Science.gov

Sample records for minimal non-extendably collapsible

  1. Metal-air cells comprising collapsible foam members and means for minimizing internal pressure buildup

    NASA Technical Reports Server (NTRS)

    Woodruff, Glenn (Inventor); Putt, Ronald A. (Inventor)

    1994-01-01

    This invention provides a prismatic zinc-air cell including, in general, a prismatic container having therein an air cathode, a separator and a zinc anode. The container has one or more oxygen access openings, and the air cathode is disposed in the container in gaseous communication with the oxygen access openings so as to allow access of oxygen to the cathode. The separator has a first side in electrolytic communication with the air cathode and a second side in electrolytic communication with the zinc anode. The separator isolates the cathode and the zinc anode from direct electrical contact and allows passage of electrolyte therebetween. An expansion chamber adjacent to the zinc anode is provided which accommodates expansion of the zinc anode during discharge of the cell. A suitable collapsible foam member generally occupies the expansion space, providing sufficient resistance tending to oppose movement of the zinc anode away from the separator while collapsing upon expansion of the zinc anode during discharge of the cell. One or more vent openings disposed in the container are in gaseous communication with the expansion space, functioning to satisfactorily minimize the pressure buildup within the container by venting gasses expelled as the foam collapses during cell discharge.

  2. Collapsed Lung

    MedlinePlus

    A collapsed lung happens when air enters the pleural space, the area between the lung and the chest wall. If it is a total collapse, it is called pneumothorax. If only part of the lung is affected, ...

  3. Collapsed Lung

    MedlinePlus

    A collapsed lung happens when air enters the pleural space, the area between the lung and the chest wall. If it is a ... is called pneumothorax. If only part of the lung is affected, it is called atelectasis. Causes of ...

  4. Tracheal collapse.

    PubMed

    Hedlund, C S

    1991-06-01

    Tracheal collapse, one form of tracheal obstruction, is classically described as occurring in middle-aged or older toy breed dogs with a history of chronic "goose-honk" cough. Many dogs with tracheal collapse fit this description, but others are young and may wheeze, hack, or have no cough at all. Patients with a history and physical examination compatible with tracheal collapse are definitively diagnosed based on the findings of the following respiratory tract examinations: inspiratory/expiratory radiographs, fluoroscopy, culture and susceptibility, and a thorough endoscopic evaluation. Prosthetic ring tracheoplasty relieves many of the signs of tracheal obstruction but does not cure the disease. Early diagnosis and treatment are expected to give the dog a better quality life. Following prosthetic ring tracheoplasty, most dogs are more active, breathe easier, cough less, and require less medical treatment for respiratory disease. PMID:1802250

  5. Collapsing Containers.

    ERIC Educational Resources Information Center

    Brown, Justina L.; Battino, Rubin

    1994-01-01

    Describes variations on atmospheric pressure demonstrations and some systematic studies. Demonstrations use steam, generated either externally or internally to the container, to sweep out residual air. Preferred vessels collapsed slowly. Demonstrations use plastic milk jugs set in layers of aluminum foil, pop bottles immersed in 4-L beakers…

  6. Collapse Miscellany

    NASA Astrophysics Data System (ADS)

    Pearle, Philip

    An introduction to the CSL (Continuous Spontaneous Localization) theory of dynamical wave function collapse is provided, including a derivation of CSL from two postulates, a new result. There follows a review of applications to a free particle, or to a `small' rigid cluster of free particles, in a single wave-packet and in interfering packets: the latter result is new. [Editors note: for a video of the talk given by Prof. Pearle at the Aharonov-80 conference in 2012 at Chapman University, see http://quantum.chapman.edu/talk-11.

  7. Collapse Tubes

    NASA Technical Reports Server (NTRS)

    2006-01-01

    [figure removed for brevity, see original site] Context image for PIA02154 Collapse Tubes

    The discontinuous channels in this image are collapsed lava tubes.

    Image information: VIS instrument. Latitude -19.7N, Longitude 317.5E. 17 meter/pixel resolution.

    Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time.

    NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. The Thermal Emission Imaging System (THEMIS) was developed by Arizona State University, Tempe, in collaboration with Raytheon Santa Barbara Remote Sensing. The THEMIS investigation is led by Dr. Philip Christensen at Arizona State University. Lockheed Martin Astronautics, Denver, is the prime contractor for the Odyssey project, and developed and built the orbiter. Mission operations are conducted jointly from Lockheed Martin and from JPL, a division of the California Institute of Technology in Pasadena.

  8. Geophysical observations at cavity collapse

    NASA Astrophysics Data System (ADS)

    Jousset, Philippe; Bazargan-Sabet, Behrooz; Lebert, François; Bernardie, Séverine; Gourry, Jean-Christophe

    2010-05-01

    In Lorraine region (France) salt layers at about 200 meters depth are exploited by Solvay using solution mining methodology which consists in extracting the salt by dissolution, collapsing the cavern overburden during the exploitation phase and finally reclaiming the landscape by creating a water area. In this process, one of the main challenges for the exploiting company is to control the initial 120-m diameter collapse so as to minimize possible damages. In order to detect potential precursors and understand processes associated with such collapses, a wide series of monitoring techniques including micro seismics, broad-band seismology, hydro-acoustic, electromagnetism, gas probing, automatic leveling, continuous GPS, continuous gravity and borehole extensometry was set-up in the frame of an in-situ study carried out by the "Research Group for the Impact and Safety of Underground Works" (GISOS, France). Equipments were set-up well before the final collapse, giving a unique opportunity to analyze a great deal of information prior to and during the collapse process which has been successfully achieved on February the 13th, 2009 by controlling the cavity internal pressure. In this work, we present the results of data recorded by a network of 3 broadband seismometers, 2 accelerometers, 2 tilt-meters and a continuously gravity meter. We relate the variations of the brine pumping rate with the evolutions of the induced geophysical signals and finally we propose a first mechanical model for describing the controlled collapse. Beyond the studied case, extrapolation of the results obtained might contribute to the understanding of uncontrolled cavity collapses, such as pit-craters or calderas at volcanoes.

  9. Collapsable seal member

    SciTech Connect

    Sherrell, Dennis L.

    1990-01-01

    A hollow, collapsable seal member normally disposed in a natural expanded state offering fail-safe pressure sealing against a seating surface and adapted to be evacuated by a vacuum force for collapsing the seal member to disengage the same from said seating surface.

  10. Collapsable seal member

    SciTech Connect

    Sherrell, D.L.

    1983-12-08

    A hollow, collapsable seal member normally disposed in a natural expanded state offering fail-safe pressure sealing against a seating surface and adapted to be evacuated by a vacuum force for collapsing the seal member to disengage the same from said seating surface.

  11. Critical chemotactic collapse

    NASA Astrophysics Data System (ADS)

    Lushnikov, Pavel M.

    2010-04-01

    A Keller-Segel model describes macroscopic dynamics of bacterial colonies and biological cells as well as dynamics of a gas of self-gravitating Brownian particles. Bacteria secret chemical which attracts other bacteria so that they move towards chemical gradient creating nonlocal attraction between bacteria. If bacterial (or Brownian particle) density exceeds a critical value then the density collapses (blows up) in a finite time which corresponds to bacterial aggregation or gravitational collapse. Collapse in the Keller-Segel model has striking qualitative similarities with a nonlinear Schrödinger equation including critical collapse in two dimensions and supercritical collapse in three dimensions. A self-similar solution near blow up point is studied in the critical two-dimensional case and it has a form of a rescaled steady state solution which contains a critical number of bacteria. Time dependence of scaling of that solution has square root scaling law with logarithmic modification.

  12. Collapse in Thermal Plumes

    NASA Astrophysics Data System (ADS)

    Pears, M. I.; Lithgow-Bertelloni, C. R.; Dobson, D. P.; Davies, R.

    2013-12-01

    Collapsing thermal plumes have been investigated through experimental and numerical simulations. Collapsing plumes are an uncommon fluid dynamical phenomenon, usually seen when the buoyancy source is turned off. A series of fluid dynamical experiments were conducted on thermal plumes at a variety of temperature and viscosity contrasts, in a 26.5 cm^3 cubic tank heated by a constant temperature heater 2 cm in diameter and no-slip bottom and top surfaces. Working fluids included Lyle's Golden Syrup and ADM's Liquidose 436 syrup, which have strongly-temperature dependent viscosity and high Pr number (10^3-10^7 at experimental conditions). Visualisation included white light shadowgraphs and PIV of the central plane. Temperature contrasts ranged from 3-60°C, and two differing forms of collapse were identified. At very low temperature differences 'no rise' collapse was discovered, where the plumes stagnate in the lower third of the tank before collapsing. At temperature differences between 10-23°C normal evolution occurred until 'lens shape' collapse developed between midway and two-thirds of the distance from the base. The lens shape originated in the top of the conduit and was present throughout collapse. At temperatures above ΔT=23°C the plumes follow the expected growth and shape and flatten out at the top of the tank. Thermal collapse remains difficult to explain given experimental conditions (continuous heating). Instead it is possible that small density differences arising from crystallization at ambient temperatures changes plume buoyancy-inducing collapse. We show results on the evolution of the refractive index of the syrup through time to ascertain this possibility. Preliminary numerical results using Fluidity will be presented to explore a greater parameter range of viscosity contrasts and tank aspect ratios.

  13. Magnetorotational iron core collapse

    NASA Technical Reports Server (NTRS)

    Symbalisty, E. M. D.

    1984-01-01

    During its final evolutionary stages, a massive star, as considered in current astrophysical theory, undergoes rapid collapse, thereby triggering a sequence of a catastrophic event which results in a Type II supernova explosion. A remnant neutron star or a black hole is left after the explosion. Stellar collapse occurs, when thermonuclear fusion has consumed the lighter elements present. At this stage, the core consists of iron. Difficulties arise regarding an appropriate model with respect to the core collapse. The present investigation is concerned with the evolution of a Type II supernova core including the effects of rotation and magnetic fields. A simple neutrino model is developed which reproduced the spherically symmetric results of Bowers and Wilson (1982). Several two-dimensional computational models of stellar collapse are studied, taking into account a case in which a 15 solar masses iron core was artificially given rotational and magnetic energy.

  14. Collapse of Surface Nanobubbles

    NASA Astrophysics Data System (ADS)

    Chen, Longquan; Chan, Chon U.; Arora, Manish; Ohl, Claus-Dieter

    2014-11-01

    Surface nanobubbles are nanoscopic gaseous domains that entrap on immersed solid surfaces in water. They are surprisingly stable and are difficult to be distinguished from polymeric/hydrophobic drops and solid particles (contamination). Here, we report a comparative study of contact line motion across surface nanobubbles, polymeric drops and solid particles. We show that surface nanobubbles spontaneously collapse once contact line touches them while a fast jump process and a pinning process are observed on polymeric drops and on solid particles, respectively. These distinct contact line dynamics provide a new approach to identify surface nanobubbles. The collapse of surface nanobubbles demonstrates their gaseous property and also indicates that they are metastable. The collapse process last few milliseconds with a characteristic speed of 0.1 mm/s, which is much longer and slower than that of hydrodynamic phenomena. We further show that the collapse phenomenon can be explained with a microscopic contact line dynamics.

  15. Collapse transition in proteins.

    PubMed

    Ziv, Guy; Thirumalai, D; Haran, Gilad

    2009-01-01

    The coil-globule transition, a tenet of the physics of polymers, has been identified in recent years as an important unresolved aspect of the initial stages of the folding of proteins. We describe the basics of the collapse transition, starting with homopolymers and continuing with proteins. Studies of denatured-state collapse under equilibrium are then presented. An emphasis is placed on single-molecule fluorescence experiments, which are particularly useful for measuring properties of the denatured state even under conditions of coexistence with the folded state. Attempts to understand the dynamics of collapse, both theoretically and experimentally, are then described. Only an upper limit for the rate of collapse has been obtained so far. Improvements in experimental and theoretical methodology are likely to continue to push our understanding of the importance of the denatured-state thermodynamics and dynamics for protein folding in the coming years. PMID:19081910

  16. Countdown to Systems Collapse.

    ERIC Educational Resources Information Center

    Tysseling, John C.; Easton, Jeff; Weaks, Julie

    2002-01-01

    Describes how the University of New Mexico Albuquerque developed a strategic business plan for renewing its utility systems when faced with the imminent collapse of its entire energy infrastructure and a $75-100 million price tag for upgrades. (EV)

  17. Collapsed lung (pneumothorax)

    MedlinePlus

    Air around the lung; Air outside the lung; Pneumothorax dropped lung; Spontaneous pneumothorax ... Collapsed lung can be caused by an injury to the lung. Injuries can include a gunshot or knife wound ...

  18. Relativistic dynamical collapse model

    NASA Astrophysics Data System (ADS)

    Pearle, Philip

    2015-05-01

    A model is discussed where all operators are constructed from a quantum scalar field whose energy spectrum takes on all real values. The Schrödinger picture wave function depends upon space and time coordinates for each particle, as well as an inexorably increasing evolution parameter s which labels a foliation of spacelike hypersurfaces. The model is constructed to be manifestly Lorentz invariant in the interaction picture. Free particle states and interactions are discussed in this framework. Then, the formalism of the continuous spontaneous localization (CSL) theory of dynamical collapse is applied. The collapse-generating operator is chosen to be the particle number space-time density. Unlike previous relativistically invariant models, the vacuum state is not excited. The collapse dynamics depends upon two parameters, a parameter Λ which represents the collapse rate/volume and a scale factor ℓ. A common example of collapse dynamics, involving a clump of matter in a superposition of two locations, is analyzed. The collapse rate is shown to be identical to that of nonrelativistic CSL when the GRW-CSL choice of ℓ=a =1 0-5 cm , is made, along with Λ =λ /a3 (GRW-CSL choice λ =1 0-16s-1). The collapse rate is also satisfactory with the choice ℓ as the size of the Universe, with Λ =λ /ℓa2. Because the collapse narrows wave functions in space and time, it increases a particle's momentum and energy, altering its mass. It is shown that, with ℓ=a , the change of mass of a nucleon is unacceptably large but, when ℓ is the size of the Universe, the change of mass over the age of the Universe is acceptably small.

  19. Ascraeus Mons Collapse Pits

    NASA Technical Reports Server (NTRS)

    2004-01-01

    [figure removed for brevity, see original site]

    We will be looking at collapse pits for the next two weeks. Collapse pits on Mars are formed in several ways. In volcanic areas, channelized lava flows can form roofs which insulate the flowing lava. These features are termed lava tubes on Earth and are common features in basaltic flows. After the lava has drained, parts of the roof of the tube will collapse under its own weight. These collapse pits will only be as deep as the bottom of the original lava tube. Another type of collapse feature associated with volcanic areas arises when very large eruptions completely evacuate the magma chamber beneath the volcano. The weight of the volcano will cause the entire edifice to subside into the void space below it. Structural features including fractures and graben will form during the subsidence. Many times collapse pits will form within the graben. In addition to volcanic collapse pits, Mars has many collapse pits formed when volatiles (such as subsurface ice) are released from the surface layers. As the volatiles leave, the weight of the surrounding rock causes collapse pits to form.

    These collapse pits are found on the flank of Ascraeus Mons. The pits and channels are all related to lava tube formation and emptying.

    Image information: IR instrument. Latitude 8, Longitude 253.9 East (106.1 West). 100 meter/pixel resolution.

    Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time.

    NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science

  20. Canine tracheal collapse.

    PubMed

    Tappin, S W

    2016-01-01

    Tracheal collapse occurs most commonly in middle-aged, small breed dogs. Clinical signs are usually proportional to the degree of collapse, ranging from mild airway irritation and paroxysmal coughing to respiratory distress and dyspnoea. Diagnosis is made by documenting dynamic airway collapse with radiographs, bronchoscopy or fluoroscopy. Most dogs respond well to medical management and treatment of any concurrent comorbidities. Surgical intervention may need to be considered in dogs that do not respond or have respiratory compromise. A variety of surgical techniques have been reported although extraluminal ring prostheses or intraluminal stenting are the most commonly used. Both techniques have numerous potential complications and require specialised training and experience but are associated with good short- and long-term outcomes. PMID:26780854

  1. Collapsible high gain antenna

    NASA Technical Reports Server (NTRS)

    Cribb, H. E. (Inventor)

    1973-01-01

    A lightweight small high gain antenna which is capable of being packaged in a collapsed form and automatically expanded when in use is described. The antenna includes a cylindrical housing having a rod with a piston adjacent to one end extending through it. Attached to the outer end of the rod in a normally collapsed state is a helical wire coil. When the gas producing means is activated the piston and rod are shifted outwardly to expand the wire coil. A latch is provided for holding the helical coil in the expanded position.

  2. Dynamical collapse of trajectories

    NASA Astrophysics Data System (ADS)

    Biemond, J. J. Benjamin; de Moura, Alessandro P. S.; Grebogi, Celso; van de Wouw, Nathan; Nijmeijer, Henk

    2012-04-01

    Friction induces unexpected dynamical behaviour. In the paradigmatic pendulum and double-well systems with friction, modelled with differential inclusions, distinct trajectories can collapse onto a single point. Transversal homoclinic orbits display collapse and generate chaotic saddles with forward dynamics that is qualitatively different from the backward dynamics. The space of initial conditions converging to the chaotic saddle is fractal, but the set of points diverging from it is not: friction destroys the complexity of the forward dynamics by generating a unique horseshoe-like topology.

  3. Collapsible Geostrut Structure

    NASA Technical Reports Server (NTRS)

    Robertson, Glen A.

    1994-01-01

    Portable truss structure collapsible into smaller volume for storage and transportation. At new site, reerected quickly, without need to reassemble parts. Structure could be tent, dome, tunnel, or platform. Key element in structure joint, called "geostrut joint," includes internal cable. Structure is network of struts attached to geostrut joints. Pulling cables taut in all joints makes structure rigid. Releasing cables relaxes structure.

  4. Collapsing Enormous Stars

    NASA Astrophysics Data System (ADS)

    Kohler, Susanna

    2015-09-01

    One of the big puzzles in astrophysics is how supermassive black holes (SMBHs) managed to grow to the large sizes weve observed in the very early universe. In a recent study, a team of researchers examines the possibility that they were formed by the direct collapse of supermassive stars.Formation MysterySMBHs billions of times as massive as the Sun have been observed at a time when the universe was less than a billion years old. But thats not enough time for a stellar-mass black hole to grow to SMBH-size by accreting material so another theory is needed to explain the presence of these monsters so early in the universes history. A new study, led by Tatsuya Matsumoto (Kyoto University, Japan), poses the following question: what if supermassive stars in the early universe collapsed directly into black holes?Previous studies of star formation in the early universe have suggested that, in the hot environment of these primordial times, stars might have been able to build up mass much faster than they can today. This could result in early supermassive stars roughly 100,000 times more massive than the Sun. But if these early stars end their lives by collapsing to become massive black holes in the same way that we believe massive stars can collapse to form stellar-mass black holes today this should result in enormously violent explosions. Matusmoto and collaborators set out to model this process, to determine what we would expect to see when it happens!Energetic BurstsThe authors modeled the supermassive stars prior to collapse and then calculated whether a jet, created as the black hole grows at the center of the collapsing star, would be able to punch out of the stellar envelope. They demonstrated that the process would work much like the widely-accepted collapsar model of massive-star death, in which a jet successfully punches out of a collapsing star, violently releasing energy in the form of a long gamma-ray burst (GRB).Because the length of a long GRB is thought to

  5. 1. UPPER NOTTINGHAM MINE. COLLAPSED ADIT AND COLLAPSED WOODEN STRUCTURE. ...

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

    1. UPPER NOTTINGHAM MINE. COLLAPSED ADIT AND COLLAPSED WOODEN STRUCTURE. CAMERA IS POINTED EAST. - Florida Mountain Mining Sites, Upper Nottingham Mine, West face of Florida Mountain, head of Jacobs Gulch, Silver City, Owyhee County, ID

  6. Small, Lightweight, Collapsible Glove Box

    NASA Technical Reports Server (NTRS)

    James, Jerry

    2009-01-01

    A small, lightweight, collapsible glove box enables its user to perform small experiments and other tasks. Originally intended for use aboard a space shuttle or the International Space Station (ISS), this glove box could also be attractive for use on Earth in settings in which work space or storage space is severely limited and, possibly, in which it is desirable to minimize weight. The development of this glove box was prompted by the findings that in the original space-shuttle or ISS setting, (1) it was necessary to perform small experiments in a large general-purpose work station, so that, in effect, they occupied excessive space; and it took excessive amounts of time to set up small experiments. The design of the glove box reflects the need to minimize the space occupied by experiments and the time needed to set up experiments, plus the requirement to limit the launch weight of the box and the space needed to store the box during transport into orbit. To prepare the glove box for use, the astronaut or other user has merely to insert hands through the two fabric glove ports in the side walls of the box and move two hinges to a locking vertical position (see figure). The user could do this while seated with the glove box on the user fs lap. When stowed, the glove box is flat and has approximately the thickness of two pieces of 8-in. (.20 cm) polycarbonate.

  7. Mechanics of collapsing cavitation bubbles.

    PubMed

    van Wijngaarden, Leen

    2016-03-01

    A brief survey is given of the dynamical phenomena accompanying the collapse of cavitation bubbles. The discussion includes shock waves, microjets and the various ways in which collapsing bubbles produce damage. PMID:25890856

  8. Rigid collapsible dish structure

    NASA Technical Reports Server (NTRS)

    Palmer, William B. (Inventor); Giebler, Martin M. (Inventor)

    1982-01-01

    A collapsible dish structure composed of a plurality of rows of rigid radial petal assemblies concentric with the axis of the dish. The petal assemblies consist of a center petal and two side petals, the center petal hinged on an axis tangent to a circle concentric with the axis of the dish and the side petals hinged to the center petal at their mating edge. The center petal is foldable inwardly and the side petals rotate about their hinges such that the collapsed dish structure occupies a much smaller volume than the deployed dish. Means of controlling the shape of the dish to compensate for differential expansion of the deployed dish are also provided.

  9. Collapse of an antibubble.

    PubMed

    Zou, Jun; Ji, Chen; Yuan, BaoGang; Ruan, XiaoDong; Fu, Xin

    2013-06-01

    In contrast to a soap bubble, an antibubble is a liquid globule surrounded by a thin film of air. The collapse behavior of an antibubble is studied using a high-speed video camera. It is found that the retraction velocity of the thin air film of antibubbles depends on the thickness of the air film, e, the surface tension coefficient σ, etc., and varies linearly with (σ/ρe)(1/2), according to theoretical analysis and experimental observations. During the collapse of the antibubble, many tiny bubbles can be formed at the rim of the air film due to the Rayleigh instability. In most cases, a larger bubble will emerge finally, which holds most of the volume of the air film. PMID:23848619

  10. Collapse of an antibubble

    NASA Astrophysics Data System (ADS)

    Zou, Jun; Ji, Chen; Yuan, BaoGang; Ruan, XiaoDong; Fu, Xin

    2013-06-01

    In contrast to a soap bubble, an antibubble is a liquid globule surrounded by a thin film of air. The collapse behavior of an antibubble is studied using a high-speed video camera. It is found that the retraction velocity of the thin air film of antibubbles depends on the thickness of the air film, e, the surface tension coefficient σ, etc., and varies linearly with (σ/ρe)1/2, according to theoretical analysis and experimental observations. During the collapse of the antibubble, many tiny bubbles can be formed at the rim of the air film due to the Rayleigh instability. In most cases, a larger bubble will emerge finally, which holds most of the volume of the air film.

  11. Collapsing angiokeloidal dermatofibroma.

    PubMed

    Schnebelen, Alicia M; Brown, J Ahmad; Cheung, Wang L; Hiatt, Kim M; Smoller, Bruce R

    2012-10-01

    A heterogeneous group of benign fibrohistiocytic lesions has been assembled under the umbrella term, dermatofibroma. These lesions share a morphology of bland spindled cells encompassed by and intercalating through thick dermal collagen; unique variants have been described based on secondary histologic features, some of which include aneurysmal, myxoid, lipidized, signet ring, angiomatous, and keloidal. Here, we present a distinct dermatofibroma variant henceforth known as collapsing angiokeloidal dermatofibroma identified in 2 patients with slowly growing nodules of the buttock and the arm. Microscopically, the lesions have a characteristic dermatofibroma appearance but are accompanied by unusual diffuse small caliber vessels whose walls are collapsed by a thick, eosinophilic, keloid-like substance. The eosinophilic material resembles the adjacent dermal collagen; however, it does not stain for type-4 collagen or type-1 procollagen, amyloid, or glycogen. Although the exact composition of the keloidal material remains ambiguous, the architectural novelty of collapsing angiokeloidal dermatofibroma serves to further expand the morphologic spectrum of benign fibrous histiocytomas, although highlighting the difficulty in distinguishing between it and similar lesions. PMID:22576077

  12. Core-collapse Supernovae

    SciTech Connect

    Hix, William Raphael; Lentz, E. J.; Baird, Mark L; Chertkow, Merek A; Lee, Ching-Tsai; Blondin, J. M.; Bruenn, S. W.; Messer, Bronson; Mezzacappa, Anthony

    2013-01-01

    Marking the inevitable death of a massive star, and the birth of a neutron star or black hole, core-collapse supernovae bring together physics at a wide range in spatial scales, from kilometer-sized hydrodynamic motions (growing to gigameter scale) down to femtometer scale nuclear reactions. Carrying 10$^{51}$ ergs of kinetic energy and a rich-mix of newly synthesized atomic nuclei, core-collapse supernovae are the preeminent foundries of the nuclear species which make up ourselves and our solar system. We will discuss our emerging understanding of the convectively unstable, neutrino-driven explosion mechanism, based on increasingly realistic neutrino-radiation hydrodynamic simulations that include progressively better nuclear and particle physics. Recent multi-dimensional models with spectral neutrino transport from several research groups, which slowly develop successful explosions for a range of progenitors, have motivated changes in our understanding of the neutrino reheating mechanism. In a similar fashion, improvements in nuclear physics, most notably explorations of weak interactions on nuclei and the nuclear equation of state, continue to refine our understanding of how supernovae explode. Recent progress on both the macroscopic and microscopic effects that affect core-collapse supernovae are discussed.

  13. Collapse, environment, and society

    PubMed Central

    2012-01-01

    Historical collapse of ancient states poses intriguing social-ecological questions, as well as potential applications to global change and contemporary strategies for sustainability. Five Old World case studies are developed to identify interactive inputs, triggers, and feedbacks in devolution. Collapse is multicausal and rarely abrupt. Political simplification undermines traditional structures of authority to favor militarization, whereas disintegration is preconditioned or triggered by acute stress (insecurity, environmental or economic crises, famine), with breakdown accompanied or followed by demographic decline. Undue attention to stressors risks underestimating the intricate interplay of environmental, political, and sociocultural resilience in limiting the damages of collapse or in facilitating reconstruction. The conceptual model emphasizes resilience, as well as the historical roles of leaders, elites, and ideology. However, a historical model cannot simply be applied to contemporary problems of sustainability without adjustment for cumulative information and increasing possibilities for popular participation. Between the 14th and 18th centuries, Western Europe responded to environmental crises by innovation and intensification; such modernization was decentralized, protracted, flexible, and broadly based. Much of the current alarmist literature that claims to draw from historical experience is poorly focused, simplistic, and unhelpful. It fails to appreciate that resilience and readaptation depend on identified options, improved understanding, cultural solidarity, enlightened leadership, and opportunities for participation and fresh ideas. PMID:22371579

  14. Collapse, environment, and society.

    PubMed

    Butzer, Karl W

    2012-03-01

    Historical collapse of ancient states poses intriguing social-ecological questions, as well as potential applications to global change and contemporary strategies for sustainability. Five Old World case studies are developed to identify interactive inputs, triggers, and feedbacks in devolution. Collapse is multicausal and rarely abrupt. Political simplification undermines traditional structures of authority to favor militarization, whereas disintegration is preconditioned or triggered by acute stress (insecurity, environmental or economic crises, famine), with breakdown accompanied or followed by demographic decline. Undue attention to stressors risks underestimating the intricate interplay of environmental, political, and sociocultural resilience in limiting the damages of collapse or in facilitating reconstruction. The conceptual model emphasizes resilience, as well as the historical roles of leaders, elites, and ideology. However, a historical model cannot simply be applied to contemporary problems of sustainability without adjustment for cumulative information and increasing possibilities for popular participation. Between the 14th and 18th centuries, Western Europe responded to environmental crises by innovation and intensification; such modernization was decentralized, protracted, flexible, and broadly based. Much of the current alarmist literature that claims to draw from historical experience is poorly focused, simplistic, and unhelpful. It fails to appreciate that resilience and readaptation depend on identified options, improved understanding, cultural solidarity, enlightened leadership, and opportunities for participation and fresh ideas. PMID:22371579

  15. Gravitational waves from gravitational collapse

    SciTech Connect

    Fryer, Christopher L; New, Kimberly C

    2008-01-01

    Gravitational wave emission from stellar collapse has been studied for nearly four decades. Current state-of-the-art numerical investigations of collapse include those that use progenitors with more realistic angular momentum profiles, properly treat microphysics issues, account for general relativity, and examine non-axisymmetric effects in three dimensions. Such simulations predict that gravitational waves from various phenomena associated with gravitational collapse could be detectable with ground-based and space-based interferometric observatories. This review covers the entire range of stellar collapse sources of gravitational waves: from the accretion induced collapse of a white dwarf through the collapse down to neutron stars or black holes of massive stars to the collapse of supermassive stars.

  16. Shearfree cylindrical gravitational collapse

    SciTech Connect

    Di Prisco, A.; Herrera, L.; MacCallum, M. A. H.; Santos, N. O.

    2009-09-15

    We consider diagonal cylindrically symmetric metrics, with an interior representing a general nonrotating fluid with anisotropic pressures. An exterior vacuum Einstein-Rosen spacetime is matched to this using Darmois matching conditions. We show that the matching conditions can be explicitly solved for the boundary values of metric components and their derivatives, either for the interior or exterior. Specializing to shearfree interiors, a static exterior can only be matched to a static interior, and the evolution in the nonstatic case is found to be given in general by an elliptic function of time. For a collapsing shearfree isotropic fluid, only a Robertson-Walker dust interior is possible, and we show that all such cases were included in Cocke's discussion. For these metrics, Nolan and Nolan have shown that the matching breaks down before collapse is complete, and Tod and Mena have shown that the spacetime is not asymptotically flat in the sense of Berger, Chrusciel, and Moncrief. The issues about energy that then arise are revisited, and it is shown that the exterior is not in an intrinsic gravitational or superenergy radiative state at the boundary.

  17. PREFACE: Collapse Calderas Workshop

    NASA Astrophysics Data System (ADS)

    Gottsmann, Jo; Aguirre-Diaz, Gerardo

    2008-10-01

    Caldera-formation is one of the most awe-inspiring and powerful displays of nature's force. Resultant deposits may cover vast areas and significantly alter the immediate topography. Post-collapse activity may include resurgence, unrest, intra-caldera volcanism and potentially the start of a new magmatic cycle, perhaps eventually leading to renewed collapse. Since volcanoes and their eruptions are the surface manifestation of magmatic processes, calderas provide key insights into the generation and evolution of large-volume silicic magma bodies in the Earth's crust. Despite their potentially ferocious nature, calderas play a crucial role in modern society's life. Collapse calderas host essential economic deposits and supply power for many via the exploitation of geothermal reservoirs, and thus receive considerable scientific, economic and industrial attention. Calderas also attract millions of visitors world-wide with their spectacular scenic displays. To build on the outcomes of the 2005 calderas workshop in Tenerife (Spain) and to assess the most recent advances on caldera research, a follow-up meeting was proposed to be held in Mexico in 2008. This abstract volume presents contributions to the 2nd Calderas Workshop held at Hotel Misión La Muralla, Querétaro, Mexico, 19-25 October 2008. The title of the workshop `Reconstructing the evolution of collapse calderas: Magma storage, mobilisation and eruption' set the theme for five days of presentations and discussions, both at the venue as well as during visits to the surrounding calderas of Amealco, Amazcala and Huichapan. The multi-disciplinary workshop was attended by more than 40 scientist from North, Central and South America, Europe, Australia and Asia. Contributions covered five thematic topics: geology, geochemistry/petrology, structural analysis/modelling, geophysics, and hazards. The workshop was generously supported by the International Association of Volcanology and the Chemistry of The Earth's Interior

  18. Gravitational collapse of Hagedorn fluids

    NASA Astrophysics Data System (ADS)

    Malafarina, Daniele

    2016-05-01

    We consider a toy model for the relativistic collapse of a homogeneous perfect fluid that takes into account an equation of state for high density matter, in the form of a Hagedorn phase, and semiclassical corrections in the strong field. We show that collapse reaches a critical minimum size and then bounces. We discuss the conditions needed for the collapse to halt and form a compact object. We argue that implications of models such as the one presented here are of great importance for astrophysics as they show that black holes may not be the only final outcome of collapse of very massive stars.

  19. Magnetized Tolman-Bondi collapse

    NASA Astrophysics Data System (ADS)

    Germani, Cristiano; Tsagas, Christos G.

    2006-03-01

    We investigate the gravitational implosion of magnetized matter by studying the inhomogeneous collapse of a weakly magnetized Tolman-Bondi spacetime. The role of the field is analyzed by looking at the convergence of neighboring particle world lines. In particular, we identify the magnetically related stresses in the Raychaudhuri equation and use the Tolman-Bondi metric to evaluate their impact on the collapsing dust. We find that, despite the low energy level of the field, the Lorentz force dominates the advanced stages of the collapse, leading to a strongly anisotropic contraction. In addition, of all the magnetic stresses, those that resist the collapse are found to grow faster.

  20. The Nimitz Freeway Collapse

    NASA Astrophysics Data System (ADS)

    Feldman, Bernard J.

    2004-10-01

    One of the most tragic sights created by the Loma Prieta earthquake of Oct. 17, 1989, was the collapse of the double-deck Nimitz Freeway (the Cypress Street Viaduct on Interstate 880) just south and east of the San Francisco-Oakland Bay Bridge in Oakland. Along a 1.4-km north-south stretch, the upper deck of the freeway fell on top of the lower deck of the freeway, killing 42 motorists (see Fig. 1). Even though the earthquake occurred during rush hour (5:04 p.m.), traffic was extremely light that day because the third game of the World Series between the Oakland Athletics and the San Francisco Giants was about to begin and many commuters were already at home in front of their television sets.

  1. Collapse of Surface Nanobubbles

    NASA Astrophysics Data System (ADS)

    Chan, Chon U.; Chen, Longquan; Arora, Manish; Ohl, Claus-Dieter

    2015-03-01

    Surface attached nanobubbles populate surfaces submerged in water. These nanobubbles have a much larger contact angle and longer lifetime than predicted by classical theory. Moreover, it is difficult to distinguish them from hydrophobic droplets, e.g., polymeric contamination, using standard atomic force microscopy. Here, we report fast dynamics of a three phase contact line moving over surface nanobubbles, polymeric droplets, and hydrophobic particles. The dynamics is distinct: across polymeric droplets the contact line quickly jumps and hydrophobic particles pin the contact line, while surface nanobubbles rapidly shrink once merging with the contact line, suggesting a method to differentiate nanoscopic gaseous, liquid, and solid structures. Although the collapse process of surface nanobubbles occurs within a few milliseconds, we show that it is dominated by microscopic dynamics rather than bulk hydrodynamics.

  2. Endograft collapse following endovascular repair of traumatic aortic injury.

    PubMed

    Annamalai, Ganesan; Cook, Richard; Martin, Michael

    2011-03-01

    The advent of endovascular treatment of traumatic thoracic aortic injuries offers a valuable, minimally invasive alternative to open surgical repair. However, there are limitations of the current endovascular stent graft technology for this group of patients. After endovascular repair meticulous follow-up is required with a high index of suspicion for potential complications including the lethal complication of endograft collapse. PMID:19784919

  3. Collapse pressures of biodegradable stents.

    PubMed

    Venkatraman, Subbu; Poh, Tan Lay; Vinalia, Tjong; Mak, Koon Hou; Boey, Freddy

    2003-05-01

    Biodegradable stent prototypes were produced from poly L-lactic acid polymers with different molecular weights. The effects of molecular weight, drug incorporation and stent design on the collapse pressure of the stents were evaluated. While molecular weights did not show a significant effect on the collapse pressure of the stents, drug incorporation at high percentage decreased the collapse pressure of the stents substantially. Cryogenic fracture surfaces showed significant drug agglomeration as the concentration increased. The design of the stent was also found to a have significant effect on the collapse pressure. The stent produced from the same material has a higher collapse pressure when the load bearing surface area is increased. PMID:12628831

  4. Minimal Reduplication

    ERIC Educational Resources Information Center

    Kirchner, Jesse Saba

    2010-01-01

    This dissertation introduces Minimal Reduplication, a new theory and framework within generative grammar for analyzing reduplication in human language. I argue that reduplication is an emergent property in multiple components of the grammar. In particular, reduplication occurs independently in the phonology and syntax components, and in both cases…

  5. Gravitational collapse of Vaidya spacetime

    NASA Astrophysics Data System (ADS)

    Vertogradov, Vitalii

    2016-03-01

    The gravitational collapse of generalized Vaidya spacetime is considered. It is known that the endstate of gravitational collapse, as to whether a black hole or a naked singularity is formed, depends on the mass function M(v,r). Here we give conditions for the mass function which corresponds to the equation of the state P = αρ where α ∈ (0, 1 3] and according to these conditions we obtain either a black hole or a naked singularity at the endstate of gravitational collapse. Also we give conditions for the mass function when the singularity is gravitationally strong.

  6. Theory of the antibubble collapse.

    PubMed

    Sob'yanin, Denis Nikolaevich

    2015-03-13

    A theory of the collapse of a punctured antibubble is developed. The motion of the rim of air formed at the edge of the collapsing air film cannot be described by a potential flow and is characterized by high Reynolds numbers. The rim velocity is not constant but gradually decreases with time and is determined by the balance between the surface tension and hydrodynamic drag forces. A collapse equation is derived and solved. The agreement between the theory and existing experiments is shown. PMID:25815936

  7. Taxonomic minimalism.

    PubMed

    Beattle, A J; Oliver, I

    1994-12-01

    Biological surveys are in increasing demand while taxonomic resources continue to decline. How much formal taxonomy is required to get the job done? The answer depends on the kind of job but it is possible that taxonomic minimalism, especially (1) the use of higher taxonomic ranks, (2) the use of morphospecies rather than species (as identified by Latin binomials), and (3) the involvement of taxonomic specialists only for training and verification, may offer advantages for biodiversity assessment, environmental monitoring and ecological research. As such, formal taxonomy remains central to the process of biological inventory and survey but resources may be allocated more efficiently. For example, if formal Identification is not required, resources may be concentrated on replication and increasing sample sizes. Taxonomic minimalism may also facilitate the inclusion in these activities of important but neglected groups, especially among the invertebrates, and perhaps even microorganisms. PMID:21236933

  8. [Placement of intraluminal stents for treating tracheal collapse in dogs].

    PubMed

    Glaus, T M; Matos, J M; Baloi, P; Wenger, M

    2011-11-01

    Tracheal collapse is a progressive disease particularly of small breed dogs. In the terminal stage, when dyspnea becomes the dominating sign and is no longer manageable with medical treatment, a surgical procedure is necessary. With increasing frequency intraluminal tracheal stents are implanted minimal-invasively. In individual animals this is a lifesaving procedure, leading to immediate elimination of dyspnea. In most dogs cough for some time has to be anticipated as the stent acts as a foreign body, but severe complications like excessive formation of granulation tissue, stent migration or stent fracture are rare. Stents represent an attractive treatment modality for tracheal collapse in dogs with dyspnea. PMID:22045455

  9. Stress evolution during caldera collapse

    NASA Astrophysics Data System (ADS)

    Holohan, E. P.; Schöpfer, M. P. J.; Walsh, J. J.

    2015-07-01

    The mechanics of caldera collapse are subject of long-running debate. Particular uncertainties concern how stresses around a magma reservoir relate to fracturing as the reservoir roof collapses, and how roof collapse in turn impacts upon the reservoir. We used two-dimensional Distinct Element Method models to characterise the evolution of stress around a depleting sub-surface magma body during gravity-driven collapse of its roof. These models illustrate how principal stress orientations rotate during progressive deformation so that roof fracturing transitions from initial reverse faulting to later normal faulting. They also reveal four end-member stress paths to fracture, each corresponding to a particular location within the roof. Analysis of these paths indicates that fractures associated with ultimate roof failure initiate in compression (i.e. as shear fractures). We also report on how mechanical and geometric conditions in the roof affect pre-failure unloading and post-failure reloading of the reservoir. In particular, the models show how residual friction within a failed roof could, without friction reduction mechanisms or fluid-derived counter-effects, inhibit a return to a lithostatically equilibrated pressure in the magma reservoir. Many of these findings should be transferable to other gravity-driven collapse processes, such as sinkhole formation, mine collapse and subsidence above hydrocarbon reservoirs.

  10. Convection, nucleosynthesis, and core collapse

    NASA Technical Reports Server (NTRS)

    Bazan, Grant; Arnett, David

    1994-01-01

    We use a piecewise parabolic method hydrodynamics code (PROMETHEUS) to study convective burning in two dimensions in an oxygen shell prior to core collapse. Significant mixing beyond convective boundaries determined by mixing-length theory brings fuel (C-12) into the convective regon, causing hot spots of nuclear burning. Plumes dominate the velocity structure. Finite perturbations arise in a region in which O-16 will be explosively burned to Ni-56 when the star explodes; the resulting instabilities and mixing are likely to distribute Ni-56 throughout the supernova envelope. Inhomogeneities in Y(sub e) may be large enough to affect core collapse and will affect explosive nucleosynthesis. The nature of convective burning is dramatically different from that assumed in one-dimensional simulations; quantitative estimates of nucleosynthetic yields, core masses, and the approach to core collapse will be affected.

  11. Minimal cosmography

    NASA Astrophysics Data System (ADS)

    Piazza, Federico; Schücker, Thomas

    2016-04-01

    The minimal requirement for cosmography—a non-dynamical description of the universe—is a prescription for calculating null geodesics, and time-like geodesics as a function of their proper time. In this paper, we consider the most general linear connection compatible with homogeneity and isotropy, but not necessarily with a metric. A light-cone structure is assigned by choosing a set of geodesics representing light rays. This defines a "scale factor" and a local notion of distance, as that travelled by light in a given proper time interval. We find that the velocities and relativistic energies of free-falling bodies decrease in time as a consequence of cosmic expansion, but at a rate that can be different than that dictated by the usual metric framework. By extrapolating this behavior to photons' redshift, we find that the latter is in principle independent of the "scale factor". Interestingly, redshift-distance relations and other standard geometric observables are modified in this extended framework, in a way that could be experimentally tested. An extremely tight constraint on the model, however, is represented by the blackbody-ness of the cosmic microwave background. Finally, as a check, we also consider the effects of a non-metric connection in a different set-up, namely, that of a static, spherically symmetric spacetime.

  12. GRAVITATIONAL WAVES FROM STELLAR COLLAPSE

    SciTech Connect

    C. L. FRYER

    2001-01-01

    Stellar core-collapse plays an important role in nearly all facets of astronomy: cosmology (as standard candles), formation of compact objects, nucleosynthesis and energy deposition in galaxies. In addition, they release energy in powerful explosions of light over a range of energies, neutrinos, and the subject of this meeting, gravitational waves. Because of this broad range of importance, astronomers have discovered a number of constraints which can be used to help them understand the importance of stellar core-collapse as gravitational wave sources.

  13. Protostellar Collapse with a Shock

    NASA Technical Reports Server (NTRS)

    Tsai, John C.; Hsu, Juliana J. L.

    1995-01-01

    We reexamine both numerically and analytically the collapse of the singular isothermal sphere in the context of low-mass star formation. We consider the case where the onset of collapse is initiated by some arbitrary process which is accompanied by a central output of either heat or kinetic energy. We find two classes of numerical solutions describing this manner of collapse. The first approaches in time the expansion wave solution of Shu, while the second class is characterized by an ever-decreasing central accretion rate and the presence of an outwardly propagating weak shock. The collapse solution which represents the dividing case between these two classes is determined analytically by a similarity analysis. This solution shares with the expansion wave solution the properties that the gas remains stationary with an r(sup -2) density profile at large radius and that, at small radius, the gas free-falls onto a nascent core at a constant rate which depends only on the isothermal sound speed. This accretion rate is a factor of approx. 0.1 that predicted by the expansion wave solution. This reduction is due in part to the presence of a weak shock which propagates outward at 1.26 times the sound speed. Gas in the postshock region first moves out subsonically but is then decelerated and begins to collapse. The existence of two classes of numerical collapse solutions is explained in terms of the instability to radial perturbations of the analytic solution. Collapse occurring in the manner described by some of our solutions would eventually unbind a finite-sized core. However, this does not constitute a violation of the instability properties of the singular isothermal sphere which is unstable both to collapse and to expansion. To emphasize this, we consider a purely expanding solution for isothermal spheres. This solution is found to be self-similar and results in a uniform density core in the central regions of the gas. Our solutions may be relevant to the 'luminosity

  14. Protostellar Collapse with a Shock

    NASA Technical Reports Server (NTRS)

    Tsai, John C.; Hsu, Juliana J.

    1995-01-01

    We reexamine both numerically and analytically the collapse of the singular isothermal sphere in the context of low-mass star formation. We consider the case where the onset of collapse is initiated by some arbitrary process which is accompanied by a central output of either heat or kinetic energy. We find two classes of numerical solutions describing this manner of collapse. The first approaches in time the expansion wave solution of Shu, while the second class is characterized by an ever-decreasing central accretion rate and the presence of an outwardly propagating weak shock. The collapse solution which represents the dividing case between these two classes is determined analytically by a similarity analysis. This solution shares with the expansion wave solution the properties that the gas remains stationary with an r(exp -2) density profile at large radius and that, at small radius, the gas free-falls onto a nascent core at a constant rate which depends only on the isothermal sound speed. This accretion rate is a factor of approx. 0.1 that predicted by the expansion wave solution. This reduction is due in part to the presence of a weak shock which propagates outward at 1.26 times the sound speed. Gas in the postshock region first moves out subsonically but is then decelerated and begins to collapse. The existence of two classes of numerical collapse solutions is explained in terms of the instability to radial perturbations of the analytic solution. Collapse occurring in the manner described by some of our solutions would eventually unbind a finite-sized core. However, this does not constitute a violation of the instability properties of the singular isothermal sphere which is unstable both to collapse and to expansion. To emphasize this, we consider a purely expanding solution for isothermal spheres. This solution is found to be self-similar and results in a uniform density core in the central regions of the gas. Our solutions may be relevant to the 'luminosity

  15. Semiclassical environment of collapsing shells

    NASA Astrophysics Data System (ADS)

    Banerjee, Kinjal; Paranjape, Aseem

    2009-12-01

    We explore in detail the semiclassical environment of collapsing shells of matter, and determine the semiclassical flux measured by a variety of observers. This study is a preliminary step in a broader investigation of thermodynamic properties of the geometry of collapsing objects. Specifically, in this paper we consider spherically symmetric null and timelike collapsing shells which form an event horizon, and calculate the flux measured by observers both inside and outside the shell, and both inside and outside the event horizon, and find nontrivial results in most of the cases. Additionally, we also investigate the environment of a shell which collapses but does not form a horizon, halting at some radius larger than the Schwarzschild radius, and find that such an object generically gives rise to a pulse of radiation which is sharply peaked as it travels inwards and is reflected at the origin, and eventually emerges from the shell in a thermalized form. Our results have potential consequences in addressing questions pertaining, e.g. to black hole entropy and backreaction.

  16. Bellechester, Minnesota, USA, lagoon collapses

    NASA Astrophysics Data System (ADS)

    Alexander, E. C.; Broberg, J. S.; Kehren, A. R.; Graziani, M. M.; Turri, W. L.

    1993-12-01

    Bellechester, Minnesota, is a small community of approximately 155 residents located on the county line between Goodhue and Wabasha counties in southeast Minnesota's karst region. Bellechester is served by a 21-year-old wastewater treatment facility (WWTF) consisting of three waste-stabilization ponds. On 28 April 1992 six sinkholes were discovered to have drained cell 2 of the WWTF resulting in the loss of approximately 8.7×106 1 of partially treated effluent and about 600 m3 of soil into previously undetected subsurface voids of unknown dimensions. In the week following the collapse, approximately 200 water wells located within a 5-km radius of the WWTF were sampled in an after-the-fact, emergency sampling program. Twelve samples with elevated fecal coliform levels, 18 samples with nitrate-nitrogen greater than the 10 mg/1 standard, and no samples with elevated chlorides were found. However, the elevated levels could not be unambiguously attributed to the WWTF collapse. This is the third WWTF to fail by sinkhole collapse in southeast Minnesota since 1974. All three collapsed lagoons have been located in similar geomorphic and stratigraphic settings. However, at least two lagoons have collapsed in the adjacent area in northeast Iowa, and these lagoons are located at different stratigraphic positions. Twenty-two WWTFs constructed in southeast Minnesota's karst region in the last 25 years have been identified as subject to potential sinkhole collapse. An unknown but significant number of manure storage lagoons, flood control structures, etc., have also been constructed in the karst region and are at risk. Public agencies are beginning to develop plans to deal with the risk associated with existing and future waste lagoons in this environment. The critical hydrogeologic parameters that can be used to prioritize the risk of collapse at existing facilities include: (1) the lithology of the first bedrock beneath each lagoon, (2) the thickness of surficial materials

  17. Collapsing thin shells with rotation

    NASA Astrophysics Data System (ADS)

    Delsate, Térence; Rocha, Jorge V.; Santarelli, Raphael

    2014-06-01

    We construct exact solutions describing the motion of rotating thin shells in a fully backreacted five-dimensional rotating black hole spacetime. The radial equation of motion follows from the Darmois-Israel junction conditions, where both interior and exterior geometries are taken to be equal angular momenta Myers-Perry solutions. We show that rotation generates anisotropic pressures and momentum along the shell. Gravitational collapse scenarios including rotation are analyzed and a new class of stationary solutions is introduced. Energy conditions for the anisotropic matter shell are briefly discussed. We find that the weak energy condition is not violated for the collapse scenario where the shell starts at rest from infinity, nor for the new class of stationary solutions in anti-de Sitter. We further prove that the cosmic censorship conjecture is always satisfied in our setup.

  18. Collapsed Thunderstorm, Southwest Pacific Ocean

    NASA Technical Reports Server (NTRS)

    1992-01-01

    This collapsed thunderstorm was observed over the open ocean (9.0N, 120.0E) between the Philippine island of Mindoro and Borneo, Malaysia. The cleared area in the center is the result of the clouds being driven from there by the sudden rush of katabatic air spreading downward and outward from the dying thunderstorm. Around the edges of the downdrafted air, new though smaller storms are developing. The two small coral atolls are the Tubbataha Reefs.

  19. Bubble-induced cave collapse.

    PubMed

    Girihagama, Lakshika; Nof, Doron; Hancock, Cathrine

    2015-01-01

    Conventional wisdom among cave divers is that submerged caves in aquifers, such as in Florida or the Yucatan, are unstable due to their ever-growing size from limestone dissolution in water. Cave divers occasionally noted partial cave collapses occurring while they were in the cave, attributing this to their unintentional (and frowned upon) physical contact with the cave walls or the aforementioned "natural" instability of the cave. Here, we suggest that these cave collapses do not necessarily result from cave instability or contacts with walls, but rather from divers bubbles rising to the ceiling and reducing the buoyancy acting on isolated ceiling rocks. Using familiar theories for the strength of flat and arched (un-cracked) beams, we first show that the flat ceiling of a submerged limestone cave can have a horizontal expanse of 63 meters. This is much broader than that of most submerged Florida caves (~ 10 m). Similarly, we show that an arched cave roof can have a still larger expanse of 240 meters, again implying that Florida caves are structurally stable. Using familiar bubble dynamics, fluid dynamics of bubble-induced flows, and accustomed diving practices, we show that a group of 1-3 divers submerged below a loosely connected ceiling rock will quickly trigger it to fall causing a "collapse". We then present a set of qualitative laboratory experiments illustrating such a collapse in a circular laboratory cave (i.e., a cave with a circular cross section), with concave and convex ceilings. In these experiments, a metal ball represented the rock (attached to the cave ceiling with a magnet), and the bubbles were produced using a syringe located at the cave floor. PMID:25849088

  20. Collapse models and perceptual processes

    NASA Astrophysics Data System (ADS)

    Carlo Ghirardi, Gian; Romano, Raffaele

    2014-04-01

    Theories including a collapse mechanism have been presented various years ago. They are based on a modification of standard quantum mechanics in which nonlinear and stochastic terms are added to the evolution equation. Their principal merits derive from the fact that they are mathematically precise schemes accounting, on the basis of a unique universal dynamical principle, both for the quantum behavior of microscopic systems as well as for the reduction associated to measurement processes and for the classical behavior of macroscopic objects. Since such theories qualify themselves not as new interpretations but as modifications of the standard theory they can be, in principle, tested against quantum mechanics. Recently, various investigations identifying possible crucial test have been discussed. In spite of the extreme difficulty to perform such tests it seems that recent technological developments allow at least to put precise limits on the parameters characterizing the modifications of the evolution equation. Here we will simply mention some of the recent investigations in this direction, while we will mainly concentrate our attention to the way in which collapse theories account for definite perceptual process. The differences between the case of reductions induced by perceptions and those related to measurement procedures by means of standard macroscopic devices will be discussed. On this basis, we suggest a precise experimental test of collapse theories involving conscious observers. We make plausible, by discussing in detail a toy model, that the modified dynamics can give rise to quite small but systematic errors in the visual perceptual process.

  1. Collapse Mechanisms Of Masonry Structures

    SciTech Connect

    Zuccaro, G.; Rauci, M.

    2008-07-08

    The paper outlines a possible approach to typology recognition, safety check analyses and/or damage measuring taking advantage by a multimedia tool (MEDEA), tracing a guided procedure useful for seismic safety check evaluation and post event macroseismic assessment. A list of the possible collapse mechanisms observed in the post event surveys on masonry structures and a complete abacus of the damages are provided in MEDEA. In this tool a possible combination between a set of damage typologies and each collapse mechanism is supplied in order to improve the homogeneity of the damages interpretation. On the other hand recent researches of one of the author have selected a number of possible typological vulnerability factors of masonry buildings, these are listed in the paper and combined with potential collapse mechanisms to be activated under seismic excitation. The procedure takes place from simple structural behavior models, derived from the Umbria-Marche earthquake observations, and tested after the San Giuliano di Puglia event; it provides the basis either for safety check analyses of the existing buildings or for post-event structural safety assessment and economic damage evaluation. In the paper taking advantage of MEDEA mechanisms analysis, mainly developed for the post event safety check surveyors training, a simple logic path is traced in order to approach the evaluation of the masonry building safety check. The procedure starts from the identification of the typological vulnerability factors to derive the potential collapse mechanisms and their collapse multipliers and finally addresses the simplest and cheapest strengthening techniques to reduce the original vulnerability. The procedure has been introduced in the Guide Lines of the Regione Campania for the professionals in charge of the safety check analyses and the buildings strengthening in application of the national mitigation campaign introduced by the Ordinance of the Central Government n. 3362

  2. Collapse Mechanisms Of Masonry Structures

    NASA Astrophysics Data System (ADS)

    Zuccaro, G.; Rauci, M.

    2008-07-01

    The paper outlines a possible approach to typology recognition, safety check analyses and/or damage measuring taking advantage by a multimedia tool (MEDEA), tracing a guided procedure useful for seismic safety check evaluation and post event macroseismic assessment. A list of the possible collapse mechanisms observed in the post event surveys on masonry structures and a complete abacus of the damages are provided in MEDEA. In this tool a possible combination between a set of damage typologies and each collapse mechanism is supplied in order to improve the homogeneity of the damages interpretation. On the other hand recent researches of one of the author have selected a number of possible typological vulnerability factors of masonry buildings, these are listed in the paper and combined with potential collapse mechanisms to be activated under seismic excitation. The procedure takes place from simple structural behavior models, derived from the Umbria-Marche earthquake observations, and tested after the San Giuliano di Puglia event; it provides the basis either for safety check analyses of the existing buildings or for post-event structural safety assessment and economic damage evaluation. In the paper taking advantage of MEDEA mechanisms analysis, mainly developed for the post event safety check surveyors training, a simple logic path is traced in order to approach the evaluation of the masonry building safety check. The procedure starts from the identification of the typological vulnerability factors to derive the potential collapse mechanisms and their collapse multipliers and finally addresses the simplest and cheapest strengthening techniques to reduce the original vulnerability. The procedure has been introduced in the Guide Lines of the Regione Campania for the professionals in charge of the safety check analyses and the buildings strengthening in application of the national mitigation campaign introduced by the Ordinance of the Central Government n. 3362

  3. Hierarchical Gravitational Fragmentation. I. Collapsing Cores within Collapsing Clouds

    NASA Astrophysics Data System (ADS)

    Naranjo-Romero, Raúl; Vázquez-Semadeni, Enrique; Loughnane, Robert M.

    2015-11-01

    We investigate the Hierarchical Gravitational Fragmentation scenario through numerical simulations of the prestellar stages of the collapse of a marginally gravitationally unstable isothermal sphere immersed in a strongly gravitationally unstable, uniform background medium. The core developes a Bonnor-Ebert (BE)-like density profile, while at the time of singularity (the protostar) formation the envelope approaches a singular-isothermal-sphere (SIS)-like r-2 density profile. However, these structures are never hydrostatic. In this case, the central flat region is characterized by an infall speed, while the envelope is characterized by a uniform speed. This implies that the hydrostatic SIS initial condition leading to Shu's classical inside-out solution is not expected to occur, and therefore neither should the inside-out solution. Instead, the solution collapses from the outside-in, naturally explaining the observation of extended infall velocities. The core, defined by the radius at which it merges with the background, has a time-variable mass, and evolves along the locus of the ensemble of observed prestellar cores in a plot of M/MBE versus M, where M is the core's mass and MBE is the critical BE mass, spanning the range from the “stable” to the “unstable” regimes, even though it is collapsing at all times. We conclude that the presence of an unstable background allows a core to evolve dynamically from the time when it first appears, even when it resembles a pressure-confined, stable BE-sphere. The core can be thought of as a ram-pressure confined BE-sphere, with an increasing mass due to the accretion from the unstable background.

  4. Universal Scaling Law for the Collapse of Viscous Nanopores.

    PubMed

    Lu, Jiakai; Yu, Jiayun; Corvalan, Carlos M

    2015-08-11

    Below a threshold size, a small pore nucleated in a fluid sheet will contract to minimize the surface energy. Such behavior plays a key role in nature and technology, from nanopores in biological membranes to nanopores in sensors for rapid DNA and RNA sequencing. Here we show that nanopores nucleated in viscous fluid sheets collapse following a universal scaling law for the pore radius. High-fidelity numerical simulations reveal that the scaling is largely independent of the initial conditions, including the size, shape, and thickness of the original nanopore. Results further show that the scaling law yields a constant speed of collapse as observed in recent experiments. Nanopores in fluid sheets of moderate viscosity also attain this constant terminal speed provided that they are sufficiently close to the singularity. PMID:26230279

  5. Bubble-Induced Cave Collapse

    PubMed Central

    Girihagama, Lakshika; Nof, Doron; Hancock, Cathrine

    2015-01-01

    Conventional wisdom among cave divers is that submerged caves in aquifers, such as in Florida or the Yucatan, are unstable due to their ever-growing size from limestone dissolution in water. Cave divers occasionally noted partial cave collapses occurring while they were in the cave, attributing this to their unintentional (and frowned upon) physical contact with the cave walls or the aforementioned “natural” instability of the cave. Here, we suggest that these cave collapses do not necessarily result from cave instability or contacts with walls, but rather from divers bubbles rising to the ceiling and reducing the buoyancy acting on isolated ceiling rocks. Using familiar theories for the strength of flat and arched (un-cracked) beams, we first show that the flat ceiling of a submerged limestone cave can have a horizontal expanse of 63 meters. This is much broader than that of most submerged Florida caves (~ 10 m). Similarly, we show that an arched cave roof can have a still larger expanse of 240 meters, again implying that Florida caves are structurally stable. Using familiar bubble dynamics, fluid dynamics of bubble-induced flows, and accustomed diving practices, we show that a group of 1-3 divers submerged below a loosely connected ceiling rock will quickly trigger it to fall causing a “collapse”. We then present a set of qualitative laboratory experiments illustrating such a collapse in a circular laboratory cave (i.e., a cave with a circular cross section), with concave and convex ceilings. In these experiments, a metal ball represented the rock (attached to the cave ceiling with a magnet), and the bubbles were produced using a syringe located at the cave floor. PMID:25849088

  6. Dynamic simulation of voltage collapses

    SciTech Connect

    Deuse, J.; Stubbe, M. )

    1993-08-01

    Most of the time the voltage collapse phenomena are studied by means of computer programs designed for the calculation of steady state conditions. But in the real world, the simultaneous occurrences of losses of synchronism, of AVR dynamics or of transformer tap changes call for a full dynamic simulation of voltage phenomena. The present paper shows some examples of dynamic simulations of voltage phenomena using a new general purpose stability program (EUROSTAG), covering in a continuous way the classical fields of transient, mid-term and long-term stability, and also the quasi steady state conditions of a power system.

  7. Dynamics of dissipative gravitational collapse

    SciTech Connect

    Herrera, L.; Santos, N.O.

    2004-10-15

    The Misner and Sharp approach to the study of gravitational collapse is extended to the dissipative case in, both, the streaming out and the diffusion approximations. The role of different terms in the dynamical equation are analyzed in detail. The dynamical equation is then coupled to a causal transport equation in the context of Israel-Stewart theory. The decreasing of the inertial mass density of the fluid, by a factor which depends on its internal thermodynamics state, is reobtained, at any time scale. In accordance with the equivalence principle, the same decreasing factor is obtained for the gravitational force term. Prospective applications of this result to some astrophysical scenarios are discussed.

  8. Avalanche Collapse of Interdependent Networks

    NASA Astrophysics Data System (ADS)

    Baxter, G. J.; Dorogovtsev, S. N.; Goltsev, A. V.; Mendes, J. F. F.

    2012-12-01

    We reveal the nature of the avalanche collapse of the giant viable component in multiplex networks under perturbations such as random damage. Specifically, we identify latent critical clusters associated with the avalanches of random damage. Divergence of their mean size signals the approach to the hybrid phase transition from one side, while there are no critical precursors on the other side. We find that this discontinuous transition occurs in scale-free multiplex networks whenever the mean degree of at least one of the interdependent networks does not diverge.

  9. Collapse phenomenon during Chartis collateral ventilation assessment.

    PubMed

    Gesierich, Wolfgang; Samitas, Konstantinos; Reichenberger, Frank; Behr, Juergen

    2016-06-01

    Chartis is increasingly used for bronchoscopic assessment of collateral ventilation before endobronchial valve (EBV) treatment for severe emphysema. Its prognostic value is, however, limited by the airway collapse phenomenon. The frequency and clinical significance of the collapse phenomenon remain largely unknown.We performed a retrospective analysis of 92 patients undergoing Chartis evaluation under spontaneous breathing (n=55) or jet ventilation (n=37) from May 2010 to November 2013. Collateral ventilation status (positive/negative/collapse phenomenon/unclear) was reassessed and correlated with high-resolution computed tomography (HRCT) fissure analysis and clinical response.In the absence of the collapse phenomenon, the predictive value of Chartis measurements and HRCT fissural analysis was comparable. The collapse phenomenon was observed in 31.5% of all assessments, and was more frequent in lower lobes (44.9% versus 16.9% in upper lobes) and under jet ventilation (41.4% versus 22.1% under spontaneous breathing). 69.8% of lobes with the collapse phenomenon had complete fissures. Most patients with the collapse phenomenon in the target lobe and complete fissures treated with EBVs were responders (n=11/15). All valve-treated collapse phenomenon patients with fissure defects were nonresponders (n=3).In the absence of the collapse phenomenon Chartis measurement is reliable to predict response to valve treatment. In patients with the collapse phenomenon, treatment decisions should be based on HRCT detection of fissure integrity. Chartis assessment should be performed under spontaneous breathing. PMID:27076587

  10. Silo collapse under granular discharge.

    PubMed

    Gutiérrez, G; Colonnello, C; Boltenhagen, P; Darias, J R; Peralta-Fabi, R; Brau, F; Clément, E

    2015-01-01

    We investigate, at a laboratory scale, the collapse of cylindrical shells of radius R and thickness t induced by a granular discharge. We measure the critical filling height for which the structure fails upon discharge. We observe that the silos sustain filling heights significantly above an estimation obtained by coupling standard shell-buckling and granular stress distribution theories. Two effects contribute to stabilize the structure: (i) below the critical filling height, a dynamical stabilization due to granular wall friction prevents the localized shell-buckling modes to grow irreversibly; (ii) above the critical filling height, collapse occurs before the downward sliding motion of the whole granular column sets in, such that only a partial friction mobilization is at play. However, we notice also that the critical filling height is reduced as the grain size d increases. The importance of grain size contribution is controlled by the ratio d/√[Rt]. We rationalize these antagonist effects with a novel fluid-structure theory both accounting for the actual status of granular friction at the wall and the inherent shell imperfections mediated by the grains. This theory yields new scaling predictions which are compared with the experimental results. PMID:25615503

  11. Collapse Features on Arsia Mons

    NASA Technical Reports Server (NTRS)

    2005-01-01

    [figure removed for brevity, see original site]

    This VIS image is located on the SE flank of Arsia Mons where it meets the plains. As with yesterday's image, collapse features are present at the margin of the volcano. These collapse features likely occur over lava tubes that served as conduits for flows from within the volcano.

    Image information: VIS instrument. Latitude -11.3, Longitude 240.4 East (119.6 West). 17 meter/pixel resolution.

    Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time.

    NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. The Thermal Emission Imaging System (THEMIS) was developed by Arizona State University, Tempe, in collaboration with Raytheon Santa Barbara Remote Sensing. The THEMIS investigation is led by Dr. Philip Christensen at Arizona State University. Lockheed Martin Astronautics, Denver, is the prime contractor for the Odyssey project, and developed and built the orbiter. Mission operations are conducted jointly from Lockheed Martin and from JPL, a division of the California Institute of Technology in Pasadena.

  12. Dyadosphere formed in gravitational collapse

    SciTech Connect

    Ruffini, Remo; Xue Shesheng

    2008-10-10

    We first recall the concept of Dyadosphere (electron-positron-photon plasma around a formed black holes) and its motivation, and recall on (i) the Dirac process: annihilation of electron-positron pairs to photons; (ii) the Breit-Wheeler process: production of electron-positron pairs by photons with the energy larger than electron-positron mass threshold; the Sauter-Euler-Heisenberg effective Lagrangian and rate for the process of electron-positron production in a constant electric field. We present a general formula for the pair-production rate in the semi-classical treatment of quantum mechanical tunneling. We also present in the Quantum Electro-Dynamics framework, the calculations of the Schwinger rate and effective Lagrangian for constant electromagnetic fields. We give a review on the electron-positron plasma oscillation in constant electric fields, and its interaction with photons leading to energy and number equipartition of photons, electrons and positrons. The possibility of creating an overcritical field in astrophysical condition is pointed out. We present the discussions and calculations on (i) energy extraction from gravitational collapse; (ii) the formation of Dyadosphere in gravitational collapsing process, and (iii) its hydrodynamical expansion in Reissner Nordstroem geometry. We calculate the spectrum and flux of photon radiation at the point of transparency, and make predictions for short Gamma-Ray Bursts.

  13. Grain Growth in Collapsing Clouds

    NASA Astrophysics Data System (ADS)

    Rossi, S. C. F.; Benevides-Soares, P.; Barbuy, B.

    1990-11-01

    RESUMEN. Se ha considerado un proceso de coagulaci6n de granos en nubes colapsantes de diferentes metalicidades. Se aplicaron los calculos al intervalo de densidades n = lO to , forrespondiendo a la fase isotermica de contracci6n de nubes. A lo largo de esta fase en el colap- so, la temperatura es por lo tanto constante, en donde se alcanza T Q lOKpara nubes de metalicidad solar y T 100 K para nubes de baja metalicidad. El tamano final del grano es mayor para las mayores metali- cidades. ABSTRACT. A process of grain coagulation in collapsing clouds of different metallicities is considered. The calculations are applied to the density range n = 1O to , corresponding to the isothermal phase of cloud contraction. Along this phase in the collapse, the temperature is thus a constant, where T % 10 K for solar-metallicity clouds, and T % 100 K for low metallicity clouds is reached. The final grain size is larger for the higher metallicities. Keq : INTERSTELLAR-CLOUDS - INTERSTELLAR-CRAINS

  14. Collapsible Cryogenic Storage Vessel Project

    NASA Technical Reports Server (NTRS)

    Fleming, David C.

    2002-01-01

    Collapsible cryogenic storage vessels may be useful for future space exploration missions by providing long-term storage capability using a lightweight system that can be compactly packaged for launch. Previous development efforts have identified an 'inflatable' concept as most promising. In the inflatable tank concept, the cryogen is contained within a flexible pressure wall comprised of a flexible bladder to contain the cryogen and a fabric reinforcement layer for structural strength. A flexible, high-performance insulation jacket surrounds the vessel. The weight of the tank and the cryogen is supported by rigid support structures. This design concept is developed through physical testing of a scaled pressure wall, and through development of tests for a flexible Layered Composite Insulation (LCI) insulation jacket. A demonstration pressure wall is fabricated using Spectra fabric for reinforcement, and burst tested under noncryogenic conditions. An insulation test specimens is prepared to demonstrate the effectiveness of the insulation when subject to folding effects, and to examine the effect of compression of the insulation under compressive loading to simulate the pressure effect in a nonrigid insulation blanket under the action atmospheric pressure, such as would be seen in application on the surface of Mars. Although pressure testing did not meet the design goals, the concept shows promise for the design. The testing program provides direction for future development of the collapsible cryogenic vessel concept.

  15. Gravitational collapse and the cosmological constant

    SciTech Connect

    Deshingkar, S. S.; Jhingan, S.; Chamorro, A.; Joshi, P. S.

    2001-06-15

    We consider here the effects of a nonvanishing cosmological term on the final fate of a spherical inhomogeneous collapsing dust cloud. It is shown that, depending on the nature of the initial data from which the collapse evolves, and for a positive value of the cosmological constant, we can have a globally regular evolution where a bounce develops within the cloud. We characterize precisely the initial data causing such a bounce in terms of the initial density and velocity profiles for the collapsing cloud. In the cases otherwise, the result of collapse is either the formation of a black hole or a naked singularity resulting as the end state of collapse. We also show here that a positive cosmological term can cover a part of the singularity spectrum which is visible in the corresponding dust collapse models for the same initial data.

  16. Is Collapsing C1q Nephropathy Another MYH9-Associated Kidney Disease? A Case Report

    PubMed Central

    Reeves-Daniel, Amber M.; Iskandar, Samy S.; Bowden, Donald W.; Bostrom, Meredith A.; Hicks, Pamela J.; Comeau, Mary E.; Langefeld, Carl D.; Freedman, Barry I.

    2009-01-01

    C1q nephropathy is a rare kidney disease that can present with nephrotic syndrome and typically has the histological phenotype of either minimal change disease (MCD) or focal segmental glomerulosclerosis (FSGS). Disagreement exists as to whether it is a distinct immune complex-mediated glomerulopathy or whether it resides in the spectrum of FSGS-MCD. Two African American patients with C1q nephropathy histologically presenting as the collapsing variant of FSGS (collapsing C1q nephropathy) and rapid loss of kidney function were genotyped for polymorphisms in the non-muscle myosin heavy chain 9 gene (MYH9). Both cases were homozygous for the MYH9 E1 risk haplotype; the variant strongly associated with idiopathic FSGS, collapsing FSGS in Human Immunodeficiency Virus-associated nephropathy and focal global glomerulosclerosis (historically attributed to hypertensive nephrosclerosis). Collapsing C1q nephropathy with rapid progression to ESRD appears to reside in the MYH9-associated disease spectrum. PMID:20116156

  17. Gravitational radiation from collapsing magnetized dust

    SciTech Connect

    Sotani, Hajime; Yoshida, Shijun; Kokkotas, Kostas D.

    2007-04-15

    In this article we study the influence of magnetic fields on the axial gravitational waves emitted during the collapse of a homogeneous dust sphere. We found that while the energy emitted depends weakly on the initial matter perturbations it has strong dependence on the strength and the distribution of the magnetic field perturbations. The gravitational wave output of such a collapse can be up to an order of magnitude larger or smaller calling for detailed numerical 3D studies of collapsing magnetized configurations.

  18. Endotracheal stenting therapy in dogs with tracheal collapse.

    PubMed

    Sun, Fei; Usón, Jesús; Ezquerra, Javier; Crisóstomo, Verónica; Luis, Laura; Maynar, Manuel

    2008-02-01

    Tracheal collapse in dogs is a common respiratory disorder, typically presenting with a history of chronic cough, increasing respiratory difficulties, and episodes of dyspnoea. Medical treatment is the therapy of choice and surgical repair is considered when patients do not respond well. Minimally invasive endotracheal stenting is a promising new therapy under investigation, but there remain significant challenges to overcome potential complications. The purpose of this article is to provide a comparative overview of intra-luminal stenting of the trachea in human and veterinary medicine. The currently available stents and their potential clinical application to the veterinary patient will be discussed. PMID:17368061

  19. A comprehensive classification of collapse calderas

    NASA Astrophysics Data System (ADS)

    Geyer, A.; Marti, J.; Acocella, V.; Aguirre-Diaz, G. J.; Cas, R. A.

    2012-12-01

    Collapse calderas are volcanic depressions that result from the disruption of the magma chamber roof during an eruption or lateral intrusion of magma. Their formation implies a perturbation of the structure and dynamics of the associated magma chambers. Collapse calderas are present in any geodynamic environment and may be associated with a wide range of magma compositions. Caldera morphology and structure yield information on subsidence mechanisms, evolutionary stage of collapse and the associated magma chamber, while any eruptive product provides the clues on magma composition and eruption dynamics. The term "caldera" has been commonly used to define certain sizes of collapses in volcanic areas, rather than a specific process. Moreover, several different classifications of collapse caldera have been proposed considering separately various aspects such as morphology, structure, composition, style of subsidence, size, eruption dynamics, or tectonic controls. However, the causative relationships between the resulting caldera types are not always well defined, thus causing confusion on the causes and results of each caldera process. This study has two main goals. 1) First, we provide a timely definition for calderas: we propose to restrict the term collapse caldera to those cases in which there is a direct interaction of the structures controlling collapse with an underlying magma chamber, independently of its size. 2) We present a comprehensive classification of collapse calderas based on an event tree structure that considers a hierarchy of criteria that we analyse in a logical sequence. This classification allows identifying any collapse caldera as a function of its dynamic, geometric, evolutionary and compositional conditions.

  20. Constructing black hole entropy from gravitational collapse

    NASA Astrophysics Data System (ADS)

    Acquaviva, Giovanni; Ellis, George F. R.; Goswami, Rituparno; Hamid, Aymen I. M.

    2015-03-01

    Based on a recent proposal for the gravitational entropy of free gravitational fields, we investigate the thermodynamic properties of black hole formation through gravitational collapse in the framework of the semitetrad 1 +1 +2 covariant formalism. In the simplest case of an Oppenheimer-Snyder-Datt collapse, we prove that the change in gravitational entropy outside a collapsing body is related to the variation of the surface area of the body itself, even before the formation of horizons. As a result, we are able to relate the Bekenstein-Hawking entropy of the black hole end state to the variation of the vacuum gravitational entropy outside the collapsing body.

  1. Dynamics of the constrained polymer collapse.

    SciTech Connect

    Aranson, I. S.; Tsimring, L. S.; Materials Science Division; Univ. of California-San Diego

    2003-06-01

    The dynamics of polymer collapse with a fixed distance between endpoints is studied analytically and numerically by the Nose-Hoover algorithm. We find that at the pearling stage of the collapse the number of pearls decays as t{sup -1/2} leading to anomalously long collapse time. To understand the effect of Stokes drag we reduced the problem of long-polymer-chain collapse to the one-dimensional diffusion-limited coalescence of particles with the mass-dependent mobility. In this case the number of pearls decays slower, as t{sup -3/7}.

  2. Axisymmetric collapses of granular columns

    NASA Astrophysics Data System (ADS)

    Lube, Gert; Huppert, Herbert E.; Sparks, R. Stephen J.; Hallworth, Mark A.

    2004-06-01

    Experimental observations of the collapse of initially vertical columns of small grains are presented. The experiments were performed mainly with dry grains of salt or sand, with some additional experiments using couscous, sugar or rice. Some of the experimental flows were analysed using high-speed video. There are three different flow regimes, dependent on the value of the aspect ratio a {=} h_i/r_i, where h_i and r_i are the initial height and radius of the granular column respectively. The differing forms of flow behaviour are described for each regime. In all cases a central, conically sided region of angle approximately 59(°) , corresponding to an aspect ratio of 1.7, remains undisturbed throughout the motion. The main experimental results for the final extent of the deposit and the time for emplacement are systematically collapsed in a quantitative way independent of any friction coefficients. Along with the kinematic data for the rate of spread of the front of the collapsing column, this is interpreted as indicating that frictional effects between individual grains in the bulk of the moving flow only play a role in the last instant of the flow, as it comes to an abrupt halt. For a {<} 1.7, the measured final runout radius, r_infty, is related to the initial radius by r_infty {=} r_i(1 {+} 1.24a); while for 1.7 {<} a the corresponding relationship is r_infty {=} r_i(1 {+} 1.6a(1/2) ). The time, t_infty, taken for the grains to reach r_infty is given by t_infty {=} 3(h_i/g)(1/2} {=} 3(r_i/g)({1/2}a^{1/2)) , where g is the gravitational acceleration. The insights and conclusions gained from these experiments can be applied to a wide range of industrial and natural flows of concentrated particles. For example, the observation of the rapid deposition of the grains can help explain details of the emplacement of pyroclastic flows resulting from the explosive eruption of volcanoes.

  3. Completely quantized collapse and consequences

    SciTech Connect

    Pearle, Philip

    2005-08-15

    Promotion of quantum theory from a theory of measurement to a theory of reality requires an unambiguous specification of the ensemble of realizable states (and each state's probability of realization). Although not yet achieved within the framework of standard quantum theory, it has been achieved within the framework of the continuous spontaneous localization (CSL) wave-function collapse model. In CSL, a classical random field w(x,t) interacts with quantum particles. The state vector corresponding to each w(x,t) is a realizable state. In this paper, I consider a previously presented model, which is predictively equivalent to CSL. In this completely quantized collapse (CQC) model, the classical random field is quantized. It is represented by the operator W(x,t) which satisfies [W(x,t),W(x{sup '},t{sup '})]=0. The ensemble of realizable states is described by a single state vector, the 'ensemble vector'. Each superposed state which comprises the ensemble vector at time t is the direct product of an eigenstate of W(x,t{sup '}), for all x and for 0{<=}t{sup '}{<=}t, and the CSL state corresponding to that eigenvalue. These states never interfere (they satisfy a superselection rule at any time), they only branch, so the ensemble vector may be considered to be, as Schroedinger put it, a 'catalog' of the realizable states. In this context, many different interpretations (e.g., many worlds, environmental decoherence, consistent histories, modal interpretation) may be satisfactorily applied. Using this description, a long-standing problem is resolved, where the energy comes from the particles gain due to the narrowing of their wave packets by the collapse mechanism. It is shown how to define the energy of the random field and its energy of interaction with particles so that total energy is conserved for the ensemble of realizable states. As a by-product, since the random-field energy spectrum is unbounded, its canonical conjugate, a self-adjoint time operator, can be

  4. Esophagectomy - minimally invasive

    MedlinePlus

    Minimally invasive esophagectomy; Robotic esophagectomy; Removal of the esophagus - minimally invasive; Achalasia - esophagectomy; Barrett esophagus - esophagectomy; Esophageal cancer - esophagectomy - laparoscopic; Cancer of the ...

  5. Higgs portals to pulsar collapse

    NASA Astrophysics Data System (ADS)

    Bramante, Joseph; Elahi, Fatemeh

    2015-06-01

    Pulsars apparently missing from the Galactic center could have been destroyed by asymmetric fermionic dark matter (mX=1 - 100 GeV ) coupled to a light scalar (mϕ=5 - 20 MeV ), which mixes with the Higgs boson. We point out that this pulsar-collapsing dark sector can resolve the core-cusp problem and will either be excluded or discovered by upcoming direct detection experiments. Another implication is a maximum pulsar age curve that increases with distance from the Galactic center, with a normalization that depends on the couplings and masses of dark sector particles. In addition, we use old pulsars outside the Galactic center to place bounds on asymmetric Higgs portal models.

  6. Understand rotating isothermal collapses yet

    SciTech Connect

    Tohline, J.E.

    1985-01-01

    A scalar virial equation is used to describe the dynamic properties of equilibrium gas clouds, taking into account the relative effects of surface pressure, rotation, self gravity and internal isothermal pressure. Details concerning the internal structure of the clouds are ignored in order to obtain a globalized analytical expression. The obtained solution to the equation is found to agree with the surface-pressure-dominated model of Stahler (1983), and the rotation-dominated model of Hayashi, Narita, and Miyama (1982). On the basis of the analytical expression of virial equilibrium in the clouds, some of the limiting properties of isothermal clouds are described, and a realistic starting model for cloud collapse is proposed. 18 references.

  7. Abdominal Distension and Vascular Collapse.

    PubMed

    Cosentino, Gina; Uwaifo, Gabriel I

    2016-04-01

    We present the case of a 43-year-old gentleman who presented to the emergency room with acute abdominal distension, confusion and vascular collapse. The emergent radiologic imaging obtained showed massive bilateral adrenal enlargement, but despite the initial clinical suspicion of possible overwhelming sepsis and/or massive abdominal/intralesional hemorrhage, lab tests based obtained rapidly confirmed the diagnosis of acute Addisonian crisis which responded dramatically to adrenocorticoid hormone replacement therapy and aggressive fluid resuscitation. The patient's established history of metastatic lung cancer confirmed this as a case of metastatic massive bilateral adrenal metastases with an initial presentation of acute adrenal insufficiency which is uncommon in the setting of metastatic carcinomatosis but more typically associated with lymphomas. Recognition of this clinical possibility is vital to enable rapid diagnosis and consequent life saving therapy. PMID:27328473

  8. Nonadiabatic charged spherical gravitational collapse

    SciTech Connect

    Di Prisco, A.; Herrera, L.; Le Denmat, G.; MacCallum, M. A. H.; Santos, N. O.

    2007-09-15

    We present a complete set of the equations and matching conditions required for the description of physically meaningful charged, dissipative, spherically symmetric gravitational collapse with shear. Dissipation is described with both free-streaming and diffusion approximations. The effects of viscosity are also taken into account. The roles of different terms in the dynamical equation are analyzed in detail. The dynamical equation is coupled to a causal transport equation in the context of Israel-Stewart theory. The decrease of the inertial mass density of the fluid, by a factor which depends on its internal thermodynamic state, is reobtained, with the viscosity terms included. In accordance with the equivalence principle, the same decrease factor is obtained for the gravitational force term. The effect of the electric charge on the relation between the Weyl tensor and the inhomogeneity of the energy density is discussed.

  9. Critical perspectives on historical collapse

    PubMed Central

    Butzer, Karl W.; Endfield, Georgina H.

    2012-01-01

    Historical collapse of ancient states or civilizations has raised new awareness about its possible relevance to current issues of sustainability, in the context of global change. This Special Feature examines 12 case studies of societies under stress, of which seven suffered severe transformation. Outcomes were complex and unpredictable. Five others overcame breakdown through environmental, political, or socio-cultural resilience, which deserves as much attention as the identification of stressors. Response to environmental crises of the last millennium varied greatly according to place and time but drew from traditional knowledge to evaluate new information or experiment with increasing flexibility, even if modernization or intensification were decentralized and protracted. Longer-term diachronic experience offers insight into how societies have dealt with acute stress, a more instructive perspective for the future than is offered by apocalyptic scenarios. PMID:22371580

  10. Gravitational collapse in Hořava-Lifshitz theory

    NASA Astrophysics Data System (ADS)

    Greenwald, Jared; Lenells, Jonatan; Satheeshkumar, V. H.; Wang, Anzhong

    2013-07-01

    We study gravitational collapse of a spherical fluid in nonrelativistic general covariant theory of the Hořava-Lifshitz gravity with the projectability condition and an arbitrary coupling constant λ, where |λ-1| characterizes the deviation of the theory from general relativity in the infrared limit. The junction conditions across the surface of a collapsing star are derived under the (minimal) assumption that the junctions be mathematically meaningful in terms of distribution theory. When the collapsing star is made of a homogeneous and isotropic perfect fluid, and the external region is described by a stationary spacetime, the problem reduces to the matching of six independent conditions. If the perfect fluid is pressureless (a dust fluid), it is found that the matching is also possible. In particular, in the case λ=1, the external spacetime is described by the Sch-(anti-)de Sitter solution written in Painlevé-Gullstrand coordinates. In the case λ≠1, the external spacetime is static but not asymptotically flat. Our treatment can be easily generalized to other versions of Hořava-Lifshitz gravity or, more generally, to any theory of higher-order derivative gravity.

  11. Collapse transition of randomly branched polymers: renormalized field theory.

    PubMed

    Janssen, Hans-Karl; Stenull, Olaf

    2011-05-01

    We present a minimal dynamical model for randomly branched isotropic polymers, and we study this model in the framework of renormalized field theory. For the swollen phase, we show that our model provides a route to understand the well-established dimensional-reduction results from a different angle. For the collapse θ transition, we uncover a hidden Becchi-Rouet-Stora supersymmetry, signaling the sole relevance of tree configurations. We correct the long-standing one-loop results for the critical exponents, and we push these results on to two-loop order. For the collapse θ' transition, we find a runaway of the renormalization group flow, which lends credence to the possibility that this transition is a fluctuation-induced first-order transition. Our dynamical model allows us to calculate for the first time the fractal dimension of the shortest path on randomly branched polymers in the swollen phase as well as at the collapse transition and related fractal dimensions. PMID:21728509

  12. Gravitational Collapse With Distributed Adaptive Mesh Refinement

    NASA Astrophysics Data System (ADS)

    Liebling, Steven; Lehner, Luis; Motl, Patrick; Neilsen, David; Rahman, Tanvir; Reula, Oscar

    2006-04-01

    Gravitational collapse is studied using distributed adaptive mesh refinement (AMR). The AMR infrastructure includes a novel treatment of adaptive boundaries which allows for high orders of accuracy. Results of the collapse of Brill waves to black holes are presented. Combining both vertex centered and cell centered fields in the same evolution is discussed.

  13. Domain Collapse in Grooved Magnetic Garnet Material

    NASA Technical Reports Server (NTRS)

    Peredo, J.; Fedyunin, Y.; Patterson, G.

    1995-01-01

    Domain collapse fields in grooved garnet material were investigated by experimental observation and numerical simulation. The results indicate that the change in domain collapse field is largely due to magnetostatic effects produced by the groove edge. A simplified model based on the effective field produced at a groove edge, and local changes in the material thickness explain the observed trends very well.!.

  14. Equations determine coiled tubing collapse pressure

    SciTech Connect

    Avakov, V.; Taliaferro, W.

    1995-07-24

    A set of equations has been developed for calculating pipe collapse pressure for oval tubing such as coiled tubing. When coiled tubing is placed onto a reel, the tubing is forced into an oval shape and never again returns to perfect roundness because the coiling process exceeds the plasticity limits of the tubing. Straightening the tubing for the trip into the well does not restore roundness. The consequence of this physical property is that all coiled tubing collapse pressure calculations should be made considering oval tubing, not round tubing. Tubing collapse can occur when formation pressure against the coiled tubing exceeds the collapse resistance inherent in the coiled tubing. As coiled tubing becomes more oval in shape, it becomes more oval in shape, it becomes more susceptible to collapse from outside pressure.

  15. Are Collapse Models Testable via Flavor Oscillations?

    NASA Astrophysics Data System (ADS)

    Donadi, Sandro; Bassi, Angelo; Curceanu, Catalina; Di Domenico, Antonio; Hiesmayr, Beatrix C.

    2013-07-01

    Collapse models predict the spontaneous collapse of the wave function, in order to avoid the emergence of macroscopic superpositions. In their mass-dependent formulation, they claim that the collapse of any system's wave function depends on its mass. Neutral K, D, B mesons are oscillating systems that are given by Nature as superposition of two distinct mass eigenstates. Thus they are unique laboratory for testing collapse models that are sensitive to the mass. In this paper we derive—for the single mesons and bipartite entangled mesons—the effect of the mass-proportional CSL (Continuous Spontaneous Localization) collapse model on the dynamics on neutral mesons. We compare the theoretical prediction with experimental data from different accelerator facilities.

  16. Architecture of collapsed-paleocave reservoirs

    SciTech Connect

    Loucks, R.G. ); Mescher, P. )

    1996-01-01

    It is important to investigate the architecture of collapsed-paleocave reservoirs at interwell scales in outcrops because reservoir heterogeneities cannot be adequately characterized by cores and log correlation sections. A 3000-foot long quarry wall of Ellenburger strata in central Texas displays the lithologic and pore network heterogeneities at typical well spacings (1300 to 2600 feet). The quarry wall exposes the transition from stratified host rock into a complex collapsed-paleocave system showing several developmental episodes. This paleocave system has over 2600 feet of laterally continuous chaotic breccias. The dimensions of these breccias are similar as to what is imaged by 3-D seismic over paleocave reservoirs. Collapsed-paleocave reservoirs are not single collapsed passages of tens of feet across, but are homogenized collapsed-cave systems hundreds to several thousand feet across. This concept of scale is very important because collapsed-paleocave systems offer larger exploration targets than individual cave passages. Collapsed-paleocave systems are complex because they are the homogenization of chaotic breccias and cave-sediment fill from passages, chambers, and shafts and of crackle breccias from roof- and wall-rock and pillars. Pore networks are associated with chaotic breakdown breccias, cave roof- and wall-crackle breccias, and/or clastic sediment fill. Strong heterogeneity within a collapsed paleocave system should be expected. Lateral and vertical changes in collapsed-paleocave-related facies have the strongest effect on reservoir heterogeneity and quality. Within individual facies there can be distinct reservoir quality variation, such as between the cave-sediment fill and associated blocks. Tectonic fractures, however, can interconnect the highly variable pore networks within a collapsed-paleocave reservoir.

  17. Architecture of collapsed-paleocave reservoirs

    SciTech Connect

    Loucks, R.G.; Mescher, P.

    1996-12-31

    It is important to investigate the architecture of collapsed-paleocave reservoirs at interwell scales in outcrops because reservoir heterogeneities cannot be adequately characterized by cores and log correlation sections. A 3000-foot long quarry wall of Ellenburger strata in central Texas displays the lithologic and pore network heterogeneities at typical well spacings (1300 to 2600 feet). The quarry wall exposes the transition from stratified host rock into a complex collapsed-paleocave system showing several developmental episodes. This paleocave system has over 2600 feet of laterally continuous chaotic breccias. The dimensions of these breccias are similar as to what is imaged by 3-D seismic over paleocave reservoirs. Collapsed-paleocave reservoirs are not single collapsed passages of tens of feet across, but are homogenized collapsed-cave systems hundreds to several thousand feet across. This concept of scale is very important because collapsed-paleocave systems offer larger exploration targets than individual cave passages. Collapsed-paleocave systems are complex because they are the homogenization of chaotic breccias and cave-sediment fill from passages, chambers, and shafts and of crackle breccias from roof- and wall-rock and pillars. Pore networks are associated with chaotic breakdown breccias, cave roof- and wall-crackle breccias, and/or clastic sediment fill. Strong heterogeneity within a collapsed paleocave system should be expected. Lateral and vertical changes in collapsed-paleocave-related facies have the strongest effect on reservoir heterogeneity and quality. Within individual facies there can be distinct reservoir quality variation, such as between the cave-sediment fill and associated blocks. Tectonic fractures, however, can interconnect the highly variable pore networks within a collapsed-paleocave reservoir.

  18. Infrared spectra of protostellar collapse

    NASA Technical Reports Server (NTRS)

    Hollenbach, David J.; Ceccarelli, Cecilia; Neufeld, David A.; Tielens, Alexander G. G. M.

    1995-01-01

    Theoretical models of the formation of low mass stars by cloud collapse predict that OI(63 micrometers) and IR rotational lines of CO and H2O dominate the cooling in the freefalling region 10-1000 AU from the protostar. The freefalling gas supersonically hits the protoplanetary disk orbiting the protostar, forming an accretion shock with strong IR emission in rotational lines of H2O and OH, and OI(63 microns). The accretion shock spectra and line profiles depend on the mass flux through the shock and the typical distance r-bar at which the freefalling gas strikes the disk. The line widths are of order the Keplerian speed, or approx. 10(r-bar/10AU)(exp -0.5) km/s, for the accretion shock lines, and less for the lines from the infalling gas. Measurements of the IR line fluxes and profiles from the freefalling gas and the accretion shock diagnoses how a protostar and disk are formed and requires high sensitivity and high spectral and spatial resolving power. SOFIA will be the optimum observatory for many of these lines, although ISO will contribute and the KAO may make a few pioneering detections.

  19. Jet dynamics after cavity collapse

    NASA Astrophysics Data System (ADS)

    Gordillo, Jose Manuel; Gekle, Stephan; van der Meer, Devaraj; Lohse, Detlef

    2008-11-01

    It has been recently shown -Gekle, Gordillo, van der Meer and Lohse, Phys. Rev. Lett., 2008 (submitted)- that the liquid velocity field after cavity collapse can be analytically described as a superposition of a discontinuous line of sinks plus a concentrated point sink. This theory is able to quantitatively predict the axial and radial positions of the base of the high speed jets ejected. Nevertheless, the flow field within the fast sharp pointed jets shooting up and downwards cannot be predicted using this simplified description. Instead, we will show that downstream of a small region with a size of the order of the jet base, in which the liquid is accelerated upwards, liquid velocity and jet shape can be described by a simple unidirectional model in remarkable agreement with simulations. Up to first order, fluid particles conserve their velocities but we also show that, no matter how large the local Weber number at pinch-off is, capillarity ends up playing a role in the breakup of the ejected liquid jets.

  20. Costa Rica's Chain of laterally collapsed volcanoes.

    NASA Astrophysics Data System (ADS)

    Duarte, E.; Fernandez, E.

    2007-05-01

    From the NW extreme to the SW end of Costa Rica's volcanic backbone, a number of laterally collapsed volcanoes can be observed. Due to several factors, attention has been given to active volcanoes disregarding the importance of collapsed features in terms of assessing volcanic hazards for future generations around inhabited volcanoes. In several cases the typical horseshoe shape amphitheater-like depression can be easily observed. In other cases due to erosion, vegetation, topography, seismic activity or drastic weather such characteristics are not easily recognized. In the order mentioned above appear: Orosi-Cacao, Miravalles, Platanar, Congo, Von Frantzius, Cacho Negro and Turrialba volcanoes. Due to limited studies on these structures it is unknown if sector collapse occurred in one or several phases. Furthermore, in the few studied cases no evidence has been found to relate collapses to actual eruptive episodes. Detailed studies on the deposits and materials composing dome-like shapes will shed light on unsolved questions about petrological and chemical composition. Volume, form and distance traveled by deposits are part of the questions surrounding most of these collapsed volcanoes. Although most of these mentioned structures are extinct, at least Irazú volcano (active volcano) has faced partial lateral collapses recently. It did presented strombolian activity in the early 60s. Collapse scars show on the NW flank show important mass removal in historic and prehistoric times. Moreover, in 1994 a minor hydrothermal explosion provoked the weakening of a deeply altered wall that holds a crater lake (150m diameter, 2.6x106 ). A poster will depict images of the collapsed volcanoes named above with mayor descriptive characteristics. It will also focus on the importance of deeper studies to assess the collapse potential of Irazú volcano with related consequences. Finally, this initiative will invite researchers interested in such topic to join future studies in

  1. Minimal change disease

    MedlinePlus

    Minimal change nephrotic syndrome; Nil disease; Lipoid nephrosis; Idiopathic nephrotic syndrome of childhood ... which filter blood and produce urine. In minimal change disease, there is damage to the glomeruli. These ...

  2. Minimal change disease

    MedlinePlus

    ... seen under a very powerful microscope called an electron microscope. Minimal change disease is the most common ... biopsy and examination of the tissue with an electron microscope can show signs of minimal change disease.

  3. Naked singularity resolution in cylindrical collapse

    SciTech Connect

    Kurita, Yasunari; Nakao, Ken-ichi

    2006-03-15

    In this paper, we study the gravitational collapse of null dust in cylindrically symmetric spacetime. The naked singularity necessarily forms at the symmetry axis. We consider the situation in which null dust is emitted again from the naked singularity formed by the collapsed null dust and investigate the backreaction by this emission for the naked singularity. We show a very peculiar but physically important case in which the same amount of null dust as that of the collapsed one is emitted from the naked singularity as soon as the ingoing null dust hits the symmetry axis and forms the naked singularity. In this case, although this naked singularity satisfies the strong curvature condition by Krolak (limiting focusing condition), geodesics which hit the singularity can be extended uniquely across the singularity. Therefore, we may say that the collapsing null dust passes through the singularity formed by itself and then leaves for infinity. Finally, the singularity completely disappears and the flat spacetime remains.

  4. Voltage collapse in complex power grids

    PubMed Central

    Simpson-Porco, John W.; Dörfler, Florian; Bullo, Francesco

    2016-01-01

    A large-scale power grid's ability to transfer energy from producers to consumers is constrained by both the network structure and the nonlinear physics of power flow. Violations of these constraints have been observed to result in voltage collapse blackouts, where nodal voltages slowly decline before precipitously falling. However, methods to test for voltage collapse are dominantly simulation-based, offering little theoretical insight into how grid structure influences stability margins. For a simplified power flow model, here we derive a closed-form condition under which a power network is safe from voltage collapse. The condition combines the complex structure of the network with the reactive power demands of loads to produce a node-by-node measure of grid stress, a prediction of the largest nodal voltage deviation, and an estimate of the distance to collapse. We extensively test our predictions on large-scale systems, highlighting how our condition can be leveraged to increase grid stability margins. PMID:26887284

  5. Cooperation, cheating, and collapse in biological populations

    NASA Astrophysics Data System (ADS)

    Gore, Jeff

    2014-03-01

    Natural populations can collapse suddenly in response to small changes in environmental conditions, and recovery from such a collapse can be difficult. We have used laboratory microbial ecosystems to directly measure theoretically proposed early warning signals of impending population collapse. Yeast cooperatively break down the sugar sucrose, meaning that below a critical size the population cannot sustain itself. We have demonstrated experimentally that changes in the fluctuations of the population size can serve as an early warning signal that the population is close to collapse. The cooperative nature of yeast growth on sucrose suggests that the population may be susceptible to ``cheater'' cells, which do not contribute to the public good and instead merely take advantage of the cooperative cells. We confirm this possibility experimentally and find that such social parasitism decreases the resilience of the population.

  6. Arsia Mons Collapse Pits in IR

    NASA Technical Reports Server (NTRS)

    2004-01-01

    [figure removed for brevity, see original site]

    We will be looking at collapse pits for the next two weeks. Collapse pits on Mars are formed in several ways. In volcanic areas, channelized lava flows can form roofs which insulate the flowing lava. These features are termed lava tubes on Earth and are common features in basaltic flows. After the lava has drained, parts of the roof of the tube will collapse under its own weight. These collapse pits will only be as deep as the bottom of the original lava tube. Another type of collapse feature associated with volcanic areas arises when very large eruptions completely evacuate the magma chamber beneath the volcano. The weight of the volcano will cause the entire edifice to subside into the void space below it. Structural features including fractures and graben will form during the subsidence. Many times collapse pits will form within the graben. In addition to volcanic collapse pits, Mars has many collapse pits formed when volatiles (such as subsurface ice) are released from the surface layers. As the volatiles leave, the weight of the surrounding rock causes collapse pits to form.

    These collapse pits are found on the flank of Arsia Mons and are related to lava tube collapse.

    Image information: IR instrument. Latitude -8.8, Longitude 240.4 East (119.6 West). 100 meter/pixel resolution.

    Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time.

    NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. The Thermal

  7. Detailed Jet Dynamics in a Collapsing Bubble

    NASA Astrophysics Data System (ADS)

    Supponen, Outi; Obreschkow, Danail; Kobel, Philippe; Farhat, Mohamed

    2015-12-01

    We present detailed visualizations of the micro-jet forming inside an aspherically collapsing cavitation bubble near a free surface. The high-quality visualizations of large and strongly deformed bubbles disclose so far unseen features of the dynamics inside the bubble, such as a mushroom-like flattened jet-tip, crown formation and micro-droplets. We also find that jetting near a free surface reduces the collapse time relative to the Rayleigh time.

  8. Climate and the collapse of civilization

    SciTech Connect

    Abate, T.

    1994-09-01

    This article looks at the archaeological debate over two important questions: whether abrupt climate changes caused or contributed to the collapse of ancient civilizations and, if the archaeological and paleoclimatological record yields evidence to that effect, what would it mean in a world that today debates whether industrial civilization is altering Earth's climate with uncertain consequences. Areas discussed include the following: climate hints from archaeological sites; hesitations about whether climate change caused civilizations to collapse; and the interdisciplinary checks on each side.

  9. Tracheal collapse in a young boxer.

    PubMed

    Radlinsky, M A; Fossum, T W

    2000-01-01

    A four-month-old, female boxer developed severe inspiratory dyspnea three days after elective ear crop surgery. Radiographs confirmed the diagnosis of collapse of the distal cervical trachea. The puppy was treated with oxygen, aminophylline, and ampicillin, but required emergency tracheostomy to stent the collapsed region. Clinical signs resolved following application of five polypropylene total-ring prostheses, and the puppy continued to do well despite significant growth to maturity. PMID:10914529

  10. Cardiovascular collapse with attempted pericardial drain withdrawal

    PubMed Central

    Kraus, Molly B; Spitznagel, Rachel A; Kugler, Jane A

    2016-01-01

    Cardiac tamponade is a rare but serious emergency condition in the pediatric population. As treatment, a pericardial drain is often placed to evacuate the fluid. We present a case of a 4-year-old girl with cardiac tamponade secondary to renal failure. After the tamponade resolved, she suffered cardiovascular collapse upon attempted drain withdrawal. This case highlights an unusual cause for cardiovascular collapse, which occurred on blind removal of a pericardial drain. PMID:27625522

  11. Gravitational collapse of a scalar field

    SciTech Connect

    Maithreyan, T.

    1985-01-01

    A self-similar collapse of massless scalar waves is considered, and the Einstein field equations in classical general relativity are solved to obtain the metric for the collapse. These scalar waves satisfy the massless wave equation and the energy momentum tensor associated with them is derived from their Lagrangian density. The collapse begins at t = 0 before which spacetime is flat, empty spacetime described by the Minkowski metric. Self similarity assumes that a homothetic Killing vector exists for the collapse, which satisfies the corresponding homothetic Killing equation. The solution obtained contains a constant c/sup 2/ whose value determines the nature of the collapse and the kind of singularity formed by the collapsing scalar waves. The three different cases are outlined and the corresponding Penrose diagrams are given. The apparent horizons, defined by Hawking as the limit of the trapped surfaces surrounding the singularity, are calculated for each case. A quantum correction is given for the above classical picture using the method developed originally by Hawking, to study particle creation by a black hole.

  12. Four tails problems for dynamical collapse theories

    NASA Astrophysics Data System (ADS)

    McQueen, Kelvin J.

    2015-02-01

    The primary quantum mechanical equation of motion entails that measurements typically do not have determinate outcomes, but result in superpositions of all possible outcomes. Dynamical collapse theories (e.g. GRW) supplement this equation with a stochastic Gaussian collapse function, intended to collapse the superposition of outcomes into one outcome. But the Gaussian collapses are imperfect in a way that leaves the superpositions intact. This is the tails problem. There are several ways of making this problem more precise. But many authors dismiss the problem without considering the more severe formulations. Here I distinguish four distinct tails problems. The first (bare tails problem) and second (structured tails problem) exist in the literature. I argue that while the first is a pseudo-problem, the second has not been adequately addressed. The third (multiverse tails problem) reformulates the second to account for recently discovered dynamical consequences of collapse. Finally the fourth (tails problem dilemma) shows that solving the third by replacing the Gaussian with a non-Gaussian collapse function introduces new conflict with relativity theory.

  13. Increased Fracture Collapse after Intertrochanteric Fractures Treated by the Dynamic Hip Screw Adversely Affects Walking Ability but Not Survival

    PubMed Central

    Fang, Christian; Gudushauri, Paata; Wong, Tak-Man; Lau, Tak-Wing; Pun, Terence; Leung, Frankie

    2016-01-01

    In osteoporotic hip fractures, fracture collapse is deliberately allowed by commonly used implants to improve dynamic contact and healing. The muscle lever arm is, however, compromised by shortening. We evaluated a cohort of 361 patients with AO/OTA 31.A1 or 31.A2 intertrochanteric fracture treated by the dynamic hip screw (DHS) who had a minimal follow-up of 3 months and an average follow-up of 14.6 months and long term survival data. The amount of fracture collapse and shortening due to sliding of the DHS was determined at the latest follow-up and graded as minimal (<1 cm), moderate (1-2 cm), or severe (>2 cm). With increased severity of collapse, more patients were unable to maintain their premorbid walking function (minimal collapse = 34.2%, moderate = 33.3%, severe = 62.8%, and p = 0.028). Based on ordinal regression of risk factors, increased fracture collapse was significantly and independently related to increasing age (p = 0.037), female sex (p = 0.024), A2 fracture class (p = 0.010), increased operative duration (p = 0.011), poor reduction quality (p = 0.000), and suboptimal tip-apex distance of >25 mm (p = 0.050). Patients who had better outcome in terms of walking function were independently predicted by younger age (p = 0.036), higher MMSE marks (p = 0.000), higher MBI marks (p = 0.010), better premorbid walking status (p = 0.000), less fracture collapse (p = 0.011), and optimal lag screw position in centre-centre or centre-inferior position (p = 0.020). According to Kaplan-Meier analysis, fracture collapse had no association with mortality from 2.4 to 7.6 years after surgery. In conclusion, increased fracture collapse after fixation of geriatric intertrochanteric fractures adversely affected walking but not survival. PMID:26955637

  14. Increased Fracture Collapse after Intertrochanteric Fractures Treated by the Dynamic Hip Screw Adversely Affects Walking Ability but Not Survival.

    PubMed

    Fang, Christian; Gudushauri, Paata; Wong, Tak-Man; Lau, Tak-Wing; Pun, Terence; Leung, Frankie

    2016-01-01

    In osteoporotic hip fractures, fracture collapse is deliberately allowed by commonly used implants to improve dynamic contact and healing. The muscle lever arm is, however, compromised by shortening. We evaluated a cohort of 361 patients with AO/OTA 31.A1 or 31.A2 intertrochanteric fracture treated by the dynamic hip screw (DHS) who had a minimal follow-up of 3 months and an average follow-up of 14.6 months and long term survival data. The amount of fracture collapse and shortening due to sliding of the DHS was determined at the latest follow-up and graded as minimal (<1 cm), moderate (1-2 cm), or severe (>2 cm). With increased severity of collapse, more patients were unable to maintain their premorbid walking function (minimal collapse = 34.2%, moderate = 33.3%, severe = 62.8%, and p = 0.028). Based on ordinal regression of risk factors, increased fracture collapse was significantly and independently related to increasing age (p = 0.037), female sex (p = 0.024), A2 fracture class (p = 0.010), increased operative duration (p = 0.011), poor reduction quality (p = 0.000), and suboptimal tip-apex distance of >25 mm (p = 0.050). Patients who had better outcome in terms of walking function were independently predicted by younger age (p = 0.036), higher MMSE marks (p = 0.000), higher MBI marks (p = 0.010), better premorbid walking status (p = 0.000), less fracture collapse (p = 0.011), and optimal lag screw position in centre-centre or centre-inferior position (p = 0.020). According to Kaplan-Meier analysis, fracture collapse had no association with mortality from 2.4 to 7.6 years after surgery. In conclusion, increased fracture collapse after fixation of geriatric intertrochanteric fractures adversely affected walking but not survival. PMID:26955637

  15. Fishing amplifies forage fish population collapses

    PubMed Central

    Essington, Timothy E.; Moriarty, Pamela E.; Froehlich, Halley E.; Hodgson, Emma E.; Koehn, Laura E.; Oken, Kiva L.; Siple, Margaret C.; Stawitz, Christine C.

    2015-01-01

    Forage fish support the largest fisheries in the world but also play key roles in marine food webs by transferring energy from plankton to upper trophic-level predators, such as large fish, seabirds, and marine mammals. Fishing can, thereby, have far reaching consequences on marine food webs unless safeguards are in place to avoid depleting forage fish to dangerously low levels, where dependent predators are most vulnerable. However, disentangling the contributions of fishing vs. natural processes on population dynamics has been difficult because of the sensitivity of these stocks to environmental conditions. Here, we overcome this difficulty by collating population time series for forage fish populations that account for nearly two-thirds of global catch of forage fish to identify the fingerprint of fisheries on their population dynamics. Forage fish population collapses shared a set of common and unique characteristics: high fishing pressure for several years before collapse, a sharp drop in natural population productivity, and a lagged response to reduce fishing pressure. Lagged response to natural productivity declines can sharply amplify the magnitude of naturally occurring population fluctuations. Finally, we show that the magnitude and frequency of collapses are greater than expected from natural productivity characteristics and therefore, likely attributed to fishing. The durations of collapses, however, were not different from those expected based on natural productivity shifts. A risk-based management scheme that reduces fishing when populations become scarce would protect forage fish and their predators from collapse with little effect on long-term average catches. PMID:25848018

  16. Geophysical mapping of solution and collapse dolines

    NASA Astrophysics Data System (ADS)

    Kaufmann, Georg

    2014-05-01

    Karst rocks such as limestone, dolomite, anhydrite, gypsum, or salt can be dissolved physically by water or chemically by water enriched with carbon dioxide. The dissolution driven by water flowing through the karst aquifer either occurs along fractures and bedding partings in telogenetic rocks, or within the primary interconnected pore space in eogenetic rocks. The enlargement of either fractures or pores by dissolution creates a large secondary porosity typical for karst rocks, which is often very heterogenously distributed and results in preferential flow pathes in the sub-surface, with cavities as large-scale end members of the sub-surface voids. Once the sub-surface voids enlarged by dissolution grow to a certain size, the overburden rock can become instable and voids and caves can collapse. Depending of the type of overburden, the collapse initiated at depth propagates towards the surface and finally results in a collapse structure, such as collapse dolines, sinkholes, and tiangkengs on the very large scale. We present results from geophysical surveys over existing karst structures based on gravimetric, electrical, and geomagnetical methods. We have chosen two types of dolines, solution and collapse dolines, to capture and compare the geophysical signals resulting from these karst structures. We compare and discuss our geophysical survey results with simplified theoretical models describing the evolution of the karst structure and three-dimensional structural models for the current situation derived for the different locations.

  17. Atomistic simulations of langmuir monolayer collapse.

    PubMed

    Lorenz, Christian D; Travesset, Alex

    2006-11-21

    Monolayers at the vapor/water interface collapse by exploring the third dimension at sufficient lateral compression, either by forming three-dimensional structures or by solubilization into the aqueous solution. In this paper, we provide an atomistic description of collapse from molecular dynamics (MD) simulations. More specifically, we investigate monolayers of arachidic acids spread on pure water and in an aqueous solution with Ca2+ ions in the subphase. In both cases, it is found that the collapsed systems generally lead to the formation of multilayer structures, which in the system with Ca2+ ions, proceeds by an intermediate regime where the monolayer exhibits significant roughness (of the order of 4 A). If no roughness is present, the system forms collapsed structures into the aqueous solution. The computational cost of atomic MD limits our simulations to relatively small system sizes, fast compression rates, and temporal scales on the order of a nanosecond. We discuss the issues caused by these limitations and present a detailed discussion of how the collapse regime proceeds at long time scales. We conclude with a summary of the implications of our results for further theoretical and experimental studies. PMID:17106994

  18. Fishing amplifies forage fish population collapses.

    PubMed

    Essington, Timothy E; Moriarty, Pamela E; Froehlich, Halley E; Hodgson, Emma E; Koehn, Laura E; Oken, Kiva L; Siple, Margaret C; Stawitz, Christine C

    2015-05-26

    Forage fish support the largest fisheries in the world but also play key roles in marine food webs by transferring energy from plankton to upper trophic-level predators, such as large fish, seabirds, and marine mammals. Fishing can, thereby, have far reaching consequences on marine food webs unless safeguards are in place to avoid depleting forage fish to dangerously low levels, where dependent predators are most vulnerable. However, disentangling the contributions of fishing vs. natural processes on population dynamics has been difficult because of the sensitivity of these stocks to environmental conditions. Here, we overcome this difficulty by collating population time series for forage fish populations that account for nearly two-thirds of global catch of forage fish to identify the fingerprint of fisheries on their population dynamics. Forage fish population collapses shared a set of common and unique characteristics: high fishing pressure for several years before collapse, a sharp drop in natural population productivity, and a lagged response to reduce fishing pressure. Lagged response to natural productivity declines can sharply amplify the magnitude of naturally occurring population fluctuations. Finally, we show that the magnitude and frequency of collapses are greater than expected from natural productivity characteristics and therefore, likely attributed to fishing. The durations of collapses, however, were not different from those expected based on natural productivity shifts. A risk-based management scheme that reduces fishing when populations become scarce would protect forage fish and their predators from collapse with little effect on long-term average catches. PMID:25848018

  19. Modelling Glacier Retreat after Ice Shelf Collapse

    NASA Astrophysics Data System (ADS)

    De Rydt, J.; Gudmundsson, G. H.; Rott, H.; Bamber, J. L.

    2014-12-01

    Satellite measurements have shown the consistent and ongoing speed-up and retreat of glaciers that were once buttressed by the collapsed Larsen B ice shelf. Understanding the response of grounded ice to ice shelf collapse is a prerequisite to future predictions of sea level rise as other ice shelfs such as Scar Inlet or the Larsen Ice Shelf further weaken due to changing atmospheric and ocean conditions.We present model results for a number of sensitivity experiments that aim to simulate the response of glaciers to the collapse of Larsen B. For this purpose we use a state of the art shallow shelf model with grounding line resolving capabilities. The model is initialized to observed pre-2002 conditions with the ice shelf in place, and transient runs are done that study the response to a weakening and removal of the ice shelf. Results are compared to a novel dataset of observed ice velocities, which provides the most comprehensive overview of dynamical changes after the collapse to-date. In addition, we investigate glacier response to the future collapse of Scar Inlet, a remnant of the Larsen B ice shelf which has been suggested to show signs of weakening in recent years. Results will also be used to inform a future Antartic Peninsula-wide modelling study.

  20. SPH and Eulerian underwater bubble collapse simulations

    SciTech Connect

    Swegle, J.W.; Kipp, M.E.

    1998-05-01

    SPH (Smoothed Particle Hydrodynamics) is a gridless Lagrangian technique which is appealing as a possible alternative to numerical techniques currently used to analyze high deformation impulsive loading events. Previously, the SPH algorithm has been subjected to detailed testing and analysis to determine the feasibility of using the coupled finite-element/SPH code PRONTO/SPH for the analysis of various types of underwater explosion problems involving fluid-structure and shock-structure interactions. Here, SPH and Eulerian simulations are used to study the details of underwater bubble collapse, particularly the formation of re-entrant jets during collapse, and the loads generated on nearby structures by the jet and the complete collapse of the bubble. Jet formation is shown to be due simply to the asymmetry caused by nearby structures which disrupt the symmetry of the collapse. However, the load generated by the jet is a minor precursor to the major loads which occur at the time of complete collapse of the bubble.

  1. Critical material properties for pattern collapse mitigation

    NASA Astrophysics Data System (ADS)

    Winroth, Gustaf; Younkin, Todd R.; Blackwell, James M.; Gronheid, Roel

    2012-07-01

    Modern high-resolution lithography, which employs a chemically amplified resist (CAR) at either 193 or 13.5 nm wavelength, is often limited by pattern collapse. While the general concepts of how CAR platforms work are widely understood, the influence of composition on pattern collapse has been studied to a lesser extent. In addition, the subject is often further complicated by non-disclosure of the resist chemistry used in the lithographic evaluation. Open-source photoresist platforms can be beneficial for fundamental studies on how individual components influence pattern collapse. Such platforms should mimic a typical CAR, containing-apart from the polymer-additional components such as photo acid generators (PAGs) and base quenchers. Here, 193 nm and extreme ultraviolet lithography open-source platforms are presented wherein the chemistry, composition, and concentration are all disclosed. With the aim of fundamentally understand how resist composition and behavior influences pattern collapse, the molecular weight of the polymer backbone and the concentration of both PAG and base quencher were varied. These sets of resists were exposed using high-end optical lithography scanners. The results are presented such that the probability of pattern collapse is derived as a function of the exposure wavelength, chemistry, and component concentrations.

  2. Critical material properties for pattern collapse mitigation

    NASA Astrophysics Data System (ADS)

    Winroth, Gustaf; Younkin, Todd R.; Blackwell, James M.; Gronheid, Roel

    2012-03-01

    Modern high-resolution lithography, which employs a chemically amplified resist (CAR) at either 193 or 13.5 nm wavelength, is often limited by pattern collapse. While the general concepts of how CAR platforms work are widely understood, the influence of composition on pattern collapse has been studied to a lesser extent. In addition, the subject is often further complicated by non-disclosure of the resist chemistry used in the lithographic evaluation. Open-source photoresist platforms can be beneficial for fundamental studies on how individual components influence pattern collapse. Such platforms should mimic a typical CAR, containing - apart from the polymer - additional components such as photo acid generators (PAGs) and base quenchers. In this paper, 193 nm and EUVL open-source platforms are presented wherein the chemistry, composition, and concentration are all disclosed. With the aim to fundamentally understand how resist composition and behavior influences pattern collapse, the molecular weight of the polymer backbone and the concentration of both PAG and base quencher were varied. These sets of resists were exposed using both high-end optical lithography scanners. The results are presented such that the probability of pattern collapse is derived as a function of the exposure wavelength, chemistry, and component concentrations.

  3. Gravitational collapse of a homogeneous scalar field in deformed phase space

    NASA Astrophysics Data System (ADS)

    Rasouli, S. M. M.; Ziaie, A. H.; Marto, J.; Moniz, P. V.

    2014-02-01

    We study the gravitational collapse of a homogeneous scalar field, minimally coupled to gravity, in the presence of a particular type of dynamical deformation between the canonical momenta of the scale factor and of the scalar field. In the absence of such a deformation, a class of solutions can be found in the literature [R. Goswami and P. S. Joshi], whereby a curvature singularity occurs at the collapse end state, which can be either hidden behind a horizon or be visible to external observers. However, when the phase space is deformed, as implemented herein this paper, we find that the singularity may be either removed or instead, attained faster. More precisely, for negative values of the deformation parameter, we identify the emergence of a negative pressure term, which slows down the collapse so that the singularity is replaced with a bounce. In this respect, the formation of a dynamical horizon can be avoided depending on the suitable choice of the boundary surface of the star. Whereas for positive values, the pressure that originates from the deformation effects assists the collapse toward the singularity formation. In this case, since the collapse speed is unbounded, the condition on the horizon formation is always satisfied and furthermore the dynamical horizon develops earlier than when the phase-space deformations are absent. These results are obtained by means of a thoroughly numerical discussion.

  4. Spherical collapse and halo mass function in f(R) theories

    NASA Astrophysics Data System (ADS)

    Kopp, Michael; Appleby, Stephen A.; Achitouv, Ixandra; Weller, Jochen

    2013-10-01

    We compute the critical density of collapse for spherically symmetric overdensities in a class of f(R) modified gravity models. For the first time we evolve the Einstein, scalar field and nonlinear fluid equations, making the minimal simplifying assumptions that the metric potentials and scalar field remain quasistatic throughout the collapse. Initially evolving a top-hat profile, we find that the density threshold for collapse depends significantly on the initial conditions imposed, specifically the choice of size and shape. By imposing “natural” initial conditions, we obtain a fitting function for the spherical collapse δc as a function of collapse redshift, mass of the overdensity and fR0, the background scalar field value at z=0. By extending δc into a drifting and diffusing barrier within the context of excursion set theory, we obtain a realistic mass function that might be used to confront this class of scalar-tensor models with observations of dark-matter halos. The proposed analytic formula for the halo mass function was tested against Monte Carlo random walks for a wide class of moving barriers and can therefore be applied to other modified gravity theories.

  5. Collapse of DNA under Alternating Electric Fields

    PubMed Central

    Zhou, Chunda; Riehn, Robert

    2016-01-01

    Recent studies have shown that double-stranded DNA can collapse in presence of a strong electric field. Here we provide an in-depth study of the collapse of DNA under weak confinement in microchannels as a function of buffer strength, driving frequency, applied electric field strength, and molecule size. We find that the critical electric field at which DNA molecules collapse (10s of kV/cm) is strongly dependent on driving frequency dependent (100 … 800 Hz) and molecular size (20 … 160 kbp), and weakly dependent on the ionic strength (8 … 60 mM). We argue that an apparent stretching at very high electric fields is an artifact of the finite frame time of video microscopy. PACS numbers: 87.14.gk, 36.20.Ey, 82.35.Lr, 82.35.Rs PMID:26274209

  6. Inflationary gravitational waves in collapse scheme models

    NASA Astrophysics Data System (ADS)

    Mariani, Mauro; Bengochea, Gabriel R.; León, Gabriel

    2016-01-01

    The inflationary paradigm is an important cornerstone of the concordance cosmological model. However, standard inflation cannot fully address the transition from an early homogeneous and isotropic stage, to another one lacking such symmetries corresponding to our present universe. In previous works, a self-induced collapse of the wave function has been suggested as the missing ingredient of inflation. Most of the analysis regarding the collapse hypothesis has been solely focused on the characteristics of the spectrum associated to scalar perturbations, and within a semiclassical gravity framework. In this Letter, working in terms of a joint metric-matter quantization for inflation, we calculate, for the first time, the tensor power spectrum and the tensor-to-scalar ratio corresponding to the amplitude of primordial gravitational waves resulting from considering a generic self-induced collapse.

  7. Effect of Rotation in Cloud Core Collapse

    NASA Astrophysics Data System (ADS)

    Tsuribe, T.

    The collapse of rotating clouds is investigated.At first, isothermal collapse of an initially uniform-density, uniform-rotating, molecular cloud core with pressure and self-gravity is investigated to determine the conditions under which a cloud is unstable to fragmentation. A semianalytic model for the collapse of rotating spheroids is developed with the method of characteristics for inwardly propagating rarefaction waves. Three-dimensional self-gravitating hydrodynamical calculations are performed for the initially uniform-density rigid-rotating sphere. Both investigations show that the criterion for fragmentation is modified from the one in the literature if the property of the non-homologous collapse is taken into account. It is shown that the central flatness, that is, the axial ratio of the isodensity contour in the central region, is a good indicator for the fate of the cloud. We derive the criterion for the fragmentation considering the evolution of the flatness of the central core. If the central flatness becomes greater than the critical value ˜ 4π, a collapsing cloud with moderate perturbations is unstable for fragmentation, while if the central flatness stays smaller than the critical value, it does not fragment at least before adiabatic core formation. Warm clouds (α0 ≳ 0.5) are not expected to fragment before adiabatic core formation almost independent of the initial rotation (β0) and the properties of the initial perturbation. The effect of the initial density central concentration is also investigated. If it exists, distortion or flattening of a cloud core is suppressed even if α0 ≲ 0.5 in small rotation cases due to stronger nonhomologous property of the collapse. We conclude that the binary fragmentation is difficult during isothermal stage if a core collapse had started from near spherical configurations with moderate thermal energy or small rotation. We suggest that the close binary fragmentation may be possible in the nonisothermal

  8. Collapse of composite tubes under end moments

    NASA Technical Reports Server (NTRS)

    Stockwell, Alan E.; Cooper, Paul A.

    1992-01-01

    Cylindrical tubes of moderate wall thickness such as those proposed for the original space station truss, may fail due to the gradual collapse of the tube cross section as it distorts under load. Sometimes referred to as the Brazier instability, it is a nonlinear phenomenon. This paper presents an extension of an approximate closed form solution of the collapse of isotropic tubes subject to end moments developed by Reissner in 1959 to include specially orthotropic material. The closed form solution was verified by an extensive nonlinear finite element analysis of the collapse of long tubes under applied end moments for radius to thickness ratios and composite layups in the range proposed for recent space station truss framework designs. The finite element analysis validated the assumption of inextensional deformation of the cylindrical cross section and the approximation of the material as specially orthotropic.

  9. Scaling of curvature in subcritical gravitational collapse

    NASA Astrophysics Data System (ADS)

    Garfinkle, David; Duncan, G. Comer

    1998-09-01

    We perform numerical simulations of the gravitational collapse of a spherically symmetric scalar field. For those data that just barely do not form black holes we find the maximum curvature at the position of the central observer. We find a scaling relation between this maximum curvature and distance from the critical solution. The scaling relation is analogous to that found by Choptuik for the black hole mass for those data that do collapse to form black holes. We also find a periodic wiggle in the scaling exponent.

  10. Structural control on karst collapse sinkhole formation

    NASA Astrophysics Data System (ADS)

    Santo, Antonio; Ascione, Alessandra; Mazzoli, Stefano; Santangelo, Nicoletta

    2013-04-01

    Collapse sinkholes owing their formation to erosion and deformation phenomena caused by subsurface karstification are widespread in the carbonate massifs of peninsular Italy. In contrast with solution dolines, which are densely distributed on the subplanar top surfaces of the carbonate massifs, the collapse sinkholes (hereinafter labelled karst collapse sinkholes) generally occur as isolated landforms and mostly affect the slopes and piedmont areas. In the latter instances, the sinkholes also affect alluvial fan conglomerates, or slope debris, overlying the carbonate rocks. We investigated the karst collapse sinkholes of the southern-central Apennines mountain belt (Italy), which is representative of a young orogenic system, characterised by recent tectonic activity and strong seismicity. The aim of the study is the identification of the causative factors which control the occurrence of such hazardous phenomena. The study was based on a regional scale analysis on sinkhole distribution in relation to the local geological-structural, geomorphological and hydrogeological contexts, and was paralleled with field analysis of some selected areas. The regional scale analysis indicates that the karst collapse sinkholes are not the mere response to the concurrence of the climatic and lithological conditions which commonly favour the development of karst processes, the occurrence of such landforms appearing strongly influenced by distinctive structural and hydrogeological conditions. In particular, a close relationship between the karst collapse sinkholes and the main extensional faults showing evidence of late Quaternary activity may be envisaged. This is inferred from the spatial distribution of the karst collapse sinkholes, which is strikingly uneven, the sinkholes generally occurring in alignments following large late Quaternary fault zones, or being clustered at the terminations of those faults. In addition, areas affected by the occurrence of groups of sinkholes, are

  11. Glacier surge after ice shelf collapse.

    PubMed

    De Angelis, Hernán; Skvarca, Pedro

    2003-03-01

    The possibility that the West Antarctic Ice Sheet will collapse as a consequence of ice shelf disintegration has been debated for many years. This matter is of concern because such an event would imply a sudden increase in sea level. Evidence is presented here showing drastic dynamic perturbations on former tributary glaciers that fed sections of the Larsen Ice Shelf on the Antarctic Peninsula before its collapse in 1995. Satellite images and airborne surveys allowed unambiguous identification of active surging phases of Boydell, Sjögren, Edgeworth, Bombardier, and Drygalski glaciers. This discovery calls for a reconsideration of former hypotheses about the stabilizing role of ice shelves. PMID:12624263

  12. Minimally Invasive Valve Surgery

    PubMed Central

    Pope, Nicolas H.; Ailawadi, Gorav

    2014-01-01

    Cardiac valve surgery is life saving for many patients. The advent of minimally invasive surgical techniques has historically allowed for improvement in both post-operative convalescence and important clinical outcomes. The development of minimally invasive cardiac valve repair and replacement surgery over the past decade is poised to revolutionize the care of cardiac valve patients. Here, we present a review of the history and current trends in minimally invasive aortic and mitral valve repair and replacement, including the development of sutureless bioprosthetic valves. PMID:24797148

  13. Collapse of modern carbonate platform margins

    SciTech Connect

    Mullins, H.T.; Hine, A.C.; Gardulski, A.

    1985-01-01

    Modern carbonate platform margins in the Florida-Bahama region have been viewed as depositional or constructional features. However, recent studies have shown that carbonate escarpments, such as the Blake-Bahama and West Florida Escarpments, are erosional in origin where the platform margins have a scalloped or horse-shoe shape. Seismic reflection data from one of these crescentic features along the west Florida platform margin indicate that it originated by large scale gravity collapse (slump). This collapse structure extends for at least 120 km along the margin and has removed about 350 m of strata as young as early Neogene. Although at least three generations of slope failure are recognized, catastrophic collapse appears to have occurred in the mid-Miocene. Gravitational instability due to high rates of sediment accumulation may have been the triggering mechanism. These data suggest that submarine slumping is an important process in the retreat of limestone escarpments and in the generation of carbonate megabreccia debris flows. Scalloped platform margins occur on satellite images of northern Exuma Sound and Columbus Basin in the Bahamas. The authors suggest that large-scale submarine slumping can cause elongation of structurally controlled intraplatform basins (Exuma South), and produce anomalous horse-shoe shaped basins (Columbus Basin) by mega-collapse processes.

  14. Geophysical mapping of solution and collapse sinkholes

    NASA Astrophysics Data System (ADS)

    Kaufmann, Georg

    2014-12-01

    Karst rocks such as limestone, dolomite, anhydrite, gypsum, or salt can be dissolved physically by water or chemically by water enriched with carbon dioxide. The dissolution is driven by water flowing through the karst aquifer and either occurs along fractures and bedding partings in telogenetic rocks, or within the primary interconnected pore space in eogenetic rocks. The enlargement of either fractures or pores by dissolution creates a large secondary porosity typical of soluble rocks, which is often very heterogenously distributed and results in preferential flow paths in the sub-surface, with cavities as large-scale end members of the sub-surface voids. Once the sub-surface voids enlarged by dissolution grow to a certain size, the overburden rock can become unstable and voids and caves can collapse. Depending on the type of overburden, the collapse initiated at depth may propagate towards the surface and finally results at the surface as collapse sinkholes and tiangkengs on the very large scale. We present results from geophysical surveys over existing karst structures based on gravimetric, electrical, and geomagnetical methods. We have chosen two types of sinkholes, solution and collapse sinkholes, to capture and compare the geophysical signals resulting from these karst structures. We compare and discuss our geophysical survey results with simplified theoretical models describing the evolution of the karst structure, and we derive three-dimensional structural models of the current situation for the different locations with our numerical tool PREDICTOR.

  15. Pathogen webs in collapsing honey bee colonies

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Recent losses in honey bee colonies are unusual in their severity, geographical distribution, and, in some cases, failure to present recognized symptoms of known disease. Domesticated honey bees face numerous pests and pathogens, tempting hypotheses that colony collapses arise from exposure to new o...

  16. Colony Collapse Disorder: A descriptive studey

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Over the last two winters, there have been large-scale, unexplained losses of managed honey bee (Apis mellifera L.) colonies in the United States. In the absence of a known cause, this syndrome was named Colony Collapse Disorder (CCD) because the main trait was a rapid loss of adult worker bees. We ...

  17. When Communities Collapse: Implications for Rural America.

    ERIC Educational Resources Information Center

    Fitchen, Janet M.

    1987-01-01

    The decline of agriculture in the 1920s and 1930s was compounded by the subsequent collapse of the rural social community, leaving the rural poor without a community and thus exacerbating and prolonging their poverty. Present restructuring of agriculture in the United States may have a similar impact on rural communities. (JHZ)

  18. Neutrino-antineutrino annihilation around collapsing star

    NASA Technical Reports Server (NTRS)

    Berezinsky, V. S.; Prilutsky, O. F.

    1985-01-01

    Stellar collapse is accompanied by emission of E sub neutrino approximately 10 MeV neutrinos and antineutrinos with the energy output W sub neutrino approximately 10 to the 53rd power to 10 to the 54th power erg. Annihilation of these particles in the vicinity of collapsar is considered. The physical consequences are discussed.

  19. Collapsible structure for an antenna reflector

    NASA Technical Reports Server (NTRS)

    Trubert, M. R. (Inventor)

    1973-01-01

    A collapsible support for an antenna reflector for use in supporting spacecraft antennas is described. The support has a regid base and a number of struts which are pivoted at the base. The deployment of the struts and their final configuration for supporting the antenna are illustrated.

  20. CCSNMultivar: Core-Collapse Supernova Gravitational Waves

    NASA Astrophysics Data System (ADS)

    Engels, Bill; Gossan, Sarah

    2016-04-01

    CCSNMultivar aids the analysis of core-collapse supernova gravitational waves. It includes multivariate regression of Fourier transformed or time domain waveforms, hypothesis testing for measuring the influence of physical parameters, and the Abdikamalov et. al. catalog for example use. CCSNMultivar can optionally incorporate additional uncertainty due to detector noise and approximate waveforms from anywhere within the parameter space.

  1. Some analytical models of radiating collapsing spheres

    SciTech Connect

    Herrera, L.; Di Prisco, A; Ospino, J.

    2006-08-15

    We present some analytical solutions to the Einstein equations, describing radiating collapsing spheres in the diffusion approximation. Solutions allow for modeling physical reasonable situations. The temperature is calculated for each solution, using a hyperbolic transport equation, which permits to exhibit the influence of relaxational effects on the dynamics of the system.

  2. Graphene wrinkling: formation, evolution and collapse

    NASA Astrophysics Data System (ADS)

    Wang, Changguo; Liu, Yuanpeng; Lan, Lan; Tan, Huifeng

    2013-05-01

    In this paper we focus on the studies of graphene wrinkling, from its formation to collapse, and its dependence on aspect ratio and temperature using molecule dynamics simulation. Based on our results, the first wrinkle is not formed on the edge but in the interior of graphene. The fluctuations of edge slack warps drive the wrinkling evolution in graphene which is distinguished from the bifurcation in continuum film. There are several obvious stages in wrinkling progress, including incubation, infancy, youth, maturity and gerontism periods which are identified by the atomic displacement difference due to the occurrences of new wrinkles. The wrinkling progress is over when the C-C bonds in highly stretched corners are broken which contributes to the wrinkling collapse. The critical wrinkling strain, the wrinkling pattern and extent depend on the aspect ratio of graphene, the wrinkling level and collapsed strains do not. Only the collapsed strain is sensitive to the temperature, the other wrinkling parameters are independent of the temperature. Our results would benefit the understanding of the physics of graphene wrinkling and the design of nanomechanical devices by tuning the wrinkles.

  3. Advanced collapsible tank for liquid containment

    NASA Technical Reports Server (NTRS)

    Flanagan, David T.; Hopkins, Robert C.

    1993-01-01

    Tanks for bulk liquid containment will be required to support advanced planetary exploration programs. Potential applications include storage of potable, process, and waste water, and fuels and process chemicals. The launch mass and volume penalties inherent in rigid tanks suggest that collapsible tanks may be more efficient. Collapsible tanks are made of lightweight flexible material and can be folded compactly for storage and transport. Although collapsible tanks for terrestrial use are widely available, a new design was developed that has significantly less mass and bulk than existing models. Modelled after the shape of a sessible drop, this design features a dual membrane with a nearly uniform stress distribution and a low surface-to-volume ratio. It can be adapted to store a variety of liquids in nearly any environment with constant acceleration field. Three models of 10L, 50L, and 378L capacity have been constructed and tested. The 378L (100 gallon) model weighed less than 10 percent of a commercially available collapsible tank of equivalent capacity, and required less than 20 percent of the storage space when folded for transport.

  4. Prostate resection - minimally invasive

    MedlinePlus

    ... are: Erection problems (impotence) No symptom improvement Passing semen back into your bladder instead of out through ... Whelan JP, Goeree L. Systematic review and meta-analysis of transurethral resection of the prostate versus minimally ...

  5. Minimizing Shortness of Breath

    MedlinePlus

    ... Top Doctors in the Nation Departments & Divisions Home Health Insights Stress & Relaxation Breathing and Relaxation Minimizing Shortness of Breath ... Management Assess Your Stress Coping Strategies Identifying ... & Programs Health Insights Doctors & Departments Research & Science Education & Training Make ...

  6. Minimally invasive hip replacement

    MedlinePlus

    ... Smits SA, Swinford RR, Bahamonde RE. A randomized, prospective study of 3 minimally invasive surgical approaches in total hip arthroplasty: comprehensive gait analysis. J Arthroplasty . 2008;23:68-73. PMID: 18722305 ...

  7. Minimal Orderings Revisited

    SciTech Connect

    Peyton, B.W.

    1999-07-01

    When minimum orderings proved too difficult to deal with, Rose, Tarjan, and Leuker instead studied minimal orderings and how to compute them (Algorithmic aspects of vertex elimination on graphs, SIAM J. Comput., 5:266-283, 1976). This paper introduces an algorithm that is capable of computing much better minimal orderings much more efficiently than the algorithm in Rose et al. The new insight is a way to use certain structures and concepts from modern sparse Cholesky solvers to re-express one of the basic results in Rose et al. The new algorithm begins with any initial ordering and then refines it until a minimal ordering is obtained. it is simple to obtain high-quality low-cost minimal orderings by using fill-reducing heuristic orderings as initial orderings for the algorithm. We examine several such initial orderings in some detail.

  8. Minimalism. Clip and Save.

    ERIC Educational Resources Information Center

    Hubbard, Guy

    2002-01-01

    Provides background information on the art movement called "Minimalism" discussing why it started and its characteristics. Includes learning activities and information on the artist, Donald Judd. Includes a reproduction of one of his art works and discusses its content. (CMK)

  9. Spherical gravitational collapse in N dimensions

    SciTech Connect

    Goswami, Rituparno; Joshi, Pankaj S.

    2007-10-15

    We investigate here spherically symmetric gravitational collapse in a space-time with an arbitrary number of dimensions and with a general type I matter field, which is a broad class that includes most of the physically reasonable matter forms. We show that given the initial data for matter in terms of the initial density and pressure profiles at an initial surface t=t{sub i} from which the collapse evolves, there exist the rest of the initial data functions and classes of solutions of Einstein equations which we construct here, such that the space-time evolution goes to a final state which is either a black hole or a naked singularity, depending on the nature of initial data and evolutions chosen, and subject to validity of the weak energy condition. The results are discussed and analyzed in the light of the cosmic censorship hypothesis in black hole physics. The formalism here combines the earlier results on gravitational collapse in four dimensions in a unified treatment. Also the earlier work is generalized to higher-dimensional space-times to allow a study of the effect of the number of dimensions on the possible final outcome of the collapse in terms of either a black hole or naked singularity. No restriction is adopted on the number of dimensions, and other limiting assumptions such as self-similarity of space-time are avoided, in order to keep the treatment general. Our methodology allows us to consider to an extent the genericity and stability aspects related to the occurrence of naked singularities in gravitational collapse.

  10. Formation of planetesimals in collapsing pebble clouds

    NASA Astrophysics Data System (ADS)

    Wahlberg Jansson, K.; Johansen, A.

    2014-07-01

    Asteroids and Kuiper belt objects are remnant planetesimals from the epoch of planet formation. Their physical properties hold important clues to understanding how minor bodies formed in the Solar Nebula. The first stage of the planet formation process is the accumulation of dust and ice grains into mm-cm-sized pebbles. Due to the interaction with the gas in the protoplanetary disk, these pebbles can clump together through the streaming instability and form gravitationally bound particle pebble 'clouds'. Pebbles in the cloud collide with each other, dissipating energy into heat. As the cloud loses energy, it contracts, and one would expect the particles to move faster and faster due to the negative heat capacity nature of self-gravitating systems. However, for high-mass clouds, the collapse is limited by free-fall and the cloud does not have time to virialize. This in turn leads to lower collision speeds but thanks to increased density also to increased collision rates and a runaway collapse. We investigate three important properties of the collapse: (i) the time-scale to collapse to solid density, (ii) the temporal evolution of the size spectrum of the pebbles, and (iii) the multiplicity of the resulting planetesimals. We find that planetesimals larger than 100 km in radius collapse on the free-fall time-scale of about 25 years. Lower-mass clouds have longer pebble collision time-scales and hence collapse much more slowly, with collapse times of a few hundred years for 10-km-scale planetesimals and a few thousand years for 1-km-scale planetesimals. The mass of the pebble cloud also determines the structure of the resulting planetesimal. The collision speed among the pebbles in low- mass clouds is below the threshold for fragmentation, forming pebble- pile planetesimals consisting of the primordial pebbles from the nebula. Planetesimals above 100 km in radius, on the other hand, consist of mixtures of dust (pebble fragments) and pebbles which have undergone

  11. Collapse of Corroded Pipelines under Combined Tension and External Pressure.

    PubMed

    Ye, Hao; Yan, Sunting; Jin, Zhijiang

    2016-01-01

    In this work, collapse of corroded pipeline under combined external pressure and tension is investigated through numerical method. Axially uniform corrosion with symmetric imperfections is firstly considered. After verifying with existing experimental results, the finite element model is used to study the effect of tension on collapse pressure. An extensive parametric study is carried out using Python script and FORTRAN subroutine to investigate the influence of geometric parameters on the collapse behavior under combined loads. The results are used to develop an empirical equation for estimating the collapse pressure under tension. In addition, the effects of loading path, initial imperfection length, yielding anisotropy and corrosion defect length on the collapse behavior are also investigated. It is found that tension has a significant influence on collapse pressure of corroded pipelines. Loading path and anisotropic yielding are also important factors affecting the collapse behavior. For pipelines with relatively long corrosion defect, axially uniform corrosion models could be used to estimate the collapse pressure. PMID:27111544

  12. Collapse of Corroded Pipelines under Combined Tension and External Pressure

    PubMed Central

    Ye, Hao; Yan, Sunting; Jin, Zhijiang

    2016-01-01

    In this work, collapse of corroded pipeline under combined external pressure and tension is investigated through numerical method. Axially uniform corrosion with symmetric imperfections is firstly considered. After verifying with existing experimental results, the finite element model is used to study the effect of tension on collapse pressure. An extensive parametric study is carried out using Python script and FORTRAN subroutine to investigate the influence of geometric parameters on the collapse behavior under combined loads. The results are used to develop an empirical equation for estimating the collapse pressure under tension. In addition, the effects of loading path, initial imperfection length, yielding anisotropy and corrosion defect length on the collapse behavior are also investigated. It is found that tension has a significant influence on collapse pressure of corroded pipelines. Loading path and anisotropic yielding are also important factors affecting the collapse behavior. For pipelines with relatively long corrosion defect, axially uniform corrosion models could be used to estimate the collapse pressure. PMID:27111544

  13. Minimally invasive procedures

    PubMed Central

    Baltayiannis, Nikolaos; Michail, Chandrinos; Lazaridis, George; Anagnostopoulos, Dimitrios; Baka, Sofia; Mpoukovinas, Ioannis; Karavasilis, Vasilis; Lampaki, Sofia; Papaiwannou, Antonis; Karavergou, Anastasia; Kioumis, Ioannis; Pitsiou, Georgia; Katsikogiannis, Nikolaos; Tsakiridis, Kosmas; Rapti, Aggeliki; Trakada, Georgia; Zissimopoulos, Athanasios; Zarogoulidis, Konstantinos

    2015-01-01

    Minimally invasive procedures, which include laparoscopic surgery, use state-of-the-art technology to reduce the damage to human tissue when performing surgery. Minimally invasive procedures require small “ports” from which the surgeon inserts thin tubes called trocars. Carbon dioxide gas may be used to inflate the area, creating a space between the internal organs and the skin. Then a miniature camera (usually a laparoscope or endoscope) is placed through one of the trocars so the surgical team can view the procedure as a magnified image on video monitors in the operating room. Specialized equipment is inserted through the trocars based on the type of surgery. There are some advanced minimally invasive surgical procedures that can be performed almost exclusively through a single point of entry—meaning only one small incision, like the “uniport” video-assisted thoracoscopic surgery (VATS). Not only do these procedures usually provide equivalent outcomes to traditional “open” surgery (which sometimes require a large incision), but minimally invasive procedures (using small incisions) may offer significant benefits as well: (I) faster recovery; (II) the patient remains for less days hospitalized; (III) less scarring and (IV) less pain. In our current mini review we will present the minimally invasive procedures for thoracic surgery. PMID:25861610

  14. Why do naked singularities form in gravitational collapse? II

    SciTech Connect

    Joshi, Pankaj S.; Goswami, Rituparno; Dadhich, Naresh

    2004-10-15

    We examine physical features that could lead to formation of a naked singularity rather than black hole, as end state of spherical collapse. Generalizing earlier results on dust collapse to general type I matter fields, it is shown that collapse always creates black hole if shear vanishes or density is homogeneous. It follows that nonzero shear is a necessary condition for singularity to be visible to external observers, when trapped surface formation is delayed by shearing forces or inhomogeneity within the collapsing cloud.

  15. Surgical repair of traumatically induced collapsing trachea in an ostrich.

    PubMed

    McClure, S R; Taylor, T S; Johnson, J H; Heisterkamp, K B; Sanders, E A

    1995-08-15

    A region of tracheal collapse was identified by endoscopy after surgical repair of a traumatic injury to the neck in an ostrich. During periods of excitation, the ostrich would become dyspneic and collapse. A tracheal split-ring prosthesis was placed surgically to support the collapsing trachea. This technique, which is frequently used in dogs, is applicable for use in birds with collapsing trachea. PMID:7591952

  16. Wavefunction Collapse via a Nonlocal Relativistic Variational Principle

    SciTech Connect

    Harrison, Alan K.

    2012-06-18

    Since the origin of quantum theory in the 1920's, some of its practitioners (and founders) have been troubled by some of its features, including indeterminacy, nonlocality and entanglement. The 'collapse' process described in the Copenhagen Interpretation is suspect for several reasons, and the act of 'measurement,' which is supposed to delimit its regime of validity, has never been unambiguously defined. In recent decades, nonlocality and entanglement have been studied energetically, both theoretically and experimentally, and the theory has been reinterpreted in imaginative ways, but many mysteries remain. We propose that it is necessary to replace the theory by one that is explicitly nonlinear and nonlocal, and does not distinguish between measurement and non-measurement regimes. We have constructed such a theory, for which the phase of the wavefunction plays the role of a hidden variable via the process of zitterbewegung. To capture this effect, the theory must be relativistic, even when describing nonrelativistic phenomena. It is formulated as a variational principle, in which Nature attempts to minimize the sum of two spacetime integrals. The first integral tends to drive the solution toward a solution of the standard quantum mechanical wave equation, and also enforces the Born rule of outcome probabilities. The second integral drives the collapse process. We demonstrate that the new theory correctly predicts the possible outcomes of the electron two-slit experiment, including the infamous 'delayed-choice' variant. We observe that it appears to resolve some long-standing mysteries, but introduces new ones, including possible retrocausality (a cause later than its effect). It is not clear whether the new theory is deterministic.

  17. Minimally Invasive Radiofrequency Devices.

    PubMed

    Sadick, Neil; Rothaus, Kenneth O

    2016-07-01

    This article reviews minimally invasive radiofrequency options for skin tightening, focusing on describing their mechanism of action and clinical profile in terms of safety and efficacy and presenting peer-reviewed articles associated with the specific technologies. Treatments offered by minimally invasive radiofrequency devices (fractional, microneedling, temperature-controlled) are increasing in popularity due to the dramatic effects they can have without requiring skin excision, downtime, or even extreme financial burden from the patient's perspective. Clinical applications thus far have yielded impressive results in treating signs of the aging face and neck, either as stand-alone or as postoperative maintenance treatments. PMID:27363771

  18. Sudden Unexpected Postnatal Collapse of the Newborn.

    PubMed

    Ferrarello, Debi; Carmichael, Tanya

    2016-01-01

    Sudden unexpected postnatal collapse is a rare but devastating neonatal event. A well-appearing, full-term newborn with Agpar scores of eight or more suddenly crashes, often with full respiratory and cardiac arrest. Up to half of newborns with sudden unexpected postnatal collapse die, with many survivors suffering serious neurological damage. The first 2 hours of life are the hours of greatest risk, coinciding with the time frame when nurses encourage breastfeeding and uninterrupted skin-to-skin contact between women and newborns. Nursing assessments and measures to promote neonates' optimal transition to extrauterine life through skin-to-skin contact and early breastfeeding while decreasing the risk of this catastrophic event are described. Nursing surveillance to promote optimal transition in a safe environment is essential, and birth facilities should allocate staffing resources accordingly. PMID:27287353

  19. Collapse of the Late Proterozoic ecosystem

    NASA Technical Reports Server (NTRS)

    Schopf, J. W.

    1991-01-01

    Evidence accumulated over the past two decades is now sufficient to permit an initial quantitative assessment of the patterns of biotic diversity and extinction that occurred during Proterozoic time. Because of limitations in both the quality and quantity of data currently available, however, generalizations thus derived must be regarded as tentative. Nevertheless, read literally, available palaeontological data appear to indicate that the global ecosystem experienced a gradual but massive collapse between 1 000 Ma and the beginning of the Phanerozoic, a supposition consistent with other lines of geological and geochemical evidence. A possible forcing agent for such a collapse appears to have been a decrease in ambient levels of carbon dioxide and a resultant decrease in average global temperature, photosynthetic efficiency, and primary productivity.

  20. Bosonization approach for "atomic collapse" in graphene

    NASA Astrophysics Data System (ADS)

    Kagimura, Aya; Onogi, Tetsuya

    2016-02-01

    We study quantum electrodynamics with 2+1 dimensional massless Dirac fermion around a Coulomb impurity. Around a large charge with atomic number Z > 137, the QED vacuum is expected to collapse due to the strong Coulombic force. While the relativistic quantum mechanics fails to make reliable predictions for the fate of the vacuum, the heavy ion collision experiment also does not give clear understanding of this system. Recently, the "atomic collapse" resonances were observed on graphene where an artificial nuclei can be made. In this paper, we present our nonperturbative study of the vacuum structure of the quasiparticles in graphene with a charge impurity which contains multi-body effect using bosonization method.

  1. Energy balance in the WTC collapse

    NASA Astrophysics Data System (ADS)

    Zhu, Kaiqi; Xu, Kang; Ansourian, Peter; Tahmasebinia, Faham; Alonso-Marroquin, Fernando

    2016-08-01

    The main aim of this report is to provide an analysis of Twin Towers of the New York City's World Trade Centre collapsed after attacked by two jet aircrafts. The approach mainly focused on the effect of temperature on mechanical properties of the building, by modelling heat energy in the south tower. Energy balance during the collapse between the energy inputs by aircraft petrol and the transient heat to the towers was conducted. Both the overall structure between 80 to 83 stories and individual elements was modelled. The main elements contributed to the heat transition includes external and internal columns. Heat applied in 2D and 3D models for single elements was through convection and conduction. Analysis of transient heat was done using Strand7.

  2. 2-d Collapsed Polymers on a Cylinder

    NASA Astrophysics Data System (ADS)

    Hsu, Hsiao-Ping; Grassberger, Peter

    2002-08-01

    Partially confined collapsed polymers with attractive interactions are studied in two dimensions. They are described by self-avoiding random walks with nearest-neighbour attractions on the surface of an infinitely long cylinder. We employ the pruned-enriched-Rosenbluth method (PERM) to study this model with different cylinder circumference h, to understand the properties of collapsed polymers affected by confining geometries. The cases of free polymers and of polymers confined to finite volumes were discussed already in [Phys. Rev. E 65, 031807 (2002)] by Grassberger and Hsu. There, we had verified the existence of a surface term in the infinite volume free energy, and a T-dependent bulk chemical potential. Here we present further results on the surface tension and it's T-dependence. We also show that the chemical potential has, in the limit of very long chains, a minimum at a finite value of h.

  3. Anelastic collapse of small cavities in metals

    NASA Astrophysics Data System (ADS)

    Ferrari, Loris

    2015-05-01

    The stability of a small cavity in a virtually infinite solid is studied in the context of anelasticity for two metals (Al and Cu). It is shown that the collapse occurs due to the dependence of the shear modulus on the relative volume change. It is shown that above a minimum external pressure P min the system cannot self-sustain, unless the internal pressure does exceed a critical value, compensating the collapsing effect. The different models of anelasticity adopted are shown to have a scarce influence on the main results. In particular, the value of P min turns out to range about the 10% of the bulk modulus at zero pressure, for both metals and almost independently from the anelastic model.

  4. Collapse and revival in holographic quenches

    NASA Astrophysics Data System (ADS)

    da Silva, Emilia; Lopez, Esperanza; Mas, Javier; Serantes, Alexandre

    2015-04-01

    We study holographic models related to global quantum quenches in finite size systems. The holographic set up describes naturally a CFT, which we consider on a circle and a sphere. The enhanced symmetry of the conformal group on the circle motivates us to compare the evolution in both cases. Depending on the initial conditions, the dual geometry exhibits oscillations that we holographically interpret as revivals of the initial field theory state. On the sphere, this only happens when the energy density created by the quench is small compared to the system size. However on the circle considerably larger energy densities are compatible with revivals. Two different timescales emerge in this latter case. A collapse time, when the system appears to have dephased, and the revival time, when after rephasing the initial state is partially recovered. The ratio of these two times depends upon the initial conditions in a similar way to what is observed in some experimental setups exhibiting collapse and revivals.

  5. Collapse of vacuum bubbles in a vacuum

    SciTech Connect

    Ng, Kin-Wang; Wang, Shang-Yung

    2011-02-15

    We revisit the dynamics of a false vacuum bubble in a background de Sitter spacetime. We find that there exists a large parameter space that allows the bubble to collapse into a black hole or to form a wormhole. This may have interesting implications for the creation of a baby universe in the laboratory, the string landscape where the bubble nucleation takes place among a plenitude of metastable vacua, and the inflationary physics.

  6. Ultrasonographic evaluation of tracheal collapse in dogs.

    PubMed

    Eom, Kidong; Moon, Kumjung; Seong, Yunsang; Oh, Taeho; Yi, Sungjoon; Lee, Keunwoo; Jang, Kwangho

    2008-12-01

    Tracheal ultrasonography was performed to measure the width of the tracheal ring shadow and to assess the clinical relevance of these measurements for identifying tracheal collapse. The first tracheal ring width (FTRW) and thoracic inlet tracheal ring width (TITRW) were measured on both expiration and inspiration. The mean of the FTRW width (129 dogs) was greater in expiration (10.97 plusmn; 1.02 mm, p = 0.001) than that in inspiration (9.86 plusmn; 1.03 mm). For 51 normal dogs, the mean of the TITRW width was greater in expiration (9.05 plusmn; 1.52 mm, p = 0.001) than in inspiration (8.02 plusmn; 1.43 mm). For 78 tracheal collapse dogs, the mean of the TITRW width was greater in expiration (15.89 plusmn; 1.01 mm, p = 0.001) than in inspiration (14.85 plusmn; 1.17 mm). The TITRW/FTRW ratio of the normal dogs was higher (p = 0.001) in expiration (0.81 plusmn; 0.09) than that in inspiration (0.79 plusmn; 0.10). When compared between the normal and tracheal collapse dogs, the TITRW/FTRW ratio was also increased (p = 0.001) both in expiration (1.54 plusmn; 0.09) and inspiration (1.47 plusmn; 0.08), respectively. Based on these results, the cutoff level of the TITRW/FTRW ratio was statistically analyzed according to the receiver operating characteristic curve and it could be set at 1.16 in expiration and at 1.13 in inspiration. We have demonstrated that tracheal ultrasonography is a useful technique for the evaluation of tracheal collapse and it can be a supportive tool together with the radiographic findings for making the correct diagnosis. PMID:19043316

  7. Tracheal and airway collapse in dogs.

    PubMed

    Maggiore, Ann Della

    2014-01-01

    Tracheal and airway collapse (bronchomalacia) are common causes of chronic cough in middle-aged to older dogs where weakening of cartilage within the respiratory system leads to narrowing of airways, coughing, wheezing, and other secondary effects. Successful treatment involves correct identification of the problem, recognition of concurrent problems, and appropriate medical therapy. Surgical and noninvasive treatment options are becoming readily available, and it is important to understand indications for such procedures. PMID:24268337

  8. Collapsible sheath fluid reservoirs for flow cytometers

    DOEpatents

    Mark, Graham A.

    2000-01-01

    The present invention is a container in the form of a single housing for holding fluid, including a first collapsible reservoir having a first valve. The first reservoir initially contains a volume of fluid. The container also includes a second reservoir, initially empty (or substantially empty), expandable to a second volume. The second reservoir has a second valve. As the volume of said first reservoir decreases, the volume of the second reservoir proportionally increases.

  9. Simulated Cytoskeletal Collapse via Tau Degradation

    PubMed Central

    Sendek, Austin; Fuller, Henry R.; Hayre, N. Robert; Singh, Rajiv R. P.; Cox, Daniel L.

    2014-01-01

    We present a coarse-grained two dimensional mechanical model for the microtubule-tau bundles in neuronal axons in which we remove taus, as can happen in various neurodegenerative conditions such as Alzheimers disease, tauopathies, and chronic traumatic encephalopathy. Our simplified model includes (i) taus modeled as entropic springs between microtubules, (ii) removal of taus from the bundles due to phosphorylation, and (iii) a possible depletion force between microtubules due to these dissociated phosphorylated taus. We equilibrate upon tau removal using steepest descent relaxation. In the absence of the depletion force, the transverse rigidity to radial compression of the bundles falls to zero at about 60% tau occupancy, in agreement with standard percolation theory results. However, with the attractive depletion force, spring removal leads to a first order collapse of the bundles over a wide range of tau occupancies for physiologically realizable conditions. While our simplest calculations assume a constant concentration of microtubule intercalants to mediate the depletion force, including a dependence that is linear in the detached taus yields the same collapse. Applying percolation theory to removal of taus at microtubule tips, which are likely to be the protective sites against dynamic instability, we argue that the microtubule instability can only obtain at low tau occupancy, from 0.06–0.30 depending upon the tau coordination at the microtubule tips. Hence, the collapse we discover is likely to be more robust over a wide range of tau occupancies than the dynamic instability. We suggest in vitro tests of our predicted collapse. PMID:25162587

  10. Combined method of compaction of collapsible soils

    SciTech Connect

    Bagdasarov, Yu.A.

    1994-07-01

    The writer proposes a combined method of compaction of collapsible soils. He presents results of investigations carried out to study compacted zones of pads punched (tamped-out) by rammers 10 and 20 tons in mass, as well as a comparative analysis of the pads over against compacted zones obtained by means of plane rammers. The analysis results are illustrated by the {open_quotes}arch effect{close_quotes} on the stress conditions of the soaked soil mass.

  11. Cooperation, cheating, and collapse in microbial populations

    NASA Astrophysics Data System (ADS)

    Gore, Jeff

    2012-02-01

    Natural populations can suffer catastrophic collapse in response to small changes in environmental conditions, and recovery after such a collapse can be exceedingly difficult. We have used laboratory yeast populations to study proposed early warning signals of impending extinction. Yeast cooperatively breakdown the sugar sucrose, meaning that there is a minimum number of cells required to sustain the population. We have demonstrated experimentally that the fluctuations in the population size increase in magnitude and become slower as the population approaches collapse. The cooperative nature of yeast growth on sucrose suggests that the population may be susceptible to cheater cells, which do not contribute to the public good and instead merely take advantage of the cooperative cells. We have confirmed this possibility experimentally by using a cheater yeast strain that lacks the gene encoding the cooperative behavior [1]. However, recent results in the lab demonstrate that the presence of a bacterial competitor may drive cooperation within the yeast population.[4pt] [1] Gore et al, Nature 459, 253 -- 256 (2009)

  12. Gopherus agassizii (desert tortoise). Burrow collapse

    USGS Publications Warehouse

    Loughran, Caleb L.; Ennen, Joshua; Lovich, Jeffrey E.

    2011-01-01

    In the deserts of the southwestern U.S., burrows are utilized by the Desert Tortoise to escape environmental extremes (reviewed by Ernst and Lovich 2009. Turtles of the United States and Canada. 2nd ed. Johns Hopkins Univ. Press, Baltimore, Maryland. 827 pp.). However, the potential for mortality through burrow collapse and entrapment is poorly documented. Nicholson and Humphreys (1981. Proceedings of the Desert Tortoise Council, pp. 163−194) suggested that collapse due to livestock trampling may cause mortality. In addition, Lovich et al. (2011. Chelon. Cons. Biol. 10[1]:124–129) documented a Desert Tortoise that used a steel culvert as a burrow surrogate. The culvert filled completely with sediment following a significant rain event, entombing the animal and ultimately resulting in its death. We note that this mortality was associated with an anthropogenic structure; because tortoises are prodigious diggers, one might hypothesize that they have the ability to dig out of collapsed natural burrows in most situations. Circumstances described here presented us with an opportunity to test this hypothesis.

  13. Essential Ingredients in Core-collapse Supernovae

    SciTech Connect

    Hix, William Raphael; Lentz, E. J.; Endeve, Eirik; Baird, Mark L.; Chertkow, Merek A.; Harris, James A.; Messer, Bronson; Mezzacappa, Anthony; Bruenn, S. W.; Blondin, J. M.

    2014-03-27

    Marking the inevitable death of a massive star, and the birth of a neutron star or black hole, core-collapse supernovae bring together physics at a wide range in spatial scales, from kilometer-sized hydrodynamic motions (eventually growing to gigameter scale) down to femtometer scale nuclear reactions. Carrying 10$^{44}$ joules of kinetic energy and a rich-mix of newly synthesized atomic nuclei, core-collapse supernovae are the preeminent foundries of the nuclear species which make up ourselves and our solar system. We will discuss our emerging understanding of the convectively unstable, neutrino-driven explosion mechanism, based on increasingly realistic neutrino-radiation hydrodynamic simulations that include progressively better nuclear and particle physics. Recent multi-dimensional models with spectral neutrino transport from several research groups, which slowly develop successful explosions for a range of progenitors, have motivated changes in our understanding of the neutrino reheating mechanism. In a similar fashion, improvements in nuclear physics, most notably explorations of weak interactions on nuclei and the nuclear equation of state, continue to refine our understanding of how supernovae explode. Recent progress on both the macroscopic and microscopic effects that affect core-collapse supernovae are discussed.

  14. Essential ingredients in core-collapse supernovae

    SciTech Connect

    Hix, W. Raphael; Lentz, Eric J.; Chertkow, M. Austin; Harris, J. Austin; Endeve, Eirik; Baird, Mark; Messer, O. E. Bronson; Mezzacappa, Anthony; Bruenn, Stephen; Blondin, John

    2014-04-15

    Carrying 10{sup 44} joules of kinetic energy and a rich mix of newly synthesized atomic nuclei, core-collapse supernovae are the preeminent foundries of the nuclear species which make up our solar system and ourselves. Signaling the inevitable death of a massive star, and the birth of a neutron star or black hole, core-collapse supernovae combine physics over a wide range in spatial scales, from kilometer-sized hydrodynamic motions (eventually growing to gigameter scale) down to femtometer-scale nuclear reactions. We will discuss our emerging understanding of the convectively-unstable, neutrino-driven explosion mechanism, based on increasingly realistic neutrino radiation hydrodynamic simulations that include progressively better nuclear and particle physics. Multi-dimensional models with spectral neutrino transport from several research groups, which slowly develop successful explosions for a range of progenitors, have recently motivated changes in our understanding of the neutrino reheating mechanism. In a similar fashion, improvements in nuclear physics, most notably explorations of weak interactions on nuclei and the nuclear equation of state, continue to refine our understanding of the births of neutron stars and the supernovae that result. Recent progress on both the macroscopic and microscopic effects that affect core-collapse supernovae are discussed.

  15. Precombination Cloud Collapse and Baryonic Dark Matter

    NASA Technical Reports Server (NTRS)

    Hogan, Craig J.

    1993-01-01

    A simple spherical model of dense baryon clouds in the hot big bang 'strongly nonlinear primordial isocurvature baryon fluctuations' is reviewed and used to describe the dependence of cloud behavior on the model parameters, baryon mass, and initial over-density. Gravitational collapse of clouds before and during recombination is considered including radiation diffusion and trapping, remnant type and mass, and effects on linear large-scale fluctuation modes. Sufficiently dense clouds collapse early into black holes with a minimum mass of approx. 1 solar mass, which behave dynamically like collisionless cold dark matter. Clouds below a critical over-density, however, delay collapse until recombination, remaining until then dynamically coupled to the radiation like ordinary diffuse baryons, and possibly producing remnants of other kinds and lower mass. The mean density in either type of baryonic remnant is unconstrained by observed element abundances. However, mixed or unmixed spatial variations in abundance may survive in the diffuse baryon and produce observable departures from standard predictions.

  16. Essential Ingredients in Core-collapse Supernovae

    DOE PAGESBeta

    Hix, William Raphael; Lentz, E. J.; Endeve, Eirik; Baird, Mark L.; Chertkow, Merek A.; Harris, James A.; Messer, Bronson; Mezzacappa, Anthony; Bruenn, S. W.; Blondin, J. M.

    2014-03-27

    Marking the inevitable death of a massive star, and the birth of a neutron star or black hole, core-collapse supernovae bring together physics at a wide range in spatial scales, from kilometer-sized hydrodynamic motions (eventually growing to gigameter scale) down to femtometer scale nuclear reactions. Carrying 10more » $$^{44}$$ joules of kinetic energy and a rich-mix of newly synthesized atomic nuclei, core-collapse supernovae are the preeminent foundries of the nuclear species which make up ourselves and our solar system. We will discuss our emerging understanding of the convectively unstable, neutrino-driven explosion mechanism, based on increasingly realistic neutrino-radiation hydrodynamic simulations that include progressively better nuclear and particle physics. Recent multi-dimensional models with spectral neutrino transport from several research groups, which slowly develop successful explosions for a range of progenitors, have motivated changes in our understanding of the neutrino reheating mechanism. In a similar fashion, improvements in nuclear physics, most notably explorations of weak interactions on nuclei and the nuclear equation of state, continue to refine our understanding of how supernovae explode. Recent progress on both the macroscopic and microscopic effects that affect core-collapse supernovae are discussed.« less

  17. Essential ingredients in core-collapse supernovae

    NASA Astrophysics Data System (ADS)

    Hix, W. Raphael; Lentz, Eric J.; Endeve, Eirik; Baird, Mark; Chertkow, M. Austin; Harris, J. Austin; Messer, O. E. Bronson; Mezzacappa, Anthony; Bruenn, Stephen; Blondin, John

    2014-04-01

    Carrying 1044 joules of kinetic energy and a rich mix of newly synthesized atomic nuclei, core-collapse supernovae are the preeminent foundries of the nuclear species which make up our solar system and ourselves. Signaling the inevitable death of a massive star, and the birth of a neutron star or black hole, core-collapse supernovae combine physics over a wide range in spatial scales, from kilometer-sized hydrodynamic motions (eventually growing to gigameter scale) down to femtometer-scale nuclear reactions. We will discuss our emerging understanding of the convectively-unstable, neutrino-driven explosion mechanism, based on increasingly realistic neutrino radiation hydrodynamic simulations that include progressively better nuclear and particle physics. Multi-dimensional models with spectral neutrino transport from several research groups, which slowly develop successful explosions for a range of progenitors, have recently motivated changes in our understanding of the neutrino reheating mechanism. In a similar fashion, improvements in nuclear physics, most notably explorations of weak interactions on nuclei and the nuclear equation of state, continue to refine our understanding of the births of neutron stars and the supernovae that result. Recent progress on both the macroscopic and microscopic effects that affect core-collapse supernovae are discussed.

  18. Bubble collapse near a solid boundary

    NASA Astrophysics Data System (ADS)

    Zaleski, Stephane; Popinet, Stephane

    2000-11-01

    The effect of viscosity on jet formation for bubbles collapsing near solid boundaries is studied numerically. A connected marker technique is used which allows the Navier-Stokes equations with free-surface boundary conditions to be solved accurately and efficiently. Good agreement is obtained between experimental data and numerical simulations for the collapse of large bubbles. A parametric study of the effect of viscosity on jet impact velocity is undertaken. The jet impact velocity is found to decrease as viscosity increases and above a certain threshold jet impact is impossible. We study how the critical Reynolds number depends on the compression ratio and the initial distance from the wall. A simple scaling law is found to link this critical Reynolds number to the other non-dimensional parameters of the problem. A simple model of the collapse and jet formation allows to recover the principal features of the numerical data. More information at http://www.lmm.jussieu.fr/ ~zaleski/zaleski.html .

  19. Ways To Minimize Bullying.

    ERIC Educational Resources Information Center

    Mueller, Mary Ellen; Parisi, Mary Joy

    This report delineates a series of interventions aimed at minimizing incidences of bullying in a suburban elementary school. The social services staff was scheduled to initiate an anti-bullying incentive in fall 2001 due to the increased occurrences of bullying during the prior year. The target population consisted of third- and fourth-grade…

  20. Periodic minimal surfaces

    NASA Astrophysics Data System (ADS)

    Mackay, Alan L.

    1985-04-01

    A minimal surface is one for which, like a soap film with the same pressure on each side, the mean curvature is zero and, thus, is one where the two principal curvatures are equal and opposite at every point. For every closed circuit in the surface, the area is a minimum. Schwarz1 and Neovius2 showed that elements of such surfaces could be put together to give surfaces periodic in three dimensions. These periodic minimal surfaces are geometrical invariants, as are the regular polyhedra, but the former are curved. Minimal surfaces are appropriate for the description of various structures where internal surfaces are prominent and seek to adopt a minimum area or a zero mean curvature subject to their topology; thus they merit more complete numerical characterization. There seem to be at least 18 such surfaces3, with various symmetries and topologies, related to the crystallographic space groups. Recently, glyceryl mono-oleate (GMO) was shown by Longley and McIntosh4 to take the shape of the F-surface. The structure postulated is shown here to be in good agreement with an analysis of the fundamental geometry of periodic minimal surfaces.

  1. Minimally invasive pancreatic surgery.

    PubMed

    Yiannakopoulou, E

    2015-12-01

    Minimally invasive pancreatic surgery is feasible and safe. Laparoscopic distal pancreatectomy should be widely adopted for benign lesions of the pancreas. Laparoscopic pancreaticoduodenectomy, although technically demanding, in the setting of pancreatic ductal adenocarcinoma has a number of advantages including shorter hospital stay, faster recovery, allowing patients to recover in a timelier manner and pursue adjuvant treatment options. Furthermore, it seems that progression-free survival is longer in patients undergoing laparoscopic pancreaticoduodenectomy in comparison with those undergoing open pancreaticoduodenectomy. Minimally invasive middle pancreatectomy seems appropriate for benign or borderline tumors of the neck of the pancreas. Technological advances including intraoperative ultrasound and intraoperative fluorescence imaging systems are expected to facilitate the wide adoption of minimally invasive pancreatic surgery. Although, the oncological outcome seems similar with that of open surgery, there are still concerns, as the majority of relevant evidence comes from retrospective studies. Large multicenter randomized studies comparing laparoscopic with open pancreatectomy as well as robotic assisted with both open and laparoscopic approaches are needed. Robotic approach could be possibly shown to be less invasive than conventional laparoscopic approach through the less traumatic intra-abdominal handling of tissues. In addition, robotic approach could enable the wide adoption of the technique by surgeon who is not that trained in advanced laparoscopic surgery. A putative clinical benefit of minimally invasive pancreatic surgery could be the attenuated surgical stress response leading to reduced morbidity and mortality as well as lack of the detrimental immunosuppressive effect especially for the oncological patients. PMID:26530291

  2. The Minimal Era

    ERIC Educational Resources Information Center

    Van Ness, Wilhelmina

    1974-01-01

    Described the development of Minimal Art, a composite name that has been applied to the scattering of bland, bleak, non-objective fine arts painting and sculpture forms that proliferated slightly mysteriously in the middle 1960's as Pop Art began to decline. (Author/RK)

  3. Collapse and fragmentation of molecular cloud cores. 2: Collapse induced by stellar shock waves

    NASA Technical Reports Server (NTRS)

    Boss, Alan P.

    1995-01-01

    The standard scenario for low-mass star formation involves 'inside-out' collapse of a dense molecular cloud core following loss of magnetic field support through ambipolar diffusion. However, isotopic anomalies in presolar grains and meteoritical inclusions imply that the collapse of the presolar cloud may have been triggered by a stellar shock wave. This paper explores 'outside-in' collapse, that is, protostellar collapse initiated directly by the compression of quiescent dense cloud cores impacted by relatively slow stellar shock waves. A second-order accurate, gravitational hydrodynamics code has been used to study both the spherically symmetrical and three-dimensional evolution of initially centrally condensed, isothermal, self-gravitating, solar-mass cloud cores that are struck by stellar shock waves with velocities up to 25 km/s and postshock temperatures of 10 to 10,000 K. The models show that such mild shock waves do not completely shred and destroy the cloud, and that the dynamical ram pressure can compress the cloud to the verge of self-gravitational collapse. However, compression caused by a high postshock temperature is a considerably more effective means of inducing collapse. Shock-induced collapse produces high initial mass accretion rates (greater than 10(exp -4) solar mass/yr in a solar-mass cloud) that decline rapidly to much lower values, depending on the presence (approximately 10(exp -6) solar mass/yr) or absence (approximately 10(exp -8) to 10(exp -7) solar mass/yr) of an infinite reservoir of mass. Stellar mass accretion rates approximately 10(exp -7) solar mass/yr have been previously inferred from the luminosities of T Tauri stars; balanced mass accretion (stellar rate = envelope rate) at approximately 10(exp -7) solar mass/yr could then be possible if accretion occurs from a finite mass reservoir. Fluid tracers are used to determine what fraction of the stellar shock material is incorporated into the resulting protostellar object and disk

  4. Is spontaneous wave function collapse testable at all?

    NASA Astrophysics Data System (ADS)

    Diósi, Lajos

    2015-07-01

    Mainstream literature on spontaneous wave function collapse never reflects on or profits from the formal coincidence and conceptual relationship with standard collapse under time-continuous quantum measurement (monitoring). I propose some easy lessons of standard monitoring theory which would make spontaneous collapse models revise some of their claims. In particular, the objective detection of spontaneous collapse remains impossible as long as the correct identification of what corresponds to the signal in standard monitoring is missing from spontaneous collapse models, the physical detectability of the “signal” is not stated explicitly and, finally, the principles of physical detection are not revealed.

  5. Waste Minimization Crosscut Plan

    SciTech Connect

    Not Available

    1992-05-13

    On November 27, 1991, the Secretary of Energy directed that a Department of Energy (DOE) crosscut plan for waste minimization (WMin) be prepared and submitted by March 1, 1992. This Waste Minimization Crosscut Plan responds to the Secretary`s direction and supports the National Energy Strategy (NES) goals of achieving greater energy security, increasing energy and economic efficiency, and enhancing environmental quality. It provides a DOE-wide planning framework for effective coordination of all DOE WMin activities. This Plan was jointly prepared by the following Program Secretarial Officer (PSO) organizations: Civilian Radioactive Waste Management (RW); Conservation and Renewable Energy (CE); Defense Programs (DP); Environmental Restoration and Waste Management (EM), lead; Energy Research (ER); Fossil Energy (FE); Nuclear Energy (NE); and New Production Reactors (NP). Assistance and guidance was provided by the offices of Policy, Planning, and Analysis (PE) and Environment, Safety and Health (EH). Comprehensive application of waste minimization within the Department and in both the public and private sectors will provide significant benefits and support National Energy Strategy goals. These benefits include conservation of a substantial proportion of the energy now used by industry and Government, improved environmental quality, reduced health risks, improved production efficiencies, and longer useful life of disposal capacity. Taken together, these benefits will mean improved US global competitiveness, expanded job opportunities, and a better quality of life for all citizens.

  6. Minimally invasive radioguided parathyroidectomy.

    PubMed

    Costello, D; Norman, J

    1999-07-01

    The last decade has been characterized by an emphasis on minimizing interventional techniques, hospital stays, and overall costs of patient care. It is clear that most patients with sporadic HPT do not require a complete neck exploration. We now know that a minimal approach is appropriate for this disease. Importantly, the MIRP technique can be applied to most patients with sporadic HPT and can be performed by surgeons with modest advanced training. The use of a gamma probe as a surgical tool converts the sestamibi to a functional and anatomical scan eliminating the need for any other preoperative localizing study. Quantification of the radioactivity within the removed gland eliminates the need for routine frozen section histologic examination and obviates the need for costly intraoperative parathyroid hormone measurements. This radioguided technique allows the benefit of local anesthesia, dramatically reduces operative times, eliminates postoperative blood tests, provides a smaller scar, requires minimal time spent in the hospital, and almost assures a rapid, near pain-free recovery. This combination is beneficial to the patient whereas helping achieve a reduction in overall costs. PMID:10448697

  7. Mass tree mortality leads to mangrove peat collapse at Bay Islands, Honduras after Hurricane Mitch

    USGS Publications Warehouse

    Cahoon, D.R.; Hensel, P.; Rybczyk, J.; McKee, K.L.; Proffitt, C.E.; Perez, B.C.

    2003-01-01

    We measured sediment elevation and accretion dynamics in mangrove forests on the islands of Guanaja and Roatan, Honduras, impacted by Hurricane Mitch in 1998 to determine if collapse of underlying peat was occurring as a result of mass tree mortality. Little is known about the balance between production and decomposition of soil organic matter in the maintenance of sediment elevation of mangrove forests with biogenic soils. Sediment elevation change measured with the rod surface elevation table from 18 months to 33 months after the storm differed significantly among low, medium and high wind impact sites. Mangrove forests suffering minimal to partial mortality gained elevation at a rate (5 mm yeara??1) greater than vertical accretion (2 mm yeara??1) measured from artificial soil marker horizons, suggesting that root production contributed to sediment elevation. Basin forests that suffered mass tree mortality experienced peat collapse of about 11 mm yeara??1 as a result of decomposition of dead root material and sediment compaction. Low soil shear strength and lack of root growth accompanied elevation decreases. Model simulations using the Relative Elevation Model indicate that peat collapse in the high impact basin mangrove forest would be 37 mm yeara??1 for the 2 years immediately after the storm, as root material decomposed. In the absence of renewed root growth, the model predicts that peat collapse will continue for at least 8 more years at a rate (7 mm yeara??1) similar to that measured (11 mm yeara??1). Mass tree mortality caused rapid elevation loss. Few trees survived and recovery of the high impact forest will thus depend primarily on seedling recruitment. Because seedling establishment is controlled in large part by sediment elevation in relation to tide height, continued peat collapse could further impair recovery rates.

  8. 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.

  9. 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.

  10. Jeans type analysis of chemotactic collapse

    NASA Astrophysics Data System (ADS)

    Chavanis, Pierre-Henri; Sire, Clément

    2008-07-01

    We perform a linear dynamical stability analysis of a general hydrodynamic model of chemotactic aggregation [P.H. Chavanis, C. Sire, Physica A 384 (2007) 199]. Specifically, we study the stability of an infinite and homogeneous distribution of cells against “chemotactic collapse”. We discuss the analogy between the chemotactic collapse of biological populations and the gravitational collapse (Jeans instability) of self-gravitating systems. Our hydrodynamic model involves a pressure force which can take into account several effects like anomalous diffusion or the fact that the organisms cannot interpenetrate. We also take into account the degradation of the chemical which leads to a shielding of the interaction like for a Yukawa potential. Finally, our hydrodynamic model involves a friction force which quantifies the importance of inertial effects. In the strong friction limit, we obtain a generalized Keller-Segel model similar to the generalized Smoluchowski-Poisson system describing self-gravitating Langevin particles. For small frictions, we obtain a hydrodynamic model of chemotaxis similar to the Euler-Poisson system describing a self-gravitating barotropic gas. We show that an infinite and homogeneous distribution of cells is unstable against chemotactic collapse when the “velocity of sound” in the medium is smaller than a critical value. We study in detail the linear development of the instability and determine the range of unstable wavelengths, the growth rate of unstable modes and the damping rate, or the pulsation frequency, of the stable modes as a function of the friction parameter and shielding length. For specific equations of state, we express the stability criterion in terms of cell density.

  11. Core-collapse supernovae and nucleosynthesis

    SciTech Connect

    Haxton, W.C.

    1994-12-01

    I discuss some of the physics that governs the collapse and explosion of a massive star, including issues such as lepton number losses in the infall stage and neutrino heating and convection following the core bounce. I review recent work on the neutrino process and the r-process, describing how the nucleosynthesis depends on the explosion mechanism. Some of the interesting possibilities for oscillations of closure mass {nu}{sub {tau}}s are discussed, along with their signatures in terrestrial detectors and in nucleosynthesis.

  12. A collapsible trap for capturing ruffe

    USGS Publications Warehouse

    Edwards, Andrew J.; Czypinski, Gary D.; Selgeby, James H.

    1998-01-01

    A modified version of the Windermere trap was designed, constructed, and tested for its effectiveness in capturing ruffe Gymnocephalus cernuus. The inexpensive, lightweight, collapsible trap was easily deployed and retrieved from a small boat. Field tests conducted at the St. Louis River estuary in western Lake Superior in spring 1995 and 1996 indicated that the trap was effective in capturing ruffe. Proportions of the ruffe in trap and bottom trawl catches were similar in 1995 and 1996. This trap could be a useful tool in surveillance, monitoring, or control programs for ruffe or similar species, either to augment existing sampling programs or especially in situations where gillnetting or bottom trawling are not feasible.

  13. Critical conditions for core-collapse supernovae.

    PubMed

    Keshet, Uri; Balberg, Shmuel

    2012-06-22

    The explosion of a core-collapse supernova can be approximated by the breakdown of steady-state solutions for accretion onto a proto-neutron star (PNS). We analytically show that as the neutrino luminosity exceeds a critical value L(c), the neutrinosphere pressure exceeds the hydrostatic limit even for an optimal shock radius R. This yields L(c) [proportionally] M(2)T(2) (with logarithmic corrections) and R [proportionally] M/T, in agreement with numerical results, where M and T are the PNS mass and neutrino temperature, respectively. The near-critical flow can be approximated as a ballistic shell on top of an isothermal layer. PMID:23004581

  14. Nuclear Physics in Core-Collapse Supernovae

    SciTech Connect

    Liebendoerfer, Matthias; Fischer, T.; Froelich, C.; Hix, William Raphael; Langanke, Karlheinz; Martinez-Pinedo, Gabriel; Mezzacappa, Anthony; Scheidegger, Simon; Thielemann, Friedrich-Karl W.; Whitehouse, Stuart

    2008-01-01

    Core-collapse and the launch of a supernova explosion form a very short episode of few seconds in the evolution of a massive star, during which an enormous gravitational energy of several times 1053 erg is transformed into observable neutrino-, kinetic-, and electromagnetic radiation energy. We emphasize the wide range of matter conditions that prevail in a supernova event and sort the conditions into distinct regimes in the density and entropy phase diagram to briefly discuss their different impact on the neutrino signal, gravitational wave emission, and ejecta.

  15. Scalar field collapse with negative cosmological constant

    NASA Astrophysics Data System (ADS)

    Baier, R.; Nishimura, H.; Stricker, S. A.

    2015-07-01

    The formation of black holes or naked singularities is studied in a model in which a homogeneous time-dependent scalar field with an exponential potential couples to four-dimensional gravity with negative cosmological constant. An analytic solution is derived and its consequences are discussed. The model depends only on one free parameter, which determines the equation of state and decides the fate of the spacetime. Without fine tuning the value of this parameter the collapse ends in a generic formation of a black hole or a naked singularity. The latter case violates the cosmic censorship conjecture.

  16. Collapse models for dark interstellar clouds

    NASA Technical Reports Server (NTRS)

    Villere, K. R.; Black, D. C.

    1982-01-01

    Properties of self-consistent numerical hydrodynamic models are compared with observed properties of several dark clouds. The results are consistent with the view that these clouds are undergoing gravitational collapse. The clouds appear to have evolved from similar initial states and to have ages comparable to their free-fall times. Derived cloud masses range between 10 and 1000 solar masses, correlating with cloud size. The models reproduce observed cloud-to-cloud variations in the (C-13)O abundance, and they offer additional evidence that the (C-13)O abundance varies within individual clouds.

  17. Karst collapse in cities and mining areas, China

    SciTech Connect

    Jian Chen )

    1988-08-01

    Karst collapse is a dynamic geological phenomenon, in which the rock mass or deposits overlying the karstified zone subsides down along the karst cavity, resulting in a collapse pit or sinkhole. After discussing the typical examples of collapse emerging in the karst cities and mines in provinces and regions of South China, such as Guangdong, Guangxi, Hunan, Hubei, Zhejiang, Yunnan, Guizhou, and Jiangxi, it is considered that human activities of economy and production have become a major effect in causing karst collapse. Man-made collapses make 66.4 percent of the total, whereas natural ones 33.6 percent. Most of the collapses occurred to the area with soil overburden (96.7 percent), only a few in areas of bedrock overburden (3.3 percent). The karst collapses have a close relationship with the extent of karst development, the character and the thickness of overburden, and the dynamic condition of underground water. Collapse usually occurs in those parts of an area that are more intensely karstified, with soil thickness less than 5 m and a high amplitude of water table fluctuation. Many kinds of mechanical effects are caused by pumping or draining on the over-burden and destroying its equilibrium, leading to the collapse. These effects included the support loss and load-added effect, penetrating suffusion, gas explosion, water-hammer, suction pressure erosion, and liquefaction effects. The collapses are the result of varied comprehensive effects, particularly the support loss and load-added, and penetrating suffusion.

  18. Minimally invasive mediastinal surgery

    PubMed Central

    Melfi, Franca M. A.; Mussi, Alfredo

    2016-01-01

    In the past, mediastinal surgery was associated with the necessity of a maximum exposure, which was accomplished through various approaches. In the early 1990s, many surgical fields, including thoracic surgery, observed the development of minimally invasive techniques. These included video-assisted thoracic surgery (VATS), which confers clear advantages over an open approach, such as less trauma, short hospital stay, increased cosmetic results and preservation of lung function. However, VATS is associated with several disadvantages. For this reason, it is not routinely performed for resection of mediastinal mass lesions, especially those located in the anterior mediastinum, a tiny and remote space that contains vital structures at risk of injury. Robotic systems can overcome the limits of VATS, offering three-dimensional (3D) vision and wristed instrumentations, and are being increasingly used. With regards to thymectomy for myasthenia gravis (MG), unilateral and bilateral VATS approaches have demonstrated good long-term neurologic results with low complication rates. Nevertheless, some authors still advocate the necessity of maximum exposure, especially when considering the distribution of normal and ectopic thymic tissue. In recent studies, the robotic approach has shown to provide similar neurological outcomes when compared to transsternal and VATS approaches, and is associated with a low morbidity. Importantly, through a unilateral robotic technique, it is possible to dissect and remove at least the same amount of mediastinal fat tissue. Preliminary results on early-stage thymomatous disease indicated that minimally invasive approaches are safe and feasible, with a low rate of pleural recurrence, underlining the necessity of a “no-touch” technique. However, especially for thymomatous disease characterized by an indolent nature, further studies with long follow-up period are necessary in order to assess oncologic and neurologic results through minimally

  19. Minimally invasive mediastinal surgery.

    PubMed

    Melfi, Franca M A; Fanucchi, Olivia; Mussi, Alfredo

    2016-01-01

    In the past, mediastinal surgery was associated with the necessity of a maximum exposure, which was accomplished through various approaches. In the early 1990s, many surgical fields, including thoracic surgery, observed the development of minimally invasive techniques. These included video-assisted thoracic surgery (VATS), which confers clear advantages over an open approach, such as less trauma, short hospital stay, increased cosmetic results and preservation of lung function. However, VATS is associated with several disadvantages. For this reason, it is not routinely performed for resection of mediastinal mass lesions, especially those located in the anterior mediastinum, a tiny and remote space that contains vital structures at risk of injury. Robotic systems can overcome the limits of VATS, offering three-dimensional (3D) vision and wristed instrumentations, and are being increasingly used. With regards to thymectomy for myasthenia gravis (MG), unilateral and bilateral VATS approaches have demonstrated good long-term neurologic results with low complication rates. Nevertheless, some authors still advocate the necessity of maximum exposure, especially when considering the distribution of normal and ectopic thymic tissue. In recent studies, the robotic approach has shown to provide similar neurological outcomes when compared to transsternal and VATS approaches, and is associated with a low morbidity. Importantly, through a unilateral robotic technique, it is possible to dissect and remove at least the same amount of mediastinal fat tissue. Preliminary results on early-stage thymomatous disease indicated that minimally invasive approaches are safe and feasible, with a low rate of pleural recurrence, underlining the necessity of a "no-touch" technique. However, especially for thymomatous disease characterized by an indolent nature, further studies with long follow-up period are necessary in order to assess oncologic and neurologic results through minimally invasive

  20. Minimally refined biomass fuel

    DOEpatents

    Pearson, Richard K.; Hirschfeld, Tomas B.

    1984-01-01

    A minimally refined fluid composition, suitable as a fuel mixture and derived from biomass material, is comprised of one or more water-soluble carbohydrates such as sucrose, one or more alcohols having less than four carbons, and water. The carbohydrate provides the fuel source; water solubilizes the carbohydrates; and the alcohol aids in the combustion of the carbohydrate and reduces the vicosity of the carbohydrate/water solution. Because less energy is required to obtain the carbohydrate from the raw biomass than alcohol, an overall energy savings is realized compared to fuels employing alcohol as the primary fuel.

  1. Wake Vortex Minimization

    NASA Technical Reports Server (NTRS)

    1977-01-01

    A status report is presented on research directed at reducing the vortex disturbances of aircraft wakes. The objective of such a reduction is to minimize the hazard to smaller aircraft that might encounter these wakes. Inviscid modeling was used to study trailing vortices and viscous effects were investigated. Laser velocimeters were utilized in the measurement of aircraft wakes. Flight and wind tunnel tests were performed on scale and full model scale aircraft of various design. Parameters investigated included the effect of wing span, wing flaps, spoilers, splines and engine thrust on vortex attenuation. Results indicate that vortives may be alleviated through aerodynamic means.

  2. The ZOOM minimization package

    SciTech Connect

    Fischler, Mark S.; Sachs, D.; /Fermilab

    2004-11-01

    A new object-oriented Minimization package is available for distribution in the same manner as CLHEP. This package, designed for use in HEP applications, has all the capabilities of Minuit, but is a re-write from scratch, adhering to modern C++ design principles. A primary goal of this package is extensibility in several directions, so that its capabilities can be kept fresh with as little maintenance effort as possible. This package is distinguished by the priority that was assigned to C++ design issues, and the focus on producing an extensible system that will resist becoming obsolete.

  3. Minimally Invasive Parathyroidectomy

    PubMed Central

    Starker, Lee F.; Fonseca, Annabelle L.; Carling, Tobias; Udelsman, Robert

    2011-01-01

    Minimally invasive parathyroidectomy (MIP) is an operative approach for the treatment of primary hyperparathyroidism (pHPT). Currently, routine use of improved preoperative localization studies, cervical block anesthesia in the conscious patient, and intraoperative parathyroid hormone analyses aid in guiding surgical therapy. MIP requires less surgical dissection causing decreased trauma to tissues, can be performed safely in the ambulatory setting, and is at least as effective as standard cervical exploration. This paper reviews advances in preoperative localization, anesthetic techniques, and intraoperative management of patients undergoing MIP for the treatment of pHPT. PMID:21747851

  4. Shear flow induced unfolding of collapsed polymers.

    NASA Astrophysics Data System (ADS)

    Alexander-Katz, Alfredo; Netz, Roland

    2006-03-01

    In the process of clotting in small vessels, platelets form a plug in an injured zone only in the presence of a protein known as the von Willebrand Factor (vWF). The absence or malfunction of the vWF leads to a bleeding disorder, the so-called von Willebrand disease. It is believed that the protein is collapsed (or globular) when released into the blood flow, and that it undergoes a transition at high shear rates that allows it to bind platelets. Using hydrodynamic simulations of a simple model of the vWF in shear flow, we show that a globular polymer undergoes a globule-stretch transition at a critical shear rate. Below this threshold shear rate the polymer remains collapsed and slightly deformed, while above it the chain displays strong elongations in the direction of the flow. Finally, we discuss the relevance of our results in the case of blood flow, and compare them to the physiological values present in the body.

  5. Critical Collapse of Rotating Radiation Fluids

    NASA Astrophysics Data System (ADS)

    Baumgarte, Thomas W.; Gundlach, Carsten

    2016-06-01

    We present results from the first fully relativistic simulations of the critical collapse of rotating radiation fluids. We observe critical scaling both in subcritical evolutions—in which case the fluid disperses to infinity and leaves behind flat space—and in supercritical evolutions, which lead to the formation of black holes. We measure the mass and angular momentum of these black holes, and find that both show critical scaling with critical exponents that are consistent with perturbative results. The critical exponents are universal: they are not affected by angular momentum, and are independent of the direction in which the critical curve, which separates subcritical from supercritical evolutions in our two-dimensional parameter space, is crossed. In particular, these findings suggest that the angular momentum decreases more rapidly than the square of the mass, so that, as criticality is approached, the collapse leads to the formation of a nonspinning black hole. We also demonstrate excellent agreement of our numerical data with new closed-form extensions of power-law scalings that describe the mass and angular momentum of rotating black holes formed close to criticality.

  6. Sudden trust collapse in networked societies

    NASA Astrophysics Data System (ADS)

    da Gama Batista, João; Bouchaud, Jean-Philippe; Challet, Damien

    2015-03-01

    Trust is a collective, self-fulfilling phenomenon that suggests analogies with phase transitions. We introduce a stylized model for the build-up and collapse of trust in networks, which generically displays a first order transition. The basic assumption of our model is that whereas trustworthiness begets trustworthiness, panic also begets panic, in the sense that a small decrease in trustworthiness may be amplified and ultimately lead to a sudden and catastrophic drop of collective trust. We show, using both numerical simulations and mean-field analytic arguments, that there are extended regions of the parameter space where two equilibrium states coexist: a well-connected network where global confidence is high, and a poorly connected network where global confidence is low. In these coexistence regions, spontaneous jumps from the well-connected state to the poorly connected state can occur, corresponding to a sudden collapse of trust that is not caused by any major external catastrophe. In large systems, spontaneous crises are replaced by history dependence: whether the system is found in one state or in the other essentially depends on initial conditions. Finally, we document a new phase, in which agents are well connected yet distrustful.

  7. Critical Collapse of Rotating Radiation Fluids.

    PubMed

    Baumgarte, Thomas W; Gundlach, Carsten

    2016-06-01

    We present results from the first fully relativistic simulations of the critical collapse of rotating radiation fluids. We observe critical scaling both in subcritical evolutions-in which case the fluid disperses to infinity and leaves behind flat space-and in supercritical evolutions, which lead to the formation of black holes. We measure the mass and angular momentum of these black holes, and find that both show critical scaling with critical exponents that are consistent with perturbative results. The critical exponents are universal: they are not affected by angular momentum, and are independent of the direction in which the critical curve, which separates subcritical from supercritical evolutions in our two-dimensional parameter space, is crossed. In particular, these findings suggest that the angular momentum decreases more rapidly than the square of the mass, so that, as criticality is approached, the collapse leads to the formation of a nonspinning black hole. We also demonstrate excellent agreement of our numerical data with new closed-form extensions of power-law scalings that describe the mass and angular momentum of rotating black holes formed close to criticality. PMID:27314710

  8. Quantum corrected spherical collapse: A phenomenological framework

    SciTech Connect

    Ziprick, Jonathan; Kunstatter, Gabor

    2010-08-15

    A phenomenological framework is presented for incorporating quantum gravity motivated corrections into the dynamics of spherically symmetric collapse. The effective equations are derived from a variational principle that guarantees energy conservation and the existence of a Birkhoff theorem. The gravitational potential can be chosen as a function of the areal radius to yield specific nonsingular static spherically symmetric solutions that generically have two horizons. For a specific choice of potential, the effective stress energy tensor violates only the dominant energy condition. The violations are maximum near the inner horizon and die off rapidly. A numerical study of the quantum corrected collapse of a spherically symmetric scalar field in this case reveals that the modified gravitational potential prevents the formation of a central singularity and ultimately yields a static, mostly vacuum, spacetime with two horizons. The matter 'piles up' on the inner horizon giving rise to mass inflation at late times. The Cauchy horizon is transformed into a null, weak singularity, but in contrast to Einstein gravity, the absence of a central singularity renders this null singularity stable.

  9. The collapse of the midnight ionosphere and behavior of meridional neutral winds at Townsville over a full solar cycle

    NASA Astrophysics Data System (ADS)

    Dandenault, P. B.; Richards, P. G.

    2015-11-01

    This paper investigates the causes of the sudden descent (midnight collapse) of the ionosphere at Townsville, Australia, during the equinox periods of years between 1970 and 1980. The collapse of hmF2 at midnight is found to occur on 89% of the 330 equinox nights that are investigated, and the mean magnitude of the midnight collapse is 84 km in the March equinox periods and 99 km in the September equinox periods. Observations of hmF2 are used to determine equivalent meridional neutral winds using a first principles physics model. Harmonic analysis of these derived winds reveals the existence of significant diurnal (24 h), semidiurnal (12 h), and terdiurnal (8 h) tidal components. The contribution of wind harmonics to the midnight collapse is determined by band-pass filtering the winds to only allow certain tides and then modeling their effect on hmF2 near midnight. The results indicate that the diurnal, semidiurnal, and terdiurnal components of the meridional neutral wind all play a significant role at various times, but the effect of the 6 h wind component is minimal. The spectral analysis also reveals that the terdiurnal wind component becomes dominant during solar maximum. Electric fields do not appear to be responsible for the midnight hmF2 collapse because it is seldom seen at the near-conjugate station of Akita, Japan.

  10. Minimizing hazardous waste

    SciTech Connect

    DeClue, S.C.

    1996-06-01

    Hazardous waste minimization is a broad term often associated with pollution prevention, saving the environment or protecting Mother Earth. Some associate hazardous waste minimization with saving money. Thousands of hazardous materials are used in processes every day, but when these hazardous materials become hazardous wastes, dollars must be spent for disposal. When hazardous waste is reduced, an organization will spend less money on hazardous waste disposal. In 1993, Fort Bragg reduced its hazardous waste generation by over 100,000 pounds and spent nearly $90,000 less on hazardous waste disposal costs than in 1992. Fort Bragg generates a variety of wastes: Vehicle maintenance wastes such as antifreeze, oil, grease and solvents; helicopter maintenance wastes, including solvents, adhesives, lubricants and paints; communication operation wastes such as lithium, magnesium, mercury and nickel-cadmium batteries; chemical defense wastes detection, decontamination, and protective mask filters. The Hazardous Waste Office has the responsibility to properly identify, characterize, classify and dispose of these waste items in accordance with US Environmental Protection Agency (EPA) and US Department of Transportation (DOT) regulations.

  11. Gravitationally collapsing shells in (2+1) dimensions

    SciTech Connect

    Mann, Robert B.; Oh, John J.

    2006-12-15

    We study gravitationally collapsing models of pressureless dust, fluids with pressure, and the generalized Chaplygin gas (GCG) shell in (2+1)-dimensional spacetimes. Various collapse scenarios are investigated under a variety of the background configurations such as anti-de Sitter (AdS) black hole, de Sitter (dS) space, flat and AdS space with a conical deficit. As with the case of a disk of dust, we find that the collapse of a dust shell coincides with the Oppenheimer-Snyder type collapse to a black hole provided the initial density is sufficiently large. We also find - for all types of shell - that collapse to a naked singularity is possible under a broad variety of initial conditions. For shells with pressure this singularity can occur for a finite radius of the shell. We also find that GCG shells exhibit diverse collapse scenarios, which can be easily demonstrated by an effective potential analysis.

  12. Inherently unstable networks collapse to a critical point

    NASA Astrophysics Data System (ADS)

    Sheinman, M.; Sharma, A.; Alvarado, J.; Koenderink, G. H.; MacKintosh, F. C.

    2015-07-01

    Nonequilibrium systems that are driven or drive themselves towards a critical point have been studied for almost three decades. Here we present a minimalist example of such a system, motivated by experiments on collapsing active elastic networks. Our model of an unstable elastic network exhibits a collapse towards a critical point from any macroscopically connected initial configuration. Taking into account steric interactions within the network, the model qualitatively and quantitatively reproduces results of the experiments on collapsing active gels.

  13. GENERAL: Non-Spherical Gravitational Collapse of Strange Quark Matter

    NASA Astrophysics Data System (ADS)

    S, Zade S.; D, Patil K.; N, Mulkalwar P.

    2008-05-01

    We study the non-spherical gravitational collapse of the strange quark null fluid. The interesting feature which emerges is that the non-spherical collapse of charged strange quark matter leads to a naked singularity whereas the gravitational collapse of neutral quark matter proceeds to form a black hole. We extend the earlier work of Harko and Cheng [Phys. Lett. A 266 (2000) 249] to the non-spherical case.

  14. Protostellar collapse in a self-gravitating sheet

    NASA Technical Reports Server (NTRS)

    Hartmann, Lee; Boss, Alan; Calvet, Nuria; Whitney, Barbara

    1994-01-01

    We present preliminary calculations of protostellar cloud collapse starting from an isothermal, self-gravitating gaseous layer in hydrostatic equilibrium. This gravitationally unstable layer collapses into a flattened or toroidal density distribution, even in the absence of rotation or magnetic fields. We suggest that the flat infalling envelope recently observed in HL Tau by Hayashi et al.is the result of collapse from an initially nonspherical layer. We also speculate that the later evolution of such a flattened, collapsing envelope can produce a structure similar to the 'flared disk' invoked by Kenyon and Hartmann to explain the infrared excesses of many T Tauri stars.

  15. Interacting dark energy collapse with matter components separation

    SciTech Connect

    Delliou, M. Le; Barreiro, T. E-mail: tmbarreiro@ulusofona.pt

    2013-02-01

    We use the spherical collapse model of structure formation to investigate the separation in the collapse of uncoupled matter (essentially baryons) and coupled dark matter in an interacting dark energy scenario. Following the usual assumption of a single radius of collapse for all species, we show that we only need to evolve the uncoupled matter sector to obtain the evolution for all matter components. This gives us more information on the collapse with a simplified set of evolution equations compared with the usual approaches. We then apply these results to four quintessence potentials and show how we can discriminate between different quintessence models.

  16. Surgical management of atypical lateral tracheal collapse in a dog.

    PubMed

    Johnson, L R; Krahwinkel, D J; McKiernan, B C

    1993-12-15

    Tracheal collapse is often diagnosed in small-breed dogs through use of conventional radiography or fluoroscopy, by which the dorsoventral orientation of the collapse can be seen. In the dog of this report, an unusual lateral form of tracheal collapse was diagnosed by means of bronchoscopy after multiple radiographic procedures had failed to define a cause for cough and dyspnea. Surgical reinforcement of the abnormal region of the trachea resulted in resolution of clinical signs and in reduction in dynamic airway collapse, which was documented on follow-up bronchoscopy. PMID:8307818

  17. A Search for Protostellar Collapse in Late Class I Sources

    NASA Astrophysics Data System (ADS)

    Gregersen, E. M.; Mardones, D.; Evans, N. J., II; Myers, P. C.; Shirley, Y. L.; Wilson, C. D.

    2000-10-01

    Asymmetric spectra of optically thick spectral lines are associated with protostellar collapse in young stellar objects. Such asymmetries have been believed to be confined solely to the Class 0 stage, but collapse signatures have now been observed in Class I sources with Tbol < 200 K. We present partial results of a survey that extends earlier results in Class 0 and I sources of HCO+, a molecule that shows strong line asymmetry in simulations of collapsing clouds, to Class I sources with Tbol < 650 K to find when protostellar collapse ends and how infall motions change with time.

  18. Developing empirical collapse fragility functions for global building types

    USGS Publications Warehouse

    Jaiswal, K.; Wald, D.; D'Ayala, D.

    2011-01-01

    Building collapse is the dominant cause of casualties during earthquakes. In order to better predict human fatalities, the U.S. Geological Survey’s Prompt Assessment of Global Earthquakes for Response (PAGER) program requires collapse fragility functions for global building types. The collapse fragility is expressed as the probability of collapse at discrete levels of the input hazard defined in terms of macroseismic intensity. This article provides a simple procedure for quantifying collapse fragility using vulnerability criteria based on the European Macroseismic Scale (1998) for selected European building types. In addition, the collapse fragility functions are developed for global building types by fitting the beta distribution to the multiple experts’ estimates for the same building type (obtained from EERI’s World Housing Encyclopedia (WHE)-PAGER survey). Finally, using the collapse probability distributions at each shaking intensity level as a prior and field-based collapse-rate observations as likelihood, it is possible to update the collapse fragility functions for global building types using the Bayesian procedure.

  19. Atomistic modeling of shock-induced void collapse in copper

    SciTech Connect

    Davila, L P; Erhart, P; Bringa, E M; Meyers, M A; Lubarda, V A; Schneider, M S; Becker, R; Kumar, M

    2005-03-09

    Nonequilibrium molecular dynamics (MD) simulations show that shock-induced void collapse in copper occurs by emission of shear loops. These loops carry away the vacancies which comprise the void. The growth of the loops continues even after they collide and form sessile junctions, creating a hardened region around the collapsing void. The scenario seen in our simulations differs from current models that assume that prismatic loop emission is responsible for void collapse. We propose a new dislocation-based model that gives excellent agreement with the stress threshold found in the MD simulations for void collapse as a function of void radius.

  20. A rational characterization of proprietary High Collapse casing grades

    SciTech Connect

    Klementich, E.F.

    1995-12-31

    An increasing number of users are finding it necessary to utilize {open_quotes}High Collapse{close_quotes} casing grades for deep set and intermediate size drilling and production casing strings. Unfortunately, the great variety of proprietary (non-API) high collapse casing grades has made it extremely difficult for drilling and completion engineers to logically select the optimum size, weight, and grade of pipe meeting the design objective, due to the wide variation in collapse resistance claims and the guaranteed pipe dimensional and mechanical properties supporting that claim. This paper provides a technically sound method for selecting and safely using high collapse pipe.

  1. Spreading and collapse of big basaltic volcanoes

    NASA Astrophysics Data System (ADS)

    Puglisi, Giuseppe; Bonforte, Alessandro; Guglielmino, Francesco; Peltier, Aline; Poland, Michael

    2016-04-01

    Among the different types of volcanoes, basaltic ones usually form the most voluminous edifices. Because volcanoes are growing on a pre-existing landscape, the geologic and structural framework of the basement (and earlier volcanic landforms) influences the stress regime, seismicity, and volcanic activity. Conversely, the masses of these volcanoes introduce a morphological anomaly that affects neighboring areas. Growth of a volcano disturbs the tectonic framework of the region, clamps and unclamps existing faults (some of which may be reactivated by the new stress field), and deforms the substratum. A volcano's weight on its basement can trigger edifice spreading and collapse that can affect populated areas even at significant distance. Volcano instability can also be driven by slow tectonic deformation and magmatic intrusion. The manifestations of instability span a range of temporal and spatial scales, ranging from slow creep on individual faults to large earthquakes affecting a broad area. In the frame of MED-SVU project, our work aims to investigate the relation between basement setting and volcanic activity and stability at three Supersite volcanoes: Etna (Sicily, Italy), Kilauea (Island of Hawaii, USA) and Piton de la Fournaise (La Reunion Island, France). These volcanoes host frequent eruptive activity (effusive and explosive) and share common features indicating lateral spreading and collapse, yet they are characterized by different morphologies, dimensions, and tectonic frameworks. For instance, the basaltic ocean island volcanoes of Kilauea and Piton de la Fournaise are near the active ends of long hotspot chains while Mt. Etna has developed at junction along a convergent margin between the African and Eurasian plates and a passive margin separating the oceanic Ionian crust from the African continental crust. Magma supply and plate velocity also differ in the three settings, as to the sizes of the edifices and the extents of their rift zones. These

  2. Minimal noise subsystems

    NASA Astrophysics Data System (ADS)

    Wang, Xiaoting; Byrd, Mark; Jacobs, Kurt

    2016-03-01

    A system subjected to noise contains a decoherence-free subspace or subsystem (DFS) only if the noise possesses an exact symmetry. Here we consider noise models in which a perturbation breaks a symmetry of the noise, so that if S is a DFS under a given noise process it is no longer so under the new perturbed noise process. We ask whether there is a subspace or subsystem that is more robust to the perturbed noise than S . To answer this question we develop a numerical method that allows us to search for subspaces or subsystems that are maximally robust to arbitrary noise processes. We apply this method to a number of examples, and find that a subsystem that is a DFS is often not the subsystem that experiences minimal noise when the symmetry of the noise is broken by a perturbation. We discuss which classes of noise have this property.

  3. Minimal quiver standard model

    SciTech Connect

    Berenstein, David; Pinansky, Samuel

    2007-05-01

    This paper discusses the minimal quiver gauge theory embedding of the standard model that could arise from brane world type string theory constructions. It is based on the low energy effective field theory of D branes in the perturbative regime. The model differs from the standard model by the addition of one extra massive gauge boson, and contains only one additional parameter to the standard model: the mass of this new particle. The coupling of this new particle to the standard model is uniquely determined by input from the standard model and consistency conditions of perturbative string theory. We also study some aspects of the phenomenology of this model and bounds on its possible observation at the Large Hadron Collider.

  4. [Minimally invasive breast surgery].

    PubMed

    Mátrai, Zoltán; Gulyás, Gusztáv; Kunos, Csaba; Sávolt, Akos; Farkas, Emil; Szollár, András; Kásler, Miklós

    2014-02-01

    Due to the development in medical science and industrial technology, minimally invasive procedures have appeared in the surgery of benign and malignant breast diseases. In general , such interventions result in significantly reduced breast and chest wall scars, shorter hospitalization and less pain, but they require specific, expensive devices, longer surgical time compared to open surgery. Furthermore, indications or oncological safety have not been established yet. It is quite likely, that minimally invasive surgical procedures with high-tech devices - similar to other surgical subspecialties -, will gradually become popular and it may form part of routine breast surgery even. Vacuum-assisted core biopsy with a therapeutic indication is suitable for the removal of benign fibroadenomas leaving behind an almost invisible scar, while endoscopically assisted skin-sparing and nipple-sparing mastectomy, axillary staging and reconstruction with latissimus dorsi muscle flap are all feasible through the same short axillary incision. Endoscopic techniques are also suitable for the diagnostics and treatment of intracapsular complications of implant-based breast reconstructions (intracapsular fluid, implant rupture, capsular contracture) and for the biopsy of intracapsular lesions with uncertain pathology. Perception of the role of radiofrequency ablation of breast tumors requires further hands-on experience, but it is likely that it can serve as a replacement of surgical removal in a portion of primary tumors in the future due to the development in functional imaging and anticancer drugs. With the reduction of the price of ductoscopes routine examination of the ductal branch system, guided microdochectomy and targeted surgical removal of terminal ducto-lobular units or a "sick lobe" as an anatomical unit may become feasible. The paper presents the experience of the authors and provides a literature review, for the first time in Hungarian language on the subject. Orv. Hetil

  5. Minimally invasive parathyroid surgery

    PubMed Central

    Noureldine, Salem I.; Gooi, Zhen

    2015-01-01

    Traditionally, bilateral cervical exploration for localization of all four parathyroid glands and removal of any that are grossly enlarged has been the standard surgical treatment for primary hyperparathyroidism (PHPT). With the advances in preoperative localization studies and greater public demand for less invasive procedures, novel targeted, minimally invasive techniques to the parathyroid glands have been described and practiced over the past 2 decades. Minimally invasive parathyroidectomy (MIP) can be done either through the standard Kocher incision, a smaller midline incision, with video assistance (purely endoscopic and video-assisted techniques), or through an ectopically placed, extracervical, incision. In current practice, once PHPT is diagnosed, preoperative evaluation using high-resolution radiographic imaging to localize the offending parathyroid gland is essential if MIP is to be considered. The imaging study results suggest where the surgeon should begin the focused procedure and serve as a road map to allow tailoring of an efficient, imaging-guided dissection while eliminating the unnecessary dissection of multiple glands or a bilateral exploration. Intraoperative parathyroid hormone (IOPTH) levels may be measured during the procedure, or a gamma probe used during radioguided parathyroidectomy, to ascertain that the correct gland has been excised and that no other hyperfunctional tissue is present. MIP has many advantages over the traditional bilateral, four-gland exploration. MIP can be performed using local anesthesia, requires less operative time, results in fewer complications, and offers an improved cosmetic result and greater patient satisfaction. Additional advantages of MIP are earlier hospital discharge and decreased overall associated costs. This article aims to address the considerations for accomplishing MIP, including the role of preoperative imaging studies, intraoperative adjuncts, and surgical techniques. PMID:26425454

  6. Ice sheet collapse affects ocean circulation

    NASA Astrophysics Data System (ADS)

    Tretkoff, Ernie

    2011-06-01

    As Earth's climate warms and ice melts, freshwater input to oceans could weaken the large-scale Atlantic meridional overturning circulation, which acts as an important conveyor of heat and has significant effects on climate. Green et al. used an intermediate complexity climate model to study how freshwater input to oceans can affect the meridional overturning circulation. They applied their model to the collapse of the Barents ice sheet about 140,000 years ago—the first study of this kind for the time period—which resulted in a huge influx of freshwater to the North Atlantic Ocean as large icebergs calved off of the ice sheet. (Paleoceanography, doi:10.1029/ 2010PA002088, 2011)

  7. Nonlinear cosmological spherical collapse of quintessence

    NASA Astrophysics Data System (ADS)

    Rekier, J.; Füzfa, A.; Cordero-Carrión, I.

    2016-02-01

    We present a study of the fully relativistic spherical collapse in the presence of quintessence using on numerical relativity, following the method proposed by the authors in a previous article [Phys. Rev. D 91, 024025 (2015)]. We ascertain the validity of the method by studying the evolution of a spherically symmetric quintessence inhomogeneity on a de Sitter background and we find that it has an impact on the local expansion around the center of coordinates. We then proceed to compare the results of our method to those of the more largely adopted top-hat model. We find that quintessence inhomogeneities do build up under the effect that matter inhomogeneities have on the local space-time, yet remain very small due to the presence of momentum transfer from the over-dense to the background regions. We expect that these might have an even more important role in modified theories of gravitation.

  8. Rebuild cooling tower after partial collapse

    SciTech Connect

    Michell, F.L.; Demjanenko, W.

    1995-07-01

    When this tower suddenly went down, it forced the associated powerplant out of service. To restore operation required a quick assessment of the damage and fast action to reconstruct the tower. The partial collapse and prompt rebuild of a cooling tower at Columbus Southern Co`s Conesville station Unit 4 is a story of what can go wrong and what can be done to set matters right -- in a hurry. The utility is one of seven operating companies in American Electric Power Co`s system. Unit 4 is jointly owned with Cincinnati Gas and Electric Co and Dayton Power and Light Co. The 780-MW coal-fired unit`s closed-loop cooling-water system is served by two double-flow, seven-cell, mechanical-draft cooling towers (4A and 4B). The design basis calls for operating all 14 cells to maintain full load in the summer months.

  9. Gravitational Waves from Core Collapse Supernovae

    SciTech Connect

    Yakunin, Konstantin; Marronetti, Pedro; Mezzacappa, Anthony; Bruenn, S. W.; Lee, Ching-Tsai; Chertkow, Merek A; Hix, William Raphael; Blondin, J. M.; Lentz, Eric J; Messer, Bronson; Yoshida, S.

    2010-01-01

    We present the gravitational wave signatures for a suite of axisymmetric core collapse supernova models with progenitor masses between 12 and 25 M{sub odot}. These models are distinguished by the fact that they explode and contain essential physics (in particular, multi-frequency neutrino transport and general relativity) needed for a more realistic description. Thus, we are able to compute complete waveforms (i.e. through explosion) based on non-parameterized, first-principles models. This is essential if the waveform amplitudes and time scales are to be computed more precisely. Fourier decomposition shows that the gravitational wave signals we predict should be observable by AdvLIGO across the range of progenitors considered here. The fundamental limitation of these models is in their imposition of axisymmetry. Further progress will require counterpart three-dimensional models.

  10. Electron acceleration by magnetic collapse during decoupling

    NASA Astrophysics Data System (ADS)

    Bennet, Euan D.; Potts, Hugh E.; Teodoro, Luis F. A.; Diver, Declan A.

    2014-12-01

    This paper identifies the non-equilibrium evolution of magnetic field structures at the onset of large-scale recombination of an inhomogeneously ionized plasma. The context for this is the Universe during the epoch of recombination. The electromagnetic treatment of this phase transition can produce energetic electrons scattered throughout the Universe, localized near the edges of magnetic domains. This is confirmed by a numerical simulation in which a magnetic domain is modelled as a uniform field region produced by a thin surrounding current sheet. Conduction currents sustaining the magnetic structure are removed as the charges comprising them combine into neutrals. The induced electric field accompanying the magnetic collapse is able to accelerate ambient stationary electrons (that is, electrons not participating in the current sheet) to energies of up to order 10keV. This is consistent with theoretical predictions. The localized electron acceleration leads to local imbalances of charge which has implications for charge separation in the early Universe.

  11. Dewetting-induced collapse of hydrophobic particles

    PubMed Central

    Huang, X.; Margulis, C. J.; Berne, B. J.

    2003-01-01

    A molecular dynamics study of the depletion of water (drying) around a single and between two hydrophobic nanoscale oblate plates in explicit water as a function of the distance of separation between them, their size, and the strength of the attraction between the plates and the water molecules is presented. A simple macroscopic thermodynamic model based on Young's law successfully predicts drying between the stacked plates and accounts for the free-energy barriers to this drying. However, because drying around a single plate is not macroscopic, a molecular theory is required to describe it. The data are consistent with the rate-determining step in the hydrophobic collapse of the two plates being a large-scale drying fluctuation, characterized by a free-energy barrier that grows with particle size. PMID:14507993

  12. Gravitational waves from collapsing domain walls

    SciTech Connect

    Hiramatsu, Takashi; Kawasaki, Masahiro; Saikawa, Ken'ichi E-mail: kawasaki@icrr.u-tokyo.ac.jp

    2010-05-01

    We study the production of gravitational waves from cosmic domain walls created during phase transition in the early universe. We investigate the process of formation and evolution of domain walls by running three dimensional lattice simulations. If we introduce an approximate discrete symmetry, walls become metastable and finally disappear. This process might occur by a pressure difference between two vacua if a quantum tunneling is neglected. We calculate the spectrum of gravitational waves produced by collapsing metastable domain walls. Extrapolating the numerical results, we find that the signal of gravitational waves produced by domain walls whose energy scale is around 10{sup 10}-10{sup 12}GeV will be observable in the next generation gravitational wave interferometers.

  13. Petascale Core-Collapse Supernova Simulation

    NASA Astrophysics Data System (ADS)

    Messer, Bronson

    2009-11-01

    The advent of petascale computing brings with it the promise of substantial increases in physical fidelity for a host of scientific problems. However, the realities of computing on these resources are daunting, and the architectural features of petascale machines will require considerable innovation for effective use. Nevertheless, there exists a class of scientific problems whose ultimate answer requires the application of petascale (and beyond) computing. One example is ascertaining the core-collapse supernova mechanism and explaining the rich phenomenology associated with these events. These stellar explosions produce and disseminate a dominant fraction of the elements in the Universe; are prodigious sources of neutrinos, gravitational waves, and photons across the electromagnetic spectrum; and lead to the formation of neutron stars and black holes. I will describe our recent multidimensional supernova simulations performed on petascale platforms fielded by the DOE and NSF.

  14. Core-Collapse Supernovae -- the Outliers

    NASA Astrophysics Data System (ADS)

    Woosley, Stan

    2011-04-01

    After a brief review of current efforts to model the explosion mechanism for "ordinary," core collapse supernovae and the neutrino signal expected from them, some of the outliers predicted by current theory will be discussed. Chief among these are the pulsational-pair instability supernovae, which can occur for stars as light as 80 solar masses or as heavy as 140 solar masses, or more. These explosions, which would have been common in the early universe and persist today, can make supernovae that do or do not recur, and that can be either exceptionally faint or bright or both. They leave behind black holes with masses near 40 solar masses, and produce an abundance pattern that is rich in CNO, much like that seen in the ultra-iron poor stars. Other models for unusual supernovae, including magnetar-powered supernovae and 8 - 10 solar mass supernovae will be mentioned as time allows.

  15. Crystallization and collapse in relativistically degenerate matter

    SciTech Connect

    Akbari-Moghanjoughi, M.

    2013-04-15

    In this paper, it is shown that a mass density limit exists beyond which the relativistically degenerate matter would crystallize. The mass density limit, found here, is quite analogous to the mass limit predicted by Chandrasekhar for a type of compact stars called white dwarfs (M{sub Ch} Asymptotically-Equal-To 1.43 Solar Mass). In this study, the old problem of white dwarf core collapse, which has been previously investigated by Chandrasekhar using hydrostatic stability criteria, is revisited in the framework of the quantum hydrodynamics model by inspection of the charge screening at atomic scales in the relativistic degeneracy plasma regime taking into account the relativistic Fermi-Dirac statistics and electron interaction features such as the quantum statistical pressure, Coulomb attraction, electron exchange-correlation, and quantum recoil effects. It is revealed that the existence of ion correlation and crystallization of matter in the relativistically degenerate plasma puts a critical mass density limit on white dwarf core region. It is shown that a white dwarf star with a core mass density beyond this critical limit can undergo the spontaneous core collapse (SCC). The SCC phenomenon, which is dominantly caused by the electron quantum recoil effect (interference and localization of the electron wave function), leads to a new exotic state of matter. In such exotic state, the relativistic electron degeneracy can lead the white dwarf crystallized core to undergo the nuclear fusion and an ultimate supernova by means of the volume reduction (due to the enhanced compressibility) and huge energy release (due to the increase in cohesive energy), under the stars huge inward gravitational pressure. Moreover, it is found that the SCC phenomenon is significantly affected by the core composition (it is more probable for heavier plasmas). The critical mass density found here is consistent with the values calculated for core density of typical white dwarf stars.

  16. Pathogen Webs in Collapsing Honey Bee Colonies

    PubMed Central

    Cornman, R. Scott; Tarpy, David R.; Chen, Yanping; Jeffreys, Lacey; Lopez, Dawn; Pettis, Jeffery S.; vanEngelsdorp, Dennis; Evans, Jay D.

    2012-01-01

    Recent losses in honey bee colonies are unusual in their severity, geographical distribution, and, in some cases, failure to present recognized characteristics of known disease. Domesticated honey bees face numerous pests and pathogens, tempting hypotheses that colony collapses arise from exposure to new or resurgent pathogens. Here we explore the incidence and abundance of currently known honey bee pathogens in colonies suffering from Colony Collapse Disorder (CCD), otherwise weak colonies, and strong colonies from across the United States. Although pathogen identities differed between the eastern and western United States, there was a greater incidence and abundance of pathogens in CCD colonies. Pathogen loads were highly covariant in CCD but not control hives, suggesting that CCD colonies rapidly become susceptible to a diverse set of pathogens, or that co-infections can act synergistically to produce the rapid depletion of workers that characterizes the disorder. We also tested workers from a CCD-free apiary to confirm that significant positive correlations among pathogen loads can develop at the level of individual bees and not merely as a secondary effect of CCD. This observation and other recent data highlight pathogen interactions as important components of bee disease. Finally, we used deep RNA sequencing to further characterize microbial diversity in CCD and non-CCD hives. We identified novel strains of the recently described Lake Sinai viruses (LSV) and found evidence of a shift in gut bacterial composition that may be a biomarker of CCD. The results are discussed with respect to host-parasite interactions and other environmental stressors of honey bees. PMID:22927991

  17. Collapse of Synchronization in a Memristive Network

    NASA Astrophysics Data System (ADS)

    Lü, Mi; Wang, Chun-Ni; Tang, Jun; Ma, Jun

    2015-12-01

    For an oscillating circuit or coupled circuits, damage in electric devices such as inductor, resistance, memristor even capacitor can cause breakdown or collapse of the circuits. These damage could be associated with external attack or aging in electric devices, and then the bifurcation parameters could be deformed from normal values. Resonators or signal generators are often synchronized to produce powerful signal series and this problem could be investigated by using synchronization in network. Complete synchronization could be induced by linear coupling in a two-dimensional network of identical oscillators when the coupling intensity is beyond certain threshold. The collective behavior and synchronization state are much dependent on the bifurcation parameters. Any slight fluctuation in parameter and breakdown in bifurcation parameter can cause transition of synchronization even collapse of synchronization in the network. In this paper, a two-dimensional network composed of the resonators coupled with memristors under nearest-neighbor connection is designed, and the network can reach complete synchronization by carefully selecting coupling intensity. The network keeps synchronization after certain transient period, then a bifurcation parameter in a resonator is switched from the previous value and the adjacent resonators (oscillators) are affected in random. It is found that the synchronization area could be invaded greatly in a diffusive way. The damage area size is much dependent on the selection of diffusive period of damage and deformation degree in the parameter. Indeed, the synchronization area could keep intact at largest size under intermediate deformation degree and coupling intensity. Supported by the National Natural Science of China under Grant Nos. 11265008 and 11365014

  18. Fingerprinting Hydrogen in Core-Collapse Supernovae

    NASA Astrophysics Data System (ADS)

    Nance, Sarafina; Parrent, Jerod; Soderberg, Alicia Margarita

    2016-01-01

    This is a preliminary report on the mass of remaining hydrogen envelopes for stars massive enough to explode under core collapse. Using the stellar evolution code, MESA, our initial findings suggest that a significant fraction of massive stars with M_ZAMS = 20-60 Msun lose all but 10^-3 Msun -10^-1 Msun as they near eventual core collapse. This result is dependent on the mass-loss prescription, degree of rotation, metallicity, rates of nuclear burning in the core, and the final stellar configuration. Nevertheless, each of our test cases include a few stars that retain trace amounts of surface hydrogen, which would then be detected as faint H in type IIb/Ib/Ic supernova spectra. We also compare our findings to the progenitor candidate identified for iPTF13bvn using the most recent photometric corrections. We agree with the previous conclusion found by Groh et al. (2013) that the progenitor had an initial mass of 32 Msun, but now with an additional condition of 0.06 Msun of hydrogen on its surface just prior to the explosion. We demonstrate through our study that not all Type Ib supernovae are fully devoid of hydrogen at the time of explosion, which has implications for the nature of the progenitor star and thus provides impetus for a revised classification scheme for 'stripped envelope' supernovae. This work was supported in part by the NSF REU and DoD ASSURE programs under NSF grant no. 1262851 and by the Smithsonian Institution.

  19. Driven neutron star collapse: Type I critical phenomena and the initial black hole mass distribution

    NASA Astrophysics Data System (ADS)

    Noble, Scott C.; Choptuik, Matthew W.

    2016-01-01

    We study the general relativistic collapse of neutron star (NS) models in spherical symmetry. Our initially stable models are driven to collapse by the addition of one of two things: an initially ingoing velocity profile, or a shell of minimally coupled, massless scalar field that falls onto the star. Tolman-Oppenheimer-Volkoff (TOV) solutions with an initially isentropic, gamma-law equation of state serve as our NS models. The initial values of the velocity profile's amplitude and the star's central density span a parameter space which we have surveyed extensively and which we find provides a rich picture of the possible end states of NS collapse. This parameter space survey elucidates the boundary between Type I and Type II critical behavior in perfect fluids which coincides, on the subcritical side, with the boundary between dispersed and bound end states. For our particular model, initial velocity amplitudes greater than 0.3 c are needed to probe the regime where arbitrarily small black holes can form. In addition, we investigate Type I behavior in our system by varying the initial amplitude of the initially imploding scalar field. In this case we find that the Type I critical solutions resemble TOV solutions on the 1-mode unstable branch of equilibrium solutions, and that the critical solutions' frequencies agree well with the fundamental mode frequencies of the unstable equilibria. Additionally, the critical solution's scaling exponent is shown to be well approximated by a linear function of the initial star's central density.

  20. Numerical simulations of non-spherical bubble collapse

    PubMed Central

    JOHNSEN, ERIC; COLONIUS, TIM

    2009-01-01

    A high-order accurate shock- and interface-capturing scheme is used to simulate the collapse of a gas bubble in water. In order to better understand the damage caused by collapsing bubbles, the dynamics of the shock-induced and Rayleigh collapse of a bubble near a planar rigid surface and in a free field are analysed. Collapse times, bubble displacements, interfacial velocities and surface pressures are quantified as a function of the pressure ratio driving the collapse and of the initial bubble stand-off distance from the wall; these quantities are compared to the available theory and experiments and show good agreement with the data for both the bubble dynamics and the propagation of the shock emitted upon the collapse. Non-spherical collapse involves the formation of a re-entrant jet directed towards the wall or in the direction of propagation of the incoming shock. In shock-induced collapse, very high jet velocities can be achieved, and the finite time for shock propagation through the bubble may be non-negligible compared to the collapse time for the pressure ratios of interest. Several types of shock waves are generated during the collapse, including precursor and water-hammer shocks that arise from the re-entrant jet formation and its impact upon the distal side of the bubble, respectively. The water-hammer shock can generate very high pressures on the wall, far exceeding those from the incident shock. The potential damage to the neighbouring surface is quantified by measuring the wall pressure. The range of stand-off distances and the surface area for which amplification of the incident shock due to bubble collapse occurs is determined. PMID:19756233

  1. Minimal Marking: A Success Story

    ERIC Educational Resources Information Center

    McNeilly, Anne

    2014-01-01

    The minimal-marking project conducted in Ryerson's School of Journalism throughout 2012 and early 2013 resulted in significantly higher grammar scores in two first-year classes of minimally marked university students when compared to two traditionally marked classes. The "minimal-marking" concept (Haswell, 1983), which requires…

  2. Temperature-Induced Collapse, and Arrested Collapse, of Anisotropic Endoskeleton Droplets.

    PubMed

    Caggioni, Marco; Lenis, Jessica; Bayles, Alexandra V; Furst, Eric M; Spicer, Patrick T

    2015-08-11

    Micron-scale rod-shaped droplets with a range of aspect ratios are produced using extrusion of oil containing a soft wax crystal network to permit shape customization. A physical model of the droplet shape stability is developed based on balancing interfacial stresses with the internal crystal network yield stress. The model predicts the mechanical properties required for particular droplet size stability, in a given physicochemical environment, and is tested by microscopic observations of droplets over a range of relevant applied temperatures. The time-dependent response to temperature of individual rods is monitored and used to identify the collapse temperature based on structural yielding. Precise temperature control allows variation of the droplet endoskeleton yield stress and direct determination of the droplet stability as a function of size, by observing the onset of collapse by interfacial compression, and enables validation of the model predictions. Mapping the regions of droplet stability and instability for various-sized droplets yields a basis for designing droplet shapes for multiple applications using easily measured physical variables. The phenomenon of arrested collapse is also explored as a means of transforming simple rod-shaped starting materials into more complex shapes and enhancing adhesion to targeted solid surfaces, enabling exploitation of the hybrid solid-liquid nature of these droplets. PMID:26177777

  3. Minimal distances between SCFTs

    NASA Astrophysics Data System (ADS)

    Buican, Matthew

    2014-01-01

    We study lower bounds on the minimal distance in theory space between four-dimensional superconformal field theories (SCFTs) connected via broad classes of renormalization group (RG) flows preserving various amounts of supersymmetry (SUSY). For = 1 RG flows, the ultraviolet (UV) and infrared (IR) endpoints of the flow can be parametrically close. On the other hand, for RG flows emanating from a maximally supersymmetric SCFT, the distance to the IR theory cannot be arbitrarily small regardless of the amount of (non-trivial) SUSY preserved along the flow. The case of RG flows from =2 UV SCFTs is more subtle. We argue that for RG flows preserving the full =2 SUSY, there are various obstructions to finding examples with parametrically close UV and IR endpoints. Under reasonable assumptions, these obstructions include: unitarity, known bounds on the c central charge derived from associativity of the operator product expansion, and the central charge bounds of Hofman and Maldacena. On the other hand, for RG flows that break = 2 → = 1, it is possible to find IR fixed points that are parametrically close to the UV ones. In this case, we argue that if the UV SCFT possesses a single stress tensor, then such RG flows excite of order all the degrees of freedom of the UV theory. Furthermore, if the UV theory has some flavor symmetry, we argue that the UV central charges should not be too large relative to certain parameters in the theory.

  4. Swarm robotics and minimalism

    NASA Astrophysics Data System (ADS)

    Sharkey, Amanda J. C.

    2007-09-01

    Swarm Robotics (SR) is closely related to Swarm Intelligence, and both were initially inspired by studies of social insects. Their guiding principles are based on their biological inspiration and take the form of an emphasis on decentralized local control and communication. Earlier studies went a step further in emphasizing the use of simple reactive robots that only communicate indirectly through the environment. More recently SR studies have moved beyond these constraints to explore the use of non-reactive robots that communicate directly, and that can learn and represent their environment. There is no clear agreement in the literature about how far such extensions of the original principles could go. Should there be any limitations on the individual abilities of the robots used in SR studies? Should knowledge of the capabilities of social insects lead to constraints on the capabilities of individual robots in SR studies? There is a lack of explicit discussion of such questions, and researchers have adopted a variety of constraints for a variety of reasons. A simple taxonomy of swarm robotics is presented here with the aim of addressing and clarifying these questions. The taxonomy distinguishes subareas of SR based on the emphases and justifications for minimalism and individual simplicity.

  5. Spatial distribution of pipe collapses in Goodwin Creek Watershed, Mississippi

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Internal erosion of soil pipes can induce pipe collapses that affect soil erosion process and landform evolution. The objective of this study was to determine the spatial distribution of pipe collapses in agricultural fields of Goodwin Creek watershed. Ground survey was carried out to detect pipe co...

  6. PREVENTION OF PHOTORESIST PATTERN COLLAPSE BY USING LIQUID CARBON DIOXIDE

    EPA Science Inventory

    Photoresist polymers with small aspect ratios are presently cleaned with aqueous solutions. For small aspect ratios, the pattern collapses during the drying step. The origin of resist pattern collapse is the surface tension of the rinse liquid. Following a theoretic model, we pre...

  7. Can a collapse of global civilization be avoided?

    PubMed Central

    Ehrlich, Paul R.; Ehrlich, Anne H.

    2013-01-01

    Environmental problems have contributed to numerous collapses of civilizations in the past. Now, for the first time, a global collapse appears likely. Overpopulation, overconsumption by the rich and poor choices of technologies are major drivers; dramatic cultural change provides the main hope of averting calamity. PMID:23303549

  8. The Tacoma Narrows Bridge Collapse on Film and Video

    ERIC Educational Resources Information Center

    Olson, Don; Hook, Joseph; Doescher, Russell; Wolf, Steven

    2015-01-01

    This month marks the 75th anniversary of the Tacoma Narrows Bridge collapse. During a gale on Nov. 7, 1940, the bridge exhibited remarkable oscillations before collapsing spectacularly (Figs. 1-5). Physicists over the years have spent a great deal of time and energy studying this event. By using open-source analysis tools and digitized footage of…

  9. Maternal Postpartum Role Collapse as a Theory of Postpartum Depression

    ERIC Educational Resources Information Center

    Amankwaa, Linda Clark

    2005-01-01

    The purpose of this paper is to discuss the development of a theory of maternal postpartum role collapse. The influences of traditional role theory and symbolic interactionism are presented. The development of the maternal postpartum role collapse theory emerged from the study of postpartum depression among African-American women (Amankwaa, 2000).…

  10. Can a collapse of global civilization be avoided?

    PubMed

    Ehrlich, Paul R; Ehrlich, Anne H

    2013-03-01

    Environmental problems have contributed to numerous collapses of civilizations in the past. Now, for the first time, a global collapse appears likely. Overpopulation, overconsumption by the rich and poor choices of technologies are major drivers; dramatic cultural change provides the main hope of averting calamity. PMID:23303549

  11. Collapsing glomerulopathy associated with hepatitis B infection: A case report

    PubMed Central

    Mantan, M.; Grover, R.; Kaur, S.; Batra, V.

    2016-01-01

    Collapsing glomerulopathy has been classified as a variant of focal segmental glomerulosclerosis. It is associated with infections, inflammations, and certain medications. While its association with human immunodeficiency virus has been well established its occurrence with hepatitis B has not been reported. We present here a case of collapsing glomerulopathy in a child with hepatitis B infection. PMID:27512304

  12. 2. EMPIRE STATE MINE. VIEW OF COLLAPSED BUILDINGS AT MINE ...

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

    2. EMPIRE STATE MINE. VIEW OF COLLAPSED BUILDINGS AT MINE WITH TAILINGS ON RIGHT. CAMERA POINTED SOUTHWEST. COLLAPSED ADIT APPROXIMATELY 25 YARDS UPHILL TO THE LEFT OF FAR BUILDING. TIP TOP AND ONTARIO ARE LOCATED OUT OF THE PICTURE TO THE RIGHT. - Florida Mountain Mining Sites, Empire State Mine, West side of Florida Mountain, Silver City, Owyhee County, ID

  13. Rising catch variability preceded historical fisheries collapses in Alaska.

    PubMed

    Litzow, Michael A; Mueter, Franz J; Urban, J Daniel

    2013-09-01

    Statistical indicators such as rising variance and rising skewness in key system parameters may provide early warning of "regime shifts" in communities and populations. However, the utility of these indicators has rarely been tested in the large, complex ecosystems that are of most interest to managers. Crustacean fisheries in the Gulf of Alaska and Bering Sea experienced a series of collapses beginning in the 1970s, and we used spatially resolved catch data from these fisheries to test the predictions that increasing variability and skewness would precede stock collapse. Our data set consisted of catch data from 14 fisheries (12 collapsing and two non-collapsing), spanning 278 cumulative years. Our sampling unit for analysis was the Alaska Department of Fish and Game statistical reporting area (mean n for individual fisheries = 42 areas, range 7-81). We found that spatial variability in catches increased prior to stock collapse: a random-effects model estimating trend in variability across all 12 collapsing fisheries showed strong evidence of increasing variability prior to collapse. Individual trends in variability were statistically significant for only four of the 12 collapsing fisheries, suggesting that rising variability might be most effective as an indicator when information from multiple populations is available. Analyzing data across multiple fisheries allowed us to detect increasing variability 1-4 years prior to collapse, and trends in variability were significantly different for collapsing and non-collapsing fisheries. In spite of theoretical expectations, we found no evidence of pre-collapse increases in catch skewness. Further, while models generally predict that rising variability should be a transient phenomenon around collapse points, increased variability was a persistent feature of collapsed fisheries in our study. We conclude that this result is more consistent with fishing effects as the cause of increased catch variability, rather than the

  14. Solid-solid collapse transition in a two dimensional model molecular system

    NASA Astrophysics Data System (ADS)

    Singh, Rakesh S.; Bagchi, Biman

    2013-11-01

    Solid-solid collapse transition in open framework structures is ubiquitous in nature. The real difficulty in understanding detailed microscopic aspects of such transitions in molecular systems arises from the interplay between different energy and length scales involved in molecular systems, often mediated through a solvent. In this work we employ Monte-Carlo simulation to study the collapse transition in a model molecular system interacting via both isotropic as well as anisotropic interactions having different length and energy scales. The model we use is known as Mercedes-Benz (MB), which, for a specific set of parameters, sustains two solid phases: honeycomb and oblique. In order to study the temperature induced collapse transition, we start with a metastable honeycomb solid and induce transition by increasing temperature. High density oblique solid so formed has two characteristic length scales corresponding to isotropic and anisotropic parts of interaction potential. Contrary to the common belief and classical nucleation theory, interestingly, we find linear strip-like nucleating clusters having significantly different order and average coordination number than the bulk stable phase. In the early stage of growth, the cluster grows as a linear strip, followed by branched and ring-like strips. The geometry of growing cluster is a consequence of the delicate balance between two types of interactions, which enables the dominance of stabilizing energy over destabilizing surface energy. The nucleus of stable oblique phase is wetted by intermediate order particles, which minimizes the surface free energy. In the case of pressure induced transition at low temperature the collapsed state is a disordered solid. The disordered solid phase has diverse local quasi-stable structures along with oblique-solid like domains.

  15. Solid-solid collapse transition in a two dimensional model molecular system.

    PubMed

    Singh, Rakesh S; Bagchi, Biman

    2013-11-21

    Solid-solid collapse transition in open framework structures is ubiquitous in nature. The real difficulty in understanding detailed microscopic aspects of such transitions in molecular systems arises from the interplay between different energy and length scales involved in molecular systems, often mediated through a solvent. In this work we employ Monte-Carlo simulation to study the collapse transition in a model molecular system interacting via both isotropic as well as anisotropic interactions having different length and energy scales. The model we use is known as Mercedes-Benz (MB), which, for a specific set of parameters, sustains two solid phases: honeycomb and oblique. In order to study the temperature induced collapse transition, we start with a metastable honeycomb solid and induce transition by increasing temperature. High density oblique solid so formed has two characteristic length scales corresponding to isotropic and anisotropic parts of interaction potential. Contrary to the common belief and classical nucleation theory, interestingly, we find linear strip-like nucleating clusters having significantly different order and average coordination number than the bulk stable phase. In the early stage of growth, the cluster grows as a linear strip, followed by branched and ring-like strips. The geometry of growing cluster is a consequence of the delicate balance between two types of interactions, which enables the dominance of stabilizing energy over destabilizing surface energy. The nucleus of stable oblique phase is wetted by intermediate order particles, which minimizes the surface free energy. In the case of pressure induced transition at low temperature the collapsed state is a disordered solid. The disordered solid phase has diverse local quasi-stable structures along with oblique-solid like domains. PMID:24320339

  16. Energy ejection in the collapse of a cold spherical self-gravitating cloud

    NASA Astrophysics Data System (ADS)

    Joyce, M.; Marcos, B.; Sylos Labini, F.

    2009-08-01

    When an open system of classical point particles interacting by Newtonian gravity collapses and relaxes violently, an arbitrary amount of energy may, in principle, be carried away by particles which escape to infinity. We investigate here, using numerical simulations, how this released energy and other related quantities (notably the binding energy and size of the virialized structure) depend on the initial conditions, for the one-parameter family of starting configurations given by randomly distributing N cold particles in a spherical volume. Previous studies have established that the minimal size reached by the system scales approximately as N1/3, a behaviour which follows trivially when the growth of perturbations (which regularize the singularity of the cold collapse in the N -> ∞ limit) is assumed to be unaffected by the boundaries. Our study shows that the energy ejected grows approximately in proportion to N1/3, while the fraction of the initial mass ejected grows only very slowly with N, approximately logarithmically, in the range of N simulated. We examine in detail the mechanism of this mass and energy ejection, showing explicitly that it arises from the interplay of the growth of perturbations with the finite size of the system. A net lag of particles compared to their uniform spherical collapse trajectories develops first at the boundaries and then propagates into the volume during the collapse. Particles in the outer shells are then ejected as they scatter through the time-dependent potential of an already re-expanding central core. Using modified initial configurations, we explore the importance of fluctuations at different scales and discreteness (i.e. non-Vlasov) effects in the dynamics.

  17. Minimal Higgs inflation

    NASA Astrophysics Data System (ADS)

    Hamada, Yuta; Kawai, Hikaru; Oda, Kin-ya

    2014-02-01

    We consider a possibility that the Higgs field in the Standard Model (SM) serves as an inflaton when its value is around the Planck scale. We assume that the SM is valid up to an ultraviolet cutoff scale Λ , which is slightly below the Planck scale, and that the Higgs potential becomes almost flat above Λ . Contrary to the ordinary Higgs inflation scenario, we do not assume the huge non-minimal coupling, of O(10^4), of the Higgs field to the Ricci scalar. We find that Λ must be less than 5× 10^{17} {GeV} in order to explain the observed fluctuation of the cosmic microwave background, no matter how we extrapolate the Higgs potential above Λ . The scale 10^{17} {GeV} coincides with the perturbative string scale, which suggests that the SM is directly connected with string theory. For this to be true, the top quark mass is restricted to around 171 GeV, with which Λ can exceed 10^{17} {GeV}. As a concrete example of the potential above Λ , we propose a simple log-type potential. The predictions of this specific model for the e-foldings N_*=50-60 are consistent with the current observation, namely, the scalar spectral index is n_s=0.977hbox {-}0.983 and the tensor to scalar ratio 0

  18. General polytropic Larson-Penston-type collapses

    NASA Astrophysics Data System (ADS)

    Lou, Yu-Qing; Shi, Chun-Hui

    2014-12-01

    We investigate self-similar hydrodynamics of a general polytropic (GP) gas with spherical symmetry under self-gravity and extend the conventional polytropic (CP) relation n = 2 - γ for the self-similar index n and the polytropic index γ to a general relation n = 2(q + γ - 2)/(3q - 2), where q is a real parameter by specific entropy conservation along streamlines. We derive GP Larson-Penston (LP)-type solutions for q > 2/3 and γ > 4/3; Larson-Penston-Hunter (LPH)-type solutions are also constructed in a GP gas by a time-reversal operation on a GP-LP-type solution and by connecting to a GP free-fall-type solution across t = 0. These GP-LPH solutions describe dynamic processes that a GP gas globule, static and dense initially, undergoes a runaway collapse under self-gravity, forms a central mass singularity, and keeps accreting during a free-fall stage. We apply such GP-LPH-type solutions with variable envelope mass infall rates (EMIRs) for the dynamic evolution of globules and dense cores in star-forming molecular clouds. In particular, a GP-LPH-type solution can sustain an EMIR as low as 10-8 ˜ 10-6 M⊙ yr-1 or even lower - much lower than that of Shu's isothermal model for a cloud core in Class 0 and Class I phases. Such GP-LPH-type solutions with EMIRs as low as 10-9 ˜ 10-8 M⊙ yr-1 offer a sensible viable mechanism of forming brown dwarfs during the accretion stage in a collapsed GP globules with 1.495 ≤ γ ≤ 1.50 and 0.99 ≤ n ≤ 1.0. The GP-LPH solutions with 0.94 < n < 0.99 and 1.47 < γ < 1.495 can even give extremely low EMIRs of 10-12 ˜ 10-9 M⊙ yr-1 to form gaseous planet-type objects in mini gas globules.

  19. Seepage Model for PA Including Dift Collapse

    SciTech Connect

    G. Li; C. Tsang

    2000-12-20

    The purpose of this Analysis/Model Report (AMR) is to document the predictions and analysis performed using the Seepage Model for Performance Assessment (PA) and the Disturbed Drift Seepage Submodel for both the Topopah Spring middle nonlithophysal and lower lithophysal lithostratigraphic units at Yucca Mountain. These results will be used by PA to develop the probability distribution of water seepage into waste-emplacement drifts at Yucca Mountain, Nevada, as part of the evaluation of the long term performance of the potential repository. This AMR is in accordance with the ''Technical Work Plan for Unsaturated Zone (UZ) Flow and Transport Process Model Report'' (CRWMS M&O 2000 [153447]). This purpose is accomplished by performing numerical simulations with stochastic representations of hydrological properties, using the Seepage Model for PA, and evaluating the effects of an alternative drift geometry representing a partially collapsed drift using the Disturbed Drift Seepage Submodel. Seepage of water into waste-emplacement drifts is considered one of the principal factors having the greatest impact of long-term safety of the repository system (CRWMS M&O 2000 [153225], Table 4-1). This AMR supports the analysis and simulation that are used by PA to develop the probability distribution of water seepage into drift, and is therefore a model of primary (Level 1) importance (AP-3.15Q, ''Managing Technical Product Inputs''). The intended purpose of the Seepage Model for PA is to support: (1) PA; (2) Abstraction of Drift-Scale Seepage; and (3) Unsaturated Zone (UZ) Flow and Transport Process Model Report (PMR). Seepage into drifts is evaluated by applying numerical models with stochastic representations of hydrological properties and performing flow simulations with multiple realizations of the permeability field around the drift. The Seepage Model for PA uses the distribution of permeabilities derived from air injection testing in niches and in the cross drift to

  20. Management of advanced tracheal collapse in dogs using intraluminal self-expanding biliary wallstents.

    PubMed

    Moritz, Andreas; Schneider, Matthias; Bauer, Natali

    2004-01-01

    Twenty-four client-owned dogs with tracheal collapse refractory to conventional treatment underwent management with an intraluminal self-expanding stainless-steel endoprosthesis (Wallstent). Initial improvement of clinical signs was observed in 95.8% of the dogs. Two dogs (8.3%) died within a median interval of 6 days after stent implantation due to incorrect placement and size of the stent and emphysema, respectively. A dry cough occurred temporarily in most of the patients. One dog each (4.1%) suffered mild transient tracheal hemorrhage and pneumomediastinum. The results showed that the initial survival rate of intraluminal stabilization was comparable with surgical implantation of extratracheal prostheses. Clinical reevaluation was performed in 18 dogs within a median interval of 68 days after treatment. Of the dogs treated, 30.4% were reported to be asymptomatic after stent implantation, 60.9% improved markedly, and 4.3% remained symptomatic. In all patients undergoing endoscopy, the Wallstents were almost completely covered with tracheal epithelium. A median shortening of 27.3% of the endoprosthesis within a median interval of 175 days after stent implantation in 15 of 18 dogs was noted. The shortening was associated with clinical signs in 2 patients. In 5 dogs, steroid-responsive granuloma formation resulted in a severe reduction of the tracheal lumen in 3 patients. The results suggest that implantation of Wallstents was minimally invasive and provided stabilization of collapsed thoracic tracheal portions in addition to the cervical part of the trachea. This minimally invasive method for the management of severe tracheal collapse therefore provides an attractive alternative to surgery. PMID:14765729

  1. Characterization of granular collapse onto hard substrates by acoustic emissions

    NASA Astrophysics Data System (ADS)

    Farin, Maxime; Mangeney, Anne; Toussaint, Renaud; De Rosny, Julien

    2013-04-01

    Brittle deformation in granular porous media can generate gravitational instabilities such as debris flows and rock avalanches. These phenomena constitute a major natural hazard for the population in mountainous, volcanic and coastal areas but their direct observation on the field is very dangerous. Recent studies showed that gravitational instabilities can be detected and characterized (volume, duration,...) thanks to the seismic signal they generate. In an avalanche, individual block bouncing and rolling on the ground are expected to generated signals of higher frequencies than the main flow spreading. The identification of the time/frequency signature of individual blocks in the recorded signal remains however difficult. Laboratory experiments were conducted to investigate the acoustic signature of diverse simple sources corresponding to grains falling over thin plates of plexiglas and rock blocks. The elastic energy emitted by a single bouncing steel bead into the support was first quantitatively estimated and compared to the potential energy of fall and to the potential energy change during the shock. Next, we consider the collapse of granular columns made of steel spherical beads onto hard substrates. Initially, these columns were held by a magnetic field allowing to suppress suddenly the cohesion between the beads, and thus to minimize friction effects that would arise from side walls. We varied systematically the column volume, the column aspect ratio (height over length) and the grain size. This is shown to affect the signal envelope and frequency content. In the experiments, two types of acoustic sensors were used to record the signals in a wide frequency range: accelerometers (1 Hz to 56 kHz) and piezoelectric sensors (100 kHz to 1 MHz). The experiments were also monitored optically using fast cameras. We developed a technique to use quantitatively both types of sensors to evaluate the elastic energy emitted by the sources. Eventually, we looked at what

  2. Unstable equilibrium behaviour in collapsible tubes.

    PubMed

    Bertram, C D

    1986-01-01

    Thick-walled silicone rubber tube connected to rigid pipes upstream and downstream was externally pressurised (pe) to cause collapse while aqueous fluid flowed through propelled by a constant upstream head. Three types of equilibrium were found: stable equilibria (steady flow) at high downstream flow resistance R2, self-excited oscillations at low R2, and 'unattainable' (by varying external pressure) or exponentially unstable equilibria at intermediate R2. The self-excited oscillations were highly non-linear and appeared in four, apparently discrete, frequency bands: 2.7 Hz, 3.8-5.0 Hz, 12-16 Hz and 60-63 Hz, suggesting that the possible oscillation modes may be harmonically related. Stable, intermediate 'two-in-every-three-beats' oscillation was also observed, with a repetition frequency in the 3.8-5.0 Hz band. As pe was increased, self-excited oscillations were eventually suppressed, leaving internal fluid pressure varying with no single dominant frequency as a result of turbulent jet dissipation at the downstream rigid pipe connection. Comparison of pressure-wave velocity calculated from the local pressure-area relation for the tube with fluid velocity indicated that supercritical velocities were attained in the course of the self-excited oscillations. PMID:2936743

  3. Songlines from Direct Collapse Seed Black Holes

    NASA Astrophysics Data System (ADS)

    Aykutalp, Aycin; Wise, John; Spaans, Marco; Meijerink, Rowin

    2015-01-01

    In the last decade, the growth of supermassive black holes (SMBHs) has been intricately linked to galaxy formation and evolution, and is a key ingredient in the assembly of galaxies. Observations of SMBHs with masses of 109 solar at high redshifts (z~7) poses challenges to the theory of seed black hole formation and their growth in young galaxies. Fundamental to understanding their existence within the first billion years after the Big Bang, is the identification of their formation processes, growth rate and evolution through cosmic time. We perform cosmological hydrodynamic simulations following the growth of direct collapse seed black holes (DCBH) including X-ray irradiation from the central black hole, stellar feedback both from metal-free and metal-rich stars and H2 self-shielding. These simulations demonstrate that X-ray irradiation from the central black hole regulates its growth and influence the formation of stellar population in the host halo. In particular, X-ray radiation enhances H2 formation in metal-free gas and initially induces the star formation in the halo. However, in the long term, X-ray irradiation from the accreting seed DCBH stifles the initial growth relative to the Eddington rate argument. This further complicates the explanation for the existence of SMBHs in the early universe.

  4. Flux-driven simulations of turbulence collapse

    SciTech Connect

    Park, G. Y.; Kim, S. S.; Jhang, Hogun; Rhee, T.; Diamond, P. H.; Xu, X. Q.

    2015-03-15

    Using three-dimensional nonlinear simulations of tokamak turbulence, we show that an edge transport barrier (ETB) forms naturally once input power exceeds a threshold value. Profiles, turbulence-driven flows, and neoclassical coefficients are evolved self-consistently. A slow power ramp-up simulation shows that ETB transition is triggered by the turbulence-driven flows via an intermediate phase which involves coherent oscillation of turbulence intensity and E×B flow shear. A novel observation of the evolution is that the turbulence collapses and the ETB transition begins when R{sub T} > 1 at t = t{sub R} (R{sub T}: normalized Reynolds power), while the conventional transition criterion (ω{sub E×B}>γ{sub lin} where ω{sub E×B} denotes mean flow shear) is satisfied only after t = t{sub C} ( >t{sub R}), when the mean flow shear grows due to positive feedback.

  5. Rippling Instability of a Collapsing Bubble

    NASA Technical Reports Server (NTRS)

    daSilveira, Rava; Chaieb, Sahraoui; Mahadevan, L.

    1999-01-01

    The rippling instability of a liquid sheet was first observed by Debregeas, de Gennes, an Brochard-Wyart [Science 279, 1704 (1998)] on a hemispherical bubble resting on a free surface. Unlike a soap bubble, it collapses under its own weight while bursting, and folds into a wavy structure which breaks the original axisymmetry. In fact, this effect occurs for both purely elastic and purely viscous (liquid) sheets, and an analogy can be made between the two mechanisms. We present a theory for the onset of the instability in both cases, in which the growth of the corrugation out of an inextensible initial condition is governed by the competition between gravitational and bending (shearing) forces. The instability occurs for a range of densities, stiffnesses (viscosities), and sizes, a result which arises less from dynamics than from geometry, suggesting a wide validity. We further obtain a quantitative expression for the number of ripples. Finally, we present the results of experiments, which are consistent with our predictions.

  6. Collapsing avian community on a Hawaiian island.

    PubMed

    Paxton, Eben H; Camp, Richard J; Gorresen, P Marcos; Crampton, Lisa H; Leonard, David L; VanderWerf, Eric A

    2016-09-01

    The viability of many species has been jeopardized by numerous negative factors over the centuries, but climate change is predicted to accelerate and increase the pressure of many of these threats, leading to extinctions. The Hawaiian honeycreepers, famous for their spectacular adaptive radiation, are predicted to experience negative responses to climate change, given their susceptibility to introduced disease, the strong linkage of disease distribution to climatic conditions, and their current distribution. We document the rapid collapse of the native avifauna on the island of Kaua'i that corresponds to changes in climate and disease prevalence. Although multiple factors may be pressuring the community, we suggest that a tipping point has been crossed in which temperatures in forest habitats at high elevations have reached a threshold that facilitates the development of avian malaria and its vector throughout these species' ranges. Continued incursion of invasive weeds and non-native avian competitors may be facilitated by climate change and could also contribute to declines. If current rates of decline continue, we predict multiple extinctions in the coming decades. Kaua'i represents an early warning for the forest bird communities on the Maui and Hawai'i islands, as well as other species around the world that are trapped within a climatic space that is rapidly disappearing. PMID:27617287

  7. Colony Collapse Disorder: A Descriptive Study

    PubMed Central

    vanEngelsdorp, Dennis; Evans, Jay D.; Saegerman, Claude; Mullin, Chris; Haubruge, Eric; Nguyen, Bach Kim; Frazier, Maryann; Frazier, Jim; Cox-Foster, Diana; Chen, Yanping; Underwood, Robyn; Tarpy, David R.; Pettis, Jeffery S.

    2009-01-01

    Background Over the last two winters, there have been large-scale, unexplained losses of managed honey bee (Apis mellifera L.) colonies in the United States. In the absence of a known cause, this syndrome was named Colony Collapse Disorder (CCD) because the main trait was a rapid loss of adult worker bees. We initiated a descriptive epizootiological study in order to better characterize CCD and compare risk factor exposure between populations afflicted by and not afflicted by CCD. Methods and Principal Findings Of 61 quantified variables (including adult bee physiology, pathogen loads, and pesticide levels), no single measure emerged as a most-likely cause of CCD. Bees in CCD colonies had higher pathogen loads and were co-infected with a greater number of pathogens than control populations, suggesting either an increased exposure to pathogens or a reduced resistance of bees toward pathogens. Levels of the synthetic acaricide coumaphos (used by beekeepers to control the parasitic mite Varroa destructor) were higher in control colonies than CCD-affected colonies. Conclusions/Significance This is the first comprehensive survey of CCD-affected bee populations that suggests CCD involves an interaction between pathogens and other stress factors. We present evidence that this condition is contagious or the result of exposure to a common risk factor. Potentially important areas for future hypothesis-driven research, including the possible legacy effect of mite parasitism and the role of honey bee resistance to pesticides, are highlighted. PMID:19649264

  8. Pseudospectral method for gravitational wave collapse

    NASA Astrophysics Data System (ADS)

    Hilditch, David; Weyhausen, Andreas; Brügmann, Bernd

    2016-03-01

    We present a new pseudospectral code, bamps, for numerical relativity written with the evolution of collapsing gravitational waves in mind. We employ the first-order generalized harmonic gauge formulation. The relevant theory is reviewed, and the numerical method is critically examined and specialized for the task at hand. In particular, we investigate formulation parameters—gauge- and constraint-preserving boundary conditions well suited to nonvanishing gauge source functions. Different types of axisymmetric twist-free moment-of-time-symmetry gravitational wave initial data are discussed. A treatment of the axisymmetric apparent horizon condition is presented with careful attention to regularity on axis. Our apparent horizon finder is then evaluated in a number of test cases. Moving on to evolutions, we investigate modifications to the generalized harmonic gauge constraint damping scheme to improve conservation in the strong-field regime. We demonstrate strong-scaling of our pseudospectral penalty code. We employ the Cartoon method to efficiently evolve axisymmetric data in our 3 +1 -dimensional code. We perform test evolutions of the Schwarzschild spacetime perturbed by gravitational waves and by gauge pulses, both to demonstrate the use of our black-hole excision scheme and for comparison with earlier results. Finally, numerical evolutions of supercritical Brill waves are presented to demonstrate durability of the excision scheme for the dynamical formation of a black hole.

  9. Collapsing avian community on a Hawaiian island

    PubMed Central

    Paxton, Eben H.; Camp, Richard J.; Gorresen, P. Marcos; Crampton, Lisa H.; Leonard, David L.; VanderWerf, Eric A.

    2016-01-01

    The viability of many species has been jeopardized by numerous negative factors over the centuries, but climate change is predicted to accelerate and increase the pressure of many of these threats, leading to extinctions. The Hawaiian honeycreepers, famous for their spectacular adaptive radiation, are predicted to experience negative responses to climate change, given their susceptibility to introduced disease, the strong linkage of disease distribution to climatic conditions, and their current distribution. We document the rapid collapse of the native avifauna on the island of Kaua‘i that corresponds to changes in climate and disease prevalence. Although multiple factors may be pressuring the community, we suggest that a tipping point has been crossed in which temperatures in forest habitats at high elevations have reached a threshold that facilitates the development of avian malaria and its vector throughout these species’ ranges. Continued incursion of invasive weeds and non-native avian competitors may be facilitated by climate change and could also contribute to declines. If current rates of decline continue, we predict multiple extinctions in the coming decades. Kaua‘i represents an early warning for the forest bird communities on the Maui and Hawai‘i islands, as well as other species around the world that are trapped within a climatic space that is rapidly disappearing. PMID:27617287

  10. Tourism's collapse puts Gambian women at risk.

    PubMed

    Coker, M S

    1995-06-01

    Despite efforts of the Gambian government, which established a ministry in 1981 that would tackle gender issues, improve women's health, and promote empowerment, women are underrepresented in government and business, and 84% are illiterate. Child mortality is among the highest in Africa; 134 children per 1000 die before their fifth birthday. In the mid-1980s austerity measures adopted by the World Bank and IMF left the ministry without funds. Rice and vegetable production, the main source of income for women, fell in the 1990s. In 1994, paddy production dropped 23% from the previous year; this was due to a lack of technical and financial assistance. The collapse of tourism with Capt. Yahya Jammeh's seizure of power has put prostitutes catering to tourists out of work, but women who have lost jobs in the hotel industry may be pushed into local prostitution to survive. The impact of this on the HIV/AIDS epidemic is unclear. Although Gambia is one of the world's most aid-dependent countries (more than a quarter of the GNP before the coup), corruption and mismanagement in the nongovernmental sector is widespread. The director of the Women in Development Programme, a $15m World Bank project, was forced to resign over allegations of fraud. The political process sidelines women; only village chiefs, who are traditionally men, are allowed to vote when new heads are elected. PMID:12289043

  11. Tulsa Oklahoma Oktoberfest Tent Collapse Report

    PubMed Central

    Deal, Kelly E.; Synovitz, Carolyn K.; Goodloe, Jeffrey M.; King, Brandi; Stewart, Charles E.

    2012-01-01

    Background. On October 17, 2007, a severe weather event collapsed two large tents and several smaller tents causing 23 injuries requiring evacuation to emergency departments in Tulsa, OK. Methods. This paper is a retrospective analysis of the regional health system's response to this event. Data from the Tulsa Fire Department, The Emergency Medical Services Authority (EMSA), receiving hospitals and coordinating services were reviewed and analyzed. EMS patient care reports were reviewed and analyzed using triage designators assigned in the field, injury severity scores, and critical mortality. Results. EMT's and paramedics from Tulsa Fire Department and EMSA provided care at the scene under unified incident command. Of the 23 patients transported by EMS, four were hospitalized, one with critical spinal injury and one with critical head injury. One patient is still in ongoing rehabilitation. Discussion. Analysis of the 2007 Tulsa Oktoberfest mass casualty incident revealed rapid police/fire/EMS response despite challenges of operations at dark under severe weather conditions and the need to treat a significant number of injured victims. There were no fatalities. Of the patients transported by EMS, a minority sustained critical injuries, with most sustaining injuries amenable to discharge after emergency department care. PMID:22649732

  12. Numerical simulation of a collapsing bubble subject to gravity

    NASA Astrophysics Data System (ADS)

    Koukouvinis, P.; Gavaises, M.; Supponen, O.; Farhat, M.

    2016-03-01

    The present paper focuses on the simulation of the expansion and aspherical collapse of a laser-generated bubble subjected to an acceleration field and comparison of the results with instances from high-speed videos. The interaction of the liquid and gas is handled with the volume of fluid method. Compressibility effects have been included for each phase to predict the propagation of pressure waves. Initial conditions were estimated through the Rayleigh Plesset equation, based on the maximum bubble size and collapse time. The simulation predictions indicate that during the expansion the bubble shape is very close to spherical. On the other hand, during the collapse the bubble point closest to the bottom of the container develops a slightly higher collapse velocity than the rest of the bubble surface. Over time, this causes momentum focusing and leads to a positive feedback mechanism that amplifies the collapse locally. At the latest collapse stages, a jet is formed at the axis of symmetry, with opposite direction to the acceleration vector, reaching velocities of even 300 m/s. The simulation results agree with the observed bubble evolution and pattern from the experiments, obtained using high speed imaging, showing the collapse mechanism in great detail and clarity.

  13. Void collapse under distributed dynamic loading near material interfaces

    NASA Astrophysics Data System (ADS)

    Shpuntova, Galina; Austin, Joanna

    2012-11-01

    Collapsing voids cause significant damage in diverse applications from biomedicine to underwater propulsion to explosives. While shock-induced void collapse has been studied extensively, less attention has been devoted to stress wave loading, which will occur instead if there are mechanisms for wave attenuation or if the impact velocity is relatively low. A set of dynamic experiments was carried out in a model experimental setup to investigate the effect of acoustic heterogeneities in the surrounding medium on void collapse. Two tissue-surrogate polymer materials of varying acoustic properties were used to create flowfield geometries involving a boundary and a void. A stress wave, generated by projectile impact, triggered void collapse in the gelatinous polymer medium. When the length scales of features in the flow field were on the same order of magnitude as the stress wave length scale, the presence of the boundary was found to affect the void collapse process relative to collapse in the absence of a boundary. This effect was quantified for a range of geometries and impact conditions using a two-color, single-frame particle image velocimetry technique. Research supported by NSF Award #0954769, ``CAREER: Dynamics and damage of void collapse in biological materials under stress wave loading'' with Prof. Henning Winter as Program Manager.

  14. Unexpected collapses during isotropic consolidation of model granular materials

    NASA Astrophysics Data System (ADS)

    Doanh, Thiep; Le Bot, Alain; Abdelmoula, Nouha; Gribaa, Lassad; Hans, Stéphane; Boutin, Claude

    2016-02-01

    This paper reports the unexpected instantaneous instabilities of idealized granular materials under simple isotropic drained compression. Specimens of monosized glass beads submitted to isotropic compression exhibit a series of local collapses under undetermined external stress with partial liquefaction, experience sudden volumetric compaction and axial contraction of various amplitude. Short-lived excess pore water pressure vibrates like an oscillating underdamped system in the first dynamic transient phase and rapidly disperses in the subsequent longer dissipation phase. However, very dense samples maintain a collapse-free behaviour below a threshold void ratio e30col at 30 kPa of stress. The potential mechanisms that could explain these spontaneous collapses are discussed.

  15. Particle creation in (2+1) circular dust collapse

    SciTech Connect

    Gutti, Sashideep; Singh, T. P.

    2007-09-15

    We investigate the quantum particle creation during the circularly symmetric collapse of a 2+1 dust cloud, for the cases when the cosmological constant is either zero or negative. We derive the Ford-Parker formula for the 2+1 case, which can be used to compute the radiated quantum flux in the geometric optics approximation. It is shown that no particles are created when the collapse ends in a naked singularity, unlike in the 3+1 case. When the collapse ends in a Banados-Teitelboim-Zanelli black hole, we recover the expected Hawking radiation.

  16. Hamiltonian treatment of the gravitational collapse of thin shells

    NASA Astrophysics Data System (ADS)

    Crisóstomo, Juan; Olea, Rodrigo

    2004-05-01

    A Hamiltonian treatment of the gravitational collapse of thin shells is presented. The direct integration of the canonical constraints reproduces the standard shell dynamics for a number of known cases. The formalism is applied in detail to three-dimensional spacetime and the properties of the (2+1)-dimensional charged black hole collapse are further elucidated. The procedure is also extended to deal with rotating solutions in three dimensions. The general form of the equations providing the shell dynamics implies the stability of black holes, as they cannot be converted into naked singularities by any shell collapse process.

  17. Dissipative gravitational collapse of an (an)isotropic star

    NASA Astrophysics Data System (ADS)

    Das, Shyam; Sharma, Ranjan; Paul, Bikash Chandra; Deb, Rumi

    2016-03-01

    We develop a framework to study the effects of pressure anisotropy on the evolution of a collapsing star dissipating energy in the form of radial heat flux. In this construction, the star begins its collapse from an initial static configuration described by Paul and Deb (Astrophys. Space Sci. 354:421, 2014) solution in the presence (or absence) of anisotropic stresses. The form of the initial static solution, which is a generalization of Pant and Sah (Phys. Rev. D 32:1538, 1985) model, complies with all the requirements of a realistic star and provides a simple method to analyze the impacts of anisotropy onto the collapse.

  18. A new model for submarine volcanic collapse formation

    NASA Astrophysics Data System (ADS)

    Engels, Jennifer L.; Edwards, Margo H.; Fornari, Daniel J.; Perfit, Michael R.; Cann, Johnson R.

    2003-09-01

    Collapse pits and an associated suite of collapse-related features that form in submarine lava flows are ubiquitous on the global mid-ocean ridge crest. Collapse pits, the lava tube systems they expose, and lenses of talus created by the collapse process combine to produce a permeable region in the shallow ocean crust and are thought to contribute significantly to the 100-300 m thick low velocity zone observed at intermediate to fast-spreading mid-ocean ridges. This horizon of low-density, high-porosity material is likely to be an important aquifer for the transfer of hydrothermal fluids in the upper ocean crust. In a recent survey of the East Pacific Rise at 9°37'N, we used photographs, video and observations from the submersible Alvin, and DSL-120A side scan data to determine that 13% of the 720,000 m2 of seafloor imaged had foundered to form collapse pits. In 98% of the images collapse pits occurred in lobate flows, and the rest in sheet flows. On the basis of our observations and analyses of collapse features, and incorporating data from previous models for collapse formation plus laboratory and theoretical models of basalt lava behavior in the deep ocean, we develop a detailed multistage physical model for collapse formation in the deep ocean. In our model, lava extruded on the seafloor traps pockets of seawater beneath the flow that are instantly vaporized to a briny steam. The seawater is transformed to vapor at temperatures above 480°C with a 20 times expansion in volume. Bubbles of vapor rise through the lava and concentrate below the chilled upper crust of the lava flow, creating gas-filled cavities at magmatic temperatures. Fluid lava from the cavity roofs drips into the vapor pockets to create delicate drip and septa structures, a process that may be enhanced by water vapor diffusing into the magma and reducing its melting point. As the vapor pocket cools, the pressure within it drops, causing a pressure gradient to develop across the upper crust. The

  19. Use of ultrasonography in the diagnosis of tracheal collapse.

    PubMed

    Rudorf, H; Herrtage, M E; White, R A

    1997-11-01

    Ultrasonographic imaging of the cervical trachea was performed with the neck in both a neutral and a hyperextended position in 10 dogs with tracheal collapse. Tracheoscopy was used to confirm a diagnosis of tracheal collapse. The ultrasound investigation was repeated in 10 dogs of similar size but without tracheal abnormality. The ultrasonographic findings of the affected dogs were compared with those of the normal group and showed an alteration in the shape of the tracheal lumen in the ventrodorsal projection. This study highlights the possibility of identifying changes in the shape of the tracheal lumen during ultrasound investigations as an aid to the diagnosis of tracheal collapse. PMID:9403811

  20. Bohmian mechanics, collapse models and the emergence of classicality

    NASA Astrophysics Data System (ADS)

    Toroš, Marko; Donadi, Sandro; Bassi, Angelo

    2016-09-01

    We discuss the emergence of classical trajectories in Bohmian mechanics, when a macroscopic object interacts with an external environment. We show that in such a case the conditional wave function of the system follows a dynamics which, under reasonable assumptions, corresponds to that of the Ghirardi–Rimini–Weber (GRW) collapse model. As a consequence, Bohmian trajectories evolve classically. Our analysis also shows how the GRW (istantaneous) collapse process can be derived by an underlying continuous interaction of a quantum system with an external agent, thus throwing a light on how collapses can emerge from a deeper level theory.

  1. The Genesis and Collapse of Third Millennium North Mesopotamian Civilization

    NASA Astrophysics Data System (ADS)

    Weiss, H.; Courty, M.-A.; Wetterstrom, W.; Guichard, F.; Senior, L.; Meadow, R.; Curnow, A.

    1993-08-01

    Archaeological and soil-stratigraphic data define the origin, growth, and collapse of Subir, the third millennium rain-fed agriculture civilization of northern Mesopotamia on the Habur Plains of Syria. At 2200 B.C., a marked increase in aridity and wind circulation, subsequent to a volcanic eruption, induced a considerable degradation of land-use conditions. After four centuries of urban life, this abrupt climatic change evidently caused abandonment of Tell Leilan, regional desertion, and collapse of the Akkadian empire based in southern Mesopotamia. Synchronous collapse in adjacent regions suggests that the impact of the abrupt climatic change was extensive.

  2. Compact objects from gravitational collapse: an analytical toy model

    NASA Astrophysics Data System (ADS)

    Malafarina, Daniele; Joshi, Pankaj S.

    2015-12-01

    We develop here a procedure to obtain regular static configurations resulting from dynamical gravitational collapse of a massive matter cloud in general relativity. Under certain general physical assumptions for the collapsing cloud, we find the class of dynamical models that lead to an equilibrium configuration. To illustrate this, we provide a class of perfect fluid collapse models that lead to a static constant density object as limit. We suggest that similar models might possibly constitute the basis for the description of formation of compact objects in nature.

  3. Catastrophic Ecosystem Collapse in Pleistocene Australia

    NASA Astrophysics Data System (ADS)

    Miller, G. H.; Fogel, M.; Magee, J. W.; Gagan, M.

    2002-12-01

    Extinction of the Australian megafauna (50ñ5ka) occurred shortly after human colonization (55ñ5ka). A link between the two has been suggested, including the possibility that landscape modification was influential, but pinpointing the role of humans remains elusive. To evaluate changes at the ecosystem level across the extinction event we utilize dietary information recorded by d13C preserved in eggshells of the extant emu (Dromaius novaehollandiae), a large flightless bird. Emus are opportunistic feeders; their diet reflects the range of food sources available in the weeks before nesting (June). d13C quantifies the proportion of C3 vs C4 vegetation that constitutes the emu's diet. A 150,000-year record of emu dietary intact has been reconstructed using more than 300 individuals from Lake Eyre (south-central Australia) dated by 14C, luminescence and/or racemization. Prior to 50 ka emu diet was highly variable, ranging from 100% C3 to 100% C4. However, immediately after 50 ka, emu diet shifted dramatically: the C4 contribution never exceeded 50% (n=200) after 50 ka, whereas more than half the samples older than 50 ka old contain >50% C4 dietary sources. We attribute the observed changes in emu diet to a fundamental rearrangement of the plant ecosystems in semi-arid central Australia. Such a change in plant communities may have contributed to the extinction of many dependent herbivores. The coincidence in time of megafauna extinction and ecosystem collapse shortly after human colonization suggests there may be a causal link. Development of similar records of vegetation change for other regions of Australia are currently underway to evaluate whether the Lake Eyre record reflects a continental scale reorganization of the Australian biota.

  4. SEEPAGE MODEL FOR PA INCLUDING DRIFT COLLAPSE

    SciTech Connect

    C. Tsang

    2004-09-22

    The purpose of this report is to document the predictions and analyses performed using the seepage model for performance assessment (SMPA) for both the Topopah Spring middle nonlithophysal (Tptpmn) and lower lithophysal (Tptpll) lithostratigraphic units at Yucca Mountain, Nevada. Look-up tables of seepage flow rates into a drift (and their uncertainty) are generated by performing numerical simulations with the seepage model for many combinations of the three most important seepage-relevant parameters: the fracture permeability, the capillary-strength parameter 1/a, and the percolation flux. The percolation flux values chosen take into account flow focusing effects, which are evaluated based on a flow-focusing model. Moreover, multiple realizations of the underlying stochastic permeability field are conducted. Selected sensitivity studies are performed, including the effects of an alternative drift geometry representing a partially collapsed drift from an independent drift-degradation analysis (BSC 2004 [DIRS 166107]). The intended purpose of the seepage model is to provide results of drift-scale seepage rates under a series of parameters and scenarios in support of the Total System Performance Assessment for License Application (TSPA-LA). The SMPA is intended for the evaluation of drift-scale seepage rates under the full range of parameter values for three parameters found to be key (fracture permeability, the van Genuchten 1/a parameter, and percolation flux) and drift degradation shape scenarios in support of the TSPA-LA during the period of compliance for postclosure performance [Technical Work Plan for: Performance Assessment Unsaturated Zone (BSC 2002 [DIRS 160819], Section I-4-2-1)]. The flow-focusing model in the Topopah Spring welded (TSw) unit is intended to provide an estimate of flow focusing factors (FFFs) that (1) bridge the gap between the mountain-scale and drift-scale models, and (2) account for variability in local percolation flux due to

  5. Influenza SIRS with Minimal Pneumonitis

    PubMed Central

    Erramilli, Shruti; Mannam, Praveen; Manthous, Constantine A.

    2016-01-01

    Although systemic inflammatory response syndrome (SIRS) is a known complication of severe influenza pneumonia, it has been reported very rarely in patients with minimal parenchymal lung disease. We here report a case of severe SIRS, anasarca, and marked vascular phenomena with minimal or no pneumonitis. This case highlights that viruses, including influenza, may cause vascular dysregulation causing SIRS, even without substantial visceral organ involvement.

  6. Guidelines for mixed waste minimization

    SciTech Connect

    Owens, C.

    1992-02-01

    Currently, there is no commercial mixed waste disposal available in the United States. Storage and treatment for commercial mixed waste is limited. Host States and compacts region officials are encouraging their mixed waste generators to minimize their mixed wastes because of management limitations. This document provides a guide to mixed waste minimization.

  7. Waste minimization handbook, Volume 1

    SciTech Connect

    Boing, L.E.; Coffey, M.J.

    1995-12-01

    This technical guide presents various methods used by industry to minimize low-level radioactive waste (LLW) generated during decommissioning and decontamination (D and D) activities. Such activities generate significant amounts of LLW during their operations. Waste minimization refers to any measure, procedure, or technique that reduces the amount of waste generated during a specific operation or project. Preventive waste minimization techniques implemented when a project is initiated can significantly reduce waste. Techniques implemented during decontamination activities reduce the cost of decommissioning. The application of waste minimization techniques is not limited to D and D activities; it is also useful during any phase of a facility`s life cycle. This compendium will be supplemented with a second volume of abstracts of hundreds of papers related to minimizing low-level nuclear waste. This second volume is expected to be released in late 1996.

  8. MHD Simulations of Core Collapse Supernovae with Cosmos++

    NASA Astrophysics Data System (ADS)

    Akiyama, Shizuka; Salmonson, Jay

    2010-10-01

    We performed 2D, axisymmetric, MHD simulations with Cosmos++ in order to examine the growth of the magnetorotational instability (MRI) in core-collapse supernovae. We have initialized a non-rotating 15 Msolar progenitor, infused with differential rotation and poloidal magnetic fields. The collapse of the iron core is simulated with the Shen EOS, and the parametric Ye and entropy evolution. The wavelength of the unstable mode in the post-collapse environment is expected to be only ~200 m. In order to achieve the fine spatial resolution requirement, we employed remapping technique after the iron core has collapsed and bounced. The MRI unstable region appears near the equator and angular momentum and entropy are transported outward. Higher resolution remap run display more vigorous overturns and stronger transport of angular momentum and entropy. Our results are in agreement with the earlier work by Akiyama et al. [1] and Obergaulinger et al. [2].

  9. 3. View of collapsed structure (type A) next to type ...

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

    3. View of collapsed structure (type A) next to type B structure, facing east-northeast - Nevada Test Site, Japanese Village, Area 4, Yucca Flat, 4-04 Road near Rainier Mesa Road, Mercury, Nye County, NV

  10. Instability of black hole formation in gravitational collapse

    SciTech Connect

    Joshi, Pankaj S.; Malafarina, Daniele

    2011-01-15

    We consider here the classic scenario given by Oppenheimer, Snyder, and Datt, for the gravitational collapse of a massive matter cloud, and examine its stability under the introduction of small tangential stresses. We show, by offering an explicit class of physically valid tangential stress perturbations, that an introduction of tangential pressure, however small, can qualitatively change the final fate of collapse from a black hole final state to a naked singularity. This shows instability of black hole formation in collapse and sheds important light on the nature of cosmic censorship hypothesis and its possible formulations. The key effect of these perturbations is to alter the trapped surface formation pattern within the collapsing cloud and the apparent horizon structure. This allows the singularity to be visible, and implications are discussed.

  11. 3. UPPER NOTTINGHAM MINE, COLLAPSED ADIT. CAMERA IS POINTED EAST. ...

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

    3. UPPER NOTTINGHAM MINE, COLLAPSED ADIT. CAMERA IS POINTED EAST. - Florida Mountain Mining Sites, Upper Nottingham Mine, West face of Florida Mountain, head of Jacobs Gulch, Silver City, Owyhee County, ID

  12. 9. South abutment, detail of collapsed east wing wall; also ...

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

    9. South abutment, detail of collapsed east wing wall; also detail of bottom lateral bracing and stringers; looking southeast - Dodd Ford Bridge, County Road 147 Spanning Blue Earth River, Amboy, Blue Earth County, MN

  13. Deep ocean early warning signals of an Atlantic MOC collapse

    NASA Astrophysics Data System (ADS)

    Feng, Qing Yi; Viebahn, Jan P.; Dijkstra, Henk A.

    2014-08-01

    A future collapse of the Atlantic Meridional Overturning Circulation (MOC) has been identified as one of the most dangerous tipping points in the climate system. It is therefore crucial to develop early warning indicators for such a potential collapse based on relatively short time series. So far, attempts to use indicators based on critical slowdown have been marginally successful. Based on complex climate network reconstruction, we here present a promising new indicator for the MOC collapse that efficiently monitors spatial changes in deep ocean circulation. Through our analysis of the performance of this indicator, we formulate optimal locations of measurement of the MOC to provide early warning signals of a collapse. Our results imply that an increase in spatial resolution of the Atlantic MOC observations (i.e., at more sections) can improve early detection, because the spatial coherence in the deep ocean arising near the transition is better captured.

  14. 28. Rear lot of the Adelman Block. The collapsed truss ...

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

    28. Rear lot of the Adelman Block. The collapsed truss roof (ca. 1932) originally sheltered an automobile sales garage - Lockport Historic District, Bounded by Eighth, Hamilton & Eleventh Streets & Illinois & Michigan Canal, Lockport, Will County, IL

  15. 5. TIP TOP MINE. EAST SIDE OF STRUCTURE WITH COLLAPSED ...

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

    5. TIP TOP MINE. EAST SIDE OF STRUCTURE WITH COLLAPSED ADIT. CAMERA POINTED WEST. - Florida Mountain Mining Sites, Tip Top Mine, West face Florida Mountain, approximately 150 feet below summit, Silver City, Owyhee County, ID

  16. Spherical collapse and halo mass function in the symmetron model

    NASA Astrophysics Data System (ADS)

    Taddei, Laura; Catena, Riccardo; Pietroni, Massimo

    2014-01-01

    We study the gravitational clustering of spherically symmetric overdensities and the statistics of the resulting dark matter halos in the "symmetron model," in which a new long range force is mediated by a Z2 symmetric scalar field. Depending on the initial radius of the overdensity, we identify two distinct regimes: for small initial radii the symmetron mediated force affects the spherical collapse at all redshifts; for initial radii larger than some critical size this force vanishes before collapse because of the symmetron screening mechanism. As a consequence, halos with initial radii smaller than some critical value collapse earlier than in the ΛCDM and statistically tend to form more massive dark matter halos. Regarding the halo mass function of these objects, we observe departures from standard ΛCDM predictions at the few percent level. The formalism developed here can be easily applied to other models where fifth forces participate to the dynamics of the gravitational collapse.

  17. Critical fitness collapse in three-dimensional spatial population genetics

    NASA Astrophysics Data System (ADS)

    Lavrentovich, Maxim O.

    2015-05-01

    If deleterious mutations near a fitness maximum in a spatially distributed population are sufficiently frequent or detrimental, the population can undergo a fitness collapse, similarly to the Muller's ratchet effect in well-mixed populations. Recent studies of 1D habitats (e.g. the frontier of a 2D range expansion) have shown that the onset of the fitness collapse is described by a directed percolation phase transition with its associated critical exponents. We consider population fitness collapse in 3D range expansions with both inflating and fixed-size frontiers (applicable to, e.g. expanding and treadmilling spherical tumors, respectively). We find that the onset of fitness collapse in these two cases obeys different scaling laws, and that competition between species at the frontier leads to a deviation from directed percolation scaling. As in 2D range expansions, inflating frontiers modify the critical behavior by causally disconnecting well-separated portions of the population.

  18. Battery Weymouth Combined Observation Station ruin, collapsed; view to west ...

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

    Battery Weymouth Combined Observation Station ruin, collapsed; view to west - Fort McKinley, Battery Weymouth Combined Observation Station, West side of East Side Drive, approximately 125 feet south of Weymouth Way, Great Diamond Island, Portland, Cumberland County, ME

  19. Battery Carpenter Observation Station, collapsed ruin showing south wall; view ...

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

    Battery Carpenter Observation Station, collapsed ruin showing south wall; view northeast - Fort McKinley, Battery Carpenter Observation Station, West side of East Side Drive, approximately 275 feet south of Weymouth Way, Great Diamond Island, Portland, Cumberland County, ME

  20. BRIDGE ABUTMENTS WITH ARCH SEGMENTS ON RIVER BOTTOM. ARCHES COLLAPSED ...

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

    BRIDGE ABUTMENTS WITH ARCH SEGMENTS ON RIVER BOTTOM. ARCHES COLLAPSED AROUND EIGHT YEARS BEFORE THIS DATE. - Whittlesey Road Bridge, Spanning Black River at Whittlesey Road, Lyons Falls, Lewis County, NY

  1. 31. VIEW OF COLLAPSED APRON OF BRIDGE NO. 10 AND ...

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

    31. VIEW OF COLLAPSED APRON OF BRIDGE NO. 10 AND ELEMENTS OF SUSPENSION STRUCTURE. LOOKING SOUTH. - Greenville Yard, Transfer Bridge System, Port of New York/New Jersey, Upper New York Bay, Jersey City, Hudson County, NJ

  2. Thermal Design of a Collapsible Cryogenic Vessel

    NASA Technical Reports Server (NTRS)

    Hegab, Hisham E.

    2001-01-01

    Strategic planning for human exploration missions to Mars has conclusively identified in-situ resource utilization (ISRU) as an enabling technology. Most mission scenarios include an ISRU plant to produce propellants for ascent from Mars as well as the production of backup reserves of water, oxygen, and process gases. Current mission scenarios call for an ISRU plant to be deployed and then produce and store the required propellants and life support reserves before the arrival of the first human mission. Reliable cryogenic propellant liquefaction and storage technologies for extended period missions are especially critical. This report examines the cryogenic storage problem for liquid oxygen produced by an ISRU plant for a human mission scenario. The analysis examines various hardware configurations including insulation types, packaging techniques, and required cryocoolers to minimize the initial launch mass to low Earth orbit. Results of the analyses indicate that high vacuum insulation systems requiring vacuum pressures below one millitorr will be required to minimize the 'initial launch mass into low Earth orbit even though the temperature on the surface of Mars is much lower than Earth.

  3. Can plumes collapse?: Experimental results and applications to Iceland.

    NASA Astrophysics Data System (ADS)

    Pears, M.; Lithgow-Bertelloni, C.

    2012-04-01

    Iceland has produced magma in a series of episodic events. From lava chemistry it has been inferred that the plume temperature decreased over the first 5 Myr by ~50°C and for the next 3 Myr following continental break up it continued to oscillate by ~25°C. Such data has been used to infer possible episodic collapse of the Iceland plume. Collapsing plumes are not common fluid dynamical features. In thermochemical plumes it is possible to achieve collapse by varying the relative buoyancy due to chemistry and due to temperature. In thermal plumes however, with a constant heat source we would expect plumes not to collapse but to not continue to rise after reaching a point of neutral buoyancy. We expect thermal plumes, like those Earth's bottom thermal boundary layer is capable of producing, to either rise to the surface or be deflected but not to collapse. We have designed an experimental setup to investigate the conditions that may lead to collapse in thermal plumes with constant heat sources. We used high-Prandtl number fluids with strongly temperature-dependent viscosities (Lyle Golden syrup and Liquidose 436) as analogues to Earth's high viscosity mantle in a cubic Plexiglas tank (26.5cm inner sides), heated by a circular 2cm diameter heater (flat with the base of the tank). We explored ΔTs between 3-60°C. The flow was visualized with shadowgraphs and an automated -3D Stereoscopic Particle Image Velocimetry (SPIV) system to measure velocities. In Lyle's Golden Syrup collapse occurred at ΔTs as high as 8°C, while in Liquidose 436 the 8°C ΔT run showed only partial collapse. The difference is not unexpected given the different physical properties. Partial collapse was seen even for ΔTs as high as 50°C. Both complete and partial collapse manifested themselves as downwelling flow in the central part of the conduit. Collapse stopped in the hotter plumes when the downwelling fluid met the hottest part of the conduit. The observed results suggest that diffusive

  4. Can plumes collapse?: Experimental results and applications to Iceland

    NASA Astrophysics Data System (ADS)

    Pears, M.; Lithgow-Bertelloni, C. R.

    2011-12-01

    Iceland has produced magma in a series of episodic events. From lava chemistry it has been inferred that the plume temperature decreased over the first 5 Myr by ~50°C and for the next 3 Myr following continental break up it continued to oscillate by ~25°C. Such data has been used to infer possible episodic collapse of the Iceland plume. Collapsing plumes are not common fluid dynamical features. In thermochemical plumes it is possible to achieve collapse by varying the relative buoyancy due to chemistry and due to temperature. In thermal plumes however, with a constant heat source we would expect plumes not to collapse but to not continue to rise after reaching a point of neutral buoyancy. We expect thermal plumes, like those Earth's bottom thermal boundary layer is capable of producing, to either rise to the surface or be deflected but not to collapse. We have designed an experimental setup to investigate the conditions that may lead to collapse in thermal plumes with constant heat sources. We used high-Prandtl number fluids with strongly temperature-dependent viscosities (Lyle Golden syrup and Liquidose 436) as analogues to Earth's high viscosity mantle in a cubic Plexiglas tank (26.5cm inner sides), heated by a circular 2cm diameter heater (flat with the base of the tank). We explored ΔTs between 3-60°C. The flow was visualized with shadowgraphs and an automated -3D Stereoscopic Particle Image Velocimetry (SPIV) system to measure velocities. In Lyle's Golden Syrup collapse occurred at ΔTs as high as 8°C, while in Liquidose 436 the 8° ΔT run showed only partial collapse. The difference is not unexpected given the different physical properties. Partial collapse was seen even for ΔTs as high as 50°C. Both complete and partial collapse manifested themselves as downwelling flow in the central part of the conduit. Collapse stopped in the hotter plumes when the downwelling fluid met the hottest part of the conduit. The observed results suggest that diffusive

  5. Gravitational Collapse with Cosmological Constant and Anisotropic Pressure

    NASA Astrophysics Data System (ADS)

    Ahmad, Zahid; Malik, Sania Abdul

    2016-01-01

    We investigate the gravitational collapse of anisotropic perfect fluid by applying junction conditions and spherically symmetric space-times in the presence of cosmological constant. We show that the cosmological constant slows down the collapsing process and also reduces the size of black hole.This work provides a generalization of the previous studies by Cissoko et al. (arXiv: gr-qc/9809057) for dust and by Sharif and Ahmad (Mod. Phys. Lett. A, 22:1493, 2007) for perfect fluid.

  6. The Collapse of the I-35W Bridge in Minneapolis

    ERIC Educational Resources Information Center

    Feldman, Bernard J.

    2010-01-01

    On Wednesday, Aug. 1, 2007, at 6:05 p.m. (during evening rush hour), the I-35W bridge across the Mississippi River in Minneapolis collapsed, killing 13 people and injuring 145. At the time of the collapse, repair work was in progress on the deck of the bridge, resulting in an additional 287 tons of construction material and equipment being on the…

  7. Quantum collapse rules from the maximum relative entropy principle

    NASA Astrophysics Data System (ADS)

    Hellmann, Frank; Kamiński, Wojciech; Paweł Kostecki, Ryszard

    2016-01-01

    We show that the von Neumann-Lüders collapse rules in quantum mechanics always select the unique state that maximises the quantum relative entropy with respect to the premeasurement state, subject to the constraint that the postmeasurement state has to be compatible with the knowledge gained in the measurement. This way we provide an information theoretic characterisation of quantum collapse rules by means of the maximum relative entropy principle.

  8. Collapse of the soap-film bridge - Quasistatic description

    NASA Technical Reports Server (NTRS)

    Cryer, Steven A.; Steen, Paul H.

    1992-01-01

    Observations of the collapse of a soap-film bridge from a connected to a disconnected state are recorded. The equilibrium framework for this nonequilibrium event is classical. Experiments confirm predictions of stable and unstable equilibria. A quasistatic description is introduced for the dynamic states to extend the static theory. It is found to adequately describe the collapse trajectory while the bridge is still connected.

  9. Towards the Core-Collapse Supernova Explosion Mechanism

    SciTech Connect

    Cardall, Christian Y; Endeve, Eirik; Budiardja, R. D.; Marronetti, Pedro; Mezzacappa, Anthony

    2012-01-01

    Core-collapse supernovae are amazing displays of astrohysical fireworks - and the optical emission is only a tiny part of the story. These events involve virtually all branches of physics and spawn phenomena observale by every kind of astronomical observation. This richness of theory and observation presents a formidable challenge to their understanding via computer simulations, but we are entering a new era of realism and maturity in modeling the key processes by collapse and explosion.

  10. Improvement in UOE pipe collapse resistance by thermal aging

    SciTech Connect

    Al-Sharif, A.M.; Preston, R.

    1996-12-31

    A recent investigation has shown that the UOE pipe manufacturing process significantly degrades the collapse resistance of high strength line pipe. This paper assesses the degree of strength recovery that can be achieved by aging the pipe. An experimental investigation was performed in order to develop a quantitative relationship between time and temperature of aging, which produces an increase in compressive yield strength, with consequent increase in collapse resistance to external pressure loading.

  11. Estimating the Collapse Pressure of an Inflatable Aerodynamic Decelerator

    NASA Technical Reports Server (NTRS)

    Baginski, Frank E.; Brakke, Kenneth A.; Cruz, Juan R.

    2013-01-01

    The collapse pressure of an inflatable membrane is the minimum differential pressure which will sustain a specific desired shape under an applied load. In this paper, we present a method for estimating the collapse pressure of a tension-cone inflatable aerodynamic decelerator (IAD) that is subject to a static aerodynamic load. The IAD surface is modeled as an elastic membrane. For a given aerodynamic load and sufficiently high torus differential pressure, the IAD assumes a stable axisymmetric equilibrium shape. When the torus pressure is reduced sufficiently, the symmetric equilibrium state becomes unstable and we define this instance to be the critical pressure Pcr. In this paper, we will compare our predicted critical torus pressure with the corresponding observed torus collapse pressure (OTCP) for fifteen tests that were conducted by the third author and his collaborators at the NASA Glenn Research Center 10x10 Supersonic Wind Tunnel in April 2008. One of the difficulties with these types of comparisons is establishing the instance of torus collapse and determining the OTCP from quantities measured during the experiment. In many cases, torus collapse is gradual and the OTCP is not well-defined. However, in eight of the fifteen wind tunnel tests where the OTCP is well-defined, we find that the average of the relative differences (Pcr - OTCP/Pcr) was 8.9%. For completeness, we will also discuss the seven tests where the observed torus collapse pressure is not well-defined.

  12. Collapse of differentially rotating supermassive stars: Post black hole formation

    SciTech Connect

    Saijo, Motoyuki; Hawke, Ian

    2009-09-15

    We investigate the collapse of differentially rotating supermassive stars (SMSs) by means of 3+1 hydrodynamic simulations in general relativity. We particularly focus on the onset of collapse to understand the final outcome of collapsing SMSs. We find that the estimated ratio of the mass between the black hole and the surrounding disk from the equilibrium star is roughly the same as the results from numerical simulation. This suggests that the picture of axisymmetric collapse is adequate, in the absence of nonaxisymmetric instabilities, to illustrate the final state of the collapse. We also find that quasiperiodic gravitational waves continue to be emitted after the quasinormal mode frequency has decayed. We furthermore have found that when the newly formed black hole is almost extreme Kerr, the amplitude of the quasiperiodic oscillation is enhanced during the late stages of the evolution. Geometrical features, shock waves, and instabilities of the fluid are suggested as a cause of this amplification behavior. This alternative scenario for the collapse of differentially rotating SMSs might be observable by the Laser Interferometer Space Antenna.

  13. Collapse of ordered spatial pattern in neuronal network

    NASA Astrophysics Data System (ADS)

    Song, Xinlin; Wang, Chunni; Ma, Jun; Ren, Guodong

    2016-06-01

    Spatiotemporal systems can emerge some regular spatial patterns due to self organization or under external periodical pacing while external attack or intrinsic collapse can destroy the regularity in the spatial system. For an example, the electrical activities of neurons in nervous system show regular spatial distribution under appropriate coupling and connection. It is believed that distinct regularity could be induced in the media by appropriate forcing or feedback, while a diffusive collapse induced by continuous destruction can cause breakdown of the media. In this paper, the collapse of ordered spatial distribution is investigated in a regular network of neurons (Morris-Lecar, Hindmarsh-Rose) in two-dimensional array. A stable target wave is developed regular spatial distribution emerges by imposing appropriate external forcing with diversity, or generating heterogeneity (parameter diversity in space). The diffusive invasion could be produced by continuous parameter collapse or switch in local area, e.g, the diffusive poisoning in ion channels of potassium in Morris-Lecar neurons causes breakdown in conductance of channels. It is found that target wave-dominated regularity can be suppressed when the collapsed area is diffused in random. Statistical correlation functions for sampled nodes (neurons) are defined to detect the collapse of ordered state by series analysis.

  14. Radiation from collapsing shells, semiclassical backreaction, and black hole formation

    NASA Astrophysics Data System (ADS)

    Paranjape, Aseem; Padmanabhan, T.

    2009-08-01

    We provide a detailed analysis of quantum field theory around a collapsing shell and discuss several conceptual issues related to the emission of radiation flux and formation of black holes. Explicit calculations are performed using a model for a collapsing shell, which turns out to be analytically solvable. We use the insights gained in this model to draw reliable conclusions regarding more realistic models. We first show that any shell of mass M, which collapses to a radius close to r=2M, will emit approximately thermal radiation for a period of time. In particular, a shell that collapses from some initial radius to a final radius 2M(1-γ2)-1 (where γ≪1) without forming a black hole, will emit thermal radiation during the period M≲t≲Mln⁡(1/γ2). Later on (t≫Mln⁡(1/γ2)), the flux from such a shell will decay to zero exponentially. We next study the effect of backreaction computed using the vacuum expectation value of the stress tensor on the collapse. We find that, in any realistic collapse scenario, the backreaction effects do not prevent the formation of the event horizon. The time at which the event horizon is formed is, of course, delayed due to the radiated flux—which decreases the mass of the shell—but this effect is not sufficient to prevent horizon formation. We also clarify several conceptual issues and provide pedagogical details of the calculations in the Appendices to the paper.

  15. Dynamics of concerted bubble cluster collapse in shock wave lithotripsy

    NASA Astrophysics Data System (ADS)

    Pishchalnikov, Yuri A.; McAteer, James A.; Evan, Andrew P.; Sapozhnikov, Oleg A.; Cleveland, Robin O.; Colonius, Tim; Bailey, Michael R.; Crum, Lawrence A.

    2003-10-01

    Cavitation bubble cluster collapse at the surface of artificial kidney stones during shock wave lithotripsy was investigated in vitro by means of multiframe high-speed photography, passive cavitation detection (PCD), and pressure waveform measurements using a fiber-optic probe hydrophone (FOPH). It was observed that after the passage of the lithotripter shock pulse the stone was covered by numerous individual bubbles. During their growth phase the bubbles coalesced into bubble clusters, with the biggest cluster at the proximal face of the stone. High-speed camera images suggested that cluster collapse started at the periphery and ended with a violent collapse in a small region in the center of the surface of the stone. Shadowgraphy resolved numerous secondary shock waves emitted during this focused collapse. Shock wave emission during cluster collapse was confirmed by PCD. Measurement with the FOPH showed that these shock waves were typically of short duration (0.2 μs). The majority of the shock waves emanating from cluster collapse were low amplitude but some shock waves registered amplitudes on the order of the incident shock pulse (tens of MPa). [Work supported by NIH DK43881, DK55674.

  16. Newton force from wave function collapse: speculation and test

    NASA Astrophysics Data System (ADS)

    Diósi, Lajos

    2014-04-01

    The Diosi-Penrose model of quantum-classical boundary postulates gravity-related spontaneous wave function collapse of massive degrees of freedom. The decoherence effects of the collapses are in principle detectable if not masked by the overwhelming environmental decoherence. But the DP (or any other, like GRW, CSL) spontaneous collapses are not detectable themselves, they are merely the redundant formalism of spontaneous decoherence. To let DP collapses become testable physics, recently we extended the DP model and proposed that DP collapses are responsible for the emergence of the Newton gravitational force between massive objects. We identified the collapse rate, possibly of the order of 1/ms, with the rate of emergence of the Newton force. A simple heuristic emergence (delay) time was added to the Newton law of gravity. This non-relativistic delay is in peaceful coexistence with Einstein's relativistic theory of gravitation, at least no experimental evidence has so far surfaced against it. We derive new predictions of such a 'lazy' Newton law that will enable decisive laboratory tests with available technologies. The simple equation of 'lazy' Newton law deserves theoretical and experimental studies in itself, independently of the underlying quantum foundational considerations.

  17. Dipole collapse and reversal precursors in a numerical dynamo

    NASA Astrophysics Data System (ADS)

    Olson, Peter; Driscoll, Peter; Amit, Hagay

    2009-03-01

    Precursors to extreme geomagnetic field changes are examined in a numerical dynamo with a reversing dipolar magnetic field. A dynamo model with compositional convection in a rotating spherical shell produces a strongly dipolar external magnetic field over 6 Myr of simulated paleomagnetic time, with stable polarity epochs and occasional dipole collapses, some of which result in polarity reversals or dipole axis excursions. We analyze the model behavior during two dipole collapses, one that leads to a polarity reversal and one that does not, focusing on observable precursors. Reversed magnetic field induced in the dynamo interior by intermittent convective variability is the primary cause of dipole collapse. Spots of reversed magnetic flux emerge on the outer boundary at an early stage, then re-emerge with greater intensity at the height of the collapse. The energy in the external field cascades to higher harmonics as these reversed patches appear. Butterfly diagrams showing the reversed and normal flux contributions to the axial dipole reveal poleward migration of the patches during dipole collapse. Axial dipole reduction by precursory reversed flux is several times larger in the reversing case, compared to the non-reversing case. A butterfly diagram of the geomagnetic field since 1840 shows high latitude reversed flux emerging on the core-mantle boundary. Although the reversed geomagnetic flux is presently too weak to be labeled a reversal precursor, it is consistent with early stage dipole collapse in the dynamo model.

  18. Ocean wave generation by collapsing ice shelves

    NASA Astrophysics Data System (ADS)

    Macayeal, D. R.; Bassis, J. N.; Okal, E. A.; Aster, R. C.; Cathles, L. M.

    2008-12-01

    The 28-29 February, 2008, break-up of the Wilkins Ice Shelf, Antarctica, exemplifies the now-familiar, yet largely unexplained pattern of explosive ice-shelf break-up. While environmental warming is a likely ultimate cause of explosive break-up, several key aspects of their short-term behavior need to be explained: (1) The abrupt, near-simultaneous onset of iceberg calving across long spans of the ice front margin; (2) High outward drift velocity (about 0.3 m/s) of a leading phalanx of tabular icebergs that originate from the seaward edge of the intact ice shelf prior to break-up; (3) Rapid coverage of the ocean surface in the wake of this leading phalanx by small, capsized and dismembered tabular icebergs; (4) Extremely large gravitational potential energy release rates, e.g., up to 3 × 1010 W; (5) Lack of proximal iceberg-calving triggers that control the timing of break-up onset and that maintain the high break-up calving rates through to the conclusion of the event. Motivated by seismic records obtained from icebergs and the Ross Ice Shelf that show hundreds of micro- tsunamis emanating from near the ice shelf front, we re-examine the basic dynamic features of ice- shelf/ocean-wave interaction and, in particular, examine the possibility that collapsing ice shelves themselves are a source of waves that stimulate the disintegration process. We propose that ice-shelf generated surface-gravity waves associated with initial calving at an arbitrary seed location produce stress perturbations capable of triggering the onset of calving on the entire ice front. Waves generated by parting detachment rifts, iceberg capsize and break-up act next to stimulate an inverted submarine landslide (ice- slide) process, where gravitational potential energy released by upward movement of buoyant ice is radiated as surface gravity waves in the wake of the advancing phalanx of tabular icebergs. We conclude by describing how field research and remote sensing can be used to test the

  19. Minimizing waste in environmental restoration

    SciTech Connect

    Moos, L.; Thuot, J.R.

    1996-07-01

    Environmental restoration, decontamination and decommissioning and facility dismantelment projects are not typically known for their waste minimization and pollution prevention efforts. Typical projects are driven by schedules and milestones with little attention given to cost or waste minimization. Conventional wisdom in these projects is that the waste already exists and cannot be reduced or minimized. In fact, however, there are three significant areas where waste and cost can be reduced. Waste reduction can occur in three ways: beneficial reuse or recycling; segregation of waste types; and reducing generation of secondary waste. This paper will discuss several examples of reuse, recycle, segregation, and secondary waste reduction at ANL restoration programs.

  20. Mitral valve surgery - minimally invasive

    MedlinePlus

    ... that does many of these procedures. Minimally invasive heart valve surgery has improved greatly in recent years. These ... WT, Mack MJ. Transcatheter cardiac valve interventions. Surg Clin North Am . 2009;89:951-66. ...

  1. Heart bypass surgery - minimally invasive

    MedlinePlus

    ... in 30-day outcomes in high-risk patients randomized to off-pump versus on-pump coronary bypass ... Thiele H, Neumann-Schniedewind P, Jacobs S, et al. Randomized comparison of minimally invasive direct coronary artery bypass ...

  2. Cover-collapse sinkholes of the Franconian Alb / Germany

    NASA Astrophysics Data System (ADS)

    Trappe, M.; Heckmann, T.; Mehlhorn, S.; Umstädter, K.; Miedaner, H.; Becht, M.

    2012-04-01

    Recent events of cover-collapse sinkhole formation, the geomorphological, geological and hydrological conditions of selected sinkholes and the spatial and temporal occurrences of such landforms were studied in the Franconian Alb, a karst area located in southeastern Germany. The Franconian Alb consists of karstified limestones and dolomites of Jurassic Age. It is partly covered by Cretaceous and Miocene deposits and a clayey to loamy overburden. The thickness of the loamy cover ranges from a few decimetres up to ten meters. Sinkholes are widely distributed in the area, to some extent they were formed by cover-collapse processes. In order to prepare a geohazard map, historical records from different archives (municipalities, counties, water management agencies, governmental archives, newspapers) were used for a compilation of sinkholes which resulted from collapses. The frequency of occurrence of cover-collapse sinkholes differs in areas with agricultural or forestal use. Farmers often backfill these surficial cavities immediately after their formation, before they can be registered officially. Therefore a documentation of such collapse events may be restricted in terms of detailed statistical analyses. Nevertheless seasonal clusters of collapses can be observed. Recent collapses show close relations to climatic conditions. During winter or spring the majority of collapse events is associated with snow melt or heavy rainfall resulting in an increase of the soil moisture and a decrease of shear strength within the loamy cover. Consequently, loose material overlaying cavities can be washed down, or the sediment itself moves downward. For single events, the antecedent climatic development (precipitation, thickness of snow cover, air temperature, soil temperature) was analysed for identification of the triggering factors. In this context, small-scale surficial karst depressions without outlet (underlain by thick loamy deposits) show an efficient drainage via a few

  3. Refined applications of the collapse of the wave function

    NASA Astrophysics Data System (ADS)

    Stodolsky, L.

    2015-05-01

    In a two-part system, the collapse of the wave function of one part can put the other part in a state which would be difficult or impossible to achieve otherwise, in particular, one sensitive to small effects in the "collapse" interaction. We present some applications to the very symmetric and experimentally accessible situations of the decays ϕ (1020 )→KoKo , ψ (3770 )→DoDo, or ϒ (4 s )→BoBo , involving the internal state of the two-state Ko, Do, or Bo mesons. The collapse of the wave function occasioned by a decay of one member of the pair (away side) fixes the state vector of that side's two-state system. Bose-Einstein statistics then determines the state of the recoiling meson (near side), whose evolution can then be followed further. In particular, the statistics requirement dictates that the "away side" and "near side" internal wave functions must be orthogonal at the time of the collapse. Thus a C P violation in the away side decay implies a complementary C P impurity on the near side, which can be detected in the further evolution. The C P violation so manifested is necessarily direct C P violation, since neither the mass matrix nor time evolution was involved in the collapse. A parametrization of the direct C P violation is given, and various manifestations are presented. Certain rates or combination of rates are identified which are nonzero only if there is direct C P violation. The very explicit and detailed use made of the collapse of the wave function makes the procedure interesting with respect to the fundamentals of quantum mechanics. We note an experimental consistency test for our treatment of the collapse of the wave function, which can be carried out by a certain measurement of partial decay rates.

  4. Endograft Collapse After Endovascular Treatment for Thoracic Aortic Disease

    SciTech Connect

    Bandorski, Dirk Brueck, Martin; Guenther, Hans-Ulrich; Manke, Christoph

    2010-06-15

    Endovascular treatment is an established therapy for thoracic aortic disease. Collapse of the endograft is a potentially fatal complication. We reviewed 16 patients with a thoracic endograft between 2001 and 2006. Medical records of the treated patients were studied. Data collected include age, gender, diagnosis, indication for endoluminal treatment, type of endograft, and time of follow up. All patients (n = 16; mean age, 61 years; range, 21-82 years) underwent computed tomography (CT) for location of the lesion and planning of the intervention. Time of follow-up with CT scan ranged from 1 to 61 months. Indications for endovascular treatment were degenerative aneurysm (n = 7; 44%), aortic dissection (n = 2; 12%), perforated aortic ulcer (n = 4; 25%), and traumatic aortic injury (n = 3; 19%). Three patients suffered from a collapse of the endograft (one patient distal, two patients proximal) between 3 and 8 days after endovascular treatment. These patients were younger (mean age, 37 {+-} 25 years vs. 67 {+-} 16 years; P < 0.05) and showed more oversizing (proximal, 36 {+-} 19.8% vs. 29 {+-} 20.7% [P > 0.05]; distal, 45 {+-} 23.5% vs. 38 {+-} 21.7% [P > 0.05]). Proximal collapse was corrected by placing a bare stent. In conclusion, risk factors for stent-graft collapse are a small lumen of the aorta and a small radius of the aortic arch curvature (young patients), as well as oversizing, which is an important risk factor and is described for different types of endografts and protheses (Gore TAG and Cook Zenith). Dilatation of the collapsed stent-graft is not sufficient. Following therapy implantation of a second stent or surgery is necessary in patients with a proximal endograft collapse. Distal endograft collapse can possibly be treated conservatively under close follow-up.

  5. On the number density of "direct collapse" black hole seeds

    NASA Astrophysics Data System (ADS)

    Habouzit, Mélanie; Volonteri, Marta; Latif, Muhammad; Dubois, Yohan; Peirani, Sébastien

    2016-08-01

    Supermassive black holes (BHs) reside in the center of most local galaxies, but they also power active galactic nuclei and quasars, detected up to z = 7. These quasars put constraints on early BH growth and the mass of BH seeds. The scenario of "direct collapse" is appealing as it leads to the formation of large mass BH seeds, 10^4-10^6 {M_{⊙}}, which eases explaining how quasars at z = 6 - 7 are powered by BHs with masses >109 M⊙. Direct collapse, however, appears to be rare, as the conditions required by the scenario are that gas is metal-free, the presence of a strong photo-dissociating Lyman-Werner flux, and large inflows of gas at the center of the halo, sustained for 10 - 100 Myr. We performed several cosmological hydrodynamical simulations that cover a large range of box sizes and resolutions, thus allowing us to understand the impact of several physical processes on the distribution of direct collapse BHs. We identify halos where direct collapse can happen, and derive the number density of BHs. We also investigate the discrepancies between hydrodynamical simulations, direct or post-processed, and semi-analytical studies. Under optimistic assumptions, we find that for direct collapse to account for BHs in normal galaxies, the critical Lyman-Werner flux required for direct collapse must be about two orders of magnitude lower than predicted by 3D simulations that include detailed chemical models. However, when supernova feedback is relatively weak, enough direct collapse BHs to explain z = 6 - 7 quasars can be obtained for Lyman-Werner fluxes about one order of magnitude lower than found in 3D simulations.

  6. Shock-induced nanobubble collapse and its applications

    NASA Astrophysics Data System (ADS)

    Vedadi, Mohammad Hossein

    The shock-induced collapse of nanobubbles in water is investigated using molecular dynamics simulations based on a reactive force field. Monitoring the collapse of a cavitation nanobubble, we observe a focused nanojet at the onset of bubble shrinkage and a water hammer shock wave upon bubble collapse. The nanojet length scales linearly with the nanobubble radius, as observed in experiments on micron-to-millimeter size bubbles. The shock induces dramatic structural changes, including an ice-VII-like structural motif at a particle velocity of approximately 1 km/s. The incipient ice VII formation and the calculated Hugoniot curve are in good agreement with experimental results. Moreover, a substantial number of positive and negative ions appear when the nanojet hits the distal side of the nanobubble and the water hammer shock forms. Furthermore, two promising applications of shock-induced nanobubble collapse have been explored. Our simulations of poration in lipid bilayers due to shock-induced collapse of nanobubbles reveal penetration of nanojets into lipid bilayers. The nanojet impact generates shear flow of water on bilayer leaflets and pressure gradients across them, which transiently enhance the bilayer permeability by creating nanopores through which water molecules translocate across the bilayer. The effects of nanobubble size and temperature on the porosity of lipid bilayers are examined. Finally, the shock-induced collapse of CO2-filled nanobubbles in water is investigated. The energetic nanojet and high-pressure water hammer shock formed during and after collapse of the nanobubble trigger mechano-chemical H2O-CO2 reactions, some of which lead to splitting of water molecules. The dominant pathways through which splitting of water molecules occur are identified.

  7. Minimizing pollutants with multimedia strategies

    SciTech Connect

    Phillips, J.B.; Hindawi, M.A.

    1997-01-01

    A multimedia approach to pollution prevention that focuses on minimizing or eliminating production of pollutants is one of the most advantageous strategies to adopt in preparing an overall facility environmental plan. If processes are optimized to preclude or minimize the manufacture of streams containing pollutants, or to reduce the levels of pollutants in waste streams, then the task of multimedia pollution prevention becomes more manageable simply as a result of a smaller problem needing to be addressed. An orderly and systematic approach to waste minimization can result in a comprehensive strategy to reduce the production of waste streams and simultaneously improve the profitability of a process or industrial operation. There are a number of miscellaneous strategies for a waste minimization that attack the problem via process chemistry or engineering. Examples include installation of low-NO{sub x} burners, selection of valves that minimize fugitive emissions, high-level switches on storage tanks, the use of in-plant stills for recycling and reusing solvents and using water-based products instead of hydrocarbon-based products wherever possible. Other waste minimization countermeasures can focus on O and M issues.

  8. Tumor-selective mitochondrial network collapse induced by atmospheric gas plasma-activated medium

    PubMed Central

    Saito, Kosuke; Asai, Tomohiko; Fujiwara, Kyoko; Sahara, Junki; Koguchi, Haruhisa; Fukuda, Noboru; Suzuki-Karasaki, Miki; Soma, Masayoshi; Suzuki-Karasaki, Yoshihiro

    2016-01-01

    Non-thermal atmospheric gas plasma (AGP) exhibits cytotoxicity against malignant cells with minimal cytotoxicity toward normal cells. However, the mechanisms of its tumor-selective cytotoxicity remain unclear. Here we report that AGP-activated medium increases caspase-independent cell death and mitochondrial network collapse in a panel of human cancer cells, but not in non-transformed cells. AGP irradiation stimulated reactive oxygen species (ROS) generation in AGP-activated medium, and in turn the resulting stable ROS, most likely hydrogen peroxide (H2O2), activated intracellular ROS generation and mitochondrial ROS (mROS) accumulation. Culture in AGP-activated medium resulted in cell death and excessive mitochondrial fragmentation and clustering, and these responses were inhibited by ROS scavengers. AGP-activated medium also increased dynamin-related protein 1-dependent mitochondrial fission in a tumor-specific manner, and H2O2 administration showed similar effects. Moreover, the vulnerability of tumor cells to mitochondrial network collapse appeared to result from their higher sensitivity to mROS accumulation induced by AGP-activated medium or H2O2. The present findings expand our previous observations on death receptor-mediated tumor-selective cell killing and reinforce the importance of mitochondrial network remodeling as a powerful target for tumor-selective cancer treatment. PMID:26942565

  9. Tumor-selective mitochondrial network collapse induced by atmospheric gas plasma-activated medium.

    PubMed

    Saito, Kosuke; Asai, Tomohiko; Fujiwara, Kyoko; Sahara, Junki; Koguchi, Haruhisa; Fukuda, Noboru; Suzuki-Karasaki, Miki; Soma, Masayoshi; Suzuki-Karasaki, Yoshihiro

    2016-04-12

    Non-thermal atmospheric gas plasma (AGP) exhibits cytotoxicity against malignant cells with minimal cytotoxicity toward normal cells. However, the mechanisms of its tumor-selective cytotoxicity remain unclear. Here we report that AGP-activated medium increases caspase-independent cell death and mitochondrial network collapse in a panel of human cancer cells, but not in non-transformed cells. AGP irradiation stimulated reactive oxygen species (ROS) generation in AGP-activated medium, and in turn the resulting stable ROS, most likely hydrogen peroxide (H2O2), activated intracellular ROS generation and mitochondrial ROS (mROS) accumulation. Culture in AGP-activated medium resulted in cell death and excessive mitochondrial fragmentation and clustering, and these responses were inhibited by ROS scavengers. AGP-activated medium also increased dynamin-related protein 1-dependent mitochondrial fission in a tumor-specific manner, and H2O2 administration showed similar effects. Moreover, the vulnerability of tumor cells to mitochondrial network collapse appeared to result from their higher sensitivity to mROS accumulation induced by AGP-activated medium or H2O2. The present findings expand our previous observations on death receptor-mediated tumor-selective cell killing and reinforce the importance of mitochondrial network remodeling as a powerful target for tumor-selective cancer treatment. PMID:26942565

  10. A Real-Time Decision Support System for Voltage Collapse Avoidance in Power Supply Networks

    NASA Astrophysics Data System (ADS)

    Chang, Chen-Sung

    This paper presents a real-time decision support system (RDSS) based on artificial intelligence (AI) for voltage collapse avoidance (VCA) in power supply networks. The RDSS scheme employs a fuzzy hyperrectangular composite neural network (FHRCNN) to carry out voltage risk identification (VRI). In the event that a threat to the security of the power supply network is detected, an evolutionary programming (EP)-based algorithm is triggered to determine the operational settings required to restore the power supply network to a secure condition. The effectiveness of the RDSS methodology is demonstrated through its application to the American Electric Power Provider System (AEP, 30-bus system) under various heavy load conditions and contingency scenarios. In general, the numerical results confirm the ability of the RDSS scheme to minimize the risk of voltage collapse in power supply networks. In other words, RDSS provides Power Provider Enterprises (PPEs) with a viable tool for performing on-line voltage risk assessment and power system security enhancement functions.

  11. Collapsing lattice animals and lattice trees in two dimensions

    NASA Astrophysics Data System (ADS)

    Hsu, Hsiao-Ping; Grassberger, Peter

    2005-06-01

    We present high statistics simulations of weighted lattice bond animals and lattice trees on the square lattice, with fugacities for each non-bonded contact and for each bond between two neighbouring monomers. The simulations are performed using a newly developed sequential sampling method with resampling, very similar to the pruned-enriched Rosenbluth method (PERM) used for linear chain polymers. We determine with high precision the line of second-order transitions from an extended to a collapsed phase in the resulting two-dimensional phase diagram. This line includes critical bond percolation as a multicritical point, and we verify that this point divides the line into different universality classes. One of them corresponds to the collapse driven by contacts and includes the collapse of (weakly embeddable) trees. There is some evidence that the other is subdivided again into two parts with different universality classes. One of these (at the far side from collapsing trees) is bond driven and is represented by the Derrida-Herrmann model of animals having bonds only (no contacts). Between the critical percolation point and this bond-driven collapse seems to be an intermediate regime, whose other end point is a multicritical point P* where a transition line between two collapsed phases (one bond driven and the other contact driven) sparks off. This point P* seems to be attractive (in the renormalization group sense) from the side of the intermediate regime, so there are four universality classes on the transition line (collapsing trees, critical percolation, intermediate regime, and Derrida-Herrmann). We obtain very precise estimates for all critical exponents for collapsing trees. It is already harder to estimate the critical exponents for the intermediate regime. Finally, it is very difficult to obtain with our method good estimates of the critical parameters of the Derrida-Herrmann universality class. As regards the bond-driven to contact-driven transition in the

  12. Detecting the Collapse of Cooperation in Evolving Networks.

    PubMed

    Cavaliere, Matteo; Yang, Guoli; Danos, Vincent; Dakos, Vasilis

    2016-01-01

    The sustainability of biological, social, economic and ecological communities is often determined by the outcome of social conflicts between cooperative and selfish individuals (cheaters). Cheaters avoid the cost of contributing to the community and can occasionally spread in the population leading to the complete collapse of cooperation. Although such collapse often unfolds unexpectedly, it is unclear whether one can detect the risk of cheater's invasions and loss of cooperation in an evolving community. Here, we combine dynamical networks and evolutionary game theory to study the abrupt loss of cooperation with tools for studying critical transitions. We estimate the risk of cooperation collapse following the introduction of a single cheater under gradually changing conditions. We observe an increase in the average time it takes for cheaters to be eliminated from the community as the risk of collapse increases. We argue that such slow system response resembles slowing down in recovery rates prior to a critical transition. In addition, we show how changes in community structure reflect the risk of cooperation collapse. We find that these changes strongly depend on the mechanism that governs how cheaters evolve in the community. Our results highlight novel directions for detecting abrupt transitions in evolving networks. PMID:27492876

  13. Can static regular black holes form from gravitational collapse?

    NASA Astrophysics Data System (ADS)

    Zhang, Yiyang; Zhu, Yiwei; Modesto, Leonardo; Bambi, Cosimo

    2015-02-01

    Starting from the Oppenheimer-Snyder model, we know how in classical general relativity the gravitational collapse of matter forms a black hole with a central spacetime singularity. It is widely believed that the singularity must be removed by quantum-gravity effects. Some static quantum-inspired singularity-free black hole solutions have been proposed in the literature, but when one considers simple examples of gravitational collapse the classical singularity is replaced by a bounce, after which the collapsing matter expands for ever. We may expect three possible explanations: (i) the static regular black hole solutions are not physical, in the sense that they cannot be realized in Nature, (ii) the final product of the collapse is not unique, but it depends on the initial conditions, or (iii) boundary effects play an important role and our simple models miss important physics. In the latter case, after proper adjustment, the bouncing solution would approach the static one. We argue that the "correct answer" may be related to the appearance of a ghost state in de Sitter spacetimes with super Planckian mass. Our black holes have indeed a de Sitter core and the ghost would make these configurations unstable. Therefore we believe that these black hole static solutions represent the transient phase of a gravitational collapse but never survive as asymptotic states.

  14. Correlated random walks caused by dynamical wavefunction collapse.

    PubMed

    Bedingham, D J; Ulbricht, H

    2015-01-01

    Wavefunction collapse models modify Schrödinger's equation so that it describes the collapse of a superposition of macroscopically distinguishable states as a dynamical process. This provides a basis for the resolution of the quantum measurement problem. An additional generic consequence of the collapse mechanism is that it causes particles to exhibit a tiny random diffusive motion. Here it is shown that for the continuous spontaneous localization (CSL) model—one of the most well developed collapse models—the diffusions of two sufficiently nearby particles are positively correlated. An experimental test of this effect is proposed in which random displacements of pairs of free nanoparticles are measured after they have been simultaneously released from nearby traps. The experiment must be carried out at sufficiently low temperature and pressure in order for the collapse effects to dominate over the ambient environmental noise. It is argued that these constraints can be satisfied by current technologies for a large region of the viable parameter space of the CSL model. The effect disappears as the separation between particles exceeds the CSL length scale. The test therefore provides a means of bounding this length scale. PMID:26303388

  15. Collapses of stellar protogalaxies from aspheric initial conditions

    NASA Technical Reports Server (NTRS)

    Miller, R. H.; Smith, B. F.

    1981-01-01

    Numerical experimens are presented which were intended to verify the independence of bar formation in rotating galaxy models from special initial conditions. Three-dimensional n-body programs were run starting from aspherical initial conditions characterized by particle rotational and peculiar velocities and offsets from sphericity for a set of 100,000 particles. All the initial configurations examined are observed to collapse to a thin form, overshoot, collapse again and again overshoot, with diameters and central densities similar to those observed under spheric initial conditions. Every aspheric collapse is also found to result in bar formation within two rotation periods, which is even sooner than in initially spherical conditions. In the intermediate stages of collapse, transient sheet patterns are found to be destroyed at asymmetries of 2-3%, while transient rings survived asymmetries of 6-7% but not 15-18%. It is noted that the results may be applicable to galaxy formation in the early universe, and possible mechanisms for the arresting of protogalactic collapse are indicated.

  16. Gravitational collapse of depletion-induced colloidal gels.

    PubMed

    Harich, R; Blythe, T W; Hermes, M; Zaccarelli, E; Sederman, A J; Gladden, L F; Poon, W C K

    2016-05-11

    We study the ageing and ultimate gravitational collapse of colloidal gels in which the interparticle attraction is induced by non-adsorbing polymers via the depletion effect. The gels are formed through arrested spinodal decomposition, whereby the dense phase arrests into an attractive glass. We map the experimental state diagram onto a theoretical one obtained from computer simulations and theoretical calculations. Discrepancies between the experimental and simulated gel regions in the state diagram can be explained by the particle size and density dependence of the boundary below which the gel is not strong enough to resist gravitational stress. Visual observations show that gravitational collapse of the gels falls into two distinct regimes as the colloid and polymer concentrations are varied, with gels at low colloid concentrations showing the onset of rapid collapse after a delay time. Magnetic resonance imaging (MRI) was used to provide quantitative, spatio-temporally resolved measurements of the solid volume fraction in these rapidly collapsing gels. We find that during the delay time, a dense region builds up at the top of the sample. The rapid collapse is initiated when the gel structure is no longer able to support this dense layer. PMID:27001686

  17. Signatures of Star Cluster Formation by Cold Collapse

    NASA Astrophysics Data System (ADS)

    Kuznetsova, Aleksandra; Hartmann, Lee; Ballesteros-Paredes, Javier

    2015-12-01

    Subvirial gravitational collapse is one mechanism by which star clusters may form. Here we investigate whether this mechanism can be inferred from observations of young clusters. To address this question, we have computed smoothed particle hydrodynamics simulations of the initial formation and evolution of a dynamically young star cluster through cold (subvirial) collapse, starting with an ellipsoidal, turbulently seeded distribution of gas, and forming sink particles representing (proto)stars. While the initial density distributions of the clouds do not have large initial mass concentrations, gravitational focusing due to the global morphology leads to cluster formation. We use the resulting structures to extract observable morphological and kinematic signatures for the case of subvirial collapse. We find that the signatures of the initial conditions can be erased rapidly as the gas and stars collapse, suggesting that kinematic observations need to be made early in cluster formation and/or at larger scales, away from the growing cluster core. Our results emphasize that a dynamically young system is inherently evolving on short timescales, so that it can be highly misleading to use current-epoch conditions to study aspects such as star formation rates as a function of local density. Our simulations serve as a starting point for further studies of collapse including other factors such as magnetic fields and stellar feedback.

  18. Detecting the Collapse of Cooperation in Evolving Networks

    PubMed Central

    Cavaliere, Matteo; Yang, Guoli; Danos, Vincent; Dakos, Vasilis

    2016-01-01

    The sustainability of biological, social, economic and ecological communities is often determined by the outcome of social conflicts between cooperative and selfish individuals (cheaters). Cheaters avoid the cost of contributing to the community and can occasionally spread in the population leading to the complete collapse of cooperation. Although such collapse often unfolds unexpectedly, it is unclear whether one can detect the risk of cheater’s invasions and loss of cooperation in an evolving community. Here, we combine dynamical networks and evolutionary game theory to study the abrupt loss of cooperation with tools for studying critical transitions. We estimate the risk of cooperation collapse following the introduction of a single cheater under gradually changing conditions. We observe an increase in the average time it takes for cheaters to be eliminated from the community as the risk of collapse increases. We argue that such slow system response resembles slowing down in recovery rates prior to a critical transition. In addition, we show how changes in community structure reflect the risk of cooperation collapse. We find that these changes strongly depend on the mechanism that governs how cheaters evolve in the community. Our results highlight novel directions for detecting abrupt transitions in evolving networks. PMID:27492876

  19. Subsidence and collapse sinkholes in soluble rock: a numerical perspective

    NASA Astrophysics Data System (ADS)

    Kaufmann, Georg; Romanov, Douchko; Hiller, Thomas

    2016-04-01

    Soluble rocks such as limestone, gypsum, anhydrite, and salt are prone to subsidence and the sudden creation of collapse sinkholes. The reason for this behaviour stems from the solubility of the rock: Water percolating through fissures and bedding partings can remove material from the rock walls and thus increase the permeability of the host rock by orders of magnitudes. This process occurs on time scales of 1,000-100,000 years, resulting in enlarged fractures, voids and cavities, which then carry flow efficiently through the rock. The enlargement of sub-surface voids to the meter-size within such short times creates mechanical conditions prone to collapse. The collapse initiates at depth, but then propagates to the surface. By means of numerical modelling, we discuss the long-term evolution of secondary porosity in gypsum rocks, resulting in zones of sub-surface voids, which then become mechanically unstable and collapse. We study two real-world case scenarios, in which we can relate field observations to our numerical model: (i) A dam-site scenario, where flow around the dam caused widespread dissolution of gypsum and subsequent subsidence of the dam and a nearby highway. (ii) A natural collapse sinkhole forming as a result of freshwater inflow into a shallow anhydrite formation with rapid evolution of voids in the sub-surface.

  20. Reconstructing core-collapse supernovae waveforms with advanced era interferometers

    NASA Astrophysics Data System (ADS)

    McIver, Jessica; LIGO Scientific Collaboration

    2015-04-01

    Among of the wide range of potentially interesting astrophysical sources for Advanced LIGO and Advanced Virgo are galactic core-collapse supernovae. Although detectable core-collapse supernovae have a low expected rate (a few per century, or less) these signals would yield a wealth of new physics in the form of many messengers. Of particular interest is the insight into the explosion mechanism driving core-collapse supernovae that can be gleaned from the reconstructed gravitational wave signal. A well-reconstructed waveform will allow us to assess the likelihood of different explosion models, perform model selection, and potentially map unexpected features to new physics. This talk will present a study evaluating the current performance of the reconstruction of core-collapse supernovae gravitational wave signals. We used simulated waveforms modeled after different explosion mechanisms that we first injected into fake strain data re-colored to the expected Advanced LIGO/Virgo noise curves and then reconstructed using the pipelines Coherent Waveburst 2G and BayesWave. We will discuss the impact of these results on our ability to accurately reconstruct core-collapse supernovae signals, and by extension, other potential astrophysical generators of rich, complex waveforms.

  1. Near-Field Microscopy Studies of Lung Surfactant Collapse

    NASA Astrophysics Data System (ADS)

    Aga, Rachel; Dunn, Robert

    2003-03-01

    Respiratory distress syndrome (RDS), the fourth leading cause of infant mortality in the United States, arises from an insufficiently developed lung surfactant (LS). Healthy LS, a mixture of lipids and proteins that coats the inner surface of the lungs, reduces the alveolar surface tension to a few millinewtons per meter and, thus, facilitates breathing by stabilizing the large surface area changes associated with respiration. In the absence of an effective LS, surfactant collapse pressure (i.e., monolayer compressibility) and the ability of the monolayer to re-spread during the breathing cycle are reduced, resulting in labored breathing, reduced oxygen transport, and often death in those afflicted. In this study, we investigate the mechanism of collapse and re-spreading of a monolayer formed by a replacement surfactant commonly used in treatment of RDS. Through confocal microscopy fluorescence images obtained at a series of pressures near collapse, we find evidence for multilayer formation in the films. A further understanding of the collapse mechanism is obtained by comparing high resolution fluorescence and topography information measured with near-field scanning optical microscopy. The combined data from both confocal and near-field measurements are used to develop a model of lung surfactant collapse and re-spreading.

  2. On Rapidly Rotating Magnetic Core-Collapse Supernovae

    SciTech Connect

    Wilson, J R; Mathews, G J; Dalhed, H E

    2004-12-20

    The authors have analyzed magnetic effects which may occur in rapidly rotating core collapse supernovae. They consider effects from both magnetic turbulence and the formation of magnetic bubbles. For magnetic turbulence they have made a perturbative analysis for the spherically symmetric core-collapse supernova model that incorporates the build up of magnetic field energy in the matter accreting onto the proto-neutron star shortly after collapse and bounce. This significantly modifies the pressure profile and increases the heating of the material above the proto-neutron star resulting in an explosion even in rotating stars which would not explode otherwise. Regarding magnetic bubbles it is shown that a model with an initial uniform magnetic field ({approx} 10{sup 8}) gauss and uniform angular velocity of ({approx} 0.1 rad sec{sup -1}) can form magnetic bubbles due to the very non homologous nature of the collapse. It is estimated that the buoyancy of the bubbles causes matter in the proto-neutron star to rise, carrying neutrino-rich material to the neutron-star surface. This increases the neutrino luminosity sufficiently at early times to achieve a successful neutrino-driven explosion. Both magnetic mechanisms thus provide new means for initiating a Type II core-collapse supernova.

  3. Correlated random walks caused by dynamical wavefunction collapse

    NASA Astrophysics Data System (ADS)

    Bedingham, D. J.; Ulbricht, H.

    2015-08-01

    Wavefunction collapse models modify Schrödinger’s equation so that it describes the collapse of a superposition of macroscopically distinguishable states as a dynamical process. This provides a basis for the resolution of the quantum measurement problem. An additional generic consequence of the collapse mechanism is that it causes particles to exhibit a tiny random diffusive motion. Here it is shown that for the continuous spontaneous localization (CSL) model—one of the most well developed collapse models—the diffusions of two sufficiently nearby particles are positively correlated. An experimental test of this effect is proposed in which random displacements of pairs of free nanoparticles are measured after they have been simultaneously released from nearby traps. The experiment must be carried out at sufficiently low temperature and pressure in order for the collapse effects to dominate over the ambient environmental noise. It is argued that these constraints can be satisfied by current technologies for a large region of the viable parameter space of the CSL model. The effect disappears as the separation between particles exceeds the CSL length scale. The test therefore provides a means of bounding this length scale.

  4. Gravitational wave burst signal from core collapse of rotating stars

    SciTech Connect

    Dimmelmeier, Harald; Ott, Christian D.; Marek, Andreas; Janka, H.-Thomas

    2008-09-15

    We present results from detailed general relativistic simulations of stellar core collapse to a proto-neutron star, using two different microphysical nonzero-temperature nuclear equations of state as well as an approximate description of deleptonization during the collapse phase. Investigating a wide variety of rotation rates and profiles as well as masses of the progenitor stars and both equations of state, we confirm in this very general setup the recent finding that a generic gravitational wave burst signal is associated with core bounce, already known as type I in the literature. The previously suggested type II (or 'multiple-bounce') waveform morphology does not occur. Despite this reduction to a single waveform type, we demonstrate that it is still possible to constrain the progenitor and postbounce rotation based on a combination of the maximum signal amplitude and the peak frequency of the emitted gravitational wave burst. Our models include to sufficient accuracy the currently known necessary physics for the collapse and bounce phase of core-collapse supernovae, yielding accurate and reliable gravitational wave signal templates for gravitational wave data analysis. In addition, we assess the possibility of nonaxisymmetric instabilities in rotating nascent proto-neutron stars. We find strong evidence that in an iron core-collapse event the postbounce core cannot reach sufficiently rapid rotation to become subject to a classical bar-mode instability. However, many of our postbounce core models exhibit sufficiently rapid and differential rotation to become subject to the recently discovered dynamical instability at low rotation rates.

  5. Thoracoscopic surgical navigation system for cancer localization in collapsed lung based on estimation of lung deformation.

    PubMed

    Nakamoto, Masahiko; Aburaya, Naoki; Sato, Yoshinobu; Konishi, Kozo; Yoshino, Ichiro; Hashizume, Makoto; Tamura, Shinichi

    2007-01-01

    We have developed a thoracoscopic surgical navigation system for lung cancer localization. In our system, the thoracic cage and mediastinum are localized using rigid registration between the intraoperatively digitized surface points and the preoperative CT surface model, and then the lung deformation field is estimated using nonrigid registration between the registered and digitized point datasets on the collapsed lung surface and the preoperative CT lung surface model to predict cancer locations. In this paper, improved methods on key components of the system are investigated to realize clinically acceptable usability and accuracy. Firstly, we implement a non-contact surface digitizer under thoracoscopic control using an optically tracked laser pointer. Secondly, we establish a rigid registration protocol which minimizes the influence of the deformation in different patient's positions by analyzing MR images of volunteers. These techniques were evaluated by in vitro and clinical experiments. PMID:18044554

  6. Equation of state for nuclear matter in core-collapse supernovae by the variational method

    NASA Astrophysics Data System (ADS)

    Togashi, H.; Takehara, Y.; Yamamuro, S.; Nakazato, K.; Suzuki, H.; Sumiyoshi, K.; Takano, M.

    2014-12-01

    We construct a new nuclear equation of state (EOS) for core-collapse supernova (SN) simulations using the variational many-body theory. For uniform nuclear matter, the EOS is constructed with the cluster variational method starting from the realistic nuclear Hamiltonian composed of the Argonne v18 two-body potential and the Urbana IX three-body potential. The masses and radii of neutron stars calculated with the obtained EOS at zero temperature are consistent with recent observational data. For non-uniform nuclear matter, we construct the EOS in the Thomas-Fermi approximation. In this approximation, we assume a functional form of the density distributions of protons, neutrons, and alpha-particles, and minimize the free energy density in a Wigner-Seitz cell with respect to the parameters included in the assumed density distribution functions. The phase diagram of hot nuclear matter at a typical temperature is reasonable as compared with that of the Shen EOS.

  7. Effect of the rinse solution to avoid 193-nm resist line collapse: a study for modification of resist polymer and process conditions

    NASA Astrophysics Data System (ADS)

    Masuda, Seiya; Kobayashi, Masakazu; Kim, Woo-Kyu; Anyadiegwu, Clement; Padmanaban, Munirathna; Dammel, Ralph R.; Tanaka, Keiichi; Yamada, Yoshiaki

    2004-05-01

    The device design rule is continuously shrinking toward optical resolution limit where k1 factor is below 0.3. The requirement for 193 nm photoresist below 90 nm node is quite challenging at the manufacturing phase. Using DI water rinse after development gives a significant amount of line collapse when the aspect ratio is over 3. To avoid line collapse, we co-developed special rinse solution for FIRM process with Tokyo Electron Ltd. Utilizing FIRM process, 90 nm dense line collapse was measured by CD SEM using focus-exposure matrices. The line collapse property has been observed using experimental 193 nm positive tone resist by varying monomer ratio of the polymer and process conditions. The surface property of the resist was also studied to investigate the interaction with rinse solution at the de-protected polymer region. However, a high surfactant concentration in the DI water rinse leads the swelling of the resist pattern profile. The resist component is the key to determine adequate surfactant concentration in rinse solution to minimize line collapse and pattern deformation

  8. Outer Shock Interaction in Young Core-Collapse SNRs

    NASA Astrophysics Data System (ADS)

    Lee, Jae-Joon

    2014-01-01

    Studying the environments in which core-collapse supernovae (SNe) explode and then subsequently evolve is essential to establish the nature of the mass loss and the explosion of the progenitor star. The spatial structure of the outer shock in young core-collapse SNRs provides an opportunity to study the nature of the medium into which the remnant has been expanding. We present our X-ray study of the outer shocks in young core-collapse SNRs in our Galaxy. For Cas A and G292.0+1.8, we find that both remnants have been likely interacting with dense red supergiant winds. For other remnants with bright thermal X-ray emission from the shell, we suggest that they are interacting with pre-existing circumstellar structure. We discuss the nature of the winds and the progenitor stars.

  9. Nano-artifact metrics based on random collapse of resist

    PubMed Central

    Matsumoto, Tsutomu; Hoga, Morihisa; Ohyagi, Yasuyuki; Ishikawa, Mikio; Naruse, Makoto; Hanaki, Kenta; Suzuki, Ryosuke; Sekiguchi, Daiki; Tate, Naoya; Ohtsu, Motoichi

    2014-01-01

    Artifact metrics is an information security technology that uses the intrinsic characteristics of a physical object for authentication and clone resistance. Here, we demonstrate nano-artifact metrics based on silicon nanostructures formed via an array of resist pillars that randomly collapse when exposed to electron-beam lithography. The proposed technique uses conventional and scalable lithography processes, and because of the random collapse of resist, the resultant structure has extremely fine-scale morphology with a minimum dimension below 10 nm, which is less than the resolution of current lithography capabilities. By evaluating false match, false non-match and clone-resistance rates, we clarify that the nanostructured patterns based on resist collapse satisfy the requirements for high-performance security applications. PMID:25142401

  10. Renormalized field theory of collapsing directed randomly branched polymers.

    PubMed

    Janssen, Hans-Karl; Wevelsiep, Frank; Stenull, Olaf

    2009-10-01

    We present a dynamical field theory for directed randomly branched polymers and in particular their collapse transition. We develop a phenomenological model in the form of a stochastic response functional that allows us to address several interesting problems such as the scaling behavior of the swollen phase and the collapse transition. For the swollen phase, we find that by choosing model parameters appropriately, our stochastic functional reduces to the one describing the relaxation dynamics near the Yang-Lee singularity edge. This corroborates that the scaling behavior of swollen branched polymers is governed by the Yang-Lee universality class as has been known for a long time. The main focus of our paper lies on the collapse transition of directed branched polymers. We show to arbitrary order in renormalized perturbation theory with epsilon expansion that this transition belongs to the same universality class as directed percolation. PMID:19905335

  11. On testing for the stage of collapse in quantum mechanics

    NASA Astrophysics Data System (ADS)

    Becker, Lon Stephen

    The question was considered whether it is possible to experimentally narrow down the time of collapse in the measurement process of quantum mechanics. A form of experiment was developed towards that end. The proof of John von Neumann that it is impossible to determine the time of collapse was analyzed, and its hidden assumptions were exploited in the design of the experiment. The reinterpretation of quantum mechanics by David Bohm was introduced to give an alternative way of looking at quantum mechanics. An objection to this view was discussed but rejected. Finally a pair of thought experiments were offered with the potential to be converted in the future into tests for whether collapse has occurred at various points in the measurement process.

  12. Collapsing Glomerulopathy in a Child with Galloway-Mowat Syndrome

    PubMed Central

    Zeybek, Cengiz; Basbozkurt, Gokalp; Hamcan, Salih; Ozcan, Ayhan; Gul, Davut; Gok, Faysal

    2016-01-01

    Galloway-Mowat syndrome (GMS) is an autosomal recessive disorder with a poor prognosis that was first defined as a triad of central nervous system involvement, hiatal hernia, and nephrotic syndrome. However, this syndrome is now known to have a heterogeneous clinical presentation. The nephrotic syndrome is steroid resistant and is responsible for the outcome. The combination of collapsing glomerulopathy and GMS is very rare. A 26-month-old boy presented with steroid-resistant nephrotic syndrome associated with neurologic findings, including microcephaly, psychomotor retardation, and nystagmus. Magnetic resonance imaging showed marked cerebral atrophy, optic atrophy, and hypomyelination. A renal biopsy was consistent with collapsing glomerulopathy. If collapsing glomerulopathy is associated with neurological abnormalities, especially with microcephaly, clinicians should consider GMS as a possible underlying cause.

  13. Collapse of magnetized hypermassive neutron stars in general relativity.

    PubMed

    Duez, Matthew D; Liu, Yuk Tung; Shapiro, Stuart L; Shibata, Masaru; Stephens, Branson C

    2006-01-27

    Hypermassive neutron stars (HMNSs)--equilibrium configurations supported against collapse by rapid differential rotation--are possible transient remnants of binary neutron-star mergers. Using newly developed codes for magnetohydrodynamic simulations in dynamical spacetimes, we are able to track the evolution of a magnetized HMNS in full general relativity for the first time. We find that secular angular momentum transport due to magnetic braking and the magnetorotational instability results in the collapse of an HMNS to a rotating black hole, accompanied by a gravitational wave burst. The nascent black hole is surrounded by a hot, massive torus undergoing quasistationary accretion and a collimated magnetic field. This scenario suggests that HMNS collapse is a possible candidate for the central engine of short gamma-ray bursts. PMID:16486677

  14. The Impact of Nuclear Physics During Stellar Core Collapse

    SciTech Connect

    Hix, William Raphael; Baird, Mark L; Lentz, Eric J; Messer, Bronson; Mezzacappa, Anthony

    2008-01-01

    Nuclear electron capture and the nuclear equation of state play important roles during the collapse of a massive star and the subsequent supernova. The nuclear equation of state controls the nature of the bounce which initially forms the supernova shock while electron capture determines the location where the shock forms. Advances in nuclear structure theory have allowed a more realistic treatment of electron capture on heavy nuclei to be developed. We will review how this improvement has led to a change in our understanding of stellar core collapse, with electron capture on nuclei with masses larger than 50 found to dominate electron capture on free protons, resulting is significant changes in the hydrodynamics of core collapse and bounce. We will also demonstrate the impact of a variety of nuclear equations of state on supernova shock propagation. Of particular note is the interplay between the nuclear composition determined by the equation of state and nuclear electron capture.

  15. Cluster coarsening during polymer collapse: Finite-size scaling analysis

    NASA Astrophysics Data System (ADS)

    Majumder, Suman; Janke, Wolfhard

    2015-06-01

    We study the kinetics of the collapse of a single flexible polymer when it is quenched from a good solvent to a poor solvent. Results obtained from Monte Carlo simulations show that the collapse occurs through a sequence of events with the formation, growth and subsequent coalescence of clusters of monomers to a single compact globule. Particular emphasis is given in this work to the cluster growth during the collapse, analyzed via the application of finite-size scaling techniques. The growth exponent obtained in our analysis is suggestive of the universal Lifshitz-Slyozov mechanism of cluster growth. The methods used in this work could be of more general validity and applicable to other phenomena such as protein folding.

  16. Modeling colony collapse disorder in honeybees as a contagion.

    PubMed

    Kribs-Zaleta, Christopher M; Mitchell, Christopher

    2014-12-01

    Honeybee pollination accounts annually for over $14 billion in United States agriculture alone. Within the past decade there has been a mysterious mass die-off of honeybees, an estimated 10 million beehives and sometimes as much as 90% of an apiary. There is still no consensus on what causes this phenomenon, called Colony Collapse Disorder, or CCD. Several mathematical models have studied CCD by only focusing on infection dynamics. We created a model to account for both healthy hive dynamics and hive extinction due to CCD, modeling CCD via a transmissible infection brought to the hive by foragers. The system of three ordinary differential equations accounts for multiple hive population behaviors including Allee effects and colony collapse. Numerical analysis leads to critical hive sizes for multiple scenarios and highlights the role of accelerated forager recruitment in emptying hives during colony collapse. PMID:25365602

  17. Collapsing shells, critical phenomena, and black hole formation

    NASA Astrophysics Data System (ADS)

    Cardoso, Vitor; Rocha, Jorge V.

    2016-04-01

    We study the gravitational collapse of two thin shells of matter, in asymptotically flat spacetime or constrained to move within a spherical box. We show that this simple two-body system has surprisingly rich dynamics, which includes prompt collapse to a black hole, perpetually oscillating solutions or black hole formation at arbitrarily large times. Collapse is induced by shell crossing and the black hole mass depends sensitively on the number of shell crossings. At certain critical points, the black hole mass exhibits critical behavior, determined by the change in parity (even or odd) of the number of crossings, with or without mass-gap during the transition. Some of the features we observe are reminiscent of confined scalars undergoing "turbulent" dynamics.

  18. Lateral stress relaxation and collapse in lipid monolayers†

    PubMed Central

    Pocivavsek, Luka; Frey, Shelli L.; Krishan, Kapilanjan; Gavrilov, Kseniya; Ruchala, Piotr; Waring, Alan J.; Walther, Frans J.; Dennin, Michael; Witten, Thomas A.; Lee, Ka Yee C.

    2009-01-01

    Surfactants at air/water interfaces are often subjected to mechanical stresses as the interfaces they occupy are reduced in area. The most well characterized forms of stress relaxation in these systems are first order phase transitions from lower density to higher density phases. Here we study stress relaxation in lipid monolayers that occurs once chemical phase transitions have been exhausted. At these highly compressed states, the monolayer undergoes global mechanical relaxations termed collapse. By studying four different types of monolayers, we determine that collapse modes are most closely linked to in-plane rigidity. We characterize the rigidity of the monolayer by analyzing in-plane morphology on numerous length scales. More rigid monolayers collapse out-of-plane via a hard elastic mode similar to an elastic membrane, while softer monolayers relax in-plane by shearing. PMID:19657472

  19. Mutation Accumulation and Fitness Collapse at Population Frontiers

    NASA Astrophysics Data System (ADS)

    Lavrentovich, Maxim; Nelson, David

    2015-03-01

    Rapid, deleterious mutations occurring in, e.g., viral populations and cancerous tissue, may accumulate and lead to fitness loss. Previous studies show that sufficiently rapid accumulation in one-dimensional populations leads to a fitness collapse, governed by the directed percolation (DP) universality class. We compare this situation to the collapse in effectively two-dimensional populations, such as the frontiers of three-dimensional range expansions. A phase diagram is computed as a function of the mutation rate μ and strength s. Relative to one-dimensional populations, we find that the collapse occurs in a smaller region of phase space. The scaling combination governing the phase diagram shape is μ | lns | / s (μ /s2 for one-dimensional populations). We argue that the evolutionary dynamics is described by a set of coupled DP Langevin equations near the transition, and that the coupling terms lead to deviations from expected DP scaling.

  20. Nano-artifact metrics based on random collapse of resist

    NASA Astrophysics Data System (ADS)

    Matsumoto, Tsutomu; Hoga, Morihisa; Ohyagi, Yasuyuki; Ishikawa, Mikio; Naruse, Makoto; Hanaki, Kenta; Suzuki, Ryosuke; Sekiguchi, Daiki; Tate, Naoya; Ohtsu, Motoichi

    2014-08-01

    Artifact metrics is an information security technology that uses the intrinsic characteristics of a physical object for authentication and clone resistance. Here, we demonstrate nano-artifact metrics based on silicon nanostructures formed via an array of resist pillars that randomly collapse when exposed to electron-beam lithography. The proposed technique uses conventional and scalable lithography processes, and because of the random collapse of resist, the resultant structure has extremely fine-scale morphology with a minimum dimension below 10 nm, which is less than the resolution of current lithography capabilities. By evaluating false match, false non-match and clone-resistance rates, we clarify that the nanostructured patterns based on resist collapse satisfy the requirements for high-performance security applications.

  1. Tunneling into microstate geometries: quantum effects stop gravitational collapse

    NASA Astrophysics Data System (ADS)

    Bena, Iosif; Mayerson, Daniel R.; Puhm, Andrea; Vercnocke, Bert

    2016-07-01

    Collapsing shells form horizons, and when the curvature is small classical general relativity is believed to describe this process arbitrarily well. On the other hand, quantum information theory based (fuzzball/firewall) arguments suggest the existence of some structure at the black hole horizon. This structure can only form if classical general relativity stops being the correct description of the collapsing shell before it reaches the horizon size. We present strong evidence that classical general relativity can indeed break down prematurely, by explicitly computing the quantum tunneling amplitude of a collapsing shell of branes into smooth horizonless microstate geometries. We show that the amplitude for tunneling into microstate geometries with a large number of topologically non-trivial cycles is parametrically larger than e - S BH , which indicates that the shell can tunnel into a horizonless configuration long before the horizon has any chance to form. We also use this technology to investigate the tunneling of M2 branes into LLM bubbling geometries.

  2. Observing atomic collapse resonances in artificial nuclei on graphene.

    PubMed

    Wang, Yang; Wong, Dillon; Shytov, Andrey V; Brar, Victor W; Choi, Sangkook; Wu, Qiong; Tsai, Hsin-Zon; Regan, William; Zettl, Alex; Kawakami, Roland K; Louie, Steven G; Levitov, Leonid S; Crommie, Michael F

    2013-05-10

    Relativistic quantum mechanics predicts that when the charge of a superheavy atomic nucleus surpasses a certain threshold, the resulting strong Coulomb field causes an unusual atomic collapse state; this state exhibits an electron wave function component that falls toward the nucleus, as well as a positron component that escapes to infinity. In graphene, where charge carriers behave as massless relativistic particles, it has been predicted that highly charged impurities should exhibit resonances corresponding to these atomic collapse states. We have observed the formation of such resonances around artificial nuclei (clusters of charged calcium dimers) fabricated on gated graphene devices via atomic manipulation with a scanning tunneling microscope. The energy and spatial dependence of the atomic collapse state measured with scanning tunneling microscopy revealed unexpected behavior when occupied by electrons. PMID:23470728

  3. Numerical study of axisymmetric collapses of submarine granular > columns

    NASA Astrophysics Data System (ADS)

    Monsorno, Davide; Varsakelis, Christos

    2014-11-01

    In this talk, we report on the results of a numerical study of the axisymmetric collapse of subaqueous granular columns. Our study is based on a 2-pressure, 2-velocity continuum flow model for fluid-saturated granular materials. This model is integrated via a multi-phase projection method that incorporates a regularization method for the treatment of material interfaces. In our simulations, a dense column of a granular material immersed in water is placed on a horizontal plane and is allowed to collapse and spread due to its weight. Emphasis is placed on the run-out distance and the termination height and their correlation with the aspect ratio, the volume fraction and the diameter of the grains. Comparisons against experimental measurements and previous numerical predictions are also performed. Finally, in order to examine and quantify the role of the interstitial fluid, we compare our numerical predictions against experimental results from column collapses of dry granular materials.

  4. Coagulation of grains in static and collapsing protostellar clouds

    NASA Technical Reports Server (NTRS)

    Weidenschilling, S. J.; Ruzmaikina, T. V.

    1993-01-01

    The wavelength dependence of extinction in the diffuse interstellar medium implies that it is produced by particles of dominant size of approximately 10(exp -5) cm. There is some indication that in the cores of dense molecular clouds, sub-micron grains can coagulate to form larger particles; this process is probably driven by turbulence. The most primitive meteorites (carbonaceous chondrites) are composed of particles with a bimodal size distribution with peaks near 1 micron (matrix) and 1 mm (chondrules). Models for chondrule formation that involve processing of presolar material by chemical reactions or through an accretion shock during infall assume that aggregates of the requisite mass could form before or during collapse. The effectiveness of coagulation during collapse has been disputed; it appears to depend on specific assumptions. The first results of detailed numerical modeling of spatial and temporal variations of particle sizes in presolar clouds, both static and collapsing, is reported in this article.

  5. Endobronchial Cartilage Rupture: A Rare Cause of Lobar Collapse.

    PubMed

    Dasa, Osama; Siddiqui, Nauman; Ruzieh, Mohammed; Javaid, Toseef

    2016-01-01

    Endobronchial cartilage rupture is a rare clinical condition, which can present in patients with severe emphysema with sudden onset shortness of breath. We present a case of a 62-year-old male who presented to our emergency department with sudden onset shortness of breath. Chest X-ray showed lung hyperinflation and a right lung field vague small density. Chest Computed Tomography confirmed the presence of right middle lobe collapse. Bronchoscopy revealed partial right middle lobe atelectasis and an endobronchial cartilage rupture. Endobronchial cartilage rupture is a rare condition that can present as sudden onset shortness of breath due to lobar collapse in patients with emphysema and can be triggered by cough. Bronchoscopic findings include finding a collapsed lung lobe and a visible ruptured endobronchial cartilage. A high index of suspicion, chest imaging, and early bronchoscopy can aid in the diagnosis and help prevent complications. PMID:27525149

  6. Critical Phenomena in Velocity-Induced Perfect Fluid Collapse

    NASA Astrophysics Data System (ADS)

    Noble, Scott C.; Choptuik, Matthew W.

    2003-04-01

    We consider critical collapse of spherically-symmetric, general relativistic neutron star models. In order to induce collapse in nominally static star solutions, we give the stars initially "in-going" velocity profiles, where an overall amplitude factor of the profile is tuned to produce a critical solution that sits at the threshold of black hole formation. By examining how the global maximum of the Ricci scalar varies with the control parameter, we are able to measure the critical scaling exponents associated with the critical solutions. For a stiff fluid model, we calculate a scaling exponent consistent with previous investigations of ultra-relativistic fluid collapse. However, our exponent is in disagreement with a recent study by J. Novak (2001) which used the same initial data prescription but failed to resolve the dynamics at the threshold of black hole formation.

  7. Centrifugal Force Induced Collapse of Strange Stars Into Black Holes

    NASA Astrophysics Data System (ADS)

    de Paolis, F.; Ingrosso, G.; Nucita, A. A.; Qadir, Asghar

    It has been suggested that there could be objects even more compact than neutron stars, like the so-called strange stars, P-stars, and magnetars. Strange stars are collapsed stars consisting of u, d, and s quarks. P-stars are a new class of compact stars made of u and d quarks in β-equilibrium with electrons in an Abelian chromomagnetic condensate. It has also been shown that a particle in a circular orbit around a stationary black hole is subject to a centrifugal force that turns out to be directed inwards if the particle orbit radius is between the Schwarzschild radius rs and 3rs/2. Here it is proposed that rotation of a sufficiently compact collapsed object may lead to a centrifugal force induced collapse to a black hole that could emit short gamma-ray bursts.

  8. Unexplained Neonatal Cardiorespiratory Collapse at Five Minutes of Age

    PubMed Central

    Zaleta, Sona; Miller, Sarah; Kumar, Prashant

    2016-01-01

    We report a case in which a term neonate suffered cardiorespiratory collapse at five minutes of age following an uncomplicated delivery and Apgar score of eight at one minute. Following prolonged cardiopulmonary resuscitation, the infant recovered well with no neurological deficit. Although sudden and unexpected postnatal collapse has been extensively described, this case does not fulfil its definition criteria. It provides a diagnostic challenge for clinicians and to the best of our knowledge is the first report of unexplained cardiorespiratory collapse at five minutes of age. The case serves as a timely reminder that cord gas analysis is recommended in all cases of potential fetal compromise and that Apgar scores should be used with caution as a predictor of neurological sequelae. PMID:27006848

  9. Endobronchial Cartilage Rupture: A Rare Cause of Lobar Collapse

    PubMed Central

    Siddiqui, Nauman; Javaid, Toseef

    2016-01-01

    Endobronchial cartilage rupture is a rare clinical condition, which can present in patients with severe emphysema with sudden onset shortness of breath. We present a case of a 62-year-old male who presented to our emergency department with sudden onset shortness of breath. Chest X-ray showed lung hyperinflation and a right lung field vague small density. Chest Computed Tomography confirmed the presence of right middle lobe collapse. Bronchoscopy revealed partial right middle lobe atelectasis and an endobronchial cartilage rupture. Endobronchial cartilage rupture is a rare condition that can present as sudden onset shortness of breath due to lobar collapse in patients with emphysema and can be triggered by cough. Bronchoscopic findings include finding a collapsed lung lobe and a visible ruptured endobronchial cartilage. A high index of suspicion, chest imaging, and early bronchoscopy can aid in the diagnosis and help prevent complications. PMID:27525149

  10. The Tacoma Narrows Bridge Collapse on Film and Video

    NASA Astrophysics Data System (ADS)

    Olson, Don; Hook, Joseph; Doescher, Russell; Wolf, Steven

    2015-11-01

    This month marks the 75th anniversary of the Tacoma Narrows Bridge collapse. During a gale on Nov. 7, 1940, the bridge exhibited remarkable oscillations before collapsing spectacularly (Figs. 1-5). Physicists over the years have spent a great deal of time and energy studying this event. By using open-source analysis tools and digitized footage of the disaster, physics students in both high school and college can continue in this tradition. Students can watch footage of "Galloping Gertie," ask scientific questions about the bridge's collapse, analyze data, and draw conclusions from that analysis. Students should be encouraged to pursue their own investigations, but the question that drove our inquiry was this: "When physics classes watch modern video showing the oscillations and the free fall of the bridge fragments, are these scenes sped up, slowed down, or at the correct speed compared to what was observed by the eyewitnesses on Nov. 7, 1940?"

  11. Theoretical analysis of wake-induced parachute collapse

    SciTech Connect

    Spahr, H.R.; Wolf, D.F.

    1981-01-01

    During recent drop tests of a prototype weapon system, the parachute collapsed soon after it became fully inflated. The magnitude and duration of the collapses were severe enough to degrade parachute performance drastically. A computer-assisted analysis is presented which models parachute inflation, forebody and parachute wake generation, and interaction between the wake and the inflating or collapsing parachute. Comparison of the analysis results with full-scale drop test results shows good agreement for two parachute sizes; both parachutes were tested with and without permanent reefing. Computer-generated graphics (black and white drawings, color slides, and color movies) show the forebody and inflating parachute, the wake, and the wake and parachute interaction.

  12. Minimally invasive video-assisted versus minimally invasive nonendoscopic thyroidectomy.

    PubMed

    Fík, Zdeněk; Astl, Jaromír; Zábrodský, Michal; Lukeš, Petr; Merunka, Ilja; Betka, Jan; Chovanec, Martin

    2014-01-01

    Minimally invasive video-assisted thyroidectomy (MIVAT) and minimally invasive nonendoscopic thyroidectomy (MINET) represent well accepted and reproducible techniques developed with the main goal to improve cosmetic outcome, accelerate healing, and increase patient's comfort following thyroid surgery. Between 2007 and 2011, a prospective nonrandomized study of patients undergoing minimally invasive thyroid surgery was performed to compare advantages and disadvantages of the two different techniques. There were no significant differences in the length of incision to perform surgical procedures. Mean duration of hemithyroidectomy was comparable in both groups, but it was more time consuming to perform total thyroidectomy by MIVAT. There were more patients undergoing MIVAT procedures without active drainage in the postoperative course and we also could see a trend for less pain in the same group. This was paralleled by statistically significant decreased administration of both opiates and nonopiate analgesics. We encountered two cases of recurrent laryngeal nerve palsies in the MIVAT group only. MIVAT and MINET represent safe and feasible alternative to conventional thyroid surgery in selected cases and this prospective study has shown minimal differences between these two techniques. PMID:24800227

  13. The New Minimal Standard Model

    SciTech Connect

    Davoudiasl, Hooman; Kitano, Ryuichiro; Li, Tianjun; Murayama, Hitoshi

    2005-01-13

    We construct the New Minimal Standard Model that incorporates the new discoveries of physics beyond the Minimal Standard Model (MSM): Dark Energy, non-baryonic Dark Matter, neutrino masses, as well as baryon asymmetry and cosmic inflation, adopting the principle of minimal particle content and the most general renormalizable Lagrangian. We base the model purely on empirical facts rather than aesthetics. We need only six new degrees of freedom beyond the MSM. It is free from excessive flavor-changing effects, CP violation, too-rapid proton decay, problems with electroweak precision data, and unwanted cosmological relics. Any model of physics beyond the MSM should be measured against the phenomenological success of this model.

  14. The White Pine Mine explosively induced, controlled collapse experiment

    SciTech Connect

    Pearson, D.C.; Stump, B.W.; Phillips, W.S.

    1996-09-01

    On September 3, 1995, the White Pine Mine, which is owned by Copper Range Company, conducted the first of a planned series of explosive removal of existing pillars in their underground mining operations. The purpose of this operation is to evaluate the effectiveness of pillar rubbilization and roof collapse for planned in-situ leaching of the copper ore from the rock mass. This type of seismic source is unique in that a large, delay fired, explosive source was expected to be followed by collapse of the rock immediately above the explosion into the void created. Characterization of this type of mining source is of interest to the Comprehensive Test Ban Treaty (CTBT) R&D Seismic Program due to its unique properties. These include the controlled nature of the source in time, location, and magnitude, the fact that the source is located in an active region of underground mining, and that natural collapse of large portions of this mine have occurred in the recent past. The Mine operator is concerned with the characterization of the vibration induced by both the explosive and implosive components of the procedure and determination of the depth to which chimneying of the roof proceeded. This report will document: The reasons for conducting both the explosively induced collapse and the Los Alamos National Laboratory CTBT R&D Experimental Field Program experiment; The local and regional seismic, acoustic, and videographic data acquired; Analysis of the explosion/collapse seismic signal generated; Analysis and location of the aftershocks associated with the collapse; and Conclusions made concerning this type of mining explosion in relation to verification of a Comprehensive Test Ban Treaty.

  15. Mechanical parameters determining pharyngeal collapsibility in patients with sleep apnea.

    PubMed

    Oliven, Arie; Kaufman, Eran; Kaynan, Rotem; Oliven, Ron; Steinfeld, Uri; Tov, Nave; Odeh, Majed; Gaitini, Luis; Schwartz, Alan R; Kimmel, Eitan

    2010-10-01

    The relative impact of mechanical factors on pharyngeal patency in patients with obstructive sleep apnea is poorly understood. The present study was designed to evaluate parameters of the "tube law" on pharyngeal pressure-flow relationships and collapsibility in patients with obstructive sleep apnea. We developed a mathematical model that considered the collapsible segment of the pharynx to represent an orifice of varying diameter. The model enabled us to assess the effects of pharyngeal compliance (C), neutral cross-sectional area (A(o)), external peripharyngeal pressure (P(ex)), and the resistance proximal to the site of collapse on flow mechanics and pharyngeal collapsibility [critical pressure (P(crit))]. All parameters were measured in 15 patients with obstructive sleep apnea under propofol anesthesia, both at rest and during mandibular advancement and electrical stimulation of the genioglossus. The data was used both to confirm the validity of the model and to compare expected and actual relationships between the tube-law parameters and the pharyngeal pressure-flow relationship and collapsibility. We found a close correlation between predicted and measured P(crit) (R = 0.98), including changes observed during pharyngeal manipulations. C and A(o) were closely and directly interrelated (R = 0.93) and did not correlate with P(crit). A significant correlation was found between P(ex) and P(crit) (R = 0.77; P < 0.01). We conclude that the pharynx of patients with obstructive sleep apnea can be modeled as an orifice with varying diameter. Pharyngeal compliance and A(o) are closely interrelated. Pharyngeal collapsibility depends primarily on the surrounding pressure. PMID:20576847

  16. Collapse of DNA in a.c. electric fields

    PubMed Central

    Zhou, Chunda; Reisner, Walter W.; Staunton, Rory J.; Ashan, Amir; Austin, Robert H.; Riehn, Robert

    2013-01-01

    We report that double-stranded DNA collapses in presence of a.c. electric fields at frequencies of a few hundred Hertz, and does not stretch as commonly assumed. In particular, we show that confinement-stretched DNA can collapse to about one quarter of its equilibrium length. We propose that this effect is based on finite relaxation times of the counterion cloud, and the subsequent partitioning of the molecule into mutually attractive units. We discuss alternative models of those attractive units. PMID:21770604

  17. Collapse Arrest in Instantaneous Kerr Media via Parametric Interactions

    NASA Astrophysics Data System (ADS)

    Pasquazi, Alessia; Peccianti, Marco; Clerici, Matteo; Conti, Claudio; Morandotti, Roberto

    2014-09-01

    We demonstrate, theoretically and experimentally, that a four-wave mixing parametric interaction is able to arrest the collapse of a two-dimensional multicolor beam in an instantaneous Kerr medium. We consider two weak idlers interacting via a third order nonlinearity with two pump beams and we show that a class of collapse-free quasisolitary solutions can be experimentally observed in a normal dispersion Kerr glass. This observation is sustained by rigorous theoretical analysis demonstrating the stability of the observed self-trapped beams.

  18. Spontaneous symmetry breaking and collapse in bosonic Josephson junctions

    SciTech Connect

    Mazzarella, Giovanni; Salasnich, Luca

    2010-09-15

    We investigate an attractive atomic Bose-Einstein condensate (BEC) trapped by a double-well potential in the axial direction and by a harmonic potential in the transverse directions. We obtain numerically a quantum phase diagram which includes all the three relevant phases of the system: Josephson, spontaneous symmetry breaking (SSB), and collapse. We consider also the coherent dynamics of the BEC and calculate the frequency of population-imbalance mode in the Josephson phase and in the SSB phase up to the collapse. We show that these phases can be observed by using ultracold vapors of {sup 7}Li atoms in a magneto-optical trap.

  19. Trumpet solution from spherical gravitational collapse with puncture gauges

    SciTech Connect

    Thierfelder, Marcus; Bernuzzi, Sebastiano; Hilditch, David; Bruegmann, Bernd; Rezzolla, Luciano

    2011-03-15

    We investigate the stationary end state obtained by evolving a collapsing spherical star with the gauges routinely adopted to study puncture black holes. We compare the end state of the collapse with the trumpet solution found in the evolution of a single wormhole slice and show that the two solutions closely agree. We demonstrate that the agreement is caused by the use of the Gamma-driver shift condition, which allows the matter to fall inwards into a region of spacetime that is not resolved by the numerical grid, and which simultaneously finds the stationary coordinates of the trumpet outside the matter.

  20. 4f electron delocalization and volume collapse in praseodymium metal

    SciTech Connect

    Bradley, Joseph A.; Moore, Kevin T.; Lipp, Magnus J.; Mattern, Brian A.; Pacold, Joseph I.; Seidler, Gerald T.; Chow, Paul; Rod, Eric; Xiao, Yuming; Evans, William J.

    2012-04-17

    We study the pressure evolution of the 4f electrons in elemental praseodymium metal compressed through several crystallographic phases, including the large volume-collapse transition at 20 GPa. Using resonant x-ray emission, we directly and quantitatively measure the development of multiple electronic configurations with differing 4f occupation numbers, the key quantum observable related to the delocalization of the strongly correlated 4f electrons. These results provide a high-fidelity test of prior predictions by dynamical mean-field theory, and support the hypothesis of a strong connection between electronic and structural degrees of freedom at the volume-collapse transition.

  1. Analogue of Caldera Dynamics: the Controlled Salt Cavern Collapse

    NASA Astrophysics Data System (ADS)

    Jousset, P. G.; Rohmer, J.

    2012-12-01

    Caldera collapse (or pit-crater) dynamics are inferred from geological observations and laboratory experiments. Here, we present an analogue of caldera collapse at field scale and possible analogy with large scale caldera dynamics. Through an original exploitation technique in sedimentary environment, a salt layer is emptied, leaving a brine-filled cavern, which eventually collapses after overburden falls into the cavern. Such a collapse was monitored in East France by many instruments (including GPS, extensometers, geophones, broadband seismological sensors, tiltmeter, gravity meter, … ), which allowed us to describe mechanisms of the collapse. Micro-seismicity is a good indicator of spatio-temporal evolution of physical properties of rocks prior to catastrophic events like volcanic eruptions or landslides and may be triggered by a number of causes including dynamic characteristics of processes in play or/and external forces. We show evidence of triggered micro-seismicity observed in the vicinity of this underground salt cavern prone to collapse by a remote M~7.2 earthquake, which occurred ~12000 kilometres away. High-dynamic broadband records reveal the strong time-correlation between a dramatic change in the rate of local high-frequency micro-seismicity and the passage of low-frequency seismic waves, including body, Love and Rayleigh surface waves. Pressure was lowered in the cavern by pumping operations of brine out of the cavern. We demonstrate the near critical state of the cavern before the collapse by means of 2D axisymmetric elastic finite-element simulations. Stress oscillations due to the seismic waves may have exceeded the strength required for the rupture of the complex media made of brine and rock triggering micro-earthquakes and leading to damage of the overburden and eventually collapse of the salt cavern. The increment of stress necessary for the failure of a Dolomite layer is of the same order or magnitude as the maximum dynamic stress magnitude

  2. Tracheal collapse. Diagnosis and medical and surgical treatment.

    PubMed

    Johnson, L

    2000-11-01

    Tracheal collapse remains a common clinical problem in middle-aged, small-breed dogs. Clinical signs are characteristic, and the diagnostic work-up serves to identify predisposing triggers of disease and to allow optimization of therapy for individual animals. Bronchoscopic confirmation of airway collapse aids in characterizing the extent of airway damage and allows collection of airway samples to rule out infectious or inflammatory airway disease. Once coincident diseases have been managed, cough suppressants are used to control signs and reduce chronic airway injury. PMID:11221980

  3. Poration of lipid bilayers by shock-induced nanobubble collapse

    NASA Astrophysics Data System (ADS)

    Choubey, Amit; Vedadi, Mohammad; Nomura, Ken-ichi; Kalia, Rajiv K.; Nakano, Aiichiro; Vashishta, Priya

    2011-01-01

    We investigate molecular mechanisms of poration in lipid bilayers due to shock-induced collapse of nanobubbles. Our multimillion-atom molecular dynamics simulations reveal dynamics of nanobubble shrinkage and collapse, leading to the formation and penetration of nanojets into lipid bilayers. The nanojet impact generates shear flow of water on bilayer leaflets and pressure gradients across them, which transiently enhance the bilayer permeability by creating nanopores through which water molecules translocate rapidly across the bilayer. Effects of nanobubble size and temperature on the porosity of lipid bilayers are examined.

  4. An Elastoplastic Model for Partially Saturated Collapsible Rocks

    NASA Astrophysics Data System (ADS)

    Ma, Jianjun

    2016-02-01

    A unified elastoplastic model for describing the stress-strain behavior of partially saturated collapsible rocks is proposed. The elastic-plastic response due to loading and unloading is captured using bounding surface plasticity. The coupling effect of hydraulic and mechanical responses is addressed by applying the effective stress concept. Special attention is paid to the rock-fluid characteristic curve (RFCC), effective stress parameter, and suction hardening. A wide range of saturation degree is considered. The characteristics of mechanical behavior in partially saturated collapsible rocks are captured for all cases considered.

  5. Dynamics of a vapor nanobubble collapsing near a solid boundary

    NASA Astrophysics Data System (ADS)

    Magaletti, Francesco; Gallo, Mirko; Marino, Luca; Massimo Casciola, Carlo

    2015-12-01

    In the present paper a diffuse interface approach [1] is used to address the collapse of a sub-micron vapor bubble near solid boundaries. This formulation enables an unprecedented description of interfacial flows that naturally takes into account topology modification and phase changes (both vapor/liquid and vapor/supercritical fluid transformations). Results from numerical simulations are exploited to discuss the complex sequence of events associated with the bubble collapse near a wall, encompassing shock-wave emissions in the liquid and reflections from the wall, their successive interaction with the expanding bubble, the ensuing asymmetry of the bubble and the eventual jetting phase.

  6. Thermoinertial bouncing of a relativistic collapsing sphere: A numerical model

    SciTech Connect

    Herrera, L.; Di Prisco, A.; Barreto, W.

    2006-01-15

    We present a numerical model of a collapsing radiating sphere, whose boundary surface undergoes bouncing due to a decreasing of its inertial mass density (and, as expected from the equivalence principle, also of the 'gravitational' force term) produced by the 'inertial' term of the transport equation. This model exhibits for the first time the consequences of such an effect, and shows that under physically reasonable conditions this decreasing of the gravitational term in the dynamic equation may be large enough as to revert the collapse and produce a bouncing of the boundary surface of the sphere.

  7. The Effect of Spontaneous Collapses on Neutrino Oscillations

    NASA Astrophysics Data System (ADS)

    Donadi, Sandro; Bassi, Angelo; Ferialdi, Luca; Curceanu, Catalina

    2013-09-01

    We compute the effect of collapse models on neutrino oscillations. The effect of the collapse is to modify the evolution of the spatial part of the wave function and we will show that this indirectly amounts to a change on the flavor components. For the analysis we use the mass proportional CSL model, and perform the calculation to second order perturbation theory. As we will show, the CSL effect is very small—mainly due to the very small mass of neutrinos—and practically undetectable.

  8. Characteristic microwave background distortions from collapsing domain wall bubbles

    NASA Technical Reports Server (NTRS)

    Goetz, Guenter; Noetzold, Dirk

    1990-01-01

    The magnitude and angular pattern of distortions of the microwave background are analyzed by collapsing spherical domain walls. A characteristic pattern of redshift distortions of red or blue spikes surrounded by blue discs was found. The width and height of a spike is related to the diameter and magnitude of the disc. A measurement of the relations between these quantities thus can serve as an unambiguous indicator for a collapsing spherical domain wall. From the redshift distortion in the blue discs an upper bound was found on the surface energy density of the walls sigma is less than or approximately 8 MeV cubed.

  9. Source Analysis of the Crandall Canyon, Utah, Mine Collapse

    SciTech Connect

    Dreger, D S; Ford, S R; Walter, W R

    2008-02-28

    Analysis of seismograms from a magnitude 3.9 seismic event on August 6, 2007 in central Utah reveals an anomalous radiation pattern that is contrary to that expected for a tectonic earthquake, and which is dominated by an implosive component. The results show the seismic event is best modeled as a shallow underground collapse. Interestingly, large transverse surface waves require a smaller additional non-collapse source component that represents either faulting in the rocks above the mine workings or deformation of the medium surrounding the mine.

  10. Minimally invasive aortic valve surgery.

    PubMed

    Castrovinci, Sebastiano; Emmanuel, Sam; Moscarelli, Marco; Murana, Giacomo; Caccamo, Giuseppa; Bertolino, Emanuela Clara; Nasso, Giuseppe; Speziale, Giuseppe; Fattouch, Khalil

    2016-09-01

    Aortic valve disease is a prevalent disorder that affects approximately 2% of the general adult population. Surgical aortic valve replacement is the gold standard treatment for symptomatic patients. This treatment has demonstrably proven to be both safe and effective. Over the last few decades, in an attempt to reduce surgical trauma, different minimally invasive approaches for aortic valve replacement have been developed and are now being increasingly utilized. A narrative review of the literature was carried out to describe the surgical techniques for minimally invasive aortic valve surgery and report the results from different experienced centers. Minimally invasive aortic valve replacement is associated with low perioperative morbidity, mortality and a low conversion rate to full sternotomy. Long-term survival appears to be at least comparable to that reported for conventional full sternotomy. Minimally invasive aortic valve surgery, either with a partial upper sternotomy or a right anterior minithoracotomy provides early- and long-term benefits. Given these benefits, it may be considered the standard of care for isolated aortic valve disease. PMID:27582764

  11. LLNL Waste Minimization Program Plan

    SciTech Connect

    Not Available

    1990-02-14

    This document is the February 14, 1990 version of the LLNL Waste Minimization Program Plan (WMPP). The Waste Minimization Policy field has undergone continuous changes since its formal inception in the 1984 HSWA legislation. The first LLNL WMPP, Revision A, is dated March 1985. A series of informal revision were made on approximately a semi-annual basis. This Revision 2 is the third formal issuance of the WMPP document. EPA has issued a proposed new policy statement on source reduction and recycling. This policy reflects a preventative strategy to reduce or eliminate the generation of environmentally-harmful pollutants which may be released to the air, land surface, water, or ground water. In accordance with this new policy new guidance to hazardous waste generators on the elements of a Waste Minimization Program was issued. In response to these policies, DOE has revised and issued implementation guidance for DOE Order 5400.1, Waste Minimization Plan and Waste Reduction reporting of DOE Hazardous, Radioactive, and Radioactive Mixed Wastes, final draft January 1990. This WMPP is formatted to meet the current DOE guidance outlines. The current WMPP will be revised to reflect all of these proposed changes when guidelines are established. Updates, changes and revisions to the overall LLNL WMPP will be made as appropriate to reflect ever-changing regulatory requirements. 3 figs., 4 tabs.

  12. WASTE MINIMIZATION OPPORTUNITY ASSESSMENT MANUAL

    EPA Science Inventory

    Waste minimization (WM) is a policy specifically mandated by the U.S. Congress in the 1984 Hazardous and Solid Wastes Amendments to the Resource Conservation and Recovery Act (RCRA). The RCRA regulations require that generators of hazardous waste have a program in place to reduce...

  13. Assembly of a minimal protocell

    NASA Astrophysics Data System (ADS)

    Rasmussen, Steen

    2007-03-01

    What is minimal life, how can we make it, and how can it be useful? We present experimental and computational results towards bridging nonliving and living matter, which results in life that is different and much simpler than contemporary life. A simple yet tightly coupled catalytic cooperation between genes, metabolism, and container forms the design underpinnings of our protocell, which is a minimal self-replicating molecular machine. Experimentally, we have recently demonstrated this coupling by having an informational molecule (8-oxoguanine) catalytically control the light driven metabolic (Ru-bpy based) production of container materials (fatty acids). This is a significant milestone towards assembling a minimal self-replicating molecular machine. Recent theoretical investigations indicate that coordinated exponential component growth should naturally emerge as a result from such a catalytic coupling between the main protocellular components. A 3-D dissipative particle simulation (DPD) study of the full protocell life-cycle exposes a number of anticipated systemic issues associated with the remaining experimental challenges for the implementation of the minimal protocell. Finally we outline how more general self-replicating materials could be useful.

  14. A Defense of Semantic Minimalism

    ERIC Educational Resources Information Center

    Kim, Su

    2012-01-01

    Semantic Minimalism is a position about the semantic content of declarative sentences, i.e., the content that is determined entirely by syntax. It is defined by the following two points: "Point 1": The semantic content is a complete/truth-conditional proposition. "Point 2": The semantic content is useful to a theory of…

  15. Minimally invasive aortic valve surgery

    PubMed Central

    Castrovinci, Sebastiano; Emmanuel, Sam; Moscarelli, Marco; Murana, Giacomo; Caccamo, Giuseppa; Bertolino, Emanuela Clara; Nasso, Giuseppe; Speziale, Giuseppe; Fattouch, Khalil

    2016-01-01

    Aortic valve disease is a prevalent disorder that affects approximately 2% of the general adult population. Surgical aortic valve replacement is the gold standard treatment for symptomatic patients. This treatment has demonstrably proven to be both safe and effective. Over the last few decades, in an attempt to reduce surgical trauma, different minimally invasive approaches for aortic valve replacement have been developed and are now being increasingly utilized. A narrative review of the literature was carried out to describe the surgical techniques for minimally invasive aortic valve surgery and report the results from different experienced centers. Minimally invasive aortic valve replacement is associated with low perioperative morbidity, mortality and a low conversion rate to full sternotomy. Long-term survival appears to be at least comparable to that reported for conventional full sternotomy. Minimally invasive aortic valve surgery, either with a partial upper sternotomy or a right anterior minithoracotomy provides early- and long-term benefits. Given these benefits, it may be considered the standard of care for isolated aortic valve disease. PMID:27582764

  16. Exercise-Associated Collapse in Endurance Events: A Classification System.

    ERIC Educational Resources Information Center

    Roberts, William O.

    1989-01-01

    Describes a classification system devised for exercise-associated collapse in endurance events based on casualties observed at six Twin Cities Marathons. Major diagnostic criteria are body temperature and mental status. Management protocol includes fluid and fuel replacement, temperature correction, and leg cramp treatment. (Author/SM)

  17. Collapse of charged scalar field in dilaton gravity

    SciTech Connect

    Borkowska, Anna; Rogatko, Marek; Moderski, Rafal

    2011-04-15

    We elaborated the gravitational collapse of a self-gravitating complex charged scalar field in the context of the low-energy limit of the string theory, the so-called dilaton gravity. We begin with the regular spacetime and follow the evolution through the formation of an apparent horizon and the final central singularity.

  18. Exploring the dewetting transition in the hydrophobic collapse of melittin

    NASA Astrophysics Data System (ADS)

    Varilly, Patrick; Patel, Amish J.; Chandler, David

    2011-03-01

    We present our recent results on understanding the hydrophobic collapse of melittin dimers. Melittin dimers have large, complementary hydrophobic patches, and the dimer collapse mechanism involves a dewetting transition [Liu, Huang, Zhou and Berne, Nature 437, 159--162 (2005)]. As a result, melittin has become a model system for studying dewetting transitions in proteins. We apply our recently- developed tools for probing density fluctuations in water [Patel, Varilly and Chandler, JPCB 114, 1632--1637 (2010)] to understand this dewetting transition in terms of free energy surfaces, their bistability and their barrier heights. We show how the hydrophobic character of melittin's tetramerization surface results in an enhanced probability of density depletion next to that surface. When two dimers come together, the density depletion is further enhanced, so that even at large separations, there is a metastable dry phase in the region between the dimers. As the dimers come together, the dry phase is stabilized and eventually the wet phase is destabilized, leading to the collapse of the dimers. We explore how mutations that have been observed to suppress the dewetting transition affect the corresponding free energy surfaces and discuss our ongoing efforts to fully map out the reaction coordinate of melittin collapse.

  19. An elastocapillary model of wood-fibre collapse

    PubMed Central

    Akbari, Amir; Hill, Reghan J.; van de Ven, Theo G. M.

    2015-01-01

    An elastocapillary model for drying-induced collapse is proposed. We consider a circular elastic membrane with a hole at the centre that is deformed by the capillary pressure of simply and doubly connected menisci. The membrane overlays a cylindrical cavity with rigid walls, trapping a prescribed volume of water. This geometry may be suitable for studying structural failures and stiction in micro-electromechanical systems during wet etching, where capillary surfaces experience catastrophic transitions. The dry state is determined using the dihedral-angle and volume-turning-point stability criteria. Open and collapsed conformations are predicted from the scaled hole radius, cavity aspect ratio, meniscus contact angle with the membrane and cavity walls, and an elastocapillary number measuring the membrane stretching rigidity relative to the water surface tension. For a given scaled hole radius and cavity aspect ratio, there is a critical elastocapillary number above which the system does not collapse upon drying. The critical elastocapillary number is weakly influenced by the contact angle over a wide range of the scaled hole radius, thus indicating a limitation of surface hydrophobization for controlling the dry-state conformation. The model is applied to the drying of wood fibres above the fibre saturation point, determining the conditions leading to collapse. PMID:26345085

  20. Numerical simulations of the translation of collapsing bubbles

    NASA Astrophysics Data System (ADS)

    Igualada-Villodre, Elena; Fuster, Daniel; Rodriguez-Rodriguez, Javier

    2015-11-01

    In this work we present a numerical method developed to solve the collapse of single non-spherical bubbles in an incompressible liquid. The Gerris software is used to solve for the 3D conservation equations in both phases in a system where the total volume changes in the gas are imposed. The numerical results are used to discriminate various bubble collapse regimes as a function of the collapse intensity and the strength of a non-symmetrical force (e.g. gravity). At low Weber numbers and non-zero Froude numbers, the bubble remains approximately spherical. In this regime the solution numerically obtained is shown to converge in the inviscid case to the theoretical solution. For large Weber numbers, a fast jet breaks the bubble dissipating an important part of energy during the collapse. Interestingly, it is possible to identify regimes for moderate Weber numbers where the initiation of jet formation influences its translational motion without breaking the bubble. In accordance with numerical results, experiments with bubbles generated by water electrolysis subjected to shock waves show that bubbles suffer non-spherical interface deformations. The results of this study may help to further develop medical applications using bubbles as drug-carriers.

  1. Quasirelativistic quasilocal finite wave-function collapse model

    SciTech Connect

    Pearle, Philip

    2005-03-01

    A Markovian wave-function collapse model is presented where the collapse-inducing operator, constructed from quantum fields, is a manifestly covariant generalization of the mass-density operator utilized in the nonrelativistic continuous spontaneous localization (CSL) wave-function collapse model. However, the model is not Lorentz invariant because two such operators do not commute at spacelike separation, i.e., the time-ordering operation in one Lorentz frame, the 'preferred' frame, is not the time-ordering operation in another frame. However, the characteristic spacelike distance over which the commutator decays is the particle's Compton wavelength so, since the commutator rapidly gets quite small, the model is 'almost' relativistic. This quasirelativistic CSL (QRCSL) model is completely finite: unlike previous, relativistic, models, it has no (infinite) energy production from the vacuum state. QRCSL calculations are given of the collapse rate for a single free particle in a superposition of spatially separated packets, and of the energy production rate for any number of free particles: these reduce to the CSL rates if the particle's Compton wavelength is small compared to the model's distance parameter. One motivation for QRCSL is the realization that previous relativistic models entail excitation of nuclear states which exceeds that of experiment, whereas QRCSL does not; an example is given involving quadrupole excitation of the {sup 74}Ge nucleus.

  2. 8. COLLAPSED AND SCATTERED BUILDING ON FLOOR OF PIT, WITH ...

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

    8. COLLAPSED AND SCATTERED BUILDING ON FLOOR OF PIT, WITH PILE OF RHYOLITE BOULDERS IN BACKGROUND, VIEW TO SOUTH - Iron Springs Quarry, 150 feet west of Grand Loop Road, 20 miles east of U.S. Highway 287, West Thumb, Teton County, WY

  3. European Neolithic societies showed early warning signals of population collapse.

    PubMed

    Downey, Sean S; Haas, W Randall; Shennan, Stephen J

    2016-08-30

    Ecosystems on the verge of major reorganization-regime shift-may exhibit declining resilience, which can be detected using a collection of generic statistical tests known as early warning signals (EWSs). This study explores whether EWSs anticipated human population collapse during the European Neolithic. It analyzes recent reconstructions of European Neolithic (8-4 kya) population trends that reveal regime shifts from a period of rapid growth following the introduction of agriculture to a period of instability and collapse. We find statistical support for EWSs in advance of population collapse. Seven of nine regional datasets exhibit increasing autocorrelation and variance leading up to collapse, suggesting that these societies began to recover from perturbation more slowly as resilience declined. We derive EWS statistics from a prehistoric population proxy based on summed archaeological radiocarbon date probability densities. We use simulation to validate our methods and show that sampling biases, atmospheric effects, radiocarbon calibration error, and taphonomic processes are unlikely to explain the observed EWS patterns. The implications of these results for understanding the dynamics of Neolithic ecosystems are discussed, and we present a general framework for analyzing societal regime shifts using EWS at large spatial and temporal scales. We suggest that our findings are consistent with an adaptive cycling model that highlights both the vulnerability and resilience of early European populations. We close by discussing the implications of the detection of EWS in human systems for archaeology and sustainability science. PMID:27573833

  4. Xylem Wall Collapse in Water-Stressed Pine Needles

    PubMed Central

    Cochard, Hervé; Froux, Fabienne; Mayr, Stefan; Coutand, Catherine

    2004-01-01

    Wall reinforcement in xylem conduits is thought to prevent wall implosion by negative pressures, but direct observations of xylem geometry during water stress are still largely lacking. In this study, we have analyzed the changes in xylem geometry during water stress in needles of four pine species (Pinus spp.). Dehydrated needles were frozen with liquid nitrogen, and xylem cross sections were observed, still frozen, with a cryo-scanning electron microscope and an epifluorescent microscope. Decrease in xylem pressure during drought provoked a progressive collapse of tracheids below a specific threshold pressure (Pcollapse) that correlates with the onset of cavitation in the stems. Pcollapse was more negative for species with smaller tracheid diameter and thicker walls, suggesting a tradeoff between xylem efficiency, xylem vulnerability to collapse, and the cost of wall stiffening. Upon severe dehydration, tracheid walls were completely collapsed, but lumens still appeared filled with sap. When dehydration proceeded further, tracheids embolized and walls relaxed. Wall collapse in dehydrated needles was rapidly reversed upon rehydration. We discuss the implications of this novel hydraulic trait on the xylem function and on the understanding of pine water relations. PMID:14657404

  5. High-speed cylindrical collapse of two perfect fluids

    NASA Astrophysics Data System (ADS)

    Sharif, M.; Ahmad, Zahid

    2007-09-01

    In this paper, the study of the gravitational collapse of cylindrically distributed two perfect fluid system has been carried out. It is assumed that the collapsing speeds of the two fluids are very large. We explore this condition by using the high-speed approximation scheme. There arise two cases, i.e., bounded and vanishing of the ratios of the pressures with densities of two fluids given by c s , d s . It is shown that the high-speed approximation scheme breaks down by non-zero pressures p 1, p 2 when c s , d s are bounded below by some positive constants. The failure of the high-speed approximation scheme at some particular time of the gravitational collapse suggests the uncertainty on the evolution at and after this time. In the bounded case, the naked singularity formation seems to be impossible for the cylindrical two perfect fluids. For the vanishing case, if a linear equation of state is used, the high-speed collapse does not break down by the effects of the pressures and consequently a naked singularity forms. This work provides the generalisation of the results already given by Nakao and Morisawa (Prog Theor Phys 113:73, 2005) for the perfect fluid.

  6. 6. Remains Beneath Collapsed Engine House Roof, Showing Foundation Timbers ...

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

    6. Remains Beneath Collapsed Engine House Roof, Showing Foundation Timbers and Automobile Engine Connected to Pulley Wheel, Looking Southwest - David Renfrew Oil Rig, East side of Connoquenessing Creek, 0.4 mile North of confluence with Thorn Creek, Renfrew, Butler County, PA

  7. Resolving the Formation of Protogalaxies. II.Central Gravitational Collapse

    SciTech Connect

    Wise, John H.; Turk, Matthew J.; Abel, Tom

    2007-10-15

    Numerous cosmological hydrodynamic studies have addressed the formation of galaxies. Here we choose to study the first stages of galaxy formation, including non-equilibrium atomic primordial gas cooling, gravity and hydrodynamics. Using initial conditions appropriate for the concordance cosmological model of structure formation, we perform two adaptive mesh refinement simulations of {approx} 10{sup 8} M{sub {circle_dot}} galaxies at high redshift. The calculations resolve the Jeans length at all times with more than 16 cells and capture over 14 orders of magnitude in length scales. In both cases, the dense, 10{sup 5} solar mass, one parsec central regions are found to contract rapidly and have turbulent Mach numbers up to 4. Despite the ever decreasing Jeans length of the isothermal gas, we only find one site of fragmentation during the collapse. However, rotational secular bar instabilities transport angular momentum outwards in the central parsec as the gas continues to collapse and lead to multiple nested unstable fragments with decreasing masses down to sub-Jupiter mass scales. Although these numerical experiments neglect star formation and feedback, they clearly highlight the physics of turbulence in gravitationally collapsing gas. The angular momentum segregation seen in our calculations plays an important role in theories that form supermassive black holes from gaseous collapse.

  8. View east from western edge of complex. Collapsed overhead conveyor ...

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

    View east from western edge of complex. Collapsed overhead conveyor in foreground carried ganister down to the brickyard from crushing and grinding facility on the mountain. - Harbison-Walker Refractories Company, West end of Shirley Street, Mount Union, Huntingdon County, PA

  9. Meteorological Station, interior with collapsed roof showing remnant wooden equipment ...

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

    Meteorological Station, interior with collapsed roof showing remnant wooden equipment switch box on east wall; view southeast - Fort McKinley, Meteorological Station, East side of Weymouth Way, approximately 225 feet south of Cove Side Drive, Great Diamond Island, Portland, Cumberland County, ME

  10. Collapse results for query languages in database theory

    NASA Astrophysics Data System (ADS)

    Dudakov, S. M.; Taitslin, M. A.

    2006-04-01

    This is a survey of collapse results obtained mainly by members of the Tver State University seminar on the theoretical foundations of computer science. Attention is focused on the relative isolation and pseudo-finite homogeneity properties and universes without the independence property. The Baldwin-Benedikt reducibility theorem is proved for these universes. The Dudakov boundedness theorem is proved for reducible theories. The relative isolation theorem is proved for reducible and bounded theories, and as a consequence the collapse theorem is obtained for reducible theories. It is noted that reducibility is equivalent to the relative isolation property. On the other hand, results of Dudakov are presented showing that the effectively reducible theories having an effective almost indiscernible sequence admit an effective collapse of locally generic queries using not only ordering and names of stored tables but also relations and operations of the universe, into queries not using the relations and operations of the universe. Also presented is Dudakov's example of an enrichment of the Presburger arithmetic for which the collapse theorem fails but the elementary theory of the enrichment is decidable. This answers some open questions in the negative.

  11. Interplay of Neutrino Opacities in Core-collapse Supernova Simulations

    SciTech Connect

    Lentz, Eric J; Mezzacappa, Anthony; Messer, Bronson; Hix, William Raphael; Bruenn, S. W.

    2012-01-01

    We have conducted a series of numerical experiments using spherically symmetric, general relativistic, neutrino radiation hydrodynamics with the code Agile-BOLTZTRAN to examine the effects of including, and improving, the calculation of neutrino opacities on the development of supernova simulations by removing, or replacing, each opacity individually, or removing opacities in groups. We find that during core collapse improvements to electron capture (EC) on nuclei, namely EC on an ensemble of nuclei based on the hybrid model, relative to the simpler independent-particle approximation (IPA) for a mean nucleus, plays the most important role of all tested neutrino opacities. Low-energy neutrinos emitted by nuclear EC preferentially escape during collapse leading to larger deleptonization of the collapsing core, without the energy downscattering via non-isoenergetic scattering (NIS) on electrons required for the models with IPA nuclear EC. During shock breakout the primary influence on the emergent neutrinos arises from NIS on electrons. For the accretion phase NIS on free nucleons and pair emission by $e^+e^-$-annihilation have the largest impact on the neutrino emission and shock evolution. Other opacities evaluated including nucleon-nucleon bremsstrahlung and especially neutrino-positron scattering have little measurable impact on neutrino emission or shock dynamics. Modern treatments of nuclear electron capture, $e^+e^-$-annihilation pair emission, and non-isoenergetic scattering on electrons and free nucleons are critical elements of core-collapse simulations of all dimensionality.

  12. Bar Mode Instability in Gravitational Collapsing Cloud Core

    NASA Astrophysics Data System (ADS)

    Hanawa, T.

    1999-12-01

    We discuss dynamical collapse of a dense core with emphasis on the bar mode instability. Recent numerical simulations show that a dynamically collapsing core changes its form from sphere through disk to filament. The filament is much longer than the Jeans length and likely to be unstable against fragmentation. We discuss the mechanism of filament formation on the basis of linear stability analysis. According to our analysis, a dynamically collapsing gas sphere is unstable against the bar mode, i.e., a non-spherical density perturbation proportional to, Y 2 m(θ,ϕ) . The filament formation is due to the bar mode instability. The bar mode grows with the time, t , in proportion to ěrt t - t 0 ěrt -σ while the central density increases in proportion to (t - t 0 ) -2 . When the collapse is isothermal, the growth rate is σ = 0.354 . The growth rate is larger when the sound speed decreases with the increase in the density. This bar mode instability may lead to fragmentation in a core and may be related to binary formation.

  13. Radiation magnetohydrodynamic simulations of protostellar collapse: Low-metallicity environments

    SciTech Connect

    Tomida, Kengo

    2014-05-10

    Among many physical processes involved in star formation, radiation transfer is one of the key processes because it dominantly controls the thermodynamics. Because metallicities control opacities, they are one of the important environmental parameters that affect star formation processes. In this work, I investigate protostellar collapse in solar-metallicity and low-metallicity (Z = 0.1 Z {sub ☉}) environments using three-dimensional radiation hydrodynamic and magnetohydrodynamic simulations. Because radiation cooling in high-density gas is more effective in low-metallicity environments, first cores are colder and have lower entropies. As a result, first cores are smaller, less massive, and have shorter lifetimes in low-metallicity clouds. Therefore, first cores would be less likely to be found in low-metallicity star forming clouds. This also implies that first cores tend to be more gravitationally unstable and susceptible to fragmentation. The evolution and structure of protostellar cores formed after the second collapse weakly depend on metallicities in the spherical and magnetized models, despite the large difference in the metallicities. Because this is due to the change of the heat capacity by dissociation and ionization of hydrogen, it is a general consequence of the second collapse as long as the effects of radiation cooling are not very large during the second collapse. On the other hand, the effects of different metallicities are more significant in the rotating models without magnetic fields, because they evolve slower than other models and therefore are more affected by radiation cooling.

  14. Excision technique in constrained formulations of Einstein equations: collapse scenario

    NASA Astrophysics Data System (ADS)

    Cordero-Carrión, I.; Vasset, N.; Novak, J.; Jaramillo, J. L.

    2015-04-01

    We present a new excision technique used in constrained formulations of Einstein equations to deal with black hole in numerical simulations. We show the applicability of this scheme in several scenarios. In particular, we present the dynamical evolution of the collapse of a neutron star to a black hole, using the CoCoNuT code and this excision technique.

  15. Allee effects and colony collapse disorder in honey bees

    Technology Transfer Automated Retrieval System (TEKTRAN)

    We propose a mathematical model to quantify the hypothesis that a major ultimate cause of Colony Collapse Disorder (CCD) in honey bees is the presence of an Allee effect in the growth dynamics of honey bee colonies. In the model, both recruitment of adult bees as well as mortality of adult bees have...

  16. Unveiling the High Energy Obscured Universe: Hunting Collapsed Objects Physics

    NASA Technical Reports Server (NTRS)

    Ubertini, P.; Bazzano, A.; Cocchi, M.; Natalucci, L.; Bassani, L.; Caroli, E.; Stephen, J. B.; Caraveo, P.; Mereghetti, S.; Villa, G.

    2005-01-01

    A large part of energy from space is coming from collapsing stars (SN, Hypernovae) and collapsed stars (black holes, neutron stars and white dwarfs). The peak of their energy release is in the hard-X and gamma-ray wavelengths where photons are insensitive to absorption and can travel from the edge the Universe or the central core of the Galaxy without loosing the primordial information of energy, time signature and polarization. The most efficient process to produce energetic photons is gravitational accretion of matter from a "normal" star onto a collapsed companion (LGxMcollxdMacc/dtx( 1Rdisc)-dMacc/dt x c2), exceeding by far the nuclear reaction capability to generate high energy quanta. Thus our natural laboratory for "in situ" investigations are collapsed objects in which matter and radiation co-exist in extreme conditions of temperature and density due to gravitationally bent geometry and magnetic fields. This is a unique opportunity to study the physics of accretion flows in stellar mass and super-massive Black Holes (SMBHs), plasmoids generated in relativistic jets in galactic microQSOs and AGNs, ionised plasma interacting at the touching point of weakly magnetized NS surface, GRB/Supernovae connection, and the mysterious origins of "dark" GRB and X-ray flash.

  17. Metal Ion Dependence of Cooperative Collapse Transitions in RNA

    SciTech Connect

    Moghaddam, Sarvin; Caliskan, Gokhan; Chauhan, Seema; Hyeon, Changbong; Briber, R.M.; Thirumalai, D.; Woodson, Sarah A.

    2010-10-12

    Positively charged counterions drive RNA molecules into compact configurations that lead to their biologically active structures. To understand how the valence and size of the cations influences the collapse transition in RNA, small-angle X-ray scattering was used to follow the decrease in the radius of gyration (R{sub g}) of the Azoarcus and Tetrahymena ribozymes in different cations. Small, multivalent cations induced the collapse of both ribozymes more efficiently than did monovalent ions. Thus, the cooperativity of the collapse transition depends on the counterion charge density. Singular value decomposition of the scattering curves showed that folding of the smaller and more thermostable Azoarcus ribozyme is well described by two components, whereas collapse of the larger Tetrahymena ribozyme involves at least one intermediate. The ion-dependent persistence length, extracted from the distance distribution of the scattering vectors, shows that the Azoarcus ribozyme is less flexible at the midpoint of transition in low-charge-density ions than in high-charge-density ions. We conclude that the formation of sequence-specific tertiary interactions in the Azoarcus ribozyme overlaps with neutralization of the phosphate charge, while tertiary folding of the Tetrahymena ribozyme requires additional counterions. Thus, the stability of the RNA structure determines its sensitivity to the valence and size of the counterions.

  18. Testing gravity-induced collapse models with torsion pendulums

    NASA Astrophysics Data System (ADS)

    Helou, Bassam; Wipf, Christopher; Chen, Yanbei

    2016-03-01

    Wavefunction collapse models have been proposed to resolve the measurement problem in QM. Some, , such as Diosi-Penrose model, are motivated by gravity. We first present the theory of such models, highlighting new results, such as fixing the only free paramater in the model. We then propose torsion pendulums as a promising optomechanical platform to test such models.

  19. Simulating the entropic collapse of coarse-grained chromosomes.

    PubMed

    Shendruk, Tyler N; Bertrand, Martin; de Haan, Hendrick W; Harden, James L; Slater, Gary W

    2015-02-17

    Depletion forces play a role in the compaction and decompaction of chromosomal material in simple cells, but it has remained debatable whether they are sufficient to account for chromosomal collapse. We present coarse-grained molecular dynamics simulations, which reveal that depletion-induced attraction is sufficient to cause the collapse of a flexible chain of large structural monomers immersed in a bath of smaller depletants. These simulations use an explicit coarse-grained computational model that treats both the supercoiled DNA structural monomers and the smaller protein crowding agents as combinatorial, truncated Lennard-Jones spheres. By presenting a simple theoretical model, we quantitatively cast the action of depletants on supercoiled bacterial DNA as an effective solvent quality. The rapid collapse of the simulated flexible chromosome at the predicted volume fraction of depletants is a continuous phase transition. Additional physical effects to such simple chromosome models, such as enthalpic interactions between structural monomers or chain rigidity, are required if the collapse is to be a first-order phase transition. PMID:25692586

  20. 5. EMPIRE STATE MINE. COLLAPSED SOUTHERN MOST BUILDING, CAMERA POINTED ...

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

    5. EMPIRE STATE MINE. COLLAPSED SOUTHERN MOST BUILDING, CAMERA POINTED WEST. VISIBLE THROUGH WINDOW OPENING IS 'GRIZZLEY' IN ID-31-D-6 AND ON THE RIGHT SIDE OF BUILDING IS THE BED SPRINGS IN ID-31-D-9. - Florida Mountain Mining Sites, Empire State Mine, West side of Florida Mountain, Silver City, Owyhee County, ID

  1. Electromagnetic Powers Of Merging And Collapsing Compact Objects

    NASA Astrophysics Data System (ADS)

    Lyutikov, Maxim

    2011-09-01

    Understanding possible EM signatures of the merging and collapsing compact object is important for identifying possible sources of LIGO & LISA signals. We estimate the electromagnetic powers that can be produced as a precursor to the merger, as a prompt emission during the collapse of a NS and at the spin-down stage of the resulting Kerr BH. In particular, we find exact non-linear time-dependent structure of magnetospheres of spinning and collapsing NSs in Schwarzschild geometry. Based on this solution, we argue that the collapse of a NS into the BH happens smoothly, without natural formation of current sheets or other dissipative structures on the open field lines and, thus, does not allow the magnetic field to become disconnected from the star and escape to infinity. Thus, as long as an isolated Kerr BH can produce plasma and currents, it does not lose its open magnetic field lines, its magnetospheric structure evolved towards a split monopole and the BH spins down electromagnetically (the closed field lines get absorbed by the hole). The "no hair theorem", which assumes that the outside medium is a vacuum, is not applicable in this case: highly conducting plasma introduces a topological constraint forbidding the disconnection of the magnetic field lines from the BH. Eventually, a single random large scale spontaneous reconnection event will lead to magnetic field release, shutting down the BH engine forever.

  2. Temperature considerations in numerical simulations of collapsing bubbles

    NASA Astrophysics Data System (ADS)

    Johnsen, Eric; Alahyari Beig, Shahaboddin

    2014-11-01

    In naval and biomedical engineering applications, the inertial collapse of cavitation bubbles is known to damage its surroundings. While significant attention has been dedicated to investigating the pressures produced by this process, less is known about heating of the surrounding medium, which may be important when collapse occurs near objects whose properties strongly depend on temperature (e.g., polymers). Euler simulations are capable of predicting the high pressures thereby generated. However, numerical errors can occur when solving the Navier-Stokes equations for compressible interface problems. Using a newly developed computational approach that prevents such errors, we investigate the dynamics of shock-induced and Rayleigh collapse of individual and collections of gas bubbles, in a free field and near rigid surfaces. We characterize the temperature rises based on the relevant non-dimensional parameters entering the problem. In particular, we show that the temperature of a neighboring object rises due to two mechanisms: the shock produced at collapse and heat diffusion from the hot bubble as it moves toward the object. This work was supported by ONR Grant N00014-12-1-0751.

  3. High temperatures produced by bubble collapse near a rigid wall

    NASA Astrophysics Data System (ADS)

    Alahyari Beig, Shahaboddin; Aboulhasanzadeh, Bahman; Johnsen, Eric

    2015-11-01

    The collapse of a cavitation bubble is known to have damaging effects on its surroundings. Although numerous investigations have been conducted to predict the pressures produced by this process, fewer have been devoted to determine the heating produced by the bubble collapse. Such heating of the surrounding medium may be important for materials whose mechanical properties depend on temperature (e.g., polymeric coatings). A newly developed computational method to solve the compressible Navier-Stokes equations for gas/liquid flows is used to investigate the dynamics of non-spherical collapse of gas bubbles near rigid surfaces. The subsequent temperature fields are characterized based on the relevant non-dimensional parameters entering the problem, and a model is developed to determine the temperature of the wall based on the temperature of the flow in contact with the wall. We demonstrate that significant wall temperatures may be achieved, depending on the initial location of the collapsing bubble and the heat diffusivity of the material.

  4. 26. DETAIL OF STRUCTURAL COLLAPSE OF TOP FLOOR OF MILL, ...

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

    26. DETAIL OF STRUCTURAL COLLAPSE OF TOP FLOOR OF MILL, ABOVE ORE BIN, LOOKING WEST FROM TOP OF STAIRWAY IN CA-290-25. THE PIPE AT CENTER WAS USED TO SPREAD CRUSHED ORE COMING FROM THE JAW CRUSHER EVENLY TO ALL AREA OF THE ORE BIN BELOW. - Skidoo Mine, Park Route 38 (Skidoo Road), Death Valley Junction, Inyo County, CA

  5. Collapse of composite tubes under uniform external hydrostatic pressure

    NASA Astrophysics Data System (ADS)

    Smith, P. T.; Ross, C. T. F.; Little, A. P. F.

    2009-08-01

    This paper describes an experimental and a theoretical investigation into the collapse of 22 circular cylindrical composite tubes under external hydrostatic pressure. The investigations were on the collapse of fibre reinforced plastic tube specimens made from a mixture of three carbon and two E-glass fibre layers. The theoretical investigations were carried out using an in-house finite element computer program called BCLAM, together with the commercial computer package, namely ANSYS. It must be emphasised here that BS 5500 does not appear to exclusively cater for the buckling of composite shells under external hydrostatic pressure, so the work presented here is novel and should be useful to industry. The experimental investigations showed that the composite specimens behaved similarly to isotropic materials previously tested, in that the short vessels collapsed through axisymmetric deformation while the longer tubes collapsed through non-symmetric bifurcation buckling. Furthermore it was discovered that the models failed at changes of the composite lay-up due to the manufacturing process of these models. These changes seemed to be the weak points of the specimens.

  6. Time evolution of simple molecules during proto-star collapse

    NASA Astrophysics Data System (ADS)

    Das, Ankan; Chakrabarti, Sandip K.; Acharyya, Kinsuk; Chakrabarti, Sonali

    2008-10-01

    We study the formation and evolution of several molecules in a collapsing interstellar cloud using a reasonably large reaction network containing more than four hundred atomic and molecular species. We employ a time dependent, spherically symmetric, hydrodynamics code to follow the hydrodynamic and chemical evolution of the collapsing cloud. The flow is assumed to be self-gravitating. We use two models to study the hydrodynamic evolution: in the first model, we inject matter into an initially low density region and in the second model, we start with a constant density cloud and let it collapse due to self-gravity. We study the evolution of the central core for both the cases. We include the grain chemistry to compute the formation of molecular hydrogen and carried out the effect of gas and grain chemistry at each time step. We follow the collapse for more than 10 14 s (about 3 million years) and present the time evolution of the globally averaged abundances of various simple but biologically important molecules, such as glycine, alanine etc. We compare our results with those obtained from observations and found that for lighter molecules the agreement is generally very good. For complex molecules we tend to under predict the abundances. This indicates that other pathways could be present to form these molecules or more accurate reaction rates were needed.

  7. 12. Photocopy of photograph. Photographer unknown undated COLLAPSIBLE FORM FOR ...

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

    12. Photocopy of photograph. Photographer unknown undated COLLAPSIBLE FORM FOR CONCRETE AREA ON TANNER CREEK RAILROAD VIADUCT. Original historic photograph located at the Bonneville Powerhouse, Bonneville, Oregon. NOTE: PRINT FROM 8X10 NEGATIVE - Bonneville Project, Fish Hatchery, On Columbia River bordered on South by Union Pacific, Bonneville, Multnomah County, OR

  8. Computational Astrophysics at the Bleeding Edge: Simulating Core Collapse Supernovae

    NASA Astrophysics Data System (ADS)

    Mezzacappa, Anthony

    2013-04-01

    Core collapse supernovae are the single most important source of elements in the Universe, dominating the production of elements between oxygen and iron and likely responsible for half the elements heavier than iron. They result from the death throes of massive stars, beginning with stellar core collapse and the formation of a supernova shock wave that must ultimately disrupt such stars. Past, first-principles models most often led to the frustrating conclusion the shock wave stalls and is not revived, at least given the physics included in the models. However, recent progress in the context of two-dimensional, first-principles supernova models is reversing this trend, giving us hope we are on the right track toward a solution of one of the most important problems in astrophysics. Core collapse supernovae are multi-physics events, involving general relativity, hydrodynamics and magnetohydrodynamics, nuclear burning, and radiation transport in the form of neutrinos, along with a detailed nuclear physics equation of state and neutrino weak interactions. Computationally, simulating these catastrophic stellar events presents an exascale computing challenge. I will discuss past models and milestones in core collapse supernova theory, the state of the art, and future requirements. In this context, I will present the results and plans of the collaboration led by ORNL and the University of Tennessee.

  9. Abrupt climate change and collapse of deep-sea ecosystems

    USGS Publications Warehouse

    Yasuhara, Moriaki; Cronin, T. M.; Demenocal, P.B.; Okahashi, H.; Linsley, B.K.

    2008-01-01

    We investigated the deep-sea fossil record of benthic ostracodes during periods of rapid climate and oceanographic change over the past 20,000 years in a core from intermediate depth in the northwestern Atlantic. Results show that deep-sea benthic community "collapses" occur with faunal turnover of up to 50% during major climatically driven oceanographic changes. Species diversity as measured by the Shannon-Wiener index falls from 3 to as low as 1.6 during these events. Major disruptions in the benthic communities commenced with Heinrich Event 1, the Inter-Aller??d Cold Period (IACP: 13.1 ka), the Younger Dryas (YD: 12.9-11.5 ka), and several Holocene Bond events when changes in deep-water circulation occurred. The largest collapse is associated with the YD/IACP and is characterized by an abrupt two-step decrease in both the upper North Atlantic Deep Water assemblage and species diversity at 13.1 ka and at 12.2 ka. The ostracode fauna at this site did not fully recover until ???8 ka, with the establishment of Labrador Sea Water ventilation. Ecologically opportunistic slope species prospered during this community collapse. Other abrupt community collapses during the past 20 ka generally correspond to millennial climate events. These results indicate that deep-sea ecosystems are not immune to the effects of rapid climate changes occurring over centuries or less. ?? 2008 by The National Academy of Sciences of the USA.

  10. Simulating the Entropic Collapse of Coarse-Grained Chromosomes

    PubMed Central

    Shendruk, Tyler N.; Bertrand, Martin; de Haan, Hendrick W.; Harden, James L.; Slater, Gary W.

    2015-01-01

    Depletion forces play a role in the compaction and decompaction of chromosomal material in simple cells, but it has remained debatable whether they are sufficient to account for chromosomal collapse. We present coarse-grained molecular dynamics simulations, which reveal that depletion-induced attraction is sufficient to cause the collapse of a flexible chain of large structural monomers immersed in a bath of smaller depletants. These simulations use an explicit coarse-grained computational model that treats both the supercoiled DNA structural monomers and the smaller protein crowding agents as combinatorial, truncated Lennard-Jones spheres. By presenting a simple theoretical model, we quantitatively cast the action of depletants on supercoiled bacterial DNA as an effective solvent quality. The rapid collapse of the simulated flexible chromosome at the predicted volume fraction of depletants is a continuous phase transition. Additional physical effects to such simple chromosome models, such as enthalpic interactions between structural monomers or chain rigidity, are required if the collapse is to be a first-order phase transition. PMID:25692586

  11. Key variables influencing patterns of lava dome growth and collapse

    NASA Astrophysics Data System (ADS)

    Husain, T.; Elsworth, D.; Voight, B.; Mattioli, G. S.; Jansma, P. E.

    2013-12-01

    Lava domes are conical structures that grow by the infusion of viscous silicic or intermediate composition magma from a central volcanic conduit. Dome growth can be characterized by repeated cycles of growth punctuated by collapse, as the structure becomes oversized for its composite strength. Within these cycles, deformation ranges from slow long term deformation to sudden deep-seated collapses. Collapses may range from small raveling failures to voluminous and fast-moving pyroclastic flows with rapid and long-downslope-reach from the edifice. Infusion rate and magma rheology together with crystallization temperature and volatile content govern the spatial distribution of strength in the structure. Solidification, driven by degassing-induced crystallization of magma leads to the formation of a continuously evolving frictional talus as a hard outer shell. This shell encapsulates the cohesion-dominated soft ductile core. Here we explore the mechanics of lava dome growth and failure using a two-dimensional particle-dynamics model. This meshless model follows the natural evolution of a brittle carapace formed by loss of volatiles and rheological stiffening and avoids difficulties of hour-glassing and mesh-entangelment typical in meshed models. We test the fidelity of the model against existing experimental and observational models of lava dome growth. The particle-dynamics model follows the natural development of dome growth and collapse which is infeasible using simple analytical models. The model provides insight into the triggers that lead to the transition in collapse mechasnism from shallow flank collapse to deep seated sector collapse. Increase in material stiffness due to decrease in infusion rate results in the transition of growth pattern from endogenous to exogenous. The material stiffness and strength are strongly controlled by the magma infusion rate. Increase in infusion rate decreases the time available for degassing induced crystallization leading to a

  12. Three-dimensional hydrodynamic instabilities in stellar core collapses

    NASA Astrophysics Data System (ADS)

    Lou, Yu-Qing; Lian, Biao

    2012-03-01

    A spherically symmetric hydrodynamic stellar core collapse process under gravity is time-dependent and may become unstable once disturbed. Subsequent non-linear evolutions of such growth of hydrodynamic instabilities may lead to various physical consequences. Specifically for a homologous collapse of a stellar core characterized by a polytropic exponent Γ= 4/3, we examine oscillations and/or instabilities of three-dimensional (3D) general polytropic perturbations. Being incompressible, the radial component of vorticity perturbation always grows unstably during the same homologous core collapse. For compressible 3D perturbations, the polytropic index γ of perturbations can differ from Γ= 4/3 of the general polytropic hydrodynamic background flow, where the background specific entropy is conserved along streamlines and can vary in radius and time. Our model formulation here is more general than previous ones. The Brunt-Väisälä buoyancy frequency ? does not vanish, allowing for the existence of internal gravity g- modes and/or g+ modes, depending on the sign of ? respectively. Eigenvalues and eigenfunctions of various oscillatory and unstable perturbation modes are computed, given asymptotic boundary conditions. As studied in several specialized cases of Goldreich & Weber and of Lou & Cao and Cao & Lou, we further confirm that acoustic p modes and surface f modes remain stable in the current more general situations. In comparison, g- modes and sufficiently high radial order g+ modes are unstable, leading to inevitable convective motions within the collapsing stellar interior; meanwhile, sufficiently low radial order g+ modes remain stably trapped in the collapsing core. Unstable growths of 3D g-mode disturbances are governed dominantly by the angular momentum conservation and modified by the gas pressure restoring force. We note in particular that unstable temporal growths of 3D vortical perturbations exist even when the specific entropy distribution becomes

  13. Intense electromagnetic outbursts from collapsing hypermassive neutron stars

    NASA Astrophysics Data System (ADS)

    Lehner, Luis; Palenzuela, Carlos; Liebling, Steven L.; Thompson, Christopher; Hanna, Chad

    2012-11-01

    We study the gravitational collapse of a magnetized neutron star using a novel numerical approach able to capture both the dynamics of the star and the behavior of the surrounding plasma. In this approach, a fully general relativistic magnetohydrodynamics implementation models the collapse of the star and provides appropriate boundary conditions to a force-free model which describes the stellar exterior. We validate this strategy by comparing with known results for the rotating monopole and aligned rotator solutions and then apply it to study both rotating and nonrotating stellar collapse scenarios and contrast the behavior with what is obtained when employing the electrovacuum approximation outside the star. The nonrotating electrovacuum collapse is shown to agree qualitatively with a Newtonian model of the electromagnetic field outside a collapsing star. We illustrate and discuss a fundamental difference between the force-free and electrovacuum solutions, involving the appearance of large zones of electric-dominated field in the vacuum case. This provides a clear demonstration of how dissipative singularities appear generically in the nonlinear time evolution of force-free fluids. In both the rotating and nonrotating cases, our simulations indicate that the collapse induces a strong electromagnetic transient, which leaves behind an uncharged, unmagnetized Kerr black hole. In the case of submillisecond rotation, the magnetic field experiences strong winding, and the transient carries much more energy. This result has important implications for models of gamma-ray bursts. Even when the neutron star is surrounded by an accretion torus (as in binary merger and collapsar scenarios), a magnetosphere may emerge through a dynamo process operating in a surface shear layer. When this rapidly rotating magnetar collapses to a black hole, the electromagnetic energy released can compete with the later output in a Blandford-Znajek jet. Much less electromagnetic energy is

  14. Diversity waves in collapse-driven population dynamics

    SciTech Connect

    Maslov, Sergei; Sneppen, Kim

    2015-09-14

    Populations of species in ecosystems are often constrained by availability of resources within their environment. In effect this means that a growth of one population, needs to be balanced by comparable reduction in populations of others. In neutral models of biodiversity all populations are assumed to change incrementally due to stochastic births and deaths of individuals. Here we propose and model another redistribution mechanism driven by abrupt and severe collapses of the entire population of a single species freeing up resources for the remaining ones. This mechanism may be relevant e.g. for communities of bacteria, with strain-specific collapses caused e.g. by invading bacteriophages, or for other ecosystems where infectious diseases play an important role. The emergent dynamics of our system is cyclic ‘‘diversity waves’’ triggered by collapses of globally dominating populations. The population diversity peaks at the beginning of each wave and exponentially decreases afterwards. Species abundances are characterized by a bimodal time-aggregated distribution with the lower peak formed by populations of recently collapsed or newly introduced species while the upper peak - species that has not yet collapsed in the current wave. In most waves both upper and lower peaks are composed of several smaller peaks. This self-organized hierarchical peak structure has a long-term memory transmitted across several waves. It gives rise to a scale-free tail of the time-aggregated population distribution with a universal exponent of 1.7. We show that diversity wave dynamics is robust with respect to variations in the rules of our model such as diffusion between multiple environments, species-specific growth and extinction rates, and bet-hedging strategies.

  15. Diversity waves in collapse-driven population dynamics

    DOE PAGESBeta

    Maslov, Sergei; Sneppen, Kim

    2015-09-14

    Populations of species in ecosystems are often constrained by availability of resources within their environment. In effect this means that a growth of one population, needs to be balanced by comparable reduction in populations of others. In neutral models of biodiversity all populations are assumed to change incrementally due to stochastic births and deaths of individuals. Here we propose and model another redistribution mechanism driven by abrupt and severe collapses of the entire population of a single species freeing up resources for the remaining ones. This mechanism may be relevant e.g. for communities of bacteria, with strain-specific collapses caused e.g.more » by invading bacteriophages, or for other ecosystems where infectious diseases play an important role. The emergent dynamics of our system is cyclic ‘‘diversity waves’’ triggered by collapses of globally dominating populations. The population diversity peaks at the beginning of each wave and exponentially decreases afterwards. Species abundances are characterized by a bimodal time-aggregated distribution with the lower peak formed by populations of recently collapsed or newly introduced species while the upper peak - species that has not yet collapsed in the current wave. In most waves both upper and lower peaks are composed of several smaller peaks. This self-organized hierarchical peak structure has a long-term memory transmitted across several waves. It gives rise to a scale-free tail of the time-aggregated population distribution with a universal exponent of 1.7. We show that diversity wave dynamics is robust with respect to variations in the rules of our model such as diffusion between multiple environments, species-specific growth and extinction rates, and bet-hedging strategies.« less

  16. Collapse in High-Grade Stenosis during Pulsatile Flow Experiments

    NASA Astrophysics Data System (ADS)

    Kobayashi, Shunichi; Tang, Dalin; Ku, David N.

    It has been hypothesized that blood flow through high grade stenotic arteries may produce conditions in which elastic flow choking may occur. The development of atherosclerotic plaque fracture may be exacerbated by the compressive stresses during collapse. This study explored the effects of pulsatile flow on stenotic flow collapse. Pulsatile flow was produced using a gear pump controlled by a digitized physiologic waveform. Upstream and downstream mean pressures and pulsatile flow rates were measured and digitized. An improved model of arterial stenosis was created using an elastomer with an incremental modulus of elasticity matched to a bovine carotid artery in the relevant range of collapse. Additionally, the model retained a very thick wall in the stenotic region similar to arterial disease. Flow choking was observed for pulsatile pressure drops close to those previously reported for steady flow. The phase difference between flow rate and pressure between upstream and downstream of the stenosis occurred by the compliance of tube and stenosis resistance. For 80% nominal stenosis by diameter and 100+/-30mmHg upstream pressure, collapse occurred for average pulsatile pressure drops of 93mmHg. Pulsatile flow experiments in this model revealed the range of conditions for the flow choking and the paradoxical collapse of the stenosis during systole with expansion during diastole. The stenosis severity was dynamic through the pulse cycle and was significantly greater under flow than the nominal severity. The results indicate that flow choking and stenotic compression may be significant in thick-walled arterial stenoses subjected to pulsatile flow.

  17. A numerical study of shock induced cavity collapse

    NASA Astrophysics Data System (ADS)

    Ozlem, Melih

    Motivated by the need for an improved understanding of a prominent mechanism of the generation of hot spots, a model of shock-induced void collapse in a solid material is examined numerically. The problem arises in the context of a solid explosive, where hot spots are the discrete sites of preferential reaction, and play a crucial role in the ignition of a shocked heterogeneous explosive. Specifically, an axisymmetric configuration consisting of a single gas cavity in a solid matrix is considered. The mathematical model is a system of hyperbolic PDEs, the Euler equations of gas dynamics, supplemented by nonideal equation of state for the solid and ideal equation of state for the gas constituent. A mixture formulation is introduced, and the interface is treated as an artificial zone of finite thickness extending over a few computational cells. A finite-volume numerical strategy is employed; it incorporates adaptive mesh refinement and is based on a variant of the Godunov scheme modified to suppress nonphysical instabilities in the vicinity of shocks and interfaces. Complete histories of cavity collapse induced by an incident shock are presented for a variety of cavity shapes and configurations. Hydrodynamic features produced by the shock-cavity interaction are carefully followed, and special attention is paid to mechanisms leading to the evolution of regions of high temperature or pressure. In the case of a spherical shaped cavity the on-axis collapse mechanism is examined as the cause of hot spot formation, and in the case of a tall elliptical cavity and some multiple bubble configurations an off-axis collapse mechanism is discovered. Off-axis collapse mechanisms are found to yield higher temperature and pressure peaks during hot-spot generation.

  18. Relativistic Collapse of Rotating Supermassive Stars to Supermassive Black Holes

    NASA Astrophysics Data System (ADS)

    Shapiro, Stuart L.

    2003-10-01

    There is compelling evidence that supermassive black holes (SMBHs) exist. Yet the origin of these objects, or their seeds, is still unknown. We are performing general relativistic simulations of gravitational collapse to black holes in different scenarios to help reveal how SMBH seeds might arise in the universe. SMBHs with ~ 109 Msolar must have formed by z > 6, or within 109 yrs after the Big Bang, to power quasars. It may be difficult for gas accretion to build up such a SMBH by this time unless the initial seed black hole already has a substantial mass. One plausible progenitor of a massive seed black hole is a supermassive star (SMS). We have followed the collapse of a SMS to a SMBH by means of 3D hydrodynamic simulations in post-Newtonian gravity and axisymmetric simulations in full general relativity. The initial SMS of arbitrary mass M in these simulations rotates uniformly at the mass-shedding limit and is marginally unstable to radial collapse. The final black hole mass and spin are determined to be Mh/M ~ 0.9 and Jh/Mh2 ~ 0.75. The remaining mass goes into a disk of mass Mdisk/M ~ 0.1. This disk arises even though the total spin of the progenitor star, J/M2 = 0.97, is safely below the Kerr limit. The collapse generates a mild burst gravitational radiation. Nonaxisymmetric bars or one-armed spirals may arise during the quasi-stationary evolution of a SMS, during its collapse, or in the ambient disk about the hole, and are potential sources of quasi-periodic waves, detectable by LISA.

  19. Toward a Minimal Artificial Axon.

    PubMed

    Ariyaratne, Amila; Zocchi, Giovanni

    2016-07-01

    The electrophysiology of action potentials is usually studied in neurons, through relatively demanding experiments which are difficult to scale up to a defined network. Here we pursue instead the minimal artificial system based on the essential biological components-ion channels and lipid bilayers-where action potentials can be generated, propagated, and eventually networked. The fundamental unit is the classic supported bilayer: a planar bilayer patch with embedded ion channels in a fluidic environment where an ionic gradient is imposed across the bilayer. Two such units electrically connected form the basic building block for a network. The system is minimal in that we demonstrate that one kind of ion channel and correspondingly a gradient of only one ionic species is sufficient to generate an excitable system which shows amplification and threshold behavior. PMID:27049652

  20. Minimal Doubling and Point Splitting

    SciTech Connect

    Creutz, M.

    2010-06-14

    Minimally-doubled chiral fermions have the unusual property of a single local field creating two fermionic species. Spreading the field over hypercubes allows construction of combinations that isolate specific modes. Combining these fields into bilinears produces meson fields of specific quantum numbers. Minimally-doubled fermion actions present the possibility of fast simulations while maintaining one exact chiral symmetry. They do, however, introduce some peculiar aspects. An explicit breaking of hyper-cubic symmetry allows additional counter-terms to appear in the renormalization. While a single field creates two different species, spreading this field over nearby sites allows isolation of specific states and the construction of physical meson operators. Finally, lattice artifacts break isospin and give two of the three pseudoscalar mesons an additional contribution to their mass. Depending on the sign of this mass splitting, one can either have a traditional Goldstone pseudoscalar meson or a parity breaking Aoki-like phase.

  1. Anaesthesia for minimally invasive surgery

    PubMed Central

    Dec, Marta

    2015-01-01

    Minimally invasive surgery (MIS) is rising in popularity. It offers well-known benefits to the patient. However, restricted access to the surgical site and gas insufflation into the body cavities may result in severe complications. From the anaesthetic point of view MIS poses unique challenges associated with creation of pneumoperitoneum, carbon dioxide absorption, specific positioning and monitoring a patient to whom the anaesthetist has often restricted access, in a poorly lit environment. Moreover, with refinement of surgical procedures and growing experience the anaesthetist is presented with patients from high-risk groups (obese, elderly, with advanced cardiac and respiratory disease) who once were deemed unsuitable for the laparoscopic technique. Anaesthetic management is aimed at getting the patient safely through the procedure, minimizing the specific risks arising from laparoscopy and the patient's coexisting medical problems, ensuring quick recovery and a relatively pain-free postoperative course with early return to normal function. PMID:26865885

  2. Minimal universal quantum heat machine.

    PubMed

    Gelbwaser-Klimovsky, D; Alicki, R; Kurizki, G

    2013-01-01

    In traditional thermodynamics the Carnot cycle yields the ideal performance bound of heat engines and refrigerators. We propose and analyze a minimal model of a heat machine that can play a similar role in quantum regimes. The minimal model consists of a single two-level system with periodically modulated energy splitting that is permanently, weakly, coupled to two spectrally separated heat baths at different temperatures. The equation of motion allows us to compute the stationary power and heat currents in the machine consistent with the second law of thermodynamics. This dual-purpose machine can act as either an engine or a refrigerator (heat pump) depending on the modulation rate. In both modes of operation, the maximal Carnot efficiency is reached at zero power. We study the conditions for finite-time optimal performance for several variants of the model. Possible realizations of the model are discussed. PMID:23410316

  3. Principle of minimal work fluctuations.

    PubMed

    Xiao, Gaoyang; Gong, Jiangbin

    2015-08-01

    Understanding and manipulating work fluctuations in microscale and nanoscale systems are of both fundamental and practical interest. For example, in considering the Jarzynski equality 〈e-βW〉=e-βΔF, a change in the fluctuations of e-βW may impact how rapidly the statistical average of e-βW converges towards the theoretical value e-βΔF, where W is the work, β is the inverse temperature, and ΔF is the free energy difference between two equilibrium states. Motivated by our previous study aiming at the suppression of work fluctuations, here we obtain a principle of minimal work fluctuations. In brief, adiabatic processes as treated in quantum and classical adiabatic theorems yield the minimal fluctuations in e-βW. In the quantum domain, if a system initially prepared at thermal equilibrium is subjected to a work protocol but isolated from a bath during the time evolution, then a quantum adiabatic process without energy level crossing (or an assisted adiabatic process reaching the same final states as in a conventional adiabatic process) yields the minimal fluctuations in e-βW, where W is the quantum work defined by two energy measurements at the beginning and at the end of the process. In the classical domain where the classical work protocol is realizable by an adiabatic process, then the classical adiabatic process also yields the minimal fluctuations in e-βW. Numerical experiments based on a Landau-Zener process confirm our theory in the quantum domain, and our theory in the classical domain explains our previous numerical findings regarding the suppression of classical work fluctuations [G. Y. Xiao and J. B. Gong, Phys. Rev. E 90, 052132 (2014)]. PMID:26382367

  4. Principle of minimal work fluctuations

    NASA Astrophysics Data System (ADS)

    Xiao, Gaoyang; Gong, Jiangbin

    2015-08-01

    Understanding and manipulating work fluctuations in microscale and nanoscale systems are of both fundamental and practical interest. For example, in considering the Jarzynski equality =e-β Δ F , a change in the fluctuations of e-β W may impact how rapidly the statistical average of e-β W converges towards the theoretical value e-β Δ F, where W is the work, β is the inverse temperature, and Δ F is the free energy difference between two equilibrium states. Motivated by our previous study aiming at the suppression of work fluctuations, here we obtain a principle of minimal work fluctuations. In brief, adiabatic processes as treated in quantum and classical adiabatic theorems yield the minimal fluctuations in e-β W. In the quantum domain, if a system initially prepared at thermal equilibrium is subjected to a work protocol but isolated from a bath during the time evolution, then a quantum adiabatic process without energy level crossing (or an assisted adiabatic process reaching the same final states as in a conventional adiabatic process) yields the minimal fluctuations in e-β W, where W is the quantum work defined by two energy measurements at the beginning and at the end of the process. In the classical domain where the classical work protocol is realizable by an adiabatic process, then the classical adiabatic process also yields the minimal fluctuations in e-β W. Numerical experiments based on a Landau-Zener process confirm our theory in the quantum domain, and our theory in the classical domain explains our previous numerical findings regarding the suppression of classical work fluctuations [G. Y. Xiao and J. B. Gong, Phys. Rev. E 90, 052132 (2014), 10.1103/PhysRevE.90.052132].

  5. Minimizing liability during internal investigations.

    PubMed

    Morris, Cole

    2010-01-01

    Today's security professional must appreciate the potential landmines in any investigative effort and work collaboratively with others to minimize liability risks, the author points out. In this article he examines six civil torts that commonly arise from unprofessionally planned or poorly executed internal investigations-defamation, false imprisonment. intentional infliction of emotional distress, assault and battery, invasion of privacy, and malicious prosecution and abuse of process. PMID:20873494

  6. Elastic Langmuir layers and membranes subjected to unidirectional compression: wrinkling and collapse.

    PubMed

    Danov, Krassimir D; Kralchevsky, Peter A; Stoyanov, Simeon D

    2010-01-01

    We apply the two-dimensional elastic continuum model to describe the wrinkling of elastic Langmuir layers (membranes) subjected to unidirectional compression. The effects of the dilatational, shear, and bending elasticities are taken into account. Among the numerous solutions of the generalized Laplace equation, corresponding to different membrane tensions, we determine the membrane shape as the profile that minimizes the energy of the system. In the case of small deformations, the problem can be linearized. Its solution predicts a wavelike shape of the compressed membrane. At negligibly small bending elasticity, the energy of the system is minimal for a sinusoidal profile, whose amplitude and wavelength tend to zero. In the opposite limiting case, where the effect of bending elasticity prevails over the effect of gravity, the membrane has a half-wave profile. When the two effects are comparable, the membrane shape exhibits multiple periodic wrinkles (ripples). An expression is derived for calculating the bending elasticity (rigidity) from the wavelength, and reasonable values are obtained from available experimental data. To determine the membrane shape at larger out-of-plane deformations, we solved numerically the respective nonlinear problem. Depending on the values of the physical parameters, the theory predicts various shapes: nonharmonic oscillations, toothed profiles, and profiles with two characteristic wavelengths. The results can be used for determining the bending elastic modulus of Langmuir films (membranes) as well as for the interpretation of buckling and collapse of monolayers. PMID:19928973

  7. Effects of frictional losses and pulsatile flow on the collapse of stenotic arteries.

    PubMed

    Downing, J M; Ku, D N

    1997-08-01

    High-grade stenosis can produce conditions in which the artery may collapse. A one-dimensional numerical model of a compliant stenosis was developed from the collapsible tube theory of Shapiro. The model extends an earlier model by including the effects of frictional losses and unsteadiness. The model was used to investigate the relative importance of several physical parameters present in the in vivo environment. The results indicated that collapse can occur within the stenosis. Frictional loss was influential in reducing the magnitude of collapse. Large separation losses could prevent collapse outright even with low downstream resistances. However, the degree of stenosis was still the primary parameter governing the onset of collapse. Pulsatile solutions demonstrated conditions that produce cyclic collapse within the stenosis. This study predicts certain physiologic conditions in which collapse of arteries may occur for high-grade stenoses. PMID:9285345

  8. A COMPARISON OF COLLAPSING AND PRECISE ARRIVAL-TIME MAPPING OF MICROSEISMICITY

    SciTech Connect

    RUTLEDGE, JAMES T.; JONES, ROB H.

    2007-01-05

    In this paper they compare the improvements in microseismic location images obtained using precise arrival times with that obtained by the collapsing technique. They first collapse the initial locations for a hydraulic-fracture data set from the Carthage Cotton Valley gas field, they then use the precise-arrival-time locations as measure for the effectiveness of the collapsing. Finally, they examine the changes when applying collapsing to the precise-arrival-time locations.

  9. Transluminal aortic valve placement. A feasibility study with a newly designed collapsible aortic valve.

    PubMed

    Moazami, N; Bessler, M; Argenziano, M; Choudhri, A F; Cabreriza, S E; Allendorf, J D; Rose, E A; Oz, M C

    1996-01-01

    Percutaneous stents are used in vascular applications in conjunction with angioplasty and in combination with graft material for repair of abdominal aneurysms. The authors have designed a collapsible bioprosthetic aortic valve for placement by a transluminal catheter technique. This trileaflet stent valve is composed of stainless steel and bovine pericardium. Stent valves, 23 and 29 mm, were tested in a pulse duplicator system with rigid rings from 21 to 31 mm in 2 mm increments. At a mean flow of 3.1 L/min (+/-0.7), normal systemic aortic pressure was generated with a transvalvular gradient of 14.9 +/- 7 mmHg (mean +/- SD). Regurgitation fraction ranged from 10 to 18% (mean 13.8 +/- 3%) in the best ring size. Valves with the best hemodynamic profile were used for implantation in three 70 kg pigs in an open chest model. The valve was collapsed in a 24 Fr catheter designed to allow slow, controlled release. After resection of the native leaflets, the new valve was placed in the subcoronary position. No additional sutures were used for securing the valve. Two animals were successfully weaned from cardiopulmonary bypass and maintained systemic pressures of 100/45 (+/-10) and 116/70 (+/-15) mmHg, respectively. Intraoperative color echocardiography revealed minimal regurgitation, central flow, full apposition of all leaflets, and no interference with coronary blood flow. Both animals were sacrificed after being off bypass for 2 hr. Postmortem examination revealed the valves to be securely anchored. The third animal was weaned from cardiopulmonary bypass but developed refractory ventricular fibrillation because of valve dislodgment due to structural failure. Although long term survival data are needed, development of a hemodynamically acceptable prosthetic aortic valve for transluminal placement is feasible. PMID:8944912

  10. Mechanism and prevention of karst collapse near mine areas in China

    SciTech Connect

    Xu Weiguo; Zhao Guirong )

    1988-08-01

    The authors of this article have described essential conditions and environmental forms of collapse in covered karst mine areas in China as well as external causes such as drastic lowering of the ground water surface. The authors present a theory of suction action causing collapse, and an air-charging method to prevent the collapse. The result obtained by this method is favorable.

  11. Risk minimization through portfolio replication

    NASA Astrophysics Data System (ADS)

    Ciliberti, S.; Mã©Zard, M.

    2007-05-01

    We use a replica approach to deal with portfolio optimization problems. A given risk measure is minimized using empirical estimates of asset values correlations. We study the phase transition which happens when the time series is too short with respect to the size of the portfolio. We also study the noise sensitivity of portfolio allocation when this transition is approached. We consider explicitely the cases where the absolute deviation and the conditional value-at-risk are chosen as a risk measure. We show how the replica method can study a wide range of risk measures, and deal with various types of time series correlations, including realistic ones with volatility clustering.

  12. Diagnosis of minimal hepatic encephalopathy.

    PubMed

    Weissenborn, Karin

    2015-03-01

    Minimal hepatic encephalopathy (mHE) has significant impact upon a liver patient's daily living and health related quality of life. Therefore a majority of clinicians agree that mHE should be diagnosed and treated. The optimal means for diagnosing mHE, however, is controversial. This paper describes the currently most frequently used methods-EEG, critical flicker frequency, Continuous Reaction time Test, Inhibitory Control Test, computerized test batteries such as the Cognitive Drug Research test battery, the psychometric hepatic encephalopathy score (PHES) and the Repeatable Battery for the Assessment of Neuropsychological Status (RBANS)-and their pros and cons. PMID:26041959

  13. About the ZOOM minimization package

    SciTech Connect

    Fischler, M.; Sachs, D.; /Fermilab

    2004-11-01

    A new object-oriented Minimization package is available for distribution in the same manner as CLHEP. This package, designed for use in HEP applications, has all the capabilities of Minuit, but is a re-write from scratch, adhering to modern C++ design principles. A primary goal of this package is extensibility in several directions, so that its capabilities can be kept fresh with as little maintenance effort as possible. This package is distinguished by the priority that was assigned to C++ design issues, and the focus on producing an extensible system that will resist becoming obsolete.

  14. Prepulse minimization in KALI-5000.

    PubMed

    Kumar, D Durga Praveen; Mitra, S; Senthil, K; Sharma, Vishnu K; Singh, S K; Roy, A; Sharma, Archana; Nagesh, K V; Chakravarthy, D P

    2009-07-01

    A pulse power system (1 MV, 50 kA, and 100 ns) based on Marx generator and Blumlein pulse forming line has been built for generating high power microwaves. The Blumlein configuration poses a prepulse problem and hence the diode gap had to be increased to match the diode impedance to the Blumlein impedance during the main pulse. A simple method to eliminate prepulse voltage using a vacuum sparkgap and a resistor is given. Another fundamental approach of increasing the inductance of Marx generator to minimize the prepulse voltage is also presented. Experimental results for both of these configurations are given. PMID:19655979

  15. Prepulse minimization in KALI-5000

    NASA Astrophysics Data System (ADS)

    Kumar, D. Durga Praveen; Mitra, S.; Senthil, K.; Sharma, Vishnu K.; Singh, S. K.; Roy, A.; Sharma, Archana; Nagesh, K. V.; Chakravarthy, D. P.

    2009-07-01

    A pulse power system (1 MV, 50 kA, and 100 ns) based on Marx generator and Blumlein pulse forming line has been built for generating high power microwaves. The Blumlein configuration poses a prepulse problem and hence the diode gap had to be increased to match the diode impedance to the Blumlein impedance during the main pulse. A simple method to eliminate prepulse voltage using a vacuum sparkgap and a resistor is given. Another fundamental approach of increasing the inductance of Marx generator to minimize the prepulse voltage is also presented. Experimental results for both of these configurations are given.

  16. Minimizing medical litigation, part 2.

    PubMed

    Harold, Tan Keng Boon

    2006-01-01

    Provider-patient disputes are inevitable in the healthcare sector. Healthcare providers and regulators should recognize this and plan opportunities to enforce alternative dispute resolution (ADR) a early as possible in the care delivery process. Negotiation is often the main dispute resolution method used by local healthcare providers, failing which litigation would usually follow. The role of mediation in resolving malpractice disputes has been minimal. Healthcare providers, administrators, and regulators should therefore look toward a post-event communication-cum-mediation framework as the key national strategy to resolving malpractice disputes. PMID:16711089

  17. The minimal scenario of leptogenesis

    NASA Astrophysics Data System (ADS)

    Blanchet, Steve; Di Bari, Pasquale

    2012-12-01

    We review the main features and results of thermal leptogenesis within the type I seesaw mechanism, the minimal extension of the Standard Model explaining neutrino masses and mixing. After presenting the simplest approach, the vanilla scenario, we discuss various important developments of recent years, such as the inclusion of lepton and heavy neutrino flavour effects, a description beyond a hierarchical heavy neutrino mass spectrum and an improved kinetic description within the density matrix and the closed-time-path formalisms. We also discuss how leptogenesis can ultimately represent an important phenomenological tool to test the seesaw mechanism and the underlying model of new physics.

  18. Critical phenomena in the aspherical gravitational collapse of radiation fluids

    NASA Astrophysics Data System (ADS)

    Baumgarte, Thomas W.; Montero, Pedro J.

    2015-12-01

    We study critical phenomena in the gravitational collapse of a radiation fluid. We perform numerical simulations in both spherical symmetry and axisymmetry, and observe critical scaling in both supercritical evolutions, which lead to the formation of a black hole, and subcritical evolutions, in which case the fluid disperses to infinity and leaves behind flat space. We identify the critical solution in spherically symmetric collapse, find evidence for its universality, and study the approach to this critical solution in the absence of spherical symmetry. For the cases that we consider, aspherical deviations from the spherically symmetric critical solution decay in damped oscillations in a manner that is consistent with the behavior found by Gundlach in perturbative calculations. Our simulations are performed with an unconstrained evolution code, implemented in spherical polar coordinates, and adopting "moving-puncture" coordinates.

  19. Catastrophic collapse of the west Florida carbonate platform margin

    SciTech Connect

    Mullins, H.T.; Gardulski, A.F.; Hine, A.C.

    1986-02-01

    A large truncation surface has been discovered on seismic reflection profiles along the distally steepened ramp of the west Florida carbonate platform margin. This structure, interpreted as a submarine slide scar, is at least 120 km across and up to 30 km wide; the slide has removed as much as 300-350 m of late Paleogene and early Neogene strata. Collapse occurred in the middle Miocene within an episode of seaward progradation during a relative sea-level highstand. Postcollapse depositional sequences thicken abruptly across the structure; this suggests catastrophic slope failure. Gravitational instability, created by high rates of sediment accumulation, is believed to have been the triggering mechanism. Such large-scale platform-margin collapse is likely to generate megabreccia debris flows as well as aid in the landward retreat of precipitous, high-relief carbonate escarpments.

  20. Space shuttle solid rocket booster water entry cavity collapse loads

    NASA Technical Reports Server (NTRS)

    Keefe, R. T.; Rawls, E. A.; Kross, D. A.

    1982-01-01

    Solid rocket booster cavity collapse flight measurements included external pressures on the motor case and aft skirt, internal motor case pressures, accelerometers located in the forward skirt, mid-body area, and aft skirt, as well as strain gages located on the skin of the motor case. This flight data yielded applied pressure longitudinal and circumferential distributions which compare well with model test predictions. The internal motor case ullage pressure, which is below atmospheric due to the rapid cooling of the hot internal gas, was more severe (lower) than anticipated due to the ullage gas being hotter than predicted. The structural dynamic response characteristics were as expected. Structural ring and wall damage are detailed and are considered to be attributable to the direct application of cavity collapse pressure combined with the structurally destabilizing, low internal motor case pressure.

  1. Kax and kol: Collapse and resilience in lowland Maya civilization

    PubMed Central

    Dunning, Nicholas P.; Beach, Timothy P.; Luzzadder-Beach, Sheryl

    2012-01-01

    Episodes of population loss and cultural change, including the famous Classic Collapse, punctuated the long course of Maya civilization. In many cases, these downturns in the fortunes of individual sites and entire regions included significant environmental components such as droughts or anthropogenic environmental degradation. Some afflicted areas remained depopulated for long periods, whereas others recovered more quickly. We examine the dynamics of growth and decline in several areas in the Maya Lowlands in terms of both environmental and cultural resilience and with a focus on downturns that occurred in the Terminal Preclassic (second century Common Era) and Terminal Classic (9th and 10th centuries CE) periods. This examination of available data indicates that the elevated interior areas of the Yucatán Peninsula were more susceptible to system collapse and less suitable for resilient recovery than adjacent lower-lying areas. PMID:22371571

  2. Source analysis of the Crandall Canyon, Utah, mine collapse.

    PubMed

    Dreger, Douglas S; Ford, Sean R; Walter, William R

    2008-07-11

    Analysis of seismograms from a magnitude 3.9 seismic event on 6 August 2007 in central Utah reveals an anomalous radiation pattern that is contrary to that expected for a tectonic earthquake and which is dominated by an implosive component. The results show that the seismic event is best modeled as a shallow underground collapse. Interestingly, large transverse surface waves require a smaller additional noncollapse source component that might represent either faulting in the rocks above the mine workings or deformation of the medium surrounding the mine. Seismic moment tensor results for nuclear explosions, explosion and other mining cavity collapses, and tectonic earthquakes are compared, and the separation of the different populations indicates that the seismic moment tensor may be used for source-type discrimination. PMID:18621662

  3. Inelastic X-ray Scattering Studies of Zeolite Collapse

    SciTech Connect

    Greaves, G. Neville; Kargl, Florian; Ward, David; Holliman, Peter; Meneau, Florian

    2009-01-29

    In situ inelastic x-ray scattering (IXS) experiments have been used to probe heterogeneity and deformability in zeolte Y as this thermally collapses to a high density amorphous (HDA) aluminosilicate phase. The Landau-Placzek ratio R{sub LP} falls slowly as amorphisation advances, increasing in the later stages of collapse clearly showing how homogeneity improves non-linearly--behaviour linked closely with the decline in molar volume V{sub Molar}. The Brillouin frequency {omega}{sub Q} also decreases with amorphisation in a similar fashion, signifying a non-uniform decrease in the speed of sound v{sub l}. All of these changes with zeolite amorphisation infer formation of an intermediate low density amorphous (LDA) phase. This low entropy or 'perfect glass' has mechanical properties which are closer to the zeolite rather to the HDA glass--notably a very small value of Poisson's Ratio signifying unusually low resistance to deformation.

  4. Traumatic Eye Injuries From Collapsible Wire Laundry Hampers

    PubMed Central

    Prickett, Adam L.; Salar, Senem; Chow, Clement C.; Traish, Aisha S.; Leiderman, Yannek I.; Chau, Felix Y.

    2013-01-01

    Two patients presented to the University of Illinois at Chicago Eye and Ear Infirmary within 1 year with penetrating eye injuries caused by similar collapsible cloth and wire laundry hampers. Penetrating eye injuries in children are relatively rare but can result in poor visual outcomes and multiple vision-threatening complications. Both injuries at the University of Illinois resulted in an eye laceration as well as retinal complications similar to those reported with a high velocity injury. This now represents a significant pattern of eye injury and suggests that there exists a nontrivial risk for all children in households with this type of collapsible laundry hamper. Parents should receive a warning of the risks of these hampers. PMID:23821700

  5. The collapse of quantum states: A new interpretation

    NASA Astrophysics Data System (ADS)

    Malin, Shimon

    1993-06-01

    The collapse of quantum states is analyzed in terms of a breakdown into two generic phases: Phase I, in which the field of potentialities that the quantum state represents undergoes a discontinuous and unpredictable change into one of the base states which corresponds to the measurement performed, and phase II, in which a transition from the level of potentialities to the level of actualities takes place. Phase I is discussed in relation to a comment about collapse, made by Dirac in conversation with the author, “Nature makes a choice.” An analysis of phase II leads to the suggestion that it occurs only through and as an act of experience. This postulate is shown to elucidate basic questions regarding the interpretation of quantum mechanics, such as the elusive demarcation line between the classical and quantum domains, and the controversy of the ontological vs. epistemological interpretation of quantum mechanics.

  6. Luminescence from Collapsing Centimeter Bubbles Expanded by Chemical Reaction

    NASA Astrophysics Data System (ADS)

    Duplat, Jérôme; Villermaux, Emmanuel

    2015-08-01

    We report on a new method for realizing an exceptionally strong inertial confinement of a gas in a liquid: A centimetric spherical bubble filled with a reactive gaseous mixture in a liquid is expanded by an exothermic chemical reaction whose products condense in the liquid at the bubble wall. Hence, the cavity formed in this way is essentially empty as it collapses. The temperatures reached at maximum compression, inferred from the cavity radius dynamics and further confirmed by spectroscopic measurements exceed 20 000 K. Because the cavity is typically big, our findings also provide unique space and time resolved sequences of the events accompanying the collapse, notably the development of the inertial instability notoriously known to deter strong compression.

  7. Path to collapse for an isolated Néel skyrmion

    NASA Astrophysics Data System (ADS)

    Rohart, S.; Miltat, J.; Thiaville, A.

    2016-06-01

    A path method is implemented in order to precisely and generally describe the collapse of isolated skyrmions in a Co/Pt(111) monolayer, on the basis of atomic scale simulations. Two collapse mechanisms with different energy barriers are found. The most obvious path, featuring a homogeneous shrinking, gives the largest energy, whereas the lowest energy barrier is shown to comply with the outcome of Langevin dynamics under a destabilizing field of 0.25 T, with a lifetime of 20 ns at around 80 K. For this lowest energy barrier path, skyrmion destabilization occurs much before any topology change, suggesting that topology plays a minor role in the skyrmion stability. On the contrary, an important role appears devoted to the Dzyaloshinskii-Moriya interaction, establishing a route towards improved skyrmion stability.

  8. Cellular membrane collapse by atmospheric-pressure plasma jet

    SciTech Connect

    Kim, Kangil; Sik Yang, Sang E-mail: ssyang@ajou.ac.kr; Jun Ahn, Hak; Lee, Jong-Soo E-mail: ssyang@ajou.ac.kr; Lee, Jae-Hyeok; Kim, Jae-Ho

    2014-01-06

    Cellular membrane dysfunction caused by air plasma in cancer cells has been studied to exploit atmospheric-pressure plasma jets for cancer therapy. Here, we report that plasma jet treatment of cervical cancer HeLa cells increased electrical conductivity across the cellular lipid membrane and caused simultaneous lipid oxidation and cellular membrane collapse. We made this finding by employing a self-manufactured microelectrode chip. Furthermore, increased roughness of the cellular lipid membrane and sequential collapse of the membrane were observed by atomic force microscopy following plasma jet treatment. These results suggest that the cellular membrane catastrophe occurs via coincident altered electrical conductivity, lipid oxidation, and membrane roughening caused by an atmospheric-pressure plasma jet, possibly resulting in cellular vulnerability to reactive species generated from the plasma as well as cytotoxicity to cancer cells.

  9. The rheology of collapsing zeolites amorphized by temperature and pressure.

    PubMed

    Greaves, G N; Meneau, F; Sapelkin, A; Colyer, L M; ap Gwynn, I; Wade, S; Sankar, G

    2003-09-01

    Low-density zeolites collapse to the rigid amorphous state at temperatures that are well below the melting points of crystals of the same composition but of conventional density. Here we show, by using a range of experimental techniques, how the phenomenon of amorphization is time dependent, and how the dynamics of order-disorder transitions in zeolites under temperature and pressure are equivalent. As a result, thermobaric regions of instability can be charted, which are indicative of polyamorphism. Moreover, the boundaries of these zones depend on the rate at which temperature or pressure is ramped. By directly comparing the rheology of collapse with structural relaxation in equivalent melts, we conclude that zeolites amorphize like very strong liquids and, if compression occurs slowly, this is likely to lead to the synthesis of perfect glasses. PMID:12942072

  10. Controlling condensate collapse and expansion with an optical Feshbach resonance.

    PubMed

    Yan, Mi; DeSalvo, B J; Ramachandhran, B; Pu, H; Killian, T C

    2013-03-22

    We demonstrate control of the collapse and expansion of an (88)Sr Bose-Einstein condensate using an optical Feshbach resonance near the (1)S(0)-(3)P(1) intercombination transition at 689 nm. Significant changes in dynamics are caused by modifications of scattering length by up to ± 10a(bg), where the background scattering length of (88)Sr is a(bg) = -2a(0) (1a(0) = 0.053 nm). Changes in scattering length are monitored through changes in the size of the condensate after a time-of-flight measurement. Because the background scattering length is close to zero, blue detuning of the optical Feshbach resonance laser with respect to a photoassociative resonance leads to increased interaction energy and a faster condensate expansion, whereas red detuning triggers a collapse of the condensate. The results are modeled with the time-dependent nonlinear Gross-Pitaevskii equation. PMID:25166803

  11. Neutrinos and nucleosynthesis in core-collapse supernovae

    SciTech Connect

    Fröhlich, C.; Casanova, J.; Hempel, M.; Liebendörfer, M.; Melton, C. A.; Perego, A.

    2014-01-01

    Massive stars (M > 8-10 M{sub ⊙}) undergo core collapse at the end of their life and explode as supernova with ~ 10⁵¹ erg of kinetic energy. While the detailed supernova explosion mechanism is still under investigation, reliable nucleosynthesis calculations based on successful explosions are needed to explain the observed abundances in metal-poor stars and to predict supernova yields for galactic chemical evolution studies. To predict nucleosynthesis yields for a large number of progenitor stars, computationally efficient explosion models are required. We model the core collapse, bounce and subsequent explosion of massive stars assuming spherical symmetry and using detailed microphysics and neutrino physics combined with a novel method to artificially trigger the explosion (PUSH). We discuss the role of neutrinos, the conditions in the ejecta, and the resulting nucleosynthesis.

  12. Gravitational collapse with rotating thin shells and cosmic censorship

    NASA Astrophysics Data System (ADS)

    Delsate, Térence; Rocha, Jorge V.; Santarelli, Raphael

    2015-04-01

    The study of gravitational collapse is a subject of great importance, both from an astrophysical and a holographic point of view. In this respect, exact solutions can be very helpful but known solutions are very scarce, especially when considering dynamical processes with rotation. We describe a setup in which gravitational collapse of rotating matter shells can be addressed with analytic tools, at the expense of going to higher dimensions and considering equal angular momenta spacetimes. The framework for an exact treatment of the dynamics, relying on a thin shell approximation, is developed. Our analysis allows the inclusion of a non-vanishing cosmological constant. Finally, we discuss applications of this machinery to the construction of stationary solutions describing matter around rotating black holes and to the cosmic censorship conjecture.

  13. Wavefunction collapse through backaction of counting weakly interacting photons

    NASA Astrophysics Data System (ADS)

    Harrell, L. E.

    2016-03-01

    We apply the formalism of quantum measurement theory to the idealized measurement of the position of a particle with an optical interferometer, finding that the backaction of counting entangled photons systematically collapses the particle's wavefunction toward a narrow Gaussian wavepacket at the location xest determined by the measurement without appeal to environmental decoherence or other spontaneous collapse mechanism. Further, the variance in the particle's position, as calculated from the post-measurement wavefunction, agrees precisely with shot-noise limited uncertainty of the measured xest. Both the identification of the absolute square of the particle's initial wavefunction as the probability density for xest and the de Broglie hypothesis emerge as consequences of interpreting the intensity of the optical field as proportional to the probability of detecting a photon. Linear momentum information that is encoded in the particle's initial wavefunction survives the measurement, and the pre-measurement expectation values are preserved in the ensemble average.

  14. Exercise-Associated Collapse: Is Hyponatremia in Our Head?

    PubMed

    Krabak, Brian J; Parker, Kelsey M; DiGirolamo, Anthony

    2016-03-01

    Exercise-associated hyponatremia (EAH) is one of the most common causes of exercise-associated collapse. The primary pathogenesis of EAH is largely the result of excessive fluid intake but is influenced by other factors, including hormonal abnormalities (ie, inappropriate arginine vasopressin secretion), renal abnormalities, and mobilization of sodium stores. Early recognition of EAH is crucial to appropriate treatment, because symptoms are varied and may be confused with other causes of exercise-associated collapse. Onsite testing of [Na+] will confirm the diagnosis but is not always available. Rapid treatment of EAH will depend upon the type and severity of symptoms. Treatment protocols range from fluid restriction or oral hypertonic fluids for mild symptoms to intravenous hypertonic fluids for more severe symptoms. Preventative strategies should emphasize fluid consumption based on thirst and athlete/coach/staff education regarding proper hydration practices. PMID:26972268

  15. Coupled dynamics of translation and collapse of acoustically driven microbubbles.

    PubMed

    Reddy, Anil J; Szeri, Andrew J

    2002-10-01

    Pressure gradients drive the motion of microbubbles relative to liquids in which they are suspended. Examples include the hydrostatic pressure due to a gravitational field, and the pressure gradients in a sound field, useful for acoustic levitation. In this paper, the equations describing the coupled dynamics of radial oscillation and translation of a microbubble are given. The formulation is based on a recently derived expression for the hydrodynamic force on a bubble of changing size in an incompressible liquid [J. Magnaudet and D. Legendre, Phys. Fluids 10, 550-556 (1998)]. The complex interaction between radial and translation dynamics is best understood by examination of the added momentum associated with the liquid motion caused by the moving bubble. Translation is maximized when the bubble collapses violently. The new theory for coupled collapse and translation dynamics is compared to past experiments and to previous theories for decoupled translation dynamics. Special attention is paid to bubbles of relevance in biomedical applications. PMID:12398441

  16. Weak-interaction processes in core-collapse supernovae

    SciTech Connect

    Langanke, K.

    2015-02-24

    Weak interaction processes play an important role for the dynamics of a core-collapse supernova. Due to progress of nuclear modeling and constrained by data it has been possible to improve the rates of these processes for supernova conditions decisively. This manuscript describes the recent advances and the current status in deriving electron capture rates on nuclei and of inelastic neutrino-nucleus scattering for applications in supernova simulations and briefly discusses their impact on such studies.

  17. Numerical study of rotating interstellar clouds: equilibrium and collapse

    SciTech Connect

    Norman, M.L.

    1980-06-01

    Equilibrium and collapse of rotating, axisymmetric, idealized interstellar gas clouds is calculated with a 2D hydrodynamics code. The hydrodynamics features an improved angular momentum advection algorithm. Angular momentum is advected consistently with mass by deriving angular momentum fluxes from mass fluxes and the local distribution of specific angular momentum. Local conservation is checked by a graph of mass versus specific angular momentum for the cloud as a whole.

  18. Dynamics and avalanches in a system exhibiting granular collapse

    NASA Astrophysics Data System (ADS)

    Sánchez, R.; Huerta, A.

    2015-11-01

    The dynamics of an experimental driven quasi-2D system of polydisperse particles in a cluster formed by granular collapse is characterized via the self-intermediate scattering function and the mean-squared displacement and is compared with monodisperse experimental and computational systems. The dynamics, despite the difference in dimensionality, is shown to resemble that of de-vitrification in certain simulations of 3D colloidal monodisperse hard sphere glasses in that avalanches are a key feature.

  19. iPTF Discoveries of Recent Core-Collapse Supernovae

    NASA Astrophysics Data System (ADS)

    Taddia, F.; Ferretti, R.; Papadogiannakis, S.; Petrushevska, T.; Fremling, C.; Karamehmetoglu, E.; Nyholm, A.; Roy, R.; Hangard, L.; Horesh, A.; Khazov, D.; Knezevic, S.; Johansson, J.; Leloudas, G.; Manulis, I.; Rubin, A.; Soumagnac, M.; Vreeswijk, P.; Yaron, O.; Bar, I.; Cao, Y.; Kulkarni, S.; Blagorodnova, N.

    2016-05-01

    The intermediate Palomar Transient Factory (ATel #4807) reports the discovery and classification of the following core-collapse SNe. Our automated candidate vetting to distinguish a real astrophysical source (1.0) from bogus artifacts (0.0) is powered by three generations of machine learning algorithms: RB2 (Brink et al. 2013MNRAS.435.1047B), RB4 (Rebbapragada et al. 2015AAS...22543402R) and RB5 (Wozniak et al. 2013AAS...22143105W).

  20. Multidimensional, multiphysics simulations of core-collapse supernovae

    SciTech Connect

    Messer, Bronson; Mezzacappa, Anthony; Blondin, J. M.; Bruenn, S. W.; Hix, William Raphael

    2008-01-01

    CHIMERA is a multi-dimensional radiation hydrodynamics code designed to study core-collapse supernovae. The code is made up of three essentially independent parts: a hydrodynamics module, a nuclear burning module, and a neutrino transport solver combined within an operator-split approach. We review the code s architecture and some recently improved implementations used in the code. We also briefly discuss preliminary results obtained with the code in three spatial dimensions.

  1. Multidimensional, multiphysics simulations of core-collapse supernovae

    SciTech Connect

    Messer, Bronson; Mezzacappa, Anthony; Blondin, J. M.; Bruenn, S. W.; Hix, William Raphael

    2008-01-01

    CHIMERA is a multi-dimensional radiation hydrodynamics code designed to study core-collapse supernovae. The code is made up of three essentially independent parts: a hydrodynamics module, a nuclear burning module, and a neutrino transport solver combined within an operator-split approach. We review the code's architecture and some recently improved implementations used in the code. We also briefly discuss preliminary results obtained with the code in three spatial dimensions.

  2. Perturbation analysis of a general polytropic homologously collapsing stellar core

    NASA Astrophysics Data System (ADS)

    Cao, Yi; Lou, Yu-Qing

    2009-12-01

    For dynamic background models of Goldreich & Weber and Lou & Cao, we examine three-dimensional perturbation properties of oscillations and instabilities in a general polytropic homologously collapsing stellar core of a relativistically hot medium with a polytropic index γ = 4/3. Perturbation behaviours, especially internal gravity g modes, depend on the variation of specific entropy in the collapsing core. Among possible perturbations, we identify acoustic p modes and surface f modes as well as internal gravity g+ and g- modes. As in stellar oscillations of a static star, we define g+ and g- modes by the sign of the Brunt-Väisälä buoyancy frequency squared for a collapsing stellar core. A new criterion for the onset of instabilities is established for a homologous stellar core collapse. We demonstrate that the global energy criterion of Chandrasekhar is insufficient to warrant the stability of general polytropic equilibria. We confirm the acoustic p-mode stability of Goldreich & Weber, even though their p-mode eigenvalues appear in systematic errors. Unstable modes include g- modes and sufficiently high-order g+ modes, corresponding to core instabilities. Such instabilities occur before the stellar core bounce, in contrast to instabilities in other models of supernova (SN) explosions. The breakdown of spherical symmetry happens earlier than expected in numerical simulations so far. The formation and motion of the central compact object are speculated to be much affected by such g-mode instabilities. By estimates of typical parameters, unstable low-order l = 1 g-modes may produce initial kicks of the central compact object. Other high-order and high-degree unstable g modes may shred the nascent neutron core into pieces without an eventual compact remnant (e.g. SN 1987A). Formation of binary pulsars and planets around neutron stars might originate from unstable l = 2 g-modes and high-order high-degree g modes, respectively.

  3. Gravitational wave extraction in simulations of rotating stellar core collapse

    SciTech Connect

    Reisswig, C.; Ott, C. D.; Sperhake, U.; Schnetter, E.

    2011-03-15

    We perform simulations of general relativistic rotating stellar core collapse and compute the gravitational waves (GWs) emitted in the core-bounce phase of three representative models via multiple techniques. The simplest technique, the quadrupole formula (QF), estimates the GW content in the spacetime from the mass-quadrupole tensor only. It is strictly valid only in the weak-field and slow-motion approximation. For the first time, we apply GW extraction methods in core collapse that are fully curvature based and valid for strongly radiating and highly relativistic sources. These techniques are not restricted to weak-field and slow-motion assumptions. We employ three extraction methods computing (i) the Newman-Penrose (NP) scalar {Psi}{sub 4}, (ii) Regge-Wheeler-Zerilli-Moncrief master functions, and (iii) Cauchy-characteristic extraction (CCE) allowing for the extraction of GWs at future null infinity, where the spacetime is asymptotically flat and the GW content is unambiguously defined. The latter technique is the only one not suffering from residual gauge and finite-radius effects. All curvature-based methods suffer from strong nonlinear drifts. We employ the fixed-frequency integration technique as a high-pass waveform filter. Using the CCE results as a benchmark, we find that finite-radius NP extraction yields results that agree nearly perfectly in phase, but differ in amplitude by {approx}1%-7% at core bounce, depending on the model. Regge-Wheeler-Zerilli-Moncrief waveforms, while, in general, agreeing in phase, contain spurious high-frequency noise of comparable amplitudes to those of the relatively weak GWs emitted in core collapse. We also find remarkably good agreement of the waveforms obtained from the QF with those obtained from CCE. The results from QF agree very well in phase and systematically underpredict peak amplitudes by {approx}5%-11%, which is comparable to the NP results and is certainly within the uncertainties associated with core collapse

  4. Diversity Waves in Collapse-Driven Population Dynamics

    PubMed Central

    Maslov, Sergei; Sneppen, Kim

    2015-01-01

    Populations of species in ecosystems are often constrained by availability of resources within their environment. In effect this means that a growth of one population, needs to be balanced by comparable reduction in populations of others. In neutral models of biodiversity all populations are assumed to change incrementally due to stochastic births and deaths of individuals. Here we propose and model another redistribution mechanism driven by abrupt and severe reduction in size of the population of a single species freeing up resources for the remaining ones. This mechanism may be relevant e.g. for communities of bacteria, with strain-specific collapses caused e.g. by invading bacteriophages, or for other ecosystems where infectious diseases play an important role. The emergent dynamics of our system is characterized by cyclic ‘‘diversity waves’’ triggered by collapses of globally dominating populations. The population diversity peaks at the beginning of each wave and exponentially decreases afterwards. Species abundances have bimodal time-aggregated distribution with the lower peak formed by populations of recently collapsed or newly introduced species while the upper peak - species that has not yet collapsed in the current wave. In most waves both upper and lower peaks are composed of several smaller peaks. This self-organized hierarchical peak structure has a long-term memory transmitted across several waves. It gives rise to a scale-free tail of the time-aggregated population distribution with a universal exponent of 1.7. We show that diversity wave dynamics is robust with respect to variations in the rules of our model such as diffusion between multiple environments, species-specific growth and extinction rates, and bet-hedging strategies. PMID:26367172

  5. Quantum Superposition, Collapse, and the Default Specification Principle

    NASA Astrophysics Data System (ADS)

    Nikkhah Shirazi, Armin

    2014-03-01

    Quantum Superposition and collapse lie at the heart of the difficulty in understanding what quantum mechanics is exactly telling us about reality. We present here a principle which permits one to formulate a simple and general mathematical model that abstracts these features out of quantum theory. A precise formulation of this principle in terms of a set-theoretic axiom added to standard set theory may directly connect the foundations of physics to the foundations of mathematics.

  6. Dangers of collapsible ventricular drainage systems. Technical note.

    PubMed

    Kaye, A H; Wallace, D

    1982-02-01

    Ventricular drainage systems employing a collapsible plastic bag for fluid collection were postulated to cause an increasing back-pressure produced in part by the elasticity of the bag. This postulate was shown to be correct in an experimental situation. There was a logarithmic rise in cerebrospinal fluid pressure as the bag filled. By increasing the size of the bag, the problem was overcome. PMID:7054446

  7. Distributional Enstrophy Dissipation Via the Collapse of Three Point Vortices

    NASA Astrophysics Data System (ADS)

    Gotoda, Takeshi; Sakajo, Takashi

    2016-06-01

    Dissipation of enstrophy in 2D incompressible flows in the zero viscous limit is considered to play a significant role in the emergence of the inertial range corresponding to the forward enstrophy cascade in the energy spectrum of 2D turbulent flows. However, since smooth solutions of the 2D incompressible Euler equations conserve the enstrophy, we need to consider non-smooth inviscid and incompressible flows so that the enstrophy dissipates. Moreover, it is physically uncertain what kind of a flow evolution gives rise to such an anomalous enstrophy dissipation. In this paper, in order to acquire an insight about the singular phenomenon mathematically as well as physically, we consider a dispersive regularization of the 2D Euler equations, known as the Euler-α equations, for the initial vorticity distributions whose support consists of three points, i.e., three α -point vortices, and take the α → 0 limit of its global solutions. We prove with mathematical rigor that, under a certain condition on their vortex strengths, the limit solution becomes a self-similar evolution collapsing to a point followed by the expansion from the collapse point to infinity for a wide range of initial configurations of point vortices. We also find that the enstrophy always dissipates in the sense of distributions at the collapse time. This indicates that the triple collapse is a mechanism for the anomalous enstrophy dissipation in non-smooth inviscid and incompressible flows. Furthermore, it is an interesting example elucidating the emergence of the irreversibility of time in a Hamiltonian dynamical system.

  8. Stellar collapse and the formation of black holes.

    SciTech Connect

    Fryer, C. L.; Dupuis, R.

    2003-01-01

    We review the engines behind neutrino-driven supernovae and gamma-ray bursts. Combined with our understanding of the convection-enhanced, neutrino-driven supernova mechanism, the stellar collapse can explain all of the supernova-like explosions observed from normal supernovae, to weak explosions and jet-like hypernovae. Combining this theoretical understanding with observations suggests that the collapsar rate is roughly 1/1000th that of normal supernovae.

  9. The OCD phase transition and supernova core collapse

    SciTech Connect

    Gentile, N.A.; Mathews, G.J.; Wilson, J.R.

    1993-10-01

    We examine the implications for stellar core collapse of a phase transition occurring at densities of a few times nuclear matter density. We use an equation of state that describes a phase transition between bulk nuclear matter and a phase consisting of unbound quarks and gluons. We analyze the effect on the prompt shock, the production of strange matter, and the effect on the neutrino signal and the delayed mechanism.

  10. Diversity Waves in Collapse-Driven Population Dynamics.

    PubMed

    Maslov, Sergei; Sneppen, Kim

    2015-09-01

    Populations of species in ecosystems are often constrained by availability of resources within their environment. In effect this means that a growth of one population, needs to be balanced by comparable reduction in populations of others. In neutral models of biodiversity all populations are assumed to change incrementally due to stochastic births and deaths of individuals. Here we propose and model another redistribution mechanism driven by abrupt and severe reduction in size of the population of a single species freeing up resources for the remaining ones. This mechanism may be relevant e.g. for communities of bacteria, with strain-specific collapses caused e.g. by invading bacteriophages, or for other ecosystems where infectious diseases play an important role. The emergent dynamics of our system is characterized by cyclic ''diversity waves'' triggered by collapses of globally dominating populations. The population diversity peaks at the beginning of each wave and exponentially decreases afterwards. Species abundances have bimodal time-aggregated distribution with the lower peak formed by populations of recently collapsed or newly introduced species while the upper peak--species that has not yet collapsed in the current wave. In most waves both upper and lower peaks are composed of several smaller peaks. This self-organized hierarchical peak structure has a long-term memory transmitted across several waves. It gives rise to a scale-free tail of the time-aggregated population distribution with a universal exponent of 1.7. We show that diversity wave dynamics is robust with respect to variations in the rules of our model such as diffusion between multiple environments, species-specific growth and extinction rates, and bet-hedging strategies. PMID:26367172

  11. Three-Dimensional Hydrodynamic Simulations of Collapsing Prolate Clouds

    NASA Astrophysics Data System (ADS)

    Nelson, R. P.; Papaloizou, J. C. B.

    1993-12-01

    We present the results of collapse calculations for elongated clouds performed using the numerical method of smoothed particle hydrodynamics (SPH). The clouds considered are isothermal, prolate spheroids with different axial ratios (a/b). Results are obtained for different values of a/b and mbarL, the mean mass per unit length. It is found that initially uniform clouds undergo fragmentation when the collapse is preferentially down on to the major axis, due to the intrinsic instability of a linear configuration. This occurs when the value of mbarL is sufficiently large. A criterion for elongated clouds to undergo linear collapse is derived using the tensor virial theorem, and it is found that the numerically obtained value of mbarL for which fragmentation occurs corresponds closely to that expected from analytical considerations. The addition of small density perturbations simply results in clouds that fragment more easily, particularly for cases in which a/b is close to unity. Previous calculations, presented by other authors for the case of finite cylinders, show that clouds with cylindrical geometries are highly unstable to the formation of two fragments that occur at the ends of the cylinder. We find that collapsing, prolate spheroids show qualitatively different behaviour, with no preferred tendency to form fragments at the ends of the cloud. Instead fragmentation appears to occur more readily towards the centre of the cloud where the local mass per unit length is greatest. Our implementation of SPH employs spatially variable smoothing lengths, h. In order to obtain a Hamiltonian system, we incorporate terms involving the spatial variability of h in the particle equations of motion, not included in previous implementations. We find that inclusion of these ∇h terms results in much improved energy conservation, but has little effect on the qualitative outcome of the calculations presented here. (fset 'queer "∇")

  12. Atmospheric Heat Redistribution and Collapse on Tidally Locked Rocky Planets

    NASA Astrophysics Data System (ADS)

    Wordsworth, Robin

    2015-06-01

    Atmospheric collapse is likely to be of fundamental importance to tidally locked rocky exoplanets, but it remains understudied. Here, general results on the heat transport and stability of tidally locked terrestrial-type atmospheres are reported. First, the problem is modeled with an idealized three-dimensional (3D) general circulation model (GCM) with gray gas radiative transfer. It is shown that over a wide range of parameters that the atmospheric boundary layer, rather than the large-scale circulation, is the key to understanding the planetary energy balance. Through a scaling analysis of the interhemispheric energy transfer, theoretical expressions for the day-night temperature difference and surface wind speed are created that reproduce the GCM results without tuning. Next, the GCM is used with correlated-k radiative transfer to study heat transport for two real gases ({{CO}}2 and CO). For {{CO}}2, empirical formulae for the collapse pressure as a function of planetary mass and stellar flux are produced, and critical pressures for atmospheric collapse at Earth’s stellar flux are obtained that are around five times higher (0.14 bar) than previous gray gas estimates. These results provide constraints on atmospheric stability that will aid in future interpretations of observations and exoplanet habitability modeling.

  13. Growth, collapse, and self-organized criticality in complex networks

    PubMed Central

    Wang, Yafeng; Fan, Huawei; Lin, Weijie; Lai, Ying-Cheng; Wang, Xingang

    2016-01-01

    Network growth is ubiquitous in nature (e.g., biological networks) and technological systems (e.g., modern infrastructures). To understand how certain dynamical behaviors can or cannot persist as the underlying network grows is a problem of increasing importance in complex dynamical systems as well as sustainability science and engineering. We address the question of whether a complex network of nonlinear oscillators can maintain its synchronization stability as it expands. We find that a large scale avalanche over the entire network can be triggered in the sense that the individual nodal dynamics diverges from the synchronous state in a cascading manner within a relatively short time period. In particular, after an initial stage of linear growth, the network typically evolves into a critical state where the addition of a single new node can cause a group of nodes to lose synchronization, leading to synchronization collapse for the entire network. A statistical analysis reveals that the collapse size is approximately algebraically distributed, indicating the emergence of self-organized criticality. We demonstrate the generality of the phenomenon of synchronization collapse using a variety of complex network models, and uncover the underlying dynamical mechanism through an eigenvector analysis. PMID:27079515

  14. Interplay of Neutrino Opacities in Core-collapse Supernova Simulations

    NASA Astrophysics Data System (ADS)

    Lentz, Eric J.; Mezzacappa, Anthony; Messer, O. E. Bronson; Hix, W. Raphael; Bruenn, Stephen W.

    2012-11-01

    We have conducted a series of numerical experiments using spherically symmetric, general relativistic, neutrino radiation hydrodynamics with the code Agile-BOLTZTRAN to examine the effects of modern neutrino opacities on the development of supernova simulations. We test the effects of opacities by removing opacities or by undoing opacity improvements for individual opacities and groups of opacities. We find that improvements to electron capture (EC) on nuclei, namely EC on an ensemble of nuclei using modern nuclear structure models rather than the simpler independent-particle approximation (IPA) for EC on a mean nucleus, plays the most important role during core collapse of all tested neutrino opacities. Low-energy neutrinos emitted by modern nuclear EC preferentially escape during collapse without the energy downscattering on electrons required to enhance neutrino escape and deleptonization for the models with IPA nuclear EC. During shock breakout the primary influence on the emergent neutrinos arises from non-isoenergetic scattering (NIS) on electrons. For the accretion phase, NIS on free nucleons and pair emission by e + e - annihilation have the largest impact on the neutrino emission and shock evolution. Other opacities evaluated, including nucleon-nucleon bremsstrahlung and especially neutrino-positron scattering, have little measurable impact on neutrino emission or shock dynamics. Modern treatments of nuclear EC, e + e --annihilation pair emission, and NIS on electrons and free nucleons are critical elements of core-collapse simulations of all dimensionality.

  15. Spherically Symmetric Core Collapse Supernova Simulations With Boltzmann Neutrino Transport

    NASA Astrophysics Data System (ADS)

    Messer, O. E. B.

    2001-12-01

    I will describe the results of several spherically symmetric core collapse supernova simulations performed with AGILE-BOLTZTRAN, a state-of-the-art radiation hydrodynamics code incorporating Boltzmann neutrino transport. Collapse simulations comparing two 15 M⊙ progenitor models with significant differences in initial Ye (Woosley & Weaver 1995, Heger et al. 2000) exhibit no differences in Ye at bounce, and, consequently, no difference in homologous core mass and shock formation radius. Fully dynamic simulations of core collapse, rebound, and shock propagation for 15 M⊙ and 20 M⊙ progenitor models of Nomoto & Hashimoto (1988) fail to produce explosions. In both cases, the shock stalls at 200 km, then recedes for several hundred milliseconds. The marked similarities observed in all these simulations highlight the need for both improved progenitor models and the incorporation of improved microphysics in modern supernova codes. Spherically symmetric simulations are, for the immediate future, the only computationally feasible way to investigate the nature of the explosion mechanism while including the requisite level of detailed neutrino transport. They also provide one of the few opportunities to delineate the effects of various feedback mechanisms present in the problem. This research was supported by funds from the Joint Institute for Heavy Ion Research and a DOE PECASE award, and made use of the resources of the National Energy Research Scientific Computing Center, which is supported by the Office of Science of the U.S. Department of Energy under Contract No. DE-AC03-76SF00098.

  16. The reopening of a collapsed fluid-filled elastic tube

    NASA Astrophysics Data System (ADS)

    Juel, Anne; Heap, Alexandra

    We present an experimental study of the reopening mechanics of a collapsed liquid-filled elastic tube. The experiment is a simple mechanical model of pulmonary airway reopening and aims to assess the robustness of existing theoretical models. A metre-long horizontal elastic tube of inner radius R_i {=} 4.88 ± 0.14mm is filled with silicone oil and is carefully collapsed mechanically. The injection of nitrogen at a constant flow rate results in the steady propagation of an air finger, after the decay of initial transients. This behaviour is observed over the realizable range of the capillary numbers Ca, which measures the ratio of viscous and capillary forces. With increasing Ca, the transition region between the collapsed and reopened sections of the tube shortens, and the height of the tube behind the bubble tip increases. We also find that air fingers can propagate in partially reopened tubes, in which the transmural pressure is negative far behind the finger tip.

  17. The collapse of white dwarfs to neutron stars

    NASA Technical Reports Server (NTRS)

    Woosley, S. E.; Baron, E.

    1992-01-01

    The observable consequences of an accreting white dwarf collapsing directly to a neutron star are considered. The outcome depends critically upon the nature of the wind that is driven by neutrino absorption in the surface layers as the dwarf collapses. Unlike previous calculations which either ignored mass loss or employed inadequate zoning to resolve it, a characteristic mass-loss rate of about 0.005 solar mass/s and an energy input of 5 x 10 exp 50 ergs/s is found. Such a large mass-loss rate almost completely obscures any prompt electromagnetic display and certainly rules out the production by this model of gamma-ray bursts situated at cosmological distances. The occurrence of such collapses with the Milky Way Galaxy might, however, be detected and limited by their nucleosynthesis and gamma-ray line emission. To avoid the overproduction of rare neutron-rich isotopes heavier than iron, such events must be very infrequent, probably happening no more than once every thousand years.

  18. Growth, collapse, and self-organized criticality in complex networks

    NASA Astrophysics Data System (ADS)

    Wang, Yafeng; Fan, Huawei; Lin, Weijie; Lai, Ying-Cheng; Wang, Xingang

    2016-04-01

    Network growth is ubiquitous in nature (e.g., biological networks) and technological systems (e.g., modern infrastructures). To understand how certain dynamical behaviors can or cannot persist as the underlying network grows is a problem of increasing importance in complex dynamical systems as well as sustainability science and engineering. We address the question of whether a complex network of nonlinear oscillators can maintain its synchronization stability as it expands. We find that a large scale avalanche over the entire network can be triggered in the sense that the individual nodal dynamics diverges from the synchronous state in a cascading manner within a relatively short time period. In particular, after an initial stage of linear growth, the network typically evolves into a critical state where the addition of a single new node can cause a group of nodes to lose synchronization, leading to synchronization collapse for the entire network. A statistical analysis reveals that the collapse size is approximately algebraically distributed, indicating the emergence of self-organized criticality. We demonstrate the generality of the phenomenon of synchronization collapse using a variety of complex network models, and uncover the underlying dynamical mechanism through an eigenvector analysis.

  19. Quasiparticle collapsing in an anisotropic t -J ladder

    NASA Astrophysics Data System (ADS)

    Zhu, Zheng; Weng, Zheng-Yu

    2015-12-01

    Quasiparticle collapsing is a central issue in the study of strongly correlated electron systems. In the one-dimensional case, the quasiparticle collapsing in a form of spin-charge separation has been well established, but the problem remains elusive in dimensions higher than one. By using the density matrix renormalization group (DMRG) algorithm, we show that in an anisotropic two-leg t -J ladder, an injected single hole behaves like a well-defined quasiparticle in the strong rung limit but undergoes a "phase transition" with the effective mass diverging at a quantum critical point (QCP) towards the isotropic limit. After the transition, the quasiparticle collapses into a loosely bound object of a charge (holon) and a spin-1/2 (spinon) accompanied by an unscreened phase string as well as a substantially enhanced binding energy between two doped holes. A phase diagram of multileg ladders is further obtained, which extrapolates the QCP towards the two-dimensional limit. The underlying mechanism generic for any dimensions is also discussed.

  20. Relativistic structure, stability, and gravitational collapse of charged neutron stars

    SciTech Connect

    Ghezzi, Cristian R.

    2005-11-15

    Charged stars have the potential of becoming charged black holes or even naked singularities. We present a set of numerical solutions of the Tolman-Oppenheimer-Volkov equations that represents spherical charged compact stars in hydrostatic equilibrium. The stellar models obtained are evolved forward in time integrating the Einstein-Maxwell field equations. We assume an equation of state of a neutron gas at zero temperature. The charge distribution is taken as being proportional to the rest mass density distribution. The set of solutions present an unstable branch, even with charge-to-mass ratios arbitrarily close to the extremum case. We perform a direct check of the stability of the solutions under strong perturbations and for different values of the charge-to-mass ratio. The stars that are in the stable branch oscillate and do not collapse, while models in the unstable branch collapse directly to form black holes. Stars with a charge greater than or equal to the extreme value explode. When a charged star is suddenly discharged, it does not necessarily collapse to form a black hole. A nonlinear effect that gives rise to the formation of a shell of matter (in supermassive stars), is negligible in the present simulations. The results are in agreement with the third law of black hole thermodynamics and with the cosmic censorship conjecture.