WorldWideScience

Sample records for transition critical bubbles

  1. Critical bubbles and fluctuations at the electroweak phase transition

    CERN Document Server

    Kripfganz, J; Schmidt, M G

    1995-01-01

    We discuss the critical bubbles of the electroweak phase transition using an effective high-temperature 3-dimensional action for the Higgs field \\varphi. The separate integration of gauge and Goldstone boson degrees of freedom is conveniently described in the 't Hooft-Feynman covariant background gauge. The effective dimensionless gauge coupling g_3(T)^2 in the broken phase is well behaved throughout the phase transition. However, the behavior of the one-loop Z(\\varphi) factors of the Higgs and gauge kinetic terms signalizes the breakdown of the derivative expansion and of the perturbative expansion for a range of small \\varphi values increasing with the Higgs mass m_H. Taking a functional S_z[\\varphi] with constant Z(\\varphi)=z instead of the full non-local effective action in some neighborhood of the saddlepoint we are calculating the critical bubbles for several temperatures. The fluctuation determinant is calculated to high accuracy using a variant of the heat kernel method. It gives a strong suppression ...

  2. Critical scattering by bubbles

    International Nuclear Information System (INIS)

    Fiedler-Ferrari, N.; Nussenzveig, H.M.

    1986-11-01

    We apply the complex angular momentum theory to the problem of the critical scattering of light by spherical cavities in the high frequency limit (permittivity greater than the external media) (e.g, air bubble in water) (M.W.O.) [pt

  3. The transition from gas bubble to void growth

    International Nuclear Information System (INIS)

    Hayns, M.R.

    1977-05-01

    A natural feature of the rate theory of void swelling is that it completely describes the growth of a cavity from a gas bubble through a transition growth region to a void in the presence of an evolving microstructure. This transition from a gas bubble to void growth is expressed in terms of a critical radius and it is shown that this is a very useful tool for interpreting the early life kinetics of void growth. As an example the initial helium gas bubble population expected in pre-injected samples of 316 stainless steel used in simulation void swelling experiments has been calculated using a sophisticated bubble nucleation and growth model. Applying the critical radius arguments to these calculated bubble size distributions a consistent and simple interpretation of the observed void concentrations in subsequent irradiations is obtained. The implications following from these arguments for the interpretation of the neutron irradiated steels are discussed. (author)

  4. Rational speculative bubbles: A critical view

    Directory of Open Access Journals (Sweden)

    Radonjić Ognjen

    2007-01-01

    Full Text Available According to the theory of rational bubbles, the bubble is present whenever asset prices progressively diverge from their fundamental value, which occurs because agents expect that asset prices will continue to grow exponentially (self-fulfilling prophecies far in the future and consistently, which promises the realization of ever larger capital gains. In our opinion, the basic shortcoming of this theory refers to the assumption that all market agents are perfectly informed and rational and, accordingly, form homogeneous expectations. The model does not explain decision-making processes or expectation formation, nor does it detect potential psychological and institutional factors that might significantly influence decision making processes and market participants’ reactions to news. Since assumptions of the model critically determine its validity, we conclude that comprehensiveness of the rational bubble model is, to put it mildly, limited.

  5. Topology changing transitions in bubbling geometries

    International Nuclear Information System (INIS)

    Horava, Petr; Shepard, Peter G.

    2005-01-01

    Topological transitions in bubbling half-BPS Type IIB geometries with SO(4) x SO(4) symmetry can be decomposed into a sequence of n elementary transitions. The half-BPS solution that describes the elementary transition is seeded by a phase space distribution of fermions filling two diagonal quadrants. We study the geometry of this solution in some detail. We show that this solution can be interpreted as a time dependent geometry, interpolating between two asymptotic pp-waves in the far past and the far future. The singular solution at the transition can be resolved in two different ways, related by the particle-hole duality in the effective fermion description. Some universal features of the topology change are governed by two-dimensional Type 0B string theory, whose double scaling limit corresponds to the Penrose limit of AdS 5 x S 5 at topological transition. In addition, we present the full class of geometries describing the vicinity of the most general localized classical singularity that can occur in this class of half-BPS bubbling geometries. (author)

  6. New mechanism for bubble nucleation: Classical transitions

    International Nuclear Information System (INIS)

    Easther, Richard; Giblin, John T. Jr; Hui Lam; Lim, Eugene A.

    2009-01-01

    Given a scalar field with metastable minima, bubbles nucleate quantum mechanically. When bubbles collide, energy stored in the bubble walls is converted into kinetic energy of the field. This kinetic energy can facilitate the classical nucleation of new bubbles in minima that lie below those of the 'parent' bubbles. This process is efficient and classical, and changes the dynamics and statistics of bubble formation in models with multiple vacua, relative to that derived from quantum tunneling.

  7. CosmoTransitions: Computing cosmological phase transition temperatures and bubble profiles with multiple fields

    Science.gov (United States)

    Wainwright, Carroll L.

    2012-09-01

    I present a numerical package (CosmoTransitions) for analyzing finite-temperature cosmological phase transitions driven by single or multiple scalar fields. The package analyzes the different vacua of a theory to determine their critical temperatures (where the vacuum energy levels are degenerate), their supercooling temperatures, and the bubble wall profiles which separate the phases and describe their tunneling dynamics. I introduce a new method of path deformation to find the profiles of both thin- and thick-walled bubbles. CosmoTransitions is freely available for public use.Program summaryProgram Title: CosmoTransitionsCatalogue identifier: AEML_v1_0Program summary URL: http://cpc.cs.qub.ac.uk/summaries/AEML_v1_0.htmlProgram obtainable from: CPC Program Library, Queen's University, Belfast, N. IrelandLicensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.htmlNo. of lines in distributed program, including test data, etc.: 8775No. of bytes in distributed program, including test data, etc.: 621096Distribution format: tar.gzProgramming language: Python.Computer: Developed on a 2009 MacBook Pro. No computer-specific optimization was performed.Operating system: Designed and tested on Mac OS X 10.6.8. Compatible with any OS with Python installed.RAM: Approximately 50 MB, mostly for loading plotting packages.Classification: 1.9, 11.1.External routines: SciPy, NumPy, matplotLibNature of problem: I describe a program to analyze early-Universe finite-temperature phase transitions with multiple scalar fields. The goal is to analyze the phase structure of an input theory, determine the amount of supercooling at each phase transition, and find the bubble-wall profiles of the nucleated bubbles that drive the transitions.Solution method: To find the bubble-wall profile, the program assumes that tunneling happens along a fixed path in field space. This reduces the equations of motion to one dimension, which can then be solved using the overshoot

  8. THE VISCOUS TO BRITTLE TRANSITION IN CRYSTAL- AND BUBBLE-BEARING MAGMAS

    Directory of Open Access Journals (Sweden)

    Mattia ePistone

    2015-11-01

    Full Text Available The transition from viscous to brittle behaviour in magmas plays a decisive role in determining the style of volcanic eruptions. While this transition has been determined for one- or two-phase systems, it remains poorly constrained for natural magmas containing silicic melt, crystals, and gas bubbles. Here we present new experimental results on shear-induced fracturing of three-phase magmas obtained at high-temperature (673-1023 K and high-pressure (200 MPa conditions over a wide range of strain-rates (5·10-6 s-1 to 4·10-3 s-1. During the experiments bubbles are deformed (i.e. capillary number are in excess of 1 enough to coalesce and generate a porous network that potentially leads to outgassing. A physical relationship is proposed that quantifies the critical stress required for magmas to fail as a function of both crystal (0.24 to 0.65 and bubble volume fractions (0.09 to 0.12. The presented results demonstrate efficient outgassing for low crystal fraction ( 0.44 promote gas bubble entrapment and inhibit outgassing. The failure of bubble-free, crystal-bearing systems is enhanced by the presence of bubbles that lower the critical failure stress in a regime of efficient outgassing, while the failure stress is increased if bubbles remain trapped within the crystal framework. These contrasting behaviours have direct impact on the style of volcanic eruptions. During magma ascent, efficient outgassing reduces the potential for an explosive eruption and favours brittle behaviour, contributing to maintain low overpressures in an active volcanic system resulting in effusion or rheological flow blockage of magma at depth. Conversely, magmas with high crystallinity experience limited loss of exsolved gas, permitting the achievement of larger overpressures prior to a potential sudden transition to brittle behaviour, which could result in an explosive volcanic eruption.

  9. Bubble nucleation and growth in slow cosmological phase transitions

    Science.gov (United States)

    Mégevand, Ariel; Ramírez, Santiago

    2018-03-01

    We study the dynamics of cosmological phase transitions in the case of small velocities of bubble walls, vw development of the phase transition. We consider different kinds of approximations and refinements for relevant aspects of the dynamics, such as the dependence of the wall velocity on hydrodynamics, the distribution of the latent heat, and the variation of the nucleation rate. Although in this case the common simplifications of a constant wall velocity and an exponential nucleation rate break down due to reheating, we show that a delta-function rate and a velocity which depends linearly on the temperature give a good description of the dynamics and allow to solve the evolution analytically. We also consider a Gaussian nucleation rate, which gives a more precise result for the bubble size distribution. We discuss the implications for the computation of cosmic remnants.

  10. Satellite formation during bubble transition through an interface between immiscible liquids

    KAUST Repository

    Li, Erqiang

    2014-03-12

    When a bubble rises to an interface between two immiscible liquids, it can pass through the interface, if this is energetically favourable, i.e. The bubble preferring the side of the interface with the lower air-liquid surface tension. Once the intermediate film between the bubble and the interface has drained sufficiently, the bubble makes contact with the interface, forming a triple-line and producing strong capillary waves which travel around the bubble and can pinch off a satellite on the opposite side, akin to the dynamics in the coalescence cascade. We identify the critical Ohnesorge numbers where such satellites are produced and characterize their sizes. The total transition time scales with the bubble size and differential surface tension, while the satellite pinch-off time scales with the capillary-inertial time of the pool liquid, which originally surrounds the bubble. We also use high-speed video imaging to study the motion of the neck of the contact. For low viscosity we show that it grows in time with a power-law exponent between 0.44 and 0.50, with a prefactor modified by the net sum of the three interfacial tensions. Increasing the viscosity of the receiving liquid drop drastically slows down the motion of the triple-line, when the Ohnesorge number exceeds ${\\\\sim }$0.08. This differs qualitatively from the coalescence of two miscible drops of different viscosities, where the lower viscosity sets the coalescence speed. We thereby propose a strong resistance from the triple-line. © 2014 Cambridge University Press.

  11. Bubbles

    DEFF Research Database (Denmark)

    Dholakia, Nikhilesh; Turcan, Romeo V.

    2013-01-01

    A goal of our ongoing research stream is to develop a multidisciplinary metatheory of bubbles. In this viewpoint paper we put forward a typology of bubbles by comparing four types of assets – entertainment, commodities, financial securities (stocks), and housing properties – where bubbles could a...

  12. The bubble to jetting transition mechanism of plasmas in NaNO3 solutions sustained by pulsed power

    International Nuclear Information System (INIS)

    Hsieh, An-hsuan; Chang, Hung-wen; Hsu, Cheng-che

    2012-01-01

    Plasmas in NaNO 3 solutions sustained by pulsed power with T on = 10-500 µs are studied. With an applied voltage equal to or lower than 100 V, the bubble mode is observed. In this mode, bubbles, a few hundred μm in diameter, are formed and detached continuously at the electrode surface because of the buoyant force. An increase in the applied voltage to 125 V results in a bubble to jetting transition. When this transition occurs, bubbles with diameters smaller than 100 µm are formed and are rapidly jetted away continuously. The examination of various conditions shows that the transition occurs when the power and energy input simultaneously exceed critical values 4.4 × 10 -3 ± 6 × 10 -4 J and 45 ± 5 W, respectively, within T on . Given the electrode surface area, this critical power is equivalent to a heat flux of 229 ± 25 MW m -2 , which is close to the heat flux required, 223 MW m -2 , for the occurrence of explosive vaporization reported in the literature. Such an observation strongly supports the hypothesis that the bubble to jetting transition is induced by the electrothermal effect.

  13. Mode transition in bubbly Taylor-Couette flow measured by PTV

    International Nuclear Information System (INIS)

    Yoshida, K; Tasaka, Y; Murai, Y; Takeda, T

    2009-01-01

    The drag acting to the inner cylinder in Taylor-Couette flow system can be reduced by bubble injection. In this research, relationship between drag reduction and change of vortical structure in a Taylor-Couette flow is investigated by Particle Tracking Velocimetry (PTV). The velocity vector field in the r-z cross section and the bubble concentration in the front view (z-θ plane) are measured. This paper describes the change of vortical structures with bubbles, and the mode transition that is sensitively affected by the bubbles is discussed. The bubbles accumulate in the three parts relative to vortex position by the interaction between bubbles and vortices. The status of bubble's distribution is different depending on position. This difference affects mode transition as its trigger significantly. The presence of bubbles affects the transition from toroidal mode to spiral mode but does not induce the transition from spiral mode to toroidal mode. Further we found that Taylor vortex bifurcates and a pair of vortices coalesces when the flow switches between spiral mode and toroidal mode.

  14. Phase transitions and critical phenomena

    CERN Document Server

    Domb, Cyril

    2001-01-01

    The field of phase transitions and critical phenomena continues to be active in research, producing a steady stream of interesting and fruitful results. It has moved into a central place in condensed matter studies.Statistical physics, and more specifically, the theory of transitions between states of matter, more or less defines what we know about 'everyday' matter and its transformations.The major aim of this serial is to provide review articles that can serve as standard references for research workers in the field, and for graduate students and others wishing to obtain reliable in

  15. Bubble nucleation in first-order inflation and other cosmological phase transitions

    International Nuclear Information System (INIS)

    Turner, M.S.; Weinberg, E.J.; Widrow, L.M.

    1992-01-01

    We address in some detail the kinematics of bubble nucleation and percolation in first-order cosmological phase transitions, with the primary focus on first-order inflation. We study how a first-order phase transition completes, describe measures of its progress, and compute the distribution of bubble sizes. For example, we find that the typical bubble size in a successful transition is of order 1% to 100% of the Hubble radius, and depends very weakly on the energy scale of the transition. We derive very general conditions that must be satisfied by Γ/H 4 to complete the phase transition (Γ=bubble nucleation rate per unit volume; H=expansion rate; physically, Γ/H 4 corresponds to the volume fraction of space occupied by bubbles nucleated over a Hubble time). In particular, Γ/H 4 must exceed 9/4π to successfully end inflation. To avoid the deleterious effects of bubbles nucleated early during inflation on primordial nucleosynthesis and on the isotropy and spectrum of the cosmic microwave background radiation, during most of inflation Γ/H 4 must be less than order 10 -4 --10 -3 . Our constraints imply that in a successful model of first-order inflation the phase transition must complete over a period of at most a few Hubble times and all but preclude individual bubbles from providing an interesting source of density perturbation. We note, though, that it is just possible for Poisson fluctuations in the number of moderately large-size bubbles to lead to interesting isocurvature perturbations, whose spectrum is not scale invariant. Finally, we analyze in detail several recently proposed models of first-order inflation

  16. Novel gas holdup and regime transition correlation for two-phase bubble columns

    Science.gov (United States)

    Besagni, G.; Inzoli, F.

    2017-11-01

    The gas holdup is dimensionless parameter of fundamental and practical importance in the operation, design and scale-up of bubble columns. Unfortunately, the many relationships between the bubble column fluid dynamic parameters and the various variables characterizing the system make it difficult to find general correlations for the precise estimation of the gas holdup. Wilkinson et al. (1992), in their pioneering paper, proposed a correlation to predict the gas holdup in industrial-scale bubble columns, based on the physical properties of the phases and the operating conditions. However, this correlation lacks in generality, as it does not take in account the bubble column design. In this paper, we propose a generalization of the Wilkinson et al. (1992) gas holdup correlation to take into also the bubble column design parameters. Starting from considerations concerning the flow regime transition, corrective parameters are included to account for the effects introduced by the gas sparger openings, the bubble column aspect ratio and the bubble column diameter. The proposed correlation has been found to predict fairly well previously published gas holdup and flow regime transition data.

  17. Phase transitions and critical phenomena

    CERN Document Server

    Domb, Cyril

    2000-01-01

    The field of phase transitions and critical phenomena continues to be active in research, producing a steady stream of interesting and fruitful results. No longer an area of specialist interest, it has acquired a central focus in condensed matter studies. The major aim of this serial is to provide review articles that can serve as standard references for research workers in the field, and for graduate students and others wishing to obtain reliable information on important recent developments.The two review articles in this volume complement each other in a remarkable way. Both deal with what m

  18. Optical characterization of bubbly flows with a near-critical-angle scattering technique

    Energy Technology Data Exchange (ETDEWEB)

    Onofri, Fabrice R.A.; Krzysiek, Mariusz [IUSTI, UMR, CNRS, University of Provence, Polytech' DME, Technopole Chateau-Gombert, Marseille (France); Mroczka, Janusz [CEPM, Technical University of Wroclaw, Wroclaw (Poland); Ren, Kuan-Fang [CORIA, UMR, CNRS, University of Rouen, Saint-Etienne-du-Rouvray (France); Radev, Stefan [IMECH, Bulgarian Academy of Sciences, Sofia (Bulgaria); Bonnet, Jean-Philippe [M2P2, UMR, CNRS, University Paul Cezanne, Aix-en-Provence (France)

    2009-10-15

    The newly developed critical angle refractometry and sizing technique (CARS) allows simultaneous and instantaneous characterization of the local size distribution and the relative refractive index (i.e. composition) of a cloud of bubbles. The paper presents the recent improvement of this technique by comparison of different light scattering models and inversion procedures. Experimental results carried in various air/water and air/water-ethanol bubbly flows clearly demonstrate the efficiency and the potential of this technique. (orig.)

  19. Gravitational wave generation from bubble collisions in first-order phase transitions: an analytic approach

    CERN Document Server

    Caprini, Chiara; Servant, Géraldine

    2008-01-01

    Gravitational wave production from bubble collisions was calculated in the early nineties using numerical simulations. In this paper, we present an alternative analytic estimate, relying on a different treatment of stochasticity. In our approach, we provide a model for the bubble velocity power spectrum, suitable for both detonations and deflagrations. From this, we derive the anisotropic stress and analytically solve the gravitational wave equation. We provide analytical formulae for the peak frequency and the shape of the spectrum which we compare with numerical estimates. In contrast to the previous analysis, we do not work in the envelope approximation. This paper focuses on a particular source of gravitational waves from phase transitions. In a companion article, we will add together the different sources of gravitational wave signals from phase transitions: bubble collisions, turbulence and magnetic fields and discuss the prospects for probing the electroweak phase transition at LISA.

  20. Homogeneous-Heterogeneous Regime Transition in Bubble Columuns

    Czech Academy of Sciences Publication Activity Database

    Růžička, Marek; Zahradník, Jindřich; Drahoš, Jiří; Thomas, N. H.

    2001-01-01

    Roč. 56, č. 15 (2001), s. 4609-4626 ISSN 0009-2509 R&D Projects: GA ČR GA104/98/1435 Grant - others:INCO-COPERNICUS(XE) ERB IC15-CT98-0904 Institutional research plan: CEZ:AV0Z4072921 Keywords : bubble column * flow regime * stability Subject RIV: CI - Industrial Chemistry, Chemical Engineering Impact factor: 1.547, year: 2001

  1. Clarifications to questions and criticisms on the Johansen-Ledoit-Sornette financial bubble model

    Science.gov (United States)

    Sornette, Didier; Woodard, Ryan; Yan, Wanfeng; Zhou, Wei-Xing

    2013-10-01

    The Johansen-Ledoit-Sornette (JLS) model of rational expectation bubbles with finite-time singular crash hazard rates has been developed to describe the dynamics of financial bubbles and crashes. It has been applied successfully to a large variety of financial bubbles in many different markets. Having been developed over a decade ago, the JLS model has been studied, analyzed, used and criticized by several researchers. Much of this discussion is helpful for advancing the research. However, several serious misconceptions seem to be present within this literature both on theoretical and empirical aspects. Several of these problems stem from the fast evolution of the literature on the JLS model and related works. In the hope of removing possible misunderstanding and of catalyzing useful future developments, we summarize these common questions and criticisms concerning the JLS model and synthesize the current state of the art and existing best practice.

  2. The Critical Moment of Transition

    DEFF Research Database (Denmark)

    Svalgaard, Lotte

    2018-01-01

    By providing a holding environment to acknowledge sensitivities and address emotions, leadership programmes prove to be powerful spaces for increasing self- and social awareness. However, the challenge is for one to maintain the newly gained self- and social awareness after leaving the holding...... – within the context of an international MBA program – of MBA students applying their knowledge from a Leadership Stream in an International Consultancy Project. This paper contributes to the theory and practice of management learning by providing lenses to understand subjective experiences of critical...

  3. Gravitational waves from first-order phase transitions: towards model separation by bubble nucleation rate

    Science.gov (United States)

    Jinno, Ryusuke; Lee, Sangjun; Seong, Hyeonseok; Takimoto, Masahiro

    2017-11-01

    We study gravitational-wave production from bubble collisions in a cosmic first-order phase transition, focusing on the possibility of model separation by the bubble nucleation rate dependence of the resulting gravitational-wave spectrum. By using the method of relating the spectrum with the two-point correlator of the energy-momentum tensor , we first write down analytic expressions for the spectrum with a Gaussian correction to the commonly used nucleation rate, Γ propto eβ tarrow eβ t-γ2t2, under the thin-wall and envelope approximations. Then we quantitatively investigate how the spectrum changes with the size of the Gaussian correction. It is found that the spectral shape shows Script O(10)% deviation from Γ propto eβ t case for some physically motivated scenarios. We also briefly discuss detector sensitivities required to distinguish different spectral shapes.

  4. Critical Transition in Critical Zone of Intensively Managed Landscapes

    Science.gov (United States)

    Kumar, P.

    2017-12-01

    Intensification of industrial agriculture has resulted in severe unintended global impacts, including degradation of arable land and eutrophication of receiving water bodies. Modern agricultural practices rely on significant direct and indirect human energy inputs, which have created imbalances between increased rates of biogeochemical processes related to production and background rates of natural processes. These imbalances have cascaded through the deep inter-dependencies between carbon, soil, water, nutrient and ecological processes, resulting in a critical transition of the Critical Zone and creating emergent dynamics and evolutionary trajectories. Understanding of these novel organization and function of the Critical Zone is vital for developing sustainable agricultural practices.

  5. Effects of free-stream turbulence intensity on transition in a laminar separation bubble formed over an airfoil

    Science.gov (United States)

    Istvan, Mark S.; Yarusevych, Serhiy

    2018-03-01

    The laminar-to-turbulent transition process in a laminar separation bubble formed over a NACA 0018 airfoil is investigated experimentally. All experiments are performed for an angle of attack of 4°, chord Reynolds numbers of 80,000 and 125,000, and free-stream turbulence intensities between 0.06 and 1.99%. The results show that increasing the level of free-stream turbulence intensity leads to a decrease in separation bubble length, attributed to a downstream shift in mean separation and an upstream shift in mean reattachment, the later ascribed to an upstream shift in mean transition. Maximum spatial amplification rates of disturbances in the separated shear layer decrease with increasing free-stream turbulence intensity, implying that the larger initial amplitudes of disturbances are solely responsible for the upstream shift in mean transition and as a result mean reattachment. At the baseline level of turbulence intensity, coherent structures forming in the aft portion of the bubble are characterized by strong spanwise coherence at formation, and undergo spanwise deformations leading to localized breakup in the vicinity of mean reattachment. As the level of free-stream turbulence intensity is increased, the spanwise coherence of the shear layer rollers is reduced, and spanwise undulations in the vortex filaments start to take place at the mean location of roll-up. At the highest level of turbulence intensity investigated, streamwise streaks originating in the boundary layer upstream of the separation bubble are observed within the bubble. These streaks signify an onset of bypass transition upstream of the separation bubble, which gives rise to a highly three-dimensional shear layer roll-up. A quantitative analysis of the associated changes in salient characteristics of the coherent structures is presented, connecting the effect of elevated free-stream turbulence intensity on the time-averaged and dynamic characteristics of the separation bubble.

  6. Reduction of Gas Bubbles and Improved Critical Current Density in Bi-2212 Round Wire by Swaging

    CERN Document Server

    Jiang, J; Huang, Y; Hong, S; Parrell, J; Scheuerlein, C; Di Michiel, M; Ghosh, A; Trociewitz, U; Hellstrom, E; Larbalestier, D

    2013-01-01

    Bi-2212 round wire is made by the powder-in-tube technique. An unavoidable property of powder-in-tube conductors is that there is about 30% void space in the as-drawn wire. We have recently shown that the gas present in the as-drawn Bi-2212 wire agglomerates into large bubbles and that they are presently the most deleterious current limiting mechanism. By densifying short 2212 wires before reaction through cold isostatic pressing (CIPping), the void space was almost removed and the gas bubble density was reduced significantly, resulting in a doubled engineering critical current density (JE) of 810 A/mm2 at 5 T, 4.2 K. Here we report on densifying Bi-2212 wire by swaging, which increased JE (4.2 K, 5 T) from 486 A/mm2 for as-drawn wire to 808 A/mm2 for swaged wire. This result further confirms that enhancing the filament packing density is of great importance for making major JE improvement in this round-wire magnet conductor.

  7. Electrochemistry of single nanobubbles. Estimating the critical size of bubble-forming nuclei for gas-evolving electrode reactions.

    Science.gov (United States)

    German, Sean R; Edwards, Martin A; Chen, Qianjin; Liu, Yuwen; Luo, Long; White, Henry S

    2016-12-12

    In this article, we address the fundamental question: "What is the critical size of a single cluster of gas molecules that grows and becomes a stable (or continuously growing) gas bubble during gas evolving reactions?" Electrochemical reactions that produce dissolved gas molecules are ubiquitous in electrochemical technologies, e.g., water electrolysis, photoelectrochemistry, chlorine production, corrosion, and often lead to the formation of gaseous bubbles. Herein, we demonstrate that electrochemical measurements of the dissolved gas concentration, at the instant prior to nucleation of an individual nanobubble of H 2 , N 2 , or O 2 at a Pt nanodisk electrode, can be analyzed using classical thermodynamic relationships (Henry's law and the Young-Laplace equation - including non-ideal corrections) to provide an estimate of the size of the gas bubble nucleus that grows into a stable bubble. We further demonstrate that this critical nucleus size is independent of the radius of the Pt nanodisk employed (gas. For example, the measured critical surface concentration of H 2 of ∼0.23 M at the instant of bubble formation corresponds to a critical H 2 nucleus that has a radius of ∼3.6 nm, an internal pressure of ∼350 atm, and contains ∼1700 H 2 molecules. The data are consistent with stochastic fluctuations in the density of dissolved gas, at or near the Pt/solution interface, controlling the rate of bubble nucleation. We discuss the growth of the nucleus as a diffusion-limited process and how that process is affected by proximity to an electrode producing ∼10 11 gas molecules per second. Our study demonstrates the advantages of studying a single-entity, i.e., an individual nanobubble, in understanding and quantifying complex physicochemical phenomena.

  8. Empirical Investigation of Critical Transitions in Paleoclimate

    Science.gov (United States)

    Loskutov, E. M.; Mukhin, D.; Gavrilov, A.; Feigin, A.

    2016-12-01

    In this work we apply a new empirical method for the analysis of complex spatially distributed systems to the analysis of paleoclimate data. The method consists of two general parts: (i) revealing the optimal phase-space variables and (ii) construction the empirical prognostic model by observed time series. The method of phase space variables construction based on the data decomposition into nonlinear dynamical modes which was successfully applied to global SST field and allowed clearly separate time scales and reveal climate shift in the observed data interval [1]. The second part, the Bayesian approach to optimal evolution operator reconstruction by time series is based on representation of evolution operator in the form of nonlinear stochastic function represented by artificial neural networks [2,3]. In this work we are focused on the investigation of critical transitions - the abrupt changes in climate dynamics - in match longer time scale process. It is well known that there were number of critical transitions on different time scales in the past. In this work, we demonstrate the first results of applying our empirical methods to analysis of paleoclimate variability. In particular, we discuss the possibility of detecting, identifying and prediction such critical transitions by means of nonlinear empirical modeling using the paleoclimate record time series. The study is supported by Government of Russian Federation (agreement #14.Z50.31.0033 with the Institute of Applied Physics of RAS). 1. Mukhin, D., Gavrilov, A., Feigin, A., Loskutov, E., & Kurths, J. (2015). Principal nonlinear dynamical modes of climate variability. Scientific Reports, 5, 15510. http://doi.org/10.1038/srep155102. Ya. I. Molkov, D. N. Mukhin, E. M. Loskutov, A.M. Feigin, (2012) : Random dynamical models from time series. Phys. Rev. E, Vol. 85, n.3.3. Mukhin, D., Kondrashov, D., Loskutov, E., Gavrilov, A., Feigin, A., & Ghil, M. (2015). Predicting Critical Transitions in ENSO models. Part II

  9. A dry-spot model for the prediction of critical heat flux in water boiling in bubbly flow regime

    International Nuclear Information System (INIS)

    Ha, Sang Jun; No, Hee Cheon

    1997-01-01

    This paper presents a prediction of critical heat flux (CHF) in bubbly flow regime using dry-spot model proposed recently by authors for pool and flow boiling CHF and existing correlations for forced convective heat transfer coefficient, active site density and bubble departure diameter in nucleate boiling region. Without any empirical constants always present in earlier models, comparisons of the model predictions with experimental data for upward flow of water in vertical, uniformly-heated round tubes are performed and show a good agreement. The parametric trends of CHF have been explored with respect to variation in pressure, tube diameter and length, mass flux and inlet subcooling

  10. Modelling and critical analysis of bubbly flows of dilute nanofluids in a vertical tube

    Energy Technology Data Exchange (ETDEWEB)

    Li, Xiangdong; Yuan, Yang [School of Aerospace, Mechanical and Manufacturing Engineering, RMIT University, PO Box 71, Bundoora, VIC 3083 (Australia); Tu, Jiyuan, E-mail: jiyuan.tu@rmit.edu.au [School of Aerospace, Mechanical and Manufacturing Engineering, RMIT University, PO Box 71, Bundoora, VIC 3083 (Australia); Key Laboratory of Ministry of Education for Advanced Reactor Engineering and Safety, Institute of Nuclear and New Energy Technology, Tsinghua University, PO Box 1021, Beijing 100086 (China)

    2016-04-15

    Highlights: • The classic two-fluid model needs improvement for nanofluid bubbly flows. • The nanoparticle self-assembly changes the interfacial behaviours of bubbles. • Key job is to reformulate the interfacial transfer terms. - Abstract: The bubbly flows of air–nanofluid and air–water in a vertical tube were numerically simulated using the two-fluid model. Comparison of the numerical results against the experimental data of Park and Chang (2011) demonstrated that the classic two-fluid model, although agreed well with the air–water data, was not applicable to the air–nanofluid bubbly flow. It was suggested that in a bubbly flow system, the existence of interfaces allows the spontaneous formation of a thin layer of nanoparticle assembly at the interfaces, which significantly changes the interfacial behaviours of the air bubbles and the roles of the interfacial forces. As the conservation equations of the classic two-fluid model are still applicable to nanofluids, the mechanisms underlying the modified interfacial behaviours need to be carefully taken into account when modelling air–nanofluid bubbly flows. Thus, one of the key tasks when modelling bubbly flows of air–nanofluid using the two-fluid model is to reformulate the interfacial transfer terms according to the interfacial behaviour modifications induced by nanoparticles.

  11. Critical Transitions in Social Network Activity

    DEFF Research Database (Denmark)

    Kuehn, Christian; Martens, Erik Andreas; Romero, Daniel M

    2014-01-01

    a priori known events are preceded by variance and autocorrelation growth. Our findings thus clearly establish the necessary starting point to further investigate the relationship between abstract mathematical theory and various classes of critical transitions in social networks....... for a priori unknown events in society are present in social networks is an exciting open problem, to which at present only highly speculative answers can be given. Here, we instead provide a first step towards tackling a simpler question by focusing on a priori known events and analyse a social media data set...... with a focus on classical variance and autocorrelation warning signs. Our results thus pertain to one absolutely fundamental question: Can the stochastic warning signs known from other areas also be detected in large-scale social media data? We answer this question affirmatively as we find that several...

  12. Toward a molecular theory of homogeneous bubble nucleation: II. Calculation of the number density of critical nuclei and the rate of nucleation.

    Science.gov (United States)

    Torabi, Korosh; Corti, David S

    2013-10-17

    In the present paper, we develop a method to calculate the rate of homogeneous bubble nucleation within a superheated L-J liquid based on the (n,v) equilibrium embryo free energy surface introduced in the first paper (DOI: 10.1021/jp404149n). We express the nucleation rate as the product of the concentration of critical nuclei within the metastable liquid phase and the relevant forward rate coefficient. We calculate the forward rate coefficient of the critical nuclei from their average lifetime as determined from MD simulations of a large number of embryo trajectories initiated from the transitional region of the metastable liquid configuration space. Therefore, the proposed rate coefficient does not rely on any predefined reaction coordinate. In our model, the critical nuclei belong to the region of the configuration space where the committor probability is about one-half, guaranteeing the dynamical relevance of the proposed embryos. One novel characteristic of our approach is that we define a limit for the configuration space of the equilibrium metastable phase and do not include the configurations that have zero committor probability in the nucleation free energy surface. Furthermore, in order to take into account the transitional degrees of freedom of the critical nuclei, we develop a simulation-based approach for rigorously mapping the free energy of the (n,v) equilibrium embryos to the concentration of the critical nuclei within the bulk metastable liquid phase.

  13. Freeze/thaw-induced embolism: probability of critical bubble formation depends on speed of ice formation

    Directory of Open Access Journals (Sweden)

    Sanna eSevanto

    2012-06-01

    Full Text Available Bubble formation in the conduits of woody plants sets a challenge for uninterrupted water transportation from the soil up to the canopy. Freezing and thawing of stems has been shown to increase the number of air-filled (embolized conduits, especially in trees with large conduit diameters. Despite numerous experimental studies, the mechanisms leading to bubble formation during freezing have not been addressed theoretically. We used classical nucleation theory and fluid mechanics to show which mechanisms are most likely to be responsible for bubble formation during freezing and what parameters determine the likelihood of the process. Our results confirm the common assumption that bubble formation during freezing is most likely due to gas segregation by ice. If xylem conduit walls are not permeable to the salts expelled by ice during the freezing process, osmotic pressures high enough for air seeding could be created. The build-up rate of segregated solutes in front of the ice-water interface depends equally on conduit diameter and freezing velocity. Therefore, bubble formation probability depends on these variables. The dependence of bubble formation probability on freezing velocity means that the experimental results obtained for cavitation threshold conduit diameters during freeze/thaw cycles depend on the experimental setup; namely sample size and cooling rate. The velocity dependence also suggests that to avoid bubble formation during freezing trees should have narrow conduits where freezing is likely to be fast (e.g. branches or outermost layer of the xylem. Avoidance of bubble formation during freezing could thus be one piece of the explanation why xylem conduit size of temperate and boreal zone trees varies quite systematically.

  14. Air bubbles induce a critical continuous stress to prevent marine biofouling accumulation

    Science.gov (United States)

    Belden, Jesse; Menesses, Mark; Dickenson, Natasha; Bird, James

    2017-11-01

    Significant shear stresses are needed to remove established hard fouling organisms from a ship hull. Given that there is a link between the amount of time that fouling accumulates and the stress required to remove it, it is not surprising that more frequent grooming requires less shear stress. One approach to mitigate marine biofouling is to continuously introduce a curtain of air bubbles under a submerged surface; it is believed that this aeration exploits the small stresses induced by rising bubbles to continuously prevent accumulation. Although curtains of rising bubbles have successfully prevented biofouling accumulation, it is unclear if a single stream of bubbles could maintain a clean surface. In this talk, we show that single bubble stream aeration can prevent biofouling accumulation in regions for which the average wall stress exceeds approximately 0.01 Pa. This value is arrived at by comparing observations of biofouling growth and prevention from field studies with laboratory measurements that probe the associated flow fields. We also relate the spatial and temporal characteristics of the flow to the size and frequency of the rising bubbles, which informs the basic operating conditions required for aeration to continuously prevent biofouling accumulation.

  15. A dry-spot model for the prediction of critical heat flux in water boiling in bubbly flow regime

    Energy Technology Data Exchange (ETDEWEB)

    Ha, Sang Jun; No, Hee Cheon [Korea Advanced Institute of Science and Technology, Taejon (Korea, Republic of)

    1997-12-31

    This paper presents a prediction of critical heat flux (CHF) in bubbly flow regime using dry-spot model proposed recently by authors for pool and flow boiling CHF and existing correlations for forced convective heat transfer coefficient, active site density and bubble departure diameter in nucleate boiling region. Without any empirical constants always present in earlier models, comparisons of the model predictions with experimental data for upward flow of water in vertical, uniformly-heated round tubes are performed and show a good agreement. The parametric trends of CHF have been explored with respect to variations in pressure, tube diameter and length, mass flux and inlet subcooling. 16 refs., 6 figs., 1 tab. (Author)

  16. Primordial bubbles of colour superconducting quark matter

    International Nuclear Information System (INIS)

    Masperi, L.; Orsaria, M.

    2004-01-01

    We analyze the possibility that bubbles of quark matter surviving the confinement phase transition might have become superconducting due to the enormous compression they suffer. Because of the relatively high temperature of the process we compare the initially unpaired quark matter with the colour-flavour locked alternative when the extremely large chemical potential could have increased the critical temperature sufficiently and find that this latter phase would be more stable before the bubble compression stops. If other physical effects had not affected completely their stability, these bubbles might still exist today and perhaps be observed as strangelets

  17. Experiments performed with bubbly flow in vertical pipes at different flow conditions covering the transition region: simulation by coupling Eulerian, Lagrangian and 3D random walks models

    Science.gov (United States)

    Muñoz-Cobo, José; Chiva, Sergio; El Aziz Essa, Mohamed; Mendes, Santos

    2012-08-01

    Two phase flow experiments with different superficial velocities of gas and water were performed in a vertical upward isothermal cocurrent air-water flow column with conditions ranging from bubbly flow, with very low void fraction, to transition flow with some cap and slug bubbles and void fractions around 25%. The superficial velocities of the liquid and the gas phases were varied from 0.5 to 3 m/s and from 0 to 0.6 m/s, respectively. Also to check the effect of changing the surface tension on the previous experiments small amounts of 1-butanol were added to the water. These amounts range from 9 to 75 ppm and change the surface tension. This study is interesting because in real cases the surface tension of the water diminishes with temperature, and with this kind of experiments we can study indirectly the effect of changing the temperature on the void fraction distribution. The following axial and radial distributions were measured in all these experiments: void fraction, interfacial area concentration, interfacial velocity, Sauter mean diameter and turbulence intensity. The range of values of the gas superficial velocities in these experiments covered the range from bubbly flow to the transition to cap/slug flow. Also with transition flow conditions we distinguish two groups of bubbles in the experiments, the small spherical bubbles and the cap/slug bubbles. Special interest was devoted to the transition region from bubbly to cap/slug flow; the goal was to understand the physical phenomena that take place during this transition A set of numerical simulations of some of these experiments for bubbly flow conditions has been performed by coupling a Lagrangian code, that tracks the three dimensional motion of the individual bubbles in cylindrical coordinates inside the field of the carrier liquid, to an Eulerian model that computes the magnitudes of continuous phase and to a 3D random walk model that takes on account the fluctuation in the velocity field of the

  18. Early warning signals for critical transitions in a thermoacoustic system

    Science.gov (United States)

    Gopalakrishnan, E. A.; Sharma, Yogita; John, Tony; Dutta, Partha Sharathi; Sujith, R. I.

    2016-01-01

    Dynamical systems can undergo critical transitions where the system suddenly shifts from one stable state to another at a critical threshold called the tipping point. The decrease in recovery rate to equilibrium (critical slowing down) as the system approaches the tipping point can be used to identify the proximity to a critical transition. Several measures have been adopted to provide early indications of critical transitions that happen in a variety of complex systems. In this study, we use early warning indicators to predict subcritical Hopf bifurcation occurring in a thermoacoustic system by analyzing the observables from experiments and from a theoretical model. We find that the early warning measures perform as robust indicators in the presence and absence of external noise. Thus, we illustrate the applicability of these indicators in an engineering system depicting critical transitions. PMID:27767065

  19. Study on ex-vessel cooling of RPV (behavior of coalesced bubbles and trigger condition of critical heat flux on inclined plate)

    International Nuclear Information System (INIS)

    Ohtake, H.; Koizumi, Y.; Takano, K.I.

    2001-01-01

    The Ex-vessel cooling of Reactor-Pressure-Vessel in Light-Water-Reactor at the severe accident have been proposed for future nuclear reactors. The estimation of Critical-Heat-Flux on a downward-facing curvilinear surface, like a hemisphere, is important to the assessment of the cooling. In this study, the CHFs on inclined surfaces were examined experimentally focusing on orientation of the heating surface. In order to discuss detailed mechanism of the CHF, the behaviors of coalesced bubbles near the heating surface were investigated through visual observations. The critical heat flux obtained in the present experiments increased with the inclined angle over the present experimental range. The dependence of the inclined angle on the critical heat flux was q CHF,R-113 [q] = f (q 0.33 ) for the present experimental results. The effect of the surface orientation on the critical heat flux was roughly explained by using the simple analytical model based on the macro-layer model and Kelvin-Helmholtz instability. From visual observations for behavior of bubbles near the heating surface, whereas the coalesced bubble covered over the heating surface for the inclined angle of 0 degree, the coalesced bubble moved upward to avoid packing the bubble on the surface above 5 degree. As the inclined angle increased, the velocity of the coalesced bubble was high, the period covered the heater and the bubble length were small. The results suggested that the CHF was closely related to forming the coalesced bubble and the behavior of the bubble. (author)

  20. Critical slowing down governs the transition to neuron spiking.

    Directory of Open Access Journals (Sweden)

    Christian Meisel

    2015-02-01

    Full Text Available Many complex systems have been found to exhibit critical transitions, or so-called tipping points, which are sudden changes to a qualitatively different system state. These changes can profoundly impact the functioning of a system ranging from controlled state switching to a catastrophic break-down; signals that predict critical transitions are therefore highly desirable. To this end, research efforts have focused on utilizing qualitative changes in markers related to a system's tendency to recover more slowly from a perturbation the closer it gets to the transition--a phenomenon called critical slowing down. The recently studied scaling of critical slowing down offers a refined path to understand critical transitions: to identify the transition mechanism and improve transition prediction using scaling laws. Here, we outline and apply this strategy for the first time in a real-world system by studying the transition to spiking in neurons of the mammalian cortex. The dynamical system approach has identified two robust mechanisms for the transition from subthreshold activity to spiking, saddle-node and Hopf bifurcation. Although theory provides precise predictions on signatures of critical slowing down near the bifurcation to spiking, quantitative experimental evidence has been lacking. Using whole-cell patch-clamp recordings from pyramidal neurons and fast-spiking interneurons, we show that 1 the transition to spiking dynamically corresponds to a critical transition exhibiting slowing down, 2 the scaling laws suggest a saddle-node bifurcation governing slowing down, and 3 these precise scaling laws can be used to predict the bifurcation point from a limited window of observation. To our knowledge this is the first report of scaling laws of critical slowing down in an experiment. They present a missing link for a broad class of neuroscience modeling and suggest improved estimation of tipping points by incorporating scaling laws of critical slowing

  1. Interval Mathematics Applied to Critical Point Transitions

    Directory of Open Access Journals (Sweden)

    Benito A. Stradi

    2012-03-01

    Full Text Available The determination of critical points of mixtures is important for both practical and theoretical reasons in the modeling of phase behavior, especially at high pressure. The equations that describe the behavior of complex mixtures near critical points are highly nonlinear and with multiplicity of solutions to the critical point equations. Interval arithmetic can be used to reliably locate all the critical points of a given mixture. The method also verifies the nonexistence of a critical point if a mixture of a given composition does not have one. This study uses an interval Newton/Generalized Bisection algorithm that provides a mathematical and computational guarantee that all mixture critical points are located. The technique is illustrated using several example problems. These problems involve cubic equation of state models; however, the technique is general purpose and can be applied in connection with other nonlinear problems.

  2. Research to Operations: The Critical Transition

    Science.gov (United States)

    Fogarty, Jennifer A.

    2009-01-01

    Space Life Sciences Directorate (SLSD) specializes in transitioning technology and knowledge to medical operations. This activity encompasses funding a spectrum of research and technology efforts, such as understanding fundamental biological mechanisms altered by microgravity and executing technology watches for state of the art diagnostic imaging equipment. This broad spectrum approach to fulfilling the need to protect crewmember health and performance during long and short duration missions to the International Space Station, moon and Mars is made possible by having a line of site between research and operations. Currently, SLSD's line of site is articulated in a transition to medical practice (TMP) process. This process is designed to shepherd information and knowledge gained through fundamental and mechanistic research toward the development of an operational solution such as a pre-flight selection criteria; an in-flight countermeasure, monitoring capability or treatment; or a post-flight reconditioning program. The TMP process is also designed to assist with the customization of mature hardware or technology for NASA specific use. The benefits of this process are that the concept of operational usability is interjected early in the research, design, or acquisition phase, and stakeholders are involved early to identify requirements and also periodically asked to assess requirements compliance of research or technology development project. Currently a device known as the actiwatch is being assessed for the final transition to operational use. Specific examples of research to operations transition success help to illustrate the process and bolster communication between the research and medical operations communities.

  3. A dry-spot model of critical heat flux and transition boiling in pool and subcooled forced convection boiling

    International Nuclear Information System (INIS)

    Ha, Sang Jun

    1998-02-01

    A new dry-spot model for critical heat flux (CHF) is proposed. The new concept for dry area formation based on Poisson distribution of active nucleation sites and the critical active site number is introduced. The model is based on the boiling phenomena observed in nucleate boiling such as Poisson distribution of active nucleation sites and formation of dry spots on the heating surface. It is hypothesized that when the number of bubbles surrounding one bubble exceeds a critical number, the surrounding bubbles restrict the feed of liquid to the microlayer under the bubble. Then a dry spot of vapor will form on the heated surface. As the surface temperature is raised, more and more bubbles will have a population of surrounding active sites over the critical number. Consequently, the number of the spots will increase and the size of dry areas will increase due to merger of several dry spots. If this trend continues, the number of effective sites for heat transport through the wall will diminish, and CHF and transition boiling occur. The model is applicable to pool and subcooled forced convection boiling conditions, based on the common mechanism that CHF and transition boiling are caused by the accumulation and coalescences of dry spots. It is shown that CHF and heat flux in transition boiling can be determined without any empirical parameter based on information on the boiling parameters such as active site density and bubble diameter, etc., in nucleate boiling. It is also shown that the present model well represents actual phenomena on CHF and transition boiling and explains the mechanism on how parameters such as flow modes (pool or flow) and surface wettability influence CHF and transition boiling. Validation of the present model for CHF and transition boiling is achieved without any tuning parameter always present in earlier models. It is achieved by comparing the predictions of CHF and heat flux in transition boiling using measured boiling parameters in nucleate

  4. A New Statistical Parameter for Identifying the Main Transition Velocities in Bubble Columns.

    Science.gov (United States)

    Nedeltchev, Stoyan; Rabha, Swapna; Hampel, Uwe; Schubert, Markus

    2015-11-01

    The identification of the main flow regime boundaries in bubble columns is essential since the degrees of mixing and mass and heat transfer vary with the flow regime. In this work, a new statistical parameter was extracted from the time series of the cross-sectional averaged gas holdup. The measurements were performed in bubble columns by means of conductivity wire-mesh sensors at very high sampling frequency. The columns were operated with an air/deionized water system under ambient conditions. As a flow regime indicator, a new dimensionless statistical parameter called "relative maximum number of visits in a region" was introduced. This new parameter is a function of the difference between the maximum numbers of visits in a region, calculated from two different division schemes of the signal range.

  5. Partial dynamical symmetry at critical points of quantum phase transitions.

    Science.gov (United States)

    Leviatan, A

    2007-06-15

    We show that partial dynamical symmetries can occur at critical points of quantum phase transitions, in which case underlying competing symmetries are conserved exactly by a subset of states, and mix strongly in other states. Several types of partial dynamical symmetries are demonstrated with the example of critical-point Hamiltonians for first- and second-order transitions in the framework of the interacting boson model, whose dynamical symmetries correspond to different shape phases in nuclei.

  6. Partial Dynamical Symmetry at Critical Points of Quantum Phase Transitions

    International Nuclear Information System (INIS)

    Leviatan, A.

    2007-01-01

    We show that partial dynamical symmetries can occur at critical points of quantum phase transitions, in which case underlying competing symmetries are conserved exactly by a subset of states, and mix strongly in other states. Several types of partial dynamical symmetries are demonstrated with the example of critical-point Hamiltonians for first- and second-order transitions in the framework of the interacting boson model, whose dynamical symmetries correspond to different shape phases in nuclei

  7. Boiling crisis as inhibition of bubble detachment by the vapor recoil force

    International Nuclear Information System (INIS)

    Nikolayev, V.S.; Beysens, D.; Garrabos, Y.

    2004-01-01

    Boiling crisis is a transition between nucleate and film boiling. In this communication we present a physical model of the boiling crisis based on the vapor recoil effect. Our numerical simulations of the thermally controlled bubble growth at high heat fluxes show how the bubble begins to spread over the heater thus forming a germ for the vapor film. The vapor recoil force not only causes the vapor spreading, it also creates a strong adhesion to the heater that prevents the bubble departure, thus favoring the further bubble spreading. Near the liquid-gas critical point, the bubble growth is very slow and allows the kinetics of the bubble spreading to be observed. Since the surface tension is very small in this regime, only microgravity conditions can preserve a convex bubble shape. Under such conditions, we observed an increase of the apparent contact angle and spreading of the dry spot under the bubble, thus confirming our model of the boiling crisis. (authors)

  8. Ten years of transition Stiglitz's criticism and counterarguments

    Directory of Open Access Journals (Sweden)

    Đurđević Ljiljana

    2004-01-01

    Full Text Available IMF supports the transition process in most ex-socialist countries through concessionary financing, recommendations for economic policy and technical assistance. Results vary across countries and have been analyzed by a number of authors. In this context, some authors have dealt with the IMF's "guilt" Stiglitz's criticism having struck the most responsive chord in public triggering violent reactions. The paper deals with the key hypotheses of this criticism as well as the main counter arguments.

  9. Condensate-induced transitions and critical spin chains

    NARCIS (Netherlands)

    Månsson, T.; Lahtinen, V.; Suorsa, J.; Ardonne, E.

    2013-01-01

    We show that condensate-induced transitions between two-dimensional topological phases provide a general framework to relate one-dimensional spin models at their critical points. We demonstrate this using two examples. First, we show that two well-known spin chains, namely, the XY chain and the

  10. Phase transitions and critical behaviour for charged black holes

    International Nuclear Information System (INIS)

    Carlip, S; Vaidya, S

    2003-01-01

    We investigate the thermodynamics of a four-dimensional charged black hole in a finite cavity in asymptotically flat and asymptotically de Sitter spaces. In each case, we find a Hawking-Page-like phase transition between a black hole and a thermal gas very much like the known transition in asymptotically anti-de Sitter space. For a 'supercooled' black hole - a thermodynamically unstable black hole below the critical temperature for the Hawking-Page phase transition - the phase diagram has a line of first-order phase transitions that terminates in a second-order point. For the asymptotically flat case, we calculate the critical exponents at the second-order phase transition and find that they exactly match the known results for a charged black hole in anti-de Sitter space. We find strong evidence for similar phase transitions for the de Sitter black hole as well. Thus many of the thermodynamic features of charged anti-de Sitter black holes do not really depend on asymptotically anti-de Sitter boundary conditions; the thermodynamics of charged black holes is surprisingly universal

  11. Model for the resistive critical current transition in composite superconductors

    International Nuclear Information System (INIS)

    Warnes, W.H.

    1988-01-01

    Much of the research investigating technological type-II superconducting composites relies on the measurement of the resistive critical current transition. We have developed a model for the resistive transition which improves on older models by allowing for the very different nature of monofilamentary and multifilamentary composite structures. The monofilamentary model allows for axial current flow around critical current weak links in the superconducting filament. The multifilamentary model incorporates an additional radial current transfer between neighboring filaments. The development of both models is presented. It is shown that the models are useful for extracting more information from the experimental data than was formerly possible. Specific information obtainable from the experimental voltage-current characteristic includes the distribution of critical currents in the composite, the average critical current of the distribution, the range of critical currents in the composite, the field and temperature dependence of the distribution, and the fraction of the composite dissipating energy in flux flow at any current. This additional information about the distribution of critical currents may be helpful in leading toward a better understanding of flux pinning in technological superconductors. Comparison of the models with several experiments is given and shown to be in reasonable agreement. Implications of the models for the measurement of critical currents in technological composites is presented and discussed with reference to basic flux pinning studies in such composites

  12. Bubble and drop interfaces

    CERN Document Server

    Miller

    2011-01-01

    The book aims at describing the most important experimental methods for characterizing liquid interfaces, such as drop profile analysis, bubble pressure and drop volume tensiometry, capillary pressure technique, and oscillating drops and bubbles. Besides the details of experimental set ups, also the underlying theoretical basis is presented in detail. In addition, a number of applications based on drops and bubbles is discussed, such as rising bubbles and the very complex process of flotation. Also wetting, characterized by the dynamics of advancing contact angles is discussed critically. Spec

  13. Bubble Formation within Filaments of Melt-Processed Bi2212 wires and its strongly negative effect on the Critical Current Density

    CERN Document Server

    Kametani, F; Jiang, J; Scheuerlein, C; Malagoli, A; Di Michiel, M; Huang, Y; Miao, H; Parrell, J A; Hellstrom, E E; Larbalestier, D C

    2011-01-01

    Most studies of Bi2Sr2CaCu2Ox (Bi2212) show that the critical current density Jc is limited by the connectivity of the filaments, but what determines the connectivity is still elusive. Here we report on the role played by filament porosity in limiting Jc. By a microstructural investigation of wires quenched from the melt state, we find that porosity in the unreacted wire agglomerates into bubbles that segment the Bi2212 melt within the filaments into discrete sections. These bubbles do not disappear during subsequent processing because they are only partially filled by Bi2212 grains as the Bi2212 forms on cooling. Correlating the microstructure of quenched wires to their final, fully processed Jc values shows an inverse relation between Jc and bubble density. Bubbles are variable between conductors and perhaps from sample to sample, but they occur frequently and almost completely fill the filament diameter, so they exert a strongly variable but always negative effect on Jc. Bubbles reduce the continuous Bi221...

  14. Think Bubbles and Socrates: Teaching Critical Thinking to Millennials in Public Relations Classes

    Science.gov (United States)

    Tallent, Rebecca J.; Barnes, Justin J.

    2015-01-01

    Critical thinking skills are crucial in the public relations profession, but teaching these skills to the Millennial Generation is vastly different from previous generations. How can a professor get past No Child Left Behind's dependence on test review guides and "everybody wins" in getting students to think for themselves? Using the…

  15. Transit of micro-bubbles through the pulmonary circulation of Thoroughbred horses during exercise.

    Science.gov (United States)

    La Gerche, A; Daffy, J R; Mooney, D J; Forbes, G; Davie, A J

    2013-10-01

    It has been observed that microbubbles may pass through the pulmonary circulation of dogs and humans during exercise. In humans, this phenomenon has been associated with lower pulmonary artery pressures, enhanced right ventricular function and greater exercise capacity. In the exercising Thoroughbred horse, extraordinarily high cardiac outputs exert significant pulmonary vascular stresses. The aim of this study was to determine, using contrast echocardiography, whether Thoroughbred horses performing strenuous exercise developed pulmonary transit of agitated contrast microbubbles (PTAC). At rest, agitated contrast was observed in the right ventricle, but not in the left ventricle. However, post-exercise microbubbles were observed in the left ventricle, confirming the occurrence of PTAC with exercise but not at rest. Further investigation is warranted to investigate whether this phenomenon may be associated with superior physiology and performance measures as has been implicated in other species. Copyright © 2013 Elsevier Ltd. All rights reserved.

  16. Critical phase transitions during ablation of atrial fibrillation

    Science.gov (United States)

    Iravanian, Shahriar; Langberg, Jonathan J.

    2017-09-01

    Atrial fibrillation (AF) is the most common sustained cardiac arrhythmia with significant morbidity and mortality. Pharmacological agents are not very effective in the management of AF. Therefore, ablation procedures have become the mainstay of AF management. The irregular and seemingly chaotic atrial activity in AF is caused by one or more meandering spiral waves. Previously, we have shown the presence of sudden rhythm organization during ablation of persistent AF. We hypothesize that the observed transitions from a disorganized to an organized rhythm is a critical phase transition. Here, we explore this hypothesis by simulating ablation in an anatomically-correct 3D AF model. In 722 out of 2160 simulated ablation, at least one sudden transition from AF to an organized rhythm (flutter) was noted (33%). They were marked by a sudden decrease in the cycle length entropy and increase in the mean cycle length. At the same time, the number of reentrant wavelets decreased from 2.99 ± 0.06 in AF to 1.76 ± 0.05 during flutter, and the correlation length scale increased from 13.3 ± 1.0 mm to 196.5 ± 86.6 mm (both P < 0.0001). These findings are consistent with the hypothesis that transitions from AF to an anatomical flutter behave as phase transitions in complex non-equilibrium dynamical systems with flutter acting as an absorbing state. Clinically, the facilitation of phase transition should be considered a novel mechanism of ablation and may help to design effective ablation strategies.

  17. Science Bubbles

    DEFF Research Database (Denmark)

    Hendricks, Vincent Fella; Pedersen, David Budtz

    2013-01-01

    Much like the trade and trait sof bubbles in financial markets,similar bubbles appear on the science market. When economic bubbles burst, the drop in prices causes the crash of unsustainable investments leading to an investor confidence crisis possibly followed by a financial panic. But when bubb...... bubbles appear in science, truth and reliability are the first victims. This paper explores how fashions in research funding and research management may turn science into something like a bubble economy.......Much like the trade and trait sof bubbles in financial markets,similar bubbles appear on the science market. When economic bubbles burst, the drop in prices causes the crash of unsustainable investments leading to an investor confidence crisis possibly followed by a financial panic. But when...

  18. Supply and demand drive a critical transition to dysfunctional fisheries.

    Science.gov (United States)

    Fryxell, John M; Hilborn, Ray; Bieg, Carling; Turgeon, Katrine; Caskenette, Amanda; McCann, Kevin S

    2017-11-14

    There is growing awareness of the need for fishery management policies that are robust to changing environmental, social, and economic pressures. Here we use conventional bioeconomic theory to demonstrate that inherent biological constraints combined with nonlinear supply-demand relationships can generate threshold effects due to harvesting. As a result, increases in overall demand due to human population growth or improvement in real income would be expected to induce critical transitions from high-yield/low-price fisheries to low-yield/high-price fisheries, generating severe strains on social and economic systems as well as compromising resource conservation goals. As a proof of concept, we show that key predictions of the critical transition hypothesis are borne out in oceanic fisheries (cod and pollock) that have experienced substantial increase in fishing pressure over the past 60 y. A hump-shaped relationship between price and historical harvest returns, well demonstrated in these empirical examples, is particularly diagnostic of fishery degradation. Fortunately, the same heuristic can also be used to identify reliable targets for fishery restoration yielding optimal bioeconomic returns while safely conserving resource abundance. Copyright © 2017 the Author(s). Published by PNAS.

  19. On the characteristics of the equations of motion for a bubbly flow and the related problem of critical flow

    NARCIS (Netherlands)

    Prosperetti, Andrea; van Wijngaarden, L.

    1976-01-01

    For the study of transients in gas-liquid flows, the equations of the so-called separated flow model are inadequate, because they possess, in the general case where gas and liquid move at different velocities, complex characteristics. This paper is concerned with the equations of motion for bubbly

  20. Black holes as critical point of quantum phase transition.

    Science.gov (United States)

    Dvali, Gia; Gomez, Cesar

    We reformulate the quantum black hole portrait in the language of modern condensed matter physics. We show that black holes can be understood as a graviton Bose-Einstein condensate at the critical point of a quantum phase transition, identical to what has been observed in systems of cold atoms. The Bogoliubov modes that become degenerate and nearly gapless at this point are the holographic quantum degrees of freedom responsible for the black hole entropy and the information storage. They have no (semi)classical counterparts and become inaccessible in this limit. These findings indicate a deep connection between the seemingly remote systems and suggest a new quantum foundation of holography. They also open an intriguing possibility of simulating black hole information processing in table-top labs.

  1. Black Holes as Critical Point of Quantum Phase Transition

    CERN Document Server

    Dvali, Gia

    2014-01-01

    We reformulate the quantum black hole portrait in the language of modern condensed matter physics. We show that black holes can be understood as a graviton Bose-Einstein condensate at the critical point of a quantum phase transition, identical to what has been observed in systems of cold atoms. The Bogoliubov modes that become degenerate and nearly gapless at this point are the holographic quantum degrees of freedom responsible for the black hole entropy and the information storage. They have no (semi)classical counterparts and become inaccessible in this limit. These findings indicate a deep connection between the seemingly remote systems and suggest a new quantum foundation of holography. They also open an intriguing possibility of simulating black hole information processing in table-top labs.

  2. Bubble systems

    CERN Document Server

    Avdeev, Alexander A

    2016-01-01

    This monograph presents a systematic analysis of bubble system mathematics, using the mechanics of two-phase systems in non-equilibrium as the scope of analysis. The author introduces the thermodynamic foundations of bubble systems, ranging from the fundamental starting points to current research challenges. This book addresses a range of topics, including description methods of multi-phase systems, boundary and initial conditions as well as coupling requirements at the phase boundary. Moreover, it presents a detailed study of the basic problems of bubble dynamics in a liquid mass: growth (dynamically and thermally controlled), collapse, bubble pulsations, bubble rise and breakup. Special emphasis is placed on bubble dynamics in turbulent flows. The analysis results are used to write integral equations governing the rate of vapor generation (condensation) in non-equilibrium flows, thus creating a basis for solving a number of practical problems. This book is the first to present a comprehensive theory of boil...

  3. The use of spatio-temporal correlation to forecast critical transitions

    NARCIS (Netherlands)

    Karssenberg, D.J.; Bierkens, M.F.P.

    2011-01-01

    Complex dynamical systems may have critical thresholds at which the system shifts abruptly from one state to another. Such critical transitions have been observed in systems ranging from the human body system to financial markets and the Earth system. Forecasting the timing of critical transitions

  4. Multivariate bubbles and antibubbles

    Science.gov (United States)

    Fry, John

    2014-08-01

    In this paper we develop models for multivariate financial bubbles and antibubbles based on statistical physics. In particular, we extend a rich set of univariate models to higher dimensions. Changes in market regime can be explicitly shown to represent a phase transition from random to deterministic behaviour in prices. Moreover, our multivariate models are able to capture some of the contagious effects that occur during such episodes. We are able to show that declining lending quality helped fuel a bubble in the US stock market prior to 2008. Further, our approach offers interesting insights into the spatial development of UK house prices.

  5. Droplets, Bubbles and Ultrasound Interactions.

    Science.gov (United States)

    Shpak, Oleksandr; Verweij, Martin; de Jong, Nico; Versluis, Michel

    2016-01-01

    The interaction of droplets and bubbles with ultrasound has been studied extensively in the last 25 years. Microbubbles are broadly used in diagnostic and therapeutic medical applications, for instance, as ultrasound contrast agents. They have a similar size as red blood cells, and thus are able to circulate within blood vessels. Perfluorocarbon liquid droplets can be a potential new generation of microbubble agents as ultrasound can trigger their conversion into gas bubbles. Prior to activation, they are at least five times smaller in diameter than the resulting bubbles. Together with the violent nature of the phase-transition, the droplets can be used for local drug delivery, embolotherapy, HIFU enhancement and tumor imaging. Here we explain the basics of bubble dynamics, described by the Rayleigh-Plesset equation, bubble resonance frequency, damping and quality factor. We show the elegant calculation of the above characteristics for the case of small amplitude oscillations by linearizing the equations. The effect and importance of a bubble coating and effective surface tension are also discussed. We give the main characteristics of the power spectrum of bubble oscillations. Preceding bubble dynamics, ultrasound propagation is introduced. We explain the speed of sound, nonlinearity and attenuation terms. We examine bubble ultrasound scattering and how it depends on the wave-shape of the incident wave. Finally, we introduce droplet interaction with ultrasound. We elucidate the ultrasound-focusing concept within a droplets sphere, droplet shaking due to media compressibility and droplet phase-conversion dynamics.

  6. The Regime Shift Associated with the 2004-2008 US Housing Market Bubble.

    Science.gov (United States)

    Tan, James; Cheong, Siew Ann

    2016-01-01

    The Subprime Bubble preceding the Subprime Crisis of 2008 was fueled by risky lending practices, manifesting in the form of a large abrupt increase in the proportion of subprime mortgages issued in the US. This event also coincided with critical slowing down signals associated with instability, which served as evidence of a regime shift or phase transition in the US housing market. Here, we show that the US housing market underwent a regime shift between alternate stable states consistent with the observed critical slowing down signals. We modeled this regime shift on a universal transition path and validated the model by estimating when the bubble burst. Additionally, this model reveals loose monetary policy to be a plausible cause of the phase transition, implying that the bubble might have been deflatable by a timely tightening of monetary policy.

  7. The Regime Shift Associated with the 2004–2008 US Housing Market Bubble

    Science.gov (United States)

    Cheong, Siew Ann

    2016-01-01

    The Subprime Bubble preceding the Subprime Crisis of 2008 was fueled by risky lending practices, manifesting in the form of a large abrupt increase in the proportion of subprime mortgages issued in the US. This event also coincided with critical slowing down signals associated with instability, which served as evidence of a regime shift or phase transition in the US housing market. Here, we show that the US housing market underwent a regime shift between alternate stable states consistent with the observed critical slowing down signals. We modeled this regime shift on a universal transition path and validated the model by estimating when the bubble burst. Additionally, this model reveals loose monetary policy to be a plausible cause of the phase transition, implying that the bubble might have been deflatable by a timely tightening of monetary policy. PMID:27583633

  8. The Regime Shift Associated with the 2004-2008 US Housing Market Bubble.

    Directory of Open Access Journals (Sweden)

    James Tan

    Full Text Available The Subprime Bubble preceding the Subprime Crisis of 2008 was fueled by risky lending practices, manifesting in the form of a large abrupt increase in the proportion of subprime mortgages issued in the US. This event also coincided with critical slowing down signals associated with instability, which served as evidence of a regime shift or phase transition in the US housing market. Here, we show that the US housing market underwent a regime shift between alternate stable states consistent with the observed critical slowing down signals. We modeled this regime shift on a universal transition path and validated the model by estimating when the bubble burst. Additionally, this model reveals loose monetary policy to be a plausible cause of the phase transition, implying that the bubble might have been deflatable by a timely tightening of monetary policy.

  9. Critical Transition in Tissue Homeostasis Accompanies Murine Lung Senescence

    Science.gov (United States)

    D'Alessio, Franco R.; Metzger, Shana L.; Misono, Kaori; Poonyagariyagorn, Hataya; Lopez-Mercado, Armando; Ku, Therese; Lauer, Thomas; Cheadle, Christopher; Talbot, C. Conover; Jie, Chunfa; McGrath-Morrow, Sharon; King, Landon S.; Walston, Jeremy; Neptune, Enid R.

    2011-01-01

    Background Respiratory dysfunction is a major contributor to morbidity and mortality in aged populations. The susceptibility to pulmonary insults is attributed to “low pulmonary reserve”, ostensibly reflecting a combination of age-related musculoskeletal, immunologic and intrinsic pulmonary dysfunction. Methods/Principal Findings Using a murine model of the aging lung, senescent DBA/2 mice, we correlated a longitudinal survey of airspace size and injury measures with a transcriptome from the aging lung at 2, 4, 8, 12, 16 and 20 months of age. Morphometric analysis demonstrated a nonlinear pattern of airspace caliber enlargement with a critical transition occurring between 8 and 12 months of age marked by an initial increase in oxidative stress, cell death and elastase activation which is soon followed by inflammatory cell infiltration, immune complex deposition and the onset of airspace enlargement. The temporally correlative transcriptome showed exuberant induction of immunoglobulin genes coincident with airspace enlargement. Immunohistochemistry, ELISA analysis and flow cytometry demonstrated increased immunoglobulin deposition in the lung associated with a contemporaneous increase in activated B-cells expressing high levels of TLR4 (toll receptor 4) and CD86 and macrophages during midlife. These midlife changes culminate in progressive airspace enlargement during late life stages. Conclusion/Significance Our findings establish that a tissue-specific aging program is evident during a presenescent interval which involves early oxidative stress, cell death and elastase activation, followed by B lymphocyte and macrophage expansion/activation. This sequence heralds the progression to overt airspace enlargement in the aged lung. These signature events, during middle age, indicate that early stages of the aging immune system may have important correlates in the maintenance of tissue morphology. We further show that time-course analyses of aging models, when

  10. Critical transition in tissue homeostasis accompanies murine lung senescence.

    Directory of Open Access Journals (Sweden)

    Carla L Calvi

    Full Text Available BACKGROUND: Respiratory dysfunction is a major contributor to morbidity and mortality in aged populations. The susceptibility to pulmonary insults is attributed to "low pulmonary reserve", ostensibly reflecting a combination of age-related musculoskeletal, immunologic and intrinsic pulmonary dysfunction. METHODS/PRINCIPAL FINDINGS: Using a murine model of the aging lung, senescent DBA/2 mice, we correlated a longitudinal survey of airspace size and injury measures with a transcriptome from the aging lung at 2, 4, 8, 12, 16 and 20 months of age. Morphometric analysis demonstrated a nonlinear pattern of airspace caliber enlargement with a critical transition occurring between 8 and 12 months of age marked by an initial increase in oxidative stress, cell death and elastase activation which is soon followed by inflammatory cell infiltration, immune complex deposition and the onset of airspace enlargement. The temporally correlative transcriptome showed exuberant induction of immunoglobulin genes coincident with airspace enlargement. Immunohistochemistry, ELISA analysis and flow cytometry demonstrated increased immunoglobulin deposition in the lung associated with a contemporaneous increase in activated B-cells expressing high levels of TLR4 (toll receptor 4 and CD86 and macrophages during midlife. These midlife changes culminate in progressive airspace enlargement during late life stages. CONCLUSION/SIGNIFICANCE: Our findings establish that a tissue-specific aging program is evident during a presenescent interval which involves early oxidative stress, cell death and elastase activation, followed by B lymphocyte and macrophage expansion/activation. This sequence heralds the progression to overt airspace enlargement in the aged lung. These signature events, during middle age, indicate that early stages of the aging immune system may have important correlates in the maintenance of tissue morphology. We further show that time-course analyses of aging

  11. Third-order gas-liquid phase transition and the nature of Andrews critical point

    Directory of Open Access Journals (Sweden)

    Tian Ma

    2011-12-01

    Full Text Available The main objective of this article is to study the nature of the Andrews critical point in the gas-liquid transition in a physical-vapor transport (PVT system. A dynamical model, consistent with the van der Waals equation near the Andrews critical point, is derived. With this model, we deduce two physical parameters, which interact exactly at the Andrews critical point, and which dictate the dynamic transition behavior near the Andrews critical point. In particular, it is shown that 1 the gas-liquid co-existence curve can be extended beyond the Andrews critical point, and 2 the transition is first order before the critical point, second-order at the critical point, and third order beyond the Andrews critical point. This clearly explains why it is hard to observe the gas-liquid phase transition beyond the Andrews critical point. Furthermore, the analysis leads naturally the introduction of a general asymmetry principle of fluctuations and the preferred transition mechanism for a thermodynamic system. The theoretical results derived in this article are in agreement with the experimental results obtained in (K. Nishikawa and T. Morita, Fluid behavior at supercritical states studied by small-angle X-ray scattering, Journal of Supercritical Fluid, 13 (1998, pp. 143-148. Also, the derived second-order transition at the critical point is consistent with the result obtained in (M. Fisher, Specific heat of a gas near the critical point, Physical Review, 136:6A (1964, pp. A1599-A1604.

  12. Cognitive Bubbles

    OpenAIRE

    Ciril Bosch-Rosa; Thomas Meissner; Antoni Bosch-Domènech

    2015-01-01

    Smith et al. (1988) reported large bubbles and crashes in experimental asset markets, a result that has been replicated by a large literature. Here we test whether the occurrence of bubbles depends on the experimental subjects' cognitive sophistication. In a two-part experiment, we first run a battery of tests to assess the subjects' cognitive sophistication and classify them into low or high levels of cognitive sophistication. We then invite them separately to two asset market experimen...

  13. Bubbling away

    International Nuclear Information System (INIS)

    Anon.

    1993-01-01

    Bubble chambers may have almost vanished from the front line of physics research, but the vivid memory of their intricate and sometimes beautiful patterns of particle tracks lives on, and has greatly influenced the computer graphics of track reconstruction in today's big experiments. 'Seeing' an interaction makes it more understandable. Bubble chambers, with their big collaborations of physicists from many widely scattered research institutes, started another ball rolling. The groups formed are even now only surpassed in size by the big collaborations working on today's major detectors at colliding beam machines. From 14-16 July, about 130 physicists gathered at CERN to commemorate the 40th anniversary of the invention of the bubble chamber by Donald Glaser. The meeting, organized by Derek C. Colley from Birmingham, gave a comprehensive overview of bubble chamber contributions to physics, their challenging technology, and the usefulness of bubble chamber photographs in education, both for physics and the public at large. After opening remarks by CERN Director Carlo Rubbia, Donald Glaser began with a brief review of the work which led to his invention - there was much more to it than idly watching beer bubbles rise up the wall of the glass - before turning to his present line of research, biophysics, also very visually oriented

  14. Growth rate and critical diameter of a vapor bubble in saturated liquid boiling under conditions of natural convection

    International Nuclear Information System (INIS)

    Kutateladze, S.S.; Gogonin, I.I.

    1979-01-01

    Reviewed are experimental studies of boiling of the following liquids: water, ethanol, nitrogen, methanol, benzene, freon-12. A criterion dependence is obtained, and the results of experimental data processing are presented according to separation dimension of vapor bubble at boiling of the above mentioned liquids in the presence range of 0.01-100 atm. As a result of the study, an importance of taking account of a statistical character of separation dimension is noted. This parameter is shown to be strongly conditioned by liquid-material combination of heat-emissive surface. Estimated are experiments made at water boiling on surfaces being under load for a long period of time and those being fresh-prepared. A clear stratification of these data is observed which reaches 50 % in the high-pressure range

  15. Order, disorder, and criticality advanced problems of phase transition theory

    CERN Document Server

    Holovatch, Yurij

    2004-01-01

    This book reviews some of the classic aspects in the theory of phasetransitions and critical phenomena, which has a longhistory. Recently, these aspects are attracting much attention due toessential new contributions. The topics presented in this bookinclude: mathematical theory of the Ising model; equilibrium andnon-equilibrium criticality of one-dimensional quantum spin chains;influence of structural disorder on the critical behaviour of thePotts model; criticality, fractality and multifractality of linkedpolymers; field-theoretical approaches in the superconducting phasetransitions.

  16. Critical Phenomena of the Disorder Driven Localization-Delocalization Transition

    International Nuclear Information System (INIS)

    Marc Ruehlaender

    2001-01-01

    Metal-to-insulator transitions are generally linked to two phenomena: electron-electron correlations and disorder. Although real systems are usually responding to a mixture of both, they can be classified as undergoing a Mott-transition, if the former process dominates, or an Anderson-transition, if the latter dominates. High-T c superconductors, e.g., are a candidate for the first class. Materials in which disorder drives the metal-to-insulator transition include doped semiconductors and amorphous materials. After briefly reviewing the previous research on transport in disordered materials and the disorder-induced metal-to-insulator transition, a summary of the model and the methods used in subsequent chapters is given

  17. Lack of Critical Slowing Down Suggests that Financial Meltdowns Are Not Critical Transitions, yet Rising Variability Could Signal Systemic Risk.

    Science.gov (United States)

    Guttal, Vishwesha; Raghavendra, Srinivas; Goel, Nikunj; Hoarau, Quentin

    2016-01-01

    Complex systems inspired analysis suggests a hypothesis that financial meltdowns are abrupt critical transitions that occur when the system reaches a tipping point. Theoretical and empirical studies on climatic and ecological dynamical systems have shown that approach to tipping points is preceded by a generic phenomenon called critical slowing down, i.e. an increasingly slow response of the system to perturbations. Therefore, it has been suggested that critical slowing down may be used as an early warning signal of imminent critical transitions. Whether financial markets exhibit critical slowing down prior to meltdowns remains unclear. Here, our analysis reveals that three major US (Dow Jones Index, S&P 500 and NASDAQ) and two European markets (DAX and FTSE) did not exhibit critical slowing down prior to major financial crashes over the last century. However, all markets showed strong trends of rising variability, quantified by time series variance and spectral function at low frequencies, prior to crashes. These results suggest that financial crashes are not critical transitions that occur in the vicinity of a tipping point. Using a simple model, we argue that financial crashes are likely to be stochastic transitions which can occur even when the system is far away from the tipping point. Specifically, we show that a gradually increasing strength of stochastic perturbations may have caused to abrupt transitions in the financial markets. Broadly, our results highlight the importance of stochastically driven abrupt transitions in real world scenarios. Our study offers rising variability as a precursor of financial meltdowns albeit with a limitation that they may signal false alarms.

  18. Bubble dynamics equations in Newton fluid

    International Nuclear Information System (INIS)

    Xiao, J

    2008-01-01

    For the high-speed flow of Newton fluid, bubble is produced and expanded when it moves toward the surface of fluid. Bubble dynamics is a very important research field to understand the intrinsic feature of bubble production and motion. This research formulates the bubble expansion by expansion-local rotation transformation, which can be calculated by the measured velocity field. Then, the related dynamic equations are established to describe the interaction between the fluid and the bubble. The research shows that the bubble production condition can be expressed by critical vortex value and fluid pressure; and the bubble expansion rate can be obtained by solving the non-linear dynamic equation of bubble motion. The results may help the related research as it shows a special kind of fluid motion in theoretic sense. As an application example, the nanofiber radium-voltage relation and threshold voltage-surface tension relation in electrospinning process are discussed

  19. Evaluating early-warning indicators of critical transitions in natural aquatic ecosystems

    Science.gov (United States)

    Gsell, Alena Sonia; Scharfenberger, Ulrike; Ozkundakci, Deniz; Walters, Annika W.; Hansson, Lars-Anders; Janssen, Annette B. G.; Noges, Peeter; Reid, Philip; Schindler, Daniel; van Donk, Ellen; Dakos, Vasilis; Adrian, Rita

    2016-01-01

    Ecosystems can show sudden and persistent changes in state despite only incremental changes in drivers. Such critical transitions are difficult to predict, because the state of the system often shows little change before the transition. Early-warning indicators (EWIs) are hypothesized to signal the loss of system resilience and have been shown to precede critical transitions in theoretical models, paleo-climate time series, and in laboratory as well as whole lake experiments. The generalizability of EWIs for detecting critical transitions in empirical time series of natural aquatic ecosystems remains largely untested, however. Here we assessed four commonly used EWIs on long-term datasets of five freshwater ecosystems that have experienced sudden, persistent transitions and for which the relevant ecological mechanisms and drivers are well understood. These case studies were categorized by three mechanisms that can generate critical transitions between alternative states: competition, trophic cascade, and intraguild predation. Although EWIs could be detected in most of the case studies, agreement among the four indicators was low. In some cases, EWIs were detected considerably ahead of the transition. Nonetheless, our results show that at present, EWIs do not provide reliable and consistent signals of impending critical transitions despite using some of the best routinely monitored freshwater ecosystems. Our analysis strongly suggests that a priori knowledge of the underlying mechanisms driving ecosystem transitions is necessary to identify relevant state variables for successfully monitoring EWIs.

  20. Effects of stressor characteristics on early warning signs of critical transitions and "critical coupling" in complex dynamical systems

    Science.gov (United States)

    Blume, Steffen O. P.; Sansavini, Giovanni

    2017-12-01

    Complex dynamical systems face abrupt transitions into unstable and catastrophic regimes. These critical transitions are triggered by gradual modifications in stressors, which push the dynamical system towards unstable regimes. Bifurcation analysis can characterize such critical thresholds, beyond which systems become unstable. Moreover, the stochasticity of the external stressors causes small-scale fluctuations in the system response. In some systems, the decomposition of these signal fluctuations into precursor signals can reveal early warning signs prior to the critical transition. Here, we present a dynamical analysis of a power system subjected to an increasing load level and small-scale stochastic load perturbations. We show that the auto- and cross-correlations of bus voltage magnitudes increase, leading up to a Hopf bifurcation point, and further grow until the system collapses. This evidences a gradual transition into a state of "critical coupling," which is complementary to the established concept of "critical slowing down." Furthermore, we analyze the effects of the type of load perturbation and load characteristics on early warning signs and find that gradient changes in the autocorrelation provide early warning signs of the imminent critical transition under white-noise but not for auto-correlated load perturbations. Furthermore, the cross-correlation between all voltage magnitude pairs generally increases prior to and beyond the Hopf bifurcation point, indicating "critical coupling," but cannot provide early warning indications. Finally, we show that the established early warning indicators are oblivious to limit-induced bifurcations and, in the case of the power system model considered here, only react to an approaching Hopf bifurcation.

  1. Effects of stressor characteristics on early warning signs of critical transitions and "critical coupling" in complex dynamical systems.

    Science.gov (United States)

    Blume, Steffen O P; Sansavini, Giovanni

    2017-12-01

    Complex dynamical systems face abrupt transitions into unstable and catastrophic regimes. These critical transitions are triggered by gradual modifications in stressors, which push the dynamical system towards unstable regimes. Bifurcation analysis can characterize such critical thresholds, beyond which systems become unstable. Moreover, the stochasticity of the external stressors causes small-scale fluctuations in the system response. In some systems, the decomposition of these signal fluctuations into precursor signals can reveal early warning signs prior to the critical transition. Here, we present a dynamical analysis of a power system subjected to an increasing load level and small-scale stochastic load perturbations. We show that the auto- and cross-correlations of bus voltage magnitudes increase, leading up to a Hopf bifurcation point, and further grow until the system collapses. This evidences a gradual transition into a state of "critical coupling," which is complementary to the established concept of "critical slowing down." Furthermore, we analyze the effects of the type of load perturbation and load characteristics on early warning signs and find that gradient changes in the autocorrelation provide early warning signs of the imminent critical transition under white-noise but not for auto-correlated load perturbations. Furthermore, the cross-correlation between all voltage magnitude pairs generally increases prior to and beyond the Hopf bifurcation point, indicating "critical coupling," but cannot provide early warning indications. Finally, we show that the established early warning indicators are oblivious to limit-induced bifurcations and, in the case of the power system model considered here, only react to an approaching Hopf bifurcation.

  2. Leverage bubble

    Science.gov (United States)

    Yan, Wanfeng; Woodard, Ryan; Sornette, Didier

    2012-01-01

    Leverage is strongly related to liquidity in a market and lack of liquidity is considered a cause and/or consequence of the recent financial crisis. A repurchase agreement is a financial instrument where a security is sold simultaneously with an agreement to buy it back at a later date. Repurchase agreement (repo) market size is a very important element in calculating the overall leverage in a financial market. Therefore, studying the behavior of repo market size can help to understand a process that can contribute to the birth of a financial crisis. We hypothesize that herding behavior among large investors led to massive over-leveraging through the use of repos, resulting in a bubble (built up over the previous years) and subsequent crash in this market in early 2008. We use the Johansen-Ledoit-Sornette (JLS) model of rational expectation bubbles and behavioral finance to study the dynamics of the repo market that led to the crash. The JLS model qualifies a bubble by the presence of characteristic patterns in the price dynamics, called log-periodic power law (LPPL) behavior. We show that there was significant LPPL behavior in the market before that crash and that the predicted range of times predicted by the model for the end of the bubble is consistent with the observations.

  3. Shape/Phase Transitions and Critical Point Symmetries in Atomic Nuclei

    OpenAIRE

    Bonatsos, Dennis

    2008-01-01

    Shape/phase transitions in atomic nuclei have first been discovered in the framework of the Interacting Boson Approximation (IBA) model. Critical point symmetries appropriate for nuclei at the transition points have been introduced as special solutions of the Bohr Hamiltonian, stirring the introduction of additional new solutions describing wide ranges of nuclei. A short review of these recent developments will be attempted.

  4. Detecting critical state before phase transition of complex biological systems by hidden Markov model.

    Science.gov (United States)

    Chen, Pei; Liu, Rui; Li, Yongjun; Chen, Luonan

    2016-07-15

    Identifying the critical state or pre-transition state just before the occurrence of a phase transition is a challenging task, because the state of the system may show little apparent change before this critical transition during the gradual parameter variations. Such dynamics of phase transition is generally composed of three stages, i.e. before-transition state, pre-transition state and after-transition state, which can be considered as three different Markov processes. By exploring the rich dynamical information provided by high-throughput data, we present a novel computational method, i.e. hidden Markov model (HMM) based approach, to detect the switching point of the two Markov processes from the before-transition state (a stationary Markov process) to the pre-transition state (a time-varying Markov process), thereby identifying the pre-transition state or early-warning signals of the phase transition. To validate the effectiveness, we apply this method to detect the signals of the imminent phase transitions of complex systems based on the simulated datasets, and further identify the pre-transition states as well as their critical modules for three real datasets, i.e. the acute lung injury triggered by phosgene inhalation, MCF-7 human breast cancer caused by heregulin and HCV-induced dysplasia and hepatocellular carcinoma. Both functional and pathway enrichment analyses validate the computational results. The source code and some supporting files are available at https://github.com/rabbitpei/HMM_based-method lnchen@sibs.ac.cn or liyj@scut.edu.cn Supplementary data are available at Bioinformatics online. © The Author 2016. Published by Oxford University Press. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com.

  5. Transition from Critical Ontology To Metaphysical Foundations of Natural Science

    Directory of Open Access Journals (Sweden)

    Juan Csno De Pablo

    2015-03-01

    Full Text Available The Critique of Pure Reason out lines an a priori ontology of nature. We find in the Critique the category of substance, which is totally a priori. However, the metaphysical principles of natural science come from the notion of matter, which is empirical. This article shows the transition carried out by Kant between two areas of knowledge. For this purpose, we will relate two Kantian texts: Prologomena to Any Future Metaphysics Which Shall Lay Claim to Being a Science and Metaphysical Foundations of Natural Science.

  6. Transitions through critical temperatures in nematic liquid crystals

    KAUST Repository

    Majumdar, Apala

    2013-08-06

    We obtain estimates for critical nematic liquid crystal (LC) temperatures under the action of a slowly varying temperature-dependent control variable. We show that biaxiality has a negligible effect within our model and that these delay estimates are well described by a purely uniaxial model. The static theory predicts two critical temperatures: the supercooling temperature below which the isotropic phase loses stability and the superheating temperature above which the ordered nematic states do not exist. In contrast to the static problem, the isotropic phase exhibits a memory effect below the supercooling temperature in the dynamic framework. This delayed loss of stability is independent of the rate of change of temperature and depends purely on the initial value of the temperature. We also show how our results can be used to improve estimates for LC material constants. © 2013 American Physical Society.

  7. Blowing bubbles

    Energy Technology Data Exchange (ETDEWEB)

    Casteel, K.

    1999-04-01

    The article, based on a series of interviews with column flotation equipment suppliers, reviews and comments on the progress of bubble generator design. Developments mentioned include the Air/Water sparger from Cominco, the SparJet and SlamJet from CPT, the CISA sparger from Sevala CISA, Microcel flotation columns from Birtley Engineering, Flotaire column flotation cells from LMC International, and the Variable Gap Sparger from MinnovEX. 1 fig., 2 photo.

  8. Phase Transitions, Geometrothermodynamics, and Critical Exponents of Black Holes with Conformal Anomaly

    Directory of Open Access Journals (Sweden)

    Jie-Xiong Mo

    2014-01-01

    Full Text Available We investigate the phase transitions of black holes with conformal anomaly in canonical ensemble. Some interesting and novel phase transition phenomena have been discovered. It is shown that there are striking differences in both Hawking temperature and phase structure between black holes with conformal anomaly and those without it. Moreover, we probe in detail the dependence of phase transitions on the choice of parameters. The results show that black holes with conformal anomaly have much richer phase structure than those without it. There would be two, only one, or no phase transition points depending on the parameters. The corresponding parameter regions are derived both numerically and graphically. Geometrothermodynamics are built up to examine the phase structure we have discovered. It is shown that Legendre invariant thermodynamic scalar curvature diverges exactly where the specific heat diverges. Furthermore, critical behaviors are investigated by calculating the relevant critical exponents. And we prove that these critical exponents satisfy the thermodynamic scaling laws.

  9. Critical Behavior at the L-L Phase Transition of Lysozyme Protein Solutions

    Science.gov (United States)

    Gorti, Sridhar; Forsythe, Elizabeth; Laxson, Nicole; Pusey, Marc

    2003-01-01

    Recent efforts suggest the possibility that crystallization, and liquid-liquid (L-L) phase transitions and critical phenomena are characteristics universal to all macromolecular solutions. Of particular interest to protein crystallographers are the predictions of a critical slowing of crystal growth and subsequent formation of nascent crystals at the L-L phase boundary. Herein, the effects of the L-L phase transition on both crystal growth rates and microcrystal formation are experimentally determined. In general, it was determined that critical slowing down of protein crystal growth rates occurred, as predicted. The L-L phase transition, however, had a net negative influence in the formation of nascent protein crystals. Although crystal nucleation was not induced by the L-L phase transition, it is considered that the phase behavior of macromolecular solutions can be universally defined.

  10. Ethics and culture dialogic: transit critical-reflective in education

    Directory of Open Access Journals (Sweden)

    Marcos Alexandre Alves

    2014-06-01

    Full Text Available This paper shows that there is not ethically neutral education. In the process of forming an individual it becomes impossible to separate the issue of education from a set of ethical attributes. This paper examines the issue of (co relation between ethics and education, in order to discuss the nature and function of the educational act, considering the implications and results in the formation of the individual. It argues that it is up to the educator to develop critical-reflexive dimension, exploring themes of motivation and proximity to the real conditions of existential and experiential learners, prompt the mentality of the research and the pursuit of knowledge autonomously, demonstrate the causes and reasons of oppression, motivate dialogue and hear what the students have to say and take their ethical responsibility to citizenship clarified.

  11. Quantum critical matter. Quantum phase transitions with multiple dynamics and Weyl superconductors

    International Nuclear Information System (INIS)

    Meng, Tobias

    2012-01-01

    In this PhD thesis, the physics of quantum critical matter and exotic quantum state close to quantum phase transitions is investigated. We will focus on three different examples that highlight some of the interesting phenomena related to quantum phase transitions. Firstly, we discuss the physics of quantum phase transitions in quantum wires as a function of an external gate voltage when new subbands are activated. We find that at these transitions, strong correlations lead to the formation of an impenetrable gas of polarons, and identify criteria for possible instabilities in the spin- and charge sectors of the model. Our analysis is based on the combination of exact resummations, renormalization group techniques and Luttinger liquid approaches. Secondly, we turn to the physics of multiple divergent time scales close to a quantum critical point. Using an appropriately generalized renormalization group approach, we identify that the presence of multiple dynamics at a quantum phase transition can lead to the emergence of new critical scaling exponents and thus to the breakdown of the usual scaling schemes. We calculate the critical behavior of various thermodynamic properties and detail how unusual physics can arise. It is hoped that these results might be helpful for the interpretation of experimental scaling puzzles close to quantum critical points. Thirdly, we turn to the physics of topological transitions, and more precisely the physics of Weyl superconductors. The latter are the superconducting variant of the topologically non-trivial Weyl semimetals, and emerge at the quantum phase transition between a topological superconductor and a normal insulator upon perturbing the transition with a time reversal symmetry breaking perturbation, such as magnetism. We characterize the topological properties of Weyl superconductors and establish a topological phase diagram for a particular realization in heterostructures. We discuss the physics of vortices in Weyl

  12. Critical current anomaly at the topological quantum phase transition in a Majorana Josephson junction

    Energy Technology Data Exchange (ETDEWEB)

    Huang, Hong [School of Physics, Sun Yat-sen University, Guangzhou 510275 (China); Liang, Qi-Feng [Department of Physics, Shaoxing University, Shaoxing 312000 (China); Yao, Dao-Xin, E-mail: yaodaox@mail.sysu.edu.cn [School of Physics, Sun Yat-sen University, Guangzhou 510275 (China); Wang, Zhi, E-mail: physicswangzhi@gmail.com [School of Physics, Sun Yat-sen University, Guangzhou 510275 (China)

    2017-06-28

    Majorana bound states in topological Josephson junctions induce a 4π period current-phase relation. Direct detection of the 4π periodicity is complicated by the quasiparticle poisoning. We reveal that Majorana bound states are also signaled by the anomalous enhancement on the critical current of the junction. We show the landscape of the critical current for a nanowire Josephson junction under a varying Zeeman field, and reveal a sharp step feature at the topological quantum phase transition point, which comes from the anomalous enhancement of the critical current at the topological regime. In multi-band wires, the anomalous enhancement disappears for an even number of bands, where the Majorana bound states fuse into Andreev bound states. This anomalous critical current enhancement directly signals the existence of the Majorana bound states, and also provides a valid signature for the topological quantum phase transition. - Highlights: • We introduce the critical current step as a signal for the topological quantum phase transition. • We study the quantum phase transition in the topological nanowire under a rotating Zeeman field. • We show that the critical current anomaly gradually disappears for systems with more sub-bands.

  13. Bubble bath soap poisoning

    Science.gov (United States)

    ... medlineplus.gov/ency/article/002762.htm Bubble bath soap poisoning To use the sharing features on this page, please enable JavaScript. Bubble bath soap poisoning occurs when someone swallows bubble bath soap. ...

  14. A universal indicator of critical state transitions in noisy complex networked systems.

    Science.gov (United States)

    Liang, Junhao; Hu, Yanqing; Chen, Guanrong; Zhou, Tianshou

    2017-02-23

    Critical transition, a phenomenon that a system shifts suddenly from one state to another, occurs in many real-world complex networks. We propose an analytical framework for exactly predicting the critical transition in a complex networked system subjected to noise effects. Our prediction is based on the characteristic return time of a simple one-dimensional system derived from the original higher-dimensional system. This characteristic time, which can be easily calculated using network data, allows us to systematically separate the respective roles of dynamics, noise and topology of the underlying networked system. We find that the noise can either prevent or enhance critical transitions, playing a key role in compensating the network structural defect which suffers from either internal failures or environmental changes, or both. Our analysis of realistic or artificial examples reveals that the characteristic return time is an effective indicator for forecasting the sudden deterioration of complex networks.

  15. Discrete Bubble Modeling for Cavitation Bubbles

    Science.gov (United States)

    Choi, Jin-Keun; Chahine, Georges; Hsiao, Chao-Tsung

    2007-03-01

    Dynaflow, Inc. has conducted extensive studies on non-spherical bubble dynamics and interactions with solid and free boundaries, vortical flow structures, and other bubbles. From these studies, emerged a simplified Surface Averaged Pressure (SAP) spherical bubble dynamics model and a Lagrangian bubble tracking scheme. In this SAP scheme, the pressure and velocity of the surrounding flow field are averaged on the bubble surface, and then used for the bubble motion and volume dynamics calculations. This model is implemented using the Fluent User Defined Function (UDF) as Discrete Bubble Model (DBM). The Bubble dynamics portion can be solved using an incompressible liquid modified Rayleigh-Plesset equation or a compressible liquid modified Gilmore equation. The Discrete Bubble Model is a very suitable tool for the studies on cavitation inception of foils and turbo machinery, bubble nuclei effects, noise from the bubbles, and can be used in many practical problems in industrial and naval applications associated with flows in pipes, jets, pumps, propellers, ships, and the ocean. Applications to propeller cavitation, wake signatures of waterjet propelled ships, bubble-wake interactions, modeling of cavitating jets, and bubble entrainments around a ship will be presented.

  16. Self-organized criticality in sandpiles - Nature of the critical phenomenon. [dynamic models in phase transition

    Science.gov (United States)

    Carlson, J. M.; Chayes, J. T.; Swindle, G. H.; Grannan, E. R.

    1990-01-01

    The scaling behavior of sandpile models is investigated analytically. First, it is shown that sandpile models contain a set of domain walls, referred to as troughs, which bound regions that can experience avalanches. It is further shown that the dynamics of the troughs is governed by a simple set of rules involving birth, death, and coalescence events. A simple trough model is then introduced, and it is proved that the model has a phase transition with the density of the troughs as an order parameter and that, in the thermodynamic limit, the trough density goes to zero at the transition point. Finally, it is shown that the observed scaling behavior is a consequence of finite-size effects.

  17. Soliton bubbles and phase transformations

    International Nuclear Information System (INIS)

    Masperi, L.

    1989-01-01

    It is shown that no topological classical solutions in form of bubbles of a real scalar field theory with Lagrangian of quartet and sextet self interactions in 1+1 dimensions are responsible to discontinue transitions in the quantum problem between phases with degenerated and disordered excited level. (M.C.K.)

  18. Bubbles & Squat

    DEFF Research Database (Denmark)

    Højbjerre Larsen, Signe

    Years Eve they arranged a similar event, and on their facebook event they wrote that ‘Your last training in 2016 might as well be a party’. The concept has been popular, and in the spring of 2017 it evolved into similar events such as ‘Cocktails & Kettlebells’. Our paper aims to contribute......In Denmark a new fitness chain has seen the light of day. It is called Repeat and on their facebook page it is presented as “A new breed of fitness. Metropolitan environment. Flexible terms & prices. Join the revolution.” As part of this ‘fitness revolution’ they introduced, in the autumn of 2016......, a new concept called ‘Bubbles & Squat’, where fitness training is combined with Champagne and a live DJ. One of the invitations for this event describes how “we spice up your friday training with live DJ and lots of refreshing bubbles, to make sure that you are ready for the weekend (...).” Before New...

  19. Assessing the dynamic material criticality of infrastructure transitions: A case of low carbon electricity

    International Nuclear Information System (INIS)

    Roelich, Katy; Dawson, David A.; Purnell, Phil; Knoeri, Christof; Revell, Ruairi; Busch, Jonathan; Steinberger, Julia K.

    2014-01-01

    Highlights: • We present a method to analyse material criticality of infrastructure transitions. • Criticality is defined as the potential for, and exposure to, supply disruption. • Our method is dynamic reducing the probability of lock-in to at-risk technologies. • We show that supply disruption potential is reducing but exposure is increasing. - Abstract: Decarbonisation of existing infrastructure systems requires a dynamic roll-out of technology at an unprecedented scale. The potential disruption in supply of critical materials could endanger such a transition to low-carbon infrastructure and, by extension, compromise energy security more broadly because low carbon technologies are reliant on these materials in a way that fossil-fuelled energy infrastructure is not. Criticality is currently defined as the combination of the potential for supply disruption and the exposure of a system of interest to that disruption. We build on this definition and develop a dynamic approach to quantifying criticality, which monitors the change in criticality during the transition towards a low-carbon infrastructure goal. This allows us to assess the relative risk of different technology pathways to reach a particular goal and reduce the probability of being ‘locked in’ to currently attractive but potentially future-critical technologies. To demonstrate, we apply our method to criticality of the proposed UK electricity system transition, with a focus on neodymium. We anticipate that the supply disruption potential of neodymium will decrease by almost 30% by 2050; however, our results show the criticality of low carbon electricity production increases ninefold over this period, as a result of increasing exposure to neodymium-reliant technologies

  20. Several Indicators of Critical Transitions for Complex Diseases Based on Stochastic Analysis.

    Science.gov (United States)

    Wang, Gang; Li, Yuanyuan; Zou, Xiufen

    2017-01-01

    Many complex diseases (chronic disease onset, development and differentiation, self-assembly, etc.) are reminiscent of phase transitions in a dynamical system: quantitative changes accumulate largely unnoticed until a critical threshold is reached, which causes abrupt qualitative changes of the system. Understanding such nonlinear behaviors is critical to dissect the multiple genetic/environmental factors that together shape the genetic and physiological landscape underlying basic biological functions and to identify the key driving molecules. Based on stochastic differential equation (SDE) model, we theoretically derive three statistical indicators, that is, coefficient of variation (CV), transformed Pearson's correlation coefficient (TPC), and transformed probability distribution (TPD), to identify critical transitions and detect the early-warning signals of the phase transition in complex diseases. To verify the effectiveness of these early-warning indexes, we use high-throughput data for three complex diseases, including influenza caused by either H3N2 or H1N1 and acute lung injury, to extract the dynamical network biomarkers (DNBs) responsible for catastrophic transition into the disease state from predisease state. The numerical results indicate that the derived indicators provide a data-based quantitative analysis for early-warning signals for critical transitions in complex diseases or other dynamical systems.

  1. Phase Transitions towards Criticality in a Neural System with Adaptive Interactions

    Science.gov (United States)

    Levina, Anna; Herrmann, J. Michael; Geisel, Theo

    2009-03-01

    We analytically describe a transition scenario to self-organized criticality (SOC) that is new for physics as well as neuroscience; it combines the criticality of first and second-order phase transitions with a SOC phase. We consider a network of pulse-coupled neurons interacting via dynamical synapses, which exhibit depression and facilitation as found in experiments. We analytically show the coexistence of a SOC phase and a subcritical phase connected by a cusp bifurcation. Switching between the two phases can be triggered by varying the intensity of noisy inputs.

  2. Critical nonequilibrium relaxation in cluster algorithms in the BKT and weak first-order phase transitions

    Science.gov (United States)

    Nonomura, Yoshihiko; Tomita, Yusuke

    Recently we showed that the critical nonequilibrium relaxation in cluster algorithms is widely described by the stretched-exponential decay of physical quantities in the Ising or Heisenberg models. Here we make a similar analysis in the Berezinsky-Kosterlitz-Thouless (BKT) phase transition in the 2D XY model (simple exponential decay) and in the weak first-order phase transition in the 2D q = 5 Potts model (power-law decay), which means that these phase transitions can clearly be characterized by the present analysis. These relaxation behaviors are compared with those in the 3D and 4D XY models (second-order phase transition) and in the 2D q-state Potts models (2 = 6 for strong first-order phase transitions.

  3. STUDENTS’ CRITICAL THINKING IN WRITING A THESIS USING THE TRANSITIVITY SYSTEM

    OpenAIRE

    Emi Emilia

    2016-01-01

    Abstract: Students’ Critical Thinking in Writing a Thesis Using the Transitivity System. This paper reports on a small part of the results of a study in attempting to identify students’ ability and difficulties in writing an English undergraduate thesis in a state university in Indonesia. The paper centres around the students’ ability and difficulties in writing a data presentation and discussion chapter, which are related to critical capacity looked at in this study. The paper begins with a ...

  4. Hilbert-Glass Transition: New Universality of Temperature-Tuned Many-Body Dynamical Quantum Criticality

    Directory of Open Access Journals (Sweden)

    David Pekker

    2014-03-01

    Full Text Available We study a new class of unconventional critical phenomena that is characterized by singularities only in dynamical quantities and has no thermodynamic signatures. One example of such a transition is the recently proposed many-body localization-delocalization transition, in which transport coefficients vanish at a critical temperature with no singularities in thermodynamic observables. Describing this purely dynamical quantum criticality is technically challenging as understanding the finite-temperature dynamics necessarily requires averaging over a large number of matrix elements between many-body eigenstates. Here, we develop a real-space renormalization group method for excited states that allows us to overcome this challenge in a large class of models. We characterize a specific example: the 1 D disordered transverse-field Ising model with generic interactions. While thermodynamic phase transitions are generally forbidden in this model, using the real-space renormalization group method for excited states we find a finite-temperature dynamical transition between two localized phases. The transition is characterized by nonanalyticities in the low-frequency heat conductivity and in the long-time (dynamic spin correlation function. The latter is a consequence of an up-down spin symmetry that results in the appearance of an Edwards-Anderson-like order parameter in one of the localized phases.

  5. Critical Time Intervention for Homeless People Making the Transition to Community Living: A Randomized Controlled Trial

    NARCIS (Netherlands)

    Vet, R. de; Beijersbergen, M.D.; Jonker, I.E.; Lako, D.A.M.; Hemert, A.M. van; Herman, D.B.; Wolf, J.R.L.M.

    2017-01-01

    To help create an evidence base in Europe for effective interventions that improve the well-being of homeless people, we tested whether critical time intervention (CTI), a time-limited intervention developed to support vulnerable people during times of transition, is effective outside the United

  6. Critical exponents in the transition to chaos in one-dimensional ...

    Indian Academy of Sciences (India)

    We report the numerically evaluated critical exponents associated with the scaling of generalized fractal dimensions during the transition from order to chaos. The analysis is carried out in detail in the context of unimodal and bimodal maps representing typical one-dimensional discrete dynamical systems. The behavior of ...

  7. Study of near-critical states of liquid-vapor phase transition of magnesium

    International Nuclear Information System (INIS)

    Emelyanov, A N; Shakhray, D V; Golyshev, A A

    2015-01-01

    Study of thermodynamic parameters of magnesium in the near-critical point region of the liquid-vapor phase transition and in the region of metal-nonmetal transition was carried out. Measurements of the electrical resistance of magnesium after shock compression and expansion into gas (helium) environment in the process of isobaric heating was carried out. Heating of the magnesium surface by heat transfer with hot helium was performed. The registered electrical resistance of expanded magnesium was about 10 4 -10 5 times lower than the electrical resistance of the magnesium under normal condition at the density less than the density of the critical point. Thus, metal-nonmetal transition was found in magnesium. (paper)

  8. Phase transitions, nonequilibrium dynamics, and critical behavior of strongly interacting systems

    Energy Technology Data Exchange (ETDEWEB)

    Mottola, E.; Bhattacharya, T.; Cooper, F. [and others

    1998-12-31

    This is the final report of a three-year, Laboratory Directed Research and Development project at Los Alamos National Laboratory. In this effort, large-scale simulations of strongly interacting systems were performed and a variety of approaches to the nonequilibrium dynamics of phase transitions and critical behavior were investigated. Focus areas included (1) the finite-temperature quantum chromodynamics phase transition and nonequilibrium dynamics of a new phase of matter (the quark-gluon plasma) above the critical temperature, (2) nonequilibrium dynamics of a quantum fields using mean field theory, and (3) stochastic classical field theoretic models with applications to spinodal decomposition and structural phase transitions in a variety of systems, such as spin chains and shape memory alloys.

  9. Early-warning signals of critical transition: Effect of extrinsic noise

    Science.gov (United States)

    Qin, Shanshan; Tang, Chao

    2018-03-01

    Complex dynamical systems often have tipping points and exhibit catastrophic regime shift. Despite the notorious difficulty of predicting such transitions, accumulating studies have suggested the existence of generic early-warning signals (EWSs) preceding upcoming transitions. However, previous theories and models were based on the effect of the intrinsic noise (IN) when a system is approaching a critical point, and did not consider the pervasive environmental fluctuations or the extrinsic noise (EN). Here, we extend previous theory to investigate how the interplay of EN and IN affects EWSs. Stochastic simulations of model systems subject to both IN and EN have verified our theory and demonstrated that EN can dramatically alter and diminish the EWS. This effect is stronger with increasing amplitude and correlation time scale of the EN. In the presence of EN, the EWS can fail to predict or even give a false alarm of critical transitions.

  10. The use of spatio-temporal correlation to forecast critical transitions

    Science.gov (United States)

    Karssenberg, Derek; Bierkens, Marc F. P.

    2010-05-01

    Complex dynamical systems may have critical thresholds at which the system shifts abruptly from one state to another. Such critical transitions have been observed in systems ranging from the human body system to financial markets and the Earth system. Forecasting the timing of critical transitions before they are reached is of paramount importance because critical transitions are associated with a large shift in dynamical regime of the system under consideration. However, it is hard to forecast critical transitions, because the state of the system shows relatively little change before the threshold is reached. Recently, it was shown that increased spatio-temporal autocorrelation and variance can serve as alternative early warning signal for critical transitions. However, thus far these second order statistics have not been used for forecasting in a data assimilation framework. Here we show that the use of spatio-temporal autocorrelation and variance in the state of the system reduces the uncertainty in the predicted timing of critical transitions compared to classical approaches that use the value of the system state only. This is shown by assimilating observed spatio-temporal autocorrelation and variance into a dynamical system model using a Particle Filter. We adapt a well-studied distributed model of a logistically growing resource with a fixed grazing rate. The model describes the transition from an underexploited system with high resource biomass to overexploitation as grazing pressure crosses the critical threshold, which is a fold bifurcation. To represent limited prior information, we use a large variance in the prior probability distributions of model parameters and the system driver (grazing rate). First, we show that the rate of increase in spatio-temporal autocorrelation and variance prior to reaching the critical threshold is relatively consistent across the uncertainty range of the driver and parameter values used. This indicates that an increase in

  11. Speculative bubbles and crashes in stock markets: an interacting-agent model of speculative activity

    Science.gov (United States)

    Kaizoji, Taisei

    2000-12-01

    In this paper, we present an interacting-agent model of speculative activity explaining bubbles and crashes in stock markets. We describe stock markets through an infinite-range Ising model to formulate the tendency of traders getting influenced by the investment attitude of other traders. Bubbles and crashes are understood and described qualitatively and quantitatively in terms of the classical phase transitions. When the interactions among traders become stronger and reach some critical values, a second-order phase transition and critical behavior can be observed, and a bull market phase and a bear market phase appear. When the system stays at the bull market phase, speculative bubbles occur in the stock market. For a certain range of the investment environment (the external field), multistability and hysteresis phenomena are observed. When the investment environment reaches some critical values, the rapid changes (the first-order phase transitions) in the distribution of investment attitude are caused. The phase transition from a bull market phase to a bear market phase is considered as a stock market crash. Furthermore, we estimate the parameters of the model using the actual financial data. As an example of large crashes we analyze Japan crisis (the bubble and the subsequent crash in the Japanese stock market in 1987-1992), and show that the good quality of the fits, as well as the consistency of the parameter values are obtained from Japan crisis. The results of the empirical study demonstrate that Japan crisis can be explained quite naturally by the model that bubbles and crashes have their origin in the collective crowd behavior of many interacting agents.

  12. Magnetic-field control of quantum critical points of valence transition.

    Science.gov (United States)

    Watanabe, Shinji; Tsuruta, Atsushi; Miyake, Kazumasa; Flouquet, Jacques

    2008-06-13

    We study the mechanism of how critical end points of first-order valence transitions are controlled by a magnetic field. We show that the critical temperature is suppressed to be a quantum critical point (QCP) by a magnetic field, and unexpectedly, the QCP exhibits nonmonotonic field dependence in the ground-state phase diagram, giving rise to the emergence of metamagnetism even in the intermediate valence-crossover regime. The driving force of the field-induced QCP is clarified to be cooperative phenomena of the Zeeman and Kondo effects, which create a distinct energy scale from the Kondo temperature. This mechanism explains the peculiar magnetic response in CeIrIn(5) and the metamagnetic transition in YbXCu(4) for X=In as well as the sharp contrast between X=Ag and Cd.

  13. On the critical behavior of the inverse susceptibility of a model of structural phase transitions

    International Nuclear Information System (INIS)

    Pisanova, E.S.; Ivanov, S.I.

    2013-01-01

    An exactly solvable lattice model describing structural phase transitions in an anharmonic crystal with long-range interaction is considered in the neighborhoods of the quantum and classical critical points at the corresponding upper critical dimensions. In a broader neighborhood of the critical region the inverse susceptibility of the model is exactly calculated in terms of the Lambert W-function and graphically presented as a function of the deviation from the critical point and the upper critical dimension. For quantum and classical systems with real physical dimensions (chains, thin layers and three-dimensional systems) the exact results are compared with the asymptotic ones on the basis of some numerical data for their ratio. Relative errors are also provided

  14. Search for signatures of phase transition and critical point in heavy ion collisions

    International Nuclear Information System (INIS)

    Tokarev, M.V.; Kechechyan, A.; Alakhverdyants, A.; Zborovsky, I.

    2011-01-01

    The general concepts in the critical phenomena related with the notions of 'scaling' and 'universality' are considered. Behavior of various systems near a phase transition is displayed. Search for clear signatures of the phase transition of the nuclear matter and location of the critical point in heavy ion collisions (HIC) is discussed. The experimental data on inclusive spectra measured in HIC at RHIC and SPS over a wide range of energies s NN 1/2 = 9-200 GeV are analyzed in the framework of z-scaling. A microscopic scenario of the constituent interactions is presented. Dependence of the energy loss on the momentum of the produced hadron, energy and centrality of the collision is studied. Self-similarity of the constituent interactions described in terms of momentum fractions is used to characterize the nuclear medium by 'specific heat' and colliding nuclei by fractal dimensions. Preferable kinematical regions to search for signatures of the phase transition of the nuclear matter produced in HIC are discussed. Discontinuity of the 'specific heat' is assumed to be a signature of the phase transition and the critical point

  15. Phase transitions and self-organized criticality in networks of stochastic spiking neurons

    Science.gov (United States)

    Brochini, Ludmila; de Andrade Costa, Ariadne; Abadi, Miguel; Roque, Antônio C.; Stolfi, Jorge; Kinouchi, Osame

    2016-11-01

    Phase transitions and critical behavior are crucial issues both in theoretical and experimental neuroscience. We report analytic and computational results about phase transitions and self-organized criticality (SOC) in networks with general stochastic neurons. The stochastic neuron has a firing probability given by a smooth monotonic function Φ(V) of the membrane potential V, rather than a sharp firing threshold. We find that such networks can operate in several dynamic regimes (phases) depending on the average synaptic weight and the shape of the firing function Φ. In particular, we encounter both continuous and discontinuous phase transitions to absorbing states. At the continuous transition critical boundary, neuronal avalanches occur whose distributions of size and duration are given by power laws, as observed in biological neural networks. We also propose and test a new mechanism to produce SOC: the use of dynamic neuronal gains - a form of short-term plasticity probably located at the axon initial segment (AIS) - instead of depressing synapses at the dendrites (as previously studied in the literature). The new self-organization mechanism produces a slightly supercritical state, that we called SOSC, in accord to some intuitions of Alan Turing.

  16. Phase transitions and self-organized criticality in networks of stochastic spiking neurons.

    Science.gov (United States)

    Brochini, Ludmila; de Andrade Costa, Ariadne; Abadi, Miguel; Roque, Antônio C; Stolfi, Jorge; Kinouchi, Osame

    2016-11-07

    Phase transitions and critical behavior are crucial issues both in theoretical and experimental neuroscience. We report analytic and computational results about phase transitions and self-organized criticality (SOC) in networks with general stochastic neurons. The stochastic neuron has a firing probability given by a smooth monotonic function Φ(V) of the membrane potential V, rather than a sharp firing threshold. We find that such networks can operate in several dynamic regimes (phases) depending on the average synaptic weight and the shape of the firing function Φ. In particular, we encounter both continuous and discontinuous phase transitions to absorbing states. At the continuous transition critical boundary, neuronal avalanches occur whose distributions of size and duration are given by power laws, as observed in biological neural networks. We also propose and test a new mechanism to produce SOC: the use of dynamic neuronal gains - a form of short-term plasticity probably located at the axon initial segment (AIS) - instead of depressing synapses at the dendrites (as previously studied in the literature). The new self-organization mechanism produces a slightly supercritical state, that we called SOSC, in accord to some intuitions of Alan Turing.

  17. Magnet Lab Highlight: Upper critical field reaches 90 tesla near the Mott transition in fulleride superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Mcdonald, Ross David [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2017-06-05

    The alkali-doped fullerides provide the first example of a transition from a three-dimensional Mott insulator to a superconductor, enabling the effects of both dimensionality and electron correlation on superconductivity to be explored. Chemically the alkali species tunes the superconductivity in the vicinity of the the Mott transition via sample volume. Measuring the relationship between the superconducting transition temperature and upper critical field reveals a crossover from weak- to strong-coupling associated with the dynamical Jahn–Teller effect as the Mott transition is approached. The use of pulsed magnets is required because the upper critical field is enhanced in the vicinity of the Mott insulating phase, reaching 90 T for RbxCs3-xC60 — the highest among cubic crystals. This required close collaboration between Prof Kasahara’s group and the Mag Lab to design rf-measurements compatible with sample encapsulation in an inert atmosphere. The concomitant increase of pairing strength with lattice volume near the Mott transition suggest that the cooperative interplay between molecular electronic structure and strong electron correlations plays a key role in realizing robust superconductivity (with high-TC and high-HC2).

  18. Scaling, phase transitions, and nonuniversality in a self-organized critical cellular-automaton model

    International Nuclear Information System (INIS)

    Christensen, K.; Olami, Z.

    1992-01-01

    We present a two-dimensional continuous cellular automaton that is equivalent to a driven spring-block model. Both the conservation and the anisotropy in the model are controllable quantities. Above a critical level of conservation, the model exhibits self-organized criticality. The self-organization of this system and hence the critical exponents depend on the conservation and the boundary conditions. In the critical isotropic nonconservative phase, the exponents change continuously as a function of conservation. Furthermore, the exponents vary continuously when changing the boundary conditions smoothly. Consequently, there is no universality of the critical exponents. We discuss the relevance of this for earthquakes. Introducing anisotropy changes the scaling of the distribution function, but not the power-law exponent. We explore the phase diagram of this model. We find that at low conservation levels a localization transition occurs. We see two additional phase transitions. The first is seen when moving from the conservative into the nonconservative model. The second appears when passing from the anisotropic two-dimensional system to the purely one-dimensional system

  19. Critical transitions in chronic disease: transferring concepts from ecology to systems medicine.

    Science.gov (United States)

    Trefois, Christophe; Antony, Paul M A; Goncalves, Jorge; Skupin, Alexander; Balling, Rudi

    2015-08-01

    Ecosystems and biological systems are known to be inherently complex and to exhibit nonlinear dynamics. Diseases such as microbiome dysregulation or depression can be seen as complex systems as well and were shown to exhibit patterns of nonlinearity in their response to perturbations. These nonlinearities can be revealed by a sudden shift in system states, for instance from health to disease. The identification and characterization of early warning signals which could predict upcoming critical transitions is of primordial interest as prevention of disease onset is a major aim in health care. In this review, we focus on recent evidence for critical transitions in diseases and discuss the potential of such studies for therapeutic applications. Copyright © 2014 The Authors. Published by Elsevier Ltd.. All rights reserved.

  20. Probing Critical Point Energies of Transition Metal Dichalcogenides: Surprising Indirect Gap of Single Layer WSe 2

    KAUST Repository

    Zhang, Chendong

    2015-09-21

    By using a comprehensive form of scanning tunneling spectroscopy, we have revealed detailed quasi-particle electronic structures in transition metal dichalcogenides, including the quasi-particle gaps, critical point energy locations, and their origins in the Brillouin zones. We show that single layer WSe surprisingly has an indirect quasi-particle gap with the conduction band minimum located at the Q-point (instead of K), albeit the two states are nearly degenerate. We have further observed rich quasi-particle electronic structures of transition metal dichalcogenides as a function of atomic structures and spin-orbit couplings. Such a local probe for detailed electronic structures in conduction and valence bands will be ideal to investigate how electronic structures of transition metal dichalcogenides are influenced by variations of local environment.

  1. Critical exponents in the transition to chaos in one-dimensional ...

    Indian Academy of Sciences (India)

    obey the relation λ. µ µ∞ ν. (1) where µ∞ is the value of the control parameter µ at the Feigenbaum point or accumulation point of period doubling transitions andν is the associated critical exponent. In the context of unimodal maps like the logistic map,ν is given by the Huberman–Rudnick (HR) relation ν(z) = ln 2 ln δ(z). (2).

  2. Dynamics of bubbles in general relativity

    International Nuclear Information System (INIS)

    Berezin, V.A.; Kuzmin, V.A.; Tkachev, I.I.

    1987-01-01

    This is a systematic study of the evolution of thin shell bubbles in general relativity. We develop the general thin-wall formalism first elaborated by Israel and apply it to the investigation of the motion of various bubbles arising in the course of phase transitions in the very early Universe including new phase bubbles, old phase remnants, and domains. We consider metric junction conditions and derive constraints both on the decay of metastable states and on the evolution of non- equilibrium scalar field configurations (fluctuations) following from the global geometry of spacetime

  3. Primordial black hole formation by vacuum bubbles

    Science.gov (United States)

    Deng, Heling; Vilenkin, Alexander

    2017-12-01

    Vacuum bubbles may nucleate during the inflationary epoch and expand, reaching relativistic speeds. After inflation ends, the bubbles are quickly slowed down, transferring their momentum to a shock wave that propagates outwards in the radiation background. The ultimate fate of the bubble depends on its size. Bubbles smaller than certain critical size collapse to ordinary black holes, while in the supercritical case the bubble interior inflates, forming a baby universe, which is connected to the exterior region by a wormhole. The wormhole then closes up, turning into two black holes at its two mouths. We use numerical simulations to find the masses of black holes formed in this scenario, both in subcritical and supercritical regime. The resulting mass spectrum is extremely broad, ranging over many orders of magnitude. For some parameter values, these black holes can serve as seeds for supermassive black holes and may account for LIGO observations.

  4. Critical behavior in reaction-diffusion systems exhibiting absorbing phase transition

    CERN Document Server

    Ódor, G

    2003-01-01

    Phase transitions of reaction-diffusion systems with site occupation restriction and with particle creation that requires n>1 parents and where explicit diffusion of single particles (A) exists are reviewed. Arguments based on mean-field approximation and simulations are given which support novel kind of non-equilibrium criticality. These are in contradiction with the implications of a suggested phenomenological, multiplicative noise Langevin equation approach and with some of recent numerical analysis. Simulation results for the one and two dimensional binary spreading 2A -> 4A, 4A -> 2A model display a new type of mean-field criticality characterized by alpha=1/3 and beta=1/2 critical exponents suggested in cond-mat/0210615.

  5. Critical temperature transition of an interacting Boson-Fermion mixture gas

    International Nuclear Information System (INIS)

    Nguyen Tuan Anh

    2007-01-01

    We study the self-consistent theory of Bose-Einstein condensation in the dilute interacting boson-fermion mixture gas at finite temperature. First, we generalize the idea of the theory using the 2PI effective action formalism. Second, we show the effects of repulsive interactions on the critical temperature for the Bose-Einstein transition. The calculations provide the lowest order correction of the critical temperature (at constant density) by a positive amount proportional to the scattering length a bf and the fermion density n f . The change of the critical temperature yields T c ≅ T 0 + c 1 .a bf /m bf .n f , with c 1 = 2.342. (author)

  6. Fama on Bubbles

    DEFF Research Database (Denmark)

    Engsted, Tom

    2016-01-01

    While Eugene Fama has repeatedly expressed his discontent with the notion of an “irrational bubble,” he has never publicly expressed his opinion on “rational bubbles.” On empirical grounds Fama rejects bubbles by referring to the lack of reliable evidence that price declines are predictable...

  7. Fama on bubbles

    DEFF Research Database (Denmark)

    Engsted, Tom

    . On empirical grounds Fama rejects bubbles by referring to the lack of reliable evidence that price declines are predictable. However, this argument cannot be used to rule out rational bubbles because such bubbles do not necessarily imply return predictability. On data samples that include the 1990s...

  8. Merger transitions in brane-black-hole systems: Criticality, scaling, and self-similarity

    International Nuclear Information System (INIS)

    Frolov, Valeri P.

    2006-01-01

    We propose a toy model for studying merger transitions in a curved spacetime with an arbitrary number of dimensions. This model includes a bulk N-dimensional static spherically symmetric black hole and a test D-dimensional brane (D≤N-1) interacting with the black hole. The brane is asymptotically flat and allows a O(D-1) group of symmetry. Such a brane-black-hole (BBH) system has two different phases. The first one is formed by solutions describing a brane crossing the horizon of the bulk black hole. In this case the internal induced geometry of the brane describes a D-dimensional black hole. The other phase consists of solutions for branes which do not intersect the horizon, and the induced geometry does not have a horizon. We study a critical solution at the threshold of the brane-black-hole formation, and the solutions which are close to it. In particular, we demonstrate that there exists a striking similarity of the merger transition, during which the phase of the BBH system is changed, both with the Choptuik critical collapse and with the merger transitions in the higher dimensional caged black-hole-black-string system

  9. Critical parameters of Quark-Hadron phase transition with interacting and massive quarks

    International Nuclear Information System (INIS)

    Singh, C.P.; Patra, B.K.

    1994-06-01

    Current techniques to simulate the dynamical behaviour of Quark-Gluon Plasma (QGP) reveal that the order of the phase transition as well as the values of the critical parameters depend on the number of quark flavours as well as on the quark-masses included in the simulation. We attempt to show here the effects of the number of quark flavours and quark-masses on critical parameters by using the perturbative, finite temperature field theory to g 3 s order in the strong coupling g s . We treat the hadrons as particles with finite size and its implications on the equation of state for hadron gas are studied. We find that the critical temperature T c is lowered by 9 MeV as we move from two to three quark flavours. The nature of the phase transition always remains as first order. However, the inclusion of quark-masses in our calculation does not affect the result much. (author). 14 refs, 3 figs

  10. Investigation of shape phase transition in the U(5) ↔ SO(6) transitional region by catastrophe theory and critical exponents of some quantities

    International Nuclear Information System (INIS)

    Fathi, H.; Ghadami, M.; Sabri, H.; Fouladi, N.; Jafarizadeh, M.A.

    2014-01-01

    In this paper, we have analyzed the critical behavior of even–even Ru and Pd isotopes between U(5) and SO(6) limits of interacting boson model via Catastrophe Theory in combination with a coherent state formalism to generate energy surfaces. The parameters of the Hamiltonian are determined via least-square fitting to the experimental data for different Ru and Pd isotopes. Our results suggest a second-order phase transition in these isotopic chains and propose the best candidates for E(5) critical symmetry. Also, the analogy between the critical exponents of ground state quantum phase transition and Landau values for the critical exponents of thermodynamic phase transitions are described. (author)

  11. Critical behaviour of continuous phase transitions with infinitely many absorbing states

    International Nuclear Information System (INIS)

    Hua Dayin; Wang Lieyan; Chen Ting

    2006-01-01

    A lattice gas model is proposed for the A 2 + 2B 2 → 2B 2 A reaction system with particle diffusion. In the model, A 2 dissociates in the random dimer-filling mechanism and B 2 dissociation is in the end-on dimer-filling mechanism. A reactive window appears and the system exhibits a continuous phase transition from a reactive state to a covered state with infinitely many absorbing states. When the diffusion of particle A and AB is included, there are still infinitely many absorbing states for the continuous phase transition, but it is found that the critical behaviour changes from the directed percolation (DP) class to the pair contact process with diffusion (PCPD) class

  12. Cinematic Operation of the Cerebral Cortex Interpreted via Critical Transitions in Self-Organized Dynamic Systems.

    Science.gov (United States)

    Kozma, Robert; Freeman, Walter J

    2017-01-01

    Measurements of local field potentials over the cortical surface and the scalp of animals and human subjects reveal intermittent bursts of beta and gamma oscillations. During the bursts, narrow-band metastable amplitude modulation (AM) patters emerge for a fraction of a second and ultimately dissolve to the broad-band random background activity. The burst process depends on previously learnt conditioned stimuli (CS), thus different AM patterns may emerge in response to different CS. This observation leads to our cinematic theory of cognition when perception happens in discrete steps manifested in the sequence of AM patterns. Our article summarizes findings in the past decades on experimental evidence of cinematic theory of cognition and relevant mathematical models. We treat cortices as dissipative systems that self-organize themselves near a critical level of activity that is a non-equilibrium metastable state. Criticality is arguably a key aspect of brains in their rapid adaptation, reconfiguration, high storage capacity, and sensitive response to external stimuli. Self-organized criticality (SOC) became an important concept to describe neural systems. We argue that transitions from one AM pattern to the other require the concept of phase transitions, extending beyond the dynamics described by SOC. We employ random graph theory (RGT) and percolation dynamics as fundamental mathematical approaches to model fluctuations in the cortical tissue. Our results indicate that perceptions are formed through a phase transition from a disorganized (high entropy) to a well-organized (low entropy) state, which explains the swiftness of the emergence of the perceptual experience in response to learned stimuli.

  13. A Mathematical Framework for Critical Transitions: Normal Forms, Variance and Applications

    Science.gov (United States)

    Kuehn, Christian

    2013-06-01

    Critical transitions occur in a wide variety of applications including mathematical biology, climate change, human physiology and economics. Therefore it is highly desirable to find early-warning signs. We show that it is possible to classify critical transitions by using bifurcation theory and normal forms in the singular limit. Based on this elementary classification, we analyze stochastic fluctuations and calculate scaling laws of the variance of stochastic sample paths near critical transitions for fast-subsystem bifurcations up to codimension two. The theory is applied to several models: the Stommel-Cessi box model for the thermohaline circulation from geoscience, an epidemic-spreading model on an adaptive network, an activator-inhibitor switch from systems biology, a predator-prey system from ecology and to the Euler buckling problem from classical mechanics. For the Stommel-Cessi model we compare different detrending techniques to calculate early-warning signs. In the epidemics model we show that link densities could be better variables for prediction than population densities. The activator-inhibitor switch demonstrates effects in three time-scale systems and points out that excitable cells and molecular units have information for subthreshold prediction. In the predator-prey model explosive population growth near a codimension-two bifurcation is investigated and we show that early-warnings from normal forms can be misleading in this context. In the biomechanical model we demonstrate that early-warning signs for buckling depend crucially on the control strategy near the instability which illustrates the effect of multiplicative noise.

  14. Regularity and chaos at critical points of first-order quantum phase transitions

    International Nuclear Information System (INIS)

    Macek, M.; Leviatan, A.

    2011-01-01

    We study the interplay between regular and chaotic dynamics at the critical point of a generic first-order quantum phase transition in an interacting boson model of nuclei. A classical analysis reveals a distinct behavior of the coexisting phases in a broad energy range. The dynamics is completely regular in the deformed phase and, simultaneously, strongly chaotic in the spherical phase. A quantum analysis of the spectra separates the regular states from the irregular ones, assigns them to particular phases, and discloses persisting regular rotational bands in the deformed region.

  15. Upper critical fields and superconducting transition temperatures of some zirconium-base amorphous transition-metal alloys

    International Nuclear Information System (INIS)

    Karkut, M.G.; Hake, R.R.

    1983-01-01

    Superconducting upper critical fields H/sub c/2(T), transition temperatures T/sub c/, and normal-state electrical resistivities rho/sub n/ have been measured in the amorphous transition-metal alloy series Zr/sub 1-z/Co/sub x/, Zr/sub 1-x/Ni/sub x/, (Zr/sub 1-x/Ti/sub x/)/sub 0.78/Ni/sub 0.22/, and (Zr/sub 1-x/Nb/sub x/)/sub 0.78/Ni/sub 0.22/. Structural integrity of these melt-spun alloys is indicated by x-ray, density, bend-ductility, normal-state electrical resistivity, superconducting transition width, and mixed-state flux-pinning measurements. The specimens display T/sub c/ = 2.1--3.8 K, rho/sub n/ = 159--190 μΩ cm, and Vertical Bar(dH/sub c/2/dT)cVertical Bar = 28--36 kG/K. These imply electron mean free paths lroughly-equal2--6 A, zero-temperature Ginzburg-Landau coherence distances xi/sub G/0roughly-equal50--70 A, penetration depths lambda/sub G/0roughly-equal(7--10) x 10 3 A, and extremely high dirtiness parameters xi 0 /lroughly-equal300--1300. All alloys display H/sub c/2(T) curves with negative curvature and (with two exceptions) fair agreement with the standard dirty-limit theory of Werthamer, Helfand, Hohenberg, and Maki (WHHM) for physically reasonable values of spin-orbit-coupling induced, electron-spin-flip scattering time tau/sub so/. This is in contrast to the anomalously elevated H/sub c/2(T) behavior which is nearly linear in T that is observed by some, and the unphysically low-tau/sub so/ fits to WHHM theory obtained by others, for various amorphous alloys

  16. The Influence of the Distributor Plate on the Bottom Zone of a Fluidized Bed Approaching the Transition from Bubbling to Turbulent Fluidization

    OpenAIRE

    Paiva, J. M.; Pinho, C.; Figueiredo, R.

    2004-01-01

    The dynamics of the bottom zone of a narrow fluidized bed, from bubbling to turbulent regimes, was studied in a cold model of 0.1 m i.d. and 1.3 m high. Tested distributor types were perforated perspex plates, with six different perforation grids, metallic mesh and porous ceramic, with pressures drops ranging from 0.05 to 350 kPa, corresponding to superficial air velocities from 0.1 to 2.3m s-1. Group B silica ballotini, within the range 0.355-0.425 mm, were used as bed material. The experime...

  17. The stability of bubbles formed from supersaturated solutions, and homogeneous nucleation of gas bubbles from solution, both revisited.

    Science.gov (United States)

    Goldman, Saul

    2008-12-25

    The solution of the problem of the relative stability of all possible equilibrium bubble states that can form from a closed, finite, supersaturated gas-liquid solution, maintained at a fixed temperature and a fixed external pressure is given. The supersaturated solution may contain any number of dissolved volatile solutes. The full solution to this problem has remained elusive for decades, because of the complication of pressure inequalities between the bubbles and the constant external (or reservoir) pressure. The method of solution is one that had been used previously to solve the related problem of the stability of a liquid droplet in a supersaturated vapor, where the same complication occurred. The derived equations were found to reduce correctly when simplified; they were consistent with experiment, and the system Gibbs free energy appropriately obeyed the Law of Corresponding States. The expressions were used in the context of transition state theory to provide semiempirical predictions of the rate of homogeneous bubble formation from a supersaturated solution, and the "critical pressure for homogeneous nucleation (P(crit))". The nucleation Gibbs free energy expression derived here had a lower barrier height and resulted in a reduction of P(crit) values, relative to what was obtained from the basis of a pre-existing approximate expression taken from the literature. Applications to chemical engineering and human decompression modeling are briefly described.

  18. Identifying driving gene clusters in complex diseases through critical transition theory

    Science.gov (United States)

    Wolanyk, Nathaniel; Wang, Xujing; Hessner, Martin; Gao, Shouguo; Chen, Ye; Jia, Shuang

    A novel approach of looking at the human body using critical transition theory has yielded positive results: clusters of genes that act in tandem to drive complex disease progression. This cluster of genes can be thought of as the first part of a large genetic force that pushes the body from a curable, but sick, point to an incurable diseased point through a catastrophic bifurcation. The data analyzed is time course microarray blood assay data of 7 high risk individuals for Type 1 Diabetes who progressed into a clinical onset, with an additional larger study requested to be presented at the conference. The normalized data is 25,000 genes strong, which were narrowed down based on statistical metrics, and finally a machine learning algorithm using critical transition metrics found the driving network. This approach was created to be repeatable across multiple complex diseases with only progression time course data needed so that it would be applicable to identifying when an individual is at risk of developing a complex disease. Thusly, preventative measures can be enacted, and in the longer term, offers a possible solution to prevent all Type 1 Diabetes.

  19. Critical space-time networks and geometric phase transitions from frustrated edge antiferromagnetism

    Science.gov (United States)

    Trugenberger, Carlo A.

    2015-12-01

    Recently I proposed a simple dynamical network model for discrete space-time that self-organizes as a graph with Hausdorff dimension dH=4 . The model has a geometric quantum phase transition with disorder parameter (dH-ds) , where ds is the spectral dimension of the dynamical graph. Self-organization in this network model is based on a competition between a ferromagnetic Ising model for vertices and an antiferromagnetic Ising model for edges. In this paper I solve a toy version of this model defined on a bipartite graph in the mean-field approximation. I show that the geometric phase transition corresponds exactly to the antiferromagnetic transition for edges, the dimensional disorder parameter of the former being mapped to the staggered magnetization order parameter of the latter. The model has a critical point with long-range correlations between edges, where a continuum random geometry can be defined, exactly as in Kazakov's famed 2D random lattice Ising model but now in any number of dimensions.

  20. Simulating the phosphorus fluid-liquid phase transition up to the critical point

    International Nuclear Information System (INIS)

    Ghiringhelli, Luca M; Meijer, Evert Jan

    2007-01-01

    We report a Car-Parrinello molecular dynamics study of the temperature dependence of the fluid-liquid phase transition in phosphorous, involving the transformation of a molecular fluid phase into a network-like phase. We employed density-functional theory (DFT) with a gradient-corrected functional (B-LYP) to describe the electronic structure and interatomic interactions and performed simulations in a constant pressure ensemble. We spanned a temperature interval ranging from 2500 to 3500 K. With increasing temperature, we found that the structural conversion from the molecular P 4 fluid into the network liquid occurs at decreasing pressures, consistent with experimental observations. At lower temperatures the transition is characterized by a sudden increase of density in the sample. The magnitude of the density change decreases with increasing temperature and vanishes at 3500 K. In the temperature range 3100-3500 K we found signals of near- and super-criticality. We identified local structural changes that serve as seeds triggering the overall structural transition

  1. The charged bubble oscillator: Dynamics and thresholds

    Indian Academy of Sciences (India)

    of day-to-day medical devices and techniques using ultrasound ... When a pressure wave is incident on the bubble in the liquid .... Dependence of the expansion-compression ratio on the driving pressure amplitude Ps. we will merely cite the result here. We find the critical. Blake radius and the critical liquid pressure to be.

  2. The constructed catchment Chicken Creek as Critical Zone Observatory under transition

    Science.gov (United States)

    Gerwin, Werner; Schaaf, Wolfgang; Elmer, Michael; Hinz, Christoph

    2014-05-01

    The constructed catchment Chicken Creek was established in 2005 as an experimental landscape laboratory for ecosystem research. The 6 ha area with clearly defined horizontal as well as vertical boundary conditions was left for an unrestricted primary succession. All Critical Zone elements are represented at this site, which allows the study of most processes occurring at the interface of bio-, pedo-, geo- and hydrosphere. It provides outstanding opportunities for investigating interactions and feedbacks between different evolving compartments during ecosystem development. The catchment is extensively instrumented since 2005 in order to detect transition stages of the ecosystem. Data recorded with a high spatial and temporal resolution include hydrological, geomorphological, pedological, limnological as well as biological parameters. In contrast to other Critical Zone Observatories, this site offers the unique situation of an early stage ecosystem with highly dynamic system properties. The first years of development were characterized by a fast formation of geomorphological structures due to massive erosion processes at the initially non-vegetated surface. Hydrological processes led to the establishment of a local groundwater body within 5 years. In the following years the influence of biological structures like vegetation patterns gained an increasing importance. Feedbacks between developing vegetation and e.g. hydrological features became more and more dominant. As a result, different phases of ecosystem development could be distinguished until now. This observatory offers manifold possibilities to identify and disentangle complex interactions between Critical Zone processes in situ under natural conditions. The originally low complexity of the system is growing with time facilitating the identification of influences of newly developing structures on system functions. Thus, it is possible to study effects of small-scale processes on the whole system at the

  3. Criticality of the zero-temperature jamming transition probed by self-propelled particles.

    Science.gov (United States)

    Liao, Qinyi; Xu, Ning

    2018-01-31

    We perform simulations of athermal systems of self-propelled particles (SPPs) interacting via harmonic repulsion in the vicinity of the zero-temperature jamming transition at point J. Every particle is propelled by a constant force f pointing to a randomly assigned and fixed direction. When f is smaller than the yield force f y , the system is statically jammed. We find that f y increases with packing fraction and exhibits finite size scaling, implying the criticality of point J. When f > f y , SPPs flow forever and their velocities satisfy the k-Gamma distribution. Velocity distributions at various packing fractions and f collapse when the particle velocity is scaled by the average velocity v[combining macron], suggesting that v[combining macron] is a reasonable quantity to characterize the response to f. We thus define a response function R(ϕ,f) = v[combining macron](ϕ,f)/f. The function exhibits critical scaling nicely, implying again the criticality of point J. Our analysis and results indicate that systems of SPPs behave analogically to sheared systems, although their driving mechanisms are apparently distinct.

  4. Transition process leading to microbubble emission boiling on horizontal circular heated surface in subcooled pool

    Science.gov (United States)

    Ueno, Ichiro; Ando, Jun; Horiuchi, Kazuna; Saiki, Takahito; Kaneko, Toshihiro

    2016-11-01

    Microbubble emission boiling (MEB) produces a higher heat flux than critical heat flux (CHF) and therefore has been investigated in terms of its heat transfer characteristics as well as the conditions under which MEB occurs. Its physical mechanism, however, is not yet clearly understood. We carried out a series of experiments to examine boiling on horizontal circular heated surfaces of 5 mm and of 10 mm in diameter, in a subcooled pool, paying close attention to the transition process to MEB. High-speed observation results show that, in the MEB regime, the growth, condensation, and collapse of the vapor bubbles occur within a very short time. In addition, a number of fine bubbles are emitted from the collapse of the vapor bubbles. By tracking these tiny bubbles, we clearly visualize that the collapse of the vapor bubbles drives the liquid near the bubbles towards the heated surface, such that the convection field around the vapor bubbles under MEB significantly differs from that under nucleate boiling. Moreover, the axial temperature gradient in a heated block (quasi-heat flux) indicates a clear difference between nucleate boiling and MEB. A combination of quasi-heat flux and the measurement of the behavior of the vapor bubbles allows us to discuss the transition to MEB. This work was financially supported by the 45th Research Grant in Natural Sciences from The Mitsubishi Foundation (2014 - 2015), and by Research Grant for Boiler and Pressurized Vessels from The Japan Boiler Association (2016).

  5. Prospects for bubble fusion

    Energy Technology Data Exchange (ETDEWEB)

    Nigmatulin, R.I. [Tyumen Institute of Mechanics of Multiphase Systems (TIMMS), Marx (Russian Federation); Lahey, R.T. Jr. [Rensselaer Polytechnic Institute, Troy, NY (United States)

    1995-09-01

    In this paper a new method for the realization of fusion energy is presented. This method is based on the superhigh compression of a gas bubble (deuterium or deuterium/thritium) in heavy water or another liquid. The superhigh compression of a gas bubble in a liquid is achieved through forced non-linear, non-periodic resonance oscillations using moderate amplitudes of forcing pressure. The key feature of this new method is a coordination of the forced liquid pressure change with the change of bubble volume. The corresponding regime of the bubble oscillation has been called {open_quotes}basketball dribbling (BD) regime{close_quotes}. The analytical solution describing this process for spherically symmetric bubble oscillations, neglecting dissipation and compressibility of the liquid, has been obtained. This solution shown no limitation on the supercompression of the bubble and the corresponding maximum temperature. The various dissipation mechanisms, including viscous, conductive and radiation heat losses have been considered. It is shown that in spite of these losses it is possible to achieve very high gas bubble temperatures. This because the time duration of the gas bubble supercompression becomes very short when increasing the intensity of compression, thus limiting the energy losses. Significantly, the calculated maximum gas temperatures have shown that nuclear fusion may be possible. First estimations of the affect of liquid compressibility have been made to determine possible limitations on gas bubble compression. The next step will be to investigate the role of interfacial instability and breaking down of the bubble, shock wave phenomena around and in the bubble and mutual diffusion of the gas and the liquid.

  6. Precise Measurements of the Density and Critical Phenomena Near Phase Transitions in Liquid Helium

    Science.gov (United States)

    Yeh, Nai-Chang

    1997-01-01

    The first-year progress for the project of precise measurements of the density and critical phenomena of helium near phase transitions is summarized below: (1) completion of a cryogenic sample probe for the proposed measurements, and the rehabilitation of a designated laboratory at Caltech for this project; (2) construction and testing of a superconducting niobium cavity; (3) acquisition of one phase-locked-loop system for high-resolution frequency control and read- out; (4) setting up high-resolution thermometry (HRT) for temperature readout and control; (5) developing new approaches for calibrating the coefficient between the resonant frequency shift (delta f) and the helium density (rho), as well as for measuring the effect of gravity on T(sub lambda) to a much better precision; (6) programming of the interface control of all instruments for automatic data acquisition; and (7) improving data analyses and fitting procedures.

  7. Discoidin domain receptor 2 is a critical regulator of epithelial-mesenchymal transition

    Science.gov (United States)

    Walsh, Logan A.; Nawshad, Ali; Medici, Damian

    2011-01-01

    Discoidin domain receptor 2 (DDR2) is a collagen receptor that is expressed during epithelial-mesenchymal transition (EMT), a cellular transformation that mediates many stages of embryonic development and disease. However, the functional significance of this receptor in EMT is unknown. Here we show that Transforming Growth Factor-beta1 (TGF-β1), a common stimulator of EMT, promotes increased expression of type I collagen and DDR2. Inhibiting expression of COL1A1 or DDR2 with siRNA is sufficient to perturb activity of the NF-βB and LEF-1 transcription factors and to inhibit EMT and cell migration induced by TGF-β1. Furthermore, knockdown of DDR2 expression with siRNA inhibits EMT directly induced by type I collagen. These data establish a critical role for type I collagen-dependent DDR2 signaling in the regulation of EMT. PMID:21477649

  8. Bohr model description of the critical point for the first order shape phase transition

    Science.gov (United States)

    Budaca, R.; Buganu, P.; Budaca, A. I.

    2018-01-01

    The critical point of the shape phase transition between spherical and axially deformed nuclei is described by a collective Bohr Hamiltonian with a sextic potential having simultaneous spherical and deformed minima of the same depth. The particular choice of the potential as well as the scaled and decoupled nature of the total Hamiltonian leads to a model with a single free parameter connected to the height of the barrier which separates the two minima. The solutions are found through the diagonalization in a basis of Bessel functions. The basis is optimized for each value of the free parameter by means of a boundary deformation which assures the convergence of the solutions for a fixed basis dimension. Analyzing the spectral properties of the model, as a function of the barrier height, revealed instances with shape coexisting features which are considered for detailed numerical applications.

  9. Bohr model description of the critical point for the first order shape phase transition

    Directory of Open Access Journals (Sweden)

    R. Budaca

    2018-01-01

    Full Text Available The critical point of the shape phase transition between spherical and axially deformed nuclei is described by a collective Bohr Hamiltonian with a sextic potential having simultaneous spherical and deformed minima of the same depth. The particular choice of the potential as well as the scaled and decoupled nature of the total Hamiltonian leads to a model with a single free parameter connected to the height of the barrier which separates the two minima. The solutions are found through the diagonalization in a basis of Bessel functions. The basis is optimized for each value of the free parameter by means of a boundary deformation which assures the convergence of the solutions for a fixed basis dimension. Analyzing the spectral properties of the model, as a function of the barrier height, revealed instances with shape coexisting features which are considered for detailed numerical applications.

  10. Static critical exponents of the ferromagnetic transition in spin glass re-entrant systems.

    Science.gov (United States)

    Haetinger, Cláudia M; Ghivelder, Luis; Schaf, Jacob; Pureur, Paulo

    2009-12-16

    The static critical phenomenology near the Curie temperature of the re-entrant metallic alloys Au(0.81)Fe(0.19), Ni(0.78)Mn(0.22), Ni(0.79)Mn(0.21) and amorphous a-Fe(0.98)Zr(0.08) is studied using a variety of experimental techniques and methods of analysis. We have generally found that the values for the exponents α, β, γ and δ depart significantly from the predictions for the 3D Heisenberg model and are intermediate between these expectations and the values characterizing a typical spin glass transition. Comparing the exponents obtained in our work with indices for other re-entrant systems reported in the literature, a weak universality class may be defined where the exponents are distributed within a certain range around average values.

  11. Beyond the gas bubble

    International Nuclear Information System (INIS)

    Hilt, R.H.

    1990-01-01

    The deliverability issue currently being discussed within the natural gas industry involves both near-term and long-term questions. In the near-term, over the next two or three years, it is probable that the natural gas industry will need to mobilize for much greater levels of investment than have been the experience over the past few years. In the longer-term, it is expected that new opportunities for gas will arise as the nation seeks to meet increasing energy requirements within new environmental constraints. Methane for emissions control, CNG vehicles, expanded gas-fired electricity generation, and increased efficiency of traditional energy services are just a few examples. The issues in the longer-term center on the ability of the gas industry to meet increasing supply requirements reliably and at cost-competitive prices for these markets. This paper begins by reviewing the historical situation of gas deliverability that is the capability of the gas producing and transportation portions of the industry. The delivery system's ability to handle shifts in the centers of consumption and production is discussed, with an emphasis on regional problems of gas deliverability and potential bottlenecks. On the production side, the paper reviews the capability and the required investment necessary to handle an orderly transition to a stable supply and demand balance once the elusive bubble had finally disappeared

  12. Bubbles, Banks, and Financial Stability

    OpenAIRE

    Kosuke Aoki; Kalin Nikolov

    2011-01-01

    This paper asks two main questions: (1) What makes some asset price bubbles more costly for the real economy than others? and (2) When do costly bubbles occur? We construct a model of rational bubbles under credit frictions and show that when bubbles held by banks burst this is followed by a costly financial crisis. In contrast, bubbles held by ordinary savers have relatively muted effects. Banks tend to invest in bubbles when financial liberalisation decreases their profitability.

  13. Critical transition between cohesive and population-dividing responses to change.

    Science.gov (United States)

    Muneepeerakul, Rachata; Qubbaj, Murad R; Aggarwal, Rimjhim M; Anderies, John M; Janssen, Marco A

    2012-12-07

    Globalization and global climate change will probably be accompanied by rapid social and biophysical changes that may be caused by external forcing or internal nonlinear dynamics. These changes often subject residing populations (human or otherwise) to harsh environments and force them to respond. Research efforts have mostly focused on the underlying mechanisms that drive these changes and the characteristics of new equilibria towards which populations would adapt. However, the transient dynamics of how populations respond under these new regimes is equally, if not more, important, and systematic analysis of such dynamics has received less attention. Here, we investigate this problem under the framework of replicator dynamics with fixed reward kernels. We show that at least two types of population responses are possible--cohesive and population-dividing transitions--and demonstrate that the critical transition between the two, as well as other important properties, can be expressed in simple relationships between the shape of reward structure, shift magnitude and initial strategy diversity. Importantly, these relationships are derived from a simple, yet powerful and versatile, method. As many important phenomena, from political polarization to the evolution of distinct ecological traits, may be cast in terms of division of populations, we expect our findings and method to be useful and applicable for understanding population responses to change in a wide range of contexts.

  14. Flow visualization using bubbles

    International Nuclear Information System (INIS)

    Henry, J.P.

    1974-01-01

    Soap bubbles were used for visualizing flows. The tests effected allowed some characteristics of flows around models in blow tunnels to be precised at mean velocities V 0 5 . The velocity of a bubble is measured by chronophotography, the bulk envelope of the trajectories is also registered [fr

  15. HCDA bubble experiment, (2)

    International Nuclear Information System (INIS)

    Sakata, Kaoru; Mashiko, Hiroyuki; Oka, Yoshiaki; An, Shigehiro; Isozaki, Tadashi.

    1981-06-01

    An experiment simulating the behavior of the very large steam bubbles generated at the time of an accident of core collapse was carried out with a warm water tank, and the applicability of the theory of very small bubble disappearance known at present was examined. The bubbles generated in HCDA (hypothetical core disruptive accident) are expected to be very large, containing sodium, fuel, FP gas and so on, and play important role in the mechanism of emitting radioactive substances in the safety analysis of LMFBRs. In this experiment, the degree of subcool of the warm water pool, the initial radii of steam bubbles and the blowoff pressure of steam were taken as the parameters. The radius of the steam bubbles generated in the experiment was about 6.5 cm, and the state of disappearance was different above and below the degree of unsaturation of 10 deg C. Comparing the disappearance curve obtained by the experiment with the theory of disappearance of small bubbles, the experimental values were between inertia-controlled disappearance and heat transfer-controlled disappearance, and this result was able to be explained generally with the model taking the pressure change within steam bubbles into account. The rise of bubbles was also observed. (Kako, I.)

  16. Viscosity Destabilizes Sonoluminescing Bubbles

    NARCIS (Netherlands)

    Tögel, R.; Luther, S.; Lohse, Detlef

    2006-01-01

    In single-bubble sonoluminescence (SBSL) microbubbles are trapped in a standing sound wave, typically in water or water-glycerol mixtures. However, in viscous liquids such as glycol, methylformamide, or sulphuric acid it is not possible to trap the bubble in a stable position. This is very peculiar

  17. Bubbles in graphene

    DEFF Research Database (Denmark)

    Settnes, Mikkel; Power, Stephen; Lin, Jun

    2015-01-01

    Strain-induced deformations in graphene are predicted to give rise to large pseudomagnetic fields. We examine theoretically the case of gas-inflated bubbles to determine whether signatures of such fields are present in the local density of states. Sharp-edged bubbles are found to induce Friedel...

  18. Evaporation, Boiling and Bubbles

    Science.gov (United States)

    Goodwin, Alan

    2012-01-01

    Evaporation and boiling are both terms applied to the change of a liquid to the vapour/gaseous state. This article argues that it is the formation of bubbles of vapour within the liquid that most clearly differentiates boiling from evaporation although only a minority of chemistry textbooks seems to mention bubble formation in this context. The…

  19. Turbulence, bubbles and drops

    NARCIS (Netherlands)

    van der Veen, Roeland

    2016-01-01

    In this thesis, several questions related to drop impact and Taylor-Couette turbulence are answered. The deformation of a drop just before impact can cause a bubble to be entrapped. For many applications, such as inkjet printing, it is crucial to control the size of this entrapped bubble. To study

  20. Phase transition and critical behaviors of spin-orbital coupling spinel compound CdV2O4

    Science.gov (United States)

    Wang, Li; Sun, Duohua; Wang, Rongjuan; Zhu, Yuanyuan; Lu, Zhihong; Xiong, Rui; Liu, Yong; Shi, Jing

    2016-03-01

    The temperature dependent susceptibility and specific heat of spinel compound CdV2O4 were investigated. The structural transition accompanied with orbital order appearing at 89.6 K is confirmed to be a first order transition, while the magnetic transitions at 30.2 K is revealed to be a second order one. For the paramagnetism-antiferromagnetic transition, the width of critical region was estimated to be about 1.5 K by differentiating with Gaussian fluctuation. In critical region, the critical behavior of specific heat was compared with renormalization-group theory. Critical exponent α and critical amplitude ratio (A+/A-) fitting to the data was found to be -0.017 and 1.26, respectively. The value of A+/A- shows the critical behavior of CdV2O4's deviates from 3D-Heisenberg and shifts to 3D-XY. The analysis of specific heat in low temperature range gives out that Debye temperature ΘD for CdV2O4 is estimated to be 190 K.

  1. STUDENTS’ CRITICAL THINKING IN WRITING A THESIS USING THE TRANSITIVITY SYSTEM

    Directory of Open Access Journals (Sweden)

    Emi Emilia

    2016-02-01

    Full Text Available Abstract: Students’ Critical Thinking in Writing a Thesis Using the Transitivity System. This paper reports on a small part of the results of a study in attempting to identify students’ ability and difficulties in writing an English undergraduate thesis in a state university in Indonesia. The paper centres around the students’ ability and difficulties in writing a data presentation and discussion chapter, which are related to critical capacity looked at in this study. The paper begins with a brief introduction, which presents the background and the theories underpinning the study. This will be followed by an account of the methodology, in which it is argued that the study used a case study method, particularly text analysis  and involved  nine theses  selected randomly and analysed based on the elements of a conventional research report and the Transitivity system of systemic functional grammar, developed by Halliday. The paper then delineates the results, showing that despite their  good control in the discourse semantic level, students in general still need a lot of guidance and assistance in writing a data presentation and discussion chapter. Recommendation for further research will conclude the paper. Abstrak: Kemampuan Berpikir Kritis Mahasiswa dalam Menulis Tesis. Artikel ini membahas sebagian hasil penelitian yang berupaya untuk mengidentifikasi kemampuan dan kesulitan mahasiswa dalam menulis skripsi. Pembahasan difokuskan pada kemampuan dan kesulitan mahasiswa dalam menulis bab pemaparan dan pembahasan data, yang sangat erat kaitannya dengan kemampuan berpikir kritis. Penelitian ini menggunakan rancangan studi kasus, khususnya analisis teks dan melibatkan 9 skrip yang dipilih secara acak. Data dianalisis berdasarkan struktur organisasi atau elemen-elemen yang seharusnya ada dalam laporan penelitian konvensional dan sistem Transitivity dari tata bahasa sistemik fungsional yang dikembangkan oleh Halliday. Hasil penelitian

  2. Dependence of the brittle ductile transition on strain-rate-dependent critical homologous temperature

    Science.gov (United States)

    Davis, Paul M.

    2017-05-01

    Earthquakes mainly occur in crust or mantle that is below a critical temperature for the tectonic strain-rate, \\dot{e}_t, such that stress builds up to the breaking point before it can relax due to creep. Then long-range stress correlation gives rise to power law seismicity including large events. The limiting temperature depends on pressure, which is taken into account by finding a critical homologous temperature THc = T/TM above which earthquakes are rarely observed (where T, TM are temperature and average melting temperature of constituent minerals). We find that THc for ocean plates is ∼0.55. For California earthquakes, it is also close to 0.55. The uppermost mantle layer of oceanic plates of thickness ∼50 km is composed of harzburgite and depleted peridotite from which basalt has been removed to form ocean crust. Thus it has a higher melting temperature than the peridotite of the surrounding mantle, or the lower halves of plates. Thicknesses of seismicity in deep subduction zones, determined from 2-D polynomial fits to a relocated catalogue, are ∼50 km, which suggests that the earthquake channel is confined to this layer. We construct models to find homologous temperatures in slabs, and find that seismicity thicknesses are also, on average, confined to TH ≤ 0.55 ± 0.05. The associated rheology is compared with that obtained from flexure models of ocean lithosphere. The brittle-ductile transition occurs where viscosity drops from high values in the cold cores of slabs to values of 1022-1023 Pa s, that is, where creep strain-rates become comparable to tectonic rates. The cut-off for deep earthquakes is not sharp. However they appear unlikely to occur if homologous temperature is high TH > 0.55. Exceptions to the rule are anomalously deep earthquakes such as those beneath the Iceland and the Hawaiian hotspots, and the Newport Inglewood Fault. These are smaller events with short-range stress correlation, and can be explained if strain-rates are two to

  3. Edge states in the climate system: exploring global instabilities and critical transitions

    Science.gov (United States)

    Lucarini, Valerio; Bódai, Tamás

    2017-07-01

    Multistability is a ubiquitous feature in systems of geophysical relevance and provides key challenges for our ability to predict a system’s response to perturbations. Near critical transitions small causes can lead to large effects and—for all practical purposes—irreversible changes in the properties of the system. As is well known, the Earth climate is multistable: present astronomical and astrophysical conditions support two stable regimes, the warm climate we live in, and a snowball climate characterized by global glaciation. We first provide an overview of methods and ideas relevant for studying the climate response to forcings and focus on the properties of critical transitions in the context of both stochastic and deterministic dynamics, and assess strengths and weaknesses of simplified approaches to the problem. Following an idea developed by Eckhardt and collaborators for the investigation of multistable turbulent fluid dynamical systems, we study the global instability giving rise to the snowball/warm multistability in the climate system by identifying the climatic edge state, a saddle embedded in the boundary between the two basins of attraction of the stable climates. The edge state attracts initial conditions belonging to such a boundary and, while being defined by the deterministic dynamics, is the gate facilitating noise-induced transitions between competing attractors. We use a simplified yet Earth-like intermediate complexity climate model constructed by coupling a primitive equations model of the atmosphere with a simple diffusive ocean. We refer to the climatic edge states as Melancholia states and provide an extensive analysis of their features. We study their dynamics, their symmetry properties, and we follow a complex set of bifurcations. We find situations where the Melancholia state has chaotic dynamics. In these cases, we have that the basin boundary between the two basins of attraction is a strange geometric set with a nearly zero

  4. Critical temperature and the transition from quantum to classical order parameter fluctuations in the three-dimensional Heisenberg antiferromagnet

    OpenAIRE

    Sandvik, A. W.

    1998-01-01

    We present results of extensive quantum Monte Carlo simulations of the three-dimensional (3D) S=1/2 Heisenberg antiferromagnet. Finite-size scaling of the spin stiffness and the sublattice magnetization gives the critical temperature Tc/J = 0.946 +/- 0.001. The critical behavior is consistent with the classical 3D Heisenberg universality class, as expected. We discuss the general nature of the transition from quantum mechanical to classical (thermal) order parameter fluctuations at a continuo...

  5. Powder keg divisions in the critical state regime: transition from continuous to explosive percolation

    Science.gov (United States)

    Zhou, Zongzheng; Tordesillas, Antoinette

    2017-06-01

    The underlying microstructure and dynamics of a dense granular material as it evolves towards the "critical state", a limit state in which the system deforms with an essentially constant volume and stress ratio, remains widely debated in the micromechanics of granular media community. Strain localization, a common mechanism in the large strain regime, further complicates the characterization of this limit state. Here we revisit the evolution to this limit state within the framework of modern percolation theory. Attention is paid to motion transfer: in this context, percolation translates to the emergence of a large-scale connectivity in graphs that embody information on individual grain displacements. We construct each graph G(r) by connecting nodes, representing the grains, within a distance r in the displacement-state-space. As r increases, we observe a percolation transition on G(r). The size of the jump discontinuity increases in the lead up to failure, indicating that the nature of percolation transition changes from continuous to explosive. We attribute this to the emergence of collective motion, which manifests in increasingly isolated communities in G(r). At the limit state, where the jump discontinuity is highest and invariant across the different unjamming cycles (drops in stress ratio), G(r) encapsulates multiple kinematically distinct communities that are mediated by nodes corresponding to those grains in the shear band. This finding casts light on the dual and opposing roles of the shear band: a mechanism that creates powder keg divisions in the sample, while simultaneously acting as a mechanical link that transfers motion through such subdivisions moving in relative rigid-body motion.

  6. Theory calculation of combination of 'embryo' bubble growing-up visible bubble in bubble chamber

    International Nuclear Information System (INIS)

    Ye Zipiao; Sheng Xiangdong; Dai Changjiang

    2004-01-01

    By aid of island combination theory of 'embryo' bubble, it is resolved well the question which 'embryo' bubble grows up a visible bubble in the bubble chamber. Through theory calculation it is shown that radius of the big' embryo' bubble combinated not only relates with work matter such as surface tension coefficient, saturation vapour pressure and boiling point of liquid, but also does absorbing quantity of heat and the numbers of 'embryo' bubbles combination. It is explained reasonably that the radius of bubbles in bubble chamber is different for the same energies of neutrons and proton. The track of neutron in bubble chamber is long and thin, and the track of proton in bubble chamber is wide and short. It is also explained reasonably that the bubble radius of the incident particles with more charges which there are the same energies will be wider than that of the incident particles with less charges in the track. (author)

  7. Critical Radius of Supercooled Water Droplets: On the Transition toward Dendritic Freezing.

    Science.gov (United States)

    Buttersack, Tillmann; Bauerecker, Sigurd

    2016-01-28

    The freezing of freely suspended supercooled water droplets with a diameter of bigger than a few micrometers splits into two rather different freezing stages. Within the first very fast dendritic freezing stage a spongy network ice with an ice portion of less than one-third forms and more than two-thirds of liquid water remain. In the present work the distribution of the ice portion in the droplet directly after the dendritic freezing phase as well as the evolution of the ice and temperature distribution has been investigated in dependence of the most relevant parameters as droplet diameter, dendritic freezing velocity (which correlates with the supercooling) and heat transfer coefficient to the surroundings (which correlates with the relative droplet velocity compared to the ambient air and with the droplet size). For this purpose on the experimental side acoustically levitated droplets in climate chambers have been investigated in combination with high-speed cameras. The obtained results have been used for finite element method (FEM) simulations of the dendritic freezing phase under consideration of the beginning second, much slower heat-transfer dominated freezing phase. A theoretical model covering 30 layers and 5 shells of the droplet has been developed which allows one to describe the evolution of both freezing phases at the same time. The simulated results are in good agreement with experimental as well as with calculated results exploiting the heat balance equation. The most striking result of this work is the critical radius of the droplet which describes the transition of one-stage freezing of the supercooled water droplet toward the thermodynamically forced dendritical two-stage freezing in which the droplet cannot sufficiently get rid of the formation heat anymore. Depending on the parameters named above this critical radius was found to be in the range of 0.1 to 1 μm by FEM simulation.

  8. Bubbles, shocks and elementary technical trading strategies

    Science.gov (United States)

    Fry, John

    2014-01-01

    In this paper we provide a unifying framework for a set of seemingly disparate models for bubbles, shocks and elementary technical trading strategies in financial markets. Markets operate by balancing intrinsic levels of risk and return. This seemingly simple observation is commonly over-looked by academics and practitioners alike. Our model shares its origins in statistical physics with others. However, under our approach, changes in market regime can be explicitly shown to represent a phase transition from random to deterministic behaviour in prices. This structure leads to an improved physical and econometric model. We develop models for bubbles, shocks and elementary technical trading strategies. The list of empirical applications is both interesting and topical and includes real-estate bubbles and the on-going Eurozone crisis. We close by comparing the results of our model with purely qualitative findings from the finance literature.

  9. Critical metal-insulator transition and divergence in a two-particle irreducible vertex in disordered and interacting electron systems

    Czech Academy of Sciences Publication Activity Database

    Janiš, Václav; Pokorný, Vladislav

    2014-01-01

    Roč. 90, č. 4 (2014), "045143-1"-"045143-11" ISSN 1098-0121 Institutional support: RVO:68378271 Keywords : metal-insulator transition * disordered and interacting electron systems * dynamical mean-field theory * critical behavior Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 3.736, year: 2014

  10. bubble chamber lens

    CERN Multimedia

    Before the days of electronic detectors, visual techniques were used to detect particles, using detectors such as spark chambers and bubble chambers. This plexiglass lens was used to focus the image of tracks so they could be photographed.

  11. Critical roles of p53 in epithelial-mesenchymal transition and metastasis of hepatocellular carcinoma cells.

    Directory of Open Access Journals (Sweden)

    Zheng Wang

    Full Text Available Hepatocellular carcinoma (HCC is one of the most malignant tumors and the biggest obstacle in curing HCC is its high metastasis potential. Alteration of p53 is the most frequent genetic change found in HCC. Although the biological function of p53 in tumor initiation and progression has been well characterized, whether or not p53 is implicated in metastasis of HCC is largely unknown. In this study, we analyzed the potential functions of p53 in epithelial-mesenchymal transition (EMT and metastasis of HCC cells. Both insulin- and TGF-β1-induced changes of critical EMT markers were greatly enhanced by p53 knockdown in HCC cells. The insulin- and TGF-β1-stimulated migration of HCC cells were enhanced by p53 knockdown. Furthermore, in vivo metastasis of HCC cells using different mouse models was robustly enhanced by p53 knockdown. In addition, we found that p53 regulation on EMT and metastasis involves β-catenin signaling. The nuclear accumulation and transcriptional activity of β-catenin was modulated by p53. The enhanced EMT phenotype, cell migration and tumor metastasis of HCC cells by p53 knockdown were abrogated by inhibiting β-catenin signal pathway. In conclusion, this study reveals that p53 plays a pivotal role in EMT and metastasis of HCC cells via its regulation on β-catenin signaling.

  12. Influence of the disorder in doped germanium changed by compensation on the critical indices of the metal-insulator transition

    International Nuclear Information System (INIS)

    Rentzsch, R.; Reich, Ch.; Ionov, A.N.; Ginodman, V.; Slimak, I.; Fozooni, P.; Lea, M.J.

    1999-01-01

    We present a critical review of the present status of the critical exponent puzzle of the metal-insulator transition of doped semiconductors with the emphasis on the role of meso- and macroscopy inhomogeneity caused by the disorder of acceptors and donors in the crystals. By using the isotopic and engineering and the neutron transmutation doping of germanium we found for low compensations (at K = 1.4 and 12%) that the critical exponents of the localization length and the dielectric constant are nearly ν = 1/2 and ξ = 1, which double for medium compensations (at K = 39 and 54%) to ν 1 and ξ = 2, respectively

  13. Bubble chamber: antiproton annihilation

    CERN Multimedia

    1971-01-01

    These images show real particle tracks from the annihilation of an antiproton in the 80 cm Saclay liquid hydrogen bubble chamber. A negative kaon and a neutral kaon are produced in this process, as well as a positive pion. The invention of bubble chambers in 1952 revolutionized the field of particle physics, allowing real tracks left by particles to be seen and photographed by expanding liquid that had been heated to boiling point.

  14. Magnetic-bubble devices

    International Nuclear Information System (INIS)

    Fairholme, R.J.

    1978-01-01

    Magnetic bubbles were first described only ten years ago when research workers were discussing orthoferrites containing μm diameter bubbles. However, problems of material fabrication limit crystals to a few mm across which severely curtailed device development. Since then materials have changed and rare-earth-iron garnet films can be grown up 3 inches in diameter with bubble diameters down to sizes below 1 μm. The first commercial products have device capacities in the range 64 000 to 100 000 bits with bubble diameters between 4 and 6 μm. Chip capacities of 1 Mbit are presently under development in the laboratory, as are new techniques to use submicrometre bubbles. The operation and fabrication of a bubble device is described using the serial loop devices currently being manufactured at Plessey as models. Chip organization is one important variable which directly affects the access time. A range of access times and capacities is available which offers a wide range of market opportunities, ranging from consumer products to fixed head disc replacements. some of the application areas are described. (author)

  15. Bubble transport in bifurcations

    Science.gov (United States)

    Bull, Joseph; Qamar, Adnan

    2017-11-01

    Motivated by a developmental gas embolotherapy technique for cancer treatment, we examine the transport of bubbles entrained in liquid. In gas embolotherapy, infarction of tumors is induced by selectively formed vascular gas bubbles that originate from acoustic vaporization of vascular droplets. In the case of non-functionalized droplets with the objective of vessel occlusion, the bubbles are transported by flow through vessel bifurcations, where they may split prior to eventually reach vessels small enough that they become lodged. This splitting behavior affects the distribution of bubbles and the efficacy of flow occlusion and the treatment. In these studies, we investigated bubble transport in bifurcations using computational and theoretical modeling. The model reproduces the variety of experimentally observed splitting behaviors. Splitting homogeneity and maximum shear stress along the vessel walls is predicted over a variety of physical parameters. Maximum shear stresses were found to decrease with increasing Reynolds number. The initial bubble length was found to affect the splitting behavior in the presence of gravitational asymmetry. This work was supported by NIH Grant R01EB006476.

  16. Quantum critical scaling for field-induced quantum phase transition in a periodic Anderson-like model polymer chain

    Energy Technology Data Exchange (ETDEWEB)

    Ding, L.J., E-mail: dinglinjie82@126.com; Zhong, Y.

    2017-07-15

    Highlights: • The quantum critical scaling is investigated by Green’s function theory. • The obtained power-law critical exponents (β, δ and α) obey the critical scaling relation α + β(1 + δ) = 2. • The scaling hypothesis equations are proposed to verify the scaling analysis. - Abstract: The quantum phase transition and thermodynamics of a periodic Anderson-like polymer chain in a magnetic field are investigated by Green’s function theory. The T-h phase diagram is explored, wherein a crossover temperature T{sup ∗} denoting the gapless phase crossover into quantum critical regimes, smoothly connects near the critical fields to the universal linear line T{sup ∗} ∼ (h − h{sub c,s}), and ends at h{sub c,s}, providing a new route to capture quantum critical point (QCP). The quantum critical scaling around QCPs is demonstrated by analyzing magnetization, specific heat and Grüneisen parameter Γ{sub h}, which provide direct access to distill the power-law critical exponents (β, δ and α) obeying the critical scaling relation α + β(1 + δ) = 2, analogous to the quantum spin system. Furthermore, scaling hypothesis equations are proposed to check the scaling analysis, for which all the data collapse onto a single curve or two independent branches for the plot against an appropriate scaling variable, indicating the self-consistency and reliability of the obtained critical exponents.

  17. Dynamical Quantum Phase Transitions in Spin Chains with Long-Range Interactions: Merging Different Concepts of Nonequilibrium Criticality

    Science.gov (United States)

    Žunkovič, Bojan; Heyl, Markus; Knap, Michael; Silva, Alessandro

    2018-03-01

    We theoretically study the dynamics of a transverse-field Ising chain with power-law decaying interactions characterized by an exponent α , which can be experimentally realized in ion traps. We focus on two classes of emergent dynamical critical phenomena following a quantum quench from a ferromagnetic initial state: The first one manifests in the time-averaged order parameter, which vanishes at a critical transverse field. We argue that such a transition occurs only for long-range interactions α ≤2 . The second class corresponds to the emergence of time-periodic singularities in the return probability to the ground-state manifold which is obtained for all values of α and agrees with the order parameter transition for α ≤2 . We characterize how the two classes of nonequilibrium criticality correspond to each other and give a physical interpretation based on the symmetry of the time-evolved quantum states.

  18. Critical slowing down associated with regime shifts in the US housing market

    Science.gov (United States)

    Tan, James Peng Lung; Cheong, Siew Siew Ann

    2014-02-01

    Complex systems are described by a large number of variables with strong and nonlinear interactions. Such systems frequently undergo regime shifts. Combining insights from bifurcation theory in nonlinear dynamics and the theory of critical transitions in statistical physics, we know that critical slowing down and critical fluctuations occur close to such regime shifts. In this paper, we show how universal precursors expected from such critical transitions can be used to forecast regime shifts in the US housing market. In the housing permit, volume of homes sold and percentage of homes sold for gain data, we detected strong early warning signals associated with a sequence of coupled regime shifts, starting from a Subprime Mortgage Loans transition in 2003-2004 and ending with the Subprime Crisis in 2007-2008. Weaker signals of critical slowing down were also detected in the US housing market data during the 1997-1998 Asian Financial Crisis and the 2000-2001 Technology Bubble Crisis. Backed by various macroeconomic data, we propose a scenario whereby hot money flowing back into the US during the Asian Financial Crisis fueled the Technology Bubble. When the Technology Bubble collapsed in 2000-2001, the hot money then flowed into the US housing market, triggering the Subprime Mortgage Loans transition in 2003-2004 and an ensuing sequence of transitions. We showed how this sequence of couple transitions unfolded in space and in time over the whole of US.

  19. Critical behavior within 20 fs drives the out-of-equilibrium laser-induced magnetic phase transition in nickel.

    Science.gov (United States)

    Tengdin, Phoebe; You, Wenjing; Chen, Cong; Shi, Xun; Zusin, Dmitriy; Zhang, Yingchao; Gentry, Christian; Blonsky, Adam; Keller, Mark; Oppeneer, Peter M; Kapteyn, Henry C; Tao, Zhensheng; Murnane, Margaret M

    2018-03-01

    It has long been known that ferromagnets undergo a phase transition from ferromagnetic to paramagnetic at the Curie temperature, associated with critical phenomena such as a divergence in the heat capacity. A ferromagnet can also be transiently demagnetized by heating it with an ultrafast laser pulse. However, to date, the connection between out-of-equilibrium and equilibrium phase transitions, or how fast the out-of-equilibrium phase transitions can proceed, was not known. By combining time- and angle-resolved photoemission with time-resolved transverse magneto-optical Kerr spectroscopies, we show that the same critical behavior also governs the ultrafast magnetic phase transition in nickel. This is evidenced by several observations. First, we observe a divergence of the transient heat capacity of the electron spin system preceding material demagnetization. Second, when the electron temperature is transiently driven above the Curie temperature, we observe an extremely rapid change in the material response: The spin system absorbs sufficient energy within the first 20 fs to subsequently proceed through the phase transition, whereas demagnetization and the collapse of the exchange splitting occur on much longer, fluence-independent time scales of ~176 fs. Third, we find that the transient electron temperature alone dictates the magnetic response. Our results are important because they connect the out-of-equilibrium material behavior to the strongly coupled equilibrium behavior and uncover a new time scale in the process of ultrafast demagnetization.

  20. Colliding with a crunching bubble

    Energy Technology Data Exchange (ETDEWEB)

    Freivogel, Ben; Freivogel, Ben; Horowitz, Gary T.; Shenker, Stephen

    2007-03-26

    In the context of eternal inflation we discuss the fate of Lambda = 0 bubbles when they collide with Lambda< 0 crunching bubbles. When the Lambda = 0 bubble is supersymmetric, it is not completely destroyed by collisions. If the domain wall separating the bubbles has higher tension than the BPS bound, it is expelled from the Lambda = 0 bubble and does not alter its long time behavior. If the domain wall saturates the BPS bound, then it stays inside the Lambda = 0 bubble and removes a finite fraction of future infinity. In this case, the crunch singularity is hidden behind the horizon of a stable hyperbolic black hole.

  1. Rounding by disorder of first-order quantum phase transitions: emergence of quantum critical points.

    Science.gov (United States)

    Goswami, Pallab; Schwab, David; Chakravarty, Sudip

    2008-01-11

    We give a heuristic argument for disorder rounding of a first-order quantum phase transition into a continuous phase transition. From both weak and strong disorder analysis of the N-color quantum Ashkin-Teller model in one spatial dimension, we find that, for N > or =3, the first-order transition is rounded to a continuous transition and the physical picture is the same as the random transverse field Ising model for a limited parameter regime. The results are strikingly different from the corresponding classical problem in two dimensions where the fate of the renormalization group flows is a fixed point corresponding to N-decoupled pure Ising models.

  2. Hydrodynamics of ultra-relativistic bubble walls

    Directory of Open Access Journals (Sweden)

    Leonardo Leitao

    2016-04-01

    Full Text Available In cosmological first-order phase transitions, gravitational waves are generated by the collisions of bubble walls and by the bulk motions caused in the fluid. A sizeable signal may result from fast-moving walls. In this work we study the hydrodynamics associated to the fastest propagation modes, namely, ultra-relativistic detonations and runaway solutions. We compute the energy injected by the phase transition into the fluid and the energy which accumulates in the bubble walls. We provide analytic approximations and fits as functions of the net force acting on the wall, which can be readily evaluated for specific models. We also study the back-reaction of hydrodynamics on the wall motion, and we discuss the extrapolation of the friction force away from the ultra-relativistic limit. We use these results to estimate the gravitational wave signal from detonations and runaway walls.

  3. The Fermi Bubbles

    Science.gov (United States)

    Finkbeiner, Douglas P.

    2015-01-01

    The Fermi Bubbles are a pair of giant lobes at the heart of the Milky Way, extending roughly 50 degrees north and south of the Galactic Center, and emitting photons with energies up to 100 GeV. This previously unknown structure could be evidence for past activity of the central supermassive black hole, or enhanced star formation towards the inner Galaxy. We will describe the path to discovery of the Bubbles in multiwavelength data, from the first hints in microwave radiation measured by WMAP and X-rays from ROSAT, to the unveiling of their shape and spectrum using public gamma-ray data from the Fermi Gamma-ray Space Telescope, to more recent measurements by Planck and XMM-Newton. We will outline the current state of knowledge of the Bubbles' spectrum, morphology and internal structure, and discuss theoretical proposals and numerical simulations for their nature and origin.

  4. Phase transition in anisotropic holographic superfluids with arbitrary dynamical critical exponent z and hyperscaling violation factor α

    Energy Technology Data Exchange (ETDEWEB)

    Park, Miok [Korea Institute for Advanced Study, Seoul (Korea, Republic of); Park, Jiwon; Oh, Jae-Hyuk [Hanyang University, Department of Physics, Seoul (Korea, Republic of)

    2017-11-15

    Einstein-scalar-U(2) gauge field theory is considered in a spacetime characterized by α and z, which are the hyperscaling violation factor and the dynamical critical exponent, respectively. We consider a dual fluid system of such a gravity theory characterized by temperature T and chemical potential μ. It turns out that there is a superfluid phase transition where a vector order parameter appears which breaks SO(3) global rotation symmetry of the dual fluid system when the chemical potential becomes a certain critical value. To study this system for arbitrary z and α, we first apply Sturm-Liouville theory and estimate the upper bounds of the critical values of the chemical potential. We also employ a numerical method in the ranges of 1 ≤ z ≤ 4 and 0 ≤ α ≤ 4 to check if the Sturm-Liouville method correctly estimates the critical values of the chemical potential. It turns out that the two methods are agreed within 10 percent error ranges. Finally, we compute free energy density of the dual fluid by using its gravity dual and check if the system shows phase transition at the critical values of the chemical potential μ{sub c} for the given parameter region of α and z. Interestingly, it is observed that the anisotropic phase is more favored than the isotropic phase for relatively small values of z and α. However, for large values of z and α, the anisotropic phase is not favored. (orig.)

  5. Critical properties of phase transitions in lattices of coupled logistic maps

    International Nuclear Information System (INIS)

    Marcq, Philippe; Chate, Hugues; Manneville, Paul

    2006-01-01

    We numerically demonstrate that collective bifurcations in two-dimensional lattices of locally coupled logistic maps share most of the defining features of equilibrium second-order phase transitions. Our simulations suggest that these transitions between distinct collective dynamical regimes belong to the universality class of Miller and Huse model with synchronous update. (author)

  6. Survey of Professional Opinion on Critical Transition Skills for Adolescents and Young Adults Who Are Deaf.

    Science.gov (United States)

    Bullis, Michael; Reiman, John W.

    1989-01-01

    Surveyed national sample of 307 professionals in relevant fields to obtain professional opinion on critical competencies necessary for deaf individuals to live and work successfully in the community. Findings identified 12 critical skills in employment and 10 critical skills in independent living. (Author/NB)

  7. Single-bubble dynamics in pool boiling of one-component fluids

    KAUST Repository

    Xu, Xinpeng

    2014-06-04

    We numerically investigate the pool boiling of one-component fluids with a focus on the effects of surface wettability on the single-bubble dynamics. We employed the dynamic van der Waals theory [Phys. Rev. E 75, 036304 (2007)], a diffuse-interface model for liquid-vapor flows involving liquid-vapor transition in nonuniform temperature fields. We first perform simulations for bubbles on homogeneous surfaces. We find that an increase in either the contact angle or the surface superheating can enhance the bubble spreading over the heating surface and increase the bubble departure diameter as well and therefore facilitate the transition into film boiling. We then examine the dynamics of bubbles on patterned surfaces, which incorporate the advantages of both hydrophobic and hydrophilic surfaces. The central hydrophobic region increases the thermodynamic probability of bubble nucleation while the surrounding hydrophilic region hinders the continuous bubble spreading by pinning the contact line at the hydrophobic-hydrophilic intersection. This leads to a small bubble departure diameter and therefore prevents the transition from nucleate boiling into film boiling. With the bubble nucleation probability increased and the bubble departure facilitated, the efficiency of heat transfer on such patterned surfaces is highly enhanced, as observed experimentally [Int. J. Heat Mass Transfer 57, 733 (2013)]. In addition, the stick-slip motion of contact line on patterned surfaces is demonstrated in one-component fluids, with the effect weakened by surface superheating.

  8. Single-bubble dynamics in pool boiling of one-component fluids.

    Science.gov (United States)

    Xu, Xinpeng; Qian, Tiezheng

    2014-06-01

    We numerically investigate the pool boiling of one-component fluids with a focus on the effects of surface wettability on the single-bubble dynamics. We employed the dynamic van der Waals theory [Phys. Rev. E 75, 036304 (2007)], a diffuse-interface model for liquid-vapor flows involving liquid-vapor transition in nonuniform temperature fields. We first perform simulations for bubbles on homogeneous surfaces. We find that an increase in either the contact angle or the surface superheating can enhance the bubble spreading over the heating surface and increase the bubble departure diameter as well and therefore facilitate the transition into film boiling. We then examine the dynamics of bubbles on patterned surfaces, which incorporate the advantages of both hydrophobic and hydrophilic surfaces. The central hydrophobic region increases the thermodynamic probability of bubble nucleation while the surrounding hydrophilic region hinders the continuous bubble spreading by pinning the contact line at the hydrophobic-hydrophilic intersection. This leads to a small bubble departure diameter and therefore prevents the transition from nucleate boiling into film boiling. With the bubble nucleation probability increased and the bubble departure facilitated, the efficiency of heat transfer on such patterned surfaces is highly enhanced, as observed experimentally [Int. J. Heat Mass Transfer 57, 733 (2013)]. In addition, the stick-slip motion of contact line on patterned surfaces is demonstrated in one-component fluids, with the effect weakened by surface superheating.

  9. Laser-induced nucleation of carbon dioxide bubbles

    Science.gov (United States)

    Ward, Martin R.; Jamieson, William J.; Leckey, Claire A.; Alexander, Andrew J.

    2015-04-01

    A detailed experimental study of laser-induced nucleation (LIN) of carbon dioxide (CO2) gas bubbles is presented. Water and aqueous sucrose solutions supersaturated with CO2 were exposed to single nanosecond pulses (5 ns, 532 nm, 2.4-14.5 MW cm-2) and femtosecond pulses (110 fs, 800 nm, 0.028-11 GW cm-2) of laser light. No bubbles were observed with the femtosecond pulses, even at high peak power densities (11 GW cm-2). For the nanosecond pulses, the number of bubbles produced per pulse showed a quadratic dependence on laser power, with a distinct power threshold below which no bubbles were observed. The number of bubbles observed increases linearly with sucrose concentration. It was found that filtering of solutions reduces the number of bubbles significantly. Although the femtosecond pulses have higher peak power densities than the nanosecond pulses, they have lower energy densities per pulse. A simple model for LIN of CO2 is presented, based on heating of nanoparticles to produce vapor bubbles that must expand to reach a critical bubble radius to continue growth. The results suggest that non-photochemical laser-induced nucleation of crystals could also be caused by heating of nanoparticles.

  10. Cohesion of Bubbles in Foam

    Science.gov (United States)

    Ross, Sydney

    1978-01-01

    The free-energy change, or binding energy, of an idealized bubble cluster is calculated on the basis of one mole of gas, and on the basis of a single bubble going from sphere to polyhedron. Some new relations of bubble geometry are developed in the course of the calculation. (BB)

  11. The ductile/brittle transition provides the critical test for materials failure theory

    Science.gov (United States)

    Christensen, Richard M.

    2018-02-01

    It is reasoned that any materials failure theory that claims generality must give full account of ductile versus brittle failure behaviour. Any such proposed theory especially must admit the capability to generate the ductile/brittle transition. A derivation of the failure surface orientations from a particular isotropic materials failure theory reveals that uniaxial tension has its ductile/brittle transition at T/C = 1/2, where T and C are the uniaxial strengths. Between this information and the corresponding ductile/brittle transition in uniaxial compression it becomes possible to derive the functional form for the fully three-dimensional ductile/brittle transition. These same general steps of verification must be fulfilled for any other candidate general failure theory.

  12. Heavy liquid bubble chamber

    CERN Multimedia

    CERN PhotoLab

    1965-01-01

    The CERN Heavy liquid bubble chamber being installed in the north experimental hall at the PS. On the left, the 1180 litre body; in the centre the magnet, which can produce a field of 26 800 gauss; on the right the expansion mechanism.

  13. MISSING: BUBBLE CHAMBER LENS

    CERN Multimedia

    2001-01-01

    Would the person who borrowed the large bubble chamber lens from the Microcosm workshops on the ISR please return it. This is a much used piece from our object archives. If anybody has any information about the whereabouts of this object, please contact Emma.Sanders@cern.ch Thank you

  14. bubble chamber lens

    CERN Multimedia

    Was used in a PS experiment. Before the days of electronic detectors, visual techniques were used to detect particles, using detectors such as spark chambers and bubble chambers. This plexiglass lens was used to focus the image of tracks so they could be photographed.

  15. Scanning bubble chamber pictures

    CERN Multimedia

    1974-01-01

    These were taken at the 2 m hydrogen bubble chamber. The photo shows an early Shiva system where the pre-measurements needed to qualify the event were done manually (cf photo 7408136X). The scanning tables were located in bld. 12. Gilberte Saulmier sits on foreground, Inge Arents at centre.

  16. BEBC bubble chamber

    CERN Multimedia

    CERN PhotoLab

    1972-01-01

    Looking up into the interior of BEBC bubble chamber from the expansion cylinder. At the top of the chamber two fish-eye lenses are installed and three other fish-eye ports are blanked off. In the centre is a heat exchanger.

  17. Soap Bubbles and Crystals

    Indian Academy of Sciences (India)

    Jean Taylor is Professor. Emerita at Rutgers. University and currently a. Visitor at the Courant. Institute, NYU. She works on problems related to soap bubble froths, crystals, and how they evolve under various physical laws. Much of her recent research has been interdisciplinary, joint work with materials scientists ...

  18. Simulations of bubble-wall collision and bouncing

    Science.gov (United States)

    Towfighi, Sohrab; Mehrabian, Hadi; Zenit, Roberto; Feng, James J.

    2012-11-01

    The collision of a rising bubble with a hydrophilic upper wall is studied numerically using an axisymmetric phase-field model. Prior experiments show bubble bouncing or adhesion depending on its incoming velocity. Using experimental parameters, our computation reproduces these different behaviors, including bubble breakup, arrest, and rebound. In particular, dimples are observed on both the fore and aft sides. We further investigate the scaling of the coefficient of restitution and the critical condition delineating arrest from rebound. The latter is plotted as a phase diagram in terms of the Ohnesorge and Weber numbers. We acknowledge financial support from NSERC.

  19. Bubble properties of heterogeneous bubbly flow in a square bubble column

    NARCIS (Netherlands)

    Bai, Wei; Deen, Niels G.; Kuipers, J.A.M.

    2010-01-01

    The present work focuses on the measurements of bubble properties in heterogeneous bubbly flows in a square bubble column. A four-point optical fibre probe was used for this purpose. The accuracy and intrusive effect of the optical probe was investigated first. The results show that the optical

  20. TRANSIT

    Indian Academy of Sciences (India)

    First page Back Continue Last page Overview Graphics. TRANSIT. SYSTEM: DETERMINE 2D-POSITION GLOBALLY BUT INTERMITTENT (POST-FACTO). IMPROVED ACCURACY. PRINCIPLE: POLAR SATELLITES WITH INNOVATIONS OF: GRAVITY-GRADIENT ATTITUDE CONTROL; DRAG COMPENSATION. WORKS ...

  1. Bubble Dynamics and Shock Waves

    CERN Document Server

    2013-01-01

    This volume of the Shock Wave Science and Technology Reference Library is concerned with the interplay between bubble dynamics and shock waves. It is divided into four parts containing twelve chapters written by eminent scientists. Topics discussed include shock wave emission by laser generated bubbles (W Lauterborn, A Vogel), pulsating bubbles near boundaries (DM Leppinen, QX Wang, JR Blake), interaction of shock waves with bubble clouds (CD Ohl, SW Ohl), shock propagation in polydispersed bubbly liquids by model equations (K Ando, T Colonius, CE Brennen. T Yano, T Kanagawa,  M Watanabe, S Fujikawa) and by DNS (G Tryggvason, S Dabiri), shocks in cavitating flows (NA Adams, SJ Schmidt, CF Delale, GH Schnerr, S Pasinlioglu) together with applications involving encapsulated bubble dynamics in imaging (AA Doinikov, A Novell, JM Escoffre, A Bouakaz),  shock wave lithotripsy (P Zhong), sterilization of ships’ ballast water (A Abe, H Mimura) and bubbly flow model of volcano eruptions ((VK Kedrinskii, K Takayama...

  2. Ring Bubbles of Dolphins

    Science.gov (United States)

    Shariff, Karim; Marten, Ken; Psarakos, Suchi; White, Don J.; Merriam, Marshal (Technical Monitor)

    1996-01-01

    The article discusses how dolphins create and play with three types of air-filled vortices. The underlying physics is discussed. Photographs and sketches illustrating the dolphin's actions and physics are presented. The dolphins engage in this behavior on their own initiative without food reward. These behaviors are done repeatedly and with singleminded effort. The first type is the ejection of bubbles which, after some practice on the part of the dolphin, turn into toroidal vortex ring bubbles by the mechanism of baroclinic torque. These bubbles grow in radius and become thinner as they rise vertically to the surface. One dolphin would blow two in succession and guide them to fuse into one. Physicists call this a vortex reconnection. In the second type, the dolphins first create an invisible vortex ring in the water by swimming on their side and waving their tail fin (also called flukes) vigorously. This vortex ring travels horizontally in the water. The dolphin then turns around, finds the vortex and injects a stream of air into it from its blowhole. The air "fills-out" the core of the vortex ring. Often, the dolphin would knock-off a smaller ring bubble from the larger ring (this also involves vortex reconnection) and steer the smaller ring around the tank. One other dolphin employed a few other techniques for planting air into the fluke vortex. One technique included standing vertically in the water with tail-up, head-down and tail piercing the free surface. As the fluke is waved to create the vortex ring, air is entrained from above the surface. Another technique was gulping air in the mouth, diving down, releasing air bubbles from the mouth and curling them into a ring when they rose to the level of the fluke. In the third type, demonstrated by only one dolphin, the longitudinal vortex created by the dorsal fin on the back is used to produce 10-15 foot long helical bubbles. In one technique she swims in a curved path. This creates a dorsal fin vortex since

  3. PARITY ODD BUBBLES IN HOT QCD.

    Energy Technology Data Exchange (ETDEWEB)

    KHARZEEV,D.; PISARSKI,R.D.; TYTGAT,M.H.G.

    1998-04-16

    We consider the topological susceptibility for an SU(N) gauge theory in the limit of a large number of colors, N {r_arrow} {infinity}. At nonzero temperature, the behavior of the topological susceptibility depends upon the order of the deconfining phase transition. The most interesting possibility is if the deconfining transition, at T = T{sub d}, is of second order. Then we argue that Witten's relation implies that the topological susceptibility vanishes in a calculable fashion at Td. As noted by Witten, this implies that for sufficiently light quark masses, metastable states which act like regions of nonzero {theta}--parity odd bubbles--can arise at temperatures just below T{sub d}. Experimentally, parity odd bubbles have dramatic signatures: the {eta}{prime} meson, and especially the {eta} meson, become light, and are copiously produced. Further, in parity odd bubbles, processes which are normally forbidden, such as {eta} {r_arrow} {pi}{sup 0}{pi}{sup 0}, are allowed. The most direct way to detect parity violation is by measuring a parity odd global asymmetry for charged pions, which we define.

  4. Review on fiber morphology obtained by bubble electrospinning and blown bubble spinning

    Directory of Open Access Journals (Sweden)

    He Ji-Huan

    2012-01-01

    Full Text Available Here we show an intriguing phenomenon in the bubble electrospinning process that the ruptured film might be stripped upwards by an electronic force to form a very thin and long plate-like strip, which might been received in the metal receiver as discontinuous backbone-like wrinkled materials, rather than smooth nano-fibers or microspheres. The processes are called the bubble electrospinning. The electronic force can be replaced by a blowing air, and the process is called as the blown bubble spinning. We demonstrate that the size and thickness of the ruptured film are the crucial parameters that are necessary to understand the various observations including beads and nanoporous materials. We identify the conditions required for a ruptured film to form discontinuous structure, and a critical width of the ruptured film to form a cylindrical fiber, above which a long and thin plate-like strip might be obtained, and a criterion for oscillatory jet diameter, which leads to bead morphology of the obtained fibers. The space of the adjacent beads depends on the fiber size. We anticipate our assay to be a starting point for more sophisticated study of the bubble electrospinning and the blown bubble spinning and for mass-production of both nanofibers and nanoscale discontinuous materials.

  5. Intermittency at critical transitions and aging dynamics at the onset of ...

    Indian Academy of Sciences (India)

    We recall that at both the intermittency transitions and the Feigenbaum attractor, in unimodal maps of non-linearity of order > 1, the dynamics rigorously obeys the Tsallis statistics. We account for the -indices and the generalized Lyapunov coefficients that characterize the universality classes of the pitchfork and ...

  6. Intermittency at critical transitions and aging dynamics at the onset of ...

    Indian Academy of Sciences (India)

    México 01000 D.F., Mexico. E-mail: robledo@fisica.unam.mx. Abstract. We recall that at both the intermittency transitions and the Feigenbaum attractor, in unimodal maps of non-linearity of order ζ > 1, the dynamics rigorously obeys the Tsallis statistics. We account for the q-indices and the generalized Lyapunov coefficients ...

  7. A Critical Analysis on Primary Schools Preparedness for the Transition of Autistic Children in Kenya

    Science.gov (United States)

    Otina, Salmon O.; Thinguri, Ruth W.

    2016-01-01

    Autistic children, characterized by impaired social interactions, impaired communication, repetitive and stereotyped patterns of behaviors, are also entitled to education just like the other children in the society. It is therefore important that primary schools in Kenya get prepared so that the children are able to transit to schools from their…

  8. The Family Life Cycle and Critical Transitions: Utilizing Cinematherapy to Facilitate Understanding and Increase Communication

    Science.gov (United States)

    Ballard, Mary B.

    2012-01-01

    Transitioning successfully from one stage of development to the next in the family life cycle requires the accomplishment of certain developmental tasks. Couples and families who fail to accomplish these tasks often become "stuck" and unable to move forward. This impasse frequently leads to heightened stress reactions and crippled channels of…

  9. Seed and seedling traits affecting critical life stage transitions and recruitment outcomes in dryland grasses

    Science.gov (United States)

    1. Seeding native plants is a key management practice to counter land degradation across the globe, yet the majority of seeding efforts fail, limiting the ability of this tool to accelerate ecosystem recovery. 2. Seedling recruitment requires transitions through several life stages, some of which ma...

  10. Constrained Vapor Bubble Experiment

    Science.gov (United States)

    Gokhale, Shripad; Plawsky, Joel; Wayner, Peter C., Jr.; Zheng, Ling; Wang, Ying-Xi

    2002-11-01

    Microgravity experiments on the Constrained Vapor Bubble Heat Exchanger, CVB, are being developed for the International Space Station. In particular, we present results of a precursory experimental and theoretical study of the vertical Constrained Vapor Bubble in the Earth's environment. A novel non-isothermal experimental setup was designed and built to study the transport processes in an ethanol/quartz vertical CVB system. Temperature profiles were measured using an in situ PC (personal computer)-based LabView data acquisition system via thermocouples. Film thickness profiles were measured using interferometry. A theoretical model was developed to predict the curvature profile of the stable film in the evaporator. The concept of the total amount of evaporation, which can be obtained directly by integrating the experimental temperature profile, was introduced. Experimentally measured curvature profiles are in good agreement with modeling results. For microgravity conditions, an analytical expression, which reveals an inherent relation between temperature and curvature profiles, was derived.

  11. On the critical temperature discontinuity at the theoretical bcc-fcc phase transition in compressed selenium and tellurium superconductors

    Science.gov (United States)

    Szczęśniak, D.; Wrona, I. A.; Drzazga, E. A.; Kaczmarek, A. Z.; Szewczyk, K. A.

    2017-11-01

    Recent hydrides-driven advent in the high-pressure phonon-mediated superconductivity motivates research on chemical elements which compound with hydrogen. It is desired that such elements should allow chemical pre-compression of hydrogen to assure the induction of the superconducting phase with the high transition temperature (T C). Herein, we present detailed theoretical insight into the properties of the superconducting state induced under pressure (p) in two of such component elements, namely selenium (Se) and tellurium (Te) at p=250 GPa and p=70 GPa, respectively. The assumed external pressure conditions allow us to conduct our analysis just above previously theoretically predicted bcc-fcc structural phase transition of Se and Te, and identify the possible associated discontinuity effect of the critical temperature. In particular, our numerical analysis is conducted within Migdal-Eliashberg formalism, due to the confirmed electron-phonon pairing mechanism and relatively high electron-phonon coupling constant in the materials of interest. We predict that T C values in Se and Te equal 8.13 K and 5.96 K, respectively, and mark the highest critical temperature values for these elements within the postulated fcc phase. Additionally, we supplement these results by the estimated maximum values of the superconducting energy band gap and the effective mass of electrons. We predict that all these parameters can be used as a guidelines for experimental observation of the critical temperature discontinuity and the corresponding bcc-fcc phase transition in Se and Te superconductors. Moreover, we show that the thermodynamics of superconducting phase in both elements may exhibit deviations from the conventional estimates of the Bardeen-Cooper-Schrieffer theory, and suggest existence of the strong-coupling and retardation effects. Finally, we note that our results can be also instructive for future screening of chemical elements for applications in superconducting hydrides.

  12. Bubble dynamics in drinks

    Science.gov (United States)

    Broučková, Zuzana; Trávníček, Zdeněk; Šafařík, Pavel

    2014-03-01

    This study introduces two physical effects known from beverages: the effect of sinking bubbles and the hot chocolate sound effect. The paper presents two simple "kitchen" experiments. The first and second effects are indicated by means of a flow visualization and microphone measurement, respectively. To quantify the second (acoustic) effect, sound records are analyzed using time-frequency signal processing, and the obtained power spectra and spectrograms are discussed.

  13. Nucleation of relativistic first-order phase transitions

    International Nuclear Information System (INIS)

    Csernai, L.P.; Kapusta, J.I.

    1992-01-01

    The authors apply the general formalism of Langer to compute the nucleation rate for systems of relativistic particles with zero or small baryon number density and which undergo first-order phase transitions. In particular, the pre-exponential factor is computed and it is proportional to the viscosity. The initial growth rate of a critical size bubble or droplet is limited by the ability of dissipative processes to transport latent heat away from the surface. 30 refs., 4 figs

  14. Understanding Transgender and Medically Assisted Gender Transition: Feminism as a Critical Resource.

    Science.gov (United States)

    Nelson, Jamie Lindemann

    2016-11-01

    Feminism has fought the trivialization of women's experiences, championed women's security, and insisted on respect for women's choices. In so doing, feminism has developed important perspectives on the complicated connections between what gender means as it plays itself in people's lives, and the inequalities of power and authority that structure much of human experience. Here, I put a few of these perspectives into contact with an issue where the interactions of gender and power are squarely in play: medicine's role in assisting gender transitioning generally and, specifically, the enduring controversy between medicine and many transgender people about the pathologization of transgender and the role of clinicians as gatekeepers to gender-transition interventions. © 2016 American Medical Association. All Rights Reserved.

  15. Critical linear thermal expansion in the smectic-A phase near the nematic-smectic phase transition.

    Science.gov (United States)

    Anesta, E; Iannacchione, G S; Garland, C W

    2004-10-01

    Recent high-resolution x-ray investigations of the smectic- A (SmA) phase near the nematic-to-SmA transition provide information about the critical behavior of the linear thermal expansion coefficient alpha// parallel to the director. Combining such data with available volume thermal expansion alpha(V) data yields the in-plane linear expansion coefficient alpha(perpendicular) . The critical behaviors of alpha// and alpha(perpendicular) are the same as those for alpha(V) and the heat capacity Cp. However, for any given liquid crystal, alpha//(crit) and alpha(perpendicular)(crit) differ in sign. Furthermore, the quantity alpha// (crit) is positive for SmAd partial bilayer smectics, while it is negative for nonpolar SmAm monomeric smectics. This feature is discussed in terms of the molecular structural aspects of these smectic phases.

  16. Chaotic state to self-organized critical state transition of serrated flow dynamics during brittle-to-ductile transition in metallic glass

    Energy Technology Data Exchange (ETDEWEB)

    Wang, C.; Wang, W. H.; Bai, H. Y., E-mail: hybai@aphy.iphy.ac.cn [Institute of Physics, Chinese Academy of Sciences, Beijing 100190 (China); Sun, B. A. [Centre for Advanced Structural Materials, Department of Mechanical and Biomedical Engineering, City University of Hong Kong, Kowloon Tong, Kowloon (Hong Kong)

    2016-02-07

    We study serrated flow dynamics during brittle-to-ductile transition induced by tuning the sample aspect ratio in a Zr-based metallic glass. The statistical analysis reveals that the serrated flow dynamics transforms from a chaotic state characterized by Gaussian-distribution serrations corresponding to stick-slip motion of randomly generated and uncorrelated single shear band and brittle behavior, into a self-organized critical state featured by intermittent scale-free distribution of shear avalanches corresponding to a collective motion of multiple shear bands and ductile behavior. The correlation found between serrated flow dynamics and plastic deformation might shed light on the plastic deformation dynamic and mechanism in metallic glasses.

  17. A critical transition in leaf evolution facilitated the Cretaceous angiosperm revolution.

    Science.gov (United States)

    de Boer, Hugo Jan; Eppinga, Maarten B; Wassen, Martin J; Dekker, Stefan C

    2012-01-01

    The revolutionary rise of broad-leaved (flowering) angiosperm plant species during the Cretaceous initiated a global ecological transformation towards modern biodiversity. Still, the mechanisms involved in this angiosperm radiation remain enigmatic. Here we show that the period of rapid angiosperm evolution initiated after the leaf interior (post venous) transport path length for water was reduced beyond the leaf interior transport path length for CO2 at a critical leaf vein density of 2.5-5 mm mm(-2). Data and our modelling approaches indicate that surpassing this critical vein density was a pivotal moment in leaf evolution that enabled evolving angiosperms to profit from developing leaves with more and smaller stomata in terms of higher carbon returns from equal water loss. Surpassing the critical vein density may therefore have facilitated evolving angiosperms to develop leaves with higher gas exchange capacities required to adapt to the Cretaceous CO2 decline and outcompete previously dominant coniferous species in the upper canopy.

  18. Cell-State Transitions Regulated by SLUG Are Critical for Tissue Regeneration and Tumor Initiation

    Directory of Open Access Journals (Sweden)

    Sarah Phillips

    2014-05-01

    Full Text Available Perturbations in stem cell activity and differentiation can lead to developmental defects and cancer. We use an approach involving a quantitative model of cell-state transitions in vitro to gain insights into how SLUG/SNAI2, a key developmental transcription factor, modulates mammary epithelial stem cell activity and differentiation in vivo. In the absence of SLUG, stem cells fail to transition into basal progenitor cells, while existing basal progenitor cells undergo luminal differentiation; together, these changes result in abnormal mammary architecture and defects in tissue function. Furthermore, we show that in the absence of SLUG, mammary stem cell activity necessary for tissue regeneration and cancer initiation is lost. Mechanistically, SLUG regulates differentiation and cellular plasticity by recruiting the chromatin modifier lysine-specific demethylase 1 (LSD1 to promoters of lineage-specific genes to repress transcription. Together, these results demonstrate that SLUG plays a dual role in repressing luminal epithelial differentiation while unlocking stem cell transitions necessary for tumorigenesis.

  19. Phenomenological Equations Relating Various Critical Anomalies above a Cubic-to-Tetragonal Phase Transition Point

    Science.gov (United States)

    Hamano, Katsumi; Hirotsu, Shunsuke

    1980-01-01

    Phenomenological equations are derived which interrelate the anomalies in various thermodynamic quantities above the transition point of a cubic-to-tetragonal phase transition caused by an instability of a triply degenerate soft mode. The anomalous part of the Gibbs free energy is assumed to be a simple sum of the three parts which represent the contributions from the three fluctuation components. A cylindrical approximation is adopted to each of the three contributions by taking into account the symmetry of the fluctuations. The theory predicts that the adiabatic elastic compliances, s11s, s12s, and also s11s-s12s should exhibit anomalies proportional to the anomaly in the specific heat at constant pressure. This is in marked contrast with the result of the generalized Pippard equations derived by Garland, and by Janovec. The new equations are successfully tested for KMnF3, CsPbCl3, and CsPbBr3. The β-γ transition of NH4Br is also discussed.

  20. Critical phase transitions of three-dimensional Ising-like dipolar ferromagnets

    Energy Technology Data Exchange (ETDEWEB)

    Nicolaides, Demetris

    2001-06-01

    In ferromagnets with low critical temperatures, dipolar interactions are the reason for the reduction of the critical dimension above which mean-field behavior prevails. Specifically, it is shown that a three-dimensional uniaxial system with dipole{endash}dipole interactions falls into the universality class of a four-dimensional strictly short-range system, whose behavior is mean field with subtle logarithmic corrections which reflect the nonmean-field behavior that sets in fully below four space dimensions. {copyright} 2001 American Institute of Physics.

  1. Food-web stability signals critical transitions in temperate shallow lakes

    NARCIS (Netherlands)

    Kuiper, Jan J.; van Altena, Cassandra; de Ruiter, P.C.; Van Gerven, Luuk P.A.; Janse, Jan H.; Mooij, Wolf M.

    2015-01-01

    A principal aim of ecologists is to identify critical levels of environmental change beyond which ecosystems undergo radical shifts in their functioning. Both food-web theory and alternative stable states theory provide fundamental clues to mechanisms conferring stability to natural systems. Yet, it

  2. Food-web stability signals critical transitions in temperate shallow lakes

    NARCIS (Netherlands)

    Kuiper, J.J.; Altena, Van Cassandra; Ruiter, De P.C.; Gerven, Van L.P.A.; Janse, J.H.; Mooij, W.M.

    2015-01-01

    A principal aim of ecologists is to identify critical levels of environmental change beyond which ecosystems undergo radical shifts in their functioning. Both food-web theory and alternative stable states theory provide fundamental clues to mechanisms conferring stability to natural systems. Yet,

  3. Critical Transitions: A Mixed Methods Examination of Sleep from Inpatient Alcohol Rehabilitation Treatment to the Community.

    Directory of Open Access Journals (Sweden)

    Alyssa Todaro Brooks

    Full Text Available This prospective, repeated measures study utilized a convergent parallel mixed methods approach to assess sleep experiences among individuals who were alcohol-dependent undergoing inpatient detoxification and treatment at a clinical research facility across the transition periods associated with the rehabilitation process: the initial adjustment to becoming an inpatient and the transition from inpatient to outpatient status.This study included individual semi-structured interviews and quantitative measures relating to psychological distress, sleep quality, daytime sleepiness, and sleep-related beliefs and behavior (n = 33; 66.7% male. Interviews were conducted and questionnaires were administered within one week of participants' scheduled discharge date and again four to six weeks post-discharge when they returned for a follow-up visit (or via phone.Participants self-reported significant sleep disturbances at both study time points. Of those participants with valid data at both time points (n = 28, there were no significant changes in mean scores from pre- to post-discharge with the exception of self-efficacy for sleep (SE-S being significantly higher post-discharge. Preliminary qualitative findings suggested differences between those with ongoing sleep disturbances, those whose sleep disturbances had resolved, and those with no sleep disturbances at either time point.This analysis highlights individual variation in sleep throughout the process of inpatient treatment and transition to outpatient aftercare in individuals with alcohol dependence. Collecting quantitative and qualitative data concurrently and combining emerging themes from qualitative data with quantitative analyses allowed for a more thorough examination of this relatively novel area of research and provided information that can be utilized to inform future behavioral sleep interventions.

  4. Critical exponents for a transition from integrability to non-integrability via localization of invariant tori in the Hamiltonian system

    Energy Technology Data Exchange (ETDEWEB)

    Leonel, Edson D; De Oliveira, Juliano A; Saif, Farhan, E-mail: edleonel@rc.unesp.br [Departamento de EstatIstica, Matematica Aplicada e Computacao, UNESP-Univ. Estadual Paulista, Av. 24A, 1515, Bela Vista, 13506-900 Rio Claro, Sao Paulo (Brazil)

    2011-07-29

    Critical exponents that describe a transition from integrability to non-integrability in a two-dimensional, nonlinear and area-preserving map are obtained via localization of the first invariant spanning curve (invariant tori) in the phase space. In a general class of systems, the position of the first invariant tori is estimated by reducing the mapping of the system to the standard mapping where a transition takes place from local to global chaos. The phase space of the mapping shows a large chaotic sea surrounding periodic islands and limited by a set of invariant tori whose position of the first of them depends on the control parameters. The formalism leads us to obtain analytically critical exponents that describe the behaviour of the average variable (action) along the chaotic sea. The result is compared to several models in the literature confirming the approach is of large interest. The formalism used is general and the procedure can be extended to many other different systems. (fast track communication)

  5. Nature of the Blue-Phase-III endash isotropic critical point: An analogy with the liquid-gas transition

    International Nuclear Information System (INIS)

    Anisimov, M.A.; Agayan, V.A.; Collings, P.J.

    1998-01-01

    The analogy with the liquid-gas critical point is analyzed to clarify the nature of the pretransitional behavior of physical properties in the vicinity of the Blue-Phase-III endash isotropic transition in chiral liquid crystalline systems. The analogy is unusual: temperature serves as the ordering field and entropy plays the role of the order parameter. Both mean field and parametric equations of state are formulated in terms of scaling fields. The scaling fields are linear combinations of the physical fields, which are temperature and chirality. It is shown that mixing of the physical field variables naturally leads to a strong asymmetry with respect to the transition temperature in the behavior of the physical properties that cannot be described by simple power laws. While the mean field theory gives a good description of the experimental data, the scaling theory, if one incorporates mixing of the field variables, gives even better agreement with the experimental data, placing this transition in the same universality class as the three-dimensional Ising model. copyright 1998 The American Physical Society

  6. Evidence for reentrant spin glass behavior in transition metal substituted Co-Ga alloys near critical concentration

    Science.gov (United States)

    Yasin, Sk. Mohammad; Srinivas, V.; Kasiviswanathan, S.; Vagadia, Megha; Nigam, A. K.

    2018-04-01

    In the present study magnetic and electrical transport properties of transition metal substituted Co-Ga alloys (near critical cobalt concentration) have been investigated. Analysis of temperature and field dependence of dc magnetization and ac susceptibility (ACS) data suggests an evidence of reentrant spin glass (RSG) phase in Co55.5TM3Ga41.5 (TM = Co, Cr, Fe, Cu). The magnetic transition temperatures (TC and Tf) are found to depend on the nature of TM element substitution with the exchange coupling strength Co-Fe > Co-Co > Co-Cu > Co-Cr. From magnetization dynamics precise transition temperatures for the glassy phases are estimated. It is found that characteristic relaxation times are higher than that of spin glasses with minimal spin-cluster formation. The RSG behavior has been further supported by the temperature dependence of magnetotransport studies. From the magnetic field and substitution effects it has been established that the magnetic and electrical transport properties are correlated in this system.

  7. Bubble measuring instrument and method

    Science.gov (United States)

    Kline-Schoder, Robert (Inventor); Magari, Patrick J. (Inventor)

    2003-01-01

    Method and apparatus are provided for a non-invasive bubble measuring instrument operable for detecting, distinguishing, and counting gaseous embolisms such as bubbles over a selectable range of bubble sizes of interest. A selected measurement volume in which bubbles may be detected is insonified by two distinct frequencies from a pump transducer and an image transducer, respectively. The image transducer frequency is much higher than the pump transducer frequency. The relatively low-frequency pump signal is used to excite bubbles to resonate at a frequency related to their diameter. The image transducer is operated in a pulse-echo mode at a controllable repetition rate that transmits bursts of high-frequency ultrasonic signal to the measurement volume in which bubbles may be detected and then receives the echo. From the echo or received signal, a beat signal related to the repetition rate may be extracted and used to indicate the presence or absence of a resonant bubble. In a preferred embodiment, software control maintains the beat signal at a preselected frequency while varying the pump transducer frequency to excite bubbles of different diameters to resonate depending on the range of bubble diameters selected for investigation.

  8. Helium bubble bursting in tungsten

    International Nuclear Information System (INIS)

    Sefta, Faiza; Juslin, Niklas; Wirth, Brian D.

    2013-01-01

    Molecular dynamics simulations have been used to systematically study the pressure evolution and bursting behavior of sub-surface helium bubbles and the resulting tungsten surface morphology. This study specifically investigates how bubble shape and size, temperature, tungsten surface orientation, and ligament thickness above the bubble influence bubble stability and surface evolution. The tungsten surface is roughened by a combination of adatom “islands,” craters, and pinholes. The present study provides insight into the mechanisms and conditions leading to various tungsten topology changes, which we believe are the initial stages of surface evolution leading to the formation of nanoscale fuzz

  9. Neutron detection via bubble chambers.

    Science.gov (United States)

    Jordan, D V; Ely, J H; Peurrung, A J; Bond, L J; Collar, J I; Flake, M; Knopf, M A; Pitts, W K; Shaver, M; Sonnenschein, A; Smart, J E; Todd, L C

    2005-01-01

    Research investigating the application of pressure-cycled bubble chambers to fast neutron detection is described. Experiments with a Halon-filled chamber showed clear sensitivity to an AmBe neutron source and insensitivity to a (137)Cs gamma source. Bubble formation was documented using high-speed photography, and a ceramic piezo-electric transducer element registered the acoustic signature of bubble formation. In a second set of experiments, the bubble nucleation response of a Freon-134a chamber to an AmBe neutron source was documented with high-speed photography.

  10. Neutron detection via bubble chambers

    Energy Technology Data Exchange (ETDEWEB)

    Jordan, D.V. [Pacific Northwest National Laboratory, MS P8-20, P.O. Box 999, Richland, WA 99352 (United States)]. E-mail: david.jordan@pnl.gov; Ely, J.H. [Pacific Northwest National Laboratory, MS P8-20, P.O. Box 999, Richland, WA 99352 (United States); Peurrung, A.J. [Pacific Northwest National Laboratory, MS P8-20, P.O. Box 999, Richland, WA 99352 (United States); Bond, L.J. [Pacific Northwest National Laboratory, MS P8-20, P.O. Box 999, Richland, WA 99352 (United States); Collar, J.I. [Department of Physics and Enrico Fermi Institute, University of Chicago, 5640 S. Ellis Ave., LASR 214, Chicago, IL 60637 (United States); Flake, M. [Pacific Northwest National Laboratory, MS P8-20, P.O. Box 999, Richland, WA 99352 (United States); Knopf, M.A. [Pacific Northwest National Laboratory, MS P8-20, P.O. Box 999, Richland, WA 99352 (United States); Pitts, W.K. [Pacific Northwest National Laboratory, MS P8-20, P.O. Box 999, Richland, WA 99352 (United States); Shaver, M. [Pacific Northwest National Laboratory, MS P8-20, P.O. Box 999, Richland, WA 99352 (United States); Sonnenschein, A. [Department of Physics and Enrico Fermi Institute, University of Chicago, 5640 S. Ellis Ave., LASR 214, Chicago, IL 60637 (United States); Smart, J.E. [Pacific Northwest National Laboratory, MS P8-20, P.O. Box 999, Richland, WA 99352 (United States); Todd, L.C. [Pacific Northwest National Laboratory, MS P8-20, P.O. Box 999, Richland, WA 99352 (United States)

    2005-12-01

    Research investigating the application of pressure-cycled bubble chambers to fast neutron detection is described. Experiments with a Halon-filled chamber showed clear sensitivity to an AmBe neutron source and insensitivity to a {sup 137}Cs gamma source. Bubble formation was documented using high-speed photography, and a ceramic piezo-electric transducer element registered the acoustic signature of bubble formation. In a second set of experiments, the bubble nucleation response of a Freon-134a chamber to an AmBe neutron source was documented with high-speed photography.

  11. Geometry of criticality, supercriticality, and Hawking-Page transitions in Gauss-Bonnet-AdS black holes

    Science.gov (United States)

    Sahay, Anurag; Jha, Rishabh

    2017-12-01

    We obtain the Ruppeiner geometry associated with the nonextended state space (Λ constant) of the charged Gauss-Bonnet AdS (GB-AdS) black holes and confirm that the state space Riemannian manifold becomes strongly curved in regions where the black hole system develops strong statistical correlations in the grand canonical ensemble (M and Q fluctuating). We establish the exact proportionality between the state space scalar curvature R and the inverse of the singular free energy near the isolated critical point for the grand canonical ensemble in spacetime dimension d =5 , thus hopefully moving a step closer to the agenda of a concrete physical interpretation of R for black holes. On the other hand, we show that while R signals the Davies transition points (which exist in GB-AdS black holes for d ≥6 ) through its divergence, it does not scale as the inverse of the singular free energy there. Furthermore, adapting to the black hole case the ideas developed in [1] in the context of pure fluids, we find that the state space geometry encodes phase coexistence and first order transitions, identifies the asymptotically critical region and even suggests a Widom-line-like crossover regime in the supercritical region for 5 -d case. The sign of R appears to imply a significant difference between the microscopic structure of the small and the large black hole branches in d =5 . We show that thermodynamic geometry informs the microscopic nature of coexisting thermal GB-AdS and black hole phases near the Hawking-Page phase transition.

  12. Critical exponents in the transition to chaos in one-dimensional ...

    Indian Academy of Sciences (India)

    Our calculations show that for q values in the range from 10 to 10, each D q has three characteristic ... f(Xn,µ) has a single critical point Xc = 1. 2 ... Xn·1 = f(Xn,β,µ) =X3 n βXn +µ. (8). Here the parameter β controls the non-linearity term and µ is an additive parameter, which controls the dynamics of the system. Generally ...

  13. Critical dynamics of Hopf bifurcations in the corticothalamic system: Transitions from normal arousal states to epileptic seizures.

    Science.gov (United States)

    Yang, Dong-Ping; Robinson, P A

    2017-04-01

    A physiologically based corticothalamic model of large-scale brain activity is used to analyze critical dynamics of transitions from normal arousal states to epileptic seizures, which correspond to Hopf bifurcations. This relates an abstract normal form quantitatively to underlying physiology that includes neural dynamics, axonal propagation, and time delays. Thus, a bridge is constructed that enables normal forms to be used to interpret quantitative data. The normal form of the Hopf bifurcations with delays is derived using Hale's theory, the center manifold theorem, and normal form analysis, and it is found to be explicitly expressed in terms of transfer functions and the sensitivity matrix of a reduced open-loop system. It can be applied to understand the effect of each physiological parameter on the critical dynamics and determine whether the Hopf bifurcation is supercritical or subcritical in instabilities that lead to absence and tonic-clonic seizures. Furthermore, the effects of thalamic and cortical nonlinearities on the bifurcation type are investigated, with implications for the roles of underlying physiology. The theoretical predictions about the bifurcation type and the onset dynamics are confirmed by numerical simulations and provide physiologically based criteria for determining bifurcation types from first principles. The results are consistent with experimental data from previous studies, imply that new regimes of seizure transitions may exist in clinical settings, and provide a simplified basis for control-systems interventions. Using the normal form, and the full equations from which it is derived, more complex dynamics, such as quasiperiodic cycles and saddle cycles, are discovered near the critical points of the subcritical Hopf bifurcations.

  14. Bubble Coalescence: Effect of Bubble Approach Velocity and Liquid Viscosity

    Czech Academy of Sciences Publication Activity Database

    Orvalho, Sandra; Růžička, Marek; Olivieri, G.; Marzocchella, A.

    2015-01-01

    Roč. 134, SEP 29 (2015), s. 205-216 ISSN 0009-2509 R&D Projects: GA MŠk(CZ) LD13018 Institutional support: RVO:67985858 Keywords : bubble coalescence * bubble approach velocity * liquid viscosity Subject RIV: CI - Industrial Chemistry, Chemical Engineering Impact factor: 2.750, year: 2015

  15. Magnetic Bubble Research

    Science.gov (United States)

    1974-09-01

    x-axis intercept in Figure 20 is twice the coercive field, which for this sample is 0.3 oersted . In this experiment, the laser beam diameter was...the ion im- planted region. From the theory of optical waveguides, Namba, et al., have shown that the minimum refractive index change in an...resulting in bubble outputs at both A + B and A • B outputs. Our first devices of this type were found to have 6 to 7 Oersted bias field margins for

  16. Critical care transition programs and the risk of readmission or death after discharge from an ICU: a systematic review and meta-analysis.

    Science.gov (United States)

    Niven, Daniel J; Bastos, Jaime F; Stelfox, Henry T

    2014-01-01

    To determine whether critical care transition programs reduce the risk of ICU readmission or death, when compared with standard care among adults who survived their incident ICU admission. MEDLINE, EMBASE, CENTRAL, CINAHL, and two clinical trial registries were searched from inception to October 2012. Studies that examined the effects of critical care transition programs on the risk of ICU readmission or death among patients discharged from ICU were selected for review. A critical care transition program included any rapid response team, medical emergency team, critical care outreach team, or ICU nurse liaison program that provided follow-up for patients discharged from ICU. Two reviewers independently extracted data on study characteristics, transition program characteristics, and outcomes (number of ICU readmissions and in-hospital deaths following discharge from ICU). From 3,120 citations, nine before-and-after studies were included. The studies examined medical-surgical populations and described transition programs that were a component of a hospital's outreach team (n = 6) or nurse liaison program (n = 3). Meta-analysis using a fixed-effect model demonstrated a reduced risk of ICU readmission (risk ratio, 0.87 [95% CI, 0.76-0.99]; p = 0.03; I2 = 0%) but no significant reduction in hospital mortality (risk ratio, 0.84 [95% CI, 0.66-1.05]; p = 0.1; I2 = 16%) associated with a critical care transition program. The risk of ICU readmission was similar whether the transition program was included within an outreach team or a nurse liaison program and did not depend on the presence of an intensivist. Critical care transition programs appear to reduce the risk of ICU readmission in patients discharged from ICU to a general hospital ward. Given methodological limitations of the included before-and-after studies, additional research should confirm these observations and explore the ideal model for these programs before recommending implementation.

  17. Stable tridimensional bubble clusters in multi-bubble sonoluminescence (MBSL).

    Science.gov (United States)

    Rosselló, J M; Dellavale, D; Bonetto, F J

    2015-01-01

    In the present work, stable clusters made of multiple sonoluminescent bubbles are experimentally and theoretically studied. Argon bubbles were acoustically generated and trapped using bi-frequency driving within a cylindrical chamber filled with a sulfuric acid aqueous solution (SA85w/w). The intensity of the acoustic pressure field was strong enough to sustain, during several minutes, a large number of positionally and spatially fixed (without pseudo-orbits) sonoluminescent bubbles over an ellipsoidally-shaped tridimensional array. The dimensions of the ellipsoids were studied as a function of the amplitude of the applied low-frequency acoustic pressure (PAc(LF)) and the static pressure in the fluid (P0). In order to explain the size and shape of the bubble clusters, we performed a series of numerical simulations of the hydrodynamic forces acting over the bubbles. In both cases the observed experimental behavior was in excellent agreement with the numerical results. The simulations revealed that the positionally stable region, mainly determined by the null primary Bjerknes force (F→Bj), is defined as the outer perimeter of an axisymmetric ellipsoidal cluster centered in the acoustic field antinode. The role of the high-frequency component of the pressure field and the influence of the secondary Bjerknes force are discussed. We also investigate the effect of a change in the concentration of dissolved gas on the positional and spatial instabilities through the cluster dimensions. The experimental and numerical results presented in this paper are potentially useful for further understanding and modeling numerous current research topics regarding multi-bubble phenomena, e.g. forces acting on the bubbles in multi-frequency acoustic fields, transient acoustic cavitation, bubble interactions, structure formation processes, atomic and molecular emissions of equal bubbles and nonlinear or unsteady acoustic pressure fields in bubbly media. Copyright © 2014 Elsevier B

  18. The phase transition of the first order in the critical region of the gas-liquid system

    Directory of Open Access Journals (Sweden)

    I.R. Yukhnovskii

    2014-12-01

    Full Text Available This is a summarising investigation of the events of the phase transition of the first order that occur in the critical region below the liquid-gas critical point. The grand partition function has been completely integrated in the phase-space of the collective variables. The basic density measure is the quartic one. It has the form of the exponent function with the first, second, third and fourth degree of the collective variables. The problem has been reduced to the Ising model in an external field, the role of which is played by the generalised chemical potential μ*. The line μ*(η =0, where η is the density, is the line of the phase transition. We consider the isothermal compression of the gas till the point where the phase transition on the line μ*(η =0 is reached. When the path of the pressing reaches the line μ* =0 in the gas medium, a droplet of liquid springs up. The work for its formation is obtained, the surface-tension energy is calculated. On the line μ* =0 we have a two-phase system: the gas and the liquid (the droplet one. The equality of the gas and of the liquid chemical potentials is proved. The process of pressing is going on. But the pressure inside the system has stopped, two fixed densities have arisen: one for the gas-phase ηG=ηc(1-d/2 and the other for the liquid-phase ηL=ηc(1+d/2 (symmetrically to the rectlinear diameter, where ηc=0.13044 is the critical density. Starting from that moment the external pressure works as a latent work of pressure. Its value is obtained. As a result, the gas-phase disappears and the whole system turns into liquid. The jump of the density is equal to ηc d, where d=(D/2G1/2 ~ τν/2. D and G are coefficients of the Hamiltonian in the last cell connected with the renormalisation-group symmetry. The equation of state is written.

  19. Influence of viscoelasticity on bubble coalescence in wormlike micellar solutions

    Science.gov (United States)

    Chandran Suja, Vineeth; Kannan, Aadithya; Andrew Kubicka, Bruce; Fuller, Gerald

    2017-11-01

    The stability of bubbles against coalescence in wormlike micellar (WLM) solutions is of importance for many industries. The viscoelasticity of the WLM solutions plays a key role in the bubble stability and can be tuned to change the various stages in the drainage of the thin film between bubbles leading to coalescence. Using a single bubble thin film interferometric technique, we have studied the influence of WLM solution (CTAB /Sodium Salicylate) viscoelasticity on the three stages of thin film drainage- the fluid entrainment, dimple formation and its stability, and the transition to a black film prior to coalescence. The fluid entrained decreased with a decrease in the viscoelastic moduli. The bubble also deformed resulting in the formation of a dimple. The dimple formation and its washout depends on the viscoelastic properties of the solution. For lower surfactant concentration, the dimples were seen to become unstable and have larger washout velocities. Further, depending on the relaxation time of the WLM solution, complex washout dynamics involving rapid dimple deceleration, recoil and oscillatory washouts are observed. As the film thins further, we observe stark step-wise transition to a black film, as opposed to pure surfactant systems that exhibit multiple steps.

  20. Bubble chamber: colour enhanced tracks

    CERN Document Server

    1998-01-01

    This artistically-enhanced image of real particle tracks was produced in the Big European Bubble Chamber (BEBC). Liquid hydrogen is used to create bubbles along the paths of the particles as a piston expands the medium. A magnetic field is produced in the detector causing the particles to travel in spirals, allowing charge and momentum to be measured.

  1. Bubble coalescence in breathing DNA

    DEFF Research Database (Denmark)

    Novotný, Tomas; Pedersen, Jonas Nyvold; Ambjörnsson, Tobias

    2007-01-01

    We investigate the coalescence of two DNA bubbles initially located at weak segments and separated by a more stable barrier region in a designed construct of double-stranded DNA. The characteristic time for bubble coalescence and the corresponding distribution are derived, as well as the distribu...

  2. Bubble columns : Structures or stability?

    NARCIS (Netherlands)

    Harteveld, W.K.

    2005-01-01

    The aim of the thesis is to contribute to the understanding of the hydrodynamics of the gravity driven bubbly flow that can be found in bubble columns. Special attention is paid to the large scale structures that have a strong impact on several key parameters such as the degree of mixing, mass and

  3. Sonoporation from jetting cavitation bubbles

    NARCIS (Netherlands)

    Ohl, C.D.; Arora, M.; Ikink, Roy; de Jong, N.; Versluis, Michel; Delius, Michael; Lohse, Detlef

    2006-01-01

    The fluid dynamic interaction of cavitation bubbles with adherent cells on a substrate is experimentally investigated. We find that the nonspherical collapse of bubbles near to the boundary is responsible for cell detachment. High-speed photography reveals that a wall bounded flow leads to the

  4. Sonoporation from jetting cavitation bubbles

    NARCIS (Netherlands)

    C.-D. Ohl (Claus-Dieter); M. Arora (Manish); R. Ikink (Roy); N. de Jong (Nico); M. Versluis (Michel); M. Delius (Michael); D. Lohse (Detlef)

    2006-01-01

    textabstractThe fluid dynamic interaction of cavitation bubbles with adherent cells on a substrate is experimentally investigated. We find that the nonspherical collapse of bubbles near to the boundary is responsible for cell detachment. High-speed photography reveals that a wall bounded flow leads

  5. Sonoluminescing Air Bubbles Rectify Argon

    NARCIS (Netherlands)

    Lohse, Detlef; Brenner, Michael P.; Dupont, Todd F.; Hilgenfeldt, Sascha; Johnston, Blaine

    1997-01-01

    The dynamics of single bubble sonoluminescence (SBSL) strongly depends on the percentage of inert gas within the bubble. We propose a theory for this dependence, based on a combination of principles from sonochemistry and hydrodynamic stability. The nitrogen and oxygen dissociation and subsequent

  6. Bubble Formation in Basalt-like Melts

    DEFF Research Database (Denmark)

    Jensen, Martin; Keding, Ralf; Yue, Yuanzheng

    2011-01-01

    The effect of the melting temperature on bubble size and bubble formation in an iron bearing calcium aluminosilicate melt is studied by means of in-depth images acquired by optical microscopy. The bubble size distribution and the total bubble volume are determined by counting the number of bubbles...... and their diameter. The variation in melting temperature has little influence on the overall bubble volume. However, the size distribution of the bubbles varies with the melting temperature. When the melt is slowly cooled, the bubble volume increases, implying decreased solubility of the gaseous species. Mass...

  7. Marxist Theory in Critical Transitions: The Democratization of the Media in Post-Neoliberal Argentina

    Directory of Open Access Journals (Sweden)

    Pablo Castagno

    2012-05-01

    Full Text Available This article contends that for socialist emancipation to occur it is crucial to investigate how political cadres conceal, regulate or displace the demands of citizens and workers in the context of the calamitous effects of global capitalism. Analyzing the constitutive relationship between politics and the media is an essential component in researching those practices of state ideological production. Specifically looking into the transformation of media policy in the case of Argentina, this article problematizes the different political forms through which the state has cloaked its fundamental contradiction: alleged representation of the general interests of citizens, when explored in critical depth, reveals the state’s actual adjustment to a process of capitalist transnationalization that increases irrationality, social inequality and misery. Through this lens, the article emphasizes the value of Marxist dialectic method and theory in imagining a true democratic future.

  8. Food-web stability signals critical transitions in temperate shallow lakes.

    Science.gov (United States)

    Kuiper, Jan J; van Altena, Cassandra; de Ruiter, Peter C; van Gerven, Luuk P A; Janse, Jan H; Mooij, Wolf M

    2015-07-15

    A principal aim of ecologists is to identify critical levels of environmental change beyond which ecosystems undergo radical shifts in their functioning. Both food-web theory and alternative stable states theory provide fundamental clues to mechanisms conferring stability to natural systems. Yet, it is unclear how the concept of food-web stability is associated with the resilience of ecosystems susceptible to regime change. Here, we use a combination of food web and ecosystem modelling to show that impending catastrophic shifts in shallow lakes are preceded by a destabilizing reorganization of interaction strengths in the aquatic food web. Analysis of the intricate web of trophic interactions reveals that only few key interactions, involving zooplankton, diatoms and detritus, dictate the deterioration of food-web stability. Our study exposes a tight link between food-web dynamics and the dynamics of the whole ecosystem, implying that trophic organization may serve as an empirical indicator of ecosystem resilience.

  9. Critical capacity, travel time delays and travel time distribution of rapid mass transit systems

    Science.gov (United States)

    Legara, Erika Fille; Monterola, Christopher; Lee, Kee Khoon; Hung, Gih Guang

    2014-07-01

    We set up a mechanistic agent-based model of a rapid mass transit system. Using empirical data from Singapore's unidentifiable smart fare card, we validate our model by reconstructing actual travel demand and duration of travel statistics. We subsequently use this model to investigate two phenomena that are known to significantly affect the dynamics within the RTS: (1) overloading in trains and (2) overcrowding in the RTS platform. We demonstrate that by varying the loading capacity of trains, a tipping point emerges at which an exponential increase in the duration of travel time delays is observed. We also probe the impact on the rail system dynamics of three types of passenger growth distribution across stations: (i) Dirac delta, (ii) uniform and (iii) geometric, which is reminiscent of the effect of land use on transport. Under the assumption of a fixed loading capacity, we demonstrate the dependence of a given origin-destination (OD) pair on the flow volume of commuters in station platforms.

  10. Emergent Self-Organized Criticality in Gene Expression Dynamics: Temporal Development of Global Phase Transition Revealed in a Cancer Cell Line

    Science.gov (United States)

    Tsuchiya, Masa; Giuliani, Alessandro; Hashimoto, Midori; Erenpreisa, Jekaterina; Yoshikawa, Kenichi

    2015-01-01

    Background The underlying mechanism of dynamic control of the genome-wide expression is a fundamental issue in bioscience. We addressed it in terms of phase transition by a systemic approach based on both density analysis and characteristics of temporal fluctuation for the time-course mRNA expression in differentiating MCF-7 breast cancer cells. Methodology In a recent work, we suggested criticality as an essential aspect of dynamic control of genome-wide gene expression. Criticality was evident by a unimodal-bimodal transition through flattened unimodal expression profile. The flatness on the transition suggests the existence of a critical transition at which up- and down-regulated expression is balanced. Mean field (averaging) behavior of mRNAs based on the temporal expression changes reveals a sandpile type of transition in the flattened profile. Furthermore, around the transition, a self-similar unimodal-bimodal transition of the whole expression occurs in the density profile of an ensemble of mRNA expression. These singular and scaling behaviors identify the transition as the expression phase transition driven by self-organized criticality (SOC). Principal Findings Emergent properties of SOC through a mean field approach are revealed: i) SOC, as a form of genomic phase transition, consolidates distinct critical states of expression, ii) Coupling of coherent stochastic oscillations between critical states on different time-scales gives rise to SOC, and iii) Specific gene clusters (barcode genes) ranging in size from kbp to Mbp reveal similar SOC to genome-wide mRNA expression and ON-OFF synchronization to critical states. This suggests that the cooperative gene regulation of topological genome sub-units is mediated by the coherent phase transitions of megadomain-scaled conformations between compact and swollen chromatin states. Conclusion and Significance In summary, our study provides not only a systemic method to demonstrate SOC in whole-genome expression

  11. Growing bubbles rising in line

    Directory of Open Access Journals (Sweden)

    John F. Harper

    2001-01-01

    Full Text Available Over many years the author and others have given theories for bubbles rising in line in a liquid. Theory has usually suggested that the bubbles will tend towards a stable distance apart, but experiments have often showed them pairing off and sometimes coalescing. However, existing theory seems not to deal adequately with the case of bubbles growing as they rise, which they do if the liquid is boiling, or is a supersaturated solution of a gas, or simply because the pressure decreases with height. That omission is now addressed, for spherical bubbles rising at high Reynolds numbers. As the flow is then nearly irrotational, Lagrange's equations can be used with Rayleigh's dissipation function. The theory also works for bubbles shrinking as they rise because they dissolve.

  12. Critical temperature of liquid-gas phase transition for hot nuclear matter and three-body force effect

    International Nuclear Information System (INIS)

    Zuo Wei; Lu Guangcheng; Li Zenghua; Luo Peiyan; Chinese Academy of Sciences, Beijing

    2005-01-01

    The finite temperature Brueckner-Hartree-Fock (FTBHF) approach is extended by introducing a microscopic three-body force. Within the extended approach, the three-body force effects on the equation of state of hot nuclear matter and its temperature dependence have been investigated. The critical properties of the liquid-gas phase transition of hot nuclear matter have been calculated. It is shown that the three-body force provides a repulsive contribution to the equation of state of hot nuclear matter. The repulsive effect of the three-body force becomes more pronounced as the density and temperature increase and consequently inclusion of the three-body force contribution in the calculation reduces the predicted critical temperature from about 16 MeV to about 13 MeV. By separating the contribution originated from the 2σ-exchange process coupled to the virtual excitation of a nucleon-antinucleon pair from the full three-body force, the connection between the three-body force effect and the relativistic correction from the Dirac-Brueckner-Hartree-Fock has been explored. It turns out that the contribution of the 2σ-N(N-bar) part is more repulsive than that of the full three-body force and the calculated critical temperature is about 11 MeV if only the 2σ-N(N-bar) component of the three-body force is included which is lower than the value obtained in the case of including the full three-body force and is close to the value predicted by the Dirac-Brueckner-Hartree-Fock (DBHF) approach. Our result provides a reasonable explanation for the discrepancy between the values of critical temperature predicted from the FTBHF approach including the three-body force and the DBHF approach. (authors)

  13. Bubble length affects bubble speed in a rough microfluidic channel

    Science.gov (United States)

    Zhang, Quan; Turitsyn, Konstantin; Witten, Tom

    2010-03-01

    We discuss the creeping motion of bubbles of different length in rough capillary tubes filled with carrier fluids. This extends the results of BrethertonfootnotetextF.P.Bretherton, 1961, J. Fluid Mech., 10, 166. for an infinite-length bubble at small capillary number Ca in a circular tube. We first derive the asymptotic corrections to the speed owing to finite length. This dependence on length is exponentially small, with a decay length much shorter than the tube radius R. Then we discuss the effect of azimuthal roughness of the tube on the bubble speed. Tube roughness leads to a carrier fluid flow in the azimuthal plane; this flow controls the relaxation of the bubble shape to its infinite length limit. For long-wavelength roughness, we find that the above decay length becomes much longer and even comparable to R. This implies a much-enhanced dependence of the bubble velocity on length. A shorter bubble should then catch up with a longer bubble ahead of it in the same channel. This mechanism may explain catch-up effects seen experimentally.footnotetextR.Ismagilov, private communication.

  14. The living times of bubbles at the interface

    Science.gov (United States)

    Cameron, Benjamin; Bourouiba, Lydia; Vandenberghe, Nicolas; Villermaux, Emmanuel

    2014-11-01

    The lifetime of a water bubble at the surface of a pool prior to its burst remains an open question. It is known that the death of a bubble is initiated by the nucleation of a hole in its shell. However, the mechanisms governing the occurrence of such nucleation sites and prescribing the lifetime of bubbles remain unclear. Combining original visualizations, quantitative measurements of bubbles lifetimes and simple theoretical ideas, we report direct observations of the onset of the bursting process and rationalize the link between the rich interfacial events leading to the hole nucleation on the shell and the resulting robust bubble lifetimes distributions. These play a critical role in shaping the final size distribution of the droplets emitted. We will underline the consequences of the process in the sensible world, like air-sea water vapor exchanges. Bubbles bursting at the surface of water sources also allow for high levels of contamination and long-term exposure to a range of respiratory human pathogens and irritants indoors. Indeed, the droplets created by such bursts can contribute to the transfer of pathogens to the air, followed by their dispersal, thus bridging this subtle problem with unexpected new areas in health. Thanks to the financial support of the MISTI-FRANCE MIT program.

  15. Speculation and the 2008 oil bubble: The DCOT Report analysis

    International Nuclear Information System (INIS)

    Tokic, Damir

    2012-01-01

    This article analyzes the CFTC's Disaggregated Commitments of Traders (DCOT) Report to get more insights into the behavior of different traders during the 2008 oil bubble. The analysis shows that: (1) the Money Manager category perfectly played the oil bubble, got in early and started selling shortly before the bubble peak; (2) the Producer/Merchant/Processor/User category and the Nonreportable category were covering their short positions into the peak of the bubble; (3) the Swap/Dealer category benefited while the price of oil was rising, but incurred heavy losses as the price of oil collapsed; (4) we find no indications of speculation by any group of traders via the positive feedback trading or rational destabilization; and (5) we do, however, criticize the commercial hedgers for failing to arbitrage the soaring oil prices in 2008. - Highlights: ► We analyze the DCOT Report to study the behavior of traders during the 2008 oil bubble. ► the Money Manger category perfectly played the oil bubble. ► the Producer/Merchant/Processor/User and the Nonreportables engaged in short covering. ► the Swap/Dealer incurred heavy losses as the price of oil collapsed. ► We find no indications of speculation by any category.

  16. Wrinkling in the deflation of elastic bubbles

    KAUST Repository

    Aumaitre, Elodie

    2013-03-01

    The protein hydrophobin HFBII self-assembles into very elastic films at the surface of water; these films wrinkle readily upon compression. We demonstrate and study this wrinkling instability in the context of non-planar interfaces by forming HFBII layers at the surface of bubbles whose interfaces are then compressed by deflation of the bubble. By varying the initial concentration of the hydrophobin solutions, we are able to show that buckling occurs at a critical packing fraction of protein molecules on the surface. Independent experiments show that at this packing fraction the interface has a finite positive surface tension, and not zero surface tension as is usually assumed at buckling. We attribute this non-zero wrinkling tension to the finite elasticity of these interfaces. We develop a simple geometrical model for the evolution of the wrinkle length with further deflation and show that wrinkles grow rapidly near the needle (used for deflation) towards the mid-plane of the bubble. This geometrical model yields predictions for the length of wrinkles in good agreement with experiments independently of the rheological properties of the adsorbed layer. © 2013 EDP Sciences, SIF, Springer-Verlag Berlin Heidelberg.

  17. Wrinkling in the deflation of elastic bubbles.

    Science.gov (United States)

    Aumaitre, Elodie; Knoche, Sebastian; Cicuta, Pietro; Vella, Dominic

    2013-03-01

    The protein hydrophobin HFBII self-assembles into very elastic films at the surface of water; these films wrinkle readily upon compression. We demonstrate and study this wrinkling instability in the context of non-planar interfaces by forming HFBII layers at the surface of bubbles whose interfaces are then compressed by deflation of the bubble. By varying the initial concentration of the hydrophobin solutions, we are able to show that buckling occurs at a critical packing fraction of protein molecules on the surface. Independent experiments show that at this packing fraction the interface has a finite positive surface tension, and not zero surface tension as is usually assumed at buckling. We attribute this non-zero wrinkling tension to the finite elasticity of these interfaces. We develop a simple geometrical model for the evolution of the wrinkle length with further deflation and show that wrinkles grow rapidly near the needle (used for deflation) towards the mid-plane of the bubble. This geometrical model yields predictions for the length of wrinkles in good agreement with experiments independently of the rheological properties of the adsorbed layer.

  18. Low-Frequency Optical Studies of High Critical Transition Temperature Superconductors

    Science.gov (United States)

    Voss, Karl Friedrich

    also seem to determine the transition temperature. The dissertation ends with a summary of the results.

  19. Ricci flows, wormholes and critical phenomena

    Energy Technology Data Exchange (ETDEWEB)

    Husain, Viqar; Seahra, Sanjeev S [Department of Mathematics and Statistics, University of New Brunswick, Fredericton, NB E3B 5A3 (Canada)

    2008-11-21

    We study the evolution of wormhole geometries under the Ricci flow using numerical methods. Depending on values of initial data parameters, wormhole throats either pinch off or evolve to a monotonically growing state. The transition between these two behaviors exhibits a form of critical phenomena reminiscent of that observed in gravitational collapse. Similar results are obtained for initial data that describe space bubbles attached to asymptotically flat regions. Our numerical methods are applicable to 'matter-coupled' Ricci flows derived from conformal invariance in string theory. (fast track communication)

  20. The bubble legacy

    Science.gov (United States)

    Hecht, Jeff

    2010-05-01

    Imagine an optics company - let's call it JDS Uniphase - with a market capitalization approaching the gross domestic product (GDP) of Ireland. Now imagine it merging with a laser company - say, SDL - that has a stock valuation of 41bn, higher than the GDP of Costa Rica. Finally, imagine a start-up with 109m in venture capital in its pocket but no product to its name (Novalux) turning down an offer of 500m as insufficient. It may be hard to believe, but these tales are true: they occurred in the year 2000 - an era when the laser, fibre-optics and photonics industries were the darlings of the financial world. Such was the madcap nature of that brief period that survivors call it simply "the bubble".

  1. Direct numerical simulation of bubble dynamics in subcooled and near-saturated convective nucleate boiling

    International Nuclear Information System (INIS)

    Lal, Sreeyuth; Sato, Yohei; Niceno, Bojan

    2015-01-01

    Highlights: • We simulate convective nucleate pool boiling with a novel phase-change model. • We simulate four cases at different sub-cooling and wall superheat levels. • We investigate the flow structures around the growing bubble and analyze the accompanying physics. • We accurately simulate bubble shape elongation and enhanced wall cooling due to the sliding and slanting motions of bubbles. • Bubble cycle durations show good agreement with experimental observations. - Abstract: With the long-term objective of Critical Heat Flux (CHF) prediction, bubble dynamics in convective nucleate boiling flows has been studied using a Direct Numerical Simulation (DNS). A sharp-interface phase change model which was originally developed for pool boiling flows is extended to convective boiling flows. For physical scales smaller than the smallest flow scales (smaller than the grid size), a micro-scale model was used. After a grid dependency study and a parametric study for the contact angle, four cases of simulation were carried out with different wall superheat and degree of subcooling. The flow structures around the growing bubble were investigated together with the accompanying physics. The relation between the heat flux evolution and the bubble growth was studied, along with investigations of bubble diameter and bubble base diameter evolutions across the four cases. As a validation, the evolutions of bubble diameter and bubble base diameter were compared to experimental observations. The bubble departure period and the bubble shapes show good agreement between the experiment and the simulation, although the Reynolds number of the simulation cases is relatively low

  2. Sonochemistry and the acoustic bubble

    CERN Document Server

    Grieser, Franz; Enomoto, Naoya; Harada, Hisashi; Okitsu, Kenji; Yasui, Kyuichi

    2015-01-01

    Sonochemistry and the Acoustic Bubble provides an introduction to the way ultrasound acts on bubbles in a liquid to cause bubbles to collapse violently, leading to localized 'hot spots' in the liquid with temperatures of 5000° celcius and under pressures of several hundred atmospheres. These extreme conditions produce events such as the emission of light, sonoluminescence, with a lifetime of less than a nanosecond, and free radicals that can initiate a host of varied chemical reactions (sonochemistry) in the liquid, all at room temperature. The physics and chemistry behind the p

  3. Effect of hockey-stick-shaped molecules on the critical behavior at the nematic to isotropic and smectic-A to nematic phase transitions in octylcyanobiphenyl.

    Science.gov (United States)

    Chakraborty, Anish; Chakraborty, Susanta; Das, Malay Kumar

    2015-03-01

    In the field of soft matter research, the characteristic behavior of both nematic-isotropic (N-I) and smectic-A nematic(Sm-A N) phase transitions has gained considerable attention due to their several attractive features. In this work, a high-resolution measurement of optical birefringence (Δn) has been performed to probe the critical behavior at the N-I and Sm-A N phase transitions in a binary system comprising the rodlike octylcyanobiphenyl and a laterally methyl substituted hockey-stick-shaped mesogen, 4-(3-n-decyloxy-2-methyl-phenyliminomethyl)phenyl 4-n-dodecyloxycinnamate. For the investigated mixtures, the critical exponent β related to the limiting behavior of the nematic order parameter close to the N-I phase transition has come out to be in good conformity with the tricritical hypothesis. Moreover, the yielded effective critical exponents (α', β', γ') characterizing the critical fluctuation near the Sm-A N phase transition have appeared to be nonuniversal in nature. With increasing hockey-stick-shaped dopant concentration, the Sm-A N phase transition demonstrates a strong tendency to be driven towards a first-order nature. Such a behavior has been accounted for by considering a modification of the effective intermolecular interactions and hence the related coupling between the nematic and smectic order parameters, caused by the introduction of the angular mesogenic molecules.

  4. Effect of hockey-stick-shaped molecules on the critical behavior at the nematic to isotropic and smectic-A to nematic phase transitions in octylcyanobiphenyl

    Science.gov (United States)

    Chakraborty, Anish; Chakraborty, Susanta; Das, Malay Kumar

    2015-03-01

    In the field of soft matter research, the characteristic behavior of both nematic-isotropic (N -I ) and smectic-A nematic (Sm -A N ) phase transitions has gained considerable attention due to their several attractive features. In this work, a high-resolution measurement of optical birefringence (Δ n ) has been performed to probe the critical behavior at the N -I and Sm -A N phase transitions in a binary system comprising the rodlike octylcyanobiphenyl and a laterally methyl substituted hockey-stick-shaped mesogen, 4-(3-n -decyloxy-2-methyl-phenyliminomethyl)phenyl 4-n -dodecyloxycinnamate. For the investigated mixtures, the critical exponent β related to the limiting behavior of the nematic order parameter close to the N -I phase transition has come out to be in good conformity with the tricritical hypothesis. Moreover, the yielded effective critical exponents (α', β', γ') characterizing the critical fluctuation near the Sm -A N phase transition have appeared to be nonuniversal in nature. With increasing hockey-stick-shaped dopant concentration, the Sm -A N phase transition demonstrates a strong tendency to be driven towards a first-order nature. Such a behavior has been accounted for by considering a modification of the effective intermolecular interactions and hence the related coupling between the nematic and smectic order parameters, caused by the introduction of the angular mesogenic molecules.

  5. A numerical study of three-dimensional bubble merger in the Rayleigh endash Taylor instability

    International Nuclear Information System (INIS)

    Li, X.L.

    1996-01-01

    The Rayleigh endash Taylor instability arises when a heavy fluid adjacent to a light fluid is accelerated in a direction against the density gradient. Under this unstable configuration, a perturbation mode of small amplitude grows into bubbles of the light fluid and spikes of the heavy fluid. Taylor discovered the steady state motion with constant velocity for a single bubble or periodic bubbles in the Rayleigh endash Taylor instability. Read and Youngs studied the motion of a randomly perturbed fluid interface in the Rayleigh endash Taylor instability. They reported constant acceleration for the overall bubble envelope. Bubble merger is believed to cause the transition from constant velocity to constant acceleration. In this paper, we present a numerical study of this important physical phenomenon. It analyzes the physical process of bubble merger and the relationship between the horizontal bubble expansion and the vertical interface acceleration. A dynamic bubble velocity, beyond Taylor close-quote s steady state value, is observed during the merger process. It is believed that this velocity is due to the superposition of the bubble velocity with a secondary subharmonic unstable mode. The numerical results are compared with experiments. copyright 1996 American Institute of Physics

  6. New evidence on the first financial bubble

    NARCIS (Netherlands)

    Frehen, R.G.P.; Goetzmann, W.; Rouwenhorst, K.G.

    2013-01-01

    The Mississippi Bubble, South Sea Bubble and the Dutch Windhandel of 1720 together represent the world's first global financial bubble. We hand-collect cross-sectional price data and investor account data from 1720 to test theories about market bubbles. Our tests suggest that innovation was a key

  7. Taxing the rich: recombinations and bubble growth during reionization

    Science.gov (United States)

    Furlanetto, Steven R.; Oh, S. Peng

    2005-11-01

    Reionization is inhomogeneous for two reasons: the clumpiness of the intergalactic medium (IGM), and clustering of the discrete ionizing sources. While numerical simulations can in principle take both into account, they are at present limited by small box sizes. On the other hand, analytic models have only examined the limiting cases of a clumpy IGM (with uniform ionizing emissivity) and clustered sources (embedded in a uniform IGM). Here, we present the first analytic model that includes both factors. At first, recombinations can be ignored and ionized bubbles grow primarily through major mergers, because at any given moment the bubbles have a well-defined characteristic size. As a result, reionization resembles `punctuated equilibrium,' with a series of well-separated sharp jumps in the ionizing background. These features are local effects and do not reflect similar jumps in the global ionized fraction. We then combine our bubble model with a simple description of recombinations in the IGM. We show that the bubbles grow until recombinations balance ionizations, when their expansion abruptly halts. If the IGM density structure is similar to that at moderate redshifts, this limits the bubble radii to ~20 comoving Mpc; however, if the IGM is significantly clumpier at higher redshifts (because of minihalo formation, for example), the limit could be much smaller. Once a bubble reaches saturation, that region of the Universe has for all intents and purposes entered the `post-overlap' stage. Because different HII regions saturate over a finite time interval, the overlap epoch actually has a finite width. Our model also predicts a mean recombination rate several times larger than expected for a uniformly illuminated IGM. This picture naturally explains the substantial large-scale variation in Lyman-series opacity along the lines of sight to the known z > 6 quasars. More quasar spectra will shed light on the transition between the `bubble-dominated' topology

  8. Bubble nucleation in stout beers

    Science.gov (United States)

    Lee, W. T.; McKechnie, J. S.; Devereux, M. G.

    2011-05-01

    Bubble nucleation in weakly supersaturated solutions of carbon dioxide—such as champagne, sparkling wines, and carbonated beers—is well understood. Bubbles grow and detach from nucleation sites: gas pockets trapped within hollow cellulose fibers. This mechanism appears not to be active in stout beers that are supersaturated solutions of nitrogen and carbon dioxide. In their canned forms these beers require additional technology (widgets) to release the bubbles which will form the head of the beer. We extend the mathematical model of bubble nucleation in carbonated liquids to the case of two gases and show that this nucleation mechanism is active in stout beers, though substantially slower than in carbonated beers and confirm this by observation. A rough calculation suggests that despite the slowness of the process, applying a coating of hollow porous fibers to the inside of a can or bottle could be a potential replacement for widgets.

  9. Holography in small bubble chambers

    International Nuclear Information System (INIS)

    Lecoq, P.

    1984-01-01

    This chapter reports on an experiment to determine the total charm cross section at different incident momenta using the small, heavy liquid bubble chamber HOBC. Holography in liquid hydrogen is also tested using the holographic lexan bubble chamber HOLEBC with the aim of preparing a future holographic experiment in hydrogen. The high intensity tests show that more than 100 incident tracks per hologram do not cause a dramatic effect on the picture quality. Hydrogen is more favorable than freon as the bubble growth is much slower in hydrogen. An advantage of holography is to have the maximum resolution in the full volume of the bubble chamber, which allows a gain in sensitivity by a factor of 10 compared to classical optics as 100 tracks per hologram look reasonable. Holograms are not more difficult to analyze than classical optics high-resolution pictures. The results show that holography is a very powerful technique which can be used in very high resolution particle physics experiments

  10. Circulatory osmotic desalination driven by a mild temperature gradient based on lower critical solution temperature (LCST) phase transition materials.

    Science.gov (United States)

    Mok, Yeongbong; Nakayama, Daichi; Noh, Minwoo; Jang, Sangmok; Kim, Taeho; Lee, Yan

    2013-11-28

    Abrupt changes in effective concentration and osmotic pressure of lower critical solution temperature (LCST) mixtures facilitate the design of a continuous desalination method driven by a mild temperature gradient. We propose a prototype desalination system by circulating LCST mixtures between low and high temperature (low T and high T) units. Water molecules could be drawn from a high-salt solution to the LCST mixture through a semipermeable membrane at a temperature lower than the phase transition temperature, at which the effective osmotic pressure of the LCST mixture is higher than the high-salt solution. After transfer of water to the high T unit where the LCST mixture is phase-separated, the water-rich phase could release the drawn water into a well-diluted solution through the second membrane due to the significant decrease in effective concentration. The solute-rich phase could be recovered in the low T unit via a circulation process. The molar mass, phase transition temperature, and aqueous solubility of the LCST solute could be tuneable for the circulatory osmotic desalination system in which drawing, transfer, release of water, and the separation and recovery of the solutes could proceed simultaneously. Development of a practical desalination system that draws water molecules directly from seawater and produces low-salt water with high purity by mild temperature gradients, possibly induced by sunlight or waste heat, could be attainable by a careful design of the molecular structure and combination of the circulatory desalination systems based on low- and high-molar-mass LCST draw solutes.

  11. Dynamics of the central entrapped bubble during drop impact

    Science.gov (United States)

    Jian, Zhen; Channa, Murad Ali; Thoraval, Marie-Jean

    2017-11-01

    When a drop impacts onto a liquid surface, it entraps a thin central air disk. The air is then brought towards the axis of symmetry by surface tension. This contraction dynamics is very challenging to capture, due to the small length scales (a few micrometers thin air disk) and time scales (contracting in a few hundred microseconds). We use the open source two-phase flow codes Gerris and Basilisk to study this air entrapment phenomenon. The effects of liquid properties such as viscosity and surface tension, and of the impact velocity were investigated. We focus on the morphology of the contracting air disk. The bubble is expected to contract into a single spherical bubble. However, in some cases, the air can be stretched vertically by the liquid inertia and split into two smaller bubbles. The convergence of capillary waves on the air disk towards the axis of symmetry can also make it rupture at the center, thus forming a toroidal bubble. In other cases, vorticity shedding can deform the contracting bubble, leading to more complex structures. A parameter space analysis based on the Reynolds and Weber numbers was then done to classify the different regimes and explain the transitions. Full affiliation:State Key Laboratory for Strength and Vibration of Mechanical Structures,Shaanxi Key Laboratory of Environment and Control for Flight Vehicle,International Center for Applied Mechanics,School of Aerospace,Xi'an Jiaotong University.

  12. Temperature measurements in cavitation bubbles

    Science.gov (United States)

    Coutier-Delgosha, Olivier

    2016-11-01

    Cavitation is usually a nearly isothermal process in the liquid phase, but in some specific flow conditions like hot water or cryogenic fluids, significant temperature variations are detected. In addition, a large temperature increase happens inside the cavitation bubbles at the very end of their collapse, due to the fast compression of the gas at the bubble core, which is almost adiabatic. This process is of primary interest in various biomedical and pharmaceutical applications, where the mechanisms of bubble collapse plays a major role. To investigate the amplitude and the spatial distribution of these temperature variations inside and outside the cavitation bubbles, a system based on cold wires has been developed. They have been tested in a configuration of a single bubble obtained by submitting a small air bubble to a large amplitude pressure wave. Some promising results have been obtained after the initial validation tests. This work is funded by the Office of Naval Research Global under Grant N62909-16-1-2116, Dr. Salahuddin Ahmed & Ki-Han Kim program managers.

  13. From rational bubbles to crashes

    Science.gov (United States)

    Sornette, D.; Malevergne, Y.

    2001-10-01

    We study and generalize in various ways the model of rational expectation (RE) bubbles introduced by Blanchard and Watson in the economic literature. Bubbles are argued to be the equivalent of Goldstone modes of the fundamental rational pricing equation, associated with the symmetry-breaking introduced by non-vanishing dividends. Generalizing bubbles in terms of multiplicative stochastic maps, we summarize the result of Lux and Sornette that the no-arbitrage condition imposes that the tail of the return distribution is hyperbolic with an exponent μbubble model to arbitrary dimensions d: a number d of market time series are made linearly interdependent via d× d stochastic coupling coefficients. We derive the no-arbitrage condition in this context and, with the renewal theory for products of random matrices applied to stochastic recurrence equations, we extend the theorem of Lux and Sornette to demonstrate that the tails of the unconditional distributions associated with such d-dimensional bubble processes follow power laws, with the same asymptotic tail exponent μmodel and the non-stationary growth rate model) of the RE bubble model that provide two ways of reconciliation with the stylized facts of financial data.

  14. Bubble bursting at an interface

    Science.gov (United States)

    Kulkarni, Varun; Sajjad, Kumayl; Anand, Sushant; Fezzaa, Kamel

    2017-11-01

    Bubble bursting is crucial to understanding the life span of bubbles at an interface and more importantly the nature of interaction between the bulk liquid and the outside environment from the point of view of chemical and biological material transport. The dynamics of the bubble as it rises from inside the liquid bulk to its disappearance on the interface after bursting is an intriguing process, many aspects of which are still being explored. In our study, we make detailed high speed imaging measurements to examine carefully the hole initiation and growth in bursting bubbles that unearth some interesting features of the process. Previous analyses available in literature are revisited based on our novel experimental visualizations. Using a combination of experiments and theory we investigate the role of various forces during the rupturing process. This work aims to further our current knowledge of bubble dynamics at an interface with an aim of predicting better the bubble evolution from its growth to its eventual integration with the liquid bulk.

  15. Measuring online social bubbles

    Directory of Open Access Journals (Sweden)

    Dimitar Nikolov

    2015-12-01

    Full Text Available Social media have become a prevalent channel to access information, spread ideas, and influence opinions. However, it has been suggested that social and algorithmic filtering may cause exposure to less diverse points of view. Here we quantitatively measure this kind of social bias at the collective level by mining a massive datasets of web clicks. Our analysis shows that collectively, people access information from a significantly narrower spectrum of sources through social media and email, compared to a search baseline. The significance of this finding for individual exposure is revealed by investigating the relationship between the diversity of information sources experienced by users at both the collective and individual levels in two datasets where individual users can be analyzed—Twitter posts and search logs. There is a strong correlation between collective and individual diversity, supporting the notion that when we use social media we find ourselves inside “social bubbles.” Our results could lead to a deeper understanding of how technology biases our exposure to new information.

  16. Neutron-induced nucleation inside bubble chambers using Freon 115 as the active medium

    Science.gov (United States)

    Ghilea, M. C.; Meyerhofer, D. D.; Sangster, T. C.

    2011-08-01

    Neutron imaging is used in inertial confinement fusion (ICF) experiments to measure the core symmetry of imploded targets. Liquid bubble chambers have the potential to obtain higher resolution images of the targets for a shorter source-target distance than typical scintillator arrays. Due to the fact that nucleation models used in gel detectors research cannot always give correct estimates for the neutron-induced bubble density inside a liquid bubble chamber, an improved theoretical model to describe the mechanism of bubble formation for Freon 115 as the active medium has been developed. It shows that the size of the critical radius for the nucleation process determines the mechanism of bubble formation and the sensitivity of the active medium to the 14.1-MeV incident neutrons resulting from ICF implosions. The bubble-growth mechanism is driven by the excitation of the medium electronic levels and not by electrons ejected from the medium's atoms as happens for the bubble chambers used to detect charged particles. The model accurately predicts the neutron-induced bubble density measured on OMEGA with both liquid bubble chambers and gel detectors.

  17. Neutron-induced nucleation inside bubble chambers using Freon 115 as the active medium

    Energy Technology Data Exchange (ETDEWEB)

    Ghilea, M.C., E-mail: mghi@lle.rochester.edu [Laboratory for Laser Energetics, University of Rochester, 250 East River Road, Rochester, NY 14623-1299 (United States); Meyerhofer, D.D.; Sangster, T.C. [Laboratory for Laser Energetics, University of Rochester, 250 East River Road, Rochester, NY 14623-1299 (United States)

    2011-08-21

    Neutron imaging is used in inertial confinement fusion (ICF) experiments to measure the core symmetry of imploded targets. Liquid bubble chambers have the potential to obtain higher resolution images of the targets for a shorter source-target distance than typical scintillator arrays. Due to the fact that nucleation models used in gel detectors research cannot always give correct estimates for the neutron-induced bubble density inside a liquid bubble chamber, an improved theoretical model to describe the mechanism of bubble formation for Freon 115 as the active medium has been developed. It shows that the size of the critical radius for the nucleation process determines the mechanism of bubble formation and the sensitivity of the active medium to the 14.1-MeV incident neutrons resulting from ICF implosions. The bubble-growth mechanism is driven by the excitation of the medium electronic levels and not by electrons ejected from the medium's atoms as happens for the bubble chambers used to detect charged particles. The model accurately predicts the neutron-induced bubble density measured on OMEGA with both liquid bubble chambers and gel detectors.

  18. Low temperature calorimetry and transmission electron microscopy of helium bubbles in Cu

    International Nuclear Information System (INIS)

    Syskakis, E.

    1985-08-01

    Helium has been introduced into 100 μm thick pure Cu specimens by implantation of α-particles at T = 300 K. Post-implantation annealing of the specimens at high temperatures caused helium to precipitate into bubbles. We have measured the low-temperature heat capacity of helium confined in bubbles of average radius of less than 100 A. The size of the bubbles was obtained by transmission electron microscope investigations. We have observed that helium liquifies at low temperatures and undergoes the transition to the superfluid state in bubbles of average radius larger than 35 A. The confining geometry of bubbles is new and possesses unique features for investigations of confined helium. It provides the possibility to study properties of extremely small, spherical, completely isolated Bose ''particles'' consisting of 10 4 helium atoms each. Furthermore, as we show, it can be known with better accuracy than formerly investigated confining geometries. (orig./BHO)

  19. Tumor Reversion: Mesenchymal-Epithelial Transition as a Critical Step in Managing the Tumor-Microenvironment Cross-Talk.

    Science.gov (United States)

    Bizzarri, Mariano; Cucina, Alessandra; Proietti, Sara

    2017-01-01

    Tumour reversion represents a promising field of investigation. The occurrence of cancer reversion both in vitro and in vivo has been ascertained by an increasing number of reports. The reverting process may be triggered in a wide range of different cancer types by both molecular and physical cues. This process encompasses mandatorily a change in the cell-stroma interactions, leading to profound modification in tissue architecture. Indeed, cancer reversion may be obtained by only resetting the overall burden of biophysical cues acting on the cell-stroma system, thus indicating that conformational changes induced by cell shape and cytoskeleton remodelling trigger downstream the cascade of molecular events required for phenotypic reversion. Ultimately, epigenetic regulation of gene expression (chiefly involving presenilin-1 and translationally controlled tumour protein) and modulation of a few critical biochemical pathways trigger the mesenchymal-epithelial transition, deemed to be a stable cancer reversion. As cancer can be successfully 'reprogrammed' by modifying the dynamical cross-talk with its microenvironment thus the cell-stroma interactions must be recognized as targets for pharmacological intervention. Yet, understanding cancer reversion remains challenging and refinement in modelling such processes in vitro as well as in vivo is urgently warranted. This new approach bears huge implications, from both a theoretical and clinical perspective, as it may facilitate the design of a novel anticancer strategy focused on mimicking or activating the tumour reversion pathway. Copyright© Bentham Science Publishers; For any queries, please email at epub@benthamscience.org.

  20. Constructing Perceptions of Sexual Orientation: A Corpus-based Critical Discourse Analysis of Transitivity in the Irish Press

    Directory of Open Access Journals (Sweden)

    Leanne Bartley

    2015-03-01

    Full Text Available During the Celtic Tiger period, Ireland grows faster than the Eurozone only to later suffer the harsh impact of the recession. This coincides with increased in-group essentialism leading to prejudice against minorities (Zagefka et al. 2013. Whilst extremist politicians justify anti-immigration beliefs, racism becomes a problem in Ireland. Attacks on certain groups rise dramatically: Women, Travellers, Africans or homosexuals endure verbal and physical mistreatment. Financial crises cause social and discursive marginalisation (Gabrielatos and Baker 2008, and intolerance inevitably contributes to discriminatory views underpinning old-fashioned values. In such a context, we argue that there will be a tendency to nurse the demonisation of the Other (Said 1978, and that the ideological bent of the media sources (see Fowler 1991, Rosen 1999, Barnhurst 2005, van Dijk 2006 will have some impact on how otherness is portrayed. The latter justifies an analysis of how bias fostering exclusion is reinforced in the public domain (Wodak and Chilton 2005. Given Irish gays’ new status following the controversy around same-sex marriage, here we examine newspaper articles to observe  the discourse construction of homosexuality (Collier 1995, Stychin 1995, Naidoo 1997, McGhee 2001, Baker  2005, and detect any instances of homophobia. To do so, a corpus-based critical discourse analysis is conducted with our focus on the notion of transitivity (Halliday and Matthiessen 2014 as a means to reveal people’s perspectives on the topic at hand.

  1. IL-13/STAT6 signaling plays a critical role in the epithelial-mesenchymal transition of colorectal cancer cells.

    Science.gov (United States)

    Cao, Hui; Zhang, Jing; Liu, Hong; Wan, Ledong; Zhang, Honghe; Huang, Qiong; Xu, Enping; Lai, Maode

    2016-09-20

    Colorectal cancer (CRC) is one of the most common causes of cancer-related death worldwide due to the distant metastases. Compelling evidence has reported that epithelial-mesenchymal transition (EMT) is involved in promoting cancer invasion and metastasis. However, the precise molecular events that initiate this complex EMT process remain poorly understood. Here, we showed that the pleiotropic cytokine interleukin-13 (IL-13) could induce an aggressive phenotype displaying EMT by enhancing the expression of EMT-promoting factor ZEB1. Importantly, STAT6 signaling inhibitor and STAT6 knockdown significantly reversed IL-13-induced EMT and ZEB1 induction in CRC cells, whereas ectopic STAT6 expression in STAT6null CRC cell line markedly promoted EMT in the present of IL-13. ChIP-PCR and Luciferase assays revealed that activated STAT6 directly bound to the promoter of ZEB1. Otherwise, we found IL-13 also up-regulated the stem cell markers (nanog, CD44, CD133 and CD166) and promoted cell migration and invasion through STAT6 pathway. We also found that siRNA-mediated knockdown of IL-13Rα1 could reverse IL-13-induced ZEB1 and EMT changes by preventing STAT6 signaling. Finally, we demonstrated positive correlation between IL-13Rα1 and ZEB1 at mRNA levels in human CRC samples. Taken together, our findings first demonstrated that IL-13/IL-13Rα1/STAT6/ZEB1 pathway plays a critical role in promoting EMT and aggressiveness of CRC.

  2. Bubble Rise and Break-Up in Volcanic Conduits

    Science.gov (United States)

    Soldati, A.; Cashman, K. V.; Rust, A.; Rosi, M.

    2013-12-01

    bubble break-up implies that there is a maximum size a system of a certain shape and size can deliver. The size of the upper daughter bubble has been measured in a variety of experiments, and it has been found to be independent of the original slug size, but related to the conduit-upper reservoir transition geometry. It has therefore been possible to establish a relation between conduit geometry and first emerging daughter bubble size. Under the reasonable assumption of a non-limiting supply of gas, this allowed to successfully design the envisaged model of conduit geometry inferral from delivered bubbles size. Data on the size of emerging bubbles, necessary to feed the model, can be obtained through infrasound techniques, as a bursting over-pressurized gas bubble produces a characteristic seismoacoustic signal, from which it is possible to infer its size.

  3. Interactions between bubble formation and heating surface in nucleate boiling

    International Nuclear Information System (INIS)

    Luke, Andrea

    2009-01-01

    The heat transfer and bubble formation is investigated in pool boiling of propane. Size distributions of active nucleation sites on single horizontal copper and steel tubes with different diameter and surface finishes have been calculated from heat transfer measurements over wide ranges of heat flux and selected pressure. The model assumptions of Luke and Gorenflo for the heat transfer near growing and departing bubbles, which were applied in the calculations, have been slightly modified and the calculated results have been compared to experimental investigations by high speed video techniques. The calculated number of active sites shows a good coincidence for the tube with smaller diameter, while the results for the tube with larger diameter describe the same relative increase of the active sites. The comparison of the cumulative size distribution of the active and potential nucleation sites demonstrates the same slope of the curve and that the critical radius of a stable bubble nuclei is smaller than the average cavity size. (author)

  4. Switch of sensitivity dynamics revealed with DyGloSA toolbox for dynamical global sensitivity analysis as an early warning for system's critical transition.

    Science.gov (United States)

    Baumuratova, Tatiana; Dobre, Simona; Bastogne, Thierry; Sauter, Thomas

    2013-01-01

    Systems with bifurcations may experience abrupt irreversible and often unwanted shifts in their performance, called critical transitions. For many systems like climate, economy, ecosystems it is highly desirable to identify indicators serving as early warnings of such regime shifts. Several statistical measures were recently proposed as early warnings of critical transitions including increased variance, autocorrelation and skewness of experimental or model-generated data. The lack of automatized tool for model-based prediction of critical transitions led to designing DyGloSA - a MATLAB toolbox for dynamical global parameter sensitivity analysis (GPSA) of ordinary differential equations models. We suggest that the switch in dynamics of parameter sensitivities revealed by our toolbox is an early warning that a system is approaching a critical transition. We illustrate the efficiency of our toolbox by analyzing several models with bifurcations and predicting the time periods when systems can still avoid going to a critical transition by manipulating certain parameter values, which is not detectable with the existing SA techniques. DyGloSA is based on the SBToolbox2 and contains functions, which compute dynamically the global sensitivity indices of the system by applying four main GPSA methods: eFAST, Sobol's ANOVA, PRCC and WALS. It includes parallelized versions of the functions enabling significant reduction of the computational time (up to 12 times). DyGloSA is freely available as a set of MATLAB scripts at http://bio.uni.lu/systems_biology/software/dyglosa. It requires installation of MATLAB (versions R2008b or later) and the Systems Biology Toolbox2 available at www.sbtoolbox2.org. DyGloSA can be run on Windows and Linux systems, -32 and -64 bits.

  5. Switch of Sensitivity Dynamics Revealed with DyGloSA Toolbox for Dynamical Global Sensitivity Analysis as an Early Warning for System's Critical Transition

    Science.gov (United States)

    Baumuratova, Tatiana; Dobre, Simona; Bastogne, Thierry; Sauter, Thomas

    2013-01-01

    Systems with bifurcations may experience abrupt irreversible and often unwanted shifts in their performance, called critical transitions. For many systems like climate, economy, ecosystems it is highly desirable to identify indicators serving as early warnings of such regime shifts. Several statistical measures were recently proposed as early warnings of critical transitions including increased variance, autocorrelation and skewness of experimental or model-generated data. The lack of automatized tool for model-based prediction of critical transitions led to designing DyGloSA – a MATLAB toolbox for dynamical global parameter sensitivity analysis (GPSA) of ordinary differential equations models. We suggest that the switch in dynamics of parameter sensitivities revealed by our toolbox is an early warning that a system is approaching a critical transition. We illustrate the efficiency of our toolbox by analyzing several models with bifurcations and predicting the time periods when systems can still avoid going to a critical transition by manipulating certain parameter values, which is not detectable with the existing SA techniques. DyGloSA is based on the SBToolbox2 and contains functions, which compute dynamically the global sensitivity indices of the system by applying four main GPSA methods: eFAST, Sobol's ANOVA, PRCC and WALS. It includes parallelized versions of the functions enabling significant reduction of the computational time (up to 12 times). DyGloSA is freely available as a set of MATLAB scripts at http://bio.uni.lu/systems_biology/software/dyglosa. It requires installation of MATLAB (versions R2008b or later) and the Systems Biology Toolbox2 available at www.sbtoolbox2.org. DyGloSA can be run on Windows and Linux systems, -32 and -64 bits. PMID:24367574

  6. High energy heavy ion tracks in bubble detectors

    CERN Document Server

    Guo, S L; Guo, H Y; Tu, C Q; Wang, Y L; Doke, T; Kato, T; Ozaki, K; Kyan, A; Piao, Y; Murakami, T

    1999-01-01

    Bubble detectors which are commonly used as neutron detectors have been demonstrated through this study to be good detectors for registration of high energy heavy ion tracks. Large size bubble detectors made in China Institute of Atomic Energy were irradiated to heavy ions Ar and C up to 650 MeV/u and 400 MeV/u, respectively. Very clear features of stringy tracks of high energy heavy ions and their fragmentations are manifested and distinguishable. A single track created by a specific high energy heavy ion is composed of a line of bubbles, which is visible by naked eyes and retained for months without reduction in size. The creation of heavy ion tracks in bubble detectors is governed by a threshold whose essence is approximately a critical value of energy loss rate (dE/dX) sub c similar to that of etch track detectors. Ranges of heavy ions in bubble detectors are apparent and predictable by existing formulas. Identification of high energy heavy ions and the applications to heavy ion physics, cosmic rays, exot...

  7. Method to increase the transition temperature and for the critical magnetic field strength of the known intermetallic compounds of vanadium or niobium

    International Nuclear Information System (INIS)

    Winter, H.

    1977-01-01

    The invention deals with a method to raise the transition temperature and critical magnetic field strength of superconducting, intermetallic compounds of vanadium and niobium. For example, a niobium alloy with 4 wt.% Al in melted in vacuum electric arc and formed into a sheet of about 1 mm thick. Strips of this sheet are electrically heated up to 1,900 0 C for one hour in a high-vacuum oven. The strips are then annealed in evacuated quartz ampoules for 120 hours at 800 0 C. These strips have a transition temperature of 24 K and a critical magnetic field strength of 600 kg; the critical current density was 5 x 10 4 A/cm 2 . (HPOE) [de

  8. Spherical Solutions of an Underwater Explosion Bubble

    Directory of Open Access Journals (Sweden)

    Andrew B. Wardlaw

    1998-01-01

    Full Text Available The evolution of the 1D explosion bubble flow field out to the first bubble minimum is examined in detail using four different models. The most detailed is based on the Euler equations and accounts for the internal bubble fluid motion, while the simplest links a potential water solution to a stationary, Isentropic bubble model. Comparison of the different models with experimental data provides insight into the influence of compressibility and internal bubble dynamics on the behavior of the explosion bubble.

  9. On the Inception of Financial Representative Bubbles

    Directory of Open Access Journals (Sweden)

    Massimiliano Ferrara

    2017-11-01

    Full Text Available In this work, we aim to formalize the inception of representative bubbles giving the condition under which they may arise. We will find that representative bubbles may start at any time, depending on the definition of a behavioral component. This result is at odds with the theory of classic rational bubbles, which are those models that rely on the fulfillment of the transversality condition by which a bubble in a financial asset can arise just at its first trade. This means that a classic rational bubble (differently from our model cannot follow a cycle since if a bubble exists, it will burst by definition and never arise again.

  10. Ethnic diversity deflates price bubbles.

    Science.gov (United States)

    Levine, Sheen S; Apfelbaum, Evan P; Bernard, Mark; Bartelt, Valerie L; Zajac, Edward J; Stark, David

    2014-12-30

    Markets are central to modern society, so their failures can be devastating. Here, we examine a prominent failure: price bubbles. Bubbles emerge when traders err collectively in pricing, causing misfit between market prices and the true values of assets. The causes of such collective errors remain elusive. We propose that bubbles are affected by ethnic homogeneity in the market and can be thwarted by diversity. In homogenous markets, traders place undue confidence in the decisions of others. Less likely to scrutinize others' decisions, traders are more likely to accept prices that deviate from true values. To test this, we constructed experimental markets in Southeast Asia and North America, where participants traded stocks to earn money. We randomly assigned participants to ethnically homogeneous or diverse markets. We find a marked difference: Across markets and locations, market prices fit true values 58% better in diverse markets. The effect is similar across sites, despite sizeable differences in culture and ethnic composition. Specifically, in homogenous markets, overpricing is higher as traders are more likely to accept speculative prices. Their pricing errors are more correlated than in diverse markets. In addition, when bubbles burst, homogenous markets crash more severely. The findings suggest that price bubbles arise not only from individual errors or financial conditions, but also from the social context of decision making. The evidence may inform public discussion on ethnic diversity: it may be beneficial not only for providing variety in perspectives and skills, but also because diversity facilitates friction that enhances deliberation and upends conformity.

  11. On shapes and motion of an elongated bubble in downward liquid pipe flow

    Science.gov (United States)

    Fershtman, A.; Babin, V.; Barnea, D.; Shemer, L.

    2017-11-01

    In stagnant liquid, or in a steady upward liquid pipe flow, an elongated (Taylor) bubble has a symmetric shape. The translational velocity of the bubble is determined by buoyancy and the liquid velocity profile ahead of it. In downward flow, however, the symmetry of the bubble nose can be lost. Taylor bubble motion in downward flow is important in numerous applications such as chemical plants and cooling systems that often contain countercurrent gas-liquid flow. In the present study, the relation between the Taylor bubble shape and its translational velocity is investigated experimentally in a vertical pipe for various downward liquid flow rates. At higher downward velocities, the bubble may be forced by the background flow to propagate downward against buoyancy. In order to include those cases as well in our experimental analysis, the bubbles were initially injected into stagnant liquid, whereas the downward flow was initiated at a later stage. This experimental procedure allowed us to identify three distinct modes of translational velocities for a given downward background liquid flow; each velocity corresponds to a different bubble shape. Hydrodynamic mechanisms that govern the transition between the modes observed in the present study are discussed.

  12. Field-driven chiral bubble dynamics analysed by a semi-analytical approach

    Science.gov (United States)

    Vandermeulen, J.; Leliaert, J.; Dupré, L.; Van Waeyenberge, B.

    2017-12-01

    Nowadays, field-driven chiral bubble dynamics in the presence of the Dzyaloshinskii-Moriya interaction are a topic of thorough investigation. In this paper, a semi-analytical approach is used to derive equations of motion that express the bubble wall (BW) velocity and the change in in-plane magnetization angle as function of the micromagnetic parameters of the involved interactions, thereby taking into account the two-dimensional nature of the bubble wall. It is demonstrated that the equations of motion enable an accurate description of the expanding and shrinking convex bubble dynamics and an expression for the transition field between shrinkage and expansion is derived. In addition, these equations of motion show that the BW velocity is not only dependent on the driving force, but also on the BW curvature. The absolute BW velocity increases for both a shrinking and an expanding bubble, but for different reasons: for expanding bubbles, it is due to the increasing importance of the driving force, while for shrinking bubbles, it is due to the increasing importance of contributions related to the BW curvature. Finally, using this approach we show how the recently proposed magnetic bubblecade memory can operate in the flow regime in the presence of a tilted sinusoidal magnetic field and at greatly reduced bubble sizes compared to the original device prototype.

  13. Baryogenesis and Gravitational Waves from Runaway Bubble Collisions

    CERN Document Server

    Katz, Andrey

    2016-11-07

    We propose a novel mechanism for production of baryonic asymmetry in the early Universe. The mechanism takes advantage of the strong first order phase transition that produces runaway bubbles in the hidden sector that propagate almost without friction with ultra-relativistic velocities. Collisions of such bubbles can non-thermally produce heavy particles that further decay out-of-equilibrium into the SM and produce the observed baryonic asymmetry. This process can proceed at the very low temperatures, providing a new mechanism of post-sphaleron baryogenesis. In this paper we present a fully calculable model which produces the baryonic asymmetry along these lines as well as evades all the existing cosmological constraints. We emphasize that the Gravitational Waves signal from the first order phase transition is completely generic and can potentially be detected by the future eLISA interferometer. We also discuss other potential signals, which are more model dependent, and point out the unresolved theoretical q...

  14. Critical evaluation of measured rotational-vibrational transitions of four sulphur isotopologues of S16O2

    Science.gov (United States)

    Tóbiás, Roland; Furtenbacher, Tibor; Császár, Attila G.; Naumenko, Olga V.; Tennyson, Jonathan; Flaud, Jean-Marie; Kumar, Praveen; Poirier, Bill

    2018-03-01

    A critical evaluation and validation of the complete set of previously published experimental rotational-vibrational line positions is reported for the four stable sulphur isotopologues of the semirigid SO2 molecule - i.e., 32S16O2, 33S16O2, 34S16O2, and 36S16O2. The experimentally measured, assigned, and labeled transitions are collated from 43 sources. The 32S16O2, 33S16O2, 34S16O2, and 36S16O2 datasets contain 40,269, 15,628, 31,080, and 31 lines, respectively. Of the datasets collated, only the extremely limited 36S16O2 dataset is not subjected to a detailed analysis. As part of a detailed analysis of the experimental spectroscopic networks corresponding to the ground electronic states of the 32S16O2, 33S16O2, and 34S16O2 isotopologues, the MARVEL (Measured Active Rotational-Vibrational Energy Levels) procedure is used to determine the rovibrational energy levels. The rovibrational levels and their vibrational parent and asymmetric-top quantum numbers are compared to ones obtained from accurate variational nuclear-motion computations as well as to results of carefully designed effective Hamiltonian models. The rovibrational energy levels of the three isotopologues having the same labels are also compared against each other to ensure self-consistency. This careful, multifaceted analysis gives rise to 15,130, 5852, and 10,893 validated rovibrational energy levels, with a typical accuracy of a few 0.0001 cm-1 , for 32S16O2, 33S16O2, and 34S16O2, respectively. The extensive list of validated experimental lines and empirical (MARVEL) energy levels of the S16O2 isotopologues studied are deposited in the Supplementary Material of this article, as well as in the distributed information system ReSpecTh (http://respecth.hu).

  15. From resilience to vulnerability: Mechanistic insights into the effects of stress on transitions in critical period plasticity

    Directory of Open Access Journals (Sweden)

    Bridget Laura Callaghan

    2013-08-01

    Full Text Available While early experiences are proposed to be important for the emergence of anxiety and other mental health problems, there is little empirical research examining the impact of such experiences on the development of emotional learning. Of the research that has been performed in this area, however, a complex picture has emerged in which the maturation of emotion circuits is influenced by the early experiences of the animal. For example, under typical laboratory rearing conditions infant rats rapidly forget learned fear associations (infantile amnesia and express a form of extinction learning which is relapse-resistant (i.e., extinction in infant rats may be due to fear erasure. In contrast, adult rats exhibit very long-lasting memories of past learned fear associations, and express a form of extinction learning that is relapse-prone (i.e., the fear returns in a number of situations. However, when rats are reared under stressful conditions then they exhibit adult-like fear retention and extinction behaviours at an earlier stage of development (i.e., good retention of learned fear and relapse-prone extinction learning. In other words, under typical rearing conditions infant rats appear to be protected from exhibiting anxiety whereas after adverse rearing fear learning appears to make those infants more vulnerable to the later development of anxiety. While the effects of different experiences on infant rats’ fear retention and extinction are becoming better documented, the mechanisms which mediate the early transition seen following stress remain unclear. Here we suggest that rearing stress may lead to an early maturation of the molecular and cellular signals shown to be involved in the closure of critical period plasticity in sensory modalities (e.g., maturation of GABAergic neurons, development of perineuronal nets, and speculate that these signals could be manipulated in adulthood to re-open infant forms of emotional learning (i.e., those that

  16. Ultrasound-Stimulated Mutual Interaction Forces between Optically Configured Micro-Bubble Pairs

    Science.gov (United States)

    Prentice, Paul A.; Campbell, Paul A.

    2007-05-01

    The mutual interaction between two oscillating encapsulated microbubbles was investigated using a novel optical trapping arrangement. This approach facilitated the development of an arbitrary, stable, initial spatial configuration for a two-bubble system. Critically, exercising optical control over such a binary bubble system meant that it could be isolated from the resident population of microbubbles during exposure to ultrasound. This ensured that any early stage dynamical evolution of the system was dominated by the mutual interaction of the two bubbles in view, rather than any extraneous influence arising from `crosstalk' with the rest of the bubble population. We observed, using high speed microphotography at 4×105 frames per second, that the action of secondary radiation forces leads to mutual bubble attraction. Phenomena such as coalescence and `bounce' were observed. Estimates of the microbubble [Sonovue™] compressibility could also be made, and tally well with published values obtained for other shelled contrast agents.

  17. Modelling of grain face bubbles coalescence in irradiated UO{sub 2} fuel

    Energy Technology Data Exchange (ETDEWEB)

    Veshchunov, M.S. [Nuclear Safety Institute (IBRAE), Russian Academy of Sciences, 52, B. Tulskaya, Moscow 115191 (Russian Federation)], E-mail: vms@ibrae.ac.ru

    2008-02-29

    Two different mechanisms of grain face bubbles coalescence in irradiated UO{sub 2} fuel are critically analysed and further developed. Coalescence of face bubbles due to their random migration is reconsidered on the base of the general theory for evolution of two-dimensional array of bubbles and shown to be effective for steady irradiation conditions and apparently insufficient for description of high-temperature annealing regimes. On the contrary, the improved mechanism of coalescence by growth and impingement of randomly distributed bubbles predicts rather weak decrease of face bubbles concentration under steady state irradiation conditions, however, becomes effective for simulation of high-temperature annealing tests with noticeable gas release. On this base, the general coalescence model which includes superposition of the two complementary mechanisms is formulated and proposed for implementation in the MFPR code.

  18. Hamiltonian description of bubble dynamics

    International Nuclear Information System (INIS)

    Maksimov, A. O.

    2008-01-01

    The dynamics of a nonspherical bubble in a liquid is described within the Hamiltonian formalism. Primary attention is focused on the introduction of the canonical variables into the computational algorithm. The expansion of the Dirichlet-Neumann operator in powers of the displacement of a bubble wall from an equilibrium position is obtained in the explicit form. The first three terms (more specifically, the second-, third-, and fourth-order terms) in the expansion of the Hamiltonian in powers of the canonical variables are determined. These terms describe the spectrum and interaction of three essentially different modes, i.e., monopole oscillations (pulsations), dipole oscillations (translational motions), and surface oscillations. The cubic nonlinearity is analyzed for the problem associated with the generation of Faraday ripples on the wall of a bubble in an acoustic field. The possibility of decay processes occurring in the course of interaction of surface oscillations for the first fifteen (experimentally observed) modes is investigated.

  19. Semi-analytic techniques for calculating bubble wall profiles

    International Nuclear Information System (INIS)

    Akula, Sujeet; Balazs, Csaba; White, Graham A.

    2016-01-01

    We present semi-analytic techniques for finding bubble wall profiles during first order phase transitions with multiple scalar fields. Our method involves reducing the problem to an equation with a single field, finding an approximate analytic solution and perturbing around it. The perturbations can be written in a semi-analytic form. We assert that our technique lacks convergence problems and demonstrate the speed of convergence on an example potential. (orig.)

  20. Methane Bubbles Transport Particles From Contaminated Sediment to a Lake Surface

    Science.gov (United States)

    Delwiche, K.; Hemond, H.

    2017-12-01

    Methane bubbling from aquatic sediments has long been known to transport carbon to the atmosphere, but new evidence presented here suggests that methane bubbles also transport particulate matter to a lake surface. This transport pathway is of particular importance in lakes with contaminated sediments, as bubble transport could increase human exposure to toxic metals. The Upper Mystic Lake in Arlington, MA has a documented history of methane bubbling and sediment contamination by arsenic and other heavy metals, and we have conducted laboratory and field studies demonstrating that methane bubbles are capable of transporting sediment particles over depths as great as 15 m in Upper Mystic Lake. Methane bubble traps were used in-situ to capture particles adhered to bubble interfaces, and to relate particle mass transport to bubble flux. Laboratory studies were conducted in a custom-made 15 m tall water column to quantify the relationship between water column height and the mass of particulate transport. We then couple this particle transport data with historical estimates of ebullition from Upper Mystic Lake to quantify the significance of bubble-mediated particle transport to heavy metal cycling within the lake. Results suggest that methane bubbles can represent a significant pathway for contaminated sediment to reach surface waters even in relatively deep water bodies. Given the frequent co-occurrence of contaminated sediments and high bubble flux rates, and the potential for human exposure to heavy metals, it will be critical to study the significance of this transport pathway for a range of sediment and contaminant types.

  1. A novel methodology to measure methane bubble sizes in the water column

    Science.gov (United States)

    Hemond, H.; Delwiche, K.; Senft-Grupp, S.; Manganello, T.

    2014-12-01

    The fate of methane ebullition from lake sediments is dependent on initial bubble size. Rising bubbles are subject to dissolution, reducing the fraction of methane that ultimately enters the atmosphere while increasing concentrations of aqueous methane. Smaller bubbles not only rise more slowly, but dissolve more rapidly larger bubbles. Thus, understanding methane bubble size distributions in the water column is critical to predicting atmospheric methane emissions from ebullition. However, current methods of measuring methane bubble sizes in-situ are resource-intensive, typically requiring divers, video equipment, sonar, or hydroacoustic instruments. The complexity and cost of these techniques points to the strong need for a simple, autonomous device that can measure bubble size distributions and be deployed unattended over long periods of time. We describe a bubble sizing device that can be moored in the subsurface and can intercept and measure the size of bubbles as they rise. The instrument uses a novel optical measurement technique with infrared LEDs and IR-sensitive photodetectors combined with a custom-designed printed circuit board. An on-board microcomputer handles raw optical signals and stores the relevant information needed to calculate bubble volume. The electronics are housed within a pressure case fabricated from standard PVC fittings and are powered by size C alkaline batteries. The bill of materials cost is less than $200, allowing us to deploy multiple sensors at various locations within Upper Mystic Lake, MA. This novel device will provide information on how methane bubble sizes may vary both spatially and temporally. We present data from tests under controlled laboratory conditions and from deployments in Upper Mystic Lake.

  2. Fluid dynamics of bubbly flows

    International Nuclear Information System (INIS)

    Ziegenhein, Thomas

    2016-01-01

    Bubbly flows can be found in many applications in chemical, biological and power engineering. Reliable simulation tools of such flows that allow the design of new processes and optimization of existing one are therefore highly desirable. CFD-simulations applying the multi-fluid approach are very promising to provide such a design tool for complete facilities. In the multi-fluid approach, however, closure models have to be formulated to model the interaction between the continuous and dispersed phase. Due to the complex nature of bubbly flows, different phenomena have to be taken into account and for every phenomenon different closure models exist. Therefore, reliable predictions of unknown bubbly flows are not yet possible with the multi-fluid approach. A strategy to overcome this problem is to define a baseline model in which the closure models including the model constants are fixed so that the limitations of the modeling can be evaluated by validating it on different experiments. Afterwards, the shortcomings are identified so that the baseline model can be stepwise improved without losing the validity for the already validated cases. This development of a baseline model is done in the present work by validating the baseline model developed at the Helmholtz-Zentrum Dresden-Rossendorf mainly basing on experimental data for bubbly pipe flows to bubble columns, bubble plumes and air-lift reactors that are relevant in chemical and biological engineering applications. In the present work, a large variety of such setups is used for validation. The buoyancy driven bubbly flows showed thereby a transient behavior on the scale of the facility. Since such large scales are characterized by the geometry of the facility, turbulence models cannot describe them. Therefore, the transient simulation of bubbly flows with two equation models based on the unsteady Reynolds-averaged Navier-Stokes equations is investigated. In combination with the before mentioned baseline model these

  3. Propagation of a finite bubble in a Hele-Shaw channel of variable depth

    Science.gov (United States)

    Juel, Anne; Franco-Gomez, Andres; Thompson, Alice; Hazel, Andrew

    2017-11-01

    We study the propagation of finite bubbles in a Hele-Shaw channel, where a centred rail is introduced to provide a small axially-uniform depth constriction. We demonstrate experimentally that this channel geometry can be used as a passive sorting device. Single air bubbles carried within silicone oil are generally transported on one side of the rail. However, for flow rates marginally larger than a critical value, a narrow band of bubble sizes on the order of the rail width can propagate over the rail, while bubbles of other sizes segregate to the side of the rail. The width of this band of bubble sizes increases with flow rate and the size of the most stable bubble can be tuned by varying the rail width. We present a depth-averaged theory which reveals that the mechanism relies on a non-trivial interaction between capillary and viscous forces that is fully dynamic, rather than being a simple modification of capillary static solutions. In contrast, for larger bubbles and sufficiently large imposed flow rates, we find that initially centred bubbles do not converge onto a steady mode of propagation. Instead they transiently explore weakly unstable steady modes, an evolution which results in their break-up and eventual settling into a steady state of changed topology. The financial support of CONICYT and the Leverhulme Trust are gratefully acknowledged.

  4. Microgravity Two-Phase Flow Transition

    Science.gov (United States)

    Parang, M.; Chao, D.

    1999-01-01

    Two-phase flows under microgravity condition find a large number of important applications in fluid handling and storage, and spacecraft thermal management. Specifically, under microgravity condition heat transfer between heat exchanger surfaces and fluids depend critically on the distribution and interaction between different fluid phases which are often qualitatively different from the gravity-based systems. Heat transfer and flow analysis in two-phase flows under these conditions require a clear understanding of the flow pattern transition and development of appropriate dimensionless scales for its modeling and prediction. The physics of this flow is however very complex and remains poorly understood. This has led to various inadequacies in flow and heat transfer modeling and has made prediction of flow transition difficult in engineering design of efficient thermal and flow systems. In the present study the available published data for flow transition under microgravity condition are considered for mapping. The transition from slug to annular flow and from bubbly to slug flow are mapped using dimensionless variable combination developed in a previous study by the authors. The result indicate that the new maps describe the flow transitions reasonably well over the range of the data available. The transition maps are examined and the results are discussed in relation to the presumed balance of forces and flow dynamics. It is suggested that further evaluation of the proposed flow and transition mapping will require a wider range of microgravity data expected to be made available in future studies.

  5. Using trading strategies to detect phase transitions in financial markets

    Science.gov (United States)

    Forró, Z.; Woodard, R.; Sornette, D.

    2015-04-01

    We show that the log-periodic power law singularity model (LPPLS), a mathematical embodiment of positive feedbacks between agents and of their hierarchical dynamical organization, has a significant predictive power in financial markets. We find that LPPLS-based strategies significantly outperform the randomized ones and that they are robust with respect to a large selection of assets and time periods. The dynamics of prices thus markedly deviate from randomness in certain pockets of predictability that can be associated with bubble market regimes. Our hybrid approach, marrying finance with the trading strategies, and critical phenomena with LPPLS, demonstrates that targeting information related to phase transitions enables the forecast of financial bubbles and crashes punctuating the dynamics of prices.

  6. Using trading strategies to detect phase transitions in financial markets.

    Science.gov (United States)

    Forró, Z; Woodard, R; Sornette, D

    2015-04-01

    We show that the log-periodic power law singularity model (LPPLS), a mathematical embodiment of positive feedbacks between agents and of their hierarchical dynamical organization, has a significant predictive power in financial markets. We find that LPPLS-based strategies significantly outperform the randomized ones and that they are robust with respect to a large selection of assets and time periods. The dynamics of prices thus markedly deviate from randomness in certain pockets of predictability that can be associated with bubble market regimes. Our hybrid approach, marrying finance with the trading strategies, and critical phenomena with LPPLS, demonstrates that targeting information related to phase transitions enables the forecast of financial bubbles and crashes punctuating the dynamics of prices.

  7. Computing bubble-points of CO

    NARCIS (Netherlands)

    Ramdin, M.; Balaji, S.P.; Vicent Luna, J.M.; Torres-Knoop, A; Chen, Q.; Dubbeldam, D.; Calero, S; de Loos, T.W.; Vlugt, T.J.H.

    2016-01-01

    Computing bubble-points of multicomponent mixtures using Monte Carlo simulations is a non-trivial task. A new method is used to compute gas compositions from a known temperature, bubble-point pressure, and liquid composition. Monte Carlo simulations are used to calculate the bubble-points of

  8. Mechanics of gas-vapor bubbles

    NARCIS (Netherlands)

    Hao, Yue; Zhang, Yuhang; Prosperetti, Andrea

    2017-01-01

    Most bubbles contain a mixture of vapor and incondensible gases. While the limit cases of pure vapor and pure gas bubbles are well studied, much less is known about the more realistic case of a mixture. The bubble contents continuously change due to the combined effects of evaporation and

  9. Determining hydrodynamic forces in bursting bubbles using DNA nanotube mechanics

    Science.gov (United States)

    Hariadi, Rizal F.; Winfree, Erik; Yurke, Bernard

    2015-01-01

    Quantifying the mechanical forces produced by fluid flows within the ocean is critical to understanding the ocean’s environmental phenomena. Such forces may have been instrumental in the origin of life by driving a primitive form of self-replication through fragmentation. Among the intense sources of hydrodynamic shear encountered in the ocean are breaking waves and the bursting bubbles produced by such waves. On a microscopic scale, one expects the surface-tension–driven flows produced during bubble rupture to exhibit particularly high velocity gradients due to the small size scales and masses involved. However, little work has examined the strength of shear flow rates in commonly encountered ocean conditions. By using DNA nanotubes as a novel fluid flow sensor, we investigate the elongational rates generated in bursting films within aqueous bubble foams using both laboratory buffer and ocean water. To characterize the elongational rate distribution associated with a bursting bubble, we introduce the concept of a fragmentation volume and measure its form as a function of elongational flow rate. We find that substantial volumes experience surprisingly large flow rates: during the bursting of a bubble having an air volume of 10 mm3, elongational rates at least as large as ϵ˙=1.0×108 s−1 are generated in a fragmentation volume of ∼2×10−6 μL. The determination of the elongational strain rate distribution is essential for assessing how effectively fluid motion within bursting bubbles at the ocean surface can shear microscopic particles and microorganisms, and could have driven the self-replication of a protobiont. PMID:26504222

  10. Understanding the Critical Role of the Ag Nanophase in Boosting the Initial Reversibility of Transition Metal Oxide Anodes for Lithium-Ion Batteries.

    Science.gov (United States)

    Lee, Daehee; Wu, Mihye; Kim, Dong-Hyun; Chae, Changju; Cho, Min Kyung; Kim, Ji-Young; Lee, Sun Sook; Choi, Sungho; Choi, Youngmin; Shin, Tae Joo; Chung, Kyung Yoon; Jeong, Sunho; Moon, Jooho

    2017-07-05

    The initial reversible capacity, a critical impediment in transition metal oxide-based anodes, is augmented in conversion-reaction-involved CoO anodes for lithium-ion batteries, by incorporating a chemically synthesized Ag nanophase. With an increase in the added amount of Ag nanophase from 5 to 15 wt %, the initial capacity loss decreases linearly up to 31.7%. The Ag nanophase maintains its pristine metallic nature without undergoing phase transformations, even during repeated vigorous electrochemical reactions of the active CoO phase. Complementary ex situ chemical/physical analyses suggest that the Ag nanophase promotes the catalytic generation of reversible gel-like/polymeric films wherein lithium ions are stored capacitively in the low-voltage region below 0.7 V during discharging. These scientific findings would provide a heretofore unrecognized pathway to resolving a major issue associated with the critical irreversibility in conversion-type transition metal oxide anodes.

  11. Droplets, Bubbles and Ultrasound Interactions

    NARCIS (Netherlands)

    Shpak, O.; Verweij, M.; de Jong, N.; Versluis, Michel; Escoffre, J.M.; Bouakaz, A.

    2016-01-01

    The interaction of droplets and bubbles with ultrasound has been studied extensively in the last 25 years. Microbubbles are broadly used in diagnostic and therapeutic medical applications, for instance, as ultrasound contrast agents. They have a similar size as red blood cells, and thus are able to

  12. Electrolysis Bubbles Make Waterflow Visible

    Science.gov (United States)

    Schultz, Donald F.

    1990-01-01

    Technique for visualization of three-dimensional flow uses tiny tracer bubbles of hydrogen and oxygen made by electrolysis of water. Strobe-light photography used to capture flow patterns, yielding permanent record that is measured to obtain velocities of particles. Used to measure simulated mixing turbulence in proposed gas-turbine combustor and also used in other water-table flow tests.

  13. Impurity bubbles in a BEC

    Science.gov (United States)

    Timmermans, Eddy; Blinova, Alina; Boshier, Malcolm

    2013-05-01

    Polarons (particles that interact with the self-consistent deformation of the host medium that contains them) self-localize when strongly coupled. Dilute Bose-Einstein condensates (BECs) doped with neutral distinguishable atoms (impurities) and armed with a Feshbach-tuned impurity-boson interaction provide a unique laboratory to study self-localized polarons. In nature, self-localized polarons come in two flavors that exhibit qualitatively different behavior: In lattice systems, the deformation is slight and the particle is accompanied by a cloud of collective excitations as in the case of the Landau-Pekar polarons of electrons in a dielectric lattice. In natural fluids and gases, the strongly coupled particle radically alters the medium, e.g. by expelling the host medium as in the case of the electron bubbles in superfluid helium. We show that BEC-impurities can self-localize in a bubble, as well as in a Landau-Pekar polaron state. The BEC-impurity system is fully characterized by only two dimensionless coupling constants. In the corresponding phase diagram the bubble and Landau-Pekar polaron limits correspond to large islands separated by a cross-over region. The same BEC-impurity species can be adiabatically Feshbach steered from the Landau-Pekar to the bubble regime. This work was funded by the Los Alamos LDRD program.

  14. Neutron Detection via Bubble Chambers

    Energy Technology Data Exchange (ETDEWEB)

    Jordan, David V.; Ely, James H.; Peurrung, Anthony J.; Bond, Leonard J.; Collar, J. I.; Flake, Matthew; Knopf, Michael A.; Pitts, W. K.; Shaver, Mark W.; Sonnenschein, Andrew; Smart, John E.; Todd, Lindsay C.

    2005-10-06

    The results of a Pacific Northwest National Laboratory (PNNL) exploratory research project investigating the feasibility of fast neutron detection using a suitably prepared and operated, pressure-cycled bubble chamber are described. The research was conducted along two parallel paths. Experiments with a slow pressure-release Halon chamber at the Enrico Fermi Institute at the University of Chicago showed clear bubble nucleation sensitivity to an AmBe neutron source and insensitivity to the 662 keV gammas from a 137Cs source. Bubble formation was documented via high-speed (1000 frames/sec) photography, and the acoustic signature of bubble formation was detected using a piezo-electric transducer element mounted on the base of the chamber. The chamber’s neutron sensitivity as a function of working fluid temperature was mapped out. The second research path consisted of the design, fabrication, and testing of a fast pressure-release Freon-134a chamber at PNNL. The project concluded with successful demonstrations of the PNNL chamber’s AmBe neutron source sensitivity and 137Cs gamma insensitivity. The source response tests of the PNNL chamber were documented with high-speed photography.

  15. Models of cylindrical bubble pulsation.

    Science.gov (United States)

    Ilinskii, Yurii A; Zabolotskaya, Evgenia A; Hay, Todd A; Hamilton, Mark F

    2012-09-01

    Three models are considered for describing the dynamics of a pulsating cylindrical bubble. A linear solution is derived for a cylindrical bubble in an infinite compressible liquid. The solution accounts for losses due to viscosity, heat conduction, and acoustic radiation. It reveals that radiation is the dominant loss mechanism, and that it is 22 times greater than for a spherical bubble of the same radius. The predicted resonance frequency provides a basis of comparison for limiting forms of other models. The second model considered is a commonly used equation in Rayleigh-Plesset form that requires an incompressible liquid to be finite in extent in order for bubble pulsation to occur. The radial extent of the liquid becomes a fitting parameter, and it is found that considerably different values of the parameter are required for modeling inertial motion versus acoustical oscillations. The third model was developed by V. K. Kedrinskii [Hydrodynamics of Explosion (Springer, New York, 2005), pp. 23-26] in the form of the Gilmore equation for compressible liquids of infinite extent. While the correct resonance frequency and loss factor are not recovered from this model in the linear approximation, it provides reasonable agreement with observations of inertial motion.

  16. "Financial Bubbles" and Monetary Policy

    Science.gov (United States)

    Tikhonov, Yuriy A.; Pudovkina, Olga E.; Permjakova, Juliana V.

    2016-01-01

    The relevance of this research is caused by the need of strengthening a role of monetary regulators to prevent financial bubbles in the financial markets. The aim of the article is the analysis of a problem of crisis phenomena in the markets of financial assets owing to an inadequate growth of their cost, owing to subjective reasons. The leading…

  17. Axial stability of Taylor bubbles

    NARCIS (Netherlands)

    Lu, X.; Prosperetti, Andrea

    2006-01-01

    Long gas bubbles rising in a vertical tube are observed to lose axial symmetry and become unstable in a downward liquid flow. In this paper an approximate linear stability analysis of this phenomenon is presented. It is found that, under the combined effect of gravity and the pressure gradient which

  18. Response of a continuous anaerobic digester to temperature transitions: A critical range for restructuring the microbial community structure and function.

    Science.gov (United States)

    Kim, Jaai; Lee, Changsoo

    2016-02-01

    Temperature is a crucial factor that significantly influences the microbial activity and so the methanation performance of an anaerobic digestion (AD) process. Therefore, how to control the operating temperature for optimal activity of the microbes involved is a key to stable AD. This study examined the response of a continuous anaerobic reactor to a series of temperature shifts over a wide range of 35-65 °C using a dairy-processing byproduct as model wastewater. During the long-term experiment for approximately 16 months, the reactor was subjected to stepwise temperature increases by 5 °C at a fixed HRT of 15 days. The reactor showed stable performance within the temperature range of 35-45 °C, with the methane production rate and yield being maximum at 45 °C (18% and 26% greater, respectively, than at 35 °C). However, the subsequent increase to 50 °C induced a sudden performance deterioration with a complete cessation of methane recovery, indicating that the temperature range between 45 °C and 50 °C had a critical impact on the transition of the reactor's methanogenic activity from mesophilic to thermophilic. This serious process perturbation was associated with a severe restructuring of the reactor microbial community structure, particularly of methanogens, quantitatively as well as qualitatively. Once restored by interrupted feeding for about two months, the reactor maintained fairly stable performance under thermophilic conditions until it was upset again at 65 °C. Interestingly, in contrast to most previous reports, hydrogenotrophs largely dominated the methanogen community at mesophilic temperatures while acetotrophs emerged as a major group at thermophilic temperature. This implies that the primary methanogenesis route of the reactor shifted from hydrogen- to acetate-utilizing pathways with the temperature shifts from mesophilic to thermophilic temperatures. Our observations suggest that a mesophilic digester may not need to be cooled at up

  19. Bubble fusion: fact or fiction?

    Energy Technology Data Exchange (ETDEWEB)

    Pennicott, Katie

    2002-04-01

    Physicists in the US claim to have seen nuclear fusion in a table-top experiment but their work has met with a hostile reaction from other researchers. In sonoluminescence, flashes of light are emitted by bubbles that are forced to expand and then collapse by sound waves, although this process is still not fully understood (see Physics World May 1998 pp38-42, print version). Physicists have long speculated that the considerable compression forces inside the collapsing bubbles could be large enough to spark nuclear reactions. If this was the case, it could lead to a new source of clean energy. In their experiment, Taleyarkhan and co-workers at Oak Ridge, the Rensselaer Polytechnic Institute in the US, and the Russian Academy of Sciences used 14 MeV neutrons to create bubbles about 10 nano metres across in acetone in which the ordinary hydrogen atoms had been replaced by deuterium atoms (C{sub 3}D{sub 6O}). An acoustic signal then forced these bubbles - and the acetone vapour inside them - to first expand to about a millimetre in size, and then collapse. Two deuterium nuclei can fuse to produce either a tritium nucleus and a proton, or a helium-3 nucleus and a neutron with an energy of 2.45 MeV. Taleyarkhan and co-workers claim to have seen evidence for both tritium and 2.45 MeV neutrons in their experiments. They have also calculated that temperatures of a million or even 10 million degrees - the temperature at the Sun's core - must have existed inside the bubbles for these reactions to proceed. Some other experiments and the controversy discussions of the researchers are summarized. (U.K.)

  20. Hydrodynamics in a swarm of rising bubbles

    International Nuclear Information System (INIS)

    Riboux, G.

    2007-04-01

    In many applications, bubbles are used to agitate a liquid in order to enhance mixing and transfer. This work is devoted to the study of the hydrodynamics in a stable bubble column. Experimentally, we have determined the properties of the velocity fluctuations inside and behind a homogeneous swarm of rising bubbles for different bubble sizes and gas volume fractions α: self-similarity in α 0,4 , spectrum in k -3 and integral length scale controlled by buoyancy. Numerically, we have reproduced these properties by means of large-scale simulations, the bubbles being modeled by volume-forces. This confirms that the dynamics is controlled by wake interactions. (author)

  1. Bubble Universe Dynamics After Free Passage

    Energy Technology Data Exchange (ETDEWEB)

    Ahlqvist, Pontus [Department of Physics, Columbia University, New York, New York 10027 (United States); Eckerle, Kate [Department of Applied Mathematics, Columbia University, New York, New York 10027 (United States); Greene, Brian [Department of Physics, Columbia University, New York, New York 10027 (United States); Department of Applied Mathematics, Columbia University, New York, New York 10027 (United States)

    2015-03-06

    We consider bubble collisions in single scalar field theories with multiple vacua. Recent work has argued that at sufficiently high impact velocities, collisions between such bubble vacua are governed by ‘free passage’ dynamics in which field interactions can be ignored during the collision, providing a systematic process for populating local minima without quantum nucleation. We focus on the time period that follows the bubble collision and provide evidence that, for certain potentials, interactions can drive significant deviations from the free-passage bubble profile, thwarting the production of bubbles with different field values.

  2. Lidar signature from bubbles in the sea.

    Science.gov (United States)

    Churnside, James H

    2010-04-12

    The lidar signature from a collection of bubbles is proportional to the volume backscatter coefficient at a scattering angle of 180 degrees . This quantity, calculated using a combination of geometric optics and diffraction, is proportional to the void fraction of the bubbles in the water for any bubble size distribution. The constant of proportionality is 233 m(-1) sr(-1)for clean bubbles, slightly less for bubbles coated with a thin layer of organic material, and as large as 1445 m(-1) sr(-1) for a thick coating of protein.

  3. Critical success factors for the transition to business models for sustainability in the food and beverage industry in the Netherlands

    NARCIS (Netherlands)

    Long, Thomas B.; Looijen, Arnold; Blok, Vincent

    2018-01-01

    Businesses will play a key role in helping the transition towards greater sustainability. To maximise business sustainability performance, sustainability characteristics must be integrated at the business model level, creating business models for sustainability. Creating a business model for

  4. Investigation of the critical edge ion heat flux for L-H transitions in Alcator C-Mod and its dependence on B T

    Science.gov (United States)

    Schmidtmayr, M.; Hughes, J. W.; Ryter, F.; Wolfrum, E.; Cao, N.; Creely, A. J.; Howard, N.; Hubbard, A. E.; Lin, Y.; Reinke, M. L.; Rice, J. E.; Tolman, E. A.; Wukitch, S.; Ma, Y.; ASDEX Upgrade Team; Alcator C-Mod Team

    2018-05-01

    This paper presents investigations on the role of the edge ion heat flux for transitions from L-mode to H-mode in Alcator C-Mod. Previous results from the ASDEX Upgrade tokamak indicated that a critical value of edge ion heat flux per particle is needed for the transition. Analysis of C-Mod data confirms this result. The edge ion heat flux is indeed found to increase linearly with density at given magnetic field and plasma current. Furthermore, the Alcator C-Mod data indicate that the edge ion heat flux at the L-H transition also increases with magnetic field. Combining the data from Alcator C-Mod and ASDEX Upgrade yields a general expression for the edge ion heat flux at the L-H transition. These results are discussed from the point of view of the possible physics mechanism of the L-H transition. They are also compared to the L-H power threshold scaling and an extrapolation for ITER is given.

  5. Acute Pancreatitis as a Model to Predict Transition of Systemic Inflammation to Organ Failure in Trauma and Critical Illness

    Science.gov (United States)

    2017-10-01

    AWARD NUMBER: W81XWH-14-1-0376 TITLE: Acute Pancreatitis as a Model to Predict Transition of Systemic Inflammation to Organ Failgure in Trauma...COVERED 22 Sep 2016 - 21 Sep 2017 4. TITLE AND SUBTITLE 5a. CONTRACT NUMBER Acute Pancreatitis as a Model to Predict Transition of Systemic...Distribution Unlimited 13. SUPPLEMENTARY NOTES 14. ABSTRACT Trauma, extensive burns, bacterial infections, and acute pancreatitis (AP) are common

  6. Critical success factors for the transition to business models for sustainability in the food and beverage industry in the Netherlands

    OpenAIRE

    Long, Thomas B.; Looijen, Arnold; Blok, Vincent

    2018-01-01

    Businesses will play a key role in helping the transition towards greater sustainability. To maximise business sustainability performance, sustainability characteristics must be integrated at the business model level, creating business models for sustainability. Creating a business model for sustainability, or transitioning from a traditional business model, is likely to be a complicated and challenging process. Previous research has identified a range of barriers, such as low financial rewar...

  7. An equation of motion for bubble growth

    International Nuclear Information System (INIS)

    Lesage, F.J.; Cotton, J.S.; Robinson, A.J.

    2009-01-01

    A mathematical model is developed which describes asymmetric bubble growth, either during boiling or bubble injection from submerged orifices. The model is developed using the integral form of the continuity and momentum equations, resulting in a general expression for the acceleration of the bubble's centre of gravity. The proposed model highlights the need to include acceleration due to an asymmetric gain or loss of mass in order to accurately predict bubble motion. Some scenarios are posed by which the growth of bubbles, particularly idealized bubbles that remain a section of a sphere, must include the fact that bubble growth can be asymmetric. In particular, for approximately hemispherical bubble growth the sum of the forces acting on the bubble is negligible compared with the asymmetric term. Further, for bubble injection from a submerged needle this component in the equation of motion is very significant during the initial rapid growth phase as the bubble issues from the nozzle changing from a near hemisphere to truncated sphere geometry. (author)

  8. Agitation, Mixing, and Transfers Induced by Bubbles

    Science.gov (United States)

    Risso, Frédéric

    2018-01-01

    Bubbly flows involve bubbles randomly distributed within a liquid. At large Reynolds number, they experience an agitation that can combine shear-induced turbulence (SIT), large-scale buoyancy-driven flows, and bubble-induced agitation (BIA). The properties of BIA strongly differ from those of SIT. They have been determined from studies of homogeneous swarms of rising bubbles. Regarding the bubbles, agitation is mainly caused by the wake-induced path instability. Regarding the liquid, two contributions must be distinguished. The first one corresponds to the anisotropic flow disturbances generated near the bubbles, principally in the vertical direction. The second one is the almost isotropic turbulence induced by the flow instability through a population of bubbles, which turns out to be the main cause of horizontal fluctuations. Both contributions generate a k‑3 spectral subrange and exponential probability density functions. The subsequent issue will be to understand how BIA interacts with SIT.

  9. Contracting bubbles in Hele-Shaw cells with a power-law fluid

    International Nuclear Information System (INIS)

    McCue, Scott W; King, John R

    2011-01-01

    The problem of bubble contraction in a Hele-Shaw cell is studied for the case in which the surrounding fluid is of power-law type. A small perturbation of the radially symmetric problem is first considered, focussing on the behaviour just before the bubble vanishes, it being found that for shear-thinning fluids the radially symmetric solution is stable, while for shear-thickening fluids the aspect ratio of the bubble boundary increases. The borderline (Newtonian) case considered previously is neutrally stable, the bubble boundary becoming elliptic in shape with the eccentricity of the ellipse depending on the initial data. Further light is shed on the bubble contraction problem by considering a long thin Hele-Shaw cell: for early times the leading-order behaviour is one-dimensional in this limit; however, as the bubble contracts its evolution is ultimately determined by the solution of a Wiener–Hopf problem, the transition between the long thin limit and the extinction limit in which the bubble vanishes being described by what is in effect a similarity solution of the second kind. This same solution describes the generic (slit-like) extinction behaviour for shear-thickening fluids, the interface profiles that generalize the ellipses that characterize the Newtonian case being constructed by the Wiener–Hopf calculation

  10. Measuring the Transition Rates of Coalescence Events during Double Phase Separation in Microgravity

    Directory of Open Access Journals (Sweden)

    Ana Oprisan

    2017-07-01

    Full Text Available Phase transition is a ubiquitous phenomenon in nature, science and technology. In general, the phase separation from a homogeneous phase depends on the depth of the temperature quench into the two-phase region. Earth’s gravity masks the details of phase separation phenomena, which is why experiments were performed under weightlessness. Under such conditions, the pure fluid sulphur hexafluoride (SF 6 near its critical point also benefits from the universality of phase separation behavior and critical slowing down of dynamics. Initially, the fluid was slightly below its critical temperature with the liquid matrix separated from the vapor phase. A 0.2 mK temperature quench further cooled down the fluid and produced a double phase separation with liquid droplets inside the vapor phase and vapor bubbles inside the liquid matrix, respectively. The liquid droplets and the vapor bubbles respective distributions were well fitted by a lognormal function. The evolution of discrete bins of different radii allowed the derivation of the transition rates for coalescence processes. Based on the largest transition rates, two main coalescence mechanisms were identified: (1 asymmetric coalescences between one small droplet of about 20 μ m and a wide range of larger droplets; and (2 symmetric coalescences between droplets of large and similar radii. Both mechanisms lead to a continuous decline of the fraction of small radii droplets and an increase in the fraction of the large radii droplets. Similar coalescence mechanisms were observed for vapor bubbles. However, the mean radii of liquid droplets exhibits a t 1 / 3 evolution, whereas the mean radii of the vapor bubbles exhibit a t 1 / 2 evolution.

  11. Transition to Critical Care Practice Within an Academic-Service Partnership: A Case Report of the First 3 Years of Clinical Immersion in Trauma-Burn and Neuroscience Critical Care.

    Science.gov (United States)

    Bay, Esther; Sherzer, Andrea; Darnbrook, Emily

    In response to regulators of nursing education and the Institute of Medicine, an academic-service partnership was formed between a research-intensive school of nursing and a tertiary health care facility. In that partnership, clinical experiences occurred mostly within 1 organization. This case report showcases the development, implementation, and revisions within our capstone immersion course, designed to ease the new graduates' transition into practice, including transitions to critical care nursing. Herein, we highlight our successes and challenges of implementing the clinical component within 2 critical care units focused on trauma and neurosurgical care of complex patients. Its purpose is to describe the planning and orientation phase, illustrate the mentoring processes used to achieve the educational outcomes, and describe the benefits and challenges of such an immersion experience. Our redesigned clinical immersion course in high-acuity nursing is facilitated by our partnership and resulted in improved RN-NCLEX rates, facilitation of best practices, and ease of transition into novice graduate nurse roles.

  12. Critical high-dimensional state transitions in cell populations or why cancers follow the principle ``What does not kill me makes me stronger''

    Science.gov (United States)

    Huang, Sui

    Transitions between high-dimensional attractor states in the quasi-potential landscape of the gene regulatory network, induced by environmental perturbations and/or facilitated by mutational rewiring of the network, underlie cell phenotype switching in development as well as in cancer progression, including acquisition of drug-resistant phenotypes. Considering heterogeneous cell populations as statistical ensembles of cells, and single-cell resolution gene expression profiling of cell populations undergoing a cell phenotype shift allow us now to map the topography of the landscape and its distortion. From snapshots of single-cell expression patterns of a cell population measured during major transitions we compute a quantity that identifies symmetry-breaking destabilization of attractors (bifurcation) and concomitant dimension-reduction of the state space manifold (landscape distortion) which precede critical transitions to new attractor states. The model predicts, and we show experimentally, the almost inevitable generation of aberrant cells associated with such critical transitions in multi-attractor landscapes: therapeutic perturbations which seek to push cancer cells to the apoptotic state, almost always produce ``rebellious'' cells which move in the ``opposite direction'': instead of dying they become more stem-cell-like and malignant. We show experimentally that the inadvertent generation of more malignant cancer cells by therapy indeed results from transition of surviving (but stressed) cells into unforeseen attractor states and not simply from selection of inherently more resistant cells. Thus, cancer cells follow not so much Darwin, as generally thought (survival of the fittest), but rather Nietzsche (What does not kill me makes me stronger). Supported by NIH (NCI, NIGMS), Alberta Innovates.

  13. Modification of shape oscillations of an attached bubble by surfactants

    Directory of Open Access Journals (Sweden)

    Tihon J.

    2013-04-01

    Full Text Available Surface-active agents (surfactants, e.g. washing agents strongly modifies properties of gas-liquid interface. We have carried out extensive experiments, in which we study effect of surfactants on the shape oscillations of a bubble, which is attached at a tip of a capillary. In the experiments, shape oscillations of a bubble are invoked by a motion of a capillary, to which the bubble is injected. Decaying oscillations are recorded and their frequency and damping are evaluated. By changing the excitation frequency, three lowest oscillation modes are studied. Experiments were repeated in aqueous solution of several surfactants (terpineol, SDS, CTAB, Triton X-100, Triton X-45 at various concentrations. Generally, these features are observed: Initially a surfactant addition leads to an increase of the oscillation frequency (though surface tension is decreasing; this effect can be attributed to the increasing interfacial elasticity. The decay time of oscillation is strongly decreasing, as a consequence of energy dissipation linked with Marangoni stresses. At a certain critical concentration, frequency decreases abruptly and the decay time passes by a minimum. With further addition of surfactant, frequency decreases, and the decay time slightly lengthens. Above critical micelle concentration, all these parameters stabilize. Interestingly, the critical concentration, at which frequency drop occurs, depends on mode order. This clearly shows that the frequency drop and minimum decay time are not a consequence of some abrupt change of interfacial properties, but are a consequence of some phenomena, which still need to be explained.

  14. Modification of shape oscillations of an attached bubble by surfactants

    Science.gov (United States)

    Vobecká, L.; Vejražka, J.; Tihon, J.

    2013-04-01

    Surface-active agents (surfactants, e.g. washing agents) strongly modifies properties of gas-liquid interface. We have carried out extensive experiments, in which we study effect of surfactants on the shape oscillations of a bubble, which is attached at a tip of a capillary. In the experiments, shape oscillations of a bubble are invoked by a motion of a capillary, to which the bubble is injected. Decaying oscillations are recorded and their frequency and damping are evaluated. By changing the excitation frequency, three lowest oscillation modes are studied. Experiments were repeated in aqueous solution of several surfactants (terpineol, SDS, CTAB, Triton X-100, Triton X-45) at various concentrations. Generally, these features are observed: Initially a surfactant addition leads to an increase of the oscillation frequency (though surface tension is decreasing); this effect can be attributed to the increasing interfacial elasticity. The decay time of oscillation is strongly decreasing, as a consequence of energy dissipation linked with Marangoni stresses. At a certain critical concentration, frequency decreases abruptly and the decay time passes by a minimum. With further addition of surfactant, frequency decreases, and the decay time slightly lengthens. Above critical micelle concentration, all these parameters stabilize. Interestingly, the critical concentration, at which frequency drop occurs, depends on mode order. This clearly shows that the frequency drop and minimum decay time are not a consequence of some abrupt change of interfacial properties, but are a consequence of some phenomena, which still need to be explained.

  15. Bubble entrapment through topological change

    KAUST Repository

    Thoroddsen, Sigurdur T.

    2010-05-03

    When a viscousdrop impacts onto a solid surface, it entraps a myriad of microbubbles at the interface between liquid and solid. We present direct high-speed video observations of this entrapment. For viscousdrops, the tip of the spreading lamella is separated from the surface and levitated on a cushion of air. We show that the primary mechanism for the bubble entrapment is contact between this precursor sheet of liquid with the solid and not air pulled directly through cusps in the contact line. The sheet makes contact with the solid surface,forming a wetted patch, which grows in size, but only entraps a bubble when it meets the advancing contact line. The leading front of this wet patch can also lead to the localized thinning and puncturing of the liquid film producing strong splashing of droplets.

  16. Prominence Bubble Shear Flows and the Coupled Kelvin-Helmholtz — Rayleigh-Taylor Instability

    Science.gov (United States)

    Berger, Thomas; Hillier, Andrew

    2017-08-01

    Prominence bubbles are large arched structures that rise from below into quiescent prominences, often growing to heights on the order of 10 Mm before going unstable and generating plume upflows. While there is general agreement that emerging flux below pre-existing prominences causes the structures, there is lack of agreement on the nature of the bubbles and the cause of the instability flows. One hypothesis is that the bubbles contain coronal temperature plasma and rise into the prominence above due to both magnetic and thermal buoyancy, eventually breaking down via a magnetic Rayleigh-Taylor (RT) instability to release hot plasma and magnetic flux and helicity into the overlying coronal flux rope. Another posits that the bubbles are actually just “arcades” in the prominence indicating a magnetic separator line between the bipole and the prominence fields with the observed upflows and downflows caused by reconnection along the separator. We analyze Hinode/SOT, SDO/AIA, and IRIS observations of prominence bubbles, focusing on characteristics of the bubble boundary layers that may discriminate between the two hypotheses. We find speeds on the order of 10 km/s in prominence plasma downflows and lateral shear flows along the bubble boundary. Inflows to the boundary gradually increase the thickness and brightness of the layer until plasma drains from there, apparently around the dome-like bubble domain. In one case, shear flow across the bubble boundary develops Kelvin-Helmholtz (KH) vortices that we use to infer flow speeds in the low-density bubble on the order of 100 km/sec. IRIS spectra indicate that plasma flows on the bubble boundary at transition region temperatures achieve Doppler speeds on the order of 50 km/s, consistent with this inference. Combined magnetic KH-RT instability analysis leads to flux density estimates of 10 G with a field angle of 30° to the prominence, consistent with vector magnetic field measurements. In contrast, we find no evidence

  17. Bubble formation during drop impact on a heated pool

    Science.gov (United States)

    Tian, Yuansi; Alhazmi, Muath; Kouraytem, Nadia; Thoroddsen, Sigurdur

    2017-11-01

    Ultra high-speed video imaging, at up to 200 kfps, is used to investigate a drop impinging onto a high temperature pool. The room-temperature perfluorohexane drop, which has a boiling temperature as low as 56 °C impacts on the soybean oil pool heated up to around 200 °C, which is overwhelmingly higher than the boiling temperature of the drop. The bottom of the drop is therefore covered by a layer of vapor which prevents contact between the two immiscible liquid surfaces, akin to the Leidenfrost effect However, as the pool temperature is reduced, one starts seeing contact and the dynamics transition into the vapor explosion regime. At the boundary of this regime we observe some entrapment of scattered or a toroidal ring of small bubbles. Experimental video data will be presented to show this novel phenomenon and explain how these bubbles are formed and evolve.

  18. BEBC Big European Bubble Chamber

    CERN Multimedia

    CERN PhotoLab

    1974-01-01

    A view of the dismantling of the magnet of BEBC, the 3.7 m European Bubble Chamber : iron magnetic shielding ; lower and upper parts of the vacuum enclosure of the magnet; turbo-molecular vacuum pumps for the "fish-eye" windows; the two superconducting coils; a handling platform; the two cryostats suspended from the bar of the travelling crane which has a 170 ton carrying capacity. The chamber proper, not dismantled, is inside the shielding.

  19. Informational pathologies and interest bubbles

    DEFF Research Database (Denmark)

    Hendricks, Vincent Fella; Wiewiura, Joachim Schmidt

    2017-01-01

    This article contends that certain configurations of information networks facilitate specific cognitive states that are instrumental for decision and action on social media. Group-related knowledge and belief states—in particular common knowledge and pluralistic ignorance—may enable strong public...... signals. Indeed, some network configurations and attitude states foster informational pathologies that may fuel interest bubbles affecting agenda-setting and the generation of narratives in public spheres....

  20. Soap bubbles in paintings: Art and science

    Science.gov (United States)

    Behroozi, F.

    2008-12-01

    Soap bubbles became popular in 17th century paintings and prints primarily as a metaphor for the impermanence and fragility of life. The Dancing Couple (1663) by the Dutch painter Jan Steen is a good example which, among many other symbols, shows a young boy blowing soap bubbles. In the 18th century the French painter Jean-Simeon Chardin used soap bubbles not only as metaphor but also to express a sense of play and wonder. In his most famous painting, Soap Bubbles (1733/1734) a translucent and quavering soap bubble takes center stage. Chardin's contemporary Charles Van Loo painted his Soap Bubbles (1764) after seeing Chardin's work. In both paintings the soap bubbles have a hint of color and show two bright reflection spots. We discuss the physics involved and explain how keenly the painters have observed the interaction of light and soap bubbles. We show that the two reflection spots on the soap bubbles are images of the light source, one real and one virtual, formed by the curved surface of the bubble. The faint colors are due to thin film interference effects.

  1. When Will Occur the Crude Oil Bubbles?

    International Nuclear Information System (INIS)

    Su, Chi-Wei; Li, Zheng-Zheng; Chang, Hsu-Ling; Lobonţ, Oana-Ramona

    2017-01-01

    In this paper, we apply a recursive unit root test to investigate whether there exist multiple bubbles in crude oil price. The method is best suited for a practical implementation of a time series and delivers a consistent date-stamping strategy for the origination and termination of multiple bubbles. The empirical result indicates that there exist six bubbles during 1986–2016 when the oil price deviate from its intrinsic value based on market fundamentals. Specifically, oil price contains the fundamentals and bubble components. The dates of the bubbles correspond to specific events in the politics and financial markets. The authorities should actively fight speculative bubbles or just observe their evolutions and speculation activities may decrease, which is favour of the stabilisation of the staple commodities including crude oil price. These findings have important economic and policy implications to recognise the cause of bubbles and take corresponding measures to reduce the impact on the real economy cause of the fluctuation of crude oil price. - Highlights: • Investigate multiple bubbles in crude oil price. • Indicate six bubbles deviate from its intrinsic value based on market fundamentals. • The bubbles correspond to specific events in the politics and financial markets. • Reduce the impact on the real economy cause of the fluctuation of crude oil price.

  2. Armoring confined bubbles in concentrated colloidal suspensions

    Science.gov (United States)

    Yu, Yingxian; Khodaparast, Sepideh; Stone, Howard

    2016-11-01

    Encapsulation of a bubble with microparticles is known to significantly improve the stability of the bubble. This phenomenon has recently gained increasing attention due to its application in a variety of technologies such as foam stabilization, drug encapsulation and colloidosomes. Nevertheless, the production of such colloidal armored bubble with controlled size and particle coverage ratio is still a great challenge industrially. We study the coating process of a long air bubble by microparticles in a circular tube filled with a concentrated microparticles colloidal suspension. As the bubble proceeds in the suspension of particles, a monolayer of micro-particles forms on the interface of the bubble, which eventually results in a fully armored bubble. We investigate the phenomenon that triggers and controls the evolution of the particle accumulation on the bubble interface. Moreover, we examine the effects of the mean flow velocity, the size of the colloids and concentration of the suspension on the dynamics of the armored bubble. The results of this study can potentially be applied to production of particle-encapsulated bubbles, surface-cleaning techniques, and gas-assisted injection molding.

  3. The stability of the flow in a laminar separation bubble

    Science.gov (United States)

    Niew, Tai Ran

    1993-09-01

    This dissertation reports a study into the underlying concepts used to analyze incompressible laminar separation bubbles. The suggestion that absolute instability could play a role in bubble flows was further developed, and was the focal point of this project. From a review of previous work and preliminary experiments on a backward faxing step, it was suggested that for some bubbles the reattachment region of the flow field could be absolutely unstable. A cornerstone of this view is that the completion of transition is not a prerequisite for the start of reattachment; and that a more fundamental mechanism involves significant interaction between the two processes. This concept was first tested by solving the eigenvalue problem of the Orr-Sommerfeld equation for a family of reverse flow profiles. The results indicated that with sufficient reverse flow, wall-bounded separated shear-layers that are similar to experimentally measured profiles can be absolutely unstable. This is consistent with the hypothesis outlined above. The numerical study also showed that for convectively unstable profiles, the predominant parameter that determines the spatial growth rate of instability waves is the distance of the separated shear layer from the wall. Furthermore, viscosity only has a weak effect on the stability characteristics of both absolutely and convectively unstable profiles at generic bubble Reynolds numbers. Experiments were then carried out on the flow behind a backward facing step using artificially excited instability waves, and the key issues in formulating a conceptually robust experimental method to test the above hypothesis was discussed. If the forcing was carried out with a non-acoustic source, it was shown that the use of impulse excitation could provide a rigorous procedure. Two qualitatively different transition mechanisms, 'wave' and 'spot' type, were also observed in these experiments. A new perspective of bubble behavior was then developed that considered

  4. IUPAC critical evaluation of the rotational–vibrational spectra of water vapor, Part III: Energy levels and transition wavenumbers for H216O

    International Nuclear Information System (INIS)

    Tennyson, Jonathan; Bernath, Peter F.; Brown, Linda R.; Campargue, Alain; Császár, Attila G.; Daumont, Ludovic; Gamache, Robert R.; Hodges, Joseph T.; Naumenko, Olga V.; Polyansky, Oleg L.; Rothman, Laurence S.; Vandaele, Ann Carine; Zobov, Nikolai F.; Al Derzi, Afaf R.; Fábri, Csaba; Fazliev, Alexander Z.; Furtenbacher, Tibor

    2013-01-01

    This is the third of a series of articles reporting critically evaluated rotational–vibrational line positions, transition intensities, and energy levels, with associated critically reviewed labels and uncertainties, for all the main isotopologues of water. This paper presents experimental line positions, experimental-quality energy levels, and validated labels for rotational–vibrational transitions of the most abundant isotopologue of water, H 2 16 O. The latest version of the MARVEL (Measured Active Rotational–Vibrational Energy Levels) line-inversion procedure is used to determine the rovibrational energy levels of the electronic ground state of H 2 16 O from experimentally measured lines, together with their self-consistent uncertainties, for the spectral region up to the first dissociation limit. The spectroscopic network of H 2 16 O containstwo components, an ortho (o) and a para (p) one. For o-H 2 16 O and p-H 2 16 O, experimentally measured, assigned, and labeled transitions were analyzed from more than 100 sources. The measured lines come from one-photon spectra recorded at room temperature in absorption, from hot samples with temperatures up to 3000 K recorded in emission, and from multiresonance excitation spectra which sample levels up to dissociation. The total number of transitions considered is 184 667 of which 182 156 are validated: 68 027 between para states and 114 129 ortho ones. These transitions give rise to 18 486 validated energy levels, of which 10 446 and 8040 belong to o-H 2 16 O and p-H 2 16 O, respectively. The energy levels, including their labeling with approximate normal-mode and rigid-rotor quantum numbers, have been checked against ones determined from accurate variational nuclear motion computations employing exact kinetic energy operators as well as against previous compilations of energy levels. The extensive list of MARVEL lines and levels obtained are deposited in the supplementary data of this paper, as well as in a

  5. Two melts phase separation in the liquid Sb-Sb2S3 system: critical sound wave propagation and metal-non-metal transition

    Directory of Open Access Journals (Sweden)

    Kakimuma F.

    2011-05-01

    Full Text Available The sound velocity and magnetic susceptibility as a function of temperature and composition were measured to investigate critical sound wave propagation and metal-non-metal transition in the liquid Sb-Sb2S3 system. The sound velocity in a homogeneous alloy around 60 at.% of Sb decreases very rapidly and the rate of decrease increases as the two melts phase is approached, which is the typical temperature dependence of the sound velocity in a liquid with a miscibility gap. Below the critical point, the sound velocity was measured along the phase boundary. Using those data, the phase boundary was precisely determined. The critical point is located at 901±2°C and 41.5 ±0.5 at.% S, and the critical exponent of the phase boundary is about 1/3. On the other hand, the magnetic susceptibility as a function of temperature and composition indicates that the electronic state is metallic in liquid Sb and non-metallic in molten Sb2Se3, and crossover form the metallic to non-metallic state occurs around the critical composition.

  6. Critical analysis of the paramagnetic to ferromagnetic phase transition in Pr0.55K0.05Sr0.4MnO3

    Science.gov (United States)

    Thaljaoui, R.; Pękała, M.; Fagnard, J.-F.; Vanderbemden, Ph.

    2016-02-01

    The critical properties of monovalent doped manganite Pr0.55K0.05Sr0.4MnO3 around the paramagnetic to ferromagnetic phase transition were investigated through various methods: the modified Arrott plots (MAP), the Kouvel-Fisher method and the critical isotherm analysis. Data obtained near Tc were examined in the framework of the mean field theory, the 3D-Heisenberg model, the 3D-Ising model, and tricritical mean field. The deduced critical exponents values obtained using MAP method were found to be β=0.44(4) with TC≈303 K and γ=1.04(1) with TC≈302 K. Kouvel-Fisher method supplies the critical values to be β=0.41(2) with TC≈302 K and γ=1.09(1) with TC≈302 K. The obtained critical parameters show a tendency towards the mean-field behavior, suggesting the existence of long-range ferromagnetic order in the compound studied. The exponent δ deduced separately from isotherm analysis at T=303 K was found to obey to the Widom scaling relation δ=1+γ/β. The reliability of obtained exponents was confirmed by using the universal scaling hypothesis. The itinerant character of ferromagnetism in the present system was also tested by using Rhodes-Wohlfarth's criterion.

  7. Disentangling phase transitions and critical points in the proton–neutron interacting boson model by catastrophe theory

    Directory of Open Access Journals (Sweden)

    J.E. García-Ramos

    2014-09-01

    Full Text Available We introduce the basic concepts of catastrophe theory needed to derive analytically the phase diagram of the proton–neutron interacting boson model (IBM-2. Previous studies [1–3] were based on numerical solutions. We here explain the whole IBM-2 phase diagram including the precise order of the phase transitions in terms of the cusp catastrophe.

  8. A critical evaluation of student radiographers' experience of the transition from the classroom to their first clinical placement

    International Nuclear Information System (INIS)

    Hyde, Emma

    2015-01-01

    Introduction: Students studying for qualifications which enable them to apply for registration as health care professionals are expected to undertake a large amount of clinical placement to support their learning. The BSc Hons Diagnostic Radiography at one post-1992 UK University is no exception. It was identified in a previous study by this researcher that a relatively large number of first year student radiographers were unsure, or nervous, about some aspects of the transition to their first clinical placement. It was felt that further investigation into the student experience of the transition to the first clinical placement was warranted. Methodology: A mixed-methods survey approach was used to elicit quantitative and qualitative data from current radiography students, academic staff and clinical staff about student experience of the transition to the first clinical placement. Results: In general, most students enjoyed their first clinical placement, and the opportunity to put theory into practice. However, three key themes emerged from the data that caused students difficulty in the first clinical placement; working with clinical staff, working with very ill patients, and moving around the department each week. Key Conclusions: This study has identified that some aspects of the transition into the first clinical placement need to be improved. Recommendations have been made for curriculum development in the academic block prior to the first clinical placement, and to improve student support during clinical placement. The implementation of these recommendations is crucial to reduce the dissonance between theory and practice, and improve student experience of the transition to the first clinical placement. - Highlights: • Issues for student radiographers during their first clinical placement are identified. • Recommendations made for curriculum development to improve preparation for clinical placement. • Recommendations made to improve student support in

  9. The KEK 1 m hydrogen bubble chamber

    International Nuclear Information System (INIS)

    Doi, Yoshikuni; Araoka, Osamu; Hayashi, Kohei; Hayashi, Yoshio; Hirabayashi, Hiromi.

    1978-03-01

    A medium size hydrogen bubble chamber has been constructed at the National Laboratory for High Energy Physics, KEK. The bubble chamber has been designed to be operated with a maximum rate of three times per half a second in every two second repetition time of the accelerator, by utilizing a hydraulic expansion system. The bubble chamber has a one meter diameter and a visible volume of about 280 l. A three-view stereo camera system is used for taking photographic pictures of the chamber. A 2 MW bubble chamber magnet is constructed. The main part of the bubble chamber vessel is supported by the magnet yoke. The magnet gives a maximum field of 18.4 kG at the centre of the fiducial volume of the chamber. The overall system of the KEK 1 m hydrogen bubble chamber facility is described in some detail. Some operational characteristics of the facility are also reported. (auth.)

  10. Formation of soap bubbles by gas jet

    Science.gov (United States)

    Zhou, Maolei; Li, Min; Chen, Zhiyuan; Han, Jifeng; Liu, Dong

    2017-12-01

    Soap bubbles can be easily generated by various methods, while their formation process is complicated and still worth studying. A model about the bubble formation process was proposed in the study by Salkin et al. [Phys. Rev. Lett. 116, 077801 (2016)] recently, and it was reported that the bubbles were formed when the gas blowing velocity was above one threshold. However, after a detailed study of these experiments, we found that the bubbles could be generated in two velocity ranges which corresponded to the laminar and turbulent gas jet, respectively, and the predicted threshold was only effective for turbulent gas flow. The study revealed that the bubble formation was greatly influenced by the aerodynamics of the gas jet blowing to the film, and these results will help to further understand the formation mechanism of the soap bubble as well as the interaction between the gas jet and the thin liquid film.

  11. Asset Bubbles, Endogenous Growth, and Financial Frictions

    OpenAIRE

    Hirano, Tomohiro; Yanagawa, Noriyuki

    2016-01-01

    This paper analyzes the effects of bubbles in an infinitely-lived agent model of endogenous growth with financial frictions and heterogeneous agents. We provide a complete characterization on the relationship between financial frictions and the existence of bubbles. Our model predicts that if the degree of pledgeability is sufficiently high or sufficiently low, bubbles can not exist. They can only arise at an intermediate degree. This suggests that improving the financial market condition mig...

  12. Bubbles, Financial Crises, and Systemic Risk

    OpenAIRE

    Markus K. Brunnermeier; Martin Oehmke

    2012-01-01

    This chapter surveys the literature on bubbles, financial crises, and systemic risk. The first part of the chapter provides a brief historical account of bubbles and financial crisis. The second part of the chapter gives a structured overview of the literature on financial bubbles. The third part of the chapter discusses the literatures on financial crises and systemic risk, with particular emphasis on amplification and propagation mechanisms during financial crises, and the measurement of sy...

  13. On Bubble Rising in Countercurrent Flow

    Czech Academy of Sciences Publication Activity Database

    Večeř, M.; Leštinský, P.; Wichterle, K.; Růžička, Marek

    2012-01-01

    Roč. 10, č. 2012 (2012), A30 ISSN 1542-6580 R&D Projects: GA ČR GA104/09/0972; GA ČR GA104/07/1110 Grant - others:GA MŠMT(CZ) CZ.1.05/2.1.00/03.0069 Institutional support: RVO:67985858 Keywords : ellipsoidal bubble * bubble shape * bubble velocity Subject RIV: CI - Industrial Chemistry, Chemical Engineering Impact factor: 0.790, year: 2011

  14. Order-disorder type critical behavior at the magnetoelectric phase transition in multiferroic DyMnO3

    Science.gov (United States)

    Schiebl, M.; Shuvaev, A.; Pimenov, Anna; Johnstone, G. E.; Dziom, V.; Mukhin, A. A.; Ivanov, V. Yu.; Pimenov, A.

    2015-06-01

    We present the results of detailed dielectric investigations of the relaxation dynamics in DyMnO3 multiferroic manganite. A strong low-frequency relaxation process near the paraelectric-ferroelectric phase transition is observed. We provide experimental evidence to show that this relaxation mode corresponds to a chirality switching of the spin cycloid in DyMnO3. We demonstrate that the relaxation dynamics in DyMnO3 is typical for an order-disorder phase transition and may be understood within a simple model with a double-well potential. These results suggest the interpretation of the paraelectric sinusoidal phase in manganites as a dynamical equilibrium of magnetic cycloids with opposite chiralities.

  15. Modeling shear-sensitive dinoflagellate microalgae growth in bubble column photobioreactors.

    Science.gov (United States)

    López-Rosales, Lorenzo; García-Camacho, Francisco; Sánchez-Mirón, Asterio; Contreras-Gómez, Antonio; Molina-Grima, Emilio

    2017-12-01

    The shear-sensitive dinoflagellate microalga Karlodinium veneficum was grown in a sparged bubble column photobioreactor. The influence of mass transfer and shear stress on cell growth and physiology (concentration of reactive oxygen species, membrane fluidity and photosynthetic efficiency) was studied, and a model describing cell growth in term of mass transfer and culture parameters (nozzle sparger diameter, air flow rate, and culture height) was developed. The results show that mass transfer limits cell growth at low air-flow rates, whereas the shear stress produced by the presence of bubbles is critically detrimental for air flow rates above 0.1vvm. The model developed in this paper adequately represents the growth of K. veneficum. Moreover, the parameters of the model indicate that bubble rupture is much more harmful for cells than bubble formation. Copyright © 2017 Elsevier Ltd. All rights reserved.

  16. Critical heat flux and transition boiling characteristics for a sodium-heated steam generator tube for LMFBR applications

    Energy Technology Data Exchange (ETDEWEB)

    Wolf, S.; Holmes, D.H.

    1977-04-01

    An experimental program was conducted to characterize critical heat flux (CHF) in a sodium-heated steam generator tube model at a proposed PLBR steam generator design pressure of 7.2 MPa. Water was circulated vertically upward in the tube and the heating sodium was flowing counter-current downward. The experimental ranges were: mass flux, 110 to 1490 kg/s.m/sup 2/ (0.08 to 1.10 10/sup 6/ lbm/h.ft/sup 2/); critical heat flux, 0.16 to 1.86 MW/m/sup 2/ (0.05 to 0.59 10/sup 6/ Btu/h.ft/sup 2/); and critical quality, 0.48 to 1.0. The CHF phenomenon for the experimental conditions is determined to be dryout as opposed to departure from nucleate boiling (DNB). The data are divided into high- and low-mass flux regions.

  17. The neglected social dimensions to a vehicle-to-grid (V2G) transition: a critical and systematic review

    Science.gov (United States)

    Sovacool, Benjamin K.; Noel, Lance; Axsen, Jonn; Kempton, Willett

    2018-01-01

    Vehicle-to-grid (V2G) refers to efforts to bi-directionally link the electric power system and the transportation system in ways that can improve the sustainability and security of both. A transition to V2G could enable vehicles to simultaneously improve the efficiency (and profitability) of electricity grids, reduce greenhouse gas emissions for transport, accommodate low-carbon sources of energy, and reap cost savings for owners, drivers, and other users. To understand the recent state of this field of research, here we conduct a systematic review of 197 peer-reviewed articles published on V2G from 2015 to early 2017. We find that the majority of V2G studies in that time period focus on technical aspects of V2G, notably renewable energy storage, batteries, or load balancing to minimize electricity costs, in some cases including environmental goals as constraints. A much lower proportion of studies focus on the importance of assessing environmental and climate attributes of a V2G transition, or on the role of consumer acceptance and knowledge of V2G systems. Further, there is need for exploratory work on natural resource use and externalities, discourses and narratives as well as social justice, gender, and urban resilience considerations. These research gaps need to be addressed if V2G is to achieve the societal transition its advocates seek.

  18. Improvised bubble continuous positive airway pressure (BCPAP ...

    African Journals Online (AJOL)

    Improvised bubble continuous positive airway pressure (BCPAP) device at the National Hospital Abuja gives immediate improvement in respiratory rate and oxygenation in neonates with respiratory distress.

  19. Multiple Spark-Generated Bubble Interactions

    Science.gov (United States)

    Khoo, Boo Cheong; Adikhari, Deepak; Fong, Siew Wan; Klaseboer, Evert

    The complex interactions of two and three spark-generated bubbles are studied using high speed photography. The corresponding simulations are performed using a 3D Boundary Element Method (BEM) code. The bubbles generated are between 3 to 5 mm in radius, and they are either in-phase or out-of-phase with one another. The possible interaction phenomena between two identically sized bubbles are summarized. Depending on their relative distances and phase differences, they can coalesce, jet towards or away from one another, split into smaller bubbles, or 'catapult' away from one another. The 'catapult' effect can be utilized to generated high speed jet in the absence of a solid boundary or shockwave. Also three bubble interactions are highlighted. Complicated phenomena such as bubble forming an elliptical shape and bubble splitting are observed. The BEM simulations provide insight into the physics of the phenomena by providing details such as detailed bubble shape changes (experimental observations are limited by the temporal and spatial resolution), and jet velocity. It is noted that the well-tested BEM code [1,2] utilized here is computationally very efficient as compared to other full-domain methods since only the bubble surface is meshed.

  20. Dynamics of Bubbly-magma Flow in Conduits: Stress and Expansion Regimes of Magma Fragmentation

    Science.gov (United States)

    Mitani, N. K.; Koyaguchi, T.; Ida, Y.

    2002-12-01

    Explosive volcanic eruptions are characterized by magma fragmentation, that is, the process through which a bubbly magma is changed into a gas-pyroclast dispersion. Two criteria of mechanisms have been proposed for the magma fragmentation so far. First, magma fragments when stress or strain rate of magma around bubbles exceeds a critical value. Second, magma disrupts due to the instability of thin magma-foam. Which criterion is actually applicable is not yet known. In order to clarify the physics of the magma fragmentation, we numerically study one-dimensional steady flows with bubble growth in conduits. The spherical cell model is used to calculate expansion of bubbles in ascending visco-elastic magma. The stress around bubbles generally grows as magma ascends and the pressure difference between bubbles and surrounding magma increases. In some conditions, the stress becomes critically large only when the flow velocity approaches the sound speed meeting the choking condition. In other conditions, the stress becomes large enough as magma pressure drops with bubble pressure kept almost unchanged. These two distinct types may correspond to the above two criteria of fragmentation mechanisms. In the former case, void fraction becomes close to unity before the stress reaches the strength of magma. In such case, the magma does not fragment due to the visco-elastic deformations but fragments by the instability of the thin magma-foam (`expansion' regime). In the latter case, on the other hand, the stress reaches the magma strength at much lower void fractions. In such case, the magma fragments due to the visco-elastic deformation around bubbles (`stress' regime). The `expansion' and `stress' regimes occur when the ratio of the initial wall-friction stress to the magma strength is sufficiently smaller and greater than unity, respectively.

  1. A Double Bubble in a Ternary System with Inhibitory Long Range Interaction

    Science.gov (United States)

    Ren, Xiaofeng; Wei, Juncheng

    2013-04-01

    The free energy of a ternary system with a self-organization property includes an interface energy and a longer ranging, inhibitory interaction energy. In a planar domain, if the two energies are properly balanced and two of the three constituents make up an equal but small fraction, the free energy admits a local minimizer that is shaped like a perturbed double bubble. Most difficulties in the proof of this result are related to the triple junction phenomenon that the three constituents of the ternary system meet at a point. Two techniques are developed to deal with the triple junction. First, one defines restricted classes of perturbed double bubbles. Each perturbed double bubble in a restricted class is obtained from a standard double bubble by a special perturbation. The two triple junction points of the standard double bubble can only move along the line connecting them, in opposite directions, and by the same distance. The second technique is the use of the so called internal variables. These variables derive from the more geometric quantities that describe perturbed double bubbles in restricted classes. The advantage of the internal variables is that they are only subject to linear constraints, and perturbed double bubbles in a restricted class represented by internal variables are elements of a Hilbert space. A local minimizer of the free energy in each restricted class is found as a fixed point of a nonlinear equation by a contraction mapping argument. The second variation at the fixed point within its restricted class is positive. This perturbed double bubble satisfies three of the four equations for critical points of the free energy. The unsolved equation is the 120 degree angle condition at triple junction points. Then perform another minimization among the local minimizers from all restricted classes. A minimum of minimizers emerges and solves all the equations for critical points.

  2. Liquid jet formation through the interactions of a laser-induced bubble and a gas bubble

    Directory of Open Access Journals (Sweden)

    Bing Han

    2017-10-01

    Full Text Available The mechanisms of the liquid jet formation from the interaction of the laser-induced and gas bubble pair are investigated and compared with the jet formation from the interaction of the laser-induced anti-phase bubble pair. The strobe photography experimental method and numerical simulations are implemented to obtain the parameter space of the optimum liquid jet, i.e. highest speed and lowest diameter. It is found that due to the enhanced “catapult effect”, which is induced by the protrusion of the first bubble into the second bubble and the flip back of the elongated part of the first bubble, the optimum liquid jet of the second bubble of the laser-induced anti-phase bubble pair compared to that of the laser-induced and gas bubble pair is 54 %, 65 % and 11 % faster in speed, and 4 %, 44 % and 64 % smaller in diameter, for the 500 μm, 50 μm and 5 μm sized bubbles, respectively. The optimum dimensionless distance for the optimum jet of the laser-induced and the gas bubble is around 0.7, when the maximum bubble radius increases from ∼ 5μm to ∼500 μm, which is different from the laser-induced anti-phase bubble pairs. Besides, the optimum jet of the laser-induced bubble appeared when the bubbles are equal sized, while that of the gas bubble is independent of the relative bubble size, i.e. the liquid jet of the gas bubble has higher robustness in real liquid jet assisted applications when the laser-induced bubble size varies. However, the jet of bubble 2 could maintain a high speed (20 m/s - 35 m/s and a low diameter (∼5 % of the maximum bubble diameter over a big range of the dimensionless distance (0.6 - 0.9 for both of the 50 μm and 500 μm sized laser-induced equal sized anti-phase bubble pairs.

  3. Liquid jet formation through the interactions of a laser-induced bubble and a gas bubble

    Science.gov (United States)

    Han, Bing; Liu, Liu; Zhao, Xiong-Tao; Ni, Xiao-Wu

    2017-10-01

    The mechanisms of the liquid jet formation from the interaction of the laser-induced and gas bubble pair are investigated and compared with the jet formation from the interaction of the laser-induced anti-phase bubble pair. The strobe photography experimental method and numerical simulations are implemented to obtain the parameter space of the optimum liquid jet, i.e. highest speed and lowest diameter. It is found that due to the enhanced "catapult effect", which is induced by the protrusion of the first bubble into the second bubble and the flip back of the elongated part of the first bubble, the optimum liquid jet of the second bubble of the laser-induced anti-phase bubble pair compared to that of the laser-induced and gas bubble pair is 54 %, 65 % and 11 % faster in speed, and 4 %, 44 % and 64 % smaller in diameter, for the 500 μm, 50 μm and 5 μm sized bubbles, respectively. The optimum dimensionless distance for the optimum jet of the laser-induced and the gas bubble is around 0.7, when the maximum bubble radius increases from ˜ 5μm to ˜500 μm, which is different from the laser-induced anti-phase bubble pairs. Besides, the optimum jet of the laser-induced bubble appeared when the bubbles are equal sized, while that of the gas bubble is independent of the relative bubble size, i.e. the liquid jet of the gas bubble has higher robustness in real liquid jet assisted applications when the laser-induced bubble size varies. However, the jet of bubble 2 could maintain a high speed (20 m/s - 35 m/s) and a low diameter (˜5 % of the maximum bubble diameter) over a big range of the dimensionless distance (0.6 - 0.9) for both of the 50 μm and 500 μm sized laser-induced equal sized anti-phase bubble pairs.

  4. Dynamic morphology of gas hydrate on a methane bubble in water: Observations and new insights for hydrate film models

    Science.gov (United States)

    Warzinski, Robert P.; Lynn, Ronald; Haljasmaa, Igor; Leifer, Ira; Shaffer, Frank; Anderson, Brian J.; Levine, Jonathan S.

    2014-10-01

    Predicting the fate of subsea hydrocarbon gases escaping into seawater is complicated by potential formation of hydrate on rising bubbles that can enhance their survival in the water column, allowing gas to reach shallower depths and the atmosphere. The precise nature and influence of hydrate coatings on bubble hydrodynamics and dissolution is largely unknown. Here we present high-definition, experimental observations of complex surficial mechanisms governing methane bubble hydrate formation and dissociation during transit of a simulated oceanic water column that reveal a temporal progression of deep-sea controlling mechanisms. Synergistic feedbacks between bubble hydrodynamics, hydrate morphology, and coverage characteristics were discovered. Morphological changes on the bubble surface appear analogous to macroscale, sea ice processes, presenting new mechanistic insights. An inverse linear relationship between hydrate coverage and bubble dissolution rate is indicated. Understanding and incorporating these phenomena into bubble and bubble plume models will be necessary to accurately predict global greenhouse gas budgets for warming ocean scenarios and hydrocarbon transport from anthropogenic or natural deep-sea eruptions.

  5. A study of velocity discontinuity for single air bubbles rising in an associative polymer

    Science.gov (United States)

    Soto, E.; Goujon, C.; Zenit, R.; Manero, O.

    2006-12-01

    The motion of air bubbles in aqueous solutions of a hydrophobic alkali-swellable associative polymer is studied in this work. The associative nature of these polymer systems dictates their rheological properties: for moderate values of the shear rate, the formation of structure can lead to a shear-thickening behavior and to the appearance of first normal stress difference. For larger shear rates, the polymer associations can be broken, leading to shear thinning. In general, these fluids show a Newtonian behavior for small values of the shear rate, but behave as viscoelastic liquids for large shear rates. Experimental results show the appearance of a critical bubble volume at which a discontinuity in the relation velocity-volume occurs; however, the velocity increase found in this case is not as large as that previously reported for the case of shear-thinning viscoelastic fluids. The discontinuity is associated with a significant change of the bubble shape: before the critical volume, the bubbles are convex spheroids, while past the critical volume a sharp cusped end appears. The appearance of the tail is also associated with the appearance of an inflection point (change of curvature) on the bubble surface. Moreover, since the rheology of the liquids is measured it was found that the discontinuity, and hence the change of shape, occurs when the elastic nature of the liquid first manifests itself (appearance of a first normal stress difference). A comparison of the measured velocities for small bubbles with predictions from a Stokes-Hadamard law shows a discrepancy. The Newtonian viscosity measured in a viscometric flow was smaller than that determined from a falling-ball arrangement. Considering the viscosity measured under this nonviscometric flow, the comparison between theory and experiments was very good for bubbles having volumes lower than the critical one. Moreover, due to the importance of the elasticity, and due to the change of the shape of the bubble, a

  6. HUBBLE-BUBBLE 1. A computer program for the analysis of non-equilibrium flows of water

    International Nuclear Information System (INIS)

    Mather, D.J.

    1978-02-01

    A description is given of the computer program HUBBLE-BUBBLE I which simulates the non-equilibrium flow of water and steam in a pipe. The code is designed to examine the transient flow developing in a pipe containing hot compressed water following the rupture of a retaining diaphragm. Allowance is made for an area change in the pipe. Particular attention is paid to the non-equilibrium development of vapour bubbles and to the transition from a bubble-liquid regime to a droplet-vapour regime. The mathematical and computational model is described together with a summary of the FORTRAN subroutines and listing of data input. (UK)

  7. Effect of Transition From a Unit-Based Team to External Transport Team for a Pediatric Critical Care Unit.

    Science.gov (United States)

    Cummings, Brian M; Kaliannan, Kanakaraju; Yager, Phoebe H; Noviski, Natan

    2017-12-01

    Pediatric hospitals must consider staff, training, and direct costs required to maintain a pediatric specialized transport team, balanced with indirect potential benefits of marketing and referral volume. The effect of transitioning a unit-based transport team to an external service on the pediatric intensive care unit (PICU) is unknown, but information is needed as hospital systems focus on population management. We examined the impact on PICU transports after transition to an external transport vendor. Single-center retrospective review performed of PICU admissions, referrals, and transfers during baseline, post-, and maintenance period with a total of 9-year follow-up. Transfer volume was analyzed during pre-, post-, and maintenance phase with descriptive statistics and statistical process control charts from 1999 to 2012. Total PICU admissions increased with an annual growth rate of 3.7%, with mean annual 626 admissions prior to implementation to the mean of 890 admissions at the end of period, P < .001. The proportion of transport to total admissions decreased from 27% to 21%, but mean annual transports were unchanged, 175 to 183, P = .6, and mean referrals were similar, 186 to 203, P = .8. Seasonal changes in transport volume remained as a predominant source of variability. Annual transport refusals increased initially in the postimplementation phase, mean 11 versus 33, P < .03, but similar to baseline in the maintenance phase, mean 20/year, P = .07. Patient refusals were due to bed and staffing constraints, with 7% due to the lack of transport vendor availability. In a transition to a regional transport service, PICU transport volume was maintained in the long-term follow-up and total PICU admissions increased. Further research on the direct and indirect impact of transport regionalization is needed to determine the optimal cost-benefit and quality of care as health-care systems focus on population management.

  8. Critical divergence of the symmetric (A1 g) nonlinear elastoresistance near the nematic transition in an iron-based superconductor

    Science.gov (United States)

    Palmstrom, J. C.; Hristov, A. T.; Kivelson, S. A.; Chu, J.-H.; Fisher, I. R.

    2017-11-01

    We report the observation of a nonlinear elastoresistivity response for the prototypical underdoped iron pnictide Ba (Fe0.975Co0.025)2As2 . Our measurements reveal a large quadratic term in the isotropic (A1 g) electronic response that was produced by a purely shear (B2 g) strain. The divergence of this quantity upon cooling towards the structural phase transition reflects the temperature dependence of the nematic susceptibility. This observation shows that nematic fluctuations play a significant role in determining even the isotropic properties of this family of compounds.

  9. Energy Budget of Cosmological First-order Phase Transitions

    CERN Document Server

    Espinosa, Jose R; No, Jose M; Servant, Geraldine

    2010-01-01

    The study of the hydrodynamics of bubble growth in first-order phase transitions is very relevant for electroweak baryogenesis, as the baryon asymmetry depends sensitively on the bubble wall velocity, and also for predicting the size of the gravity wave signal resulting from bubble collisions, which depends on both the bubble wall velocity and the plasma fluid velocity. We perform such study in different bubble expansion regimes, namely deflagrations, detonations, hybrids (steady states) and runaway solutions (accelerating wall), without relying on a specific particle physics model. We compute the efficiency of the transfer of vacuum energy to the bubble wall and the plasma in all regimes. We clarify the condition determining the runaway regime and stress that in most models of strong first-order phase transitions this will modify expectations for the gravity wave signal. Indeed, in this case, most of the kinetic energy is concentrated in the wall and almost no turbulent fluid motions are expected since the s...

  10. Turbulent Spot/Separation Bubble Interactions in a Spatially Evolving Supersonic Boundary-Layer Flow

    National Research Council Canada - National Science Library

    Krishnan, L; Sandham, N. D

    2004-01-01

    ...., is capable of advancing the transition process). A substantial increase in the lateral spreading of the spot was observed due to the spot/bubble interaction. Locally averaged profiles of the flow quantities within the spot showed behavior similar to developed turbulent flows.

  11. A fluctuating state and the critical behavior of the depinning transition in driven vortex matter in superconductors

    Science.gov (United States)

    Shaw, Gorky; Mandal, Pabitra; Banerjee, S. S.; Niazi, A.; Rastogi, A. K.; Sood, A. K.; Tulapurkar, A.; Ramakrishnan, S.; Grover, A. K.

    2012-06-01

    A status report is presented on explorations in 2H-NbS2 which have revealed a new protocol that generates vortex states corresponding to two limiting ends of critical current density (Jlc(H) and Jhc (H)) for a given vortex density deep in the mixed state. An ordered vortex array set in motion with transport current I (Ilc < I < Ihc) explores its other option of non-moving jammed state of higher end Ihc while steadily enhancing the driving force. Attempts to further unjam the re-pinned state unmask (i) a moving fluctuating state and (ii) the diverging (life) times along with an underlying critical behaviour at the threshold limit of de-pinning the disordered-jammed state, from both below as well as above Ihc.

  12. Critical role of γ-phosphate in structural transition of Na,K-ATPase upon ATP binding

    Science.gov (United States)

    Petrushanko, Irina Yu.; Mitkevich, Vladimir A.; Anashkina, Anastasia A.; Klimanova, Elizaveta A.; Dergousova, Elena A.; Lopina, Olga D.; Makarov, Alexander A.

    2014-06-01

    Active transport of sodium and potassium ions by Na,K-ATPase is accompanied by the enzyme conformational transition between E1 and E2 states. ATP and ADP bind to Na,K-ATPase in the E1 conformation with similar affinity but the properties of enzyme in complexes with these nucleotides are different. We have studied thermodynamics of Na,K-ATPase binding with adenine nucleotides at different temperatures using isothermal titration calorimetry. Our data indicate that β-phosphate is involved in complex formation by increasing the affinity of adenine nucleotides to Na,K-ATPase by an order of magnitude, while γ-phosphate does not affect it. ATP binding to Na,K-ATPase in contrast to ADP binding generates a structural transition in the enzyme, which is consistent with the movement of a significant portion of the surface area to a solvent-protected state. We propose that ATP binding leads to convergence of the nucleotide-binding and phosphorylation domains transferring the enzyme from the ``E1-open'' to ``E1-closed'' conformation ready for phosphorylation.

  13. Development and validation of models for bubble coalescence and breakup

    International Nuclear Information System (INIS)

    Liao, Yiaxiang

    2013-01-01

    A generalized model for bubble coalescence and breakup has been developed, which is based on a comprehensive survey of existing theories and models. One important feature of the model is that all important mechanisms leading to bubble coalescence and breakup in a turbulent gas-liquid flow are considered. The new model is tested extensively in a 1D Test Solver and a 3D CFD code ANSYS CFX for the case of vertical gas-liquid pipe flow under adiabatic conditions, respectively. Two kinds of extensions of the standard multi-fluid model, i.e. the discrete population model and the inhomogeneous MUSIG (multiple-size group) model, are available in the two solvers, respectively. These extensions with suitable closure models such as those for coalescence and breakup are able to predict the evolution of bubble size distribution in dispersed flows and to overcome the mono-dispersed flow limitation of the standard multi-fluid model. For the validation of the model the high quality database of the TOPFLOW L12 experiments for air-water flow in a vertical pipe was employed. A wide range of test points, which cover the bubbly flow, turbulent-churn flow as well as the transition regime, is involved in the simulations. The comparison between the simulated results such as bubble size distribution, gas velocity and volume fraction and the measured ones indicates a generally good agreement for all selected test points. As the superficial gas velocity increases, bubble size distribution evolves via coalescence dominant regimes first, then breakup-dominant regimes and finally turns into a bimodal distribution. The tendency of the evolution is well reproduced by the model. However, the tendency is almost always overestimated, i.e. too much coalescence in the coalescence dominant case while too much breakup in breakup dominant ones. The reason of this problem is discussed by studying the contribution of each coalescence and breakup mechanism at different test points. The redistribution of the

  14. Neutron Detection with Bubble Chambers

    Science.gov (United States)

    Ghilea, M. C.; Lerche, R. A.; Disdier, L.

    2005-10-01

    To improve neutron imaging resolution, we have developed a general imaging design tool for inertial confinement fusion facilities that can simulate aperture errors, generate arbitrary neutron source distributions, simulate arbitrary aperture shapes, calculate point-spread functions using ray tracing, and reconstruct source images using a variety of filter functions. Predicted system performance can be compared to various concepts before construction. This software design tool is being developed for the UR/LLE OMEGA laser and the NIF as part of a process to design and build an imaging system based on a bubble chamber detectorootnotetextR. A. Lerche et al., Rev. Sci. Instrum. 74, 1709 (2003). for the UR/LLE OMEGA laser. This talk will present the latest results on aperture contributions to system performance and review the conceptual design of the bubble chamber-based imaging system, its conceptual design being reviewed in the second part of the presentation. This work was supported by the U.S. Department of Energy Office of Inertial Confinement Fusion under Cooperative Agreement No. DE-FC52-92SF19460.

  15. Acoustic Energy Storage in Single Bubble Sonoluminescence

    NARCIS (Netherlands)

    Brenner, Michael P.; Hilgenfeldt, Sascha; Lohse, Detlef; Rosales, Rodolfo R.

    1996-01-01

    Single bubble sonoluminescence is understood in terms of a shock focusing towards the bubble center. We present a mechanism for significantly enhancing the effect of shock focusing, arising from the storage of energy in the acoustic modes of the gas. The modes with strongest coupling are not

  16. Steady State Vapor Bubble in Pool Boiling.

    Science.gov (United States)

    Zou, An; Chanana, Ashish; Agrawal, Amit; Wayner, Peter C; Maroo, Shalabh C

    2016-02-03

    Boiling, a dynamic and multiscale process, has been studied for several decades; however, a comprehensive understanding of the process is still lacking. The bubble ebullition cycle, which occurs over millisecond time-span, makes it extremely challenging to study near-surface interfacial characteristics of a single bubble. Here, we create a steady-state vapor bubble that can remain stable for hours in a pool of sub-cooled water using a femtosecond laser source. The stability of the bubble allows us to measure the contact-angle and perform in-situ imaging of the contact-line region and the microlayer, on hydrophilic and hydrophobic surfaces and in both degassed and regular (with dissolved air) water. The early growth stage of vapor bubble in degassed water shows a completely wetted bubble base with the microlayer, and the bubble does not depart from the surface due to reduced liquid pressure in the microlayer. Using experimental data and numerical simulations, we obtain permissible range of maximum heat transfer coefficient possible in nucleate boiling and the width of the evaporating layer in the contact-line region. This technique of creating and measuring fundamental characteristics of a stable vapor bubble will facilitate rational design of nanostructures for boiling enhancement and advance thermal management in electronics.

  17. Microfluidics with ultrasound-driven bubbles

    NARCIS (Netherlands)

    Marmottant, P.; Marmottant, P.G.M.; Raven, J.P.; Gardeniers, Johannes G.E.; Bomer, Johan G.; Hilgenfeldt, Sascha; Hilgenfeldt, S.

    2006-01-01

    Microstreaming from oscillating bubbles is known to induce vigorous vortex flow. Here we show how to harness the power of bubble streaming in an experiment to achieve directed transport flow of high velocity, allowing design and manufacture of microfluidic MEMS devices. By combining oscillating

  18. Laminar separation bubbles: Dynamics and control

    Indian Academy of Sciences (India)

    surface of a flat plate by appropriately contouring the top wall of the wind tunnel. First, a basic ... of thin aerofoils, on gas turbine blades and on low Reynolds number micro-aero-vehicle wings. Presence of bubbles ... ied its effect on the loss reduction in a gas turbine blade due to periodic quenching of the separation bubble.

  19. The life and death of film bubbles

    Science.gov (United States)

    Poulain, S.; Villermaux, E.; Bourouiba, L.

    2017-11-01

    Following its burst, the fragmentation of a large bubble (film bubble) at the air-water interface can release hundreds of micrometer-sized film-drops in the air we breathe. This mechanism of droplet formation is one of the most prominent sources of sea spray. Indoor or outdoor, pathogens from contaminated water are transported by these droplets and have also been linked to respiratory infection. The lifetime and thickness of bubbles govern the number and size of the droplets they produce. Despite these important implications, little is known about the factors influencing the life and death of surface film bubbles. In particular, the fundamental physical mechanisms linking bubble aging, thinning, and lifetime remain poorly understood. To address this gap, we present the results of an extensive investigation of the aging of film-drop-producing bubbles in various ambient air, water composition, and temperature conditions. We present and validate a generalized physical picture and model of bubble cap thickness evolution. The model and physical picture are linked to the lifetime of bubbles via a series of cap rupture mechanisms of increasing efficiency.

  20. Bubble Swarm Rise Velocity in Fluidized Beds.

    Czech Academy of Sciences Publication Activity Database

    Punčochář, Miroslav; Růžička, Marek; Šimčík, Miroslav

    2016-01-01

    Roč. 152, OCT 2 (2016), s. 84-94 ISSN 0009-2509 R&D Projects: GA ČR(CZ) GA15-05534S Institutional support: RVO:67985858 Keywords : bubbling fluidized bed * gas-solid * bubble swarm velocity Subject RIV: CI - Industrial Chemistry, Chemical Engineering Impact factor: 2.895, year: 2016

  1. Galactic Teamwork Makes Distant Bubbles

    Science.gov (United States)

    Kohler, Susanna

    2016-03-01

    During the period of reionization that followed the dark ages of our universe, hydrogen was transformed from a neutral state, which is opaque to radiation, to an ionized one, which is transparent to radiation. But what generated the initial ionizing radiation? The recent discovery of multiple distant galaxies offers evidence for how this process occurred.Two Distant GalaxiesWe believe reionization occurred somewhere between a redshift of z = 6 and 7, because Ly-emitting galaxies drop out at roughly this redshift. Beyond this distance, were generally unable to see the light from these galaxies, because the universe is no longer transparent to their emission. This is not always the case, however: if a bubble of ionized gas exists around a distant galaxy, the radiation can escape, allowing us to see the galaxy.This is true of two recently-discovered Ly-emitting galaxies, confirmed to be at a redshift of z~7 and located near one another in a region known as the Bremer Deep Field. The fact that were able to see the radiation from these galaxies means that they are in an ionized HII region presumably one of the earlier regions to have become reionized in the universe.But on their own, neither of these galaxies is capable of generating an ionized bubble large enough for their light to escape. So what ionized the region around them, and what does this mean for our understanding of how reionization occurred in the universe?A Little Help From FriendsLocation in different filters of the objects in the Hubble Bremer Deep Field catalog. The z~7 selection region is outlined by the grey box. BDF-521 and BDF-3299 were the two originally discovered galaxies; the remaining red markers indicate the additional six galaxies discovered in the same region. [Castellano et al. 2016]A team of scientists led by Marco Castellano (Rome Observatory, INAF) investigated the possibility that there are other, faint galaxies near these two that have helped to ionize the region. Performing a survey

  2. Effect of bubble size on internal characteristics of upward bubble flow

    International Nuclear Information System (INIS)

    Matsui, Goichi; Kumazawa, Toshio; Yamashita, Yutaka.

    1987-01-01

    Bubble flow characteristics were investigated experimentally in nitrogen gas-water in a spuare channel using a laser Doppler anemometer and a double-sensor conductance probe under the same flow rate conditions. The size of the bubbles was controlled by changing the mixing conditions and by adding a surface active agent to water. Thus, four sets of experiments were conducted. Experimental results show that the reduction in bubble size flattens the gas-phase distribution and increases the number density of bubbles. The reduction in bubble size leads to a decrease in turbulence and an increase in water and bubble velocities, but an extreme reduction does not bring about a further increase in both velocities, although it leads to a further decrease in turbulence. Turbulence suppression was observed in layer-type bubble flows. This type of flow has a peculiar profile of water velocity. (author)

  3. Para a crítica da transição nutricional For a critic to the nutritional transition

    Directory of Open Access Journals (Sweden)

    Maria do Socorro Quirino Escoda

    2002-01-01

    Full Text Available Discuto neste artigo as características da transição nutricional. Utilizo dados dos estudos nutricionais de população, conceitos e categorias analíticas. Correlaciono essas características com as especificidades do nosso processo de desenvolvimento. Questiono o sentido dessa transição que migrou: 1 De um perfil inicialmente marcado pela alta prevalência da má nutrição por déficits, nas formas graves de desnutrição energético-protéica e carências específicas. 2 Se o ponto de corte utilizado para contagem dos desnutridos graves, situados abaixo do percentil três do padrão de classificação do NCHS (National Center of Health Statistiscs, ao eleger a gravidade como hierarquização para a atenção nutricional, não mascara a prevalência do déficit de peso e de estatura da população estudada. 3 Conseqüentemente, a real extensão das formas leves, moderadas e a cronicidade da desnutrição. 4 A reprodução da iniqüidade entre os desnutridos. 5 Se essa transição traz em sua trajetória as características de otimização ou de complexificação da situação nutricional da população brasileira.I discuss in this article the characteristics of the nutritional transition. For that, I use the data of nutritional researches of the population, concepts and analytic categories. I make a correlation between these characteristics and the specificities of our development process. Then, I question: 1 The sense of this transition, which comes from a stage initially signed by high prevalence of deficits malnutrition, on gravity forms. 2 If the breakpoint used to reckon the gravity malnutrition occurrences, located under the percentile 3 of the international standard classification - of the National Center of Health Statistics (NCHS -, is not to choose gravity as hierarchy of the nutritional attention. 3 If this procedure does not mask the real extension of the moderate and light forms of malnutrition deficits. 4 If the selected

  4. Constraining hadronic models of the Fermi bubbles

    Science.gov (United States)

    Razzaque, Soebur

    2018-01-01

    The origin of sub-TeV gamma rays detected by Fermi-LAT from the Fermi bubbles at the Galactic center is unknown. In a hadronic model, acceleration of protons and/or nuclei and their subsequent interactions with gas in the bubble volume can produce observed gamma ray. Such interactions naturally produce high-energy neutrinos, and detection of those can discriminate between a hadronic and a leptonic origin of gamma rays. Additional constraints on the Fermi bubbles gamma-ray flux in the PeV range from recent HAWC observations restrict hadronic model parameters, which in turn disfavor Fermi bubbles as the origin of a large fraction of neutrino events detected by IceCube along the bubble directions. We revisit our hadronic model and discuss future constraints on parameters from observations in very high-energy gamma rays by CTA and in neutrinos.

  5. Bubble mobility in mud and magmatic volcanoes

    Science.gov (United States)

    Tran, Aaron; Rudolph, Maxwell L.; Manga, Michael

    2015-03-01

    The rheology of particle-laden fluids with a yield stress, such as mud or crystal-rich magmas, controls the mobility of bubbles, both the size needed to overcome the yield stress and their rise speed. We experimentally measured the velocities of bubbles and rigid spheres in mud sampled from the Davis-Schrimpf mud volcanoes adjacent to the Salton Sea, Southern California. Combined with previous measurements in the polymer gel Carbopol, we obtained an empirical model for the drag coefficient and bounded the conditions under which bubbles overcome the yield stress. Yield stresses typical of mud and basaltic magmas with sub-mm particles can immobilize millimeter to centimeter sized bubbles. At Stromboli volcano, Italy, a vertical yield stress gradient in the shallow conduit may immobilize bubbles with diameter ≲ 1 cm and hinder slug coalescence.

  6. Bubble streams rising beneath an inclined surface

    Science.gov (United States)

    Bird, James; Brasz, Frederik; Kim, Dayoung; Menesses, Mark; Belden, Jesse

    2017-11-01

    Bubbles released beneath a submerged inclined surface can tumble along the wall as they rise, dragging the surrounding fluid with them. This effect has recently regained attention as a method to mitigate biofouling in marine environment, such as a ship hull. It appears that the efficacy of this approach may be related to the velocity of the rising bubbles and the extent that they spread laterally as they rise. Yet, it is unclear how bubble stream rise velocity and lateral migration depend on bubble size, flow rate, and inclination angle. Here we perform systematic experiments to quantify these relationships for both individual bubble trajectories and ensemble average statistics. Research supported by the Office of Naval Research under Grant Number award N00014-16-1-3000.

  7. Gas Bubble Dynamics under Mechanical Vibrations

    Science.gov (United States)

    Mohagheghian, Shahrouz; Elbing, Brian

    2017-11-01

    The scientific community has a limited understanding of the bubble dynamics under mechanical oscillations due to over simplification of Navier-Stockes equation by neglecting the shear stress tensor and not accounting for body forces when calculating the acoustic radiation force. The current work experimental investigates bubble dynamics under mechanical vibration and resulting acoustic field by measuring the bubble size and velocity using high-speed imaging. The experimental setup consists of a custom-designed shaker table, cast acrylic bubble column, compressed air injection manifold and an optical imaging system. The mechanical vibrations resulted in accelerations between 0.25 to 10 times gravitational acceleration corresponding to frequency and amplitude range of 8 - 22Hz and 1 - 10mm respectively. Throughout testing the void fraction was limited to definition of Bjerknes force in combination with Rayleigh-Plesset equation. Physical behavior of the system was capture and classified. Bubble size, velocity as well as size and spatial distribution will be presented.

  8. Transition from intravenous insulin to subcutaneous long-acting insulin in critical care patients on enteral or parenteral nutrition.

    Science.gov (United States)

    Ramos, Analía; Zapata, Lluis; Vera, Paula; Betbese, Antoni J; Pérez, Antonio

    2017-12-01

    The optimal initial dose of subcutaneous (SC) insulin after intravenous (IV) infusion is controversial, especially in patients receiving continuous enteral nutrition (EN) or total parenteral nutrition (TPN). The aim of this study was to evaluate the strategy used at our hospital intensive care unit (ICU) in patients switched from IV insulin to SC insulin glargine while receiving EN or TPN. A retrospective analysis was made of 27 patients on EN and 14 on TPN switched from IV infusion insulin to SC insulin. The initial dose of SC insulin was estimated as 50% of the daily IV insulin requirements, extrapolated from the previous 12h. A corrective dose of short-acting insulin (lispro) was used when necessary. Mean blood glucose (BG) level during SC insulin treatment was 136±35mg/dL in the EN group and 157±37mg/dL in the TPN group (p=0.01). In the TPN group, mean BG was >180mg/dL during the first three days after switching, and a 41% increase in the glargine dose was required to achieve the target BG. In the EN group, mean BG remained <180mg/dL throughout the days of transition and the dose of glargine remained unchanged. In the transition from IV to SC insulin therapy, initial insulin glargine dose estimated as 50% of daily IV insulin requirements is adequate for patients on EN, but inadequate in those given TPN. Copyright © 2017 SEEN y SED. Publicado por Elsevier España, S.L.U. All rights reserved.

  9. IUPAC critical evaluation of the rotational-vibrational spectra of water vapor. Part I-Energy levels and transition wavenumbers for H217O and H218O

    International Nuclear Information System (INIS)

    Tennyson, Jonathan; Bernath, Peter F.; Brown, Linda R.; Campargue, Alain; Carleer, Michel R.; Csaszar, Attila G.; Gamache, Robert R.; Hodges, Joseph T.; Jenouvrier, Alain; Naumenko, Olga V.; Polyansky, Oleg L.; Rothman, Laurence S.; Toth, Robert A.; Vandaele, Ann Carine; Zobov, Nikolai F.; Daumont, Ludovic; Fazliev, Alexander Z.; Furtenbacher, Tibor; Gordon, Iouli E.; Mikhailenko, Semen N.

    2009-01-01

    This is the first part of a series of articles reporting critically evaluated rotational-vibrational line positions, transition intensities, pressure dependence and energy levels, with associated critically reviewed assignments and uncertainties, for all the main isotopologues of water. The present article contains energy levels and data for line positions of the singly substituted isotopologues H 2 17 O and H 2 18 O. The procedure and code MARVEL, standing for measured active rotational-vibrational energy levels, is used extensively in all stages of determining the validated levels and lines and their self-consistent uncertainties. The spectral regions covered for both isotopologues H 2 17 O and H 2 18 O are 0-17125cm -1 . The energy levels are checked against ones determined from accurate variational calculations. The number of critically evaluated and recommended levels and lines are, respectively, 2687 and 8614 for H 2 17 O, and 4839 and 29 364 for H 2 18 O. The extensive lists of MARVEL lines and levels obtained are deposited in the Supplementary Material, as well as in a distributed information system applied to water, W-DIS, where they can easily be retrieved. A distinguishing feature of the present evaluation of water spectroscopic data is the systematic use of all available experimental data and validation by first-principles theoretical calculations.

  10. Evolution of a gas bubble in porous matrix filled by methane hydrate

    Science.gov (United States)

    Tsiberkin, Kirill; Lyubimov, Dmitry; Lyubimova, Tatyana; Zikanov, Oleg

    2013-04-01

    Behavior of a small isolated hydrate-free inclusion (a bubble) within hydrate-bearing porous matrix is studied analytically and numerically. An infinite porous matrix of uniform properties with pores filled by methane hydrates and either water (excessive water situation) or methane gas (excessive gas situation) is considered. A small spherical hydrate-free bubble of radius R0 exists at initial moment within the matrix due to overheating relative to the surrounding medium. There is no continuing heat supply within the bubble, so new hydrate forms on its boundary, and its radius decreases with time. The process is analysed in the framework of the model that takes into account the phase transition and accompanying heat and mass transport processes and assumes spherical symmetry. It is shown that in the case of small (~ 10-2-10-1 m) bubbles, convective fluxes are negligible and the process is fully described by heat conduction and phase change equations. A spherically symmetric Stefan problem for purely conduction-controlled evolution is solved analytically for the case of equilibrium initial temperature and pressure within the bubble. The self-similar solution is verified, with good results, in numerical simulations based on the full filtration and heat transfer model and using the isotherm migration method. Numerical simulations are also conducted for a wide range of cases not amenable to analytical solution. It is found that, except for initial development of an overheated bubble, its radius evolves with time following the self-similar formula: R(t) ( t)1-2 R0-= 1 - tm- , (1) where tm is the life-time of bubble (time of its complete freezing). The analytical solution shows that tm follows 2 tm ~ (R0-?) , (2) where ? is a constant determined by the temperature difference ΔT between the bubble's interior and far field. We consider implications for natural hydrate deposits. As an example, for a bubble with R0 = 4 cm and ΔT = 0.001 K, we find tm ~ 5.7 ? 106 s (2

  11. On the One-Dimensional Modeling of Vertical Upward Bubbly Flow

    Directory of Open Access Journals (Sweden)

    C. Peña-Monferrer

    2018-01-01

    Full Text Available The one-dimensional two-fluid model approach has been traditionally used in thermal-hydraulics codes for the analysis of transients and accidents in water–cooled nuclear power plants. This paper investigates the performance of RELAP5/MOD3 predicting vertical upward bubbly flow at low velocity conditions. For bubbly flow and vertical pipes, this code applies the drift-velocity approach, showing important discrepancies with the experiments compared. Then, we use a classical formulation of the drag coefficient approach to evaluate the performance of both approaches. This is based on the critical Weber criteria and includes several assumptions for the calculation of the interfacial area and bubble size that are evaluated in this work. A more accurate drag coefficient approach is proposed and implemented in RELAP5/MOD3. Instead of using the Weber criteria, the bubble size distribution is directly considered. This allows the calculation of the interfacial area directly from the definition of Sauter mean diameter of a distribution. The results show that only the proposed approach was able to predict all the flow characteristics, in particular the bubble size and interfacial area concentration. Finally, the computational results are analyzed and validated with cross-section area average measurements of void fraction, dispersed phase velocity, bubble size, and interfacial area concentration.

  12. Characteristics of micro-nano bubbles and potential application in groundwater bioremediation.

    Science.gov (United States)

    Li, Hengzhen; Hu, Liming; Song, Dejun; Lin, Fei

    2014-09-01

    Content of oxygen in water is a critical factor in increasing bioremediation efficiency for contaminated groundwater. Micro-nano bubbles (MNBs) injection seems to be an effective technique for increasing oxygen in water compared with traditional air sparging technology with macrobubbles. Micro-nano bubbles have larger interfacial area, higher inner pressure and density, and lower rising velocity in water, superior to that of macrobubbles. In this paper, MNBs with diameters ranging from 500 nm to 100 microm are investigated, with a specific focus on the oxygen mass transfer coefficient from inner bubbles to surrounding water. The influence of surfactant on the bubbles formation and dissolution is studied as well. The stability of MNBs is further investigated by means of zeta potential measurements and rising velocity analysis. The results show that MNBs can greatly increase oxygen content in water. Higher surfactant concentration in water will decrease the bubbles size, reduce the dissolution rate, and increase the zeta potential. Moreover, MNBs with greater zeta potential value tend to be more stable. Besides, the low rising velocity of MNBs contributes to the long stagnation in water. It is suggested that micro-nano bubble aeration, a potential in groundwater remediation technology, can largely enhance the bioremediation effect.

  13. Bubble Entropy: An Entropy Almost Free of Parameters.

    Science.gov (United States)

    Manis, George; Aktaruzzaman, Md; Sassi, Roberto

    2017-11-01

    Objective : A critical point in any definition of entropy is the selection of the parameters employed to obtain an estimate in practice. We propose a new definition of entropy aiming to reduce the significance of this selection. Methods: We call the new definition Bubble Entropy . Bubble Entropy is based on permutation entropy, where the vectors in the embedding space are ranked. We use the bubble sort algorithm for the ordering procedure and count instead the number of swaps performed for each vector. Doing so, we create a more coarse-grained distribution and then compute the entropy of this distribution. Results: Experimental results with both real and synthetic HRV signals showed that bubble entropy presents remarkable stability and exhibits increased descriptive and discriminating power compared to all other definitions, including the most popular ones. Conclusion: The definition proposed is almost free of parameters. The most common ones are the scale factor r and the embedding dimension m . In our definition, the scale factor is totally eliminated and the importance of m is significantly reduced. The proposed method presents increased stability and discriminating power. Significance: After the extensive use of some entropy measures in physiological signals, typical values for their parameters have been suggested, or at least, widely used. However, the parameters are still there, application and dataset dependent, influencing the computed value and affecting the descriptive power. Reducing their significance or eliminating them alleviates the problem, decoupling the method from the data and the application, and eliminating subjective factors. Objective : A critical point in any definition of entropy is the selection of the parameters employed to obtain an estimate in practice. We propose a new definition of entropy aiming to reduce the significance of this selection. Methods: We call the new definition Bubble Entropy . Bubble Entropy is based on permutation

  14. Long-Range Order and Critical Scattering of Neutrons below the Transition Temperature in β-Brass

    DEFF Research Database (Denmark)

    Als-Nielsen, Jens Aage; Dietrich, O.W.

    1967-01-01

    The temperature dependence of long-range order langPrang has been determined from the temperature variation of a superlattice Bragg reflection. The results fitted a power law langPrang prop (Tc-T)beta with Tc the critical temperature and beta = 0.305plusmn0.005, in agreement with the theoretical...... prediction 0.303 profiles of the (1, 0, 0) superlattice reflection at 15.5 and 2.2deg below Tc. The ratio between the susceptibilities chi+(DeltaT) and chi-(DeltaT) DeltaT deg below and above Tc was found to be 5.5plusmn2.0 at DeltaT = 4.4deg and 8...

  15. Ohio study shows that insurance coverage is critical for children with special health care needs as they transition to adulthood.

    Science.gov (United States)

    Goudie, Anthony; Carle, Adam C

    2011-12-01

    Nearly 30 percent of young adults with special health care needs in Ohio lack health insurance, compared to 5 percent of the state's children with special health care needs. As children with such needs become too old for Medicaid or insurance through their parents' employer, they face great challenges in obtaining insurance. Lack of insurance is highly predictive of unmet needs, which in turn are predictive of costly hospital-based encounters. Young adults with special health care needs who are uninsured are more than twice as likely as their peers with insurance to forgo filling prescriptions and getting care and to have problems getting care. Even after insurance status is accounted for, young adults with special health care needs are more likely than children with such needs to not fill prescriptions because of cost and to delay or forgo needed care. This study demonstrates that continuous and adequate health insurance is vital to the continued well-being of children with special health care needs as they transition to young adulthood.

  16. Cavitation inception from bubble nuclei

    DEFF Research Database (Denmark)

    Mørch, Knud Aage

    2015-01-01

    The tensile strength of ordinary water such as tap water or seawater is typically well below 1 bar. It is governed by cavitation nuclei in the water, not by the tensile strength of the water itself, which is extremely high. Different models of the nuclei have been suggested over the years....... The cavitation nuclei may be free gas bubbles in the bulk of water, or interfacial gaseous voids located on the surface of particles in the water, or on bounding walls. The tensile strength of these nuclei depends not only on the water quality but also on the pressure-time history of the water. A recent model...... and associated experiments throw new light on the effects of transient pressures on the tensile strength of water, which may be notably reduced or increased by such pressure changes....

  17. Diving decompression models and bubble metrics: modern computer syntheses.

    Science.gov (United States)

    Wienke, B R

    2009-04-01

    A quantitative summary of computer models in diving applications is presented, underscoring dual phase dynamics and quantifying metrics in tissue and blood. Algorithms covered include the multitissue, diffusion, split phase gradient, linear-exponential, asymmetric tissue, thermodynamic, varying permeability, reduced gradient bubble, tissue bubble diffusion, and linear-exponential phase models. Defining relationships are listed, and diver staging regimens are underscored. Implementations, diving sectors, and correlations are indicated for models with a history of widespread acceptance, utilization, and safe application across recreational, scientific, military, research, and technical communities. Presently, all models are incomplete, but many (included above) are useful, having resulted in diving tables, underwater meters, and dive planning software. Those herein employ varying degrees of calibration and data tuning. We discuss bubble metrics in tissue and blood as a backdrop against computer models. The past 15 years, or so, have witnessed changes and additions to diving protocols and table procedures, such as shorter nonstop time limits, slower ascent rates, shallow safety stops, ascending repetitive profiles, deep decompression stops, helium based breathing mixtures, permissible reverse profiles, multilevel techniques, both faster and slower controlling repetitive tissue halftimes, smaller critical tensions, longer flying-after-diving surface intervals, and others. Stimulated by Doppler and imaging technology, table and decompression meter development, theory, statistics, chamber and animal testing, or safer diving consensus, these modifications affect a gamut of activity, spanning bounce to decompression, single to multiday, and air to mixed gas diving. As it turns out, there is growing support for many protocols on operational, experimental, and theoretical grounds, with bubble models addressing many concerns on plausible bases, but with further testing or

  18. Determination of the solid surface critical exponent β1 from contact-angle variation on approach to a wetting transition: Cyclohexane/aniline/quartz

    Science.gov (United States)

    Pallas, Norman R.

    2016-03-01

    The three-phase contact angle (θ) for the system cyclohexane/aniline/quartz has been measured from drop shapes as a function of temperature on approach to the cyclohexane/aniline upper consolute solution temperature Tc. The experiments employed exacting criteria previously established for thermodynamic-quality measurements at fluid interfaces. A first-order wetting transition from partial wetting to complete wetting was observed at a temperature Tw, 2.12 K below Tc. The contact angle vanishes at Tw, scaling as cos θ ˜ |T - Tc|β1-μ for T contact angle near the critical point for this system. These results are in marked contrast to previous measurements on this system from measurements of capillary rise and meniscus curvature.

  19. Numerical modeling of bubble dynamics in magmas

    Science.gov (United States)

    Huber, Christian; Su, Yanqing; Parmigiani, Andrea

    2014-05-01

    Understanding the complex non-linear physics that governs volcanic eruptions is contingent on our ability to characterize the dynamics of bubbles and its effect on the ascending magma. The exsolution and migration of bubbles has also a great impact on the heat and mass transport in and out of magma bodies stored at shallow depths in the crust. Multiphase systems like magmas are by definition heterogeneous at small scales. Although mixture theory or homogenization methods are convenient to represent multiphase systems as a homogeneous equivalent media, these approaches do not inform us on possible feedbacks at the pore-scale and can be significantly misleading. In this presentation, we discuss the development and application of bubble-scale multiphase flow modeling to address the following questions : How do bubbles impact heat and mass transport in magma chambers ? How efficient are chemical exchanges between the melt and bubbles during magma decompression? What is the role of hydrodynamic interactions on the deformation of bubbles while the magma is sheared? Addressing these questions requires powerful numerical methods that accurately model the balance between viscous, capillary and pressure stresses. We discuss how these bubble-scale models can provide important constraints on the dynamics of magmas stored at shallow depth or ascending to the surface during an eruption.

  20. Average properties of bidisperse bubbly flows

    Science.gov (United States)

    Serrano-García, J. C.; Mendez-Díaz, S.; Zenit, R.

    2018-03-01

    Experiments were performed in a vertical channel to study the properties of a bubbly flow composed of two distinct bubble size species. Bubbles were produced using a capillary bank with tubes with two distinct inner diameters; the flow through each capillary size was controlled such that the amount of large or small bubbles could be controlled. Using water and water-glycerin mixtures, a wide range of Reynolds and Weber number ranges were investigated. The gas volume fraction ranged between 0.5% and 6%. The measurements of the mean bubble velocity of each species and the liquid velocity variance were obtained and contrasted with the monodisperse flows with equivalent gas volume fractions. We found that the bidispersity can induce a reduction of the mean bubble velocity of the large species; for the small size species, the bubble velocity can be increased, decreased, or remain unaffected depending of the flow conditions. The liquid velocity variance of the bidisperse flows is, in general, bound by the values of the small and large monodisperse values; interestingly, in some cases, the liquid velocity fluctuations can be larger than either monodisperse case. A simple model for the liquid agitation for bidisperse flows is proposed, with good agreement with the experimental measurements.

  1. Bubbles in live-stranded dolphins.

    Science.gov (United States)

    Dennison, S; Moore, M J; Fahlman, A; Moore, K; Sharp, S; Harry, C T; Hoppe, J; Niemeyer, M; Lentell, B; Wells, R S

    2012-04-07

    Bubbles in supersaturated tissues and blood occur in beaked whales stranded near sonar exercises, and post-mortem in dolphins bycaught at depth and then hauled to the surface. To evaluate live dolphins for bubbles, liver, kidneys, eyes and blubber-muscle interface of live-stranded and capture-release dolphins were scanned with B-mode ultrasound. Gas was identified in kidneys of 21 of 22 live-stranded dolphins and in the hepatic portal vasculature of 2 of 22. Nine then died or were euthanized and bubble presence corroborated by computer tomography and necropsy, 13 were released of which all but two did not re-strand. Bubbles were not detected in 20 live wild dolphins examined during health assessments in shallow water. Off-gassing of supersaturated blood and tissues was the most probable origin for the gas bubbles. In contrast to marine mammals repeatedly diving in the wild, stranded animals are unable to recompress by diving, and thus may retain bubbles. Since the majority of beached dolphins released did not re-strand it also suggests that minor bubble formation is tolerated and will not lead to clinically significant decompression sickness.

  2. Integrative systems analysis of diet-induced obesity identified a critical transition in the transcriptomes of the murine liver and epididymal white adipose tissue.

    Science.gov (United States)

    Kim, J; Kwon, E-Y; Park, S; Kim, J-R; Choi, S-W; Choi, M-S; Kim, S-J

    2016-02-01

    It is well known that high-fat diet (HFD) can cause immune system-related pathological alterations after a significant body weight gain. The mechanisms of the delayed pathological alterations during the development of diet-induced obesity (DIO) are not fully understood. To elucidate the mechanisms underlying DIO development, we analyzed time-course microarray data obtained from a previous study. First, differentially expressed genes (DEGs) were identified at each time point by comparing the hepatic transcriptome of mice fed HFD with that of mice fed normal diet. Next, we clustered the union of DEGs and identified annotations related to each cluster. Finally, we constructed an 'integrated obesity-associated gene regulatory network (GRN) in murine liver'. We analyzed the epididymal white adipose tissue (eWAT) transcriptome usig the same procedure. Based on time-course microarray data, we found that the genes associated with immune responses were upregulated with an oscillating expression pattern between weeks 2 and 8, relatively downregulated between weeks 12 and 16, and eventually upregulated after week 20 in the liver of the mice fed HFD. The genes associated with immune responses were also upregulated at late stage, in the eWAT of the mice fed HFD. These results suggested that a critical transition occurred in the immune system-related transcriptomes of the liver and eWAT around week 16 of the DIO development, and this may be associated with the delayed pathological alterations. The GRN analysis suggested that Maff may be a key transcription factor for the immune system-related critical transition thatoccurred at week 16. We found that transcription factors associated with immune responses were centrally located in the integrated obesity-associated GRN in the liver. In this study, systems analysis identified regulatory network modules underlying the delayed immune system-related pathological changes during the development of DIO and could suggest possible

  3. MAGNETIC TOPOLOGY OF BUBBLES IN QUIESCENT PROMINENCES

    International Nuclear Information System (INIS)

    Dudík, J.; Aulanier, G.; Schmieder, B.; Zapiór, M.; Heinzel, P.

    2012-01-01

    We study a polar-crown prominence with a bubble and its plume observed in several coronal filters by the SDO/AIA and in Hα by the MSDP spectrograph in Białków (Poland) to address the following questions: what is the brightness of prominence bubbles in EUV with respect to the corona outside of the prominence and the prominence coronal cavity? What is the geometry and topology of the magnetic field in the bubble? What is the nature of the vertical threads seen within prominences? We find that the brightness of the bubble and plume is lower than the brightness of the corona outside of the prominence, and is similar to that of the coronal cavity. We constructed linear force-free models of prominences with bubbles, where the flux rope is perturbed by inclusion of parasitic bipoles. The arcade field lines of the bipole create the bubble, which is thus devoid of magnetic dips. Shearing the bipole or adding a second one can lead to cusp-shaped prominences with bubbles similar to the observed ones. The bubbles have complex magnetic topology, with a pair of coronal magnetic null points linked by a separator outlining the boundary between the bubble and the prominence body. We conjecture that plume formation involves magnetic reconnection at the separator. Depending on the viewing angle, the prominence can appear either anvil-shaped with predominantly horizontal structures, or cusp-shaped with predominantly vertical structuring. The latter is an artifact of the alignment of magnetic dips with respect to the prominence axis and the line of sight.

  4. The Minnaert bubble: an acoustic approach

    Energy Technology Data Exchange (ETDEWEB)

    Devaud, Martin; Hocquet, Thierry; Bacri, Jean-Claude [Laboratoire Matiere et Systemes Complexes, Universite Paris Diderot and CNRS UMR 7057, 10 rue Alice Domont et Leonie Duquet, 75013 Paris (France); Leroy, Valentin [Laboratoire Ondes et Acoustique, Universite Paris 7 and CNRS UMR 7587, ESPCI, 10 rue Vauquelin, 75005 Paris (France)], E-mail: martin.devaud@univ-paris-diderot.fr

    2008-11-15

    We propose an ab initio introduction to the well-known Minnaert pulsating bubble at graduate level. After a brief recall of the standard stuff, we begin with a detailed discussion of the radial movements of an air bubble in water. This discussion is managed from an acoustic point of view, and using the Lagrangian rather than the Eulerian variables. In unbounded water, the air-water system has a continuum of eigenmodes, some of them correspond to regular Fabry-Perot resonances. A singular resonance, the lowest one, is shown to coincide with that of Minnaert. In bounded water, the eigenmodes spectrum is discrete, with a finite fundamental frequency. A spectacular quasi-locking of the latter occurs if it happens to exceed the Minnaert frequency, which provides an unforeseen one-bubble alternative version of the famous 'hot chocolate effect'. In the (low) frequency domain in which sound propagation inside the bubble reduces to a simple 'breathing' (i.e. inflation/deflation), the light air bubble can be 'dressed' by the outer water pressure forces, and is turned into the heavy Minnaert bubble. Thanks to this unexpected renormalization process, we demonstrate that the Minnaert bubble definitely behaves like a true harmonic oscillator of the spring-bob type, but with a damping term and a forcing term in apparent disagreement with those commonly admitted in the literature. Finally, we underline the double role played by the water. In order to tell the water motion associated with water compressibility (i.e. the sound) from the simple incompressible accompaniment of the bubble breathing, we introduce a new picture analogous to the electromagnetic radiative picture in Coulomb gauge, which naturally leads us to split the water displacement in an instantaneous and a retarded part. The Minnaert renormalized mass of the dressed bubble is then automatically recovered.

  5. Dynamics of two-dimensional bubbles

    Science.gov (United States)

    Piedra, Saúl; Ramos, Eduardo; Herrera, J. Ramón

    2015-06-01

    The dynamics of two-dimensional bubbles ascending under the influence of buoyant forces is numerically studied with a one-fluid model coupled with the front-tracking technique. The bubble dynamics are described by recording the position, shape, and orientation of the bubbles as functions of time. The qualitative properties of the bubbles and their terminal velocities are described in terms of the Eötvos (ratio of buoyancy to surface tension) and Archimedes numbers (ratio of buoyancy to viscous forces). The terminal Reynolds number result from the balance of buoyancy and drag forces and, consequently, is not an externally fixed parameter. In the cases that yield small Reynolds numbers, the bubbles follow straight paths and the wake is steady. A more interesting behavior is found at high Reynolds numbers where the bubbles follow an approximately periodic zigzag trajectory and an unstable wake with properties similar to the Von Karman vortex street is formed. The dynamical features of the motion of single bubbles are compared to experimental observations of air bubbles ascending in a water-filled Hele-Shaw cell. Although the comparison is not strictly valid in the sense that the effect of the lateral walls is not incorporated in the model, most of the dynamical properties observed are in good qualitative agreement with the numerical calculations. Hele-Shaw cells with different gaps have been used to determine the degree of approximation of the numerical calculation. It is found that for the relation between the terminal Reynolds number and the Archimedes number, the numerical calculations are closer to the observations of bubble dynamics in Hele-Shaw cells of larger gaps.

  6. The Minnaert bubble: an acoustic approach

    International Nuclear Information System (INIS)

    Devaud, Martin; Hocquet, Thierry; Bacri, Jean-Claude; Leroy, Valentin

    2008-01-01

    We propose an ab initio introduction to the well-known Minnaert pulsating bubble at graduate level. After a brief recall of the standard stuff, we begin with a detailed discussion of the radial movements of an air bubble in water. This discussion is managed from an acoustic point of view, and using the Lagrangian rather than the Eulerian variables. In unbounded water, the air-water system has a continuum of eigenmodes, some of them correspond to regular Fabry-Perot resonances. A singular resonance, the lowest one, is shown to coincide with that of Minnaert. In bounded water, the eigenmodes spectrum is discrete, with a finite fundamental frequency. A spectacular quasi-locking of the latter occurs if it happens to exceed the Minnaert frequency, which provides an unforeseen one-bubble alternative version of the famous 'hot chocolate effect'. In the (low) frequency domain in which sound propagation inside the bubble reduces to a simple 'breathing' (i.e. inflation/deflation), the light air bubble can be 'dressed' by the outer water pressure forces, and is turned into the heavy Minnaert bubble. Thanks to this unexpected renormalization process, we demonstrate that the Minnaert bubble definitely behaves like a true harmonic oscillator of the spring-bob type, but with a damping term and a forcing term in apparent disagreement with those commonly admitted in the literature. Finally, we underline the double role played by the water. In order to tell the water motion associated with water compressibility (i.e. the sound) from the simple incompressible accompaniment of the bubble breathing, we introduce a new picture analogous to the electromagnetic radiative picture in Coulomb gauge, which naturally leads us to split the water displacement in an instantaneous and a retarded part. The Minnaert renormalized mass of the dressed bubble is then automatically recovered

  7. Probing the Mechanical Strength of an Armored Bubble and Its Implication to Particle-Stabilized Foams

    Directory of Open Access Journals (Sweden)

    Nicolas Taccoen

    2016-02-01

    Full Text Available Bubbles are dynamic objects that grow and rise or shrink and disappear, often on the scale of seconds. This conflicts with their uses in foams where they serve to modify the properties of the material in which they are embedded. Coating the bubble surface with solid particles has been demonstrated to strongly enhance the foam stability, although the mechanisms for such stabilization remain mysterious. In this paper, we reduce the problem of foam stability to the study of the behavior of a single spherical bubble coated with a monolayer of solid particles. The behavior of this armored bubble is monitored while the ambient pressure around it is varied, in order to simulate the dissolution stress resulting from the surrounding foam. We find that above a critical stress, localized dislocations appear on the armor and lead to a global loss of the mechanical stability. Once these dislocations appear, the armor is unable to prevent the dissolution of the gas into the surrounding liquid, which translates into a continued reduction of the bubble volume, even for a fixed overpressure. The observed route to the armor failure therefore begins from localized dislocations that lead to large-scale deformations of the shell until the bubble completely dissolves. The critical value of the ambient pressure that leads to the failure depends on the bubble radius, with a scaling of ΔP_{collapse}∝R^{-1}, but does not depend on the particle diameter. These results disagree with the generally used elastic models to describe particle-covered interfaces. Instead, the experimental measurements are accounted for by an original theoretical description that equilibrates the energy gained from the gas dissolution with the capillary energy cost of displacing the individual particles. The model recovers the short-wavelength instability, the scaling of the collapse pressure with bubble radius, and the insensitivity to particle diameter. Finally, we use this new microscopic

  8. A Paradigm Shift in Water Quality Governance in a Transitional Context: A Critical Study about the Empowerment of Local Governance in Georgia

    Directory of Open Access Journals (Sweden)

    Sisira S. Withanachchi

    2018-01-01

    Full Text Available The management of water quality is an important part of natural resource governance. Assurance of water quality therefore requires formulation of the regulatory framework and institutional process. Water quality-related problems and their management are mainly recognized as local responsibilities in Integrated Water Resources Management (IWRM. The politics of environmental policy-making should consider the political economic dynamics and socio-ecological patterns. Decentralization by providing more power to the local level and moving to a new spatial management system that is based on water basins are the two strong entreaties in the new water governance paradigm. Transitional countries facing rapid institutional adjustment, restructuring of regulations, and political-economic changes are encountering these demands internally and externally in their policy formulations. In this context, this study critically examines the case of Georgia, a transitional country. In particular, the focus is on how local governance entities can be empowered and what obstacles water quality governance encounters in Georgia. Qualitative research design is the main research method implemented in this study. The key findings from the research analysis are as follows: the existing regulations and governance system do not facilitate the active engagement of local entities in water quality governance. The application of new water polices may fail again if a top-down governance model is put in place that only creates a narrow space for local governance entities to effectively govern water quality.

  9. Baryogenesis and gravitational waves from runaway bubble collisions

    Energy Technology Data Exchange (ETDEWEB)

    Katz, Andrey [Theory Division, CERN,CH-1211 Geneva 23 (Switzerland); Département de Physique Théorique and Center for Astroparticle Physics (CAP),Université de Genève, 24 quai Ansermet, CH-1211 Genève 4 (Switzerland); Riotto, Antonio [Département de Physique Théorique and Center for Astroparticle Physics (CAP),Université de Genève, 24 quai Ansermet, CH-1211 Genève 4 (Switzerland)

    2016-11-07

    We propose a novel mechanism for production of baryonic asymmetry in the early Universe. The mechanism takes advantage of the strong first order phase transition that produces runaway bubbles in the hidden sector that propagate almost without friction with ultra-relativistic velocities. Collisions of such bubbles can non-thermally produce heavy particles that further decay out-of-equilibrium into the SM and produce the observed baryonic asymmetry. This process can proceed at the very low temperatures, providing a new mechanism of post-sphaleron baryogenesis. In this paper we present a fully calculable model which produces the baryonic asymmetry along these lines as well as evades all the existing cosmological constraints. We emphasize that the Gravitational Waves signal from the first order phase transition is completely generic and can potentially be detected by the future eLISA interferometer. We also discuss other potential signals, which are more model dependent, and point out the unresolved theoretical questions related to our proposal.

  10. Numerical investigation of bubble nonlinear dynamics characteristics

    Energy Technology Data Exchange (ETDEWEB)

    Shi, Jie, E-mail: shijie@hrbeu.edu.cn; Yang, Desen; Shi, Shengguo; Hu, Bo [Acoustic Science and Technology Laboratory, Harbin Engineering University, Harbin 150001 (China); College of Underwater Acoustic Engineering, Harbin Engineering University, Harbin 150001 (China); Zhang, Haoyang; Jiang, Wei [College of Underwater Acoustic Engineering, Harbin Engineering University, Harbin 150001 (China)

    2015-10-28

    The complicated dynamical behaviors of bubble oscillation driven by acoustic wave can provide favorable conditions for many engineering applications. On the basis of Keller-Miksis model, the influences of control parameters, including acoustic frequency, acoustic pressure and radius of gas bubble, are discussed by utilizing various numerical analysis methods, Furthermore, the law of power spectral variation is studied. It is shown that the complicated dynamic behaviors of bubble oscillation driven by acoustic wave, such as bifurcation and chaos, further the stimulated scattering processes are revealed.

  11. Blackbody spectra for sonoluminescing hydrogen bubbles.

    Science.gov (United States)

    Vazquez, George; Camara, C; Putterman, S J; Weninger, K

    2002-05-13

    The dynamical motion of sonoluminescing bubbles formed from a mixture of water and hydrogen gas indicates that these bubbles contain hydrogen. Their spectrum is well matched by an ideal 6000 K blackbody radiating from a surface with a radius less than 1/4 microm. According to this model, the state of matter inside the collapsed bubble is so stressed that the photon mean free path is much smaller than 1 microm. Implications for various theories of the light-emitting mechanism and the role of chemical reactions are discussed.

  12. Holography in a freon bubble chamber

    International Nuclear Information System (INIS)

    Lecoq, P.; Olivier, P.

    1982-01-01

    After some tests in a PS beam in the summer of 1981, the run took place in October 1981 in the H2 beam of the SPS. Although some problems of heat dissipation in freon limited the expansion rate of the bubble chamber, more than 11000 holograms were taken, showing 10 μm bubble tracks, with very good image quality and contrast. More than 100 tracks can be stored on a hologram without affecting the quality if all the bubbles are small. In addition, the analysis of the holograms does not look more complex than the exploitation of conventional high-resolution pictures. (orig./HSI)

  13. Bubble detectors in individual neutron dosimetry

    International Nuclear Information System (INIS)

    Spurny, F.; Votockova, I.

    1996-01-01

    Bubble detectors be able to fulfill requirements following from the ICRP 60 recommendations as far as individual neutron dosemeter is concerned. Particularly, the lowest limit of detection seems to be decreased down to about 10 μSv or even lower. At the moment there are two types of such detectors commercially available: bubble damage neutron detectors (BDNDs -Bubble Technology Industries, Chalk River) and superheated drop detectors (SDDs - Apfel Enterpr., New Haven). Both these types have been tested in our studies from the point of view of personal dosimetry. Particular attention is devoted their energetic dependences and their responses in the fields in which they should be wed to determine occupational exposures. (author)

  14. Experimental investigation of shock wave - bubble interaction

    Energy Technology Data Exchange (ETDEWEB)

    Alizadeh, Mohsen

    2010-04-09

    In this work, the dynamics of laser-generated single cavitation bubbles exposed to lithotripter shock waves has been investigated experimentally. The energy of the impinging shock wave is varied in several steps. High-speed photography and pressure field measurements simultaneously with image acquisition provide the possibility of capturing the fast bubble dynamics under the effect of the shock wave impact. The pressure measurement is performed using a fiber optic probe hydrophone (FOPH) which operates based on optical diagnostics of the shock wave propagating medium. After a short introduction in chapter 1 an overview of the previous studies in chapter 2 is presented. The reported literatures include theoretical and experimental investigations of several configurations of physical problems in the field of bubble dynamics. In chapter 3 a theoretical description of propagation of a shock wave in a liquid like water has been discussed. Different kinds of reflection of a shock wave at an interface are taken into account. Undisturbed bubble dynamics as well as interaction between a planar shock wave and an initially spherical bubble are explored theoretically. Some physical parameters which are important in this issue such as the velocity of the shock-induced liquid jet, Kelvin impulse and kinetic energy are explained. The shock waves are generated in a water filled container by a focusing piezoelectric generator. The shock wave profile has a positive part with pulse duration of ∼1 μs followed by a longer tension tail (i.e. ∼3 μs). In chapter 4 high-speed images depict the propagation of a shock wave in the water filled tank. The maximum pressure is also derived for different intensity levels of the shock wave generator. The measurement is performed in the free field (i.e. in the absence of laser-generated single bubbles). In chapter 5 the interaction between lithotripter shock waves and laserinduced single cavitation bubbles is investigated experimentally. An

  15. CP-violating profile of the electroweak bubble wall

    Energy Technology Data Exchange (ETDEWEB)

    Funakubo, Koichi [Saga Univ. (Japan). Dept. of Physics; Kakuto, Akira; Otsuki, Shoichiro; Takenaga, Kazunori; Toyoda, Fumihiko

    1995-11-01

    In any scenario of the electroweak baryogenesis, the profile of the CP violating bubble wall, created at the first-order phase transition, plays an essential role. We attempt to determine it by solving the equations of motion for the scalars in the two-Higgs-doublet model at the transition temperature. According to the parameters in the potential, we found three solutions. Two of them smoothly connect the CP-violating broken phase and the symmetric phase, while the other connects CP-conserving vacua but violates CP in the intermediate region. We also estimate the chiral charge flux, which will be turned into the baryon density in the symmetric phase by the sphaleron process. (author).

  16. A model established of a 'Embryo' bubble growing-up some visible bubble in bubble chamber and its primary theory calculation

    International Nuclear Information System (INIS)

    Ye Zipiao; Sheng Xiangdong

    2006-01-01

    A model of a 'embryo' bubble growing up a visible bubble in the bubble chamber is established. Through primary theory calculation it is shown that the 'embryo' bubble is not only absorbing quantity of heat, but also some molecules get into the 'embryo' bubble from its environment. It is explained reasonably that the radius of bubbles in bubble camber is different for the same energies of neutrons and proton. The track of neutron in bubble camber is long and thin, and the track of proton in bubble camber is wide and short. It is explained reasonably that the bubble radius of the incident particles with more charges which there are the same energies will be wider than that of the incident particles with less charges in the track. It is also explained reasonably that there are a little different radius of the bubbles of a track at the some region. It can be predicted theoretically that there should be big bubbles to burst when incident particles enter the bubble chamber at first. The sensitivity and the detective efficiency of bubble camber can be enhanced by choosing appropriate work matter. (authors)

  17. Critical scattering

    International Nuclear Information System (INIS)

    Stirling, W.G.; Perry, S.C.

    1996-01-01

    We outline the theoretical and experimental background to neutron scattering studies of critical phenomena at magnetic and structural phase transitions. The displacive phase transition of SrTiO 3 is discussed, along with examples from recent work on magnetic materials from the rare-earth (Ho, Dy) and actinide (NpAs, NpSb, USb) classes. The impact of synchrotron X-ray scattering is discussed in conclusion. (author) 13 figs., 18 refs

  18. Critical scattering

    Energy Technology Data Exchange (ETDEWEB)

    Stirling, W.G. [Liverpool Univ., Dep. of Physics, Liverpool (United Kingdom); Perry, S.C. [Keele Univ. (United Kingdom). Dept. of Physics

    1996-12-31

    We outline the theoretical and experimental background to neutron scattering studies of critical phenomena at magnetic and structural phase transitions. The displacive phase transition of SrTiO{sub 3} is discussed, along with examples from recent work on magnetic materials from the rare-earth (Ho, Dy) and actinide (NpAs, NpSb, USb) classes. The impact of synchrotron X-ray scattering is discussed in conclusion. (author) 13 figs., 18 refs.

  19. Nonequilibrium all-atom molecular dynamics simulation of the bubble cavitation and application to dissociate amyloid fibrils

    Science.gov (United States)

    Hoang Viet, Man; Derreumaux, Philippe; Nguyen, Phuong H.

    2016-11-01

    The cavitation of gas bubbles in liquids has been applied to different disciplines in life and natural sciences, and in technologies. To obtain an appropriate theoretical description of effects induced by the bubble cavitation, we develop an all-atom nonequilibrium molecular-dynamics simulation method to simulate bubbles undergoing harmonic oscillation in size. This allows us to understand the mechanism of the bubble cavitation-induced liquid shear stress on surrounding objects. The method is then employed to simulate an Aβ fibril model in the presence of bubbles, and the results show that the bubble expansion and contraction exert water pressure on the fibril. This yields to the deceleration and acceleration of the fibril kinetic energy, facilitating the conformational transition between local free energy minima, and leading to the dissociation of the fibril. Our work, which is a proof-of-concept, may open a new, efficient way to dissociate amyloid fibrils using the bubble cavitation technique, and new venues to investigate the complex phenomena associated with amyloidogenesis.

  20. Dynamic observations of vesiculation reveal the role of silicate crystals in bubble nucleation and growth in andesitic magmas

    Science.gov (United States)

    Pleše, P.; Higgins, M. D.; Mancini, L.; Lanzafame, G.; Brun, F.; Fife, J. L.; Casselman, J.; Baker, D. R.

    2018-01-01

    Bubble nucleation and growth control the explosivity of volcanic eruptions, and the kinetics of these processes are generally determined from examinations of natural samples and quenched experimental run products. These samples, however, only provide a view of the final state, from which the initial conditions of a time-evolving magmatic system are then inferred. The interpretations that follow are inexact due to the inability of determining the exact conditions of nucleation and the potential detachment of bubbles from their nucleation sites, an uncertainty that can obscure their nucleation location - either homogeneously within the melt or heterogeneously at the interface between crystals and melts. We present results of a series of dynamic, real-time 4D X-ray tomographic microscopy experiments where we observed the development of bubbles in crystal bearing silicate magmas. Experimentally synthesized andesitic glasses with 0.25-0.5 wt% H2O and seed silicate crystals were heated at 1 atm to induce bubble nucleation and track bubble growth and movement. In contrast to previous studies on natural and experimentally produced samples, we found that bubbles readily nucleated on plagioclase and clinopyroxene crystals, that their contact angle changes during growth and that they can grow to sizes many times that of the silicate on whose surface they originated. The rapid heterogeneous nucleation of bubbles at low degrees of supersaturation in the presence of silicate crystals demonstrates that silicates can affect when vesiculation ensues, influencing subsequent permeability development and effusive vs. explosive transition in volcanic eruptions.

  1. Dynamic observations of vesiculation reveal the role of silicate crystals in bubble nucleation and growth in andesitic magmas

    Energy Technology Data Exchange (ETDEWEB)

    Pleše, P.; Higgins, M. D.; Mancini, L.; Lanzafame, G.; Brun, F.; Fife, J. L.; Casselman, J.; Baker, D. R.

    2018-01-01

    Bubble nucleation and growth control the explosivity of volcanic eruptions, and the kinetics of these processes are generally determined from examinations of natural samples and quenched experimental run products. These samples, however, only provide a view of the final state, from which the initial conditions of a time-evolving magmatic system are then inferred. The interpretations that follow are inexact due to the inability of determining the exact conditions of nucleation and the potential detachment of bubbles from their nucleation sites, an uncertainty that can obscure their nucleation location – either homogeneously within the melt or heterogeneously at the interface between crystals and melts. We present results of a series of dynamic, real-time 4D X-ray tomographic microscopy experiments where we observed the development of bubbles in crystal bearing silicate magmas. Experimentally synthesized andesitic glasses with 0.25–0.5 wt% H2O and seed silicate crystals were heated at 1 atm to induce bubble nucleation and track bubble growth and movement. In contrast to previous studies on natural and experimentally produced samples, we found that bubbles readily nucleated on plagioclase and clinopyroxene crystals, that their contact angle changes during growth and that they can grow to sizes many times that of the silicate on whose surface they originated. The rapid heterogeneous nucleation of bubbles at low degrees of supersaturation in the presence of silicate crystals demonstrates that silicates can affect when vesiculation ensues, influencing subsequent permeability development and effusive vs. explosive transition in volcanic eruptions.

  2. Conservation of bubble size distribution during gas reactive absorption in bubble column reactors

    Directory of Open Access Journals (Sweden)

    P. L.C. LAGE

    1999-12-01

    Full Text Available Conservation of the bubble size distribution function was applied to the reactive absorption of carbon dioxide in a bubble column reactor. The model developed was solved by the method of characteristics and by a Monte Carlo method. Simulations were carried out using simplified models for the liquid phase and for the gas-liquid mass transfer. Predictions of gas holdup and outlet gas composition showed that the concept of a mean bubble diameter is not applicable when the bubble size distribution is reasonably polydispersed. In these cases, the mass mean velocity and the numerical mean velocity of the bubbles are very different. Therefore, quantification of the polydispersion of bubbles was shown to be essential to gas-phase hydrodynamics modeling.

  3. Interactions of multiple spark-generated bubbles with phase differences

    Science.gov (United States)

    Fong, Siew Wan; Adhikari, Deepak; Klaseboer, Evert; Khoo, Boo Cheong

    2009-04-01

    This paper aims to study the complex interaction between multiple bubbles, and to provide a summary and physical explanation of the phenomena observed during the interaction of two bubbles. High-speed photography is utilized to observe the experiments involving multiple spark-generated bubbles. Numerical simulations corresponding to the experiments are performed using the Boundary Element Method (BEM). The bubbles are typically between 3 and 5 mm in radius and are generated either in-phase (at the same time) or with phase differences. Complex phenomena are observed such as bubble splitting, and high-speed jetting inside a bubble caused by another collapsing bubble nearby (termed the ‘catapult’ effect). The two-bubble interactions are broadly classified in a graph according to two parameters: the relative inter-bubble distance and the phase difference (a new parameter introduced). The BEM simulations provide insight into the physics, such as bubble shape changes in detail, and jet velocities. Also presented in this paper are the experimental results of three bubble interactions. The interesting and complex observations of multiple bubble interaction are important for a better understanding of real life applications in medical ultrasonic treatment and ultrasonic cleaning. Many of the three bubble interactions can be explained by isolating bubble pairs and classifying their interaction according to the graph for the two bubble case. This graph can be a useful tool to predict the behavior of multiple bubble interactions.

  4. Stability of a Bubble Expanding and Translating Through an Inviscid ...

    Indian Academy of Sciences (India)

    A bubble expands adiabatically and translates in an incompressible and inviscid liquid. We investigate the number of equilibrium points of the bubble and the nature of stability of the bubble at these points. We find that there is only one equilibrium point and the bubble is stable there.

  5. Tropical Bubbles : Asset Prices in Latin America, 1980-2001

    OpenAIRE

    Herrera, Santiago; Perry, Guillermo

    2001-01-01

    The authors test for the existence of asset price bubbles in Latin America in 1980-2001, focusing mainly on stock prices. Based on unit root and cointegration tests, they find that they cannot reject the hypothesis of bubbles. They arrive at the same conclusion using Froot and Obstfeld's intrinsic bubbles model. To examine empirical regularities of these bubble episodes in the region, the ...

  6. MARANGONI CONVECTION AROUND A VENTILATED AIR BUBBLE UNDER MICROGRAVITY CONDITIONS

    NARCIS (Netherlands)

    HOEFSLOOT, HCJ; JANSSEN, LPBM; HOOGSTRATEN, HW

    Under microgravity conditions in both parabolic and sounding rocket flights, the mass-transfer-induced Marangoni convection around an air bubble was studied. To prevent the bubble from becoming saturated, the bubble was ventilated. It turned out that the flow rate of the air through the bubble

  7. Multiple Size Group Modeling of Polydispersed Bubbly Flow in the Mold: An Analysis of Turbulence and Interfacial Force Models

    Science.gov (United States)

    Liu, Zhongqiu; Qi, Fengsheng; Li, Baokuan; Jiang, Maofa

    2015-04-01

    An inhomogeneous Multiple Size Group (MUSIG) model based on the Eulerian-Eulerian approach has been developed to describe the polydispersed bubbly flow inside the continuous-casting mold. A laboratory scale mold has been simulated using four different turbulence closure models (modified k - ɛ, RNG k - ɛ, k - ω, and SST) with the purpose of critically comparing their predictions of bubble Sauter mean diameter distribution with previous experimental data. Furthermore, the influences of all the interfacial momentum transfer terms including drag force, lift force, virtual mass force, wall lubrication force, and turbulent dispersion force are investigated. The breakup and coalescence effects of the bubbles are modeled according to the bubble breakup by the impact of turbulent eddies while for bubble coalescence by the random collisions driven by turbulence and wake entrainment. It has been found that the modified k - ɛ model shows better agreement than other models in predicting the bubble Sauter mean diameter profiles. Further, simulations have also been performed to understand the sensitivity of different interfacial forces. The appropriate drag force coefficient, lift force coefficient, virtual mass force coefficient, and turbulent dispersion force coefficient are chosen in accordance with measurements of water model experiments. However, the wall lubrication force does not have much effect on the current polydispersed bubbly flow system. Finally, the MUSIG model is then used to estimate the argon bubble diameter in the molten steel of the mold. The argon bubble Sauter mean diameter generated in molten steel is predicted to be larger than air bubbles in water for the similar conditions.

  8. Black Hole Blows Big Bubble

    Science.gov (United States)

    2010-07-01

    Combining observations made with ESO's Very Large Telescope and NASA's Chandra X-ray telescope, astronomers have uncovered the most powerful pair of jets ever seen from a stellar black hole. This object, also known as a microquasar, blows a huge bubble of hot gas, 1000 light-years across, twice as large and tens of times more powerful than other known microquasars. The discovery is reported this week in the journal Nature. "We have been astonished by how much energy is injected into the gas by the black hole," says lead author Manfred Pakull. "This black hole is just a few solar masses, but is a real miniature version of the most powerful quasars and radio galaxies, which contain black holes with masses of a few million times that of the Sun." Black holes are known to release a prodigious amount of energy when they swallow matter. It was thought that most of the energy came out in the form of radiation, predominantly X-rays. However, the new findings show that some black holes can release at least as much energy, and perhaps much more, in the form of collimated jets of fast moving particles. The fast jets slam into the surrounding interstellar gas, heating it and triggering an expansion. The inflating bubble contains a mixture of hot gas and ultra-fast particles at different temperatures. Observations in several energy bands (optical, radio, X-rays) help astronomers calculate the total rate at which the black hole is heating its surroundings. The astronomers could observe the spots where the jets smash into the interstellar gas located around the black hole, and reveal that the bubble of hot gas is inflating at a speed of almost one million kilometres per hour. "The length of the jets in NGC 7793 is amazing, compared to the size of the black hole from which they are launched," says co-author Robert Soria [1]. "If the black hole were shrunk to the size of a soccer ball, each jet would extend from the Earth to beyond the orbit of Pluto." This research will help

  9. IMPLEMENTATION OF SERIAL AND PARALLEL BUBBLE SORT ON FPGA

    Directory of Open Access Journals (Sweden)

    Dwi Marhaendro Jati Purnomo

    2016-06-01

    Full Text Available Sorting is common process in computational world. Its utilization are on many fields from research to industry. There are many sorting algorithm in nowadays. One of the simplest yet powerful is bubble sort. In this study, bubble sort is implemented on FPGA. The implementation was taken on serial and parallel approach. Serial and parallel bubble sort then compared by means of its memory, execution time, and utility which comprises slices and LUTs. The experiments show that serial bubble sort required smaller memory as well as utility compared to parallel bubble sort. Meanwhile, parallel bubble sort performed faster than serial bubble sort

  10. Lattice Boltzmann Simulation of Multiple Bubbles Motion under Gravity

    Directory of Open Access Journals (Sweden)

    Deming Nie

    2015-01-01

    Full Text Available The motion of multiple bubbles under gravity in two dimensions is numerically studied through the lattice Boltzmann method for the Eotvos number ranging from 1 to 12. Two kinds of initial arrangement are taken into account: vertical and horizontal arrangement. In both cases the effects of Eotvos number on the bubble coalescence and rising velocity are investigated. For the vertical arrangement, it has been found that the coalescence pattern is similar. The first coalescence always takes place between the two uppermost bubbles. And the last coalescence always takes place between the coalesced bubble and the bottommost bubble. For four bubbles in a horizontal arrangement, the outermost bubbles travel into the wake of the middle bubbles in all cases, which allows the bubbles to coalesce. The coalescence pattern is more complex for the case of eight bubbles, which strongly depends on the Eotvos number.

  11. Optimization of the bubble radius in a moving single bubble sonoluminescence

    Energy Technology Data Exchange (ETDEWEB)

    Mirheydari, Mona; Sadighi-Bonabi, Rasoul; Rezaee, Nastaran; Ebrahimi, Homa, E-mail: sadighi@sharif.ir [Department of Physics, Sharif University of Technology, 11365-91, Tehran (Iran, Islamic Republic of)

    2011-05-01

    A complete study of the hydrodynamic force on a moving single bubble sonoluminescence in N-methylformamide is presented in this work. All forces exerted, trajectory, interior temperature and gas pressure are discussed. The maximum values of the calculated components of the hydrodynamic force for three different radii at the same driving pressure were compared, while the optimum bubble radius was determined. The maximum value of the buoyancy force appears at the start of bubble collapse, earlier than the other forces whose maximum values appear at the moment of bubble collapse. We verified that for radii larger than the optimum radius, the temperature peak value decreases.

  12. Optimization of the bubble radius in a moving single bubble sonoluminescence

    International Nuclear Information System (INIS)

    Mirheydari, Mona; Sadighi-Bonabi, Rasoul; Rezaee, Nastaran; Ebrahimi, Homa

    2011-01-01

    A complete study of the hydrodynamic force on a moving single bubble sonoluminescence in N-methylformamide is presented in this work. All forces exerted, trajectory, interior temperature and gas pressure are discussed. The maximum values of the calculated components of the hydrodynamic force for three different radii at the same driving pressure were compared, while the optimum bubble radius was determined. The maximum value of the buoyancy force appears at the start of bubble collapse, earlier than the other forces whose maximum values appear at the moment of bubble collapse. We verified that for radii larger than the optimum radius, the temperature peak value decreases.

  13. Bubble collisions and measures of the multiverse

    Energy Technology Data Exchange (ETDEWEB)

    Salem, Michael P., E-mail: salem@cosmos.phy.tufts.edu [Department of Physics, Stanford University, Stanford, CA 94305 (United States)

    2012-01-01

    To compute the spectrum of bubble collisions seen by an observer in an eternally-inflating multiverse, one must choose a measure over the diverging spacetime volume, including choosing an ''initial'' hypersurface below which there are no bubble nucleations. Previous calculations focused on the case where the initial hypersurface is pushed arbitrarily deep into the past. Interestingly, the observed spectrum depends on the orientation of the initial hypersurface, however one's ability observe the effect rapidly decreases with the ratio of inflationary Hubble rates inside and outside one's bubble. We investigate whether this conclusion might be avoided under more general circumstances, including placing the observer's bubble near the initial hypersurface. We find that it is not. As a point of reference, a substantial appendix reviews relevant aspects of the measure problem of eternal inflation.

  14. Loop exponent in DNA bubble dynamics

    Science.gov (United States)

    Kaiser, Vojtěch; Novotný, Tomáš

    2014-08-01

    Dynamics of DNA bubbles are of interest for both statistical physics and biology. We present exact solutions to the Fokker-Planck equation governing bubble dynamics in the presence of a long-range entropic interaction. The complete meeting time and meeting position probability distributions are derived from the solutions. Probability distribution functions (PDFs) reflect the value of the loop exponent of the entropic interaction. Our results extend previous results which concentrated mainly on the tails of the PDFs and open a way to determining the strength of the entropic interaction experimentally which has been a matter of recent discussions. Using numerical integration, we also discuss the influence of the finite size of a DNA chain on the bubble dynamics. Analogous results are obtained also for the case of subdiffusive dynamics of a DNA bubble in a heteropolymer, revealing highly universal asymptotics of meeting time and position probability functions.

  15. Why do bubbles in Guinness sink?

    Science.gov (United States)

    Benilov, E. S.; Cummins, C. P.; Lee, W. T.

    2013-02-01

    Stout beers show the counter-intuitive phenomena of sinking bubbles, while the beer is settling. Previous research suggests that this phenomenon is due to the small size of the bubbles in these beers and the presence of a circulatory current, directed downwards near the side of the wall and upwards in the interior of the glass. The mechanism by which such a circulation is established and the conditions under which it will occur has not been clarified. In this paper, we use simulations and experiments to demonstrate that the flow in a glass of stout beer depends on the shape of the glass. If it narrows downwards (as the traditional stout glass, the pint, does), the flow is directed downwards near the wall and upwards in the interior and sinking bubbles will be observed. If the container widens downwards, the flow is opposite to that described above and only rising bubbles will be seen.

  16. The 2008 oil bubble: Causes and consequences

    International Nuclear Information System (INIS)

    Tokic, Damir

    2010-01-01

    We argue that 'the 2008 Oil Bubble' was directly and indirectly created by the Federal Reserve in response to deflationary risks that resurfaced after the housing bubble burst and the resulting credit crisis of 2008. Deflationary risks first appeared after the dot.com bubble burst in 2000 and after the terrorist attacks on September 11, 2001. Manipulation of the US dollar value has been one of the key emergency tools in the Fed's arsenal. During the entire period from 2000 to 2008, the US dollar has been falling, while the price of crude oil has been rising, with the culmination in July 2008. If other global central banks embrace the Fed's anti-deflationary strategies, the consequences could be dire for the global economy, potentially resulting in an ultimate gold bubble.

  17. Universe out of a breathing bubble

    International Nuclear Information System (INIS)

    Guendelman, Eduardo I.; Sakai, Nobuyuki

    2008-01-01

    We consider the model of a false-vacuum bubble with a thin wall where the surface energy density is composed of two different components, 'domain-wall' type and 'dust' type, with opposite signs. We find stably oscillating solutions, which we call 'breathing bubbles'. By decay to a lower mass state, such a breathing bubble could become either (i) a child universe or ii) a bubble that 'eats up' the original universe, depending on the sign of the surface energy of the domain-wall component. We also discuss the effect of the finite-thickness corrections to the thin-wall approximation and possible origins of the energy contents of our model

  18. Modelling of large-scale dense gas-solid bubbling fluidised beds using a novel discrete bubble model

    NARCIS (Netherlands)

    Bokkers, G.A.; Laverman, J.A.; van Sint Annaland, M.; Kuipers, J.A.M.

    2006-01-01

    In order to model the complex hydrodynamic phenomena prevailing in industrial scale gas–solid bubbling fluidised bed reactors and especially the macro-scale emulsion phase circulation patterns induced by bubble–bubble interactions and bubble coalescence, a discrete bubble model (DBM) has been

  19. Electron acceleration in the bubble regime

    Energy Technology Data Exchange (ETDEWEB)

    Jansen, Oliver

    2014-02-03

    The bubble regime of laser-wakefield acceleration has been studied over the recent years as an important alternative to classical accelerators. Several models and theories have been published, in particular a theory which provides scaling laws for acceleration parameters such as energy gain and acceleration length. This thesis deals with numerical simulations within the bubble regime, their comparison to these scaling laws and data obtained from experiments, as well as some specific phenomenona. With a comparison of the scaling laws with numerical results a parameter scan was able to show a large parameter space in which simulation and theory agree. An investigation of the limits of this parameter space revealed boundaries to other regimes, especially at very high (a{sub 0} > 100) and very low laser amplitudes (a{sub 0} < 4). Comparing simulation data with data from experiments concerning laser pulse development and electron energies, it was found that experimental results can be adequately reproduced using the Virtual-Laser-Plasma-Laboratory code. In collaboration with the Institut fuer Optik und Quantenelektronik at the Friedrich-Schiller University Jena synchrotron radiation emitted from the inside of the bubble was investigated. A simulation of the movement of the electrons inside the bubble together with time dependent histograms of the emitted radiation helped to prove that the majority of radiation created during a bubble acceleration originates from the inside of the bubble. This radiation can be used to diagnose the amplitude of oscillation of the trapped electrons. During a further study it was proven that the polarisation of synchrotron radiation from a bubble contains information about the exact oscillation direction. This oscillation was successfully controlled by using either a laser pulse with a tilted pulse front or an asymmetric laser pulse. First results of ongoing studies concerning injecting electrons into an existing bubble and a scheme called

  20. Sono-chemiluminescence from a single cavitation bubble in water

    International Nuclear Information System (INIS)

    Brotchie, Adam; Shchukin, Dmitry; Moehwald, Helmuth; Schneider, Julia; Pflieger, Rachel

    2012-01-01

    In summary, this study has revealed the conditions required for a single bubble to be sono-chemically active. Evidence of radical-induced processes surrounding the bubble was only observed below the SL threshold, where the bubble was not spatially stable, and did not correlate with emission from excited molecular states inside the bubble. Moreover, this work substantiates recent progress that has been made in bridging the gap between single and multi-bubble cavitation. (authors)

  1. Test ventilation with smoke, bubbles, and balloons

    International Nuclear Information System (INIS)

    Pickering, P.L.; Cucchiara, A.L.; McAtee, J.L.; Gonzales, M.

    1987-01-01

    The behavior of smoke, bubbles, and helium-filled balloons was videotaped to demonstrate the mixing of air in the plutonium chemistry laboratories, a plutonium facility. The air-distribution patterns, as indicated by each method, were compared. Helium-filled balloons proved more useful than bubbles or smoke in the visualization of airflow patterns. The replay of various segments of the videotape proved useful in evaluating the different techniques and in identifying airflow trends responsible for air mixing. 6 refs

  2. Numerical simulation of single bubble boiling behavior

    Directory of Open Access Journals (Sweden)

    Junjie Liu

    2017-06-01

    Full Text Available The phenomena of a single bubble boiling process are studied with numerical modeling. The mass, momentum, energy and level set equations are solved using COMSOL multi-physics software. The bubble boiling dynamics, the transient pressure field, velocity field and temperature field in time are analyzed, and reasonable results are obtained. The numeral model is validated by the empirical equation of Fritz and could be used for various applications.

  3. Bubble nonlinear dynamics and stimulated scattering process

    Science.gov (United States)

    Jie, Shi; De-Sen, Yang; Sheng-Guo, Shi; Bo, Hu; Hao-Yang, Zhang; Shi-Yong, Hu

    2016-02-01

    A complete understanding of the bubble dynamics is deemed necessary in order to achieve their full potential applications in industry and medicine. For this purpose it is first needed to expand our knowledge of a single bubble behavior under different possible conditions including the frequency and pressure variations of the sound field. In addition, stimulated scattering of sound on a bubble is a special effect in sound field, and its characteristics are associated with bubble oscillation mode. A bubble in liquid can be considered as a representative example of nonlinear dynamical system theory with its resonance, and its dynamics characteristics can be described by the Keller-Miksis equation. The nonlinear dynamics of an acoustically excited gas bubble in water is investigated by using theoretical and numerical analysis methods. Our results show its strongly nonlinear behavior with respect to the pressure amplitude and excitation frequency as the control parameters, and give an intuitive insight into stimulated sound scattering on a bubble. It is seen that the stimulated sound scattering is different from common dynamical behaviors, such as bifurcation and chaos, which is the result of the nonlinear resonance of a bubble under the excitation of a high amplitude acoustic sound wave essentially. The numerical analysis results show that the threshold of stimulated sound scattering is smaller than those of bifurcation and chaos in the common condition. Project supported by the Program for Changjiang Scholars and Innovative Research Team in University, China (Grant No. IRT1228) and the Young Scientists Fund of the National Natural Science Foundation of China (Grant Nos. 11204050 and 11204049).

  4. Bubble chamber: Omega production and decay

    CERN Multimedia

    1973-01-01

    This image is taken from one of CERN's bubble chambers and shows the decay of a positive kaon in flight. The decay products of this kaon can be seen spiraling in the magnetic field of the chamber. The invention of bubble chambers in 1952 revolutionized the field of particle physics, allowing real tracks left by particles to be seen and photographed by expanding liquid that has been heated to boiling point.

  5. Bayesian Analysis of Bubbles in Asset Prices

    OpenAIRE

    Andras Fulop; Jun Yu

    2017-01-01

    We develop a new model where the dynamic structure of the asset price, after the fundamental value is removed, is subject to two different regimes. One regime reflects the normal period where the asset price divided by the dividend is assumed to follow a mean-reverting process around a stochastic long run mean. The second regime reflects the bubble period with explosive behavior. Stochastic switches between two regimes and non-constant probabilities of exit from the bubble regime are both all...

  6. Beer tapping: dynamics of bubbles after impact

    Science.gov (United States)

    Mantič-Lugo, V.; Cayron, A.; Brun, P.-T.; Gallaire, F.

    2015-12-01

    Beer tapping is a well known prank where a bottle of beer is impacted from the top by a solid object, usually another bottle, leading to a sudden foam overflow. A description of the shock-driven bubble dynamics leading to foaming is presented based on an experimental and numerical study evoking the following physical picture. First, the solid impact produces a sudden downwards acceleration of the bottle creating a strong depression in the liquid bulk. The existing bubbles undergo a strong expansion and a sudden contraction ending in their collapse and fragmentation into a large amount of small bubbles. Second, the bubble clouds present a large surface area to volume ratio, enhancing the CO2 diffusion from the supersaturated liquid, hence growing rapidly and depleting the CO2. The clouds of bubbles migrate upwards in the form of plumes pulling the surrounding liquid with them and eventually resulting in the foam overflow. The sudden pressure drop that triggers the bubble dynamics with a collapse and oscillations is modelled by the Rayleigh-Plesset equation. The bubble dynamics from impact to collapse occurs over a time (tb ≃ 800 μs) much larger than the acoustic time scale of the liquid bulk (tac = 2H/c ≃ 80 μs), for the experimental container of height H = 6 cm and a speed of sound around c ≃ 1500 m/s. This scale separation, together with the comparison of numerical and experimental results, suggests that the pressure drop is controlled by two parameters: the acceleration of the container and the distance from the bubble to the free surface.

  7. Bubbles on the river of time

    International Nuclear Information System (INIS)

    Gribbin, J.

    1988-01-01

    The paper is concerned with modern cosmology, and the possibility that our Universe is just one bubble among many in some greater suprauniverse. These ideas are connected with the concept of inflation; inflation occurred shortly after the moment of creation of the Universe and just before the fireball stage that represents the big bang proper. A description is given of inflation and its use to explain the creation of the Universe from bubbles of mass-energy. (U.K.)

  8. Bubble parameters analysis of gas-liquid two-phase sparse bubbly flow based on image method

    International Nuclear Information System (INIS)

    Zhou Yunlong; Zhou Hongjuan; Song Lianzhuang; Liu Qian

    2012-01-01

    The sparse rising bubbles of gas-liquid two-phase flow in vertical pipe were measured and studied based on image method. The bubble images were acquired by high-speed video camera systems, the characteristic parameters of bubbles were extracted by using image processing techniques. Then velocity variation of rising bubbles were drawn. Area and centroid variation of single bubble were also drawn. And then parameters and movement law of bubbles were analyzed and studied. The test results showed that parameters of bubbles had been analyzed well by using image method. (authors)

  9. Fearless versus fearful speculative financial bubbles

    Science.gov (United States)

    Andersen, J. V.; Sornette, D.

    2004-06-01

    Using a recently introduced rational expectation model of bubbles, based on the interplay between stochasticity and positive feedbacks of prices on returns and volatility, we develop a new methodology to test how this model classifies nine time series that have been previously considered as bubbles ending in crashes. The model predicts the existence of two anomalous behaviors occurring simultaneously: (i) super-exponential price growth and (ii) volatility growth, that we refer to as the “fearful singular bubble” regime. Out of the nine time series, we find that five pass our tests and can be characterized as “fearful singular bubbles”. The four other cases are the information technology Nasdaq bubble and three bubbles of the Hang Seng index ending in crashes in 1987, 1994 and 1997. According to our analysis, these four bubbles have developed with essentially no significant increase of their volatility. This paper thus proposes that speculative bubbles ending in crashes form two groups hitherto unrecognized, namely those accompanied by increasing volatility (reflecting increasing risk perception) and those without change of volatility (reflecting an absence of risk perception).

  10. One thousand and one bubbles

    Science.gov (United States)

    Ávila, Jesús; Ramírez, Pedro F.; Ruipérez, Alejandro

    2018-01-01

    We propose a novel strategy that permits the construction of completely general five-dimensional microstate geometries on a Gibbons-Hawking space. Our scheme is based on two steps. First, we rewrite the bubble equations as a system of linear equations that can be easily solved. Second, we conjecture that the presence or absence of closed timelike curves in the solution can be detected through the evaluation of an algebraic relation. The construction we propose is systematic and covers the whole space of parameters, so it can be applied to find all five-dimensional BPS microstate geometries on a Gibbons-Hawking base. As a first result of this approach, we find that the spectrum of scaling solutions becomes much larger when non-Abelian fields are present. We use our method to describe several smooth horizonless multicenter solutions with the asymptotic charges of three-charge (Abelian and non-Abelian) black holes. In particular, we describe solutions with the centers lying on lines and circles that can be specified with exact precision. We show the power of our method by explicitly constructing a 50-center solution. Moreover, we use it to find the first smooth five-dimensional microstate geometries with arbitrarily small angular momentum.

  11. The influence of microstructure on blistering and bubble formation by He ion irradiation in Al alloys

    International Nuclear Information System (INIS)

    Soria, S.R.; Tolley, A.; Sánchez, E.A.

    2015-01-01

    The influence of microstructure and composition on the effects of ion irradiation in Al alloys was studied combining Atomic Force Microscopy, Scanning Electron Microscopy and Transmission Electron Microscopy. For this purpose, irradiation experiments with 20 keV He + ions at room temperature were carried out in Al, an Al–4Cu (wt%) supersaturated solid solution, and an Al-5.6Cu-0.5Si-0.5Ge (wt.%) alloy with a very high density of precipitates, and the results were compared. In Al and Al–4Cu, He bubbles were found with an average size in between 1 nm and 2 nm that was independent of fluence. The critical fluence for bubble formation was higher in Al–4Cu than in Al. He bubbles were also observed below the critical fluence after post irradiation annealing in Al–4Cu. The incoherent interfaces between the equilibrium θ phase and the Al matrix were found to be favorable sites for the formation of He bubbles. Instead, no bubbles were observed in the precipitate rich Al-5.6Cu-0.5Si-0.5Ge alloy. In all alloys, blistering was observed, leading to surface erosion by exfoliation. The blistering effects were more severe in the Al-5.6Cu-0.5Si-0.5Ge alloy, and they were enhanced by increasing the fluence rate. - Highlights: • In Al and Al–4Cu, He bubbles were formed, but no bubbles were observed in Al-5.6Cu-0.5Si-0.5Ge. • Bubble formation was enhanced at incoherent matrix/precipitate interfaces in Al–4Cu. • The bubble size was insensitive to displacement rate in pure Al. • In Al and Al-5.6Cu-0.5Si-0.5Ge blistering was observed, which was more severe in the alloy. • Blistering effects were enhanced by increasing the displacement rate in Al and Al–4Cu.

  12. Non-singular bounce transitions in the multiverse

    Energy Technology Data Exchange (ETDEWEB)

    Garriga, Jaume [Departament de Fisica Fonamental i Institut de Ciencies del Cosmos, Universitat de Barcelona, Marti i Franques, 1, 08028, Barcelona (Spain); Vilenkin, Alexander; Zhang, Jun, E-mail: jaume.garriga@ub.edu, E-mail: vilenkin@cosmos.phy.tufts.edu, E-mail: jun.zhang@tufts.edu [Institute of Cosmology, Department of Physics and Astronomy, Tufts University, Medford, MA 02155 (United States)

    2013-11-01

    According to classical GR, negative-energy (AdS) bubbles in the multiverse terminate in big crunch singularities. It has been conjectured, however, that the fundamental theory may resolve these singularities and replace them by non-singular bounces. Here we explore possible dynamics of such bounces using a simple modification of the Friedmann equation, which ensures that the scale factor bounces when the matter density reaches some critical value ρ{sub c}. This is combined with a simple scalar field 'landscape', where the energy barriers between different vacua are small compared to ρ{sub c}. We find that the bounce typically results in a transition to another vacuum, with a scalar field displacement Δφ ∼ 1 in Planck units. If the new vacuum is AdS, we have another bounce, and so on, until the field finally transits to a positive-energy (de Sitter) vacuum. We also consider perturbations about the homogeneous solution and discuss some of their amplification mechanisms (e.g., tachyonic instability and parametric resonance). For a generic potential, these mechanisms are much less efficient than in models of slow-roll inflation. But the amplification may still be strong enough to cause the bubble to fragment into a mosaic of different vacua.

  13. On AdS to dS transitions in higher-curvature gravity

    Energy Technology Data Exchange (ETDEWEB)

    Camanho, Xián O. [Max-Planck-Institut für Gravitationsphysik, Albert-Einstein-Institut,14476 Golm (Germany); Edelstein, José D. [Department of Particle Physics and IGFAE, Universidade de Santiago de Compostela,E-15782 Santiago de Compostela (Spain); Gomberoff, Andrés [Universidad Andres Bello, Departamento de Ciencias Físicas,Av. República 252, Santiago (Chile); Sierra-García, J. Aníbal [Department of Particle Physics and IGFAE, Universidade de Santiago de Compostela,E-15782 Santiago de Compostela (Spain)

    2015-10-27

    We study the possible existence of gravitational phase transitions from AdS to dS geometries in the context of higher-curvature gravities. We use Lanczos-Gauss-Bonnet (LGB) theory with a positive cosmological constant as a toy model. This theory has two maximally symmetric vacua with positive (dS) and negative (AdS) constant curvature. We show that a phase transition from the AdS vacuum to a dS black hole geometry takes place when the temperature reaches a critical value. The transition is produced by nucleation of bubbles of the new phase that expand afterwards. We claim that this phenomenon is not particular to the model under study, that contains Boulware-Deser instabilities, but shall also be part of generic gravitational theories with higher-curvature terms, where these problems are absent. A salient feature that emerges when a positive cosmological constant is considered is that the temperature in which these bubbles may form is bounded from above. Thermodynamically this property is related to quite an uncommon feature that this system exhibits, namely, the existence of a zeroth-order phase transition.

  14. Phase transitions

    CERN Document Server

    Sole, Ricard V; Solé, Ricard V; Solé, Ricard V; Sol, Ricard V; Solé, Ricard V

    2011-01-01

    Phase transitions--changes between different states of organization in a complex system--have long helped to explain physics concepts, such as why water freezes into a solid or boils to become a gas. How might phase transitions shed light on important problems in biological and ecological complex systems? Exploring the origins and implications of sudden changes in nature and society, Phase Transitions examines different dynamical behaviors in a broad range of complex systems. Using a compelling set of examples, from gene networks and ant colonies to human language and the degradation of diverse ecosystems, the book illustrates the power of simple models to reveal how phase transitions occur. Introductory chapters provide the critical concepts and the simplest mathematical techniques required to study phase transitions. In a series of example-driven chapters, Ricard Solé shows how such concepts and techniques can be applied to the analysis and prediction of complex system behavior, including the origins of ...

  15. Occurrence of critical heat flux during blowdown with flow reversal

    International Nuclear Information System (INIS)

    Leung, J.C.M.

    1976-04-01

    A small-scale experiment using Freon-11 at 130 0 F and 65 psia in a well-instrumented transparent annular test section was used to study the occurrence of critical heat flux (CHF) during blowdown with flow reversal. The inner stainless steel tube of the annulus was uniformly heated over its 2 ft length. Inlet and exit void fractions were measured by a capacitance technique. Flow regime transition was observed with high speed photography. A 1-hr contact time between Freon-11 and nitrogen at 130 0 F and 60 psig was found to greatly affect the steady-state subcooled boiling initial conditions. Delay in bubble growth was observed in adiabatic blowdown runs. This was caused by the thermodynamic nonequilibrium conditions required for the unstable bubble growth. For the diabatic runs, equilibrium was more closely approached in the test section during the early phase of blowdown. Critical heat flux did not occur immediately during the flow decay in an approximately 60 msec reversal period. The first or early CHF which occurred at about 400 msec was independent of the blowdown volume and did not propagate upward. An annular flow pattern appeared at the onset of this CHF which occurred only at the lower 8 in. of the heated zone

  16. Development of three-dimensional individual bubble-velocity measurement method by bubble tracking

    International Nuclear Information System (INIS)

    Kanai, Taizo; Furuya, Masahiro; Arai, Takahiro; Shirakawa, Kenetsu; Nishi, Yoshihisa

    2012-01-01

    A gas-liquid two-phase flow in a large diameter pipe exhibits a three-dimensional flow structure. Wire-Mesh Sensor (WMS) consists of a pair of parallel wire layers located at the cross section of a pipe. Both the parallel wires cross at 90o with a small gap and each intersection acts as an electrode. The WMS allows the measurement of the instantaneous two-dimensional void-fraction distribution over the cross-section of a pipe, based on the difference between the local instantaneous conductivity of the two-phase flow. Furthermore, the WMS can acquire a phasic-velocity on the basis of the time lag of void signals between two sets of WMS. Previously, the acquired phasic velocity was one-dimensional with time-averaged distributions. The authors propose a method to estimate the three-dimensional bubble-velocity individually WMS data. The bubble velocity is determined by the tracing method. In this tracing method, each bubble is separated from WMS signal, volume and center coordinates of the bubble is acquired. Two bubbles with near volume at two WMS are considered as the same bubble and bubble velocity is estimated from the displacement of the center coordinates of the two bubbles. The validity of this method is verified by a swirl flow. The proposed method can successfully visualize a swirl flow structure and the results of this method agree with the results of cross-correlation analysis. (author)

  17. MASS-TRANSFER AND BUBBLE-SIZE IN A BUBBLE-COLUMN UNDER PRESSURE

    NARCIS (Netherlands)

    WILKINSON, PM; HARINGA, H; VANDIERENDONCK, LL

    The influence of pressure on the gas hold-up in a bubble column is determined for a sodium sulphite solution in combination with the volumetric mass transfer coefficient. Furthermore, for the same conditions the bubble size is also estimated from photos. The results of these experiments show that

  18. Application of coalescence and breakup models in a discrete bubble model for bubble columns

    NARCIS (Netherlands)

    van den Hengel, E.I.V.; Deen, N.G.; Kuipers, J.A.M.

    2005-01-01

    In this work, a discrete bubble model (DBM) is used to investigate the hydrodynamics, coalescence, and breakup occurring in a bubble column. The DBM, originally developed by Delnoij et al. (Chem. Eng. Sci. 1997, 52, 1429-1458; Chem. Eng. Sci. 1999, 54, 2217-2226),1,2 was extended to incorporate

  19. Cumulative distribution functions associated with bubble-nucleation processes in cavitation

    KAUST Repository

    Watanabe, Hiroshi

    2010-11-15

    Bubble-nucleation processes of a Lennard-Jones liquid are studied by molecular dynamics simulations. Waiting time, which is the lifetime of a superheated liquid, is determined for several system sizes, and the apparent finite-size effect of the nucleation rate is observed. From the cumulative distribution function of the nucleation events, the bubble-nucleation process is found to be not a simple Poisson process but a Poisson process with an additional relaxation time. The parameters of the exponential distribution associated with the process are determined by taking the relaxation time into account, and the apparent finite-size effect is removed. These results imply that the use of the arithmetic mean of the waiting time until a bubble grows to the critical size leads to an incorrect estimation of the nucleation rate. © 2010 The American Physical Society.

  20. Financial Bubbles, Real Estate Bubbles, Derivative Bubbles, and the Financial and Economic Crisis

    Science.gov (United States)

    Sornette, Didier; Woodard, Ryan

    The financial crisis of 2008, which started with an initially well-defined epicenter focused on mortgage backed securities (MBS), has been cascading into a global economic recession, whose increasing severity and uncertain duration has led and is continuing to lead to massive losses and damage for billions of people. Heavy central bank interventions and government spending programs have been launched worldwide and especially in the USA and Europe, with the hope to unfreeze credit and bolster consumption. Here, we present evidence and articulate a general framework that allows one to diagnose the fundamental cause of the unfolding financial and economic crisis: the accumulation of several bubbles and their interplay and mutual reinforcement have led to an illusion of a "perpetual money machine" allowing financial institutions to extract wealth from an unsustainable artificial process. Taking stock of this diagnostic, we conclude that many of the interventions to address the so-called liquidity crisis and to encourage more consumption are ill-advised and even dangerous, given that precautionary reserves were not accumulated in the "good times" but that huge liabilities were. The most "interesting" present times constitute unique opportunities but also great challenges, for which we offer a few recommendations.

  1. Convective mass transfer around a dissolving bubble

    Science.gov (United States)

    Duplat, Jerome; Grandemange, Mathieu; Poulain, Cedric

    2017-11-01

    Heat or mass transfer around an evaporating drop or condensing vapor bubble is a complex issue due to the interplay between the substrate properties, diffusion- and convection-driven mass transfer, and Marangoni effects, to mention but a few. In order to disentangle these mechanisms, we focus here mainly on the convective mass transfer contribution in an isothermal mass transfer problem. For this, we study the case of a millimetric carbon dioxide bubble which is suspended under a substrate and dissolved into pure liquid water. The high solubility of CO2 in water makes the liquid denser and promotes a buoyant-driven flow at a high (solutal) Rayleigh number (Ra˜104 ). The alteration of p H allows the concentration field in the liquid to be imaged by laser fluorescence enabling us to measure both the global mass flux (bubble volume, contact angle) and local mass flux around the bubble along time. After a short period of mass diffusion, where the boundary layer thickens like the square root of time, convection starts and the CO2 is carried by a plume falling at constant velocity. The boundary layer thickness then reaches a plateau which depends on the bubble cross section. Meanwhile the plume velocity scales like (dV /d t )1 /2 with V being the volume of the bubble. As for the rate of volume loss, we recover a constant mass flux in the diffusion-driven regime followed by a decrease in the volume V like V2 /3 after convection has started. We present a model which agrees well with the bubble dynamics and discuss our results in the context of droplet evaporation, as well as high Rayleigh convection.

  2. Non-intuitive bubble effects in reactor and containment technology

    International Nuclear Information System (INIS)

    Moody, F.J.

    1991-01-01

    Most people know a lot about bubbles, including how they rise in liquids and the way they appear when the cap is removed from a bottle of carbonated beverage. A lot of bubble knowledge is obtained from bubbling air through water in aquariums to keep the fish alive and happy, or watching scuba divers feed the sharks in large glass tanks at the local zoo. But innocent bubbles can be sources of structural loadings and sometimes destructive fluid behavior. In fact, there are many non-intuitive effects associated with bubbles which have been discovered by experiments and analyses. It has been necessary to design various reactor and containment components in the nuclear energy industry to accommodate the fact that bubbles can expand like compressed springs, or oscillate, or collapse abruptly, and create structural loads. This paper describes several important phenomena associated with bubble action in nuclear reactor and containment systems and the associated loads exerted. An awareness of these effects can help to avoid unwelcome surprises in general thermal-hydraulic applications when a system is disturbed by bubble behavior. Major topics discussed include expanding and collapsing submerged bubbles, steam chugging and ringout, bubble shattering, surprising hot bubble action in a saturated pool, bubble effects on fluid-structure-interaction, waterhammer from collapsing bubble in pipes, and vapor bubble effects on sound speed in saturated mixtures

  3. Interplay between developing flow length and bubble departure diameter during macroconvection enhanced pool boiling

    Science.gov (United States)

    Jaikumar, A.; Emery, T. S.; Kandlikar, S. G.

    2018-02-01

    Enhanced boiling structures based on the concept of separate liquid-vapor (L-V) pathways rely on the motion of the bubbles departing from the nucleating regions (NRs) to induce a macroconvective liquid jet impingement flow over adjacent non-boiling regions. Heat transfer in the non-boiling regions can be improved by incorporating microchannels which act as feeder channels (FCs) that also improve liquid directionality towards the NR. We hypothesize that the single-phase flow characteristics in the developing region of the FC contribute to the boiling enhancement and explore the interplay between the FC length, developing flow length, and departure bubble diameter. FC lengths shorter than the developing flow length benefit from the enhancement due to developing boundary layers over their entire length. However, FC lengths shorter than the departure bubble diameter suffer from bubble interference while FC lengths that are considerably longer than the developing flow length exhibit lower heat transfer rates in the fully developed region. This hypothesis was verified by conducting pool boiling experiments with four feeder channel lengths between 1 mm and 3 mm using HFE-7000, PP1, PP1C, and water. Three distinct regions: (i) interfering bubble, (ii) efficient L-V pathways, and (iii) diminished jet were identified to explain the boiling performance enhancement. This analysis will be beneficial in the pursuit to enhance critical heat flux (CHF) and heat transfer coefficient (HTC) on surfaces utilizing macroconvection mechanisms during boiling with different liquids.

  4. On the rise velocity discontinuity of a deformable bubble in unbounded viscoelastic solutions

    Science.gov (United States)

    Tsamopoulos, John; Fraggedakis, Dimitris; Dimakopoulos, Yiannis

    2014-11-01

    It is well-documented experimentally, but not well-understood that a bubble steadily rising in a viscoelastic solution exhibits a negative wake and a jump discontinuity in its rise velocity, when its radius exceeds a critical value. In all experiments, the bubble shape forms a cusp in its back side and in some experiments it loses axial symmetry forming a wedge. Some authors have related the velocity jump with the existence of the negative wake or even the wedge formation. We have undertaken a computational study to explore the mechanisms behind these phenomena. To this end, we have used the ePTT model and determined its rheological parameters by fitting it to experiments. Then we developed an FE code (using elliptic grid generation and the SUPG and EVSS methods) and calculated the bubble rise and deformation as its radius increases. This simultaneously affects all parameters: Bond, Archimedes and Deborah numbers. Our predictions reproduce very accurately bubble shapes and the results up to the velocity jump or, in certain cases, beyond it using arc-length continuation. The discontinuity is attributed to a hysteresis loop, but does not require the presence of a wedge in the bubble shape and the negative wake is predicted even before this jump. Supported financially by the General Secretariat of Research & Technology of Greece through the program ``Thalis'' (Grant titled ``COVISCO'') co-funded by the ESF and National resources.

  5. A grid-independent EMMS/bubbling drag model for bubbling and turbulent fluidization

    DEFF Research Database (Denmark)

    Luo, Hao; Lu, Bona; Zhang, Jingyuan

    2017-01-01

    The EMMS/bubbling drag model takes the effects of meso-scale structures (i.e. bubbles) into modeling of drag coefficient and thus improves coarse-grid simulation of bubbling and turbulent fluidized beds. However, its dependence on grid size has not been fully investigated. In this article, we adopt...... a periodic domain show the new drag model is less sensitive to grid size because of the additional dependence on local slip velocity. When applying the new drag model to simulations of realistic bubbling and turbulent fluidized beds, we find grid-independent results are easier to obtain for high......-velocity turbulent fluidized bed cases. The simulation results indicate that the extended EMMS/bubbling drag model is a potential method for coarse-grid simulations of large-scale fluidized beds....

  6. Coordination of IVI and transit signal priority on transit evacuations.

    Science.gov (United States)

    2011-02-01

    During an emergency evacuation, execution time is always critical to the evacuees who are : transit dependent. Transit Signal Priority (TSP) can speed up the transit services by prioritizing : the approaching bus at a signalized intersection. With th...

  7. Numerical and experimental study of dissociation in an air-water single-bubble sonoluminescence system

    Science.gov (United States)

    Puente, Gabriela F.; Urteaga, Raúl; Bonetto, Fabián J.

    2005-10-01

    We performed a comprehensive numerical and experimental analysis of dissociation effects in an air bubble in water acoustically levitated in a spherical resonator. Our numerical approach is based on suitable models for the different effects considered. We compared model predictions with experimental results obtained in our laboratory in the whole phase parameter space, for acoustic pressures from the bubble dissolution limit up to bubble extinction. The effects were taken into account simultaneously to consider the transition from nonsonoluminescence to sonoluminescence bubbles. The model includes (1) inside the bubble, transient and spatially nonuniform heat transfer using a collocation points method, dissociation of O2 and N2 , and mass diffusion of vapor in the noncondensable gases; (2) at the bubble interface, nonequilibrium evaporation and condensation of water and a temperature jump due to the accommodation coefficient; (3) in the liquid, transient and spatially nonuniform heat transfer using a collocation points method, and mass diffusion of the gas in the liquid. The model is completed with a Rayleigh-Plesset equation with liquid compressible terms and vapor mass transfer. We computed the boundary for the shape instability based on the temporal evolution of the computed radius. The model is valid for an arbitrary number of dissociable gases dissolved in the liquid. We also obtained absolute measurements for R(t) using two photodetectors and Mie scattering calculations. The robust technique used allows the estimation of experimental results of absolute R0 and Pa . The technique is based on identifying the bubble dissolution limit coincident with the parametric instability in (Pa,R0) parameter space. We take advantage of the fact that this point can be determined experimentally with high precision and replicability. We computed the equilibrium concentration of the different gaseous species and water vapor during collapse as a function of Pa and R0 . The model

  8. Determination of the solid surface critical exponent β_1 from contact-angle variation on approach to a wetting transition: Cyclohexane/aniline/quartz

    International Nuclear Information System (INIS)

    Pallas, Norman R.

    2016-01-01

    The three-phase contact angle (θ) for the system cyclohexane/aniline/quartz has been measured from drop shapes as a function of temperature on approach to the cyclohexane/aniline upper consolute solution temperature T_c. The experiments employed exacting criteria previously established for thermodynamic-quality measurements at fluid interfaces. A first-order wetting transition from partial wetting to complete wetting was observed at a temperature T_w, 2.12 K below T_c. The contact angle vanishes at T_w, scaling as cos θ ∼ |T − T_c|"β"_1"−"μ for T < T_w and cos θ = 1.0 for T_w < T < T_c. The experimental results give a value for β_1 = 0.74 ± 0.03, in agreement with theoretical calculations. The data clearly rule out higher order contributions to the change in the contact angle near the critical point for this system. These results are in marked contrast to previous measurements on this system from measurements of capillary rise and meniscus curvature.

  9. Determination of the solid surface critical exponent β{sub 1} from contact-angle variation on approach to a wetting transition: Cyclohexane/aniline/quartz

    Energy Technology Data Exchange (ETDEWEB)

    Pallas, Norman R., E-mail: Sam-7-iam@hotmail.com [BP Research Centre Warrensville, 4440 Warrensville Center Road, Cleveland, Ohio 44128 (United States)

    2016-03-21

    The three-phase contact angle (θ) for the system cyclohexane/aniline/quartz has been measured from drop shapes as a function of temperature on approach to the cyclohexane/aniline upper consolute solution temperature T{sub c}. The experiments employed exacting criteria previously established for thermodynamic-quality measurements at fluid interfaces. A first-order wetting transition from partial wetting to complete wetting was observed at a temperature T{sub w}, 2.12 K below T{sub c}. The contact angle vanishes at T{sub w}, scaling as cos θ ∼ |T − T{sub c}|{sup β{sub 1}−μ} for T < T{sub w} and cos θ = 1.0 for T{sub w} < T < T{sub c}. The experimental results give a value for β{sub 1} = 0.74 ± 0.03, in agreement with theoretical calculations. The data clearly rule out higher order contributions to the change in the contact angle near the critical point for this system. These results are in marked contrast to previous measurements on this system from measurements of capillary rise and meniscus curvature.

  10. The stability of large oscillating bubbles

    Science.gov (United States)

    Blake, John; Pearson, Antony

    2002-11-01

    In a most remarkable paper, in October 1942, Penney & Price developed a theory for the stability of large oscillating bubbles; in their case they were interested in underwater explosions. Much of our current understanding on the stability of oscillating bubbles can be traced to the theoretical and experimental insight shown in this paper. While interest in this particular area continues with regard ship survivability to underwater explosions, other newer areas include the oscillatory behaviour of of seismic airgun generated bubbles. Apart from large volume oscillations with a characteristic period, the other dominant parameter is associated with buoyancy. An appropriate parameter is chosen that provides a measure of the distance of migration of a bubble over one period. An analytical and computational analysis of this class of problem reveals that this pressure gradient driven instability, normally observed in the form of a high speed liquid jet threading the bubble, is the most dominant surface instability, a characteristic feature borne out in most experimental and practical applications due to the presence of an incipient pressure gradient associated with hydrostatics, dynamics or boundaries

  11. Drop impact entrapment of bubble rings

    KAUST Repository

    Thoraval, M.-J.

    2013-04-29

    We use ultra-high-speed video imaging to look at the initial contact of a drop impacting on a liquid layer. We observe experimentally the vortex street and the bubble-ring entrapments predicted numerically, for high impact velocities, by Thoraval et al. (Phys. Rev. Lett., vol. 108, 2012, article 264506). These dynamics mainly occur within 50 -s after the first contact, requiring imaging at 1 million f.p.s. For a water drop impacting on a thin layer of water, the entrapment of isolated bubbles starts through azimuthal instability, which forms at low impact velocities, in the neck connecting the drop and pool. For Reynolds number Re above -12 000, up to 10 partial bubble rings have been observed at the base of the ejecta, starting when the contact is -20% of the drop size. More regular bubble rings are observed for a pool of ethanol or methanol. The video imaging shows rotation around some of these air cylinders, which can temporarily delay their breakup into micro-bubbles. The different refractive index in the pool liquid reveals the destabilization of the vortices and the formation of streamwise vortices and intricate vortex tangles. Fine-scale axisymmetry is thereby destroyed. We show also that the shape of the drop has a strong influence on these dynamics. 2013 Cambridge University Press.

  12. Argonne Bubble Experiment Thermal Model Development III

    Energy Technology Data Exchange (ETDEWEB)

    Buechler, Cynthia Eileen [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2018-01-11

    This report describes the continuation of the work reported in “Argonne Bubble Experiment Thermal Model Development” and “Argonne Bubble Experiment Thermal Model Development II”. The experiment was performed at Argonne National Laboratory (ANL) in 2014. A rastered 35 MeV electron beam deposited power in a solution of uranyl sulfate, generating heat and radiolytic gas bubbles. Irradiations were performed at beam power levels between 6 and 15 kW. Solution temperatures were measured by thermocouples, and gas bubble behavior was recorded. The previous report2 described the Monte-Carlo N-Particle (MCNP) calculations and Computational Fluid Dynamics (CFD) analysis performed on the as-built solution vessel geometry. The CFD simulations in the current analysis were performed using Ansys Fluent, Ver. 17.2. The same power profiles determined from MCNP calculations in earlier work were used for the 12 and 15 kW simulations. The primary goal of the current work is to calculate the temperature profiles for the 12 and 15 kW cases using reasonable estimates for the gas generation rate, based on images of the bubbles recorded during the irradiations. Temperature profiles resulting from the CFD calculations are compared to experimental measurements.

  13. Inflation and bubbles in general relativity

    Science.gov (United States)

    Laguna-Castillo, Pablo; Matzner, Richard A.

    1986-11-01

    Following Israel's study of singular hypersurfaces and thin shells in general relativity, the complete set of Einstein's field equations in the presence of a bubble boundary SIGMA is reviewed for all spherically symmetric embedding four-geometries M+/-. The mapping that identifies points between the boundaries Σ+ and Σ- is obtained explicitly when the regions M+ and M- are described by a de Sitter and a Minkowski metric, respectively. In addition, the evolution of a bubble with vanishing surface energy density is studied in a spatially flat Robertson-Walker space-time, for region M- radiation dominated with a vanishing cosmological constant, and an energy equation in M+ determined by the matching. It is found that this type of bubble leads to a ``worm-hole'' matching; that is, an infinite extent exterior of a sphere is joined across the wall to another infinite extent exterior of a sphere. Interior-interior matches are also possible. Under this model, solutions for a bubble following a Hubble law are analyzed. Numerical solutions for bubbles with constant tension are also obtained.

  14. Pattern Identification on the Nonlinear Radial Motion of an Oscillating Spherical Bubble Using Neural Networks

    Directory of Open Access Journals (Sweden)

    S. Malvar

    Full Text Available Abstract The main goal of this article is to study the oscillatory motion of a spherical gas bubble immersed in a Newtonian liquid subjected to a harmonic pressure excitation. We use the classical Rayleigh-Plesset equation to study the radial motion of the bubble undergoing a forcing acoustic pressure field. The second order nonlinear ordinary differential equation that governs the bubble motion is solved through a robust fifth order Runge-Kutta scheme with adaptive time-step. Several interesting patterns are identified. First we develop an asymptotic solution for low amplitudes of excitation pressure to validate our numerical code. Then we develop a bifurcation diagram in order to show how the parameters of the flow modify the vibrational patterns of the bubble. We also train a neural network to identify the vibrational pattern through its FFT data. The combination of neural networks with a bifurcation diagram could be useful for the identification of the flow physical parameters in practical applications. For each pattern we also provide an analysis of the motion of the bubble on the phase-space and interpret physically the system behavior with its FFT. In addition, we analyze nonlinear patterns using standard tools of dynamical systems such as Poincaré sections and calculate the Lyapunov exponents of the system. Based on that, we have identified topological transitions in phase plane using for instance the analysis of Poincaré sections and the solution in the frequency spectrum. We have seen that the mechanisms that dominate the dynamics of the oscillating bubble is the competition of the acoustic field excitation with surface tension forces and momentum diffusion by the action of the surrounding fluid viscosity.

  15. Improved prediction of critical heat flux in liquid metal pool boiling

    International Nuclear Information System (INIS)

    Bankoff, S.G.; Fauske, H.K.

    1974-01-01

    The Kutateladze criterion for the pool boiling critical heat flux, which works well for nonmetallic liquids at or above atmospheric pressure, fails for the alkali liquid metals in the pressure range of interest for Liquid Metal Fast Breeder Reactor applications. In this pressure range bubble growth of the alkali liquid metals is largely inertia-controlled, in view of the large thermal conductivities, which implies a significant condensing heat flux within the bubbles themselves. The bubble growth is assumed to be described by the Mikic, Rohsenow, and Griffith equation. In this way a mean bubble age is determined, and hence a mean bubble thermal boundary layer thickness. The time-average critical heat flux is then obtained as the sum of the Kutateladze flux and the flux due to condensation on the bubble surfaces. No empirical parameters are employed. The present analysis predicts critical heat fluxes lying generally within the data band. (U.S.)

  16. Study of the hovering period and bubble size in fully developed pool nucleate boiling of saturated liquid with a time-dependent heat source

    International Nuclear Information System (INIS)

    Pasamehmetoglu, K.O.; Nelson, R.A.

    1987-01-01

    In this paper, the bubble behavior in saturated pool boiling with a time-dependent heat source is analyzed. The study is restricted to the period from fully developed nucleate boiling until critical heat flux occurs. The hovering period and the departure volume of the bubble are selected as the characteristic parameters for bubble behavior. These parameters are quantified by solving the equation of motion for an idealized bubble. This equation is solved for cases in which the surface heat flux changes linearly and exponentially as a function of time. After nondimensionalization, the results are compared directly with the results of the steady-state problem. The comparison shows that the transient heat input has practically no effect on the hovering period. However, the transient heat flux causes a decreased volume at bubble departure. The volume decrease is dependent on the severity of the transient. These results are in qualitative agreement with the experimental observation quoted in the literature

  17. Wall slip of bubbles in foams

    Science.gov (United States)

    Saugey, A.; Drenckhan, W.; Weaire, D.

    2006-05-01

    We present a computational analysis of the flow of liquid foam along a smooth wall, as encountered in the transport of foams in vessels and pipes. We concentrate on the slip of the bubbles at the wall and present some novel finite element calculations of this motion for the case of fully mobile gas/liquid interfaces. Our two-dimensional simulations provide for the first time the bubble shapes and entire flow field, giving detailed insight into the distribution of stresses and dissipation in the system. In particular, we investigate the relationship between the drag force and the slip velocity of the bubble, which for small slip velocities obeys power laws, as predicted by previous semianalytical treatments.

  18. High energy neutrinos from the Fermi bubbles.

    Science.gov (United States)

    Lunardini, Cecilia; Razzaque, Soebur

    2012-06-01

    Recently the Fermi-LAT data have revealed two gamma-ray emitting bubble-shaped structures at the Galactic center. If the observed gamma rays have hadronic origin (collisions of accelerated protons), the bubbles must emit high energy neutrinos as well. This new, Galactic, neutrino flux should trace the gamma-ray emission in spectrum and spatial extent. Its highest energy part, above 20-50 TeV, is observable at a kilometer-scale detector in the northern hemisphere, such as the planned KM3NeT, while interesting constraints on it could be obtained by the IceCube Neutrino Observatory at the South Pole. The detection or exclusion of neutrinos from the Fermi bubbles will discriminate between hadronic and leptonic models, thus bringing unique information on the still mysterious origin of these objects and on the time scale of their formation.

  19. Bubbles, sparks, and the postwar laboratory

    International Nuclear Information System (INIS)

    Galison, P.

    1989-01-01

    The development and use of bubble chambers and spark chambers in the 1950s form the main thrust of this article, the bubble chamber as an example of ''image-producing'' instruments and the spark chamber as a ''logic'' device. Work on a cloud chamber by Glaser led to the development of the bubble chamber detector using liquid hydrogen, which was later linked to a computer for accurate automatic track analysis. It made possible demonstrations of the existence of a particle or interaction. Spark chambers were easier to build and so soon became common, various types being developed across the world. The development of spark chambers originated in the need for timing devices for the Manhattan Project, but work on their design occurred in a number of units worldwide. (UK)

  20. Fermi Bubbles: Formation Scenarios and Substructure

    Science.gov (United States)

    Finkbeiner, Douglas P.

    2013-04-01

    The Milky Way has gamma-ray lobes extending several kpc above and below the Galactic center, known as the "Fermi Bubbles." Although the Galactic center is quiet today, these bubbles are a hint of past AGN activity, a burst of star formation, or some other dramatic energy injection. In the three years since their discovery, they have been modeled analytically and numerically, and additional radio and x-ray data have been obtained, leading to a number of ideas about their origins. I will review the latest data and report on some possible formation scenarios. I will also give an update on our tentative claim last year of a linear jet-like structure within the bubbles (arXiv:1205.5852).

  1. Experimental investigation of bubble plume structure instability

    Energy Technology Data Exchange (ETDEWEB)

    Marco Simiano; Robert Zboray; Francois de Cachard [Thermal-Hydraulics Laboratory, Paul Scherrer Institut, 5232 Villigen PSI (Switzerland); Djamel Lakehal; George Yadigaroglu [Institute of Energy Technology, Swiss Federal Institute of Technology, ETH-Zentrum/CLT, 8092 Zurich (Switzerland)

    2005-07-01

    Full text of publication follows: The hydrodynamic properties of a 3D bubble plume in a large water pool are investigated experimentally. Bubble plumes are present in various industrial processes, including chemical plants, stirred reactors, and nuclear power plants, e.g. in BWR suppression pools. In these applications, the main issue is to predict the currents induced by the bubbles in the liquid phase, and to determine the consequent mixing. Bubble plumes, especially large and unconfined ones, present strong 3D effects and a superposition of different characteristic length scales. Thus, they represent relevant test cases for assessment and verification of 3D models in thermal-hydraulic codes. Bubble plumes are often unsteady, with fluctuations in size and shape of the bubble swarm, and global movements of the plume. In this case, local time-averaged data are not sufficient to characterize the flow. Additional information regarding changes in plume shape and position is required. The effect of scale on the 3D flow structure and stability being complex, there was a need to conduct studies in a fairly large facility, closer to industrial applications. Air bubble plumes, up to 30 cm in base diameter and 2 m in height were extensively studied in a 2 m diameter water pool. Homogeneously sized bubbles were obtained using a particular injector. The main hydrodynamic parameters. i.e., gas and liquid velocities, void fraction, bubble shape and size, plume shape and position, were determined experimentally. Photographic and image processing techniques were used to characterize the bubble shape, and double-tip optical probes to measure bubble size and void fraction. Electromagnetic probes measured the recirculation velocity in the pool. Simultaneous two-phase flow particle image velocimetry (STPFPIV) in a vertical plane containing the vessel axis provided instantaneous velocity fields for both phases and therefore the relative velocity field. Video recording using two CCD

  2. ON THE ANALYSIS OF BUBBLE CHAMBER TRACKS

    International Nuclear Information System (INIS)

    Bradner, H.; Solmitz, F.

    1958-01-01

    Since its invention by Glaser in 1953, the bubble chamber has become a most valuable tool in high-energy physics. It combines a number of advantages of various older methods of particle detection: it offers high spatial resolution, rapid accumulation of data, some time resolution, and some choice of the nucleus whose interaction one wants to study (bubble chambers have been made to operate with a large number of different liquids, including H 2 , D 2 , He, Xe, and several hydrocarbons). In order to exploit the advantages of spatial resolution and rapid data accumulation, high-speed high-precision analysis procedures must be developed. In this article they discuss some of the problems posed by such analysis. The discussion is based largely on experience gained in performing hydrogen bubble chamber experiments with the University of California's Bevatron (6-Bev proton synchrotron)

  3. Risk bubbles and market instability

    Science.gov (United States)

    Marsili, Matteo; Raffaelli, Giacomo

    2006-10-01

    We discuss a simple model of correlated assets capturing the feedback effects induced by portfolio investment in the covariance dynamics. This model predicts an instability when the volume of investment exceeds a critical value. Close to the critical point the model exhibits dynamical correlations very similar to those observed in real markets. Maximum likelihood estimates of the model's parameter for empirical data indeed confirms this conclusion. We show that this picture is confirmed by the empirical analysis for different choices of the time horizon.

  4. Bubble separation at the interface between a liquid metal and a liquid slag

    Science.gov (United States)

    Chevrier, Vincent F.

    Due to more specific consumer demand, most steel manufacturers are developing techniques to produce quality steels by limiting the number of defects in the final product. There are several aspects to be considered when producing "clean steels", and this research project will focus on one of them: inclusion and bubble separation. Large inclusions (solid or liquid) and gas bubbles have to be removed from the liquid metal before casting, and separation occurs mostly at the slag-metal interface. The objective of this study to develop a fundamental understanding of bubble separation at the slag-metal interface by looking at the chemical engineering literature on separation and coalescence, and by studying experimentally bubble separation at a liquid-liquid interface, first using a water-oil system and then with a metal-slag system. The literature review and the water modeling experiments have shown that four separate steps need to be considered when studying the removal of a buoyant phase particle at a liquid-liquid interface: the transport to the interface, the separation at the interface (film drainage), the film rupture and the removal from the interface. The major factors influencing the rest-time of an argon bubble at an oil-water interface are determined experimentally. The high temperature apparatus permits direct visualization of bubble behavior in metal and slag. The separation of argon bubbles at the slag-metal interface exhibits a behavior similar to what is observed in water modeling: the bubbles impact the interface and rest there for some time before coalescing. A methodology of studying the separation of solid and liquid inclusions is also established using two complementary techniques: x-ray fluoroscopy and confocal scanning electron microscopy. This experimental study showed that inclusions and bubbles do not separate immediately upon reaching the slag-metal interface but can rest in the metal phase for long periods of time before separating. Enhancing

  5. Theory Description, Critical Reflection, and Theory Evaluation of the Transitions Theory of Meleis et al according to Chinn and Kramer (2011).

    Science.gov (United States)

    Bohner, Katja

    Transitions Theory (TT) states that change and transition are phenomena that make humans more vulnerable to health risks. Transitions Theory was evaluated through a text analysis of 4 publications, 3 nursing expert focus group interviews in Switzerland, and a mapping review of the transition literature of the last 5 years. Although the implementation of TT into Swiss nursing practice seems problematic due to conceptual deficiencies, transition is a meaningful nursing topic. The connection between TT, research, and practice is weak. Yet guidelines for theory description, theory analysis, and theory actualization could enhance and strengthen the body of knowledge in nursing.

  6. Single-bubble sonoluminescence as Dicke superradiance at finite temperature

    Science.gov (United States)

    Aparicio Alcalde, M.; Quevedo, H.; Svaiter, N. F.

    2014-12-01

    Sonoluminescence is a process in which a strong sound field is used to produce light in liquids. We explain sonoluminescence as a phase transition from ordinary fluorescence to a superradiant phase. We consider a spin-boson model composed of a single bosonic mode and an ensemble of N identical two-level atoms. We assume that the whole system is in thermal equilibrium with a reservoir at temperature β-1. We show that, in a ultrastrong-coupling regime, between the two-level atoms and the electromagnetic field it is possible to have a cooperative interaction of the molecules of the gas in the interior of the bubble with the field, generating sonoluminescence.

  7. Acoustical bubble trapper applied to hemodialysis.

    Science.gov (United States)

    Palanchon, P; Birmelé, B; Tranquart, F

    2008-04-01

    Gaseous microemboli can arise in extracorporeal lines and devices such as dialysis machines. They are associated with severe pulmonary side effects in patients undergoing chronic hemodialysis sessions. The goal of this study was to develop a gaseous emboli trapper using ultrasound waves to remove any air bubble from the tubing system before they reach the patient. A homemade bubble trapper, developed in the laboratory, consists of a Perspex block containing a main channel connected to the tubing of a hemodialysis machine and a second subchannel positioned perpendicularly to the main one, used to trap the air microemboli. The microemboli flowing in the main channel were insonified through an acoustic window with an ultrasound wave, at a frequency of 500 kHz and with a maximal acoustic pressure of 500 kPa, generated by a single-element transducer positioned 3 cm away from the main flow. The radiation force induced by the ultrasound beam acts directly on the flowing air emboli, by pushing them into the subchannel. Two Doppler probes operating both at 2 MHz, connected to a DWL Doppler machine were placed before and after the bubble trapper to count sequentially the number of embolic events. The flow of the machine was varied between 200 mL/min and 500 mL/min. Depending on the flow velocity, the number of microembolic signals (MES) detected by the Doppler probes before and after the trapping system was identical and ranged from 5 to 150 MES/min in absence of the ultrasound irradiation. When the air bubble trapper was activated, a reduction of the number of MES, up to 70%, was achieved. Doppler recordings suggest that the circulating bubbles were either fragmented into smaller bubble fragments or directly got pushed into the second subchannel where they were collected. This simple approach using an ultrasound-based trapping system was shown to operate adequately with the current settings and can be used to filter air microemboli.

  8. The multiphase flow system used in exploiting depleted reservoirs: water-based Micro-bubble drilling fluid

    Science.gov (United States)

    Li-hui, Zheng; Xiao-qing, He; Li-xia, Fu; Xiang-chun, Wang

    2009-02-01

    Water-based micro-bubble drilling fluid, which is used to exploit depleted reservoirs, is a complicated multiphase flow system that is composed of gas, water, oil, polymer, surfactants and solids. The gas phase is separate from bulk water by two layers and three membranes. They are "surface tension reducing membrane", "high viscosity layer", "high viscosity fixing membrane", "compatibility enhancing membrane" and "concentration transition layer of liner high polymer (LHP) & surfactants" from every gas phase centre to the bulk water. "Surface tension reducing membrane", "high viscosity layer" and "high viscosity fixing membrane" bond closely to pack air forming "air-bag", "compatibility enhancing membrane" and "concentration transition layer of LHP & surfactants" absorb outside "air-bag" to form "incompact zone". From another point of view, "air-bag" and "incompact zone" compose micro-bubble. Dynamic changes of "incompact zone" enable micro-bubble to exist lonely or aggregate together, and lead the whole fluid, which can wet both hydrophilic and hydrophobic surface, to possess very high viscosity at an extremely low shear rate but to possess good fluidity at a higher shear rate. When the water-based micro-bubble drilling fluid encounters leakage zones, it will automatically regulate the sizes and shapes of the bubbles according to the slot width of fracture, the height of cavern as well as the aperture of openings, or seal them by making use of high viscosity of the system at a very low shear rate. Measurements of the rheological parameters indicate that water-based micro-bubble drilling fluid has very high plastic viscosity, yield point, initial gel, final gel and high ratio of yield point and plastic viscosity. All of these properties make the multiphase flow system meet the requirements of petroleum drilling industry. Research on interface between gas and bulk water of this multiphase flow system can provide us with information of synthesizing effective agents to

  9. Bubble dynamics in a superheated liquid

    International Nuclear Information System (INIS)

    Sha, W.T.; Shah, V.L.

    1977-09-01

    The report presents an extensive literature survey on bubble dynamics. Growth of a single spherical bubble moving in a uniformly superheated liquid is considered. Equations of motion and energy are presented in the forms that take into consideration the interaction between the motion and the growth. The fourth-order Runge-Kutta method is used to obtain a simultaneous solution of equations of motion and growth rate, and the solution is compared with available experimental results. Results for liquid sodium are presented for a range of pressures and Jakob numbers

  10. Partial coalescence from bubbles to drops

    KAUST Repository

    Zhang, F. H.

    2015-10-07

    The coalescence of drops is a fundamental process in the coarsening of emulsions. However, counter-intuitively, this coalescence process can produce a satellite, approximately half the size of the original drop, which is detrimental to the overall coarsening. This also occurs during the coalescence of bubbles, while the resulting satellite is much smaller, approximately 10 %. To understand this difference, we have conducted a set of coalescence experiments using xenon bubbles inside a pressure chamber, where we can continuously raise the pressure from 1 up to 85 atm and thereby vary the density ratio between the inner and outer fluid, from 0.005 up to unity. Using high-speed video imaging, we observe a continuous increase in satellite size as the inner density is varied from the bubble to emulsion-droplet conditions, with the most rapid changes occurring as the bubble density grows up to 15 % of that of the surrounding liquid. We propose a model that successfully relates the satellite size to the capillary wave mode responsible for its pinch-off and the overall deformations from the drainage. The wavelength of the primary wave changes during its travel to the apex, with the instantaneous speed adjusting to the local wavelength. By estimating the travel time of this wave mode on the bubble surface, we also show that the model is consistent with the experiments. This wavenumber is determined by both the global drainage as well as the interface shapes during the rapid coalescence in the neck connecting the two drops or bubbles. The rate of drainage is shown to scale with the density of the inner fluid. Empirically, we find that the pinch-off occurs when 60 % of the bubble fluid has drained from it. Numerical simulations using the volume-of-fluid method with dynamic adaptive grid refinement can reproduce these dynamics, as well as show the associated vortical structure and stirring of the coalescing fluid masses. Enhanced stirring is observed for cases with second

  11. A large bubble around the Crab Nebula

    Science.gov (United States)

    Romani, Roger W.; Reach, William T.; Koo, Bon Chul; Heiles, Carl

    1990-01-01

    IRAS and 21 cm observations of the interstellar medium around the Crab nebula show evidence of a large bubble surrounded by a partial shell. If located at the canonical 2 kpc distance of the Crab pulsar, the shell is estimated to have a radius of about 90 pc and to contain about 50,000 solar masses of swept-up gas. The way in which interior conditions of this bubble can have important implications for observations of the Crab are described, and the fashion in which presupernova evolution of the pulsar progenitor has affected its local environment is described.

  12. Bubble chamber: Omega production and decay

    CERN Multimedia

    1973-01-01

    This image is of real particle tracks taken from the CERN 2 m liquid hydrogen bubble chamber and shows the production and decay of a negative omega particle. A negative kaon enters the chamber which decays into many particles, including a negative omega that travels a short distance before decaying into more particles. The invention of bubble chambers in 1952 revolutionized the field of particle physics, allowing real tracks left by particles to be seen and photographed by expanding liquid that had been heated to boiling point.

  13. Stochastic modelling for financial bubbles and policy

    Directory of Open Access Journals (Sweden)

    John Fry

    2015-12-01

    Full Text Available In this paper, we draw upon the close relationship between statistical physics and mathematical finance to develop a suite of models for financial bubbles and crashes. By modifying previous approaches, we are able to derive novel analytical formulae for evaluation problems and for the expected timing of future change points. In particular, we help to explain why previous approaches have systematically overstated the timing of changes in market regime. The list of potential empirical applications is deep and wide ranging, and includes contemporary housing bubbles, the Eurozone crisis and the Crash of 2008.

  14. Simulations of Bubble Motion in an Oscillating Liquid

    Science.gov (United States)

    Kraynik, A. M.; Romero, L. A.; Torczynski, J. R.

    2010-11-01

    Finite-element simulations are used to investigate the motion of a gas bubble in a liquid undergoing vertical vibration. The effect of bubble compressibility is studied by comparing "compressible" bubbles that obey the ideal gas law with "incompressible" bubbles that are taken to have constant volume. Compressible bubbles exhibit a net downward motion away from the free surface that does not exist for incompressible bubbles. Net (rectified) velocities are extracted from the simulations and compared with theoretical predictions. The dependence of the rectified velocity on ambient gas pressure, bubble diameter, and bubble depth are in agreement with the theory. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

  15. A note on effects of rational bubble on portfolios

    Science.gov (United States)

    Wang, Chan; Nie, Pu-yan

    2018-02-01

    In general, demand increases in wealth and decreases in price in microeconomics. We thereby propose a completely different perspective. By establishing expected utility function of investors, this article introduces one rational bubble asset and one bubble free asset in portfolios and focuses on the effects of bubble on investment portfolios from wealth and price perspectives. All conclusions are obtained by theoretical analysis with microeconomics theory. We argue that inferior goods and Giffen behavior can occur for the bubble free asset in microeconomic fields. The results can help investors to recognize bubble assets and bubble free assets more scientifically. Both bubble and bubble free assets can be inferior goods under some conditions, so we cannot to say which asset better than the other one absolutely.

  16. Bubbles, jets, and clouds in active galactic nuclei

    International Nuclear Information System (INIS)

    Smith, M.D.; Smarr, L.; Norman, M.L.; Wilson, J.R.

    1983-01-01

    The Blandford and Reese 1974 fluid twin-exhaust model for jet formation is thoroughly investigated. We perform detailed analytic calculations of all aspects of the cavity-nozzle structures for the nonrelativistic case: the preshock flow, the central shock, cavity flow, and the nozzle. Our analytic results are in excellent agreement with recent sophisticated numerical calculations. We find that for a given central confining gas cloud, only a finite range of jet powers is possible. The sound speed ratio between cavity and cloud must be less than 30. Central masses of approx.10 9 M/sub sun/ within 1 pc are necessary for high-powered (10 46 ergs s -1 ) extragalactic jets. For a fixed confining cloud sound speed C 0 , there are three regimes determined by the central engine's luminosity. For low luminosity, a stream of bubbles emerges; for a middle range of luminosities, a jet forms; for too high a luminosity, large clouds are emitted. In the jet regime we find that L/sub j/approx.C 0 5 . The critical dependence of jet power on confining cloud sound speed enables a schematic picture for active galactic nuclei to be proposed. Seyfert galaxies and quasars are placed in the bubble regime. Variable compact radio sources reach the cloud regime. Evolutionary paths are suggested and may provide an indirect test for this picture

  17. Contact Lens Wear at Altitude: Subcontact Lens Bubble Formation

    Science.gov (United States)

    1987-11-01

    incidence of (PMMA) lenses . Reported here are the results of contact lens subcontact lens bubble formation under scleral lenses at bubble studies with soft...vision from formation of large bubbles greater than 6,096 m (20,000 It). With soft contact lenses , bubble under their contact lenses . They also found...always located at the limbus and were without sequela to vision or corneal epithelial integrity. scleral lenses used by Jaeckle were permeable to gases

  18. Magnetic field induced motion behavior of gas bubbles in liquid

    OpenAIRE

    Keliang Wang; Pucheng Pei; Yu Pei; Ze Ma; Huachi Xu; Dongfang Chen

    2016-01-01

    The oxygen evolution reaction generally exists in electrochemical reactions. It is a ubiquitous problem about how to control the motion of oxygen bubbles released by the reaction. Here we show that oxygen bubbles during oxygen evolution reaction exhibit a variety of movement patterns in the magnetic field, including directional migration and rotational motion of oxygen bubbles when the magnet in parallel with the electrode, and exclusion movement of oxygen bubbles when the magnet perpendicula...

  19. Boundary curvature effects on gas bubble oscillations in underwater explosion

    OpenAIRE

    Matsumoto, Kazuhiro

    1996-01-01

    The oscillation of a gas bubble produced as a result of underwater explosion could cause the severe whipping damage on nearby marine vehicle. The effects of rigid boundary curvatures to explosive gas bubble oscillation behavior in underwater were investigated. The analyses were conducted using a multimaterial Lagrangian-Eulerian finite element code, MSC/DYTRAN. The incident shock wave pressure, bubble pulse pressure, gas bubble radius and period were calculated for the case of detonation of a...

  20. Critical role of free cytosolic calcium, but not uncoupling, in mitochondrial permeability transition and cell death induced by diclofenac oxidative metabolites in immortalized human hepatocytes

    International Nuclear Information System (INIS)

    Lim, M.S.; Lim, Priscilla L.K.; Gupta, Rashi; Boelsterli, Urs A.

    2006-01-01

    Diclofenac is a widely used nonsteroidal anti-inflammatory drug that has been associated with rare but serious hepatotoxicity. Experimental evidence indicates that diclofenac targets mitochondria and induces the permeability transition (mPT) which leads to apoptotic cell death in hepatocytes. While the downstream effector mechanisms have been well characterized, the more proximal pathways leading to the mPT are not known. The purpose of this study was to explore the role of free cytosolic calcium (Ca 2+ c ) in diclofenac-induced cell injury in immortalized human hepatocytes. We show that exposure to diclofenac caused time- and concentration-dependent cell injury, which was prevented by the specific mPT inhibitor cyclosporin A (CsA, 5 μM). At 8 h, diclofenac caused increases in [Ca 2+ ] c (Fluo-4 fluorescence), which was unaffected by CsA. Combined exposure to diclofenac/BAPTA (Ca 2+ chelator) inhibited cell injury, indicating that Ca 2+ plays a critical role in precipitating mPT. Diclofenac decreased the mitochondrial membrane potential, ΔΨ m (JC-1 fluorescence), even in the presence of CsA or BAPTA, indicating that mitochondrial depolarization was not a consequence of the mPT or elevated [Ca 2+ ] c . The CYP2C9 inhibitor sulphaphenazole (10 μM) protected from diclofenac-induced cell injury and prevented increases in [Ca 2+ ] c , while it had no effect on the dissipation of the ΔΨ m . Finally, diclofenac exposure greatly increased the mitochondria-selective superoxide levels secondary to the increases in [Ca 2+ ] c . In conclusion, these data demonstrate that diclofenac has direct depolarizing effects on mitochondria which does not lead to cell injury, while CYP2C9-mediated bioactivation causes increases in [Ca 2+ ] c , triggering the mPT and precipitating cell death