1 Mpc. The filament's deprojected density in terms of the critical density of the Universe is measured as (206 ± 46) ρcrit, a value that lies at the very high end of the range predicted by numerical simulations. Finally, we study the distribution of stellar mass in the

  2. Chemistry of C3 and carbon chain molecules in DR21(OH)

    NASA Astrophysics Data System (ADS)

    Mookerjea, B.; Hassel, G. E.; Gerin, M.; Giesen, T.; Stutzki, J.; Herbst, E.; Black, J. H.; Goldsmith, P. F.; Menten, K. M.; Krełowski, J.; De Luca, M.; Csengeri, T.; Joblin, C.; Kaźmierczak, M.; Schmidt, M.; Goicoechea, J. R.; Cernicharo, J.

    2012-10-01

    Context. C3 is the smallest pure carbon chain detected in the dense environment of star-forming regions, although diatomic C2 is detected in diffuse clouds. Measurement of the abundance of C3 and the chemistry of its formation in dense star-forming regions has remained relatively unexplored. Aims: We aim to identify the primary C3 formation routes in dense star-forming regions following a chemical network producing species like CCH and c-C3H2 in the star-forming cores associated with DR21(OH), a high-mass star-forming region. Methods: We observed velocity resolved spectra of four ro-vibrational far-infrared transitions of C3 between the vibrational ground state and the low-energy ν2 bending mode at frequencies between 1654-1897 GHz using HIFI on board Herschel, in DR21(OH). Several transitions of CCH and c-C3H2 were also observed with HIFI and the IRAM 30 m telescope. Rotational temperatures and column densities for all chemical species were estimated. A gas and grain warm-up model was used to obtain estimates of densities and temperatures of the envelope. The chemical network in the model was used to identify the primary C3 forming reactions in DR21(OH). Results: We detected C3 in absorption in four far-infrared transitions, P(4), P(10), Q(2), and Q(4). The continuum sources MM1 and MM2 in DR21(OH), though spatially unresolved, are sufficiently separated in velocity to be identified in the C3 spectra. All C3 transitions are detected from the embedded source MM2 and the surrounding envelope, whereas only Q(4) and P(4) are detected toward the hot core MM1. The abundance of C3 in the envelope and MM2 is ~6 × 10-10 and ~3 × 10-9, respectively. For CCH and c-C3H2, we only detect emission from the envelope and MM1. The observed CCH, C3 and c-C3H2 abundances are most consistent with a chemical model with nH2 ~ 5 × 106 cm-3, a post-warm-up dust temperature Tmax = 30 K, and a time of ~0.7-3 Myr. Conclusions: Post-warm-up gas phase chemistry of CH4 released from the

  3. Discovery of a Large-Scale Filament Connected to the Massive Galaxy Cluster MACS J0717.5+3745 at z=0.551,

    NASA Astrophysics Data System (ADS)

    Ebeling, H.; Barrett, E.; Donovan, D.

    2004-07-01

    We report the detection of a 4 h-170 Mpc long large-scale filament leading into the massive galaxy cluster MACS J0717.5+3745. The extent of this object well beyond the cluster's nominal virial radius (~2.3 Mpc) rules out prior interaction between its constituent galaxies and the cluster and makes it a prime candidate for a genuine filament as opposed to a merger remnant or a double cluster. The structure was discovered as a pronounced overdensity of galaxies selected to have V-R colors close to the cluster red sequence. Extensive spectroscopic follow-up of over 300 of these galaxies in a region covering the filament and the cluster confirms that the entire structure is located at the cluster redshift of z=0.545. Featuring galaxy surface densities of typically 15 Mpc-2 down to luminosities of 0.13L*V, the most diffuse parts of the filament are comparable in density to the clumps of red galaxies found around A851 in the only similar study carried out to date (Kodama et al.). Our direct detection of an extended large-scale filament funneling matter onto a massive distant cluster provides a superb target for in-depth studies of the evolution of galaxies in environments of greatly varying density and supports the predictions from theoretical models and numerical simulations of structure formation in a hierarchical picture. Some of the data presented herein were obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration. The observatory was made possible by the generous financial support of the W. M. Keck Foundation. Based partly on observations obtained at the Gemini Observatory, which is operated by the Association of Universities for Research in Astronomy, Inc., under a cooperative agreement with the NSF on behalf of the Gemini partnership: the National Science Foundation (US), the Particle Physics and Astronomy

  4. Massive envelopes and filaments in the NGC 3603 star forming region⋆⋆⋆⋆⋆⋆

    NASA Astrophysics Data System (ADS)

    Hummel, C. A.; Stanke, T.; Galván-Madrid, R.; Koribalski, B. S.

    2015-10-01

    The formation of massive stars and their arrival on the zero-age main-sequence occurs hidden behind dense clouds of gas and dust. In the giant H ii region NGC 3603, the radiation of a young cluster of OB stars has dispersed dust and gas in its vicinity. At a projected distance of 2.5 pc from the cluster, a bright mid-infrared (MIR) source (IRS 9A) was identified as a massive young stellar object (MYSO), located on the side of a molecular clump (MM2) of gas facing the cluster. We investigated the physical conditions in MM2, based on APEX sub-mm observations using the SABOCA and SHFI instruments, and archival ATCA 3 mm continuum and CS spectral line data. We resolved MM2 into several compact cores, one of them closely associated with IRS 9A. These are likely to be infrared dark clouds because they do not show the typical hot-core emission lines and are mostly opaque against the MIR background. The compact cores have masses of up to several hundred times the solar mass and gas temperatures of about 50 K, without evidence of internal ionizing sources. We speculate that IRS 9A is younger than the cluster stars, but is in an evolutionary state after the compact cores. Based in part on observations collected at the European Southern Observatory, Chile (Prop. No. 088.C-0093 and 090.C-0644).Observations were obtained with the Australia Telescope which is funded by the Commonwealth of Australia for operations as a National Facility managed by CSIRO.Appendix A is available in electronic form at http://www.aanda.orgThe final reduced FITS (cubes) of the data presented in the paper are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/582/A66

  5. A MALT90 study of the chemical properties of massive clumps and filaments of infrared dark clouds

    NASA Astrophysics Data System (ADS)

    Miettinen, O.

    2014-02-01

    Context. Infrared dark clouds (IRDCs) provide a useful testbed in which to investigate the genuine initial conditions and early stages of massive-star formation. Aims: We attempt to characterise the chemical properties of a sample of 35 massive clumps of IRDCs through multi-molecular line observations. We also search for possible evolutionary trends among the derived chemical parameters. Methods: The clumps are studied using the MALT90 (Millimetre Astronomy Legacy Team 90 GHz) line survey data obtained with the Mopra 22 m telescope. The survey covers 16 different transitions near 90 GHz. The spectral-line data are used in concert with our previous LABOCA (Large APEX BOlometer CAmera) 870 μm dust emission data. Results: Eleven MALT90 transitions are detected towards the clumps at least at the 3σ level. Most of the detected species (SiO, C2H, HNCO, HCN, HCO+, HNC, HC3N, and N2H+) show spatially extended emission towards many of the sources. Most of the fractional abundances of the molecules with respect to H2 are found to be comparable to those determined in other recent similar studies of IRDC clumps. We found that the abundances of SiO, HNCO, and HCO+ are higher in IR-bright clumps than in IR-dark sources, reflecting a possible evolutionary trend. A hint of this trend is also seen for HNC and HC3N. An opposite trend is seen for the C2H and N2H+ abundances. Moreover, a positive correlation is found between the abundances of HCO+ and HNC, and between those of HNC and HCN. The HCN and HNC abundances also appear to increase as a function of the N2H+ abundance. The HNC/HCN and N2H+/HNC abundance ratios are derived to be near unity on average, while that of HC3N/HCN is ~10%. The N2H+/HNC ratio appears to increase as the clump evolves, while the HNC/HCO+ ratio shows the opposite behaviour. Conclusions: The detected SiO emission is probably caused by shocks driven by outflows in most cases, although shocks resulting from the cloud formation process could also play a role

  6. Characterizing filaments in regions of high-mass star formation: High-resolution submilimeter imaging of the massive star-forming complex NGC 6334 with ArTéMiS

    NASA Astrophysics Data System (ADS)

    André, Ph.; Revéret, V.; Könyves, V.; Arzoumanian, D.; Tigé, J.; Gallais, P.; Roussel, H.; Le Pennec, J.; Rodriguez, L.; Doumayrou, E.; Dubreuil, D.; Lortholary, M.; Martignac, J.; Talvard, M.; Delisle, C.; Visticot, F.; Dumaye, L.; De Breuck, C.; Shimajiri, Y.; Motte, F.; Bontemps, S.; Hennemann, M.; Zavagno, A.; Russeil, D.; Schneider, N.; Palmeirim, P.; Peretto, N.; Hill, T.; Minier, V.; Roy, A.; Rygl, K. L. J.

    2016-07-01

    Context. Herschel observations of nearby molecular clouds suggest that interstellar filaments and prestellar cores represent two fundamental steps in the star formation process. The observations support a picture of low-mass star formation according to which filaments of ~0.1 pc width form first in the cold interstellar medium, probably as a result of large-scale compression of interstellar matter by supersonic turbulent flows, and then prestellar cores arise from gravitational fragmentation of the densest filaments. Whether this scenario also applies to regions of high-mass star formation is an open question, in part because the resolution of Herschel is insufficient to resolve the inner width of filaments in the nearest regions of massive star formation. Aims: In an effort to characterize the inner width of filaments in high-mass star-forming regions, we imaged the central part of the NGC 6334 complex at a resolution higher by a factor of >3 than Herschel at 350 μm. Methods: We used the large-format bolometer camera ArTéMiS on the APEX telescope and combined the high-resolution ArTéMiS data at 350 μm with Herschel/HOBYS data at 70-500 μm to ensure good sensitivity to a broad range of spatial scales. This allowed us to study the structure of the main narrow filament of the complex with a resolution of 8″ or <0.07 pc at d ~ 1.7 kpc. Results: Our study confirms that this filament is a very dense, massive linear structure with a line mass ranging from ~500 M⊙/pc to ~2000 M⊙/pc over nearly 10 pc. It also demonstrates for the first time that its inner width remains as narrow as W ~ 0.15 ± 0.05 pc all along the filament length, within a factor of <2 of the characteristic 0.1 pc value found with Herschel for lower-mass filaments in the Gould Belt. Conclusions: While it is not completely clear whether the NGC 6334 filament will form massive stars in the future, it is two to three orders of magnitude denser than the majority of filaments observed in Gould Belt

  7. Filament disappearances

    NASA Technical Reports Server (NTRS)

    Wagner, William J.

    1986-01-01

    The phenomenon of the sudden filament disappearance (Disparition Brusque) is a familiar one to observers at H alpha telescopes. Nevertherless, the importance in Disparition Brusques (DB) continues to grow for several reasons which are cited in the discussion. It is reported that there seems to be more interest on building and maintain filaments than in destroying them. As a consequence, this sub-group is smaller than most of the others. All the same, progress in this area of filament disapperences seems steady and assured. The importance and interest in DBs is discussed and future directions are indicated.

  8. Helical filaments

    NASA Astrophysics Data System (ADS)

    Barbieri, Nicholas; Hosseinimakarem, Zahra; Lim, Khan; Durand, Magali; Baudelet, Matthieu; Johnson, Eric; Richardson, Martin

    2014-06-01

    The shaping of laser-induced filamenting plasma channels into helical structures by guiding the process with a non-diffracting beam is demonstrated. This was achieved using a Bessel beam superposition to control the phase of an ultrafast laser beam possessing intensities sufficient to induce Kerr effect driven non-linear self-focusing. Several experimental methods were used to characterize the resulting beams and confirm the observed structures are laser air filaments.

  9. Filament winding

    NASA Astrophysics Data System (ADS)

    Shibley, A. M.

    The major aspects of filament winding are discussed, emphasizing basic reinforcement and matrix materials, winding procedures, process controls, and cured composite properties. Fiberglass (E-glass and S-glass strengths are 500,000 and 665,000 psi respectively) and polyester resins are the principal reinforcement constituent materials. Graphite and aramid reinforcements are being used more frequently, primarily for the more critical pressure vessels. Matrix systems are most commonly based on epoxy as it has superior mechanical properties, fatigue behavior, and heat resistance as compard with polyesters. A fiberglass overwrap of PVC pipe is an anticipated development in on-site winding and combination winding, and the compression molding of filament wound lay-ups will be investigated. The fabrication of weight-sensitive structural components may be achieved by using such moldings.

  10. Filamentous Fungi.

    PubMed

    Powers-Fletcher, Margaret V; Kendall, Brian A; Griffin, Allen T; Hanson, Kimberly E

    2016-06-01

    Filamentous mycoses are often associated with significant morbidity and mortality. Prompt diagnosis and aggressive treatment are essential for good clinical outcomes in immunocompromised patients. The host immune response plays an essential role in determining the course of exposure to potential fungal pathogens. Depending on the effectiveness of immune response and the burden of organism exposure, fungi can either be cleared or infection can occur and progress to a potentially fatal invasive disease. Nonspecific cellular immunity (i.e., neutrophils, natural killer [NK] cells, and macrophages) combined with T-cell responses are the main immunologic mechanisms of protection. The most common potential mold pathogens include certain hyaline hyphomycetes, endemic fungi, the Mucorales, and some dematiaceous fungi. Laboratory diagnostics aimed at detecting and differentiating these organisms are crucial to helping clinicians make informed decisions about treatment. The purpose of this chapter is to provide an overview of the medically important fungal pathogens, as well as to discuss the patient characteristics, antifungal-therapy considerations, and laboratory tests used in current clinical practice for the immunocompromised host. PMID:27337469

  11. CO gas kinematics and excitation in a filamentary IRDC: Filament-filament interaction and accretion processes.

    NASA Astrophysics Data System (ADS)

    Jimenez-Serra, Izaskun; Caselli, Paola; Fontani, Francesco; Tan, Jonathan C.; Henshaw, Jonathan D.; Kainulainen, Jouni; Hernandez, Audra K.

    2013-07-01

    Some theories of molecular cloud formation propose that molecular clouds form in highly dynamical environments characterized by the interaction of converging gas flows or cloud-cloud collisions. The determination of the dynamics and physical conditions of the molecular gas in clouds at the early stages of their evolution is thus essential to establish the dynamical imprints of such collisions, and to infer the physical processes involved in their formation. We present large-scale (~1.7pc x 3.4 pc) multi-transition 13CO and C18O on-the-fly maps carried out with the IRAM 30m and JCMT telescopes toward the Infrared-Dark Cloud G035.39-00.33. This cloud shows a very filamentary structure and relatively little star formation activity, suggestive of its youth, and where evidence for a flow-flow collision has recently been reported. Consistent with previous studies, the 13CO and C18O line maps toward G035.39-00.33 reveal that the molecular gas in this cloud is distributed in three different filaments separated in velocity space by ~3 kms-1 (Filaments 1, 2 and 3). The massive dense cores in this IRDC are preferentially found at the intersecting regions between Filaments 1 and 3, where most of the CO gas is accumulated. The analysis of the 13CO and C18O lines show that the three filaments have a similar kinematic structure with relatively smooth velocity gradients (of ~0.4-0.8 kms-1pc-1) that seem to converge onto core H6, the most massive core in the region located in the center of the IRDC. Several possible scenarios are proposed to explain this velocity gradient, including rotation, global gas accretion along the filaments and large-scale turbulence motions with a steep turbulent power spetrum. The 13CO and C18O gas motions are supersonic across G035.39-00.33 with the line emission showing broader linewidths toward the edges of the IRDC. This may indicate energy dissipation at the densest regions in the IRDC as a consequence of the filament-filament interaction. The

  12. 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. PMID:17872439

  13. Filaments from L5

    NASA Technical Reports Server (NTRS)

    Sterling, Alphonse C.

    2011-01-01

    We've been investigating filament eruptions in recent years. Why do eruptions occur? Basic mechanism is magnetic, and can often include coronal mass ejections (CMEs), flares, and filament eruptions. Use filament eruptions as markers of the more-general eruption. From our studies, we can identify directions for future work to help predict when eruptions might occur.

  14. 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.

  15. Massive Stars

    NASA Astrophysics Data System (ADS)

    Livio, Mario; Villaver, Eva

    2009-11-01

    Participants; Preface Mario Livio and Eva Villaver; 1. High-mass star formation by gravitational collapse of massive cores M. R. Krumholz; 2. Observations of massive star formation N. A. Patel; 3. Massive star formation in the Galactic center D. F. Figer; 4. An X-ray tour of massive star-forming regions with Chandra L. K. Townsley; 5. Massive stars: feedback effects in the local universe M. S. Oey and C. J. Clarke; 6. The initial mass function in clusters B. G. Elmegreen; 7. Massive stars and star clusters in the Antennae galaxies B. C. Whitmore; 8. On the binarity of Eta Carinae T. R. Gull; 9. Parameters and winds of hot massive stars R. P. Kudritzki and M. A. Urbaneja; 10. Unraveling the Galaxy to find the first stars J. Tumlinson; 11. Optically observable zero-age main-sequence O stars N. R. Walborn; 12. Metallicity-dependent Wolf-Raynet winds P. A. Crowther; 13. Eruptive mass loss in very massive stars and Population III stars N. Smith; 14. From progenitor to afterlife R. A. Chevalier; 15. Pair-production supernovae: theory and observation E. Scannapieco; 16. Cosmic infrared background and Population III: an overview A. Kashlinsky.

  16. Externally refuelled optical filaments

    NASA Astrophysics Data System (ADS)

    Scheller, Maik; Mills, Matthew S.; Miri, Mohammad-Ali; Cheng, Weibo; Moloney, Jerome V.; Kolesik, Miroslav; Polynkin, Pavel; Christodoulides, Demetrios N.

    2014-04-01

    Plasma channels produced in air through femtosecond laser filamentation hold great promise for a number of applications, including remote sensing, attosecond physics and spectroscopy, channelling microwaves and lightning protection. In such settings, extended filaments are desirable, yet their longitudinal span is limited by dissipative processes. Although various techniques aiming to prolong this process have been explored, the substantial extension of optical filaments remains a challenge. Here, we experimentally demonstrate that the natural range of a plasma column can be enhanced by at least an order of magnitude when the filament is prudently accompanied by an auxiliary beam. In this arrangement, the secondary low-intensity `dressing' beam propagates linearly and acts as a distributed energy reservoir, continuously refuelling the optical filament. Our approach offers an efficient and viable route towards the generation of extended light strings in air without inducing premature wave collapse or an undesirable beam break-up into multiple filaments.

  17. Massive Hemoptysis.

    PubMed

    Rali, Parth; Gandhi, Viral; Tariq, Cheema

    2016-01-01

    Hemoptysis, or coughing of blood, oftentimes triggers anxiety and fear for patients. The etiology of hemoptysis will determine the clinical course, which includes watchful waiting or intensive care admission. Any amount of hemoptysis that compromises the patient's respiratory status is considered massive hemoptysis and should be considered a medical emergency. In this article, we review introduction, definition, bronchial circulation anatomy, etiology, and management of massive hemoptysis. PMID:26919675

  18. 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.

  19. Sympathetic Solar Filament Eruptions

    NASA Astrophysics Data System (ADS)

    Wang, Rui; Liu, Ying D.; Zimovets, Ivan; Hu, Huidong; Dai, Xinghua; Yang, Zhongwei

    2016-08-01

    The 2015 March 15 coronal mass ejection as one of the two that together drove the largest geomagnetic storm of solar cycle 24 so far was associated with sympathetic filament eruptions. We investigate the relations between the different filaments involved in the eruption. A surge-like small-scale filament motion is confirmed as the trigger that initiated the erupting filament with multi-wavelength observations and using a forced magnetic field extrapolation method. When the erupting filament moved to an open magnetic field region, it experienced an obvious acceleration process and was accompanied by a C-class flare and the rise of another larger filament that eventually failed to erupt. We measure the decay index of the background magnetic field, which presents a critical height of 118 Mm. Combining with a potential field source surface extrapolation method, we analyze the distributions of the large-scale magnetic field, which indicates that the open magnetic field region may provide a favorable condition for F2 rapid acceleration and have some relation with the largest solar storm. The comparison between the successful and failed filament eruptions suggests that the confining magnetic field plays an important role in the preconditions for an eruption.

  20. Detection of stacked filament lensing between SDSS luminous red galaxies

    NASA Astrophysics Data System (ADS)

    Clampitt, Joseph; Miyatake, Hironao; Jain, Bhuvnesh; Takada, Masahiro

    2016-04-01

    We search for the lensing signal of massive filaments between 135 000 pairs of luminous red galaxies (LRGs) from the Sloan Digital Sky Survey. We develop a new estimator that cleanly removes the much larger shear signal of the neighbouring LRG haloes, relying only on the assumption of spherical symmetry. We consider two models: a `thick'-filament model constructed from ray-tracing simulations for Λ cold dark matter model, and a `thin'-filament model which models the filament by a string of haloes along the line connecting the two LRGs. We show that the filament lensing signal is in nice agreement with the thick simulation filament, while strongly disfavouring the thin model. The magnitude of the lensing shear due to the filament is below 10-4. Employing the likelihood ratio test, we find a 4.5σ significance for the detection of the filament lensing signal, corresponding to a null hypothesis fluctuation probability of 3 × 10-6. We also carried out several null tests to verify that the residual shear signal from neighbouring LRGs and other shear systematics are minimized.

  1. Tilt Angles of Quiescent Filaments and Filaments of Active Regions

    NASA Astrophysics Data System (ADS)

    Tlatov, A. G.; Kuzanyan, K. M.; Vasil'yeva, V. V.

    2016-04-01

    We carry out study of tilt angles of solar filaments using the data from the two observatories: Meudon Observatory and Kislovodsk Mountain Astronomical Station for the century-long period 1919-2014. We developed special software for digitization of the filaments structures on Hα synoptic maps. The filaments were vectorized in semi-automatic mode. The tilt angles of filaments with respect to the equator (τ) were analyzed. Approximately 2/3 of the filaments have positive angles τ >0, which is defined as when the eastern end of the filaments are closer to the poles than the western ones. We have separated tilts for the filaments which are close to the active region structures and those of quiescent filaments. We found that long quiescent filaments mainly have negative tilts. The filaments which are close to active regions mainly have positive tilt angles.

  2. 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...

  3. Massive Fibroid

    PubMed Central

    Weekes, Leroy R.

    1977-01-01

    This ten-year study of the massive fibroid at the Queen of Angels Hospital will reveal an average of 66 cases per year which could be classified as large and massive. Only about ten cases per year qualify as massive (four gestational months or larger). There were none considered giant size (25 lbs or more). The literature is replete with these, one of which (weighing 100.2 lbs) will be reported in detail. The mortality rate continues to be considerable in these (14.8 to 16.7 percent). In the smaller tumors, mortality is rare and morbidity is minimal. Bleeding, pain, and pressure symptoms, due to impingement on neighboring organs, are the principal symptoms. Sarcomatous change, fortunately, still remains quite rare. Treatment usually involves a pre-operative dilatation and curettage when bleeding is a problem, followed by total abdominal hysterectomy and bilateral salpingo-oophorectomy where indicated. Appendectomy is usually incidental. Anesthesia is usually spinal, if not otherwise contraindicated. Ultrasound is a new and refined diagnostic tool. PMID:833892

  4. Massive Bleeding and Massive Transfusion

    PubMed Central

    Meißner, Andreas; Schlenke, Peter

    2012-01-01

    Massive bleeding in trauma patients is a serious challenge for all clinicians, and an interdisciplinary diagnostic and therapeutic approach is warranted within a limited time frame. Massive transfusion usually is defined as the transfusion of more than 10 units of packed red blood cells (RBCs) within 24 h or a corresponding blood loss of more than 1- to 1.5-fold of the body's entire blood volume. Especially male trauma patients experience this life-threatening condition within their productive years of life. An important parameter for clinical outcome is to succeed in stopping the bleeding preferentially within the first 12 h of hospital admission. Additional coagulopathy in the initial phase is induced by trauma itself and aggravated by consumption and dilution of clotting factors. Although different aspects have to be taken into consideration when viewing at bleedings induced by trauma compared to those caused by major surgery, the basic strategy is similar. Here, we will focus on trauma-induced massive hemorrhage. Currently there are no definite, worldwide accepted algorithms for blood transfusion and strategies for optimal coagulation management. There is increasing evidence that a higher ratio of plasma and RBCs (e.g. 1:1) endorsed by platelet transfusion might result in a superior survival of patients at risk for trauma-induced coagulopathy. Several strategies have been evolved in the military environment, although not all strategies should be transferred unproven to civilian practice, e.g. the transfusion of whole blood. Several agents have been proposed to support the restoration of coagulation. Some have been used for years without any doubt on their benefit-to-risk profile, whereas great enthusiasm of other products has been discouraged by inefficacy in terms of blood transfusion requirements and mortality or significant severe side effects. This review surveys current literature on fluid resuscitation, blood transfusion, and hemostatic agents currently

  5. Evolution of filament barbs.

    NASA Astrophysics Data System (ADS)

    Liu, R.; Xu, Y.; Wang, H.

    We present a selected few cases in which the sense of chirality of filament barbs changed within periods as short as hours. We investigate in detail a quiescent filament on 2003 September 10 and 11. Of its four barbs displaying such changes, only one overlays a small polarity inversion line inside the EUV filament channel (EFC). No magnetic elements with magnitude above the noise level were detected at the endpoints of all barbs. In particular, a pair of barbs first approached toward, and then departed from, each other in Halpha , with the barb endpoints migrating as far as ˜ 10 arcsec. We conclude that the evolution of the barbs was driven by flux emergence and cancellation of small bipolar units at the EFC border.

  6. 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.

  7. 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.

  8. Lens tilting effect on filamentation and filament-induced fluorescence

    NASA Astrophysics Data System (ADS)

    Kamali, Y.; Sun, Q.; Daigle, J.-F.; Azarm, A.; Bernhardt, J.; Chin, S. L.

    2009-03-01

    In filament-induced fluorescence spectroscopy, we experimentally found that if the lens used for the creation and localization of filament is tilted, the signal to noise ratio of spectral measurement increases. Further study shows that with lens tilting, astigmatism occurs and the filament is split into shorter parts. In turn the shortening of filament reduces the generation of white light which is the major 'noise' source of the spectra.

  9. 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. PMID:27039023

  10. Investigating galaxy-filament alignments in hydrodynamic simulations using density ridges

    NASA Astrophysics Data System (ADS)

    Chen, Yen-Chi; Ho, Shirley; Tenneti, Ananth; Mandelbaum, Rachel; Croft, Rupert; DiMatteo, Tiziana; Freeman, Peter E.; Genovese, Christopher R.; Wasserman, Larry

    2015-12-01

    In this paper, we study the filamentary structures and the galaxy alignment along filaments at redshift z = 0.06 in the MassiveBlack-II simulation, a state-of-the-art, high-resolution hydrodynamical cosmological simulation which includes stellar and AGN feedback in a volume of (100 Mpc h-1)3. The filaments are constructed using the subspace constrained mean shift (SCMS; Ozertem & Erdogmus; Chen et al.). First, we show that reconstructed filaments using galaxies and reconstructed filaments using dark matter particles are similar to each other; over 50 per cent of the points on the galaxy filaments have a corresponding point on the dark matter filaments within distance 0.13 Mpc h-1 (and vice versa) and this distance is even smaller at high-density regions. Second, we observe the alignment of the major principal axis of a galaxy with respect to the orientation of its nearest filament and detect a 2.5 Mpc h-1 critical radius for filament's influence on the alignment when the subhalo mass of this galaxy is between 109 M⊙ h-1 and 1012 M⊙ h-1. Moreover, we find the alignment signal to increase significantly with the subhalo mass. Third, when a galaxy is close to filaments (less than 0.25 Mpc h-1), the galaxy alignment towards the nearest galaxy group is positively correlated with the galaxy subhalo mass. Finally, we find that galaxies close to filaments or groups tend to be rounder than those away from filaments or groups.

  11. Magnetically driven filament probe.

    PubMed

    Schmid, A; Herrmann, A; Rohde, V; Maraschek, M; Müller, H W

    2007-05-01

    A radially movable probe has been developed for studies of filamentary transport in ASDEX Upgrade during edge localized modes (ELMs) by means of Langmuir tips and magnetic pickup coils. The probe is permanently installed at the low field side in the ASDEX Upgrade vacuum vessel and is not subject to limitations in probe size, as, for example, probes on a shared manipulator are. The probe is moved by a magnetic drive, which allows for easy installation in the vessel, and has moderate machine requirements, as it will only require an electric feedthrough and an external power supply. The drive gives a linear motion with a radial range of 5 cm within 50 ms, where range and velocity can be largely scaled according to experimental requirements. The probe has been installed in the outer midplane of the ASDEX Upgrade vessel, where ELM filaments are expected to have their maximum amplitude. Filaments are coherent substructures within an ELM, carrying a fraction of the ELM released energy towards the wall. The new probe allows to measure the structure of these filaments, in particular, parameters such as filament rotation (by time delay measurements) and size (by peak width analysis). Activating the drive moves the probe from a safe position behind the limiter to a position in front of the limiters, i.e., exposes the Langmuir pins to the scrape-off layer plasma. PMID:17552815

  12. 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. PMID:22423993

  13. Preserved Filamentous Microbial Biosignatures in the Brick Flat Gossan, Iron Mountain, California.

    PubMed

    Williams, Amy J; Sumner, Dawn Y; Alpers, Charles N; Karunatillake, Suniti; Hofmann, Beda A

    2015-08-01

    A variety of actively precipitating mineral environments preserve morphological evidence of microbial biosignatures. One such environment with preserved microbial biosignatures is the oxidized portion of a massive sulfide deposit, or gossan, such as that at Iron Mountain, California. This gossan may serve as a mineralogical analogue to some ancient martian environments due to the presence of oxidized iron and sulfate species, and minerals that only form in acidic aqueous conditions, in both environments. Evaluating the potential biogenicity of cryptic textures in such martian gossans requires an understanding of how microbial textures form biosignatures on Earth. The iron-oxide-dominated composition and morphology of terrestrial, nonbranching filamentous microbial biosignatures may be distinctive of the underlying formation and preservation processes. The Iron Mountain gossan consists primarily of ferric oxide (hematite), hydrous ferric oxide (HFO, predominantly goethite), and jarosite group minerals, categorized into in situ gossan, and remobilized iron deposits. We interpret HFO filaments, found in both gossan types, as HFO-mineralized microbial filaments based in part on (1) the presence of preserved central filament lumina in smooth HFO mineral filaments that are likely molds of microbial filaments, (2) mineral filament formation in actively precipitating iron-oxide environments, (3) high degrees of mineral filament bending consistent with a flexible microbial filament template, and (4) the presence of bare microbial filaments on gossan rocks. Individual HFO filaments are below the resolution of the Mars Curiosity and Mars 2020 rover cameras, but sinuous filaments forming macroscopic matlike textures are resolvable. If present on Mars, available cameras may resolve these features identified as similar to terrestrial HFO filaments and allow subsequent evaluation for their biogenicity by synthesizing geochemical, mineralogical, and morphological analyses. Sinuous

  14. Preserved Filamentous Microbial Biosignatures in the Brick Flat Gossan, Iron Mountain, California

    PubMed Central

    Sumner, Dawn Y.; Alpers, Charles N.; Karunatillake, Suniti; Hofmann, Beda A.

    2015-01-01

    Abstract A variety of actively precipitating mineral environments preserve morphological evidence of microbial biosignatures. One such environment with preserved microbial biosignatures is the oxidized portion of a massive sulfide deposit, or gossan, such as that at Iron Mountain, California. This gossan may serve as a mineralogical analogue to some ancient martian environments due to the presence of oxidized iron and sulfate species, and minerals that only form in acidic aqueous conditions, in both environments. Evaluating the potential biogenicity of cryptic textures in such martian gossans requires an understanding of how microbial textures form biosignatures on Earth. The iron-oxide-dominated composition and morphology of terrestrial, nonbranching filamentous microbial biosignatures may be distinctive of the underlying formation and preservation processes. The Iron Mountain gossan consists primarily of ferric oxide (hematite), hydrous ferric oxide (HFO, predominantly goethite), and jarosite group minerals, categorized into in situ gossan, and remobilized iron deposits. We interpret HFO filaments, found in both gossan types, as HFO-mineralized microbial filaments based in part on (1) the presence of preserved central filament lumina in smooth HFO mineral filaments that are likely molds of microbial filaments, (2) mineral filament formation in actively precipitating iron-oxide environments, (3) high degrees of mineral filament bending consistent with a flexible microbial filament template, and (4) the presence of bare microbial filaments on gossan rocks. Individual HFO filaments are below the resolution of the Mars Curiosity and Mars 2020 rover cameras, but sinuous filaments forming macroscopic matlike textures are resolvable. If present on Mars, available cameras may resolve these features identified as similar to terrestrial HFO filaments and allow subsequent evaluation for their biogenicity by synthesizing geochemical, mineralogical, and morphological analyses

  15. Preserved filamentous microbial biosignatures in the Brick Flat gossan, Iron Mountain, California

    USGS Publications Warehouse

    Williams, Amy J.; Sumner, Dawn Y.; Alpers, Charles N.; Karunatillake, Suniti; Hofmann, Beda A

    2015-01-01

    A variety of actively precipitating mineral environments preserve morphological evidence of microbial biosignatures. One such environment with preserved microbial biosignatures is the oxidized portion of a massive sulfide deposit, or gossan, such as that at Iron Mountain, California. This gossan may serve as a mineralogical analogue to some ancient martian environments due to the presence of oxidized iron and sulfate species, and minerals that only form in acidic aqueous conditions, in both environments. Evaluating the potential biogenicity of cryptic textures in such martian gossans requires an understanding of how microbial textures form biosignatures on Earth. The iron-oxide-dominated composition and morphology of terrestrial, nonbranching filamentous microbial biosignatures may be distinctive of the underlying formation and preservation processes. The Iron Mountain gossan consists primarily of ferric oxide (hematite), hydrous ferric oxide (HFO, predominantly goethite), and jarosite group minerals, categorized into in situ gossan, and remobilized iron deposits. We interpret HFO filaments, found in both gossan types, as HFO-mineralized microbial filaments based in part on (1) the presence of preserved central filament lumina in smooth HFO mineral filaments that are likely molds of microbial filaments, (2) mineral filament formation in actively precipitating iron-oxide environments, (3) high degrees of mineral filament bending consistent with a flexible microbial filament template, and (4) the presence of bare microbial filaments on gossan rocks. Individual HFO filaments are below the resolution of the Mars Curiosity and Mars 2020 rover cameras, but sinuous filaments forming macroscopic matlike textures are resolvable. If present on Mars, available cameras may resolve these features identified as similar to terrestrial HFO filaments and allow subsequent evaluation for their biogenicity by synthesizing geochemical, mineralogical, and morphological analyses. Sinuous

  16. 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. PMID:25730393

  17. Filaments and sheets of the warm-hot intergalactic medium

    NASA Astrophysics Data System (ADS)

    Klar, J. S.; Mücket, J. P.

    2012-06-01

    Filaments, forming in the context of cosmological structure formation, are not only supposed to host the majority of the baryons at low redshifts in the form of the warm-hot intergalactic medium (WHIM), but also to supply forming galaxies at higher redshifts with a substantial amount of cold gas via cold steams. In order to get insight into the hydro- and thermodynamical characteristics of these structures, we performed a series of hydrodynamical simulations. Instead of analysing extensive simulations of cosmological structure formation, we simulate certain well-defined structures and study the impact of different physical processes as well as of the scale dependencies. In this paper, we continue our work, and extend our simulations into three dimensions. Instead of a pancake structure, we now obtain a configuration consisting of well-defined sheets, filaments and a gaseous halo. We use a set of simulations, parametrized by the length of the initial perturbation L, to obtain detailed information on the state of the gas and its evolution inside the filament. For L > 4 Mpc, we obtain filaments which are fully confined by an accretion shock. Additionally, they exhibit an isothermal core, in which temperature is balanced by radiative cooling and heating due to the extragalactic ultraviolet background. This indicates on a multiphase structure for the medium temperature WHIM. We obtain scaling relations for the main quantities of this core. After its formation, the core becomes shielded against further infall of gas on to the filament, and its mass content decreases with time. In the vicinity of the halo, the filament's core can be attributed to the cold streams found in cosmological hydrosimulations. They are constricted by the outwards moving accretion shock of the halo. Thermal conduction can lead to a complete evaporation of the cold stream for L > 6 Mpc h-1. This corresponds to haloes more massive than Mhalo= 1013 M⊙, and implies that star formation in more

  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. CVD-produced boron filaments

    NASA Technical Reports Server (NTRS)

    Wawner, F. E.; Debolt, H. E.; Suplinskas, R. D.

    1980-01-01

    A technique for producing boron filaments with an average tensile strength of 6.89 GPa has been developed which involves longitudinal splitting of the filament and core (substrate) removal by etching. Splitting is accomplished by a pinch wheel device which continuously splits filaments in lengths of 3.0 m by applying a force to the side of the filament to create a crack which is then propagated along the axis by a gentle sliding action. To facilitate the splitting, a single 10 mil tungsten substrate is used instead of the usual 0.5 mil substrate. A solution of hot 30% hydrogen peroxide is used to remove the core without attacking the boron. An alternative technique is to alter the residual stress by heavily etching the filament. Average strengths in the 4.83-5.52 GPa range have been obtained by etching an 8 mil filament to 4 mil.

  20. Magnetic vortex filament flows

    SciTech Connect

    Barros, Manuel; Cabrerizo, Jose L.; Fernandez, Manuel; Romero, Alfonso

    2007-08-15

    We exhibit a variational approach to study the magnetic flow associated with a Killing magnetic field in dimension 3. In this context, the solutions of the Lorentz force equation are viewed as Kirchhoff elastic rods and conversely. This provides an amazing connection between two apparently unrelated physical models and, in particular, it ties the classical elastic theory with the Hall effect. Then, these magnetic flows can be regarded as vortex filament flows within the localized induction approximation. The Hasimoto transformation can be used to see the magnetic trajectories as solutions of the cubic nonlinear Schroedinger equation showing the solitonic nature of those.

  1. 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.

  2. 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.

  3. Solar Filament Extraction and Characterizing

    NASA Astrophysics Data System (ADS)

    Yuan, Yuan; Shih, F. Y.; Jing, J.; Wang, H.

    2010-05-01

    This paper presents a new method to extract and characterize solar filaments from H-alpha full-disk images produced by Big Bear Solar Observatory. A cascading Hough Transform method is designed to identify solar disk center location and radius. Solar disks are segmented from the background, and unbalanced illumination on the surface of solar disks is removed using polynomial surface fitting. And then a localized adaptive thresholding is employed to extract solar filament candidates. After the removal of small solar filament candidates, the remaining larger candidates are used as the seeds of region growing. The procedure of region growing not only connects broken filaments but also generate complete shape for each filament. Mathematical morphology thinning is adopted to produce the skeleton of each filament, and graph theory is used to prune branches and barbs to get the main skeleton. The length and the location of the main skeleton is characterized. The proposed method can help scientists and researches study the evolution of solar filament, for instance, to detect solar filament eruption. The presented method has already been used by Space Weather Research Lab of New Jersey Institute of Technology (http://swrl.njit.edu) to generate the solar filament online catalog using H-alpha full-disk images of Global H-alpha Network (http://swrl.njit.edu/ghn_web/).

  4. Gravitational infall onto molecular filaments

    SciTech Connect

    Heitsch, Fabian

    2013-06-01

    Two aspects of filamentary molecular cloud evolution are addressed: (1) exploring analytically the role of the environment for the evolution of filaments demonstrates that considering them in isolation (i.e., just addressing the fragmentation stability) will result in unphysical conclusions about the filament's properties. Accretion can also explain the observed decorrelation between FWHM and peak column density. (2) Free-fall accretion onto finite filaments can lead to the characteristic 'fans' of infrared-dark clouds around star-forming regions. The fans may form due to tidal forces mostly arising at the ends of the filaments, consistent with numerical models and earlier analytical studies.

  5. Galactic cold cores. VII. Filament formation and evolution: Methods and observational constraints

    NASA Astrophysics Data System (ADS)

    Rivera-Ingraham, A.; Ristorcelli, I.; Juvela, M.; Montillaud, J.; Men'shchikov, A.; Malinen, J.; Pelkonen, V.-M.; Marston, A.; Martin, P. G.; Pagani, L.; Paladini, R.; Paradis, D.; Ysard, N.; Ward-Thompson, D.; Bernard, J.-P.; Marshall, D. J.; Montier, L.; Tóth, L. V.

    2016-06-01

    Context. The association of filaments with protostellar objects has made these structures a priority target in star formation studies. However, little is known about the link between filament properties and their local environment. Aims: The datasets from the Herschel Galactic Cold cores key programme allow for a statistical study of filaments with a wide range of intrinsic and environmental characteristics. Characterisation of this sample can therefore be used to identify key physical parameters and quantify the role of the environment in the formation of supercritical filaments. These results are necessary to constrain theoretical models of filament formation and evolution. Methods: Filaments were extracted from fields at distance D< 500 pc with the getfilaments algorithm and characterised according to their column density profiles and intrinsic properties. Each profile was fitted with a beam-convolved Plummer-like function, and the filament structure was quantified based on the relative contributions from the filament "core", represented by a Gaussian, and "wing" component, dominated by the power-law behaviour of the Plummer-like function. These filament parameters were examined for populations associated with different background levels. Results: Filaments increase their core (Mline,core) and wing (Mline,wing) contributions while increasing their total linear mass density (Mline,tot). Both components appear to be linked to the local environment, with filaments in higher backgrounds having systematically more massive Mline,core and Mline,wing. This dependence on the environment supports an accretion-based model of filament evolution in the local neighbourhood (D ≤ 500 pc). Structures located in the highest backgrounds develop the highest central AV, Mline,core, and Mline,wing as Mline,tot increases with time, favoured by the local availability of material and the enhanced gravitational potential. Our results indicate that filaments acquiring a significantly

  6. A study of the region of massive star formation L379IRS1 in radio lines of methanol and other molecules

    NASA Astrophysics Data System (ADS)

    Kalenskii, S. V.; Shchurov, M. A.

    2016-04-01

    The results of spectral observations of the region of massive star formation L379IRS1 (IRAS18265-1517) are presented. The observations were carried out with the 30-m Pico Veleta radio telescope (Spain) at seven frequencies in the 1-mm, 2-mm, and 3-mm wavelength bands. Lines of 24 molecules were detected, from simple diatomic or triatomic species to complex eight- or nine-atom compounds such as CH3OCHO or CH3OCH3. Rotation diagrams constructed from methanol andmethyl cyanide lines were used to determine the temperature of the quiescent gas in this region, which is about 40-50 K. In addition to this warm gas, there is a hot component that is revealed through high-energy lines of methanol and methyl cyanide, molecular lines arising in hot regions, and the presence of H2O masers and Class II methanol masers at 6.7 GHz, which are also related to hot gas. One of the hot regions is probably a compact hot core, which is located near the southern submillimeter peak and is related to a group of methanol masers at 6.7 GHz. High-excitation lines at other positions may be associated with other hot cores or hot post-shock gas in the lobes of bipolar outflows. The rotation diagrams can be use to determine the column densities and abundances of methanol (10-9) and methyl cyanide (about 10-11) in the quiescent gas. The column densities of A- and E-methanol in L379IRS1 are essentually the same. The column densities of other observedmolecules were calculated assuming that the ratios of the molecular level abundances correspond to a temperature of 40 K. The molecular composition of the quiescent gas is close to that in another region of massive star formation, DR21(OH). The only appreciable difference is that the column density of SO2 in L379IRS1 is at least a factor of 20 lower than the value in DR21(OH). The SO2/CS and SO2/OCS abundance ratios, which can be used as chemical clocks, are lower in L379IRS1 than in DR21(OH), suggesting that L379IRS1 is probably younger than DR21(OH).

  7. 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.

  8. Massive transfusion and massive transfusion protocol

    PubMed Central

    Patil, Vijaya; Shetmahajan, Madhavi

    2014-01-01

    Haemorrhage remains a major cause of potentially preventable deaths. Rapid transfusion of large volumes of blood products is required in patients with haemorrhagic shock which may lead to a unique set of complications. Recently, protocol based management of these patients using massive transfusion protocol have shown improved outcomes. This section discusses in detail both management and complications of massive blood transfusion. PMID:25535421

  9. Filament identification through mathematical morphology

    NASA Astrophysics Data System (ADS)

    Koch, Eric W.; Rosolowsky, Erik W.

    2015-10-01

    We present a new algorithm for detecting filamentary structure FILFINDER. The algorithm uses the techniques of mathematical morphology for filament identification, presenting a complementary approach to current algorithms which use matched filtering or critical manifolds. Unlike other methods, FILFINDER identifies filaments over a wide dynamic range in brightness. We apply the new algorithm to far-infrared imaging data of dust emission released by the Herschel Gould Belt Survey team. Our preliminary analysis characterizes both filaments and fainter striations. We find a typical filament width of 0.09 pc across the sample, but the brightness varies from cloud to cloud. Several regions show a bimodal filament brightness distribution, with the bright mode (filaments) being an order of magnitude brighter than the faint mode (striations). Using the Rolling Hough Transform, we characterize the orientations of the striations in the data, finding preferred directions that agree with magnetic field direction where data are available. There is a suggestive but noisy correlation between typical filament brightness and literature values of the star formation rates for clouds in the Gould Belt.

  10. Intermediate Filaments: A Historical Perspective

    PubMed Central

    Oshima, Robert G.

    2007-01-01

    Intracellular protein filaments intermediate in size between actin microfilaments and microtubules are composed of a surprising variety of tissue specific proteins commonly interconnected with other filamentous systems for mechanical stability and decorated by a variety of proteins that provide specialized functions. The sequence conservation of the coiled-coil, alpha-helical structure responsible for polymerization into individual 10 nm filaments defines the classification of intermediate filament proteins into a large gene family. Individual filaments further assemble into bundles and branched cytoskeletons visible in the light microscope. However, it is the diversity of the variable terminal domains that likely contributes most to different functions. The search for the functions of intermediate filament proteins has led to discoveries of roles in diseases of the skin, heart, muscle, liver, brain, adipose tissues and even premature aging. The diversity of uses of intermediate filaments as structural elements and scaffolds for organizing the distribution of decorating molecules contrasts with other cytoskeletal elements. This review is an attempt to provide some recollection of how such a diverse field emerged and changed over about 30 years. PMID:17493611

  11. 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.

  12. 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

  13. Centromeres of filamentous fungi

    PubMed Central

    Smith, Kristina M.; Galazka, Jonathan M.; Phatale, Pallavi A.; Connolly, Lanelle R.; Freitag, Michael

    2012-01-01

    How centromeres are assembled and maintained remains one of the fundamental questions in cell biology. Over the past 20 years the idea of centromeres as precise genetic loci has been replaced by the realization that it is predominantly the protein complement that defines centromere localization and function. Thus, placement and maintenance of centromeres are excellent examples of epigenetic phenomena in the strict sense. In contrast, the highly derived “point centromeres” of the budding yeast Saccharomyces cerevisiae and its close relatives are counterexamples for this general principle of centromere maintenance. While we have learned much in the past decade, it remains unclear if mechanisms for epigenetic centromere placement and maintenance are shared amongst various groups of organisms. For that reason it seems prudent to examine species from many different phylogenetic groups with the aim to extract comparative information that will yield a more complete picture of cell division in all eukaryotes. This review addresses what has been learned by studying the centromeres of filamentous fungi, a large, heterogeneous group of organisms that includes important plant, animal and human pathogens, saprobes and symbionts that fulfill essential roles in the biosphere, as well as a growing number of taxa that have become indispensable for industrial use. PMID:22752455

  14. Centromeres of filamentous fungi.

    PubMed

    Smith, Kristina M; Galazka, Jonathan M; Phatale, Pallavi A; Connolly, Lanelle R; Freitag, Michael

    2012-07-01

    How centromeres are assembled and maintained remains one of the fundamental questions in cell biology. Over the past 20 years, the idea of centromeres as precise genetic loci has been replaced by the realization that it is predominantly the protein complement that defines centromere localization and function. Thus, placement and maintenance of centromeres are excellent examples of epigenetic phenomena in the strict sense. In contrast, the highly derived "point centromeres" of the budding yeast Saccharomyces cerevisiae and its close relatives are counter-examples for this general principle of centromere maintenance. While we have learned much in the past decade, it remains unclear if mechanisms for epigenetic centromere placement and maintenance are shared among various groups of organisms. For that reason, it seems prudent to examine species from many different phylogenetic groups with the aim to extract comparative information that will yield a more complete picture of cell division in all eukaryotes. This review addresses what has been learned by studying the centromeres of filamentous fungi, a large, heterogeneous group of organisms that includes important plant, animal and human pathogens, saprobes, and symbionts that fulfill essential roles in the biosphere, as well as a growing number of taxa that have become indispensable for industrial use. PMID:22752455

  15. Alignments of galaxies within cosmic filaments from SDSS DR7

    SciTech Connect

    Zhang, Youcai; Yang, Xiaohu; Wang, Huiyuan; Wang, Lei; Mo, H. J.; Van den Bosch, Frank C. E-mail: xyang@sjtu.edu.cn

    2013-12-20

    Using a sample of galaxy groups selected from the Sloan Digital Sky Survey Data Release 7, we examine the alignment between the orientation of galaxies and their surrounding large-scale structure in the context of the cosmic web. The latter is quantified using the large-scale tidal field, reconstructed from the data using galaxy groups above a certain mass threshold. We find that the major axes of galaxies in filaments tend to be preferentially aligned with the directions of the filaments, while galaxies in sheets have their major axes preferentially aligned parallel to the plane of the sheets. The strength of this alignment signal is strongest for red, central galaxies, and in good agreement with that of dark matter halos in N-body simulations. This suggests that red, central galaxies are well aligned with their host halos, in quantitative agreement with previous studies based on the spatial distribution of satellite galaxies. There is a luminosity and mass dependence that brighter and more massive galaxies in filaments and sheets have stronger alignment signals. We also find that the orientation of galaxies is aligned with the eigenvector associated with the smallest eigenvalue of the tidal tensor. These observational results indicate that galaxy formation is affected by large-scale environments and strongly suggest that galaxies are aligned with each other over scales comparable to those of sheets and filaments in the cosmic web.

  16. 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.

  17. 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.

  18. Flux Cancellation and the Evolution of the Eruptive Filament of 2011 June 7

    NASA Astrophysics Data System (ADS)

    Yardley, S. L.; Green, L. M.; Williams, D. R.; van Driel-Gesztelyi, L.; Valori, G.; Dacie, S.

    2016-08-01

    We investigate whether flux cancellation is responsible for the formation of a very massive filament resulting in the spectacular eruption on 2011 June 7. We analyze and quantify the amount of flux cancellation that occurs in NOAA AR 11226 and its two neighboring active regions (ARs 11227 & 11233) using line-of-sight magnetograms from the Heliospheric Magnetic Imager. During a 3.6 day period building up to the eruption of the filament, 1.7 × 1021 Mx, 21% of AR 11226's maximum magnetic flux, was canceled along the polarity inversion line (PIL) where the filament formed. If the flux cancellation continued at the same rate up until the eruption then up to 2.8 × 1021 Mx (34% of the AR flux) may have been built into the magnetic configuration that contains the filament plasma. The large flux cancellation rate is due to an unusual motion of the positive-polarity sunspot, which splits, with the largest section moving rapidly toward the PIL. This motion compresses the negative polarity and leads to the formation of an orphan penumbra where one end of the filament is rooted. Dense plasma threads above the orphan penumbra build into the filament, extending its length, and presumably injecting material into it. We conclude that the exceptionally strong flux cancellation in AR 11226 played a significant role in the formation of its unusually massive filament. In addition, the presence and coherent evolution of bald patches in the vector magnetic field along the PIL suggest that the magnetic field configuration supporting the filament material is that of a flux rope.

  19. Higher dimensional massive bigravity

    NASA Astrophysics Data System (ADS)

    Do, Tuan Q.

    2016-08-01

    We study higher-dimensional scenarios of massive bigravity, which is a very interesting extension of nonlinear massive gravity since its reference metric is assumed to be fully dynamical. In particular, the Einstein field equations along with the following constraint equations for both physical and reference metrics of a five-dimensional massive bigravity will be addressed. Then, we study some well-known cosmological spacetimes such as the Friedmann-Lemaitre-Robertson-Walker, Bianchi type I, and Schwarzschild-Tangherlini metrics for the five-dimensional massive bigravity. As a result, we find that massive graviton terms will serve as effective cosmological constants in both physical and reference sectors if a special scenario, in which reference metrics are chosen to be proportional to physical ones, is considered for all mentioned metrics. Thanks to the constancy property of massive graviton terms, consistent cosmological solutions will be figured out accordingly.

  20. The structural basis for the intrinsic disorder of the actin filament: the "lateral slipping" model.

    PubMed

    Bremer, A; Millonig, R C; Sütterlin, R; Engel, A; Pollard, T D; Aebi, U

    1991-11-01

    Three-dimensional (3-D) helical reconstructions computed from electron micrographs of negatively stained dispersed F-actin filaments invariably revealed two uninterrupted columns of mass forming the "backbone" of the double-helical filament. The contact between neighboring subunits along the thus defined two long-pitch helical strands was spatially conserved and of high mass density, while the intersubunit contact between them was of lower mass density and varied among reconstructions. In contrast, phalloidinstabilized F-actin filaments displayed higher and spatially more conserved mass density between the two long-pitch helical strands, suggesting that this bicyclic hepta-peptide toxin strengthens the intersubunit contact between the two strands. Consistent with this distinct intersubunit bonding pattern, the two long-pitch helical strands of unstabilized filaments were sometimes observed separated from each other over a distance of two to six subunits, suggesting that the intrastrand intersubunit contact is also physically stronger than the interstrand contact. The resolution of the filament reconstructions, extending to 2.5 nm axially and radially, enabled us to reproducibly "cut out" the F-actin subunit which measured 5.5 nm axially by 6.0 nm tangentially by 3.2 nm radially. The subunit is distinctly polar with a massive "base" pointing towards the "barbed" end of the filament, and a slender "tip" defining its "pointed" end (i.e., relative to the "arrowhead" pattern revealed after stoichiometric decoration of the filaments with myosin subfragment 1). Concavities running approximately parallel to the filament axis both on the inner and outer face of the subunit define a distinct cleft separating the subunit into two domains of similar size: an inner domain confined to radii less than or equal to 2.5-nm forms the uninterrupted backbone of the two long-pitch helical strands, and an outer domain placed at radii of 2-5-nm protrudes radially and thus predominantly

  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. Droplets engulfing on a filament

    NASA Astrophysics Data System (ADS)

    Wu, Xiang-Fa; Yu, Meng; Zhou, Zhengping; Bedarkar, Amol; Zhao, Youhao

    2014-03-01

    Two immiscible droplets wetting on a filament may assume engulfing, partial-engulfing, or non-engulfing morphology that depends on the wetting behavior and geometries of the resulting droplet-on-filament system. This paper studies the wetting behavior of two immiscible droplets contacting and sitting symmetrically on a straight filament. A set of ordinary differential equations (ODEs) is formulated for determining the wetting morphology of the droplet-on-filament system. In the limiting case of engulfing or non-engulfing, the morphology of the droplet-on-filament system is determined in explicit form. In the case of partial-engulfing, surface finite element method is further employed for determining the wetting morphology, surface energy, and internal pressures of droplets of the system. Numerical scaling study is performed to explore their dependencies upon the wetting properties and geometries of the system. The study can be applicable for analysis and design of textiles with tailorable wetting properties and development of novel multifunctional fibrous materials for environmental protection such as oil-spill sorption, etc.

  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. Buckling of Branched Cytoskeletal Filaments

    NASA Astrophysics Data System (ADS)

    Quint, D. A.; Schwarz, J. M.

    2011-03-01

    In vitro experiments of growing dendritic actin networks demonstrate reversible stress-softening at high loads, above some critical load. The transition to the stress-softening regime has been attributed to the elastic buckling of individual actin filaments. To estimate the critical load above which softening should occur, we extend the elastic theory of buckling of individual filaments embedded in a network to include the buckling of branched filaments, a signature trait of growing dendritic actin networks. Under certain assumptions, there will be approximately a seven-fold increase in the classical critical bucking load, when compared to the unbranched filament, which is entirely due to the presence of a branch. Moreover, we go beyond the classical buckling regime to investigate the effect of entropic fluctuations. The result of compressing the filament in this case leads to an increase in these fluctuations and eventually the harmonic approximation breaks down signifying the onset of the buckling transition. We compute corrections to the classical critical buckling load near this breakdown.

  5. Nonequilibrium transport in superconducting filaments

    NASA Technical Reports Server (NTRS)

    Arutyunov, K. YU.; Danilova, N. P.; Nikolaeva, A. A.

    1995-01-01

    The step-like current-voltage characteristics of highly homogeneous single-crystalline tin and indium thin filaments has been measured. The length of the samples L approximately 1 cm was much greater than the nonequilibrium quasiparticle relaxation length Lambda. It was found that the activation of a successive i-th voltage step occurs at current significantly greater than the one derived with the assumption that the phase slip centers are weakly interacting on a scale L much greater than Lambda. The observation of 'subharmonic' fine structure on the voltage-current characteristics of tin filaments confirms the hypothesis of the long-range phase slip centers interaction.

  6. 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.

  7. Coiling of a viscous filament

    NASA Astrophysics Data System (ADS)

    Samuel, A. D. T.; Ryu, W. S.; Mahadevan, L.

    1997-11-01

    A classic demonstration of fluid buckling is a daily occurence at the breakfast table, where a continuous stream of viscous fluid (honey) is often poured onto a flat surface (toast) from a sufficient height. The thin fluid filament quickly settles into a steady state; near the surface it bends into a helical shape while simultaneously rotating about the vertical and is laid out in a regular coil. This behavior is reminiscent of the coiling of a falling flexible rope. We derive a simple scaling law that predicts the coiling frequency in terms of the filament radius and the flow rate. We also verify this scaling law with the results of experiments.

  8. Octonic Massive Field Equations

    NASA Astrophysics Data System (ADS)

    Demir, Süleyman; Kekeç, Seray

    2016-03-01

    In the present paper we propose the octonic form of massive field equations based on the analogy with electromagnetism and linear gravity. Using the advantages of octon algebra the Maxwell-Dirac-Proca equations have been reformulated in compact and elegant way. The energy-momentum relations for massive field are discussed.

  9. Octonic Massive Field Equations

    NASA Astrophysics Data System (ADS)

    Demir, Süleyman; Kekeç, Seray

    2016-07-01

    In the present paper we propose the octonic form of massive field equations based on the analogy with electromagnetism and linear gravity. Using the advantages of octon algebra the Maxwell-Dirac-Proca equations have been reformulated in compact and elegant way. The energy-momentum relations for massive field are discussed.

  10. The origin of massive clusters: from hyper-massive clouds to mini-bursts of star formation

    NASA Astrophysics Data System (ADS)

    Motte, Frederique; Louvet, Fabien; Nguyen Luong, Quang

    2015-08-01

    Herschel revealed high-density cloud filaments of several pc^3, which are forming clusters of OB-type stars. Counting Herschel protostars gives a direct measure of the mass of stars forming in a period of ~10^5 yrs, the ``instantaneous'' star formation activity. Given their activity, these so-called mini-starburst cloud ridges could be seen as "miniature and instant models" of starburst galaxies. Their characteristics could shed light on the origin of massive clusters.

  11. Core and filament formation in magnetized, self-gravitating isothermal layers

    SciTech Connect

    Van Loo, Sven; Keto, Eric; Zhang, Qizhou

    2014-07-01

    We examine the role of the gravitational instability in an isothermal, self-gravitating layer threaded by magnetic fields on the formation of filaments and dense cores. Using a numerical simulation, we follow the non-linear evolution of a perturbed equilibrium layer. The linear evolution of such a layer is described in the analytic work of Nagai et al. We find that filaments and dense cores form simultaneously. Depending on the initial magnetic field, the resulting filaments form either a spiderweb-like network (for weak magnetic fields) or a network of parallel filaments aligned perpendicular to the magnetic field lines (for strong magnetic fields). Although the filaments are radially collapsing, the density profile of their central region (up to the thermal scale height) can be approximated by a hydrodynamical equilibrium density structure. Thus, the magnetic field does not play a significant role in setting the density distribution of the filaments. The density distribution outside of the central region deviates from the equilibrium. The radial column density distribution is then flatter than the expected power law of r {sup –4} and similar to filament profiles observed with Herschel. Our results do not explain the near constant filament width of ∼0.1pc. However, our model does not include turbulent motions. It is expected that the accretion-driven amplification of these turbulent motions provides additional support within the filaments against gravitational collapse. Finally, we interpret the filamentary network of the massive star forming complex G14.225-0.506 in terms of the gravitational instability model and find that the properties of the complex are consistent with being formed out of an unstable layer threaded by a strong, parallel magnetic field.

  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. 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

  14. 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...

  15. Role of Intermediate Filaments in Vesicular Traffic.

    PubMed

    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

  16. 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)

  17. The global velocity field of the filament in NGC 6334

    NASA Astrophysics Data System (ADS)

    Zernickel, A.; Schilke, P.; Smith, R. J.

    2013-06-01

    Aims: Star formation involves the collapse of gas from the scale of giant molecular clouds down to dense cores. Our aim is to trace the velocities in the filamentary, massive star-forming region NGC 6334 and to explain its dynamics. Methods: The main filament was mapped with the single-dish telescope APEX in HCO+ (J = 3-2) at 267.6 GHz to trace the dense gas. In order to reproduce the position-velocity diagram, we use a 3D radiative transfer code and create a model of a cylinder that undergoes a gravitational collapse toward its center. Results: We find a velocity gradient in the filament from the end toward its center, with the highest masses being found at both ends. Similar velocities have been predicted by recent calculations of the gravitational collapse of a sheet or cylinder of gas, and the observed velocities are consistent with these predictions. The 3D structure is revealed by taking the inclination and curvature of the filament into account. The free-fall collapse timescale of the filamentary molecular cloud is estimated to be ~1 Myr. This publication is based on data acquired with the Atacama Pathfinder Experiment (APEX). APEX is a collaboration between the Max-Planck-Institut für Radioastronomie, the European Southern Observatory, and the Onsala Space Observatory.

  18. Diamond film by hot filament CVD method

    NASA Technical Reports Server (NTRS)

    Hirose, Y.

    1988-01-01

    Diamond synthesis by the hot filament CVD method is discussed. A hot filament decomposes gas mixtures and oxygen containing organic compounds such as alcohols. which are carbon sources. The resulting thin films, growth mechanisms, and characteristics and problems associated with the hot filament CVD method are analyzed and evaluated.

  19. Single turnovers of fluorescent ATP bound to bipolar myosin filament during actin filaments sliding

    PubMed Central

    Maruta, Takahiro; Kobatake, Takahiro; Okubo, Hiroyuki; Chaen, Shigeru

    2013-01-01

    The nucleotide turnover rates of bipolar myosin thick filament along which actin filament slides were measured by the displacement of prebound fluorescent ATP analog 2′(3′)-O-[N-[2-[(Cy3)]amindo]ethyl] carbamoyl]-adenosine 5′ triphosphate (Cy3-EDA-ATP) upon flash photolysis of caged ATP. The fluorescence of the thick filament where actin filament slides decayed with two exponential processes. The slower rate constant was the same as that without actin filament. Along bipolar myosin thick filament, actin filaments slide at a fast speed towards the central bare zone (forward), but more slowly away from the bare zone (backward). The displacement rate constant of fluorescent ATP from the myosin filament where actin filament moved forward was 5.0 s−1, whereas the rate constant where the actin filament slid backward was 1.7 s−1. These findings suggest that the slow ADP release rate is responsible for the slow backward sliding movement.

  20. Massive Stellar Outflows From the Combined Action of Multiple Stellar Jets

    NASA Astrophysics Data System (ADS)

    Mac Low, Mordecai-Mark; Peters, T.; Klaassen, P.; Schrön, M.; Klessen, R.

    2014-01-01

    The formation of high-mass stars is usually accompanied by powerful protostellar outflows. Such high-mass outflows are not simply scaled-up versions of their lower-mass counterparts, since observations seem to suggest that the collimation degree degrades with stellar mass. Theoretically, the origins of massive outflows are not well understood because radiative feedback and gravitational fragmentation of the accretion flow around the high-mass star impede the driving of magnetic disk winds. We here present the first 3D simulation of massive star formation that simultaneously includes feedback by non-ionizing and ionizing radiation as well as a subgrid-scale model for protostellar outflows. We ran this model with the Flash adaptive mesh refinement hydrocode. We find that stars that form in a common accretion flow have aligned outflow axes, so that the individual jets of lower-mass companion stars combine to form a collective outflow. We compare our simulation to observations with synthetic H2 and CO observations and find that the morphology and kinematics of this collective outflow is very similar to observed massive outflows, such as Cepheus A and DR 21. The properties of high-mass outflows are therefore generally consistent with the formation of massive stars in gravitationally unstable accretion flows. We acknowledge support from SNF grant 200020 137896, U. Zurich grant FK-13-112, NSF grant AST11-09395, and DFG grant KL 1358/14-1, as well as SBB 811, and computing time at the LRZ (project h1343), the CSCS (Project 364), and the Juelich Supercomputing Center (project HHD14).

  1. Swirling around filaments: are large-scale structure vortices spinning up dark haloes?

    NASA Astrophysics Data System (ADS)

    Laigle, C.; Pichon, C.; Codis, S.; Dubois, Y.; Le Borgne, D.; Pogosyan, D.; Devriendt, J.; Peirani, S.; Prunet, S.; Rouberol, S.; Slyz, A.; Sousbie, T.

    2015-01-01

    The kinematic analysis of dark matter and hydrodynamical simulations suggests that the vorticity in large-scale structure is mostly confined to, and predominantly aligned with, their filaments, with an excess of probability of 20 per cent to have the angle between vorticity and filaments direction lower than 60° relative to random orientations. The cross-sections of these filaments are typically partitioned into four quadrants with opposite vorticity sign, arising from multiple flows, originating from neighbouring walls. The spins of haloes embedded within these filaments are consistently aligned with this vorticity for any halo mass, with a stronger alignment for the most massive structures up to an excess of probability of 165 per cent. The global geometry of the flow within the cosmic web is therefore qualitatively consistent with a spin acquisition for smaller haloes induced by this large-scale coherence, as argued in Codis et al. In effect, secondary anisotropic infall (originating from the vortex-rich filament within which these lower-mass haloes form) dominates the angular momentum budget of these haloes. The transition mass from alignment to orthogonality is related to the size of a given multi-flow region with a given polarity. This transition may be reconciled with the standard tidal torque theory if the latter is augmented so as to account for the larger scale anisotropic environment of walls and filaments.

  2. Supersymmetrizing massive gravity

    NASA Astrophysics Data System (ADS)

    Malaeb, O.

    2013-07-01

    When four scalar fields with global Lorentz symmetry are coupled to gravity and take a vacuum expectation value, breaking diffeomorphism invariance spontaneously, the graviton becomes massive. This model is supersymmetrized by considering four N=1 chiral superfields with global Lorentz symmetry. The global supersymmetry is promoted to a local one using the rules of tensor calculus of coupling the N=1 supergravity Lagrangian to the four chiral multiplets. When the scalar components of the chiral multiplets zA acquire a vacuum expectation value, both diffeomorphism invariance and local supersymmetry are broken spontaneously. The global Lorentz index A becomes identified with the space-time Lorentz index, making the scalar fields zA vectors and the chiral spinors ψA spin-3/2 Rarita-Schwinger fields. We show that the spectrum of the model in the broken phase consists of a massive spin-2 field, two massive spin-3/2 fields with different mass and a massive vector.

  3. Massive Oral Decoding.

    ERIC Educational Resources Information Center

    Janicke, Eugene M.

    1981-01-01

    An intensive reading clinic used the Massive Oral Decoding (MOD) technique to help 10 reading disabled students (grades 7 and 8) increase independent reading skills. MOD stresses large amounts of reading practice at the student's independent level. (CL)

  4. Quantum massive conformal gravity

    NASA Astrophysics Data System (ADS)

    Faria, F. F.

    2016-04-01

    We first find the linear approximation of the second plus fourth order derivative massive conformal gravity action. Then we reduce the linearized action to separated second order derivative terms, which allows us to quantize the theory by using the standard first order canonical quantization method. It is shown that quantum massive conformal gravity is renormalizable but has ghost states. A possible decoupling of these ghost states at high energies is discussed.

  5. Galaxy pairs align with Galactic filaments

    NASA Astrophysics Data System (ADS)

    Tempel, E.; Tamm, A.

    2015-04-01

    Context. Gravitational collapse theory and numerical simulations suggest that the velocity field within large-scale galaxy filaments is dominated by motions along the filaments. Aims: Our aim is to check whether observational data reveal any preferred orientation of galaxy pairs with respect to the underlying filaments as a result of the expectedly anisotropic velocity field. Methods: We use galaxy pairs and galaxy filaments identified from Sloan Digital Sky Survey data. For filament extraction, we use the Bisous model that is based on the marked point process technique. During the filament detection, we use the centre point of each pair instead of the positions of galaxies to avoid a built-in influence of pair orientation on the filament construction. For pairs lying within filaments (3012 cases), we calculate the angle between the line connecting the galaxies of each pair and their host filaments. To avoid redshift-space distortions, the angle is measured in the plane of the sky. Results: The alignment analysis shows that the orientation of galaxy pairs correlates strongly with their host filaments. The alignment signal is stronger for loose pairs, with at least 25% excess of aligned pairs compared to a random distribution. The alignment of galaxy pairs and filaments measured from the observational data is in good agreement with the alignment in the Millennium simulation and thus provides support to the ΛCDM formalism.

  6. 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.

  7. 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).

  8. Partial Slingshot Reconnection between Two Filaments

    NASA Astrophysics Data System (ADS)

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

    2013-02-01

    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 γ-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.

  9. 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.

  10. The formation of massive star systems by accretion.

    PubMed

    Krumholz, Mark R; Klein, Richard I; McKee, Christopher F; Offner, Stella S R; Cunningham, Andrew J

    2009-02-01

    Massive stars produce so much light that the radiation pressure they exert on the gas and dust around them is stronger than their gravitational attraction, a condition that has long been expected to prevent them from growing by accretion. We present three-dimensional radiation-hydrodynamic simulations of the collapse of a massive prestellar core and find that radiation pressure does not halt accretion. Instead, gravitational and Rayleigh-Taylor instabilities channel gas onto the star system through nonaxisymmetric disks and filaments that self-shield against radiation while allowing radiation to escape through optically thin bubbles. Gravitational instabilities cause the disk to fragment and form a massive companion to the primary star. Radiation pressure does not limit stellar masses, but the instabilities that allow accretion to continue lead to small multiple systems. PMID:19150809

  11. Filamentation as primitive growth mode?

    PubMed

    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. PMID:26718101

  12. 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.

  13. Intermediate Filaments in Caenorhabditis elegans.

    PubMed

    Zuela, Noam; Gruenbaum, Yosef

    2016-01-01

    More than 70 different genes in humans and 12 different genes in Caenorhabditis elegans encode the superfamily of intermediate filament (IF) proteins. In C. elegans, similar to humans, these proteins are expressed in a cell- and tissue-specific manner, can assemble into heteropolymers and into 5-10nm wide filaments that account for the principal structural elements at the nuclear periphery, nucleoplasm, and cytoplasm. At least 5 of the 11 cytoplasmic IFs, as well as the nuclear IF, lamin, are essential. In this chapter, we will include a short review of our current knowledge of both cytoplasmic and nuclear IFs in C. elegans and will describe techniques used for their analyses. PMID:26795488

  14. 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.

  15. 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.

  16. ALMA observations of cold molecular gas filaments trailing rising radio bubbles in PKS 0745-191

    NASA Astrophysics Data System (ADS)

    Russell, H. R.; McNamara, B. R.; Fabian, A. C.; Nulsen, P. E. J.; Edge, A. C.; Combes, F.; Murray, N. W.; Parrish, I. J.; Salomé, P.; Sanders, J. S.; Baum, S. A.; Donahue, M.; Main, R. A.; O'Connell, R. W.; O'Dea, C. P.; Oonk, J. B. R.; Tremblay, G.; Vantyghem, A. N.; Voit, G. M.

    2016-05-01

    We present ALMA observations of the CO(1-0) and CO(3-2) line emission tracing filaments of cold molecular gas in the central galaxy of the cluster PKS 0745-191. The total molecular gas mass of 4.6± 0.3× 109 M_{⊙}, assuming a Galactic XCO factor, is divided roughly equally between three filaments each extending radially 3-5 kpc from the galaxy centre. The emission peak is located in the SE filament ˜ 1 arcsec (2 kpc) from the nucleus. The velocities of the molecular clouds in the filaments are low, lying within ± 100 { km s^{-1}} of the galaxy's systemic velocity. Their full width at half-maximum (FWHM) are less than 150 { km s^{-1},} which is significantly below the stellar velocity dispersion. Although the molecular mass of each filament is comparable to a rich spiral galaxy, such low velocities show that the filaments are transient and the clouds would disperse on < 107 yr time-scales unless supported, likely by the indirect effect of magnetic fields. The velocity structure is inconsistent with a merger origin or gravitational free-fall of cooling gas in this massive central galaxy. If the molecular clouds originated in gas cooling even a few kpc from their current locations their velocities would exceed those observed. Instead, the projection of the N and SE filaments underneath X-ray cavities suggests they formed in the updraft behind bubbles buoyantly rising through the cluster atmosphere. Direct uplift of the dense gas by the radio bubbles appears to require an implausibly high coupling efficiency. The filaments are coincident with low temperature X-ray gas, bright optical line emission and dust lanes indicating that the molecular gas could have formed from lifted warmer gas that cooled in situ.

  17. Extreme Mergers from the Massive Cluster Survey

    NASA Astrophysics Data System (ADS)

    Morris, Roger

    2010-09-01

    We propose to observe two extraordinary, high-redshift galaxy clusters from the Massive Cluster Survey. Both targets are very rare, triple merger systems (one a nearly co-linear merger), and likely lie at the deepest nodes of the cosmic web. Both targets show multiple strong gravitational lensing arcs in the cluster cores. These targets only possess very short (10ks) Chandra observations, and are unobserved by XMM-Newton. The X-ray data will be used to probe the mass distribution of hot, baryonic gas, and to reveal the details of the merger physics and the process of cluster assembly. We will also search for hints of X-ray emission from filaments between the merging clumps. Subaru and Hubble Space Telescope imaging data are in hand; we request additional HST coverage for one object.

  18. Extreme Mergers from the Massive Cluster Survey

    NASA Astrophysics Data System (ADS)

    Morris, R.

    2010-09-01

    We will observe an extraordinary, high-redshift galaxy cluster from the Massive Cluster Survey. The target is a very rare, triple merger system, and likely lies at the one of deepest nodes of the cosmic web. The target shows multiple strong gravitational lensing arcs in the cluster core. This target only possesses a very short {10ks} Chandra observations, and is unobserved by XMM-Newton. The X-ray data from this joint Chandra/HST proposal will be used to probe the mass distribution of hot, baryonic gas, and to reveal the details of the merger physics and the process of cluster assembly. We will also search for hints of X-ray emission from filaments between the merging clumps. Subaru and some Hubble Space Telescope imaging data are in hand; we will gather additional HST coverage for a lensing analysis.

  19. Filamentation of Metabolic Enzymes in Saccharomyces cerevisiae.

    PubMed

    Shen, Qing-Ji; Kassim, Hakimi; Huang, Yong; Li, Hui; Zhang, Jing; Li, Guang; Wang, Peng-Ye; Yan, Jun; Ye, Fangfu; Liu, Ji-Long

    2016-06-20

    Compartmentation via filamentation has recently emerged as a novel mechanism for metabolic regulation. In order to identify filament-forming metabolic enzymes systematically, we performed a genome-wide screening of all strains available from an open reading frame-GFP collection in Saccharomyces cerevisiae. We discovered nine novel filament-forming proteins and also confirmed those identified previously. From the 4159 strains, we found 23 proteins, mostly metabolic enzymes, which are capable of forming filaments in vivo. In silico protein-protein interaction analysis suggests that these filament-forming proteins can be clustered into several groups, including translational initiation machinery and glucose and nitrogen metabolic pathways. Using glutamine-utilising enzymes as examples, we found that the culture conditions affect the occurrence and length of the metabolic filaments. Furthermore, we found that two CTP synthases (Ura7p and Ura8p) and two asparagine synthetases (Asn1p and Asn2p) form filaments both in the cytoplasm and in the nucleus. Live imaging analyses suggest that metabolic filaments undergo sub-diffusion. Taken together, our genome-wide screening identifies additional filament-forming proteins in S. cerevisiae and suggests that filamentation of metabolic enzymes is more general than currently appreciated. PMID:27312010

  20. 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.

  1. Mechanical properties of branched actin filaments.

    PubMed

    Razbin, Mohammadhosein; Falcke, Martin; Benetatos, Panayotis; Zippelius, Annette

    2015-07-01

    Cells moving on a two dimensional substrate generate motion by polymerizing actin filament networks inside a flat membrane protrusion. New filaments are generated by branching off existing ones, giving rise to branched network structures. We investigate the force-extension relation of branched filaments, grafted on an elastic structure at one end and pushing with the free ends against the leading edge cell membrane. Single filaments are modeled as worm-like chains, whose thermal bending fluctuations are restricted by the leading edge cell membrane, resulting in an effective force. Branching can increase the stiffness considerably; however the effect depends on branch point position and filament orientation, being most pronounced for intermediate tilt angles and intermediate branch point positions. We describe filament networks without cross-linkers to focus on the effect of branching. We use randomly positioned branch points, as generated in the process of treadmilling, and orientation distributions as measured in lamellipodia. These networks reproduce both the weak and strong force response of lamellipodia as measured in force-velocity experiments. We compare properties of branched and unbranched networks. The ratio of the network average of the force per branched filament to the average force per unbranched filament depends on the orientation distribution of the filaments. The ratio exhibits compression dependence and may go up to about 4.5 in networks with a narrow orientation distribution. With orientation distributions measured in lamellipodia, it is about two and essentially independent from network compression, graft elasticity and filament persistence length. PMID:26040560

  2. Mechanical properties of branched actin filaments

    NASA Astrophysics Data System (ADS)

    Razbin, Mohammadhosein; Falcke, Martin; Benetatos, Panayotis; Zippelius, Annette

    2015-07-01

    Cells moving on a two dimensional substrate generate motion by polymerizing actin filament networks inside a flat membrane protrusion. New filaments are generated by branching off existing ones, giving rise to branched network structures. We investigate the force-extension relation of branched filaments, grafted on an elastic structure at one end and pushing with the free ends against the leading edge cell membrane. Single filaments are modeled as worm-like chains, whose thermal bending fluctuations are restricted by the leading edge cell membrane, resulting in an effective force. Branching can increase the stiffness considerably; however the effect depends on branch point position and filament orientation, being most pronounced for intermediate tilt angles and intermediate branch point positions. We describe filament networks without cross-linkers to focus on the effect of branching. We use randomly positioned branch points, as generated in the process of treadmilling, and orientation distributions as measured in lamellipodia. These networks reproduce both the weak and strong force response of lamellipodia as measured in force-velocity experiments. We compare properties of branched and unbranched networks. The ratio of the network average of the force per branched filament to the average force per unbranched filament depends on the orientation distribution of the filaments. The ratio exhibits compression dependence and may go up to about 4.5 in networks with a narrow orientation distribution. With orientation distributions measured in lamellipodia, it is about two and essentially independent from network compression, graft elasticity and filament persistence length.

  3. Averaged implicit hydrodynamic model of semiflexible filaments.

    PubMed

    Chandran, Preethi L; Mofrad, Mohammad R K

    2010-03-01

    We introduce a method to incorporate hydrodynamic interaction in a model of semiflexible filament dynamics. Hydrodynamic screening and other hydrodynamic interaction effects lead to nonuniform drag along even a rigid filament, and cause bending fluctuations in semiflexible filaments, in addition to the nonuniform Brownian forces. We develop our hydrodynamics model from a string-of-beads idealization of filaments, and capture hydrodynamic interaction by Stokes superposition of the solvent flow around beads. However, instead of the commonly used first-order Stokes superposition, we do an equivalent of infinite-order superposition by solving for the true relative velocity or hydrodynamic velocity of the beads implicitly. We also avoid the computational cost of the string-of-beads idealization by assuming a single normal, parallel and angular hydrodynamic velocity over sections of beads, excluding the beads at the filament ends. We do not include the end beads in the averaging and solve for them separately instead, in order to better resolve the drag profiles along the filament. A large part of the hydrodynamic drag is typically concentrated at the filament ends. The averaged implicit hydrodynamics methods can be easily incorporated into a string-of-rods idealization of semiflexible filaments that was developed earlier by the authors. The earlier model was used to solve the Brownian dynamics of semiflexible filaments, but without hydrodynamic interactions incorporated. We validate our current model at each stage of development, and reproduce experimental observations on the mean-squared displacement of fluctuating actin filaments . We also show how hydrodynamic interaction confines a fluctuating actin filament between two stationary lateral filaments. Finally, preliminary examinations suggest that a large part of the observed velocity in the interior segments of a fluctuating filament can be attributed to induced solvent flow or hydrodynamic screening. PMID:20365783

  4. 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.

  5. 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.

  6. 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.

  7. Spin alignments within the cosmic web: a theory of constrained tidal torques near filaments

    NASA Astrophysics Data System (ADS)

    Codis, Sandrine; Pichon, Christophe; Pogosyan, Dmitry

    2015-10-01

    The geometry of the cosmic web drives in part the spin acquisition of galaxies. This can be explained in a Lagrangian framework, by identifying the specific long-wavelength correlations within the primordial Gaussian random field (GRF), which are relevant to spin acquisition. Tidal torque theory is revisited in the context of such anisotropic environments, biased by the presence of a filament within a wall. The point process of filament-type saddles represents it most efficiently. The constrained misalignment between the tidal and the inertia tensors in the vicinity of filament-type saddles simply explains the distribution of spin directions. This misalignment implies in particular an azimuthal orientation for the spins of more massive galaxies and a spin alignment with the filament for less massive galaxies. This prediction is found to be in qualitative agreement with measurements in GRFs and N-body simulations. It relates the transition mass to the geometry of the saddle, and accordingly predicts its measured scaling with the mass of non-linearity. Implications for galaxy formation and weak lensing are briefly discussed, as is the dual theory of spin alignments in walls.

  8. HST imaging of the dusty filaments and nucleus swirl in NGC4696 at the centre of the Centaurus Cluster

    NASA Astrophysics Data System (ADS)

    Fabian, A. C.; Walker, S. A.; Russell, H. R.; Pinto, C.; Canning, R. E. A.; Salome, P.; Sanders, J. S.; Taylor, G. B.; Zweibel, E. G.; Conselice, C. J.; Combes, F.; Crawford, C. S.; Ferland, G. J.; Gallagher, J. S.; Hatch, N. A.; Johnstone, R. M.; Reynolds, CS.

    2016-06-01

    Narrow-band HST imaging has resolved the detailed internal structure of the 10 kpc diameter Hα+[NII] emission line nebulosity in NGC4696, the central galaxy in the nearby Centaurus cluster, showing that the dusty, molecular, filaments have a width of about 60pc. Optical morphology and velocity measurements indicate that the filaments are dragged out by the bubbling action of the radio source as part of the AGN feedback cycle. Using the drag force we find that the magnetic field in the filaments is in approximate pressure equipartition with the hot gas. The filamentary nature of the cold gas continues inward, swirling around and within the Bondi accretion radius of the central black hole, revealing the magnetic nature of the gas flows in massive elliptical galaxies. HST imaging resolves the magnetic, dusty, molecular filaments at the centre of the Centaurus cluster to a swirl around and within the Bondi radius.

  9. HST imaging of the dusty filaments and nucleus swirl in NGC4696 at the centre of the Centaurus Cluster

    NASA Astrophysics Data System (ADS)

    Fabian, A. C.; Walker, S. A.; Russell, H. R.; Pinto, C.; Canning, R. E. A.; Salome, P.; Sanders, J. S.; Taylor, G. B.; Zweibel, E. G.; Conselice, C. J.; Combes, F.; Crawford, C. S.; Ferland, G. J.; Gallagher, J. S., III; Hatch, N. A.; Johnstone, R. M.; Reynolds, C. S.

    2016-09-01

    Narrow-band HST imaging has resolved the detailed internal structure of the 10 kpc diameter H α+[N II] emission line nebulosity in NGC4696, the central galaxy in the nearby Centaurus cluster, showing that the dusty, molecular, filaments have a width of about 60 pc. Optical morphology and velocity measurements indicate that the filaments are dragged out by the bubbling action of the radio source as part of the active galactic nucleus feedback cycle. Using the drag force we find that the magnetic field in the filaments is in approximate pressure equipartition with the hot gas. The filamentary nature of the cold gas continues inwards, swirling around and within the Bondi accretion radius of the central black hole, revealing the magnetic nature of the gas flows in massive elliptical galaxies. HST imaging resolves the magnetic, dusty, molecular filaments at the centre of the Centaurus cluster to a swirl around and within the Bondi radius.

  10. Introduction to Massive Gravity

    NASA Astrophysics Data System (ADS)

    de Rham, Claudia

    We review recent progress on massive gravity. We first show how extra dimensions prove to be a useful tool in building theories of modified gravity, including Galileon theories and their DBI extensions. DGP arises from an infinite size extra dimension, and we show how massive gravity arises from `deconstructing' the extra dimension in the vielbein formalism. We then explain how the ghost issue is resolved in that special theory of massive gravity. The viability of such models relies on the Vainshtein mechanism which is best described in terms of Galileons. While its implementation is successful in most of these models it also comes hand in hand with superluminalities and strong coupling which are reviewed and their real consequences are discussed.

  11. Resummation of Massive Gravity

    SciTech Connect

    Rham, Claudia de; Gabadadze, Gregory; Tolley, Andrew J.

    2011-06-10

    We construct four-dimensional covariant nonlinear theories of massive gravity which are ghost-free in the decoupling limit to all orders. These theories resume explicitly all the nonlinear terms of an effective field theory of massive gravity. We show that away from the decoupling limit the Hamiltonian constraint is maintained at least up to and including quartic order in nonlinearities, hence excluding the possibility of the Boulware-Deser ghost up to this order. We also show that the same remains true to all orders in a similar toy model.

  12. The nonlinear evolution of magnetized solar filaments

    NASA Technical Reports Server (NTRS)

    Sparks, L.; Van Hoven, G.; Schnack, D. D.

    1990-01-01

    Thermal instability driven by optically thin radiation is believed to initiate the formation of plasma filaments in the solar corona. The fact that filaments are observed generally to separate regions of opposite, line-of-sight, magnetic polarity in the underlying photosphere suggests that filament formation requires the presence of a highly sheared, local magnetic field. Two-dimensional, nonlinear, magnetohydrodynamic simulations of the local genesis and growth of solar filaments in a force-free, sheared, magnetic field were performed, and the evolution of generic perturbations possessing broad spatial profiles was traced. It was found that simulations of the evolution of initial random-noise perturbations produce filamentary plasma structures that exhibit densities and temperatures characteristic of observed solar filaments. Furthermore, in each of these simulations, the filament axis lies at a finite angle with respect to the local magnetic field, consistent with solar observations.

  13. 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

  14. Evolution of Barb Angle and Filament Eruption

    NASA Astrophysics Data System (ADS)

    Su, J. T.; Liu, Y.; Zhang, H. Q.; Kurokawa, H.; Yurchyshyn, V.; Shibata, K.; Bao, X. M.; Wang, G. P.; Li, C.

    2005-09-01

    Hα observations of a quiescent U-shaped filament were obtained at Big Bear Solar Observatory and at Hida Observatory with the Flare Monitoring Telescope. The filament was located in the southern hemisphere on 1998 November 4. We study the evolution of the angle of a barb with respect to the axis of the filament and find the evolution can be divided into two phases: a rise from the acute phase to the obtuse phase and a fall. Thus, this indicates that the chirality of this barb changes with time. Moreover, in the process of evolution, we find that interconnection of the part of the filament bearing the barb with the whole filament became either weakened or strengthened. We impute the final eruption of the filament to the chirality evolution of the barb.

  15. Remote electrical arc suppression by laser filamentation.

    PubMed

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

    2015-11-01

    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. PMID:26561133

  16. 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.

  17. How bio-filaments twist membranes.

    PubMed

    Fierling, Julien; Johner, Albert; Kulić, Igor M; Mohrbach, Hervé; Müller, Martin Michael

    2016-06-29

    We study the deformations of a fluid membrane imposed by adhering stiff bio-filaments due to the torques they apply. In the limit of small deformations, we derive a general expression for the energy and the deformation field of the membrane. This expression is specialised to different important cases including closed and helical bio-filaments. In particular, we analyse interface-mediated interactions and membrane wrapping when the filaments apply a local torque distribution on a tubular membrane. PMID:27291854

  18. 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.

  19. Recent observations of the formation of filaments

    NASA Astrophysics Data System (ADS)

    Martin, Sara F.

    1986-12-01

    Two examples of the formation of small filaments in H alpha are described and illustrated. In both cases, the formation is seen to be the spontaneous appearance of strands of absorbing mass that evolve from no previous structure. The initial development of the filaments appears to consist of the accumulation of these absorptive strands along approximately parallel paths in a channel between large-scale, opposite polarity magnetic fields on either side of the filaments. The strands exhibit continuous changes in shape and degree of absorption which can be due to successive condensations resulting in new strands, mass motions within the strands, and outflow of the mass from the strands. For at least several hours before the formation of both filaments, small-scale fragments of opposite polarity, line-of-sight magnetic flux adjacent to or immediately below the filaments, and at the ends of the filaments, were cancelling. This type of magnetic flux disappearance continued during the development of the filaments and is commonly observed in association with established filaments. Cancellation is interpreted as an important evolutionary change in the magnetic field that can lead to configurations suitable for the formation of filaments.

  20. Methods for modeling cytoskeletal and DNA filaments

    NASA Astrophysics Data System (ADS)

    Andrews, Steven S.

    2014-02-01

    This review summarizes the models that researchers use to represent the conformations and dynamics of cytoskeletal and DNA filaments. It focuses on models that address individual filaments in continuous space. Conformation models include the freely jointed, Gaussian, angle-biased chain (ABC), and wormlike chain (WLC) models, of which the first three bend at discrete joints and the last bends continuously. Predictions from the WLC model generally agree well with experiment. Dynamics models include the Rouse, Zimm, stiff rod, dynamic WLC, and reptation models, of which the first four apply to isolated filaments and the last to entangled filaments. Experiments show that the dynamic WLC and reptation models are most accurate. They also show that biological filaments typically experience strong hydrodynamic coupling and/or constrained motion. Computer simulation methods that address filament dynamics typically compute filament segment velocities from local forces using the Langevin equation and then integrate these velocities with explicit or implicit methods; the former are more versatile and the latter are more efficient. Much remains to be discovered in biological filament modeling. In particular, filament dynamics in living cells are not well understood, and current computational methods are too slow and not sufficiently versatile. Although primarily a review, this paper also presents new statistical calculations for the ABC and WLC models. Additionally, it corrects several discrepancies in the literature about bending and torsional persistence length definitions, and their relations to flexural and torsional rigidities.

  1. Actively Contracting Bundles of Polar Filaments

    NASA Astrophysics Data System (ADS)

    Kruse, K.; Jülicher, F.

    2000-08-01

    We introduce a phenomenological model to study the properties of bundles of polar filaments which interact via active elements. The stability of the homogeneous state, the attractors of the dynamics in the unstable regime, and the tensile stress generated in the bundle are discussed. We find that the interaction of parallel filaments can induce unstable behavior and is responsible for active contraction and tension in the bundle. The interaction between antiparallel filaments leads to filament sorting. Our model could apply to simple contractile structures in cells such as stress fibers.

  2. 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.

  3. Measurement of birefringence inside a filament

    SciTech Connect

    Yuan Shuai; Wang, Tie-Jun; Chin, See Leang; Kosareva, Olga; Panov, Nikolay; Makarov, Vladimir; Zeng Heping

    2011-07-15

    We quantified the ultrafast birefringence induced in the filament in an atomic gas by measuring the filament-induced polarization rotation of a probe pulse. Based on the dephasing of the probe's orthogonal polarization components in argon, the experiment was done at 1 atm by copropagating a linearly polarized 400-nm probe pulse with an 800-nm pump pulse which generated the filament. The probe's elliptical polarization states were shown under various initial pump-probe polarization schemes. These states were verified by comparing the filament-induced probe polarization rotation angle and the ellipticity of the probe polarization.

  4. Chaperonin filaments: The archaeal cytoskeleton?

    PubMed Central

    Trent, Jonathan D.; Kagawa, Hiromi K.; Yaoi, Takuro; Olle, Eric; Zaluzec, Nestor J.

    1997-01-01

    Chaperonins are high molecular mass double-ring structures composed of 60-kDa protein subunits. In the hyperthermophilic archaeon Sulfolobus shibatae the two chaperonin proteins represent ≈4% of its total protein and have a combined intracellular concentration of >30 mg/ml. At concentrations ≥ 0.5 mg/ml purified chaperonins form filaments in the presence of Mg2+ and nucleotides. Filament formation requires nucleotide binding (not hydrolysis), and occurs at physiological temperatures in biologically relevant buffers, including a buffer made from cell extracts. These observations suggest that chaperonin filaments may exist in vivo and the estimated 4600 chaperonins per cell suggest that such filaments could form an extensive cytostructure. We observed filamentous structures in unfixed, uranyl-acetate-stained S. shibatae cells, which resemble the chaperonin filaments in size and appearance. ImmunoGold (Janssen) labeling using chaperonin antibodies indicated that many chaperonins are associated with insoluble cellular structures and these structures appear to be filamentous in some areas, although they could not be uranyl-acetate-stained. The existence of chaperonin filaments in vivo suggests a mechanism whereby their protein-folding activities can be regulated. More generally, the filaments themselves may play a cytoskeletal role in Archaea. PMID:9144246

  5. Observations of an active region filament

    NASA Astrophysics Data System (ADS)

    Zong, W. G.; Tang, Y. H.; Fang, C.; Xu, A. A.

    An active region filament was well observed on September 4, 2002 with THEMIS at the Teide observatory and SOHO/MDI. The full Stokes parameters of the filament were obtained in Hα and FeI 6302 Å lines. Using the data, we have studied the fine structure of the filament and obtained the parameters at the barb endpoints, including intensity, velocity and longitudinal magnetic field. Our results indicate: (a) the Doppler velocities are quiet different at barb endpoints; (b) the longitudinal magnetic fields at the barb endpoints are very weak; (c) there is a strong magnetic field structure under the filament spine.

  6. Origin of Enigmatic Galactic-center Filaments Revealed

    NASA Astrophysics Data System (ADS)

    2004-06-01

    blown off from individual stars." The star-forming regions associated with the filaments may contain about 100 massive stars each. The center of the Milky Way Galaxy is shrouded from optical telescopes by dense clouds of dust and gas. Radio telescopes, however, are able to pierce through the optical veil and see the features within. Concealed at the very heart of our Galaxy is a supermassive black hole. Known as Sagittarius A* (pronounced A-star), this area is a very powerful source of radio waves and was first detected by Karl Jansky in 1932. While the VLA can image fine scale structures with great precision, it can not always detect extended radio emission. The GBT, however, can help fill in the gaps. Together, they create a more complete image than either instrument could produce separately. "The ability to combine the data from the two telescopes," said Cotton, "gives us a very powerful tool for understanding how the smallest features relate to the overall structure. This is particularly important when you want to study an area like the center of our Galaxy." In addition to Yusef-Zadeh, Hewitt, and Cotton, the GBT survey was conducted by Casey Law and Douglas Roberts of Northwestern University; and Ron Maddalena of the National Radio Astronomy Observatory. The VLA is a single radio telescope made up of 27 separate antennas located on the Plains of San Agustin near Socorro, New Mexico. The GBT is the world’s largest fully steerable radio telescope, and it is located in Green Bank, West Virginia. Both telescopes are operated by the NRAO. The National Radio Astronomy Observatory is a facility of the National Science Foundation, operated under cooperative agreement by Associated Universities, Inc.

  7. Massive and Open

    ERIC Educational Resources Information Center

    Fasimpaur, Karen

    2013-01-01

    MOOCs--massive open online courses--are all the rage these days, with hundreds of thousands of participants signing up and investors plunking down millions to get a piece of the pie. Why is there so much excitement about this new disruptive form of online learning, and how does this model apply to professional learning for teachers? Traditional…

  8. Massive Stars: Stellar Populations

    NASA Astrophysics Data System (ADS)

    Bianchi, Luciana

    2007-07-01

    Massive stars dominate the chemical and dynamical evolution of the ISM, and ultimately of their parent galaxy and the universe, because of their fast evolution and intense supersonic winds. Four decades ago, the first rocket UV spectra of massive stars revealed the importance of mass loss and began to change our understanding of their evolution. Recently, advances in stellar modeling, and the observation of crucial ions in the far-UV spectral range, led to the resolution of long-standing issues in our understanding of massive star atmospheres. A revised (downwards) calibration of Teff for early spectral types is emerging as a result. Meanwhile, HST imaging, and large ground-based telescopes with multislit spectroscopic capabilities, had opened the possibility of resolved studies of stellar populations in Local Group galaxies, which sample a variety of metallicity and environment conditions. More recently, GALEX is providing a global, deep view of the young stellar populations for hundreds of nearby galaxies, revealing their recent star-formation history and modalities. The wide-field coverage and sensitivity of the GALEX UV imaging, easily detecting extremely low levels of star formation, is again changing some of our views on massive star formation in galaxies.

  9. New massive supergravity multiplets

    NASA Astrophysics Data System (ADS)

    Gates, S. James, Jr.; Kuzenko, Sergei M.; Tartaglino-Mazzucchelli, Gabriele

    2007-02-01

    We present new off-shell formulations for the massive superspin-3/2 multiplet. In the massless limit, they reduce respectively to the old minimal (n = -1/3) and non-minimal (n≠-1/3,0) linearized formulations for 4D Script N = 1 supergravity. Duality transformations, which relate the models constructed, are derived.

  10. Supertwistors and massive particles

    SciTech Connect

    Mezincescu, Luca; Routh, Alasdair J.; Townsend, Paul K.

    2014-07-15

    In the (super)twistor formulation of massless (super)particle mechanics, the mass-shell constraint is replaced by a “spin-shell” constraint from which the spin content can be read off. We extend this formalism to massive (super)particles (with N-extended space–time supersymmetry) in three and four space–time dimensions, explaining how the spin-shell constraints are related to spin, and we use it to prove equivalence of the massive N=1 and BPS-saturated N=2 superparticle actions. We also find the supertwistor form of the action for “spinning particles” with N-extended worldline supersymmetry, massless in four dimensions and massive in three dimensions, and we show how this simplifies special features of the N=2 case. -- Highlights: •Spin-shell constraints are related to Poincaré Casimirs. •Twistor form of 4D spinning particle for spin N/2. •Twistor proof of scalar/antisymmetric tensor equivalence for 4D spin 0. •Twistor form of 3D particle with arbitrary spin. •Proof of equivalence of N=1 and N=2 BPS massive 4D superparticles.

  11. Filament L1482 in the California molecular cloud

    NASA Astrophysics Data System (ADS)

    Li, D. L.; Esimbek, J.; Zhou, J. J.; Lou, Y.-Q.; Wu, G.; Tang, X. D.; He, Y. X.

    2014-07-01

    Aims: The process of gravitational fragmentation in the L1482 molecular filament of the California molecular cloud is studied by combining several complementary observations and physical estimates. We investigate the kinematic and dynamical states of this molecular filament and physical properties of several dozens of dense molecular clumps embedded therein. Methods: We present and compare molecular line emission observations of the J = 2-1 and J = 3-2 transitions of 12CO in this molecular complex, using the Kölner Observatorium für Sub-Millimeter Astronomie (KOSMA) 3-m telescope. These observations are complemented with archival data observations and analyses of the 13CO J = 1-0 emission obtained at the Purple Mountain Observatory (PMO) 13.7-m radio telescope at Delingha Station in QingHai Province of west China, as well as infrared emission maps from the Herschel Space Telescope online archive, obtained with the SPIRE and PACS cameras. Comparison of these complementary datasets allows for a comprehensive multiwavelength analysis of the L1482 molecular filament. Results: We have identified 23 clumps along the molecular filament L1482 in the California molecular cloud. For these molecular clumps, we were able to estimate column and number densities, masses, and radii. The masses of these clumps range from ~6.8 to 62.8 M⊙ with an average value of 24.7-16.2+31.1 M⊙. Eleven of the identified molecular clumps appear to be associated with protostars and are thus referred to as protostellar clumps. Protostellar clumps and the remaining starless clumps of our sample appear to have similar temperatures and linewidths, yet on average, the protostellar clumps appear to be slightly more massive than the latter. All these molecular clumps show supersonic nonthermal gas motions. While surprisingly similar in mass and size to the much better known Orion molecular cloud, the formation rate of high-mass stars appears to be suppressed in the California molecular cloud

  12. Wide-field SCUBA-2 observations of NGC 2264: submillimetre clumps and filaments

    NASA Astrophysics Data System (ADS)

    Buckle, J. V.; Richer, J. S.

    2015-10-01

    We present wide-field observations of the NGC 2264 molecular cloud in the dust continuum at 850 and 450 μm using SCUBA-2 on the James Clerk Maxwell Telescope. Using 12CO 3 → 2 molecular line data, we determine that emission from CO contaminates the 850 μm emission at levels ˜30 per cent in localized regions associated with high-velocity molecular outflows. Much higher contamination levels of 60 per cent are seen in shocked regions near the massive star S Mon. If not removed, the levels of CO contamination would contribute an extra 13 per cent to the dust mass in NGC 2264. We use the FELLWALKER routine to decompose the dust into clumpy structures, and a Hessian-based routine to decompose the dust into filamentary structures. The filaments can be described as a hub-filament structure, with lower column density filaments radiating from the NGC 2264 C protocluster hub. Above mean filament column densities of 2.4 × 1022 cm-2, star formation proceeds with the formation of two or more protostars. Below these column densities, filaments are starless, or contain only a single protostar.

  13. An Excursion Set Model of the Cosmic Web: the Abundance of Sheets, Filaments And Halos

    SciTech Connect

    Shen, Jiajian; Abel, Tom; Mo, Houjun; Sheth, Ravi; /Pennsylvania U.

    2006-01-11

    We discuss an analytic approach for modeling structure formation in sheets, filaments and knots. This is accomplished by combining models of triaxial collapse with the excursion set approach: sheets are defined as objects which have collapsed along only one axis, filaments have collapsed along two axes, and halos are objects in which triaxial collapse is complete. In the simplest version of this approach, which we develop here, large scale structure shows a clear hierarchy of morphologies: the mass in large-scale sheets is partitioned up among lower mass filaments, which themselves are made-up of still lower mass halos. Our approach provides analytic estimates of the mass fraction in sheets, filaments and halos, and its evolution, for any background cosmological model and any initial fluctuation spectrum. In the currently popular {Lambda}CDM model, our analysis suggests that more than 99% of the mass in sheets, and 72% of the mass in filaments, is stored in objects more massive than 10{sup 10}M{sub {circle_dot}} at the present time. For halos, this number is only 46%. Our approach also provides analytic estimates of how halo abundances at any given time correlate with the morphology of the surrounding large-scale structure, and how halo evolution correlates with the morphology of large scale structure.

  14. FORMATION OF MASSIVE MOLECULAR CLOUD CORES BY CLOUD-CLOUD COLLISION

    SciTech Connect

    Inoue, Tsuyoshi; Fukui, Yasuo

    2013-09-10

    Recent observations of molecular clouds around rich massive star clusters including NGC 3603, Westerlund 2, and M20 revealed that the formation of massive stars could be triggered by a cloud-cloud collision. By using three-dimensional, isothermal, magnetohydrodynamics simulations with the effect of self-gravity, we demonstrate that massive, gravitationally unstable, molecular cloud cores are formed behind the strong shock waves induced by cloud-cloud collision. We find that the massive molecular cloud cores have large effective Jeans mass owing to the enhancement of the magnetic field strength by shock compression and turbulence in the compressed layer. Our results predict that massive molecular cloud cores formed by the cloud-cloud collision are filamentary and threaded by magnetic fields perpendicular to the filament.

  15. 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

  16. Force-Induced Dynamical Properties of Multiple Cytoskeletal Filaments Are Distinct from that of Single Filaments

    PubMed Central

    Das, Dipjyoti; Das, Dibyendu; Padinhateeri, Ranjith

    2014-01-01

    How cytoskeletal filaments collectively undergo growth and shrinkage is an intriguing question. Collective properties of multiple bio-filaments (actin or microtubules) undergoing hydrolysis have not been studied extensively earlier within simple theoretical frameworks. In this paper, we study the collective dynamical properties of multiple filaments under force, and demonstrate the distinct properties of a multi-filament system in comparison to a single filament. Comparing stochastic simulation results with recent experimental data, we show that multi-filament collective catastrophes are slower than catastrophes of single filaments. Our study also shows further distinctions as follows: (i) force-dependence of the cap-size distribution of multiple filaments are quantitatively different from that of single filaments, (ii) the diffusion constant associated with the system length fluctuations is distinct for multiple filaments, and (iii) switching dynamics of multiple filaments between capped and uncapped states and the fluctuations therein are also distinct. We build a unified picture by establishing interconnections among all these collective phenomena. Additionally, we show that the collapse times during catastrophes can be sharp indicators of collective stall forces exceeding the additive contributions of single filaments. PMID:25531397

  17. Microcyle Conidiation in Filamentous Fungi

    PubMed Central

    Jung, Boknam; Kim, Soyeon

    2014-01-01

    The typical life cycle of filamentous fungi commonly involves asexual sporulation after vegetative growth in response to environmental factors. The production of asexual spores is critical in the life cycle of most filamentous fungi. Normally, conidia are produced from vegetative hyphae (termed mycelia). However, fungal species subjected to stress conditions exhibit an extremely simplified asexual life cycle, in which the conidia that germinate directly generate further conidia, without forming mycelia. This phenomenon has been termed as microcycle conidiation, and to date has been reported in more than 100 fungal species. In this review, first, we present the morphological properties of fungi during microcycle conidiation, and divide microcycle conidiation into four simple categories, even though fungal species exhibit a wide variety of morphological differences during microcycle conidiogenesis. Second, we describe the factors that influence microcycle conidiation in various fungal species, and present recent genetic studies that have identified the genes responsible for this process. Finally, we discuss the biological meaning and application of microcycle conidiation. PMID:24808726

  18. Microcyle conidiation in filamentous fungi.

    PubMed

    Jung, Boknam; Kim, Soyeon; Lee, Jungkwan

    2014-03-01

    The typical life cycle of filamentous fungi commonly involves asexual sporulation after vegetative growth in response to environmental factors. The production of asexual spores is critical in the life cycle of most filamentous fungi. Normally, conidia are produced from vegetative hyphae (termed mycelia). However, fungal species subjected to stress conditions exhibit an extremely simplified asexual life cycle, in which the conidia that germinate directly generate further conidia, without forming mycelia. This phenomenon has been termed as microcycle conidiation, and to date has been reported in more than 100 fungal species. In this review, first, we present the morphological properties of fungi during microcycle conidiation, and divide microcycle conidiation into four simple categories, even though fungal species exhibit a wide variety of morphological differences during microcycle conidiogenesis. Second, we describe the factors that influence microcycle conidiation in various fungal species, and present recent genetic studies that have identified the genes responsible for this process. Finally, we discuss the biological meaning and application of microcycle conidiation. PMID:24808726

  19. 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. PMID:25401574

  20. The effect of ambipolar diffusion on low-density molecular ISM filaments

    NASA Astrophysics Data System (ADS)

    Ntormousi, Evangelia; Hennebelle, Patrick; André, Philippe; Masson, Jacques

    2016-05-01

    Context. The filamentary structure of the molecular interstellar medium and the potential link of this morphology to star formation have been brought into focus recently by high resolution observational surveys. An especially puzzling matter is that local interstellar filaments appear to have the same thickness, independent of their column density. This requires a theoretical understanding of their formation process and the physics that governs their evolution. Aims: In this work we explore a scenario in which filaments are dissipative structures of the large-scale interstellar turbulence cascade and ion-neutral friction (also called ambipolar diffusion) is affecting their sizes by preventing small-scale compressions. Methods: We employ high-resolution (5123 and 10243), 3D magnetohydrodynamic (MHD) simulations, performed with the grid code RAMSES, to investigate non-ideal MHD turbulence as a filament formation mechanism. We focus the analysis on the mass and thickness distributions of the resulting filamentary structures. Results: Simulations of both driven and decaying MHD turbulence show that the morphologies of the density and the magnetic field are different when ambipolar diffusion is included in the models. In particular, the densest structures are broader and more massive as an effect of ion-neutral friction and the power spectra of both the velocity and the density steepen at a smaller wavenumber. Conclusions: The comparison between ideal and non-ideal MHD simulations shows that ambipolar diffusion causes a shift of the filament thickness distribution towards higher values. However, none of the distributions exhibit the pronounced peak found in the observed local filaments. Limitations in dynamical range and the absence of self-gravity in these numerical experiments do not allow us to conclude at this time whether this is due to the different filament selection or due to the physics inherent of the filament formation.

  1. 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.”

  2. 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.

  3. Massive Stars in the Quintuplet Cluster

    NASA Astrophysics Data System (ADS)

    Figer, Donald F.; McLean, Ian S.; Morris, Mark

    1999-03-01

    We present near-infrared photometry and K-band spectra of newly identified massive stars in the Quintuplet cluster, one of the three massive clusters projected within 50 pc of the Galactic center. We find that the cluster contains a variety of massive stars, including more unambiguously identified Wolf-Rayet stars than any cluster in the Galaxy, and over a dozen stars in earlier stages of evolution, i.e., luminous blue variables (LBVs), Ofpe/WN9, and OB supergiants. One newly identified star is the second luminous blue variable in the cluster, after the ``Pistol star.'' Although we are unable to provide certain spectral classifications for the five enigmatic Quintuplet-proper members, we tentatively propose that they are extremely dusty versions of the WC stars found elsewhere in the cluster and similar to the dozen or so known examples in the Galaxy. Although the cluster parameters are uncertain because of photometric errors and uncertainties in stellar models, i.e., extrapolating initial masses and estimating ionizing fluxes, we have the following conclusions. Given the evolutionary stages of the identified stars, the cluster appears to be about 4+/-1 Myr old, assuming coeval formation. The total mass in observed stars is ~103 Msolar, and the implied mass is ~104 Msolar, assuming a lower mass cutoff of 1 Msolar and a Salpeter initial mass function. The implied mass density in stars is greater than or similar to a few thousand Msolar pc-3. The newly identified stars increase the estimated ionizing flux from this cluster by about an order of magnitude with respect to earlier estimates, to 1050.9 photons s-1, or roughly what is required to ionize the nearby ``Sickle'' H II region (G0.18-0.04). The total luminosity from the massive cluster stars is ~107.5 Lsolar, enough to account for the heating of the nearby molecular cloud, M0.20-0.033. We propose a picture that integrates most of the major features in this part of the sky, excepting the nonthermal filaments. We

  4. [Sr II] Detected in a Nebular Filament Near Eta Carinae

    NASA Technical Reports Server (NTRS)

    Gull, T.R.; Fisher, Richard (Technical Monitor)

    2000-01-01

    Observations with the Space Telescope Imaging Spectrograph on the Hubble Space Telescope reveal a peculiar emission line region in the close vicinity to Eta Carinae. The lines of [SrII], [MnII], [CoII], [TiII], [NiII] and [FeI] are detected in the 6400-7000 Angstrom spectral interval at a blue-shifted velocity of approximately 95 km/sec and seem to be associated with a long, narrow filament with dimensions of less than 0.5 inches by 1.1 inches. The filament is notable as it is separate both in velocity and structure from the bright emission of the Integral Nebula. This filament is buried within the Homunculus and is not visible in direct images which are dominated by reflection nebulosities. In our literature searches we have found no evidence of strontium emission lines in nebulae. We are aware of permitted transitions of strontium seen in AGB stars. S-processed elements like strontium are not expected in the ejecta of a massive star like Eta Carinae. Detection of [SrII] and the fact that the [NiII], [MnII] and [CoII] lines are unusually strong compared to [FeI] are quite a surprise. It has long been known that nitrogen is overabundant in the ejecta of Eta Carinae. Is this processed material from the present star(s)? Has there been processed material ejected from a more evolved companion? The situation is decidedly mysterious. This research has been supported by NASA through STScI grants and the STIS GTO funding.

  5. Star formation efficiency in the outer filaments of Centaurus A

    NASA Astrophysics Data System (ADS)

    Salomé, Q.; Salomé, P.; Combes, F.; Hamer, S.; Heywood, I.

    2015-12-01

    We present a multi-wavelength study of the northern filaments of Centaurus A (at a distance of ˜ 20 kpc from the galaxy center) based on FUV (GALEX), FIR (Herschel) and CO (SEST and ALMA) emission. We also searched for HCN and HCO^+ (ATCA) and observed optical emission lines (VLT/MUSE) in different places of the filament. An upper limit of the dense gas of L'_{HCN}<4.8× 10^3 K.km.s^{-1}.pc^2 at 3σ leads to a dense-to-molecular gas fraction <23% in this region. We compared the CO masses with the SFR estimates and found very long depletion times (11 Gyr on 730 pc scales) and a large scatter in the KS-relation with a standard conversion factor. Applying a metallicity correction to the CO/H_2 conversion factor would lead to even more massive clouds with higher depletion times. Using ALMA archive data, we found 3 unresolved CO(2-1) clumps of size <37× 21 pc and masses around 10^4 M_⊙. The 3 clumps show resolved line profiles (Δ v˜ 10 km.s^{-1}) and are all three dynamically clearly separated by ˜ 10-20 km.s^{-1}. We derived a virial parameter α_{vir}˜ 10-16 which indicates that the clumps are not gravitationally bound and input of energy likely inhibits star formation.

  6. 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 ...

  7. 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…

  8. Scaling laws for laser-induced filamentation

    NASA Astrophysics Data System (ADS)

    Zhokhov, P. A.; Zheltikov, A. M.

    2014-04-01

    Despite all the complexity of the underlying nonlinear physics, the filamentation of ultrashort optical field wave forms is shown to obey a set of physically transparent scaling laws. This scaling is applicable within a remarkably broad range of laser powers, pulse widths, gas pressures, and propagation paths, suggesting specific recipes for the power scaling of filamentation-based pulse compression.

  9. How cofilin severs an actin filament.

    PubMed

    De La Cruz, Enrique M

    2009-05-15

    The actin regulatory protein, cofilin, promotes actin assembly dynamics by severing filaments and increasing the number of ends from which subunits add and dissociate. Recent studies provide biophysical descriptions of cooperative filament interactions in energetic, mechanical and structural terms. A one-dimensional Ising model with nearest-neighbor interactions permits thermodynamic analysis of cooperative binding and indicates that one or a few cofilin molecules can sever a filament. Binding and cooperative interactions are entropically driven. A significant fraction of the binding free energy results from the linked dissociation of filament-associated ions (polyelectrolyte effect), which modulate filament structure, stability and mechanics. The remaining binding free energy and essentially all of the cooperative free energy arise from the enhanced conformational dynamics of the cofilactin complex. Filament mechanics are modulated by cofilin such that cofilin-saturated filaments are approximately 10- to 20-fold more compliant in bending and twisting than bare filaments. Cofilin activity is well described by models in which discontinuities in topology, mechanics and conformational dynamics generate stress concentration and promote fracture at junctions of bare and decorated segments, analogous to the grain boundary fracture of crystalline materials and the thermally driven formation of shear transformation zones in colloidal glass. PMID:20700473

  10. 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.

  11. Scanning For Hotspots In Lamp Filaments

    NASA Technical Reports Server (NTRS)

    Powers, Charles E.; Van Sant, Tim; Leidecker, Henning

    1993-01-01

    Scanning photometer designed for use in investigation of failures of incandescent lamp filaments. Maps brightness as function of position along each filament to identify bright (hot) spots, occurring at notches and signifying incipient breaks or rewelds. Also used to measure nonuniformity in outputs of such linear devices as light-emitting diodes, and to measure diffraction patterns of lenses.

  12. Process for making silver metal filaments

    SciTech Connect

    Bamberger, C.E.

    1998-04-01

    This invention relates to a process for making filaments of metal compounds and more particularly to a process for making silver metal filaments. The United States Government has rights to this invention pursuant to Contract No. DE-AC05-8421400 with Lockheed Martin Energy Systems, Inc. awarded by the US Department of Energy.

  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. Hydrodynamics of pairs of interacting cytoskeletal filaments

    NASA Astrophysics Data System (ADS)

    Shinar, Tamar; Shelley, Michael

    2011-11-01

    Pairwise filament interactions underlie the dynamics of complex cytoskeletal networks in cells. These networks in turn play a crucial role in many cellular processes such as formation of the mitotic spindle and cell cleavage in cytokinesis. We model interactions of pairs of filaments immersed in a viscous, fluidic environment. The filaments are modeled using a slender body approximation, capturing their indirect interactions mediated by the immersing fluid. Direct filament interactions via molecular motors complexes induce alignment and parallel or anti-parallel sliding. The motor proteins are modeled as simple spring-like structures that walk directionally toward one end of the filament. We examine the resulting stresses in the fluid to better understand how the microscopic interactions lead to bulk behavior of cytoskeletal networks.

  15. A new paradigm for solar filament eruptions

    NASA Astrophysics Data System (ADS)

    Rust, David M.

    2001-11-01

    This article discusses the formation, magnetic structure, and eruption of solar filaments in terms of two contrasting paradigms. The standard paradigm is that filaments are formed by condensation of plasma on coronal magnetic fields that are twisted or dimpled as a result of photospheric motions. According to this paradigm, filaments erupt when photospheric motions shear the fields, increasing their energy and decreasing their stability. According to a new paradigm, subsurface motions generate toroidal magnetic flux ropes, and after these flux ropes emerge to form active regions, the most twisted parts migrate into the corona to form filaments. Filaments become unstable and are ejected after a sufficient accumulation of twist (i.e., magnetic helicity). Various proposed mechanisms for producing the needed helicity are reviewed, and several observational tests are proposed to differentiate among the possible mechanisms.

  16. Massive cold cloud clusters

    NASA Astrophysics Data System (ADS)

    Toth, L. Viktor; Marton, Gabor; Zahorecz, Sarolta

    2015-08-01

    The all-sky Planck catalogue of Galactic Cold Clumps (PGCC, Planck 2015 results XXVIII 2015) allows an almost unbiased study of the early phases of star-formation in our Galaxy. Several thousand of the clumps have also distance estimates allowing a mass, and density determination. The nature of Planck clumps varies from IRDCs to tiny nearby cold clouds with masses ranging from one to several tens of thousands solar masses. Some of the clumps are embedded in GMCs, others are isolated. Some are close or even very close to OB associations, while others lay far from any UV luminous objects.The small scale clustering of these objects was studied with the improved Minimum Spanning Tree method of Cartwright & Whitworth identifying groups in 3D space. As a result also massive cold cloud clusters were identified. We analyse the MST structures, and discuss their relation to ongoing and future massive star formation.

  17. Skyrmions with massive pions

    SciTech Connect

    Battye, Richard A.; Sutcliffe, Paul M.

    2006-05-15

    In the Skyrme model with massless pions, the minimal energy multi-Skyrmions are shell-like, with the baryon density localized on the edges of a polyhedron that is approximately spherical and generically of the fullerene-type. In this paper we show that in the Skyrme model with massive pions these configurations are unstable for sufficiently large baryon number. Using numerical simulations of the full nonlinear field theory, we show that these structures collapse to form qualitatively different stable Skyrmion solutions. These new Skyrmions have a flat structure and display a clustering phenomenon into lower charge components, particularly components of baryon numbers three and four. These new qualitative features of Skyrmions with massive pions are encouraging in comparison with the expectations based on real nuclei.

  18. New improved massive gravity

    NASA Astrophysics Data System (ADS)

    Dereli, T.; Yetişmişoğlu, C.

    2016-06-01

    We derive the field equations for topologically massive gravity coupled with the most general quadratic curvature terms using the language of exterior differential forms and a first-order constrained variational principle. We find variational field equations both in the presence and absence of torsion. We then show that spaces of constant negative curvature (i.e. the anti de-Sitter space AdS 3) and constant torsion provide exact solutions.

  19. 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.

  20. Cell crawling on filamentous tracks

    NASA Astrophysics Data System (ADS)

    Lopez, Jorge; Schwarz, Jennifer; Das, Moumita

    2014-03-01

    Recent experiments suggest that the migration of some cells in three dimensions has strong resemblance to one-dimensional migration. Motivated by this observation, we simulate a one-dimensional model cell made of beads and springs that moves on a tense semiflexible filamentous track. Physical parameters, such as the spring constants and friction coefficients, are calculated using effective theories. We investigate the mechanical feedback between the model cell and this track, as mediated by the active myosin-driven contractility and the catch/slip bond behavior of the focal adhesions, as the model cell crawls. We then compare our calculations of cell speed and the amount of deformation in the track with experiments.

  1. 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.

  2. 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. PMID:26780357

  3. Young Massive Star Clusters

    NASA Astrophysics Data System (ADS)

    Portegies Zwart, Simon F.; McMillan, Stephen L. W.; Gieles, Mark

    2010-09-01

    Young massive clusters (YMCs) are dense aggregates of young stars that form the fundamental building blocks of galaxies. Several examples exist in the Milky Way Galaxy and the Local Group, but they are particularly abundant in starburst and interacting galaxies. The few YMCs that are close enough to resolve are of prime interest for studying the stellar mass function and the ecological interplay between stellar evolution and stellar dynamics. The distant unresolved clusters may be effectively used to study the star-cluster mass function, and they provide excellent constraints on the formation mechanisms of young cluster populations. YMCs are expected to be the nurseries for many unusual objects, including a wide range of exotic stars and binaries. So far only a few such objects have been found in YMCs, although their older cousins, the globular clusters, are unusually rich in stellar exotica. In this review, we focus on star clusters younger than ˜100 Myr, more than a few current crossing times old, and more massive than ˜104M⊙; the size of the cluster and its environment are considered less relevant as distinguishing parameters. We describe the global properties of the currently known young massive star clusters in the Local Group and beyond, and discuss the state of the art in observations and dynamical modeling of these systems. In order to make this review readable by observers, theorists, and computational astrophysicists, we also review the cross-disciplinary terminology.

  4. 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

  5. Filament Activation in Response to Magnetic Flux Emergence and Cancellation in Filament Channels

    NASA Astrophysics Data System (ADS)

    Li, Ting; Zhang, Jun; Ji, Haisheng

    2015-06-01

    We conducted a comparative analysis of two filaments that showed a quite different activation in response to the flux emergence within the filament channels. The observations from the Solar Dynamics Observatory (SDO) and Global Oscillation Network Group (GONG) were made to analyze the two filaments on 2013 August 17 - 20 (SOL2013-08-17) and September 29 (SOL2013-09-29). The first event showed that the main body of the filament was separated into two parts when an active region (AR) emerged with a maximum magnetic flux of about 6.4×1021 Mx underlying the filament. The close neighborhood and common direction of the bright threads in the filament and the open AR fan loops suggest a similar magnetic connectivity of these two flux systems. The equilibrium of the filament was not destroyed three days after the start of the emergence of the AR. To our knowledge, similar observations have never been reported before. In the second event, the emerging flux occurred nearby a barb of the filament with a maximum magnetic flux of 4.2×1020 Mx, about one order of magnitude lower than that of the first event. Two patches of parasitic polarity in the vicinity of the barb merged, then cancelled with nearby network fields. About 20 hours after the onset of the emergence, the filament erupted. Our findings imply that the location of emerging flux within the filament channel is probably crucial to filament evolution. If the flux emergence appears nearby the barbs, it is highly likely that the emerging flux and the filament magnetic fields will cancel, which may lead to the eruption of the filament. The comparison of the two events shows that the emergence of a small AR may still not be enough to disrupt the stability of a filament system, and the actual eruption only occurs after the flux cancellation sets in.

  6. HOW MASSIVE ARE MASSIVE COMPACT GALAXIES?

    SciTech Connect

    Muzzin, Adam; Van Dokkum, Pieter; Marchesini, Danilo; Franx, Marijn; Kriek, Mariska; Labbe, Ivo

    2009-11-20

    Using a sample of nine massive compact galaxies at zapprox 2.3 with rest-frame optical spectroscopy and comprehensive U -> 8 mum photometry, we investigate how assumptions in spectral energy distribution (SED) modeling change the stellar mass estimates of these galaxies, and how this affects our interpretation of their size evolution. The SEDs are fitted to tau-models with a range of metallicities, dust laws, and different stellar population synthesis codes. These models indicate masses equal to, or slightly smaller than, our default masses. The maximum difference is 0.16 dex for each parameter considered, and only 0.18 dex for the most extreme combination of parameters. Two-component populations with a maximally old stellar population superposed with a young component provide reasonable fits to these SEDs using the models of Bruzual and Charlot; however, when using models with updated treatment of TP-AGB stars, the fits are poorer. The two-component models predict masses that are 0.08-0.22 dex larger than the tau-models. We also test the effect of a bottom-light initial mass function (IMF) and find that it would reduce the masses of these galaxies by 0.3 dex. Considering the range of allowable masses from the tau-models, two-component fits, and IMF, we conclude that on average these galaxies lie below the mass-size relation of galaxies in the local universe by a factor of 3-9, depending on the SED models used.

  7. 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.

  8. Automatic Detect and Trace of Solar Filaments

    NASA Astrophysics Data System (ADS)

    Fang, Cheng; Chen, P. F.; Tang, Yu-hua; Hao, Qi; Guo, Yang

    We developed a series of methods to automatically detect and trace solar filaments in solar Hα images. The programs are able to not only recognize filaments and determine their properties, such as the position, the area and other relevant parameters, but also to trace the daily evolution of the filaments. For solar full disk Hα images, the method consists of three parts: first, preprocessing is applied to correct the original images; second, the Canny edge-detection method is used to detect the filaments; third, filament properties are recognized through the morphological operators. For each Hα filament and its barb features, we introduced the unweighted undirected graph concept and adopted Dijkstra shortest-path algorithm to recognize the filament spine; then, using polarity inversion line shift method for measuring the polarities in both sides of the filament to determine the filament axis chirality; finally, employing connected components labeling method to identify the barbs and calculating the angle between each barb and spine to indicate the barb chirality. Our algorithms are applied to the observations from varied observatories, including the Optical & Near Infrared Solar Eruption Tracer (ONSET) in Nanjing University, Mauna Loa Solar Observatory (MLSO) and Big Bear Solar Observatory (BBSO). The programs are demonstrated to be effective and efficient. We used our method to automatically process and analyze 3470 images obtained by MLSO from January 1998 to December 2009, and a butterfly diagram of filaments is obtained. It shows that the latitudinal migration of solar filaments has three trends in the Solar Cycle 23: The drift velocity was fast from 1998 to the solar maximum; after the solar maximum, it became relatively slow and after 2006, the migration became divergent, signifying the solar minimum. About 60% filaments with the latitudes larger than 50 degree migrate towards the Polar Regions with relatively high velocities, and the latitudinal migrating

  9. Striation and convection in penumbral filaments

    NASA Astrophysics Data System (ADS)

    Spruit, H. C.; Scharmer, G. B.; Löfdahl, M. G.

    2010-10-01

    Observations with the 1-m Swedish Solar Telescope of the flows seen in penumbral filaments are presented. Time sequences of bright filaments show overturning motions strikingly similar to those seen along the walls of small isolated structures in the active regions. The filaments show outward propagating striations with inclination angles suggesting that they are aligned with the local magnetic field. We interpret it as the equivalent of the striations seen in the walls of small isolated magnetic structures. Their origin is then a corrugation of the boundary between an overturning convective flow inside the filament and the magnetic field wrapping around it. The outward propagation is a combination of a pattern motion due to the downflow observed along the sides of bright filaments, and the Evershed flow. The observed short wavelength of the striation argues against the existence of a dynamically significant horizontal field inside the bright filaments. Its intensity contrast is explained by the same physical effect that causes the dark cores of filaments, light bridges and “canals”. In this way striation represents an important clue to the physics of penumbral structure and its relation with other magnetic structures on the solar surface. We put this in perspective with results from the recent 3-D radiative hydrodynamic simulations. 4 movies are only available in electronic form at http://www.aanda.org

  10. Solar filament impact on 21 January 2005: Geospace consequences

    NASA Astrophysics Data System (ADS)

    Kozyra, J. U.; Liemohn, M. W.; Cattell, C.; De Zeeuw, D.; Escoubet, C. P.; Evans, D. S.; Fang, X.; Fok, M.-C.; Frey, H. U.; Gonzalez, W. D.; Hairston, M.; Heelis, R.; Lu, G.; Manchester, W. B.; Mende, S.; Paxton, L. J.; Rastaetter, L.; Ridley, A.; Sandanger, M.; Soraas, F.; Sotirelis, T.; Thomsen, M. W.; Tsurutani, B. T.; Verkhoglyadova, O.

    2014-07-01

    On 21 January 2005, a moderate magnetic storm produced a number of anomalous features, some seen more typically during superstorms. The aim of this study is to establish the differences in the space environment from what we expect (and normally observe) for a storm of this intensity, which make it behave in some ways like a superstorm. The storm was driven by one of the fastest interplanetary coronal mass ejections in solar cycle 23, containing a piece of the dense erupting solar filament material. The momentum of the massive solar filament caused it to push its way through the flux rope as the interplanetary coronal mass ejection decelerated moving toward 1 AU creating the appearance of an eroded flux rope (see companion paper by Manchester et al. (2014)) and, in this case, limiting the intensity of the resulting geomagnetic storm. On impact, the solar filament further disrupted the partial ring current shielding in existence at the time, creating a brief superfountain in the equatorial ionosphere—an unusual occurrence for a moderate storm. Within 1 h after impact, a cold dense plasma sheet (CDPS) formed out of the filament material. As the interplanetary magnetic field (IMF) rotated from obliquely to more purely northward, the magnetotail transformed from an open to a closed configuration and the CDPS evolved from warmer to cooler temperatures. Plasma sheet densities reached tens per cubic centimeter along the flanks—high enough to inflate the magnetotail in the simulation under northward IMF conditions despite the cool temperatures. Observational evidence for this stretching was provided by a corresponding expansion and intensification of both the auroral oval and ring current precipitation zones linked to magnetotail stretching by field line curvature scattering. Strong Joule heating in the cusps, a by-product of the CDPS formation process, contributed to an equatorward neutral wind surge that reached low latitudes within 1-2 h and intensified the

  11. Optical Filaments and Gas Dynamics in Air

    NASA Astrophysics Data System (ADS)

    Yeak, Jeremy

    Until now, the propagation dynamics of intense ultrashort laser pulses leading to optical filamentation in air has only been investigated in the frame of a dynamic balance between linear diffraction, Kerr self-focusing and plasma defocusing. This has led to the development of different theories surrounding the generation and persistence of optical filaments propagating over many Rayleigh lengths in air. These theories include wave-guiding model, moving focus model, dynamic spatial replenishment model and conical wave model. However, these models fail to capture the gas dynamics that arise from optical filaments interacting with air. In this work, we demonstrate that initial conditions are critical to the formation of optical filaments through the use of an aerodynamic window. Filament characteristics in air, such as spectral broadening, electrical conductivity and fluorescence, are measured and presented. Using these as diagnostic tools, we also show that the optical filamentation of ultrashort laser pulses can be enhanced at high repetition rates because of the thermal response of air, resulting from the interaction of each laser pulse with the modified atmospheric density distribution left behind by the preceding pulse. This is explained by the sudden deposition of energy by a filament in the air which generates a cylindrical shock wave, leaving behind a column of rarefied air. This low-density region persists for an extended period and can materially affect the propagation dynamics of an ensuing pulse that follows before the low-density region has relaxed sufficiently to ambient conditions. By further increasing the repetition rate, the onset of ionization is shifted downstream and the spectral continuum displays a stronger broadening on both sides of the original pulse spectrum. This gas dynamic interaction regime of filamentation can be utilized to enhance the length and spectral width of filaments for remote sensing and long range laser-induced high voltage

  12. THERMAL AND CHEMICAL EVOLUTION OF COLLAPSING FILAMENTS

    SciTech Connect

    Gray, William J.; Scannapieco, Evan

    2013-05-10

    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 Almost-Equal-To 0.1 Z{sub Sun} 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 a dense, cold core containing a substantial fraction of molecules. In high-redshift, Z = 10{sup -3} Z{sub Sun} filaments, the collapse proceeds much more slowly. This is mostly due to the lower initial temperatures, which lead 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 starbursting 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 occurs. 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.

  13. 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.

  14. Filaments in simulations of molecular cloud formation

    SciTech Connect

    Gómez, Gilberto C.; Vázquez-Semadeni, Enrique

    2014-08-20

    We report on the filaments that develop self-consistently in a new numerical simulation of cloud formation by colliding flows. As in previous studies, the forming cloud begins to undergo gravitational collapse because it rapidly acquires a mass much larger than the average Jeans mass. Thus, the collapse soon becomes nearly pressureless, proceeding along its shortest dimension first. This naturally produces filaments in the cloud and clumps within the filaments. The filaments are not in equilibrium at any time, but instead are long-lived flow features through which the gas flows from the cloud to the clumps. The filaments are long-lived because they accrete from their environment while simultaneously accreting onto the clumps within them; they are essentially the locus where the flow changes from accreting in two dimensions to accreting in one dimension. Moreover, the clumps also exhibit a hierarchical nature: the gas in a filament flows onto a main, central clump but other, smaller-scale clumps form along the infalling gas. Correspondingly, the velocity along the filament exhibits a hierarchy of jumps at the locations of the clumps. Two prominent filaments in the simulation have lengths ∼15 pc and masses ∼600 M {sub ☉} above density n ∼ 10{sup 3} cm{sup –3} (∼2 × 10{sup 3} M {sub ☉} at n > 50 cm{sup –3}). The density profile exhibits a central flattened core of size ∼0.3 pc and an envelope that decays as r {sup –2.5} in reasonable agreement with observations. Accretion onto the filament reaches a maximum linear density rate of ∼30 M {sub ☉} Myr{sup –1} pc{sup –1}.

  15. THE SPIN AND ORIENTATION OF DARK MATTER HALOS WITHIN COSMIC FILAMENTS

    SciTech Connect

    Zhang Youcai; Yang Xiaohu; Lin Weipeng; Faltenbacher, Andreas; Springel, Volker; Wang Huiyuan

    2009-11-20

    Clusters, filaments, sheets, and voids are the building blocks of the cosmic web. Forming dark matter halos respond to these different large-scale environments, and this in turn affects the properties of galaxies hosted by the halos. It is therefore important to understand the systematic correlations of halo properties with the morphology of the cosmic web, as this informs both about galaxy formation physics and possible systematics of weak lensing studies. In this study, we present and compare two distinct algorithms for finding cosmic filaments and sheets, a task which is far less well established than the identification of dark matter halos or voids. One method is based on the smoothed dark matter density field and the other uses the halo distributions directly. We apply both techniques to one high-resolution N-body simulation and reconstruct the filamentary/sheet like network of the dark matter density field. We focus on investigating the properties of the dark matter halos inside these structures, in particular, on the directions of their spins and the orientation of their shapes with respect to the directions of the filaments and sheets. We find that both the spin and the major axes of filament halos with masses approx<10{sup 13} h {sup -1} M{sub sun} are preferentially aligned with the direction of the filaments. The spins and major axes of halos in sheets tend to lie parallel to the sheets. There is an opposite mass dependence of the alignment strength for the spin (negative) and major (positive) axes, i.e. with increasing halo mass the major axis tends to be more strongly aligned with the direction of the filament, whereas the alignment between halo spin and filament becomes weaker with increasing halo mass. The alignment strength as a function of the distance to the most massive node halo indicates that there is a transit large-scale environment impact: from the two-dimensional collapse phase of the filament to the three-dimensional collapse phase of the

  16. Hot filament cvd of boron nitride films

    SciTech Connect

    Rye, R.R.

    1992-01-07

    This patent describes a method for coating a substrate with a boron nitride film. It comprises: providing a substrate and a hot filament in a gas chamber; and introducing a borazine gas into the gas chamber so as to heat the borazine gas with the hot filament and deposit the boron nitride film on the substrate, wherein the hot filament is heated to a temperature of from about 1000[degrees] to 1800[degrees] C and the substrate is maintained at a temperature of from 100[degrees]C to 400[degrees]C.

  17. 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.

  18. 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.

  19. 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.

  20. Natural plasmids of filamentous fungi.

    PubMed Central

    Griffiths, A J

    1995-01-01

    Among eukaryotes, plasmids have been found in fungi and plants but not in animals. Most plasmids are mitochondrial. In filamentous fungi, plasmids are commonly encountered in isolates from natural populations. Individual populations may show a predominance of one type, but some plasmids have a global distribution, often crossing species boundaries. Surveys have shown that strains can contain more than one type of plasmid and that different types appear to be distributed independently. In crosses, plasmids are generally inherited maternally. Horizontal transmission is by cell contact. Circular plasmids are common only in Neurospora spp., but linear plasmids have been found in many fungi. Circular plasmids have one open reading frame (ORF) coding for a DNA polymerase or a reverse transcriptase. Linear plasmids generally have two ORFs, coding for presumptive DNA and RNA polymerases with amino acid motifs showing homology to viral polymerases. Plasmids often attain a high copy number, in excess of that of mitochondrial DNA. Linear plasmids have a protein attached to their 5' end, and this is presumed to act as a replication primer. Most plasmids are neutral passengers, but several linear plasmids integrate into mitochondrial DNA, causing death of the host culture. Inferred amino acid sequences of linear plasmid ORFs have been used to plot phylogenetic trees, which show a fair concordance with conventional trees. The circular Neurospora plasmids have replication systems that seem to be evolutionary intermediates between the RNA and the DNA worlds. PMID:8531891

  1. Massively Parallel QCD

    SciTech Connect

    Soltz, R; Vranas, P; Blumrich, M; Chen, D; Gara, A; Giampap, M; Heidelberger, P; Salapura, V; Sexton, J; Bhanot, G

    2007-04-11

    The theory of the strong nuclear force, Quantum Chromodynamics (QCD), can be numerically simulated from first principles on massively-parallel supercomputers using the method of Lattice Gauge Theory. We describe the special programming requirements of lattice QCD (LQCD) as well as the optimal supercomputer hardware architectures that it suggests. We demonstrate these methods on the BlueGene massively-parallel supercomputer and argue that LQCD and the BlueGene architecture are a natural match. This can be traced to the simple fact that LQCD is a regular lattice discretization of space into lattice sites while the BlueGene supercomputer is a discretization of space into compute nodes, and that both are constrained by requirements of locality. This simple relation is both technologically important and theoretically intriguing. The main result of this paper is the speedup of LQCD using up to 131,072 CPUs on the largest BlueGene/L supercomputer. The speedup is perfect with sustained performance of about 20% of peak. This corresponds to a maximum of 70.5 sustained TFlop/s. At these speeds LQCD and BlueGene are poised to produce the next generation of strong interaction physics theoretical results.

  2. Actin Filament Segmentation Using Dynamic Programming

    PubMed Central

    Li, Hongsheng; Shen, Tian; Huang, Xiaolei

    2011-01-01

    We introduce a novel algorithm for actin filament segmentation in 2D TIRFM image sequences. This problem is difficult because actin filaments dynamically change shapes during their growth, and the TIRFM images are usually noisy. We ask a user to specify the two tips of a filament of interest in the first frame. We then model the segmentation problem in an image sequence as a temporal chain, where its states are tip locations; given candidate tip locations, actin filaments' body points are inferred by a dynamic programming method, which adaptively generates candidate solutions. Combining candidate tip locations and their inferred body points, the temporal chain model is efficiently optimized using another dynamic programming method. Evaluation on noisy TIRFM image sequences demonstrates the accuracy and robustness of this approach. PMID:21761674

  3. 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

  4. 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...

  5. 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.

  6. 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. PMID:25975455

  7. Intermediate filaments in small configuration spaces.

    PubMed

    Nöding, Bernd; Köster, Sarah

    2012-02-24

    Intermediate filaments play a key role in cell mechanics. Apart from their great importance from a biomedical point of view, they also act as a very suitable micrometer-sized model system for semiflexible polymers. We perform a statistical analysis of the thermal fluctuations of individual filaments confined in microchannels. The small channel width and the resulting deflections at the walls give rise to a reduction of the configuration space by about 2 orders of magnitude. This circumstance enables us to precisely measure the intrinsic persistence length of vimentin intermediate filaments and to show that they behave as ideal wormlike chains; we observe that small fluctuations in perpendicular planes decouple. Furthermore, the inclusion of results for confined actin filaments demonstrates that the Odijk confinement regime is valid over at least 1 order of magnitude in persistence length. PMID:22463576

  8. Sonographic probing of laser filaments in air.

    PubMed

    Yu, Jin; Mondelain, Didier; Kasparian, Jérôme; Salmon, Estelle; Geffroy, Sylvain; Favre, Catherine; Boutou, Véronique; Wolf, Jean-Pierre

    2003-12-20

    The acoustic wave emitted from the plasma channel associated with a filament induced by a femtosecond laser pulse in air was detected with a microphone. This sonographic detection provides a new method to determine the length and the spatial profile of the free-electron density of a filament. The acoustic wave is emitted owing to the expansion of the gas in the filament, which is heated through collisions with high-energy photoelectrons generated by multiphoton ionization. Compared with other methods, the acoustic detection is simpler, more sensitive, and with higher spatial resolution, making it suitable for field measurements over kilometer-range distances or laboratory-scale studies on the fine structure of a filament. PMID:14717285

  9. Pressure effects on the femtosecond laser filamentation

    NASA Astrophysics Data System (ADS)

    Qi, Xiexing; Ma, Cunliang; Lin, Wenbin

    2016-01-01

    We investigate the pressure effects on the propagation of the laser pulse with wavelength of 800 nm by numerical simulations. We consider the effects on the on-axis intensity, the beam radius and the energy of the filament, as well as the on-axis density of plasma. Numerical results show that when the pressures increase, the length, radius and energy of the light filament become shorter, narrower and lower, respectively. Moreover, we find that the length and the radius of filament are approximately inversely proportional to the pressure and the square root of pressure, respectively, and the pulse with shorter duration is easier to be affected by the pressure. We also obtain the conclusion that the plasma is not necessary to generate the filament in gases in various pressures, as stated by Béjot et al. [1] for the case of standard atmosphere pressure.

  10. Can we determine the filament chirality by the filament footpoint location or the barb-bearing?

    NASA Astrophysics Data System (ADS)

    Hao, Qi; Guo, Yang; Fang, Cheng; Chen, Peng-Fei; Cao, Wen-Da

    2016-01-01

    We attempt to propose a method for automatically detecting the solar filament chirality and barb bearing. We first introduce the concept of an unweighted undirected graph and adopt the Dijkstra shortest path algorithm to recognize the filament spine. Then, we use the polarity inversion line (PIL) shift method for measuring the polarities on both sides of the filament, and employ the connected components labeling method to identify the barbs and calculate the angle between each barb and the spine to determine the bearing of the barbs, i.e., left or right. We test the automatic detection method with Hα filtergrams from the Big Bear Solar Observatory (BBSO) Hα archive and magnetograms observed with the Helioseismic and Magnetic Imager (HMI) on board the Solar Dynamics Observatory (SDO). Four filaments are automatically detected and illustrated to show the results. The barbs in different parts of a filament may have opposite bearings. The filaments in the southern hemisphere (northern hemisphere) mainly have left-bearing (right-bearing) barbs and positive (negative) magnetic helicity, respectively. The tested results demonstrate that our method is efficient and effective in detecting the bearing of filament barbs. It is demonstrated that the conventionally believed one-to-one correspondence between filament chirality and barb bearing is not valid. The correct detection of the filament axis chirality should be done by combining both imaging morphology and magnetic field observations.

  11. 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.

  12. A Robust Actin Filaments Image Analysis Framework.

    PubMed

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

    2016-08-01

    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 grown in

  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. 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.

  15. Effect of ATP on actin filament stiffness.

    PubMed

    Janmey, P A; Hvidt, S; Oster, G F; Lamb, J; Stossel, T P; Hartwig, J H

    1990-09-01

    Actin is an adenine nucleotide-binding protein and an ATPase. The bound adenine nucleotide stabilizes the protein against denaturation and the ATPase activity, although not required for actin polymerization, affects the kinetics of this assembly Here we provide evidence for another effect of adenine nucleotides. We find that actin filaments made from ATP-containing monomers, the ATPase activity of which hydrolyses ATP to ADP following polymerization, are stiff rods, whereas filaments prepared from ADP-monomers are flexible. ATP exchanges with ADP in such filaments and stiffens them. Because both kinds of actin filaments contain mainly ADP, we suggest the alignment of actin monomers in filaments that have bound and hydrolysed ATP traps them conformationally and stores elastic energy. This energy would be available for release by actin-binding proteins that transduce force or sever actin filaments. These data support earlier proposals that actin is not merely a passive cable, but has an active mechanochemical role in cell function. PMID:2168523

  16. Inconsistency of topologically massive hypergravity

    NASA Technical Reports Server (NTRS)

    Aragone, C.; Deser, S.

    1985-01-01

    The coupled topologically massive spin-5/2 gravity system in D = 3 dimensions whose kinematics represents dynamical propagating gauge invariant massive spin-5/2 and spin-2 excitations, is shown to be inconsistent, or equivalently, not locally hypersymmetric. In contrast to D = 4, the local constraints on the system arising from failure of the fermionic Bianchi identities do not involve the 'highest spin' components of the field, but rather the auxiliary spinor required to construct a consistent massive model.

  17. Alternative flagellar filament types in the haloarchaeon Haloarcula marismortui.

    PubMed

    Pyatibratov, Michael G; Beznosov, Sergey N; Rachel, Reinhard; Tiktopulo, Elizabeth I; Surin, Alexei K; Syutkin, Alexei S; Fedorov, Oleg V

    2008-10-01

    Many Archaea use rotation of helical flagellar filaments for swimming motility. We isolated and characterized the flagellar filaments of Haloarcula marismortui, an archaeal species previously considered to be nonmotile. Two Haloarcula marismortui phenotypes were discriminated--their filaments are composed predominantly of either FlaB or FlaA2 flagellin, and the corresponding genes are located on different replicons. FlaB and FlaA2 filaments differ in antigenicity and thermostability. FlaA2 filaments are distinctly thicker (20-22 nm) than FlaB filaments (16-18 nm). The observed filaments are nearly twice as thick as those of other characterized euryarchaeal filaments. The results suggest that the helicity of Haloarcula marismortui filaments is provided by a mechanism different from that in the related haloarchaeon Halobacterium salinarum, where 2 different flagellin molecules present in comparable quantities are required to form a helical filament. PMID:18923552

  18. Higher dimensional nonlinear massive gravity

    NASA Astrophysics Data System (ADS)

    Do, Tuan Q.

    2016-05-01

    Inspired by a recent ghost-free nonlinear massive gravity in four-dimensional spacetime, we study its higher dimensional scenarios. As a result, we are able to show the constantlike behavior of massive graviton terms for some well-known metrics such as the Friedmann-Lemaitre-Robertson-Walker, Bianchi type I, and Schwarzschild-Tangherlini (anti-) de Sitter metrics in a specific five-dimensional nonlinear massive gravity under an assumption that its fiducial metrics are compatible with physical ones. In addition, some simple cosmological solutions of the five-dimensional massive gravity are figured out consistently.

  19. Problems of massive gravities

    NASA Astrophysics Data System (ADS)

    Deser, S.; Izumi, K.; Ong, Y. C.; Waldron, A.

    2015-01-01

    The method of characteristics is a key tool for studying consistency of equations of motion; it allows issues such as predictability, maximal propagation speed, superluminality, unitarity and acausality to be addressed without requiring explicit solutions. We review this method and its application to massive gravity (mGR) theories to show the limitations of these models' physical viability: Among their problems are loss of unique evolution, superluminal signals, matter coupling inconsistencies and micro-acausality (propagation of signals around local closed time-like curves (CTCs)/closed causal curves (CCCs)). We extend previous no-go results to the entire three-parameter range of mGR theories. It is also argued that bimetric models suffer a similar fate.

  20. Massively parallel mathematical sieves

    SciTech Connect

    Montry, G.R.

    1989-01-01

    The Sieve of Eratosthenes is a well-known algorithm for finding all prime numbers in a given subset of integers. A parallel version of the Sieve is described that produces computational speedups over 800 on a hypercube with 1,024 processing elements for problems of fixed size. Computational speedups as high as 980 are achieved when the problem size per processor is fixed. The method of parallelization generalizes to other sieves and will be efficient on any ensemble architecture. We investigate two highly parallel sieves using scattered decomposition and compare their performance on a hypercube multiprocessor. A comparison of different parallelization techniques for the sieve illustrates the trade-offs necessary in the design and implementation of massively parallel algorithms for large ensemble computers.

  1. Massive acute arsenic poisonings.

    PubMed

    Lech, Teresa; Trela, Franciszek

    2005-07-16

    Arsenic poisonings are still important in the field of toxicology, though they are not as frequent as about 20-30 years ago. In this paper, the arsenic concentrations in ante- and post-mortem materials, and also forensic and anatomo-pathological aspects in three cases of massive acute poisoning with arsenic(III) oxide (two of them with unexplained criminalistic background, in which arsenic was taken for amphetamine and one suicide), are presented. Ante-mortem blood and urine arsenic concentrations ranged from 2.3 to 6.7 microg/ml, respectively. Post-mortem tissue total arsenic concentrations were also detected in large concentrations. In case 3, the contents of the duodenum contained as much as 30.1% arsenic(III) oxide. The high concentrations of arsenic detected in blood and tissues in all presented cases are particularly noteworthy in that they are very rarely detected at these concentrations in fatal arsenic poisonings. PMID:15939162

  2. Aspergilloma and massive haemoptysis

    PubMed Central

    Ding, Wern Yew; Chan, Tze; Yadavilli, Rajesh Kumar; McWilliams, Richard

    2014-01-01

    A 40-year-old homeless woman who was a known intravenous drug user and heroin smoker, presented with massive haemoptysis. Initial CT-pulmonary angiogram (CT-PA) did not show active haemorrhage but found an opacity in a right upper lobe cavity likely to represent a mycetoma. She was started on antifungal therapy but haemoptysis persisted and bronchial angiography was performed. Again no active haemorrhage was identified but abnormal vasculature was seen supplying the right upper lobe. This was empirically embolised with particles which did not improve her symptoms. A subsequent CT-PA identified a pulmonary artery pseudoaneurysm in the cavity wall which was successfully embolised. There was no further haemoptysis and a repeat CT-PA 3 weeks later showed continuing occlusion of the pulmonary artery aneurysm. Investigations for tuberculosis were negative and she was discharged clinically well and on long-term antifungal therapy. PMID:24739651

  3. A Census of Large-scale (≥10 PC), Velocity-coherent, Dense Filaments in the Northern Galactic Plane: Automated Identification Using Minimum Spanning Tree

    NASA Astrophysics Data System (ADS)

    Wang, Ke; Testi, Leonardo; Burkert, Andreas; Walmsley, C. Malcolm; Beuther, Henrik; Henning, Thomas

    2016-09-01

    Large-scale gaseous filaments with lengths up to the order of 100 pc are on the upper end of the filamentary hierarchy of the Galactic interstellar medium (ISM). Their association with respect to the Galactic structure and their role in Galactic star formation are of great interest from both an observational and theoretical point of view. Previous “by-eye” searches, combined together, have started to uncover the Galactic distribution of large filaments, yet inherent bias and small sample size limit conclusive statistical results from being drawn. Here, we present (1) a new, automated method for identifying large-scale velocity-coherent dense filaments, and (2) the first statistics and the Galactic distribution of these filaments. We use a customized minimum spanning tree algorithm to identify filaments by connecting voxels in the position–position–velocity space, using the Bolocam Galactic Plane Survey spectroscopic catalog. In the range of 7\\buildrel{\\circ}\\over{.} 5≤slant l≤slant 194^\\circ , we have identified 54 large-scale filaments and derived mass (∼ {10}3{--}{10}5 {M}ȯ ), length (10–276 pc), linear mass density (54–8625 {M}ȯ pc‑1), aspect ratio, linearity, velocity gradient, temperature, fragmentation, Galactic location, and orientation angle. The filaments concentrate along major spiral arms. They are widely distributed across the Galactic disk, with 50% located within ±20 pc from the Galactic mid-plane and 27% run in the center of spiral arms. An order of 1% of the molecular ISM is confined in large filaments. Massive star formation is more favorable in large filaments compared to elsewhere. This is the first comprehensive catalog of large filaments that can be useful for a quantitative comparison with spiral structures and numerical simulations.

  4. Relationship of species-specific filament levels to filamentous bulking in activated sludge.

    PubMed

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

    2004-04-01

    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 x 10(8) micro m 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

  5. The evolution of massive stars

    NASA Technical Reports Server (NTRS)

    1982-01-01

    The hypotheses underlying theoretical studies of the evolution of massive model stars with and without mass loss are summarized. The evolutionary tracks followed by the models across theoretical Hertzsprung-Russell (HR) diagrams are compared with the observed distribution of B stars in an HR diagram. The pulsational properties of models of massive star are also described.

  6. Outflow Feedback Regulated Massive Star Formation in Parsec-Scale Cluster Forming Clumps

    SciTech Connect

    Wang, Peng; Li, Zhi-Yun; Abel, Tom; Nakamura, Fumitaka; /Niigata U.

    2010-02-15

    We investigate massive star formation in turbulent, magnetized, parsec-scale clumps of molecular clouds including protostellar outflow feedback using three dimensional numerical simulations of effective resolution 2048{sup 3}. The calculations are carried out using a block structured adaptive mesh refinement code that solves the ideal MHD equations including self-gravity and implements accreting sink particles. We find that, in the absence of regulation by magnetic fields and outflow feedback, massive stars form readily in a turbulent, moderately condensed clump of {approx} 1,600 M{sub {circle_dot}} (containing {approx} 10{sup 2} initial Jeans masses), along with a cluster of hundreds of lower mass stars. The massive stars are fed at high rates by (1) transient dense filaments produced by large-scale turbulent compression at early times, and (2) by the clump-wide global collapse resulting from turbulence decay at late times. In both cases, the bulk of the massive star's mass is supplied from outside a 0.1 pc-sized 'core' that surrounds the star. In our simulation, the massive star is clump-fed rather than core-fed. The need for large-scale feeding makes the massive star formation prone to regulation by outflow feedback, which directly opposes the feeding processes. The outflows reduce the mass accretion rates onto the massive stars by breaking up the dense filaments that feed the massive star formation at early times, and by collectively slowing down the global collapse that fuel the massive star formation at late times. The latter is aided by a moderate magnetic field of strength in the observed range (corresponding to a dimensionless clump mass-to-flux ratio {lambda} {approx} a few); the field allows the outflow momenta to be deposited more efficiently inside the clump. We conclude that the massive star formation in our simulated turbulent, magnetized, parsec-scale clump is outflow-regulated and clump-fed (ORCF for short). An important implication is that the

  7. Massive stars: Starbursts

    NASA Astrophysics Data System (ADS)

    González Delgado, Rosa María

    2007-07-01

    Starbursts are the preferred place where massive stars form; the main source of thermal and mechanical heating in the interstellar medium, and the factory where the heavy elements form. Thus, starbursts play an important role in the origin and evolution of galaxies. Starbursts are bright at ultraviolet (UV) wavelengths, and after the pioneering IUE program, high spatial and spectral resolution UV observations of local starburst galaxies, mainly taken with HST and FUSE, have made relevant contributions to the following issues: a) The determination of the initial mass function (IMF) in violent star forming systems in low and high metallicity environments, and in dense (e.g. in stellar clusters) and diffuse environments: A Salpeter IMF with high-mass stars constrains well the UV properties. b) Stellar clusters are an important mode of star formation in starbursts. c) The role of starbursts in AGN: Nuclear starbursts can dominate the UV light in Seyfert 2 galaxies, having bolometric luminosities similar to the estimated bolometric luminosities of the obscured AGN. d) The interaction between massive stars and the interstellar medium: Outflows in cold, warm and coronal phases leave their imprints on the UV interstellar lines. Outflows of a few hundred km s%u22121 are ubiquitous phenomena in starbursts. Despite the very significant progress obtained over the past two decades of UV observations of starbursts, there are important problems that still need to be solved. High-spatial resolution UV observations of nearby starbursts are crucial to further progress in understanding the violent star formation processes in galaxies, the interaction between the stellar clusters and the interstellar medium, and the variation of the IMF. High-spatial resolution spectra are also needed to isolate the light from the center to the disk in UV luminous galaxies found by GALEX. Thus, a new UV mission furnished with an intermediate spectral resolution spectrograph with high spatial

  8. The kinetics underlying the velocity of smooth muscle myosin filament sliding on actin filaments in vitro.

    PubMed

    Haldeman, Brian D; Brizendine, Richard K; Facemyer, Kevin C; Baker, Josh E; Cremo, Christine R

    2014-07-25

    Actin-myosin interactions are well studied using soluble myosin fragments, but little is known about effects of myosin filament structure on mechanochemistry. We stabilized unphosphorylated smooth muscle myosin (SMM) and phosphorylated smooth muscle myosin (pSMM) filaments against ATP-induced depolymerization using a cross-linker and attached fluorescent rhodamine (XL-Rh-SMM). Electron micrographs showed that these side polar filaments are very similar to unmodified filaments. They are ~0.63 μm long and contain ~176 molecules. Rate constants for ATP-induced dissociation and ADP release from acto-myosin for filaments and S1 heads were similar. Actin-activated ATPases of SMM and XL-Rh-SMM were similarly regulated. XL-Rh-pSMM filaments moved processively on F-actin that was bound to a PEG brush surface. ATP dependence of filament velocities was similar to that for solution ATPases at high [actin], suggesting that both processes are limited by the same kinetic step (weak to strong transition) and therefore are attachment- limited. This differs from actin sliding over myosin monomers, which is primarily detachment-limited. Fitting filament data to an attachment-limited model showed that approximately half of the heads are available to move the filament, consistent with a side polar structure. We suggest the low stiffness subfragment 2 (S2) domain remains unhindered during filament motion in our assay. Actin-bound negatively displaced heads will impart minimal drag force because of S2 buckling. Given the ADP release rate, the velocity, and the length of S2, these heads will detach from actin before slack is taken up into a backwardly displaced high stiffness position. This mechanism explains the lack of detachment- limited kinetics at physiological [ATP]. These findings address how nonlinear elasticity in assemblies of motors leads to efficient collective force generation. PMID:24907276

  9. The Kinetics Underlying the Velocity of Smooth Muscle Myosin Filament Sliding on Actin Filaments in Vitro*

    PubMed Central

    Haldeman, Brian D.; Brizendine, Richard K.; Facemyer, Kevin C.; Baker, Josh E.; Cremo, Christine R.

    2014-01-01

    Actin-myosin interactions are well studied using soluble myosin fragments, but little is known about effects of myosin filament structure on mechanochemistry. We stabilized unphosphorylated smooth muscle myosin (SMM) and phosphorylated smooth muscle myosin (pSMM) filaments against ATP-induced depolymerization using a cross-linker and attached fluorescent rhodamine (XL-Rh-SMM). Electron micrographs showed that these side polar filaments are very similar to unmodified filaments. They are ∼0.63 μm long and contain ∼176 molecules. Rate constants for ATP-induced dissociation and ADP release from acto-myosin for filaments and S1 heads were similar. Actin-activated ATPases of SMM and XL-Rh-SMM were similarly regulated. XL-Rh-pSMM filaments moved processively on F-actin that was bound to a PEG brush surface. ATP dependence of filament velocities was similar to that for solution ATPases at high [actin], suggesting that both processes are limited by the same kinetic step (weak to strong transition) and therefore are attachment-limited. This differs from actin sliding over myosin monomers, which is primarily detachment-limited. Fitting filament data to an attachment-limited model showed that approximately half of the heads are available to move the filament, consistent with a side polar structure. We suggest the low stiffness subfragment 2 (S2) domain remains unhindered during filament motion in our assay. Actin-bound negatively displaced heads will impart minimal drag force because of S2 buckling. Given the ADP release rate, the velocity, and the length of S2, these heads will detach from actin before slack is taken up into a backwardly displaced high stiffness position. This mechanism explains the lack of detachment-limited kinetics at physiological [ATP]. These findings address how nonlinear elasticity in assemblies of motors leads to efficient collective force generation. PMID:24907276

  10. Theory of a filament initiated nitrogen laser

    NASA Astrophysics Data System (ADS)

    Kartashov, Daniil; Ališauskas, Skirmantas; Pugžlys, Audrius; Shneider, Mikhail N.; Baltuška, Andrius

    2015-05-01

    We present the theoretical model for a single-pass, discharge-type standoff nitrogen laser initiated by a femtosecond filament in nitrogen gas. The model is based on the numerical solution of the kinetic equation for the electron energy distribution function self-consistently with balance equations for nitrogen species and laser equations. We identify the kinetic mechanisms responsible for a buildup of population inversion in the filament afterglow plasma and determine the dependence of population inversion density and the parameters of nitrogen lasing at a 337 nm wavelength corresponding to the transition between the C3Πu (v = 0) excited and the X1Σg (v = 0) ground electronic states in a nitrogen molecule on the polarization and wavelength of the driver laser pulse used to produce the filament. We show that population inversion is achieved on an ultrafast time scale of ≈10 ps and decays within the time: <100 ps. We derive the low-signal gain 2.2 cm-1 for lasing from a circularly polarized 0.8 μm near-IR filament and 0.16 cm-1 for a linearly polarized 4 μm mid-IR filament. The results of the numerical simulations demonstrate good quantitative agreement with the experimental measurements.

  11. Nonlinear elasticity of semiflexible filament networks.

    PubMed

    Meng, Fanlong; Terentjev, Eugene M

    2016-08-10

    We develop a continuum theory for equilibrium elasticity of a network of crosslinked semiflexible filaments, spanning the full range between flexible entropy-driven chains to stiff athermal rods. We choose the 3-chain constitutive model of network elasticity over several plausible candidates, and derive analytical expressions for the elastic energy at arbitrary strain, with the corresponding stress-strain relationship. The theory fits well to a wide range of experimental data on simple shear in different filament networks, quantitatively matching the differential shear modulus variation with stress, with only two adjustable parameters (which represent the filament stiffness and the pre-tension in the network, respectively). The general theory accurately describes the crossover between the positive and negative Poynting effect (normal stress on imposed shear) on increasing the stiffness of filaments forming the network. We discuss the network stability (the point of marginal rigidity) and the phenomenon of tensegrity, showing that filament pre-tension on crosslinking into the network determines the magnitude of linear modulus G0. PMID:27444846

  12. Kinematics of Filaments in Serpens and Perseus

    NASA Astrophysics Data System (ADS)

    Dhabal, Arnab; Mundy, Lee G.; Rizzo, Maxime; Storm, Shaye; Teuben, Peter J.; Chen, Che-Yu; Ostriker, Eve C.

    2016-01-01

    Following up on the CARMA Large Area Star Formation Survey (CLASSy), we observed specific filaments in the Serpens and Perseus clouds using H13CO+, H13CN, and HNC J=1-0 transitions at 7" angular resolution and 0.16 km/s spectral resolution. The isotopologues containing 13C are optically thin; hence they trace the high column density regions of dense gas (ncrit ~ 105 cm-3) better than their more abundant 12C counterparts which were observed previously (Lee et al. 2014). The HNC lines show significant self-absorption features from overlying lower density gas along many lines of sight. Many of the filaments showed velocity gradients perpendicular to the long axis of filaments in H13CO+ and H13CN emission, thereby supporting the model by Chen and Ostriker (2014) in which filaments form in the dense layer created by colliding turbulent cells. The signature velocity gradient occurs because the filaments are primarily accreting material in a 2-D flow within the dense layer.

  13. Nebulin binding impedes mutant desmin filament assembly

    PubMed Central

    Baker, Laura K.; Gillis, David C.; Sharma, Sarika; Ambrus, Andy; Herrmann, Harald; Conover, Gloria M.

    2013-01-01

    Desmin intermediate filaments (DIFs) form an intricate meshwork that organizes myofibers within striated muscle cells. The mechanisms that regulate the association of desmin to sarcomeres and their role in desminopathy are incompletely understood. Here we compare the effect nebulin binding has on the assembly kinetics of desmin and three desminopathy-causing mutant desmin variants carrying mutations in the head, rod, or tail domains of desmin (S46F, E245D, and T453I). These mutants were chosen because the mutated residues are located within the nebulin-binding regions of desmin. We discovered that, although nebulin M160–164 bound to both desmin tetrameric complexes and mature filaments, all three mutants exhibited significantly delayed filament assembly kinetics when bound to nebulin. Correspondingly, all three mutants displayed enhanced binding affinities and capacities for nebulin relative to wild-type desmin. Electron micrographs showed that nebulin associates with elongated normal and mutant DIFs assembled in vitro. Moreover, we measured significantly delayed dynamics for the mutant desmin E245D relative to wild-type desmin in fluorescence recovery after photobleaching in live-cell imaging experiments. We propose a mechanism by which mutant desmin slows desmin remodeling in myocytes by retaining nebulin near the Z-discs. On the basis of these data, we suggest that for some filament-forming desmin mutants, the molecular etiology of desminopathy results from subtle deficiencies in their association with nebulin, a major actin-binding filament protein of striated muscle. PMID:23615443

  14. 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.

  15. 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.

  16. Galaxy alignment as a probe of large-scale filaments

    NASA Astrophysics Data System (ADS)

    Rong, Yu; Liu, Yuan; Zhang, Shuang-Nan

    2016-01-01

    The orientations of the red galaxies in a filament are aligned with the orientation of the filament. We thus develop a location-alignment-method (LAM) of detecting filaments around clusters of galaxies, which uses both the alignments of red galaxies and their distributions in two-dimensional images. For the first time, the orientations of red galaxies are used as probes of filaments. We apply LAM to the environment of Coma cluster, and find four filaments (two filaments are located in sheets) in two selected regions, which are compared with the filaments detected with the method of Falco et al.. We find that LAM can effectively detect the filaments around a cluster, even with 3σ confidence level, and clearly reveal the number and overall orientations of the detected filaments. LAM is independent of the redshifts of galaxies, and thus can be applied at relatively high redshifts and to the samples of red galaxies without the information of redshifts.

  17. Massive gauge-flation

    NASA Astrophysics Data System (ADS)

    Nieto, Carlos M.; Rodríguez, Yeinzon

    2016-06-01

    Gauge-flation model at zeroth-order in cosmological perturbation theory offers an interesting scenario for realizing inflation within a particle physics context, allowing us to investigate interesting possible connections between inflation and the subsequent evolution of the Universe. Difficulties, however, arise at the perturbative level, thus motivating a modification of the original model. In order to agree with the latest Planck observations, we modify the model such that the new dynamics can produce a relation between the spectral index ns and the tensor-to-scalar ratio r allowed by the data. By including an identical mass term for each of the fields of the system, we find interesting dynamics leading to slow-roll inflation of the right length. The presence of the mass term has the potential to modify the ns versus r relation so as to agree with the data. As a first step, we study the model at zeroth-order in cosmological perturbation theory, finding the conditions required for slow-roll inflation and the number of e-foldings of inflation. Numerical solutions are used to explore the impact of the mass term. We conclude that the massive version of gauge-flation offers a viable inflationary model.

  18. Massive soliton stars

    NASA Technical Reports Server (NTRS)

    Chiu, Hong-Yee

    1990-01-01

    The structure of nontopological solutions of Einstein field equations as proposed by Friedberg, Lee, and Pang (1987) is examined. This analysis incorporates finite temperature effects and pair creation. Quarks are assumed to be the only species that exist in interior of soliton stars. The possibility of primordial creation of soliton stars in the incomplete decay of the degenerate vacuum in early universe is explored. Because of dominance of pair creation inside soliton stars, the luminosity of soliton stars is not determined by its radiative transfer characteristics, and the surface temperature of soliton stars can be the same as its interior temperature. It is possible that soliton stars are intense X-ray radiators at large distances. Soliton stars are nearly 100 percent efficient energy converters, converting the rest energy of baryons entering the interior into radiation. It is possible that a sizable number of baryons may also be trapped inside soliton stars during early epochs of the universe. In addition, if soliton stars exist they could assume the role played by massive black holes in galactic centers.

  19. Two-color resonant filamentation in gases

    NASA Astrophysics Data System (ADS)

    Doussot, J.; Béjot, P.; Faucher, O.

    2016-07-01

    In this paper, it is shown that two-photon resonance involving a fundamental field and one of its odd harmonic strongly influences the filamentation process, i.e., the nonlinear propagation of an ultrashort and ultraintense laser field. This particular situation happens, for instance, when a 400 nm fundamental field propagates together with its third harmonic in krypton. Using three-dimensional ab initio calculations, the optical response of krypton is evaluated and the underlying nonlinear refractive indices are extracted. It is found that the resonance also exacerbates higher-order nonlinear processes. Injecting the retrieved higher-order Kerr indices in a nonlinear propagation solver, it is found that the resonance leads to an enhanced defocusing cross-phase modulation that strongly participates to the filament stabilization. This work sheds a light on the mechanism of filamentation, in particular, in the ultraviolet range, where two-color two-photon resonances are expected to occur in many atomic gases.

  20. Filament-assisted growth of diamond films

    NASA Astrophysics Data System (ADS)

    Lee, C. H.; Fu, T. D.; Chen, Y. F.

    1993-01-01

    Filament-assisted pyrolytic growth of diamond films on (100) Si wafers was investigated in an attempt to grow quality layers for semiconductor applications. The work was carried out in hydrogen ambient under a reduced pressure condition of about 100 torr. Using isopropanol and methanol as carbon source chemicals, the growth process and film properties were characterized as functions of reactant concentration, filament and substrate temperature, reaction pressure and the total gas flow rate. Diamond films of good quality were grown under condition of low source concentration and small flow rate. However, the growth rates were generally slow. The films were polycrystalline. The filament and substrate temperatures were fairly critical to the nucleation and growth processes. The substrate surface finishing from diamond paste polishing predominated the nucleation site and grain size of the deposits.

  1. Extending optical filaments using auxiliary dress beams

    NASA Astrophysics Data System (ADS)

    Mills, Matthew; Heinrich, Matthias; Kolesik, Miroslav; Christodoulides, Demetrios

    2015-05-01

    Dressed optical filaments offer a way to greatly protract an optical filament’s natural length while at the same time mitigating nonlinear losses and unwanted multifilamentation effects. In this article, we first theoretically reexamine the quasi-linear propagation dynamics of a standard Gaussian-ring wavefront and then proceed to explore several optical dress beam arrangements of equal-energy. The purpose of this study is to numerically simulate configurations which more economically utilize the finite amount of energy available for filament prolongation. In general, we find that parameters such as beam width and inward radial chirp, when adjusted in unison, play an important role in extending a filament whereas the spatial distribution of power in the optical dress only affects the characteristic intensity fluctuations seen during refocusing cycles.

  2. 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. PMID:24483663

  3. 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.

  4. 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. PMID:26261319

  5. 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

  6. 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.

  7. Solar Magnetized "Tornadoes:" Relation to Filaments

    NASA Astrophysics Data System (ADS)

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

    2012-09-01

    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.

  8. Spatiotemporal Rogue Events in Optical Multiple Filamentation

    NASA Astrophysics Data System (ADS)

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

    2013-12-01

    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.

  9. Theoretical and Experimental study on multiple filaments in air

    SciTech Connect

    Zhang Jie; Lu Xin; Hao Zuoqiang; Xi Tingting; Zhang Zhe; Jin Zhan

    2007-07-11

    The physics of filaments formed by femtosecond laser pulses propagating in air is revealed both in theory and in experiment. An analytical method is used to investigate the interaction of two filaments. The interaction Hamiltonian of two filaments with different phase shifts is obtained and used to judge the properly of filaments interaction. The analytical results are in good agreement with simulation results. The influence of energy background on propagation of filaments is investigated in experiment. It is found that the characteristics of filaments can be changed by spatial and temporal control of laser pulses.

  10. U. radio emission from quiescent filaments

    NASA Technical Reports Server (NTRS)

    Lang, Kenneth R.

    1989-01-01

    Full-disk Very Large Array (VLA) synthesis maps of the quiet Sun indicate that filaments can be seen in emission at 91.6 cm wavelength; they are detected in absorption at shorter microwave wavelengths. The 91.6 cm emission has a brightness temperature of T sub B = 3 x 10(exp 5) K. It is hotter, wider and longer than the underlying filament detected at H alpha wavelengths, but the similarity between the shape, position, elongation and orientation of the radio and optical features suggests their close association. The 91.6 cm emission is attributed to the thermal-bremsstrahlung of a hot transition sheath that envelopes the H alpha filament and acts as an interface between the cool, dense H alpha filament and the hotter, rarefied corona. The transition sheath is seen in emission because of the lower optical depth of the corona at 90 cm wavelength, and the width of this sheet is 10(exp 9) cm. A power law gradient in pressure provides a better match to the observations than a constant pressure model; definitive tests of theoretical models await simultaneous multi-wavelength studies of filaments at different observing angles. When the thermal bremsstrahlung is optically thin, the magnetic field strength in the transition sheath can be inferred from the observed circular polarization. Variable physical parameters of the sheath, such as width, electron density, and electron temperature, can explain controversial reports of the detection of, or the failure to detect, the meter-wavelength counterpart of H alpha filaments.

  11. Herschel-HIFI view of mid-IR quiet massive protostellar objects

    NASA Astrophysics Data System (ADS)

    Herpin, F.; Chavarría, L.; Jacq, T.; Braine, J.; van der Tak, F.; Wyrowski, F.; van Dishoeck, E. F.; Baudry, A.; Bontemps, S.; Kristensen, L.; Schmalzl, M.; Mata, J.

    2016-03-01

    Aims: We present Herschel/HIFI observations of 14 water lines in a small sample of Galactic massive protostellar objects: NGC 6334I(N), DR21(OH), IRAS 16272-4837, and IRAS 05358+3543. Using water as a tracer of the structure and kinematics, we individually study each of these objects with the aim to estimate the amount of water around them, but to also to shed light on the high-mass star formation process. Methods: We analyzed the gas dynamics from the line profiles using Herschel-HIFI observations acquired as part of the WISH key-project of 14 far-IR water lines (H_216O, H_217O, H_218O) and several other species. Then through modeling the observations using the RATRAN radiative transfer code, we estimated outflow, infall, turbulent velocities, and molecular abundances and investigated the correlation with the evolutionary status of each source. Results: The four sources (and the previously studied W43-MM1) have been ordered in terms of evolution based on their spectral energy distribution from youngest to older: 1) NGC 64334I(N); 2) W43-MM1; 3) DR21(OH); 4) IRAS 16272-4837; 5) IRAS 05358+3543. The molecular line profiles exhibit a broad component coming from the shocks along the cavity walls that is associated with the protostars, and an infalling (or expanding, for IRAS 05358+3543) and passively heated envelope component, with highly supersonic turbulence that probably increases with the distance from the center. Accretion rates between 6.3 × 10-5 and 5.6 × 10-4M⊙ yr-1 are derived from the infall observed in three of our sources. The outer water abundance is estimated to be at the typical value of a few 10-8, while the inner abundance varies from 1.7 × 10-6 to 1.4 × 10-4 with respect to H2 depending on the source. Conclusions: We confirm that regions of massive star formation are highly turbulent and that the turbulence probably increases in the envelope with the distance to the star. The inner abundances are lower than the expected, 10-4, perhaps because

  12. Geometrically frustrated filament assemblies: Unravelling the connection between bundle shape and inter-filament order

    NASA Astrophysics Data System (ADS)

    Grason, Gregory

    2014-03-01

    From steel cables and textile fibers to filamentous protein bundles in cells and tissues, densely-packed assemblies of filaments are vital structural elements of the worlds around us and inside of us. Despite the ubiquity and utility of dense-filament assemblies in such diverse materials (across 7 orders of magnitude in size!) surprisingly little is known about the fundamental rules that govern their structure. This talk will discuss recent progress in our understanding of the non-linear relationship between the geometry of a rope-like assembly and the structure and energetics of inter-filament packing. In particular, we focus on mathematical models of the geometric frustration between twist - as in macroscopic cables or chiral biofilament bundles - and the preference for isometric, or ``constant spacing,'' packing of filaments in the cross section. Any measure of twist makes it geometrically impossible to evenly space filaments in bundles, begging the question what is the optimal packing of a twisted bundle? We show that geometry of interfilament contact can be mapped formally onto a problem of packing on a 2D non-Euclidean surfaces, whose intrinsically-curved geometry points to the necessity of a complex spectrum defects in the ground-state packing. We confirm the existence of defects and their sensitivity to bundle twist and radius through simulations of energy-minimizing assemblies of cohesive filaments.

  13. 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.

  14. Terahertz radiation from a laser plasma filament.

    PubMed

    Wu, H-C; Meyer-Ter-Vehn, J; Ruhl, H; Sheng, Z-M

    2011-03-01

    By the use of two-dimensional particle-in-cell simulations, we clarify the terahertz (THz) radiation mechanism from a plasma filament formed by an intense femtosecond laser pulse. The nonuniform plasma density of the filament leads to a net radiating current for THz radiation. This current is mainly located within the pulse and the first cycle of the wakefield. As the laser pulse propagates, a single-cycle and radially polarized THz pulse is constructively built up forward. The single-cycle shape is mainly due to radiation damping effect. PMID:21517604

  15. 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.

  16. 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.

  17. Current filamentation instability in laser wakefield accelerators.

    PubMed

    Huntington, C M; Thomas, A G R; McGuffey, C; Matsuoka, T; Chvykov, V; Kalintchenko, G; Kneip, S; Najmudin, Z; Palmer, C; Yanovsky, V; Maksimchuk, A; Drake, R P; Katsouleas, T; Krushelnick, K

    2011-03-11

    Experiments using an electron beam produced by laser-wakefield acceleration have shown that varying the overall beam-plasma interaction length results in current filamentation at lengths that exceed the laser depletion length in the plasma. Three-dimensional simulations show this to be a combination of hosing, beam erosion, and filamentation of the decelerated beam. This work suggests the ability to perform scaled experiments of astrophysical instabilities. Additionally, understanding the processes involved with electron beam propagation is essential to the development of wakefield accelerator applications. PMID:21469796

  18. Current Filamentation Instability in Laser Wakefield Accelerators

    SciTech Connect

    Huntington, C. M.; Drake, R. P.; Thomas, A. G. R.; McGuffey, C.; Matsuoka, T.; Chvykov, V.; Kalintchenko, G.; Yanovsky, V.; Maksimchuk, A.; Krushelnick, K.; Kneip, S.; Najmudin, Z.; Palmer, C.; Katsouleas, T.

    2011-03-11

    Experiments using an electron beam produced by laser-wakefield acceleration have shown that varying the overall beam-plasma interaction length results in current filamentation at lengths that exceed the laser depletion length in the plasma. Three-dimensional simulations show this to be a combination of hosing, beam erosion, and filamentation of the decelerated beam. This work suggests the ability to perform scaled experiments of astrophysical instabilities. Additionally, understanding the processes involved with electron beam propagation is essential to the development of wakefield accelerator applications.

  19. Electromagnetic properties of massive neutrinos

    SciTech Connect

    Dobrynina, A. A. Mikheev, N. V.; Narynskaya, E. N.

    2013-10-15

    The vertex function for a virtual massive neutrino is calculated in the limit of soft real photons. A method based on employing the neutrino self-energy operator in a weak external electromagnetic field in the approximation linear in the field is developed in order to render this calculation of the vertex function convenient. It is shown that the electric charge and the electric dipole moment of the real neutrino are zero; only the magnetic moment is nonzero for massive neutrinos. A fourth-generation heavy neutrino of mass not less than half of the Z-boson mass is considered as a massive neutrino.

  20. Cores, Filaments, and Bundles: Hierarchical core formation in the B213 filament in Taurus

    NASA Astrophysics Data System (ADS)

    Hacar, Alvaro; Tafalla, Mario; Kauffmann, Jens; Kovacs, Attila

    2013-07-01

    Characterizing the dense core formation in filaments is a critical step for our understanding of the star formation process within molecular clouds. Using different molecular tracers to study the gas kinematics at different scales and density regimes, we have investigated the dense core formation in the B213/L1495 filament in Taurus, one of the most prominent structures identified in nearby clouds (see Hacar et al 2013, A&A, 554, A55). Our analysis of its internal kinematics demonstrates that this filament is actually a bundle of 35 velocity-coherent filaments, typically with lengths of ˜ 0.5 pc and oscillatory-like and sonic velocity field, each of them exhibiting linear masses close to the expected mass for a filament in hydrostatic equilibrium. Among them, only a small fraction of these filaments (˜1/4) are "fertile" and efficiently fragment forming all the cores identified within this region, while most of them (˜3/4) do not form cores and remain "sterile". Our observations then suggest that core formation in Taurus occurs in two steps. First, 0.5 pc-long velocity-coherent filaments condense out of the cloud gas, probably as a result of the turbulent cascade. After that, the dense cores condense quasi-statically in only those "fertile" filaments that have accumulated enough mass to became gravitational unstable, inheriting their kinematic properties. The formation of these velocity-coherent filaments appears therefore as a critical step on the star formation process being the first subsonic structures formed out of the turbulent regime that dominates the cloud dynamics at large scales.

  1. Formation of cold clumps and filaments around superbubbles

    NASA Astrophysics Data System (ADS)

    Ntormousi, Evangelia; Dawson, Joanne; Del Sordo, Fabio; Hennebelle, Patrick

    2015-08-01

    The combined feedback of supernova explosions and stellar winds from associations of massive stars has a dramatic impact on their environment: Large amounts of energy coming from the ejecta create dense shocks around the associations, compressing the surrounding ISM and triggering the formation of molecular clouds and new stars. In this work we employ high-resolution, three-dimensional simulations of this process with the MHD code RAMSES to explore the effects of self-gravity and magnetic fields on the structure of the shells. Two superbubbles expand and collide in a turbulent diffuse medium. In the expansion phase rich dense structure appears on the surface of the shocks due to hydrodynamic and hydromagnetic instabilities. Although gravity seems to play a minor role in the formation and evolution of these dense clumps, magnetic fields completely alter both the expansion of the superbubble and the morphology of the dense gas, slowing the expansion down and causing the appearance of large-scale filaments. The collision does not help increase the amount of cold gas, but rather destroys a lot of the pre-existing dense structures. Finally, we compare clouds formed in these simulations with observations of a molecular cloud crushed between two superbubbles.

  2. Rupture and recoil of bent-core liquid crystal filaments.

    PubMed

    Salili, S M; Ostapenko, T; Kress, O; Bailey, C; Weissflog, W; Harth, K; Eremin, A; Stannarius, R; Jákli, A

    2016-05-25

    The recoil process of free-standing liquid crystal filaments is investigated experimentally and theoretically. We focus on two aspects, the contraction speed of the filament and a spontaneously formed undulation instability. At the moment of rupture, the filaments buckle similarly to the classical Euler buckling of elastic rods. The tip velocity decays with decreasing filament length. The wavelength of buckling affinely decreases with the retracting filament tip. The energy gain related to the decrease of the total length and surface area of the filaments is mainly dissipated by layer rearrangements during thickening of the fibre. A flow back into the meniscus is relevant only in the final stage of the recoil process. We introduce a model for the quantitative description of the filament retraction speed. The dynamics of this recoil behaviour may find relevance as a model for biology-related filaments. PMID:27140824

  3. 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.

  4. Multiple Filamentation of Laser Pulses in a Glass

    NASA Astrophysics Data System (ADS)

    Apeksimov, D. V.; Bukin, O. A.; Golik, S. S.; Zemlyanov, A. A.; Iglakova, A. N.; Kabanov, A. M.; Kuchinskaya, O. I.; Matvienko, G. G.; Oshlakov, V. K.; Petrov, A. V.; Sokolova, E. B.

    2016-03-01

    Results are presented of experiments on investigation of the spatial characteristics of multi-filamentation region of giga- and terawatt pulses of a Ti:sapphire laser in a glass. Dependences are obtained of the coordinate of the beginning of filamentation region, number of filaments, their distribution along the laser beam axis, and length of filaments on the pulse power. It is shown that with increasing radiation power, the number of filaments in the multi-filamentation region decreases, whereas the filament diameter has a quasiconstant value for all powers realized in the experiments. It is shown that as a certain power of the laser pulse with Gauss energy density distribution is reached, the filamentation region acquires the shape of a hollow cone with apex directed toward the radiation source.

  5. GRAVITATIONAL INFALL ONTO MOLECULAR FILAMENTS. II. EXTERNALLY PRESSURIZED CYLINDERS

    SciTech Connect

    Heitsch, Fabian

    2013-10-10

    Two aspects of the evolution of externally pressurized, hydrostatic filaments are discussed. (1) The free-fall accretion of gas onto such a filament will lead to filament parameters (specifically, FWHM-column-density relations) inconsistent with the observations of Arzoumanian et al., except for two cases: for low-mass, isothermal filaments, agreement is found as in the analysis by Fischera and Martin. Magnetized cases, for which the field scales weakly with the density as B∝n {sup 1/2}, also reproduce observed parameters. (2) Realistically, the filaments will be embedded not only in gas of non-zero pressure, but also of non-zero density. Thus, the appearance of sheet-embedded filaments is explored. Generating a grid of filament models and comparing the resulting column density ratios and profile shapes with observations suggests that the three-dimensional filament profiles are intrinsically flatter than isothermal, beyond projection and evolution effects.

  6. Filament Guides for Silicon-Ribbon Growth

    NASA Technical Reports Server (NTRS)

    Morrison, A. D.

    1985-01-01

    Contamination reduced in modified growth system. In Silicon-ribbongrowth apparatus, capillary filament guides are integral parts of crucible, extending from bottom to top of melt. Addition of guides expected to result in better thermal control of growth process and higher silicon purity.

  7. 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.

  8. Filament-wound composite vessel materials technology

    NASA Technical Reports Server (NTRS)

    Lark, R. F.

    1973-01-01

    Review of recent developments in advanced filament-wound fiber/resin composite vessel technology for cryogen and high-pressure gas containment applications. Design and fabrication procedures have been developed for small-diameter closed-end vessels equipped with thin elastomeric or thin metallic liners. Specific results are discussed.

  9. 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...

  10. Multiple breathers on a vortex filament

    NASA Astrophysics Data System (ADS)

    Salman, H.

    2014-10-01

    In this paper we investigate the correspondence between the Da Rios-Betchov equation, which appears in the three-dimensional motion of a vortex filament, and the nonlinear Schrödinger equation. Using this correspondence we map a set of solutions corresponding to breathers in the nonlinear Schrödinger equation to waves propagating along a vortex filament. The work presented generalizes the recently derived family of vortex configurations associated with these breather solutions to a wider class of configurations that are associated with combination homoclinic/heteroclinic orbits of the 1D self-focussing nonlinear Schrödinger equation. We show that by considering these solutions of the governing nonlinear Schrödinger equation, highly nontrivial vortex filament configurations can be obtained that are associated with a pair of breather excitations. These configurations can lead to loop-like excitations emerging from an otherwise weakly perturbed helical vortex. The results presented further demonstrate the rich class of solutions that are supported by the Da Rios-Betchov equation that is recovered within the local induction approximation for the motion of a vortex filament.

  11. Nonlinear Binormal Flow of Vortex Filaments

    NASA Astrophysics Data System (ADS)

    Strong, Scott; Carr, Lincoln

    2015-11-01

    With the current advances in vortex imaging of Bose-Einstein condensates occurring at the Universities of Arizona, São Paulo and Cambridge, interest in vortex filament dynamics is experiencing a resurgence. Recent simulations, Salman (2013), depict dissipative mechanisms resulting from vortex ring emissions and Kelvin wave generation associated with vortex self-intersections. As the local induction approximation fails to capture reconnection events, it lacks a similar dissipative mechanism. On the other hand, Strong&Carr (2012) showed that the exact representation of the velocity field induced by a curved segment of vortex contains higher-order corrections expressed in powers of curvature. This nonlinear binormal flow can be transformed, Hasimoto (1972), into a fully nonlinear equation of Schrödinger type. Continued transformation, Madelung (1926), reveals that the filament's square curvature obeys a quasilinear scalar conservation law with source term. This implies a broader range of filament dynamics than is possible with the integrable linear binormal flow. In this talk we show the affect higher-order corrections have on filament dynamics and discuss physical scales for which they may be witnessed in future experiments. Partially supported by NSF.

  12. Conformational phases of membrane bound cytoskeletal filaments

    NASA Astrophysics Data System (ADS)

    Quint, David A.; Grason, Gregory; Gopinathan, Ajay

    2013-03-01

    Membrane bound cytoskeletal filaments found in living cells are employed to carry out many types of activities including cellular division, rigidity and transport. When these biopolymers are bound to a membrane surface they may take on highly non-trivial conformations as compared to when they are not bound. This leads to the natural question; What are the important interactions which drive these polymers to particular conformations when they are bound to a surface? Assuming that there are binding domains along the polymer which follow a periodic helical structure set by the natural monomeric handedness, these bound conformations must arise from the interplay of the intrinsic monomeric helicity and membrane binding. To probe this question, we study a continuous model of an elastic filament with intrinsic helicity and map out the conformational phases of this filament for various mechanical and structural parameters in our model, such as elastic stiffness and intrinsic twist of the filament. Our model allows us to gain insight into the possible mechanisms which drive real biopolymers such as actin and tubulin in eukaryotes and their prokaryotic cousins MreB and FtsZ to take on their functional conformations within living cells.

  13. 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

  14. SMART Observation of Magnetic Helicity in Solar Filaments

    NASA Astrophysics Data System (ADS)

    Hagino, M.; Kitai, R.; Shibata, K.

    2006-08-01

    We examined the magnetic helicity of solar filaments from their structure in the chromosphere and corona. The H-alpha telescope of the Solar Magnetic Activity Research Telescope (SMART) observed 239 intermediate filaments from 2005 July 1 to 2006 May 15. The intermediate filament usually locates between two active regions. Using these images, we identified the filament spine and its barbs, and determined the chromospheric filament helicity from the mean angle between each barbs and a spine. We found that 71% (78 of 110) of intermediate filaments in the northern hemisphere are negative helicity and 67% (87 of 129) of filaments in the southern hemisphere are positive, which agreed with the well-known hemispheric tendency of the magnetic helicity. Additionally, we studied the coronal helicity of intermediate filaments. The coronal filament helicity is defined as the crossing angle of threads formed a filament. The helicity pattern of coronal filaments obtained with EIT/SOHO 171A also shows the helicity hemispheric tendency. Namely, 65% (71 of 110) of coronal filaments in the northern hemisphere exhibit negative helicity and the 65% (84 of 129) of filaments in the southern hemisphere show negative helicity. These data were observed in the same day with the SMART H-alpha data. Moreover, we found 12 filament eruptions in our data. The 7 of 12 filaments show the clear opposite sign of the hemispheric tendency of the magnetic helicity. The helicity seems to be change during temporal evolution. This results suggest that filament instability may be driven by the opposite sign helicity injection from the foot point of the barb.

  15. Electric events synchronized with laser filaments in thunderclouds.

    PubMed

    Kasparian, Jérôme; Ackermann, Roland; André, Yves-Bernard; Méchain, Grégoire; Méjean, Guillaume; Prade, Bernard; Rohwetter, Philipp; Salmon, Estelle; Stelmaszczyk, Kamil; Yu, Jin; Mysyrowicz, André; Sauerbrey, Roland; Wöste, Ludger; Wolf, Jean-Pierre

    2008-04-14

    We investigated the possibility to trigger real-scale lightning using ionized filaments generated by ultrashort laser pulses in the atmosphere. Under conditions of high electric field during two thunderstorms, we observed a statistically significant number of electric events synchronized with the laser pulses, at the location of the filaments. This observation suggests that corona discharges may have been triggered by filaments. PMID:18542684

  16. Direct Observation of Subunit Exchange along Mature Vimentin Intermediate Filaments

    PubMed Central

    Nöding, Bernd; Herrmann, Harald; Köster, Sarah

    2014-01-01

    Actin filaments, microtubules, and intermediate filaments (IFs) are central elements of the metazoan cytoskeleton. At the molecular level, the assembly mechanism for actin filaments and microtubules is fundamentally different from that of IFs. The former two types of filaments assemble from globular proteins. By contrast, IFs assemble from tetrameric complexes of extended, half-staggered, and antiparallel oriented coiled-coils. These tetramers laterally associate into unit-length filaments; subsequent longitudinal annealing of unit-length filaments yields mature IFs. In vitro, IFs form open structures without a fixed number of tetramers per cross-section along the filament. Therefore, a central question for the structural biology of IFs is whether individual subunits can dissociate from assembled filaments and rebind at other sites. Using the fluorescently labeled IF-protein vimentin for assembly, we directly observe and quantitatively determine subunit exchange events between filaments as well as with soluble vimentin pools. Thereby we demonstrate that the cross-sectional polymorphism of donor and acceptor filaments plays an important role. We propose that in segments of donor filaments with more than the standard 32 molecules per cross-section, subunits are not as tightly bound and are predisposed to be released from the filament. PMID:25517157

  17. Solar filament material oscillations and drainage before eruption

    SciTech Connect

    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.

  18. A penny-shaped crack in a filament-reinforced matrix. I - The filament model. II - The crack problem

    NASA Technical Reports Server (NTRS)

    Erdogan, F.; Pacella, A. H.

    1974-01-01

    The study deals with the elastostatic problem of a penny-shaped crack in an elastic matrix which is reinforced by filaments or fibers perpendicular to the plane of the crack. An elastic filament model is first developed, followed by consideration of the application of the model to the penny-shaped crack problem in which the filaments of finite length are asymmetrically distributed around the crack. Since the primary interest is in the application of the results to studies relating to the fracture of fiber or filament-reinforced composites and reinforced concrete, the main emphasis of the study is on the evaluation 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. Using the filament model developed, the elastostatic interaction problem between a penny-shaped crack and a slender inclusion or filament in an elastic matrix is formulated.

  19. 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.

  20. 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

  1. FRAGMENTATION AT THE EARLIEST PHASE OF MASSIVE STAR FORMATION

    SciTech Connect

    Zhang Qizhou; Wang Yang; Pillai, Thushara; Rathborne, Jill

    2009-05-01

    We present 1.3 mm continuum and spectral line images of two massive molecular clumps P1 and P2 in the G28.34+0.06 region with the Submillimeter Array (SMA). While the two clumps contain masses of 1000 and 880 M {sub sun}, respectively, P1 has a luminosity OF <10{sup 2} L {sub sun}, and a lower gas temperature and smaller line width than P2. Thus, P1 appears to be at a much earlier stage of massive star formation than P2. The high-resolution SMA observations reveal two distinctive cores in P2 with masses of 97 and 49 M {sub sun}, respectively. The 4 GHz spectral bandpass captures line emission from CO isotopologues, SO, CH{sub 3}OH, and CH{sub 3}CN, similar to hot molecular cores harboring massive young stars. The P1 clump, on the other hand, is resolved into five cores along the filament with masses from 22 to 64 M {sub sun} and an average projected separation of 0.19 pc. Except {sup 12}CO, no molecular line emission is detected toward the P1 cores at a 1{sigma} rms of 0.1 K. Since strong {sup 12}CO and C{sup 18}O emissions are seen with the single-dish telescope at a resolution of 11'', the nondetection of these lines with the SMA indicates a depletion factor up to 10{sup 3}. While the spatial resolution of the SMA is better than the expected Jeans length, the masses in P1 cores are much larger than the thermal Jeans mass, indicating the importance of turbulence and/or magnetic fields in cloud fragmentation. The hierarchical structures in the P1 region provide a glimpse of the initial phase of massive star and cluster formation.

  2. Holographically viable extensions of topologically massive and minimal massive gravity?

    NASA Astrophysics Data System (ADS)

    Altas, Emel; Tekin, Bayram

    2016-01-01

    Recently [E. Bergshoeff et al., Classical Quantum Gravity 31, 145008 (2014)], an extension of the topologically massive gravity (TMG) in 2 +1 dimensions, dubbed as minimal massive gravity (MMG), which is free of the bulk-boundary unitarity clash that inflicts the former theory and all the other known three-dimensional theories, was found. Field equations of MMG differ from those of TMG at quadratic terms in the curvature that do not come from the variation of an action depending on the metric alone. Here we show that MMG is a unique theory and there does not exist a deformation of TMG or MMG at the cubic and quartic order (and beyond) in the curvature that is consistent at the level of the field equations. The only extension of TMG with the desired bulk and boundary properties having a single massive degree of freedom is MMG.

  3. Stormy Clouds of Star Birth

    NASA Technical Reports Server (NTRS)

    2004-01-01

    Hidden behind a shroud of dust in the constellation Cygnus is an exceptionally bright source of radio emission called DR21. Visible light images reveal no trace of what is happening in this region because of heavy dust obscuration. In fact, visible light is attenuated in DR21 by a factor of more than 10,000,000,000,000,000,000,000,000,000, 000,000,000,000 (ten thousand trillion heptillion).

    New images from NASA's Spitzer Space Telescope allow us to peek behind the cosmic veil and pinpoint one of the most massive natal stars yet seen in our Milky Way galaxy. The never-before-seen star is 100,000 times as bright as the Sun. Also revealed for the first time is a powerful outflow of hot gas emanating from this star and bursting through a giant molecular cloud.

    This image shows a 24-micron image mosaic, obtained with the Multiband Imaging Photometer aboard Spitzer (MIPS). This image maps the cooler infrared emission from interstellar dust found throughout the interstellar medium. The DR21 complex is clearly seen near the center of the strip, which covers about twice the area of the IRAC image.

    Perhaps the most fascinating feature in this image is a long and shadowy linear filament extending towards the 10 o'clock position of DR21. This jet of cold and dense gas, nearly 50 light-years in extent, appears in silhouette against a warmer background. This filament is too long and massive to be a stellar jet and may have formed from a pre-existing molecular cloud core sculpted by DR21's strong winds. Regardless of its true nature, this jet and the numerous other arcs and wisps of cool dust signify the interstellar turbulence normally unseen by the human eye.

  4. Fracture of boron filaments in an aluminum matrix.

    NASA Technical Reports Server (NTRS)

    Steele, J. H.; Herring, H. W.

    1972-01-01

    The B-Al composite specimens tested in this study were fabricated by diffusion bonding of 1230 aluminum foil and boron filaments placed in alternate layers, using an acrylic resin solution to maintain filament spacing. The specimens were put under tensile stresses parallel to the filaments, and filament fracture was monitored acoustically under loads. Fracture of specimens under loads was caused by break propagation with a characteristic wedge-type fragmentation pattern indicating its direction. The aluminum foil matrix of the specimens failed by ductile shear type fracture after the break of the filaments.

  5. Laser filamentation induced bubbles and their motion in water.

    PubMed

    Liu, Fengjiang; Yuan, Shuai; Zuo, Zhong; Li, Wenxue; Ding, Liang'en; Zeng, Heping

    2016-06-13

    We demonstrate femtosecond filamentation induced convection in water by using a microscope directly observing the dynamic processes of the generated bubbles on a macroscopic time scale. The bubbles are driven by the filament in water and do directional movements. The angles between the bubbles' moving directions and the laser propagation direction varied at different positions along the filament, exhibiting a fusiform distribution. It indicates a fluid dynamic phenomenon depending on the local filament intensity, and reveals the convection processes induced by filamentation in water indirectly. PMID:27410343

  6. Stability of spiral wave vortex filaments with phase twists

    NASA Astrophysics Data System (ADS)

    Nam, Keeyeol; Ott, Edward; Guzdar, Parvez N.; Gabbay, Michael

    1998-08-01

    In this paper we investigate the stability of a straight vortex filament with phase twist described by the three-dimensional complex Ginzburg-Landau equation (CGLE). The results of the linear stability analysis show that the straight filament is stable in a limited region of the two parameter space of the CGLE. The stable region is dependent on the phase twist imposed on the filament and shrinks in size as the phase twist is increased. It is also shown numerically that the nonlinear evolution of an unstable initial straight filament can lead to a helical filament.

  7. 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)

  8. High-Resolution Observations of Sympathetic Filament Eruptions by NVST

    NASA Astrophysics Data System (ADS)

    Su, Yingna; Li, Shangwei; Zhou, Tuanhui; Ji, Haisheng

    2016-05-01

    We investigate the sympathetic eruptions of two solar filaments side by side as observed by the New Vacuum Solar Telescope (NVST) on 2015 October 15. These two filaments start from the complex active region NOAA 12434 (north) and end in a large quiescent region (south). The corresponding SDO/HMI magnetic field observations suggest that the two small filaments are located above two different polarity inversion lines in the northern part. The SDO/AIA observations of the eruption show that these two filaments appear to merge into one in the southern quiescent region. The north-eastern filament starts eruption firstly, which is followed by the north-western filament eruption about 20 minutes later. Clear untwisting motions (i.e., signature of flux ropes) are observed in both filaments during the eruption. After the lifts off of the north-western filament, mini filaments are observed to emerge from the surface and rise up multiple times. The high-resolution observations reveal the fact that the filament is composed of multiple sections and multiple layers. The filament in the lower layer can merge into the upper layer, which leads to the increase of non-potentiality of the upper layer. Magnetic field models using the flux rope insertion method are also constructed in order to understand the complex magnetic configuration as well as the initiation and dynamics of the eruptions.

  9. 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.

  10. 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

  11. Massive ascites of unknown origin

    PubMed Central

    Yuan, Shi-Min

    2014-01-01

    Massive ascites of unknown origin is an uncommon condition, which represent a diagnostic challenge. Patients with delayed diagnosis and treatment may have a poor prognosis. A 22-year-old female was referred to this hospital due to a 4-year progressive abdominal distension with massive ascites of unknown origin. By thorough investigations, she was eventually diagnosed as chronic calcified constrictive pericarditis. She received pericardiectomy and had an uneventful postoperative course. With a few day paracentesis, ascites did not progress any more. She was doing well at 5-month follow-up and has returned to work. Extracardiac manifestations, such as massive ascites and liver cirrhosis, were rare in patients with constrictive pericarditis. Pericardiectomy can be a radical solution for the treatment of chronic constrictive pericarditis. In order to avoid delayed diagnosis and treatment, physicians have to bear in mind this rare manifestation of chronic calcified constrictive pericarditis. PMID:24600502

  12. Positive signs in massive gravity

    NASA Astrophysics Data System (ADS)

    Cheung, Clifford; Remmen, Grant N.

    2016-04-01

    We derive new constraints on massive gravity from unitarity and analyticity of scattering amplitudes. Our results apply to a general effective theory defined by Einstein gravity plus the leading soft diffeomorphism-breaking corrections. We calculate scattering amplitudes for all combinations of tensor, vector, and scalar polarizations. The high-energy behavior of these amplitudes prescribes a specific choice of couplings that ameliorates the ultraviolet cutoff, in agreement with existing literature. We then derive consistency conditions from analytic dispersion relations, which dictate positivity of certain combinations of parameters appearing in the forward scattering amplitudes. These constraints exclude all but a small island in the parameter space of ghost-free massive gravity. While the theory of the "Galileon" scalar mode alone is known to be inconsistent with positivity constraints, this is remedied in the full massive gravity theory.

  13. 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.

  14. 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.

  15. Ionic wave propagation along actin filaments.

    PubMed

    Tuszyński, J A; Portet, S; Dixon, J M; Luxford, C; Cantiello, H F

    2004-04-01

    We investigate the conditions enabling actin filaments to act as electrical transmission lines for ion flows along their lengths. We propose a model in which each actin monomer is an electric element with a capacitive, inductive, and resistive property due to the molecular structure of the actin filament and viscosity of the solution. Based on Kirchhoff's laws taken in the continuum limit, a nonlinear partial differential equation is derived for the propagation of ionic waves. We solve this equation in two different regimes. In the first, the maximum propagation velocity wave is found in terms of Jacobi elliptic functions. In the general case, we analyze the equation in terms of Fisher-Kolmogoroff modes with both localized and extended wave characteristics. We propose a new signaling mechanism in the cell, especially in neurons. PMID:15041636

  16. Collective dynamics of active filament complexes

    NASA Astrophysics Data System (ADS)

    Nogucci, Hironobu; Ishihara, Shuji

    2016-05-01

    Networks of biofilaments are essential for the formation of cellular structures that support various biological functions. For the most part, previous studies have investigated the collective dynamics of rodlike biofilaments; however, the shapes of the actual subcellular components are often more elaborate. In this study, we considered an active object composed of two active filaments, which represents the progression from rodlike biofilaments to complex-shaped biofilaments. Specifically, we numerically assessed the collective behaviors of these active objects in two dimensions and observed several types of dynamics, depending on the density and the angle of the two filaments as shape parameters of the object. Among the observed collective dynamics, a moving density band that we named a "moving smectic" is introduced here for the first time. By analyzing the trajectories of individual objects and the interactions among them, this study demonstrated how interactions among active biofilaments with complex shapes could produce collective dynamics in a nontrivial manner.

  17. 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.

  18. Filament-wound composite vessels material technology

    NASA Technical Reports Server (NTRS)

    Lark, R. F.

    1973-01-01

    Programs are reviewed that were conducted to establish a technology base for applying advanced fibers or resins to high performance filament-wound pressure vessels for containment of cryogens and high pressure gases. Materials evaluated included boron, graphite, PRD 49-1 and 3/epoxy and S-glass/polyimide composites. Closed-end cylindrical, and oblate spheroid-shaped vessels were fabricated in 4- and 8-inch diameter sizes. Vessels were subjected to single-cycle burst, low-cycle fatigue, and sustained loading tests over a -423 F to room temperature range for epoxy composites and a -423 to 500 F temperature range for the polyimide composites. Vessels tested at cryogenic and/or 500 F had thin (3 to 20 mils) metallic liners whereas vessels tested at room temperature had elastomeric liners. Correlations between acoustic emissions and burst and cyclic properties of PRD 49-1 filament-wound vessels are discussed.

  19. Three Dimension Filamentous Human Cardiac Tissue Model

    PubMed Central

    Ma, Zhen; Koo, Sangmo; Finnegan, Micaela A.; Loskill, Peter; Huebsch, Nathaniel; Marks, Natalie C.; Conklin, Bruce R.; Grigoropoulos, Costas P.; Healy, Kevin E.

    2013-01-01

    A human in vitro cardiac tissue model would be a significant advancement for understanding, studying, and developing new strategies for treating cardiac arrhythmias and related cardiovascular diseases. We developed an in vitro model of three-dimensional (3D) human cardiac tissue by populating synthetic filamentous matrices with cardiomyocytes derived from healthy wild-type volunteer (WT) and patient-specific long QT syndrome type 3 (LQT3) induced pluripotent stem cells (iPS-CMs) to mimic the condensed and aligned human ventricular myocardium. Using such a highly controllable cardiac model, we studied the contractility malfunctions associated with the electrophysiological consequences of LQT3 and their response to a panel of drugs. By varying the stiffness of filamentous matrices, LQT3 iPS-CMs exhibited different level of contractility abnormality and susceptibility to drug-induced cardiotoxicity. PMID:24268663

  20. 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.

  1. Merging and energy exchange between optical filaments

    SciTech Connect

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

    2015-10-28

    We investigate nonlinear interaction between collinear femtosecond laser pulses with power slightly above the critical for self-focusing P{sub cr} 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.

  2. Transverse-mode dependence of femtosecond filamentation.

    PubMed

    Song, Zhenming; Zhang, Zhigang; Nakajima, Takashi

    2009-07-20

    We theoretically investigate the transverse-mode dependence of femtosecond filamentation in Ar gas. Three different transverse modes, Bessel, Gaussian, and Laguerre modes, are considered for incident laser pulses. By solving the extended nonlinear Schrödinger equation coupled with the electron density equation, we find that the lengths of the filament and the plasma channel induced by the Bessel incident beam is much longer than the other transverse modes with the same peak intensity, pulse duration, and beam diameter. Moreover we find that the temporal profile of the pulse with the Bessel incident mode is nearly undistorted during the propagation. Since the pulse energy that the Bessel beam can carry is more than one order of magnitude larger than the other modes for the same peak intensity, pulse duration, and beam diameter, the Bessel beam can be a very powerful tool in ultrafast nonlinear optics involving propagation in a Kerr medium. PMID:19654624

  3. Feedback During Massive Star Formation

    NASA Astrophysics Data System (ADS)

    Tanaka, Kei; Tan, Jonathan C.; Zhang, Yichen

    2016-01-01

    We present models of photoionization of massive protostellar cores, and show the impact of this ionization feedback on the efficiency of star formation and its observational features. Based on the Core Accretion scenario, we construct the collapse model of rotating massive-protostellar cloud cores together with a protostellar evolutional calculation, including feedback effects from a MHD disk wind, photoionization and radiation pressure. First, the MHD wind creates a bipolar outflow whose opening angle increases over the timescale of mass accretion. The ionizing luminosity dramatically increases after the protostar reaches ~ 5 Msun due to Kelvin-Helmholz contraction, and the MHD wind is photoionized when the protostellar mass reaches ~ 10 - 20 Msun. As the ionizing and bolometric luminosities increase, the outflow opening angle becomes wider due to radiation pressure feedback. By this combination of feedback processes, the envelope is eroded and the mass infall rate is significantly reduced to that arriving only from the disk-shielded equatorial region. At a protostellar mass of ~ 50 - 100 Msun, depending on the initial core properties, the mass accretion is halted by disk photoevaporation. In this way, feedback significantly reduces the star formation efficiency when forming massive stars from massive cloud cores, which could produce a cutoff at the high-mass end of the initial mass function. Along this evolutionary calculation, we also compute the detailed structure of the photoionized regions using a ray-tracing radiative transfer code and evaluate their emission signatures. Their free-free continuum and recombination line emissions are consistent with the variety of observed radio sources associated with massive protostars, i.e., jets and ultra/hyper-compact HII regions. The comparison between our models and such observations enables us to better define the evolutionary sequence of massive star formation.

  4. 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.

  5. 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.

  6. Self-reconstruction of light filaments.

    PubMed

    Dubietis, A; Kucinskas, E; Tamosauskas, G; Gaizauskas, E; Porras, M A; Di Trapani, P

    2004-12-15

    By observing how a light filament generated in water reconstructs itself after hitting a beam stopper in the presence and in the absence of a nonlinear medium, we describe the occurrence of an important linear contribution to reconstruction that is associated with the conical nature of the wave. A possible scenario by which conical wave components are generated inside the medium by the distributed stopper or reflector created by nonlinear losses or plasma is presented. PMID:15645815

  7. 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

  8. Periodic femtosecond filamentation in birefringent media

    NASA Astrophysics Data System (ADS)

    Blonskyi, I.; Kadan, V.; Shynkarenko, Y.; Yarusevych, O.; Korenyuk, P.; Puzikov, V.; Grin', L.

    2015-09-01

    We report on the experimental observation of periodic modulation of the axial luminescence intensity along the femtosecond filament track in sapphire and crystal quartz. The physical reason for the modulation is a cyclic transformation of the polarization state of the light pulse traveling in birefringent medium, caused by the phase raid between the ordinary and extraordinary rays, and different cross sections of multiphoton absorption for linear and circular polarizations.

  9. Origin and Evolution of Filament-Prominence Systems

    NASA Astrophysics Data System (ADS)

    Martens, Petrus C.; Zwaan, Cornelis

    2001-09-01

    We present a ``head-to-tail'' linkage model for the formation, evolution, and eruption of solar filaments. The magnetic field structure of our model is based on the observation that filaments form exclusively in filament channels with no apparent magnetic connections above the polarity inversion line. The formation of a filament in this configuration is driven by flux convergence and cancellation, which produces looplike filament segments with a half-turn. Filament segments of like chirality may connect and form long quiescent filaments. Such filaments are stabilized through footpoint anchoring until further cancellation at the footpoints causes their eruption. The eruption restores the original filament channel so that filament formation may resume immediately. We then demonstrate that the combined workings of Hale's polarity law, Joy's law, and differential rotation introduce a strong hemispheric preference in the chirality of filaments formed poleward of the sunspot belt, which is in agreement with observations. We analyze the magnetic fine structure of filaments formed through our model and find consistency with the observed hemispheric preference for barb orientation and a simple explanation for barb formation. Finally, we consider the flux tubes retracted below the surface in the process of filament formation. We show that every cancellation event that generates a filament obeying the hemispheric chirality preference injects a flux tube below the surface with a poloidal field opposite that of the ongoing cycle. We suggest that this pattern of submergence of flux represents the specific mechanism for the reversal of the poloidal flux in a Babcock-Leighton-Durney-type model for the solar dynamo.

  10. Population synthesis of massive stars

    NASA Astrophysics Data System (ADS)

    Vanbeveren, Dany

    2014-09-01

    This review deals with massive star population synthesis with a realistic population of binaries. We focus on the comparison between observed star numbers (as a function of metallicity) and theoretically predicted numbers of stellar populations in regions of continuous star formation and in starburst regions. Special attention is given to the O-type/WR/red supergiant stellar population, the population of blue supergiants, the pulsar and binary pulsar population, and the supernova rates. Finally, we consider massive double compact star mergers and the link with gravitational wave sources (the advanced LIGO II) and r-process element production sites.

  11. Sedeonic Equations of Massive Fields

    NASA Astrophysics Data System (ADS)

    Mironov, Sergey V.; Mironov, Victor L.

    2015-01-01

    Prior work on space-time sedeon algebra models relativistic quantum mechanical equation of motion with corresponding field equations, mediated by massive or massless spin-1 or spin-1/2 particles. In the massless spin-1 case, such exchange particles mediate fields in analogy to Maxwell's equations in Lorentz gauge. This paper demonstrates fundamental aspects of massive field's theory, such as gauge invariance, charge conservation, Poynting's theorem, potential of a stationary scalar point source, plane wave solution, and interaction between point sources. We briefly discuss some aspects of sedeonic algebra and their potential physical applications.

  12. Massive Gravitons on Bohmian Congruences

    NASA Astrophysics Data System (ADS)

    Fathi, Mohsen; Mohseni, Morteza

    2016-08-01

    Taking a quantum corrected form of Raychaudhuri equation in a geometric background described by a Lorentz-violating massive theory of gravity, we go through investigating a time-like congruence of massive gravitons affected by a Bohmian quantum potential. We find some definite conditions upon which these gravitons are confined to diverging Bohmian trajectories. The respective behaviour of those quantum potentials are also derived and discussed. Additionally, and through a relativistic quantum treatment of a typical wave function, we demonstrate schematic conditions on the associated frequency to the gravitons, in order to satisfy the necessity of divergence.

  13. Interferometric Mapping of Magnetic Fields: The ALMA View of the Massive Star-forming Clump W43-MM1

    NASA Astrophysics Data System (ADS)

    Cortes, Paulo C.; Girart, Josep M.; Hull, Charles L. H.; Sridharan, Tirupati K.; Louvet, Fabien; Plambeck, Richard; Li, Zhi-Yun; Crutcher, Richard M.; Lai, Shih-Ping

    2016-07-01

    Here, we present the first results from ALMA observations of 1 mm polarized dust emission toward the W43-MM1 high-mass star-forming clump. We have detected a highly fragmented filament with source masses ranging from 14 M {}ȯ to 312 M {}ȯ , where the largest fragment, source A, is believed to be one of the most massive in our Galaxy. We found a smooth, ordered, and detailed polarization pattern throughout the filament, which we used to derived magnetic field morphologies and strengths for 12 out of the 15 fragments detected ranging from 0.2 to 9 mG. The dynamical equilibrium of each fragment was evaluated finding that all the fragments are in a super-critical state that is consistent with previously detected infalling motions toward W43-MM1. Moreover, there are indications suggesting that the field is being dragged by gravity as the whole filament is collapsing.

  14. Filament-stretching rheometry of complex fluids

    NASA Astrophysics Data System (ADS)

    McKinley, Gareth H.; Sridhar, Tamarapu

    Filament-stretching rheometers are devices for measuring the extensional viscosity of moderately viscous non-Newtonian fluids such as polymer solutions. In these devices, a cylindrical liquid bridge is initially formed between two circular end-plates. The plates are then moved apart in a prescribed manner such that the fluid sample is subjected to a strong extensional deformation. Asymptotic analysis and numerical computation show that the resulting kinematics closely approximate those of an ideal homogeneous uniaxial elongation. The evolution in the tensile stress (measured mechanically) and the molecular conformation (measured optically) can be followed as functions of the rate of stretching and the total strain imposed. The resulting rheological measurements are a sensitive discriminant of molecularly based constitutive equations proposed for complex fluids. The dynamical response of the elongating filament is also coupled to the extensional rheology of the polymeric test fluid, and this can lead to complex viscoelastic-flow instabilities such as filament necking and rupture or elastic peeling from the rigid end-plates.

  15. 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

  16. 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

  17. Filament Channel Formation by Helicity Condensation

    NASA Astrophysics Data System (ADS)

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

    2013-12-01

    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 also represents magnetic helicity, which is conserved under reconnection. Consequently, the observations raise the question: Why is helicity observed to be concentrated along PILs? Preliminary results of 3D MHD simulations using the Adaptively Refined MHD Solver (ARMS) are presented that support the magnetic-helicity condensation model of filament-channel formation (Antiochos 2013). In this work, we address the problem of filament-channel formation by considering supergranular twisting of a quasi-potential flux system, bounded by a PIL and containing a coronal hole (CH). The magnetic helicity injected by 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 boundary. This, in effect, produces field lines that are both sheared and smooth and, in agreement with Antiochos (2013), are sheared in opposite senses at the PIL and the CH. We present a detailed analysis of our simulation results and discuss their implications for observations.

  18. 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.

  19. 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.

  20. Mechanical Properties of Intermediate Filament Proteins.

    PubMed

    Charrier, Elisabeth E; Janmey, Paul A

    2016-01-01

    Purified intermediate filament (IF) proteins can be reassembled in vitro to produce polymers closely resembling those found in cells, and these filaments form viscoelastic gels. The cross-links 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 nonlinear elasticity with stiffness, as quantified by shear modulus, increasing an order of magnitude as the networks are deformed to large strains resembling those that soft tissues undergo in vivo. Individual IFs can be stretched to more than two or three times their resting length without breaking. At least 10 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 cytoplasmic IFs 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

  1. ACQUA: Automated Cyanobacterial Quantification Algorithm for toxic filamentous genera using spline curves, pattern recognition and machine learning.

    PubMed

    Gandola, Emanuele; Antonioli, Manuela; Traficante, Alessio; Franceschini, Simone; Scardi, Michele; Congestri, Roberta

    2016-05-01

    Toxigenic cyanobacteria are one of the main health risks associated with water resources worldwide, as their toxins can affect humans and fauna exposed via drinking water, aquaculture and recreation. Microscopy monitoring of cyanobacteria in water bodies and massive growth systems is a routine operation for cell abundance and growth estimation. Here we present ACQUA (Automated Cyanobacterial Quantification Algorithm), a new fully automated image analysis method designed for filamentous genera in Bright field microscopy. A pre-processing algorithm has been developed to highlight filaments of interest from background signals due to other phytoplankton and dust. A spline-fitting algorithm has been designed to recombine interrupted and crossing filaments in order to perform accurate morphometric analysis and to extract the surface pattern information of highlighted objects. In addition, 17 specific pattern indicators have been developed and used as input data for a machine-learning algorithm dedicated to the recognition between five widespread toxic or potentially toxic filamentous genera in freshwater: Aphanizomenon, Cylindrospermopsis, Dolichospermum, Limnothrix and Planktothrix. The method was validated using freshwater samples from three Italian volcanic lakes comparing automated vs. manual results. ACQUA proved to be a fast and accurate tool to rapidly assess freshwater quality and to characterize cyanobacterial assemblages in aquatic environments. PMID:27012737

  2. Mass loss of massive stars

    NASA Astrophysics Data System (ADS)

    Martins, F.

    2015-12-01

    In this contribution we review the properties of the winds of massive stars. We focus on OB stars, red supergiants, Luminous Blue Variables (LBVs) and Wolf-Rayet stars. For each type of star, we summarize the main wind properties and we give a brief description of the physical mechanism(s) responsible for mass loss.

  3. Massively parallel visualization: Parallel rendering

    SciTech Connect

    Hansen, C.D.; Krogh, M.; White, W.

    1995-12-01

    This paper presents rendering algorithms, developed for massively parallel processors (MPPs), for polygonal, spheres, and volumetric data. The polygon algorithm uses a data parallel approach whereas the sphere and volume renderer use a MIMD approach. Implementations for these algorithms are presented for the Thinking Machines Corporation CM-5 MPP.

  4. Dark matter in massive galaxies

    NASA Astrophysics Data System (ADS)

    Gerhard, Ortwin

    2013-07-01

    The spatial distributions of luminous and dark matter in massive early-type galaxies (ETGs) reflect the formation processes which shaped these systems. This article reviews the predictions of cosmological simulations for the dark and baryonic components of ETGs, and the observational constraints from lensing, hydrostatic X-ray gas atmospheres, and outer halo stellar dynamics.

  5. Sinus histiocytosis with massive lymphadenopathy

    SciTech Connect

    Pastakia, B.; Weiss, S.H.

    1987-11-01

    Gallium uptake corresponding to the extent of the disease in a patient with histologically proven sinus histiocytosis with massive lymphadenopathy (SHML) is reported. Computerized tomography confirmed the presence of bilateral retrobulbar masses, involvement of both lateral recti, erosion of the bony orbital floor with encroachment of tumor into the right maxillary antrum, and retropharyngeal involvement.

  6. Understanding massively open online courses.

    PubMed

    Billings, Diane M

    2014-02-01

    Massively open online courses (MOOCs) are an innovative delivery system for educational offerings. MOOCs have been hailed with optimism for making education accessible to many, but at the same time, they have been criticized for poor participant completion rates. Nurse educators are considering whether and how to use MOOCs; this column explains MOOCs and their advantages and disadvantages for nurse educators. PMID:24494660

  7. 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

  8. 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. PMID:24519712

  9. Motions and oscillations in a filament preceding its eruption

    NASA Astrophysics Data System (ADS)

    Mashnich, G. P.; Bashkirtsev, V. S.

    2016-02-01

    The Doppler motions in a filament and the underlying photosphere over the several days before its eruption are analyzed. A large filament in the northern hemisphere near the central meridian observed from August 31-September 2, 2014 erupted on September 2, 2014. The filament lost the bulk of its mass as a result of its eruption, and the process of its reconstruction had begun a day later. Observations of this filament in a spectral range encompassing the Hβ λ 486.1 nm (chromospheric) and Fe I λ 485.9 nm (photospheric) lines were carried out on the Horizontal Solar Telescope of the Sayan Solar Observatory on August 31-September 2, 2014. Analysis of the Doppler motions in and beneath the filament yielded the following results. Strong rotational motions were present in the filament over a prolonged period (the entire three days of observations). The coincidence of the steady-state motions of the photosphere and filament was disrupted at the moment of destabilization of the filament by the emergence of new magnetic flux. Short-period (about five-minute) photospheric oscillationswith a train-like character arose in filament from time to time several hours before the eruption. Large segments underwent nearly vertical oscillations in the initial phase of the ascent of the filament.

  10. 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. PMID:26240174

  11. 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).

  12. Microtubule-dependent transport and dynamics of vimentin intermediate filaments

    PubMed Central

    Hookway, Caroline; Ding, Liya; Davidson, Michael W.; Rappoport, Joshua Z.; Danuser, Gaudenz; Gelfand, Vladimir I.

    2015-01-01

    We studied two aspects of vimentin intermediate filament dynamics—transport of filaments and subunit exchange. We observed transport of long filaments in the periphery of cells using live-cell structured illumination microscopy. We studied filament transport elsewhere in cells using a photoconvertible-vimentin probe and total internal reflection microscopy. We found that filaments were rapidly transported along linear tracks in both anterograde and retrograde directions. Filament transport was microtubule dependent but independent of microtubule polymerization and/or an interaction with the plus end–binding protein APC. We also studied subunit exchange in filaments by long-term imaging after photoconversion. We found that converted vimentin remained in small clusters along the length of filaments rather than redistributing uniformly throughout the network, even in cells that divided after photoconversion. These data show that vimentin filaments do not depolymerize into individual subunits; they recompose by severing and reannealing. Together these results show that vimentin filaments are very dynamic and that their transport is required for network maintenance. PMID:25717187

  13. Geometry of flexible filament cohesion: better contact through twist?

    PubMed

    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. PMID:25381544

  14. Dynamics of solar filaments. IV - Structure and mass flow of an active region filament

    NASA Technical Reports Server (NTRS)

    Schmieder, B.; Malherbe, J. M.; Simon, G.; Poland, A. I.

    1985-01-01

    An active region filament near the center of the solar disk was observed on September 29-30, 1980, with the Multichannel Subtractive Double Pass Spectrograph of the Meudon solar tower and the UV Spectrograph and Polarimeter aboard the SMM satellite. H-alpha and C IV measurements are presently used to study brightness and material velocity in the 10,000 and 100,000 K temperature ranges, and photospheric magnetograms are used to investigate the underlying magnetic field. Attention is given to the constraints imposed on possible filament structures by observations, as well as the expected MHD relationships.

  15. Filament Recognition In Solar Images With The Neural Network Technique

    NASA Astrophysics Data System (ADS)

    Zharkova, V. V.; Schetinin, V.

    2005-05-01

    We describe a new technique developed for an automated recognition of solar filaments visible in Hα hydrogen line full-disk spectroheliograms. These filaments are difficult to recognize because of variability in the background caused by atmospheric conditions. The presented technique is based on an artificial neural network (ANN) consisting of two hidden neurons and one output neuron which learn to exclude the contribution of a changeable background to a filament. The ANN is trained on a single image fragment labeled manually to recognize the filament elements depicted on a local background. The background contribution is approximated with linear and parabolic functions. This technique applied to the filament recognition in 54 cropped images reveals better detection results for a parabolic approximation than for a linear one approaching an accuracy of about 82% of the total filament pixels.

  16. Simulation of Current Filaments in Photoconductive Semiconductor Switches

    NASA Astrophysics Data System (ADS)

    Kambour, K.; Myles, Charles W.

    2005-03-01

    Optically-triggered, high-power photoconductive semiconductor switches (PCSS's) using semi-insulating GaAs are under development at Sandia. These switches carry current in high carrier-density filaments. The properties of these filaments can be explained by collective impact ionization theory in which energy redistribution by carrier-carrier scattering within the filament enhances the impact ionization. This allows these filaments to be sustained by fields which are relatively low compared to the bulk breakdown fields. For GaAs, the sustaining field is approximately 4.5 kV/cm. For this talk, a hydrodynamic implementation of the collective impact ionization theory is used to compute the properties of these filaments. These continuum calculations are based on previous calculations in which the steady-state properties of filaments are computed using a Monte Carlo method to solve the Boltzmann equation. The effects of defects will also be considered in the presentation of the results.

  17. Filamentation Instability of Counterpropagating Charged Particle Beams: Statistical Properties

    SciTech Connect

    Dieckmann, M. E.

    2008-10-15

    The filamentation instability (FI) driven by beams of counter-propagating electrons is examined with one-dimensional (1D) and two-dimensional (2D) particle-in-cell (PIC) simulations. The 1D simulation reveals the saturation mechanism of the FI. The magnetic pressure gradient displaces the electrons. The resulting electrostatic field inhibits together with the magnetic field a further growth of the filaments by suppressing the electron motion. The FI evolves into a stationary equilibrium in 1D, which shows a statistical distribution of the filament sizes that resembles a Gumbel distribution. The 2D PIC simulation allows the filaments to move around each other and filaments carrying currents of equal polarity can merge. The time-evolution of the characteristic size of the filaments in the 2D simulation is measured. It increases linearly with the time.

  18. A filament supported by different magnetic field configurations

    NASA Astrophysics Data System (ADS)

    Guo, Y.; Schmieder, B.; Démoulin, P.; Wiegelmann, T.; Aulanier, G.; Török, T.; Bommier, V.

    2011-08-01

    A nonlinear force-free magnetic field extrapolation of vector magnetogram data obtained by THEMIS/MTR on 2005 May 27 suggests the simultaneous existence of different magnetic configurations within one active region filament: one part of the filament is supported by field line dips within a flux rope, while the other part is located in dips within an arcade structure. Although the axial field chirality (dextral) and the magnetic helicity (negative) are the same along the whole filament, the chiralities of the filament barbs at different sections are opposite, i.e., right-bearing in the flux rope part and left-bearing in the arcade part. This argues against past suggestions that different barb chiralities imply different signs of helicity of the underlying magnetic field. This new finding about the chirality of filaments will be useful to associate eruptive filaments and magnetic cloud using the helicity parameter in the Space Weather Science.

  19. 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

  20. Concentration profiles in drying cylindrical filaments

    NASA Astrophysics Data System (ADS)

    Czaputa, Klaus; Brenn, Günter; Meile, Walter

    2008-12-01

    We analyze theoretically the drying of cylindrical filaments. For modelling the mass transfer on the gas side of the liquid-gas interface of the shrinking circular cylindrical filament, we apply the model of Abramzon and Sirignano, which was originally developed for spherical geometry. As a consequence of mass transfer at constant Sherwood number, we obtain a d2-law for the shrinkage of the cylinder as in the case of the spherical geometry, which expresses that the cross-sectional area of the cylinder shrinks at a constant rate with time. For this situation, the diffusion equation for the liquid phase mixture components becomes separable upon transformation into similarity coordinates and is solved analytically to obtain the concentration profiles inside the filament as functions of time. The dependency of the profiles on the radial coordinate is determined by a series of Kummer’s functions. Applying this result, we study the evolution of the concentration profiles in the liquid phase with time as dependent on a parameter given as the ratio of rate of shrinkage of the cross-sectional area of the cylinder to liquid-phase diffusion coefficient, which was identified as relevant for the shape of the concentration profiles formed in the liquid during the drying process. As an example, we present computed results for the constant evaporation rate regime in the dry-spinning process of a polyvinyl-alcohol (PVA)-water system. Comparison of our analytical results with full numerical solutions of the diffusion equation from the literature, achieved with concentration-dependent diffusion coefficient, reveals very good agreement.

  1. 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.

  2. Self-organized Propagation of Femtosecond Laser Filamentation in Air

    NASA Astrophysics Data System (ADS)

    Zhang, Jie; Hao, Zuoqiang; Xi, Tingting; Lu, Xin; Zhang, Zhe; Yang, Hui; Jin, Zhan; Wang, Zhaohua; Wei, Zhiyi

    A long plasma channel is formed with a length up to a few hundred meters when intense femtosecond laser pulses propagate in air. We find that the propagation of the filaments in the channel shows a very complicated process including the evolution from a single filament into two and three and even more distinct filaments periodically, and the merging of multiple filaments into two filaments that propagate stably and fade away eventually. From the point of view of applications, the lifetime of the plasma channel can be prolonged to the order of microseconds when another sub-ns laser pulse is introduced. The filaments' distribution is optimized using a pinhole with different diameters. Our experiments also demonstrate simultaneous triggering and guiding of large gap discharges in air by laser filaments. A new concept of "laser plasma channel propulsion" is proposed. It is demonstrated that the plasma channel can continuously propel a light paper airplane without complicated focusing optics. As for the long distance propagation of the laser pulses, the filamentation process and the surpercontinuum (SC) emission are closely dependent on the initial negative chirp and the divergence angle of the laser beam. Most of laser energy deposited in the background serves as an energy reservoir for further propagation of the filamentation. We have shown that an energy reservoir over ten times the size of the filament core (mm size) is necessary to feed a single filament undisturbed propagation. At last, the characteristics of the multiple filaments formed by pre-focused and freely propagating fs laser pulses are investigated and compared.

  3. Filamentation of ultrashort laser pulses propagating in tenuous plasmas

    SciTech Connect

    Andreev, N. E.; Gorbunov, L. M.; Mora, P.; Ramazashvili, R. R.

    2007-08-15

    The filamentation of ultrashort laser pulses (shorter than a plasma period) propagating in tenuous plasmas is studied. In this regime relativistic and ponderomotive nonlinearities tend to cancel each other. Time-dependent residual nonlinear plasma response brings about the dynamical filamentation with the maximum unstable transverse wave number decreasing in the course of laser pulse propagation. Dynamics of a hot spot that seeds the filamentation instability is studied numerically and reveals a good agreement with the analytical results.

  4. A Conceptual Model of the Formation of Filament Barbs

    NASA Astrophysics Data System (ADS)

    Martin, S. F.

    1997-05-01

    Barbs are the structures along the sides of a filament that connect its horizontal axis to chromosphere. The barbs, previously called 'legs' can be considered as magnetic field conduits along which mass is continuously guided and transported to and from the chromosphere. In the model presented, the barbs represent a secondary stage in filament formation which follows an intial stage in which a nearly horizontal axial magnetic field is first formed along a filament channel. Barb formation is most effectively and readily illustrated where the filament channel is broad and well-developed such as exists among the decaying network remnants of active regions. In these circumstances, the filament channel is a region of relatively low magnetic flux density compared to adjacent areas further from the polarity inversion. H-alpha filtergrams show that the axial parts of the filament are low and nearly contiguous with the chromosphere. The low height of the axial field, and the relative absence of concentrations of network magnetic field, are favorable conditions for magnetic reconnection between the axial field of the filament and new ephemeral regions and intranetwork magnetic fields beneath the filament. These reconnections lead to the formation of the barbs joining parts of the newly emerged fields to the axial field of the filament. Barb formation and motions seen in H-alpha filtergrams provide the evidence for this initial part of the conceptual model. The remaining part of the model is a demonstration of why only right-bearing barbs are seen on dextral filaments and left-bearing barbs on sinistral filaments; this is due to the sinistral or dextral magnetic configuration of the filament channel which does not permit the survival of barbs of the non-observed chirality as will be illustrated.

  5. Case study of a complex active-region filament eruption

    NASA Astrophysics Data System (ADS)

    Yan, X. L.; Qu, Z. Q.; Kong, D. F.; Deng, L. H.; Xue, Z. K.

    2013-09-01

    Context. We investigated a solar active-region filament eruption associated with a C6.6 class flare and a coronal mass ejection (CME) in NOAA active region 08858 on 2000 February 9. Aims: We aim to better understand the relationship between filament eruptions and the associated flares and CMEs. Methods: Using BBSO, SOHO/EIT, and TRACE observational data, we analyzed the process of the active-region filament eruption in the chromosphere and the corona. Using the SOHO/MDI magnetograms, we investigated the change of the magnetic fields in the photosphere. Using the GOES soft X-ray flux and the SOHO/LASCO images, we identified the flare and CME, which were associated with this active-region filament eruption. Results: The brightenings in the chromosphere are a precursor of the filament expansion. The eruption itself can be divided into four phases: In the initial phase, the intertwined bright and dark strands of the filament expand. Then, the bright strands are divided into three parts with different expansion velocity. Next, the erupting filament-carrying flux rope expands rapidly and combines with the lower part of the expanding bright strands. Finally, the filament erupts accompanied by other dark strands overlying the filament.The overlying magnetic loops and the expansion of the filament strands can change the direction of the eruption. Conclusions: The time delay between the velocity peaks of the filament and that of the two parts of the bright strands clearly demonstrates that the breakup of the bright loops tying on the filament into individual strands is important for its eruption. The eruption is a collection of multiple processes that are physically coupled rather than a single process.

  6. Filamentous Basidiomycetes in the Clinical Laboratory

    PubMed Central

    2015-01-01

    Filamentous basidiomycetes are difficult to identify in the clinical laboratory, mostly due to lack of sporulation, and their role as agents of fungal infection can be difficult to assess. More cases of infection with these agents are being reported as more laboratories gain proficiency with the recognition of their subtle morphologic features and the use of DNA-based methods for identification. Most infections occur in the respiratory tract and sinuses, although brain infection has been reported. Susceptibility testing suggests that these agents will respond well to azole drugs other than fluconazole. PMID:26512308

  7. Filamentous bacteria transport electrons over centimetre distances.

    PubMed

    Pfeffer, Christian; Larsen, Steffen; Song, Jie; Dong, Mingdong; Besenbacher, Flemming; Meyer, Rikke Louise; Kjeldsen, Kasper Urup; Schreiber, Lars; Gorby, Yuri A; El-Naggar, Mohamed Y; Leung, Kar Man; Schramm, Andreas; Risgaard-Petersen, Nils; Nielsen, Lars Peter

    2012-11-01

    Oxygen consumption in marine sediments is often coupled to the oxidation of sulphide generated by degradation of organic matter in deeper, oxygen-free layers. Geochemical observations have shown that this coupling can be mediated by electric currents carried by unidentified electron transporters across centimetre-wide zones. Here we present evidence that the native conductors are long, filamentous bacteria. They abounded in sediment zones with electric currents and along their length they contained strings with distinct properties in accordance with a function as electron transporters. Living, electrical cables add a new dimension to the understanding of interactions in nature and may find use in technology development. PMID:23103872

  8. Hamiltonian Dynamics of Protein Filament Formation

    NASA Astrophysics Data System (ADS)

    Michaels, Thomas C. T.; Cohen, Samuel I. A.; Vendruscolo, Michele; Dobson, Christopher M.; Knowles, Tuomas P. J.

    2016-01-01

    We establish the Hamiltonian structure of the rate equations describing the formation of protein filaments. We then show that this formalism provides a unified view of the behavior of a range of biological self-assembling systems as diverse as actin, prions, and amyloidogenic polypeptides. We further demonstrate that the time-translation symmetry of the resulting Hamiltonian leads to previously unsuggested conservation laws that connect the number and mass concentrations of fibrils and allow linear growth phenomena to be equated with autocatalytic growth processes. We finally show how these results reveal simple rate laws that provide the basis for interpreting experimental data in terms of specific mechanisms controlling the proliferation of fibrils.

  9. 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.

  10. Filamentation of laser in an inhomogeneous plasma

    SciTech Connect

    Singh, Ranjeet; Tripathi, V. K.

    2011-02-15

    Filamentation of an intense short pulse laser in an inhomogeneous plasma is investigated when laser propagates along the direction of density gradient and nonlinearity arises due to the relativistic mass variation and ponderomotive force. The ion motion is neglected; however, the effect of dielectric swelling is included. The inhomogeneity in the density profile introduces dielectric swelling of the pump intensity enhancing the plasma permittivity and the growth rate of the instability. The perturbation in laser amplitude grows faster than exponential as the laser penetrates deeper into the denser plasma.

  11. The interaction energy of charged filaments in an electrolyte: Results for all filament spacings.

    PubMed

    Smith, D A

    2011-05-01

    Electrically charged long-chain macromolecules in an electrolyte can form an ordered lattice whose spacing is greater than their diameter. If entropic effects are neglected, these nematic structures can be predicted from a balance of Coulomb repulsion and van-der-Waals attraction forces. To enhance the utility of such theories, this paper extends existing results for the interaction between charged filaments, and gives approximate formulae for the screened Coulomb and van-der-Waals potentials over the whole range of their centre-to-centre spacing d. The repulsive Coulomb potential is proportional to exp(-λd)/λd for all spacings when the Debye screening length 1/λ is smaller than the sum of the filament radii. The attractive van-der-Waals potential is asymptotic to d⁻⁵ at large d. For smaller spacings, the potential is calculated by numerical integration and compared with published formulae: the series expansion of Brenner and McQuarrie converges too slowly, whereas the interpolation formula of Moisescu provides reasonable accuracy over the whole range of d. Combining these potentials shows that there is a finite range of charge densities for which a nematic crystal lattice is stable, but this conclusion ignores entropic effects associated with motile filaments. The role of electrostatic forces in aligning filaments and stabilizing a nematic liquid-crystal phase is discussed, in conjunction with other mechanisms such as motor proteins, crosslinkers or scaffolding structures. PMID:21295590

  12. Assembly of Simple Epithelial Keratin Filaments: Deciphering the Ion Dependence in Filament Organization.

    PubMed

    Hémonnot, Clément Y J; Mauermann, Monika; Herrmann, Harald; Köster, Sarah

    2015-10-12

    The intermediate filament proteins keratin K8 and K18 constitute an essential part of the cytoskeleton in simple epithelial cell layers, structurally enforcing their mechanical resistance. K8/K18 heterodimers form extended filaments and higher-order structures including bundles and networks that bind to cell junctions. We study the assembly of these proteins in the presence of monovalent or divalent ions by small-angle X-ray scattering. We find that both ion species cause an increase of the filament diameter when their concentration is increased; albeit, much higher values are needed for the monovalent compared to the divalent ions for the same effect. Bundling occurs also for monovalent ions and at comparatively low concentrations of divalent ions, very different from vimentin intermediate filaments, a fibroblast-specific cytoskeleton component. We explain these differences by variations in charge and hydrophobicity patterns of the proteins. These differences may reflect the respective physiological situation in stationary cell layers versus single migrating fibroblasts. PMID:26327161

  13. 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.

  14. Properties of cosmological filaments extracted from Eulerian simulations

    NASA Astrophysics Data System (ADS)

    Gheller, C.; Vazza, F.; Favre, J.; Brüggen, M.

    2015-10-01

    Using a new parallel algorithm implemented within the VisIt framework, we analysed large cosmological grid simulations to study the properties of baryons in filaments. The procedure allows us to build large catalogues with up to ˜3 × 104 filaments per simulated volume and to investigate the properties of cosmic filaments for very large volumes at high resolution (up to 3003 Mpc3 simulated with 20483 cells). We determined scaling relations for the mass, volume, length and temperature of filaments and compared them to those of galaxy clusters. The longest filaments have a total length of about 200 Mpc with a mass of several 1015 M⊙. We also investigated the effects of different gas physics. Radiative cooling significantly modifies the thermal properties of the warm-hot-intergalactic medium of filaments, mainly by lowering their mean temperature via line cooling. On the other hand, powerful feedback from active galactic nuclei in surrounding haloes can heat up the gas in filaments. The impact of shock-accelerated cosmic rays from diffusive shock acceleration on filaments is small and the ratio between cosmic ray and gas pressure within filaments is of the order of ˜10-20 per cent.

  15. 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.

  16. Interaction of Two Filament Channels of Different Chiralities

    NASA Astrophysics Data System (ADS)

    Joshi, Navin Chandra; Filippov, Boris; Schmieder, Brigitte; Magara, Tetsuya; moon, Young-Jae; Uddin, Wahab

    2016-07-01

    We present observations of the interactions between the two filament channels of different chiralities and associated dynamics that occurred during 2014 April 18–20. While two flux ropes of different helicity with parallel axial magnetic fields can only undergo a bounce interaction when they are brought together, the observations at first glance show that the heated plasma is moving from one filament channel to the other. The SDO/AIA 171 Å observations and the potential-field source-surface magnetic field extrapolation reveal the presence of a fan-spine magnetic configuration over the filament channels with a null point located above them. Three different events of filament activations, partial eruptions, and associated filament channel interactions have been observed. The activation initiated in one filament channel seems to propagate along the neighboring filament channel. We believe that the activation and partial eruption of the filaments brings the field lines of flux ropes containing them closer to the null point and triggers the magnetic reconnection between them and the fan-spine magnetic configuration. As a result, the hot plasma moves along the outer spine line toward the remote point. Utilizing the present observations, for the first time we have discussed how two different-chirality filament channels can interact and show interrelation.

  17. 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.

  18. 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.

  19. Electron tunneling into superconducting filaments using mechanically adjustable barriers

    NASA Astrophysics Data System (ADS)

    Moreland, John; Ekin, J. W.

    1985-07-01

    A new type of squeezable electron tunneling (SET) junction has been developed for tunneling into superconducting filaments. Stable, mechanically adjustable tunneling barriers between the native surfaces of sputtered Nb films and 30-μm-diam Nb filaments were established in liquid helium at 4 K. The current versus voltage characteristics of these SET junctions were used to determine the superconducting energy gap at the surface of the filaments. Since the filaments were etched from commercial superconducting magnet wire, this type of tunnel junction shows promise as a diagnostic probe of superconducting materials for high-field magnets.

  20. 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.

  1. 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.

  2. 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

  3. Plasma temperature clamping in filamentation laser induced breakdown spectroscopy.

    PubMed

    Harilal, S S; Yeak, J; Phillips, M 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 filament 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 explain the near absence of ion emission but strong atomic neutral emission from plumes produced during fs LIBS in air. PMID:26480372

  4. Modeling Vertical Plasma Flows in Solar Filament Barbs

    NASA Astrophysics Data System (ADS)

    Litvinenko, Y.

    2003-12-01

    Speeds of observed flows in quiescent solar filaments are typically much less than the local Alfvén speed. This is why the flows in filament barbs can be modeled by perturbing a local magnetostatic solution describing the balance between the Lorentz force, gravity, and gas pressure in a barb. Similarly, large-scale filament flows can be treated as adiabatically slow deformations of a force-free magnetic equilibrium that describes the global structure of a filament. This approach reconciles current theoretical models with the puzzling observational result that some of the flows appear to be neither aligned with the magnetic field nor controlled by gravity.

  5. Chiral description of massive gravity

    NASA Astrophysics Data System (ADS)

    Alexandrov, Sergei; Krasnov, Kirill; Speziale, Simone

    2013-06-01

    We propose and study a new first order version of the ghost-free massive gravity. Instead of metrics or tetrads, it uses a connection together with Plebanski's chiral 2-forms as fundamental variables, rendering the phase space structure similar to that of SU(2) gauge theories. The chiral description simplifies computations of the constraint algebra, and allows us to perform the complete canonical analysis of the system. In particular, we explicitly compute the secondary constraint and carry out the stabilization procedure, thus proving that in general the theory propagates 7 degrees of freedom, consistently with previous claims. Finally, we point out that the description in terms of 2-forms opens the door to an infinite class of ghost-free massive bi-gravity actions. Our results apply directly to Euclidean signature. The reality conditions to be imposed in the Lorentzian signature appear to be more complicated than in the usual gravity case and are left as an open issue.

  6. Massive gravity on a brane

    SciTech Connect

    Chacko, Z.; Graesser, M.L.; Grojean, C.; Pilo, L.

    2003-12-11

    At present no theory of a massive graviton is known that is consistent with experiments at both long and short distances. The problem is that consistency with long distance experiments requires the graviton mass to be very small. Such a small graviton mass however implies an ultraviolet cutoff for the theory at length scales far larger than the millimeter scale at which gravity has already been measured. In this paper we attempt to construct a model which avoids this problem. We consider a brane world setup in warped AdS spacetime and we investigate the consequences of writing a mass term for the graviton on a the infrared brane where the local cutoff is of order a large (galactic) distance scale. The advantage of this setup is that the low cutoff for physics on the infrared brane does not significantly affect the predictivity of the theory for observers localized on the ultraviolet brane. For such observers the predictions of this theory agree with general relativity at distances smaller than the infrared scale but go over to those of a theory of massive gravity at longer distances. A careful analysis of the graviton two-point function, however, reveals the presence of a ghost in the low energy spectrum. A mode decomposition of the higher dimensional theory reveals that the ghost corresponds to the radion field. We also investigate the theory with a brane localized mass for the graviton on the ultraviolet brane, and show that the physics of this case is similar to that of a conventional four dimensional theory with a massive graviton, but with one important difference: when the infrared brane decouples and the would-be massive graviton gets heavier than the regular Kaluza-Klein modes, it becomes unstable and it has a finite width to decay off the brane into the continuum of Kaluza-Klein states.

  7. Efficient, massively parallel eigenvalue computation

    NASA Technical Reports Server (NTRS)

    Huo, Yan; Schreiber, Robert

    1993-01-01

    In numerical simulations of disordered electronic systems, one of the most common approaches is to diagonalize random Hamiltonian matrices and to study the eigenvalues and eigenfunctions of a single electron in the presence of a random potential. An effort to implement a matrix diagonalization routine for real symmetric dense matrices on massively parallel SIMD computers, the Maspar MP-1 and MP-2 systems, is described. Results of numerical tests and timings are also presented.

  8. Spatial evolution of multiple filaments in air induced by femtosecond laser pulses.

    PubMed

    Hao, Zuo-Qiang; Zhang, Jie; Lu, Xin; Xi, Ting-Ting; Li, Yu-Tong; Yuan, Xiao-Hui; Zheng, Zhi-Yuan; Wang, Zhao-Hua; Ling, Wei-Jun; Wei, Zhi-Yi

    2006-01-23

    The spatial evolution of plasma filaments in air induced by femtosecond laser pulses is investigated experimentally. Several major filaments and small scaled additional filaments are detected in the plasma channel. The complicated interaction process of filaments as splitting, fusion and spreading is observed. The major filaments propagate stably, and the small scaled additional filaments can be attracted to the major filaments and merged with them. The major filaments are formed due to the perturbation of initial beam profile and the small scaled filaments are mainly caused by the transverse modulational instability. PMID:19503396

  9. Analytics for Massive Heat Maps

    SciTech Connect

    Bohn, Shawn J.; Payne, Deborah A.; Nakamura, Grant C.; Love, Douglas V.

    2009-01-19

    High throughput instrumentation for genomics is producing data orders of magnitude greater than even a decade before. Biologists often visualize the data of these experiments through the use of heat maps. For large datasets, heat map visualizations do not scale. These visualizations are only capable of displaying a portion of the data, making it difficult for scientists to find and detect patterns that span more than a subsection of the data. We present a novel method that provides an interactive visual display for massive heat maps [O(108)]. Our process shows how a massive heat map can be decomposed into multiple levels of abstraction to represent the underlying macrostructures. We aggregate these abstractions into a framework that can allow real-time navigation of the space. To further assist pattern discovery, we ground our system on the principle of focus+context. Our framework also addresses the issue of balancing the memory and display resolution and heat map size. We will show that this technique for biologists provides a powerful new visual metaphor for analyzing massive datasets.

  10. Massive photon and dark energy

    NASA Astrophysics Data System (ADS)

    Kouwn, Seyen; Oh, Phillial; Park, Chan-Gyung

    2016-04-01

    We investigate the cosmology of massive electrodynamics and explore the possibility whether the massive photon could provide an explanation of dark energy. The action is given by the scalar-vector-tensor theory of gravity, which is obtained by nonminimal coupling of the massive Stueckelberg QED with gravity; its cosmological consequences are studied by paying particular attention to the role of photon mass. We find that the theory allows for cosmological evolution where the radiation- and matter-dominated epochs are followed by a long period of virtually constant dark energy that closely mimics a Λ CDM model. We also find that the main source of the current acceleration is provided by the nonvanishing photon mass governed by the relation Λ ˜m2 . A detailed numerical analysis shows that the nonvanishing photon mass on the order of ˜1 0-34 eV is consistent with current observations. This magnitude is far less than the most stringent limit on the photon mass available so far, which is on the order of m ≤1 0-27 eV .

  11. Analytics for massive heat maps

    NASA Astrophysics Data System (ADS)

    Bohn, Shawn J.; Payne, Deborah; Nakamura, Grant; Love, Douglass

    2009-01-01

    High throughput instrumentation for genomics is producing data orders of magnitude greater than even a decade before. Biologists often visualize the data of these experiments through the use of heat maps. For large datasets, heat map visualizations do not scale. These visualizations are only capable of displaying a portion of the data, making it difficult for scientists to find and detect patterns that span more than a subsection of the data. We present a novel method that provides an interactive visual display for massive heat maps [O(108)]. Our process shows how a massive heat map can be decomposed into multiple levels of abstraction to represent the underlying macrostructures. We aggregate these abstractions into a framework that can allow near real-time navigation of the space. To further assist pattern discovery, we ground our system on the principle of focus+context. Our framework also addresses the issue of balancing the memory and display resolution and heat map size. We will show that this technique for biologists provides a powerful new visual metaphor for analyzing massive datasets.

  12. Extinction in young massive clusters

    NASA Astrophysics Data System (ADS)

    De Marchi, Guido; Panagia, Nino

    2016-01-01

    Up to ages of ~100 Myr, massive clusters are still swamped in large amounts of gas and dust, causing considerable and uneven levels of extinction. At the same time, large grains (ices?) produced by type II supernovae profoundly alter the interstellar medium (ISM), thus resulting in extinction properties very different from those of the diffuse ISM. To obtain physically meaningful parameters of stars (luminosities, effective temperatures, masses, ages, etc.) we must understand and measure the local extinction law. We have developed a powerful method to unambiguously determine the extinction law everywhere across a cluster field, using multi-band photometry of red giant stars belonging to the red clump (RC) and are applying it to young massive clusters in the Local Group. In the Large Magellanic Cloud, with about 20 RC stars per arcmin2, for each field we can easily derive an accurate extinction curve over the entire wavelength range of the photometry. As an example, we present the extinction law of the Tarantula nebula (30 Dor) based on thousands of stars observed as part of the Hubble Tarantula Treasury Project. We discuss how the incautious adoption of the Milky Way extinction law in the analysis of massive star forming regions may lead to serious underestimates of the fluxes and of the star formation rates by factors of 2 or more.

  13. The Golgi apparatus: insights from filamentous fungi.

    PubMed

    Pantazopoulou, Areti

    2016-05-01

    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. PMID:26932185

  14. Alfven wave filamentation and dispersive phase mixing

    SciTech Connect

    Sulem, P. L.; Passot, T.; Laveder, D.; Borgogno, D.

    2009-11-10

    The formation of three-dimensional magnetic structures from quasi-monochromatic left-hand polarized dispersive Alfven waves, under the effect of transverse collapse and/or the lensing effect of density channels aligned with the ambient magnetic field is discussed, both in the context of the usual Hall-MHD and using a fluid model retaining linear Landau damping and finite Larmor radius corrections. It is in particular shown that in a small-{beta} plasma (that is stable relatively to the filamentation instability in the absence of inhomogeneities), a moderate density enhancement leads the wave energy to concentrate into a filament whose transverse size is prescribed by the dimension of the channel, while for a strong density perturbation, this structure later on evolves to thin helical ribbons where the strong gradients permit dissipation processes to become efficient and heat the plasma. The outcome of this 'dispersive phase mixing' that leads to small-scale formation on relatively extended regions contrasts with the more localized oblique shocks formed in the absence of dispersion. Preliminary results on the effect of weak collisions that lead to an increase of the transverse ion temperature are also briefly mentioned.

  15. Current filamentation and onset in magnetoplasmadynamic thrusters

    NASA Astrophysics Data System (ADS)

    Giannelli, Sebastiano; Misuri, Tommaso; Andrenucci, Mariano

    2011-06-01

    The possible role of current filamentation in the operation of magnetoplasmadynamic thrusters is investigated here by means of a stability analysis of a current-carrying plasma in a simplified coaxial configuration. Magnetoplasmadynamic thrusters are known to enter a strongly unstable regime, named onset in the literature, when operated above a threshold current level, given the propellant mass flow rate. During onset, a transition from diffuse to spotty current pattern occurs, leading to intense fluctuations of thruster terminal voltage and to severe anode damage with commonly employed anode materials. Despite several experimental and theoretical efforts in the last few decades, no complete and definitive understanding of the physical nature of this phenomenon is yet available. In this work it is shown that conditions suitable for azimuthal symmetry breaking and the subsequent development of this instability can actually exist in magnetoplasmadynamic thrusters. A physically coherent explanation of the complex onset phenomenology is then proposed, showing that both the plasma dynamics and the voltage fluctuations can be ultimately explained in terms of the filamentation instability and its effects.

  16. Supercoiling of f-actin filaments.

    PubMed

    Lednev, V V; Popp, D

    1990-05-01

    In the X-ray diffraction pattern from oriented gels of actin-containing filaments sampling of layer lines indicating the development of a well-ordered pseudo-hexagonal lattice within the gels at interfilament spacings as large as 13 nm is observed. This value exceeds by 3 nm the largest estimate of an external diameter of pure f-actin. The development of layer line sampling is always accompanied by: (i) the appearance of strong forbidden meridional reflections on the 5.9- and 5.1-nm layer lines; (ii) a drastic intensification of the first (expected) 2.75-nm meridional reflection by a factor of about 4; (iii) the appearance of streaks, connecting near-meridional reflections on the 5.9-, 5.1-, and 37-nm layer lines; and (iv) a slight decrease in the number of subunits per turn of the basic f-actin helix. All these features strongly indicate that f-actin filaments are supercoiled and make regular local contacts between themselves, which may lead to periodic distortions of the mobile external domain in the actin subunits. PMID:2261308

  17. Production of cutinolytic esterase by filamentous bacteria.

    PubMed

    Fett, W F; Wijey, C; Moreau, R A; Osman, S F

    2000-07-01

    Thirty-eight strains of filamentous bacteria, many of which are thermophilic or thermotolerant and commonly found in composts and mouldy fodders, were examined for their ability to produce cutinolytic esterase (cutinase) in culture media supplemented with cutin, suberin or cutin-containing agricultural by-products. Initially, the ability of culture supernatants to hydrolyse the artificial substrate p-nitrophenyl butyrate was determined by spectrophotometric assays. Only one bacterium, Thermoactinomyces vulgaris NRRL B-16117, exhibited cutinolytic esterase production. The enzyme was highly inducible, was repressed by the presence of glucose in the medium and hydrolysed both apple and tomato cutins. Inducers included apple cutin, apple pomace, tomato peel, potato suberin and commercial cork. Unlike similar fungal enzymes, the T. vulgaris cutinolytic esterase was not inducible by cutin hydrolysate. The cutinolytic esterase exhibited a half-life of over 60 min at 70 degrees C and a pH optimum of >/= 11.0. This study indicates that thermophylic filamentous bacteria may be excellent commercial sources of heat-stable cutin-degrading enzymes that can be produced by fermentation of low cost feedstocks. PMID:10886609

  18. Massive Stars in Interactive Binaries

    NASA Astrophysics Data System (ADS)

    St.-Louis, Nicole; Moffat, Anthony F. J.

    Massive stars start their lives above a mass of ~8 time solar, finally exploding after a few million years as core-collapse or pair-production supernovae. Above ~15 solar masses, they also spend most of their lives driving especially strong, hot winds due to their extreme luminosities. All of these aspects dominate the ecology of the Universe, from element enrichment to stirring up and ionizing the interstellar medium. But when they occur in close pairs or groups separated by less than a parsec, the interaction of massive stars can lead to various exotic phenomena which would not be seen if there were no binaries. These depend on the actual separation, and going from wie to close including colliding winds (with non-thermal radio emission and Wolf-Rayet dust spirals), cluster dynamics, X-ray binaries, Roche-lobe overflow (with inverse mass-ratios and rapid spin up), collisions, merging, rejuventation and massive blue stragglers, black-hole formation, runaways and gamma-ray bursts. Also, one wonders whether the fact that a massive star is in a binary affects its parameters compared to its isolated equivalent. These proceedings deal with all of these phenomena, plus binary statistics and determination of general physical properties of massive stars, that would not be possible with their single cousins. The 77 articles published in these proceedings, all based on oral talks, vary from broad revies to the lates developments in the field. About a third of the time was spent in open discussion of all participants, both for ~5 minutes after each talk and 8 half-hour long general dialogues, all audio-recorded, transcribed and only moderately edited to yield a real flavour of the meeting. The candid information in these discussions is sometimes more revealing than the article(s) that preceded them and also provide entertaining reading. The book is suitable for researchers and graduate students interested in stellar astrophysics and in various physical processes involved when

  19. Formation of a solar Hα filament from orphan penumbrae

    NASA Astrophysics Data System (ADS)

    Buehler, D.; Lagg, A.; van Noort, M.; Solanki, S. K.

    2016-05-01

    Aims: The formation and evolution of an Hα filament in active region (AR) 10953 is described. Methods: Observations from the Solar Optical Telescope (SOT) aboard the Hinode satellite starting from UT 18:09 on 27th April 2007 until UT 06:08 on 1st May 2007 were analysed. 20 scans of the 6302 Å Fe I line pair recorded by SOT/SP were inverted using the spatially coupled version of the SPINOR code. The inversions were analysed together with co-spatial SOT/BFI G-band and Ca II H and SOT/NFI Hα observations. Results: Following the disappearance of an initial Hα filament aligned along the polarity inversion line (PIL) of the AR, a new Hα filament formed in its place some 20 h later, which remained stable for, at least, another 1.5 days. The creation of the new Hα filament was driven by the ascent of horizontal magnetic fields from the photosphere into the chromosphere at three separate locations along the PIL. The magnetic fields at two of these locations were situated directly underneath the initial Hα filament and formed orphan penumbrae already aligned along the Hα filament channel. The 700 G orphan penumbrae were stable and trapped in the photosphere until the disappearance of the overlying initial Hα filament, after which they started to ascend into the chromosphere at 10 ± 5 m/s. Each ascent was associated with a simultaneous magnetic flux reduction of up to 50% in the photosphere. The ascended orphan penumbrae formed dark seed structures in Hα in parallel with the PIL, which elongated and merged to form an Hα filament. The filament channel featured horizontal magnetic fields of on average 260 G at log (τ) = -2 suspended above the nearly field-free lower photosphere. The fields took on an overall inverse configuration at log (τ) = -2 suggesting a flux rope topology for the new Hα filament. The destruction of the initial Hα filament was likely caused by the flux emergence at the third location along the PIL. Conclusions: We present a new

  20. Formation of a solar Hα filament from orphan penumbrae

    NASA Astrophysics Data System (ADS)

    Buehler, D.; Lagg, A.; van Noort, M.; Solanki, S. K.

    2016-04-01

    Aims: The formation and evolution of an Hα filament in active region (AR) 10953 is described. Methods: Observations from the Solar Optical Telescope (SOT) aboard the Hinode satellite starting from UT 18:09 on 27th April 2007 until UT 06:08 on 1st May 2007 were analysed. 20 scans of the 6302 Å Fe I line pair recorded by SOT/SP were inverted using the spatially coupled version of the SPINOR code. The inversions were analysed together with co-spatial SOT/BFI G-band and Ca II H and SOT/NFI Hα observations. Results: Following the disappearance of an initial Hα filament aligned along the polarity inversion line (PIL) of the AR, a new Hα filament formed in its place some 20 h later, which remained stable for, at least, another 1.5 days. The creation of the new Hα filament was driven by the ascent of horizontal magnetic fields from the photosphere into the chromosphere at three separate locations along the PIL. The magnetic fields at two of these locations were situated directly underneath the initial Hα filament and formed orphan penumbrae already aligned along the Hα filament channel. The 700 G orphan penumbrae were stable and trapped in the photosphere until the disappearance of the overlying initial Hα filament, after which they started to ascend into the chromosphere at 10 ± 5 m/s. Each ascent was associated with a simultaneous magnetic flux reduction of up to 50% in the photosphere. The ascended orphan penumbrae formed dark seed structures in Hα in parallel with the PIL, which elongated and merged to form an Hα filament. The filament channel featured horizontal magnetic fields of on average 260 G at log (τ) = -2 suspended above the nearly field-free lower photosphere. The fields took on an overall inverse configuration at log (τ) = -2 suggesting a flux rope topology for the new Hα filament. The destruction of the initial Hα filament was likely caused by the flux emergence at the third location along the PIL. Conclusions: We present a new

  1. Proper horizontal photospheric flows in a filament channel

    NASA Astrophysics Data System (ADS)

    Schmieder, B.; Roudier, T.; Mein, N.; Mein, P.; Malherbe, J. M.; Chandra, R.

    2014-04-01

    Context. An extended filament in the central part of the active region NOAA 11106 crossed the central meridian on Sept. 17, 2010 in the southern hemisphere. It has been observed in Hα with the THEMIS telescope in the Canary Islands and in 304 Å with the EUV imager (AIA) onboard the Solar Dynamic Observatory (SDO). Counterstreaming along the Hα threads and bright moving blobs (jets) along the 304 Å filament channel were observed during 10 h before the filament erupted at 17:03 UT. Aims: The aim of the paper is to understand the coupling between magnetic field and convection in filament channels and relate the horizontal photospheric motions to the activity of the filament. Methods: An analysis of the proper photospheric motions using SDO/HMI continuum images with the new version of the coherent structure tracking (CST) algorithm developed to track granules, as well as the large scale photospheric flows, was performed for three hours. Using corks, we derived the passive scalar points and produced a map of the cork distribution in the filament channel. Averaging the velocity vectors in the southern hemisphere in each latitude in steps of 3.5 arcsec, we defined a profile of the differential rotation. Results: Supergranules are clearly identified in the filament channel. Diverging flows inside the supergranules are similar in and out of the filament channel. Converging flows corresponding to the accumulation of corks are identified well around the Hα filament feet and at the edges of the EUV filament channel. At these convergence points, the horizontal photospheric velocity may reach 1 km s-1, but with a mean velocity of 0.35 km s-1. In some locations, horizontal flows crossing the channel are detected, indicating eventually large scale vorticity. Conclusions: The coupling between convection and magnetic field in the photosphere is relatively strong. The filament experienced the convection motions through its anchorage points with the photosphere, which are

  2. Far-ultraviolet morphology of star-forming filaments in cool core brightest cluster galaxies

    NASA Astrophysics Data System (ADS)

    Tremblay, G. R.; O'Dea, C. P.; Baum, S. A.; Mittal, R.; McDonald, M. A.; Combes, F.; Li, Y.; McNamara, B. R.; Bremer, M. N.; Clarke, T. E.; Donahue, M.; Edge, A. C.; Fabian, A. C.; Hamer, S. L.; Hogan, M. T.; Oonk, J. B. R.; Quillen, A. C.; Sanders, J. S.; Salomé, P.; Voit, G. M.

    2015-08-01

    We present a multiwavelength morphological analysis of star-forming clouds and filaments in the central (≲50 kpc) regions of 16 low-redshift (z < 0.3) cool core brightest cluster galaxies. New Hubble Space Telescope imaging of far-ultraviolet continuum emission from young (≲10 Myr), massive (≳5 M⊙) stars reveals filamentary and clumpy morphologies, which we quantify by means of structural indices. The FUV data are compared with X-ray, Lyα, narrow-band Hα, broad-band optical/IR, and radio maps, providing a high spatial resolution atlas of star formation locales relative to the ambient hot (˜107-8 K) and warm ionized (˜104 K) gas phases, as well as the old stellar population and radio-bright active galactic nucleus (AGN) outflows. Nearly half of the sample possesses kpc-scale filaments that, in projection, extend towards and around radio lobes and/or X-ray cavities. These filaments may have been uplifted by the propagating jet or buoyant X-ray bubble, or may have formed in situ by cloud collapse at the interface of a radio lobe or rapid cooling in a cavity's compressed shell. The morphological diversity of nearly the entire FUV sample is reproduced by recent hydrodynamical simulations in which the AGN powers a self-regulating rain of thermally unstable star-forming clouds that precipitate from the hot atmosphere. In this model, precipitation triggers where the cooling-to-free-fall time ratio is tcool/tff ˜ 10. This condition is roughly met at the maximal projected FUV radius for more than half of our sample, and clustering about this ratio is stronger for sources with higher star formation rates.

  3. 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.

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

    NASA Astrophysics Data System (ADS)

    Huang, Mu-Jie; Kapral, Raymond

    2015-06-01

    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.

  5. 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.

  6. Process for the production of superconductor containing filaments

    DOEpatents

    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.

  7. 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.

  8. 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.

  9. Regulation of filamentation in the human fungal pathogen Candida tropicalis.

    PubMed

    Zhang, Qiuyu; Tao, Li; Guan, Guobo; Yue, Huizhen; Liang, Weihong; Cao, Chengjun; Dai, Yu; Huang, Guanghua

    2016-02-01

    The yeast-filament transition is essential for the virulence of a variety of fungi that are pathogenic to humans. N-acetylglucosamine (GlcNAc) is a potent inducer of filamentation in Candida albicans and thermally dimorphic fungi such as Histoplasma capsulatum and Blastomyces dermatitidis. However, GlcNAc suppresses rather than promotes filamentation in Candida tropicalis, a fungal species that is closely related to C. albicans. Despite the intensive study in C. albicans, the regulatory mechanism of filamentation is poorly understood. In this study, we demonstrate that the cAMP signaling pathway plays a central role in the regulation of filamentation in C. tropicalis. By screening an overexpression library of 156 transcription factors, we have identified approximately 40 regulators of filamentous growth. Although most of the regulators (e.g., Tec1, Gat2, Nrg1, Sfl1, Sfl2 and Ash1) demonstrate a conserved role in the regulation of filamentation, similar to their homologues in C. albicans or Saccharomyces cerevisiae, a number of transcription factors (e.g., Wor1, Bcr1, Stp4, Efh1, Csr1 and Zcf17) play a specific role in C. tropicalis. Our findings indicate that multiple interconnected signaling pathways are involved in the regulation of filamentation in C. tropicalis. These mechanisms have conserved and divergent features among different Candida species. PMID:26466925

  10. Treadmilling and length distributions of active polar filaments

    NASA Astrophysics Data System (ADS)

    Erlenkämper, C.; Kruse, K.

    2013-10-01

    The cytoskeleton is a network of filamentous proteins, notably, actin filaments and microtubules. These filaments are active as their assembly is driven by the hydrolysis of nucleotides bound to the constituting protomers. In addition, the assembly kinetics differs at the two respective ends, making them active polar filaments. Experimental evidence suggests, that, in vivo, actin filaments and microtubules can grow at one and shrink at the other end at the same rate, a state that is known as treadmilling. In this work, we use a generic discrete two-state model for active polar filaments to analyze the conditions leading to treadmilling. We find that a single filament can self-organize into the treadmilling state for a broad range of monomer concentrations. In this regime the corresponding length distribution has a pronounced maximum at a finite value. We then extend our description to consider specifically the dynamics of actin filaments. We show that actin treadmilling should be observable in vitro in the presence of appropriate depolymerization promoting factors.

  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. 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…

  13. An Observational Detection of the Bridge Effect of Void Filaments

    NASA Astrophysics Data System (ADS)

    Shim, Junsup; Lee, Jounghun; Hoyle, Fiona

    2015-12-01

    The bridge effect of void filaments is a phrase coined by Park & Lee to explain the correlations found in a numerical experiment between the luminosity of the void galaxies and the degree of straightness of their host filaments. Their numerical finding implies that a straight void filament provides a narrow channel for the efficient transportation of gas and matter particles from the surroundings into void galaxies. Analyzing the Sloan void catalog constructed by Pan et al., we identify the filamentary structures in void regions and determine the specific size of each void filament as a measure of its straightness. To avoid possible spurious signals caused by Malmquist bias, we consider only those void filaments whose redshifts are in the range 0≤slant z≤slant 0.02 and find a clear tendency that the void galaxies located in the straighter filaments are on average more luminous, which is in qualitative agreement with the numerical prediction. It is also shown that the strength of correlation increases with the number of member galaxies in the void filaments, which can be understood physically on the grounds that the more stretched filaments can connect the dense surroundings even to galaxies located deep in the central parts of the voids. This observational evidence may provide a key clue to the puzzling issue of why the void galaxies have higher specific star formation rates and bluer colors than their wall counterparts.

  14. Biophysics of filament length regulation by molecular motors

    NASA Astrophysics Data System (ADS)

    Kuan, Hui-Shun; Betterton, M. D.

    2013-06-01

    Regulating physical size is an essential problem that biological organisms must solve from the subcellular to the organismal scales, but it is not well understood what physical principles and mechanisms organisms use to sense and regulate their size. Any biophysical size-regulation scheme operates in a noisy environment and must be robust to other cellular dynamics and fluctuations. This work develops theory of filament length regulation inspired by recent experiments on kinesin-8 motor proteins, which move with directional bias on microtubule filaments and alter microtubule dynamics. Purified kinesin-8 motors can depolymerize chemically-stabilized microtubules. In the length-dependent depolymerization model, the rate of depolymerization tends to increase with filament length, because long filaments accumulate more motors at their tips and therefore shorten more quickly. When balanced with a constant filament growth rate, this mechanism can lead to a fixed polymer length. However, the mechanism by which kinesin-8 motors affect the length of dynamic microtubules in cells is less clear. We study the more biologically realistic problem of microtubule dynamic instability modulated by a motor-dependent increase in the filament catastrophe frequency. This leads to a significant decrease in the mean filament length and a narrowing of the filament length distribution. The results improve our understanding of the biophysics of length regulation in cells.

  15. Bending Flexibility of Actin Filaments during Motor-Induced Sliding

    PubMed Central

    Vikhorev, Petr G.; Vikhoreva, Natalia N.; Månsson, Alf

    2008-01-01

    Muscle contraction and other forms of cell motility occur as a result of cyclic interactions between myosin molecules and actin filaments. Force generation is generally attributed to ATP-driven structural changes in myosin, whereas a passive role is ascribed to actin. However, some results challenge this view, predicting structural changes in actin during motor activity, e.g., when the actin filaments slide on a myosin-coated surface in vitro. Here, we analyzed statistical properties of the sliding filament paths, allowing us to detect changes of this type. It is interesting to note that evidence for substantial structural changes that led to increased bending flexibility of the filaments was found in phalloidin-stabilized, but not in phalloidin-free, actin filaments. The results are in accordance with the idea that a high-flexibility structural state of actin is a prerequisite for force production, but not the idea that a low-to-high flexibility transition of the actin filament should be an important component of the force-generating step per se. Finally, our data challenge the general view that phalloidin-stabilized filaments behave as native actin filaments in their interaction with myosin. This has important implications, since phalloidin stabilization is a routine procedure in most studies of actomyosin function. PMID:18835897

  16. 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).

  17. 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

  18. The extreme nonlinear optics of gases and femtosecond optical filamentation

    SciTech Connect

    Milchberg, H. M.; Chen, Y.-H.; Cheng, Y.-H.; Jhajj, N.; Palastro, J. P.; Rosenthal, E. W.; Varma, S.; Wahlstrand, J. K.; Zahedpour, S.

    2014-10-15

    Under certain conditions, powerful ultrashort laser pulses can form greatly extended, propagating filaments of concentrated high intensity in gases, leaving behind a very long trail of plasma. Such filaments can be much longer than the longitudinal scale over which a laser beam typically diverges by diffraction, with possible applications ranging from laser-guided electrical discharges to high power laser propagation in the atmosphere. Understanding in detail the microscopic processes leading to filamentation requires ultrafast measurements of the strong field nonlinear response of gas phase atoms and molecules, including absolute measurements of nonlinear laser-induced polarization and high field ionization. Such measurements enable the assessment of filamentation models and make possible the design of experiments pursuing applications. In this paper, we review filamentation in gases and some applications, and discuss results from diagnostics developed at Maryland for ultrafast measurements of laser-gas interactions.

  19. Beam wandering of femtosecond laser filament in air.

    PubMed

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

    2015-10-01

    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. PMID:26480079

  20. 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.

  1. 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.

  2. Ubiquitination and filamentous structure of cytidine triphosphate synthase.

    PubMed

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

    2016-07-01

    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

  3. Programmable smart electron emission controller for hot filament

    NASA Astrophysics Data System (ADS)

    Flaxer, Eli

    2011-02-01

    In electron ionization source, electrons are produced through thermionic emission by heating a wire filament, accelerating the electrons by high voltage, and ionizing the analyzed molecules. In such a system, one important parameter is the filament emission current that determines the ionization rate; therefore, one needs to regulate this current. On the one hand, fast responses control is needed to keep the emission current constant, but on the other hand, we need to protect the filament from damage that occurs by large filaments current transients and overheating. To control our filament current and emission current, we developed a digital circuit based on a digital signal processing controller that has several modes of operation. We used a smart algorithm that has a fast response to a small signal and a slow response to a large signal. In addition, we have several protective measures that prevent the current from reaching unsafe values.

  4. 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.

  5. 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.

  6. Filament capturing with the Multimaterial Moment-of-Fluid method

    SciTech Connect

    Jemison, Matthew; Sussman, Mark; Shashkov, Mikhail

    2015-03-15

    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. 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.

  7. Intermediate Filaments and Polarization in the Intestinal Epithelium.

    PubMed

    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

  8. Colloquium: Geometry and optimal packing of twisted columns and filaments

    NASA Astrophysics Data System (ADS)

    Grason, Gregory M.

    2015-04-01

    This Colloquium presents recent progress in understanding constraints and consequences of close-packing geometry of filamentous or columnar materials possessing nontrivial textures, focusing, in particular, on the common motifs of twisted and toroidal structures. The mathematical framework is presented that relates spacing between linelike, filamentous elements to their backbone orientations, highlighting the explicit connection between the interfilament metric properties and the geometry of non-Euclidean surfaces. The consequences of the hidden connection between packing in twisted filament bundles and packing on positively curved surfaces, like the Thomson problem, are demonstrated for the defect-riddled ground states of physical models of twisted filament bundles. The connection between the "ideal" geometry of fibrations of curved three-dimensional space, including the Hopf fibration, and the non-Euclidean constraints of filament packing in twisted and toroidal bundles is presented, with a focus on the broader dependence of metric geometry on the simultaneous twisting and folding of multifilament bundles.

  9. Spontaneous Scalarization of Massive Fields

    NASA Astrophysics Data System (ADS)

    Ramazanoglu, Fethi M.; Pretorius, Frans

    2014-03-01

    Spontaneous scalarization is a phenomenon in certain scalar-tensor theories where large deviations from general relativity can be observed inside compact stars, while the known observational bounds can also be satisfied far away. This scenario has been investigated for massless scalars and binary neutron stars using numerical relativity, but the parameter space for such theories have been severely restricted by recent observations. Here, we present our results on the spontaneous scalarization of massive scalars. We simulate cases with different equations of state and scalar field parameters, and comment on the detectability of the scalar field effects from the gravitational wave signal.

  10. Detecting weakly interacting massive particles.

    NASA Astrophysics Data System (ADS)

    Drukier, A. K.; Gelmini, G. B.

    The growing synergy between astrophysics, particle physics, and low background experiments strengthens the possibility of detecting astrophysical non-baryonic matter. The idea of direct detection is that an incident, massive weakly interacting particle could collide with a nucleus and transfer an energy that could be measured. The present low levels of background achieved by the PNL/USC Ge detector represent a new technology which yields interesting bounds on Galactic cold dark matter and on light bosons emitted from the Sun. Further improvements require the development of cryogenic detectors. The authors analyse the practicality of such detectors, their optimalization and background suppression using the "annual modulation effect".

  11. Quantum aspects of massive gravity

    NASA Astrophysics Data System (ADS)

    Park, Minjoon

    2011-05-01

    We consider the effect of quantum interactions on Pauli-Fierz massive gravity. With generic graviton cubic interactions, we observe that the 1-loop counterterms do not conform to the tree level structure of Pauli-Fierz action, resulting in the reappearance of the sixth mode ghost. Then to explore the quantum effects to the full extent, we calculate the resummed graviton propagator with an arbitrary interaction and analyze its complete structure, from which a minimal condition for the absence of the ghost is obtained.

  12. Cosmological perturbations in massive bigravity

    SciTech Connect

    Lagos, Macarena; Ferreira, Pedro G. E-mail: p.ferreira1@physics.ox.ac.uk

    2014-12-01

    We present a comprehensive analysis of classical scalar, vector and tensor cosmological perturbations in ghost-free massive bigravity. In particular, we find the full evolution equations and analytical solutions in a wide range of regimes. We show that there are viable cosmological backgrounds but, as has been found in the literature, these models generally have exponential instabilities in linear perturbation theory. However, it is possible to find stable scalar cosmological perturbations for a very particular choice of parameters. For this stable subclass of models we find that vector and tensor perturbations have growing solutions. We argue that special initial conditions are needed for tensor modes in order to have a viable model.

  13. Models of Filament-Prominence Formation

    NASA Astrophysics Data System (ADS)

    Welsch, Brian T.

    Martens and Zwaan (ApJ v. 558 872) have proposed a prominence/ filament formation model in which differential rotation drives reconnection between two initially unconnected active regions to form helical field lines that support mass and are held down by overlying field. Using an MHD solver with adaptive refinement we simulated this process by imposing a shear flow meant to mimic differential rotation on two bipolar flux distributions meant to mimic distinct active regions. In some runs the flux systems are initially potential while in others they have been twisted by footpoint rotation to inject helicity prior to imposing the shear flow. The resulting structures are studied to understand the role of helicity in the formation of prominence-like structures.

  14. Phase control of two-color filamentation

    NASA Astrophysics Data System (ADS)

    Doussot, J.; Béjot, P.; Karras, G.; Billard, F.; Faucher, O.

    2015-09-01

    An original way to control the nonlinear propagation of an intense pulse is presented. The co-propagation of a weak (≃ 1%) third-harmonic pulse with an intense laser pulse experiencing filamentation allows control of the nonlinear propagation of the latter. Because of quantum interference during the two-color ionisation process, the latter can be significantly enhanced or suppressed by a simple tuning of the relative phase between the two fields. As a first application, we demonstrate the production and control of an axially modulated plasma channel. Finally, an analytical formula describing the two-color ionisation rate as a function of the relative phase and intensity of the two fields is presented and tested in a propagation code. The numerical results successfully reproduce the experimental ones.

  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. Hamiltonian Dynamics of Protein Filament Formation.

    PubMed

    Michaels, Thomas C T; Cohen, Samuel I A; Vendruscolo, Michele; Dobson, Christopher M; Knowles, Tuomas P J

    2016-01-22

    We establish the Hamiltonian structure of the rate equations describing the formation of protein filaments. We then show that this formalism provides a unified view of the behavior of a range of biological self-assembling systems as diverse as actin, prions, and amyloidogenic polypeptides. We further demonstrate that the time-translation symmetry of the resulting Hamiltonian leads to previously unsuggested conservation laws that connect the number and mass concentrations of fibrils and allow linear growth phenomena to be equated with autocatalytic growth processes. We finally show how these results reveal simple rate laws that provide the basis for interpreting experimental data in terms of specific mechanisms controlling the proliferation of fibrils. PMID:26849615

  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. 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.

  19. Rods-on-string idealization captures semiflexible filament dynamics

    NASA Astrophysics Data System (ADS)

    Chandran, Preethi L.; Mofrad, Mohammad R. K.

    2009-01-01

    We present an approach to modeling the two-dimensional Brownian dynamics of semiflexible filaments in the worm-model description as uniform, isotropic, and continuously flexible. Experimental observations increasingly show that the mechanical behavior of semiflexible filament networks departs from conventional knowledge. A force-balance-based dynamic simulation of the filament networks has multiple advantages as an approach to understanding their anomalous mechanics. However, a major disadvantage is the difficulty of capturing filament hydrodynamics and bending mechanics in a computationally efficient and physically consistent manner. To that end, we propose a strategy for modeling semiflexible filaments which involves idealizing a semiflexible filament as a contiguous string of flexible rods, and considering the Brownian forces on it as Einsteinian-like point normal and tangential forces. By idealizing the filament as a string of rods, we avoid the complex hydrodynamic treatment involved in beads-on-string idealizations, and implement large-deflection beam mechanics and filament inextensibility in a natural manner, while reducing the computational size of the problem. By considering the Brownian forces as point normal and tangential forces, we decompose the Brownian forces on straight and curved segments into a combination of classical resultant forces and couples whose distribution is shown to be governed by the rod diffusion coefficients. The decomposition allows solution of the Euler beam equations to second-order continuity between segments and fifth-order continuity within segments. We show that the approach is physically consistent by capturing multiple Brownian phenomena ranging from the rigid to the semiflexible limit: the translational and rotational diffusion of rigid rods; the thermal fluctuation of semirigid cantilever filaments; and the shape, bending, and time relaxation of freely diffusing, semiflexible actin filaments.

  20. Rods-on-string idealization captures semiflexible filament dynamics.

    PubMed

    Chandran, Preethi L; Mofrad, Mohammad R K

    2009-01-01

    We present an approach to modeling the two-dimensional Brownian dynamics of semiflexible filaments in the worm-model description as uniform, isotropic, and continuously flexible. Experimental observations increasingly show that the mechanical behavior of semiflexible filament networks departs from conventional knowledge. A force-balance-based dynamic simulation of the filament networks has multiple advantages as an approach to understanding their anomalous mechanics. However, a major disadvantage is the difficulty of capturing filament hydrodynamics and bending mechanics in a computationally efficient and physically consistent manner. To that end, we propose a strategy for modeling semiflexible filaments which involves idealizing a semiflexible filament as a contiguous string of flexible rods, and considering the Brownian forces on it as Einsteinian-like point normal and tangential forces. By idealizing the filament as a string of rods, we avoid the complex hydrodynamic treatment involved in beads-on-string idealizations, and implement large-deflection beam mechanics and filament inextensibility in a natural manner, while reducing the computational size of the problem. By considering the Brownian forces as point normal and tangential forces, we decompose the Brownian forces on straight and curved segments into a combination of classical resultant forces and couples whose distribution is shown to be governed by the rod diffusion coefficients. The decomposition allows solution of the Euler beam equations to second-order continuity between segments and fifth-order continuity within segments. We show that the approach is physically consistent by capturing multiple Brownian phenomena ranging from the rigid to the semiflexible limit: the translational and rotational diffusion of rigid rods; the thermal fluctuation of semirigid cantilever filaments; and the shape, bending, and time relaxation of freely diffusing, semiflexible actin filaments. PMID:19257068

  1. TRACE and SVST Observations of an Active-Region Filament

    NASA Astrophysics Data System (ADS)

    van Ballegooijen, A. A.; Deluca, E. E.

    1999-05-01

    In June 1998 the Transition Region and Coronal Explorer (TRACE) observed filaments and prominences in coordination with various ground-based solar observatories, including the Swedish Vacuum Solar Telescope (SVST) on La Palma. Here we present results for an active-region filament observed on June 21-22. This horse-shoe shaped filament had a "barb" that reached down from the filament spine to the chomosphere below. We use high-resolution images obtained at the SVST on June 21 from 18:03 to 19:04 UT to study the fine structure and dynamics of plasmas in the barb and other parts of the filament. The data consist of narrowband Hα images taken with the Lockheed Tunable Filtergraph operating at a cadence of 20 s. We present Doppler maps derived from these images. The filament erupted six hours after the SVST observations. The eruption was observed with TRACE, which obtained images in Fe IX/X 171, Fe XII 195, Fe XV 284 and H I Lyalpha . At the start of the event, a thin bright loop appears high above the filament at the location of the barb. We interpret this feature as the outline of a magnetic "bubble" which forms as a result of kink instability in the magnetic field that supports the filament. The bright loop appears to be due to particle acceleration and impulsive heating along certain field lines on the periphery of this magnetic structure. A few minutes later, the dark filament threads turn into emission and move outward, exhibiting a helical structure. We discuss the magnetic structure of the barb and its possible role in the filament eruption.

  2. RADIATION SPECTRAL SYNTHESIS OF RELATIVISTIC FILAMENTATION

    SciTech Connect

    Frederiksen, Jacob Trier; Haugboelle, Troels; Medvedev, Mikhail V.; Nordlund, Ake

    2010-10-10

    Radiation from many astrophysical sources, e.g., gamma-ray bursts and active galactic nuclei, is believed to arise from relativistically shocked collisionless plasmas. Such sources often exhibit highly transient spectra evolving rapidly compared with source lifetimes. Radiation emitted from these sources is typically associated with nonlinear plasma physics, complex field topologies, and non-thermal particle distributions. In such circumstances, a standard synchrotron paradigm may fail to produce accurate conclusions regarding the underlying physics. Simulating spectral emission and spectral evolution numerically in various relativistic shock scenarios is then the only viable method to determine the detailed physical origin of the emitted spectra. In this Letter, we present synthetic radiation spectra representing the early stage development of the filamentation (streaming) instability of an initially unmagnetized plasma, which is relevant for both collisionless shock formation and reconnection dynamics in relativistic astrophysical outflows as well as for laboratory astrophysics experiments. Results were obtained using a highly efficient in situ diagnostics method, based on detailed particle-in-cell modeling of collisionless plasmas. The synthetic spectra obtained here are compared with those predicted by a semi-analytical model for jitter radiation from the filamentation instability, the latter including self-consistent generated field topologies and particle distributions obtained from the simulations reported upon here. Spectra exhibit dependence on the presence-or the absence-of an inert plasma constituent, when comparing baryonic plasmas (i.e., containing protons) with pair plasmas. The results also illustrate that considerable care should be taken when using lower-dimensional models to obtain information about the astrophysical phenomena generating observed spectra.

  3. Radiation Spectral Synthesis of Relativistic Filamentation

    NASA Astrophysics Data System (ADS)

    Frederiksen, Jacob Trier; Haugbølle, Troels; Medvedev, Mikhail V.; Nordlund, Åke

    2010-10-01

    Radiation from many astrophysical sources, e.g., gamma-ray bursts and active galactic nuclei, is believed to arise from relativistically shocked collisionless plasmas. Such sources often exhibit highly transient spectra evolving rapidly compared with source lifetimes. Radiation emitted from these sources is typically associated with nonlinear plasma physics, complex field topologies, and non-thermal particle distributions. In such circumstances, a standard synchrotron paradigm may fail to produce accurate conclusions regarding the underlying physics. Simulating spectral emission and spectral evolution numerically in various relativistic shock scenarios is then the only viable method to determine the detailed physical origin of the emitted spectra. In this Letter, we present synthetic radiation spectra representing the early stage development of the filamentation (streaming) instability of an initially unmagnetized plasma, which is relevant for both collisionless shock formation and reconnection dynamics in relativistic astrophysical outflows as well as for laboratory astrophysics experiments. Results were obtained using a highly efficient in situ diagnostics method, based on detailed particle-in-cell modeling of collisionless plasmas. The synthetic spectra obtained here are compared with those predicted by a semi-analytical model for jitter radiation from the filamentation instability, the latter including self-consistent generated field topologies and particle distributions obtained from the simulations reported upon here. Spectra exhibit dependence on the presence—or the absence—of an inert plasma constituent, when comparing baryonic plasmas (i.e., containing protons) with pair plasmas. The results also illustrate that considerable care should be taken when using lower-dimensional models to obtain information about the astrophysical phenomena generating observed spectra.

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

    NASA Technical Reports Server (NTRS)

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

    1973-01-01

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

  5. The onset of massive star formation: The evolution of temperature and density structure in an infrared dark cloud

    SciTech Connect

    Battersby, Cara; Ginsburg, Adam; Bally, John; Darling, Jeremy; Longmore, Steve; Dunham, Miranda

    2014-06-01

    We present new NH{sub 3} (1, 1), (2, 2), and (4, 4) observations from the Karl G. Jansky Very Large Array compiled with work in the literature to explore the range of conditions observed in young, massive star-forming regions. To sample the effects of evolution independent from those of distance/resolution, abundance, and large-scale environment, we compare clumps in different evolutionary stages within a single infrared dark cloud (IRDC), G32.02+0.06. We find that the early stages of clustered star formation are characterized by dense, parsec-scale filamentary structures interspersed with complexes of dense cores (<0.1 pc cores clustered in complexes separated by ∼1 pc) with masses from about 10 to 100 M {sub ☉}. The most quiescent core is the most extended while the star forming cores are denser and more compact, showing very similar column density structure before and shortly after the onset of massive star formation, with peak surface densities Σ ≳ 1 g cm{sup –2}. Quiescent cores and filaments show smoothly varying temperatures from 10 to 20 K, rising to over 40 K in star-forming cores. We calculate virial parameters for 16 cores and find that the level of support provided by turbulence is generally insufficient to support them against gravitational collapse ((α{sub vir}) ∼ 0.6). The star-forming filaments show smooth velocity fields, punctuated by discontinuities at the sites of active star formation. We discuss the massive molecular filament (M ∼ 10{sup 5} M {sub ☉}, length >60 pc) hosting the IRDC, hypothesizing that it may have been shaped by previous generations of massive stars.

  6. Solid holography and massive gravity

    NASA Astrophysics Data System (ADS)

    Alberte, Lasma; Baggioli, Matteo; Khmelnitsky, Andrei; Pujolàs, Oriol

    2016-02-01

    Momentum dissipation is an important ingredient in condensed matter physics that requires a translation breaking sector. In the bottom-up gauge/gravity duality, this implies that the gravity dual is massive. We start here a systematic analysis of holographic massive gravity (HMG) theories, which admit field theory dual interpretations and which, therefore, might store interesting condensed matter applications. We show that there are many phases of HMG that are fully consistent effective field theories and which have been left overlooked in the literature. The most important distinction between the different HMG phases is that they can be clearly separated into solids and fluids. This can be done both at the level of the unbroken spacetime symmetries as well as concerning the elastic properties of the dual materials. We extract the modulus of rigidity of the solid HMG black brane solutions and show how it relates to the graviton mass term. We also consider the implications of the different HMGs on the electric response. We show that the types of response that can be consistently described within this framework is much wider than what is captured by the narrow class of models mostly considered so far.

  7. [Treatment alternatives in massive hemorrhage].

    PubMed

    Fernández-Hinojosa, E; Murillo-Cabezas, F; Puppo-Moreno, A; Leal-Noval, S R

    2012-10-01

    Massive hemorrhage is the main cause of mortality and morbidity in trauma patients, and is one of the most important causes in any patient following major surgery. Conventional treatment consists of volume replacement, including the transfusion of blood products, so that tissue perfusion and oxygenation may be maintained. Associated hypothermia, acidosis and coagulopathy is a lethal triad. This review focuses on the latest therapeutic management of massive hemorrhage. The authors advocate the use of crystalloids as per protocol (controlled volumes) in order to achieve a systolic blood pressure of 85mmHg. The administration of the three blood products (red cells, plasma, and platelets) should be on a 1:1:1 basis. Where possible, this in turn should be guided by thromboelastography performed at point of care near the patient. Coagulopathy can occur early and late. With the exception of tranexamic acid, the cost-benefit relationships of the hemostatic agents, such as fibrinogen, prothrombin complex, and recombinant F VII, are subject to discussion. PMID:22321860

  8. Sinus histiocytosis with massive lymphadenopathy: a "massive" misnomer.

    PubMed

    Sardana, Divesh; Goyal, Ashima; Gauba, Krishan

    2015-04-01

    Sinus histiocytosis with massive lymphadenopathy also known as Rosai-Dorfman disease is a rare, benign, histiocytic disorder of unknown origin characterized by lymphadenopathy. Since its original description by Rosai and Dorfman in 1969, small number of cases has been reported; hence no specific diagnostic criteria and treatment guidelines have been suggested. The purpose of this article is to present and discuss a case of Rosai Dorfman Syndrome in 4-year-old child diagnosed with the help of Fine Needle Aspiration Cytology. The swelling resolved over a period of 18 months without any recurrence in 2-year follow-up period. This case report highlights the role of Fine Needle Aspiration Cytology in the diagnosis of Rosai-Dorfman disease and the importance of regular follow ups using a careful wait and watch approach in its management. The report also briefly discusses the various dilemmas associated with its diagnosis and treatment. PMID:25088489

  9. Massive Binaries in the Galactic Center

    NASA Astrophysics Data System (ADS)

    Figer, D. F.; Kim, S. S.

    We review the status of massive-star interaction research in the Galactic center (GC). Given the short lifetimes of massive stars, massive binaries will necessarily be located near their formation sites in starburst clusters. The GC contains three recently formed clusters having a very high stellar density, as high as 106 stars pc-3. We discuss these extreme environments, and possible massive binaries therein. In addition, we argue that they may host the products of massive stellar mergers and collisions. In particular, we predict that at least one massive star in the Arches cluster has already experienced stellar merger events in its short lifetime. Further, the Pistol Star, in the nearby Quintuplet cluster, might owe its apparent relative youth to a rejuvinating stellar merger. Finally, the apparently young stars in the central arcsecond could be products of either collisions, inducing atmospheric stripping, or mergers.

  10. On "new massive" 4D gravity

    NASA Astrophysics Data System (ADS)

    Bergshoeff, Eric A.; Fernández-Melgarejo, J. J.; Rosseel, Jan; Townsend, Paul K.

    2012-04-01

    We construct a four-dimensional (4D) gauge theory that propagates, unitarily, the five polarization modes of a massive spin-2 particle. These modes are described by a "dual" graviton gauge potential and the Lagrangian is 4th-order in derivatives. As the construction mimics that of 3D "new massive gravity", we call this 4D model (linearized) "new massive dual gravity". We analyse its massless limit, and discuss similarities to the Eddington-Schrödinger model.

  11. Massive gravity with N=1 local supersymmetry

    NASA Astrophysics Data System (ADS)

    Malaeb, O.

    2013-09-01

    A consistent theory of massive gravity, where the graviton acquires mass by spontaneously breaking diffeomorphism invariance, is now well established. We supersymmetrize this construction using N=1 fields. Coupling to N=1 supergravity is done by applying the rules of tensor calculus to construct an action invariant under local N=1 supersymmetry. The supersymmetric action is shown, at the quadratic level, to be free of ghosts and have as its spectrum a massive graviton, two gravitinos (with different masses) and a massive vector.

  12. 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

  13. ERUPTION OF A SOLAR FILAMENT CONSISTING OF TWO THREADS

    SciTech Connect

    Bi Yi; Jiang Yunchun; Li Haidong; Hong Junchao; Zheng Ruisheng E-mail: jyc@ynao.ac.cn

    2012-10-10

    The trigger and driving mechanism for the eruption of a filament consisting of two dark threads was studied with unprecedented high cadence and resolution of He II 304 A observations made by the Atmospheric Imagining Assembly (AIA) on board the Solar Dynamics Observatory (SDO) and the observations made by the Solar Magnetic Activity Research Telescope and the Extreme Ultraviolet Imager (EUVI) telescope on board the Solar Terrestrial Relations Observatory Ahead (STEREO-A). The filament was located at the periphery of the active region NOAA 11228 and erupted on 2011 June 6. At the onset of the eruption, a turbulent filament thread was found to be heated and to elongate in stride over a second one. After it rose slowly, most interestingly, the elongating thread was driven to contact and interact with the second one, and it then erupted with its southern leg being wrapped by a newly formed thread produced by the magnetic reconnection between fields carried by the two threads. Combining the observations from STEREO-A/EUVI and SDO/AIA 304 A images, the three-dimensional shape of the axis of the filament was obtained and it was found that only the southern leg of the eruptive filament underwent rotation. We suggest that the eruption was triggered by the reconnection of the turbulent filament thread and the surrounding magnetic field, and that it was mainly driven by the kink instability of the southern leg of the eruptive filament that possessed a more twisted field introduced by the reconnection-produced thread.

  14. Single Filaments to Reveal the Multiple Flavors of Actin.

    PubMed

    Jégou, Antoine; Romet-Lemonne, Guillaume

    2016-05-24

    A number of key cell processes rely on specific assemblies of actin filaments, which are all constructed from nearly identical building blocks: the abundant and extremely conserved actin protein. A central question in the field is to understand how different filament networks can coexist and be regulated. Discoveries in science are often related to technical advances. Here, we focus on the ongoing single filament revolution and discuss how these techniques have greatly contributed to our understanding of actin assembly. In particular, we highlight how they have refined our understanding of the many protein-based regulatory mechanisms that modulate actin assembly. It is now becoming apparent that other factors give filaments a specific identity that determines which proteins will bind to them. We argue that single filament techniques will play an essential role in the coming years as we try to understand the many ways actin filaments can take different flavors and unveil how these flavors modulate the action of regulatory proteins. We discuss different factors known to make actin filaments distinguishable by regulatory proteins and speculate on their possible consequences. PMID:27224479

  15. A nebulin ruler does not dictate thin filament lengths.

    PubMed

    Castillo, Angelica; Nowak, Roberta; Littlefield, Kimberly P; Fowler, Velia M; Littlefield, Ryan S

    2009-03-01

    To generate force, striated muscle requires overlap between uniform-length actin and myosin filaments. The hypothesis that a nebulin ruler mechanism specifies thin filament lengths by targeting where tropomodulin (Tmod) caps the slow-growing, pointed end has not been rigorously tested. Using fluorescent microscopy and quantitative image analysis, we found that nebulin extended 1.01-1.03 mum from the Z-line, but Tmod localized 1.13-1.31 mum from the Z-line, in seven different rabbit skeletal muscles. Because nebulin does not extend to the thin filament pointed ends, it can neither target Tmod capping nor specify thin filament lengths. We found instead a strong correspondence between thin filament lengths and titin isoform sizes for each muscle. Our results suggest the existence of a mechanism whereby nebulin specifies the minimum thin filament length and sarcomere length regulates and coordinates pointed-end dynamics to maintain the relative overlap of the thin and thick filaments during myofibril assembly. PMID:19254544

  16. A Nebulin Ruler Does Not Dictate Thin Filament Lengths

    PubMed Central

    Castillo, Angelica; Nowak, Roberta; Littlefield, Kimberly P.; Fowler, Velia M.; Littlefield, Ryan S.

    2009-01-01

    To generate force, striated muscle requires overlap between uniform-length actin and myosin filaments. The hypothesis that a nebulin ruler mechanism specifies thin filament lengths by targeting where tropomodulin (Tmod) caps the slow-growing, pointed end has not been rigorously tested. Using fluorescent microscopy and quantitative image analysis, we found that nebulin extended 1.01–1.03 μm from the Z-line, but Tmod localized 1.13–1.31 μm from the Z-line, in seven different rabbit skeletal muscles. Because nebulin does not extend to the thin filament pointed ends, it can neither target Tmod capping nor specify thin filament lengths. We found instead a strong correspondence between thin filament lengths and titin isoform sizes for each muscle. Our results suggest the existence of a mechanism whereby nebulin specifies the minimum thin filament length and sarcomere length regulates and coordinates pointed-end dynamics to maintain the relative overlap of the thin and thick filaments during myofibril assembly. PMID:19254544

  17. Automated detection, characterization, and tracking of filaments from SDO data

    NASA Astrophysics Data System (ADS)

    Buchlin, Eric; Vial, Jean-Claude; Mercier, Claude

    2016-07-01

    Thanks to the cadence and continuity of AIA and HMI observations, SDO offers unique data for detecting, characterizing, and tracking solar filaments, until their eruptions, which are often associated with coronal mass ejections. Because of the requirement of short latency when aiming at space weather applications, and because of the important data volume, only an automated detection can be worked out. We present the code "FILaments, Eruptions, and Activations detected from Space" (FILEAS) that we have developed for the automated detection and tracking of filaments. Detections are based on the analysis of AIA 30.4 nm He II images and on the magnetic polarity inversion lines derived from HMI. Following the tracking of filaments as they rotate with the Sun, filament characteristics are computed and a database of filaments parameters is built. We present the algorithms and performances of the code, and we compare its results with the filaments detected in Hα and already present in the Heliophysics Events Knowledgebase. We finally discuss the possibility of using such a code to detect eruptions in real time.

  18. Numerical simulations of a shock-filament interaction

    NASA Astrophysics Data System (ADS)

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

    2016-05-01

    We present 3D hydrodynamic adiabatic simulations of a shock interacting with a dense, elongated cloud. We compare how the nature of the interaction changes with the filament's length and its orientation to the shock, and with the shock Mach number and the density contrast of the filament. We then examine the differences with respect to 3D spherical-cloud calculations. We find significant differences in the morphology of the interaction when M = 10 and χ = 102: in many cases, three parallel rolls are formed, and spread furthermore apart with time, and periodic vortex shedding can occur off the ends of oblique filaments. Sideways-on filaments are accelerated more quickly, and initially lose mass more quickly than spherical clouds due to their greater surface area to volume ratio. However, at late stages, they lose mass more slowly, due to the reduced relative speed between the filament and the post-shock flow. The acceleration and mixing time-scales can vary by a factor of 2 as the filament orientation changes. Oblique filaments can achieve transverse velocities up to 10 per cent of the shock speed. Some aspects of our simulations are compared against experimental and numerical work on rigid cylinders.

  19. Motor-driven dynamics of cytoskeletal filaments in motility assays.

    PubMed

    Banerjee, Shiladitya; Marchetti, M Cristina; Müller-Nedebock, Kristian

    2011-07-01

    We model analytically the dynamics of a cytoskeletal filament in a motility assay. The filament is described as rigid rod free to slide in two dimensions. The motor proteins consist of polymeric tails tethered to the plane and modeled as linear springs and motor heads that bind to the filament. As in related models of rigid and soft two-state motors, the binding and unbinding dynamics of the motor heads and the dependence of the transition rates on the load exerted by the motor tails play a crucial role in controlling the filament's dynamics. Our work shows that the filament effectively behaves as a self-propelled rod at long times, but with non-Markovian noise sources arising from the coupling to the motor binding and unbinding dynamics. The effective propulsion force of the filament and the active renormalization of the various friction and diffusion constants are calculated in terms of microscopic motor and filament parameters. These quantities could be probed by optical force microscopy. PMID:21867220

  20. Star-forming filaments in warm dark matter models

    NASA Astrophysics Data System (ADS)

    Gao, Liang; Theuns, Tom; Springel, Volker

    2015-06-01

    We performed a hydrodynamical cosmological simulation of the formation of a Milky Way-like galaxy in a warm dark matter (WDM) cosmology. Smooth and dense filaments, several comoving mega parsec long, form generically above z ˜ 2 in this model. Atomic line cooling allows gas in the centres of these filaments to cool to the base of the cooling function, resulting in a very striking pattern of extended Lyman-limit systems (LLSs). Observations of the correlation function of LLSs might hence provide useful limits on the nature of the dark matter. We argue that the self-shielding of filaments may lead to a thermal instability resulting in star formation. We implement a sub-grid model for this, and find that filaments rather than haloes dominate star formation until z ˜ 6, although this depends on how stars form in WDM. Reionization decreases the gas density in filaments, and the more usual star formation in haloes dominates below z ˜ 6, although star formation in filaments continues until z = 2. 15 per cent of the stars of the z = 0 galaxy formed in filaments. At higher redshift, these stars give galaxies a stringy appearance, which, if observed, might be a strong indication that the dark matter is warm.

  1. 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

  2. Geometric Frustration Selects Morphology in Chiral Filament Bundles

    NASA Astrophysics Data System (ADS)

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

    Assemblies of twisted filaments appear in a range of biological contexts, from extracellular filament bundles to amyloid fibrils. Owing to numerous distinctions in molecular structures and interactions underlying these diverse assemblies, a framework to predict and classify the basic mechanisms of structure formation in twisted filament assemblies is still lacking. In this study, we model how the size and shape of self-assembled fibers are controlled by competition between the elastic costs of inter-filament frustration, bending deformation of filaments and bundle surface energy. Exploiting a geometric mapping between inter-filament packing in twisted bundles and packing on positively-curved 2D surfaces, we show that the anisotropy of the bundle cross-section is determined by a single parameter describing the competition between elastic and bending costs. We compare the continuum model's predictions for stability of cylindrical and tape-like twisted morphologies to numerical simulations of cohesive filament bundles and observations of micron-scale amyloid fibers assembled from hydrolyzed protein fragments. Nsf (CAREER) DMR-0955760.

  3. Simulation of Filament Heater for Uniform Emission from Dispenser Cathode

    NASA Astrophysics Data System (ADS)

    Singh, Narendra Kr.; Bhattacharya, Ranojoy; Khatun, Hasina; Singh, Udaybir; Sinha, A. K.

    2012-06-01

    This paper presents the design study of toroid shape filament heater for dispenser cathode.The filament heater will be used in cathode assembly of 200 kW 42 GHz gyrotron. A 3 D model of cathode assembly is designed using electromagnetic and thermal simulation software, ANSYS. The simulations are performed for optimizing the input filament heater power with respect to cathode surface temperature. The parametric study shows that the input power and cathode surface temperature depends strongly on the potting material, diameter of filament, number of turns, position and height of the filament heater with respect to cathode pellet. The design analyses are also carried out for two different filament heater materials i.e. tungsten and molybdenum. Further, the thermal, structural and transient analyses are also carried out to study the mechanical strength of the filament heater. It is concluded that the input heater power should be greater than 200 W to achieve cathode surface temperature greater than 1,000°C.

  4. Femtosecond laser filamentation in condensed media with Bessel beams

    NASA Astrophysics Data System (ADS)

    Dota, Krithika; Pathak, Abhishek; Dharmadhikari, J. A.; Mathur, D.; Dharmadhikari, A. K.

    2012-08-01

    Bessel beams possess a nondiffractive property that makes them suitable for propagating optical energy over long distances. We have utilized an axicon-generated Bessel beam to carry out a systematic study of the physics that governs propagation of intense, femtosecond-long pulses in a transparent crystal (barium fluoride). Filamentation and supercontinuum generation have been studied using axicon lenses of different cone angles. Emission induced by six-photon absorption of 800-nm photons is utilized to visualize the filaments within the crystal. Our results show that higher incident energy, Ein (≥ 600 μJ), is required to generate filaments inside the crystal when an axicon is used, as compared to a spherical lens (6 μJ). Increase in cone angles increases the value of Ein for filament formation. The size of the filaments is found to be independent of whether an axicon or a spherical lens is used. For a given axicon cone angle, variation of the input energy enables us to observe the transition from steady Bessel filamentation to a nonlinear, unbalanced, Bessel regime. Varying the separation distance between the axicon and the crystal enables differences in periodicity (distance between two focusing-refocusing events) in the filaments to be quantified. Supercontinuum generation is also probed as a function of distance of sample from the tip of the axicon and with different incident beam sizes. The input beam diameter is shown to have a distinct effect on axicon-generated white light.

  5. Evolving Photospheric Flux Concentrations and Filament Dynamic Changes

    NASA Astrophysics Data System (ADS)

    Schmieder, B.; Aulanier, G.; Mein, P.; López Ariste, A.

    2006-11-01

    We analyze the role of weak photospheric flux concentrations that evolve in a filament channel, in the triggering of dynamic changes in the shape of a filament. The high polarimetric sensitivity of THEMIS allowed us to detect weak flux concentrations (few Gauss) associated with the filament development. The synoptic instruments (MDI, SOLIS) even if their sensitivity is much less than THEMIS were useful to follow any subsequent strengthening of these flux concentrations after their identification in the THEMIS magnetograms. We found that (1) the northern part of the filament develops an Hα barb at the same time that weak minority polarity elements develop near a plage; (2) a section in the southern part of the Hα filament gradually disappears and later reforms at the same time that several mixed-polarity magnetic elements appear, then subsequently cancel or spread away from each other. These changes correspond to increases in EUV emission, as observed by TRACE, EIT, and CDS. This suggests that the plasma is temporarily heated along the filament spine. An idealized sequence of force-free models of this filament channel, based on plasma-supporting magnetic dips occurring in the windings of a very weakly twisted flux tube, naturally explains the evolution of its southern part as being due to changes in the topology of the coronal magnetic field as the photospheric flux concentrations evolve.

  6. How Very Massive Metal Free Stars Start Cosmological Reionization

    SciTech Connect

    Wise, John H.; Abel, Tom

    2007-11-07

    The initial conditions and relevant physics for the formation of the earliest galaxies are well specified in the concordance cosmology. Using ab initio cosmological Eulerian adaptive mesh refinement radiation hydrodynamical calculations, we discuss how very massive stars start the process of cosmological reionization. The models include non-equilibrium primordial gas chemistry and cooling processes and accurate radiation transport in the Case B approximation using adaptively ray traced photon packages, retaining the time derivative in the transport equation. Supernova feedback is modeled by thermal explosions triggered at parsec scales. All calculations resolve the local Jeans length by at least 16 grid cells at all times and as such cover a spatial dynamic range of {approx}10{sup 6}. These first sources of reionization are highly intermittent and anisotropic and first photoionize the small scales voids surrounding the halos they form in, rather than the dense filaments they are! embedded in. As the merging objects form larger, dwarf sized galaxies, the escape fraction of UV radiation decreases and the H II regions only break out on some sides of the galaxies making them even more anisotropic. In three cases, SN blast waves induce star formation in overdense regions that were formed earlier from ionization front instabilities. These stars form tens of parsecs away from the center of their parent DM halo. Approximately 5 ionizing photons are needed per sustained ionization when star formation in 10{sup 6} M{sub {circle_dot}} halos are dominant in the calculation. As the halos become larger than {approx}10{sup 7} M{sub {circle_dot}}, the ionizing photon escape fraction decreases, which in turn increases the number of photons per ionization to 15--50, in calculations with stellar feedback only. Supernova feedback in these more massive halos creates a more diffuse medium, allowing the stellar radiation to escape more easily and maintaining the ratio of 5 ionizing

  7. MESSENGER Observations of Cusp Plasma Filaments at Mercury

    NASA Astrophysics Data System (ADS)

    Poh, Gangkai; Slavin, James; Jia, Xianzhe; DiBraccio, Gina; Raines, Jim; Imber, Suzanne; Gershman, Daniel; Anderson, Brian; Korth, Haje; McNutt, Ralph; Solomon, Sean

    2015-04-01

    The MESSENGER spacecraft, in orbit about Mercury, has documented highly localized, ~1-2-s-long reductions in the dayside magnetospheric magnetic field of the planet with amplitudes up to 90% of the ambient intensity. These magnetic field depressions which we have termed cusp filaments are observed from just poleward of the magnetospheric cusp to mid-latitudes, i.e., from ~55 to 85oN. Minimum variance analysis and superposed epoch analysis of the Magnetometer (MAG) data indicate that the filaments are simple two dimensional flux tubes. If the filaments move over the spacecraft at the polar convection speed, then these filaments have a mean diameter of ~230km, which is an order of magnitude larger than the gyro-radius of a 1 keV H+ ion, i.e., ~ 23 km. During these events, MESSENGER's Fast Imaging Plasma Spectrometer (FIPS) measured H+ ions with magnetosheath-like energies consistent with the view that the magnetic field depressions are diamagnetic and most probably the low-altitude extensions of flux transfer events (FTEs) that form at the magnetopause as a result of reconnection. Here we analyze 349 filaments identified in MESSENGER magnetic field and plasma data to determine the physical properties of these structures. MESSENGER observations during the spacecraft's final low-altitude campaign confirm that these cusp filaments extend down to very low altitudes. We calculate an average particle precipitation rate onto the surface from all of the filaments at any given time of ~ 2x1025 #s-1. This precipitation rate is comparable to published estimates of the total precipitation rate in the cusp proper. The existence of these cusp filaments has important implications for surface sputtering and our understanding of Mercury's northern cusp. 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

  8. 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

  9. 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.

  10. Controlling plasma channels through ultrashort laser pulse filamentation

    NASA Astrophysics Data System (ADS)

    Ionin, Andrey A.; Seleznev, Leonid V.; Sunchugasheva, Elena S.

    2013-10-01

    A review of studies fulfilled at the Lebedev Institute in collaboration with the Moscow State University and Institute of Atmospheric Optics in Tomsk (Siberia) on influence of various characteristics of ultrashort laser pulse on plasma channels formed under its filamentation is presented. Filamentation of high-power laser pulses with wavefront controlled by a deformable mirror, with cross-sections spatially formed by various diaphragms and with different wavelengths was experimentally and numerically studied. An application of plasma channels formed due to filamentation of ultrashort laser pulse including a train of such pulses for triggering and guiding electric discharge is discussed.

  11. 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.

  12. Production of ozone and nitrogen oxides by laser filamentation

    SciTech Connect

    Petit, Yannick; Henin, Stefano; Kasparian, Jerome; Wolf, Jean-Pierre

    2010-07-12

    We have experimentally measured that laser filaments in air generate up to 10{sup 14}, 3x10{sup 12}, and 3x10{sup 13} molecules of O{sub 3}, NO, and NO{sub 2}, respectively. The corresponding local concentrations in the filament active volume are 10{sup 16}, 3x10{sup 14}, and 3x10{sup 15} cm{sup -3}, and allows efficient oxidative chemistry of nitrogen, resulting in concentrations of HNO{sub 3} in the parts per million range. The latter forming binary clusters with water, our results provide a plausible pathway for the efficient nucleation recently observed in laser filaments.

  13. Nonquasineutral relativistic current filaments and their X-ray emission

    SciTech Connect

    Gordeev, A. V.; Losseva, T. V.

    2009-02-15

    Nonquasineutral electron current filaments with the azimuthal magnetic field are considered that arise due to the generation of electron vorticity in the initial (dissipative) stage of evolution of a current-carrying plasma, when the Hall number is small ({sigma}B/en{sub e}c << 1) because of the low values of the plasma conductivity and magnetic field strength. Equilibrium filamentary structures with both zero and nonzero net currents are considered. Structures with a zero net current type form on time scales of t < t{sub sk} = (r{sub 0{omega}pe}/c){sup 2}t{sub st}, where t{sub sk} is the skin time, t{sub st} is the typical time of electron-ion collisions, and r{sub 0} is the radius of the filament. It is shown that, in nonquasineutral filaments in which the current is carried by electrons drifting in the crossed electric (E{sub r}) and magnetic (B{sub {theta}}) fields, ultrarelativistic electron beams on the typical charge-separation scale r{sub B} = B/(4{pi}en{sub e}) (the so-called magnetic Debye radius) can be generated. It is found that, for comparable electron currents, the characteristic electron energy in filaments with a nonzero net current is significantly lower than that in zero-net-current filaments that form on typical time scales of t < t{sub sk}. This is because, in the latter type of filaments, the oppositely directed electron currents repel one another; as a result, both the density and velocity of electrons increase near the filament axis, where the velocities of relativistic electrons are maximum. Filaments with a zero net current can emit X rays with photon energies h {omega} up to 10 MeV. The electron velocity distributions in filaments, the X-ray emission spectra, and the total X-ray yield per unit filament length are calculated as functions of the current and the electron number density in the filament. Analytical estimates of the characteristic lifetime of a radiating filament and the typical size of the radiating region as functions of the

  14. Merlin - Massively parallel heterogeneous computing

    NASA Technical Reports Server (NTRS)

    Wittie, Larry; Maples, Creve

    1989-01-01

    Hardware and software for Merlin, a new kind of massively parallel computing system, are described. Eight computers are linked as a 300-MIPS prototype to develop system software for a larger Merlin network with 16 to 64 nodes, totaling 600 to 3000 MIPS. These working prototypes help refine a mapped reflective memory technique that offers a new, very general way of linking many types of computer to form supercomputers. Processors share data selectively and rapidly on a word-by-word basis. Fast firmware virtual circuits are reconfigured to match topological needs of individual application programs. Merlin's low-latency memory-sharing interfaces solve many problems in the design of high-performance computing systems. The Merlin prototypes are intended to run parallel programs for scientific applications and to determine hardware and software needs for a future Teraflops Merlin network.

  15. PRISM Polarimetry of Massive Stars

    NASA Astrophysics Data System (ADS)

    Kerkstra, Brennan; Lomax, Jamie R.; Bjorkman, Karen S.; Bjorkman, Jon Eric; Skiff, Brian; Covey, Kevin R.; Wisniewski, John P.

    2016-01-01

    We present the early results from our long-term, multi-epoch filter polarization survey of massive stars in and around young Galactic clusters. These BVRI polarization data were obtained using the PRISM instrument mounted on the 1.8m Perkins Telescope at Lowell Observatory. We first detail the creation of our new semi-automated polarization data reduction pipeline that we developed to process these data. Next, we present our analysis of the instrumental polarization properties of the PRISM instrument, via observations of polarized and unpolarized standard stars. Finally, we present early results on the total and intrinsic polarization behavior of several isolated, previously suggested classical Be stars, and discuss these results in the context of the larger project.BK acknowledges support from a NSF/REU at the University of Oklahoma. This program was also supported by NSF-AST 11411563, 1412110, and 1412135.

  16. Derivative couplings in massive bigravity

    NASA Astrophysics Data System (ADS)

    Gao, Xian; Heisenberg, Lavinia

    2016-03-01

    In this work we study the cosmological perturbations in massive bigravity in the presence of non-minimal derivative couplings. For this purpose we consider a specific subclass of Horndeski scalar-tensor interactions that live on the unique composite effective metric. For the viability of the model both metrics have to be dynamical. Nevertheless, the number of allowed kinetic terms is crucial. We adapt to the restriction of having one single kinetic term. After deriving the full set of equations of motion for flat Friedmann-Lemaitre-Robertson-Walker background, we study linear perturbations on top of it. We show explicitly that only four tensor, two vector and two scalar degrees of freedom propagate, one of which being the Horndeski scalar, while the Boulware-Deser ghost can be integrated out.

  17. Massively parallel MRI detector arrays

    NASA Astrophysics Data System (ADS)

    Keil, Boris; Wald, Lawrence L.

    2013-04-01

    Originally proposed as a method to increase sensitivity by extending the locally high-sensitivity of small surface coil elements to larger areas via reception, the term parallel imaging now includes the use of array coils to perform image encoding. This methodology has impacted clinical imaging to the point where many examinations are performed with an array comprising multiple smaller surface coil elements as the detector of the MR signal. This article reviews the theoretical and experimental basis for the trend towards higher channel counts relying on insights gained from modeling and experimental studies as well as the theoretical analysis of the so-called “ultimate” SNR and g-factor. We also review the methods for optimally combining array data and changes in RF methodology needed to construct massively parallel MRI detector arrays and show some examples of state-of-the-art for highly accelerated imaging with the resulting highly parallel arrays.

  18. Massively Parallel MRI Detector Arrays

    PubMed Central

    Keil, Boris; Wald, Lawrence L

    2013-01-01

    Originally proposed as a method to increase sensitivity by extending the locally high-sensitivity of small surface coil elements to larger areas, the term parallel imaging now includes the use of array coils to perform image encoding. This methodology has impacted clinical imaging to the point where many examinations are performed with an array comprising multiple smaller surface coil elements as the detector of the MR signal. This article reviews the theoretical and experimental basis for the trend towards higher channel counts relying on insights gained from modeling and experimental studies as well as the theoretical analysis of the so-called “ultimate” SNR and g-factor. We also review the methods for optimally combining array data and changes in RF methodology needed to construct massively parallel MRI detector arrays and show some examples of state-of-the-art for highly accelerated imaging with the resulting highly parallel arrays. PMID:23453758

  19. Massively parallel MRI detector arrays.

    PubMed

    Keil, Boris; Wald, Lawrence L

    2013-04-01

    Originally proposed as a method to increase sensitivity by extending the locally high-sensitivity of small surface coil elements to larger areas via reception, the term parallel imaging now includes the use of array coils to perform image encoding. This methodology has impacted clinical imaging to the point where many examinations are performed with an array comprising multiple smaller surface coil elements as the detector of the MR signal. This article reviews the theoretical and experimental basis for the trend towards higher channel counts relying on insights gained from modeling and experimental studies as well as the theoretical analysis of the so-called "ultimate" SNR and g-factor. We also review the methods for optimally combining array data and changes in RF methodology needed to construct massively parallel MRI detector arrays and show some examples of state-of-the-art for highly accelerated imaging with the resulting highly parallel arrays. PMID:23453758

  20. Massively parallel quantum computer simulator

    NASA Astrophysics Data System (ADS)

    De Raedt, K.; Michielsen, K.; De Raedt, H.; Trieu, B.; Arnold, G.; Richter, M.; Lippert, Th.; Watanabe, H.; Ito, N.

    2007-01-01

    We describe portable software to simulate universal quantum computers on massive parallel computers. We illustrate the use of the simulation software by running various quantum algorithms on different computer architectures, such as a IBM BlueGene/L, a IBM Regatta p690+, a Hitachi SR11000/J1, a Cray X1E, a SGI Altix 3700 and clusters of PCs running Windows XP. We study the performance of the software by simulating quantum computers containing up to 36 qubits, using up to 4096 processors and up to 1 TB of memory. Our results demonstrate that the simulator exhibits nearly ideal scaling as a function of the number of processors and suggest that the simulation software described in this paper may also serve as benchmark for testing high-end parallel computers.

  1. Stable massive particles at colliders

    SciTech Connect

    Fairbairn, M.; Kraan, A.C.; Milstead, D.A.; Sjostrand, T.; Skands, P.; Sloan, T.; /Lancaster U.

    2006-11-01

    We review the theoretical motivations and experimental status of searches for stable massive particles (SMPs) which could be sufficiently long-lived as to be directly detected at collider experiments. The discovery of such particles would address a number of important questions in modern physics including the origin and composition of dark matter in the universe and the unification of the fundamental forces. This review describes the techniques used in SMP-searches at collider experiments and the limits so far obtained on the production of SMPs which possess various colour, electric and magnetic charge quantum numbers. We also describe theoretical scenarios which predict SMPs, the phenomenology needed to model their production at colliders and interactions with matter. In addition, the interplay between collider searches and open questions in cosmology such as dark matter composition are addressed.

  2. Massive supersymmetric quantum gauge theory

    NASA Astrophysics Data System (ADS)

    Grigore, D. R.; Gut, M.; Scharf, G.

    2005-08-01

    We continue the study of the supersymmetric vector multiplet in a purely quantum framework. We obtain some new results which make the connection with the standard literature. First we construct the one-particle physical Hilbert space taking into account the (quantum) gauge structure of the model. Then we impose the condition of positivity for the scalar product only on the physical Hilbert space. Finally we obtain a full supersymmetric coupling which is gauge invariant in the supersymmetric sense in the first order of perturbation theory. By integrating out the Grassmann variables we get an interacting Lagrangian for a massive Yang-Mills theory related to ordinary gauge theory; however the number of ghost fields is doubled so we do not obtain the same ghost couplings as in the standard model Lagrangian.

  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. 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

  5. High-Latitude Molecular Clouds in an HI Filament towards the MBM 53, 54, and 55 Complex

    NASA Astrophysics Data System (ADS)

    Yamamoto, H.; Onishi, T.; Mizuno, A.; Fukui, Y.

    We carried out a CO survey of high galactic latitude molecular clouds towards an HI filament that contains a molecular cloud complex, MBM 53, 54, and 55. The filament is found to consist of many clumpy molecular clouds, and we identified 110 12CO (J = 1 --0) clouds in the region, whose total mass was estimated to be ˜ 1200 M⊙. 13CO (J = 1--0) and C18O (J = 1--0) observations were carried out towards the region of high 12CO and 13CO intensities, respectively. There was no detection of the C18O line towards the positions of strong 13CO detection, indicating that there are no clouds dense enough to form stars in the near future. We have found a massive cloud, HLCG 92-35, around (l, b) ˜ (92o, -35o) of mass ˜ 330 M⊙. This cloud occupies the galactic western half of a circular-shaped HI gas cloud in the HI filament, and the HI to CO mass ratio is estimated to be the largest in the observed region. The far-infrared excess over HI emission, which is a good indicator of the existence of molecular hydrogen, towards HLCG 92-35 is also the largest in the observed region, implying that there is a large amount of molecular hydrogen in spite of the small optical depth of CO. These facts indicate that HLCG 92-35 is a CO-forming cloud, which is younger than the MBM clouds in terms of molecular cloud formation. Some past explosive event towards the HI filament has been suggested by Gir et al. (1994). The molecular gas may be formed by the compression of an expanding HI shell.

  6. A Massive Warm Baryonic Halo in the Coma Cluster

    NASA Technical Reports Server (NTRS)

    Bonamente, Massimiliano; Joy, Marshall K.; Lieu, Richard

    2003-01-01

    Several deep PSPC observations of the Coma Cluster reveal a very large scale halo of soft X-ray emission, substantially in excess of the well-known radiation from the hot intracluster medium. The excess emission, previously reported in the central region of the cluster using lower sensitivity Extreme Ultraviolet Explorer (EUVE) and ROSAT data, is now evident out to a radius of 2.6 Mpc, demonstrating that the soft excess radiation from clusters is a phenomenon of cosmological significance. The X-ray spectrum at these large radii cannot be modeled nonthermally but is consistent with the original scenario of thermal emission from warm gas at approx. 10(exp 6) K. The mass of the warm gas is on par with that of the hot X-ray-emitting plasma and significantly more massive if the warm gas resides in low-density filamentary structures. Thus, the data lend vital support to current theories of cosmic evolution, which predict that at low redshift approx. 30%-40% of the baryons reside in warm filaments converging at clusters of galaxies.

  7. Tubular filamentation for laser material processing.

    PubMed

    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 10(13) W/cm(2) 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

  8. On the interaction of dipolar filaments.

    PubMed

    Messina, René; Spiteri, Ludovic

    2016-08-01

    The interactions of dipolar filaments such as magnetic needles and chains in strong homogeneous magnetic/electric field are investigated theoretically. Revisiting the case of uniformly magnetized/polarized parallel needles of finite size L and separated by a distance R , all the relevant regimes of attraction and/or repulsion are properly addressed and discussed. At short inter-needle separation ( R/L ≲ 0.2, the repuive pair potential of two facing needles is governed by R(-1) in strong contrast with R(-3) at long separations (R/L ≳ 2.5). This softening is attributed to an efficient long-range screening owing to the relatively long needle extension in this regime. This whole understanding of dipolar needles effective interaction is then used to grasp that of dipolar chains made up of spherical dipolar beads. When excluded-volume correlations are weak (i.e., the chains are a few beads apart), chains and needles possess virtually the same effective interaction. However, at short separation there is a remarkable hardening upon approaching two chains in registry in qualitative contrast to the needles case. PMID:27562832

  9. Repair of filament wound composite pipes

    NASA Astrophysics Data System (ADS)

    Amali, Ramin; Arnall, Heather

    2015-07-01

    Filament wound pipes are used in a wide variety of industries, due to the advantages composites have over metal pipes, such as a high strength to weight ratio, and resistance against frost, corrosion and heat. Composite pipes require minimal maintenance to ensure they are safe. Any damage occurring in composite pipes could lead to failure; therefore all damage should be assessed through NDT. If it is decided that the damage makes the pipe unsafe then a decision needs to be made whether to repair or replace the pipe. Repairing a composite pipe can be quicker, easier and cheaper than replacing it and can restore the strength of the pipe effectively. This investigation looks at the repair process and the parameters involved in determining the strength of the pipe following repair through the use of over 150 models in FEA software, Abaqus. Parameters considered include the pipe diameter and thickness, damage removal size and wrap width and thickness. It was found that if the pipe is thin-walled then it can be assumed that the pipe's thickness has no effect on the FOS following repair. Formulas were created to predict the FOS following repair for varying pipe diameters, damage sizes and wrap thickness. Formulas were also created to determine the wrap width required for varying wrap thicknesses and damage sizes.

  10. Pyrene degradation by yeasts and filamentous fungi.

    PubMed

    Romero, M Cristina; Salvioli, Mónica L; Cazau, M Cecilia; Arambarri, A M

    2002-01-01

    The saprotrophic soil fungi Fusarium solani (Mart.) Sacc., Cylindrocarpon didymum (Hartig) Wollenw, Penicillium variabile Sopp. and the yeasts Rhodotorula glutinis (Fresenius) Harrison and Rhodotorula minuta (Saito) Harrison were cultured in mineral medium with pyrene. The remaining pyrene concentrations were periodically determined during 20 incubation days, using HPLC. To assess the metabolism of pyrene degradation we added 0.1 microCi of [4,5,9,10] 14C-pyrene to each fungi culture and measured the radioactivity in the volatile organic substances, extractable, aqueous phase, biomass and 14CO2 fractions. The assays demonstrated that F. solani and R. glutinis metabolized pyrene as a sole source of carbon. Differences in their activities at the beginning of the cultures disappeared by the end of the experiment, when 32 and 37% of the original pyrene concentration was detected, for the soil fungi and yeasts, respectively. Among the filamentous fungi, F. solani was highly active and oxidized pyrene; moreover, small but significant degradation rates were observed in C. didymum and P. variahile cultures. An increase in the 14CO2 evolution was observed at the 17th day with cosubstrate. R. glutinis and R. minuta cultures showed similar ability to biotransform pyrene, and that 35% of the initial concentration was consumed at the end of the assay. The same results were obtained in the experiments with or without glucose as cosubstrate. PMID:11843531

  11. 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. PMID:9847417

  12. Enhancing Nonribosomal Peptide Biosynthesis in Filamentous Fungi

    PubMed Central

    Soukup, Alexandra A.; Keller, Nancy P.; Wiemann, Philipp

    2016-01-01

    Filamentous fungi are historically known as rich sources for production of biologically active natural products, so-called secondary metabolites. One particularly pharmaceutically relevant chemical group of secondary metabolites is the nonribosomal peptides synthesized by nonribosomal peptide synthetases (NRPSs). As most of the fungal NRPS gene clusters leading to production of the desired molecules are not expressed under laboratory conditions, efforts to overcome this impediment are crucial to unlock the full chemical potential of each fungal species. One way to activate these silent clusters is by overexpressing and deleting global regulators of secondary metabolism. The conserved fungal-specific regulator of secondary metabolism, LaeA, was shown to be a valuable target for sleuthing of novel gene clusters and metabolites. Additionally, modulation of chromatin structures by either chemical or genetic manipulation has been shown to activate cryptic metabolites. Furthermore, NRPS-derived molecules seem to be affected by cross talk between the specific gene clusters and some of these metabolites have a tissue- or developmental-specific regulation. This chapter summarizes how this knowledge of different tiers of regulation can be combined to increase production of NRPS-derived metabolites in fungal species. PMID:26831707

  13. 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.

  14. 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

  15. The Apis mellifera Filamentous Virus Genome

    PubMed Central

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

    2015-01-01

    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. PMID:26184284

  16. Characterization of erythrose reductases from filamentous fungi.

    PubMed

    Jovanović, Birgit; Mach, Robert L; Mach-Aigner, Astrid R

    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

  17. Laser control of filament-induced shock wave in water

    NASA Astrophysics Data System (ADS)

    Potemkin, F. V.; Mareev, E. I.; Podshivalov, A. A.; Gordienko, V. M.

    2014-09-01

    We discovered that tight focusing of Cr:forsterite femtosecond laser radiation in water provides the unique opportunity of long filament generation. The filament becomes a source of numerous spherical shock waves whose radius tends to saturate with the increase of energy. These overlapping waves create a contrast cylindrical shock wave. The laser-induced shock wave parameters such as shape, amplitude and speed can be effectively controlled by varying energy and focusing geometry of the femtosecond pulse. Aberrations added to the optical scheme lead to multiple dotted plasma sources for shock wave formation, spaced along the optical axis. Increasing the laser energy launches filaments at each dot that enhance the length of the entire filament and as a result, the shock impact on the material.

  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. 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.

  20. History and phylogeny of intermediate filaments: Now in insects

    PubMed Central

    2011-01-01

    Intermediate filaments include the nuclear lamins, which are universal in metazoans, and the cytoplasmic intermediate filaments, which are much more varied and form cell type-specific networks in animal cells. Until now, it has been thought that insects harbor lamins only. This view is fundamentally challenged by the discovery, reported in BMC Biology, of an intermediate filament-like cytoplasmic protein, isomin, in the hexapod Isotomurus maculatus. Here we briefly review the history of research on intermediate filaments, and discuss the implications of this latest finding in the context of what is known of their structure and functions. See research article: http://www.biomedcentral.com/1741-7007/9/17 PMID:21356127

  1. Tropomyosin diffusion over actin subunits facilitates thin filament assembly

    PubMed Central

    Fischer, Stefan; Rynkiewicz, Michael J.; Moore, Jeffrey R.; Lehman, William

    2016-01-01

    Coiled-coil tropomyosin binds to consecutive actin-subunits along actin-containing thin filaments. Tropomyosin molecules then polymerize head-to-tail to form cables that wrap helically around the filaments. Little is known about the assembly process that leads to continuous, gap-free tropomyosin cable formation. We propose that tropomyosin molecules diffuse over the actin-filament surface to connect head-to-tail to partners. This possibility is likely because (1) tropomyosin hovers loosely over the actin-filament, thus binding weakly to F-actin and (2) low energy-barriers provide tropomyosin freedom for 1D axial translation on F-actin. We consider that these unique features of the actin-tropomyosin interaction are the basis of tropomyosin cable formation. PMID:26798831

  2. 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.

  3. 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.

  4. 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. PMID:27446051

  5. Broken Detailed Balance of Filament Dynamics in Active Networks.

    PubMed

    Gladrow, J; Fakhri, N; MacKintosh, F C; Schmidt, C F; Broedersz, C P

    2016-06-17

    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. PMID:27367410

  6. 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...

  7. 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.

  8. HFCVD of diamond at low substrate and low filament temperatures

    SciTech Connect

    Tolt, Z.L.; Heatherly, L.; Clausing, R.E.; Shaw, R.W.; Feigerle, C.S.

    1995-12-31

    It has been discovered that the addition of a small amount of oxygen to the CH{sub 4} and H{sub 2} feed gas permits HFCVD of diamond at significantly lower filament and substrate temperatures. The effective O/C ratio here is much lower than that used in most studies of the oxygen effect. Careful control of the O/C and C/H ratios were found to be crucial to success. The effects of substrate and filament temperatures on growth rate and film quality were studied. Optimum conditions were found that gave reasonable growth rates ( {approximately}0.5 {mu}m/h ) with high film quality at filament temperatures below 1750{degrees}C and substrate temperatures below 600C. As a result, low temperature deposition has been realized. Power consumption can be reduced 50%, and the filament lifetime is extended indefinitely.

  9. Light Echoes from Linear Filaments in Astronomical Settings

    NASA Astrophysics Data System (ADS)

    Zhong, Qi; Nemiroff, Robert J.

    2016-01-01

    Stellar flashes are known to create light echoes by scattering off ambient dust. Here light echoes from straight, linear, one-dimensional dust filaments are specifically considered in detail. On an infinite straight filament, a flash will necessarily create a superluminal spot pair creation event. The actual and perceived locations, speeds, and relative brightnesses of these diverging spot pairs are computed. On filaments of finite length, only one light spot will typically be seen. Geometries where this spot appears to move angularly toward the flash are shown to be possible. It is also shown that it is possible to completely orient a linear filament in three-dimensional space by recording two separated detections of the light-echo spot. Recoverable information in theory and in practice will be reviewed.

  10. 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

  11. Non-equilibrium States of Active Filament Networks

    NASA Astrophysics Data System (ADS)

    Blackwell, Robert A.; Betterton, Meredith D.; Sweezy, Oliver M.; Glaser, Matthew A.

    2014-03-01

    Active networks of filamentous proteins and crosslinking motor proteins play a critical role in many cellular processes. Among the most important active networks is the mitotic spindle, an assembly of microtubules and crosslinking motor proteins that forms during cell division and that ultimately separates chromosomes into two daughter cells. To evolve a better understanding of spindle formation, structure, and dynamics, we have developed course-grained models of active networks composed of filaments, modeled as hard spherocylinders, in diffusive equilibrium with a reservoir of crosslinking motors, modeled as Hookean springs that can adsorb to microtubules and translocate at finite velocity along the microtubule axis. We explore the phase diagram and other characteristics of this model in two and three dimensions as a function of filament packing fraction, and of crosslink concentration, velocity, and adsorption and desorption rates. We observe a variety of interesting emergent behaviors including sorting of filaments into polar domains, generation of extensile stress, and superdiffusive transport. DMR-0820579

  12. High Mass Star Formation in the Vicinity of a Young Massive Protocluster IRAS 04073+5102 (SH 209)

    NASA Astrophysics Data System (ADS)

    Chibueze, James

    2015-08-01

    IRAS 04073+5102 (SH 209) is a massive high mass star forming regions hosting massive protoclusters. Star formation in the vicinity of expanding HII region could toll different path from those of pristine environment. IRAS 04073+5102 (SH 209) provides an ideal region to study the influence of expanding region on the star formation activities in a region. We performed a 15-pointing mosaic observation of the region at 230 GHz with submillimeter array (SMA) and detected dust continuum emissions, 12CO, 13CO, C18O and SO. We used SMA dust continuum and CO data to identify and characterize the major filaments and cores in the complex. The brightest mm clump of 4000 M⊙ observed at low resolution fragments into just three cores and the prominent core is an excellent candidate for a massive protocluster. Comparing of SMA images with Spitzer images, we could isolate very young filaments containing pre-protoclusters that would likely form clusters. The expanding HII region may have contributed to the formation of the observed filamentary structures and in triggering star formation in the region. We performed core-core velocity dispersion analysis of the region. Scaling the distance of our target to the distance of Orion molecular cloud (OMC), we compared star formation in both regions.

  13. Massive Star Burps, Then Explodes

    NASA Astrophysics Data System (ADS)

    2007-04-01

    Berkeley -- In a galaxy far, far away, a massive star suffered a nasty double whammy. On Oct. 20, 2004, Japanese amateur astronomer Koichi Itagaki saw the star let loose an outburst so bright that it was initially mistaken for a supernova. The star survived, but for only two years. On Oct. 11, 2006, professional and amateur astronomers witnessed the star actually blowing itself to smithereens as Supernova 2006jc. Swift UVOT Image Swift UVOT Image (Credit: NASA / Swift / S.Immler) "We have never observed a stellar outburst and then later seen the star explode," says University of California, Berkeley, astronomer Ryan Foley. His group studied the event with ground-based telescopes, including the 10-meter (32.8-foot) W. M. Keck telescopes in Hawaii. Narrow helium spectral lines showed that the supernova's blast wave ran into a slow-moving shell of material, presumably the progenitor's outer layers ejected just two years earlier. If the spectral lines had been caused by the supernova's fast-moving blast wave, the lines would have been much broader. artistic rendering This artistic rendering depicts two years in the life of a massive blue supergiant star, which burped and spewed a shell of gas, then, two years later, exploded. When the supernova slammed into the shell of gas, X-rays were produced. (Credit: NASA/Sonoma State Univ./A.Simonnet) Another group, led by Stefan Immler of NASA's Goddard Space Flight Center, Greenbelt, Md., monitored SN 2006jc with NASA's Swift satellite and Chandra X-ray Observatory. By observing how the supernova brightened in X-rays, a result of the blast wave slamming into the outburst ejecta, they could measure the amount of gas blown off in the 2004 outburst: about 0.01 solar mass, the equivalent of about 10 Jupiters. "The beautiful aspect of our SN 2006jc observations is that although they were obtained in different parts of the electromagnetic spectrum, in the optical and in X-rays, they lead to the same conclusions," says Immler. "This

  14. Stefan-Boltzmann Law for Massive Photons

    NASA Astrophysics Data System (ADS)

    Moreira, E. S.; Ribeiro, T. G.

    2016-08-01

    This paper generalizes the Stefan-Boltzmann law to include massive photons. A crucial ingredient to obtain the correct formula for the radiance is to realize that a massive photon does not travel at the speed of (massless) light. It follows that, contrary to what could be expected, the radiance is not proportional to the energy density times the speed of light.

  15. Gravitational massive modes from extended gravity

    NASA Astrophysics Data System (ADS)

    Basini, Giuseppe; Capozziello, Salvatore; de Laurentis, Mariafelicia

    2016-02-01

    Further gravitational massive modes emerge by extending the geometrical sector of Hilbert-Einstein theory in the most general theory including curvature invariants. Besides massless spin-2, also spin-0 and spin-2 massive and ghost fields have to be considered. We investigate the possible detectability of such additional modes by the Large Hadron Collider and calculate the detectable energy density of the spectrum.

  16. Massive OB stars at varying Z

    NASA Astrophysics Data System (ADS)

    Herrero, A.; Garcia, M.; Simón-Díaz, S.; Camacho, I.; Sabín-Sanjulián, C.; Castro, N.

    2015-01-01

    Massive stars play a key role in environments with very different metallicities. To interpret the role of massive stars in these systems we have to know their properties at different metallicities. The Local Group offers an excellent laboratory to this aim.

  17. Stefan-Boltzmann Law for Massive Photons

    NASA Astrophysics Data System (ADS)

    Moreira, E. S.; Ribeiro, T. G.

    2016-04-01

    This paper generalizes the Stefan-Boltzmann law to include massive photons. A crucial ingredient to obtain the correct formula for the radiance is to realize that a massive photon does not travel at the speed of (massless) light. It follows that, contrary to what could be expected, the radiance is not proportional to the energy density times the speed of light.

  18. Calcium ion-regulated thin filaments from vascular smooth muscle.

    PubMed Central

    Marston, S B; Trevett, R M; Walters, M

    1980-01-01

    Myosin and actin competition tests indicated the presence of both thin-filament and myosin-linked Ca2+-regulatory systems in pig aorta and turkey gizzard smooth-muscle actomyosin. A thin-filament preparation was obtained from pig aortas. The thin filaments had no significant ATPase activity [1.1 +/- 2.6 nmol/mg per min (mean +/- S.D.)], but they activated skeletal-muscle myosin ATPase up to 25-fold [500 nmol/mg of myosin per min (mean +/- S.D.)] in the presence of 10(-4) M free Ca2+. At 10(-8) M-Ca2+ the thin filaments activated myosin ATPase activity only one-third as much. Thin-filament activation of myosin ATPase activity increased markedly in the range 10(-6)-10(-5) M-Ca2+ and was half maximal at 2.7 x 10(-6) M (pCa2+ 5.6). The skeletal myosin-aorta-thin-filament mixture gave a biphasic ATPase-rate-versus-ATP-concentration curve at 10(-8) M-Ca2+ similar to the curve obtained with skeletal-muscle thin filaments. Thin filaments bound up to 9.5 mumol of Ca2+/g in the presence of MgATP2-. In the range 0.06-27 microM-Ca2+ binding was hyperbolic with an estimated binding constant of (0.56 +/- 0.07) x 10(6) M-1 (mean +/- S.D.) and maximum binding of 8.0 +/- 0.8 mumol/g (mean +/- S.D.). Significantly less Ca2+ bound in the absence of ATP. The thin filaments contained actin, tropomyosin and several other unidentified proteins. 6 M-Urea/polyacrylamide-gel electrophoresis at pH 8.3 showed proteins that behaved like troponin I and troponin C. This was confirmed by forming interspecific complexes between radioactive skeletal-muscle troponin I and troponin C and the aorta thin-filament proteins. The thin filaments contained at least 1.4 mumol of a troponin C-like protein/g and at least 1.1 mumol of a troponin I-like protein/g. PMID:6446898

  19. 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.

  20. 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.